JPH0551592A - Electroviscous fluid - Google Patents

Abstract

PURPOSE:To prepare an electroviscous fluid excellent in storage stability as well as in the response properties, reproducibility, durability, and thickening effect over a wide temp. range including a high-temp. region by mixing a substance having a specified HLB value into a specific electroviscous fluid. CONSTITUTION:A substance having an BLB value of 2-30 is mixed into an electroviscous fluid which comprises an electric insulating fluid (e.g. a paraffin oil or a synthetic hydrocarbon), porous solid particles (e.g. a silica or alumina gel), and a polyhydric alcohol (e.g. ethylene glycol or glycerol) and/or a partial deriv. of a polyhydric alcohol having at least one hydroxyl group (e. g. a partial ether prepd. by substituting some of terminal hydroxyl groups of the polyhydric alcohol with methyl groups). The prepd. electroviscous fluid is excellent in storage stability as well as in the response properties. reproducibility. durability, and thickening effect and useful for, e.g. a control unit utilizing viscosity change.

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art Electro-Rheological Fluid (Electro-Rheological 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 a considerable electrorheological effect. 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. 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 (such as silica gel) 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 a shear resistance force against stress, that is, an ER effect is developed.

Winslow has also proposed an electrorheological fluid using paraffin and silica gel powder and water to make the system slightly conductive (Winslow, WM, J. of Appli.
ed Physics, Vol.20 (1949) 1137). According to this Winslow study, the electrorheological effect of electrorheological fluid is called the Winslow effect.

In such a solid dispersion type ER fluid, from the viewpoint of improving the viscosity characteristics and stability of the ER fluid while considering the mechanism of expression of the ER effect, for example, a ferroelectric powder is used. Using a silicon dioxide-based fine powder adsorbing a small amount of water (Japanese Patent Laid-Open No. 53-175).
No. 85), a polyhydric alcohol is used in place of water which is a polarizing agent, and the ER effect in a high temperature region is enhanced.

[0006]

However, the polyhydric alcohol has poor solubility in an electrically insulating fluid, and there is a difference in specific gravity between the polyhydric alcohol and the electrically insulating fluid. For example, a dispersant such as succinimide is used. Since polyhydric alcohol precipitates even when used together, ER with polyhydric alcohol added
It has been found that it is necessary to improve the performance and storage stability of the fluid as an ER fluid.

An object of the present invention is to provide an ER fluid which can reduce the sedimentation property of polyhydric alcohol and stably maintain the ER effect.

[0008]

The electrorheological fluid of the present invention comprises an electrically insulating fluid, porous solid particles, and a polyhydric alcohol and / or a partial derivative of the polyhydric alcohol having at least one hydroxyl group. HL for viscous fluids
It is characterized by blending a substance having a B value of 2 to 30.

Examples of the electrically insulating fluid include mineral oils and synthetic lubricating oils, and specifically, paraffinic mineral oils, naphthenic mineral oils, poly-α-olefins, polyalkylene glycols, silicones, diesters, polyol esters, and phosphoric acid esters. Oils such as silicon compounds, fluorine compounds, polyphenyl ethers, and synthetic hydrocarbons can be used.
The viscosity range of these electrically insulating fluids is 5 cSt at 40 ° C.
It can be used up to 300 cSt.

Conventional porous solid particles are used, and for example, silica gel, hydrous resin, diatomaceous earth, alumina, silica-alumina, zeolite, ion exchange resin, cellulose and the like can be used. These porous solid particles, which usually have a particle size of 10 nm to 200 μm, are
It is used in a proportion of 0.1 wt% to 50 wt%. If it is less than 0.1 wt%, the ER effect is small, and if it exceeds 50 wt%, the dispersibility is deteriorated, which is not preferable.

Next, the polyhydric alcohol or its partial derivative which is a polarization promoting agent will be described.

Examples of the polyhydric alcohol include dihydric alcohols and trihydric alcohols such as ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol, glycerin, propanediol, butanediol, pentanediol and hexanediol. be able to.

The partial derivative of polyhydric alcohol is a partial derivative of polyhydric alcohol having at least one hydroxyl group, and some of the terminal hydroxyl groups of the above polyhydric alcohol are methyl group, ethyl group and propyl 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 terminal hydroxyl groups are esters with acetic acid, propionic acid, butyric acid, etc. And partial esters thereof.

These polyhydric alcohols and / or their partial derivatives are usually contained in an amount of 1% by weight to 10% by weight relative to the porous solid particles.
0 wt%, particularly preferably 2 wt% to 80 wt% is used. If the added amount is less than 1 wt%, the ER effect is small, and if it exceeds 100 wt%, the current easily flows, which is not preferable. It goes without saying that water may be used together with the polyhydric alcohols to the extent that the ER effect is not impaired.

The present invention is characterized in that a substance having an HLB value of 2 to 30 is mixed in such an electro-electrorheological fluid.

HLB (Hydrophile-Lipophile-Balance
The value means the hydrophilic / hydrophobic ratio of the substance. A low HLB value indicates strong hydrophobicity, and a high HLB value indicates strong hydrophilicity.

This substance is compatible with the polar polyhydric alcohols dispersed in the electrically insulating fluid and is oil-soluble, and has an HLB value of 2 to 30, preferably 4 to 20. It is preferable to use a polyhydric alcohol, and it is possible to stably hold polyhydric alcohols having poor solubility in an electrically insulating fluid as a dispersion medium and having a specific gravity difference in the electrically insulating fluid.

As such a substance, nonionic type such as polyoxyalkylene glycol derivative and glucose derivative, anion or cation such as carboxylate, amino acid salt and ammonium sulfonate, or amphoteric type is used. Good to do.

Examples of such substances include (1) polyoxyethylene alkyl ether represented by the formula RO- (CH ₂ CH ₂ 0) _n H
Is an alkyl group having 8 to 22 carbon atoms, n is an integer of 2 to 50, and specifically, polyoxyethylene lauryl ether, polyoxyethylene cetyl ether, polyoxyethylene stearyl ether, polyoxyethylene oleyl ether, Examples thereof include polyoxyethylene behenyl ether, polyoxyethylene synthetic alkyl ether, and polyoxyethylene secondary alkyl ether.

(2) A polyoxyethylene polyoxypropylene alkyl ether represented by the formula RO- {CH ₂ CH (CH ₃ ) 0} _m- (CH ₂ CH ₂ 0) _n H, wherein R has 8 to 8 carbon atoms. 22 alkyl groups,
The ratio of m and n is 1 to 6: 8 to 1, and m + n is 2 to 50. Specific examples thereof include polyoxyethylene polyoxypropylene cetyl ether and polyoxyethylene polyoxypropylene tetradecyl ether. Be done.

Equation (3)

[0022]

[Chemical 1]

Is a polyoxyethylene alkylphenyl ether represented by the formula, R is an alkyl group having 8 to 22 carbon atoms,
n is an integer of 2 to 50, and specific examples thereof include polyoxyethylene nonylphenyl ether, polyoxyethylene octylphenyl ether, and the like, and a part of the ethylene group may be substituted with a propylene group.

Examples of the N-acyl amino acid salt include cocoyl sarcosine sodium, lauroyl sarcosine sodium, lauroyl sarcosine sodium, lauroyl sarcosine potassium, myristoyl sarcosine sodium, palmitoyl sarcosine sodium, oleoyl sarcosine, sodium lauroyl methylalanine and the like.

Examples of the sulfonate include sodium di-2-ethylhexyl sulfosuccinate, sodium lauryl sulfoacetate, and sodium α-olefin sulfonate.

Examples of the polyoxyalkylene alkyl ether sulfates include sodium polyoxyethylene alkyl ether sulfate, triethanolamine polyoxyethylene alkyl ether sulfate, and more specifically, sodium polyoxyethylene lauryl ether sulfate and polyoxyethylene lauryl. Ether triethanolamine,
Examples thereof include ammonium polyoxyethylene lauryl ether sulfate, sodium polyoxyethylene nonylphenyl ether sulfate, and triethanolamine polyoxyethylene nonylphenyl ether sulfate, and a part of the ethylene group may be replaced with a propylene group.

Examples of the alkyl ammonium salt include lauryl trimethyl ammonium chloride, cetyl trimethyl ammonium chloride, stearyl trimethyl ammonium chloride, tallow alkyl trimethyl ammonium chloride, behenyl trimethyl ammonium chloride, dioctyl dimethyl ammonium chloride, distearyl dimethyl ammonium chloride and the like. Be done.

These substances have a ratio of 1 to the polarization promoter.
It is advisable to add 0 to 1000 mol%, preferably 50 to 300 mol%.

Further, a dispersant may be used to uniformly and stably disperse the porous solid particles, for example, sulfonates, phenates, phosphonates, succinimides, amines, nonionic dispersions. Agents are used,
Specific examples include magnesium sulfonate, calcium sulfonate, calcium phosphonate, polybutenyl succinimide, sorbitan monooleate and sorbitan sesquioleate. These are typically used in proportions of 0.1 wt% to 10 wt% of the total ER fluid.

Further, an acid, salt or base component may be added as a polarization promoting agent.

Examples of such an acid component include inorganic acids such as sulfuric acid, hydrochloric acid, nitric acid, perchloric acid, chromic acid, phosphoric acid and boric acid,
Alternatively, organic acids such as acetic acid, formic acid, propionic acid, butyric acid, isobutyric acid, valeric acid, oxalic acid and malonic acid are used.

As the salt, a metal or a basic group (N
H ₄ ⁺ , N ₂ H ₅ ^+, etc.) and an acid group,
Any of these can be used. Among them, polyhydric alcohols, polyhydric alcohol partial derivatives, or polyhydric alcohols and / or polyhydric alcohol partial derivatives which are dissolved in a water system to dissociate, for example, alkali metal and alkaline earth metal halides are typical. Preferred are those capable of forming various ionic crystals, alkali metal salts of organic acids, and the like.

As salts of this kind, LiCl, NaCl,
KCl, MgCl ₂ , CaCl ₂ , BaCl ₂ , LiB
r, NaBr, KBr, MgBr ₂ , LiI, NaI,
_{KI, AgNO 3, Ca (NO} 3) 2, NaNO 2, NH
₄ NO ₃ , K ₂ SO ₄ , Na ₂ SO ₄ , NaHSO ₄ ,
(NH ₄ ) ₂ SO ₄ or alkaline metal salts of formic acid, acetic acid, oxalic acid, succinic acid and the like.

The base that can be used in the present invention is an alkali metal or alkaline earth metal hydroxide, an alkali metal carbonate, an amine, etc., and it is a polyhydric alcohol, a polyhydric alcohol partial derivative, or a polyhydric alcohol partial derivative. It is preferable to dissolve the dissociation of the polyhydric alcohol and / or the polyhydric alcohol partial derivative in a water system. As this kind of base, NaOH, K
OH, Ca (OH) ₂ , Na ₂ CO ₃ , NaHCO ₃ ,
Examples include K ₃ PO ₄ , Na ₃ PO ₄ , aniline, alkylamines and ethanolamine. The salt and the base described above can be used in combination.

Acids, salts and bases can increase the polarization effect, but by using in combination with polyhydric alcohol and / or polyhydric alcohol partial derivative, the polarization effect can be further enhanced. It is possible, and it is advisable to use it in a proportion of 0.01 wt% to 5 wt% in the entire ER fluid. If it is less than 0.01 wt%, the ER effect is small, and
If it exceeds 5% by weight, it becomes easier to energize and power consumption increases, which is not preferable. Further, the ER fluid of the present invention contains acid,
When adding a salt or a base component, it is necessary that the partial esterified product of the polyhydric alcohol is not hydrolyzed.

Further, it is preferable to add an antioxidant and / or a corrosion inhibitor to the ER fluid of the present invention.

The antioxidant is for the purpose of preventing the oxidation of the electrically insulating liquid as well as the oxidation of the polyhydric alcohol, the polyhydric alcohol partial derivative, etc., which is the polarization promoting agent.

As the antioxidant, it is preferable to use one which is inactive to the polarization accelerator, the porous solid particles and the like, and the conventional phenol-based and amine-based antioxidants can be used. 2.6-di-t as a phenol type
-Butylparacresol, 4,4'-methylenebis (2
・ 6-di-t-butylphenol), 2,6-di-t-
Butylphenol and the like, and as the amine type, dioctyldiphenylamine, phenyl-α-naphthylamine, alkyldiphenylamine, N-nitrosodiphenylamine and the like can be used, and 0.01 to the entire ER fluid can be used.
~ 10wt%, preferably 0.1-2.0wt% can be used, less than 0.01wt% has no antioxidant effect,
If it exceeds wt%, 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 that is inactive to the polarization promoter, the porous solid particles, etc. Specifically, for the nitrogen compound, benzotriazole and its derivative, imidazoline, For compounds containing sulfur and nitrogen such as pyrimidine derivatives, 1.3.4-thiadiazole polysulfide, 1.3.4-thiadiazolyl-2.5-bisdialkyldithiocarbamate, 2- (alkyldithio) benzimidazole, etc., and β- (o-carboxyl Benzylthio) propionnitrile or propionic acid, etc. can be used, and is 0.0 to the whole ER fluid.
01-10 wt%, preferably 0.01-1.0 wt% may be used.
If less than 0.001wt%, there is no corrosion prevention effect, and 10wt%
%, Deterioration of hue, generation of turbidity, generation of sludge,
There are problems such as increased viscosity.

Further, additives such as an antiwear agent, an extreme pressure agent and an antifoaming agent may be added to such an extent that the ER effect is not affected.

[0041]

In the ER fluid, by adding polyhydric alcohol and / or polyhydric alcohol partial derivative as a polarization accelerator, a stable thickening effect can be obtained in a wide temperature range up to a high temperature region. Alcohol and /
Alternatively, the polyhydric alcohol partial derivative has poor solubility in an electrically insulating fluid, and there is a difference in specific gravity between the polyhydric alcohol and / or the polyhydric alcohol partial derivative and the electrically insulating fluid,
For example, even if a dispersant such as succinimide is used together, there is a problem that the polarization promoting agent and the electrically insulating fluid are separated.

The present invention uses a substance that is compatible with the polyhydric alcohol-based polarization accelerator and also with the electrically insulating fluid so that the polarization accelerator can be stably retained in the electrically insulating fluid. It is possible to improve the performance of the ER fluid, and the storage stability can be excellent.

The present invention will be described below based on examples, but the present invention is not limited to these examples.

[Example 1] Were mixed to prepare an ER fluid.

All of these samples were 80 cSt at 40 ° C.
The viscosity of the mineral oil was adjusted so that

Example 2 The same amount of polyoxyethylene (n = 2) octyl phenyl ether was used in place of the polyoxyethylene (n = 2) nonyl phenyl ether of Example 1 as in Example 1. An ER fluid was prepared.

Example 3 The same amount of triethylene glycol was used instead of the ethylene glycol monomethyl ether of Example 1, and the same amount of polyoxyethylene (n = 2) was used instead of polyoxyethylene (n = 2) nonylphenyl ether. 2) An ER fluid was prepared as in Example 1 using octyl phenyl ether.

Comparative Example In the ER fluid of Example 1,
ER fluids were prepared without the addition of polyoxyethylene (n = 2) nonylphenyl ether.

Each of these ER fluids was allowed to stand for 30 days, and the sedimentation amount of the polarization promoting agent was measured.

The results are shown in the table below.

[0051]

[Table 1]

Next, this ER fluid was treated at 40 ° C. and 90 ° C.
Using a rotational viscometer capable of applying a voltage, the following items were measured and evaluated as an ER fluid.

Responsiveness: AC electric field from 0 to 2.0 × 10 ⁶ (V
/ m) is evaluated by how many seconds the viscosity stabilizes.

Reproducibility: AC electric field 0 → 2.0 × 10 ⁶ (V /
m) → 0 cycle repeated, electric field 1.4 × 10 ⁶ (V /
Evaluated by the change rate of viscosity at m).

Durability: When the AC electric field was kept constant at 2.0 × 10 ⁶ (V / m), the change in viscosity with time (%) (measurement time 50 hours) was evaluated.

Thickening effect-Evaluated by the magnification of the viscosity when the AC electric field was 1.4 × 10 ⁶ (V / m), as compared with when the electric field was 0.

The results are shown in the table below.

[0058]

[Table 2]

As can be seen from the table, the ER fluid of the present invention has excellent responsiveness, reproducibility, and reproducibility in a wide temperature range up to a high temperature range.
It has excellent thickening effect and durability.

[0060]

EFFECTS OF THE INVENTION The ER fluid of the present invention is excellent in storage stability and responsiveness, reproducibility, durability and thickening effect in a wide temperature range up to a high temperature region. It is useful for the controlled equipment and
The control accuracy, especially the control accuracy under high temperature use, can be remarkably improved.

[0061]

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI technical display location C10M 133: 16) C10N 20:00 Z 8217-4H 20:06 Z 8217-4H 30:02 30: 08 40:14

Claims (1)

[Claims] 1. An electrorheological fluid comprising an electrically insulating fluid, porous solid particles, and a polyhydric alcohol and / or a partial derivative of the polyhydric alcohol having at least one hydroxyl group, has an HLB value of 2 to 30. An electrorheological fluid, characterized in that it contains a substance.