JPH079418A - Production of modified wood - Google Patents

Abstract

PURPOSE:To produce modified wood excellent in humidity resistance by acetylating thin wooden pieces in a gaseous phase and accumulating acetylated thin wooden pieces to integrally mold them. CONSTITUTION:The bottom part of a reactor is filled with acetic anhydride being an acetylating agent and a support material composed of a stainless steel wire net is provided above the acetylating agent under tension and thin wooden pieces are placed on the support material. Acetic anhydride is heated to generate acetic anhydride vapor which is, in turn, brought into contact with the thin wooden pieces to acetylate the wooden pieces. Prior to acetylation, the thin wooden pieces are dipped in a 1-10% aq. soln. of acetate such as sodium acetate to be pretreated and the pretreated wooden pieces are dried. An adhesive is applied to the surfaces of the acetylated thin wooden pieces and these wooden pieces are received in a mold to be cured and integrated under heating and pressure. By this constitution, plate-shaped modified wood low in moisture absorbability and water absorbability and excellent in humidity resistance can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing modified wood, in which wood flakes are acetylated in a gas phase, and the acetylated wood flakes are integrated and integrally molded to have a low hygroscopic property, which is excellent. It also has moisture resistance.

[0002]

2. Description of the Related Art A wood material, which is made from wood flakes as a raw material and is bonded and molded by a synthetic resin binder to be integrated, is already known. This wood-based material is obtained by cutting wood into pieces each having a length of several mm to several tens of mm, and preferably one piece having a length of 4 mm.
A thin piece of 0 to 80 mm is formed, and this thin piece is integrated and molded with an adhesive.

This product has the characteristics that it has little directionality, is homogeneous and easy to process, and that it is not limited to a flat shape but can be formed into a curved surface and can be mass-produced.
It has a porous property due to the voids between the flakes and has a large substantial surface area, so that it has a high moisture absorption rate and a poor moisture resistance.

[0004]

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to obtain a method for producing a modified wood such as a thin plate having a high moisture resistance.

[0005]

This problem can be solved by acetylating wood flakes in the gas phase, accumulating the acetylated wood flakes, and integrally molding them.

The present invention will be described in detail below. The wood flakes used in the manufacturing method of the present invention are those obtained by cutting wood. Further, as this wood thin piece, a thin piece is preferable because the acetylation reaction proceeds well, for example, about 0.1 to 0.8 mm, preferably 0.1.
A thickness of 4 to 0.6 mm is used.

The wood flakes thus obtained are then acetylated in the gas phase. Prior to acetylation, it is preferable to dry the wood thin pieces to have a water content of 3% or less, preferably 1% or less. In the present invention, acetylation is performed in the gas phase. That is, the vaporized vapor of the acetylating agent is brought into contact with the wood flakes in the vapor phase to cause the acetylation reaction. As the acetylating agent, acetic acid, acetic anhydride, chloroacetic acid or the like is used, and acetic anhydride is preferable.

As a concrete method of acetylation in the gas phase, for example, the bottom of the reaction vessel is filled with acetic anhydride or the like as a supply source of the acetylating agent, and a net made of stainless wire or the like is provided above this. There is a method in which a support material is stretched, a thin wooden piece is placed on this net, acetic anhydride is heated to generate acetic anhydride vapor, and the thin wooden piece and the acetic anhydride vapor are brought into contact with each other. The reaction time is about 15 minutes to 3 hours, but can be appropriately changed depending on the required degree of acetylation. The temperature of the acetylating agent vapor used in the reaction is 1
The reaction pressure is about 20 to 160 ° C., and the reaction pressure is usually atmospheric pressure to 2 atm.

In addition, an inert solvent which does not react with an acetylating agent such as acetic anhydride during the acetylation,
For example, it can be diluted with xylene before use. The amount of xylene used in this case is 70% of the total amount with the acetylating agent.
It is to be less than or equal to wt%. By using a mixture of such an acetylating agent and a solvent, the acetyl reaction, which is an exothermic reaction, can be proceeded in a mild state, the reaction operation is facilitated, and excessive acetylation and heat deterioration of the wood flakes are suppressed. be able to.

In the present invention, the wood flakes can be pretreated with a catalyst prior to the acetylation in the gas phase. In this pretreatment, wood flakes obtained by cutting are treated with 1 to 1 of acetate such as sodium acetate and potassium acetate.
It can be performed by a method of immersing it in a 0% aqueous solution for about 10 minutes to 2 hours. The wood thin piece subjected to this pretreatment will undergo the above-mentioned acetylation reaction after drying.

By performing the pretreatment with this catalyst,
The acetylation reaction in the next step is promoted, the reaction can be completed in a short time, and a product having a high degree of acetylation can be obtained.

The degree of acetylation of the wood flakes by the above-mentioned acetylation is usually about 10 to 30% in terms of weight increase rate, but it can be appropriately changed depending on the required moisture resistance.

The wood flakes which have been subjected to the acetylation reaction in the gas phase are then washed with water or warm water to remove the adhering acetylating agent, and then dried to a predetermined water content. Next, the acetylated wood flakes are accumulated and solidified to form a modified wood having an arbitrary shape such as a plate or a column.

This accumulation and solidification is carried out by applying a binder such as a synthetic resin adhesive to the surface of the acetylated wood thin piece, filling this into a mold, heating and pressurizing to cure, and integrating by a conventional method. It can be carried out.

According to such a manufacturing method, the acetylation of the wood flakes is carried out in the gas phase, so that the amount of the acetylating agent used is reduced as compared with that in the liquid phase. For example, in order to acetylate 60 g of wood flakes to an acetylation degree of about 20%, the amount of acetic anhydride used is 50 in vapor phase acetylation.
˜70 ml is sufficient, while the liquid phase acetylation is also 2000 ml, and the amount used is markedly reduced. In addition, since the reaction is carried out in the gas phase, the amount of acetylating agent remaining in the wood flakes after the reaction is smaller than that in the liquid phase, and the acetylating agent and the reaction product by blowing hot air or washing with water. Is easily removed, and no odor of acetic acid remains on the produced modified wood.

A specific example will be shown below.

[Example] 60 g of all dried wood flakes obtained by cutting wood was prepared. On the other hand, as a supply source of the acetylating agent, 100 ml of acetic anhydride, a mixture of 70 ml of acetic anhydride and 30 ml of xylene, 50 ml of acetic anhydride and 50 m of xylene.
1 mixture and acetic anhydride 30 ml and xylene 70 ml
Prepare 4 kinds of the mixture of the above, fill the bottom of a 3 liter separable flask, and put all the above-mentioned flakes so as not to be immersed in the acetylating agent, then heat the flask to 140 ° C. and react for 1 hour. Let After the reaction, the flakes were taken out, washed with warm water, and then dried until the water content became 5%.

Then, a phenol resin adhesive serving as a binder was sprayed on the thin pieces, filled in a mold, and heated and pressed to cure the binder to obtain a plate-shaped molded product. This molded product is left under the condition of 35 ° C. and 95% RH for 48 hours,
The change in thickness due to moisture absorption was measured. The results are shown in Table 1.

(Conventional Example) A plate-shaped molded article was obtained in the same manner as in Example except that acetylation was not carried out. Similarly, the thickness change of this product due to moisture absorption was obtained. The results are shown in Table 1.

Comparative Example 60 g of wood flakes similar to the wood flakes used in the above examples were placed in a 3 liter flask, and 100 ml of acetic anhydride was added thereto without touching the wood flakes, and at 140 ° C. The wood flakes were acetylated by gas phase reaction for 1 hour. After the reaction, the thin piece was taken out of the flask, washed with warm water, and dried to obtain the degree of acetylation due to the increase in weight, which was 20%. Further, when the amount of acetic anhydride was set to 500 ml and the reaction was conducted under the same conditions, the degree of acetylation was 22%.
The degree of acetylation was 21% when the amount was 0 ml. From this result, according to acetylation in the gas phase (Example),
Even if you reduce the amount of acetylating agent for the same amount of wood flakes,
It can be seen that almost the same high degree of acetylation can be obtained. 20%, 22%, and 21% of the above acetylation degree are considered to be measurement errors caused by small-scale implementation.

[0020]

[Table 1]

[0021]

As described above, according to the method for producing modified wood of the present invention, wood flakes obtained by cutting wood are acetylated in the gas phase, and the acetylated wood flakes are accumulated and integrated. Since it is molded, it is possible to manufacture modified wood having low hygroscopicity and water absorption and excellent moisture resistance. Also, since acetylation is performed in the gas phase, the amount of acetylating agent used can be greatly reduced compared to that used in the liquid phase.
The effect that the production cost can be kept low is obtained.

[Procedure amendment]

[Submission date] July 26, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] Claim 1

[Correction method] Change

[Correction content]

[Procedure Amendment 2]

[Document name to be amended] Statement

[Name of item to be corrected] 0002

[Correction method] Change

[Correction content]

[0002]

2. Description of the Related Art A wood material, which is made from wood flakes as a raw material and is bonded and molded by a synthetic resin binder to be integrated, is already known. This wood-based material is obtained by cutting wood into pieces each having a length of several mm to several tens of mm, and preferably one piece having a length of 4 mm.
0 to 80 mm and the other piece has a length of 5 to 15 mm,
Or the length of one piece is 40 to 80 mm and the length of the other piece is
Make a thin piece of about the same size, and integrate this thin piece with an adhesive,
It is molded. This one has little directionality,
Quality and easy processing, not limited to flat shape,
Features such as being able to mold even products and mass producing
However, it has a porous property due to the voids between the flakes,
High moisture absorption rate due to its large surface area
It has inferior drawbacks.

[Procedure 3]

[Document name to be amended] Statement

[Name of item to be corrected] 0003

[Correction method] Change

[Correction content]

In order to improve the moisture resistance of wood, the wood is
It is well known that cetylization is used, but how to handle it
The method has traditionally relied on liquid phase reactions. However, of wood
If the shape is flaky, it will be bulky when deposited.
In addition, when trying to submerge it, the acetylation treatment solution becomes large.
Depending on the volume, a large reaction solution may require a high reaction temperature.
It is difficult to raise the temperature in a short time,
Handling of processing liquids
No, the cost of disposing of it is also likely to be high. Solving this drawback
Acetylation of the wood by a gas phase reaction to determine
Is expected. A wood test piece is
Attempts to make cetyl are known, but by known gas-phase reactions.
If so, the shape of the object to be treated will be acetylated in the wood block.
It is difficult to do so, and at best it is tried to treat small pieces of wood.
It was only seen. Liquid reversal even in those treatments
The moisture-proof effect was inferior to that of the case. And the reason
In the case of gas phase reaction, the solvent is used to
Since it does not have the effect of expanding the visual structure, it is processed into wood.
It is considered that diffusion of the agent vapor takes time. Also,
There is a direction in the diffusion rate of the treatment agent into the wood, and
Direction is dominant, diffusion rate in the direction perpendicular to the grain
Was inferior.

[Procedure amendment 4]

[Document name to be amended] Statement

[Name of item to be corrected] 0005

[Correction method] Change

[Correction content]

[0005] Such a problem is that acetylating agent on wood flakes
Of the acetylated wood flakes, and the acetylated wood flakes are integrated and integrally molded to solve the problem. If the shape of the wood is flaky,
The distance when the treatment agent diffuses from the wood surface to the deepest inside is
Since it is short, the progress of the process is not affected even if the diffusion speed is low.
For the same reason, the diffusion speed due to diffusion in the direction perpendicular to the grain
The disadvantages due to the low degree are also overcome. Also, the wood is flaky
Therefore, the volume of the object to be processed is smaller than the surface area.
Therefore, even if the diffusion speed is low, the progress of the process is not much affected. A
Molded products made of cetylized wood flakes are
For metal parts used when joining or assembling
In order to prevent rust from forming when touching,
It is preferable to avoid impregnating wood flakes with chilling catalysts.
However, even if it makes the reaction mild, the above
Will be overcome for the reason. Wood by chemical reaction of wood components
The principle of this reaction as a method of modifying materials is as follows.
Sea urchin (W) has acetyl groups (O)
COCH ₃ ). _{[W] -OH + (CH 3} CO) 2 O → [W] -OC
OCH ₃ + CH ₃ COOH + (54kcal)

[Procedure Amendment 5]

[Document name to be amended] Statement

[Correction target item name] 0007

[Correction method] Change

[Correction content]

The wood flakes thus obtained are then acetylated in the gas phase. Prior to acetylation, it is preferable to dry the wood thin pieces to have a water content of 3% or less, preferably 1% or less. If the water content is too high, acetyl
The acetic anhydride in the vaporizing agent reacts with the water first to form acetic anhydride.
Will be consumed and the amount of acetylating agent used will increase,
Or the degree of acetylation due to lack of acetic anhydride supply
Is easy to decrease. In the present invention, acetylation is performed in the gas phase. That is, the vaporized vapor of the acetylating agent is brought into contact with the wood flakes in the vapor phase to cause the acetylation reaction. As the acetylating agent, acetic acid, acetic anhydride, chloroacetic acid or the like is used, and acetic anhydride is preferable.

[Procedure correction 6]

[Document name to be amended] Statement

[Correction target item name] 0011

[Correction method] Change

[Correction content]

By performing the pretreatment with this catalyst,
The acetylation reaction in the next step is promoted, the reaction can be completed in a short time, and a product having a high degree of acetylation can be obtained. However, since the acetylation reaction is an exothermic reaction, this
When the fever of
Since it may turn into a
In order to avoid sudden heat generation, do not use a catalyst.
And are effective. Also, the use of catalyst is
It is suitable for shortening the time period and improving the degree of acetylation.
However, if a catalyst is used, the catalyst is
A plate made of wood flakes, since the components tend to remain.
When adhering or painting molded products such as shapes, the adhesive strength and coating density
It is not preferable because it may adversely affect the adhesion.

[Procedure Amendment 7]

[Document name to be amended] Statement

[Correction target item name] 0019

[Correction method] Change

[Correction content]

The object was used (Comparative Example) In the above Example
60 g of wood flakes similar to the treated wood flakes were placed in a 3 liter flask, and 100 ml of acetic anhydride was added thereto without touching the wood flakes, and the wood flakes were acetylated by a gas phase reaction at 140 ° C. for 1 hour. Let After the reaction, this
Remove the wood flakes from the flask, wash with warm water,
When the degree of acetylation due to weight increase was obtained by drying,
It was 20%. When the amount of acetic anhydride was 500 ml and the reaction was conducted under the same conditions, the degree of acetylation was 22%, and when the amount was 1000 ml, the degree of acetylation was 21%. 20% each of the above acetylation degree, 22
% And 21% are extremely significant from this measurement scale.
It is judged that there is no difference. From this result, according to the method of acetylating in the gas phase, even if the amount of acetylating agent is reduced for the same amount of wood thin piece, a large amount of acetylating agent is produced.
It can be seen that a high degree of acetylation, which is almost the same as in the case of, can be obtained.

[Procedure Amendment 8]

[Document name to be amended] Statement

[Correction target item name] 0021

[Correction method] Change

[Correction content]

[0021]

As described in the foregoing, production process of the modified wood of the present invention, the wood flakes obtained by cutting the timber, acetate
The vapor of the chilling agent is contacted , the wood flakes are acetylated in the gas phase, and the acetylated wood flakes are collected and integrated,
Since it is molded, it is possible to manufacture modified wood having low hygroscopicity and water absorption and excellent moisture resistance. In addition, since acetylation is performed in the gas phase, the amount of acetylating agent used can be significantly reduced compared to that used in the liquid phase, and production costs can be kept low. To be

Claims (4)

[Claims] 1. A wood slice obtained by cutting wood is acetylated in a gas phase, and the acetylated wood slice is accumulated.
A method for producing modified wood characterized by being integrally molded. 2. The method for producing modified wood according to claim 1, wherein the acetylation in the gas phase is performed by a source of an acetylating agent consisting of acetic anhydride alone. 3. The method for producing modified wood according to claim 1, wherein the acetylation in the gas phase is performed by a source of the acetylating agent which is a mixture of acetic anhydride and a solvent. 4. The method for producing modified wood according to claim 3, wherein the solvent is xylene.