JPH09100110A - Dilatant fluid - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a dilatant fluid capable of being prepared easily and at a low cost, generating a dilatant characteristic rapidly and controlling a fluid characteristic. SOLUTION: This dilatant fluid is obtained by dispersing inorganic oxide particles in 80-90wt.% ratio with water by using a polymer-based dispersing agent in 0.01-0.1wt.% ratio. In this way, it is possible to generate a dilatant characteristic extremely rapidly and to control a fluid characteristic, i.e., the characteristic of a change in viscosity according to a shearing rate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a dilatant fluid,
In particular, it relates to a dilatant fluid with improved fluid properties.

[0002]

2. Description of the Related Art A dilatant fluid is a fluid having a characteristic that its viscosity increases with an increase in shear rate, and this characteristic is applied to various devices and the like.

Conventionally proposed dilatant fluids are those in which a polymer is dispersed in a polar solvent such as water, those in which silica is dispersed in ammonia water, or those in which clay minerals are dispersed in water. is there.

Of these, those in which clay minerals are dispersed in water are disclosed in Japanese Patent Application Laid-Open No. 5-237367.

In the above publication, a water-swelling clay mineral is swollen in an aqueous solution or dispersion containing a nonionic surfactant having an unsaturated bond in the molecule and having a specific hydrophilic-lipophilic balance (HLB). A technique for obtaining an aqueous solution which exhibits dilatancy or reverse thixotropic properties even at a low concentration is disclosed by allowing and dispersing. In this dilatant fluid, when a shearing force is applied, the viscosity of the liquid increases 2 to 50 times, and sometimes 100 times or more in a few seconds to a few minutes.

[0006]

However, in the dilatant fluid described in the above-mentioned conventional publication, it takes a few seconds to a few minutes to change the viscosity with respect to the change in the shear rate as described above. However, there is a problem in that it is very slow and difficult to apply to devices.

Further, the conventional dilatant fluid in which a polymer is dispersed in a polar solvent such as water requires a step of polymerizing the polymer and further adjusting the dispersion concentration by concentrating, so that it takes a lot of time and cost. there were. Such a polymer-dispersed fluid rapidly increases in viscosity when it reaches a certain shear rate. Therefore, when it is applied to, for example, a power transmission device or a vibration isolation device, smooth control of the device becomes impossible. There was also a problem.

Further, in the case of the conventional dilatant fluid in which silica is dispersed in aqueous ammonia, since the boiling point of ammonia is -33.4 ° C, there is a high possibility that ammonia volatilizes and the physical properties of the fluid change. There was a problem.
Further, since ammonia water is strongly alkaline, it is difficult to handle it. Furthermore, in a fluid in which such silica is dispersed in ammonia water, the viscosity gradually increases as the shear rate increases, so it can be used for the purpose that requires high-speed operation such as switching. There was a problem that I could not.

The present invention has been made in view of the above-mentioned conventional problems, and an object thereof is to easily and inexpensively adjust the dilatant characteristics and to control the fluid characteristics. It is to provide a dilatant fluid.

[0010]

In order to achieve the above object, the first invention is a dilatant fluid having a characteristic of thickening with an increase in shear rate, which is from 80 wt% to 9 wt%.
The inorganic oxide particles of 0 wt% are dispersed in water by the polymer dispersant of 0.01 wt% to 0.1 wt%.

The second invention is characterized in that, in the dilatant fluid of the first invention, the inorganic oxide particles are silica particles.

The third invention is a method for controlling the fluid characteristics of the dilatant fluid according to the first invention, characterized in that the average particle diameter of the inorganic oxide particles is varied between 50 nm and 10 μm. .

A fourth aspect of the present invention is the method for controlling the fluid characteristics of the dilatant fluid according to the first aspect of the invention, which is characterized in that either one of the amount of water and the amount of dispersant in the dilatant fluid is changed.

[0014]

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

The dilatant fluid according to the present invention is 80 w
Inorganic oxide particles occupying the ratio of t% to 90 wt%
It is characterized in that a very small amount of a polymer-based dispersant that occupies a proportion of 0.01 wt% to 0.1 wt% is used and dispersed in water as a dispersion medium. As the dispersion medium,
In addition to water, a low viscosity polar solvent may be used.

As the above-mentioned inorganic oxide particles, for example,
Silica, alumina, magnesia, zirconia, and others can be used. Further, as the polymer-based dispersant,
For example, polyacrylic acid ester and its salt, polymethacrylic acid ester and its salt, and the like can be used.

Dispersion of these is very easy, and a uniform fluid can be obtained by simply stirring for a while. Further, since it does not contain volatile components, the characteristics of the fluid are extremely stable except for the evaporation of water. If the inorganic oxide particles settle down, they can be easily redispersed by stirring the fluid. Furthermore, since it does not contain harmful substances, such as poisonous substances, it is easy to handle.

As described above, the proportion of the inorganic oxide particles is preferably 80 wt% to 90 wt%, but 80 wt%
When the amount is less, the filling state becomes rough and the dilatant property is not exhibited. On the other hand, if it exceeds 90 wt%, the dispersed state becomes poor and stable fluid characteristics cannot be obtained.

As described above, in order to impart dilatant property to the fluid, it is necessary to increase the proportion of the inorganic oxide particles in the dispersion medium such as water. When expressed by, the volume of water in the fluid 30 cc is about 4 cc. Therefore, it is necessary to use the above-mentioned dispersant in order to maintain a good dispersion state in the dispersion medium and maintain the liquid state even if the proportion of the inorganic oxide particles is increased. The proportion of the dispersant is 0.01 wt% to 0.1 wt%
Is preferable.

When the proportion of the dispersant is less than 0.01 wt%, it becomes difficult to disperse the inorganic oxide particles, and it becomes impossible to form a fluid. Also, the proportion of dispersant is 0.1 wt.
When it is more than%, the fluid property becomes Newtonian or thixotropic and it becomes impossible to make it a dilatant fluid.

The average particle size of the inorganic oxide particles is preferably in the range of 50 nm to 10 μm. If the average particle size is smaller than 50 nm, the surface area becomes too large, and therefore a large amount of dispersant or a dispersion medium such as water is required to obtain a good dispersion state, and the fluid does not exhibit dilatant properties. On the other hand, when the average particle diameter is larger than 10 μm, the inorganic oxide particles in the fluid settle down and it becomes impossible to maintain a stable dispersed state.

The average particle size of the above-mentioned inorganic oxide particles has a great influence on the fluid characteristics of the dilatant fluid according to the present invention, that is, the characteristics of the change in viscosity with respect to the shear rate. FIG. 1 shows the relationship between the average particle size of the inorganic oxide particles and the fluid characteristics of the dilatant fluid.

As shown in FIG. 1 (a), when the average particle size is in the range of 50 nm to 1 μm, the fluid characteristics are such that the viscosity rapidly rises when the shear rate reaches a predetermined value. When the average particle size is in the range of 1 μm to 10 μm, as shown in FIG. 1B, after the shear rate reaches a predetermined value, the viscosity gradually increases with the increase of the shear rate.

By changing the average particle size of the inorganic oxide particles in this way, different fluid characteristics can be obtained. Therefore, it becomes possible to control the fluid characteristics by the average particle diameter of the inorganic oxide particles, and to provide the dilatant fluid having the fluid characteristics according to each application. For example, FIG.
The fluid as shown in (a), which exhibits a rapid thickening property at a certain shear rate, can be used for a switch or the like that requires rapid power transmission. Further, as shown in FIG. 1 (b), a fluid whose viscosity gradually rises with the increase of the shear rate when it exceeds a certain shear rate can be used for a clutch or the like which requires smooth power transmission.

On the other hand, when the amount of water as the dispersion medium or the amount of the dispersant is changed, the point at which the viscosity rises can be controlled. FIG. 2 shows changes in the point where the viscosity increases.

For example, the average particle size of the inorganic oxide particles is 5
When the one having a thickness of 0 nm to 1 μm is used and the amount of water or the dispersion material is changed, the point at which the viscosity sharply rises can be changed as shown in FIG. 2 (a).

When the amount of water or the dispersion material is changed by using the inorganic oxide particles having an average particle size in the range of 1 μm to 10 μm, the viscosity gradually rises as shown in FIG. 2 (b). You can change the starting point.

The dilatant fluid according to the present invention obtained as described above has a relatively stable dispersion state,
A good dispersed state can be maintained for several days, but in order to keep the dispersed state stable for a longer period of time, a structural viscosity imparting agent may be added. When the structural viscosity imparting agent is added, the particles can be prevented from settling due to gelation of the structural viscosity imparting agent in a state where no shearing is applied, and the dispersed state can be stabilized. Also, when shear is applied, the structure of the structural viscosity-imparting agent is broken and the viscosity decreases, so dilatant properties are expressed,
It does not affect the properties of the dilatant fluid.
As such a structural viscosity imparting agent, a general one such as clay mineral can be used.

Next, using silica as the inorganic oxide,
The measurement results of the fluid characteristics of the dilatant fluid according to the present invention when the average particle diameter is changed will be described in the following examples.

Example FIG. 3 shows the measurement results of the viscosity with respect to the shear rate of the dilatant fluid according to this example.

In the figure, (1) has the following composition.

Silica (average particle size 1.75 μm) 45.0 g Water 6.0 g Dispersant (polyacrylate) 0.03 g Further, in the figure, □ has the following composition.

Silica (average particle size 0.2 μm) 45.0 g Water 9.25 g Dispersant (polyacrylate) 0.03 g The dilatant fluid according to this example prepared under the above conditions is shown in FIG. As described above, when the average particle diameter of silica is 0.2 μm, the shear rate is 400 (1 /
In s), the viscosity rises sharply. When the average particle size of silica is 1.75 μm, the shear rate is 15
The viscosity gradually increases from around 0 (1 / s) as the shear rate increases.

As described above, the fluid characteristics of the dilatant fluid can be greatly changed by changing the particle size of silica.

[0035]

As described above, according to the present invention,
Because of the simple structure of inorganic oxide particles, a small amount of dispersant, and water, it is easy to adjust the dilatant fluid,
And it can be inexpensive. In this case, the polymer-based dispersant adheres to the surface of the inorganic oxide particles and improves the hydrophilicity, so that the dispersibility of the inorganic oxide particles can be improved.

The expression of the dilatant characteristic of the dilatant fluid according to the present invention is about 100 msec, and the extremely rapid expression of the dilatant characteristic can be realized.

Further, the fluid characteristics of the dilatant fluid can be controlled by changing the average particle diameter of the inorganic oxide particles.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing an example of dilatant characteristics of a dilatant fluid according to the present invention.

FIG. 2 is an explanatory diagram showing a state of change of a point of increasing viscosity of the dilatant fluid according to the present invention.

FIG. 3 is an explanatory diagram of an example showing the relationship between the average particle size of inorganic oxide particles and fluid characteristics in the dilatant fluid according to the present invention.

Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI Technical display location C09K 3/00 C09K 3/00 P C10M 161/00 C10M 161/00 173/02 173/02 // F16D 35 / 00 F16D 35/00 631D (C10M 161/00 125: 26 145: 14) C10N 40:08

Claims (4)

[Claims] 1. A dilatant fluid having a property of thickening with an increase in shear rate, wherein the inorganic oxide particles are contained in a proportion of 80 wt% to 90 wt%.
A dilatant fluid, wherein the dilatant fluid is dispersed in water with a proportion of 0.01 wt% to 0.1 wt% of a polymer dispersant. 2. The dilatant fluid according to claim 1, wherein the inorganic oxide particles are silica particles. 3. The method for controlling the fluid characteristics of a dilatant fluid according to claim 1, wherein the average particle diameter of the inorganic oxide particles is varied between 50 nm and 10 μm. Control method. 4. The method for controlling fluid characteristics of a dilatant fluid according to claim 1, wherein either one of the amount of water and the amount of dispersant in the dilatant fluid is changed. Method.