Aqueous polyuretane dispersions, process for their preparation and their use in aqueous coating compositions.

摘要

The coating composition contains: I) from 40 to 100% by weight of a film former in the form of an aqueous dispersion of one or more polyurethane resins having a number average molecular weight (Mn) of from 2500 to 1,000,000 and a content of ionic groups, hydrophilic groups and/or groups which can be converted into ionic groups of from 5 to 200 meq per 100 g of solid resin, and at least one CH-acidic group per molecule and an OH number of from 0 to 100, where all or some of the CH-acidic groups can, for chain extension, be reacted with one or more compounds which are capable of reacting with at least two CH-acidic groups, and II) from 60 to 0% by weight of one or more crosslinking agents based on compounds which are capable of reacting with at least two CH-acidic groups, based on formaldehyde condensation resins and/or polyisocyanates containing free or blocked isocyanate groups, where the percentages by weight of I) and II) are based on the resin solids content and add up to 100% by weight, and optionally pigments, fillers, organic solvents and/or additives which are conventional in paints (surface coatings, lacquers, varnishes, enamels).