| 摘要 |
Process for preparing a flexible polyurethane foam comprising reacting at an isocyanate index of 70 to 130, preferably 80-120, most preferably 100-115, 1) 40-65 and preferably 45-63 parts by weight of a polyisocyanate composition comprising a) 80-100% by weight of a diphenylmethane diisocyanate (MDI) component comprising, based on 100 parts by weight of the MDI component, 1) 75-100 and preferably 85-100 parts by weight of diphenylmethane diisocyanate comprising 15-75, preferably 25-75 and most preferably 30 to 70 parts by weight of 4,4'-diphenylmethane diisocyanate, and 25 to 85, preferably 25 to 75 and most preferably 30 to 70 parts by weight of 2,4'-MDI, and 2,2'-MDI and/or a liquid variant of such diphenylmethane diisocyanate, and 2) 0 to 25 and preferably 0-15 parts by weight of homologues of diphenylmethane diisocyanates having an isocyanate functionality of 3 or more; and b) 20-0% by weight of toluene diisocyanate; 2) 20 to 45, preferably 20-40 parts by weight of a polyether polyol (polyol 2) having an average molecular weight of 4500-10000, an average nominal functionality of 2-6 and preferably 2-4 and comprising oxypropylene and optionally oxyethylene groups, the amount of oxypropylene groups being at least 70% by weight calculated on the weight of this polyol; 3) 3 to 20 parts by weight of a polyether polyol (polyol 3) having an average molecular weight of 700-4000 and preferably of 1000-2000, an average nominal functionality of 2-6 and an hydroxyl value of at most 225 mg KOH/g and comprising oxyethylene and optionally oxypropylene groups, the amount of oxyethylene groups being at least 70% by weight calculated on the weight of this polyol; and 4) 2-6 parts by weight of water, the amount of polyisocyanate 1), polyol 2), polyol 3) and water being 100 parts by weight.
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