| 摘要 |
RD-18713 METHOD FOR PREPARING POLYCARBONATES OF CONTROLLED MOLECULAR WEIGHT FROM BISCHLOROFORMATES Aromatic polycarbonates having a predetermined relatively low weight average molecular weight, as well as a low molecular weight distribution, are prepared by partially capping an aromatic bischloroformate composition, preferably a bisphenol A bischloroformate composition, with a monohydroxyaromatic compound and subsequently converting the partially capped composition to a polycarbonate, using a base which provides a buffered pH in the range of about 12-13. The preferred base is calcium hydroxide, which is soluble in water in precisely the amount required to provide the desired pH.
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