To provide a technique for preparing aromatic polycarbonates with long lasting favorable hues and small amounts of foreign materials of gel and so forth in an early period of the reaction time after starting production with a new producing apparatus or re-start of production after a period of production suspension.
The surface treatment is carried out for a reaction vessel discharging an aromatic polycarbonate of a viscosity-average molecular weight of less than 8,000 in the substantial absence of the polycarbonate in the reaction vessel in an atmosphere mainly comprising an inert gas for surface treatment with an oxygen concentration of 0.1 volume % or less, and for a reaction vessel introducing the aromatic polycarbonate of a viscosity-average molecular weight of 4,000 or over while discharging the aromatic polycarbonate of a viscosity- average molecular weight of 8,000 or over from the reaction vessel in an atmosphere for surface treatment with an oxygen concentration of 10-30 volume %.
SAWAKI TORU
SASAKI KATSUJI
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