Patent ID: 7534830

Claim:
An aqueous dispersion of polyurethane-addition polymer, comprising hybrid particles having a weight average mean diameter of less than 1000 nm comprised of: i) polyurethane polymer; ii) addition copolymer of ethylenically unsaturated copolymerisable monomers, where the polyurethane polymer of i) is the reaction product of: a) aromatic polyisocyanate that is essentially free of sterically hindered isocyanate moieties; b) aliphatic polyisocyanate, wherein the isocyanate functionality of the aromatic polyisocyanate is from 1.8 to 2.3 and the isocyanate functionality of the aliphatic polyisocyanate is up to 4; c) compound containing two hydroxyl moieties reactive with the isocyanate moieties of a) and b); d) compound containing at least one dispersing moiety and at least one moiety reactive with the isocyanate moieties of a) and b), wherein the ratio of the total number of isocyanate moieties from the aromatic polyisocyanate to the total number of the isocyanate reactive moieties of c) and d) is from 0.50 to 1.45; and e) chain extender compound.