JP3095868B2 - Electrorheological fluid composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

FIELD OF THE INVENTION The present invention relates to an electrorheological fluid composition. More specifically, an electrorheological fluid composition that generates a large shear stress even when a relatively weak electric field is applied, the current density flowing at that time is small, and the generated shear stress and the current density have excellent stability over time. It is about things.

[0002]

2. Description of the Related Art An electrorheological fluid is obtained by, for example, dispersing dispersed phase particles made of a dielectric in an electrically insulating dispersion medium.
A fluid whose rheological or flow properties change to a viscoplastic type property by applying an electric field change.In general, when an external electric field is applied, the viscosity significantly increases and a large shear stress is induced, so-called Winslow effect Also known as fluid. Since this Winslow effect has the characteristic of quick response, the electrorheological fluid is used for clutches, brakes, engine mounts, dampers, valves,
Applications to various devices such as shock absorbers and actuators and electrorheological fluid ink jets have been attempted.

[0003] An electrorheological fluid is a composition comprising dispersed phase particles, an electrically insulating dispersion medium and a dispersant added as required. For example, an electrorheological fluid such as silicone oil, diphenyl chloride, or trans oil is used. To cellulose,
What disperse | distributed the disperse phase particle | grains, such as a starch, a silica gel, an ion exchange resin, and zeolite, is known.

[0004] However, no electrorheological fluid has been put into practical use yet, and even today, the shear stress value obtained when an electric field is applied to the electrorheological fluid, the current density at that time, and the improvement of their temporal stability are improved. Active research and development is ongoing. For example, in research and development relating to dispersed phase particles, a fluid using organic semiconductor particles such as poly (acene-quinone) as dispersed phase particles (Japanese Patent Application Laid-Open No. 61-216202), a conductive thin film mainly on organic solid particles, Fluid (Japanese Patent Application Laid-Open No. 63-97694) using dielectric particles having a three-layer structure having a layer and an electrically insulating thin film layer as dispersed phase particles, and conductive particles such as carbon black dispersed in a resin. Using dispersed dielectric particles as dispersed phase particles (JP-A-1-236291)
Etc. have been proposed.

However, regarding the electrically insulating dispersion medium,
Research and development aimed at improving such shear stress, current density and their temporal stability have not been proposed so far, and by increasing the specific gravity of the dispersion medium of the dispersion medium, the specific gravity difference with the dispersed phase particles is increased. Research has only been conducted from the viewpoint of reducing the particle size and preventing sedimentation of the dispersed phase particles.

On the other hand, for silicone oil, which is generally used as an electrically insulating dispersion medium for an electrorheological fluid, the value of the shear stress generated when an electric field is applied, the current density flowing at that time, and the stability over time are studied. However, the properties relating to the temporal stability of the shear stress value and the current density are not always sufficient, and a dispersion medium that provides an electrorheological fluid excellent in those properties has been demanded.

[0007]

SUMMARY OF THE INVENTION The present invention addresses the above need for an electrically insulating dispersion medium. That is, an object of the present invention is to generate an electro-rheological fluid composition which generates a large shear stress by applying an electric field, the current density flowing at that time is small, and the generated shear stress and the current density have excellent stability over time. Is to provide.

Further, the present invention dramatically improves the above-mentioned properties without impairing the excellent properties of an electrorheological fluid using silicone oil as a dispersion medium, which does not attack resins and rubbers and has a high flash point and is flame-retardant. It is intended to provide an electrorheological fluid composition which has been improved.

[0009]

According to the present invention, there is provided an electrorheological fluid composition comprising dispersed phase particles and an electrically insulating dispersion medium, wherein silicone oil (A) 7 is used as the electrically insulating dispersion medium.
5 to 99% by weight and the following hydrocarbon compounds (B)
The present invention relates to an electrorheological fluid composition using a mixed dispersion medium containing 25% by weight as an essential component and optionally adding another electrically insulating compound (C).

[0010]

The silicone oil (A) used in the present invention includes, for example, dimethyl silicone oil, methylphenyl silicone oil, fluorosilicone oil and the like. The kinematic viscosity at 25 ° C. is 100 cSt.
The following silicone oils are preferred.

The hydrocarbon compound (B) used in the present invention
Is composed of only a hydrogen atom and a carbon atom, and a carbon-carbon bond forming a so-called sp, sp ² hybrid orbital, such as an aromatic double bond, an alkene double bond, or an alkyne triple bond, is contained in a molecule. all SANYO to form a mixed dispersion medium by dissolving at least one has and silicone oil (a), for example 1-decene, long chain alkenes such as 1-dodecene; diphenylmethane, 1,2-diphenylethane, Methyl biphenyl, ethyl biphenyl; long-chain alkyl aromatic hydrocarbons such as hexylbenzene, dodecylbenzene, dodecylnaphthalene; hydrocarbon polymers having an unsaturated bond in a molecule such as polybutene, polybutadiene, and poly-α-olefin; It can be mentioned as an essential component, and one or more of these can be selected and used.

The mixing ratio of the silicone oil (A) and the hydrocarbon compound (B) in the mixed dispersion medium used in the present invention is 75 to 99% by weight of the silicone oil (A) and 1 to 25% by weight of the hydrocarbon compound (B). %, Particularly preferably silicone oil (A) 85-95.
% By weight and 5 to 15% by weight of the hydrocarbon compound (B). If the amount of the hydrocarbon compound (B) used is less than 1% by weight, an electrorheological fluid excellent in properties relating to shear stress, current density, and their temporal stability cannot be obtained. Even when used in a large amount at a proportion exceeding 25% by weight, the above-mentioned properties are not improved, and on the contrary, the flash point is lowered, which may cause a practical problem of the electrorheological fluid.

In the mixed dispersion medium of the present invention, an electrically insulating compound (C) other than the silicone oil (A) and the hydrocarbon compound (B) can be blended. % Is preferable. Examples of such other compounds (C) include aliphatic hydrocarbons such as dodecane and liquid paraffin; halogenated hydrocarbons such as chlorobenzene, bromobenzene, chloronaphthalene and chlorodecane; polyalkylene glycols, polyol esters, diesters, Examples thereof include polyphenyl esters and phosphoric esters.

The mixed dispersion medium comprising the silicone oil (A) and the hydrocarbon compound (B) as essential components in the present invention may optionally contain an antioxidant, a metal corrosion inhibitor,
A pour point depressant or the like can be added, but the kinematic viscosity at 25 ° C. of the mixed dispersion medium is 100 cSt or less and the flash point is 150
It is preferable that the temperature be adjusted to not less than ° C. If the kinematic viscosity of the mixed dispersion medium exceeds 100 cSt, an electrorheological fluid may be obtained which lacks the balance of the above-described characteristics.

The dispersed phase particles that can be used in the present invention are dielectric particles that directly contribute to the development of the electrorheological effect. Examples of such dielectric particles include organic particles having a hydrophilic group such as starch, cellulose, ion exchange resin, and sulfonic acid group-containing polystyrene-based polymer particles; hydrophilic inorganic particles such as silica and alumina; and organic solid particles. A conductive thin film layer is formed on the surface around
Further, particles having a three-layer structure in which an electrically insulating thin film layer is formed, particles in which a thin film insulating film is formed on the surface of conductive particles such as aluminum, and particles in which conductive particles such as carbon black are dispersed in a resin. Composite semiconductor particles; organic semiconductor particles such as poly (acene-quinone); and ferroelectric particles such as barium titanate and lithium tartrate.
Among the above-mentioned dielectric particles, the sulfonic acid group-containing polystyrene has a large shear stress value obtained when an electric field is applied, a low current density flowing at that time, and excellent stability over time. The use of polymer particles is preferred.

The shape and the average particle size of the dispersed phase particles are preferably spherical or elliptical spherical and 1 to 50 μm. In the case where the shape of the dispersed phase particles is other than spherical or elliptical spherical, the problem that a large shear stress cannot be obtained when an electric field is applied to the prepared electrorheological fluid composition or the electric field was continuously applied. There may be a problem that the stability over time in the state is poor. When the average particle diameter of the dispersed phase particles is less than 1 μm, a problem occurs that a large shear stress cannot be obtained when an electric field is applied to the prepared electrorheological fluid composition. In addition, when a certain electric field is applied to the prepared electrorheological fluid composition, a shear stress value obtained becomes irregular, which may cause a problem that stability is difficult.

The electrorheological fluid composition of the present invention is obtained by dispersing dispersed phase particles in the mixed dispersion medium described above, and the mixing ratio of the dispersed phase particles to the mixed dispersion medium in the composition is 100 parts by weight of the former. In contrast, the latter is preferably 50 to 500 parts by weight. When the amount of the dispersion medium exceeds 500 parts by weight, the shear stress obtained when an electric field is applied to the prepared electrorheological fluid composition may not be sufficiently large. In addition, when the amount of the dispersion medium is less than 50 parts by weight, the fluidity of the prepared composition itself is reduced, and it may be difficult to use the composition as an electrorheological fluid.

In the present invention, for example, a surfactant, a polymer dispersant, and a polymer thickener may be used to improve the dispersibility of the dispersed phase particles in the mixed dispersion medium, to adjust the viscosity of the electrorheological fluid composition, or to increase the shear stress. Various additives such as agents can be added to the composition.

[0019]

EXAMPLES The present invention will be described below with reference to examples, but the scope of the present invention is not limited only to these examples.

[0020]

Reference Example 1 1.2 liters of water was charged into a 3 liter four-neck separable flask equipped with a stirrer, a reflux condenser and a thermometer, and polyoxyethylene nonyl phenyl ether sulfate (Daiichi Kogyo) After dispersing 1.8 g of Hytenol N-08 (manufactured by Pharmaceutical Co., Ltd.), 284 g of styrene and industrial divinylbenzene (manufactured by Wako Pure Chemical Industries, Ltd., 55 wt% of divinylbenzene, 35 wt% of ethylstyrene, etc.) A mixture consisting of 16 g) and 5 g of azobisisobutyronitrile was added. Thereafter, the contents in the flask were dispersed at a stirring speed of 4000 rpm using a disperser to control the particle size. Then 2 at 65 ° C
After polymerization for an hour, the polymerization temperature was further raised to 90 ° C.
Heated for hours. After completion of the reaction, the obtained solid was filtered and washed with water at 80 ° C. for 12 hours without washing with water.
After drying for a time, the spherical crosslinked polymer (hereinafter referred to as "polymerized crosslinked polymer (1)"). ｝ 291 g were obtained.

A 2-liter four-neck separable flask equipped with a stirrer, thermometer and dropping funnel was charged with 50 g of the crosslinked polymer (1), and the reaction vessel was cooled to 0 ° C. in an ice bath. 500 g of fuming sulfuric acid was added thereto to obtain a uniform dispersion. After stirring for 12 hours in this state, the ice bath was removed and 8
The mixture was heated and stirred at 0 ° C. for 3 hours to carry out a sulfonation reaction.
Thereafter, the reaction mixture was poured into water at 0 ° C., filtered,
Washed with water. The obtained solid was neutralized with a 10% by weight aqueous sodium hydroxide solution (310 ml), and then sufficiently washed with water. Next, it is dried at 80 ° C. for 10 hours using a vacuum drier, and the dispersed phase particles composed of 102 g of a spherical sulfonated polymer are hereinafter referred to as dispersed phase particles (1). I got｝.

The average particle size of the obtained dispersed phase particles (1) was measured using a particle size distribution analyzer, and was found to be 20 μm. When the ion exchange capacity of the dispersed phase particles (1) was quantified by neutralization titration and elemental analysis, it was 5.5 mg equivalent / g by neutralization titration and 5.6 mg equivalent / g by elemental analysis. The water content in the dispersed phase particles (1) was measured using a Karl Fischer moisture meter, and was 2.4 parts by weight.

[0023]

Reference Example 2 1.2 liters of water was charged into a 3 liter four-neck separable flask equipped with a stirrer, a reflux condenser and a thermometer, and polyoxyethylene nonylphenyl ether sulfate (Daiichi Kogyo) After dispersing 1.8 g of Hytenol N-08 (manufactured by Pharmaceutical Co., Ltd.), 280 g of ethyl acrylate, industrial divinylbenzene (manufactured by Wako Pure Chemical Industries, Ltd., 55% by weight of divinylbenzene, 35% by weight of ethylstyrene) % Of a mixture) and 10 g of benzoyl peroxide. Then 4
The contents in the flask were dispersed at a stirring speed of 000 rpm, and polymerized at 75 ° C. for 1 hour. Further, the polymerization temperature is 95 ° C.
And heated for 4 hours. The solid obtained is filtered off,
After sufficiently washing with water, the resultant was dried at 80 ° C. for 12 hours using a hot-air drier to obtain 286 g of a spherical polymer crosslinked product (2).

In a 2-liter four-neck separable flask equipped with a stirrer, a thermometer and a dropping funnel, 50 g of the crosslinked polymer (2) was charged, and 1 liter of ethanol in which 60 g of sodium hydroxide was previously dissolved was added. A dispersion was obtained. Next, the temperature was raised to the reflux temperature, and the reaction mixture was heated and stirred for 6 hours while refluxing, thereby performing a hydrolysis reaction. Thereafter, the reaction mixture was poured into water at 0 ° C., filtered, and washed with water. Next, 10 seconds at 80 ° C. using a vacuum dryer.
After drying for a time, dispersed phase particles composed of a spherical sodium polyacrylate polymer (hereinafter referred to as dispersed phase particles (2)) were obtained.

When the average particle size of the obtained dispersed phase particles (2) was measured by using a particle size distribution analyzer, it was 15 μm. When the ion exchange capacity in the sodium polyacrylate particles was determined by neutralization titration and elemental analysis, it was 9.8 mg equivalent / g by neutralization titration and 9.7 mg equivalent / g by elemental analysis. When the water content in the dispersed phase particles (2) was measured using a Karl Fischer moisture meter, it was 7.5 parts by weight.

[0026]

Example 1 Dispersed phase particles (1) 30 obtained in Reference Example 1
Parts by weight of a dimethyl silicone oil (KF96-20cS manufactured by Shin-Etsu Chemical Co., Ltd.) and 63 parts by weight of dodecylbenzene in a mixed dispersion medium having a kinematic viscosity of 18 cSt at 25 ° C. A product (1) {hereinafter referred to as a fluid composition (1)} was prepared.

[0027]

Example 2 Dispersed phase particles (1) 30 obtained in Reference Example 1
A kinetic viscosity at 25 ° C of 43 cS consisting of 65 parts by weight of dimethyl silicone oil (KF96-50cS manufactured by Shin-Etsu Chemical Co., Ltd.) and 5 parts by weight of p-ethylbiphenyl was used.
The dispersion was dispersed in the mixed dispersion medium of Example 1 to prepare an electrorheological fluid composition (2) of the present invention {hereinafter referred to as a fluid composition (2)}.

[0028]

Example 3 Dispersed phase particles (1) 30 obtained in Reference Example 1
25 parts by weight of 60 parts by weight of dimethyl silicone oil (KF96-50cS manufactured by Shin-Etsu Chemical Co., Ltd.), 3 parts by weight of methylphenyl silicone oil (KF-54 manufactured by Shin-Etsu Chemical Co., Ltd.), and 7 parts by weight of 1-dodecene Was dispersed in a mixed dispersion medium having a kinematic viscosity of 50 cSt to prepare an electrorheological fluid composition (3) of the present invention {hereinafter referred to as a fluid composition (3)}.

[0029]

Example 4 Dispersed phase particles (2) 30 obtained in Reference Example 2
63 parts by weight of dimethyl silicone oil (KF96-20cS manufactured by Shin-Etsu Chemical Co., Ltd.) and 5 parts by weight of dodecylbenzene 5
The electrorheological fluid composition (4) of the present invention was dispersed in a mixed dispersion medium having a kinematic viscosity of 18 cSt at 25 ° C. consisting of 2 parts by weight of 1,2-diphenylethane and 2 parts by weight of 1,2-diphenylethane. ) Was prepared.

[0030]

Example 5 Dispersed phase particles (2) 30 obtained in Reference Example 2
25 parts by weight of 65 parts by weight of dimethyl silicone oil (KF96-20cS manufactured by Shin-Etsu Chemical Co., Ltd.) and 5 parts by weight of polybutene (LV-10 manufactured by Nippon Petrochemical Co., Ltd.)
Dispersed in a mixed dispersion medium having a kinematic viscosity at 16 ° C. of 16 cSt,
An electrorheological fluid composition (5) of the present invention (hereinafter referred to as a fluid composition (5)) was prepared.

[0031]

Comparative Example 1 Dispersed phase particles (1) 30 obtained in Reference Example 1
Parts by weight were dispersed in 70 parts by weight of dimethyl silicone oil (KF96-20cS manufactured by Shin-Etsu Chemical Co., Ltd.), and an electrorheological fluid composition for comparison (1) {hereinafter referred to as a comparative fluid composition (1)}. Was prepared.

[0032]

Comparative Example 2 Dispersed Phase Particles (1) 30 Obtained in Reference Example 1
Parts by weight were dispersed in 70 parts by weight of dimethyl silicone oil (KF96-50cS, manufactured by Shin-Etsu Chemical Co., Ltd.), and a comparative electrorheological fluid composition (2) (hereinafter referred to as a comparative fluid composition (2)) was used. Was prepared.

[0033]

Comparative Example 3 Dispersed phase particles (2) 30 obtained in Reference Example 1
An electrorheological fluid composition for comparison was prepared by dispersing a part by weight of a dimethyl silicone oil (KF96-20cS manufactured by Shin-Etsu Chemical Co., Ltd.) 65 parts by weight and 5 parts by weight of dodecane in a mixed dispersion medium having a kinematic viscosity of 19 cSt at 25 ° C. (3) Hereinafter, {this is referred to as comparative fluid composition (3)} was prepared.

[0034]

Example 6 Each of the fluid compositions (1) to (5) and comparative fluid compositions (1) to (3) obtained in Examples 1 to 5 and Comparative Examples 1 to 3 was rotated with a coaxial electric field. Put in the viscometer,
Shear stress value (initial value) when an external AC electric field of 5000 V / mm (frequency: 60 Hz) is applied under the conditions of an inner / outer cylinder gap of 1.0 mm, a shear rate of 400 s- ¹ and a temperature of 25 ° C.
The current density (initial value) flowing at that time was measured.

The shear stress value (value after 3 days) and the current density (value after 3 days) after continuous operation of the viscometer at 25 ° C. for 3 days with an external electric field of 5000 V / mm were applied. The fluid composition was measured to determine the stability over time.

The results are shown in Table 1.

[0037]

[Table 1]

An electrorheological fluid is a fluid having excellent shear stress characteristics such that the shear stress value obtained when a relatively weak electric field is applied is large, and the current characteristics such that the current density flowing at that time is small are excellent. It is particularly preferable that both the shear stress characteristic and the current characteristic are excellent. Therefore, as a parameter for judging superiority by simultaneously evaluating the shear stress characteristic and the current characteristic, a ratio of a shear stress value obtained when a constant electric field is applied to a current density flowing at that time, that is, (shear stress value) / ( This value is hereinafter referred to as Z value. ｝ Is effective. That is, an electrorheological fluid composition having both excellent shear stress characteristics and current characteristics has a large Z value.

Each of the fluid compositions (1) to (5) and the comparative fluid compositions (1) to (3) was determined from the shear stress value and the current density observed when an electric field of 5000 V / mm was applied. Initial value of Z value of each fluid composition and 3
The values after day are shown in Table 1.

As apparent from Table 1, the fluid compositions (1) to (5) of the present invention can obtain a large shear stress even when a relatively weak electric field is applied, and the current density flowing at that time is small. The current characteristics were excellent and the shear stress and the current density generated over time were very excellent in stability. In addition, the fluid compositions (1) to (3) of the present invention have a Z value of 2.9 or more at the initial stage, and a Z value of 2.9 or more even after 3 days. It was found that the composition was an electrorheological fluid composition which was also excellent in the stability over time of the balance.

On the other hand, the comparative fluid compositions (1) to (3)
The stability over time of the shear stress and the current density was inferior to the fluid composition of the present invention.

[0042]

According to the present invention, there is provided an electrorheological fluid composition excellent in stability over time, which can provide a large shear stress even when a relatively weak electric field is applied and maintain the generated shear stress for a long period of time. The electrorheological fluid composition thus produced can be effectively used for clutches, dampers, brakes, shock absorbers and the like.

──────────────────────────────────────────────────続 き Continuation of the front page (51) Int.Cl. ⁷ Identification code FI C10M 107: 08 151: 02) C10N 20:00 20:02 20:06 40:14 (56) References JP-A-3-35095 JP-A-4-28793 (JP, A) JP-A-1-275699 (JP, A) JP-A-3-84093 (JP, A) JP-A-51-104598 (JP, A) 54-22600 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) C10M 107/50 C10M 105/02-105/06 C10M 107/08-107/10 C10M 151/00 -151/04 C10N 40:14

Claims (3)

(57) [Claims] In an electrorheological fluid composition comprising dispersed phase particles and an electrically insulating dispersion medium, 75 to 99% by weight of silicone oil (A) and 1 to 25 hydrocarbon compounds (B) are used as the electrically insulating dispersion medium. wt% Ri name using a mixed dispersion medium comprising in addition other electrically insulating compound (C) optionally comprises, as essential components, a hydrocarbon compound (B), long-chain alkenes, long-chain alkyl
Consisting of aromatic hydrocarbons and poly-α-olefins
At least one Der Ru electrorheological fluid composition selected from the group. 2. A method comprising: disperse phase particles and an electrically insulating dispersion medium.
In an electrorheological fluid composition, as an electrically insulating dispersion medium
75-99% by weight of silicone oil (A) and hydrocarbon
Element compound (B) must be contained as an essential component in an amount of 1 to 25% by weight.
Add other electrically insulating compounds (C) as necessary.
And a hydrocarbon compound (B) containing 1-dodecene and p-ethylbicarbonate.
Phenyl, 1,2-diphenylethane, dodecylbenze
And at least one selected from the group consisting of
An electrorheological fluid composition. 3. The electrorheological fluid composition according to claim 1, wherein the dispersed phase particles are sulfonic acid group-containing polystyrene polymer particles.