Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
  • H01F1/00—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties
  • H01F1/44—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of magnetic liquids, e.g. ferrofluids
  • H01F1/447—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of magnetic liquids, e.g. ferrofluids characterised by magnetoviscosity, e.g. magnetorheological, magnetothixotropic, magnetodilatant liquids
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10M—LUBRICATING COMPOSITIONS; USE OF CHEMICAL SUBSTANCES EITHER ALONE OR AS LUBRICATING INGREDIENTS IN A LUBRICATING COMPOSITION
  • C10M171/00—Lubricating compositions characterised by purely physical criteria, e.g. containing as base-material, thickener or additive, ingredients which are characterised exclusively by their numerically specified physical properties, i.e. containing ingredients which are physically well-defined but for which the chemical nature is either unspecified or only very vaguely indicated
  • C10M171/001—Electrorheological fluids; smart fluids
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
  • H01F1/00—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties
  • H01F1/44—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of magnetic liquids, e.g. ferrofluids
  • H01F1/445—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of magnetic liquids, e.g. ferrofluids the magnetic component being a compound, e.g. Fe3O4
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10M—LUBRICATING COMPOSITIONS; USE OF CHEMICAL SUBSTANCES EITHER ALONE OR AS LUBRICATING INGREDIENTS IN A LUBRICATING COMPOSITION
  • C10M2201/00—Inorganic compounds or elements as ingredients in lubricant compositions
  • C10M2201/04—Elements
  • C10M2201/05—Metals; Alloys
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10M—LUBRICATING COMPOSITIONS; USE OF CHEMICAL SUBSTANCES EITHER ALONE OR AS LUBRICATING INGREDIENTS IN A LUBRICATING COMPOSITION
  • C10M2209/00—Organic macromolecular compounds containing oxygen as ingredients in lubricant compositions
  • C10M2209/02—Macromolecular compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds
  • C10M2209/08—Macromolecular compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds containing monomers having an unsaturated radical bound to a carboxyl radical, e.g. acrylate type
  • C10M2209/084—Acrylate; Methacrylate
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10M—LUBRICATING COMPOSITIONS; USE OF CHEMICAL SUBSTANCES EITHER ALONE OR AS LUBRICATING INGREDIENTS IN A LUBRICATING COMPOSITION
  • C10M2217/00—Organic macromolecular compounds containing nitrogen as ingredients in lubricant compositions
  • C10M2217/04—Macromolecular compounds from nitrogen-containing monomers obtained otherwise than by reactions only involving carbon-to-carbon unsaturated bonds
  • C10M2217/044—Polyamides
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10M—LUBRICATING COMPOSITIONS; USE OF CHEMICAL SUBSTANCES EITHER ALONE OR AS LUBRICATING INGREDIENTS IN A LUBRICATING COMPOSITION
  • C10M2217/00—Organic macromolecular compounds containing nitrogen as ingredients in lubricant compositions
  • C10M2217/04—Macromolecular compounds from nitrogen-containing monomers obtained otherwise than by reactions only involving carbon-to-carbon unsaturated bonds
  • C10M2217/045—Polyureas; Polyurethanes
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10N—INDEXING SCHEME ASSOCIATED WITH SUBCLASS C10M RELATING TO LUBRICATING COMPOSITIONS
  • C10N2040/00—Specified use or application for which the lubricating composition is intended
  • C10N2040/14—Electric or magnetic purposes
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10N—INDEXING SCHEME ASSOCIATED WITH SUBCLASS C10M RELATING TO LUBRICATING COMPOSITIONS
  • C10N2040/00—Specified use or application for which the lubricating composition is intended
  • C10N2040/14—Electric or magnetic purposes
  • C10N2040/16—Dielectric; Insulating oil or insulators
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10N—INDEXING SCHEME ASSOCIATED WITH SUBCLASS C10M RELATING TO LUBRICATING COMPOSITIONS
  • C10N2040/00—Specified use or application for which the lubricating composition is intended
  • C10N2040/14—Electric or magnetic purposes
  • C10N2040/17—Electric or magnetic purposes for electric contacts
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10N—INDEXING SCHEME ASSOCIATED WITH SUBCLASS C10M RELATING TO LUBRICATING COMPOSITIONS
  • C10N2040/00—Specified use or application for which the lubricating composition is intended
  • C10N2040/14—Electric or magnetic purposes
  • C10N2040/175—Pantographs, i.e. printing devices
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10N—INDEXING SCHEME ASSOCIATED WITH SUBCLASS C10M RELATING TO LUBRICATING COMPOSITIONS
  • C10N2040/00—Specified use or application for which the lubricating composition is intended
  • C10N2040/14—Electric or magnetic purposes
  • C10N2040/18—Electric or magnetic purposes in connection with recordings on magnetic tape or disc
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10N—INDEXING SCHEME ASSOCIATED WITH SUBCLASS C10M RELATING TO LUBRICATING COMPOSITIONS
  • C10N2040/00—Specified use or application for which the lubricating composition is intended
  • C10N2040/14—Electric or magnetic purposes
  • C10N2040/185—Magnetic fluids

Definitions

• the present invention relates to a fluid having a characteristic of a magnetic fluid susceptible to a magnetic field and a characteristic of an electrorheological fluid whose viscosity can increase with an applied electric field at the same time, and particularly to a fluid capable of outputting a large force at a high response speed.
• a magnetic fluid is a colloidal solution, which is a uniform dispersion of ferromagnetic particles in a solvent, and, when a magnet is provided near the magnetic fluid, the entire fluid is attracted towards the magnet and behaves as if the entire fluid is apparently charged with a magnetism.
• the magnetic fluid has such a characteristic that a large force can be induced in the magnetic fluid with an applied magnetic field.
• the magnetic fluid is utilized for rotating shaft sealing, and further application to dampers, actuators, gravity separation, jet printers, etc. can be expected.
• a typical process for preparing a magnetic fluid is a chemical coprecipitation process disclosed in JP-A 51-44579, where an aqueous slurry of magnetic prepared from an aqueous solution of ferrous sulfate and an aqueous solution of ferric sulfate is admixed with a surfactant, followed by water washing, drying and dispersion into an organic solvent, thereby preparing a magnetic fluid.
• An electrorheological fluid is a suspension of inorganic or polymeric particles in an electrically insulating liquid, whose viscosity can be rapidly and reversibly changed from a liquid state to a plastic state or to a solid state or vice versa upon application of an electric field thereto.
• a high response speed is one of the characteristics.
• dispersion particles those whose surfaces are readily depolarizable under an electric field are usually used.
• silica is disclosed in US Patent No. 3,047,507, British Patent No. 1,076,754 and JP-A 61-44998
• zeolite is disclosed in JP-A 62-95397.
• polymeric dispersion particles arginic acid, glucose having carboxyl groups and glucose having sulfone groups are disclosed in JP-A 51-33783; polyacrylic acid cross-linked with divinylbenzene is disclosed in JP-A 53-93186; and resol-type phenol resin is disclosed in JP-A 58-179259.
• mineral oil silicone oil, fluorohydrocarbon-based oil, halogenated aromatic oil, etc. are known.
• the electrorheological fluid contains a small amount of water.
• Mechanism of increase in the viscosity of an electrorheological fluid with an applied electric field can be clarified on the basis of the electric double layer theory. That is, an electric double layer is formed on the surfaces of dispersion particles of an electrorheological fluid, and when there is no application of an electric field, dispersion particles repulse one another on the surfaces and are never in a particle alignment structure.
• an electric field is applied thereto, on the other hand, an electrical deviation occurs in the electrical double layers on the surfaces of dispersion particles, and the dispersion particles are electrostatically aligned to one another, thereby forming bridges of dispersion particles.
• the viscosity of the fluid is increased, and sometimes the fluid is solidified.
• the water contained in the fluid can promote formation of the electrical double layer.
• the magnetic fluid still has such problems that neither high permeability nor higher response speed as aims to a quick response is obtainable.
• a low sealability is also one of the problems.
• the electrorheological fluid still has such a problem that the torque induced upon application of an electrical field is so small that no larger force can be obtained.
• An object of the present invention is to provide a fluid capable of producing a large torque at a high response speed.
• the present invention provides a fluid having magnetic and electrorheological effects simultaneously, which comprises a magnetic field-susceptible component, an electric field-susceptible component, and a solvent.
• Magnetic field-susceptible components include magnetic particles, particularly ferromagnetic particles, more specifically magnetic particles of oxides such as magnetite, manganese ferrite, barium ferrite, etc.; magnetic particles of metals such as iron, cobalt, nickel, permite, etc.; particles of iron nitride, etc.
• Magnetic particles preferably have particle sizes of 0.003 to 200 ⁇ m, and particularly hard magnetic particles preferably have particle sizes of 0.003 to 0.5 ⁇ m and soft magnetic particles preferably have particle sizes of 0.1 to 200 ⁇ m.
• soft magnetic particles having particle sizes of 1 to 100 ⁇ m are preferable. Below 0.003 ⁇ m, the particles fail to show a magnetism, whereas above 200 m the dispersibility in the fluid is much deteriorated.
• electric field-susceptible components include known dispersion particles used in the electrorheological fluid, more specifically particles of silica, zeolite, titanium, ion exchange resin, starch, gelatin, cellulose, arginic acid, glucose derivatives, sodium polyacrylate, resol-type phenol resin, polyaniline, sulfonated polystyrene, barium titanate, carbon, etc.
• the dispersion particles have particle sizes of 0.01 to 500 ⁇ m, preferably 1.0 to 100 ⁇ m. Below 0.01 ⁇ m, no more satisfactory electrorheological effect can be obtained, whereas above 500 ⁇ m no more satisfactory dispersion stability can be obtained.
• the electric field-susceptible component includes liquid state, low molecular liquid crystals such as nitrobenzene, methoxybenzylidenebutylaniline, etc., and Solvent-soluble polymers such as liquid crystalline polymers and poly(vinylidene fluoride-tetrafluoroethylene). Since these kinds of electric field-susceptible component exist in a liquid state or in a solution state in the fluid, such a disadvantage as precipitation when electric field-susceptible particles are used can be completely overcome. Among these kinds of electric field-susceptible component, liquid crystalline polymers are preferable, because a shear stress obtained upon application of an electric field is higher than those of others.
• the liquid crystalline polymer includes lyotropic liquid crystalline polymers and thermotropic liquid crystalline polymers, among which lyotropic liquid crystalline polymers are preferable.
• the lyotropic liquid crystalline polymers include, for example, polypeptides, poly( ⁇ -amino acid), aromatic polyamide, cellulose and its derivatives, polyamide hydrazide, polyhydrazide, polyisocyanate, polyphosphagen, amphiphatic block copolymer, ribonucleic acid, deoxyribonucleic acid, etc., among which polypeptides and poly( ⁇ -amino acid) represented by poly( ⁇ -glutamate)s are preferable.
• poly( ⁇ -glutamate)s it is particularly preferable to use those having constituents represented by the following general formulae (1) and (2): wherein R1 is alkyl having 1 to 7 carbon atoms, aralkyl, aryl, cycloalkyl or a mixed group of at least two thereof, and R2 is alkyl having 8 to 30 carbon atoms, aralkyl, aryl, cycloalkyl or a mixed group of at least two thereof, and a composition ratio of (2) to (1) is 100:0 to 10:90.
• R1 is alkyl having 1 to 7 carbon atoms, aralkyl, aryl, cycloalkyl or a mixed group of at least two thereof
• R2 is alkyl having 8 to 30 carbon atoms, aralkyl, aryl, cycloalkyl or a mixed group of at least two thereof
• a composition ratio of (2) to (1) is 100:0 to 10:90.
• R1 includes, for example, alkyls such as methyl, ethyl, propyl, butyl, pentyl, hexyl, etc.; aryls such as phenyl, etc., aralkyls such as benzyl, etc.; cycloalkyls such as cyclohexyl, etc. It is preferable to use methyl and benzyl as R1. R1s are not always the same in polymers.
• R2 includes, for example, alkyls such as octyl, nonyol, decyl, dodecyl, oleyl, etc.; aralkyls such as butylbenzyl, etc.; aryls such as butylphenyl, etc.; cycloalkyls such as butylcyclohexyl, etc. It is preferable to use octyl, decyl, dodecyl, oleyl, and butylphenyl as R2. It is more preferable to use dodecyl and oleyl as R2, because they can effectively increase a solubility in hydrocarbon-based oil or ester-based oil, which can be used as preferable solvents. R2s in polymers are not always the same.
• R2 is important for making the poly( ⁇ -glutamate)s soluble in hydrocarbon-based oil or ester-based oil.
• R2 has less than 8 carbon atoms, solubility in hydrocarbon-based oil or ester-based oil will be not satisfactory, whereas when R2 has more than 30 carbon atoms, it will be very difficult to synthesize such poly( ⁇ -gutamate)s.
• Composition ratio of the general formula (2) to the general formula (1) is 100:0 to 10:90, preferably 80:20 to 30:70.
• n/m is less than 10/90, solubility in hydrocarbon-based oil or ester-based oil will be not satisfactory.
• the constituents of general formulae (1) and (2) can be arranged in an alternate, block or random state. Alternater or random arrangement is preferable.
• Poly( ⁇ -glutamate)s having constituents of general formulae (1) and (2) can be prepared by polymerizing corresponding ⁇ -glutamates, using phosgene, or by exchanging poly( ⁇ -glutamate) consisting only of R1-containing units with alcohol or ester corresponding to R2, or by any other known procedure for producing poly( ⁇ -glutamate)s.
• poly( ⁇ -amino acid)s those having structural units of the following general formula (3) are particularly preferably used: wherein R3 is alkyl having 1 to 30 carbon atoms, aralkyl, aryl, cycloalkyl or a mixed group of at least two thereof, and l is a degree of polymerization, which is 5 to 10,000, preferably 10 to 5,000, where below 5, the resulting electrorheological effect is not satisfactory, whereas above 10,000 the solubility in a solvent is lowered.
• R3 is alkyl having 1 to 30 carbon atoms, aralkyl, aryl, cycloalkyl or a mixed group of at least two thereof
• l is a degree of polymerization, which is 5 to 10,000, preferably 10 to 5,000, where below 5, the resulting electrorheological effect is not satisfactory, whereas above 10,000 the solubility in a solvent is lowered.
• R3 includes, for example, alkyls such as methyl, ethyl, propyl, butyl, pentyl, hexyl, octyl, nonyl, decyl, dodecyl, tetradodecyl, oleyl, etc.; aryls such as phenyl, butylphenyl, etc.; aralkyls such as benzyl, butylbenzyl, etc.; cycloalkyls such as cyclohexyl, butylcyclohexyl, etc. It is particularly preferable to use alkyl having 6 to 16 carbon atoms, aralkyl, aryl and cycloalkyl as R3.
• alkyls such as methyl, ethyl, propyl, butyl, pentyl, hexyl, octyl, nonyl, decyl, dodecyl, tet
• R3 it is more preferable to use octyl, docyl, dodecyl, tetradecyl and hexadecyl as R3, because they can effectively increase a solubility in hydrocarbon-based oil or ester-based oil, which can be used as preferable solvents.
• R3s in polymers are not always the same.
• Poly( ⁇ -aminoacid)s represented by the general formula (3) can be prepared by polymerization corresponding ⁇ -amino acids through N-carboxy anhydride, using phosgene (NCA polymerization process).
• liquid crystallizable polymer component those having a plurality of liquid crystallizable groups bonded to one molecular chain directly or through a spacer can be also used, and include, for example, a side chain type having pendant liquid crystallizable groups bonded to one molecular chain directly or through a spacer as branches; a main chain type having liquid crystgallizable groups and the molecular chain on the main chain; and a complex type having a liquid crystallizable chain further bonded to the liquid crystallizable groups or the molecular chain of a main chain type, liquid crystallizable polymer compound.
• the liquid crystallizable polymer component has a molecular weight of preferably 500 to 1,000,000, more preferably 2,000 to 500,000. Below 500, the resulting electrorheological effect will be not satisfactory, whereas above 1,000,000 the solubility in a solvent will be lowered.
• Integrated form of the magnetic field-susceptible component and the electric field-susceptible component includes dispersion or solution of the respective components separately in a solvent, or particles that integrate these two component, that is, integrated particles, when the electric field-susceptible component is in the form of dispersion particles. Integrated particles are preferable for obtaining higher response speed and torque.
• Integrated particles of the present invention can be prepared, for example, in the following manner:
• the first procedure comprises dispersing ferromagnetic particles into an aqueous solution containing a component having an electrorheological effect, for example, an aqueous solution of sodium polyacrylate, then separating sodium polyacrylate having ferromagnetic particles dispersed therein by reprecipitation, or the like, followed by drying and pulverization.
• a component having an electrorheological effect for example, an aqueous solution of sodium polyacrylate
• the second procedure comprises subjecting a raw material for the component having an electrorheological effect, for example, sodium polyacrylate, to emulsion or suspension polymerization in the presence of ferromagnetic particles, thereby fixing a layer of sodium polyacrylate to the surfaces of ferromagnetic particles.
• a raw material for the component having an electrorheological effect for example, sodium polyacrylate
• the third procedure comprises dispersing ferromagnetic particles in a solution of metal alkoxide, for example, tetraethoxysilane, and obtaining ferromagnetic particle-dispersed silica by sol-gel process, followed by pulverisation, when, required, thereby forming integrated particles.
• metal alkoxide for example, tetraethoxysilane
• raw materials for the ferromagnetic particles for example, sulfates, carbonyl compounds, etc. can be used in place of the ferromagnetic particles, to form ferromagnetic particles in the course of preparing integrated particles.
• Integrated particles can be prepared according to any other known procedure than the above-mentioned ones.
• a mixing ratio of the magnetic field-susceptible component to the electric field-susceptible component is preferably 99.8 -0 3 wt.% to 0.2 - 97 wt.%, more preferably 99 - 10 wt.% to 1 - 90 wt.%.
• the electric field-susceptible component is below 0.2 wt.%, no electrorheological effect can be obtained, whereas above 97 wt.% only the electrorheological effect can be obtained.
• a mixing ratio of the magnetic field-susceptible component to the electric field-susceptible component is preferably 99 - 10 wt.% to 1 - 90 wt.%, more preferably 97 - 30 wt.% to 3 - 70 wt.%.
• the electric field-susceptible component is less than 1 wt.%, no electrorheological effect can be obtained, whereas above 90 wt.% only the electrorheological effect can be obtained.
• a mixing ratio of the magnetic field-susceptible component to the electric field-susceptible component is preferably 99.8 - 3 wt.% to 0.2 - 97 wt.%, more preferably 99 - 30 wt.% to 1 - 70 wt.%.
• the electric field-susceptible component is less than 0.2 wt.%, no electrorheological effect can be obtained, whereas above 97 wt.% only the electrorheological effect can be obtained.
• the solvent for use in the present invention includes, for example, polar solvents such as dioxane, tetrahydrofuran, cresol, etc.; chlorinated solvents such as methylene chloride, chloroform, chlorobenzene, o-dichlorobenzene, etc.; hydrocarbon-based oils such as mineral oil, alkylbenzene, alkylnaphthalene, poly- ⁇ -olefin, etc.; ester-based oils such as dibutyl phthalate, dioctyl phthalate, dibutyl sebacate, etc.; ether-based oils such as oligophenylene oxide, etc.; silicone oils; and fluorocarbon-based oils, among which hydrocarbon-based oils and ester-based oils or particularly preferable from the viewpoints of less toxicity and less electric current passage. These oils can be used in mixture.
• polar solvents such as dioxane, tetrahydrofuran, cresol, etc.
• the boiling point of the solvent is preferably 150°C or higher under the atmospheric pressure, more preferably 150°C to 700°C, most preferably 200 to 650°C. Below 150°C, the solvent is more vaporizable, and thus this is not preferable.
• the viscosity is preferably 1 to 500 cSt at 40°C, more preferably 5 to 300 cSt at 40°C.
• a ratio of sum total of the magnetic field-susceptible component and the electric field-susceptible component to the solvent is preferably 1 - 90 wt.% to 99 - 10 wt.%, more preferably 10 - 80 wt.% to 90 - 20 wt.%.
• the solvent is less than 10 wt.%, the viscosity of the fluid will be increased, thereby deteriorating the function as a fluid, whereas above 99 wt.%, neither magnetic nor electrorheological effect can be obtained.
• a mixing ratio of sum total of the magnetic field-susceptible component and the electric field-susceptible component to the solvent is preferably 1 - 90 wt.% to 99 - 10 wt.%, more preferably 20 - 80 wt.% to 80 - 20 wt.%.
• the solvent is less than 10 wt.%, the viscosity of the fluid will be increased, thereby deteriorating the function as a fluid, whereas above 99 wt.% neither magnetic nor electrorheological effect can be obtained.
• a mixing ratio of sum total of the magnetic field-susceptible component and the electric field-susceptible component to the solvent is preferably 2 - 70 wt.% to 98 - 30 wt.%, more preferably 10 - 50 wt.% to 90 - 50 wt.%.
• the sum total is more than 70 wt.%, the viscosity of the fluid will be considerably increased under no application of either magnetic field or electric field or both. This is practically not preferable.
• the electric field-susceptible component is a liquid crystallizable component in the present invention
• An electrorheological effect can be obtained even at such a concentration as not to show a liquid crystal phase.
• a fluid having a magnetic effect and an electrorheological effect simultaneously can be prepared by dissolving the liquid crystallizable polymer component in a magnetic fluid prepared in a well known procedure, or by mixing a magnetic fluid prepared in a well known procedure with a solution of the liquid crystallizable polymer component.
• addition of a small amount of water can promote an electrorheological effect in some cases.
• An amount of water to be added is preferably not more than 30 wt.% on the basis of the electric field-susceptible component.
• additives such as a surfactant to the fluid within such a range as not to deteriorate the effect of the present invention.
• both magnetic field and electric field can be applied at the same time with constant intensities, or while changing the intensities in accordance with changes in the necessary torque, or one of the magnetic field and the electric field can be applied continuously with a constant intensity while changing the applied intensity of other field in accordance with changes in the necessary torque. It is particularly preferable to apply a magnetic field with a constant intensity to obtain a torque to some degree, and change applied intensity of an electric field by making fine adjustment of the necessary torque.
• the present fluid can be applied to engine mounts, shock-damping apparatuses such as shock absorbers, etc., clutches, torque converters, brake systems, valves, dampers, suspensions, actuators, vibrators, inject printers, seals, gravity separation, bearings, polishing, control valves, vibration-preventing materials, etc.
• shock-damping apparatuses such as shock absorbers, etc.
• the integrated particles (1-1) was dispersed into 70 g of silicone oil KF-96 (trademark of a product made by Shinetzu Silicone K.K., Japan) having a viscosity of 20 cSt at 25°C, and 5 wt.% of water was added thereto on the basis of the integrated particles (1-1) to prepare a fluid (1-2).
• the fluid (1-2) had a saturation magnetization of 390 Gauss and it was found that the fluid (1-2) was attracted to a magnet.
• a high voltage-applicable test provided with two electrode each having an area of 400 mm2 and being faced to each other at a clearance of 1 mm, and with an electromagnet on both electrodes was placed sideways, and then the fluid (1-2) was filled into the cell to determine magnetic and electrorheological characteristics, while determining torques by changing the position of the upper electrode in the horizontal direction.
• the response speed was determined with an oscillograph by measuring a delay in a torque following application of either magnetic or electric field or both.
• the fluid (1-2) had a torque of 26 g ⁇ cm under no application of both magnetic and electric fields.
• the torque was 205 g ⁇ cm and the response speed was 0.37 sec.
• the particles were recovered therefrom by filtration, and dried at 100°C/2 mmHg for 6 hours, whereby soft magnetic ferrite particles (2-1) coated with sodium polyacrylate were obtained.
• the thus obtained integrated particles (2-1) contained 87 wt.% of soft magnetic ferrite.
• a fluid (2-2) was prepared in the same manner as in Example 1.
• the fluid (2-2) had a saturation magnetization of 260 Gauss, and it was found that the fluid (2-2) was attracted to a magnet.
• the integrated particles (3-1) contained 54 wt.% of iron.
• a fluid (3-2) was prepared in the same manner as in Example 1.
• the fluid (3-2) had a saturation magnetization of 410 Gauss, and it was found that the fluid (3-2) was attracted to a magnet.
• a fluid (4-2) was prepared in the same manner as in Example 1, except that sodium polyacrylate having a degree of polymerization of 22,000 to 70,000 and particle sizes of 20 ⁇ m were used in place of the dispersion particles for the fluid used in Example 1.
• a fluid (5-2) was prepared in the same manner as in Example 1.
• the fluid (5-2) had a saturation magnetization of 400 Gauss and it was found that the fluid (5-2) was attracted to a magnet.
• the magnetite cake was recovered therefrom by filtration under suction, and washed with water and finally with methanol to remove the residual oleic acid. Then, the magnetite cake was dried in a vacuum drier, whereby magnetite particles with oleic acid adsorbed thereon were obtained.
• the magnetite particles were dispersed into hexane, and particles having larger particle sizes were removed therefrom by centrifugal separation under 8,000 G for one hour. Then, the dispersion freed from the particles having larger particle size by the centrifugal separation was admixed with ⁇ -methylnaphthalene in an amount 1.2 times as large as the weight of the magnetite particles contained in the dispersion, and then hexane was distilled off, whereby a magnetic fluid (6-1) was obtained.
• the thus obtained magnetic fluid (6-1) had a saturation magnetization of 180 Gauss and it was found that the magnetic fluid was attracted to a magnet.
• the resulting solution was added to a large amount of ethanol to reprecipitate the polymers.
• The, the polymers were recovered by filtration and thorough washed with ethanol, and then dissolved again into dichloroethane. Three runs of this purification step was carried out, and the ultimately recovered polymers were dried at 80°C/2 mmHg to obtain 4.4 g of purified polymers (1). It was found by NMR analysis that the polymers (1) were poly( ⁇ -benzyl L-glutamate-co- ⁇ -dodecyl L-glutamate), where 71% of benzyl groups were replaced with dodecyl groups.
• polymers (2) were obtained in the same manner as in Synthesis Example 1, except that 20 g of dodecyl alcohol of Synthesis Example 2 was replaced with 28.9 g of oleyl alcohol. It was found by NMR analysis that polymers (2) were poly( ⁇ -benzyl L-glutamate-co- ⁇ -oleyl L-glutamate), where 59% of benzyl groups were replaced with oleyl groups.
• a fluid (8-1) was prepared in the same manner as in Example 1, except that the polymers (1) of Example 5 were replaced with the polymers (2) obtained in Synthesis Example 2.
• the fluid (8-1) had a saturation magnetization of 89 Gauss, and it was found that the fluid (8-1) was attracted to a magnet.
• Magnetic and electrorheological characteristics of the fluid (8-1) were investigated in the same manner as in Example 1. Under no application of both magnetic and electric fields, the fluid had a torque of 71 g ⁇ cm. When only a magnetic field of 1,500 Oe was applied to the fluid (8-1), a torque of 171 g.cm and a response speed of 0.24 sec. were obtained. When only an electric field of 3 kV/mm was applied to the fluid (8-1), a torque of 348 g ⁇ cm and a response speed of 0.02 sec. were obtained. It was found that the fluid (8-1) had both magnetic and electrorheological effects.
• a fluid (9-1) was prepared in the same manner as in Example 1, except that the polymers (1) of Example 5 were replaced with poly(L- ⁇ -aminolauric acid) having a molecular weight of 300,000, synthesized by polymerization of L- ⁇ -aminolauric acid through N-carboxy anhydride, using phosgene (NCA polymerization process).
• the thus obtained fluid (9-1) had a saturation magnetization of 91 Gauss, and it was found that the fluid (9-1) was attracted to a magnet.
• Magnetic and electrorheological characteristics of the fluid (9-1) were investigated in the same manner as in Example 1. Under no application of both magnetic and electric fields, the fluid (-1) had a torque of 63 g ⁇ cm. When only a magnetic field of 1,500 Oe was applied to the fluid (9-1), a torque of 169 g ⁇ cm and a response time of 0.28 sec. were obtained. When only an electric field of 3 kV/mm was applied to the fluid (9-1), a torque of 322 g ⁇ cm and a response time of 0.02 sec. were obtained, and it was found that the fluid (9-1) had both magnetic and electrorheological effects.
• Magnetic and electrorheological characteristics of the magnetic fluid (6-1) prepared in Synthesis Example 1 were investigated in the same manner as in Example 1. Under no application of both magnetic and electric fields, the magnetic fluid (6-1) had a torque of 103 g ⁇ cm. When only a magnetic field of 1,500 Oe was applied to the magnetic fluid (6-1), a torque of 225 g ⁇ cm and a response speed of 0.33 sec. were obtained. When only an electric field of 3 kV/mm was applied to the magnetic fluid (6-1), there was no change in the torque at all, and it was found that the magnetic fluid (6-1) had no electrorheological effect. When a magnetic field of 1,500 Oe and an electric field of 3 kV/mm were applied to the magnetic fluid (6-1) at the same time, the same torque and response speed were obtained as those obtained when only the electric field was applied to the magnetic field (6-1).
• Example 7 0.5 g of poly (L- ⁇ -aminolauric acid) used in Example 7 was completely dissolved in 9.5 g of ⁇ -methylnaphthalene in the same manner as in Example 1 to prepare a solution (11-1). Magnetic and electrorheological characteristics of the solution (11-1) were investigated.
• the solution (11-1) had a torque of 31 g ⁇ cm.
• a magnetic field of 1,500 Oe was applied to the solution (11-1)
• there was no change in the torque i.e. 31 g ⁇ cm
• the solution (11-1) was not attracted to a magnet and was not susceptible to a magnetic field at all.
• a torque of 343 g.cm and a response speed of 0.02 sec. were obtained, and it was found that the solution (11-1) had only an electrorheological effect.
• a magnetic field of 1,500 Oe and an electric field of 3 kV/mm were applied to the solution (11-1) at the same time, the same torque and response speed were obtained as those obtained when only an electric field was applied thereto.
• the present fluid having magnetic and electrorheological effects simultaneously has a larger torque than that of a fluid having only a magnetic effect or an electrorheological effect, and furthermore has a higher response speed, characteristic of an electrorheological fluid.
• a fluid containing a liquid crystallizable polymer as an electrorheological component has a good dispersion stability for a longer time.
• the present fluid has a larger torque, a higher response speed and a good dispersion stability for a longer time, and can be applied to engine mounts, shock damping apparatuses such as shock absorbers, etc., clutches, torque converters, brake systems, valves, dampers, suspensions, actuators, vibrators, inject printers, seals, gravity separation, bearings, polishing, packings, control valves, vibration-preventing materials, etc.
• shock damping apparatuses such as shock absorbers, etc., clutches, torque converters, brake systems, valves, dampers, suspensions, actuators, vibrators, inject printers, seals, gravity separation, bearings, polishing, packings, control valves, vibration-preventing materials, etc.

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• 1993
  • 1993-07-15 DE DE69321301T patent/DE69321301T2/de not_active Expired - Fee Related
  • 1993-07-15 EP EP93111379A patent/EP0579229B1/de not_active Expired - Lifetime

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