Abstract: A grease composition for a rolling bearing comprising, based on 100 parts by weight of a base oil, 10 to 60 parts by weight of a mixture of diurea compounds as a thickener having a composition of 25 to 90 mol % of a diurea compound represented by the formula (1), 9 to 50 mol % of a diurea compound represented by the formula (2), 1 to 30 mol % of a diurea compound represented by the formula (3), wherein R.sup.1 stands for an aromatics-containing hydrocarbon group having 7 to 12 carbon atoms, R.sup.2 stands for a divalent aromatics-containing hydrocarbon group having 6 to 15 carbon atoms, and R.sup.3 stands for a cyclohexyl group or an alkylcyclohexyl group having 7 to 12 carbon atoms, a value of (number of R.sup.1 /(number of R.sup.1 +number of R.sup.3)) in the mixture being 0.55 to 0.95.

Abstract: A grease composition comprising a base oil and a thickener, in which the thickener comprises a lithium soap of C.sub.12 -C.sub.24 fatty acid containing no hydroxyl group and a lithium soap of C.sub.12 -C.sub.24 fatty acid containing a hydroxyl group and the base oil has kinematic viscosity of 25 to 200 mm.sup.2 /sec at 40.degree. C. and contains 10 to 70% by weight of an ester oil, the grease composition containing from 20 to 30% by weight of the two specific thickeners. Prolonged continuous operation of bearings into which the grease composition is sealed does not cause an amount of splashing grease to increase and noiseless property to be deteriorated.

Abstract: A grease composition comprising a base oil containing not less than 10% by weight of an ester oil based on the total base oil and having a kinematic viscosity of 50 to 200 mm.sup.2 /sec at 40.degree. C. and 15 to 35% by weight, based on the total grease composition, of a diurea compound represented by formula (I): ##STR1## wherein R.sub.2 represents an aromatic hydrocarbon group having 6 to 15 carbon atoms; and R.sub.1 and R.sub.3, which may be the same or different, each represent an aromatic hydrocarbon group having 6 to 12 carbon atoms or an aliphatic hydrocarbon group having 8 to 20 carbon atoms, the proportion of the aromatic hydrocarbon groups in the total of R.sub.1 and R.sub.3 being 50 to 100 mol %. When applied to outer race rotating bearings, the grease composition is excellent in flaking resistance, leak resistance, and low noise properties and prevents premature seizing under high temperature and high speed conditions.

Abstract: In a roller bearing, surface layers are formed on the inner surfaces of flanges which confront with the end faces of cylindrical rollers. The surface layers contain solid lubricant. The end faces of the cylindrical rollers are brought into slide contact with the surface layers. Hence, even when the roller bearing is insufficiently lubricated, the temperature rise is effectively suppressed, thus being free from the occurrence of seizure.

Abstract: A magnetic fluid composition comprising a low-volatile organic solvent as a carrier having dispersed therein ferromagnetic fine particles coated with a surface active agent having a lipophilic group having affinity to said low-volatile organic solvent, and a thixotropy-imparting agent is disclosed. The composition is prevented from splashing for an extended period of time even when used in a magnetic fluid-sealed apparatus operated at such a high speed that the rotational speed of the sealing part is 2 m/sec or higher.

Abstract: A magnetic fluid seal is improved by coating parts of the sealing mechanism and/or adjacent surfaces with a fluorine-containing surfactant as an oil-repelling layer. The surfactant is effective to prevent the spread of the oil-based magnetic fluid into interior mechanisms of the sealed apparatus, which may typically require a high degree of cleanliness.

Abstract: A magnetic fluid sealing device is provided for sealing a gap between a first member and a second member movable relative to each other. The device has a magnetic fluid and a magnet for retaining the magnetic fluid in the gap. A two-dimensionally bonded monomolecular layer is formed as an oil-repelling layer from a coupling agent on at least an intermediate surface area of at least one of the first and second members, which intermediate surface area is located between a fluid-deposited surface area and a fluid-free surface area.

Abstract: A heat-resistant, water-resistant, low-viscosity magnetic fluid and a process for producing same has a dispersion medium made of a low-volatile organic solvent, a low molecular weight dispersant having a lipophilic group and a polar group, the lipophilic group having an affinity for the organic solvent, ferromagnetic particles dispersed in the organic solvent, the surface of each of the ferromagnetic particles being covered with the dispersant, and an additive added to the dispersion medium having a lipophilic group and a polar group, the lipophilic group having a macromolecular chain. The process includes a step of adding the additive to the dispersion medium. The lipophilic group includes a macromolecular chain. The magnetic fluid is suitable for service, e.g., in a shaft seal.

Abstract: An electroconductive magnetic fluid composition is disclosed comprising a low volatility organic solvent as a carrier, a surface active agent having an lipophilic group with a strong affinity for the solvent, fine ferromagnetic particles coated at the surface thereof with the surface active agent and dispersed in the organic solvent, and a tertiary amine and an organic acid as an electrifying agent. The electroconductive magnetic fluid composition of the present invention is produced, preferably, including the steps of admixing fine ferromagnetic particles, a low boiling point organic solvent an surface active agent and separating to remove any fine particles of poor dispersibility.

Abstract: A magnetic fluid composition comprising a less volatile organic solvent as a dispersing medium, a dispersing agent having oleophilic groups exhibiting an affinity therewith, fine ferromagnetic particles coated at the surface thereof with the dispersing agent and dispersed in the less volatile organic solvent and a fluorocarbon surface active material having an organophobic portion and an organophilic portion together in a unitary molecular structure. The magnetic fluid is prepared by the steps of adding the low boiling organic solvent and the dispersant having oleophilic groups to fine ferromagnetic particles to obtain an intermediate medium, separating the fine particles of poor dispersibility from the intermediate medium and, then adding the less volatile organic solvent and heating the resulting material to evaporate the low boiling organic solvent thereby obtaining a magnetic fluid and, further, adding the fluorocarbon surface active material to the magnetic fluid.

Abstract: A ferrofluid composition is defined by fine particles of ferromagnetic material, a liquid carrier for dispersing the ferromagnetic material and a surfactant or surfactants acting as a dispersant. The surfactant is required to have such relation to the carrier that the surfactant has, as its hydrophobic group portion, a structure equivalent to the carrier, and the carrier is selected to be either an alkylpolyphenyl ether oil, an alkylnaphthalene oil or both. By virtue of this structural feature, fine ferromagnetic particles are uniformly and stably dispersed throughout the carrier which has low viscosity and is thermally very stable.

Abstract: An aqueous magnetic fluid composition comprising water as a dispersion medium and fine ferromagnetic particles as a dispersed phase, in which a coupling agent having a hydrophilic group and at least one hydrolyzable group is chemically bonded by way of the reaction product of the hydrolyzable group to the surface of the fine ferromagnetic particles. The magnetic fluid composition is prepared by way of obtaining an intermediate medium by chemically bonding the coupling agent by way of the hydrolysis product to the fine particles and separating fine particles of poor dispersibility and evaporating the composite product of the hydrolysis and at least a portion of water.

Abstract: A ferrofluid composition consists of organic solvent or solvents to be used as liquid carriers, a charge-transfer complex or complexes for imparting electrical conductivity to the composition, fine particles of ferromagnetic material and additives for stably dispersing the aforesaid fine particles of ferromagnetic material into the organic solvent(s). According to this ferrofluid composition electrical conductivity of the fluid is given by the charge-transfer complex, which enhances the electrical conductivity, that is, functions to prevent electrification from occurring. The charge-transfer complex is dissolved, solubilized or dispersed in the carrier either by itself or by the aid of any additives. The ferromagnetic particles act to adsorb the additives and disperse them stably in the carrier and thus contribute to imparting magnetic properties to the carrier.