Process for the production of polyurethane urea resin dispersions

摘要

A process for the production of an aqueous polyurethane urea resin dispersion with a carboxyl number of 10 to 50 mg KOH/g resin solids and a ketone content of 5 to 10 wt.% relative to resin solids, comprising the steps:
1) producing a carboxylate-functional, non-gelled, water-dispersible polyurethane prepolymer with a free isocyanate group content of 1.5 to 3 wt.% by reacting at least one polyol, at least one tertiary amine-neutralized polyhydroxycarboxylic acid and at least one polyisocyanate, in the presence of at least one ketone,
2) converting the ketone solution into an aqueous dispersion by mixing with water, and
3) chain extending the polyurethane prepolymer by reacting the free isocyanate groups thereof with water and/or at least one compound, having at least two amino groups capable of addition to isocyanate groups, to form urea groups,
wherein the proportion of the ketone or ketones used in step 1) is selected in such a way that the aqueous polyurethane urea resin dispersion, obtained contains 5 to 10 wt.% of ketone relative to the resin solids.