JPH0873877A - Homogeneous electroviscous fluid - Google Patents

Abstract

PURPOSE: To obtain a homogeneous electroviscous fluid, producible at a low cost without any problems in settling and separation of particles and capable of manifesting stable and excellent responsiveness. CONSTITUTION: This homogeneous electroviscous fluid comprises a polymeric compound constituted of a hard segment comprising a low-molecular weight polymer and a soft segment comprising a low-molecular weight polymer. The polymeric compound has >=10<8> Ω volume resistivity and >=1000 molecular weight. The fluid can stably be used for new compact actuators such as a valve, a clutch, a brake and a torque converter operated by electronic control for a long period and expected for development into servo control systems with a high accuracy.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a uniform electrorheological fluid and is used as an actuator for vibration absorption, torque transmission, servo control and the like.

[0002]

2. Description of the Related Art Electrorheological fluids whose viscosity changes remarkably instantaneously and reversibly when a voltage is applied are well known as so-called Winslow fluids in which water-containing fine particles such as silica and starch are dispersed in insulating oil since the 1940s. ing. After that, many improvements have been proposed, such as a method of using ion-exchange resin particles or zeolite particles as the water-containing fine particles and a method of using non-water-containing particles such as organic semiconductor particles, surface-insulated conductive particles, and liquid crystal polymer particles. However, the method using these particles shows excellent performance in the short term, but in the long term, the problems of sedimentation and separation of particles and agglomeration of sedimented particles are unavoidable, which is a major obstacle to practical use. There is.

On the other hand, as a uniform material which does not use particles, for example, a method using a polar fluid such as nitromethane or nitrobenzene and a method using various low molecular weight liquid crystals have been studied and reported. No electrorheological effect has been obtained. On the other hand, by combining a plurality of liquid crystalline groups with a molecular chain of an appropriate length or polymerizing them,
A method has been proposed in which the binding force between the domains of the liquid crystal when aligned by an electric field is increased to obtain a large increase in viscosity (Japanese Patent Application Laid-Open No. Hei 5-
51590, JP-A-5-32988, and JP-A5-1.
71147, JP-A-5-323294, and JP-A-5-339594).

However, the electrorheological fluid using such a liquid crystalline substance has a drawback that it becomes expensive because a large amount of liquid crystalline groups which are complicated to synthesize are used. Urethane-based polymer solutions have recently been proposed as a homogeneous electrorheological fluid that can be manufactured at low cost [Dynamics
& Design Conference '94 "Functional Materials and Intelligent Materials / Structural Systems" Symposium Proceedings K519], it has been found that electrorheological effects can be obtained even with polymer compounds other than liquid crystals. In this urethane-based polymer solution, it is considered that the urethane moiety of the hard segment forms a higher-order structure in response to an external electric field, but it has not yet reached a large electrorheological effect.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and it is a homogeneous system, does not have the problem of particle settling, can be manufactured at low cost, and is stable and has a large electrorheological effect. The purpose is to provide a more practical electrorheological fluid.

[0006]

Means for Solving the Problems The inventors of the present invention have made extensive studies as to the cause of the low electrorheological effect of the above urethane-based polymer solution. As a result, propylene glycol was used as a soft segment of the polymer and a diluent. The present invention has been completed by finding that an electric current flows due to the use, and the electrorheological effect cannot be obtained, or even if it is obtained, it decreases with time.

That is, the present invention is an electrorheological fluid composed of a polymer compound composed of a hard segment composed of a low molecular weight polymer and a soft segment composed of a low molecular weight polymer, the volume resistance of the polymer compound being 10 ⁸
It is an electrorheological fluid having an Ωcm or more and an average molecular weight of 1,000 or more. The hard segment as referred to in the present invention has an aromatic hydrocarbon and / or a short chain aliphatic hydrocarbon as a main constituent element, and has a hydrogen bonding group such as an amide bond, a urethane bond, a urea bond, an ester bond, or a carbonate. Bond, ether bond,
A molecular chain containing polar groups such as sulfone bonds and sulfoxide bonds, which forms domains by the cohesive force of aromatic rings and aliphatic chains, the cohesive force between hydrogen bonding groups and polar groups, and is responsive to electric fields. Is the part that expresses.

The soft segment referred to in the present invention is
The long and flexible molecular chain is the main component, and
Amorphous and shaped by the above hard segment without agglomeration
Those that play a role in connecting the created domains to each other
Is. The flexible molecular chain used here is
Rukiren, oxyalkylene having 4 or more carbon atoms, fluoro
Alkylene, oxyfluoroalkylene, siloxane
An electrically safe unit consisting of repeating units selected from the group consisting of
The specific ones include alkylene and polytetramethyl.
Oki with 4 or more carbon atoms, such as ren glycol
Sialkylene and siloxane are preferable because they can be used at low cost.
Yes. The term “electrically stable” as used herein means to form the bent chain.
When a polymer is formed by repeating units, the volume of the polymer
Resistance is 10 ⁸It means that it becomes Ωcm or more. Oxy
Oxyethylene, oxypropylene in the alkylene chain
If the chain has 3 or less carbon atoms, the electrical resistance is low,
It causes deterioration of the electrical properties of the final polymer.
Therefore, it is not suitable as the soft segment of the present invention.
Yes.

The hard and soft segments of the polymer compound used in the present invention are characterized by being composed of a low molecular weight polymer obtained from a single monomer or a plurality of monomers. That is, a single or a plurality of monomers react with each other by addition, condensation, or ring-opening reaction to form a chain, and the degree of polymerization of the chain is preferably in the range of 2 to 100. Used as a soft segment.

As the method for synthesizing the polymer compound used in the present invention, a hard segment, a soft segment, or both are prepared in advance as a prepolymer or an oligomer, and the desired structure is obtained by connecting them later. Any method may be used, such as a method for making a hard segment and a soft segment at the same time by a one-step reaction.

The existence form of the hard segment and the soft segment in the molecule may be any of linear triblock, multiblock and radial block, or may be a graft form. Although the reason why the polymer compound of the present invention exerts a large electrorheological effect is not known, for example, a domain composed of a hard segment forms a higher-order structure by the action of an electric field, and the higher-order structure substantially corresponds to the electric field. It can be explained that a large resistance to a shearing force is generated and the apparent viscosity is increased by being connected by a soft segment composed of an insensitive bending chain. Thinking from that point,
For example, in a polymer compound having a linear triblock structure, it is preferable that the blocks at both ends are hard segments and the central block is a soft segment.

The ratio of the hard segment and the soft segment is not particularly limited as long as they both form a microphase-separated structure. When the ratio of the other to one increases and the microphase-separated structure is not formed,
It is considered that the balance between the formation of domains and the connection between domains as described above is lost, and a large electrorheological effect is not exhibited.

In order to obtain a stable and large electrorheological effect in the polymer compound of the present invention, it is essential that the polymer compound has a volume resistance of 10 ⁸ Ωcm or more and an average molecular weight of 1000 or more. Is. When the volume resistance is less than 10 ⁸ Ωcm, a stable electrorheological effect cannot be obtained, which is not preferable. Further, when the average molecular weight is less than 1000, a large electrorheological effect cannot be obtained. This can be interpreted, for example, because the cohesive force of the domain consisting of the hard segment is weak due to the small molecular weight, or the soft segment connecting the domains cannot exhibit sufficient resistance to shearing. The upper limit of the molecular weight is not particularly limited, but one having a molecular weight of 20,000 or less is usually used. When the molecular weight exceeds 20,000, the viscosity of the polymer compound itself becomes too high, and the change in viscosity depending on the presence or absence of an electric field may not appear remarkably.

The polymer compound of the present invention may be modified or added with various additives within a range not impairing the object of the present invention. For example, introduction of a polar functional group as a terminal or side chain of a polymer chain is a preferable means from the viewpoint of improving the responsiveness of the molecule to an electric field.
Also, adding a diluent or a plasticizer to the polymer compound is one of the preferable means in that the viscosity of the polymer compound itself can be lowered and the change in viscosity when an electric field is applied can be increased. In particular, by using a diluent having a structure close to the soft segment of the polymer compound, the molecular mobility of the soft segment can be increased without impairing the formation of the hard segment domain, and a large viscosity can be obtained when an electric field is applied. You can bring out change.

Particularly preferred examples of the polymer compound of the present invention are polyurethane-based thermoplastic elastomers and polyester-based thermoplastic elastomers as exemplified in "Rubber / Elastomer Utilization Note" (edited by Rubber / Elastomer Research Group, Industrial Research Group). Elastomers and thermoplastic polyamide-based elastomers, and among these elastomers, those having polydimethylsiloxane as the flexible segment flexible molecular chain are preferably used. Furthermore, for example, J. Po
A block copolymer of polysulfone and polydimethylsiloxane as described in Lymer Science, Part A-1, Vol. 9, page 3147 (1971) can also be preferably used.

[0016]

The present invention will be specifically described below with reference to examples, but the scope of the present invention is not limited to these examples. The electrorheological effect was measured according to the following method. Parallel plate with a pair of parallel disks (lower disk connected to a motor to rotate, upper disk connected to a torque meter to measure shear stress) modified so that the entire plate facing surface forms electrodes. The electroviscous effect was measured using a rotational viscometer of the type. The sample was sandwiched between electrodes set to have a facing electrode diameter of 32 mm and an electrode interval of 0.50 mm, the sample was sheared at a predetermined temperature at a shear rate of 10 sec ^-1 , and a DC voltage of 0 to 2 kV / mm was applied. The shear stress at that time was measured. The generated shear stress referred to in the present invention is the increment of the shear stress due to the application of voltage.

The volume resistance of the polymer is JIS C21.
It was measured according to 01.

[0018]

Example 1 1) Synthesis of hard segment 35 parts by weight of 4,4'-methylenediphenyl diisocyanate and 100 parts by weight of 1,4-butanediol were reacted in dimethylformamide at room temperature for 10 hours to obtain compound A after isolation and purification. Obtained.

[0019]

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2) Synthesis of soft segment 4,4'-methylenediphenyl diisocyanate 100
By weight, 50 parts by weight of polydimethylsiloxane having hydroxyl groups at both ends (manufactured by Shin-Etsu Silicone, average molecular weight 1000) were mixed and reacted at 80 ° C. for 2 hours to obtain a compound B.

[0021]

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3) Synthesis of polymer Compound B 100 parts by weight in dichloromethane solution and compound A
22 parts by weight of dimethylformamide solution were mixed and reacted at room temperature for 2 hours. The unreacted NCO end group was crushed with ethylene cyanohydrin, and then isolated and purified to give an average molecular weight of 7
600 polyurethanes were obtained. The volume resistance of this polymer was 2 × 10 ¹² Ωcm. 4) Electrorheological effect 100 parts by weight of this polyurethane and phenyl-modified polysiloxane (made by Toray Silicone, 125 cSt, specific gravity 1.0)
7) 50 parts by weight were mixed and the electroviscous effect was measured at 120 ° C. The results are shown in Table 1.

[0023]

Comparative Example 1 A polymer was synthesized in the same manner as in Example 1 except that polypropylene glycol (average molecular weight 1000) was used instead of polydimethylsiloxane having hydroxyl groups at both ends. The average molecular weight of the obtained polyurethane is 740.
At 0, the volume resistance was 8 × 10 ⁷ Ωcm. This polyurethane is polypropylene glycol (average molecular weight 10
00) and the electroviscous effect was measured at 60 ° C. As shown in Table 1, the electrorheological effect was inferior to that of Example 1.

[0024]

COMPARATIVE EXAMPLE 2 100 parts by weight of 4,4'-methylenediphenyldiisocyanate and 15 parts by weight of 1,3-bis (3-hydroxypropyl) -1,1,3,3-tetramethyldisiloxane were added to dimethylformamide at room temperature. After reacting for 10 hours, it was treated with ethylene cyanohydrin to obtain Compound C (molecular weight 925) after purification. The volume resistance of this compound was 9 × 10 ¹¹ Ωcm. The electrorheological effect was measured at 60 ° C., but as shown in Table 1, it was inferior to that of Example 1.

[0025]

[Chemical 3]

[0026]

Example 2 1) Synthesis of hard segment 114 parts by weight of bisphenol A was dissolved in a mixed solvent of chlorobenzene and dimethylsulfoxide (volume ratio 1: 1), and an aqueous solution of 20 parts by weight of sodium hydroxide was added.
This mixture was heated to about 180 ° C. and azeotropically removed water in the system. Next, a chlorobenzene solution containing 95 parts by weight of dichlorodiphenyl sulfone was added, and the mixture was heated to 180 ° C. again and the reaction was continued for 3 hours while distilling off chlorobenzene.
The reaction mixture was poured into a large excess of water that was weakly acidified with hydrochloric acid,
The precipitated solid is washed with water and purified by reprecipitation to obtain Compound D.
(Average molecular weight 1000) was obtained.

[0027]

[Chemical 4]

Next, 100 parts by weight of compound D is dissolved in chlorobenzene, and tetrabutylammonium hydrogen sulfate 3 is added.
3 parts by weight and allyl bromide 97 parts by weight were added, and further 80 parts by weight of sodium hydroxide was added as a 12.5 N aqueous solution, and the mixture was vigorously stirred at room temperature for 3 hours. After the reaction, the organic layer was separated, washed with dilute hydrochloric acid and then poured into excess methanol to obtain a polymer. It was confirmed by NMR measurement that this polymer had the structure of compound E.

[0029]

[Chemical 5]

2) Polymer Synthesis 80 parts by weight of compound E and a polydimer having SiH groups at both ends
Cylsiloxane (Shin-Etsu Silicone, average molecular weight 200)
0) Dissolve 100 parts by weight of chlorobenzene and add a small amount of
A chloroplatinic acid catalyst was added and reacted at 100 ° C. for 5 hours.
The reaction mixture was added to a large amount of methanol and the precipitated poly
The average molecular weight of 8000
A block polymer of The volume resistance of this polymer is
6 x 10 ¹¹It was Ωcm. 3) Electrorheological effect 100 parts by weight of this polymer and phenyl modified polysiloxa
(Toray Silicone, 125 cSt, specific gravity 1.07)
Mix 50 parts by weight and measure the electrorheological effect at 120 ° C.
It was Table 1 shows the results.

[0031]

[Table 1]

[0032]

INDUSTRIAL APPLICABILITY The present invention does not have the problem of sedimentation and separation of particles, which is one of the major drawbacks of the electrorheological fluids of particle dispersion systems that have been proposed so far, can be manufactured at low cost, and has stable and excellent response Provide a homogeneous electrorheological fluid exhibiting properties. INDUSTRIAL APPLICABILITY The electrorheological fluid of the present invention can be stably used for a long period of time in new compact, electronically controlled actuators such as valves, clutches, brakes and torque converters. Especially, it is expected to be applied to high precision servo control system.

Claims (3)

[Claims] 1. An electrorheological fluid composed of a polymer compound composed of a hard segment composed of a low molecular weight polymer and a soft segment composed of a low molecular weight polymer, the volume resistance of the polymer compound being 10 ⁸ Ωcm or more. And an average molecular weight of 1000 or more, an electrorheological fluid. 2. The electrorheological fluid according to claim 1, wherein the flexible molecular chain constituting the main part of the soft segment is composed of a repeating unit forming a polymer having a volume resistance of 10 ⁸ Ωcm or more. . 3. The flexible molecular chain constituting the main part of the soft segment comprises a repeating unit selected from the group consisting of alkylene, oxyalkylene having 4 or more carbon atoms, fluoroalkylene, oxyfluoroalkylene and siloxane. The electrorheological fluid according to claim 2, which is characterized in that.