JPH1177616A - Artificial drying method for wood - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable drying wood of various cross-sectional configurations by heating it under a liquid phase of specific heated melt, reduce greatly drying time while refraining the generation of superficial checks and try to recycle waste of a specific heating medium liquid. SOLUTION: Immediately a non-dried wood is submerged in a heating tank filled with a melt of specific non-hydrophilic petroleum oil or natural fats and oils heated to a temperature of 100 deg.C for continuos heating, heat is transmitted from the superficial layer of the wood into the interior thereof, this promoting a rapid drying of the wood by virtue of vapour pressure generated inside the wood. The device according to the invention is simple and easy for use as with a fryer used in the food industry. In addition, in the case of paraffin used as a heating medium, when wood is kept submerged therein for cooling down after heating is stopped, paraffin permeates into the wood and hardens therein, thereby imparting the wood water and weathering resistances. In addition, browned waste water from paraffin liquid can be recycled for use as paint for wood, solidifying processing agent for waste oil and a raw material for candles.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for artificially drying wood such as logs and lumber of cedar, hinoki and other tree species.

[0002]

[Prior art] Artificial drying of wood is performed by steam, dehumidification,
Generally, it is a "gas-phase drying method" such as a high-frequency decompression method. These various gas-phase drying methods are properly used depending on the wood species and the use of the wood. Generally, undried wood has properties such as "shrinking, bending, warping, and cracking" which are said to be defects of wood. Desiccant is an effective means to substantially eliminate these disadvantages. Compared with laminated wood, etc., the evaluation of a dry wood as a building material is not low in terms of product performance such as dimensional stability and strength improvement. In the current general steam drying method, for example, in the case of the drying of the prism,
It takes several days to two weeks of drying time. In addition, there is a problem that surface cracks are more likely to occur as the degree of drying is higher, which generally causes an increase in drying cost. Various drying schedules are being sought to overcome these problems.However, a drying schedule that can ignore individual differences in wood such as the water content and specific gravity of the wood and a drying work mechanism that can ensure sufficient quality as a drying material are configured. It has not been possible.

[0003] Next, log-shaped lumber, log-shaped wood such as piles and round slabs, and wood with a large cross-sectional area such as a flat square are difficult to pile and are difficult to dry within an allowable time. The situation has not been implemented. Since these are naturally dried, demand cannot be expected to increase due to the occurrence of surface cracks and the degree of drying.

On the other hand, in recent years, regulations on the use of specific chemical substances in wood-improving materials have been expanding from the viewpoint of global environmental protection, and further safety is required in the development of technology for improving the weather resistance of wood.

[0005]

In recent years, the domestic lumber industry has a production capacity of about 1,000 rods per plant per day at a pillar angle. Assuming that some of the wood is artificially dried, a drying treatment speed that is in equilibrium with the production speed of sawmills such as prisms is required. Naturally, it is also essential to guarantee the quality such as the moisture content standard of the dried material. The present invention shortens the artificial drying time, enables artificial drying of log-shaped wood and large-section wood, prevention of occurrence of cracks in the surface of the artificial drying material,
It is an object of the present invention to provide an artificial drying method which aims at quality assurance of drying materials and cost reduction as a whole.

[Means for Solving the Problems]

Reduction of drying time The temperature of the wood is continuously increased while the wood is immersed in a heated melt of non-hydrophilic petroleum or natural fats and oils, and the internal temperature of the wood is raised to a specific temperature of 100 ° C. or more. To hold. Enables artificial drying of log-shaped wood and large-section wood.By using a weight jig to immerse these woods in a heated melt, it is possible to dry log-shaped wood and wood with a flat cross section such as a flat square. Make it possible. Prevention of surface cracks in artificially dried lumber To prevent surface cracks, cracks and hair cracks after rough sawing before drying are prevented. To do so, either perform a quick drying process immediately after coarse grinding, or
Take measures to prevent cracks at the mouth and minimize cracking before drying. When using paraffin as the heating solvent according to the present invention,
For recycling of paraffin waste liquid after use,
Utilizes the properties of paraffin, which is solid at room temperature and has high water resistance.

[Action]

In general, water vaporization phenomena include spontaneous evaporation at room temperature and boiling above the boiling point. The latter has a much shorter vaporization time of water than spontaneous evaporation. On the other hand, the saturation of wood, which is the reverse concept of wood drying, is often performed by boiling with hot water. If wood is immersed and boiled in a heat-melted substance with a boiling point of 100 ° C or more with non-hydrophilic petroleum oils or natural fats and oils, the water in the wood is heated to 100 ° C or more and turns into steam, which is rapidly discharged by the vapor pressure. You. Immerse undried logs or rough sawn lumber so that the convection of the molten liquid as the heating medium is smooth, and continuously heat it until it is reduced to the dry weight according to the wood species and target moisture content, and it is generated inside the wood structure This is an ultra-high-speed artificial drying method for wood that discharges water in a very short time by the vapor pressure.

[0008] In the vapor phase drying, the form of stacking in the drying furnace and the thickness of the crosspiece also become factors such as variations in the wind speed and temperature in the furnace. It is possible to dry small log-shaped wood and wood with a large cross-sectional area such as a flat square.

It is thought that surface cracks are caused by a difference in shrinkage due to a temperature difference or a difference in the degree of wetness between the outer layer and the inner layer of the wood, and an internal stress of the wood. Although it is dried, since the temperature is about 80 ° C. or higher, which is called the thermal softening point of wood, surface cracking due to a difference in shrinkage does not occur. However, if the wood is removed before the thermal softening action reaches the center of the wood, surface cracks occur rapidly due to the difference between the wood surface temperature and the atmospheric temperature.

[0010] When incompletely dried materials due to various variations unique to wood such as weight, density, and moisture content of wood are generated, only these incompletely dried materials are immediately immersed again to obtain a weight corresponding to a predetermined target moisture content. This is a flexible drying method, such as continuous heating until the amount is reduced to achieve the target quality.Since a simple method of drying wood using a heat medium in a heat-resistant heating tank, conventional drying schedule management is used. It is no longer necessary to obscure the idea.

Illustrated by the method of the invention

As a heating medium for wood, paraffin wax was used here. It has little toxicity and is relatively easy to handle even for non-chemical experts. When heated continuously to 100 ° C or higher using molten paraffin wax as a heat medium, the wood is heated in the direction from the wood surface to the wood core, and the water content of the wood is turned into steam, which is reduced by the internal steam pressure of the wood for a short time. As a result, moisture is discharged in the form of bubbles from the wood surface and the wood surface.

<Drying Time and Moisture Content> The primary goal of wood drying according to the present invention is to reduce the drying time according to the target moisture content of logs and sawn timber. For example, in the case of cedar and hinoki cypress short square lumber (square lumber having a side length of 33 cm and 100 cm each having a side length of 10 cm), in the case of cedar lumber having an initial moisture content of about 100%, the drying time up to JAS standard D20 is only about one day. is there. It takes about half a day in cypress. Further, there is almost no influence of the drying time due to the difference in the material length.

<Drying of log-shaped and large-section lumber> In the present invention, even in the case of a log-shaped or large-section member, drying can be performed in a short time because of an efficient heating method in a paraffin wax liquid. In a cedar log-shaped member (diameter 10 cm, material length 100 cm) having an initial water content of 80% to 100%, the water content became 20% or less in about 10 hours. Large cross section (cedar wood 12cm × 24cm) material length 100c
m) also took about 20 hours to reduce the initial moisture content from 90% to 20%.

<Suppression of Surface Cracking> In the case of the drying treatment of the pillar corner of the cedar, many "material surface cracks / penetration cracks" often occur. In the present invention, since the wood is heated in a short time in the paraffin wax liquid, a difference in shrinkage between the outer layer and the inner layer of the wood does not occur, or it is considered that the heat softening action at a wood temperature of about 80 ° C. "Cracks etc."

<Suppression of turning> The artificial drying method according to the present invention releases the residual stress of undried wood,
It is possible to suppress the occurrence of turning of the back plate or the like during sawing. When the square wood having a length of 1 m and a length of 10 cm long after drying was longitudinally ground into five pieces with a thickness of about 2 cm, almost no bending occurred.

<Drying Apparatus> The drying method according to the present invention employs a method such as "coarse sawing such as square material and plate material" or "log" so as to ensure smooth convection of the heated paraffin wax liquid in a heat-resistant immersion tank. Is a simple drying device for immersion heating. However, the buoyancy of the wood at the end of drying gradually increases in proportion to the wood volume and the progress of the drying, and is several tons. Therefore, an immersion device is required. This is a method of suppressing warpage and bending similar to pressing and drying. As the heating device, general wood chip burning, oil burning, or the like can be used, and it is almost the same as a commercial fryer.

<Reuse of used paraffin wax>
When paraffin wax is used in the drying method of the present invention, various components of wood are eluted with steam and the paraffin wax is gradually turned brown, but since it does not contain any metal substance and the like, various recycling methods are possible. .

<Provision of Wood Functionality such as Water Resistance and Weather Resistance by Injection of Paraffin Wax Waste Liquid> After the artificial drying is completed, the paraffin wax is allowed to cool down to the melting point or less, and the paraffin wax is injected and solidified into the surface layer of the wood. Wood is provided with waterproofness and weather resistance. The initial moisture content of the cedar short square wood with a side length of 10 cm and a length of 30 cm was about 90%, but the heating was interrupted at the end of the drying process when the estimated moisture content was reduced to D20 specified by JAS while measuring the weight change, and then released as it was. After the paraffin wax was cooled and solidified, it was heated and melted again, and the weight of the short bar was measured. This is the result of the paraffin wax being injected and solidified into the wood surface. Although this cedar short angle wood did not have surface cracks as described, it came into contact with the soil and was left in a harsh environment of high temperature and humidity for two months, and then exposed to the sun for two months, resulting in decay. No change occurred in the material surface such as cracks and surface cracks. General wood can be dipped for a short time in a heated melt of used paraffin wax to paint the wood.
Since paraffin is a solid at room temperature, it has a natural color of brown and has a high permanence of coating effect and high water resistance. . It can be reused as a coagulant for kitchen waste oil from ordinary households. A paraffin wax of about 20% of the waste oil volume was heated and mixed, and allowed to cool to solidify. The molten paraffin wax waste liquid was poured into an appropriate container provided with a core such as a kite string and allowed to cool and solidify, and could be reused as a candle usable in outdoor camps and the like.

According to the present invention, the drying time is drastically reduced while suppressing surface cracks regardless of the cross-sectional shape and size of the material to be dried, and the quality assurance of the dried material is promoted.

Claims (6)

[Claims] 1. An artificial drying method of wood characterized by continuous boiling in a liquid phase in which viscous petroleum oils and natural fats and oils having a high flash point without hydrophilicity such as paraffin wax are heated and melted at a specific temperature. . 2. In the method for artificially drying wood in the liquid phase according to claim 1, in addition to general column corners and plates, it is also possible to dry log-shaped wood or a thick corner having a large cross section in a short time. An artificial drying method for wood characterized by being able to do so. 3. The method for artificially drying wood according to claim 1, wherein the method for artificially drying wood in a liquid phase hardly causes surface cracks. 4. In the method for artificially drying wood in the liquid phase according to claim 1 or 2, when individuals having not achieved the target moisture content are derived, it is possible to re-immerse only these individuals and perform additional boiling. An artificial drying method for wood. 5. In the method for artificially drying wood in the liquid phase according to claim 1, wherein paraffin and natural fats and oils are used as a heating medium, the dried wood is immersed in the melt after repeated use. A method for producing highly weather-resistant wood, in which paraffin and natural fats and oils are injected into the wood surface layer and solidified by suspending heating and allowing the wood to cool. 6. In the method for artificially drying wood in a liquid phase according to claim 1, when paraffin and natural fats and oils are used as a heating medium, used paraffin browned with various components of wood eluted with each use. And a method of reusing natural fats and oils as coating materials for general wood, coagulation material for household waste oil, candles for outdoor camping, etc.