JP3442229B2 - Dimensional stabilization method for wood - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dimensional stabilization treatment method for wood materials, and more particularly to a treatment method for wood materials by improving the dimensional stability of wood materials by supplying high-pressure steam into the wood materials. Regarding the improvement of the method.

[0002]

BACKGROUND ART Wood swells or contracts by absorbing and releasing water. This means solid sawn wood, thin wood (thickness 0.2
mm to 10 mm), particle board, MDF, O
The same applies to SB, plywood, etc. When a wood material is used as a building or furniture material, it is not preferable that the wood material swells or shrinks depending on the environment, and it is desired that the wood material has dimensional stability independent of the environment.

As a countermeasure therefor, a method has been used in which a wood material is vertically sandwiched by a press board, placed in an autoclave, and treated with high-pressure steam for several minutes to stabilize the size of the wood material. However, in this method, in addition to large-scale equipment, it is difficult for high-pressure steam to penetrate into the interior of the wood material (central part), and the treatment conditions at the central part and the peripheral part of the wood material may differ.

In order to eliminate the inconvenience, the applicant of the present invention arranges a wood material in a natural dry state between the heating plates of a flat plate press having a heating plate used in the conventional wood processing, and elastically surrounds the surrounding wooden members. After placing an elastic sealing material such as silicon material into a sealed state, high-pressure steam is supplied from the steam supply holes provided in the upper and lower hot plates to vaporize the water contained in the wood material, and the size of the wood material. We have proposed a method to stabilize it (Japanese Patent Laid-Open No. 6-2
38616). This treatment method has an advantage that the treatment is simplified because the dimension stabilization treatment of the wood material is performed by using a flat plate press having an ordinary heating plate. Further, in this treatment, according to the experiments by the present inventors, about 150 ° C.
High-pressure steam (saturated steam or superheated steam) at a temperature close to 230 ° C. is supplied into the sealed space to heat the wood material at about 180 ° C.
We have experienced that the treatment proceeds effectively by elevating the temperature to a temperature close to 200 ° C. to vaporize the water content of the wood material.

The above-described dimensional stabilization treatment of wood materials by high-pressure steam brings high dimensional stability to wood materials, and a clean treatment method in which chemicals such as phenol and formalin are not used and no chemicals remain after the treatment. That is also useful.

The present inventors further conducted research to obtain a wood material that was subjected to a stabilization treatment more uniformly, and during the dimension stabilization treatment, decompress the sealed space containing the wood material,
We perceive that it is effective to introduce high-pressure steam, and based on that, we have proposed a further improved method for stabilizing the dimension of wood materials (Japanese Patent Application No. 8-45173).
issue). It was confirmed that by adopting this method, the high-pressure steam can be surely permeated into the wood material and supplied evenly, and the treated wood material can be given more uniform and high dimensional stability.

Further, in the conventional high-pressure steam treatment of the wood material, the wood material is in a normal state at room temperature, that is, even if the water content is low, it is about 7% to 10%, and the temperature is 15 ° C to 25 ° C.
The wood material in a natural dry state of about ℃ is placed in the sealed space formed between the hot platen presses etc. as it is, and the treatment is carried out. By the time the water contained in the wood material is vaporized. To heat the wood material and vaporize the water with a high water content into high pressure steam, approximately 150 ° C as described above.
Focusing on the fact that the energy of high-pressure steam of about ~ 230 ° C is mainly used, the production cost of this high-pressure steam is high, and that it takes a long time to heat the wood material. However, as a solution to this, the wood material to be treated is heated and dried by a separately prepared drying facility to a water content lower than the water content in the naturally dried state, and the wood material subjected to the heat drying treatment is applied. A method has also been proposed in which a wood material is housed in a sealed space, and high-pressure steam is supplied into the sealed space so that the wood material is subjected to a dimension stabilization treatment (see Japanese Patent Application No. 8-192426). .

According to this treatment method, as compared with the conventional method, the treatment effect equivalent to that of the conventional product can be obtained in a shorter high-pressure steam treatment time, the cost required for producing the high-pressure steam can be reduced, and the treatment unit price can be reduced. It is possible to lower it.

[0009]

The above-mentioned method that has already been proposed is effective because it contributes to the reduction of energy cost, but as described above, the wood material to be treated is preheated. It is necessary to carry out a drying process, and it is necessary to separately prepare a drying facility for that purpose. In addition, it is necessary to move the dried wood material from the drying facility to the high-pressure steam treatment facility, and it is necessary to have a temporary storage place as well as the time and effort required for the movement.

In the process of continuing the research and experiment on the high-pressure steam treatment of wood materials, taking into consideration such restrictions on equipment and location, the wood materials in a natural dry state were sealed in a high-pressure steam treatment facility. By placing it in a space and then repeating the process of introducing high-pressure steam and releasing the pressure as one cycle a plurality of times in the same sealed space, even if the wood material is not preheat-dried, it can be preheat-dried in a short treatment time. It was perceived that the processing effect equivalent to the case of performing was possible.

[0011]

The method for stabilizing the dimension of a wood material according to the present invention is based on the above-mentioned perception. Basically, the wood material is housed in a sealed space, and the wood space is stored in the sealed space. It is characterized in that the cycle of introducing high-pressure steam and releasing the pressure in the sealed space is continuously repeated at least twice or more in the same sealed space to stabilize the dimension of the wood material.

In the present invention, the wood material to be treated is not particularly limited, and not only solid wood such as veneer or plywood, but also medium quality fiberboard (MDF), oriented board (OSB), particle board (PB), etc. Wood processing materials can also be processed. In the case of a wood working material, it is particularly effective to carry out the treatment of the present invention while applying a pressure and compression by a press board, since it is possible to carry out not only the consolidation treatment but also the dimension stabilization treatment. Further, the treated wood material used in the present invention may be in a naturally dried state and does not require a preliminary drying treatment by a special heating and drying facility.

The wood material is housed in a sealed space. The sealed space is capable of introducing high pressure steam and releasing pressure,
Further, preferably, provided that it is possible to reduce the pressure in the sealed space, the sealed space may be a pressure-resistant pressure vessel conventionally used for treating wood materials, which may be used for the compression of wood materials or the composite material. It may be a sealed space formed between press plates mounted on a flat plate press conventionally used for manufacturing.

When it is possible to reduce the pressure in the sealed space,
Preferably, prior to the first introduction of high-pressure steam,
Depressurize the sealed space. According to the experiments by the inventors,
By introducing high-pressure steam into the space previously decompressed, the water content reduction of the wood material after pressure release is promoted, and
It was confirmed that the dimensional stabilization treatment was evenly applied to the center of the wood material. Decompression is 700 mmHg-750 mmHg
The degree is preferable, and according to the experiments by the present inventors, 750 m
A sufficient effect was obtained with a reduced pressure of about mHg. Note that this depressurization may be performed prior to the introduction of high-pressure steam in each cycle, in which case a treatment effect is expected with a smaller amount of high-pressure steam supply (that is, with a shorter high-pressure steam treatment time). There are advantages.

The pressure resistant pressure vessel or the press board may or may not have a heat source.
Those having a heat source are especially recommended. The heat source may be an electric heating means such as a heater or a band heater incorporated in a pressure-resistant pressure vessel or a press plate, heating steam, high-frequency heating including microwave, or the like, and the temperature source is preheated. The wood material is housed in the sealed space. The elevated temperature is preferably in a temperature range (about 180 ° C. to 200 ° C.) in which the dimensional stabilization treatment with high-pressure steam proceeds in the wood material.

High-pressure steam, which is saturated steam or superheated steam (steam having a temperature higher than that of saturated steam) at about 150 ° C. to 230 ° C., is introduced into the sealed space containing the wood material. The pressure of the high-pressure steam varies depending on the type of wood material to be treated, etc., but is several kgf / cm ^{2 to} 30 k
It may be gf / cm ² .

The method of supplying high-pressure steam to the sealed space and depressurizing the inside of the sealed space when necessary is arbitrary. For example, the sealed space is formed between press plates and the press plate is externally provided. In the case of having a large number of communicating pores, the pores of one press platen are connected to a conventionally known high-pressure steam generation source through appropriate pipes and valve means, and the other press platen is connected. It is possible to connect the pores to a conventionally known and preferably heat-resistant vacuum pump or a vacuum source such as a suction blower through appropriate pipes and valve means.

As another method of supplying and depressurizing high-pressure steam, another member having a large number of pores and having pressure resistance and heat resistance may be arranged between the upper and lower press plates and the wood material. You may In that case, one said separate member is connected to a high pressure steam generation source, and the other said separate member is connected to a vacuum source. As a result, it becomes possible to supply high-pressure steam to the wood material through the pores of the separate member and to perform vacuuming. A preferred embodiment of this type of separate member is composed of a box-shaped member having an internal space capable of accommodating a wood material to be treated and a lid member for sealing the internal space.

When the pressure in the sealed space is reduced, the high-pressure steam that is jetted receives the action of suction force in addition to the jetting force,
Kinetic energy increases. As a result, it is possible to surely permeate the interior of the wood material in a shorter time than the conventional method, and to evenly and uniformly spread the wood material. As a result, the dimensional stabilization process proceeds rapidly and over the entire area.

After introducing the high-pressure steam in the first cycle for the required time, the pressure in the sealed space is released. It is preferable that the high-pressure steam is introduced at least continuously until the temperature of the wood material reaches a temperature (about 180 ° C. to 200 ° C.) at which the dimensional stabilization treatment with high-pressure steam proceeds. The pressure release may be performed immediately after raising the temperature to a predetermined temperature,
It may be performed after stopping the introduction of high-pressure steam and leaving it for a while.

Immediately after the pressure is released, or after leaving for 1 to 2 minutes to close the decompression valve, the same process as in the first cycle is repeated in the same sealed space. At that time, the “decompression in the sealed space” treatment is optional even in the second and subsequent cycles, and when it is performed, there is an advantage that the high-pressure steam treatment time can be shortened. Further, it is preferable that the “introduction of high-pressure steam into the sealed space” processing time in the second and subsequent cycles is longer than that in the first cycle. According to an experiment by the present inventor, in the first cycle (or several cycles in the initial stage when 3 or more cycles are performed), a high water content and normal temperature wood material are applied in a sealed space. Under a pressure condition, the temperature is raised to about 180 ° C to 200 ° C, and when the pressure is released next time, the moisture inside the wood material is released to the outside together with the supplied steam, and the water content is reduced to 3%.
This is because the temperature is lowered to about 10% and it does not take a long time to raise the temperature of the wood material. In addition, when the wood material is subjected to the same high-pressure steam treatment as the conventional method after the water content is reduced, it is effective to continuously keep the high-temperature and high-pressure conditions for a relatively long time. It depends on what you did.

The treatment cycle is repeated as described above, and when the required dimensional stabilization treatment is achieved, the treatment is terminated and the treated wood material is taken out from the sealed space. According to the experiments by the present inventors, the wood material treated by the above method has higher dimensional stability as compared with the untreated one, and compared with the one treated without repeating the cycle. The same dimensional stability can be obtained in a shorter processing time,
Further, as compared with the case of treating with a wood material whose water content has been lowered in advance, the same degree of dimensional stability was obtained despite the same high-pressure steam treatment time.

Although the reason why the above-described effect is obtained by the method of the present invention is not always clear, the treatment of (reducing pressure as needed) → introduction of high-pressure steam → relieving pressure as one cycle is repeated a plurality of times. Means that the excessive flow of high-pressure steam and the vertical fluctuation of the pressure are repeatedly applied to the wood material, which destroys the wall holes in the wood element of the wood material to be treated, and the treatment effect is improved. It is understood that it extends quickly and reaches the central part. In fact, in experiments, particularly high treatment effects have been obtained for materials with large elements (solid wood, blockboard, plywood, etc.).

[0024]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will now be described in more detail with reference to the drawings. FIG. 1 shows an example of an apparatus for carrying out the method for stabilizing the dimension of wood material according to the present invention. In the figure, 1a and 1b are press plates similar to those mounted on a flat plate press used in conventional wood processing, each provided with a heater 2a and 2b as a heat source, and a wood material W to be processed. A large number of pores 3a, 3b are formed in the surface portion that comes into contact with. The pores 3a formed in the upper press platen 1a are connected to the high-pressure steam generation source S via the pipe 4a and the opening / closing valve V, and the pores 3b formed in the lower press platen 1b are connected via the pipe 4b. Connected to the vacuum pump VP. A branch pipe 4c is connected to the pipe 4b via a three-way valve V _T , and the other end of the branch pipe 4c is open to the atmosphere. A blower (not shown in FIG. 1) may be used instead of the vacuum pump.

In carrying out the treatment method according to the present invention using this apparatus, first, the flat wood material W to be treated is placed on the lower press board 1b at the position where the pores 3b are formed. Place. On the other hand, a rectangular thickness regulating jig 10 made of stainless steel or the like is fixed to the upper press board 1a by a screw (not shown) or the like at a position where the wood material W can be accommodated. In the figure, 11 is an elastic seal material attached to the lower edge of the thickness regulating jig 10. The thickness regulating jig 10 may be fixedly attached to the lower press board 1b.

Next, the press plates 1a, 1b are brought close to each other until they are regulated by the thickness regulating jig 10 and stopped. Although not shown, a sealing material may be arranged around the wooden material W as described above to form a sealed space between the press plates 1a and 1b. As shown in the embodiment, the formed sealed space may be a sealed space having a height slightly larger than the initial thickness of the wood material W to be treated.

In that state, the on-off valve V provided in the pipe 4a on the side of the high-pressure steam generator S is closed, and the vacuum pump VP (or
The blower) is operated and the three-way valve V _T is operated to evacuate the pores 3b formed in the lower press platen 1b. When the pressure is reduced to a predetermined pressure, the three-way valve V _T is operated to close the pipe 4b. Next, the on-off valve V provided in the pipe 4a on the high-pressure steam generation source S side is opened, and high-pressure steam is jetted into the sealed space from the pores 3a formed in the press board 1a. The water vapor ejected from the pores 3a toward the wood material W or toward the sealed space receives the force due to the suction force in addition to the ejection force, and easily and evenly reaches the inside of the wood material W. The wood material W reaches the temperature at which the internal water vaporizes.

After the ejection of a desired amount of high-pressure steam is completed, the three-way valve V _T is operated to open the sealed space to the atmosphere via the branch pipe 4c to release the pressure. By decompressing, the water content in the wood material is released together with the supplied water vapor, and the water content of the wood material decreases. This completes the first cycle.
After releasing the pressure, preferably about 1 to 5 minutes, 2
In the second cycle, the three-way valve V _T is operated again to connect the sealed space to the vacuum pump VP side, and the pressure in the sealed space is reduced. The same operation is repeated the required number of times until the water content of the wood material reaches a predetermined value (about 3%). At that time, it is effective to gradually increase the time for the high-pressure steam introduction process.

When the wood material reaches a predetermined water content, the above cycle is repeated again. However, in this case, it is desirable to supply the high-pressure steam for a longer time than before. Further, it is not always necessary to perform the first depressurization operation in the second and subsequent cycles. The above cycle is repeated a necessary number of times, and when a predetermined dimension stabilization treatment is achieved, the wood material is taken out while performing a cooling step as required, and the method for stabilizing the dimension of the wood material according to the present invention ends.

FIG. 2 shows another example of an apparatus for carrying out the method for stabilizing the dimension of wood material according to the present invention. This example is a suitable example when a flat plate press in which the press plate is not provided with pores communicating with the outside is used in the processing method of the present invention, and is a flat plate-shaped first having pores 23a for jetting steam. The separate member 20a is fixed to the upper press platen 1a with the screw 21a, and the second plate-like second separate member 20b having the pores 23b for vacuuming is further installed with the screw 21b. It is fixed to. Each of the pores 23a and 23b is connected to the high-pressure steam generation source S and the vacuum pump VP, as in the case of the device shown in FIG. The method of using this device is substantially the same as in the case of FIG. Even in this case, as shown in the embodiment, the formed sealed space may have a height slightly larger than the initial thickness of the wood material W to be treated.

[0031]

EXAMPLES The present invention will be described below based on examples. [Example 1] MDF having a size of 15 x 300 x 1800 mm and a water content of 7.7% at room temperature was heated to 195 ° C in advance by heating with a heater 16 x 330 x 1
It was placed in a pressure-resistant container of 850 mm. The inside of the container was sealed, the pressure in the container was reduced to 750 mmHg in the first cycle, and then saturated steam of 15 kgf / cm ² at 195 ° C. was introduced into the container for 3 minutes. The pressure release valve was opened to release the pressure inside the container. The water content of MDF after depressurization was 3.3%.
After 1 minute, the pressure relief valve was closed and the inside was sealed, and then the same saturated steam was introduced for 6 minutes as the second cycle. afterwards,
The decompression valve was operated again to return to normal pressure, and the treated MDF was taken out.

[Comparative Example 1] The dimensions are 15 × 300 × 180.
MDF having a water content of 0% and a water content of 7.7% at room temperature is heated by a heater after lowering the board temperature to 136 ° C and the water content to 3.5% by a jet dryer with a hot air temperature of 150 ° C and a wind speed of 25 m. It was placed in a pressure vessel having a size of 16 × 330 × 1850 mm heated to 195 ° C. The inside of this container was sealed and the pressure was reduced to 750 mmHg, and then saturated steam of 15 kgf / cm ² and 195 ° C. was introduced into the container for 10 minutes. After the treatment, the decompression valve was operated to return the inside of the container to normal pressure, and the treated MDF was taken out.

[Comparative Example 2] The dimensions are 15 × 300 × 180.
MDF with a water content of 0 mm and a water content of 7.7% at room temperature was previously heated to 195 ° C. by heating with a heater.
It was placed in a pressure-resistant container of × 330 × 1850 mm. After sealing the inside of this container and reducing the pressure to 700 mmHg, saturated steam of 15 kgf / cm ² and 195 ° C. was added to the inside of the container for 20 times.
Introduced for a minute. After stopping the supply of steam, the decompression valve was opened to return to normal pressure, and the treated wood material was taken out.

[Embodiment 2] The dimensions are 15 × 300 × 180.
A particle board having a water content of 0 mm and a water content of 7.7% at room temperature was placed in a pressure-resistant container having a size of 16 × 330 × 1850 mm preheated to 195 ° C. by heating with a heater. The inside of this container is sealed and the inside of the container is
After decompressing to 700 mmHg, 17.5k inside the container
Saturated steam of gf / cm ² at 205 ° C. was introduced for 1 minute. Then, the pressure release valve was opened to release the pressure inside the container. 1 minute later, as the second cycle, after closing and sealing the pressure relief valve,
The inside of the container was depressurized to 700 mmHg, and then the same saturated steam was introduced into the inside of the container for 2 minutes. The water content of the particle board after decompression was 3.5%. Next, as the third cycle, the inside of the container was sealed, the pressure was reduced to 700 mmHg, and then saturated steam of 15 kgf / cm ² and 205 ° C. was introduced into the container for 10 minutes. After the treatment, the decompression valve was operated to return the inside of the container to normal pressure, and the treated particle board was taken out.

[Comparative Example 3] The dimensions are 15 × 300 × 180.
Particle board having a water content of 0 mm and a water content of 7.7% at room temperature is heated to 146 ° C and the water content is 3.7% by high-frequency heating, and then steam-heated to 205 ° C in advance.
It was placed in a pressure-resistant container having a size of 16 × 330 × 1850 mm heated. The inside of this container is sealed and 700 mmHg
After depressurizing to 17.5 kgf / cm ² ,
Saturated steam at 205 ° C. was introduced for 15 minutes. After that, the pressure release valve was opened to release the pressure inside the container, and the treated particle board was taken out.

[Comparative Example 4] The dimensions are 15 × 300 × 180.
A particle board having a water content of 0 mm and a water content of 7.7% at room temperature was placed in a pressure vessel having a size of 16 × 330 × 1850 mm which was previously heated to 205 ° C. by steam heating. The inside of this container was sealed and the pressure was reduced to 700 mmHg, and then saturated steam of 17.5 kgf / cm ² and 205 ° C. was introduced into the container for 25 minutes. After that, the pressure release valve was opened to release the pressure inside the container, and the treated particle board was taken out.

[Evaluation Test] The wood materials used in Examples 1 and 2 and Comparative Examples 1 to 4 and Examples and Comparative Examples, which were not treated, had a thickness expansion coefficient and a peel strength. (K
gf / cm ² ) was measured. The results are shown in Table 1. The coefficient of expansion of thickness is (T ₁ −T ₀ ) / T ₀ × 100, where T ₀ = thickness in absolute dry condition and T ₁ = thickness in saturated water. In the peeling test, a 5 cm square test piece was attached to a peeling test jig, an internal peeling test of the test piece was performed to obtain an internal peeling force, and the value was divided by a test piece area of 25 cm ² to obtain 1 cm
The internal peel stress per ² was obtained.

[0038]

[Table 1]

[Discussion] As shown in Table 1, in the product of the present invention, the treatment of (reduction of pressure →) introduction of high-pressure steam → relief of pressure is repeated two or three times to obtain no treatment. In comparison, high dimensional stability was obtained, and comparable dimensional stability was obtained in a shorter treatment time as compared with those treated without repeating the cycle (Comparative Examples 2 and 4). It can be seen that the same dimensional stability can be obtained with the same high-pressure steam treatment time, as compared with those treated with the wood material having a reduced rate (Comparative Examples 1 and 3).

[0040]

EFFECTS OF THE INVENTION According to the dimension stabilization treatment method for a wood material according to the present invention, the same treatment effect can be achieved with a shorter high-pressure steam treatment time as compared with the conventional method. As a result, the cost for producing high-pressure steam can be reduced, and the processing unit price can be reduced. In addition, since it is not necessary to pre-dry the treated wood material, there is no need for a cost and installation site for the drying facility, and the wood material absorbs moisture before the high-pressure steam treatment after pre-drying. The loss caused by the loss is also avoided.

[Brief description of drawings]

FIG. 1 is a diagram showing an example of an apparatus for performing a dimensional stabilization treatment method for wood materials.

FIG. 2 is a view showing another example of an apparatus for carrying out the dimension stabilization treatment method for wood materials.

[Explanation of symbols]

1a, 1b ... Press board, 2a, 2b ... Heater, 3a ... High-pressure steam introduction pore, 3b ... Vacuum suction pore, 4a ... High-pressure steam supply pipe, 5b ... Vacuum suction pipe, 10 ... Thickness regulation Jig, W ... Wood material, S ... High-pressure steam supply source, V ...
The opening and closing valve, V _T ... three-way valve, VP ... vacuum pump

─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-6-238616 (JP, A) JP-A-9-193104 (JP, A) JP-A-10-86106 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) B27K 5/00 B27K 5/06

Claims (9)

(57) [Claims] 1. A wood material is housed in a sealed space, and a cycle of introducing high-pressure steam into the sealed space and releasing pressure in the sealed space is continuously performed in the same sealed space for at least 2 cycles. A method for stabilizing the dimension of a wood material, characterized in that the dimension of the wood material is stabilized by repeating the procedure at least once. 2. The method for stabilizing dimension of wood material according to claim 1, wherein the sealed space is a sealed space having a height slightly wider than an initial thickness of the wood material to be treated. 3. The pressure reduction in the sealed space is performed prior to the introduction of high-pressure steam into the sealed space.
Alternatively, the method for stabilizing the dimension of the wood material according to 2 above. 4. The method for stabilizing the dimension of a wood material according to claim 3, wherein the depressurization is performed for each cycle. 5. The sealed space is preheated, and a wood material is stored therein.
A method for stabilizing the dimension of a wood material according to any one of the items. 6. The method according to claim 1, wherein the treatment is performed while compressing and compressing a wood material in the sealed space.
4. A method for stabilizing the dimension of a wood material according to 4 or 5. 7. The method for stabilizing the dimension of wood material according to claim 1, wherein the sealed space is formed between two press plates. 8. The sealed space formed between the two press plates is a sealed space having a height wider than the initial thickness of the wood material to be treated. Dimensional stabilization treatment method for wood. 9. The method for stabilizing the dimension of wood material according to claim 7, wherein depressurization and introduction of high-pressure steam in the sealed space are performed through the press board.