JPH0551565A - One-part crosslinkable aqueous adhesive - Google Patents

Abstract

PURPOSE:To obtain a one-pack room-temperature crosslinking aqueous adhesive by adding a metal acetylacetonate, as a crosslinking agent, made hydrophobia by surface-coating with a wax to a water-dispersible polymer having carboxyl groups in the molecule. CONSTITUTION:An adhesive prepared by adding 0.5-20 PHR of a metal acetylacetonate (e.g. aluminum acetylacetonate) surface-coated with a wax (e.g. PE of an m.p. of 80-150 deg.C) as a crosslinking agent to a water-dispersible polymer having carboxyl groups in the molecule (e.g. a polymer of an acrylic ester or chloroprene) as a principal component. When this adhesive is applied to an adherend and then dried by heating, the wax is molten and the crosslinking agent causes a crosslinking reaction with the principal component at room temperature to allow the adhesive to develop adhesiveness.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a room temperature curing type one-pack type crosslinkable water-based adhesive.

[0002]

2. Description of the Related Art Conventionally, a method for improving heat resistance and water resistance by adding a crosslinking agent to a pressure-sensitive adhesive or adhesive obtained by adding various functional groups to an acrylic copolymer or the like to increase cohesive force. It is taken. For example, there was a method of adding an epoxy compound or an isocyanate compound as a cross-linking agent to an acrylic copolymer or chloroprene polymer having a functional group of a hydroxyl group or a carboxyl group, but the thickening with time is large,
The coating workability deteriorated.

An adhesive using a metal salt of acetylacetone as a cross-linking agent is also disclosed in JP-A-1-69681.
It is disclosed in Japanese Patent Laid-Open No. 2-251589.

[0004]

However, since any of the above is a two-pack type, it is necessary to uniformly stir and disperse the crosslinking agent component in the main component, and the use time after mixing is limited. was there. That is, the highly reactive cross-linking agent could not be liquefied due to the large viscosity increase with time, and the low reactivity of the cross-linking agent required high temperature treatment after adhesion.

Therefore, an object of the present invention is to provide a one-pack type crosslinkable water-based adhesive which is a one-pack type which does not require stirring and mixing, and which further enhances cohesive force by a crosslinking reaction to improve heat resistance and water resistance. And

[0006]

The present invention is characterized in that a water-dispersed polymer having a carboxyl group in the molecule is a main component, and a acetylacetone metal salt whose surface is coated with wax is added as a crosslinking agent. It is a one-pack type crosslinkable water-based adhesive.

As the polymer having a carboxyl group in the molecule used in the present invention, one or more kinds of ethylene-based or diene-based monomers and one or more kinds of unsaturated carboxylic acids are used. It is a polymer obtained by emulsion polymerization in water, and the amount of unsaturated carboxylic acid to be used is appropriately 2 to 30% (weight) with respect to the total monomers. Here, as the ethylene-based or diene-based monomer, ethylene, propylene, butadiene, isoprene, chloroprene, styrene, α-methylstyrene, dimethylstyrene, divinyltoluene, vinyl acetate, vinyl propionate, vinyl ether, vinyl chloride, vinylidene chloride. , Methyl acrylate, ethyl acrylate, n-butyl acrylate,
acrylic acid ester such as iso-butyl acrylate, 2-ethylhexyl acrylate, lauryl acrylate, methyl methacrylate, ethyl methacrylate,
There are methacrylic acid esters such as n-butyl methacrylate, iso-butyl methacrylate, 2-ethylhexyl methacrylate, and lauryl methacrylate. As unsaturated carboxylic acids, acrylic acid, methacrylic acid,
Examples thereof include crotonic acid, itaconic acid, maleic anhydride and the like. Among these, a polymer obtained by acid-modifying a polymer of acrylic acid ester or chloroprene with acrylic acid or methacrylic acid is most suitable.

Further, an aromatic or alicyclic copolymer used as a tackifier or a heat resistance improver, for example,
Styrene, rosin, terpene, cyclopentadiene, C
There is also a polymer having a carboxyl group obtained by emulsion polymerization of 9-type petroleum resin, phenol resin, xylene resin, coumarone-indene resin, vinyltoluene, α-methylstyrene, etc., and unsaturated carboxylic acid as described above in water. ..

Next, the acetylacetone metal salt as a cross-linking agent component is a crystalline powder and is an intramolecular complex salt type chelate compound having various colors depending on the difference in the valence of the metal ion. ).

Formula (1):

[0011]

[Chemical 1]

However, M = Al, Cr, Zn, Cu, N
i, Co, Fe, Mg, Mn, etc., and n = 2 to 4.

Of these, acetylacetone aluminum salt is the most suitable from the viewpoints of workability and adhesive performance, and the addition amount of 0.5 to 20 PHR is suitable.

Next, the following method can be used to obtain an acetylacetone metal salt surface-coated with wax as a crosslinking agent.

Spray drying method 5% of wax (petroleum wax having a melting point of 50 to 150 ° C.) in a true solvent (aromatic type, ester type, ketone type, etc.)
It can be obtained by spray-mixing a solution dissolved in the following concentration and a powdery acetylacetone metal salt (crosslinking agent component) with an air spray in a hot air atmosphere.

Precipitation method: A solution obtained by heating and dissolving a wax in a true solvent is added and mixed with a cross-linking agent component and cooled for precipitation, or a poor solvent (alcohol, etc.) is added for dilution and precipitation. It is obtained by doing.

In the present invention, in addition to the above main component and the cross-linking agent,
If necessary, various modifiers such as tackifiers (rosins, petroleum resins, etc.), plasticizers (phthalates, polyhydric alcohols, etc.), and fillers (inorganic fillers, etc.) can be added and blended. ..

[0018]

INDUSTRIAL APPLICABILITY In the present invention, the surface of the acetylacetone metal salt as the cross-linking agent component is coated with a wax having a lacquer property. Therefore, it was added to a water-dispersible polymer having a functional group such as a carboxyl group. At room temperature, no cross-linking reaction occurs and the stable state is maintained, so no viscosity increase over time is observed even with the one-pack type.

When applied to an adherend and dried by heating to remove water to form a film, the wax on the surface of the crosslinking agent is dissolved, the acetylacetone metal salt is exposed, and the carboxyl group in the main component is exposed. , And the metal cross-linking reaction proceeds even at room temperature to increase the molecular weight and strengthen the cohesive force.
Improves heat resistance and water resistance.

Examples will be described below, and parts indicate parts by weight.

[0021]

【Example】

Example 1 [Main component] 2 parts of nonylphenol polyether ammonium sulfate as an emulsifier and 100 parts of water were placed in a flask at 80 ° C.
Stirring while maintaining at 100 parts, 2-ethylhexyl acrylate 100 parts, vinyl acetate monomer 10 parts and acrylic acid monomer 2 parts are added dropwise together with 2 parts of 10% ammonium persulfate aqueous solution as a catalyst for 3 hours to carry out emulsion polymerization. The main component according to the present invention is a water-dispersible polymer having a carboxyl group in the molecule. [Crosslinking Agent] Also, 2 parts of polyethylene wax having a melting point of 80 ° C. and an average molecular weight of 2000 is added to 98 parts of toluene heated to 80 ° C. and dissolved with stirring. After completely dissolving, 1 part of acetylacetone aluminum salt was added to 2% wax-toluene solution at the same temperature (80 ° C.) with stirring to uniformly disperse the solution, and the mixture was stirred with 30% stirring.
After cooling to ℃ and standing still, acetylacetone aluminum salt surface-coated with wax was precipitated and precipitated, filtered, and dried at 30 ° C for 5 hours to obtain a crosslinking agent according to the present invention.

The adhesive of Example 1 was obtained by adding and mixing 2 parts of the crosslinking agent to 100 parts of the main component.

Comparative Example 1 An adhesive of Comparative Example 1 was prepared by adding 2 parts of untreated acetylacetone aluminum salt to 100 parts of the above main component and mixing them.

With the initial viscosities at 40 ° C. of the adhesives of Example 1 and Comparative Example 1 being 100, the results of measuring the rate of change in viscosity with time after 8 hours, 24 hours and 30 days are shown in Table 1.
Shown in.

Further, the contact adhesiveness (presence or absence) and the adhesion force (tensile shear strength; Kg / cm ² , 180) under the following adhesion conditions:
Table 1 shows the measured values of degree peel strength; Kg / 25 mm width).

Adhesion conditions Coating amount: 120 g / m ² (per surface), double-side coating Substrate: Tensile shear strength: Plywood x Steel plate 180 degree peeling: No. 9 canvas x Aluminum plate Drying; 100 ° C, 3 minutes compression 3 kg / cm ² , 5 seconds curing; 7 days, room temperature Measurement temperature: 20 ℃, 60 ℃

[0027]

[Table 1]

Claims (1)

[Claims] 1. A one-pack type crosslinkable water-based adhesive comprising a water-dispersible polymer having a carboxyl group in the molecule as a main component, and an acetylacetone metal salt surface-treated with wax as a crosslinking agent. Agent.