EP0472991A1 - Electroviscous fluids based on polymerdispersions with an eletrolyte containing disperser phase - Google Patents

Electroviscous fluids based on polymerdispersions with an eletrolyte containing disperser phase Download PDF

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EP0472991A1
EP0472991A1 EP91113465A EP91113465A EP0472991A1 EP 0472991 A1 EP0472991 A1 EP 0472991A1 EP 91113465 A EP91113465 A EP 91113465A EP 91113465 A EP91113465 A EP 91113465A EP 0472991 A1 EP0472991 A1 EP 0472991A1
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Prior art keywords
electroviscous
optionally
evf
component
viscosity
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EP91113465A
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German (de)
French (fr)
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EP0472991B1 (en
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Robert Dr. Bloodworth
Günther Dr. Penners
Günter Dr. Oppermann
Roland Dr. Flindt
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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 solids in hydrophobic and electrically non-conductive oils, the viscosity of which changes very quickly and reversibly from the liquid to the plastic or solid state under the influence of a sufficiently strong electric field.
  • the viscosity reacts to both DC electrical fields and AC fields, whereby the current flow through the EVF should be very low.
  • 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 increase in viscosity in an EVF when an electric field is applied can be explained qualitatively as follows:
  • the colloidally chemically stable disperse particles polarize in the electric field and agglomerate through dipole interaction in the field direction, which leads to an increase in viscosity.
  • the agglomeration is reversible: if the electric field is switched off, the particles redisperse and the viscosity is reduced to the original value.
  • the polarizability of the disperse phase is therefore an important prerequisite for the development of the electroviscous effect. For this reason, ionically or electronically conductive materials are often used as the disperse phase.
  • the disperse phase consists of organic solids, such as Saccharides (DE 2 530 694), starch (EP 2 842 268 A2, US 3 970 573), polymers (EP 150994, A1, DE 3 310 959 A1, GB 1 570 234, US 4 129 513, ion exchange resins (JP 92 278 / 975, JP 31 221/1985, US 3 047 507), or silicone resins (DE 3 912 888 A1), but inorganic materials such as 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).
  • Saccharides DE 2 530 694
  • starch EP 2 842 268 A2, US 3 970 573
  • polymers EP 150994, A1, DE 3 310 959 A1, GB 1 570 234, US 4 129
  • the electroviscous effect of the substances mentioned is due to the loading of the solids with water. Small amounts of water increase the ionic conductivity, and thus the polarizability of the disperse particles, which is essential for the formation of the effect. However, hydrated systems have poor chemical stability. In addition, the temperature range in which these liquids can be used is limited.
  • the EVF described are , due to the hardness of the dispersed particles, being abrasive and therefore only of limited use for practical applications in which high shear stresses occur, including soot-filled bead polymers (JP 016 093) or conductive polymers, such as polypyrene or polyacetylene (JP 0126 0710) Replacement for the hydrated phase discussed.
  • soot-filled bead polymers JP 016 093
  • conductive polymers such as polypyrene or polyacetylene (JP 0126 0710) Replacement for the hydrated phase discussed.
  • the optimal properties of the disperse phase can be easily adjusted by varying the water content or by modifying the solid matrix.
  • patent specification DE 2 802 494 C2 describes an improvement in the electroviscous effect by introducing free or neutralized acid groups into a water-containing polymer phase.
  • the high conductivity of the feedstocks often requires post-treatment of the dispersion particles.
  • the passivation of carbon black-filled bead polymers by the subsequent coating of the polymer particles with polyvinylidene fluoride was described in the patent specification JP 016 093.
  • the manufacturing effort is greatly increased by such post-treatments.
  • EVF corresponding to the prior art are generally obtained by dispersing a solid in a dispersion medium, such as e.g. halogen-free or halogenated hydrocarbons, aromatics or silicone oil.
  • a dispersion medium such as e.g. halogen-free or halogenated hydrocarbons, aromatics or silicone oil.
  • 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 when using non-spherical particles.
  • the object of the invention was to provide an anhydrous, non-abrasive, sedimentation-stable EVF with good to provide electroviscous properties which, despite a high volume fraction of disperse phase, are distinguished by a low basic viscosity.
  • electroviscous liquids can be produced on the basis of anhydrous polymers which contain the dissolved electrolyte.
  • the electroviscous properties of these liquids can be adjusted over a wide range by the type and concentration of the electrolyte.
  • the electroviscous dispersions according to the invention are anhydrous and have a high dielectric strength.
  • the EVFs described are settling-stable and not abrasive and have low basic viscosities despite high volume fractions of the disperse phase.
  • the dispersion polymerization of electrolyte-containing monomers is particularly suitable as a process for producing the EVF according to the invention.
  • the polymerization should preferably be carried out in the dispersion medium which also represents the continuous phase of the EVF, since this eliminates the need for subsequent redispersion.
  • the EVF according to the invention essentially contains the following substances (I) in the disperse phase: a polymer or polymer mixture, (11): a dissolved electrolyte and optionally (III): an additive which is miscible with the solution of (I) and (11).
  • the mixture of substances and their starting products are also referred to as templates.
  • the template that 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 (IV) before, during or after the dispersing step. This modification influences the consistency of the disperse phase in the finished EVF through the partial or complete implementation of the functional groups in the template.
  • a suitable dispersant (V) is used for the dispersion.
  • the size of the dispersed particles in the EVF according to the invention is between 0.1 and 200 ⁇ m.
  • the viscosity of the EVF is between 3 and 5000 cp at room temperature, depending on the composition of the liquid and the basic viscosity of the dispersion medium.
  • the EVF according to the invention essentially contains the following substances (I) in the disperse phase: a polymer (11): a dissolved electrolyte and optionally (III): an additive which is miscible with the solution of (I) and (11).
  • linear or cross-linked polyethers or their copolymers polyethylene adipate, polyethylene succinate and polyphosphazene.
  • polyethers or polymers which can be prepared by crosslinking di- or trifunctional polyether oligomers are particularly preferred.
  • linear polyether oligomers are polyethylene glycols, polypropylene glycols, statistical ethylene glycol-propylene glycol copolymers or else ethylene glycol-propylene glycol block copolymers, such as those e.g. are sold by GAF under the trade name "Pluronic".
  • Branched polyether oligomers are, for example, tris (polypropylene oxide) w-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 glycols is between 62 and 1,000,000, but preferably between 100 and 10,000.
  • the oligomers may optionally contain functional end groups. Amines, allyl or vinyl groups, or also carboxyl groups are examples of such functional end groups.
  • Polyethylene or polypropylene mono- or diamines can be purchased under the trade name "Jeffamin" from TEXACO. Examples of vinyl group-containing products are the esters of glycols with corresponding acids, e.g. Acrylic acid.
  • Other preferred polymers are e.g. the polyesters among others by the company BAYER AG under the trade name "De
  • electrolytes (11) are substances which are soluble in the polymer (I) in molecular or ionic form.
  • electrolytes are, for example, free acids or their salts with alkali or alkaline earth metals or organic cations.
  • the electrolytes thus include salts such as KCI, LiN0 3 , CH 3 COONa, LiClO 4 , Mg (ClO 4 ) 2 , KSCN, LiBr, Lil, LiBF 4 , LiPF 6 , NaB (C 6 H 5 ) 4 , LiCF 3 S0 3 , N (C 2 H 4 ) 4 CI etc.
  • Additives (III) in the sense of the invention are those compounds which, when mixed with (I) and (11), give a homogeneous, solid or liquid solution.
  • capped low molecular weight polyethers e.g. bismethylated trimethylolpropane or the esters of phthalic acid, suitable as an additive.
  • an additive (IV) for example crosslinking agent
  • a crosslinking agent for example crosslinking agent
  • viscous or solid particles, their spherical geomes, form trie is maintained during and after the reaction.
  • di- or multifunctional isocyanates are preferably used as crosslinking agents (IV).
  • Isocyanates of different structures are sold under the trade name "Desmodur” by the company BAYER AG.
  • the use of tolylene diisocyanate as crosslinking agent is particularly suitable.
  • the acetate, amine, benzamide, oxime and alkoxy crosslinkers customary in silicone chemistry can also be used for crosslinking. Radical crosslinking systems are suitable for the conversion of allyl or vinyl (acrylic or methacrylic) group-modified polymer templates.
  • the EVF according to the invention contains the disperse phase (the product from the initial charge and (IV)) in an amount of 10-95% by weight, but preferably 40-70% by weight.
  • Dispersants (V) for the disperse phase which can be used are surfactants which are soluble in the dispersion medium and are derived, for example, from amines, imidazolines, oxazolines, alcohols, glycol or sorbitol. Polymers soluble in the dispersion medium can also be used. Suitable are, for example, polymers which contain 0.1 to 10% by weight of N and / or OH and 25 to 83% by weight of C 4 -C 24 -alkyl groups and have a molecular weight in the range from 5000 to 1,000,000.
  • the N and OH-containing compounds in these polymers can be, for example, amine, amide, imide, nitrile, 5- to 6-membered N-containing heterocyclic rings or an alcohol, and the C 4 -C 24 - Alkyl group esters of acrylic or methacrylic acid.
  • Examples of the N- and OH-containing compounds mentioned are N, N-dimethylaminoethyl methacrylate, tert-butyl acrylamide, maleimide, acrylonitrile, N-vinyl pyrrolidone, vinyl pyridine 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 are preferably used, as are available, for example, under the trade name "Tegopren” from GOLDSCHMIDT AG in Essen (FRG).
  • An example of a particularly preferred dispensing agent for the production of an EVF are polysiloxane polyethers with an ethylene oxide-propylene oxide weight ratio of 49:51, which are 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 hydroxyl-functional polysiloxane with aminosilanes.
  • liquid hydrocarbons such as e.g. Paraffins, olefins and aromatic hydrocarbons
  • silicone oils such as polydimethylsiloxanes 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 mm 2 / s at room temperature.
  • the low-viscosity oils with a viscosity of 3 to 20 mm 2 / 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.
  • fluorine-containing siloxanes which are used as pure substance or as a mixture with other silicone oils, to produce EVFs according to the invention which, despite their low basic viscosity, have no sedimentation for weeks.
  • the initial charge is mixed with the reactive additive or the crosslinking agent (IV).
  • 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. If necessary, after the dispersion has been carried out, the product is allowed to react for a long time at a suitable temperature, which is typically in a range of 15-150 ° C., depending on the reactivity of the crosslinking agent.
  • the crosslinking agent is only mixed into the dispersion after the dispersion process.
  • the disperse phase can be separated from the original dispersant after the reaction and transferred to a new dispersion medium.
  • 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 0.50 mm is approximately 78 cm 2 , 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. With this device, both static and dynamic measurements are possible.
  • the EVF can be excited with both DC voltage 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 O ⁇ D ⁇ 2640s -1 is set and the dependence of the shear stress 7 on the electric field strength E is measured.
  • alternating fields up to a maximum effective field strength of 2370 kV / m at a maximum effective Current of 4 mA and a frequency between 50 and 550 Hz can be generated.
  • measurement is preferably carried out at 50 Hz, because then the total current is the lowest and the electrical power required is the lowest.
  • Flow curves corresponding to Fig. 1 are obtained. It can be seen that the shear stress 7 initially increases parabolically with small field strengths and linearly with larger field strengths.
  • the relative increase in viscosity determines the switching behavior of an EVF in practice and is therefore, in addition to the absolute effect S, an important parameter.
  • comparative approaches 1 to 5 correspond to the prior art.
  • the EVF described in Comparative Examples 1 to 3 contain, as the disperse phase, water-containing polymers with free or neutralized acid groups with covalently bonded to them. They are based on Examples 1, 2 and 7 of patent specification DE 2 820 494 C2.
  • the liquids described in these examples, which are representative of the patent, show good electroviscous effects, but have a high plastic viscosity, which means that the relative effect is significantly smaller.
  • the EVF described in Comparative Examples 4 and 5 contain anhydrous, differently coated aluminum particles as the disperse phase. They are taken from Japanese Laid-Open Specification 64-6093 (Examples 1 and 4 there). The EVF described have poor sedimentation properties due to the density and size of the disperse particles (> 20 ⁇ m).
  • Examples 1 to 10 are EVFs according to the invention.
  • the mean particle diameter is approximately 2 ⁇ m.
  • the maximum particle diameter is 6 ⁇ m.
  • the samples were measured at a temperature of 60 ° C.
  • Table 1 lists the electroviscous properties of the EVF according to the invention and their viscosity. Particularly noteworthy is the low basic viscosity of the liquids and the resulting high relative electroviscous effect.
  • Fig. 3 shows the course of the electroviscous effect S, and the viscosity of an EVF, produced according to Example 9, at a shear rate of 1000 s -1 depending on the weight concentration of the disperse phase. It can be seen that the liquid according to the invention is characterized by low viscosities despite high solids concentrations.
  • Example 2 of DE 2 830 494 C2 30 vol% dispersion of a methacrylic acid crosslinked with divinylbenzene in a polychlorinated diphenyl fraction.
  • the electroviscous effect at 30 ° C. was 690 Pa ⁇ mm / kV.
  • Example 7 of DE 2 820 494 C2 30% by volume dispersion of lithium / chromium polymethacrylate in a polychlorinated diphenyl fraction.
  • the electroviscous effect at 30 C was 1960 Pa ⁇ mm / kV.
  • Example 1 of Japanese Patent Application 64-6093 20% by volume dispersion of an aluminum oxide coated aluminum powder in TRIMEX T-08.
  • the electroviscous effect at an alternating voltage of 60 Hz was 327 Pa ⁇ mm / kV.
  • Example 4 of Japanese Laid-Open Publication 64-6093 20 vol.% Dispersion of an aluminum oxide coated aluminum powder in TRIMEX T-08.
  • the electroviscous effect at an alternating voltage of 60 Hz was 371 Pa ⁇ mm / kV.
  • 0.6 g of the dispersant is dissolved in 20 g of the dispersion medium in a beaker with a nominal volume of 100 ml.
  • 17.5 g of the glycol are mixed with 6.79 g of the crosslinker.
  • 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 reactive mixture of glycol and crosslinker is emulsified into the dispersant solution immediately after homogenization 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 2 min. The samples were subsequently reacted at 90 C for 15 hours.

Abstract

The invention relates to electroviscous fluids, containing essentially   (I) a polymer or polymer mixture,   (II) an electrolyte dissolved in (I),   (III) optionally an additive miscible with the solution of (I) and (II),   (IV) optionally an additive of increased viscosity, reacting with (I),   (V) a dispersant and   (VI) a non-aqueous dispersing medium. <IMAGE>

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 Feststoffe in hydrophoben und elektrisch nicht leitenden Ölen, deren Viskosität sich unter dem Einfluß eines hinreichend starken elektrischen Feldes sehr schell 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. EVF lassen sich 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 solids in hydrophobic and electrically non-conductive oils, the viscosity of which changes very quickly and reversibly from the liquid to the plastic or solid state under the influence of a sufficiently strong electric field. The viscosity reacts to both DC electrical fields and AC fields, whereby the current flow through the EVF should be very low. 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 gestellen 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 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.

Der Viskositätsanstieg in einer EVF bei Anlegen eines elektrischen Feldes ist qualitativ folgendermaßen zu erklären: Die kolloidchemisch stabilen dispersen Teilchen polarisieren im elektrischen Feld, und agglomerieren durch Dipolwechselwirkung in der Feldrichtung, was zum Anstieg der Viskosität führt. Die Agglomeration ist reversibel: wird das elektrische Feld abgeschaltet, redispergieren die Teilchen und die Viskosität wird auf den ursprünglichen Wert erniedrigt. Die Polarisierbarkeit der dispersen Phase ist somit eine wichtige Voraussetzung für die Ausbildung des elektroviskosen Effektes. Deshalb werden oft ionisch oder elektronisch leitfähige Materialien als disperse Phase verwendet.The increase in viscosity in an EVF when an electric field is applied can be explained qualitatively as follows: The colloidally chemically stable disperse particles polarize in the electric field and agglomerate through dipole interaction in the field direction, which leads to an increase in viscosity. The agglomeration is reversible: if the electric field is switched off, the particles redisperse and the viscosity is reduced to the original value. The polarizability of the disperse phase is therefore an important prerequisite for the development of the electroviscous effect. For this reason, ionically or electronically conductive materials are often used as the disperse phase.

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 2 842 268 A2, US 3 970 573), Polymere (EP 150994, A1, DE 3 310 959 A1, GB 1 570 234, US 4 129 513, lonenaustauscherharze (JP 92 278/975, JP 31 221/1985, 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.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 2 842 268 A2, US 3 970 573), polymers (EP 150994, A1, DE 3 310 959 A1, GB 1 570 234, US 4 129 513, ion exchange resins (JP 92 278 / 975, JP 31 221/1985, US 3 047 507), or silicone resins (DE 3 912 888 A1), but inorganic materials such as 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).

Der elektroviskose Effekt ist bei den genannten Substanzen auf die Beladung der Feststoffe mit Wasser zurückzuführen. Geringe Wasseranteile erhöhen die ionische Leitfähigkeit, und somit die für die Ausbildung des Effektes unerläßliche Polarisierbarkeit der dispersen Teilchen. Wasserhaltige Systeme haben jedoch eine geringe chemische Stabilität. Außerdem ist der Temperaturbereich, in dem diese Flüssigkeiten eingesetzt werden können, beschränkt.The electroviscous effect of the substances mentioned is due to the loading of the solids with water. Small amounts of water increase the ionic conductivity, and thus the polarizability of the disperse particles, which is essential for the formation of the effect. However, hydrated systems have poor chemical stability. In addition, the temperature range in which these liquids can be used is limited.

Bei anderen elektroviskosen Flüssigkeiten wurde versucht, die genannten Nachteile dadurch zu beheben, 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 0117 2496), oder Dielektrica wie z.B. Ti02 (SU 715 596), CaTi03 oder BaTi03 (JP 53/17585), Hydrolysaten von Metall-Alkoxiden (EP 341 737 oder Glashohlkörpern (J 0117 2496) be steht. 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. Auch rußgefüllte Perlpolymerisate (JP 016 093), oder leitfähige Polymeren, wie z.B. Polypyrol oder Polyacetylen (JP 0126 0710) wurden als Ersatz für die wasserhaltige Phase diskutiert.In the case of other electroviscous liquids, attempts have been made to remedy the disadvantages mentioned 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 aluminum (JP 016 093, JP 0117 2496 ), or dielectrics such as Ti0 2 (SU 715 596), CaTi0 3 or BaTi0 3 (JP 53/17585), hydrolysates of metal alkoxides (EP 341 737 or glass hollow bodies (J 0117 2496)). However, the EVF described are , due to the hardness of the dispersed particles, being abrasive and therefore only of limited use for practical applications in which high shear stresses occur, including soot-filled bead polymers (JP 016 093) or conductive polymers, such as polypyrene or polyacetylene (JP 0126 0710) Replacement for the hydrated phase discussed.

Bei den wasserhaltigen Systemen lassen sich die optimalen Eigenschaften der dispersen Phase, durch Variation des Wassergehaltes oder durch Modifikation der Feststoffmatrix, gut einstellen. So wurde in der Patentschrift DE 2 802 494 C2 eine Verbesserung des elektroviskosen Effektes durch das Einbringen von freien oder neutralisierten Säuregruppen in eine wasserhaltige polymere Phase beschrieben. Bei der Herstellung von EVF auf der Basis elektronisch leitfähiger disperser Phasen bedarf es, bedingt durch die hohe Leitfähigkeit der Einsatzstoffe, oft einer Nachbehandlung der Dispersionsteilchen. So wurde in der Patentschrift JP 016 093 die Passivierung von rußgefüllten Perlpolymerisaten durch die nachträgliche Beschichtung der Polymerpartikel mit Polyvinylidenfluorid beschrieben. Durch solche Nachbehandlungen wird der Herstellungsaufwand jedoch stark erhöht.In the case of water-containing systems, the optimal properties of the disperse phase can be easily adjusted by varying the water content or by modifying the solid matrix. For example, patent specification DE 2 802 494 C2 describes an improvement in the electroviscous effect by introducing free or neutralized acid groups into a water-containing polymer phase. In the production of EVF based on electronically conductive disperse phases, the high conductivity of the feedstocks often requires post-treatment of the dispersion particles. For example, the passivation of carbon black-filled bead polymers by the subsequent coating of the polymer particles with polyvinylidene fluoride was described in the patent specification JP 016 093. However, the manufacturing effort is greatly increased by such post-treatments.

Die obengenannten, dem Stand der Technik entsprechenden EVF werden in der Regel durch eindispergieren eines Feststoffes in ein Dispersionsmedium, wie z.B. halogenfreie bzw. halogenierte Kohlenwasserstoffe, Aromate oder Silikonöl, 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 bei der Verwendung nicht sphärischer Teilchen nur schwer zu erreichen.The above-mentioned EVF corresponding to the prior art are generally obtained by dispersing a solid in a dispersion medium, such as e.g. halogen-free or halogenated hydrocarbons, aromatics or silicone oil. 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 when using non-spherical particles.

Aufgabe der Erfindung war es, eine wasserfreie, nicht-abrasive, sedimentationsstabile EVF mit guten elektroviskosen Eigenschaften bereitzustellen, die sich trotz hohen Volumenanteils an disperser Phase durch eine geringe Basisviskosität auszeichnet.The object of the invention was to provide an anhydrous, non-abrasive, sedimentation-stable EVF with good to provide electroviscous properties which, despite a high volume fraction of disperse phase, are distinguished by a low basic viscosity.

Es wurde gefunden, daß auf der Basis von wasserfreien Polymeren die gelösten Elektrolyt enthalten, solche elektroviskose Flüssigkeiten hergestellt werden können. Die elektroviskosen Eigenschaften dieser Flüssigkeiten lassen sich durch die Art und die Konzentration des Elektrolyten über weite Bereiche gezielt einstellen. Darüber hinaus sind die erfindungsgemäßen elektroviskosen Dispersionen wasserfrei und haben 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. Als Verfahren zur Herstellung der erfindungsgemäßen EVF ist die Dispersionspolymerisation von elektrolythaltigen Monomeren besonders geeignet. Die Polymerisation sollte vorzugsweise in dem Dispersionsmedium durchgeführt werden, daß auch die kontinuierliche Phase der EVF darstellt, da hierdurch eine nachträgliche Umdispergierung entfällt.It has been found that such electroviscous liquids can be produced on the basis of anhydrous polymers which contain the dissolved electrolyte. The electroviscous properties of these liquids can be adjusted over a wide range by the type and concentration of the electrolyte. In addition, the electroviscous dispersions according to the invention are anhydrous and 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 dispersion polymerization of electrolyte-containing monomers is particularly suitable as a process for producing the EVF according to the invention. The polymerization should preferably be carried out in the dispersion medium which also represents the continuous phase of the EVF, since this eliminates the need for subsequent redispersion.

Die erfindungsgemäße EVF enthält in der dispersen Phase im Wesentlichen folgende Substanzen (I): ein Polymer oder Polymergemisch, (11): ein gelöstes Elektrolyt und gegebenenfalls (III): ein mit der Lösung aus (I) und (11) mischbares Additiv.The EVF according to the invention essentially contains the following substances (I) in the disperse phase: a polymer or polymer mixture, (11): a dissolved electrolyte and optionally (III): an additive which is miscible with the solution of (I) and (11).

Das Substanzgemisch bzw. ihre Ausgangsprodukte werden des Weiteren als Vorlage bezeichnet. Die Vorlage, die 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 (IV) vor, während oder nach dem Dispergierschritt chemisch modifiziert werden. Diese Modifizierung beeinflußt durch die teilweise oder völlige Umsetzung der funktionellen Gruppen in der Vorlage, die Konsistenz der dispersen Phase in der fertigen EVF.The mixture of substances and their starting products are also referred to as templates. The template that 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 (IV) before, during or after the dispersing step. This modification influences the consistency of the disperse phase in the finished EVF through the partial or complete implementation of the functional groups in the template.

Um bei der Verwendung flüssiger Phasen Koaleszenz zu vermeiden, wird bei der Dispergierung ein geeignetes Dispergiermittel (V) verwendet. Die Größe der dispergierten Teilchen in der erfindungsgemäßen EVF beträgt zwischen 0,1 und 200 um. Die Viskosität der EVF beträgt bei Raumtemperatur, je nach Zusammensetzung der Flüssigkeit und der Basisviskosität des Dispersionsmedium, zwischen 3 und 5000 cp.In order to avoid coalescence when using liquid phases, a suitable dispersant (V) is used for the dispersion. The size of the dispersed particles in the EVF according to the invention is between 0.1 and 200 μm. The viscosity of the EVF is between 3 and 5000 cp at room temperature, depending on the composition of the liquid and the basic viscosity of the dispersion medium.

Die erfindungsgemäße EVF enthält in der dispersen Phase im Wesentlichen folgende Substanzen (I): ein Polymer (11): ein gelöstes Elektrolyt und gegebenenfalls (III): ein mit der Lösung aus (I) und (11) mischbares Additiv.The EVF according to the invention essentially contains the following substances (I) in the disperse phase: a polymer (11): a dissolved electrolyte and optionally (III): an additive which is miscible with the solution of (I) and (11).

Als Polymere (I) können im Prinzip alle Substanzen verwendet werden, die eine Elektrolytlöslichkeit aufweisen wie z.B. lineare oder vernetzte Polyether oder deren Copolymerisate, Polyethylenadipat, Polyethylensuccinat und Polyphosphazen. Besonders bevorzugt sind jedoch Polyether oder Polymere, die durch Vernetzung von di- oder trifunktionellen Polyetheroligomeren hergestellt werden können. Beispiele linearer Polyetheroligomere sind Polyethylenglycole, Polypropylenglycole, statistische Ethylenglycol-Propylenglycol-Copolymerisate oder auch Ethylenglycol-Propylenglycol-Blockcopolymerisate, wie sie z.B. unter dem Handelsnamen "Pluronic" von der Firma GAF vertrieben werden. Verzweigte Polyetheroligomere sind beispielsweise Tris(polypropylenoxid)w-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 Glycole liegt zwischen 62 und 1.000.000, vorzugsweise jedoch zwischen 100 und 10.000. Gegebenenfalls können die Oligomere funktionelle Endgruppen enthalten. Amine, Allyl- bzw. Vinylgruppen, oder auch Carboxylgruppen stellen Beispiele solcher funktioneller Endgruppen dar. Polyethylen- bzw. Polypropylen-mono- oder Diamine sind unter dem Handelsnamen "Jeffamin" bei der Firma TEXACO zu erwerben. Beispiele vinylgruppenhaltiger Produkte sind die Ester der Glycole mit entsprechenden Säuren, z.B. Acrylsäure. Weitere bevorzugte Polymere sind z.B. die Polyester die u.A. durch die Firma BAYER AG unter dem Handelsnamen "Desmophen" vertrieben werden.In principle, all substances which have electrolyte solubility, such as e.g. linear or cross-linked polyethers or their copolymers, polyethylene adipate, polyethylene succinate and polyphosphazene. However, polyethers or polymers which can be prepared by crosslinking di- or trifunctional polyether oligomers are particularly preferred. Examples of linear polyether oligomers are polyethylene glycols, polypropylene glycols, statistical ethylene glycol-propylene glycol copolymers or else ethylene glycol-propylene glycol block copolymers, such as those e.g. are sold by GAF under the trade name "Pluronic". Branched polyether oligomers are, for example, tris (polypropylene oxide) w-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 glycols is between 62 and 1,000,000, but preferably between 100 and 10,000. The oligomers may optionally contain functional end groups. Amines, allyl or vinyl groups, or also carboxyl groups are examples of such functional end groups. Polyethylene or polypropylene mono- or diamines can be purchased under the trade name "Jeffamin" from TEXACO. Examples of vinyl group-containing products are the esters of glycols with corresponding acids, e.g. Acrylic acid. Other preferred polymers are e.g. the polyesters among others by the company BAYER AG under the trade name "Desmophen".

Elektrolyte (11) im Sinne der Erfindung sind solche Substanzen, die in molekularer, bzw. ionischer Form im Polymer (I) löslich sind. Beispiele solcher Elektrolyte sind z.B. freie Säuren, bzw. deren Salze mit Alkali- bzw. Erdalkalimetallen oder organischen Kationen. Zu den Elektrolyten gehören somit Salze wie KCI, LiN03, CH3COONa, LiClO4, Mg(ClO4)2, KSCN, LiBr, Lil, LiBF4, LiPF6, NaB(C6H5)4, LiCF3S03, N(C2H4)4CI usw.For the purposes of the invention, electrolytes (11) are substances which are soluble in the polymer (I) in molecular or ionic form. Examples of such electrolytes are, for example, free acids or their salts with alkali or alkaline earth metals or organic cations. The electrolytes thus include salts such as KCI, LiN0 3 , CH 3 COONa, LiClO 4 , Mg (ClO 4 ) 2 , KSCN, LiBr, Lil, LiBF 4 , LiPF 6 , NaB (C 6 H 5 ) 4 , LiCF 3 S0 3 , N (C 2 H 4 ) 4 CI etc.

Additive (III) im Sinne der Erfindung sind solche Verbindungen die gemischt mit (I) und (11) eine homogene, feste oder flüssige, Lösung ergeben. So sind z.B. bei der Verwendung eines Polyethers als Polymer, verkappte niedermolekulare Polyether, wie z.B. bismethyliertes Trimethylolpropan oder die Ester der Phthalsäure, als Additiv geeignet.Additives (III) in the sense of the invention are those compounds which, when mixed with (I) and (11), give a homogeneous, solid or liquid solution. For example, when using a polyether as a polymer, capped low molecular weight polyethers, e.g. bismethylated trimethylolpropane or the esters of phthalic acid, suitable as an additive.

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), 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 before or after the emulsification of the template, which by reaction with the functional end groups of the compounds (I), to build up the molecular weight in the emulsion droplets, or else leads 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, their spherical geomes, form trie is maintained during and after the reaction.

Enthält die Vorlage ein Glycol als Komponente (I), werden vorzugsweise di- oder multifunktionelle Isocyanate als Vernetzer (IV) eingesetzt. Isocyanate unterschiedlicher Struktur werden unter dem Handelsnamen "Desmodur" durch die Firma BAYER AG vertrieben. Bei der Verwendung von tri- oder höherfunktionellen Glycolen ist der Einsatz von Toluylen-diisocyanat als Vernetzer besonders geeignet. Zur Vernetzung sind jedoch auch die in der Siliconchemie gängigen Acetat-, Amin-, Benzamid-, Oxim- und Alkoxyvernetzer einsetzbar. Für den Umsatz von allyl, bzw. vinyl-(acryl- bzw. methacryl-)gruppenmodifizierte Polymervorlagen sind radikalische Vernetzersysteme geeignet.If the template contains a glycol as component (I), di- or multifunctional isocyanates are preferably used as crosslinking agents (IV). Isocyanates of different structures are sold under the trade name "Desmodur" by the company BAYER AG. When using trifunctional or higher functional glycols, the use of tolylene diisocyanate as crosslinking agent is particularly suitable. However, the acetate, amine, benzamide, oxime and alkoxy crosslinkers customary in silicone chemistry can also be used for crosslinking. Radical crosslinking systems are suitable for the conversion of allyl or vinyl (acrylic or methacrylic) group-modified polymer templates.

In den erfindungsgemäßen EVF ist die disperse Phase (das Produkt aus Vorlage und (IV), zu 10-95 Gew.-%, vorzugsweise jedoch zu 40-70 Gew.-% enthalten.The EVF according to the invention contains the disperse phase (the product from the initial charge and (IV)) in an amount of 10-95% by weight, but preferably 40-70% by weight.

Als Dispergiermittel (V) für die disperse Phase können im Dispersionsmedium lösliche Tenside verwendet werden, die z.B. von Aminen, Imidazolinen, Oxazolinen, Alkoholen, Glycol 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 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- oder 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.Dispersants (V) for the disperse phase which can be used are surfactants which are soluble in the dispersion medium and are derived, for example, from amines, imidazolines, oxazolines, alcohols, glycol or sorbitol. Polymers soluble in the dispersion medium can also be used. Suitable are, for example, polymers which contain 0.1 to 10% by weight of N and / or OH and 25 to 83% by weight of C 4 -C 24 -alkyl groups and have a molecular weight in the range from 5000 to 1,000,000. The N and OH-containing compounds in these polymers can be, for example, amine, amide, imide, nitrile, 5- to 6-membered N-containing heterocyclic rings or an alcohol, and the C 4 -C 24 - Alkyl group esters of acrylic or methacrylic acid. Examples of the N- and OH-containing compounds mentioned are N, N-dimethylaminoethyl methacrylate, tert-butyl acrylamide, maleimide, acrylonitrile, N-vinyl pyrrolidone, vinyl pyridine 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 jedoch bevorzugt Polysiloxan-Polyether-Copolymere verwendet, wie sie beispielsweise unter dem Handelsnamen "Tegopren" bei der Firma GOLDSCHMIDT AG in Essen (BRD) verfügbar sind. Ein Beispiel eines besonders bevorzugten Dispermittels für die Herstellung einer EVF sind Polysiloxan Polyether mit einem Ethylenoxid-Propylenoxid-Gewichtsverhältnisvon 49:51, die bei der Firma GOLDSCHMIDT unter dem Namen "Tegopren 5830" geführt werden.For the dispersion in silicone oil, however, polysiloxane-polyether copolymers are preferably used, as are available, for example, under the trade name "Tegopren" from GOLDSCHMIDT AG in Essen (FRG). An example of a particularly preferred dispensing agent for the production of an EVF are polysiloxane polyethers with an ethylene oxide-propylene oxide weight ratio of 49:51, which are 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 hydroxifunktionellen 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 hydroxyl-functional polysiloxane with aminosilanes.

Als Dispersionsmedium (VI) für die disperse Phase werden, neben flüssigen Kohlenwasserstoffen, wie z.B. Paraffine, Olefine und aromatische Kohlenwasserstoffe, vorzugsweise Silikonöle wie Polydimethylsiloxane 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.In addition to liquid hydrocarbons such as e.g. Paraffins, olefins and aromatic hydrocarbons, preferably silicone oils such as polydimethylsiloxanes 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.

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.The viscosity of the oils is between 3 and 300 mm 2 / s at room temperature. In general, the low-viscosity oils with a viscosity of 3 to 20 mm 2 / 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 Siliconölen 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 silicone oils, to 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 imgb0001

n=1-10

  • m = 2-18
  • p=1-5
Fluorine-containing siloxanes of the general structure are particularly suitable for producing sedimentation-stable EVF:
Figure imgb0001
n = 1-10
  • m = 2-18
  • p = 1-5

Bei einer typischen Art der Herstellung der erfindungsgemäßen EVF wird die Vorlage mit dem reaktiven Additiv bzw. dem Vernetzer (IV) 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 um nicht überschreiten. Gegebenenfalls läßt man nach erfolgter Dispergierung das Produkt bei einer geeigneter Temperatur, die abhängig von der Reaktivität des Vernetzers typischerweise in einem Bereich von 15-150` 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 (IV). 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. If necessary, after the dispersion has been carried out, the product is allowed to react for a long time at a suitable temperature, which is typically in a range of 15-150 ° C., depending on the reactivity of the crosslinking agent.

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.

Gegebenenfalls kann man, unabhängig von der Herstellungsweise, die disperse Phase nach der Reaktion von dem ursprünglichen Dispergiermittel trennen und in ein neues Dispersionsmedium überführen.If necessary, regardless of the method of preparation, the disperse phase can be separated from the original dispersant after the reaction and transferred to a new dispersion medium.

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), Seite 1137-1140 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), page 1137-1140.

Die Elektrodenfläche des inneren rotierenden Zylinders mit einem Durchmesser von 0,50 mm beträgt ca. 78 cm2, die Spaltweite zwischen den Elektroden 0,50 mm. Bei den dynamsichen Messungen kann die Scherbelastung mit maximal 2640 s-1 eingestellt werden. Der Meßbereich der Schubspannung des Viskosimeters beträgt maximal 750 Pa. Mit dieser Apparatur sind sowohl statische als auch dynamische Messungen möglich. 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 0.50 mm is approximately 78 cm 2 , 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. With this device, both static and dynamic measurements are possible. The EVF can be excited with both DC voltage 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 O<D<2640s-1 ein und mißt die Abhängigkeit der Schubspannung 7 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 Abb.1. Man erkennt, daß die Schubspannung 7 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'mm/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:

Figure imgb0002
To determine the electroreactivity, a constant shear rate O <D <2640s -1 is set and the dependence of the shear stress 7 on the electric field strength E is measured. With the test apparatus, alternating fields up to a maximum effective field strength of 2370 kV / m at a maximum effective Current of 4 mA and a frequency between 50 and 550 Hz can be generated. However, measurement is preferably carried out at 50 Hz, because then the total current is the lowest and the electrical power required is the lowest. Flow curves corresponding to Fig. 1 are obtained. It can be seen that the shear stress 7 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'mm / kV. From the point of intersection of the straight line S with the straight line τ = τ o (shear stress without an electric field), the threshold value Eo of the electric field strength is determined in kV / m. The following applies to the increase in shear stress τ (E) -τo in the electric field E> Eo:
Figure imgb0002

Hieraus ergibt sich für die relative Viskositätszunahme, Vr(E), die durch Anlegen eines elektrischen Feldes mit Feldstärke E erreicht wird, folgende Beziehung:

Figure imgb0003
This gives the following relationship for the relative increase in viscosity, V r (E), which is achieved by applying an electric field with field strength E:
Figure imgb0003

Die relative Viskositätszunahme bestimmt das Schaltverhalten einer EVF in der Praxis und ist somit, neben dem absolutem Effekt S eine wichtige Kenngröße.The relative increase in viscosity determines the switching behavior of an EVF in practice and is therefore, in addition to the absolute effect S, an important parameter.

Bei den nachfolgend beschriebenen Ausführungsbeispielen entsprechen die Vergleichsansätze 1 bis 5 dem Stand der Technik. Die in den Vergleichsbeispielen 1 bis 3 beschriebenen EVF enthalten als disperse Phase wasserhaltige Polymere, mit daran kovalent gebunden, freie oder neutralisierte Säuregruppen. Ihnen liegen die Beispiele 1, 2 und 7 der Patentschrift DE 2 820 494 C2 zugrunde. Die in diesen Beispielen beschriebenen, für das Patent representativen, Flüssigkeiten zeigen gute elektroviskose Effekte, weisen aber eine hohe plastische Viskosität auf, wodurch der relative Effekt deutlich kleiner ausfällt.In the exemplary embodiments described below, comparative approaches 1 to 5 correspond to the prior art. The EVF described in Comparative Examples 1 to 3 contain, as the disperse phase, water-containing polymers with free or neutralized acid groups with covalently bonded to them. They are based on Examples 1, 2 and 7 of patent specification DE 2 820 494 C2. The liquids described in these examples, which are representative of the patent, show good electroviscous effects, but have a high plastic viscosity, which means that the relative effect is significantly smaller.

Die in den Vergleichsbeispielen 4 und 5 beschriebenen EVF enthalten als disperse Phase wasserfreie, unterschiedlich beschichtete Aluminiumteilchen. Sie sind der japanischen Offenlegunggschrift 64-6093 (dort Beispiele 1 und 4) entnommen. Die beschriebenen EVF haben, bedingt durch die Dichte und Größe der dispersen Teilchen (>20 um) schlechte Sedimentationseigenschaften.The EVF described in Comparative Examples 4 and 5 contain anhydrous, differently coated aluminum particles as the disperse phase. They are taken from Japanese Laid-Open Specification 64-6093 (Examples 1 and 4 there). The EVF described have poor sedimentation properties due to the density and size of the disperse particles (> 20 µm).

Bei den Beispielen 1 bis 10 handelt es sich um erfindungsgemäße EVF. Bei allen beschriebenen Proben beträgt der mittlere Teilchendurchmesser ungefähr 2 um. Der maximale Teilchendurchmesser beträgt 6 um. Die Proben wurden bei einer Temperatur von 60 C vermessen.Examples 1 to 10 are EVFs according to the invention. In all of the samples described, the mean particle diameter is approximately 2 µm. The maximum particle diameter is 6 µm. The samples were measured at a temperature of 60 ° C.

In Tabelle 1 sind die elektroviskosen Eigenschaften der erfindungsgemäßen EVF, sowie deren Viskosität aufgeführt. Besonders hervorzuheben ist die niedrige Basisviskosität der Flüssigkeiten, und der dadurch bedingte hohe relative elektroviskose Effekt.Table 1 lists the electroviscous properties of the EVF according to the invention and their viscosity. Particularly noteworthy is the low basic viscosity of the liquids and the resulting high relative electroviscous effect.

In Abb. 2 ist für LiN03-haltige, auf der Basis von vernetzen Glycolen hergestellte EVF (Beispiele 1 bis 6), der Zusammenhang zwischen dem elektroviskosen Effekt S, und den auf den Ethylenoxidgehalt bezogenen molaren Li-Anteil grafisch dargestellt.In Fig. 2 for LiN0 3 -containing EVF based on cross-linked glycols (Examples 1 to 6), the relationship between the electroviscous effect S, and the molar proportion of Li related to the ethylene oxide content is shown graphically.

Abb. 3 zeigt den Verlauf des elektroviskosen Effektes S, sowie der Viskosität einer EVF, hergestellt gemäß Beispiel 9, bei einer Schergeschwindigkeit von 1000 s-1 in Abhängigkeit von der Gewichtskonzentration der dispersen Phase. Es zeigt sich, daß sich die erfindungsgemäße Flüssigkeit trotz hoher Feststoffkonzentrationen durch geringe Viskositäten kennzeichnet.Fig. 3 shows the course of the electroviscous effect S, and the viscosity of an EVF, produced according to Example 9, at a shear rate of 1000 s -1 depending on the weight concentration of the disperse phase. It can be seen that the liquid according to the invention is characterized by low viscosities despite high solids concentrations.

AusführungsbeispieleEmbodiments

Dispersionsmedium : Polydimethylsiloxan (Siliconöl) Viskosität bei 25 C : 5 mm2/s Dichte bei 25 C:

  • : 0,9 g/cm3 Dielektrizitätszahl ∈r nach DIN 53483 bei 0° C und 50 Hz : 2,8 Dispergierte Phase : Trifunktionelles Polyethylenglykol mit einem Molekulargewicht von 675, hergestellt durch Ethoxylierung von Trimethylolpropan
  • Dispergiermittel : Rektionsprodukt aus 100 Gew.-Teilen eines OH-endgestoppten Polydimethylsiloxans mit einem Molekulargewicht von 18200 und einem Gew.-Teil Aminopropyltriethoxysilan
  • Vernetzer : Toluylen-Diisocyanat (TDI)
Dispersion medium: polydimethylsiloxane (silicone oil) Viscosity at 25 C: 5 mm 2 / s Density at 25 C:
  • : 0.9 g / cm 3 dielectric constant ∈r according to DIN 53483 at 0 ° C and 50 Hz: 2.8 Dispersed phase: Trifunctional polyethylene glycol with a molecular weight of 675, produced by ethoxylation of trimethylolpropane
  • Dispersant: Rection product of 100 parts by weight of an OH-terminated polydimethylsiloxane with a molecular weight of 18200 and one part by weight of aminopropyltriethoxysilane
  • Crosslinker: tolylene diisocyanate (TDI)

Vergleichsbeispiel 1Comparative Example 1

Beispiel 1 der DE 2 820 494 C2: 30 Vol-%ige Dispersion einer mit Divinylbenzol vernetzten Polyacrylsäure in einer polychlorierten Diphenylfraktion. Abhängig von Wassergehalt (1.3-5 Gew.-%) betrug der elektroviskose Effekt bei 30 C zwischen 975-1070 Pa·mm/kV. Die plastische Viskosität betrug 220 mPa.s. V, (3000) =10.7-12.6.Example 1 of DE 2 820 494 C2: 30 vol% dispersion of a polyacrylic acid crosslinked with divinylbenzene in a polychlorinated diphenyl fraction. Depending on the water content (1.3-5% by weight), the electroviscous effect at 30 C was between 975-1070 Pa · mm / kV. The plastic viscosity was 220 mPa.s. V, (3000) = 10.7-12.6.

Vergleichsbeispiel 2Comparative Example 2

Beispiel 2 der DE 2 830 494 C2: 30 Vol-%ige Dispersion einer mit Divinylbenzol vernetzten Methacrylsäuresäure in einer polychlorierten Diphenylfrakion. Bei einem Wassergehalt < 6,2 Gew.-% betrug der elektroviskose Effekt bei 30° C, 690 Pa·mm/kV. Die plastische Viskosität betrug 260 mPa.s Vr(3000) = 8,1.Example 2 of DE 2 830 494 C2: 30 vol% dispersion of a methacrylic acid crosslinked with divinylbenzene in a polychlorinated diphenyl fraction. With a water content of <6.2% by weight, the electroviscous effect at 30 ° C. was 690 Pa · mm / kV. The plastic viscosity was 260 mPa.s V r (3000) = 8.1.

Vergleichsbeispiel 3Comparative Example 3

Beispiel 7 der DE 2 820 494 C2: 30 Vol-%ige Dispersion von Lithium/Chrom-Polymethacrylat in einer polychlorierten Diphenylfraktion. Bei Umgebungsfeuchte betrug der elektroviskose Effekt bei 30 C 1960 Pa·mm/kV. Die plastische Viskosität betrug 236 mPa.s Vr(3000)=17,9.Example 7 of DE 2 820 494 C2: 30% by volume dispersion of lithium / chromium polymethacrylate in a polychlorinated diphenyl fraction. At ambient humidity, the electroviscous effect at 30 C was 1960 Pa · mm / kV. The plastic viscosity was 236 mPa.s V r (3000) = 17.9.

Vergleichsbeispiel 4Comparative Example 4

Beispiel 1 der japanischen Offenlegungsschrift 64-6093: 20 Vol-%ige Dispersion eines mit Aluminiumoxid beschichteten Aluminiumpulver in TRIMEX T-08. Der elektroviskose Effekt bei einer Wechselspannung von 60 Hz betrug 327 Pa·mm/kV.Example 1 of Japanese Patent Application 64-6093: 20% by volume dispersion of an aluminum oxide coated aluminum powder in TRIMEX T-08. The electroviscous effect at an alternating voltage of 60 Hz was 327 Pa · mm / kV.

Vergleichsbeispiel 5Comparative Example 5

Beispiel 4 der japanischen Offenlegunggschrift 64-6093: 20 Vol-%ige Dispersion eines mit Aluminiumoxid beschichteten Aluminiumpulver in TRIMEX T-08. Der elektroviskose Effekt bei einer Wechselspannung von 60 Hz betrug 371 Pa·mm/kV.Example 4 of Japanese Laid-Open Publication 64-6093: 20 vol.% Dispersion of an aluminum oxide coated aluminum powder in TRIMEX T-08. The electroviscous effect at an alternating voltage of 60 Hz was 371 Pa · mm / kV.

Vergleichsbeispiel 6Comparative Example 6

In einem Becherglas mit einem Nennvolumen von 100 ml werden 0,6 g des Dispergiermittels in 20 g des Dispersionsmediums gelöst. In einem zweiten Becherglas werden 17,5 g des Glycols mit 6,79 g des Vernetzers 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 reative Gemisch aus Glycol und Vernetzer wird sofort nach der Homogenisierung mittels eines Rotor-Stator-Scherhomogenisators (Ultra-Turrax T25 der Firma IKA Labortechnik) in die Dispergiermittel-Lösung emulgiert. Die Emulgierzeit bei einer Umlaufgeschwindigkeit des Rotors von 10.000 U/min beträgt 2 min. Nachträglich wurden die Proben 15 Stunden bei 90 C durchreagiert.0.6 g of the dispersant is dissolved in 20 g of the dispersion medium in a beaker with a nominal volume of 100 ml. In a second beaker, 17.5 g of the glycol are mixed with 6.79 g of the crosslinker. 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 reactive mixture of glycol and crosslinker is emulsified into the dispersant solution immediately after homogenization 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 2 min. The samples were subsequently reacted at 90 C for 15 hours.

Beispiel 1example 1

Entsprechend der unter Vergleichsbeispiel 6 angegebenen Arbeitsweise wurden eine EVF hergestellt, in dem Glycol wurde jedoch vor der weiteren Verarbeitung 0,0273 g festes, wasserfreies LiN03 gelöst. Dies entspricht, bezogen auf die Zahl der Ethylenoxideinheiten im Glycol, einem Molaren Li:EO-Verhältnis von 1:1000.An EVF was produced in accordance with the procedure given under Comparative Example 6, but 0.0273 g of solid, anhydrous LiNO 3 was dissolved in the glycol before further processing. Based on the number of ethylene oxide units in the glycol, this corresponds to a molar Li: EO ratio of 1: 1000.

Beispiel 2Example 2

Herstellung gemäß Beispiel 1, jedoch mit 0,109 g LiN03 (Li:EO-Verhältnis 4:1000).Preparation according to Example 1, but with 0.109 g LiN0 3 (Li: EO ratio 4: 1000).

Beispiel 3Example 3

Herstellung gemäß Beispiel 1, jedoch mit 0,218 g LiN03 (Li:EO-Verhältnis 8:1000).Preparation according to Example 1, but with 0.218 g LiN0 3 (Li: EO ratio 8: 1000).

Beispiel 4Example 4

Herstellung gemäß Beispiel 1, jedoch mit 0,328 g LiN03 (Li:EO-Verhältnis 12:1000).Preparation according to Example 1, but with 0.328 g LiN0 3 (Li: EO ratio 12: 1000).

Beispiel 5Example 5

Herstellung gemäß Beispiel 1, jedoch mit 0,564 g LiN03 (Li:EO-Verhältnis 20:1000).Preparation according to Example 1, but with 0.564 g LiN0 3 (Li: EO ratio 20: 1000).

Beispiel 6Example 6

Herstellung gemäß Beispiel 1, jedoch wurde als Elektrolyt 1,253 g Nonansäure verwendet (H:EO-Verhältnis 2:1000).Preparation according to Example 1, but 1.253 g of nonanoic acid was used as the electrolyte (H: EO ratio 2: 1000).

Beispiel 7Example 7

Herstellung gemäß Beispiel 1, jedoch wurde als Elektrolyt 1,313 g Tetraethylammoniumchlorid verwendet (N(CH3-CH2)4:EO-Verhältnis 2:1000).Preparation according to Example 1, but 1.313 g of tetraethylammonium chloride was used as the electrolyte det (N (CH 3 -CH 2 ) 4 : EO ratio 2: 1000).

Beispiel 8Example 8

Herstellung gemäß Vergleichsbeispiel 7, jedoch mit 0,0273 g LiN03 (Li:EO-Verhältnis 2:1000).Preparation according to Comparative Example 7, but with 0.0273 g LiN0 3 (Li: EO ratio 2: 1000).

Beispiel 9Example 9

3,9 g LiNO3 wurden in 305,46 g Glykol gelöst. Diese Lösung wurde mit 116,4 g Vernetzer gemischt, und gemäß Vergleichsbeispiel 6 in eine Lösung aus 6 g Dispergiermittel in 200 g Siliconöl dispergiert bzw. weiterverarbeitet. Der Feststoffgehalt dieser EVF wurde durch Zugabe von Siliconöl auf Werte zwischen 39 und 64 % eingestellt. Der Verlauf des elektroviskosen Effektes S und der Viskosität der EVF bei einer Schergeschwindigkeit von 1000 s-1 ist in Abb. 3 dargestellt.3.9 g of LiNO 3 were dissolved in 305.46 g of glycol. This solution was mixed with 116.4 g of crosslinking agent and, according to comparative example 6, dispersed or processed further in a solution of 6 g of dispersant in 200 g of silicone oil. The solids content of this EVF was adjusted to between 39 and 64% by adding silicone oil. The course of the electroviscous effect S and the viscosity of the EVF at a shear rate of 1000 s -1 is shown in Fig. 3.

Figure imgb0004
Figure imgb0004

Claims (8)

1. Elektroviskose Flüssigkeiten, enthaltend im wesentlichen (I) ein Polymer oder Polymergemisch, (II) ein in (I) gelöster Elektrolyt, (III) gegebenenfalls ein mit der Lösung aus (I) und (II) mischbares Additiv, (IV) gegebenenfalls ein Viskositäts-erhöhendes, mit (I) reagierendes Additiv; (V) ein Dispergiermittel, sowie (VI) ein nicht-wäßriges Dispersionsmedium. 1. Electroviscous liquids containing essentially (I) a polymer or polymer mixture, (II) an electrolyte dissolved in (I), (III) optionally an additive which is miscible with the solution of (I) and (II), (IV) optionally a viscosity-increasing additive which reacts with (I); (V) a dispersant, as well (VI) a non-aqueous dispersion medium. 2. Elektroviskose Flüssigkeiten gemäß Anspruch 1, dadurch gekennzeichnet, daß (I) aus linearen oder verzweigten, gegebenenfalls funktionalisierten Polyethern oder deren Oligomonomeren, oder dem Umsetzungsprodukt solcher Polyethers bzw. der Oligomonomere mit mono- oder oligofunktionellen Verbindungen besteht.2. Electroviscous liquids according to claim 1, characterized in that (I) consists of linear or branched, optionally functionalized polyethers or their oligomonomers, or the reaction product of such polyethers or the oligomonomers with mono- or oligofunctional compounds. 3. Elektroviskose Flüssigkeiten gemäß Anspruch 1 oder 2, dadurch gekennzeichnet, daß (I), bzw. dessen Monomeren, bzw. oligomeren Ausgangssubstanzen während des Dispergiervorganges in flüssiger Form vorliegen, gegebenenfalls jedoch durch den Zusatz von reaktiven Additiven (IV) vor, während oder nach der Dispergierung in eine höherviskose, bzw. feste Form überführt werden.3. Electroviscous liquids according to claim 1 or 2, characterized in that (I), or its monomers, or oligomeric starting substances are present in liquid form during the dispersing process, but optionally by adding reactive additives (IV) before, during or after the dispersion, be converted into a more viscous or solid form. 4. Elektroviskose Flüssigkeit gemäß einem der Ansprüche 1 bis 3, dadurch gekennzeichnet, daß sie als Komponente (VI) ein Siliconöl enthält.4. Electroviscous liquid according to one of claims 1 to 3, characterized in that it contains a silicone oil as component (VI). 5. Elektroviskose Flüssigkeit gemäß einem der Ansprüche 1 bis 3, dadurch gekennzeichnet, daß sie als Komponente (VI) ein fluorhaltiges Siloxan enthält.5. Electroviscous liquid according to one of claims 1 to 3, characterized in that it contains a fluorine-containing siloxane as component (VI). 6. Elektrovikose Flüssigkeit gemäß einem der Ansprüche 1 bis 3, dadurch gekennzeichnet, daß sie als Komponente (VI) einen Kohlenwasserstoff enthält.6. Electrovicous fluid according to one of claims 1 to 3, characterized in that it contains a hydrocarbon as component (VI). 7. Elektroviskose Flüssigkeiten gemäß einem der Ansprüche 1 bis 5, dadurch gekennzeichnet, daß sie als Komponente (V) ein Polysiloxan-Polyether-Copolymerisat enthält.7. Electroviscous liquids according to one of claims 1 to 5, characterized in that they contain as component (V) a polysiloxane-polyether copolymer. 8. Elektroviskose Flüssigkeiten gemäß einem der Ansprüche 1 bis 5, dadurch gekennzeichnet, daß sie als Komponente (V) gegebenenfalls ein Aminogruppenhaltiges Alkoxy- bzw.ein Acetoxypolysiloxan enthält.8. Electroviscous liquids according to one of claims 1 to 5, characterized in that they optionally contain an amino group-containing alkoxy or an acetoxypolysiloxane as component (V).
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