JPH04266996A - Electroviscous fluid - Google Patents

Abstract

PURPOSE:To improve electroviscous effects of an electroviscous fluid using fine powder of a quaternary ammonium salt group-containing silicone resin and further improve settling and redispersibility of a disperse phase. CONSTITUTION:An electroviscous fluid is characterized as follows. The aforementioned fluid is composed of 1-60wt.% fine powder of a quaternary ammonium salt group-containing silicone resin, containing 0.1-20wt.% moisture and having 0.05-100mum average particle diameter and 99-40wt.% fluorosilicone oil having 5-1000cSt viscosity at 25 deg.C.

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrorheological fluid whose viscosity is increased by the application of voltage. BACKGROUND OF THE INVENTION Electrorheological fluids are suspensions of finely divided dielectric solids dispersed in non-conducting oil, and are highly resistant to electro-rheological fluids under the action of a sufficiently strong electric field. It is a fluid whose viscosity increases rapidly and reversibly. [0003] In order to change the viscosity, not only a direct current electric field but also an alternating current electric field can be used.The required current is very small, and a small current can cause a large change in viscosity from a liquid to a solid state. , as components for controlling devices and parts such as clutches, valves, shock absorbers, vibrators, various anti-vibration rubbers, actuators, robot arms, vibration damping materials, etc.
Electrorheological fluids have been considered. Conventionally, solid fine particles have been used as a component of the dispersed phase of electrorheological fluids, and these solid particles can be made of finely divided cellulose, starch, silica gel, ion exchange resin, polyester, etc. by adsorbing water on their surfaces. Lithium acrylate, zeolite, etc. are known. Other known liquid phase components include PCB, butyl sebacate, trans oil, hydrocarbon oil, chlorinated paraffin, and silicone oil. However, these materials have little practical value, and there is still no usable electrorheological fluid with extremely high performance and high stability that has practical value. The reason why electrorheological fluids have not yet been put to practical use is that the specific gravity of the solid particles that form the dispersed phase is generally greater than the specific gravity of the liquid phase component, which causes phase separation and sedimentation when left for a long period of time. This is because a precipitate is formed which is difficult to redisperse. [0006] As a means of solving such problems, there are two methods: employing solid particles with a small specific gravity to reduce the difference in specific gravity with the liquid phase component, or using a liquid phase component with a high specific gravity and reducing the difference in specific gravity with the solid fine particles. There is a way to make it smaller. However, silica (specific gravity: 1.9-2.0)
Solid particles suitable for electrorheological fluids, such as lithium polyacrylate (specific gravity: 1.4), have a high specific gravity. Therefore, in order to bring the specific gravity closer to the liquid phase component with a specific gravity of 1 or less, such as dimethyl silicone oil and hydrocarbon oil, which are generally disclosed as the liquid phase of electrorheological fluids, hollow particles (Japanese Patent Application Laid-Open No. 1-96295) were devised. Although it has been
There are a limited number of materials that can be hollowed out. On the other hand, in order to bring the specific gravity of the liquid phase close to that of solid fine particles with high specific gravity, chlorinated paraffin (specific gravity: 1.1-1.3), polytrichloromonofluoroethylene (specific gravity: ~1.9), perfluoropolyether ( Halogenated hydrocarbons such as halogenated diphenylmethane (specific gravity: ~2.0) and halogenated diphenylmethane (specific gravity: 1.2 to 1.8) are also being considered; may cause swelling or be harmful to the human body. [0008] In many devices that utilize electrorheological fluids, the electrorheological fluid is used in direct contact with a material that has rubber-like elasticity, such as in the case of anti-vibration rubber filled with electrorheological fluid. Therefore, it is desirable that the liquid phase of the electrorheological fluid does not swell polymer materials such as rubber. From this perspective, JP-A-61-4
No. 4988 proposes an electrorheological fluid using silica gel as the dispersed phase, polydimethylsiloxane oil as the liquid phase, and an amino-, hydroxy-, acetoxy-, or alkoxy-functional polysiloxane as the dispersant. However, due to the large difference in specific gravity between silica gel and polydimethylsiloxane, the problem of sedimentation of the dispersed phase remains unsolved. [Problems to be Solved by the Invention] Therefore, in order to bring the specific gravity of the dispersed phase powder closer to that of polydimethylsiloxane, the inventors have developed an electrorheological fluid containing a quaternary ammonium base as a dispersed phase of an electrorheological fluid with a light specific gravity. Developed carbon-functional silicone resin fine powder (JP-A-1-266137, JP-A-1-
No. 266195). The object of the present invention is to improve the electrorheological effect of an electrorheological fluid using the silicone resin fine powder and to further improve the settling and redispersibility of the dispersed phase. [Means for Solving the Problems] The electrorheological fluid according to the present invention is a quaternary ammonium base-containing silicone resin containing 0.1 to 20% by weight of water and having an average particle diameter of 0.05 to 100 μm. It is characterized by consisting of 1 to 60% by weight of fine powder and 99 to 40% by weight of fluorosilicone oil having a viscosity of 5 to 1000 centistokes at 25°C. The quaternary ammonium base-containing silicone resin used as the dispersed phase in the electrorheological fluid of the present invention is a homopolymer consisting of RSiO3/2 units;
It is composed of either a copolymer consisting of RSiO3/2 units and SiO2 units, or a copolymer consisting of RSiO3/2 units, SiO2 units and R2SiO2 units. [0012] When the quaternary ammonium base-containing silicone resin is a copolymer consisting of RSiO3/2 units and SiO2 units, the content ratio of each constitutional unit is not particularly limited and can be determined as appropriate depending on the application. . [0013] The quaternary ammonium base-containing silicone resin contains RSiO3/2 units, SiO2 units and R2S
In the case of a copolymer consisting of iO units, this R2
The content of SiO 2 units is 20 mol% or less. If the content of this unit exceeds 20 mol %, it becomes difficult to make the obtained silicone resin into a fine powder. RSiO3 constituting the silicone resin
/2 The group R in the unit accounts for at least 0.1 mol %, preferably from 1 to 50 mol %, of quaternary ammonium group-containing carbon-functional groups. By including a quaternary ammonium base in the silicone resin in this manner, it can function as a dispersed phase of an electrorheological fluid. This content is 0
．． If it is less than 1 mol %, hardly any electrorheological effect will be exhibited even if it is used as a dispersed phase of an electrorheological fluid. This quaternary ammonium group-containing carbon functional group has the general formula: (R
1) 3N+X-Q1- or (R1)3N+X-Q2N
HQ1- (in the formula, R1 is an alkyl group, Q1 is a carbon number of 3 to
6 is an alkylene group, Q2 is an alkylene group having 2 to 4 carbon atoms, and X- is an anion). [0016] R1 may be the same or different from each other,
Methyl group, ethyl group, propyl group, butyl group, pentyl group, hexyl group, octyl group, decyl group, dodecyl group,
Examples include a tetradecyl group, a hexadecyl group, an octadecyl group, and an eicosyl group. Among these, it is preferable that at least two of the three groups R1 bonded to one nitrogen atom are methyl groups because synthesis is easy. In this case, the remaining group R1 is preferably an alkyl group having 12 to 18 carbon atoms because the raw materials are easily available. RSiO3 constituting the silicone resin
/2 Group R other than the quaternary ammonium base in the unit
Preferred examples include alkyl groups such as methyl, ethyl, propyl, butyl, pentyl, and hexyl, and phenyl. Among these, a methyl group or a phenyl group is preferable because they can impart excellent heat resistance to the obtained silicone resin fine powder, and a methyl group is particularly preferable because it is easy to synthesize. The above silicone resin fine powder can be obtained by hydrolysis of an alkoxysilane having a quaternary ammonium base-containing carbon functional group alone, or by hydrolysis of an alkoxysilane having a quaternary ammonium group-containing carbon functional group, or having a desired silicon functional group other than the alkoxysilane and the carbon functional group. It can be obtained by cohydrolyzing alkoxysilane. In the present invention, the quaternary ammonium base-containing silicone resin fine powder constituting the dispersed phase of the electrorheological fluid is 0.1 to 10% by weight, preferably 0.5 to 5% by weight.
of water. A fine powder with a moisture content of less than 0.1% by weight hardly exhibits an electrorheological effect, and a fine powder with a water content of more than 10% by weight consumes excessive power. The average particle size of the silicone resin fine powder suitable as the dispersed phase of the electrorheological fluid is 0.05 to 100 μm.
m range, preferably 1 to 20 μm. If the average particle size is less than 0.05 μm, the initial viscosity in the absence of an electric field will be significantly large, resulting in a small electrorheological effect, and if the average particle size exceeds 100 μm, sufficient stability as a dispersed phase of a fluid will not be obtained. The silicone resin fine powder preferably has a specific gravity in the range of 1 to 1.4 when containing 0.1 to 10% by weight of water. As the content of SiO2 units in the silicone resin fine powder increases, the specific gravity increases, and conversely, as the content of R2SiO 2 units increases, the specific gravity decreases. Further, as the number of carbon atoms in the group R increases, the specific gravity of the silicone resin fine powder decreases. Fluorosilicone oil constitutes the liquid phase of the electrorheological fluid, eliminates sedimentation of the dispersed phase over time, and provides excellent electrorheological effects. This fluorosilicone oil has the general formula R2aR3bSiO(4-
a-b)/2 (R2 is the same or different monovalent perfluoroalkyl group having 3 to 11 carbon atoms, R3 is a monovalent perfluoroalkyl group having 1 to 6 carbon atoms
represents a substituted or unsubstituted same or different monovalent hydrocarbon group, and is represented by 1.8<a+b<2.3;0<a/b≦1). As R2, 3, 3, 3-trifluoropropyl group, 3, 3, 4, 4, 5,
5, 6, 6, 6- nonafluorohexyl group, 3
, 3, 4, 4, 5, 6, 6, 7, 7,
Examples include 8, 8, 9, 9, 10, 10, 10-heptadecafluorodecyl group. Among these substituents, 3,3,3-trifluoropropyl group is particularly preferred since it is easy to obtain this fluorosilicone oil. Substituent R3 is, for example, a methyl group, an ethyl group, a propyl group,
It is selected from alkyl groups such as butyl groups, cycloalkyl groups such as cyclohexyl groups, phenyl groups, etc., and among them, methyl groups or phenyl groups are preferred. A method for producing such a fluorosilicone oil is already known, and for example, a cyclic polysiloxane containing a perfluoroalkyl group, hexamethyldisiloxane, and a cyclic polyalkylsiloxane are mixed with trifluoromethanesulfonic acid or activated clay. Polymerization method under acidic catalyst (Japanese Patent Publication No. 35-8345, Japanese Patent Publication No. 47-1983)
47880). The structure of such fluorosilicone oil may be linear, branched, cyclic, or a mixture thereof, but the viscosity at 25° C.
~1000 cSt (centistokes), preferably 1
Use one with a weight of 0 to 100 cSt. If the viscosity is too low, the stability of the fluid will deteriorate, and if the viscosity is too high, it will be difficult to efficiently cloud the silicone resin fine powder, and the electrorheological effect will be insufficient. Further, the value of a/b in the general formula R2aR3bSiO(4-a-b)/2 of this fluorosilicone oil is 0 or more (>0), but from the stability of electrorheological fluid, it is 0.1 It is more preferable that it is above. The specific gravity of the fluorosilicone oil in the present invention is 1 to 1.4, preferably 1, in order to approximate the specific gravity of the silicone resin fine powder containing a quaternary ammonium base.
．． 1 to 1.25 is used. R2 containing fluorine
The specific gravity of the fluorosilicone oil increases as the amount of groups increases and the content of fluorine in the R2 group increases. Therefore, by adjusting the content and type of the R2 group, the specific gravity of the silicone resin fine powder can be easily adjusted. You can obtain fluorosilicone oil close to . The volume resistivity of the fluorosilicone oil suitable for the electrorheological fluid in the present invention is 10 11 Ω·cm or more, preferably 10 12 Ω·cm or more. If the volume resistivity is less than 10 11 Ω·cm, the amount of power consumed when voltage is applied increases. The ratio of the fine silicone resin powder containing a quaternary ammonium base to the fluorosilicone oil in the electrorheological fluid of the present invention is such that the fine silicone resin powder containing water is 1 to 60% by weight, preferably 10 to 50% by weight. %
and the fluorosilicone oil is 99 to 40% by weight,
Preferably it is 50 to 90% by weight. If the amount of the silicone resin fine powder is less than 1% by weight, the electrorheological effect is small;
When it exceeds 60% by weight, the initial viscosity in the absence of an electric field becomes significantly large. The electrorheological fluid of the present invention may contain various additives such as surfactants, dispersants, and inorganic salts within a range that does not impair the effects of the present invention. [0030] The present invention will be explained in more detail with reference to examples below, but the present invention is not limited to the following examples. [Example 1] 300 parts of water, 300 parts of isopropanol and 10 parts of 28% aqueous ammonia solution were uniformly mixed,
A hydrolysis solution was prepared. While stirring while maintaining the temperature at 30°C, a mixture of 300 parts of a methanol solution containing 10% octadecylmethyl(trimethoxysilylpropyl)ammonium chloride and 150 parts of methylmethoxysilane was added, and upon further stirring, a fine powder was formed. A silicone resin was formed, and the liquid became cloudy. Next, the resulting powder was suction filtered and dried at 150°C. After drying, the powder was introduced into a jet pulverizer to obtain a fine silicone resin powder with an average particle size of 5 μm. Further, this fine powder was dried at 120° C. for 8 hours to have a water content of 2.9% by weight, and a fine powder with a true specific gravity of about 1.2 was obtained. Silicone resin fine powder 15 obtained here
Volume % and kinematic viscosity at room temperature 300 centistokes (
An electrorheological fluid was obtained by mixing 85% by volume of fluorosilicone oil (specific gravity: 1.25, volume resistivity: 4×10 11 Ω·cm) consisting of polytrifluoropropylmethylsiloxane (cSt) for 30 minutes in an automatic mortar. [Example 2] Fluorosilicone oil (specific gravity: 1.231, Volume resistivity:
5×10 11 Ω·cm) was mixed in an automatic mortar for 30 minutes to obtain an electrorheological fluid. [Comparative Example 1] Silicone oil (specific gravity:
0.970, volume resistivity: 5 x 1012 Ω・cm) 85
The volume percent was mixed in an automatic mortar for 30 minutes to obtain an electrorheological fluid. [Comparative Example 2] Commercially available sodium polyacrylate fine powder (
Specific gravity: 1.4, average particle size: 10 μm, water content: 1
0% by weight) was dispersed in 85% by volume of the same silicone oil as in Comparative Example 1 in the same manner as in Example 1 to obtain an electrorheological fluid. [Comparative Example 3] Commercially available silica gel fine powder (specific gravity: 2.0,
Average particle size: 0.016 μm, water content: 6% by weight)
3% by volume was dispersed in 97% by volume of the same silicone oil as in Comparative Example 1 in the same manner as in Example 1 to obtain an electrorheological fluid. The electrorheological effects of the electrorheological fluids of Examples 1 to 2 and Comparative Examples 1 to 3 were measured using a double cylinder rotational viscometer.
Shearing rate 366 when DC voltage is applied between the inner and outer cylinders
Evaluation was made based on the apparent viscosity increase (25°C) at s-1. Regarding the sedimentation property of the electrorheological fluid, the fluid was allowed to stand in a sample bottle at room temperature for 15 days, and the degree of sedimentation of the silicone resin phase was observed. The electrorheological effect and sedimentation test results are shown below. ■Viscosity ■Viscosity
Electrorheological effect Degree of sedimentation of dispersed phase
(OKV/mm) (2KV/m
m) ■−■
Example 1 5.94 P
43.36 P 37.42 P
None Example 2
1.86 P 18.10 P
16 25 P None
Comparative example 1 5.20 P
10.95 P 5.75 P
Small Comparative example 2
5.68 P 8.13 P 2
．． 45P large
Comparative Example 3 6.97 P 8.
66 P 1.69 P
As is clear from the above results, the electrorheological fluids of Examples 1 and 2 exhibited significantly greater electrorheological effects than the electrorheological fluids of Comparative Examples 1 and 3, and even after being left standing for 15 days, the electrorheological fluids exhibited almost no electrorheological effect. Although the dispersed phase did not settle, the fluids of Comparative Examples 2-3 produced obvious sediment. [0039] The electrorheological fluid of the present invention exhibits a large electrorheological effect, does not cause sedimentation of the dispersed phase powder, and exhibits an excellent electrorheological effect for a long period of time.

Claims (1)

[Claims] 1. Quaternary ammonium base-containing fine silicone resin powder having an average particle size of 0.05 to 100 μm and containing 0.1 to 20% by weight of water and 2 to 60% by weight.
An electrorheological fluid comprising 99 to 40% by weight of a fluorosilicone oil having a viscosity of 5 to 1000 centistokes at 5°C.