US4178171A
Expired / Lapsed
US
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Manufacture of acicular ferromagnetic iron particles
Assignee: BASF SE
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Filing: 1978-03-20
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Granted: 1979-12-11
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Expires: 1998-03-20
Abstract
Abstract A process for the manufacture of acicular ferromagnetic iron particles by reducing acicular iron(III) oxide hydroxides which consist of pure synthetic lepidocrocite or a mixture of synthetic goethite and at least 70% by weight of synthetic lepidocrocite. The iron(III) oxide hydroxides used carry, on their surface, an alkaline earth metal cation and an anion of a monobasic, dibasic or tribasic aliphatic carboxylic acid of up to 6 carbon atoms or an organic compound containing at least two groups capable of chelating the alkaline earth metal cation, and are produced in such a way that they consist of at least 70 percent by weight of lepidocrocite and have a length-to-width ratio of not less than 15:1. Reduction of such iron(III) oxide hydroxides gives iron particles with pronounced shape anisotropy, which exhibit both good magnetic properties and a narrow field strength distribution.
Inventors
- 👤 Werner Steck
- 👤 Rudolf Brodt
- 👤 Wilhelm Sarnecki
- 👤 Helmut Jakusch
- 👤 Manfred Ohlinger
- 👤 Eberhard Koester
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 19:32
CPC Classifications
H; H01; H01F; H01F1/00; H01F1/01; H01F1/03; H01F1/032; H01F1/04; H01F1/06; H01F1/065; B; B22; B22F; B22F9/00; B22F9/16; B22F9/18; B22F9/20; B22F9/22; C; C21; C21B; C21B15/00; G; G11; G11B; G11B5/00; G11B5/62; G11B5/68; G11B5/70; G11B5/714
Claims Analysis
Total Claims: 6
Claim 1
Independent Claim
112 words
A process for the manufacture of acicular ferromagnetic iron particles, which process comprises reducing an acicular iron(III) oxide hydroxide which carries on the surface of its particles a compound of calcium, strontium or barium and a monobasic, dibasic or tribasic aliphatic carboxylic acid of up to 6 carbon atoms or a chelate of calcium, strontium or barium and an organic compound containing at least two groups capable of chelating a calcium, strontium or barium cation, the reduction being carried out with hydrogen at from 275° to 380° C. and the acicular iron(III) oxide hydroxide having a length-to-width ratio of at least 15:1 and consisting of at least 70% by weight of lepidocrocite.
Claim 2
Dependent Claim
112 words
A process for the manufacture of acicular ferromagnetic iron particles, which process comprises reducing an acicular iron(III) oxide hydroxide which carries on the surface of its particles a compound of calcium, strontium or barium and a monobasic, dibasic or tribasic aliphatic carboxylic acid of up to 6 carbon atoms or a chelate of calcium, strontium or barium and an organic compound containing at least two groups capable of chelating a calcium, strontium or barium cation, the reduction being carried out with hydrogen at from 275° to 380° C. and the acicular iron(III) oxide hydroxide having a length-to-width ratio of at least 15:1 and consisting of at least 70% by weight of lepidocrocite.
Claim 3
Dependent Claim
36 words
A process as claimed in claim 1, wherein the acicular iron(III) oxide hydroxide has a length-to-width ratio of at least 15:1 and consists of a mixture of goethite and at least 70% by weight of lepidocrocite.
Claim 4
Dependent Claim
42 words
A process as claimed in claim 1, wherein the particle surfaces carry the alkaline earth metal/carboxylic acid compound or the chelate in a total collective amount of from 0.2% to 10% by weight of the total amount of acicular iron(III) oxide hydroxide.
Claim 5
Dependent Claim
69 words
A process as claimed in claim 1, wherein the acicular iron(III) oxide hydroxide has a length-to-width ratio of at least 15:1 and consists of lepidocrocite or of a mixture of goethite and at least 70% by weight of lepidocrocite, and wherein the particle surfaces carry from 0.2% to 10% by weight of a precipitate of a barium salt of an aliphatic dicarboxylic acid of up to 6 carbon atoms.
Claim 6
Dependent Claim
58 words
A process as claimed in claim 1, wherein the acicular iron(III) oxide hydroxide has a length-to-width ratio of at least 15:1 and consists of a mixture of goethite and at least 70% by weight of lepidocrocite, and wherein the particle surfaces carry from 0.2 to 10% by weight of a chelate of a soluble barium salt and acetylacetone.
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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) | 1982-12-10 | 1983-06-11 | 1983-12-11 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1986-12-10 | 1987-06-11 | 1987-12-11 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1990-12-10 | 1991-06-11 | 1991-12-11 | $7700.00 | Window Closed / Lapsed |