Atmospheric pressure process for preparing pure cyclic esters
First Claim
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1. An improved process for making a highly pure cyclic ester of the form ##STR2## wherein R1 and R2 can be independently hydrogen or an aliphatic hydrocarbon having from I to about 6 carbon atoms by cracking a prepolymer comprising a polymer of an α
- -hydroxy acid or its ester or a block copolymer of an α
-hydroxy acid or its ester on a thermally stable polyether wherein the improvement comprises cracking the prepolymer at a suitable temperature and at a pressure at or above atmospheric pressure while maintaining a sufficiently large flow of an inert gas, the inert gas being in intimate contact with the liquid prepolymer so as to create a large interfacial area between the prepolymer and the inert gas, to evolve the cyclic ester vapors.
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Abstract
This invention relates to an improved process for preparing highly pure cyclic esters by heating a polymer of the corresponding α-hydroxy acid or its ester or a copolymer of α-hydroxy acid or its ester and a thermally stable polyether in the presence of an inert gas at atmospheric pressure. The cyclic ester is carried from the reaction with the inert gas to a solvent system.
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19 Claims
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1. An improved process for making a highly pure cyclic ester of the form ##STR2## wherein R1 and R2 can be independently hydrogen or an aliphatic hydrocarbon having from I to about 6 carbon atoms by cracking a prepolymer comprising a polymer of an α
- -hydroxy acid or its ester or a block copolymer of an α
-hydroxy acid or its ester on a thermally stable polyether wherein the improvement comprises cracking the prepolymer at a suitable temperature and at a pressure at or above atmospheric pressure while maintaining a sufficiently large flow of an inert gas, the inert gas being in intimate contact with the liquid prepolymer so as to create a large interfacial area between the prepolymer and the inert gas, to evolve the cyclic ester vapors. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19)
- -hydroxy acid or its ester or a block copolymer of an α
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