EP0636683B1 - Elektrorheologische Flüssigkeit - Google Patents

Elektrorheologische Flüssigkeit Download PDF

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Publication number
EP0636683B1
EP0636683B1 EP19940304455 EP94304455A EP0636683B1 EP 0636683 B1 EP0636683 B1 EP 0636683B1 EP 19940304455 EP19940304455 EP 19940304455 EP 94304455 A EP94304455 A EP 94304455A EP 0636683 B1 EP0636683 B1 EP 0636683B1
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Prior art keywords
polymer
group
electrorheological fluid
composite
weight
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EP19940304455
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English (en)
French (fr)
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EP0636683A1 (de
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Satoru Ono
Ryuji Aizawa
Yoshinobu Asako
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Nippon Shokubai Co Ltd
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Nippon Shokubai Co Ltd
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    • C—CHEMISTRY; METALLURGY
    • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
    • C10M—LUBRICATING COMPOSITIONS; USE OF CHEMICAL SUBSTANCES EITHER ALONE OR AS LUBRICATING INGREDIENTS IN A LUBRICATING COMPOSITION
    • C10M171/00—Lubricating compositions characterised by purely physical criteria, e.g. containing as base-material, thickener or additive, ingredients which are characterised exclusively by their numerically specified physical properties, i.e. containing ingredients which are physically well-defined but for which the chemical nature is either unspecified or only very vaguely indicated
    • C10M171/001—Electrorheological fluids; smart fluids

Definitions

  • the present invention relates to an electrorheological fluid. More specifically, it relates to an electrorheological fluid which has excellent properties in that a large shear stress and low current density can be generated even when a reratively low electrical field is applied to the fluid and the generated shear stress and current density has excellent stability properties with time (durability).
  • the invention also has excellent properties in regard to dispersion stability under the conditions of no electrical field (the ability to uniformly maintain an electrorheological fluid and not settle or float the disperse phase therein), redispersibility (the ability to duplicate a uniform electrorheological fluid by applying a simple external force when the dispersed phase therein has settled and floats in a non-uniform state), and fluidity (having a low viscosity under the conditions of no electrical field).
  • electrorheological fluid generating high shear stress a fluid in which a powdered ion-exchange resin is dispersed in the higher alkyl ester of an aromatic carboxylic acid (JP-A-50-92278), a composition composed of a crystalline material which conducts current only along one of the three crystalline axes, a dielectrical fluid, and suspension stabilizing agent (JP-A-1-170693), and a fluid using, as a disperse phase, a conductive particle covered with a film layer of insulating material (JP-A-64-6093).
  • these electrorheological fluids have the disadvantages of poor dispersion stability under the conditions of no electricalal field, poor re-dispersibility after sedimentation and floatation, and poor fluidity when the concentration of the disperse phase is increased.
  • electrorheological fluids using fine particles as the composite polymer (JP-A-3-160094 and JP-A-3-166295) or the like.
  • these electrorheological fluids have problems in that the shear stress obtained when an electrical field is applied, decreases due to the addition of the fine particles, the conditions of use for the electrorheological fluids are defined due to the poor dispersion stability, and it is necessary for the device used to be equipped with an additional re-dispersibility system.
  • An electrorheological fluid which uses a copolymer obtained by polymerizing a raw-material monomer mixture having as essential components thereof a polymerizable monomer (A) such as (meth)acryloyl group-containing poly(methylene glycol) and at least one polymerizable monomer (B) selected from the group consisting of cross-linking monomers and silicone type polymerizable monomers and optionally containing another polymerizable monomer (C) as an composite polymer capable of improving dispersion stability, redispersibility, and fluidity has been proposed (EP-0 529 166).
  • This electrorheological fluid exhibits poor fluidity because it requires use of the composite polymer in a large amount for the sake of improving the dispersion stability.
  • the object of this invention is to provide an electrorheological fluid which has excellent properties in that a large shear stress and low current density can be generated even when a relatively low electric field is applied to the fluid and the generated shear stress and current density has excellent stability properties with time (durability).
  • the electrorheological fluid of this invention also has excellent properties in regard to dispersion stability under the conditions of no electric field (the ability to uniformly maintain an electrorheological fluid and not settle or float the disperse phase, therein), re-dispersibility (the ability to duplicate a uniform electrorheological fluid by applying a simple external force when the disperse phase therein has settled and floats in a non-uniform state), and fluidity (having a low viscosity under the conditions of no electric field).
  • an electrorheological fluid which comprises a disperse phase formed of dielectric particles, a dispersive medium in the form of an electrical insulating oil and a composite polymer, in which the composite polymer exhibits substantial insolubility in the electrical insulating oil and possesses a silicone component-containing structural unit (A) and a disperse phase-absorbing chain-containing structural unit (B), and in which the composite polymer is obtainable by compositing a polysiloxane-containing polymer with organic or inorganic particles which are substantially insoluble in the insulating oil.
  • the electrorheological fluid of this invention exhibits excellent properties in that a large shear stress and low current density can be generated even when a reratively low electric field is applied to the fluid and the generated shear stress and current density has excellent stability properties with time (durability).
  • the electrorheological fluid of this invention also has excellent properties in regard to dispersion stability under the conditions of no electric field (the ability to uniformly maintain an electrorheological fluid and not settle or float the disperse phase therein), re-dispersibility (the ability to duplicate a uniform electrorheological fluid by applying a simple external force when the disperse phase therein has settled and floats in a non-uniform state), and fluidity (having a low viscosity under the conditions of no electric field). Therefore, the electrorheological fluid of this invention can be effectively used for engine mount, clutch, damper, brakes, shock absorber, actuator, value, and the like.
  • an electrorheological fluid In order to develope devices operating by an electrorheological fluid, it is necessary that dispersion stability, redisperbility and fluidity of the fluid are good. It is particularly desirable that an electrorheological fluid has good shear stress property, current property and durability in addition to good dispersion stability, redispersibility and fluidity. We supposed that the properties (dispersion stability, redispersibility and fluidity) were dependent on the state of existence of the disperse phase in the dispersive medium. Then we found that the properties of an electrorheological fluid were ideally improved when the fluid exhibited structural viscosity while it possessed low viscosity in absence of supply of an electric field. The electrorheological fluid of this invention, therefore, is required to manifest the specific viscosity and the structural viscosity which is represented by the specific condition formula, mentioned above.
  • structural viscosity manifested by an electrorheological fluid means the specific viscous form to be caused by a structure which is composed of disperse phase particles and a dispersive medium in consequence of weak aggregation of the disperse phase particles in the dispersive medium. This structural viscosity is controlled by the intensity of an interaction between a disperse phase particle and other disperse phase particle, and it gives suitable dispersion stability and suitable redispersibility to the electrorheological fluid.
  • the viscosity of the electrorheological fluid of this invention is required to be not more than 0.2 Pa ⁇ s at a shear rate of 33/s when measured at 25°C in the absence of an electric field preferably to be in the range of 0.01 to 0.1 Pa ⁇ s. If the viscosity exceeds 0.2 Pa ⁇ s, the produced electrorheological fluid is at a disadvantage in exhibiting only poor fluidity and, at the same time, failing to acquire a sufficient electrorheological effect in consequence of the supply of an electric field or presenting difficulties to the design of a device.
  • the structural viscosity which is manifested by the electrorheological fluid of this invention is required to satisfy the condition of the following formula (1). 0.01 Pa ⁇ s ⁇ ⁇ 1 - ⁇ 2 ⁇ 0.5 Pa ⁇ s wherein ⁇ 1 is the viscosity of at a shear rate of 3.3/s when measured at 25°C in the absence of supply of an electric field and ⁇ 2 is a viscosity at a shear rate of 33/s when measured at 25°C in the absence of supply of an electric field (hereinafter the difference, ⁇ 1 - ⁇ 2 , will be referred to simply as "Ti”)].
  • the Ti value of the electrorheological fluid of this invention is required to be in the range from not less than 0.01 Pa ⁇ s to not more than 0.5 Pa ⁇ s. Preferably, this range is from not less than 0.05 Pa ⁇ s to not less than 0.1 Pa ⁇ s.
  • the electrorheological fluid satisfies the dispersion stability, the redispersibility, and the fluidity at higher levels. If the Ti value is less than 0.1 Pa ⁇ s, the structural viscosity is insufficient and the dispersion stability is insufficient. If the Ti value exceeds 0.5 Pa ⁇ s, the fluidity is insufficient.
  • the dielectric particles to be used as disperse phase are preferable to have an average particle diameter of 1-50 ⁇ m, more preferably 3-20 ⁇ m. If the average particle diameter is not more than 1 mm, the resultant electrorheological fluid is not likely to induce a large shear stress when an electric field is applied. Adversely, if the average particle diameter is not less than 50 mm, it is difficult to obtain an electrorheological fluid with excellent dispersion stability.
  • the dielectric particles are particles which can be polarized when an electric field is applied.
  • the dielectric particles are, but not limited to, organic particles having an hydrophilic group such as starch, cellulose, an ion-exchange resin, and a sulphonic acid group-containing polystyrene polymer; hydrophilic inorganic particles such as silica and alumina; a composite particle being a particle having three layers with an organic solid particle for center portion, a conductive film layer covering the organic solid particle, and an electric insulating film layer covering the conductive film layer, a particle in which the surface of a conductive particle such as aluminum is covered with a thin insulating film, a carbonaceous powder, a particle obtained by dispersing a conductive particle such as carbon black into a resin; an organic semiconductive particle such as poly(acene-quinone); strong dielectric particles such as barium titanate, lithium tartrate.
  • a sulfate such as starch, cellulose, an ion-exchange resin
  • the dispersive medium to be used for the electrorheological fluid of the present invention is an electrical insulating oil.
  • the dispersive medium is present in the range of 50 to 500 parts by weight based on 100 parts by weight of the disperse phase.
  • the dispersive medium are, but not limited to, silicone oils such as polydimethylsiloxane, a partially octyl replaced polydimethyl-siloxane, a partially phenyl replaced polydimethyl-siloxane, hydrocarbons such as fluid paraffin, decane, methyl naphthalene, decalin, diphenylmethane, and a partially hydrogenated triphenyl; halogenated hydrocarbons such as chlorobenzene, dichlorobenzene, bromobenzene, chlorodiphenyl methane; fluorides of organic compound such as Difloil (a product sold by Daikin Industries Ltd.
  • the viscosity of the dispersive medium is preferably not more than 0.05 Pa ⁇ s.
  • the electrical insulating oil is preferable to be a silicon element-containing insulating oil or a fluorine element-containing insulating oil.
  • the silicon element-containing insulating oil has no particular restriction except for the requirement that it should have a silicone oil as a main component thereof and should be a substantially electrical insulating liquid.
  • the silicone oil possesses siloxane structure and generally finds utilities in brake oil, air insulating oil, saturation oil, lubricating oil, polish, component for cosmetic articles, mold release agent, defoaming agent, and the like. As concrete examples of the silicone oil, those already mentioned above may be cited.
  • the fluorine element-containing insulating oil has no particular restriction except for the requirement that it should have a fluoride of organic compounds as a main component thereof and should be a substantially electrical insulating liquid.
  • Low polymers of ethylene trifluoride chloride which are generally used for lubricants and mold release agents, perfluoropolyether oils which are generally used as for lubricants, and fluorine-modified silicone oils which are used as for lubricants may be cited as typical examples.
  • the method for enabling an electrorheologicalfluid to be endowed with the structural viscosity represented by the specific conditional formula while retaining the specific viscosity mentioned above is not particularly limited.
  • Use of an composite polymer in the electrorheological fluid or treatment of the surface of the particles of the disperse phase with a polymeric compound is effective in implementing the endowment mentioned above.
  • the composite polymer a composite polymer which is substantially insoluble in an electrical insulating oil and is possessed both of a silicone component-containing structural unit (A) and a disperse phase-adsorbing chain-containing structural unit (B) may be used for example.
  • the electrorheological fluid can be endowed with the structural viscosity represented by the specific conditional formula while retaining the specific viscosity and, at the same time, can be vested with highly satisfactory dispersion stability, redispersibility, and fluidity.
  • the composite polymer is preferable to be substantially insoluble in an electric insulating oil, it may contain not more than 90% by weight of soluble materials. Further, the composite polymer may be partially swelled or wholly swelled by absorbing an electrical insulating oil so long as it avoids being solved in an electrical insulating oil and converted into a homogeneous solution. If the composite polymer dissolves in an electrical insulating oil or instead contains 90% or more by weight of soluble materials, the produced electrorheological fluid will be possibly at a disadvantage in being deficient in redispersibility.
  • the composite polymer is preferable to be possess of a silicone component-containing structural unit (A). If the composite polymer does not possess this structural unit (A), the produced electrorheological fluid will be possibly at a disadvantage in being deficient in dispersion stability or fluidity.
  • silicone component means polysiloxane groups such as, for example, a polydimethylsiloxane group, a partially alkyl group-substituted polydimethylsiloxane group, a partially aryl group-substituted polydimethylsiloxane group, or a tris(trialkylsiloxy)-cyclopropyl group.
  • the composite polymer is preferable to be possess disperse phase-adsorbing chain-containing structural unit (B). If the composite polymer does not possess the structural unit (B), the produced electrorheological fluid will possibly be at a disadvantage In being deficient in dispersion stability.
  • the adsorption may be in the form of chemical adsorption or physical adsorption. When the interaction between the composite polymer and the surface of the particles of the disperse phase is unduly intense, it will possibly degrade the redispersibility and the fluidity of the produced electrorheological fluid. Thus, the adsorption is desired to be in the form of physical adsorption or electrostatic chemical adsorption.
  • the term "disperse phase-adsorbing chain” means functional groups such as a hydrocarbon groups, a atomic groups containing oxygen atom which exhibit the Lewis basicity.
  • a composite (1) which is obtainable by compositing particles (I) substantially insoluble in an electrical insulating oil with a polysiloxane-containing polymer (II), the polymer (II) having as the silicone component-containing structural unit (A) thereof a polysiloxane-containing structural unit (A-1) represented by the general formula (2): wherein A is -COO- or phenylene group, R 1 is hydrogen atom or methyl group, R 2 is an alkylene group of 1 to 6 carbon atoms, R 3 to R 13 are independently an aryl group, an alkyl group of 1 to 6 carbon atoms, or an alkoxy group of 1 to 10 carbon atoms, a is an arbitrary integer, c and d are independently an integer in the range of 0 to 10, and b is an integer in the range of
  • the composite polymer When the composite polymer is used, it is preferable to be added in the amount in the range of 0.01 to 6 parts by weight, based on 100 parts by weight of the disperse phase. If the amount of the composite polymer is less than 0.01 part by weight, the produced electrorheological fluid will be possibly at a disadvantage in exhibiting no structural viscosity or acquiring no dispersion stability. If the amount of the composite polymer exceeds 6 parts by weight, the produced electrorheological fluid will be possibly at a disadvantage in having the redispersibility and the fluidity thereof notably degraded. It is particularly preferable to use the composite polymer in the amount falling in the range of 0.1 to 5 parts by weight.
  • this composite (1) is obtained by complexing the particle (I) which are substantially insoluble in an electrical insulating oil with a polysiloxane-containing polymer (II) which comprises a polysiloxane-containing structural unit (A-1) and a disperse phase-adsorbing chain-containing structural unit (B) as described above.
  • a polysiloxane-containing polymer (II) which comprises a polysiloxane-containing structural unit (A-1) and a disperse phase-adsorbing chain-containing structural unit (B) as described above.
  • the structural unit (B) at least one member selected from the group consisting of an alkyleneoxide chain-containing structural unit (B-1), a nitrogen atom-containing chain-containing structural unit (B-2), and a hydrocarbon chain-containing structural unit (B-3) mentioned above can be used.
  • the composite (1) to be used in this invention possess a moitety of the particle (I) which are substantially insoluble in an electrical insulating oil.
  • the composite(1) itself therefore, is substantially insoluble in an insulating oil. Since the composite(1) is substantially insoluble in the oil, the mutual contact of the particles of the disperse phase can be obstructed in the electrorheological fluid and the electrorheological fluid can be endowed with highly satisfactory redispersibility and fluidity. If the composite polymer is soluble substantially in the electrical insulating oil, the produced electrorheological fluid will be possibly at a disadvantage in being incapable of acquiring redispersibility and fluidity.
  • the particle (I) which is substantially insoluble in an electric insulating oil and which is compositeed with the polysiloxane-containing polymer (II) have no particular restriction except for the requirement that they should be substantially insoluble in an electrical insulating oil.
  • organic particle such as of polystyrene, poly(meth)acrylate, polyacrylonitrile, phenol resin, benzoguanamine resin, and melamine resin
  • inorganic particles such as of silica and alumina
  • organic or inorganic particles having such polymerization reaction groups as styryl group and (meth)acryloyl group may be cited.
  • the composite (1) to be used in this invention possesses a polysiloxane-containing polymer (II) moiety having a polysiloxane-containing structural unit (A-1) and a disperse phase-adsorbing chain-containing structural unit (B) as essential components thereof.
  • a polysiloxane-containing structural unit (A-1) in the composite (1) a suitable interaction can be caused between the composite (1) and the dispersive medium to endow the electrorheological fluid with dispersion stability and fluidity. If the composite (1) possesses no polysiloxane-containing structural unit (A-1), the electrorheological fluid will be possibly at a disadvantage in encountering degradation of dispersion stability and fluidity.
  • the ratio of the polysiloxane-containing polymer (II) to the particle (I) substantially insoluble in an electrical insulating oil in the composite (1) is preferable to be such that the proportion of the polymer (II) is in the range of 0.1 to 100 parts by weight, particularly preferably 1 to 10 parts by weight, based on 100 parts by weight of the particle (I). If the proportion of the polymer (II) is less than 0.1 part by weight, the electrorheological fluid will be possibly at a disadvantage in being endowed with no dispersion stability. If the proportion of the polymer (II) exceeds 100 parts by weight, the electrorheological fluid will be possibly at a disadvantage in being endowed with neither redispersibility nor fluidity.
  • the composite (1) is obtained by compositeing the particle (I) substantially insoluble in an electric insulating oil with the polysiloxane-containing polymer (II). It is not particularly limited by the form of this compositeing reaction.
  • the composite (1) is desired to be such that the polymer (II) has been fixed on the surface of the particle (I) in consequence of the complexing. If the polymer (II) has not been fixed on the surface of the particle (I) by the complexing reaction, the electrorheological fluid will be possibly at a disadvantage in being endowed with no dispersion stability.
  • the method for obtaining the composite (1) by complexing the particle (I) substantially insoluble in an electrical insulating oil with the polysiloxane-containing polymer (II) has no particular restriction.
  • a method which comprises forming the particle (I) in the presence of the polymer (II) thereby simultaneously effecting formation of the particle (I) and the complexing reaction (ii) a method which comprises forming the polymer (II) in the presence of the particle (I) thereby simultaneously effecting formation of the polymer (II) and the complexing, and (iii) a method which comprises synthesizing the particle (I) and the polymer (II) independently of each other, mixing or kneading them, and then subjecting the resultant mixture to a treatment with heat or radiation thereby effecting the complexing reaction are available for the production of the composite (1).
  • the composite (1) is synthesized, for example, by (i-1) a method which comprises polymerization of the monomer mixture (X) thereby forming the polysiloxane-containing polymer (II) and dispersion polymerization of a polimerizable monomer ( ⁇ ) capable of producing the particle (I) in the presence of the polymer (II), (i-2) a method which comprises polymerization of the monomer mixture (X) thereby forming the polysiloxane-containing polymer (II) and emulsion polymerization of the polimerizable monomer ( ⁇ ) in an aqueous medium in the presence of the polymer (II), (i-3) a method which comprises polymerization of the monomer mixture (X) thereby forming the polysiloxane-containing polymer (II) and solusion polymerization of the polynerizable monomer ( ⁇ ) in the presence of the polymer (II).
  • the method of (i-1) and the method of (i-2) are used advantageously in respect that the composite (1) having the polymer (II) fixed on the surface of the particle (I) by the oomplexing is easily obtained with high repeatability.
  • the polymer which has an ethylenically unsaturated group therein in advance because this polymer allows the composite(1) having the polymer (II) fixed on the surface of the particle (I) by a chemical bonding to be easily obtained with high repeatability.
  • the polysiloxane-containing polymer (II) is obtained by polymerizing the monomer mixture (X) containing a silicone-containig macromer (am) represented by the general formula (6): wherein F is -COO- or phenylene group, R 21 is hydrogen atom or methyl group, R 22 is an alkylene group of 1 to 6 carbon atoms, R 23 to R 33 are independently an aryl group, an alkyl group of 1 to 6 carbon atoms, or an alkoxy group of 1 to 10 carbon atoms, j and k are independently an integer in the range of 0 to 10, and 1 for an integer in the range of 0 to 200, and at least one disperse phase-adsorbing chain-containing monomer (b) selected from the group consisting of an alkyleneoxide chain-containing macromer (bm-1) represented by the general formula (7): wherein G is -COO- or phenylene group, R 34 is hydrogen atom or methyl group, R 35 is an alky
  • the ratio of a silicone-containing macromer (am) is preferably 10-90%, and more preferably 20-80% by weight, based on the weight of the monomer mixture (X). If the ratio of a silicone-containing macromer (am) is less than 10% by weight or more than 90% by weight, the electrorheological fluid does not have dispersion stability and fluidity.
  • the ratio of a disperse phase adsorbing chain-containing monomer (b) is preferably 10-90%, and more preferably 20-80% by weight, based on the weight of the monomer mixture (X). If the ratio of monomer (b) is less than 10% by weight or more than 90% by weight, the electrorheological fluid does not have full dispersion stability properties.
  • the ratio of the optional monomer is preferably 0 to 80% by weight. The sum of the monomers used is 100% by weight.
  • alkylene oxide chain-containing monomer (bm-1) used as the disperse phase-adsorbing chain monomer
  • a polyalkylene glycol having a double bond such as a (meth)acryloyl group-containing polyethylene glycol, a styryl group-containing polyethylene glycol, a p-isopropenyl benzyl group-containing polyethylene glycol, a (meth)acryloyl group-containing polypropylene glycol, a styryl group-containing polypropylene glycol, a p-isopropenyl benzyl group-containing polypropylene glycol, a (meth)acryloyl group-containing polytetramethylene glycol, a styryl group-containing polytetramethylene glycol, and a p-isopropenyl benzyl group-containing polytetramethylene glycol.
  • these one or more members may be used.
  • nitrogen atom-containing monomer (b-2) there are cited monomers including one or more basic nitrogen atoms and an ethylenically unsaturated bond.
  • nitrogen atom-containing monomer (b-2) are, but not limited to, nitrogen-containing (meth)acrylic acid derivatives, (meth)acrylonitrile, and unsaturated monomers containing a nitrogen heterocyclic ring.
  • modified (meth)acrylic esters in which the ester portion includes a substituted or non substituted amino group
  • (meth)acrylic acid amide preferably aminoalkyl (meth)acrylate and (meth)acrylic acid amide.
  • aminoalkyl (meth)acrylate are N, N-dimethyl amino ethyl (meth)acrylate, N, N-diethyl amino ethyl (meth)acrylate, N, N-dimethyl amino propyl (meth)acrylate, and N, N-dimethyl amino butyl (meth)acrylate or the like.
  • unsaturated monomers containing a nitrogen heterocyclic ring there are cited, for instance, monomers in which a hetrocyclic ring made of a single ring or multiple rings including one to three, preferably one or two nitrogen atoms, bonds to a vinyl group.
  • vinyl pyrrolidones such as 2-vinyl-2-pyrrolidone, and 1-vinyl-3-pyrrolidone
  • vinyl pyridines such as 2-vinyl pyridine, 4-vinyl pyridine, and 5-methyl-2-vinyl pyridine
  • vinylimidazoles such as 1-vinyl imidazole, and 1-vinyl-2-methyl imidazole
  • (meth)acrylic esters such as methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, dodecyl (meth)acrylate, cetyl (meth)acrylate, stearyl (meth)acrylate, 2-methylstearyl (meth)acrylate, and eicosyl (meth)acrylate; or alkyl group substituted styrenes such as methyl styrene, ethyl styrene, butyl styrene, octyl styrene, dodecyl styrene, and stearyl styrene. Of these one or more members may be used.
  • the optional monomer (c) there are cited, for instance, polymerizable monomers of olefins such as ethylene, propylene, and cyclohexene; alkyldienes such as butadiene, isoprene, and cyclopentadiene; halogenated olefins such as vinyl fluoride, vinylidene fluoride, vinyl chloride, and vinylidene chloride; aromatic vinyl compounds such as styrene, ⁇ -methyl styrene, p-methyl styrene, vinyl naphthalene, vinyl anthracene, chlorostyrene, and chloromethyl styrene; (meth)acrylic alkoxy alkyl esters such as methoxy ethyl (moth)acrylate; (meth)acrylic hydroxyl alkyl esters such as 2-hydroxyl ethyl (meth)acrylate, and hydroxyl butyl (meth)acrylate; esters
  • Polysiloxane-containing polymer (II) is produced by a known procedure, e.g. solution polymerization using a radical generating catalyst.
  • the radical generating catalyst there are cited, for instance, conventional catalysts for the polymerization of vinyl monomers.
  • the radical generating catalyst are, but not limited to, azo compounds such as 2, 2'-azobisisobutyronitrile, and 2, 2'-azobis (2, 4-dimethylvaleronitrile); and per-oxide compounds such as benzoyl peroxide, di-tert-butyl peroxide, tert-butyl peroctate, and tert-butylperoxy-2-ethylhexanoate.
  • the amount of the radical generating catalyst to be added is usually 0.2-10 parts by weight, preferably 0.5-5 parts by weight, based on 100 parts of the monomer used.
  • the reaction temperature of polymerization is usually 60°-100°C for 1 to 15 hours.
  • a solvent may be used.
  • the solvent are, but not limited to, aliphatic hydrocarbons such as hexane, heptane, and octane; aromatic hydrocarbons benzene, toluene, and xylene; alcohols such as isopropyl alcohol, and butanol; ketones such as methyl isobutyl ketone, and methyl ethyl ketone; esters such as ethyl acetate, isobutyl acetate, amyl acetate, 2-ethyl hexyl acetate; and Cellosolve such as methyl cellosolve, and ethyl cellosolve.
  • a solution of the polymer (II) thus obtained can be used for synthesizing the composite (1) as it is or can be used after separating the polymer (II) by distilling off the solvent.
  • Polymer (II) preferably has an ethylenically unsaturated group, which is introduced by the reaction of a monomer with an ethylenically unsaturated group.
  • an ethylenically unsaturated group into polymer (II) is carried out, for instance, by adopting, as a component of a monomer mixture (X), an acid group-containing monomer such as acrylic acid, methacrylic acid, maleic acid, and vinyl sulfonic acid to form the precursor of polymer (II), and then reacting with the acid group of the precursor a glycidyl group-containing unsaturated monomer such as glycidyl (meth)acrylate or allyl glycidyl ether.
  • an acid group-containing monomer such as acrylic acid, methacrylic acid, maleic acid, and vinyl sulfonic acid
  • the composite (1) is then produced by dispersion-polymerizing polymerizable monomer ( ⁇ ) in the presence of polymer (II) in the method (i-1).
  • the meaning of dispersion polymerization of the method (i-1) is polymerization carried out in the presence of a dispersion stabilizing agent using an organic solvent capable of dissolving polymerizable monomer ( ⁇ ) and not capable of dissolving the resultant polymer.
  • the organic solvent is capable of dissolving both of polymer (II) and polymerizable monomer ( ⁇ ) and substantially not capable of dissolving the resultant composite.
  • organic solvent examples include, but not limited to, aliphatic hydrocarbons such as hexane, heptane, and octane; aromatic hydrocarbons such as benzene, toluene, and xylene; alcohols such as methyl alcohol, ethyl alcohol, isopropyl alcohol, and n-butyl alcohol; ethers such as cellosolve, butylcellosolve, and diethylene glycol monobutyl ether; esters such as ethyl acetate, and isobutyl acetate; and ketones and the like. Of these one or more members may be used.
  • aliphatic hydrocarbons such as hexane, heptane, and octane
  • aromatic hydrocarbons such as benzene, toluene, and xylene
  • alcohols such as methyl alcohol, ethyl alcohol, isopropyl alcohol, and n-butyl alcohol
  • ethers
  • polymerizable monomer ( ⁇ ) which is polymerized by the method (i-1) there are cited, for instance, aromatic compounds such as styrene, vinyl toluene, vinyl p-ohlorotoluene, and vinyl pyridine; and (meth)acrylic acid esters such as methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, and benzyl (meth)acrylate.
  • the dispersion polymerization for synthesizing the composite (1) to be used in the method (i-1), is carried out usually using a radical generating catalyst.
  • the radical generating catalyst are, but not limited to, azo compounds such as 2, 2'-azobisisobutyronitrile, and 2, 2'-azobis(2,4-dimethylvaleronitrile); and peroxides such as benzoyl peroxide, and lauroyl peroxide.
  • the amount of the catalyst is usually 0.2-10 parts by weight, preferably 0.5-5 parts by weight, based on 100 parts by weight of polymerizable monomer ( ⁇ ).
  • the proportion of polymer (II) is preferably 0.1-10 parts by weight, more preferably 1-6 parts by weight, to 100 parts by weight of polymerizable monomer ( ⁇ ) in the method (i-1). If the proportion of polymer (II) is not more than 0.1 part by weight, the polymerization for producing the composite are not reproducible and if obtained, the dispersion stability of electrorheological fluid is poor. Adversely, if the proportion is not less than the 10 parts by weight, the resultant electrorheological fluid is liable to be poor in re-dispersibility and fluidity properties.
  • the total concentration of polymerizable monomer ( ⁇ ) and polymer (II) in the reaction mixture is usually 5-50% by weight, preferably 10-30% by weight. Further, a conventional surfactant or a dispersion stabilizer such as high polymers may be added.
  • the dispersion polymerization may be carried out usually at 60°-100°C and for 0.5-30 hours. After polymerization, a post treatment may be carried out for solvent replacement, solvent distillation, drying, and grinding. When the polymerization solvent used is replaced with a silicone insulating oil, the workability of producing electrorheological fluid is improved.
  • Process for synthesizing the composite (10 by the method (i-2) is shown as follows.
  • the composite (1) used in the method (i-2) is obtained by emulsion-polymerizing the polymerizable monomer ( ⁇ ) in a medium mainly comprising water in the presence of the polymer (III).
  • the emulsion polymerization is preferred using a radical generating catalyst soluble in water.
  • the radical generating catalyst is a conventional one for emulsion polymerization of vinyl monomers. Examples of the radical generating catalyst are, but not limited to, sodium persulfate, potassium persulfate, ammonium persulfate, 4, 4'-azobis-4-cyanovaleric acid, and 2, 2'-azobis-aminopropane hydrochloric acid salt.
  • the total concentration of polymerizable monomer ( ⁇ ) and polymer (II) is preferably 5-50% by weight, more preferably 10-30% by weight, based on the weight of the aqueous solvent used.
  • the emulsion-polymerization for synthesizing the composite (1) by the method (i-2) can be carried out in water or in an aqueous medium comprizing water and an organic solvent.
  • the organic solvent there are an organic solvent having a high affinity to water, e.g. alcohols such as methanol, ethanol, and isopropanol; Cellosolve such as methylcellosolve, and ethylcellosolve; glycols such as ethylene glycol, and diethylene glycol.
  • the mixture it is preferred for polymerizable monomer ( ⁇ ) not to dissolve into the solvent.
  • the polymerization for synthesizing the composite (I) in the method (i-2) may be carried out at 50°-100°C for 2-40 hours.
  • the procedure of polymerization is carried out by charging water and polymer (II) into a reactor, mixing the resultant mixture to form an uniform dispersion, adding a part or whole of polymerizable monomer ( ⁇ ) into the dispersion, regulating the temperature of the dispersion, and adding a radical generating catalyst into the regulated dispersion to start polymerization.
  • the polymerization is carried out in the emulsified state at a prescribed temperature by adding the residual polymerizable monomer ( ⁇ ), if present.
  • a post treatment may be carried out for solvent replacement, solvent distillation, drying and grinding.
  • an organic or inorganic fine particle with (e) a compound having polymerizable reactive group can be used as the particle (I) which is substantially insoluble in the electical insulating liquid used in the method (ii-3).
  • the fine particle having polymerizable reactive group is, for example, a compound (e) having both functional group capable of reacting with the functional group existed on the surface of the organic or inorganic fine particle and the polymerizable reactive group and can be obtained by treating the organic or inorganic fine particle.
  • compound (e) examples include vinyl group-containing silane coupling agents such as g-(meth)acryloxy propyl trimethoxy silane, vinyl trimethoxy silane, vinyl triethoxy silane, and vinyl trichloro silane; and glycidyl group-containing unsaturated compounds such as glycidyl (meth)acrylate, and allyl glycidyl ether.
  • vinyl group-containing silane coupling agents such as g-(meth)acryloxy propyl trimethoxy silane, vinyl trimethoxy silane, vinyl triethoxy silane, and vinyl trichloro silane
  • glycidyl group-containing unsaturated compounds such as glycidyl (meth)acrylate, and allyl glycidyl ether.
  • the amount of compound (e) is usually 10-100 parts by weight, based on 100 parts by weight of the organic or inorganic fine particle used.
  • the polymerization of the monomer mixture (X) for producing the composite (I) by the method (ii-3) may be carried out using a polymerization initiator in the presence of particle (I) which has a polymerizable group thereon in an organic solvent.
  • organic solvent examples include, but not limited to, aliphatic hydrocarbons such as hexane, heptane, and octane; aromatic hydrocarbons such as benzene, toluene, and xylene; alcohols such as methyl alcohol, ethyl alcohol, isopropyl alcohol, and n-butyl alcohol; ethers such as methyl cellosolve, ethyl cellosolve, butyl cellosolve, diethylene glycol monobutyl ether; esters such as ethyl acetate, and isobutyl acetate; and ketones. Of these one or more members may be used.
  • aliphatic hydrocarbons such as hexane, heptane, and octane
  • aromatic hydrocarbons such as benzene, toluene, and xylene
  • alcohols such as methyl alcohol, ethyl alcohol, isopropyl alcohol, and n-but
  • the polymerization initiator may be peroxide initiators such as benzoyl peroxide, and lauroyl peroxide; azo initiators such as 2, 2'-azobisisobutyronitrile, 2, 2'-azobis (2, 4'-dimethyl valeronitrile).
  • peroxide initiators such as benzoyl peroxide, and lauroyl peroxide
  • azo initiators such as 2, 2'-azobisisobutyronitrile, 2, 2'-azobis (2, 4'-dimethyl valeronitrile).
  • the mentioned polymerization may be carried out at 50°-100°C for 0.5-15 hours.
  • a post treatment may be carried out for solvent replacement, solvent distillation, drying and grinding.
  • vinyl group-containing silane type coupling agents such as ⁇ -(meth)acryloxypropyl trimethoxy silane, vinyl trimethoxy silane, vinyl triethoxy silane, and vinyl trichlorosilane and glycidyl group-containing unsaturated compounds such as glycidyl (meth)acrylate and allyl glycidyl ether may be cited.
  • the amount of the compound (e) to be used for the introduction of the polymerization reaction group into the very minute organic or inorganic particles is not particularly limited, the compound (e) is desired to be used in an amount in the range of 10 to 100 parts by weight based on 100 parts by weight of the very minute organic or inorganic particles.
  • the polymerization of the monomer mixture (Y) is desired to be effected in an organic solvent by use of a polymerization initiator in the presence of the particles (I) which are formed of very minute organic or inorganic particles having the polymerization reaction group incorporated therein.
  • organic solvent to be used for the polymerization aliphatic hydrocarbons such as hexane, heptane, and octane; aromatic hydrocarbons such as benzene, toluene, and xylene; alcohols such as methyl alcohol, ethyl alcohol, isopropyl alcohol, and n-butyl alcohol; and ether type, ketone type, and ester type organic solvents such as methyl cellosolve, ethyl cellosolve, butyl cellosolve, diethylene glycol monobutyl ether, ethyl acetate, and isobutyl acetate may be cited.
  • One member or a mixture of two or more members selected from the group of organic solvents cited above may be used.
  • the polymerization is carried out at a temperature of 50°-100°C generally for 0.5-15 hours.
  • the producedpolymerization solution may be optionally treated by the well-known methods of displacement of solvent, expulsion of solvent by distillation, drying, and pulverization.
  • composite polymer dispersion (1) a silicone oil dispersion of a composite polymer (1) of a styrene type graft polymer having a composite polymer (1) content of 20% by weight
  • the monomer mixture consisting of 50 g of methyl methacrylate and 5 g of industrial grade divinyl benzene (a mixture of 55% by weight of divinyl benzene, 35% by weight of ethyl styrene, etc.; produced by Wako Pure Chemical Industries, Ltd.) was stirred at 20,000 r.p.m. by use of a dispersing device for two minutes as kept swept meanwhile with nitrogen gas.
  • the resultant mixture was heated at 70°C for 3 hours and further heated at 90°C for 3 hours to be polymerized.
  • the reaction solution was subjected to azeotropic distillation to displace water with isopropyl alcohol as the dispersive medium.
  • cross-linked polymer (1) a cross-linked polymer in the shape of beads
  • the product was then dried at 80°C for 10 hours by use of a vacuum drier to obtain 298 g of sulfonic acid group-containing polystyrene polymer particles having an average particle diameter of 6 ⁇ m (hereinafter referred to as "disperse particles (1)").
  • the disperse particles (1) were found to have an anion dissociating group density of 4.2 mg equivalent/g.
  • An electrorheological fluid (2) of this invention was obtained by following the procedure of Example 1 while using 0.5 g of the composite polymer dispersion (2) obtained in Referential Example 2 in the place of the composite polymer dispersion (1) and 69.5 g of a mineral type electric insulating oil of 0.01Pa ⁇ s (a high-tension insulating oil produced by Cosmo Oil Co., Ltd.) in the place of the silicone oil of 0.02Pa ⁇ s.
  • Fluid (1) for comparison An electrorheological fluid for comparison (hereinafter referred to as "fluid (1) for comparison”) was obtained by drying 30 g of the disperse particles (1) obtained in Example 1 at 150°C for 3 hours, allowing the dried particles to absorb the moisture in the air until the water content thereof reached 2.0% by weight, and dispersing the wet particles by stirring in 70 g of a silicone oil of 0.02Pa ⁇ s (produced by Shin-etsu Chemical Industry Co., Ltd. and marketed under product code of KF96-20cs").
  • Fluid (2) for comparison An electrorheological fluid for comparison (hereinafter referredto as "fluid (2) for comparison”) was obtained by drying 30 g of the disperse particles (1) obtained in Example 1 at 150°C for 3 hours, allowing the dry particles to absorb the moisture in the air until the water content thereof reached 2.0% by weight, and dispersing the particles by stirring in 70 g of a mineral electrical insulating oil of 0.01Pa ⁇ s (a high-tension insulating oil; produced by Cosmo Oil Co., Ltd.).
  • Fluid (3) for comparison An electrorheological fluid for comparison (hereinafter referred to as "fluid (3) for comparison”) was obtained by drying 30 g of the disperse particles (1) obtained in Example 1 at 150°C for 3 hours, allowing the dry particles to absorb the moisture in the air until the water content thereof reached 2.0% by weight, and dispersing the particles uniformly by stirring in a dispersive medium prepared by adding 1.2 g of a powdery silica having an average particle diameter of 0.007 ⁇ m (produced by Japan Aerosil Ltd. and marketed under trademark designation of "AEROSIL 380") to 68.8. g of a silicone oil of 0.02Pa ⁇ s (produced by Shin-etsu Chemical Industry Co., Ltd. and marketed under product code of "KF96-20cs").
  • Fluid (4) for comparison An electrorheological fluid for comparison (hereinafter referredto as "fluid (4) for comparison”) was obtained by drying 30 g of the disperse particles (1) obtained in Example 1 at 150°C for 3 hours, allowing the dry particles to absorb the moisture in the air until the water content thereof reached 2.0% by weight, and dispersing the particles by stirring in 68 g of a mineral electrical insulating oil (a high-tension insulating oil; produced by Cosmo Oil Co., Ltd.) having dissolved in advance therein 2.0 g of the composite polymer (1) for comparison obtained in Referential Example 3
  • a mineral electrical insulating oil a high-tension insulating oil; produced by Cosmo Oil Co., Ltd.
  • the electrorheological fluids (1) and (2) of this invention and the fluids (1) to (4) for comparison obtained respectively in Examples 1 and2 and Controls 1 to 4 were severally tested for viscosity at 25°C in the absence of supply of an electric field under the conditions of shear rates respectively of 3.3/s and 33/s to determine the Ti values thereof in accordance with the formula (1) mentioned above. Then, the electrorheological fluids were severally placed in test tubes 150 mm in height and 15 mm in diameter to a height of 100 mm from the bottom, tightly sealed therein, and left standing at room temperature to allow observation of the condition of gradual sedimentation of the disperse particles in the test tubes.
  • the electrorheological fluids were evaluated for the dispersion stability by measuring the heights of sediment layers formed in the test tubes in consequence of the sedimentation of disperse particles of the electrorheological fluids after one day and one week. Then, 50 ml of each of the electrorheological fluids were severally placed in containers having an inner volume of 100 ml, tightly stoppered, and left standing for a month. The containers were rotated at a rate of 30 r.p.m. to find the total numbers of revolutions required for the electrorheological fluids to resume the former homogeneous state and evaluate the redispersibility thereof. The results are shown in Table 1.
  • Electrorheolgial fluid of this invention (1) 0.13 0.073 0.057 93 90 5 Electrorheolgial fluid of this invention (2) 0.18 0.11 0.07 85 81 12 Electrorheolgial fluid for comparison (1) 0.047 0.045 0.002 35 35 60 Electrorheolgial fluid for comparison (2) 0.032 0.030 0.002 35 36 60 Electrorheolgial fluid for comparison (3) 0.82 0.29 0.53 91 91 >100 Electrorheolgial fluid for comparison (4) 0.69 0.22 0.54 83 83 >100
  • the electrorheological fluids were measured for the values of shear stress (initial value) and the current density (initial value) using coaxial rotational viscometer with electrical fields when an AC external electric field of 4,000 V/mm (frequency: 50 Hz) was applied under the conditions of an inner/outer cylinder gap of 1.0 mm, a shear rate of 33/s, and a temperature of 25°C to the electrorheological fluids were continuously treated using the external electric field of 4,000 V/mm at 25°C for 3 days and then measured for the values of shear stress (the value after the three days' operation) and the current density (the value after the three days' operation) to evaluate the durability.
  • the results are shown in Table 2.
  • Electrorheological fluid of this invention (1) 21 21 18 18 Electrorheological fluid of this invention (2) 15 15 14 14 Electrorheological fluid for comparison (1) 18 18 17 18 Electrorheological fluid for comparison (2) 16 16 16 Electrorheological fluid for comparison (3) 19 19 18 17 Electrorheological fluid for comparison (4) 4 4 8 9
  • the electrorheological fluids (1) and (2) of this invention were endowed with structural viscosity and therefore were excellent in dispersion stability and redispersibility as evinced by the fact that the values of ⁇ 2 were not more than 0.2Pa ⁇ s and the Ti values were in the range of satisfying the condition of the formula (1).
  • the fluids (1) and (2) for comparison were not endowed with structural viscosity and were deficient in dispersion stability and redispersibility notwithstanding the values of ⁇ 2 were not more than 0.2Pa ⁇ s.
  • the fluids (3) and (4) for comparison were deficient in redispersibility because the values of ⁇ 2 exceeded 0.2Pa ⁇ s and the Ti values exceeded 0.5Pa ⁇ s. From Table 2, it is clearly noted that the electrorheological fluids (1) and (2) of this invention retained as satisfactory shear stress property and current property as the fluids (1) and (2) for comparison.
  • cross-linked polymer (2) a cross-linked polymer of the shape of beads
  • the solid product consequently obtained was neutralized with 500 ml of an aqueous 10 wt% sodium hydroxide solution and then thoroughly washed with water. Then, the wet solid product was dried at 80°C for 10 hours by use of a vacuum drier to obtain 180 g of sulfonic acid group-containing polystyrene type polymer particles having an average particle diameter of 5 ⁇ m(hereinafter referred to as "disperse particles (2)").
  • the disperse particles (2) were found to have an anion dissociating group density of 4.3 mg equivalent/g.
  • An electrorheological fluid (3) of this invention was obtained by uniformly dispersing the disperse particles (2) of the adjusted water content in the dispersive medium prepared by adding 4 g of the composite polymer dispersion (3) to a mixture consisting of 16 g of a silicone oil of 0.2 Pa ⁇ s (produced by Shin-etsu Chemical Industry Co., Ltd. and marketed under product code of "KF96-20cs") and 50 g of a fluorine element-containing oil (produced by Daikin Industries Co., Ltd. and marketed under trademark designation of "Daifloil #1").
  • fluid (5) for comparison An electrorheological fluid for comparison (hereinafter referred to as "fluid (5) for comparison") was obtained by dispersing the disperse particles in 70 g of a silicone oil of 20 cs (produced by Shin-etsu Chemical Industry Co., Ltd. and marketed under product code of KF96-20cs").
  • Fluid (6) for comparison An electrorheological fluid for comparison (hereinafter referred to as "fluid (6) for comparison”) was obtained by uniformly dispersing the disperse particles in a dispersive medium prepared by adding 1.5 g of a powdery silica having an average particle diameter of 0.007 ⁇ m(produced by Japan Aerosil Co., Ltd. and marketed under trademark designation of "AEROSIL380”) to 68.5 g of silicone oil (produced by Shin-etsu Chemical Industry Co., Ltd. and marketed under product code of KF96-20cs").
  • the electrorheological fluid (3) of this invention and the fluids (5) and (6) for comparison obtained respectively in Example 4 and Controls 5 and 6 were severally measured for viscosity at 25°C in the absence of supply of an electric field under the conditions of a shear rate of 3.3/s and a share rate of 33/s to find the viscosities, ⁇ 1 and ⁇ 2 , and determine the Ti values thereof in accordance with the formula (1) mentioned above. Then, the electrorheological fluids were severally placed in test tubes 150 mm in height and 15 mm in diameter to a height of 100 mm from the bottom, tightly sealed therein, and left standing at room temperature to allow observation of the condition of gradual sedimentation of the disperse particles in the test tubes.
  • the electrorheological fluids were evaluated for dispersion stability of by measuring the heights of sediment layers formed in the test tubes in consequence of the sedimentation of disperse particles of the electrorheological fluids after one day and one week. Then, 50 ml of each of the electrorheological fluids were severally placed in containers having an inner volume of 100 ml, tightly stoppered, and left standing for a month. The containers were rotated at a rate of 30 r.p.m. to find the total numbers of revolutions required for the electrorheological fluids to resume the former homogeneous state and evaluate the redispersibility thereof.
  • the electrorheological fluids were measured for the values of shear stress (initial value) and the current density (initial value) using coaxial field rotational viscometer with electric fields when an AC external electric field of 4,000 V/mm (frequency: 50 Hz) was applied under the conditions of an inner/outer cylinder gap of 1.0 mm, a shear rate of 400/s, and a temperature of 25°C .
  • the electrorheological fluids were continuously treated using the external electric field of 4,000 V/mm at 25°C for 3 days and then measured for the values of shear stress (the value after the 3 days' operation) and the current density (the value after the 3 days' operation) to evaluate the durability. The results are shown in Table 3.
  • Viscosity Pa ⁇ s
  • Disposition stability(mm) Redispersibility Number of revolutions
  • Values of shear stress g/cm 2
  • Current density ⁇ A/cm 2
  • the electrorheological fluid (3) of this invention was endowed with structural viscosity and was: consequently excellent in dispersion stability of and redispersibility as evinced by the fact that the magnitudes of ⁇ 2 were not more than 0.2 Pa ⁇ s and the Ti values were in the range of satisfying the condition of the formula (1).
  • the fluid (5) for control was deficient in dispersion stability of because the Ti value thereof was small.
  • the fluid (6) for comparison was deficient in redispersibility because the value of ⁇ 2 exceeded 0.2 Pa ⁇ s.
  • the electrorheological fluid (3) of this invention invariably maintained excellent shear property and electric property. 30 minutes as kept swept meanwhile with nitrogen gas. The resultant mixture was heated at 70°C for 24 hours to be polymerized.
  • composite (2) (composite (2) content 20% by weight; hereinafter referred to as “composite polymer dispersion (8)").
  • composite (3) (composite (3) content 20% by weight; hereinafter referred to as “composite polymer dispersion (9)”).
  • the resultant mixture was heated at 80°C for 2 hours to be polymerized. It was further left reacting with 5 g of glycidyl methacrylate and 1 g of dimethyl amino ethanol at 100°C for 5 hours. After the reaction was completed, the reaction solution consequently obtained was heated in an evaporator under reduced pressure to expel the solvent by distillation and obtain an oily polymer (7).
  • the resultant reaction solution, with 66 g of silicone oil of 0.02 Pa ⁇ s (produced by Shin-etsu Chemical Industry Co., Ltd.
  • composite polymer dispersion (12) a silicone oil dispersion of a composite (6) (composite (6) content 20% by weight; hereinafter referred to as “composite polymer dispersion (12)").
  • composite polymer dispersion (2) for comparison a silicone oil dispersion of polystyrene particles (polystyrene particles content 20% by weight; hereinafter referred to as “composite polymer dispersion (2) for comparison”).
  • composite polymer dispersion (3) for comparison a silicone oil dispersion of an composite polymer (3) for comparison (comparison composite polymer (3) content 20% by weight; hereinafter referred to as “composite polymer dispersion (3) for comparison”.
  • the solution and a monomer component consisting of 35 g of styrene and 15 g of industrial divinyl benzene (mixture of 55% by weight of divinyl benzene, 35% by weight of ethyl styrene, etc.; produced by Wako Pure Chemical Industries, Ltd.) were emulsified by stirring at a rate of 20,000 r.p.m. for 2 minutes by use of a dispersing device as kept swept meanwhile with nitrogen gas.
  • the emulsified mixture was heated at 70°C for 3 hours and then further heated at 90°C for 4 hours to be polymerized.
  • the resultant reaction solution was heated in an evaporator under a reduced pressure to expel the water and then dried in an air oven at 80°C to obtain cross-linked polymer particles (hereinafter referred to as "composite polymer (5) for comparison").
  • An composite polymer dispersion (6) for comparison was obtained by adding 0.2 g of the polymer (3) synthesized in Referential Example 8 to 20 g of the composite polymer dispersion (2) for comparison prepared in Referential Example 15 and stirring them for dispersion.
  • the dispersion was heated in an evaporator under reduced pressure to expel the solvent and dried at 50°C in a vacuum drier to obtain a reactant. Then 150 ml of toluene was charged into a flask having inner volume of 200 ml and 15 g of the reactant was dispersed.
  • the reaction solution, with 66 g of silicone oil of 0.02 Pa ⁇ s (produced by Shin-etsu Chemical Industry Co., Ltd.
  • composite polymer dispersion (7) for comparison a silicone oil dispersion of an composite polymer (7) for comparison (comparison composite polymer (7) content 20% by weight; hereinafter referred to as “composite polymer dispersion (7) for comparison”).
  • cross-linked polymer (3) a cross-linked polymer in the shape of beads
  • the product was then dried at 80°C for 10 hours by use of a vacuum drier to obtain 372 g of sulfonic acid group-containing polystyrene polymer particles having an average particle diameter of 6 ⁇ m(hereinafter referred to as "disperse particles (3)").
  • the disperse particles (3) were found to have an anion dissociating group density of 4.2 mg equivalent/g.
  • the amount 30 g of the disperse particles (3) was dried at 150°C for 3 hours, left absorbing the moisture in the air until the water content thereof reached 2.0% by weight, and uniformly dispersed in a dispersive medium prepared by adding 4 g of the composite polymer dispersion (7) obtained in Referential Example 8 to 66 g of silicone oil of 0.2 Pa ⁇ s (produced by Shin-etsu Chemical Industry Co., Ltd. and marketed under product code of "KF96-20cs”), to produce an electrorheological fluid (7) of this invention.
  • An electrorheological fluid (8) of this invention was obtained by following the procedure of Example 9 while using 3 g of the composite polymer dispersion (8) obtained in Referential Example 9 in the place of the composite polymer dispersion (7) and 67 g of silicone oil (produced by Shin-etsu Chemical Industry Co., Ltd. and marketed under product code of "KF96-10cs") in the place of the silicone oil of 0.02 Pa ⁇ s.
  • silicone oil produced by Shin-etsu Chemical Industry Co., Ltd. and marketed under product code of "KF96-10cs
  • An electrorheological fluid (9) of this invention was obtained by following the procedure of Example 9 while using 5 g of the composite polymer dispersion (9) obtained in Referential Example 10 in the place of the composite polymer dispersion (7) and changing the amount of the silicone oil (Shin-etsu Chemical Industry Co., Ltd. and marketed under product code of "KF96-20cs") to 65 g.
  • An electrorheological fluid (10) of this invention was obtained by following the procedure of Example 9 while using 5 g of the composite polymer dispersion (10) obtained in Referential Example 11 in the place of the composite polymer dispersion (7) and changing the amount of the silicone oil (produced by Shin-etsu Chemical Industry Co., Ltd. and marketed under product code of "KF96-20cs") to 65 g.
  • An electrorheological fluid (11) of this invention was obtained by following the procedure of Example 9 while using 5 g of the composite polymer dispersion (12) obtained in Referential Example 12 in the place of the composite polymer dispersion (7) and changing the amount of the silicone oil (produced by Shin-etsu Chemical Industry Co., Ltd. and marketed under product code of "KF96-20cs") to 65 g.
  • cross-linked polymer (3) a cross-linked polymer in the shape of beads
  • the product was then dried at 80°C for 10 hours by use of a vacuum drier to obtain 173 g of sulfonic acid group-containing polystyrene polymer particles having an average particle diameter of 2.5 ⁇ m(hereinafter referred to as "disperse particles (4)").
  • the disperse particles (4) were found to have an anion dissociating group density of 4.1 mg equivalent/g.
  • the amount 30 g of the disperse particles (4) was dried at 150°C for 3 hours, left absorbing the moisture in the air until the water content thereof reached 2.0% by weight, and uniformly dispersed in a dispersive medium prepared by adding 7 g of the composite polymer dispersion (12) obtained in Referential Example 13 to 63 g of silicone oil of 0.02 Pa ⁇ s (produced by Shin-etsu Chemical Industry Co., Ltd. and marketed under product code of "KF96-20cs”), to produce an electrorheological fluid (12) of this invention.
  • An electrorheological fluid (13) of this invention was obtained by following the procedure of Example 14 while using 4 g of the composite polymer dispersion (13) obtained in Referential Example 14 in the place of the composite polymer dispersion (12).
  • An electrorheological fluid (14) of this invention was obtained by drying 30 g of zeolite particles having an average particle diameter of 3 ⁇ m(produced by Sigma Corp. and marketed under trademark designation of "Zeolite”; hereinafter referred to as "disperse particles (5)") at 150°C for 3 hours, allowing the dried zeolite particles to absorb the moisture in the air until the water content thereof reached 10.0%, and uniformly dispersing the zeolite particles in a dispersive medium prepared by adding 4 g of the composite polymer dispersion (7) obtained in Referential Example 8 to 66 g of silicone oil of 0.02 Pa ⁇ s (produced by Shin-etsu Chemical Industry Co., Ltd. and marketed under product code of "KF96-20cs").
  • Fluid (7) for comparison An electrorheological fluid for comparison (hereinafter referred to as "fluid (7) for comparison”) was obtained by drying 30 g of the disperse particles (3) obtained in Example 9 at 150°C for 3 hours, then allowing the dry disperse particles to absorb the moisture in the air until the water content thereof reached 2.0% by weight, and dispersing wet disperse particles in 70 g of silicone oil of 0.02 Pa ⁇ s (produced by Shin-etsu Chemical Industry Co., Ltd. and marketed under product code of "KF96-20cs").
  • Fluid (8) for comparison An electrorheological fluid for comparison (hereinafter referred to as "fluid (8) for comparison”) was obtained by drying 30 g of the disperse particles (3) obtained in Example 9 at 150°C for 3 hours, then allowing the dry disperse particles to absorb the moisture in the air until the water content thereof reached 2.0% by weight, and dispersing the wet disperse particles in 70 g of silicone oil of 0.01 Pa ⁇ s (produced by Shin-etsu Chemical Industry Co., Ltd. and marketed under product code of "KF96-10cs").
  • Fluid (9) for comparison An electrorheological fluid for comparison (hereinafter referred to as "fluid (9) for comparison”) was obtained by drying 30 g of the disperse particles (4) obtained in Example 14 at 150°C for 3 hours, then allowing the dry disperse particles to absorb the moisture in the air until the water content thereof reached 2.0% by weight, and dispersing the wet disperse particles in 70 g of silicone oil of 0.02 Pa ⁇ s (produced by Shin-etsu Chemical Industry Co., Ltd. and marketed under product code of "KF96-20cs").
  • Fluid (10) for comparison An electrorheological fluid for comparison (hereinafter referred to as "fluid (10) for comparison”) was obtained by following the procedure of Example 9 while using 4 g of the composite polymer dispersion (2) for comparison obtained in Referential Example 15 in the place of the composite polymer dispersion (7) and changing the amount of the silicone oil (produced by Shin-etsu Chemical Industry Co., Ltd. and marketed under product code of "KF96-20cs”) to 66 g.
  • silicone oil produced by Shin-etsu Chemical Industry Co., Ltd. and marketed under product code of "KF96-20cs
  • Fluid (11) for comparison An electrorheological fluid for comparison (hereinafter referred to as "fluid (11) for comparison”) was obtained by following the procedure of Example 9 while using 4 g of the composite polymer dispersion (3) for comparison obtained in Referential Example 16 in the place of the composite polymer dispersion (7) and changing the amount of the silicone oil (produced by Shin-etsu Chemical Industry Co., Ltd. and marketed under product code of "KF96-20cs”) to 66 g.
  • silicone oil produced by Shin-etsu Chemical Industry Co., Ltd. and marketed under product code of "KF96-20cs
  • Fluid (12) for comparison An electrorheological fluid for comparison (hereinafter referred to as "fluid (12) for comparison”) was obtained by following the procedure of Example 9 while using 5 g of the composite polymer dispersion (4) for comparison obtained in Referential Example 17 in the place of the composite polymer dispersion (7) and changing the amount of the silicone oil (produced by Shin-etsu Chemical Industry Co., Ltd. and marketed under product code of "KF96-20cs”) to 65 g.
  • silicone oil produced by Shin-etsu Chemical Industry Co., Ltd. and marketed under product code of "KF96-20cs
  • Fluid (13) for comparison An electrorheological fluid for comparison (hereinafter referred to as "fluid (13) for comparison”) was obtained by following the procedure of Example 9 while using 1 g of the composite polymer dispersion (5) for comparison obtained in Referential Example 18 in the place of the composite polymer dispersion (7) and changing the amount of the silicone oil (produced by Shin-etsu Chemical Industry Co., Ltd. and marketed under product code of "KF96-20cs”) to 69 g.
  • silicone oil produced by Shin-etsu Chemical Industry Co., Ltd. and marketed under product code of "KF96-20cs
  • Fluid (14) for comparison An electrorheological fluid for comparison (hereinafter referred to as "fluid (14) for comparison”) was obtained by following the procedure of Example 9 while using 5 g of the composite polymer dispersion (6) for comparison obtained in Referential Example 19 in the place of the composite polymer dispersion (7) and changing the amount of the silicone oil (produced by Shin-etsu Chemical Industry Co., Ltd. and marketed under product code of "KF96-20cs”) to 65 g.
  • silicone oil produced by Shin-etsu Chemical Industry Co., Ltd. and marketed under product code of "KF96-20cs
  • Fluid (15) for comparison An electrorheological fluid for comparison (hereinafter referred to as "fluid (15) for comparison”) was obtained by following the procedure of Example 14 while using 5 g of the composite polymer dispersion (7) for comparison obtained in Referential Example 20 in the place of the composite polymer dispersion (12) and changing the amount of the silicone oil (produced by Shin-etsu Chemical Industry Co.. Ltd. and marketed under product code of "KF96-20cs”) to 65 g.
  • silicone oil produced by Shin-etsu Chemical Industry Co.. Ltd. and marketed under product code of "KF96-20cs
  • Fluid (16) for comparison An electrorheological fluid for comparison (hereinafter referred to as "fluid (16) for comparison”) was obtained by drying 30 g of the disperse particles (5) obtained in Example 16 at 150°C for 3 hours, then allowing the dry disperse particles to absorb the moisture in the air until the water content thereof reached 10.0% by weight, and dispersing the disperse particles in 70 g of silicone oil of 0.02 Pa ⁇ s (produced by Shin-etsu Chemical Industry Co., Ltd. and marketed under product code of "KF96-20cs").
  • Fluid (17) for comparison An electrorheological fluid for comparison (hereinafter referred to as "fluid (17) for comparison”) was obtained by following the procedure of Example 9 while using 20 g of the composite polymer dispersion (8) for comparison obtained in Referential Example 21 in the place of the composite polymer dispersion (7) and changing the amount of the silicone oil (produced by Shin-etsu Chemical Industry Co., Ltd. and marketed under product code of "KF96-20cs”) to 50 g.
  • silicone oil produced by Shin-etsu Chemical Industry Co., Ltd. and marketed under product code of "KF96-20cs
  • Fluid (18) for comparison An electrorheological fluid for comparison (hereinafter referred to as "fluid (18) for comparison”) was obtained by following the procedure of Example 9 while using 2.5 g of the composite polymer dispersion (9) for comparison obtained in Referential Example 22 in the place of the composite polymer dispersion (7) and changing the amount of the silicone oil (produced by Shin-etsu Chemical Industry Co., Ltd. and marketed under product code of "KF96-20cs”) to 67.5 g.
  • silicone oil produced by Shin-etsu Chemical Industry Co., Ltd. and marketed under product code of "KF96-20cs
  • the electrorheological fluids (7) to (14) of this invention and the fluids (7) and (10) for comparison obtained respectively in Examples 9 to 16 and Controls 7 to 18 were severally tested for viscosity at 25°C in the absence of supply of an electric field under the conditions of a shear rates of 3.3/s and 33/s to find the viscosities, ⁇ 1 and ⁇ 2 , and determine the Ti values thereof in accordance with the formula (1) mentioned above. Then, the electrorheological fluids were severally placed in test tubes 150 mm in height and 15 mm in diameter to a height of 100 mm from the bottom, tightly sealed therein, and left standing at room temperature to allow observation of the condition of gradual sedimentation of the disperse particles in the test tubes.
  • the electrorheological fluids were evaluated for dispersion stability by measuring the heights of sediment layers formed in the test tubes in consequence of the sedimentation of disperse particles of the electrorheological fluids after one day and one week. Then, 50 ml of each of the electrorheological fluids were severally placed in containers having an inner volume of 100 ml, tightly stoppered, and left standing for a month. The containers were rotated at a rate of 30 r.p.m to find the total numbers of revolutions required for the electrorheological fluids to resume the former homogeneous state and evaluate the redispersibility thereof. The results are shown in Table 4.
  • the electrorheological fluids were measured for the values of shear stress (initial value) and the current density (initial value) using coaxial rotational viscometer with electric filed.
  • an AC external electric field of 4,000 V/mm (frequency: 50 Hz) was applied under the conditions of an inner/outer cylinder gap of 1.0 mm, a shear rate of 400/s, and a temperature of 25°C.
  • the electrorheological fluids were continuously treated using the external electric field of 4,000 V/mm at 25°C for 3 days and then the sample was tested for the value of shear stress (the value after the three days' operation) and the current density (the value after the three days' operation) to evaluate the durability.
  • the results are shown in Table 4.
  • the electrorheological fluids (7) to (14) of this invention were endowed with structural viscosity and therefore were excellent in dispersion stability, redispersibility, and fluidity as evinced by the fact that the values of ⁇ 2 were not more than 0.2 Pa ⁇ s and the Ti values were in the range of satisfying the condition of the formula (1).
  • the fluids (7) to (9), (11) and (16) to (18) for comparison were deficient in dispersion stability because of small Ti values.
  • the fluids (10), (12) to (15), and (17) were deficient in redispersibility and fluidity because their values of ⁇ 2 exceeded 0.2 Pa ⁇ s.

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Claims (15)

  1. Elektrorheologisches Fluid, welches eine dispergierte Phase, die aus dielektrischen Partikeln geformt ist, ein dispergierendes Medium in der Form eines elektrisch isolierenden Öls und ein Polymergemisch umfasst, bei welcher dass Polymergemisch eine beachtliche Unlöslichkeit im elektrisch isolierenden Öl aufweist und eine Struktureinheit (A), die eine Siliciumkomponente enthält, und eine Struktureinheit (B) besitzt, die eine Kette enthält, die eine dispergierte Phase absorbiert, und bei welcher das Polymergemisch dadurch erhältlich ist, dass man ein Polymer, das ein Polysiloxan enthält, mit organischen oder anorganischen Partikeln mischt, die im isolierenden Öl im wesentlichen unlöslich sind, und
    wobei das Fluid eine Viskosität, gemessen bei 25 °C ohne Anlegen eines elektrischen Feldes, von nicht mehr als 0,2 Pa.s bei einer Scherrate von 33/o und eine strukturelle Viskosität aufweist, die der Bedingung der Formel (1) genügt: 0,01 Pa.s ≦ η1 - η2 ≦ 0,5 Pa.s wobei η1 die Viskosität bei einer Scherrate von 3,3/s ist, die bei 25 °C ohne Anlegen eines elektrischen Feldes gemessen wird, und η2 die Viskosität bei einer Scherrate von 33/s ist, die bei 25 °C ohne Anlegen eines elektrischen Feldes gemessen wird.
  2. Elektrorheologisches Fluid, wie in Anspruch 1 beansprucht, dadurch gekennzeichnet, dass die dielektrischen Partikel einen mittleren Partikeldurchmesser im Bereich von 1 bis 50 µm haben.
  3. Elektrorheologisches Fluid, wie in Anspruch 1 oder Anspruch 2 beansprucht, dadurch gekennzeichnet, dass die Menge des dispergierenden Mediums im Bereich von 50 bis 500 Gewichtsteile, bezogen auf 100 Gewichtsteile der dispergierten Phase, ist.
  4. Elektrorheologisches Fluid, wie in irgendeinem vorrangehenden Anspruch beansprucht, dadurch gekennzeichnet, dass das elektrisch isolierende Öl ein isolierendes Öl, das ein Siliciumelement enthält, oder ein isolierendes Öl ist, das ein Fluorelement enthält.
  5. Elektrorheologisches Fluid, wie in irgendeinem vorrangehenden Anspruch beansprucht, dadurch gekennzeichnet, dass das Polymergemisch in einer Menge im Bereich von 0,01 bis 6 Gewichtsteile, bezogen auf 100 Gewichtsteile der dispergierten Phase, vorliegt.
  6. Elektrorheologisches Fluid, wie in irgendeinem vorrangehenden Anspruch beansprucht, dadurch gekennzeichnet, dass das Polymergemisch ein Gemisch (1) ist, welches dadurch erhältlich ist, dass man Partikel (I) die im wesentlichen im elektrisch isolierenden Öl unlöslich sind, mit einem Polymer (II), das ein Polysiloxan enthält, mischt, und das Polymer (II) als Struktureinheit (A), die eine Siliciumverbindung enthält, eine Struktureinheit (A-1), die ein Polysiloxan enthält und die durch die allgemeine Formel (2) dargestellt wird:
    Figure 00810001
    wobei A -COO- oder eine Phenylengruppe ist, wobei R1 ein Wasserstoffatom oder eine Methylgruppe ist, wobei R2 eine Alkylengruppe mit 1 bis 6 Kohlenstoffatomen ist, wobei R3 bis R13 unabhängig eine Arylgruppe, eine Alkylgruppe mit 1 bis 6 Kohlenstoffatomen oder eine Alkoxygruppe mit 1 bis 10 Kohlenstoffatomen sind, wobei a eine zufällige ganze Zahl ist, wobei c und d unabhängig eine ganze Zahl im Bereich von 0 bis 10 sind, wobei b eine ganze Zahl im Bereich von 0 bis 200 ist, und als Struktureinheit (B), die eine Kette enthält, die eine dispergierte Phase absorbiert, eine Struktureinheit (B-1), die eine Alkylenoxidkette enthält und die durch die allgemeine Formel (3) dargestellt wird:
    Figure 00810002
    wobei B -COO- oder eine Phenylengruppe ist, wobei R14 ein Wasserstoffatom oder eine Methylgruppe ist, wobei R15 eine Alkylengruppe mit 2 bis 4 Kohlenstoffatomen ist, wobei R16 ein Wasserstoffatom oder eine Alkylgruppe ist, wobei e eine zufällige ganze Zahl ist und wobei f eine ganze Zahl im Bereich von 2 bis 100 ist,
    eine Struktureinheit (B-2), die ein Kette enthält, die ein Stickstoffatom enthält, die durch die allgemeine Formel (4) dargestellt wird:
    Figure 00820001
    wobei D
    Figure 00820002
    oder ein Substituent ist, der einen Heterocyclus enthält, der Stickstoff enthält, wobei R17 ein Wasserstoffatom oder eine Methylgruppe ist, wobei R18 ein Wasserstoffatom oder eine Alkylgruppe ist, wobei g eine zufällige ganze Zahl ist und wobei h eine ganze Zahl im Bereich von 2 bis 6 ist,
    und/oder eine Struktureinheit (B-3) hat, die eine Kohlenwasserstoffkette enthält und die durch die allgemeine Formel (5) dargestellt wird:
    Figure 00820003
    wobei E -COO- oder eine Phenylengruppe ist, wobei R19 ein Wasserstoffatom oder eine Methylgruppe ist, wobei R20 eine Alkylgruppe mit 1 bis 30 Kohlenstoffatomen ist und wobei i eine zufällige ganze Zahl ist.
  7. Elektrorheologisches Fluid, wie in Anspruch 6 beansprucht, dadurch gekennzeichnet, dass R20 von B-3 eine Alkylgruppe mit 8 bis 30 Kohlenstoffatomen ist.
  8. Elektrorheologisches Fluid, wie in Anspruch 6 oder Anspruch 7 beansprucht, dadurch gekennzeichnet, dass das Verhältnis der Partikel (I) dem Polymer (II), das ein Polysiloxan enthält, 100 : 0,1 - 100 Gewichtsteile ist.
  9. Elektrorheologisches Fluid, wie in Anspruch 6 bis Anspruch 8 beansprucht, dadurch gekennzeichnet, dass im Gemisch (1) das Polymer (II), das ein Polysiloxan enthält, auf der Oberfläche der Partikel (I) befestigt ist.
  10. Elektrorheologisches Fluid, wie in irgendeinem der Ansprüche 6 bis 9 beansprucht, dadurch gekennzeichnet, dass die Partikel (I) durch eine chemische Bindung mit dem Polymer (II), das ein Polysiloxan enthält, verbunden sind.
  11. Elektrorheologisches Fluid gemäß irgendeinem der Ansprüche 8 bis 10, wobei das Polymer (II), das ein Polysiloxan enthält, dadurch erhältlich ist, dass man eine Monomermischung (X) polymerisiert, die ein Makromer (am), das Silicium enthält und das durch die allgemeine Formel (6) dargestellt wird:
    Figure 00830001
    wobei F -COO- oder eine Phenylengruppe ist, wobei R21 ein Wasserstoffatom oder eine Methylgruppe ist, wobei R22 eine Alkylengruppe mit 1 bis 6 Kohlenstoffatomen ist, wobei R23 bis R33 unabhängig eine Arylgruppe, eine Alkylgruppe mit 1 bis 6 Kohlenstoffatomen oder eine Alkoxygruppe mit 1 bis 10 Kohlenstoffatomen sind,
    wobei j und k unabhängig eine ganze Zahl im Bereich von 0 bis 10 sind und wobei 1 eine ganze Zahl im Bereich von 0 bis 200 ist,
    und mindestens ein Monomer (b), das eine Kette enthält, die eine dispergierte Phase absorbiert, ausgewählt aus einem Makromer (bm-1), das eine Alkylenoxidkette enthält und das durch die allgemeine Formel (7) dargestellt wird:
    Figure 00830002
    wobei G -COO- oder eine Phenylengruppe ist, wobei R34 ein Wasserstoffatom oder eine Methylgruppe ist, wobei R35 eine Alkylengruppe mit 2 bis 4 Kohlenstoffatomen ist, wobei R36 ein Wasserstoffatom oder eine Alkylgruppe ist und wobei m eine ganze Zahl im Bereich von 2 bis 100 ist,
    einem Monomer (b-2), das eine Stickstoff-enthaltende Kette enthält und das durch die allgemeine Formel (8) dargestellt wird:
    Figure 00840001
    wobei J
    Figure 00840002
    oder ein Substiuent ist, der einen Stickstoff-enthaltenden Heterocyclus enthält, wobei R37 ein Wasserstoffatom oder eine Methylgruppe ist, wobei R38 ein Wasserstoffatom oder eine Alkylgruppe ist und wobei r eine ganze Zahl im Bereich von 2 bis 6 ist,
    und einem Monomer (b-3), das eine Kohlenwasserstoffkette enthält und das durch die allgemeine Formel (9) dargestellt wird:
    Figure 00840003
    wobei K -COO- oder eine Phenylengruppe ist, wobei R39 ein Wasserstoffatom oder eine Methylgruppe ist und wobei R40 eine Alkylgruppe mit 1 bis 30
    Kohlenstoffatomen ist,
    als wesentliche Komponenten und ein optionales Monomer (c) umfasst.
  12. Elektrorheologisches Fluid, wie in Anspruch 11 beansprucht, dadurch gekennzeichnet, dass R40 von b-3 eine Alkylgruppe mit 8 bis 30 Kohlenstoffatomen ist.
  13. Elektrorheologisches Fluid, wie in Anspruch 11 oder Anspruch 12 beansprucht,
    dadurch gekennzeichnet, dass die Monomermischung (X) 10 bis 90 Gew. % des Monomers (am), das Silicium enthält, 10 bis 90 Gew. % des Monomers (b), das eine Kette enthält, die dispergierte Phase absorbiert, und 0 bis 80 Gew. % des optionalen Monomers (c) enthält, unter der Vorraussetzung, dass die Summe der verwendeten Monomere 100 Gew. % ist.
  14. Elektrorheologisches Fluid, wie in irgendeinem der Ansprüche 6 bis 13 beansprucht, dadurch gekennzeichnet, dass das Gemisch (1) dadurch erhältlich ist, dass man ein polymerisierbares Monomer (α) in der Gegenwart des Polymers (II), das ein Polysiloxan enthält, dispersionspolymerisiert, um die Partikel (I) herzustellen, die in einem elektrisch isolierenden Öl im wesentlichen unlöslich sind.
  15. Elektrorheologisches Fluid, wie in irgendeinem der Ansprüche 6 bis 13 beansprucht, dadurch gekennzeichnet, dass das Gemisch (1) dadurch erhältlich ist, dass man ein polymerisierbares Monomer (α) in einem wässrigen Medium in der Gegenwart des Polymers (II), das ein Polysiloxan enthält, emulsionspolymerisiert, um die Partikel (I) herzustellen.
EP19940304455 1993-07-30 1994-06-20 Elektrorheologische Flüssigkeit Expired - Lifetime EP0636683B1 (de)

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US4992192A (en) * 1989-04-21 1991-02-12 Hercules Incorporated Electrorheological fluids
EP0432601B1 (de) * 1989-12-14 1996-05-15 Bayer Ag Elektroviskose Flüssigkeiten auf der Basis dispergierter Polyether
DE4119670A1 (de) * 1991-06-14 1992-12-17 Bayer Ag Elektroviskose fluessigkeit auf basis von polyetheracrylaten als disperse phase
EP0529166A1 (de) * 1991-08-29 1993-03-03 Nippon Shokubai Co., Ltd. Elektrorheologische Flüssigkeiten
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