Patent ID: 7501481
Filing Date: 2009-03-10
Classification: C08G

Abstract:
1. A method of producing a copolycarbonate with improved color wherein the method comprises the steps of, i. preparing a molten reaction mixture in a monomer mix tank wherein the reaction mixture comprises a first dihydroxy aromatic compound comprising monomer residue (a), a second dihydroxy aromatic compound comprising monomer residue (b), and a carbonate source, ii. introducing a polymerization catalyst to the reaction mixture or monomer residues prior to melting in said monomer mix tank with the proviso that the residence time of the process from the start of melting until substantial polymerization has occurred is less than 4 hours, iii. introducing the reaction mixture to a series of process units, wherein said series of process units comprises a plurality of polymerization process units in which polymerization occurs and copolymer molecular weight increases, and iv. allowing the reaction mixture to polymerize in the series of process units thereby forming copolycarbonate, wherein the copolycarbonate has improved color as compared to a copolycarbonate formed in a melt process wherein said residence time is not less than 4 hours.