JPS6326151B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to electroviscous fluid compositions.
The present invention is an improved invention of the invention described in British Patent Application No. 30456/74 (corresponding to Japanese Patent Application Laid-open No. 51-33783) filed by the applicant on July 9, 1974. . The electrically viscous liquid composition of the present invention is used in fields where it is desired to control mechanical motion with a very small amount of electricity, such as in automobile clutches and brakes. For electrorheological clutches, 2
The electrorheological effect of the composition is produced by disposing the composition between the surfaces of two conductive members and applying electricity between the members. The above-mentioned prior application describes a composition that is normally liquid but whose apparent density increases under the action of an electric field.
at least one granular polyhydric alcohol having an open structure that absorbs a large amount of water, and a non-conductive hydrophobic liquid (oil carrier) in which the granular polyhydric alcohol is dispersed; Consisting of A wide variety of polymeric materials containing acid groups are currently available for use as solid media for electrorheological fluids, and it has been found that polymers with acid groups exhibit superior performance compared to polymers without acid groups. That is, polymers with acid groups have up to three times the electroviscous effect response compared to fluids with corresponding polymers without acid groups.
showed that. Accordingly, the electrorheological fluid composition provided by the present invention comprises water-containing particles of a polymer having free or neutralized acid groups dispersed in a non-conductive hydrophobic liquid, wherein the polymer is a non-conductive hydrophobic liquid. It has a moisture absorption capacity specified by , and a density of 1.8 or less. As noted above, the present invention provides an alternative polymeric material to traditional polyhydric alcohols. It has been found that the introduction of acid groups into neutral solid materials improves the electrorheological effects of fluids containing the solids. These improved effects are obtained whether the acid groups are in free form or in neutralized form as salts, providing superior EV over conventional EV fluids.
Fluid is obtained. By using a solid phase material that inherently provides a superior EV response, as is the case with the fluids of the present invention, a good EV response can be obtained even with polymers of lower water content;
On the other hand, when the water content in the solid phase is the same, the EV is stronger.
You can get a response. In the former case, lower water content is advantageous. For example, the no-field properties of fluids are improved;
Generally, the lower the content in the solid, the lower the current. This advantage of lower water content is offset to some extent because the acid groups themselves promote higher currents, and if the water content is maintained for a better EV response. The disadvantage is that a somewhat higher current is consumed than the corresponding neutral solid. However, the improvement in EV response outweighs the drawbacks mentioned above. In general, it is necessary to design an EV fluid to obtain the best performance for a given duty, and using the solids of the present invention, starch,
The range of optimization can be extended over conventional solids such as silica or alginic acid. The acid group in the polymer may be any type of group as long as it can increase the hydrogen ion concentration in the medium into which the polymer is introduced, preferably carboxylic acid groups and sulfate-containing groups (e.g. sulfate groups, sulfonic acid groups). or sulfinic acid group). It is preferable that the acid groups are neutralized, and for neutralization, metal cations (eg, alkali metal ions) are introduced into the polymer. All or part of the acid groups may be neutralized by metal cations, and one or more cations may be introduced into certain polymers. Certain organic cations can also be used to neutralize the acid groups of the polymer. Particularly preferred polymers as the polymer backbone are addition polymers containing at least one monomer having at least one acid group and/or at least one group convertible into an acid group after polymerization of the monomer. Examples of the monomer include acrylic acid, methacrylic acid, methyl acrylate, and methyl methacrylate. The polymer may be composed of only one of the above monomers, or may be a copolymer of any combination of the above monomers. In either case, these monomers are substituted with unsaturated monomers such as olefins or vinyl acetate, maleic acid, maleic anhydride, N
- other vinyl monomers such as vinylpyrrolidone) may be further copolymerized. Generally, the polymer to be used in the electrorheological fluid of the present invention must be at least somewhat hydrophilic in terms of water retention. This is because it is an essential requirement for the polymer to contain water in order to exhibit the electrorheological effect. moreover,
The amount of water retained by a polymer is an important factor in establishing the EV properties exhibited by fluids containing the polymer. Another important factor related to EV properties is the environment of water retained within the polymer. The invention is not limited by the following description of the factors governing the EV response of the fluids of the invention, but the basic idea of the invention is that the polymer must be present in the electrorheological fluid. The aim is to provide the right environment for water. It is believed that the present invention requires that a certain amount of water be absorbed at a given energy position in the polymer. The energy generated as a result of the absorption of water molecules into the polymer structure is
It probably depends on the environment surrounding the water molecules. This relationship between water and polymer can be confirmed from the viewpoint of hydrophilicity or water retention of the polymer. One factor that influences the absorption site energy of the polymer in the fluids of the present invention will be the degree of charge on the polymer near the location. The effect of the acid groups in the polymer mentioned above is thought to be that the acid groups are ionized and the polymer acquires a negative charge with respect to the water molecules absorbed into the polymer, and as a result, the electric field is applied to the polymer, water is expelled from the polymer by electroosmosis. Therefore, if the polymer includes a solid phase of an electrorheological fluid, the shear properties of the fluid will be changed by applying an electric field. From the above it will be appreciated that the number and strength of acid groups in the polymer are important in that they significantly control the water environment present in the polymer. The properties of the polymer itself that govern the EV response of the fluids of the present invention will be ascertained from a single parameter: the hydrophilic-lipophilic balance of the polymer. As mentioned above, the polymer must have some degree of hydrophilicity, but preferably should not be water soluble. This is because, when water soluble, foreign substances are difficult to remove and also tend to deposit as a dense layer on the electrode during use, requiring frequent removal and cleaning. The soluble solids described above are very difficult to work with because they tend to absorb ambient moisture and become "viscous" and thus clog rather than flow freely. However, it is also important that the polymer must not be too lipophilic. This is because if the polymer is lipophilic, it will swell in the hydrophobic liquid in which it is suspended, and the non-electric field properties of the polymer-containing electrorheological fluid will be greatly deteriorated. The water content of the polymer can be varied as desired to maximize the EV properties of a fluid containing a given polymer within the range defined by the water absorption capacity of the polymer. The water absorption capacity of a polymer is a measure of its openness to water penetration;
The upper limit is set based on the possible water content of the polymer. Since the optimal performance of the electrorheological fluid of the present invention is highly dependent on the water content of the solid phase, the specification regarding this water absorption capacity parameter is very important in terms of performance. In the present invention, the water absorption capacity of a polymer is determined by equilibrating a sample of the polymer with moisture.
When the sample is heated to constant weight under vacuum at a temperature that does not decompose the polymer, the sample loses at least 8% of its weight and is dissolved in air at an ambient relative humidity of about 60% and a temperature of 20°C. It has been found that the sample must be able to recover at least 40% of its lost weight when exposed. The heating step is typically carried out at a temperature of about 50-60°C, although higher temperatures may be employed for many polymers. EV shown by fluids containing polymers
In terms of effectiveness, the influence of the actual water content of the polymer is as follows. In other words, the higher the water content, the closer the EV response (change in breakdown point per applied unit voltage) is to the limit, the lower the threshold voltage, and the more current flows. The fluid has further superior dynamic properties such that when a voltage is applied the fluid is effectively delayed in an already sheared system. Fluids with high water content respond rapidly to changes in the applied field and generally give reproducible results. However, if the water content is too high, the non-field characteristics deteriorate and the voltage working range decreases due to arcing at low field strengths and poor response even at higher voltages in some cases. Therefore, increasing the voltage does not increase the shear resistance. On the other hand, in the case of a fluid with a low content, even if the threshold voltage is high, the current is small and the voltage operating range is wide. Non-electric properties are usually good. However, in use the fluid exhibits good static properties, i.e. two initially stationary components.
components), but
Its dynamic properties are poor. As a result of having a static yield point higher than the dynamic yield point, the fluid undergoes a hysteresis effect and forms a "viscous slip". EV fluids with low water content respond relatively slowly to changes in the applied field. From the above, it should be clear that in all EV fluids, water content is a key parameter in optimizing the fluid for a given application. The range of water contents at which good electrorheological response and acceptable current levels are obtained for the EV fluids of the present invention is wider than for conventional fluids. Typically, for the EV fluids of the present invention, when the application is static, the water content of the polymer is equal to the parallel relative humidity (ERH; defined as the RH of air in equilibrium with the solid at a known temperature). should be approximately 1% at 30°C,
For dynamic applications up to about 5% water per weight of polymer must also be added to the polymer. This will increase the ERH of the polymer by up to about 60% (even higher water contents are allowed in some cases). In terms of the structure of the polymer, properties that influence the behavior of electrorheological fluids can be achieved by crosslinking the polymeric compound by factors such as the inclusion of non-ionized hydrophilic groups (e.g. pyrrolidone groups) in the polymer. Affected by neutralizing acid groups to form salts. These various modifying factors all affect the energy distribution of water absorption sites in the polymer and thus improve the performance of fluid compositions containing the modified polymer.
Changes EV response. Polymer crosslinking affects EV response and
It has a profound effect on the non-electrical properties of the final fluid. When the polymer is uncrosslinked or only slightly crosslinked, it is believed that the solids will contain small amounts of absorbed water-soluble low molecular weight material that will move to some degree within the polymer. Such mobile materials have a "flocculating effect" on the polymer particles, thereby increasing the non-field flow resistance of the fluid. In this context, removal of these mobile components from the solid by thorough washing with water greatly improves the non-electrical properties of the final fluid, but since these components are soluble, It has been found that such cleaning is generally impractical with completely uncrosslinked polymers. In the case of more completely crosslinked polymers this problem is avoided and the non-electrical properties of fluids containing said polymers are even better than with other types of polymers. Polymers may be crosslinked using a crosslinking agent in accordance with conventional methods, but care must be taken to ensure that the crosslinking agent is not hydrophilic, especially if the polymer itself is not hydrophilic. Should.
Therefore, lipophilic crosslinkers such as divinylbenzene can be used if the polymer itself is fairly hydrophilic (e.g., an acrylate polymer), but typically N,N'-methylenebis-acrylamide or diallyl is used. Crosslinking agents such as ethers are suitable. Other crosslinking methods that avoid the introduction of other substances include:
It is a method of irradiating a polymer with radiation under conditions that do not damage the polymer backbone, and the formation of salts using polyvalent cations is also effective for crosslinking polymer chains. Forming polymer salts with metal or organic base cations further controls the EV properties of polymer-containing fluids and also increases polymer stability. Cations exist in the backbone of the polymer,
The presence of correspondingly charged groups considerably influences the polarity of the polymer and thereby also its water absorption properties. When the cation has a high charge density, as is the case with calcium, ammonium and chromium cations, charge separation will be minimal and the solid will be non-polar and fairly lipophilic. However, even though the cations are useful for performing X-bonding of the polymer chains, the polymer must contain cations with low or moderate charge density to compensate for lipophilicity. At the other end for cations with high charge density, ions with low charge density, such as organic base cations, are held relatively loosely at charged positions on the polymer chain, and the resulting polymer salt is highly hydrophilic. or are deliquescent and unsuitable for use in EV fluids. Therefore,
In general, polymer salts with cations with moderate charge density provide good water penetration into charge centers and controlled water absorption, as required for strong EV effects. most appropriately used together. Suitable cations of this type are the metals of groups A and B of the periodic table, especially those of low atomic weight such as lithium, sodium, potassium and copper (2009). Instead of using a single salt with a single metal cation, similar results can also be achieved by using mixed salts in which two or more different metal cations are present.
Note that at least one metal cation may have a high charge density and at least one metal cation may have a low charge density. In this case, the effects of various cations are averaged, and a polymer salt having properties similar to those of a polymer salt with a cation having an appropriate charge density is obtained. In fact, the use of mixed salts allows for more precise control of the properties of the polymer by appropriate selection of the various cations and their properties in the salt. Also, if you use mixed salt, as mentioned above,
Since at least a portion of polyvalent cations are used in the salt, crosslinking of the polymer chains can be carried out simultaneously. From all points of view, mixtures of monovalent and trivalent cations have been found to be suitable. For example, mixtures of cations of Periodic Table and Group metals. Hydrophilicity of polymers as a useful indicator of EV properties
Lipophilic properties are used to describe a series of salts of poly(methacrylic acid) with monovalent cations of guanidinium, lithium, ammonium, and trivalent cations of chromium. The order of increasing field-free shear resistance in electrorheological fluids containing these salts is: Lithium; Guanidinium/Chromium; Guanidinium/Ammonium Lithium/Aluminum Chromium; Aluminum (highest) This order corresponds to the order of increase in the proportion of covalent bonds of metal cations to acid groups of the polymer, that is, corresponds to the order of increase in the lipophilicity of the polymer salt. For this order, the "baseline" of EV response in fluids containing such polymeric salts will be relatively high because field-free viscosity increases with increasing lipophilicity.
Therefore, when the fluid does not have a large EV response capability, as a result of the inherently high response of the fluid composition and/or as a result of using a large amount of solid phase in the fluid, the The viscosity change will be quite low and the fluid will not be very useful. The use of mixed metal polymer salts is also advantageous in the following respects. When the salt includes at least some amount of highly charged cations, very little metal is present in the salt and the density of the salt is minimized. This is important in that it is possible to use less dense hydrophobic liquids or to reduce the proportion of dense oils, at least if the densities are matched, which makes it economical. meaningful from the perspective of
Dense oils tend to be more viscous. As more dense oils are used, the volume of solid phase material must be gradually reduced in order to maintain the field-free viscosity of the liquid at a reasonable level. When the solid capacity is low, the absolute level of EV response is also low;
In this case a solid with good EV response capability would have to be used. In practice, 1.8
Suitable hydrophobic liquids are not available with densities higher than this, so the polymer or polymer salt should not have a density higher than this, with a practical lower limit of about 1.2. Other general properties of the polymer are that it must be chemically stable and resistant to chemical attack or thermal or photodegradation.
The inversion temperature of the polymer is important in connection with the application and in this case refers to the selection of the polymer. Some of the polymers suitable for the fluid compositions of the present invention are commercially available, prepared by radical polymerization methods if the monomers are water-soluble, or by conventional suspension of the corresponding ester monomers in an aqueous solvent. If at least some of the monomers are not water-soluble after polymerization or emulsion polymerization, they can be prepared by hydrolyzing the ester groups. Since the step of hydrolyzing polyester to obtain a polymer having acid groups requires very severe conditions and is difficult to implement, there is a need for a method for easily obtaining acid group-containing polymers from such monomers. Therefore, the present inventor searched for a means to directly produce a poly(acid) polymer from an acid group-containing monomer when the monomer is water-insoluble. This new manufacturing method involves suspending or emulsifying acid group-containing monomers (optionally with comonomers) in a perfluoropolyether in which the monomers (and the resulting polymer) are not dissolved. and finally separating the insoluble polymer formed. It will be appreciated that this procedure provides the desired poly(acid) polymer very simply and directly. Because this polymer has a tendency to entrain certain perfluorinated materials, and because this material is quite expensive,
After the polymer has passed from the polymerization solvent, it is most advantageous to extract the polymer with a substance that dissolves the perfluorinated polyether and can then be easily separated. A particularly suitable substance for extraction is trichlorotrifluoroethane. Alternatively, radiation polymerization may be employed, either by conventionally polymerizing ester monomers or directly producing acid group-containing polymers by the novel method described above. However, the above substances must not be destroyed. For polymer salts used as the solid phase of EV fluids, it is advantageous to start with a salt of a polymer and a monovalent cation and add a sufficient amount of trivalent metal to make the salt water-insoluble. was discovered. Generally, these salts are manufactured by the following method. In the case of metals having water-soluble hydroxides, an aqueous solution of the appropriate hydroxide may be added to the well-stirred polymeric acid solution. Plot the titration curve to find the end point. Another suitable method is to add a solution of a soluble salt of the metal (a polymeric salt of the metal is desired) after preparing a salt of the type described above, in which case the polymeric salt of the metal precipitates from the solution. There are several methods. Other than when preparing mixed salts, it is necessary to add at least a stoichiometric amount of polymer. It is desirable to homogenize the solution during precipitation to avoid trapping droplets of the soluble polymer solution inside the insoluble polymer. It is also advantageous to wash the precipitate thoroughly with distilled water so that it is free of any residual salts. Other methods for making single metal salts include titrating a solution of a polymeric acid with a strong base to establish the amount of base necessary to neutralize the acid groups in the polymer. The amount of metal salt required to be added can be easily calculated. Mixed metal salts can be formed by metathesis from single metal salts. For example, in the case of lithium/chromium polymethacrylate, chromium chloride may be added to the lithium polymethacrylate sample. When producing the electrorheological fluid of the present invention,
The polymer is dispersed in a hydrophobic liquid in granular form. Examples of hydrophobic liquids particularly suitable for the present invention include:
FluorolubeFS-5 (Hooker Chemical
Polymer of trifluorovinyl chloride), Arocler 1242, a registered trademark of Corporation.
(a registered trademark of Monsanto Chemical Corporation, polychlorinated biphenyl) and orthodichlorobenzene. Other hydrophobic liquids useful in making the fluid compositions of the present invention include xylene and p-chlorotoluene. In a preferred embodiment of the invention using a mixed hydrophobic liquid, which is a mixture of two hydrophobic liquids to obtain a suitable density for the polymer, Floroube FS is used as the high density component.
-5 (density 1.87; viscosity at room temperature approximately 20 cps) or
It is particularly suitable to use Fomblin Type Y2 (density 1.85) and as low density component Arocler 1242 (density 1.38) or orthodichlorobenzene (density 1.30). Proper mixing of Fluorolube and Arocler is expected to result in a fluid composition having a viscosity of about 22 cps at 30°C. In the preferred embodiment described above, dichlorobenzene is not very viscous in the absence of an electric field and has no risk of environmental pollution.
Preferable to Arocler 1242. However, when dichlorobenzene is incorporated into the fluid composition of the present invention, it has the disadvantage that about twice as much current flows as Arocler 1242. Combinations of fluorinated hydrocarbons with other chlorides or simply carbon atoms can also be effective hydrophobic liquids. It is advantageous to avoid using polymer particles that are too small (less than about 1 micron in size). This is because particles of such size introduce undesirable non-electric field properties in the fluid. Preferably, the particles should not be too large for the operating clearance of the device using the fluid. This is because if particles larger than about 1/10 of the minimum gap in the flow circuit are used, the fluid in the gap becomes inhomogeneous, leading to operational abnormalities. Therefore, an upper limit of particle size of about 50 microns has been found to be best when the working clearance is 0.5 mm. It is considered that the particle size of the solid phase substance should be within this range. If the hydrophobic liquid in the EV fluid of the invention has a density comparable to that of the solid phase material, a mixture of two or more hydrophobic liquids is required. Factors that influence the density of liquid and solid phase materials are described in the applicant's prior applications, so please refer to them. The viscosity of a hydrophobic liquid determines how much solid polymer can be used in an EV fluid designed for any particular application. For example, Aroclor
When using a mixture of 1242 and Fluorolube FS-5, a pumpable fluid with a solids content of about 30% and a viscosity of about 20 mpa.s. is obtained. In some applications higher viscosities and therefore higher solids capacities are acceptable, while in other applications lower viscosities must be used. The capacity of the polymer should be as high as possible providing a fluid composition suitable for the desired application. Fluid compositions with high polymer capacity exhibit a greater rate of increase in apparent viscosity under the influence of a transient electric field than fluid compositions with lower polymer capacity, but in this case, even in the absence of an electric field, the viscosity of the fluid remains relatively constant. to rise. For fluid compositions to be pumped into the system at room temperature, the polymer capacity should be 30-35%, taking into account the increase in apparent viscosity under the influence of an electric field and the viscosity of the fluid composition in the absence of an electric field. Although preferred, higher capacities can be tolerated, for example when the solid polymer particles are surface treated or when the viscosity of the hydrophobic liquid is particularly low. For applications where the fluid composition does not have to be pumped, such as in electrorheological clutches, the polymer capacity can be reduced by about 5% from the above values.
It may be increased. Since the viscosity of a fluid composition increases rapidly with decreasing temperature, the capacity of the polymer is set depending on the temperature at which the fluid composition is operated. Therefore, a lower amount of polymer is required in a fluid composition used at lower temperatures, and a higher amount of polymer is required in a fluid composition used at higher temperatures. Examples of manufacturing the electrorheological fluid of the present invention and the results obtained thereby will be described below. The behavior of electrorheological fluids was investigated using the following method. A coaxial cylindrical apparatus is provided to hold a sample of electrorheological fluid in an annular gap between a grounded external cylinder and a rotor disposed therein. An electric field is applied across the gap to apply increased torque to the rotor. At this time, measure the voltage and torque.
The current flowing through the fluid sample is also measured. Since the characteristic parameters of the fluid (especially the current) depend on the temperature,
The entire apparatus is maintained at a constant temperature during the test. Regarding fluid parameters, the "yield point" is taken as the value of torque at which supported rotation is observed. When the yield point is plotted against the applied voltage, the curve is basically a straight line, but a threshold voltage V ₀ is usually observed, and below this V ₀ no electrorheological effect is observed at all. The mechanical behavior of electrorheological fluids can be observed from two parameters: the threshold voltage V ₀ and the slope of the straight part of the yield point/voltage curve, denoted by S/V. For so-called "dynamic" measurements, the fluid is sheared and three-dimensional plots are produced for all variables. To obtain another parameter characteristic of a given fluid, the dc current passed through the fluid is measured and correlated with the voltage applied across the actuation gap. The relationship between voltage and current is as follows. Current/unit area = P (V) + Q (V) ² Although this relationship tends to break down at low voltage values, resulting in a negative value of P, for all practical purposes this law holds over the entire operating range of the fluid. It is accurate enough. The constants P and Q are easily determined by performing a linear regression of conductivity against voltage based on empirical results for current and voltage. Q is obtained from the slope of the regression curve, and P is obtained from the intercept on the conductivity axis. The values of P and Q appear to be less sensitive to fluid shear. P is practically temperature independent, whereas Q has a Boltzmann type dependence. The specific data are highly dependent on the polymer content, which is not optimized in every case. If the polymer used is in its dry form, the water content is stated as "ambient water content". If further water is added in the vapor phase, the amount thus added is taken as % by weight of the "dry" polymer, i.e. "ambient water content + X %".
Described as . The polymer is ground in a ball mill and sieved.
Tested after removing particles larger than 50 microns in size. EV response measurements are made with Aroclor unless otherwise specified.
30 solids suspended in 1242 (Monsanto)
%V/V suspension, the measurement temperature was 30
It was warm at ℃. All the results cited were obtained using a device with a working clearance of 0.5 mm. Field-free properties (i.e. yield point and plastic viscosity)
was measured using a standard cone and plate viscometer (Haakc) with a 1.89° cone. Unless otherwise specified, solids are Aroclor 1242 (Monsanto)
Measurement was carried out at 30°C using a 30% V/V suspension suspended in . Example 1 A sample of divinylbenzene crosslinked polyacrylic acid was prepared as follows. 142.5 ml of methyl acrylate was introduced into a separatory funnel, washed with dilute alkali to remove the stabilizer, and then washed with water. After similarly treating divinylbenzene (7.5 ml of 50-60 W/W% in ethyl vinylbenzene), both monomers were mixed and 1.5 g of benzoyl peroxide was added to the mixture. This solution was then immediately added to a well-stirred aqueous solution containing 1 g of calcium stearate in 200 ml of water contained in the reaction solution. The mixture was then stirred at reflux for 8 hours at 60° C. under a slight pressure of nitrogen (this operation removed oxygen that would inhibit polymerization). The mixture was then cooled and the solids were removed and washed with water. The solids were then resuspended in a 5:1 acetone:caustic soda mixture and refluxed in a water bath for approximately 30 hours. A solid that is not obviously swollen or has no change in appearance is collected by decantation, washed several times with distilled water by decantation to remove particulate rubbery matter, and finally filtered. Washed on the filter with distilled water. The resulting material was then resuspended in 3% aqueous potassium hydroxide solution and boiled under reflux with stirring for an additional 20 hours. It was collected again and washed by decantation with distilled water. At this time, no obvious change was observed in its appearance. The product was then suspended in water: concentrated hydrochloric acid (4:1) and stirred with fresh acid for an additional 4 hours. Finally, it was thoroughly washed with distilled water and vacuum dried. The product thus produced was a self-granular material, very similar in appearance to sugar. The water content after drying was 0.9 (g water/g solid weight). As expected, cross-linking greatly reduced the water holding capacity of the material. The solids were ground for 3 hours and one sample was tested for density. The size of the product after milling has been reduced (by microscopic observation) to about twice the radius of the starch, i.e.
The particle radius was 10 microns. The density was 1.36. (Compare polyacrylic acid = 1.42; polymethacrylic acid = 1.35). As expected, the density decreased with the introduction of hydrocarbon monomers. Unlike commercially available polyacrylic acid, the crosslinked polymer was insoluble and therefore had no tackiness. The size of most of the product after overnight grinding is 3-5
Although it had been reduced to microns (microscopic observation), some coarse particles remained. This coarse particle
It was removed by sieving with boltingcloth. The static method was used to investigate the EV characteristics of solids.
The batches are dried to a desired level and then a series of samples are rehydrated under vacuum to a known degree;
Tested as 30% by volume fluid in Aroclor. Table 1 shows the measurement results for the characteristic values of the famous fluids.

[Table] As is clear from Table 1, as the water content increases, the V ₀ value decreases and the flowing current increases.
The S/V value changed only slightly. This solid was found to be a useful fluid in practice, as the V ₀ value dropped below usability before the current value became unacceptably high. Measurements of non-electric field properties showed that the yield point was 92 Pa and the plastic viscosity was 0.22 Pa.s. Example 2 135ml methyl acrylate and 15ml (10%)
divinylbenzyl (50% in ethylvinylbenzene)
Example 1 except that ~60W/W%) was used.
repeated. The product was a white particulate material with a density of 1.34. After grinding to a size of 3 to 5 microns
Fluids were prepared in Aroclor (30V/V%). The water content in this case was "ambient" + 6.2% by weight. The static test data were as follows: S/V 1.38±0.07 Pa/v V ₀ 0.33 KV P 8.75±67.7 amps/v×7.87×10 ⁶ Q 23.56±100 amps/v ² ×7.87×10 ⁹ The electric field characteristics were as follows: Yield point: 33 Pa Plastic viscosity: 0.26 Pa.s Example 3 142.5 ml of acrylic acid and divinylbenzene (7.5
ml) and benzoyl peroxide (2 g) and the whole was added to 1 Kg (530 ml) of Fomblin and kept at 70°C with vigorous stirring in a creased flask [polymerization inhibitor ( Note that p-methoxy-phenol) cannot be easily removed from acrylic acid. For this reason, twice the amount of benzoyl peroxide was used for immersion]. Nitrogen was passed over the surface of the reaction mixture to remove oxygen as usual. The reaction vessel was equipped with a thermometer and a reflux condenser. After stirring the mixture for 1 hour, the whole solidified rapidly and the stirrer was stopped (to prevent damage).
It is important that this stirrer is connected to the drive motor via a slip-coupling). The solid was then cooled, removed from the reaction vessel, and dried. The resulting product was white and crumbly. The polymer adhering to the stirrer was removed, coarsely ground, and washed on a filter with trichlorotrifluoroethane (TCTFE).
It was then thoroughly extracted with the solvent in batches in a Soxhlet apparatus and finally dried and ground. Note that about 3/1 of Fomblin is entrained in the solid. Less than 10g total after filtration
Although Fomblin was lost, the recovery rate was satisfactory. The solid was obtained as a pure white powder. Its density is
1.37 (compare with the density of the product of Example 1, which is 1.36 by conventional methods). When placed in water, some swelling was observed. The originally hard particles swelled slightly and became translucent and rubbery. 3.5 of the solid polymer according to the experiment of Example 1.
EV of the solid as a 30% suspension in Aroclor after trapping a known amount of solid with an amount of water equal to wt%
tested the properties. The results of the static test were as follows. S/V 1.90 Pa/v V ₀ 0.52 P 3.59±0.63 amp/volt×7.87×10 ⁶ Q 6.4±0.48 amp/volt ² ×7.87×10 ⁹ Example 4 148.5 ml of acrylic acid and 1.5 ml (1%) Example 3 was repeated except using a divinylbenzene solution of . The density of the product was 3.39. Static tests are carried out using Aroclor® products containing ambient moisture.
The test was carried out on a 30V/V% solution suspended in
The results obtained are as follows. S/V 2.00±0.16 Pa/v V ₀ 0.48±0.18 KV P 0.44±0.63 amp/volt×7.87×10 ⁶ Q 13.30±0.58 amp/volt ² ×7.87×10 ^9Example 5 Commercially available pure poly A static test for EV characteristics was conducted using acrylic acid and polymethacrylic acid as 30V/V% Aroclor. The results are shown in Table 2. The non-electric field property values were measured values for polymethacrylic acid. Example 6 4.1 kg of lithium hydroxide (manufactured by BDH) was prepared in a small amount of distilled water (approximately 16 kg) and slowly added to the 20% aqueous solution of polymethacrylic acid (manufactured by BDH) in 1 while stirring. . When the PH change was constantly observed during mixing, the PH changed rapidly at first, then changed gradually, and then suddenly changed rapidly again. At this point, the addition of lithium was stopped. The pH was approximately 9. The resulting solution was then evaporated in the lowest possible vacuum at a temperature above 80°C. During this drying, it is preferred to agitate the surface intermittently to prevent skinning, which retards evaporation. It is also preferred to heat the solid at 80° C. under a vacuum of about 4 mm Hg at least overnight to completely dry the solid. After drying, the solid was ground in a vibrating ball mill and then dried again to remove moisture absorbed during grinding before granulation. The solid is then granulated,
The fraction below 20 microns was collected and the larger particles were dried again and returned to the mill for grinding. The fine particles were hydrated as follows. The solid was kept at 30°C and at a constant controlled humidity (RH approximately 1% for static measurements, R.
A stream of air having a concentration of about 60% H. After hydrating the solid (yield 8.82Kg) immediately 2.66Kg
Fluorolube FS-5 (Hocker Chemicals, and
Plastics Corporation) and 9.45Kg Aroclor/
1242 (manufactured by Monsanto), the hydrated solids must be mixed immediately, as without the base oil the solids will rapidly pick up moisture. Then the non-electric field properties and static EV of the fluid composition
Characteristics were measured. The results are shown in Table 2. Example 7 109g of 20% aqueous solution of polymethacrylic acid (BDH
diluted with distilled water to 200 ml. 6.2% in the solution
Lithium hydroxide solution (using solid made from BDH)
was added dropwise to adjust the pH to 9.0. 186 ml of lithium hydroxide solution was required. A solution of lithium polymethacrylate was homogenized using an “Ilado” homogenizer, and in this state chromium chloride (Hopkin &
Williams Ltd) aqueous solution (29 W/V%) was slowly added. When the ratio of moles of Cr ³⁺ added/moles of Li ⁺ required for initial neutralization was 0.294, the solution was completely gelled. At this point, the addition of chromium chloride was stopped. The obtained gel was dispersed in distilled water, filtered, and further washed with distilled water.
It was granulated dry on a fluidized bed dryer and then sieved to remove particles larger than 50 microns in size. After this, the resulting dark gray-green solid is Aroclor
(30V/V%), non-electric field characteristics and E.
V. Conducted tests on characteristics. Table 2 shows the results.
Shown below. Example 8 A chemically crosslinked lithium polymethacrylate polymer salt was prepared by the following method. 1 of distilled water and 100 g of methacrylic acid (manufactured by Kochlight Laboratories), 48.8 g of lithium hydroxide monohydrate (manufactured by BDH Ltd.) and 35.8 g of methylenebisacrylamide (manufactured by Koch-Light Laboratories).
Laboratories) was placed in a No. 5 beaker and stirred with a magnetic stirrer. The contents were warmed to 70° C. and when no more solution was proceeding, 1.5 g of potassium persulfate was added to the solution. If heating and stirring are continued, the liquid will rapidly gel after about 15 minutes and the temperature will reach about 20°C.
(The final temperature at this point can be kept below 100°C to prevent the contents from spilling out of the beaker due to water vapor pressure, or if the reaction is carried out in a closed thread and the manufacturing process is carried out under pressure. good). With gelling acid content, the beaker was moved away from the direct heating element and placed in a hot water bath. The gel was kept in a hot water bath until it was stiff enough to shrink and crack. The time was about 2 hours. The white opaque gel was removed from the beaker, cooled and ground into small pieces. Approximately 3 g of distilled water was then added and the suspension was homogenized using an Ilado homogenizer at approximately 10000 rpm. The milled polymer was then washed to remove soluble material. This washing was carried out by placing the suspension in a tube with a diameter of about 10 g and having a glass sintered disk at the bottom, and slowly passing distilled water through the top of the tube. Using a peristaltic pump, distilled water was pumped through the disk to the bottom of the tube at a flow rate of approximately 500 ml/h (this flow rate was such that the polymer in suspension did not sink to the bottom of the tube and (selected so that it does not float to the top edge). Washing was continued for at least 24 hours, after which the solids were collected by filtration and dehydrated in a fluidized bed dryer at 60° C. for about 3 hours and until dry. Approximately 130 g of white friable powder was obtained.
After vacuum drying and pulverization, the product was suspended in Aroclor 1242 to prepare a 30V/V% suspension. Table 2 shows the results of the static test of the product obtained and its further hydrated material. Example 9 Example 8 was repeated except that the initial neutralization of the methacrylic acid was carried out using guanidinium carbonate according to the method of Example 6. The product obtained was a white friable solid. After drying with silica gel, it was suspended in Aroclor 1242 to prepare a 30 V/V% suspension and a static test was performed. The results are shown in Table 2. The two samples obtained in this example were further hydrated by adding 2.5% and 4.9% water (% based on the weight of the polymer), respectively, and the results after testing in the same manner are shown in Table 2.

【table】

[Table] As is clear from the results in Table 2, when 12% of the sites in the mixed salt (Example 7) are occupied by lithium, compared to a simple equivalent salt (Example 6), at least trivalent ions When is chromium, the completely non-electric shear resistance is sufficiently reduced. Additive N,N'-methylene bis-, not trivalent chromium ion
Similar results were obtained when acrylamide was used to crosslink lithium polymethacrylate salts. However, as shown in Table 2, crosslinked polymer salts have the advantage of lower density than mixed salts and simple non-crosslinked lithium polymethacrylates. Furthermore, cross-linked lithium salts are easier to handle than non-cross-linked salts because they do not tend to absorb moisture. For a polymer salt with a density of 1.43, density-adjustment (density-
matching) Only 13% Fluorolube needs to be present in the mixed Arolcor-Fluorolube hydrophobic liquid. A vehicle containing 22% Fluorolube is required for non-crosslinked lithium polymethacrylate salts and 31% for mixed lithium/chromium salts.
Compare that a vehicle containing Fluorolube is required. It should also be noted that Fluorolube is an expensive substance. For the guanidinium salt of Example 9, Example 8
A hydrophobic liquid with a lower density than the lithium salt is required, otherwise it has been found to be somewhat unsatisfactory due to the extreme sensitivity of the guanidium salt to moisture. After all, N, N′−
Lithium polymethacrylate, cross-linked to the minimum possible extent with methylene bis-acrylamide, is a preferred salt, resulting in a solid material that is easy to wash and handle. Example 10 Ceroclor (commercially available molecular formula
Preparation of 16 electrorheological fluids with different solids capacity in the fluid using partially chlorinated hydrocarbon paraffin with C ₁₂ H ₂₁ Cl ₁₅ ) and non-crosslinked lithium methacrylate (water content 18%) as solid. did. An electric field of 3 KV/mm was applied to the surface of the clutch (gap 1/2 mm) under static conditions, and the yield point of each fluid was measured. The results are as follows. Solid capacity (%) Yield point (KPa) 0 0 2.5 0.3 5 0.5 7.5 0.8 10 1.2 12.5 1.6 15 2.0 17.5 2.4 20 2.9 22.5 3.6 25 4.4 27.5 5.2 30 6.0 32.5 7.2 35 8 .7 37.5 10.2 40 12.0 All solids capacity tested The electrorheological effect was confirmed. Example 11 Lithium polymethacrylate crosslinked with methylene bisacrylamide was prepared, dried and ground to a suitable moisture content. The hydrophobic liquid used was Flectrolube T4, which consists of 60% polychlorinated phenyltolylmethane and 40% trichlorobenzene. It has a suitable density and viscosity of about 20 mPas and is probably more biologically safe than polychlorinated biphenyl. Eight electrorheological fluids were prepared and tested with varying polymer volumes. The results are shown in the table below. The results excluding sample H are also shown in FIGS. 1 to 4. Sample H showed different results in terms of yield point and current than the other samples. This suggests that air bubbles were present because the fluid is quite viscous even at zero electric field.

[Table] As is clear from the above results, the solid capacity is 10 to 40
%, the electrorheological effect becomes more pronounced as the solid capacity increases (S/V increases and V ₀ decreases). The current also increases (Q increases and P becomes more negative). It is believed that S/V is correlated with solids content. Therefore, it can be said that the electrorheological effect is observed over a very wide range of solid volumes.

[Brief explanation of the drawing]

1 to 4 are graphs showing the effects of the electrorheological fluid composition of the present invention.

Claims (1)

[Scope of Claims] 1. An electrorheological fluid composition comprising water-containing polymer particles dispersed in a non-conductive hydrophobic liquid, wherein the polymer has free or neutralized acid groups. has a density of 1.8 or less, and loses at least 8% of its weight when a sample of the polymer, after equilibration with moisture, is heated to constant weight at a temperature that does not cause the polymer to decompose. , loses at least its weight when exposed to air at an ambient relative humidity of approximately 60% and a temperature of 20°C.
An electrorheological fluid composition having a water absorption capacity of 40% recovery, provided that the polymer is not a polyhydric alcohol. 2. The fluid composition according to claim 1, wherein the acid group comprises a carboxylic acid group, a sulfuric acid group, a sulfonic acid group, or a sulfinic acid group. 3. A fluid composition according to claim 1 or 2, wherein the polymer is an addition polymer. 4. The fluid composition of claim 3, wherein said polymer is an addition polymer of one or more monomers selected from acrylic acid and substituted acrylic acids. 5. The fluid composition of claim 4, wherein the substituted acrylic acid is methacrylic acid. 6. A fluid composition according to claim 3, wherein the addition polymer is derived from a monomer having at least one group convertible to an acid group after polymerization of the monomer. 7. Fluid composition according to claim 6, wherein the monomer is an alkyl acrylate, in particular methyl acrylate or ethyl acrylate. 8. According to any of claims 3 to 7, the polymer contains at least one other monomer component, such as olefin, maleic acid, maleic anhydride, vinyl acetate or N-vinylpyrrolidone. fluid composition. 9. A fluid composition according to any of claims 3 to 8, wherein the polymer is crosslinked using divinylbenzene, diallyl ether or N,N'-dimethylene bis-acrylamide. 10. The fluid composition according to any one of claims 1 to 9, wherein at least a portion of the acid groups of the polymer are neutralized to form a salt. 11. The fluid composition of claim 10, wherein the acid groups are neutralized by metal or organic cations. 12 The metal is selected from Groups 1, 2 and 3 of the periodic table, in particular lithium,
12. A fluid composition according to claim 11 selected from sodium, potassium, copper, magnesium, aluminum and chromium. 13 The above polymer is a salt of polymethacrylic acid,
12. Fluid composition according to claim 11, in particular a lithium salt, a quanidinium salt or a lithium-chromium mixed salt. 14. The fluid composition of claim 13, wherein said polymer has an equilibrium relative humidity of 1 to 65%. 15. A fluid composition according to any of claims 1 to 14, wherein the particles of the polymer have a size of 1 to 50 microns. 16. A fluid composition according to any one of claims 1 to 15, containing 20 to 40% by volume of polymer. 17 The equilibrium relative humidity of the solid consists of particles of lithium polymethacrylate with a water content of 1 to 65%, the particles accounting for 25 to 35% by volume of the fluid composition, the remainder being non-solids with a density of 1.40 to 1.50. A fluid composition consisting of an electrically conductive hydrophobic liquid. 18. Claim 17, wherein the polymethacrylate is crosslinked with N-N'-methylenebis-acrylamide and has a density of less than 1.45.
Fluid composition as described in Section.