EP0432601A1 - Electroviscous fluids based on dispersed polyethers - Google Patents

Electroviscous fluids based on dispersed polyethers Download PDF

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EP0432601A1
EP0432601A1 EP90123063A EP90123063A EP0432601A1 EP 0432601 A1 EP0432601 A1 EP 0432601A1 EP 90123063 A EP90123063 A EP 90123063A EP 90123063 A EP90123063 A EP 90123063A EP 0432601 A1 EP0432601 A1 EP 0432601A1
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electroviscous
weight
evf
component
viscosity
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German (de)
French (fr)
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EP0432601B1 (en
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Udo Dr. Herrmann
Gunther Dr. Penners
Günter Dr. Oppermann
Roland Dr. Flindt
Hans-Horst Dr. Steinbach
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Momentive Performance Materials GmbH
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Bayer AG
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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 invention relates to an electroviscous liquid, the viscosity of which is increased when a voltage is applied.
  • Electroviscous liquids are dispersions of finely divided, hydrophilic solids in hydrophobic and electrically non-conductive oils, whose viscosity changes very quickly and reversibly under the influence of a sufficiently strong electric field from the liquid to the plastic or solid state.
  • the viscosity reacts to both DC electrical fields and AC fields, whereby the current flow through the EVF should be very low. Therefore EVF can be used wherever the transmission of large forces with the help of low electrical power is required, e.g. in couplings, hydraulic valves, shock absorbers, vibrators or devices for positioning and fixing workpieces.
  • the abrasiveness and settling stability of the disperse phase play an important role in practical use.
  • the disperse phase should not sediment as far as possible, but in any case it should be easy to redisperse and should not cause any abrasion even under extreme mechanical stress.
  • the disperse phase consists of organic solids, such as Saccharides (DE 2 530 694), starch (EP 284 268 A2, US 3 970 573), polymers (EP 150 994 A1, DE 3 310 959 A1, GB 1 570 234, US 4 129 513), ion exchange resins (JP 92 278 / 1975, JP 32 221/1985, US 3 047 507), or silicone resins (DE 3 912 888 A1).
  • inorganic materials such as e.g.
  • Li hydrazine sulfate (US 4,772,407 A), zeolites (EP 265 252 A2), silica gel (DE 3,517,281 A1, DE 3,427,499 A1), and aluminum silicates (DE 3,536,934 A1) are used.
  • the electroviscous effect of the substances mentioned is due to the loading of the solids with water. Small amounts of water enable the migration of ions and thereby increase the ionic conductivity or the polarizability of the disperse particles, which is essential for the formation of the effect.
  • the electroviscous effect arises from the fact that the polarized particles of the disperse phase agglomerate in an external electrical field by means of dipole-dipole interactions.
  • Soot-filled bead polymers JP 016 093 or conductive polymers such as polypyrene or polyacetylene (JP 01 260 710) have also been used as replacements for the water-containing ones Phase discussed. However, such systems are expensive or complex to manufacture.
  • the above-mentioned EVF corresponding to the prior art are generally produced by dispersing a solid into a dispersion medium.
  • the viscosity of the resulting suspension depends on the shape and size, or the size distribution of the dispersed particles, and on the solids concentration and the dispersing action of any dispersing agents used. High volume-related solids contents with low viscosity are difficult to achieve.
  • solids which consist of particles with a spherical geometry, the volume fraction of the disperse phase and thus the electroviscous effect can be increased while maintaining the viscosity.
  • the object of the invention was to provide an anhydrous, non-abrasive, sedimentation-stable EVF with good electroviscous properties, which despite high volume fractions of the disperse phase is characterized by a low basic viscosity and low electrical conductivity.
  • the EVF according to the invention contains, dispersed in a non-conductive liquid in pure form or as a reaction product with other substances, 1 to 80% by weight, preferably 1 to 60% by weight, particularly preferably 20 to 60% by weight, of one Polyether.
  • the mixture of polyether and any additives, called template, which is dispersed into the non-conductive liquid during the EVF manufacturing process, should preferably be in liquid form.
  • the template can be chemically modified by adding suitable reagents before, during or after the dispersing step. This modification influences the consistency and, through the partial or complete implementation of the functional groups of the template, the conductivity of the disperse phase in the finished EVF.
  • a suitable dispersing agent is used for the dispersion.
  • the size of the dispersed particles in the EVF according to the invention is 0.05, preferably 0.1 to 200 ⁇ m.
  • the viscosity of the EVF at room temperature is between 0.5, preferably 3, and
  • a preferably liquid template is used for the disperse phase, which contains at least one of the following substances: (I): a linear or branched, optionally functionalized polyether, (II): the reaction product of (I) with mono- or oligofunctional compounds, such as additives such as polyols, aliphatic carboxylic acids or amines, alcohols, esters etc., in different stoichiometric ratios, (III): a mixture of (I) and / or (II) with other non-reactive additives, which in the finished EVF influence the electrical or mechanical properties of the disperse phase, such as conductivity and elastic behavior.
  • Additives (III) with plasticizer function in the sense of Invention are capped low molecular weight polyethers such as bismethylated trimethylpropane or the esters of phthalic acid.
  • linear polyethers examples are polyethylene glycols, polypropylene glycols, polybutylene glycols, statistical ethylene glycol-propylene glycol copolymers or else ethylene glycol-propylene glycol block polymers, such as those e.g. are sold by GAF under the trade name "Pluronic".
  • Branched polyethers are, for example, tris (polypropylene oxide) ⁇ -ol) glycidyl ether or other substances which are obtained by ethoxylation or propoxylation of higher-functionality hydroxy compounds, e.g. Pentaerythritol or 1,1,1-trimethylolpropane can be obtained.
  • the molecular weight of the polyglycols is between 62 and 1,000,000, preferably below 100,000, particularly preferably between 100 and 10,000.
  • the polyglycols can optionally contain functional end groups. Amines, allyl or vinyl groups, or carboxyl groups are examples of such functional end groups.
  • Polyethylene or polypropylene mono- or diamines can be obtained under the trade name "Jeffamin” from the company "TEXACO”. Examples of products containing acrylic groups are the esters of glycols with corresponding acids, e.g. Acrylic acid.
  • the substances mentioned under (II) include e.g. the polyesters common in polymethane chemistry, which are sold by BAYER AG under the trade name "Desmophen".
  • an additive (IV) for example crosslinking agent
  • a crosslinking agent for example crosslinking agent
  • emulsification of the template which by reaction with the functional end groups of the compounds (I), (II) and / or (III) leads to molecular weight build-up in the emulsion droplets, or also to a reduction in the number of functional end groups.
  • viscous or solid particles are formed, the spherical geometry of which is retained during and after the reaction.
  • crosslinkers examples are di- or multifunctional isocyanates with different structures, which are sold, for example, under the trade name "Desmodur” by BAYER AG.
  • Tri- or higher functional Glycol is particularly preferred to use tolylene diisocyanate as a crosslinker.
  • the so-called acetate, amine, benzamide, oxime and alkoxy crosslinkers commonly used in silicone chemistry can also be used for crosslinking.
  • the isocyanate crosslinking agent is preferably used in amounts such that 20 to 100%, preferably up to 80%, of the OH groups of the glycol are reacted. Radical crosslinking systems are suitable for the conversion of allyl or vinyl group-modified compounds of groups (I) to (III).
  • the EVF according to the invention contains the disperse phase (the reaction product from the initial charge and (IV)) to 10 to 85% by weight, but preferably to 40 to 70% by weight.
  • silicone oils such as polydimethylsiloxanes or also polysiloxanes with higher alkyl groups, fluorine-containing siloxanes and liquid methylphenylsiloxanes are used. These can be used alone or in combination of two or more types.
  • the solidification point of the dispersion media is preferably set below -30 ° C, the boiling point above 150 ° C.
  • the viscosity of the oils is between 3 and 300 mm2 / s at room temperature. In general, the low-viscosity oils with a viscosity of 3 to 20 mm2 / s are preferred because they achieve a lower basic viscosity of the EVF.
  • the oil should also have a density that approximately corresponds to the density of the disperse phase.
  • a density that approximately corresponds to the density of the disperse phase.
  • Fluorine-containing siloxanes of the general structure are particularly suitable for producing sedimentation-stable EVF:
  • Suitable dispersants for the disperse phase are surfactants which are soluble in the dispersion medium and which, e.g. are derived from amines, imidazolines, oxazolines, alcohols, glycol or sorbitol.
  • Polymers soluble in the dispersion medium can also be used. Suitable are e.g. Polymers which contain 0.1 to 10% by weight of N and / or OH, and 25 to 83% by weight of C4-C24-alkyl groups and have a molecular weight in the range from 5000 to 1,000,000.
  • the N- and / or OH-containing compounds in these polymers can e.g.
  • Amine, amide, imide, nitrile, 5- to 6-membered N-containing heterocyclic rings, or an alcohol, and the C4-C24-alkyl groups are esters of acrylic or methacrylic acid.
  • N and OH-containing compounds mentioned are N, N-dimethylaminoethyl methacrylate, tert-butylacrylamide, maleimide, acrylonitrile, N-vinylpyrrolidone, vinylpyridine and 2-hydroxyethyl methacrylate.
  • the abovementioned polymeric dispersants generally have the advantage over the low molecular weight surfactants that the dispersions prepared with them are more stable with regard to the settling behavior.
  • Polysiloxane-polyether copolymers as are available, for example, under the trade name "Tegopren” from GOLDSCHMIDT AG in Essen (FRG), are preferably used for the dispersion in silicone oil.
  • Particularly preferred dispersants from this class are polysiloxane polyethers with an ethylene oxide-propylene oxide weight ratio of approximately 1: 1.
  • Such one Product, with an ethylene oxide-propylene oxide weight ratio of 49:51, is sold by GOLDSCHMIDT under the name "Tegopren 5830".
  • the reaction products of hydroxy-functional polysiloxanes with a wide variety of silanes are dispersants for the preparation of the EVF according to the invention.
  • Particularly preferred dispersants from this class of substances are the reaction products of a hydroxy-functional polysiloxane with aminosilanes.
  • the dispersant should be present in the EVF in amounts of 0.1 to 4% by weight, preferably 0.5 to 3% by weight.
  • EVF which is produced with silicone oil
  • silicone oil it applies that they are stable in settling, physiologically indifferent (non-toxic), and are very compatible with elastomeric materials, in particular with rubber.
  • they are heat and cold resistant within an unusually wide temperature range and have only a slight pressure dependence of the viscosity.
  • the electroviscous dispersions according to the invention have a high dielectric strength. It should be emphasized as a further advantage that the EVFs described are settling-stable and not abrasive and have low basic viscosities despite high volume fractions of the disperse phase.
  • the initial charge is mixed with the reactive additive or the crosslinking agent.
  • the mixture is dispersed in a liquid phase containing the dispersant.
  • shear homogenizers, high-pressure homogenizers or ultrasound can be used for this purpose.
  • the dispersion should be carried out so that the particle size does not exceed 200 ⁇ m, preferably 100 ⁇ m.
  • the product is allowed to react for a relatively long time at a suitable temperature which, depending on the reactivity of the crosslinking agent, is typically in a range from 0 ° C., preferably 15 ° C. to 150 ° C.
  • the crosslinking agent is only mixed into the dispersion after the dispersion process.
  • the template is sprayed with or without surfactant or additive (IV) into a fine powder, and the resulting powder is subsequently dispersed into the liquid phase.
  • the electrode area of the inner rotating cylinder with a diameter of 50 mm is approx. 78 cm2, the gap between the electrodes is 0.50 mm.
  • the shear load can be set to a maximum of 2640 s ⁇ 1.
  • the measuring range of the shear stress of the viscometer is a maximum of 750 Pa.
  • the EVF can be excited with both DC and AC voltage.
  • the EVF is preferably tested with AC voltage and with dynamic shear stress. This gives well-reproducible flow curves.
  • a constant shear rate of 0 ⁇ D ⁇ 2640 s ⁇ 1 is set and the dependence of the shear stress ⁇ on the electrical field strength E is measured effective current of 4 mA and a frequency between 50 and 550 Hz. Preferably, however, is measured at 50 Hz, because then the total current at lowest, and therefore the required electrical power is lowest.
  • Flow curves corresponding to FIG. 1 are obtained. It can be seen that the shear stress ⁇ initially increases parabolically with small field strengths and linearly with larger field strengths. The slope S of the linear part of the curve can be seen in the figure and is given in Pa.m / kV.
  • comparison approaches 1 to 3 correspond to the prior art. They are based on Examples 6, 7 and 9 of DE 3 536 934 A1. The liquids described in these examples are distinguished by particularly good electroviscous properties.
  • Examples 1 to 12 are EVFs according to the invention.
  • Table I lists the electroviscous properties of the EVF I to 11 according to the invention and the comparative samples at different temperatures.
  • EVF 2 to 4 shows the relationship between some properties (electro-viscous effect S, threshold value of the electric field strength E o and viscosity V at a rotational speed of the rotor of 1,000 rpm) of the EVF described in Examples 1 to 5 and the Amount of hydroxyl groups reacted with isocyanate at a measuring temperature of 25 ° C.
  • the arrows on the ordinate represent typical values for an EVF according to Comparative Example 2. It should be particularly emphasized that many EVF according to the invention are characterized by very good electroviscous effects despite their low viscosity and low threshold field strength.
  • the EVF was produced in accordance with the procedure given in Example 1. However, no crosslinker was added, so that the conversion of the hydroxyl groups of the glycol is 0 mol%.
  • the dispersant (b) 0.6 g of the dispersant (b) are dissolved in 20 g of the dispersion medium (a). 17.5 g of the glycol (a) are mixed with 7.61 g of the crosslinking agent (a). In the case of a quantitative reaction, this amount of crosslinker leads to the stoichiometric conversion of the hydroxyl groups in the glycol and thus corresponds to an OH conversion of 100 mol%.
  • the mixture is emulsified into the dispersant solution immediately after the preparation according to Example 1. The samples were subsequently reacted for 48 hours at room temperature.
  • the dispersant (b) 0.6 g of the dispersant (b) are dissolved in 20 g of the dispersion medium (a). 17.5 g of the trifunctional glycol (b) are mixed with 6.79 g of the crosslinker (a). In the case of a quantitative reaction, this amount of crosslinker leads to the stoichiometric conversion of the hydroxyl groups in the glycol and thus corresponds to an OH conversion of 100 mol%.
  • the mixture is emulsified into the dispersant solution immediately after the preparation according to Example 1. Subsequently, the samples were fully reacted at 90 ° C. for 8 hours.
  • dispersant (b) 0.5 g of the dispersant (b) are dissolved in 20 g of the dispersion medium (a). 15.0 g of the bifunctional glycol (a) are mixed with 4.14 g of the crosslinker (b). In the case of a quantitative reaction, this amount of crosslinker leads to an OH conversion of 75 mol%.
  • the mixture is emulsified into the dispersant solution immediately after the preparation according to Example 1. Subsequently, the samples were left to react for 48 hours at room temperature.
  • the dispersant (b) 0.6 g of the dispersant (b) are dissolved in 20 g of the dispersion medium (b). 17.5 g of the trifunctional glycol (b) are mixed with 6.79 g of the crosslinker (a). In the case of a quantitative reaction, this amount of crosslinker leads to the stoichiometric conversion of the hydroxyl groups in the glycol and thus corresponds to an OH conversion of 100 mol%.
  • the mixture is emulsified into the dispersant solution immediately after the preparation according to Example 1. The samples were subsequently fully reacted at 90 ° C. for 8 hours.
  • Example 6 of patent DE 3 536 934 A1 50 parts by weight of an erionite (composition: 62% by weight SiO2, 18% by weight Al2O3, 10% by weight Na2O) in 50 parts by weight of a polydimethylsiloxane -Silicone oil with a viscosity of 5 mm2 / s (at 25 ° C) dispersed.
  • the moisture content of the erionite according to DIN 55 921 was 6% by weight.
  • 2.5 parts by weight of the dispersant 1 (amino-functional siloxane) described in the patent were used as the dispersant.
  • Example 7 of patent DE 3 536 934 A1 40 parts by weight of an Al silicate (composition: 75% by weight SiO2, 9% by weight Al2O3, 7% by weight Na2O) were converted into 60 parts by weight a polydimethylsiloxane silicone oil with a viscosity of 5 mm2 / s (at 25 ° C) dispersed.
  • the moisture of the Al silicate according to DIN 55 921 was 6% by weight. 6 parts by weight of the dispersant 1 described in the patent were used as the dispersant.
  • Example 9 of patent DE 3 536 934 A1 50 parts by weight of a zeolite Y (Na form) (composition: 58% by weight SiO2, 20% by weight Al2O3, 12% by weight Na2O) were added in 50 Part by weight of a polydimethylsiloxane silicone oil with a viscosity of 5 mm2 / s (at 25 ° C) dispersed.
  • the moisture of the zeolite Y according to DIN 55 921 was 6% by weight.
  • 2.5 parts by weight of the dispersant 1 described in the patent were used as the dispersant.

Abstract

The present invention relates to electroviscous liquids, essentially containing A) a linear and/or branched, optionally functionalised polyether or monomers thereof, the reaction product of such a polyether or of the monomers with monofunctional or oligofunctional compounds and optionally also further additives, B) dispersants and C) a non-aqueous dispersion medium. s

Description

Die Erfindung betrifft eine elektroviskose Flüssigkeit, deren Viskosität beim Anlegen einer Spannung erhöht wird.The invention relates to an electroviscous liquid, the viscosity of which is increased when a voltage is applied.

Elektroviskose Flüssigkeiten (EVF) sind Dispersionen feinteiliger, hydrophiler Feststoffe in hydrophoben und elektrisch nicht leitenden Ölen, deren Viskosität sich unter dem Einfluß eines hinreichend starken elektrischen Feldes sehr schnell und reversibel vom flüssigen bis zum plastischen oder festen Zustand ändert. Die Viskosität reagiert sowohl auf elektrische Gleichfelder als auch auf Wechselfelder, wobei der Stromfluß durch die EVF sehr gering sein sollte. Daher lassen sich EVF überall dort einsetzen, wo es der Übertragung großer Kräfte mit Hilfe geringer elektrischer Leistungen bedarf, wie z.B. in Kupplungen, Hydraulikventilen, Stoßdämpfern, Vibratoren oder Vorrichtungen zum Positionieren und Fixieren von Werkstücken.Electroviscous liquids (EVF) are dispersions of finely divided, hydrophilic solids in hydrophobic and electrically non-conductive oils, whose viscosity changes very quickly and reversibly under the influence of a sufficiently strong electric field from the liquid to the plastic or solid state. The viscosity reacts to both DC electrical fields and AC fields, whereby the current flow through the EVF should be very low. Therefore EVF can be used wherever the transmission of large forces with the help of low electrical power is required, e.g. in couplings, hydraulic valves, shock absorbers, vibrators or devices for positioning and fixing workpieces.

Neben den allgemeinen an eine EVF gestellten Anforderungen, wie guter elektroviskoser Effekt, hohe Temperaturstabilität und chemische Beständigkeit spielen bei der praktischen Nutzung die Abrasivität und die Absetzstabilität der dispersen Phase eine wichtige Rolle. Die disperse Phase sollte möglichst nicht sedimentieren, sich jedoch in jedem Fall gut redispergieren lassen und auch unter extremer mechanischer Beanspruchung keinen Abrieb verursachen.In addition to the general requirements placed on an EVF, such as a good electroviscous effect, high temperature stability and chemical resistance, the abrasiveness and settling stability of the disperse phase play an important role in practical use. The disperse phase should not sediment as far as possible, but in any case it should be easy to redisperse and should not cause any abrasion even under extreme mechanical stress.

Bei einem Teil der EVF, die dem Stand der Technik entsprechen, besteht die disperse Phase aus organischen Feststoffen, wie z.B. Saccharide (DE 2 530 694), Stärke (EP 284 268 A2, US 3 970 573), Polymere (EP 150 994 A1, DE 3 310 959 A1, GB 1 570 234, US 4 129 513), Ionenaustauscherharze (JP 92 278/1975, JP 32 221/1985, US 3 047 507), oder Siliconharze (DE 3 912 888 A1). Es wurden aber auch anorganische Materialien, wie z.B. Li-Hydrazinsulfat (US 4 772 407 A), Zeolithe (EP 265 252 A2), Silicagel (DE 3 517 281 A1, DE 3 427 499 A1), und Aluminiumsilicate (DE 3 536 934 A1) eingesetzt. Der elektroviskose Effekt ist bei den genannten Substanzen auf die Beladung der Feststoffe mit Wasser zurückzuführen. Geringe Wasseranteile ermöglichen die Migration von Ionen und erhöhen dadurch die ionische Leitfähigkeit, bzw. die für die Ausbildung des Effektes unerläßliche Polarisierbarkeit der dispersen Teilchen. Der elektroviskose Effekt kommt dadurch zustande, daß die polarisierten Teilchen der dispersen Phase in einem externen elektrischen Feld durch Dipol-Dipol-Wechselwirkungen agglomerieren. Diese Agglomeration ist reversibel: wird das elektrische Feld abgeschaltet, redispergieren die Teilchen und die Viskosität wird auf den ursprünglichen Wert erniedrigt. Wasserhaltige Systeme haben jedoch eine geringe chemische Stabilität und können zudem zur Korrosion führen. Außerdem ist der Temperaturbereich, in dem diese Flüssigkeiten eingesetzt werden können, beschränkt.In part of the EVF, which correspond to the prior art, the disperse phase consists of organic solids, such as Saccharides (DE 2 530 694), starch (EP 284 268 A2, US 3 970 573), polymers (EP 150 994 A1, DE 3 310 959 A1, GB 1 570 234, US 4 129 513), ion exchange resins (JP 92 278 / 1975, JP 32 221/1985, US 3 047 507), or silicone resins (DE 3 912 888 A1). However, inorganic materials such as e.g. Li hydrazine sulfate (US 4,772,407 A), zeolites (EP 265 252 A2), silica gel (DE 3,517,281 A1, DE 3,427,499 A1), and aluminum silicates (DE 3,536,934 A1) are used. The electroviscous effect of the substances mentioned is due to the loading of the solids with water. Small amounts of water enable the migration of ions and thereby increase the ionic conductivity or the polarizability of the disperse particles, which is essential for the formation of the effect. The electroviscous effect arises from the fact that the polarized particles of the disperse phase agglomerate in an external electrical field by means of dipole-dipole interactions. This agglomeration is reversible: if the electric field is switched off, the particles redisperse and the viscosity is reduced to the original value. However, water-based systems have low chemical stability and can also lead to corrosion. In addition, the temperature range in which these liquids can be used is limited.

Bei anderen elektroviskosen Flüssigkeiten wurden die genannten Nachteile dadurch behoben, daß man die wasserhaltige, disperse Phase durch eine praktisch wasserfreie, elektronisch leitfähige Phase ersetzt, die aus zum Teil beschichteten, feindispersen Metallen, wie z.B. Aluminium (JP 016 093, JP 01 172 496), oder Dielektrica wie z.B. TiO₂ (SU 715 596), CaTiO₃ oder BaTiO₃ (JP 53/17 585) besteht. Die beschriebenen EVF sind jedoch, bedingt durch die Härte der dispergierten Teilchen abrasiv und dadurch für praktische Anwendungen, bei denen hohe Scherbeanspruchungen auftreten, nur bedingt brauchbar.In the case of other electroviscous liquids, the disadvantages mentioned have been eliminated by replacing the water-containing, disperse phase with a practically water-free, electronically conductive phase, which consists of partially coated, finely dispersed metals, such as e.g. Aluminum (JP 016 093, JP 01 172 496), or dielectric such as e.g. TiO₂ (SU 715 596), CaTiO₃ or BaTiO₃ (JP 53/17 585). However, the EVF described are, due to the hardness of the dispersed particles, abrasive and therefore only of limited use for practical applications in which high shear stresses occur.

Auch rußgefüllte Perlpolymerisate (JP 016 093), oder leitfähige Polymere, wie z.B. Polypyrol oder Polyacetylen (JP 01 260 710) wurden als Ersatz für die wasserhaltige Phase diskutiert. Solche Systeme sind jedoch teuer oder aufwendig in der Herstellung.Soot-filled bead polymers (JP 016 093) or conductive polymers such as polypyrene or polyacetylene (JP 01 260 710) have also been used as replacements for the water-containing ones Phase discussed. However, such systems are expensive or complex to manufacture.

Das bei allen genannten EVF in mehr oder weniger starkem Maße auftretende Problem der Sedimentation hat man durch Anwendung von Flüssigphasen mit einem hohen spezifischen Gewicht zu lösen versucht. Durch die Anhebung des spezifischen Gewichtes der Flüssigkeit, z.B. durch Einsatz fluorierter, chlorierter oder bromierter Kohlenwasserstoffe, nimmt die Dichte-Differenz zwischen der flüssigen und dispersen Phase, und somit die Sedimentation der Feststoffteilchen ab. So wurden z.B. zur Dispergierung der Feststoffe Lithiumpolyacrylat, Silicagel bzw. Salze der vernetzten Polymethacrylsäure in US-PS 4 502 973 halogeniertes Diphenylmethan als flüssige Phase verwendet, in EP-PS 284 268 A2 Polychlortrifluorethylen und in DE-PS 3 310 959 bromiertes Diphenylmethan. Die mangelnde Umweltverträglichkeit der substituierten Flüssigkeiten kann jedoch ein gravierendes Problem darstellen.The problem of sedimentation, which occurs to a greater or lesser extent with all of the EVFs mentioned, has been attempted by using liquid phases with a high specific weight. By increasing the specific weight of the liquid, e.g. by using fluorinated, chlorinated or brominated hydrocarbons, the difference in density between the liquid and disperse phase decreases, and thus the sedimentation of the solid particles. For example, used to disperse the solids lithium polyacrylate, silica gel or salts of the crosslinked polymethacrylic acid in US Pat. No. 4,502,973 halogenated diphenylmethane as the liquid phase, in EP-PS 284,268 A2 polychlorotrifluoroethylene and in DE-PS 3,310,959 brominated diphenylmethane. The lack of environmental compatibility of the substituted liquids can, however, be a serious problem.

Die obengenannten, dem Stand der Technik entsprechenden EVF werden in der Regel durch Eindispergieren eines Feststoffes in ein Dispersionsmedium hergestellt. Die Viskosität der entstehenden Suspension hängt dabei ab von der Form und der Größe, bzw. der Größenverteilung der dispergierten Teilchen, sowie von der Feststoffkonzentration und der Dispergierwirkung eventuell eingesetzter Dispergierhilfsmittel. Hohe volumenbezogene Feststoffgehalte bei geringer Viskosität sind dabei nur schwer zu erreichen. Durch den Einsatz von Feststoffen, die aus Teilchen mit einer kugelförmigen Geometrie bestehen, kann bei gleichbleibender Viskosität der Volumenanteil der dispersen Phase, und damit der elektroviskose Effekt gesteigert werden. Beispiele solcher Feststoffe sind Hydrolysate von Metall-Alkoxiden (EP 341 737), die bereits genannten Perlpolymerisate (JP 016 093), oder kugelförmige Glashohlkörper (JP 01 172 496). Sie weisen jedoch Nachteile hinsichtlich Kosten und Aufwand der Herstellung, Sedimentationsverhalten bzw. Scherstabilität auf.The above-mentioned EVF corresponding to the prior art are generally produced by dispersing a solid into a dispersion medium. The viscosity of the resulting suspension depends on the shape and size, or the size distribution of the dispersed particles, and on the solids concentration and the dispersing action of any dispersing agents used. High volume-related solids contents with low viscosity are difficult to achieve. Through the use of solids, which consist of particles with a spherical geometry, the volume fraction of the disperse phase and thus the electroviscous effect can be increased while maintaining the viscosity. Examples of such solids are hydrolyzates of metal alkoxides (EP 341 737), the already mentioned bead polymers (JP 016 093), or spherical glass hollow bodies (JP 01 172 496). However, they have disadvantages with regard to the costs and expenditure of production, sedimentation behavior and shear stability.

Aufgabe der Erfindung war es, eine wasserfreie, nicht-abrasive, , sedimentationsstabile EVF mit guten elektroviskosen Eigenschaften bereitzustellen, die sich trotz hohen Volumenanteilen der dispersen Phase durch eine geringe Basisviskosität sowie niedrige elektrische Leitfähigkeit auszeichnet.The object of the invention was to provide an anhydrous, non-abrasive, sedimentation-stable EVF with good electroviscous properties, which despite high volume fractions of the disperse phase is characterized by a low basic viscosity and low electrical conductivity.

Die erfindungsgemäße EVF enthält, dispergiert in einer nicht leitenden Flüssigkeit in reiner Form, oder als Reaktionsprodukt mit anderen Substanzen, 1 bis 80 Gew.-%, vorzugsweise 1 bis 60 Gew.-%, besonders bevorzugt 20 bis 60 Gew.-%, eines Polyethers. Das Gemisch aus Polyether und eventuellen Additiven, Vorlage genannt, das während des Herstellungsprozesses der EVF in die nicht leitende Flüssigkeit eindispergiert wird, sollte vorzugsweise in flüssiger Form vorliegen. Gegebenenfalls kann die Vorlage, durch die Zugabe geeigneter Reagenzien vor, während oder nach dem Dispergierschritt, chemisch modifiziert werden. Diese Modifizierung beeinflußt die Konsistenz, sowie, durch die teilweise oder völlige Umsetzung der funktionellen Gruppen der Vorlage, die Leitfähigkeit der dispersen Phase in der fertigen EVF.The EVF according to the invention contains, dispersed in a non-conductive liquid in pure form or as a reaction product with other substances, 1 to 80% by weight, preferably 1 to 60% by weight, particularly preferably 20 to 60% by weight, of one Polyether. The mixture of polyether and any additives, called template, which is dispersed into the non-conductive liquid during the EVF manufacturing process, should preferably be in liquid form. If necessary, the template can be chemically modified by adding suitable reagents before, during or after the dispersing step. This modification influences the consistency and, through the partial or complete implementation of the functional groups of the template, the conductivity of the disperse phase in the finished EVF.

Um bei der Verwendung flüssiger Phasen Koaleszenz zu vermeiden, wird bei der Dispergierung ein geeignetes Dispergiermittel verwendet.In order to avoid coalescence when using liquid phases, a suitable dispersing agent is used for the dispersion.

Die Größe der dispergierten Teilchen in der erfindungsgemäßen EVF beträgt 0,05, vorzugsweise 0,1, bis 200 µm. Die Viskosität der EVF beträgt bei Raumtemperatur, je nach Zusammensetzung der Flüssigkeit und der Basisviskosität des Dispersionsmediums, zwischen 0,5, vorzugsweise 3, und

Figure imgb0001
The size of the dispersed particles in the EVF according to the invention is 0.05, preferably 0.1 to 200 μm. The viscosity of the EVF at room temperature, depending on the composition of the liquid and the basic viscosity of the dispersion medium, is between 0.5, preferably 3, and
Figure imgb0001

Zur Herstellung der erfindungsgemäßen EVF wird für die disperse Phase eine vorzugsweise flüssige Vorlage verwendet, die mindestens eine der folgenden Substanzen enthält: (I): einen linearen oder verzweigten, gegebenenfalls funktionalisierten Polyether, (II): das Umsetzungsprodukt von (I) mit mono- oder oligofunktionellen Verbindungen, wie z.B. Additiven wie z.B. Polyole, aliphatische Carbonsäuren oder Amine, Alkoholen, Estern usw., in unterschiedlichen stöchiometrischen Verhältnissen, (III): ein Gemisch aus (I) und/oder (II) mit anderen nichtreaktiven Additiven, die in die fertigen EVF die elektrischen bzw. mechanischen Eigenschaften der dispersen Phase, wie Leitfähigkeit und elastisches Verhalten beeinflussen. Additive (III) mit Weichmacherfunktion im Sinne der Erfindung sind z.B. verkappte niedermolekulare Polyether, wie z.B. bismethyliertes Trimethylpropan oder die Ester der Phthalsäure.To produce the EVF according to the invention, a preferably liquid template is used for the disperse phase, which contains at least one of the following substances: (I): a linear or branched, optionally functionalized polyether, (II): the reaction product of (I) with mono- or oligofunctional compounds, such as additives such as polyols, aliphatic carboxylic acids or amines, alcohols, esters etc., in different stoichiometric ratios, (III): a mixture of (I) and / or (II) with other non-reactive additives, which in the finished EVF influence the electrical or mechanical properties of the disperse phase, such as conductivity and elastic behavior. Additives (III) with plasticizer function in the sense of Invention are capped low molecular weight polyethers such as bismethylated trimethylpropane or the esters of phthalic acid.

Beispiele der genannten linearen Polyether sind Polyethylenglykole, Polypropylenglykole, Polybutylenglykole, statistische Ethylenglykol-Propylenglykol-Copolymerisate oder auch Ethylenglykol-Propylenglykol-Blockpolymerisate, wie sie z.B. unter dem Handelsnamen "Pluronic" von der Firma GAF vertrieben werden. Verzweigte Polyether sind beispielsweise Tris(polypropylenoxid)ω-ol)glycidylether oder andere Substanzen, die durch Ethoxylierung oder Propoxylierung von höherfunktionellen Hydroxyverbindungen, wie z.B. Pentaerythrit oder 1,1,1-Trimethylolpropan, erhalten werden. Das Molekulargewicht der Polyglykole liegt zwischen 62 und 1 000 000, vorzugsweise unter 100 000, besonders bevorzugt jedoch zwischen 100 und 10 000. Gegebenenfalls können die Polyglykole funktionelle Endgruppen enthalten. Amine, Allyl- bzw. Vinylgruppen, oder auch Carboxylgruppen stellen Beispiele solcher funktioneller Endgrupen dar. Polyethylen- bzw. Polypropylen-mono-oder Diamine sind unter dem Handelsnamen "Jeffamin" der Firma "TEXACO" zu erwerben. Beispiele acrylgruppenhaltiger Produkte sind die Ester der Glykole mit entsprechenden Säuren, z.B. Acrylsäure. Zu den unter (II) genannten Substanzen gehören z.B. die in der Polymethanchemie gängigen Polyester, die u.a durch die Firma BAYER AG unter dem Handelsnamen "Desmophen" vertrieben werden.Examples of the linear polyethers mentioned are polyethylene glycols, polypropylene glycols, polybutylene glycols, statistical ethylene glycol-propylene glycol copolymers or else ethylene glycol-propylene glycol block polymers, such as those e.g. are sold by GAF under the trade name "Pluronic". Branched polyethers are, for example, tris (polypropylene oxide) ω-ol) glycidyl ether or other substances which are obtained by ethoxylation or propoxylation of higher-functionality hydroxy compounds, e.g. Pentaerythritol or 1,1,1-trimethylolpropane can be obtained. The molecular weight of the polyglycols is between 62 and 1,000,000, preferably below 100,000, particularly preferably between 100 and 10,000. The polyglycols can optionally contain functional end groups. Amines, allyl or vinyl groups, or carboxyl groups are examples of such functional end groups. Polyethylene or polypropylene mono- or diamines can be obtained under the trade name "Jeffamin" from the company "TEXACO". Examples of products containing acrylic groups are the esters of glycols with corresponding acids, e.g. Acrylic acid. The substances mentioned under (II) include e.g. the polyesters common in polymethane chemistry, which are sold by BAYER AG under the trade name "Desmophen".

Bei der Verwendung flüssiger Vorlagen wird gegebenenfalls vor bzw. nach der Emulgierung der Vorlage dem System ein Additiv (IV) (z.B. Vernetzer) zugesetzt, das durch Reaktion mit den funktionellen Endgruppen der Verbindungen (I), (II) und/oder (III) zum Molekulargewichtsaufbau in den Emulsionströpfchen, oder auch zur Reduzierung der Zahl der funktionellen Endgruppen führt. Je nach Art und Menge der eingesetzten Mischkomponenten und des Additivs bilden sich viskose oder feste Teilchen, deren kugelförmige Geometrie während und nach der Reaktion erhalten bleibt.When using liquid templates, an additive (IV) (for example crosslinking agent) is added to the system, if appropriate before or after the emulsification of the template, which by reaction with the functional end groups of the compounds (I), (II) and / or (III) leads to molecular weight build-up in the emulsion droplets, or also to a reduction in the number of functional end groups. Depending on the type and amount of the mixing components and the additive used, viscous or solid particles are formed, the spherical geometry of which is retained during and after the reaction.

Beispiele solche Vernetzer sind di- oder multifunktionelle Isocyanate mit unterschiedlicher Struktur, die z.B. unter dem Handelsnamen "Desmodur" durch die Firma BAYER AG vertrieben werden. Bei der Verwendung von tri- oder höherfunktionellen Glykolen ist der Einsatz von Toluylen-diisocyanat als Vernetzer besonders bevorzugt. Zur Vernetzung sind jedoch auch die in der Siliconchemie gängigen sog. Acetat-, Amin-, Benzamid-, Oxim- und Alkoxyvernetzer einsetzbar. Vorzugsweise wird der Isocyanat-Vernetzer in solchen Mengen eingesetzt, daß 20 bis 100 %, vorzugsweise bis 80 % der OH-Gruppen des Glykols umgesetzt werden. Für den Umsatz von Allyl, bzw. vinylgruppenmodifizierte Verbindungen der Gruppen (I) bis (III) sind radikalische Vernetzersysteme geeignet.Examples of such crosslinkers are di- or multifunctional isocyanates with different structures, which are sold, for example, under the trade name "Desmodur" by BAYER AG. When using tri- or higher functional Glycol is particularly preferred to use tolylene diisocyanate as a crosslinker. However, the so-called acetate, amine, benzamide, oxime and alkoxy crosslinkers commonly used in silicone chemistry can also be used for crosslinking. The isocyanate crosslinking agent is preferably used in amounts such that 20 to 100%, preferably up to 80%, of the OH groups of the glycol are reacted. Radical crosslinking systems are suitable for the conversion of allyl or vinyl group-modified compounds of groups (I) to (III).

In den erfindungsgemäßen EVF ist die disperse Phase (das Reaktionsprodukt aus Vorlage und (IV)), zu 10 bis 85 Gew.-%, vorzugsweise jedoch zu 40 bis 70 Gew.%, enthalten.The EVF according to the invention contains the disperse phase (the reaction product from the initial charge and (IV)) to 10 to 85% by weight, but preferably to 40 to 70% by weight.

Als Dispersionsmedium für die disperse Phase werden, neben flüssigen Kohlenwasserstoffen, wie z.B. Paraffine, Olefine und aromatische Kohlenwasserstoffe, vorzugsweise Silikonöle wie Polydimethylsiloxane oder auch Polysiloxane mit höheren Alkylgruppen, fluorhaltige Siloxane und flüssige Methylphenylsiloxane verwendet. Diese können allein, oder in Kombination aus zwei oder mehreren Arten eingesetzt werden. Der Erstarrungspunkt der Dispersionsmedien wird vorzugsweise niedriger als -30°C eingestellt, der Siedepunkt größer als 150°C. Die Viskosität der Öle liegt bei Raumtemperatur zwischen 3 und 300 mm²/s. Im allgemeinen sind die niedrigviskosen Öle mit einer Viskosität von 3 bis 20 mm²/s zu bevorzugen, weil hiermit eine niedrigere Grundviskosität der EVF erreicht wird.In addition to liquid hydrocarbons, e.g. Paraffins, olefins and aromatic hydrocarbons, preferably silicone oils such as polydimethylsiloxanes or also polysiloxanes with higher alkyl groups, fluorine-containing siloxanes and liquid methylphenylsiloxanes are used. These can be used alone or in combination of two or more types. The solidification point of the dispersion media is preferably set below -30 ° C, the boiling point above 150 ° C. The viscosity of the oils is between 3 and 300 mm² / s at room temperature. In general, the low-viscosity oils with a viscosity of 3 to 20 mm² / s are preferred because they achieve a lower basic viscosity of the EVF.

Um Sedimentation zu vermeiden, sollte das Öl außerdem eine Dichte haben, die annähernd der Dichte der dispersen Phase entspricht. So lassen sich z.B. durch die Verwendung von fluorhaltigen Siloxanen, die als Reinsubstanz oder als Gemisch mit anderen Ölen eingesetzt werden, erfindungsgemäße EVF herstellen, die trotz geringer Basisviskosität auch über Wochen hinaus keine Sedimentation aufweisen.In order to avoid sedimentation, the oil should also have a density that approximately corresponds to the density of the disperse phase. For example, by using fluorine-containing siloxanes, which are used as pure substance or as a mixture with other oils, produce EVFs according to the invention which, despite their low basic viscosity, have no sedimentation for weeks.

Besonders geeignet zur Herstellung sedimentationsstabiler EVF sind fluorhaltige Siloxane der allgemeinen Struktur:

Figure imgb0002
Fluorine-containing siloxanes of the general structure are particularly suitable for producing sedimentation-stable EVF:
Figure imgb0002

Als Dispergiermittel für die disperse Phase können im Dispersionsmedium lösliche Tenside verwendet werden, die z.B. von Aminen, Imidazolinen, Oxazolinen, Alkoholen, Glykol oder Sorbitol abgeleitet sind. Auch können im Dispersionsmedium lösliche Polymere eingesetzt werden. Geeignet sind z.B. Polymere, welche 0,1 bis 10 Gew.-% N und/oder OH, sowie 25 bis 83 Gew.-% C₄-C₂₄-Alkylgruppen enthalten und ein Molekulargewicht im Bereich von 5000 bis 1 000 000 aufweisen. Die N- und/oder OH-haltigen Verbindungen in diesen Polymeren können z.B. Amin-, Amid-, Imid-, Nitril-, 5- bis 6-gliedrige N-haltige heterocyclische Ringe, bzw. ein Alkohol sein, und die C₄-C₂₄-Alkylgruppen Ester von Acryl- bzw. Methacrylsäure. Beispiele für die genannten N- und OH-haltigen Verbindungen sind N,N-Dimethylaminoethylmethacrylat, tert-Butylacrylamid, Maleinimid, Acrylnitril, N-Vinylpyrrolidon, Vinylpyridin und 2-Hydroxyethylmethacrylat. Die vorgenannten polymeren Dispergiermittel haben gegenüber den niedermolekularen Tensiden im allgemeinen den Vorteil, daß die hiermit hergestellten Dispersionen bezüglich des Absetzverhaltens stabiler sind.Suitable dispersants for the disperse phase are surfactants which are soluble in the dispersion medium and which, e.g. are derived from amines, imidazolines, oxazolines, alcohols, glycol or sorbitol. Polymers soluble in the dispersion medium can also be used. Suitable are e.g. Polymers which contain 0.1 to 10% by weight of N and / or OH, and 25 to 83% by weight of C₄-C₂₄-alkyl groups and have a molecular weight in the range from 5000 to 1,000,000. The N- and / or OH-containing compounds in these polymers can e.g. Amine, amide, imide, nitrile, 5- to 6-membered N-containing heterocyclic rings, or an alcohol, and the C₄-C₂₄-alkyl groups are esters of acrylic or methacrylic acid. Examples of the N and OH-containing compounds mentioned are N, N-dimethylaminoethyl methacrylate, tert-butylacrylamide, maleimide, acrylonitrile, N-vinylpyrrolidone, vinylpyridine and 2-hydroxyethyl methacrylate. The abovementioned polymeric dispersants generally have the advantage over the low molecular weight surfactants that the dispersions prepared with them are more stable with regard to the settling behavior.

Für die Dispergierung in Siliconöl werden bevorzugt Polysiloxan-Polyether-Copolymere eingesetzt, wie sie beispielsweise unter dem Handelsnamen "Tegopren" bei der Firma GOLDSCHMIDT AG in Essen (BRD) verfügbar sind. Besonders bevorzugte Dispergiermittel aus dieser Klasse sind Polysiloxan-Polyether mit einem Ethylenoxid-Propylenoxid-Gewichtsverhältnis von ungefähr 1:1. Ein solches Produkt, mit einem Ethylenoxid-Propylenoxid Gewichtsverhältnis von 49:51, wird bei der Firma GOLDSCHMIDT unter dem Namen "Tegopren 5830" geführt.Polysiloxane-polyether copolymers, as are available, for example, under the trade name "Tegopren" from GOLDSCHMIDT AG in Essen (FRG), are preferably used for the dispersion in silicone oil. Particularly preferred dispersants from this class are polysiloxane polyethers with an ethylene oxide-propylene oxide weight ratio of approximately 1: 1. Such one Product, with an ethylene oxide-propylene oxide weight ratio of 49:51, is sold by GOLDSCHMIDT under the name "Tegopren 5830".

Neben den Polyether-Polysiloxanen stellen die Reaktionsprodukte von hydroxyfunktionellen Polysiloxanen mit den unterschiedlichsten Silanen Dispergiermittel zur Herstellung der erfindungsgemäßen EVF dar. Besonders bevorzugte Dispergiermittel aus dieser Substanzklasse sind die Umsetzungsprodukte eines hydroxyfunktionellen Polysiloxans mit Aminosilanen.In addition to the polyether polysiloxanes, the reaction products of hydroxy-functional polysiloxanes with a wide variety of silanes are dispersants for the preparation of the EVF according to the invention. Particularly preferred dispersants from this class of substances are the reaction products of a hydroxy-functional polysiloxane with aminosilanes.

Das Dispergiermittel soll in der EVF in Mengen von 0,1 bis 4 Gew.-%, vorzugsweise 0,5 bis 3 Gew.-%, vorhanden sein.The dispersant should be present in the EVF in amounts of 0.1 to 4% by weight, preferably 0.5 to 3% by weight.

Für erfindungsgemäße, mit Silikonöl hergestellte EVF gilt, daß sie absetzstabil, physiologisch indifferent (ungiftig), und mit elastomeren Werkstoffen, insbesondere mit Gummi bestens verträglich sind. Außerdem sind sie innerhalb eines ungewöhnlich weiten Temperaturbereichs wärme- und kältebeständig und weisen nur eine geringfügige Druckabhängigkeit der Viskosität auf. Darüber hinaus haben die erfindungsgemäßen elektroviskosen Dispersionen eine hohe elektrische Durchschlagsfestigkeit. Als weiterer Vorteil ist hervorzuheben, daß die beschriebenen EVF absetzstabil und nicht abrasiv sind und trotz hoher Volumenanteile an disperser Phase geringe Basisviskositäten aufweisen.For EVF according to the invention, which is produced with silicone oil, it applies that they are stable in settling, physiologically indifferent (non-toxic), and are very compatible with elastomeric materials, in particular with rubber. In addition, they are heat and cold resistant within an unusually wide temperature range and have only a slight pressure dependence of the viscosity. In addition, the electroviscous dispersions according to the invention have a high dielectric strength. It should be emphasized as a further advantage that the EVFs described are settling-stable and not abrasive and have low basic viscosities despite high volume fractions of the disperse phase.

Bei einer typischen Art der Herstellung der erfindungsgemäßen EVF wird die Vorlage mit dem reaktiven Additiv, bzw. dem Vernetzer vermischt. Nach Homogenisierung der Komponenten wird das Gemisch in einer, das Dispergiermittel enthaltenden, flüssigen Phase dispergiert. Hierzu können, um einen entsprechenden Dispergiergrad zu erreichen, Scherhomogenisatoren, Hochdruckhomogenisatoren oder Ultraschall verwendet werden. Die Dispergierung sollte jedoch so durchgeführt werden, daß die Teilchengröße 200 µm, vorzugsweise 100 µm, nicht überschreitet. Gegebenenfalls läßt man nach erfolgter Dispergierung das Produkt bei einer geeigneten Temperatur, die abhängig von der Reaktivität des Vernetzers typischerweise in einem Bereich von 0°C, vorzugsweise 15°C, bis 150°C liegt, über längere Zeit ausreagieren.In a typical way of producing the EVF according to the invention, the initial charge is mixed with the reactive additive or the crosslinking agent. After the components have been homogenized, the mixture is dispersed in a liquid phase containing the dispersant. To achieve a corresponding degree of dispersion, shear homogenizers, high-pressure homogenizers or ultrasound can be used for this purpose. However, the dispersion should be carried out so that the particle size does not exceed 200 μm, preferably 100 μm. If appropriate, after the dispersion has been carried out, the product is allowed to react for a relatively long time at a suitable temperature which, depending on the reactivity of the crosslinking agent, is typically in a range from 0 ° C., preferably 15 ° C. to 150 ° C.

Bei einer alternativen Herstellungsweise wird der Vernetzer erst nach dem Dispergiervorgang in die Dispersion eingemischt.In an alternative production method, the crosslinking agent is only mixed into the dispersion after the dispersion process.

Bei einer anderen Art der Herstellung wird die Vorlage mit oder ohne Tensid, bzw. Additiv (IV) zu einem feinen Pulver versprüht, und das entstandene Pulver nachträglich in die flüssige Phase eindispergiert.In another type of production, the template is sprayed with or without surfactant or additive (IV) into a fine powder, and the resulting powder is subsequently dispersed into the liquid phase.

Die so hergestellten EVF wurden in einem modifizierten Rotationsviskosimeter, wie es bereits von W.M. Winslow in J. Appl. Phys. 20 (1949), Seiten 1137 bis 1140 beschrieben wurde, untersucht.The EVF thus produced were processed in a modified rotary viscometer, as already described by W.M. Winslow in J. Appl. Phys. 20 (1949), pages 1137 to 1140.

Die Elektrodenfläche des inneren rotierenden Zylinders mit einem Durchmesser von 50 mm beträgt ca. 78 cm², die Spaltweite zwischen den Elektroden 0,50 mm. Bei den dynamischen Messungen kann die Scherbelastung mit maximal 2640 s⁻¹ eingestellt werden. Der Meßbereich der Schubspannung des Viskosimeters beträgt maximal 750 Pa. Die Anregung der EVF kann sowohl mit Gleichspannung als auch mit Wechselspannung erfolgen.The electrode area of the inner rotating cylinder with a diameter of 50 mm is approx. 78 cm², the gap between the electrodes is 0.50 mm. For dynamic measurements, the shear load can be set to a maximum of 2640 s⁻¹. The measuring range of the shear stress of the viscometer is a maximum of 750 Pa. The EVF can be excited with both DC and AC voltage.

Bei Anregung mit Gleichspannung können bei einigen Flüssigkeiten neben der spontanen Erhöhung der Viskosität oder der Fließgrenze beim Einschalten des Feldes auch noch elektrophoretische Abscheidevorgänge der festen Teilchen auf den Elektrodenoberflächen wahrgenommen werden, insbesondere bei kleinen Schergeschwindigkeiten, bzw. bei statischen Messungen. Daher wird die Prüfung der EVF bevorzugt mit Wechselspannung und bei dynamischer Scherbeanspruchung durchgeführt. Man erhält so gut reproduzierbare Fließkurven.In the case of excitation with direct voltage, in addition to the spontaneous increase in viscosity or the yield point when the field is switched on, some liquids can also perceive electrophoretic deposition of the solid particles on the electrode surfaces, especially at low shear rates or with static measurements. Therefore, the EVF is preferably tested with AC voltage and with dynamic shear stress. This gives well-reproducible flow curves.

Zur Bestimmung der Elektroreaktivität stellt man eine konstante Schergeschwindigkeit 0<D<2640 s⁻¹ ein und mißt die Abhängigkeit der Schubspannung τ von der elektrischen Feldstärke E. Mit der Prüfapparatur können Wechselfelder bis zu einer maximalen effektiven Feldstärke von 2370 kV/m bei einem maximalen effektiven Strom von 4 mA und einer Frequenz zwischen 50 und 550 Hz erzeugt werden. Vorzugsweise wird jedoch bei 50 Hz gemessen, weil dann der Gesamtstrom am niedrigsten, und dadurch die benötigte elektrische Leistung am geringsten ist. Man erhält dabei Fließkurven entsprechend der Fig. 1. Man erkennt, daß die Schubspannung τ bei kleinen Feldstärken zunächst parabelförmig und bei größeren Feldstärken linear ansteigt. Die Steigung S des linearen Teils der Kurve kann aus der Abbildung entnommen werden und wird in Pa.m/kV angegeben. Aus dem Schnittpunkt der Geraden S mit der Geraden τ=τo (Schubspannung ohne elektrisches Feld) wird der Schwellwert Eo der elektrischen Feldstärke in kV/m bestimmt. Für die Erhöhung der Schubspannung τ(E)-τo im elektrischen Feld E>Eo gilt:

τ(E)-τo=S(E-Eo).

To determine the electroreactivity, a constant shear rate of 0 <D <2640 s⁻¹ is set and the dependence of the shear stress τ on the electrical field strength E is measured effective current of 4 mA and a frequency between 50 and 550 Hz. Preferably, however, is measured at 50 Hz, because then the total current at lowest, and therefore the required electrical power is lowest. Flow curves corresponding to FIG. 1 are obtained. It can be seen that the shear stress τ initially increases parabolically with small field strengths and linearly with larger field strengths. The slope S of the linear part of the curve can be seen in the figure and is given in Pa.m / kV. The threshold value Eo of the electric field strength in kV / m is determined from the point of intersection of the straight line S with the straight line τ = τ o (shear stress without an electric field). The following applies to the increase in shear stress τ (E) -τ o in the electric field E> Eo:

τ (E) -τ o = S (EE o ).

Bei den nachfolgend beschriebenen Ausführungsbeispielen entsprechen die Vergleichsansätze 1 bis 3 dem Stand der Technik. Ihnen liegen die Beispiele 6,7 und 9 von DE 3 536 934 A1 zugrunde. Die in diesen Beispielen beschriebenen Flüssigkeiten zeichnen sich durch besonders gute elektroviskose Eigenschaften aus.In the exemplary embodiments described below, comparison approaches 1 to 3 correspond to the prior art. They are based on Examples 6, 7 and 9 of DE 3 536 934 A1. The liquids described in these examples are distinguished by particularly good electroviscous properties.

Bei den Beispielen 1 bis 12 handelt es sich um erfindungsgemäße EVF.Examples 1 to 12 are EVFs according to the invention.

In Tabelle I sind die elektroviskosen Eigenschaften der erfindungsgemäßen EVF I bis 11, sowie der Vergleichsproben bei unterschiedlichen Temperaturen aufgeführt.Table I lists the electroviscous properties of the EVF I to 11 according to the invention and the comparative samples at different temperatures.

In Fig. 2 bis 4 ist der Zusammenhang zwischen einigen Eigenschaften (Elektroviskoser Effekt S, Schwellwert der elektrischen Feldstärke Eo und Viskosität V bei einer Umlaufgeschwindigkeit des Rotors von 1 000 U/min.) der in den Beispielen 1 bis 5 beschriebenen EVF und der Menge der mit Isocyanat umgesetzten Hydroxylgruppen bei einer Meßtemperatur von 25°C dargestellt. Zum Vergleich geben die Pfeile an der Ordinate typische Werte für eine EVF gemäß Vergleichsbeispiel 2 wieder. Besonders hervorzuheben ist, daß viele erfindungsgemäße EVF sich trotz geringer Viskosität und geringer Schwellfeldstärke durch sehr gute elektroviskose Effekte kennzeichnen.

Figure imgb0003
2 to 4 shows the relationship between some properties (electro-viscous effect S, threshold value of the electric field strength E o and viscosity V at a rotational speed of the rotor of 1,000 rpm) of the EVF described in Examples 1 to 5 and the Amount of hydroxyl groups reacted with isocyanate at a measuring temperature of 25 ° C. For comparison, the arrows on the ordinate represent typical values for an EVF according to Comparative Example 2. It should be particularly emphasized that many EVF according to the invention are characterized by very good electroviscous effects despite their low viscosity and low threshold field strength.
Figure imgb0003

Beispiel 1example 1

1,25 g des Dispergiermittels (a) werden in 20 g des Dispersionsmediums (a) gelöst. In einem Becherglas von 100 ml wird in diese Lösung mittels eines Rotor-Stator-Scherhomogenisators (Ultra-Turrax T25 der Firma IKA Labortechnik) 17,5 g des bifunktionellen Glykols (a) bei 25°C emulgiert. Die Emulgierzeit bei einer Umlaufgeschwindigkeit des Rotors von 10 000 U/min beträgt 3 min. Zu der fertigen Emulsion wird unter Rühren 7,61 g des Vernetzers (a) zugetropft. Diese Vernetzermenge führt bei einer quantitativen Reaktion zum stöchiometrischen Umsatz der Hydroxylgruppen im Glykol. Diese Einsatzmenge entspricht somit einem OH-Umsatz von 100 Mol-%. Die Proben wurden nach Zugabe des Vernetzers 48 Stunden mit einem Propellerrührer bei niedriger Umlaufgeschwindigkeit nachgerührt.1.25 g of the dispersant (a) are dissolved in 20 g of the dispersion medium (a). In a 100 ml beaker, 17.5 g of the bifunctional glycol (a) is emulsified at 25 ° C. in this solution using a rotor-stator shear homogenizer (Ultra-Turrax T25 from IKA Labortechnik). The emulsification time at a rotational speed of the rotor of 10,000 rpm is 3 minutes. 7.61 g of the crosslinking agent (a) are added dropwise to the finished emulsion with stirring. In the case of a quantitative reaction, this amount of crosslinker leads to the stoichiometric conversion of the hydroxyl groups in the glycol. This amount therefore corresponds to an OH conversion of 100 mol%. After the addition of the crosslinker, the samples were stirred for 48 hours with a propeller stirrer at a low circulation speed.

Beispiel 2Example 2

Entsprechend der unter Beispiel 1 angegebenen Arbeitsweise wurde eine EVF hergestellt, jedoch mit einer Vernetzermenge von 5,71 g. Dies entspricht einem OH-Umsatz von 75 Mol-%.An EVF was produced in accordance with the procedure given in Example 1, but with a crosslinker amount of 5.71 g. This corresponds to an OH conversion of 75 mol%.

Beispiel 3Example 3

Herstellung gemäß Beispiel 1, jedoch mit einer Vernetzermenge von 3,81 g (OH-Umsatz 50 Mol-%).Preparation according to Example 1, but with a crosslinker amount of 3.81 g (OH conversion 50 mol%).

Beispiel 4Example 4

Herstellung gemäß Beispiel 1, jedoch mit einer Vernetzermenge von 1,90 g (OH-Umsatz 25 Mol-%).Preparation according to Example 1, but with a crosslinker amount of 1.90 g (OH conversion 25 mol%).

Beispiel 5Example 5

Die EVF wurde entsprechend der unter Beispiel 1 angegebenen Arbeitsweise hergestellt. Es wurde jedoch kein Vernetzer zugegeben, so daß der Umsatz der Hydroxylgrupen des Glykols 0 Mol-% beträgt.The EVF was produced in accordance with the procedure given in Example 1. However, no crosslinker was added, so that the conversion of the hydroxyl groups of the glycol is 0 mol%.

Beispiel 6Example 6

0,6 g des Dispergiermittels (b) werden in 20 g des Dispersionsmediums (a) gelöst. 17,5 g des Glykols (a) werden mit 7,61 g des Vernetzers (a) vermischt. Diese Vernetzermenge führt bei einer quantitativen Reaktion zum stöchiometrischen Umsatz der Hydroxylgruppen im Glykol und entspricht somit einem OH-Umsatz von 100 Mol-%. Das Gemisch wird sofort nach der Herstellung gemäß Beispiel 1 in die Dispergiermittel-Lösung emulgiert. Nachträglich wurden die Proben 48 Stunden bei Raumtemperatur ausreagiert.0.6 g of the dispersant (b) are dissolved in 20 g of the dispersion medium (a). 17.5 g of the glycol (a) are mixed with 7.61 g of the crosslinking agent (a). In the case of a quantitative reaction, this amount of crosslinker leads to the stoichiometric conversion of the hydroxyl groups in the glycol and thus corresponds to an OH conversion of 100 mol%. The mixture is emulsified into the dispersant solution immediately after the preparation according to Example 1. The samples were subsequently reacted for 48 hours at room temperature.

Beispiel 7Example 7

Entsprechend der unter Beispiel 6 angegebenen Arbeitsweise wurde eine EVF hergestellt, jedoch mit einer Vernetzermenge von 5,71 g. Dies entspricht einem OH-Umsatz von 75 Mol-%.An EVF was produced in accordance with the procedure given in Example 6, but with a crosslinker amount of 5.71 g. This corresponds to an OH conversion of 75 mol%.

Beispiel 8Example 8

Herstellung gemäß Beispiel 6, jedoch mit einer Vernetzermenge von 3,81 g (OH-Umsatz 50 Mol-%).Preparation according to Example 6, but with a crosslinker amount of 3.81 g (OH conversion 50 mol%).

Beispiel 9Example 9

Herstellung gemäß Beispiel 6, jedoch mit einer Vernetzermenge von 1,90 g (OH-Umsatz 25 Mol-%).Preparation according to Example 6, but with a crosslinker amount of 1.90 g (OH conversion 25 mol%).

Beispiel 10Example 10

0,6 g des Dispergiermittels (b) werden in 20 g des Dispersionsmediums (a) gelöst. 17,5 g des trifunktionellen Glykols (b) werden mit 6,79 g des Vernetzers (a) vermischt. Diese Vernetzermenge führt bei einer quantitativen Reaktion zum stöchiometrischen Umsatz der Hydroxylgrupen im Glykol und entspricht somit einem OH-Umsatz von 100 Mol-%. Das Gemisch wird sofort nach der Herstellung gemäß Beispiel 1 in die Dispergiermittel-Lösung emulgiert Nachträglich wurden die Proben 8 Stunden bei 90°C ausreagiert.0.6 g of the dispersant (b) are dissolved in 20 g of the dispersion medium (a). 17.5 g of the trifunctional glycol (b) are mixed with 6.79 g of the crosslinker (a). In the case of a quantitative reaction, this amount of crosslinker leads to the stoichiometric conversion of the hydroxyl groups in the glycol and thus corresponds to an OH conversion of 100 mol%. The mixture is emulsified into the dispersant solution immediately after the preparation according to Example 1. Subsequently, the samples were fully reacted at 90 ° C. for 8 hours.

Beispiel 11Example 11

0,5 g des Dispergiermittels (b) werden in 20 g des Dispersionsmediums (a) gelöst. 15,0 g des bifunktionellen Glykols (a) werden mit 4,14 g des Vernetzers (b) vermischt. Diese Vernetzermenge führt bei einer quantitativen Reaktion zu einem OH-Umsatz von 75 Mol-%. Das Gemisch wird sofort nach der Herstellung gemäß Beispiel 1 in die Dispergiermittel-Lösung emulgiert Nachträglich wurden die Proben 48 Stunden bei Raumtemperatur ausreagiert.0.5 g of the dispersant (b) are dissolved in 20 g of the dispersion medium (a). 15.0 g of the bifunctional glycol (a) are mixed with 4.14 g of the crosslinker (b). In the case of a quantitative reaction, this amount of crosslinker leads to an OH conversion of 75 mol%. The mixture is emulsified into the dispersant solution immediately after the preparation according to Example 1. Subsequently, the samples were left to react for 48 hours at room temperature.

Beispiel 12Example 12

0,6 g des Dispergiermittels (b) werden in 20 g des Dispersionsmediums (b) gelöst. 17,5 g des trifunktionellen Glykols (b) werden mit 6,79 g des Vernetzers (a) vermischt. Diese Vernetzermenge führt bei einer quantitativen Reaktion zum stöchiometrischen Umsatz der Hydroxylgruppen im Glykol und entspricht somit einem OH-Umsatz von 100 Mol-%. Das Gemisch wird sofort nach der Herstellung gemäß Beispiel 1 in die Dispergiermittel-Lösung emulgiert. Nachträglich wurden die Proben 8 Stunden bei 90°C ausreagiert.0.6 g of the dispersant (b) are dissolved in 20 g of the dispersion medium (b). 17.5 g of the trifunctional glycol (b) are mixed with 6.79 g of the crosslinker (a). In the case of a quantitative reaction, this amount of crosslinker leads to the stoichiometric conversion of the hydroxyl groups in the glycol and thus corresponds to an OH conversion of 100 mol%. The mixture is emulsified into the dispersant solution immediately after the preparation according to Example 1. The samples were subsequently fully reacted at 90 ° C. for 8 hours.

Zentrifugation der Probe (30 min bei 2000 g) führte, trotz der niedrigen Viskosität zu keiner sichtbaren Abtrennung der dispersen Phase vom Dispersionsmedium. Bei einer Vergleichsprobe gemäß Vergleichsbeispiel 2 hatte sich jedoch die disperse Phase als festes Sediment auf den Boden des Zentrifugenröhrchens abgesetzt. Dieses Sediment war nur durch starke Scherbeanspruchung wieder zu redispergieren.Centrifugation of the sample (30 min at 2000 g), despite the low viscosity, did not result in any visible separation of the disperse phase from the dispersion medium. In a comparative sample according to comparative example 2, however, the disperse had Phase deposited as solid sediment on the bottom of the centrifuge tube. This sediment could only be redispersed by strong shear stress.

Vergleichsbeispiel 1Comparative Example 1

Gemäß Beispiel 6 des Patentes DE 3 536 934 A1 wurden 50 Gew.-Teile eines Erionits (Zusammensetzung: 62 Gew.-% SiO₂, 18 Gew.-% Al₂O₃, 10 Gew.-% Na₂O) in 50 Gew.-Teile eines Polydimethylsiloxan-Siliconöls mit einer Viskosität von 5 mm²/s (bei 25°C) eindispergiert. Die Feuchte des Erionits nach DIN 55 921 betrug 6 Gew.-%. Als Dispergiermittel wurden 2,5 Gew.-Teile des in der Patentschrift beschriebenen Dispergiermittels 1 (aminofunktionelles Siloxan) eingesetzt.According to Example 6 of patent DE 3 536 934 A1, 50 parts by weight of an erionite (composition: 62% by weight SiO₂, 18% by weight Al₂O₃, 10% by weight Na₂O) in 50 parts by weight of a polydimethylsiloxane -Silicone oil with a viscosity of 5 mm² / s (at 25 ° C) dispersed. The moisture content of the erionite according to DIN 55 921 was 6% by weight. 2.5 parts by weight of the dispersant 1 (amino-functional siloxane) described in the patent were used as the dispersant.

Vergleichsbeispiel 2Comparative Example 2

Gemäß Beispiel 7 des Patentes DE 3 536 934 A1 wurden 40 Gew.-Teile eines Al-Silikates (Zusammensetzung: 75 Gew.-% SiO₂, 9 Gew.-% Al₂O₃, 7 Gew.-% Na₂O) in 60 Gew.-Teile eines Polydimethylsiloxan-Siliconöls mit einer Viskosität von 5 mm²/s (bei 25°C) eindispergiert. Die Feuchte des Al-Silikates nach DIN 55 921 betrug 6 Gew.-%. Als Dispergiermittel wurden 6 Gew.-Teile des in der Patentschrift beschriebenen Dispergiermittels 1 eingesetzt.According to Example 7 of patent DE 3 536 934 A1, 40 parts by weight of an Al silicate (composition: 75% by weight SiO₂, 9% by weight Al₂O₃, 7% by weight Na₂O) were converted into 60 parts by weight a polydimethylsiloxane silicone oil with a viscosity of 5 mm² / s (at 25 ° C) dispersed. The moisture of the Al silicate according to DIN 55 921 was 6% by weight. 6 parts by weight of the dispersant 1 described in the patent were used as the dispersant.

Vergleichsbeispiel 3Comparative Example 3

Gemäß Beispiel 9 des Patentes DE 3 536 934 A1 wurden 50 Gew.-Teile eines Zeoliths Y (Na-Form) (Zusammensetzung: 58 Gew.-% SiO₂, 20 Gew.-% Al₂O₃, 12 Gew.-% Na₂O) in 50 Gew.-Teile eines Polydimethylsiloxan-Siliconöls mit einer Viskosität von 5 mm²/s (bei 25°C) eindispergiert. Die Feuchte des Zeoliths Y nach DIN 55 921 betrug 6 Gew.-%. Als Dispergiermittel wurden 2,5 Gew.-Teile des in der Patentschrift beschriebenen Dispergiermittels 1 eingesetzt.

Figure imgb0004
According to Example 9 of patent DE 3 536 934 A1, 50 parts by weight of a zeolite Y (Na form) (composition: 58% by weight SiO₂, 20% by weight Al₂O₃, 12% by weight Na₂O) were added in 50 Part by weight of a polydimethylsiloxane silicone oil with a viscosity of 5 mm² / s (at 25 ° C) dispersed. The moisture of the zeolite Y according to DIN 55 921 was 6% by weight. 2.5 parts by weight of the dispersant 1 described in the patent were used as the dispersant.
Figure imgb0004

Claims (7)

Elektroviskose Flüssigkeiten, enthaltend im wesentlichen A) einen linearen und/oder verzweigten, gegebenenfalls funktionalisierten Polyether oder dessen Monomere, das Umsetzungsprodukt eines solchen Polyethers bzw. der Monomere mit mono- oder oligofunktionellen Verbindungen und gegebenenfalls zusätzlich weitere Additive, B) Dispergiermittel sowie C) ein Nicht-wäßriges Dispersionsmedium. Electroviscous liquids, containing essentially A) a linear and / or branched, optionally functionalized polyether or its monomers, the reaction product of such a polyether or the monomers with mono- or oligofunctional compounds and, if appropriate, additional additives, B) dispersant and C) a non-aqueous dispersion medium. Elektroviskose Flüssigkeiten gemäß Anspruch 1, dadurch gekennzeichnet, daß die Phase A) während des Dispergiervorganges in flüssiger Form vorliegt, gegebenenfalls jedoch durch den Zusatz von reaktiven Additiven vor, während oder nach der Dispergierung in eine höherviskose bzw. feste Form überführt wird.Electroviscous liquids according to Claim 1, characterized in that phase A) is in liquid form during the dispersing process, but is optionally converted into a more viscous or solid form by adding reactive additives before, during or after the dispersion. Elektroviskose Flüssigkeit gemäß einem der Ansprüche 1 oder 2, dadurch gekennzeichnet, daß sie als Komponente C) ein Siliconöl enthält.Electroviscous liquid according to one of claims 1 or 2, characterized in that it contains a silicone oil as component C). Elektroviskose Flüssigkeit gemäß einem der Ansprüche 1 bis 3, dadurch gekennzeichnet, daß sie als Komponente C) ein fluorhaltiges Siloxan, gegebenenfalls im Gemisch mit fluorfreien Siloxanen, enthält.Electroviscous liquid according to one of Claims 1 to 3, characterized in that it contains a fluorine-containing siloxane as component C), optionally in a mixture with fluorine-free siloxanes. Elektroviskose Flüssigkeit gemäß einem der Ansprüche 1 oder 2, dadurch gekennzeichnet, daß sie als Komponente C) einen Kohlenwasserstoff enthält.Electroviscous liquid according to one of claims 1 or 2, characterized in that it contains a hydrocarbon as component C). Elektroviskose Flüssigkeiten gemäß einem der Ansprüche 1 bis 5, dadurch gekennzeichnet, daß sie als Komponente B) ein Polysiloxan-Polyether-Copolymerisat enthält.Electroviscous liquids according to one of Claims 1 to 5, characterized in that they contain a polysiloxane-polyether copolymer as component B). Elektroviskose Flüssigkeiten gemäß einem der Ansprüche 1 bis 5, dadurch gekennzeichnet, daß sie als Komponente B) Alkoxy- bzw. ein Acetoxypolysiloxan enthält.Electroviscous liquids according to one of claims 1 to 5, characterized in that they contain alkoxy- or an acetoxypolysiloxane as component B).
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EP0472991A1 (en) * 1990-08-25 1992-03-04 Bayer Ag Electroviscous fluids based on polymerdispersions with an eletrolyte containing disperser phase
WO1992022623A1 (en) * 1991-06-14 1992-12-23 Bayer Aktiengesellschaft An electroviscous fluid based on polyether acrylates as disperse phase
EP0521638A1 (en) * 1991-06-29 1993-01-07 Dow Corning Limited Electrorheological fluid comprising a polysiloxane having a fluorohexylalkyl group
EP0529166A1 (en) * 1991-08-29 1993-03-03 Nippon Shokubai Co., Ltd. Electrorheological fluids
WO1993006199A1 (en) * 1991-09-19 1993-04-01 Bayer Aktiengesellschaft Electroviscous liquid
WO1993007244A1 (en) * 1991-10-10 1993-04-15 The Lubrizol Corporation Electrorheological fluids containing polyanilines
WO1993007243A1 (en) * 1991-10-10 1993-04-15 The Lubrizol Corporation Electrorheological fluids containing electronically conductive polymers
EP0543377A1 (en) * 1991-11-20 1993-05-26 Dow Corning Toray Silicone Company, Limited Electroviscous fluid
EP0636683A1 (en) * 1993-07-30 1995-02-01 Nippon Shokubai Co., Ltd. Electrorheological fluid
FR2712600A1 (en) * 1993-11-18 1995-05-24 Rhone Poulenc Chimie Anhydrous electro-rheological fluid
US5595680A (en) * 1991-10-10 1997-01-21 The Lubrizol Corporation Electrorheological fluids containing polyanilines
US5843331A (en) * 1995-11-13 1998-12-01 The Lubrizol Corporation Polymeric materials to self-regulate the level of polar activators in electrorheological fluids
US6065572A (en) * 1995-11-13 2000-05-23 The Lubrizol Corporation Polymeric materials to self-regulate the level of polar activators in electrorheological fluids

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US5268118A (en) * 1990-08-25 1993-12-07 Bayer Aktiengesellschaft Electroviscous liquids based on polymer dispersions with an electrolyte-containing disperse phase
EP0472991A1 (en) * 1990-08-25 1992-03-04 Bayer Ag Electroviscous fluids based on polymerdispersions with an eletrolyte containing disperser phase
WO1992022623A1 (en) * 1991-06-14 1992-12-23 Bayer Aktiengesellschaft An electroviscous fluid based on polyether acrylates as disperse phase
US5462687A (en) * 1991-06-14 1995-10-31 Bayer Aktiengesellschaft Electroviscous fluid based on polyether acrylates as disperse phase
EP0521638A1 (en) * 1991-06-29 1993-01-07 Dow Corning Limited Electrorheological fluid comprising a polysiloxane having a fluorohexylalkyl group
EP0529166A1 (en) * 1991-08-29 1993-03-03 Nippon Shokubai Co., Ltd. Electrorheological fluids
WO1993006199A1 (en) * 1991-09-19 1993-04-01 Bayer Aktiengesellschaft Electroviscous liquid
WO1993007243A1 (en) * 1991-10-10 1993-04-15 The Lubrizol Corporation Electrorheological fluids containing electronically conductive polymers
US5435932A (en) * 1991-10-10 1995-07-25 The Lubrizol Corporation Electrorheological fluids containing eletronically conductive polymers
US5437806A (en) * 1991-10-10 1995-08-01 The Lubrizol Corporation Electrorheological fluids containing polyanilines
WO1993007244A1 (en) * 1991-10-10 1993-04-15 The Lubrizol Corporation Electrorheological fluids containing polyanilines
US5595680A (en) * 1991-10-10 1997-01-21 The Lubrizol Corporation Electrorheological fluids containing polyanilines
EP0543377A1 (en) * 1991-11-20 1993-05-26 Dow Corning Toray Silicone Company, Limited Electroviscous fluid
EP0636683A1 (en) * 1993-07-30 1995-02-01 Nippon Shokubai Co., Ltd. Electrorheological fluid
FR2712600A1 (en) * 1993-11-18 1995-05-24 Rhone Poulenc Chimie Anhydrous electro-rheological fluid
US5843331A (en) * 1995-11-13 1998-12-01 The Lubrizol Corporation Polymeric materials to self-regulate the level of polar activators in electrorheological fluids
US6065572A (en) * 1995-11-13 2000-05-23 The Lubrizol Corporation Polymeric materials to self-regulate the level of polar activators in electrorheological fluids

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