Process for preparing high molecular weight polycarbonates

Claim 1

A process for preparing a high molecular weight polycarbonate comprising (A) reacting phosgene with a dihydroxydiarylalkane at a temperature of from 0° to 80° C in the presence of an acid acceptor and a solvent by adding a monohydric phenol and at least one member selected from the group consisting of compounds having the formulas ##STR3## where R is a hydrocarbon residue having 1 to 10 carbon atoms selected from the group consisting of saturated aliphatic hydrocarbon residues, aliphatic hydrocarbon residues having an aromatic group substituent and alicyclic hydrocarbon residues; X is chloro or bromo; the quantity of monohydric phenol is from 0.1 to 5 mole percent, based on the dihydroxydiarylalkane; and the amount of compound according to Formulas (1) and (2) is from 0.5 to 100 mole percent, based on the dihydroxydiarylalkane, to produce a polycarbonate prepolymer having the chains terminated with residues of compounds (1) and/or (2) and an intrinsic viscosity of 0.01 to 0.40, determined with an Ostwald viscosimeter in methylene chloride at 25° C, and (B) heating and melting under reduced pressure the prepolymer so formed to cause polycondensation thereof at a temperature of 220° to 320° C.