Grease composition and constant-velocity joint enclosing same

Abstract

The present invention provides a grease composition containing (a) a diurea-based thickener, (b) a base oil, (c) overbased calcium sulfonate, and (d) disodium sebacate, wherein the content of the component (c) is 0.1%-10% by mass based on the total mass of the composition, and the content of the component (d) is 0.01%-5% by mass based on the total mass of the composition.

Description

Grease composition and constant velocity joint containing the same

[0001] The present invention relates to a grease composition that can be suitably used for constant velocity joints, particularly for outboard constant velocity joints.

[0002] Front-wheel-drive (FF) vehicles have become widespread due to their lightweight design and increased interior space, which are key factors in reducing CO2 emissions and improving vehicle environmental friendliness. In FF vehicles, constant velocity joints (CVJs) are widely used to transmit torque from the engine, motor, and other powertrain units to the tires. In recent years, the automotive industry has been working to reduce CO2 emissions and improve fuel economy and electricity costs in response to the drive toward a decarbonized society. These efforts necessitate the need for compact, lightweight joints capable of handling high loads. Because CVJs rotate at an angle, the components inside the joint engage in complex rolling and sliding motions. Outboard CVJs, in particular, have a large steering angle, which increases the rolling and sliding distance within the CVJ and significantly increases the maximum load per ball. Furthermore, reducing the size and weight of CVJs requires that all components within the CVJ be smaller, requiring greases with even higher load-bearing capacity. If this high load-bearing capacity is insufficient, flaking due to minute seizures caused by metal contact may occur, resulting in abnormal noise. To address these issues, structural improvements have been made to CVJs themselves, but cost has been a major issue, leading to a demand for greases with high load-bearing capacity. Therefore, greases containing additive compositions with high load-bearing capacity are required for compact, high-capacity CVJs. Various grease compositions have been proposed as greases capable of preventing flaking in CVJs. For example, Patent Document 1 proposes a grease composition containing a base oil, a urea-based thickener, molybdenum disulfide, and a specific calcium salt. Patent Document 2 proposes a grease composition for constant velocity joints containing a base oil, a urea-based thickener, molybdenum disulfide, a specific calcium salt, a metal-free sulfur-phosphorus-based extreme pressure agent, and molybdenum dithiocarbamate. Patent Document 3 discloses a method for manufacturing an oil-in-oil composition comprising a base oil selected from the group consisting of mineral oil, ether-based synthetic oil, ester-based synthetic oil, hydrocarbon-based synthetic oil, and a mixture of two or more of these oils, and a diurea-based thickener represented by the following formula: 4 -NH-CO-NH-C6H4-p-CH2-C6H4-p-NH-CO-NHR 5 (R 4 and R5 is an alkyl group having 8 carbon atoms), molybdenum disulfide, molybdenum sulfide dialkyldithiocarbamate represented by the following formula, (R 6 R 7 N-CS-S)2-Mo2OmSn (wherein, R 6 , R 7 are independently an alkyl group having 1 to 24 carbon atoms, m is 0 to 3, n is 4 to 1, and m+n=4. A composition for constant velocity joints has been proposed, which contains at least one calcium salt selected from the group consisting of calcium salts of petroleum sulfonic acids and overbased calcium salts of petroleum sulfonic acids, 1.5 to 10 mass% of a sulfur-phosphorus extreme pressure agent based on the composition, and vegetable oil.

[0003] JP-A-9-194871 JP-A-9-324189 JP-A-2006-96949

[0004] Thus, while the flaking resistance life of grease compositions for CVJs to date has been investigated by bench tests and SRV tests under low loads, it cannot be said that sufficient research has been conducted into the anti-seizure properties that can withstand the extremely high loads that accompany the trend toward smaller, higher capacity CVJs. Therefore, an object of the present invention is to provide a grease composition that has excellent anti-seizure properties, taking into account the trend toward smaller, higher capacity CVJs.

[0005] The present invention provides the following greases: 1. A grease composition comprising: (a) a diurea thickener; (b) a base oil; (c) 0.1 to 10 mass % of an overbased calcium sulfonate, based on the total mass of the composition; and (d) 0.01 to 5 mass % of disodium sebacate, based on the total mass of the composition. 2. The grease composition according to 1 above, wherein component (c) has a base number of 200 to 500 mg KOH / g. 3. The grease composition according to 1 or 2 above, wherein component (a) is a diurea compound represented by the following formula (1): R 1 -NHCONH-R 2 -NHCONH-R 3 (1) (wherein, R 1 and R 3may be the same or different and are an alkyl group having 8 to 18 carbon atoms, an aryl group having 6 carbon atoms, or a cyclohexyl group. 2 is a divalent aromatic hydrocarbon group having 6 to 15 carbon atoms. 4. The grease composition according to any one of 1 to 3 above, further comprising at least one member selected from the group consisting of component (e-1) oil-insoluble molybdenum dialkyldithiocarbamate (MoDTC) and component (e-2) oil-soluble molybdenum dialkyldithiocarbamate (MoDTC). 5. The grease composition according to 4 above, containing component (e-1) and component (e-2). 6. The grease composition according to any one of 1 to 5 above, which does not contain neutral zinc sulfonate. 7. The grease composition according to any one of 1 to 6 above, which is for use in a constant velocity joint. 8. The grease composition according to any one of 1 to 7 above, which is for use in an outboard constant velocity joint. 9. A constant velocity joint filled with the grease composition according to any one of 1 to 8 above.

[0006] The present invention provides a grease composition with extremely high seizure resistance. Without being bound by any theory, it is believed that the grease composition of the present invention forms a strong additive film, preventing contact between metal base materials, and is also capable of quickly forming a dense oxide film even if metal contact occurs and a new surface is created due to wear.

[0007] (a) Diurea-based thickener The thickener of the present invention is a diurea-based thickener. Diurea-based thickeners tend to soften quickly due to shear, so they can adequately supply grease to the sliding parts in the CVJ. The thickener of the present invention is preferably a diurea compound represented by the following formula (1): R 1 -NHCONH-R 2 -NHCONH-R 3 (1) (wherein, R 1 and R 3 may be the same or different and are an alkyl group having 8 to 18 carbon atoms, an aryl group having 6 carbon atoms, or a cyclohexyl group. 2is a divalent aromatic hydrocarbon group having 6 to 15 carbon atoms.) Diurea compounds are obtained by reacting a diisocyanate component with a monoamine component. Examples of diisocyanates include diphenylmethane diisocyanate, octadecane diisocyanate, decane diisocyanate, hexane diisocyanate, and toluene diisocyanate. Examples of monoamines include octylamine, dodecylamine, hexadecylamine, stearylamine, oleylamine, aniline, p-toluidine, cyclohexylamine, and mixtures thereof.

[0008] Among the diurea compounds represented by formula (1), a diurea compound selected from the group consisting of an aliphatic diurea compound, an aromatic diurea compound, an alicyclic diurea compound, an alicyclic aromatic diurea compound, and an alicyclic aliphatic diurea compound is preferably used as the diurea-based thickener of the present invention. Among these, the alicyclic aromatic diurea compound uses a mixture of cyclohexylamine and an aromatic amine as the raw amine, and therefore the diurea compound obtained by the reaction is a mixture of an alicyclic diurea compound, an aromatic diurea compound, and an alicyclic aromatic diurea compound. In other words, the alicyclic aromatic diurea compound is a mixture of diurea compounds represented by the following formulas (1-1), (1-2), and (1-3). R 1 -NHCONH-R 2 -NHCONH-R 1 (1-1) R 1 -NHCONH-R 2 -NHCONH-R 3 (1-2) R 3 -NHCONH-R 2 -NHCONH-R 3 (1-3) In the formula, R 1 is a cyclohexyl group, and R 3 is an aryl group having 6 carbon atoms, and R 2 is as defined above. 1 and R 3 The molar ratio of R 1 :R 3The ratio is preferably 60:40 to 80:20, and more preferably 65:35 to 75:25.

[0009] Similarly, since a mixture of cyclohexylamine and an aliphatic amine is used as the raw amine for the alicyclic aliphatic diurea compound, the diurea compound obtained by the reaction is a mixture of an alicyclic diurea compound, an aliphatic diurea compound, and an alicyclic aliphatic diurea compound. In other words, the alicyclic aliphatic diurea compound is a mixture of diurea compounds represented by the following formulas (1-1), (1-2), and (1-3). R 1 -NHCONH-R 2 -NHCONH-R 1 (1-1) R 1 -NHCONH-R 2 -NHCONH-R 3 (1-2) R 3 -NHCONH-R 2 -NHCONH-R 3 (1-3) In the formula, R 1 is a cyclohexyl group, and R 3 is an alkyl group having 8 to 18 carbon atoms, and R 2 is as defined above. 1 and R 3 The molar ratio of R 1 :R 3 The ratio is preferably 70:30 to 95:5, and more preferably 75:25 to 93:7.

[0010] When two types of alkylamines are used as the raw amines, the diurea compounds obtained by the reaction are also a mixture. That is, it is a mixture of diurea compounds represented by the following formulas (1-1), (1-2), and (1-3). R 1 -NHCONH-R 2 -NHCONH-R 1 (1-1) R 1 -NHCONH-R 2 -NHCONH-R 3 (1-2) R 3 -NHCONH-R 2 -NHCONH-R 3(1-3) In the formula, R 1 is an alkyl group having 8 to 18 carbon atoms, and R 3 is another alkyl group having 8 to 18 carbon atoms, and R 2 is as defined above. 1 and R 3 The molar ratio of R 1 :R 3 The ratio is preferably 70:30 to 30:70, and more preferably 60:40 to 40:60.

[0011] As the thickener of the present invention, an alicyclic aromatic diurea compound, an alicyclic aliphatic diurea compound, and an aliphatic diurea compound are more preferred. In particular, in formulas (1-1) and (1-2), R 1 is a cyclohexyl group, and in formulas (1-2) and (1-3), R 3 is an alicyclic aromatic diurea compound in which R 1 is a cyclohexyl group, and in formulas (1-2) and (1-3), R 3 is a phenyl group, and R 1 :R 3 or an alicyclic aromatic diurea compound in which R 1 is a cyclohexyl group, and in formulas (1-2) and (1-3), R 3 is an alicyclic aliphatic diurea compound in which R 1 is a cyclohexyl group, and in formulas (1-2) and (1-3), R 3 is an alkyl group having 18 carbon atoms, and R 1 :R 3 or an alicyclic aliphatic diurea compound in which R 1 and R 3 are each an alkyl group having 8 carbon atoms, or 1 is an alkyl group having 8 or 18 carbon atoms, and in formulas (1-2) and (1-3), R 3are the same or different alkyl groups having 8 or 18 carbon atoms, or 1 is an alkyl group having 8 carbon atoms, and in formulas (1-2) and (1-3), R 3 is an alkyl group having 18 carbon atoms, or 1 is an alkyl group having 8 carbon atoms, and in formulas (1-2) and (1-3), R 3 is an alkyl group having 18 carbon atoms, and R 1 :R 3 Preferably, the aliphatic diurea compound has a molar ratio of 5:5.

[0012] Among them, in the formulas (1-1) and (1-2), R 1 is a cyclohexyl group, and in formulas (1-2) and (1-3), R 3 is a phenyl group, and R 1 :R 3 or an alicyclic aromatic diurea compound in which R 1 is a cyclohexyl group, and in formulas (1-2) and (1-3), R 3 is an alkyl group having 18 carbon atoms, and R 1 :R 3 or an alicyclic aliphatic diurea compound in which R 1 and R 3 are each an alkyl group having 8 carbon atoms, or 1 is an alkyl group having 8 carbon atoms, and in formulas (1-2) and (1-3), R 3 is an alkyl group having 18 carbon atoms, and R 1 :R 3 In particular, an aliphatic diurea compound in which R is 5:5 (molar ratio) is preferred. 1 is a cyclohexyl group, and in formulas (1-2) and (1-3), R 3 is a phenyl group, and R 1 :R 3Alicyclic aromatic diurea compounds in which the molar ratio is 7:3 are preferred.

[0013] From the viewpoint of ease of filling the lubricated parts with the grease, the content of the diurea-based thickener is preferably 3 to 20 mass%, more preferably 4 to 18 mass%, and even more preferably 5 to 16 mass%, based on the total mass of the composition. By including the thickener in such a range, the grease has a hardness (consistency of 300 to 380) that allows it to flow easily within the lubricated parts, ensuring that the grease can flow into the lubricated parts immediately after the start of use. In this specification, the term "consistency" refers to the 60-stroke worked consistency measured in accordance with JIS K 2220 7.

[0014] (b) Base Oil The type of base oil used in the present invention is not particularly limited. The base oil used in the present invention may be either a mineral oil or a synthetic oil. As the mineral oil, paraffinic mineral oil and naphthenic mineral oil may be used alone or in combination. As the synthetic oil, various synthetic oils such as synthetic hydrocarbon oils typified by polyalphaolefins and polybutenes, ether-based synthetic oils typified by alkyldiphenyl ethers, ester oils, silicone oils, and fluorinated oils may be mentioned. The synthetic oil may be so-called biomass oil produced from biological resources derived from animals and plants. For example, biomass ester oils synthesized from various fatty acids and alcohols derived from vegetable oils, or biomass hydrocarbon oils derived from vegetable oils such as palm oil, corn oil, and soybean oil, may also be used. The base oil may be used alone or in combination. Of these, mineral oils are preferred from the standpoint of cost, and paraffinic mineral oils, which are easily available, are particularly preferred.

[0015] The kinematic viscosity of the base oil of the present invention at 100°C is 6 mm from the viewpoint of ensuring the oil film thickness of the base oil in the lubricated portion and further preventing metal contact to improve durability. 2 / s or more, and 2The higher the kinematic viscosity at 100°C, the better, since the oil film thickness of the base oil can be secured in the lubricating parts of the CVJ, and durability can be improved by preventing metal contact. However, the viscosity at low temperatures increases, so the kinematic viscosity at 100°C should be 20 mm 2 / s or less, and 16 mm 2 In this specification, the kinematic viscosity is measured in accordance with JIS K 2283. The base oil of the present invention preferably has a kinematic viscosity at 100°C of 8 to 16 mm / s. 2 Paraffinic mineral oils having a base oil content of 1 / 2 wt. / s are particularly preferred. From the viewpoint of ease of filling the lubricated parts with the grease, the content of the base oil is preferably 60 to 95 mass%, more preferably 65 to 94 mass%, and even more preferably 70 to 92 mass%, based on the total mass of the composition. By including the base oil in such a range, the consistency becomes 300 to 380, which is a hardness that makes it easy to fill the lubricated parts.

[0016] (c) Overbased Calcium Sulfonate Examples of the overbased calcium sulfonate used in the present invention include overbased calcium salts of alkyl aromatic sulfonic acids, overbased calcium salts of petroleum sulfonic acids, overbased calcium salts of oxidized waxes, and combinations thereof. Among these, overbased calcium salts of alkyl aromatic sulfonic acids are preferred. The overbased calcium sulfonate is not particularly limited in terms of base number, provided it is overbased. The base number, as measured in accordance with JIS K 2501, is, for example, 200 to 500 mgKOH / g, preferably 230 to 470 mgKOH / g, and more preferably 250 to 450 mgKOH / g. As long as the total base number is within the above range, the overbased calcium sulfonate may be used in combination with a calcium sulfonate other than the overbased calcium sulfonate (e.g., a neutral calcium sulfonate). The content of the overbased calcium sulfonate is 0.1 to 10% by mass, preferably 0.5 to 5% by mass, and more preferably 1.5 to 3.5% by mass, based on the total mass of the composition. By including the overbased calcium sulfonate in this range, sufficient extreme pressure performance can be obtained.

[0017] (d) Disodium Sebacate Disodium sebacate that can be used in the present invention can be represented by the following general formula (4): NaOOC-R 12 -COONa (4) (R in the formula 12 represents a saturated hydrocarbon group having 8 carbon atoms.) Disodium sebacate may be synthesized by a known method, or a commercially available product may be used. The content of disodium sebacate is 0.01 to 5 mass%, more preferably 0.1 to 2 mass%, and even more preferably 0.2 to 1 mass%, based on the total mass of the composition. By including disodium sebacate in such a range, sufficient extreme pressure properties can be obtained.

[0018] In addition to the above components, the grease composition of the present invention may further contain at least one selected from the group consisting of (e-1) oil-insoluble molybdenum dialkyldithiocarbamate (MoDTC) and (e-2) oil-soluble molybdenum dialkyldithiocarbamate (MoDTC). The oil-insoluble MoDTC is preferably one represented by the following formula (2): [R 13 2N-CS-S]2-Mo2O m1 S n1 (2) (wherein, R 13 is a primary or secondary alkyl group having 1 to 4 carbon atoms, preferably a primary or secondary alkyl group having 2 to 4 carbon atoms, m1 is 0 to 3, n1 is 1 to 4, and m1+n1=4.) The oil-soluble MoDTC is preferably one represented by the following formula (3): [R 14 2N-CS-S]2-Mo2O m2 S n2 (3) (wherein, R 14is a primary or secondary alkyl group having 5 to 24 carbon atoms, m2 is 0 to 3, n2 is 1 to 4, and m2 + n2 = 4.) From the viewpoint of low friction, the content of the oil-insoluble MoDTC is preferably 0.01 to 10 mass%, more preferably 0.1 to 5 mass%, and more preferably 0.3 to 3 mass%, based on the total mass of the composition. From the viewpoint of low friction, the content of the oil-soluble MoDTC is preferably 0.01 to 10 mass%, more preferably 0.1 to 5 mass%, and more preferably 0.5 to 3 mass%, based on the total mass of the composition.

[0019] In addition to the above components, the grease composition of the present invention may further contain additives commonly used in grease compositions, such as molybdenum disulfide, solid lubricants other than those (d) and (e-1), extreme pressure additives, antioxidants, rust inhibitors, oiliness agents, etc. Examples of solid lubricants include inorganic substances such as soil graphite, flaky graphite, carbon black, boron nitride, potassium borate, and calcium carbonate, and organic substances such as melamine cyanurate, polytetrafluoroethylene, copper salts and iron salts of dithiocarbamic acid, stearic acid, and calcium, aluminum, sodium, and lithium salts of sebacic acid. Examples of extreme pressure additives include phosphate esters such as triphenyl phosphate, triphenylthiophosphate, triaryl phosphate, tricresyl phosphate, and zinc dialkyldithiophosphate; organic acid salts such as zinc and copper naphthenates and zinc dithiocarbamates; azole compounds such as benzotriazole and dialkylmercaptothiadiazole; fatty acids obtained by decomposing and modifying oils and fats obtained from animals and plants; mono- and diglycerides; polyhydric alcohols such as glycerin; alkyd resins; hardened oils; chlorinated oils and fats; sulfurized oils and fats; and sulfurized esters. Examples of antioxidants include amines and phenols. Examples of rust inhibitors include sulfonates such as sodium sulfonate and lithium sulfonate; carboxylic acids such as succinic acid, half esters and diesters of succinic acid; and amines such as diphenylamine compounds. Examples of oily agents include fats and oils obtained from animals and plants, such as beef tallow, lard, fish oil, castor oil, palm oil, soybean oil, and rapeseed oil; esters such as trimethylolpropane oleate, pentaerythritol stearate, dioctyl sebacate, dioctyl adipate, dioctyl phthalate, and dibutyl phthalate; higher alcohols such as cetyl alcohol, stearyl alcohol, and oleyl alcohol; glycerin; and glycerides obtained by reacting glycerin with alcohol. It is preferable that the optional additive does not contain neutral zinc sulfonate. The content of such optional additives is, for example, 0.01 to 10% by mass, preferably 0.1 to 5% by mass, based on the total mass of the composition.

[0020] The grease composition of the present invention is preferably used in constant velocity joints, and more preferably in outboard constant velocity joints. The lubrication pattern of outboard joints is point contact, where the balls come into contact with the rolling surfaces of the inner and outer rings, and requires higher extreme pressure resistance than the lubrication pattern of inboard joints, which is mainly line contact. Constant velocity joints are made of metal.

[0021] The grease composition of the present invention contains: (a) a diurea-based thickener represented by the formulas (1-1) and (1-2), where R 1 is a cyclohexyl group, and in formulas (1-2) and (1-3), R 3 is a phenyl group, and R 1 :R 3 (b) an alicyclic aromatic diurea compound having a kinematic viscosity at 100°C of 8 to 16 mmHg as a base oil; 2 Particularly preferred is a grease composition containing: (a) a paraffinic mineral oil having a KOH / g content of 250 to 450 mgKOH / g, in an amount of 1.5 to 3.5 mass%, based on the total mass of the composition, of an overbased calcium sulfonate having a KOH / g content of 250 to 450 mgKOH / g; and (b) disodium sebacate in an amount of 0.2 to 1 mass%, based on the total mass of the composition. It is preferred that the grease composition further contains (e-1) an oil-insoluble Molybdenum Dioxide (MODTC) in an amount of 0.3 to 3 mass%, based on the total mass of the composition, and (e-2) an oil-soluble Molybdenum Dioxide (MODTC) in an amount of 0.5 to 3 mass%, based on the total mass of the composition. It is particularly preferred that any of the above grease compositions is for use in constant velocity joints, and even more particularly preferred that it is for use in outboard constant velocity joints.

[0022] The following components were used to prepare the grease compositions of the Examples and Comparative Examples. <Thickener> (a) Thickener Alicyclic aromatic diurea: reaction product of 1 mole of 4,4'-diphenylmethane diisocyanate with 2 moles of raw material amine (cyclohexylamine:aniline = 7:3 (molar ratio)) Aliphatic diurea A: reaction product of 1 mole of 4,4'-diphenylmethane diisocyanate with 2 moles of raw material amine (octylamine:octadecylamine = 5:5 (molar ratio)) Aliphatic diurea B: reaction product of 1 mole of 4,4'-diphenylmethane diisocyanate with 2 moles of raw material amine (octylamine) Alicyclic aliphatic diurea: reaction product of 1 mole of 4,4'-diphenylmethane diisocyanate with 2 moles of raw material amine (cyclohexylamine:stearylamine = 8:2 (molar ratio))

[0023] <Base oil> (b) Paraffinic mineral oil (500 neutral oil, kinematic viscosity at 100°C = 11 mm 2 / s) <Additives> (c) Ca sulfonate (overbased): calcium salt of alkyl aromatic sulfonic acid ((LUBRIZOL 5283C, manufactured by The Lubrizol Corporation, base number 350 to 400 mg KOH / g) (d) sodium salt of sebacate (e-1) MoDTC (oil-insoluble): molybdenum dithiocarbamate (ADEKA Sakuralube 600, manufactured by ADEKA) (e-2) MoDTC (oil-soluble): molybdenum dithiocarbamate (ADEKA Sakuralube 525, manufactured by ADEKA) (f) Ca sulfonate (neutral): calcium salt of alkyl aromatic sulfonic acid (Alox 2292B, manufactured by LUBLIZOL, base number 0 to 10 mg KOH / g) (g) Zn sulfonate (neutral): zinc salt of alkyl aromatic sulfonic acid (Na-sul Zs, manufactured by KING, base number 0 to 10 mg KOH / g)

[0024] <Preparation of Grease Composition> The raw materials of the thickener were reacted in the base oil, the temperature was raised, and after cooling, the mixture was milled in a three-stage roll mill to obtain a base grease. Additives were added to the base grease to obtain the grease compositions of the Examples and Comparative Examples.

[0025] <Test Method> <Consistency> The consistency was standardized to NLGI No. 1 grade (310 to 340). The consistency was measured according to JIS K2220. <SRV Test> - SRV Test Under High Load Seizure resistance was evaluated by measuring the load that led to seizure according to the method specified in ASTM D5706. [Test conditions] Ball: Material SUJ2 steel, shape diameter 10 mm Plate: Material AISI52100 steel, roughness Ra = 0.28 μm Load: 50 N, 100 N, 200 N and thereafter increase in 100 N increments Amplitude: 1 mm Frequency: 50 Hz Test temperature: 80°C Speed: 100 mm / s Time: 2 minutes for each test load (load increased every 2 minutes) [Evaluation criteria] ○ (Pass): The load at which seizure occurs is 1500 N or more × (Fail): The load at which seizure occurs is less than 1500 N

[0026] In actual use of the outboard constant velocity joint, evaluation based on surface pressure rather than load has technical significance. Load (N) is expressed as surface pressure (Pa or N / m 2 ), the grease composition of the present invention, which has an extremely high load that causes seizure, can be said to have excellent seizure resistance even under extremely high surface pressure conditions.

Claims

1. A grease composition comprising: (a) a diurea thickener; (b) a base oil; (c) 0.1 to 10 mass % of an overbased calcium sulfonate, based on the total mass of the composition; and (d) 0.01 to 5 mass % of disodium sebacate, based on the total mass of the composition.

2. The grease composition according to claim 1, wherein the base number of component (c) is 200 to 500 mg KOH / g.

3. The grease composition according to claim 1, wherein component (a) is a diurea compound represented by the following formula (1): 1 -NHCONH-R 2 -NHCONH-R 3 (1) (wherein, R 1 and R 3 may be the same or different and are an alkyl group having 8 to 18 carbon atoms, an aryl group having 6 carbon atoms, or a cyclohexyl group. 2 is a divalent aromatic hydrocarbon group having 6 to 15 carbon atoms.

4. The grease composition according to claim 1, further comprising at least one member selected from the group consisting of component (e-1) oil-insoluble molybdenum dialkyldithiocarbamate (MoDTC) and component (e-2) oil-soluble molybdenum dialkyldithiocarbamate (MoDTC).

5. The grease composition according to claim 4, which contains component (e-1) and component (e-2).

6. The grease composition of claim 1, which is free of neutral zinc sulfonates.

7. The grease composition according to claim 1, which is for use in constant velocity joints.

8. The grease composition according to claim 1, which is for use in an outboard constant velocity joint.

9. A constant velocity joint filled with the grease composition according to any one of claims 1 to 8.

Images