US4701221A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Process for the production of black pigments based on iron
Assignee: Bayer AG
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Filing: 1986-05-09
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Granted: 1987-10-20
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Expires: 2006-05-09
Abstract
Abstract A process for the production of black iron oxide pigments having a magnetite structure from iron ion-containing acidic waste water which comprises precipitating the iron ions with alkaline substances in a first stage at ambient temperature to produce a raw slurry and in a second stage, concentrating the raw slurry adjusted to a pH of from 5.0 to 8.0 with acidic substances and then ripening the concentrated slurry at temperatures above 70 DEG C.
Inventors
- 👤 Horst Brunn
- 👤 Gerd-Hermann Schulten
- 👤 Werner Fuhr
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-31 16:06
CPC Classifications
C; C02; C02F; C02F1/00; C02F1/66; C01; C01G; C01G49/00; C01G49/02; C01G49/08; C09; C09C; C09C1/00; C09C1/22; C09C1/24; C01P; C01P2006/00; C01P2006/12; C01P2006/60; C01P2006/63; C01P2006/64; C02F11/00; C02F11/18; C02F2101/00; C02F2101/10; C02F2101/20; C02F2101/203
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
89 words
A process for the production of black iron oxide pigments having a magnetite structure from iron ion-containing acidic waste water which comprises forming a precipitate of iron ions in a ratio of iron(III)/iron(II) of 1.0 to 2.4 with alkaline substances at pH greater than 8 in a first stage at ambient temperature to produce a raw slurry and, in a second stage, concentrating the raw slurry adjusted to a pH of from 5.0 to 8.0 with acidic substances and then ripening the concentrated slurry at temperatures above 70° C.
Claim 2
Dependent Claim
89 words
A process for the production of black iron oxide pigments having a magnetite structure from iron ion-containing acidic waste water which comprises forming a precipitate of iron ions in a ratio of iron(III)/iron(II) of 1.0 to 2.4 with alkaline substances at pH greater than 8 in a first stage at ambient temperature to produce a raw slurry and, in a second stage, concentrating the raw slurry adjusted to a pH of from 5.0 to 8.0 with acidic substances and then ripening the concentrated slurry at temperatures above 70° C.
Claim 3
Dependent Claim
24 words
A process according to claim 1 wherein the precipitation produces raw slurry with an Fe 3+ /Fe 2+ ratio of from 1.5 to 2.4.
Claim 4
Dependent Claim
25 words
A process according to claim 2 wherein the Fe 3+ /Fe 2+ ratio is regulated by air oxidation or by addition of Fe 2+ salts.
Claim 5
Dependent Claim
29 words
A process according to claim 1, 2 or 3 wherein the raw slurry is concentrated in the second stage to a solids content of from 200 to 1200 g/l.
Claim 6
Dependent Claim
20 words
A process according to claim 1 wherein the pH adjustment in the second stage is by addition of sulphuric acid.
Claim 7
Dependent Claim
21 words
A process according to claim 1 wherein the pH adjustment in the second stage is by addition of acidic waste water.
Claim 8
Dependent Claim
29 words
A process according to claim 5 or 6 wherein the pH of the raw slurry in the second stage is adjusted to a pH of from 6.5 to 7.5.
Claim 9
Dependent Claim
28 words
A process according to claims 1, 2 or 3 wherein the raw slurry in the second stage is brought to temperatures above 70° C. before adjusting the pH.
Claim 10
Dependent Claim
30 words
A process according to claim 1, 2 or 3 wherein the ripening of the concentrated slurry in the second stage is at a temperature of from 70° to 100° C.
Claim 11
Dependent Claim
29 words
A process according to claim 1, 2 or 3 wherein the ripening of the concentrated slurry in the second stage is at temperatures above 100° C. under autoclave conditions.
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) | 1990-10-19 | 1991-04-20 | 1991-10-20 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1994-10-19 | 1995-04-20 | 1995-10-20 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1998-10-19 | 1999-04-20 | 1999-10-20 | $7700.00 | Window Closed / Lapsed |