Patent US5536842A successfully refreshed from Google Patents.
US5536842A
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Purification of indigo
Assignee: BASF SE
•
Filing: 1994-10-21
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Granted: 1996-07-16
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Expires: 2014-10-21
Abstract
Abstract A process for purifying indigo comprises extracting an aqueous leuco indigo alkali metal salt solution with an inert solvent under oxygen-excluding conditions and conventionally regenerating the indigo by oxidation.
Inventors
- 👤 Udo Bergmann
- 👤 Manfred Gang
- 👤 Reinhold Kohlhaupt
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-03 09:49
CPC Classifications
C; C09; C09B; C09B7/00; C09B7/02
Claims Analysis
Total Claims: 7
Claim 1
Independent Claim
30 words
A process for purifying indigo, which comprises extracting an aqueous leuco indigo alkali metal salt solution with an inert solvent under oxygen-excluding conditions and conventionally regenerating the indigo by oxidation.
Claim 2
Dependent Claim
30 words
A process for purifying indigo, which comprises extracting an aqueous leuco indigo alkali metal salt solution with an inert solvent under oxygen-excluding conditions and conventionally regenerating the indigo by oxidation.
Claim 3
Dependent Claim
27 words
A process as claimed in claim 1, wherein the extraction of the leuco indigo alkali metal salt solution is carried out at from 25° to 100° C.
Claim 4
Dependent Claim
29 words
A process as claimed in claim 1, wherein the extraction is carried out with a weight ratio of leuco indigo alkali metal salt solution:solvent of from 1:0.1 to 1:10.
Claim 5
Dependent Claim
13 words
A process as claimed in claim 1, wherein the solvent used is toluene.
Claim 6
Dependent Claim
18 words
A process as claimed in claim 2, wherein the temperature of extraction ranges from 40° to 70° C.
Claim 7
Dependent Claim
21 words
A process as claimed in claim 3, wherein said weight ratio of salt solution to solvent ranges from 1:0.5 to 1:5.
References Cited (Backward Citations)
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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) | 1999-07-16 | 2000-01-15 | 2000-07-16 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2003-07-16 | 2004-01-15 | 2004-07-16 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2007-07-16 | 2008-01-15 | 2008-07-16 | $7700.00 | Window Closed / Lapsed |