JPH01304187A - Electroviscous liquid - Google Patents

Abstract

PURPOSE:To provide an electroviscous liq. having excellent stability and electrical response characteristics by conducting solvent replacement of a silica sol comprising a predetermined amt. of SiO2 dispersed in water or an org. solvent and using a non-reactive (modified) silicone oil having a predetermined specific gravity as a dispersion medium. CONSTITUTION:A silica sol comprising 5-50wt.% SiO2 dispersed in water or an org. solvent (e.g., methanol) is provided. Then, an electroviscous liq. is produced by conducting solvent replacement of the silica sol and using a non- reactive silicone oil or modified silicone oil having a specific gravity of 0.9-1.3 as a dispersion medium. Such solvent replacement can be attained by a method comprising distilling off water and low b.p. substances, a method comprising using an ultrafilter membrane, or other methods. The obtd. electroviscous liq. can be used in such a state that it is in direct contact with a rubber-like elastic material, because the electroviscous liq. does not contain any oil, solvent or the like which swells or dissolves the rubber-like elastic material.

Description

DETAILED DESCRIPTION OF THE INVENTION (1) Objects of the Invention (1) The present invention relates to an electrorheological liquid whose viscosity is increased by the application of voltage.

[A soil-surfacing electrorheological liquid is a suspension in which finely divided hydrophilic solids are dispersed in a hydrophobic, non-conductive, so-called insulating oil, and is capable of resisting the action of a sufficiently strong electric field. The viscosity of the liquid increases very quickly and reversibly at the bottom, making it appear as if it were a plastic or a solid.

In order to change the viscosity, an alternating current electric field can be used instead of a direct current electric field.The required current is very small, and it provides a strong force with a small amount of electric power, so it can be used, for example, in clutches, hydraulic valves, shock It can be used as a component in absorbers, vibrator-1 insulation rubbers, or electro-mechanical interfaces for controlling systems that hold workpieces in place. In many components that utilize electrorheological liquids,
Electrorheological liquids are used in direct contact with materials having rubber-like elasticity.

Conventionally, the solid particles that are 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 the dispersion media that are the other constituents have been made of chloride. There are products that use diphenyl, dibutyl sebacate, trans oil, chlorinated paraffin, silicone oil, etc., but they have little practical value.
There is still no usable electrorheological liquid with extremely high performance and high stability that has practical value.

The main reason why electrorheological liquids are not put into practical use is
Generally, due to reasons such as the specific gravity of the fine powder that becomes the dispersed phase being greater 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. be.

As means for solving such problems, there are a method of reducing the difference in specific gravity and a method of modifying the surface of the dispersed phase to increase solubility.

As an example of the former, a combination of halogenated insulating oil with high specific gravity and fine particles of lithium polyacrylate has been proposed as in Japanese Patent Application Laid-Open No. 53-93186.

As an example of the latter, in Japanese Patent Application Publication No. 61-44998,
Electrorheological fluids based on silica gels and silicone oils have been proposed using amino-, hydroxy-, acetoxy- or alkoxy-functional polysiloxanes as dispersants.

However, when these methods are left standing for a long period of time, the particles of the dispersed phase settle, causing phase separation, and it takes effort to re-disperse them. That was the reality.

In view of the above-mentioned circumstances, the present inventors aimed to make fine particles to be used as a dispersed phase have both dispersion stability and chargeability, and focused on the fact that fine particles of so-called silica sol are stably dispersed. As a result of intensive studies from the perspective of the use of silica sol, we have found that silica sol dispersed in water or organic solvent in an amount of 5 to 50% by weight as SiO□ can be replaced with an insulating oil as the dispersion medium to achieve good electroviscosity. The present invention was achieved by discovering that a liquid can be prepared, and that the electrorheological liquid using the silica sol of the present invention has an extremely low initial viscosity compared to the electrorheological liquid prepared from powder.

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

Structure of the Invention The electrorheological liquid according to the present invention contains 5 to 50% by weight of Si
It is characterized in that a silica sol in which O* is dispersed in water or an organic solvent is replaced with a non-reactive silicone oil or modified silicone oil having a specific gravity of 0.90 to 1.30 as a dispersion medium.

Generally, silica sol contains 0.01 to 50% by weight of stag and alkali metal in SiO*/Me*0
(M e is a monovalent alkali metal atom) as a molar ratio of 5 to
5,000, including infinity in some cases, silica particle size 1 to 150 mμ, dispersion medium generally water or glycols such as methanol, ethanol, l-propanol, t-butanol, ethylene glycol and polyethylene glycol, Hydrophilic organic solvents such as acetone, dimethylformamide, and tetrahydrofuran, or mixed solvents of water and hydrophilic organic solvents are used.

All of these belong to the category of silica sol, which is a raw material for the electrorheological liquid of the present invention. Furthermore, alkyl silicates such as ethyl silicate or hydrolysates thereof also belong to the same category.

The solid content of the silica sol is 5 to 60% by weight as Sin, preferably 10 to 50% by weight, in order to supply 5 to 50% by weight of StO into the electrorheological liquid.

The electrorheological liquid of the present invention can be obtained by replacing the silica sol with a solvent. As a method for replacing the solvent, a method of removing water and low-boiling substances by distillation, a method of using an ultrafiltration membrane, a method of using molecular sieves, etc. can be adopted, but any method that can replace the solvent M can be used. However, in general, distillation methods use solvents with relatively low boiling points, such as water, methanol,
A silica sol using ethanol, ①-propertool, acetone, etc. is preferable, and in the ultrafiltration method, a silica sol using a relatively low viscosity solvent is preferable.

The electrorheological liquid obtained by replacing the solvent in this way contains some water, although it differs depending on the method of solvent replacement.The amount of water remaining in the electrorheological liquid of the present invention is determined by 0.003 per 100 parts by weight of 8102
It is necessary that up to 10 parts by weight of water be adsorbed, preferably 0.03 to 8 parts by weight, and more preferably 0.05 to 5 parts by weight. If the amount of water is less than 0.003 parts by weight, the electrorheological effect will be insufficient, and if it is more than 10.0 parts by weight, the current will flow too much and the electrorheological effect will be inhibited, and at the same time the durability will deteriorate significantly. .

In principle, the dispersion medium to be used for the electrorheological liquid of the present invention can be mineral oil, high flash point hydrocarbon oil, poly(1-1)
Hydrocarbon oils such as octene, aromatic oils such as isopropylbiphenyl and diisopropylnaphthalene, halogenated oils such as chlorinated diphenyl and chlorinated paraffin, ester oils such as dibutyl sebacate, benzyl neodecaprate, and phthalate esters, and fluorinated oils. These include oil and silicone oil, but in many components that utilize electrorheological fluids, electrorheological fluids are used in direct contact with materials that have rubber-like elasticity, so they are not suitable for rubber-like elastic materials. It is used in many components that utilize electrorheological liquids, from the viewpoint of avoiding substances that have adverse effects such as deterioration, swelling, and in some cases, dissolution, and because it generates hydrogen halide when stimulated by heat, force, etc. From the two viewpoints of avoiding substances that corrode metals, polydimethylsiloxane, polymethylphenylsiloxane, polydiphenylsiloxane, polymethylchlorophenylsiloxane,
At least one unit selected from polymethyl long-chain alkylsiloxane, polymethylcyanopropylsiloxane, polymethyl-3,3,3-)lifluoromethylsiloxane or a copolymer thereof, or a mixture thereof, etc. Among the silicone oils and modified silicone oils exemplified above, non-reactive ones are preferably used.

The specific gravity of non-reactive silicone oil or modified silicone oil used as a dispersion medium is 0.90 to 1.30,
Preferably 0.91 to 1.10, more preferably 0.9
It is desirable that it is 3 to 1.05.

In addition, the viscosity of non-reactive silicone oil or modified silicone oil used as a dispersion medium is 3 to 3 at room temperature.
It is necessary to use a material having a viscosity of 300 centivoise (cp), preferably 5 to 250 centivoise (cp), more preferably 5 to 50 centivoise (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. If the viscosity of the dispersion medium, which can impart high electrical responsiveness to electrorheological liquids, is less than 3 centivoises (cp), the thermal stability of the dispersion medium will be extremely poor;
If it is more than p), the initial viscosity will become high, resulting in poor electrical response.

In the electrorheological liquid of the present invention, in addition to the above-mentioned constituent requirements, it is desirable to use a suitable dispersion stabilizer in order to stabilize the electrorheological liquid.

In the present invention, the dispersion stabilizer plays the following roles:
That is, a. The role of preventing agglomeration between fine particles existing in the sol, which causes phase separation due to sedimentation of the dispersed phase in the electrorheological liquid, and as a result increasing the stability of the electrorheological liquid.

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.

There are two points.

Dispersion stabilizers that play this role include the following (
Items such as a) to (f) can be used.

(a) At least one type or more general formula %formula%() A compound containing silicon element in the molecule.

In the compound containing the silicon element in the molecule, it is necessary that the substituent X in the general formulas (I) and (n) have a hydrophobic structure.

Examples of hydrophobic substituents for the structure (I) include methyl group, ethyl group, n-propyl group, l-propyl group, n-propyl group,
-butyl group, 1-butyl group, s-butyl group, t-butyl group, n-pentyl group, n-hexyl group, C-hexyl group, n-heptyl group, n-octyl group, n-nonyl group,
Saturated hydrocarbon groups such as n-decyl group, n-dodecyl group, stearyl group, unsaturated hydrocarbon groups such as vinyl group, allyl group, aromatic hydrocarbon groups such as phenyl group, benzyl group, naphthyl group, biphenyl group , a halogenated hydrocarbon group, a monofunctional hydrophobic substituent having a polysiloxane structure, etc. are typical examples, and for the structure of (Il), a methylene group, an ethylene group, a trimethylene group, a tetramethylene group, etc. basis,
Pentamethylene group, octamethylene group, propylene group,
Saturated hydrocarbon groups such as ethylidene groups, unsaturated hydrocarbon groups such as vinylene groups and propenylene groups, aromatic hydrocarbon groups such as phenylene groups and naphthylene groups, halogenated hydrocarbon groups,
A typical example is a bifunctional hydrophobic substituent having a polysiloxane structure or the like.

(b) Modified silicone oil with basic reactive groups.

Examples of the modified silicone oil having a basic reactive group include those having at least ■ out of the three structural units represented by the general formula %, or those having a combination of ■ and ■ and/or ■. is selected from a mixture thereof.

The viscosity of the amino-modified silicone or oil is 5 to 300 centivoise (cp) at room temperature, preferably 8 to 2.
50 centivoise (cp), more preferably 5 to 50
It is necessary to use a material having a viscosity of centivoice (cp). If the viscosity of the amino-modified silicone oil is less than 5 centivoise (cp), the dispersion stability performance will be extremely poor, and if it is more than 300 centivoice (cp), the initial viscosity will become high, resulting in poor electrical response. It gets worse.

(C) Modified silicone oil having a polyethylene glycol structure and/or a polypropylene glycol structure in the molecule.

The modified silicone oil is selected from those having at least ■ out of the three structural units represented by the general formula %, those having a combination of ■ and ■ and/or ■, or a mixture thereof. The one prepared is used.

The viscosity of the modified silicone oil is 5 to 3 at room temperature.
It is necessary to use a material having a viscosity of 0.00 centivoise (c'p), preferably 8 to 250 centivoise (cp), more preferably 5 to 50 centivoise (cp). The viscosity of the modified silicone oil is 5 centiboise (cp)
If it is less than 30, the dispersion stability performance will be extremely poor.
If it exceeds 0 centivoice (cp), the initial viscosity will become high, resulting in poor electrical response.

(d) Alcohols or glycols.

Examples of these include methanol, ethanol, l-propertool, n-propertool, n-butyl alcohol, ethylene glycol, trimethylene glycol, propylene glycol, polyethylene glycol, hydroxyethyl acrylate, hydroxyethyl methacrylate, polyvinyl alcohol acrylate, Examples include those having a hydroxyl group structure in the molecule, such as polyvinyl alcohol methacrylate, polyvinyl alcohol diacrylate, polyvinyl alcohol dimethacrylate, allyloxy polyvinyl alcohol, and diallyloxy polyvinyl alcohol.

(e) An oligomer having a polyethylene glycol structure and/or a polypropylene glycol structure in its molecule.

Examples of these include polyethylene glycol, polypropylene glycol, polyethylene glycol acrylate, methoxypolyethylene glycol acrylate,
Examples include polyethylene glycol methacrylate, methoxypolyethylene glycol methacrylate, polyethylene glycol diacrylate, methoxypolyethylene glycol diacrylate, polyethylene glycol dimethacrylate, methoxypolyethylene glycol dimethacrylate, allyloxypolyethylene glycol, methoxyallyloxypolyethylene glycol, diallyloxypolyethylene glycol, etc. .

(f) Quaternary ammonium salts of long chain alkyl amines or polyamines.

The dispersion stabilizers (a) to (f) described above may be used alone or in combination.

Further, the electrorheological liquid of the present invention includes S10. It is possible to mix a charge extender that plays a role in controlling the amount of charge on the surface of the fine particles composed of and, as a result, improving the performance of the electrorheological liquid.

Electrorheological properties on the surface of microparticles? Charge extenders that play a role in imparting a charged structure to increase the body strength include cationic structures represented by ammonium salt structures and phosphonium salt structures, metal carboxylates, metal sulfonates, and metal phosphates. Those having one or both of the representative anion structures are preferably used.

Specific examples of the charge extender include the following general formula: X-8l-+OR)! A compound containing silicon element represented by (m) in the molecule, in which the substituent X is
It has either or both of the following structures: an ammonium salt structure, a cation structure represented by a phosphonium salt structure, an anion structure represented by a metal carboxylate salt, a metal sulfonate salt, a metal phosphate structure, or N,N-dimethylaminoethyl acrylate and its quaternary salt, N,N-dimethylaminoethyl methacrylate and its quaternary salt, N,N-dimethylaminoethyl acrylamide and its quaternary salt, N,N-dimethylaminoethyl acrylate and its quaternary salt, , N-dimethylaminoethyl methacrylamide and its quaternary salt, N
, N-dimethylaminopropyl acrylate and its 4
N,N-dimethylaminopropyl methacrylate and its quaternary salt, N,N-dimethylaminopropylacrylamide and its quaternary salt, N,N-dimethylaminopropyl methacrylamide and its quaternary salt, allylamine and its quaternary salt Examples include derivatives of amine or quaternary ammonium salts represented by acrylamide, acrylamide and its derivatives, methacrylamide and its derivatives, and acryloylmorpholine.

From the perspective of improving the performance of electrorheological liquids, the above charge extenders and the above dispersion stabilizers can of course produce good results even when used alone, but their effects are most noticeable when both are used in combination. be able to.

Furthermore, the types of dispersion stabilizer and charge extender are not limited to the above specific examples as long as they do not depart from the spirit of the present invention.

The total amount of the dispersion stabilizer and charge extender is desirably 1 to 80 parts by weight, preferably 5 to 50 parts by weight, and more preferably 8 to 40 parts by weight, based on 100 parts by weight of solid content in the sol. Parts by weight are preferred.

The ratio of dispersion stabilizer and charge extender is 100:0 to 5.
:95, preferably 90:10 to 15:85, more preferably 80:20 to 30:70. If the dispersion stabilizer ratio is 0%, the stability of the electrorheological liquid will deteriorate.

In the electrorheological liquid of the present invention, the amount of dispersed phase is 5 to 45
If the amount of the dispersed phase is less than 5% by weight, the electrorheological effect will be poor; If it exceeds this, the initial viscosity will increase, resulting in poor electrical response.

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 the gist of the present invention is exceeded.

``L Doctor'' 2 Commercially available silica sol (Snowtex C: manufactured by Nissan Chemical;
An electrorheological liquid was prepared by distilling Si0.20% by weight using a commercially available silicone oil (manufactured by Toshiba Silicone ■: TSF451-10) having a viscosity of 20 cp and a specific gravity of 0.95 at room temperature. At this time, octadecyldimethyl(3-()rimethoxysilyl)propyl]ammonium chloride (manufactured by Toray Silicone ■: AY43-021) and stearyltrimethoxysilane (manufactured by Toshiba Silicone ■: TSL8185) were used as dispersants.

Commercially available silica sol (Snowtex C: manufactured by Nissan Chemical);
An electrorheological liquid was prepared by replacing the solvent with a commercially available silicone oil (manufactured by Toshiba Silicone ■: TSF451-10) having a viscosity of 20 cp and a specific gravity of 0.95 at room temperature. At this time, γ-aminopropyltrimethoxysilane (manufactured by Toshiba Silicone ■: TSL8185) was used as a dispersant.

Hi "Nijishi" 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 having a diameter of about 10 μm was dispersed in silicone oil (manufactured by Toshiba Silicone ■: TSF451-20) having a viscosity of 20 cp and a specific gravity of 0.95 at room temperature to form a suspension.

1 and 1'' 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 L1 sample was measured using a double cylindrical rotational viscometer, applying voltage between the inner and outer cylinders, and applying the same shear rate (375 s).
, e c-'), the values expressed in terms of axial force (torque) of the viscometer are shown in Table 1.

Table 1 *1D Electric field strength E and torque T at a constant shear rate
In Figure 1, which shows the relationship between Not observed.

For evaluation of sedimentation, an electrorheological liquid was placed in a measuring cylinder and left at room temperature for 3 days, and the sedimentation status was visually evaluated. The evaluated values are shown in Table 2.

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, has a low initial viscosity, and has a high stability as a result. It was extremely excellent in electrical response.

C1 Effects of the Invention The electrorheological liquid of the present invention is stable over a long period of time, exhibits excellent electrical responsiveness, and contains no oil or solvent that causes swelling or dissolution of materials exhibiting rubber-like elasticity. It can be used in direct contact with a shaped 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
o represents the critical electric field and E. No electrorheological effect is observed below.

Claims (1)

[Claims] A silica sol in which 5 to 50% by weight of SiO_2 is dispersed in water or an organic solvent is replaced with a solvent to obtain a specific gravity of 0.90 to 1.30.
An electrorheological liquid characterized by comprising a non-reactive silicone oil or a modified silicone oil as a dispersion medium.