Process for the production of aqueous dispersions of polyurethane polyureas, the dispersions obtainable by this process and their use as coating compositions

摘要

The present invention is directed to a process for the production of aqueous polyurethane-polyurea dispersions by reacting NCO-prepolymers having an average NCO-functionality of 2 to 2.3 and an average molecular weight of about 700 to about 5000 with organic polyamines having an average amine functionality of 2.05 to about 3 and an average molecular weight of 60 to about 2000 containing primary and/or secondary amino groups at an NCO/NH ratio about 1.05:1 to about 7:1 in the presence of a water-miscible, weakly polar solvent inert to isocyanate groups and having a boiling point at normal pressure below 100 DEG C., converting the resulting solution of the reaction products into an aqueous dispersion by the addition of water and optionally removing the solvent used by distillation, characterized in that the reactants and amounts used are selected such that the resulting reaction products have an NCO-functionality of 2.2 to about 3 and NCO-content of about 0.1 to 5% by weight. The present invention is also directed to the products of this process and their use for the production of coatings.