JP2000154500A - Woody board and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a woody board excellent in mechanical strength and to provide a method for producing the woody board with a good operating efficiency. SOLUTION: This woody board is produced by binding 100 pts.wt. of a woody raw material with 0.1-20 pts.wt. of a binder. A binder comprising 99.9-50 wt.% of a polyvinyl alcohol-based resin powder containing >=70 wt.% of particles having <=500 μm particle diameter and 0.1-50 wt.% of a gelling agent is used as the binder.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wooden board widely used as a building material for flooring, tatami flooring, wall materials, ceiling finishing and the like, and a method for producing the same.

[0002]

2. Description of the Related Art A wood board is obtained by adding starch and its derivative or polyvinyl alcohol (hereinafter abbreviated as PVA) resin as a binder to a fibrous material obtained by opening wood such as waste wood. It is manufactured by extruding a woody slurry by an extrusion molding method or a papermaking molding method and then drying it. These molded articles are widely used as building materials such as flooring materials, tatami flooring materials, wall materials, ceiling finishing materials and the like.

[0003] Among the binders used in the production of the above-mentioned wood-based boards, starch and derivatives thereof must be heated in water to form a dispersion beforehand in order to exert the binder power. Some drawbacks are that they are inferior in workability because they are easily rotted, and the obtained wood board also has drawbacks such as insufficient water resistance and easy decay.

[0004] In order to improve these drawbacks, a method has been used in which a PVA-based resin powder which hardly dissolves substantially in a wood slurry (for example, completely saponified unmodified PVA powder) is used as a binder. The PVA-based resin does not need to be gelatinized in advance, and is dispersed in a wood slurry as PVA particles as it is, and after being formed by papermaking or the like,
It is melted by applying heat in the drying step, and a binder effect can be obtained. Further, since the PVA-based resin hardly rots, there is an advantage that workability is good and productivity is improved. Furthermore, the obtained wood board is superior to that using starch in terms of water resistance, decay and the like. However, since the particle size is larger than starch, dispersibility cannot be said to be sufficient, and the PVA-based resin dissolved in the drying step is easily absorbed by wood-based raw materials such as wood-based fibers, and the surface yield is poor. There is a tendency that the binder power is not sufficiently exerted. Therefore, the amount of addition must be increased, and the cost-performance ratio of the binder is inferior to starch. Therefore, there is a need for a method of inexpensively producing a small amount of a wooden board having higher mechanical strength.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide a wooden board having a higher mechanical strength than a conventional board and a method for manufacturing the same by a simple operation.

[0006]

According to the present invention, there is provided the present invention, in which 100 parts by weight of a wood-based raw material is PVA having a particle size of 500 μm or less and a weight ratio of 70% or more.
99.9-50% by weight of a base resin powder and 0.1-5% of a gelling agent
The weight ratio of the wood-based board and the wood-based raw material being 100 parts by weight combined with 0.1 to 20 parts by weight of a binder consisting of 0% by weight is 70% or more with a particle diameter of 500 μm or less. PVA-based resin powder 99.9-5
0.1 to 20 parts by weight of a binder comprising 0% by weight and 0.1 to 50% by weight of a gelling agent is mixed with water to form a woody slurry, and the obtained slurry is formed, dewatered and dried. A method for producing a wooden board, characterized in that:

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below. The wood-based raw material used in the present invention is a wood-based fiber such as wood pulp obtained by opening waste materials and the like, waste paper pulp and the like, and a wood-based material such as wood-based flake. Pulps such as pulp and synthetic pulp are preferred. Further, synthetic fibers such as vinylon and polyamide fibers, and inorganic fibers such as glass fibers and carbon fibers may be added as necessary.

[0008] PV used as a binder in the present invention
The A-based resin powder has a content of fine powder having a particle diameter of 500 μm or less of 70% or more, preferably 80% or less.
More preferably, it is 90% or more. The particle size can be sufficiently uniformly dispersed in the wood slurry within the above range, which leads to improvement in the strength of the wood board.

The PVA resin powder does not dissolve in the woody slurry, absorbs the water contained in the slurry, swells, and reacts with the gelling agent to form water-absorbing gel granules. It is desirable that it can be present in the inside or in the molded product, but any water-soluble one may be used as long as it forms water-absorbing gel particles as described above by reaction with the gelling agent. It may be any of unmodified ordinary PVA and modified PVA. Modified PVA
Examples of PVA are PVA obtained by copolymerizing α-olefins such as ethylene and propylene, PVA obtained by copolymerizing unsaturated carboxylic acids such as itaconic acid and maleic acid, and ion-modified by introducing a sulfate group or a phosphate group. Examples thereof include PVA, PVA into which an acetoacetyl group or a silyl group is introduced, and the like. These PVA-based resin powders may be used alone or in combination of two or more. Also, PVA
The degree of polymerization of the base resin powder is not particularly limited, but is preferably 500 or more. When the PVA-based resin of 500 or more is used, the strength of the obtained molded product can be further increased. The saponification degree of the PVA-based resin powder is also not particularly limited, but is preferably at least 80 mol%, more preferably at least 90 mol%, even more preferably at least 95 mol%.

In the present invention, the gelling agent used as a binder together with the PVA-based resin powder is to form the PVA-based resin powder into the form of a water-absorbing gel, to suppress dissolution in the woody slurry and to absorb water by heating and drying. By making the gel particles less likely to be absorbed by wood-based raw materials such as wood-based fibers at the time of dissolution, the surface yield is improved, the binder power is sufficiently exhibited, and the strength of the wood-based board is improved. Examples of the gelling agent include boric acid, borax, ammonium borate, various divalent and trivalent iron salts, lead salts, zirconium salts, aluminum salts, chromates and the like. Among these, boric acid and borax are particularly preferred. One of these gelling agents may be used, or two or more thereof may be used in combination if they do not adversely affect each other.

The mixing ratio of the PVA-based resin powder and the gelling agent in the binder is from 99.9 / 0.1 when the ratio is expressed as PVA-based resin (parts by weight) / gelling agent (parts by weight).
50/50, preferably 99/1 to 60 /
40. If the gelling agent is less than 0.1 parts by weight, PVA
The surface yield of the resin is low, and it is difficult to improve the strength of the wooden board. On the other hand, when the amount of the gelling agent exceeds 50 parts by weight, the solubility of the binder when heated in the drying step is reduced, and the effect of improving the strength of the wooden board is reduced.

The amount of the PVA resin and the binder of the gelling agent blended in the above ratio is 0.1 to 20 parts by weight, preferably 0.5 to 20 parts by weight, based on 100 parts by weight of the woody raw material.
１５15 parts by weight. If the amount of the binder is less than 0.1 part by weight, it is difficult to improve the strength of the wood board,
If the amount is more than 0 parts by weight, the amount of the binder becomes too large, so that the binder emerges on the surface of the obtained wooden board, which may cause problems such as poor releasability during drying and poor appearance. is there.

[0013] In addition, in the preparation of woody slurry, P
The method of adding the VA-based resin and the gelling agent may be any of various methods, for example, a method of mixing the PVA-based resin and the gelling agent in advance and then adding the mixture to a slurry composed of a wood-based material and water, and the like. A method of mixing a resin, a gelling agent, and a wood-based raw material into a wood slurry with water after mixing,
A method in which a PVA-based resin and a gelling agent are separately added to a slurry composed of a wood-based raw material and water is used. Other components may be added as needed.

The solid content of the woody slurry can be of various concentrations, but is generally preferably 1 to 90% by weight. The mixing method for preparing the woody slurry can be mixed by various methods, for example, by using a mixer type mixer, a screw type kneader, a Peller type kneader or the like. As the mixing conditions at this time, it is desirable to employ conditions that do not dissolve the PVA-based resin powder and form water-absorbing gel particles. For example, it is desirable to adjust the temperature of the slurry to 80 ° C. or lower, preferably 50 ° C. or lower.

The shaping method for shaping the wood slurry prepared by the above method is not particularly limited, and examples thereof include a mold forming method, an extrusion forming method, and a paper forming method.

In this way, the molded product containing the binder particles dispersed therein is heated and dried, and at the same time, the binder in the form of the water-absorbing gel is dissolved to finally produce a uniform wooden board. As the heat drying method at that time, various known heat drying methods can be adopted. This heat drying is preferably performed at 100 to 180 ° C. for 30 minutes to 2 hours.

The wooden board obtained as described above has a higher mechanical strength than conventional boards, and
It can be effectively used for building materials such as tatami flooring, wall materials, and ceiling finishing.

[0018]

The present invention will be described more specifically with reference to the following examples. Incidentally, the density of the obtained molded product in the following examples,
The bending strength was determined as follows. (1). Density: Determined as the value of the weight / volume of the test piece according to JIS A5905 "Density test". (2). Bending strength: According to JIS A5905 "Bending strength test", span length 150 mm, average deformation speed 10 mm
/ Min.

Example 1 PVA resin powder [Type A shown in Table 1: Degree of polymerization 170
0, saponification degree 98.5 mol%, 30 mesh (500 μ
m) Pass product] 90 parts by weight of a binder obtained by mixing 90 parts by weight of borax, 90 parts by weight of wood pulp, and 10 parts by weight of waste paper pulp are mixed together, and then water is added to give a solid content concentration of 5 parts by weight. % Slurry was prepared. The slurry was poured into a mold provided with a 5-mesh wire mesh, and then dewatered by press so that the solid content concentration was 70 to 80% by weight, to produce a 10 mm thick plate. The plate was dried in a blow drying at 150 ° C. for 60 minutes. A test piece was taken from the obtained plate material, and its density and bending strength were determined by the methods described above. As shown in Table 2, the results were excellent.

Example 2 PVA resin powder [Type B shown in Table 1: Degree of polymerization 170]
0, saponification degree 98.5 mol%, 30 mesh (500 μ
m) 80% by weight of the amount passed through a sieve] 1.9 parts, 90 parts by weight of wood pulp and 10 parts by weight of waste paper pulp are mixed together,
Water was added to form a slurry having a solid content of 20% by weight.
After adding 0.1 parts by weight of borax to this slurry and stirring, water was further added to prepare a slurry having a solid content of 10% by weight. This slurry was poured into a mold provided with a 5-mesh wire net, and then dewatered by press so that the solid content concentration was 70 to 80% by weight, to produce a 10 mm thick plate. This plate was dried in a blow dryer at 150 ° C. for 60 minutes. A test piece was taken from the obtained plate material, and its density and bending strength were determined by the methods described above. As shown in Table 2, the results were excellent.

Examples 3 to 8 Except that the PVA-based resin and the gelling agent used were changed to those shown in Tables 1 and 2, molding was carried out in the same manner as in Example 1, and a test piece was obtained from the obtained plate material. And its density and bending strength were determined by the methods described above. As shown in Table 2, the results were excellent.

Comparative Examples 1-4 Molding was carried out in the same manner as in Example 1 except that the PVA resin and the gelling agent were changed to those shown in Tables 1 and 2, and a test piece was taken from the obtained plate material. Then, the density and the bending strength were determined by the methods described above. As a result, as shown in Table 2, the bending strength was remarkably inferior.

Comparative Example 5 Molding was carried out in the same manner as in Example 1 except that the PVA resin and the gelling agent were changed to those shown in Tables 1 and 2, but the binder emerged on the surface of the plate after drying. As a result, the film was formed and irregularities occurred. The measurement was not performed because it is not suitable as a wooden board.

[0024]

[Table 1]

[0025]

[Table 2]

Comparative Example 6 90 parts by weight of wood pulp and 10 parts by weight of waste paper pulp were mixed with 10 parts by weight of corn starch previously heated and gelatinized at 80 ° C., and water was added to the mixture to add 5 parts by weight of solids. % Slurry was prepared. This slurry was molded in the same manner as in Example 1, and a test piece was taken from the obtained plate material.
The density and bending strength were determined by the methods described above. As a result, as shown in Table 3, the bending strength was remarkably inferior.

Comparative Example 7 Molding was performed in the same manner as in Example 1 except that 90 parts by weight of wood pulp and 10 parts by weight of waste paper pulp were used without using a binder.
A test piece was taken from the obtained plate material, and its density and bending strength were determined by the methods described above. As a result, as shown in Table 3, the bending strength was remarkably inferior.

[0028]

[Table 3]

[0029]

According to the present invention, it is possible to extremely easily obtain a wood-based board having excellent mechanical strength as compared with a conventional board, and it is industrially very useful.

Claims (2)

[Claims] 1. 100 parts by weight of a wood-based raw material has a particle size of 50
0.1 to 20% by weight of a binder comprising 99.9 to 50% by weight of a polyvinyl alcohol-based resin powder having a weight ratio of 0% or less of 70% or more and 0.1 to 50% by weight of a gelling agent.
A wooden board characterized by being joined by weight. 2. 100 parts by weight of a wood-based raw material and a particle size of 50
0.1 to 20% by weight of a binder comprising 99.9 to 50% by weight of a polyvinyl alcohol-based resin powder having a weight ratio of 0% or less of 70% or more and 0.1 to 50% by weight of a gelling agent.
A method for producing a wood-based board, comprising mixing a water-based part with water to form a wood-based slurry, shaping the obtained wood-based slurry, dehydrating, and drying by heating.