COPOLYMER LATEX

PROBLEM TO BE SOLVED: To provide a copolymer latex for a chipping-resistant paint, which can provide a composition for a low-temperature drying type water-based paint having excellent dryability and chipping resistance and satisfying both of adhesion to a base material and crack resistance of a paint film in a well-balanced state. SOLUTION: The copolymer latex is obtained by emulsion polymerization of a monomer mixture comprising (a) 30-70 mass% of a conjugated diene-based monomer, (b) 0.1-15 mass% of an ethylenically unsaturated carboxylic acid monomer, and (c) 15-69.9 mass% of one or more other copolymerizable monomers. A toluene-insoluble content in a dried product obtained by drying the copolymer latex is 95-100 mass%, a mass ratio of a toluene-swollen toluene-insoluble content to a dried toluene-insoluble content (a toluene swelling degree) is 6.6-10.0, and the copolymer latex has a number average particle diameter of 200-500 nm. In differential scanning calorimetry, a dried product obtained by drying the copolymer latex has a glass transition initiation temperature in the range of -70 to -20°C and a glass transition termination temperature in the range of 10 to 100°C. COPYRIGHT: (C)2011,JPO&INPIT