Patent US4018882A successfully refreshed from Google Patents.
US4018882A
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Manufacture of gamma-iron (III) oxide
Assignee: BASF SE
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Filing: 1975-09-25
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Granted: 1977-04-19
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Expires: 1995-09-25
Abstract
Abstract A process for the manufacture of acicular magnetic gamma-iron(III) oxide by reducing acicular alpha-iron(III) oxide to magnetite and then oxidizing it to gamma-iron(III) oxide, wherein the alpha-iron(III) oxide is treated with a water-soluble alkaline earth metal compound and an alkylphenol with one to three alkyl radicals, each of 4 to 24 carbon atoms, on the benzene nucleus. Gamma-iron(III) oxides manufactured in this way show better magnetic orientability in the binder-containing dispersion, and a higher coercive force than prior art magnetic pigments.
Inventors
- 👤 Eberhard Koester
- 👤 Gerd Wunsch
- 👤 Eduard Schoenafinger
- 👤 Hans Henning Schneehage
- 👤 Helmut Jakusch
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-26 20:27
CPC Classifications
G; G11; G11B; G11B5/00; G11B5/62; G11B5/68; G11B5/70; G11B5/706; G11B5/70626; G11B5/70642; G11B5/70652; G11B5/70663; C; C01; C01G; C01G49/00; C01G49/02; C01G49/06; C01P; C01P2004/00; C01P2004/10; C01P2006/00; C01P2006/42
Claims Analysis
Total Claims: 6
Claim 1
Independent Claim
190 words
A process for producing acicular magnetic gamma-iron(III) oxide comprising the steps of: a. suspending an acicular non-magnetic iron(III) oxide in water to form a slurry, b. adding to said slurry a solution of a water-soluble inorganic alkaline earth metal compound, said alkaline earth metal selected from the group consisting of magnesium, calcium, barium and strontium, in an amount of from 1 to 5 percent by weight of the alkaline earth metal compound based on the iron(III) oxide, c. adding to said slurry an alkylphenol of the formula ##STR2## wherein R 1 , R 2 and R 3 are hydrogen or alkyl of 4 to 24 carbon atoms, with the proviso that at least one of R 1 , R 2 and R 3 is alkyl, in a molar ratio of alkylphenol to alkaline earth metal compound of 0.2 to 2.0:1, d. filtering the slurry, e. drying the residue, f. reducing the residue consisting essentially of non-magnetic iron(III) oxide with a gaseous reducing agent at from 300° to 500° C, to magnetite; and subsequently g. oxidizing the magnetite with an oxygen-containing gas, at from 200° to 400° C, to gamma-iron(III) oxide.
Claim 2
Dependent Claim
190 words
A process for producing acicular magnetic gamma-iron(III) oxide comprising the steps of: a. suspending an acicular non-magnetic iron(III) oxide in water to form a slurry, b. adding to said slurry a solution of a water-soluble inorganic alkaline earth metal compound, said alkaline earth metal selected from the group consisting of magnesium, calcium, barium and strontium, in an amount of from 1 to 5 percent by weight of the alkaline earth metal compound based on the iron(III) oxide, c. adding to said slurry an alkylphenol of the formula ##STR2## wherein R 1 , R 2 and R 3 are hydrogen or alkyl of 4 to 24 carbon atoms, with the proviso that at least one of R 1 , R 2 and R 3 is alkyl, in a molar ratio of alkylphenol to alkaline earth metal compound of 0.2 to 2.0:1, d. filtering the slurry, e. drying the residue, f. reducing the residue consisting essentially of non-magnetic iron(III) oxide with a gaseous reducing agent at from 300° to 500° C, to magnetite; and subsequently g. oxidizing the magnetite with an oxygen-containing gas, at from 200° to 400° C, to gamma-iron(III) oxide.
Claim 3
Dependent Claim
17 words
A process as set forth in claim 1, wherein the acicular non-magnetic iron(III) oxide is acicular goethite.
Claim 4
Dependent Claim
32 words
A process as set forth in claim 1 wherein the alkaline earth metal compound is a hydroxide selected from the group consisting of barium hydroxide, magnesium hydroxide, calcium hydroxide and strontium hydroxide.
Claim 5
Dependent Claim
28 words
A process as set forth in claim 1 wherein the alkaline earth metal compound is selected from the group consisting of barium hydroxide, barium nitrate and calcium nitrate.
Claim 6
Dependent Claim
15 words
A process as set forth in claim 1 wherein the alkylphenol is a mono-alkyl-substituted phenol.
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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) | 1980-04-18 | 1980-10-18 | 1981-04-19 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1984-04-18 | 1984-10-18 | 1985-04-19 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1988-04-18 | 1988-10-18 | 1989-04-19 | $7700.00 | Window Closed / Lapsed |