US4604222A
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US
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Stable ferrofluid composition and method of making and using same
Assignee: Ferrotec USA Corp
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Filing: 1985-05-21
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Granted: 1986-08-05
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Expires: 2005-05-21
Abstract
Abstract A stable ferrofluid composition and the method of preparing and using the ferrofluid composition, such as in a ferrofluid seal apparatus, and which ferrofluid composition comprises: a liquid carrier; ferromagnetic particles sufficient to provide magnetic properties to the ferrofluid dispersed in the liquid carrier; and a dispersing amount of a cationic surfactant to provide a stable ferrofluid composition. The stable ferrofluid compositions have improved electrical conductivity and are useful in sealing computer disc drives and in sputtering apparatus in the semiconductive industry.
Inventors
- 👤 Lucian Borduz
- 👤 Kuldip Raj
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-25 14:04
CPC Classifications
H; H01; H01F; H01F1/00; H01F1/44
Claims Analysis
Total Claims: 34
Claim 1
Independent Claim
97 words
A stable ferrofluid composition which comprises: (a) an organic liquid carrier; (b) magnetic particles in an amount sufficient to provide magnetic properties to the ferrofluid composition; and (c) a dispersing agent in an amount sufficient to disperse and stabilize the magnetic particles in the organic liquid carrier, which dispersing agent comprises: a cationic surfactant composed of a cationic positively charged head portion and a long-chain tail portion, the long-chain tail portion compatible with or soluble in the organic liquid carrier, to provide a stable ferrofluid composition having an electrical resistivity of about 10 6 ohms-cm or less.
Claim 2
Dependent Claim
97 words
A stable ferrofluid composition which comprises: (a) an organic liquid carrier; (b) magnetic particles in an amount sufficient to provide magnetic properties to the ferrofluid composition; and (c) a dispersing agent in an amount sufficient to disperse and stabilize the magnetic particles in the organic liquid carrier, which dispersing agent comprises: a cationic surfactant composed of a cationic positively charged head portion and a long-chain tail portion, the long-chain tail portion compatible with or soluble in the organic liquid carrier, to provide a stable ferrofluid composition having an electrical resistivity of about 10 6 ohms-cm or less.
Claim 3
Dependent Claim
26 words
The composition of claim 1 wherein the cationic surfactant is present in a ratio by weight of surfactant to magnetic particles from about 1:1 to 20:1.
Claim 4
Dependent Claim
35 words
The composition of claim 1 wherein the organic liquid carrier comprises a hydrocarbon or polyalphaolefine oil, and wherein the long chain portion of the cationic surfactant comprises a C 6 to about C 30 hydrocarbon.
Claim 5
Dependent Claim
34 words
The composition of claim 1 wherein the cationic surfactant comprises from about 4 to 25 moles of a polyalkoxylate portion, and wherein the organic liquid carrier comprises an ester, a glycol or an esterglycol.
Claim 6
Dependent Claim
26 words
The process of claim 1 wherein the organic liquid carrier is selected from the group consisting of liquid hydrocarbons, liquid esters, liquid glycols and silicone oils.
Claim 7
Dependent Claim
22 words
The composition of claim 1 wherein the magnetic particles comprise ferromagnetic particles having a diameter ranging from about 20 to 500 angstroms.
Claim 8
Dependent Claim
38 words
The composition of claim 1 wherein the magnetic particles comprise ferromagnetic particles having a diameter of from about 20 to 200 angstroms, and wherein the cationic surfactant has a long chain portion of about 10 to 50 angstroms.
Claim 9
Dependent Claim
61 words
The composition of claim 1 wherein the cationic surfactant comprises a quaternary ammonium cationic surfactant having a quaternary ammonium head portion of the molecule and a long chain tail portion of the molecule, the long chain tail portion of the molecule selected from the group consisting of: a long chain hydrocarbon; a long chain fatty acid; or a poly alkoxylated chain.
Claim 10
Dependent Claim
34 words
The composition of claim 1 wherein the cationic surfactant is selected from a group consisting from a fatty acid quaternary imidazoline salt; a polypropoxy quaternary ammonium salt; an acylated polyamine salt; and combinations thereof.
Claim 11
Dependent Claim
56 words
The composition of claim 1 wherein the cationic surfactant comprises a quaternary ammonium cationic surfactant having the structural formula: ##STR4## wherein R 1 is a long-chain aliphatic radical; R 2 and R 3 are selected from the group consisting of hydrogen or an alkyl and a hydroxy-containing alkyl radical; and X - is an anionic-salt radical.
Claim 12
Dependent Claim
52 words
The composition of claim 1 wherein the cationic surfactant comprises a quaternary ammonium surfactant having the structural formula: ##STR5## wherein R 1 is a long chain radical; R 2 and R 3 are poly alkoxy radicals, and R 4 is a lower alkyl radical; and X - is an anionic salt radical.
Claim 13
Dependent Claim
37 words
The composition of claim 1 wherein the cationic surfactant comprises a quaternary ammonium cationic surfactant having the structural formula: ##STR6## wherein n is a number from 1 to 20; and X - is an anionic salt radical.
Claim 14
Dependent Claim
19 words
The composition of claim 1 wherein the composition has an electrical resistivity of about 10 5 ohm-cm or less.
Claim 15
Dependent Claim
12 words
The composition of claim 1 which includes a nonionic or anionic surfactant.
Claim 16
Dependent Claim
54 words
The composition of claim 1 which includes a first dispersing agent of a long-chain acid anionic surfactant forming a first layer on the magnetic particles and a second dispersing agent of a cationic surfactant which comprises a quaternary ammonium surfactant having a tail portion soluble in the organic liquid carrier forming a second layer.
Claim 17
Dependent Claim
120 words
A stable ferrofluid composition, which composition comprises: (a) an organic liquid carrier, which organic liquid carrier is selected from the group consisting of hydrocarbons, esters and glycols; (b) finely divided ferromagnetic particles in an amount to provide magnetic properties of the ferrofluid composition and having a diameter ranging from about 20 to 300 angstroms; and (c) a dispersing agent in an amount sufficient to disperse and stabilize the magnetic particles in the organic liquid carrier, which dispersing agent comprises a quaternary ammonium surfactant selected from a group consisting of: fatty quaternary imidozoline salts; polypropoxy quaternary ammonium salts; acylated polyamine salts; and combinations thereof, to provide a stable ferrofluid composition having an electrical resistivity of about 10 6 ohms-cm or less.
Claim 18
Dependent Claim
120 words
A stable ferrofluid composition, which composition comprises: (a) an organic liquid carrier, which organic liquid carrier is selected from the group consisting of hydrocarbons, esters and glycols; (b) finely divided ferromagnetic particles in an amount to provide magnetic properties of the ferrofluid composition and having a diameter ranging from about 20 to 300 angstroms; and (c) a dispersing agent in an amount sufficient to disperse and stabilize the magnetic particles in the organic liquid carrier, which dispersing agent comprises a quaternary ammonium surfactant selected from a group consisting of: fatty quaternary imidozoline salts; polypropoxy quaternary ammonium salts; acylated polyamine salts; and combinations thereof, to provide a stable ferrofluid composition having an electrical resistivity of about 10 6 ohms-cm or less.
Claim 19
Dependent Claim
28 words
The composition of claim 16 which includes a first dispersing layer of an anionic surfactant on the ferromagnetic particles and a second dispersing layer of the cationic surfactant.
Claim 20
Independent Claim
77 words
A method of providing a ferrofluid seal about a rotating member subject to the accumulation of static charges, which method comprises: sealing the rotary member with an electrically conductive ferrofluid composition, which ferrofluid composition includes therein a dispersing and electrically conductive amount of a quaternary ammonium cationic surfactant, to provide an electrically conductive path to ground for the electrically conductive ferrofluid composition, to provide a ferrofluid composition having an electrical resistivity of 10 6 ohms-cm or less.
Claim 21
Independent Claim
77 words
A method of providing a ferrofluid seal about a rotating member subject to the accumulation of static charges, which method comprises: sealing the rotary member with an electrically conductive ferrofluid composition, which ferrofluid composition includes therein a dispersing and electrically conductive amount of a quaternary ammonium cationic surfactant, to provide an electrically conductive path to ground for the electrically conductive ferrofluid composition, to provide a ferrofluid composition having an electrical resistivity of 10 6 ohms-cm or less.
Claim 22
Independent Claim
80 words
A method of preparing a stable ferrofluid composition, which method comprises dispersing magnetic particles in an organic liquid carrier employing a dispersing amount of a cationic surfactant sufficient to provide a stable, dispersed ferrofluid composition, the cationic surfactant composed of a positively charged head portion and a long-chain tail portion, the tail portion of the cationic surfactant soluble in the organic liquid carrier, to provide a stable ferrofluid composition having an electrical resistivity of about 10 6 ohms-cm or less.
Claim 23
Independent Claim
80 words
A method of preparing a stable ferrofluid composition, which method comprises dispersing magnetic particles in an organic liquid carrier employing a dispersing amount of a cationic surfactant sufficient to provide a stable, dispersed ferrofluid composition, the cationic surfactant composed of a positively charged head portion and a long-chain tail portion, the tail portion of the cationic surfactant soluble in the organic liquid carrier, to provide a stable ferrofluid composition having an electrical resistivity of about 10 6 ohms-cm or less.
Claim 24
Dependent Claim
23 words
The method of claim 19 wherein the cationic surfactant comprises a quaternary ammonium cationic surfactant having a long chain hydrocarbon or alkyoxy group.
Claim 25
Dependent Claim
92 words
The method of claim 19 wherein the organic liquid character comprises a hydrocarbon or polyalphaolefine oil, and which method comprises: dispersing the magnetic particles in the organic liquid carrier in the presence of from about 5 to 25 percent by weight of the magnetic particles of an anionic surfactant to provide a first layer of surfactants, and thereafter dispersing the anionic surfactant containing magnetic particles in the organic liquid carrier employing a cationic surfactant, whereby the ratio by weight of the cationic surfactant to magnetic particles varies from about 1:1 to 40:1.
Claim 26
Dependent Claim
22 words
The method of claim 21 wherein the anionic surfactant has more than 8 carbon atoms and contains one or more polar groups.
Claim 27
Dependent Claim
42 words
The method of claim 19 wherein the cationic surfactant employed as the second layer surfactant in the method of dispersing and preparing the ferrofluid composition comprises: a quaternary ammonium cationic surfactant having a C 6 -C 30 hydrocarbon or alkoxy tail portion.
Claim 28
Dependent Claim
41 words
The method of claim 19 wherein the cationic surfactant employed as a second layer surfactant has from about 5 to 25 moles of a polyoxyethoxylate tail portion, and wherein the organic liquid carrier comprises an ester, a glycol or an ester-glycol.
Claim 29
Dependent Claim
34 words
The method of claim 19 wherein the cationic surfactant is selected from a group consisting of: a fatty acid quaternary imizozoline salt; a polypropoxy quaternary ammonium salt; an acylated polyamine salt; and combinations thereof.
Claim 30
Dependent Claim
29 words
The method of claim 21 wherein the anionic surfactant comprises a long chain carboxylic acid anionic surfactant and wherein the cationic surfactant comprises a long chain quaternary ammonium surfactant.
Claim 31
Dependent Claim
34 words
The method of claim 26 wherein the cationic surfactant is selected from a group consisting of: a fatty acid quaternary imidozoline salt; a polypropoxy quaternary ammonium salt; an acylated polyamine salt; or combinations thereof.
Claim 32
Dependent Claim
43 words
The composition of claim 10 wherein R 1 comprises a C 8 -C 18 monocarboxylic acid radical, R 2 and R 3 are selected from the group consisting of hydrogen or C 1 -C 4 alkyl and --C 2 H 4 OH radicals.
Claim 33
Dependent Claim
29 words
The composition of claim 11 wherein R 1 comprises a monocarboxylic acid radical, and R 2 and R 3 are polyoxypropylenated radicals, and R 4 is a methyl radical.
Claim 34
Dependent Claim
16 words
The composition of claim 17 wherein the anionic surfactant comprises a long-chain carboxylic acid anionic surfactant.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1989-08-04 | 1990-02-03 | 1990-08-05 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1993-08-04 | 1994-02-03 | 1994-08-05 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1997-08-04 | 1998-02-03 | 1998-08-05 | $7700.00 | Window Closed / Lapsed |