JPH05179280A - Electro-viscous fluid - Google Patents

Abstract

PURPOSE:To obtain an electro-viscous fluid having high electro-viscous effect and excellent response and useful for the electrical control of a variable damping damper, engine mount, bearing damper, clutch, etc., by using a ferroelectric liquid crystal substance as a main component. CONSTITUTION:The objective electro-viscous fluid is composed mainly of a ferroelectric liquid crystal substance. The ferroelectric liquid crystal substance is preferably the compounds of formula I, formula II, etc., having a spontaneous polarization of >=3X10<-9>C/cm<2>. The use of a mixture of various liquid crystal substances is preferable for improving the liquid crystal characteristics. The electro-viscous fluid may be incorporated with an antioxidant and/or a metal corrosion preventing agent and conventional agent for improving friction and abrasion resistance.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrorheological fluid capable of electrically controlling mechanical devices such as a variable damping damper, an engine mount, a bearing damper, a clutch, a valve and a shock absorber.

[0002]

2. Description of the Related Art Electrorheological fluids whose viscosity changes with the application of voltage have been known for a long time. At first, the electrorheological fluid focused on a liquid-only system, but thereafter, a solid-dispersed electrorheological fluid has been developed by Winslow et al.

Such electrorheological fluids are usually mineral oils,
Solid particles such as synthetic oil and polarisers are dispersed in an electrically insulating fluid, and it is necessary to uniformly disperse the solid particles in the electrically insulating fluid in order to achieve its effect. However, even if a dispersant is used, solid particles tend to precipitate,
Therefore, problems such as a decrease in electrorheological effect, instability of properties, and blockage in various parts of the machine are likely to occur, a problem of friction and wear in various parts of the machine, and a problem that the electrorheological effect is low at room temperature or lower.

It has been reported that azomethine type liquid crystals have an electrorheological effect in the presence of an electric field (Jpn.JA.
ppl.Phys.17 (1978) P1525), but the present inventors are studying the application of liquid crystal as an electrorheological fluid for mechanical devices such as variable damping dampers, engine mounts, bearing dampers, clutches, valves and shock absorbers. It was found that the azomethine type liquid crystal has a small electroviscous effect, and the effect is further lowered when it is brought into contact with the atmosphere, and cannot be used for mechanical devices.

The electrorheological fluid composed of nematic liquid crystal has a response of several msec to several tens of msec, but a faster response is required depending on the mechanical system using the electrorheological fluid.

[0006]

An object of the present invention is to provide an electrorheological fluid having a higher electrorheological effect when liquid crystal is used as the electrorheological fluid, and particularly to provide an electrorheological fluid having excellent responsiveness. It is an issue.

[0007]

The electrorheological fluid of the present invention contains a ferroelectric liquid crystal substance as a main component.

The ferroelectric liquid crystal in the present invention preferably has a spontaneous polarization of 3 × 10 ^-9 C / cm ² or more, for example,

[0009]

[Chemical 1]

[0010]

[Chemical 2]

As the (2S, 3S) -3-methyl-2-halopentanoic acid 4 ', 4 "-alkoxybiphenyl ester, for example, halogen is chlorine and n = 7, and halogen is chlorine and n. = 8, halogen is chlorine, and n = 9. Ferroelectric liquid crystal shows the same fluidity as a liquid at room temperature alone or in a mixture, and exhibits an excellent electrorheological effect. Therefore, unlike the conventional electrorheological fluid containing solid particles, it does not cause the problem of precipitation, and is superior in friction and wear resistance to ordinary lubricating oils. Alternatively, they may be mixed and used, and preferably mixed with various liquid crystal substances in order to improve liquid crystal characteristics.

In the present invention, a nematic liquid crystal may be blended with the ferroelectric liquid crystal.

The nematic liquid crystal is a liquid crystal substance having no azomethine bond (-CH = N-bond) in the structural formula and is a liquid crystal represented by the following formulas (1) and (2).

[0014]

[Chemical 3]

[0015]

[Chemical 4]

-C≡C-, -N = N- (trans type),
_{-COO -, - (CH 2)} n -, - CH 2 O -, - R '
-, -COS-, -CH = C (CN)-, -CH = C
_{(Cl) -, - COCH 2} -, - O- (CH 2) 2 -O
-, - CH = CH-COO -, - COO-C 6 H 5 -C
OO-, X, Y _{are, -C 6 H 5, -NHCOCH 3} , -
_{CN, -OR, -NO 2, -F} , -Cl, -Br, -N
_{R 2, -R, H, -OCOR} , -COOH, -CHO,
_{-NCS, -N 3, -NH 2,} -CH 2 CH (Cl) C
_{N, -C (CH 3) =} NOH, -COR, -C≡CH,
_{-CH 2 COOH, -NCO, -R'CN,} -R'C
^{l, -R *, -ROR *,} -OCOOR, R is, C _n H
_{2n + 1, C 2 H 5} -CH (CH 3) -CH 2 -, C 2 H 5
_{-CH (CH 3) -CH 2 O-} , C 2 H 5 -CH (CH
₃ ) —C ₃ H ₆ —, R ′ is C _n H _2n , R ^* is an optically active alkyl group, Z and Z ′ are a cyano group, a fluorine atom,
It represents a chlorine atom, an iodine atom, a bromine atom, a nitro group or a methyl group, n in R and R'is an integer of 1 to 20, and the number of carbon atoms in R ^* is the same as R and R '.

As the liquid crystal represented by the formulas (1) and (2),
For example, the following structural formulas can be mentioned.

[0018]

[Chemical 5]

[0019]

[Chemical 6]

[0020]

[Chemical 7]

In the above example, (3) is an azo type, (4)
Is an azoxy type, (5) is a benzoic acid phenyl ester type,
(6) is a cyanobiphenyl type, (7) is a cyanoterphenyl type, (8) is a cyclohexylcarboxylic acid phenyl ester type, (9) is a phenylcyclohexane type, (1)
0) is biphenylcyclohexane type, (11) is phenylpyrimidine type, (12) is phenyldioxane type,
(13) is cyclohexylcyclohexane ester type,
(14) is cyclohexylethane type, (15) is cyclohexene type, (16) is alkylalkoxytran type,
(17) is an alkylcyclohexylalkoxytolan type, (18) is an alkenyl type, (19) is a 2,3-difluorophenylene type, (20) is a cyclohexylcyclohexane type, (21) is a bicyclooctane type, (22).
Is a Cuban-based liquid crystal, (23) is a dicyanohydroquinone-based liquid crystal, (24) is a cyanothiophenyl ester-based liquid crystal, and in the formula, X, Y, R, and R'are X, Y in the above formulas (1) and (2), It is synonymous with R and R '. The nematic liquid crystal may be contained in an amount of 1 to 99% by weight based on the ferroelectric liquid crystal. Further, an antioxidant and / or a metal corrosion inhibitor may be added as an additive to the electrorheological fluid of the present invention.

As the antioxidant, commonly used phenol-based and amine-based antioxidants can be used. Specifically, the phenol-based antioxidant is 2,6-di-t-butylparacresol, 4.4. '-Methylenebis (2.6-di-
t-butylphenol), 2,6-di-t-butylphenol, etc., and dioctyldiphenylamine, phenyl-α-naphthylamine, alkyldiphenylamine, N-nitrosodiphenylamine, etc. can be used as the amine type, and the whole electrorheological fluid can be used. 0.01 to 10 wt
%, Preferably 0.1-2.0 wt% can be used,
If it is less than 01 wt%, there is no antioxidant effect, and if it exceeds 10 wt%, there are problems such as deterioration of hue, generation of turbidity, generation of sludge, and increase in viscosity.

Corrosion inhibitors may be added. Specifically, for nitrogen compounds, benzotriazole and its derivatives, imidazoline, pyrimidine derivatives and the like, and for compounds containing sulfur and nitrogen, 1.3.4-thiadiazole polysulfide, 1.3. .4-thiadiazolyl-2.5-bisdialkyldithiocarbamate, 2- (alkyldithio) benzimidazole, etc., β- (o-carboxybenzylthio)
Propionnitrile, propionic acid or the like can be used, and 0.001 to 10% by weight, preferably 0.01 to 1.0% by weight, based on the whole electrorheological fluid is used. If it is less than 0.001 wt%, there is no corrosion preventing effect, and if it exceeds 10 wt%, there are problems such as deterioration of hue, generation of turbidity, generation of sludge, and increase in viscosity.

Further, a conventional friction and wear resistant agent such as dibenzyl sulfide, dibutyl sulfide, chlorinated paraffin and chlorinated diphenyl may be added, and an extreme pressure agent and an antifoaming agent may be added. Good.

[0025]

[Operation and effect of the invention] Liquid crystal has anisotropy, has crystallinity even though it is a liquid, and is aligned in a certain direction due to its dipole moment in the presence of an electric field. It is known to cause rheological changes and increase apparent viscosity. Also, in the presence of an electric field, resistance is generated against the flow that passes between both electrodes and each molecule is attracted by electrostatic attraction, resulting in stronger resistance, which is considered to lead to an increase in viscosity. There is.
Further, the electrorheological fluid made of conventional mineral oil or the like remarkably lowers the electrorheological effect at a low temperature below room temperature, but when liquid crystal is used as the electrorheological fluid, the electrorheological effect is maintained even at a low temperature. The applicable temperature range can be expanded.

The present inventors have found that by using a ferroelectric liquid crystal as an electrorheological fluid, an electrorheological fluid having a better response can be obtained. ^It has a large spontaneous polarization of ^-9 C / cm ² or more, its driving force is very large in the presence of an electric field, and its response time can be as short as msec or less. It is possible.

Examples of the present invention will be shown below.

[0028]

Example 2 Ferroelectric Liquid Crystal (2S, 3S) -3-Methyl-2-chloropentanoic acid 4 ', 4 "-octyloxybiphenyl ester (Magnitude of spontaneous polarization: 1.8
× 10 ⁻⁷ C / cm ² ) was used as the electrorheological fluid.

[0029]

Example 2 Nematic liquid crystal [trade name, NEM133
(N) Fuji Dye Co., Ltd., viscosity 50 cP (20 ° C.)], and ferroelectric liquid crystal (2S, 3S) -3-methyl-2-chloropentanoic acid 4 ′, 4 ″ -octyloxybiphenyl ester (spontaneous Size of polarization 1.8 × 10 ^-7 C / c
m ² at 40 ° C.) was added at 20% by weight to obtain an electrorheological fluid.

[0030]

[Comparative Example] Nematic liquid crystal [trade name, NEM133
(N) Fuji Dye Co., Ltd., viscosity 50 cP (20 ° C.)] was used alone as an electrorheological fluid.

The thickening effect of each sample was 5
It was measured at 0 ° C. using a rotational viscometer capable of applying a voltage. Thickening effect, at a shear rate 600 sec. ^-1, the electric field 0 AC field on the viscosity at the time (V / m) 2.0 × 10 6 (V
/ m) was compared by the magnification of the viscosity.

Regarding the responsivity of each sample, a measuring device comprising a piston and a cylinder provided with a flow path for an electrorheological fluid and capable of applying a voltage between the piston and the cylinder was prepared, and each sample was placed in the cylinder. After filling, turn on the electric field while gravity dropping the piston at 50 ° C.
The response time (msec) was measured by turning off.

The results are shown in the table below.

[0034]

[Table 1]

The electrorheological fluid of the present invention is
It can be seen that the thickening effect and responsiveness are excellent.

Claims (1)

[Claims] 1. An electrorheological fluid containing a ferroelectric liquid crystal material as a main component.