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Patent US4501774A successfully refreshed from Google Patents.
US4501774A
Expired / Lapsed
US
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Process for the production of cobalt-containing magnetic iron oxide powder
Assignee: Ishihara Sangyo Kaisha Ltd
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Filing: 1982-09-29
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Granted: 1985-02-26
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Expires: 2002-09-29
Abstract
Abstract A process is provided for coating the particle surfaces of a phosphor-containing magnetic iron oxide powder with a cobalt compound after subjecting said powder to an activation treatment with an aqueous alkaline and/or acidic medium. The cobalt-containing magnetic iron oxide powder obtained according to this process has excellent coercivity and thermal stability, and the magnetic tape produced by using said powder has not only high coercivity but also excellent squareness, orientability and remanent induction.
Inventors
- 👤 Kokichi Miyazawa
- 👤 Kazuo Nakata
- 👤 Tsuneo Ishikawa
- 👤 Ichiro Honma
- 👤 Masaharu Hirai
- 👤 Makoto Ogasawara
- 👤 Toshihiko Kawamura
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-30 04:58
CPC Classifications
C; C01; C01G; C01G49/00; G; G11; G11B; G11B5/00; G11B5/62; G11B5/68; G11B5/70; G11B5/706; G11B5/70626; G11B5/70642; G11B5/70678; G11B5/70684; G11B5/70652; G11B5/70668; G11B5/70673; H; H01; H01F; H01F1/00; H01F1/01; H01F1/03; H01F1/032; H01F1/10; H01F1/11; Y; Y10; Y10S; Y10S428/00; Y10S428/90; Y10T; Y10T428/00; Y10T428/29; Y10T428/2982; Y10T428/2991
Claims Analysis
Total Claims: 13
Claim 1
Independent Claim
141 words
In a process for producing a cobalt-containing magnetic iron oxide powder, comprising preparing acicular hydrous iron oxide from a solution of a ferrous compound and an alkali, dehydrating and, subsequently, reducing or reducing and oxidizing said hydrous iron oxide to form an acicular magnetic iron oxide powder, in which a phosphorus compound is present due to adding to either step of preparing said hydrous iron oxide or step of converting said hydrous iron oxide to said iron oxide powder, and then coating the surface of said iron oxide powder with a cobalt compound or a combination of cobalt and another metallic compound or compounds, the improvement comprising, before the coating step, of: treating said phosphorus-containing iron oxide powder with an aqueous alkaline medium and/or an aqueous acidic medium under atmospheric pressure and recovering the treated iron oxide powder from the medium.
Claim 2
Dependent Claim
141 words
In a process for producing a cobalt-containing magnetic iron oxide powder, comprising preparing acicular hydrous iron oxide from a solution of a ferrous compound and an alkali, dehydrating and, subsequently, reducing or reducing and oxidizing said hydrous iron oxide to form an acicular magnetic iron oxide powder, in which a phosphorus compound is present due to adding to either step of preparing said hydrous iron oxide or step of converting said hydrous iron oxide to said iron oxide powder, and then coating the surface of said iron oxide powder with a cobalt compound or a combination of cobalt and another metallic compound or compounds, the improvement comprising, before the coating step, of: treating said phosphorus-containing iron oxide powder with an aqueous alkaline medium and/or an aqueous acidic medium under atmospheric pressure and recovering the treated iron oxide powder from the medium.
Claim 3
Dependent Claim
23 words
The process according to claim 1, wherein the treatment with the aqueous medium is conducted at a temperature of 10° to 95° C.
Claim 4
Dependent Claim
23 words
The process according to claim 2, wherein the treatment with the aqueous medium is conducted at a temperature of 20° to 80° C.
Claim 5
Dependent Claim
18 words
The process according to claim 3, wherein the treatment with the aqueous medium is conducted at 25° C.
Claim 6
Dependent Claim
23 words
The process according to claim 2, wherein the treatment with the aqueous medium is conducted at a temperature of 30° to 70° C.
Claim 7
Dependent Claim
22 words
The process according to claim 1 or 2, wherein the alkali concentration of the aqueous alkaline medium is 0.005 to 3 mol/l.
Claim 8
Dependent Claim
22 words
The process according to claim 1 or 2, wherein the acid concentration of the aqueous acidic medium is 0.01 to 1 mol/l.
Claim 9
Dependent Claim
32 words
The process according to claim 1 or 2, wherein the phosphor containing magnetic iron oxide powder is first treated with an aqueous acidic medium and then treated with an aqueous alkaline medium.
Claim 10
Dependent Claim
32 words
The process according to claim 1 or 2, wherein the phosphor containing magnetic iron oxide powder is first treated with an aqueous alkaline medium and then treated with an aqueous acidic medium.
Claim 11
Dependent Claim
28 words
The process according to claim 1 or 2, wherein the particle surfaces of the magnetic iron oxide powder are coated with a cobalt compound and a ferrous compound.
Claim 12
Dependent Claim
21 words
The process according to claim 1 or 2, which further comprises heating the coated particles in the presence of water vapor.
Claim 13
Dependent Claim
19 words
The process according to claim 1 or 2, which further comprises subjecting the coated particles to a hydrothermal treatment.
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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) | 1988-02-26 | 1988-08-27 | 1989-02-26 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1992-02-26 | 1992-08-27 | 1993-02-26 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1996-02-26 | 1996-08-27 | 1997-02-26 | $7700.00 | Window Closed / Lapsed |