Classifications

• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10M—LUBRICATING COMPOSITIONS; USE OF CHEMICAL SUBSTANCES EITHER ALONE OR AS LUBRICATING INGREDIENTS IN A LUBRICATING COMPOSITION
  • C10M171/00—Lubricating compositions characterised by purely physical criteria, e.g. containing as base-material, thickener or additive, ingredients which are characterised exclusively by their numerically specified physical properties, i.e. containing ingredients which are physically well-defined but for which the chemical nature is either unspecified or only very vaguely indicated
  • C10M171/001—Electrorheological fluids; smart fluids

Definitions

• the present invention relates to an electroviscous fluid, the viscosity of which can be controlled by applying voltage, and in particular to an electroviscous fluid, in which the viscosity is changed rapidly and reversibly from low temperature range to high temperature range when voltage is applied and a long and stable electroviscous effect is obtained and which can be used for electrical control of mechanical devices such as a clutch, valve or shock absorber.
• Winslow proposed an electroviscous fluid, using paraffin, silica gel powder and adding water to make the system slightly electroconductive (Winslow, W.M., J. of Applied Physics, Vol. 20 (1949) 1137). From this study by Winslow, the electroviscous (electro-rheological) effect of the electroviscous fluid is called the ER effect or Winslow effect.
• each particle forms a bridge (cross-linkage) between electrodes and the shear-resistant force to the external stress, i.e., ER effect.
• the electroviscous fluid according to this invention consists of electrically insulating fluid , dispersed porous solid particles, at least one acid, salt or base, at least one polyhydric alcohol and/or water, and an antioxidant and/or corrosion inhibitor.
• an antioxidant and/or corros­ion inhibitor are added to such electroviscous fluid to obtain better effects in the responsiveness of viscosity change in a wide temperature range up to high temperature, reproducibility, electroviscous effect and, especially, durability.
• a mineral oil or synthetic lubricant oil can for example be used. More specifically, there are oils such as a paraffinic oil, naphthenic oil, poly- ⁇ -olefin, polyalky­lene glycol, silicone oil, diester, polyolester, phosphoric acid ester, silicon compound, fluorine compound or poly­phenylether.
• oils such as a paraffinic oil, naphthenic oil, poly- ⁇ -olefin, polyalky­lene glycol, silicone oil, diester, polyolester, phosphoric acid ester, silicon compound, fluorine compound or poly­phenylether.
• An electroviscous fluid having the viscosity of 5 - 300 cP at 40°C can be used.
• porous solid particles for example, silica gel, moisture-containing resin, diatomaceous earth, alumina, silica-alumina, zeolite, ion exchange resin or cellulose, can be used.
• the porous solid particles having a particle size of 10 nm - 200 ⁇ m are used in the ratio of 0.1 - 50 wt%. If it is less than 0.1 wt%. the ER effect is too low, and it exceeds 50 wt%, the dispersing property is decreased.
• a dispersing agent may optionally be used in the electroviscous fluid of this invention in order to disperse the porous solid particles evenly and stably.
• Suitable dispersing agents are sulphonates , phenates, phosphonates, succinic acid imides, amines or non-ionic dispersing agents, e. g., magnesium sulphonate, calcium sulphonate, calcium phosphonate, polybutenyl succinic acid imide, sorbitan mono-oleate or sorbitan sesqui-oleate. These are normally used at the ratio of 0.1 - 10 wt%, while they need not be used if the porous solid particles are easily dispersed.
• Polyhydric alcohol components, and acid, salt or base components may be used alone to obtain the higher ER effect.
• Polyhydric alcohol components keep the ER effect at high temperature, while acid, salt or base components can increase the polarization effect. By using these components simultaneously, it is possible to increase the ER effect at high temperature.
• polyhydric alcohol dihydric alcohol and trihy­dric alcohol are effective. It is preferable to use ethylene glycol, glycerin, propanediol, butanediol or hexanediol, and to use these substance at the ratio of 1 - 30 wt% to porous solid particles, and more preferably at 2 - 15 wt%. If it is less than 1 wt%, the ER effect is too low. If it exceeds 30 wt%, it is undesirable because electric current then flows too easily.
• inorganic acids such as sulfu­ric acid, hydrochloric acid, nitric acid, perchloric acid, chromic acid, phosphoric acid or boric acid, or inorganic acids such as acetic acid, formic acid, propionic acid, lactic acid, isolactic acid, valeric acid, oxalic acid or malonic acid can be used.
• any compound consisting of a metal or base radical (such as NH4+, N2H5+) and acid radical can be used.
• a substance which dissolves in a polyhydric alcohol or mixture of polyhydric alcohol and water and is dissociated, or typical ionic crystal such as a halogenated compound of an alkali metal or alkali earth metal, or the alkali salt of an organic acid; e.g., LiCl, NaCl, KCl, MgCl2, CaCl2, BaCl2, LiBr, NaBr, KBr, MgBr2, LiI, NaI, KI, AgNO3, Ca(NO3)2, NaNO2, NH4NO3, K2SO4, Na2SO4, NaHSO4, (NH4)2SO4 or an alkali salt of an acid such as formic acid, acetic acid, oxalic acid or succinic acid.
• a base to be used can be a hydroxide of an alkali earth metal, carbonate of an alkali metal or amine . It is preferable to use a substance which is dissolved in poly­hydric alcohol or in the mixture of polyhydric alcohol and water and is dissociates, e. g., NaOH, KOH, Ca(OH)2, Na2CO3, NaHCO3, K3PO4, Na3PO4, aniline, an alkylamine or ethanolamine.
• the salt and the base as described above may be used simultaneously.
• the acid, salt or base may be used in the ratio of 0.01 - 5 wt% to the entire electroviscous fluid. If it is less than 0.01 wt%, the ER effect is too low; and if it exceeds 5 wt%, it is not desirable because electric current flows more easily and the electric power consumption increase.
• the present invention is characterized in that an antioxidant and/or corrosion inhibitor is added to the electroviscous fluid.
• Antioxidant is added to prevent the oxidation of the electrically insulating liquid and polyhydric alcohol and also to stop the increase of electric conductivity due to oxidation products.
• Corrosion inhibitor is added to prevent the increase of electrical conductivity caused by the generation of metallic ions due to the corrosion of the electrode (such as copper) under high voltage.
• Antioxidants inactive to polarizing agent and porous solid particles may be used.
• Phenol type or amine type antioxidants can be used. Suitable phenoltype antioxidants, are 2,6-di- t -butylparacresol, 4,4′-methylenebis (2,6-di-­ t -butylphenol) and 2,6-di-t-butylphenol,
• amine type antioxidants there are dioctyldiphenylamine, phenyl-­ ⁇ -naphthylamine, alkyldiphenylamine or N-nitrodiphenylamine.
• 2,6-di-t-butylparacresol or dioctyldiphenylamine are used.
• These substances can be used in the ratio of 0.01 - 10 wt% to the entire electroviscous fluid, and more preferably at 0.1 - 2.0 wt%. If it is less than 0.01 wt%, antioxidant effect is too low. If it exceeds 10 wt%, problems occur such as color tone deterioration, increased turbidity, generation of sludge and increase of viscosity.
• a corrosion inhibitor which is inactive to the polarizing agent and porous solid parti­ cles, e. g., nitrogen compounds such as benzotriazole and its derivatives, imidazoline, pyrimidine derivative, and compounds containing sulfur and nitrogen, such as 1,3,4-­thiadiazolepolysulfide, 1,3,4-thiadiazolil-2,5-bisdialkyl­dithiocarbamate, 2-(alkyldithio)-benzoimidazole or ⁇ -­(o-carboxybenzylthio) propionitrile or propionic acid; more preferably, benzotriazole or its derivatives can be used.
• nitrogen compounds such as benzotriazole and its derivatives, imidazoline, pyrimidine derivative, and compounds containing sulfur and nitrogen, such as 1,3,4-­thiadiazolepolysulfide, 1,3,4-thiadiazolil-2,5-bisdialkyl­dithiocarbamate, 2-(alkyldi
• these substances in the ratio of 0.001 - 10 wt% to the entire electroviscous fluid, and more preferably at 0.01 - 1.0 wt%. If it is less than 0.001 wt%, there is no corrosion inhibition effect. If it exceeds 10 wt%, problems occur such as color tone deterioration, increased turbidity, generation of sludge, and increase in the consistency of the fluid.
• the above substances are mixed together to make a basic fluid.
• the viscosity of the mineral oil was adjusted in such manner that all of these samples have a viscosity of 80 cP at 40°C.
• Example 1 40°C 1 or less ⁇ 2 100 5 90°C 1 or less ⁇ 2 96 7
• Example 2 40°C 1 or less ⁇ 2 100 5 90°C 1 or less ⁇ 2 95 7
• Example 3 40°C 1 or less ⁇ 2 100 5 90°C 1 or less ⁇ 2 98 7
• Example 4 40°C 1 or less ⁇ 2 100 5 90°C 1 or less ⁇ 2 97 7
• Example 5 40°C 1 or less ⁇ 2 100 5 90°C 1 or less ⁇ 2 98 8
• Example 6 40°C 1 or less ⁇ 2 100 5 90°C 1 or less ⁇ 2 94 7
• Example 7 40°C 1 or less ⁇ 2 100 5 90°C 1 or less ⁇ 2 98 8
• Example 8 40°C 1 or less ⁇ 2 100 4 90°C 1 or less ⁇ 2 93 7 Comparative example 40°C 1 or less ⁇ 2 100 5 90°C 1 or less ⁇ 2 100 5 90°C 1 or less ⁇ 2 96 7
• Example 2

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• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• General Chemical & Material Sciences (AREA)
• Oil, Petroleum & Natural Gas (AREA)
• Organic Chemistry (AREA)
• Lubricants (AREA)

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Cited By (8)

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• 1989
  • 1989-04-26 JP JP10699789A patent/JPH02284992A/ja active Pending
• 1990
  • 1990-04-24 EP EP90304402A patent/EP0395359B1/de not_active Expired - Lifetime
  • 1990-04-24 DE DE1990603434 patent/DE69003434T2/de not_active Expired - Fee Related

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