POLYISOCYANATE MIXTURES, A PROCESS FOR THEIR PRODUCTION AND THEIR USE FOR THE PRODUCTION OF POLYURETHANES

摘要

POLYISOCYANATE MIXTURES, A PROCESS FOR THEIR PRODUCTION AND THEIR USE FOR THE PRODUCTION OF POLYURETHANES The present invention relates to polyisocyanate mixtures which are solid below 40.degree.C and liquid above 125.degree.C and which have a) an average isocyanate functionality of at least 2.1, b) a content of free isocyanate groups bonded to tertiary (cyclo)aliphatic carbon atoms (calculated as NCO; molecular weight = 42) of 5 to 22 wt.%, c) a urethane group content calculated as -NH-CO-O-; molecular weight = 59) of 2 to 30 wt.%, d) an isocyanate group content (calculated as C3N3O3; molecular weight = 126) of 0 to 30 wt.% and e) a carboxylic acid ester group content (calculated as -CO-O-; molecular weight= 44) of 0 to 25 wt.% and/or f) a carbonate group content (calculated as -O-CO-O-; molecular weight = 60) of from 0 to 34wt.% with the proviso that the total amount of ester groups e) and carbonate groups f) is at least 2 wt.%. The present invention also relates to a process for the production of these polyisocyanate mixtures and to their use for the production of polyurethanes, inparticular as the crosslinking component in heat-curable two-component polyurethane powder coatings for coating heat-resistant substrates.