JPH01284595A - Electroviscous fluid excellent in high-temperature stability and response - Google Patents

Abstract

PURPOSE:To obtain an electroviscous fluid which undergoes a rapid reversible viscosity change according as the applied voltage and is stable over a long period of time by mixing a dispersion medium comprising an electrical insulating liquid with dispersoids comprising porous solid particles and a polyhydric alcohol. CONSTITUTION:This electroviscous fluid consists of a dispersion medium comprising an electrical insulating liquid, dispersoids comprising porous solid particles and a polyhydric alcohol, and optionally a dispersant. As the electrical insulating liquid, a mineral oil and a synthetic lubricating oil may be used, and examples thereof including a naphthenic mineral oil, a paraffinic mineral oil, a polyalkylene glycol, a silicone, a phosphate, a fluorine compound, and a synthetic hydrocarbon. Examples of the porous solid particles include particles of silica gel, a water-containing resin, a diatomaceous earth, alumina, a zeolite, an ion exchange resin, and cellulose. Examples of the polyhydric alcohol include ethylene glycol, glycerin, and butanediol.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to an electrorheological fluid whose viscosity can be controlled by applying an electric field (voltage). The present invention also relates to an electrorheological fluid whose viscosity changes quickly and reversibly from a low temperature region to a high temperature region, and which is stable over a long period of time.

(Prior art) Electrorheological fluid (Elcctro-1?heological fluid) whose viscosity changes by applying an electric field (voltage)
l-1uid.

It is also called Electroviscus Fluid, or ER cold fluid for short. ) has been known for a long time. That is, ER cold fluids were discovered already at the end of the 19th century (Duff, A.W., phy.
sical Review Vol, 4. No, 1. (
1896) 23).

[Initial research on R fluids focused on liquid-only systems, and the effects were insufficient. after that,
As we moved from research on liquid-only systems to solid-dispersion fluids, we were able to obtain considerable electrorheological effects. For example, Winslow proposed an ER cold fluid using paraffin and silica gel powder, plus water to make the system slightly conductive (Winslow, W.) 1. , J, of
Applied physics, Vol. 20 (
1949) 1137). According to Winslow's research, the electrorheological effect of the ER cold fluid was determined by El? This effect is now called the slow effect.

On the other hand, progress has also been made in elucidating the mechanism by which the viscosity increasing effect (ER effect) occurs in R fluids. 4i1j (Induced Po1arizati
on of the Double Layer), and this is said to be the main cause (Klass, D, I-
,,el: al,,j,(汀Applied pby
sics.

Vol, 38. No. 1 (1967) 67).

This is called an electric double layer.
1ayer), ions adsorbed around a dispersoid (such as silica gel) are either [(electric field) - 〇 sharps arranged uniformly on the outer surface of the dispersoid or [(electric S)
-When the value is finite, the ion distribution becomes biased, and each particle comes to have an electrostatic effect on each other within the electric field. In this way, each particle is bridged between the electrodes.
, and develops shear resistance against stress, that is, develops an ER effect.

Regarding the [1< fluid] of the solid particle dispersion system described above, various proposals have been made from the viewpoint of improving the viscosity characteristics of the ER fluid, improving the stability, etc. while taking into account the mechanism by which the ER effect occurs. For example, one that uses ferroelectric powder and silicon dioxide-based fine powder that has adsorbed a small amount of water (
Akira Machimon! No. 13-17585), 1 to 1 as a dispersed phase
In order to stabilize a dispersion system consisting of silica gel with a water content of 5W1% and silicone oil as a liquid phase, a high molecular weight dispersant having a functional group is used (Japanese Patent Application Laid-open No. 6-1-1999).
44998S), etc. have been proposed.

(Problem to be solved by the invention) However, despite various proposals, the conventional (21)
Fluids are characterized by rapid and reversible viscosity change responsiveness (sensitivity) to the application of an electric field (voltage), [reproducibility of R effect],
Stable El over a long period? It cannot be said that it is still sufficient in terms of maintaining the effect. In particular, since water is used in these [R fluids, the water evaporates rapidly in the high temperature range of 80°C or higher, reducing the thickening effect. The problem is that the viscosity changes under constant voltage and is unstable.

The present inventors conducted a thorough investigation to solve the above-mentioned problems in Ell fluids, and as a result, they discovered a solid particle dispersion system with water adsorbed (l-1) (in the fluid, the water is replaced with polyhydric alcohol). The inventors have discovered that an ER fluid with extremely excellent properties can be obtained by this method, and have completed the present invention.

[Structure of the invention]

(Means for Solving the Problems) To summarize the present invention, the present invention is characterized by comprising an electrically insulating liquid as a dispersion medium, porous solid particles as a dispersoid, and a polyhydric alcohol. This relates to an electrorheological fluid ([1 (fluid)] which is characterized by being made by adding a dispersant to these components and exhibiting excellent stability and responsiveness from a low temperature range to a high temperature range.

Hereinafter, the configuration of the present invention will be explained in detail.

The electrically insulating liquid as a dispersion medium used in the R fluid of the present invention may be any electrically insulating liquid and is not particularly limited.

Examples of this type of electrically insulating liquid include mineral oils and synthetic lubricating oils, and more specifically, naphthic mineral oils, paraffinic mineral oils, polyalzur Δrefine, polyalkylene chloride, silicone, diester, polio-1
Examples include 11-choster, nistyl phosphate, silicon compounds, fluorine compounds, polyphenylnidel, and synthetic hydrocarbons.

The viscosity range of these electrically insulating liquids is preferably 5 to 300 Cρ at d3 at 40°C.

The porous solid particles used as the dispersoid used in the ER fluid of the present invention are those commonly used and are not subject to any particular limitations.

Porous solid particles of this type include, for example, silica gel, aqueous resin containing, diatomite, alumina, silica-alumina, zeolite i~, ion exchange resin, cellulose, and the like.

These porous solid particles usually have a particle size of 10n...~? 0
0P is used in a proportion of 0.1 to 50 wt%.

Less than 0.1 wt% has little ER effect, and 50 wt%
%, it is not preferable because the dispersibility deteriorates.

The dispersant used in the ER fluid of the present invention is used to make the dispersion state of the porous solid particles in the dispersion medium uniform and stable, and therefore a conventional one can be used.

Examples of this type of dispersant include sulfone-1,
Phenes 1~, small sulfonates, succinimides,
Amines, Nisdels, nonionic dispersants, etc., more specifically magnesium sulfone-1~, calcium-sulfone-1, calcium phenate, calcium phosphone-1~, polybutenyl succinimide, There are sorbitan monoole 1~, sorbitan sesquiole 1~, etc. These are usually used in an amount of 0.1 to 10 wt%.

However, the dispersant may not be used if the dispersibility of the solid particles is good.

Next, the [R fluid odor-C is the biggest feature of the present invention]
We will explain the "polyhydric alcohol" component and its effects.

In the present invention, by using monopolyhydric alcohol as a component of the ER fluid as described above, an extremely excellent ER effect can be exhibited, particularly in a high temperature region. As this type of polyhydric alcohol, dihydric alcohols and trihydric alcohols are useful, and examples include ethylene glycol, glycerin, propanediol, butanediol, and hexanediol. These "polyhydric alcohol" components exhibit particularly excellent effects when combined with silica gel. In the present invention, it goes without saying that these polyhydric alcohols may be used alone or in combination.

These monopolyhydric alcohol components are generally used in a proportion of 1 to 30 wt%, particularly preferably 2 to 15 wt%, based on the porous solid particles. If it is less than 1 wt%, the ER effect will be small, and if it exceeds 30 wt%, current will flow easily, which is not preferable.

(Function) Responsiveness (sensitivity) of viscosity changes in the temperature range, reproducibility,
It is possible to exhibit excellent effects in terms of stability over time, thickening effect (magnification of thickening when an electric field is applied compared to when no electric field is applied), etc.

The present inventors speculate as follows whether the mechanism by which these excellent effects are expressed has not been sufficiently theoretically elucidated.

In conventional ER fluids, typically consisting of mineral oil, water, and solid particles, the causes of the ER effect are believed to be as follows. That is, water adsorbed on solid particles forms a thin film of water, which undergoes dielectric polarization in the electric field due to its polarity, and is stretched in the direction of the electric field to mutually begin to form a bridge. Then, as a bridge is completed between the electrodes, the viscosity increases in the vertical direction due to the electric field, which results in the ER effect.

Therefore, the thickness of the water film is extremely important for the expression of the ER effect, but since water has a low molecular weight and evaporates easily, the thickness of the water film can be easily reduced by changes in the external environment, especially external temperature. It fluctuates, and this becomes a factor that destabilizes the ER effect.

In the present invention, a polyhydric alcohol such as ethylene glycol or glycerin is used instead of water as a polar liquid that has a strong affinity with solid particles and is easily affected by electric fields. In comparison, these polyhydric alcohols have large molecular weights, are difficult to evaporate, and are stably adsorbed onto solid particles, so that they form stable films with little variation in film thickness on the surfaces of solid particles. This is considered to be the reason why a [R fluid] is obtained which exhibits a stable ER effect from a low temperature region to a high temperature region, especially in a high temperature region.

Additionally, polyhydric alcohols have a lower ionization rate than water and are less likely to dissociate, making it difficult for electric current to flow through them. Therefore, it is possible to apply a higher voltage to a polyhydric alcohol-based material compared to an aqueous-based material, and this is considered to be advantageous in achieving a high thickening effect.

In the ER fluid system of the present invention, water was mentioned in the explanation of (effect) above, and it goes without saying that water may be used within a range that does not inhibit the ER effect.

〔Example〕

Hereinafter, the present invention will be explained in detail based on Examples, but the present invention is not limited to these Examples.

(Examples 1-2) / (Comparative Examples 1-3) (*) Preparation of ER fluid The solid particles shown in Table 1 below were mixed with a dispersant (succinimide) and mineral oil (solid particles): Dispersant]: [Mineral oil] −
6:4:9o (weight ratio) to prepare "R fluid" and these samples were all mixed at 40 °C.
The viscosity of the mineral oil was adjusted to a viscosity of 0 cp.

(1j) Experimental conditions and El? Fluid evaluation fill + term 11 [
The R fluid was heated to 40°C and 90°C, and evaluated for the following items using a rotational viscometer that can apply voltage.

・Responsiveness・・・・Electric field from O to 1.4×10G
The viscosity was evaluated based on how many seconds it took for the viscosity to stabilize when the temperature was changed to (\1 h). .

・Re-m ta --- electric field from O→1. /1x106
(V/m) ->0 cycles were repeated, and evaluation was made based on the variation rate (%) of viscosity when the electric field was -1.4 x 106 (V/m).

・Stability・・・・・・Electric field 1.4X106 (V/
When the viscosity is kept constant at 100 m), it is evaluated by the amount of change in viscosity over time (%) (between 04 and 1 h of measurement).

・Thickening effect...Electric field 011. ! Compared to i,
Evaluation was made using the viscosity magnification when the electric field was set to 1./1×10 6 (V/m).

(iii) Results The results are shown in Table 2.

(Left below) Table 1 Table 2 [Effects of the Invention] The electrorheological fluid (ER fluid) of the present invention has extremely good stability even in a high temperature environment and has a large viscosity increasing effect. Furthermore, the ER fluid of the present invention is significantly superior in responsiveness (sensitivity) and recirculation property to conventional fluids from low-temperature to high-temperature regions.

Therefore, the [R fluid of the present invention is useful for, for example, control devices that utilize viscosity changes, and can dramatically improve the control accuracy, especially the control accuracy of A3 when used at high temperatures.

Patent applicant: Toa Fuel Industry Co., Ltd. Ne1

Claims (1)

[Claims] 1. An electrorheological fluid with excellent high temperature stability and responsiveness, characterized by comprising an electrically insulating liquid as a dispersion medium, porous solid particles as a dispersoid, and a polyhydric alcohol. 2. An electrorheological fluid with excellent high-temperature stability and responsiveness, characterized by comprising an electrically insulating liquid as a dispersion medium, porous solid particles as a dispersoid, a polyhydric alcohol, and a dispersant.