Patent ID: 7034099

Claim:
A method of producing a copolycarbonate with improved color wherein the method comprises the steps of, i. preparing a molten reaction mixture comprising a first dihydroxy aromatic compound comprising monomer residue (a), a second dihydroxy aromatic compound comprising monomer residue (b), a carbonate source, and a polymerization catalyst, wherein monomer residue (a) is a quinone structure or a structure capable of forming a quinone structure upon oxidation, wherein monomer residue (b) is a quinone structure or a structure capable of forming a quinone structure upon oxidation different from monomer residue (a), or is, where B is —O—, —CO—, —S—, —SO 2 —, a C 6 –C 20 aromatic radical, or a C 6 –C 20 cycloaliphatic radical; the groups R 1 and R 2 are independently a hydrogen atom, C 1 –C 20 alkyl radical, C 4 –C 20 cycloalkyl radical, or C 4 –C 20 aryl radical; or R 1 and R 2 together form a C 4 –C 20 cycloaliphatic ring which is optionally substituted by one or more C 1 –C 20 alkyl, C 6 –C 20 aryl, C 5 –C 21 aralkyl, C 5 –C 20 cycloalkyl groups or a combination thereof, R 3 is a divalent hydrocarbylene group, and R 4 and R 5 are independently a hydrogen atom, halogen atom, nitro group, cyano group, C 1 –C 20 alkyl radical C 4 –C 20 cycloalkyl radical, or C 6 –C 20 aryl radical and p and q are both integers from 0 to 4, ii. introducing an antioxidant selected from the group consisting of hydroxycarboxylic acids, benzofuranones, phenolic antioxidants, hydroxylamines, functionalized aliphatic hydroxylamines, and substituted dibenzylhydroxylamine to the reaction mixture in an amount sufficient to result in a product copolycarbonate with improved color, iii. introducing the reaction mixture to a series of process units, and iv. allowing the reaction mixture to polymerize thereby forming copolycarbonate, wherein the copolycarbonate has improved color as compared to a copolycarbonate formed in a melt process without the introduction of antioxidant.