JP2016030404A - Production method of heat-treated lumber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a production method of a heat-treated lumber which provides efficiently a heat-treated lumber suppressed in secular discoloration due to light, being excellent in dimensional stability and resistant to problems of chips and differences in color tone during shape formation and keeping texture of wood.SOLUTION: A production method of a heat-treated lumber includes: a pressure reduction treatment step of housing a to-be-treated lumber, or natural wood, in a closed space and keeping the internal pressure of the closed space at 50 kPa or lower; a super-heated steam treatment step of introducing super-heated steam into the closed space to house the to-be-treated lumber decreased in oxygen content by the pressure reduction treatment to heat the to-be-treated lumber to a temperature of 170°C or higher; and a discoloration acceleration step of subjecting the to-be-treated lumber after the super-heated steam treatment step to a discoloration acceleration treatment.SELECTED DRAWING: None

Description

  The present invention relates to a method for producing heat-treated wood.

Solid wood made from logs is used as an interior material for buildings and as a member for furniture while taking advantage of the texture of wood. However, since wood contains lignin that is easily decomposed by light, there is a problem that the color changes over time under exposure to sunlight. For example, when using solid wood as a flooring, if there is a part that is exposed to sunlight and a part that is not exposed to sunlight due to a shield such as a carpet, a difference in color occurs between the two after the passage of one or two years. It looks bad when the shield is removed. On the other hand, if wood is painted with a paint containing a pigment in order to conceal the aging of the surface, the texture of the wood is lost.
Solid wood is easy to change in size due to moisture absorption / release and temperature changes.For example, when solid wood is used as flooring for floor heating, the floor may be affected by humidity and temperature differences that occur on the front and back surfaces. There may be a gap in the seam of the material or warping of the flooring.

  In Patent Document 1, after heating wood in a sealed space formed between hot plates of a hot press apparatus, the wood is treated with high-pressure steam in the sealed space, and then the tea system of wood generated by the heat treatment. Techniques have been proposed for correcting coloring by dipping in a bleaching agent. According to the technology related to the proposal, the dimensional stability of wood is improved by heat treatment, while the wood is partially carbonized and weakened by heat treatment, for example, when actual processing for connecting flooring materials is performed In such cases, unintentional chipping is likely to occur in males and the like. In addition, since the color tone is adjusted by dipping in a bleaching agent, there is a problem that the bleaching agent remains.

  In addition, Patent Document 2 discloses a method of coloring a slice veneer used as a decorative material on the surface of wood, by heating the wood before slicing with high-pressure steam so as to polymerize light fast inside the wood. A technique for generating a colored product has been proposed. However, even if a slice veneer used as a decorative material on the surface of wood is colored by high-pressure steam treatment, high dimensional stability cannot be obtained for members used as interior materials for buildings, members for furniture, and the like. In other words, the cited document 2 does not describe any method for obtaining high dimensional stability required for a floor heating-compatible floor material.

  Patent Document 3 proposes a technique for suppressing browning of the wood surface while improving the dimensional stability of the wood by heat-treating only the inside of the wood with high frequency. However, according to the technology, the inside of the wood is browned by heating, so that, for example, when heat treatment wood is subjected to actual processing for connecting flooring materials, the tea is colored. There is a problem in that the inside is exposed on the surface and a color difference is produced with other parts.

JP 2004-345183 A JP 2011-25591 A JP 2008-137290 A

  The objective of this invention is providing the manufacturing method of the heat-processed wood which can eliminate the various fault which a prior art has.

  The present invention relates to a decompression treatment step in which treated wood, which is a solid material, is accommodated in a sealed space and the internal pressure of the sealed space is maintained at 50 kPa or less, and the treated wood in which the oxygen content is reduced by the decompression treatment step. Superheated steam is introduced into the sealed space containing the heat, and the wood to be treated is heated to a temperature of 170 ° C. or more, and the discoloration promoting treatment is performed on the wood to be treated after the superheated steam treatment step. The present invention provides a method for producing heat-treated wood including a discoloration promoting step.

  According to the method for producing a heat-treated wood of the present invention, there is provided a heat-treated wood in which aged discoloration due to light is suppressed, dimensional stability is excellent, a problem of chipping or color difference is hardly caused at the time of shape processing, and the texture of wood is maintained. Obtained efficiently.

FIG. 1 is a perspective view showing an example of the shape of the wood to be treated. FIG. 2 is a cross-sectional view showing a solid floor material obtained by performing actual processing on both end faces in the width direction of the treated wood of FIG. FIG. 3 is a graph showing changes in atmospheric pressure and temperature in the examples. FIG. 4 is a graph showing the width shrinkage rate when the reduced pressure process and the superheated steam process are performed and when the reduced pressure process and the superheated steam process are not performed, when the wet condition is changed to the overdried condition. FIG. 5 is a graph showing a color difference “ΔE” before and after the time-dependent color change acceleration test when the color change acceleration process is performed after the decompression process and the superheated steam process.

Hereinafter, the present invention will be described based on preferred embodiments thereof.
In a preferred embodiment of the present invention, the wood to be treated, which is a solid material, is subjected to a decompression treatment and a superheated steam treatment in this order. The wood to be treated subjected to these treatments is a solid material. The solid material means a finger joint material in which only the wood and the end portion of the wood having no joint portion are joined in the length direction, and laminated wood, plywood, LVL, particle board and the like are not included.
Moreover, it is desirable that the wood to be treated after the heat treatment to be subjected to the discoloration promotion treatment is a solid material that has been processed into a shape close to a product by processing of actual processing.
The tree species of the solid wood used as the treated wood is not particularly limited and may be any tree species. Moreover, although it may be a conifer or a broad-leaved tree, a broad-leaved tree has a large amount of oxygen in the material of the conduit part, and partial carbonization is likely to occur around the conduit by high-temperature treatment, so the effect of the present invention is more remarkable. Easy to appear.
Examples of solid wood species include, for example, beech family broadleaf trees such as red oak and white oak; Examples include deciduous broad-leaved trees, conifers such as cedar, pine, and cypress.

  The size of the solid wood used as the wood to be treated is not particularly limited. For example, when producing heat treated wood for flooring (including solid flooring for floor heating), for example, in the longitudinal direction The length L is 20 to 100 cm, the width W is 8 to 20 cm, and the thickness T is 1.5 to 2.5 cm (see FIG. 1).

(Decompression treatment process)
For the decompression process, for example, a decompression and heat treatment apparatus including a decompression chamber capable of reducing the internal pressure to 20 kPa or less can be used. The decompression chamber may be cylindrical or may have a shape other than a cylindrical shape, for example, a cubic shape. The decompression chamber is provided with an openable / closable door for taking in and out the wood to be treated. The decompression chamber has an intake / exhaust pipe that can be switched between a communication state and a non-communication state inside and outside the decompression chamber by controlling a valve such as a solenoid valve. A vacuum pump capable of depressurization, a steaming device capable of injecting steam into the decompression chamber if desired, a superheated steam introducing device, and a cooling and humidifying device using a sprinkler are attached.

  The apparatus for introducing superheated steam is configured to be able to introduce superheated steam directly into the decompression chamber via an introduction pipe that opens toward the decompression chamber. Superheated steam is steam obtained by heating saturated steam evaporated at 100 ° C. to a higher temperature. As a mechanism for generating superheated steam, various known mechanisms can be adopted. Indirect heating method in which a saturated steam evaporated at 100 ° C. is secondarily heated by a burner through a pipe through which the saturated steam passes, at 100 ° C. A direct heating method or the like in which a heating element or the like that generates heat with a heating wire is arranged and heated in a flow path through which evaporated saturated water vapor passes can be adopted.

  A plurality of woods to be treated to be accommodated in the decompression process are arranged side by side on a support such as a shelf or a base made of a heat-resistant material such as metal installed in a decompression chamber. And after arrangement | positioning of to-be-processed wood, the door of a decompression chamber is closed and the inside is sealed. Further, the vacuum pump is operated to discharge the air in the decompression chamber to decompress the inside. As shown in the graph of the embodiment shown in FIG. 3, at the start of decompression, steaming is performed in which steam is introduced into the decompression chamber and the wood to be treated is heated to 100 ° C. or higher (preferably 110 ° C. or higher). It is preferable from the viewpoint of suppressing a decrease in material temperature due to a loss of heat of evaporation accompanying vacuum drying.

In the reduced pressure treatment step, the inside of the sealed space containing the wood to be treated is preferably decompressed to 50 kPa or less, more preferably 30 kPa or less, and even more preferably 20 kPa or less. The time during which the wood to be treated is subjected to such reduced pressure (treatment time) can be appropriately determined according to the thickness and pressure of the wood to be treated. For example, when the internal pressure of the sealed space (decompression chamber) is 20 kPa or less. , Preferably 10 minutes or more, more preferably 1 hour or more, further preferably 2 hours or more, and when the internal pressure of the sealed space (decompression chamber) is 50 kPa or less, preferably 1 hour or more, More preferably, it is 3 hours or more, More preferably, it is 5 hours or more.
As shown in the graph of the embodiment shown in FIG. 3, the decompression treatment is performed while maintaining the temperature of the wood to be treated in the sealed space (decompression chamber) in the range of 60 to 90 ° C., particularly in the range of 70 to 80 ° C. It is preferable to perform it from the viewpoint of continuous drying under reduced pressure.

(Superheated steam treatment process)
The superheated steam treatment is started by introducing superheated steam into a sealed space in which the wood to be treated in a state where the oxygen content is reduced by the decompression treatment step, and the wood to be treated is heated at a temperature of 170 ° C. or higher. As a result of the above-described decompression treatment, the content of air contained in the wood to be treated has been greatly reduced, and the oxygen content has also been greatly reduced as compared with the wood to be treated before the decompression treatment. In this embodiment, by bringing superheated steam into contact with the wood to be treated in a state in which the oxygen content is reduced, partial carbonization of the wood to be treated, which is likely to occur when no decompression treatment is performed, is effectively suppressed. can do.
On the other hand, after the decompression process, when the interior of the decompression chamber is opened to the same level as the atmospheric pressure by opening the decompression chamber door or connecting the inside and outside of the decompression chamber with the intake and exhaust pipes, the decompression process reduces the air and oxygen content. The content of air and oxygen in the wood to be treated returns to the original, and partial carbonization tends to occur in the wood to be treated during heat treatment with superheated steam. From such a viewpoint, it is preferable that the superheated steam treatment is performed without removing the wood to be treated from the sealed space and the sealed state is maintained, in other words, switching from the decompression process to the superheated steam process. Is preferably performed while maintaining the sealed state of the sealed space. In addition, the superheated steam treatment is preferably started by introducing superheated steam into the sealed space in which the wood to be treated with a reduced oxygen content is accommodated, and the outside air is introduced until the high temperature treatment described below is completed. Even more preferably not.

In the superheated steam treatment, the wood to be treated is heated to a temperature of 170 ° C. or higher. By heating the wood to be treated to a temperature of 170 ° C. or higher, the dimensional stability of the heat-treated wood obtained is greatly improved. The reason is that hemicellulose, which is a component in wood that greatly changes the size of the wood by moisture absorption, is efficiently decomposed in the entire area of the wood to be treated by heat treatment with superheated steam.
From the viewpoint of improving the dimensional stability of heat-treated wood and improving the decomposition efficiency of hemicellulose, the superheated steam treatment step preferably includes a high-temperature treatment step of heating the wood to be treated to 170 ° C or higher, and heats to 180 ° C or higher. It is more preferable to include a high temperature treatment step, and it is further preferable to include a high temperature treatment step of heating to 190 ° C. or higher. From the same point of view, the high temperature treatment time for heating to 170 ° C. or higher is 120 minutes or longer, the high temperature treatment time for heating to 180 ° C. or higher is 90 minutes or longer, and the high temperature treatment time for heating to 190 ° C. or higher is 60 minutes or longer. Preferably there is. The temperature of the high temperature treatment is preferably 220 ° C. or lower, particularly 210 ° C. or lower, more preferably 200 ° C. or lower. In addition, the temperature here is the temperature of the surface of to-be-processed wood, for example, is measured with a thermocouple thermometer.

  It is preferable that the superheated steam treatment step includes a material temperature uniform temperature raising step before the high temperature treatment step. The temperature rise until reaching the temperature of the high-temperature treatment step is due to superheated steam introduced in the sealed space (decompression chamber). As shown in the graph of the embodiment shown in FIG. By providing the time for stopping the temperature increase, the front and back surfaces and the internal temperature of the wood to be treated can be raised substantially evenly, and the uniformity of the color tone of the heat-treated wood obtained is improved.

  Note that the high temperature treatment step of heating to 170 ° C. or higher with superheated steam can be performed at 110 kPa or lower, unlike the conventional heating with high pressure and high temperature steam, as shown in the graph of the embodiment shown in FIG. It is also possible to carry out under almost the same atmospheric pressure. Maintaining the internal pressure of the sealed space at a pressure of 110 kPa or less and being able to perform the treatment at a high temperature of 170 ° C. or higher is preferable in terms of ensuring safety during operation of the facility. In the high temperature treatment step, it is also preferable to exhaust gas generated by decomposition of hemicellulose and maintain the internal pressure of the sealed space at 110 kPa or less, more preferably at 105 kPa or less. Such exhaust is not considered to release the sealed state of the sealed space.

  After the high-temperature treatment step, introduction of superheated steam by the superheated steam introduction device and other heating devices used as desired are stopped to cool the sealed space. Cooling in the sealed space is preferably performed by continuously injecting water vapor, and after the temperature is sufficiently lowered, the door of the sealed space may be opened to promote cooling. Moreover, it is also preferable that the heat-treated wood to be treated is humidified simultaneously with cooling by sprinkling water in the sealed space using a sprinkler. Then, after the temperature in the sealed space is sufficiently lowered, the heat-treated wood to be treated is taken out from the sealed space (decompression chamber).

(Discoloration promotion process)
In the above-mentioned superheated steam treatment, particularly high-temperature treatment heated to 170 ° C. or higher, components such as hemicellulose in wood are decomposed by heating, and the degradation products react with other components such as lignin to give a dark colored substance Therefore, the wood to be treated is likely to change to a dark color such as dark brown. On the other hand, such a colored substance is decomposed by ultraviolet rays such as sunlight, and the color of the treated wood is changed due to the decomposition.
In the present invention, the discoloration of the wood to be treated accompanying the decomposition of the coloring substance is promoted to forcibly cause the discoloration of the wood to be treated, thereby suppressing the discoloration of the heat treated wood obtained thereby.

  In the discoloration promoting treatment for the wood to be treated, for example, after applying a liquid containing a chlorine-based or oxygen-based oxidizing agent to the wood to be treated, heating or ultraviolet irradiation is performed. Examples of the chlorine-based oxidant include hypochlorous acid or a salt thereof (sodium salt, etc.), chlorous acid or a salt thereof (sodium salt, etc.), sodium dichloroisocyanurate, etc. Examples include hydrogen peroxide, sodium percarbonate, sodium perborate, sodium monopersulfate, and the like. Instead of sodium salt, potassium salt or calcium salt can be used. The liquid containing the oxidizing agent is, for example, an aqueous solution, and the application method of the liquid containing the oxidizing agent is preferably brush coating or spray coating, a sponge roll coater, or the like. An ultraviolet lamp or the like may be used for ultraviolet irradiation, but exposure to sunlight is preferable. Moreover, commercially available bleaching agents can also be used for the liquid containing a chlorine-type or oxygen-type oxidizing agent, and these are used by diluting to an appropriate concentration if desired. For the heating after the application of the liquid containing the oxidizing agent, for example, a hot air dryer or the like can be used.

  Moreover, it is also preferable to perform the discoloration promoting treatment after performing processing such as shape processing for obtaining a final product form on the wood to be treated after the superheated steam treatment process. Examples of the processing here include planar processing, chamfering processing, drilling processing, groove processing, and actual processing. As the discoloration promotion treatment, the wood to be treated after being treated with an oxidizing agent and heated or irradiated with ultraviolet rays is preferably washed after being washed with water in order to reduce the remaining bleaching agent.

According to the present invention, for example, heat-treated wood is obtained in this way.
The heat-treated wood obtained in the present invention is improved in dimensional stability by being heated to a high temperature of 170 ° C. or higher with superheated steam, and is shaped by being heated relatively uniformly on the surface and inside. Sometimes the problem of color difference is less likely to occur. Moreover, partial carbonization of the wood is less likely to occur by performing the decompression process prior to the superheated steam process. Therefore, for example, as shown in FIG. 2, in order to use as a solid floor material, both ends 2 and 3 in the width direction are subjected to actual processing for connecting floor materials to each other, male fruit 5, Unintentional chipping is unlikely to occur in the thin portion of the female fruit 6 that overlaps the male fruit 5, and a large difference in color between the exposed part and the other part is less likely to occur. Moreover, the discoloration promotion treatment is performed on the wood to be treated after the superheated steam, so that secular discoloration due to light hardly occurs.

  The heat-treated wood obtained in the present invention is preferably used as an interior material such as a wooden building or a component of furniture utilizing all or part of such properties, for example, flooring, particularly for floor heating. It is preferably used as a flooring. The heat-treated wood may be coated on the whole or a part of the surface as long as the texture of the wood is not impaired. For example, the heat-treated wood may be thinly coated with a dye-based paint or painted with an oil finish.

  Next, the present invention will be specifically described based on examples and comparative examples, but the present invention is not limited to the following examples.

  45 or more solid plates made of red oak, walnut, maple and cherry (length: 300 mm, width: 125 mm, thickness: 22 mm) are prepared for each tree species. On the other hand, 40 or more plate materials are accommodated in the decompression chamber of the decompression and heat treatment apparatus, and the pressure in the decompression chamber and the temperature of the plate material are as shown in FIG. The pressure was reduced, the superheated steam treatment, and the subsequent cooling were performed.

While the plate material after the heat treatment subjected to the decompression treatment and the superheated steam treatment is left as an untreated group in which 20 or more plate materials are not subjected to the discoloration promotion treatment (aging treatment) for each tree species, about 20 or more plate materials The discoloration promotion treatment (aging treatment) was performed under the following conditions.
Used “Liquid containing oxidizer”: Chlorine bleach “SunFresh” made by RJ Co., Ltd. 2 times diluted with water Treatment method: Liquid containing oxidizer is applied to the surface of the plate by brush. After coating m ^2, it was left to stand in direct sunlight for 1 hour to dry, and then washed with running water using a brush. Then, it was left to stand in direct sunlight for 3 hours and dried.

(Evaluation of dimensional stability against changes in humidity)
The width shrinkage rate for the “heat treatment group” that has been subjected to the reduced pressure treatment, the superheated steam treatment, and the color change promoting treatment, and the width for the “untreated group” that has not been subjected to any of the reduced pressure treatment, the superheated steam treatment, or the color change promoting treatment. The shrinkage rate was measured, and the results (average value) for the “heat treated group” and the results (average value) for the “untreated group” were shown side by side for each tree type in FIG.
The width shrinkage ratio was determined by measuring the width W1 (the width corresponding to W in FIG. 1) measured after leaving each plate material under a humid condition of a temperature of 23 ° C. and a relative humidity of 90% for 40 hours. Then, the width W2 after drying for 24 hours was measured and calculated by the following formula based on the measured values.
Width shrinkage rate (%) = [(W1-W2) / W1] × 100

(Evaluation of aged discoloration effect by discoloration promotion treatment)
A weather meter (Iwasaki Electric Co., Ltd.) was used for each of the “aging process group” that had been subjected to reduced pressure treatment, superheated steam treatment and discoloration promotion treatment, and the “aging untreated group” that had been subjected to decompression treatment and superheated steam treatment but not discoloration promotion treatment. A time-dependent discoloration acceleration test was conducted under the following conditions using an “Eye Super UV Tester”).
Then, using a color difference meter (CR-400) manufactured by Konica Minolta Sensing Co., Ltd., the L ^* a ^* b ^* color system L ^* value, a ^* value, The b ^* value was measured, and the color difference “ΔE” before and after the time-dependent color change acceleration test was calculated. The result is shown in FIG.
(Conditions for accelerated discoloration test over time)
6 cycles of irradiation intensity of 90 mW / cm ² , irradiation temperature of 63-70 ° C., 4 hours of irradiation and 4 hours of condensation (35 ° C., 98% RH) (assuming 2 years of indoor environment use).

  From the results shown in FIG. 4, it can be seen that the dimensional stability can be improved by performing the decompression process and the superheated steam process in the present invention. From the results shown in FIG. 5, it can be seen that the color change with time can be suppressed by performing the discoloration promoting treatment after the decompression treatment and the superheated steam treatment.

1 Wood to be treated 5 Male 6 Female

Claims (8)

  A treated wood, which is a solid material, is accommodated in the sealed space, and a reduced pressure treatment step for maintaining the internal pressure of the sealed space at 50 kPa or less, and a sealed containing the treated wood whose oxygen content has been reduced by the reduced pressure treatment step. A superheated steam treatment step in which superheated steam is introduced into the space and the wood to be treated is heated to a temperature of 170 ° C. or higher; and a color change promotion step in which the wood to be treated after the superheated steam treatment step is subjected to a color change promoting treatment. A method for producing heat-treated wood, comprising:   2. The method for producing heat-treated wood according to claim 1, wherein in the decompression treatment step, an internal pressure of the sealed space is maintained at 20 kPa or less, and in the superheated steam treatment step, the wood to be treated is heated to 180 ° C. or more. .   The method for producing heat-treated wood according to claim 1 or 2, wherein switching from the reduced pressure treatment step to the superheated steam treatment step is performed while maintaining a sealed state of the sealed space.   The method for producing heat-treated wood according to any one of claims 1 to 3, wherein the superheated steam treatment step is performed while maintaining an internal pressure of the sealed space at 110 kPa or less.   In the said discoloration acceleration | stimulation process, after apply | coating the liquid containing a chlorine type or an oxygen type oxidizing agent to the to-be-processed wood after a superheated steam treatment process, it heats or irradiates with an ultraviolet-ray. 2. A method for producing heat-treated wood according to item 1.   The method for producing heat-treated wood according to claim 5, wherein the wood to be treated after the heating or ultraviolet irradiation is washed with water.   The method for producing heat-treated wood according to any one of claims 1 to 6, wherein the use of the heat-treated wood to be produced is a solid flooring material for floor heating.   Heat-treated wood obtained by the method for producing heat-treated wood according to any one of claims 1 to 7.

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