A grease composition including: an ester base oil; and a thickener, in which the thickener contains diurea expressed by the following formula (1): R1-NHCONH-C6H4-CH2-C6H4-NHCONH-R2 (1), in which R1 and R2 each independently represents one of: (A) an alicyclic group A expressed by R3-C6H10- (R3 represents hydrogen, a 2-methyl group, a 3-methyl group, or a 4-methyl group); (B) an alkyl group B expressed by n-CmH2m+1 (m represents an integer of 6 to 10); and (C) an alkyl group C expressed by n-CmH2m+1 (m represents an integer of 16 to 20), and in which the diurea is arranged so that the alicyclic group A is 5 to 35 mol %, a total of the alicyclic group A and the alkyl group B is 55 to 95 mol %, and the remainder is the alkyl group C, based on a total of R1 and R2.

The invention provides a grease composition for a speed reducer part of an on-vehicle electric component, the grease composition containing a base oil and a thickener, wherein the base oil is poly-α-olefin or a mixed oil of poly-α-olefin and mineral oil having a kinematic viscosity of 4 to 19 mm.sup.2/s at 100° C. and a pour point of −30° C. or lower, the thickener is a mixture of a diurea compound expressed by formula (1) and a diurea compound expressed by formula (2)

R.sub.1—NHCONH—R.sub.2—NHCONH—R.sub.1  (1)

R.sub.3—NHCONH—R.sub.2—NHCONH—R.sub.3  (2)

wherein R.sub.1 is a straight-chain alkyl group having 8 or 18 carbon atoms, R.sub.2 is a divalent aromatic hydrocarbon group having 6 to 15 carbon atoms, and R.sub.3 is an aryl group having 6 to 7 carbon atoms, and a penetration of the grease composition is 220 to 280.

The invention provides a grease composition for a speed reducer part of an on-vehicle electric component, the grease composition containing a base oil and a thickener, wherein the base oil is poly-α-olefin or a mixed oil of poly-α-olefin and mineral oil having a kinematic viscosity of 4 to 19 mm.sup.2/s at 100° C. and a pour point of −30° C. or lower, the thickener is a mixture of a diurea compound expressed by formula (1) and a diurea compound expressed by formula (2)

R.sub.1—NHCONH—R.sub.2—NHCONH—R.sub.1  (1)

R.sub.3—NHCONH—R.sub.2—NHCONH—R.sub.3  (2)

wherein R.sub.1 is a straight-chain alkyl group having 8 or 18 carbon atoms, R.sub.2 is a divalent aromatic hydrocarbon group having 6 to 15 carbon atoms, and R.sub.3 is an aryl group having 6 to 7 carbon atoms, and a penetration of the grease composition is 220 to 280.

A grease composition may contain a base oil (A) and a urea-based thickener (B). Particles containing the urea-based thickener (B) in the grease composition may satisfy requirement (I). The base oil (A) may be a mixed base oil containing a high-viscosity base oil (A1) having a kinematic viscosity at 40° C. of 250 mm.sup.2/s to 550 mm.sup.2/s, a low-viscosity base oil (A2) having a kinematic viscosity at 40° C. of 5.0 mm.sup.2/s to 110 mm.sup.2/s, and an ultra-high viscosity hydrocarbon-based synthetic oil (A3) having a number average molecular weight (Mn) of 2,500 to 4,500 and a kinematic viscosity at 40° C. of 25,000 mm.sup.2/s to 50,000 mm.sup.2/s. The base oil (A) may have a kinematic viscosity at 40° C. of 25 mm.sup.2/s to 105 mm.sup.2/s and a viscosity index of 120 or more. Both low-temperature characteristics and a lubricating life can be achieved.

A constant velocity joint having a boot constructed from a thermoplastic polyether ester as the boot material. The boot includes a lubricating grease composition for lubricating the constant velocity joint, the lubricating grease composition comprising calcium lignin sulfonate.

A constant velocity joint having a boot constructed from a thermoplastic polyether ester as the boot material. The boot includes a lubricating grease composition for lubricating the constant velocity joint, the lubricating grease composition comprising calcium lignin sulfonate.

A grease composition which contains a base oil (A), a urea-based thickener (B), a sarcosine derivative (C), and a fatty acid zinc salt (D), wherein particles containing the urea-based thickener (B) in the grease composition satisfies Requirement (I). The base oil (A) is a blended base oil containing a high viscosity hydrocarbon-based synthetic oil having a specific kinematic viscosity (A1). A low viscosity hydrocarbon-based synthetic oil having a specific kinematic viscosity (A2). An ultra-high viscosity hydrocarbon-based synthetic oil has a number average molecular weight (Mn) of 2,500 to 4,500 and a specific kinematic viscosity (A3). A 40° C. kinematic viscosity of the base oil (A) is 500 mm.sup.2/s to 1,500 mm.sup.2/s. A viscosity index of the base oil (A) is 140 or more. A content of the fatty acid zinc salt (D) is 10 mass % to 20 mass % based on a total amount of the grease composition.

Disclosed is food-grade lubricating grease and a method for preparing the same, belonging to the technical field of lubricating grease. The food-grade lubricating grease is prepared from the following components in percentage by mass: 75% to 85% of food-grade white oil, 6% to 16% of stearic acid, 2.0% to 3.0% of benzoic acid, 4.7% to 8.7% of aluminum isopropoxide, 1.0% to 1.5% of water and 1.0% to 7.0% of nano-PTFE, and has good extreme-pressure, abrasion-resistant and friction-reduction properties, a last non-seizure load (P.sub.B) reaching 411.6 N, a sintering load (P.sub.D) reaching 1,960 N, and a friction coefficient reduced by 18.5%. The lubricating grease can be used for a food production industry and in household food appliances, the service life of a device and the service life of the food-grade lubricating grease are effectively prolonged, and meanwhile, food security is guaranteed to a certain degree.

A grease composition comprising a thickener and a lubricating base oil, wherein the lubricating base oil has a viscosity in the range of from 5-1000 cSt (at 40° C.). The thickener is present in an amount of 5-40 wt. %, based on total weight of the grease composition. The thickener comprises an ester terminated oligomer which has the general formula: “R1—O—[CO—R2—CO—NH—R3—NH—CO—R2—CO]n-O—R1”. “R1” represents a hydrocarbon group containing 4-22 carbon atoms. “R2” represents a hydrocarbon group containing 4-42 carbon atoms. “R3” represents a hydrocarbon group containing 2-9 carbon atoms. “n” represents an integer in the range of 1-20. The weight ratio between the lubricating base oil and the ester terminated oligomer (oil/oligomer) is larger than 1. The grease composition can be used for lubricating a mechanical component having a metal surface and/or for protecting a mechanical component having a metal surface against corrosion, wear and/or fretting.

A grease composition comprising a thickener and a lubricating base oil, wherein the lubricating base oil has a viscosity in the range of from 5-1000 cSt (at 40° C.). The thickener is present in an amount of 5-40 wt. %, based on total weight of the grease composition. The thickener comprises an ester terminated oligomer which has the general formula: “R1—O—[CO—R2—CO—NH—R3—NH—CO—R2—CO]n-O—R1”. “R1” represents a hydrocarbon group containing 4-22 carbon atoms. “R2” represents a hydrocarbon group containing 4-42 carbon atoms. “R3” represents a hydrocarbon group containing 2-9 carbon atoms. “n” represents an integer in the range of 1-20. The weight ratio between the lubricating base oil and the ester terminated oligomer (oil/oligomer) is larger than 1. The grease composition can be used for lubricating a mechanical component having a metal surface and/or for protecting a mechanical component having a metal surface against corrosion, wear and/or fretting.