FR2907461A1 - GREASE COMPOSITION FOR USE IN HOMOCINETIC JOINTS - Google Patents

Abstract

To provide a grease composition having good compatibility with rubber or thermoplastic elastomer bellows, and also giving low wear and friction, a grease composition for use in constant velocity joints, including an oil composition base (b) at least one trinuclear molybdenum compound having the formula Mo3SkLnQz 'in which L are independently selected ligands having organo groups having a sufficient number of carbon atoms to render the compound soluble or dispersible in the oil, n is 1 to 4, k is 4 to 7, Q is selected from the group of neutral electron donating compounds such as amines, alcohols, phosphines and ethers, and z is in a range of 0 to 5 and includes non-stoichiometric values, c) at least one thickener based on a urea derivative.

Description

DESCRIPTION The present invention relates to a lubricating grease which is

  intended to be mainly used in universal homokinetic joints, in particular spherical joints or tripod joints, which are used in the transmission members of motor vehicles.

  The movements of the components in the homokinetic joints (JH) are complex with a combination of rolling, sliding or sliding and rotation.  When the seals are subjected to torque, the components are loaded at the same time, which can not only cause wear on the contact surfaces of the components, but also fatigue on the rolling contact and significant frictional forces between the components. surfaces.  Wear can cause joint failure and frictional forces can cause noise, vibration, and hardness or roughness (BVD) in the transmission member.  BVDs are normally measured by determining the axial forces generated in a dipping type JH.  Ideally, the greases used in constant velocity joints need not only to reduce wear, but must also have a low coefficient of friction to reduce frictional forces and to reduce or prevent BVD.  The constant velocity joints also have sealing bellows made of an elastomeric material that usually have a bellows shape, one of their ends being connected to the outer portion of the JH and the other end to the connecting or output shaft of the JH.  The bellows retain the grease in the seal and leave the dust and water outside.  The grease must not only reduce wear and friction and prevent the premature start of rolling contact fatigue in a JH, but it must also be compatible with the elastomeric material of which the bellows is made.  Otherwise, there is a degradation of the bellows material which causes premature failure of the bellows, which would allow the escape of the fat and finally the failure of the JH.  The two main types of materials used for JH bellows are polychloroprene rubber (CR) and thermoplastic elastomer (TPE), especially thermoplastic ether-ester copolymer elastomer (TPC-ET) .  Typical JH fats have base oils which are mixtures of naphthenic (saturated rings) and paraffinic (saturated linear and branched) mineral oils.  Synthetic oils can also be added.  It is known that said base oils have a great influence on the deterioration (swelling or shrinkage) of both CR and TPC-ET bellows.  Both mineral and synthetic base oils extract the plasticizers and other oil-soluble protective agents from the bellows materials.  Paraffinic mineral oils and synthetic base oils with poly-α-olefins (PAO) diffuse very little in bellows particularly made of shrinking rubber materials, but otherwise naphthenic mineral oils and synthetic esters the bellows materials and act as plasticizers and can cause swelling.  The exchange of plasticizers or plasticizer compositions for the naphthenic mineral oil can significantly reduce bellows performance, particularly at low temperatures, and can cause cold cracking bellows failure, ultimately resulting in JH failure.  If significant swelling or softening occurs, the high speed capability of the bellows is reduced due to low speed stability and / or excessive radial expansion.  In order to solve the above-mentioned problems, US 6,656,890 B1 suggests a combination of special base oils comprising from 10 to 35% by weight of one or more poly-α-olefin (s), from 3 to 15% by weight of one or more synthetic organic ester (s), from 20 to 30% by weight of one or more naphthenic oil (s), the remaining of the combination being one or more paraffinic oil (s), and, in addition, a lithium soap thickener, and a sulfur-free friction modifier, which may be an organo-molybdenum complex, and a dithiophosphate molybdenum, and zinc dialkyldithiophosphate and other additives such as corrosion inhibitors, antioxidants, extreme pressure additives, and tackifiers.  However, the coefficient of friction and wear of the grease compositions according to US 6,656,890 B1 as measured by SRV tests (abbreviation of the German term Schwingungen, Reibung, Verschlei (3) need to be improved.  It is therefore the object of the present invention to provide a grease composition, primarily for use in homokinetic joints, which has good compatibility with bellows made of thermoplastic elastomer or rubber, and which also produces a low wear and low friction when used in a JH.  Said object or object of the present invention is solved by a grease composition for use in constant velocity joints comprising a) a base oil composition; and b) at least one trinuclear molybdenum compound, preferably from 0.25 wt.% to 5 wt.%, more preferably from 0.3 wt.% to 3 wt.%, based on the total amount. of the grease composition, having the formula Mo3SkL ,, Qz '(I) wherein L are independently selected ligands having organo groups having a sufficient number of carbon atoms to render the compound soluble or dispersible in the oil , n is 1 to 4, k is 4 to 7, Q is selected from the group of neutral electron donor compounds such as amines, alcohols, phosphines and ethers, and z is within a range of 0 to 25 and includes non-stoichiometric values; c) at least one thickener based on a urea derivative.  The present invention relates to a grease composition for use in constant velocity joints comprising a) a base oil composition; B) at least one trinuclear molybdenum compound having the formula wherein L are independently selected ligands having organo groups having a sufficient number of carbon atoms to render the compound soluble or dispersible in oil, n is 1 to 4, k is 4 to 7, Q is selected from the group of neutral electron donating compounds such as amines, alcohols, phosphines and ethers, and z is in a range of 0 to 5 and includes non-stoichiometric values; c) at least one thickener based on a urea derivative.  In addition, the grease composition according to the invention is further characterized in that: the urea derivative thickener is selected from the group consisting of diurea and / or polyurea compounds and mixtures thereof; said compounds with calcium-based thickeners; It further comprises at least one zinc dithiophosphate, a molybdenum dithiocarbamate and / or a molybdenum dithiophosphate; the amount of zinc dithiophosphates, molybdenum dithiophosphates and / or molybdenum dithiocarbamates is in a range from 0.1 wt.% to 5 wt.%, based on the total amount of the fat composition; the weight percentage added, based on the total amount of the fat composition, of each of the zinc dithiophosphates, the molybdenum dithiophosphates and / or the molybdenum dithiocarbamates is essentially identical; It further comprises an agent comprising at least one anti-oxidation agent, a corrosion inhibitor, an antiwear agent, a wax, a friction modifier and / or an extreme pressure agent (EP agent); it comprises from 50% by weight to 98.9% by weight of the base oil composition, from 0.1% by weight to 5% by weight of at least one trinuclear molybdenum compound, of 1% by weight to 25% by weight of at least one urea derivative thickener, in each case based on the total amount of the fat composition; it comprises from 70% by weight to 92% by weight of the base oil composition, from 0.3% by weight to 2% by weight of the at least one trinuclear molybdenum compound, of 4.5% by weight weight at 20% by weight of the at least one urea derivative thickener, from 1.5% by weight to 3.5% by weight of at least one molybdenum dithiocarbamate, from 0.5% by weight to 3% by weight of the at least one zinc dithiophosphate, and from 0.5% by weight to 2% by weight of at least one wax; The weight percentage added, based on the total amount of the fat composition, of trinuclear molybdenum compounds is substantially identical to the added weight percent of each of the zinc dithiophosphate, the molybdenum dithiophosphate and / or the dithiocarbamate. molybdenum; The weight percentage added, based on the total amount of the grease composition, of trinuclear molybdenum compounds is 4 to 10 times lower than the weight percentage of the total amount of zinc dithiophosphates, molybdenum dithiophosphates and / or or added molybdenum dithiocarbamates; The coefficient of sliding or sliding friction is at most 0.08.  The number of carbon atoms present in the trinuclear molybdenum compound among all ligands, organo groups is at least 21 carbon atoms, preferably at least 25, more preferably at least 25, and most preferably at least 35.  The trinuclear molybdenum compounds that can be employed in the present invention are described in US 6,172,013 B1, the disclosure of which forms an integral part of the present invention by reference.  The presence of at least 0.25% by weight of the trinuclear molybdenum compound according to the invention is preferred and significantly reduces the coefficient of friction as well as the wear when used in the JH.  As a base oil composition according to the present invention, it is preferable to employ a base oil composition as described in US 6,656,890 B1, the disclosure of which forms an integral part of this invention. description by reference.  However, any other kind of base oil compositions may be employed, particularly a mineral oil blend, a synthetic oil blend, or a blend of a combination of mineral oils and synthetic oils.  The base oil composition should preferably have a kinematic viscosity of about 32 to about 250 mm 2 / s at 40 ° C and about 5 to about 25 mm 2 / s at 100 ° C.  The mineral oils are preferably selected from the group consisting of at least one naphthenic oil and / or at least one paraffinic oil.  The synthetic oils that can be used in the present invention are selected from a group comprising at least one poly-α-olefin (PAO) and / or at least one synthetic organic ester.  The synthetic organic ester is preferably a dicarboxylic acid derivative having subgroups based on aliphatic alcohols.  The aliphatic alcohols preferably have linear or branched primary carbon chains having from 2 to 20 carbon atoms.  The synthetic organic ester is preferably selected from a group consisting of bis (2-ethylhexyl ester) sebacic acid (dioctyl sebacate (DOS)), bis (2-ethylhexyl ester) adipic acid (dioctyl adipate (DOA)). ), and / or bis (2-ethylhexyl ester) azelaic acid (dioctyl azelate (DOZ)).  If poly-α-olefin is present in the base oil composition, the poly-α-olefins are preferably selected having a viscosity of about 2 to about 40 centistokes at 100 ° C.  The naphthenic oils selected for the base oil compositions preferably have a viscosity of from about 20 to about 150 mm 2 / s at 40 C, whereas if paraffinic oils were present in the base oil composition, the paraffinic oils preferably have a viscosity of about 25 to about 170 mm 2 / s at 40 C.  According to the present invention, the fat composition comprises at least one thickener based on a urea derivative.  The urea derivative thickener employed in accordance with the present invention may also be a urea complex thickener, which is defined as a mixture of at least one thickener based on a urea derivative with at least one other thickener which is not a thickener based on a urea derivative.  Particularly preferred urea complex thickeners according to the present invention are mixtures of at least one thickener based on a urea derivative with at least one calcium and / or lithium thickener. and / or a complex thickener.  As the urea derivative thickener in the present invention, a urea thickener made by Kyodo Yushi Co. is particularly used. , Ltd. , Tokyo, Japan, as defined in US 5,559,444.  The urea thickener is preferably a product of the reaction of at least one organic aliphatic amine with at least one organic phenyl isocyanate.  However, the urea thickener is not limited to specific products and may also be, for example, a diurea compound and / or a polyurea compound.  Examples of diurea compounds include those obtained from the reaction of a monoamine with a diisocyanate compound.  Examples of useful diisocyanates include phenylene diisocyanate, diphenylenediisocyanate, phenyldiisocyanate, diphenylmethane diisocyanate, octadecanediisocyanate, decane diisocyanate, and hexane diisocyanate.  Examples of useful monoamines include octylamine, dodecylamine, hexadecylamine, octadecylamine, oliylamine, aniline, t-toluidine, and cyclohexylamine.  Especially preferred diurale compounds are compounds obtained by reaction of 4,4'-methylenediphenyl diisocyanate (MDI) with octadecylamine.  Examples of useful polyurea compounds include those obtained from a reaction of a diamine with a diisocyanate compound.  Examples of useful diisocyanate compounds include those employed for the formation of the diurea compounds mentioned above, while examples of useful diamines include ethylenediamine, propane diamine, butane diamine, hexane diamine, octane diamine, phenylenediamine, tolylenediamine, and xylenediamine.  Most preferred examples of urea-type thickeners include those obtained by the reaction of arylamine such as aniline or p-toluidine, cyclohexylamine or a mixture thereof with a diisocyanate.  The aryl group in the diurea compound preferably has 6 or 7 carbon atoms.  In a preferred embodiment of the present invention, the urea derivative thickener is selected from the group consisting of urea complex thickeners.  Urea complex thickeners are defined as a mixture of at least one thickener based on a urea derivative with another type of thickener, particularly calcium thickeners.  A mixture of a urea derivative thickener as defined above with at least one calcium complex thickener and / or calcium based thickener (calcium thickeners) is particularly preferred. preferred as a thickener based on a urea complex according to the present invention.  In the sense of the present invention, a calcium-based thickener (soap) is a product of the reaction of at least one fatty acid with calcium hydroxide.  Preferably, the thickener may be a simple calcium soap made from 12-hydroxy stearic acid or from other similar fatty acids or mixtures thereof or methyl esters of these acids.  Alternatively, a calcium complex (soap) thickener consisting of, for example, a mixture of long chain fatty acids with a mixture of short and / or medium chain carboxylic acids may be employed.  However, mixtures of all the thickeners mentioned above can be used.  The urea derivative thickener may be present in the fat composition according to the invention in an amount of from about 1% by weight to about 25% by weight, based on the total amount of the the grease composition, most preferably in an amount of from about 3% by weight to about 11% by weight, based on the total amount of the grease composition.  In another embodiment of the present invention, the grease composition according to the invention further comprises at least one zinc dithiophosphate, a molybdenum dithiocarbamate and / or a molybdenum dithiophosphate as a set of additives.  Preferably, the amount of zinc dithiophosphates, molybdenum dithiophosphates and / or molybdenum dithiocarbamates is from about 0.1% by weight to about 7% by weight, preferably about 5% by weight, such as more preferably from about 0.3% by weight to about 2% by weight, based in each case on the total amount of the fat composition.  Most preferably, the percent weight added with respect to the total amount of the fat composition, each of the zinc dithiophosphates, the molybdenum dithiophosphates and / or the molybdenum dithiocarbamates is substantially the same.  In such an embodiment of the present invention, the amount of zinc dithiophosphates, molybdenum dithiophosphates and / or molybdenum dithiocarbamates is preferably about 0.4% by weight, 0.5% by weight, 0.6% by weight, and / or 0.7% by weight, in each case based on the total amount of the fat composition.  In a preferred embodiment of the present invention, the other molybdenum-containing compound is selected from the group consisting of molybdenum dithiocarbamates and / or molybdenum dithiophosphates.  The at least one molybdenum dithiophosphate (MoDTP) and / or molybdenum dithiocarbamate (MoDTC) is preferably present in the fat composition according to the present invention in an amount of about 0.3% by weight, more preferably from about 0.5% by weight, most preferably from about 1.5% by weight to about 3.5% by weight, most preferably about 3% by weight, in each case relative to the total amount of the fat composition.  However, any other molybdenum-containing compound may be present in the grease composition of the present invention as component c), of which organic molybdenum compounds are preferred.  The grease composition according to the present invention may contain one or more MoDTCs and / or MoDTPs, and especially mixtures thereof.  The MoDTP according to the present invention has the following general formula: wherein X or Y represents S or O and each of R1 to R4 inclusive may be the same or different and each represents a primary (linear chain) or secondary ( branched chain) having from 6 to 30 carbon atoms.  MoDTC according to the present invention has the following general formula: [(R5) (R6) N-CS-S] 2-Mo2OmSa (III) wherein R5 and R6 each independently represent an alkyl group having from 1 to 24, preferably from 3 to 18 carbon atoms; m has a value of 0 to 3 and n has a value of 4 to 1, provided that m + n = 4.  The grease composition comprises, in the additive package, at least one zinc compound additive, more preferably a zinc compound additive in an amount of about 0.1 wt. about 3.5% by weight, preferably about 2.5% by weight, more preferably about 0.5% by weight to about 2.0% by weight, based on the total amount of fat composition.  The most preferred zinc compound additive is selected from the group consisting of at least one of zinc dithiophosphates (ZnDTPs) and / or zinc dithiocarbamates (ZnDTCs), and ZnDTPs are most preferred.  The zinc dithiophosphate is preferably selected from the group of zinc dialkyldithiophosphate having the following general formula: ## STR2 ## wherein R7 to R10 inclusive may be the same or different and each represents a primary or secondary alkyl group, of which all of the primary alkyl groups having from 1 to 24, preferably from 3 to 20, are most preferred, most preferably from 3 to 5 carbon atoms.  In particular, excellent effects can be expected if the substituents R7, R8, R9 and R10 are a combination of primary and secondary alkyl groups each having 3 to 8 carbon atoms.  The zinc dithiocarbamate may be preferably selected from zinc dialkyldithiocarbamate having the following general formula: wherein R11, R12, R'3, and R14 may be the same or different and each represents a primary or secondary alkyl group having 1 to 24 carbon atoms or an aryl group having 6 to 30 carbon atoms.  By adding at least one zinc compound additive to the grease composition according to the invention, the coefficient of friction as well as the wear in the JH are further reduced significantly.  According to another embodiment of the present invention, the grease composition may further comprise an agent comprising at least one anti-oxidation agent, a corrosion inhibitor, an anti-wear agent, a wax, a friction modifier, and and / or extreme pressure or extreme pressure agents (EP agents), which may also be part of the additive package.  Thus, the additive package may comprise not only zinc dithiophosphates, molybdenum dithiocarbamates and / or molybdenum dithiophosphates, but also the aforementioned agents.  The EP agent is preferably a metal-free polysulfide or a mixture thereof, for example, sulfurized fatty acid methyl ester agents preferably having a viscosity of about 25 mm 2 / s at 40 C, which is preferably present in an amount of from about 0.1 to about 3% by weight, preferably from 0.3 to about 2% by weight, based on the total amount of the fat composition.  The total amount of inactive sulfur of the EP agent at room temperature is from about 8 to about 50% by weight, preferably about 45% by weight.  The amount of active sulfur as measured according to ASTM D1662 can be up to about 1% by weight, preferably up to about 8% by weight at 100%, and preferably up to about 20% by weight at 140%. C, the weight percentage being relative to the amount of the EP agent itself.  These EP agents have excellent effects in preventing contact friction of internal JH components.  If the sulfur content exceeds the upper limit defined above, it can promote the onset of rolling contact fatigue and wear of the metal contact components, which can lead to the degradation of the JH bellows material. .  As the anti-oxidation agent, the fat composition of the present invention may comprise an amine, preferably an aromatic amine, more preferably a phenyl-α-naphthylamine or a di-phenylamine or derivatives thereof. this.  The anti-oxidation agent is used to prevent deterioration of the fat composition associated with oxidation.  The fat composition according to the present invention may range from about 0.1 to about 2% by weight, based on the total amount of the fat composition, of an antioxidant to inhibit the oxidative degradation of the base oil composition, as well as to extend the life of the grease composition, thereby extending the life of the JH.  Typically, the last operation prior to assembly of the JH is a wash to remove residues from the machining, and it is therefore necessary for the grease to absorb all traces of the remaining water and prevent the water from causing a problem. corrosion and effects adversely affecting the performance of the JH, and therefore a corrosion inhibitor is required.  As a corrosion inhibitor, the grease composition according to the present invention may comprise at least one metal or dimetallic salt selected from the group consisting of metal salts of oxidized waxes, metal salts of petroleum sulfonates, specially prepared by sulfonating aromatic hydrocarbon components present in lubricating oil fractions, and / or alkyl aromatic sulfonate metal salts, such as dinonylnaphthalene sulfonic acids, alkylbenzene sulfonic acids, or sulphonic acid sulphonates; superbasic alkylbenzene.  Examples of the metal salts include sodium salts, potassium salts, calcium salts, magnesium salts, zinc salts, quaternary ammonium salts, calcium salts being most preferred.  The calcium salts of the oxidized waxes also provide an excellent effect.  Especially preferred as a corrosion inhibitor is disodium sebacate.  The antiwear agents of the present invention prevent metal to metal contact by adding film-forming compounds to protect the surface either by physical absorption or by chemical reaction.  ZnDTP compounds can also be used as anti-wear agents.  As anticorrosion agents according to the present invention, calcium sulphonate salts are preferably used, preferably in an amount of about 0.5 to about 3% by weight, based on the total amount of the fat.  As a wax compound, the fat composition of the present invention may comprise any kind of wax, preferably fatty wax, known in the state of the art for use in a fat composition or mixtures thereof, of which the lignite waxes, in particular the lignite ester waxes being a reaction product of at least one acid lignite wax with an ester, and the polyolefin waxes, including the lignite waxes and or micronized polyolefin, or mixtures thereof, are most preferred.  The lignite waxes in the sense of the present invention preferably comprise C22-C34 fatty acid esters and optionally wax alcohols having from 24 to 28 carbon atoms.  Esters may be present in the lignite wax according to the present invention in an amount in a range from about 35% by weight to about 70% by weight.  In addition, free fatty acids as well as free wax alcohols and lignite resins may be present.  Useful lignite waxes are provided, for example, by Clariant GmbH, 86005 Augsburg, Germany, especially the lignite waxes offered and marketed under the trade name "Licowax".  The polyolefin waxes that may be used in the sense or context of the present invention are especially polypropylene and / or polyethylene waxes or mixtures thereof, also comprising modified polyolefin waxes, obtained in particular by copolymerization of polyolefins. ethylene with useful comonomers such as vinyl esters or acrylic acid.  The wax preferably has a viscosity of at least about 50 mPa * s at 100 ° C, more preferably at least about 100 mPa * s at 100 ° C, and most preferably at least about 100 mPa * s at 100 ° C. about 200 mPa * s at 100 C, measured according to DIN 53 018.  The wax used in the grease composition can be supplied in the form of a powder or flakes, and is added to the grease composition with a long stirring period, preferably at elevated temperatures, especially at temperatures above 200.degree. about 80 ° C to about 100 ° C.  Conventional friction modifiers employed in the present invention such as fatty acid amides and fatty amine phosphates have been used in fats and other lubricants for many years (see, for example, the modifiers described herein). in Klamann, Dieter-Lubricants, Verlag Chemie GmbH 1983, edition, chapter 9. 6).  Their role is to provide the lubricant with stable but not necessarily low friction over a wide range of operating conditions.  In a preferred embodiment of the present invention, the grease composition according to the invention comprises from about 50% by weight to about 98.9% by weight of the base oil composition, about 0.1% by weight. % by weight to about 5% by weight of at least one trinuclear molybdenum compound, from about 1% by weight to about 25% by weight of at least one urea derivative thickener .  More preferably, the fat composition according to the present invention comprises from about 55% by weight to about 98.1% by weight, preferably about 97.8% by weight, more preferably about 92.8% by weight. % by weight, most preferably about 92.5% by weight of the base oil composition, from about 0.1% by weight to about 5% by weight, preferably about 0, From about 3% by weight to about 2% by weight, of the trinuclear molybdenum compound, from about 1% by weight to about 25% by weight of the urea derivative thickener, about 0.5% by weight from about 0.1% by weight to at least about 5% by weight 0.1 wt.% To about 5 wt.% Of at least one MoDTP, and from about 0.1 wt.% To about 5 wt.% Of at least one MoDTC.  A urea derivative thickener may be present from about 5 to about 20% by weight.  Most preferably, a fat composition comprising about 70% by weight, preferably about 80% by weight, about 92% by weight, preferably about 92.4% by weight, more preferably to about 92.7% by weight of the base oil composition, from about 0.3% by weight to about 2% by weight, preferably about 1.2% by weight of at least one trinuclear molybdenum compound, from about 4.5% by weight to about 20% by weight, preferably about 11% by weight, of at least one urea derivative thickener, about 1%, From 5% by weight to about 3.5% by weight of at least one molybdenum dithiocarbamate, from about 0.5% by weight to about 3% by weight of at least one zinc dithiophosphate, and from about 0% by weight From 5% by weight to about 2% by weight of at least one wax.  In addition, from about 0.3% by weight to about 2% by weight of an EP additive is preferably added.  Preferably, the grease composition according to the present invention is characterized in that the weight percentage added, based on the total amount of the grease composition, of trinuclear molybdenum compounds, is substantially identical to the weight percentage of each of the zinc dithiophosphate, molybdenum dithiophosphate and / or molybdenum dithiocarbamate added.  The compounds mentioned above may also be composed of various zinc dithiophosphates, molybdenum dithiophosphates and / or molybdenum dithiocarbamates, and thus may have a mixture of different zinc dithiophosphates, molybdenum dithiophosphates and the like. / or molybdenum dithiocarbamates.  For clarification purposes, it is noted that the substantial identity of the weight percent of the trinuclear molybdenum compound or mixtures of these added compounds refers to each of the added compounds, and not to mixtures of the various compounds mentioned.  In another preferred embodiment of the present invention, the fat composition is characterized in that the weight percent added, based on the total amount of the fat composition, of the trinuclear molybdenum compound or mixtures of different Trinuclear molybdenum compounds are 4 to 10 times less than the weight percent of all zinc dithiophosphate, molybdenum dithiophosphate and / or molybdenum dithiocarbamate added.  If, for example, in the fat composition, 2% by weight of dithiophosphate (s) and 1% by weight of molybdenum dithiocarbamate (s) are present as well as 0.5% by weight of a trinuclear molybdenum compound then, the weight percent of the trinuclear molybdenum compound added is 6 times less than the weight percent of added zinc dithiophosphate (s) and molybdenum dithiocarbamate (s).  It should be noted that zinc dithiophosphate, molybdenum dithiophosphate and / or molybdenum dithiocarbamate may also be present as mixtures of said compounds having different structural formulas.  In addition, the grease composition according to the present invention has a coefficient of sliding or slip friction of no greater than 0.08 as measured with an SRV test.  BEST MODE FOR CARRYING OUT THE INVENTION In order to determine the effect of reducing the coefficient of friction as well as wear by the grease composition according to the invention, SRV tests are carried out using an SRV tester from Optimol Instruments.  From flat bottom disc specimens made of 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 a standard industrial test and is particularly relevant for fat testing for JH.  The test consists of a top ball specimen with a diameter of 10 mm made of 100Cr6 standard bearing steel having a back-and-forth movement supported on the lower specimen of the aforementioned flat disc.  In the tripod joint simulation tests a frequency of 7 Hz (for examples D1 and D2 only) and 40 Hz respectively, with an applied load of 200 N applied for 60 minutes (including break-in) or 3 hours (for examples D1 and D2 only) at 80 C, or 40 C (examples D1 and D2 only).  The stroke was 0.5 mm (for examples D1 and D2 only), 1.5 mm and 3.0 mm, respectively.  The friction coefficients obtained were recorded by computer.  For each grease, the reported value is an average of four data (two data for the examples D1 and D2) at the end of the tests in four series or two series respectively (two series with a stroke of 1.5 mm and two series with a stroke of 3.0 mm with the exception of examples D1 and D2 with two series with a stroke of 0.5 mm).  Wear is measured by means of 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 using the digital planimeter.  The level of wear is evaluated by V = SI, where V is the volume of wear and I is the stroke.  The speed of wear (Wr) is obtained by W = V / L [m3 / m], where L is the total sliding distance in the tests.  For break-in, this is started with an applied load of 50 N for 1 minute under the conditions mentioned above.  Subsequently, the applied load is increased for 30 seconds from 50 N to 200 N.  Next, the welding force exerted on the JHs with a different grease composition is measured according to an EP bear 4 lease test according to the IP-239 standard (Energy Institute, London, United Kingdom).  The following materials are employed in the grease compositions examined: Base oil composition (blend of oils) The base oil compositions employed have a kinematic viscosity of about 32 to about 250 mm 2 / s at 40.degree. C and from about 5 to about 25 mm 2 / s at 100 C.  Two base oil mixtures are used in the present invention.  The base oil mixture A is a mixture of one or more naphthenic oil (s) in a range of about 10 to about 60% by weight, one or more paraffinic oil (s). (s) in a range of about 30 to about 80% by weight and one or more poly-alpha-olefin (s) (PAO) in a range of about 5 to about 40% by weight, in relation to the total amount of the oil mixture.  The blend of oils A does not contain an organic synthetic ester, while the blend of oils B contains DOS in a range of about 2 to about 10% by weight based on the total amount of the blend. oils.  The naphthenic oils are selected with a viscosity range of about 20 to about 180 mm 2 / s at 40 C, paraffinic oils of about 25 to about 400 mm 2 / s at 40 C, and PAOs of about 6 to about 40 mm2 / s to 100 C.  Tri-Mol Molenbdenum Compound (TNMoS) The tri-molecular molybdenum compound employed in the grease composition of the present invention is a sulfur-containing trinuclear molybdenum compound marketed under the tradename C9455B by Infineum International Ltd. , UK.  Its structure is defined in US 6 172 013 B1.  2907461 Other Molybdenum Compounds A molybdenum dithiophosphate (MoDTP) sold under the tradename Sakuralube 300 (S-300) is used by Asahi Denka Co.  Ltd. , Japan, having the chemical formula 2-ethylhexyl dithiophosphate molybdenum, diluted with mineral oil.  In addition, a molybdenum dithiocarbamate (MoDTC) sold under the trade name Sakuralube 600 (S-600) in the solid state, produced by Asahi Denka Co., is employed.  Limited, Japan.  Zinc Compound Additive As zinc compound additives, ZnDTP marketed by Infineum International Ltd. is used. , Oxfordshire, United Kingdom, under the trademark C9425, which is a zinc dialkyldithiophosphate with primary and / or secondary alkyl groups, especially having from 3 to 8 carbon atoms, preferably having from 4 to 5 carbon atoms. carbon, diluted with mineral oil.  Thickener The urea thickener ("thickener" in the examples) manufactured by Kyodo Yushi Co. , Ltd. , Tokyo, Japan, is employed as defined in US 5,589,444 (hereinafter referred to as a thickener), and is a reaction product of 4,4'-methylenediphenyl diisocyanate with octadecylamine.  In addition, a calcium complex thickener (calcium compound thickener) is used which is a product of the reaction of calcium hydroxide with two carboxylic acids, one having a short chain of carbons having a length of 2 to 5 carbon atoms and the other having a long carbon chain of 16 to 20 carbon atoms in which the ratio of the short chain to the long chain is from 1: 2 to 1: 5.  Examples having mixtures containing

  a urea-based thickener and a calcium complex thickener, therefore, comprising a urea-complex thickener as defined by the present invention. Wax As a wax compound, a fatty lignite wax marketed by Clariant GmbH, Augsburg, Germany, under the trade name "Licowax OP", 10 being a wax of ester lignite, partially saponified, with a drop point of about 100 C (DIN 51 801/1 or ASTM D 127) and a viscosity of about 300 mPa * s at 120 ° C (DIN 53 018) is used ("lignite wax" in the examples).

Corrosion Inhibitor As a corrosion inhibitor, disodium sebacate is used. Antioxidation Agent As an anti-oxidation agent (antioxidant), a diphenylamine with butyl and / or octyl groups is used, marketed by Ciba Specialty Chemicals, Switzerland under the trade name "L57" (Irganox L57).

EP Additive As an EP agent, a sulfurized organic compound (di-t-butyl polysulfide) marketed under the trade name C9002 by Infineum International Ltd., Oxfordshire, UK, with an inactive sulfur content of 30.degree. about 45% ("EP additive" in the examples) at room temperature (20 ° C or 25 ° C) and a quantity of active sulfur at 100 ° C of about 5% by weight, and at about 290 ° C (140 ° C) 15% by weight, the weight percentage being based on the amount of EP agent itself, is used. First, the advantages of the grease composition according to the present invention have been examined by measuring the coefficient of friction and the welding force. Six different compositions of fats were produced, listed in Table 1: Table 1 Composition of Example Example Example Example Example Example fat Al A2 A3 A4 A5 A6% by weight) TNMoS 0.5 0.5 0.5 0.5 0 0.5 ZnDTP 0.5 0.5 0.5 - 0.5 0.5 MoDTP 0.5 0.5 0.5 - 0.5 MoDTC 0.5 0.5 0.5 0.5 - Thickener based on 3.0 3.0 3.0 3.0 3.0 Calcium complex Oil mixture 87 90 88 85 85 85 Thickener L 8 8 8 8 8 8 The results of the SRV measurements of the coefficient of friction As well as measurements of the welding force of Examples A1 to A6 can be derived from Figure 1. Example A2 contains no calcium complex thickeners and / or no calcium thickeners, and therefore, it does not include a urea complex thickener, while the other examples include a urea compound thickener. In addition, the amounts of the additive package and the composition thereof are varied in Examples A1 to A6. The coefficient of friction of Example A1 is less than 0.06 and is the lowest coefficient of friction measured in said series of tests. The coefficient of friction of Example A2 is greater than 0.08 and is the highest coefficient of friction measured. In addition, the friction coefficients of Examples A4 and A5 are likewise slightly higher than the coefficients of friction of Examples A1, A3 and A6. It can be deduced from the coefficients of friction measurements that the addition of a set of additives containing at least one ZnDTP, at least one MoDTP, and at least one MoDTC gives the lowest values for the coefficient of friction. In addition, the addition of at least one ZnDTP as well as at least one MoDTP, preferably in combination with each other (see Example A6) is preferred. It can be deduced from the measurements of the welding force in Fig. 1 (b) that the welding force of Example A1 as well as Example A5 is higher than the measured welding or welding force for the others. examples. Therefore, the grease composition according to Example A1 shows the best values not only for the coefficient of friction, but also with regard to the welding force and therefore has good performance for extreme pressure.

In another series of tests, the amount of TNMoS as well as the composition of the additive package are varied. Three fat compositions were prepared according to Table 2. Table 2 Fat composition Example Example Example (% by weight) B1 = A1 B2 B3 TNMoS 0.5 1.0 0.1 ZnDTP 0.5 1.0 0.1 MoDTP 0.5 1.0 0.1 MoDTC 0.5 1.0 0.1 Complex Thickener 3.0 3.0 3.0 Calcium Mixture of Oils 87 85 88.6 Thickener 8 8 8 20 In all Examples B1 to B3, the amount of thickener remains unchanged, while the amount of the TNMoS compound as well as the components of the additive package were changed to 0.1% by weight, at 0.degree. , 5% by weight and 1.0% by weight, respectively, in each case relative to the total amount of the fat composition. The results of the SRV measurements with respect to the coefficient of friction as well as with respect to the welding force can be observed on or deduced from FIG. 2. Example B1 (= Al) has the lowest coefficient of friction and the highest welding force, and therefore has very good extreme pressure performance compared to Examples B2 and B3. In addition, the reduction of the amount of the TNMoS compound as well as the components of the additive package to values of about 0.1% by weight clearly results in an increase in the coefficient of friction and a decrease in the welding force. Therefore, at least about 0.25% by weight of the TNMoS compound as well as at least one of ZnDTPs, MoDTPs and MoDTCs should preferably be present in the fat composition.

In a third series of tests, the effect of adding a calcium compound thickener added to four fat compositions C1 to C4 according to Table 3 is investigated. Table 3 Fat composition Example Example Example Example (% by weight) C l = A1 C2 = A2 C3 C4 TNMoS 0.5 0.5 0.5 0.5 ZnDTP 0.5 0.5 0.5 0.5 MoDTP 0.5 0.5 0 , 0.5 0.5 MoDTC 0.5 0.5 0.5 0.5 Thickener based on 3.0 1.5 15 Calcium complex Mixture of oils 87 90 88.5 75 Thickener 8 8 8 8 20 The Example C2 is identical to Example A2. It can be deduced from the SRV measurements of the coefficient of friction as well as the measurement of the welding force 2907461 or welding (see FIG. 3) that the addition of 3% by weight of calcium compound-based thickener resulted in lower coefficient of friction values and a weld force greater than 3000 N. The welding force is particularly increased by adding 15% by weight of calcium complex thickener in accordance with FIG. Example C4, and, however, the coefficient of friction is also increased to values of about 0.08. This third series of tests indicates that the amount of calcium complex thickener employed in the fat composition may be from about 0.5% by weight to about 20% by weight, preferably about 15% by weight. thus constituting a thickener based on a urea compound with the thickener. More preferred grease compositions are the grease compositions listed in Table 4. Table 4 Grease Composition Example Example (wt%) D 1 D2 TNMoS 0.5 0.5 ZnDTP 1.0 2.0 MoDTC 2.5 2.5 Lignite wax 1.0 1.0 Corrosion inhibitor 0.2 0.2 Antioxidant 0.5 0.5 Additive EP 0.5 Mixture of oils 88.3 86.8 Thickener 6 As can be seen from FIG. 4, the coefficient of friction of Example D2 is less than 0.05, and even lower than the coefficient of friction of Example C1. Wear of Example D2 is not detectable (Figure 5). Therefore, the addition of an EP additive as well as the increase in the amount of ZnDTP results in a fat composition with greatly preferred properties, when they include D1 and D2.

In summary, the grease composition according to the present invention has a significant advantageous influence on the coefficient of friction and the wear, leading to good performance at extreme pressures as well as good performance of the BVDs of the JH. Of course, the invention is not limited to the embodiments described and shown in the accompanying drawings. Modifications are possible, particularly from the point of view of the constitution of the various elements or by substitution of technical equivalents, without departing from the scope of protection of the invention.

Claims (11)

  A grease composition for use in constant velocity joints comprising a) a base oil composition; b) at least one trinuclear molybdenum compound having the formula Mo3 SkLnQz 'wherein L are independently selected ligands having organo groups having a sufficient number of carbon atoms to render the compound soluble or dispersible in the oil; n is 1 to 4, k is 4 to 7, Q is selected from the group of neutral electron donor compounds such as amines, alcohols, phosphines and ethers, and z is in the range of 0 at 5 and includes non-stoichiometric values; c) at least one thickener based on a urea derivative. 15   2. Fat composition according to claim 1, characterized in that the thickener based on a urea derivative is chosen from the group comprising diurea and / or polyurea compounds and mixtures of said compounds with thickeners. calcium base.   3. The grease composition according to claim 1, characterized in that it further comprises at least one zinc dithiophosphate, a molybdenum dithiocarbamate and / or a molybdenum dithiophosphate.   A grease composition according to any of the preceding claims, characterized in that the amount of zinc dithiophosphates, molybdenum dithiophosphates and / or molybdenum dithiocarbamates is in the range of 0.1 wt% to 5 wt. % by weight, based on the total amount of the fat composition.   5. Fat composition according to claim 4, characterized in that the percentage by weight added, based on the total amount of the fat composition, of each of the zinc dithiophosphates, the 2907461 27 molybdenum dithiophosphates and / or the dithiocarbamates Molybdenum is essentially the same.   6. Grease composition according to any one of the preceding claims, characterized in that it further comprises an agent comprising at least one anti-oxidation agent, a corrosion inhibitor, an anti-wear agent, a wax, a friction modifier and / or an extreme pressure agent (EP agent).   A grease composition according to any one of the preceding claims, characterized in that it comprises from 50% by weight to 98.9% by weight of the base oil composition, from 0.1% by weight to 5% by weight of at least one trinuclear molybdenum compound, from 1% by weight to 25% by weight of at least one thickener based on a urea derivative, in each case based on the total amount of the fat composition.   A grease composition according to any one of the preceding claims, characterized in that it comprises from 70% by weight to 92% by weight of the base oil composition, from 0.3% by weight to 2% by weight of the at least one trinuclear molybdenum compound, from 4.5% by weight to 20% by weight of the at least one urea derivative thickener, from 1.5% by weight to 3.5% by weight at least one molybdenum dithiocarbamate, from 0.5% by weight to 3% by weight of the at least one zinc dithiophosphate, and from 0.5% by weight to 2% by weight of at least one wax.   A grease composition according to any one of the preceding claims, characterized in that the percentage by weight added, based on the total amount of the grease composition, of trinuclear molybdenum compounds is substantially identical to the weight percentage added of each of zinc dithiophosphate, molybdenum dithiophosphate and / or molybdenum dithiocarbamate.   10. A grease composition according to any of the preceding claims, characterized in that the percentage by weight added, based on the total amount of the grease composition, of trinuclear molybdenum compounds is 4 to 10 times lower than the percentage by weight. the total amount of zinc dithiophosphates, molybdenum dithiophosphates and / or molybdenum dithiocarbamates added.   11. Grease composition according to one of the preceding claims, characterized in that the coefficient of sliding or sliding friction is at most 0.08.