Recovery of hydroxycarboxylic acid values from poly(hydroxycarboxylic acids)
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United States of America Patent
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Aug 30, 1994
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app pub date -
Mar 3, 1993
filing date -
Mar 3, 1993
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Abstract
A improved process for depolymerizing a poly(alpha-hydroxycarboxylic acid) to its corresponding dimeric cyclic ester is disclosed. The process comprises: (i) depolymerizing the poly(alpha-hydroxycarboxylic acid) to its corresponding dimeric cyclic ester by heating the poly(alpha-hydroxycarboxylic acid) in a reaction zone at a temperature and pressure at which the poly(alpha-hydroxycarboxylic acid) is molten; (ii) forming a vapor product stream containing the dimeric cyclic ester; (iii) removing the vapor product stream from the reaction zone; and (iv) recovering the dimeric cyclic ester from the product stream; the improvement comprising: adding the dimeric cyclic ester to step (i) in the ratio of 0.01 to 0.5 part by weight of dimeric cyclic ester per part by weight of the poly(alpha-hydroxycarboxylic acid).
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