JPH0959665A - Electrorheological fluid - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an electrorhrological fluid excellent in actuation stability by incorporating thereunto predetermined amts. of s plurality of compds. having a specific content of the sum of liq. crystalline groups and non liq crystalline groups based on the total no. of flexible molecular chain units. SOLUTION: A polymer having a degree of polymn. of about 5 to 100 and comprising flexible molecular chain units selected from among siloxanes, oxyalkylences, fluorooxyalkylences, etc., is used. There are prepared a compd. (A) of 25 to 80% in content of the sum of liq. crystalline groups such benzoic ester, dipheny groups and the like and nonlig crystalline groups contg. a nitrile group and/or a benzene skeleton based n the total no. of the flexible molecular chain units in the polymer, and a compd. (B) of 5 to 20% in the above-mentioned content. 60-90 pts.wt. compd. (A) is mixed with 40-10 pts.wt. compd. (B), provided that (A)+(B)=100 pts.wt. Subsequently, 100 pts.wt. mixture is admixed with about 10-200 pts.wt., pref about 20-90 pts.wt., diluent such as a silicone oil to obtain an electrorheological fluid.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel electrorheological fluid, which is used as a homogeneous electrorheological fluid that stably exhibits a large electrorheological effect for a long period of time, and is used for vibration absorption, torque transmission, dampers, and machine positioning control. It is used for applications such as actuators.

[0002]

2. Description of the Related Art Winslow is an electrorheological fluid.
For about half a century since the invention of, a large number of so-called dispersion fluids have been proposed in which water-containing particles or dielectric particles such as conductive particles or semiconductor particles whose surface is coated with an insulating thin film are dispersed in insulating oil. . However, these fluids have a poor dispersion stability of particles and have an essential problem of particle sedimentation, and have not been put into practical use. On the other hand, a lot of studies have been conducted on polar liquids, liquid crystals, polymer solutions, etc. for homogeneous electrorheological fluids that do not use particles, but their electrorheological effects have been extremely small and neglected. Recently, as the difficulty of a dispersed electrorheological fluid has become clear, the possibility of a homogeneous fluid has been revisited, and reports and patents on a homogeneous electrorheological fluid without particles have begun to be published. For example, poly (γ-benzyl-L-glutamate)
Lyotropic liquid crystal in which dioxane is dissolved in JP-A-4-266997, or a thermotropic liquid crystalline compound in which a plurality of liquid crystalline groups are bonded in a chain (Japanese Patent Laid-Open No.
In the fluid using No. 32988), a large electrorheological effect superior to the conventional dispersion system is obtained.

[0003]

Although the electrorheological fluid using the above lyotropic liquid crystal or thermotropic liquid crystal exhibits a large electrorheological effect, the solvent used in the lyotropic liquid crystal generally has a high polarity. Many of them are electrically conductive and highly volatile, which limits their practical use. In addition, the latter one using thermotropic liquid crystal has excellent electrical insulation and durability, but generally has a high viscosity (basic viscosity) in the absence of voltage application, and therefore has a narrow operating temperature range, especially at low temperatures. It tends to be difficult to operate. Further, both of them have a problem that the cost is high because the raw materials are generally expensive and many steps are required for the production.

[0004]

In order to lower the base viscosity of the thermotropic liquid crystal, the content of the liquid crystalline group may be lowered, but at the same time, the electrorheological effect itself is also reduced, which is not a preferable method. Therefore, the present inventors have earnestly studied a method of reducing the base viscosity without sacrificing the electrorheological effect and expanding the operating temperature range. as a result,
The present invention has been completed by finding the fact that the basal viscosity can be reduced without lowering the electrorheological effect by replacing a part of the liquid crystalline group with a certain functional group.

That is, the present invention is as follows. 1. A compound in which a plurality of liquid crystalline groups and a non-liquid crystalline group containing at least one or both of a nitrile group and a benzene skeleton are simultaneously contained in a polymer composed of one flexible molecular chain unit. An electrorheological fluid containing. 2. The compound of the above-mentioned 1, wherein the total content of the liquid crystalline group and the non-liquid crystalline group is 25 to 80% with respect to the total number of the flexible molecular chain units, and the compound of the above 1. The total content of the liquid crystalline group and the non-liquid crystalline group is 5 to 20 with respect to the total number of flexible molecular chain units.
% Of the compound (II) at the same time, and the mixing ratio of the compound (I) and the compound (II) is 1 by the total weight of both.
An electrorheological fluid in which the compound (I) is in the range of 60 to 90 parts by weight and the compound (II) is in the range of 40 to 10 parts by weight with respect to 00 parts by weight. 3. The electrorheological fluid according to 1 or 2 above, wherein the flexible molecular chain unit is siloxane, oxyalkylene, or fluorooxyalkylene.

Hereinafter, the present invention will be described in detail. The liquid crystalline group referred to in the present invention, Schiff base type, azo type, azoxy type, benzoic acid ester type, biphenyl type, terphenyl type, naphthalene type, cyclohexylcarboxylic acid type, phenylcyclohexane type, biphenylcyclohexane type,
Pyrimidine-based, dioxane-based, cyclohexylcyclohexane-based, cyclohexylethane-based, cyclohexene-based, and tolan-based commonly known low-molecular liquid crystals and ferroelectric liquid crystals (For details, see Shoichi Matsumoto and Ichiyoshi Kakuda "Liquid Crystal The basic groups and applications "of Industrial Research Committee, P.107-162) are representative examples.) A functional group containing a core molecular structure (generally called a mesogen) that exhibits liquid crystallinity. Further, a hydrogen bond type liquid crystal exhibiting liquid crystallinity by forming a molecular complex pair by a plurality of molecules by hydrogen bond, an ionic liquid crystal in which a quaternized nitrogen atom or metal atom is introduced into the molecule,
Ion-dipole interaction type liquid crystal in which crown ether is introduced into the above mesogen and complexed with a metal salt (for details, Takashi Kato, Production Research, 46 [6] P. 313 (19)
A typical example is described in 94). ) Is also included in the liquid crystalline group referred to in the present invention.

The non-liquid crystalline group containing at least one or both of a nitrile group and a benzene skeleton in the present invention is a functional group different from the above-mentioned mesogen showing liquid crystallinity and is shown below. A typical example is a molecular structure.

[0008]

Embedded image

The flexible molecular chain unit constituting the polymer referred to in the present invention includes (1) dimethylsiloxane, phenylmethylsiloxane, etc. --OSiR ₁ R _2- (wherein R ₁ and R ₂ are alkyl groups or phenyl groups. Is shown.)
Siloxane represented by (2) oxyethylene, oxypropylene, oxybutylene, etc. oxyalkylene represented by -OC _m H _2m- (m represents an integer of 1 to 5), and (3) difluorooxy. Ethylene, trifluorooxyethylene, pentafluorooxypropylene, etc. --OC _m H _2m-n F _n- (where m is an integer from 1 to 3,
n represents an integer in the range of 0 <n <2m. ) Fluorooxyalkylene represented by (4), methylene, ethylene,
Propylene, such as -C _m H _2m - (where m is an integer of 1 to 8.), Etc. alkylene represented by. In particular, (1) to (3) are excellent in flexibility even at low temperatures and are suitable for use in the present invention.

The compound of the present invention comprises a plurality of liquid crystalline groups,
A non-liquid crystalline group is contained at the same time, and (a) a main chain type compound, (b) a side chain type compound, and
The compound can be classified into a terminal type compound (c) and a complex type compound in which a plurality of structures of (d) (a) to (c) are present in a polymer. First, in the main chain type compound (a), the liquid crystalline group and the non-liquid crystalline group are bonded to the flexible molecular chain unit of the above (1) to (4) directly or via a bonding group to form a polymer main chain. Make up a chain. As the bonding group used here, -O-, -COO-, -CO-, -CONH
-, - OCOO -, - S -, - SO -, - SO 2 - groups such as and the like. These linking groups can also be used to bond the same or different flexible molecular chain units to each other to form a new flexible main chain.

Next, the side chain type compound (b) and the terminal type compound (c) will be explained. The liquid crystal group and the non-liquid crystal group are the main chain of the polymer composed of flexible molecular chain units in (b). And / or in a chain other than the end of the branched chain, and in (c) the main chain and / or the terminal end of the branched chain of the polymer composed of flexible molecular chain units, respectively, directly or via a linking group. It
The polymer composed of flexible molecular chain units here means a homopolymer of the molecular chain units of the above (1) to (4),
It is a copolymer of these molecular chain units or with different molecular chain units. Further, as the bonding group used here,
-C _p H _2p - (where p is from 1 to 20 integer), - C _p
H _2p-q F _q − (where p is an integer from 1 to 20, and q is 1 ≦
integer) in the range of q ≦ 2p, - Si (CH 3) 2 -, - O
Representative examples include groups such as —, —COO—, —CO—, and —CONH— and chains obtained by combining these groups. Furthermore, a branched structure represented by the following formula may be present in the bonding group, and a plurality of liquid crystalline groups and / or non-liquid crystalline groups may be bonded to the molecular chain via one bonding group.

[0012]

Embedded image

The liquid crystalline group and the non-liquid crystalline group are R ₁ or R ₂ in the flexible chain having the structure shown in (1).
And a part of H in the flexible chains having the structures shown in (2) to (4) are bound to the polymer either directly or through the above-mentioned linking groups. Furthermore, a part of the remaining R ₁ , R ₂ and H may be substituted with an alkyl group having a chain length of 20 or less, a fluoroalkyl group, oligosiloxane or the like. In any of the above forms (a) to (d), the degree of polymerization of the compound of the present invention is preferably in the range of 2 to 300, preferably 2 to 100, and more preferably 5 to 100. The shape of the polymer may be linear, branched or star-shaped.

When the above-mentioned non-liquid crystalline group is introduced into the molecular chain, the increase in viscosity is smaller than that in the case where the same number of liquid crystalline groups are introduced into the same molecular chain, and a compound having a low base viscosity is obtained. It is suitable. Moreover, an electric field acts on the dipole moment of the nitrile group in the non-liquid crystalline group and the π electron of the benzene ring, so that the non-liquid crystalline group and the bonding group bonded to the non-liquid crystalline group have the same orientation and orientation as the liquid crystalline group. Since some higher-order structure such as aggregation can be formed, there is no fear that the electrorheological effect will be significantly reduced as compared with a compound in which only a liquid crystal group is introduced.

From the viewpoint of the electrorheological effect, it is preferable that the total number of liquid crystalline groups and non-liquid crystalline groups contained in one molecular chain is three or more. However, when the content of liquid crystalline groups is increased, the base viscosity is increased. , The liquid crystal group and the non-liquid crystal group content must be determined in consideration of this point. Although not particularly limited, it is preferable that the total number of liquid crystal groups introduced based on the total number of repeating units of the flexible molecular chain is 80% or less. A suitable ratio of the liquid crystal group and the non-liquid crystal group is 1% or more and 95% or less, and more preferably 5% or more and 80% or less based on the total number of both contained in one molecular chain. , And more preferably 10% or more and 60% or less. When the proportion of the non-liquid crystalline group is small, the basal viscosity is insufficiently reduced and the operating temperature range is not improved. On the contrary, when the ratio of the non-liquid crystalline group increases, the base viscosity decreases,
The electrorheological effect also tends to decrease at the same time. For the liquid crystalline group and the non-liquid crystalline group, one type is used,
A plurality of items can be used in combination.

The compound of the present invention may be used alone as an electrorheological fluid, but for the purpose of lowering the base viscosity and improving the handling property, for example, a heavy chain composed of the same unit as the molecular chain of the compound is used. It can also be used by diluting it with a compound having affinity to the polymer or the molecular chain but having low affinity to the liquid crystal group and the non-liquid crystal group (hereinafter referred to as a diluent). Typical examples of diluents include silicone oil, modified silicone oil, paraffinic mineral oil, naphthene mineral oil, synthetic hydrocarbon oil such as olefin (co) polymer / alkylbenzene / alkylnaphthalene, and fluorine-containing aromatic compound. Can be mentioned. The ratio of diluent is
Although not particularly limited, a range of 10 parts by weight or more and 200 parts by weight or less is preferable, and a range of 20 parts by weight or more and 90 parts by weight or less is more preferable, based on 100 parts by weight of the compound of the present invention.

When a diluent is used, the diluent and the compound of the present invention may separate when the voltage is repeatedly applied or the voltage is continuously applied for a long time. In this case, instead of using one kind of compound as the compound of the present invention, the compound (I) having a high content of the liquid crystal group and the non-liquid crystal group and the compound (II) having a low content thereof are mixed. As a result, the compatibility with the diluent can be improved, and an electrorheological fluid which is free from separation and is more excellent in operation stability especially at low temperature can be obtained. The preferable content of the liquid crystalline group and the non-liquid crystalline group in the compound (I) is such that the total number of the total of the liquid crystalline group and the non-liquid crystalline group introduced based on the total number of repeating units of the flexible molecular chain is 25% or more. The range is 80% or less, more preferably 25% or more and 50% or less.
On the other hand, in the compound (II), the total number is 5 as well.
% Or more and 20% or less, and more preferably 10% or more and 20% or less. By adjusting the content of the liquid crystalline group and the non-liquid crystalline group in the compound (I) and the compound (II) to fall within these ranges, a large electrorheological effect is exhibited, and the electricity can be stably used for a long time even under an electric field. A viscous fluid can be obtained. In this case, 60 to 90 parts by weight of the compound (I) and 100 parts by weight of the compound (II) based on the total weight of 100 parts by weight.
Are mixed in an amount of 40 to 10 parts by weight, and a diluent is added, and the total weight of the compounds (I) and (II) is 10
By using 10 to 200 parts by weight, more preferably 20 to 90 parts by weight with respect to 0 parts by weight, an electrorheological fluid having the best balance between the electrorheological effect and the operation stability at low temperature can be obtained. .

The kinds and compositions of the liquid crystal group and the non-liquid crystal group in the compound (I) and the compound (II) do not have to be the same. In addition, it is preferable that the compound (I), the compound (II), and the molecular chain species of the diluent are all the same from the viewpoint of compatibility. The compound (I), the compound (II), and the diluent may be mixed at the stage of starting materials such as prepolymers and monomers and then synthesized at the same time and used as they are, or they may be independently synthesized and then mixed. Good. As a mixing method,
A solution mixing method in which each component is dissolved in a common solvent and then the solvent is evaporated and dried, a heating mixing method in which each component is heated to reduce its viscosity, and then stirred and mixed, and a machine for mixing using a roll kneader, etc. Any method such as a mixing method may be used without any particular limitation.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be specifically described below with reference to Examples. The basal viscosity (viscosity without voltage application) and the electrorheological effect of the sample were measured according to the following methods. <Measurement method of basal viscosity and electrorheological effect> A pair of parallel disks modified so that the entire plate facing surface forms an electrode (the lower disk is connected to the motor to rotate, the upper disk is connected to the torque meter). The shearing stress is measured with a parallel plate type rotational viscometer. The sample is sandwiched between electrodes set to have a facing electrode diameter of 32 mm and an electrode interval of 0.50 mm, and 200 sec ^-1 at a predetermined temperature.
The sample is sheared at a shear rate of 0 to 2 kV / DC voltage.
Shear stress was measured when mm was applied. The generated shear stress referred to in the present invention is an increment of the shear stress due to the application of a voltage.

[0020]

Example 1 1) Synthesis of Liquid Crystalline Group 100 g potassium hydroxide, 120 ml water, ethanol 5
P-Hydroxybenzoic acid 99 was added to 00 ml of the mixed solution.
g and potassium iodide 0.7 g were dissolved, allyl bromide 86 g was added dropwise, and the mixture was heated under reflux at 80 ° C. for 12 hours. After cooling, 150 ml of water was added and the pH was adjusted to 2 with hydrochloric acid. The deposited precipitate was separated by filtration, dried, and recrystallized from ethanol to obtain 90 g of Compound A shown in Chemical Formula 3 below.

[0021]

Embedded image

To compound A, 29.2 ml of thionyl chloride and a few drops of dimethylformamide were added, and the mixture was stirred at 40 ° C. for 2 hours to give an acid chloride form. Excess thionyl chloride was distilled off under vacuum. The acid chloride form dissolved in 50 ml of tetrahydrofuran was used as 23.8 g of p-cyanophenol, 36.2 ml of triethylamine, and 150 m of tetrahydrofuran.
It was added dropwise to the mixed solution of 1 at 0 ° C., and the mixture was returned to room temperature and stirred for 12 hours. The reaction mixture was poured into water and extracted with ethyl acetate,
Dried and concentrated. The precipitated solid was recrystallized from ethanol to obtain 52.1 g of compound B shown in Chemical formula 4 below.

[0023]

Embedded image

2) Synthesis of non-liquid crystalline group 17.9 g of p-cyanophenol, anhydrous potassium carbonate 5
1.8 g, allyl bromide 19.5 ml, and methyl ethyl ketone 200 ml were mixed, and the mixture was heated with stirring at 80 ° C. for 4 hours. After allowing to cool, the reaction mixture was poured into water and extracted with ethyl acetate. After drying and concentration, the obtained crude product was purified by silica gel column chromatography to give compound C shown in the following chemical formula 5.
23.4g was obtained.

[0025]

Embedded image

3) Synthesis of Polymer A polymer having a molar ratio of liquid crystal groups to non-liquid crystal groups of 6: 4 and a total content of 40% was synthesized. Dimethylsiloxane / methylhydrogensiloxane random copolymer (polymer D) 3.00 having the average composition shown in Chemical formula 6
g, compound B (2.81 g) and compound C (1.07 g) were dissolved in tetrahydrofuran (35 ml), a catalytic amount of chloroplatinic acid was added, and the mixture was reacted at 60 ° C. for 2 hours. By high performance liquid chromatography and FT-IR analysis, it was confirmed that the compounds B and C almost completely disappeared and reacted with the polymer D. Subsequently, 2.9 g of 1-pentene was added to the unreacted Si.
After completely crushing the -H group, the solvent was distilled off to recover the product (Polymer E). The structure of this polymer E was confirmed by NMR, and the average molecular weight by GPC was about 5,800.

[0027]

[Chemical 6]

The basal viscosity of the obtained polymer E was measured,
The results are shown in Table 1. Further, 100 parts by weight of Polymer E was dissolved in a small amount of tetrahydrofuran together with 50 parts by weight of 20 cSt polydimethylsiloxane oil, and the solvent was further distilled off under vacuum to prepare a mixture, and the electroviscous effect of this mixture was measured. Table 2 shows the results. As shown in Table 2, it can be seen that the operating temperature range extends to 30 ° C. and a large electrorheological effect can be obtained.

[0029]

Comparative Example 1 A polymer containing only the same liquid crystal group as that used in Example 1 at a content rate of 40% was synthesized. The above polymer D (3.00 g) and compound B (4.69 g) were dissolved in tetrahydrofuran (35 ml), and a catalytic amount of chloroplatinic acid was added to the mixture to prepare 60.
The reaction was carried out at 2 ° C. for 2 hours. High performance liquid chromatography and FT-IR
It was confirmed that the compound B had almost completely disappeared and reacted with the polymer D by the analysis by. Subsequently, 2.9 g of 1-pentene was added to completely crush unreacted Si-H groups, and then the solvent was distilled off to recover a product (polymer F).
The structure of this polymer F was confirmed by NMR, and the average molecular weight by GPC was about 6,500. The base viscosity of the obtained polymer F was measured. The results are shown in Table 1. Further, 100 parts by weight of Polymer F was dissolved in a small amount of tetrahydrofuran together with 50 parts by weight of 20 cSt polydimethylsiloxane oil, and the solvent was further distilled off under vacuum to prepare a mixture, and the electrorheological effect was measured. Since the slip phenomenon occurred at 40 ° C. or lower, the measurement of the electrorheological effect became unstable. It can be seen that the basal viscosity of Example 1 in which the liquid crystalline group and the non-liquid crystalline group are combined is significantly lower than that of Comparative Example 1 in which only the liquid crystalline group is used.

[0030]

Example 2 A polymer having a molar ratio of liquid crystal groups to non-liquid crystal groups of 6: 4 and a total content of 17% was synthesized.
4.00 g of dimethyl siloxane-methyl hydrogen siloxane random copolymer (polymer G) having the average composition shown in Chemical formula 7, compound B 1.78 g, compound C 0.6
8 g was dissolved in 30 ml of tetrahydrofuran, a catalytic amount of chloroplatinic acid was added, and the mixture was reacted at 60 ° C. for 2 hours. By high performance liquid chromatography and FT-IR analysis, it was confirmed that the compounds B and C almost completely disappeared and reacted with the polymer G. Subsequently, 3.7 g of 1-pentene was added to completely crush unreacted Si-H groups, and then the solvent was distilled off to recover a product (polymer H). The structure of this polymer H was confirmed by NMR, and the average molecular weight by GPC was about 9
600.

[0031]

[Chemical 7]

67 parts by weight of the polymer E synthesized in Example 1, 33 parts by weight of the above polymer H, and 50 parts by weight of polydimethylsiloxane oil of 20 cSt were dissolved in a small amount of tetrahydrofuran, and the solvent was distilled off under vacuum to prepare a mixture. Then, the electrorheological effect of this mixture was measured. Table 2 shows the results. The operating temperature range expanded to a temperature lower than that of Example 1.

[0033]

[Table 1]

[0034]

[Table 2]

[0035]

INDUSTRIAL APPLICABILITY The present invention has a narrow operating temperature range, which is one of the major drawbacks of the previously proposed homogeneous electrorheological fluid using the lyotropic liquid crystal or thermotropic liquid crystal, and operates particularly at a low temperature side. It has become possible to provide an electrorheological fluid with excellent stability that solves the problem of being difficult to do. The electrorheological fluid of the present invention includes a valve, a clutch,
It can be stably used for a long period of time in new compact and electronically controlled actuators such as brakes and torque converters. Especially, it is useful for the development of high precision machine control system.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location C10N 30:08 40:04 40:06 40:14

Claims (3)

[Claims] 1. A polymer comprising one flexible molecular chain unit, and a plurality of liquid crystalline groups, and a non-liquid crystalline group containing at least one or both of a nitrile group and a benzene skeleton. An electrorheological fluid containing a compound that comprises at the same time. 2. The compound according to claim 1, wherein the total content of the liquid crystal group and the non-liquid crystal group is 25 to 80% with respect to the total number of flexible molecular chain units. The compound according to claim 1, wherein the total content of the liquid crystal group and the non-liquid crystal group is 5 to 20% based on the total number of flexible molecular chain units, and the compound (II) is contained at the same time. Further, the mixing ratio of the compound (I) and the compound (II) is 60 to 90 parts by weight of the compound (I) and 40 to 40 parts by weight of the compound (II) with respect to 100 parts by weight of the total weight of the both.
An electrorheological fluid in the range of 10 parts by weight. 3. The electrorheological fluid according to claim 1, wherein the flexible molecular chain unit is siloxane, oxyalkylene, or fluorooxyalkylene.