US5085789A
Expired / Lapsed
US
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Ferrofluid compositions
Assignee: NSK Ltd
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Filing: 1990-04-30
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Granted: 1992-02-04
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Expires: 2010-04-30
Abstract
Abstract A ferrofluid composition is defined by fine particles of ferromagnetic material, a liquid carrier for dispersing the ferromagnetic material and a surfactant or surfactants acting as a dispersant. The surfactant is required to have such relation to the carrier that the surfactant has, as its hydrophobic group portion, a structure equivalent to the carrier, and the carrier is selected to be either an alkylpolyphenyl ether oil, an alkylnaphthalene oil or both. By virtue of this structural feature, fine ferromagnetic particles are uniformly and stably dispersed throughout the carrier which has low viscosity and is thermally very stable.
Inventors
- 👤 Atsushi Yokouchi
- 👤 Toshikazu Yabe
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-04 02:13
CPC Classifications
H; H01; H01F; H01F1/00; H01F1/44
Claims Analysis
Total Claims: 4
Claim 1
Independent Claim
54 words
A ferrofluid composition consisting essentially of: (a) fine particles of ferromagnetic material; (b) a liquid carrier which comprises an alkylnaphthalene; (c) a surfactant consisting of a direct combination of a hydrophilic portion and a hydrophobic portion, the hydrophobic portion consisting of an alkylnaphthalene structure "substantially identical to the alkylnaphthalene structure of said liquid carrier".
Claim 2
Dependent Claim
54 words
A ferrofluid composition consisting essentially of: (a) fine particles of ferromagnetic material; (b) a liquid carrier which comprises an alkylnaphthalene; (c) a surfactant consisting of a direct combination of a hydrophilic portion and a hydrophobic portion, the hydrophobic portion consisting of an alkylnaphthalene structure "substantially identical to the alkylnaphthalene structure of said liquid carrier".
Claim 3
Dependent Claim
24 words
A ferrofluid composition as claimed in claim 1, wherein said liquid carrier is eicocylnaphthalene and said surfactant is a sodium salt of sulfonated eicocylnaphthalene.
Claim 4
Dependent Claim
21 words
A ferrofluid composition as claimed in claim 1, wherein said liquid carrier is eicocylnaphthalene and said surfactant is eicocylnaphthalene sulfonic acid.
References Cited (Backward Citations)
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Cited
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Cited
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Cited
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Cited
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Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1995-02-03 | 1995-08-05 | 1996-02-04 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1999-02-03 | 1999-08-05 | 2000-02-04 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2003-02-03 | 2003-08-05 | 2004-02-04 | $7700.00 | Window Closed / Lapsed |