COATING COMPOSITIONS AND A PROCESS FOR THE PRODUCTION OF POLYURETHANE COATINGS

摘要

The present invention relates to thermally cross-linkable coating compositions which are liquid and stable in storage at room temperature and which contain combinations of dialkyl-malonate-blocked polyisocyanates and organic polyhydroxyl compounds as binders and, optionally, auxiliaries and additives, being characterized in that the binder comprises a) a polyisocyanate component containing dialkyl-malonate-blocked isocyanate groups and a content of blocked isocyanate groups, expressed as NCO, based on the weight of the polyisocyanate component excluding the weight of the blocking agent, of from about 3 to 33.6% by weight, comprising aa) at least one dialkyl-malonate-blocked, optionally alkyl-substituted diisocyanato-diphenyl methane and/or ab) at least one dialkyl-malonate-blocked NCO-prepolymer based on excess quantities of optionally alkyl-substituted diisocyanatodiphenyl methane and organic compounds containing at least two hydroxyl groups and b) a polyol component having an average hydroxyl functionality of greater than 2 and a content of alcoholic hydroxyl groups of from about 1.5 to 8% by weight, comprising at least one polyester polyol in quantities corresponding to an equivalent ratio of blocked isocyanate groups to hydroxyl groups of from about 0.6:1 to 2:1. The present invention also relates to a process for the production of coatings by coating heat-resistant substrates of any type with these coating compositions and subsequently hardening the coating at about 90 to 220.degree.C.