PREPARATION OF COMPACT OR CELLULAR POLYURETHANES, POLYISOCYANATE COMPOSITIONS CONTAINING URETHANE GROUPS WHICH CAN BE USED FOR THIS PURPOSE, AND THEIR USE

摘要

The invention relates to a process for the preparation of compact or cellular polyurethanes by reacting relatively high-molecular-weight polyhydroxyl compounds with a liquid polyisocyanate composition containing urethane groups in the presence or absence of chain extenders and/or crosslinking agents, the polyisocyanate composition being obtainable from mixtures of diphenylmethane diisocyanates and polyphenylpolymethylene polyisocyanates and linear, branched or cyclic, saturated or olefinically unsaturated, low-molecular-weight monoalcohols, to the liquid polyisocyanate compositions containing urethane groups which can be used for this purpose, and to their use for the preparation of preferably highly crosslinked polyurethanes, in particular rigid PU (molded) foams.