JPH04278302A - Manufacture of resin treated ligneous material - Google Patents

Abstract

PURPOSE:To provide resin impregnated ligneous material, which presents the appearance intrinsic to ligneous material and, at the same time, is excellent in dimensional stability, stain resistance, handling characteristics and workability. CONSTITUTION:Aqueous phenolic resin solution, which is prepared by mixing proper amount of acid such as toluenesulfonic acid, benzenesulfonic acid or the like with water and contains 40wt.% or less of nonvolatile content, is infiltrated in the ligneous material so as to infiltrate the aqueous phenolic resin solution diluted with a large number of water in the cell wall of the ligneous material. Next, by volatilizing water content infiltrated in the ligneous material, large gaps such as cell lumina are made to be empty and, at the same time, the phenolic resin left in the ligneous material is made to be more sticky and further hardened under the state being made to be hard to flow out of the fine gap of the cell wall by heating.

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 a resin-treated wood material that has excellent dimensional stability, durability, stain resistance, workability, etc., and exhibits the appearance of wood.

0002

BACKGROUND OF THE INVENTION Phenol resin-treated wood materials, which are modified wood materials, have been known. This kind of phenolic resin-treated wood is made by injecting and filling resin into the minute voids in the cell walls of wood to improve stain resistance, dimensional stability, and strength, which are the drawbacks of wood. It is.

0003

[Problem to be Solved by the Invention] However, when resin is injected into wood materials and cured, if the resin is injected into large voids such as the inner cavities of wood cells and cured, the characteristics of the wood materials will be affected. Not only does some machinability deteriorate and lightness is impaired, but darkening and brittleness occur.

[0004] Therefore, it is desirable to selectively fill the fine voids in the cell walls of wood with phenolic resin, but in order to improve its permeability into wood, it is necessary to dilute it to a low viscosity with a solvent. On the other hand, there is a drawback that when phenolic resin is heated to cure it, the resin that has penetrated the resin tends to flow out together with the solvent.

[0005] However, when attempting to cure a phenolic resin using a catalyst, there is a problem in that the treatment liquid becomes highly viscous before being injected into the wood material, resulting in poor permeability into the wood material.

The present invention was made in view of these problems, and it is possible to efficiently inject phenolic resin and harden it, so that the original appearance of the wood is maintained despite the injection of resin, and the machinability is improved. The present invention provides a method for producing a resin-treated wood material that exhibits excellent physical properties such as lightness, dimensional stability, durability, and stain resistance.

[0007]

[Means for Solving the Problems] In order to achieve the above object, the method for producing resin-treated wood materials of the present invention includes adding an acid such as toluenesulfonic acid or benzenesulfonic acid to the non-volatile content of 40% by weight or less. The process involves impregnating a wooden material with an aqueous solution of phenolic resin, volatilizing the water in the wood to increase the viscosity of the resin, and then heating the wood to a temperature that allows the resin to harden. This is a characteristic feature.

[0008]

[Action] Since the phenolic resin is diluted with a large amount of water, even if an acid is added, the water suppresses the polycondensation reaction of the resin and prevents the phenol resin aqueous solution from increasing in viscosity, making it hydrophilic. It easily penetrates into the cell walls of woody materials. After injecting the treatment solution into the wood, when the water in the treatment solution in the wood is evaporated, most of the water is easily released from the large pores such as the intracellular cavities of the wood to the outside of the wood, causing the resin to deteriorate. On the other hand, the treatment liquid remains in small voids within the cell wall.

[0009] At this time, in the resin injected portion where water content has decreased, a reaction between the acid and the resin begins gradually, and the phenol resin begins to become highly viscous, making it difficult for the resin to flow out. Here, when sufficient heating is applied to cause the polycondensation reaction of the phenol resin, the resin remaining in the wood material fills and solidifies. Therefore, the wood material can be modified to improve its dimensional stability while retaining its porous nature.

0010

[Example] Next, to describe the example of the present invention in detail, an appropriate amount An injection treatment solution is prepared by adding this acid. As the acid, organic acids such as toluenesulfonic acid, benzenesulfonic acid, phenolsulfonic acid, xylene sulfonic acid, oxalic acid, boric acid, and phosphoric acid, or inorganic acids such as sulfuric acid and hydrochloric acid can be used. Note that the concentration, type of acid, and amount added are selected so that the injection treatment liquid maintains a low viscosity at room temperature within a range that does not impede penetration into the wood material.

[0011] Next, the treatment liquid is injected into the wood material. This injection method is carried out by reduced pressure or pressure injection, but it can also be carried out by immersion, which is suitable for the shape and size of the wood, permeability, and tree species so that the synthetic resin aqueous solution is evenly injected and impregnated into the wood. The method and conditions may be selected as appropriate. Furthermore, the wood material to be injected may be any of thick sawn timber products such as square timber, board timber, and hollow timber, laminated timber, plywood, and thin boards such as veneer, and the species of the wood is not particularly limited.

When the treatment liquid is injected into the wood material using such an appropriate injection means, since a large amount of water is present in the phenolic resin aqueous solution, the water injects the treatment liquid before or during injection. This suppresses the increase in viscosity between the acid and phenol resin, prolongs the pot life of the treatment liquid, and allows the treatment liquid to easily penetrate into the cell walls of hydrophilic wood materials.

[0013] After injecting the treatment liquid into the wood material, the resin-infused wood material is left in the atmosphere, or heated under reduced pressure or under slow conditions with a hot air dryer to impregnate relatively large voids in the wood material. volatilizes the water in the treated solution,
Exclude. Note that as the water removal means, a commonly used drying means for wood materials such as high frequency heating or a hot plate may be used.

When water, which is a solvent in the treatment liquid, is volatilized in this way, most of the water is released out of the wood material mainly from large voids such as the intracellular cavities of the wood, and the voids (cells) that are not filled with resin are removed. A lumen) is formed, while small voids within the cell wall remain filled with resin.

[0015] At this time, the acidity of the treatment liquid containing an acid is increased by removing water, but it is desirable to lower the pH to 4 or less in order to smoothly carry out the reaction with the phenol resin. In this way, as the pH decreases due to the removal of water in the treatment liquid, the viscosity of the acid and resin begins to gradually increase, and once the phenolic resin has penetrated into the wood, it becomes difficult to flow out of the wood. Become.

Next, in order to accelerate the curing of the phenol resin, the curing temperature is kept in the range of 40 to 150°C for several minutes.
It lasts several hours. The presence of an acid can ease the curing conditions of the phenol resin, such as the curing temperature and time, thereby suppressing the discoloration of the coloring component of the wood material and the decrease in brittleness, as well as preventing the phenol resin from darkening.

As a result, the cell cavities, which are large voids within the wood, are hardly filled with resin and become hollow, and the resin is injected into the small voids within the cell walls and hardened, giving the appearance of natural wood. The result is treated wood with a color that maintains its original color. In addition, if the resin filling rate in the voids of the wood material increases, adverse effects such as coloring and cost increase due to the phenol resin will occur, so the concentration of the phenol resin aqueous solution should be adjusted within the above range of 40% by weight or less. It is something.

[0018] Furthermore, as is clear from the test results below, even if the wood species of the tree has a specific gravity of 0.3 to 0.5, the dimensions can be improved by injecting a phenolic resin aqueous solution with a concentration of 10 to 25% by weight. Modifying effects such as stability can be achieved, so even with wood materials with poor resin injectability or wood materials with a high specific gravity of 0.8, by injecting a phenol resin aqueous solution with a concentration of 40%, the dimensional stability and stability can be improved. This makes it possible to improve stain resistance.

Next, specific examples and experimental examples of the present invention will be shown. Example 1 A phenolic resin aqueous solution containing 10% by weight of resin non-volatile content to which 0.5% by weight of para-toluenesulfonic acid was added was applied to a veneer of Japanese hemlock 0.5 mm thick, 10 cm wide, and 1 m long under reduced pressure of 40 torr. Vacuum/pressure injection was carried out for 30 minutes under a pressure of 5 kg/cm2, and for 30 minutes under a pressure of 5 kg/cm2. Next, this resin-injected veneer was left to stand for 20 days to remove moisture, and then the injected resin was reacted and cured in a hot air dryer at 105° C. for 12 hours. The thus obtained treated veneer had an appearance in which the redness and burnt characteristic of conventional phenolic resins disappeared and the color tone before treatment was maintained. Furthermore, even when this treated veneer was exposed outdoors for 45 days, stains were hardly noticeable and it had excellent stain resistance.

Example 2 Thickness: 25 mm, Width: 10 cm: A phenolic resin aqueous solution containing 10% by weight of resin non-volatile content to which 0.5% by weight of para-toluenesulfonic acid was added was added to a 1m long piece of hemlock lumber at 40 Torr. Vacuum/pressure injection was performed for 2 hours under reduced pressure and for 8 hours under an increased pressure of 10 Kg/cm2. The resin-infused lumber was then placed in a high frequency vacuum dryer under a vacuum of 40 torr for one day to remove moisture, and then
The injected resin was reactively cured for 6 hours at a temperature of 120°C. The treated veneer thus obtained exhibited good cosmetic properties without the appearance of redness or burntness characteristic of conventional phenolic resins. Further, even after being exposed outdoors for a long period of time, stains were hardly noticeable, and the stain resistance was excellent.

Experimental Example In an aqueous phenolic resin solution containing 0.5% by weight of para-toluenesulfonic acid, the nonvolatile content was reduced to 5% by weight.
Treatment solutions adjusted to 10, 15, 20, 25, 30, 40, and 50% by weight were prepared, and the treatment solutions at each concentration were applied to a Hemlock veneer (thickness 1.5%) with an absolute dry specific gravity of 0.43. 5mm
, width 50 mm, length 50 mm), respectively, the above Example 1
The weight increase rate and dimensional stabilization rate of each treated veneer were calculated using the following equations, and a diagram as shown in FIG. 1 was obtained. Weight increase rate = [(weight after treatment - bone dry weight before treatment) / bone dry weight before treatment] x 100, dimensional stabilization rate = [(water absorption shrinkage rate of untreated material - water absorption shrinkage rate of treated material) / untreated material Water absorption shrinkage rate]×100.

[0022] In the dimensional stabilization test, water was injected into the treated veneer and the untreated veneer under reduced pressure and pressure, and after the veneer was left to stand for 2 days, the dimensions were measured, and the dimensions were further dried at 105°C overnight. The shrinkage ratio was calculated using the difference between the two as the shrinkage dimension.

As is clear from FIG. 1 showing the above test results, the treatment liquid concentration (non-volatile content) was 15% and the weight increase rate was 30%.
%, the dimensional stabilization almost reaches its peak, and if the treatment liquid concentration exceeds 40% by weight, the modification effect will be poor. Note that such a modification effect appears when the weight increase rate is between 5 and 40%, but in consideration of machinability, it is desirable to use a phenolic resin aqueous solution with a nonvolatile content of 5 to 25% by weight.

[0024]

As described above, according to the method for producing resin-treated wood materials of the present invention, wood materials are impregnated with a phenolic resin aqueous solution diluted to a non-volatile content of 40% by weight or less and to which an appropriate amount of acid is added. However, the method is characterized in that the moisture in the wood material is evaporated to increase the viscosity of the resin, and then the wood material is heated to a temperature at which the resin can be cured to cure the resin. Since the aqueous resin solution is diluted with a large amount of water, the viscosity of the resin does not increase even when acid is added. Therefore, it can be easily penetrated into small voids in the cell walls of wood while maintaining a low viscosity. Not only can it be impregnated with the phenolic resin aqueous solution, but by volatilizing the water after this impregnation process, large cavities such as the cell cavities of the wood material can be hollowed out, and fine cavities can be made to absorb the high viscosity of the phenolic resin. The phenol resin can be cured in a state in which it is difficult to flow out from the fine voids in the cell wall by a subsequent heat treatment.

Furthermore, in the resin curing process by heating, the presence of an acid makes it possible to relax the curing conditions of the phenol resin, such as curing temperature and time, suppressing the discoloration of the coloring component of the wood material and the decrease in toughness. Darkening of the resin can be prevented. In addition, even if an acid is added when preparing a treatment liquid, the phenol resin aqueous solution is prevented from condensation polymerization by a large amount of water before treatment, making it easier to maintain pot life and adjust viscosity.

[0026] Therefore, it is possible to efficiently inject into the cell wall of wood material.
The hardened phenolic resin can prevent moisture and contaminants from entering the wood material, and can improve dimensional stability, stain resistance, and rot and insect repellency. Furthermore, since the wood material remains porous with large voids such as intracellular cavities, it is possible to prevent discoloration unlike the conventional manufacturing method of resin-treated wood materials in which the voids are filled with resin. To obtain a wood material that maintains the original appearance of natural wood material and exhibits excellent cosmetic properties, and also to produce a wood material that is excellent in machinability and lightness.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the weight increase rate and dimensional stabilization rate with respect to the injection treatment solution concentration.

Claims (1)

[Claims] Claim 1: Diluted to a non-volatile content of 40% by weight or less,
In addition, a wooden material is impregnated with an aqueous phenolic resin solution to which an appropriate amount of acid has been added, and the moisture in the wood is evaporated to increase the viscosity of the phenolic resin, and then the wood material is heated to a temperature that allows the resin to harden. A method for producing resin-treated wood material, which comprises curing the resin by heating.