EP0845790B1 - Magnetorheological fluids and polymer coated magnetic particles - Google Patents
Magnetorheological fluids and polymer coated magnetic particles Download PDFInfo
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- EP0845790B1 EP0845790B1 EP97120063A EP97120063A EP0845790B1 EP 0845790 B1 EP0845790 B1 EP 0845790B1 EP 97120063 A EP97120063 A EP 97120063A EP 97120063 A EP97120063 A EP 97120063A EP 0845790 B1 EP0845790 B1 EP 0845790B1
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- magnetisable particles
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H01F1/00—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties
- H01F1/01—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials
- H01F1/03—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity
- H01F1/032—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of hard-magnetic materials
- H01F1/04—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of hard-magnetic materials metals or alloys
- H01F1/06—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of hard-magnetic materials metals or alloys in the form of particles, e.g. powder
- H01F1/061—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of hard-magnetic materials metals or alloys in the form of particles, e.g. powder with a protective layer
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H01F1/00—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties
- H01F1/44—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of magnetic liquids, e.g. ferrofluids
- H01F1/447—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of magnetic liquids, e.g. ferrofluids characterised by magnetoviscosity, e.g. magnetorheological, magnetothixotropic, magnetodilatant liquids
Definitions
- the invention relates to new magnetorheological fluids, a method for their manufacture and their use as well as processes for the manufacture of with a organic polymer coated magnetizable particles.
- Magnetorheological fluids consist of a carrier liquid and magnetizable particles dispersed therein. These dispersions change their flow behavior when a magnetic field is applied. Possible areas of application of magnetorheological fluids are, for example Couplings, dampers and bearings.
- Magnetorheological fluids Another problem that is also still insufficiently solved Magnetorheological fluids is the abrasiveness that is particularly critical as it is too a premature failure of the one operated with the magnetorhelical liquid Device can lead.
- US-A-5 354 488 discloses magnetorheological fluids which are a carrier, include magnetizable particles and a particulate dispersant.
- EP-A-0023265 discloses fine-particle solids that have a coating of polymer Have organosilicon compounds, and their use as pigments.
- the object of the invention is therefore to provide MRFs which are in the prior art Technology known disadvantages do not have problems.
- magnetorheological fluids containing a contain organic polymer-coated, previously silanized, magnetizable particles, improved colloid stability, improved settling stability and decreased Have abrasiveness.
- the invention therefore relates to magnetorheological liquids made of magnetizable particles coated with an organic polymer, at least one oleophilic liquid and optionally a thickener, characterized in that the magnetizable particles are such particles deals, the surface before coating with the organic polymer mentioned has been subjected to silanization.
- Preferred magnetorheological liquids are 45 to 95% by weight, particularly preferably 60 to 95% by weight, very particularly preferably 75 to 95% by weight, of the magnetizable particles coated with an organic polymer, and 2 to 45% by weight an oleophilic liquid and 0 to 20 wt .-% thickener, the Sum of the% by weight results in 100% by weight.
- Magnetizable particles in the sense of the invention are paramagnetic, superparamagnetic and ferromagnetic substances.
- Examples include: iron, iron nitride, iron carbide, steel with less than 1% carbon, nickel and cobalt. Mixtures of the substances mentioned and iron alloys with aluminum, silicon, cobalt, nickel, vanadium, molybdenum, chromium, tungsten and manganese are also suitable.
- Iron-nickel alloys and iron-cobalt alloys can be mentioned as well-suited alloys.
- Magnetic oxides of chromium and iron, such as chromium dioxide, gamma-Fe 2 O 3 and Fe 3 O 4 are also suitable.
- Iron and / or iron alloys are preferred magnetizable particles.
- the mean longest dimension of the invention is preferably, with an organic polymer coated magnetizable particles, based on their mass (mass average), 0.1 to 100 microns, particularly preferably 1 to 50 microns.
- the shape of the magnetizable particles can also be irregular, rod-shaped or be needle-shaped.
- the spherical shape or a shape similar to the spherical shape is especially preferred when high fill levels are desired.
- Organic polymers in the sense of the invention are natural polymers, such as e.g. Gelatin or cellulose, modified natural polymers, in particular cellulose derivatives, and synthetic polymers, with synthetic polymers being preferred.
- gelatin includes gelatin coacervates and gelatin-like complex coacervates. Combinations of are particularly suitable as gelatin-containing complex coacervates Gelatin with synthetic polyelectrolytes preferred. Suitable synthetic polyelectrolytes are those which are obtained by homo- or copolymerization of e.g. maleic acid, Acrylic acid, methacrylic acid, acrylamide and methacrylamide emerge.
- gelatin also includes those with conventional hardening agents such as e.g. formaldehyde or glutardialdehyde further cross-linked gelatin.
- Suitable synthetic polymers are: polyester, polyurethane, in particular polyester urethanes and polyether urethanes, polycarbonates, polyester-polycarbonate copolymers, Polyureas, melamine resins, polysiloxanes, fluoropolymers and vinyl polymers.
- suitable vinyl polymers are called: polyvinyl chloride, polyvinyl esters, e.g. Polyvinyl acetate, polystyrene, Polyacrylic esters, such as polymethyl methacrylate, polyethylhexyl acrylate, polylauryl methacrylate, Polystearyl methacrylate or polyethylacrylate, polyvinyl acetals, such as polyvinyl butyral.
- Other synthetic polymers are also copolymers or terpolymers from various Vinyl and vinylidene monomers such as e.g. Polystyrene-co-acrylonitrile and copolymers from (meth) acrylic acid and (meth) acrylic esters.
- Particularly preferred organic Polymers are vinyl polymers, polyureas and / or polyurethanes.
- the molecular weight of the polymer can be chosen arbitrarily for this application become. Usual suitable polymers have a weight average of 30,000 - 1,000,000 daltons. The polymers can also be cross-linked.
- the magnetorheological liquids according to the invention contain as oleophilic Liquid (carrier liquid) preferably mineral oils, paraffin oils, hydraulic oils, oils containing chlorinated aromatics (so-called transformer oils), and chlorinated and fluorinated oils. Likewise preferred are silicone oils, fluorinated silicone oils, polyethers, fluorinated polyethers and polyether polysiloxane copolymers.
- the viscosity of the carrier liquid is preferably 1 to 1000 mPas, particularly preferably 3 to 800 mPas, measured at 25 ° C.
- the magnetorheological liquids as carrier liquid at least one mineral oil or at least one silicone oil.
- the invention magnetorheological liquids additionally at least one thickener, which gives the magnetorheological fluid a thixotropy and increases the settling stability of the magnetizable particles.
- thickeners e.g. finely divided inorganic or organic microparticles.
- silicates such as bentonite or metal oxides such as titanium dioxide, aluminum oxide or Silicon dioxide and / or flame-hydrolytically obtained highly disperse silicas, which e.g. under the trade names Aerosil® or HDK® from Degussa AG, Germany, or Wacker Chemie GmbH, Germany, commercially available are, with all microparticles an average particle diameter of less than 1 micron exhibit.
- the amount of thickeners is 0.1 to 20 wt .-%, preferably 0.5 to 5 wt .-%.
- the magnetorheological liquids according to the invention can also contain dispersing agents contain.
- dispersants are lecithin, oleic acid and oleates such as iron oleate, fatty acids, alkali soaps such as lithium stearate, sodium stearate, Aluminum tristearate, sulfonates and phosphonates with lipophilic residues as well Glycerol esters such as glycerol monostearate.
- the dispersants are preferably in amounts of 0.01 to 2% by weight, particularly preferably 0.1 to 0.5% by weight, based on the magnetizable particles.
- the weight fraction of the coating of those coated with organic polymer magnetizable particles is 0.1 to 50% by weight, preferably 0.5 to 20 Wt .-%.
- the invention also relates to a method for producing the organic polymers coated magnetizable particles, after which the organic Polymer in molten form or from a solvent by precipitation or vaporization is applied to the magnetizable particles.
- the invention also relates to a further method for producing the organic polymers coated magnetizable particles, after which in the presence the magnetizable particles are organic monomer components by means of polycondensation, Polyaddition or polymerization implemented to an organic polymer become.
- the organic monomer components are, for example, the Combination of aliphatic diols and aromatic or aliphatic dicarboxylic acids, dicarboxylic acid chlorides, for the polyaddition, for example, the combination of diols, polyester and / or Polyether diols with di- or triisocyanates and for the polymerization, for example, olefinically unsaturated compounds, such as Styrene, acrylic acid ester, methacrylic acid ester and / or vinyl acetate are preferred.
- Silanization means surface treatment with silanes, preferably those silanes are used which have at least one functional group, e.g. OH, Cl.
- radicals R 1 are methyl, ethyl, propyl, n-butyl, tert-butyl, hexyl, octyl, ethylhexyl, decyl, dodecyl, stearyl, vinyl or allyl.
- substituted R 1 radicals are: and or
- R 2 is preferably a phenyl or a C 1 -C 6 alkyl radical, such as methyl, ethyl, propyl, n-butyl, tert-butyl, pentyl or hexyl.
- the hydrolyzable groups on the Si atom symbolized by X comprise, for example, halogen atoms, in particular chlorine and bromine, C 1 -C 6 alkoxy groups, preferably methoxy and ethoxy, and carboxylate groups, such as acetate and propionate.
- silane must be matched to the following polymer coating his.
- silanes 3 or 4 a silane is also used polymerizable double bonds applied to the magnetizable particles.
- a polymer coating by radical Polymerization of monomers e.g. Acrylic acid esters, creating a solid chemical bond is established between the silane and the polymer coating, prefers.
- isocyanate-containing compounds e.g. with stearyl isocyanate for reaction brought, whereby a polymer coating with urea units is formed. Silanization with silanes 3, 4, 7 and / or 9 is therefore preferred.
- the implementation can be done by simply mixing the components with usual stirring or mixing devices.
- the temperature during the implementation is preferably in the range from 0 ° C to 100 ° C and the reaction time is preferably 0.1 h to 10 h.
- the amount of silane used can be varied within wide limits; it lies preferably in the range from 0.01 to 25% by weight, particularly preferably 0.1 to 10 % By weight, based on the magnetizable particles.
- the silanization is preferably carried out in the presence of at least one aprotic Solvent carried out.
- Suitable solvents are e.g. Acetone, butanone, Dichloromethane, trichloromethane, toluene, ethyl acetate or tetrahydrofuran.
- a catalyst can also be used in the silanization.
- suitable Catalysts are protonic acids such as acetic acid or hydrogen chloride as well amines; such as dicyclohexylamine.
- the amount of the catalyst is preferably 0.01 up to 5 wt .-%, based on the silane.
- the silane used in the silanization can initially with acid catalysis e.g. molar amounts of water are hydrolyzed, the hydrolyzable residues X are converted into OH groups, and then the freshly prepared OH compound reacted with the magnetizable particle in a solvent becomes.
- the invention also relates to a method for producing the invention magnetorheological fluids, after which in an oleophilic fluid, optionally in the presence of a thickener, which is also according to the invention Process produced, coated with an organic polymer magnetizable particles are dispersed.
- the carrier liquid is first with the thickener using high shear forces, i.e. preferably at dispersing energies between 50 and 500 W / l, for example with the help of an Ultraturrax®, available from IKA-Labortechnik, Germany, homogeneous mixed and then stirred in the coated magnetizable particles.
- high shear forces i.e. preferably at dispersing energies between 50 and 500 W / l, for example with the help of an Ultraturrax®, available from IKA-Labortechnik, Germany, homogeneous mixed and then stirred in the coated magnetizable particles.
- the invention also relates to the use of the nonaqueous compositions according to the invention magnetorheological fluids in couplings, dampers and / or To store.
- silanized carbonyl iron was slurried in 2000ml butanone and with 190g Stearyl methacrylate, 10 g ethylene glycol dimethacrylate and 6 g azoisobutyronitrile added. The mixture was stirred and refluxed at 70 ° C for 2 h and 2 h heated. The solid is filtered off after cooling, three times with 1500 ml each Washed butanone and dried in vacuo at 50 ° C for 12 h.
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Description
Die Erfindung betrifft neue magnetorheologische Flüssigkeiten, ein Verfahren zu deren Herstellung und deren Verwendung sowie Verfahren zur Herstellung von mit einem organischen Polymer beschichteten magnetisierbaren Teilchen.The invention relates to new magnetorheological fluids, a method for their manufacture and their use as well as processes for the manufacture of with a organic polymer coated magnetizable particles.
Als magnetorheologische Flüssigkeiten (MRF) werden Dispersionen bezeichnet, die aus einer Trägerflüssigkeit und darin dispergierten magnetisierbaren Teilchen bestehen. Diese Dispersionen ändern ihr Fließverhalten bei Anlegen eines magnetischen Feldes. Mögliche Einsatzgebiete der magnetorheologischen Flüssigkeiten sind beispielsweise Kupplungen, Dämpfer und Lager.Dispersions are called magnetorheological fluids (MRF) consist of a carrier liquid and magnetizable particles dispersed therein. These dispersions change their flow behavior when a magnetic field is applied. Possible areas of application of magnetorheological fluids are, for example Couplings, dampers and bearings.
Für den Einsatz in magnetorheologischen Flüssigkeiten werden bislang als magnetisierbare Teilchen paramagnetische, superparamagnetische und ferromagnetische Stoffe eingesetzt.So far, for use in magnetorheological fluids magnetizable particles paramagnetic, superparamagnetic and ferromagnetic Fabrics used.
Trotz einer umfangreichen Forschung auf diesem Gebiet gelang es nicht, das Problem der Absetzstabilität befriedigend zu lösen. Die bislang bekannten Methoden, wie z.B. die Zugabe von Kohlenstoffasem, gemäß EP-A 406 692, Silicagel, gemäß US-A 4 992 190 oder Polystyrolperlen, gemäß JP-A 419 8297, führten nur zu geringfügigen Verbesserungen.Despite extensive research in this area, the Settling stability problem to be solved satisfactorily. The previously known methods, such as e.g. the addition of carbon fibers, according to EP-A 406 692, silica gel, according to US-A 4 992 190 or polystyrene beads, according to JP-A 419 8297, led to only minor ones Improvements.
Ein weiteres ebenfalls noch unzureichend gelöstes Problem bei magnetorheologischen Flüssigkeiten ist die Abrasivität, die besonders kritisch ist, da sie zu einem vorzeitigen Versagen des mit der magnetorhelogischenFlüssigkeit betriebenen Gerätes führen kann.Another problem that is also still insufficiently solved Magnetorheological fluids is the abrasiveness that is particularly critical as it is too a premature failure of the one operated with the magnetorhelical liquid Device can lead.
Selbst die in US-A 5 354 488 beschriebenen, mit einer isolierenden Hülle aus Siliziumdioxid beschichteten magnetisierbaren Teilchen, zeigen keine verbesserte Abrasivität.Even those described in US-A 5,354,488, with an insulating sheath Silicon dioxide coated magnetizable particles show no improved Abrasiveness.
Die US-A-5 354 488 offenbart magnetorheologische Flüssigkeiten, die einen Träger, magnetisierbare Teilchen und ein partikelförmiges Dispergiermittel umfassen. Die EP-A-0023265 offenbart feinteilige Festkörper, die eine Umhüllung aus polymeren siliciumorganischen Verbindungen aufweisen, und ihre Verwendung als Pigmente. US-A-5 354 488 discloses magnetorheological fluids which are a carrier, include magnetizable particles and a particulate dispersant. EP-A-0023265 discloses fine-particle solids that have a coating of polymer Have organosilicon compounds, and their use as pigments.
Es besteht daher ein Bedarf an magnetorheologischen Flüssigkeiten, die über eine geringe Abrasivität und eine hohe Absetzstabilität verfügen.There is therefore a need for magnetorheological fluids that have a low abrasiveness and high settling stability.
Aufgabe der Erfindung ist daher die Bereitstellung von MRF's, die die im Stand der Technik bekannten Nachteile Probleme nicht aufweisen.The object of the invention is therefore to provide MRFs which are in the prior art Technology known disadvantages do not have problems.
Es wurde nun gefunden, daß magnetorheologische Flüssigkeiten, die mit einem organischen Polymer beschichtete, vorab silanisierte, magnetisierbare Teilchen enthalten, eine verbesserte Kolloidstabilität, eine verbesserte Absetzstabilität und eine verringerte Abrasivität aufweisen.It has now been found that magnetorheological fluids containing a contain organic polymer-coated, previously silanized, magnetizable particles, improved colloid stability, improved settling stability and decreased Have abrasiveness.
Gegenstand der Erfindung sind daher magnetorheologische Flüssigkeiten, bestehend aus magnetisierbaren Teilchen, die mit einem organischen Polymer beschichtet sind, mindestens einer oleophilen Flüssigkeit und gegebenenfalls einem Verdickungsmittel, dadurch gekennzeichnet, daß es sich bei den magnetisierbaren Teilchen um solche Teilchen handelt, deren Oberfläche vor der Beschichtung mit dem genannten organischen Polymer einer Silanisierung unterworfen wurde.The invention therefore relates to magnetorheological liquids made of magnetizable particles coated with an organic polymer, at least one oleophilic liquid and optionally a thickener, characterized in that the magnetizable particles are such particles deals, the surface before coating with the organic polymer mentioned has been subjected to silanization.
Bevorzugt sind solche magnetorheologischen Flüssigkeiten, die 45 bis 95 Gew.%, besonders bevorzugt 60 bis 95 Gew.-%, ganz besonders bevorzugt 75- 95 Gew.%, der mit einem organischen Polymer beschichteten magnetisierbaren Teilchen, sowie 2 bis 45 Gew.% einer oleophile Flüssigkeit und 0 bis 20 Gew.-% Verdickungsmittel enthalten, wobei die Summe der Gew.-% 100 Gew.% ergibt.Preferred magnetorheological liquids are 45 to 95% by weight, particularly preferably 60 to 95% by weight, very particularly preferably 75 to 95% by weight, of the magnetizable particles coated with an organic polymer, and 2 to 45% by weight an oleophilic liquid and 0 to 20 wt .-% thickener, the Sum of the% by weight results in 100% by weight.
Magnetisierbare Teilchen im Sinne der Erfindung sind paramagnetische, superparamagnetische und ferromagnetische Stoffe. Beispielhaft seien genannt: Eisen, Eisennitrid, Eisencarbid, Stahl mit weniger als 1 % Kohlenstoff, Nickel und Kobalt. Geeignet sind auch Mischungen der genannten Stoffe und Eisen-Legierungen mit Aluminium, Silizium, Cobalt, Nickel, Vanadium, Molybdän, Chrom, Wolfram und Mangan. Als gut geeignete Legierungen sind Eisen-Nickel-Legierungen und Eisen-Kobaltlegierungen zu nennen. Weiterhin geeignet sind magnetische Oxyde des Chroms und Eisens, wie Chromdioxid, gamma-Fe2O3 und Fe3O4.Magnetizable particles in the sense of the invention are paramagnetic, superparamagnetic and ferromagnetic substances. Examples include: iron, iron nitride, iron carbide, steel with less than 1% carbon, nickel and cobalt. Mixtures of the substances mentioned and iron alloys with aluminum, silicon, cobalt, nickel, vanadium, molybdenum, chromium, tungsten and manganese are also suitable. Iron-nickel alloys and iron-cobalt alloys can be mentioned as well-suited alloys. Magnetic oxides of chromium and iron, such as chromium dioxide, gamma-Fe 2 O 3 and Fe 3 O 4, are also suitable.
Eisen und/oder Eisenlegierungen sind dabei bevorzugte magnetisierbare Teilchen. Iron and / or iron alloys are preferred magnetizable particles.
Besonders bevorzugt ist das sogenannte Carbonyleisen, das durch thermische Zersetzung von Pentacarbonyleisen(0) gewonnen wird.The so-called carbonyl iron, which is produced by thermal Decomposition of pentacarbonyl iron (0) is obtained.
Vorzugsweise beträgt die mittlere längste Ausdehnung der erfindungsgemäßen, mit einem organischen Polymer beschichteten magnetisierbaren Teilchen, bezogen auf deren Masse (Massenmittel), 0.1 bis 100 µm, besonders bevorzugt 1 bis 50 µm.The mean longest dimension of the invention is preferably, with an organic polymer coated magnetizable particles, based on their mass (mass average), 0.1 to 100 microns, particularly preferably 1 to 50 microns.
Die Form der magnetisierbaren Teilchen kann auch unregelmäßig, stäbchen- oder nadelförmig sein. Die Kugelform oder eine der Kugelform ähnliche Form ist insbesondere dann bevorzugt, wenn hohe Füllgrade angestrebt werden.The shape of the magnetizable particles can also be irregular, rod-shaped or be needle-shaped. The spherical shape or a shape similar to the spherical shape is especially preferred when high fill levels are desired.
Organische Polymere im Sinne der Erfindung sind natürliche Polymere, wie z.B. Gelatine oder Cellulose, abgewandelte natürliche Polymere, insbesondere Cellulose-derivate, und synthetische Polymere, wobei synthetische Polymere bevorzugt sind.Organic polymers in the sense of the invention are natural polymers, such as e.g. Gelatin or cellulose, modified natural polymers, in particular cellulose derivatives, and synthetic polymers, with synthetic polymers being preferred.
Der Begriff Gelatine umfaßt dabei Gelatine-Koazervate und gelatineartige Komplexkoazervate. Als gelatinehaltige Komplexkoazervate sind vor allem Kombinationen von Gelatine mit synthetischen Polyelektrolyten bevorzugt. Geeignete synthetische Polyelektrolyte sind solche, die durch Homo- oder Copolymerisation von z.B. Maleinsäure, Acrylsäure, Methacrylsäure, Acrylamid und Methacrylamid hervorgehen. Der Begriff Gelatine umfaßt auch die mit üblichen Härtungsmitteln wie z.B. Formaldehyd oder Glutardialdehyd weiter vernetzte Gelatine.The term gelatin includes gelatin coacervates and gelatin-like complex coacervates. Combinations of are particularly suitable as gelatin-containing complex coacervates Gelatin with synthetic polyelectrolytes preferred. Suitable synthetic polyelectrolytes are those which are obtained by homo- or copolymerization of e.g. maleic acid, Acrylic acid, methacrylic acid, acrylamide and methacrylamide emerge. The The term gelatin also includes those with conventional hardening agents such as e.g. formaldehyde or glutardialdehyde further cross-linked gelatin.
Als geeignete synthetische Polymere seien genannt: Polyester, Polyurethane, insbesondere Polyesterurethane und Polyetherurethane, Polycarbonate, Polyester-Polycarbonat-Copolymere, Polyharnstoffe, Melaminharze, Polysiloxane, Fluorpolymere und Vinylpolymerisate. Als Beispiele für geeignete Vinylpolymerisate seien genannt: Polyvinylchlorid, Polyvinylester, wie z.B. Polyvinylacetat, Polystyrol, Polyacrylester, wie Polymethylmethacrylat, Polyethylhexylacrylat, Polylaurylmethacrylat, Polystearylmethacrylat oder Polyethylacrylat, Polyvinylacetale, wie Polyvinylbutyral. Weitere synthetische Polymere sind auch Co- oder Terpolymere aus verschiedenen Vinyl- und Vinylidenmonomeren, wie z.B. Poly-styrol-co-acrylnitril und Copolymere aus (Meth)acrylsäure und (Meth)acrylestern. Besonders bevorzugte organische Polymere sind dabei Vinylpolymerisate Polyharnstoffe und/oder Polyurethane.Suitable synthetic polymers are: polyester, polyurethane, in particular polyester urethanes and polyether urethanes, polycarbonates, polyester-polycarbonate copolymers, Polyureas, melamine resins, polysiloxanes, fluoropolymers and vinyl polymers. Examples of suitable vinyl polymers are called: polyvinyl chloride, polyvinyl esters, e.g. Polyvinyl acetate, polystyrene, Polyacrylic esters, such as polymethyl methacrylate, polyethylhexyl acrylate, polylauryl methacrylate, Polystearyl methacrylate or polyethylacrylate, polyvinyl acetals, such as polyvinyl butyral. Other synthetic polymers are also copolymers or terpolymers from various Vinyl and vinylidene monomers such as e.g. Polystyrene-co-acrylonitrile and copolymers from (meth) acrylic acid and (meth) acrylic esters. Particularly preferred organic Polymers are vinyl polymers, polyureas and / or polyurethanes.
Das Molekulargwicht des Polymers kann für diese Anwendung beliebig gewählt werden. Übliche geeignete Polymere weisen ein Gewichtsmittel von 30.000 - 1.000.000 Dalton auf. Die Polymere können auch vernetzt sein.The molecular weight of the polymer can be chosen arbitrarily for this application become. Usual suitable polymers have a weight average of 30,000 - 1,000,000 daltons. The polymers can also be cross-linked.
Die erfindungsgemäßen magnetorheologischen Flüssigkeiten enthalten als oleophile Flüssigkeit (Trägerflüssigkeit) bevorzugt Mineralöle, Paraffinöle, hydraulische Öle, chlorierte Aromaten enthaltende Öle (sog. Transformatoröle), sowie chlorierte und fluorierte Öle. Bevorzugt sind ebenfalle Siliconöle, fluorierte Siliconöle, Polyether, fluorierte Polyether und Polyetherpolysiloxancopolymere. Die Viskosität der Trägerflüssigkeit beträgt vorzugsweise 1 bis 1000 mPas, besonders bevorzugt 3 bis 800 mPas, gemessen bei 25°C.The magnetorheological liquids according to the invention contain as oleophilic Liquid (carrier liquid) preferably mineral oils, paraffin oils, hydraulic oils, oils containing chlorinated aromatics (so-called transformer oils), and chlorinated and fluorinated oils. Likewise preferred are silicone oils, fluorinated silicone oils, polyethers, fluorinated polyethers and polyether polysiloxane copolymers. The viscosity of the carrier liquid is preferably 1 to 1000 mPas, particularly preferably 3 to 800 mPas, measured at 25 ° C.
In einer besonders bevorzugten Ausführungsform der Erfindung enthalten die magnetorheologischen Flüssigkeiten als Trägerflüssigkeit mindestens ein Mineralöl oder mindestens ein Siliconöl.In a particularly preferred embodiment of the invention, the magnetorheological liquids as carrier liquid at least one mineral oil or at least one silicone oil.
In einer weiteren bevorzugten Ausführungsform der Erfindung enthalten die erfindungsgemäßen magnetorheologischen Flüssigkeiten zusätzlich mindestens ein Verdickungsmittel, das der magnetorheologischen Flüssigkeit eine Thixotropie verleiht und die Absetzstabilität der magnetisierbaren Teilchen erhöht. Verdickungsmittel sind z.B. feinteilige anorganische oder organische Micropartikel. Als solche sind bevorzugt Gele, Silikate wie Bentonit oder Metalloxide wie Titandioxid, Aluminiumoxid oder Siliziumdioxid und/oder flammhydrolytisch gewonnene hochdisperse Kieselsäuren, die z.B. unter den Handelsbezeichnungen Aerosil® oder HDK® bei der Firma Degussa AG, Deutschland, bzw. Wacker Chemie GmbH, Deutschland, kommerziell verfügbar sind, wobei alle Mikropartikel einen mittleren Teilchendurchmesser von kleiner 1 µm aufweisen. In a further preferred embodiment of the invention contain the invention magnetorheological liquids additionally at least one thickener, which gives the magnetorheological fluid a thixotropy and increases the settling stability of the magnetizable particles. Are thickeners e.g. finely divided inorganic or organic microparticles. As such are preferred Gels, silicates such as bentonite or metal oxides such as titanium dioxide, aluminum oxide or Silicon dioxide and / or flame-hydrolytically obtained highly disperse silicas, which e.g. under the trade names Aerosil® or HDK® from Degussa AG, Germany, or Wacker Chemie GmbH, Germany, commercially available are, with all microparticles an average particle diameter of less than 1 micron exhibit.
In dieser bevorzugten Ausführungsform beträgt die Menge der Verdickungsmittel 0.1 bis 20 Gew.-%, vorzugsweise 0.5 bis 5 Gew.-%.In this preferred embodiment, the amount of thickeners is 0.1 to 20 wt .-%, preferably 0.5 to 5 wt .-%.
Die erfindungsgemäßen magnetorheologische Flüssigkeiten können auch Dispergierhilfsmittel enthalten. Beispiele fiir Dispergiermittel sind Lecithin, Ölsäure und Oleate wie Eisenoleat, Fettsäuren, Alkaliseifen wie Lithiumstearat, Natriumstearat, Aluminiumtristearat, Sulfonate und Phosphonate mit lipophilen Resten sowie Glycerinester wie Glycerinmonostearat.The magnetorheological liquids according to the invention can also contain dispersing agents contain. Examples of dispersants are lecithin, oleic acid and oleates such as iron oleate, fatty acids, alkali soaps such as lithium stearate, sodium stearate, Aluminum tristearate, sulfonates and phosphonates with lipophilic residues as well Glycerol esters such as glycerol monostearate.
Die Dispergiermittel sind vorzugsweise in Mengen von 0,01 bis 2 Gew.-%, besonders bevorzugt 0,1 bis 0,5 Gew.-%, bezogen auf die magnetisierbaren Teilchen, vorhanden.The dispersants are preferably in amounts of 0.01 to 2% by weight, particularly preferably 0.1 to 0.5% by weight, based on the magnetizable particles.
Der Gewichtsanteil der Beschichtung der mit organischem Polymer beschichteten magnetisierbaren Teilchen beträgt 0.1 bis 50 Gew.-%, vorzugsweise 0,5 bis 20 Gew.-%.The weight fraction of the coating of those coated with organic polymer magnetizable particles is 0.1 to 50% by weight, preferably 0.5 to 20 Wt .-%.
Gegenstand der Erfindung ist zudem ein Verfahren zur Herstellung der mit organischen Polymeren beschichteten magnetisierbaren Teilchen, wonach das organische Polymer in geschmolzener Form oder aus einem Lösemittel durch Ausfällen oder Verdampfen auf die magnetisierbaren Teilchen aufgebracht wird.The invention also relates to a method for producing the organic polymers coated magnetizable particles, after which the organic Polymer in molten form or from a solvent by precipitation or vaporization is applied to the magnetizable particles.
Ebenfalls Gegenstand der Erfindung ist ein weiteres Verfahren zur Herstellung der mit organischen Polymeren beschichteten magnetisierbaren Teilchen, wonach in Gegenwart der magnetisierbaren Teilchen organische Monomerbestandteile mittels Polykondensation, Polyaddition oder Polymerisation zu einem organischen Polymer umgesetzt werden.The invention also relates to a further method for producing the organic polymers coated magnetizable particles, after which in the presence the magnetizable particles are organic monomer components by means of polycondensation, Polyaddition or polymerization implemented to an organic polymer become.
Für die Polykondensation sind als organische Monomerbestandteile beispielsweise die Kombination aus aliphatischen Diolen und aromatischen oder aliphatischen Dicarbonsäuren, Dicarbonsäurechloride, für die Polyaddition beispielsweise die Kombination aus Diolen, Polyester- und/oder Polyetherdiolen mit Di- oder Triisocyanaten und für die Polymerisation beispielsweise olefinisch ungesättigte Verbindungen, wie Styrol, Acrylsäureester, Methacylsäureester und/oder Vinylacetat bevorzugt.For the polycondensation, the organic monomer components are, for example, the Combination of aliphatic diols and aromatic or aliphatic dicarboxylic acids, dicarboxylic acid chlorides, for the polyaddition, for example, the combination of diols, polyester and / or Polyether diols with di- or triisocyanates and for the polymerization, for example, olefinically unsaturated compounds, such as Styrene, acrylic acid ester, methacrylic acid ester and / or vinyl acetate are preferred.
Für die Polykondensation, Polyaddition oder Polymerisation sind gängige Reaktionsbedingungen anwendbar.Common reaction conditions are for polycondensation, polyaddition or polymerization applicable.
Es wurde gefunden, daß besonders gut haftende Polymerbeschichtungen erzielbar sind, wenn die magnetisierbaren Partikel vor der Polymerbeschichtung silanisiert werden. Unter Silanisierung wird die Oberflächenbehandlung mit Silanen verstanden, wobei vorzugsweise solche Silane eingesetzt werden, die über mindestens eine funktionelle Gruppe, wie z.B. OH, Cl, verfügen.It has been found that polymer coatings which adhere particularly well can be achieved are when the magnetizable particles silanized before the polymer coating become. Silanization means surface treatment with silanes, preferably those silanes are used which have at least one functional group, e.g. OH, Cl.
In einer bevorzugten Ausführungsform der Erfindung werden vor der Beschichtung die magnetisierbaren Teilchen mit einem Silan der Formel (I) in der
- R1
- ein C1 - C20-Alkylrest oder C2 - C20-Alkylenrest, der gegebenenfalls mit einer Amino-, Isocyanato- Methacryloyoxy- Acryloyloxy-, Epoxy- oder Mercaptogruppe substituiert sein und / oder durch -O-, -NH-, -COO- oder -NH-COO unterbrochen sein kann
- R2
- ein Phenyl, ein C1 - C18-Alkylrest oder ein C2 - C18-Alkylenrest
- X
- eine hydrolisierbare Gruppe bedeuten und
- a
- den Wert 0, 1 oder 2 annimmt, silanisiert.
- R 1
- a C 1 - C 20 alkyl radical or C 2 - C 20 alkylene radical which may be substituted by an amino, isocyanato, methacryloyoxy, acryloyloxy, epoxy or mercapto group and / or by -O-, -NH-, - COO- or -NH-COO can be interrupted
- R 2
- a phenyl, a C 1 -C 18 -alkyl radical or a C 2 - C 18 -alkylene radical
- X
- mean a hydrolyzable group and
- a
- assumes the value 0, 1 or 2, silanized.
Beispiele für Reste R1 sind Methyl, Ethyl, Propyl, n-Butyl, tert.-Butyl, Hexyl, Octyl, Ethylhexyl, Decyl, Dodecyl, Stearyl, Vinyl oder Allyl. Als substituierte R1-Reste seien beispielhaft genannt: und/oder Examples of radicals R 1 are methyl, ethyl, propyl, n-butyl, tert-butyl, hexyl, octyl, ethylhexyl, decyl, dodecyl, stearyl, vinyl or allyl. Examples of substituted R 1 radicals are: and or
R2 ist vorzugsweise ein Phenyl oder ein C1-C6-Alkylrest, wie z.B. Methyl, Ethyl, Propyl, n-Butyl, tert.-Butyl, Pentyl oder Hexyl.R 2 is preferably a phenyl or a C 1 -C 6 alkyl radical, such as methyl, ethyl, propyl, n-butyl, tert-butyl, pentyl or hexyl.
Die durch X symbolisierten hydrolisierbaren Gruppen am Si-Atom umfassen beispielsweise Halogenatome, insbesondere Chlor und Brom, C1-C6-Alkoxygruppen, vorzugsweise Methoxy und Ethoxy, sowie Carboxylatgruppen, wie Acetat und Propionat.The hydrolyzable groups on the Si atom symbolized by X comprise, for example, halogen atoms, in particular chlorine and bromine, C 1 -C 6 alkoxy groups, preferably methoxy and ethoxy, and carboxylate groups, such as acetate and propionate.
Beispiele fiir besonders bevorzugte Silane sind in der nachstehenden Übersicht aufgelistet: Examples of particularly preferred silanes are listed in the overview below:
Selbstverständlich muß das Silan auf die folgende Polymerbeschichtung abgestimmt sein.Of course, the silane must be matched to the following polymer coating his.
Erfolgt die Silanisierung beispielsweise mit den Silanen 3 oder 4, so wird ein Silan mit polymerisierbaren Doppelbindungen auf die magnetisierbaren Teilchen aufgebracht. In diesem Fall ist das Aufbringen einer Polymerbeschichtung durch radikalische Polymerisation von Monomeren, wie z.B. Acrylsäureestern, wodurch eine feste chemische Bindung zwischen dem Silan und der Polymerbeschichtung aufgebaut wird, bevorzugt. Oberflächen, die mit dem Silan 7 oder 9 modifiziert wurden, können leicht mit isocyanathaltigen Verbindungen, wie z.B. mit Stearylisocyanat zur Reaktion gebracht werden, wobei eine Polymerbeschichtung mit Harnstoffeinheiten entsteht. Daher ist die Silanisierung mit den Silanen 3, 4, 7 und/oder 9 bevorzugt.If the silanization takes place, for example, with silanes 3 or 4, a silane is also used polymerizable double bonds applied to the magnetizable particles. In In this case, the application of a polymer coating by radical Polymerization of monomers, e.g. Acrylic acid esters, creating a solid chemical bond is established between the silane and the polymer coating, prefers. Surfaces that have been modified with Silane 7 or 9 can easily with isocyanate-containing compounds, e.g. with stearyl isocyanate for reaction brought, whereby a polymer coating with urea units is formed. Silanization with silanes 3, 4, 7 and / or 9 is therefore preferred.
Die Umsetzung kann bereits durch einfaches Vermischen der Komponenten mit üblichen Rühr- oder Mischgeräten erfolgen. Die Temperatur bei der Umsetzung liegt vorzugsweise im Bereich von 0°C bis 100°C und die Reaktionsdauer beträgt vorzugsweise 0,1 h bis 10 h.The implementation can be done by simply mixing the components with usual stirring or mixing devices. The temperature during the implementation is preferably in the range from 0 ° C to 100 ° C and the reaction time is preferably 0.1 h to 10 h.
Die Menge des eingesetzten Silans kann in weiten Grenzen variiert werden, sie liegt vorzugsweise im Bereich von 0,01 bis 25 Gew.-%, besonders bevorzugt 0,1 bis 10 Gew.-%, bezogen auf die magnetisierbaren Teilchen.The amount of silane used can be varied within wide limits; it lies preferably in the range from 0.01 to 25% by weight, particularly preferably 0.1 to 10 % By weight, based on the magnetizable particles.
Die Silanisierung wird vorzugsweise in Anwesenheit mindestens eines aprotischen Lösungsmittels durchgeführt. Geeignete Lösungsmittel sind z.B. Aceton, Butanon, Dichlormethan, Trichlormethan, Toluol, Essigester oder Tetrahydrofuran.The silanization is preferably carried out in the presence of at least one aprotic Solvent carried out. Suitable solvents are e.g. Acetone, butanone, Dichloromethane, trichloromethane, toluene, ethyl acetate or tetrahydrofuran.
Bei der Silanisierung kann zusätzlich ein Katalysator eingesetzt werden. Geeignete Katalysatoren sind Protonensäuren, wie Essigsäure oder Chlorwasserstoff sowie Amine; wie Dicyclohexylamin. Die Menge des Katalysators beträgt vorzugsweise 0,01 bis 5 Gew.-%, bezogen auf das Silan. A catalyst can also be used in the silanization. suitable Catalysts are protonic acids such as acetic acid or hydrogen chloride as well amines; such as dicyclohexylamine. The amount of the catalyst is preferably 0.01 up to 5 wt .-%, based on the silane.
Das bei der Silanisierung eingesetzte Silan kann zunächst unter saurer Katalyse mit z.B. molaren Mengen Wasser hydrolysiert werden, wobei die hydrolisierbaren Reste X in OH-Gruppen überführt werden, und dann die frisch hergestellte OH-Verbindung in einem Lösungsmittel mit dem magnetisierbaren Teilchen zur Reaktion gebracht wird.The silane used in the silanization can initially with acid catalysis e.g. molar amounts of water are hydrolyzed, the hydrolyzable residues X are converted into OH groups, and then the freshly prepared OH compound reacted with the magnetizable particle in a solvent becomes.
Gegenstand der Erfindung ist zudem ein Verfahren zur Herstellung der erfindungsgemäßen magnetorheologischen Flüssigkeiten, wonach in einer oleophilen Flüssigkeit, gegebenfalls in Anwesenheit eines Verdickungsmittels, die nach dem ebenfalls erfindungsgemäßen Verfahren hergestellten, mit einem organischen Polymer beschichteten magnetisierbare Teilchen dispergiert werden.The invention also relates to a method for producing the invention magnetorheological fluids, after which in an oleophilic fluid, optionally in the presence of a thickener, which is also according to the invention Process produced, coated with an organic polymer magnetizable particles are dispersed.
In einer bevorzugten Ausführungsform der Erfindung wird zunächst die Trägerflüssigkeit mit dem Verdickungsmittel unter Anwendung hoher Scherkräfte, d.h. vorzugsweise bei Dispergierenergien zwischen 50 und 500 W/l, beispielsweise mit Hilfe eines Ultraturrax®, erhältlich bei der Firma IKA-Labortechnik, Deutschland, homogen gemischt und anschließend die beschichteten magnetisierbaren Teilchen eingerührt.In a preferred embodiment of the invention, the carrier liquid is first with the thickener using high shear forces, i.e. preferably at dispersing energies between 50 and 500 W / l, for example with the help of an Ultraturrax®, available from IKA-Labortechnik, Germany, homogeneous mixed and then stirred in the coated magnetizable particles.
Gegenstand der Erfindung ist zudem die Verwendung der erfindungsgemäßen nichtwäßrigen magnetorheologische Flüssigkeiten in Kupplungen, Dämpfern und/oder Lagern.The invention also relates to the use of the nonaqueous compositions according to the invention magnetorheological fluids in couplings, dampers and / or To store.
Die Erfindung soll anhand des vorliegenden Beispiele erläutert werden. Die Erfindung ist dabei jedoch nicht auf diese Beispiele beschränkt. The invention will be explained on the basis of the present examples. The invention is not limited to these examples.
Durch 30-minütiges Mischen von 200 g gamma-Methacryloxypropyltrimethoxysilan, 352 g E-Wasser und 2.6 g Eisessig in einem Becherglas bei Raumtemperatur wurde eine Silanisierungslösung erzeugt. In einem heizbaren 4l-Dreihalskolben mit Glasrührer, Thermometer und Intensivkühler wurden 1000 g Carbonyleisen EN der Firma BASF AG, Deutschland, mit einer mittleren Teilchengröße (gemessen gemäß ASTM B 330) von 4-5 µm, das folgende Verunreinigungen C: 0,8 Gew.-%, N: 0,8 Gew.-%, O: 0,3 Gew.-% aufweist, in 2000 ml Butanon vorgelegt und mit der Silanisierungslösung versetzt. Das Gemisch wurde 16 h bei 40°C gerührt. Nach dem Abkühlen wird der Feststoff auf einer Nutsche abgesaugt, mehrfach mir Butanon gewaschen und bei 80°C 10 h getrocknet.By mixing 200 g of gamma-methacryloxypropyltrimethoxysilane for 30 minutes, 352 g of deionized water and 2.6 g of glacial acetic acid were placed in a beaker at room temperature creates a silanization solution. In a heatable 4l three-necked flask with Glass stirrer, thermometer and intensive cooler were 1000 g of carbonyl iron Company BASF AG, Germany, with an average particle size (measured according to ASTM B 330) of 4-5 µm, the following impurities C: 0.8% by weight, N: 0.8% by weight, O: 0.3% by weight, placed in 2000 ml of butanone and mixed with the Silanization solution added. The mixture was stirred at 40 ° C for 16 h. After this After cooling, the solid is suctioned off on a suction filter, several times with butanone washed and dried at 80 ° C for 10 h.
Das silanisierte Carbonyleisen wurde in 2000ml Butanon aufgeschlämmt und mit 190g Stearylmethacrylat, 10 g Ethylenglycoldimethacrylat und 6g Azoisobuttersäuredinitril versetzt. Das Gemisch wurde unter Rühren 2 h bei 70°C und weitere 2h am Rückfluß erhitzt. Der Feststoff wird nach dem Abkühlen abfiltriert, dreimal mit je 1500 ml Butanon gewaschen und 12 h lang bei 50°C im Vakuum getrocknet.The silanized carbonyl iron was slurried in 2000ml butanone and with 190g Stearyl methacrylate, 10 g ethylene glycol dimethacrylate and 6 g azoisobutyronitrile added. The mixture was stirred and refluxed at 70 ° C for 2 h and 2 h heated. The solid is filtered off after cooling, three times with 1500 ml each Washed butanone and dried in vacuo at 50 ° C for 12 h.
50 g gamma-Aminopropyltriethoxysilan wurden in 1000 ml Cloroform gelöst. In diese Lösung wurden 1000 g Carbonyleisen EN der Firma BASF AG, Deutschland, mit einer mittleren Teilchengröße (gemessen gemäß ASTM B 330) von 4-5 µm, das folgende Verunreinigungen C: 0,8 Gew.-%, N: 0,8 Gew.-%, O: 0,3 Gew.-% aufweist, bei Raumtemperatur eingestreut und unter gelegentlichem Umschütteln 1 h stehen gelassen. Anschließend wurde das beschichtete Carbonyleisen intensiv mit 1000 ml Chloroform gewaschen, 1 d bei Raumtemperatur und Atmosphärendruck sowie 18 h bei 50°C im Hochvakuum getrocknet.50 g of gamma-aminopropyltriethoxysilane was dissolved in 1000 ml of chloroform. In these The solution was 1000 g of carbonyl iron EN from BASF AG, Germany an average particle size (measured according to ASTM B 330) of 4-5 µm, the has the following impurities C: 0.8% by weight, N: 0.8% by weight, O: 0.3% by weight, Sprinkle in at room temperature and stand for 1 hour, shaking occasionally calmly. Then the coated carbonyl iron became intensive with 1000 ml Washed chloroform, 1 d at room temperature and atmospheric pressure and 18 h dried at 50 ° C in a high vacuum.
32 g silanisiertes Carbonyleisen aus Beispiel 2 wurden mit 0,04 g Diazabicyclo[2.2.2]oktan in 8,0 g eines trifunktionellen Polyethylenglycols mit einem Molekulargewicht von 1015, hergestellt durch Ethoxylierung von Trimethylolpropan, eingerührt. Diese Mischung wurde mit Hilfe eines Ultraturrax® in eine Lösung aus 0,84 g des Umsetzungsproduktes aus 40 Teilen Octamethylcyclotetrasiloxan mit 2 Teilen N-(β-Aminoethyl)-γ-aminopropylmethyldiethoxysilan in 13,3 g Siliconöl (Baysilone® M 5,erhältlich bei der Bayer AG, Deutschland) eindispergiert. Zu dieser Dispersion wurden unter Scherung 2,05 g Toluoldiisocyanat hinzugegeben und 30 s nachdispergiert. Anschließend wurde die Dispersion 12 h bei 80°C zur gebrauchsfertigen magnetorheologischen Flüssigkeit ausgehärtet.32 g of silanized carbonyl iron from Example 2 were octane with 0.04 g of diazabicyclo [2.2.2] in 8.0 g of a trifunctional polyethylene glycol with a Molecular weight of 1015, produced by ethoxylation of trimethylolpropane, stirred. This mixture was made into a solution using an Ultraturrax® 0.84 g of the reaction product from 40 parts of octamethylcyclotetrasiloxane with 2 Share N- (β-aminoethyl) -γ-aminopropylmethyldiethoxysilane in 13.3 g of silicone oil (Baysilone® M 5, available from Bayer AG, Germany). To this Dispersion was added under shear 2.05 g of toluene diisocyanate and 30 s further dispersed. The dispersion was then ready for use at 80 ° C. for 12 h magnetorheological fluid cured.
Claims (15)
- Magnetorheological liquids, consisting of magnetisable particles which are coated with an organic polymer, at least one oleophilic liquid and optionally a thickener, characterised in that the magnetisable particles are particles, the surface of which has been subjected to silanisation before coating with said organic polymer.
- Magnetorheological liquids according to claim 1, characterised in that they contain 45 to 98 % by weight of magnetisable particles coated with an organic polymer, 2 to 45 % by weight of an oleophilic liquid, and 0 to 20% by weight of a thickener, wherein the sum of the percentages by weight is 100 % by weight.
- Magnetorheological liquids according to either one of claims 1 or 2, characterised in that the average longest dimension of the magnetisable particles which are coated with an organic polymer, with respect to the weight of the particles, is 0.1 to 100 µm.
- Magnetorheological liquids according to one or more of claims 1 to 3, characterised in that the proportion by weight of the coating of the magnetisable particles which are coated with an organic polymer is 0.1 to 50 % by weight with respect to the magnetisable particles.
- Magnetorheological liquids according to one or more of claims 1 to 4, characterised in that the organic polymers are vinyl polymers, polyureas and/or polyurethanes.
- Magnetorheological liquids according to one or more of claims 1 to 5, characterised in that the magnetisable particles comprise iron and/or iron alloys.
- Magnetorheological liquids according to one or more of claims 1 to 6, characterised in that the thickeners are gels, silicates, metal oxides and/or microdispersed hydrated silicas obtained by flame hydrolysis with an average particle diameter less than 1 µm.
- Magnetorheological liquids according to one or more of claims 1 to 7, characterised in that the amount of thickener is 0.1 to 20 % by weight.
- Magnetorheological liquids according to one or more of claims 1 to 8, characterised in that the oleophilic liquid is at least one mineral oil or at least one silicone oil.
- Magnetisable particles which are coated with an organic polymer, characterised in that the magnetisable particles are particles, the surface of which has been subjected to silanisation before coating with said organic polymer.
- Magnetisable particles according to claim 10, characterised in that silanisation of the magnetic particles is effected by reaction with a silane of formula (I) where
- R1
- is a C1-C20 alkyl radical or a C2-C20 alkylene radical which may optionally be substituted with an amino, isocyanato, methacryloyloxy, acryloyloxy, epoxy or mercapto group, and/or interrupted by -O-, -NH-, -COO- or NH-COO,
- R2
- represents a phenyl or a C1-C6 alkyl radical,
- X
- represents a hydrolysable group, and
- a
- assumes the value 0, 1 or 2.
- A process for producing magnetisable particles according to claims 10 or 11, characterised in that organic monomer constituents are reacted to form an organic polymer by means of polycondensation, polyaddition or polymerisation in the presence of the magnetisable particles.
- A process for producing magnetisable particles according to claims 10 or 11, characterised in that the organic polymer is deposited in molten form, or is precipitated from a solvent, or is deposited by evaporation of the solvent on to the silanised, magnetisable particles.
- A process for producing magnetorheological liquids according to one or more of claims 1 to 9, characterised in that the magnetisable particles according to claims 10 or 11 are dispersed in the oleophilic liquid, optionally in the presence of a thickener.
- Use of the magnetorheological liquids according to one or more of claims 1 to 9 in couplings, dampers and/or bearings.
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US5296773A (en) * | 1993-04-20 | 1994-03-22 | General Motors Corporation | Composite rotor for a synchronous reluctance machine |
-
1997
- 1997-11-17 DE DE59707683T patent/DE59707683D1/en not_active Expired - Lifetime
- 1997-11-17 EP EP97120063A patent/EP0845790B1/en not_active Expired - Lifetime
- 1997-11-24 US US08/976,555 patent/US5989447A/en not_active Expired - Lifetime
- 1997-11-25 JP JP9338245A patent/JPH10163021A/en active Pending
- 1997-11-27 KR KR1019970063473A patent/KR19980042844A/en not_active Application Discontinuation
Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO2012004236A1 (en) | 2010-07-09 | 2012-01-12 | Eckart Gmbh | Lamina-like iron pigments, magnetorheological fluid and device |
DE102010026782A1 (en) | 2010-07-09 | 2012-01-12 | Eckart Gmbh | Platelet-shaped iron pigments, magnetorheological fluid and device |
Also Published As
Publication number | Publication date |
---|---|
EP0845790A1 (en) | 1998-06-03 |
US5989447A (en) | 1999-11-23 |
KR19980042844A (en) | 1998-08-17 |
JPH10163021A (en) | 1998-06-19 |
DE59707683D1 (en) | 2002-08-14 |
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