US4274865A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Production of magnetic powder
Assignee: Kanto Denka Kogyo Co Ltd
•
Filing: 1979-03-07
•
Granted: 1981-06-23
•
Expires: 1999-03-07
Abstract
Abstract The magnetic characteristics of magnetic powder consisting mainly of iron are improved by pre-treating the starting material from which the magnetic powder is prepared by reductions, with an aqueous solution and/or suspension of one member selected from the group consisting of zinc, chromium and copper compounds and mixtures thereof.
Inventors
- 👤 Shintaro Suzuki
- 👤 Sadao Iizuka
- 👤 Yoshimi Moriya
- 👤 Yuichi Omote
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 18:49
CPC Classifications
H; H01; H01F; H01F1/00; H01F1/01; H01F1/03; H01F1/032; H01F1/04; H01F1/06; H01F1/065; B; B22; B22F; B22F1/00; B22F1/17; Y; Y10; Y10T; Y10T428/00; Y10T428/12; Y10T428/12181
Claims Analysis
Total Claims: 21
Claim 1
Independent Claim
217 words
A process for producing a magnetic powder consisting essentially of acicular iron powders and containing at least one metal selected from the group consisting of zinc, chromium and copper suitable for magnetic recording which comprises the steps of (a) treating a finely divided starting material selected from the group consisting of (i) iron oxyhydroxide, (ii) iron oxyhydroxide containing a doping component selected from Co, Mn, Ni, Ti, Bi, Mo, Ag, Cr, Zn, Si, Al and mixtures thereof, (iii) iron oxides and (iv) iron oxides containing a doping component selected from Co, Mn, Ti, Bi, Mo, Ag, Cr, Zn, Si, Al and mixtures thereof, with an aqueous (i) solution or (ii) suspension of an applied metal compound selected from the group consisting of zinc, chromium and copper compounds and mixtures thereof or a mixture of said aqueous solution and said aqueous suspension so that said applied metal compound is applied to said starting material, (b) filtering the thus treated material off the liquid medium to form a cake and drying said cake, and (c) reducing said dry cake in a reducing gas stream at a temperature up to about 600° C. to form an acicular magnetic powder consisting essentially of iron and said applied metal selected from the group consisting of zinc, chromium and copper and mixtures thereof.
Claim 2
Dependent Claim
217 words
A process for producing a magnetic powder consisting essentially of acicular iron powders and containing at least one metal selected from the group consisting of zinc, chromium and copper suitable for magnetic recording which comprises the steps of (a) treating a finely divided starting material selected from the group consisting of (i) iron oxyhydroxide, (ii) iron oxyhydroxide containing a doping component selected from Co, Mn, Ni, Ti, Bi, Mo, Ag, Cr, Zn, Si, Al and mixtures thereof, (iii) iron oxides and (iv) iron oxides containing a doping component selected from Co, Mn, Ti, Bi, Mo, Ag, Cr, Zn, Si, Al and mixtures thereof, with an aqueous (i) solution or (ii) suspension of an applied metal compound selected from the group consisting of zinc, chromium and copper compounds and mixtures thereof or a mixture of said aqueous solution and said aqueous suspension so that said applied metal compound is applied to said starting material, (b) filtering the thus treated material off the liquid medium to form a cake and drying said cake, and (c) reducing said dry cake in a reducing gas stream at a temperature up to about 600° C. to form an acicular magnetic powder consisting essentially of iron and said applied metal selected from the group consisting of zinc, chromium and copper and mixtures thereof.
Claim 3
Dependent Claim
29 words
A process as claimed in claim 1 in which the starting material is selected from the group consisting of of α-, β- and γ-iron oxyhydroxide FeOOH and mixtures thereof.
Claim 4
Dependent Claim
19 words
A process as claimed in claim 2 in which the starting material is an iron oxyhydroxide doped with Co.
Claim 5
Dependent Claim
46 words
A process as claimed in claim 1 in which the starting material is selected from the group consisting of α-Fe 2 O 3 , γ-Fe 2 O 3 , Fe 3 O 4 and the Berthollide compound γ-Fe 2 O 3 -Fe 3 O 4 .
Claim 6
Dependent Claim
16 words
A process as claimed in claim 4 in which the starting material is doped with Co.
Claim 7
Dependent Claim
22 words
A process as claimed in claim 1 in which the applied metal compound is in the form of a water soluble salt.
Claim 8
Dependent Claim
17 words
A process as claimed in claim 1 in which the applied metal is a colloid forming compound.
Claim 9
Dependent Claim
51 words
A process as claimed in claim 1 in which the applied metal compound is a metal compound used in such an amount that the starting material is supplied with the compound in an amount of about 1% to about 10% by weight of the weight of Fe in the starting material.
Claim 10
Dependent Claim
20 words
A process as claimed in claim 1 in which said aqueous solution or suspension or mixture thereof contains a surfactant.
Claim 11
Dependent Claim
23 words
A process as claimed in claim 9 in which the surfactant is selected from the group conisting of sodium oleate and sodium alginte.
Claim 12
Dependent Claim
30 words
A process as claimed in claim 1 in which the application of said applied metal compound on the starting material is effected by adsorption or absorption or a mixture thereof.
Claim 13
Dependent Claim
23 words
A process as claimed in claim 1 in which the application of said applied metal on the starting material is effected by deposition.
Claim 14
Dependent Claim
16 words
A process as claimed in claim 1 in which the reducing gas consists essentially of hydrogen.
Claim 15
Dependent Claim
26 words
A process as claimed in claim 1 in which the reduction is carried out at a temperature of from about 200° C. to about 600° C.
Claim 16
Dependent Claim
35 words
A process as claimed in claim 1 which comprises a further step of treating the reduced material with a stream comprising an inert gas and a minor proprotion of air to stabilize the product powder.
Claim 17
Dependent Claim
23 words
A process as claimed in claim 15 in which during the stabilization the proportion of air in the treatment stream is gradually increased.
Claim 18
Dependent Claim
19 words
A process as claimed in claim 1 or claim 8 or claim 15 wherein said applied metal is zinc.
Claim 19
Dependent Claim
19 words
A process as claimed in claim 1 or claim 8 or claim 15 wherein said applied metal is chromium.
Claim 20
Dependent Claim
19 words
A process as claimed in claim 1 or claim 8 or claim 15 wherein said applied metal is copper.
Claim 21
Dependent Claim
45 words
A process as claimed in claim 1 wherein the applied metal compound is a metal compound used in such an amount that after reduction, the acicular magnetic powder contains at least about 0.3 molar percent of the applied metal on the basis of the iron.
References Cited (Backward Citations)
US2687349A
Cited
GB743792A
Cited
GB1125093A
Cited
US3598568A
Cited
GB1264994A
Cited
DE1907691A1
Cited
GB1221733A
Cited
US3607220A
Cited
GB1268458A
Cited
GB1318579A
Cited
US3702270A
Cited
GB1312227A
Cited
GB1347615A
Cited
DE2212934A1
Cited
GB1419598A
Cited
US4067755A
Cited
US4063000A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1984-06-22 | 1984-12-22 | 1985-06-23 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1988-06-22 | 1988-12-22 | 1989-06-23 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1992-06-22 | 1992-12-22 | 1993-06-23 | $7700.00 | Window Closed / Lapsed |