| 摘要 |
A process for preparing a polyurethane elastomer having an apparent overall density of more than 150 kg/m3 comprising reacting a polyisocyanate and an isocyanate-reactive composition, optionally in the presence of water, wherei n the reaction is conducted at an isocyanate index of 85 to 120, the polyisocyanate consists ofa) 80-100 % by weight of a diphenylmethane diisocyanate comprising at least 40 % by weight of 4,4'-diphenylmethane diisocyanate and/or a derivative of said diphenylmethane diisocyanate which derivative is liquid at 25 ~C and has an NCO value of at least 20% by weight , and 20-0 % by weight of another polyisocyanate, and wherein the isocyanate- reactive composition consists of a) 80-100 % by weight of a polyether polyol having an average nominal functionality of 2-8, an average equivalent weight of 750-5000, an average molecular weight of 2000-12000, an oxyethylene conte nt of 60-90 % by weight and a primary hydroxyl content of 70-100 % calculated o n the total number of primary and secondary hydroxyl groups in the polyol, b) an isocyanate-reactive chain extender in an amount such that the hard block rat io is less than 0.50 and c) 20-0 % by weight of one or more other isocyanate- reactive compounds excluding water, the amount of polyol a) and isocyanate- reactive compound c) beingcalculated on the total amount of this polyol a) and compound c).
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