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US 4,743,676 AGranted
Method for preparing polycarbonate of controlled molecular weight from aromatic bischloroformate
AssigneeGeneral Electric Company
InventorsJames M. Silva, Robert A. Pyles
Life of this patent
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Abstract
Linear polycarbonates of controlled molecular weight are prepared by first reacting a bischloroformate composition with a monohydroxyaromatic compound in a system comprising water, a base and a suitable organic liquid, and then converting the resulting partially capped bischloroformate composition to linear polycarbonate by contact with an interfacial polycarbonate formation catalyst in an alkaline medium. By this method, the efficiency of the capping agent is improved.
Claims20
A method for preparing a linear aromatic polycarbonate of controlled molecular weight which comprises the steps of:
- (A) reacting an aromatic bischloroformate composition with a monohydroxyaromatic compound or salt thereof in an essentially phosgene-free reaction system also comprising water, a substantially inert, substantially water-insoluble organic liquid and an alkali or alkaline earth metal base, to produce a partially capped bischloroformate composition;
- and
- (B) contacting said partially capped bischloroformate composition with an interfacial polycarbonate formation catalyst and an aqueous alkali metal or alkaline earth metal base to form said linear aromatic polycarbonate.
Dependencies are inferred from the claim text.