JPH0694122B2 - Method for producing modified wood - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing modified wood used for building materials, furniture, and the like.

[Conventional technology]

Conventionally, a method of modifying a wood material by injecting a synthetic resin liquid into the wood material and curing it has been widely used. Particularly, it has good permeability to the wood cell wall for the purpose of improving dimensional stability and weather resistance. Water-soluble synthetic resin is injected and cured.

[Problems to be Solved by the Invention]

However, if the wood material in which the water-soluble synthetic resin liquid has been injected is heat-cured by ordinary means, cracks may occur during heat-curing or drying, or the injected resin may flow out as water vapor evaporates, and the resin residual rate may decrease. Has drawbacks,
This tendency becomes particularly noticeable when the wood material has a thickness of 10 mm or more, such as sawn timber.

Cracking during curing and drying causes a large water content gradient between the center of the material and the surface layer due to the rapid movement of water in the material during heating, causing cracks and irregularity due to the difference in shrinkage stress between the two. This is because a drop due to shrinkage occurs, and in addition, the injected synthetic resin liquid hardens (surface hardens) on the surface of the material before the central part, and residual water tends to be released to the outside of the material. This is because the water vapor pressure in the central part causes an explosion.

Therefore, attempts have been made to heat the inside of the wood by induction heating using high frequency to cure the synthetic resin inside it, but when using induction heating, the temperature near the + electrode plate is high and the temperature near the − electrode plate is high. However, there is a problem in that temperature unevenness occurs depending on the position between the electrodes, and the temperature of volatile unreacted substances such as a defective curing portion and residual formalin which is a resin component rises.

The present invention completely solves such problems, and is particularly effective for the modification treatment of thick wood materials such as lumber products, and increases the filling resin ratio to improve performance such as dimensional stability and safety. The present invention provides a method for producing modified wood that can be used.

[Means for Solving the Problems]

In order to achieve the above-mentioned object, the method for producing modified wood of the present invention comprises the steps of injecting an aqueous dehydration condensation type resin solution into a wood material, and then sandwiching the wood material between heating plates capable of adjusting temperature, and synthesizing the wood material under reduced pressure. It is characterized in that dehydration is carried out under reduced pressure below the curing temperature of the resin, and then the heating plate is heated under reduced pressure to heat and cure the synthetic resin.

[Action]

After injecting a water-soluble dehydration-condensation type synthetic resin liquid into a wood material, and performing a vacuum dehydration treatment at a temperature not higher than the curing temperature of the synthetic resin, the solvent injected at a temperature not higher than the curing temperature of the resin gradually decreases due to a boiling point drop of water. While evaporating, the initial condensation reaction occurs as the dehydration progresses, and the resin content easily remains in the wall,
The outflow of resin is reduced, and the residual resin ratio is increased.

Next, while maintaining the depressurized state, when the temperature of the heating plate holding the wood material is raised, the resin in the wood material is heated and the difference in shrinkage stress due to dehydration between the inside and the surface of the wood material. Is gradually dehydrated and condensed with almost no occurrence of
Cracks due to the shrinkage ability are less likely to occur, and the variation in the curing reaction is reduced to improve the filling resin ratio and wrinkles are less likely to occur, so that the natural grain can be maintained.

Further, since the resin is hardened uniformly over the entire wood material, the residual volatile unreacted substances such as formalin are extremely reduced, and a highly safe modified wood can be obtained.

〔Example〕

Explaining the examples of the present invention in detail, first, an aqueous solution of dehydration condensation type synthetic resin is injected into a wood material by an appropriate means such as a dipping method, a reduced pressure heating method or a combination thereof.

As the wood material into which the resin liquid is injected, square wood and plate materials,
Thick lumber products such as hollow materials, and further laminated wood are used, but even a thin plate such as a single plate can of course be injected.

In addition, as the synthetic resin to be injected, formalin resin such as melamine or phenol which penetrates the wood cell wall and forms an insoluble or infusible substance in the cell wall structure is used. It may be mixed with a mold resin (cyclic urea resin) or may be injected into the wood material as a co-condensed resin liquid.

Specific examples of such synthetic resin include phenol,
Resorcinol, melamine, dimethylol ethylene urea, dimethylol propylene urea, dimethylol dihydroxy ethylene urea, dimethylol glyoxal monourein, dimethylol triazone, dimethylol urone, etc., especially as a formalin resin, the initial condensation product When used, it easily penetrates into the cell wall, and is less likely to be washed out of the material in the solvent volatilization step described later, improving the fat content,
It is suitable.

Such a wood material infused with such a synthetic resin liquid is used alone or in the case of a thin plate, a plurality of the wood materials are superposed and sandwiched between heating plates whose temperature can be adjusted up and down. At this time, in order to improve productivity,
It is preferable to stack and process a large number of wooden materials sandwiched between heating plates.

As the heating plate, an electrothermal type planar heating plate, a heating plate incorporating a heater wire, or an aluminum plate having a steam / silicon oil medium flow pipe built therein, which has a fast temperature rising rate and is easy to control the temperature, is used. .

Then, the wood material sandwiched between the heating plates is placed in a decompression chamber, and the chamber is decompressed to 100 Torr or less, preferably 40 to 50 Torr and the heating plate is injected at a temperature of 70 ° C. or less, preferably the curing temperature of the resin liquid, preferably The solvent (water) is adjusted and maintained at 40 to 50 ° C, and the solvent (water) injected is volatilized until the water content becomes 10 to 50%, and initial drying is performed.

In addition, it is preferable to interpose a mesh sheet material between the heating plate and the wood material in advance. By interposing the mesh sheet material in this way, dehydration from the surface of the wood material is effectively performed to the outside through the mesh. Not only can it be discharged into the chamber, but also in the subsequent curing reaction, the surface of the wood material is completely adhered to the heating plate to prevent the formation of a resin cured film, preventing surface curing and promoting uniform curing. Can be made.

In this way, under reduced pressure of the wood material, when the dehydration treatment is performed, the injected solvent (water) is evaporated, the initial condensation reaction of the injected resin proceeds as the dehydration progresses, and the resin component remains in the fine voids of the wood. It becomes difficult to flow out.

In addition, since it is a dehydration treatment under reduced pressure, when the boiling point of water is reduced and the resin components are volatilized along with the evaporation of water vapor, it is not preferable in terms of lowering the fat content and the working environment, so that power adjustment or energization of the heating plate The heating temperature is adjusted by turning on and off.

Subsequently, the process proceeds to the heat-curing step of the resin-injected wood material under reduced pressure. In this step, the temperature of the heating plate sandwiching the wood material is raised to 100 to 150 ° C, and the material temperature is increased to inject the resin. The reaction of.

At this time, high-temperature heat treatment is performed while maintaining the above reduced pressure while forcibly exhausting the reduced pressure chamber, and volatile components such as formalin remaining in the wood due to the reduced pressure and residual moisture, and a condensation reaction of the resin. It evaporates and reduces the generated water and forcibly discharges it, and cures the resin by heating at high temperature. At this time, volatile components, moisture, and the like diffused from the surface of the wood material are easily discharged through the voids of the mesh sheet material interposed between the heating plate and the wood material.

The curing temperature of the injected resin is set within the above temperature range according to the type of the injected resin.

As described above, the reaction of the resin by continuously performing the step of evaporating the water in the wood material to remove the volatile components under the low temperature of the wood material under the reduced pressure and the step of heating and heating the wood material under the reduced pressure. Is to be completed.

In addition, in the final heat curing temperature (100 ° C. or higher), the drying step and the curing step, hot air or hot pressing may be subsequently used after releasing the reduced pressure.

In addition, when performing the above treatment with a plurality of layers of wood material in a laminated state, use a hard plate-shaped heating plate at the uppermost and lowermost parts and use a flexible heating sheet as a heating member interposed between them. In this case, if a sheet having a roughened surface is used as the heating sheet, it is possible to eliminate the use of the mesh sheet.

Next, specific examples of the present invention will be shown.

(Example) A phenol resin aqueous solution (concentration 10%) was injected under reduced pressure into a Bitsuga lumber product (thickness 18 x width 100 x length 1000 mm) to obtain a resin injection treated material.

Two pieces of the resin injection treatment material are piled up two by two, and they are sequentially sandwiched between the upper and lower heating plates of ten electric heating type sheet heating plates, and the whole is clamp-set, and then loaded into a vacuum dryer.
Then, the treated material is dried under reduced pressure (50 torr, material temperature about 40 ° C) in this reduced pressure dryer to a water content of about 30%, and then heated at a reduced pressure of 50 torr and heated at 140 ° C for 3 hours. Treatment was performed to obtain modified wood.

The weight gain of the obtained modified wood was 18.2%. The results of the dimensional stability test (pressure reduction and pressure absorption test) of this modified wood are shown below.

Anti-expansion rate (AE) 54.3% Anti-shrinkage rate (ASE) 55.3% Leach rate 1.7% Thus, the modified wood obtained had low leaching rate and excellent dimensional stability. The residual formalin was measured and found to be 1 ppm or less.

(Comparative Example) After the same resin aqueous solution as in Example 1 was injected into the lumber product in Example 1, the water content was reduced to 20% by a high-frequency vacuum dryer (40 torr, 41 ° C), and subsequently 140 ° C by high-frequency wave. As a result of heating and curing for 3 hours, resin-injection-cured wood with a weight increase rate of 18.5% was obtained. As a result of measuring residual formalin in the same manner as in Example 1, there was a concentration of 403 ppm. The reaction was found to be incomplete.

〔The invention's effect〕

As described above, according to the method for producing modified wood of the present invention, after the dehydration condensation type resin aqueous solution is injected into the wood material, the wood material is sandwiched between the temperature-adjustable heating plates, and the synthetic resin It is dehydrated below the curing temperature, and then the synthetic resin is heated and cured by heating the heating plate in a reduced pressure state, so that the resin liquid that has penetrated into the wood cell wall is dehydrated under reduced pressure. Due to the boiling point decrease, the solvent injected below the curing temperature of the resin gradually evaporates and the initial condensation reaction occurs as the dehydration progresses, and the resin component remains in the wall, increasing the resin residual ratio in the cell. Not only is it difficult for the wood cell wall to fall, but it is also possible to modify the wood with a high filling resin rate because it can bind to wood components or generate insoluble and infusible substances in the cell wall structure. Stabilization( Rukingu effect) can be achieved.

Furthermore, by heating with a heating plate under reduced pressure, the resin in wood hardens while producing water due to dehydration condensation, and as a result, the water content gradient in the material decreases and cracking due to shrinkage stress does not easily occur, and the curing reaction Variation is reduced and wrinkles are less likely to occur, the natural grain can be maintained, and as described above, a resin cured product exists in the lumen of cells and a cured product is also generated in the cell wall. Therefore, modified wood that can be expected to have an antiseptic and insecticidal effect can be obtained.

Further, since the resin is hardened evenly over the entire wood material, the amount of residual formalin and other volatile unreacted substances is extremely reduced, and a modified wood with high safety in use can be obtained.

Claims (1)

[Claims] 1. A method of injecting an aqueous solution of dehydration-condensation resin into a wood material, sandwiching the wood material between heating plates whose temperature can be adjusted, dehydrating under reduced pressure below the curing temperature of the synthetic resin, and then under reduced pressure. A method for producing modified wood, characterized in that the heating plate is heated to heat and cure the synthetic resin.