JPH1192738A - Adhesive composition for wpc - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a water-based adhesive which can cope with the range of the water content of a ply wood base and can prevent the surface of a product from forming cracks by mixing an amino resin with an aqueous resin emulsion, a dissolving agent and a hiding agent in a specified compositional ratio. SOLUTION: The amino resin (A) is a cocondensate of a formaldehyde with an amino compound (e.g. urea) and has a degree of conversion of formaldehyde groups into methylol groups of 10-60% and a degree of conversion into ethylene ether bonds of 2-30%. The aqueous resin emulsion (B) has a particle diameter of the disperse phase of 0.01-5 μm and is exemplified by a vinyl acetate resin emulsion. The dissolving agent (C) used is exemplified by a ketone resin precondensate such as an acetone/formaldehyde resin or an acetone/urea formaldehyde resin. The hiding agent (D) is exemplified by a coloring pigment, especially desirably titanium dioxide. The mixing ratio among components A, B, C and D is 100 pts.wt./(10-500 pts.wt.)/(5-50 pts.wt.)/(10-150 pts.wt.).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to bonding of a veneer, and more particularly, to a water-based adhesive for using WPC as a veneer.

[0002]

2. Description of the Related Art WPC (Wood Plastic C)
Generally, a composite of wood and plastic is obtained by injecting a plastic monomer or oligomer into voids or cell walls in wood and polymerizing the wood. When such a WPC is used for a veneer bonded plywood, a method of bonding a veneer impregnated with a monomer such as styrene, methyl methacrylate, or unsaturated polyester to a base plate plywood via an adhesive is usually used.

Conventionally, a solvent-type polyester resin has been used as an adhesive. However, since the solvent is dissipated, the working environment is degraded, which is not preferable from the viewpoint of occupational hygiene. Due to poor adhesion such as blisters immediately after hot pressing, the width of the manufacturing process was narrow and process control was difficult.
In recent years, aqueous vinyl urethane has begun to be used as an aqueous adhesive, but the workable time is short, and if the deposition time after the adhesive is applied is long, poor adhesion occurs, so the width of the manufacturing process is narrow and process management is difficult. In addition, there are many problems such as toxicity of isocyanate.

[0004] Further, in a decorative laminated plywood in which a veneer veneer is bonded to a base plywood, a method of adding a glycol such as polyethylene glycol or an aqueous epoxy compound to an adhesive is known as a measure for preventing cracks on the surface. ing.
In this method, when the material to be bonded to the base plate is a veneer veneer, there is a certain effect in terms of suppression of crack generation. However, as in the present invention, when the WPC is bonded, the adhesion to the plastic portion is reduced. Slightly difficult, crack prevention,
There was a drawback that sufficient effects could not be exhibited in both adhesiveness. Therefore, there is a need for a water-based adhesive having no problem in the bonding process.

[0005]

DISCLOSURE OF THE INVENTION The present invention solves the above-mentioned problems when using WPC for veneer laminated plywood, prevents the occurrence of cracks on the product surface corresponding to the width of the water content of the plywood. It is intended to provide a water-based adhesive to be obtained.

[0006]

Means for Solving the Problems The present inventors have made intensive studies to overcome this problem and as a result, have found that an adhesive composition comprising an aqueous resin emulsion, a dissolving agent and a concealing agent mixed with an amino resin is obtained. When used in the manufacture of decorative plywood with WPC as veneer, it does not cause poor adhesion even to a high moisture content base plate.
The inventors have found that the occurrence of cracks on the product surface is drastically reduced, and have completed the present invention. That is, the present invention provides an aqueous resin emulsion 10 to 5 parts by weight based on 100 parts by weight of an amino resin.
00 parts by weight, dissolving agent 5 to 50 parts by weight, concealing agent 10 to 15
It is a WPC adhesive composition containing 0 parts by weight.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION In bonding a veneer, an adhesive force,
Amino resins have been used in the past in terms of water resistance, but amino resins form a three-dimensional network after curing, so they are tough, but cannot follow shrinkage of the veneer, and cracks frequently on the surface Will be. For this reason, an aqueous emulsion is used in combination for the purpose of suppressing the occurrence of cracks and preventing glue staining. However, in the case of veneer bonding using WPC, since a polymerizable monomer or oligomer is impregnated in the veneer, unlike when bonding an unimpregnated veneer alone, the adhesive has poor wettability,
Interfacial peeling is likely to occur.

The present inventors have found that in order to solve this problem, it is necessary to interpose a substance that improves the affinity (affinity) between these hydrophobic substances and the aqueous adhesive. That is, the dissolving agent in the present invention is a substance having a solvent effect and / or a plasticizing effect and having an action of increasing the adhesion by the interaction between the hydrophobic substance and the aqueous adhesive. The solubilizer used in the present invention includes a ketone resin initial condensate such as acetone / formaldehyde resin, acetone / urea / formaldehyde resin, acetone / melamine / formaldehyde resin, and Solfit (3-
Methyl-3-methoxy-1-butanol), methyl cellosolve (2-methoxyethanol), ethyl cellosolve (2-ethoxyethanol), acetone, methanol,
There are solvents such as benzene, toluene, and xylene, which can be used alone or in combination of two or more.
Among them, an acetone resin is most preferred.

Examples of the concealing agent include inorganic or organic coloring pigments. Titanium dioxide is particularly preferred. Particularly, in the adhesive for WPC of the present invention, a rutile type adhesive is suitable for choking. It is practically preferable because it does not occur.

The composition ratio of the essential components constituting the WPC adhesive composition in the present invention is such that 10 to 500 parts by weight of an aqueous resin emulsion, 5 to 50 parts by weight of a dissolving agent, and 100 parts by weight of an amino resin. Although the proportion of the concealing agent is 10 to 150 parts by weight, preferably, 100 to 300 parts by weight of the aqueous resin emulsion is added to 100 parts by weight of the amino resin.
10 to 30 parts by weight of a dissolving agent and 10 to 50 parts by weight of a masking agent. If the composition ratio deviates from this range, problems such as poor curing of the adhesive, exudation of the adhesive, and exposure of the background of the plywood of the base plate may occur.

The present invention also relates to a copolycondensate of a formaldehyde and an amino compound and a modified resin thereof, wherein the degree of conversion of methylol group in all formaldehyde is 10 to 60% and the degree of conversion of dimethylene ether bond is 10 to 60%. Is 2
-30%. Methylol group conversion is 10 to 60% and dimethylene ether bond conversion is 2
The reason for limiting the range of the functional group to ~ 30% is that the resin having various functional group compositions is synthesized to prepare an adhesive composition, veneer veneer plywood is prepared, and the performance test is repeated. By choice. Probably, when an amino-based resin having a functional group composition in this range is used as a matrix constituting an adhesive for a WPC veneer decorative plywood, the curing speed of the aqueous emulsion and the dissolving agent is appropriately balanced, and flexibility is improved. It is presumed that a rich network can be constructed. Each of these functional group compositions was measured using ¹³ C-NMR. The measurement conditions and the analysis of the obtained signals are described in [Jour
nal of Polymer Science: Po
lymer Chemistry Edition V
ol. 17, 3205-3215 page (197
9)].

Further, the present invention is characterized in that the particle size of the aqueous resin emulsion is 0.01 to 5 μm. When the particle size is 0.01 μm or less, the viscosity after mixing with the amino resin or the dissolving agent changes over time, and the water resistance decreases. When it is 5 μm or more, there is no problem in terms of performance, but the polymerization reaction time is prolonged and productivity is lowered, so that it is not practically preferable.

The amino resin used in the present invention includes a condensation resin of one or more amino compounds such as urea, melamine, guanamine and the like with formaldehyde, or these resins are phenols, resorcinols, Modified resins modified with polyvinyl alcohol, furfuryl alcohol and the like can be mentioned.

The aqueous resin emulsion used in the present invention includes emulsions such as vinyl acetate resin emulsion, ethylene / vinyl acetate copolymer resin emulsion, acrylic resin emulsion, ethylene / acrylic acid copolymer resin emulsion, chloroprene latex, polyacrylic There are latexes such as an ester latex, a polyvinylidene chloride latex, and a styrene / butadiene latex, and these can be used alone or in combination of two or more.

Since the adhesive composition of the present invention is a self-crosslinking type, it is not particularly necessary to add a curing agent. However, in order not to impair the effect of the present invention, ammonium chloride, Inorganic salts such as ammonium sulfate, inorganic acids such as sulfuric acid and hydrochloric acid, and organic acids such as malic acid and oxalic acid can be used in combination. If necessary, a bulking agent such as wheat flour, barley flour, coconut shell flour, corn gluten, starch, soybean meal, rapeseed meal, calcium carbonate, clay, and the like, which are commonly used for bonding wood, may be used in combination. Further, the adhesive composition of the present invention has been conventionally used for crack prevention, such as polyethylene glycol, polypropylene glycol, glycols such as polyethylene glycol methacrylate, ethylene glycol diglycidyl ether, propylene glycol diglycidyl ether and the like. An aqueous epoxy compound, a silane coupling agent, or a polyvalent metal compound such as a zirconium compound may be blended.

[0016]

Embodiments of the present invention will be described below, but the gist of the present invention is not limited thereto.

Embodiment 1 FIG. Acrylic resin emulsion (SS-600 manufactured by HONEN CORPORATION)
1: solid content 50%, average particle size 0.30μ) 70 parts by weight,
Melamine resin (M made by Honen Corporation)
L-60: solid content 75%, degree of methylol group conversion 40%,
30% by weight of dimethylene ether bond conversion degree)
-6 parts by weight of ethoxyethanol, 10 parts by weight of titanium oxide and 50 parts by weight of flour were mixed and stirred to prepare an adhesive composition for WPC of the present invention.

Embodiment 2 FIG. Styrene-butadiene latex (SS-30 manufactured by HONEN CORPORATION)
02: solid content 48%, average particle size 0.32μ) 100 parts by weight, urea melamine resin (manufactured by Honen Corporation MW-090): solid content 70%, methylol group conversion degree 25%, dimethylene ether bond conversion Degree 7%) 3
0 parts by weight, 10 parts by weight of acetone resin (HR-935 manufactured by Honen Corporation: 55% solid content), 10 parts by weight of titanium oxide, and 40 parts by weight of flour are mixed and stirred, and the adhesive composition for WPC of the present invention is mixed. Was prepared.

Embodiment 3 FIG. Vinyl acetate resin emulsion (SS-700 manufactured by HONEN CORPORATION)
1: 50% solids, average particle size 0.50μ) 80 parts by weight,
Melamine resin (M made by Honen Corporation)
W-5: solid content 58%, conversion of methylol group 30%, conversion of dimethylene ether bond 13%) 30 parts by weight, 3-
5 parts by weight of methyl-3-methoxy-1-butanol, 10 parts by weight of titanium oxide and 40 parts by weight of flour were mixed and stirred to prepare an adhesive composition for WPC of the present invention.

Comparative Example 1 45 parts by weight of an epoxy acrylate resin (EA-01, Dainippon Ink and Chemicals, Inc.), 45 parts by weight of calcium carbonate, 5 parts by weight of silica, and 2 parts by weight of benzoyl peroxide were mixed and stirred to prepare an adhesive composition.

Comparative Example 2 100 parts by weight of an aqueous vinyl urethane resin (KR-138 manufactured by Koyo Sangyo Co., Ltd.) and 10 parts by weight of a crosslinking agent (isocyanate) were mixed and stirred to prepare an adhesive composition.

Comparative Example 3 Vinyl acetate resin emulsion (SS-700 manufactured by HONEN CORPORATION)
1: 50% solids, average particle size 0.50μ) 80 parts by weight,
Melamine resin (M made by Honen Corporation)
W-5: solid content 58%, conversion of methylol group 30%, conversion of dimethylene ether bond 13%) 30 parts by weight, 10 parts by weight of titanium oxide and 40 parts by weight of flour are mixed and stirred to prepare an adhesive composition. did.

Performance Test The adhesive composition (size liquid) prepared as described above was applied to a plywood board (5 layers of Kapol material: 30 cm square, 12 mm thick, water content 1).
0%) (coating amount: 12 g / 900 cm ² )
Veneer impregnated with polyester resin (pine: thickness
0.35mm), temperature 130 ° C, pressure 10Kg / cm
Heating was carried out at ² for 8 minutes. One day and night after the heat pressure, the JAS class of immersion peeling test and the cold repeated B test were performed. Immediately after the hot pressing, the presence or absence of blisters at the time of exit from the hot press was visually determined. In addition, the workability was determined by comprehensively measuring the viscosity increase, temporary adhesiveness, and the like of the size liquid. Furthermore, the environmental properties were judged from the volatilization and toxicity of the solvent. The results are shown in the table.

[0024] Note: In the table, ○ indicates good, Δ indicates slightly poor, and × indicates defective.

As can be seen from the results in the tables, Examples 1 to 3 are shown.
The WPC using the adhesive of Example 1 showed good results in the JAS test, and also had good workability and environmental properties. Comparative Examples 1 and 2, which are ordinary wood adhesives, and Comparative Example 3, in which the dissolving agent was removed from the composition of Example 3, did not show good results.

Claims (4)

[Claims] An adhesive composition for WPC comprising 100 parts by weight of an amino resin, 10 to 500 parts by weight of an aqueous resin emulsion, 5 to 50 parts by weight of a solubilizer, and 10 to 150 parts by weight of a concealing agent. 2. The WPC adhesive composition according to claim 1, wherein the solubilizer is a ketone resin. 3. The amino resin is a co-condensate of a formaldehyde and an amino compound, and the degree of conversion of methylol group in all formaldehyde is 10 to 60% and the degree of conversion of dimethylene ether bond is 2 to 30%. The adhesive composition for WPC according to claim 1 or 2, wherein: 4. An aqueous resin emulsion having a particle size of 0.01
The adhesive composition for a WPC according to any one of claims 1 to 3, wherein the adhesive composition has a thickness of from 5 to 5 µm.