US4626370A
Expired / Lapsed
US
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Magnetic fluid
Assignee: TDK Corp
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Filing: 1985-09-12
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Granted: 1986-12-02
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Expires: 2005-09-12
Abstract
Abstract A magnetic fluid comprising metal fine particles of iron, 50 to 100 wt % of the metal particles of a surface-active agent selected from phospholipids, and 100 to 800 wt % of the metal particles of a medium in the form of a diester of an aliphatic dicarboxylic acid exhibits remarkably high saturation magnetization.
Inventors
- 👤 Katsuhiko Wakayama
- 👤 Hiraku Harada
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-04 23:42
CPC Classifications
H; H01; H01F; H01F1/00; H01F1/44; H01F1/442
Claims Analysis
Total Claims: 13
Claim 1
Independent Claim
36 words
A magnetic fluid comprising metal fine particles of iron, a phospholipid surface-active agent, and a medium, the improvement wherein said medium is at least one member selected from the group consisting of diesters of dicarboxylic acids.
Claim 2
Dependent Claim
36 words
A magnetic fluid comprising metal fine particles of iron, a phospholipid surface-active agent, and a medium, the improvement wherein said medium is at least one member selected from the group consisting of diesters of dicarboxylic acids.
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 100 Å.
Claim 4
Dependent Claim
26 words
A magnetic fluid according to claim 1 wherein the dicarboxylic diester is a diester of a saturated aliphatic dicarboxylic acid having 6 to 10 carbon atoms.
Claim 5
Dependent Claim
28 words
A magnetic fluid according to claim 1 wherein the dicarboxylic diester is an ester of a dicarboxylic acid with an aliphatic alcohol having 1 to 10 carbon atoms.
Claim 6
Dependent Claim
28 words
A magnetic fluid according to claim 3 wherein the dicarboxylic diester is an ester of a dicarboxylic acid with an aliphatic alcohol having 1 to 10 carbon atoms.
Claim 7
Dependent Claim
31 words
A magnetic fluid according to claim 1 wherein the dicarboxylic diester medium is present in an amount of 100 to 800% by weight of the weight of the metal fine particles.
Claim 8
Dependent Claim
12 words
A magnetic fluid according to claim 1 wherein the phospholipid is lecithin.
Claim 9
Dependent Claim
29 words
A magnetic fluid according to claim 1 wherein the surface-active agent is present in an amount of 50 to 100% of the metal fine particles on a weight basis.
Claim 10
Dependent Claim
39 words
A magnetic fluid comprising metal fine particles of iron, a surface-active agent, an effective amount of an antioxidant, and a medium wherein said medium is at least one member selected from the group consisting of diesters of dicarboxylic acids.
Claim 11
Dependent Claim
39 words
A magnetic fluid comprising metal fine particles of iron, a surface-active agent, an effective amount of an antioxidant, and a medium wherein said medium is at least one member selected from the group consisting of diesters of dicarboxylic acids.
Claim 12
Dependent Claim
12 words
A magnetic fluid according to claim 9 wherein the antioxidant is tocopherol.
Claim 13
Dependent Claim
28 words
A magnetic fluid according to claim 9 wherein the antioxidant is present in an amount of 0.8 to 10% of the metal fine particles on a weight basis.
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) | 1989-12-01 | 1990-06-02 | 1990-12-02 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1993-12-01 | 1994-06-02 | 1994-12-02 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1997-12-01 | 1998-06-02 | 1998-12-02 | $7700.00 | Window Closed / Lapsed |