JP2009270034A5 - - Google Patents

Claims (10)

An aqueous resin composition for an enamel paint comprising an aqueous resin dispersion and a crosslinking agent as essential components ,
As a high Tg resin component of the aqueous resin dispersion, an alkoxysilane group-containing polymerizable monomer (A) and a cycloalkyl group-containing polymerizable monomer (B) are included,
An aqueous resin composition, wherein no reactive emulsifier is used as a high Tg resin component of the aqueous resin dispersion. The aqueous resin dispersion is an aqueous resin dispersion obtained by polymerization using two or more kinds of polymerizable monomers having different glass transition temperatures (Tg), and the aqueous resin dispersion has a glass transition It consists of a high Tg resin component having a temperature (Tg) of 50 ° C. or higher and a low Tg resin component having a glass transition temperature (Tg) of 40 ° C. or lower, and the ratio of the high Tg resin component to the low Tg resin component is high Tg resin component / The aqueous resin composition according to claim 1, comprising a low Tg resin component (weight ratio) = 46/54 to 70/30. The aqueous resin composition according to claim 1 or 2 , comprising a carboxyl group-containing polymerizable monomer and a hydroxyl group-containing polymerizable monomer as a low Tg resin component of the aqueous resin dispersion. . The crosslinking agent is at least one selected from a compound having an isocyanate group, a compound having an aziridine ring, a compound having an oxazoline ring, and a compound having a carbodiimide group, and the blending amount thereof is a function of the aqueous resin dispersion. It is 0.1-2 equivalent with respect to group, The aqueous resin composition in any one of Claims 1-3 characterized by the above-mentioned. The aqueous resin composition according to any one of claims 1 to 4 , wherein the aqueous resin dispersion also contains a Si-containing compound represented by the following formula (1).
_{^{(R 1) n -Si- (R}} 2) 4-n (1)
(In the formula, n is an integer of 0 to 3, and R ¹ is selected from hydrogen, an aliphatic hydrocarbon group having ^{1 to} 16 carbon atoms, an aryl group having 5 to 10 carbon atoms, and a cycloalkyl group having 5 to 6 carbon atoms. N R ^{1 s} may be the same or different, R ² is selected from an alkoxy group having 1 to 8 carbon atoms, an acetoxy group, and a hydroxyl group, and 4-n R ^{2 s} are the same. Or it may be different.) The amount exceeding 50% of the total polymerizable monomers used for obtaining the aqueous resin dispersion according to claim 1-5 in which the solubility of water at 20 ° C. is characterized in that at least 0.1 wt% The aqueous resin composition according to any one of the above. The aqueous resin according to any one of claims 1 to 6 , wherein the polymerizable monomer of the low Tg resin component of the aqueous resin dispersion contains 5% by mass or more of methyl methacrylate and cyclohexyl methacrylate, respectively. Composition. A structure in which the high Tg resin component of the aqueous resin dispersion is composed of a central portion (core) of the aqueous resin dispersion particles, and the low Tg resin component of the aqueous resin dispersion is composed of an outer portion (shell) of the aqueous resin dispersion particles. The aqueous resin composition according to any one of claims 1 to 7 , wherein The aqueous resin composition according to any one of claims 1 to 8 , which is obtained by emulsion polymerization in two or more steps. The aqueous resin composition according to claim 9 , wherein the aqueous resin composition is produced at a pH of 4 or less during emulsion polymerization.