JPH05230491A - Electroviscous fluid composition - Google Patents

Abstract

PURPOSE:To provide the title composition which produces high shear stress and is excellent in electric current characteristics, dielectric strength characteristics, long-term stability and dispersion stability. CONSTITUTION:An electroviscous fluid composition made by dispersing dielectric particles in an electrical insulating liquid, in which the dielectric particles are immersed in a hydrophilic organic solvent and the water in the particles is removed with the evaporation of the solvent.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION This invention relates to electrorheological fluid compositions. More specifically, a large shear stress is generated even by applying a relatively weak electric field, the current density flowing at that time is small, and it has excellent withstand voltage characteristics that dielectric breakdown does not easily occur when an electric field is applied. The present invention relates to an electrorheological fluid composition having excellent shear stress and current density stability over time and excellent dispersion stability.

[0002]

2. Description of the Related Art An electrorheological fluid is, for example, a fluid obtained by dispersing and suspending dispersed phase particles in an electrically insulating dispersion medium, and its rheological or flow properties are viscoplastic due to an electric field change. It is a fluid that changes to the nature of the mold,
It is generally known as a fluid exhibiting a so-called Winslow effect in which a viscosity is remarkably increased when an external electric field is applied and a large shear stress is induced.

Since the Winslow effect is characterized by a quick response, the electrorheological fluid is applied to torque transmitting actuators such as clutches and brakes, control actuators such as engine mounts, dampers and valves, and electrorheological fluid ink jets. Is being applied.

The electrorheological fluid is composed of cellulose in an electrically insulating oil such as silicone oil, diphenyl chloride and transformer oil.
Starch, silica gel, ion exchange resin, poly (meta)
It is known that dielectric particles such as crosslinked acrylate are dispersed as dispersed phase particles.In electrorheological fluids using these dielectric particles as dispersed phase particles, water is present in the dispersed phase particles. It is known that the Winslow effect is effectively exhibited by doing so. However, if the amount of water in the dispersed phase particles is unnecessarily large, the insulating property of the electrorheological fluid will decrease, and the current density that flows when an electric field is applied will increase. Becomes very bad. Therefore, it is necessary to adjust the amount of water in the dispersed phase particles to an appropriate amount (hereinafter referred to as the optimum water content).

On the other hand, the above-mentioned dielectric particles generally have hygroscopicity because they have a strong affinity with water, and contain a specific amount of water depending on the composition and shape of the dielectric particles, so that the dielectric particles have a different atmosphere. It is in balance. The water content (equilibrium water content of the dielectric particles) in which the dielectric particles are in equilibrium with the surrounding atmosphere is larger than the optimum water content when the dielectric particles are used as dispersed phase particles of the electrorheological fluid. When the particles are used as dispersed phase particles, it is necessary to remove the water content in the dielectric particles to adjust the water content.

However, as a method of removing water, when water is removed by heating the dielectric particles, the dielectric particles aggregate, and the obtained dispersed phase particles cannot be uniformly dispersed in the dispersion medium. It was In addition, the obtained electrorheological fluid has dispersion stability (the ability to hold the electrorheological fluid in a uniform state for a long time without causing the dispersed phase particles to settle or float).
However, there is a problem in that it is poor in the withstand voltage characteristic.

[0007]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems of conventional electrorheological fluids using dielectric particles as dispersed phase particles. Therefore, the object of the present invention is to
Large shear stress is also generated by applying a relatively weak electric field, the current density flowing at that time is small, and it has excellent withstand voltage characteristics that dielectric breakdown does not easily occur when a strong electric field is applied. An object of the present invention is to provide an electrorheological fluid composition having excellent current density stability over time and dispersion stability.

[0008]

DISCLOSURE OF THE INVENTION The present invention is a composition in which dispersed phase particles composed of dielectric particles (A) containing a water content below the equilibrium water content in the atmosphere are dispersed in an electrically insulating dispersion medium. The dielectric particles (A) are obtained by immersing the dielectric particles in a hydrophilic organic solvent and then removing the water content in the dielectric particles together with the distilling of the hydrophilic organic solvent. The present invention relates to an electrorheological fluid composition.

[0009]

The dielectric particles in the present invention are particles of a substance that is dielectrically polarized when an electric field is applied, and are liberated in a polar solvent such as a hydroxyl group, a sulfonic acid group, a carboxylic acid group, an amino group or an amide group. Particles of a compound having a functional group may be mentioned.

The dispersed phase particles used in the present invention must be dielectric particles (A) that contain an appropriate amount of water (optimum water content) for exhibiting the Winslow effect below the equilibrium water content in the atmosphere. I won't. The equilibrium water content in the atmosphere referred to in the present invention means drying at 150 ° C. for 3 hours at a reduced pressure of 0.1 torr or less, and then leaving it in the atmosphere at 25 ° C. and 60% relative humidity for 24 hours. The water content when equilibrated.

As the dielectric particles (A), for example, starch, cellulose, ion exchange resins, crosslinked poly (meth) acrylic acid salts, sulfonated polymers having an aromatic ring substituted with a sulfonic acid group, etc. are liberated. Organic dielectric particles having a group; silica gel, inorganic fine particles such as alumina, and the like. Among them, the use of sulfonated polymer particles having an aromatic ring substituted with a sulfonic acid group as dispersed phase particles produces a large shear stress under the application of a relatively weak electric field, resulting in a small current density. It is preferable because an electrorheological fluid having excellent properties and excellent stability with time of generated shear stress and current density can be obtained. Usually, the water present in the dielectric particles includes free water existing inside the particles or between the particles without interacting with the dissociative groups in the dielectric particles. In the presence of this free water, when the dispersed phase particles were dispersed in the electrically insulating dispersion medium, the dispersed phase particles aggregated, and only an electrorheological fluid with poor dispersion stability was obtained, and an electric field was applied. At that time, there arises a problem that a large current flows and the withstand voltage characteristic is deteriorated.

Therefore, in the present invention, as described above, it is necessary to set the water content in the dielectric particles to the optimum water content below the equilibrium water content in the atmosphere. The optimum moisture content of the dielectric particles varies depending on the composition and shape of the dielectric particles used, but is generally 0.1 to 10%. However, the dielectric particles contain water having a water content equal to or higher than the equilibrium water content in the atmosphere, unless water management such as drying and storage after drying is performed.
It is not preferable to use the electrorheological fluid as the dispersed phase particles as it is. Therefore, when the dielectric particles are used as the dispersed phase particles, it is necessary to remove excess water before use.

In the present invention, when the dielectric particles (A) containing water having a moisture content less than the equilibrium water content in the atmosphere used as dispersed phase particles are obtained, the dielectric particles are removed in order to remove unnecessary water from the dielectric particles. Is immersed in a hydrophilic organic solvent, and then the water content in the dielectric particles is distilled off together with the hydrophilic organic solvent. In particular, the water content after evaporation is preferably in the range of 0.1 to 2%.

By dipping the hydrophilic organic solvent after dipping it in the hydrophilic organic solvent, free water existing in the dielectric particles is replaced with the hydrophilic organic solvent, so that the cohesive force between the dielectric particles is increased. It can be suppressed. As a result, the obtained dielectric particles (A) can be easily crushed by a crusher having a relatively simple mechanism, because they have only point bonding or slight surface bonding at their interfaces. The crushed dielectric particles (A) can be easily dispersed in an electrically insulating dispersion medium.

Dielectric particles (A) obtained in the present invention
Is less than the equilibrium water content in the atmosphere, preferably within the range of the optimum water content described above, and a hygroscopic operation may be carried out as necessary, and the dielectric particles (A) after hygroscopicity can be easily dispersed in an electrically insulating manner. It can be dispersed in a medium.

When the water content is removed by direct drying or the like without performing the immersion treatment in the hydrophilic organic solvent according to the present invention, the dielectric particles are agglomerated or fused. As a result, the obtained dielectric particles are strongly surface-bonded to each other at their interfaces, so that a very large amount of energy is required when crushing with a crusher. The dielectric particles obtained by crushing in this way do not maintain a spherical shape, and aggregates are also mixed, so that the obtained electrorheological fluid has a large current density when an electric field is applied. However, there are problems such as poor dispersion stability and poor withstand voltage. The hydrophilic organic solvent used in the present invention is not particularly limited as long as it can be mixed with water at an arbitrary ratio, and examples thereof include alcohols such as methanol, ethanol, propanol and isopropanol; ethers such as tetrahydrofuran; acetone and methyl ethyl ketone. And the like, and one or more of them can be used.

The method of distilling the water content from the dielectric particles together with the hydrophilic organic solvent is not particularly limited, and known methods such as hot air drying method, vacuum drying method, radiation drying method and conduction drying method can be used. it can. In addition, the device that can be used at this time is not particularly limited, and a known dryer can be used.

Further, when removing water from the dielectric particles, it is preferable to distill off the hydrophilic organic solvent under a vacuum or in an inert gas atmosphere.

The dielectric particles (A) are used as dispersed phase particles after being classified, if necessary.

The shape of the dispersed phase particles used in the present invention is preferably spherical. When the shape of the dispersed phase particles is a shape other than spherical, the problem that a large shear stress cannot be obtained when an electric field is applied to the prepared electrorheological fluid composition and the state in which the electric field is continuously applied There may be a problem that the stability with time becomes poor.

The average particle size of the dispersed phase particles used in the present invention is preferably in the range of 1 to 50 μm. In the electrorheological fluid composition of the present invention, the shear stress obtained when an electric field is applied to the prepared electrorheological fluid composition tends to decrease as the particle diameter of the dispersed phase decreases, and When the average particle size is less than 1 μm,
There may be a problem that a large shear stress cannot be obtained when an electric field is applied to the prepared electrorheological fluid composition. Further, when the average particle size of the dispersed phase particles exceeds 50 μm, the shear stress value obtained when a certain electric field is applied to the prepared electrorheological fluid composition becomes irregular and difficult to stabilize. Points can occur.

The dispersed phase particles composed of the obtained dielectric particles (A) are dispersed in an electrically insulating dispersion medium to produce the electrorheological fluid composition of the present invention. The ratio of the dispersed phase particles and the electrically insulating dispersion medium in the electrorheological fluid composition of the present invention is
It is preferable that the former range from 50 to 500 parts by weight relative to the former 100 parts by weight. If 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 high. When the amount of the dispersion medium is less than 50 parts by weight,
The fluidity of the prepared composition itself may be lowered, and it may be difficult to use it as an electrorheological fluid.

The electrically insulating dispersion medium that can be used in the present invention is not particularly limited, and examples thereof include silicone oils such as polydimethylsiloxane and polyphenylmethylsiloxane; liquid paraffin, decane, dodecane, methylnaphthalene and dimethylnaphthalene. , Hydrocarbons such as ethylnaphthalene, biphenyl, decalin and partially hydrogenated triphenyl; ether compounds such as biphenyl ether; chlorobenzene, dichlorobenzene, trichlorobenzene, bromobenzene, dibromobenzene, chloronaphthalene, dichloronaphthalene, bromonaphthalene, Chlorobiphenyl, dichlorobiphenyl, trichlorobiphenyl, bromobiphenyl, chlorodiphenylmethane, dichlorodiphenylmethane, trichlorodiphenylmethane, bromodiphenyl Halogenated hydrocarbons such as phenylmethane, chlorodecane, dichlorodecane, trichlorodecane, bromodecane, chlorododecane, dichlorododecane, bromododecane; halogenated diphenyl ether compounds such as chlorodiphenyl ether, dichlorodiphenyl ether, trichlorodiphenyl ether, bromodiphenyl ether; Daifloyl (Daikin Industries ( Examples of such compounds include fluorinated compounds (such as manufactured by K.K.), DENNUM (manufactured by Daikin Industries, Ltd.), and ester compounds such as dioctyl phthalate, trioctyl trimellitate, and dibutyl sebacate, and one or two of these compounds. The above can be used.

In the present invention, when the dispersed phase particles are dispersed in the electrically insulating dispersion medium, a known disperser such as an ultrasonic disperser or a homogenizer can be used.

Further, in order to improve the dispersion stability of the electrorheological fluid composition, a dispersant such as a surfactant or a polymer additive may be added and used.

[0026]

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

[0027]

[Reference Example 1] Wako gel LC-5 which is silica gel particles
K (manufactured by Wako Pure Chemical Industries, Ltd., particle diameter 5 μm) 50 g 150
Vacuum drying was performed at 3 ° C for 3 hours. At this time, the water content is 0.2
%Met. After drying, the particles are placed in a thermo-hygrostat at 25 ° C.
The equilibrium water content was 12% when the equilibrium water content was determined by leaving it at a humidity of 60% RH for 24 hours.

[0028]

[Reference Example 2] 1.2 liters of water was charged into a 3 liter four-necked separable flask equipped with a stirrer, a reflux condenser and a thermometer, and Kuraray Poval PVA-205 (Co., Ltd.) was used.
16.0g of polyvinyl alcohol made by Kuraray)
After being dissolved, a mixture of 280 g of ethyl acrylate, 20 g of industrial divinylbenzene (a mixture of Wako Pure Chemical Industries, Ltd., 55% by weight of divinylbenzene, 35% by weight of ethylstyrene, etc.) and 10 g of benzoyl peroxide. Was added. Then, the contents in the flask were dispersed at a stirring speed of 5000 rpm, and polymerization was carried out at 75 ° C for 1 hour. Further, the polymerization temperature was raised to 95 ° C. and heated for 4 hours. The obtained solid matter was separated by filtration, washed thoroughly with water, and then dried at 80 ° C. for 12 hours using a hot air drier to obtain 286 g of a spherical crosslinked polymer (1).

In a 2-liter four-necked separable flask equipped with a stirrer, a thermometer and a dropping funnel, 50 g of the crosslinked polymer (1) was dispersed in 1 liter of ethanol containing 60 g of sodium hydroxide to obtain a uniform dispersion liquid. And The reaction mixture was refluxed and heated and stirred for 6 hours to carry out a hydrolysis reaction. Then, the reaction mixture was poured into water at 0 ° C., filtered and washed with water. Then, using a vacuum dryer, 8
It was dried at 0 ° C. for 10 hours to obtain 42 g of spherical sodium polyacrylate particles.

The average particle size of the obtained sodium polyacrylate particles was measured by a particle size distribution measuring device (manufactured by Shimadzu Corporation,
When measured using SALD-1000), it is 5 μm.
Met. When the ion exchange capacity in the sodium polyacrylate particles was quantified by the neutralization titration method and the elemental analysis method, it was 9.8 mg equivalent / g in the neutralization titration method and 9.7 mg equivalent / g in the elemental analysis method.

1 g of 25 g of sodium polyacrylate particles
Vacuum drying was performed at 50 ° C. for 3 hours. At this time, the water content was 0.3%. After drying, the particles were allowed to stand in a thermo-hygrostat at 25 ° C. and 60% RH for 24 hours, and the equilibrium water content was 19%.

[0032]

[Reference Example 3] MCI gel CK08C (manufactured by Mitsubishi Kasei Co., Ltd., particle size 18 μm, Na, which is a strong acid type cation exchange resin)
50 g of mold) was vacuum dried at 150 ° C. for 3 hours. At this time, the water content was 0.5%. After drying, the particles were allowed to stand in a thermo-hygrostat at 25 ° C. and 60% RH for 24 hours, and the equilibrium water content was calculated to be 25%.

[0033]

[Reference Example 4] 1.2 liters of water was charged into a 3 liter four-necked separable flask equipped with a stirrer, a reflux condenser and a thermometer, and Kuraray Poval PVA-205 (Co., Ltd.)
16.0g of polyvinyl alcohol made by Kuraray)
After being dissolved, 260 g of styrene and divinylbenzene for industrial use (mixture of 55% by weight of divinylbenzene, 35% by weight of ethylstyrene, manufactured by Wako Pure Chemical Industries, Ltd.) 4
A mixture consisting of 0 g and 10 g of benzoyl peroxide was added. Then, the contents in the flask were dispersed at a stirring speed of 8000 rpm, and polymerization was carried out at 75 ° C for 1 hour. Further, the polymerization temperature was raised to 95 ° C. and heated for 4 hours. The solid matter obtained was filtered off, washed thoroughly with water, and then dried at 80 ° C. for 12 hours using a hot air drier to give a spherical polymerized crosslinked product (2) 2
86 g was obtained.

A 2 liter four-necked separable flask equipped with a stirrer, a thermometer and a dropping funnel was charged with 50 g of the crosslinked polymer (2), and 500 g of 98% by weight concentrated sulfuric acid was added to obtain a uniform dispersion liquid. After raising the temperature of the reaction mixture to 80 ° C., the mixture was heated and stirred at the same temperature for 24 hours to carry out a sulfonation reaction. Then, the reaction mixture was poured into water at 0 ° C., filtered and washed with water / acetone. The obtained solid matter was neutralized with 330 ml of a 10 wt% sodium hydroxide aqueous solution and then thoroughly washed with water. Then, using a vacuum dryer, it was dried at 80 ° C. for 10 hours to obtain 120 g of spherical sulfonated polymer particles.

The average particle diameter of the obtained sulfonated polymer particles was measured by a particle size distribution measuring device (manufactured by Shimadzu Corporation, SALD).
-1000), it was 5 micrometers. The number of sulfonic acid groups in the sulfonated polymer particles was quantified by the neutralization titration method and the elemental analysis method. In the neutralization titration method, 155 per 100 aromatic rings in the sulfonated polymer, the elemental analysis method was used. Was 156 with respect to 100 aromatic rings in the sulfonated polymer.

50 g of the sulfonated polymer particles were vacuum dried at 150 ° C. for 3 hours. At this time, the water content was 1.5%. After drying, the particles were allowed to stand in a thermo-hygrostat at 25 ° C. and 60% RH for 24 hours, and the equilibrium water content was 39%.

[0037]

[Reference Example 5] 30 g of toluene, methoxy polyethylene glycol methacrylate (N produced by Shin-Nakamura Chemical Co., Ltd.)
5 g of K ester M-230G and 23 units of ethylene glycol), 13 g of p-methoxystyrene and 12 g of lauryl methacrylate, and 0.1 g of azobisisobutyronitrile as an initiator were added, and the mixture was stirred at room temperature for 30 minutes. Then, after heating and stirring at 65 ° C. for 24 hours, further 90
Polymerization was carried out by heating at 0 ° C for 2 hours. Toluene solution of the obtained polymer (hereinafter referred to as polymer solution (1)
Say. ), The solid content was measured to be 51% by weight.
Met.

[0038]

Example 1 10 g of silica gel particles having an equilibrium water content of 12% obtained in Reference Example 1 was dispersed in 100 ml of tetrahydrofuran, stirred for 30 minutes and then filtered. Tetrahydrofuran and water were removed from the obtained solid content by using a vacuum dryer at 150 ° C. for 3 hours. After the removal of water, the water content was 0.2%. The particles were made to absorb moisture in a thermo-hygrostat to have a water content of 5.5% to prepare dispersed phase particles (1).

5 g of the obtained dispersed phase particles (1) was added with 0.2 g of modified silicone oil KF869 (amino silicone oil manufactured by Shin-Etsu Chemical Co., Ltd.) and Shin-Etsu silicone oil KF96-20CS (manufactured by Shin-Etsu Chemical Co., Ltd.). Dimethyl silicone oil) of 12 g, and uniformly mixed and dispersed in a dispersion medium obtained by adding Biomixer BM-1 type (manufactured by Nippon Seiki Co., Ltd.) to obtain an electrorheological fluid composition of the present invention. Object {Hereafter, this is referred to as fluid (1). } Was obtained.

[0040]

Example 2 10 g of sodium polyacrylate particles having an equilibrium water content of 19% obtained in Reference Example 2 was dispersed in 100 ml of acetone, stirred for 30 minutes and then filtered. The obtained solid content was dried at 150 ° C for 3 times using a vacuum dryer.
Acetone and water were removed over time. After the removal of water, the water content was 0.2%. The particles were made to absorb moisture in a thermo-hygrostat to have a water content of 7% to prepare dispersed phase particles (2).

5 g of the obtained dispersed phase particles (2) was added to 0.5 g of the polymer solution (1) obtained in Reference Example 5 in Therm S 9
00 (partially hydrogenated triphenyl hydride manufactured by Nippon Steel Chemical Co., Ltd.) was uniformly mixed and dispersed in a dispersion medium obtained by using Biomixer BM-1 type, and Electrorheological fluid composition {hereinafter referred to as fluid (2). } Was obtained.

[0042]

Example 3 In a 2 liter four-necked separable flask equipped with a stirrer, a thermometer and a dropping funnel, 50 g of the polymerized crosslinked product (1) obtained in Reference Example 2 was added with 60% sodium hydroxide.
g was dissolved in 1 liter of dissolved ethanol to give a uniform dispersion. The reaction mixture is refluxed and heated and stirred for 6 hours,
A hydrolysis reaction was performed. Then, the reaction mixture was poured into water at 0 ° C., filtered and washed with water. After washing, the filtered sodium polyacrylate particles were dispersed in 1 liter of acetone, stirred for 30 minutes, and then filtered. This operation was repeated once. Then, using a vacuum dryer,
After drying at 80 ° C. for 10 hours, 42 g of spherical sodium polyacrylate particles were obtained.

The average particle size of the obtained sodium polyacrylate particles was measured by a particle size distribution measuring device (manufactured by Shimadzu Corporation,
When measured using SALD-1000), it is 5 μm.
Met. When the ion exchange capacity in the sodium polyacrylate particles was quantified by the neutralization titration method and the elemental analysis method, it was 9.8 mg equivalent / g in the neutralization titration method and 9.7 mg equivalent / g in the elemental analysis method.

The obtained sodium polyacrylate particles were vacuum dried at 150 ° C. for 3 hours. At this time, the water content was 0.3%. The particles were made to absorb moisture in a thermo-hygrostat to adjust the water content to 7% to prepare dispersed phase particles (3).

5 g of the dispersed phase particles (3) thus obtained were mixed with 0.5 g of the polymer solution (1) obtained in Reference Example 5 by Therm S9.
00 (partially hydrogenated triphenyl hydride manufactured by Nippon Steel Chemical Co., Ltd.) was uniformly mixed and dispersed in a dispersion medium obtained by using Biomixer BM-1 type, and An electrorheological fluid composition (hereinafter referred to as fluid (3)) was obtained.

[0046]

Example 4 10 g of strong acid type cation exchange resin particles having an equilibrium water content of 25% obtained in Reference Example 3 were dispersed in 100 ml of isopropyl alcohol, stirred for 30 minutes and then filtered. The obtained solid content is removed by using a vacuum dryer.
Isopropyl alcohol and water were removed at 0 ° C. for 3 hours. After the removal of water, the water content was 0.5%. Moisture content of these particles in a thermo-hygrostat is 2.0%
To prepare dispersed phase particles (4).

30 g of the obtained dispersed phase particles (4) and 0.5 g of the polymer solution (1) obtained in Reference Example 5 were therms 900 (a partially hydrogenated trihydrogenated product of Nippon Steel Chemical Co., Ltd.). (Phenyl) 12 g, and uniformly mixed and dispersed in a dispersion medium obtained by using Biomixer BM-1 type,
The electrorheological fluid composition of the present invention {hereinafter referred to as fluid (4)
Say. } Was obtained.

[0048]

Example 5 10 g of the sulfonated polymer particles having an equilibrium water content of 39% obtained in Reference Example 4 were dispersed in 100 ml of methanol, stirred for 30 minutes and then filtered. The solid content thus obtained was removed of methanol and water by using a vacuum dryer at 150 ° C. for 3 hours. After the removal of water was completed, the water content was 1.5%. The particles were made to absorb moisture in a thermo-hygrostat to adjust the water content to 2.0% to prepare dispersed phase particles (5).

5 g of the obtained dispersed phase particles (5) were added to 0.5 g of the polymer solution (1) obtained in Reference Example 5 in Therm S9.
00 (partially hydrogenated triphenyl hydride manufactured by Nippon Steel Chemical Co., Ltd.) was uniformly mixed and dispersed in a dispersion medium obtained by using Biomixer BM-1 type, and Electrorheological fluid composition {hereinafter referred to as fluid (5). } Was obtained.

[0050]

Example 6 10 g of sulfonated polymer particles having a water content of 1.5% obtained by vacuum drying at 150 ° C. for 3 hours in Reference Example 4 were dispersed in 100 ml of methanol.
After stirring for 0 minutes, it was filtered. The obtained solid content was subjected to removal of methanol and water by using a vacuum dryer at 150 ° C. for 3 hours. The water content after removal of water was 1.1%. Moisture content of these particles in a thermo-hygrostat is 2.0%
To prepare dispersed phase particles (6).

5 g of the dispersed phase particles (6) thus obtained were mixed with 0.5 g of the polymer solution (1) obtained in Reference Example 5 by Therm S9.
00 (partially hydrogenated triphenyl hydride manufactured by Nippon Steel Chemical Co., Ltd.) was uniformly mixed and dispersed in a dispersion medium obtained by using Biomixer BM-1 type, and Electrorheological fluid composition {hereinafter referred to as fluid (6). } Was obtained.

[0052]

Comparative Example 1 10 g of silica gel particles having an equilibrium water content of 12% obtained in Reference Example 1 was vacuum dried at 150 ° C. for 3 hours as it was. After the completion of drying, the water content was 0.3%. The particles were absorbed in a thermo-hygrostat to have a water content of 5.5% to prepare comparative dispersed phase particles (1).

5 g of the obtained comparative dispersed phase particles (1), 0.2 g of modified silicone oil KF869 (amino silicone oil manufactured by Shin-Etsu Chemical Co., Ltd.) and Shin-Etsu silicone oil KF96-20CS (Shin-Etsu Chemical Co., Ltd.) (Dimethyl silicone oil manufactured by K.K.) was uniformly mixed and dispersed by using Biomixer BM-1 type, and an electrorheological fluid composition for comparison {hereinafter, referred to as comparative fluid (1). }
Got

[0054]

Comparative Example 2 10 g of sodium polyacrylate particles having an equilibrium water content of 19% obtained in Reference Example 2 was directly used at 150 ° C.
It was vacuum dried for 3 hours. Moisture content after drying is 0.2
%Met. The particles were absorbed in a thermo-hygrostat to have a water content of 7.0% to prepare comparative dispersed phase particles (2).

5 g of the obtained comparative dispersed phase particles (2) and 0.5 g of the polymer solution (1) obtained in Reference Example 5 were partially hydrogenated by Therm S 900 (manufactured by Nippon Steel Chemical Co., Ltd.). Triphenyl) 12 g, and uniformly mixed and dispersed in a dispersion medium obtained by using Biomixer BM-1 type, and an electrorheological fluid composition for comparison {hereinafter, referred to as comparative fluid (2). .. } Was obtained.

[0056]

Comparative Example 3 10 g of strongly acidic cation exchange resin particles having an equilibrium water content of 25% obtained in Reference Example 3 were vacuum dried at 150 ° C. for 3 hours as they were. Water content is 0.8% after drying
Met. The particles were absorbed in a thermo-hygrostat to adjust the water content to 2.0% to prepare comparative dispersed phase particles (3).

5 g of the obtained comparative dispersed phase particles (3) and 0.5 g of the polymer solution (1) obtained in Reference Example 5 were partially hydrogenated by Therm S 900 (manufactured by Nippon Steel Chemical Co., Ltd.). Triphenyl) 12 g, and uniformly mixed and dispersed in a dispersion medium obtained by using a biomixer BM-1 type, and a comparative electrorheological fluid composition {hereinafter, referred to as comparative fluid (3). .. } Was obtained.

[0058]

Comparative Example 4 10 g of the sulfonated polymer particles having an equilibrium water content of 39% obtained in Reference Example 4 was vacuum dried at 150 ° C. for 3 hours as it was. After the completion of drying, the water content was 1.5%. Moisture content of these particles in a thermo-hygrostat is 2.0%
The comparative dispersed phase particles (4) were prepared.

5 g of the obtained comparative dispersed phase particles (4) and 0.5 g of the polymer solution (1) obtained in Reference Example 5 were partially hydrogenated by Therm S 900 (manufactured by Nippon Steel Chemical Co., Ltd.). Triphenyl) 12 g, and uniformly mixed and dispersed in a dispersion medium obtained by using Biomixer BM-1 type, and an electrorheological fluid composition for comparison {hereinafter, referred to as comparative fluid (4). .. } Was obtained.

[0060]

Fifth Embodiment Each of the electrorheological fluids (1) to (6) and the comparative fluids (1) to (4) of the present invention obtained in Examples 1 to 6 and Comparative Examples 1 to 4 is 150 mm in height, A test tube having a diameter of 15 mm was filled up to 100 mm from the bottom and sealed.
Then, the mixture was allowed to stand for 3 days, the degree of sedimentation of dispersed phase particles was observed, and the dispersion stability of the electrorheological fluid was examined. The results are shown in Table 1.

Further, each of the electrorheological fluid compositions was placed in a double cylinder type rotational viscometer with a coaxial electric field, and the inner / outer tube gap was 1.0.
mm, shear rate 400 s ~ ¹ , temperature 25 ° C, shear stress value (initial value) and current density (initial value) when applying an external AC electric field of 4 kV / mm (frequency: 50 Hz) did. 4kV / mm (frequency:
Viscometer at 25 ° C with an external electric field of 50 Hz applied
The shear stress value (value after 3 days) and the current density (value after 3 days) after continuous operation for 3 days were measured to examine the stability of the electrorheological fluid with time. The results are shown in Table 1. Also,
Inner / outer tube gap 1.0mm, shear rate 400s ~ ¹ , temperature 2
AC external electric field 0 to 10 kV / mm (frequency:
The application stability test was performed within the range of 50 Hz. Table 1 shows the maximum applied voltage that can maintain the applied stability.

[0062]

[Table 1]

As is clear from Table 1, the electrorheological fluids (1) to (6) of the present invention were fluids having excellent dispersion stability. Also, in terms of application stability, the electrorheological fluids (1) to (6) of the present invention had high maximum applied voltages. In particular, the electrorheological fluids (4) to (6) of the present invention can be applied even at 10 kV / mm, and showed excellent application stability.

On the other hand, the comparative fluids (1) to (4) were inferior in dispersion stability to the electrorheological fluid of the present invention. Also, the application stability was inferior to the electrorheological fluid of the present invention.

[0065]

INDUSTRIAL APPLICABILITY The present invention has excellent stability over time that a large shear stress can be obtained even when a relatively weak electric field is applied and that the generated shear stress is maintained for a long period of time, and further has excellent withstand voltage characteristics and dispersion stability. The present invention provides a method for easily producing an electrorheological fluid, and the electrorheological fluid thus produced can be effectively used for a clutch, a damper, a brake, a shock absorber and the like.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Reference number within the agency FI Technical indication location C10N 60:10 70:00 (72) Minor Kobayashi 1-25 25 Kannondai, Tsukuba-shi, Ibaraki 12 Incorporated company Nippon Shokubai Tsukuba Research Institute

Claims (2)

[Claims] 1. A composition in which dispersed phase particles composed of dielectric particles (A) containing water having a water content less than the equilibrium water content in the atmosphere are dispersed in an electrically insulating dispersion medium. A) is an electrorheological fluid composition obtained by immersing dielectric particles in a hydrophilic organic solvent, and then removing the water content in the dielectric particles together with distilling off the hydrophilic organic solvent. 2. The electrorheological fluid composition according to claim 1, wherein the dielectric particles (A) are sulfonated polymer particles having an aromatic ring substituted with a sulfonic acid group.