Patent ID: 9718918
Date: 2017-08-01
CPC Classifications: C08G

Claim:
1. A method for preparing polycarbonate copolymer by an interfacial method, comprising phosgenating a mixture comprising an aromatic dihydroxy compound, water, an organic solvent substantially immiscible with water, and a condensation catalyst to form a reaction mixture; cofeeding an aqueous high heat comonomer feed to the reaction mixture during the phosgenation step, wherein during phosgenation, a ratio of high heat comonomer/phosgene weight/weight dry basis is about 1.75 to about 9; and maintaining the pH of the reaction mixture during the phosgenation step at greater than 7 to less than 11, to form a polycarbonate copolymer comprising greater than about 30 mole % structural units derived from the high heat comonomer.