JPH0441715B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to electrorheological fluids.

Prior Art and Problems to be Solved by the Invention U.S. Patent No. 1 by Winslow
No. 2417850 describes finely divided solids,
For example, starch, limestone or its derivatives, gypsum, flour, gelatin or carbon can be added to non-conductive liquids, such as light transformer oils, transformer insulators,
Techniques have been disclosed in which certain suspensions dispersed in olive oil or mineral oil increase the flow resistance if a potential difference is applied to the suspension. This effect is sometimes called the Winslow effect. The increase in flow resistance caused by the application of an electric field was initially interpreted as an increase in viscosity, and materials exhibiting this effect were called "electrorheological fluids." However, subsequent research has shown that the increase in flow resistance is not only due to an increase in viscosity as in Newtonian fluids, but also due to Bingham plasticity induced by an applied electric field. Suspensions that exhibit such a Winslow effect have come to be called "electrorheological fluids."

Much research has been carried out to improve both the dispersed and continuous phases of electrorheological fluids (e.g. UK Patent No. 1501635, Equivalent No. 1570234, UK Patent Application No. 2100740A, Equivalent No.
2119392A and 2153372A).
However, the mechanism by which electrorheological phenomena occur has not been fully elucidated. The lack of understanding regarding this mechanism and especially the lack of quantitative theory to explain this phenomenon has hindered the development of improved electrorheological fluids.

All prior electrorheological fluids for practical use contain a small amount of water, which is believed to be primarily associated with the dispersed phase. If drying is strictly performed, electrorheological fluids do not exhibit sufficient electrorheological phenomena. However, from a practical point of view, the presence of water is undesirable. That is, the presence of water results in corrosion of the device, limitations in operating temperature, and significant power consumption (which in itself impairs the thermal stability of the device).

The present invention has been made to provide an electrorheological fluid that improves at least the above-mentioned problems.

Means for Solving the Problems According to the present invention, the present invention comprises a liquid continuous phase and at least one dispersed phase dispersed within the liquid continuous phase, and when at least the dispersed phase is substantially anhydrous. Electrorheological fluids are provided that behave as rheological fluids. Preferred electrorheological fluids are those that behave as electrorheological fluids when the fluid is substantially anhydrous.

As used herein, the term "anhydrous", with respect to a particular or each dispersed phase, means that after removal of the catalyst, the dispersed phase is dried under vacuum at 70° C. for 3 days to a constant weight; with respect to the continuous phase, the term "anhydrous" refers to means that the continuous phase is passed through an activated alumina column at an elevated temperature (for example, 70° C.) as desired.

Suitably, the electrorheological fluid according to the invention contains an electron conductor in its dispersed phase. Here, the term "electronic conductor" refers to a substance that conducts electricity using electrons or holes rather than ions. Examples of such conductors include semiconductors, particularly organic semiconductors, and organic semiconductors are preferred.
Here, "semiconductor" means an electrical conductivity of 10 ⁰ to 10 ^-11 mhocm ^-1 at ambient temperature, for example 10 ^-2 to
10 ^-10 mhocm ^-1 , typically 10 ^-4 to 10 ^-9 mhoicm ^-1
, meaning a substance with a positive temperature-conductivity coefficient.

Particularly preferred organic semiconductors include unsaturated condensed polycyclic system-containing substance systems such as violanthrone B. The unsaturated fused polycyclic system is preferably electron rich. Preferably, the unsaturated bonds have conjugated π bonds, in particular aromatic fused polycyclic systems which may contain at least one heteroatom, for example a nitrogen atom or an oxygen atom.

A group of such electron conductors suitable for use in the present invention includes organic semiconductors in which the fused polycyclic system comprises substituted or unsubstituted porphine or azaporphin systems, e.g. This includes organic semiconductors containing phthalocyanines such as. In such systems, the metal is suitably a transition metal. Here, the term "transition metal" refers to metals belonging to groups VA to V and IB of the periodic table, such as copper. The electrical conductivity of copper phthalocyanine at ambient temperature is about 10 ^-7 mhocm ^-1 .

The organic semiconductor may be a monomer, usually a crystalline monomer, or it may be a polymer.

Organic polymeric semiconductors useful in the present invention having phthalocyanine moieties can also be prepared using 1,2,4,5-benzenetetracarboxylic dianhydride in place of the phthalic anhydride used in conventional synthetic methods. good.

Another group of electron conductors that can be used in the present invention includes organic semiconductors in which fused polycyclic systems are included in poly(acene-quinone) polymers. Such polymers utilize Friedel-Crafts reactions to synthesize at least one substituted or unsubstituted acene, such as biphenyl, terphenyl, naphthalene, anthracene, phenanthrene, pyrene, chrysene, triphenylchloromethane, triphenylmethane, fluoranthene. , pericin, dibenzpyran and sanderutsch compounds such as picene or ferron with at least one substituted or unsubstituted polyacylated aromatic compound, such as a substituted or unsubstituted aromatic polycarboxylic acid or its precursor, such as 1,2,4 , 5-benzenetetracarboxylic dianhydride or acid chloride in the presence of an excess of a Lewis acid such as zinc chloride or aluminum chloride. The polymerylated compound preferably has pairs, preferably two pairs, of acyl groups or precursors thereof attached to the vicinal carbon atoms, each pair participating in ring formation in the Friedel-Crafts reaction. The electrical conductivity of poly(acene-quinone) polymers at ambient temperature is about 10 ^-8 to ^{10 -9} mhocm ^-1 .

Yet another group of organic semiconductors suitable for use in the present invention includes polymeric Schiff bases.
These may be prepared by methods analogous to those for the preparation of certain thermotropic polymers (see, for example, GB 1545106). Aniline black is also a polymer of this type and may be prepared by known methods, such as the oxidation of aqueous aniline hydrochloride with sodium chlorate.

Polymers of this type and further suitable organic semiconductors are disclosed in the following article by HA Pohl et al.; J. Phys. Chem., Vol. 66 ( 1962),
Pages 2085-2095. The electrical properties of all these materials may be modified by doping.

The continuous phase of the electrorheological fluid according to the invention can be any of the liquids mentioned above in this role.

Desirable properties of such liquids are as follows.

1. High boiling point and low freezing point such that the electrorheological fluid maintains its properties over a wide range of temperatures (ideally from below -40°C to at least 150°C and above) and low vapor pressure at standard operating temperatures.

2 low viscosity, such that the electrorheological fluid has a low no-fied viscosity;
Or low viscosities that allow higher amounts of solids to be included in electrorheological fluids without excessive no-field viscosity to enhance the Winslow effect.

3. High electrical resistance and high dielectric strength such that the electrorheological fluid conducts little current and can be used over a wide range of applied field strengths.

4 Generally 1.2 gcm ^-3 or more, typically 1.3 to 1.6 g
cm ^-3 high density (high density is preferred because the solid and liquid components of the electrorheological fluid have the same density to reduce precipitation during downtime).

5. Chemical stability to prevent degradation during storage and use, despite the presence of many potential catalytic surfaces provided by particles in electrorheological fluids that increase harmful decomposition products. sex.

It is clear that, in general, not all of these properties are possessed by a given liquid. However, these do not prevent the liquid from being used as the continuous phase of an electrorheological fluid. Therefore, even liquids with densities that are significantly different from the dispersed phase can become electrorheological fluids if the fluid is circulated when not in use to keep the dispersed phase in suspension. May be used for

Very suitable continuous phase materials include fluid hydrocarbons or our British Patent No. 1501635;
Examples include the fluid hydrocarbons disclosed in British Patent Application No. 1570234, British Patent Application No. 2100740A and British Patent Application No. 2153372A. Halogenated aromatic liquids are particularly preferred continuous phase materials.

Electrorheological fluids according to the present invention are prepared by comminution of the dispersed phase to the desired particle size and then mixing the comminutionated dispersed phase with the selected continuous phase. The content of the dispersed phase should be at least 15~15 for practical electrorheological fluids.
45% v/v, especially 25-35% v/v is preferred,
Even a small amount of 5% v/v or 1% v/v is effective.

According to the invention, when the fluid is substantially anhydrous,
An electrorheological fluid as described above is provided which develops a static yield stress of at least 0.5 Pa, suitably 0.5 kPa, such as 1 to 3 kPa, preferably 5 kPa or more under an applied electric field not exceeding 3 MVm ^-1 be done. Also according to the invention, when the fluid is substantially anhydrous, an electric current of a density not exceeding 400 Am ^-2 , preferably not exceeding 40 Am ^-2 is passed under an applied electric field not exceeding 1 MVm ^-1 . There is provided an electrorheological fluid as described above which can be used.

Although the present invention provides for the first time a practical anhydrous electrorheological fluid, it is possible to use electrorheological fluids such as those described above that contain small amounts of water in the fluid, typically not exceeding 1-5% v/v. It is also an aspect of the invention to provide a rheological fluid.

FIG. 1 is a side cross-sectional view of a yield point meter used to measure the change in static yield stress developed by electric field strength applied to an electrorheological fluid according to the present invention.

2 to 16 are graphs showing the relationship between electric field strength (horizontal axis) and yield stress or current density (vertical axis) obtained for the fluid according to the present invention.

In FIG. 1, a yield point meter 1 has a conductive receptacle 2 containing an electrorheological fluid 3 to be tested, which receptacle acts as a first electrode. The top of the receptacle has a glass rod 4 polished with silicone grease.
are arranged parallel and horizontally, and a second glass rod is installed on the glass rod.
An electrode 5 is slidably mounted. The gap between the two electrodes is 0.5 mm. The micromeasuring screw 6 is arranged to transmit the acting force to a third order lever 7, a part of which is arranged as a deflectable beam 8 between the second electrode and the pivot 9. This beam carries a strain gauge bridge 10, the strain of which is monitored by an associated recording device (not shown).

In use, the electrorheological fluid 3 to be measured is placed in the receptacle 2, and the second electrode 5 is placed on the glass rod 4, with the aforementioned gap provided for contact with the electrorheological fluid. The beam 8 is then actuated by rotating the side screw 6, causing the second electrode to move along the rod and thus through the fluid. Frictional drag causes deflection of the beam prior to slip.
This maximum deflection is recorded graphically and peak x ₀
is proportional to the frictional resistance of the device. Two electrodes 2 and 5 are connected to a 2kV unidirectional variable power supply and an ammeter 1.
5 (not shown) for direct current connection. This operation is repeated for a series of applied electric field strengths. The peak x recorded is proportional to the frictional resistance and the static yield stress developed in the fluid. (x-
The plot of x ₀ ) is a measure of the dependence of the developed static yield stress on the applied electric field strength.

Absolute values may be obtained by calibrating a yield point meter. This operation is carried out by applying a series of different loads, for example a weight W, to apply a force to the second electrode 5 without changing the side fine screws. The area of the second electrode is 4
×10 ⁻⁴ m ² , so the yield stress x can be quantified from the quotient of load/area.

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

EXAMPLE 1 A series of electrorheological fluids according to the invention were mixed with different amounts of copper phthalocyanine (commercially available from Eastman Kodak; dried at 50° C. for 72 hours) or metal-free phthalocyanine (I.C. commercially available from ICI plc]
Paraffin oil and paraffin glue (commercial product from BDH Chemicals Ltd.) were dried by passing through an alumina column (commercial product from Woelm Phama) at 70°C. ) (viscosity at ambient temperature: approximately 50 cs). These fluids were tested using the yield point meter described above. Second test result
As shown in FIGS.

Figure 2 is a graph showing the change in developed static yield strength (kPa) (vertical axis) with applied electric field strength (MVm ^-1 ) (horizontal axis) for a 15% v/v copper phthalocyanine suspension. be.

Figure 3 is a graph showing the change in developed static yield strength (kPa) (vertical axis) with applied electric field strength (MVm ^-1 ) (horizontal axis) for a 22% v/v copper phthalocyanine suspension. be.

Figure 4 shows the concentration of copper phthalocyanine suspension at 25%.
v/v (▲), 15% v/v (○) or 8% v/v
It is a graph showing the change in the developed static yield strength (kPa) (vertical axis) depending on the square of the applied electric field strength (MVm ^-1 ) ² (horizontal axis) for the case (●).

FIG. 5 is a graph showing the relationship between current density (Am ⁻² ) (vertical axis) and applied electric field strength (MVm ⁻¹ ) (horizontal axis) for the fluid related to FIG. 2.

Figure 6 shows the change in developed static yield strength (kPa) (vertical axis) with applied electric field strength (MVm ^-1 ) (horizontal axis) for a 7% v/v metal-free phthalocyanine suspension. It is a graph.

Example 2 This example relates to the preparation of a series of poly(acene-quinones) and their formulation and testing as electrorheological fluids according to the present invention.

Equimolar amounts of 1,2,4,5-benzenetetracarboxylic dianhydride (commercially available from Aldrich Chemicals Co. Ltd.) and aromatic acene (Hopkin and Williams Ltd.) )] or pyrene, available from Aldrich Chemicals, Inc., are ground and mixed in a mortar. 2 moles of zinc chloride (commercially available from BDH Chemicals) per mole of the dianhydride.
was added to the mixture as a catalyst, and the mixture was then transferred into a Pyrex tube (PYREX is a registered trademark) and placed in a constant temperature bath.
Heated at 300°C for 24 hours. Experiments by Paul et al. (see above) have shown that the presence or absence of oxygen in the reaction vessel has little effect on the conductivity of the resulting polymer; therefore, this series of polymer adjustments was In this case, only a stopper was attached to the Pyrex pipe.

After heating, the obtained polymer was collected by filtration and ground into a fine powder. This powder was subjected to a leaching treatment using 2N hydrochloric acid for 24 hours to supplement the removal of zinc chloride.
After leaching, the powder was extracted with distilled deionized water using a Soxhlet extractor for 24 hours, then extracted with ethanol (May and Baker).
Ltd. (commercial product) for 24 hours and benzene (May & Baker, commercial product) for 72 hours.

Poly(acene-quinone) in a vacuum oven for 50 min.
Dry at ℃ for 72 hours. The dried black polymer was finely ground using a micronising mill and stored in a desiccator.

The densities of poly(pyrene-quinone) and poly(naphthalene-quinone) are 1.51 g cm ^-3 and
It was 1.50 gcm ^-3 . in a 3:1 mixture of paraffin oil and paraffin grease with a viscosity that allows the preparation of a stable polymer dispersion.
Each polymer was dispersed at different volume fractions as described below. Additionally, polychlorinated hydrocarbons (IC) were added to each polymer at different volume fractions as described below.
A stable polymer dispersion was prepared by dispersing it in CERECLOR 50 LV, a commercially available product from Eye Corporation. Stable polymer dispersions were prepared by further dispersing each polymer in different volume fractions in silicone oil (DC 550, commercially available from Hopkin & Williams).

These dispersions are electrorheological fluids according to the invention and were tested using the yield point meter described above. The results of the test are shown in FIGS. 7 to 16.

Figure 7 shows 17% v/v of poly(pyrene-quinone)
Applied electric field strength (MVm ^-1 ) of developed static yield strength (kPa) (vertical axis) for paraffin suspension
(horizontal axis).

Figures 8, 9 and 10 show the concentration of poly(pyrene-quinone) in the paraffin suspension, respectively.
Changes in the developed static yield strength (kPa) (vertical axis) depending on the applied electric field strength (MVm ^-1 ) (horizontal axis) in the cases of 21% v/v, 33% v/v and 40% v/v are shown below. This is a graph showing.

Figure 11 shows 30%v/poly(pyrene-quinone)
3 is a graph showing the change in the developed static yield strength (kPa) (vertical axis) depending on the applied electric field strength (MVm ⁻¹ ) (horizontal axis) for the v silicone oil suspension.

Figure 12 shows 40%v/poly(pyrene-quinone)
5 is a graph showing the change in the developed static yield strength (kPa) (vertical axis) depending on the applied electric field strength (MVm ⁻¹ ) (horizontal axis) for a polychlorinated hydrocarbon suspension.

Figures 13 and 14 show the concentration of poly(naphthalene-quinone) in the paraffin suspension, respectively.
It is a graph showing changes in the developed static yield strength (kPa) (vertical axis) depending on the applied electric field strength (MVm ⁻¹ ) (horizontal axis) in the cases of 30% v/v and 38% v/v.

Figure 15 shows 40% of poly(naphthalene-quinone)
It is a graph showing a change in the developed static yield strength (kPa) (vertical axis) depending on the applied field pressure intensity (MVm ⁻¹ ) (horizontal axis) for a v/v polychlorinated hydrocarbon suspension.

FIG. 16 shows the fluid related to FIG. 15.
It is a graph showing the relationship between current density (Am ⁻² ) (vertical axis) and applied electric field strength (MVm ⁻¹ ).

In each of the above cases, the yield stress was expressed in the absence of water. The yield stress developed from chlorinated hydrocarbon dispersions of poly(acene-quinone) in chlorinated hydrocarbons was particularly pronounced.

[Brief explanation of drawings]

FIG. 1 is a side cross-sectional view of a yield point meter used to measure the change in static yield stress developed by electric field strength applied to an electrorheological fluid according to the present invention. 2 to 16 are graphs showing the relationship between electric field strength (horizontal axis) and yield stress or current density (vertical axis) obtained for the fluid according to the present invention. 1 is a yield point meter, 2 is a conductive receptacle, 3 is an electrorheological fluid, 4 is a glass rod, 5 is a second electrode, 6 is a micrometer screw, 7 is a third order lever, 8 is a beam, and 9 is a pivot. .

Claims (1)

[Scope of Claims] 1. The liquid continuous phase contains at least one semiconductor having an electrical conductivity of 10 ⁰ to 10 ^-11 mhocm ^-1 at ambient temperature as a dispersed phase, and the dispersed phase is substantially anhydrous. An electrorheological fluid that behaves as an electrorheological fluid even in . 2. The electrorheological fluid of claim 1, which behaves as an electrorheological fluid when the fluid is substantially anhydrous. 3. The first semiconductor in which the semiconductor contains an unsaturated fused polycyclic system
Electrorheological fluids as described in Section. 4 The third type in which the unsaturated fused polycyclic system is electron rich
Electrorheological fluids as described in Section. 5. The electrorheological fluid according to item 3 or 4, wherein the unsaturated fused polycyclic system is an aromatic fused polycyclic system. 6 Items 3 to 5 where the organic semiconductor is a polymer
The electrorheological fluid according to any one of paragraphs. 7. The electrorheological fluid of claim 6, wherein the organic semiconductor is a poly(acene-quinone) polymer. 8 Poly(acene-quinone) polymers are prepared by reacting at least one substituted or unsubstituted acene and at least one substituted or unsubstituted polyacylated aromatic compound under Friedel-Crafts acylation conditions. 8. The electrorheological fluid of claim 7, wherein the electrorheological fluid is a polyester-derived polymer. 9 The first phase in which the continuous phase contains a halogenated aromatic substance
The electrorheological fluid according to any one of items 8 to 8. 10 The content of the dispersed phase in the continuous phase is 15 to 40% v/
The electrorheological fluid according to any one of clauses 1 to 9, wherein v. 11. An electrorheological fluid according to any one of clauses 1 to 10, which develops a static yield stress of at least 0.5 kPa under an applied electric field of not more than 3 MVm ^-1 when the fluid is substantially anhydrous. 12. An electrorheological fluid according to any one of clauses 1 to 11, which conducts an electric current with a density not exceeding 400 Am ^-2 under an applied electric field not exceeding 1 MVm ^-1 when the fluid is substantially anhydrous. 13. The electrorheological fluid according to any one of items 1 to 12, which contains water. 14. The electrorheological fluid according to clause 13, wherein the water content in the fluid does not exceed 5% v/v.