JPH01304188A - Electroviscous liquid - Google Patents

Abstract

PURPOSE:To provide an electroviscous liq. having excellent stability and electrical response characteristics by composing the same of a dispersed phase of grains obtd. by modifying an inorg. sol with a particular silicon compd. and a liq. phase of a (modified) silicon oil having a predetermined specific gravity. CONSTITUTION:An inorg. sol (e.g., silica sol) dispersed in water or an org. solvent is modified by adding thereto a soln. obtd. by dissolving a compd. of formula I or II (wherein X is a hydrophobic substituent or a substituent having a cationic structure or an anionic structure) (e.g., phenyltrimethoxysilane) in water or an org. solvent, and dried, thereby preparing grains having a diameter of 5-100mmu. Then, an electroviscous liq. is produced by composing the same of a dispersed phase comprising 5-50wt.% thus prepared grains and a liq. phase comprising 95-50wt.% nonreactive silicon oil (e.g., polydimethylsiloxane) or modified silicon oil having a specific gravity of 0.9-1.3.

Description

DETAILED DESCRIPTION OF THE INVENTION A.4 Objectives of the Invention f The present invention relates to an electrorheological liquid whose viscosity is increased by the application of voltage.

[i Standing I] An electrorheological liquid is a suspension of finely divided hydrophilic solids dispersed in a hydrophobic, non-conducting oil, which reacts very rapidly under the action of a sufficiently strong electric field. Moreover, the viscosity of the liquid increases reversibly, making it appear as if it were a plastic or solid state.

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 strong force is given with a small amount of electric power. It can be used as a component in a sober, a vibrator-1 anti-vibration rubber, or an electro-mechanical interface for controlling a system that holds a workpiece in place.

In many components that utilize electrorheological liquids, the electrorheological liquid is used in direct contact with a rubber-like elastic material.

Conventionally, solid particles, which are one of the constituent components of electrorheological liquids, have been made of cellulose, starch, silica gel, ion-exchange resins, etc. that have water adsorbed on their surfaces, and dispersion media, which are other constituents, have been used. , chlorinated biphenyl, dibutyl sebacate, trans oil, chlorinated paraffin, silicone oil, etc. exist or have little practical value, but there are extremely high performance and highly stable electrorheological liquids that have practical value. This is a situation that does not yet exist.

The main reason why electrorheological liquids are not put into practical use is
- Due to reasons such as the specific gravity of the fine powder that becomes the dispersed phase in S being higher than the specific gravity of the liquid phase components, when left for a long time, phase separation occurs and settles, forming a precipitate that is difficult to disperse again. It's for a reason.

As a means of solving this problem, there is a method of reducing the difference in specific gravity by using a fine powder with a low specific gravity as a dispersed phase or a liquid with a high specific gravity as a dispersion medium.

In the former case, the fine powder is limited to organic substances such as starch, and its electrical properties lack long-term stability.

In the latter case, in order to improve the electrorheological effect,
When using, for example, fine particles of lithium polyacrylate as the dispersed phase as disclosed in No. 3-93180,
Since the specific gravity of these fine particles is about 1.4, it is necessary to use a liquid phase component with a high specific gravity such as halogenated diphenyl or halogenated paraffin.
In many components that utilize electrorheological liquids, electrorheological liquids are used in direct contact with materials that have rubber-like elasticity, so electrorheological liquids that use chlorinated diphenyl, chlorinated paraffin, etc. are rubber-like elastic materials. It is not suitable for components used in direct contact with materials having rubber-like elasticity such as those mentioned above, since it has adverse effects such as deterioration, swelling, and in some cases, dissolution.

Additionally, halides such as diphenyl chloride and paraffin chloride generate hydrogen halide when stimulated by heat, force, etc., which corrodes metals used in many components that utilize electrorheological liquids.

In order to solve this problem, Japanese Patent Application Publication No. 61-44998 uses silica gel and silicone oil as dispersants, and uses amino-functional, hydroxy-functional, acetoxy-functional,
Alternatively, an electrorheological liquid using an alkoxy-functional polysiloxane has been proposed, but when left standing for a long period of time, particles of the dispersed phase settle and phase separation occurs, and it takes effort to disperse again. The reality is that the sedimentation properties mentioned above are still not practical.

An object of the present invention is to provide an electrorheological liquid that is stable for a long period of time, exhibits high electrical responsiveness, and can be used in direct contact with a rubber-like elastic material. shall be.

1. Constitution of the Invention The electrorheological liquid of the present invention is dispersed in an inorganic sol dispersed in water or an organic solvent with the general formula %) [where X is a hydrophobic substituent or the cationic structure is an anion. A substituent having the structure] is modified by adding a solution of at least one of the compounds represented by dissolved in water or an organic solvent, and then dried to form a compound with a diameter of 5 to 1.
It is characterized by being composed of a dispersed phase consisting of 5 to 50% by weight of fine particles prepared to have a diameter of 0.000 mμ and a liquid phase of 95 to 50% by weight of non-reactive silicone oil or modified silicone oil with a specific gravity of 0.90 to 1.30. do.

The fine powder used as the dispersed phase in the present invention is a compound containing at least one silicon element expressed by the general formula % () in an inorganic sol dispersed in water or an organic solution M. It can be obtained by adding a solution in which at least one of the following is dissolved in water or an organic solvent to modify it, and then drying it.

The inorganic sol used for the fine powder as the dispersed phase of the electrorheological liquid of the present invention is selected from colloidal silica (silica sol), alumina sol, zirconia sol, antimony oxide sol, etc., or a mixture thereof. , as long as it is an inorganic sol, it is not limited to these.

In addition, the compound containing at least one silicon element in its molecule and represented by the general formula % formula % () used for modifying the fine powder as the dispersed phase of the electrorheological liquid of the present invention is It plays the following three important roles:

A. The role of preventing agglomeration between fine particles present in the sol, which causes phase separation due to sedimentation of the dispersed phase in electrorheological liquids, and as a result, increasing the stability of electrorheological liquids.

B. The role of preventing the deterioration or dissolution of fine particles present in the sol caused by trace amounts of base components present in the electrorheological liquid, and as a result, increasing the stability of the electrorheological liquid.

First, it plays a role in controlling the amount of charge on the surface of the fine particles present in the sol, thereby improving the performance of the electrorheological liquid.

In order to play the above role, the above-mentioned at least one compound contained in the silicon element molecule serves to hydrophobize the surface of the fine particles, and imparts a charged structure to the surface of the fine particles to enhance the electrorheological effect. It is preferable to use two types of compounds that play the role of

Among the above-mentioned compounds containing at least one silicon element in the molecule, compounds that play a role in making the surface of fine particles hydrophobic are compounds in which the substituent X in the general formula % () has a hydrophobic structure. It is necessary that there be. The hydrophobic substituents for the structure (I) include methyl group, ethyl group, n-propyl group, i-propyl group, n-butyl group, 1-butyl group, S-butyl group,
t-butyl group, n-pentyl group, n-hexyl group, C-
Saturated hydrocarbon groups such as hexyl group, n-hebutyl group, n-octyl group, n-nonyl group, n-decyl group, n-dodecyl group, stearyl group, unsaturated hydrocarbon groups such as vinyl group, allyl group, etc. , phenyl group, benzyl group, naphthyl group, aromatic hydrocarbon group such as biphenyl group, halogenated hydrocarbon group, monofunctional hydrophobic substituent group having the structure of polysiloxane, etc. are representative. ) structures, saturated hydrocarbon groups such as methylene group, ethylene group, trimethylene group, tetramethylene group, pentamethylene group, octamethylene group, propylene group, ethylidene group, and vinylene group.

Unsaturated hydrocarbon groups such as propenylene groups, phenylene groups,
Typical examples include aromatic hydrocarbon groups such as naphthylene groups, halogenated hydrocarbon groups, and bifunctional hydrophobic substituents having a polysiloxane structure.

In addition, substances that play a role in imparting a charged structure to the surface of fine particles to enhance the electrorheological effect include cation purification represented by ammonium salt structures and phosphonium salt structures, metal carboxylate salts, and metal sulfonate salts. A substituent having either or both of the anion structures represented by metal phosphate salts is preferably used.

Of course, the effects of the above two types of compounds can be exhibited even if only one of them is used, or the effects can be most recognized when both are used in combination.

The total amount of the compound represented by the above general formula containing at least one silicon element in the molecule must be 3 to 80 parts by weight based on 100 parts by weight of solid content in the inorganic sol. and preferably 5 to 50 parts by weight, more preferably 8 to 40 parts by weight, even if the amount of the compound containing one or more silicon elements in the molecule is 3 parts by weight or less. , 80 parts by weight or more, the durability of the electrorheological liquid using the dispersed phase becomes extremely poor.

The fine powder forming the dispersed phase in the electrorheological liquid of the present invention is obtained by being modified in an inorganic sol solution and then dried.

Further, the fine powder obtained by the above method contains 0.03 to 10 parts by weight, preferably 0.05 to 8 parts by weight per 100 parts by weight of the fine powder.
It is necessary that 0.03 parts by weight of water be adsorbed.
If the amount is less than 10 parts by weight, the electrorheological effect will be insufficient;
．． If it exceeds 0 parts by weight, too much current will flow, inhibiting the electrorheological effect, and at the same time, the durability will deteriorate significantly. The amount of adsorbed water can be revealed by leaving the fine powder in the air or in a constant temperature and humidity chamber, but any method can be used as long as the amount of adsorbed water is within the above range. good.

Furthermore, as the dispersion medium to be used in the electrorheological liquid of the present invention, non-reactive ones among silicone oils and modified silicone oils are preferably used, and examples thereof include polydimethylsiloxane, polymethylphenylsiloxane, At least one unit or copolymer of units selected from polydiphenylsiloxane, polymethylchlorophenylsiloxane, polymethyl long-chain alkylsiloxane, polymethylcyanopropylsiloxane, and polymethyl-3,3,3-trifluoromethylsiloxane, or those It is important to select a mixture whose specific gravity is the same as that of the above-mentioned dispersed phase, usually 0.90.
-1.30, preferably 0.91-1.10, more preferably 0.93-1.05.

The viscosity of the non-reactive silicone oil or modified silicone oil used as the dispersion medium is 3 to 300 at room temperature.
centivoise (cp), preferably 5 to 250 centipoise (cp), more preferably 5 to 50 centipoise (cp)
It is necessary to use a material having a viscosity of cp). When the viscosity of the dispersion medium is within an appropriate range, the lower the viscosity, the lower the viscosity of the electrorheological liquid using the dispersion medium, and as a result, the dynamic range of viscosity change due to electrical response is increased. High electrical responsiveness can be imparted to electrorheological liquids.

If the viscosity of the dispersion medium is less than 3 centivoices (cp), the stability of the electrorheological liquid becomes extremely poor due to separation and sedimentation of the dispersed phase, and if it is more than 300 centivoices (cp), the initial viscosity becomes high. As a result, electrical responsiveness deteriorates.

EXAMPLES The present invention will be explained in more detail with reference to Examples and Comparative Examples below, but the present invention is not limited to the following Examples unless it goes beyond the gist of the present invention.

Nomu 1 Colloidal Silica (Snowtex C: Manufactured by 8 San Kagaku)
2.8g of TSL8173 (manufactured by Toshiba Silicone Tai: Phenyltrimethoxysilane) and TSL8331 in 40g
(Manufactured by Toshiba Silicone ■: Y-aminopropyltrimethoxysilane) An aqueous solution of 1.2 g dissolved in 7.2 g of water was gradually added to prepare a modified colloidal silica aqueous solution, and the aqueous solution was vacuum-dried to form a crude fine powder. body was prepared. The crude fine powder was left to stand at room temperature for 3 days to obtain a fine powder having a particle size of 180 mμ, which was a dispersion of an electrorheological liquid.

Nomu 2 40 g of colloidal silica (Snowtex C), treatment agent (manufactured by Toshiba Silicone ■) according to the method of Dispersed Phase Synthesis Example 1:
TSL8173: Octadecyldimethyl(3-(trimethoxysilyl)propyl)ammonium chloride)2
．． 8g, processing agent (manufactured by Toray Silicone: AY43-
021) Fine powder was prepared using 1°0g.

2. 30% by weight of the fine powder obtained by the method of Synthesis Example 1 was added to a silicone oil (viscosity 20 cp and specific gravity 0.95 at room temperature).
It was dispersed in Toshiba Silicone ■: TSF451-20) to form a suspension.

30% by weight of the fine powder obtained by the method of Synthesis Example 2 was added to a silicone oil (viscosity 20cp, specific gravity 0.95) at room temperature.
It was dispersed in Toshiba Silicone ■: TSF451-20) to form a suspension.

Hi "L Doctor" 2 Average grains obtained by adding 30 parts by weight of water to 100 parts by weight of lithium polyacrylate obtained by neutralizing commercially available polyacrylic acid with lithium hydroxide, and crushing and sizing the mixture. 30% by weight of hydrated lithium polyacrylate with a diameter of approximately 10 μm,
It was dispersed in silicone oil (manufactured by Toshiba Silicone ■: TSF451-20) with a viscosity of 20 cp and a specific gravity of 0.95 at room temperature to form a suspension.

Using amino-modified polysiloxane as a commercially available silica powder dispersant with a particle size of 200 mμ, silicone oil (manufactured by Toshiba Silicone: TSF451-20) with a viscosity of 20 cp and a specific gravity of 0.95 at room temperature was dispersed. It was made into a suspension.

The viscosity of each sample was measured using a double cylindrical rotational viscometer, applying voltage between the inner and outer cylinders at the same shear rate (375 s).
Table 1 shows the values expressed in terms of axial force (torque) of the viscometer at (e c-').

Table 1 *1D Electric field strength E and torque T at a constant shear rate
In Figure 1, which shows the relationship between the two, To is the torque when no electric field is applied, S is the rate of change in torque with respect to the applied electric field, and Eo is the critical electric field, and below Eo, no electrorheological effect is observed.

Further, the sedimentation property was evaluated by putting an electrorheological liquid in a measuring cylinder and leaving it at room temperature for 3 days, and visually evaluating the sedimentation status. The evaluated values are shown in Table 2.

(Left below) Table 2■ As is clear from Tables 1 and 2, the electrorheological liquid using the dispersed phase of the present invention has extremely controlled phenomena such as sedimentation and separation, and as a result has improved stability. It collapses very easily and has excellent electrical response.

Effects of the Invention The electrorheological liquid of the present invention is stable over a long period of time, exhibits excellent electrical responsiveness, and does not contain oil or solvents that can swell and dissolve materials exhibiting rubber-like elasticity. , it can be used in direct contact with a rubber-like elastic material, and furthermore, since the dispersed phase is lightweight, it is possible to reduce the weight of the electrorheological liquid, and it can be usefully used in various devices.

[Brief explanation of the drawing]

Figure 1 shows the relationship between electric field strength E and torque T at a constant shear rate, where To is the torque when no electric field is applied, S is the rate of change in torque with respect to the applied electric field, and E
, represents the critical electric field, and no electrorheological effect is observed below E0.

Claims (1)

[Claims] An inorganic sol dispersed in water or an organic solvent has a general formula ▲ has a mathematical formula, a chemical formula, a table, etc. ▼ (I) or ▲ has a mathematical formula, a chemical formula, a table, etc. ▼ (II) [However, X is A hydrophobic substituent or a substituent having a cationic structure or anionic structure] is modified by adding a solution in which at least one of the compounds represented by the above is dissolved in water or an organic solvent, and then dried to obtain a 5-1.
It is characterized by being composed of a dispersed phase consisting of 5 to 50% by weight of fine particles prepared to have a particle size of 0.000 mμ and a liquid phase of 95 to 50% by weight of non-reactive silicone oil or modified silicone oil with a specific gravity of 0.90 to 1.30. electrorheological liquid.