Patent ID: 7057004

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), and a carbonate source, 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. selecting a catalyst introduction strategy sufficient to result in a product copolycarbonate with improved color, wherein the catalyst introduction strategy is selected from the group consisting of, 1. introducing a polymerization catalyst to the molten reaction mixture after monomer residues (a), monomer residues (b), and carbonate source are melted and prior to substantial polymerization, 2. introducing a polymerization catalyst to the reaction mixture or monomer residues prior to melting with the proviso that residence time of the process from the start of melting until substantial polymerization has occurred is less than 4 hours, and 3. or a combination thereof, wherein the polymerization catalyst is an inorganic catalyst, an organic catalyst, or both inorganic and organic catalyst which may be introduced separately or together, iii. introducing the catalyst according to the selected catalyst introduction strategy, iv. introducing the reaction mixture to a series of process units, and v. 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 without the steps of selecting a catalyst introduction strategy and introducing catalyst according to the selected strategy.