EP0845790B1 - Fluides magnétorhéologiques et particules magnétiques revêtues d'un polymère - Google Patents

Fluides magnétorhéologiques et particules magnétiques revêtues d'un polymère Download PDF

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Publication number
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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Prior art keywords
weight
magnetisable particles
particles
organic polymer
magnetorheological
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EP97120063A
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German (de)
English (en)
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EP0845790A1 (fr
Inventor
Wolfgang Dr. Podszun
Olaf Dr. Halle
Johan Dr. Kijlstra
Robert Dr. Bloodworth
Eckhard Dr. Wendt
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Fludicon GmbH
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Fludicon GmbH
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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
    • 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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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Soft Magnetic Materials (AREA)
  • Lubricants (AREA)

Claims (15)

  1. Fluides magnétorhéologiques constitués de particules magnétisables revêtues d'un polymère organique, d'au moins un liquide oléophile et éventuellement d'un épaississant, caractérisés en ce que les particules magnétisables sont des particules dont la surface a été soumise à une silanisation avant le revêtement avec ledit polymère organique.
  2. Fluides magnétorhéologiques selon la revendication 1, caractérisés en ce qu'ils contiennent de 45 à 98 % en masse de particules magnétisables revêtues d'un polymère organique, de 2 à 45 % en masse d'un liquide oléophile et de 0 à 20 % en masse d'un épaississant, la somme des pourcentages en masse étant égale à 100 % en masse.
  3. Fluides magnétorhéologiques selon l'une des revendications 1 ou 2, caractérisés en ce que la grande dimension moyenne des particules magnétisables revêtues d'un polymère organique, par rapport à leur masse, est de 0,1 à 100 µm.
  4. Fluides magnétorhéologiques selon l'une ou plusieurs des revendications 1 à 3, caractérisés en ce que la fraction en masse du revêtement des particules magnétisables revêtues d'un polymère organique est de 0,1 à 50 % en masse par rapport aux particules magnétisables.
  5. Fluides magnétorhéologiques selon l'une ou plusieurs des revendications 1 à 4, caractérisés en ce que le polymère organique est un polymère vinylique, une polyurée et/ou un polyuréthane.
  6. Fluides magnétorhéologiques selon l'une ou plusieurs des revendications 1 à 5, caractérisés en ce que les particules magnétisables sont constituées de fer et/ou d'alliages de fer.
  7. Fluides magnétorhéologiques selon l'une ou plusieurs des revendications 1 à 6, caractérisés en ce que les épaississants sont des gels, des silicates, des oxydes métalliques et/ou des acides siliciques très dispersés obtenus par hydrolyse à la flamme, ayant un diamètre de particules moyen inférieur à 1 µm.
  8. Fluides magnétorhéologiques selon l'une ou plusieurs des revendications 1 à 7, caractérisés en ce que la quantité d'épaississant est de 0,1 à 20 % en masse.
  9. Fluides magnétorhéologiques selon l'une ou plusieurs des revendications 1 à 8, caractérisés en ce que le liquide oléophile est constitué d'au moins une huile minérale ou d'au moins une huile de silicone.
  10. Particules magnétisables revêtues d'un polymère organique, caractérisées en ce que ces particules magnétisables sont des particules dont la surface a été soumise à une silanisation avant le revêtement avec ledit polymère organique.
  11. Particules magnétisables selon la revendication 10, caractérisées en ce que la silanisation des particules magnétisables a été effectuée par réaction avec un silane de formule (I)
    Figure 00200001
    dans laquelle
    R1
    représente un reste alkyle en C1-C20 ou un reste alkylène en C2-C20 éventuellement substitué par un groupe amino, isocyanato, méthacryloyloxy, acryloyloxy, époxy ou mercapto et/ou interrompu par -O-, -NH-, -COO- ou NH-COO,
    R2
    représente un reste phényle ou alkyle en C1-C6, et
    X
    représente un groupe hydrolysable, et
    a
    est égal à 0,1 ou 2.
  12. Procédé de préparation de particules magnétisables selon la revendication 10 ou 11, caractérisé en ce que l'on transforme des constituants monomères organiques en un polymère organique par polycondensation, polyaddition ou polymérisation en présence des particules magnétisables silanisées.
  13. Procédé de préparation de particules magnétisables selon la revendication 10 ou 11, caractérisé en ce que l'on dépose le polymère organique sous forme fondue ou précipitée à partir d'un solvant ou par évaporation du solvant sur les particules magnétisables silanisées.
  14. Procédé de préparation de fluides magnétorhéologiques selon l'une ou plusieurs des revendications 1 à 9, caractérisé en ce que l'on disperse les particules magnétisables selon la revendication 10 ou 11 dans le liquide oléophile, éventuellement en présence d'un épaississant.
  15. Utilisation des fluides magnétorhéologiques selon l'une ou plusieurs des revendications 1 à 9 dans des embrayages, des amortisseurs et/ou des paliers.
EP97120063A 1996-11-28 1997-11-17 Fluides magnétorhéologiques et particules magnétiques revêtues d'un polymère Expired - Lifetime EP0845790B1 (fr)

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JP (1) JPH10163021A (fr)
KR (1) KR19980042844A (fr)
DE (1) DE59707683D1 (fr)

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WO2012004236A1 (fr) 2010-07-09 2012-01-12 Eckart Gmbh Pigments de fer en forme de feuillets, fluide magnéto-rhéologique, et dispositif correspondant
DE102010026782A1 (de) 2010-07-09 2012-01-12 Eckart Gmbh Plättchenförmige Eisenpigmente, magnetorheologisches Fluid und Vorrichtung

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JPH10163021A (ja) 1998-06-19
EP0845790A1 (fr) 1998-06-03
US5989447A (en) 1999-11-23
DE59707683D1 (de) 2002-08-14
KR19980042844A (ko) 1998-08-17

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