Patent ID: 7045573

Claim:
An aqueous polyurethane dispersion comprising A) a polyurethane prepolymer having an NCO content of from about 2 to about 4 by weight, prepared by reacting: a) an isocyanate selected from the group consisting of i) an aliphatic and/or a cycloaliphatic isocyanate, ii) a mixture of an aromatic isocyanate and an aliphatic and/or a cycloaliphatic isocyanate, b) a di- or polyhydroxy compound having a number average molecular weight of from 700 to about 16,000, and c) optionally, a dihydroxy and/or polyhydroxyl compound having a number average molecular weight of less than 700, with the provisos that 1) at least one of components a), b) or c) has a functionality of more than 2 and 2) if both component a) and component b) are difunctional, component c) cannot be a trihydroxy component of the formula: R—(OH) 3 where R is a saturated straight chain or branched chain aliphatic group of from 2 to 8 carbon atoms B) a compound having an anionic or potentially anionic group and two groups which are reactive to isocyanate groups, and C) a chain extender having two amine groups which are reactive with isocyanate groups, wherein said component B) is a diamine or polyamine which contains alkali metal sulfonate groups.