JPH0427926B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention is a method for removing internal residual stress in resin plates, sheets, or films containing cellulosic differential aggregates such as wood flour, rice husk flour, or bakasu flour. In order to ensure reliable lamination and integration on the plywood surface, we provide flooring or wall materials that do not warp or distort.

[Prior art and its problems] Recently, with the shortage of high-quality natural wood, improvements have been made to plywood and other synthetic or laminated building materials.
It has come to be used in many different fields.

Such building materials are usually provided by pasting together miscellaneous trees or wood with poor grain, or by compressing plywood or crushed wood waste, but they have a poor appearance compared to building materials made of natural wood. It was extremely inferior, and also had many disadvantages in terms of water resistance and durability.

In particular, creating a living space with a wood-like appearance based on the characteristics of building materials is important not only in terms of harmony with the house structure or furniture, but also in terms of creating a comfortable and calm living space. By printing a wood grain pattern on the surface of the above-mentioned plywood or compressed board, or pasting a vinyl chloride film printed with a wood grain pattern, a product whose appearance resembles a natural board material is provided. It's coming to an end.

On the other hand, resin moldings as building materials have also been used in a wide variety of fields, and their advantages as resin molding materials have been effectively utilized, but in general, synthetic resin moldings are limited by the materials used. Due to the relationship between molding conditions and molding conditions, variations in the composition of the molded product, such as density and density, and residual internal stress occur depending on the molding conditions during molding.The problem of such residual internal stress can be solved by cooling after molding. Problems such as warping and twisting of the molded product occur due to shrinkage, shrinkage over time, or expansion and contraction due to temperature changes.

As a means of preventing warpage, twisting, etc. in such molded products, attempts have been made to mix various aggregates into resin molded products, and it has been found that this can produce considerable effects depending on the purpose of use. It is something.

However, if the resin molded product is a board or the like, it is difficult to completely correct the distortion of the molded product even if such aggregate is mixed in, and the molded product often warps, twists, etc. This caused the problem.

In addition, conventional plywood or compressed boards have disadvantages such as poor durability and water resistance, corrode within a relatively short period of time, and they imitate the grain of natural wood. It was clear and gave the building itself an image of being cheap.

Furthermore, if a large amount of cellulose aggregate is mixed into a resin molded product, this mixed aggregate will extremely inhibit the fluidity of the molded resin, resulting in higher than expected internal stress in the molded resin product. This is what was left behind.

If such internal residual stress is left as is,
Molded products are distorted in the direction of the stress, causing many inconveniences in use.

Such residual internal stress is caused by the inhibition of the fluidity of the molding resin due to the mixing of cellulose aggregate, which causes pulsations in the molding resin, and the fact that the direction of the residual stress is not necessarily constant. This is causing inconvenience.

In addition, the problem of residual internal stress becomes even more apparent when a resin molded product is subjected to secondary processing, and when the resin molded product is reprocessed by hot pressing, etc. This caused more warping and twisting than expected.

[Means for Solving the Problems] The present invention removes residual stress in a resin molded plate having a particularly large amount of cellulose aggregate in such a resin molded product, and allows the resin molded product to be used as is or further reprocessed. In order to prevent distortion of the molded plate when it is used, a thermoplastic molded plate containing fine cellulose aggregate is heat-cured under specified conditions, and the resin hardened layer portion on the surface of the heat-cured resin molded plate is Decorative plywood is provided by attaching and bonding a wood resin molded board, which has been sanded to remove internal stress and has a decorative surface, on a suitable plywood.

As a result, the resin molded board laminated on the plywood surface is semi-permanently bonded in close contact with the plywood surface, which partially prevents warping and distortion, and guarantees a good wood-like appearance. It is.

[Example] Hereinafter, a typical example of the present invention will be described with reference to the accompanying drawings.

First of all, the aggregate a mixed in the prerequisite molding of wood composite materials is cellulose-based materials such as wood chips, pulp, bakasu, or rice husks with an air-dried moisture content within 7 wt% (preferably within 7 wt%). After measuring the weakening of the structure of the material, a urea-based resin solution is applied and impregnated into this structure and heated to 100 to 200℃.
Heating, drying, and crushing are performed within a temperature range of .

Due to the impregnation, impregnation, hardening and crushing of the urea-based resin liquid, each aggregate a has a portion of hardened urea-based resin material, which eliminates the disadvantage of re-absorption of moisture in the cellulosic material. In addition to preventing gas evaporation, the aggregate (a) is provided with appropriate lubricity.

In addition, such treatment of aggregate a is carried out by mixing cellulose aggregate a into the resin material during resin molding,
This is done in consideration of the fact that when hot molding is performed, a larger amount of wood acid gas and water vapor are generated than the mixed aggregate a, and that this wood acid gas and water vapor have various adverse effects on the molding machine and the product. In particular, the generated wood acid gas and water vapor cause inconveniences such as corrosion and damage to the cylinder, cylinder die, cylinder screw, etc. of the molding machine, and also cause bubbles and roughness on the surface of the product.

In addition, since the mixed aggregate has been pre-cured with a urea-based resin liquid, it is said that the mixed aggregate has good lubricity and mixes well with the resin material. Not only that, but also there is little frictional resistance with the molding surface of the molding machine during molding, making it possible to perform good extrusion or injection.

The aggregate a thus provided is basically 100
It is made into a fine powder with a mesh size of 80 mesh below the sieve to 200 mesh above the sieve, and the moisture content is within 5 wt%, preferably within 3 wt%. As,
Vinyl chloride resin, ABS resin, vinyl acetate resin,
20 for thermoplastic resin materials such as polycarbonate resin
It is mixed in a range of ~80wt% and is molded with a customary resin.

The plate-shaped, sheet-shaped or film-shaped resin molded plate A formed by any method such as extrusion or roll forming is heated at 60 to 130°C.
After being heated for 24 hours within a temperature range of
It has been subjected to

Such heat treatment conditions are such that the heating conditions are set at a high temperature and the time cannot be shortened, and in the case of the wood composite material containing 20 to 80 wt% of aggregate a in this invention, the heating condition is set at a high temperature at 70 ° C / 24 hours. This is considered optimal.

Such heat treatment is usually a method that tends to leave internal stress.
In particular, it is a product that is forced to shrink in the extrusion direction during molding, and under the above conditions, the length of 200cm
A shrinkage of about 20 cm was caused in the board material in the longitudinal direction of the board material (the shrinkage in the width direction is extremely small).

Such quenching of the resin is to bring out in advance distortions caused by the residual stress existing inside the wood composite material A, the density of the structure, etc.

In this way, the x equivalent of the surface skin layer of the wood composite board A is sanded to minimize shrinkage distortion and prevent the wood composite board from warping or twisting due to subsequent resin molding or shrinkage over time. The y portion, which is located inside the skin layer and appears to have relatively no residual internal stress, is directly exposed as the surface.

The removal of the surface x portion is intended to remove the portion where the resin material b is dense, as is clear from the illustrated example. In other words, in resin molding with aggregate a mixed in, the presence of the aggregate causes resin material b to ooze out onto the surface of the molded product, creating a skin layer, and the tissue density of the resin material in this surface region is extremely high.

In addition, the surface skin layer, which is the dense part of the resin material b, absorbs internal stress caused by the difference between the density and the flow direction due to the pulsation of the resin molding material during molding, and the direction perpendicular to the flow. This is the part that was specifically chosen to remain.

Therefore, sanding and cutting of this surface x portion has particular meaning, and this surface x
When the part is removed, the internal residual stresses have been largely eliminated.

In addition, in this sanding process, scratches g are provided on the surface of the wood composite board A to be sanded, and these scratches g are in one direction of the essential composite board A, specifically, in the wood grain pattern provided later. They are aligned in the direction of the wood grain. That scratch
Specifically, the sanding was performed by roll sanding, and sanding blades were protruded randomly on the circumferential surface of the sanding roll, resulting in countless scratches on the surface of the wood composite board A. The scratches are randomly placed in one direction, and the scratches have different sizes and depths. In addition, when this scratch g is created by a sanding roll, only the interval where the roll is in contact is scraped, so each scratch g is relatively short, and moreover, it The shape of the scratch is shallow at the end and deep at the center, and the surface shape is closer to the grain of the wood, and the internal stress remaining in the part can be released depending on the depth of the scratch. It is something.

By applying a wood grain pattern embossing using a press or a roll machine to a wood composite board that has been heat treated in the above process and also has been subjected to a sanding process that has scratches on the surface of the molded board (on one or both sides), The wood grain pattern created by the press or roll machine is accurately molded onto the surface of the composite board, and the molded wood grain pattern is completely prevented from sagging or blurring after the molding. be.

As a result, when the wood grain pattern of a press or roll machine is set to a normal natural board shape, the formed composite board also has the appearance of a board made of natural wood, and this board material The appearance is maintained semi-permanently.

The wood grain pattern thus provided is the same as the scratch g
Through this molding, the surface of the composite board A was created with a grain pattern almost identical to that of natural wood, and its appearance was said to be particularly good.

After such molding, using customary painting means,
The surface of this molded synthetic material was colored and adhered to the plywood surface B for use, but when molding the synthetic material, appropriate pigments were mixed into the resin material used, The composite board itself has a certain color and can be used as is by adhering it to the B side of the plywood.

[Effects of the Invention] In the decorative plywood in which the wood composite boards having a wood grain pattern according to the present invention are laminated, the following specific effects were achieved based on the characteristic structure described above. That is, in this invention, (1) The wear resistance is better than the usual hard PVC surface material as follows, and it is most suitable as a wall surface or a walking surface, especially as a floor material that is subject to severe wear. It is.

Amount of wear in this case (on the decorative surface of PVC plywood): 35.9 / Amount of wear on normal PVC: 46.6 (However, load 1Kg, rotation speed 70rpm, wear wheel CS-17 calibrase)
mg/1000 rotations) (2) It is water resistant and has moderate moisture absorption, absorbs sweat from the skin when it comes in contact with it, provides a good adhesion to the skin such as the soles of the feet, and has a soft texture. Brought.

Water absorption rate of this case 0.44/Water absorption rate of regular PVC 0.09
(However, 25℃ according to JIS K7209 water absorption test method,
(Water absorption rate per unit area in 24 hours) (3) The wood grain pattern on the decorative surface is created precisely by creating scratches (g) in advance, so that the wood grain is almost indistinguishable from the natural wood grain. The wood grain that has been made and shaped will not sag or fade naturally over a long period of time, giving it a natural wood-like texture.

That is, the surface skin layer of the decorative composite board on which the wood grain pattern is imprinted is removed by sanding;
By exposing the aggregate a part, the residual internal stress of the skin layer is removed, and at the same time it is possible to mold the surface with less resin material b, allowing for precise molding and the resin material after molding. This method eliminates the unwinding of the wood and leaves the wood grain exactly as it was patterned on the patterned surface. In addition, the skin layer portion formed by the resin material b exuding on the surface of the decorative composite board to be molded has a dense structure and is hard, making it unsuitable for precise molding. However, by removing this, precise molding became possible.

(4) The molded wood grain pattern was made into a wood grain pattern with a more natural texture by sanding the skin layer and providing scratches on the sanded surface. That is, as the skin layer is sanded, cellulose aggregates such as wood flour a
is exposed on the surface, resulting in a texture and texture with scratches similar to natural wood, and by molding the wood grain onto this, a decorative composite board that almost looks like natural wood was created.

(5) The texture of the surface of the sanded and molded decorative composite board is close to that of natural wood due to surface scratches and exposure of the molded surface and mixed aggregate, with moderate frictional resistance and slight It has a moisture absorption function (to the extent that it does not make you sweat), and has a function as a substitute for wood, as well as ensuring excellent rot resistance and water resistance.

(6) Similarly, the paint treatment on the surface of the decorative composite board that has been sanded and molded is done reliably by the paint particles adhering to the aggregate surface exposed on the sanded surface, and the paint sag is prevented. This makes it possible to create precise painted surfaces without any peeling or peeling.

(7) Heat treatment (quenching) and sanding of the skin layer of the molded composite board will reduce distortion due to structural changes over time in the composite board (accompanied by chemical changes in the molded resin material) or thermal damage to the composite board. Distortion caused by changes is reliably prevented, eliminating any inconveniences such as warping and twisting in composite boards.

(8) Adhesion of wood composite board A to plywood B is ensured due to the presence of exposed aggregate a, and since there is no distortion in wood composite board A, there is no strain on the adhesive surface and continuous good adhesion is achieved. was retained.

This invention eliminates the internal stress in the wood composite board A laminated on plywood B as described above, and provides a decorative plywood having a good decorative surface.

[Brief explanation of drawings]

Figure 1 is an enlarged cut-away end view of the decorative composite board before sanding the surface x portion, which is the skin layer.
The figure is an enlarged cut end view after the same sanding process, FIG. 3 is an enlarged cut sectional view of the same cut in a different direction, and FIG. 4 is a perspective view of the plywood having a patterned decorative composite board. In addition, in the figure A...synthetic material, B...plywood, a...aggregate, b
...resin material, g...indicates scratches.

Claims (1)

[Scope of Claims] 1 A thermoplastic molded plate having a cellulose-based fine aggregate is heat-cured under predetermined conditions, and the hardened resin layer portion on the surface of the heat-cured resin molded plate is sanded to remove internal stress. 1. A method for forming decorative plywood, characterized in that a wood resin molded board having a decorative surface is attached and adhered to a suitable plywood. 2. The method for forming decorative plywood according to claim 1, wherein the decorative surface is a patterned surface with a wood grain pattern. 3. The method for forming decorative plywood according to claim 1, wherein the heat curing is performed at 60 to 130°C for 24 hours. 4. The method for forming decorative plywood according to claim 1, wherein the aggregate has a moisture content of 80 mesh below to 200 mesh sieve and within 3 wt%.