US4835293A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Atmospheric pressure process for preparing pure cyclic esters
Assignee: Ecological Chemical Products
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Filing: 1987-02-24
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Granted: 1989-05-30
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Expires: 2007-02-24
Abstract
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.
Inventors
- 👤 Kamlesh K. Bhatia
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 22:06
CPC Classifications
C; C07; C07D; C07D319/00; C07D319/10; C07D319/12; B; B01; B01J; B01J19/00; B01J19/18; B01J19/1862; B01J2219/00; B01J2219/00049; B01J2219/00051; B01J2219/00121
Claims Analysis
Total Claims: 20
Claim 1
Independent Claim
128 words
An improved process for making a highly pure cyclic ester of the form ##STR2## wherein R 1 and R 2 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.
Claim 2
Dependent Claim
128 words
An improved process for making a highly pure cyclic ester of the form ##STR2## wherein R 1 and R 2 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.
Claim 3
Dependent Claim
21 words
The process of claim 1 comprising the further step of scrubbing the cyclic ester vapors and inert gas in a solvent.
Claim 4
Dependent Claim
26 words
The process of claim 1 wherein the temperature is from about 215° to 290° C. and the pressure from about 0 psig. to about 10 psig.
Claim 5
Dependent Claim
13 words
The process of claim 1 wherein the cyclic ester is glycolide or lactide.
Claim 6
Dependent Claim
27 words
The process of claim 3 wherein the temperature is from about 230° to 260° C. and the pressure is from about 0 psig. to about 5 psig.
Claim 7
Dependent Claim
27 words
The process of claim 4 wherein the temperature is from about 240° to 255° C. and the pressure is from about 0 psig. to about 10 psig.
Claim 8
Dependent Claim
20 words
The process of claim 1 wherein the inert gas flow is 5 to 30 scfm per cubic foot of prepolymer.
Claim 9
Dependent Claim
20 words
The process of claim 4 wherein the inert gas flow is 10 to 20 scfm per cubic foot of prepolymer.
Claim 10
Dependent Claim
11 words
The process of claim 7 wherein the inert gas is nitrogen.
Claim 11
Dependent Claim
11 words
The process of claim 8 wherein the inert gas is nitrogen.
Claim 12
Dependent Claim
17 words
The process of claim 2 comprising the additional step of separating the cyclic ester from the solvent.
Claim 13
Dependent Claim
23 words
The process of claim 2 wherein the solvent is a polar solvent in which the impurities are more soluble than the cyclic ester.
Claim 14
Dependent Claim
23 words
The process of claim 11 wherein the solvent is a polar solvent in which the impurities are more soluble than the cyclic ester.
Claim 15
Dependent Claim
15 words
The process of claim 12 wherein the cyclic ester is essentially insoluble in the solvent.
Claim 16
Dependent Claim
11 words
The process of claim 12 wherein the solvent is isopropyl alcohol.
Claim 17
Dependent Claim
21 words
The process of claim 13 wherein the temperature of the solvent is lower than the freezing point of the cyclic ester.
Claim 18
Dependent Claim
18 words
The process of claim 16 wherein the temperature of the solvent is between about 20° and 45° C.
Claim 19
Dependent Claim
17 words
The process of claim 17 wherein the cyclic ester is separated from the solvent by mechanical means.
Claim 20
Dependent Claim
13 words
The process of claim 18 wherein the mechanical means is filtration or centrifugation.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1992-05-29 | 1992-11-28 | 1993-05-30 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1996-05-29 | 1996-11-28 | 1997-05-30 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2000-05-29 | 2000-11-28 | 2001-05-30 | $7700.00 | Window Closed / Lapsed |