JPH02209997A - Electrically viscous fluid - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to electrorheological fluids.

An electrorheological fluid is a fluid that exhibits the so-called electrorheological effect, in which its apparent viscosity changes rapidly and reversibly by the action of applied voltage (OFF, ON, voltage change).

[Prior Art] Conventionally, as one type of electrorheological fluid, one obtained by vigorously stirring an electrically insulating liquid, fine particles adsorbing or containing ions, and a small amount of water is known.

The electrorheological effect in P fluid can be considered as follows. In other words, water migrates into the fine particles through strong stirring to create an electrolyte solution, and when a voltage is applied, the ions in the electrolyte solution thus obtained move and become unevenly distributed within the fine particles, causing the particles to become polarized. do. The fine particles aggregate with each other due to the D electric attraction based on the polarization, and as a result, an electrorheological effect is developed. By the way, the fine particles in the viscous fluid as described above are not particularly limited as long as they maintain a stable dispersion state, and both inorganic and organic fine particles can be used.

Conventionally, pulverized silica particles have been used as inorganic fine particles because of their simplicity.

[Problems with conventional technology] Clutches, hydraulic valves, vibration isolators, etc. that use electrorheological fluids,
In vibrators and the like, it is common to utilize the change in viscosity when the fluid passes through a gap between electric cells for applying an electric field. Therefore, wear between the particles, which are the dispersed phase, and the walls of the device becomes a problem.

In this regard, electrorheological fluids using pulverized silica particles as a dispersed phase have a serious problem of wear due to the sharp edges of the silica, and an improvement is desired.

Furthermore, particles of the electrorheological fluid form a crosslinked structure when a voltage is applied between the electric bridges. Therefore, in the case of pulverized particles, the particles come into contact with each other at sharp edges, resulting in a low dielectric strength.

[Means for Solving the Problems] An object of the present invention is to provide an electrorheological fluid that has improved the above-mentioned problems. This can be easily achieved using an electrorheological fluid using spherical particles containing an electrolyte solution, the fine particles of which are obtained by hydrolyzing and polycondensing a penta-metal alkoxide or its derivative.

The present invention will be described in detail below.8 The electrorheological fluid according to the present invention is obtained by hydrolyzing and polycondensing a metal alkoxide or its derivative as particles dispersed in an insulating liquid, and has an average particle size of 0. .05~2μ
It uses spherical particles of m.

As the metal alkoxide, rMetal Alko
xides (D, C, Bradley, R, C, Me
co-authored by D. P. Gaur) Acadea
Various alkoxides described in +ic Press 1978J are possible, but typical examples include alkoxides such as Si, Ti, and Zr, and Ba-Ti.
%5r-Ti, Pb-Ti, Pb-Ti-Zr, Li-
Examples include complex alkoxides such as Nb.

Hydrolysis of metal alkoxides is generally carried out by mixing an alcohol solution in which the alkoxide is dissolved with an alcohol aqueous solution, but by appropriately adjusting the hydrolysis rate, the amorphous form of the metal oxide can be substantially removed. It can be precipitated as spherical particles. The hydrolysis rate is usually adjusted by the molar ratio and concentration of alkoxide and water in the reaction system, the amount of a hydrolysis catalyst (alkali, acid, etc.) added as necessary, and the like. The conditions for obtaining spherical particles vary depending on the type of alkoxide and cannot be determined unconditionally, but for example, Si
(OCz Hs), Ti(OCx Ha)4
, Zr (OCz H6), t, usually [)1
．． 0]/[alcoxa 463 molar ratio is preferably 1-150, hali-100, concentration of alkoxide (mo
l/l) from 0.05 to 10, more preferably from 0.05 to
5. Water concentration (m o 1 / I) is 0.1-20
, more preferably in the range of 0.1 to 10.

FIG. 1 shows 31 (OCx Ha)4 in Example 1.
This is a running electron micrograph (magnification: 10.000x) of spherical particles of silica obtained by hydrolysis of .

Spherical silica is obtained by separating the solid content from an alcohol solution by filtration or centrifugal sedimentation, and drying it using a rotary evaporator, etc., and has an average particle size of 0.
, 05 to 2 μm. The spherical particles need only contain an electrolyte solution, and the ions in the solution produce an electrorheological effect based on the above-mentioned principle. The electrolyte that makes up the solution is not particularly limited as long as it dissociates into ions in a polar solvent such as water; for example, N) f s Na OHlNai.
l, LiC1, B! On CaO1Mg5Oa,
Examples include inorganic compounds such as Fe (NOs)z %, and ionic surfactants such as sodium sulfonate, sodium carboxylate, sodium alkylbenzene sulfonate, sodium polystyrene sulfonate, fatty acid calcium salts, and formalin condensate of naphthalene sulfonic acid. It will be done.

As the solvent constituting the electrolyte solution, any conversion solvent can be used as long as it can sufficiently dissolve the electrolyte used.

The concentration and content of the electrolyte solution are appropriately selected within a range that does not cause conduction when an electric field is applied.
Usually 0. ! The content is selected from the range of ~90% by weight, preferably 5-50% by weight, and the content is selected from the range of 0.1-20% by weight, preferably 1-10% by weight.

As mentioned above, the hydrolysis and polycondensation of metal alkoxides are performed using N )! Since it can be carried out in the presence of a catalyst such as No. 3,
In such a case, the catalyst can be used as it is as an electrolyte. That is, after hydrolysis and polycondensation of metal alkoxide, spherical silica is separated from the alcohol solution and dried, but the weight decreases when heated to 200°C in air without completely drying. By drying the electrolyte solution to a concentration of 0.1 to 20% by weight, preferably 1 to 10% by weight, spherical particles containing an electrolyte solution in the above range can be obtained. In addition, the above heating weight reduction is
This is a value obtained by differential thermal analysis at a heating rate of 10° C./min.

Of course, it is also possible to completely carry out the above-mentioned drying or washing with water before drying, and then add the electrolyte solution. In such cases, it is preferable to use a solvent with a higher boiling point than water as the corrosive solvent constituting the electrolytic solution.
In other words, if an electrorheological fluid using a low boiling point solvent such as water is used for a long period of time in an environment that generates heat due to high temperature or high shear force, the solvent will volatilize, and as a result, it will not work properly. Although there is a problem that the electrorheological effect is no longer expressed, such problems can be solved at once by using a high boiling point solvent. Examples of the high boiling point separating solvent used for the above purpose include glycol and ethanolamine, among which ethylene glycol is preferably used. At this time, impregnation with the electrolyte solution can be carried out by mixing the spherical particles, electrolyte, solvent, and electrically insulating liquid for several hours in a ball mill, or by impregnating the spherical particles into the electrolyte solution. be able to.

The electrically insulating liquid used is one that can stably disperse spherical particles, has high insulation resistance, and does not dissolve the electrolyte solution, and specifically, silicone oil, transformer oil, engine oil, ester, paraffin, olefin, or Appropriately selected from aromatic hydrocarbons and the like.

The usage of spherical particles for electrically insulating liquids is usually 5~
50% by volume is used, preferably 10-40% by volume.

For the splitting method, general mixing and dispersing machines such as ball mills and ultrasonic dispersion machines can be used.

To measure the electrorheological effect, use a coaxial double cylinder rotational viscometer to find the increase in shear stress at the same shear rate (1625 ec-'l) when a voltage is applied between the inner and outer cylinders, and calculate this as the viscosity. This can be done by converting it into a change.

Since the flow characteristics of electrorheological fluids can be controlled by applying voltage, it is expected that they will be used in the field of computer-controlled mechatronics in the future. Here are some examples of specific applications. In the automobile industry, application parts such as clutches, torque converters, valves, shock absorbers, brake systems, and power steering are being considered. It is also being applied to various actuators in the field of industrial robots.

EXAMPLES The present invention will be specifically explained below with reference to Examples, but the present invention is not limited to the following Examples unless it exceeds the gist thereof.

Example 1 Si (oc, )(S) 4 (reagent special grade) 1
88.0g to ethyl alcohol (reagent grade) 670.7
A solution dissolved in g and 281f% NH,OH aqueous solution 223
．． 6g, water 173.9g and ethyl alcohol 19g
Mix B solution dissolved in 99.5g and make a diameter of 0.56μm.
The standard deviation of the diameter of 0 particles of precipitated silica particles is 1.
It was 05. Particles were separated from this slurry according to a conventional method and vacuum dried at 100° C. for 1 hour to obtain powder particles. These particles contain NH, (1,31%), water (4,1%),
Contains ethanol (0.6%) and ethanol (0.6%).
ff1ffi decreases by 6 when heated in air at 200℃
%0 Next, 30.1 g of these particles were mixed with 32.8 g of silicone oil (Toshi Silicone 5H200, 10cs).
In addition, the mixture was dispersed and mixed in a ball mill for 12 hours.

Regarding the electrorheological fluid of the present invention obtained in this manner, shear was measured at the same shear rate (162 sec-') when a voltage was applied between the inner and outer cylinders using a coaxial double cylinder rotational viscometer. Stress was measured (distance between electrodes 111 mm, fA degree 2
5°C), the results obtained are shown in Figure 2, the initial viscosity was 1.7.
It can be seen that the number of voices increases to 28 voices when an electric field strength of 2 kv/mm is applied. Note that when this liquid was allowed to stand at room temperature and measured again 10 days later, no change in properties was observed.

Example 2 The spherical silica used in Example 1 was heated at 250°C for 1
5.5% by weight NaOH aqueous solution 4 for 40g of particles heated for 6 hours to sufficiently remove NH, water, and ethanol.
After adding 8 g, vacuum drying was performed at 100° C. for 1 hour to obtain powder particles. These particles are made of NaOH (5,2% M%
), contains water (9.7ffiffi%), and contains 200
ff1ffi decreases by 9.7% when heated in air at ℃
Met. Next, add 30.1 g of these particles to 328 g of silicone oil (Toshi Silicone 5H200, 1 ocs).
In addition, the mixture was dispersed and mixed in a ball mill for 12 hours. The initial viscosity of the fluid thus obtained was 1°5 voices, 2
When an electric field of kV/mm is applied, 16 voids (1
62sec”).

Example 3 The spherical silica used in Example 1 was heated at 250°C for 1
10.0 g of particles heated for 6 hours to sufficiently remove NHs, water, and ethanol, and ammonia water (NH, concentration 2
5% by weight) was added to 18.7 g of silicone oil (Toshi Silicone 5H200, 10cs) and dispersed and mixed in a ball mill for 12 hours. The initial viscosity of the fluid thus obtained was 0.2 voices, which increased to 22 voices (162 sec-') when an electric field of 1.8 kV/mm was applied.

Example 4 The spherical silica used in Example 1 was heated at 250°C for 1
10.0 g of particles heated for 6 hours to sufficiently remove NH, water, and ethanol and an aqueous NaOH solution (NaOH concentration 4
1.3 g of silicone oil (Toshi Silicone SH200, 1 ocs) was added to 18.7 g of silicone oil (Toshi Silicone SH200, 1 ocs), and the mixture was dispersed and mixed in a ball mill for 12 hours. The initial viscosity of the fluid thus obtained was 0.3 poise, which increased to 16 voices (162 sec-') when an electric field of 2 kV/mm was applied.

Example 5 The spherical silica used in Example 1 was heated at 250°C for 1
10.0 g of particles heated for 6 hours to sufficiently remove NH, water, and ethanol and NaOH were dissolved in ethylene glycol in advance and mixed with L/kfd solution (NaOHaffl, 8
Add 0.7 g of silicone oil (Toshi Silicone S H2O0, JOcs) to 18.7 g of silicone oil (Toshi Silicone S H2O0, JOcs),
The mixture was dispersed and mixed in a ball mill for 12 hours. Of the fluid thus obtained? , IJ stage viscosity is 0.8 voice, 2kV
/ mm When an electric field of m is applied, 17 voices (162 se
c-') & increased.

Work 9116 20.0 g of the spherical silica used in Example 1 was mixed with dioctyl adipate (C6H1?0OC-(C)[,)
37.1 g of C00C,H, ) and dispersion-mixed in a ball mill for 12 hours. The initial viscosity of the fluid thus obtained was 0.6 voices, which increased to 25 voices (162 sec'') when an electric field of 2 kV/mm was applied.

Example 7 Spherical silica used in Example 1 20.0g39.4
g and dispersion-mixed in a ball mill for 12 hours. The initial viscosity of the fluid thus obtained is 1,1 poise, and 2
When an electric field of kV/mm is applied, 37 voids (
162 sec-').

Example 8 20.0 g of the spherical silica used in Example 1 was mixed with 7.0 g of hydrocarbon-based low viscosity mineral oil (Mitsubishi Oil RO-2,2cs).
and silicone oil (Higashi Silicone 5H200, 5c
s) It was added to 33.4 g of the mixed solution and dispersed and mixed in a ball mill for 12 hours. The initial viscosity of the fluid thus obtained was 0.2 poise, which increased to 11 poise (162 sec-') when an electric field of 2 kV/mm was applied.

Comparative Example 1 The spherical silica used in Example 1 was heated at 250°C for 1
10.0 g of particles that had been heated for 6 hours to sufficiently remove N Hs, water, and ethanol were added to 18.7 g of silicone oil (Toshi Silicone 5H20010cs), and dispersed and mixed in a ball mill for 12 hours. As a result of measuring the electrorheological effect of the fluid thus obtained, no increase in viscosity was shown.

Comparative Example 2 The spherical silica used in Example 1 was heated at 250°C for 1
10.0 g of distilled water was added to 10.0 g of particles that had been heated for 6 hours to sufficiently remove NH, water, and ethanol, and then vacuum-dried to obtain particles containing 16.81% of water.

Next, 10.0 g of these particles were added to 18.7 g of silicone oil (Toshi Silicone S It 200, LOcs) and dispersed and mixed in a ball mill for 12 hours. The electrorheological effect of the resulting fluid was measured. It showed no viscosity increase.

Comparative Example 3 When the electrorheological effect was measured using crushed silica gel instead of the spherical silica particles in Example 3, it was found to be 0.5
When an electric field of kV/mm was applied, a discharge occurred and subsequent measurements could not be made.

[Effects of the Invention] As described above, the present invention provides an electrorheological fluid with higher stability than the compositions disclosed in the prior art.

[Brief explanation of the drawing]

FIG. 1 is a scanning electron micrograph showing the particle structure of spherical silica particles obtained in Examples. FIG. 2 is a graph showing the thickening effect of the electrorheological fluid of Example 1 with respect to the applied electric field, and the horizontal axis is the applied electric field (kV/m
m), the vertical axis is viscosity (poise).

Claims (1)

[Claims] (1) The fine particles are composed of an electrically insulating liquid and fine particles dispersed therein, and the fine particles are spherical particles containing an electrolyte solution obtained by hydrolyzing and polycondensing a metal alkoxide or its derivative. Features of electrorheological fluid.