KR101124974B1 - Grease composition for use in constant velocity joints comprising at least one tri-nuclear molybdenum compound - Google Patents

Abstract

The present invention addresses the problem of providing a new grease composition that gives preferentially low wear and low friction to a constant velocity joint, the grease composition comprising: a) a base oil mixture; And b) at least one tri-nuclear molybdenum compound of 0.25 wt% to 5 wt%, of the formula:

Mo ₃ S _k L _n Q _z

Wherein L is an independently selected ligand consisting of an organic group having a sufficient amount of carbon atoms to provide a compound that is soluble or dispersible in oil, n is from 1 to 4, k is from 4 to 7 Wherein Q is selected from the group of compounds that contribute to neutral electrons such as amines, alcohols, phosphines and ethers, z ranges from 0 to 5 and includes nonstoichiometric values.

Constant velocity joint, grease composition, base oil mixture, trinuclear molybdenum compound, abrasion, coefficient of friction

Description

Grease composition for use in constant velocity joints comprising at least one tri-nuclear molybdenum compound

The present invention relates to lubricating greases intended for preferential use in constant velocity universal joints, in particular ball joints or triangular joints, used in power transmission systems of motor vehicles.

The movement of the components in a constant velocity joint (CVJ) is complicated by the combination of rolling, sliding and spinning. When the joint is under torque, the components are loaded against each other, which can cause wear to the contact surfaces of the components as well as cause rolling contact fatigue and significant friction between the surfaces. The wear can cause breakage of the joints and the friction can cause noise, vibration and roughness (NVH) in the power transmission system. The NV is usually measured by determining the axial force generated at the plunging type constant velocity joint. Ideally, greases used in constant velocity joints are needed not only to reduce wear, but also to have a low coefficient of friction in order to reduce friction and reduce or prevent end-effects.

The constant velocity joint also has sealing boots of elastic material, usually in a bellows shape, one end of which is connected to the external component of the constant velocity joint and the other end of which is connected to the interconnect or output shaft of the constant velocity joint. The boot retains grease in the joint and prevents dirt or water from entering.

The grease must not only reduce wear and friction, but also prevent premature onset of rolling contact fatigue at constant velocity joints and must be compatible with the elastic material forming the boot. Otherwise there will be degeneration of the boot material causing grease leakage and premature failure of the constant velocity joint allowing for ultimate failure of the constant velocity joint. Two main types of materials used for constant velocity joint boots are polychloroprene rubber (CR) and thermoplastic elastomers (TPE), in particular ether-ester block copolymer thermoplastic elastomers (TPC-ET).

Typical constant velocity joint greases have a base oil which is a mixture of naphthenic (saturated rings) and paraffinic (straight and branched saturated chain) mineral oils. Synthetic oils can also be added. The base oil is known to have a significant effect on the deterioration (swelling or sinking) of two boots made of CR and TPC-ET. Both mineral and synthetic base oils exert plasticizers and other oil dissolution protectors from the boot material. Paraffinic mineral oils and poly-alpha (α) -olefins (PAO) synthetic base oils diffuse very small amounts into special boots made of rubber that causes shrinkage, while naphthenic mineral oils and synthetic esters It can diffuse into the boot material, act as a plasticizer and cause swelling. The exchange of plasticizers or plasticizer mixtures for naphthenic mineral oils can significantly reduce the boot performance, especially at low temperatures, which can cause failures by causing the boots to crack, ultimately break the constant velocity joint. If significant swelling or softening occurs, the fastest performance of the boot is reduced due to the lack of stability in speed and / or excessive radial expansion.

To solve the problems as described above, US Pat. No. 6,656,890 B1 discloses 10 to 35 wt% of one or more poly-alpha-olefins, 3 to 15 wt% of one or more synthetic organic esters, 20 to 30 wt% of one or more naphthenes. Organic molybdenum complex, and molybdenum dithiophosphate, and zinc dialkyldithiophosphate, including the remainder of the base oil, the balance of one or more paraffinic oil phosphorus binders, and additionally lithium soap thickeners, and sulfur-free friction modifiers. And further proposed a special base oil combination comprising additional additives such as corrosion inhibitors, antioxidants, extreme pressure additives and takiness agents. However, the friction and coefficient of friction of the grease composition according to US Pat. No. 6,656,890 B1 need to be improved as measured by SRV (abbreviations of German Schwingungen, Reibung, Verschleiβ) tests.

It is an object of the present invention to provide a grease composition for use in original constant velocity joints which has good compatibility with boots made of rubber or thermoplastic elastomers and also provides low wear and low friction for use in constant velocity joints.

The object of the present invention as described above has been solved by a grease composition for use in a constant velocity joint, the grease composition comprising:

a) base oil mixture; And

b) with respect to the total amount of the grease composition, consisting of 0.25 wt% to 5 wt%, preferably 0.3 wt% to 3 wt% of at least one tri-nuclear molybdenum compound,

Mo ₃ S _k L _n Q _z

Wherein L is an independently selected ligand consisting of an organic group having a sufficient amount of carbon atoms to provide a compound that is soluble or dispersible in oil, n is from 1 to 4, k is from 4 to 7 Q is selected from the group of compounds that contribute to neutral electrons such as amines, alcohols, phosphines and ethers, z ranges from 0 to 5 and includes nonstoichiometric values.

The number of carbon atoms is present in the trinuclear molybdenum compound of all ligands, and the organic group is at least 21, preferably at least 25, more preferably at least 30, and most preferably at least 35 carbon atoms. Trinuclear molybdenum compounds usable in the present invention are disclosed in US Pat. No. 6,172,013 B1, the disclosure of which is incorporated herein by reference. The inventors of the present invention have found that the presence of at least 0.25 wt% of the trinuclear molybdenum compound according to claim 1 significantly reduces the coefficient of friction as well as the wear of the constant velocity joint in use. Surprisingly, the presence of less than 0.2 wt% trinuclear molybdenum compounds prevented further wear or even lower coefficients of friction when used in constant velocity joints.

In the base oil mixture according to the invention, base oil mixtures such as those disclosed in US Pat. No. 6,656,890 B1, the disclosure of which is hereby incorporated by reference, are preferably used. However, any other kind of base oil mixture, in particular a mixture of mineral oils, a mixture of synthetic oils or a mixture by mixing minerals and synthetic oils may be used. The base oil mixture should preferably have a kinematic viscosity between about 32 and about 250 mm ² / s at 40 ° C. and a kinematic viscosity between about 5 and about 25 mm ² / s at 100 ° C. The mineral oil is preferably selected from the group comprising at least one naphthenic oil and / or at least one paraffinic oil. Synthetic oils usable in the present invention are selected from the group comprising at least one poly-alpha-olefin (PAO) and / or at least one organic synthetic ester. The organic synthetic ester is preferably a di-carboxylic acid derivative consisting of a subgroup based on fatty alcohols. Preferably, the fatty alcohol has a primary, straight or branched carbon chain having 2 to 20 carbon atoms. Preferably, the organic synthetic ester is sebacic acid-bis (2-ethylhexylester) ("dioctyl sebacate" (DOS)), adipic acid-bis (adipaic acid) -bis) (2-ethylhexyl ester) ("dioctyl adipate" (DOA)), and / or azelic acid-bis (2-ethylhexyl ester) ("di Octyl azelate "(DOZ)).

If the poly-alpha-olefin is present in the base oil mixture, the poly-alpha-olefin is preferably selected to have a viscosity ranging from about 2 to 40 centistokes at 100 ° C. The naphthenic oil selected for the base oil mixture preferably has a viscosity in the range of 20 to 180 mm ² / s at 40 ° C., whereas if paraffinic oil is present in the base oil mixture, preferably the paraffinic oil is 40 At a temperature in the range of 25 to 400 mm ² / s.

In a further embodiment of the invention, the grease composition further comprises a zinc compound additive in an amount of at least one zinc compound additive, more preferably from about 0.1 wt% to about 1.5 wt%. Most preferred zinc compound additives are selected from the group consisting of one or more of zinc dithiophosphate (ZnDTP) and / or zinc dithiocarbamate (ZnDTC), ZnO and / or ZnS. The zinc dithiophosphate is preferably selected from the group of zinc dialkyldithiophosphates of the general formula:

(R ¹ O) (R ² O) SP-S-Zn-S-PS (OR ³ ) (OR ⁴ )

Herein, each of R ¹ to R ⁴ inclusive may be the same or different and each may be a first or second having 1 to 24, preferably 3 to 20, most preferably 3 to 5 carbon atoms 2 alkyl group. In particular, excellent effects can be expected if the substitutions R ¹ , R ² , R ³ and R ⁴ represent a combination of the first and second alkyl groups each having 3 to 8 carbon atoms. .

The zinc dithiocarbamate may be preferably selected from zinc dialkyldithiophosphates of the general formula:

Here, R ⁵ , R ⁶ , R ⁷ and R ⁸ may be the same or different and each represents an alkyl group having 1 to 24 carbon atoms or an alkyl group having 6 to 30 carbon atoms.

By adding one or more zinc compound additives to the grease composition according to the invention, the coefficient of friction as well as the abrasion at the constant velocity joints are significantly reduced.

According to an embodiment of the present invention, the grease composition further comprises a thickener selected from the group consisting of lithium soap, calcium soap, lithium complex soap, calcium complex soap and / or urea-derivative type thickener. . The urea derivative type thickener is not limited to any one, and may be, for example, a diuretic compound and / or a polyurea compound.

In the context of the present invention, lithium soap and calcium soap are reaction products of one or more fatty acids with lithium hydroxide or calcium hydroxide. Preferably, the thickener may be simple lithium or calcium soap formed from stearic acid, 12-hydroxystearic acid, hydrogenated castor oil or from other similar fatty acids or mixtures thereof or methyl esters of the acids. Alternatively, for example, lithium and / or calcium complex soaps formed from mixtures of long chain fatty acids with complexing agents, for example borate salts of one or more dicarboxylic acids or mixtures of short and / or medium chain carboxylic acids, may be used. have. The use of such composite lithium and / or calcium soaps allows the grease composition according to the invention to operate up to a temperature of about 180 ° C., while a simple lithium and / or calcium soap, grease composition may only operate up to a temperature of about 120 ° C. will be. However, all mixtures of the thickeners described above can be used.

According to a further embodiment of the present invention, the grease composition further comprises an additive package selected from the group consisting of antioxidants, corrosion inhibitors, antiwear agents, friction modifiers, and / or extreme pressure agents (EP agents). do.

The EP agent is preferably a sulfided fatty acid methyl ester with a viscosity of about 25 mm ² / s at 40 ° C., preferably present in a base metal, in an amount between 0.1 wt% and 3 wt%, relative to the total amount of the grease composition. The total sulfur amount of the EP agent is preferably in the range of about 8 wt% to 10 wt% and the activated sulfur amount is about 1 wt%. Such EP agents exhibit excellent effects in connection with the prevention of seizure of constant velocity joints. If the sulfur content exceeds the upper limit defined above, it may promote the onset of wear and rolling contact fatigue of the contact metal components.

In the antioxidant, the grease composition of the present invention may comprise an amine, preferably an aromatic amine, more preferably phenyl-alpha-naphthylamine or diphenylamine or derivatives thereof. . The antioxidant is used to prevent degradation of the grease composition associated with oxidation. The grease composition according to the invention ranges from about 0.1 wt% to 2 wt% with respect to the total amount of the grease composition, in order not only to prolong the life of the grease composition and to extend the life of the constant velocity joints, but also to inhibit the oxidative degradation of the base oil. Phosphorus antioxidants.

In general, the last operation prior to assembly of the constant velocity joint is cleaned to remove machining debris, thus absorbing any traces of remaining water and causing the water to corrode and adversely affect the performance of the constant velocity joint. Grease is needed to prevent this, and it is also necessary to add corrosion inhibitors. In corrosion inhibitors, the grease composition according to the invention is a metal salt of oxidized wax, in particular a metal salt of petroleum sulfonate prepared by sulfonating aromatic hydrocarbon components present in the lubricant of the lubricating oil, and / or dinonylnaphthalene sulfonic acid, alkyl One or more metal salts selected from the group consisting of metal salts of alkyl aromatic sulfonates such as benzene sulfonic acid or overbased alkylbenzene sulfonic acid. Examples of the metal salts include sodium salts, potassium salts, calcium salts, magnesium salts, zinc salts, and ammonium salts, with the calcium salts being most preferred. In addition, the calcium salt of the oxidized wax ensures an excellent effect.

The antiwear agents according to the present invention prevent metal to metal contact by adding film forming compounds to protect the surface by physical adsorption or chemical action. ZnDTP compounds can also be used as anti-wear agents. In the corrosion inhibitor according to the present invention, calcium sulfonate is preferably used in an amount of about 0.5 wt% to 3 wt% with respect to the total amount of the grease composition.

Common friction modifiers such as fatty acid amides and fatty amine phosphates have been used in greases and other lubricants for many years (eg Klaman, Dieter- "Lubricants", Verlag Chemie GmbH 1983, first edition, chapter 9.6). Their role is to provide adequate lubrication, but for a wide range of operating conditions it should not necessarily be low friction.

In another preferred embodiment of the invention, the grease composition is in particular having a kinematic viscosity between about 32 and about 250 mm ² / s at 40 ° C. and a kinematic viscosity between about 5 and about 25 mm ² / s at 100 ° C. 55 wt% to about 97.5 wt% of a base oil mixture, about 0.3 wt% to about 3 wt% of at least one trinuclear molybdenum compound, about 0.1 wt% to about 1.5 wt% of at least one zinc compound additive, and about 2 wt% to About 25 wt% of one or more thickeners are included in each case relative to the total amount of the grease composition. Preferably, the urea thickener is contained in the range of about 5 wt% to about 20 wt%, the lithium soap thickener is contained in the range of about 2 wt% to 15 wt%, and the calcium composite soap thickener is contained in the range of about 8 wt% to 25 wt%. It is contained in the range.

In addition, the grease composition according to the present invention has a sliding coefficient of friction of 0.1 or more as measured using the SRV test.

1 is a graph showing the SRV-measurement results of wear and friction coefficient for the Examples and Comparative Examples of the present invention.

2A and 2B are graphs showing SRV test results for coefficient of friction and wear.

FIG. 3 is a graph showing results from SRV tests performed in relation to examples and comparative examples of the present invention. FIG.

Figure 4 is a graph showing the results of the friction coefficient and wear measurements.

5 is a graph showing the results of SRV tests of coefficient of friction and wear.

In order to determine the effect of lowering the coefficient of friction as well as wear through the grease composition according to the invention, the SRV test was carried out using an Optimol Instruments SRV tester. The flat lower disc specimen was made of 100Cr6 standard bearing steel by Optimol Instruments Pruftechnik GmbH, Westendstrasse 125, Munich, and was contacted with the grease composition to be irradiated with a suitable cleaning and preparation with solvent. The SRV test is an industry standard test and relates in particular to the test of grease for constant velocity joints. The test consisted of an upper ball specimen with a diameter of 10 mm made from 100Cr6 bearing steel reciprocating under load on the flat disc lower specimen indicated above. In the test to simulate a triangular joint, a frequency of 40 Hz with an applied 200 N load was applied at 80 ° C. for 60 minutes (including running-in). Strokes are 1.5 mm and 3.0 mm. The coefficient of friction obtained was recorded on a computer. For each grease, the reported value is the average of four data at the end of the test during four runs (two at 1.5 mm stroke and two at 3.0 mm stroke). Abrasion was measured using a profilometer and a digital planetarometer. By using the profilometer, a profile of the cross section in the middle of the worn surface can be obtained. The area S of the cross section can be measured using a digital planetary meter. The amount of wear was assessed through V = SI, where V is the volume of wear and I is the stroke. The wear rate (Wr) was obtained from Wr = V / L [μm ³ / m], where L is the total sliding distance during the tests. For running-in, it was started by applying a load of 50 N for 1 minute under the conditions specified above. Later, the applied load was increased for 30 seconds from 50N to 200N.

The following materials are used in the investigated grease compositions.

Base oil mixture

The base oil mixture used has a kinematic viscosity between about 32 and about 250 mm ² / s at 40 ° C. and a kinematic viscosity between about 5 and about 25 mm ² / s at about 40 ° C. The base oil mixture A is at least one naphthenic oil in the range of about 10 wt% to about 60 wt%, at least one paraffinic oil in the range of about 30 wt% to about 80 wt%, based on the total amount of the oil mixture, about 5 wt% A mixture of one or more poly-alpha-olefins (PAO) that ranges from% to about 40 wt%. The oil mixture A does not contain an organic synthetic ester, while the oil mixture B contains DOS which ranges from about 2 wt% to about 10 wt% with respect to the total amount of the oil mixture.

The naphthenic oil is selected at a viscosity range between about 20 and about 180 mm ² / s at 40 ° C, the paraffinic oil is selected at a viscosity range between about 25 and about 400 mm ² / s at about 40 ° C, and PAO is about The viscosity ranges between about 6 and about 40 mm ² / s at 100 ° C.

Trinuclear Molybdenum Compounds (TNMoS)

The trinuclear molybdenum compound used in the grease compositions according to the invention is a sulfur containing trinuclear molybdenum compound obtainable under the trade name C9455B by Infineum International Ltd. of the United States. Its structure is shown in US Pat. No. 6,172,013 B1.

Additional Molybdenum Compounds for Comparative Examples

For comparative examples, molybdenum dithiophosphate (MoDTP), sold under the trade name RC3580 by Rhein Chemie Rheinau GmbH, Germany, diluted with mineral oil, was used as the chemical formula 2-ethylnuclear molybdenum dithiophosphate. In addition, molybdenum dithiocarbamate manufactured by Asahi Denka Co., Limited, Japan, sold under the trade name Adeka Sakuralube 600 (S-600) in solid state and under the trade name Sakuralube 515 (S-515) in liquid state. (MoDTC) is used. In addition to US R.T. One organic molybdenum of an amine sold under the trade name Sakuralube 700 (S-700) manufactured by Asahi Denka Co., Limited, as well as an organic molybdenum complex (organic Mo amide) of organic amides sold under the name Molyvan 855 by Vanderbilt. Composites (organic Mo amines) are used.

Zinc compound additives

As the zinc compound additive, ZnDTP sold by Infineum International Ltd. under the trade name Paranox-15 or Rhein Chemie, Germany under trade name RC3038 is used, and the first and second alkyl groups preferably diluted with actual mineral oils are used. Zinc dialkyldithiophosphate having the same ratio. In addition, US R.T. ZnO and ZnS as well as ZnDTC sold under the name Vanlube AZ by Vanderbilt are used as zinc compound additives.

Thickener

As lithium soaps (Li soaps), reaction products of fatty acids such as stearic acid or 12-hydrostearic acid consisting of lithium hydroxide monohydrate are used. In addition, one having a short carbon chain length of 2 to 5 carbon atoms and one having two long carbon chain lengths of 16 to 20 carbon atoms, wherein the ratio of short and long chains is between 1: 2 and 1: 5. Calcium complex soap (calcium complex soap) which is a reaction product of calcium hydroxide composed of an acid is used.

additive

As antioxidant (antioxidant), diphenylamine consisting of butyl and / or octyl-groups is used and is supplied by Ciba Specialty Chemicals, Switzerland under the trade name L-57 (Irganox L57). As EP, sulfur organic compounds (fatty acid methyl esters) sold under the name DeoAdd MD 10 ("EP additive" in the example) by DOG Deutsche Oelfabrik, Gesellschaft fur chemische Erzeugnisse mbH und Co, Hamburg, Germany are used. Another example of an EP agent is a grease consisting of calcium sulfonate thickener, manufactured by Brugarolas S.A. under the trade name Ca-S grease (Ca-S grease).

As a corrosion inhibitor, trade name NaSul 729 (Ca-sulfonate), US CT, Norwalk, King Industries Co. The calcium salt of dinonylnaphthalene sulfonate classified for example by Ltd. is used.

First, the advantages of the grease composition according to the invention were investigated by comparing the wear and friction coefficients with organic molybdenum containing other marketed additives (example A). Six different grease compositions were prepared as listed in Table 1 below.

Grease composition
[wt%] Example A1 Example A2 Example A3 Example A4 Example A5 Example A6 TNMoS 1.0 MoDTP 1.0 MoDTC (Solid) 1.0 Organic Mo Amide 2.0 Organic Mo Amine 1.0 1.0 ZnDTP 1.0 1.0 1.0 1.0 1.0 1.0 Antioxidant 0.25 0.25 0.25 0.25 0.25 0.25 Oil Mixture A 81.75 81.75 81.75 80.75 81.75 82.75 Calcium Complex Soap 16.0 16.0 16.0 16.0 16.0 16.0

SRV-measurement results of wear and friction coefficients of Examples A1 to A6 can be obtained from FIG. 1. Only example A1 is the grease composition according to the invention, while examples A2 to A6 comprise other commercially available organic molybdenum containing additives (A2 to A5) or molybdenum free additives (A6). The coefficient of friction for example A1 was clearly reduced to 0.09 or less as compared to the coefficient of friction of the comparative examples. In addition, the measured wear of Example A1 exhibited the lowest wear of about 165 μm ³ / m in the test series of Examples A1 to A6.

In a further series of tests, further grease compositions according to the invention were prepared including different concentrations of sulfur containing trinuclear molybdenum compounds (TNMoS) as listed in Table 2.

Grease composition
[wt%] Example
B1 = A6 Example
B2 Example
B3 Example
B4 = A1 Example
B5 Example
B6 Example
B7 Example
B8 TNMoS 0.0 0.1 0.2 0.3 0.5 1.0 2.0 3.0 ZnDTP 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 Antioxidant 0.25 0.25 0.25 0.25 0.25 0.25 0.25 0.25 Oil mixture
A 82.75 82.65 82.55 82.45 82.25 81.75 80.75 79.75 Calcium complex
soap 16.0 16.0 16.0 16.0 16.0 16.0 16.0 16.0

SRV test results for the coefficient of friction and wear are shown in FIG. 2.

As can be obtained from FIG. 2A, the coefficient of friction of the grease compositions B1 to B3 is clearly about 0.1. The grease compositions B1 to B3 are not according to the invention. The concentration of sulfur containing up to 0.2 wt% trinuclear molybdenum compound is easily seen from FIG. 2A, which does not significantly lower the coefficient of friction, whereas the grease composition B4 according to the present invention is at least about 25 when compared to Examples B1 to B3. The coefficient of friction lowered by%. Thus, according to the present invention, amounts of sulfur containing about 0.25 wt% trinuclear molybdenum compound relative to the total amount of the grease composition resulted in lower wear values and preferably lower coefficients of friction, as seen from FIG. 2B.

In the third test series, the effect on the addition of zinc compound additives of the grease composition according to the invention was investigated by preparing the grease composition according to Table 3.

Grease composition
[wt%] Example
C1 Example
C2 Example
C3 = B7 Example
C4 Example
C5 Example
C6 TNMoS 2.0 2.0 2.0 2.0 2.0 2.0 ZnDTP 0.5 1.0 ZnDTC 1.0 ZnO 0.20 ZnS 0.20 Antioxidant 0.25 0.25 0.25 0.25 0.25 0.25
Oil mixture
A 81.75 81.25 80.75 80.75 81.55 81.55
Calcium complex
soap 16.0 16.0 16.0 16.0 16.0 16.0

Results from the SRV tests performed in relation to examples C1 to C6 are shown in FIG. 3.

As shown by comparison of Examples C1 without Examples of Zinc Compound Additives with Examples C2 to C6, it is shown that wear is significantly lowered (not measurable), especially when zinc compound additives are added to the grease composition according to the invention. In addition, the coefficient of friction was also lowered and did not exceed the value of 0.08. In particular, it is preferable to add ZnDTP (example C2 and C3) or ZnS (example C6).

In addition, the effect of adding the EP agent to the grease composition according to the invention was demonstrated by preparing various grease compositions according to Table 4.

Grease composition
[wt%] Example
D1 Example
D2 Example
D3 Example
D4 Example
D5 Example
D6 Example
D7 Example
D8 TNMoS 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 ZnDTP 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 EP additive 0.1 0.3 0.5 Ca-sulfonate 2.5 2,0 1.0 Ca-S Grease 3.0 Antioxidant 0.3 0.3 0.3 0.3 0.3 0.3 0.3 0.3 Oil mixture
B 91.7 91.6 91.4 91.2 89.2 89.7 90.7 88.7 Li soap 6.0 6.0 6.0 6.0 6.0 6.0 6.0 6.0

The friction coefficient and the results of the wear measurements are shown in FIG. 4.

The coefficient of friction was lowered by the addition of EP agent, a sulfur organic compound sold under the trade name DeoAdd MD10, in particular up to about 0.4 wt% EP agent "EP additive". In addition, the friction coefficient is further lowered by participating in sulfur-containing compounds Ca-sulfonate 1 and 2 (examples D6 to D8). In addition, the wear was lowered, in particular in examples D3, D7 and D8. From example D4, the addition of 0.5 wt% EP additives as the EP agent did not reach reducing the value of the coefficient of friction, but one could be derived which gave a higher value in relation to the measured wear. Therefore, the addition of more than 0.5 wt% EP additives as EP agents should be avoided.

Finally, the effect of the use of various thickeners in the grease composition according to the invention has been demonstrated by preparing the various grease compositions according to Table 5.

Grease composition
[wt%] Example
E1 = A1 Example
E2 = A6 Example
E3 = D1 Example
E4 TNMoS 1.0 1.0 ZnDTP 1.0 1.0 1.0 1.0 Antioxidant 0.25 0.25 0.3 0.3 Oil mixture
A 81.75 80.75 Oil mixture
B 91.7 92.7 Calcium complex
soap 16.0 16.0 Li soap 6 6 Urea thickener

The results of the SRV tests of the coefficient of friction and wear are shown in FIG. 5.

Compared with Comparative Examples E2 and E4, the preferred influence on the addition of the trinuclear molybdenum sulfur-containing compound to the grease composition according to the invention by Examples E1 and E3 can be easily derived from the friction coefficient measurements shown in FIG. In addition, the addition of lithium soap thickeners leads to a reduction in the coefficient of friction compared to grease compositions comprising calcium complex soaps.

The grease composition according to the invention leads to a low wear and low friction in the constant velocity joint, which has a desirable important influence on the coefficient of friction and wear and prevents the premature onset of rolling contact fatigue at the joint.

Claims (9)

In grease compositions for use in constant velocity joints, a) base oil mixture; And b) A grease composition for use in a constant velocity joint, comprising at least one trinuclear molybdenum compound, characterized in that it comprises at least one tri-nuclear molybdenum compound of 0.25 wt% to 5 wt% of the formula: Mo ₃ S _k L _n Q _z L is an independently selected ligand consisting of an organic group with a sufficient amount of carbon atoms to provide a compound that is soluble or dispersible in oil, n is from 1 to 4, k is changed from 4 to 7 , Q is selected from the group of compounds that contribute to neutral electrons such as amines, alcohols, phosphines and ethers, z ranges from 0 to 5 and includes nonstoichiometric values. The grease composition of claim 1 comprising at least one trinuclear molybdenum compound further comprising at least one zinc compound additive. 3. The composition for use in constant velocity joints according to claim 2 comprising at least one trinuclear molybdenum compound, characterized in that at least one zinc compound additive is contained in an amount of 0.1 wt% to 2.5 wt% relative to the total amount of the grease composition. Grease composition. The at least one trinuclear molybdenum of claim 3, wherein the zinc compound is selected from the group consisting of one or more of zinc dithiophosphate (ZnDTP), zinc dithiocarbamate (ZnDTC), ZnO and ZnS. Grease compositions for use in constant velocity joints, including compounds. The thickener according to any one of claims 1 to 4, further comprising a thickener selected from the group consisting of lithium soap, calcium soap, lithium complex soap, calcium complex soap and urea-derivative type thickener. A grease composition for use in a constant velocity joint, comprising at least one trinuclear molybdenum compound. 3. The base oil mixture of claim 1 or 2, wherein the base oil mixture comprises at least one trinuclear molybdenum compound, characterized in that it comprises at least one selected from poly-alpha-olefins, naphthenic oils, paraffinic oils and synthetic organic esters. Grease composition for use in constant velocity joints. 6. The at least one trinuclear molybdenum compound according to claim 5, further comprising an additive package selected from the group of agents consisting of antioxidants, corrosion inhibitors, antiwear agents, friction modifiers, and extreme pressure agents (EP agents). Grease composition for use in constant velocity joints, including. The process of claim 5, wherein in each case relative to the total amount of the grease composition, from 55 wt% to 97.5 wt% of the base oil mixture, from 0.3 wt% to 3 wt% of at least one trinuclear molybdenum compound, from 0.1 wt% to 1.5 A grease composition for use in a constant velocity joint comprising at least one zinc compound additive in wt% and at least one trinuclear molybdenum compound, each comprising from 2 wt% to 25 wt% of one or more thickeners. The grease composition for use in a constant velocity joint, comprising at least one trinuclear molybdenum compound, characterized in that the sliding friction coefficient of the grease composition is 0.1 or less.

Images