| abstract |
The object of the present invention is to provide an aqueous coating composition which exhibits a small viscosity change and can form a coating film having a superior coating film appearance even when the amount of the solvent contained in the aqueous coating composition is reduced due to changes in the coating environment.The present invention provides an aqueous coating composition comprising an acrylic resin dispersion (A) and a melamine resin (B), wherein the acrylic resin dispersion (A) has a core/shell structure, the acrylic resin dispersion (A) is a dispersion of a solution-polymerization product of a core part preparation monomer (a-1) and a shell part preparation monomer (a-2), wherein the shell part preparation monomer (a-2) comprises an acid group-containing polymerizable monomer, the mass ratio of the core part to the shell part of the acrylic resin dispersion (A) is in the range of core part/shell part = 30/70 to 70/30, the shell part of the acrylic resin dispersion (A) has an acid group, and the neutralization rate of the acid groups in the shell part is 50% or more, the weight-average molecular weight of the acrylic resin dispersion (A) is in the range of 10,000 to 70,000, the core part preparation monomer (a-1) has an acid value of 10 mg KOH/g or less, and the shell part preparation monomer (a-2) has an acid value of 10 mg KOH/g or more and 70 mg KOH/g or less, the whole monomer mixture comprising the core part preparation monomer (a-1) and the shell part preparation monomer (a-2) has an acid value of 10 mg KOH/g or more and 30 mg KOH/g or less, the glass transition temperature of the acrylic resin dispersion (A) is in the range of -10 to 60°C, and the melamine resin (B) comprises a hydrophobic melamine resin. |