| abstract |
This invention relates to a method for coating leather with an anionically modified polyurethane urea prepared by (1) reacting (A) an aromatic diisocyanate, (B) a polyether polyol having a number average molecular weight greater than 1500, (C) at least one compound containing 1 to 2 isocyanate-reactive groups and at least one ionic group, and (D) a polyamine having a number average molecular weight of at least 32, wherein the average total functionality of compounds (B), (C), and (D) is 1.85 to 2.2 and the molar ratio between the NCO groups of component (A) and the NCO-reactive groups of components (B), (C), and (D) is greater than 1, thereby forming an intermediate having residual NCO groups, and (2) mixing the intermediate product with water to form an aqueous dispersion of an anionically modified polyurethane urea having 800 to 1500 mmol of urethane groups and 800 to 1800 mmol of urethane plus urea groups per kilogram of the polyurethane urea. |