JPH07329007A - Production of fancy veneer overlaid plywood - Google Patents

Abstract

PURPOSE:To produce fancy veneer overlaid plywood excellent in warm water resistance and heat boiling-resistant adhesive strength without generating exudation and dry cracking by using an adhesive prepared by compounding ammonium zinc carbonate with an acrylic emulsion having a single-layered structure and an acrylic emulsion having a two-layered structure. CONSTITUTION:An adhesive is prepared by compounding ammonium zinc carbonate with an acrylic emulsion having a single-layered structure containing a copolymer of an aromatic vinyl monomer, an unsaturated carboxylic ester monomer, an acrylic monomer having an amide group and unsaturated carboxylic acid and an acrylic emulsion having a two-layered structure wherein a core layer is composed of a copolymer of an acrylic monomer and unsaturated carboxylic acid and a shell layer is composed of a copolymer of an aromatic vinyl monomer, an unsaturated carboxylic ester monomer and unsaturated carboxylic acid. This adhesive is used to produce fancy veneer overlaid plywood wherein the exudation of the adhesive to the surface of veneer is prevented and the dry cracking of veneer is eliminated and warm water-resistant adhesive strength is excellent.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a veneer decorative plywood using plywood as a substrate. For more details,
The present invention relates to a method for producing a veneer decorative plywood having excellent adhesiveness against hot water and boiling resistance, without preventing the veneer from leaching and contaminating the surface of the veneer and without causing cracks in the veneer due to repeated cold and heat tests.

[0002]

2. Description of the Related Art Conventionally, as an adhesive or binder for a veneer decorative plywood, thermosetting urea-based condensation resin, melamine-based condensation resin, melamine-urea-based condensation resin, or urea-
Melamine-based condensation resins (hereinafter simply referred to as amino-based condensation resins) are used alone, and blends of these amino-based condensation resins and vinyl acetate emulsions or styrene-butadiene copolymer latex are widely used. . Usually, in the actual use of these adhesives or binders, after mixing water, flour, a curing agent, etc. (hereinafter abbreviated as a compounding paste), they are applied to the adherend by various methods, and heat-pressed to produce them. ing.

[0003]

As is well known, veneer decorative plywood is widely used for floor materials, wall materials, furniture and the like. As the thickness of the veneer becomes thinner, there is a problem that the adhesive seeps out to the surface of the veneer and many dry cracks (fine cracks along the grain) occur. Occurrence of cracking on the veneer occurs during and after hot pressing, or due to repeated cold heat due to seasonal temperature changes. When an amino-based condensation resin is used as the adhesive for the veneer, the adhesive strength such as hot water resistance and boiling resistance is excellent, but since the adhesive is a thermosetting resin, the adhesive cured product is too hard and a thin veneer At the same time as causing numerous cracks, the amino-based condensation resin oozes and shines on the surface of the veneer, significantly reducing the commercial value, and there is a problem that a large amount of oozing prevents the product from becoming a commercial product.

Various attempts have been made to improve the amino-based condensation resin, but the cracking on the surface of the veneer can be slightly improved, but the result is not satisfactory. Further, a method of blending a resin emulsion such as a thermoplastic vinyl acetate emulsion with an amino condensation resin, or a styrene-butadiene copolymer latex having a low glass transition temperature (hereinafter abbreviated as Tg) and a pH in a neutral range. As described above, an attempt has been made to blend an elastomer with an amino condensation resin. When the former vinyl acetate emulsion is used as the adhesive for veneer, it is necessary to mix a large amount of amino-based condensation resin in order to compensate for hot water resistance and boiling resistance (hereinafter referred to as water resistant adhesion). Although cracking was slightly improved as compared with the amino-based condensation resin, it was not satisfactory. Even when the latter styrene-butadiene copolymer latex is used, it is necessary to use a small amount of an amino-based condensation resin together in order to supplement the water-resistant adhesive strength, and the vinyl acetate-based emulsion was also used for cracking of the veneer. If you are better than you are not satisfied. When a styrene-butadiene copolymer latex is used, it lacks miscibility with wheat flour and the compounding paste has high viscosity and poor fluidity, and the coating property and mechanical stability when the compounding paste is applied with a roll coater or the like. It is difficult to obtain a stable coating state,
Not only the cracking, but also the water-resistant adhesive strength is significantly reduced. There are some examples in which the compounding ratio of amino condensation resin, thermoplastic vinyl acetate emulsion, styrene-butadiene copolymer latex, etc. was changed, but veneer cracking, adhesive leaching contamination, water resistant adhesive strength, etc. The result does not satisfy all of the above.

[0005]

The present inventors have found that acrylic emulsions have miscibility with wheat flour and mechanical stability, and have cracked veneer, adhesive leaching contamination, and water-resistant adhesion. As a result of repeated studies on the development of emulsion type adhesives that have strength, the miscibility with wheat flour and the mechanical stability during coating with a roll coater, etc.
It was found that the effect of Tg of acrylic emulsion and generally-known functional group monomer is extremely large in preventing dry cracking of veneer, leaching contamination of adhesive and improving water resistant adhesive strength. . That is, it is most effective to copolymerize an acrylic monomer having an amide group in order to impart water-resistant adhesive strength, but the miscibility with wheat flour is significantly impaired. This miscibility is imparted by copolymerizing an unsaturated carboxylic acid and adjusting it to a low pH range. In order to combine these two physical properties, it is possible to achieve the purpose by forming a heterophase structure like a core-shell structure, using an acrylic monomer having an amide group in the core layer, and copolymerizing an unsaturated carboxylic acid in the shell layer. I found it. In addition, in the ordinary one-layer structure acrylic emulsion, unlike the acrylic emulsion, the miscibility with wheat flour is poor because it does not have a heterophasic structure, but by adding an aqueous Poval solution, miscibility with wheat flour is imparted. I found that I was able to achieve the purpose. It was further found that the unsaturated carboxylic acid in the acrylic emulsion is metal-crosslinked with a zinc compound or a strong acid is added to cause a self-crosslinking reaction, and the water-resistant adhesive strength is remarkably improved. The present invention has been completed based on the above findings.

That is, the present invention is as follows (1) to (7). (1) Acrylic emulsion (a) and / or core layer having a single layer structure, which is a copolymer of an aromatic vinyl monomer, an unsaturated carboxylic acid ester monomer, an amide group-containing acrylic monomer and an unsaturated carboxylic acid, is aromatic. Group vinyl-based monomer, unsaturated carboxylic acid ester monomer, amide group-containing acrylic monomer and unsaturated carboxylic acid copolymer, shell layer containing aromatic vinyl-based monomer, unsaturated carboxylic acid ester monomer and unsaturated carboxylic acid copolymer A method for producing a veneer decorative plywood, which comprises using an adhesive in which zinc ammonium carbonate or a strong acid (c) is blended as an essential component in an acrylic emulsion (b) having a two-layer structure, which is a polymer. (2) The glass transition temperature (Tg) of the acrylic emulsion (a) is −30 to + 90 ° C., and the glass transition temperature (Tg) of the core layer of the acrylic emulsion (b) is −10.
+ 90 ° C, glass transition temperature (Tg) of shell layer is -50
It is +20 degreeC, The manufacturing method of the veneer decorative plywood as described in (1) characterized by the above-mentioned. (3) The veneer according to (1), wherein the monomer composition ratio of the core layer / shell layer of the acrylic emulsion (b) is 30 to 70/70 to 30 parts by weight per 100 parts by weight of the total amount of monomers. Manufacturing method of decorative plywood. (4) The acrylic emulsion (a) contains 1 to 6 parts by weight of an amide group-containing acrylic monomer and 1 to 10 parts of an unsaturated carboxylic acid per 100 parts by weight of the total amount of constituent monomers.
By weight, the core layer of the acrylic emulsion (b) is copolymerized, and the total amount of monomers constituting the core layer is 1
1 to 6 parts by weight each of an acrylic monomer having an amide group and an unsaturated carboxylic acid, and the shell layer
The method for producing a veneer decorative plywood according to (1), wherein the unsaturated carboxylic acid is copolymerized in an amount of 1 to 10 parts by weight per 100 parts by weight of the total amount of monomers constituting the shell layer. (5) The method for producing a veneer decorative plywood according to (1), wherein the acrylic emulsions (a) and (b) are adjusted to a pH range of 4 to 6 with aqueous ammonia. (6) 15-20 ammonium zinc carbonate (c) consisting of water, ammonium carbonate, zinc oxide and aqueous ammonia
The method for producing a veneer decorative plywood according to (1), which is a transparent aqueous solution having a concentration of wt% and is adjusted to pH 9 to 10. (7) The method for producing a veneer decorative plywood according to (1), wherein the strong acid (c) has an acid dissociation constant (pKa) of 3 or less.

Aromatic vinyl monomers used for emulsion polymerization of acrylic emulsions (a) and (b) include styrene, α-methylstyrene and divinylbenzene, and unsaturated ester monomers include methyl methacrylate and ethyl acrylate. , Isobutyl methacrylate, tert butyl methacrylate, vinyl acetate, acrylonitrile, isobutyl acrylate, n-butyl acrylate, 2 ethylhexyl acrylate, 2 ethylhexyl methacrylate, lauryl methacrylate, etc. Acrylic acid or methacrylic acid having 4 to 12 alkyl groups Examples thereof include acid esters, and among them, a combination of styrene and / or methyl methacrylate and n-butyl acrylate is preferable in terms of economy and ease of emulsion polymerization. Acryl monomers having an amide group include acrylamide, methacrylamide, maleimide, N
-Methylol acrylamide, N-methylol methacrylamide, N-methoxymethyl acrylamide, N-
Isopropoxymethylacrylamide, N-butoxymethylacrylamide, N-isobutoxymethylacrylamide, N-octyloxymethylacrylamide, N-
Examples thereof include carboxymethyl acrylamide, and among them, N-methylol acrylamide and N-methylol methacrylamide having a methylol group are preferable from the viewpoint of adhesive strength, water resistance, warm water resistance, boiling resistance and the like.

Examples of the unsaturated carboxylic acid of the acrylic emulsions (a) and (b) include acrylic acid, methacrylic acid, crotonic acid, etc. as monocarboxylic acids.
Examples of the dicarboxylic acid include itaconic acid, maleic acid, fumaric acid and the like. Acrylic emulsion (a)
The unsaturated carboxylic acid is preferably a monocarboxylic acid in view of copolymerizability with an acrylic monomer having an amide group, stability and mechanical stability during emulsion polymerization, and mechanical stability and flour. Considering miscibility, a dicarboxylic acid is preferable, and specifically, a combination of monocarboxylic acid and dicarboxylic acid is preferable. Acrylic emulsion (b)
In the unsaturated carboxylic acid, a monocarboxylic acid is preferable from the viewpoint of copolymerizability with an acrylic monomer having an amide group in the core layer and stability during emulsion polymerization and mechanical stability. On the other hand, the shell layer is preferably a dicarboxylic acid which is easily polymerized in an aqueous solution and which exists at the interface of emulsion particles and is highly established. It particularly effectively acts on the mechanical stability of the acrylic emulsion in the low pH range and the miscibility with wheat flour. Specifically, acrylic acid or methacrylic acid is preferable as the monocarboxylic acid used for the core layer, and itaconic acid is preferable as the dicarboxylic acid used for the shell layer.

The monomer composition ratio of the core layer / shell layer of the acrylic emulsion (b) of the present invention is 1 total monomer.
It is 30 to 70/70 to 30 parts by weight in 00 parts by weight.
It is preferably 50/50 parts by weight. If the monomer composition ratio is out of this range, the fluidity is poor due to lack of miscibility with wheat flour, and the coating property when coating the compounding paste with a roll coater or the like is poor and a stable coating state on the adherend is obtained. It becomes impossible to obtain it, or the stability due to mechanical shearing when the compounding paste is applied with a roll coater or the like is deteriorated, and a stable application state to the adherend cannot be obtained. In addition, the balance of water-resistant adhesive strength cannot be maintained, making it unsuitable as an acrylic emulsion for bonding veneer decorative plywood. As a specific example, when the shell layer is more than 70 parts by weight, the miscibility with wheat flour and the mechanical stability in a roll coater are improved, but the water-resistant adhesive strength is impaired. On the other hand, when the amount is less than 30 parts by weight, the water-resistant adhesive strength is obtained, but the miscibility with wheat flour is significantly reduced.

The Tg of the acrylic emulsion (a) is-
It is 30- + 90 degreeC. Preferably -15 to + 60 ° C
From the viewpoint of the film-forming property of the emulsion at room temperature, the cracking property of the veneer, and the water-resistant adhesive strength, −15 to + 60 ° C. is preferable.
If Tg is less than -30 ° C, water resistant adhesive strength cannot be obtained, and +9
If it exceeds 0 ° C, the stability during emulsion polymerization is insufficient, and in some cases there is a risk of gelation during emulsion polymerization, and the effect of preventing cracking of the veneer cannot be obtained.

The acrylic emulsion (b) has a core layer Tg of -10 to + 90 ° C and a shell layer Tg of -50.
It is + 20 ° C. Preferably, the Tg of the core layer and the shell layer is 0 to + 60 ° C. and −40 to 0 ° C., and the Tg of the shell layer is low in view of the film-forming property of the emulsion at room temperature, the cracking property of the veneer, and the water-resistant adhesive strength. Is preferred. Core layer T
When g is less than -10 ° C, water-resistant adhesive strength cannot be obtained, and +90
When the temperature is higher than 0 ° C, the stability during emulsion polymerization is insufficient, and in some cases there is a risk of gelation during emulsion polymerization, and the effect of preventing cracking of the veneer cannot be obtained. Moreover, the shell layer Tg is −50 ° C.
If it is less than 20%, the water-resistant adhesive strength is not obtained, and if it exceeds + 20 ° C., the water-resistant adhesive strength and the normal-state adhesive strength are lowered, and the effect of preventing cracking of the veneer is also remarkably lowered.

The amount of the amide group-containing acrylic monomer in the acrylic emulsion (a) of the present invention is 1 total monomer.
It is 1 to 6 parts by weight in 00 parts by weight. The amount is preferably 2 to 5 parts by weight in view of the stability during emulsion polymerization and the water resistant adhesive strength.
If the amount is less than 1 part by weight, the water-resistant adhesive strength cannot be obtained, and if the amount is more than 6 parts by weight, the stability during emulsion polymerization is remarkably reduced and there is a high risk of gelation during emulsion polymerization.

The amount of unsaturated carboxylic acid is 100 total monomers.
It is 1 to 10 parts by weight in parts by weight. It is preferably 2 to 5 parts by weight of the monocarboxylic acid and the dicarboxylic acid in 100 parts by weight of the total amount of the monomers, from the viewpoint of copolymerizability with an acrylic monomer having an amide group and stability during emulsion polymerization and mechanical stability. Looking at the combination of monocarboxylic acid and dicarboxylic acid, the monocarboxylic acid is contained in 100 parts by weight of the total amount of the monomers.
In consideration of mechanical stability and miscibility with wheat flour, 0.5 to 5 parts by weight improves the miscibility with wheat flour when the dicarboxylic acid is 0.5 to 5 parts by weight in 100 parts by weight of the total amount of monomers. . This miscibility is further improved by adding a small amount of Poval's aqueous solution. The Poval aqueous solution means an aqueous solution of completely saponified or partially saponified polyvinyl alcohol having a polymerization degree of 300 to 1700.

When monocarboxylic acid or dicarboxylic acid is used alone, the monocarboxylic acid is used in 100 parts by weight of the total amount of monomers.
If the amount is less than 1 part by weight, the stability during emulsion polymerization deteriorates and gelation occurs during polymerization, or the mechanical stability decreases, and the coatability during coating with a roll coater or the like deteriorates and the adhesiveness to adherends is reduced. A stable coating state cannot be obtained. When the amount is more than 10 parts by weight, the emulsion polymerization rate is remarkably reduced, the polymerization is not completed within a predetermined emulsion polymerization time, the amount of residual monomer is increased, and the water-resistant adhesive strength is not obtained. Further, when the amount of dicarboxylic acid is less than 1 part by weight in 100 parts by weight of the total amount of the monomers, the amount of the aqueous solution of Povar increases because the dicarboxylic acid has miscibility with flour. When the amount of the POVAL aqueous solution is increased, the water resistant adhesive strength is reduced because POVAL itself is water-soluble. Dicarboxylic acid in 100 parts by weight of the total amount of monomers,
When the amount is more than 10 parts by weight, the emulsion polymerization rate is remarkably reduced, the polymerization is not completed within a predetermined emulsion polymerization time, the amount of residual monomer is increased, and the water-resistant adhesive strength is not obtained.

The amount of amide groups and unsaturated carboxylic acid in the core layer of the acrylic emulsion (b) of the present invention is 1 to 6 parts by weight per 100 parts by weight of the total amount of core layer monomers. The amount is preferably 2 to 5 parts by weight in view of the stability during emulsion polymerization and the water resistant adhesive strength. If the amount is less than 1 part by weight, the water-resistant adhesive strength cannot be obtained, and if the amount is more than 6 parts by weight, the stability during emulsion polymerization is remarkably reduced and there is a high risk of gelation during emulsion polymerization. The amount of unsaturated carboxylic acid in the shell layer of the acrylic emulsion (b) is 100% of the total amount of monomers in the shell layer.
It is 1 to 10 parts by weight in parts by weight. It is preferably 2 to 5 parts by weight. When the amount is less than 1 part by weight, the miscibility with wheat flour is insufficient and the coatability becomes poor at the time of coating with a roll coater or the like, so that a stable coating state on the adherend cannot be obtained. In addition, the mechanical stability at the time of application becomes poor. When the amount is more than 10 parts by weight, the emulsion polymerization rate is remarkably reduced, the polymerization is not completed within a predetermined emulsion polymerization time, the amount of residual monomer is increased, and the water-resistant adhesive strength is not obtained.

The pH of the acrylic emulsions (a) and (b) is adjusted to 4 to 6 using aqueous ammonia. More preferably, it is 4.5 to 5.5. When it is less than 4, the above-mentioned mechanical stability cannot be obtained and a stable coating state on the adherend cannot be obtained. When it is more than 6, the miscibility with flour is remarkably lowered and the coatability deteriorates. A stable coating state cannot be obtained, which causes problems. Acrylic emulsion (a),
Regarding the blending ratio of (b), it is usually used alone, but both may be blended and used. Also,
When both are used in combination, the miscibility with wheat flour becomes better as the mixing ratio of the acrylic emulsion (b) increases, so that the amount of the aqueous Poval solution may be small.

Zinc ammonium carbonate (c) is 15 to 20
It is a transparent aqueous solution having a concentration of 5% by weight, and its pH is adjusted to 9 to 10. The zinc concentration in this aqueous solution is 4 to 5
% By weight. This aqueous solution is prepared by mixing 12 parts by weight of zinc oxide and 20 parts by weight of ammonium carbonate with stirring in 112 parts by weight of distilled water, and using about 50 parts by weight of 28% ammonia water.
By gradually adding H to 9 to 10, a transparent aqueous solution of 16 wt% zinc ammonium carbonate (zinc concentration: 4.5%) is obtained. The compounding ratio of the zinc ammonium carbonate (c) is the acrylic emulsion (a),
By mixing 0.1 to 1.0 mol of zinc in terms of the number of moles of zinc with respect to the total amount of unsaturated carboxylic acid in (b), the water-resistant adhesive strength and the like are remarkably improved by the chelate reaction between the carboxyl group and zinc. When the amount is less than 0.1 mol, sufficient water resistant adhesive force cannot be obtained, and when the amount is more than equimolar, the solid content and viscosity of the adhesive composition decrease, and at the same time, the water resistant adhesive force is in an equilibrium state and there is no point in increasing the amount.

The strong acid (c) is the dissociation constant (pKa) of the strong acid.
Is an organic or inorganic acid having 3 or less, and examples thereof include maleic acid, sulfuric acid, hydrochloric acid, nitric acid, and paratoluenesulfonic acid. In the actual use of a strong acid, an acrylic emulsion obtained by copolymerizing N-methylol acrylamide having a methylol group and N-methylol methacrylamide is used, and the active ingredient diluted with water to 30% or less is used. . If it exceeds 30%, the acrylic emulsion causes a shock at the time of addition, and the fluidity of the compounded paste is significantly lowered. In addition, because agglomeration partially occurs and a stable coating state cannot be obtained, and the curing of the compounding paste proceeds before heat pressing, not only the normal strength of the veneer decorative plywood molded product but also the water resistant adhesive strength can be obtained. Absent. The mixing ratio of the strong acid is the acrylic emulsion (a), (b) in the mixed paste.
By blending 0.2 to 2.0 parts by weight of an acid active ingredient with respect to 100 parts by weight, the self-crosslinking reaction improves the water resistant adhesive strength. If the amount is less than 0.2 parts by weight, sufficient curing will not proceed under hot pressing and water-resistant adhesive strength will not be obtained. If it exceeds 2.0 parts by weight, the acrylic emulsion causes a shock at the time of addition, and the fluidity of the compounded paste is remarkably reduced. In addition, because agglomeration partially occurs and a stable coating state cannot be obtained, and the curing of the compounding paste proceeds before heat pressing, not only the normal strength of the veneer decorative plywood molded product but also the water resistant adhesive strength can be obtained. Disappear. The dissociation constant (pKa) is the logarithm of the reciprocal of the acid dissociation constant.

As described above, the acrylic emulsion for wood adhesion according to the present invention can obtain water-resistant adhesive strength in the adhesion of plywood and veneer without using amino-condensation resin which is a conventional adhesive, and it has a good working environment. There is no problem, and it has excellent miscibility with wheat flour used as a bulking agent, including mechanical stability and coatability at the time of coating with a roll coater, etc., especially leaching of adhesive on the sliced veneer surface and contamination and drying. Since the crack occurrence rate is low, its practical value as an adhesive for veneer decorative plywood is extremely high, and its significance is great.

The acrylic emulsions (a) and (b) used in the present invention may be produced by a general emulsion polymerization method.
An emulsion polymerization method in which water, the acrylic monomer mixture, a surfactant, a chain transfer agent (polymerization degree modifier), and a radical polymerization initiator are the basic components, and the surfactant is a fatty acid soap or rosin acid. Anionic surfactants such as soaps, alkyl sulfonates, alkyl benzene sulfonates, dialkyl aryl sulfonates, alkyl sulfosuccinates, polyoxyethylene alkyl sulfates, polyoxyethylene alkylaryl sulfates, polyoxyethylene alkyl ethers , Polyoxyethylene alkylaryl ethers, polyoxyethylene sorbitan fatty acid esters, oxyethyleneoxypropylene block copolymers, and other nonionic surfactants, usually anionic surfactants alone or anionic surfactants and nonionic surfactants. Mixture of agents The proportion for the monomer mixture used in the system ranges from 0.01 to 5% by weight is common. N-octyl mercaptan as a chain transfer agent,
Examples thereof include mercaptans such as n-dodecyl mercaptan, t-dodecyl mercaptan and mercaptoethanol, and halogenated hydrocarbons such as carbon tetrachloride. Radical polymerization initiators include persulfates such as potassium persulfate, sodium persulfate and ammonium persulfate, hydrogen peroxide, benzoyl peroxide, t-butyl hydroperoxide,
Peroxides such as cumene hydroperoxide, 2,2-
Examples thereof include azobis compounds such as azobisisobutyronitrile, with persulfate being most preferred. The polymerization temperature is usually in the range of 60 to 90 ° C., but low temperature redox polymerization in which a reducing agent such as sodium bisulfite, ascorbic acid (salt) and Rongalit is combined with a radical polymerization initiator can also be used. . If desired, a polymerization regulator such as a pH regulator such as sodium hydroxide, potassium hydroxide, sodium hydrogen carbonate, sodium carbonate, etc. can be added.

As a concrete acrylic emulsion for veneer decorative plywood of the present invention, for example, acrylic emulsions (a) and (b) having a solid content of 50% are collected in a 1-liter beaker, and 16% of zinc carbonate is stirred while stirring. It can be obtained by mixing an ammonium aqueous solution or an aqueous solution of a strong acid and mixing with stirring. When the actual plywood and the veneer are adhered, 10 to 100 g of wheat flour and, if necessary, water are added to 100 g of the acrylic emulsion (a) and / or (b), and the mixture is uniformly mixed before use. The above 16% aqueous solution of zinc ammonium carbonate and the strong acid aqueous solution may be blended before or after the blending of wheat flour in some cases. When the acrylic emulsion (a) is used alone, the Poval aqueous solution is preferably added before the flour. The acrylic emulsion for veneer decorative plywood of the present invention is a preservative, water, a dispersant, a defoaming agent, a film-forming aid, in a range that does not inhibit the desired effect.
You may use together a plasticizer, a coloring agent, an antifreezing agent, a polyisocyanate resin, and an amino-type condensation resin.

[0022]

EXAMPLES Hereinafter, production examples, examples and comparative examples of the present invention will be described. Parts and% in the examples are by weight unless otherwise specified. The numbers in the table represent parts by weight unless otherwise specified.

Stability indication during emulsion polymerization G: Very little adherence in flask and coarse particles (good) LP: Coarse particles GL: Gelation NP: Unreacted (large amount of residual monomer) Name of monomer ST: Styrene nBA : N-butyl acrylate N-MAM: N-methylol acrylamide N-MMAM: N-methylol methacrylamide MAM: methacrylamide AA: acrylic acid IA: itaconic acid HEMA: hydroxyethyl methacrylate MMA: methyl methacrylate tDM: tert dodecyl mercaptan

Preparation Example Acrylic Emulsion (a) A mixture of 100 parts of a mixed monomer having a composition ratio shown in Table 1 and a chain transfer agent (tDM) was separately weighed in advance, and 50 parts of distilled water and sodium dodecylbenzenesulfonate were respectively weighed. It was dripped into 0.5 parts under stirring and used as a pre-emulsified monomer. Separately, add 95 parts of distilled water and 0.1 part of sodium dodecylbenzenesulfonate to a 1 liter flask, heat to 70 ° C. with stirring under a nitrogen blanket, and seed with 0.5 part of potassium persulfate and emulsion. Therefore, an equal amount of mixed monomers of n-butyl acrylate, methyl methacrylate and hydroxyethyl methacrylate was charged and reacted for 30 minutes to form seeds of emulsion particles. Then, the pre-emulsified monomer was continuously added dropwise over 3 hours, the reaction of the residual monomer was carried out for 3 hours, cooled to 40 ° C., adjusted to pH 5 with 14% ammonia water, and filtered with a 100 mesh wire net, An acrylic emulsion having a solid content of 50% was obtained.

Production Example Acrylic Emulsion (b) A mixture of 100 parts of the mixed monomer for the core and shell layers and the chain transfer agent (tDM) having the compositional ratios shown in Table 1 was separately weighed in advance, and 50 parts of distilled water was used for each. , 0.5 parts of sodium dodecylbenzene sulfonate was added dropwise under stirring to prepare a pre-emulsified monomer. Separately, 95 parts of distilled water and 0.1 part of sodium dodecylbenzene sulfonate were charged into a 1 liter flask, and the temperature was raised to 70 ° C. with stirring under a nitrogen blanket.
In order to form 0.5 parts of potassium persulfate and the seed of the emulsion, an equivalent mixed monomer of n-butyl acrylate, methyl methacrylate and hydroxyethyl methacrylate was charged and reacted for 30 minutes to form seeds of emulsion particles. Then, the pre-emulsified monomer for core was continuously added dropwise over 3 hours in proportion to the core / shell ratio shown in Table 1, and the residual monomer was reacted for 1 hour after the addition was completed. Subsequently, the emulsified monomer for shell was added dropwise over the same proportion as described above for 3 hours, and the reaction of the remaining monomer was carried out for 3 hours, followed by 40 ° C.
And cool to pH 5 with 14% aqueous ammonia,
It was filtered through a wire mesh of 00 mesh to obtain an acrylic emulsion having a solid content of 50%.

[0026]

[Table 1]

[0027]

[Table 2]

[0028]

[Table 3]

[0029]

[Table 4]

[0030]

[Table 5]

Examples 1 to 36 Acrylic emulsion (a) 10 obtained in Production Examples 1 to 9
To 0 part, 3.5 parts of 20% aqueous solution of Poval (Kuraray Co., Ltd., trade name, Kuraray Poval ^# 205, saponification degree 89
(Mole% and average degree of polymerization 1700 dissolved in water) were mixed with stirring. Then, 30 parts of flour (manufactured by Japan Flour Milling Co., Ltd., trade name, red peony (high gluten content product)) was mixed into 100 parts of the acrylic emulsion under stirring, and a 16% aqueous zinc ammonium carbonate solution (as zinc concentration) was added. 4.5%)
Alternatively, a 20% p-toluenesulfonic acid aqueous solution is added,
An adhesive for veneer decorative plywood having a viscosity of 5,000 to 10,000 cps was prepared. In addition, 100 parts of the acrylic emulsion (b) obtained in Production Examples 19 to 27 was mixed with 30 parts of the above wheat flour under stirring to prepare a 16% aqueous zinc ammonium carbonate solution (4.5% zinc concentration) or 20%. % Para-toluene sulfonic acid aqueous solution is added, and the viscosity is 5000 to 1000.
The adhesive was adjusted to 0 cps for veneer decorative plywood. In Examples 31 to 36, the acrylic emulsions (a) and (b) obtained in Production Examples 1 to 9 and 19 to 27 were used in combination, and 100 parts of the acrylic emulsion (a) was mixed with 1. 101.5 parts of 5 parts and 100 parts of the acrylic emulsion (b) were mixed with stirring. Next, 60 parts of the above wheat flour was mixed under stirring, and an aqueous solution of 16% zinc ammonium carbonate (4.5% zinc concentration) was added.
Alternatively, a 20% p-toluenesulfonic acid aqueous solution is added,
An adhesive for veneer decorative plywood having a viscosity of 5,000 to 10,000 cps was prepared.

Example 37 100 parts of the acrylic emulsion (a) obtained in Production Example 1 was mixed with 30 parts of the above flour and 10.0 parts of 20% p-toluenesulfonic acid with stirring to give a viscosity of 5000 to 10000.
It was adjusted to an adhesive for veneer decorative plywood with cps. (Example 5
(Excluding Povar aqueous solution)

This veneer veneer decorative plywood adhesive was applied with a spreader at 10 g per 12 mm thick plywood shank and covered with a 0.25 mm thick white oak veneer that had been previously immersed in water and pressed with a 115 ° C. heat press. 10 kg / c
It was pressed under m ² for 1 minute, cooled to room temperature, and baked and coated with aminoalkyd resin. The results of the evaluation tests shown below are shown in Table 2.

<Evaluation test> 1. Workability The presence or absence of fluidity when blending flour was visually observed and displayed as shown below. ◯: Easy to mix and has fluidity and sufficient roll coater coating is possible. Δ: Mixable, but roll coater can be coated although it has high viscosity and lacks fluidity. X: Mixing is difficult and powder is left as it is, and roll coater coating is not possible. Possible 2. Second-class immersion peeling test From the sample, a square piece having a side of 75 mm was cut into 4 pieces, immersed in hot water at 70 ° C for 2 hours, and then dried at 60 ° C for 3 hours to obtain a portion of the same adhesive layer which was not peeled off. The length was measured on each side. Judged according to the JAS conformity standard and displayed the number of passing pieces. The JAS conformity criterion is that the length of the non-peeling portion of the same adhesive layer is 50 mm or more on each side surface. 3. 1st type immersion peeling test A sample similar to the 2nd type immersion peeling test was immersed in boiling water for 4 hours, dried in a 60 ° C dryer for 20 hours, then again immersed in boiling water for 4 hours and dried in a 60 ° C dryer for 3 hours. Then, the same evaluation as above was performed and the same display was made. 4. Repeated cold heat test From the above sample, two pieces each having a square shape with a side of 15 cm were cut into two pieces, and then dried at 80 ° C. for 2 hours and at −20 ° C. for 2 hours as one cycle for 2 cycles (total 8 hours) and then at room temperature. After returning, the number of dry cracks on the surface of the veneer was measured and displayed. The JAS conformance standard means that the test piece does not crack, swell, or wrinkle. ○: No number of dry cracks per area △: 〃 1 to less than 5 places ×: 〃 5 or more places 5. Adhesive leaching contamination The easiness of peeling from the press plate immediately after hot pressing and the adhesive leaching on the surface of the veneer were observed and displayed as shown below. ◯: Good peeling from the press board and no leaching of adhesive on the surface of the veneer △: Good peeling from the press board, but some leaching of adhesive on the surface of the veneer ×: Hard to peel off from the press board and veneer There is seepage of adhesive on the surface. 6. Overall Judgment The judgment of pass / fail is displayed according to the JAS conformity criteria of Evaluation Tests 1 to 5. ◯: Pass JAS conformance standard X: Fail JAS conformance standard

[0035]

[Table 6]

[0036]

[Table 7]

Comparative Examples 1 to 21 Acrylic emulsions (a) obtained in Production Examples 10 to 15
In the same test as in Example, 3.5 parts of 20% Poval aqueous solution and 30 parts of wheat flour were mixed with stirring, and 16% concentration of zinc ammonium carbonate aqueous solution or 20% paratoluene sulfonic acid aqueous solution was added. The results obtained are shown in Table 3. The evaluation of Production Examples 16, 17 and 18 was stopped due to gelation. The acrylic emulsion (b) obtained in Production Examples 28 to 35 was blended with 30 parts of the same flour as in Example under stirring to prepare a 16% concentration aqueous solution of zinc ammonium carbonate, or
A 20% p-toluenesulfonic acid aqueous solution was mixed and subjected to the same test as in the example, and the results are shown in Table-3. The evaluations of Production Examples 36, 37 and 38 were stopped due to gelation.

Comparative Example 22 The same test as in Example 1 was carried out except that the 16% zinc ammonium carbonate aqueous solution was removed from Example 1, and the results are shown in Table 3. Comparative Example 23 20% p-toluenesulfonic acid of Example 4 was mixed with 25.0 parts of acrylic emulsion (a) in an amount of 25.0 and subjected to the same test as in Example 1 and the results are shown in Table 3. Comparative Example 24 A 16% aqueous zinc ammonium carbonate solution from Example 1 was subjected to the same test as in Example 1 except that the molar ratio of zinc to unsaturated carboxylic acid was 1.5, and the results are shown in Table 3.

Comparative Example 25 The acrylic emulsion (a) used in Example 1 was converted into styrene-butadiene latex (SBR) (manufactured by Mitsui Toatsu Chemicals, Inc., trade name Polylac 750, solid content 48%, viscosity 100 cps, pH 7). , Tg + 8 ℃, acrylic acid 2
%, N-methylolacrylic amide 2% modified), except that 16% zinc ammonium carbonate and wheat flour were blended in the same manner as in Example 1 and subjected to the same test as in Example 1 and the results are shown in Table 3. . Comparative Example 26 A 16% aqueous solution of zinc ammonium carbonate was removed from the composition of Comparative Example 25, and an amino-based condensation resin (Mitsui Toatsu Chemicals, Inc., trade name Euroid 310, solid content 50%, viscosity 190 cps) was used instead. The mixture of parts was subjected to the same test as in Example 1 and the results are shown in Table 3.

[0040]

[Table 8]

[0041]

[Table 9]

[0042]

The method for producing a veneer decorative plywood of the present invention uses an acrylic emulsion in the adhesion between the plywood and the veneer, and does not have the use of an amino-based condensation resin as in conventional adhesives to provide hot water resistance. And excellent in boiling resistance and the like. Further, there is no problem in working environment, and it is excellent in miscibility with wheat flour used as a bulking agent. In other words, it has fluidity, including mechanical stability during roll coater application, workability, and stable application to adherends, and especially leaching of adhesive onto the sliced veneer surface and contamination and cracking. Since the incidence is low, it has a high practical value as a method for producing veneer decorative plywood.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Akihiro Takahashi 1190 Kasama-cho, Sakae-ku, Yokohama-shi Kanagawa Mitsui Toatsu Chemical Co., Ltd. Incorporated (72) Inventor Toshiaki Mutsuya 1190 Kasama-cho, Sakae-ku, Yokohama-shi, Kanagawa Mitsui Toatsu Chemical Co., Ltd.

Claims (7)

[Claims] 1. A single layer structure acrylic emulsion (a) and / or core layer which is a copolymer of an aromatic vinyl monomer, an unsaturated carboxylic acid ester monomer, an amide group-containing acrylic monomer and an unsaturated carboxylic acid. Is a copolymer of an aromatic vinyl monomer, an unsaturated carboxylic acid ester monomer, an amide group-containing acrylic monomer and an unsaturated carboxylic acid, and the shell layer is an aromatic vinyl monomer, an unsaturated carboxylic acid ester monomer and an unsaturated carboxylic acid A method for producing a veneer decorative plywood, characterized by using an adhesive prepared by mixing zinc ammonium carbonate or strong acid (c) as an essential component in an acrylic emulsion (b) having a two-layer structure, which is a copolymer of . 2. The glass transition temperature (Tg) of the acrylic emulsion (a) is −30 to + 90 ° C., and the glass transition temperature (Tg) of the core layer of the acrylic emulsion (b) is −.
The glass transition temperature (Tg) of the shell layer is 10 to + 90 ° C, and the glass transition temperature (Tg) is -50 to + 20 ° C. 3. The monomer composition ratio of the core layer / shell layer of the acrylic emulsion (b) is 30 to 70/70 to 30 parts by weight per 100 parts by weight of the total amount of the monomers. Method for manufacturing veneer decorative plywood. 4. The acrylic emulsion (a) comprises 1 to 6 parts by weight of an amide group-containing acrylic monomer and 1 part of an unsaturated carboxylic acid per 100 parts by weight of the total amount of constituent monomers.
10 to 10 parts by weight, and the core layer of the acrylic emulsion (b) has an amide group-containing acrylic monomer and an unsaturated carboxylic acid in an amount of 1 to 6 per 100 parts by weight of the total amount of core layer-constituting monomers. Parts by weight, the shell layer, per 100 parts by weight of the total amount of monomers constituting the shell layer,
The method for producing a veneer decorative plywood according to claim 1, wherein 1 to 10 parts by weight of the unsaturated carboxylic acid is copolymerized. 5. Acrylic emulsions (a) and (b)
The method of manufacturing a veneer decorative plywood according to claim 1, wherein the pH is adjusted to a range of pH 4 to 6 with ammonia water. 6. The ammonium zinc carbonate (c) comprises water, ammonium carbonate, zinc oxide and aqueous ammonia 15.
The method for producing a veneer decorative plywood according to claim 1, which is a transparent aqueous solution having a concentration of -20% by weight and is adjusted to pH 9-10. 7. The strong acid (c) is a dissociation constant (pKa) 3 of the acid.
The method for manufacturing a veneer decorative plywood according to claim 1, wherein: