Preparation of by the bischloroformate process of soft segment polycarbonate

A process for the preparation of a thermoplastic, copolyestercarbonate having a polymer backbone made up of recurring carbonate structural units of the formula:

• ##STR5## wherein D is a divalent aromatic radical residue of a dihydric phenol of the formula:
• ##STR6## wherein A is a divalent hydrocarbon radical containing from 1 to about 15 carbon atoms;
• or a substituted divalent hydrocarbon radical containing from 1 to about 15 carbon atoms and halogen substituents;
• --S--;
• --S--S--;
• --S(.dbd.O)--;
• --S(.dbd.O).sub.2 --;
• --O--:
• or --C(.dbd.O)--;
• wherein each X is independently selected from the group consisting of hydrogen, halogen, an alkyl group of from 1 to about 8 carbon atoms, an aryl group of from 6-18 carbon atoms, an aralkyl group of from 7 to about 14 carbon atoms, an alkaryl group of from 7 to about 14 carbon atoms, an alkoxy group of from 1 to about 8 carbon atoms, and an aryloxy group of from 6 to 18 carbon atoms;
• and wherein m is zero or 1 and n is an integer of from 0 to 5 employed in a preparative polymerization reaction;
• and repeating or recurring carboxylic chain units of the formula:
• ##STR7## wherein n is a whole number integer of from 6 to 36, which comprises;
• a) phosgenating a dihydric phenol in the presence of an aliphatic dicarboxylic acid of formula:
• ##STR8## wherein n is as defined above, at a temperature of from 0.degree. to 100.degree. C. to yield an excess of chloroformate end-groups relative to phenolic or carboxylic acid moieties;
• and no phosgene remains;
• b) adding a carbonate forming reagent and a chain stopper;
• and
• c) polymerizing the chloromates with any remaining phenols and carbonate acids at a pH of from 10 to 12.5.