| 摘要 |
<p><P>PROBLEM TO BE SOLVED: To provide a method for producing a polycarbonate resin that has a low photoelastic constant, yet has few number of gels and is suitable especially for optical uses. <P>SOLUTION: The method for producing a polycarbonate includes using at least two kinds of diols and a polycarbonate precursor substance. When the polycarbonate precursor substance is melted and polymerized in the condition that the amount of a cyclic acetal-based diol represented by formula (A) (wherein R<SB>1</SB>-R<SB>4</SB>are each independently a hydrogen atom or 1-10C alkyl) fed is 10-90 mol% based on the molar number of the all diols, the final resin temperature, the number of moles of residual cyclic acetal-based diols in the number of moles of all diols and a specific viscosity are controlled in a step for adjusting a final degree of vacuum to≤40 and≥8 kPa, a step for adjusting the final degree of vacuum to <8 and≥1 kPa and a step for adjusting the final degree of vacuum to <1 kPa. <P>COPYRIGHT: (C)2011,JPO&INPIT</p> |
