JPH06234985A - Electroviscous fluid - Google Patents

Abstract

PURPOSE:To obtain an electroviscous fluid which, upon application of a given voltage, undergoes a viscosity change at a lower value of electric current flowing through the fluid and which has a low initial viscosity. CONSTITUTION:The electroviscous fluid is a dispersion of either a particulate carbonaceous substance produced through melting at 300-500 deg.C or a particulate carbonaceous substance produced from a material scarcely containing any nitrogen, oxygen, and sulfur.

Description

Detailed Description of the Invention

[0001]

[Industrial application] An electrorheological fluid is a fluid that exhibits a phenomenon in which the apparent viscosity of the fluid changes rapidly and reversibly when an electric field is applied to the fluid, and is generally an oil with excellent electrical insulation properties. It is configured by dispersing fine particles as a dielectric in a medium.

The characteristics of this electrorheological fluid have been known for a long time, and its application as a component for electrically controlling devices and parts such as clutches, valves, engine mounts, actuators, robot arms, etc. has been studied. The present invention relates to such an electrorheological fluid.

[0003]

2. Description of the Related Art Heretofore, as solid fine particles used as a constituent component of a dispersed phase of an electrorheological fluid, cellulose, starch, silica gel, ion exchange resins, etc., which are miniaturized to adsorb water on the surface, are known. As other liquid phase constituents, oily media with high electrical insulation such as PCB, butyl sebacate, spindle oil, transformer oil, chlorinated paraffin, and silicone oil are known. Such electrorheological fluids are disclosed, for example, in US Pat. No. 2,886,151,
No. 3047507 or JP-A No. 53-17585.
JP-A-53-93186, JP-A-57-47234
JP-A-61-44998, JP-A-61-2597
52, JP-A-62-95397, JP-A-1-207.
No. 395 and the like. However, since the electrorheological fluid that has been mainly developed so far is one in which moisture is adsorbed on solid fine particles, the operating temperature range is -20 ° C to +7.
It is as narrow as 0 ° C, and has the drawback that its performance is likely to deteriorate due to the evaporation of water in the long term, and it is not practical. Very high performance and highly stable electrorheological fluids of practical value have not been developed.

Therefore, various improvements have been made in various fields in order to eliminate the drawbacks of the conventional electrorheological fluid. Its mainstream does not use water as a high dielectric liquid,
This is the development of non-aqueous solid particles. As typical examples thereof, for example, JP-A-1-284594 and JP-A-1-16482.
No. 3, JP-A-2-235994, and the like.

[0005]

The mechanism of manifestation of the electrorheological effect in electrorheological fluids has not yet been fully clarified. However, it is generally said that the solid particles are polarized by an external electric field, and the polarized particles are bonded to each other by electrostatic attraction to cause cross-linking, resulting in an increase in viscosity.

Considering this supposed mechanism, an electrorheological fluid in which carbonaceous powder having a moderately controlled carbonization degree (ratio of C / H and carbon atoms to hydrogen atoms) is dispersed as solid fine particles has excellent performance. Solved problems such as narrow operating temperature range, which was a problem of electro-rheological fluid that came from using conventional water-absorbing solid fine particles, and instability of performance due to long-term use. It is considered to contribute greatly to practicality. From this point of view, the present inventors have mainly disclosed that carbonaceous powders having strictly controlled qualities such as carbonization degree (C / H) have extremely high performance as non-aqueous solid fine particles (special feature). Kaihei 3-27920
No. 6). According to the invention described in JP-A-3-279206, an organic compound selected from the group consisting of coal, coal-based tar / pitch, coal liquefaction, cokes, petroleum-based tar / pitch and resins is used as a raw material. It has been shown that the carbonaceous powder obtained by heat-treating an organic substance at 300 to 800 ° C. and then adjusting the particle size exhibits excellent performance as solid fine particles for electrorheological fluid. The present invention is intended to provide an electrorheological fluid having higher performance among electrorheological fluids in which carbonaceous powders expected to exhibit excellent performance are dispersed as solid fine particles.

[0007]

According to the present invention, there are no problems such as a narrow operating temperature range which a conventional electrorheological fluid has, and instability of performance in long-term use.
The purpose is to further improve an electrorheological fluid using carbonaceous dielectric fine particles exhibiting an excellent electrorheological effect. It is a carbonaceous powder whose carbonization degree is adjusted, and is 300 to 500 during the carbonization reaction. The basic requirement is an electrorheological fluid in which a carbonaceous powder made of an organic compound that undergoes a softening and melting state in a temperature range of ° C and / or an organic compound that does not substantially contain nitrogen, oxygen and sulfur components is dispersed. Further, it is more preferable that the raw material of the carbonaceous powder is a pitch obtained by polymerizing a condensed aromatic ring compound. Here, the softening and melting means a state in which powder, particles or lumps of the carbonization reaction product are melted in the reaction tank to form a uniform liquid phase.

The characteristics required of the electrorheological fluid are:
In addition to causing a large viscosity change (increase in apparent viscosity) due to low current under an external electric field, solid fine particles do not settle in an oily medium, and are stable against long-term use and temperature change. And the like, and the viscosity of the fluid when an electric field is not applied (hereinafter referred to as initial viscosity) is as low as possible.

That is, if the current is low under an external electric field,
It is possible to improve the energy efficiency of various devices using an electrorheological fluid. Further, the carbonaceous powder that achieves a fluid having a low initial viscosity can increase the amount of carbonaceous powder compounded in a fluid that requires a predetermined initial viscosity, as compared to the carbonaceous powder of a fluid that has a high initial viscosity. As a result, a high electrorheological change can be realized.

Regarding the requirements for the carbonaceous powder satisfying the characteristics required for such an electrorheological fluid, for example, JP-A-3-279206 discloses a ratio of carbon atoms to hydrogen atoms (C /
H) is in the range of 1.70 to 3.50, the average particle size is 0.5 to 40 μm, and the light content is small.
It is mentioned that the content of fine particles is small, and further that it does not contain free carbon. In addition, as a method for producing such a carbonaceous powder, various organic compounds are used.
Disclosed is a method for producing by solvent extraction or heat treatment in several steps, if necessary, within a temperature range of up to 800 ° C.

The present inventors have studied in detail the mechanism of the electrorheological effect of the carbonaceous powder in the electrorheological fluid.
As a result, the electrorheological effect of the carbonaceous powder in the electrorheological fluid is due to the polycondensation reaction and the elimination of the functional group that occur when the organic compound that is the starting material for the carbonaceous powder is heat-treated. And the electronic polarization and the orientation polarization caused by the remaining side chain compound. Normally, the polycyclic aromatic compound grows as the heat treatment temperature rises, and the dielectric constant increases, but at the same time, the electrical conductivity also rises, and the increase in viscosity and the current value when an electric field is applied in a fluid Together they will rise.

However, during heat treatment and carbonization of the organic compound raw material, when the content shows a softening and melting state at a heat treatment temperature of 300 to 500 ° C., the performance of the electrorheological fluid in which the obtained carbonaceous powder is dispersed is obtained. However, it has been found that superior performance can be obtained as compared with the case where carbonization is performed without showing a softened and molten state. Furthermore, it was also found that the improvement of the performance of the electrorheological fluid is further promoted when an organic compound containing substantially no nitrogen, oxygen and sulfur components is used in the starting material.

The term "performance" as used herein means that a change in the viscosity of a fluid that occurs when a constant voltage is applied can be realized with a smaller current value flowing in the fluid and that a fluid having a lower initial viscosity can be manufactured. Although the factors related to these properties have not been clarified, many polycyclic aromatic compounds that are rich in π-electrons and have excellent planarity during heat treatment of organic compounds are considered in terms of achieving large viscosity changes. I think it is important to generate. This requires the molecules of the smaller fused aromatic compound to rearrange in parallel, which requires 300-500 ° C.
It is expected that it is necessary to exhibit a softened and melted state in.

Thus, the carbonaceous powder obtained by carbonizing after passing through the softening and melting state in the temperature range of 300 to 500 ° C. has more planar polycyclic aromatic components, resulting in such carbonaceous material. Fluids with dispersed powders show large viscosity changes due to excellent dielectric polarization. When an organic compound containing nitrogen, oxygen, or sulfur atoms in the molecule is used as a starting material, those atoms remaining in the ring of the polycyclic aromatic molecule in the carbonaceous powder or as a functional group are polarized in the molecule. It is presumed that this will increase the polarity of and increase the conductivity. As a factor for further lowering the initial viscosity, 300-
It is considered that the softening and melting state in the temperature range of 500 ° C. makes it difficult for pores to be generated in the carbonaceous powder, and the powder having a small specific surface area can be produced. It is presumed that the lower the specific surface area of the powder, the smaller the contact area with the electrically insulating oil such as silicone oil and the better the dispersibility.

Examples of the organic compound which exhibits a softened and melted state in the temperature range of 300 to 500 ° C. in this patent include thermoplastic resins such as polyvinyl chloride and polyvinyl alcohol, coal-based or petroleum-based tars, pitches and acenaphthylene. Examples thereof include polymers of condensed aromatic compounds such as naphthalene, methylnaphthalene, and anthracene, and monomers or polymers such as naphthacene. In addition, compounds such as acenaphthylene and hydrogenated pyrene that undergo a polymerization reaction by heat treatment can also be used as long as they exhibit a softening and melting state in the temperature range of 300 to 500 ° C. during heat treatment. Examples of these polymers include polymers produced using an acid catalyst such as HF-BF ₃ .

These organic compounds may be used alone as a starting material for the carbonaceous powder, or may be used as a mixture of two or more kinds. Also, acenaphthylene, naphthalene,
Polymers of polycyclic aromatic compounds such as anthracene and naphthacene are also examples of organic compounds containing substantially no nitrogen, oxygen or sulfur components.

Here, "not substantially containing" means nitrogen,
It means that the total amount of oxygen and sulfur components is 1% by weight or less, preferably 0.1% by weight or less, singly or as a mixture.

The electrorheological fluid of the present invention comprises a carbonaceous powder obtained by heat treating and pulverizing and classifying the above-mentioned organic compound and an electrically insulating oily medium, and if necessary, the powder is dispersed in the oily medium. A dispersant for stabilizing the state and an additive for further increasing the amount of change in viscosity when a voltage is applied are added and used.

The above-mentioned heat treatment conditions for the organic compound are such that the carbonization degree (C / H), which is the ratio of the number of carbon atoms and hydrogen atoms of the carbonaceous powder finally obtained, is in the range of 1.70 to 3.50, Preferably 2.00 to 3.50, particularly preferably 2.20.
It adjusts so that it may become a range of -3.00. Carbonization degree is 1.
When it is lower than 70, no change in viscosity occurs when a voltage is applied when a fluid is used. If it exceeds 3.50, the electric conductivity of the powder becomes too high and the energy loss becomes large in practical use.

Further, such heat treatment is carried out in a thermobalance (TGA) of the finally obtained carbonaceous powder under a nitrogen flow from room temperature to room temperature at a temperature of 10 ° C. continuously for 1 minute. It is preferable to carry out until the weight loss rate in the temperature range of 200 ° C. is 0.5% by weight or less, preferably 0.3% by weight or less. Such low-boiling components volatilize from the powder during use at high temperatures or during long-term use, and their characteristics fluctuate.

The heat treatment conditions for satisfying the above characteristics differ depending on the organic compound as a raw material. For example, a coal tar pitch is 400 to 600 ° C. for 5 hours or more, and a naphthalene pitch is a softening point (temperature at which the viscosity is 100 poise). ) Uses a pitch of 245 ° C., 400-5
It is 3 hours or more at 50 ° C.

The above reaction may be a single heat treatment, but it is more preferable that the heat treatment is performed once at a temperature of 300 to 500 ° C. for softening and melting, followed by washing with a solvent such as hexane and further heat treatment. .

The heat-treated product satisfying the above characteristics is pulverized and classified to have an average particle size of 0.5 to 40 μm, preferably 2 to 40 μm, and particularly 2 to 10 μm. If it exceeds 40 μm, the particles tend to settle in the oily medium. With particles smaller than 0.5 μm, the initial viscosity when made into a fluid is significantly increased and the electrorheological effect is reduced. The particle size described here is measured using a Coulter counter.

This carbonaceous powder is contained in an electrically insulating oily medium such as spindle oil, transformer oil, chlorinated paraffin or silicone oil in an amount of 1 to 60% by weight, preferably 20 to 50% by weight.
Disperse evenly to obtain an electrorheological fluid. If the amount of carbonaceous powder is less than 1% by weight, the electrorheological effect is small, and if it exceeds 60% by weight, the initial viscosity is remarkably increased and the electrorheological effect is reduced.

[0025]

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.

(Example 1) Naphthalene pitch obtained by polymerizing naphthalene using an HF-BF ₃ catalyst and containing substantially no nitrogen, oxygen, or sulfur components (AR manufactured by Mitsubishi Gas Chemical Co., Inc.) ^R softening point of 245 ° C.) was heat-treated at 450 ° C. for 3 hours in an inert atmosphere. At this time, the naphthalene pitch showed a liquid phase state in the temperature range of 300 to 450 ° C. The heat-treated product was pulverized and classified to adjust the average particle size to the range of 3.5 to 4.0 μm. At this time, particle size 1
The proportion of particles of 0 μm or more and particles of less than 1.6 μm was 1.0% by weight or less. The carbonaceous powder thus obtained was further subjected to dry nitrogen atmosphere at 450 ° C., 470 ° C., 48 ° C.
Reheat treatment was carried out for 3 hours at four levels of temperatures of 0 ° C and 500 ° C to obtain the target carbonaceous powder. Carbonization degree of carbonaceous powder (C /
H) are 2.12, 2.24, 2.30, 2.
It was 45. The carbonization degree (C / H) of the carbonaceous powder is defined by the ratio of the number of carbon atoms and hydrogen atoms by elemental analysis (the same applies to Example 2 and the following).

The carbonaceous powder was uniformly dispersed in 36% by weight of silicone oil oil having a viscosity of 0.1 poise at room temperature, which is an electrically insulating oily medium, to obtain four kinds of electrorheological fluids. The initial viscosity of each of these fluids was 0.65 poise. A voltage of 2 kv / mm 2 was applied to the electrorheological fluid at room temperature, the change in viscosity of the fluid and the value of the current flowing in the fluid at this time were measured, and the performance as the electrorheological fluid was evaluated. Double-cylinder type rotational viscometer (inner cylinder radius 25 mm, outer cylinder radius 26 mm, inner cylinder height 20 m)
m) was used to measure the apparent viscosity at a shear rate of 366 / sec when a DC voltage was applied between the inner and outer cylinders. The obtained results are shown in Table 1 together with Comparative Examples.

(Example 2) Polyvinyl chloride containing substantially no nitrogen, oxygen and sulfur components in an inert atmosphere at 450 ° C.
And heat treated for 3 hours. At this time, the heat-treated product was in a liquid phase at 450 ° C. The heat-treated product is further washed with hexane, and then 450, 480,
Reheat at 4 levels of 500,520 ℃ for 3 hours,
Four types of carbonaceous powder were obtained. At this time, the carbonization degree (C / H) of the carbonaceous powder is 2.30, 2.35 and 2.4, respectively.
It was 5,2.52. Also, any carbonaceous powder is T
The weight loss rate of GA in the temperature range of room temperature to 200 ° C. was adjusted to 0.1% by weight or less. The carbonaceous powder was pulverized and classified to adjust the average particle size to a range of 3.5 to 4.0 μm. At this time, particles of 10 μm or more and 1.6 μm
The proportion of particles less than m was 1.0% by weight or less, and the target carbonaceous powder was obtained. An electrorheological fluid was prepared from this carbonaceous powder in the same manner as in Example 1, and its performance was evaluated in the same manner as in Example 1. The initial viscosity of this fluid was 0.65 poise in each case. The obtained results are shown in Table 1 together with Comparative Examples.

(Example 3) Coal tar pitch containing no free carbon (nitrogen content, oxygen content: 1.1 each)
%, 1.0% by weight) was heat treated at 510 ° C. for 3 hours in an inert atmosphere. At this time, coal tar pitch is 400
A liquid phase was exhibited during the heat treatment at ˜500 ° C. The heat-treated product is extracted with tar oil (boiling range 120 to 250 ° C.) and washed, and then 350,400 in a dry nitrogen atmosphere,
Reheat for 3 hours at 4 levels of 450,500 ℃,
Four types of carbonaceous powder were obtained. At this time, the carbonization degree (C / H) of the carbonaceous powder is 2.20, 2.34, 2.4, respectively.
It was 2,2.48. Further, the weight reduction rate of any carbonaceous powder in the temperature range of room temperature to 200 ° C. under a nitrogen atmosphere was adjusted to 0.1% by weight or less. The carbonaceous powder is further crushed and classified to have an average particle diameter of 3.5 to 4.0 μm.
The range was adjusted to m. At this time, the proportion of particles having a particle size of 10 μm or more and particles having a particle size of less than 1.6 μm was 1.0% by weight or less, and the target carbonaceous powder was obtained. An electrorheological fluid was prepared in the same manner as in Example 1 using the carbonaceous powder,
The performance was evaluated as in Example 1. The initial viscosity of each fluid was 0.66 poise. The obtained results are shown in Table 1 together with Comparative Examples.

[0030] (Comparative Example 1) manufactured by thermosetting phenol resin (Kanebo Co. Bellpearl ^R R-500, nitrogen content,
Oxygen content: 0.6% by weight and 19% by weight, respectively, and the average particle size obtained by pulverizing and classifying 3 to 5 μm, particles of 10 μm or more and particles of less than 1.6 μm are all 1.0% by weight. % Resin powder in a dry nitrogen atmosphere at 530,54
Heat treatment was performed for 12 hours at four levels of temperatures of 0,550,560 ° C. In each of the four types of carbonaceous powders obtained, some fusion was observed between the particles, but the particles returned to the particle size before heat treatment by crushing with an atomizer. At this time, the carbonization degree (C / H) of the carbonaceous powder was 2.59, 2.77, 2.8, respectively.
It was 2,2.90. An electrorheological fluid was prepared from this carbonaceous powder in the same manner as in Example 1, and its performance was evaluated in the same manner as in Example 1. The initial viscosity of this fluid is 0.75
It was in the range of ~ 1.1 poise. The obtained results are shown in Table 1.

(Comparative Example 2) Polyvinylidene chloride containing substantially no nitrogen, oxygen and sulfur components was dried in a dry nitrogen atmosphere.
It heat-processed at the temperature of 4 levels of 80,500,530,560 degreeC for 3 hours. At this time, none of the powders softened and melted in the solid state. After washing the heat-treated product with hexane,
Furthermore, under a dry nitrogen atmosphere, 480,500,530,5
Reheat treatment was performed for three hours at four levels of temperature of 60 ° C. to obtain four kinds of carbonized products. The carbonization degree (C / H) at this time was 2.35, 2.40, 2.45, and 2.48, respectively. Further, the weight reduction rate of each carbonaceous powder in TGA in the temperature range of room temperature to 200 ° C. was adjusted to 0.1% by weight or less. The carbonaceous powder was pulverized and classified to adjust the average particle size to a range of 3.5 to 4.0 μm. At this time 10μ
The proportion of particles of m or more and particles of less than 1.6 μm was 1.0% by weight or less, and the target carbonaceous powder was obtained. An electrorheological fluid was prepared from this carbonaceous powder in the same manner as in Example 1, and its performance was evaluated in the same manner as in Example 1. The initial viscosity of this fluid was in the range of 0.77 to 1.2 poise. The obtained results are shown in Table 1 together with Comparative Examples.

[0032]

As can be seen from the results in Table 1, the carbonaceous powder heat-treated at the softening and melting temperature using as a starting material an organic compound that softens and melts in the temperature range of 300 to 500 ° C. in the heat treatment in the process of producing the carbonaceous powder. The electrorheological fluid in which is dispersed has the same viscosity change as that of the electrorheological fluid in which the organic compound that does not soften and melt at 300 to 500 ° C. is used as the starting material and the carbonaceous powder that is heat-treated in the same temperature range is dispersed. The current value at the time of showing was small, and it was shown to have excellent performance.

It was also shown that when a naphthalene polymerized pitch, which is a pitch obtained by polymerizing a condensed aromatic ring compound, was used as a starting material, the current value was smaller and the performance was excellent.

[0035]

INDUSTRIAL APPLICABILITY The electrorheological fluid of the present invention is obtained by dispersing carbonaceous powder obtained by heat-treating an organic compound that softens and melts in a specific temperature range at a temperature that softens and melts in an oil medium as dielectric fine particles. This is an electrorheological fluid, and the viscosity change of the fluid that occurs when a constant voltage is applied can be realized with a smaller current value flowing in the fluid, and the initial viscosity is small. As a result, the energy efficiency of various devices using the electrorheological fluid is greatly improved, and the amount of carbonaceous powder can be increased in the electrorheological fluid that requires a predetermined initial viscosity. Change can be realized.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hitomi Hatano, 1 Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba, Kawasaki Steel Corporation Technical Research Division (72) Inventor Noriyoshi Fukuda Chuo-ku, Chiba, Chiba Kawasaki-cho No. 1 Kawasaki Steel Corporation Technical Research Headquarters (72) Inventor Tsubasa Saito 3-1-1 Ogawahigashi-cho, Kodaira-shi, Tokyo (72) Inventor Takao Ogino 3-chome, Ogawa-higashi, Kodaira-shi, Tokyo 1-1 (72) Inventor Takayuki Maruyama 3-1-1 Ogawahigashi-cho, Kodaira-shi, Tokyo

Claims (5)

[Claims] 1. An electrorheological fluid obtained by dispersing dielectric fine particles in an oily medium having excellent electric insulation, wherein a carbonaceous powder produced through a softening and melting state during heat treatment at 300 to 500 ° C. is a dispersoid. An electrorheological fluid. 2. An electrorheological fluid obtained by dispersing dielectric fine particles in an oil medium having excellent electrical insulation, wherein the raw material of carbonaceous powder is an organic compound substantially free of nitrogen, oxygen and sulfur components. An electrorheological fluid containing carbonaceous powder as a dispersoid. 3. The carbonaceous powder raw material is 300 during the carbonization reaction.
The electrorheological fluid according to claim 1, which is an organic compound that is in a softened and melted state at ˜500 ° C. 4. The electrorheological fluid according to claim 3, wherein the raw material of the carbonaceous powder is an organic compound substantially free of nitrogen, oxygen and sulfur components. 5. The electrorheological fluid according to claim 4, wherein the raw material of the carbonaceous powder is a pitch obtained by polymerizing a condensed aromatic ring compound.