JPH04348192A - Electro-viscous fluid - Google Patents

Abstract

PURPOSE:To provide a decidedly new non-aqueous electro-viscous fluid exhibiting excellent electro-viscous effect. CONSTITUTION:The objective electro-viscous fluid is produced by dispersing carbonaceous powder obtained by the heat-treatment of polyaniline powder in an oily medium having electrical insulation.

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] The present invention can greatly and reversibly change its viscosity characteristics through electrical control, and is suitable for electrical control of mechanical devices such as engine mounts, shock absorbers, valves, actuators, and clutches. Electro Rheol
(logical) fluids.

0002

2. Description of the Related Art The phenomenon in which the apparent viscosity of a fluid containing a certain kind of substance dispersed in an oily medium changes greatly by applying an electric field to the fluid has long been known as the Winslow effect. Early fluids that exhibited the Winslow effect were starch, starch, etc. dispersed in mineral oil or lubricating oil, but these fluids were not developed enough to recognize the importance of the electrorheological effect. However, the effects lacked reproducibility, making it impossible to utilize them in various fields.

[0003] Therefore, in order to obtain a fluid with a high electrorheological effect and good reproducibility, research has been actively conducted mainly on fine powder, and many proposals have been made. for example,
Highly water-absorbent resin fine particles having acid groups such as polyacrylic acid (JP-A-53-93186), ion exchange resin (JP-A-60-31211), alumina silicate (JP-A-62-95397) ) etc. have been proposed.

[0004] All of these electrorheological fluids are made by impregnating hydrophilic fine powder and dispersing it in an insulating oily medium, and these electrorheological effects occur when a high voltage is applied from the outside. It is believed that polarization occurs in fine powder due to the action of water, and that this polarization causes crosslinking between particles in the direction of the electric field, increasing the viscosity of the fluid.

Research on electrorheological fluids due to the action of water has been conducted so far, but in recent years, for example, fluids using organic semiconductor fine particles such as polyacenequinone (Japanese Patent Laid-Open No. 6
1-216202), a fluid using dielectric fine particles in which a conductive thin film layer is formed on the surface of organic solid particles, and an electrically insulating thin film layer is further formed thereon (JP-A-63-976).
Non-aqueous electrorheological fluids that do not contain water and that use ferroelectric substances or semiconductor particles have been proposed, such as fluids that use dielectric fine particles having cavities (Japanese Patent Application Laid-open No. 1-172496). There is.

[0006]

[Problems to be Solved by the Invention] Such non-aqueous electrorheological fluids have various defects caused by the presence of water in conventional fluids, such as an increase in the value of current flowing when voltage is applied or electricity dependence due to the presence of water ions. There are great expectations that it will have the potential to eliminate drawbacks such as increased size, and further research is underway. That is, on the assumption that the Winslow effect is based on polarization of the surface of fine particles due to an external voltage, other methods of generating polarization on the surface of fine particles, particularly dielectric fine particles, are being actively investigated. However, conventionally proposed non-aqueous electrorheological fluids using semiconductor particles made of single-layer compounds or microparticles with an insulating layer formed on their surfaces are less effective than the electrorheological effect caused by adding water. They have drawbacks such as being small, electrophoresis may occur when using direct current, and stability may not be sufficient.

[0007]Therefore, it is desired to develop a new non-aqueous electrorheological fluid that can overcome these drawbacks.

[0008]

[Means and effects for solving the problem] In order to meet the above-mentioned needs, the present inventor has made extensive studies and found that the methods using dielectric materials and semiconductor particles that have been proposed so far have no effect on the electrorheological effect. We have come to the conclusion that it is difficult to satisfy all of the requirements such as further improvement, reliably preventing electrophoresis from occurring under direct current flow, and ensuring sufficient stability. Therefore, in addition to the conventionally known dielectric materials and semiconductor particles, we conducted further studies to find particles that produce electrorheological effects.As a result, we found that carbonaceous particles obtained by heat-treating polyaniline do not contain water. The present invention was completed based on the finding that a new electrorheological fluid can be obtained by dispersing the electrorheological effect in an oily medium.

Therefore, the present invention provides an electrorheological fluid characterized by dispersing carbonaceous powder obtained by heat treating polyaniline powder in an oily medium having electrical insulation properties. be.

[0010] The present invention will be explained in more detail below. As mentioned above, the electrorheological fluid of the present invention is produced by dispersing carbonaceous powder obtained by heat-treating polyaniline powder in an oily medium having electrical insulation properties. It is a nonaqueous electrorheological fluid that does not require the addition of water to obtain the electrorheological effect.

[0011] The above polyaniline powder can be obtained by electrically or chemically oxidatively polymerizing aniline. In this case, there are no particular restrictions on the method, as long as a potential that leads to polymerization of aniline is applied by some method. Bye. Specifically, when polyaniline is obtained by electrolytic oxidation polymerization, a pair of electrode plates serving as a working electrode and a counter electrode are immersed in a solution containing an aniline monomer, and a voltage higher than the oxidation potential of aniline is applied between the two electrodes. Alternatively, a current may be applied under such conditions as to ensure a voltage sufficient to polymerize aniline, thereby producing polyaniline on the working electrode. In addition, in the chemical oxidative polymerization method, an oxidizing agent whose redox potential is about the polymerization potential of aniline is added to the solution containing the aniline monomer, such as (NH4)2.
S2O8, MnO2, PbO2, FeCl3, etc. may be administered.

Here, when polyaniline is obtained by electrical or chemical oxidative polymerization, H
It is known that when acids such as BF4, H2SO4, HCl, HClO4, etc. are mixed, the negative ions of the acids are incorporated as dopants into the synthesized polyaniline, resulting in polyaniline with good conductivity. For example, polyaniline obtained by oxidative polymerization of aniline as a polymerization raw material in the presence of HBF4 is usually in a benzonoid=amine state (formula A) or a benzonoid=ammonium state, as shown in the following formulas (A) to (D). (Formula B), doped = semiquinone radical state (Formula C), and quinoid = diimine state (Formula D), four types of polyaniline are mixed together, and such doped = semiquinone radical state (Formula C) is formed. Although it is known that polyaniline contained in polyaniline exhibits good conductivity, these mixing ratios do not particularly affect the final electrorheological effect, and in the present invention, any mixing ratio is used. be able to.

[0013]

[Chemical formula 1]

To give a more specific example of such a method for synthesizing polyaniline, a method for synthesizing polyaniline by electrolytic oxidation polymerization uses a highly conductive material such as stainless steel, platinum, or carbon as a working electrode and a counter electrode. Using plates and porous materials made of H2SO4,
Examples include a method in which polyaniline is polymerized and precipitated on the working electrode side by immersing it in an electrolytic solution containing an acid such as HBF4 and an aniline monomer and passing a current of about 0.1 to 100 mA/cm2 between the two electrodes. A method for synthesizing polyaniline using a chemical oxidative polymerization method involves adding 0.5 mol/liter of ammonium persulfate [(NH4)2S2O8] as an oxidizing agent to 1 mol/liter of H2SO4 and 0.5 mol/liter of aniline.
Ammonium persulfate has a redox potential of 2.0 V (compared to standard electrode) when administered into an aqueous solution containing 4 mol/liter.
Examples include a method in which aniline is oxidatively polymerized and polyaniline is polymerized and precipitated. The reaction at this time can be expressed by the reaction formula below.

[0015]

[Chemical 2]

[0016] When polyaniline is synthesized by mixing acids by the above method, the structural state of the polyaniline obtained differs depending on the type of acid. For example, when HBF4 is used, it is fibrillar, and when H2SO4 is used, it is fibrillar. It may become granular or finely powdered. In the present invention, any of these can be used by processing through an appropriate powdering process or granulation process, but in particular, it is important to carry out polymerization under conditions that provide an appropriate particle size distribution during synthesis. is preferred. Also, in this case,
The particle size of the polyaniline powder is not particularly limited, but the average particle size is 0.05 to 200 μm, especially 1
It is preferable to set it to 100 micrometers.

Next, as described above, carbonaceous powder is obtained by heat-treating this polyaniline, but the treatment temperature in this case is not particularly limited and can be set as appropriate depending on the required electrorheological effect and current value. However, usually 250 to 800
The temperature is preferably 450 to 600°C. If the treatment temperature is less than 250°C, sufficient electrorheological effects may not be obtained depending on the polyaniline synthesis conditions, whereas if it exceeds 800°C, the conductivity becomes too high and too much current flows. There are cases where this happens. Also,
Conditions other than processing temperature include temperature increase rate, processing time,
There are no particular restrictions on any conditions such as processing temperature,
It can be set as appropriate. For example, regarding the processing atmosphere, it is preferable to use a non-oxidizing atmosphere;
At a processing temperature below .degree. C., an oxidizing atmosphere can be used, and it is also possible to combine an oxidizing atmosphere and a non-oxidizing atmosphere. In addition, the carbonaceous powder obtained by heat-treating polyaniline has a residual carbon percentage of 20 to 80
%, particularly preferably 25 to 70%.

The electrorheological fluid of the present invention is obtained by dispersing the carbonaceous powder thus obtained in an oily medium having electrical insulation properties, and in this case, the oily medium is:
There are no particular limitations, and any oil having electrical insulation properties such as silicone oil, mineral oil, transformer oil, paraffin oil, and halogenated aromatic oil can be used.

Although there are no particular restrictions on the dispersion conditions, it is particularly important that the carbonaceous powder at the time of dispersion has an appropriate particle size distribution, with an average particle size of about 0.05 to 200 μm, particularly about 1 to 100 μm. preferable. In this case, if the particle size of the polyaniline powder is controlled within the above-mentioned suitable range, carbonaceous powder having a suitable average particle size can usually be obtained by the above-mentioned heat treatment.
If the average particle size of the carbonaceous material obtained by heat treatment is extremely small or extremely large, it can be granulated or powdered by appropriate means.

Furthermore, the amount of carbonaceous powder to be dispersed is appropriately set depending on the intended use of the obtained electrorheological fluid, and is appropriately changed depending on the required amount of viscosity change. Note that the dispersion method is not particularly limited, and any dry method that can uniformly disperse the carbonaceous powder can be employed.

[0021]

EXAMPLES The present invention will be specifically explained below with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples.

[Example 1] Aqueous solution 1 containing 0.4 mol/liter of aniline and 1.0 mol/liter of H2SO4
administering 0.5 moles of ammonium peroxide in a liter;
Polymerization was carried out by stirring for 5 hours. The resulting suspension was filtered and the solid phase was dried to obtain 40 g of polyaniline powder.

[0023] This polyaniline powder was heated in a nitrogen atmosphere for 3
The powder was heated to 530° C. at a temperature increase rate of ° C./min and fired for 1 hour to obtain a carbonaceous powder having a particle size distribution shown in FIG. 1 and a residual carbon content of 68%.

50 g of the obtained carbonaceous powder was mixed with silicone oil (TSF451-10 manufactured by Toshiba Silicone Corporation) 1
An electrorheological fluid was obtained by dispersing it in 50 g.

The electrorheological effect of this electrorheological fluid was measured. The electrorheological effect was evaluated using a double cylindrical viscometer and the viscosity at a shear rate of 366 sec-1 and a temperature of 25° C. when a voltage of 0-2 kV was applied between the inner and outer cylinders. The results are shown in Table 1.

[Example 2] Commercially available aniline black (No. 13 aniline black manufactured by Toyo Shikizai Kogyo Co., Ltd.)
was heated to 480° C. at a temperature increase rate of 3° C./min in a nitrogen atmosphere and fired for 1 hour to obtain a carbonaceous powder having a particle size distribution shown in FIG. 2 and a residual carbon content of 68%.

50 g of the obtained carbonaceous powder was mixed with silicone oil (TSF451-10 manufactured by Toshiba Silicone Co., Ltd.) 1
An electrorheological fluid was prepared by dispersing it in 50 g, and the electrorheological effect was measured in the same manner as in Example 1. The results are shown in Table 1.

[Comparative Example 1] Commercially available aniline black (No. 13 aniline black manufactured by Toyo Shikizai Kogyo Co., Ltd.)
50g directly into silicone oil (Toshiba Silicone Co., Ltd.)
An electrorheological fluid was prepared by dispersing it in 150 g of TSF451-10 (manufactured by TSF451-10), and the electrorheological effect was measured in the same manner as in Example 1. The results are shown in Table 1.

[Comparative Example 2] 50 g of polyaniline powder similar to that produced in Example 1 was directly mixed with silicone oil (TSF4 manufactured by Toshiba Silicone Co., Ltd.) without heat treatment.
51-10) An electrorheological fluid was prepared by dispersing it in 150 g, and the electrorheological effect was measured in the same manner as in Example 1. The results are shown in Table 1.

[0030]

[Table 1] * Measurement was performed at 800V because it is impossible to measure above 800V.

From the results shown in Table 1, it was confirmed that the electrorheological fluid of the present invention has a good electrorheological effect.

[0032]

As explained above, the electrorheological fluid of the present invention is a completely new non-aqueous electrorheological fluid having good electrorheological effects.

[Brief explanation of the drawing]

FIG. 1 is a graph showing the particle size distribution of carbonaceous powder used in Example 1.

FIG. 2 is a graph showing the particle size distribution of carbonaceous powder used in Example 2.

Claims (1)

[Claims] 1. An electrorheological fluid comprising carbonaceous powder obtained by heat treating polyaniline powder dispersed in an oily medium having electrical insulation properties.