Patent ID: 8404354

Claim:
A water-based paint composition comprising (A) a copolymer of (a) polymerizable unsaturated monomer having polyoxyalkylene chain, (b) hydroxyl-containing polymerizable unsaturated monomer having no polyoxyalkylene chain, (c) polymerizable unsaturated monomer having at least one cationic functional group selected from the group consisting of tertiary amino groups and quaternary ammonium salt groups, (d) at least one monomer selected from the group consisting of (d-1) bridged alicyclic hydrocarbon group-containing polymerizable unsaturated monomers and (d-2) C 6-18 alkyl or cycloalkyl group-containing polymerizable unsaturated monomers and (e) a polymerizable unsaturated monomer other than monomers (a)-(d), (B) a water-dispersible acrylic resin having a core/shell multilayer structure comprising a core of copolymer (I) obtained by copolymerizing 0.1-30 mass % of polymerizable unsaturated monomer (h) having at least two polymerizable unsaturated groups per molecule and 70-99.9 mass % of polymerizable unsaturated monomer (i) having one polymerizable unsaturated group per molecule; and a shell of copolymer (II) obtained by copolymerizing 1-35 mass % of hydroxyl-containing polymerizable unsaturated monomer (f), 5-60 mass % of hydrophobic polymerizable unsaturated monomer (j) and 5-94 mass % of polymerizable unsaturated monomer (k) other than the hydroxyl-containing polymerizable unsaturated monomer (f) and hydrophobic polymerizable unsaturated monomer (j), and the solid mass ratio of the copolymer (I)/copolymer (II) is within the range of 10/90-90/10, and (C) melamine resin having a weight-average molecular weight within the range of 1,000-5,000.