JPH03252498A - Electroviscous fluid - Google Patents

Abstract

PURPOSE:To obtain an electroviscous fluid, composed of a disperse phase of composite particles having a formed multilayered structure and specific particle size and a liquid phase of an electrical insulating oil with a specified viscosity and capable of exhibiting great electroviscous effects at high temperatures with small power consumption. CONSTITUTION:The objective electroviscous fluid composed of (A) 1-60wt.% disperse phase of composite particles, having a multilayered structure formed from an electrically conductive layer and an electrical insulating layer and composed of a ceramic material such as a metal oxide, metal nitride or glass or an organic or inorganic polymer material having 0.01-100mu average particle diameter and (B) 40-99wt.% liquid phase of an electrical insulating oil such as silicone oil having 0.65-500cSt viscosity at ambient temperature.

Description

DETAILED DESCRIPTION OF THE INVENTION Object of the Invention [Field of Industrial Application] The present invention relates to an electrorheological fluid whose viscosity is increased by the application of voltage.

[Prior Art] An electrorheological fluid is a suspension of finely divided hydrophilic solids dispersed in a hydrophobic, non-conducting oil, which rapidly transforms under the action of a sufficiently strong electric field. Moreover, the viscosity of the fluid increases reversibly and becomes a plastic or solid state.

In order to change the viscosity, not only a direct current electric field but also an alternating current electric field can be used.The required current is very small and a strong force is given with a small amount of electric power, so it can be used, for example, in clutches, hydraulic valves, shock absorbers. - Vibrator-1 can be used as a vibration isolator or as a component in an electro-mechanical interface for controlling a system that holds a workpiece in place, etc.

Conventionally, dispersed phase solid particles, which are one of the constituent elements of electrorheological fluids, have been made of cellulose, starch, silica gel, ion exchange resin, lithium polyacrylate, etc. that have been made fine by absorbing water from the surface, and other materials. As the liquid phase, which is a component, it is known that PCB, butyl sebacate, trans oil, chlorinated paraffin, silicone oil, etc. are used, but these are of little practical use. Electrorheological fluids do not yet exist.

The properties required of a practical electrorheological fluid are that it exhibits a large electrorheological effect, consumes little power when an electric field is applied, and responds instantaneously to the application and removal of an electric field.

However, in the case of a dispersed phase in which water is absorbed in order to produce the electrorheological effect as described above, as the amount of water increases, the current flowing through the particle lock simultaneously increases, which poses a major problem in terms of power consumption.

In particular, this tendency becomes stronger as the temperature increases, and the upper limit of the operating temperature of electrorheological fluids using conventional dispersed phases is 70 to 80.
℃, and if used at higher temperatures, excessive current will flow and power consumption will be extremely high.
It was impossible to apply this method to components used in high-temperature environments such as automobile engine compartments.

[Problems to be Solved by the Invention] The present invention aims to develop an electrorheological fluid that exhibits a high electrorheological effect at high temperatures but consumes less power.

8. Constitution of the invention [Means for solving the problem] The electrorheological fluid of the present invention is composed of composite particles of 1 to 60% by weight, each having an average particle size of 0.01 to 100 microns, in which a conductive layer and an electrically insulating layer form a multilayer structure. % dispersed phase and a viscosity at room temperature of 0.
It is characterized by being composed of an electrical insulating oil of 65 to 500 centistokes (cSt) and a liquid phase of 40 to 99% by weight.

The conductivity of the substance forming the conductive layer in the composite particles is 10
-'S-c+n-' or more, preferably 10-'Scm-
The above is good. If the conductivity is less than 10-'S-cm-', the concentration of charge carriers will be small, so a large electrorheological effect will not be obtained, and the response upon application and removal of an electric field will be poor.

Candidate substances include metal materials, ceramic materials such as metal oxides, metal carbides, metal nitrides, metal borides, and metal silicides, carbon materials, and organic materials such as conductive polymers that have the above-mentioned conductivity. Any substance that falls within the range of can be mentioned. Further, the material forming the conductive layer may be either an electronic conductor or an ionic conductor, but an electronic conductor is preferable because its conductivity has little temperature dependence.

Further, the conductive layer may be a continuous layer or a discontinuous layer, but a discontinuous layer is preferable since power consumption is reduced.

The conductivity of the substance forming the electrically insulating layer in the composite particles is 10-"SCm-' or less, preferably 10-"SCm-'
-1 or less is better.* l O-" If it exceeds 5-co+-', power consumption increases, which is disadvantageous as a dispersed phase of an electrorheological fluid.

Candidate substances include ceramic materials such as metal oxides, metal nitrides, and glass, organic materials such as polymers, and inorganic polymer materials such as silicone resins, as long as they fall within the above range of conductivity. Any substance can be mentioned.

The multilayer structure of the conductive layer and the electrically insulating layer may be a planar layer or a concentric inner layer, but preferably a planar layer.

In addition, the layer arrangement may be such that conductive layers and electrically insulating layers are arranged alternately or regularly, or may be randomly arranged.Furthermore, the total number of layers is 5 or more layers, and the outermost layer is an electrically insulating layer. It is preferable that there be.

Methods for forming a multilayer structure of a conductive layer and an electrically insulating layer include 1) a method of utilizing a material that already has a layered structure, and 2) a method of laminating layers using chemical or physical methods. In the case of 1), it is possible to insert an organic compound with a large residual carbon content between the layers of the electrically insulating layered structure material and then carbonize it to form a conductive layer, or to directly insert the conductive compound. An electrically insulating layer may also be formed between layers of a conductive layered structure material such as graphite. In the case of 2), thin film forming methods such as CVD, coating, spin code, vapor deposition, sputtering, and thermal spraying can be used.

Method 1) is preferable from the viewpoint of being economical and capable of forming a microscopic multilayer structure, and among these methods, from the viewpoint of practicality, it is preferable to insert an organic compound with a large residual carbon content between the layers of an electrically insulating layered structure material such as layered clay mineral. More preferred is a method in which a conductive layer is formed by carbonizing the conductive layer. The method 1) will be described below, but these do not limit the gist of the present invention in any way.

When using layered clay minerals for the electrical insulation layer in method 1),
Its layered clay minerals include kaolinite, dateskite, nacrite, hawaisite, antibolite, chrysotile, pyrophyllite, sfumetite (sfumetite is further formed by isomorphic substitution, montmorillonite, beidellite, nontronite, sabonite, hectorite, and Montmorillonite is further classified into bentonite and acid clay depending on the type of exchangeable cations), muscovite, margarite, talc, vermiculite, phlogopite, xanthophyllite, chlorite, etc. layered aluminosilicate, Q-Naz
Si20g, β-NaiSigOs, KHSiJs,
NaH5izO@'3H20, NazSi4(1+'5
HzO1NazSiaO+ t ・xHzO1NazS
iz02s'XHJ% NatSiao04+・xH
2O, HllSiJg, HiSi40s-xHtO1
H*51sO+v・xHiO, HtSi+40*e'X
HtO, layered polysilicates such as HxSlia04+'XHxO, and various others.

The organic compound with a large residual carbon content to be inserted between the eyebrows of the layered structure material may be a thermoplastic polymer or a thermosetting polymer as long as it has a limiting oxygen index (LOI) of 18 or more, and the treatment method must be selected. For example, monomers or oligomers that produce polymers with an LOI of 18 or more can also be used.

Here, LOI will be briefly described. Some organic compounds produce carbides when heat treated at high temperatures under inert gas. When an organic compound that forms a carbide is heat-treated in an inert gas, the weight loss is generally large up to 500°C, and the weight loss gradually becomes smaller after 600°C. Although a very slight weight loss is observed at temperatures above 800°C, it is small compared to the change up to 600°C.

Therefore, it is defined as the percentage of residual carbon that produces carbides during heat treatment at 850° C. under an inert gas. This residual coal percentage is also related to the combustibility of organic compounds, and its relationship with the ultimate oxygen index method (LOI method), which is a test method for twisting resistance, is determined as follows. (Flame retardant polymers, written by Hitoshi Nishizawa, published by Taiseisha) LOI = 17.5 + 〇, 4xCR In the above formula, LOI is the oxygen concentration in the mixed gas of oxygen gas and nitrogen gas, and CR is the residual carbon percentage. The value is expressed in weight percent. That is, it is known that a compound having an LOI of 17.5 or more produces carbide when heat treated under an inert gas.

Examples of organic compounds that produce carbides by heat treatment under inert gas include natural polymers such as cellulose, polyurethane, methacrylic resin, polystyrene, nylon, polypropylene, polyacrylonitrile, polyvinyl chloride,
Examples include synthetic polymers such as fluororesins, polyesters, epoxy resins, phenol resins, melamine resins, urea resins, and furan resins, and aromatic polycyclic compounds such as tar and pitch. Moreover, if the processing method is selected, it is also possible to use a 100% oligomer that produces these polymers.

As a means of inserting an organic compound with a high residual carbon content between the eyebrows of an electrically insulating layered structure material such as a layered clay mineral, the electrically insulating layered structure material is immersed in a solution of the organic compound, or There are methods such as immersion in a monomer or oligomer that produces an organic compound and then polymerizing the monomer or oligomer.

Furthermore, if it is difficult to insert these organic compounds into the glabella of the layered clay mineral, they can be inserted in the form of inclusion in cyclodextrin or the like.

For the purpose of increasing the residual carbon ratio, a quaternary ammonium salt may coexist with the organic compound between the eyebrows. Examples of quaternary ammonium salts include alkyl quaternary ammonium salts such as alkyl-trimethylammonium chloride, alkyl-trimethylammonium bromide, alkyl-dimethyl-ethylammonium chloride, alkyl-dimethyl-ethylammonium bromide, and methyl-dodecyl-benzyltrimethylammonium chloride. salts (alkyl groups preferably have 10 to 18 carbon atoms), trimethyl-dodecyl-thiomethylammonium chloride, dimethyl-oxyethyldodecyl-thiomethylammonium chloride, methyl-diethyl-octyl-thioethylammonium iodide, trimethyl-dodecyl-thiomethylammonium chloride, Alkyl quaternary ammonium salts containing elements other than carbon such as decyl-methyl-aminoethyl ammonium bromide and dodecyl-methyl-aminoethyl-trimethylammonium iodide may also be used;
Dimethyl-benzylammonium chloride, alkyl-dimethyl-3,4-dichlorobenzylammonium chloride, dimethyl-phenyl-benzylammonium chloride, myrist-amide-propyl-dimethyl-
Alkyl-benzyl quaternary ammonium salts such as benzyl ammonium chloride, diisobutyl-phenoxy-ethoxyethyl-dimethyl-benzylammonium chloride, diisobutyl-flexoxy-ethoxy-ethyl-dimethyl-benzylammonium chloride (where the alkyl group has 10 to 18 carbon atoms) preferred), and also 1-hexadecyl-pyridinium chloride, lauryl-colamino-formyl-methyl-pyridinium chloride, 2
-dodecyl-in quinolinium bromide, 2-tridecyl-1-(2-hydroxyethyl)benzyl-imidazolinium chloride, dimethyl-tubocurarine chloride, and other quaternary ammoniums having a nitrogen ring, but are not limited to these. It's not something.

The multilayered composite particles obtained in this way exhibit an electrorheological effect due to the polarization of the particles themselves, which is not dependent on moisture, so by using the composite particles as a dispersed phase, power consumption is low at high temperatures, and the electrorheological effect is reduced. It is possible to obtain an electrorheological fluid that can maintain the viscosity for a long time.

The average particle size of the multilayered composite particles suitable as a dispersed phase of an electrorheological liquid is 0.01 to 100 microns, preferably 0.01 to 100 microns.
o, in the range of 3-5 microns.

If it is less than 1 micron, the initial viscosity in the absence of an electric field will be extremely large and the change in viscosity due to the electrorheological effect will be small, and if it exceeds 100 micron, sufficient stability as a dispersed phase of the electrorheological fluid will not be obtained.

Examples of the electrically insulating oil constituting the liquid phase include hydrocarbon oil, ester oil, aromatic oil, silicone oil, and phosphazene oil. These can be used alone or in combination of two or more. Among these electrical insulating oils, silicone oils such as polydimethylsiloxane and polymethylphenylsiloxane are superior in that they can be used in direct contact with materials with rubber-like elasticity, and phosphazene oils have a low specific gravity. Since it is relatively large, it has excellent anti-settling properties.

The viscosity of the electrical insulating oil is 0.65 to 500 centistokes (C5t) at 25°C, preferably 10 to 5 centistokes (C5t).
A material having a viscosity of 0 cSt is used. If the viscosity of the liquid phase is too low, the volatile content will increase and the viscosity change due to the electrorheological effect will be small.Also, by using electrical insulating oil with a moderately low viscosity as the liquid phase, the dispersed phase can be suspended efficiently. can.

The ratio of the dispersed phase and the liquid phase constituting the electrorheological fluid of the present invention is such that the content of the dispersed phase consisting of the multilayer composite particles is 1 to 1.
60% by weight, preferably 20 to 50% by weight, and the content of the liquid phase consisting of the electrical insulating oil is 40 to 99% by weight,
Preferably it is 50 to 80% by weight. When the amount of the dispersed phase is less than 1% by weight, the electrorheological effect is small, and when it exceeds 60% by weight, the initial viscosity in the absence of an electric field becomes significantly thick.

Furthermore, the electrorheological fluid of the present invention may contain other dispersed phases, surfactants, dispersants, inorganic salts, and other additives within a range that does not impair the effects of the present invention.

Hereinafter, the present invention will be explained in more detail with reference to Examples.

[Example 1] Montmorillonite-based layered clay mineral powder with an average particle size of 2.5 microns (5ilton LP-1 manufactured by Mizutame Kagaku Kogyo ■)
100 g of benzyldimethyltetradecylammonium chloride (manufactured by Tokyo Kasei Kogyo ■)
Add to l/l aqueous solution and leave for 24 hours, then filter, wash,
After drying, a quaternary ammonium salt compound powder was obtained.

Furthermore, 80 g of this powder was immersed in 500 ml of acrylonitrile (manufactured by Kanto Kagaku Kogyo ■) and left to stand at room temperature for 30 hours to insert acrylonitrile between the eyebrows. Thereafter, the mixture was heat-treated at 50° C. for 30 hours to polymerize the acrylonitrile between the layered clay mineral layers to form polyacrylonitrile. This was then filtered, washed and dried to obtain a quaternary ammonium salt/polyacrylonitrile intercalation compound powder. This powder was carbonized at 600° C. for 3 hours (heating rate: 5° C./min) in a nitrogen gas atmosphere to obtain a carbon/layered clay mineral multilayer structure composite powder. It was confirmed by X-ray diffraction measurements that this powder had a multilayer structure in which carbon was inserted between the eyebrows of a layered clay mineral. 25% by weight of this powder was mixed with silicone oil (manufactured by Toshiba Silicone ■), which is a liquid phase component and has a viscosity of 10 cSt at 25°C.
F-451-10) was well dispersed in 75% by weight to obtain an electrorheological fluid as a suspension.

[Example 2] A quaternary ammonium salt/polyacrylonitrile intercalation compound powder was obtained in the same manner as in Example 1. This powder was heat-treated in air at 220°C for 30 hours, and then heated in a nitrogen gas atmosphere for 6 hours.
A carbon/layered clay mineral multilayer structure composite powder was obtained by carbonization treatment at 00°C for 3 hours (heating rate: 5°C/min).

25% by weight of this powder was added to silicone oil (Toshiba Silicone ■ manufactured by Toshiba Silicone) with a viscosity of 10 cSt at 25°C as a liquid phase component.
SF-451-10) was well dispersed in 75% by weight to obtain an electrorheological fluid as a suspension.

The electrorheological effect of each electrorheological liquid obtained in Example 1.2 was measured. The electrorheological effect was measured using a double cylinder rotational viscometer, with a voltage of 0 to 2 kV/2 between the inner and outer cylinders.
Shearing rate 366 s when applying a DC voltage of m m
e c-', the shear force was evaluated at temperatures of 25°C and 100°C, and at the same time, the current flowing between the inner and outer cylinders was measured.

Table 1 shows shearing force To when no voltage is applied, voltage 2kV
The shear force T when /mm is applied, the difference T - To, and the current density when a voltage of 2 kV/mm is applied.

Table 1 Carbon/carbon obtained in Example 1.2 as shown in Table 1
Each electrorheological liquid containing a layered clay mineral laminated structure composite powder as a dispersed phase exhibits a stable electrorheological effect even at high temperatures (140° C.), and has low power consumption.

Even when compared to the value at 25° C., the electrorheological effect (T-TO) is large, and the power consumption (current density) is only slightly increased.

[Effects of the Invention] An electrorheological liquid that exhibits a large electrorheological effect at high temperatures and consumes less power can be obtained.

Claims (1)

[Claims] A conductive layer and an electrically insulating layer form a multilayer structure with an average grain size of 0
．． It is composed of a dispersed phase of 1 to 60% by weight of composite particles of 0.01 to 100 microns, and a liquid phase of 40 to 99% by weight of electrical insulating oil with a viscosity of 0.65 to 500 centistokes (cSt) at room temperature. Features of electrorheological fluid.