Process for the preparation of polyesters and poly(ester-carbonates)

Claim 1

Process for preparing polyesters and poly(ester-carbonates) comprising (a) preparing a reaction mixture of (1) an aromatic polycarbonate having an inherent viscosity of about 0.1 or more and (A) having the general formula ##STR6## wherein Ar is the residue remaining after the removal of the hydroxy groups from at least one aromatic diol and optionally the residue may be substituted with alkyl groups containing 1-4 carbon atoms or phenyl, (2) an ester of a dicarboxylic acid (B) having the general formula ##STR7## wherein R may be the same or different and is selected from aliphatic, cycloaliphatic and aryl groups containing up to 8 carbon atoms, and Y is the residue remaining after removal of the carboxyl groups from an aliphatic, cycloaliphatic or armatic dicarboxylic acid, and (3) a catalytic amount of a suitable ester exchange and polymerization catalyst, (b) initially heating said reaction mixture sufficiently to substantially reduce the melt viscosity of the reaction mixture, (c) increasing the temperature as required to keep the reaction mixture molten and to distill away the dialkyl or diaryl carbonate condensation by-product, and (d) reducing pressure to further remove said by-product and to increase the molecular weight of the polymer product.