The present invention provides a grease composition comprising (a) a base oil, (b) a thickener comprising a urea compound, (c) an amine antioxidant at 0.5 to 5% by mass based on a total mass of the composition, and (d) a quinoline antioxidant at 0.5 to 5% by mass based on the total mass of the composition.

A method for producing a raw material of grease, including: preparing first thickener raw material; second thickener raw material; first lubricating oil; second lubricating oil; first solvent with a boiling point lower than those of the oils, dissolves the first oil, and does not dissolve a produced thickener; and a second solvent with a boiling point lower than those of the oils, dissolves the second oil, and does not dissolve the produced thickener; dissolving the first lubricating oil in the first solvent, and dissolving or dispersing the first thickener raw material in the first solvent to obtain a first mixed solution; dissolving the second lubricating oil in the second solvent, and dissolving or dispersing the second thickener raw material in the second solvent to obtain a second mixed solution; and mixing the first and second mixed solutions, and reacting the first and second thickener raw materials producing a thickener.

A method for producing a raw material of grease, including: preparing first thickener raw material; second thickener raw material; first lubricating oil; second lubricating oil; first solvent with a boiling point lower than those of the oils, dissolves the first oil, and does not dissolve a produced thickener; and a second solvent with a boiling point lower than those of the oils, dissolves the second oil, and does not dissolve the produced thickener; dissolving the first lubricating oil in the first solvent, and dissolving or dispersing the first thickener raw material in the first solvent to obtain a first mixed solution; dissolving the second lubricating oil in the second solvent, and dissolving or dispersing the second thickener raw material in the second solvent to obtain a second mixed solution; and mixing the first and second mixed solutions, and reacting the first and second thickener raw materials producing a thickener.

A method of making a urea containing powder by injecting an amine and an isocyanate simultaneously into a mixing chamber is disclosed. The method comprises mixing in a high-pressure impingement mixing device at a pressure of at least 2500 psi for a time less than 10 seconds. The resulting urea containing powders have defined particle sizes and molecular weight distributions as well as a stoichiometric mole ratio of isocyanates and amine functionalities. Methods of making a thickened polyurea containing master batch with the urea containing powders using a shear thickening step, and making a grease by gelling the first or second urea containing powder under heat and in the presence of an oil are also disclosed.

A method of making a urea containing powder by injecting an amine and an isocyanate simultaneously into a mixing chamber is disclosed. The method comprises mixing in a high-pressure impingement mixing device at a pressure of at least 2500 psi for a time less than 10 seconds. The resulting urea containing powders have defined particle sizes and molecular weight distributions as well as a stoichiometric mole ratio of isocyanates and amine functionalities. Methods of making a thickened polyurea containing master batch with the urea containing powders using a shear thickening step, and making a grease by gelling the first or second urea containing powder under heat and in the presence of an oil are also disclosed.

The present invention relates to a grease composition which can impart excellent durability to a bearing used under a high-speed rotation condition with a DN value of 100,000 or more, wherein the grease composition contains a base oil (A) and a urea-based thickener (B), and particles containing the urea-based thickener (B) in the grease composition satisfy requirement (I) that the particles have an arithmetic mean particle diameter of 2.0 μm or less on an area basis when measured by a laser diffraction scattering method. The grease composition is used for a bearing used under a high-speed rotation condition with a DN value of 100,000 or more.

The present invention relates to a grease composition which can impart excellent durability to a bearing used under a high-speed rotation condition with a DN value of 100,000 or more, wherein the grease composition contains a base oil (A) and a urea-based thickener (B), and particles containing the urea-based thickener (B) in the grease composition satisfy requirement (I) that the particles have an arithmetic mean particle diameter of 2.0 μm or less on an area basis when measured by a laser diffraction scattering method. The grease composition is used for a bearing used under a high-speed rotation condition with a DN value of 100,000 or more.

The grease composition including: a base oil having a kinematic viscosity of 5 to 30 mm.sup.2/s at 100° C., a thickener, a polymer having a weight average molecular weight of 1,000 to 500,000, and an aliphatic amide compound. The grease composition is used for sliding between a metal member and a resin member, and capable of reducing friction between them.

The grease composition including: a base oil having a kinematic viscosity of 5 to 30 mm.sup.2/s at 100° C., a thickener, a polymer having a weight average molecular weight of 1,000 to 500,000, and an aliphatic amide compound. The grease composition is used for sliding between a metal member and a resin member, and capable of reducing friction between them.

The present invention relates to provision of an extreme pressure agent-containing grease composition using, as a thickener, a urea-based thickener, the grease composition being excellent in both torque transmitting efficiency and leakage prevention performance and also excellent in wear resistance and load resistance. The grease composition contains a base oil (A), a urea-based thickener (B), and an extreme pressure agent (C), wherein particles containing the urea-based thickener (B) in the grease composition satisfies the following requirement (I): Requirement (I): an arithmetic average particle diameter of the particles on an area basis as measured by the laser diffraction/scattering method is 2.0 μm or less, and the extreme pressure agent (C) is at least one selected from an organic metal-based extreme pressure agent, a sulfur-based extreme pressure agent, a phosphorus-based extreme pressure agent, and a sulfur-phosphorus-based extreme pressure agent.