US4497723A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Preparation of acicular, ferrimagnetic iron oxides
Assignee: Emtec Magnetics GmbH
•
Filing: 1983-06-27
•
Granted: 1985-02-05
•
Expires: 2003-06-27
Abstract
Abstract A process for the preparation of acicular ferrimagnetic iron oxides by reducing gamma-iron(III) oxide hydroxide to magnetite, at from 280° to 620° C., by means of an organic compound which is decomposable at this temperature in the presence of iron oxide, and, optionally, a stream of reducing gas, and, if desired, then oxidizing the magnetite with oxygen-containing gases, at from 150° to 450° C., to acicular ferrimagnetic iron oxide of the formula FeO x , where x is from above 1.33 to 1.50, wherein the organic compound used for the reduction is a non-polar glycerol ester of a fatty acid which is introduced into the aqueous reaction suspension during the preparation of the gamma-iron(III) oxide hydroxide.
Inventors
- 👤 Manfred Ohlinger
- 👤 Guenter Vaeth
- 👤 Peter Rudolf
- 👤 Wilhelm Sarnecki
- 👤 Helmut Jakusch
- 👤 Eberhard Koester
- 👤 Milena Melzer
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-31 06:43
CPC Classifications
G; G11; G11B; G11B5/00; G11B5/62; G11B5/68; G11B5/70; G11B5/706; G11B5/70626; G11B5/70642; G11B5/70678; G11B5/70684; G11B5/70694; B; B82; B82Y; B82Y30/00; C; C01; C01G; C01G49/00; C01G49/02; C01G49/06; C01P; C01P2002/00; C01P2002/60; C01P2004/00; C01P2004/10; C01P2004/60; C01P2004/64; C01P2006/00; C01P2006/12; C01P2006/42
Claims Analysis
Total Claims: 4
Claim 1
Independent Claim
191 words
A process for the preparation of an acicular ferrimagnetic iron oxide by reducing gamma-iron(III) oxide hydroxide to magnetite, at from 280° to 620° C., by means of an organic compound which is decomposable at this temperature in the presence of iron oxide, and, optionally, then oxidizing the magnetite with oxygen-containing gases, at from 150° to 450° C., to acicular ferrimagnetic iron oxide of the formula FeO x , where x is from about 1.33 to 1.50, wherein the gamma-iron (III) oxide hydroxide is prepared in an aqueous reaction suspension by precipitation and oxidation of an aqueous iron (II) solution and wherein the organic compound used for the reduction is a non-polar glycerol ester of a fatty acid which is introduced into the aqueous reaction suspension during the preparation and growth of the gamma-iron(III) oxide hydroxide; the acicular ferrimagnetic iron oxide so prepared when incorporated into a tape effecting a magnetic tape having a narrower switching field distribution than a magnetic tape containing said acicular ferrimagnetic iron oxide prepared as above but where said organic compound is added at the end of the preparation and growth of the gamma-iron (III) oxide hydroxide.
Claim 2
Dependent Claim
191 words
A process for the preparation of an acicular ferrimagnetic iron oxide by reducing gamma-iron(III) oxide hydroxide to magnetite, at from 280° to 620° C., by means of an organic compound which is decomposable at this temperature in the presence of iron oxide, and, optionally, then oxidizing the magnetite with oxygen-containing gases, at from 150° to 450° C., to acicular ferrimagnetic iron oxide of the formula FeO x , where x is from about 1.33 to 1.50, wherein the gamma-iron (III) oxide hydroxide is prepared in an aqueous reaction suspension by precipitation and oxidation of an aqueous iron (II) solution and wherein the organic compound used for the reduction is a non-polar glycerol ester of a fatty acid which is introduced into the aqueous reaction suspension during the preparation and growth of the gamma-iron(III) oxide hydroxide; the acicular ferrimagnetic iron oxide so prepared when incorporated into a tape effecting a magnetic tape having a narrower switching field distribution than a magnetic tape containing said acicular ferrimagnetic iron oxide prepared as above but where said organic compound is added at the end of the preparation and growth of the gamma-iron (III) oxide hydroxide.
Claim 3
Dependent Claim
202 words
A process for the preparation of an acicular ferrimagnetic iron oxide by reducing gamma-iron(III) oxide hydroxide to magnetite, at from 280° to 620° C., by means of an organic compound which is decomposable at this temperature in the presence of iron oxide, under a stream of a reducing gas and/or an inert gas, and, optionally, then oxidizing the magnetite with oxygen-containing gases, at from 150° to 450° C., to acicular ferrimagnetic iron oxide of the formula FeO x , where x is from above 1.33 to 1.50, wherein the gamma-iron (III) oxide hydroxide is prepared in an aqueous reaction suspension by precipitation and oxidation of an aqueous iron (II) solution and wherein the organic compound used for the reduction is a non-polar glycerol ester of a fatty acid which is introduced into the aqueous reaction suspension during the preparation and growth of the gamma-iron(III) oxide hydroxide; the acicular ferrimagnetic iron oxide so prepared when incorporated into a tape effecting a magnetic tape having a narrower switching field distribution than a magnetic tape containing said acicular ferrimagnetic iron oxide prepared as above but where said organic compound is added at the end of the preparation and growth of the gamma-iron (III) oxide hydroxide.
Claim 4
Dependent Claim
202 words
A process for the preparation of an acicular ferrimagnetic iron oxide by reducing gamma-iron(III) oxide hydroxide to magnetite, at from 280° to 620° C., by means of an organic compound which is decomposable at this temperature in the presence of iron oxide, under a stream of a reducing gas and/or an inert gas, and, optionally, then oxidizing the magnetite with oxygen-containing gases, at from 150° to 450° C., to acicular ferrimagnetic iron oxide of the formula FeO x , where x is from above 1.33 to 1.50, wherein the gamma-iron (III) oxide hydroxide is prepared in an aqueous reaction suspension by precipitation and oxidation of an aqueous iron (II) solution and wherein the organic compound used for the reduction is a non-polar glycerol ester of a fatty acid which is introduced into the aqueous reaction suspension during the preparation and growth of the gamma-iron(III) oxide hydroxide; the acicular ferrimagnetic iron oxide so prepared when incorporated into a tape effecting a magnetic tape having a narrower switching field distribution than a magnetic tape containing said acicular ferrimagnetic iron oxide prepared as above but where said organic compound is added at the end of the preparation and growth of the gamma-iron (III) oxide hydroxide.
References Cited (Backward Citations)
GB675260A
Cited
US2900236A
Cited
US3382174A
Cited
US3399142A
Cited
US3498748A
Cited
US3904540A
Cited
US4059716A
Cited
US4018882A
Cited
US4071610A
Cited
US4176172A
Cited
US4137342A
Cited
US4213959A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1988-02-05 | 1988-08-06 | 1989-02-05 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1992-02-05 | 1992-08-06 | 1993-02-05 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1996-02-05 | 1996-08-06 | 1997-02-05 | $7700.00 | Window Closed / Lapsed |