| 摘要 |
PROBLEM TO BE SOLVED: To produce an optical polycarbonate having a reduced content of particulates and high quality by filtering a molten mixture of a bisphenol with a carbonic diester through a fluororesin membrane filter and subjecting the filtrate to melt polycondensation. SOLUTION: The bisphenol used is desirably bisphenol A. The bisphenol and the carbonic diester are each desirably a filtrate obtained by filtering each in a molten state through a filter. Although not particularly limited, the filter used is desirably one having an absolute filtration accuracy (pore diameter) of 20μm or below. The thus prepared molten mixture is filtered to remove therefrom impurities such as particulates in the mixture. It is desirable that the filtration is carried out by using a fluororesin membrane filter and that the filtration accuracy (pore diameter) of the filter is 1.0μm or below. After the filtration, the filtrate is subjected to melt polycondensation, and it is preferable that the formed polycarbonate is filtered through a general-purpose filter having an absolute filtration accuracy (pore diameter) of 50μm or below while the mixture is in a molten state.
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