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US4451339A
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Preparation of blue iron hexacyanoferrate-III pigments, and the pigments obtained
Assignee: BASF SE
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Filing: 1982-03-24
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Granted: 1984-05-29
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Expires: 2002-03-24
Abstract
Abstract Blue iron hexacyanoferrate-III pigments (I) are prepared by anodic oxidation of metallic iron in hydrogen cyanide, or a reaction medium containing hydrogen cyanide, at pH<7 and at an anode potential of </=0.76 V (measured against a standard hydrogen electrode) to complex iron-II hexacyanoferrate-II compounds (II), which are then oxidized to (I) in a conventional manner. The oxidation of (II) is advantageously carried out with air or oxygen at pH 0-4 and at from 70 to 95 DEG C., but can also be carried out at pH>8. The process gives readily dispersible pigments (I) which are of high color strength and give brilliant, glossy colorations.
Inventors
- 👤 Joachim Kranz
- 👤 Wolfgang Habermann
- 👤 Harry Distler
- 👤 Helmut Knittel
- 👤 Karl-Ludwig Hock
- 👤 Fritz Brunnmueller
- 👤 Rolf Schneider
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-06 16:26
CPC Classifications
C; C25; C25B; C25B1/00; C25B1/01
Claims Analysis
Total Claims: 9
Claim 1
Independent Claim
71 words
In a process for the preparation of blue iron hexacyanoferrate-III pigments, wherein the iron-II hexacyanoferate-II compound is prepared, isolated and then oxidized to the blue pigment, the improvement wherein the iron-II-hexacyanoferrate-II compound is prepared by anodic oxidation of metallic iron at pH<7 and at an anode potential of <0.76 V--measured against the standard hydrogen electrode--at from -20° to 150° C., in a reaction medium comprising hydrogen cyanide, in a suitable solvent.
Claim 2
Dependent Claim
71 words
In a process for the preparation of blue iron hexacyanoferrate-III pigments, wherein the iron-II hexacyanoferate-II compound is prepared, isolated and then oxidized to the blue pigment, the improvement wherein the iron-II-hexacyanoferrate-II compound is prepared by anodic oxidation of metallic iron at pH<7 and at an anode potential of <0.76 V--measured against the standard hydrogen electrode--at from -20° to 150° C., in a reaction medium comprising hydrogen cyanide, in a suitable solvent.
Claim 3
Dependent Claim
25 words
A process as claimed in claim 1, wherein the anodic oxidation of the iron is carried out at a pH of from 2 to 5.
Claim 4
Dependent Claim
19 words
A process as claimed in claim 1 or 2, wherein the reaction medium contains one or more conductive salts.
Claim 5
Dependent Claim
21 words
A process as claimed in claim 3, wherein the conductive salts used are potassium or ammonium salts or mixtures of these.
Claim 6
Dependent Claim
22 words
A process as claimed in claim 1 or 2, wherein the anodic oxidation is carried out at from -5° to 25° C.
Claim 7
Dependent Claim
20 words
A process as claimed in claim 3, wherein the anodic oxidation is carried out at from -5° to 25° C.
Claim 8
Dependent Claim
39 words
A process as claimed in claim 1, wherein the oxidation of the iron-II hexacyanoferrate-II compound is carried out by means of air or oxygen, at a pH of from 0 to 3 and at from 70° to 95° C.
Claim 9
Dependent Claim
31 words
A process as claimed in claim 1, wherein the oxidation of the iron-II hexacyanoferrate-II compound is carried out with air or oxygen at pH>8 and at from 20° to 50° C.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1987-05-29 | 1987-11-28 | 1988-05-29 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1991-05-29 | 1991-11-28 | 1992-05-29 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1995-05-29 | 1995-11-28 | 1996-05-29 | $7700.00 | Window Closed / Lapsed |