JP3130642B2 - Manufacturing method of electrorheological fluid - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a novel method for producing an electrorheological fluid.

[0002]

2. Description of the Related Art An electrorheological fluid is a suspension in which a dispersed phase composed of hydrophilic solid particles is dispersed in an electrically insulating dispersion medium, and is reversibly reversible under the action of an electric field. This fluid can change the viscosity. This fluid is placed between the surfaces of two conductive members, and a voltage is applied to the fluid to cause the fluid to reversibly increase in viscosity. It is capable of transmitting torque between the surfaces. Such an electrorheological fluid is used, for example, for an engine mount, a clutch, a brake, and the like of an automobile.

As the electrorheological fluid, those composed of various dispersed phases have been conventionally proposed. For example, a fluid in which polyhydric alcohol particles are dispersed (JP-A-51-33783) or solid fine particles of an acrylate or methacrylate polymer are used. Dispersed fluids (JP-B-63-26151) and the like are known.

When an electrorheological fluid is obtained by using these particles, the particles are first synthesized by a reversed-phase suspension polymerization method or a reverse emulsion polymerization method, and then the particles are washed to remove excess surfactant, and then the particles are synthesized. In order to remove the dispersion medium used in the synthesis (hereinafter referred to as “desolvation”) or to adjust the water content when water is used as an additive to the synthetic particles, the synthetic particles are dried by heating under reduced pressure. If necessary, a high-permittivity liquid such as glycerin or a high-permittivity solid such as pentaerythritol is added and adsorbed, and a predetermined amount of the particles is dispersed in a dispersion medium.

[0005]

At this time, the particles tend to agglomerate because they pass through a drying step. Therefore, in order to disperse the particles in the dispersion medium to the particle diameter at the time of synthesis, a dispersion for assisting dispersion is required. Some dispersing means was required to promote dispersion by adding a stabilizer or mixing beads or the like.

However, when such a dispersing means is used, the expression of the electrorheological effect may be reduced due to deformation, pulverization or a change in the functional group which is considered to contribute to the electrorheological effect. Has been a problem.

[0007]

SUMMARY OF THE INVENTION The present invention is an improvement of the conventional method for producing an electrorheological fluid using such solid fine particles, which is used during particle synthesis to cause aggregation of synthetic particles. Removing the dispersion medium, that is, the “desolvation” step,
It is an object of the present invention to establish a production method in which the composition of the reagent necessary for the preparation does not need to be changed in the process from the particle synthesis to the preparation of the electrorheological fluid.

According to the researches and experiments conducted by the present inventors, the purpose is to use the same electrically insulating dispersion medium as used in the electrorheological fluid during the particle polymerization, and disperse and polymerize the monomer in the dispersion medium. It has been found that this can be achieved by adjusting the amount of water in the particles through a method and a step of drying the particles alone or the particles added with an azeotropic solvent after particle synthesis under reduced pressure or under reduced pressure and heat.

Thus, the present invention provides a method for producing an electrorheological fluid, which comprises using an electrically insulating dispersion medium used for an electrorheological fluid at the time of particle polymerization, dispersing a monomer therein, and polymerizing the same. Another object of the present invention is to provide a method for producing an electrorheological fluid, which comprises adjusting the amount of water in particles through a step of drying under reduced pressure or under reduced pressure heating a single particle dispersion or an azeotropic solvent-added particle dispersion.

Accordingly, the first method for producing an electrorheological fluid according to the present invention is a method for producing an electrorheological fluid in which hydrophilic solid particles are dispersed in an electrically insulating dispersion medium. Is synthesized by reverse-phase suspension polymerization or inverse emulsion polymerization of a raw material monomer component constituting the hydrophilic solid particles in an electrically insulating hydrophobic liquid, and the electrically insulating hydrophobic liquid is subjected to electrolysis. Characterized in that it is used as a dispersion medium for a viscous fluid.

In a second method for producing an electrorheological fluid according to the present invention, in the above-mentioned method for producing an electrorheological fluid, the produced electrorheological fluid is kept under reduced pressure or azeotropes with water. It is characterized by adjusting the water content of the hydrophilic solid particles by adding a solvent and keeping under reduced pressure.

Further, a third method for producing an electrorheological fluid according to the present invention is the method for producing an electrorheological fluid according to the first aspect, wherein
Holding the manufactured electrorheological fluid under reduced pressure heating, or by adding a solvent azeotropic with water and maintaining it under reduced pressure heating, to adjust the water content of the hydrophilic solid particles, Is what you do.

DETAILED DESCRIPTION OF THE INVENTION As described above, the present invention uses an electric insulating dispersion medium used for an electrorheological fluid for particle polymerization, and disperses and polymerizes a monomer in the dispersion medium. The present invention relates to a method for producing a viscous fluid and a method for producing an electrorheological fluid comprising adjusting the amount of water in particles through a step of drying the dispersion of particles alone or a particle dispersion containing an azeotropic solvent after the synthesis of particles under reduced pressure or reduced pressure. Things.

In the present invention, the electrically insulating hydrophobic liquid used at the time of synthesizing the hydrophilic solid particles is also used as a dispersion medium of the electrorheological fluid. Therefore,
It is necessary to be able to be used as a dispersion medium for synthesizing hydrophilic solid particles by reverse phase suspension polymerization or inverse emulsion polymerization method and to be a preferable dispersion medium for hydrophilic solid particles of an electrorheological fluid. . Preferred as such an electrically insulating hydrophobic liquid are silicone oil, vegetable oil, fluorine oil, diphenyl chloride, mineral oil,
And dibutyltoluene sebacate.

The raw material monomer component constituting the hydrophilic solid particles of the electrorheological fluid is not particularly limited as long as it does not contradict the object of the present invention, but is preferably acrylic acid, methacrylic acid or a metal salt thereof, such as an alkali metal. Salts, especially sodium salts, can be used.

When such a starting monomer component is subjected to reverse phase suspension polymerization or reverse emulsion polymerization, a surfactant, N,
It is common to use a bifunctional or polyfunctional reagent such as N-methylenebisacrylamide as a crosslinking agent, and thus, in the present invention, such a surfactant or a crosslinking agent can be used. . In the present invention, such an auxiliary component which advantageously works for the purpose of the present invention can be used.

In producing an electrorheological fluid from such components, a dispersion stabilizer such as a surfactant is dissolved in an electrically insulating hydrophobic fluid, and then monomers are dropped and dispersed to carry out polymerization.

The electrorheological fluid according to the present invention has a hydrophilic solid particle size of about 0.01 μm to 1000 μm, preferably 0.1 μm to 20 μm, and has a dispersed phase (ie,
The amount of the hydrophilic solid particles is about 1 to 200 parts, preferably 10 to 100 parts, per 100 parts of the dispersion medium (that is, the electrically insulating hydrophobic liquid). Therefore, when performing reverse phase suspension polymerization or inverse emulsion polymerization, the amount of the dispersion medium and the monomer, and the polymerization conditions are set so that the desired electrorheological fluid is obtained within such a preferable range. Is preferred. If the amount of the dispersion medium of the produced electrorheological fluid is not within such a preferable range,
A preferred electrorheological fluid can be obtained by adding or removing the dispersion medium later.

In general, it is considered that the behavior of an electrorheological fluid as in the present invention is sensitive to the amount of water adsorbed on hydrophilic solid particles. The specific water content varies depending on the specific use of the electrorheological fluid, required performance, and the like, but is generally about 0.01 to 10%, preferably 0.1 to 5%.

The electrorheological fluid obtained by the above method is maintained under reduced pressure, or by adding a solvent azeotropic with water and maintaining it under reduced pressure, or by heating under reduced pressure, or azeotropic with water. The water content of the hydrophilic solid particles can be adjusted by adding a solvent to be added and maintaining the mixture under heating under reduced pressure. The present invention relates to a method for producing an electrorheological fluid in which the water content of the hydrophilic solid particles is adjusted as described above (second invention and third invention).

In the above, under reduced pressure means about 0 to 300 Torr,
Preferably, it refers to a pressure of 0 to 10 Torr, and “under heating” means room temperature to about 150 ° C., preferably 60 to 120 ° C.
Temperature conditions. Examples of the solvent that azeotropes with water include toluene, xylene, and cyclohexane. In the present invention, toluene is particularly preferable.

Specifically, the pressure, temperature, or holding time may be appropriately determined according to the degree of water content of the hydrophilic solid particles whose water content is to be adjusted and the desired performance of the electrorheological fluid.

[0023]

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.

Example 1 Silicon oil (manufactured by Shin-Etsu Silicone Co., Ltd.) was placed in a polymerization tank of a polymerization apparatus having a capacity of 500 cm ^3.
KF96L 5CS) was placed 400cm ^3. Next, 5 g of surfactant decaglycerin pentaoleate (manufactured by Nikko Chemicals Co., Ltd .: Decaglyn-50) was placed in the polymerization tank and dissolved in silicone oil. In order to remove dissolved oxygen, nitrogen was introduced for 1 hour or more.

On the other hand, acrylic acid (Wako Pure Chemical Industries, Ltd.)
Sodium hydroxide (Wako Pure Chemical Industries, Ltd.)
65.6 g of a 25.4% aqueous solution of the same was added while cooling with ice to neutralize acrylic acid, thereby preparing an aqueous solution of sodium acrylate. After returning this aqueous solution to room temperature, N, N-methylenebisacrylamide (manufactured by Wako Pure Chemical Industries, Ltd.)
03 g was dissolved. Nitrogen was introduced for one hour to remove dissolved oxygen.

The above-mentioned aqueous solution of sodium acrylate was dropped into the silicone oil while stirring the silicon oil in the polymerization tank at 200 rpm using a stirring blade to form droplets. A solution prepared by dissolving 0.3 g of azobis-2-butyronitrile (Wako Pure Chemical Industries, Ltd .: V-59) as a polymerization initiator in 2 cm ³ of toluene was further added dropwise. The polymerization apparatus was heated and polymerization was performed at 70 ° C. for 3 hours. as a result,
An electrorheological fluid consisting of a silicone oil dispersion in which 20-1000 micron sodium polyacrylate particles were dispersed was obtained.

[0027]

According to the present invention, the dispersion medium used in synthesizing the solid particles is used as the dispersion medium for the electrorheological fluid.
This eliminates the need to change the dispersion medium during the production of the electrorheological fluid, and eliminates the step of removing the dispersion medium used during the particle synthesis, that is, the step of drying the particles. Therefore, it is possible to more efficiently and economically produce the electrorheological fluid, and there is no problem that the particles aggregate when the particles are dried.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification code FI C08F 2/32 C08F 2/32 (C10M 169/04 107: 50 145: 14) C10N 10:02 20:06 30:04 40: 14 70:00 (56) References JP-A-3-88804 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C10M 145/02-145/16 C10N 40:14 WPI ( DIALOG)

Claims (3)

(57) [Claims] 1. A method for producing an electrorheological fluid in which hydrophilic solid particles are dispersed in an electrically insulating dispersion medium, wherein the synthesis of the hydrophilic solid particles is performed by using a raw material constituting the hydrophilic solid particles.
The monomer component is subjected to reverse phase suspension polymerization or inverse emulsion polymerization in an electrically insulating hydrophobic liquid , and the electrically insulating hydrophobic liquid is used as a dispersion medium for an electrorheological fluid, Manufacturing method of electrorheological fluid. 2. A method for producing electrorheological fluid according to claim 1, for holding the produced electrorheological fluid in vacuo
Or, by adding a solvent azeotropic with water by maintaining under reduced pressure, and adjusting the water content of the hydrophilic solid particles, the electrorheological fluid preparation. 3. The method for producing an electrorheological fluid according to claim 1 , wherein the produced electrorheological fluid is kept under reduced pressure and heated .
Luke, or by adding a solvent azeotropic with water by holding under vacuum heating, and adjusting the water content of the hydrophilic solid particles, the electrorheological fluid preparation. "