JPH0762370A - Electrorheological fluid - Google Patents

Abstract

(57) [Summary] [Purpose] Providing a non-hydrous electrorheological fluid. [Structure] An electrorheological fluid containing carbon-dispersed particles treated with iodine and an electrically insulating liquid, and a carbon-dispersed particle further treated with an electrically insulating film after being treated with iodine, and an electrically insulating liquid. An electrorheological fluid containing. [Effect] Despite being a non-hydrous system, it has a high electrorheological effect, and the current flow is small, so that a short circuit does not occur.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-hydrous electrorheological fluid whose viscosity can be controlled by applying an electric field.

[0002]

2. Description of the Related Art An electrorheological fluid is a suspension of inorganic or polymer particles dispersed in an electrically insulating liquid. By applying an electric field, the fluid rapidly and reversibly changes its viscosity from a liquid state to a plastic state or a solid state.
This phenomenon is called the Winslow effect.

Generally, dispersed particles are used whose surface is easily polarized by an electric field. For example, as the inorganic dispersed particles, US Pat. No. 3,047,507 and British Patent No. 10767 are used.
54 and JP-A-61-44998 describe silica, and JP-A-62-95397 describes zeolite. Further, as polymer particles, alginic acid, glucose having a carboxyl group and glucose having a sulfone group are disclosed in JP-A-53-93186.
Polyacrylic acid crosslinked with divinylbenzene is described in JP-A-58-179259, and a resol-type phenol resin is described. As the electrically insulating liquid, mineral oil, silicone oil, fluorine-based oil, halogenated aromatic oil and the like are known.

However, in any of the above techniques, it is necessary for water to be adsorbed on the surface of the dispersed particles in order to enhance the electrorheological effect, so that the system contains a small amount of water. The mechanism of increasing the viscosity of the electrorheological fluid by applying an electric field is explained by the electric double layer theory. An electric double layer is formed on the surface of dispersed particles of the electrorheological fluid, and when no electric field is applied, they do not repel each other on the surface and form a structure in which particles are lined up. However, when an electric field is applied, an electric bias is generated in the electric double layer of the dispersed particles, the particles are aligned by electrostatic attraction, and a bridge of particles is formed. For this reason,
The viscosity of the liquid increases and in some cases it may solidify. Water added to the system promotes the formation of an electric double layer.

The electrorheological fluid is expected to be applied to engine mounts, shock absorbers, clutches and the like.

However, the prior art requires the presence of water in order to obtain a sufficient electrorheological effect, which causes some problems. One of the problems is that the current easily flows as the voltage is increased, causing a short circuit. Also, for one thing, water solidifies at low temperatures below 0 ° C,
Since water evaporates at 100 ° C. or higher, the electrorheological effect decreases and the operating temperature range is limited. And, such a problem is a main factor that prevents the practical application of the electrorheological fluid.

A non-aqueous electrorheological liquid using carbon fine particles is also disclosed in JP-A-3-47896, but the carbon fine particles are only heat-treated and have a low electrorheological effect.

Furthermore, the present inventors have proposed an electrorheological fluid using carbonaceous particles that have been subjected to oxidation treatment as dispersed particles (Japanese Patent Application No. 3-358257). In this case, it has a relatively high electrorheological effect despite the non-hydrated system, but the electrorheological effect is still insufficient depending on the application.

[0009]

DISCLOSURE OF THE INVENTION The present invention provides a low temperature range of 0 ° C. or less, which has a high electrorheological effect, has a small current flow, and does not cause a short circuit even though it is a non-hydrous system. It is an object of the present invention to provide an electrorheological fluid whose performance does not deteriorate even in a high temperature range of 100 ° C or higher.

[0010]

As a result of intensive studies for solving the above problems, the present inventors have found that the problem can be solved by using carbonaceous dispersed particles treated with a specific compound as dispersed particles. The invention was completed.

That is, the present invention provides an electrorheological fluid containing carbonaceous dispersed particles treated with iodine and an electrically insulating liquid.

Further, the present invention, after being treated with iodine,
Further provided is an electrorheological fluid characterized by containing carbonaceous dispersed particles coated with an electrically insulating film and an electrically insulating liquid.

The carbonaceous dispersed particles used in the present invention are
Finely pulverized petroleum-based pitch obtained by heat-treating various types of carbon black, anthracite, bituminous coal and other finely pulverized coal, naphtha residual oil, asphalt, fluid catalytic cracking residual oil and other heavy petroleum oils. Finely pulverized coal-based pitch obtained by heat-treating heavy coal-based oil such as coal and coal tar, which has 1 carbon number
About 5 to 20 paraffins, finely ground products of carbonized products such as olefins, finely ground products of carbonized products of low molecular weight aromatic compounds such as naphthalene and biphenyl, polyethylene, methyl polyacrylate, polyvinyl chloride, phenol resin, poly Examples include finely pulverized polymer carbonized products obtained by carbonizing a polymer such as acrylonitrile.

Further, as the carbonaceous dispersed particles used in the present invention, carbonaceous matter such as petroleum pitch, coal pitch and polyvinyl chloride carbide is mesophase (liquid crystal).
Examples include mesophase spherules obtained by solidification or particles containing the same. The mesophase microspheres can be taken out as an insoluble matter of a solvent such as quinoline. In particular, those obtained from petroleum pitch and coal pitch are preferably used.

The particle size of the carbonaceous dispersed particles is 0.01 to 5
The thickness is 00 μm, preferably 1.0 to 100 μm. 0.
If it is less than 01 μm, a sufficient electrorheological effect cannot be obtained,
If it exceeds 0 μm, sufficient dispersion stability cannot be obtained.

Further, in the present invention, in order to improve the electrorheological effect, a carbonaceous substance having shape anisotropy can be used as the carbonaceous dispersed particles. A carbonaceous substance having shape anisotropy has a length of 0.02 to
10,000 μm, preferably 10-5,000 μm
And the diameter is 0.01 to 500 μm, preferably 1.0 to
100 μm with an aspect ratio of 2-1,000,00
It has a rod-like (or whisker) shape of 0, preferably 2 to 100,000, and more preferably 3 to 10,000.

If the diameter of the carbonaceous material having shape anisotropy is less than 0.01 μm, a sufficient electrorheological effect cannot be obtained, and if it exceeds 500 μm, sufficient dispersion stability (sedimentation test after standing for several hours) is obtained. I can't. When the length of the carbonaceous material having shape anisotropy is less than 0.02 μm, the effect of shape anisotropy is not sufficiently reflected in the electrorheological effect,
If it exceeds 00 μm, sufficient dispersion stability cannot be obtained. If the aspect ratio of the carbonaceous material having shape anisotropy is less than 2, the effect of shape anisotropy is not sufficiently reflected in the electrorheological effect, and if it exceeds 1,000,000, the initial viscosity in the absence of an electric field is remarkably large. It is not preferable for practical use.

There are several methods for imparting shape anisotropy to the carbonaceous material. For example, the carbonaceous material is fiberized by a known spinning method such as dry, wet or melt spinning, and then hensyl mixer or the like. The method of pulverizing with a mixer of. Furthermore, a method of obtaining a whisker-like carbonaceous substance by vapor-phase pyrolyzing a hydrocarbon having 1 to 9 carbon atoms in hydrogen in the presence of a metal catalyst can also be mentioned. It is considered that the reason why the electrorheological effect is further improved by the shape anisotropy of the carbonaceous substance is that the structure can be easily formed under the electric field as compared with the spherical or lump particles.

As a method for treating a carbonaceous substance with iodine, a method of mixing and stirring a carbonaceous substance and an iodine solution is generally used. However, petroleum pitch, coal pitch or polyacrylonitrile carbide which can be spun into fibers. Regarding, etc., after spinning, treatment with iodine,
After that, it may be finely pulverized until it becomes particulate. After the treatment with iodine is completed, the carbonaceous particles treated with iodine can be obtained by thoroughly washing and drying.

Insolubilization or treatment with acid may be carried out before and / or after the treatment with iodine. In addition, before and / or after the treatment with iodine, the treatment is carried out in an inert gas at 10
Further firing may be performed at 0 ° C to 800 ° C. The reason why the treatment with iodine improves the electrorheological effect is that the treatment with iodine causes iodine to enter the inside of the carbonaceous dispersed particles to form a charge transfer complex, which facilitates the movement of electrons under an electric field and promotes polarization. It is thought to be for.

Iodine is used by dissolving it in an organic solvent such as ethanol, but it may be treated by sublimation in a solid state. In the case of a solution, the concentration of iodine is preferably 0.01 N or higher, more preferably 0.03 to 5 N. If it is less than 0.01 N, the treatment with iodine does not proceed sufficiently.

The treatment temperature with iodine is -50 to
The temperature is preferably in the range of 300 ° C, more preferably 0 to 120 ° C. If it is less than -50 ° C, the effect of the treatment with iodine does not sufficiently appear. If it exceeds 300 ° C, rapid heat generation may occur, which is not preferable.

Further, it is more preferable to coat the carbonaceous dispersed particles treated with iodine with an electrically insulating film because the current density can be lowered. Such an electrically insulating film is formed by coating a powder from a polymer solution, hybridization in which small particles are dry-mixed and melted on the surface of the powder, surface treatment such as silane treatment, sputtering vacuum deposition, from a monomer. It is formed by polymerization of.

As the substance used for the electrically insulating film,
Synthetic polymer substances such as polyethylene, polystyrene, polymethylmethacrylate, polyvinyl acetate, polyvinyl chloride, sodium polyacrylate, epoxy resin, phenol resin, urethane resin, tetraethoxysilane, methyltrimethoxysilane, phenyltrimethoxysilane, Typical examples are silane treating agents such as hexamethyldisilazane and trimethylchlorosilane, modified silicone oils having a carboxyl group or hydroxyl group and having a dimethylpolysiloxane or phenylmethylpolysiloxane structure as the main chain, and inorganic compounds such as silica, alumina, and rutile. As.

The thickness of the electrically insulating film is 0.005 to 30 μm.
m is preferable, and 0.01-3 μm is more preferable. If the thickness of the electrically insulating film is less than 0.005 μm, the effect as an insulating layer is insufficient, and if it exceeds 30 μm, the electrorheological effect does not appear.

The electrically insulating liquid used in the present invention includes:
Mineral oils, hydrocarbon solvents such as alkylnaphthalene and polyalpha-olefins, ester-based oils such as butyl phthalate and butyl sebacate, ether-based oils such as oligophenylene oxide, silicone oils, fluorine-based oils and the like.

The ratio of the dispersed carbonaceous particles in the electrorheological fluid of the present invention and the electrically insulating liquid is 1 to 60% by weight, preferably 5 to 50% by weight, and 99 to 100% by weight of the electrically insulating liquid. It is 40% by weight, preferably 95 to 50% by weight. If the amount of dispersed particles is less than 1% by weight, a sufficient electrorheological effect cannot be obtained, and if it exceeds 60% by weight, the initial viscosity in the absence of an electric field becomes remarkably large, which is not preferable in practice.

Further, additives such as other dispersed particles and a dispersant such as a surfactant may be blended within a range that does not impair the effect of the electrorheological fluid of the present invention. Further, the addition of a small amount of water may increase the electrorheological effect, but it also causes problems such as easy current flow and a narrow operating temperature range.

The electrorheological fluid of the present invention exhibits an excellent electrorheological effect even in a non-hydrated system, and includes an engine mount, a damping device such as a shock absorber, a clutch, a torque converter, a brake system, a valve,
It can be used for applications such as dampers, suspensions, actuators, vibrators, and inkjet printers.

[0030]

EXAMPLES The present invention will be described in detail below with reference to examples, but the present invention is not limited thereto. Synthetic Example 1 Heavy oil having a boiling point of 320 ° C to 550 ° C obtained by fluid catalytic cracking of a desulfurized oil of a vacuum crude oil of Arabian crude oil at 500 ° C using a silica-alumina catalyst was used at a pressure of 15 kg /
cm ² · G, was heat-treated for three hours at a temperature of 430 ℃. The heat-treated oil was distilled at 250 ° C./1 mmHg to remove light components, and pitch (1-I) having a softening point of 98 ° C. was obtained. Next, this pitch (1-I) is heat-treated under nitrogen at a temperature of 400 ° C. for 12 hours to give a pitch (1--) having a softening point of 268 ° C.
II) was obtained. Elemental analysis revealed that the pitch (1-II) had a carbon content of 95% by weight and a hydrogen content of 5% by weight. Further, the pitch (1-II) was finely pulverized to obtain pitch particles (1-1) having a particle diameter of 11 μm. This pitch particle (1-1) 5
0g and 2.5g iodine 200ml ethanol solution
The mixture was stirred in (0.05 N) at room temperature for 5 hours. After that, it is filtered and washed with ethanol, and finally at 80 ℃ / 2mmHg.
Pitch particles (1
-2) was obtained. The carbon content of the pitch particles (1-2) by elemental analysis was 90% by weight, the hydrogen content was 6% by weight, and the iodine content was 4% by weight.

Synthesis Example 2 Coal pitch was heat-treated at 450 ° C. in nitrogen gas to obtain pitch (2-I) containing mesophase microspheres. Next, pitch particles (2-1) composed of mesophase spherules and having a particle size of 8 μm were collected from this pitch (2-I) by quinoline extraction. Carbon content of pitch (2-1) by elemental analysis is 96
The amount of hydrogen was 3% by weight, and the amount of nitrogen was 1% by weight. The pitch particles (2-1) were treated with iodine under the same conditions as in Synthesis Example 1 to obtain pitch particles (2-2). The elemental analysis revealed that the pitch particles (2-2) had a carbon content of 89% by weight, a hydrogen content of 6% by weight, and an iodine content of 5% by weight.

Synthetic Example 3 The pitch (1-II) obtained in Synthetic Example 1 was changed to a nozzle diameter of 3 mm.
After spinning into a fiber of 15 μm at 315 ° C. using a spinning machine of φ, L / D = 2, it was pulverized for 3 seconds using a Henschel mixer to obtain a pitch (3-1) having shape anisotropy. The pitch (3-1) was a rod shape having a diameter of 15 μm and an aspect ratio of 3 to 50. This pitch (3-1) was treated with iodine under the same conditions as in Synthesis Example 1 to obtain pitch particles (3-2) having shape anisotropy. Pitch particles (3-
The carbon amount of 2) was 90% by weight, the amount of hydrogen was 6% by weight, and the amount of iodine was 4% by weight.

Synthesis Example 4 10 g of pitch particles (3-2) treated with iodine in Synthesis Example 3
0.2 wt% sodium polyacrylate (degree of polymerization 2.
20,000 to 70,000) 500 ml of aqueous solution was mixed and stirred at room temperature for 8 hours. After that, this solution was reprecipitated in 3 L of ethanol, filtered and washed with ethanol, and finally at 80 ° C./2 m.
It was dried at mHg for 5 hours to obtain iodine-treated pitch particles (3-3) coated with sodium polyacrylate.

Synthesis Example 5 1 g of polyethylene was treated with decahydronaphthalene 5 at 110 ° C.
It was dissolved in 00 ml, and 10 g of the pitch particles (3-2) treated with iodine in Synthesis Example 3 was added to this solution, and the solution was added at 110 ° C. for 5 minutes.
Minutes, and the mixture was stirred at room temperature for 2 hours. After that, filtration and washing are performed, and finally, it is dried at 80 ° C./2 mmHg for 5 hours, and the iodine-treated pitch particles coated with polyethylene (3-
4) was obtained.

Synthesis Example 6 To a solution prepared by mixing 17.3 g of tetraethoxysilane and 50 g of ethanol, 10 g of the pitch particles (3-2) treated with iodine in Synthesis Example 3 was added, and 2 ml of 1.5N ammonia water was further added with stirring. Was added. Particles were generated immediately after the addition, but the reaction was then continued at 80 ° C. for 5 hours to complete the sol-gel reaction for silica formation. After the reaction, 80 ℃ / 2
It was dried at mmHg for 5 hours to obtain silica-coated iodine-treated pitch particles (3-5).

Examples 1 to 6, Comparative Examples 1 to 3 Pitches (1-2) and (2-
2), (3-2), (3-3), (3-4), (3-
5) 3 g of each was dispersed in 7 g of silicone oil having a viscosity of 20 cSt (KF-96 manufactured by Shin-Etsu Silicone) to prepare electrorheological fluids (1) to (6). Further, using the pitch particles (1-1) obtained in Synthesis Example 1 and the pitch particles (2-1) obtained in Synthesis Example 2, electrorheological fluid (7), ( 8) was prepared. Furthermore, particle size 15
Disperse 3 g of silica particles of μm in 7 g of silicone oil having a viscosity of 20 cSt (KF-96 manufactured by Shin-Etsu Silicone),
Further, 0.3 g of water was added to prepare an electrorheological fluid (9).

Next, using a double-cylinder type rotational viscometer with an electric field applying device having a cylinder diameter of 16 mm and an outer cylinder diameter of 18 mm, an applied voltage of 3 kV / mm and a shear rate of 400 s ^-1 at 25 ° C. and 70 The torque values of the electrorheological fluids (1) to (9) at temperatures of 110 ° C and 110 ° C were measured. The current value at that time was also measured. The results are shown in Table 1. The torque value was obtained as the difference between the torque before and after the application of the electric field.

[0038]

[Table 1]

The following can be said from Examples 1 to 6 and Comparative Examples 1 to 3 The electrorheological fluids using the carbonaceous dispersed particles treated with iodine as the dispersed particles of the present invention are carbonaceous dispersed particles before treatment. The electro-viscous effect is larger than that using. In addition, the electrorheological effect is large and the amount of current flowing is small compared to the case where silica particles and water are used. Especially 70
The difference in easiness of current flow is remarkable at ℃. In addition, the silica particle system is 110 ° C due to water evaporation.
Although the shear stress was significantly reduced at 1, the iodine-treated carbon-based dispersed particle system retains high shear stress. From these results, it can be seen that the carbonaceous dispersed particle system treated with iodine has excellent high temperature characteristics. In addition, the current value can be further reduced by coating the carbonaceous dispersed particles treated with iodine with the electrically insulating film.

[0040]

The electrorheological fluid using the carbonaceous dispersed particles treated with iodine or the carbonaceous dispersed particles coated with the electrically insulating film after being treated with iodine of the present invention is
It is a non-hydrous system and exhibits excellent electrorheological effects, and is used for engine mounts, shock absorbers, clutches, torque converters, braking systems, power steering, valves, dampers, suspensions, actuators, vibrators, ink jet printers, etc. be able to.

Continuation of the front page (51) Int.Cl. ⁶ Identification number Office reference number FI technical display area C10N 40:12 40:14 60:08 70:00

Claims (6)

[Claims] 1. An electrorheological fluid comprising carbonaceous dispersed particles treated with iodine and an electrically insulating liquid. 2. A carbonaceous dispersed particle having a mixing ratio of 1 to 60% by weight treated with iodine, and an electrically insulating liquid 40 to 99.
The electrorheological fluid according to claim 1, which is in weight%. 3. The carbonaceous dispersed particles have a length of 0.02.
The electrorheological fluid according to claim 1, which has a shape anisotropy of ˜10,000 μm, a diameter of 0.01 to 500 μm, and an aspect ratio of 2 to 1,000,000. 4. An electrorheological fluid, characterized in that, after being treated with iodine, it further comprises dispersed carbonaceous particles coated with an electrically insulating film and an electrically insulating liquid. 5. A carbonaceous dispersed particle 1 having a mixing ratio of after being treated with iodine and further coated with an electrically insulating film.
5. The electrorheological fluid according to claim 4, wherein the electrorheological fluid is about 60% by weight and the electrical insulating liquid is 40 to 99% by weight. 6. The carbonaceous dispersed particles have a length of 0.02.
The electrorheological fluid according to claim 4, which has a shape anisotropy of ˜10,000 μm, a diameter of 0.01 to 500 μm, and an aspect ratio of 2 to 1,000,000.