JPH027348B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a water-based adhesive with high initial adhesive strength, excellent water resistance and heat resistance, which becomes sticky when dried at room temperature and becomes non-stick over time. The present invention relates to contact adhesive compositions.

Currently, the mainstream industrial adhesives are thermosetting resin-based or emulsion-based adhesives, and solvent-free adhesives have also been used for a long time. On the other hand, most adhesives made from chloroprene rubber are solvent-based, and there is a growing movement to convert them into emulsions from the standpoint of health and safety. Solvent-based adhesives using chloroprene rubber have the following properties: (1) good contact properties, (2) high crystallinity and strong initial adhesive strength, and (3) good heat resistance and water resistance. Due to its unique characteristics, it is used in a wide range of applications such as woodworking, plywood, and vehicle adhesives. However, emulsion adhesives using chloroprene rubber have lower initial adhesion than conventional solvent-based adhesives, and are also inferior in heat resistance and water resistance. Therefore, various proposals have been made to improve these drawbacks, but nothing satisfactory has yet been achieved.

In view of these facts, the present inventors have conducted intensive studies to find a water-based contact adhesive composition that has high initial adhesive strength and excellent heat resistance and water resistance, and as a result, they have completed the present invention. It has been reached.

That is, the present invention emulsifies and disperses (A) an ethylenic monomer and a compound having one or more epoxy groups and 0.1 to 1 (meth)acryloyl group per molecule in an aqueous medium. 100 parts by weight of a polymer obtained by emulsion polymerization, (B) 5 to 100 parts by weight of an aqueous dispersion of phenolic resin, and (C) 0.1 to 2 parts of imidasol per equivalent of epoxy group of polymer (A). The present invention relates to a water-dispersed contact adhesive composition comprising molar addition.

The water-dispersed contact adhesive composition of the present invention comprises:
The film-forming action and adhesiveness of the ethylenic monomer component in the polymer can impart so-called contact properties, and the cross-linking reaction between the epoxy compound and the imidazoles over time allows for more advanced properties. It can provide adhesive properties and higher heat resistance and water resistance than conventional solvent-based adhesives. Furthermore, since the composition of the present invention involves a curing reaction, it is preferable to use it as a two-component adhesive, but since it has a long pot life and quick strength development, it can be used as a one-component adhesive. It is also possible to use

The present invention will be explained in detail below.

The ethylenic monomer used in the present invention includes acrylic acid alkyl esters such as methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, and 2-ethylhexyl acrylate, and methacrylic acid corresponding to the above alkyl esters. alkyl esters of , aromatic vinyl compounds such as styrene, α-methylstyrene, and vinyltoluene, α,β-ethylenically unsaturated dicarboxylic acids such as monobutyl maleate, dibutyl maleate, monooctyl fumarate, and dioctyl fumarate. mono- or diesters, vinyl esters such as vinyl acetate and vinyl propionate, vinyl ethers, unsaturated nitriles such as acrylonitrile and methacrylonitrile, olefins such as ethylene, butadiene and isoprene, vinyl chloride, vinylidene chloride, etc. Examples include chlorine-containing vinyl compounds. In addition, if desired, the above-mentioned ethylenic monomers may be used as main components, and ethylenic unsaturated carboxylic acids such as acrylic acid, methacrylic acid, fumaric acid, maleic acid, itaconic acid, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, etc. , hydroxyl group-containing monomers such as polyethylene glycol monomethacrylate, amide group-containing monomers such as acrylamide and methacrylamide, methylol group-containing monomers such as N-methylolacrylamide and dimethylolacrylamide, N-butoxymethyl Alkoxymethyl group-containing monomers such as acrylamide, epoxy group-containing monomers such as glycidyl acrylate and glycidyl methacrylate, divinyl monomers such as divinylbenzene, polyoxyethylene diacrylate, and polyoxyethylene dimethacrylate. Functional or cross-linking monomers such as can be combined.

The compound used in the present invention having one or more epoxy groups and 0.1 to 1 (meth)acryloyl group per molecule (hereinafter referred to as an epoxy acrylate compound) has an acrylic acid per equivalent of epoxy group in the epoxy compound. acid or methacrylic acid from 0.1 to
It is obtained by reacting in the range of 1.0 mol.

Here, the epoxy compound is a compound having one or more epoxy groups per molecule, and specific examples include resins with an epoxy equivalent of 100 to 4,000, preferably 130 to 1,000, such as epichlorohydrin or methylepichlorohydrin and phenol. Examples include condensates with other compounds. Examples of phenolic compounds in this case include 2,2'-bis(4,4'-hydroxyphenyl)propane (commonly known as bisphenol A), halogenated bisphenol A, and 2,2'-bis(4,4'-hydroxyphenyl)propane (commonly known as bisphenol A). Examples include 4'-hydroxyphenyl)methane (commonly known as bisphenol F), resorcinol, tetrahydroxyphenylethane, phenol, cresol, and a novolak type polyfunctional phenol condensed from phenol or cresol with formalin. Other diglycidyl ethers of polyalkylene glycols such as polypropylene glycol, aromatic or alicyclic glycidyl esters and dimer acid diglycidyl esters such as hexahydrophthalic acid diglycidyl ester, phthalic acid diglycidyl ester, and internal cyclic imino groups. Examples include glycidylamines obtained from hydantoin, which is a mononuclear nitrogen heterocyclic compound. If each molecule has one or less epoxy groups, the desired water resistance and heat resistance will be poor and it will not be possible to provide satisfactory results.

By using the epoxy acrylate compound obtained in this way, it is possible to improve the compatibility with the ethylenic monomer, thereby improving the storage stability of the aqueous dispersion and improving the coating film. Homogeneous transparency can be increased. If the number of (meth)acryloyl groups per molecule is less than 0.1, the resulting aqueous dispersion will be unstable and cause layer separation, and if it is more than 1, gelation will occur during emulsion polymerization, which is not practical.

The imidazoles used in the present invention have the general formula (R ₁ , R ₂ , R ₃ are H or C _o H _2o+1 (n=1 to 5)
), reaction products of this compound with acrylonitrile, ethylene oxide, propylene oxide, etc., and salts with various organic acids. Preferred examples are 2-ethyl-4-methylimidazole and 1-butyl-2-methylimidazole.

The phenolic resin aqueous dispersion used in the present invention is obtained by dispersing a novolac type or resol type phenolic resin in water by a method such as using a surfactant or the like. Novolac type or resol type phenolic resins include monophenols such as carbolic acid and cresol, bisphenol A, and bisphenol F.
It is obtained by the condensation of bisphenols such as phenols such as resorcinol, and phenolic compounds such as resorcinol with formalin.Novolak type resin can be obtained by using an acidic catalyst, and resol type resin can be obtained by using a basic catalyst. can. Examples of surfactants, dispersants, and protective colloids for dispersing this resin in water include aliphatic soaps, alkyl sulfate salts, alkylbenzene sulfonate salts,
Dialkyl sulfosuccinate salt, alkyl phosphate salt, polyoxyethylene alkyl ether, polyoxyethylene alkyl phenol ether, polyoxyethylene fatty acid ester, sorbitan fatty acid ester, polyoxyethylene sorbitan fatty acid ester, glycerin fatty acid ester, oxyethylene Examples include oxypropylene block copolymers, alkyl amine salts, polyphosphates, polyacrylates, maleic anhydride copolymer salts, and polyvinyl alcohol. The nonvolatile content of the aqueous phenolic resin dispersion is preferably 5 to 85% by weight.

The emulsion polymer used in the present invention contains an ethylenic monomer and an epoxy acrylate compound.
Stir thoroughly in advance at room temperature or at a temperature of 100°C in a ratio of 10:90 (parts by weight) to 90:10 (parts by weight), preferably 40:60 (parts by weight) to 60:40 (parts by weight). It can be obtained by a method in which a surfactant, a dispersant, a protective colloid, etc., water, and a polymerization initiator are added to this to obtain an emulsion dispersion, which is then subjected to emulsion polymerization. This emulsion polymerization method is a conventionally known method. Examples of surfactants, dispersants, and protective colloids used include aliphatic soaps, alkyl sulfates, alkylbenzene sulfonates, dialkyl fluorosuccinates, alkyl phosphates, polyoxyethylene alkyl ethers, and polyesters. Oxyethylene alkyl phenol ether, polyoxyethylene fatty acid ester, sorbitan fatty acid ester, polyoxyethylene sorbitan fatty acid ester, glycerin fatty acid ester, oxyethylene oxypropylene block copolymer, alkylamine salt, polyphosphate, polyacrylate, maleic anhydride Examples include copolymer salts, polyvinyl alcohol, and hydroxyethyl cellulose. Further, as the polymerization initiator for the ethylenic monomer, for example, a persulfate, a peroxide, an azobis compound, and a redox system in which these are combined with a reducing agent are used. Further, a PH adjuster such as sodium hydrogen phosphate or sodium hydrogen carbonate and an organic solvent are added as necessary.

By following the above emulsion polymerization method, not only the manufacturing process is simplified, but also products with less variation in quality can be manufactured.

The water-dispersed contact adhesive composition of the present invention comprises:
The imidazole is added to 1 equivalent of the epoxy group of the epoxy acrylate compound in the emulsion polymer.
It is preferably added in an amount of 0.1 to 2 moles. 0.1
If the amount is at least 2.0 mol, the resulting adhesive composition will have poor water resistance. Further, the amount of the phenolic resin aqueous dispersion is preferably 5 to 100 parts by weight based on 100 parts by weight of the total amount of the ethylenic monomer and the epoxy acrylate compound. If the amount is less than 5 parts by weight or more than 100 parts by weight, the resulting adhesive composition will have poor initial adhesive properties.

The solids content of the composition thus produced can be up to about 70% by weight, but from the standpoint of quality and efficiency, a solids content of 30 to 60% by weight is preferred.

Further, in order to improve the adhesive strength to glass etc., a silane compound such as vinyltriethoxysilane, β-(2,4-epoxycyclohexyl)ethyltrimethoxysilane, etc. can be added.

The method of using the composition of the present invention is to add and mix imidazoles and a phenolic resin aqueous dispersion to an emulsion polymer, apply the mixture to the desired thickness on an adherend, leave it for a certain period of time, and then apply the mixture to the other adherend. Either the adherend is superimposed on the part and adhered, or an emulsion polymer is applied to one side of the adherend and a curing agent component is applied to the other adherend, and the emulsion polymer of both adherends is bonded. It can be used in a method of bonding the coated surface and the hardener coated surface by overlapping them so that they are in contact with each other. In particular, the latter method has the advantage of extending pot life. In addition, various methods such as spraying, roll coating, brushing, etc. can be used for coating the surface to be adhered. Furthermore, the composition of the present invention can be used for wood, plywood,
Particle board, gypsum board, metals such as iron and aluminum, plastic film and molded products thereof,
Leather, cotton, linen cloth, glass fiber, glass cloth,
Used for bonding objects such as FRP to each other or different types.

Hereinafter, it will be explained in detail using examples. In the examples, unless otherwise specified, parts or % represent parts by weight or % by weight.

Example 1 7.2 parts of acrylic acid and 0.1 part of sodium methylate were added as catalysts to 190 parts of epoxy resin AER-331 (bisphenol A type epoxy resin, epoxy equivalent: 190, manufactured by Asahi Kasei Industries, Ltd.) in advance, and the acid value was adjusted. 1
The reaction is carried out at 130°C for about 5 hours until the temperature is below. In this way, using epoxy acrylate A having an average of 0.2 acryloyl groups and 1.8 epoxy groups per molecule, a polymerizable mixed solution was prepared as described below.

Styrene 20 parts n-butyl acrylate 20 parts Methyl methacrylate 10 parts Polyoxyethylene lauryl ether (HLB17.5) 2 parts Sodium dicyclohexyl sulfosuccinate
2 parts ammonium persulfate 2 parts epoxy acrylate A 50 parts demineralized water 30 parts Total 136 parts Pour 64 parts of demineralized water prepared separately into a flask, and add 70 parts of demineralized water.
Increase temperature to ℃. The above polymerizable mixture was added dropwise into the solution over a period of about 2 hours. Approximately 2 hours after dripping
The temperature was maintained at 70°C, and then 2 parts of ammonium persulfate was added, the temperature was raised to 80°C, and the reaction was continued for 2 hours to obtain an emulsion polymer. The obtained emulsion polymer (hereinafter referred to as emulsion polymer A) had an average particle size of 0.2 μm, was a milky white emulsion, and was stable at 40° C. for 10 days.

On the other hand, 94 parts of carbolic acid, 125 parts of a 37% formaldehyde aqueous solution, and _{4.7 parts of Ba(OH) 2.8H 2 O} were uniformly mixed and heated at 70° C. for 2 hours. Sulfuric acid was added to this to adjust the pH to 6.5. Thereafter, water was distilled off under reduced pressure without exceeding 70°C, and after 5 hours, a solid resin was obtained at room temperature. After uniformly dissolving 2 parts of polyoxyethylene propylene block copolymer (HLB16.8) in 50 parts of the resin thus obtained, 52 parts of water was added to prepare an aqueous dispersion B of resol type phenolic resin with a non-volatile content of 50%. Obtained. To this, 2-ethyl-4-
10 parts of methylimidazole was added and mixed uniformly to form a curing agent.

15 parts of the prepared curing agent were added to 200 parts of emulsion polymer A, mixed uniformly, and an attempt was made to apply it as a contact adhesive.

The pot life of this adhesive was 2 days or more. In order to bond plywood together using this adhesive, apply it to each plywood to a dry thickness of 30μ, leave it for 10 minutes, and apply a pressure of 3Kg/cm ² for about 5 seconds to bond. Ivy.

After adhesion, the adhesive strength increased with time, and the tensile shear strength after about 1 day was 41 Kg/cm ² .

Example 2 200 parts of the emulsion polymer A obtained in Example 1 was mixed with 40 parts of a commercially available phenolic resin aqueous dispersion (50% non-volatile content, manufactured by Showa Union) and 5 parts of 1-butyl-4-methylimidazole. Got contact adhesive.

The pot life of this adhesive was 3 days or more.

This adhesive was applied to each of the asbestos slate board and cotton canvas to a dry film thickness of 30μ, and after being left for 5 minutes, a pressure of 1 kg/cm ² was applied for about 2 seconds. When the adhesive was bonded, the green strength was 12 kg/cm ² . The adhesive strength increases over time, and the tensile shear strength after about 7 days is 53
Kg/cm ² was shown. When the bonded test piece was tested in an atmosphere at 60° C., it had a tensile shear strength of 36 Kg/cm ² , and after being immersed in water at room temperature for 7 days, the tensile shear strength was 23 Kg/cm ² .

Claims (1)

[Claims] 1 (A) Obtained by emulsion polymerization after emulsifying and dispersing an ethylenic monomer and a compound having one or more epoxy groups and 0.1 to 1 (meth)acryloyl group per molecule in an aqueous medium. 100 parts by weight of polymer;
(B) 5 to 100 parts by weight of an aqueous dispersion of phenolic resin;
(C) A water-dispersed contact adhesive composition in which 0.1 to 2 moles of imidasols are added per equivalent of the epoxy group of the polymer (A).