Patent ID: 7294670

Claim:
An aqueous polyurethane resin dispersion comprising: a polyurethane resin having at least one of a sulfonate group and a carboxylate group, wherein an average particle diameter of the polyurethane resin is 0.05 to 0.30 μm; and at least one anionic surfactant selected from the group consisting of dialkyl sulfosuccinic acid metal salts, dialkyl sulfosuccinic acid organic salts, alkyl benzenesulfonic acid metal salts and alkyl benzenesulfonic acid organic salts, wherein said aqueous polyurethane resin dispersion is obtained from an organic polyisocyanate (a), a polyol (b) which has at least one of a sulfonate group and a carboxylate group and also has a hydroxyl value of 10 to 350 mg KOH/g, and at least one of a polyamine having a molecular weight of 300 or less and a polyol having a molecular weight of 300 or less (c), wherein a surface tension of said aqueous polyurethane resin dispersion is 40 mN/m or less, and wherein said polyol (b) is obtained from: (1) a compound having a sulfonate group selected from the group consisting of metal salts of dicarboxylic acids, or ester derivatives thereof, containing a sulfonate group, metal salts of 2-sulfo-1,4-butanediol, and alkylene oxide adducts of metal salts of 2-sulfo-1,4-butanediol; (2) at least one of an aliphatic polyol compound and an aromatic polyol compound; and (3) a cyclic ester selected from the group consisting of ε-caprolactone and γ-valerolactone.