JPS60242003A - Improved wood - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a modified wood particularly excellent in dimensional stability and stain resistance. The present invention relates to a modified wood particularly excellent in dimensional stability and stain resistance, which is obtained by filling and curing a hydrophobic synthetic resin into the wood voids including the amorphous regions of the treated wood.

Wood has been used for a long time as a building material, as a material for furniture, and for a wide range of other purposes, but it has the disadvantage of being susceptible to decay due to attack by various fungi and insects such as termites, and is also susceptible to contamination. In addition, there are doubts about absorption and dissipation of water, moisture, etc. 1. - It has a decisive defect as a structural material and surface material in that it is susceptible to deformation such as warping, cracking, twisting, expansion and contraction. This is mainly due to the fact that fine voids in the wood structure, pores, and regions with a high rate of amorphous cellulose are expanded by the intrusion of water vapor and the like.

As means for improving such staining properties and dimensional instability, it is already known to treat wood with an anorizing agent, particularly an acedelizing agent, and to impregnate wood with a resin and harden it. However, both methods
This cannot be said to be satisfactory for the reasons stated below.

In other words, MiJ researchers treat wood with an unlubrication agent to unwrap the hydroxyl groups of wood components, especially cellulose, and reduce the hydrophilicity of the wood, thereby reducing the above-mentioned defects. However, under mild conditions, the hydroxyl groups in the wood components remain and sufficient unification cannot be achieved; therefore, sulfuric acid or perchloric acid, etc., are usually used to amorphize the cellulose crystalline regions. Measures have been taken to increase the unruling efficiency.This method increases the unruling rate, but at the same time, due to the action of the strong acid used, the essential characteristics of wood, such as lightness and toughness, are reduced. However, there are disadvantages in that workability, specific strength, and the beauty of the natural grain are impaired.

Furthermore, no galls were formed to prevent contaminants from entering the wood.

On the other hand, when wood is impregnated with resin and cured, the dimensional stability and stain resistance are not significantly improved even when a large amount of resin is impregnated. This is because the resin only penetrates into the large voids in the wood, and only the resins are homopolymerized. Therefore, the resin may penetrate into the cell wall,
Perhaps it is expected that dimensional stability and stain resistance will be greatly improved by adhesion to the cell wall, but conventional products have gaps between the cell wall and resin, poor adhesion, and water and Contaminants easily entered the system and the intended purpose could not be achieved.

The present inventors were able to obtain modified wood with excellent dimensional stability and stain resistance by combining the above-mentioned conventional techniques under appropriate conditions to prevent aqueous substances from easily penetrating the wood. This was a success and led to the completion of the present invention.

That is, in the present invention, only the cellulose amorphous region of a thin wood board is acetylated, and a hydrophobic synthetic resin is filled and hardened into the wood (pores) containing the amorphous region.

Since the product obtained by the present invention does not amorphize the cellulose crystalline region, the wood does not become brittle.
In addition, by chemically modifying cellulose hydroxyl groups, microscopic voids in the wood structure are filled with hydrophobic synthetic resin and hardened.
The penetration of water and contaminants is reduced, and dimensional stability and stain resistance can be significantly improved without impairing the essential properties of the wood.

The present invention will be explained in more detail below.

There are no particular restrictions on the species of wood that can be used in the present invention, and there is no need to perform any special pretreatment before subjecting it to the treatment process of the present invention. However, in order to facilitate chemical modification or impregnation with resin liquid, soluble components may be removed in advance by boiling, steaming, or using an alkaline aqueous solution or hot water.

A known method may be used to acetylate only the cellulose amorphous region in the wood component. [! 11. Acetic anhydride or a mixture of acetic anhydride and a fatty acid (for example, a mixture of chloroacetic anhydride and acetic acid) is chemically reacted with the hydroxyl groups in the amorphous region of cellulose in the main +4 components.

The above acetylating agent may contain a catalyst for promoting the reaction with the water side component and/or a solvent for promoting the penetration of the acetylating agent into the wood cell wall for the reasons mentioned above. Therefore, the use of strong catalysts that would amorphize the crystalline regions of wood should be avoided. Therefore, when using acetic anhydride, a typical acetylating agent, it is preferable to use sodium acetate or potassium acetate as a catalyst and to treat under mild conditions in the presence or absence of a solvent.

In order to bring the wood into contact with the above-mentioned acetylating agent, the wood may be immersed in the reactant, or the wood may be exposed to the vaporized reactant. In addition, such a method can be carried out by pressurization or reduced pressure to promote impregnation of the acedelizing agent into the wood. This reaction is used to acedelize the amorphous region of cellulose in order to prevent significant strength loss and thermoplasticization of wood.
It is preferable to adjust the increase rate of the resulting treated wood so that it does not exceed 30%.

The wood thus treated with the reactant is washed, if necessary, with a suitable solvent, dried, and subjected to the next step of filling and hardening the hydrophobic P1-synthetic resin.

This process involves immersing the treated wood in a resin solution containing a hydrophobic polymerizable monomer alone or a hydrophobic polymerizable prepolymer as the main component, or applying this resin solution to the treated wood and then rinsing it. These operations can be carried out under reduced pressure, increased pressure, or reduced pressure.

Hydrophobic polymerizable monomers used in this step include styrene monomer, methacrylate, styrene oxide, epichlorohydrin, divinylbenzene, and the like.

Examples of the polymerizable prepolymer include vinyl polymerized acrylates, melamine polymerized acrylic prepolymers, unsaturated polyester prepolymers, acrylic urethane prepolymers, and epoxy prepolymers.

A reaction initiator, plasticizer, colorant, and/or flame retardant may be added to the resin liquid as appropriate.

The treated wood impregnated with resin liquid by the method described in 2 above is subjected to the next curing process. This process requires wood from 80 to 25
It consists of heating under pressure at 0°C, or wrapping the resin liquid to prevent it from scattering, and heating under pressure. Through this treatment, the hydrophobic polymerizable monomers and polymerizable prepolymers that have penetrated into the microscopic voids in the wood polymerize with each other, or, depending on the type of resin, form a graft polymer with wood components.

Through the above series of operations, modified wood with significantly improved not only dimensional stability and stain resistance, but also desirable properties as a structural material and surface material, such as water resistance, rot resistance, strength, and hardness, is produced. Obtainable.

Example 1 A hemlock veneer with a thickness of 0 or 6 am was immersed in acetic anhydride at 130°C containing 5% by weight of sodium acetate for 10 minutes, and an acetylated monoboard with a weight increase rate (absolute dry weight ratio) of 20% was immersed. Got the board. A solution prepared by adding a small amount of a polymerization initiator (benzoyl peroxide) to a mixed solution of oligoester acrylate methyl methacrylate = 50:50 was injected into this acedelized veneer under reduced pressure. 3 at 130℃ after injection.
It was cured under heat and pressure for 0 minutes to obtain a modified veneer (A).

Example 2 A modified veneer (I3) was obtained in the same manner as in Example 1, except that general-purpose saturated polynisdel styrene-5050 was used instead of oligoester acrylate.

Example 3 A modified veneer (C) was obtained in the same manner as in Example 2, except that methacrylate was used alone instead of the polymerizable prepolymer.

The elongation rate of the acedelized veneer, which is the intermediate material of Example 1, was immersed in various solvents at room temperature for 24 hours and compared with that of the untreated veneer. The results are shown in Table 1 below.

Table 1 *Elongation rate (%) - x l (Length before immersion) The results in Table 1 show that the acedelized veneer, which is the intermediate material of the present invention, swells due to the penetration of the solvent into the cell wall. Or,
It resists swelling due to water intrusion, indicating a change in affinity.

Test Example 2 Modified veneers (A), (B) and (
C), untreated veneer (D), and veneers (E), (F), and (G) treated in the following manner were immersed in water in the same manner as in Test Example 1, and their elongation rates were compared. did.

The results are shown in Table 2.

Table 2 *(E) A veneer subjected only to acetylation treatment according to Example 1.

*(F) A veneer subjected to only resin liquid impregnation treatment according to Example 2.

*(G) A veneer subjected to only resin liquid impregnation treatment according to Example 3.

Table 2 shows that the 1J method stability of the modified veneer according to the present invention is far superior to that of the modified veneer treated by a method corresponding to the conventional method.

Test Example 3 The cross sections of the modified veneer (C) treated with the present invention and the veneer (G) treated with the method described above were photographed with a 400x magnification microscope, and the results are shown in Figures 1 and 3. Shown in Figure 2.

As a result of comparing Figures 1 and 2, it was found that the interface between the inner wall surface of the cell wall of the modified veneer (C) (Figure 1) and the filling resin was
) (Figure 2) because it is relatively less clear than that of
It can be seen that the modified veneer (C) has improved resin penetration into microscopic voids and adhesion to the inner cell walls.

[Brief explanation of drawings]

FIG. 1 is a photomicrograph showing the cross-sectional structure of a modified veneer according to the present invention, and FIG. 2 is a photomicrograph showing the cross-sectional structure of a conventional veneer. 1111th class-

Claims (1)

[Claims] 1. A modified wood characterized in that only the cellulose amorphous region of the thin wood board is acedelized, and the wood voids containing the amorphous region are filled and cured with a hydrophobic synthetic resin.