JPH1025329A - Emulsion composition and adhesive - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an emulsion composition comprising a specific aqueous emulsion and a polyvalent isocyanate compound, excellent in the storage stability, adhesive strength and water resistance of the main agent and capable of giving adhesive agents good in initial adhesivity. SOLUTION: This emulsion composition comprises (A) an aqueous emulsion obtained by emulsion-polymerizing (ii) one or more kinds of unsaturated monomers selected from ethylenic unsaturated monomers (e.g. vinyl acetate) and dienic monomers (e.g. butadiene) in the presence of (i) a modified polyvinyl alcohol having structural units of the formula [(n) is 1-20 ] as a dispersant and (B) a polyvalent isocyanate compound (e.g. polymethylenepolyphenylisocyanate). The components A and B are preferably compounded in an A/B solid content ratio of 95/5 to 20/80.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to compositions and adhesives. More particularly, the present invention relates to a composition useful for various uses, particularly, an adhesive, and an adhesive comprising the composition and having excellent initial adhesiveness, adhesive strength, and water resistance.

[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 compacted at room temperature for a relatively short time. Alone, extremely high adhesive strength and water resistance can be obtained, so that it has been awarded as an adhesive for wood (for example, JP-A-48-947).
39, 50-69139). Further, as a similar adhesive, an aqueous adhesive composition comprising a copolymer emulsion of a hydroxyl group-containing monomer such as allyl alcohol, 2-hydroxyethyl acrylate, N-methylolated acrylamide and vinyl acetate, and a divalent isocyanate compound (JP-A-49-26346), a polyvinyl acetate emulsion using polyvinyl alcohol as a dispersant (protective colloid) and a water-resistant adhesive composition comprising a polyvalent isocyanate compound (JP-A-3-33178)
Publication). Additionally, the emulsion polymer comprises an emulsion polymer stabilized with polyvinyl alcohol, the first step producing a vinyl acetate copolymer having a glass transition temperature in the range of 10 to 40 ° C, and the second step comprising 50 to 120 ° C. Adhesives produced by a two-stage polymerization process comprising producing a methyl methacrylate copolymer having a glass transition temperature of 0 ° C., wherein the ratio of vinyl acetate copolymer to methyl methacrylate copolymer ranges from 10: 1 to 10: 6. (JP-A-2-302485). Under these circumstances, JIS has recently been established for wood adhesives comprising an aqueous polymer and an isocyanate compound.

However, with the expansion of the objects to be bonded,
In some cases, there is a need to further improve the current level of adhesive performance. Specifically, there is a case where a higher degree of durability is required as a structural adhesive, and a further improvement in initial adhesiveness is also required for individual applications. In the latter case, polyvinyl alcohol (hereinafter referred to as PVA)
When a water-based emulsion of a vinyl acetate-based resin having a dispersant (which may be abbreviated as above) is frequently used, the initial adhesion is improved, but the water resistance is not sufficient. In addition, polyvinyl alcohol, which is an aqueous polymer blended in this type of adhesive, also greatly contributes to the performance of the adhesive. Specifically, when PVA having completely saponified or acetoacetyl groups is used, although the water-resistant adhesiveness is improved, the low-temperature viscosity stability of the base agent composed of the aqueous emulsion and PVA and the low-temperature viscosity stability as compared with the case of using partially saponified PVA are improved. There was a problem that storage stability deteriorated. Although the conventional adhesives as described above can exhibit a certain level of performance, those which have satisfactory performance in all respects of viscosity stability, initial adhesiveness, adhesive strength and water resistance of the main agent are not available. It has not been developed yet.

[0004]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems in the prior art, and provides an adhesive excellent in storage stability, adhesive strength and water resistance of a base material, and with good initial adhesiveness. The purpose is to do so.

[0005]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies on the above-mentioned objects, and as a result, (A) using a modified polyvinyl alcohol having a structural unit represented by the following chemical formula 2 as a dispersant: , An aqueous emulsion obtained by emulsion polymerization of one or more unsaturated monomers selected from ethylenically unsaturated monomers and diene monomers, and a composition comprising (B) a polyvalent isocyanate compound And completed the present invention.

[0006]

Embedded image (N: integer of 1 to 20)

[0007] The present invention also provides the above composition, and also provides an adhesive comprising the composition. Further, the present invention also provides a wood product obtained by bonding with the above-mentioned adhesive.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION It is essential that a modified PVA used as a dispersant for an aqueous emulsion constituting the composition of the present invention has the structural unit of the above formula (2). N in the above structural unit is an integer of 1 to 20, preferably 1 to 5, and more preferably 1 or 2. Examples of the above structural units include 2-methyl-2-propen-1-ol, 3
And a structural unit derived from a monomer such as -methyl-3-buten-1-ol. The content of the structural unit of Chemical Formula 2 is preferably 0.1 to 20 mol%,
~ 15 mol% is more preferred. The above-mentioned modified PVA which is a dispersant for the aqueous emulsion constituting the composition of the present invention.
Is obtained by saponifying a copolymer of a vinyl ester and the above monomer. Examples of the vinyl ester include vinyl formate, vinyl acetate, vinyl propionate, vinyl pivalate and the like, with vinyl acetate being preferred.

The modified PVA 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 acid, (anhydrous) 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, sodium allyl sulfonate, and the like. Further, in the presence of a thiol compound such as thiolacetic acid or mercaptopropionic acid, a terminal ester-modified PVA obtained by copolymerizing ethylene with a vinyl ester monomer such as vinyl acetate and saponifying it can also be used. . The modified PVA of the present invention is most preferably modified only by the structural unit of the above formula (2). In the case where the modified PVA of the present invention is further modified with a comonomer that gives a structural unit other than the structural unit represented by Chemical Formula 2 in view of the water solubility or water dispersibility of the modified PVA, the content of the comonomer is 5.0. It is preferably less than 3.0 mol%, more preferably less than 3.0 mol%, even more preferably less than 2.0 mol%. The saponification degree of the modified PVA is preferably 50 mol% or more, more preferably 60 mol% or more, and further preferably 70 mol% or more. Also,
The polymerization degree of the modified PVA is preferably in the range of 100 to 8000, and more preferably 200 to 2,000. The dispersoid of the aqueous emulsion in the composition of the present invention is a (co) polymer composed of one or more unsaturated monomer units selected from ethylenically unsaturated monomers and diene monomers. .

Examples of the ethylenically unsaturated monomers include olefins such as ethylene, propylene and isobutene, halogenated olefins such as vinyl chloride, vinylidene chloride, vinyl fluoride and vinylidene fluoride, vinyl formate, vinyl acetate and propion. Vinyl esters such as vinyl acrylate, vinyl versatate and vinyl pivalate, acrylic acid, methyl acrylate, ethyl acrylate, n-propyl acrylate, i-propyl acrylate, n-butyl acrylate, i-butyl acrylate Acrylates such as t-butyl acrylate, 2-ethylhexyl acrylate, dodecyl acrylate, octadecyl acrylate, hydroxypropyltrimethylammonium acrylate, methacrylic acid, methyl methacrylate, ethyl methacrylate, methacrylic acid Le acid n- propyl methacrylate i- propyl, n- butyl methacrylate, i- butyl methacrylate, t- butyl methacrylate, 2
Methacrylates such as ethylhexyl, dodecyl methacrylate, octadecyl methacrylate, hydroxypropyltrimethylammonium methacrylate, acrylamide, methacrylamide, N-methylolacrylamide, 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-methylacrylamide, N-ethylacrylamide, diacetoneacrylamide, acrylonitrile, methacrylonitrile Allyl compounds such as allyl acetate, allyl chloride, etc., styrene monomers such as styrene, α-methylstyrene, P-methylstyrenesulfonic acid and its sodium and potassium salts, and others such as N-vinylpyrrolidone Monomers. Examples of the diene-based monomer include butadiene, isoprene, and chloroprene.

In carrying out the emulsion polymerization for obtaining the aqueous emulsion of the present invention, water, the above-mentioned modified PV
A, and in the presence of a polymerization initiator, the above-mentioned monomer is added temporarily or continuously, and a normal emulsion polymerization method such as heating and stirring can be carried out. A method in which a mixture emulsified with an aqueous solution is continuously added may be used.

The amount of the modified PVA to be used is not particularly limited, but is preferably 1 to 100 parts by weight of a polymer comprising an ethylenically unsaturated monomer or a diene monomer.
It is in the range of 30 parts by weight, more preferably 2 to 20 parts by weight. When the amount is less than 1 part by weight or more than 30 parts by weight, the polymerization stability may be reduced, and the initial adhesive strength and the water-resistant adhesive strength may be reduced. As the aqueous emulsion used in the present invention, the aqueous emulsion obtained by the above method may be used as it is, but if necessary, a conventionally known polyvinyl acetate emulsion, ethylene-vinyl acetate copolymer emulsion, (meth) Acrylic ester polymer emulsions, styrene-butadiene copolymer emulsions, epoxy emulsions, urethane emulsions, and the like can be added as long as the effects of the present invention are not impaired.

As the dispersant in the aqueous emulsion of the present invention, a modified PVA having a structural unit represented by the following chemical formula 2 is used. If necessary, a conventionally known anionic, nonionic, cationic or cationic compound may be used. An amphoteric surfactant, a PVA-based polymer, hydroxyethyl cellulose or the like can be used in combination.

The polymerization initiator is not particularly restricted but includes, for example, potassium persulfate, sodium persulfate, ammonium persulfate, hydrogen peroxide, 2,2'-azobis (2-amidinopropane) dihydrochloride, Redox system in which cumene hydroperoxide, benzoyl peroxide, isopropylbenzene peroxide or the like is used alone or in combination with a reducing agent such as sodium bisulfite, tartaric acid, L-ascorbic acid, sodium formaldehyde sulfoxylate, and ferrous sulfate. .

The composition of the present invention comprises the aqueous emulsion (A) and a polyisocyanate compound (B). Here, the polyvalent isocyanate compound has two or more isocyanate groups in the molecule, and is, for example, tolylene diisocyanate (TDI); hydrogenated TD.
I; trimethylolpropane-TDI adduct (for example, manufactured by Bayer, trade name: Desmodur L); triphenylmethane triisocyanate; methylenebisdiphenyl isocyanate (MDI); hydrogenated MDI; polymerized MDI; hexamethylene diisocyanate; xylylene diisocyanate; 4,4-dicyclohexylmethane diisocyanate; isophorone diisocyanate, and the like. 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.

The composition of the present invention is obtained by blending (B) a polyvalent isocyanate compound with (A) the above-mentioned main ingredient mainly composed of an aqueous emulsion. Here, the mixing ratio of (A) the aqueous emulsion and (B) the polyvalent isocyanate compound is (A) / (B) = 99/1 to 10/90 in terms of solid content ratio.
(Weight ratio), preferably 95/5 to 2
The range of 0/80 is more preferable. If the amount of the polyvalent isocyanate compound is less than this range, the adhesive strength and water resistance will be low, and if it exceeds this range, the pot life after blending the polyvalent isocyanate will be short and not practical.

In the composition of the present invention, if necessary, various polyvinyl alcohols, starch, modified starch, oxidized starch, sodium alginate, carboxymethylcellulose, methylcellulose, hydroxymethylcellulose, maleic anhydride-isobutene copolymer Water-soluble polymer compounds such as maleic anhydride-styrene copolymer, maleic anhydride-methylvinyl ether copolymer, urea-formalin resin, urea-melamine-formalin resin, phenol-formalin resin, etc., generally used as adhesives The used thermosetting resins can also be used as appropriate. Further, the composition of the present invention includes clay,
Fillers such as kaolin, talc, calcium carbonate, wood flour,
Fillers such as flour, boric acid, reaction accelerators such as aluminum sulfate, pigments such as titanium oxide or other preservatives,
Various additives such as a rust inhibitor can be appropriately added as needed.

The adhesive of the present invention is used for bonding various adherends, and is particularly suitable for bonding wood. 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 is carried out from room temperature to 20
Heat drying at 0 ° C. may be used, but the adhesive of the present invention exhibits sufficient adhesive strength even when dried at room temperature. The feature of the adhesive of the present invention is that the storage stability of the main agent is excellent,
This is because both the initial adhesion and the water resistance in boiling water are excellent. The drying time after applying the adhesive is preferably about 30 minutes to 5 hours. The drying of the adhesive is preferably performed in a pressed state. The pressure at the time of pressing is selected in the range of 5 to ²⁰ kg / cm ^{2. When} hard wood is used as the adherend, the pressure is preferably higher, and soft wood is used as the adherend. In such a case, a pressure high enough not to break the wood is preferable.

The wood product of the present invention is a wood product adhered by the above-mentioned adhesive, and includes glued wood, furniture and the like. The type of wood in the wood product is not particularly limited, and examples include hippo, hemlock, cedar, lauan, zelkova, perpoch, rubber, oak, and the like.

[0020]

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 In a glass polymerization vessel equipped with a thermometer, a stirrer, and a nitrogen blowing port, modified PVA (PVA-1: degree of polymerization: 3.0 mol% of 3-methyl-3-buten-1-ol unit) was contained. 12
00, saponification degree 98.0 mol%) 10 parts, ion-exchanged water 9
0 parts were charged and dissolved by heating at 95 ° C. After purging with nitrogen, the temperature was set to 70 ° C., 10 parts of vinyl acetate was charged, and polymerization was started with a hydrogen peroxide / tartaric acid-based redox initiator. Thirty minutes after the start of the polymerization, the temperature was raised to 80 ° C., and 90 parts of vinyl acetate were uniformly dropped over 2 hours. After completion of the dropping, the mixture was aged for 1 hour to obtain a modified P having a solid content of 51.7%.
A polyvinyl acetate emulsion using VA as a protective colloid was obtained. Partially saponified polyvinyl alcohol (PVA-
217, manufactured by Kuraray Co., Ltd.) and a mixture of 35 parts of a 15% aqueous solution and 65 parts of calcium carbonate.
To prepare a main ingredient. Then, 30 parts of polymethylene polyphenylisocyanate (manufactured by Nippon Polyurethane Co., Ltd., trade name: Millionate MR-100) was added thereto to prepare a composition. Using this, a test was performed under the following conditions. The results are shown in Tables 1 and 2.

[Test conditions] Adhesion test An adhesion test was performed using the above composition 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: Test specimen after curing for 7 days at 20 ° C. Was immersed in boiling water for 4 hours, dried in air at 60 ° C. for 20 hours, further immersed in boiling water for 4 hours, immersed in water at room temperature until cooled, and subjected to a test in a wet state. . Initial adhesion: 10 kg / cm at 20 ° C after bonding
Press for 10 minutes at pressure ² and immediately measure compression shear bond strength

Examples 2-3 An emulsion was prepared in the same manner as in Example 1 except that the conditions shown in Table 1 were changed. The obtained emulsion was evaluated in the same manner as in Example 1. Table 1 shows the results
And Table 2.

Example 4 A pressure-resistant autoclave equipped with a nitrogen inlet, a thermometer and a stirrer was charged with 100 parts of a 4.5% aqueous solution of PVA-1, heated to 60 ° C., and replaced with nitrogen. After charging 80 parts of vinyl acetate, ethylene was pressurized to 45 kg / cm ² , and a 0.5% aqueous hydrogen peroxide / 5% Rongalite aqueous solution was injected to initiate polymerization. When the residual vinyl acetate concentration became 10%, ethylene was released, the ethylene pressure was set to 20 kg / cm ² , and a 3% aqueous hydrogen peroxide solution was injected to complete the polymerization. Modified PVA having a solid content of 49.5%
Was used to obtain an ethylene-vinyl acetate copolymer emulsion. Partially saponified polyvinyl alcohol (PV
A-217, manufactured by Kuraray Co., Ltd.) and a mixture of 35 parts of a 15% aqueous solution and 65 parts of calcium carbonate were mixed with the above emulsion 1
The main ingredient was prepared by adding 00 parts. Then, 30 parts of polymethylene polyphenylisocyanate (manufactured by Nippon Polyurethane Co., Ltd., trade name: Millionate MR-100) was added thereto to prepare a composition. Using this, a test was performed in the same manner as in Example 1. The results are shown in Tables 1 and 2.

Example 5 Five parts of PVA-2 and an anionic surfactant (A) were placed in a glass polymerization vessel equipped with a stirrer, a nitrogen inlet, and a thermometer.
erosol OT-75, manufactured by Mitsui Cytec)
100 parts of ion-exchanged water was added and dissolved by heating. The temperature was raised to 70 ° C. while performing nitrogen bubbling, 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 added to initiate polymerization. One hour after the start of polymerization, methyl methacrylate 4
0 parts and 40 parts of n-butyl acrylate 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. As a result, a methyl methacrylate-n-butyl acrylate copolymer emulsion having a solid content of 48.6% was obtained. Partially saponified polyvinyl alcohol (PVA-21)
7, Kuraray Co., Ltd.) was mixed with 35 parts of a 15% aqueous solution and 65 parts of calcium carbonate, and 100 parts of the above emulsion was added to prepare a main ingredient. Then, 30 parts of polymethylene polyphenylisocyanate (manufactured by Nippon Polyurethane Co., Ltd., trade name: Millionate MR-100) was added thereto to prepare a composition. Using this, a test was performed in the same manner as in Example 1. The results are shown in Tables 1 and 2.

Comparative Example 1 A polyvinyl acetate emulsion (solids) was prepared in the same manner as in Example 1 except that 10 parts of unmodified fully saponified PVA (PVA-117, manufactured by Kuraray) was used instead of PVA-1. Partial concentration 52.0%). A test was conducted in the same manner as in Example 1 using this emulsion. The results are shown in Tables 1 and 2.

Comparative Example 2 A polyvinyl acetate emulsion (solids) was prepared in the same manner as in Example 1 except that 10 parts of unmodified partially saponified PVA (PVA-217, manufactured by Kuraray) was used instead of PVA-1. Partial concentration 52.0%). A test was conducted in the same manner as in Example 1 using this emulsion. The results are shown in Tables 1 and 2.

[0027]

[Table 1]

PVA-1: 3-methyl-3-butene-1
The content of all units is 3.0 mol%, the degree of polymerization is 1200,
Degree of saponification 98.0 mol% PVA-2: content of 3-methyl-3-buten-1-ol unit 6.0 mol%, degree of polymerization 500, degree of saponification 98.
0 mol% PVA-3: 3-methyl-3-buten-1-ol unit content 1.0 mol%, polymerization degree 1400, saponification degree 9
2.0 mol% Aerosol OT-75: anionic surfactant (manufactured by Mitsui Cytec) PVA-117: unmodified completely saponified PVA (manufactured by Kuraray) PVA-217: unmodified partially saponified PVA (manufactured by Kuraray)

[0029]

[Table 2]

[0030]

The composition of the present invention is used for various applications including adhesives. In particular, when used as an adhesive, the initial adhesive strength is excellent, and the adhesive strength and water resistance are dramatically improved. The adhesive of the present invention can be applied to the case of bonding various kinds of materials, and can be particularly preferably used as an adhesive for wood. In addition to the adhesion between woods, it can be used for adhesion between wood and paper, textiles, inorganic plates, films and the like. Furthermore, the composition of the present invention can be effectively used as an inorganic binder, an inorganic plate, or a base paint such as a wood panel by utilizing a film having excellent water resistance.

Claims (3)

[Claims] (A) One or more selected from ethylenically unsaturated monomers and diene monomers using a modified polyvinyl alcohol having a structural unit represented by the following chemical formula 1 as a dispersant: A composition comprising an aqueous emulsion obtained by emulsion polymerization of the unsaturated monomer of (1) and (B) a polyvalent isocyanate compound. Embedded image (N: integer of 1 to 20) 2. An adhesive comprising the composition according to claim 1. 3. A wood product obtained by bonding with the adhesive according to claim 2.