JPH11279506A - Method for producing aqueous adhesive and laminate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an aqueous adhesive excellent in bonding strength, especially initial bonding strength and to provide a preparation method of the aqueous adhesive in which a stability in the preparation of a base resin is high and the base resin can be prepared at a relatively low temperature with a low energy cost and high productivity. SOLUTION: A base resin is prepared by adding (B) a polyvinyl alcohol powder which has a solubility in water of 50 wt.% or more after 1 hour of immersion in water at 40 deg.C and whose 1 wt.% aqueous solution has a surface tension of 45 mN/m or more with (A) an aqueous emulsion and further blended with (C) a polyvalent isocyanate-based compound. The base resin is preferably prepared by blended (A) and (B) under conditions of low temperatures of 60 deg.C or below.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a water-based adhesive, and more particularly, to a method for producing a water-based adhesive, which has excellent adhesive strength, especially initial adhesive strength, high stability at the time of manufacturing the main agent, and which can be used at relatively low temperatures. The present invention relates to a method for producing a water-based adhesive which can be produced and has low energy costs and high productivity.

[0002]

2. Description of the Related Art Unlike a conventional aminoplast adhesive, an adhesive containing a water-soluble polymer, an aqueous emulsion and an isocyanate compound as main components does not generate formalin, and is pressed at room temperature for a relatively short time. Alone, for extremely high adhesive strength and water resistance,
It has been awarded as an adhesive for plywood and various plastics (for example, see JP-A-48-94739, 50-90).
69139). Under these circumstances, JIS has recently been established for wood adhesives comprising an aqueous polymer and an isocyanate compound. Also, in recent years, this type of adhesive has attracted attention as an adhesive that is more friendly to the human body and the environment than amino resin-based adhesives, especially for plywood manufacturing, since there is virtually no formalin generation from the adhesive. I have.

[0003] An adhesive comprising a water-soluble polymer, an aqueous emulsion and an isocyanate compound has heretofore been used as a main ingredient mainly comprising an aqueous emulsion obtained by adding an aqueous solution obtained by heating and dissolving an aqueous polymer, polyvinyl alcohol, to an aqueous emulsion. Before use, an isocyanate compound was added as a crosslinking agent before use. However, with the expansion of production lines and the scale of production, there is an increasing need for more efficient production of main ingredients. Therefore, if the base material can be produced at a relatively low temperature, the energy cost for dissolving the water-soluble polymer into an aqueous solution is reduced, and the productivity of the adhesive base material is increased, so that the base material can be produced efficiently. Is possible. In particular, if a water-soluble polymer can be added to an aqueous emulsion and dissolved at a relatively low temperature in a short time, not only productivity and workability will be remarkably improved, but also a place where an adhesive is used, that is, on-site. A further merit arises because the adhesive can be easily compounded at the same time. Further, the above-mentioned conventional adhesives do not sufficiently satisfy the initial adhesive strength, and further improvement in the initial adhesive strength is desired.

[0004]

DISCLOSURE OF THE INVENTION The present invention solves the above-mentioned problems in the prior art, and has a high stability at the time of manufacturing the main agent, and can reduce the energy cost because the main agent can be manufactured at a relatively low temperature. It is another object of the present invention to provide a method for producing a water-based adhesive having high productivity, and to provide a water-based adhesive having excellent bonding strength, particularly excellent initial bonding strength, and further excellent boiling repetition strength.

[0005]

The object of the present invention is to provide (A) an aqueous emulsion and (B) a solubility of 50% by weight or more after immersion in water at 40 ° C. for 1 hour, and a surface tension of a 1% by weight aqueous solution. This is achieved by providing a method for producing an aqueous adhesive in which a main ingredient is prepared by blending polyvinyl alcohol powder having a viscosity of 45 mN / m or more and (C) a polyvalent isocyanate compound. The method for producing the adhesive is more preferably carried out by blending (A) and (B) and preparing the main ingredient under a condition of 60 ° C. or lower.
Further, the method for producing the adhesive is more preferably performed by using polyvinyl alcohol powder having a particle size of 500 μm or less as (B) polyvinyl alcohol powder.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION The aqueous emulsion (A) constituting the aqueous adhesive of the present invention may be a known anionic, cationic, amphoteric, nonionic low molecular surfactant or various polyvinyl alcohols as a dispersant. Emulsion polymerization type obtained by emulsion polymerization of radically polymerizable ethylenically unsaturated monomers and diene monomers in an aqueous solution containing one or more water-soluble polymers (protective colloids) such as hydroxyethyl cellulose. Aqueous emulsions obtained by the post-emulsification method of polymers represented by aqueous emulsions and polyurethane emulsions may be used alone or in combination of two or more.

The ethylenically unsaturated monomers constituting the dispersoid of the aqueous emulsion (A) constituting the aqueous adhesive of the present invention include olefins such as ethylene, propylene and isobutene, vinyl chloride, vinylidene chloride, and fluorine. Halogenated olefins such as vinyl chloride and vinylidene fluoride, vinyl esters such as vinyl formate, vinyl acetate, vinyl propionate, vinyl versatate and vinyl pivalate, acrylic acid, methyl acrylate, ethyl acrylate, and acrylic acid n -Propyl, i-propyl acrylate, n-butyl acrylate, i-butyl acrylate, t-butyl acrylate, 2-ethylhexyl acrylate,
Acrylic esters such as dodecyl acrylate, octadecyl acrylate, hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxybutyl acrylate, hydroxypropyl trimethylammonium acrylate, methacrylic acid, methyl methacrylate, ethyl methacrylate, methacrylic acid n-propyl,
I-propyl methacrylate, n-butyl methacrylate,
I-butyl methacrylate, t-butyl methacrylate, 2-ethylhexyl methacrylate, dodecyl methacrylate, octadecyl methacrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate, hydroxybutyl methacrylate, hydroxypropyl methacrylate trimethylammonium chloride, etc. Methacrylic esters, acrylamide, methacrylamide, N-
Methylol acrylamide, N, N-dimethylacrylamide, acrylamide-2-methylpropanesulfonic acid and its sodium salt acrylamide, trimethyl- (3-acrylamido-3-dimethylpropyl)-
Ammonium chloride, 3-acrylamidopropyltrimethylammonium chloride, 3-methacrylamidopropyltrimethylammonium chloride, N-
Nitriles such as methylacrylamide, N-ethylacrylamide, diacetoneacrylamide, acrylonitrile, methacrylonitrile, allyl compounds such as allyl acetate and allyl chloride, styrene, α-methylstyrene, P-
Examples include methylstyrenesulfonic acid and styrene-based monomers such as sodium and potassium salts thereof, and other N-vinylpyrrolidone, and examples of the diene-based monomer include butadiene, isoprene, and chloroprene.
Among these aqueous emulsions, an aqueous emulsion of a polymer containing a diene such as butadiene as a monomer unit, such as an aqueous emulsion of a styrene-butadiene copolymer; a monomer containing (meth) acrylic acid ester as a monomer unit Aqueous emulsion, for example, methacrylic acid ester-acrylic acid ester copolymer aqueous emulsion; polymer aqueous emulsion containing vinyl ester such as vinyl acetate as a monomer unit, for example, ethylene-vinyl acetate copolymer aqueous emulsion Are preferred.

In carrying out the emulsion polymerization for obtaining the emulsion polymerization type aqueous emulsion constituting the aqueous adhesive of the present invention, the above-mentioned monomer is added in the presence of water, the above-mentioned dispersant and a polymerization initiator. A normal emulsion polymerization method such as heating or stirring, which is added temporarily or continuously, can be carried out,
In addition, a method in which a monomer previously mixed and emulsified with an aqueous solution of a dispersant may be continuously added. The polymerization initiator is not particularly limited and includes, for example, potassium persulfate, sodium persulfate, ammonium persulfate, hydrogen peroxide, 2,2′-azobis (2-amidinopropane) dihydrochloride, cumene hydropar Oxide, benzoyl peroxide, isopropylbenzene peroxide or the like is used alone or in a redox system in combination with a reducing agent such as sodium bisulfite, tartaric acid, L-ascorbic acid, formaldehyde sodium sulfoxylate and ferrous sulfate.

The amount of the dispersant to be used in the aqueous emulsion (A) constituting the aqueous adhesive of the present invention is not particularly limited, whether it is an emulsion polymerization type aqueous emulsion or a post-emulsion type aqueous emulsion. Parts by weight is 0.2 to 50 parts by weight, preferably 0.5 to 20 parts by weight. When the amount of the dispersant is less than 0.2 parts by weight, the emulsion stability and the polymerization stability are reduced, and when the amount is more than 50 parts, the viscosity stability in the compounding of the adhesive may be reduced.

[0010] The polyvinyl alcohol (PVA) powder (B) used in the method for producing an aqueous adhesive of the present invention comprises 40
Solubility in water at 50 ° C. for 1 hour is 50% by weight or more, and the surface tension of a 1% by weight aqueous solution of PVA is 45 mN
/ M or more is important. By using a PVA powder that satisfies this requirement, as is clear from the examples described below, even when the main ingredient is prepared at a low temperature, there is no or little aggregation, and therefore the main ingredient is prepared with low energy. can do. Further, the low-temperature viscosity stability of the base material thus obtained is excellent. Furthermore, an adhesive obtained by blending a polyvalent isocyanate with this main agent is particularly excellent in initial adhesive strength and further excellent in repeated boiling adhesive strength. A preferred solubility is at least 60% by weight, more preferably at least 70% by weight. Further, a preferable surface tension is 50 mN / m or more, and more preferably 50 to 70 mN / m.
mN / m.

In the case of using a PVA powder having a solubility of less than 50% by weight or a surface tension of less than 45 mN / m and preparing the base material at a low temperature, agglomeration occurs as is apparent from a comparative example described later. Or PVA remains undissolved, and normal adhesion. The adhesive strength after repeated boiling may not be sufficient. PV having such solubility
A can be obtained by appropriately selecting the degree of saponification, degree of polymerization, particle size, and the like of PVA, and PVA having the above surface tension can be obtained by appropriately selecting the degree of saponification and degree of polymerization. As described above, PVA having the above-mentioned solubility and surface tension can be obtained by the above-mentioned various factors.
From the range of 0 to 96 mol%, the degree of polymerization is 100 to
8000, preferably from the range of 400 to 4000. It is important that the PVA is a powder, and its particle size is preferably selected from a range of 500 μm or less. By using PVA powder, there is no particular need to add PVA to water and heat it to form an aqueous solution.
The energy cost is reduced, and an adhesive having excellent initial adhesive strength and further excellent boiling repetition strength can be obtained as is apparent from the examples described later.

As the PVA powder satisfying the above conditions, for example, in the case of PVA having a degree of polymerization of 1700, PVA having a saponification degree of 87 mol% or more, preferably 94 mol% or more and a particle size of 200 or less is suitable. Is exemplified. Here, the solubility refers to a filtration rate (% by weight) calculated by adding a PVA to water at 40 ° C. so as to be 10% by weight, stirring the mixture for 1 hour, and then filtering the residue with a 200 mesh wire mesh. The surface tension refers to a value {mN (millinewton) / m (meter)} obtained by measuring a 1% by weight aqueous PVA solution (20 ° C.) with a “Wilhelmi surface tensiometer”.

[0013] Such PVA can be obtained by various methods. For example, a polymer obtained by polymerizing a vinyl ester by a conventionally known polymerization method such as bulk polymerization, solution polymerization, suspension polymerization, emulsion polymerization, or the like is used. Alternatively, it can be obtained by saponifying to a saponification degree of 70 mol% or more under acid conditions. The saponification method at this time is not particularly limited, and a conventionally known belt method or slurry method can be adopted. Examples of the vinyl ester include vinyl formate, vinyl acetate, vinyl propionate, vinyl pivalate and the like, with vinyl acetate being preferred.

Further, as the (B) PVA powder of the present invention,
It is best to use a powder having a particle size of 500 μm or less and mix it with the aqueous emulsion (A) to prepare a main ingredient in order to achieve the object of the present invention. The PVA particle size is 300
μm or less, more preferably 20 μm or less.
0 μm or less, optimally 100 μm or less. The lower limit of the particle size is preferably at least 40 μm, more preferably at least 50 μm. By using the PVA powder having such a particle size, the base material can be prepared at low energy cost, and a high-performance adhesive can be obtained. The method for obtaining such PVA powder is not particularly limited, and for example, those obtained by forcibly pulverizing various kinds of wet or dry pulverizers after saponification or those obtained by physically sieving fine powder naturally generated in the process are usually used. . P at that time
The conditions for drying the VA powder are not particularly limited, but are preferably 80 ° C. or lower, more preferably 50 ° C. or lower, from the viewpoint of the dissolution rate of the PVA powder. Here, the particle size is an average particle size, and is expressed as a particle size (median size) at a point where the integrated value of the weight for each fraction measured by a JIS sieve becomes 50%.

The (B) PVA powder used in the method for producing an aqueous adhesive of the present invention may be a copolymer of an ethylenically unsaturated monomer as long as the effects of the present invention are not impaired. Such ethylenically unsaturated monomers include, for example, ethylene, propylene, isobutene, acrylic acid,
Methacrylic acid, (phthalic anhydride), maleic anhydride, maleic anhydride, itaconic acid, acrylonitrile, methacrylonitrile, acrylamide, methacrylamide, trimethyl- (3-acrylamido-3-dimethylpropyl) -ammonium chloride, acrylamide- 2-methylpropanesulfonic acid and its sodium salt, ethyl vinyl ether, butyl vinyl ether, N-vinyl pyrrolidone, vinyl chloride, vinyl bromide, vinyl fluoride, vinylidene chloride, vinylidene fluoride, tetrafluoroethylene, sodium vinyl sulfonate, allyl And sodium sulfonate. Further, in the presence of a thiol compound such as thiolacetic acid or mercaptopropionic acid, a terminal ester modified PV obtained by polymerizing a vinyl ester monomer such as vinyl acetate and saponifying it.
A can also be used.

The above (A) aqueous emulsion is added to (B) PV
The (C) polyvalent isocyanate compound is blended with the base material to which the A powder has been added. Here, the polyvalent isocyanate compound (C) is a compound having two or more isocyanate groups in the molecule. For example, tolylene diisocyanate (TD)
I); hydrogenated TDI; trimethylolpropane-TDI
Adduct (for example, manufactured by Bayer, trade name: Desmod
ur L); triphenylmethane triisocyanate;
Methylene bisdiphenyl isocyanate (MDI); hydrogenated MDI; polymerized MDI; hexamethylene diisocyanate; xylylene diisocyanate; 4,4-dicyclohexylmethane diisocyanate; In addition, a prepolymer having a terminal group having an isocyanate group, which is previously polymerized with an excess of polyisocyanate in a polyol, may be used. In addition, (C) the polyvalent isocyanate compound may be directly added to the main ingredient, or may be diluted with various solvents that do not substantially react with the isocyanate, for example, dibutyl phthalate or toluene. By blending this (C) polyvalent isocyanate compound, excellent adhesive strength and boiling repetition strength are imparted.

In the aqueous adhesive of the present invention, the mixing ratio of (A) the aqueous emulsion and (B) the PVA powder is (A) / (B) = 99.5 / 0.5 to 50 in terms of solids weight ratio. /
50 is usually adopted as a preferable range. Also,
(C) The compounding ratio of the polyvalent isocyanate compound is {(A) + (B)} / (C) = 100 / 0.5 in terms of solid content weight ratio.
１００100/100, preferably 100
/ 1 to 100/80 are more preferable. If the polyvalent isocyanate compound is less than this range, the adhesive strength,
When the boiling repetition strength is lowered and the boiling repetition strength is increased beyond this range, there is a problem that the pot life after blending the polyvalent isocyanate becomes short, which is not practical.

In the aqueous adhesive of the present invention, starch, modified starch, oxidized starch, sodium alginate, carboxymethylcellulose, methylcellulose, hydroxymethylcellulose, maleic anhydride-isobutene copolymer, maleic anhydride may be used, if necessary. Water-soluble polymer compounds such as acid-styrene copolymer and maleic anhydride-methylvinyl ether copolymer, and urea-formalin resin, urea-melamine-formalin resin, phenol-formalin resin, etc., are generally used as adhesives. Thermosetting resins can also be used as appropriate. Further, the water-based adhesive of the present invention includes fillers such as clay, kaolin, talc, calcium carbonate, and wood flour, fillers such as flour, pigments such as titanium oxide, and various other additives such as preservatives and rust preventives. Additives can be appropriately added as needed.

Further, the present invention relates to an aqueous adhesive comprising (A) an aqueous emulsion, (B) a PVA powder added thereto, a main agent prepared at 60 ° C. or lower, and (C) a polyvalent isocyanate. A manufacturing method is also provided. The production method of the present invention has a particularly high stability at the time of production of the main agent, and can produce the main agent at a relatively low temperature. Therefore, an aqueous adhesive having low energy cost and high productivity can be obtained. The main ingredient is prepared by blending the PVA powder with the aqueous emulsion under the conditions of preferably 50 ° C. or lower, more preferably 45 ° C. or lower. A preferred lower limit is 5 ° C or higher, more preferably 10 ° C or higher. Furthermore, when the PVA powder is added to an aqueous emulsion, if the swollen PVA particles are in a so-called mamaco state in which the particles are aggregated and the solubility may be reduced, for example, an inorganic material such as calcium carbonate is previously blended with PVA. Is also preferably used.

The aqueous adhesive of the present invention is used for bonding various adherends, and various laminates can be obtained. Examples of the adherend include wood, plywood, paper, fiber, various plastics, and the like, and examples of the laminate include a wooden laminate and a plywood laminate. The application amount may be appropriately selected according to various situations. Examples of the coating method include coating with a brush and coating with a roll. Drying after applying the adhesive may be heating drying from room temperature to 200 ° C., but the adhesive of the present invention exhibits sufficient adhesive strength even when dried at room temperature.

[0021]

The present invention will be described more specifically below with reference to examples and comparative examples. In Examples and Comparative Examples,
“Parts” and “%” are based on weight unless otherwise specified.

Example 1 Ethylene-vinyl acetate copolymer emulsion (OM-420)
0, solid content 55%, made by Kuraray) and PVA powder (1) (degree of polymerization 1700, degree of saponification 95 mol%, particle size 90 μm, solubility 8)
8% by weight and a surface tension of 55 mN / m) were added in an amount of 5 parts per 100 parts by weight of the solid content of the emulsion, followed by stirring at 40 ° C. for 1 hour to prepare a main ingredient. 15 parts of polymethylene polyphenyl isocyanate (manufactured by Nippon Polyurethane Co., Ltd., trade name: Millionate MR-100) was added to 100 parts by weight of the solid content of the main agent to prepare an adhesive. Using this, a test was performed under the following conditions. The results are shown in Tables 1 to 3.

[Test conditions] Low-temperature viscosity stability of main agent: After the main agent was left at 5 ° C. for 7 days, the appearance was observed. ：: No change in appearance ×: Gelation 2. State of main agent:-Visual observation: Observed a state in which the main agent was applied thinly on a glass plate. ○: No aggregates ×: Many aggregates Adhesion test An adhesion test was performed using the above adhesive under the following conditions. Substrate: birch / birch (masa) water content 8% Application amount: 250 g / m ² (both sides applied) Deposition time: 1 minute Pressing conditions: 20 ° C., 24 hours, pressure 10 kg / cm
² (Normal strength, repeated boiling test specimens only) Measure the compressive shear adhesive strength according to JIS K-6852 Normal strength: Measured as it is after curing for 7 days at 20 ° C. Repeated boiling strength: After curing for 7 days at 20 ° C., test The pieces were immersed in boiling water for 4 hours, dried in air at 60 ° C. for 20 hours, immersed in boiling water for 4 hours, immersed in water at room temperature until cooled, and subjected to the test in a wet state. did. Initial adhesive strength: 10 kg / c at 20 ° C after bonding
It was pressed for 10 minutes at a pressure of m ² and measured immediately.

Example 2 In a glass polymerization vessel equipped with a stirrer, a nitrogen inlet, and a thermometer, PVA having a mercapto group at a terminal (degree of polymerization: 5
00, saponification degree 88.2 mol%, mercapto group content 4.
5 × 10 ⁻⁵ mol / g-PVA) and 5 parts of ion-exchanged water
0 parts were added and dissolved by heating. After cooling, the pH was adjusted to 3.0 with sulfuric acid, and then the temperature was raised to 70 ° C. while performing nitrogen bubbling. With stirring at 150 rpm, 10 parts of methyl methacrylate and 10 parts of n-butyl acrylate were added, and 10 parts of a 1% aqueous solution of potassium persulfate was further added to initiate polymerization. One hour after the start of the polymerization, methyl methacrylate 40
Parts, 38 parts of n-butyl acrylate and 2 parts of hydroxyethyl methacrylate were uniformly dropped over 2 hours. After completion of the dropwise addition, the temperature was raised to 80 ° C., and the mixture was left for 1 hour. Methyl methacrylate-n-acrylic acid having a solid content of 48.5%
A butyl-hydroxyethyl methacrylate copolymer emulsion (acrylic Em) was obtained. PVA powder (1) was added to this emulsion with an emulsion solid content of 100.
5 parts per part by weight was added and stirred at 40 ° C. for 1 hour to prepare a main ingredient. An adhesive was prepared by adding 15 parts of polymethylene polyphenylisocyanate (manufactured by Nippon Polyurethane Co., Ltd., trade name: Millionate MR-100) to 100 parts by weight of the main agent solid content. Using this, the same evaluation as in Example 1 was performed. The results are shown in Tables 1 to 3.

Example 3 Styrene-butadiene copolymer emulsion (DL-6)
12, a solid content concentration of 50%, manufactured by Asahi Kasei), 5 parts of PVA powder (1) was added per 100 parts by weight of the emulsion solid content, and the mixture was stirred at 40 ° C. for 1 hour to prepare a main ingredient. Polymethylene polyphenylisocyanate (manufactured by Nippon Polyurethane Co., trade name: Millionate M)
R-100) was added to prepare an adhesive. Using this, the same evaluation as in Example 1 was performed. Table 1 shows the results
3 are shown.

Example 4 In Example 3, PVA powder (1) was used instead of PVA powder (1).
Powder (2) (degree of polymerization 550, degree of saponification 88 mol%, particle size 2
(00 μm, solubility 90% by weight, surface tension 50 mN / m)
A main agent was prepared in the same manner as in Example 3 except that the following was used. 15 parts by weight of polymethylene polyphenyl isocyanate (manufactured by Nippon Polyurethane Co., trade name: Millionate MR-100) were added to 100 parts by weight of the solid content of the main agent. Prepared. Using this, the same evaluation as in Example 1 was performed. The results are shown in Tables 1 to 3.

Example 5 In Example 3, PVA powder (1) was used instead of PVA powder (1) per 100 parts by weight of emulsion solids.
5 parts and PVA powder (3) (degree of polymerization 1700, degree of saponification 88
(Mole%, particle size 100 μm, solubility 95 wt%, surface tension 52 mN / m) A main agent was prepared in the same manner as in Example 3 except that 2.5 parts by mass was used. An adhesive was prepared by adding 15 parts of Polyurethane Co., trade name: Millionate MR-100). Using this, the same evaluation as in Example 1 was performed. The results are shown in Tables 1 to 3.

Example 6 A base material was prepared in the same manner as in Example 3 except that the PVA powder (1) was used in an amount of 10 parts per 100 parts by weight of the solid content of the emulsion. 15 parts of phenyl isocyanate (manufactured by Nippon Polyurethane Co., trade name: Millionate MR-100) was added to prepare an adhesive. Using this, the same evaluation as in Example 1 was performed. The results are shown in Tables 1 to 3.

Example 7 A base material was prepared in the same manner as in Example 3 except that the PVA powder (1) was used in an amount of 1 part per 100 parts by weight of the solid content of the emulsion. 15 parts of phenyl isocyanate (manufactured by Nippon Polyurethane Co., trade name: Millionate MR-100) was added to prepare an adhesive. Using this, the same evaluation as in Example 1 was performed. The results are shown in Tables 1 to 3.

Example 8 An adhesive was prepared in the same manner as in Example 3, except that 3 parts of polymethylene polyphenyl isocyanate (manufactured by Nippon Polyurethane Co., Ltd., trade name: Millionate MR-100) was used. Using this, the same evaluation as in Example 1 was performed. The results are shown in Tables 1 to 3.

Example 9 The procedure of Example 3 was repeated, except that PVA powder (1) was added with 5% by weight of calcium carbonate in advance. The results are shown in Tables 1 to 3.

Comparative Example 1 In Example 3, PVA powder (4) (polymerization degree 170
0, saponification degree 70 mol%, particle size 600 μm, solubility 99% by weight, surface tension 42 mN / m)
A base was prepared in the same manner as in Example 3 except that 5 parts were used per 100 parts by weight, and 15 parts of polymethylene polyphenylisocyanate (manufactured by Nippon Polyurethane Co., trade name: Millionate MR-100) was added to 100 parts by weight of the base material solids. Then, an adhesive was prepared. Using this, the same evaluation as in Example 1 was performed. The results are shown in Tables 1 to 3.

Comparative Example 2 In Example 3, the PVA powder (5) (polymerization degree 170
0, saponification degree 95 mol%, particle size 600 μm, solubility 45 wt%, surface tension 55 mN / m)
A base was prepared in the same manner as in Example 3 except that 5 parts were used per 100 parts by weight, and 15 parts of polymethylene polyphenylisocyanate (manufactured by Nippon Polyurethane Co., trade name: Millionate MR-100) was added to 100 parts by weight of the base material solids. Then, an adhesive was prepared. Using this, the same evaluation as in Example 1 was performed. The results are shown in Tables 1 to 3.

COMPARATIVE EXAMPLE 3 In Example 3, instead of adding 5 parts by weight of PVA powder (1) per 100 parts by weight of emulsion solids,
The VA powder (1) was placed in water at 95 ° C., and stirred for 1 hour.
An adhesive was prepared in the same manner as in Example 3 by adding the PVA solid content to 5 parts by weight per 00 parts by weight.
Using this, the same evaluation as in Example 1 was performed. The results are shown in Tables 1 to 3.

Comparative Example 4 In Example 3, instead of adding 5 parts by weight of PVA powder (1) per 100 parts by weight of emulsion solids,
VA powder (6) (degree of polymerization 1700, degree of saponification 98 mol%, particle size 600 μm, solubility 21% by weight, surface tension 60
mN / m) in 95 ° C. water and stirred for 1 hour to obtain P
A VA aqueous solution (concentration 10%) was added to an emulsion solid content 100
The adhesive was added so that the PVA solid content was 5 parts by weight per part by weight, and an adhesive was prepared in the same manner as in Example 3. Using this, the same evaluation as in Example 1 was performed. Table 1 shows the results
3 are shown.

[0036]

[Table 1]

[0037]

[Table 2]

[0038]

[Table 3]

[0039]

According to the present invention, it is possible to provide a water-based adhesive having excellent adhesive strength, particularly excellent initial adhesive strength, and excellent boiling repetition strength. Since the main agent can be produced at a relatively low temperature, it is possible to provide a method for producing an aqueous adhesive which has low energy cost and high productivity.

Claims (6)

[Claims] 1. A polyvinyl alcohol having (A) an aqueous emulsion and (B) a solubility of 50% by weight or more after immersion in water at 40 ° C. for 1 hour and a surface tension of a 1% by weight aqueous solution of 45 mN / m or more. A method for producing a water-based adhesive, comprising mixing a powder to prepare a main agent, and then mixing (C) a polyvalent isocyanate compound with the main agent. 2. The method for producing an aqueous adhesive according to claim 1, wherein (A) and (B) are blended to prepare a main ingredient under a condition of 60 ° C. or lower. 3. The method for producing an aqueous adhesive according to claim 1, wherein (B) the polyvinyl alcohol powder is a polyvinyl alcohol powder having a particle size of 500 μm or less. 4. A laminate obtained by using the adhesive according to any one of claims 1 to 3. 5. A wooden laminate obtained by using the adhesive according to any one of claims 1 to 3. 6. A plywood laminate obtained by using the adhesive according to any one of claims 1 to 3.