JP3062368B2 - Wood material heat treatment method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for heat-treating a wooden material, and more particularly to a method for improving the dimensional stability or surface characteristics of a wooden material to obtain a wooden material suitable for use in buildings or furniture. The present invention relates to a method for heat-treating wood materials that can be performed.

[0002]

2. Description of the Related Art In recent years, high-quality hardwood materials have been reduced and a sufficient supply has not been obtained, and consequently, softwood materials, medium fiberboard (MDF), particle boards, and the like have been attracting attention as alternative materials to hardwood materials. However, softwoods are generally softer than hardwoods, and surface properties such as surface hardness and surface abrasion resistance,
There were problems in durability against moisture and heat, strength, and the like.
Swelling in the thickness direction with respect to moisture was a major problem for MDF and particle board.

[0003] For this reason, if the conifer is boiled or softened by steam treatment, the conifer is condensed to a thickness of about 20 to 70% of the initial thickness by hot pressing with a flat plate press. Is known. The consolidation of softwood has remarkable effects on the surface properties, durability and strength described above, but the force of the softwood consolidated by the action of one or both of moisture and heat to return to the original state , And there was a drawback that the coniferous material which had been compacted and improved in performance was restored to near the original state.

[0004] Restoration of the compacted softwood, MDF,
In order to prevent swelling of the particle board in the thickness direction, it has been attempted to subject these wood materials to a chemical treatment such as acetylation or formalization.However, this method is environmentally preferable because it uses a large amount of chemicals. There are drawbacks such as lack of uniformity, difficulty in performing uniform treatment on the entire wood material, and complicated processing steps leading to high costs. In the case of consolidated softwood, phenol resin,
Attempts have been made to impregnate with a polyester resin or the like and apply WPC (wood / plastic composite material) treatment.
This method also has the drawback that it is difficult to uniformly treat the whole wood material similarly to the above-mentioned chemical treatment, the processing step is complicated and the cost is high, and the wood material is excellent in heat insulation and air permeability. There was also a disadvantage of losing characteristics.

As another method, there is a method of placing the compacted wood material in an autoclave and treating it with high-pressure steam at 160 to 220 ° C. for several minutes to prevent the compacted wood material from being restored. Is difficult to penetrate high-pressure steam into the wood (particularly the center of the wood), the treatment effect is not uniform, and the treatment state of the center and the periphery of the wood is often different.

[0006] The applicant of the present invention has conducted intensive studies to solve the inconvenience of the conventional method of treating wood material, and not only can prevent the compacted wood material from being restored to the original thickness due to moisture or heat, A new method of processing wood materials capable of processing wood materials uniformly and efficiently over the entire wood material has been proposed and already filed (Japanese Patent Application No. 4-26922).
No. 5).

This treatment method is a method of treating a wood material by heating a compression-molded wood material in a closed pressure vessel in a high-frequency manner while restraining deformation to convert water inside the wood material into high-pressure steam. As a result, surface properties such as surface hardness and abrasion resistance of the surface are improved, and it is possible to obtain a compacted wood material suitable for construction or furniture, which has a reduced coefficient of expansion with respect to moisture and heat.

[0008]

The above-mentioned treatment method is practically effective, but requires a step of treating wood material in a pressure vessel, so that the process is complicated and the apparatus itself is large. It had to be large.
The inventor of the present invention continued the research on the processing method of the wood material, and did not process the wood material in the pressure vessel. The present inventors perceived that it was possible to obtain a wood material having a low expansion coefficient, that is, improved dimensional accuracy and improved surface characteristics, and made the present invention.

[0009]

That is, according to the present invention, a wooden material and a sealing material and a thickness regulating jig are arranged between the hot plates, and the wooden material is sandwiched between the hot plates. A method for heat-treating a wooden material, characterized in that the wooden material is heated by the method. In the present invention, a wooden material and a sealing material and a thickness regulating jig are arranged between the hot plates, and the wooden material is heated in a state where the wooden material is sandwiched between the hot plates and is compacted. Also disclosed is a method for heat treating a wooden material, characterized by the above.

[0010] The heating of the wood can be effected by means of a hot platen or by means of high frequency heating or both. Next, the present invention will be described in more detail. In the present invention, the wood material includes not only solid wood but also processed materials such as MDF and particle board, and the object can be achieved equally. The present invention is particularly effective when applied to softwoods, which are generally considered to be soft as solid wood, but can also be applied to hardwoods.

As the hot platen, an ordinary hot plate used for pressing wood or manufacturing a composite material can be arbitrarily used, but is not limited thereto. Further, high-frequency heating including microwave heating (hereinafter, referred to as high-frequency heating) may be used as a heating means. In this case, a known microwave generator or high-frequency generator may be provided near the wood material to be treated. Be prepared.

At the time of treatment, a wooden material measured to a predetermined thickness and size is placed between hot plates. Next, on four laps of wood,
An elastic sealing material having a height somewhat higher than the thickness of the wood material as the final product is disposed, and a thickness regulating jig having the same height as the thickness of the wood material as the desired final product is provided outside the sealing material. Deploy. As the elastic sealing material, any material can be used as long as it has a sealing function that does not allow water vapor generated from the inside of the wooden material due to heating of the wooden material to leak outside, and has heat resistance and compressibility. Particularly preferred. As the material of the thickness regulating jig, any material can be used as long as it has the required rigidity and heat resistance, but an aluminum material, a stainless material, or the like is preferable, and a stainless material is particularly preferable.

In one embodiment of the present invention, after the sealing material and the thickness regulating jig are arranged around the wooden material, the hot plates are brought close to each other until they come into contact with the surface of the wooden material, and the first hot plate is placed at that position by the hot plate. The next heating is performed. The heating is desirably at a temperature at which the water inside the wooden material can evaporate. This heating softens the wood material to some extent. In this state, the hot plate is further approached until it is regulated by the thickness regulating jig. The wood is thereby compacted and the four circumferences of the wood are sealed by the surrounding sealing material.

In this state, the secondary heating by the hot plate is further continued. The heating temperature at this time needs to be higher than the temperature at which the water contained in the wood material evaporates. The heating temperature may be changed step by step,
For example, discoloration due to heat on the surface of the wooden material can be prevented as much as possible by initially setting the temperature to about 200 ° C. and gradually lowering the temperature over time or by heating at a lower temperature after a predetermined time has elapsed.

In another embodiment of the present invention, high-frequency heating is used instead of heating with a hot platen. In this case, more uniform heat treatment is performed because the moisture is uniformly vaporized from the interior of the wood material. In still another embodiment of the present invention, heating by a hot plate and high-frequency heating are performed simultaneously. In this case, the processing cycle can be further shortened.

In still another embodiment of the present invention, the initial thickness of the wood material placed on the hot platen is approximately the same as the thickness of the desired final product. In that case, no particular consolidation treatment is applied to the wooden material, and the hot plate is brought close from the beginning until it is regulated by the thickness regulating jig. In this state, heating by a hot plate and / or high frequency is performed. When a consolidation treatment such as softwood is required to improve the surface state as well as the densification, it is preferable to prepare a material thicker than the thickness of the final product. In the case of a material that does not particularly require consolidation, such as a particle board, a material having a thickness substantially equal to the thickness of the final product can be prepared, and the treatment can be performed without consolidation.

Further, in the case of a material produced by reworking an intermediate material such as MDF or particle board as a material, the treatment according to the present invention may be performed in the process of forming a wooden material, and the material may be produced as a wooden material. The post-treatment may be performed on the processed material (therefore, in the present invention, the term "wood material" is used as including the intermediate material in the molding process).

After the predetermined heating is completed, the pressure is released. The decompression may be performed gradually over a certain period of time, or may be performed in a so-called cold state by supplying cooling water to a hot platen. According to the experiment, when the decompression was performed in the cold state, the dimensional change rate of the obtained final product was smaller than that in the case of other decompression, and the surface state was beautifully finished.

[0019]

The present invention will be described below with reference to examples. [Example 1] Wood materials were compacted and sealed between hot plates and heated by a hot plate. As wood materials, a plurality of cedar materials having a water content of 20%, a thickness of 30 mm, a width of 150 mm, and a length of 600 mm were prepared, and the present invention was implemented by dividing into four groups.

For all groups, each cedar is placed on the lower platen of a clamping device with a platen, with a height of 32 around the cedar.
An elastic silicon material having a width of 30 mm and a width of 30 mm was used as a sealing member, and a stainless steel material having a height of 12 mm and a width of 50 mm was disposed as a thickness-controlling jig around four rounds of the sealing member. After setting the hot plate to 200 ° C, move the hot plate to contact the cedar wood and perform primary heating for 5 minutes, then operate the pressing device to restrict the movement of the hot plate by the thickness regulating jig. The wood was gradually compacted. As a result, the cedar wood was compacted to a compression ratio of about 60%.

In this state, the first group and the second group are heated at 200 ° C. for 10 minutes by a hot plate as secondary heating, and then the first group is gradually decompressed in 5 minutes. With respect to the two groups, the pressure was gradually released over 5 minutes while cooling water was supplied to the hot platen. Further, the third group and the fourth group
The group was similarly heated on a hot plate at 200 ° C. for 20 minutes, then the third group was gradually decompressed over 5 minutes, and the fourth group was cooled for 5 minutes with cooling water supplied to the hot plate. And gradually decompressed.

Each of the decompressed final products is boiled in a boiling furnace for 2 hours and then dried to absolute dryness. The thickness of each product is measured, and the radial swelling ratio and the recovery ratio in the radial direction are determined by the following formulas. Was measured. The results are shown in Tables 1 to 4
Shown in Thickness swelling ratio = (thickness after boiling for 2 hours-absolute dry thickness before boiling)
/ (Absolute dry thickness before boiling) × 100% Recovery rate = (thickness after boiling for 2 hours after absolute drying−thickness after consolidation) /
(Thickness before consolidation−thickness after consolidation) × 100% Further, for each cedar wood, the time required from the start to the end of the treatment was measured for each group. The results are also shown in Tables 1 to 4. The surface condition was very hard, smooth and beautiful.

[Comparative Example 1] Cedar wood having the same dimensions as those used in Example 1 was immersed in hot water at 95 ° C for 20 minutes to soften it by heating (boiling treatment) at 105 ° C. Using a hot pressing machine set to a compression ratio of 60%. Next, the cedar wood was divided into two groups, and as a second step, steam treatment under high temperature and pressure was performed using an autoclave while restraining the deformation with a stainless steel jig. For 8 minutes. The steam used was 10kgf /
cm ² , the temperature in the autoclave was 180 ° C. The pressure inside the autoclave was gradually released for each group to obtain a treated wood material.

In each case, the thickness swelling ratio and the recovery ratio in the radial direction were measured at the end and the center in the same manner as in Example 1. The results are shown in Tables 5 and 6. Similarly,
For each cedar wood, the time required from the start to the end of the treatment was measured for each group. The results are also shown in Tables 5 to 6.
Although the surface condition was hard, it was not as high as that of Example 1, and a clear difference was visually observed.

Example 2 Water content 10%, thickness 15 mm,
A plurality of white oak sapwood having a width of 150 mm and a length of 600 mm were prepared and divided into four groups. Except that a stainless steel material having a height of 15 mm and a width of 50 mm was disposed as a thickness regulating jig, and that the first step including consolidation was not performed, the same treatment as in Example 1 was performed on each group, and the same method was used. Radial thickness swelling and treatment cycle measurements were made. The results are shown in Tables 7 to 10. The surface condition was very hard, smooth and beautiful as in the case of Example 1.

Comparative Example 2 White oak sapwood having the same dimensions as those used in Example 2 was divided into two groups, which were not subjected to boiling treatment and consolidation treatment, and had a height of 15 mm as a thickness regulating jig. The same treatment as in Comparative Example 1 was performed except that a stainless steel material having a width of 50 mm was arranged, and the thickness swelling ratio in the radial direction and the treatment cycle were measured by the same method. The results are shown in Tables 11 to 12. Although the surface condition was hard, it was not as high as that of Example 2, and a clear difference was visually observed.

Comparative Example 3 The white oak sapwood used in Example 2 was boiled for 2 hours in a boiling furnace as it was, and the thickness was measured to measure the thickness swelling ratio in the radial direction. The results are shown in Table 1-13.

[0028]

[Table 1]

[Consideration of Table 1] As is clear from Table 1, the wood material treated according to the present invention is almost always superior in both the radial thickness swelling rate and the recovery rate to the autoclaved one. It can be seen that the dimensional stability has been improved. At the center, the thickness swell and recovery were improved in all cases measured, demonstrating the superiority of the invention. In particular, those that have been subjected to so-called hot cold treatment have a large effect. It can also be seen that the processing time has been shortened and the productivity has been improved. Further, it can be seen that the surface condition is very beautifully finished as compared with the others.

Example 3 Wood materials were compacted and sealed between hot plates, and heating was performed by both a hot plate and high-frequency heating using a pressing device capable of high-frequency heating. As a wood material, water content 20
%, A thickness of 30 mm, a width of 150 mm, and a length of 600 mm were prepared. Each cedar material is placed on the lower hot plate of the pressing device having a hot plate, and an elastic silicon material having a height of 32 mm and a width of 30 mm is used as a sealing member on four circumferences of the cedar material. A stainless steel material having a length of 12 mm and a width of 50 mm was arranged as a thickness regulating jig.

The hot platen is maintained at 180 ° C. and moved until the hot platens come into contact with the wooden material.
Heating was performed for 2 minutes at a frequency of 56 MHz and an output of 200 V and 8 Kw. Thereafter, it was gradually pressed to consolidate to a compression ratio of 60%. Continue using the same high frequency with the hot plate,
Heating was performed for 4, 6, and 8 minutes to permanently fix the consolidated wood material. During the heating, the pressure of the steam generated from the inside of the wooden material and sealed between the hot plates was adjusted by a pressure adjusting valve so that the pressure became 10 kgf / cm ² . After heating for a predetermined time, the sealed water vapor was gradually exhausted to release the pressure.

In each case, the thickness swelling ratio and the recovery ratio in the radial direction were measured at the end and the center in the same manner as in Example 1. The results are shown in Tables 1 to 3. Similarly,
For each cedar wood, the time required from the start to the end of the treatment was measured for each group. The results are also shown in Tables 1 to 3.
The surface condition was very hard, smooth and beautiful.

Example 4 The same processing was performed using the same cedar wood as in Example 3. However, in order to rapidly reduce the temperature of the processing material, the hot platen was depressurized at once by passing cooling water through the hot platen for the purpose of rapidly lowering the temperature of the processing material. For each of them, the thickness swelling ratio and the recovery ratio in the radial direction were measured at the end and the center in the same manner as in Example 1. The results are shown in Table 2
6 is shown. Similarly, for each cedar wood, the time required from the start to the end of the treatment was measured for each group. Table 2 shows the results.
4-6. The surface condition was very hard, and the finish was smoother and more beautiful than that of Example 3.

[Comparative Example 4] The same wood used in Example 3 was used and inserted between hot presses capable of high-frequency heating provided in a closed pressure vessel.
Heating was performed for 2 minutes at a high frequency of 3.56 MHz, output 200 V, 8 kW. Then, gradually pressurize, compressibility 60%
Consolidated. Continued using the same high frequency,
Heating was performed for 4, 6, and 8 minutes to permanently fix the consolidated wood material. The pressure in the container is 10 kgf / cm ² with a pressure regulating valve.
Was adjusted to maintain. After heating for a predetermined time, the water vapor in the container was gradually exhausted to depressurize the hot press.

In each case, the thickness swelling ratio and the recovery ratio in the radial direction were measured at the end and the center in the same manner as in Example 1. The results are shown in Tables 7 to 9. Similarly,
The time required from the start to the end of the treatment was measured for each group. The results are also shown in Tables 7 to 9. Although the surface condition was hard, it was not as high as that of Example 3, and a clear difference was visually observed.

Example 5 Water content 10%, thickness 15 mm,
A plurality of white oak sapwood having a width of 150 mm and a length of 600 mm were prepared and divided into three groups. The first step including consolidation is not performed and the height regulating jig is 15 mm in height,
Each group was treated in the same manner as in Example 3 except that a stainless steel material having a width of 50 mm was arranged, and the thickness swelling ratio in the radial direction was measured by the same method. The results are shown in Table 2 at 10-1.
It is shown in FIG. Similarly, the time required from the start to the end of the treatment was measured for each group. The results are also shown in Tables 10 to 12. The surface condition was very hard, smooth and beautiful.

[Comparative Example 5] White oak sapwood having the same dimensions as those used in Example 5 was divided into three groups and subjected to deformation with a stainless steel jig without performing boiling treatment and consolidation treatment. The steam treatment under high temperature and high pressure was performed for 4, 6, and 8 minutes using an autoclave while restraining. The steam used was 10 kgf / cm ² and the temperature in the autoclave was 180
C. was maintained. The pressure inside the autoclave was gradually released for each group to obtain a treated wood material.

For each of them, the thickness swelling ratio in the radial direction was measured in the same manner as in Example 5. The results are shown in Table 2
FIG. Similarly, the time required from the start to the end of the treatment was measured for each group. The results are also shown in Tables 13 to 15. Although the surface condition was hard, it was not as high as that of Example 5, and a clear difference was visually observed.

Comparative Example 6 The same white oak material as used in Example 5 was boiled in a boiling furnace for 2 hours, and the thickness was measured, and the thickness swelling ratio in the radial direction was measured. The results are shown in Table 2-16.

[0040]

[Table 2]

[Consideration of Table 2] As is clear from Table 2, the wood material treated in accordance with the present invention is almost always superior in both the radial thickness swelling rate and the recovery rate to the autoclaved one. It can be seen that the dimensional stability has been improved. At the center, the thickness swell and recovery were improved in all cases measured, demonstrating the superiority of the invention. In particular, those that have been subjected to so-called hot cold treatment have a large effect.

Also, it can be seen that the processing time is shortened and the productivity is improved. Further, it can be seen that the surface condition is very beautifully finished as compared with the others.

[0043]

According to the treatment method of the present invention, it is possible to obtain a wood material with small dimensional change after treatment and improved surface characteristics. Moreover, the method of the present invention can be performed using a pressing device used for pressing wood or manufacturing a composite material. Therefore, it is not necessary to particularly prepare a large-scale and difficult-to-operate device such as a pressure vessel, and the process itself is simplified, so that productivity is greatly improved.

──────────────────────────────────────────────────続 き Continued on the front page (58) Fields surveyed (Int. Cl. ⁷ , DB name) B27K 5/00 B27K 5/06 B27N 7/00

Claims (7)

(57) [Claims] 1. A wood material is sandwiched between heating plates in a sealed state, and the wood material is heated in that state to convert water in the wood material into pressurized steam to perform a dimensional stabilization process. A method of heat treating a wooden material, comprising: 2. A wooden material and a sealing material and a thickness regulating jig are arranged between the hot plates, and the wooden material is heated in a state where the wooden material is sandwiched between the hot plates. A heat treatment method for wood materials, comprising subjecting water in the wood to steam under pressure, performing a dimensional stabilization process, and then performing decompression. 3. The method for heat treating a wooden material according to claim 1, wherein the wooden material is heated in a state where the wooden material is sandwiched between the hot plates and is compacted. 4. The heat treatment method for wood material according to claim 1, wherein the decompression is performed by lowering the temperature of the hot platen. 5. The method according to claim 1, wherein the heating of the wood material is performed by a hot plate. 6. The method for heat treating a wooden material according to claim 1, wherein the heating of the wooden material is performed by high frequency heating. 7. The heat treatment method for wood material according to claim 1, wherein heating of the wood material is performed by both a hot plate and high frequency heating.