| abstract |
The invention relates to a method for producing a polyurethane dispersion, comprising the steps: I) providing polyurethane polymers and/or polyurethane pre-polymers A) in a liquid phase comprising a first solvent, which solvent is miscible with water and has a lower boiling point than water; II) in the event that isocyanate functional polymers or isocyanate functional pre-polymers were provided in step I): adding NCO-reactive compounds such that, at least in part, a reaction with the polymers or pre-polymers occurs; III) distilling off the first solvent, which is miscible with water, such that an aqueous polyurethane dispersion is obtained; wherein the liquid phase in step I) still comprises water and/or after step II), water is added to the mixture obtained according to step II). Foam bubbles created during step III) are contacted at least temporarily by a second solvent. The first and second solvents are preferably acetone. The invention further relates to an apparatus for carrying out the method according to the invention. |