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Abstract

The invention relates to an aqueous dispersion of a crosslinkable polyurethane obtained by chain extension of a polyurethane prepolymer with a compound containing hydrazone functions having general formula (1), wherein Q.sup.1 and Q.sup.2 is a hydrazone functional group of formula (2), H or R.sup.1, R and R.sup.1 in formula (1) is an organic group which has no reactivity towards the hydrazone function, R.sup.2 and R.sup.3 in formula (2) is an organic group which has no reactivity towards the hydrazone function or H, x has a value from 1 to 10, and is preferably from 1 to 4 with the proviso that at least one of the groups Q.sup.1 or Q.sup.2 is of formula (2). The invention relates also to a process for a preparation of an aqueous dispersion of a crosslinkable polyurethane containing hydrazne functions, and to the application of the aqueous dispersion of a crosslinkable polyurethane together with a polyisocyanate, a polyketone--or a polyepoxide--functional material onto a substrate. ##STR1##

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First Claim