Patent ID: 8557934

Claim:
A copolymer latex obtained by emulsion polymerizing a monomer mixture containing: (a) 30% by mass to 70% by mass of a conjugated diene monomer, (b) 0.1% by mass to 15% by mass of an ethylene unsaturated carboxylic acid monomer, and (c) 15% by mass to 69.9% by mass of one or more other copolymerizable monomers (wherein (a)+(b)+(c)=100% by mass), wherein toluene-insoluble matter in a dry substance obtained by drying the copolymer latex is in a range of more than 95% by mass to 100% by mass; a ratio of a mass of a toluene wet product of the toluene-insoluble matter to a mass of the dry substance of the toluene-insoluble matter (degree of swelling in toluene) are 3.0 to 6.5; the copolymer latex has a number average particle size of 180 nm to 400 nm; and the dry substance obtained by drying the copolymer latex has a glass transition starting temperature in a range of −70° C. to −20° C., and a glass transition ending temperature in a range of 10° C. to 100° C., as measured by differential scanning calorimetry, and wherein the glass transition starting temperature is defined as a temperature at which a stepwise change of glass transition starts with respect to a base line on a low temperature side and the curve begins to depart from the base line, and the glass transition ending temperature is defined as a temperature when the stepwise change finishes with respect to the base line on a high temperature side and the curve returns to the base line.