Patent US4631090A successfully refreshed from Google Patents.
US4631090A
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Preparation and use of iron magnetic pigments
Assignee: Bayer AG
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Filing: 1985-05-31
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Granted: 1986-12-23
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Expires: 2005-05-31
Abstract
Abstract A magnetic pigment consisting essentially of iron, having an X-ray crystallite size with the 110 reflex of from 14 to 22 nm, a coercive force from 55 to 88 kA/m and a switching field distribution of the oriented pigment particles of less than 0.55 is produced by precipitating an iron (II)-salt with a super-stoichiometric quantity of an aqueous alkali metal carbonate solution and oxidizing it to produce α-FeOOH, γ-Fe 2 O 3 , Fe 3 O 4 or betholoid iron oxides, subsequently reducing it to the metal, and providing the iron oxides or oxide hydroxides with an inorganic protection from sintering at the latest during reduction.
Inventors
- 👤 Rolf Naumann
- 👤 Lutz Leitner
- 👤 Jakob Rademachers
- 👤 Gunter Buxbaum
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-27 14:20
CPC Classifications
H; H01; H01F; H01F1/00; G; G11; G11B; G11B5/00; G11B5/62; G11B5/68; G11B5/70; G11B5/712; H01F1/01; H01F1/03; H01F1/032; H01F1/04; H01F1/06; H01F1/065
Claims Analysis
Total Claims: 15
Claim 1
Independent Claim
43 words
A magnetic pigment consisting essentially of iron, having a X-ray crystallite size with the 110 reflex of from 14 to 22 nm, a coercive force from 55 to 88 kA/m and a switching field distribution of aligned pigment particles of less than 0.55.
Claim 2
Dependent Claim
43 words
A magnetic pigment consisting essentially of iron, having a X-ray crystallite size with the 110 reflex of from 14 to 22 nm, a coercive force from 55 to 88 kA/m and a switching field distribution of aligned pigment particles of less than 0.55.
Claim 3
Dependent Claim
20 words
A pigment according to claim 1, containing from 1 to 6% of SiO 2 based on the weight of iron.
Claim 4
Dependent Claim
22 words
A pigment according to claim 1, containing from 0.5 to 4.5% of Al 2 O 3 based on the weight of iron.
Claim 5
Dependent Claim
20 words
A pigment according to claim 1 containing from 1.5 to 4% of SiO 2 based on the weight of iron.
Claim 6
Dependent Claim
22 words
A pigment according to claim 4, containing from 0.5 to 4.5% of Al 2 O 3 based on the weight of iron.
Claim 7
Dependent Claim
69 words
A process for producing a pigment according to claim 1, comprising precipitating an iron (II) salt with a super-stoichiometric quantity of an aqueous alkali metal carbonate solution conducting oxidizing to produce α-FeOOH, subsequently reducing the α-FeOOH to the metal, and wherein the α-FeOOH is provided with an inorganic protection from sintering at the latest during reduction by applying a silicon-containing compound or an aluminum containing compound to the α-FeOOH.
Claim 8
Dependent Claim
17 words
A process according to claim 6, wherein the inorganic protection comprises a coating of SiO 2 .
Claim 9
Dependent Claim
32 words
A process according to claim 6, wherein the silicon-containing compound is added in a quantity such that the reduced pigment has an SiO 2 content of from 1 to 6% by weight.
Claim 10
Dependent Claim
49 words
A process according to claim 6, wherein the inorganic protection is provided by adding a soluble aluminum-containing compound during precipitation of the α-FeOOH or to the α-FeOOH in a quantity such that the reduced pigment has an Al 2 O 3 content of from 0.5 to 4.5% by weight.
Claim 11
Dependent Claim
32 words
A process according to claim 6, wherein the silicon-containing compound is added in a quantity such that the reduced pigment has an SiO 2 content of from 1.5 to 4% by weight.
Claim 12
Dependent Claim
44 words
A process according to claim 10, wherein a soluble aluminum-containing compound is added during precipitation of the α-FeOOH or to the α-FeOOH in a quantity such that the reduced pigment has an Al 2 O 3 content of from 0.5 to 4.5% by weight.
Claim 13
Dependent Claim
13 words
A magnetic data carrier comprising a magnetic iron pigment according to claim 1.
Claim 14
Dependent Claim
14 words
A carrier according to claim 12, wherein the pigment particles carry an oxide sheath.
Claim 15
Dependent Claim
100 words
A process according to claim 6, which further comprises converting the α-FeOOH to α-Fe 2 O 3 , Fe 3 O 4 or betholoid iron oxides and subsequently reducing the γ-Fe 2 O 3 , Fe 3 O 4 or betholoid iron oxides to the metal, and wherein the γ-Fe 2 O 3 , Fe 3 O 4 or betholoid iron oxides are provided with an inorganic protection from sintering at the latest during reduction by applying a silicon-containing compound or an aluminum containing compound to the γ-Fe 2 O 3 , Fe 3 O 4 or betholoid iron oxides.
References Cited (Backward Citations)
EP0063730A2
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1989-12-22 | 1990-06-23 | 1990-12-23 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1993-12-22 | 1994-06-23 | 1994-12-23 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1997-12-22 | 1998-06-23 | 1998-12-23 | $7700.00 | Window Closed / Lapsed |