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US5244549A
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Process for the reduction of dyes
Assignee: Dystar Textilfarben GmbH and Co Deutschland KG
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Filing: 1990-05-31
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Granted: 1993-09-14
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Expires: 2010-05-31
Abstract
Abstract In a process for reducing dyes in aqueous solution, a pair of electrodes is immersed in the solution. The cathode potential is maintained below the value at which hydrogen is evolved. A reducing agent is used, the redox potential of which, increased by the charge transfer overvoltage required for the reduction of the oxidized form of the reducing agent to the reduced form at the cathode, is less than the cathode potential.
Inventors
- 👤 Thomas Bechtold
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-06 09:21
CPC Classifications
D; D06; D06P; D06P1/00; D06P1/22; D06P1/221; D06P5/00; D06P5/20; D06P5/2016
Claims Analysis
Total Claims: 7
Claim 1
Independent Claim
95 words
A process for the reduction of dye in an aqueous solution having a pH greater than 9, comprising employing a reducing agent which is present dissolved in the solution in a reduced and oxidized form, wherein a pair of electrodes is introduced into the solution, the cathode potential of said electrode pair being held at a value at which essentially no hydrogen is generated but which is sufficiently negative to return essentially all of the reducing agent which is transformed into its oxidized form in the process of reducing the dye, into its reducing form.
Claim 2
Dependent Claim
95 words
A process for the reduction of dye in an aqueous solution having a pH greater than 9, comprising employing a reducing agent which is present dissolved in the solution in a reduced and oxidized form, wherein a pair of electrodes is introduced into the solution, the cathode potential of said electrode pair being held at a value at which essentially no hydrogen is generated but which is sufficiently negative to return essentially all of the reducing agent which is transformed into its oxidized form in the process of reducing the dye, into its reducing form.
Claim 3
Dependent Claim
20 words
A process, as claimed in claim 1, wherein a cathode made of Cu, Zn, Pb or stainless steel is used.
Claim 4
Dependent Claim
18 words
A process, as claimed in claim 1 or 2, wherein a cathode with basic anthraquinonoid structure is used.
Claim 5
Dependent Claim
25 words
A process, as claimed in claim 3, wherein 0.5-10 -3 mol/l to 3-10 -3 mol/l, preferably 1.5-10 -3 mol/l of the anthraquinonoid compound is used.
Claim 6
Dependent Claim
20 words
A process, as claimed in claim 1 or 2, wherein a metal complex salt is used as the reducing agent.
Claim 7
Dependent Claim
27 words
A process, as claimed in claim 5, wherein a mixture of 0.5-10 -3 mol/l to 5-10 -3 mol/l iron (II) or iron (III)-salt with triethanolamine is used.
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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) | 1996-09-13 | 1997-03-15 | 1997-09-14 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2000-09-13 | 2001-03-15 | 2001-09-14 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2004-09-13 | 2005-03-15 | 2005-09-14 | $7700.00 | Window Closed / Lapsed |