US4295879A
Expired / Lapsed
US
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Manufacture of acicular ferromagnetic iron particles
Assignee: Emtec Magnetics GmbH
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Filing: 1980-07-31
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Granted: 1981-10-20
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Expires: 2000-07-31
Abstract
Abstract A process for the manufacture of acicular ferromagnetic iron particles by reducing an iron(III) oxide which carries a shape-stabilizing surface coating and has been produced by heating acicular iron(III) oxide hydroxide at 250°-390° C. in an atmosphere containing water vapor at a partial pressure of not less than 30 mbar, with hydrogen at 275°-425° C.
Inventors
- 👤 Werner Steck
- 👤 Wilhelm Sarnecki
- 👤 Laszlo Marosi
- 👤 Manfred Ohlinger
- 👤 Horst Autzen
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-03 01:24
CPC Classifications
B; B22; B22F; B22F9/00; B22F9/16; B22F9/18; B22F9/20; B22F9/22; H; H01; H01F; H01F1/00; H01F1/01; H01F1/03; H01F1/032; H01F1/04; H01F1/06; H01F1/061; H01F1/065
Claims Analysis
Total Claims: 4
Claim 1
Independent Claim
181 words
A process for the manufacture of acicular ferromagnetic iron particles, comprising: (a) coating the surface of acicular particles of iron(III) oxide hydroxide and consisting of 20 to 100 percent by weight of lepidocrocite and 0 to 80 percent by weight of geothite with an alkaline earth metal compound and a monobasic, dibasic or tribasic aliphatic carboxylic acid of up to 6 carbon atoms, or an alkaline earth metal chelate of an organic compound containing at least two groups capable of chelating an alkaline earth metal cation, or a hydrolysis-resistant substance consisting of a phosphorus oxyacid, its ester or its inorganic salt and an aliphatic mono-, di- or tribasic carboxylic acid of 1 to 6 carbon atoms, (b) heating the so-coated particles at a temperature of from 250° to 390° C. for a period of from 10 minutes to 10 hours in an atmosphere containing water vapor at a partial pressure of from 30 to 1013 mbar, and (c) reducing the iron(III) oxide particles thus obtained with hydrogen at temperatures of from 275° to 425° C. to form acicular ferromagnetic iron particles.
Claim 2
Dependent Claim
181 words
A process for the manufacture of acicular ferromagnetic iron particles, comprising: (a) coating the surface of acicular particles of iron(III) oxide hydroxide and consisting of 20 to 100 percent by weight of lepidocrocite and 0 to 80 percent by weight of geothite with an alkaline earth metal compound and a monobasic, dibasic or tribasic aliphatic carboxylic acid of up to 6 carbon atoms, or an alkaline earth metal chelate of an organic compound containing at least two groups capable of chelating an alkaline earth metal cation, or a hydrolysis-resistant substance consisting of a phosphorus oxyacid, its ester or its inorganic salt and an aliphatic mono-, di- or tribasic carboxylic acid of 1 to 6 carbon atoms, (b) heating the so-coated particles at a temperature of from 250° to 390° C. for a period of from 10 minutes to 10 hours in an atmosphere containing water vapor at a partial pressure of from 30 to 1013 mbar, and (c) reducing the iron(III) oxide particles thus obtained with hydrogen at temperatures of from 275° to 425° C. to form acicular ferromagnetic iron particles.
Claim 3
Dependent Claim
176 words
A process for the manufacture of acicular ferromagnetic iron particles, comprising: (a) heating acicular particles of iron(III) oxide hydroxide and consisting of 20 to 100 percent by weight of lepidocrocite and 0 to 80 percent by weight of geothite at a temperature of from 250° to 390° C. for a period of from 10 minutes to 10 hours in an atmosphere containing water vapor at a partial pressure of from 30 to 1013 mbar, (b) coating the so-treated particles with an alkaline earth metal compound and a monobasic, dibasic or tribasic aliphatic carboxylic acid of up to 6 carbon atoms, or an alkaline earth metal chelate of an organic compound containing at least two groups capable of chelating an alkaline earth metal cation, or a hydrolysis-resistant substance consisting of a phosphorus oxyacid, its ester or its inorganic salt and an aliphatic mono-, di- or tribasic carboxylic acid of 1 to 6 carbon atoms, and (c) reducing the iron(III) oxide particles thus obtained with hydrogen at temperatures of from 275° C. to form acicular ferromagnetic iron particles.
Claim 4
Dependent Claim
176 words
A process for the manufacture of acicular ferromagnetic iron particles, comprising: (a) heating acicular particles of iron(III) oxide hydroxide and consisting of 20 to 100 percent by weight of lepidocrocite and 0 to 80 percent by weight of geothite at a temperature of from 250° to 390° C. for a period of from 10 minutes to 10 hours in an atmosphere containing water vapor at a partial pressure of from 30 to 1013 mbar, (b) coating the so-treated particles with an alkaline earth metal compound and a monobasic, dibasic or tribasic aliphatic carboxylic acid of up to 6 carbon atoms, or an alkaline earth metal chelate of an organic compound containing at least two groups capable of chelating an alkaline earth metal cation, or a hydrolysis-resistant substance consisting of a phosphorus oxyacid, its ester or its inorganic salt and an aliphatic mono-, di- or tribasic carboxylic acid of 1 to 6 carbon atoms, and (c) reducing the iron(III) oxide particles thus obtained with hydrogen at temperatures of from 275° C. to form acicular ferromagnetic iron particles.
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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) | 1984-10-19 | 1985-04-20 | 1985-10-20 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1988-10-19 | 1989-04-20 | 1989-10-20 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1992-10-19 | 1993-04-20 | 1993-10-20 | $7700.00 | Window Closed / Lapsed |