US4624797A
Expired / Lapsed
US
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Magnetic fluid and process for preparing the same
Assignee: TDK Corp
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Filing: 1985-09-12
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Granted: 1986-11-25
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Expires: 2005-09-12
Abstract
Abstract A magnetic fluid comprising metal fine particles of cobalt, a nonionic or oil-soluble anionic surface-active agent, and a low-volatile solvent exhibits remarkably high saturation magnetization.
Inventors
- 👤 Katsuhiko Wakayama
- 👤 Hiraku Harada
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-03 06:15
CPC Classifications
F; F16; F16J; F16J15/00; F16J15/16; F16J15/40; F16J15/43; H; H01; H01F; H01F1/00; H01F1/44; H01F1/442
Claims Analysis
Total Claims: 22
Claim 1
Independent Claim
46 words
A magnetic fluid comprising metal fine particles of cobalt, a surface-active agent selected from the group consisting of an oil-soluble anionic sulfosuccinate surface-active agent and a nonionic surface-active agent which is a polyglycerine fatty acid ester or polyethylene glycol alkyl ether, and a low-volatile solvent medium.
Claim 2
Dependent Claim
46 words
A magnetic fluid comprising metal fine particles of cobalt, a surface-active agent selected from the group consisting of an oil-soluble anionic sulfosuccinate surface-active agent and a nonionic surface-active agent which is a polyglycerine fatty acid ester or polyethylene glycol alkyl ether, and a low-volatile solvent medium.
Claim 3
Dependent Claim
22 words
A magnetic fluid according to claim 1 wherein the metal fine particles have an average particle size of 70 to 120 A.
Claim 4
Dependent Claim
23 words
A magnetic fluid according to claim 1 wherein the low-volatile solvent has a boiling point of at least 150° C. at 1 mmHg.
Claim 5
Dependent Claim
22 words
A magnetic fluid according to claim 1 wherein the low-volatile solvent is at least one member selected from ester and hydrocarbon solvents.
Claim 6
Dependent Claim
20 words
A magnetic fluid according to claim 4 wherein the ester solvent is a diester of a saturated aliphatic dicarboxylic acid.
Claim 7
Dependent Claim
19 words
A magnetic fluid according to claim 5 wherein the saturated aliphatic dicarboxylic acid has 6 to 10 carbon atoms.
Claim 8
Dependent Claim
22 words
A magnetic fluid according to claim 4 wherein the hydrocarbon solvent is a saturated aliphatic hydrocarbon having 19 to 30 carbon atoms.
Claim 9
Dependent Claim
28 words
A magnetic fluid according to claim 1 wherein the solvent is present in an amount of 50 to 300% of the metal fine particles on a weight basis.
Claim 10
Dependent Claim
18 words
A magnetic fluid according to claim 1, wherein the surface-active agent is an oil-soluble anionic sulfosuccinate surface-active agent.
Claim 11
Dependent Claim
28 words
A magnetic fluid according to claim 1, wherein the surface-active agent is a nonionic surface-active agent which is a polyglycerine fatty acid ester or polyethylene glycol alkly ether.
Claim 12
Dependent Claim
29 words
A magnetic fluid according to claim 1 wherein the surface-active agent is present in an amount of 5 to 20% of the metal fine particles on a weight basis.
Claim 13
Dependent Claim
45 words
A magentic fluid comprising metal fine particles of cobalt, a surface-active agent, and a medium, the improvement wherein said surface-active agent comprises at least one member selected from nonionic and oil-soluble anionic surface-active agents and said medium comprises a low-volatile solvent and a low-boiling solvent.
Claim 14
Dependent Claim
45 words
A magentic fluid comprising metal fine particles of cobalt, a surface-active agent, and a medium, the improvement wherein said surface-active agent comprises at least one member selected from nonionic and oil-soluble anionic surface-active agents and said medium comprises a low-volatile solvent and a low-boiling solvent.
Claim 15
Dependent Claim
20 words
A magnetic fluid according to claim 12 wherein the low-boiling solvent has a boiling point of 100° to 160° C.
Claim 16
Dependent Claim
23 words
A magnetic fluid according to claim 12 or 13 wherein the low-boiling solvent is a hydrocarbon medium having 7 to 22 carbon atoms.
Claim 17
Dependent Claim
30 words
A magnetic fluid according to claim 14 wherein the low-boiling hydrocarbon solvent is present in an amount of at least 5% of the metal fine particles on a weight basis.
Claim 18
Dependent Claim
18 words
A magnetic fluid according to claim 1 or 12 which further comprises an effective amount of an antioxidant.
Claim 19
Dependent Claim
12 words
A magnetic fluid according to claim 16 wherein the antioxidant is tocopherol.
Claim 20
Dependent Claim
29 words
A magnetic fluid according to claim 16 wherein the antioxidant is present in an amount of 0.8 to 10% by weight of the weight of the metal fine particles.
Claim 21
Dependent Claim
63 words
A process for preparing a magnetic fluid comprising metal fine particles of cobalt, a surface-active agent, and a medium, comprising the steps of: preparing a dispersion comprising metal fine particles of cobalt, a surface-active agent and a low-boiling solvent; and replacing all or a part of the low-boiling solvent by a low-volatile solvent having a nonionic or oil-soluble anionic surface-active agent dissolved therein.
Claim 22
Dependent Claim
63 words
A process for preparing a magnetic fluid comprising metal fine particles of cobalt, a surface-active agent, and a medium, comprising the steps of: preparing a dispersion comprising metal fine particles of cobalt, a surface-active agent and a low-boiling solvent; and replacing all or a part of the low-boiling solvent by a low-volatile solvent having a nonionic or oil-soluble anionic surface-active agent dissolved therein.
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) | 1989-11-24 | 1990-05-26 | 1990-11-25 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1993-11-24 | 1994-05-26 | 1994-11-25 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1997-11-24 | 1998-05-26 | 1998-11-25 | $7700.00 | Window Closed / Lapsed |