The invention relates to coating agents containing polyisocyanates that include amino silane groups and/or mercapto silane groups, further containing a stored mixture of hydroxyl group-containing compounds and alkoxysilyl-functional siloxanes, and catalysts for crosslinking silane groups. Also disclosed are the production of said coating agents and the use thereof for producing coatings on substrates, in particular plastic substrates, e.g. substrates used in the automobile industry.