Patent ID: 6265468
Filing Date: 2001-07-24
Classification: C08G,C09D

Abstract:
An aqueous polyurethane coating composition comprising:i) a hydroxyl group containing polyurethane, dispersed in water, obtainable by two-step reaction ofa polyisocyanate A having at least two isocyanate groups,a polyol B having a M.sub.n of at least 400 g/mol, selected from the group consisting of polyester polyols, polyether polyols, polyurethane polyols, and polyacrylate polyols, with a hydroxyl number of from 30 to 280 mg/g,a compound C that has at least one group capable of forming anions, and at least two groups that are reactive towards isocyanate groups, and optionally,a low molar mass polyol D with M.sub.n of from 60 to 400 g/mol to form an isocyanate-terminated intermediate, which is then reacted with at least one ofa low molar mass polyol E carrying no other isocyanate-reactive group,a compound F which is either monofunctional towards NCO or contains active hydrogen of different reactivity,a compound G selected from the group consisting of water, hydrazine and aliphatic diprimary amines like ethylene diamine, diamino propane and diamino hexane, with an OH number of from 30 to 200 mg/g and M.sub.n of from 1600 to 50000 g/mol dispersed in water,ii) a crosslinker selected from the group consisting of uncapped aliphatic and aromatic polyisocyanate compounds; andiii) an aromatic polyether, selected from the group consisting of epoxy resins, phenoxy resins and mixtures thereof.