Dispersions of crosslinked polymer micro-particles in aqueous media, a process for the preparation of these dispersions, and coating compositions containing these dispersions

A process for the preparation of a dispersion of crosslinked polymer micro-particles in an aqueous medium prepared:

• (1) by dispersing components (A) and (B) in an aqueous medium, the component (A) being a polyester-polyol containing at least 2 hydroxyl groups, and component (B) being a polyisocyanate in which the isocyanate groups are at least partially in the masked form, and the components (A) or (B) having available a number of ionic groups sufficient to form a stable dispersion, and at least one part of the components (A) and (B) containing more than 2 hydroxyl, isocyanate, or masked isocyanate groups per molecule and
• (2) by subsequently heating the dispersion thus obtained to a temperature sufficiently high for the components (A) and (B) to react to form crosslinked polymer micro-particles.

A coating composition which is composed of a dispersion of crosslinked polymer micro-particles in an aqueous medium and which, in addition to the polymer micro-particles, can also additionally contain further filmforming material, pigments and further customary additives, and which is preferentially suitable for the production of base coats of multi-coat, protective and/or decorative coatings, wherein the dispersion of crosslinked polymer micro-particles in an aqueous medium has been prepared.

• (1) by dispersing a mixture of the components (A) and (B) in an aqueous medium, the component (A) being composed of one or more polyester-polyols containing at least 2 hydroxyl groups and the component (B) being composed of one or more polyisocyanate compounds in which the isocyanate groups are at least partially in the masked form, and the components (A) or (B) having available a number of ionic groups, preferably carboxylate groups, sufficient to form a stable dispersion, and at least one part of the components (A) and (B) containing more than 2 hydroxyl, isocyanate, or masked isocyanate groups per molecule and
• (2) by subsequently heating the dispersion thus obtained to a temperature sufficiently high for the components (A) and (B) to react to form crosslinked polymer micro-particles.