JPH07292376A - Electroviscous fluid - Google Patents

Abstract

PURPOSE:To obtain an electroviscous fluid capable of allowing an electric field to effectively act on solid particles mutually cross-linked by formation of bridges in application of voltage, manifesting a higher electroviscous effect and useful for a variable-damping damper, etc., by blending specified solid particles in an electrically insulating fluid. CONSTITUTION:This electroviscous fluid is prepared by blending preferably 5 to 20wt.% solid particles having <=2.0 ratio (d75/d25 provided that d75>=d25) of the particle diameter (d75) in 75% cumulative weight percentage to that (d25) in 25% cumulative weight percentage in the particle diameter-cumulative weight percentage distribution in solid particles such as silica fine particles having 0.5 to 5mum average particle diameter in an electrically insulating fluid such as a paraffin-based mineral oil.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrorheological fluid that can be used for electrical control of variable damping dampers, engine mounts, bearing dampers, clutches, valves, shock absorbers, display elements and the like.

[0002]

2. Description of the Related Art Electro-Rheological Fluid, Electro-Viscous Fluid whose viscosity changes with the application of voltage
scous Fluid,) has been known for a long time (Duff, AWP
hysical Review Vol, 4, No.1 (1896) 23). Initial research on electrorheological fluids focused on liquid-only systems, and the effect was inadequate, but after that, we moved to research on electrorheological fluids in solid dispersion systems, and obtained considerable electrorheological effects. Came to be.

As a mechanism for producing a thickening effect (ER effect) in an electrorheological fluid, for example, Klass shows that each particle, which is a dispersoid in the electrorheological fluid, has a two-layered dielectric polarization in the electric field. Double Laye
r), which is the main cause (Klass, D.
L., et al., J. of Applied Physics, Vol.38, No1 (196
7) 67). This is an electric double layer
The ion adsorbed around the dispersoid (silica gel, etc.) is evenly arranged on the outer surface of the dispersoid when E (electric field) = 0, but when E (electric field) = finite value Causes a bias in the ion distribution, and each particle exerts an electrostatic action on each other in the electric field. In this way, each particle forms a bridge (crosslink) between the electrodes, and shear resistance against stress, that is, an ER effect is developed.

Winslow also proposed an electrorheological fluid using paraffin and silica gel powder and water as a polarizing agent (Winslow, WM, J. of Applied Physics, Vol.
20 (1949) 1137). According to this Winslow study, the electrorheological effect of electrorheological fluid is called the Winslow effect.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide an electrorheological fluid which is more excellent in the electrorheological effect in the electrorheological fluid in which solid particles are mixed in the electrically insulating fluid.

[0006]

The electrorheological fluid of the present invention has a particle size-cumulative weight ratio distribution in solid particles,
Particle diameter d _{75 at} cumulative weight ratio of 75% and cumulative weight ratio of 25%
Ratio with the particle diameter d ₂₅ at (d ₇₅ / d ₂₅ , where d ₇₅ ≧
d ₂₅ , hereinafter simply referred to as D value), solid particles having a value of 2.0 or less are blended in the electrically insulating fluid.

The electrorheological fluid of the present invention has a D value of 1.5 in the particle size-cumulative weight ratio distribution of solid particles.
It is characterized in that solid particles having a particle size of 1.0 are mixed in an electrically insulating fluid.

The electrorheological fluid of the present invention is characterized in that the solid particles are silica fine particles.

First, the solid particles in the present invention will be described. Solid particles in the present invention include fine silica particles (silica gel, silica sol, etc.), water-containing resin, diatomaceous earth,
Alumina, silica-alumina, zeolite, ion exchange resin, cellulose and the like can be mentioned, and silica fine particles are particularly preferable.

These solid particles have an average particle size of about 10 nm.
.About.200 .mu.m, preferably 0.1 .mu.m to 50 .mu.m, more preferably 0.5 .mu.m to 5 .mu.m is used in the present invention. In addition, those having a large particle size are pulverized by a pulverizer or the like.

Generally, such solid particles have a particle size distribution, for example, a particle size distribution shown by a particle size-cumulative weight ratio distribution curve. The particle size-cumulative weight ratio distribution curve, as illustrated in FIG. 1, shows the particle size on a logarithmic scale on the abscissa and the cumulative weight distribution ratio on the ordinate. It represents a relationship. In the present invention, when solid particles having a narrow particle size distribution and a uniform particle size are blended in the electrically insulating fluid, the electric field effectively acts on the solid particles forming a bridge when a voltage is applied, and the particle size is higher. It has been found that an electrorheological effect can be obtained. That is, in the particle size-cumulative weight ratio distribution in solid particles,
When solid particles having a D value of 2.0 or less, preferably 1.5 to 1.0 are blended in an electrically insulating fluid, a higher electrorheological effect can be obtained, and when the D value exceeds 2.0, The electric field does not act effectively on the solid particles, and the desired electrorheological effect cannot be obtained.

The solid particles having such a D value, which have a large particle diameter, are finely pulverized by a pulverizer or the like to have a predetermined average particle diameter, and then a turbo classifier, accucut, dispersion separator, super separator It can be obtained by classifying with a classifier such as a separator, Microbrex, elbow jet, variable impactor or the like.

These solid fine particles are contained in the electrorheological fluid in an amount of 0.1% to 50% by weight, preferably 3% by weight.
-30% by weight, more preferably 5% -20% by weight.

The electrically insulating fluid includes, for example, mineral oil and synthetic lubricating oil, specifically paraffinic mineral oil, naphthenic mineral oil, poly-α-olefin, polyalkylene glycol, silicone oil, ester, diester, polyol. Ester, phosphoric acid ester, silicon compound, fluorine oil, alkylbenzene, alkyldiphenyl ether,
Examples thereof include oils such as alkylbiphenyl, alkylnaphthalene, polyphenyl ether, and synthetic hydrocarbons, and the viscosity range is not particularly limited, but the viscosity range at 40 ° C. is 3 cSt.
~ 300 cSt, preferably 5 cSt to 100 cSt can be used.

A polarization accelerator is added to the electrorheological fluid of the present invention. Examples of the polarization accelerator include polyhydric alcohols or partial derivatives thereof, acids, salts, basic components, alkanolamines, water and the like. Among them, polyhydric alcohol is preferable.

Examples of the polyhydric alcohol include dihydric alcohols and trihydric alcohols such as ethylene glycol, glycerin, propanediol, butanediol, pentanediol, hexanediol, polyethylene glycol having 1 to 14 ethylene oxide units, and general formula R
[(OC ₃ H ₆ ) _m OH] _n (wherein R represents hydrogen or a polyhydric alcohol residue, m represents an integer of 1 to 17 and n represents an integer of 1 to 6), and the general formula R- CH (OH) (C
H ₂ ) _n OH (wherein R is hydrogen or CH ₃ (CH ₂ ) _m
Group, and m + n represents an integer of 2 to 14). Among these, triethylene glycol, tetraethylene glycol, polyethylene glycol, tripropylene glycol and mixtures thereof are particularly preferable.

Further, the partial derivative of polyhydric alcohol is a partial derivative of polyhydric alcohol having at least one hydroxyl group, and some of the hydroxyl groups of the above polyhydric alcohol are methyl group, ethyl group, propyl group, Butyl group,
Partial ethers substituted with an alkyl-substituted phenyl group (the number of carbon atoms of the alkyl group substituted with a phenyl group is 1 to 25), etc., and some of the hydroxyl groups are esterified with acetic acid, propionic acid, butyric acid, etc. And partial esters.

These polyhydric alcohols or their partial derivatives may be used in a proportion of 1% by weight to 100% by weight, preferably 2% by weight to 80% by weight, based on the solid particles.
If the amount added is less than 1% by weight, the electrorheological effect is low, and if the amount added exceeds 100% by weight, current easily flows, which is not preferable.

As the acid component, there are inorganic acids such as sulfuric acid, hydrochloric acid, nitric acid, perchloric acid, chromic acid, phosphoric acid and boric acid, or acetic acid,
Organic acids such as formic acid, propionic acid, butyric acid, isobutyric acid, valeric acid, oxalic acid and malonic acid are used. The salt is a compound consisting of a metal or basic group (NH ₄ ⁺ , N ₂ H ₅ ^+, etc.) and an acid group, and any of these can be used. Among them, those which dissolve in a system of a polyhydric alcohol or a polyhydric alcohol partial derivative to dissociate, for example, those which form typical ionic crystals such as halides of alkali metals or alkaline earth metals, or alkali metal salts of organic acids. Are preferred. As this kind of salt, LiCl, N
aCl, KCl, MgCl ₂ , CaCl ₂ , BaC
l ₂ , LiBr, NaBr, KBr, MgBr ₂ , Li
_{I, NaI, KI, AgNO 3} , Ca (NO 3) 2, Na
NO ₂ , NH ₄ NO ₃ , K ₂ SO ₄ , Na ₂ SO ₄ , N
aHSO ₄ , (NH ₄ ) ₂ SO ₄ or formic acid, acetic acid,
There are metal salts of alkaline acids such as oxalic acid and succinic acid. The base is, for example, a hydroxide of an alkali metal or an alkaline earth metal, a carbonate of an alkali metal, an amine and the like, and a base which is dissolved in a polyhydric alcohol or a polyhydric alcohol partial derivative to dissociate is preferable. As a base of this kind, NaO
H, KOH, Ca (OH) ₂ , Na ₂ CO ₃ , NaHC
_{O 3, K 3 PO 4,} Na 3 PO 4, aniline, alkyl amines, such as ethanol amine. Incidentally, the above-mentioned salt and base may be used in combination.

Other polarization accelerators include alkanolamine, water, etc., but when water is used, the current value may be high, so caution is required.

Acid, salt, base component, alkanolamine,
Water or the like can increase the polarization effect, but may be used in combination with a polyhydric alcohol and / or a partial derivative of a polyhydric alcohol as appropriate, and the addition amount thereof is 0% by weight in the entire electrorheological fluid. % To 5% by weight may be used. If it exceeds 5% by weight, it becomes undesirably easy to energize and power consumption increases.

If desired, an ashless dispersant may be added. When the ashless dispersant is added, the dispersibility of solid particles can be improved and the base viscosity of the electrorheological fluid can be lowered, so that the application range of the mechanical system using the electrorheological fluid can be expanded. As the ashless dispersant, for example, sulfonates, phenates, phosphonates, succinimides, amines, nonionic dispersants and the like are used, and specifically, magnesium sulfonate, calcium sulfonate, calcium phosphonate, polybutenyl. Examples thereof include succinimide, sorbitan monooleate and sorbitan sesquioleate. Among them, polybutenyl succinimide is preferable. These are usually 0% to 20% by weight, preferably 0.1% by weight of the total electrorheological fluid.
It is used in a proportion of from 10 to 10% by weight.

If desired, a surfactant may be added, so that the dispersibility can be further improved. As the surfactant, a nonionic surfactant, an anionic surfactant,
Cationic surfactants and amphoteric surfactants can be used.

As the nonionic surfactant, polyoxyethylene alkyl ether, polyoxyethylene alkylphenyl ether, polyoxyethylene alkylamide, polyoxyethylene-polyoxypropylene glycol, polyoxyethylene-polyoxypropylene glycol ethylenediamine, polyoxyethylene-polyoxypropylene glycol Oxyethylene fatty acid ester, polyoxyethylene-polyoxypropylene glycol fatty acid ester, polyoxyethylene sorbitan fatty acid ester, ethylene glycol fatty acid ester, propylene glycol fatty acid ester, glycerin fatty acid ester, pentaerythritol fatty acid ester,
Examples thereof include sorbitan fatty acid ester, sucrose fatty acid ester, and fatty acid ethanolamide.

As the anionic surfactant, fatty acid alkali salt, alcohol sulfate ester salt, polyoxyethylene alkyl ether sulfate ester salt, polyoxyethylene alkylphenyl ether sulfate ester salt, fatty acid polyhydric alcohol sulfate ester salt, sulfated Examples thereof include oils, fatty acid anilide sulfate ester salts, petroleum sulfonates, alkylnaphthalene sulfonates, dinaphthylmethane sulfonates, alkyldiphenyl ether disulfonates, and polyoxyethylene alkyl ether phosphate ester salts.

Further, as the cationic surfactant, a weak cationic cationic surfactant, for example, alkylamine and its polyoxyalkylene adduct, for example, octylamine, dibutylamine, trimethylamine, oleylamine, stearylamine and its ethylene oxide are used. 5 to 15 mol adduct, propylene oxide 5
˜15 mol addition product and the like. Further, as a weakly cationic cationic surfactant, a polyoxyalkylene adduct of polyamines such as alkylenediamine and dialkylenetriamine which may be substituted with a higher alkyl group, for example, ethylenediamine, ethylene oxide such as diethylenetriamine 0 to 100 mol Additive or ethylene oxide 0 to 100 mol and propylene oxide 0-1
Block or random adducts with 00 moles, oleyl propylene diamine, and ethylene oxide 0-100 mole adducts of stearyl propylene diamine are mentioned. Further, as weakly cationic cationic surfactants, polyoxyalkylene adducts such as higher fatty acid amides, for example, oleic acid amide, stearic acid amide with ethylene oxide 5 to 15 mol adduct, propylene oxide 5 to
15 mol addition products and the like can be mentioned. Examples of the strong cationic cationic surfactant include decanoyl chloride, alkylammonium salt, alkylbenzylammonium salt, and alkylamine salt. Specifically, cetyltrimethylammonium chloride, stearyltrimethylammonium chloride, behenyltrimethylammonium chloride, Examples thereof include distearyldimethylammonium chloride, stearyldimerbenzylammonium chloride, stearic acid diethylaminoethylamide, coconut amine acetate, stearyl amine acetate, coconut amine hydrochloride and stearyl amine hydrochloride. In the case of a cationic surfactant having a strong cationic property, conductivity increases when the temperature of use of the electrorheological fluid reaches a high temperature of about 100 ° C. Therefore, among the above surfactants, a weak cationic surfactant is used. Is preferable, and low conductivity can be maintained during operation in a wide temperature range from a low temperature range to a high temperature range.

The surfactant may be added in an amount of 0% by weight to 10% by weight, preferably 0.1% by weight to 5% by weight, based on the total amount of the electrorheological fluid. It is not preferable because the conductivity becomes high.

If necessary, an antioxidant, a corrosion inhibitor, an antiwear agent, an extreme pressure agent, an antifoaming agent, etc. are added to the electrorheological fluid of the present invention.

The antioxidant is intended to prevent the oxidation of the polyhydric alcohol and the partial derivative of the polyhydric alcohol, which are polarization accelerators, as well as the oxidation of the electrically insulating liquid. As the antioxidant, it is preferable to use one that is inactive to the polarization promoter and the dispersoid, and a commonly used phenol-based or amine-based antioxidant can be used. -6-di-t-butylparacresol, 4,4'-methylenebis (2.6-di-
t-butylphenol), 2,6-di-t-butylphenol, etc., and dioctyldiphenylamine, phenyl-α-naphthylamine, alkyldiphenylamine, N-nitrosodiphenylamine, etc., can be used as the amine type, and the whole electrorheological fluid can be used. 0% by weight to
10% by weight, preferably 0.1% to 2.0% by weight can be used. If it exceeds 10% by weight, there are problems such as deterioration of hue, generation of turbidity, generation of sludge, and increase in viscosity. .

Although a corrosion inhibitor may be added, it is preferable to use one which is inert to the polarization accelerator, dispersoid, etc.,
Specifically, for nitrogen compounds, benzotriazole and its derivatives, imidazoline, pyrimidine derivatives, etc., for compounds containing sulfur and nitrogen, 1.3.4-thiadiazole polysulfide, 1.3.4-thiadiazolyl-2.5-bisdialkyldithiocarbamate, 2- ( Alkyldithio) benzimidazole, etc., and β- (o-carboxybenzylthio) propionnitrile, propionic acid, etc. can be used.
It is recommended to use 0% by weight, preferably 0.01% by weight to 1.0% by weight. If it exceeds 10% by weight, there are problems such as deterioration of hue, generation of turbidity, generation of sludge, and increase in viscosity.

[0031]

In the electrorheological fluid of the present invention, by using solid particles having a narrow particle size distribution as the dispersoid, an electric field can be effectively applied to the bridge-formed solid particles when a voltage is applied. It is considered that the higher electrorheological effect is exhibited.

The present invention will be described below based on examples.

[0033]

Example 1 (Preparation of solid particles) Silica (Fuji Silysia Chemical Ltd.)
Manufactured by Silysia 310) was classified using a classifier (manufactured by Nisshin Engineering Co., Ltd., Turbo Classifier TC-15N), and the index D value of the particle size distribution was 1.3,
Solid particles of 1.5 and 1.7 were obtained and used as the solid particles in the present invention.

By mixing Silysia 310, 350 and 430 manufactured by Fuji Silysia Chemical Ltd. as silica, solid particles having a D value of 2.2 and 2.7 are obtained, and a solid for comparison is obtained. It was made into particles. The average particle diameter of the solid particles having the above D value is in the range of 1 to 3 μm.

(Composition of electrorheological fluid) Alkylbenzene [viscosity 17 mm ² / s (40 ° C.)] ・ ・ ・ 83 wt% ・ Silica produced above (D value = 1.3) ・ ・ ・ 7 wt% Triethylene glycol: 2 wt% Polybutenyl succinimide: 8 wt% (Measurement of electrorheological effect) As an electrode material, SUS30
4 is used, and the size of the electrode is 20 mm width x 50 mm length
Then, the electrodes were made to face each other with an electrode interval of 1 mm to provide an electrorheological fluid evaluation device.

In this device, while a constant flow rate (90 ml / min.) Of electrorheological fluid is flown between both electrodes, 2
An electric field of KV / mm (AC 50 Hz) was applied, and the differential pressure (Kg / cm ² ) to the fluid required to maintain the flow rate of the fluid at the above constant flow rate was measured. The results are shown in Table 1 below.

[0037]

Example 2 Instead of silica in the electrorheological fluid composition in Example 1, the same amount of the above-prepared silica having a D value of 1.5 was used to prepare an electrorheological fluid. evaluated. The results are also shown in Table 1.

[0038]

Example 3 An electrorheological fluid was prepared by using the same amount of silica having a D value of 1.7 produced above in place of the silica in the composition of electrorheological fluid in Example 1, and preparing the same as in Example 1. evaluated. The results are also shown in Table 1.

[0039]

Comparative Example 1 Instead of the silica in the electrorheological fluid composition in Example 1, the same amount of the above-prepared silica having a D value of 2.2 was used to prepare an electrorheological fluid. evaluated. The results are also shown in Table 1.

[0040]

Comparative Example 2 Instead of silica in the electrorheological fluid composition in Example 1, the same amount of the above-prepared silica having a D value of 2.7 was used to prepare an electrorheological fluid. evaluated. The results are also shown in Table 1.

[0041]

[Table 1]

From this table, it can be seen that the electrorheological fluid of the present invention has a higher electrorheological effect than the electrorheological fluid using solid particles having a wide particle size distribution.

[Brief description of drawings]

FIG. 1 is a diagram illustrating a particle size (logarithmic scale) -cumulative weight ratio distribution curve of solid particles.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Office reference number FI technical display location C10M 125: 26 105: 06 129: 16 133: 16) C10N 20:00 Z 20:06 Z 40: 04 (72) Inventor Masahiko Hayafune 1-3-1 Nishitsurugaoka, Oi-cho, Iruma-gun, Saitama Prefecture Tonen Corporation Research Institute

Claims (1)

[Claims] 1. In the particle size-cumulative weight ratio distribution of solid particles, the ratio of the particle size d _{75 at} a cumulative weight ratio of 75% to the particle size d ₂₅ at a cumulative weight ratio of 25% (d ₇₅ / d ₂₅ , where d _An electrorheological fluid, wherein solid particles having a ₇₅ ≧ d ₂₅ ) of 2.0 or less are blended in an electrically insulating fluid.