JPH04120194A - Electric viscous fluid - Google Patents

Abstract

PURPOSE:To obtain an electric viscous fluid having excellent response, reproducibility, durability, thickening effects, etc., in a wide temperature range by blending an electrical insulating fluid with porous solid particles and a dispersant and further a partially etherified substance and a partially esterified substance of polyhydric alcohol. CONSTITUTION:(A) An electrical insulating fluid comprising a mineral oil or a synthetic lubricating oil having 5-300cst viscosity (40 deg.C) is blended with (B) porous solid particles such as silica gel, diatomaceous earth or cellulose, (C) a dispersant such as sulfonates, phosphates or amines and further (D) a partially etherified substance and a partially esterified substance of polyhydric alcohol (preferably lower alkyl partially ether or lower fatty acid partial ester of dihydric or trihydric alcohol) in a ratio of usually 1-10wt.% (especially 2-80wt.%) to the component B to give the objective fluid. The fluid can reduce OV viscosity change ratio and extremely improve control accuracy in high-temperature use.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention relates to electrorheological fluids whose viscosity can be controlled by applying voltage. This invention relates to electrorheological fluids that can be used to electrically control absorbers and the like.

(Conventional technology) Electrolytic fluid (which changes its viscosity by applying voltage)
Blectro-Rheological Fluid
SBlectr (iscous fluid, ) has been known for a long time (Dul^, W, Physical
Review Vol, 4, No. 1 (
1896) 23).

The initial research on electrorheological fluids focused on liquid-only systems, and the effects were insufficient, but later the research moved to electrorheological fluids in solid dispersion systems, and considerable electrorheological effects were obtained. Now you can.

As for the mechanism of expression of the thickening effect (ER effect) in electrorheological fluid, for example, Klass is a dispersoid in electrorheological fluid, and each particle has a two-layer dielectric polarization (
Induced Po1arization of t
This is said to be the main cause (1ass, D, L, etc.).
l,, J,of Applied Physics,
Vol, 38. No. 1 (1967) 67). This is called an electric double layer (electric double 1
ayer), dispersoids (silica gel, etc.)
Ions adsorbed around are uniformly arranged on the outer surface of the dispersoid when E (electric field) - 0, but when E (electric field) - is a finite value, the ion distribution becomes uneven, and each Particles come to have an electrostatic effect on each other in an electric field. In this way, each particle forms a bridge between the electrodes and develops shear resistance against stress, that is, an ER effect.

For example, Winslow proposed an electrorheological fluid using paraffin and silica gel powder, and water to make the system slightly conductive (Winslow, W, M,
.

J, of Applied Physics, Vol.
, 20 (1949) 1137). This Winslow
Through research, the electrorheological effect of electrorheological fluids has been shown to be a win-win.
This is called the slow effect.

In such a solid dispersion type ER fluid, from the viewpoint of improving the viscosity characteristics and stability of the ER fluid while considering the mechanism of the ER effect, for example,
One uses ferroelectric powder and silicon dioxide fine powder adsorbed with a small amount of water (Japanese Patent Application Laid-Open No. 17585/1985), and one uses polyhydric alcohol instead of water as a polarizing agent, and can be used in high temperature ranges. Products have been developed that enhance the ER effect of.

(Problem to be solved by the invention) However, the ER fluid containing polyhydric alcohol,
It has been found that the initial viscosity (viscosity when no voltage is applied) increases as it is used, and that the increase in initial viscosity is significant in the high temperature range, making it impossible to maintain the ER effect.

An object of the present invention is to provide an ER fluid that can stably maintain the ER effect in a high temperature region and, in particular, can prevent an increase in initial viscosity.

(Means for Solving the Problems) The electrorheological fluid of the present invention includes an electrorheological fluid comprising an electrically insulating fluid, porous solid particles, and a dispersant, and a partially etherified polyhydric alcohol or a portion of a polyhydric alcohol. It is characterized by containing at least one substance selected from esterified products.

Examples of electrically insulating fluids include mineral oils and synthetic lubricating oils, specifically paraffinic mineral oils, naphthenic mineral oils, poly-α-olefins, polyalkylene glycols, silicones, diesters, polyol esters, phosphoric acid esters, and silicon compounds. , fluorine compounds, polyphenyl ethers,
Examples include synthetic hydrocarbon oils. The viscosity range of these electrically insulating fluids is from 5 cSt to 300 at 40°C.
cSt can be used.

Further, conventional porous solid particles can be used, such as silica gel, hydrous resin, diatomaceous earth, alumina, silica-alumina, zeolite, ion exchange resin, cellulose, and the like. These porous solid particles usually have a particle size of 10 nm to 200 μn, and the entire ER fluid contains O,1
It is used at a ratio of wt% to 50wt%. O, 1wt%
If it is less than 50 wt%, the ER effect will be small, and if it exceeds 50 wt%, the dispersibility will deteriorate, which is not preferable.

Dispersants are also used to uniformly and stably disperse porous solid particles, such as sulfonates, phenates, phosphonates, succinimides, amines, nonionic dispersants, etc. Specifically, there are magnesium sulfonate, calcium sulfonate, calcium phosphonate, polybutenyl succinimide, sorbitan monooleate, sorbitan sesquiolate, and the like.

These typically range from 1 wt to 10 wt O, 1 wt to 10 wt for the entire ER fluid
%, but it may not be used if the porous solid particles have good dispersibility.

Next, the partially etherified product of polyhydric alcohol or the partially esterified product of polyhydric alcohol in the present invention will be explained.

As the partially etherified polyhydric alcohol or partially esterified polyhydric alcohol, lower alkyl partial ethers of dihydric alcohols and trihydric alcohols, and lower fatty acid partial esters may be used. Examples of polyhydric alcohol components include ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol, glycerin, propanediol, butanediol, bentanediol, and hexanediol, and partial ethers include one of the terminal hydroxyl groups. Monoethers in which one of the terminal hydroxyl groups is substituted with a methyl group, ethyl group, propyl group, etc., and partial esters in which one of the terminal hydroxyl groups is esterified with acetic acid, propionic acid, butyric acid, etc., can be used.

Partially etherified polyhydric alcohols or partially esterified polyhydric alcohols (hereinafter referred to as polyhydric alcohol partial derivatives) improve the ER effect in high-temperature regions, and are generally effective against porous solid particles. 1wt%~100w
t%, particularly preferably 2 wt% to 80 wt%. If the amount added is less than 1 wt%, the ER effect will be small, and if it exceeds 100 wt%, current will flow easily, which is not preferable.

Of course, water may be used together with this polyhydric alcohol derivative to the extent that the ER effect is not inhibited.

Further, in the case where a partially esterified product of polyhydric alcohol is used as a polarizing agent in the ER fluid of the present invention, it is necessary that the partially esterified product of polyhydric alcohol is not hydrolyzed. Furthermore, an acid, salt, or base component may be added as a polarization accelerator.

Such acid components include inorganic acids such as sulfuric acid, hydrochloric acid, nitric acid, perchloric acid, chromic acid, phosphoric acid, and boric acid, or acetic acid, formic acid, propionic acid, butyric acid, isobutyric acid, valeric acid, oxalic acid, Organic acids such as malonic acid are used.

The salt is a compound consisting of a metal or basic group (NH, N2H3+, etc.) and an acid group, and any of these can be used. Among them, polyhydric alcohol partial derivatives, or those that dissolve and dissociate from polyhydric alcohol partial derivatives in water, such as those that form typical ionic crystals such as halides of alkali metals and alkaline earth metals;
Alternatively, alkali metal salts of organic acids are preferred.

As this kind of salt, LiCj! , NaCCKCj! 5M
gC11, CaCj! 2. BaCj! z, L 1Br
SNaBr, KBr, MgBra, Lil.

Nal, KI, AgNOs, Ca (NO3)2, N
aNO2, NH4NO3, K2 S○, , Na25O
a, Na25Oa, (NH,)2So, or alkali acid metal salts such as formic acid, acetic acid, oxalic acid, and succinic acid.

Bases that can be used in the present invention include alkali metal or alkaline earth metal hydroxides, alkali metal carbonates, amines, etc., and polyhydric alcohol partial derivatives, or polyhydric alcohol partial derivatives and water. Preferably, it dissolves in the system and dissociates.

This type of base includes NaOH, KOH, Ca(OH)
! , Naa Cow, NaHCOs, KsPO4
, Nas PO4, aniline, alkylamine, ethanolamine, etc. Incidentally, the above-mentioned salt and base can be used in combination.

Acids, salts, and bases can increase the polarization effect, but by using them in combination with polyhydric alcohol partial derivatives, the polarization effect can be further increased. 0.0b+t%~5wt
It is best to use it at a rate of %. If it is less than 0.01 wt%, the ER effect will be small, and if it exceeds 5 wt%, it becomes easy to conduct electricity, which increases power consumption, which is not preferable.

Further, it is preferable to add an antioxidant and/or a corrosion inhibitor to the ER fluid of the present invention.

The purpose of the antioxidant is not only to prevent the electrically insulating liquid from oxidizing, but also to prevent the polyhydric alcohol partial derivative, which is a polarizing agent, from oxidizing.

As the antioxidant, it is best to use one that is inert to polarizing agents and porous solid particles, and commonly used phenolic and amine antioxidants can be used.・6-di-t-butyl para-cresol, 4,4'-methylenebis(2,6-di-t-butylphenol), 2,6-di-t-butylphenol, etc. Also, as amines, dioctyl diphenylamine,
Phenyl-α-naphthylamine, alkyldiphenylamine, N-nitrosodiphenylamine, etc. can be used, and 0.01 to 10-t% of the total ER fluid,
Preferably, it can be used in an amount of 0.1 to 2.0 wt%,
If it is less than 0.01 wt%, there will be no antioxidant effect, and if it exceeds 10 wt%, there will be problems such as deterioration of hue, generation of turbidity, generation of sludge, and increase in viscosity.

In addition, as a corrosion inhibitor, it is best to use polarizing agents and those that are inert to porous solid particles. , 1.3.4-thiadiazole polysulfide, IJ
, 4-thiadiazolyl-2゜5-bisdialkyldithiocarbametolkyldithio)benzimidazole, etc., β-(0-carboxybenzylthio)propionitrile or propionic acid, etc. can be used,
0.001 to 10 wt% based on the entire ER fluid, preferably 0.001 to 10 wt%. Old~1. It is preferable to use 0wt%. 0. 00
If it is less than 1wt%, there is no corrosion prevention effect;
If it exceeds t%, problems such as deterioration of hue, generation of turbidity, generation of sludge, and increase in viscosity occur.

In addition, anti-wear agents, extreme pressure agents,
Additives such as antifoaming agents may be added.

[Effect]

In ER fluids, by adding polyhydric alcohols, a stable thickening effect can be achieved over a wide temperature range up to high temperatures. The inventors have discovered that as the temperature increases, the viscosity increases when no voltage is applied, and the increase is particularly significant when used at high temperatures.

Although the detailed reason for this is unknown, it is thought that ER fluids containing polyhydric alcohols undergo a gelation phenomenon as they are used, resulting in an increase in viscosity. By using a chemical compound or a partially esterified compound, the responsiveness of viscosity change in a wide temperature range up to high temperatures, reproducibility, and thickening effect (electric field 0
It maintains an excellent effect on the viscosity increase rate when an electric field is applied (with respect to time), and prevents the viscosity from increasing during use even when no voltage is applied, making it more durable.
It can be used as R fluid.

The present invention will be described below based on Examples, but the present invention is not limited to these Examples.

[Example 1] Mineral oil 89.2% Silica gel 6% Succinimide 4% Triethylene glycol monomethyl ether 0.4% 2,6-di-t-butylphenol 0.3% Benzotriazole derivative 0.1% (unit weight %) ) to prepare ER fluid.

The viscosity of the mineral oil was adjusted so that all of these samples had a viscosity of 80 cSt at 40°C.

Next, this ER fluid was measured for the following items at 40° C. and 90° C. using a rotational viscometer capable of applying voltage, and evaluated as an ER fluid.

・Responsiveness - AC electric field from 0 to 2. OX 10' (
Evaluate based on how many seconds it takes for the viscosity to stabilize when changing to V/+m).

・Reproducibility - change the AC electric field from 0 to 2. O x 10' (V
/m) → 0 cycle is repeated, the electric field is 1.4x
Evaluated by the rate of change in viscosity at 10'' (V/m).

・Durability - AC electric field 2. Evaluated by the amount of change in viscosity over time (%) (measurement time 5 hours) when kept constant at O XIO' (V/+m).

・Thickening effect - compared to 0 electric field, AC electric field is 1.

Evaluated by viscosity magnification when set to 4 x 10' (V/m).

- OV viscosity change rate - Evaluated by the viscosity change rate (%) at voltage Ov before and after a 5-hour durability test.

The results are shown in the table below.

[Example 2] An ER fluid was prepared using the same amount of triethylene glycol monoacetate in place of triethylene glycol monomethyl ether in Example 1, and its performance as an ER fluid was evaluated in the same manner as in Example 1. The results are shown in the table below.

[Comparative example]

ER using the same amount of triethylene glycol instead of triethylene glycol monomethyl ether in Example 1
A fluid was prepared and its performance as an ER fluid was evaluated in the same manner as in Example 1, and the results are shown in the table below.

(Left below) As can be seen from the table, the ER fluid of the present invention has the same responsiveness in a wide temperature range up to the high temperature range as the conventional ER fluid.
It exhibits reproducibility, thickening effect, and durability, and can lower the OV viscosity change rate.

(Effects of the Invention) The ER fluid of the present invention has excellent responsiveness, reproducibility, durability, and thickening effect in a wide temperature range up to high temperatures, and can reduce the OV viscosity change rate.
For example, it is useful for control equipment that utilizes viscosity changes, and can significantly improve control accuracy, particularly control accuracy under high-temperature use.

Out wish Man east Burning Co., Ltd. sub-agent

Claims (1)

[Claims] (1) An electrorheological fluid consisting of an electrically insulating fluid, porous solid particles, and a dispersant contains at least one substance selected from partially etherified polyhydric alcohols and partially esterified polyhydric alcohols. Features of electrorheological fluid.