JPH0356522B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for modifying wood materials.

(Prior art) Wood and its processed materials, such as wood veneers and wood chips, are light and strong, and have unique physical properties and textures, so they are used for a wide range of purposes such as construction materials and furniture materials. ing. However, this wood material
Not only is it susceptible to decay due to erosion by various fungi and insect damage such as termites, but it also has the disadvantage of being susceptible to deformations such as warping, twisting, and expansion/contraction due to its breathability. In order to eliminate this drawback, in recent years, a method of modifying wood materials by acetylation has been developed, in which wood materials are immersed in an acetylation reaction solution at room temperature to react, and then the wood materials are taken out from the reaction solution. A method has been proposed in which wood is washed, dried, and acetylated.

However, this method has the disadvantage that the reaction time is very long and the productivity is very poor.

On the other hand, it shortens the time required for the acetylation reaction,
In order to increase productivity, a method has also been proposed in which wood is immersed in a room-temperature reaction solution and then heated to over 100°C to acetylate it at high temperatures.

However, in this method, the wood material is immersed in the reaction solution at room temperature or higher for a long period of time, which has the disadvantage that wood components leak into the reaction solution, causing discoloration and deterioration of the wood material. . In order to prevent this, it is conceivable to shorten the immersion time of the wood material in the reaction solution, but in this case there is a drawback that the acetylation rate is low.

Moreover, in all of the above-mentioned methods, the acetylated wood is washed with water after the acetylation process, but the reaction solution is
Since it contains 70 to 200% by weight, removing it by washing with water requires time and effort, and the unreacted liquid must be discarded, which is wasteful, and the washing waste liquid must be neutralized. It also has the problem that it is troublesome.

(Problems to be Solved by the Invention) Therefore, the present invention aims to improve the wood material so that it can be highly acetylated without immersing the wood material in the reaction solution for a long time and can efficiently recover the reaction solution. lies in providing quality processing methods.

(Means for Solving the Problems) The present invention involves immersing a wood material in an acetylation reaction solution that is housed in a reaction vessel and heated to a predetermined temperature for a predetermined period of time to convert hydroxyl groups in wood components into acetylates. Then, after removing and recovering the reaction liquid that is not impregnated into the wood material from inside the reaction vessel, the inside of the reaction vessel is suctioned and depressurized to vaporize a part of the reaction liquid that is impregnated into the wood material. This is a method for modifying wood materials by removing and recovering them.

As the wood material to which the present invention is applied, wood, wood veneer, wood chips, etc., of any size can be used. However, if the thickness is 3 mm or more, it is preferable to perform a catalyst treatment in advance to promote the acetylation reaction described below.

The catalyst used in this catalytic treatment is preferably an acetate aqueous solution, such as sodium acetate or potassium acetate, which does not deteriorate the wood material and can be easily removed by washing with water. Note that the concentration of the acetate aqueous solution is not particularly limited, but is preferably 2 to 30%.

Catalyst treatment involves immersing wood materials in these aqueous solutions or heating them at temperatures between 40°C and 80°C to quickly impregnate the catalyst.
By immersing the wooden material in the aqueous solution heated to ℃,
Alternatively, the acetate aqueous solution may be injected into the wood material under reduced pressure, injected with increased pressure, or injected with reduced pressure and pressure in a pressure cooker to impregnate the wood material with the aqueous solution.

Next, the wood material impregnated with the acetate aqueous solution is appropriately dried, but it is preferable that the water content of the wood material is 10% or less.

Then, the catalyst-containing wood material obtained by drying as described above or the untreated wood material is immersed in a high temperature (approximately 100°C) acetylation reaction solution injected into the reaction vessel. The hydroxyl groups of the components are reacted with the reaction solution to acetylate the wood material.

The reaction solution is mainly composed of acetic anhydride, in which less than 30% of acetic acid or aromatic hydrocarbons such as toluene, xylene, and benzene may be used.

In this way, mixing an organic solvent with acetic anhydride reduces the amount of expensive acetic anhydride used, reduces the strong pungent odor of acetic anhydride, and improves the working environment. This is to reduce the decrease in strength.

Note that before immersing the wood material in the reaction solution, it is desirable to vacuum the wood material in advance under reduced pressure to remove air in the wood material before immersing it in the reaction solution.

In addition, the wood material may be simply immersed in the reaction solution, but it is also possible to use the reduced pressure method in a pressure cooker (reaction vessel).
Injecting the reaction liquid into the wood material in advance by a pressurization method or a vacuum pressure method is effective in shortening the time required to infiltrate the reaction solution into the wood material.

In the acetylation treatment, the reaction solution in the reaction vessel is heated and maintained at 100°C or higher, the wood material is allowed to react in that state for a predetermined period of time, and then the reaction solution that is not impregnated into the wood material is heated. After deliquifying and collecting the reaction liquid from the reaction vessel, the reaction vessel is heated, and the inside of the reaction vessel is vacuumed and depressurized with a degree of vacuum higher than 100 mmHg, for example, to lower the boiling point and remove the reaction liquid impregnated into the wood material. A portion of it is vaporized and removed from the reaction vessel together with exhaust air, and then liquefied in a condenser and recovered.

Note that when the reaction liquid vaporizes, the temperature of the wood material tends to decrease due to the latent heat of vaporization, but since the reaction vessel is heated, the temperature decrease is small.
The reaction solution can be efficiently recovered. At this time, it is possible to recover all or most of the reaction liquid impregnated into the wood by continuing suction and reduced pressure, but it takes a long time, so
Recovering 70% seems to be a good idea in terms of the number of times the device is used, cost, etc.

After a predetermined period of time has elapsed, the wood material is taken out from the reaction vessel, washed with warm water, etc., and dried to obtain the desired acetylated wood material.

The acetic acid concentration of the recovered reaction solution increases as it is used, and the acetylation rate decreases when the concentration exceeds a certain level. Therefore, it is recommended to fractionally distill the recovered reaction solution to increase the concentration of acetic anhydride and use it repeatedly. preferable.

As described above, according to the present invention, by using a pre-heated reaction solution, the acetylation reaction is carried out by omitting the time required to raise the temperature of the reaction solution to a predetermined temperature. The time required for immersion in the reaction solution is shortened. Therefore, there is no outflow of wood components, and a high degree of acetylation can be achieved in a short time without causing discoloration or deterioration of the wood material.

Moreover, since a part of the reaction liquid impregnated into the wood material is removed and recovered by vaporization, the reaction liquid can be recovered efficiently and the cleaning time can be greatly shortened. There is.

(Example) Examples according to the present invention will be described below.

12% by weight on 3mm thick larch rotary veneer
The veneer was impregnated with an aqueous acetate catalyst solution and dried, and the veneer was placed in a reaction vessel, which was a reaction vessel, and heated to 40 mmHg.
After degassing the inside of the pot under reduced pressure for 5 minutes, a reaction solution consisting of 95% by weight of acetic anhydride and 5% by weight of acetic acid was poured into the pot under reduced pressure, and the reaction solution was poured into the veneer for 10 minutes. Injected. Next, after releasing the reduced pressure state and once removing the reaction solution from the inside of the pot, the same reaction solution heated to 100°C was poured into the pot, and nitrogen gas was further supplied into the pot. The inside of the veneer was heated and pressurized to 8 kg/cm ² for 30 minutes, and the reaction solution was injected into the veneer under pressure.
During that time, the reaction solution was raised to 120°C, and the reaction was continued for 30 minutes, then the pressurized state was released and the reaction solution was drained, and then the reaction vessel was heated and maintained at 120°C. The inside of the reaction vessel was evacuated to 50 mmHg for 30 minutes, and the vaporized reaction liquid was condensed in the condenser of the reaction liquid recovery device installed between the reaction vessel and the vacuum pump and collected in the receiver. The veneer was washed and dried to obtain an acetylated veneer with an acetylation rate of 21%.

In addition, according to this example, the reaction liquid contained in the wood material could be recovered to 65% of the weight of the wood material, so the cleaning time was also significantly shortened.

(Effects of the Invention) As described above, in the present invention, by using a pre-heated reaction solution and shortening the reaction time by omitting the time required to raise the temperature of the reaction solution, acetylation due to outflow of wood components can be prevented. In addition to preventing discoloration and deterioration of the wood material, it is possible to increase the number of times the reaction device is used by shortening the reaction time, increase the operating rate of the reaction device, and reduce costs.

Furthermore, since the reaction solution that was conventionally discarded during cleaning operations can be recovered, manufacturing costs can be reduced. In particular, since acetic anhydride is expensive,
It is effective to recover the reaction solution that has been impregnated into the wood.

Claims (1)

[Claims] 1. A wooden material is immersed in an acetylation reaction liquid stored in a reaction container and heated to a predetermined temperature for a predetermined time to acetylate the hydroxyl groups in the wood component, and then impregnated into the wood material from inside the reaction container. After deliquifying and collecting the reaction liquid that has not been removed, the inside of the reaction vessel is depressurized by suction, and a part of the reaction liquid impregnated in the wood material is vaporized, removed, and recovered. Modification treatment method.