Process for the preparation of poly(ester-carbonates)

Claim 1

Process for preparation of a high molecular weight poly(ester-carbonate) comprising (a) preparing a reaction mixture of (1) an aromatic diol bis(alkylcarbonate) (A) having the general formula ##STR12## wherein R is the same or different and selected from alkyl groups containing 1-8 carbon atoms and Ar is the aromatic residue remaining after removal of hydroxyl groups from an aromatic diol, (2) 0 to 47.5 mole percent of at least one ester of at least one dicarboxylic acid (B) having the general formula ##STR13## wherein R is the same or different and selected from alkyl groups containing 1-8 carbon atoms and Y is the residue remaining after removal of the carboxyl groups from an aliphatic, cycloaliphatic or aromatic dicarboxylic acid, (3) 0 to 80 mole percent of at least one mixed carboxylate-carbonate ester of at least one aromatic hydroxy acid (C) having the general formula ##STR14## wherein R is the same or different and selected from alkyl groups containing 1-8 carbon atoms and Z is the residue remaining after removal of the hydroxyl and carboxyl groups from meta- or para-oriented aromatic hydroxy carboxylic acids, and (4) a catalytic amount of an ester exchange and polymerization catalyst, wherein the molar percentages of (A)+(B)+(C)=100%, the molar percentage of (A) is at least 5 percentile units greater than the molar percentage of (B); the molar percentage of (B) or the molar percentage of (C) may be 0, but the molar percentage of (B)+ the molar percentage of (C) is at least 5% of the total reactants, (b) heating the reaction mixture to a temperature sufficient to keep the reaction mixture molten and to distill away dialkyl carbonate condensation by-product, and (c) reducing pressure for a time sufficient to further remove dialkyl carbonate condensation product and to increase the molecular weight of the polymer.