JPH11349973A - Electroviscous fluid - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an electroviscous fluid having both high electroviscous effect and dielectric breakdown strength. SOLUTION: This electroviscous fluid is obtained by deaeration of a composition comprising carbonaceous powder of spherical particles, insulating oil and modified silicone oil; wherein the carbonaceous powder is obtained using, as raw materials, a solvent and a condensate prepared substantially through methylene-type linkage of an aromatic sulfonic acid or a salt thereof, and it is preferable that the spherical shape of the carbonaceous powder particles is such that the deviations of the maximum diameter and minimum diameter from the average diameter lie within 30% of the average diameter, and the average particle size of the carbonaceous powder is 0.1-20 μm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a powder for electrorheological fluid, and more particularly, to a high performance ER (Electro Rheological) such as a shock absorber, a clutch, and a damper for a large device used for moving equipment and firearms.
The present invention relates to an electrorheological fluid having a high dielectric strength (hereinafter, may be referred to as “withstand voltage”) that can be used for a device.

[0002]

2. Description of the Related Art An electrorheological fluid is a fluid whose viscoelastic properties are large by electrical control and can be reversibly changed. The phenomenon that the apparent viscosity of a fluid changes greatly by the application of an electric field is a Winslow effect. It has been known for a long time, and its application as a component for electrically controlling devices and components such as clutches, valves, engine mounts, actuators, and robot arms has been studied. However, the initial electrorheological fluid is obtained by dispersing powder such as starch in mineral oil or lubricating oil, and has a drawback that although the electrorheological effect is exhibited, reproducibility is poor.

[0003] For this reason, many proposals have been made, mainly for powders used as dispersoids, for the purpose of obtaining a fluid having a high electrorheological effect and excellent reproducibility. For example, JP-A-53-93186 discloses a superabsorbent resin having an acid group such as polyacrylic acid, JP-B-60-31211 discloses an ion-exchange resin, and JP-A-62-95397 describes an alumina silicate. Is described. These are all hydrophilic solid powders, which are hydrated and dispersed in an insulating oily medium, and constitute a powder by the action of water when a high voltage is applied from the outside. It is said that the particles are polarized and the polarization increases crosslinks between the particles in the direction of the electric field, thereby increasing the viscosity.

However, a hydrous electrorheological fluid using the above-mentioned hydrous powder cannot obtain a sufficient electrorheological effect in a wide temperature range, and limits the use temperature to prevent evaporation or freezing of water, and raises the temperature. Therefore, there have been many problems such as an increase in use current, instability due to transfer of moisture, and corrosion of the electrode metal when a high voltage is applied.

[0005] In order to improve this problem, a non-aqueous electrorheological fluid using no water-containing particles has been proposed. For example,
JP-A-61-216202 discloses that organic semiconductor particles such as polyacenequinone are formed. JP-A-63-97694 and JP-A-1-164823 form a conductive thin film on the surface of organic or inorganic solid particles. Further, there is described a dielectric particle having an electrically insulating thin film formed thereon, that is, a thin film-coated composite particle which essentially requires a thin film having conductive / insulating electrical characteristics. Further, surface-treated metal particles, metal-coated inorganic powder, and the like are known as dispersoid powders having controlled electric characteristics. However, non-aqueous electrorheological fluids using these powders do not provide sufficient electrorheological effects at low power consumption, and are difficult to industrially manufacture, and function only in an AC electric field. However, it has not been put to practical use yet.

In order to further improve the electrorheological effect of a non-aqueous electrorheological fluid with low power consumption, it is necessary to increase the filling rate of the dispersoid powder. Thus, there is a problem in that the initial viscosity of the fluid is improved, and as a result, the electrorheological effect at the time of applying a current is reduced.

As a method for solving this problem, Japanese Patent Laid-Open No.
Japanese Patent Application No. -90287 proposes an electrorheological fluid using a carbonaceous powder having a truly spherical shape. As described above, it is advantageous to use a uniform and spherical carbonaceous powder as the powder for the electrorheological fluid. However, when the electrorheological fluid is applied to an engine mount, an actuator, a clutch, or the like, the vibration may be reduced. Insufficient durability due to the strength of the powder has been a problem, for example, the powder is destroyed by the load of shearing stress and the viscosity in an electric field-free state increases.

[0008]

In order to solve the above-mentioned problems, the present inventors have conducted intensive studies, and have found that a condensate of aromatic sulfonic acid or a salt thereof due to a methylene type bond and a solvent are substantially used. An electrorheological fluid using a carbonaceous powder having a true spherical shape (hereinafter, may be simply referred to as “spherical carbonaceous powder”) obtained as (1) is found.
-81889). This electrorheological fluid exhibits high electrorheological effects with low power consumption over a wide temperature range,
In addition, the powder for electrorheological fluid was high in strength, hardly broken by stress load, and excellent in durability. On the other hand, high-performance ERs (Els) such as shock absorbers, clutches and dampers for large equipment used for mobile equipment and firearms
In order to apply an electrorheological fluid to an electrorheological device, it is essential to exhibit a higher electrorheological effect. However, simply using ordinary silicone oil as a dispersion medium for these electrorheological fluids has a high dielectric breakdown strength but an insufficient electrorheological effect. That is, an object of the present invention is to provide an electrorheological fluid having a high electrorheological effect and a dielectric breakdown strength.

[0009]

Means for solving the above problems are as follows. That is, <1> substantially spherical carbonaceous powder obtained from a condensate of an aromatic sulfonic acid or a salt thereof by a methylene-type bond and a solvent, an electric insulating oil, and a modified silicone An electrorheological fluid containing oil and obtained by performing a deaeration process.

<2> In the true spherical shape, deviations of the maximum diameter and the minimum diameter of the carbonaceous powder from the average diameter are each within 30% of the average diameter, and the average particle diameter of the carbonaceous powder is Is 0.1 to 20 μm, the electrorheological fluid according to <1> above.

<3> The electrorheological fluid according to <1>, wherein the kinetic viscosity of the electric insulating oil at 25 ° C. is 1 to 100 mm ² / s.

<4> The modified silicone oil is one or more modified silicone oils selected from an amino-modified silicone oil, a polyether-modified silicone oil, an alkoxy-modified silicone oil, or an epoxy-modified silicone oil, or a composite modified thereof. The electrorheological fluid according to <1>, wherein the fluid is silicone oil.

<5> The modified silicone oil is 0.01 to
<1> or <4>, which is contained in an amount of 5% by weight.
<3> The electrorheological fluid described in (1).

<6> The electrorheological fluid according to any one of <1> to <5>, which has a dielectric breakdown strength of 4.0 kV / mm or more.

<7> The electrorheological fluid according to any one of <1> to <6>, wherein bubbles are not generated under a reduced pressure environment of 10 Pa.

The present invention is characterized in that a modified silicone oil is added to a mixture of a spherical carbonaceous powder as a dispersoid and an electric insulating oil as a dispersion medium, and deaeration is performed. Thereby, an electrorheological fluid having a high electrorheological effect and a dielectric breakdown strength can be obtained. The electrorheological fluid of the present invention is improved in dispersion of dispersoids (powder particles) by adding a modified silicone oil, and greatly reduces the viscosity at the time of no electric field,
It is presumed that the electro-rheological effect is also improved, and by performing degassing treatment, air that is dissolved in the electro-rheological fluid can be removed when the modified silicone oil is added, so that the dielectric breakdown strength is improved. .

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION The electrorheological fluid of the present invention has a true spherical shape obtained by using a condensate of aromatic sulfonic acid or a salt thereof by a methylene type bond as a dispersoid and a solvent as raw materials. It contains carbonaceous powder, electric insulating oil as a dispersion medium, and further modified silicone oil, and is obtained by performing degassing treatment.

[0018] The carbonaceous powder in the form of a perfect sphere obtained from a condensate of a substantially aromatic sulfonic acid or a salt thereof, which is a dispersoid of the electrorheological fluid of the present invention, by a methylene-type bond and a solvent as raw materials. Will be described in detail including raw materials, production methods, and the like.

The aromatic sulfonic acids or salts thereof include polycyclic aromatic compounds such as naphthalene sulfonic acid, methyl naphthalene sulfonic acid, anthracene sulfonic acid, phenanthrene sulfonic acid, creosote oil, anthracene oil, tar, and bitch. A mixture obtained by sulfonating the mixture or a salt thereof can be exemplified. These sulfonic acids can be easily produced by sulfonating the corresponding aromatic compounds by a known method.
NH ₄ is used as a cation constituting the aromatic sulfonate.
⁺ Can be exemplified, but a trace amount of an alkali metal such as Na ⁺ , C
Alkaline earth metal ions such as a ²⁺ can also be mixed.

The condensate of the aromatic sulfones or salts thereof can be easily produced by a known method. That is, generally, aromatic sulfonic acids or salts thereof are condensed using formalin, paraformaldehyde, hexamethylenetetramine, or other aldehydes. Moreover, it is obtained by polymerizing an aromatic sulfone salt having a vinyl group such as polystyrene sulfonic acid. A polymer of aromatic sulfonic acids having a methylene type bond may be used. As a linking group for bonding aromatic sulfonic acids, a —CH ₂ — group is particularly preferable in view of simplicity of production and availability. _{However, - (CH 2) n -T} x - (CHR-) m - ( However, T
Represents a benzene ring or a naphthalene ring, R represents hydrogen, a lower alkyl group or a benzene ring, and n, m and x each represent an integer of 0 or 1. A compound having a linking group represented by ()) can also be used. These condensates may be a mixture of two or more condensates or a copolymer.

As an example of the condensate of the aromatic sulfonic acids or salts thereof, there is specifically mentioned a formaldehyde condensate of ammonium β-naphthalenesulfonate. This condensate is a mixture consisting of a condensate from a monomer to a 200-mer, and has an average molecular weight of 2,000 to
It is about 5,000. It is a solid at room temperature and hardly dissolves in non-polar solvents such as benzene, but it dissolves in low concentrations in polar organic solvents such as acetone and acetonitrile, and is easily soluble in aqueous solvents. The viscosity of the 40% by weight aqueous solution at 20 ° C. is several tens to several hundreds mPa.
It is about s, but it can be formed into a spherical shape by changing the degree of condensation of the condensate, the concentration of the solution and the like to adjust the viscosity appropriately.

As a molding aid for forming into a spherical shape,
Polymer compounds soluble or colloidally dispersible in various types of water or aqueous solvents can be used.
Polyalkylene oxide compounds such as condensates such as propylene oxide or condensates thereof with various alcohols, fatty acids, alkylamines, and alkylphenols;
Polyvinyl alcohol, polyvinyl compounds such as polyvinylpyrrolidone, polyacrylic acid, polyacrylamide,
A water-soluble polymer compound such as a polyacrylic acid compound such as acrylic acid-acrylamide copolymer can be used, and its molding can be facilitated by using a surfactant or an antifoaming agent for lowering the surface tension. it can. Alternatively, a formaldehyde condensate of ammonium β-naphthalenesulfonate may be dried and then crushed to adjust the viscosity to an appropriate value. Further, the aromatic sulfonic acids used in the present invention, or polystyrene sulfonic acids, which are a kind of condensate of their salts, can be used as the water-soluble polymer mentioned herein.

The method for forming the condensate of the aromatic sulfonic acids or salts thereof into microspheres is not particularly limited. For example, after dissolving the condensates of the aromatic sulfonic acids or salts thereof in a solvent, spray drying is performed. It can be formed into microspheres by a known method such as a precipitation method or a precipitation method in which an antisolvent is added. Among these molding methods, the spray-drying method is characterized in that the particle size of the obtained particles can be reduced, the shape is truly spherical, and the aromatic sulfone of the present invention is used from the viewpoints of simpler production equipment. It is suitable as a method for forming a condensate of an acid or a salt thereof into microspheres. Suitable solvents used in these methods include water; alcohols such as methanol; and polar solvents such as acetonitrile. In particular, water or an aqueous solvent obtained by mixing water with another water-soluble solvent is preferable. It is suitable from the viewpoint of. Further, the presence of non-sulfonated aromatic condensate derived from the raw material of the aromatic sulfonate makes the resulting carbonaceous powder non-uniform, but since this condensate is hardly soluble in water,
Using an aqueous solvent also has the advantage that these impurities can be easily removed.

The true spherical carbonaceous powder is a carbonaceous powder having a true spherical shape. In the present invention, the true spherical shape means that the powder particles observed with an electron microscope have a true spherical shape. The deviation of the maximum diameter and the minimum diameter of one powder particle from the average diameter is preferably within 30% of the average diameter, more preferably 2%.
It is within 0%. Further, when it is assumed that the powder particles have an ideally smooth true spherical shape, irregularities that are deviations from the surface thereof are preferably within 10% of the average diameter,
More preferably, it is within 5% of the average diameter. Most preferably, the deviation of the maximum diameter and the minimum diameter of the powder particles from the average diameter is each within 10% of the average diameter,
In addition, irregularities, which are deviations from the ideal spherical surface, are powder particles within 3% of the average diameter. Here, the average diameter of one powder particle means the average value of the maximum diameter and the minimum diameter of the powder particle.

The spherical carbonaceous powder preferably has a carbon content of 80 to 97% by weight, particularly preferably 85 to 95% by weight. The C / H ratio (carbon / hydrogen atom ratio) of the carbonaceous powder is preferably from 1.2 to 5, particularly preferably from 2 to 4.

Generally, it has long been known that the electric resistance of a dispersoid of an electrorheological fluid is in the semiconductor region [W.
M. Winslow: J. Appl. Physics
20, 1137 (1949)], a carbonaceous powder having a carbon content of less than 80% by weight and a C / H ratio of less than 1.2 is an insulator and exhibits an electrorheological effect. Little liquid is obtained. On the other hand, the carbon content exceeds 97% by weight,
Further, those having a C / H ratio of more than 5 are close to conductors, exhibit an excessive current even when a voltage is applied, and a fluid exhibiting an electrorheological effect cannot be obtained.

As a method for producing the spherical carbonaceous powder, a condensate of an aromatic sulfonic acid or a salt thereof formed into the microspheres is formed into a spherical form under an inert gas atmosphere such as nitrogen or argon. A method of carbonizing by heat treatment so as to maintain the shape is generally used.

The carbonization conditions depend on the desired powder properties and the type of the carbonaceous powder to be used as a raw material, but are usually in an inert gas atmosphere, for example, in a temperature range of 450 to 550 ° C. for 2 to 5 hours. The degree of carbonization is preferable. The inert gas is not particularly limited, but usually, for example, nitrogen gas and rare gases such as argon, helium, and xenon are used, and nitrogen gas and argon gas are preferable from the viewpoint of easy availability.

The heat treatment temperature in the carbonization step is 40
It is necessary to be in the range of 0 to 600 ° C., particularly 45 ° C.
The temperature is preferably 0 to 550 ° C., and this heat treatment may be performed twice or more. At a temperature of 400 ° C. or less, a large amount of impurities such as S, O, and N remain in the obtained carbonaceous powder, so that it is difficult to obtain sufficient electrorheological characteristics. Further, the powder treated at a temperature of 600 ° C. or more has a low electric resistance, and an excessive current flows, so that the power consumption becomes large. .

When carbonizing a condensate of an ammonium salt of an aromatic sulfonic acid, elimination of a sulfite group and an ammonium group is mainly carried out in the range of 250 to 350 ° C. In order to prevent the strength from decreasing, it is preferable to gradually increase the temperature in a temperature range of 250 to 350 ° C. or to provide a holding time in this temperature range.

When heat-treating a condensate of an aromatic sulfonic acid or a salt thereof, a sulfurous acid gas generated by thermal decomposition,
Since water vapor, lower hydrocarbons, hydrogen sulfide, hydrogen, and ammonia gas generated in the case of ammonium salts contain impurities, it is preferable to purge with the inert gas.

The average particle diameter of the spherical carbonaceous powder can be determined by using a particle diameter measuring device (for example, MIC) as described in Examples.
ROTRAC SPA / MK-II type, manufactured by Nikkiso Co., Ltd.). The average particle size of the spherical carbonaceous powder obtained after the carbonization treatment is about 0.1 to 20.
μm is preferred, and more preferably 0.5 to 15 μm. If it is less than 0.1 μm, the initial viscosity of the obtained electrorheological fluid increases, and if it exceeds 20 μm, the dispersion stability of the powder deteriorates, and both are not preferred.

The spherical carbonaceous powder has a crushing strength of 5 k.
gf / mm ² or more, and the maximum displacement is preferably 3% or more. These can be measured using a micro compression tester (for example, MCTM series, manufactured by Shimadzu Corporation) or the like which can measure the strength of each particle.
If the crushing strength is less than 5 kgf / mm ² , the strength against breaking of the particles is insufficient, and the durability when a shear force is repeatedly applied to a damper or the like is reduced. A preferable range of the crushing strength is 10 kgf / mm ² or more.

The spherical carbonaceous powder has an ash content of 0.1%.
The following is preferred. If the ash content exceeds 0.1%, impurities increase, and the electrorheological properties are impaired. Ash content can be measured by a conventional method.

The electrorheological fluid of the present invention can be obtained by dispersing the spherical carbonaceous powder obtained as described above in an electric insulating oil having a relative dielectric constant of 3 or more.

The content of the spherical carbonaceous powder as a dispersoid in the electrorheological fluid is preferably about 1 to 60% by weight, more preferably 20 to 50% by weight. When the content is less than 1% by weight, the electrorheological effect is small, and when the content is more than 60% by weight, the initial viscosity when no voltage is applied becomes high, which is not preferable.

The electric insulating oil which is a dispersion medium of the electrorheological fluid of the present invention will be described in detail.

As the electric insulating oil, a conventionally known electric insulating oil such as silicone oil can be used.
Examples include hydrocarbon oils, ester oils, aromatic oils, silicone oils, and the like.Specifically, aliphatic monocarboxylic acids such as neocapric acid, aromatic monocarboxylic acids such as benzoic acid,
Examples include aliphatic dicarboxylic acids such as adipic acid, glutaric acid, sebacic acid, and azelaic acid; aromatic dicarboxylic acids such as phthalic acid, isophthalic acid, and tetrahydrophthalic acid; and mixtures and copolymers thereof. Commercially available “TSF451-5” and “TSF4” manufactured by Toshiba Silicone Co., Ltd.
51-10 "," TSF451-20 "," TSF45
1-50 "can also be used. These may be used alone or in combination of two or more.

The above-mentioned electric insulating oil preferably has a volume resistivity at 80 ° C. of 10 ¹¹ Ω · cm or more, particularly preferably 10 ¹³ Ω · cm.
Ω · cm or more is preferable.

[0040] The electrical insulating oil, 1 to 100 mm ² / s viscosity thereof at 25 ° C., preferably 1 to 50 mm ²
/ S, more preferably 1 to ²⁰ mm ² / s. By using a dispersion medium having a suitable viscosity, powder as a dispersoid can be efficiently and stably dispersed. When the viscosity of the electric insulating oil exceeds 100 mm ² / s, the initial viscosity of the electrorheological fluid increases, and the viscosity change due to the electrorheological effect decreases. On the other hand, if it is less than 1 mm ² / s, it is easy to volatilize, and the stability of the dispersion medium deteriorates.

The content of the electric insulating oil as a dispersion medium is as follows:
In an electrorheological fluid, about 99 to 40% by weight is preferable,
0-50% by weight is more preferred. When the content is less than 1% by weight, the electrorheological effect tends to be small, and the content is 60% by weight.
If it exceeds, the initial viscosity when no voltage is applied tends to increase, which is not preferable.

The modified silicone oil used in the electrorheological fluid of the present invention will be described in detail.

The modified silicone oil is not particularly limited, and includes a modified silicone oil represented by the following general formula (1). Specifically, the modified silicone oil is represented by the general formula (1) shown in Table 1 below. Amino-modified silicone oil, polyether-modified silicone oil, fluorine-modified silicone oil, phenol-modified silicone oil, carbino-modified silicone oil, methacryl-modified silicone oil having a combination of A and B in
Examples thereof include an alkoxy-modified silicone oil, an epoxy-modified silicone oil, and a composite-modified silicone oil thereof.
The modified silicone oils may be used alone or in combination of two or more.

[0044]

Embedded image

[0045]

[Table 1]

In Table 1, R ₁ and R ₂ represent a hydrogen atom, a saturated hydrocarbon group, a hydrocarbon group containing an alicyclic group, or a hydrocarbon group containing an aromatic group. Q ₁ and Q ₂ represent an alkylene group. a represents 0 to 50. b represents 0 to 50. In the case of an amino-modified silicone oil, R ₁ is particularly preferably a methyl group.

Preferably, the modified silicone oil is
One or more modified silicone oils selected from amino-modified silicone oils, polyether-modified silicone oils, alkoxy-modified silicone oils, or epoxy-modified silicone oils, and composite modified silicone oils thereof.

Since these various modified silicone oils have an affinity for silicone oil, the modified silicone oil acts as a surfactant and improves the dispersibility of the spherical carbonaceous powder which is a dispersoid. Precipitation of the spherical carbonaceous powder can be prevented, redispersibility can be improved, and the initial viscosity of the liquid can be reduced.

The content of the modified silicone oil in the electrorheological fluid is preferably about 0.01 to 5% by weight.
1 to 3% by weight is more preferred, and 0.01 to 2% by weight is even more preferred. If the content is less than 0.01, the effect of addition is insufficient, and if it exceeds 5, the apparent viscosity upon application of a voltage becomes unstable, and both are not preferred.

The electrorheological fluid of the present invention can obtain a dielectric breakdown strength of 4.0 kV / mm or more by degassing the above material. The deaeration process is performed to prevent air or a gas (nitrogen, oxygen, argon, or the like) constituting the air from being mixed into the electrorheological fluid. A specific method will be described in a manufacturing method described later. The degree of mixing of the gas into the electrorheological fluid is confirmed by first checking the presence or absence of foaming when the electrorheological fluid is placed under a reduced pressure of 10 Pa. As a result, if foaming does not occur, it indicates that almost no gas component is contained in the flowing electrorheological fluid, and if the amount of gas does not generate bubbles in this state, mixing of gas decreases the dielectric breakdown strength. Is not considered to be involved. Therefore, in the present invention, it is preferable to perform the deaeration under the reduced pressure of 10 Pa to the extent that bubbles are not generated.

On the other hand, the problem with gas incorporation is that only gases having physical properties that cause a discharge when a high voltage is applied when they are present in a bubble state are mixed. There is no problem if you do. More specifically, in the electrorheological fluid of the present invention, 20% by volume or more of the gas contained in the electric insulating oil is a gas having a relatively large molecular weight and a high dielectric breakdown strength, in other words, electron withdrawing. High capacity, 4.0kV dielectric breakdown strength
If the gas is not less than / mm, lowering of the dielectric breakdown strength of the electrorheological fluid hardly occurs. The breakdown strength of the gas can be measured by an ordinary method, for example, by using a viscoelasticity measuring device, a high-voltage power supply, or the like.

Specifically, these gases which do not lower the withstand voltage, that is, gases having a dielectric breakdown strength of 4.0 kV / mm or more, include SF ₆ (having a halogen atom, a cyano group and a sulfone group in the molecule). Electronegativity, hereinafter, described in parentheses: 6.6 kV / mm), CCl ₂ F ₂ (6.4 kV)
/ Mm), C ₃ F ₈ (5.8 kV / mm), C ₂ F
₆ (4.8 kV / mm), C ₅ F ₈ (14.5 kV / m)
m), CF ₃ CN (9.2 kV / mm), C ₂ F ₅ CN
(11.9 kV / mm), Cl ₂ (4.1 kV / m
m), SOF ₂ (6.6 kV / mm), C ₂ ClF
₅ (6.0 kV / mm), ClO ₃ F (7.2 kV / m)
m) and the like.

Next, a method for producing an electrorheological fluid of the present invention will be described. The electrorheological fluid of the present invention is produced by degassing a spherical carbonaceous powder, an electric insulating oil and a modified silicone oil. The deaeration treatment is not particularly limited as long as air or a gas constituting the air (nitrogen, oxygen, argon, or the like) can be prevented from being mixed into the electrorheological fluid. After the electric insulating oil and the modified silicone oil are stirred and mixed under normal pressure, degassing is performed by stirring under reduced pressure, but the carbonaceous powder on a sphere, the electric insulating oil, and the modified silicone oil are mixed under reduced pressure. A deaeration treatment may be performed by stirring and mixing at. Either method can prevent gas from being mixed into the electrorheological fluid, and the withstand voltage of the electrorheological fluid is significantly improved.

In the present invention, under reduced pressure means 10 kPa
(About 0.1 atm) or less, preferably 1000 Pa or less, more preferably 100 Pa or less. Specifically, it is preferable to use a closed system and reduce the pressure with a vacuum pump or the like.

On the other hand, when depressurizing and degassing the electrorheological fluid produced at normal pressure, a mixture obtained by stirring and mixing the spherical carbonaceous powder, the electric insulating oil and the modified silicone oil is mixed under reduced pressure. It is arranged and degassed for a predetermined time, at that time,
It is preferable to carry out while heating to 40 ° C to 80 ° C and / or stirring. The reduced pressure conditions are the same as the reduced pressure conditions during manufacturing.

The heating conditions are preferably 40 ° C. to 8 ° C.
It is in the range of 0 ° C, and below 40 ° C, the viscosity of the fluid is high,
Degassing cannot be performed sufficiently, and if the temperature exceeds 80 ° C., a problem may occur in the stability of the electrorheological fluid.

In the present invention, the stirring can be carried out by a conventional method, for example, by a rotating stirring blade, or by irradiation of ultrasonic waves. In the case of rotational stirring, the rotation speed of the blade is preferably about 10 to 200 rpm, and in the case of ultrasonic irradiation, the output is preferably 30 W or more.

On the other hand, when the above-mentioned degassed electrorheological fluid having a high dielectric breakdown strength is used / stored, for example, if it is subjected to vibration in a container being transported, the gas is re-mixed and May decrease. Therefore, a gas that has a high electron-withdrawing ability and a high dielectric breakdown strength, instead of air or a gas that constitutes air, coexists with an electrorheological fluid in a device or storage container, so that the device or the storage container can be shaken during operation. Even when the electro-rheological fluid is placed in a proper state, it is possible to prevent the withstand voltage of the electrorheological fluid from lowering due to gas mixing in the fluid.

As a gas having a high dielectric breakdown strength, generally,
3. High electronegativity, specifically, a dielectric breakdown strength of 4.
A gas with a molecular weight of 0 kV / mm or more and a large molecular weight is considered.
Has a halogen atom, CN group, or SO group in the molecule
Sci-fi₆, CCl_TwoF_Two, C _ThreeF₈, C_TwoF₆, C_Five
F₈, CF_ThreeCN, C_TwoF_FiveCN, Cl_Two, SOF_Two,
C_TwoClF_Five, ClO_ThreeF and the like.

By transporting in a container filled with such a gas, high withstand voltage performance at the time of manufacturing can be maintained, and also inside a device such as a damper which is used by enclosing an electrorheological fluid. By filling such a gas, a decrease in the withstand voltage with time can be prevented, and high reliability can be maintained for a long time.

The present invention will be described in more detail with reference to specific examples below, but the present invention is not limited to the following examples.

(Evaluation of Characteristics) (1) Measurement of Particle Size The particle size of the spherical carbonaceous powder was measured by using “MICR” manufactured by Nikkiso Co., Ltd.
It was measured using "OTRAC SPA / MK-II type device". (2) Measurement of electrorheological effect (yield stress) and initial viscosity (without electric field) The shear stress of the electrorheological fluid under no electric field and at the time of applying 4 kV / mm was measured by "RDS-" manufactured by Rheometrics Far East.
Type II Viscoelasticity Measurement Device ”and Trek“ 610 ”
The initial viscosity of the liquid was determined from the stress in the absence of an electric field, and the yield stress was determined from the difference between the initial viscosity and the stress when 4 kV / mm was applied. (3) Measurement of Current Density The current density of the electrorheological fluid at the time of applying 4 kV / mm was measured using a “RDS-II type device” manufactured by Rheometrics Far East and “610 type high voltage power source” manufactured by Trek.
The measurement was performed at room temperature (about 25 ° C.). (4) Measurement of dielectric breakdown strength (withstand voltage) Using a "RDS-II type viscoelasticity measuring device" manufactured by Rheometrics Far East Co., Ltd. and a "610 type high voltage power supply" manufactured by Trek, at a shear rate of 1000 / sec. At room temperature (approximately 25 ° C.), the electric field intensity is increased from 3.0 kV / mm to 30.
When the voltage was increased at an interval of 0.1 kV / mm every second, the electric field strength at which discharge occurred was defined as the dielectric breakdown strength (withstand voltage) of the electrorheological fluid. In this case, for example, 5.0 kV / mm
Since the high voltage has already been applied for 10 minutes before reaching the value, the dielectric breakdown strength of the electrorheological fluid obtained by this method is estimated to be lower than the eigenvalue of the actual material (in other words, actually, Higher).

(Example 1) <Preparation of raw material of spherical carbonaceous powder> 1280 g of naphthalene
After adding 1050 g of sulfuric acid to the mixture and reacting at 160 ° C. for 2 hours, unreacted substances were distilled out of the system under reduced pressure. Next, 857 g of formalin having a concentration of 35% by weight was added and reacted at 105 ° C. for 5 hours to obtain a methylene-bonded condensate of β-naphthalenesulfonic acid. Furthermore, the condensate was neutralized with aqueous ammonia and filtered to obtain a filtrate. Water was added to the filtrate containing the obtained methylene-bonded condensate of β-naphthalenesulfonic acid to prepare an aqueous solution having a concentration of 20% by weight of the methylene-bonded β-naphthalenesulfonic acid ammonium salt. This aqueous solution is pneumatically pressured by a spray dryer at 5k.
g / cm ² , and granulation and drying were performed by introducing drying air. The average particle diameter (50% volume average diameter) of the spherical carbonaceous particles of the methylene-bonded condensate of sulfonic acid mainly composed of methylnaphthalene thus obtained was 7.0 μm.

<Preparation of Spherical Carbonaceous Powder> The obtained carbonaceous powder was preheated in a nitrogen gas atmosphere at 400 ° C. to obtain a spherical powder. The carbon content of this powder is 90.
8%, the carbon / hydrogen atom ratio (hereinafter referred to as C / H ratio) was 2.0, and the average particle diameter was 7.0 μm. This powder was further heated (carbonization treatment) at 530 ° C. for 4 hours in a nitrogen gas atmosphere, crushed, and classified to obtain a spherical carbonaceous powder. The carbon content of this powder is 93.6%, the C / H ratio is 2.4,
The average particle size was 6 μm.

<Adjustment of Electrorheological Fluid> 48% by weight of a spherical carbonaceous powder and a silicone oil having a kinematic viscosity of 7 mm ² / s at 25 ° C. (dimethyl silicone oil (trade name “TSF”))
451-5 "and" TSF451-10 "(1: 1 mixture), 52% by weight of Toshiba Silicone Co., Ltd.) and 0.3% by weight of polyether-modified silicone were stirred and mixed in the atmosphere, and then 10 Pa Ultrasonic treatment was performed for 15 minutes under reduced pressure to obtain an electrorheological fluid of Example 1.

<Evaluation> As a result of measuring the withstand voltage of the obtained electrorheological fluid of Example 1, at least 4.5 kV / mm was obtained.
No discharge occurred and the withstand voltage was found to be 4.5 kV / mm or more. The viscosity of the electrorheological fluid in the absence of an electric field is 120 mPa · s, the yield stress when applying 4 kV / mm is 2.9 kPa, and the current density when applying 4 kV / mm is 19 μm.
A / cm ² .

(Example 2) 52% by weight of the spherical carbonaceous powder used in Example 1 and a kinematic viscosity at 25 ° C of 7 mm ²
/ S of silicone oil (dimethyl silicone oil (1: 1 mixture of trade names “TSF451-5” and “TSF451-10”, manufactured by Toshiba Silicone Co., Ltd.)) 48% by weight;
0.3% by weight of polyether-modified silicone was stirred and mixed in the atmosphere, and then subjected to ultrasonic treatment under reduced pressure of 10 Pa for 15 minutes to obtain an electrorheological fluid of Example 2. <Evaluation> As a result of measuring the withstand voltage of the obtained electrorheological fluid of Example 2, no discharge was generated at at least 4.5 kV / mm, and it was found that the withstand voltage was 4.5 kV / mm or more. The viscosity of this electrorheological fluid in the absence of an electric field is 200 mP
The yield stress when applying a · s and 4 kV / mm is 3.7 kP
a, the current density when applying 4 kV / mm is 20 μA / cm ²
Met.

Example 3 In the preparation of the spherical carbonaceous powder raw material of Example 1, the average particle diameter after spray drying was 4%.
In the preparation of the spherical carbonaceous powder, the carbon content after the preheating treatment was 92.6% and the C / H ratio was 2.
0, the average particle diameter is 4 μm, and the temperature of the carbonization treatment is 52
0 degree, the carbon content after the carbonization treatment was 94.5%, C /
Except that the H ratio was changed to 2.4 and the average particle diameter was changed to 3 μm, the spherical carbonaceous powder obtained in the same manner as in Example 1 had 45% by weight and a kinematic viscosity at 25 ° C. of 7 mm ² / s. Silicone oil (dimethyl silicone oil (trade name "TSF451-
5: 1 and "TSF451-10" (1: 1 mixture), 48% by weight of Toshiba Silicone Co., Ltd.) and 0.3% by weight of polyether-modified silicone were stirred and mixed in the atmosphere,
Ultrasonic treatment was performed under reduced pressure of 10 Pa for 15 minutes to obtain an electrorheological fluid of Example 3. <Evaluation> As a result of measuring the withstand voltage of the obtained electrorheological fluid of Example 3, it was found that no discharge occurred at at least 4.5 kV / mm and the withstand voltage was 4.5 kV / mm or more. The viscosity of this electrorheological fluid in the absence of an electric field is 130 mP
a · s, yield stress when applying 4 kV / mm is 2.5 kP
a, the current density when applying 4 kV / mm is 19 μA / cm ²
Met.

Example 4 49% by weight of the spherical carbonaceous powder used in Example 3 had a kinematic viscosity at 25 ° C. of 7 mm ^2.
/ S of silicone oil (dimethyl silicone oil (1: 1 mixture of trade names “TSF451-5” and “TSF451-10”, manufactured by Toshiba Silicone Co., Ltd.)) 48% by weight;
0.3% by weight of polyether-modified silicone was stirred and mixed in the air, and then subjected to ultrasonic treatment under a reduced pressure of 10 Pa for 15 minutes to obtain an electrorheological fluid of Example 4. <Evaluation> As a result of measuring the withstand voltage of the obtained electrorheological fluid of Example 4, no discharge occurred at at least 4.5 kV / mm, and it was found that the withstand voltage was 4.5 kV / mm or more. The viscosity of this electrorheological fluid in the absence of an electric field is 200 mP
a · s, the yield stress when applying 4 kV / mm is 3.2 kP
a, the current density when applying 4 kV / mm is 20 μA / cm ²
Met.

Comparative Example 1 The spherical carbonaceous powder used in Example 1 was 48% by weight and the kinematic viscosity at 25 ° C. was 7 mm ^2.
/ S of 52% by weight of silicone oil (dimethyl silicone oil (1: 1 mixture of trade names “TSF451-5” and “TSF451-10”) manufactured by Toshiba Silicone Co.)
An electrorheological fluid of Comparative Example 1 was obtained by stirring and mixing 0.3% by weight of the polyether-modified silicone in the air. <Evaluation> As a result of measuring the withstand voltage of the obtained electrorheological fluid of Example 2, a discharge was generated at 3.6 kV / mm, and the withstand voltage was found to be 3.6 kV / mm. The viscosity of this electrorheological fluid in the absence of an electric field is 120 mPa · s, 4 kV / m
The yield stress when applying m was 2.9 kPa, and the current density when applying 4 kV / mm was 19 μA / cm ² .

Comparative Example 2 45% by weight of the spherical carbonaceous powder used in Example 3 had a kinematic viscosity of 7 mm ^{2 at} 25 ° C.
/ S silicone oil (dimethyl silicone oil (trade name: 1: 1 mixture of “TSF451-5” and “TSF451-10”) manufactured by Toshiba Silicone Co., Ltd.) 55% by weight;
0.3% by weight of the polyether-modified silicone was stirred and mixed in the air to obtain an electrorheological fluid of Comparative Example 2. <Evaluation> As a result of measuring the withstand voltage of the obtained electrorheological fluid of Comparative Example 2, it was found that a discharge occurred at 3.6 kV / mm and the withstand voltage was 3.6 kV / mm. The viscosity of the electrorheological fluid in the absence of an electric field is 130 mPa · s, 4 kV / m
The yield stress when applying m was 2.5 kPa, and the current density when applying 4 kV / mm was 19 μA / cm ² .

Comparative Example 3 An electrorheological fluid of Comparative Example 3 was obtained in the same manner as in Comparative Example 1, except that no polyether-modified silicone was added. <Evaluation> As a result of measuring the withstand voltage of the obtained electrorheological fluid of Comparative Example 2, no discharge was generated at 4.5 kV / mm, and it was found that the withstand voltage was 4.5 kV / mm or more. The viscosity of this electrorheological fluid in the absence of an electric field is 200 mPa · s, 4
The yield stress when applying kV / mm is 2.5 kPa, 4 kV /
The current density at the time of application of mm was 17 μA / cm ² .

Comparative Example 4 An electrorheological fluid of Comparative Example 4 was obtained in the same manner as in Comparative Example 2, except that no polyether-modified silicone was added. <Evaluation> As a result of measuring the withstand voltage of the obtained electrorheological fluid of Comparative Example 2, no discharge was generated at 4.5 kV / mm, and it was found that the withstand voltage was 4.5 kV / mm or more. The viscosity of this electrorheological fluid in the absence of an electric field is 200 mPa · s, 4
The yield stress when applying kV / mm is 2.1 kPa, 4 kV /
The current density at the time of application of mm was 17 μA / cm ² .

Table 2 shows the above results.

[0074]

[Table 2]

From Table 2, it can be seen that the electrorheological fluids of Comparative Examples 1 and 2 have higher electrorheological effects by the addition of the modified silicone oil than the electrorheological fluids of Comparative Examples 3 and 4.
It can be seen that the dielectric breakdown strength is significantly reduced. On the other hand, the electrorheological fluid subjected to degassing after stirring and mixing the spherical carbonaceous powders of Examples 1 to 3, the electrical insulating oil, and the modified silicone oil, while maintaining a high withstand voltage, and It can be seen that a high electrorheological effect is obtained.

[0076]

According to the present invention, by using a high-strength powder, it is possible to provide an electrorheological fluid having excellent durability and having a high electrorheological effect and dielectric breakdown strength.

Continued on the front page (51) Int.Cl. ⁶ Identification code FI C10N 20:06 40:14

Claims (7)

[Claims] 1. A carbonaceous powder in the form of a perfect sphere obtained from a condensate of a substantially aromatic sulfonic acid or a salt thereof by a methylene-type bond and a solvent, an electric insulating oil, and a modified silicone. An electrorheological fluid containing oil and obtained by performing a deaeration treatment. 2. The true spherical shape has a deviation of the maximum diameter and the minimum diameter of the carbonaceous powder from the average diameter within 30% of the average diameter, respectively, and the average particle diameter of the carbonaceous powder is The electrorheological fluid according to claim 1, wherein the thickness is 0.1 to 20 m. 3. The electrorheological fluid according to claim 1, wherein the kinematic viscosity of the electric insulating oil at 25 ° C. is 1 to 100 mm ² / s. 4. The modified silicone oil is one or more modified silicone oils selected from amino-modified silicone oils, polyether-modified silicone oils, alkoxy-modified silicone oils, or epoxy-modified silicone oils, or composite modified silicones thereof. The electrorheological fluid according to claim 1, wherein the fluid is oil. 5. The electrorheological fluid according to claim 1, wherein the modified silicone oil contains 0.01 to 5% by weight. 6. The electrorheological fluid according to claim 1, which has a dielectric breakdown strength of 4.0 kV / mm or more. 7. The electrorheological fluid according to claim 1, wherein bubbles are not generated under a reduced pressure environment of 10 Pa.