Aqueous polyurethane resin dispersion and process for preparing the same

An aqueous polyurethane resin dispersion which comprises a polyurethane resin obtained by reacting (A) a polyurethane prepolymer which is obtained by reacting (a) a polyisocyanate compound, (b) a polyalicyclic carbonate diol having a number average molecular weight of 2000 and a polyaliphatic carbonate diol having a number average molecular weight of 1000, (c) an acidic group-containing polyol compound, and (d) a blocking agent for an isocyanate group, which dissociates at 80 to 180° C., and (B) a chain elongating agent which has reactivity with the isocyanate group, being dispersed in an aqueous medium,

• a sum of a content of urethane bondings and a content of urea bondings is 15 to 30% by weight in terms of solid components, a content of carbonate bondings is 8% by weight or more and less than 15% by weight in terms of solid components, and a content of an isocyanate group to which the above-mentioned blocking agent has bound is 0.2 to 3% by weight in terms of solid components and calculated on the isocyanate group,
• wherein
• the polyisocyanate compound is at least one selected from the group consisting of isophorone diisocyanate and 4,4′-dicyclohexylmethane diisocyanate, and
• the acidic group-containing polyol compound is at least one selected from the group consisting of 2,2-dimethylol propionic acid and 2,2-dimethylol butanoic acid.