US4789726A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Manufacture of polyesters
Assignee: Syngenta Ltd
•
Filing: 1987-04-02
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Granted: 1988-12-06
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Expires: 2007-04-02
Abstract
Abstract A process for the manufacture of polyesters, especially polylactides or poly(lactide-co-glycolide) of specified low-medium molecular weight, by controlled hydrolysis of a higher molecular weight polyester.
Inventors
- 👤 Francis G. Hutchinson
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-27 22:19
CPC Classifications
C; C08; C08G; C08G63/00; C08G63/02; C08G63/06; C08G63/08; C08G63/91; C08G63/912
Claims Analysis
Total Claims: 8
Claim 1
Independent Claim
117 words
A process for the manufacture of a polyester, of any desired number average molecular weight, M n , less than about 20,000 as measured by size exclusion chromatography relative to polystyrene standards, characterised by the hydrolysis in homogeneous solution, with an aqueous acid, of a polyester of the same chemical composition as the desired polyester but having a higher number average molecular weight, M n o , measured as defined above, than the desired polyester product, for a period of time, t, determined from the equation: ##EQU2## wherein K is a constant which has been predetermined by a calibration experiment using the particular polyester, the particular water, acid and polyester concentrations, and the particular hydrolysis temperature desired.
Claim 2
Dependent Claim
117 words
A process for the manufacture of a polyester, of any desired number average molecular weight, M n , less than about 20,000 as measured by size exclusion chromatography relative to polystyrene standards, characterised by the hydrolysis in homogeneous solution, with an aqueous acid, of a polyester of the same chemical composition as the desired polyester but having a higher number average molecular weight, M n o , measured as defined above, than the desired polyester product, for a period of time, t, determined from the equation: ##EQU2## wherein K is a constant which has been predetermined by a calibration experiment using the particular polyester, the particular water, acid and polyester concentrations, and the particular hydrolysis temperature desired.
Claim 3
Dependent Claim
16 words
A process as claimed in claim 1 wherein the polyester is polylactic acid or poly(lactic-co-glycolic) acid.
Claim 4
Dependent Claim
14 words
A process as claimed in claim 2 wherein the aqueous acid is acetic acid.
Claim 5
Dependent Claim
68 words
A process as claimed in claim 1 for the manufacture of a product polyester of polydispersity greater than about 2.5, characterised in that a solution of the polyester starting material, of polydispersity about 2, in the aqueous acid at ambient temperature is added at a constant rate, over the predetermined time period t, to a reaction vessel heated sufficiently to reflux the polyester solution as it is added.
Claim 6
Dependent Claim
74 words
A process as claimed in claim 1 for the manufactured of a polyester product having a very broad molecular weight range distribution and a polydispersity of greater than 2.5, characterised in that a solution of the polyester starting material, of polydispersity about 2, in the aqueous acid at ambient temperature is added to a reaction vessel, heated sufficiently to reflux the polyester solution as it is added, at an accelerating rate over time t.
Claim 7
Dependent Claim
66 words
A process as claimed in claim 1 for the manufacture of a product polyester having a polynodal molecular weight distribution, characterised in that a solution of the polyester starting material material in the aqueous acid at ambient temperature is added in the two or more portions, separated by appropriate time intervals, to a reaction vessel heated sufficiently to reflux the polyester solution as it is added.
Claim 8
Dependent Claim
48 words
A process as claimed in claim 1 for the manufacture of a product polyester of polydispersity less than about 1.5, characterised in that the starting polyester has a similar polydispersity, and M n o is not more than about 5 times the M n of the desired product.
References Cited (Backward Citations)
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US3839297A
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US4273920A
Cited
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Cited
US4443430A
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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) | 1991-12-06 | 1992-06-06 | 1992-12-06 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1995-12-06 | 1996-06-06 | 1996-12-06 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1999-12-06 | 2000-06-06 | 2000-12-06 | $7700.00 | Window Closed / Lapsed |