GREASE COMPOSITION FOR CONSTANT VELOCITY JOINTS

TECHNICAL FIELD

The present disclosure relates to a grease composition which is intended primarily for use in constant velocity joints (CV joints), especially ball joints and/or tripod joints, which are used in the driveline of motor vehicles. Further, the present disclosure relates to a constant velocity joint comprising the grease composition in accordance with the present disclosure.

BACKGROUND

Front-wheel drive cars have CV joints on both ends of the drive shafts (half shafts). Inner CV joints connect the drive shafts to the transmission. Outer CV joints connect the drive shafts to the wheels. Many rear-wheel drive and four-wheel drive cars as well as trucks have CV joints. CV joints or homokinetic joints allow the drive shaft to transmit power though a variable angle, at constant rotational speed, preferably without an appreciable increase in friction or play. In front-wheel drive cars, CV joints deliver the torque to the front wheels during turns.

There are two most commonly used types of CV joints: a ball-type and a tripod-type. In front-wheel drive cars, ball-type CV joints are used on the outer side of the drive shafts (outer CV joints), while the tripod-type CV joints mostly used on the inner side (inner CV joints). The motions of components within CV joints are complex with a combination of rolling and sliding. When the joints are under torque, the components are loaded together which can not only cause wear on the contact surfaces of the components, but also rolling contact fatigue and significant frictional forces between the surfaces.

Constant velocity joints also have sealing boots of elastomeric material which are usually of bellows shape, one end being connected to the outer part of the CV joint and the other end to the interconnecting or output shaft of the CV joint. The sealing boot retains the grease in the joint and keeps out dirt and water.

Not only must the grease reduce wear and friction and prevent the premature initiation of rolling contact fatigue in a CV joint, it must also be compatible with the elastomeric material of which the sealing boot is made. Otherwise there is a degradation of the sealing boot material which causes premature failure of the sealing boot, allowing the escape of the grease and ultimately failure of the CV joint. It is one of the most common problems with the CV joints when the protective sealing boot cracks or gets damaged. Once this happens, in addition to the escape of the grease, moisture and dirt get in, causing the CV joint to wear faster and eventually fail due to lack of lubrication and corrosion. Usually, outer CV joint sealing boots break first, as they have to endure more movement than the inner ones. If a CV joint itself is worn out, it cannot be repaired, it will have to be replaced with a new or reconditioned part. The two main types of material used for CV joint sealing boots are polychloroprene rubber (CR) and thermoplastic elastomer (TPE), especially ether-ester block co-polymer thermoplastic elastomer (TPC-ET).

Typical CV joint greases have base oils which are blends of naphthenic (saturated rings) and paraffinic (straight and branched saturated chains) mineral oils. Synthetic oils may also be added. It is known that said base oils have a large influence on the deterioration (swelling or shrinking) of both sealing boots made of CR and TPC-ET. Both mineral and synthetic base oils extract the plasticisers and other oil soluble protective agents from the sealing boot materials. Paraffinic mineral oils and poly-α-olefin (PAO) synthetic base oils diffuse very little into especially sealing boots, but on the other hand naphthenic mineral oils and synthetic esters diffuse into sealing boot materials like rubber and TPC-ET and act as plasticisers and can cause swelling. The exchange of plasticiser or plasticiser compositions for the naphthenic mineral oil can significantly reduce the sealing boot performance, especially at low temperatures, and may cause the sealing boot to fail by cold cracking, ultimately resulting in failure of the CV joint. If significant swelling or softening occurs, the maximum high-speed capability of the sealing boot is reduced due to the poor stability at speed and/or excessive radial expansion.

In order to solve the aforesaid problems, U.S. Pat. No. 5,670,461 A suggests a lubricating grease for high temperature use consisting essentially of 60 to 90% by weight (wt-%) of a base oil mixture comprising at least one mineral oil and at least one synthetic oil, 5 to 16% by weight of at least one urea compound as a thickener, wherein the at least one urea compound is a reaction product of at least one fatty amine and at least one isocyanate or at least one diisocyanate, 2 to 20% weight of calcium complex grease, 1 to 4% by weight of molybdenum disulfide, 0.2 to 1% by weight of graphite powder, 0.2 to 1% by weight of polytetrafluoroethylene powder, 0.2 to 1% weight of solid particles of at least one organic molybdenum compound selected from a molybdenum dithiocarbamate (MoDTC) and a molybdenum dithiophosphate, up to 2% by weight of a metal deactivator and up to 2% by weight of a corrosion inhibitor, in each case the amounts referring to the total amount of the grease composition. However, the sealing boot compatibility of the grease compositions according to U.S. Pat. No. 5,670,461 A as measured in a boot compatibility tests as well as the lifetime of the entire CV joint needs to be improved. This holds in particular for the lifetime of the CV joint measured in a Standard Multi Block Program (SMBP) test. There is a need of further enhancement due to the fact that the additives disclosed in said grease composition may reacted with the sealing boot material that leads to early aging which also may result in a premature failure of the sealing boot. Especially, polytetrafluoroethylene (PTFE) has to be recycled due to high environmental stability as well as reproductive toxicity and the export is subject to authorization nowadays. Further on, it is known that PTFE decomposes under mechanical stress and high temperatures. In particular, alkali metals could react with PTFE which indicates that reactive degradation products would be available in the lubricant grease. Alkali metals are used in thickeners or grease formulations, e.g., in U.S. Pat. No. 5,670,461 A, a calcium complex grease is used. Not only may degradation products formed in use of the CV joint attack the sealing material leading to early failure, but also PTFE vapor being toxic may result. Based on these facts, it is recommended to improve the grease compatibility and elongate the lifetime of the sealing boot material.

Like U.S. Pat. No. 5,670,461 A, most of the commercial CV joint lubricants contain molybdenum dithiophosphate (MoDTP) or molybdenum dithiocarbamate (MoDTC), which provides anti-wear and EP performance, in particular improved anti-friction properties at early running-times (run-in) of the CV joints. However, it is also known that molybdenum dithiophosphate (MoDTP) causes swelling and softening by decomposing the sealing boot material which may lead to an early aging of the complete sealing boot.

Further on, the often-used zinc dialkyldithiophosphate (ZnDTP) or molybdenum dialkyldithiophosphate (MoDTP) provide anti-wear performance based on a tribochemical reaction on the metal surfaces of CV joints. Thereby, a layer on the metal surface is formed.

The disadvantage especially of using phosphor-containing additives like ZnDTP and MoDTP is that they show no good compatibility with sealing materials, especially sealing boots. The dialkyldithiophosphate of ZnDTP or MoDTP reacts at high temperatures with the sealing boot material and causes early aging. Additionally, the sulphur and phosphor contained in ZnDTP is chemically activated which leads to further aging of the sealing boot material. In large quantities, the grease might therefore result in an early failure of the sealing boots used in CV joints.

It would be, thus, advantageous to reduce the negative chemical effects of at least the aforesaid components of grease compositions on the sealing boot material, while maintaining the overall lubricating properties, in order to achieve a longer lifetime of the entire CV joint.

SUMMARY

It is the object of the present disclosure to provide for a grease composition, primarily for use in CV joints, which has a good compatibility with sealing boots made of rubber or thermoplastic elastomer, and which also gives enhanced endurance in the entire CV joint.

Said object of the present disclosure is solved by a grease composition for use in constant velocity joints, preferably with boots made of at least one TPE, further preferably made of at least one TPC-EP, comprising

a) at least one base oil;

b) at least one thickener;

c) zinc sulfide; and

d) molybdenum disulfide and/or tungsten disulfide.

The disclosure also relates to the use of a grease composition in accordance with the description in constant velocity joints. Further, the disclosure relates to a constant velocity joint comprising a grease composition in accordance with the description.

The advantage of the present composition for use in constant velocity joints is that the use of MoDTP, MoDTC and PTFE is not required. Instead of MoDTP, MoDTC and PTFE, a combined formulation of zinc sulfide (ZnS) with molybdenum disulfide (MoS₂) and/or tungsten disulfide (WS₂) is used. Zinc sulfide incorporates two main characteristics which are good EP performance given by the sulphur and anti-wear performance provided by the zinc. Further on, it is proven that molybdenum disulfide as well as tungsten disulfide reduce friction, provide anti-wear and enhance EP performance in grease composition. The inventors have found that a grease composition featuring a combination of zinc sulfide with molybdenum disulfide and/or tungsten disulfide effectively replaces the additives MoDTC, MoDTP and ZnDTP as well as PTFE in the grease composition while maintaining the overall lubricating properties and enabling a longer lifetime of the entire CV joint, that may be proven for example by the Standard Multi Block Program (SMBP) test. In particular, the endurance under heavy application of the CV joint, as well as the compatibility with CV joint sealing boot material are improved by the grease composition in accordance with the present invention.

Zinc sulfide provides zinc in the amount of about 1700 ppm already in 0.25 wt-% (% by weight or weight percent, in connection with this disclosure the term wt-% is used in the following) zinc sulfide, whereas the same amount of zinc is present in 2 wt-% of ZnDTP without critical chemical activity inside the molecule, in each case the wt-% referring to the total amount of a grease composition. Organic metal salts, like ZnDTP and MoDTP, decompose under heavy application into an inorganic salt and an organic radical. The organic radical may react with the sealing boot material and may lead to earlier failure. Due to the fact that zinc sulphide is an inorganic salt, no organic decomposition product results under heat or heavy application. Therefore, the reaction of zinc sulfide with sealing boot material is minimized while the tribochemical properties are maintained.

It is also advantageous that the grease composition requires less material in terms of additives. Due to the fact that molybdenum disulfide and/or tungsten disulfide enhance the tribochemical properties of zinc sulfide as a kind of a synergistic effect, the needed amounts of these additives are further reduced. The already mentioned reduction of additive quantities also leads to improved economy in the production of the grease composition, also based on the fact that salts are used instead of elaborately synthesized organic metal compounds.

The inventors have found that molybdenum disulfide and/or tungsten disulfide in suitable amounts enables the zinc sulfide to provide advantageous anti-wear and, in particular, improved anti-friction properties. In this respect, the inventors have found that zinc sulfide in combination with molybdenum disulfide and/or tungsten disulfide increases the tribology performance in combination with organic sulphur-containing additive and organic phosphor-containing additive for the early running times (run-in) of the CV joints. Consequently, not only the known synergistic effect of the organic sulphur-containing additive with organic phosphor-containing additive improves the tribology performance, but also zinc sulfide in combination with molybdenum disulfide and/or tungsten disulfide act together synergistically. This synergistic effect is well shown on the friction coefficient and wear quantity measured by a standard SRV test.

As far as the term weight percent or % by weight is used with respect to the components being comprised from the claimed grease composition, the term weight percent is referred to the amount of one or more components relative to the total amount of the grease composition throughout this specification, except where expressively stated otherwise. The expression “wt-%” is used throughout the present invention as an abbreviation for weight percent if not indicated otherwise.

In the context of the invention, the expressions “about” and “approximately” in connection with numerical values or ranges are to be understood as a tolerance range, which a person skilled in the art would consider as common or reasonable based on his or her general knowledge and in view of the disclosure as a whole. In particular, the expressions “about” and “approximately” refer to a tolerance range of ±20%, preferably ±10% and further preferably ±5% with respect to the designated value. The lower end values and the upper end values of the various ranges, especially the weight percent ranges, but not restricted thereto, claimed in the present invention may be combined with each other in order to define new ranges.

Further, in the context of the present disclosure, all references to standards, norms, or standardization protocols, e.g., ISO, ASTM, etc., in connection with properties, numerical values or ranges referred to herein are to be understood as the latest updated version of said standard, norm, or standardisation protocol being in force at the date of filling of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1a and 1b are plots of experimental results for friction and wear, respectively, for a synergetic effect of a zinc sulfide additive to a grease composition.

FIGS. 2a and 2b are plots of experimental results for friction and wear, respectively, for a synergetic effect of a molybdenum disulfide (MoS₂) additive to the grease composition.

FIGS. 3a and 3b are plots of experimental results for friction and wear, respectively, for a comparison of a plurality of grease compositions according to this disclosure with a commercial grease.

FIGS. 4a and 4b are plots of experimental results for a compatibility test of sealing boot material and a life endurance time of a CV joint with the grease composition.

DETAILED DESCRIPTION

A grease composition, primarily for use in constant velocity joints, preferably with boots made of at least one TPE, further preferably made of at least one TPC-EP, includes at least one base oil, at least one thickener, zinc sulfide, and molybdenum disulfide and/or tungsten disulfide.

Preferably, the at least one base oil used in the grease composition in accordance with the present disclosure comprises poly-α-olefines, naphthenic oils, paraffinic oils, and/or synthetic organic esters. As at least one base oil according to the present invention, a base oil as disclosed in U.S. Pat. No. 6,656,890 B1 may preferably be used, the disclosure of which is incorporated insofar herein by reference. However, any further kind of base oil, especially a blend of mineral oils, a blend of synthetic oils or a blend of a mixture of mineral and synthetic oils may be used. The at least one base oil should preferably have a kinematic viscosity of between approximately 32 and approximately 250 mm²/s at 40° C. and between approximately 5 and approximately 25 mm²/s at 100° C. The mineral oils are preferably selected from the group comprising at least one naphthenic oil and/or at least one paraffinic oil. The synthetic oils usable in the present invention are selected from a group comprising at least one paraffinic and/or at least one naphthenic oil. The organic synthetic ester is preferably a di-carboxylic acid derivative having subgroups based on aliphatic alcohols. Preferably, the aliphatic alcohols have primary, straight or branched carbon chains with 2 to 20 carbon atoms. Preferably, the organic synthetic ester is selected from a group comprising sebacic acid-bis(2-ethylhexylester) (“dioctyl sebacate” (DOS)), adipic acid-bis-(2-ethylhexylester) (“dioctyl adipate” (DOA)), dioctyl phthalate (DOP) and/or azelaic acid-bis(2-ethylhexylester) (“dioctyl azelate (DOZ)). If poly-α-olefin is present in the base oil, the poly-α-olefin is preferably selected from a group comprised of 1-dodecene oligomer, 1-decene oligomer, 1-octene or a mixture thereof, and even more preferably a copolymer comprising 1-octene, poly-1-decene oligomer, poly-1-dodecene oligomer or a mixture thereof, wherein the poly-1-decene oligomer and the poly-1-dodecene oligomer could be dimeric, trimeric, tetrameric, pentameric or higher. Preferably, poly-α-olefins are selected having a kinematic viscosity (ASTM D445) in a range from approximately 2 to approximately 60 centistokes at 40° C. The naphthenic oils selected for the at least one base oil have preferably a kinematic viscosity in a range between approximately 3 to approximately 370 mm²/s, more preferably approximately 20 to approximately 150 mm²/s at 40° C. The density (measured in accordance with ASTM D1250) is approximately 0.9 up to approximately 1.0 g/cm³at 15.6° C. The paraffinic oils present in the at least one base oil are preferably selected from a group comprising linear, branched and cyclic saturated alkanes of polyolefins, hydroisomerized Fischer-Tropsch wax, and Fischer-Tropsch oligomerized olefins, preferably isoparaffins, cycloparaffins containing mono-ring and/or multi-ring structures. Preferably the paraffinic oils have a kinematic viscosity in a range between approximately 9 to approximately 170 mm²/s at 40° C., preferably approximately 50 to approximately 130 mm²/s at 40° C. The at least one base oil is preferably present in the grease composition in accordance with the present invention in an amount of approximately 60 wt-% up to approximately 95 wt-% and further preferred in an amount of approximately 63 wt-% up to approximately 93 wt-%, further preferred in an amount of approximately 75 wt-% up to approximately 92.5 wt-%, further preferred in an amount of approximately 78 wt-% up to approximately 92 wt-%, and even further preferred in an amount of approximately 79 wt-% up to approximately 92 wt-%, in each case referred to the total amount of the grease composition in accordance with the present invention. The at least one base oil may comprise at least one paraffinic oil in an amount of approximately 30 wt-% up to approximately 85 wt-%, further preferred of approximately 35 wt-% up to approximately 75 wt-%, and even further preferred in an amount of approximately 37 wt-% up to approximately 72 wt-%, in each case referred to the total amount of the base oil. Further on, the at least one base oil may comprise at least one naphthenic oil in an amount approximately 15 wt-% up to approximately 80 wt-%, further preferred in an amount of approximately 15 wt-% up to approximately 75 wt-%, and even further preferred in an amount approximately 15 wt-% up to approximately 70 wt-%, in each case referred to the total amount of the base oil. The term base oil as used in the present invention is understood in the sense that the base oil may also be a base oil composition that consists of various components, and, especially, that the base oil is a composition comprising poly-α-olefines, naphthenic oils, paraffinic oils, and/or synthetic organic esters. Preferably, the at least one base oil comprises the at least one paraffinic oil in an amount of approximately 30 wt-% up to approximately 85 wt-%, further preferred of approximately 35 wt-% up to approximately 75 wt-%, and even further preferred approximately 37 wt-% up to approximately 72 wt-%, and at least one naphthenic oil in an amount of approximately 15 wt-% up to approximately 70 wt-%, further preferred approximately 15 wt-% up to approximately 65 wt-%, and even further preferred approximately 15 wt-% up to approximately 62 wt-%, in each case referred to the total amount of the base oil.

The at least one thickener is preferably a lithium soap thickener or an urea thickener, of which the use of a lithium soap thickener is most preferred. A lithium soap thickener is a reaction product of at least one fatty acid with lithiumhydroxide. Preferably, the thickener may be a simple lithium soap formed from stearic acid, 12-hydroxy stearic acid, hydrogenated castor oil or from other similar fatty acids or mixtures thereof or methylesters of such acids. Alternatively a lithium complex soap may be used formed for example from a mixture of long-chained fatty acids together with a complexing agent, for example a borate of one or more dicarboxylic acids. The use of complex lithium soaps allows the grease composition according to the present invention to operate up to a temperature of about 180° C., whereas with simple lithium soaps, the grease composition will only operate up to a temperature of about 120° C. The urea thickener may be chosen among diurea compounds as well as polyurea compounds. For example, diurea compounds are selected from a group obtained through a reaction of monoamine with a diisocyanate compound such as phenylene diisocyanate, diphenyl diisocyanate, phenyl diisocyanate, diphenylmethane diisocyanate, octadecane diisocyanate, decane diisocyanate and hexane diisocyanate, examples of such monoamines are octylamine, dodecylamine, hexadecylamine, octadecylamine, oleylamine, aniline, p-toluidine, and cyclohexylamine; polyurea compounds are selected from a group obtained through a reaction of diamine with a diisocyante compound such as diisocyanates as mentioned above and diamines include ethylenediamine, propanediamine, butanediamin, hexanediamine, octanediamine, phenylenediamine, tolylenediamine, and xylenediamine; or urea thickeners are selected from a group obtained through a reaction of aryl amine such as p-toluidine or aniline, cyclohexyl amine or a mixture thereof with diisocyante. The aryl group of the diurea compound, if present, is preferably comprised of 6 or 7 carbon atoms. However, mixtures of all of the aforesaid thickeners such as lithium soap thickeners and urea thickeners may also be used. The at least one thickener is preferably present in an amount of approximately 2 wt-% up to approximately 20 wt-%, further preferred in an amount of approximately 4.0 wt-% up to approximately 17.0 wt-%, in each case referred to the total amount of the grease composition in accordance with the present disclosure.

Zinc sulfide is present in a solid state. Zinc sulfide naturally occurs as cubic sphalerite or hexagonal wurtzite. Preferably industrial produced zinc sulfide powder is used, however, the crystalline structure is not further distinguished. The preferred zinc sulfide is a colorless and odourless powder with a main grain size D₉₀of 0.80 μm by a CLIAS 1064 Nass regarding ISO 13320. Further on, the density at 20° C. is up to 4.0 g/cm³, and the melting point is greater than 800° C. (sublimating). The decomposition temperature is greater than 600° C.

Zinc sulfide is present in an amount of approximately 0.1 wt-% up to approximately 2.0 wt-%, further preferred in an amount of approximately 0.2 wt-% up to approximately 1 wt-%, in each case referred to the total amount of the grease composition in accordance with the present disclosure.

The grease composition comprises molybdenum disulfide and/or tungsten disulfide. Molybdenum disulfide (molybdenum(IV) sulfide, MoS₂) is preferably used over molybdenum(VI) sulfide (MoS₃) and/or molybdenum (V) sulfide (Mo₂S₅). In the grease composition, molybdenum disulfide super fine powder is preferably used over crystals, dispersions or even as solutions in water or ethanol. The preferred used super fine molybdenum disulfide powder has a purity of 97 wt-%, a Fisher number of 0.40 up to 0.50 μm, further a particle size distribution D₉₀of 7.0 μm by laser diffraction instrument, Microtrac X100²with the standardization of ISO 13320, and a bulk density of 0.4 g/cm³. To protect molybdenum disulfide before oxidation, preferably an anti-oxidation agent might be used. Tungsten disulfide (tungsten(IV) sulfide, WS₂) is present in a solid state like molybdenum disulfide (MoS₂), more preferably as dark grey powder than as crystal, dispersion or even as solution in water or ethanol. The dark grey tungsten disulfide powder has preferably an average particle size D₉₀of 4 μm and a density of 7.5 g/cm³. Tungsten disulfide is a thermostable compound. Molybdenum disulfide and/or tungsten disulfide provides for a reduction of friction and anti-wear performance as well as EP performance.

In the grease compositions, the combination of zinc sulfide with molybdenum disulfide and/or tungsten disulfide shows a synergistic effect in the SRV test for the anti-wear and anti-friction properties of CV joints. In an example, the composition does not comprise any organic molybdenum-containing compounds. The molybdenum disulfide and/or tungsten disulfide is preferably present in an amount of approximately 0.5 wt-% up to approximately 5.0 wt-%, further preferred in an amount of approximately 1.0 wt-% up to approximately 3.0 wt-%, in each case referred to the total amount of the grease composition in accordance with the present invention. Molybdenum disulfide and/or tungsten disulfide is present in a total amount (in wt-%) relative to the amount (in wt-%) of zinc sulfide, also in combination with each other, in a range between approximately 1:1 to approximately 20:1, preferably in a range between approximately 3:1 to approximately 10:1. The total amount of zinc sulfide, molybdenum disulfide and/or tungsten disulfide is between approximately 0.6 wt-% up to approximately 7 wt-%, and further preferred approximately 1.2 wt-% up to approximately 4 wt-%, in each case referred to the total amount of the grease composition in accordance with the present disclosure.

It is also possible to include in the grease composition various known grease additives such as anti-oxidation agents, antirust agents, extreme-pressure (EP) modifier agents, anti-wear agents and oil-improvers. Preferably comprised in the grease composition are the following grease additives.

In an example, at least one grease additive containing a sulphur-containing EP modifier agent and/or a phosphorous-containing EP modifier agent is present that enhances the tribochemical effect of zinc sulfide with molybdenum disulfide and/or tungsten disulfide by a preferred simultaneous reduction of the needed amounts of molybdenum disulfide and/or tungsten disulfide. In the context of the present disclosure, the expression sulphur-containing EP modifier agent is referred to as organic sulfur-additive and the expression phosphor-containing EP modifier agent is referred to as organic phosphor-additive in the following description.

In a further example, at least one organic sulphur-additive is comprised containing at least 10 wt-% sulphur, the wt-% referring to the total amount of organic sulphur-additive. ZnDTP, ZnDTC, MoDTP and MoDTC are not considered in the sense of the present invention to be encompassed by the term organic sulphur-additives. In a further example, the at least one organic sulphur-additive is selected from a group comprising at least one olefin sulfide, alkyl thiadiazole or a combination of it. The olefin sulfide may comprise olefin monomers of ethylene, propylene, butane-1 and/or 4-methylpentene. The alkyl thiadiazole may comprise thiadiazole monomers of 1,2,3-thiadiazole, 1,2,4-thiadiazole, 1,2,5-thiadiazole and/or 1,3,4-thiadiazole. The at least one organic sulphur-additive is preferably present in an amount of approximately 0.2 wt-% up to approximately 1.0 wt-%, further preferred in an amount of approximately 0.5 wt-% up to approximately 0.7 wt-%, in each case referred to the total amount of the grease composition in accordance with the present disclosure. Further on, the at least one organic sulphur-additive comprises sulphur in an amount of at least 10 wt-%, and even more preferred between approximately 20 wt-% up to approximately 70 wt-%, the wt-% referring to the total amount of the organic sulphur-additive.

In a further example, at least one organic phosphor-additive is present in the grease composition in accordance with the present disclosure. The intended organic phosphor-additive neither is a metallic salt nor contains sulphur like ZnDTP or MoDTP. The comprised phosphor should be less activated than in the aforesaid additives to be avoided. Most important is that the at least one organic phosphor-additive is compatible with the sealing boot material which means that the organic phosphor-additive does not lead to degradation of the sealing boot, swelling or shrinking of the sealing boot material The at least one organic phosphor-additive is preferably selected from a group comprising tri-substituted organic phosphates, such as iso-butyl phosphate (TiBP) which is a derivative of phosphoric acid (H₃PO₄), where all hydrogen are substituted, for example in TiBP by iso-butyl. This special design provides an at least one organic phosphor-additive which is relatively inactive in comparison to usual phosphorous additives with only one or two substituted hydrogen atoms of the phosphoric acid by an organic sidechain. Tri-iso-butyl phosphate (TiBP) as a preferred example of a trisubstituted organic phosphor-additive provides for an enhanced EP performance and a temperature independent viscosity with a limited interaction with the sealing boot material which results in an elongated lifetime of the CV joint proven by the SMBP test. The at least one organic phosphor-additive is preferably present in an amount of approximately 0.2 wt-% up to approximately 2.0 wt-%, further preferred in an amount of approximately 0.3 wt-% up to approximately 1.0 wt-%, in each case referred to the total amount of the grease composition in accordance with the present disclosure.

In a further example, at least one anti-oxidation agent is present in the grease composition. As an at least one anti-oxidation agent, the grease composition may comprise an amine, preferably an aromatic amine, more preferably benzamine, N-phenyl compounds reacted with 2,4,4-trimethylpentene or selected from the group of octylated/butylated diphenylamine, more preferably dioctyl diphenylamine, octyl diphenylamine, octyl/styryl diphenylamine, diheptyl diphenylamine, dinonyl diphenylamine or a mixture thereof. Preferably, the at least one anti-oxidation agent is selected having a kinematic viscosity (in accordance with ASTM D445) in a range of approximately 250 to approximately 370 mm²/s at 40° C. and a density (in accordance with ASTM D1298) of approximately 0.9 to approximately 1.0 g/cm³at 20° C. The at least one anti-oxidation agent is used to prevent deterioration of the grease composition associated with oxidation. The grease composition may comprise at least one anti-oxidation agent in a range between approximately 0.1 wt-% to approximately 2 wt-%, referred to the total amount to the grease composition, in order to inhibit the oxidation degradation of the at least one base oil and/or molybdenum disulfide, as well as to lengthen the life of the grease composition, thus prolonging the life of the CV joint. The at least one anti-oxidation agent is preferably present in an amount of approximately 0.1 wt-% up to approximately 2.0 wt-%, further preferred in an amount of approximately 0.2 wt-% up to approximately 1.5 wt-%, in each case referred to the total amount of the grease composition in accordance with the present disclosure.

Further, the grease composition described herein can be used in CV joints. The CV joint especially encompasses a sealing boot, the boot being filled with the grease composition described herein, at least in part, the sealing boot having a first attachment region which is assigned to a joint, and a second attachment region which is assigned to a shaft. The sealing boot may be fixed with usual clamp devices on the joint and/or shaft.

In an example, a grease composition is defined comprising approximately 60 wt-% to approximately 95 wt-% of at least one base oil, approximately 2 wt-% to approximately 20 wt-% of at least one thickener, approximately 0.1 wt-% to approximately 2.0 wt-% of zinc sulfide, approximately 0.5 wt-% to approximately 5.0 wt-% of molybdenum disulfide and/or tungsten disulfide and approximately 0.2 wt-% to approximately 1.0 wt-% of at least one organic sulphur-additive in each case the wt-% referring to the total amount of the grease composition.

In a further example, a grease composition is defined comprising approximately 60 wt-% to approximately 95 wt-% of at least one base oil, approximately 2 wt-% to approximately 20 wt-% of at least one thickener, approximately 0.1 wt-% to approximately 2.0 wt-% of zinc sulfide, approximately 0.5 wt-% to approximately 5.0 wt-% of molybdenum disulfide and/or tungsten disulfide, approximately 0.2 wt-% to approximately 1.0 wt-% of at least one organic sulphur-additive and approximately 0.2 wt-% to approximately 1.0 wt-% of at least one organic phosphor-additive, in each case the wt-% referring to the total amount of the grease composition.

In a further example, the grease composition comprises approximately 60 wt-% to approximately 95 wt-% of at least one base oil, approximately 2 wt-% to approximately 20 wt-% of at least one thickener, approximately 0.1 wt-% to approximately 2.0 wt-% of zinc sulfide, approximately 0.5 wt-% to approximately 5.0 wt-% of molybdenum disulfide and/or tungsten disulfide, approximately 0.2 wt-% to approximately 1.0 wt-% of at least one organic sulphur-additive and approximately 0.2 wt-% to approximately 1.0 wt-% of at least one organic phosphor-additive, in each case the wt-% referring to the total amount of the grease composition, whereat the at least one base oil preferred comprises at least one paraffinic oil in an amount of approximately 30 wt-% up to approximately 85 wt-%, the latter amount referring to the total amount of the base oil, whereat the paraffinic oil is preferably selected from a group comprising linear, branched and cyclic saturated alkanes of polyolefins, hydroisomerized Fischer-Tropsch wax, and Fischer-Tropsch oligomerized olefins, preferably isoparaffins, cycloparaffins containing mono-ring and/or multi-ring structures.

In a further example, the grease composition comprises approximately 60 wt-% to approximately 95 wt-% of at least one base oil, approximately 2 wt-% to approximately 20 wt-% of at least one thickener, approximately 0.1 wt-% to approximately 2.0 wt-% of zinc sulfide, approximately 0.5 wt-% to approximately 5.0 wt-% of molybdenum disulfide and/or tungsten disulfide, approximately 0.2 wt-% to approximately 1.0 wt-% of at least one organic sulphur-additive and approximately 0.2 wt-% to approximately 1.0 wt-% of at least one organic phosphor-additive, in each case the wt-% referring to the total amount of the grease composition, whereat the at least one base oil may comprise at least one naphthenic oil in an amount approximately 15 wt-% up to approximately 80 wt-%, the latter amount referring to the total amount of the base oil, whereat the naphthenic oil is preferably selected from a group comprising saturated cyclic alkanes.

In a further example, the grease composition comprises approximately 60 wt-% to approximately 95 wt-% of at least one base oil, approximately 2 wt-% to approximately 20 wt-% of at least one thickener, approximately 0.1 wt-% to approximately 2.0 wt-% of zinc sulfide, approximately 0.5 wt-% to approximately 5.0 wt-% of molybdenum disulfide and/or tungsten disulfide, approximately 0.2 wt-% to approximately 1.0 wt-% of at least one organic sulphur-additive and approximately 0.2 wt-% to approximately 1.0 wt-% of at least one organic phosphor-additive, in each case the wt-% referring to the total amount of the grease composition, whereat the at least one thickener is selected from a group comprising lithium soap thickener and urea thickener, preferably the lithium soap thickener is a reaction product of at least one fatty acid with lithiumhydroxide and the urea thickener is at least one compound of diurea and/or polyurea.

In a further example, the grease composition comprises approximately 60 wt-% to approximately 95 wt-% of at least one base oil, approximately 2 wt-% to approximately 20 wt-% of at least one thickener, approximately 0.1 wt-% to approximately 2.0 wt-% of zinc sulfide, approximately 0.5 wt-% to approximately 5.0 wt-% of molybdenum disulfide and/or tungsten disulfide, approximately 0.2 wt-% to approximately 1.0 wt-% of at least one organic sulphur-additive and approximately 0.2 wt-% to approximately 1.0 wt-% of at least one organic phosphor-additive, in each case the wt-% referring to the total amount of the grease composition, whereat the molybdenum disulfide is present in a total amount (in wt-%) relative to the amount (in wt-%) of zinc sulfide in a range between approximately 1:1 to approximately 20:1, preferably in a range between approximately 3:1 to approximately 10:1.

In a further example, the grease composition comprises approximately 60 wt-% to approximately 95 wt-% of at least one base oil, approximately 2 wt-% to approximately 20 wt-% of at least one thickener, approximately 0.1 wt-% to approximately 2.0 wt-% of zinc sulfide, approximately 0.5 wt-% to approximately 5.0 wt-% of molybdenum disulfide and/or tungsten disulfide, approximately 0.2 wt-% to approximately 1.0 wt-% of at least one organic sulphur-additive and approximately 0.2 wt-% to approximately 1.0 wt-% of at least one organic phosphor-additive, in each case the wt-% referring to the total amount of the grease composition, whereat the at least one organic sulphur-additive comprises sulphur in an amount of at least 10 wt-%, and even more preferred between approximately 20 wt-% up to approximately 70 wt-%, the wt-% referring to the total amount of the organic sulphur-additive, and whereat the at least one organic sulphur-additive is preferably selected from a group comprising at least one alkyl thiadiazole or olefin sulfide made up of reaction products with olefin monomers as ethylene, propylene, butane-1 and/or 4-methylpentene.

In a further example, the grease composition comprises approximately 60 wt-% to approximately 95 wt-% of at least one base oil, approximately 2 wt-% to approximately 20 wt-% of at least one thickener, approximately 0.1 wt-% to approximately 2.0 wt-% of zinc sulfide, approximately 0.5 wt-% to approximately 5.0 wt-% of molybdenum disulfide and/or tungsten disulfide, approximately 0.2 wt-% to approximately 1.0 wt-% of at least one organic sulphur-additive and approximately 0.2 wt-% to approximately 1.0 wt-% of at least one organic phosphor-additive, whereat at least one organic phosphor-additive is preferably present in an amount of approximately 0.2 wt-% up to approximately 2.0 wt-%, further preferred in an amount of approximately 0.5 wt-% up to approximately 1.0 wt-%, in each case the wt-% referring to the total amount of the grease composition, whereat the at least one organic phosphor-additive is preferably selected from a group comprising tri-substituted organic phosphates, further preferred iso-butyl phosphate (TiBP).

In a further example, the grease composition comprises approximately 60 wt-% to approximately 95 wt-% of at least one base oil, approximately 2 wt-% to approximately 20 wt-% of at least one thickener, approximately 0.1 wt-% to approximately 2.0 wt-% of zinc sulfide, approximately 0.5 wt-% to approximately 5.0 wt-% of molybdenum disulfide and/or tungsten disulfide, approximately 0.2 wt-% to approximately 1.0 wt-% of at least one organic sulphur-additive and approximately 0.2 wt-% to approximately 1.0 wt-% of at least one organic phosphor-additive, in each case the wt-% referring to the total amount of the grease composition, whereat the at least one anti-oxidation agent is preferably an amine, more preferably an aromatic amine, even more preferably benzamine and/or N-phenyl compounds reacted with 2,4,4-trimethylpentene or selected from the group of octylated/butylated diphenylamine, more preferably dioctyl diphenylamine, octyl diphenylamine, octyl/styrryl diphenylamine, diheptyl diphenylamine, dinonyl diphenylamine or a mixture thereof.

In a further example, the grease composition comprises approximately 79 wt-% to approximately 92 wt-% of at least one base oil, approximately 4 wt-% to approximately 17 wt-% of at least one thickener, approximately 0.2 wt-% to approximately 1.0 wt-% of zinc sulfide, approximately 1.0 wt-% to approximately 3.0 wt-% of molybdenum disulfide and/or tungsten disulfide, approximately 0.5 wt-% to approximately 0.7 wt-% of at least one organic sulphur-additive and approximately 0.2 wt-% to approximately 1.0 wt-% of at least one organic phosphor-additive, in each case the wt-% referring to the total amount of the grease composition, whereat the at least one base oil comprises of poly-α-olefins and/or naphthenic oils and/or paraffinic oils and/or synthetic organic esters, whereat the at least one base oil preferably comprises at least one paraffinic oil in an amount of approximately 30 wt-% up to approximately 85 wt-%, the wt-% referring to the total amount of the base oil, whereat the paraffinic oil is preferably selected from a group comprising linear, branched and cyclic saturated alkanes of poyolefins, hydroisomerized Fischer-Tropsch wax, and Fischer-Tropsch oligomerized olefins, preferably isoparaffins, cycloparaffins containing mono-ring and/or multi-ring structures, whereat the at least one base oil further comprises at least one naphthenic oil in an amount of approximately 15 wt-% up to approximately 80 wt-%, the wt-% referring to the total amount of the base oil, whereat the at least one naphthenic oil comprises preferably saturated cyclic alkanes, whereat the at least one thickener is selected from a group comprising lithium soap thickener and urea thickener, whereby the lithium soap thickener is preferably a reaction product of at least one fatty acid with lithiumhydroxide and the urea thickener is preferably at least selected from a group consisting of diurea and/or polyuria, whereat zinc sulfide with molybdenum disulfide and/or tungsten disulfide are preferably in a solid state, whereat the molybdenum disulfide and/or tungsten disulfide is preferably present in a total amount (in wt-%) relative to the amount (in wt-%) of zinc sulfide in a range between approximately 1:1 to approximately 20:1, preferably in a range between approximately 3:1 to approximately 10:1, whereat the total amount of zinc sulfide with molybdenum disulfide and/or tungsten disulfide is between approximately 0.6 wt-% up to approximately 7 wt-%, and further preferred between approximately 1.2 wt-% up to approximately 4 wt-%, in each case the wt-% referring to the total amount of the grease composition, whereat the at least one organic sulphur-additive comprises sulphur in an amount of at least 10 wt-%, even more preferred between approximately 20 wt-% up to approximately 70 wt-%, the wt-% referring to the total amount of the organic sulphur-additive, whereat the at least one organic sulphur-additive is preferably selected from a group consisting of at least one alkyl thiadiazole or an olefin sulfide made up of reaction products with olefin monomers as ethylene, propylene, butane-1 and/or 4-methylpentene, whereat the at least one organic phosphor-additive is preferably present in an amount of approximately 0.2 wt-% up to approximately 2.0 wt-%, further preferred in an amount of approximately 0.3 wt-% up to approximately 1.0 wt-%, in each case the wt-% referring to the total amount of the grease composition, whereat the at least one organic phosphor-additive is preferably selected from a group consisting of tri-substituted organic phosphates, further preferred iso-butyl phosphate (TiBP), whereat the at least one anti-oxidation agent is preferably an amine, more preferably an aromatic amine, even more preferably benzamine and/or N-phenyl compounds reacted with 2,4,4-trimethylpentene or selected from the group of octylated/butylated diphenylamine, more preferably dioctyl diphenylamine, octyl diphenylamine, octyl/styrryl diphenylamine, diheptyl diphenylamine, dinonyl diphenylamine or a mixture thereof.

In a further example, a grease composition is defined comprising approximately 60 wt-% to approximately 95 wt-% of at least one base oil, approximately 2 wt-% to approximately 20 wt-% of at least one thickener, approximately 0.1 wt-% to approximately 2.0 wt-% of zinc sulfide, approximately 0.5 wt-% to approximately 5.0 wt-% of molybdenum disulfide and/or tungsten disulfide, approximately 0.2 wt-% to approximately 1.0 wt-% of at least one organic sulphur-additive, approximately 0.2 wt-% to approximately 1.0 wt-% of at least one organic phosphor-additive, and approximately 0.1 wt-% to approximately 2.0 wt-% of at least one anti-oxidation agent, in each case the wt-% referring to the total amount of the grease composition.

In a further example, the grease composition comprises approximately 60 wt-% to approximately 95 wt-% of at least one base oil, approximately 2 wt-% to approximately 20 wt-% of at least one thickener, approximately 0.1 wt-% to approximately 2.0 wt-% of zinc sulfide, approximately 0.5 wt-% to approximately 5.0 wt-% of molybdenum disulfide and/or tungsten disulfide, approximately 0.2 wt-% to approximately 1.0 wt-% of at least one organic sulphur-additive, approximately 0.2 wt-% to approximately 1.0 wt-% of at least one organic phosphor-additive, and approximately 0.1 wt-% to approximately 2.0 wt-% of at least one anti-oxidation agent, in each case the wt-% referring to the total amount of the grease composition, whereat the at least one base oil preferred comprises at least one paraffinic oil in an amount of approximately 30 wt-% up to approximately 85 wt-%, the wt-% referring to the total amount of the base oil, whereat the paraffinic oil is preferably selected from a group comprising linear, branched and cyclic saturated alkanes of polyolefins, hydroisomerized Fischer-Tropsch wax, and Fischer-Tropsch oligomerized olefins, preferably isoparaffins, cycloparaffins containing mono-ring and/or multi-ring structures.

In a further example, the grease composition comprises approximately 60 wt-% to approximately 95 wt-% of at least one base oil, approximately 2 wt-% to approximately 20 wt-% of at least one thickener, approximately 0.1 wt-% to approximately 2.0 wt-% of zinc sulfide, approximately 0.5 wt-% to approximately 5.0 wt-% of molybdenum disulfide and/or tungsten disulfide, approximately 0.2 wt-% to approximately 1.0 wt-% of at least one organic sulphur-additive, approximately 0.2 wt-% to approximately 1.0 wt-% of at least one organic phosphor-additive, and approximately 0.1 wt-% to approximately 2.0 wt-% of at least one anti-oxidation agent, in each case the wt-% referring to the total amount of the grease composition, whereat the at least one base oil may comprise at least one naphthenic oil in an amount approximately 15 wt-% up to approximately 80 wt-%, the wt-% referring to the total amount of the base oil, whereat the naphthenic oil is preferably selected from a group comprising saturated cyclic alkanes.

In a further example, the grease composition comprises approximately 60 wt-% to approximately 95 wt-% of at least one base oil, approximately 2 wt-% to approximately 20 wt-% of at least one thickener, approximately 0.1 wt-% to approximately 2.0 wt-% of zinc sulfide, approximately 0.5 wt-% to approximately 5.0 wt-% of molybdenum disulfide and/or tungsten disulfide, approximately 0.2 wt-% to approximately 1.0 wt-% of at least one organic sulphur-additive, approximately 0.2 wt-% to approximately 1.0 wt-% of at least one organic phosphor-additive, and approximately 0.1 wt-% to approximately 2.0 wt-% of at least one anti-oxidation agent, in each case the wt-% referring to the total amount of the grease composition, whereat the at least one thickener is selected from a group comprising lithium soap thickener and urea thickener, preferably the lithium soap thickener is a reaction product of at least one fatty acid with lithiumhydroxide and the urea thickener is at least one compound of diurea and/or polyurea.

In a further example, the grease composition comprises approximately 60 wt-% to approximately 95 wt-% of at least one base oil, approximately 2 wt-% to approximately 20 wt-% of at least one thickener, approximately 0.1 wt-% to approximately 2.0 wt-% of zinc sulfide, approximately 0.5 wt-% to approximately 5.0 wt-% of molybdenum disulfide and/or tungsten disulfide, approximately 0.2 wt-% to approximately 1.0 wt-% of at least one organic sulphur-additive, approximately 0.2 wt-% to approximately 1.0 wt-% of at least one organic phosphor-additive, and approximately 0.1 wt-% to approximately 2.0 wt-% of at least one anti-oxidation agent, in each case the wt-% referring to the total amount of the grease composition, whereat the molybdenum disulfide and/or tungsten disulfide is present in a total amount (in wt-%) relative to the amount (in wt-%) of zinc sulfide, also in combination with each other, in a range between approximately 1:1 to approximately 20:1, preferably in a range between approximately 3:1 to approximately 10:1.

In a further example, the grease composition comprises approximately 60 wt-% to approximately 95 wt-% of at least one base oil, approximately 2 wt-% to approximately 20 wt-% of at least one thickener, approximately 0.1 wt-% to approximately 2.0 wt-% of zinc sulfide, approximately 0.5 wt-% to approximately 5.0 wt-% of molybdenum disulfide and/or tungsten disulfide, approximately 0.2 wt-% to approximately 1.0 wt-% of at least one organic sulphur-additive, approximately 0.2 wt-% to approximately 1.0 wt-% of at least one organic phosphor-additive, and approximately 0.1 wt-% to approximately 2.0 wt-% of at least one anti-oxidation agent, whereat the total amount of zinc sulfide with molybdenum disulfide and/or tungsten disulfide is between approximately 0.6 wt-% up to approximately 7 wt-%, and further preferred approximately 1.2 wt-% up to approximately 4 wt-%, in each case the wt-% referring to the total amount of the grease composition.

In a further example, the grease composition comprises approximately 60 wt-% to approximately 95 wt-% of at least one base oil, approximately 2 wt-% to approximately 20 wt-% of at least one thickener, approximately 0.1 wt-% to approximately 2.0 wt-% of zinc sulfide, approximately 0.5 wt-% to approximately 5.0 wt-% of molybdenum disulfide and/or tungsten disulfide, approximately 0.2 wt-% to approximately 1.0 wt-% of at least one organic sulphur-additive, approximately 0.2 wt-% to approximately 1.0 wt-% of at least one organic phosphor-additive, and approximately 0.1 wt-% to approximately 2.0 wt-% of at least one anti-oxidation agent, in each case the wt-% referring to the total amount of the grease composition, whereat the at least one organic sulphur-additive comprises sulphur in an amount of at least 10 wt-%, and even more preferred between approximately 20 wt-% up to approximately 70 wt-%, the wt-% referring to the total amount of the organic sulphur-additive, and whereat the at least one organic sulphur-additive is preferably selected from a group comprising at least one alkyl thiadiazole or olefin sulfide made up of reaction products with olefin monomers as ethylene, propylene, butane-1 and/or 4-methylpentene.

In a further example, the grease composition comprises approximately 60 wt-% to approximately 95 wt-% of at least one base oil, approximately 2 wt-% to approximately 20 wt-% of at least one thickener, approximately 0.1 wt-% to approximately 2.0 wt-% of zinc sulfide, approximately 0.5 wt-% to approximately 5.0 wt-% of molybdenum disulfide and/or tungsten disulfide, approximately 0.2 wt-% to approximately 1.0 wt-% of at least one organic sulphur-additive, approximately 0.2 wt-% to approximately 1.0 wt-% of at least one organic phosphor-additive, and approximately 0.1 wt-% to approximately 2.0 wt-% of at least one anti-oxidation agent, whereat at least one organic phosphor-additive is preferably present in an amount of approximately 0.2 wt-% up to approximately 2.0 wt-%, further preferred in an amount of approximately 0.5 wt-% up to approximately 1.0 wt-%, in each case the wt-% referring to the total amount of the grease composition, whereat the at least one organic phosphor-additive is preferably selected from a group comprising tri-substituted organic phosphates, further preferred iso-butyl phosphate (TiBP).

In a further example, the grease composition comprises approximately 60 wt-% to approximately 95 wt-% of at least one base oil, approximately 2 wt-% to approximately 20 wt-% of at least one thickener, approximately 0.1 wt-% to approximately 2.0 wt-% of zinc sulfide, approximately 0.5 wt-% to approximately 5.0 wt-% of molybdenum disulfide and/or tungsten disulfide, approximately 0.2 wt-% to approximately 1.0 wt-% of at least one organic sulphur-additive, approximately 0.2 wt-% to approximately 1.0 wt-% of at least one organic phosphor-additive, and approximately 0.1 wt-% to approximately 2.0 wt-% of at least one anti-oxidation agent, in each case the wt-% referring to the total amount of the grease composition, whereat the at least one anti-oxidation agent is preferably an amine, more preferably an aromatic amine, even more preferably benzamine and/or N-phenyl compounds reacted with 2,4,4-trimethylpentene or selected from the group of octylated/butylated diphenylamine, more preferably dioctyl diphenylamine, octyl diphenylamine, octyl/styrryl diphenylamine, diheptyl diphenylamine, dinonyl diphenylamine or a mixture thereof.

In a further example, the grease composition comprises approximately 79 wt-% to approximately 92 wt-% of at least one base oil, approximately 4 wt-% to approximately 17 wt-% of at least one thickener, approximately 0.2 wt-% to approximately 1.0 wt-% of zinc sulfide, approximately 1.0 wt-% to approximately 3.0 wt-% of molybdenum disulfide and/or tungsten disulfide, approximately 0.5 wt-% to approximately 0.7 wt-% of at least one organic sulphur-additive, approximately 0.2 wt-% to approximately 1.0 wt-% of at least one organic phosphor-additive, and approximately 0.2 wt-% to approximately 1.5 wt-% of at least one anti-oxidation agent, in each case the wt-% referring to the total amount of the grease composition, whereat the at least one base oil comprises of poly-α-olefins and/or naphthenic oils and/or paraffinic oils and/or synthetic organic esters, whereat the at least one base oil preferably comprises at least one paraffinic oil in an amount of approximately 30 wt-% up to approximately 85 wt-%, the wt-% referring to the total amount of the base oil, whereat the paraffinic oil is preferably selected from a group comprising linear, branched and cyclic saturated alkanes of poyolefins, hydroisomerized Fischer-Tropsch wax, and Fischer-Tropsch oligomerized olefins, preferably isoparaffins, cycloparaffins containing mono-ring and/or multi-ring structures, whereat the at least one base oil may further comprise at least one naphthenic oil in an amount of approximately 15 wt-% up to approximately 70 wt-%, the wt-% referring to the total amount of the base oil, whereat the at least one naphthenic oil comprises preferably saturated cyclic alkanes, whereat the at least one thickener is selected from a group comprising lithium soap thickener and urea thickener, whereby the lithium soap thickener is preferably a reaction product of at least one fatty acid with lithiumhydroxide and the urea thickener is preferably at least selected from a group consisting of diurea and/or polyuria, whereat zinc sulfide with molybdenum disulfide and/or tungsten disulfide are preferably in a solid state, whereat the molybdenum disulfide and/or tungsten disulfide is preferably present in a total amount (in wt-%) relative to the amount (in wt-%) of zinc sulfide, also in combination with each other, in a range between approximately 1:1 to approximately 20:1, preferably in a range between approximately 3:1 to approximately 10:1, whereat the total amount of zinc sulfide with molybdenum disulfide and/or tungsten disulfide is between approximately 0.6 wt-% up to approximately 7 wt-%, and further preferred between approximately 1.2 wt-% up to approximately 4 wt-%, in each case the wt-% referring to the total amount of the grease composition, whereat the at least one organic sulphur-additive comprises sulphur in an amount of at least 10 wt-%, even more preferred between approximately 20 wt-% up to approximately 70 wt-%, the wt-% referring to the total amount of the organic sulphur-additive, whereat the at least one organic sulphur-additive is preferably selected from a group consisting of at least one alkyl thiadiazole or an olefin sulfide made up of reaction products with olefin monomers as ethylene, propylene, butane-1 and/or 4-methylpentene, whereat the at least one organic phosphor-additive is preferably present in an amount of approximately 0.2 wt-% up to approximately 2.0 wt-%, further preferred in an amount of approximately 0.3 wt-% up to approximately 1.0 wt-%, in each case the wt-% referring to the total amount of the grease composition, whereat the at least one organic phosphor-additive is preferably selected from a group consisting of tri-substituted organic phosphates, further preferred iso-butyl phosphate (TiBP), whereat the at least one anti-oxidation agent is preferably an amine, more preferably an aromatic amine, even more preferably benzamine and/or N-phenyl compounds reacted with 2,4,4-trimethylpentene or selected from the group of octylated/butylated diphenylamine, more preferably dioctyl diphenylamine, octyl diphenylamine, octyl/styrryl diphenylamine, diheptyl diphenylamine, dinonyl diphenylamine or a mixture thereof.

A grease composition for use in constant velocity joints which comprises at least one base oil, at least one thickener, zinc sulfide, molybdenum disulfide and/or tungsten disulfide, at least one organic sulphur-additive and at least one organic phosphor-additive, whereat the ratio between the amount of molybdenum disulfide and/or tungsten disulfide to the amount of zinc sulfide is preferably in a range between approximately 1:1 to approximately 20:1 and further preferred in a range between approximately 3:1 to approximately 10:1.

A grease composition for use in CV joints which comprises at least one base oil, at least one thickener, zinc sulfide, molybdenum disulfide and/or tungsten disulfide, at least one organic sulphur-additive and at least one organic phosphor-additive, whereat the ratio between the amount of molybdenum disulfide and/or tungsten disulfide to the amount of zinc sulfide is preferably in a range between approximately 1:1 to approximately 20:1 and further preferred in a range between approximately 3:1 to approximately 10:1, whereat the total amount of zinc sulfide with molybdenum disulfide and/or tungsten disulfide preferably is approximately 0.6 wt-% up to approximately 7 wt-% at the most, in each case the wt-% referring to the total amount of the grease composition.

A grease composition for use in CV joints which comprises at least one base oil, at least one thickener, zinc sulfide, molybdenum disulfide and/or tungsten disulfide, at least one organic sulphur-additive and at least one organic phosphor-additive, whereat the ratio between the amount of molybdenum disulfide and/or tungsten disulfide to the amount of zinc sulfide is preferably in a range between approximately 1:1 to approximately 20:1 and further preferred in a range between approximately 3:1 to approximately 10:1, whereat the total amount of zinc sulfide with molybdenum disulfide and/or tungsten disulfide preferably is approximately 0.6 wt-% up to approximately 7 wt-% at the most, characterized in that zinc sulfide is comprised in an amount of approximately 0.1 wt-% up to approximately 2.0 wt-%, in each case the wt-% referring to the total amount of the grease composition.

In an example, the grease composition for use in CV joints comprises at least one base oil, at least one thickener, zinc sulfide, molybdenum disulfide and/or tungsten disulfide, at least one organic sulphur-additive and at least one organic phosphor-additive, whereat the ratio between the amount of molybdenum disulfide and/or tungsten disulfide to the amount of zinc sulfide is preferably in a range between approximately 1:1 to approximately 20:1 and further preferred in a range between approximately 3:1 to approximately 10:1, whereat the total amount of zinc sulfide with molybdenum disulfide and/or tungsten disulfide preferably is approximately 0.6 wt-% up to approximately 7 wt-% at the most, characterized in that the molybdenum disulfide and/or tungsten disulfide is comprised in an amount of approximately 0.5 wt-% up to approximately 5.0 wt-%, in each case the wt-% referring to the total amount of the grease composition.

In an example, the grease composition for use in CV joints comprises at least one base oil, at least one thickener, zinc sulfide, molybdenum disulfide and/or tungsten disulfide, at least one organic sulphur-additive and at least one organic phosphor-additive, whereat the ratio between the amount of molybdenum disulfide and/or tungsten disulfide to the amount of zinc sulfide is preferably in a range between approximately 1:1 to approximately 20:1 and further preferred in a range between approximately 3:1 to approximately 10:1, whereat the total amount of zinc sulfide with molybdenum disulfide and/or tungsten disulfide preferably is approximately 0.6 wt-% up to approximately 7 wt-% at the most, whereat the at least one organic sulphur-additive is comprised in an amount of approximately 0.2 wt-% up to approximately 1.0 wt-%, in each case the wt-% referring to the total amount of the grease composition, and whereat the at least one organic sulphur-additive comprises sulphur in an amount of at least 10 wt-%, the wt-% referring to the total amount of the organic sulphur-additive.

In an example, the grease composition for use in CV joints comprises at least one base oil, at least one thickener, zinc sulfide, molybdenum disulfide and/or tungsten disulfide, at least one organic sulphur-additive, and at least one organic phosphor-additive, whereat the ratio between the amount of molybdenum disulfide and/or tungsten disulfide to the amount of zinc sulfide is preferably in a range between approximately 1:1 to approximately 20:1 and further preferred in a range between approximately 3:1 to approximately 10:1, whereat the total amount of zinc sulfide with molybdenum disulfide and/or tungsten disulfide preferably is approximately 0.6 wt-% up to approximately 7 wt-% at the most, whereat the at least one organic phosphor-additive is comprised in an amount of approximately 0.2 wt-% up to approximately 2.0 wt-%, in each case the wt-% referring to the total amount of the grease composition.

In an example, the grease composition for use in CV joints comprises at least one base oil, at least one thickener, zinc sulfide, molybdenum disulfide and/or tungsten disulfide, at least one organic sulphur-additive and at least one organic phosphor-additive, whereat the ratio between the amount of molybdenum disulfide and/or tungsten disulfide to the amount of zinc sulfide is preferably in a range between approximately 1:1 to approximately 20:1 and further preferred in a range between approximately 3:1 to approximately 10:1, whereat the total amount of zinc sulfide with molybdenum disulfide and/or tungsten disulfide preferably is approximately 0.6 wt-% up to approximately 7 wt-% at the most, whereat the at least one anti-oxidation agent is comprised in an amount of approximately 0.1 wt-% up to approximately 2.0 wt-%, in each case the wt-% referring to the total amount of the grease composition.

In an example, the grease composition for use in CV joints comprises at least one base oil, at least one thickener, zinc sulfide, molybdenum disulfide and/or tungsten disulfide, at least one organic sulphur-additive and at least one organic phosphor-additive, whereat the ratio between the amount of molybdenum disulfide and/or tungsten disulfide to the amount of zinc sulfide is preferably in a range between approximately 1:1 to approximately 20:1 and further preferred in a range between approximately 3:1 to approximately 10:1, whereat the total amount of zinc sulfide with molybdenum disulfide and/or tungsten disulfide preferably is approximately 0.6 wt-% up to approximately 7 wt-% at the most, whereat the at least one thickener is preferably selected from a group comprising urea thickener and lithium soap thickener, whereat the at least one thickener is comprised in an amount of approximately 4 wt-% up to approximately 20 wt-%, in each case the wt-% referring to the total amount of the grease composition.

In an example, the grease composition for use in CV joints comprises at least one base oil, at least one thickener, zinc sulfide, molybdenum disulfide and/or tungsten disulfide, at least one organic sulphur-additive and at least one organic phosphor-additive, whereat the ratio between the amount of molybdenum disulfide and/or tungsten disulfide to the amount of zinc sulfide is preferably in a range between approximately 1:1 to approximately 20:1 and further preferred in a range between approximately 3:1 to approximately 10:1, whereat the total amount of zinc sulfide with molybdenum disulfide and/or tungsten disulfide is approximately 0.6 wt-% up to approximately 7 wt-% at the most, in each case the wt-% referring to the total amount of the grease composition, whereat the at least one base oil comprises poly-α-olefines, naphthenic oils, paraffinic oils, and/or synthetic organic esters.

In an example, the grease composition for use in CV joints comprises at least one base oil, at least one thickener, zinc sulfide, molybdenum disulfide and/or tungsten disulfide, at least one organic sulphur-additive and at least one organic phosphor-additive, whereat the ratio between the amount of molybdenum disulfide and/or tungsten disulfide to the amount of zinc sulfide is preferably in a range between approximately 1:1 to approximately 20:1 and further preferred in a range between approximately 3:1 to approximately 10:1, whereat the total amount of zinc sulfide with molybdenum disulfide and/or tungsten disulfide preferably is approximately 0.6 wt-% up to approximately 7 wt-% at the most, in each case the wt-% referring to the total amount of the grease composition, whereat the at least one base oil comprises at least one paraffinic oil in an amount of approximately 30 wt-% up to approximately 85 wt-%, and/or whereat the at least one base oil may further comprise at least one naphthenic oil in an amount of approximately 15 wt-% up to approximately 70 wt-%, the wt-% referring to the total amount of the base oil.

Molybdenum disulfide as mentioned herein may be comprised from the grease composition in combination with tungsten disulfide (WS₂), whereat the tungsten disulfide partly replaces the amount of molybdenum disulfide within the wt-% ranges of the molybdenum disulfide. The above-mentioned examples of the grease composition are non-limiting preferred examples whereby different combination of the said ranges and additives are also possible.

The grease composition will be hereunder described in more detail with reference to the following non-limiting examples in accordance with the present disclosure and comparative examples of various grease compositions.

In order to determine the effect of lowering the friction coefficient as well as the wear by the grease composition disclosed herein, Schwingungs-ReibverschleiR SRV tests are carried out using an Optimol Instruments SRV tester. Flat disc lower specimen made of the 100Cr6 standard bearing steel from Optimol Instruments Prüftechnik GmbH, Westendstrasse 125, Munich, properly cleaned using a solvent are prepared and contacted with the grease composition to be examined. The SRV test is an industry standard test and is especially relevant for the testing of greases for CV joint. The test consists 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 tests for mimicking ball joints a frequency of 40 Hz with an applied load of 500 N were applied for 60 minutes (including running-in) at 80° C. The stroke was 1.5 mm. The friction coefficients obtained were recorded on computer. For each grease, the reported value is an average of two data at the end of tests in two runs. For the running-in measurement of the friction coefficient, it is started with an applied load of 50 N for 1 minute under the above-specified conditions. Afterwards, the applied load is increased for 30 seconds by 50 N up to 500 N. Wear is measured using a profilometer and a digital planimeter. By using the profilometer, a profile of the cross section in the middle of the worn surfaces can be obtained. The area (S) of this cross section can be measured by using the digital planimeter. The wear quantity is assessed by V=SI, where V is the volume of the wear and I is the stroke. The wear rate (W_r) is obtained from W_r=V/L [μm³/m], where L is the total sliding distance in the tests.

A Standard Multi Block Program SMBP Test is used to compare and evaluate the life endurance characteristics of CV joints. A CV joint is exposed to a torque at an acceleration rate of 250 Nm/sec, a jounce deflection at a rate of 100 mm/sec and a rotation speed at an acceleration rate of at least 40 rpm/sec to maximum values of at least 1000 Nm and 2000 rpm. During the program, a permanent record of the actual torque, speed and jounce deflection (angle) will be given by a test rig. The program will run defined load cycles until the CV joint gets a first sign of significant impairments. One cycle is defined by 51.3 min and 39973 revolutions. The life endurance is evaluated by the accomplished cycles until failure of the CV joint. A failure is defined as an overproportioned temperature increase or appearance of noises indicating wear. The CV joint life endurance is evaluated by the number of accomplished cycles until the failure of the CV joint. For validation of a particular grease sample in CV joint performance, 4 joints were filled with the same grease sample and tested on CV joint test rig. An average of 4 CV joints life endurance is taken to compare the grease performance. As comparison a commercial grease and the base oil without additives are used.

Further, tests regarding the compatibility properties of a thermoplastic elastomer sealing boot, Pibiflex B5050 MWR, carried out with a grease composition in accordance with the present disclosure and with one commercial grease, i.e. commercial grease composition Cl (see Table 3), were carried out with respect to the change of hardness (shore D) and the percentage change of tensile, elongation, and volume before and after a heat ageing of the sealing boot material immersed in the grease at 125° C. for 336 hours. Said values are measured in accordance with ISO 868 (shore D), ISO 37 (tensile change and elongation change), and ISO 2781 (volume change).

The base oil as used for grease compositions A1 to A12 and B1 to B2 consists of a paraffinic oil in an amount of 83 wt-% up to 84 wt-% and a naphthenic oil in an amount of 16 wt-% up to 17 wt-%, in each case the wt-% referring to the total amount of the base oil.

The following compounds were used in the grease compositions of Table 1 to Table 2. The commercial grease Cl is comprising a base oil, a Li-soap oil of 8 wt-%, MoS₂in an amount about 2.5 wt-%, and graphite of about 0.3 wt-%, in each case the wt-% referring to the total amount of the commercial grease.

Zinc sulfide (ZnS) powder having a purity of 97 wt-% and an average particle size of 0.80 μm was used. A super fine Molybdenum disulfide (MoS₂) powder having a purity of 97 wt-% and a particle size of 0.40 up to 0.50 μm (Fischer No.) was used. A tungsten disulfide (WS₂) powder having an average particle size of 7 μm as D90 was used. As an organic sulphur-additive, Anglamol 33 from Lubrizol France, 25 Quai de France, 76173 Rouen Cedex, France was used. As an organic phosphor-additive Tri-iso-butylphosphate with a purity of 99 wt-% was employed. As a Li soap thickener, Lithiumstearate obtained by reaction of 12-hydroxystearic acid with Lithiumhydroxide (LiOH) was used.

Commercial grease is in the following designated as C1, whereas the grease compositions comprising molybdenum disulfide are designated as A1, A2, A9, A10 and A11, whereas the grease compositions designated A3 to A8 and A12 are comparative samples.

TABLE 1

[wt %]
C1
A1
A2
A3
A4
A5
A6
A7
A8
A9
A10
A11
A12

Li soap
8
8
8
8
8
8
8
8
8
8
8
8
8

Base oil (sum up)
n.d.
88.5
88.8
92.0
91.5
91.0
90.5
88.5
89.0
89.0
89.0
89.5
90.0

Paraffinic oils in base oil
n.d
73.5
73.8
77.0
76.5
76.0
75.5
73.5
74.0
74.0
74.0
74.5
75.0

Naphthenic oils in base oil
n.d
15
15
15
15
15
15
15
15
15
15
15
15

ZnS
0
0.5
0.56
0
0
0.5
0.5
0
0
0.5
0.5
0.5
0

MoS₂
>2.5
2
1.69
0
0
0

3
2
2
2
2
2

organic sulphur-additive
0
0.5
0.5
0
0
0.5
0.5
0.5
0.5
0
0.5
0
0

organic phosphor-additive
0
0.5
0.5
0
0.5
0
0.5
0
0.5
0.5
0
0
0

Table 2 shows commercial grease Cl and grease compositions comprising tungsten disulfide designated as B1 to B2:B2 comprises a mixture of molybdenum sulfide and tungsten disulfide.

TABLE 2

[wt %]
C1
B1
B2

Li soap
8
8
8

Base oil (sum up)
n.d.
89.1
88.8

Paraffinic oils in base oil
n.d.
74.1
73.8

Naphthenic oils in base oil
n.d.
15
15

ZnS
0
0.25
0.25

MoS2
>2.5
0
1.5

WS₂
0
1.69
0.5

organic sulphur-additive
0
0.5
0.5

organic P-additive
0
0.5
0.5

Experimental values for friction, wear and boot compatibility are presented in Tables 3 to 4 and in FIGS. 1a, 1b, 2a, 2b, 3a, 3b, 4a and 4b as follows:

FIGS. 1a and 1b: Experimental results for friction and wear, respectively, as presented in Table 3, are shown for the synergetic effect of zinc sulfide additive in A1 to A12;

FIGS. 2a and 2b: Experimental results, as presented in Table 3, for friction and wear are shown for the synergetic effect of molybdenum disulfide (MoS₂) additive in A1 to A12;

FIGS. 3a and 3b: Experimental results, as presented in Table 4, for friction and wear are shown for the comparison of the grease composition A1, A2, B1, B2 and the commercial grease Cl; and

FIGS. 4a and 4b: Experimental results, as presented in Table 4, for the compatibility test of sealing boot material and the life endurance time of the CV joint.

Experimental results regarding the friction coefficient of the grease compositions and wear of the grease compositions as compared to commercial grease Cl are presented in Table 3.

TABLE 3

C1
A1
A2
A3
A4
A5
A6
A8
A10
A12
B1
B2

ZnS
—
0.5
0.56
0
0
0.5
0.5
0
0.5
0
0.25
0.25

MoS₂
>2.5
2
1.69
0
0
0
0
2
2
2
0
1.5

WS₂
0
0
0
0
0
0
0
0
0
0
1.69
0.5

organic
—
0.5
0.5
0
0
0.5
0.5
0.5
0.5
0
0.5
0.5

sulphur-additive

organic
—
0.5
0.5
0
0.5
0
0.5
0.5
0
0
0.5
0.5

phosphor-additive

Friction coefficient
0.105
0.044
0.055
0.1625
0.115
0.118
0.1075
0.085
0.136
0.142
0.106
0.1

Wear quantity
1181
639
380
13498
811
8905
868
918
840
8708
882
950

[μm³/m]

Experimental results regarding the life endurance of the grease composition with CV joints and compatibility of the grease composition A1 with sealing boot materials as compared to commercial grease Cl are presented in Table 4.

TABLE 4

C1
A1
B1

Endurance SMBP
ZnS
0
0.5
0.25

Test
MoS₂
x
2
0

WS₂
0
0
1.69

Life endurance
925
943
2342

[cycles until failure]

Compatibility Test
Tensile change
−47
−16
n.d.

for sealing boot
[%]

material
Elongation change
−21
+5
n.d.

[%]

Hardness change
0
−6
n.d.

(Shore D)

Volume change
+15
+11
n.d.

[%]

n.d.—not detected

Table 3 and FIG. 1a and FIG. 1b show the experimental results of grease composition A1 in accordance with the present disclosure in comparison with the base oil A3, molybdenum disulfide (MoS₂) containing grease A12, molybdenum disulfide with organic sulphur-additive A10, organic phosphor-additive A4 and molybdenum disulfide with organic phosphor- and organic sulphur-additive A8. A reduction of friction coefficients is observed step by step when adding molybdenum disulfide in the grease composition. The grease compositions A8 and A10 are commonly used in CV joints. Both grease compositions show good values for friction and wear. However, adding zinc sulfide in combination with molybdenum disulfide, organic sulphur-additive and organic phosphor-additive, there is a significant reduction of the friction coefficient from 0.072 to 0.044. The lowest wear quantity is achieved with a grease composition containing molybdenum disulfide, organic sulphur-additive, orgabic phosphor-additive and zinc sulfide. These experimental results clearly show an impact of zinc sulfide of the grease tribology performance.

FIGS. 2a and 2b show the experimental results of inventive grease composition A1 in comparison with base oil A3, organic phosphor-additive containing grease A4, zinc sulfide and organic sulphur-additive containing grease composition A5 and a grease composition A6 containing zinc sulfide, organic sulphur-additive and organic phosphor-additive. A reduction of friction coefficients is observed step by step when adding zinc sulfide in the grease composition samples. However, on adding molybdenum disulfide in combination with zinc sulfide, organic sulphur-additive and organic phosphor-additive, a large reduction of the friction coefficient from 0.108 to 0.044 is observed. The lowest wear quantity is achieved with a grease composition containing zinc sulfide, organic sulphur-additive, organic phosphor-additive and molybdenum disulfide. These experimental results clearly show an impact of molybdenum disulfide of the grease tribology performance.

In conclusion, the experimental data shown in FIG. 1a, 1b, 2a and FIG. 2b prove a synergy effect using zinc sulfide and molybdenum disulfide in a grease composition. The tribology performance is significant improved by only combining zinc sulfide and molybdenum disulfide.

FIG. 3a and FIG. 3b show the experimental results of inventive compositions A1, A2 and B1 in comparison with commercial grease composition C1 and the base oil A3. The good tribology performance still appears with a slight reduction in molybdenum disulfide quantity from 2.0 wt % of A1 to 1.69 wt % of A2. B1 contains 1.69 wt % tungsten disulfide instead of molybdenum disulfide. B2 contains a mixture of 1.5 wt-% molybdenum disulfide and 0.5 wt-% tungsten disulfide, whereas the amount of zinc sulfide has been lowered to 0.25 wt-%. Compared with the commercial grease composition C1 all the grease compositions A1, A2, B1 and B2 show a decrease of the friction coefficient and the wear quantity. The grease compositions A1 and A2 containing molybdenum disulfide show a better tribology performance than the tungsten disulfide containing grease formulation B1. The grease formulation B2 containing molybdenum disulfide and tungsten disulfide shows lower friction and anti-wear performance than B1, A1 and A2. B1 and B2 still show acceptable friction and anti-wear performance in comparison with the commercial grease C1.

Table 4 and FIGS. 4a and 4b show the compatibility of the grease compositions A1 and B1 with a CV joint boot (Pibiflex B5050 MWR) in comparison with commercial grease C1. The life endurance of the grease A1 in comparison to the commercial grease C1 is slightly higher. The grease composition B1 shows more than two times higher life endurance than the commercial grease C1. The grease composition A1 provides lower values in tensile, elongation and volume change than commercial grease C1. With respect to the commercial grease C1, the grease composition A1 provides similar values with respect to hardness change, but especially significantly improved values regarding tensile change and elongation change.

The examples of the grease compositions in accordance with the disclosure clearly demonstrate that the combination of zinc sulfide and molybdenum disulfide and/or tungsten disulfide retains the general lubricating properties of the grease composition, but in addition increases the compatibility with the sealing boot material as well as the life endurance of the CV joint.

GREASE COMPOSITION FOR CONSTANT VELOCITY JOINTS

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