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US4732706A
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Method of preparing low viscosity, electrically conductive ferrofluid composition
Assignee: Ferrotec USA Corp
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Filing: 1987-05-26
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Granted: 1988-03-22
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Expires: 2007-05-26
Abstract
Abstract A low viscosity, electrically conductive ferrofluid composition and method of making and using same, which composition comprises: a first polar liquid carrier; a second polar liquid carrier miscible in the first polar carrier and comprising a polyol, such as a tetraethylene glycol dimethyl ether; magnetic particles to impart magnetic characteristics to the ferrofluid composition; and a surfactant, particularly a cationic surfactant in an amount sufficient to stabilize and disperse the magnetic particles, the surfactant dissociated or ionized predominately by the second polar liquid carrier.
Inventors
- 👤 Lucian Borduz
- 👤 Kuldip Raj
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-07 14:12
CPC Classifications
H; H01; H01B; H01B1/00; H01B1/20; H01B1/24; F; F16; F16J; F16J15/00; F16J15/16; F16J15/40; F16J15/43; H01F; H01F1/00; H01F1/44; H01F1/442
Claims Analysis
Total Claims: 14
Claim 1
Independent Claim
107 words
A method of preparing a low viscosity, electrically conductive ferrofluid composition, which method comprises: (a) dispersing magnetic particles in an amount sufficient to provide magnetic properties in a polar liquid carrier in the presence of a surfactant to provide a ferrofluid composition; (b) the improvement which comprises: (i) adding to the ferrofluid composition a dissociation or ionizing amount of a dissociation or ionizing agent for the surfactant to provide a ferrofluid composition having an electrical resistivity of 1×10 7 ohms-centimeters or less, the agent consisting of an oxygen-containing agent selected from a group consisting of an alkylene polyol, an ether of an alkylene polyol and combinations thereof.
Claim 2
Independent Claim
107 words
A method of preparing a low viscosity, electrically conductive ferrofluid composition, which method comprises: (a) dispersing magnetic particles in an amount sufficient to provide magnetic properties in a polar liquid carrier in the presence of a surfactant to provide a ferrofluid composition; (b) the improvement which comprises: (i) adding to the ferrofluid composition a dissociation or ionizing amount of a dissociation or ionizing agent for the surfactant to provide a ferrofluid composition having an electrical resistivity of 1×10 7 ohms-centimeters or less, the agent consisting of an oxygen-containing agent selected from a group consisting of an alkylene polyol, an ether of an alkylene polyol and combinations thereof.
Claim 3
Dependent Claim
46 words
The method of claim 1 which includes adding to the ferrofluid composition finely divided carbon black particles in an amount of up to about 5 percent by weight of the composition to provide a ferrofluid composition having an electrical resistivity of 1×10 6 ohms or less.
Claim 4
Dependent Claim
44 words
The method of claim 1 which includes dispersing the magnetic particles employing a first coating layer of a first anionic surfactant then thereafter dispersing the magnetic particles employing a second coating layer of a cationic surfactant, the cationic surfactant comprising a quaternary ammonium surfactant.
Claim 5
Dependent Claim
14 words
The method of claim 3 wherein the cationic surfactant comprises a quaternary ammonium surfactant.
Claim 6
Dependent Claim
47 words
The method of claim 1 which includes adding the agent in an amount of from about 3 to 30 percent by volume of the composition and wherein the surfactant comprises a cationic surfactant in an amount in excess of the amount required to disperse the magnetic particles.
Claim 7
Dependent Claim
44 words
The method of claim 1 wherein the agent is selected from the group consisting of: diethyl glycol dibutyl ether; tetraethylene glycol dimethyl ether; triethylene glycol dimethyl ether; diethylene glycol diethyl ether; diethylene glycol dimethyl ether; ethylene glycol diethyl ether; polyethylene glycol and polypropylene glycol.
Claim 8
Dependent Claim
18 words
The method of claim 1 wherein the polar liquid carrier comprises a polyol ester or a polyalpha olefin.
Claim 9
Dependent Claim
17 words
The method of claim 1 wherein the agent comprises a di-, tri- or tetraethylene glycol alkyl ether.
Claim 10
Dependent Claim
30 words
The method of claim 1 which comprises employing a first surfactant to disperse and precoat the ferromagnetic particles and a second surfactant in excess to disperse the precoated ferromagnetic particles.
Claim 11
Dependent Claim
14 words
The method of claim 9 wherein the first and second surfactants are different surfactants.
Claim 12
Dependent Claim
44 words
The method of claim 9 wherein the first surfactant is present in an amount of from about 5 to 10 percent by volume of the composition, and the second surfactant is present in an amount of from about 2 to 12 percent by volume.
Claim 13
Dependent Claim
10 words
The ferrofluid composition prepared by the method of claim 1.
Claim 14
Dependent Claim
10 words
The ferrofluid composition prepared by the method of claim 4.
References Cited (Backward Citations)
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| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
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| 3.5 Years (Year 4) | 1991-03-22 | 1991-09-21 | 1992-03-22 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1995-03-22 | 1995-09-21 | 1996-03-22 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1999-03-22 | 1999-09-21 | 2000-03-22 | $7700.00 | Window Closed / Lapsed |