US4155748A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Manufacture of ferromagnetic metal particles consisting essentially of iron
Assignee: BASF SE
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Filing: 1977-09-29
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Granted: 1979-05-22
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Expires: 1997-09-29
Abstract
Abstract A method of preparing acicular ferromagnetic metal particles consisting essentially of iron and suitable for magnetic recording, said particles being modified at the surface with 0.02 to 0.2% by weight of carbon and with 0.5 to 1.9% by weight of phosphorus as phosphate, by reducing a finely divided acicular iron compound, wherein there are deposited on said iron compound, prior to reduction, (a) a hydrolysis-resistant substance selected from the group consisting of oxyacids of phosphorus, their esters and inorganic salts, and (b) a compound selected from the group consisting of aliphatic monobasic, dibasic and tribasic carboxylic acids of from 1 to 6 carbon atoms.
Inventors
- 👤 Werner Steck
- 👤 Hans H. Schneehage
- 👤 Christof Jaeckh
- 👤 Werner Huebner
- 👤 Manfred Ohlinger
- 👤 Werner Loeser
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-24 20:24
CPC Classifications
C; C22; C22C; C22C33/00; C22C33/02; C22C33/0235; B; B22; B22F; B22F1/00; B22F1/14; B22F1/145; 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; Y; Y10; Y10S; Y10S428/00; Y10S428/90
Claims Analysis
Total Claims: 4
Claim 1
Independent Claim
162 words
A method of preparing acicular ferromagnetic metal particles consisting essentially of iron and suitable for magnetic recording, said particles being modified at the surface with 0.02 to 0.2% by weight of carbon and with 0.5 to 1.9% by weight of phosphorus as phosphate, by reducing a finely divided acicular iron compound selected from the group consisting of iron oxide and iron oxide hydrate with a gaseous reducing agent at a temperature of from 230° to 500° C., wherein there are deposited on said iron oxide or iron oxide hydrate, prior to reduction, (a) a hydrolysis-resistant substance selected from the group consisting of oxyacids of phosphorus, their esters and inorganic salts in such an amount that 0.2 to 2% by weight of phosphorus is present, and (b) a compound selected from the group consisting of aliphatic monobasic, dibasic and tribasic carboxylic acids of from 1 to 6 carbon atoms in such an amount that 0.1 to 1.2% by weight of carbon is present.
Claim 2
Independent Claim
162 words
A method of preparing acicular ferromagnetic metal particles consisting essentially of iron and suitable for magnetic recording, said particles being modified at the surface with 0.02 to 0.2% by weight of carbon and with 0.5 to 1.9% by weight of phosphorus as phosphate, by reducing a finely divided acicular iron compound selected from the group consisting of iron oxide and iron oxide hydrate with a gaseous reducing agent at a temperature of from 230° to 500° C., wherein there are deposited on said iron oxide or iron oxide hydrate, prior to reduction, (a) a hydrolysis-resistant substance selected from the group consisting of oxyacids of phosphorus, their esters and inorganic salts in such an amount that 0.2 to 2% by weight of phosphorus is present, and (b) a compound selected from the group consisting of aliphatic monobasic, dibasic and tribasic carboxylic acids of from 1 to 6 carbon atoms in such an amount that 0.1 to 1.2% by weight of carbon is present.
Claim 3
Independent Claim
199 words
A method of preparing acicular ferromagnetic iron metal particles, said particles being modified at the surface with 0.02 to 0.2% by weight of carbon and with 0.5 to 1.9% by weight of phosphorus as phosphate, which comprises the steps of (a) dispersing acicular iron oxide hydrate in a solution of a hydrolysis-resistant substance selected from the group consisting of oxyacids of phosphorus, their esters and inorganic salts, and a compound selected from the group consisting of aliphatic, monobasic and tribasic carboxylic acids of from 1 to 6 carbon atoms; (b) removing the solvent by filtration and heating, whereby said hydrolysis-resistant substance based on oxyacids of phosphorus is applied to said iron oxide hydrate in such an amount that from 0.2 to 2% by weight of phosphorus is present, and said carboxylic acid is applied to said iron oxide hydrate in such an amount that from 0.1 to 1.2% by weight of carbon is present, and (c) reducing the so-treated acicular iron oxide hydrate by passing gaseous hydrogen at a temperature of from 230° to 450° over said treated iron oxide hydrate to form acicular iron metal particles retaining the acicular shape of the acicular iron oxide hydrate starting material.
Claim 4
Independent Claim
199 words
A method of preparing acicular ferromagnetic iron metal particles, said particles being modified at the surface with 0.02 to 0.2% by weight of carbon and with 0.5 to 1.9% by weight of phosphorus as phosphate, which comprises the steps of (a) dispersing acicular iron oxide hydrate in a solution of a hydrolysis-resistant substance selected from the group consisting of oxyacids of phosphorus, their esters and inorganic salts, and a compound selected from the group consisting of aliphatic, monobasic and tribasic carboxylic acids of from 1 to 6 carbon atoms; (b) removing the solvent by filtration and heating, whereby said hydrolysis-resistant substance based on oxyacids of phosphorus is applied to said iron oxide hydrate in such an amount that from 0.2 to 2% by weight of phosphorus is present, and said carboxylic acid is applied to said iron oxide hydrate in such an amount that from 0.1 to 1.2% by weight of carbon is present, and (c) reducing the so-treated acicular iron oxide hydrate by passing gaseous hydrogen at a temperature of from 230° to 450° over said treated iron oxide hydrate to form acicular iron metal particles retaining the acicular shape of the acicular iron oxide hydrate starting material.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1982-05-21 | 1982-11-20 | 1983-05-22 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1986-05-21 | 1986-11-20 | 1987-05-22 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1990-05-21 | 1990-11-20 | 1991-05-22 | $7700.00 | Window Closed / Lapsed |