JP2017200751A - Surface layer carbonization method for wood or woody material and product produced by the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a surface layer carbonization method for wood or woody material which solves defects of conventionally known Sho-Sugi-Ban and thermally treated wood, can enhance antiseptic property, weather resistance, termite prevention property and the like almost without lowering a mechanical strength of wood or a woody material or using a chemical agent, and also prevents cracking on a surface layer.SOLUTION: A surface layer carbonization method for wood or woody material includes: bringing a high-temperature gas impermeable member such as a hot plate into contact with wood and heating a wood surface in a state where volatilization of a thermally decomposed volatile component of the wood is suppressed to carbonize the wood from the surface to the internal part of the wood in such a degree as not to substantially lower a mechanical strength of the wood without causing cracking. A carbonized layer having a desired depth is obtained by limiting a temperature and heating time of the hot plate to a specific range. The specific range is expanded by impregnating the wood material surface layer with water glass.SELECTED DRAWING: None

Description

  The present invention relates to a method for carbonizing a surface layer of a wood or woody material.

  In order to improve the antisepticity, weather resistance, etc. of wood, it has long been known to carbonize the surface by exposing it to a flame. For example, if burnt cannabis or newspaper is used to burn one side of a board and the baked side faces the outside, it is known to have nearly 100 years even when exposed to wind and rain. Yes. At present, such a method is hardly performed, and a part of the surface layer is carbonized by baking a plate with a gas burner or an oil burner. Although the carbonized layer formed by such a method is thick, the surface is not smooth and flat, and innumerable creases (appears like cracks, hereinafter, cracks are simply referred to as cracks). This surface layer has a low mechanical strength, and black powder adheres to the finger just by lightly rubbing it with a finger. Moreover, when it rubs strongly with a hand or when an object collides, it will peel easily on the part of a crack. The thickness of the carbonized layer at the bottom of the crack is much smaller than the thickness of the portion without the crack. Since there is a risk of water entering from these cracks, it is necessary to avoid the occurrence of cracks. Obviously, if the crack is not formed, the life of the plate whose surface layer is carbonized is further extended.

  1 (a), (b), and (c), the inventor has shown that the pine board A (thickness 24 mm, width 60 mm, length 65 mm), cedar wood B (thickness 14 mm, width 45 mm, length) 90 mm) and cedar wood material C (thickness 14 mm, width 45 mm, length 65 mm), a gas burner (HBA-1700G manufactured by Kinboshi Co., Ltd.) flame (1000 ° C. or higher) was sprayed on the surface, It is the photograph of the surface in which the crack was formed. The photo (a) was baked by blowing a flame of a gas burner on Ezo pine A for 30 seconds, the photo (b) was blown by cedar wood B for 30 seconds, and the photo (c) was baked on cedar wood C by 10 seconds. FIG. 2 is a photomicrograph of a cross section including one of those cracks. Photo (a) is a cross-sectional microscope of Ezomatsu A, photo (b) is Sugibe wood B, and photo (c) is a cross-section microscope of Sugibe wood C. It is a photograph. As can be seen from FIG. 2, the cross section of the crack is the cross section of the crater, and the thickness of the carbonized layer at the bottom of the crack is significantly smaller than the thickness of the portion where there is no crack. The thickness of the carbonized layer at the bottom of the crack in the photograph (a) in FIG. 2 is 1.0 mm, whereas the thickness of the carbonized layer at the portion without the crack is 1.7 mm. The thickness of the carbonized layer at the bottom of the crack in the photograph (b) in FIG. 2 is 0.8 mm, whereas the thickness of the portion without the crack is 1.8 mm. Thus, the thickness of the carbonized layer is greatly reduced in the crack portion.

  The reason for the formation of cracks is that when a plate is exposed to a high-temperature flame in the air and the volatile components generated by thermal decomposition burn on a part of the surface, it preferentially volatilizes and burns on that part, This may be due to a sudden decrease in volume, or when pyrolysis components volatilize and burn from the entire surface exposed to a high-temperature flame, the volume decreases, and the shallow lake water dries out and the mud at the bottom of the lake dries out. It seems to be like a crack.

  FIG. 3 shows that the inventor used a commercially available gas burner (Fujiwara Sangyo Co., Ltd. One Touch Gas Torch SK-11) to radiate a flame (1000 ° C. or higher) to a pine pine board (cross section: 14 × 45 mm). It is the graph which plotted the thickness of the carbonization layer with respect to. The flame strength of this gas burner was much weaker than that of the aforementioned Kimbosi Co., Ltd. product. Three samples were prepared at the same radiation time while keeping the strength of the flame and the distance from the surface of the Ezo pine to the burner, plotting their carbonized layer thickness, and showing the polynomial approximation curve. It can be seen visually that cracking occurs when the radiation time is 4 seconds or longer. Furthermore, cracks increase as radiation continues. The thickness of the carbonized layer where there is no crack when the radiation time is 4 seconds is about 0.4 mm. Thus, the thickness of the carbonized layer that can be carbonized in a range where cracks do not occur is very small.

  Patent Document 1 shows that an anti-rotation wood having high hygroscopicity can be obtained by heating the surface of wood with a gas burner to form a carbonized layer having a thickness of 0.2 mm. It is known that even if such a thin carbonized layer is formed on the surface layer, it has an anti-corrosion effect, but such a thin carbonized layer provides sufficient weather resistance, antiseptic properties, and ant-proof properties. I can't. As a building material used in places exposed to wind and rain such as outer walls and fences, a thickness of 3 mm is usually required. In the surface carbonization by a gas burner, if an attempt is made to obtain a carbonized layer having this thickness, cracks will occur on the surface.

  In Patent Document 3, the whole of red pine is immersed in 460 ° C. molten zinc for 10 seconds to provide a carbonized layer on the surface, and the red pine is immersed in 300 ° C. molten salt for 5 to 10 seconds to carbonize on the surface. It is described that a layer is provided.

  However, as shown in FIG. 9 and Table 2 of the present invention, when floating in molten tin at 500 ° C. for 15 seconds, cracks are generated in the surface layer. Although not shown in FIG. 9 and Table 2 of the present invention, according to the experiment results of the present inventor, when wood is floated on molten tin at 500 ° C. for 10 seconds, cracks do not occur, but the carbonized layer at that time The thickness was very small, 0.45-0.52 mm. According to an experiment in which wood is immersed in a 300 ° C. tin bath for 10 seconds instead of 300 ° C. molten salt, the thickness of the surface carbonized layer is about 0.2 mm.

  The thickness of the carbonized layer obtained under the conditions shown in Patent Document 3 is not a carbonized layer having a practically sufficient thickness, and performance such as antiseptic properties, weather resistance, and ant-proof properties is insufficient. As a building material used in places exposed to wind and rain such as outer walls and fences, a thickness of 3 mm is usually required. Further, Patent Document 3 does not show conditions for increasing the thickness of the carbonized layer, and does not describe any cracks that may occur when carbonized under the conditions for increasing the thickness. Naturally, this document does not describe how to prevent the occurrence of cracks that occur when the carbonized layer is 0.7 mm or more.

  Patent Document 4 describes that wood is pressed and clamped by a mold for three-dimensional processing, and one side of the wood is carbonized by setting one of the molds to a temperature higher than the carbonization temperature of the wood. ing. However, there is no description or suggestion as to how carbonization can be performed so that cracks do not occur under such conditions. In the present invention, instead of using a metal mold, a method that does not cause cracks has been found by extensively examining the heating temperature and the heating time in a state where the hot plate is in contact as described later.

An object of the invention of Patent Document 4 is to make a carbonized layer conductive and use it for the purpose of electromagnetic shielding. However, in order to carbonize wood to make it conductive, as described in Non-Patent Document 4, page V-5, lines 16 to 18, high temperature of 800 ° C. or higher in an inert atmosphere. It is necessary to carbonize. Up to a temperature of about 600 ° C., the insulating material has a volume resistivity of 10 ¹² Ω · cm or more, and at a heating temperature of 600 to 700 ° C. exceeding this, a semiconductor having a volume resistivity of 10 ² to 10 ⁹ Ω · cm. When the temperature exceeds 800 ° C., conductivity of 10 Ω · cm or less is shown, and it is shown that the conductivity is improved as the temperature rises. When wood is brought into contact with a metal at 800 ° C. in the air, cracks are instantaneously generated on the surface of the wood. When the metal plate at 800 ° C. is separated from the wood surface, the wood surface starts to burn.

  Patent Document 4 describes that a wood surface is carbonized by a gas burner to make it conductive. Actually, even if baked for a short time with a gas burner, the carbonized layer does not become conductive. This is because when the wood burns with the gas burner, the temperature rise on the wood surface is suppressed by the heat of vaporization. This is known as the principle of preventing the satellite from burning out due to frictional heat with the air when returning to the earth. In order to burn wood and obtain a conductive carbonized layer, it is necessary to burn until the inside of the wood is red-hot and cool it in a place without air, or quench it with water. If wood of several mm thickness is burned in this way, it will burn out. Therefore, it is actually impossible to make the wood surface conductive with a gas burner.

  In place of the above-mentioned carbonization method using flame, recently, wood preservative treatment using chemicals has become common. A variety of drugs have been developed and used for this purpose. In order to infiltrate the drug inside the wood, various processes are used, such as forming cracks and holes in the wood, injecting the drug under reduced pressure, pressurizing after the reduced pressure injection of the drug, and injecting further into the interior Has been. However, when wood is used as a building material or civil engineering material, there is a concern about the influence of drugs on humans and the natural environment.

  On the other hand, in Scandinavia, it has been practiced for several decades to improve the antiseptic properties, weather resistance, heat resistance, ant repellency, etc. by treating wood with high temperatures. For example, if wood is left in an atmosphere where water vapor of 180 to 220 ° C. is present for about 2 to 20 hours, the inside of the wood is uniformly colored (it is considered that light carbonization has been performed), and the higher the processing temperature, the more colored. Increases the antiseptic and weather resistance. Although it has recently become known in Japan, it has not yet become widespread. In Scandinavia it is called thermowood and is widely used. The reason why the above temperature range is selected is that if the temperature is lower than this temperature, the effect hardly appears, and if the temperature is higher than this temperature, the mechanical strength of the wood sharply decreases. It is described on page 5-4 of Chapter 4. It is described that this high-temperature treatment significantly improves antiseptic properties, weather resistance, etc., but has almost no ant-repellent properties. Non-Patent Document 1, pages 17-4 and 18-4 describe that the use in the ground is not recommended because the antiseptic performance is insufficient at a processing temperature of 220 ° C. However, FIG. 13-4 on page 18-4 of Chapter 4 shows that the antiseptic performance and the ant proof performance are perfect when the processing temperature is 240 ° C. or higher. Further, since the mechanical strength is lower than that of the wood before treatment even at a treatment temperature of 220 ° C., it is warned not to use it as a base part or a structural material. A feature of the thermowood production method is that the processing temperature and the processing time are selected so that the mechanical strength and the antiseptic performance are moderately satisfied. According to the present invention, not only can carbonization be performed at a temperature higher than that in the thermowood production method, but also mechanical strength can be maintained. Thermowood is carbonized entirely from the surface to the inside.

  In Patent Document 2, in addition to heating wood in a high-temperature gas atmosphere, the wood is kept in contact with a bath of high-temperature liquid (for example, silicon-based oil, paraffin) or high-temperature granular material (for example, sand) for a long time. A method is described in which the inside is carbonized to form a thermowood. These liquids and particulates have very low thermal conductivity, so the efficiency of transferring heat to the wood is poor. Since the thermal conductivity is small, if the surface layer is carbonized to a certain depth (for example, around 5 mm), it must be carbonized over several tens of minutes, so if the sand temperature is high, Wood may catch fire or burn.

  Non-Patent Document 2 describes heat treatment with molten wax heated to 100 ° C. or higher, rapeseed oil heated to 180 ° C. to 220 ° C., cottonseed oil, or the like. It also describes heat treatment with mineral oil and silicon oil. However, these oils have a problem that it is difficult to heat to a high temperature as the wood is carbonized. Waxes, mineral oils, vegetable oils, silicone oils, etc. have a problem that the components volatilize or burn when heated to 240 ° C. or higher, so the maximum use temperature is limited. There is also a problem that the oil deteriorates by repeated use. Furthermore, as will be described later (particularly, Example 5), there arises a problem that the entire surface is heated simultaneously.

  Non-Patent Document 3 describes the results of research on carbonization of plywood by radiant heating. Although it is shown that carbonization is carried out to a depth of about 10 mm from the surface of the plywood toward the inside by radiant heating, there is no description of cracks. However, it has been confirmed that cracks are generated in a very short time when strong radiation heating as described in Non-Patent Document 3 is performed.

  It is known to heat wood in an electric furnace or a high-temperature chamber. For example, square wood is put in an electric furnace with an internal temperature of 300 ° C. and left until the surface is sufficiently colored (dark brown to black). Then, there is a problem that the corner of the square bar becomes brittle even if it is strongly carbonized. Furthermore, the time until the surface is sufficiently colored is several minutes to several tens of minutes, but when this is taken out of the electric furnace and cooled to room temperature, the square material is cut and the cross section is observed. It is difficult to perform surface layer carbonization. If the depth of the surface layer carbonization is kept small, the coloring of the surface becomes insufficient. Such a phenomenon was confirmed to be the same in the case of heating with the sand. It has been found that this phenomenon occurs because wood is simultaneously heated from all sides (periphery).

  The branding technique has been used for a long time. For example, it is common to form a brand name on a wooden box, a kamaboko base plate, or a leather surface. These cases are characterized by being heated to a high temperature as the baking mold becomes red-hot and instantaneously pressed against the object. Also, one of the features of the brand mark is that the portion is considerably depressed by evaporation due to thermal decomposition. In these cases, it is required that the formation of the burning mark be completed in a short time (almost instantaneously), and the baking mold is heated to a high temperature as it is red-heated, and is completed by the momentary or very short time pressing. In the branding method, the surface can be colored (carbonized) sufficiently deeply, but it is difficult to carbonize deep inside.

  It is known as a hobby to draw freehand images on wood, leather, resin plates, etc. with a hot pen, electric scissors or the like heated to about 400 ° C. or more. In these hobbies as well as in the above-mentioned branding technique, it is required to imprint or draw in a short time. Therefore, the temperature of the mold and the bowl is naturally required to be about 400 ° C. If the temperature is low, the time during which the baking mold is pressed or the time during which the ridge is pressed in one place becomes long, making practical use difficult. As described above, in the image-printing technique and the drawing by the wrinkle, a very high-temperature baking mold or wrinkle is used, but when the high-temperature baking mold or wrinkle is pressed against the same place for several seconds, that portion Is very darkened (blackened), and when the surface is rubbed with a finger, not only the black powder adheres to the finger, but also the carbonized part becomes considerably depressed. Such a phenomenon is not so much a problem in the case of stamping or freehand drawing, but it becomes a big problem when carbonizing a surface layer with a large area of wood as used in construction etc. is there. In addition, if you try to increase the carbonization depth by using the branding or thermal pen technology, if a trowel or thermal pen is pressed against the same place on the wood surface, cracks will occur before the carbonization depth of the required thickness is obtained. Resulting in.

  In view of the background art as described above, the present inventor speculates that the problem is that carbonization by the flame method is performed in the air, and when a wooden square is immersed in a solder bath, a stunning carbonized layer without cracks. I found out that Next, when hot air (heat gun) having a temperature much lower than that of the flame was blown, it was found that cracking was likely to occur, although it was much reduced compared with carbonization by a gas burner. Compared with heating by flame, heating by solder bath and heating by hot air, heating by flame or hot air can volatilize freely, but heating by solder bath prevents volatilization of pyrolysis components, so cracks The hypothesis is that the occurrence will be prevented. Therefore, when a wooden square was placed on a hot plate and heated, it was found that a thick carbonized layer without cracks was obtained as in the case of a solder bath. In addition, when a glass plate was placed on a wooden timber and heated by emitting infrared rays from above, the generation of cracks was greatly improved. From these results, it is considered that volatilization of the pyrolysis component due to heating is prevented. Furthermore, when the surface layer of wood was impregnated with water glass and heated with hot air, the generation of cracks was greatly improved. It was found that impregnation with water glass on the surface layer of wood has a great effect even in other heating methods. The presence of water glass prevented the pyrolysis components from volatilizing. The present invention was derived from these results.

  Patent Document 5 describes that wood impregnated with a flame retardant is further impregnated with water glass. The purpose is to delay the fall of the burned part by burning the wood surface into a flame at 840 ° C., burning the wood and penetrating to the back side. When not treated with water glass, it penetrated to the back side in 28 minutes, but when treated, it penetrated in 30 minutes. In the invention of Cited Document 5, the water glass is described as “acts so as to melt into a glass state under high temperature overheating to fix the carbonized residue”. On the other hand, in this invention, since it heats only to 450 degrees C or less, water glass does not fuse | melt to a glass state. Moreover, in this invention, the temperature area | region where wood burns is not included. In Patent Document 5, there is no consideration or description as to how water glass affects the occurrence of cracks.

JP 2002-283308 A Japanese Patent No. 3898764 JP-A-226303 JP 2007-98640 A JP 2004-181804 A

Published by ThermoWood Handbook Finnish Thermo Wood Association (August 4, 2003) Momohara Ikuo Heat Treatment and Durability Published by Japan Wood Conservation Society Journal “Wood Preservation” Vol.31-1 (2005) Saburo Uesugi Carbonization of plywood by radiant heating Forestry Experiment Station Research Report No. 340 (1986) 4. Professor Emeritus, Kyoto University Shigehisa Ishihara From wood to charcoal-Can charcoal become a functional material? New development by carbonization of woody materials Japan Wood Society (2004)

  The object of the present invention is to overcome the disadvantages of the conventionally known burned cedar and thermowood, in particular without using a chemical such as a preservative, without substantially reducing the mechanical strength of thick (thick) wood or woody materials. Without cracking the surface layer of wood or wood material, at least a part of the surface layer of wood or wood material is uniformly carbonized to a thickness of 0.7 mm or more (colored from black to brown) ) To provide a surface layer carbonization method capable of enhancing antiseptic properties, weather resistance, ant repellency, and the like, and to provide a product obtained by the method.

  A first method for solving the problems of the present invention is to keep the surface temperature of 240 ° C. to 450 ° C. on the surface of a carbonized region of wood or woody material while preventing volatilization of pyrolysis components. The region is carbonized to a required depth of 0.7 mm or more, that is, a desired depth, from the surface toward the inside by supplying controlled thermal energy.

  Method A for preventing volatilization of pyrolysis components in the first method of the present invention is to contact a gas-impermeable member so as to cover at least a part of the surface of the wood or wood material to be carbonized. In a state, by supplying controlled thermal energy from the member, the region is carbonized from its surface inward to the required or desired depth. In the present invention, the meaning of “contact” in “contacting a gas-impermeable member with wood” is the same as “adhesion”. For example, during carbonization of a wood flat plate, the pyrolysis component generated from the wood flat plate is In order to prevent volatilization freely, it is used in the sense that the metal plate is closely attached so as to cover the surface of the wood flat plate.

  The method for supplying thermal energy from the gas impermeable member is a method of supplying a gas impermeable member of molten metal, hot plate, hot foil, or hot roll at 240 ° C. to 450 ° C. to the surface of the wood or wood material. Is to contact. By controlling the temperature of the gas-impermeable member and the contact time with 15 seconds or more, it is possible to carbonize to a required depth of 0.7 mm or more from the surface of the wood or wood material toward the inside. .

  Method B for preventing volatilization of pyrolytic components is a method in which a member such as a glass plate which is impermeable to gas and transmits infrared rays is brought into contact with the surface of the wood or wood material, and the wood or wood material is transmitted through the member. Is to irradiate infrared rays while maintaining the surface of 240 ° C to 450 ° C. By controlling the energy intensity and irradiation time of infrared rays, carbonization is performed to a necessary depth of 0.7 mm or more from the surface of the wood or woody material toward the inside.

  Method C for preventing volatilization of pyrolytic components is to apply the method A or B after impregnating the surface layer of wood or wood material with water glass, or water glass to the surface layer of wood or wood material. Is impregnated with infrared rays so that the surface temperature is 240 ° C to 450 ° C. Water glass impregnated in the surface layer of wood or woody material prevents volatilization of the pyrolysis component and prevents the generation of cracks.

  A second method for solving the problem of the present invention is to blow hot air at a temperature of 280 ° C. to 480 ° C. on the surface of the carbonized region of the wood or woody material, so that the region is directed from the surface toward the inside. Carbonization to the required depth, ie the desired depth. The generation of cracks was greatly improved by blowing hot air at a temperature much lower than that of the gas burner flame. Also in the second method for solving the problems of the present invention, it is very effective to impregnate wood with water glass before blowing hot air.

  In the present invention, gas impermeability does not mean that gas is not completely transmitted, but does not substantially transmit gas. That is, the thermal decomposition component generated during the carbonization treatment has a gas impermeability that does not pass through the member. For example, it may be a porous material that allows gas to pass through very slowly, such as pottery or unglazed.

  In the present invention, “wood or woody material” is hereinafter simply referred to as wood. According to the present invention, by carbonizing by controlling the temperature and time, the wood is only carbonized from the surface to the inside to the required depth, so that the inside has the same mechanical strength as the original wood. To do. In addition, the surface layer of wood is much stronger than in the case of the manufacturing method of thermowood, that is, it can be carbonized at high temperature, so that performances such as antiseptic and ant repellency can be obtained far superior to thermowood. . Furthermore, since it is not necessary to use a preservative, a product having no adverse effects on the human body and the environment can be obtained. According to the method of the present invention, it is possible to obtain a uniform thickness and durability of the surface carbonized layer, which could not be realized by the conventional combustion method and gas burner method. That is, there can be obtained a surface carbonized layer which is free from cracks, has a sufficient thickness, can have a surface color of brown to black, and can hardly remove colored powder even if the surface is rubbed with a finger. Furthermore, according to the method of the present invention, it is possible to easily carbonize the surface layer of only one surface or a part of the surface of the wood or a part of the surface. In addition, the surface layer of wood having a curved surface or a complicated shape can be carbonized. For example, it is possible to easily carbonize a square member having a tenon or a tenon hole, or a square member having a groove or a hole, and a great many applications can be considered. When the surface layer carbonized wood is cut with a saw at a construction site, a non-carbonized portion is exposed on the cut surface, and this surface can be carbonized on the site.

FIG. 1 is a photograph showing the occurrence of cracks on the wood surface carbonized by a gas burner. FIG. 2 is a photomicrograph of a cross section of a portion where cracks in the wood of FIG. 1 occur. FIG. 3 is a graph in which the thickness of the carbonized layer of a sample prepared by a gas burner is plotted, and shows the conditions under which cracks start to occur. FIG. 4 is a surface photograph (a) of a carbide carbonized by the molten metal method and a cross-sectional micrograph (b) of a cracked portion. FIG. 5 is a side sectional view of one specific example of the hot plate system of the present invention. FIG. 6 shows a surface photograph (a) and a cross-sectional micrograph (b) of a crack in which a crack is generated when the temperature of the hot air is high in the hot air method. FIG. 7 shows a photograph of the surface of carbonized by the hot air method. Photo (a) shows the case where hot air of air is used, and photo (b) shows the case where hot air of carbon dioxide gas is used. FIG. 8 is a side sectional view of one specific example of the hot plate system of the present invention. FIG. 9 is a surface photograph taken by arranging samples prepared by the molten metal method of the present invention. FIG. 10 is a graph in which the carbonization depth of the sample prepared in Example 1 is plotted. FIG. 11 is a graph plotting the carbonization depth of the sample prepared in Example 2. FIG. 12 is a graph in which the carbonization depth of the sample prepared in Example 3 is plotted. FIG. 13 is a graph plotting the carbonization depth of the sample prepared in Example 4. FIG. 14 is a cross-sectional photograph of the sample prepared in Example 5. FIG. 15 shows various photographs of the sample created in Comparative Example 1. FIG. 16 shows various photographs of the sample created in Comparative Example 2.

  The molten metal used in Method A for preventing volatilization of pyrolysis components is a metal that melts at a temperature of 240 ° C. or higher, is relatively stable in air in a high-temperature molten state, and is relatively inexpensive. In addition, it is desirable that it does not volatilize in the air in a high-temperature molten state and that it does not adversely affect the environment. As a material that substantially satisfies these conditions, tin or a tin alloy represented by solder can be cited. Of these, tin is particularly desirable because it is widely used for the surface treatment of steel materials. Lead can also be used, but it is not preferable because it adversely affects the environment. It does not necessarily need to be a metal, and if there is something like a molten salt with a high thermal conductivity, it should be usable.

  In the molten metal method, which is one of the methods A for preventing volatilization of pyrolysis components, wood is floated in a bath of high-temperature molten metal, or part or all of it is treated by treatment. Therefore, only a part of the wood is immersed in the bath. Therefore, log, columnar or prismatic wood is rotated around the longitudinal axis of the wood, or the wood is submerged in the bath with an appropriate jig, or on the wood floating in the bath. The molten metal is allowed to flow through the portion of the wood that is above the bath surface and the molten metal is contacted, or a combination of these methods can be used to uniformly heat the wood surface layer. . When the wood is plate-shaped, if only one side is treated, it is only necessary to float in the bath. However, when treating both sides, this is achieved by treating one side of the plate and turning it over. One side of the board can be carbonized on the surface and the other side can be left with a wood background. Further, the moisture content of the wood is usually over 10% or more, and when the wood in this state is immersed in a high-temperature bath, steam gas is generated vigorously. Therefore, the wood may be dried in advance by an appropriate method. If the wood is sufficiently dried, even after the treatment according to the present invention, deformation is not likely to occur for a long period of time, so that there is an advantage that cracking and warping are unlikely to occur.

  The molten metal is not necessarily placed in the bathtub, and may be circulated and used by pouring it over the wood from above, or collecting and heating the molten metal that has flowed down and pouring it over the wood again. In this way, the processing bath can be small.

  One most important aspect of the present invention is that the surface layer is fully carbonized but the interior is not carbonized. The carbonized surface layer exhibits antiseptic properties, weather resistance, ant proof properties, moisture proof properties, etc., and the mechanical strength is maintained by keeping the original wood without being carbonized. Therefore, the time during which the wood is in contact with the high temperature bath and the temperature of the high temperature bath are extremely important factors. If the contact time is too short, the thickness of the carbonized surface layer is small, and if it is too long, carbonization proceeds to the inside and the mechanical strength decreases. If the temperature of the high temperature bath is low, the carbonization rate is low, and if the temperature is too high, cracks may occur. The desired contact time and bath temperature vary depending on the material of the wood and the shape such as thickness and thickness, but the contact time is suitably from 15 seconds to 120 minutes, and the bath temperature is suitably from about 240 to 450 ° C. A more desirable range is 280 ° C to 380 ° C. In this temperature range, the carbonization depth can be increased without cracks, and black powder is difficult to remove even if the surface is rubbed with a finger.

  According to the molten metal system, carbonization is performed in a high temperature molten metal bath or in contact with the molten metal, so that carbonization is performed while being substantially shielded from air (oxygen). Therefore, the reason why the surface is carbonized uniformly without the occurrence of cracks as shown in FIG. 1 is that the surface to be carbonized is blocked by molten metal. This is probably because the volume of the surface layer is hardly reduced. Further, the volatile matter adheres to the inner walls of the road pipe, temporary road pipe and the like in the surface layer, and is further confined inside through the wall hole. As a result, if it is carbonized in the air, components that volatilize or burn outside will remain in the surface layer and deeper portions, so that a large amount of so-called tar content exists in the surface layer and deeper portions, and voids in the surface layer and deeper portions. Therefore, the moisture resistance is high, which is advantageous for preventing deterioration when exposed to wind and rain. In addition, since a large amount of tar is present in the surface layer, it is advantageous for ant protection and antiseptic properties. In the case of flame carbonization in the air, these volatile components, tar components and the like are easily burned or volatilized.

  Even in the molten metal system, cracks may occur if the temperature of the molten metal is too high or the contact time between the molten metal and wood is too long. The above-mentioned desirable temperature range and contact time are determined from this viewpoint. FIG. 4 shows a cedar wood block (cross section 16 × 20 mm, length 30 mm) immersed in a bath of molten tin at 450 ° C. with a 20 × 30 mm surface for 2 minutes to a depth of about 8 mm, and then on the surface. It is the photograph (FIG.4 (a)) which shows the formed crack, and the cross-sectional microscope picture (FIG.4 (b)) of a crack. The appearance is completely different from the cracks generated by the gas burner (FIG. 1). As apparent from the cross-sectional micrograph, the crack reaches only the shallow part of the carbonized layer.

  According to the molten metal method, as described in Example 1, it is possible to easily control the thickness of the layer carbonized in a state where no cracks are generated to about 0.5 to several tens of millimeters. Therefore, the decrease in the wood strength due to carbonization can be reduced to a negligible level. The reason is considered as follows. Wood used as a structural material such as columns, beams and foundations is usually quite thick. In the case of a pillar, one side of the cross section is usually 10.5 to 12 cm. Thus, even if the surface layer is carbonized and the mechanical strength of the portion is reduced, the thick wood has the strength of the original wood. For example, when the thickness of the carbonized surface layer is 2 mm (in the thickness direction of the wood) with 12 cm square wood, about 3.3% of the cross-sectional area of the wood before carbonization is carbonized, and the wood cross section before carbonization About 96.7% will have the original wood strength. When wood is not used as a structural material, the cross-sectional area of the carbonized layer may be further increased with respect to the total cross-sectional area of the wood. In the case of a pillar, if it is desired to avoid exposing the black carbonized layer on the surface, a thin wood can be pasted on the carbonized layer. When not a structural material, for example, if it is a plywood, a carbonized plate may be laminated inside so that the carbonized layer is not exposed on the surface. Further, it can be used such that only one surface of the plate is carbonized so that the carbonized layer does not face the front side (so as not to be seen directly). In the case of LVL and CLT materials, a plate having a carbonized layer can be similarly laminated inside.

  In the molten metal system of the present invention, when wood is immersed in a molten metal bath, if the wood is a round bar, it is carbonized concentrically from the surface to the inside, but if the wood is a square, it is concentric square Is not carbonized. The reason for this is that, at the corner of the square bar, heat is applied from both sides of the corner, so that it is heated more strongly than the flat portion. As a result, a carbonized layer with rounded corners is formed between the concentric square shape and the concentric circle shape in the cross section of the square bar after carbonization. This phenomenon is the same when wood is heated and carbonized in an electric furnace. When such a phenomenon occurs, the carbonization degree of the corner portion of the square bar is more advanced than that of the side surface portion, and it is a disadvantage of this method that it becomes mechanically weak. Moreover, since the area of the non-carbonized portion inside the square member is reduced, there is a disadvantage that the mechanical strength of the square member is also reduced. If the square is very thick, this phenomenon is not a problem. In the present invention, since only one surface can be heated, such a problem can be prevented.

  In the molten metal method, as a method of avoiding the above-mentioned problems, for example, a square is placed sideways, floated on the molten metal bath surface by its own weight, heated and carbonized for an arbitrary time, and then the square is rolled and the adjacent surface is lowered. Heat and carbonize for an arbitrary time. In this way, another surface is heated and carbonized one after another. Due to the dead weight of the square, the square is slightly submerged in the molten metal bath, so that the surface of the square is uniformly heated, and the corners are extremely less heated.

  On the surface of carbonized wood manufactured by the molten metal method, a tar content sometimes precipitates and may become sticky. In such a case, in order to remove the tar content on the surface, it can be washed away with an organic solvent that dissolves the tar content. Further, the surface can be burned and removed with a strong flame such as a gas burner for a short time (about several seconds). When exposed to a flame for a long time, cracks are generated on the surface as in the case of baked cedar, so it is preferable to set it to about 2 to 3 seconds. It is also possible to prevent stickiness by applying a paint to the surface.

  When the carbonized wood produced by the molten metal method is actually used at a construction or construction site, it may be cut to a necessary length by, for example, a saw. Since the cut surface is not carbonized, the wood may start to deteriorate when the portion is exposed. Therefore, in such a case, the exposed cut surface can be carbonized by hot air or infrared rays, which is another method of the present invention.

  When carbonizing the surface layer by the molten metal method, if the surface of the wood is cracked, raised, or dented, the above-mentioned cracks, ridged portions, dents are raised when the surface layer carbonized wood is pulled up from the molten metal tank. There is a risk that molten metal may enter and remain in In order to suppress such a phenomenon, it is desirable that the surface be smoothed by polishing and polishing before the wood is carbonized. Further, when the carbonized wood is pulled up from the molten metal tank, it is possible to remove the adhered molten metal by blowing a high-temperature high-pressure gas that is equal to or higher than the melting temperature of the metal. Since a metal oxide film and slag exist on the surface of the molten metal bath, they may adhere to the surface of the carbonized wood. In such a case, it is possible to blow off with a high-pressure air jet after cooling. It can also be scraped off with a brush. It can be removed by other appropriate methods. If ani exists on the surface of the wood, a metal oxide film or slag is likely to adhere to it, so that it is desirable that the wood has been so-called degreased in advance.

  When the surface of the molten metal has been exposed to air for a long time, the surface is oxidized and a metal oxide is formed, particularly as the melting temperature is higher. As a result, an oxide film is formed on the molten metal bath surface. When wood is immersed or brought into contact with a molten metal bath, a slag-like material is generated although the mechanism is unknown. So-called slag is accumulated on the surface of the molten metal bath, including the oxide film and the slag. Therefore, it is desirable to remove the slag from the bath surface as necessary. You may drive slag towards the edge of the bathtub. It is also possible to feed the molten metal from the lower part of the molten metal tank so that the molten metal overflows from a part of the bath so that the slag generated on the bath surface always flows out of the bath. The molten metal always overflows from the upper part of the bath, and the wood can be slid and carbonized while the wood is in contact with the liquid surface.

  In order to prevent generation of metal oxides on the molten metal bath surface, the molten metal bath surface may be covered with an inert gas. For example, a molten metal bathtub can be placed in a sealed chamber and a nitrogen gas atmosphere can be obtained by sending nitrogen gas into the chamber.

  Wood usually has a moisture content of 10% or more. When wood is immersed or brought into contact with a molten metal bath, moisture in the wood is heated and volatilizes from the wood as water vapor gas, and rises in the metal bath. Blow out from the bath. At this time, a phenomenon may occur in which the molten metal is pushed up by the gas to be ejected and scattered as fine metal droplets. In particular, when the road pipe or the temporary road pipe is exposed, gas ejection from the road pipe or the temporary road pipe is vigorous. Therefore, if the exposed portion of the road pipe or the temporary road pipe is in the deep portion of the molten metal layer, the molten metal scatters intensely. In order to reduce or prevent this phenomenon, it is effective to dehydrate the wood in advance.

  Even if the moisture in the wood is completely removed, microfibrils and lignin in the wood heated by the high-temperature bath are thermally decomposed, and some of the decomposed components are volatilized as gas from the wood, just like water vapor gas The metal is spattered from the hot bath surface. If the hot tub is sufficiently larger than the wood size, there is no risk of jumping out of the tub even if the molten metal scatters. However, when the molten metal is scattered, the contact area with the air increases, so that a large amount of metal oxide may be generated. As a simple method for solving these two problems, as a molten metal scattering prevention material on the surface of the molten metal, a specific material having a specific gravity smaller than that of the molten metal, not dissolved in the molten metal, and not reacting with the molten metal, for example, minute glass It is effective to provide a layer of beads. The gas generated from the wood tries to scatter metal when it is ejected from the bath surface. However, if there is a glass bead layer on the upper surface of the bath surface, metal scatter is prevented. The gas exits into the air through the gap between the glass beads.

  The presence of the anti-scattering material also has the effect of reducing the surface oxidation of the molten metal. The size of the glass beads is suitably about 1 mm to about 5 mm. If it is too small, it tends to adhere to the carbonized wood surface when the wood is pulled up from the bath. If the size is too large, the metal may be scattered from the gap, and the antioxidant effect of the metal is reduced. The size of the beads need not be uniform and may have a distribution. An appropriate thickness of the bead layer is about 5 mm to 20 mm. When the thickness of the bead layer is small, the effects of preventing metal scattering and oxidation are reduced. Too thick is useless. As beads, glass beads, silica beads, alumina beads and the like can be used. Even if it is not a sphere like a bead, it can be used if it is granular, rod-like, or flat and is made of a material that is stable at high temperatures. The size of these may be about the same as the above beads.

  When the wood immersed in the molten metal bath is covered with aluminum foil and then immersed, the proportion of volatile components generated from the wood in contact with the molten metal is greatly reduced, and the generation of slag can be significantly reduced. Even if the volatile components leak from the joint portion of the aluminum foil in the molten metal bath, the generation of slag is much less than when the wood is directly immersed in the molten metal bath.

  In general, the length direction of the wood coincides with the direction of the road pipe or the temporary road pipe, and both end faces (cuts) of the wood are perpendicular to the direction of the road pipe or the temporary road pipe. The gas generated by pyrolysis when the wood is heated to a high temperature is likely to flow in the direction of the road pipe or the temporary road pipe, and hardly flows in the direction perpendicular thereto. Accordingly, when wood is immersed in a molten metal bath, gas is emitted violently from the end face (cut) of the wood, but there is little generation from other surfaces of the wood. As a result, the end face of the wood may be difficult to be carbonized. If the surface other than the end face of the wood is sufficiently carbonized, but the end face is insufficiently carbonized, it is desirable to additionally carbonize only the end face. If additional carbonization is required, the hot air or infrared system of the present invention is suitable.

  In the hot plate method, which is one of the methods A for preventing volatilization of the pyrolysis component, a heating device known as a metal plate, for example, a so-called hot plate is generally used as the hot plate, but a similar device can also be used. Since a hot plate is used in place of the metal that is hot-melted, the temperature conditions are almost the same as in the case of the hot-melt metal. Depending on the shape of the wood to be carbonized, it is possible to use a hot plate having a flat plate shape, rail shape, angle shape, curved surface shape, or the like. For example, in the case of heating a columnar wood such as a pile, a cylindrical heating furnace is suitable. In this case, it is desirable to make the gap between the furnace wall and the wood as small as possible. The cylindrical heating furnace may be divided into two parallel to the length direction so that the wood can be easily inserted, and after the insertion, they may be combined into a cylindrical shape. It is convenient to connect the two-part heating furnace with a butterfly plate. The heat plate may be a metal plate whose surface is covered with a heat-resistant protective film. It is desirable that the hot plate has a sufficient heat capacity or is always supplied with energy to maintain the surface temperature. For example, a hot plate apparatus incorporating an energization heating element such as a nichrome wire and a temperature control mechanism can be used. Moreover, it is desirable that the heat plate has a large thermal conductivity. Thin metal foil such as aluminum foil and copper foil can be used in the same manner as the metal plate. For example, the surface of wood can be covered with aluminum foil, and the temperature of the aluminum foil can be kept high while blowing hot air from above. When a metal plate, metal foil or the like is heated with infrared rays to form a heat plate, it is desirable that at least the surface is treated with a color that absorbs infrared rays so that the infrared rays are not reflected.

  In addition to the above method, the energy supply method to the hot plate can use the heat of combustion of wood or oil. For example, waste wood, thinned wood branches or the like are burned in a combustion chamber, the upper wall of the combustion chamber is made a flat iron plate, and this iron plate can be used as a hot plate. In this way, not only is it possible to effectively use waste wood and thinned wood, but it is also beneficial to the environment.

  As a method for supplying energy to the hot plate, a molten metal in a hot melt state can be used. For example, a metal plate can be mounted on a hot-melt metal bath, and this metal plate can be used as a hot plate. It is possible to heat similarly by floating an aluminum foil instead of a metal plate and placing wood on it. FIG. 5 is an immediate cross-sectional view of a state in which an aluminum foil is floated on a molten metal bath, a timber is placed on the aluminum foil, and a force is applied to the timber to slightly sink the timber. In FIG. 5, 1 is wood, 2 is aluminum foil, 4 is a molten metal bath, and 5 is a metal bath container. When a force 6 is applied on the wood 1, the wood 1 deforms the aluminum foil 2 and sinks a little in the bath. In other words, an aluminum foil boat with wood on a metal bath is floating. If the weight of the timber is large, the timber will sink slightly without applying force from above. The aluminum foil in the bath bends upward at the peripheral end of the lower part of the wood in the bath due to the buoyancy of the metal bath, and is in close contact with the peripheral end of the lower part of the wood, so that volatilization of the thermal decomposition component is suppressed. This suppresses the occurrence of cracks at the carbonized portion at the end. The use of aluminum foil is extremely simple and effective. Although the aluminum foil at the corner of the wood may be wrinkled, the aluminum foil in contact with the lower and side surfaces of the wood is completely flat and has no effect on carbonization.

  In the hot plate method, the hot plate and the wood are brought into contact with each other. However, since the surface of the wood is generally rough, an air layer exists between the hot plate and the wood. In the molten metal method, since the molten metal can be freely deformed, there is no air layer between the wood and the molten metal even if the surface of the wood is rough. Therefore, in the case of the hot plate method, it was speculated that the method of carbonizing the surface layer of wood would be considerably different from the case of using molten metal. However, it was surprisingly almost the same carbonized. Since the wood and the hot plate are in contact, it is assumed that the volatile components generated from the wood by heating are prevented from freely escaping from the surface of the wood and are confined inside the wood.

  In the hot plate method, since the hot plate is usually flat, only one surface of the wood can be heated. When the heating of one surface is completed, the next surface is heated. In order to simultaneously heat a plurality of surfaces, it is necessary to prepare a hot plate having a shape suitable for the surface. For example, in order to heat two adjacent surfaces simultaneously, an angle-shaped hot plate is required. When heated with an angle-shaped hot plate, the problem of preferential carbonization of the corners occurs. However, this problem can be solved by providing slit-like gaps at the corners of the angle. When carbonizing a square-like wood surface layer, two surfaces can be carbonized simultaneously by heating in a state sandwiched between two hot plates. When one surface of wood is heated with a flat hot plate, almost the same effect and result are obtained as when the wood is floated on the bath surface and heated by the molten metal method.

  The wood to be carbonized and the heat plate may be held in contact and may be stationary, but may be moved so as to slide relative to each other while the wood and the heat plate are in contact with each other. For example, wood may be placed on a hot plate, the hot plate may be fixed, and the wood may be moved to slide on the hot plate while being in contact for a set time. A plurality of hot plates having different temperatures or the same temperature may be arranged side by side, and the wood may be moved while sequentially sliding on them.

  Prior to heating and carbonization of the wood surface with a hot plate or molten metal, the wood surface can be pre-carbonized by irradiating the wood surface with infrared rays or heating by blowing hot air. In this case, it is necessary to heat in the pre-carbonization stage under the condition that no cracks are generated on the wood surface.

  Next, Method B for preventing volatilization of the pyrolysis component will be described. The gas impermeable member used in the method is a member that is transparent to infrared rays and does not transmit gas, such as a glass plate, a quartz plate, and a ceramic plate. Infrared rays include far infrared rays, part of near infrared rays, and part of visible rays, but mainly infrared rays including near infrared rays and / or far infrared rays. A specific example of a far infrared light source suitable for the present invention is a quartz glass tube heater. It is widely used for home and industrial use and is available at a relatively low cost. Hereinafter, this method B is also referred to as an infrared system. When infrared rays are irradiated on the wood surface, the temperature of the wood surface will increase as much as possible. This point is greatly different from the heating method using the molten metal, hot plate and hot air. In the case of heating with molten metal, hot plate, hot air, the temperature of the wood surface does not rise above the temperature of these heat sources, but in the case of infrared light, energy is accumulated on the wood surface at an accelerated rate and the temperature rises. . Therefore, it is necessary to control infrared radiation energy or irradiation time so that the temperature of the wood surface does not exceed 450 ° C.

  Although it is clear from Non-Patent Document 3 that wood is burnt when irradiated with infrared rays, Non-Patent Document 3 has no description of cracks. By appropriately selecting the energy intensity of the infrared source (heater, lamp, etc.), the distance from the source to the wood, the irradiation time, etc., cracks will not occur if heated while keeping the temperature of the wood surface below 450 ° C. I found In addition, a gas-impermeable transparent member such as a quartz plate or glass plate is closely attached to the surface of the wood and irradiated through it, so that molten metal method or hot plate method is applied from the surface to the inside without generating cracks. Can be carbonized to the same extent.

  The wood to be carbonized and the transparent member (glass plate, quartz plate, etc.) may be moved relatively. For example, an infrared lamp may be fixedly disposed, and the wood placed on the transport device may be slid while contacting the lower surface of the transparent member disposed below the infrared lamp. In this case, it is desirable that the transparent member be movable up and down in order to cope with roughness and unevenness of the wood surface. The wood and the transparent member may be moved together in a state where the transparent member is placed on the wood. It is also possible to place a transparent member on wood, place an infrared lamp above it, and move the infrared lamp.

  The wood and the infrared lamp may have an upside down relationship with the above. In this case, it arrange | positions so that a transparent member may contact the carbonized surface of wood. A plurality of infrared lamps may be arranged. As will be apparent from Example 4 described later, when the transparent member is arranged, the carbonization rate is reduced as compared with the case where there is no transparent member. Therefore, as long as cracks do not occur, the transparent member may be carbonized without the transparent member disposed (similar to the preliminary carbonization described in the paragraph 0060), and the transparent member may be disposed after passing through that portion. For example, a plurality of infrared lamps are arranged in parallel, the first one to a plurality are irradiated with the carbonized surface of the wood without a transparent member, and the next one to a plurality are carbonized to the wood. You may arrange | position so that the to-be-carbonized surface of wood may be irradiated in the state which made the transparent member contact the surface. By arranging in this way, it is possible to increase the efficiency of carbonization. Instead of pre-carbonization by irradiating wood with infrared rays, pre-carbonization may be performed by blowing hot air.

  As mentioned above, it can be said in common when the wood and the transparent member or the hot plate are relatively slid, but when the tip of the wood reaches the end of the hot plate or the transparent member, The tip may collide with the end of the hot plate or the transparent member and the movement may be hindered. In order to avoid this, it is desirable that the end of the hot plate or transparent member that meets the tip of the wood be processed into a taper shape.

Next, method C for preventing volatilization of the pyrolysis component will be described. The method is based on the use of wood in which a surface layer is impregnated with water glass. When using, for example, No. 1 sodium silicate solution (for example, No. 1 water glass) as the water glass used in the present invention, it is diluted with water as a stock solution (very viscous fluid), It is preferably used as an aqueous solution having a weight of about 20-60%. If it is 20% or less, the effect of water glass is small, and if it is 60% or more, a water glass film is likely to be formed on the wood surface. Preferably in the range of to the ^15g / ^{m 2 ~80g} / m 2 expressed by impregnation amount per unit area. As a method of supplying water glass to wood, a suitable method such as a known coating method, a method of lifting wood after dipping it in a water glass aqueous solution and drying it can be used. The use of water glass can also be applied in the methods A and B for solving the problems of the present invention.

  In the present invention, it is desirable that the amount of water glass impregnated in the wood is such that a water glass film is not formed on the wood surface after the water glass aqueous solution is supplied to the wood by an appropriate method and dried. Specifically, when the proportion of water glass in the water glass aqueous solution is large, a water glass film is formed on the wood surface. Even if the ratio of water glass is small, a water glass film is formed on the surface of the wood by multiple application. When the water glass film is clearly formed, when heated by the method of the present invention, the water glass film on the surface of the wood foams to form a white foam film. This phenomenon is particularly remarkable when the heating temperature is high. Even if such a foaming phenomenon occurs, if the heating is continued, the wood covered with the foamed film is carbonized, so that it does not interfere with the carbonization. As the carbonization of wood progresses, the foam film that was initially white gradually becomes black and can be easily removed by simply rubbing with a sponge or brush after cooling. Accordingly, the carbonized layer to be formed does not have an adverse effect, but it is desirable to prevent such a phenomenon from occurring because the handling surface is inclined.

  A second method for solving the problem of the present invention is to blow hot air at a temperature of 280 ° C. to 480 ° C. on the surface of the carbonized region of the wood or woody material, so that the region is directed from the surface toward the inside. Carbonization to the required depth, ie the desired depth. This second method is hereinafter referred to as a hot air method. The present inventor speculates that a carbonized layer without cracks having the same thickness as that of a high-temperature molten metal can be obtained by blowing hot air having a temperature similar to that of the high-temperature molten metal on the surface of the wood. In practice, it was found that a thickened carbonized layer was not obtained as in the case of molten metal, but a much thicker carbonized layer was obtained than in the case of a gas burner flame. The temperature of the flame is about 1000 ° C., and cracks occur during a short time of processing. In a short time treatment that does not cause cracks, the thickness of the carbonized layer is extremely small, and only the layer close to the surface is carbonized. However, if the hot air is 480 ° C. or less, it can be carbonized to a thickness of about 3 mm without generating cracks by controlling the temperature of the hot air and the blowing time. Compared with the molten metal method or hot plate method, the thickness of the carbonized layer obtained in a range where cracks do not occur is small, but this is sufficient depending on the application.

  Even in the case of carbonization with hot air, if the temperature of the hot air is high and the blowing time becomes long, cracks similar to those in the case of the gas burner are generated. FIG. 6 is a photograph of a sample obtained by heating and carbonizing Ezo pine (thickness 14 mm, width 45 mm, length 58 mm) with a heat gun (hot air temperature 480 ° C.) for 2 minutes. A photograph (a) is a photograph of the surface where many cracks are generated, and a photograph (b) is a cross-sectional micrograph of the vicinity of one crack. As described above, even when hot air is used or when the temperature is high, cracks are generated as in the case of carbonization by the gas burner even when sprayed for a short time. However, it can be seen that the shape of the cross section differs greatly between hot air carbonization and gas burner carbonization. Although the crack cross-section periphery of FIG. 2 is depressed, the crack cross-section periphery of FIG. 6 swells conversely. The reason why such a difference occurs is presumed to be that combustion occurs in the gas burner method, but combustion does not occur in the hot air method.

  Since flame treatment with gas burners and treatment with hot air blowing are performed in the air, it was thought that the volatile components in the pyrolyzed wood may be oxidized (burned) and cracks are likely to occur. When treated with hot air of carbon dioxide gas, it was confirmed that there was almost no difference from the hot air treatment of air. FIG. 7 is a photograph comparing the carbonization results of Ezo pine (thickness 14 mm, width 45 mm, length 57 mm) with hot air of carbon and hot air of carbon dioxide gas. Photo (a) is a sample carbonized with hot air and photo (b) is a photo of a sample carbonized with carbon dioxide hot air. Both hot air temperatures (480 ° C.) and spraying time (60 seconds) are exactly the same. As can be seen from FIG. 7, it was confirmed that there was almost no difference in the carbonization state between air and carbon dioxide gas. Therefore, it is understood that prevention of volatilization of pyrolyzed components is an important condition for carbonization treatment with molten metal or a hot plate. Also in the hot air method, for example, when a metal plate or a metal stay was placed on the surface and hot air was blown from above, the metal plate or the metal foil became high temperature, and it was confirmed that it could be carbonized as in the hot plate method. A method of covering wood with a metal foil or a thin metal plate and blowing hot air over the metal foil is practical and very effective. The method of covering wood with metal foil and blowing hot air over it is particularly convenient for work in the field.

  If the above assumption that the molten metal or hot plate covering the surface of the wood prevents volatilization of the volatile components of the pyrolyzed wood is correct, the surface of the wood will also contain a resin (including paint, adhesive, etc.) ) Or an inorganic substance (water glass, polysiloxane, etc.), and then it is presumed that it is advantageous to perform carbonization treatment by blowing hot air. If it is a resin-based thin film, the thin film itself is also carbonized by hot air, but if the thin carbonized film can prevent the transmission of volatile components, the guess is correct. Water glass and polysiloxane are not carbonized, but are expected to be impregnated into the surface layer of wood to prevent the transmission of volatile components.

  Therefore, as a specific example, a commercially available coating material (clear lacquer whose solid main component is an acrylic resin) and a commercially available water-soluble adhesive (main component is polyvinyl alcohol) are cedar (thickness) so that the dry thickness is 20 to 30 μm. 5 mm, width 14 mm), and after drying, hot air was blown to confirm the occurrence of cracks. In any case, it was confirmed that cracks were less likely to occur when the coating film was present. However, the effect was slight, and what was cracked by heating for 2 minutes without a coating film was an improvement to the extent that cracks were generated in 2 minutes and 30 seconds by providing the coating film. It is thought that the volatile component passed because the coating film was thin. Subsequently, when the surface layer was impregnated with a commercially available water glass aqueous solution, it was confirmed that cracks hardly occur and the carbonization depth could be increased. It is considered that the water glass component prevented the volatilization of the volatile component (see Example 7). Further, it was also confirmed that when the carbonized surface was rubbed with a finger, black powder hardly adhered to the finger. These facts are one feature of the present invention. In addition to water glass, it was found that a similar effect was obtained when a surface layer of wood was impregnated with a commercially available polysiloxane, but it was confirmed that the effect of water glass was much greater. Furthermore, water glass is overwhelmingly advantageous in terms of cost. The effect of water glass was discovered as described above.

  Since molten metal or hot plate and hot air have different heat capacity, heat conduction, etc., molten metal or hot plate has a larger carbonization capacity. In carbonization with molten metal or hot plate, heating for several minutes to several tens of minutes can achieve a sufficient degree of carbonization (degree of blackening) and carbonization depth even in the temperature range of 240 to 280 ° C. In the heating, in this temperature range, the color is hardly colored by the heating in the above time range or is lightly colored. It was confirmed that the degree of carbonization increased as the speed of blowing hot air was increased, but it was found that carbonization could not be sufficiently performed at a practical blowing speed (wind speed) in this temperature range. The temperature range of the hot air is preferably 280 to 480 ° C. More desirably, it is in the range of 300 to 400 ° C. Hot air at a temperature of 280 ° C. or lower is unrealistic because it takes a very long time to carbonize the surface layer. At 480 ° C. or higher, cracks occur in about 10 seconds, and the carbonization depth is small, which is not practical.

  Conventionally, wood has been heat-treated in an electric furnace, a heating furnace or the like, but the air in the furnace is still or is stirred or circulated. The carbonization by the hot air system of the present invention is characterized by spraying in a higher temperature range than before. In the conventional heat treatment of wood, the purpose is to treat the inside of the wood, and the entire surface of the wood is simultaneously heated over a long time. On the other hand, the present invention is characterized in that hot air having a temperature higher than that of the prior art is blown onto a part (one surface) of wood. Therefore, it is extremely important to blow hot air at high speed. In a static or circulating atmosphere, if the surface layer is sufficiently carbonized, it is weakly carbonized deep inside, resulting in a decrease in the mechanical strength of the wood. By spraying at a wind speed of a certain level or more, the surface layer can be sufficiently carbonized without being carbonized deep inside. By referring to Comparative Example 2 and Comparative Example 3, this difference can be easily understood.

  As described above, the wind speed of hot air is extremely important in the hot air system of the present invention. A desirable wind speed range is 4 m / sec or more, and more desirably 6 m / sec or more. The upper limit is limited by the hot air device or the surrounding environment. Actually, the upper limit is a wind speed of 15 to 20 m per second. The direction in which the hot air is blown onto the wood is desirably in a range of approximately 30 to 30 degrees with respect to the surface of the wood. The greater this angle is beyond this range, the less efficient the wood is heated.

  A commercially available so-called heat gun can be used as the hot air generator. Commercially available heat guns are easily available and easy to use, but the temperature and volume of hot air may not always be sufficient. It is sufficient to carbonize a small area of wood or a cut surface of a plate or a pillar, but lacks the ability to carbonize a large area. In such a case, the heat exchanger can be heated using a large-capacity heat source, and hot air that has passed through the heated heat exchanger can be used. As a large-capacity heat source, there are an electric heater, a gas burner, an oil burner and the like having a large calorific value. The heat exchanger is heated with this large-capacity heat source, and hot air that has passed through the heated heat exchanger is blown. If it is a gas burner, a compact and large-capacity carbonization apparatus is possible. In order to save energy, the hot air used for spraying can be recovered and passed again through the heat exchanger.

  The various systems of the present invention have been described above. Table 1 summarizes these systems and the features of the conventional system. Table 1 does not include the effect of water glass. As is clear from Table 1, molten metal method, hot plate method, infrared method (in the case of infrared transmissive and gas impermeable member) and gas burner (a metal plate is placed on wood and a gas burner is mounted on the metal plate) The results from (flame radiation) are very similar. On the other hand, wood exposed to the atmosphere has completely different characteristics when carbonized by the hot air method and infrared method. In the method in which the gas impermeable member is in contact, it is possible to obtain a carbonized layer (carbonization depth) with a large thickness without occurrence of cracks, but in the method in which the gas impermeable member is not in contact, Only a small thickness of the carbonized layer can be obtained under conditions where no cracks are generated.

  In each of the methods of the present invention described above, the ends (including corners, edges, edges, and ridges) of the wood are preferentially carbonized, and as a result, cracks tend to occur before in-plane. In order to prevent this, it is effective to cover the end with a thin metal plate, a metal foil or the like. For example, as a specific example of the hot plate method, when a wood timber is placed on the hot plate and heated, the volatile component rises as smoke from the four sides (entire circumference) of the square at the contact portion between the square and the hot plate. To do. Since the volatile component escapes quickly and continuously into the space, the occurrence of cracks is promoted. Therefore, the entire square is covered with a metal foil such as an aluminum foil, or at least the end of the wood and a hot plate in the vicinity thereof. It is good to coat | cover the surface and side surface which contact with.

  FIG. 8 is a side sectional view showing a specific example in which four sides (corner portions) of the end portion of the surface facing the hot plate of the square member are covered with aluminum foil. In FIG. 8, 1 is a square bar, 2 is an aluminum foil, and 3 is a hot plate. In the drawing, the thickness of the aluminum foil is exaggerated, but the actual thickness is about 13 to 17 μm. Surprisingly, it was found that the wood 1 and the hot plate 3 are not in contact with each other, and there may be such a small gap. The reason is considered to be that the pyrolysis component is confined in the gap because the periphery of the square member 1 is covered with the aluminum foil 2. By covering the periphery of the square member facing the hot plate with aluminum foil as described above, it is possible to prevent the end of the square member from cracking before the in-plane. Although there is a minute gap between the square 1 and the hot plate 3, it was confirmed that there is no difference in the degree of carbonization from the portion where the aluminum foil is present. In order to confirm how much the gap becomes large, the experiment was repeated with a plurality of aluminum foils stacked, and it was confirmed that there was no effect up to about 0.3 mm. A metal plate of 0.3 mm or less may be used instead of the aluminum foil. Even if such a large gap exists, volatilization of the pyrolysis component can be prevented. It was recognized that when the gap between the square bar and the hot plate exceeds 0.3 mm, the degree of carbonization in the portion not covered with the aluminum foil is lowered. Actually, there is a minute gap between the aluminum foil 2 and the square 1 and a part of the pyrolysis component volatilizes through this gap, but there is an effect of preventing volatilization.

  When actually carrying out carbonization of the surface layer of wood, in particular, a plate, attention must be paid to the size of the wood. When the short side of the plate is about 10 cm or more, the carbonized portion is thermally contracted if only one surface is strongly carbonized, so that the carbonized surface may be curled so as to be concave. Therefore, it is desirable to alternately carbonize both sides. Further, curling can be prevented by repeating a method of heating both surfaces simultaneously for a short time, then allowing to cool for a while and then heating again from both sides. Special care must be taken when the thickness of the plate is small. Such care is not necessary when the plate is very thick or thick square.

  According to the method of the present invention, a wood having a carbonized layer far superior to the conventional method as described above can be obtained. However, since the carbonized surface layer has many small holes derived from road pipes, temporary pipes, wall holes, and other wood, it is difficult to completely block wind and rain for many years. . Therefore, it is also effective to apply or impregnate an appropriate material to the carbonized layer obtained by the method of the present invention so that various characteristics can be maintained for a longer period of time. Various known techniques can be used for this purpose. For example, a method of impregnating water glass, a method of applying or impregnating a resin described in Patent Document 2, and the like can be used. Moreover, the surface layer carbonized wood obtained by the method of the present invention has a brown to black hue, but if an appearance other than these colors is desired, it may be painted to the desired color. When it is desired to increase the mechanical strength of the carbonized layer (for example, when it is desired to prevent black powder from being taken off by a finger when rubbed strongly with a finger), the drawback can be solved by painting the surface.

  The present invention is not limited to wood, but can also be applied to what is generally called woody material. Examples of the wood material include plywood, laminated wood, OSB, particle board (particularly MDF is preferable), LVL, CLT, and compressed wood. It is known that wood compressed with high-temperature and high-pressure steam is compressed to 1/2 to 1/3 of the original wood, its appearance changes to a high-grade brown color, and durability, antiseptic properties, etc. are improved. ing. When the method of the present invention is applied to this compressed wood, the antiseptic property, the ant-proof property and the like can be further enhanced.

  One application of the molten metal system of the present invention is to produce charcoal in a very short time. As a specific example, when a rod of 20 mm in diameter was immersed in a 400 ° C. molten tin bath for 5 minutes, it was almost carbonized to the center of the rod. Although cracks are generated on the surface, there is no problem as charcoal. In the conventional charcoal production method, according to the forestry test site “Wood Industry Handbook”, the charcoal yield at 400 ° C. is 30%. On the other hand, in this specific example (5 minutes immersion), it was 55.9%. When the rod was immersed in molten tin at 400 ° C. for 12 minutes and no vaporized gas was completely generated, the color of the rod was true black and the yield was 33%, which was almost the same as the value in the handbook. There is an advantage that charcoal is completed in just 12 minutes.

  Examples of the present invention will be described below. In the following examples, there is described a state in which there is no relative motion between the wood and the hot plate, between the wood and hot air, and between the wood and infrared rays, but there is relative motion between them. May be. For example, a system in which wood moves on a rotating heat roll may be used. Moreover, you may move, rotating a hot roll on wood. At this time, a plurality of heat rolls may be provided. It is also possible to heat the rolled wood while rolling it on a flat hot plate. In these cases, the width of the contact portion between the wood and the heating member is small, and the pyrolysis volatile component easily volatilizes, so that the heated surface of the wood is covered with a gas-impermeable member, for example, aluminum foil Is desirable. In addition to the roller moving while rotating, the pyrolysis component volatilization preventing member and the wood may slide relative to each other. Moreover, you may make it move relatively, spraying hot air on the moving wood, or irradiating infrared rays.

  FIG. 9 is a surface photograph of the carbonized side of a sample prepared by changing the melting temperature and the heating time when tin is used as the molten metal in the molten metal method. As the wood, cedar wood having a length of 20 mm, a width (direction of the temporary road pipe) of 30 mm, and a height of 16 mm was used. The tin was placed in a stainless steel bat, and the temperature of the molten tin was adjusted by adjusting the heating power of the stove by placing the bat on the gas stove. Tin was melted so that the melted tin had a depth of about 50 mm. The square was held with stainless steel tongs and held so that the square was immersed in the molten tin from the surface by about 10 mm in the height direction. Since slag is generated on the surface of the square material that is immersed in the molten tin, the location can be changed while being immersed once every 15 seconds, or the square material can be lifted and immersed in a place without slag. did. When the whole immersion time was as short as 30 seconds or less, the above place change was performed at a frequency of about once every 5 seconds. FIG. 9 also shows a photograph of a sample prepared at a temperature outside the scope of the present invention. When heat treatment exceeds 450 ° C, significant cracks occurred in 1 minute, and black powder adhered by lightly rubbing the surface with fingers, and the thickness of the carbonized layer was found to be as small as 2 mm or less. The heating temperature range of the present invention was set to 450 ° C. or lower.

  Table 2 shows the results of measuring how the depth of carbonization changes when the immersion time in molten tin is further increased in the same manner as the sample preparation in FIG. Since each sample is a natural product and varies, three samples corresponding to each temperature and time were prepared and three carbonization depths were entered. Samples were prepared at a molten metal temperature in the range of 240 ° C. to 420 ° C. and an immersion time of up to 40 minutes. The center of each sample after carbonization, which is 20 mm long, is divided vertically with a sharp knife (cutter knife) in a direction parallel to the tracheid tube, and the depth of the carbonized layer is observed while observing the cross section with a microscope. Was measured. When the surface divided vertically by the cutter knife was rough, the surface was observed after making it smooth and easy to see. In Table 2, an x mark indicates that a crack occurred at that temperature and time.

  FIG. 10 is a graph in which the average value of the carbonization depth of three samples at each temperature and immersion time in Table 2 is plotted. The melting temperature lower than 340 ° C. measured only up to 40 minutes, but it is clear from the result of the hot plate method of Example 2 that the carbonization depth is increased to about 15 mm by further increasing the immersion time. It is. At 340 ° C., cracks do not occur after immersion for 20 minutes, but cracks occurred at immersion times of 25 minutes, so the graph stops at 340 ° C. for 20 minutes. In FIG. 10, the portion indicated by the dotted line in the graph is data heated at 360 ° C. when the glass surface layer is impregnated with water glass. This is described in detail in Example 7.

  Table 3 shows how cedar wood with a height of 20 mm, a width of 30 mm (in the direction of the temporary road pipe), and a height of 16 mm is used as wood, and how the depth of carbonization changes depending on the temperature and heating time of the hot plate The result of having measured is shown. A hot plate (As One Co., Ltd. ND-1) was used as a hot plate apparatus. Similarly to Example 1, three samples corresponding to each temperature and time were prepared, and the carbonization depth of the three samples was entered. Samples were prepared with the temperature of the hot plate in the range of 240 ° C. to 340 ° C. and the heating time in the range of 15 seconds to 120 minutes. Since the maximum temperature of the hot plate was 350 ° C., an aluminum plate having a thickness of 10 mm and a size of 100 × 100 mm was placed on the molten tin of Example 1 at a temperature higher than that, and a square was placed thereon and carbonized. In Table 3, it is described as a hot plate including this case. The center of each sample after carbonization was divided vertically with a cutter knife in the direction of the temporary canal, and the depth of the carbonized layer was measured while observing the cross section with a microscope. When the surface divided by the cutter knife was rough, it was observed after making it easy to see. In Table 3, x indicates that cracks occurred at that temperature and time.

  Instead of floating the aluminum plate on the molten tin as described above, it was possible to heat similarly by floating an aluminum foil and placing wood on it. Even when an aluminum foil having a thickness of 13 μm and a size of 90 × 60 mm was floated on the molten tin bath, and the same size of wood was placed in the center of the aluminum foil, the aluminum foil hardly sunk due to the gravity of the wood. Therefore, when the wood was pushed down with a tongue and pushed down about 8 mm, the aluminum foil in the bath was bent upward at the lower peripheral end of the wood as shown in FIG. In this way, volatilization of the pyrolysis component was prevented. As a result, in the case of an aluminum plate, the generation of cracks was prevented even at a temperature and time at which cracks occurred at the carbonized portion at the end.

  FIG. 11 is a graph in which the average value of the carbonization depth of three samples at each temperature and heating time in Table 3 is plotted. At a hot plate temperature of 280 ° C. or lower, the heating time can be further extended. The carbonization depth could reach up to about 15 mm without cracks. From FIG. 10 and FIG. 11, it was found that almost the same results were obtained with the molten metal method and the hot plate method. In FIG. 11, the portion indicated by the dotted line in the graph is data when the wood surface layer is impregnated with water glass and heated at 340 ° C. This will be described in detail in Example 7, but it is shown that by impregnating with water glass, cracking does not occur even when heated for a longer time or at a higher temperature than when not impregnated, and the carbonization depth increases. .

  Table 4 shows 20 mm × 30 mm using a commercially available heat gun (Evolution Power Tool Co., Ltd. Heat Gun Hot Air Machine HDG200JP) as a hot air generating device on a cedar wood having a length of 20 mm, a width (direction of the temporary road pipe) of 30 mm, and a height of 16 mm. The result of measuring how the depth of carbonization changes with the temperature of hot air and the time of hot air blowing is shown. Since each sample is a natural product and varies, three samples corresponding to each temperature and time were prepared and the carbonization depth of the three samples was entered. Samples were prepared with the hot air temperature in the range of 280 ° C. to 480 ° C. and the spraying time in the range of up to 20 minutes. Below 280 ° C., carbonization was insufficient even after prolonged heating. The center of the vertical length of each sample after carbonization was divided vertically with a cutter knife in the direction of the temporary canal, and the depth of the carbonized layer was measured while observing the cross section with a microscope. When the surface divided by the cutter knife was rough, it was observed after making it easy to see. In Table 4, x indicates that cracking occurred at that temperature and time.

  FIG. 12 is a graph in which the average values of the carbonization depths of the three samples at each temperature and hot air blowing time in Table 4 are plotted. It was found that the carbonization depth can be reached only up to around 3 mm. However, this level of carbonization is sufficient for some applications. The biggest attraction of the hot air method is that it can be carbonized easily on site. For example, it can be easily carbonized by blowing hot air onto a cut surface of wood cut on site.

The data in Table 4 is for the case where the surface layer of wood is not impregnated with water glass, but the A square material of Example 7 (water glass impregnation amount is 29.0 g / m ² ) is heated by a hot air method, The occurrence of cracks was observed and the carbonization depth was measured. Hot air of 360 ° C. was blown on the square glass impregnated surface with time as a parameter. In the square member not impregnated with water glass, the heating time in which cracks did not occur was up to 4 minutes, but the heating time in which cracks in the A square member did not occur extended to 15 minutes. It really stretched more than three times. Moreover, the carbonization depth also increased by a factor of 2 from 2.31 mm to 4.78 mm. These results are shown by the dotted line graph in FIG. Further, even when the carbonized surface was rubbed with a finger, black powder hardly adhered.

  In the hot air method, since the wood surface is not covered with the gas-impermeable member during heating, the pyrolytic vapor components generated by the heating freely diverge from the wood surface. Therefore, it is considered that cracks occur despite the small carbonization depth. For example, when hot air at 360 ° C. is used, cracks occur in 5 minutes, but when a hot plate at the same temperature is used, cracks occur in 10 minutes. At 380 ° C., cracking is prevented when the heated wood surface is covered with a gas-impermeable member so that cracking occurs in 3 minutes with hot air and 5 minutes with a hot plate. I understand that.

  A quartz glass tube heater (outer diameter 12 mm, effective light emission length of about 200 mm, output 560 W) was used as the infrared lamp, and an AC voltage of 100 V was applied to both ends of the heater so that it could be turned on and off with a switch. Sugibe wood having a length of 20 mm, a width (direction of the temporary road pipe) of 30 mm, and a height of 16 mm was used as wood, and the distance from the surface of the infrared lamp to the sample surface was set to 10 mm or 20 mm. Three samples were prepared for the same heating time. When the irradiation time became longer or when the distance between the lamp (consent with the heater) and the sample was small, the temperature of the wood surface increased rapidly and smoke was generated. The measurement was conducted paying attention to the conditions under which cracks do not occur. At a distance of less than 10 mm, smoke was intensely generated by irradiation for 1 to 2 minutes, and ignition was sometimes caused by irradiation for 3 to 5 minutes. When the surface to be carbonized is open, it cannot be deeply carbonized without cracking. However, it was confirmed that cracks are unlikely to occur when a quartz plate is placed on a square and irradiated with infrared rays from above.

  Table 5 shows the measurement results. Q in the distance between the lamp and the wood in Table 5 indicates a case where a quartz plate having a thickness of 2.4 mm is placed on the surface of the wood. As can be seen from Table 5, when there was no quartz plate, cracks occurred in the wood after 3 minutes of irradiation, but when there was a quartz plate, cracks occurred for the first time after 10 minutes of irradiation. Moreover, it has been confirmed that the carbonization depth increases to about twice that when there is no quartz plate. Also from this example, it was confirmed that when the wood surface was not covered with a gas-impermeable member during heating, the vaporized component generated by heating vaporizes from the wood surface, and thus cracks are likely to occur. In Table 5, x indicates that cracking occurred at that temperature and time.

  FIG. 13 is a graph in which the average values of the carbonization depths of the three samples at each measurement point in Table 5 are plotted. FIG. 13 clearly shows the effect of the quartz plate (gas impermeability, infrared transmissivity). 10, 11, and 12 have similar graph shapes, but it can be seen that the shape of the graph in FIG. 13 is completely different. That is, in FIG. 13, the carbonization depth increases rapidly with time. This difference is thought to be due to the fact that the temperature of the wood surface is constant in the former three, whereas the energy accumulated on the wood surface increases with time and the temperature of the wood surface increases with time in the latter. . As a condition for preventing cracks, it is important that the temperature of the wood surface does not exceed 450 ° C.

The A square timber in the examples below 7 (water glass impregnated amount 29.0 g / ^{m 2)} and B square bar (water glass impregnated amount 72.9 g / ^{m 2)} and samples, A as in the case not using the quartz plate Square and B squares were heated by an infrared method, the occurrence of cracks was observed, and the carbonization depth was measured. The surface of the square bar impregnated with water glass was made to face the heater. When the distance between the heater and the square bar surface was 10 mm, A square bar was used, and when the distance was 20 mm, B square bar was used. In FIG. 13, the graph displayed with a dotted line is data when the surface layer of wood is impregnated with water glass. The dotted line graph on the left is the case where the distance between the wood and the lamp is 10 mm, and the dotted line graph on the right is 20 mm. When the distance was 10 mm, the time during which cracks did not occur doubled, and the carbonization depth increased from 2.24 mm to 3.68 mm. Even when the distance was 20 mm, the time during which cracks did not occur doubled and the carbonization depth increased from 4.97 mm to 9.10 mm. Thus, by impregnating the surface layer with water glass, the irradiation time during which cracks do not occur is greatly extended, and the carbonization depth is also greatly increased. Further, even when the carbonized surface was rubbed with a finger, black powder hardly adhered.

  A portion from the tip of the pine cone having a cross section of 30 mm square to 50 mm was immersed in molten tin at 300 ° C. for 5 minutes and then pulled up. The carbonized surface was uniformly carbonized, almost black and free from cracks, and even when rubbed with a finger, black powder was hardly removed. FIG. 14A shows a photograph of the cut surface taken by cutting with a band saw at a position 15 mm from the tip at a right angle in the length direction. Next, two pine cones with a 45 mm square cross section were prepared, and the portion from the tip to 25 mm was dipped in molten tin at 300 ° C. for 4 minutes and the other was immersed for 10 minutes, then pulled up, and the tip of the carbonized part (B) and (c) in FIG. 14 are photographs obtained by cutting with a band saw perpendicularly to the length direction at a distance of 10 mm from the top and photographing the cut surface. 14A, 14B, and 14C, it can be seen that the smaller the thickness of the square, the closer the cross section of the carbonized layer is to a circle, and the longer the immersion time, the closer to the circle.

Next, 30 mm square and 45 mm square pine cones were cut to a length of 40 mm. These squares are floated on the surface of molten tin at 300 ° C. so that the length direction is horizontal, 30 mm squares every 5 minutes, and 45 mm squares every 10 minutes in all directions. Was rotated in contact with the molten tin bath. After the four surfaces in the length direction were carbonized in this manner, the steel was taken out of the tin bath and allowed to cool. 30 mm squares were floated in a tin bath for a total of 20 minutes, and 45 mm squares were floated for a total of 40 minutes. (D) and (e) of FIG. 14 are photographs in which the central part is cut with a band saw at right angles to the length direction after cooling and the respective cut surfaces are photographed. The innermost shape of the carbonized layer of any one is close to a square. As is apparent from FIG. 14, it is carbonized along the shape of the square material and the control of the thickness of the carbonized layer is ensured when dipping one surface at a time rather than dipping the four surfaces simultaneously in the molten metal bath. . Moreover, the square shape of the cross-section of the square bar is maintained as a perfect square. In contrast, when the entire square bar is immersed in a tin bath, the cross-sectional outer shape of the square bar is slightly distorted as can be seen from FIG.
(Comparative Example 1)

  In order to show the problems when carbonizing by heating in a normal electric furnace, the following tests were conducted. Place a Tokoname-yaki jar with an inner diameter of 230 mm and a height of 220 mm in an electric furnace (MODEL VIKING 66, manufactured by Paragon Industries, Inc., USA). Then, each was placed at the position of the apex of a regular triangle, and a stainless steel wire mesh (wire diameter: 0.45 mm, mesh opening: 2.09 mm, 10 mesh) was laid horizontally thereon, and the electric furnace was heated to 300 ° C. After 1 hour or more has passed since the set temperature in the furnace reached 300 ° C., so that the Tokoname jar and the wire mesh are completely at 300 ° C., a 30 mm square cross section of 50 mm long pine cones on the wire mesh The sample was placed vertically so that one of the cross-sections was down, heated at 300 ° C. for 5 minutes, then taken out of the electric furnace and allowed to cool. The double structure is used in order to prevent the sample from being irradiated with infrared rays from the heater in the electric furnace. Next, similarly, the pine cones having a cross section of 45 mm square and a length of 50 mm were heated at 300 ° C. for 5 minutes and then taken out from the electric furnace. Next, two kinds of pine cones were prepared in the same manner as described above, and samples each having a heating time of 10 minutes were prepared.

FIG. 15 is a photograph of the above sample, and FIGS. 15 (a) and 15 (b) are obtained by heating a pine pine having a cross section of 30 mm square and 45 mm square at 300 ° C. for 5 minutes, FIGS. 15 (c) and 15 (d). Is a pine pine having a cross section of 30 mm square and 45 mm square heated at 300 ° C. for 10 minutes. The top photo in FIG. 15 is the top surface of each sample (surface far from the wire mesh), the second photo is the side of each sample (the central horizontal straight line is the cut portion after carbonization), and the third photo Is the bottom of each sample, and the bottom photo is the cut surface of each sample. As is apparent from FIG. 15, in such heating by a normal electric furnace, the corner portion is preferentially carbonized, and the carbonization in the plane far from the corner proceeds only at a very low speed. The carbonization of the corner portion has progressed too much, and black powder can easily adhere to the finger when rubbed with the finger. When only one surface is heated by the molten metal method or hot plate method of the present invention, such a situation does not occur, and the heated surface is uniformly carbonized. Further, only the corner portion is not strongly carbonized. In the uppermost photograph in FIG. 15D, three cracks can be confirmed, and in the third photograph, six cracks can be confirmed. This is probably because the components thermally decomposed by heating can volatilize freely in the space and are generated when the square bar contracts. It can also be seen that the outer shape is slightly distorted from the square. The degree of heating was large as much as there was a wire mesh, and many cracks occurred as carbonization progressed. On the other hand, in the present invention, since the volatilization of the pyrolyzed component is prevented, thermal shrinkage hardly occurs, and therefore cracks hardly occur.
(Comparative Example 2)

In order to more clearly show the difference between the present invention and carbonization by heating in an electric furnace, the following test was conducted. An iron plate having a thickness of 10 mm and a size of 100 mm × 160 mm was used in place of the wire mesh of Comparative Example 1, and a pine cone having a cross section of 45 mm square and a length of 50 mm was heated for 10 minutes in the same manner as in Comparative Example 1. Immediately after heating, the sample was taken out of the electric furnace and allowed to cool. FIG. 16A is a photograph of the upper surface of the obtained sample, and it can be seen that it is carbonized in substantially the same shape as the upper surface of FIG. FIG. 16B is a side view of the sample (the horizontal line in the center is a cut portion), which is almost the same as the side view of FIG. FIG. 16C is a photograph of the bottom surface of the sample. Since the bottom surface was in contact with the metal plate, it was carbonized almost uniformly and deeply. FIG. 16D is a photograph of the cut surface of the sample. It can be seen that the corner is heavily carbonized, but the surface is not carbonized much. One crack (break) occurred on the upper surface (FIG. 16 (a)), but there was no crack at the bottom. In this way, it was confirmed that when the carbonized surface was covered with a gas-impermeable member, carbonization was performed uniformly and at the same time, cracking was difficult to occur. In the bottom surface (surface in contact with the wire mesh) in FIG. 15D, the progress of carbonization is slightly larger than the top surface, but as many as six cracks were generated. This is probably because the pyrolysis component volatilized from the gaps in the wire mesh. This effect also confirmed the effect of the gas-impermeable member of the present invention. FIG. 16 (e) is a photograph of the tip (bottom surface) of the sample of FIG. 14 (c) of Example 5 (45 mm square spruce pine immersed in molten tin for 10 minutes). As is apparent from FIG. 16 (c), the surface in contact with the iron plate is almost completely carbonized and uniform. When FIG. 16 (c) and FIG. 16 (e) are compared, FIG. 16 (c) has a lower concentration. This is because the iron plate of this comparative example is not a complete hot plate, but a sample is placed on it. This is because it took time to recover to 300 ° C.
(Comparative Example 3)

  Commercially available river sand (sand used for mixing cement with gravel) was placed in a Tokoname ware bottle (inner diameter 165 mm, height 175 mm) to a height of about 8 minutes. After putting this in the electric furnace of Comparative Example 1 and keeping it at 300 ° C. for 2 hours, an Ezo pine bar having a cross section of 30 mm square and a length of 200 mm is placed in this sand, and about 50 mm from the tip is in the sand. Was inserted diagonally at an inclination of about 45 ° C. The tip of the Ezo pine bar was processed into a bowl shape in advance so that it could easily enter the sand. When the square bar was inserted and left for 5 minutes, the corner was preferentially carbonized as in Comparative Example 1, and the in-plane was hardly carbonized.

  Cut commercially available MDF board (thickness 14 mm), commercially available radial tapain laminated timber (thickness 18 mm), commercially available veneer plywood (thickness 12 mm), and commercially available OSB plywood (thickness 12 mm) into 20 x 30 mm sizes. Three samples were prepared for each. The hot plate of Example 2 was set to 300 ° C., and a set of four types of four cut plates was simultaneously placed on the hot plate and heated for 10 minutes. This operation was performed in the same manner for each group, and the thickness of the carbonized layer of three samples was measured for each of four types of wood, and the average value was calculated. As a result, the MDF plate was 4.93 mm, the laminated material was 4.28 mm, the veneer plywood was 4.72 mm, and the OSB plywood was 4.40 mm. In either case, the results were close to those of Example 2.

  It is shown that when the wood surface layer is impregnated with water glass, the surface layer carbonization of the wood according to both the examples 1 and 2 is more effectively performed. That is, the heating time or heating temperature can be increased within the range where cracks do not occur, and the carbonization depth can be further increased.

Water glass (Showa Science Co., Ltd. No. 1 sodium silicate solution (water glass No. 1, very viscous fluid), hereinafter simply referred to as water glass) is diluted with water, and the weight ratio of water glass is 34% and 58%. An aqueous solution of was prepared. A small amount of these aqueous solutions was dripped onto a large number of cedar timbers similar to those in Example 1, spread uniformly with a glass rod, and then allowed to dry horizontally. A glassy film was not formed on the dried wood surface, and it is assumed that the wood surface layer was impregnated. The wood surface and the impregnated portion of the cross section were slightly darker in color, and the depth of impregnation was about 0.2 mm. The average weight increase of the wood after impregnating the wood with water glass and fully drying it was 0.47% for the water glass 34% solution and 1.10% for the 58% solution. The former is named A square and the latter is named B square. In terms of average coating weight, A square timber each 29.0g ^{/ m} 2, B square bar was 72.9 g / ^{m 2.}

  As in Example 1, the square A was immersed in molten tin at 360 ° C. for about 10 mm with the water glass impregnated surface down, and the location was changed by immersing it once every 15 seconds. It was lifted up and immersed in a place without slag. After 5 minutes, the A square was pulled up and allowed to cool. Similarly, a total of three samples were prepared and the carbonization depth was measured. The average carbonization depth of the three samples was 6.54 mm. Cracks did not occur. Next, after the A square was immersed in molten tin at 360 ° C. for 10 minutes in the same manner, the occurrence of cracks was observed and the carbonization depth was measured. Was 9.26 mm. Subsequently, the square A was similarly immersed in molten tin at the same temperature for 15 minutes. Cracks occurred in two of the three square bars. When the same experiment was performed on the B square, a crack occurred in one of the three pieces. In any case, cracks did not occur at the stage of 13 minutes. The squares not impregnated with water glass did not generate cracks for up to 5 minutes, but when impregnated with water glass, the time during which cracks did not occur doubled and the carbonization depth was nearly doubled. Increased to. These results are shown by the dotted lines in FIG. Similar effects can be obtained at other temperature conditions. Surprisingly, it was confirmed that when water glass was impregnated, black powder hardly adhered to the finger even when the carbonized surface was rubbed with the finger. A test similar to the above was performed on a square bar that was not impregnated with water glass, and samples having the same carbonization depth were compared. As a result, it was found that the sample impregnated with water glass was much less likely to get dirt on the fingers. This effect is very advantageous in practice.

  In the same manner as in Example 2, the A square bar and the B square bar were placed on a hot plate at 340 ° C. with the water glass impregnated surface down, and the occurrence of cracks and the carbonization depth were measured using the heating time as a parameter. As a result, the A square member did not crack until 20 minutes, and cracked after 30 minutes. The B square did not crack until 30 minutes. As can be seen from FIG. 11, in the square material not impregnated with water glass, cracks did not occur at a heating temperature of 340 ° C. until 15 minutes, so the time during which cracks did not occur doubled and the carbonization depth also increased. It has increased by about 50%. These results are shown by the dotted lines in FIG. Similar effects were obtained at other temperature conditions. As in the case of carbonization with molten tin, it was confirmed that black powder hardly adhered to the finger even when the carbonized surface was rubbed with the finger.

  The cedar wood having the same dimensions as in Example 3 was covered with an aluminum foil having a thickness of 13 μm on the upper and side surfaces of the cedar wood. The aluminum foil was squeezed and adhered so that no gap was formed between the upper surface of the cedar wood and the aluminum foil. The aluminum foil was also pressed against the side so that it did not rise. The surface (upper surface) covered with the aluminum foil of the sample thus prepared was placed on a hot plate at 340 ° C. in the same manner as in Example 2 and heated for 15 minutes. After cooling, the aluminum foil was removed and the carbonized surface was observed. As a result, the surface shape was very fine and smooth compared to the case without the aluminum foil. There were no cracks. The thickness of the carbonized layer was about 9 mm when there was no aluminum foil, whereas it slightly increased to about 10 mm when there was an aluminum foil. Even when the carbonized surface was rubbed with a finger, black powder hardly adhered.

  Four cedar woods having the same dimensions as in Example 3 are arranged in 2 rows and 2 columns on a workbench with an interval of 5 mm, and the upper surface (surface of 20 × 30 mm) is 5 mm thick and the size is 100 mm square. A stainless steel plate was placed. Four samples were arranged so as to be approximately in the center of the stainless steel plate. When the flame of the gas burner (Fujiwara Sangyo Co., Ltd. One-touch gas torch SK-11) was radiated for 1 minute from the upper side of the stainless steel plate so as to be emitted uniformly over the entire surface of the stainless steel plate, a little smoke was generated. Therefore, after extinguishing the fire for 30 seconds and radiating for 20 seconds after smoke completely disappeared, a little smoke was generated again. Then, after extinguishing again for 30 seconds, after the smoke disappeared, 20 seconds were emitted, and after that, the fire extinguishing for 30 seconds and the radiation for 20 seconds were repeated 9 times. A total of 11 repetitions were performed. After the last 20 seconds of radiation, the sample was allowed to cool, the stainless steel plate was removed, and the carbonized surface of the square was observed. No cracks were generated, and the average thickness of the carbonized surface layers of the three samples was 5.82 mm. . From the state of smoke generation, it is estimated that the temperature of the sample surface was always kept below 340 ° C.

  Next, instead of the stainless steel plate, an iron plate having a thickness of 1 mm and a size of 60 × 50 mm was placed on the same cedar square material as in Example 3, and a gas burner was emitted for 10 seconds in the same manner as described above. A little occurred. So, after the fire was extinguished for 10 seconds, the smoke stopped. This was repeated 12 times. Then, after standing to cool and removing the iron plate, the thickness of the surface carbonized layer of the sample was 2.39 mm. The carbonized surface was very smooth and free from cracks. Judging from the state of smoke generation, it is presumed that the surface temperature of the sample was kept below 300 ° C. Next, instead of the above iron plate, an iron plate having a thickness of 0.3 mm and a size of 60 × 50 mm was placed on one cedar square material similar to the above, and the gas burner radiation and extinguishing were repeated in the same cycle as above. When the gas burner was radiated for 10 seconds, intense smoke was generated from the squares, and the edges ignited but soon disappeared spontaneously. When the steel plate was removed and the carbonized surface was observed, many cracks were generated. The surface temperature of the sample is estimated to be 450 ° C. or higher. Therefore, the gas burner radiation and fire extinguishing cycle was repeated for 5 seconds, and fire extinguishing for 10 seconds. There was no generation of cracks, and the thickness of the surface carbonized layer was 2.09 mm. When the thickness of the metal plate placed on the square bar is reduced in this way, the temperature of the metal plate rapidly rises due to gas burner radiation. It is important to choose

  An iron plate having a thickness of 1 mm and a size of 60 mm × 50 mm is placed on the upper surface (20 × 30 mm surface) of the cedar wood having the same dimensions as in Example 3, and using the same heat gun as in Example 3, hot air at 340 ° C. When sprayed for 5 minutes, the surface of the wood was hardly colored. Then, when the temperature of the hot air was raised to 400 ° C. and heated for 10 minutes, it became a little dark (brown). The carbonization depth of the surface layer was 2.46 mm. Next, when a similar experiment was performed using an iron plate having a thickness of 0.3 mm and a size of 60 × 50 mm instead of the iron plate having a thickness of 1 mm, a black carbonized layer having no crack and a thickness of 3.21 mm was obtained. Obtained. On the other hand, the upper surface (20 × 30 mm surface) and side surface (the whole surface in the height direction) of the cedar wood are covered with an aluminum foil having a thickness of 17 μm. The aluminum foil was squeezed so that there was no contact. The sample prepared in this manner was sprayed with hot air at 400 ° C. for 5 minutes from above the aluminum foil, and then the aluminum foil was removed. As a result, many cracks were generated on the surface of the carbonized layer. Since the aluminum foil is a thin metal, the temperature of the sample surface was brought close to 400 ° C. by hot air at 400 ° C., and the heating time was increased to 5 minutes, so cracks occurred. The iron plate or aluminum foil became a hot plate and the wood was heated in the same way as the hot plate method, but if the thickness of the metal plate is large, the efficiency of heating with hot air is bad, conversely when it becomes thin like an aluminum foil, It is important to select an appropriate temperature and time because it is easily heated.

  A cedar wood having the same dimensions as in Example 3 was used as a square material sample, and a black surface-treated iron plate having a thickness of 1 mm and a size of 60 mm × 50 mm was placed on the upper surface (surface of 20 × 30 mm), as in Example 4. A quartz glass tube heater was disposed so that the distance from the heater to the upper surface of the sample was 10 mm. After applying voltage to the heater and irradiating with infrared rays for 2 minutes, voltage application was stopped for 5 seconds, voltage was applied for 25 seconds, and then voltage application was stopped for 5 seconds. Thereafter, after applying voltage application for 25 seconds and stopping application of voltage for 16 seconds in this manner, the sample was checked after being allowed to cool. The carbonized surface was very smooth and free from cracks. The average thickness of the surface carbonized layer of the two samples thus prepared was 3.70 mm. It was estimated that the temperature of the surface of the sample was kept at 300 ° C. or lower because there was almost no smoke during repeated ON / OFF of voltage application. In addition, when the same experiment was conducted using an aluminum foil instead of the black iron plate, the square bar was hardly colored. That is, the aluminum foil reflected infrared rays and was not heated very much. Therefore, a member that absorbs infrared rays well is required for this purpose.

  Example 12 is an example in which the heat roll is rotated and moved on the surface of the plate-like wood to carbonize the surface layer of the wood, but it is difficult to obtain a heat roll with a built-in heater. The thing which floated the aluminum roll in the bath was used. An aluminum roll having a diameter of 30 mm and a length of 100 mm was used. When an aluminum roll was floated on a tin bath melted in a stainless steel bat in the same manner as in Example 1, about 18 mm of the aluminum roll was exposed from the bath surface perpendicularly from the bath surface. The temperature of the tin bath was set to 400 ° C. Next, put a cedar board with a cross section of 30 x 14 mm and a length of 300 mm on the aluminum roll so that the 30 x 14 mm surface is in contact with the aluminum roll and the aluminum roll and the cedar board are orthogonal to each other, and apply a little load. The cedar board was slowly moved horizontally in a state where about two-thirds of the aluminum roll was immersed in the tin bath. When the cedar board was moved, the aluminum roll rotated slowly in synchronization with the movement of the cedar board. The cedar board was moved 50 mm over 5 minutes. During this time, no smoke was generated. Therefore, it is estimated that the surface temperature of the cedar board where the aluminum roll and the cedar board are in contact was 340 ° C. or less. The carbonized surface was sufficiently blackened, and the carbonization depth was 1.19 mm. From the above experiments, it was confirmed that the wood surface can be carbonized by a hot roll.

  The hot plate was heated to 340 ° C. in the same manner as in Example 2. A testicle rod having a diameter of 20 mm and a length of 30 mm was placed on the hot plate, moved while slowly rotating, and when it was rotated about half a round over 8 minutes, the testicle rod was taken out of the hot plate and allowed to cool. After cooling, the carbonization depth was measured and found to be 1.34 mm.

  Next, testicle bars with the same dimensions as above and testicle bars with the same dimensions covering almost half of the circumference with 13μ thick aluminum foil are placed on a hot plate at 340 ° C, left for 15 minutes, and then covered with aluminum foil The untested testicle rod was lifted by grasping it with tongs, and when the portion of the testicle rod that was in contact with the hot plate was observed, no cracks were generated. The time required for this confirmation work is 7 to 8 seconds. Therefore, this testicle rod was immediately returned to the hot plate so that the same place was heated, and both were additionally heated for 5 minutes, then removed from the hot plate and allowed to cool. A number of large cracks occurred on the testicle bar not covered with the aluminum foil, but no crack occurred on the testicle bar covered with the aluminum foil. Thus, when the contact area with the hot plate is small, the effect of covering with the aluminum foil is tremendous.

  In Example 2, the temperature of the hot plate was set to 340 ° C. by the hot plate method, and even if the carbonized surface of the sample heated for 15 minutes was rubbed with a finger, almost no black powder adhered. Adhered to tissue paper. When the carbonized surface of such a sample was impregnated with water glass in the same manner as in Example 7, no powder adhered even when rubbed strongly with tissue paper. When paint was applied instead of water glass (Atom Support Co., Ltd. water-based spray ivory), the appearance became ivory. After fully drying, after sticking an adhesive tape (Sumitomo 3M Co., Ltd. Scotch Super Transparent Tape S) and then peeling off, all peeled off partially. The carbonized layer was thinly attached to the part that adhered to the tape and peeled off. The carbonized layer is relatively fragile on the surface side, and it is considered that water glass and aqueous spray do not reach the inside of the carbonized layer. Since the carbonized layer is relatively lipophilic, it is considered that the aqueous coating agent does not have good adhesion to the carbonized layer.

  Next, an organic solvent liquid of polysiloxane (manufactured by Shinagawa White Brick Co., Ltd. (current Shinagawa Refractories Co., Ltd.) NIC-C5) 3 drops of a solution in a mixed solvent of butyl acetate and a dropper were spread with a dropper and spread over the entire surface with a glass rod. Since the dropped liquid permeated in several tens of seconds, this operation was repeated again and then left to dry naturally. After the solvent was completely dried, no black powder adhered even when the surface of the sample was strongly rubbed with tissue paper. Next, when an adhesive tape peeling test was performed in the same manner as described above, no peeling occurred.

  Instead of the above polysiloxane, an organic solvent-based paint (Atom Support Co., Ltd. Lacquer Spray E, brown) was sprayed once. The coating was very smooth and glossy. When the adhesive tape peeling test was performed in the same manner as described above after drying for 3 hours, no peeling occurred.

  The wood obtained by the present invention has higher mechanical strength than wood (thermo wood) obtained by a conventional carbonization method, and can therefore be used as a structural material that was difficult with thermo wood. Moreover, since carbonization can be performed at a temperature higher than the carbonization temperature of the thermowood, a greater antiseptic effect can be obtained. The present invention can also be used for grilled piles used outdoors such as fields and gardens. It can be used in most other fields where wood is used. It is thought that it can contribute to the development of the Japanese timber industry, including the effective use of thinned wood.

DESCRIPTION OF SYMBOLS 1 Wood 2 Aluminum foil 3 Hot plate 4 Hot melt metal bath 5 Hot melt metal bath container 6 Force applied to wood

The thickness of the carbonized layer obtained under the conditions shown in Patent Document 3 is not a carbonized layer having a practically sufficient thickness, and performance such as antiseptic properties, weather resistance, and ant-proof properties is insufficient. As a building material used in places exposed to wind and rain such as outer walls and fences, a thickness of 3 mm is usually required. Further, Patent Document 3 does not show conditions for increasing the thickness of the carbonized layer, and does not describe any cracks that may occur when carbonized under the conditions for increasing the thickness. Naturally, this document does not describe how to prevent the occurrence of cracks that occur when the carbonized layer is 0.7 mm or more. In addition, when the entire wood is immersed, problems such as those described in the following items 0104 and 0105 occur.

In the present invention, “wood or woody material” is hereinafter simply referred to as wood. According to the present invention, by carbonizing by controlling the temperature and time, the wood is only carbonized from the surface to the inside to the required depth, so that the inside has the same mechanical strength as the original wood. To do. In addition, the surface layer of wood is much stronger than in the case of the manufacturing method of thermowood, that is, it can be carbonized at high temperature, so that performances such as antiseptic and ant repellency can be obtained far superior to thermowood. . Furthermore, since it is not necessary to use a preservative, a product having no adverse effects on the human body and the environment can be obtained. According to the method of the present invention, it is possible to obtain a uniform thickness and durability of the surface carbonized layer, which could not be realized by the conventional combustion method and gas burner method. That is, there can be obtained a surface carbonized layer which is free from cracks, has a sufficient thickness, can have a surface color of brown to black, and can hardly remove colored powder even if the surface is rubbed with a finger. Furthermore, according to the method of the present invention, it is possible to easily carbonize the surface layer of only one surface or a part of the surface of the wood or a part of the surface. In addition, the surface layer of wood having a curved surface or a complicated shape can be carbonized. For example, it is possible to easily carbonize a square member having a tenon or a tenon hole, or a square member having a groove or a hole, and a great many applications can be considered. When the surface layer carbonized wood is cut with a saw at a construction site, a non-carbonized portion is exposed on the cut surface, and this surface can be carbonized on the site.
Conventionally, a process of removing a brittle surface layer by rubbing the surface with a brush to remove cracks generated on the surface after forming the surface carbonized layer with a gas burner and so as not to get dirty when touched by hand Was sometimes done. However, when such a process is performed, there is a defect that the thick carbonized layer formed at the corner becomes thin. According to the present invention, such a problem is also solved.

  The present invention relates to a method for carbonizing a surface layer of a wood or woody material.

  In order to improve the antisepticity, weather resistance, etc. of wood, it has long been known to carbonize the surface by exposing it to a flame. For example, if burnt cannabis or newspaper is used to burn one side of a board and the baked side faces the outside, it is known to have nearly 100 years even when exposed to wind and rain. Yes. At present, such a method is hardly performed, and a part of the surface layer is carbonized by baking a plate with a gas burner or an oil burner. Although the carbonized layer formed by such a method is thick, the surface is not smooth and flat, and innumerable creases (appears like cracks, hereinafter, cracks are simply referred to as cracks). This surface layer has a low mechanical strength, and black powder adheres to the finger just by lightly rubbing it with a finger. Moreover, when it rubs strongly with a hand or when an object collides, it will peel easily on the part of a crack. The thickness of the carbonized layer at the bottom of the crack is much smaller than the thickness of the portion without the crack. Since there is a risk of water entering from these cracks, it is necessary to avoid the occurrence of cracks. Obviously, if the crack is not formed, the life of the plate whose surface layer is carbonized is further extended.

  1 (a), (b), and (c), the inventor has shown that the pine board A (thickness 24 mm, width 60 mm, length 65 mm), cedar wood B (thickness 14 mm, width 45 mm, length) 90 mm) and cedar wood material C (thickness 14 mm, width 45 mm, length 65 mm), a gas burner (HBA-1700G manufactured by Kinboshi Co., Ltd.) flame (1000 ° C. or higher) was sprayed on the surface, It is the photograph of the surface in which the crack was formed. The photo (a) was baked by blowing a flame of a gas burner on Ezo pine A for 30 seconds, the photo (b) was blown by cedar wood B for 30 seconds, and the photo (c) was baked on cedar wood C by 10 seconds. FIG. 2 is a photomicrograph of a cross section including one of those cracks. Photo (a) is a cross-sectional microscope of Ezomatsu A, photo (b) is Sugibe wood B, and photo (c) is a cross-section microscope of Sugibe wood C. It is a photograph. As can be seen from FIG. 2, the cross section of the crack is the cross section of the crater, and the thickness of the carbonized layer at the bottom of the crack is significantly smaller than the thickness of the portion where there is no crack. The thickness of the carbonized layer at the bottom of the crack in the photograph (a) in FIG. 2 is 1.0 mm, whereas the thickness of the carbonized layer at the portion without the crack is 1.7 mm. The thickness of the carbonized layer at the bottom of the crack in the photograph (b) in FIG. 2 is 0.8 mm, whereas the thickness of the portion without the crack is 1.8 mm. Thus, the thickness of the carbonized layer is greatly reduced in the crack portion.

  The reason for the formation of cracks is that when a plate is exposed to a high-temperature flame in the air and the volatile components generated by thermal decomposition burn on a part of the surface, it preferentially volatilizes and burns on that part, This may be due to a sudden decrease in volume, or when pyrolysis components volatilize and burn from the entire surface exposed to a high-temperature flame, the volume decreases, and the shallow lake water dries out and the mud at the bottom of the lake dries out. It seems to be like a crack.

  FIG. 3 shows that the inventor used a commercially available gas burner (Fujiwara Sangyo Co., Ltd. One Touch Gas Torch SK-11) to radiate a flame (1000 ° C. or higher) to a pine pine board (cross section: 14 × 45 mm). It is the graph which plotted the thickness of the carbonization layer with respect to. The flame strength of this gas burner was much weaker than that of the aforementioned Kimbosi Co., Ltd. product. Three samples were prepared at the same radiation time while keeping the strength of the flame and the distance from the surface of the Ezo pine to the burner, plotting their carbonized layer thickness, and showing the polynomial approximation curve. It can be seen visually that cracking occurs when the radiation time is 4 seconds or longer. Furthermore, cracks increase as radiation continues. The thickness of the carbonized layer where there is no crack when the radiation time is 4 seconds is about 0.4 mm. Thus, the thickness of the carbonized layer that can be carbonized in a range where cracks do not occur is very small.

  Patent Document 1 shows that an anti-rotation wood having high hygroscopicity can be obtained by heating the surface of wood with a gas burner to form a carbonized layer having a thickness of 0.2 mm. It is known that even if such a thin carbonized layer is formed on the surface layer, it has an anti-corrosion effect, but such a thin carbonized layer provides sufficient weather resistance, antiseptic properties, and ant-proof properties. I can't. As a building material used in places exposed to wind and rain such as outer walls and fences, a thickness of 3 mm is usually required. In the surface carbonization by a gas burner, if an attempt is made to obtain a carbonized layer having this thickness, cracks will occur on the surface.

  In Patent Document 3, the whole of red pine is immersed in 460 ° C. molten zinc for 10 seconds to provide a carbonized layer on the surface, and the red pine is immersed in 300 ° C. molten salt for 5 to 10 seconds to carbonize on the surface. It is described that a layer is provided.

  However, as shown in FIG. 9 and Table 2 of the present invention, when floating in molten tin at 500 ° C. for 15 seconds, cracks are generated in the surface layer. Although not shown in FIG. 9 and Table 2 of the present invention, according to the experiment results of the present inventor, when wood is floated on molten tin at 500 ° C. for 10 seconds, cracks do not occur, but the carbonized layer at that time The thickness was very small, 0.45-0.52 mm. According to an experiment in which wood is immersed in a 300 ° C. tin bath for 10 seconds instead of 300 ° C. molten salt, the thickness of the surface carbonized layer is about 0.2 mm.

  The thickness of the carbonized layer obtained under the conditions shown in Patent Document 3 is not a carbonized layer having a practically sufficient thickness, and performance such as antiseptic properties, weather resistance, and ant-proof properties is insufficient. As a building material used in places exposed to wind and rain such as outer walls and fences, a thickness of 3 mm is usually required. Further, Patent Document 3 does not show conditions for increasing the thickness of the carbonized layer, and does not describe any cracks that may occur when carbonized under the conditions for increasing the thickness. Naturally, this document does not describe how to prevent the occurrence of cracks that occur when the carbonized layer is 0.7 mm or more.

  Patent Document 4 describes that wood is pressed and clamped by a mold for three-dimensional processing, and one side of the wood is carbonized by setting one of the molds to a temperature higher than the carbonization temperature of the wood. ing. However, there is no description or suggestion as to how carbonization can be performed so that cracks do not occur under such conditions. In the present invention, instead of using a metal mold, a method that does not cause cracks has been found by extensively examining the heating temperature and the heating time in a state where the hot plate is in contact as described later.

An object of the invention of Patent Document 4 is to make a carbonized layer conductive and use it for the purpose of electromagnetic shielding. However, in order to carbonize wood to make it conductive, as described in Non-Patent Document 4, page V-5, lines 16 to 18, high temperature of 800 ° C. or higher in an inert atmosphere. It is necessary to carbonize. Up to a temperature of about 600 ° C., the insulating material has a volume resistivity of 10 ¹² Ω · cm or more, and at a heating temperature of 600 to 700 ° C. exceeding this, a semiconductor having a volume resistivity of 10 ² to 10 ⁹ Ω · cm. When the temperature exceeds 800 ° C., conductivity of 10 Ω · cm or less is shown, and it is shown that the conductivity is improved as the temperature rises. When wood is brought into contact with a metal at 800 ° C. in the air, cracks are instantaneously generated on the surface of the wood. When the metal plate at 800 ° C. is separated from the wood surface, the wood surface starts to burn.

  Patent Document 4 describes that a wood surface is carbonized by a gas burner to make it conductive. Actually, even if baked for a short time with a gas burner, the carbonized layer does not become conductive. This is because when the wood burns with the gas burner, the temperature rise on the wood surface is suppressed by the heat of vaporization. This is known as the principle of preventing the satellite from burning out due to frictional heat with the air when returning to the earth. In order to burn wood and obtain a conductive carbonized layer, it is necessary to burn until the inside of the wood is red-hot and cool it in a place without air, or quench it with water. If wood of several mm thickness is burned in this way, it will burn out. Therefore, it is actually impossible to make the wood surface conductive with a gas burner.

  In place of the above-mentioned carbonization method using flame, recently, wood preservative treatment using chemicals has become common. A variety of drugs have been developed and used for this purpose. In order to infiltrate the drug inside the wood, various processes are used, such as forming cracks and holes in the wood, injecting the drug under reduced pressure, pressurizing after the reduced pressure injection of the drug, and injecting further into the interior Has been. However, when wood is used as a building material or civil engineering material, there is a concern about the influence of drugs on humans and the natural environment.

  On the other hand, in Scandinavia, it has been practiced for several decades to improve the antiseptic properties, weather resistance, heat resistance, ant repellency, etc. by treating wood with high temperatures. For example, if wood is left in an atmosphere where water vapor of 180 to 220 ° C. is present for about 2 to 20 hours, the inside of the wood is uniformly colored (it is considered that light carbonization has been performed), and the higher the processing temperature, the more colored. Increases the antiseptic and weather resistance. Although it has recently become known in Japan, it has not yet become widespread. In Scandinavia it is called thermowood and is widely used. The reason why the above temperature range is selected is that if the temperature is lower than this temperature, the effect hardly appears, and if the temperature is higher than this temperature, the mechanical strength of the wood sharply decreases. It is described on page 5-4 of Chapter 4. It is described that this high-temperature treatment significantly improves antiseptic properties, weather resistance, etc., but has almost no ant-repellent properties. Non-Patent Document 1, pages 17-4 and 18-4 describe that the use in the ground is not recommended because the antiseptic performance is insufficient at a processing temperature of 220 ° C. However, FIG. 13-4 on page 18-4 of Chapter 4 shows that the antiseptic performance and the ant proof performance are perfect when the processing temperature is 240 ° C. or higher. Further, since the mechanical strength is lower than that of the wood before treatment even at a treatment temperature of 220 ° C., it is warned not to use it as a base part or a structural material. A feature of the thermowood production method is that the processing temperature and the processing time are selected so that the mechanical strength and the antiseptic performance are moderately satisfied. According to the present invention, not only can carbonization be performed at a temperature higher than that in the thermowood production method, but also mechanical strength can be maintained. Thermowood is carbonized entirely from the surface to the inside.

  In Patent Document 2, in addition to heating wood in a high-temperature gas atmosphere, the wood is kept in contact with a bath of high-temperature liquid (for example, silicon-based oil, paraffin) or high-temperature granular material (for example, sand) for a long time. A method is described in which the inside is carbonized to form a thermowood. These liquids and particulates have very low thermal conductivity, so the efficiency of transferring heat to the wood is poor. Since the thermal conductivity is small, if the surface layer is carbonized to a certain depth (for example, around 5 mm), it must be carbonized over several tens of minutes, so if the sand temperature is high, Wood may catch fire or burn.

  Non-Patent Document 2 describes heat treatment with molten wax heated to 100 ° C. or higher, rapeseed oil heated to 180 ° C. to 220 ° C., cottonseed oil, or the like. It also describes heat treatment with mineral oil and silicon oil. However, these oils have a problem that it is difficult to heat to a high temperature as the wood is carbonized. Waxes, mineral oils, vegetable oils, silicone oils, etc. have a problem that the components volatilize or burn when heated to 240 ° C. or higher, so the maximum use temperature is limited. There is also a problem that the oil deteriorates by repeated use. Furthermore, as will be described later (particularly, Example 5), there arises a problem that the entire surface is heated simultaneously.

  Non-Patent Document 3 describes the results of research on carbonization of plywood by radiant heating. Although it is shown that carbonization is carried out to a depth of about 10 mm from the surface of the plywood toward the inside by radiant heating, there is no description of cracks. However, it has been confirmed that cracks are generated in a very short time when strong radiation heating as described in Non-Patent Document 3 is performed.

  It is known to heat wood in an electric furnace or a high-temperature chamber. For example, square wood is put in an electric furnace with an internal temperature of 300 ° C. and left until the surface is sufficiently colored (dark brown to black). Then, there is a problem that the corner of the square bar becomes brittle even if it is strongly carbonized. Furthermore, the time until the surface is sufficiently colored is several minutes to several tens of minutes, but when this is taken out of the electric furnace and cooled to room temperature, the square material is cut and the cross section is observed. It is difficult to perform surface layer carbonization. If the depth of the surface layer carbonization is kept small, the coloring of the surface becomes insufficient. Such a phenomenon was confirmed to be the same in the case of heating with the sand. It has been found that this phenomenon occurs because wood is simultaneously heated from all sides (periphery).

  The branding technique has been used for a long time. For example, it is common to form a brand name on a wooden box, a kamaboko base plate, or a leather surface. These cases are characterized by being heated to a high temperature as the baking mold becomes red-hot and instantaneously pressed against the object. Also, one of the features of the brand mark is that the portion is considerably depressed by evaporation due to thermal decomposition. In these cases, it is required that the formation of the burning mark be completed in a short time (almost instantaneously), and the baking mold is heated to a high temperature as it is red-heated, and is completed by the momentary or very short time pressing. In the branding method, the surface can be colored (carbonized) sufficiently deeply, but it is difficult to carbonize deep inside.

  It is known as a hobby to draw freehand images on wood, leather, resin plates, etc. with a hot pen, electric scissors or the like heated to about 400 ° C. or more. In these hobbies as well as in the above-mentioned branding technique, it is required to imprint or draw in a short time. Therefore, the temperature of the mold and the bowl is naturally required to be about 400 ° C. If the temperature is low, the time during which the baking mold is pressed or the time during which the ridge is pressed in one place becomes long, making practical use difficult. As described above, in the image-printing technique and the drawing by the wrinkle, a very high-temperature baking mold or wrinkle is used, but when the high-temperature baking mold or wrinkle is pressed against the same place for several seconds, that portion Is very darkened (blackened), and when the surface is rubbed with a finger, not only the black powder adheres to the finger, but also the carbonized part becomes considerably depressed. Such a phenomenon is not so much a problem in the case of stamping or freehand drawing, but it becomes a big problem when carbonizing a surface layer with a large area of wood as used in construction etc. is there. In addition, if you try to increase the carbonization depth by using the branding or thermal pen technology, if a trowel or thermal pen is pressed against the same place on the wood surface, cracks will occur before the carbonization depth of the required thickness is obtained. Resulting in.

  In view of the background art as described above, the present inventor speculates that the problem is that carbonization by the flame method is performed in the air, and when a wooden square is immersed in a solder bath, a stunning carbonized layer without cracks. I found out that Next, when hot air (heat gun) having a temperature much lower than that of the flame was blown, it was found that cracking was likely to occur, although it was much reduced compared with carbonization by a gas burner. Compared with heating by flame, heating by solder bath and heating by hot air, heating by flame or hot air can volatilize freely, but heating by solder bath prevents volatilization of pyrolysis components, so cracks The hypothesis is that the occurrence will be prevented. Therefore, when a wooden square was placed on a hot plate and heated, it was found that a thick carbonized layer without cracks was obtained as in the case of a solder bath. In addition, when a glass plate was placed on a wooden timber and heated by emitting infrared rays from above, the generation of cracks was greatly improved. From these results, it is considered that volatilization of the pyrolysis component due to heating is prevented. Furthermore, when the surface layer of wood was impregnated with water glass and heated with hot air, the generation of cracks was greatly improved. It was found that impregnation with water glass on the surface layer of wood has a great effect even in other heating methods. The presence of water glass prevented the pyrolysis components from volatilizing. The present invention was derived from these results.

  Patent Document 5 describes that wood impregnated with a flame retardant is further impregnated with water glass. The purpose is to delay the fall of the burned part by burning the wood surface into a flame at 840 ° C., burning the wood and penetrating to the back side. When not treated with water glass, it penetrated to the back side in 28 minutes, but when treated, it penetrated in 30 minutes. In the invention of Cited Document 5, the water glass is described as “acts so as to melt into a glass state under high temperature overheating to fix the carbonized residue”. On the other hand, in this invention, since it heats only to 450 degrees C or less, water glass does not fuse | melt to a glass state. Moreover, in this invention, the temperature area | region where wood burns is not included. In Patent Document 5, there is no consideration or description as to how water glass affects the occurrence of cracks.

JP 2002-283308 A Japanese Patent No. 3898764 JP-A-226303 JP 2007-98640 A JP 2004-181804 A

Published by ThermoWood Handbook Finnish Thermo Wood Association (August 4, 2003) Momohara Ikuo Heat Treatment and Durability Published by Japan Wood Conservation Society Journal “Wood Preservation” Vol.31-1 (2005) Saburo Uesugi Carbonization of plywood by radiant heating Forestry Experiment Station Research Report No. 340 (1986) 4. Professor Emeritus, Kyoto University Shigehisa Ishihara From wood to charcoal-Can charcoal become a functional material? New development by carbonization of woody materials Japan Wood Society (2004)

  The object of the present invention is to overcome the disadvantages of the conventionally known burned cedar and thermowood, in particular without using a chemical such as a preservative, without substantially reducing the mechanical strength of thick (thick) wood or woody materials. Without cracking the surface layer of wood or wood material, at least a part of the surface layer of wood or wood material is uniformly carbonized to a thickness of 0.7 mm or more (colored from black to brown) ) To provide a surface layer carbonization method capable of enhancing antiseptic properties, weather resistance, ant repellency, and the like, and to provide a product obtained by the method.

  A first method for solving the problems of the present invention is to keep the surface temperature of 240 ° C. to 450 ° C. on the surface of a carbonized region of wood or woody material while preventing volatilization of pyrolysis components. The region is carbonized to a required depth of 0.7 mm or more, that is, a desired depth, from the surface toward the inside by supplying controlled thermal energy.

  Method A for preventing volatilization of pyrolysis components in the first method of the present invention is to contact a gas-impermeable member so as to cover at least a part of the surface of the wood or wood material to be carbonized. In a state, by supplying controlled thermal energy from the member, the region is carbonized from its surface inward to the required or desired depth. In the present invention, the meaning of “contact” in “contacting a gas-impermeable member with wood” is the same as “adhesion”. For example, during carbonization of a wood flat plate, the pyrolysis component generated from the wood flat plate is In order to prevent volatilization freely, it is used in the sense that the metal plate is closely attached so as to cover the surface of the wood flat plate.

  The method for supplying thermal energy from the gas impermeable member is a method of supplying a gas impermeable member of molten metal, hot plate, hot foil, or hot roll at 240 ° C. to 450 ° C. to the surface of the wood or wood material. Is to contact. By controlling the temperature of the gas-impermeable member and the contact time with 15 seconds or more, it is possible to carbonize to a required depth of 0.7 mm or more from the surface of the wood or wood material toward the inside. .

  Method B for preventing volatilization of pyrolytic components is a method in which a member such as a glass plate which is impermeable to gas and transmits infrared rays is brought into contact with the surface of the wood or wood material, and the wood or wood material is transmitted through the member. Is to irradiate infrared rays while maintaining the surface of 240 ° C to 450 ° C. By controlling the energy intensity and irradiation time of infrared rays, carbonization is performed to a necessary depth of 0.7 mm or more from the surface of the wood or woody material toward the inside.

  Method C for preventing volatilization of pyrolytic components is to apply the method A or B after impregnating the surface layer of wood or wood material with water glass, or water glass to the surface layer of wood or wood material. Is impregnated with infrared rays so that the surface temperature is 240 ° C to 450 ° C. Water glass impregnated in the surface layer of wood or woody material prevents volatilization of the pyrolysis component and prevents the generation of cracks.

  A second method for solving the problem of the present invention is to blow hot air at a temperature of 280 ° C. to 480 ° C. on the surface of the carbonized region of the wood or woody material, so that the region is directed from the surface toward the inside. Carbonization to the required depth, ie the desired depth. The generation of cracks was greatly improved by blowing hot air at a temperature much lower than that of the gas burner flame. Also in the second method for solving the problems of the present invention, it is very effective to impregnate wood with water glass before blowing hot air.

  In the present invention, gas impermeability does not mean that gas is not completely transmitted, but does not substantially transmit gas. That is, the thermal decomposition component generated during the carbonization treatment has a gas impermeability that does not pass through the member. For example, it may be a porous material that allows gas to pass through very slowly, such as pottery or unglazed.

  In the present invention, “wood or woody material” is hereinafter simply referred to as wood. According to the present invention, by carbonizing by controlling the temperature and time, the wood is only carbonized from the surface to the inside to the required depth, so that the inside has the same mechanical strength as the original wood. To do. In addition, the surface layer of wood is much stronger than in the case of the manufacturing method of thermowood, that is, it can be carbonized at high temperature, so that performances such as antiseptic and ant repellency can be obtained far superior to thermowood. . Furthermore, since it is not necessary to use a preservative, a product having no adverse effects on the human body and the environment can be obtained. According to the method of the present invention, it is possible to obtain a uniform thickness and durability of the surface carbonized layer, which could not be realized by the conventional combustion method and gas burner method. That is, there can be obtained a surface carbonized layer which is free from cracks, has a sufficient thickness, can have a surface color of brown to black, and can hardly remove colored powder even if the surface is rubbed with a finger. Furthermore, according to the method of the present invention, it is possible to easily carbonize the surface layer of only one surface or a part of the surface of the wood or a part of the surface. In addition, the surface layer of wood having a curved surface or a complicated shape can be carbonized. For example, it is possible to easily carbonize a square member having a tenon or a tenon hole, or a square member having a groove or a hole, and a great many applications can be considered. When the surface layer carbonized wood is cut with a saw at a construction site, a non-carbonized portion is exposed on the cut surface, and this surface can be carbonized on the site.

FIG. 1 is a photograph showing the occurrence of cracks on the wood surface carbonized by a gas burner. FIG. 2 is a photomicrograph of a cross section of a portion where cracks in the wood of FIG. 1 occur. FIG. 3 is a graph in which the thickness of the carbonized layer of a sample prepared by a gas burner is plotted, and shows the conditions under which cracks start to occur. FIG. 4 is a surface photograph (a) of a carbide carbonized by the molten metal method and a cross-sectional micrograph (b) of a cracked portion. FIG. 5 is a side sectional view of one specific example of the hot plate system of the present invention. FIG. 6 shows a surface photograph (a) and a cross-sectional micrograph (b) of a crack in which a crack is generated when the temperature of the hot air is high in the hot air method. FIG. 7 shows a photograph of the surface of carbonized by the hot air method. Photo (a) shows the case where hot air of air is used, and photo (b) shows the case where hot air of carbon dioxide gas is used. FIG. 8 is a side sectional view of one specific example of the hot plate system of the present invention. FIG. 9 is a surface photograph taken by arranging samples prepared by the molten metal method of the present invention. FIG. 10 is a graph in which the carbonization depth of the sample prepared in Example 1 is plotted. FIG. 11 is a graph plotting the carbonization depth of the sample prepared in Example 2. FIG. 12 is a graph in which the carbonization depth of the sample prepared in Example 3 is plotted. FIG. 13 is a graph plotting the carbonization depth of the sample prepared in Example 4. FIG. 14 is a cross-sectional photograph of the sample prepared in Example 5. FIG. 15 shows various photographs of the sample created in Comparative Example 1. FIG. 16 shows various photographs of the sample created in Comparative Example 2. FIG. 17 is a graph plotting the temperature immediately before the occurrence of a crack, with the horizontal axis representing the wood surface temperature and the vertical axis representing the heating time logarithmically based on the data of Example 1 and Example 2. FIG. 18 is a graph plotting the data of Example 2 with the horizontal axis representing the wood surface temperature and the vertical axis representing the maximum carbonized layer thickness without cracking.

  The molten metal used in Method A for preventing volatilization of pyrolysis components is a metal that melts at a temperature of 240 ° C. or higher, is relatively stable in air in a high-temperature molten state, and is relatively inexpensive. In addition, it is desirable that it does not volatilize in the air in a high-temperature molten state and that it does not adversely affect the environment. As a material that substantially satisfies these conditions, tin or a tin alloy represented by solder can be cited. Of these, tin is particularly desirable because it is widely used for the surface treatment of steel materials. Lead can also be used, but it is not preferable because it adversely affects the environment. It does not necessarily need to be a metal, and if there is something like a molten salt with a high thermal conductivity, it should be usable.

  In the molten metal method, which is one of the methods A for preventing volatilization of pyrolysis components, wood is floated in a bath of high-temperature molten metal, or part or all of it is treated by treatment. Therefore, only a part of the wood is immersed in the bath. Therefore, log, columnar or prismatic wood is rotated around the longitudinal axis of the wood, or the wood is submerged in the bath with an appropriate jig, or on the wood floating in the bath. The molten metal is allowed to flow through the portion of the wood that is above the bath surface and the molten metal is contacted, or a combination of these methods can be used to uniformly heat the wood surface layer. . When the wood is plate-shaped, if only one side is treated, it is only necessary to float in the bath. However, when treating both sides, this is achieved by treating one side of the plate and turning it over. One side of the board can be carbonized on the surface and the other side can be left with a wood background. Further, the moisture content of the wood is usually over 10% or more, and when the wood in this state is immersed in a high-temperature bath, steam gas is generated vigorously. Therefore, the wood may be dried in advance by an appropriate method. If the wood is sufficiently dried, even after the treatment according to the present invention, deformation is not likely to occur for a long period of time, so that there is an advantage that cracking and warping are unlikely to occur.

  The molten metal is not necessarily placed in the bathtub, and may be circulated and used by pouring it over the wood from above, or collecting and heating the molten metal that has flowed down and pouring it over the wood again. In this way, the processing bath can be small.

  One most important aspect of the present invention is that the surface layer is fully carbonized but the interior is not carbonized. The carbonized surface layer exhibits antiseptic properties, weather resistance, ant proof properties, moisture proof properties, etc., and the mechanical strength is maintained by keeping the original wood without being carbonized. Therefore, the time during which the wood is in contact with the high temperature bath and the temperature of the high temperature bath are extremely important factors. If the contact time is too short, the thickness of the carbonized surface layer is small, and if it is too long, carbonization proceeds to the inside and the mechanical strength decreases. If the temperature of the high temperature bath is low, the carbonization rate is low, and if the temperature is too high, cracks may occur. The desired contact time and bath temperature vary depending on the material of the wood and the shape such as thickness and thickness, but the contact time is suitably from 15 seconds to 120 minutes, and the bath temperature is suitably from about 240 to 450 ° C. A more desirable range is 280 ° C to 380 ° C. In this temperature range, the carbonization depth can be increased without cracks, and black powder is difficult to remove even if the surface is rubbed with a finger.

  According to the molten metal system, carbonization is performed in a high temperature molten metal bath or in contact with the molten metal, so that carbonization is performed while being substantially shielded from air (oxygen). Therefore, the reason why the surface is carbonized uniformly without the occurrence of cracks as shown in FIG. 1 is that the surface to be carbonized is blocked by molten metal. This is probably because the volume of the surface layer is hardly reduced. Further, the volatile matter adheres to the inner walls of the road pipe, temporary road pipe and the like in the surface layer, and is further confined inside through the wall hole. As a result, if it is carbonized in the air, components that volatilize or burn outside will remain in the surface layer and deeper portions, so that a large amount of so-called tar content exists in the surface layer and deeper portions, and voids in the surface layer and deeper portions. Therefore, the moisture resistance is high, which is advantageous for preventing deterioration when exposed to wind and rain. In addition, since a large amount of tar is present in the surface layer, it is advantageous for ant protection and antiseptic properties. In the case of flame carbonization in the air, these volatile components, tar components and the like are easily burned or volatilized.

  Even in the molten metal system, cracks may occur if the temperature of the molten metal is too high or the contact time between the molten metal and wood is too long. The above-mentioned desirable temperature range and contact time are determined from this viewpoint. FIG. 4 shows a cedar wood block (cross section 16 × 20 mm, length 30 mm) immersed in a bath of molten tin at 450 ° C. with a 20 × 30 mm surface for 2 minutes to a depth of about 8 mm, and then on the surface. It is the photograph (FIG.4 (a)) which shows the formed crack, and the cross-sectional microscope picture (FIG.4 (b)) of a crack. The appearance is completely different from the cracks generated by the gas burner (FIG. 1). As apparent from the cross-sectional micrograph, the crack reaches only the shallow part of the carbonized layer.

  According to the molten metal method, as described in Example 1, it is possible to easily control the thickness of the layer carbonized in a state where no cracks are generated to about 0.5 to several tens of millimeters. Therefore, the decrease in the wood strength due to carbonization can be reduced to a negligible level. The reason is considered as follows. Wood used as a structural material such as columns, beams and foundations is usually quite thick. In the case of a pillar, one side of the cross section is usually 10.5 to 12 cm. Thus, even if the surface layer is carbonized and the mechanical strength of the portion is reduced, the thick wood has the strength of the original wood. For example, when the thickness of the carbonized surface layer is 2 mm (in the thickness direction of the wood) with 12 cm square wood, about 3.3% of the cross-sectional area of the wood before carbonization is carbonized, and the wood cross section before carbonization About 96.7% will have the original wood strength. When wood is not used as a structural material, the cross-sectional area of the carbonized layer may be further increased with respect to the total cross-sectional area of the wood. In the case of a pillar, if it is desired to avoid exposing the black carbonized layer on the surface, a thin wood can be pasted on the carbonized layer. When not a structural material, for example, if it is a plywood, a carbonized plate may be laminated inside so that the carbonized layer is not exposed on the surface. Further, it can be used such that only one surface of the plate is carbonized so that the carbonized layer does not face the front side (so as not to be seen directly). In the case of LVL and CLT materials, a plate having a carbonized layer can be similarly laminated inside.

  In the molten metal system of the present invention, when wood is immersed in a molten metal bath, if the wood is a round bar, it is carbonized concentrically from the surface to the inside, but if the wood is a square, it is concentric square Is not carbonized. The reason for this is that, at the corner of the square bar, heat is applied from both sides of the corner, so that it is heated more strongly than the flat portion. As a result, a carbonized layer with rounded corners is formed between the concentric square shape and the concentric circle shape in the cross section of the square bar after carbonization. This phenomenon is the same when wood is heated and carbonized in an electric furnace. When such a phenomenon occurs, the carbonization degree of the corner portion of the square bar is more advanced than that of the side surface portion, and it is a disadvantage of this method that it becomes mechanically weak. Moreover, since the area of the non-carbonized portion inside the square member is reduced, there is a disadvantage that the mechanical strength of the square member is also reduced. If the square is very thick, this phenomenon is not a problem. In the present invention, since only one surface can be heated, such a problem can be prevented.

  In the molten metal method, as a method of avoiding the above-mentioned problems, for example, a square is placed sideways, floated on the molten metal bath surface by its own weight, heated and carbonized for an arbitrary time, and then the square is rolled and the adjacent surface is lowered. Heat and carbonize for an arbitrary time. In this way, another surface is heated and carbonized one after another. Due to the dead weight of the square, the square is slightly submerged in the molten metal bath, so that the surface of the square is uniformly heated, and the corners are extremely less heated.

  On the surface of carbonized wood manufactured by the molten metal method, a tar content sometimes precipitates and may become sticky. In such a case, in order to remove the tar content on the surface, it can be washed away with an organic solvent that dissolves the tar content. Further, the surface can be burned and removed with a strong flame such as a gas burner for a short time (about several seconds). When exposed to a flame for a long time, cracks are generated on the surface as in the case of baked cedar, so it is preferable to set it to about 2 to 3 seconds. It is also possible to prevent stickiness by applying a paint to the surface.

  When the carbonized wood produced by the molten metal method is actually used at a construction or construction site, it may be cut to a necessary length by, for example, a saw. Since the cut surface is not carbonized, the wood may start to deteriorate when the portion is exposed. Therefore, in such a case, the exposed cut surface can be carbonized by hot air or infrared rays, which is another method of the present invention.

  When carbonizing the surface layer by the molten metal method, if the surface of the wood is cracked, raised, or dented, the above-mentioned cracks, ridged portions, dents are raised when the surface layer carbonized wood is pulled up from the molten metal tank. There is a risk that molten metal may enter and remain in In order to suppress such a phenomenon, it is desirable that the surface be smoothed by polishing and polishing before the wood is carbonized. Further, when the carbonized wood is pulled up from the molten metal tank, it is possible to remove the adhered molten metal by blowing a high-temperature high-pressure gas that is equal to or higher than the melting temperature of the metal. Since a metal oxide film and slag exist on the surface of the molten metal bath, they may adhere to the surface of the carbonized wood. In such a case, it is possible to blow off with a high-pressure air jet after cooling. It can also be scraped off with a brush. It can be removed by other appropriate methods. If ani exists on the surface of the wood, a metal oxide film or slag is likely to adhere to it, so that it is desirable that the wood has been so-called degreased in advance.

  When the surface of the molten metal has been exposed to air for a long time, the surface is oxidized and a metal oxide is formed, particularly as the melting temperature is higher. As a result, an oxide film is formed on the molten metal bath surface. When wood is immersed or brought into contact with a molten metal bath, a slag-like material is generated although the mechanism is unknown. So-called slag is accumulated on the surface of the molten metal bath, including the oxide film and the slag. Therefore, it is desirable to remove the slag from the bath surface as necessary. You may drive slag towards the edge of the bathtub. It is also possible to feed the molten metal from the lower part of the molten metal tank so that the molten metal overflows from a part of the bath so that the slag generated on the bath surface always flows out of the bath. The molten metal always overflows from the upper part of the bath, and the wood can be slid and carbonized while the wood is in contact with the liquid surface.

  In order to prevent generation of metal oxides on the molten metal bath surface, the molten metal bath surface may be covered with an inert gas. For example, a molten metal bathtub can be placed in a sealed chamber and a nitrogen gas atmosphere can be obtained by sending nitrogen gas into the chamber.

  Wood usually has a moisture content of 10% or more. When wood is immersed or brought into contact with a molten metal bath, moisture in the wood is heated and volatilizes from the wood as water vapor gas, and rises in the metal bath. Blow out from the bath. At this time, a phenomenon may occur in which the molten metal is pushed up by the gas to be ejected and scattered as fine metal droplets. In particular, when the road pipe or the temporary road pipe is exposed, gas ejection from the road pipe or the temporary road pipe is vigorous. Therefore, if the exposed portion of the road pipe or the temporary road pipe is in the deep portion of the molten metal layer, the molten metal scatters intensely. In order to reduce or prevent this phenomenon, it is effective to dehydrate the wood in advance.

  Even if the moisture in the wood is completely removed, microfibrils and lignin in the wood heated by the high-temperature bath are thermally decomposed, and some of the decomposed components are volatilized as gas from the wood, just like water vapor gas The metal is spattered from the hot bath surface. If the hot tub is sufficiently larger than the wood size, there is no risk of jumping out of the tub even if the molten metal scatters. However, when the molten metal is scattered, the contact area with the air increases, so that a large amount of metal oxide may be generated. As a simple method for solving these two problems, as a molten metal scattering prevention material on the surface of the molten metal, a specific material having a specific gravity smaller than that of the molten metal, not dissolved in the molten metal, and not reacting with the molten metal, for example, minute glass It is effective to provide a layer of beads. The gas generated from the wood tries to scatter metal when it is ejected from the bath surface. However, if there is a glass bead layer on the upper surface of the bath surface, metal scatter is prevented. The gas exits into the air through the gap between the glass beads.

  The presence of the anti-scattering material also has the effect of reducing the surface oxidation of the molten metal. The size of the glass beads is suitably about 1 mm to about 5 mm. If it is too small, it tends to adhere to the carbonized wood surface when the wood is pulled up from the bath. If the size is too large, the metal may be scattered from the gap, and the antioxidant effect of the metal is reduced. The size of the beads need not be uniform and may have a distribution. An appropriate thickness of the bead layer is about 5 mm to 20 mm. When the thickness of the bead layer is small, the effects of preventing metal scattering and oxidation are reduced. Too thick is useless. As beads, glass beads, silica beads, alumina beads and the like can be used. Even if it is not a sphere like a bead, it can be used if it is granular, rod-like, or flat and is made of a material that is stable at high temperatures. The size of these may be about the same as the above beads.

  When the wood immersed in the molten metal bath is covered with aluminum foil and then immersed, the proportion of volatile components generated from the wood in contact with the molten metal is greatly reduced, and the generation of slag can be significantly reduced. Even if the volatile components leak from the joint portion of the aluminum foil in the molten metal bath, the generation of slag is much less than when the wood is directly immersed in the molten metal bath.

  In general, the length direction of the wood coincides with the direction of the road pipe or the temporary road pipe, and both end faces (cuts) of the wood are perpendicular to the direction of the road pipe or the temporary road pipe. The gas generated by pyrolysis when the wood is heated to a high temperature is likely to flow in the direction of the road pipe or the temporary road pipe, and hardly flows in the direction perpendicular thereto. Accordingly, when wood is immersed in a molten metal bath, gas is emitted violently from the end face (cut) of the wood, but there is little generation from other surfaces of the wood. As a result, the end face of the wood may be difficult to be carbonized. If the surface other than the end face of the wood is sufficiently carbonized, but the end face is insufficiently carbonized, it is desirable to additionally carbonize only the end face. If additional carbonization is required, the hot air or infrared system of the present invention is suitable.

  In the hot plate method, which is one of the methods A for preventing volatilization of the pyrolysis component, a heating device known as a metal plate, for example, a so-called hot plate is generally used as the hot plate, but a similar device can also be used. Since a hot plate is used in place of the metal that is hot-melted, the temperature conditions are almost the same as in the case of the hot-melt metal. Depending on the shape of the wood to be carbonized, it is possible to use a hot plate having a flat plate shape, rail shape, angle shape, curved surface shape, or the like. For example, in the case of heating a columnar wood such as a pile, a cylindrical heating furnace is suitable. In this case, it is desirable to make the gap between the furnace wall and the wood as small as possible. The cylindrical heating furnace may be divided into two parallel to the length direction so that the wood can be easily inserted, and after the insertion, they may be combined into a cylindrical shape. It is convenient to connect the two-part heating furnace with a butterfly plate. The heat plate may be a metal plate whose surface is covered with a heat-resistant protective film. It is desirable that the hot plate has a sufficient heat capacity or is always supplied with energy to maintain the surface temperature. For example, a hot plate apparatus incorporating an energization heating element such as a nichrome wire and a temperature control mechanism can be used. Moreover, it is desirable that the heat plate has a large thermal conductivity. Thin metal foil such as aluminum foil and copper foil can be used in the same manner as the metal plate. For example, the surface of wood can be covered with aluminum foil, and the temperature of the aluminum foil can be kept high while blowing hot air from above. When a metal plate, metal foil or the like is heated with infrared rays to form a heat plate, it is desirable that at least the surface is treated with a color that absorbs infrared rays so that the infrared rays are not reflected.

  In addition to the above method, the energy supply method to the hot plate can use the heat of combustion of wood or oil. For example, waste wood, thinned wood branches or the like are burned in a combustion chamber, the upper wall of the combustion chamber is made a flat iron plate, and this iron plate can be used as a hot plate. In this way, not only is it possible to effectively use waste wood and thinned wood, but it is also beneficial to the environment.

  As a method for supplying energy to the hot plate, a molten metal in a hot melt state can be used. For example, a metal plate can be mounted on a hot-melt metal bath, and this metal plate can be used as a hot plate. It is possible to heat similarly by floating an aluminum foil instead of a metal plate and placing wood on it. FIG. 5 is an immediate cross-sectional view of a state in which an aluminum foil is floated on a molten metal bath, a timber is placed on the aluminum foil, and a force is applied to the timber to slightly sink the timber. In FIG. 5, 1 is wood, 2 is aluminum foil, 4 is a molten metal bath, and 5 is a metal bath container. When a force 6 is applied on the wood 1, the wood 1 deforms the aluminum foil 2 and sinks a little in the bath. In other words, an aluminum foil boat with wood on a metal bath is floating. If the weight of the timber is large, the timber will sink slightly without applying force from above. The aluminum foil in the bath bends upward at the peripheral end of the lower part of the wood in the bath due to the buoyancy of the metal bath, and is in close contact with the peripheral end of the lower part of the wood, so that volatilization of the thermal decomposition component is suppressed. This suppresses the occurrence of cracks at the carbonized portion at the end. The use of aluminum foil is extremely simple and effective. Although the aluminum foil at the corner of the wood may be wrinkled, the aluminum foil in contact with the lower and side surfaces of the wood is completely flat and has no effect on carbonization.

  In the hot plate method, the hot plate and the wood are brought into contact with each other. However, since the surface of the wood is generally rough, an air layer exists between the hot plate and the wood. In the molten metal method, since the molten metal can be freely deformed, there is no air layer between the wood and the molten metal even if the surface of the wood is rough. Therefore, in the case of the hot plate method, it was speculated that the method of carbonizing the surface layer of wood would be considerably different from the case of using molten metal. However, it was surprisingly almost the same carbonized. Since the wood and the hot plate are in contact, it is assumed that the volatile components generated from the wood by heating are prevented from freely escaping from the surface of the wood and are confined inside the wood.

  In the hot plate method, since the hot plate is usually flat, only one surface of the wood can be heated. When the heating of one surface is completed, the next surface is heated. In order to simultaneously heat a plurality of surfaces, it is necessary to prepare a hot plate having a shape suitable for the surface. For example, in order to heat two adjacent surfaces simultaneously, an angle-shaped hot plate is required. When heated with an angle-shaped hot plate, the problem of preferential carbonization of the corners occurs. However, this problem can be solved by providing slit-like gaps at the corners of the angle. When carbonizing a square-like wood surface layer, two surfaces can be carbonized simultaneously by heating in a state sandwiched between two hot plates. When one surface of wood is heated with a flat hot plate, almost the same effect and result are obtained as when the wood is floated on the bath surface and heated by the molten metal method.

  The wood to be carbonized and the heat plate may be held in contact and may be stationary, but may be moved so as to slide relative to each other while the wood and the heat plate are in contact with each other. For example, wood may be placed on a hot plate, the hot plate may be fixed, and the wood may be moved to slide on the hot plate while being in contact for a set time. A plurality of hot plates having different temperatures or the same temperature may be arranged side by side, and the wood may be moved while sequentially sliding on them.

  Prior to heating and carbonization of the wood surface with a hot plate or molten metal, the wood surface can be pre-carbonized by irradiating the wood surface with infrared rays or heating by blowing hot air. In this case, it is necessary to heat in the pre-carbonization stage under the condition that no cracks are generated on the wood surface.

FIG. 17 is a plot of the wood surface temperature and the heating time immediately before the occurrence of cracks based on the data of Example 1 and Example 2. The vertical axis is a logarithmic display, and an exponential approximation curve of data is displayed. FIG. 17 shows that heating can be performed without generating cracks by heating each wood surface temperature within a heating time that is less than or equal to the exponential approximation curve. It was elucidated in the present invention. The inside of the triangle surrounded by three lines of the exponential approximation curve, the lower limit temperature, and the lower limit time in FIG. 17 is the region of the present invention.

FIG. 18 is a graph in which the data of Example 2 is plotted with the horizontal axis representing the wood surface temperature and the vertical axis representing the maximum carbonized layer thickness at which cracks do not occur. The curve in FIG. 18 is a polynomial approximation curve. In the range below the approximate curve, the range of 0.7 mm or more is the range of the thickness of the carbonized layer of the present invention.

  Next, Method B for preventing volatilization of the pyrolysis component will be described. The gas impermeable member used in the method is a member that is transparent to infrared rays and does not transmit gas, such as a glass plate, a quartz plate, and a ceramic plate. Infrared rays include far infrared rays, part of near infrared rays, and part of visible rays, but mainly infrared rays including near infrared rays and / or far infrared rays. A specific example of a far infrared light source suitable for the present invention is a quartz glass tube heater. It is widely used for home and industrial use and is available at a relatively low cost. Hereinafter, this method B is also referred to as an infrared system. When infrared rays are irradiated on the wood surface, the temperature of the wood surface will increase as much as possible. This point is greatly different from the heating method using the molten metal, hot plate and hot air. In the case of heating with molten metal, hot plate, hot air, the temperature of the wood surface does not rise above the temperature of these heat sources, but in the case of infrared light, energy is accumulated on the wood surface at an accelerated rate and the temperature rises. . Therefore, it is necessary to control infrared radiation energy or irradiation time so that the temperature of the wood surface does not exceed 450 ° C.

  Although it is clear from Non-Patent Document 3 that wood is burnt when irradiated with infrared rays, Non-Patent Document 3 has no description of cracks. By appropriately selecting the energy intensity of the infrared source (heater, lamp, etc.), the distance from the source to the wood, the irradiation time, etc., cracks will not occur if heated while keeping the temperature of the wood surface below 450 ° C. I found In addition, a gas-impermeable transparent member such as a quartz plate or glass plate is closely attached to the surface of the wood and irradiated through it, so that molten metal method or hot plate method is applied from the surface to the inside without generating cracks. Can be carbonized to the same extent.

  The wood to be carbonized and the transparent member (glass plate, quartz plate, etc.) may be moved relatively. For example, an infrared lamp may be fixedly disposed, and the wood placed on the transport device may be slid while contacting the lower surface of the transparent member disposed below the infrared lamp. In this case, it is desirable that the transparent member be movable up and down in order to cope with roughness and unevenness of the wood surface. The wood and the transparent member may be moved together in a state where the transparent member is placed on the wood. It is also possible to place a transparent member on wood, place an infrared lamp above it, and move the infrared lamp.

  The wood and the infrared lamp may have an upside down relationship with the above. In this case, it arrange | positions so that a transparent member may contact the carbonized surface of wood. A plurality of infrared lamps may be arranged. As will be apparent from Example 4 described later, when the transparent member is arranged, the carbonization rate is reduced as compared with the case where there is no transparent member. Therefore, as long as cracks do not occur, the transparent member may be carbonized without the transparent member disposed (similar to the preliminary carbonization described in the paragraph 0060), and the transparent member may be disposed after passing through that portion. For example, a plurality of infrared lamps are arranged in parallel, the first one to a plurality are irradiated with the carbonized surface of the wood without a transparent member, and the next one to a plurality are carbonized to the wood. You may arrange | position so that the to-be-carbonized surface of wood may be irradiated in the state which made the transparent member contact the surface. By arranging in this way, it is possible to increase the efficiency of carbonization. Instead of pre-carbonization by irradiating wood with infrared rays, pre-carbonization may be performed by blowing hot air.

  As mentioned above, it can be said in common when the wood and the transparent member or the hot plate are relatively slid, but when the tip of the wood reaches the end of the hot plate or the transparent member, The tip may collide with the end of the hot plate or the transparent member and the movement may be hindered. In order to avoid this, it is desirable that the end of the hot plate or transparent member that meets the tip of the wood be processed into a taper shape.

Next, method C for preventing volatilization of the pyrolysis component will be described. The method is based on the use of wood in which a surface layer is impregnated with water glass. When using, for example, No. 1 sodium silicate solution (for example, No. 1 water glass) as the water glass used in the present invention, it is diluted with water as a stock solution (very viscous fluid), It is preferably used as an aqueous solution having a weight of about 20-60%. If it is 20% or less, the effect of water glass is small, and if it is 60% or more, a water glass film is likely to be formed on the wood surface. Preferably in the range of to the ^15g / ^{m 2 ~80g} / m 2 expressed by impregnation amount per unit area. As a method of supplying water glass to wood, a suitable method such as a known coating method, a method of lifting wood after dipping it in a water glass aqueous solution and drying it can be used. The use of water glass can also be applied in the methods A and B for solving the problems of the present invention.

  In the present invention, it is desirable that the amount of water glass impregnated in the wood is such that a water glass film is not formed on the wood surface after the water glass aqueous solution is supplied to the wood by an appropriate method and dried. Specifically, when the proportion of water glass in the water glass aqueous solution is large, a water glass film is formed on the wood surface. Even if the ratio of water glass is small, a water glass film is formed on the surface of the wood by multiple application. When the water glass film is clearly formed, when heated by the method of the present invention, the water glass film on the surface of the wood foams to form a white foam film. This phenomenon is particularly remarkable when the heating temperature is high. Even if such a foaming phenomenon occurs, if the heating is continued, the wood covered with the foamed film is carbonized, so that it does not interfere with the carbonization. As the carbonization of wood progresses, the foam film that was initially white gradually becomes black and can be easily removed by simply rubbing with a sponge or brush after cooling. Accordingly, the carbonized layer to be formed does not have an adverse effect, but it is desirable to prevent such a phenomenon from occurring because the handling surface is inclined.

  A second method for solving the problem of the present invention is to blow hot air at a temperature of 280 ° C. to 480 ° C. on the surface of the carbonized region of the wood or woody material, so that the region is directed from the surface toward the inside. Carbonization to the required depth, ie the desired depth. This second method is hereinafter referred to as a hot air method. The present inventor speculates that a carbonized layer without cracks having the same thickness as that of a high-temperature molten metal can be obtained by blowing hot air having a temperature similar to that of the high-temperature molten metal on the surface of the wood. In practice, it was found that a thickened carbonized layer was not obtained as in the case of molten metal, but a much thicker carbonized layer was obtained than in the case of a gas burner flame. The temperature of the flame is about 1000 ° C., and cracks occur during a short time of processing. In a short time treatment that does not cause cracks, the thickness of the carbonized layer is extremely small, and only the layer close to the surface is carbonized. However, if the hot air is 480 ° C. or less, it can be carbonized to a thickness of about 3 mm without generating cracks by controlling the temperature of the hot air and the blowing time. Compared with the molten metal method or hot plate method, the thickness of the carbonized layer obtained in a range where cracks do not occur is small, but this is sufficient depending on the application.

  Even in the case of carbonization with hot air, if the temperature of the hot air is high and the blowing time becomes long, cracks similar to those in the case of the gas burner are generated. FIG. 6 is a photograph of a sample obtained by heating and carbonizing Ezo pine (thickness 14 mm, width 45 mm, length 58 mm) with a heat gun (hot air temperature 480 ° C.) for 2 minutes. A photograph (a) is a photograph of the surface where many cracks are generated, and a photograph (b) is a cross-sectional micrograph of the vicinity of one crack. As described above, even when hot air is used or when the temperature is high, cracks are generated as in the case of carbonization by the gas burner even when sprayed for a short time. However, it can be seen that the shape of the cross section differs greatly between hot air carbonization and gas burner carbonization. Although the crack cross-section periphery of FIG. 2 is depressed, the crack cross-section periphery of FIG. 6 swells conversely. The reason why such a difference occurs is presumed to be that combustion occurs in the gas burner method, but combustion does not occur in the hot air method.

  Since flame treatment with gas burners and treatment with hot air blowing are performed in the air, it was thought that the volatile components in the pyrolyzed wood may be oxidized (burned) and cracks are likely to occur. When treated with hot air of carbon dioxide gas, it was confirmed that there was almost no difference from the hot air treatment of air. FIG. 7 is a photograph comparing the carbonization results of Ezo pine (thickness 14 mm, width 45 mm, length 57 mm) with hot air of carbon and hot air of carbon dioxide gas. Photo (a) is a sample carbonized with hot air and photo (b) is a photo of a sample carbonized with carbon dioxide hot air. Both hot air temperatures (480 ° C.) and spraying time (60 seconds) are exactly the same. As can be seen from FIG. 7, it was confirmed that there was almost no difference in the carbonization state between air and carbon dioxide gas. Therefore, it is understood that prevention of volatilization of pyrolyzed components is an important condition for carbonization treatment with molten metal or a hot plate. Also in the hot air method, for example, when a metal plate or a metal stay was placed on the surface and hot air was blown from above, the metal plate or the metal foil became high temperature, and it was confirmed that it could be carbonized as in the hot plate method. A method of covering wood with a metal foil or a thin metal plate and blowing hot air over the metal foil is practical and very effective. The method of covering wood with metal foil and blowing hot air over it is particularly convenient for work in the field.

  If the above assumption that the molten metal or hot plate covering the surface of the wood prevents volatilization of the volatile components of the pyrolyzed wood is correct, the surface of the wood will also contain a resin (including paint, adhesive, etc.) ) Or an inorganic substance (water glass, polysiloxane, etc.), and then it is presumed that it is advantageous to perform carbonization treatment by blowing hot air. If it is a resin-based thin film, the thin film itself is also carbonized by hot air, but if the thin carbonized film can prevent the transmission of volatile components, the guess is correct. Water glass and polysiloxane are not carbonized, but are expected to be impregnated into the surface layer of wood to prevent the transmission of volatile components.

  Therefore, as a specific example, a commercially available coating material (clear lacquer whose solid main component is an acrylic resin) and a commercially available water-soluble adhesive (main component is polyvinyl alcohol) are cedar (thickness) so that the dry thickness is 20 to 30 μm. 5 mm, width 14 mm), and after drying, hot air was blown to confirm the occurrence of cracks. In any case, it was confirmed that cracks were less likely to occur when the coating film was present. However, the effect was slight, and what was cracked by heating for 2 minutes without a coating film was an improvement to the extent that cracks were generated in 2 minutes and 30 seconds by providing the coating film. It is thought that the volatile component passed because the coating film was thin. Subsequently, when the surface layer was impregnated with a commercially available water glass aqueous solution, it was confirmed that cracks hardly occur and the carbonization depth could be increased. It is considered that the water glass component prevented the volatilization of the volatile component (see Example 7). Further, it was also confirmed that when the carbonized surface was rubbed with a finger, black powder hardly adhered to the finger. These facts are one feature of the present invention. In addition to water glass, it was found that a similar effect was obtained when a surface layer of wood was impregnated with a commercially available polysiloxane, but it was confirmed that the effect of water glass was much greater. Furthermore, water glass is overwhelmingly advantageous in terms of cost. The effect of water glass was discovered as described above.

  Since molten metal or hot plate and hot air have different heat capacity, heat conduction, etc., molten metal or hot plate has a larger carbonization capacity. In carbonization with molten metal or hot plate, heating for several minutes to several tens of minutes can achieve a sufficient degree of carbonization (degree of blackening) and carbonization depth even in the temperature range of 240 to 280 ° C. In the heating, in this temperature range, the color is hardly colored by the heating in the above time range or is lightly colored. It was confirmed that the degree of carbonization increased as the speed of blowing hot air was increased, but it was found that carbonization could not be sufficiently performed at a practical blowing speed (wind speed) in this temperature range. The temperature range of the hot air is preferably 280 to 480 ° C. More desirably, it is in the range of 300 to 400 ° C. Hot air at a temperature of 280 ° C. or lower is unrealistic because it takes a very long time to carbonize the surface layer. At 480 ° C. or higher, cracks occur in about 10 seconds, and the carbonization depth is small, which is not practical.

  Conventionally, wood has been heat-treated in an electric furnace, a heating furnace or the like, but the air in the furnace is still or is stirred or circulated. The carbonization by the hot air system of the present invention is characterized by spraying in a higher temperature range than before. In the conventional heat treatment of wood, the purpose is to treat the inside of the wood, and the entire surface of the wood is simultaneously heated over a long time. On the other hand, the present invention is characterized in that hot air having a temperature higher than that of the prior art is blown onto a part (one surface) of wood. Therefore, it is extremely important to blow hot air at high speed. In a static or circulating atmosphere, if the surface layer is sufficiently carbonized, it is weakly carbonized deep inside, resulting in a decrease in the mechanical strength of the wood. By spraying at a wind speed of a certain level or more, the surface layer can be sufficiently carbonized without being carbonized deep inside. By referring to Comparative Example 2 and Comparative Example 3, this difference can be easily understood.

  As described above, the wind speed of hot air is extremely important in the hot air system of the present invention. A desirable wind speed range is 4 m / sec or more, and more desirably 6 m / sec or more. The upper limit is limited by the hot air device or the surrounding environment. Actually, the upper limit is a wind speed of 15 to 20 m per second. The direction in which the hot air is blown onto the wood is desirably in a range of approximately 30 to 30 degrees with respect to the surface of the wood. The greater this angle is beyond this range, the less efficient the wood is heated.

  A commercially available so-called heat gun can be used as the hot air generator. Commercially available heat guns are easily available and easy to use, but the temperature and volume of hot air may not always be sufficient. It is sufficient to carbonize a small area of wood or a cut surface of a plate or a pillar, but lacks the ability to carbonize a large area. In such a case, the heat exchanger can be heated using a large-capacity heat source, and hot air that has passed through the heated heat exchanger can be used. As a large-capacity heat source, there are an electric heater, a gas burner, an oil burner and the like having a large calorific value. The heat exchanger is heated with this large-capacity heat source, and hot air that has passed through the heated heat exchanger is blown. If it is a gas burner, a compact and large-capacity carbonization apparatus is possible. In order to save energy, the hot air used for spraying can be recovered and passed again through the heat exchanger.

  The various systems of the present invention have been described above. Table 1 summarizes these systems and the features of the conventional system. Table 1 does not include the effect of water glass. As is clear from Table 1, molten metal method, hot plate method, infrared method (in the case of infrared transmissive and gas impermeable member) and gas burner (a metal plate is placed on wood and a gas burner is mounted on the metal plate) The results from (flame radiation) are very similar. On the other hand, wood exposed to the atmosphere has completely different characteristics when carbonized by the hot air method and infrared method. In the method in which the gas impermeable member is in contact, it is possible to obtain a carbonized layer (carbonization depth) with a large thickness without occurrence of cracks, but in the method in which the gas impermeable member is not in contact, Only a small thickness of the carbonized layer can be obtained under conditions where no cracks are generated.

  In each of the methods of the present invention described above, the ends (including corners, edges, edges, and ridges) of the wood are preferentially carbonized, and as a result, cracks tend to occur before in-plane. In order to prevent this, it is effective to cover the end with a thin metal plate, a metal foil or the like. For example, as a specific example of the hot plate method, when a wood timber is placed on the hot plate and heated, the volatile component rises as smoke from the four sides (entire circumference) of the square at the contact portion between the square and the hot plate. To do. Since the volatile component escapes quickly and continuously into the space, the occurrence of cracks is promoted. Therefore, the entire square is covered with a metal foil such as an aluminum foil, or at least the end of the wood and a hot plate in the vicinity thereof. It is good to coat | cover the surface and side surface which contact with.

  FIG. 8 is a side sectional view showing a specific example in which four sides (corner portions) of the end portion of the surface facing the hot plate of the square member are covered with aluminum foil. In FIG. 8, 1 is a square bar, 2 is an aluminum foil, and 3 is a hot plate. In the drawing, the thickness of the aluminum foil is exaggerated, but the actual thickness is about 13 to 17 μm. Surprisingly, it was found that the wood 1 and the hot plate 3 are not in contact with each other, and there may be such a small gap. The reason is considered to be that the pyrolysis component is confined in the gap because the periphery of the square member 1 is covered with the aluminum foil 2. By covering the periphery of the square member facing the hot plate with aluminum foil as described above, it is possible to prevent the end of the square member from cracking before the in-plane. Although there is a minute gap between the square 1 and the hot plate 3, it was confirmed that there is no difference in the degree of carbonization from the portion where the aluminum foil is present. In order to confirm how much the gap becomes large, the experiment was repeated with a plurality of aluminum foils stacked, and it was confirmed that there was no effect up to about 0.3 mm. A metal plate of 0.3 mm or less may be used instead of the aluminum foil. Even if such a large gap exists, volatilization of the pyrolysis component can be prevented. It was recognized that when the gap between the square bar and the hot plate exceeds 0.3 mm, the degree of carbonization in the portion not covered with the aluminum foil is lowered. Actually, there is a minute gap between the aluminum foil 2 and the square 1 and a part of the pyrolysis component volatilizes through this gap, but there is an effect of preventing volatilization.

  When actually carrying out carbonization of the surface layer of wood, in particular, a plate, attention must be paid to the size of the wood. When the short side of the plate is about 10 cm or more, the carbonized portion is thermally contracted if only one surface is strongly carbonized, so that the carbonized surface may be curled so as to be concave. Therefore, it is desirable to alternately carbonize both sides. Further, curling can be prevented by repeating a method of heating both surfaces simultaneously for a short time, then allowing to cool for a while and then heating again from both sides. Special care must be taken when the thickness of the plate is small. Such care is not necessary when the plate is very thick or thick square.

  According to the method of the present invention, a wood having a carbonized layer far superior to the conventional method as described above can be obtained. However, since the carbonized surface layer has many small holes derived from road pipes, temporary pipes, wall holes, and other wood, it is difficult to completely block wind and rain for many years. . Therefore, it is also effective to apply or impregnate an appropriate material to the carbonized layer obtained by the method of the present invention so that various characteristics can be maintained for a longer period of time. Various known techniques can be used for this purpose. For example, a method of impregnating water glass, a method of applying or impregnating a resin described in Patent Document 2, and the like can be used. Moreover, the surface layer carbonized wood obtained by the method of the present invention has a brown to black hue, but if an appearance other than these colors is desired, it may be painted to the desired color. When it is desired to increase the mechanical strength of the carbonized layer (for example, when it is desired to prevent black powder from being taken off by a finger when rubbed strongly with a finger), the drawback can be solved by painting the surface.

  The present invention is not limited to wood, but can also be applied to what is generally called woody material. Examples of the wood material include plywood, laminated wood, OSB, particle board (particularly MDF is preferable), LVL, CLT, and compressed wood. It is known that wood compressed with high-temperature and high-pressure steam is compressed to 1/2 to 1/3 of the original wood, its appearance changes to a high-grade brown color, and durability, antiseptic properties, etc. are improved. ing. When the method of the present invention is applied to this compressed wood, the antiseptic property, the ant-proof property and the like can be further enhanced.

  One application of the molten metal system of the present invention is to produce charcoal in a very short time. As a specific example, when a rod of 20 mm in diameter was immersed in a 400 ° C. molten tin bath for 5 minutes, it was almost carbonized to the center of the rod. Although cracks are generated on the surface, there is no problem as charcoal. In the conventional charcoal production method, according to the forestry test site “Wood Industry Handbook”, the charcoal yield at 400 ° C. is 30%. On the other hand, in this specific example (5 minutes immersion), it was 55.9%. When the rod was immersed in molten tin at 400 ° C. for 12 minutes and no vaporized gas was completely generated, the color of the rod was true black and the yield was 33%, which was almost the same as the value in the handbook. There is an advantage that charcoal is completed in just 12 minutes.

  Examples of the present invention will be described below. In the following examples, there is described a state in which there is no relative motion between the wood and the hot plate, between the wood and hot air, and between the wood and infrared rays, but there is relative motion between them. May be. For example, a system in which wood moves on a rotating heat roll may be used. Moreover, you may move, rotating a hot roll on wood. At this time, a plurality of heat rolls may be provided. It is also possible to heat the rolled wood while rolling it on a flat hot plate. In these cases, the width of the contact portion between the wood and the heating member is small, and the pyrolysis volatile component easily volatilizes, so that the heated surface of the wood is covered with a gas-impermeable member, for example, aluminum foil Is desirable. In addition to the roller moving while rotating, the pyrolysis component volatilization preventing member and the wood may slide relative to each other. Moreover, you may make it move relatively, spraying hot air on the moving wood, or irradiating infrared rays.

  FIG. 9 is a surface photograph of the carbonized side of a sample prepared by changing the melting temperature and the heating time when tin is used as the molten metal in the molten metal method. As the wood, cedar wood having a length of 20 mm, a width (direction of the temporary road pipe) of 30 mm, and a height of 16 mm was used. The tin was placed in a stainless steel bat, and the temperature of the molten tin was adjusted by adjusting the heating power of the stove by placing the bat on the gas stove. Tin was melted so that the melted tin had a depth of about 50 mm. The square was held with stainless steel tongs and held so that the square was immersed in the molten tin from the surface by about 10 mm in the height direction. Since slag is generated on the surface of the square material that is immersed in the molten tin, the location can be changed while being immersed once every 15 seconds, or the square material can be lifted and immersed in a place without slag. did. When the whole immersion time was as short as 30 seconds or less, the above place change was performed at a frequency of about once every 5 seconds. FIG. 9 also shows a photograph of a sample prepared at a temperature outside the scope of the present invention. When heat treatment exceeds 450 ° C, significant cracks occurred in 1 minute, and black powder adhered by lightly rubbing the surface with fingers, and the thickness of the carbonized layer was found to be as small as 2 mm or less. The heating temperature range of the present invention was set to 450 ° C. or lower.

  Table 2 shows the results of measuring how the depth of carbonization changes when the immersion time in molten tin is further increased in the same manner as the sample preparation in FIG. Since each sample is a natural product and varies, three samples corresponding to each temperature and time were prepared and three carbonization depths were entered. Samples were prepared at a molten metal temperature in the range of 240 ° C. to 420 ° C. and an immersion time of up to 40 minutes. The center of each sample after carbonization, which is 20 mm long, is divided vertically with a sharp knife (cutter knife) in a direction parallel to the tracheid tube, and the depth of the carbonized layer is observed while observing the cross section with a microscope. Was measured. When the surface divided vertically by the cutter knife was rough, the surface was observed after making it smooth and easy to see. In Table 2, an x mark indicates that a crack occurred at that temperature and time.

  FIG. 10 is a graph in which the average value of the carbonization depth of three samples at each temperature and immersion time in Table 2 is plotted. The melting temperature lower than 340 ° C. measured only up to 40 minutes, but it is clear from the result of the hot plate method of Example 2 that the carbonization depth is increased to about 15 mm by further increasing the immersion time. It is. At 340 ° C., cracks do not occur after immersion for 20 minutes, but cracks occurred at immersion times of 25 minutes, so the graph stops at 340 ° C. for 20 minutes. In FIG. 10, the portion indicated by the dotted line in the graph is data heated at 360 ° C. when the glass surface layer is impregnated with water glass. This is described in detail in Example 7.

  Table 3 shows how cedar wood with a height of 20 mm, a width of 30 mm (in the direction of the temporary road pipe), and a height of 16 mm is used as wood, and how the depth of carbonization changes depending on the temperature and heating time of the hot plate The result of having measured is shown. A hot plate (As One Co., Ltd. ND-1) was used as a hot plate apparatus. Similarly to Example 1, three samples corresponding to each temperature and time were prepared, and the carbonization depth of the three samples was entered. Samples were prepared with the temperature of the hot plate in the range of 240 ° C. to 340 ° C. and the heating time in the range of 15 seconds to 120 minutes. Since the maximum temperature of the hot plate was 350 ° C., an aluminum plate having a thickness of 10 mm and a size of 100 × 100 mm was placed on the molten tin of Example 1 at a temperature higher than that, and a square was placed thereon and carbonized. In Table 3, it is described as a hot plate including this case. The center of each sample after carbonization was divided vertically with a cutter knife in the direction of the temporary canal, and the depth of the carbonized layer was measured while observing the cross section with a microscope. When the surface divided by the cutter knife was rough, it was observed after making it easy to see. In Table 3, x indicates that cracks occurred at that temperature and time.

  Instead of floating the aluminum plate on the molten tin as described above, it was possible to heat similarly by floating an aluminum foil and placing wood on it. Even when an aluminum foil having a thickness of 13 μm and a size of 90 × 60 mm was floated on the molten tin bath, and the same size of wood was placed in the center of the aluminum foil, the aluminum foil hardly sunk due to the gravity of the wood. Therefore, when the wood was pushed down with a tongue and pushed down about 8 mm, the aluminum foil in the bath was bent upward at the lower peripheral end of the wood as shown in FIG. In this way, volatilization of the pyrolysis component was prevented. As a result, in the case of an aluminum plate, the generation of cracks was prevented even at a temperature and time at which cracks occurred at the carbonized portion at the end.

  FIG. 11 is a graph in which the average value of the carbonization depth of three samples at each temperature and heating time in Table 3 is plotted. At a hot plate temperature of 280 ° C. or lower, the heating time can be further extended. The carbonization depth could reach up to about 15 mm without cracks. From FIG. 10 and FIG. 11, it was found that almost the same results were obtained with the molten metal method and the hot plate method. In FIG. 11, the portion indicated by the dotted line in the graph is data when the wood surface layer is impregnated with water glass and heated at 340 ° C. This will be described in detail in Example 7, but it is shown that by impregnating with water glass, cracking does not occur even when heated for a longer time or at a higher temperature than when not impregnated, and the carbonization depth increases. .

  Table 4 shows 20 mm × 30 mm using a commercially available heat gun (Evolution Power Tool Co., Ltd. Heat Gun Hot Air Machine HDG200JP) as a hot air generating device on a cedar wood having a length of 20 mm, a width (direction of the temporary road pipe) of 30 mm, and a height of 16 mm. The result of measuring how the depth of carbonization changes with the temperature of hot air and the time of hot air blowing is shown. Since each sample is a natural product and varies, three samples corresponding to each temperature and time were prepared and the carbonization depth of the three samples was entered. Samples were prepared with the hot air temperature in the range of 280 ° C. to 480 ° C. and the spraying time in the range of up to 20 minutes. Below 280 ° C., carbonization was insufficient even after prolonged heating. The center of the vertical length of each sample after carbonization was divided vertically with a cutter knife in the direction of the temporary canal, and the depth of the carbonized layer was measured while observing the cross section with a microscope. When the surface divided by the cutter knife was rough, it was observed after making it easy to see. In Table 4, x indicates that cracking occurred at that temperature and time.

  FIG. 12 is a graph in which the average values of the carbonization depths of the three samples at each temperature and hot air blowing time in Table 4 are plotted. It was found that the carbonization depth can be reached only up to around 3 mm. However, this level of carbonization is sufficient for some applications. The biggest attraction of the hot air method is that it can be carbonized easily on site. For example, it can be easily carbonized by blowing hot air onto a cut surface of wood cut on site.

The data in Table 4 is for the case where the surface layer of wood is not impregnated with water glass, but the A square material of Example 7 (water glass impregnation amount is 29.0 g / m ² ) is heated by a hot air method, The occurrence of cracks was observed and the carbonization depth was measured. Hot air of 360 ° C. was blown on the square glass impregnated surface with time as a parameter. In the square member not impregnated with water glass, the heating time in which cracks did not occur was up to 4 minutes, but the heating time in which cracks in the A square member did not occur extended to 15 minutes. It really stretched more than three times. Moreover, the carbonization depth also increased by a factor of 2 from 2.31 mm to 4.78 mm. These results are shown by the dotted line graph in FIG. Further, even when the carbonized surface was rubbed with a finger, black powder hardly adhered.

  In the hot air method, since the wood surface is not covered with the gas-impermeable member during heating, the pyrolytic vapor components generated by the heating freely diverge from the wood surface. Therefore, it is considered that cracks occur despite the small carbonization depth. For example, when hot air at 360 ° C. is used, cracks occur in 5 minutes, but when a hot plate at the same temperature is used, cracks occur in 10 minutes. At 380 ° C., cracking is prevented when the heated wood surface is covered with a gas-impermeable member so that cracking occurs in 3 minutes with hot air and 5 minutes with a hot plate. I understand that.

  A quartz glass tube heater (outer diameter 12 mm, effective light emission length of about 200 mm, output 560 W) was used as the infrared lamp, and an AC voltage of 100 V was applied to both ends of the heater so that it could be turned on and off with a switch. Sugibe wood having a length of 20 mm, a width (direction of the temporary road pipe) of 30 mm, and a height of 16 mm was used as wood, and the distance from the surface of the infrared lamp to the sample surface was set to 10 mm or 20 mm. Three samples were prepared for the same heating time. When the irradiation time became longer or when the distance between the lamp (consent with the heater) and the sample was small, the temperature of the wood surface increased rapidly and smoke was generated. The measurement was conducted paying attention to the conditions under which cracks do not occur. At a distance of less than 10 mm, smoke was intensely generated by irradiation for 1 to 2 minutes, and ignition was sometimes caused by irradiation for 3 to 5 minutes. When the surface to be carbonized is open, it cannot be deeply carbonized without cracking. However, it was confirmed that cracks are unlikely to occur when a quartz plate is placed on a square and irradiated with infrared rays from above.

  Table 5 shows the measurement results. Q in the distance between the lamp and the wood in Table 5 indicates a case where a quartz plate having a thickness of 2.4 mm is placed on the surface of the wood. As can be seen from Table 5, when there was no quartz plate, cracks occurred in the wood after 3 minutes of irradiation, but when there was a quartz plate, cracks occurred for the first time after 10 minutes of irradiation. Moreover, it has been confirmed that the carbonization depth increases to about twice that when there is no quartz plate. Also from this example, it was confirmed that when the wood surface was not covered with a gas-impermeable member during heating, the vaporized component generated by heating vaporizes from the wood surface, and thus cracks are likely to occur. In Table 5, x indicates that cracking occurred at that temperature and time.

  FIG. 13 is a graph in which the average values of the carbonization depths of the three samples at each measurement point in Table 5 are plotted. FIG. 13 clearly shows the effect of the quartz plate (gas impermeability, infrared transmissivity). 10, 11, and 12 have similar graph shapes, but it can be seen that the shape of the graph in FIG. 13 is completely different. That is, in FIG. 13, the carbonization depth increases rapidly with time. This difference is thought to be due to the fact that the temperature of the wood surface is constant in the former three, whereas the energy accumulated on the wood surface increases with time and the temperature of the wood surface increases with time in the latter. . As a condition for preventing cracks, it is important that the temperature of the wood surface does not exceed 450 ° C.

The A square timber in the examples below 7 (water glass impregnated amount 29.0 g / ^{m 2)} and B square bar (water glass impregnated amount 72.9 g / ^{m 2)} and samples, A as in the case not using the quartz plate Square and B squares were heated by an infrared method, the occurrence of cracks was observed, and the carbonization depth was measured. The surface of the square bar impregnated with water glass was made to face the heater. When the distance between the heater and the square bar surface was 10 mm, A square bar was used, and when the distance was 20 mm, B square bar was used. In FIG. 13, the graph displayed with a dotted line is data when the surface layer of wood is impregnated with water glass. The dotted line graph on the left is the case where the distance between the wood and the lamp is 10 mm, and the dotted line graph on the right is 20 mm. When the distance was 10 mm, the time during which cracks did not occur doubled, and the carbonization depth increased from 2.24 mm to 3.68 mm. Even when the distance was 20 mm, the time during which cracks did not occur doubled and the carbonization depth increased from 4.97 mm to 9.10 mm. Thus, by impregnating the surface layer with water glass, the irradiation time during which cracks do not occur is greatly extended, and the carbonization depth is also greatly increased. Further, even when the carbonized surface was rubbed with a finger, black powder hardly adhered.

  A portion from the tip of the pine cone having a cross section of 30 mm square to 50 mm was immersed in molten tin at 300 ° C. for 5 minutes and then pulled up. The carbonized surface was uniformly carbonized, almost black and free from cracks, and even when rubbed with a finger, black powder was hardly removed. FIG. 14A shows a photograph of the cut surface taken by cutting with a band saw at a position 15 mm from the tip at a right angle in the length direction. Next, two pine cones with a 45 mm square cross section were prepared, and the portion from the tip to 25 mm was dipped in molten tin at 300 ° C. for 4 minutes and the other was immersed for 10 minutes, then pulled up, and the tip of the carbonized part (B) and (c) in FIG. 14 are photographs obtained by cutting with a band saw perpendicularly to the length direction at a distance of 10 mm from the top and photographing the cut surface. 14A, 14B, and 14C, it can be seen that the smaller the thickness of the square, the closer the cross section of the carbonized layer is to a circle, and the longer the immersion time, the closer to the circle.

Next, 30 mm square and 45 mm square pine cones were cut to a length of 40 mm. These squares are floated on the surface of molten tin at 300 ° C. so that the length direction is horizontal, 30 mm squares every 5 minutes, and 45 mm squares every 10 minutes in all directions. Was rotated in contact with the molten tin bath. After the four surfaces in the length direction were carbonized in this manner, the steel was taken out of the tin bath and allowed to cool. 30 mm squares were floated in a tin bath for a total of 20 minutes, and 45 mm squares were floated for a total of 40 minutes. (D) and (e) of FIG. 14 are photographs in which the central part is cut with a band saw at right angles to the length direction after cooling and the respective cut surfaces are photographed. The innermost shape of the carbonized layer of any one is close to a square. As is apparent from FIG. 14, it is carbonized along the shape of the square material and the control of the thickness of the carbonized layer is ensured when dipping one surface at a time rather than dipping the four surfaces simultaneously in the molten metal bath. . Moreover, the square shape of the cross-section of the square bar is maintained as a perfect square. In contrast, when the entire square bar is immersed in a tin bath, the cross-sectional outer shape of the square bar is slightly distorted as can be seen from FIG.
(Comparative Example 1)

  In order to show the problems when carbonizing by heating in a normal electric furnace, the following tests were conducted. Place a Tokoname-yaki jar with an inner diameter of 230 mm and a height of 220 mm in an electric furnace (MODEL VIKING 66, manufactured by Paragon Industries, Inc., USA). Then, each was placed at the position of the apex of a regular triangle, and a stainless steel wire mesh (wire diameter: 0.45 mm, mesh opening: 2.09 mm, 10 mesh) was laid horizontally thereon, and the electric furnace was heated to 300 ° C. After 1 hour or more has passed since the set temperature in the furnace reached 300 ° C., so that the Tokoname jar and the wire mesh are completely at 300 ° C., a 30 mm square cross section of 50 mm long pine cones on the wire mesh The sample was placed vertically so that one of the cross-sections was down, heated at 300 ° C. for 5 minutes, then taken out of the electric furnace and allowed to cool. The double structure is used in order to prevent the sample from being irradiated with infrared rays from the heater in the electric furnace. Next, similarly, the pine cones having a cross section of 45 mm square and a length of 50 mm were heated at 300 ° C. for 5 minutes and then taken out from the electric furnace. Next, two kinds of pine cones were prepared in the same manner as described above, and samples each having a heating time of 10 minutes were prepared.

FIG. 15 is a photograph of the above sample, and FIGS. 15 (a) and 15 (b) are obtained by heating a pine pine having a cross section of 30 mm square and 45 mm square at 300 ° C. for 5 minutes, FIGS. 15 (c) and 15 (d). Is a pine pine having a cross section of 30 mm square and 45 mm square heated at 300 ° C. for 10 minutes. The top photo in FIG. 15 is the top surface of each sample (surface far from the wire mesh), the second photo is the side of each sample (the central horizontal straight line is the cut portion after carbonization), and the third photo Is the bottom of each sample, and the bottom photo is the cut surface of each sample. As is apparent from FIG. 15, in such heating by a normal electric furnace, the corner portion is preferentially carbonized, and the carbonization in the plane far from the corner proceeds only at a very low speed. The carbonization of the corner portion has progressed too much, and black powder can easily adhere to the finger when rubbed with the finger. When only one surface is heated by the molten metal method or hot plate method of the present invention, such a situation does not occur, and the heated surface is uniformly carbonized. Further, only the corner portion is not strongly carbonized. In the uppermost photograph in FIG. 15D, three cracks can be confirmed, and in the third photograph, six cracks can be confirmed. This is probably because the components thermally decomposed by heating can volatilize freely in the space and are generated when the square bar contracts. It can also be seen that the outer shape is slightly distorted from the square. The degree of heating was large as much as there was a wire mesh, and many cracks occurred as carbonization progressed. On the other hand, in the present invention, since the volatilization of the pyrolyzed component is prevented, thermal shrinkage hardly occurs, and therefore cracks hardly occur.
(Comparative Example 2)

In order to more clearly show the difference between the present invention and carbonization by heating in an electric furnace, the following test was conducted. An iron plate having a thickness of 10 mm and a size of 100 mm × 160 mm was used in place of the wire mesh of Comparative Example 1, and a pine cone having a cross section of 45 mm square and a length of 50 mm was heated for 10 minutes in the same manner as in Comparative Example 1. Immediately after heating, the sample was taken out of the electric furnace and allowed to cool. FIG. 16A is a photograph of the upper surface of the obtained sample, and it can be seen that it is carbonized in substantially the same shape as the upper surface of FIG. FIG. 16B is a side view of the sample (the horizontal line in the center is a cut portion), which is almost the same as the side view of FIG. FIG. 16C is a photograph of the bottom surface of the sample. Since the bottom surface was in contact with the metal plate, it was carbonized almost uniformly and deeply. FIG. 16D is a photograph of the cut surface of the sample. It can be seen that the corner is heavily carbonized, but the surface is not carbonized much. One crack (break) occurred on the upper surface (FIG. 16 (a)), but there was no crack at the bottom. In this way, it was confirmed that when the carbonized surface was covered with a gas-impermeable member, carbonization was performed uniformly and at the same time, cracking was difficult to occur. In the bottom surface (surface in contact with the wire mesh) in FIG. 15D, the progress of carbonization is slightly larger than the top surface, but as many as six cracks were generated. This is probably because the pyrolysis component volatilized from the gaps in the wire mesh. This effect also confirmed the effect of the gas-impermeable member of the present invention. FIG. 16 (e) is a photograph of the tip (bottom surface) of the sample of FIG. 14 (c) of Example 5 (45 mm square spruce pine immersed in molten tin for 10 minutes). As is apparent from FIG. 16 (c), the surface in contact with the iron plate is almost completely carbonized and uniform. When FIG. 16 (c) and FIG. 16 (e) are compared, FIG. 16 (c) has a lower concentration. This is because the iron plate of this comparative example is not a complete hot plate, but a sample is placed on it. This is because it took time to recover to 300 ° C.
(Comparative Example 3)

  Commercially available river sand (sand used for mixing cement with gravel) was placed in a Tokoname ware bottle (inner diameter 165 mm, height 175 mm) to a height of about 8 minutes. After putting this in the electric furnace of Comparative Example 1 and keeping it at 300 ° C. for 2 hours, an Ezo pine bar having a cross section of 30 mm square and a length of 200 mm is placed in this sand, and about 50 mm from the tip is in the sand. Was inserted diagonally at an inclination of about 45 ° C. The tip of the Ezo pine bar was processed into a bowl shape in advance so that it could easily enter the sand. When the square bar was inserted and left for 5 minutes, the corner was preferentially carbonized as in Comparative Example 1, and the in-plane was hardly carbonized.

  Cut commercially available MDF board (thickness 14 mm), commercially available radial tapain laminated timber (thickness 18 mm), commercially available veneer plywood (thickness 12 mm), and commercially available OSB plywood (thickness 12 mm) into 20 x 30 mm sizes. Three samples were prepared for each. The hot plate of Example 2 was set to 300 ° C., and a set of four types of four cut plates was simultaneously placed on the hot plate and heated for 10 minutes. This operation was performed in the same manner for each group, and the thickness of the carbonized layer of three samples was measured for each of four types of wood, and the average value was calculated. As a result, the MDF plate was 4.93 mm, the laminated material was 4.28 mm, the veneer plywood was 4.72 mm, and the OSB plywood was 4.40 mm. In either case, the results were close to those of Example 2.

  It is shown that when the wood surface layer is impregnated with water glass, the surface layer carbonization of the wood according to both the examples 1 and 2 is more effectively performed. That is, the heating time or heating temperature can be increased within the range where cracks do not occur, and the carbonization depth can be further increased.

Water glass (Showa Science Co., Ltd. No. 1 sodium silicate solution (water glass No. 1, very viscous fluid), hereinafter simply referred to as water glass) is diluted with water, and the weight ratio of water glass is 34% and 58%. An aqueous solution of was prepared. A small amount of these aqueous solutions was dripped onto a large number of cedar timbers similar to those in Example 1, spread uniformly with a glass rod, and then allowed to dry horizontally. A glassy film was not formed on the dried wood surface, and it is assumed that the wood surface layer was impregnated. The wood surface and the impregnated portion of the cross section were slightly darker in color, and the depth of impregnation was about 0.2 mm. The average weight increase of the wood after impregnating the wood with water glass and fully drying it was 0.47% for the water glass 34% solution and 1.10% for the 58% solution. The former is named A square and the latter is named B square. In terms of average coating weight, A square timber each 29.0g ^{/ m} 2, B square bar was 72.9 g / ^{m 2.}

  As in Example 1, the square A was immersed in molten tin at 360 ° C. for about 10 mm with the water glass impregnated surface down, and the location was changed by immersing it once every 15 seconds. It was lifted up and immersed in a place without slag. After 5 minutes, the A square was pulled up and allowed to cool. Similarly, a total of three samples were prepared and the carbonization depth was measured. The average carbonization depth of the three samples was 6.54 mm. Cracks did not occur. Next, after the A square was immersed in molten tin at 360 ° C. for 10 minutes in the same manner, the occurrence of cracks was observed and the carbonization depth was measured. Was 9.26 mm. Subsequently, the square A was similarly immersed in molten tin at the same temperature for 15 minutes. Cracks occurred in two of the three square bars. When the same experiment was performed on the B square, a crack occurred in one of the three pieces. In any case, cracks did not occur at the stage of 13 minutes. The squares not impregnated with water glass did not generate cracks for up to 5 minutes, but when impregnated with water glass, the time during which cracks did not occur doubled and the carbonization depth was nearly doubled. Increased to. These results are shown by the dotted lines in FIG. Similar effects can be obtained at other temperature conditions. Surprisingly, it was confirmed that when water glass was impregnated, black powder hardly adhered to the finger even when the carbonized surface was rubbed with the finger. A test similar to the above was performed on a square bar that was not impregnated with water glass, and samples having the same carbonization depth were compared. As a result, it was found that the sample impregnated with water glass was much less likely to get dirt on the fingers. This effect is very advantageous in practice.

  In the same manner as in Example 2, the A square bar and the B square bar were placed on a hot plate at 340 ° C. with the water glass impregnated surface down, and the occurrence of cracks and the carbonization depth were measured using the heating time as a parameter. As a result, the A square member did not crack until 20 minutes, and cracked after 30 minutes. The B square did not crack until 30 minutes. As can be seen from FIG. 11, in the square material not impregnated with water glass, cracks did not occur at a heating temperature of 340 ° C. until 15 minutes, so the time during which cracks did not occur doubled and the carbonization depth also increased. It has increased by about 50%. These results are shown by the dotted lines in FIG. Similar effects were obtained at other temperature conditions. As in the case of carbonization with molten tin, it was confirmed that black powder hardly adhered to the finger even when the carbonized surface was rubbed with the finger.

  The cedar wood having the same dimensions as in Example 3 was covered with an aluminum foil having a thickness of 13 μm on the upper and side surfaces of the cedar wood. The aluminum foil was squeezed and adhered so that no gap was formed between the upper surface of the cedar wood and the aluminum foil. The aluminum foil was also pressed against the side so that it did not rise. The surface (upper surface) covered with the aluminum foil of the sample thus prepared was placed on a hot plate at 340 ° C. in the same manner as in Example 2 and heated for 15 minutes. After cooling, the aluminum foil was removed and the carbonized surface was observed. As a result, the surface shape was very fine and smooth compared to the case without the aluminum foil. There were no cracks. The thickness of the carbonized layer was about 9 mm when there was no aluminum foil, whereas it slightly increased to about 10 mm when there was an aluminum foil. Even when the carbonized surface was rubbed with a finger, black powder hardly adhered.

  Four cedar woods having the same dimensions as in Example 3 are arranged in 2 rows and 2 columns on a workbench with an interval of 5 mm, and the upper surface (surface of 20 × 30 mm) is 5 mm thick and the size is 100 mm square. A stainless steel plate was placed. Four samples were arranged so as to be approximately in the center of the stainless steel plate. When the flame of the gas burner (Fujiwara Sangyo Co., Ltd. One-touch gas torch SK-11) was radiated for 1 minute from the upper side of the stainless steel plate so as to be emitted uniformly over the entire surface of the stainless steel plate, a little smoke was generated. Therefore, after extinguishing the fire for 30 seconds and radiating for 20 seconds after smoke completely disappeared, a little smoke was generated again. Then, after extinguishing again for 30 seconds, after the smoke disappeared, 20 seconds were emitted, and after that, the fire extinguishing for 30 seconds and the radiation for 20 seconds were repeated 9 times. A total of 11 repetitions were performed. After the last 20 seconds of radiation, the sample was allowed to cool, the stainless steel plate was removed, and the carbonized surface of the square was observed. No cracks were generated, and the average thickness of the carbonized surface layers of the three samples was 5.82 mm. . From the state of smoke generation, it is estimated that the temperature of the sample surface was always kept below 340 ° C.

  Next, instead of the stainless steel plate, an iron plate having a thickness of 1 mm and a size of 60 × 50 mm was placed on the same cedar square material as in Example 3, and a gas burner was emitted for 10 seconds in the same manner as described above. A little occurred. So, after the fire was extinguished for 10 seconds, the smoke stopped. This was repeated 12 times. Then, after standing to cool and removing the iron plate, the thickness of the surface carbonized layer of the sample was 2.39 mm. The carbonized surface was very smooth and free from cracks. Judging from the state of smoke generation, it is presumed that the surface temperature of the sample was kept below 300 ° C. Next, instead of the above iron plate, an iron plate having a thickness of 0.3 mm and a size of 60 × 50 mm was placed on one cedar square material similar to the above, and the gas burner radiation and extinguishing were repeated in the same cycle as above. When the gas burner was radiated for 10 seconds, intense smoke was generated from the squares, and the edges ignited but soon disappeared spontaneously. When the steel plate was removed and the carbonized surface was observed, many cracks were generated. The surface temperature of the sample is estimated to be 450 ° C. or higher. Therefore, the gas burner radiation and fire extinguishing cycle was repeated for 5 seconds, and fire extinguishing for 10 seconds. There was no generation of cracks, and the thickness of the surface carbonized layer was 2.09 mm. When the thickness of the metal plate placed on the square bar is reduced in this way, the temperature of the metal plate rapidly rises due to gas burner radiation. It is important to choose

  An iron plate having a thickness of 1 mm and a size of 60 mm × 50 mm is placed on the upper surface (20 × 30 mm surface) of the cedar wood having the same dimensions as in Example 3, and using the same heat gun as in Example 3, hot air at 340 ° C. When sprayed for 5 minutes, the surface of the wood was hardly colored. Then, when the temperature of the hot air was raised to 400 ° C. and heated for 10 minutes, it became a little dark (brown). The carbonization depth of the surface layer was 2.46 mm. Next, when a similar experiment was performed using an iron plate having a thickness of 0.3 mm and a size of 60 × 50 mm instead of the iron plate having a thickness of 1 mm, a black carbonized layer having no crack and a thickness of 3.21 mm was obtained. Obtained. On the other hand, the upper surface (20 × 30 mm surface) and side surface (the whole surface in the height direction) of the cedar wood are covered with an aluminum foil having a thickness of 17 μm. The aluminum foil was squeezed so that there was no contact. The sample prepared in this manner was sprayed with hot air at 400 ° C. for 5 minutes from above the aluminum foil, and then the aluminum foil was removed. As a result, many cracks were generated on the surface of the carbonized layer. Since the aluminum foil is a thin metal, the temperature of the sample surface was brought close to 400 ° C. by hot air at 400 ° C., and the heating time was increased to 5 minutes, so cracks occurred. The iron plate or aluminum foil became a hot plate and the wood was heated in the same way as the hot plate method, but if the thickness of the metal plate is large, the efficiency of heating with hot air is bad, conversely when it becomes thin like an aluminum foil, It is important to select an appropriate temperature and time because it is easily heated.

  A cedar wood having the same dimensions as in Example 3 was used as a square material sample, and a black surface-treated iron plate having a thickness of 1 mm and a size of 60 mm × 50 mm was placed on the upper surface (surface of 20 × 30 mm), as in Example 4. A quartz glass tube heater was disposed so that the distance from the heater to the upper surface of the sample was 10 mm. After applying voltage to the heater and irradiating with infrared rays for 2 minutes, voltage application was stopped for 5 seconds, voltage was applied for 25 seconds, and then voltage application was stopped for 5 seconds. Thereafter, after applying voltage application for 25 seconds and stopping application of voltage for 16 seconds in this manner, the sample was checked after being allowed to cool. The carbonized surface was very smooth and free from cracks. The average thickness of the surface carbonized layer of the two samples thus prepared was 3.70 mm. It was estimated that the temperature of the surface of the sample was kept at 300 ° C. or lower because there was almost no smoke during repeated ON / OFF of voltage application. In addition, when the same experiment was conducted using an aluminum foil instead of the black iron plate, the square bar was hardly colored. That is, the aluminum foil reflected infrared rays and was not heated very much. Therefore, a member that absorbs infrared rays well is required for this purpose.

  Example 12 is an example in which the heat roll is rotated and moved on the surface of the plate-like wood to carbonize the surface layer of the wood, but it is difficult to obtain a heat roll with a built-in heater. The thing which floated the aluminum roll in the bath was used. An aluminum roll having a diameter of 30 mm and a length of 100 mm was used. When an aluminum roll was floated on a tin bath melted in a stainless steel bat in the same manner as in Example 1, about 18 mm of the aluminum roll was exposed from the bath surface perpendicularly from the bath surface. The temperature of the tin bath was set to 400 ° C. Next, put a cedar board with a cross section of 30 x 14 mm and a length of 300 mm on the aluminum roll so that the 30 x 14 mm surface is in contact with the aluminum roll and the aluminum roll and the cedar board are orthogonal to each other, and apply a little load. The cedar board was slowly moved horizontally in a state where about two-thirds of the aluminum roll was immersed in the tin bath. When the cedar board was moved, the aluminum roll rotated slowly in synchronization with the movement of the cedar board. The cedar board was moved 50 mm over 5 minutes. During this time, no smoke was generated. Therefore, it is estimated that the surface temperature of the cedar board where the aluminum roll and the cedar board are in contact was 340 ° C. or less. The carbonized surface was sufficiently blackened, and the carbonization depth was 1.19 mm. From the above experiments, it was confirmed that the wood surface can be carbonized by a hot roll.

  The hot plate was heated to 340 ° C. in the same manner as in Example 2. A testicle rod having a diameter of 20 mm and a length of 30 mm was placed on the hot plate, moved while slowly rotating, and when it was rotated about half a round over 8 minutes, the testicle rod was taken out of the hot plate and allowed to cool. After cooling, the carbonization depth was measured and found to be 1.34 mm.

  Next, testicle bars with the same dimensions as above and testicle bars with the same dimensions covering almost half of the circumference with 13μ thick aluminum foil are placed on a hot plate at 340 ° C, left for 15 minutes, and then covered with aluminum foil The untested testicle rod was lifted by grasping it with tongs, and when the portion of the testicle rod that was in contact with the hot plate was observed, no cracks were generated. The time required for this confirmation work is 7 to 8 seconds. Therefore, this testicle rod was immediately returned to the hot plate so that the same place was heated, and both were additionally heated for 5 minutes, then removed from the hot plate and allowed to cool. A number of large cracks occurred on the testicle bar not covered with the aluminum foil, but no crack occurred on the testicle bar covered with the aluminum foil. Thus, when the contact area with the hot plate is small, the effect of covering with the aluminum foil is tremendous.

  In Example 2, the temperature of the hot plate was set to 340 ° C. by the hot plate method, and even if the carbonized surface of the sample heated for 15 minutes was rubbed with a finger, almost no black powder adhered. Adhered to tissue paper. When the carbonized surface of such a sample was impregnated with water glass in the same manner as in Example 7, no powder adhered even when rubbed strongly with tissue paper. When paint was applied instead of water glass (Atom Support Co., Ltd. water-based spray ivory), the appearance became ivory. After fully drying, after sticking an adhesive tape (Sumitomo 3M Co., Ltd. Scotch Super Transparent Tape S) and then peeling off, all peeled off partially. The carbonized layer was thinly attached to the part that adhered to the tape and peeled off. The carbonized layer is relatively fragile on the surface side, and it is considered that water glass and aqueous spray do not reach the inside of the carbonized layer. Since the carbonized layer is relatively lipophilic, it is considered that the aqueous coating agent does not have good adhesion to the carbonized layer.

  Next, an organic solvent liquid of polysiloxane (manufactured by Shinagawa White Brick Co., Ltd. (current Shinagawa Refractories Co., Ltd.) NIC-C5) 3 drops of a solution in a mixed solvent of butyl acetate and a dropper were spread with a dropper and spread over the entire surface with a glass rod. Since the dropped liquid permeated in several tens of seconds, this operation was repeated again and then left to dry naturally. After the solvent was completely dried, no black powder adhered even when the surface of the sample was strongly rubbed with tissue paper. Next, when an adhesive tape peeling test was performed in the same manner as described above, no peeling occurred.

  Instead of the above polysiloxane, an organic solvent-based paint (Atom Support Co., Ltd. Lacquer Spray E, brown) was sprayed once. The coating was very smooth and glossy. When the adhesive tape peeling test was performed in the same manner as described above after drying for 3 hours, no peeling occurred.

  The wood obtained by the present invention has higher mechanical strength than wood (thermo wood) obtained by a conventional carbonization method, and can therefore be used as a structural material that was difficult with thermo wood. Moreover, since carbonization can be performed at a temperature higher than the carbonization temperature of the thermowood, a greater antiseptic effect can be obtained. The present invention can also be used for grilled piles used outdoors such as fields and gardens. It can be used in most other fields where wood is used. It is thought that it can contribute to the development of the Japanese timber industry, including the effective use of thinned wood.

DESCRIPTION OF SYMBOLS 1 Wood 2 Aluminum foil 3 Hot plate 4 Hot melt metal bath 5 Hot melt metal bath container 6 Force applied to wood

In view of the background art as described above, the present inventor speculates that the problem is that carbonization by the flame method is performed in the air, and when a wooden square is immersed in a solder bath, a stunning carbonized layer without cracks I found out that Next, when hot air (heat gun) having a temperature much lower than that of the flame was blown, it was found that cracking was likely to occur, although it was much reduced compared with carbonization by a gas burner. Compared with heating by flame, heating by solder bath and heating by hot air, heating by flame or hot air can volatilize freely, but heating by solder bath prevents volatilization of pyrolysis components, so cracks The hypothesis is that the occurrence will be prevented. Therefore, when a wooden square was placed on a hot plate and heated, it was found that a thick carbonized layer without cracks was obtained as in the case of a solder bath. In addition, when a glass plate was placed on a wooden timber and heated by emitting infrared rays from above, the generation of cracks was greatly improved. From these results, it is considered that volatilization of the pyrolysis component due to heating is prevented. Furthermore, when the surface layer of wood was impregnated with water glass and heated with hot air, the generation of cracks was greatly improved. It was found that impregnation with water glass on the surface layer of wood has a great effect even in other heating methods. The presence of water glass prevented the pyrolysis components from volatilizing. The present invention was derived from these results.
It is known that water glass slowly changes to silicic acid by carbon dioxide in the air. It is also known to supply an acidic liquid to water glass in order to change the water glass into silicic acid in a short time. The same applies to water glass impregnated in the surface layer of wood. In particular, when an aqueous acetic acid solution is supplied to the water glass impregnated in the wood surface layer as an acidic liquid, it is instantly changed to silicic acid. Both acetic acid and sodium acetate are used as food additives and are safe substances, and are effective in the present invention.

  The present invention relates to a method for carbonizing a surface layer of a wood or woody material.

  In order to improve the antisepticity, weather resistance, etc. of wood, it has long been known to carbonize the surface by exposing it to a flame. For example, if burnt cannabis or newspaper is used to burn one side of a board and the baked side faces the outside, it is known to have nearly 100 years even when exposed to wind and rain. Yes. At present, such a method is hardly performed, and a part of the surface layer is carbonized by baking a plate with a gas burner or an oil burner. Although the carbonized layer formed by such a method is thick, the surface is not smooth and flat, and innumerable creases (appears like cracks, hereinafter, cracks are simply referred to as cracks). This surface layer has a low mechanical strength, and black powder adheres to the finger just by lightly rubbing it with a finger. Moreover, when it rubs strongly with a hand or when an object collides, it will peel easily on the part of a crack. The thickness of the carbonized layer at the bottom of the crack is much smaller than the thickness of the portion without the crack. Since there is a risk of water entering from these cracks, it is necessary to avoid the occurrence of cracks. Obviously, if the crack is not formed, the life of the plate whose surface layer is carbonized is further extended.

  1 (a), (b), and (c), the inventor has shown that the pine board A (thickness 24 mm, width 60 mm, length 65 mm), cedar wood B (thickness 14 mm, width 45 mm, length) 90 mm) and cedar wood material C (thickness 14 mm, width 45 mm, length 65 mm), a gas burner (HBA-1700G manufactured by Kinboshi Co., Ltd.) flame (1000 ° C. or higher) was sprayed on the surface, It is the photograph of the surface in which the crack was formed. The photo (a) was baked by blowing a flame of a gas burner on Ezo pine A for 30 seconds, the photo (b) was blown by cedar wood B for 30 seconds, and the photo (c) was baked on cedar wood C by 10 seconds. FIG. 2 is a photomicrograph of a cross section including one of those cracks. Photo (a) is a cross-sectional microscope of Ezomatsu A, photo (b) is Sugibe wood B, and photo (c) is a cross-section microscope of Sugibe wood C. It is a photograph. As can be seen from FIG. 2, the cross section of the crack is the cross section of the crater, and the thickness of the carbonized layer at the bottom of the crack is significantly smaller than the thickness of the portion where there is no crack. The thickness of the carbonized layer at the bottom of the crack in the photograph (a) in FIG. 2 is 1.0 mm, whereas the thickness of the carbonized layer at the portion without the crack is 1.7 mm. The thickness of the carbonized layer at the bottom of the crack in the photograph (b) in FIG. 2 is 0.8 mm, whereas the thickness of the portion without the crack is 1.8 mm. Thus, the thickness of the carbonized layer is greatly reduced in the crack portion.

  The reason for the formation of cracks is that when a plate is exposed to a high-temperature flame in the air and the volatile components generated by thermal decomposition burn on a part of the surface, it preferentially volatilizes and burns on that part, This may be due to a sudden decrease in volume, or when pyrolysis components volatilize and burn from the entire surface exposed to a high-temperature flame, the volume decreases, and the shallow lake water dries out and the mud at the bottom of the lake dries out. It seems to be like a crack.

  FIG. 3 shows that the inventor used a commercially available gas burner (Fujiwara Sangyo Co., Ltd. One Touch Gas Torch SK-11) to radiate a flame (1000 ° C. or higher) to a pine pine board (cross section: 14 × 45 mm). It is the graph which plotted the thickness of the carbonization layer with respect to. The flame strength of this gas burner was much weaker than that of the aforementioned Kimbosi Co., Ltd. product. Three samples were prepared at the same radiation time while keeping the strength of the flame and the distance from the surface of the Ezo pine to the burner, plotting their carbonized layer thickness, and showing the polynomial approximation curve. It can be seen visually that cracking occurs when the radiation time is 4 seconds or longer. Furthermore, cracks increase as radiation continues. The thickness of the carbonized layer where there is no crack when the radiation time is 4 seconds is about 0.4 mm. Thus, the thickness of the carbonized layer that can be carbonized in a range where cracks do not occur is very small.

  Patent Document 1 shows that an anti-rotation wood having high hygroscopicity can be obtained by heating the surface of wood with a gas burner to form a carbonized layer having a thickness of 0.2 mm. It is known that even if such a thin carbonized layer is formed on the surface layer, it has an anti-corrosion effect, but such a thin carbonized layer provides sufficient weather resistance, antiseptic properties, and ant-proof properties. I can't. As a building material used in places exposed to wind and rain such as outer walls and fences, a thickness of 3 mm is usually required. In the surface carbonization by a gas burner, if an attempt is made to obtain a carbonized layer having this thickness, cracks will occur on the surface.

  In Patent Document 3, the whole of red pine is immersed in 460 ° C. molten zinc for 10 seconds to provide a carbonized layer on the surface, and the red pine is immersed in 300 ° C. molten salt for 5 to 10 seconds to carbonize on the surface. It is described that a layer is provided.

  However, as shown in FIG. 9 and Table 2 of the present invention, when floating in molten tin at 500 ° C. for 15 seconds, cracks are generated in the surface layer. Although not shown in FIG. 9 and Table 2 of the present invention, according to the experiment results of the present inventor, when wood is floated on molten tin at 500 ° C. for 10 seconds, cracks do not occur, but the carbonized layer at that time The thickness was very small, 0.45-0.52 mm. According to an experiment in which wood is immersed in a 300 ° C. tin bath for 10 seconds instead of 300 ° C. molten salt, the thickness of the surface carbonized layer is about 0.2 mm.

  The thickness of the carbonized layer obtained under the conditions shown in Patent Document 3 is not a carbonized layer having a practically sufficient thickness, and performance such as antiseptic properties, weather resistance, and ant-proof properties is insufficient. As a building material used in places exposed to wind and rain such as outer walls and fences, a thickness of 3 mm is usually required. Further, Patent Document 3 does not show conditions for increasing the thickness of the carbonized layer, and does not describe any cracks that may occur when carbonized under the conditions for increasing the thickness. Naturally, this document does not describe how to prevent the occurrence of cracks that occur when the carbonized layer is 0.7 mm or more. Moreover, when the whole wood is immersed, problems as described in paragraph number 0104 and paragraph number 0105 described later occur.

  Patent Document 4 describes that wood is pressed and clamped by a mold for three-dimensional processing, and one side of the wood is carbonized by setting one of the molds to a temperature higher than the carbonization temperature of the wood. ing. However, there is no description or suggestion as to how carbonization can be performed so that cracks do not occur under such conditions. In the present invention, instead of using a metal mold, a method that does not cause cracks has been found by extensively examining the heating temperature and the heating time in a state where the hot plate is in contact as described later.

An object of the invention of Patent Document 4 is to make a carbonized layer conductive and use it for the purpose of electromagnetic shielding. However, in order to carbonize wood to make it conductive, as described in Non-Patent Document 4, page V-5, lines 16 to 18, high temperature of 800 ° C. or higher in an inert atmosphere. It is necessary to carbonize. Up to a temperature of about 600 ° C., the insulating material has a volume resistivity of 10 ¹² Ω · cm or more, and at a heating temperature of 600 to 700 ° C. exceeding this, a semiconductor having a volume resistivity of 10 ² to 10 ⁹ Ω · cm. When the temperature exceeds 800 ° C., conductivity of 10 Ω · cm or less is shown, and it is shown that the conductivity is improved as the temperature rises. When wood is brought into contact with a metal at 800 ° C. in the air, cracks are instantaneously generated on the surface of the wood. When the metal plate at 800 ° C. is separated from the wood surface, the wood surface starts to burn.

  Patent Document 4 describes that a wood surface is carbonized by a gas burner to make it conductive. Actually, even if baked for a short time with a gas burner, the carbonized layer does not become conductive. This is because when the wood burns with the gas burner, the temperature rise on the wood surface is suppressed by the heat of vaporization. This is known as the principle of preventing the satellite from burning out due to frictional heat with the air when returning to the earth. In order to burn wood and obtain a conductive carbonized layer, it is necessary to burn until the inside of the wood is red-hot and cool it in a place without air, or quench it with water. If wood of several mm thickness is burned in this way, it will burn out. Therefore, it is actually impossible to make the wood surface conductive with a gas burner.

  In place of the above-mentioned carbonization method using flame, recently, wood preservative treatment using chemicals has become common. A variety of drugs have been developed and used for this purpose. In order to infiltrate the drug inside the wood, various processes are used, such as forming cracks and holes in the wood, injecting the drug under reduced pressure, pressurizing after the reduced pressure injection of the drug, and injecting further into the interior Has been. However, when wood is used as a building material or civil engineering material, there is a concern about the influence of drugs on humans and the natural environment.

  On the other hand, in Scandinavia, it has been practiced for several decades to improve the antiseptic properties, weather resistance, heat resistance, ant repellency, etc. by treating wood with high temperatures. For example, if wood is left in an atmosphere where water vapor of 180 to 220 ° C. is present for about 2 to 20 hours, the inside of the wood is uniformly colored (it is considered that light carbonization has been performed), and the higher the processing temperature, the more colored. Increases the antiseptic and weather resistance. Although it has recently become known in Japan, it has not yet become widespread. In Scandinavia it is called thermowood and is widely used. The reason why the above temperature range is selected is that if the temperature is lower than this temperature, the effect hardly appears, and if the temperature is higher than this temperature, the mechanical strength of the wood sharply decreases. It is described on page 5-4 of Chapter 4. It is described that this high-temperature treatment significantly improves antiseptic properties, weather resistance, etc., but has almost no ant-repellent properties. Non-Patent Document 1, pages 17-4 and 18-4 describe that the use in the ground is not recommended because the antiseptic performance is insufficient at a processing temperature of 220 ° C. However, FIG. 13-4 on page 18-4 of Chapter 4 shows that the antiseptic performance and the ant proof performance are perfect when the processing temperature is 240 ° C. or higher. Further, since the mechanical strength is lower than that of the wood before treatment even at a treatment temperature of 220 ° C., it is warned not to use it as a base part or a structural material. A feature of the thermowood production method is that the processing temperature and the processing time are selected so that the mechanical strength and the antiseptic performance are moderately satisfied. According to the present invention, not only can carbonization be performed at a temperature higher than that in the thermowood production method, but also mechanical strength can be maintained. Thermowood is carbonized entirely from the surface to the inside.

  In Patent Document 2, in addition to heating wood in a high-temperature gas atmosphere, the wood is kept in contact with a bath of high-temperature liquid (for example, silicon-based oil, paraffin) or high-temperature granular material (for example, sand) for a long time. A method is described in which the inside is carbonized to form a thermowood. These liquids and particulates have very low thermal conductivity, so the efficiency of transferring heat to the wood is poor. Since the thermal conductivity is small, if the surface layer is carbonized to a certain depth (for example, around 5 mm), it must be carbonized over several tens of minutes, so if the sand temperature is high, Wood may catch fire or burn.

  Non-Patent Document 2 describes heat treatment with molten wax heated to 100 ° C. or higher, rapeseed oil heated to 180 ° C. to 220 ° C., cottonseed oil, or the like. It also describes heat treatment with mineral oil and silicon oil. However, these oils have a problem that it is difficult to heat to a high temperature as the wood is carbonized. Waxes, mineral oils, vegetable oils, silicone oils, etc. have a problem that the components volatilize or burn when heated to 240 ° C. or higher, so the maximum use temperature is limited. There is also a problem that the oil deteriorates by repeated use. Furthermore, as will be described later (particularly, Example 5), there arises a problem that the entire surface is heated simultaneously.

  Non-Patent Document 3 describes the results of research on carbonization of plywood by radiant heating. Although it is shown that carbonization is carried out to a depth of about 10 mm from the surface of the plywood toward the inside by radiant heating, there is no description of cracks. However, it has been confirmed that cracks are generated in a very short time when strong radiation heating as described in Non-Patent Document 3 is performed.

  It is known to heat wood in an electric furnace or a high-temperature chamber. For example, square wood is put in an electric furnace with an internal temperature of 300 ° C. and left until the surface is sufficiently colored (dark brown to black). Then, there is a problem that the corner of the square bar becomes brittle even if it is strongly carbonized. Furthermore, the time until the surface is sufficiently colored is several minutes to several tens of minutes, but when this is taken out of the electric furnace and cooled to room temperature, the square material is cut and the cross section is observed. It is difficult to perform surface layer carbonization. If the depth of the surface layer carbonization is kept small, the coloring of the surface becomes insufficient. Such a phenomenon was confirmed to be the same in the case of heating with the sand. It has been found that this phenomenon occurs because wood is simultaneously heated from all sides (periphery).

  The branding technique has been used for a long time. For example, it is common to form a brand name on a wooden box, a kamaboko base plate, or a leather surface. These cases are characterized by being heated to a high temperature as the baking mold becomes red-hot and instantaneously pressed against the object. Also, one of the features of the brand mark is that the portion is considerably depressed by evaporation due to thermal decomposition. In these cases, it is required that the formation of the burning mark be completed in a short time (almost instantaneously), and the baking mold is heated to a high temperature as it is red-heated, and is completed by the momentary or very short time pressing. In the branding method, the surface can be colored (carbonized) sufficiently deeply, but it is difficult to carbonize deep inside.

  It is known as a hobby to draw freehand images on wood, leather, resin plates, etc. with a hot pen, electric scissors or the like heated to about 400 ° C. or more. In these hobbies as well as in the above-mentioned branding technique, it is required to imprint or draw in a short time. Therefore, the temperature of the mold and the bowl is naturally required to be about 400 ° C. If the temperature is low, the time during which the baking mold is pressed or the time during which the ridge is pressed in one place becomes long, making practical use difficult. As described above, in the image-printing technique and the drawing by the wrinkle, a very high-temperature baking mold or wrinkle is used, but when the high-temperature baking mold or wrinkle is pressed against the same place for several seconds, that portion Is very darkened (blackened), and when the surface is rubbed with a finger, not only the black powder adheres to the finger, but also the carbonized part becomes considerably depressed. Such a phenomenon is not so much a problem in the case of stamping or freehand drawing, but it becomes a big problem when carbonizing a surface layer with a large area of wood as used in construction etc. is there. In addition, if you try to increase the carbonization depth by using the branding or thermal pen technology, if a trowel or thermal pen is pressed against the same place on the wood surface, cracks will occur before the carbonization depth of the required thickness is obtained. Resulting in.

In view of the background art as described above, the present inventor speculates that the problem is that carbonization by the flame method is performed in the air, and when a wooden square is immersed in a solder bath, a stunning carbonized layer without cracks. I found out that Next, when hot air (heat gun) having a temperature much lower than that of the flame was blown, it was found that cracking was likely to occur, although it was much reduced compared with carbonization by a gas burner. Compared with heating by flame, heating by solder bath and heating by hot air, heating by flame or hot air can volatilize freely, but heating by solder bath prevents volatilization of pyrolysis components, so cracks The hypothesis is that the occurrence will be prevented. Therefore, when a wooden square was placed on a hot plate and heated, it was found that a thick carbonized layer without cracks was obtained as in the case of a solder bath. In addition, when a glass plate was placed on a wooden timber and heated by emitting infrared rays from above, the generation of cracks was greatly improved. From these results, it is considered that volatilization of the pyrolysis component due to heating is prevented. Furthermore, when the surface layer of wood was impregnated with water glass and heated with hot air, the generation of cracks was greatly improved. It was found that impregnation with water glass on the surface layer of wood has a great effect even in other heating methods. The presence of water glass prevented the pyrolysis components from volatilizing. The present invention was derived from these results.
It is known that water glass slowly changes to silicic acid by carbon dioxide in the air. It is also known to supply an acidic liquid to water glass in order to change the water glass into silicic acid in a short time. The same applies to water glass impregnated in the surface layer of wood. In particular, when an aqueous acetic acid solution is supplied to the water glass impregnated in the wood surface layer as an acidic liquid, it is instantly changed to silicic acid. Both acetic acid and sodium acetate are used as food additives and are safe substances, and are effective in the present invention.

  Patent Document 5 describes that wood impregnated with a flame retardant is further impregnated with water glass. The purpose is to delay the fall of the burned part by burning the wood surface into a flame at 840 ° C., burning the wood and penetrating to the back side. When not treated with water glass, it penetrated to the back side in 28 minutes, but when treated, it penetrated in 30 minutes. In the invention of Cited Document 5, the water glass is described as “acts so as to melt into a glass state under high temperature overheating to fix the carbonized residue”. On the other hand, in this invention, since it heats only to 450 degrees C or less, water glass does not fuse | melt to a glass state. Moreover, in this invention, the temperature area | region where wood burns is not included. In Patent Document 5, there is no consideration or description as to how water glass affects the occurrence of cracks.

JP 2002-283308 A Japanese Patent No. 3898764 JP-A-226303 JP 2007-98640 A JP 2004-181804 A

Published by ThermoWood Handbook Finnish Thermo Wood Association (August 4, 2003) Momohara Ikuo Heat Treatment and Durability Published by Japan Wood Conservation Society Journal “Wood Preservation” Vol.31-1 (2005) Saburo Uesugi Carbonization of plywood by radiant heating Forestry Experiment Station Research Report No. 340 (1986) 4. Professor Emeritus, Kyoto University Shigehisa Ishihara From wood to charcoal-Can charcoal become a functional material? New development by carbonization of woody materials Japan Wood Society (2004)

  The object of the present invention is to overcome the disadvantages of the conventionally known burned cedar and thermowood, in particular without using a chemical such as a preservative, without substantially reducing the mechanical strength of thick (thick) wood or woody materials. Without cracking the surface layer of wood or wood material, at least a part of the surface layer of wood or wood material is uniformly carbonized to a thickness of 0.7 mm or more (colored from black to brown) ) To provide a surface layer carbonization method capable of enhancing antiseptic properties, weather resistance, ant repellency, and the like, and to provide a product obtained by the method.

  A first method for solving the problems of the present invention is to keep the surface temperature of 240 ° C. to 450 ° C. on the surface of a carbonized region of wood or woody material while preventing volatilization of pyrolysis components. The region is carbonized to a required depth of 0.7 mm or more, that is, a desired depth, from the surface toward the inside by supplying controlled thermal energy.

  Method A for preventing volatilization of pyrolysis components in the first method of the present invention is to contact a gas-impermeable member so as to cover at least a part of the surface of the wood or wood material to be carbonized. In a state, by supplying controlled thermal energy from the member, the region is carbonized from its surface inward to the required or desired depth. In the present invention, the meaning of “contact” in “contacting a gas-impermeable member with wood” is the same as “adhesion”. For example, during carbonization of a wood flat plate, the pyrolysis component generated from the wood flat plate is In order to prevent volatilization freely, it is used in the sense that the metal plate is closely attached so as to cover the surface of the wood flat plate.

  The method for supplying thermal energy from the gas impermeable member is a method of supplying a gas impermeable member of molten metal, hot plate, hot foil, or hot roll at 240 ° C. to 450 ° C. to the surface of the wood or wood material. Is to contact. By controlling the temperature of the gas-impermeable member and the contact time with 15 seconds or more, it is possible to carbonize to a required depth of 0.7 mm or more from the surface of the wood or wood material toward the inside. .

  Method B for preventing volatilization of pyrolytic components is a method in which a member such as a glass plate which is impermeable to gas and transmits infrared rays is brought into contact with the surface of the wood or wood material, and the wood or wood material is transmitted through the member. Is to irradiate infrared rays while maintaining the surface of 240 ° C to 450 ° C. By controlling the energy intensity and irradiation time of infrared rays, carbonization is performed to a necessary depth of 0.7 mm or more from the surface of the wood or woody material toward the inside.

  Method C for preventing volatilization of pyrolytic components is to apply the method A or B after impregnating the surface layer of wood or wood material with water glass, or water glass to the surface layer of wood or wood material. Is impregnated with infrared rays so that the surface temperature is 240 ° C to 450 ° C. Water glass impregnated in the surface layer of wood or woody material prevents volatilization of the pyrolysis component and prevents the generation of cracks.

  A second method for solving the problem of the present invention is to blow hot air at a temperature of 280 ° C. to 480 ° C. on the surface of the carbonized region of the wood or woody material, so that the region is directed from the surface toward the inside. Carbonization to the required depth, ie the desired depth. The generation of cracks was greatly improved by blowing hot air at a temperature much lower than that of the gas burner flame. Also in the second method for solving the problems of the present invention, it is very effective to impregnate wood with water glass before blowing hot air.

  In the present invention, gas impermeability does not mean that gas is not completely transmitted, but does not substantially transmit gas. That is, the thermal decomposition component generated during the carbonization treatment has a gas impermeability that does not pass through the member. For example, it may be a porous material that allows gas to pass through very slowly, such as pottery or unglazed.

In the present invention, “wood or woody material” is hereinafter simply referred to as wood. According to the present invention, by carbonizing by controlling the temperature and time, the wood is only carbonized from the surface to the inside to the required depth, so that the inside has the same mechanical strength as the original wood. To do. In addition, the surface layer of wood is much stronger than in the case of the manufacturing method of thermowood, that is, it can be carbonized at high temperature, so that performances such as antiseptic and ant repellency can be obtained far superior to thermowood. . Furthermore, since it is not necessary to use a preservative, a product having no adverse effects on the human body and the environment can be obtained. According to the method of the present invention, it is possible to obtain a uniform thickness and durability of the surface carbonized layer, which could not be realized by the conventional combustion method and gas burner method. That is, there can be obtained a surface carbonized layer which is free from cracks, has a sufficient thickness, can have a surface color of brown to black, and can hardly remove colored powder even if the surface is rubbed with a finger. Furthermore, according to the method of the present invention, it is possible to easily carbonize the surface layer of only one surface or a part of the surface of the wood or a part of the surface. In addition, the surface layer of wood having a curved surface or a complicated shape can be carbonized. For example, it is possible to easily carbonize a square member having a tenon or a tenon hole, or a square member having a groove or a hole, and a great many applications can be considered. When the surface layer carbonized wood is cut with a saw at a construction site, a non-carbonized portion is exposed on the cut surface, and this surface can be carbonized on the site.
Conventionally, a process of removing a brittle surface layer by rubbing the surface with a brush to remove cracks generated on the surface after forming the surface carbonized layer with a gas burner and so as not to get dirty when touched by hand Was sometimes done. However, when such a process is performed, there is a defect that the thick carbonized layer formed at the corner becomes thin. According to the present invention, such a problem is also solved.

FIG. 1 is a photograph showing the occurrence of cracks on the wood surface carbonized by a gas burner. FIG. 2 is a photomicrograph of a cross section of a portion where cracks in the wood of FIG. 1 occur. FIG. 3 is a graph in which the thickness of the carbonized layer of a sample prepared by a gas burner is plotted, and shows the conditions under which cracks start to occur. FIG. 4 is a surface photograph (a) of a carbide carbonized by the molten metal method and a cross-sectional micrograph (b) of a cracked portion. FIG. 5 is a side sectional view of one specific example of the hot plate system of the present invention. FIG. 6 shows a surface photograph (a) and a cross-sectional micrograph (b) of a crack in which a crack is generated when the temperature of the hot air is high in the hot air method. FIG. 7 shows a photograph of the surface of carbonized by the hot air method. Photo (a) shows the case where hot air of air is used, and photo (b) shows the case where hot air of carbon dioxide gas is used. FIG. 8 is a side sectional view of one specific example of the hot plate system of the present invention. FIG. 9 is a surface photograph taken by arranging samples prepared by the molten metal method of the present invention. FIG. 10 is a graph in which the carbonization depth of the sample prepared in Example 1 is plotted. FIG. 11 is a graph plotting the carbonization depth of the sample prepared in Example 2. FIG. 12 is a graph in which the carbonization depth of the sample prepared in Example 3 is plotted. FIG. 13 is a graph plotting the carbonization depth of the sample prepared in Example 4. FIG. 14 is a cross-sectional photograph of the sample prepared in Example 5. FIG. 15 shows various photographs of the sample created in Comparative Example 1. FIG. 16 shows various photographs of the sample created in Comparative Example 2. FIG. 17 is a graph plotting the temperature immediately before the occurrence of a crack, with the horizontal axis representing the wood surface temperature and the vertical axis representing the heating time logarithmically based on the data of Example 1 and Example 2. FIG. 18 is a graph plotting the data of Example 2 with the horizontal axis representing the wood surface temperature and the vertical axis representing the maximum carbonized layer thickness without cracking.

  The molten metal used in Method A for preventing volatilization of pyrolysis components is a metal that melts at a temperature of 240 ° C. or higher, is relatively stable in air in a high-temperature molten state, and is relatively inexpensive. In addition, it is desirable that it does not volatilize in the air in a high-temperature molten state and that it does not adversely affect the environment. As a material that substantially satisfies these conditions, tin or a tin alloy represented by solder can be cited. Of these, tin is particularly desirable because it is widely used for the surface treatment of steel materials. Lead can also be used, but it is not preferable because it adversely affects the environment. It does not necessarily need to be a metal, and if there is something like a molten salt with a high thermal conductivity, it should be usable.

  In the molten metal method, which is one of the methods A for preventing volatilization of pyrolysis components, wood is floated in a bath of high-temperature molten metal, or part or all of it is treated by treatment. Therefore, only a part of the wood is immersed in the bath. Therefore, log, columnar or prismatic wood is rotated around the longitudinal axis of the wood, or the wood is submerged in the bath with an appropriate jig, or on the wood floating in the bath. The molten metal is allowed to flow through the portion of the wood that is above the bath surface and the molten metal is contacted, or a combination of these methods can be used to uniformly heat the wood surface layer. . When the wood is plate-shaped, if only one side is treated, it is only necessary to float in the bath. However, when treating both sides, this is achieved by treating one side of the plate and turning it over. One side of the board can be carbonized on the surface and the other side can be left with a wood background. Further, the moisture content of the wood is usually over 10% or more, and when the wood in this state is immersed in a high-temperature bath, steam gas is generated vigorously. Therefore, the wood may be dried in advance by an appropriate method. If the wood is sufficiently dried, even after the treatment according to the present invention, deformation is not likely to occur for a long period of time, so that there is an advantage that cracking and warping are unlikely to occur.

  The molten metal is not necessarily placed in the bathtub, and may be circulated and used by pouring it over the wood from above, or collecting and heating the molten metal that has flowed down and pouring it over the wood again. In this way, the processing bath can be small.

  One most important aspect of the present invention is that the surface layer is fully carbonized but the interior is not carbonized. The carbonized surface layer exhibits antiseptic properties, weather resistance, ant proof properties, moisture proof properties, etc., and the mechanical strength is maintained by keeping the original wood without being carbonized. Therefore, the time during which the wood is in contact with the high temperature bath and the temperature of the high temperature bath are extremely important factors. If the contact time is too short, the thickness of the carbonized surface layer is small, and if it is too long, carbonization proceeds to the inside and the mechanical strength decreases. If the temperature of the high temperature bath is low, the carbonization rate is low, and if the temperature is too high, cracks may occur. The desired contact time and bath temperature vary depending on the material of the wood and the shape such as thickness and thickness, but the contact time is suitably from 15 seconds to 120 minutes, and the bath temperature is suitably from about 240 to 450 ° C. A more desirable range is 280 ° C to 380 ° C. In this temperature range, the carbonization depth can be increased without cracks, and black powder is difficult to remove even if the surface is rubbed with a finger.

  According to the molten metal system, carbonization is performed in a high temperature molten metal bath or in contact with the molten metal, so that carbonization is performed while being substantially shielded from air (oxygen). Therefore, the reason why the surface is carbonized uniformly without the occurrence of cracks as shown in FIG. 1 is that the surface to be carbonized is blocked by molten metal. This is probably because the volume of the surface layer is hardly reduced. Further, the volatile matter adheres to the inner walls of the road pipe, temporary road pipe and the like in the surface layer, and is further confined inside through the wall hole. As a result, if it is carbonized in the air, components that volatilize or burn outside will remain in the surface layer and deeper portions, so that a large amount of so-called tar content exists in the surface layer and deeper portions, and voids in the surface layer and deeper portions. Therefore, the moisture resistance is high, which is advantageous for preventing deterioration when exposed to wind and rain. In addition, since a large amount of tar is present in the surface layer, it is advantageous for ant protection and antiseptic properties. In the case of flame carbonization in the air, these volatile components, tar components and the like are easily burned or volatilized.

  Even in the molten metal system, cracks may occur if the temperature of the molten metal is too high or the contact time between the molten metal and wood is too long. The above-mentioned desirable temperature range and contact time are determined from this viewpoint. FIG. 4 shows a cedar wood block (cross section 16 × 20 mm, length 30 mm) immersed in a bath of molten tin at 450 ° C. with a 20 × 30 mm surface for 2 minutes to a depth of about 8 mm, and then on the surface. It is the photograph (FIG.4 (a)) which shows the formed crack, and the cross-sectional microscope picture (FIG.4 (b)) of a crack. The appearance is completely different from the cracks generated by the gas burner (FIG. 1). As apparent from the cross-sectional micrograph, the crack reaches only the shallow part of the carbonized layer.

  According to the molten metal method, as described in Example 1, it is possible to easily control the thickness of the layer carbonized in a state where no cracks are generated to about 0.5 to several tens of millimeters. Therefore, the decrease in the wood strength due to carbonization can be reduced to a negligible level. The reason is considered as follows. Wood used as a structural material such as columns, beams and foundations is usually quite thick. In the case of a pillar, one side of the cross section is usually 10.5 to 12 cm. Thus, even if the surface layer is carbonized and the mechanical strength of the portion is reduced, the thick wood has the strength of the original wood. For example, when the thickness of the carbonized surface layer is 2 mm (in the thickness direction of the wood) with 12 cm square wood, about 3.3% of the cross-sectional area of the wood before carbonization is carbonized, and the wood cross section before carbonization About 96.7% will have the original wood strength. When wood is not used as a structural material, the cross-sectional area of the carbonized layer may be further increased with respect to the total cross-sectional area of the wood. In the case of a pillar, if it is desired to avoid exposing the black carbonized layer on the surface, a thin wood can be pasted on the carbonized layer. When not a structural material, for example, if it is a plywood, a carbonized plate may be laminated inside so that the carbonized layer is not exposed on the surface. Further, it can be used such that only one surface of the plate is carbonized so that the carbonized layer does not face the front side (so as not to be seen directly). In the case of LVL and CLT materials, a plate having a carbonized layer can be similarly laminated inside.

  In the molten metal system of the present invention, when wood is immersed in a molten metal bath, if the wood is a round bar, it is carbonized concentrically from the surface to the inside, but if the wood is a square, it is concentric square Is not carbonized. The reason for this is that, at the corner of the square bar, heat is applied from both sides of the corner, so that it is heated more strongly than the flat portion. As a result, a carbonized layer with rounded corners is formed between the concentric square shape and the concentric circle shape in the cross section of the square bar after carbonization. This phenomenon is the same when wood is heated and carbonized in an electric furnace. When such a phenomenon occurs, the carbonization degree of the corner portion of the square bar is more advanced than that of the side surface portion, and it is a disadvantage of this method that it becomes mechanically weak. Moreover, since the area of the non-carbonized portion inside the square member is reduced, there is a disadvantage that the mechanical strength of the square member is also reduced. If the square is very thick, this phenomenon is not a problem. In the present invention, since only one surface can be heated, such a problem can be prevented.

  In the molten metal method, as a method of avoiding the above-mentioned problems, for example, a square is placed sideways, floated on the molten metal bath surface by its own weight, heated and carbonized for an arbitrary time, and then the square is rolled and the adjacent surface is lowered. Heat and carbonize for an arbitrary time. In this way, another surface is heated and carbonized one after another. Due to the dead weight of the square, the square is slightly submerged in the molten metal bath, so that the surface of the square is uniformly heated, and the corners are extremely less heated.

  On the surface of carbonized wood manufactured by the molten metal method, a tar content sometimes precipitates and may become sticky. In such a case, in order to remove the tar content on the surface, it can be washed away with an organic solvent that dissolves the tar content. Further, the surface can be burned and removed with a strong flame such as a gas burner for a short time (about several seconds). When exposed to a flame for a long time, cracks are generated on the surface as in the case of baked cedar, so it is preferable to set it to about 2 to 3 seconds. It is also possible to prevent stickiness by applying a paint to the surface.

  When the carbonized wood produced by the molten metal method is actually used at a construction or construction site, it may be cut to a necessary length by, for example, a saw. Since the cut surface is not carbonized, the wood may start to deteriorate when the portion is exposed. Therefore, in such a case, the exposed cut surface can be carbonized by hot air or infrared rays, which is another method of the present invention.

  When carbonizing the surface layer by the molten metal method, if the surface of the wood is cracked, raised, or dented, the above-mentioned cracks, ridged portions, dents are raised when the surface layer carbonized wood is pulled up from the molten metal tank. There is a risk that molten metal may enter and remain in In order to suppress such a phenomenon, it is desirable that the surface be smoothed by polishing and polishing before the wood is carbonized. Further, when the carbonized wood is pulled up from the molten metal tank, it is possible to remove the adhered molten metal by blowing a high-temperature high-pressure gas that is equal to or higher than the melting temperature of the metal. Since a metal oxide film and slag exist on the surface of the molten metal bath, they may adhere to the surface of the carbonized wood. In such a case, it is possible to blow off with a high-pressure air jet after cooling. It can also be scraped off with a brush. It can be removed by other appropriate methods. If ani exists on the surface of the wood, a metal oxide film or slag is likely to adhere to it, so that it is desirable that the wood has been so-called degreased in advance.

  When the surface of the molten metal has been exposed to air for a long time, the surface is oxidized and a metal oxide is formed, particularly as the melting temperature is higher. As a result, an oxide film is formed on the molten metal bath surface. When wood is immersed or brought into contact with a molten metal bath, a slag-like material is generated although the mechanism is unknown. So-called slag is accumulated on the surface of the molten metal bath, including the oxide film and the slag. Therefore, it is desirable to remove the slag from the bath surface as necessary. You may drive slag towards the edge of the bathtub. It is also possible to feed the molten metal from the lower part of the molten metal tank so that the molten metal overflows from a part of the bath so that the slag generated on the bath surface always flows out of the bath. The molten metal always overflows from the upper part of the bath, and the wood can be slid and carbonized while the wood is in contact with the liquid surface.

  In order to prevent generation of metal oxides on the molten metal bath surface, the molten metal bath surface may be covered with an inert gas. For example, a molten metal bathtub can be placed in a sealed chamber and a nitrogen gas atmosphere can be obtained by sending nitrogen gas into the chamber.

  Wood usually has a moisture content of 10% or more. When wood is immersed or brought into contact with a molten metal bath, moisture in the wood is heated and volatilizes from the wood as water vapor gas, and rises in the metal bath. Blow out from the bath. At this time, a phenomenon may occur in which the molten metal is pushed up by the gas to be ejected and scattered as fine metal droplets. In particular, when the road pipe or the temporary road pipe is exposed, gas ejection from the road pipe or the temporary road pipe is vigorous. Therefore, if the exposed portion of the road pipe or the temporary road pipe is in the deep portion of the molten metal layer, the molten metal scatters intensely. In order to reduce or prevent this phenomenon, it is effective to dehydrate the wood in advance.

  Even if the moisture in the wood is completely removed, microfibrils and lignin in the wood heated by the high-temperature bath are thermally decomposed, and some of the decomposed components are volatilized as gas from the wood, just like water vapor gas The metal is spattered from the hot bath surface. If the hot tub is sufficiently larger than the wood size, there is no risk of jumping out of the tub even if the molten metal scatters. However, when the molten metal is scattered, the contact area with the air increases, so that a large amount of metal oxide may be generated. As a simple method for solving these two problems, as a molten metal scattering prevention material on the surface of the molten metal, a specific material having a specific gravity smaller than that of the molten metal, not dissolved in the molten metal, and not reacting with the molten metal, for example, minute glass It is effective to provide a layer of beads. The gas generated from the wood tries to scatter metal when it is ejected from the bath surface. However, if there is a glass bead layer on the upper surface of the bath surface, metal scatter is prevented. The gas exits into the air through the gap between the glass beads.

  The presence of the anti-scattering material also has the effect of reducing the surface oxidation of the molten metal. The size of the glass beads is suitably about 1 mm to about 5 mm. If it is too small, it tends to adhere to the carbonized wood surface when the wood is pulled up from the bath. If the size is too large, the metal may be scattered from the gap, and the antioxidant effect of the metal is reduced. The size of the beads need not be uniform and may have a distribution. An appropriate thickness of the bead layer is about 5 mm to 20 mm. When the thickness of the bead layer is small, the effects of preventing metal scattering and oxidation are reduced. Too thick is useless. As beads, glass beads, silica beads, alumina beads and the like can be used. Even if it is not a sphere like a bead, it can be used if it is granular, rod-like, or flat and is made of a material that is stable at high temperatures. The size of these may be about the same as the above beads.

  When the wood immersed in the molten metal bath is covered with aluminum foil and then immersed, the proportion of volatile components generated from the wood in contact with the molten metal is greatly reduced, and the generation of slag can be significantly reduced. Even if the volatile components leak from the joint portion of the aluminum foil in the molten metal bath, the generation of slag is much less than when the wood is directly immersed in the molten metal bath.

  In general, the length direction of the wood coincides with the direction of the road pipe or the temporary road pipe, and both end faces (cuts) of the wood are perpendicular to the direction of the road pipe or the temporary road pipe. The gas generated by pyrolysis when the wood is heated to a high temperature is likely to flow in the direction of the road pipe or the temporary road pipe, and hardly flows in the direction perpendicular thereto. Accordingly, when wood is immersed in a molten metal bath, gas is emitted violently from the end face (cut) of the wood, but there is little generation from other surfaces of the wood. As a result, the end face of the wood may be difficult to be carbonized. If the surface other than the end face of the wood is sufficiently carbonized, but the end face is insufficiently carbonized, it is desirable to additionally carbonize only the end face. If additional carbonization is required, the hot air or infrared system of the present invention is suitable.

  In the hot plate method, which is one of the methods A for preventing volatilization of the pyrolysis component, a heating device known as a metal plate, for example, a so-called hot plate is generally used as the hot plate, but a similar device can also be used. Since a hot plate is used in place of the metal that is hot-melted, the temperature conditions are almost the same as in the case of the hot-melt metal. Depending on the shape of the wood to be carbonized, it is possible to use a hot plate having a flat plate shape, rail shape, angle shape, curved surface shape, or the like. For example, in the case of heating a columnar wood such as a pile, a cylindrical heating furnace is suitable. In this case, it is desirable to make the gap between the furnace wall and the wood as small as possible. The cylindrical heating furnace may be divided into two parallel to the length direction so that the wood can be easily inserted, and after the insertion, they may be combined into a cylindrical shape. It is convenient to connect the two-part heating furnace with a butterfly plate. The heat plate may be a metal plate whose surface is covered with a heat-resistant protective film. It is desirable that the hot plate has a sufficient heat capacity or is always supplied with energy to maintain the surface temperature. For example, a hot plate apparatus incorporating an energization heating element such as a nichrome wire and a temperature control mechanism can be used. Moreover, it is desirable that the heat plate has a large thermal conductivity. Thin metal foil such as aluminum foil and copper foil can be used in the same manner as the metal plate. For example, the surface of wood can be covered with aluminum foil, and the temperature of the aluminum foil can be kept high while blowing hot air from above. When a metal plate, metal foil or the like is heated with infrared rays to form a heat plate, it is desirable that at least the surface is treated with a color that absorbs infrared rays so that the infrared rays are not reflected.

  In addition to the above method, the energy supply method to the hot plate can use the heat of combustion of wood or oil. For example, waste wood, thinned wood branches or the like are burned in a combustion chamber, the upper wall of the combustion chamber is made a flat iron plate, and this iron plate can be used as a hot plate. In this way, not only is it possible to effectively use waste wood and thinned wood, but it is also beneficial to the environment.

  As a method for supplying energy to the hot plate, a molten metal in a hot melt state can be used. For example, a metal plate can be mounted on a hot-melt metal bath, and this metal plate can be used as a hot plate. It is possible to heat similarly by floating an aluminum foil instead of a metal plate and placing wood on it. FIG. 5 is an immediate cross-sectional view of a state in which an aluminum foil is floated on a molten metal bath, a timber is placed on the aluminum foil, and a force is applied to the timber to slightly sink the timber. In FIG. 5, 1 is wood, 2 is aluminum foil, 4 is a molten metal bath, and 5 is a metal bath container. When a force 6 is applied on the wood 1, the wood 1 deforms the aluminum foil 2 and sinks a little in the bath. In other words, an aluminum foil boat with wood on a metal bath is floating. If the weight of the timber is large, the timber will sink slightly without applying force from above. The aluminum foil in the bath bends upward at the peripheral end of the lower part of the wood in the bath due to the buoyancy of the metal bath, and is in close contact with the peripheral end of the lower part of the wood, so that volatilization of the thermal decomposition component is suppressed. This suppresses the occurrence of cracks at the carbonized portion at the end. The use of aluminum foil is extremely simple and effective. Although the aluminum foil at the corner of the wood may be wrinkled, the aluminum foil in contact with the lower and side surfaces of the wood is completely flat and has no effect on carbonization.

  In the hot plate method, the hot plate and the wood are brought into contact with each other. However, since the surface of the wood is generally rough, an air layer exists between the hot plate and the wood. In the molten metal method, since the molten metal can be freely deformed, there is no air layer between the wood and the molten metal even if the surface of the wood is rough. Therefore, in the case of the hot plate method, it was speculated that the method of carbonizing the surface layer of wood would be considerably different from the case of using molten metal. However, it was surprisingly almost the same carbonized. Since the wood and the hot plate are in contact, it is assumed that the volatile components generated from the wood by heating are prevented from freely escaping from the surface of the wood and are confined inside the wood.

  In the hot plate method, since the hot plate is usually flat, only one surface of the wood can be heated. When the heating of one surface is completed, the next surface is heated. In order to simultaneously heat a plurality of surfaces, it is necessary to prepare a hot plate having a shape suitable for the surface. For example, in order to heat two adjacent surfaces simultaneously, an angle-shaped hot plate is required. When heated with an angle-shaped hot plate, the problem of preferential carbonization of the corners occurs. However, this problem can be solved by providing slit-like gaps at the corners of the angle. When carbonizing a square-like wood surface layer, two surfaces can be carbonized simultaneously by heating in a state sandwiched between two hot plates. When one surface of wood is heated with a flat hot plate, almost the same effect and result are obtained as when the wood is floated on the bath surface and heated by the molten metal method.

  The wood to be carbonized and the heat plate may be held in contact and may be stationary, but may be moved so as to slide relative to each other while the wood and the heat plate are in contact with each other. For example, wood may be placed on a hot plate, the hot plate may be fixed, and the wood may be moved to slide on the hot plate while being in contact for a set time. A plurality of hot plates having different temperatures or the same temperature may be arranged side by side, and the wood may be moved while sequentially sliding on them.

  Prior to heating and carbonization of the wood surface with a hot plate or molten metal, the wood surface can be pre-carbonized by irradiating the wood surface with infrared rays or heating by blowing hot air. In this case, it is necessary to heat in the pre-carbonization stage under the condition that no cracks are generated on the wood surface.

  FIG. 17 is a plot of the wood surface temperature and the heating time immediately before the occurrence of cracks based on the data of Example 1 and Example 2. The vertical axis is a logarithmic display, and an exponential approximation curve of data is displayed. FIG. 17 shows that heating can be performed without generating cracks by heating each wood surface temperature within a heating time that is less than or equal to the exponential approximation curve. It was elucidated in the present invention. The inside of the triangle surrounded by three lines of the exponential approximation curve, the lower limit temperature, and the lower limit time in FIG. 17 is the region of the present invention.

  FIG. 18 is a graph in which the data of Example 2 is plotted with the horizontal axis representing the wood surface temperature and the vertical axis representing the maximum carbonized layer thickness at which cracks do not occur. The curve in FIG. 18 is a polynomial approximation curve. In the range below the approximate curve, the range of 0.7 mm or more is the range of the thickness of the carbonized layer of the present invention.

  Next, Method B for preventing volatilization of the pyrolysis component will be described. The gas impermeable member used in the method is a member that is transparent to infrared rays and does not transmit gas, such as a glass plate, a quartz plate, and a ceramic plate. Infrared rays include far infrared rays, part of near infrared rays, and part of visible rays, but mainly infrared rays including near infrared rays and / or far infrared rays. A specific example of a far infrared light source suitable for the present invention is a quartz glass tube heater. It is widely used for home and industrial use and is available at a relatively low cost. Hereinafter, this method B is also referred to as an infrared system. When infrared rays are irradiated on the wood surface, the temperature of the wood surface will increase as much as possible. This point is greatly different from the heating method using the molten metal, hot plate and hot air. In the case of heating with molten metal, hot plate, hot air, the temperature of the wood surface does not rise above the temperature of these heat sources, but in the case of infrared light, energy is accumulated on the wood surface at an accelerated rate and the temperature rises. . Therefore, it is necessary to control infrared radiation energy or irradiation time so that the temperature of the wood surface does not exceed 450 ° C.

  Although it is clear from Non-Patent Document 3 that wood is burnt when irradiated with infrared rays, Non-Patent Document 3 has no description of cracks. By appropriately selecting the energy intensity of the infrared source (heater, lamp, etc.), the distance from the source to the wood, the irradiation time, etc., cracks will not occur if heated while keeping the temperature of the wood surface below 450 ° C. I found In addition, a gas-impermeable transparent member such as a quartz plate or glass plate is closely attached to the surface of the wood and irradiated through it, so that molten metal method or hot plate method is applied from the surface to the inside without generating cracks. Can be carbonized to the same extent.

  The wood to be carbonized and the transparent member (glass plate, quartz plate, etc.) may be moved relatively. For example, an infrared lamp may be fixedly disposed, and the wood placed on the transport device may be slid while contacting the lower surface of the transparent member disposed below the infrared lamp. In this case, it is desirable that the transparent member be movable up and down in order to cope with roughness and unevenness of the wood surface. The wood and the transparent member may be moved together in a state where the transparent member is placed on the wood. It is also possible to place a transparent member on wood, place an infrared lamp above it, and move the infrared lamp.

  The wood and the infrared lamp may have an upside down relationship with the above. In this case, it arrange | positions so that a transparent member may contact the carbonized surface of wood. A plurality of infrared lamps may be arranged. As will be apparent from Example 4 described later, when the transparent member is arranged, the carbonization rate is reduced as compared with the case where there is no transparent member. Therefore, as long as cracks do not occur, the transparent member may be carbonized without the transparent member disposed (similar to the preliminary carbonization described in the paragraph 0060), and the transparent member may be disposed after passing through that portion. For example, a plurality of infrared lamps are arranged in parallel, the first one to a plurality are irradiated with the carbonized surface of the wood without a transparent member, and the next one to a plurality are carbonized to the wood. You may arrange | position so that the to-be-carbonized surface of wood may be irradiated in the state which made the transparent member contact the surface. By arranging in this way, it is possible to increase the efficiency of carbonization. Instead of pre-carbonization by irradiating wood with infrared rays, pre-carbonization may be performed by blowing hot air.

  As mentioned above, it can be said in common when the wood and the transparent member or the hot plate are relatively slid, but when the tip of the wood reaches the end of the hot plate or the transparent member, The tip may collide with the end of the hot plate or the transparent member and the movement may be hindered. In order to avoid this, it is desirable that the end of the hot plate or transparent member that meets the tip of the wood be processed into a taper shape.

Next, method C for preventing volatilization of the pyrolysis component will be described. The method is based on the use of wood in which a surface layer is impregnated with water glass. When using, for example, No. 1 sodium silicate solution (for example, No. 1 water glass) as the water glass used in the present invention, it is diluted with water as a stock solution (very viscous fluid), It is preferably used as an aqueous solution having a weight of about 20-60%. If it is 20% or less, the effect of water glass is small, and if it is 60% or more, a water glass film is likely to be formed on the wood surface. Preferably in the range of to the ^15g / ^{m 2 ~80g} / m 2 expressed by impregnation amount per unit area. As a method of supplying water glass to wood, a suitable method such as a known coating method, a method of lifting wood after dipping it in a water glass aqueous solution and drying it can be used. The use of water glass can also be applied in the methods A and B for solving the problems of the present invention.

  In the present invention, it is desirable that the amount of water glass impregnated in the wood is such that a water glass film is not formed on the wood surface after the water glass aqueous solution is supplied to the wood by an appropriate method and dried. Specifically, when the proportion of water glass in the water glass aqueous solution is large, a water glass film is formed on the wood surface. Even if the ratio of water glass is small, a water glass film is formed on the surface of the wood by multiple application. When the water glass film is clearly formed, when heated by the method of the present invention, the water glass film on the surface of the wood foams to form a white foam film. This phenomenon is particularly remarkable when the heating temperature is high. Even if such a foaming phenomenon occurs, if the heating is continued, the wood covered with the foamed film is carbonized, so that it does not interfere with the carbonization. As the carbonization of wood progresses, the foam film that was initially white gradually becomes black and can be easily removed by simply rubbing with a sponge or brush after cooling. Accordingly, the carbonized layer to be formed does not have an adverse effect, but it is desirable to prevent such a phenomenon from occurring because the handling surface is inclined.

  A second method for solving the problem of the present invention is to blow hot air at a temperature of 280 ° C. to 480 ° C. on the surface of the carbonized region of the wood or woody material, so that the region is directed from the surface toward the inside. Carbonization to the required depth, ie the desired depth. This second method is hereinafter referred to as a hot air method. The present inventor speculates that a carbonized layer without cracks having the same thickness as that of a high-temperature molten metal can be obtained by blowing hot air having a temperature similar to that of the high-temperature molten metal on the surface of the wood. In practice, it was found that a thickened carbonized layer was not obtained as in the case of molten metal, but a much thicker carbonized layer was obtained than in the case of a gas burner flame. The temperature of the flame is about 1000 ° C., and cracks occur during a short time of processing. In a short time treatment that does not cause cracks, the thickness of the carbonized layer is extremely small, and only the layer close to the surface is carbonized. However, if the hot air is 480 ° C. or less, it can be carbonized to a thickness of about 3 mm without generating cracks by controlling the temperature of the hot air and the blowing time. Compared with the molten metal method or hot plate method, the thickness of the carbonized layer obtained in a range where cracks do not occur is small, but this is sufficient depending on the application.

  Even in the case of carbonization with hot air, if the temperature of the hot air is high and the blowing time becomes long, cracks similar to those in the case of the gas burner are generated. FIG. 6 is a photograph of a sample obtained by heating and carbonizing Ezo pine (thickness 14 mm, width 45 mm, length 58 mm) with a heat gun (hot air temperature 480 ° C.) for 2 minutes. A photograph (a) is a photograph of the surface where many cracks are generated, and a photograph (b) is a cross-sectional micrograph of the vicinity of one crack. As described above, even when hot air is used or when the temperature is high, cracks are generated as in the case of carbonization by the gas burner even when sprayed for a short time. However, it can be seen that the shape of the cross section differs greatly between hot air carbonization and gas burner carbonization. Although the crack cross-section periphery of FIG. 2 is depressed, the crack cross-section periphery of FIG. 6 swells conversely. The reason why such a difference occurs is presumed to be that combustion occurs in the gas burner method, but combustion does not occur in the hot air method.

  Since flame treatment with gas burners and treatment with hot air blowing are performed in the air, it was thought that the volatile components in the pyrolyzed wood may be oxidized (burned) and cracks are likely to occur. When treated with hot air of carbon dioxide gas, it was confirmed that there was almost no difference from the hot air treatment of air. FIG. 7 is a photograph comparing the carbonization results of Ezo pine (thickness 14 mm, width 45 mm, length 57 mm) with hot air of carbon and hot air of carbon dioxide gas. Photo (a) is a sample carbonized with hot air and photo (b) is a photo of a sample carbonized with carbon dioxide hot air. Both hot air temperatures (480 ° C.) and spraying time (60 seconds) are exactly the same. As can be seen from FIG. 7, it was confirmed that there was almost no difference in the carbonization state between air and carbon dioxide gas. Therefore, it is understood that prevention of volatilization of pyrolyzed components is an important condition for carbonization treatment with molten metal or a hot plate. Also in the hot air method, for example, when a metal plate or a metal stay was placed on the surface and hot air was blown from above, the metal plate or the metal foil became high temperature, and it was confirmed that it could be carbonized as in the hot plate method. A method of covering wood with a metal foil or a thin metal plate and blowing hot air over the metal foil is practical and very effective. The method of covering wood with metal foil and blowing hot air over it is particularly convenient for work in the field.

  If the above assumption that the molten metal or hot plate covering the surface of the wood prevents volatilization of the volatile components of the pyrolyzed wood is correct, the surface of the wood will also contain a resin (including paint, adhesive, etc.) ) Or an inorganic substance (water glass, polysiloxane, etc.), and then it is presumed that it is advantageous to perform carbonization treatment by blowing hot air. If it is a resin-based thin film, the thin film itself is also carbonized by hot air, but if the thin carbonized film can prevent the transmission of volatile components, the guess is correct. Water glass and polysiloxane are not carbonized, but are expected to be impregnated into the surface layer of wood to prevent the transmission of volatile components.

  Therefore, as a specific example, a commercially available coating material (clear lacquer whose solid main component is an acrylic resin) and a commercially available water-soluble adhesive (main component is polyvinyl alcohol) are cedar (thickness) so that the dry thickness is 20 to 30 μm. 5 mm, width 14 mm), and after drying, hot air was blown to confirm the occurrence of cracks. In any case, it was confirmed that cracks were less likely to occur when the coating film was present. However, the effect was slight, and what was cracked by heating for 2 minutes without a coating film was an improvement to the extent that cracks were generated in 2 minutes and 30 seconds by providing the coating film. It is thought that the volatile component passed because the coating film was thin. Subsequently, when the surface layer was impregnated with a commercially available water glass aqueous solution, it was confirmed that cracks hardly occur and the carbonization depth could be increased. It is considered that the water glass component prevented the volatilization of the volatile component (see Example 7). Further, it was also confirmed that when the carbonized surface was rubbed with a finger, black powder hardly adhered to the finger. These facts are one feature of the present invention. In addition to water glass, it was found that a similar effect was obtained when a surface layer of wood was impregnated with a commercially available polysiloxane, but it was confirmed that the effect of water glass was much greater. Furthermore, water glass is overwhelmingly advantageous in terms of cost. The effect of water glass was discovered as described above.

  Since molten metal or hot plate and hot air have different heat capacity, heat conduction, etc., molten metal or hot plate has a larger carbonization capacity. In carbonization with molten metal or hot plate, heating for several minutes to several tens of minutes can achieve a sufficient degree of carbonization (degree of blackening) and carbonization depth even in the temperature range of 240 to 280 ° C. In the heating, in this temperature range, the color is hardly colored by the heating in the above time range or is lightly colored. It was confirmed that the degree of carbonization increased as the speed of blowing hot air was increased, but it was found that carbonization could not be sufficiently performed at a practical blowing speed (wind speed) in this temperature range. The temperature range of the hot air is preferably 280 to 480 ° C. More desirably, it is in the range of 300 to 400 ° C. Hot air at a temperature of 280 ° C. or lower is unrealistic because it takes a very long time to carbonize the surface layer. At 480 ° C. or higher, cracks occur in about 10 seconds, and the carbonization depth is small, which is not practical.

Conventionally, wood has been heat-treated in an electric furnace, a heating furnace or the like, but the air in the furnace is still or is stirred or circulated. The carbonization by the hot air system of the present invention is characterized by spraying in a higher temperature range than before. In the conventional heat treatment of wood, the purpose is to treat the inside of the wood, and the entire surface of the wood is simultaneously heated over a long time. On the other hand, the present invention is characterized in that hot air having a temperature higher than that of the prior art is blown onto a part (one surface) of wood. As will be described later, the two surfaces may be heated simultaneously to prevent warping. Therefore, it is extremely important to blow hot air at high speed. In a static or circulating atmosphere, if the surface layer is sufficiently carbonized, it is weakly carbonized deep inside, resulting in a decrease in the mechanical strength of the wood. By spraying at a wind speed of a certain level or more, the surface layer can be sufficiently carbonized without being carbonized deep inside. By referring to Comparative Example 2 and Comparative Example 3, this difference can be easily understood.

  As described above, the wind speed of hot air is extremely important in the hot air system of the present invention. A desirable wind speed range is 4 m / sec or more, and more desirably 6 m / sec or more. The upper limit is limited by the hot air device or the surrounding environment. Actually, the upper limit is a wind speed of 15 to 20 m per second. The direction in which the hot air is blown onto the wood is desirably in a range of approximately 30 to 30 degrees with respect to the surface of the wood. The greater this angle is beyond this range, the less efficient the wood is heated.

  A commercially available so-called heat gun can be used as the hot air generator. Commercially available heat guns are easily available and easy to use, but the temperature and volume of hot air may not always be sufficient. It is sufficient to carbonize a small area of wood or a cut surface of a plate or a pillar, but lacks the ability to carbonize a large area. In such a case, the heat exchanger can be heated using a large-capacity heat source, and hot air that has passed through the heated heat exchanger can be used. As a large-capacity heat source, there are an electric heater, a gas burner, an oil burner and the like having a large calorific value. The heat exchanger is heated with this large-capacity heat source, and hot air that has passed through the heated heat exchanger is blown. If it is a gas burner, a compact and large-capacity carbonization apparatus is possible. In order to save energy, the hot air used for spraying can be recovered and passed again through the heat exchanger.

  The various systems of the present invention have been described above. Table 1 summarizes these systems and the features of the conventional system. Table 1 does not include the effect of water glass. As is clear from Table 1, molten metal method, hot plate method, infrared method (in the case of infrared transmissive and gas impermeable member) and gas burner (a metal plate is placed on wood and a gas burner is mounted on the metal plate) The results from (flame radiation) are very similar. On the other hand, wood exposed to the atmosphere has completely different characteristics when carbonized by the hot air method and infrared method. In the method in which the gas impermeable member is in contact, it is possible to obtain a carbonized layer (carbonization depth) with a large thickness without occurrence of cracks, but in the method in which the gas impermeable member is not in contact, Only a small thickness of the carbonized layer can be obtained under conditions where no cracks are generated.

  In each of the methods of the present invention described above, the ends (including corners, edges, edges, and ridges) of the wood are preferentially carbonized, and as a result, cracks tend to occur before in-plane. In order to prevent this, it is effective to cover the end with a thin metal plate, a metal foil or the like. For example, as a specific example of the hot plate method, when a wood timber is placed on the hot plate and heated, the volatile component rises as smoke from the four sides (entire circumference) of the square at the contact portion between the square and the hot plate. To do. Since the volatile component escapes quickly and continuously into the space, the occurrence of cracks is promoted. Therefore, the entire square is covered with a metal foil such as an aluminum foil, or at least the end of the wood and a hot plate in the vicinity thereof. It is good to coat | cover the surface and side surface which contact with.

  FIG. 8 is a side sectional view showing a specific example in which four sides (corner portions) of the end portion of the surface facing the hot plate of the square member are covered with aluminum foil. In FIG. 8, 1 is a square bar, 2 is an aluminum foil, and 3 is a hot plate. In the drawing, the thickness of the aluminum foil is exaggerated, but the actual thickness is about 13 to 17 μm. Surprisingly, it was found that the wood 1 and the hot plate 3 are not in contact with each other, and there may be such a small gap. The reason is considered to be that the pyrolysis component is confined in the gap because the periphery of the square member 1 is covered with the aluminum foil 2. By covering the periphery of the square member facing the hot plate with aluminum foil as described above, it is possible to prevent the end of the square member from cracking before the in-plane. Although there is a minute gap between the square 1 and the hot plate 3, it was confirmed that there is no difference in the degree of carbonization from the portion where the aluminum foil is present. In order to confirm how much the gap becomes large, the experiment was repeated with a plurality of aluminum foils stacked, and it was confirmed that there was no effect up to about 0.3 mm. A metal plate of 0.3 mm or less may be used instead of the aluminum foil. Even if such a large gap exists, volatilization of the pyrolysis component can be prevented. It was recognized that when the gap between the square bar and the hot plate exceeds 0.3 mm, the degree of carbonization in the portion not covered with the aluminum foil is lowered. Actually, there is a minute gap between the aluminum foil 2 and the square 1 and a part of the pyrolysis component volatilizes through this gap, but there is an effect of preventing volatilization.

When actually carrying out carbonization of the surface layer of wood, in particular, a plate, attention must be paid to the size of the wood. When the short side of the plate is about 10 cm or more, the carbonized portion is thermally contracted if only one surface is strongly carbonized, so that the carbonized surface may be curled so as to be concave. Therefore, it is desirable to alternately carbonize both sides. Further, curling (warping) can be prevented by repeating a method in which both surfaces are simultaneously heated for a short time, left to cool for a while, and then heated again from both sides. It is not always necessary to heat both surfaces simultaneously for a short time and then to cool for a while, and they may be heated continuously. It is not necessary to heat both sides completely simultaneously, and there may be some deviation. That is, it may be almost simultaneous. For example, when both surfaces are heated with an infrared heater, the infrared heaters are arranged on both sides of the plate. However, the infrared heaters may not be arranged symmetrically with respect to the plate and may be slightly deviated from symmetrical positions. Special care must be taken when the thickness of the plate is small. Such care is not necessary when the plate is very thick or thick square.

  According to the method of the present invention, a wood having a carbonized layer far superior to the conventional method as described above can be obtained. However, since the carbonized surface layer has many small holes derived from road pipes, temporary pipes, wall holes, and other wood, it is difficult to completely block wind and rain for many years. . Therefore, it is also effective to apply or impregnate an appropriate material to the carbonized layer obtained by the method of the present invention so that various characteristics can be maintained for a longer period of time. Various known techniques can be used for this purpose. For example, a method of impregnating water glass, a method of applying or impregnating a resin described in Patent Document 2, and the like can be used. Moreover, the surface layer carbonized wood obtained by the method of the present invention has a brown to black hue, but if an appearance other than these colors is desired, it may be painted to the desired color. When it is desired to increase the mechanical strength of the carbonized layer (for example, when it is desired to prevent black powder from being taken off by a finger when rubbed strongly with a finger), the drawback can be solved by painting the surface.

  The present invention is not limited to wood, but can also be applied to what is generally called woody material. Examples of the wood material include plywood, laminated wood, OSB, particle board (particularly MDF is preferable), LVL, CLT, and compressed wood. It is known that wood compressed with high-temperature and high-pressure steam is compressed to 1/2 to 1/3 of the original wood, its appearance changes to a high-grade brown color, and durability, antiseptic properties, etc. are improved. ing. When the method of the present invention is applied to this compressed wood, the antiseptic property, the ant-proof property and the like can be further enhanced.

  One application of the molten metal system of the present invention is to produce charcoal in a very short time. As a specific example, when a rod of 20 mm in diameter was immersed in a 400 ° C. molten tin bath for 5 minutes, it was almost carbonized to the center of the rod. Although cracks are generated on the surface, there is no problem as charcoal. In the conventional charcoal production method, according to the forestry test site “Wood Industry Handbook”, the charcoal yield at 400 ° C. is 30%. On the other hand, in this specific example (5 minutes immersion), it was 55.9%. When the rod was immersed in molten tin at 400 ° C. for 12 minutes and no vaporized gas was completely generated, the color of the rod was true black and the yield was 33%, which was almost the same as the value in the handbook. There is an advantage that charcoal is completed in just 12 minutes.

  Examples of the present invention will be described below. In the following examples, there is described a state in which there is no relative motion between the wood and the hot plate, between the wood and hot air, and between the wood and infrared rays, but there is relative motion between them. May be. For example, a system in which wood moves on a rotating heat roll may be used. Moreover, you may move, rotating a hot roll on wood. At this time, a plurality of heat rolls may be provided. It is also possible to heat the rolled wood while rolling it on a flat hot plate. In these cases, the width of the contact portion between the wood and the heating member is small, and the pyrolysis volatile component easily volatilizes, so that the heated surface of the wood is covered with a gas-impermeable member, for example, aluminum foil Is desirable. In addition to the roller moving while rotating, the pyrolysis component volatilization preventing member and the wood may slide relative to each other. Moreover, you may make it move relatively, spraying hot air on the moving wood, or irradiating infrared rays.

  FIG. 9 is a surface photograph of the carbonized side of a sample prepared by changing the melting temperature and the heating time when tin is used as the molten metal in the molten metal method. As the wood, cedar wood having a length of 20 mm, a width (direction of the temporary road pipe) of 30 mm, and a height of 16 mm was used. The tin was placed in a stainless steel bat, and the temperature of the molten tin was adjusted by adjusting the heating power of the stove by placing the bat on the gas stove. Tin was melted so that the melted tin had a depth of about 50 mm. The square was held with stainless steel tongs and held so that the square was immersed in the molten tin from the surface by about 10 mm in the height direction. Since slag is generated on the surface of the square material that is immersed in the molten tin, the location can be changed while being immersed once every 15 seconds, or the square material can be lifted and immersed in a place without slag. did. When the whole immersion time was as short as 30 seconds or less, the above place change was performed at a frequency of about once every 5 seconds. FIG. 9 also shows a photograph of a sample prepared at a temperature outside the scope of the present invention. When heat treatment exceeds 450 ° C, significant cracks occurred in 1 minute, and black powder adhered by lightly rubbing the surface with fingers, and the thickness of the carbonized layer was found to be as small as 2 mm or less. The heating temperature range of the present invention was set to 450 ° C. or lower.

  Table 2 shows the results of measuring how the depth of carbonization changes when the immersion time in molten tin is further increased in the same manner as the sample preparation in FIG. Since each sample is a natural product and varies, three samples corresponding to each temperature and time were prepared and three carbonization depths were entered. Samples were prepared at a molten metal temperature in the range of 240 ° C. to 420 ° C. and an immersion time of up to 40 minutes. The center of each sample after carbonization, which is 20 mm long, is divided vertically with a sharp knife (cutter knife) in a direction parallel to the tracheid tube, and the depth of the carbonized layer is observed while observing the cross section with a microscope. Was measured. When the surface divided vertically by the cutter knife was rough, the surface was observed after making it smooth and easy to see. In Table 2, an x mark indicates that a crack occurred at that temperature and time.

  FIG. 10 is a graph in which the average value of the carbonization depth of three samples at each temperature and immersion time in Table 2 is plotted. The melting temperature lower than 340 ° C. measured only up to 40 minutes, but it is clear from the result of the hot plate method of Example 2 that the carbonization depth is increased to about 15 mm by further increasing the immersion time. It is. At 340 ° C., cracks do not occur after immersion for 20 minutes, but cracks occurred at immersion times of 25 minutes, so the graph stops at 340 ° C. for 20 minutes. In FIG. 10, the portion indicated by the dotted line in the graph is data heated at 360 ° C. when the glass surface layer is impregnated with water glass. This is described in detail in Example 7.

  Table 3 shows how cedar wood with a height of 20 mm, a width of 30 mm (in the direction of the temporary road pipe), and a height of 16 mm is used as wood, and how the depth of carbonization changes depending on the temperature and heating time of the hot plate The result of having measured is shown. A hot plate (As One Co., Ltd. ND-1) was used as a hot plate apparatus. Similarly to Example 1, three samples corresponding to each temperature and time were prepared, and the carbonization depth of the three samples was entered. Samples were prepared with the temperature of the hot plate in the range of 240 ° C. to 340 ° C. and the heating time in the range of 15 seconds to 120 minutes. Since the maximum temperature of the hot plate was 350 ° C., an aluminum plate having a thickness of 10 mm and a size of 100 × 100 mm was placed on the molten tin of Example 1 at a temperature higher than that, and a square was placed thereon and carbonized. In Table 3, it is described as a hot plate including this case. The center of each sample after carbonization was divided vertically with a cutter knife in the direction of the temporary canal, and the depth of the carbonized layer was measured while observing the cross section with a microscope. When the surface divided by the cutter knife was rough, it was observed after making it easy to see. In Table 3, x indicates that cracks occurred at that temperature and time.

  Instead of floating the aluminum plate on the molten tin as described above, it was possible to heat similarly by floating an aluminum foil and placing wood on it. Even when an aluminum foil having a thickness of 13 μm and a size of 90 × 60 mm was floated on the molten tin bath, and the same size of wood was placed in the center of the aluminum foil, the aluminum foil hardly sunk due to the gravity of the wood. Therefore, when the wood was pushed down with a tongue and pushed down about 8 mm, the aluminum foil in the bath was bent upward at the lower peripheral end of the wood as shown in FIG. In this way, volatilization of the pyrolysis component was prevented. As a result, in the case of an aluminum plate, the generation of cracks was prevented even at a temperature and time at which cracks occurred at the carbonized portion at the end.

  FIG. 11 is a graph in which the average value of the carbonization depth of three samples at each temperature and heating time in Table 3 is plotted. At a hot plate temperature of 280 ° C. or lower, the heating time can be further extended. The carbonization depth could reach up to about 15 mm without cracks. From FIG. 10 and FIG. 11, it was found that almost the same results were obtained with the molten metal method and the hot plate method. In FIG. 11, the portion indicated by the dotted line in the graph is data when the wood surface layer is impregnated with water glass and heated at 340 ° C. This will be described in detail in Example 7, but it is shown that by impregnating with water glass, cracking does not occur even when heated for a longer time or at a higher temperature than when not impregnated, and the carbonization depth increases. .

  Table 4 shows 20 mm × 30 mm using a commercially available heat gun (Evolution Power Tool Co., Ltd. Heat Gun Hot Air Machine HDG200JP) as a hot air generating device on a cedar wood having a length of 20 mm, a width (direction of the temporary road pipe) of 30 mm, and a height of 16 mm. The result of measuring how the depth of carbonization changes with the temperature of hot air and the time of hot air blowing is shown. Since each sample is a natural product and varies, three samples corresponding to each temperature and time were prepared and the carbonization depth of the three samples was entered. Samples were prepared with the hot air temperature in the range of 280 ° C. to 480 ° C. and the spraying time in the range of up to 20 minutes. Below 280 ° C., carbonization was insufficient even after prolonged heating. The center of the vertical length of each sample after carbonization was divided vertically with a cutter knife in the direction of the temporary canal, and the depth of the carbonized layer was measured while observing the cross section with a microscope. When the surface divided by the cutter knife was rough, it was observed after making it easy to see. In Table 4, x indicates that cracking occurred at that temperature and time.

  FIG. 12 is a graph in which the average values of the carbonization depths of the three samples at each temperature and hot air blowing time in Table 4 are plotted. It was found that the carbonization depth can be reached only up to around 3 mm. However, this level of carbonization is sufficient for some applications. The biggest attraction of the hot air method is that it can be carbonized easily on site. For example, it can be easily carbonized by blowing hot air onto a cut surface of wood cut on site.

The data in Table 4 is for the case where the surface layer of wood is not impregnated with water glass, but the A square material of Example 7 (water glass impregnation amount is 29.0 g / m ² ) is heated by a hot air method, The occurrence of cracks was observed and the carbonization depth was measured. Hot air of 360 ° C. was blown on the square glass impregnated surface with time as a parameter. In the square member not impregnated with water glass, the heating time in which cracks did not occur was up to 4 minutes, but the heating time in which cracks in the A square member did not occur extended to 15 minutes. It really stretched more than three times. Moreover, the carbonization depth also increased by a factor of 2 from 2.31 mm to 4.78 mm. These results are shown by the dotted line graph in FIG. Further, even when the carbonized surface was rubbed with a finger, black powder hardly adhered.

  In the hot air method, since the wood surface is not covered with the gas-impermeable member during heating, the pyrolytic vapor components generated by the heating freely diverge from the wood surface. Therefore, it is considered that cracks occur despite the small carbonization depth. For example, when hot air at 360 ° C. is used, cracks occur in 5 minutes, but when a hot plate at the same temperature is used, cracks occur in 10 minutes. At 380 ° C., cracking is prevented when the heated wood surface is covered with a gas-impermeable member so that cracking occurs in 3 minutes with hot air and 5 minutes with a hot plate. I understand that.

  A quartz glass tube heater (outer diameter 12 mm, effective light emission length of about 200 mm, output 560 W) was used as the infrared lamp, and an AC voltage of 100 V was applied to both ends of the heater so that it could be turned on and off with a switch. Sugibe wood having a length of 20 mm, a width (direction of the temporary road pipe) of 30 mm, and a height of 16 mm was used as wood, and the distance from the surface of the infrared lamp to the sample surface was set to 10 mm or 20 mm. Three samples were prepared for the same heating time. When the irradiation time became longer or when the distance between the lamp (consent with the heater) and the sample was small, the temperature of the wood surface increased rapidly and smoke was generated. The measurement was conducted paying attention to the conditions under which cracks do not occur. At a distance of less than 10 mm, smoke was intensely generated by irradiation for 1 to 2 minutes, and ignition was sometimes caused by irradiation for 3 to 5 minutes. When the surface to be carbonized is open, it cannot be deeply carbonized without cracking. However, it was confirmed that cracks are unlikely to occur when a quartz plate is placed on a square and irradiated with infrared rays from above.

  Table 5 shows the measurement results. Q in the distance between the lamp and the wood in Table 5 indicates a case where a quartz plate having a thickness of 2.4 mm is placed on the surface of the wood. As can be seen from Table 5, when there was no quartz plate, cracks occurred in the wood after 3 minutes of irradiation, but when there was a quartz plate, cracks occurred for the first time after 10 minutes of irradiation. Moreover, it has been confirmed that the carbonization depth increases to about twice that when there is no quartz plate. Also from this example, it was confirmed that when the wood surface was not covered with a gas-impermeable member during heating, the vaporized component generated by heating vaporizes from the wood surface, and thus cracks are likely to occur. In Table 5, x indicates that cracking occurred at that temperature and time.

  FIG. 13 is a graph in which the average values of the carbonization depths of the three samples at each measurement point in Table 5 are plotted. FIG. 13 clearly shows the effect of the quartz plate (gas impermeability, infrared transmissivity). 10, 11, and 12 have similar graph shapes, but it can be seen that the shape of the graph in FIG. 13 is completely different. That is, in FIG. 13, the carbonization depth increases rapidly with time. This difference is thought to be due to the fact that the temperature of the wood surface is constant in the former three, whereas the energy accumulated on the wood surface increases with time and the temperature of the wood surface increases with time in the latter. . As a condition for preventing cracks, it is important that the temperature of the wood surface does not exceed 450 ° C.

The A square timber in the examples below 7 (water glass impregnated amount 29.0 g / ^{m 2)} and B square bar (water glass impregnated amount 72.9 g / ^{m 2)} and samples, A as in the case not using the quartz plate Square and B squares were heated by an infrared method, the occurrence of cracks was observed, and the carbonization depth was measured. The surface of the square bar impregnated with water glass was made to face the heater. When the distance between the heater and the square bar surface was 10 mm, A square bar was used, and when the distance was 20 mm, B square bar was used. In FIG. 13, the graph displayed with a dotted line is data when the surface layer of wood is impregnated with water glass. The dotted line graph on the left is the case where the distance between the wood and the lamp is 10 mm, and the dotted line graph on the right is 20 mm. When the distance was 10 mm, the time during which cracks did not occur doubled, and the carbonization depth increased from 2.24 mm to 3.68 mm. Even when the distance was 20 mm, the time during which cracks did not occur doubled and the carbonization depth increased from 4.97 mm to 9.10 mm. Thus, by impregnating the surface layer with water glass, the irradiation time during which cracks do not occur is greatly extended, and the carbonization depth is also greatly increased. Further, even when the carbonized surface was rubbed with a finger, black powder hardly adhered.

  A portion from the tip of the pine cone having a cross section of 30 mm square to 50 mm was immersed in molten tin at 300 ° C. for 5 minutes and then pulled up. The carbonized surface was uniformly carbonized, almost black and free from cracks, and even when rubbed with a finger, black powder was hardly removed. FIG. 14A shows a photograph of the cut surface taken by cutting with a band saw at a position 15 mm from the tip at a right angle in the length direction. Next, two pine cones with a 45 mm square cross section were prepared, and the portion from the tip to 25 mm was dipped in molten tin at 300 ° C. for 4 minutes and the other was immersed for 10 minutes, then pulled up, and the tip of the carbonized part (B) and (c) in FIG. 14 are photographs obtained by cutting with a band saw perpendicularly to the length direction at a distance of 10 mm from the top and photographing the cut surface. 14A, 14B, and 14C, it can be seen that the smaller the thickness of the square, the closer the cross section of the carbonized layer is to a circle, and the longer the immersion time, the closer to the circle.

Next, 30 mm square and 45 mm square pine cones were cut to a length of 40 mm. These squares are floated on the surface of molten tin at 300 ° C. so that the length direction is horizontal, 30 mm squares every 5 minutes, and 45 mm squares every 10 minutes in all directions. Was rotated in contact with the molten tin bath. After the four surfaces in the length direction were carbonized in this manner, the steel was taken out of the tin bath and allowed to cool. 30 mm squares were floated in a tin bath for a total of 20 minutes, and 45 mm squares were floated for a total of 40 minutes. (D) and (e) of FIG. 14 are photographs in which the central part is cut with a band saw at right angles to the length direction after cooling and the respective cut surfaces are photographed. The innermost shape of the carbonized layer of any one is close to a square. As is apparent from FIG. 14, it is carbonized along the shape of the square material and the control of the thickness of the carbonized layer is ensured when dipping one surface at a time rather than dipping the four surfaces simultaneously in the molten metal bath. . Moreover, the square shape of the cross-section of the square bar is maintained as a perfect square. In contrast, when the entire square bar is immersed in a tin bath, the cross-sectional outer shape of the square bar is slightly distorted as can be seen from FIG.
(Comparative Example 1)

  In order to show the problems when carbonizing by heating in a normal electric furnace, the following tests were conducted. Place a Tokoname-yaki jar with an inner diameter of 230 mm and a height of 220 mm in an electric furnace (MODEL VIKING 66, manufactured by Paragon Industries, Inc., USA). Then, each was placed at the position of the apex of a regular triangle, and a stainless steel wire mesh (wire diameter: 0.45 mm, mesh opening: 2.09 mm, 10 mesh) was laid horizontally thereon, and the electric furnace was heated to 300 ° C. After 1 hour or more has passed since the set temperature in the furnace reached 300 ° C., so that the Tokoname jar and the wire mesh are completely at 300 ° C., a 30 mm square cross section of 50 mm long pine cones on the wire mesh The sample was placed vertically so that one of the cross-sections was down, heated at 300 ° C. for 5 minutes, then taken out of the electric furnace and allowed to cool. The double structure is used in order to prevent the sample from being irradiated with infrared rays from the heater in the electric furnace. Next, similarly, the pine cones having a cross section of 45 mm square and a length of 50 mm were heated at 300 ° C. for 5 minutes and then taken out from the electric furnace. Next, two kinds of pine cones were prepared in the same manner as described above, and samples each having a heating time of 10 minutes were prepared.

FIG. 15 is a photograph of the above sample, and FIGS. 15 (a) and 15 (b) are obtained by heating a pine pine having a cross section of 30 mm square and 45 mm square at 300 ° C. for 5 minutes, FIGS. 15 (c) and 15 (d). Is a pine pine having a cross section of 30 mm square and 45 mm square heated at 300 ° C. for 10 minutes. The top photo in FIG. 15 is the top surface of each sample (surface far from the wire mesh), the second photo is the side of each sample (the central horizontal straight line is the cut portion after carbonization), and the third photo Is the bottom of each sample, and the bottom photo is the cut surface of each sample. As is apparent from FIG. 15, in such heating by a normal electric furnace, the corner portion is preferentially carbonized, and the carbonization in the plane far from the corner proceeds only at a very low speed. The carbonization of the corner portion has progressed too much, and black powder can easily adhere to the finger when rubbed with the finger. When only one surface is heated by the molten metal method or hot plate method of the present invention, such a situation does not occur, and the heated surface is uniformly carbonized. Further, only the corner portion is not strongly carbonized. In the uppermost photograph in FIG. 15D, three cracks can be confirmed, and in the third photograph, six cracks can be confirmed. This is probably because the components thermally decomposed by heating can volatilize freely in the space and are generated when the square bar contracts. It can also be seen that the outer shape is slightly distorted from the square. The degree of heating was large as much as there was a wire mesh, and many cracks occurred as carbonization progressed. On the other hand, in the present invention, since the volatilization of the pyrolyzed component is prevented, thermal shrinkage hardly occurs, and therefore cracks hardly occur.
(Comparative Example 2)

In order to more clearly show the difference between the present invention and carbonization by heating in an electric furnace, the following test was conducted. An iron plate having a thickness of 10 mm and a size of 100 mm × 160 mm was used in place of the wire mesh of Comparative Example 1, and a pine cone having a cross section of 45 mm square and a length of 50 mm was heated for 10 minutes in the same manner as in Comparative Example 1. Immediately after heating, the sample was taken out of the electric furnace and allowed to cool. FIG. 16A is a photograph of the upper surface of the obtained sample, and it can be seen that it is carbonized in substantially the same shape as the upper surface of FIG. FIG. 16B is a side view of the sample (the horizontal line in the center is a cut portion), which is almost the same as the side view of FIG. FIG. 16C is a photograph of the bottom surface of the sample. Since the bottom surface was in contact with the metal plate, it was carbonized almost uniformly and deeply. FIG. 16D is a photograph of the cut surface of the sample. It can be seen that the corner is heavily carbonized, but the surface is not carbonized much. One crack (break) occurred on the upper surface (FIG. 16 (a)), but there was no crack at the bottom. In this way, it was confirmed that when the carbonized surface was covered with a gas-impermeable member, carbonization was performed uniformly and at the same time, cracking was difficult to occur. In the bottom surface (surface in contact with the wire mesh) in FIG. 15D, the progress of carbonization is slightly larger than the top surface, but as many as six cracks were generated. This is probably because the pyrolysis component volatilized from the gaps in the wire mesh. This effect also confirmed the effect of the gas-impermeable member of the present invention. FIG. 16 (e) is a photograph of the tip (bottom surface) of the sample of FIG. 14 (c) of Example 5 (45 mm square spruce pine immersed in molten tin for 10 minutes). As is apparent from FIG. 16 (c), the surface in contact with the iron plate is almost completely carbonized and uniform. When FIG. 16 (c) and FIG. 16 (e) are compared, FIG. 16 (c) has a lower concentration. This is because the iron plate of this comparative example is not a complete hot plate, but a sample is placed on it. This is because it took time to recover to 300 ° C.
(Comparative Example 3)

  Commercially available river sand (sand used for mixing cement with gravel) was placed in a Tokoname ware bottle (inner diameter 165 mm, height 175 mm) to a height of about 8 minutes. After putting this in the electric furnace of Comparative Example 1 and keeping it at 300 ° C. for 2 hours, an Ezo pine bar having a cross section of 30 mm square and a length of 200 mm is placed in this sand, and about 50 mm from the tip is in the sand. Was inserted diagonally at an inclination of about 45 ° C. The tip of the Ezo pine bar was processed into a bowl shape in advance so that it could easily enter the sand. When the square bar was inserted and left for 5 minutes, the corner was preferentially carbonized as in Comparative Example 1, and the in-plane was hardly carbonized.

  Cut commercially available MDF board (thickness 14 mm), commercially available radial tapain laminated timber (thickness 18 mm), commercially available veneer plywood (thickness 12 mm), and commercially available OSB plywood (thickness 12 mm) into 20 x 30 mm sizes. Three samples were prepared for each. The hot plate of Example 2 was set to 300 ° C., and a set of four types of four cut plates was simultaneously placed on the hot plate and heated for 10 minutes. This operation was performed in the same manner for each group, and the thickness of the carbonized layer of three samples was measured for each of four types of wood, and the average value was calculated. As a result, the MDF plate was 4.93 mm, the laminated material was 4.28 mm, the veneer plywood was 4.72 mm, and the OSB plywood was 4.40 mm. In either case, the results were close to those of Example 2.

  It is shown that when the wood surface layer is impregnated with water glass, the surface layer carbonization of the wood according to both the examples 1 and 2 is more effectively performed. That is, the heating time or heating temperature can be increased within the range where cracks do not occur, and the carbonization depth can be further increased.

Water glass (Showa Science Co., Ltd. No. 1 sodium silicate solution (water glass No. 1, very viscous fluid), hereinafter simply referred to as water glass) is diluted with water, and the weight ratio of water glass is 34% and 58%. An aqueous solution of was prepared. A small amount of these aqueous solutions was dripped onto a large number of cedar timbers similar to those in Example 1, spread uniformly with a glass rod, and then allowed to dry horizontally. A glassy film was not formed on the dried wood surface, and it is assumed that the wood surface layer was impregnated. The wood surface and the impregnated portion of the cross section were slightly darker in color, and the depth of impregnation was about 0.2 mm. The average weight increase of the wood after impregnating the wood with water glass and fully drying it was 0.47% for the water glass 34% solution and 1.10% for the 58% solution. The former is named A square and the latter is named B square. In terms of average coating weight, A square timber each 29.0g ^{/ m} 2, B square bar was 72.9 g / ^{m 2.}

  As in Example 1, the square A was immersed in molten tin at 360 ° C. for about 10 mm with the water glass impregnated surface down, and the location was changed by immersing it once every 15 seconds. It was lifted up and immersed in a place without slag. After 5 minutes, the A square was pulled up and allowed to cool. Similarly, a total of three samples were prepared and the carbonization depth was measured. The average carbonization depth of the three samples was 6.54 mm. Cracks did not occur. Next, after the A square was immersed in molten tin at 360 ° C. for 10 minutes in the same manner, the occurrence of cracks was observed and the carbonization depth was measured. Was 9.26 mm. Subsequently, the square A was similarly immersed in molten tin at the same temperature for 15 minutes. Cracks occurred in two of the three square bars. When the same experiment was performed on the B square, a crack occurred in one of the three pieces. In any case, cracks did not occur at the stage of 13 minutes. The squares not impregnated with water glass did not generate cracks for up to 5 minutes, but when impregnated with water glass, the time during which cracks did not occur doubled and the carbonization depth was nearly doubled. Increased to. These results are shown by the dotted lines in FIG. Similar effects can be obtained at other temperature conditions. Surprisingly, it was confirmed that when water glass was impregnated, black powder hardly adhered to the finger even when the carbonized surface was rubbed with the finger. A test similar to the above was performed on a square bar that was not impregnated with water glass, and samples having the same carbonization depth were compared. As a result, it was found that the sample impregnated with water glass was much less likely to get dirt on the fingers. This effect is very advantageous in practice.

  In the same manner as in Example 2, the A square bar and the B square bar were placed on a hot plate at 340 ° C. with the water glass impregnated surface down, and the occurrence of cracks and the carbonization depth were measured using the heating time as a parameter. As a result, the A square member did not crack until 20 minutes, and cracked after 30 minutes. The B square did not crack until 30 minutes. As can be seen from FIG. 11, in the square material not impregnated with water glass, cracks did not occur at a heating temperature of 340 ° C. until 15 minutes, so the time during which cracks did not occur doubled and the carbonization depth also increased. It has increased by about 50%. These results are shown by the dotted lines in FIG. Similar effects were obtained at other temperature conditions. As in the case of carbonization with molten tin, it was confirmed that black powder hardly adhered to the finger even when the carbonized surface was rubbed with the finger.

  The cedar wood having the same dimensions as in Example 3 was covered with an aluminum foil having a thickness of 13 μm on the upper and side surfaces of the cedar wood. The aluminum foil was squeezed and adhered so that no gap was formed between the upper surface of the cedar wood and the aluminum foil. The aluminum foil was also pressed against the side so that it did not rise. The surface (upper surface) covered with the aluminum foil of the sample thus prepared was placed on a hot plate at 340 ° C. in the same manner as in Example 2 and heated for 15 minutes. After cooling, the aluminum foil was removed and the carbonized surface was observed. As a result, the surface shape was very fine and smooth compared to the case without the aluminum foil. There were no cracks. The thickness of the carbonized layer was about 9 mm when there was no aluminum foil, whereas it slightly increased to about 10 mm when there was an aluminum foil. Even when the carbonized surface was rubbed with a finger, black powder hardly adhered.

  Four cedar woods having the same dimensions as in Example 3 are arranged in 2 rows and 2 columns on a workbench with an interval of 5 mm, and the upper surface (surface of 20 × 30 mm) is 5 mm thick and the size is 100 mm square. A stainless steel plate was placed. Four samples were arranged so as to be approximately in the center of the stainless steel plate. When the flame of the gas burner (Fujiwara Sangyo Co., Ltd. One-touch gas torch SK-11) was radiated for 1 minute from the upper side of the stainless steel plate so as to be emitted uniformly over the entire surface of the stainless steel plate, a little smoke was generated. Therefore, after extinguishing the fire for 30 seconds and radiating for 20 seconds after smoke completely disappeared, a little smoke was generated again. Then, after extinguishing again for 30 seconds, after the smoke disappeared, 20 seconds were emitted, and after that, the fire extinguishing for 30 seconds and the radiation for 20 seconds were repeated 9 times. A total of 11 repetitions were performed. After the last 20 seconds of radiation, the sample was allowed to cool, the stainless steel plate was removed, and the carbonized surface of the square was observed. No cracks were generated, and the average thickness of the carbonized surface layers of the three samples was 5.82 mm. . From the state of smoke generation, it is estimated that the temperature of the sample surface was always kept below 340 ° C.

  Next, instead of the stainless steel plate, an iron plate having a thickness of 1 mm and a size of 60 × 50 mm was placed on the same cedar square material as in Example 3, and a gas burner was emitted for 10 seconds in the same manner as described above. A little occurred. So, after the fire was extinguished for 10 seconds, the smoke stopped. This was repeated 12 times. Then, after standing to cool and removing the iron plate, the thickness of the surface carbonized layer of the sample was 2.39 mm. The carbonized surface was very smooth and free from cracks. Judging from the state of smoke generation, it is presumed that the surface temperature of the sample was kept below 300 ° C. Next, instead of the above iron plate, an iron plate having a thickness of 0.3 mm and a size of 60 × 50 mm was placed on one cedar square material similar to the above, and the gas burner radiation and extinguishing were repeated in the same cycle as above. When the gas burner was radiated for 10 seconds, intense smoke was generated from the squares, and the edges ignited but soon disappeared spontaneously. When the steel plate was removed and the carbonized surface was observed, many cracks were generated. The surface temperature of the sample is estimated to be 450 ° C. or higher. Therefore, the gas burner radiation and fire extinguishing cycle was repeated for 5 seconds, and fire extinguishing for 10 seconds. There was no generation of cracks, and the thickness of the surface carbonized layer was 2.09 mm. When the thickness of the metal plate placed on the square bar is reduced in this way, the temperature of the metal plate rapidly rises due to gas burner radiation. It is important to choose

  An iron plate having a thickness of 1 mm and a size of 60 mm × 50 mm is placed on the upper surface (20 × 30 mm surface) of the cedar wood having the same dimensions as in Example 3, and using the same heat gun as in Example 3, hot air at 340 ° C. When sprayed for 5 minutes, the surface of the wood was hardly colored. Then, when the temperature of the hot air was raised to 400 ° C. and heated for 10 minutes, it became a little dark (brown). The carbonization depth of the surface layer was 2.46 mm. Next, when a similar experiment was performed using an iron plate having a thickness of 0.3 mm and a size of 60 × 50 mm instead of the iron plate having a thickness of 1 mm, a black carbonized layer having no crack and a thickness of 3.21 mm was obtained. Obtained. On the other hand, the upper surface (20 × 30 mm surface) and side surface (the whole surface in the height direction) of the cedar wood are covered with an aluminum foil having a thickness of 17 μm. The aluminum foil was squeezed so that there was no contact. The sample prepared in this manner was sprayed with hot air at 400 ° C. for 5 minutes from above the aluminum foil, and then the aluminum foil was removed. As a result, many cracks were generated on the surface of the carbonized layer. Since the aluminum foil is a thin metal, the temperature of the sample surface was brought close to 400 ° C. by hot air at 400 ° C., and the heating time was increased to 5 minutes, so cracks occurred. The iron plate or aluminum foil became a hot plate and the wood was heated in the same way as the hot plate method, but if the thickness of the metal plate is large, the efficiency of heating with hot air is bad, conversely when it becomes thin like an aluminum foil, It is important to select an appropriate temperature and time because it is easily heated.

  A cedar wood having the same dimensions as in Example 3 was used as a square material sample, and a black surface-treated iron plate having a thickness of 1 mm and a size of 60 mm × 50 mm was placed on the upper surface (surface of 20 × 30 mm), as in Example 4. A quartz glass tube heater was disposed so that the distance from the heater to the upper surface of the sample was 10 mm. After applying voltage to the heater and irradiating with infrared rays for 2 minutes, voltage application was stopped for 5 seconds, voltage was applied for 25 seconds, and then voltage application was stopped for 5 seconds. Thereafter, after applying voltage application for 25 seconds and stopping application of voltage for 16 seconds in this manner, the sample was checked after being allowed to cool. The carbonized surface was very smooth and free from cracks. The average thickness of the surface carbonized layer of the two samples thus prepared was 3.70 mm. It was estimated that the temperature of the surface of the sample was kept at 300 ° C. or lower because there was almost no smoke during repeated ON / OFF of voltage application. In addition, when the same experiment was conducted using an aluminum foil instead of the black iron plate, the square bar was hardly colored. That is, the aluminum foil reflected infrared rays and was not heated very much. Therefore, a member that absorbs infrared rays well is required for this purpose.

  Example 12 is an example in which the heat roll is rotated and moved on the surface of the plate-like wood to carbonize the surface layer of the wood, but it is difficult to obtain a heat roll with a built-in heater. The thing which floated the aluminum roll in the bath was used. An aluminum roll having a diameter of 30 mm and a length of 100 mm was used. When an aluminum roll was floated on a tin bath melted in a stainless steel bat in the same manner as in Example 1, about 18 mm of the aluminum roll was exposed from the bath surface perpendicularly from the bath surface. The temperature of the tin bath was set to 400 ° C. Next, put a cedar board with a cross section of 30 x 14 mm and a length of 300 mm on the aluminum roll so that the 30 x 14 mm surface is in contact with the aluminum roll and the aluminum roll and the cedar board are orthogonal to each other, and apply a little load. The cedar board was slowly moved horizontally in a state where about two-thirds of the aluminum roll was immersed in the tin bath. When the cedar board was moved, the aluminum roll rotated slowly in synchronization with the movement of the cedar board. The cedar board was moved 50 mm over 5 minutes. During this time, no smoke was generated. Therefore, it is estimated that the surface temperature of the cedar board where the aluminum roll and the cedar board are in contact was 340 ° C. or less. The carbonized surface was sufficiently blackened, and the carbonization depth was 1.19 mm. From the above experiments, it was confirmed that the wood surface can be carbonized by a hot roll.

  The hot plate was heated to 340 ° C. in the same manner as in Example 2. A testicle rod having a diameter of 20 mm and a length of 30 mm was placed on the hot plate, moved while slowly rotating, and when it was rotated about half a round over 8 minutes, the testicle rod was taken out of the hot plate and allowed to cool. After cooling, the carbonization depth was measured and found to be 1.34 mm.

  Next, testicle bars with the same dimensions as above and testicle bars with the same dimensions covering almost half of the circumference with 13μ thick aluminum foil are placed on a hot plate at 340 ° C, left for 15 minutes, and then covered with aluminum foil The untested testicle rod was lifted by grasping it with tongs, and when the portion of the testicle rod that was in contact with the hot plate was observed, no cracks were generated. The time required for this confirmation work is 7 to 8 seconds. Therefore, this testicle rod was immediately returned to the hot plate so that the same place was heated, and both were additionally heated for 5 minutes, then removed from the hot plate and allowed to cool. A number of large cracks occurred on the testicle bar not covered with the aluminum foil, but no crack occurred on the testicle bar covered with the aluminum foil. Thus, when the contact area with the hot plate is small, the effect of covering with the aluminum foil is tremendous.

  In Example 2, the temperature of the hot plate was set to 340 ° C. by the hot plate method, and even if the carbonized surface of the sample heated for 15 minutes was rubbed with a finger, almost no black powder adhered. Adhered to tissue paper. When the carbonized surface of such a sample was impregnated with water glass in the same manner as in Example 7, no powder adhered even when rubbed strongly with tissue paper. When paint was applied instead of water glass (Atom Support Co., Ltd. water-based spray ivory), the appearance became ivory. After fully drying, after sticking an adhesive tape (Sumitomo 3M Co., Ltd. Scotch Super Transparent Tape S) and then peeling off, all peeled off partially. The carbonized layer was thinly attached to the part that adhered to the tape and peeled off. The carbonized layer is relatively fragile on the surface side, and it is considered that water glass and aqueous spray do not reach the inside of the carbonized layer. Since the carbonized layer is relatively lipophilic, it is considered that the aqueous coating agent does not have good adhesion to the carbonized layer.

  Next, an organic solvent liquid of polysiloxane (manufactured by Shinagawa White Brick Co., Ltd. (current Shinagawa Refractories Co., Ltd.) NIC-C5) 3 drops of a solution in a mixed solvent of butyl acetate and a dropper were spread with a dropper and spread over the entire surface with a glass rod. Since the dropped liquid permeated in several tens of seconds, this operation was repeated again and then left to dry naturally. After the solvent was completely dried, no black powder adhered even when the surface of the sample was strongly rubbed with tissue paper. Next, when an adhesive tape peeling test was performed in the same manner as described above, no peeling occurred.

  Instead of the above polysiloxane, an organic solvent-based paint (Atom Support Co., Ltd. Lacquer Spray E, brown) was sprayed once. The coating was very smooth and glossy. When the adhesive tape peeling test was performed in the same manner as described above after drying for 3 hours, no peeling occurred.

As One Neo Hot Plate HI-1000 was used as the hot plate, and the surface temperature was allowed to reach 270 ° C. A plate (width 90 mm, length 300 mm, thickness 9 mm) was placed on a hot plate, heated for 30 seconds, then turned over quickly and the opposite surface heated for 30 seconds. The reason for heating upside down is to prevent warping. Then, it was quickly turned over and heated for 1 minute, then turned over quickly and heated for 1 minute. Thereafter, the total heating time for each surface was set to 10 minutes in the same manner. The plate thus heat-treated has a brown to brownish brown appearance and looks good. By applying such heat treatment to the board, the board has an antibacterial action, so it can be used as a kitchen cutting board. It can also be used for furniture and interior decoration.

The wood obtained by the present invention has higher mechanical strength than wood (thermo wood) obtained by a conventional carbonization method, and can therefore be used as a structural material that was difficult with thermo wood. Moreover, since carbonization can be performed at a temperature higher than the carbonization temperature of the thermowood, a greater antiseptic effect can be obtained. The present invention can also be used for grilled piles , fences, tables, kennels and the like used outdoors in fields and gardens. It can be used in most other fields where wood is used. If the degree of carbonization is lowered, the appearance becomes brown, so it can be used for unpainted furniture, picture frames, bulletin boards, signboards, and other household items such as kitchen cutting boards and pans. It is thought that it can contribute to the development of the Japanese timber industry, including the effective use of thinned wood.

DESCRIPTION OF SYMBOLS 1 Wood 2 Aluminum foil 3 Hot plate 4 Hot melt metal bath 5 Hot melt metal bath container 6 Force applied to wood

Claims (8)

  A gas-impermeable member that prevents volatilization of the pyrolysis component is brought into contact with the surface of the wood or wood material, and the surface of the wood or wood material is heated within a heating temperature range of 240 ° C. to 450 ° C., A method of carbonizing a surface of a wood or wood material, wherein the surface layer of the wood or wood material is carbonized to a thickness of 0.7 mm or more without adjusting the heating time to cause cracks in the surface layer.   The gas impermeable member is any one of a heat-melted metal, a heat plate having good heat conductivity, a heat metal foil, and a heat metal roll, and the heating time is 15 seconds or more. A method for carbonizing a surface layer of a wood or wood material as described in 1.   2. The wood or wood material according to claim 1, wherein the gas impermeable member is infrared permeable, and the surface of the wood or wood material is heated by irradiating infrared light through the member. Surface layer carbonization method. The method of carbonizing a surface layer of wood or wood material according to any one of claims 1 to 3, wherein at least one gas-impermeable member and wood or wood material are slid relative to each other. .   After the surface is heated and pre-carbonized in the absence of a gas-impermeable member on the surface of wood or woody material, the surface is heated with the gas-impermeable member in contact with the surface. The method for carbonizing a surface layer of wood or wood material according to any one of claims 1 to 4.   The method for carbonizing a surface layer of wood or wood material according to any one of claims 1 to 5, wherein the surface layer is impregnated with water glass before heating the wood or wood material.   The surface of the carbonized region is covered with a metal plate or metal foil having a thickness of 0.3 mm or less before the wood or woody material is heated. A method for carbonizing a surface layer of a wood or woody material according to any one of claims 1 to 6.   A product produced by the method according to any one of claims 1 to 7.