PROCESS FOR MAKING A FLEXIBLE POLYURETHANE FOAM

598608 Disclosed herein is a flexible polyurethane foam having a density of 25-70 kg/m3 a compression load deflection at 40 % (CLD) of 5-15 kPa, a volume increase at water saturation (%) of at most 25 %, and a water buffer capacity (%) of 40-60%. Additionally disclosed is a process for making a flexible polyurethane foam comprising reacting at an isocyanate index of 20-70 and at a water index of 200-400 a polyisocyanate prepolymer having an NCO-value of 20-30 % by weight and made by reacting a polyisocyanate comprising 30-80 % by weight of diphenylmethane diisocyanate and 20-70 % by weight of homologues of this diisocyanate the homologues having an isocyanate functionality of 3 or more, the amounts both calculated on the amount of polyisocyanate, and a polyol having an average molecular weight of 62-1000 and an average nominal hydroxyl functionality of 2-4, a polyoxyethylene polyoxypropylene polyol or a mixture of such polyols, the polyol or the mixture having an average nominal hydroxyl functionality of 2-4, an average molecular weight of 2000-8000 and an average oxyethylene content of 25-50 % by weight, calculated on the weight of this polyol or mixture respectively, water, and optionally isocyanate-reactive chain extenders and/or cross-linkers having an average molecular weight of 60-1999, and optionally in the presence of auxiliaries and additives used in the polyurethanes art.