Patent ID: 8658709

Claim:
Process for preparing a polyurethane foam, according to the free rise process, the foam having a free rise density of 5-40 kg/m 3 , comprising reacting at an index of 40-65 a polyisocyanate composition consisting of diphenylmethane diisocyanate and of homologues of diphenylmethane diisocyanate, said homologues having an isocyanate functionality of 3 or more, and wherein the polyisocyanate composition has an average isocyanate functionality of 2.10-2.40 and a 2,4′-diphenylmethane diisocyanate content of 6-45% by weight with the proviso that the relationship between this functionality (F) and content (C) is: −123F+287≦C≦−123F+311, and a polyoxyethylene polyoxypropylene polyol (polyol b1) having an oxyethylene content of 5-30% by weight, a nominal functionality of 2-4 and an average equivalent weight of 1000-3000, and optionally up to 18 parts by weight, per 100 parts by weight of polyol b1), of a polyoxyalkylene polyol (polyol b2) having an oxyethylene content of at least 50% by weight, a nominal functionality of 2-6 and an average equivalent weight of 75-2000 and comprising using 5-20 parts by weight, per 100 parts by weight of polyol b1, of water as blowing agent, an effective amount of a catalyst enhancing urethane formation, and an effective amount of a surfactant, with the proviso that the amount of isocyanate-reactive ingredients having an equivalent weight of more than 374 is at least 36 parts by weight per 100 parts by weight of polyisocyanate composition and isocyanate-reactive ingredients, that the process is a one shot process and that the amount of catalyst is 0.1-2% by weight and the amount of surfactant is 0.1-5% by weight, both calculated on all isocyanate reactive ingredients.