Process for the synthesis of lactide or glycolide from lactic acid or glycolide acid oligomers
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United States of America Patent
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Dec 20, 1994
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app pub date -
Sep 30, 1993
filing date -
Sep 30, 1993
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Abstract
A process for preparing lactide or glycolide from a lactic acid oligomer or glycolic acid oligomer is disclosed where the molecular weight of the synthesis reactor residue is controlled to no more than 1.2 times that in the feed. The process is carried out at 130.degree. to 280.degree. C. and preferably 180.degree. to 210.degree. C. using from 1 to 6 weight percent catalyst in the oligomer feed to the synthesis reactor. The catalysts are tin or tin compounds, yttrium or rare earth metal compounds, or antimony compounds which are known as alphahydroxycarboxylic acid cyclic dimerization or polymerization catalysts.
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