US4608186A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Magnetic fluid
Assignee: TDK Corp
•
Filing: 1985-07-30
•
Granted: 1986-08-26
•
Expires: 2005-07-30
Abstract
Abstract A magnetic fluid comprising metal fine particles of cobalt, 25 to 60% based on the weight of the metal particles of a surface-active agent selected from the group consisting of polyglycerine fatty acid esters, sorbitan fatty acid esters, and mixtures thereof, and 50 to 250% based on the weight of the metal particles of a low boiling hydrocarbon medium exhibits remarkably high saturation magnetization.
Inventors
- 👤 Katsuhiko Wakayama
- 👤 Hiraku Harada
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-29 20:38
CPC Classifications
H; H01; H01F; H01F1/00; H01F1/44; H01F1/442
Claims Analysis
Total Claims: 16
Claim 1
Independent Claim
44 words
A magnetic fluid comprising metal fine particles of cobalt, a surface-active agent, and a hydrocarbon medium, the improvement wherein said surface-active agent is at least one member selected from the group consisting of polyglycerine fatty acid esters, sorbitan fatty acid esters, and mixtures thereof.
Claim 2
Dependent Claim
44 words
A magnetic fluid comprising metal fine particles of cobalt, a surface-active agent, and a hydrocarbon medium, the improvement wherein said surface-active agent is at least one member selected from the group consisting of polyglycerine fatty acid esters, sorbitan fatty acid esters, and mixtures thereof.
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 Å.
Claim 4
Dependent Claim
19 words
A magnetic fluid according to claim 1 wherein the polyglycerine has a degree of polymerization of 2 to 10.
Claim 5
Dependent Claim
24 words
A magnetic fluid according to claim 1 wherein the polyglycerine fatty acid ester is a partial ester of a polyglycerine with a fatty acid.
Claim 6
Dependent Claim
14 words
A magnetic fluid according to claim 1 wherein the sorbitan is 1,4-sorbitan or 1,5-sorbitan.
Claim 7
Dependent Claim
24 words
A magnetic fluid according to claim 1 wherein the sorbitan fatty acid ester is a mono or sesqui-ester of sorbitan with a fatty acid.
Claim 8
Dependent Claim
30 words
A magnetic fluid according to claim 1 wherein the fatty acid of the ester is one member selected from saturated and unsaturated fatty acids having 10 to 18 carbon atoms.
Claim 9
Dependent Claim
21 words
A magnetic fluid according to claim 7 wherein the fatty acid is selected from stearic acid, isostearic acid, and oleic acid.
Claim 10
Dependent Claim
30 words
A magnetic fluid according to claim 1 wherein the surface-active agent is present in an amount of 25 to 60% by weight of the weight of the metal fine particles.
Claim 11
Dependent Claim
17 words
A magnetic fluid according to claim 1 wherein the hydrocarbon medium has 7 to 22 carbon atoms.
Claim 12
Dependent Claim
17 words
A magnetic fluid according to claim 10 wherein the hydrocarbon medium is kerosine or an aromatic hydrocarbon.
Claim 13
Dependent Claim
30 words
A magnetic fluid according to claim 1 wherein the hydrocarbon medium is present in an amount of 50 to 250% by weight of the weight of the metal fine particles.
Claim 14
Dependent Claim
16 words
A magnetic fluid according to claim 1 which further comprises an effective amount of an antioxidant.
Claim 15
Dependent Claim
12 words
A magnetic fluid according to claim 13 wherein the antioxidant is tocopherol.
Claim 16
Dependent Claim
29 words
A magnetic fluid according to claim 13 wherein the antioxidant is present in an amount of 0.5 to 3% by weight of the weight of the metal fine particles.
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) | 1989-08-25 | 1990-02-24 | 1990-08-26 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1993-08-25 | 1994-02-24 | 1994-08-26 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1997-08-25 | 1998-02-24 | 1998-08-26 | $7700.00 | Window Closed / Lapsed |