| 摘要 |
PURPOSE: To efficiently obtain a high-purity diester compound by holding for a specified time a molten mixture containing the subject compound while gradually cooling and solidifying the mixture followed by subjecting it to cooling, grinding and washing processes. CONSTITUTION: First, a molten mixture containing anα-oxyacid's intermolecular cyclic diester of the formula (R<1> and R<2> are each H or a 1-5C alkyl) and impurities is held for a specified time while gradually cooling and solidifying the mixture within the temperature range between the solidifying point and the solidifying point minus 30 deg.C. Subsequently, the mixture is cooled at a rate of pref. <=10 deg.C/min and solidified and then ground into powder which is then washed with a solvent and purified. Preferable examples of the objective diester include L-lactide, D-lactide and DL-lactide.
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