Poly(ester-carbonates) from dicarboxylic acid chlorides

In a process for production of poly(ester-carbonate) of dihydric phenol and of aromatic or cycloaliphatic dicarboxylic acid from a reaction mixture containing dichloride of at least one such acid, dissolved in a chlorinated hydrocarbon solvent inert under the reaction conditions having from 1 to 6 carbon atoms and from 1 to 4 chlorine atoms, said process employing a tertiary nitrogen base, having pK.sub.b in aqueous solution at 25.degree. C. in the range 7-11, to catalyze condensation of such dihydric phenol with said dichloride and with phosgene employed as carbonate precursor, and to serve as HCl acceptor for the HCl generated in said condensation reactions;

• the improvement which comprises:
• (1) Feeding at least one such dihydric phenol into said dichloride solution at temperature in the range 0.degree.-100.degree. C., said dichloride solution containing at the start of said condensation reaction, phosgene in the range between 10% and 50% of the stoichiometric proportion of phosgene:
• total dihydric phenol required for formation of the poly(ester-carbonate) final product with the desired mol ratio in the range 1.00:0.05 up to 1.00:0.70 of dihydric phenol:dichloride residues;
• (2) Concurrently with the feeding of dihydric phenol, agitating the reaction mixture and feeding phosgene in a separate stream thereto, until all dihydric phenol for the reaction has been added and at least 80% but not over 97% of the stoichiometrically required phosgene for reaction with all hydroxyl groups has been added;
• (3) Maintaining during the feeding of dihydric phenol, at least a 10% molar excess of tertiary nitrogen base over that required by stoichiometry;
• (4) Then allowing time for the condensation reaction forming poly(ester-carbonate) to come essentially to completion while the phosgene added is being brought at least to the stoichiometrically required quantity for reaction with all hydroxyl groups.