| 摘要 |
PROBLEM TO BE SOLVED: To provide a process for the preparation of NCO prepolymers such that, as a result of technical improvements, the prepolymers are no longer become cloudy. SOLUTION: The process for the preparation of NCO-terminated prepolymers which are clear and are stable in storage at room temperature. The process comprises reacting more than polycarbonate polyols (1) with a stoichiometric excess of 4,4'-diphenylmethane diisocyanate (2), wherein, before reacting with 4,4'-diphenylmethane diisocyanate, the polycarbonate polyols are subjected to a short-path or thin-film distillation which results in the hydroxy value of the polycarbonate polyols (1) being reduced by at least 1.5 hydroxy value units. COPYRIGHT: (C)2006,JPO&NCIPI
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