Process for the continuous production of aqueous polyurethane dispersions and their use as a coating composition or as an adhesive

Claim 1

A continuous process for the production of an aqueous polyurethane dispersion which comprises continuously mixing a solution of (a1) a polyurethane free from isocyanate groups wherein the dispersibility in water is provided by a member selected from the group consisting of chemically incorporated potential ionic groups which are subsequently neutralized, chemically incorporated ionic groups, chemically incorporated ethylene oxide units present within terminal polyether chains, chemically incorporated ethylene oxide units present within lateral polyether chains, external emulsifiers in physical admixture with said polyurethane and mixtures thereof, or (a2) an isocyanate prepolymer containing free isocyanate groups wherein the dispersibility in water is provided by a member selected from the group consisting of chemically incorporated potential ionic groups which are subsequently neutralized, chemically incorporated ionic groups, chemically incorporated ethylene oxide units present within terminal polyether chains, chemically incorporated ethylene oxide units present within lateral polyether chains, external emulsifiers present in physical admixture with said prepolymer and mixtures thereof, in (b) an organic solvent having a boiling point below 100° C. or a mixture of said solvent with up to about 50% by weight, based on the total weight of component (b), of water, with (c) water in an amount sufficient to provide an oil-in-water emulsion, and subsequently removing by continuous distillation at least a portion of the solvent (b) from the resulting aqueous dispersion by means of a circulation-type evaporator having flooded evaporator surfaces.