AQUEOUS DISPERSION OF A POLYURETHANE CONTAINING BLOCKED REACTIVE SITES

摘要

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<1> and Q<2> is a hydrazone functional group of formula (2), H or R<1>, R and R<1> in formula (1) is an organic group which has no reactivity towards the hydrazone function, R<2> and R<3> in formula (2) is an organic group which has no reactivity towards the hydrazone function or is 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<1> or Q<2> is of formula (2). The invention relates also to a process for a preparation of an aqueous dispersion of a crosslinkable polyurethane containing hydrazone 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.