WATER-DILUTABLE BINDERS AND THEIR USE FOR COATING MATERIALS, IN PARTICULAR IN AUTOMOTIVE CONSTRUCTION

The invention relates to a water-dilutable binder and its use for the preparation of aqueous coating materials and for coating purposes. The binder can be used to provide an aqueous binder system which is suitable for the production of stone-chip-resistant coatings. The waterdilutable binder contains A) 40 to 90% by weight of base resins which become water-dilutable as a result of neutralization with acids and have a number average molecular weight Mn of 500 to 20,000 and B) 10 to 60% by weight of a completely blocked polyisocyanate mixture consisting of (1) one or more terminal blocked diisocyanates which contain urethane groups and optionally urea groups, are free of OH groups and are reaction products of H-reactive bifunctional compounds, which optionally contain tertiary amino groups, with diisocyanates, having a number average molecular weight Mn of 750 to 8,000 and an amine number of 30 to 150, and (2) aromatic and/or aliphatic blocked polyisocyanates having more than two blocked isocyanate groups and a number average molecular weight Mn of 500 to 1,500, the components B1 and B2 being present in a weight ratio of 1:1 to 1:10.