POLYISOCYANATE BASED ON DIPHENYLMETHANE DIISOCYANATE AND CONTAINING ALLOPHANATE GROUP AND BLOCKED ISOCYANATE GROUP

摘要

The present invention relates to polyisocyanates prepared from diphenylmethane diisocyanate wherein at least 95% of the isocyanate groups are blocked with diethyl malonate and wherein the polyisocyanates have, based on solids, A) a content of unblocked and blocked isocyanate groups (calculated as NCO) of 9% to 13%, B) a content of allophanate groups (calculated as C2HN2O3, molecular weight 101) of 3% to 9% and C) a calculated average functionality of 2.0 to 2.5. The present invention also relates to a process for the production of these polyisocyanates and to their use as crosslinking agents for organic polyhydroxyl compounds in polyurethane stoving lacquers.