Patent ID: 7276554

Claim:
Coating materials comprising I) one or more dispersions of hydroxyl-free polyurethanes and/or polyurethane-ureas (PU dispersions) II) one or more aqueous solutions or dispersions of ionically modified, hydroxyl-containing polyurethanes and/or polyurethane-ureas, other than the constituents of component I), and III) at least one crosslinker and IV) optionally other film-forming resins, wherein the PU dispersions used in I) are obtained by A) preparing an NCO-containing polyurethane prepolymer by reacting A1) polyisocyanates with A2) polymeric polyols and/or polyamines having number average molecular weights of 400 to 8000 g/mol, A3) optionally low molecular weight compounds having number-average molecular weights of 17 to 400 g/mol selected from the group consisting of mono- and polyalcohols, mono- and polyamines and also amino alcohols, A4) optionally isocyanate-reactive, ionically or potentially ionically hydrophilicizing compounds and/or A5) optionally isocyanate-reactive nonionically hydrophilicizing compounds A6) optionally in aliphatic ketones as solvents with the proviso that none of components A1) to A5) contains primary or secondary amino groups, B) either dissolving the prepolymer obtained from step A) in aliphatic ketones or, diluting the prepolymer solution if the preparation has already been carried out in the presence of A6) by further addition of aliphatic ketones, and C) reacting the remaining free NCO groups of the prepolymer with a chain extender component comprising C1) hydrazine and/or hydrazine hydrate and C2) optionally compounds meeting the definition of components A2), A3), A4) and/or A5), with the proviso that the compounds of component C2) contain primary and/or secondary amino groups, the total amounts of C1) and C2) are such that an arithmetic degree of chain extension of 101 to 150% is attained and the proportion of C1) and C2) is such that at least 40% of the free isocyanate groups are terminated by and/or chain-extended with amino groups from component C1) at least one of A4) and A5) is utilized to prepare the NCO-containing polyurethane prepolymer A.