US4123501A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Oxidation of metallic iron to black oxide pigments
Assignee: Bayer AG
•
Filing: 1977-04-14
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Granted: 1978-10-31
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Expires: 1997-04-14
Abstract
Abstract A metallic iron-containing starting material such as iron filings, iron powder or a reduced ore such as ilmenite is oxidized with air in the presence of 5 to 40% of iron oxide and/or iron oxide hydroxide nuclei and about 2.5 to 200% of an electrolyte, percentages being based on metallic iron by weight. The oxidation is effected in aqueous suspension at 75 DEG to 100 DEG C and a pH of 4 to 6.5. If the nuclei are magnetite-free, at least the first quarter of the oxidation should be at pH 5 to 6.5. Preferred electrolytes are transition metal salts. The pigments are more intense in color and have a more pronounced blue tinge.
Inventors
- 👤 Klaus Kohler
- 👤 Peter Woditsch
- 👤 Karl-Heinz Schultz
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-30 09:34
CPC Classifications
C; C01; C01G; C01G49/00; C01G49/02; C01G49/08; C01P; C01P2006/00; C01P2006/60
Claims Analysis
Total Claims: 6
Claim 1
Independent Claim
90 words
A process for the preparation of a black pigment comprising oxidizing a metallic iron-containing starting material in aqueous suspension with an oxygen-containing gas in the presence of about 5 to 40% of finely divided Fe 3 O 4 nuclei of magnetite structure and about 2.5 to 200% of at least one electrolyte, percentages being by weight of metallic iron, at a pH of about 4 to 6.5 and a temperature of about 75° C to 100° C, and separating the resultant Fe 3 O 4 pigment from the aqueous medium.
Claim 2
Dependent Claim
90 words
A process for the preparation of a black pigment comprising oxidizing a metallic iron-containing starting material in aqueous suspension with an oxygen-containing gas in the presence of about 5 to 40% of finely divided Fe 3 O 4 nuclei of magnetite structure and about 2.5 to 200% of at least one electrolyte, percentages being by weight of metallic iron, at a pH of about 4 to 6.5 and a temperature of about 75° C to 100° C, and separating the resultant Fe 3 O 4 pigment from the aqueous medium.
Claim 3
Dependent Claim
18 words
The process according to claim 1, wherein the electrolyte comprises at least one salt of a transition metal.
Claim 4
Dependent Claim
24 words
The process according to claim 1, wherein the metallic iron-containing starting material is finely divided iron filings, iron powder or reduced iron oxide ore.
Claim 5
Dependent Claim
15 words
The process according to claim 1, wherein the metallic iron-containing starting material is reduced ilmenite.
Claim 6
Dependent Claim
50 words
The process according to claim 1, wherein the metallic iron-containing starting material is finely divided iron filings, iron powder or reduced iron oxide ore, the oxidation is carried out at a temperature of about 80° to 100° C, and the nuclei are present in about 8 to 20% by weight.
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) | 1981-10-30 | 1982-05-01 | 1982-10-31 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1985-10-30 | 1986-05-01 | 1986-10-31 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1989-10-30 | 1990-05-01 | 1990-10-31 | $7700.00 | Window Closed / Lapsed |