Process for the preparation of fluorchlorohydrocarbon-free, low-density polyurethane soft foams and soft elastic polyurethane molding foams and polyisocyanate mixutes modified with urethane groups on diphenylmethane-diisocyanate base

Abstract From the Canadian patent

Disclosed is a method for the preparation of FCHC-free polyurethane soft (molded) foam materials with low density, by reacting (A) liquid polyisocyanate mixtures containing bound urethane groups, containing 22 to 30 weight percent of NCO groups, which in turn are prepare by reacting a mixture of diphenylmethane-diisocyanate and polyphenyl-polymethylene-polyisocyanates (raw MDI) with at least one polyoxypropylene-polyoxyethylene-polyol with a functionality between 2.5 and 3.6, a hydroxyl number between 50 and 90 and a polymerized ethylene oxide group concentration ranging from more than 30 to less than 50 weight percent relative to the, weight of the polymerized ethylene oxide and 1,2 …