US5043458A
Expired / Lapsed
US
⏱️ 0.0 years remaining
One-step continuous process for preparing cyclic esters
Assignee: Ecological Chemical Products
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Filing: 1990-05-03
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Granted: 1991-08-27
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Expires: 2010-05-03
Abstract
Abstract A continuous, gas-assisted atmospheric process for preparing cyclic esters of alpha-hydroxycarboxylic acids, such as lactide, which comprises feeding the reactants into a reactor having means for introducing an inert gas at the operating temperature, forming a reaction mass having cyclic esters in the reactor, passing a flow of said inert gas through said reactor whereby cyclic esters are swept from the reaction mass into a gaseous product stream, and recovering the cyclic esters therefrom.
Inventors
- 👤 Kamlesh K. Bhatia
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-28 00:25
CPC Classifications
C; C07; C07D; C07D319/00; C07D319/10; C07D319/12; Y; Y02; Y02P; Y02P20/00; Y02P20/50; Y02P20/582
Claims Analysis
Total Claims: 13
Claim 1
Independent Claim
155 words
A continuous process for preparing a cyclic ester having the formula, ##STR2## wherein R 1 and R 2 are independently hydrogen or an aliphatic hydrocarbyl radical having 1 to 6 carbon atoms, which process comprises (i) continously passing a feed stream containing an alpha-hydroxycarboxylic acid, HOCR 1 R 2 CO 2 H, or a salt thereof into the inlet end of a reaction zone having an inlet end and an outlet end; while (ii) maintaining the reaction zone at a temperature and pressure effective to result in a fluid reaction mass containing cyclic ester; (iii) continuously passing a flow of substance that is gaseous and non-reactive through the reaction mass, the flow being sufficiently large to sweep cyclic ester from the reaction mass and form a gaseous product stream comprising the gas and cyclic ester; (iv) removing the product stream of (iii) from the reactor; and (v) recovering the cyclic ester from the product stream.
Claim 2
Dependent Claim
155 words
A continuous process for preparing a cyclic ester having the formula, ##STR2## wherein R 1 and R 2 are independently hydrogen or an aliphatic hydrocarbyl radical having 1 to 6 carbon atoms, which process comprises (i) continously passing a feed stream containing an alpha-hydroxycarboxylic acid, HOCR 1 R 2 CO 2 H, or a salt thereof into the inlet end of a reaction zone having an inlet end and an outlet end; while (ii) maintaining the reaction zone at a temperature and pressure effective to result in a fluid reaction mass containing cyclic ester; (iii) continuously passing a flow of substance that is gaseous and non-reactive through the reaction mass, the flow being sufficiently large to sweep cyclic ester from the reaction mass and form a gaseous product stream comprising the gas and cyclic ester; (iv) removing the product stream of (iii) from the reactor; and (v) recovering the cyclic ester from the product stream.
Claim 3
Dependent Claim
19 words
The process of claim 1 wherein the reaction zone is maintained at pressure of at least about atmospheric pressure.
Claim 4
Dependent Claim
17 words
The process of claim 2 wherein the feed stream is liquid and the reaction mass is liquid.
Claim 5
Dependent Claim
42 words
The process of claim 2 wherein the reaction mass contains a catalyst effective to promote the condensation of the alpha-hydroxy acid or ammonium or amine salt thereof to an oligomer and to effect conversion of the condensation product to a cyclic ester.
Claim 6
Dependent Claim
16 words
The process of claim 3 wherein the feed stream contains a catalyst as in claim 4.
Claim 7
Dependent Claim
22 words
The process of claim 5 wherein the reaction zone temperature is in the range of from about 170° to about 270° C.
Claim 8
Dependent Claim
21 words
The process of claim 6 wherein the temperature is in the range of from about 190° C. to about 235° C.
Claim 9
Dependent Claim
14 words
The process of claim 5 or claim 6 wherein the feed stream is preheated.
Claim 10
Dependent Claim
73 words
The process of claim 2 wherein (a) the feed stream is fed at a first rate and the product stream is removed at a second rate, said rates being coordinated and adjusted as necessary to establish a steady state characterized by a substantially constant quantity of reaction mass within the reaction zone, and (b) the feed and product stream rates are maintained to provide a substantially constant rate of production of cyclic ester.
Claim 11
Dependent Claim
16 words
The process of claim 2 wherein the feed stream hydroxy acid component is an alpha-hydroxycarboxylic acid.
Claim 12
Dependent Claim
18 words
The process of claim 10 wherein the hydroxycarboxylic acid is lactic acid and the cyclic ester is lactide.
Claim 13
Dependent Claim
17 words
The process of claim 1 wherein the acid is L-lactic acid and the cyclic ester is L-lactide.
References Cited (Backward Citations)
US3457280A
Cited
US4835293A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1994-08-26 | 1995-02-25 | 1995-08-27 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1998-08-26 | 1999-02-25 | 1999-08-27 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2002-08-26 | 2003-02-25 | 2003-08-27 | $7700.00 | Window Closed / Lapsed |