US4826671A
Expired / Lapsed
US
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Preparation of acicular α-Fe2 O3
Assignee: Emtec Magnetics GmbH
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Filing: 1987-03-11
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Granted: 1989-05-02
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Expires: 2007-03-11
Abstract
Abstract Finely divided, acicular and pore-free alpha -Fe2O3 is prepared from iron(III) salts in the presence of one or more organic substances which form complexes with iron(III) ions, in alkaline suspension, at from 80 DEG to 250 DEG C.
Inventors
- 👤 Volker Arndt
- 👤 Rainer Feser
- 👤 Werner Steck
- 👤 Helmut Jakusch
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-27 21:21
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; C01P2002/00; C01P2002/50; C01P2002/52; C01P2002/54; C01P2004/00; C01P2004/10; C01P2004/54; C01P2004/60; C01P2004/62; C01P2004/80; C01P2004/82; C01P2004/84; C01P2006/00; C01P2006/42
Claims Analysis
Total Claims: 4
Claim 1
Independent Claim
126 words
A process for the preparation of acicular α-Fe 2 O 3 comprising precipitating iron(III) hydroxide from an aqueous solution of iron(III) salt in the presence of tin(IV) ions by adding an alkali metal hydroxide to an aqueous iron(III) salt solution containing from 10 -3 to 2.10 -2 mole of tin(IV) salt per mole of iron(III) salt, filtering off the resulting precipitate, suspending the precipitate in water to form an aqueous suspension of iron(III) hydroxide, and heating the aqueous suspension of iron(III) hydroxide at a temperature of from 80° to 150° C., at a pH of from 8.5 to 12, in the presence of an amount of at least one organic compound sufficient to form complexes with iron(III) ions whereby acicular α-Fe 2 O 3 is formed.
Claim 2
Dependent Claim
126 words
A process for the preparation of acicular α-Fe 2 O 3 comprising precipitating iron(III) hydroxide from an aqueous solution of iron(III) salt in the presence of tin(IV) ions by adding an alkali metal hydroxide to an aqueous iron(III) salt solution containing from 10 -3 to 2.10 -2 mole of tin(IV) salt per mole of iron(III) salt, filtering off the resulting precipitate, suspending the precipitate in water to form an aqueous suspension of iron(III) hydroxide, and heating the aqueous suspension of iron(III) hydroxide at a temperature of from 80° to 150° C., at a pH of from 8.5 to 12, in the presence of an amount of at least one organic compound sufficient to form complexes with iron(III) ions whereby acicular α-Fe 2 O 3 is formed.
Claim 3
Dependent Claim
33 words
The process of claim 1 wherein after filtering, the precipitate is suspended in water at least one time, while stirring, at a temperature not exceeding 100° C., and the precipitate is filtered off.
Claim 4
Dependent Claim
35 words
The process of claim 1 wherein the iron(III) hydroxide is precipitated from an aqueous solution of iron(III) salt in the presence of chromium(III) ions, aluminum(III) ions or mixture thereof, in addition to said tin(IV) ions.
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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) | 1992-05-01 | 1992-10-31 | 1993-05-02 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1996-05-01 | 1996-10-31 | 1997-05-02 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2000-05-01 | 2000-10-31 | 2001-05-02 | $7700.00 | Window Closed / Lapsed |