Idemitsu Kosan Company, Limited

Kazuhiro Sekiguchi

Noriyuki Kunishi

Yukiko Nagao

Masayuki Takahashi

Kenji Sasaki

Provided is a method of producing a branched polycarbonate, including: a step (a) of subjecting an alkali aqueous solution of a dihydric phenol, phosgene, and a branching agent to a phosgenation reaction in the presence of an organic solvent to provide a reaction liquid; a step (b) of adding the alkali aqueous solution of the dihydric phenol and a polymerization catalyst to the reaction liquid obtained from the step (a) to provide a reaction liquid containing a polycarbonate oligomer; a step (c) of separating the reaction liquid containing the polycarbonate oligomer obtained in the step (b) into an organic solvent phase containing the polycarbonate oligomer and an aqueous phase; and a step (d) of causing the organic solvent phase containing the polycarbonate oligomer separated in the step (c) and the alkali aqueous solution of the dihydric phenol to react with each other to provide a reaction liquid containing the branched polycarbonate, in which a ratio (x/y) of an addition amount of the polymerization catalyst to be added in the step (b), which is represented by x mol/hr, to a chloroformate group amount of the polycarbonate oligomer in the reaction liquid obtained from the step (b), which is represented by y mol/hr, is 0.0035 or more.

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Chiba, Japan

Kazuhiro Sekiguchi