US4256484A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Metallic iron particles for magnetic recording
Assignee: Pfizer Pigments Inc
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Filing: 1979-07-30
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Granted: 1981-03-17
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Expires: 1999-07-30
Abstract
Abstract In the process for preparing a magnetically stable, powder comprising the steps of reducing an iron oxide or iron oxide hydrate with a gaseous reduction agent and stabilizing the metallic powder thus produced, the improvement which comprises enhancing its reduction by coating said iron oxide or iron oxide hydrate with an antimony compound at a level of up to about 7 weight percent antimony based on the weight of the iron oxide prior to said reduction.
Inventors
- 👤 Richard H. Rodrian
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 17:38
CPC Classifications
C; C07; C07C; C07C225/00; C07C225/02; C07C225/04; C07C225/06; H; H01; H01F; H01F1/00; H01F1/01; H01F1/03; H01F1/032; H01F1/04; H01F1/06; H01F1/065; B; B22; B22F; B22F1/00; B22F1/18; B22F9/00; B22F9/16; B22F9/18; B22F9/20; B22F9/22; H01F1/061
Claims Analysis
Total Claims: 8
Claim 1
Independent Claim
95 words
In the process for preparing a magnetically stable powder comprising the steps of A. Reducing an iron oxide precursor selected from the group consisting of an iron oxide, an iron oxide hydrate, a modified iron oxide or a modified iron oxide hydrate with a gaseous reduction agent; and B. Stabilizing the metallic powder thus produced, the improvement which comprises: coating said iron oxide precursor with an antimony compound at a level of up to about 7 weight percent antimony based on the weight of the iron oxide content of said precursor prior to said reduction.
Claim 2
Dependent Claim
95 words
In the process for preparing a magnetically stable powder comprising the steps of A. Reducing an iron oxide precursor selected from the group consisting of an iron oxide, an iron oxide hydrate, a modified iron oxide or a modified iron oxide hydrate with a gaseous reduction agent; and B. Stabilizing the metallic powder thus produced, the improvement which comprises: coating said iron oxide precursor with an antimony compound at a level of up to about 7 weight percent antimony based on the weight of the iron oxide content of said precursor prior to said reduction.
Claim 3
Dependent Claim
45 words
The process of claim 1 wherein the coated iron oxide precursor is further coated with up to about 20 weight percent of at least one metal selected from the group consisting of cobalt, chromium and nickel in the form of hydroxide prior to said reduction.
Claim 4
Dependent Claim
31 words
The process of claim 1 wherein the amount of antimony employed is from about 1 to 4.5 weight percent based on the weight of the iron oxide content of said precursor.
Claim 5
Dependent Claim
19 words
The process of claim 1 wherein the antimony compound is precipitated onto the surface of the iron oxide precursor.
Claim 6
Dependent Claim
13 words
The process of claim 1 wherein the reduction is carried out in hydrogen.
Claim 7
Dependent Claim
18 words
The process of claim 1 wherein the modified iron oxide hydrate is dehydrated prior to the reduction step.
Claim 8
Dependent Claim
18 words
The process of claim 1 wherein the coating of antimony enhances the rate of reduction in step A.
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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) | 1984-03-16 | 1984-09-15 | 1985-03-17 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1988-03-16 | 1988-09-15 | 1989-03-17 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1992-03-16 | 1992-09-15 | 1993-03-17 | $7700.00 | Window Closed / Lapsed |