JPH0759692B2 - Adhesive for veneer makeup processing - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a wood-based base plate (hereinafter simply referred to as plywood) such as plywood, particle board or fiber board, and a veneer plate such as a veneer attached to the wood-based base material. The present invention relates to an adhesive for veneer decorative processing used for so-called veneer decorative processing, which has a unique aesthetic surface.

[Prior Art and Problems] Conventionally, as an adhesive for veneer decorative processing, an amino resin and wheat flour, an amino resin and homo vinyl acetate resin and wheat flour, and a mixture of amino resin and ethylene-vinyl acetate copolymer resin and wheat flour have been used. Have been served.

However, these adhesives cause bleeding of the adhesive to the surface of the veneer, which deteriorates the aesthetics of the veneer decorative processed product and lowers its commercial value.

Japanese Patent Publication No. 56-34196 discloses an adhesive having improved exudation to the surface of the veneer, a modified synthetic rubber latex obtained by copolymerizing a butadiene or an isoprene conjugated diene, and a vinyl monomer copolymerizable therewith, and an amino group. Mixed adhesives with resins have been proposed.

On the other hand, as an adhesive with improved bleeding to the surface of the veneer, the inventors of the present applicant have previously described Japanese Patent Application No. 61-3101.
Based on No. 86, an adhesive for veneer decorative processing was proposed, which is composed of an emulsion resin obtained by copolymerizing vinyl acetate, N-methylolacrylamide and acrylic acids and an amino resin. However, in the adhesive agent of a mixture of these modified synthetic rubber latex and an amino resin, and an adhesive agent of an emulsion resin and an amino resin mixture obtained by copolymerizing vinyl acetate, N-methylol acrylamide and acrylic acid,
Due to the soaring price of raw wood in veneer veneer, in order to improve the yield, it is inevitable to use veneer veneer with a very thin thickness of 0.1 to 0.5 m / m. To prevent this, veneer veneer with high water content is increasingly used.

Furthermore, the process of manufacturing a veneer decorative processed product is accelerating.Therefore, after applying the adhesive to the base plate plywood, I would like to immediately perform the heat pressure bonding process,
There is a problem that the adhesive oozes out on the surface of the veneer.

In order to prevent this bleeding on the veneer surface, after applying an adhesive such as a mixed adhesive of amino resin and vinyl acetate emulsion and modified synthetic rubber latex and amino resin to the base plate plywood, the adhesive is applied. Under the present circumstances, the process is forcibly brought to a semi-dried state with hot air, or left at room temperature for a long time to be a semi-dried state, and then the hot press bonding step is performed.

This method of performing a semi-dry state is difficult to control, and if it dries too much, the effect of preventing the exudation of the adhesive to the surface of the veneer is good, but the adhesive strength is low, and adhesion failure often occurs. Occur. On the other hand, on the contrary, in the undried state, there is a large amount of bleeding, which causes a problem in practical use.

An object of the present invention is to provide an adhesive for veneer decorative processing which solves the problems of the prior art.
It is an object of the present invention to provide a veneer decorative processed product that is sufficiently satisfactory in practical use, even if the adhesive oozes out onto the surface of the veneer without performing a working step of intentionally making the adhesive semi-dry.

[Means for Solving the Problems] The present invention is for veneer decorative processing comprising an amino resin, an aqueous emulsion resin or an aqueous latex, and ultrafine particle silica or ultrafine particle alumina having an average particle diameter of 3 to 150 mμ. Exists in the adhesive.

Examples of the amino resin used in the present invention include condensation resins of formaldehyde and one or more amino compounds such as urea, melamine, and guanamine, or these resins, phenols, polyvinyl alcohol, and frifri. Illustrative is a modified resin partially modified with alcohol.

In the above resin, the molar ratio of them is formaldehyde / amino compound = 1.0 to 3.0 and the solid content is 35 to 100% by weight.
Resins are preferred.

As the aqueous emulsion resin used in the present invention, vinyl acetate emulsion resin, acrylic emulsion resin, vinyl acetate and ethylene, styrene, acrylic acid,
A copolymer emulsion resin such as vinyl chloride is exemplified.

Examples of the aqueous latex used in the present invention include butadiene, chloroprene latex and isoprene latex having conjugated gen compounds such as budagen and isoprene, butadiene, isoprene and monomers copolymerizable therewith, such as acrylonitrile, styrene, and the like.
A copolymerized latex resin with methyl methacrylate is exemplified.

The solid content concentration of these aqueous emulsion resins and aqueous latex is preferably 30 to 65%.

In addition, these aqueous emulsion resins or aqueous latexes contain at least one reactive group capable of crosslinking with an amino resin.
Also included are emulsion resins and latexes modified with a reactive monomer having a seed side chain. Specific examples of the reactive monomer include, for example, a monomer having a carboxyl group such as maleic acid, itaconic acid and crotonic acid,
Acid anhydrides include itaconic anhydride, maleic anhydride, etc., and monomers having an N-methylol group include N-methylol acrylamide, N-methylol methacrylamide and their ethers, and monomers having a glycidyl group. Include glycidyl acrylate, glycidyl methacrylate, acrylic glycidyl ether, and the like, and monomers having a hydroxyl group include allyl alcohol, 2
-Hydroxyethyl acrylate, 2-hydroxypropyl methacrylate, 2-humanroxypropyl acrylate, monoallyl ethers of polyhydric alcohols, etc., and the monomer having an amino group includes N, N-dimethylaminoethyl acrylate, vinyl pyridine, There are tert-butylaminoethylmethacrylate and the like, and further, the amide group-containing monomer includes acrylamide, methacrylamide, maleamide and the like.

The ultrafine particle silica used in the present invention may be natural silica or synthetic silica as long as the ultrafine particle silicic acid generally called white carbon has an average particle size of 3 to 150 mμ. However, it is particularly preferable that synthetic silica is suitable because it can supply silica of constant quality.

Above all, ultrafine particulate anhydrous silica called Aerosil obtained by reacting a volatile compound containing silicon, for example, silicon tetrachloride in a gas phase is preferable.

When the average particle size is less than 3 mμ, it is difficult to disperse the particles uniformly in the adhesive and it is expensive.

On the other hand, if the average particle size exceeds 150 mμ, it is difficult to prevent the bleeding plate surface from seeping out.

If the amount of this ultrafine particulate silica is too small, the effect of preventing bleeding on the surface of the veneer is poor, and if it is too large, the spreader roll applicability of the adhesive is poor and it cannot be evenly applied to the adherend. Poor workability in which the phenomenon occurs and a phenomenon in which the adhesive performance is deteriorated occur.

The amount of the ultrafine silica added is suitably 3 to 25% by weight, and particularly preferably 10 to 25% by weight based on the total resin content of the aqueous emulsion resin or aqueous latex and the amino resin.
18% by weight.

The ultrafine particulate alumina used in the present invention is aluminum oxide having an average particle size of 3 to 150 mμ which is usually produced by a sedimentation method, a thermal decomposition method, a mineral refining method or the like.

When the average particle size is less than 3 mμ, it is difficult to disperse the particles uniformly in the adhesive and it is expensive.

On the other hand, if the average particle size exceeds 150 mμ, it is difficult to prevent the exudation to the surface of the veneer.

If the amount of this ultrafine particulate alumina added is too small, the effect of preventing the exudation of the veneer surface is poor, and if it is too large, the spreader roll applicability of the adhesive is poor and uniform application to the adherend is possible. There is a phenomenon that there is no workability and
The phenomenon that the adhesive performance is deteriorated occurs.

The amount of the ultrafine particulate alumina added is appropriately 3 to 25% by weight, and particularly preferably 10 to 25% by weight based on the total resin content of the aqueous emulsion resin or aqueous latex and the amino resin.
18% by weight.

In the present invention, by blending the amino resin, the aqueous emulsion resin or the aqueous latex, and the ultrafine particulate silica or the ultrafine particulate alumina of 3 to 150 mμ, the exudation of the adhesive to the surface of the veneer and the contamination of the adhesive are caused. The details of the reason for this are not clear, but ultrafine particle silica or ultrafine particle alumina is oriented on the surface of the veneer, closes holes such as conduits of the veneer, adsorbs the adhesive, and adheres the adhesive to the surface of the veneer. This is probably because it prevents bleeding.

As shown in Comparative Examples described later, the object of the present invention cannot be achieved by using silica powder which is not ultrafine particle silica, titanium oxide, calcium carbonate, white luster, and clay.

However, substances such as fillers, fillers, and pigments that have been added to the adhesives of the conventional veneer cosmetic processed products in the adhesive according to the present invention, such as wheat flour, starches, defatted soybean flour, blood meal, and walnut grains, etc. Organic substances and inorganic substances such as clay, kaolin, zeolite, zinc white, titanium oxide, and red iron oxide can be used in combination.

The fillers, extenders, and pigments are usually mixed in such an amount that the viscosity of the adhesive is 50 to 500 poise / 25 ° C.

Further, an aqueous polymer thickener such as polyvinyl alcohol, methyl cellulose, polyethylene oxide, carboxymethyl cellulose, hydroxyethyl cellulose and alginic acid can be added to the composition of the present invention.

Further, in the present invention, a known curing agent such as ammonium chloride, hydrochloric acid, oxalic acid, p-toluenesulfonic acid, tartaric acid, phthalic anhydride or aluminum chloride used for curing the amino resin may be used together with the adhesive. Good.

[Examples] Next, the present invention will be described with reference to Examples, but the present invention is not limited to these Examples.

Example 1 Carboxyl-modified styrene-butadiene synthetic rubber latex [JSR-0619 solid content 48% by weight (manufactured by Japan Synthetic Rubber Co., Ltd.)] was added to 100 parts by weight of urea resin (molar ratio: formaldehyde / urea = 1.8 solid content 54). 50% by weight and ultrafine silica (Aerosil 200 (Japan Aerosil Co., Ltd.)
9 parts by weight) was mixed to obtain an adhesive composition.

38 parts by weight of flour with respect to 100 parts by weight of this adhesive composition,
57 parts by weight of water was added and mixed to obtain a mixed paste solution for a veneer decorative plywood having a viscosity of 250 P / 25 ° C.

The adhesive for veneer decorative processing obtained in this way was applied uniformly to a 5 ply 12 mm thick lauan plywood with a surface thickness of 0.7 mm as shown in the next working condition, and a coating amount of 150 g / m ² was uniformly applied to obtain a moisture content of 80 to 100. %
Each of four types of 0.25 mm thick oak, birch, zelkova, pine tree, and taro veneer, the veneer is superposed on a 12 mm thick lauan plywood coated with the above-mentioned glue solution, and water is sprayed on the surface of the veneer. Within 10 seconds and after 90-100 seconds of deposition, heat and pressure conditions 110
Bonding was carried out at 7 to 8 kg / cm ² for 60 seconds.

The degree of contamination of the above-mentioned bonded veneer decorative plywood that oozes out was visually observed.

In addition, the adhesiveness of the bonded veneer decorative plywood was evaluated by conducting 5 cycles of the Type 2 immersion peeling test of the special agricultural plywood of Japanese agricultural and forestry standard.

1. working conditions bedplate: moisture content 8% to 10% front and back 0.7mm5 Purairawan plywood veneer veneer: 0.25 mm thick 80% to 100% water content oak, birch, zelkova, Douglas fir, uniform ash coated 150 g / m ² to lauan plywood Apply to: Deposition: Open deposition within 5 seconds / 20 ℃, Open chain deposition within 5 seconds / 20 ℃
20-30 seconds for open deposition, 90-100 seconds for closed deposition Water sprinkling: Water is sprinkled to the extent that water droplets accumulate on the surface of the veneer immediately after hot pressing.

Hot ^{pressing: 110 ℃, 7~8kg / cm 2} , 60 seconds 2. Staining Test method piece exuded test methods 2-1 30 cm ² square veneer decorative plywood specimen in wiping the paint (last stain Washin Chemical Industries (Co. ) Made 50
It was coated with g / m ² and the presence or absence of seepage of the adhesive was visually determined.

2-2 Adhesion performance A piece of 75 mm square veneer decorative plywood test piece is dipped in 70 ± 3 ° C warm water for 2 hours and then dried in a dryer at 60 ± 3 ° C.
The step of drying for 5 hours was performed to measure the peeling length of the adhesive layer, and 5 cycles of the 2 types of immersion peeling test of the Japanese agricultural standard of special plywood were performed.

The judgment was passed when the length of the non-peeling portion of the same adhesive layer was 50 mm or more on each side surface.

Example 2 100 parts by weight of an emulsion resin obtained by copolymerizing vinyl acetate, N-methylolacrylamide and acrylic acid (vinyl acetate 92.1% by weight, N-methylolacrylamide 6.9% by weight, acrylic acid 1.0% by weight, solid content 52%). same as below)
75 parts of urea-melamine copolymer resin (molar ratio: formaldehyde / urea-melamine = 2.2, solid content 52% by weight) and 105 parts of ultrafine silica (Aerosil 200 (average particle size: 12 mμ, Nippon Aerosil Co., Ltd.)) Then, an adhesive composition was obtained.

For each 100 parts of this composition, 35 parts of flour and 69 parts of water
Parts were added and mixed to obtain a mixed paste solution for a veneer decorative plywood having a viscosity of 250 P / 25 ° C.

The working conditions and the test method were the same as in Example 1.

Examples 3 to 7 Vinyl acetate emulsion resin (solid content 45%, viscosity 600P / 3
100 parts of urea resin (molar ratio: formaldehyde / urea = 1.9 solid content 50%, viscosity 2P / 25 ° C) to 100 parts and various types of ultrafine silica as Aerosil 130 manufactured by Nippon Aerosil Co., Ltd. (average diameter: approx. 16mμ), Aerosil 200 (average diameter about 12m
μ), Aerosil 300 (average diameter about 7mμ), Aerosil TT
-600 (average diameter of about 40 mμ) [sequentially Examples 3 to 6] and 12 parts of aluminum oxide (average diameter of about 20 mμ) [Example 7] as ultrafine particulate alumina were added and mixed to obtain adhesive compositions.

To 100 parts of each composition, 31 parts of wheat flour and water were added and mixed so that the viscosity became 250 P / 25 ° C. to obtain a mixed paste solution for veneer decorative plywood.

The working conditions and the test method were the same as in Example 1.

Comparative Examples 1 to 4 Vinyl acetate emulsion resin (solid content 45%, viscosity 600P / 3
100 parts formalin-urea resin (molar ratio: formaldehyde / urea = 1.9, solid content 50%, viscosity 2P / 25 ° C) 100 parts
Part and titanium oxide (average particle size 0.1μFA-50 (Tohoku Chemical Co., Ltd.)), calcium carbonate (average particle size 0.003μ Shiramatsu O (Shiraishi Industry Co., Ltd.), acidic hydrous kaolin clay (average particle size 0.5μ) Bergs Kaolin Clay N010 Burg Pigment Co., pulverized silica (average particle size 5μ)
12 parts of Crystallite AI (manufactured by Tatsumori Co., Ltd.) were added and mixed to obtain an adhesive composition. To 100 parts of this composition, 31 parts of wheat flour and water were added and mixed so that the viscosity was 250 P / 25 ° C. to obtain a paste solution for veneer makeup.

The working conditions and the test method were the same as in Example 1.

Comparative Example 5 Carboxy-modified styrene-butadiene synthetic rubber latex [JSR-0619 solid content 48 wt% (manufactured by Japan Synthetic Rubber Co., Ltd.) 100 parts by weight urea resin (molar ratio: formaldehyde / urea = 1.8 solid content 54%) 50 parts by weight were added and mixed to obtain an adhesive composition.

To 100 parts by weight of this composition, 28 parts by weight of flour and 15 parts by weight of water were added and mixed to obtain an adhesive for veneer decorative plywood having a viscosity of 200 P / 25 ° C.

Comparative Example 6 Emulsion resin obtained by copolymerizing vinyl acetate, N-methylol acrylamide and acrylic acid (vinyl acetate 92.1
% By weight, 6.9% by weight of N-methylolacrylamide, 1.0% by weight of acrylic acid, solid content 52% 100 parts (weight, the same applies hereinafter) to urea-melamine copolymer resin (molar ratio: formaldehyde / urea-melamine = 2.2 solid content 52 (Wt%) 30 was added and mixed to obtain a composition. To 100 parts by weight of this composition, 18 parts of wheat flour and 7 parts of water were added and mixed to obtain an adhesive for veneer decorative plywood having a viscosity of 200 P / 25 ° C.

The working conditions and the test method were the same as in Example 1.

The above results are shown in Table-1 and Table-2, respectively.

For Comparative Examples 5 and 6, as in many examples, the test results are shown in which, after the adhesive was applied to the base plate plywood, the thermocompression bonding step was immediately performed without making the adhesive semi-dried.

After applying the adhesive, forcibly making it semi-dry with hot air, or leaving it at room temperature to make it semi-dry, and then performing the hot-pressing adhesion process, the bleeding prevention effect was improved (△). , The adhesive strength was low, and all failed.

[Effects of the Invention] According to the present invention as described above, bleeding on the surface of the veneer is prevented, and bleeding on the surface of the veneer is practically sufficient without performing a working step to intentionally bring the adhesive into a semi-dried state. It was possible to obtain a satisfactory veneer adhesive for decorative processing of veneer.

Claims (2)

[Claims] 1. An adhesive for veneer decorative processing, which comprises an amino resin, an aqueous emulsion resin or an aqueous latex, and ultrafine particle silica or ultrafine particle alumina having an average particle diameter of 3 to 150 mμ. 2. The adhesive for veneer decorative processing according to claim 1, wherein the ultrafine particle silica is anhydrous ultrafine particle silica obtained by reacting a volatile compound containing silicon in a gas phase. .