JP3115672B2 - Manufacturing method of electrorheological fluid composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

FIELD OF THE INVENTION The present invention relates to a method for producing an electrorheological fluid composition .
It is about the law . More specifically, a large shear stress is generated even by applying a relatively weak electric field,
The electro-rheological property is excellent in withstand voltage characteristics that the current density flowing at that time is small and dielectric breakdown does not easily occur when an electric field is applied, the shear stress and the current density generated over time are stable, and the dispersion stability is excellent. The present invention relates to a method for producing a fluid composition.

[0002]

2. Description of the Related Art An electrorheological fluid is a fluid obtained by, for example, 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 the properties of the mold,
Generally, it is known as a fluid exhibiting the so-called Winslow effect in which the viscosity increases significantly when an external electric field is applied and a large shear stress is induced.

Since the Winslow effect has a characteristic of quick response, the electrorheological fluid is applied to torque transmitting actuators such as clutches and brakes, control actuators such as engine mounts, dampers, valves, etc., and electrorheological fluid ink jets. Has been attempted.

An electrorheological fluid is composed of cellulose, an electrically insulating oil such as silicone oil, diphenyl chloride, and trans oil.
Starch, silica gel, ion exchange resin, poly (meth)
It is known that dielectric particles such as crosslinked acrylates are dispersed as dispersed phase particles.In an electrorheological fluid using these dielectric particles as dispersed phase particles, water is present in the dispersed phase particles. It is known that by doing so, the Winslow effect is effectively exhibited. However, if the amount of water in the dispersed phase particles becomes more than necessary, the insulating properties of the electrorheological fluid decrease, the current density flowing when an electric field is applied increases, and the generated shear stress and the temporal stability of the current density increase. Becomes very bad. Therefore, the amount of water in the dispersed phase particles needs to be adjusted to an appropriate amount (hereinafter referred to as an optimum water content).

[0005] On the other hand, the above-mentioned dielectric particles generally have hygroscopicity due to strong affinity with water, and contain a specific amount of water depending on the composition and shape of the dielectric particles, and have a certain amount of water. It is in balance. The water content (equilibrium water content of the dielectric particles) at 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 an electrorheological fluid. When particles are used as dispersed phase particles, it is necessary to adjust the water content by removing the water content in the dielectric particles.

However, as a method for removing water, when water is removed by heating the dielectric particles or the like, the dielectric particles aggregate, and the resulting dispersed phase particles cannot be uniformly dispersed in a dispersion medium. Was. In addition, the obtained electrorheological fluid has dispersion stability (the ability to maintain the electrorheological fluid in a uniform state for a long time without causing the dispersed phase particles to settle or float).
And the withstand voltage characteristics are also poor.

[0007]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems of the conventional electrorheological fluid using dielectric particles as dispersed phase particles. Therefore, the object of the present invention is to
Even when a relatively weak electric field is applied, a large shear stress is generated, the current density flowing at that time is small, and when a strong electric field is applied, dielectric breakdown is less likely to occur. An object of the present invention is to provide a method for producing an electrorheological fluid composition having excellent current density stability over time and excellent dispersion stability.

[0008]

According to the present invention, there is provided a composition obtained by dispersing dispersed phase particles comprising dielectric particles (A) containing water having a water content less than the equilibrium water content in the air in an electrically insulating dispersion medium. Wherein the dielectric particles (A) are obtained by immersing the dielectric particles in a hydrophilic organic solvent and then removing water contained in the dielectric particles together with distilling off the hydrophilic organic solvent. The present invention relates to a method for producing an electrorheological fluid composition.

[0009]

The dielectric particles in the present invention are particles of a substance which undergo dielectric polarization when an electric field is applied, and are released in a polar solvent such as a hydroxyl group, a sulfonic acid group, a carboxylic acid group, an amino group and an amide group. Examples include particles of a compound having a functional group.

The dispersed phase particles used in the present invention must be dielectric particles (A) containing an appropriate amount of water (optimum water content) for the expression of the Winslow effect below the equilibrium water content in the atmosphere. No. The equilibrium water content in the air as referred to in the present invention is defined as a value obtained by drying at 150 ° C. for 3 hours at a reduced pressure of 0.1 torr or less, and then leaving it in an air atmosphere at a temperature of 25 ° C. and a relative humidity of 60% for 24 hours. Means the water content when equilibrium is maintained.

The dielectric particles (A) include, for example, starch, cellulose, ion exchange resin, crosslinked poly (meth) acrylate, sulfonated polymer having an aromatic ring substituted by a sulfonic acid group, and the like. Organic dielectric particles having a group; inorganic fine particles such as silica gel and alumina; In particular, the use of sulfonated polymer particles having an aromatic ring substituted with a sulfonic acid group as dispersed phase particles generates a large shear stress when a relatively weak electric field is applied, and the current density at that time is small. It is preferable because an electrorheological fluid having excellent characteristics and excellent stability over time of generated shear stress and current density can be obtained. Usually, the water present in the above-mentioned dielectric particles contains free water existing inside or between the particles without interacting with the dissociating group in the dielectric particles. When this free water is present, when the dispersed phase particles are dispersed in the electrically insulating dispersion medium, the dispersed phase particles aggregate, and only an electrorheological fluid having poor dispersion stability is obtained, and an electric field is applied. In this case, there arises a problem that a large current flows or a withstand voltage characteristic is deteriorated.

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

In the present invention, in obtaining dielectric particles (A) containing water having a water content lower than the equilibrium water content in the air used as dispersed phase particles, the dielectric particles are used 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 distillation is preferably in the range of 0.1 to 2%.

By immersing in a hydrophilic organic solvent and then distilling off the hydrophilic organic solvent, free water present in the dielectric particles is replaced by the hydrophilic organic solvent. Can be suppressed. As a result, the obtained dielectric particles (A) can be easily disintegrated by a pulverizer having a relatively simple mechanism since they have only a point junction or a slight surface junction at their interface. The crushed dielectric particles (A) can be easily dispersed in the electrically insulating dispersion medium.

Dielectric particles (A) obtained in the present invention
If the moisture content is less than the equilibrium moisture content in the atmosphere, preferably within the range of the above-mentioned optimum moisture content, a moisture absorbing operation may be performed if necessary, and the dielectric particles (A) after the moisture absorption can be easily dispersed in the electrically insulating state. It can be dispersed in a medium.

In the case where water is removed by direct drying or the like without performing the immersion treatment in the hydrophilic organic solvent according to the present invention, aggregation and fusion of dielectric particles occur. As a result, since the obtained dielectric particles are strongly surface-bonded at the interface, when crushing using a pulverizer, very large energy is required. Since the dielectric particles obtained by crushing in this way do not maintain a spherical shape and also contain agglomerates, the obtained electrorheological fluid has a large current density flowing when an electric field is applied. In addition, there are problems that the dispersion stability is poor and the withstand voltage is poor. 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. For example, alcohols such as methanol, ethanol, propanol and isopropanol; ethers such as tetrahydrofuran; acetone, methyl ethyl ketone and the like And the like, and one or more of these can be used.

The method for distilling off the water content from the dielectric particles together with the hydrophilic organic solvent is not particularly limited. For example, a known method such as a hot air drying method, a vacuum drying method, a radiation drying method, or a conduction drying method may be used. it can. The equipment that can be used at this time is not particularly limited, and a known dryer can be used.

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

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

The shape of the dispersed phase particles used in the present invention is preferably spherical. In the case where the shape of the dispersed phase particles is a shape other than a spherical shape, a problem that a large shear stress cannot be obtained when an electric field is applied to the prepared electrorheological fluid composition or in a state where the electric field is continuously applied. There may be a problem that stability with time is 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 size of the dispersed phase decreases, When the average particle size is less than 1 μm,
When an electric field is applied to the prepared electrorheological fluid composition, a problem that a large shear stress cannot be obtained may occur. Further, when the average particle diameter 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 it is difficult to stabilize. A point may occur.

The obtained dispersed phase particles comprising the dielectric particles (A) are dispersed in an electrically insulating dispersion medium to produce the electrorheological fluid composition of the present invention. The ratio between the dispersed phase particles and the electrically insulating dispersion medium in the electrorheological fluid composition of the present invention,
It is preferable that the amount be in the range of 50 to 500 parts by weight with respect to 100 parts by weight of the former. 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. When the amount of the dispersion medium is less than 50 parts by weight,
The fluidity of the prepared composition itself may be reduced, making it 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. For example, silicone oils such as polydimethylsiloxane and polyphenylmethylsiloxane; liquid paraffin, decane, dodecane, methylnaphthalene, dimethylnaphthalene , Ethylnaphthalene, biphenyl, decalin, partially hydrogenated hydrocarbons such as 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, and bromododecane; halogenated diphenylether compounds such as chlorodiphenylether, dichlorodiphenylether, trichlorodiphenylether, and bromodiphenylether; And demnum (manufactured by Daikin Industries, Ltd.); ester compounds such as dioctyl phthalate, trioctyl trimellitate, and dibutyl sebacate; and the like. The above can be used.

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

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

[0026]

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.

[0027]

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

[0028]

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 charged with Kuraray Povar PVA-205 (trade name).
Add 16.0 g of Kuraray's polyvinyl alcohol)
After dissolution, a mixture comprising 280 g of ethyl acrylate, 20 g of industrial divinylbenzene (a mixture of 55 wt% of divinylbenzene, 35 wt% of ethylstyrene, etc., manufactured by Wako Pure Chemical Industries, Ltd.) and 10 g of benzoyl peroxide Was added. Thereafter, the contents in the flask were dispersed at a stirring speed of 5000 rpm, and polymerized at 75 ° C. for 1 hour. Further, the polymerization temperature was raised to 95 ° C., and the mixture was heated for 4 hours. The obtained solid was separated by filtration, sufficiently washed with water, and dried at 80 ° C. for 12 hours using a hot air drier to obtain 286 g of a spherical polymer crosslinked product (1).

In a 2 liter four-neck 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 in which 60 g of sodium hydroxide was dissolved, and a uniform dispersion was obtained. And The reaction mixture was refluxed and heated and stirred for 6 hours to carry out a hydrolysis reaction. Thereafter, the reaction mixture was poured into water at 0 ° C., filtered, and washed with water. Then, using a vacuum dryer, 8
After drying at 0 ° 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 using a particle size distribution analyzer (manufactured by Shimadzu Corporation).
SALD-1000) was 5 μm
Met. When the ion exchange capacity in the sodium polyacrylate particles was quantified 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.

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 determined to be 19%.

[0032]

Reference Example 3 MCI gel CK08C, a strong acid type cation exchange resin (manufactured by Mitsubishi Kasei Corporation, particle size 18 μm, Na
(Type) 50 g 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 determined to be 25%.

[0033]

Reference Example 4 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 charged with Kuraray Povar PVA-205 (manufactured by K.K.
Add 16.0 g of Kuraray's polyvinyl alcohol)
After dissolution, 260 g of styrene and industrial divinylbenzene (a mixture of 55 wt% divinylbenzene, 35 wt% ethylstyrene, etc., manufactured by Wako Pure Chemical Industries, Ltd.) 4
A mixture consisting of 0 g and 10 g of benzoyl peroxide was added. Thereafter, the contents in the flask were dispersed at a stirring speed of 8000 rpm, and polymerized at 75 ° C. for 1 hour. Further, the polymerization temperature was raised to 95 ° C., and the mixture was heated for 4 hours. The obtained solid was separated by filtration, sufficiently washed with water, and then dried at 80 ° C. for 12 hours using a hot air drier to obtain a spherical polymerized crosslinked product (2) 2
86 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 (2), and 500 g of 98% by weight concentrated sulfuric acid was added to obtain a uniform dispersion. 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. Thereafter, the reaction mixture was poured into water at 0 ° C., filtered, and washed with water / acetone. The obtained solid was neutralized with 330 ml of a 10% by weight aqueous sodium hydroxide solution, and then sufficiently washed with water. Next, it dried at 80 degreeC for 10 hours using the vacuum dryer, and obtained 120 g of spherical sulfonated polymer particles.

The average particle size of the obtained sulfonated polymer particles was measured by a particle size distribution analyzer (SALD, manufactured by Shimadzu Corporation).
-1000) was 5 μm. The number of sulfonic acid groups in the sulfonated polymer particles was determined by neutralization titration and elemental analysis. Was 156 for 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 found to be 39%.

[0037]

[Reference Example 5] 30 g of toluene, methoxypolyethylene glycol methacrylate (N, manufactured by Shin-Nakamura Chemical Co., Ltd.)
5 g of K ester M-230G, the number of units of ethylene glycol was 23), 5 g of p-methoxystyrene 13 and 12 g of lauryl methacrylate, and 0.1 g of azobisisobutyronitrile as an initiator were added, followed by stirring at room temperature for 30 minutes. Thereafter, the mixture was heated and stirred at 65 ° C. for 24 hours, and further 90
Polymerization was carried out by heating at 2 ° C. for 2 hours. A toluene solution of the obtained polymer (hereinafter referred to as polymer solution (1)
That. )) Was 51% by weight.
Met.

[0038]

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

5 g of the obtained dispersed phase particles (1) were mixed with 0.2 g of a modified silicone oil KF869 (amino silicone oil manufactured by Shin-Etsu Chemical Co., Ltd.) and 0.2 g of Shin-Etsu Silicone Oil KF96-20CS (manufactured by Shin-Etsu Chemical Co., Ltd.) Dimethyl silicone oil), and uniformly mixed and dispersed with a biomixer BM-1 type (manufactured by Nippon Seiki Seisakusho) in a dispersion medium obtained by adding the mixture to 12 g of an electrorheological fluid composition of the present invention. This is hereinafter referred to as a fluid (1). I got｝.

[0040]

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

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

[0042]

Example 3 50 g of the polymerized crosslinked product (1) obtained in Reference Example 2 was placed in a 2-liter four-neck separable flask equipped with a stirrer, a thermometer and a dropping funnel.
g was dissolved in 1 liter of dissolved ethanol to obtain a uniform dispersion. The reaction mixture was refluxed and heated and stirred for 6 hours,
A hydrolysis reaction was performed. Thereafter, 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 diameter of the obtained sodium polyacrylate particles was measured using a particle size distribution analyzer (manufactured by Shimadzu Corporation).
SALD-1000) was 5 μm
Met. When the ion exchange capacity in the sodium polyacrylate particles was quantified 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.

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 absorbed in a thermo-hygrostat to make the water content 7% to prepare dispersed phase particles (3).

5 g of the obtained dispersed phase particles (3) was added to 0.5 g of the polymer solution (1) obtained in Reference Example 5, and
00 (partially hydrogenated triphenyl manufactured by Nippon Steel Chemical Co., Ltd.) and uniformly mixed and dispersed in a dispersion medium obtained using a Biomixer Model BM-1. 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 reduced to 15 using a vacuum dryer.
Isopropyl alcohol and water were removed at 0 ° C. for 3 hours. After completion of the water removal, the water content was 0.5%. The particles are absorbed in a thermo-hygrostat to give a water content of 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 mixed with THERM S900 (partially hydrogenated trihydrogenated product manufactured by Nippon Steel Chemical Co., Ltd.). Phenyl) and uniformly mixed and dispersed in a dispersion medium obtained by adding 12 g using a Biomixer Model BM-1.
The electrorheological fluid composition of the present invention (hereinafter referred to as fluid (4))
That. I got｝.

[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 filtered. The obtained solid content was subjected to removal of methanol and water at 150 ° C. for 3 hours using a vacuum dryer. After the completion of the water removal, the water content was 1.5%. The particles were absorbed in a thermo-hygrostat to a water content of 2.0% to prepare dispersed phase particles (5).

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

[0050]

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

5 g of the obtained dispersed phase particles (6) and 0.5 g of the polymer solution (1) obtained in Reference Example 5 were added to THERM S9.
00 (partially hydrogenated triphenyl manufactured by Nippon Steel Chemical Co., Ltd.) and uniformly mixed and dispersed in a dispersion medium obtained using a Biomixer Model BM-1. Electrorheological fluid composition (hereinafter referred to as fluid (6)). I got｝.

[0052]

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

5 g of the obtained comparative dispersed phase particles (1) and 0.2 g of modified silicone oil KF869 (amino silicone oil manufactured by Shin-Etsu Chemical Co., Ltd.) were mixed with Shin-Etsu Silicone Oil KF96-20CS (Shin-Etsu Chemical Co., Ltd.) (Dimethylsilicone oil manufactured by Nissan Co., Ltd.) and uniformly mixed and dispersed using a Biomixer Model BM-1 to obtain an electrorheological fluid composition for comparison (hereinafter referred to as Comparative Fluid (1)). ｝
I got

[0054]

Comparative Example 2 10 g of sodium polyacrylate particles having an equilibrium water content of 19% obtained in Reference Example 2 were directly used at 150 ° C.
For 3 hours under vacuum. Moisture content after drying is 0.2
%Met. The particles were absorbed in a thermo-hygrostat to 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 with THERM S900 (Nippon Steel Chemical Co., Ltd.). Triphenyl), and uniformly mixed and dispersed using a biomixer BM-1 type in a dispersion medium obtained by adding to 12 g of triphenyl). An electrorheological fluid composition for comparison (hereinafter referred to as comparative fluid (2)) . I got｝.

[0056]

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

5 g of the comparative dispersed phase particles (3) obtained and 0.5 g of the polymer solution (1) obtained in Reference Example 5 were partially hydrogenated with THERM S900 (Nippon Steel Chemical Co., Ltd.). Triphenyl) and uniformly mixed and dispersed using a biomixer BM-1 type in a dispersion medium obtained by adding to 12 g of an electrorheological fluid composition for comparison (hereinafter referred to as comparative fluid (3)). . I got｝.

[0058]

Comparative Example 4 10 g of the sulfonated polymer particles having an equilibrium water content of 39% obtained in Reference Example 4 were vacuum dried at 150 ° C. for 3 hours. After the drying was completed, the water content was 1.5%. The particles are absorbed in a thermo-hygrostat to give a water content of 2.0%.
Thus, 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 with THERM S900 (Nippon Steel Chemical Co., Ltd.). Triphenyl) and uniformly mixed and dispersed in a dispersion medium obtained using a Biomixer Model BM-1 to obtain an electrorheological fluid composition for comparison (hereinafter referred to as Comparative Fluid (4)). . I got｝.

[0060]

Example 5 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 was 150 mm in height. The test tube having a diameter of 15 mm was filled up to 100 mm from the bottom and sealed.
Thereafter, the dispersion was allowed to stand for three days, the degree of sedimentation of the dispersed phase particles was observed, and the dispersion stability of the electrorheological fluid was examined. Table 1 shows the results.

Each of the electrorheological fluid compositions was placed in a double-cylinder rotary viscometer with a coaxial electric field, and an inner / outer cylinder gap of 1.0
Measure the shear stress value (initial value) and the current density (initial value) when an AC external electric field of 4 kV / mm (frequency: 50 Hz) is applied under the conditions of mm, shear rate 400 s- ¹ and temperature 25 ° C. did. 4 kV / 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, and the temporal stability of the electrorheological fluid was examined. Table 1 shows the results. Also,
Inner / outer cylinder gap 1.0mm, shear rate 400s ~ ¹ , temperature 2
AC external electric field 0 to 10 kV / mm (frequency:
(50 Hz). Table 1 shows the maximum applied voltage that can maintain the application 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 maximum applied voltage of the electrorheological fluids (1) to (6) of the present invention was high. 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]

According to the present invention, even when a relatively weak electric field is applied, a large shear stress can be obtained and the generated shear stress can be maintained for a long period of time. The present invention provides a method for easily producing an electrorheological fluid, and the thus produced electrorheological fluid can be effectively used for clutches, dampers, brakes, shock absorbers and the like.

──────────────────────────────────────────────────続 き Continuing on the front page (51) Int.Cl. ⁷ Identification code FI C10N 40:14 70:00 (72) Inventor Minoru Minato 1-25-12 Kannondai, Tsukuba, Ibaraki Pref. (56) References JP-A-4-164996 (JP, A) JP-A-4-266996 (JP, A) JP-A-4-164997 (JP, A) JP-A-2-235994 (JP, A) ( 58) Field surveyed (Int.Cl. ⁷ , DB name) C10M 177/00 B01J 13/00 F16D 35/00 C10N 20:00 C10N 20:06 C10N 40:14 C10N 70:00

Claims (2)

(57) [Claims] 1. A composition comprising dispersed particles of dielectric particles (A) containing water having an equilibrium water content less than the equilibrium moisture content in the air in an electrically insulating dispersion medium. A) A method for producing an electrorheological fluid composition, wherein A) is obtained by immersing dielectric particles in a hydrophilic organic solvent and then removing water contained in the dielectric particles together with distilling off the hydrophilic organic solvent. 2. The process for producing an 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.