POLYISOCYANATE COMPOSITIONS

摘要

Polyisocyanate composition comprising : (A) 30-45% w of diphenylmethane diisocyanates ; (B) 28-67% w of polymethylene polyphenylene polyisocyanates having more than two free isocyanate groups in the molecule ; and (C) 3-27% w of a prepolymer from a diphenylmethane diisocyanate and a compound containing at least two isocyanate-reactive groups and having a molecular weight below 1000 ; the % w being calculated on the total amount of (A), (B) and (C) present in the composition ; the number average isocyanate functionality of the composition being at least 2.3. The compositions show improved miscibility with rigid foam polyols resulting in processing benefits. Foams made from these compositions exhibit smaller cell size and lower thermal conductivity.