US4101311A
Expired / Lapsed
US
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Process for producing ferromagnetic metal powder
Assignee: Fujifilm Holdings Corp
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Filing: 1977-08-01
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Granted: 1978-07-18
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Expires: 1997-08-01
Abstract
Abstract A ferromagnetic metal powder having a narrow distribution of coercive force produced by reducing a salt of a metal capable of forming a ferromagnetic material as an aqueous solution thereof, where the reducing reaction is carried out while maintaining the temperature of the aqueous solution during and/or after the reduction reaction at about 20 DEG C higher than the temperature or less of the aqueous solution at the immediate beginning of the reduction reaction.
Inventors
- 👤 Masashi Aonuma
- 👤 Yasuo Tamai
- 👤 Fumio Kodama
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-28 05:25
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; B22F9/24; G; G11; G11B; G11B5/00; G11B5/62; G11B5/68; G11B5/70; G11B5/706; G11B5/70605; G11B5/70615; G11B5/70621; Y; Y10; Y10T; Y10T428/00; Y10T428/31504; Y10T428/31507; Y10T428/31678; Y10T428/31681
Claims Analysis
Total Claims: 18
Claim 1
Independent Claim
102 words
A process for producing a ferromagnetic metal powder comprising: (a) adding a reducing agent to an aqueous solution of a salt of Fe, Co, Fe-Co, Fe-Ni, Co-Ni or Fe-Co-Ni at a rate of 0.1 to about 100 mole/sec. over an addition time of one minute or less, the temperature of said salt solution being -10° to 40° C at the start of said addition, and (b) during the course of the reduction maintaining the temperature of said aqueous solution at a temperature not more than about 20° C higher than the temperature of said salt solution at the start of the addition.
Claim 2
Dependent Claim
102 words
A process for producing a ferromagnetic metal powder comprising: (a) adding a reducing agent to an aqueous solution of a salt of Fe, Co, Fe-Co, Fe-Ni, Co-Ni or Fe-Co-Ni at a rate of 0.1 to about 100 mole/sec. over an addition time of one minute or less, the temperature of said salt solution being -10° to 40° C at the start of said addition, and (b) during the course of the reduction maintaining the temperature of said aqueous solution at a temperature not more than about 20° C higher than the temperature of said salt solution at the start of the addition.
Claim 3
Dependent Claim
43 words
The process of claim 1, wherein said reducing agent is selected from the group consisting of hypophosphorous acid, an alkali metal salt or alkaline earth metal salt of hypophosphorous acid, a boron hydride compound or a derivative thereof, and a gaseous reducing agent.
Claim 4
Dependent Claim
18 words
The process of claim 2 wherein said reducing agent is a boron hydride compound or a derivative thereof.
Claim 5
Dependent Claim
16 words
The process of claim 2 wherein said reducing agent is hypophosphorus acid or a derivative thereof.
Claim 6
Dependent Claim
14 words
The process of claim 1, wherein the reaction pressure is 0.5 to 5 atmospheres.
Claim 7
Dependent Claim
16 words
The process of claim 1, including applying ultrasonic vibration to the reaction solution during the reaction.
Claim 8
Dependent Claim
15 words
The process of claim 1, wherein the reaction is carried out in a magnetic field.
Claim 9
Dependent Claim
28 words
The process of claim 1, wherein the concentration of the metal ion capable of forming a ferromagnetic material in the aqueous solution is about 0.002 to 2 mole/liter.
Claim 10
Dependent Claim
27 words
The process of claim 1, wherein the concentration of the metal ion capable of forming a ferromagnetic material in the aqueous solution is 0.01 to 0.5 mole/liter.
Claim 11
Dependent Claim
18 words
The process of claim 1, wherein the concentration of said reducing agent is about 0.0002 to 10 moles/liter.
Claim 12
Dependent Claim
22 words
The process of claim 1, wherein the molar ratio of the reducing substance to the metal ion is about 0.1 to 5.
Claim 13
Dependent Claim
26 words
A magnetic recording medium which comprises a support having thereon a magnetic layer of the ferromagnetic metal powder as produced in claim 1 and a binder.
Claim 14
Dependent Claim
14 words
The process of claim 1 wherein said addition rate is 0.2 to 20 mole/second.
Claim 15
Dependent Claim
12 words
The process of claim 1 wherein the reaction volume is 10 liters.
Claim 16
Dependent Claim
21 words
The process of claim 1 wherein the reaction volume is 50 liters and the addition rate is 1 to 100 mole/second.
Claim 17
Dependent Claim
38 words
The process of claim 1 wherein said metal salt solution contains in addition a metal salt selected from the group consisting of La, Ce, Nd, Sm, Sn, Al, W, Cr, Mn, Cu, Zn, Ag, Pd, Ti and Pb.
Claim 18
Dependent Claim
14 words
The process of claim 1 wherein the addition time is 15 seconds or less.
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) | 1981-07-17 | 1982-01-16 | 1982-07-18 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1985-07-17 | 1986-01-16 | 1986-07-18 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1989-07-17 | 1990-01-16 | 1990-07-18 | $7700.00 | Window Closed / Lapsed |