US4071610A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Manufacture of gamma-iron(III) oxide
Assignee: BASF SE
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Filing: 1976-04-19
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Granted: 1978-01-31
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Expires: 1996-04-19
Abstract
Abstract A process for the manufacture of acicular gamma-iron(III) oxide, in which the non-magnetic, acicular iron(III) oxide is treated with a solution of a compound of the formula I ##STR1## where R 1 and R 2 are ##STR2## or O--R 5 , R 3 is H, OH, ##STR3## or O--R 5 , R 4 is alkyl or cycloalkyl of 1 to 16 carbon atoms and the R 4 's may be identical or different, and R 5 is alkyl, cycloalkyl or aralkyl of 3 to 18 carbon atoms, and is then converted to gamma-iron(III) oxide by reduction to magnetite, followed by oxidation. The gamma-iron(III) oxide obtained is distinguished by a high coercive force and improved magnetic orientation when used as a magnetic pigment for the manufacture of magnetic recording media.
Inventors
- 👤 Eberhard Koester
- 👤 Gerd Wunsch
- 👤 Eduard Schoenafinger
- 👤 Hans Henning Schneehage
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-28 13:24
CPC Classifications
G; G11; G11B; G11B5/00; G11B5/62; G11B5/68; G11B5/70; G11B5/706; G11B5/70626; G11B5/70642; G11B5/70652; G11B5/70668; G11B5/70673; C; C01; C01G; C01G49/00; C01G49/02; C01G49/06; G11B5/70663; C01P; C01P2006/00; C01P2006/42
Claims Analysis
Total Claims: 3
Claim 1
Independent Claim
180 words
A process for the manufacture of acicular gamma-iron(III) oxide of high coercive force and giving improved orientation, which comprises the steps of a. mixing a suspension of non-magnetic, acicular alpha-FeOOH with a solution of a compound of the formula I ##STR7## where R 1 and R 2 are ##STR8## or O--R 5 , R 3 is H, OH, ##STR9## or O--R 5 , R 4 is alkyl or cycloalkyl of 1 to 16 carbon atoms and the R 4 's may be identical or different, and R 5 is alkyl, cycloalkyl or aralkyl of 3 to 18 carbon atoms, in water or alcohols of 1 to 4 carbon atoms, and then removing the solvent, the amount of said compound I being from about 0.5 to 10 percent by weight based on said non-magnetic iron oxide, b. reducing the material, obtained according to (a), by means of gases containing hydrogen, at from b 350° to 600° C, to give magnetite, and c. oxidizing the magnetite, by means of gases containing oxygen, at from 200° to 450° C, to give gamma-iron(III) oxide.
Claim 2
Dependent Claim
180 words
A process for the manufacture of acicular gamma-iron(III) oxide of high coercive force and giving improved orientation, which comprises the steps of a. mixing a suspension of non-magnetic, acicular alpha-FeOOH with a solution of a compound of the formula I ##STR7## where R 1 and R 2 are ##STR8## or O--R 5 , R 3 is H, OH, ##STR9## or O--R 5 , R 4 is alkyl or cycloalkyl of 1 to 16 carbon atoms and the R 4 's may be identical or different, and R 5 is alkyl, cycloalkyl or aralkyl of 3 to 18 carbon atoms, in water or alcohols of 1 to 4 carbon atoms, and then removing the solvent, the amount of said compound I being from about 0.5 to 10 percent by weight based on said non-magnetic iron oxide, b. reducing the material, obtained according to (a), by means of gases containing hydrogen, at from b 350° to 600° C, to give magnetite, and c. oxidizing the magnetite, by means of gases containing oxygen, at from 200° to 450° C, to give gamma-iron(III) oxide.
Claim 3
Dependent Claim
30 words
A process as set forth in claim 1 wherein the amount of said compound I is from about 2 to 6 percent by weight based on said non-magnetic iron oxide.
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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) | 1981-01-30 | 1981-08-01 | 1982-01-31 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1985-01-30 | 1985-08-01 | 1986-01-31 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1989-01-30 | 1989-08-01 | 1990-01-31 | $7700.00 | Window Closed / Lapsed |