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The melt transesterification of polycarbonate (PC) by diphenol carbonate (DPC) and 4,4‘-dihydroxy-diphenyl-2,2-propane (BPA) using 4-(dimethylamino)pyridine (DMAP) as the catalyst was studied experimentally. It was observed that the operating conditions markedly influenced the properties of the resulting polymer. Narrow temperature control in the heat-transfer operation reduced the unwanted thermal effects. The ratio of DPC/BPA markedly influenced the intrinsic viscosity of the resulting polymer. A ratio in the range 1.03−1.05 was found to yield polymer with a high intrinsic viscosity. The molecular weight distribution of the PC product had the most probable distribution. The concentration of the catalyst reasonably affected the hue of the PC resin, and we suggest that it should not exceed 50 ppm when DMAP is used as the catalyst.
Hsu et al. (Wed,) studied this question.