JP2933674B2 - Electrorheological fluid - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a liquid that shows solidification or an increase in viscosity when an electric field is applied, and more particularly to particles and an electric insulating material that suspends or disperses the particles. The present invention relates to an electrorheological fluid having a Winslow effect composed of a liquid.

(Prior art)

When an electric field is externally applied to a liquid in which specific solid particles are dispersed or suspended in a specific electrically insulating liquid, a phenomenon is observed in which the viscosity of the liquid significantly increases or solidifies. Also known as the Winslow effect. Fluids exhibiting such characteristics are proposed to be applied to clutches, dampers, hydraulic control devices, vibrating elements, and the like.Additionally, by adding a coloring agent, the fluid can be used as a printer ink for forming an image. Applications have also been proposed.

USP2 is a fluid (electrorheological fluid) that exhibits this phenomenon.
No. 417850 discloses a fluid in which a hydrophilic powder such as starch, flour, gypsum, carbon, and lime is suspended in an insulating oil such as mineral oil, olive oil, and trans oil. Even when an electric field is applied to such a fluid, the obtained shear stress is small and cannot be put to practical use. Tokiko Sho 52-
Japanese Patent No. 30273 discloses an electrorheological fluid using an ion exchange resin as particles. Although a large shear stress can be obtained by using a specific ion exchange resin, the current density flowing when an electric field is applied is too high, and a high voltage that can provide a sufficient shear stress is obtained due to restrictions on the power supply device. There are drawbacks that it is practically impossible to apply the voltage and that a large high-voltage power supply must be used.

J. Appl. Phys. 38, (1) 67 (1967) is an example of using a surfactant in an electrorheological fluid exhibiting the Winslow effect.
Discloses a system in which a surfactant is added to a system using silica gel as particles, but there is no mention of the purpose of adding the surfactant, the structure of the surfactant, and the amount of addition. No description can be found for the water content of silica gel, but J. Appl. Phys. 20, 1137, (1949)
Conventionally, it has been considered that particles such as silica gel preferably contain a certain amount of water. In such an electrorheological fluid, the current flowing when an electric field is applied tends to be too large, similarly to the above-described electrorheological fluid. Further, when silica gel is used as the particles, there is a disadvantage that it is difficult to maintain the suspension stability of the particles.

[Problems to be solved by the invention]

An object of the present invention is to solve the above-mentioned problems and to obtain an electrorheological fluid having a large shear stress obtained when an electric field is applied and a small flowing current density.

[Means for solving the problem]

The present invention provides (A) particles containing a surfactant, but containing substantially no water and having a dissociable functional group having a particle size of 0.1 to 100 μm, in (B) an electrically insulating liquid. And an electrorheological fluid characterized by being dispersed or suspended.

 Hereinafter, the present invention will be described in more detail.

Particles having a dissociative functional group in the present invention, -COOM in the _{molecule, -SO 3 M, -OM, -SM} , - (R 1, R 2, R 3) NX, - (R
₁ , R ₂ , R ₃ ) PX (where M is hydrogen or an alkali metal such as sodium, potassium, lithium, ammonium, phosphoniums, and R ₁ , R ₂ , and R ₃ are each hydrogen or a substituent And X represents an element or a functional group that can be an anion such as halogen.). Representative examples of these particles include ion-exchange resins obtained by copolymerizing styrene and divinylbenzene and introducing the above functional groups, and copolymers of acrylic acid and N, N-methylenebisacrylamide. Acrylic acid-containing polymer, carboxymethylcellulose, those obtained by introducing the above-mentioned dissociative functional group into cellulose such as cellulose particles dyed with a reactive dye, a copolymer of acrylamide and ethylene glycol dimethacrylate, etc. Acrylamide copolymer, acid dyes, direct dyes, and basic dyes. These particles do not necessarily need to be composed entirely of a compound having a dissociative functional group as described above, for example, particles composed of polyethylene, a compound obtained by copolymerizing styrene and divinylbenzene, and the like. Particles in which the above compound having a dissociative functional group is coated in the vicinity of the surface can also be preferably used.

The particles used in the present invention are particles containing almost no water. More specifically, particles having a water content of 5% by weight or less, more preferably 1% by weight or less, are used. Particles from which water has been removed synthesize the above particles,
After purification, it can be obtained by a method such as heat drying, vacuum drying, leaving in a dry air stream, or freeze vacuum drying. An electrorheological fluid having a large shear stress can be obtained by adding moisture to the particles as described above, but the use of such particles increases the current density.

The particle size of the particles used in the present invention is preferably 0.1 to 100 μm, and if the particle size is 0.1 μm or less or 100 μm or more, a sufficient increase in viscosity due to an electric field cannot be obtained.

As the surfactant used in the present invention, any of anionic, cationic and nonionic surfactants may be used, but the nonionic surfactant is most preferable in order to reduce the current flowing when an electric field is applied. Activator. In order to obtain a sufficiently large shear stress, it is preferable to use a liquid material at normal temperature.

As a specific example of the surfactant used in the present invention,
Polyoxyethylene alkyl ethers, polyoxyethylene alkyl phenyl ethers, polyoxyethylene alkyl esters, polyoxyethylene alkyl sorbitan esters, polyoxyethylene alkyl amines, glycerin fatty acid esters, decaglycerin fatty acid esters, polyglycerin Fatty acid esters, sorbitan aliphatic esters, propylene glycol fatty acid esters, polyoxyethylene glycol fatty acid esters, polyoxyethylene polyoxypropylene alkyl ethers, polyoxyethylene polyoxypropylene block polymers, perfluoroalkyl phosphate esters And perfluoroalkyl betainic acid. Among these nonionic surfactants, it is particularly preferable to use a compound having an ethylene oxide group (polyoxyethylene group) in order to obtain a larger shear stress. In order to obtain a preferable shear stress, depending on the type of particles and surfactant, the length of the ethylene oxide group,
A compound having an appropriate length of the alkyl group is selected.

Next, as the electrically insulating liquid used in the present invention,
Conventionally, a liquid that has been used as an electrorheological fluid exhibiting the Winslow effect is used as it is. Examples of such liquids include dioctyl phthalate, didecyl phthalate, dibutyl phthalate, diethyl phthalate, dinonyl phthalate, diisononyl phthalate, di-2-ethylhexyl phthalate, ditridecyl phthalate, butyl benzyl phthalate, Aromatic carboxylic esters such as trioctyl melitate and tridecyl trimellitate, butyl sebacate, butyl oleate, butyl stearate, dibutyl adipate, butylphthalyl ethylene glycolate,
Methylphthalyl ethylene glycolate, methylphthalyl butyl glycolate, monoacetin, diacetin, triacetin, aliphatic carboxylic acid esters such as vegetable oils,
Silicone oils such as modified or unmodified polymethylsiloxane, dodecane, 2,2,3-trimethylpentane, hexadecane, ligroin, aliphatic hydrocarbons such as refined kerosene, alkylnaphthalene, triphenyl hydride, Alkyl-substituted aromatic hydrocarbons such as diphenylmethane, monoethyldiphenyl, triethyldiphenyl, diethyldiphenyl, diphenyl, terphenyl, 1,4-diphenylbenzene, phenylxylylethane, toluene, xylene, alkyl-substituted biphenyls, trichloroethylene And halogen-substituted aliphatic and aromatic hydrocarbons such as tetrachloroethylene and bromonaphthalene, ethers such as anisole, phenetole, methoxytoluene, diphenylether and veralol, and phosphazenes.

The essential components of the present invention are the particles (A) and the electrically insulating liquid (B) satisfying the above requirements (A), (B) and (C). Each of these components may be formed of a single compound, but a mixture of several compounds may be used depending on the purpose. Various additives can be added according to the purpose. For example, a gelling agent can be added to adjust the viscosity of the fluid, and an antioxidant can be added to increase the stability of the fluid. When the electrorheological fluid according to the present invention is used as an ink for image recording, a coloring agent such as a dye may be added.

Although the mechanism of the electrorheological effect has not been completely elucidated yet, the use of particles having dissociable functional groups causes the dissociated ions to move within the particles when an electric field is applied, and the electrostatic force acts between the particles. It is presumed that the electrorheological effect is exhibited in the case. It is also presumed that the surfactant in the particles promotes the dissociation of these dissociating groups and, at the same time, does not have a high electrical conductivity like water, so that the current density becomes small.

〔Example〕

Examples and comparative examples are shown below. Parts here are by weight.

Example 1 (Synthesis of particles) Styrene 94.8 parts Divinylbenzene 3.5 parts Alkylbenzene sulfonic acid 1.5 parts Potassium persulfate 0.2 part was added to 300 parts of pure water, stirred, and further heated while continuing stirring to form crosslinked styrene. A copolymer was obtained.
The crosslinked copolymer was reacted with paraformaldehyde and hydrogen chloride to form chloromethylated polystyrene, and then reacted with dimethylamine to obtain copolymer particles having a tertiary amino group. After washing the copolymer with dilute hydrochloric acid, it was further washed with pure water, and the suspension was dried by a spray-dry method. The obtained powder was vacuum-dried at 50 ° C. for 30 hours to obtain a copolymer containing a dissociable amino group having a counter ion as a chloride ion and containing substantially no water. The average particle size of the particles measured by a Coulter counter was 2.6 μm.

(Preparation) The obtained particles were prepared according to the following formulation, and agitated and excited by an ultrasonic cleaner to obtain an electrically responsive fluid.

Particles 25.0 parts Polyoxyethylene nonyl phenyl ether 1.5 parts (Ethylene oxide group 7) Tetrachloroethylene 53.0 parts Refined kerosene 20.5 parts This fluid is placed in a coaxial double cylindrical viscometer, and a DC voltage is applied between the inner and outer cylinders to the outer side. Rotational force was applied to the electrodes to measure the torque when slippage occurred between the inner and outer electrodes, and the shear stress was calculated from the torque and the effective electrode area. As a result, at an electric field strength of 5 KV / mm, the shear stress was 48 gf / cm ² and the current density was 3.8 × 10 ⁻⁸ A / cm ² .

In order to measure the sedimentation of the fluid, the fluid was placed in a glass test tube with a stopper and allowed to stand at room temperature for three months, but no sedimentation of particles was observed.

Comparative Example 1 (Use of Water-Containing Particles) In the fluid formulation of Example 1, instead of using a surfactant, 1.5 parts of water-adsorbed particles were used.
The test was performed in the same manner as in Example 1. Results in electric field strength of 5 KV / mm, the shear stress is 46gf / cm ^2, current density is 1.
It was 2 × 10 ⁻⁴ A / cm ² .

Comparative Example 2 (Use of Particles Having No Dissociative Functional Group) In the fluid formulation of Example 1, a powder of crystalline cellulose vacuum-dried in the same manner as in Example 1 was used instead of the particles synthesized in Example 1. A fluid was obtained and tested in the same manner as in Example 1. Results in a field strength of 5 KV / mm, the shear stress is 5.7gf / cm ^2, current density was ^{2.9 × 10 -8 A / cm 2} , although the current density is small, obtained only significantly weaker shear stress Did not.

Example 2 A fluid having the following formulation was obtained in the same manner as in Example 1 using the particles synthesized in Example 1.

20 parts of particles synthesized in Example 1 Polyoxyethylene lauryl ether 1 part (8 ethylene oxide groups) Trioctyl trimellitate 65 parts Didecyl phthalate 14 parts A test was conducted in the same manner as in Example 1. As a result, at an electric field strength of 5 KV / mm, the shear stress was 39 gf / cm ² and the current density was 2.7 × 10 ⁻⁸ A / cm ² .

Example 3 (Synthesis of Particles) The crosslinked copolymer of polystyrene-divinylbenzene synthesized in Example 1 was sulfonated with fuming sulfuric acid, and washed with an aqueous solution of sodium hydroxide to remove sodium as a counter ion. A polymer containing a sulfone group was obtained. The polymer was vacuum-dried at 100 ° C. to obtain particles substantially free of moisture. When the average particle size of the particles was measured by a Coulter counter, it was 5.2 μm.

(Preparation) The obtained particles were prepared according to the following formulation, and agitated and excited by an ultrasonic cleaner to obtain an electrically responsive fluid.

Particles 20.0 parts Polyoxyethylene oleylamine 0.5 parts (number of ethylene oxide groups 10) Polyoxyethylene oleic acid amide 0.5 parts (number of ethylene oxide groups 5) Silicone oil (20 cSt) 77.0 parts A test was conducted in the same manner as in Example 1. As a result, at an electric field strength of 5 KV / mm, the shear stress was 35 gf / cm ² and the current density was 5.5 × 10 ⁻⁸ A / cm ² .

Comparative Example 3 (Use of Water-Containing Particles) In the fluid formulation of Example 3, particles in which the same amount of water as the surfactant was adsorbed were used instead of the surfactant.
The test was performed in the same manner as in Example 3. At an electric field strength of 5 KV / mm, dielectric breakdown occurs and an abnormal current flows,
Measurement of shear stress was not possible.

Comparative Example 4 (Use of particles having no dissociating functional group) In the fluid formulation of Example 3, a fluid was prepared by using silica gel powder that was vacuum-dried in the same manner as in Example 3 instead of the particles synthesized in Example 3. And a test was conducted in the same manner as in Example 1. The results show that at an electric field strength of 5 KV / mm, the shear stress is
8.4 gf / cm ² , the current density is 5.6 × 10 ^-8 A / cm ² ,
Although the current density was small, only a very weak shear stress was obtained.

Example 4 A fluid having the following formulation was obtained in the same manner as in Example 1 using the particles synthesized in Example 3.

Particles synthesized in Example 3 20.0 parts Polyoxyethylene glyceryl monooleate 0.6 parts (number of ethylene oxide groups 5) Polyoxyethyloleyl ether 0.5 parts (number of ethylene oxide groups 8) Diethyldiphenyl 32.0 parts Hydrogenated triphenyl 46.9 parts Example 1 The test was performed in the same manner as in the above. As a result, at an electric field strength of 5 KV / mm, the shear stress was 37 gf / cm ² and the current density was 6.8 × 10 ⁻⁸ A / cm ² .

Example 5 (Synthesis of Particles) Sodium methacrylate 100 parts N, N'-methylenebisacrylamide 4 parts Ammonium persulfate 0.2 part A solution of purified water was prepared (solution A). 1200 parts Hexane 100 parts 1 part of a solution of sorbitan monolaurate was prepared (solution B).

70 parts of solution A and 50 parts of solution B were mixed, stirred with a stirrer, and allowed to react for 8 hours while continuing to stir vigorously. After washing the obtained product with water and removing water with a centrifugal separator, it is dried in a flowing air stream at 120 ° C., and further dried in vacuum at 50 ° C., and sodium substantially free from water is used as counter ions. Thus, polymer particles having a carboxylic acid group were obtained. When the average particle size of the particles was measured by a Coulter counter, it was 15.3 μm.

(Preparation) The obtained particles were prepared according to the following formulation, and agitated and excited by an ultrasonic cleaner to obtain an electrically responsive fluid.

Particles 25.0 parts Polyoxyethylene nonylphenyl ether 2.0 parts (Ethylene oxide group number 7) Tetrachloroethylene 55.5 parts Purified kerosene 17.5 parts The test was carried out in the same manner as in Example 1. As a result, at an electric field strength of 5 KV / mm, the shear stress was 32 gf / cm ² and the current density was 1.5 × 10 ⁻⁸ A / cm ² .

In order to measure the sedimentation property of this fluid in the same manner as in Example 1, the fluid was placed in a glass test tube with a stopper, and left at room temperature for three months, but no sedimentation of particles was observed. Was.

〔The invention's effect〕

With the viscous fluid of the present invention, a large shear stress can be obtained, and the electric density can be significantly reduced.

Continuation of the front page (51) Int.Cl. ⁶ identification code FI // C10N 20:06 40:14 (58) Field surveyed (Int.Cl. ⁶ , DB name) C10M 161/00, 129/16 C10M 149 / 02,151 / 02,145 / 02 C10N 40:14

Claims (1)

(57) [Claims] (A) a particle having a dissociative functional group containing a surfactant but containing substantially no water and having a particle size of 0.1 to 100 μm, comprising: (B) an electrically insulating liquid; An electrorheological fluid characterized by being dispersed or suspended therein.