| abstract |
Acidic impurities in dihydroxyaromatic compounds such as bisphenol A, as illustrted by sulfonic acids and mercaptocarboxylic acids, can have an adverse effect on the molecular weight of a polycarbonate prepared therefrom by transesterification. The same is true of acidic impurities in diaryl carbonates such as diphenyl carbonate, as illustrated by salicylic acid and ferric chloride. The reagents are analyzed for these impurities. Based on the analysis, the reagents are discarbed or recycled, or a compensatory amount of alkali metal hydroxide is employed as a catalyst in the reaction. |