US4020236A
Expired / Lapsed
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Process for producing a magnetic material and magnetic recording medium containing the same
Assignee: Fujifilm Holdings Corp
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Filing: 1975-07-22
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Granted: 1977-04-26
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Expires: 1995-07-22
Abstract
Abstract A ferromagnetic material having a high coercive force and good squareness ratio prepared by mixing an aqueous solution at least containing a salt of a metal capable of forming a ferromagnetic material with a solution of a reducing agent containing at least one of a boron hydride compound or a derivative thereof to perform an oxidation-reduction reaction, wherein the mixing of the solutions is after adjusting the pH of the aqueous solution of the metal salt to about 3.0 or less, and the pH of the reaction mixture at the end of the reaction is adjusted to at least about 3.0 or higher.
Inventors
- 👤 Masashi Aonuma
- 👤 Yasuo Tamai
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-25 12:51
CPC Classifications
G; G11; G11B; G11B5/00; G11B5/62; G11B5/68; G11B5/70; G11B5/706; G11B5/70605; G11B5/70621; G11B5/70615; Y; Y10; Y10S; Y10S428/00; Y10S428/90; Y10T; Y10T428/00; Y10T428/31504; Y10T428/31678
Claims Analysis
Total Claims: 17
Claim 1
Independent Claim
81 words
A process for preparing a ferromagnetic material which comprises mixing an aqueous solution containing at least a salt of Fe, Co, Fe-Co, Fe-Ni, Co-Ni and Fe-Co-Ni and whose pH has been adjusted to about 3.0 or less, with a solution of a reducing agent containing at least one boron hydride compound or a derivative thereof to perform an oxidation-reduction reaction, and adjusting the pH of the reaction mixture at the end of the reaction to at least about 3.0 or higher.
Claim 2
Dependent Claim
81 words
A process for preparing a ferromagnetic material which comprises mixing an aqueous solution containing at least a salt of Fe, Co, Fe-Co, Fe-Ni, Co-Ni and Fe-Co-Ni and whose pH has been adjusted to about 3.0 or less, with a solution of a reducing agent containing at least one boron hydride compound or a derivative thereof to perform an oxidation-reduction reaction, and adjusting the pH of the reaction mixture at the end of the reaction to at least about 3.0 or higher.
Claim 3
Dependent Claim
24 words
The process of claim 1, wherein the pH of said aqueous solution of the metal salt is adjusted with hydrochloric acid or sulfuric acid.
Claim 4
Dependent Claim
40 words
The process of claim 1, wherein said aqueous solution of the metal salt contains at least Fe, and at least one of the elements of Groups IVa, VIa, VIIa, VIII, Ib, IIb, IIIb, IVb, and Vb of the periodic table.
Claim 5
Dependent Claim
22 words
The process of claim 3, wherein the pH of said aqueous solution of the metal salt ranges from about 0.5 to 2.5.
Claim 6
Dependent Claim
27 words
The process of claim 1, wherein the concentration of the ferromagnetic metal ion in said aqueous solution of the metal salt is about 0.002 to 2 mole/liter.
Claim 7
Dependent Claim
26 words
The process of claim 5, wherein the concentration of the ferromagnetic metal ion in said aqueous solution of the metal salt is 0.01 to 0.5 mole/liter.
Claim 8
Dependent Claim
25 words
The process of claim 1, wherein the solution of the reducing agent contains an alkali metal hydroxide at a concentration of about 0.001 to 0.6N.
Claim 9
Dependent Claim
23 words
The process of claim 1, wherein the concentration of the boron hydride compound or the derivative thereof is about 0.0002 to 10 moles/liter.
Claim 10
Dependent Claim
17 words
The process of claim 1, wherein initially the oxdation-reduction reaction is at about 60° C or less.
Claim 11
Dependent Claim
17 words
The process of claim 9, wherein initially the oxdation-reduction reaction is performed at 40° C or less.
Claim 12
Dependent Claim
20 words
The process of claim 1, wherein the process further comprises treating the ferromagnetic material with an anionic surface active agent.
Claim 13
Dependent Claim
25 words
The process of claim 11, wherein the anionic surface active agent is a fatty acid containing 11 to 18 carbon atoms or a salt thereof.
Claim 14
Dependent Claim
28 words
The process of claim 12, wherein the anionic surface active agent is an alkali metal salt or alkaline earth metal salt of a saturated or unsaturated fatty acid.
Claim 15
Dependent Claim
25 words
A magnetic material comprising the ferromagnetic material produced by the process of claim 11, and having a coercive force of at least about 1,000 Oe.
Claim 16
Dependent Claim
26 words
A magnetic recording medium which comprises a support having thereon a dispersion comprising the ferromagnetic material prepared by the process of claim 1 and a binder.
Claim 17
Dependent Claim
49 words
A magnetic recording medium which comprises a support having thereon a dispersion comprising the ferromagnetic material prepared by the process of claim 11, and having a coercive force of at least about 1,000 Oe, a Bm of at least about 2,400 gauss, and Br/Bm of at least about 0.80.
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) | 1980-04-25 | 1980-10-25 | 1981-04-26 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1984-04-25 | 1984-10-25 | 1985-04-26 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1988-04-25 | 1988-10-25 | 1989-04-26 | $7700.00 | Window Closed / Lapsed |