Method for producing a polyurethane dispersion with a reduced foam formation

Abstract

The invention relates to a method for producing a polyurethane dispersion, having the steps of: I) providing isocyanate-functional prepolymers A) in a liquid phase comprising a solvent which can be mixed with water and which has a lower boiling point than water and II) adding NCO-reactive compounds to the isocyanate-functional prepolymers from step I) such that a reaction with the prepolymers is at least partly produced; wherein the liquid phase in step I) additionally comprises water and/or after step II), water is added to the mixture obtained in step II). A pressure p1 is applied to the liquid mixture with the isocyanate-functional prepolymers A) prior to and/or while carrying out step II), wherein p1 is less than the local atmospheric pressure present at said point in time. The pressure p1 is selected such that in step II), ≤50 mass. % (preferably >0 mass. % to ≤mass. %, more preferably ≥0.1 mass. % to ≤30 mass. % in particular ≥1 mass. % to ≤10 mass. %) of the originally provided solvent which can be mixed with water is distilled.

Dependencies are inferred from the claim text.