EP0583763A2 - Electrorheological fluid lased on synthetic lamellar silicate - Google Patents

Abstract

Electrorheological fluids have been developed which essentially contain an aluminium-free metal silicate hydrate possessing a sheet structure, a dispersant and an inert aprotic dispersion medium. The metal silicate hydrate is preferably of the kenyaite, magadiite and/or kanemite type. The dispersion medium is preferably a silicone oil having a viscosity range from 0.5 to 1,000 mPas or a mineral oil or a paraffin oil having a viscosity range from 0.1 to 1,000 mPas. The metal silicate hydrate is added to the electrorheological fluid in a concentration of from 1 to 50% by weight.

Description

Electrorheological fluids (ER fluid), so called to clearly differentiate them from the known electroviscous phenomena in charged colloids (TC Jordan, MT Shaw, IEEE Trans. Electr. Insul., Vol. 24, No. 5, 1989, 849 ff) dispersions of finely divided, polarizable solids in inert (hydrophobic) and electrically non-conductive liquids, the flow behavior of which changes greatly in the electric field.

Sufficiently strong electric fields lead both to a change in viscosity and to the formation of a clear yield point, i.e. if a limit shear force is undershot, the fluid behaves as an elastic solid. From a rheological point of view, the fluids change from simple liquids (Newtonian systems) to pseudoplastic liquids (Bingham bodies).

This behavior, which has been known since the 1940s (US Pat. Nos. 2,417,850 and 3,047,507), can be achieved on suitable fluids with both DC and AC voltage (TW Martinek US Pat. No. 4,502,973). It is technically desirable to achieve a low to negligible current flow. The electrorheological effect reacts to changes in the electrical voltage level in extremely short times, typically with time constants in the millisecond range. Technically, these systems, known as "Smart Fluids", can be used for the transmission and damping of large forces with the help of low electrical power in short times, such as in dampers, vibrators, couplings, as hydraulic valves and active chassis. A significant advance in the transition from conventional passive systems to electrorheological systems is due to the electrical adjustment of the viscosity flow limit to the current state of motion possible. Such active, feedback systems are increasingly required to cope with the technical problems of moving systems.

The technical use of an ER fluid requires, in addition to a sufficient ER effect, high temperature stability and chemical resistance of the fluid, low electrical conductivity, negligible electrophoretic effects, low abrasiveness and sufficient stability against shear and sedimentation. In any case, the fluid must be able to be redispersed well even after standing for a long time and must not show any swelling or dissolving on contact with elastomeric materials.

For the larger part of the ER fluids, which represent the prior art, the disperse phase consists of polyelectrolytes (US Pat. No. 3,970,573,3047507,492192,494198), zeolites and silica gels (DE 3517281 A1, DE 356934 A1) or else exotic inorganic compounds such as Li -Hydrazinium sulfate (US 4,772,407), the effect of which is achieved by loading the disperse phase with considerable amounts of water (up to 20%). The water content enables the ionic conductivity to be increased by solvation of the existing ions and surface charges and thus produces the polarizability of the disperse particles that is necessary for the ER effect. The particles polarized in the E field agglomerate due to the dipole-dipole interaction and generate an increased viscosity, and hydrogen bonding also plays a role. The effect is reversible. Such water-containing systems tend to electrolysis, show low chemical stability and are often corrosive. In addition, the usable temperature range in which these ER fluids can be reversibly used is limited to below 110 ° C.

Previous electrorheological fluids based on coated metallically conductive particles, polarizable or semiconducting polymers and anhydrous aluminum silicates suffer from insufficient dispersion stability, too small ER effects, technically unacceptable conductivities and, with the exception of organic materials, from the high material-specific abrasiveness.

The use of semiconducting organic materials fails due to the instability (redox sensitivity) and the price of the previously known materials. So no marketed products are currently known.

The task was therefore to develop an inexpensive and efficient ER fluid that had high electroactivity and low electrical conductivity in the necessary, technically relevant, temperature range (up to 140 ° C) and also had good dispersion stability and low abrasiveness. Various synthetic layered silicates were presented in pure form as anisotropic, dopable, highly polarizable dielectrics and, if appropriate, dispersed in inert oils using various dispersing aids.

Surprisingly, it has now been found that when aluminum-free metal silicate hydrates with a layer structure are used, the above-mentioned requirements are met.

The invention thus relates to electrorheological fluids containing essentially aluminum-free metal silicate hydrates with a layer structure, a dispersing aid and an inert aprotic dispersion medium.

The aluminum-free metal silicate hydrates are essentially ternary systems containing metal oxide M₂O (M preferably Na), silicon dioxide SiO₂ and water H₂O. For the ER fluids according to the invention, aluminum-free metal silicate hydrates, preferably those of the Kenyaite, Magadiite and Kanemite type, are used. The SiO₂ / M₂O molar ratio is 2-10 for kanemite, 8 to 29 for magadiite and> 19 for kenyaite. The water content before the drying step is 0 to
30% by weight.

In the ER fluids according to the invention, metal, ammonium, alkylammonium and arylammonium doped layered silicates and mixtures of the different types of structure and doping can also be used.

The metal silicate hydrates are used in concentrations of 1 to 50% by weight, preferably 15 to 40% by weight, based on the total weight of the electrorheological fluid.

The chemically pure production of the metal silicate hydrates is carried out by the hydrothermal process (DE-OS 3400130, DE-OS 3400132, DE-OS 3521227). The acid form of the layered silicates is obtained by ion exchange with mineral acids and new doped silicate hydrates are obtained by redoping with suitable metal salt or ammonium salt solutions. (DE-OS 312300, F. Wolf, W. Schwieger, Z. Anorg. General Chemistry, 457 (1979), 224).

The dispersing agents listed below and their mixtures of neutral and non-neutral surfactants and betaines are preferably used:

Cationic surfactants:

• Dialkyldimethylammonium salts, alkyl chain C₈-C₂₂, preferably C₁₆-C₁₈
• Alkyltrimethylammoniumsalze, alkyl chain C₈-C₁₈, preferably C₁₆-C₁₈
• Oxyethylated amines RN (C₂H₄O) _x H (C₂H₄O) _y H, alkyl chain C₈-C₁₈, $\text{x + y ≦ 25}$
  
  and their ammonium salts.
• Perfluoroalkyltrimethylammonium salts, alkyl chain C₈-C₁₈
• Poly-diallyldimethylammonium salts

Nonionic surfactants

• AB, ABA, BAB block copolymers of a polydimethylsiloxane block (A) and a polyoxyalkylene block (B) alkylene C length 2,3,4
• Polydimethylsiloxane block are grafted onto the polyoxyalkylene blocks
• Polyether (MW <10⁷)
• Esters and half-esters of alkanephosphonic and 1-hydroxy-1,1-alkanediphosphonic acids, alkane residues C₈-C₁₈

Anionic surfactants

• Dialkylnaphthalenesulfonic acid with formaldehyde condensed as Na salt alkyl chain: C₈-C₁₈
• Diphenyl ether sulfonic acid with formaldehyde condensed as triethanolamine salt
• 1 mol of 3-core nonylphenol novolak + 10 to 20 mol of ethylene oxide as triple sulfosuccinic acid half-Na salt
• 1 mol 7-core nonylphenol novolak + 10 to 120 mol ethylene oxide
• 1 mol 7-core nonylphenol novolak + 10 to 120 mol ethylene oxide as a mixed ester of benzoic acid and maleic acid with attached Na sulfite as Na salt
• Cross-linked copolymers of acrylic acid and acrylamide
• Cross-linked polyacrylates
• Copolymers of acrylamide and 2-acrylamido-2-methylpropanesulfonic acid
• Copolymer of 2-acrylamido-2-methylpropanesulfonic acid and methacrylic amido-N, N-dimethylmethylamine
• 1-hydroxyalkane-1,1-diphosphonate as alkylammonium, dialkylammonium, Na and Li salts, alkane radicals: C₈-C₁₈, alkyl radicals in the ammonium ion C₂-C₁₈
• Alkane phosphonate as alkylammonium, dialkylammonium, Na, and Li salts, alkane radicals: C₈-C₁₈, alkyl radicals in the ammonium ion C₂-C₁₈
• N-oleyl sarcosine Na
• N-oleyl methyl taurine Na
• Alkyl oxyalkylene sulfonic acid, alkyl radical: C₈-C₁₈, 2-7 oxyalkylene units
• 2,4,6-tributyl-1-polyethersulfonic acid benzene, 2-7 oxyalkylene units
• p-Alkylbenzenesulfonate, alkyl radical: C₈-C₁₈
• Dialkylmethanesulfonic acids Sum of the C atoms of the alkyl radicals is 14.
• Sodium o-oleyl isothionate
• Alkyl polyether sulfonates, alkyl radical C₈-C₁₄, 2-7 oxyalkylenes
• Alkyl polyether carboxylic acids, alkyl radical C₈-C₁₄, 2-7 oxyalkylenes
• Alkylaminopropane phosphonates
• Copolymers of acrylic acid and 10% by weight
  Diallylamino-methylenephosphonic acid
  Diallylamino-methylene diphosphonic acid
  Diallylamino-methanediphosphonic acid tetraethyl ester
  Allylamino-bis (methylenephosphonic acid)
  Diallylamino methylenephosphonic acid diethyl ester

Betaine

• Betainsalz aus der Substitutionsreaktion von Monochloressigsäure und Alkyldimethylaminen Alkylreste C₈-C₁₈
• Betainsalz aus der Substitutionsreaktion von Monochloressigsäure und Alkylamidopropyl-N,N-dimethylamin Alkylreste C₆-C₁₈
• Betainsalz aus der Substitutionsreaktion von Monochloressigsäurealkylester und Alkyldimethylaminen, Alkylreste in beiden Fällen C₆-C₁₈
• Betainsalz aus der Substitutionsreaktion von Monochloressigsäurealkylester und 1-Hydroxyethyl-2-alkylimidazol, Alkylreste in beiden Fällen C₆-C₁₈

Als Basisöle können inerte aprotische Dispersionsmedien eingesetzt werden. Bevorzugt werden Silikonöle in einem Viskositätsbereich von 0.5 bis 1000 mPas und Mineral- bzw. Paraffinöle in einem Viskositätsbereich von 0.1 bis 5000 mPas verwendet.

• Betaine salt from the substitution reaction of monochloroacetic acid and alkyldimethylamines alkyl radicals C₈-C₁₈
• Betaine salt from the substitution reaction of monochloroacetic acid and alkylamidopropyl-N, N-dimethylamine alkyl radicals C₆-C₁₈
• Betaine salt from the substitution reaction of alkyl monochloroacetate and alkyldimethylamines, alkyl radicals in both cases C₆-C₁₈
• Betaine salt from the substitution reaction of alkyl monochloroacetate and 1-hydroxyethyl-2-alkylimidazole, alkyl radicals in both cases C₆-C₁₈

Inert aprotic dispersion media can be used as base oils. Silicone oils in a viscosity range from 0.5 to 1000 mPas and mineral or paraffin oils in a viscosity range from 0.1 to 5000 mPas are preferably used.

The following processes proved to be favorable for the production of ER fluids:

Method 1)

The layer-structured metal silicate hydrates are in an alkaline (pH = 8-14), aqueous solution of dispersing aids with a content of 2 to 30% by weight, preferably 2 to 10% by weight, of dispersing aids based on the amount of silicate used (silicate / solution 1 : 2) dispersed and stirred at temperatures from 60 to 80 ° C for three to ten hours.

After the aqueous phase has been separated off by filtration or centrifugation, the moist solid is dried at temperatures from 80 to 180 ° C., preferably at 120 to 140 ° C.

After grinding and, if necessary, redispersion in silicone or mineral oil, the resulting mixture is ground in a ball mill.

Method 2)

After drying the layered silicate between 120 and 240 ° C, preferably 140 ° C or 180 ° C, until the weight is constant, the layered silicate is dispersed in silicone or mineral oil with 2 to 30% by weight of dispersing agent based on the amount of silicate and stirred for several hours. The dispersion is then ground in a ball mill.

Method 3)

Corresponds to method 2 only without a drying step.

Method 4)

The layered silicate is dried analogously to method 2. It is dispersed in aprotic, non-polar solvents with a dispersing agent (batches 2 to 30% by weight of the layered silicate) and stirred for several hours at temperatures corresponding to 60 to 80% of the boiling point of the solvent. The solvent is separated off by filtration or centrifugation, the remaining solid is dried, ground again and dispersed in silicone or mineral oil. This oil dispersion is then ground in a ball mill.

The following advantages are achieved with the invention:
Aluminum-free metal silicate hydrates with a layer structure that have been dried to constant weight, in particular metal-doped silicate hydrates, surprisingly show significantly greater electrorheological effects than those with different types of dielectric materials with a very low basic viscosity. The fluids are anhydrous and also active above 110 ° C. The ER effect increases with temperature, while the conductivity remains low. Electrical power consumption of 10 to 20 mW per square centimeter electrode surface at 20 ° C and 80 to 120 mW / cm² at 140 ° C are typical values.

In a further comparison to ER fluids based on layered silicates containing aluminum, the fluids according to the invention are free-flowing, not thixotropic and what is very important is dispersion-stable. In contrast to the ER effects that are too small, ER fluids with alumosilicates as dielectric show technically unacceptable conductivities and high material-specific abrasiveness, which destroys components in which the fluid is to be used.

Due to the purity of the mineral materials used in comparison to naturally occurring aluminosilicates, the structure of precisely defined ER fluids is given, which is the reason for the reproducible production and the associated defined setting of rheological properties.

The generation of pseudoplastic properties in the E-field-free state by doping the layered silicates and coating them with surface-active substances also enables very good electromechanical properties at high shear rates, which means that these fluids are used in comparison to fluids based on aluminosilicates for torque transmitters and couplings becomes possible.

It also applies to the ER fluids produced in the silicone oil dispersant that they are compatible with rubber-like materials and non-toxic (i.e. physiologically harmless).

Examples Characterization of ER fluids

The ER fluids are examined in an ER rotary rheometer from Haake, Karlsruhe with the type designation CV20 and the measuring systems PQ20, PG45, SV0.5ER, SV1.0ER, SV0.2ER and DA45, with gap widths of 0.2, 0, 5 or 1 mm and field strengths up to 10 kV are used. Static and dynamic measurements are evaluated and direct or alternating voltage is applied. A rheo controller RC20 and a rotovisko RV20 from the same company are used for data acquisition. Comparable apparatus and the measurement and evaluation methods are described in detail in the literature (cf. W. Winslow, J. Appl. Phys. 20 (1949) 1137, RT Bonnecaze, JF Brady, J. Rheol. 36 (1) 1992) .

In the tables, compared to the prior art, the structure of the fluids, i.e. used dielectric in base oil with dispersing agent and viscosity with and without field and the gain factor at 100 s 100¹ as well as the static yield point for characterization.

• 1. Inertes Dispergiermedium (bei 25 °C):
  • a) Polydimethylsiloxan (AK 10 Wacker)

    Viskosität:

    9,4 mPas

    Dichte

    0,930 - 0,933 g/cm³

  • b) Polymethylphenylsiloxan (TR 50 Wacker)

    Viskosität:

    50 ± 5 mPas

    Dichte:

    0,955 - 0,957 g/cm³

  • c) Mineralöl

    Viskosität:

    7,15 mPas

    Dichte:

    0,8399 g/cm³

  • d) Paraffinöl

    Viskosität:

    254 mPas

    Dichte:

    0,873 g/cm3

• 2. Dispergierte Festkörper
  • a) Schichtsilikat Kenyaittyp
  • b) Schichtsilikat Magadiittyp
  • c) Schichtsilikat Kanemittyp
  • d) Mischung a - c
  • e) Ionengetauschtes Schichtsilikat Typ a - c
• 3. Dispergierhilfsmittel

The first three formulations in the exemplary embodiments correspond to the comparative samples, the following examples to the ER fluids according to the invention, it being made clear that different types of composition of the disperse phase and different dispersing agents (see Examples 4-23) lead to dispersions with good ER properties, especially good effect at temperatures above 110 ° C.

• 1. Inert dispersion medium (at 25 ° C):
  • a) polydimethylsiloxane (AK 10 Wacker)

    Viscosity:

    9.4 mPas

    density

    0.930-0.933 g / cm³

  • b) polymethylphenylsiloxane (TR 50 Wacker)

    Viscosity:

    50 ± 5 mPas

    Density:

    0.955-0.957 g / cm³

  • c) mineral oil

    Viscosity:

    7.15 mPas

    Density:

    0.8399 g / cm³

  • d) paraffin oil

    Viscosity:

    254 mPas

    Density:

    0.873 g / cm3

• 2. Dispersed solids
  • a) Layered silicate Kenyaite type
  • b) Layered silicate magadiite type
  • c) Layered silicate type Kanemite
  • d) mixture a - c
  • e) Ion-exchanged layered silicate type a - c
• 3. Dispersing agents

Cationic surfactants:

• Distearyldimethylammonium chloride
• Perfluorostearyltrimethylammonium iodide

Nonionic surfactants

• AB block copolymers from a polydimethylsiloxane block (A) and a polyoxyalkylene block (B), alkylene C length 2, (Wacker retail product VP1633),

Anionic surfactants

• Dioctylnaphthalenesulfonic acid with formaldehyde condensed as Na salt
• 1 mol 7-core nonylphenol novolak + 10 to 120 mol ethylene oxide
• 1 mol 7-core nonylphenol novolak + 10 to 120 mol ethylene oxide as a mixed ester of benzoic acid and maleic acid with attached Na sulfite as Na salt
• Cross-linked Na polyacrylate
• 1-Hydroxy-dodecane-1,1-diphosphonate as the dibutylammonium salt
• Decane phosphonate as Na salt
• 2,4,6-tributyl-1-polyethersulfonic acid benzene, 7 oxyalkylene units
• p-dodecylbenzenesulfonates
• Alkyl polyether sulfonates, alkyl radicals C₁₂: C₁₃: C₁₄ ratio = 30: 1: 5, 7 oxyalkylenes
• Copolymers of acrylic acid and 10% by weight of diallylaminomethane diphosphonic acid tetraethyl ester

Betaine

• Betaine salt from the substitution reaction of monochloroacetic acid and stearyldimethylamine
• Betaine salt from the substitution reaction of stearyl monochloroacetate and 1-hydroxyethyl-2-stearylimidazole

Comparative Example 1

In accordance with Example 3 of patent application EP 0361106 A1, the ER fluid based on a pitch was produced. Dispersing aids were made analogously the patent application is not used.

Comparative Example 2

The ER fluid was developed by Advanced Fluid Systems Ltd. made available. It is an ERF fluid based on a lithium polyacrylate according to UK patent 1570234.

Comparative Example 3

Pattern according to patent application DE 3536934 A1 with 40% by weight aluminum silicate as the disperse phase and ^(R) Baysilon as a dispersing agent (5% by weight), prepared in accordance with Example 4.

Example 4

5 g of dispersing aid (dioctylnaphthalene sulfonic acid condensed with formaldehyde as Na salt) are dissolved in 1 l of water. 100 g of synthetic kenyaite is dispersed into this solution in a thermostated container using a Pendraulik dissolver LD50. The temperature is kept at 70 ° C. for 30 minutes. The suspension is centrifuged and the residue is dried at 140 ° C. in vacuo to constant weight. The material coated in this way is then ground and sieved. The fraction with particle sizes <32 µm is slurried in 70% by weight silicone oil (AK10) and homogenized in several grinding steps in a Fryma bead mill, type Co Ball Mill, to a fineness of 1 - 2 µm d₅₀. The dispersion thus obtained is not thixotropic, free-flowing and non-settling.

Example 5

Following the production method given in Example 4, an ER fluid is produced with synthetic magadiite as a solid and a mixture of a 7-core nonylphenol novolak and ethylene oxide as a dispersing aid.

Example 6

Preparation analogous to Example 4 with 1-decanephosphonic acid as a dispersing aid.

Example 7

Preparation analogous to Example 4 with block (polysiloxane) polyoxyalkylene (VP 1633 Wackerchemie) as a dispersing aid.

Example 8

Preparation analogous to Example 4 with a quaternary ammonium compound (betaine from stearyl monochloroacetate + stearyldimethylamine) as a dispersing aid.

Example 9

Preparation analogous to Example 4 with a mixture of synthetic kenyaite / magadiite (70:30) and Na polyacrylate (MW 10⁶) as a dispersing aid.

Example 10

Preparation analogous to Example 9 with a dibutylammonium salt of 1-oxy-dodecane-1,1-diphosphonate as a dispersing aid.

Example 11

Production of an ER fluid with synthetic Kanemit as a dielectric material and Baysilon OF (Bayer commercial product) as a dispersion aid. The formulation is based on Example 4.

Example 12

Preparation analogous to Example 4 with a 7-core nonylphenol novolak with ethylene oxide as a mixed ester of benzoic acid and maleic acid with added Na sulfite as a dispersing aid.

Example 13

Production of an ER fluid with a mixture of synthetic kenyaite / magadiite (cf. Example 9) and a distearyldimethylammonium chloride as a dispersing aid. An aqueous preparation step was dispensed with (cf. Example 4) and the dispersion was prepared directly in the bead mill with 16 passes.

Example 14

Production analogous to Example 13 with mineral oil as the base liquid. Dispersing aid is a dioctylnaphtalinsulfonic acid condensed with formaldehyde as Na salt.

Example 15

Preparation analogous to Example 4 with Li-ion-exchanged kenyaite and 1-oxy-dodecane-1,1-diphosphonate as a dispersing aid.

Example 16

Preparation analogous to Example 4, but instead of kenyaite, a magadiite was used with dibutylammonium p-dodecylbenzenesulfonate as a dispersing aid

Example 17

Preparation analogous to Example 16 with calcium p-dodecylbenzenesulfonate as a dispersing aid

Example 18

Preparation analogous to Example 16 with paraffin oil as base oil and calcium p-dodecylbenzenesulfonate as surfactant

Example 19

Preparation analogous to Example 16 with a dodecyl polyether sulfonate and 7 oxyethylene units as the surfactant

Example 20

Preparation analogous to Example 16 with a copolymer of acrylic acid and 10% by weight tetraethyl diallylamino-methanediphosphonic acid as surfactant

Example 21

Preparation analogous to Example 16 with a copolymer of acrylic acid and 10% by weight dialylamino-methanediphosphonic acid tetraethyl ester as dispersing aid and paraffin oil as base oil

Example 22

Preparation according to Example 16 with 2,4,6-tributyl-1-polyethersulfonic acid benzene, which contains 7 oxyethylene units, as a surfactant

Example 23

520 g of magadiite is dried to constant weight at 180 ° C. Then it is introduced into 1 l of a solution of silicone oil AK10 and the betaine from monochloroacetic acid alkyl ester and 1-hydroxyethyl-2-alkylimidazole and stirred for 3 hours with a Pendraulik dissolver LD50 at 90 ° C. In this case, the amount of betaine is 5% by weight of the amount of layered silicate used. This oil suspension is then ground in several passes in a Co-Ball-Mill MS12.

Example 24

Preparation analogous to Example 4 with distearyldimethylammonium chloride as a dispersing aid.

Example 25

Preparation analogous to Example 4 with perfluorostearyltrimethylammonium iodide as a dispersing aid.

Hierbei ist τ die gemessene Schubspannung und D die vorgegebene Scherrate. Der Indix E steht für Meßergebnisse im elektrischen Feld, der Index 0 for solche ohne Feld. Diese Größe wurde optimiert.It is essential for the assessment of an ER fluid to determine the relative power consumption under voltage compared to the field-free state.

Here τ is the measured shear stress and D is the specified shear rate. The Indix E stands for measurement results in an electrical field, the index 0 for those without a field. This size has been optimized.

From the resulting curves, the ratio of the necessary mechanical energy to be dissipated can be seen with and without an electric field at different shear rates.
This size is essential for the design of technical components.

) in Abhängigkeit der Scherrate bei verschiedenen Temperaturen und konstanter Feldstärke dar.Figures 1 and 3 show the relationship between the measured shear stress as a function of the electric field strength and the given shear rate. Figures 2, 4, 5 and 6 show the relative power consumption of the ER fluids ( $\text{Performance = product of τ and D}$

) depending on the shear rate at different temperatures and constant field strength.

Figure 7 shows a new electrorheological phenomenon. When an electric field is applied, the viscosity of the suspension drops below that of the suspension without field for shear rates> 5 s⁻¹. When the electrical field is switched off, the viscosity returns to its original value. We call this phenomenon a negative electrorheological effect.

Claims (6)

Electrorheological fluid, essentially containing an aluminum-free metal silicate hydrate with a layer structure, a dispersing aid and an inert aprotic dispersion medium. Electrorheological fluid according to claim 1, characterized in that the aluminum-free metal silicate hydrate is a silicate hydrate of the Kenyaite type of the Magadiite type and / or of the Kanemite type. Electrorheological fluid according to Claim 1, characterized in that the inert dispersion medium is a silicone oil in a viscosity range from 0.5 to 1000 mPas and / or a mineral oil and / or paraffin oil in each case in a viscosity range from 0.1 to 5000 mPas. Electrorheological fluid according to claim 1, characterized in that the dispersing aid is a cationic surfactant, an anionic surfactant, a nonionic surfactant and betaine. Electrorheological fluid according to one or more of claims 1 to 3, characterized in that the metal silicate hydrates are doped with metal, ammonium, alkyl ammonium and aryl ammonium. Electrorheological fluid according to claim I, characterized in that the metal silicate hydrates are used in concentrations of 1-50% by weight, preferably 15-40% by weight, based on the total weight.

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