| 摘要 |
Process for preparing a polyurethane foam, according to the free rise process, the foam having a free rise density of 5-40 kg/m3, comprising reacting at an index of 40-80 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 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. Foams are claimed as well. The foams show good sound absorption and/or sound insulation.
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