JPH101687A - Electroviscous fluid - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an electroviscous fluid, comprising a specific organic compound and capable of producing a high shear stress at a low electric field intensity without any temperature dependence of an electrorheological(ER) effect which is the ratio of the viscosity when applying an electric field to the basal viscosity or fluid characteristics and further providing the large ER effect and a large stress per power consumption. SOLUTION: This electroviscous fluid comprises an organic compound having a rigid rodlike structural part as a basic skeleton and a higher permittivity in the major axial direction of the molecule than that in the minor axial direction [e.g. a compound of the structure represented by formula I (A is the rigid rodlike structural part; Z is a group capable of increasing the dielectric anisotropy of the molecule; Y is a group capable of increasing the produced stress when applying an electric field thereto), concretely a compountd represented by formula II]. Furthermore, the fluid is obtained by dissolving the molecule in a solvent such as an insulating oil, e.g. a silicone oil or a fluorine-based oil when the molecule is a solid.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an improvement of an electrorheological fluid whose viscosity can be controlled by applying an electric field.

[0002]

2. Description of the Related Art An electrorheological fluid is a fluid having a so-called Winslow effect in which the viscosity changes rapidly and reversibly when an electric field is applied. Such an electrorheological fluid has been known for a long time, and for example, a suspension in which various particles of inorganic or polymer are dispersed in an electrically insulating liquid has been proposed. In recent years, as a particle-dispersed electrorheological fluid containing no water, it has excellent temperature stability and a large ER effect, which is the ratio of the viscosity when an electric field is applied to the viscosity when no electric field is applied, that is, the base viscosity. ing.

As described above, in an electrorheological fluid in which particles are dispersed, sedimentation of particles becomes a problem. for that reason,
Attempts are made to prevent the particles from settling by adjusting the specific gravity of the particles and the dispersion medium. However, it is difficult to make the specific gravities of the particles and the dispersion medium equal in all temperature ranges, and it cannot be used in an apparatus to which a large centrifugal force is applied. Also,
In addition to the problem that the dispersed particles mechanically wear the container or electrode containing the electrorheological fluid, the particles also wear and deteriorate with each other. Although it has been proposed to use polymer-based particles as particles to be dispersed for the purpose of reducing the wear, it has not been possible to completely solve the above-mentioned problem of wear.

In order to solve the above problems, Japanese Patent Application Laid-Open No. Hei 6-346080 proposes a homogeneous electrorheological fluid using a liquid crystal substance. Since the liquid crystal electrorheological fluid is a homogeneous system, it can solve the above-mentioned problems such as particle settling and abrasion.

[0005]

However, when a liquid crystalline substance is used for the electrorheological fluid, the liquid crystal is an intermediate phase between the solid and the liquid. The degree of orientation varies greatly with temperature.
For this reason, there has been a problem that the temperature dependency of the ER effect and the fluid characteristics described above becomes very large.

In order to improve the stress generated when an electric field is applied, it is conceivable to polymerize the liquid crystalline substance. However, since the polymerization increases the base viscosity, the improvement of the ER effect is limited. there were.

Further, in the above-mentioned conventional electrorheological fluid, an electric field strength of about several Kv / mm is required to obtain a practical level of shear stress, for example, a shear stress of several KPa, and a high-voltage power supply is required. As a result, there is also a problem that the cost is increased in practical use.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional problems, and has as its object the object of the present invention, which has no temperature dependence and a large
An object of the present invention is to provide an electrorheological fluid which exhibits an effect and can obtain a large shear stress with a small electric field.

[0009]

In order to achieve the above object, an electrorheological fluid according to a first aspect of the present invention has a rigid rod-like structure as a basic skeleton, and has a dielectric constant in a long axis direction of a molecule in a uniaxial direction. It is characterized by comprising an organic compound having a higher dielectric constant.

According to a second aspect of the present invention, in the electrorheological fluid of the first aspect, the rigid rod-like structure is partially replaced by a nitrogen atom, an oxygen atom, or a sulfur atom, and has a simple dielectric constant in the major axis direction. It is a cyclic structure group having a larger dielectric constant in the axial direction.

Further, the electrorheological fluid of the third invention is characterized in that
Wherein the organic compound of the invention is dissolved in a solvent.

Further, the electrorheological fluid of the fourth invention is an organic compound having the following molecular structural formula (a), (b), (c):
Characterized by having at least one of the following.

[0013]

Embedded image

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a conceptual diagram of molecules constituting an electrorheological fluid according to the present invention. Note that this molecule is an organic compound that is not a liquid crystal substance. In FIG. 1, the molecule has a rigid and rod-like structure, and has a dielectric constant ε in its major axis direction.
₁ is larger than the dielectric constant ε _{2 in the} minor axis direction.

FIG. 2 shows the operation of an electrorheological fluid composed of such molecules. As shown in FIG. 2A, when an electric field is applied to the electrorheological fluid, the dielectric constant ε _{1 in the} major axis direction is larger than the dielectric constant ε _{2 in the} minor axis direction. The major axis is oriented, and a large shear stress is generated with respect to the shear force in the direction of the arrow in the figure, and the viscosity of the fluid increases. This phenomenon is more remarkable as the difference i.e. the dielectric anisotropy of the dielectric constant epsilon ₂ of the long axis direction of the dielectric constant epsilon ₁ and the minor axis direction is large. Therefore, in order to increase the viscosity when an electric field is applied, it is necessary to increase the dielectric anisotropy of the molecule as much as possible.

Further, when the electric field is removed, the molecules are oriented in the direction of the applied shear force, the shear stress is reduced, the flow resistance is reduced, and the viscosity of the fluid is also reduced.

According to the above principle, the viscosity becomes very high when an electric field is applied, and becomes low when the electric field is removed. In addition, when the electric field is removed, the orientation of molecules generated when the electric field is applied is completely eliminated, so that the base viscosity, that is, the viscosity when no electric field is applied, is lower than that of an electrorheological fluid using liquid crystal. As a result,
It is possible to obtain an electrorheological fluid having a large ER effect, which is the ratio between the viscosity when an electric field is applied and the base viscosity.

Furthermore, since the electrorheological fluid according to the present invention does not use a liquid crystalline substance, the ER effect and fluid characteristics have no temperature dependence.

FIG. 3 shows an example of a molecular structure used in the electrorheological fluid according to the present invention. In FIG. 3, the central portion A in the molecular structure constitutes a rigid rod-like structure that is a rigid rod-like structure that does not bend even when a shearing force is applied in its longitudinal direction. In FIG. 3, the rigid rod-shaped structure portion A is constituted by two annular structural groups,
It does not necessarily have to be a ring structure. Rigid bar structure A
May have another molecular structure as long as it does not bend in the major axis direction.

A group Z for increasing the dielectric anisotropy of the molecule is bonded to at least one end in the longitudinal direction of the rigid rod-shaped structure A. Due to this group Z, the dielectric constant ε _{1 in} the major axis direction of the molecule is larger than the dielectric constant ε _{2 in the} minor axis direction. Also, if this group Z is bonded to both ends of the rigid rod-shaped structure portion A such that the dipole moments are directed in the same direction,
It is preferable because the dielectric anisotropy can be further increased.

On the other hand, a group Y can be connected to the other end of the rigid rod-shaped structure A for the purpose of increasing a certain chain length in order to increase the stress generated when an electric field is applied.

When the molecule shown in FIG. 3 is a solid, it is dissolved in a solvent and used as an electrorheological fluid, but a group Y is bonded to the solvent to enhance affinity with the solvent and facilitate dissolution. It can also be done. In this case, as the solvent, an insulating oil such as a silicone oil, a fluorine oil, or a hydrocarbon oil is used. Therefore, a group having a high affinity for these insulating oils is selected.

Instead of connecting the above-described group Z for increasing the dielectric anisotropy to one end of the rigid rod-shaped structure A in the long axis direction, the rigid rod-shaped structure A itself has a dielectric constant ε ₁ in the long axis direction. The structure may be made larger. Such an example is shown in FIG. FIG. 4 is an example in which one of the two cyclic compounds forming the rigid rod-shaped structure A is phenylpyrimidine. In phenylpyrimidine, two nitrogen atoms are arranged at target positions with respect to the long axis direction of the rigid rod-shaped structure portion A. Therefore, the dipole moment of the nitrogen atom points in the direction of the arrow shown in the figure, and the resultant vector points in the long axis direction. Therefore, the dielectric constant epsilon ₁ of the long axis direction is larger than the dielectric constant epsilon ₂ of the short axis direction, the dielectric anisotropy of the molecules increases.

As described above, the above-mentioned phenylpyrimidine shown in FIG. 5A is used as a skeleton of the rigid rod-shaped structure portion A and has a structure that increases the dielectric anisotropy in the major axis direction. In addition, dioxane shown in FIG. 5B and orthoester shown in FIG. 5C can be considered. Although not shown, a structure in which a part of the cyclic structure is substituted by a sulfur atom may be used.

FIG. 6 shows an example of a molecular structure that can be used for the rigid rod-shaped structure portion A of the molecules constituting the electrorheological fluid according to the present invention in consideration of the above points.

The rigid rod-shaped structure A is a group a in FIG.
It is composed of two or more rigid molecular structures such as group b. In FIG. 6, group a shows a structure having no dielectric anisotropy in the molecular structure itself, and group b shows a structure having a dielectric anisotropy in the molecular structure. Therefore,
In forming the rigid rod-shaped structure A, it is preferable to use at least one or more of the rigid molecular structures shown in group b in order to increase the dielectric anisotropy of the molecule.

FIG. 7 shows an example of a rigid rod-shaped structure A using the rigid molecular structure shown in FIG. As a matter of course, the rigid rod-shaped structure portion A is not limited to the one shown in FIG. 7, and may have another molecular structure as long as it does not bend in the longitudinal direction when a shearing force is applied.

In FIGS. 6 and 7, the group represented by Z in the molecular structure is a group for increasing the dielectric anisotropy as described above.

Next, the results of synthesizing molecules used in the electrorheological fluid according to the present invention using the rigid rod-shaped structure portion A shown in FIG. 7 and evaluating the performance thereof will be described as examples.

Embodiment 1 In this example, a compound having the following molecular structure was used as an electrorheological fluid.

[0032]

Embedded image 2- (4-methylphenyl) -5,5 dimethyl-
In 1,3 dioxane, a rigid rod-like structure is constituted by dioxane and a phenyl group.

FIG. 8 shows the temperature dependence of the base viscosity of the electrorheological fluid according to this example using this compound. In FIG. 8, the horizontal axis indicates temperature, and the vertical axis indicates base viscosity. As can be seen from FIG.
In the temperature range of, the base viscosity showed a value near 0.05 Pa · s, and it was found that the viscosity was as low as that of water. In addition, it was also found that the base viscosity had no temperature dependence.

FIG. 9 shows the temperature dependence of the shear stress of the electrorheological fluid according to this embodiment. In FIG. 9, the horizontal axis indicates the applied electric field strength, and the vertical axis indicates the shear stress of the electrorheological fluid corresponding to each electric field strength. At each electric field strength, the shear stress at four temperatures of 25 ° C., 50 ° C., 75 ° C., and 100 ° C. was measured. As can be seen from FIG. 9, at all temperatures, the shear stress is almost equal for each electric field strength, and it is also understood that the electrorheological fluid according to the present embodiment does not have temperature dependency at this point.

FIG. 10 shows the fluid characteristics of the electrorheological fluid according to the present embodiment. In FIG. 10, the horizontal axis indicates the shear rate, and the vertical axis indicates the shear stress corresponding to each shear rate. In FIG. 10, 0 kv / mm, 1 kv / mm, 2 kv / mm, 3 k
v / mm and 4 kv / mm are employed. As can be seen from FIG. 10, at each electric field strength, the shear stress does not depend on the shear rate, but becomes a substantially constant value, indicating a Bingham behavior.

Embodiment 2 FIG. In this example, a compound having the following molecular structure was used as an electrorheological fluid.

[0037]

Embedded image 2- (4-cyanophenyl) -5,5 dimethyl-
In 1,3 dioxane, as in Example 1, a rigid rod-shaped structure is formed by dioxane and a phenyl group. Further, a cyano group (—CN) is bonded to the phenyl group as a group that increases dielectric anisotropy. As the group to increase the dielectric anisotropy, in addition to the cyano _{group, -CF 3, -NH 2, -OH} , -NO 2, -F, -
Cl, -Br, also conceivable -SO ₂ CF ₃ and the like.

FIG. 11 shows the measurement results of the temperature dependence of the base viscosity of the electrorheological fluid according to the present embodiment. Since the compound of this example is solid at a temperature of 100 ° C. or less,
The base viscosity was measured at only two points. As shown in FIG. 11, the base viscosity was about 0.1 Pa · s, and the base viscosity of the electrorheological fluid of this example was found to be almost the same as that of water.

FIG. 12 shows the temperature dependence of the shear stress of the electrorheological fluid according to the present embodiment. In FIG.
The horizontal axis indicates the applied electric field strength, and the vertical axis indicates the shear stress of the electrorheological fluid corresponding to each electric field strength. FIG. 12 shows measurement results at two temperatures of 110 ° C. and 125 ° C. As can be seen from FIG. 12, the shear stress for each electric field strength was almost equal at any temperature, and it was found that the electrorheological fluid of the present example also had no temperature dependency in the shear stress.

In the electrorheological fluid according to the present embodiment, as shown in FIG. 12, a large shear stress exceeding 2 KPa is obtained at a low electric field strength of several hundred v / mm. It can be seen that the shear stress of the electrorheological fluid according to the present embodiment is extremely large as compared with the result of Embodiment 1 (FIG. 9). This is because the cyano group is used as a base to increase the dielectric anisotropy, extremely large compared to the methyl group effects of increasing the dielectric constant epsilon ₁ of the long axis direction is used in Example 1 molecule It is believed that there is.

Even in a conventional electrorheological fluid, 2 KPa
Some of them generated a shear stress of a degree, but required an electric field strength higher by one digit or more than in the case of this embodiment.
For example, in order to obtain a shear stress of about 2 KPa, an electric field strength of about 1000 v / mm to 6000 v / mm is usually required.

On the other hand, in the present embodiment, a high shear stress can be obtained with a low electric field strength, and a high-voltage power supply is not required. Can be.

FIG. 13 shows the fluid characteristics of the electrorheological fluid according to this embodiment. In FIG. 13, the horizontal axis shows the shear rate, and the vertical axis shows the shear stress corresponding to each shear rate. In FIG. 13, the applied electric fields are 0 v / mm, 100 v / mm, 200 v / mm, 3
00 v / mm and 400 v / mm are employed. FIG.
As can be seen from FIG. 3, at each electric field strength, the shear stress does not depend on the shear rate, and the electrorheological fluid according to the present example also shows Bingham behavior.

Next, the results of comparing the performance of the electrorheological fluid of the compounds synthesized in Examples 1 and 2 with those of a conventional electrorheological fluid will be described.

FIG. 14 shows the relationship between the applied electric field strength and the ER effect. In FIG. 14, the measurement results of Example 1 are indicated by solid circles, and the measurement results of Example 2 are indicated by solid squares. In addition, the electrorheological fluids of liquid crystal system, polymer dispersion system, and carbonaceous dispersion system are shown. (ERF) measurement results are shown.

In the case of the first embodiment, although it behaves as an electrorheological fluid, the dielectric anisotropy of the molecules is not so large, so that the electrorheological fluid has almost the same performance as the conventional electrorheological fluid. . However, in the second embodiment, an extremely high ER effect can be obtained with an extremely low electric field intensity as compared with the conventional example. This is due to the high shear stress when an electric field is applied and the low base viscosity. However, it is considered that the controllable range is widened by this characteristic, and it can be applied in a wide range of fields.

FIG. 15 shows a comparison of the power consumption of each electrorheological fluid. In FIG. 15, the voltage × current density when an electric field is applied to the electrorheological fluid is plotted on the horizontal axis, and the maximum shear stress generated on the vertical axis is shown as the maximum stress. As can be seen from FIG. 15, both the first and second embodiments consume less power than the other conventional examples. Particularly, in Example 2, although the maximum stress is slightly lower than those of the polymer dispersed ERF-B and the carbonaceous dispersed ERF, the power consumption is extremely low, and the stress generated per power consumption is extremely excellent. In this respect, a significant cost reduction can be achieved.

[0048]

As described above, according to the present invention,
Since no liquid crystal material is used as the electrorheological fluid, ER
The effects and fluid properties are independent of temperature, and the applicable range is greatly expanded.

Further, a shear stress of about 2 KPa can be generated by an electric field strength as low as several hundred v / mm,
Since the current flowing at that time is also low, the generated stress per power consumption is extremely large. Furthermore, since the base viscosity is low, the ER effect can be increased.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram of molecules used in an electrorheological fluid according to the present invention.

FIG. 2 is an explanatory diagram of the operation of the electrorheological fluid according to the present invention.

FIG. 3 is a conceptual diagram of a molecular structure used in the electrorheological fluid according to the present invention.

FIG. 4 is a view showing an example of a molecular structure having a dielectric anisotropy in a rigid rod-like structure itself.

FIG. 5 is a diagram showing an example of a molecular structure constituting a rigid rod-shaped structure.

FIG. 6 is a diagram showing an example of a molecular structure constituting a rigid rod-shaped structure.

FIG. 7 is a view showing an example of a rigid rod-shaped structure.

FIG. 8 is a diagram showing the temperature dependence of the base viscosity of Example 1 of the electrorheological fluid of the present invention.

FIG. 9 is a diagram showing the temperature dependence of the shear stress of Example 1 of the electrorheological fluid of the present invention.

FIG. 10 is a diagram illustrating fluid characteristics of an electrorheological fluid according to a first embodiment of the present invention.

FIG. 11 is a diagram showing the temperature dependence of the base viscosity of Example 2 of the electrorheological fluid according to the present invention.

FIG. 12 is a diagram showing the temperature dependence of shear stress in Example 2 of the electrorheological fluid according to the present invention.

FIG. 13 is a diagram showing fluid characteristics of an electrorheological fluid according to a second embodiment of the present invention.

FIG. 14 is a diagram showing the ER effect of the electrorheological fluid according to the first and second embodiments of the present invention and a conventional example.

FIG. 15 is a diagram showing power consumption of the electrorheological fluid according to the first embodiment, the second embodiment, and the conventional example of the present invention.

[Explanation of symbols]

 A A rigid rod-shaped structure.

Claims (4)

[Claims] 1. A rigid rod-like structure is provided as a basic skeleton,
An electrorheological fluid comprising an organic compound having a dielectric constant in a major axis direction of a molecule larger than a dielectric constant in a uniaxial direction. 2. The electrorheological fluid according to claim 1, wherein the rigid rod-like structure part is partially replaced by a nitrogen atom, an oxygen atom, or a sulfur atom, and the dielectric constant in a long axis direction is a dielectric constant in a uniaxial direction. An electrorheological fluid having a larger cyclic structure group. 3. An electrorheological fluid, wherein the organic compound according to claim 1 is dissolved in a solvent. 4. An electrorheological fluid comprising at least one of the organic compounds (a), (b), and (c) having the following molecular structural formula. Embedded image