Polycarbonates prodn. with control of alkalinity - during phosgenation of bisphenol A and polycondensation for improved thermal stability and impact strength

摘要

Polycarbonates (I) are produced by reacting a carbonate precursor with bisphenol A (II) in aq. medium contg. sufficient alkali (ne earth) hydroxide (III) to keep the pH at 8.0-10.5 during the reaction. The improved prps. of the prod. eliminate the need for additives. (II) is mixed in an aq. medium contg. a solvent for (I), a mol. wt. regulator and a catalyst (Et3N); carbonyl halide (COCl2) is introduced and (III) (NaOH) is added to maintain pH 8.0-10.5.