Method for preparing cyclic polycarbonate oligomer from bischloroformate composition
AssigneeGeneral Electric Company
InventorJames M. Silva
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Abstract
Cyclic polycarbonate oligomers are prepared by a method which is adaptable to continuous operation, by the reaction of a bisphenol bischloroformate (e.g., bisphenol A bischloroformate) with an amine (e.g., triethylamine) and an alkali metal hydroxide in a tank reactor (preferably a continuous stirred tank reactor) in a mixed aqueous-organic system, with agitation (preferably by stirring) at a rate just sufficient to prevent segregation of the aqueous and organic liquid phases. The residence time of the mixture in the reactor is preferably about 8-12 minutes.
Claims16
A method for preparing a composition comprising cyclic polycarbonate oligomers characterized by structural units of the formula ##STR3## where R is a divalent aromatic radical, which comprises:
- simultaneously charging the following to a tank reactor:
- (A) a bischloroformate composition consisting essentially of bischloroformates of the formula ##STR4## wherein n is at most 3 in a major proportion of said bischloroformates;
- (B) at least one aliphatic or heterocyclic tertiary amine which dissolves preferentially in the organic phase of the reaction mixture;
- (C) an aqueous alkali metal hydroxide solution;
- and
- (D) a substantially non-polar organic liquid which forms a two-phase system with water;
- reagent A being charged separately from reagents B and C:
- while maintaining the reaction mixture in said tank reactor under agitation conditions just sufficient to prevent segregation of the aqueous and organic liquid phases;
- allowing said reagents to react for a period of time sufficient to form the desired cyclic oligomers;
- and
- recovering said oligomers.
Dependencies are inferred from the claim text.