Preparation of chlorofluorocarbon-free flexible polyurethane foams using diphenylmethane diisocyanate-based polyisocyanate mixtures containing urethane groups, and modified polyisocyanate mixtures of this type

Abstract From the Canadian patent

The invention relates to a, process for the preparation of CFC-free flexible, polyurethane foams or molded foams by reacting A) liquid polyisocyanate mixtures containing bonded urethane groups and having a content of NCO groups of from 20 to 30% by weight, these mixtures themselves being prepared by reacting a mixture of diphenylmethane diisocyantes and polyphenyl-polymethylene polyisocyanates (crude diphenylmethane diisocyanate) with a polyether-polyol mixture having a hydroxyl number of from 120 to 25 of at, least one polyoxypropylene glycol and at least one trifunctional polyoxypropylene-polyoxyethylene glycol having a content of ethylene oxide units of from 90 to 10% by weight or by …