Grease composition for constant velocity joints

Abstract

According to the present application, there is provided a grease composition for a constant velocity joint, comprising: (a) a base oil, (b) a diurea thickening agent, (c) a molybdenum dithiocarbamate, (d) a molybdenum dithiophosphate, (e) a high basic calcium sulfonate, (f) a neutral zinc sulfonate. The composition of the present application is excellent in durability at high temperature and vibration suppression.

Description

TECHNICAL FIELD

[0001] The present application relates to a grease composition for a constant velocity joint. BACKGROUND

[0002] In automobiles, FF vehicles are widely spread in view of lightening of vehicles for the purpose of environmental protection (reduction of CO2) and securing of living space, and constant velocity joints (CVJ) indispensable for power transmission in FF vehicles are widely used.

[0003] In the form of this CVJ, since the telescopic constant velocity joint rotates in a state with an angle, the components inside the joint perform complicated rolling sliding motions with each other. At this time, sliding resistance in the axial direction is generated due to friction of the internal components, and if the sliding resistance is large, it sometimes becomes a cause of vibration and sound.

[0004] With high output of engines of automobiles in recent years, the lubrication condition inside the constant velocity joint shifts to the high face pressure side. The higher the lubrication condition is, the more the tendency to easily generate wear exists inside the constant velocity joint, and thus problems such as reduction of durability (peeling resistance) and deterioration of vibration sometimes occur.

[0005] In addition, in this constant velocity joint, it is also required to secure durability at high temperature.

[0006] As a grease excellent in vibration suppression performance, a constant velocity joint grease in which a molybdenum dithiocarbamate and a molybdenum dithiophosphate are used as additives in a urea grease or a constant velocity joint grease in which zinc dithiophosphate is mixed in these organic molybdenum compounds is proposed (see Patent Document 1); a constant velocity joint grease composition containing a base oil, a urea thickener, a molybdenum dithiocarbamate, calcium sulfonate, and a thiophosphate is proposed (see Patent Document 2). In addition, further quietness is required in recent years, and thus a constant velocity joint grease composition containing at least one of a dialkyldithiocarbamate molybdenum and a dialkyldithiophosphate molybdenum or a diaryldithiophosphate molybdenum and a mixture of an ashless dithiocarbamate or zinc dithiocarbamate in a grease composed of a base oil and a urea compound thickener is proposed (see Patent Document 3); a constant velocity joint composition containing a base oil, a diurea thickener, a sulfurized dialkyldithiocarbamate molybdenum, zinc sulfonate, a sulfur-phosphorus extreme pressure agent, and a vegetable oil and fat is proposed (see Patent Document 4).

[0007] As a grease also considering durability, a constant velocity joint composition containing a base oil, a thickener, montan wax, zinc sulfonate, and a sulfurized dialkyldithiocarbamate molybdenum is proposed (see Patent Document 5).

[0008] Thus, even if the grease composition for a CV joint in the past has exhibited excellent performance in vibration suppression, although durability has been studied at normal temperature, on the other hand, it can be said that sufficient study has not been performed in terms of durability at high temperature.

[0009] Prior Art Documents

[0010] Patent Documents

[0011] Patent Document 1: Japanese Patent No. 5-79280

[0012] Patent Document 2: Japanese Patent Application Laid-Open No. 11-172276

[0013] Patent Document 3: Japanese Patent Application Laid-Open No. 2009-235416

[0014] Patent Document 4: Japanese Patent Application Laid-Open No. 2011-37950

[0015] Patent Document 5: International Publication No. 2014 / 054797 SUMMARY

[0016] PROBLEMS TO BE SOLVED BY THE INVENTION

[0017] Therefore, an object of the present application is to provide a grease composition which is excellent in durability and vibration suppression characteristics even at high temperature.

[0018] METHOD FOR SOLVING THE PROBLEM

[0019] 1. A grease composition for a CV joint, comprising: (a) a base oil, (b) a diurea thickening agent, (c) a molybdenum dithiocarbamate, (d) a molybdenum dithiophosphate, (e) a high basic calcium sulfonate, (f) a neutral zinc sulfonate.

[0020] 2. The grease composition according to claim 1, wherein the content of component (f) is 0.1 to 10 mass% based on the total mass of the composition.

[0021] 3. The grease composition according to claim 1 or 2, wherein the content of component (f) is 0.5 to 5 mass% based on the total mass of the composition.

[0022] 4. The grease composition according to any one of claims 1 to 3, wherein the content of component (f) is 0.8 to 3 mass% based on the total mass of the composition.

[0023] 5. The grease composition according to any one of claims 1 to 4, wherein the content of component (e) is 0.1 to 10 mass% based on the total mass of the composition.

[0024] 6. The grease composition according to any one of claims 1 to 5, wherein the content of component (e) is 0.2 to 5 mass% based on the total mass of the composition.

[0025] 7. The grease composition according to any one of claims 1 to 6, wherein the content of component (e) is 1.2 to 3.5 mass% based on the total mass of the composition.

[0026] 8. The grease composition according to any one of claims 1 to 7, wherein component (b) is an aliphatic diurea-based thickener.

[0027] 9. A constant velocity joint into which the grease composition according to any one of claims 1 to 8 is enclosed.

[0028] EFFECT OF THE INVENTION

[0029] According to the present application, it is possible to provide a grease composition which is excellent in durability even at high temperatures and excellent in vibration suppression. DETAILED DESCRIPTION

[0030] (a) Base oil

[0031] The base oil which can be used in the composition of the present application is not particularly limited, and a mineral oil and / or a synthetic oil can be used. As the synthetic oil, synthetic hydrocarbon oils such as polyalphaolefins, pentaphenyl ethers, tetraphenyl ethers, monoalkyl tetraphenyl ethers, dialkyl tetraphenyl ethers, and alkyl diphenyl ether oils; alkylbenzene oils; ester oils such as monoester oils, diester oils, polyol ester oils, and aromatic ester oils; polyethylene glycol oils; silicone oils; fluorine oils; and ionic liquids can be listed.

[0032] As the base oil of the present application, from the viewpoint of cost, it is preferable to use a mineral oil. A base oil in which a synthetic oil is mixed in a mineral oil as a main component can also be used.

[0033] In the case where the base oil of the present application is a mixed oil of a mineral oil and a synthetic oil, the mineral oil is preferably 50 to 100 mass%, more preferably 70 to 100 mass%, and further preferably 90 to 100 mass% based on the total mass of the base oil.

[0034] The kinematic viscosity at 100°C of the base oil of the present application is preferably 5 to 30 mm 2 / s, and more preferably 7 to 20 mm 2 / s. In less than 5 mm 2 / s, there is a tendency that an oil film is not formed in the constant velocity joint and durability becomes insufficient, and in more than 30 mm 2 / s, there is a tendency that durability decreases due to heat generation in the CVJ.

[0035] The content of the base oil is preferably 50 to 100% by mass, more preferably 70 to 100% by mass, and further preferably 80 to 100% by mass, based on the total mass of the composition, from the viewpoint of fluidity.

[0036] (b) diurea-based thickening agent

[0037] The diurea-based thickening agent that can be used in the present application is represented by the following formula (1).

[0038] R 1 -NHCONH-R 2 -NHCONH-R 3 (1)

[0039] In the formula, R 2 is a divalent aromatic hydrocarbon group having 6 to 15 carbon atoms, and R 2 is preferably toluene diisocyanate or diphenylmethane diisocyanate, and more preferably diphenylmethane diisocyanate. R 1 and R 3 may be the same or different, and are a linear or branched alkyl group having 6 to 30 carbon atoms, an aryl group having 6 or 7 carbon atoms, or a cyclohexyl group.

[0040] As the diurea compound of formula (1), an aliphatic diurea compound in which R 1 and R 3 are both alkyl groups having 6 to 30 carbon atoms is preferred. The aliphatic diurea compound can be obtained by reacting a diisocyanate with an aliphatic monoamine.

[0041] Further, as the diurea compound of formula (1), an alicyclic aliphatic diurea compound in which either R 1 or R 3 is an alkyl group having 6 to 30 carbon atoms, and the other is a cyclohexyl group is also preferred. The alicyclic aliphatic diurea compound is obtained by reacting a diisocyanate with an alicyclic monoamine and an aliphatic monoamine, and thus is actually a mixture of an aliphatic diurea compound and an alicyclic diurea compound in addition to the alicyclic aliphatic diurea compound.

[0042] When either R 1 or R 3 is a cyclohexyl group, the other is preferably a linear alkyl group having 8 or 18 carbon atoms. In this case, from the viewpoint of fluidity, the ratio of the cyclohexyl group in the total of the cyclohexyl group and the alkyl group is preferably 70 to 100 mol%, and more preferably 80 to 100 mol%.

[0043] As the thickening agent of the present application, an aliphatic diurea compound is preferred from the viewpoint of durability.

[0044] Particularly preferred is an aliphatic diurea compound in which R 1and R 3 each independently represents an alkyl group having 8 to 30 carbon atoms, R 2 is a diurea compound of diphenylmethane diisocyanate.

[0045] R 1 and R 3 each independently represents a linear alkyl group having 8 or 18 carbon atoms, R 2 is a diurea compound of diphenylmethane diisocyanate.

[0046] The consistency of the grease composition of the present application is preferably 250 to 400, more preferably 280 to 370, and further preferably 310 to 340. Note that, in the present specification, the term "consistency" refers to the 60-stroke consistency. The consistency can be measured in accordance with JIS K2220 7.

[0047] The content of the thickening agent is preferably 10% by mass or less, more preferably 5 to 10% by mass, and further preferably 6 to 7% by mass, based on the total mass of the composition, so as to be able to set the consistency of the grease composition to the above range.

[0048] (c) molybdenum dithiocarbamate (MoDTC)

[0049] The molybdenum dithiocarbamate that can be used in the present application is a general term for substances in which the metal base of the organometallic load-resistant additive is molybdenum, and is widely used as an extreme pressure additive. Preferred examples of the molybdenum dithiocarbamate can be represented by the following formula (2).

[0050] [R 4 R 5 N-CS-S]2-Mo2O m S n (2)

[0051] In the formula, R 4 and R 5 may be the same or different from each other, and each independently represents a linear or branched alkyl group having 1 to 24, preferably 3 to 18, carbon atoms, m is 0 to 3, and n is 4 to 1, m + n = 4.

[0052] The molybdenum dithiocarbamate includes an oil-soluble molybdenum dithiocarbamate (i.e., liquid at room temperature (about 25°C)) and a non-oil-soluble molybdenum dithiocarbamate (i.e., solid at room temperature). Either can be used as the molybdenum dithiocarbamate of the present application, but if a combination of the oil-soluble molybdenum dithiocarbamate and the non-oil-soluble molybdenum dithiocarbamate is used, the durability and the suppression of heat generation and vibration inside the CVJ are excellent, and thus are preferred.

[0053] From the viewpoint of suppressing vibration, the content of the component (b) in the grease composition of the present application is preferably 0.1 to 10% by mass, more preferably 0.5 to 5% by mass, and further preferably 1 to 3% by mass, based on the total mass of the composition. Note that in the case of containing an oil-soluble molybdenum dithiocarbamate and a non-oil-soluble molybdenum dithiocarbamate, vibration suppression is excellent when the mass ratio of the oil-soluble molybdenum dithiocarbamate to the non-oil-soluble molybdenum dithiocarbamate is used in a ratio of preferably 4:6 to 10:0, and more preferably 6:4 to 8:2, and thus this is preferred.

[0054] (d) molybdenum dithiophosphate (MoDTP)

[0055] As a preferred example of the molybdenum dithiophosphate used in the present application, a substance represented by the following formula (3) can be given.

[0056] [(R 6 O)(R 7 O)PS-S]2Mo2O m S n

[0057] (In the formula, R 6 and R 7 are each independently an alkyl group having 1 to 24 carbon atoms or an aryl group having 6 to 30 carbon atoms, m is 0 to 3, n is 4 to 1, and m + n = 4.)

[0058] From the viewpoint of durability, the content of the component (d) in the grease composition of the present application is preferably 0.1% by mass or more, more preferably 0.1 to 5% by mass, and further preferably 0.2 to 2% by mass, based on the total mass of the composition.

[0059] (e) overbased calcium sulfonate

[0060] The overbased calcium sulfonate used in the present application is a calcium sulfonate having a base number of 200 mgKOH / g or more. From the viewpoint of durability, the base number is preferably 300 mgKOH / g or more, and more preferably 300 to 500 mgKOH / g. Note that in the present application, the base number is a value measured in accordance with JIS K2501.

[0061] As the component (e), a calcium salt of a sulfonic acid having an organic group as a lipophilic group can be used. As such an organic sulfonic acid, a petroleum sulfonic acid obtained by sulfonation of aromatic hydrocarbon components in a lubricating oil fraction, a dinonylnaphthalene sulfonic acid, a heavy alkylbenzene sulfonic acid, and the like can be given. As the component (e), a calcium sulfonate that becomes overbased by calcium carbonate is preferred. A calcium alkylaromatic sulfonate containing calcium carbonate is particularly preferred.

[0062] From the viewpoint of durability, the content of the component (e) in the grease composition of the present application is preferably 0.1 to 10 mass%, more preferably 0.2 to 5 mass%, further preferably 1.2 to 3.5 mass%, based on the total mass of the composition.

[0063] (f) zinc neutral sulfonate

[0064] The zinc neutral sulfonate used in the present application has a base number of 10 mgKOH / g or less.

[0065] The sulfonic acid constituting the zinc sulfonate is the same as the sulfonic acid described for the component (e).

[0066] As the zinc neutral sulfonate, zinc dinonylnaphthalene sulfonate is preferred.

[0067] From the viewpoint of durability, the content of the zinc neutral sulfonate in the grease composition of the present application is preferably 0.1 to 10 mass%, more preferably 0.5 to 5 mass%, further preferably 0.8 to 3 mass%, based on the total mass of the composition.

[0068] When the total of the component (e) and the component (f) is preferably 0.5 to 5 mass%, more preferably 1 to 3 mass%, based on the total mass of the composition, the heat resistance is excellent, and thus it is preferred.

[0069] When the mass ratio of the component (e) to the component (f) is (e):(f) = 9:1 to 1:9, the durability is excellent, and thus it is preferred. More preferably, (e):(f) = 8:2 to 3:7, further preferably (e):(f) = 7:3 to 4:6. In particular, when the total of the component (e) and the component (f) is 1 to 3 mass%, based on the total mass of the composition, and the mass ratio of the component (e) to the component (f) is (e):(f) = 7:3 to 4:6, the durability and the heat resistance are excellent, and thus it is preferred.

[0070] The grease composition of the present application can contain additives generally used in greases as needed. The content of these additives is generally 0.1 to 5 mass%, preferably 0.5 to 3 mass%, based on the total amount of the grease composition.

[0071] As such additives, for example, the following can be listed: antioxidants such as amine-based, phenol-based, quinoline-based, sulfur-based, and zinc dithiophosphate; rust preventives such as zinc-based, carboxylic acid-based, carboxylic acid salt-based (in particular, sodium sebacate, sodium azelate, sodium suberate, and other dibasic acid salts), and amine-based; abrasion resistant agents such as sulfurized oils, sulfurized olefins, phosphoric acid esters, phosphorous acid esters, and acid phosphoric acid ester amine salts; oiliness agents such as fatty acids, fatty acid esters, and phosphoric acid esters; and solid lubricants such as graphite, polytetrafluoroethylene (PTFE), and zinc oxide.

[0072] From the viewpoint of heat resistance, it is preferred to contain an antioxidant.

[0073] As the antioxidant, an amine-based antioxidant is preferred, and an alkyl diphenylamine is more preferred. The content of the antioxidant is preferably 0.1 mass% or more, more preferably 0.1 to 2 mass%, and further preferably 0.2 to 1 mass%, based on the total mass of the composition.

[0074] As the composition of the present application, it is preferred that only (a) base oil, (b) diurea-based thickener, (c) molybdenum dithiocarbamate, (d) molybdenum dithiophosphate, (e) high basicity calcium sulfonate, (f) neutral zinc sulfonate, and (g) antioxidant are contained.

[0075] At this time, the content of each component is preferably (a) 80 to 100 mass%, (b) 6 to 7 mass%, (c) 1 to 3 mass%, (d) 0.2 to 2 mass%, (e) 0.5 to 3 mass%, (f) 0.8 to 3 mass%, and (g) 0.2 to 1 mass%, based on the total mass of the composition.

[0076] As the composition of the present application, it is also preferred that (a) base oil, (b) aliphatic diurea-based thickener, (c) molybdenum dithiocarbamate, (d) molybdenum dithiophosphate, (e) high basicity calcium sulfonate having a base number of 300 mgKOH / g or more including calcium carbonate, (f) neutral zinc sulfonate, and (g) amine-based antioxidant are contained.

[0077] At this time, the content of each component is preferably (a) 80 to 100 mass%, (b) 6 to 7 mass%, (c) 1 to 3 mass%, (d) 0.2 to 2 mass%, (e) 0.5 to 3 mass%, (f) 0.8 to 3 mass%, and (g) 0.2 to 1 mass%, based on the total mass of the composition.

[0078] Further, as the composition of the present application, it is also preferred that (a) base oil, (b) aliphatic diurea-based thickener, (c) mixture of oil-soluble molybdenum dithiocarbamate and non-oil-soluble molybdenum dithiocarbamate, (d) molybdenum dithiophosphate, (e) alkyl aromatic calcium sulfonate having a base number of 300 to 500 mgKOH / g including calcium carbonate, (f) zinc dinonylnaphthalene sulfonate having a base number of 10 mgKOH / g or less, and (g) alkyl diphenylamine are contained. 1 and R 3 are each a linear alkyl group having 8 carbon atoms, and R 2 is diphenylmethane diisocyanate.

[0079] At this time, the content of each component is preferably (a) 80 to 100 mass%, (b) 6 to 7 mass%, (c) 1 to 3 mass%, (d) 0.2 to 2 mass%, (e) 0.5 to 3 mass%, (f) 0.8 to 3 mass%, and (g) 0.2 to 1 mass%, based on the total mass of the composition.

[0080] The grease composition of the present application is suitable for a constant velocity joint. Among them, if it is suitable for a telescopic constant velocity joint, particularly a tripod type constant velocity joint, a double effect compensation type constant velocity joint, particularly an inner plate side constant velocity joint, durability, vibration suppression are excellent, and thus it is preferred.

[0081] Examples

[0082] (1) Production of the grease compositions of Examples 1 to 7 and Comparative Examples 1 to 4

[0083] In the base oil, 1 mole of 4', 4-diphenylmethane diisocyanate was reacted with 2 moles of octylamine, and after warming and cooling, the additives were mixed at the proportions shown in Table 1 or Table 2, and kneaded with a 3-roll mill to produce a grease composition having a mixed consistency of 315. Note that the values in Table 1 and Table 2 represent mass % based on the total mass of the grease composition, unless otherwise specified.

[0084] (2) Production of the grease composition of Comparative Example 5

[0085] The grease composition of Comparative Example 5 was produced according to the description of Example C4 of Japanese Patent No. 6470851.

[0086] Note that the components used in the production of the grease composition are described below.

[0087] < Base oil >

[0088] • Mineral oil (kinematic viscosity at 100°C: 12.4 mm 2 / s)

[0089] • Mineral oil + synthetic oil: poly-α-olefin (kinematic viscosity at 100°C: 12.0 mm 2 / s)

[0090] < Additives >

[0091] • MoDTC (non-oil soluble): molybdenum dithiocarbamate (ADEKA SAKURA LUBE 600, manufactured by ADEKA)

[0092] • MoDTC (non-oil soluble): molybdenum dithiocarbamate (Molyvan A, manufactured by Vanderbilt, used in Comparative Example 5)

[0093] • MoDTC (oil soluble): molybdenum dithiocarbamate (ADEKA SAKURA LUBE 525, manufactured by ADEKA)

[0094] • MoDTP: Molybdenum dithiophosphate (ADEKA SAKURA LUBE 300, manufactured by ADEKA)

[0095] • MoDTP: Molybdenum dithiophosphate (Molyvan L, manufactured by Vanderbilt, used in Comparative Example 5)

[0096] • Calcium sulfonate (highly basic): Calcium salt of alkyl aromatic sulfonic acid ((LUBRIZOL 5283C, manufactured by The-Lubrizol Corporation, base number 375 mgKOH / g)

[0097] • Zinc sulfonate (neutral): Zinc salt of dinonyl naphthalene sulfonic acid (NA-SUL ZS, manufactured by KING INDUSTRIES, base number 5 mgKOH / g)

[0098] • Antioxidant

[0099] 〔2〕Evaluation of durability

[0100] (1) SRV test (high load)

[0101] Test conditions

[0102] Test speed: 11.9 mm / s (frequency: 3.3 Hz, stroke: 1.8 mm)

[0103] Test temperature: 90°C

[0104] Load: 5.5 GPa

[0105] Test piece: ball (diameter 17.5 mm, SUJ-2) / plate (SUJ-2, surface roughness Rz 0.5 μm)

[0106] [evaluation criteria]

[0107] ◎ (pass): Coefficient of friction 0.08 or less

[0108] O (pass): Coefficient of friction more than 0.08 and 0.10 or less

[0109] Δ (pass): Coefficient of friction more than 0.10 and 0.12 or less

[0110] X (fail): Occurrence of seizure or coefficient of friction more than 0.12

[0111] (2) SRV test (low load)

[0112] Test conditions

[0113] Test speed: 2.0 mm / s (frequency: 3.3 Hz, stroke: 0.3 mm)

[0114] Test temperature: 95°C

[0115] Load: 2.1 GPa

[0116] Test piece: ball (diameter 17.5 mm, SUJ-2) / plate (SUJ-2, surface roughness Rz 5 μm)

[0117] [evaluation criteria]

[0118] O (pass): friction coefficient 0.10 or less

[0119] Δ (pass): friction coefficient more than 0.10 and 0.14 or less

[0120] X (fail): seizure occurs or friction coefficient more than 0.14

[0121] 〔2〕Evaluation of vibration suppression

[0122] (1) TE77 test

[0123] TE77 tester is a vibration friction and wear tester under sliding conditions. It is reported that vibration with gimbal as a vibration source and friction coefficient under vibration conditions measured by TE77 tester exist in relation (Japanese Patent Application Laid-Open No. 2010-065194). Therefore, using TE77 tester, vibration suppression in gimbal is evaluated.

[0124] [testing conditions]

[0125] Test speed: 16 mm / s (frequency: 10 Hz, stroke: 0.8 mm) Test temperature: 40°C

[0126] Load: 1.2 GPa

[0127] Test piece: ball (diameter 17.5 mm, SUJ-2) / plate (SCM) [evaluation criteria]

[0128] O (pass): friction coefficient 0.07 or less

[0129] Δ (pass): friction coefficient more than 0.07 and 0.10 or less

[0130] X (fail): friction coefficient more than 0.10

[0131] [comprehensive evaluation]

[0132] O (pass): all of the above test results are qualified

[0133] X (fail): one or more of the above test results are not qualified The results are shown in Table 1 and Table 2.

[0134] [table 1]

[0135]

[0136] [Table 2]

[0137]

Claims

1. A grease composition for a constant velocity joint, comprising: (a) a base oil, (b) a diurea thickener, (c) a molybdenum dithiocarbamate, (d) a molybdenum dithiophosphate, (e) a high basic calcium sulfonate, (f) a neutral zinc sulfonate, the content of component (e) is 1.2 to 3.5 mass% based on the total mass of the composition, the content of component (f) is 0.8 to 3 mass% based on the total mass of the composition, the mass ratio (e):(f) of component (e) to component (f) is 7:3 to 4:

6.

2. The grease composition of claim 1, wherein, component (c) contains an oil-soluble molybdenum dithiocarbamate which is a liquid at 25°C and a non-oil-soluble molybdenum dithiocarbamate which is a solid at 25°C.

3. The grease composition of claim 2, wherein, the mass ratio of the oil-soluble molybdenum dithiocarbamate to the non-oil-soluble molybdenum dithiocarbamate is 6:4 to 8:

2.

4. The grease composition of claim 1 or 2, wherein, component (b) is an aliphatic diurea thickener.

5. A constant velocity joint into which the grease composition described in any one of claims 1 to 4 is enclosed.

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