USE OF A MONOESTER IN A LUBRICANT COMPOSITION FOR VEHICLE TRANSMISSIONS

Abstract

The present invention relates to the use of a composition comprising 1-methylheptyl laurate as a lubricant composition for transmissions.

Claims

1.-12. (canceled)

13. A method of using a composition comprising 1-methylheptyl laurate as a lubricating composition for transmissions.

14. The method according to claim 13, wherein the transmissions are (i) transmissions in internal combustion engines and/or (ii) reduction gears in electric motors.

15. The method according to claim 13, wherein the efficiency of transmissions is improved.

16. The method according to claim 13, wherein the fuel consumption of a vehicle equipped with the transmission component is reduced when the transmission is lubricated by means of said lubricating composition.

17. The method according to claim 13, wherein the transmissions are reduction gears in electric motors and wherein the efficiency performance of reduction gears in the electric motors is improved.

18. The method according to claim 13, wherein the transmissions are transmissions of an electric or hybrid vehicle and wherein the autonomy of the battery of the electric or hybrid vehicle is extended.

19. The method according to claim 13, wherein the lubricating composition comprises 5 to 50% by weight of 1-methylheptyl laurate, relative to the total weight of the lubricating composition.

20. The method according to claim 13, wherein the composition comprises: from 5 to 50% by weight of 1-methylheptyl laurate, and from 50 to 95% by weight of one or more base oils different from 1-methylheptyl laurate, with respect to the total weight of the lubricating composition.

21. The method according to claim 13, wherein said lubricating composition has a kinematic viscosity at 100 C. ranging from 1 to 6 mm.sup.2/s.

22. The method according to claim 13, wherein 1-methylheptyl laurate has a carbon content of biological origin of at least 90% by weight relative to the total weight of the carbon atoms.

23. The method according to claim 13, characterized in that said lubricating composition comprises, in addition to 1-methylheptyl laurate, at least one additive chosen from antioxidants, additives improving the viscosity index, pour point depressants, anti-foam agents, anticorrosion agents, anti-wear and/or extreme-pressure additives, friction modifiers, detergents, dispersants and mixtures thereof.

24. The method according to claim 23, wherein the additive or additives represent from 0.01 to 20% by weight, relative to the total weight of the lubricating composition.

25. A method for lubricating at least one mechanical part of a transmission member of motor vehicles, the method comprising at least one step wherein the mechanical part is brought into contact with at least one lubricating composition comprising 1-methylheptyl laurate.

26. The method according to claim 25, wherein the motor vehicle is light or heavy vehicles.

27. The method according to claim 25, wherein the transmission member is selected from a gearbox, axles, a reduction gear.

28. The method according to claim 25, wherein the composition comprises: from 5 to 50% by weight of 1-methylheptyl laurate, and from 50 to 95% by weight of one or more base oils different from 1-methylheptyl laurate, with respect to the total weight of the lubricating composition.

29. The method according to claim 25, wherein 1-methylheptyl laurate has a carbon content of biological origin of at least 90% by weight relative to the total weight of the carbon atoms.

30. The method according to claim 25, characterized in that said lubricating composition comprises, in addition to 1-methylheptyl laurate, at least one additive chosen from antioxidants, pour point depressants, anti-foam agents, anticorrosion agents, and mixtures thereof.

31. The method according to claim 30, wherein the additive or additives represent from 0.1 to 15% by weight, relative to the total weight of the lubricating composition.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0031] FIG. 1 shows schematically an electric or hybrid vehicle propulsion system.

DETAILED DESCRIPTION

[0032] Firstly, the invention relates to the use of 1-methylheptyl laurate in a lubricating composition for transmissions.

[0033] The invention relates to the use of a composition comprising 1-methylheptyl laurate as a lubricating composition for transmissions.

[0034] 1-methylheptyl laurate can be obtained by an esterification reaction between lauric acid and octane-2-ol.

[0035] Preferably, lauric acid and/or octane-2-ol are of bio-based origin. Octan-2-ol of bio-based origin can be obtained by cracking ricinoleic acid.

[0036] Thereby, preferably, 1-methylheptyl laurate has a carbon content of biological origin of at least 90% by weight, preferably of at least 95% by weight, advantageously of 100% by weight, relative to the total weight of the carbon atoms.

[0037] Within the framework of the present invention, the content of carbon of biological origin can be measured as per the standard ASTM D6866.

[0038] 1-methylheptyl laurate, also called the monoester of the invention, is used in a lubricating composition for transmissions.

Other Base Oil(s)

[0039] The lubrication composition used according to the invention may comprise, in addition to the monoester according to the invention, one or more base oils distinct from the monoester according to the invention.

[0040] Said base oil(s) optionally present in a lubrication composition according to the invention, are chosen suitably, with regard to the compatibility thereof with the monoester used according to the invention.

[0041] There can be a mixture of several base oils, e.g. a mixture of two, three, or four base oils.

[0042] Preferably, the base oil or mixture of other base oils used in lubricating composition according to the invention may have a kinematic viscosity, measured at 100 C. as per the standard ASTM D445, ranging from 1.5 to 8 mm.sup.2/s, in particular from 1.5 to 6.1 mm.sup.2/s, more particularly from 1.5 to 4.1 mm.sup.2/s, even more particularly from 1.5 to 2.1 mm.sup.2/s.

[0043] The base oils can be chosen from mineral or synthetic oils belonging to groups I to V as per the classes defined by the API classification (or the equivalents thereof as per the ATIEL classification) and shown in Table 1 hereinafter, or mixtures thereof.

TABLE-US-00001 TABLE 1 Concentration Sulfur Viscosity of saturates concentration index (VI) Group I <90% >0.03% 80 VI < 120 (mineral oils) Group II 90% 0.03% 80 VI < 120 (Hydrocracked oils) Group III 90% 0.03% 120 (Hydro-isomerized or hydrocracked oils) Group IV Polyalphaolefins (PAO) Group V Esters and other bases not included in groups I to IV

[0044] The mineral base oils include any type of base oil obtained by atmospheric distillation and vacuum distillation of crude oil, followed by refining operations such as solvent extraction, deasphalting, solvent dewaxing, hydrotreatment, hydrocracking, hydroisomerization and hydrofinishing.

[0045] Mixtures of synthetic and mineral oils which can be biosourced, can be also be used.

[0046] There is generally no limitation with regard to the use of different additional base oils for producing lubrication compositions, except that the compositions preferably have to have properties, in particular in terms of viscosity index, of content of sulfur or of resistance to oxidation, suitable for use in propulsion systems of either an electric or hybrid vehicle.

[0047] The base oils can be further chosen from synthetic oils, such as certain carboxylic acid esters and alcohol esters distinct from the diester defined according to the invention, among polyalphaolefins (PAO), and among polyalkylene glycol (PAG) obtained by polymerization or copolymerization of alkylene oxides comprising from 2 to 8 carbon atoms, more particularly from 2 to 4 carbon atoms.

[0048] The PAOs used as base oils are e.g. obtained from monomers comprising from 4 to 32 carbon atoms, e.g. from octene or decene.

[0049] The weight-average molecular weight of the PAO can vary quite significantly. Preferentially, the weight-average molecular weight of the PAO is less than 600 Da. The weight-average molecular weight of the PAO can further range from 100 to 600 Da, from 150 to 600 Da, or further from 200 to 600 Da.

[0050] For example, the PAOs used in the context of the invention, having a kinematic viscosity, measured at 100 C. as per the standard ASTM D445, ranging from 1.5 to 8 mm.sup.2/s, are sold commercially by Ineos under the trademarks Durasyn 162, Durasyn 164, Durasyn 166 and Durasyn 168.

[0051] Advantageously, the additional base oil or oils are chosen from polyalphaolefins (PAOs).

[0052] It is for a person skilled in the art to adjust the content of ancillary base oil(s) present in the lubrication composition according to the invention.

[0053] According to an embodiment, a composition according to the invention may comprise from 5 to 95% by weight, preferably from 50 to 95% by weight, else preferably from 60 to 90% by weight, of one or more base oils different from the monoester according to the invention, relative to the total weight of said composition.

Additives

[0054] A lubrication composition according to the invention may further comprise one or more additives known to a person skilled in the art in the field of lubrication of transmissions, more particularly for internal combustion engines and for propulsion systems for electric of hybrid vehicles.

[0055] The additives which can be incorporated into a composition according to the invention, can be chosen from antioxidants, pour point depressants, anti-foam agents, anticorrosion agents, anti-wear and/or extreme-pressure additives, friction modifiers, detergents, dispersants and mixtures thereof, more particularly from antioxidants, pour point depressants, anti-foam agents and anticorrosion agents.

[0056] Preferably, a lubrication composition according to the invention may further comprise one or more additives chosen from antioxidants, anti-foam agents, pour point improvers, viscosity index improvers, and anti-corrosion agents.

[0057] The addition of one or more additives chosen from anti-wear additives, friction modifiers, detergents, extreme-pressure additives and dispersants, may also prove advantageous within the framework of the use of the lubricating composition according to the invention as a multifunctional fluid, e.g. for cooling the battery and/or the electronic power components, and for lubricating parts of the propulsion system, e.g. the transmission, in an electric or hybrid vehicle.

[0058] It is understood that the nature and the amount of additives used are chosen so as not to affect the properties of the lubrication composition imparted by the monoester according to the invention.

[0059] Such additives can be introduced separately and/or as a mixture similar to the additives already available for sale for commercial lubricant formulations for vehicle engines, with a performance level as defined by ACEA (European Automobile Manufacturers Association) and/or API (American Petroleum Institute), well known to a person skilled in the art.

[0060] Said additive(s) may be present in the lubricating composition according to the invention in a content of less than or equal to 20% by weight, more particularly from 0.01 to 20% by weight, preferably from 0.1 to 15% by weight, else preferably from 0.5 to 10% by weight, relative to the total weight of said composition.

[0061] A lubricating composition according to the invention can thereby comprise at least one antioxidant additive.

[0062] The invention thereby relates, according to one of the aspects thereof, to a lubricating composition, more particularly apt to lubricate a transmission, more particularly of an internal combustion engine or of a propulsion system of an electric or hybrid vehicle, said composition comprising (i) at least one monoester according to the invention, and (ii) at least one antioxidant additive.

[0063] The antioxidant additive generally makes it possible to delay the degradation of the composition in service. Such degradation is most often seen in a deposit formation, in the presence of sludge or in an increase in the viscosity of the composition.

[0064] Antioxidant additives in particular act as radical inhibitors or destroyers of hydroperoxides. The antioxidant additives commonly used include phenolic antioxidants, amine antioxidant additives, phosphosulfur antioxidant additives. Some of such antioxidant additives, e.g. phosphosulfur antioxidant additives, can generate ashes. The phenolic antioxidant additives can be ashless or in the form of neutral or basic metal salts. The antioxidant additives can in particular be chosen from sterically hindered phenols, sterically hindered phenol esters and sterically hindered phenols comprising a thioether bridge, diphenylamines, diphenylamines substituted with at least one C.sub.1-C.sub.12 alkyl moiety, N,N-dialkyl-aryl-diamines and mixtures thereof.

[0065] Preferentially, according to the invention, the sterically hindered phenols are chosen from compounds comprising a phenol group of which at least one of the carbons neighboring the carbon atom bearing the alcohol function, is substituted by at least one C.sub.1-C.sub.10 alkyl group, preferentially a C.sub.1-C.sub.6 alkyl group, preferentially a C.sub.4 alkyl group, preferentially a tert-butyl group.

[0066] Amine compounds are another class of antioxidant additives which can optionally be used in combination with phenolic antioxidant additives. Examples of amine compounds are aromatic amines, e.g. aromatic amines with the formula NR.sup.4R.sup.5R.sup.6 wherein R.sup.4 represents an aliphatic group or a possibly substituted aromatic group, R.sup.5 represents a possibly substituted aromatic group, R.sup.6 represents a hydrogen atom, an alkyl group, an aryl group or a group with the formula R.sup.7S(O).sub.zR.sup.8 wherein R.sup.7 represents an alkylene or an alkenylene group, R.sup.8 represents an alkyl group, an alkenyl group or an aryl group and z is 0, 1 or 2.

[0067] Sulfur alkyl phenols or the alkali or alkaline-earth metal salts thereof can also be used as antioxidant additives.

[0068] Another class of antioxidant additives is the class of copper compounds, e.g. copper thio- or dithio-phosphate, copper salts and carboxylic acid salts, copper dithiocarbamates, copper sulfonates, copper phenates, copper acetylacetonates. Copper salts I and II, succinic acid salts or succinic anhydride salts can also be used.

[0069] Advantageously, a lubricating composition comprises at least one ashless antioxidant additive.

[0070] Said additive(s) may be used, in a lubricating composition according to the invention, in a proportion of 0.1 to 2% by weight, relative to the total mass of the composition.

[0071] A lubricating composition according to the invention can also comprise at least one anti-wear and/or extreme pressure additive.

[0072] Anti-wear additives and extreme pressure additives protect surfaces subject to friction by forming a protective film adsorbed on the surfaces.

[0073] There is a wide variety of anti-wear additives. Preferably, the anti-wear additives are chosen from phosphorus-sulfur additives such as metal alkylthiophosphates, more particularly zinc alkylthiophosphates, and more specifically zinc dialkyldithiophosphates or ZnDTP. Preferred compounds have the formula Zn((SP(S)(OQ.sup.2)(OQ.sup.3)).sub.2, wherein Q.sup.2 and Q.sup.3either identical or different-independently represent an alkyl group, preferentially an alkyl group including from 1 to 18 carbon atoms.

[0074] Amine phosphates are also anti-wear additives which can be used in the lubricating compositions according to the invention. However, the phosphorus provided by such additives can act as a poison in the catalytic systems of cars since same generate ash. Such effects can be minimized by partially substituting the amine phosphates with additives which do not bring phosphorous, such as e.g. polysulfides, in particular sulfur olefins.

[0075] A lubricating composition may comprise from 0.01 to 6% by weight, preferentially from 0.05 to 4% by weight, more preferentially or from 0.1 to 2% by weight of anti-wear additives and extreme-pressure additives, with respect to the total weight of the composition.

[0076] A lubricating composition according to the invention can further comprise an anti-foam agent.

[0077] The anti-foam agent can be chosen from silicones.

[0078] A lubricating composition can comprise from 0.01 to 2% by weight or from 0.01 to 5% by weight, preferentially from 0.1 to 1.5% by weight or from 0.1 to 2% by weight of anti-foam agent, with respect to the total weight of the composition.

[0079] A lubricating composition according to the invention can further comprise at least one friction modifier additive.

[0080] The friction modifier additives can be chosen from compounds providing metallic elements and ashless compounds. Compounds providing metal elements include complexes of transition metals such as Mo, Sb, Sn, Fe, Cu, Zn the ligands of which can be hydrocarbon compounds comprising oxygen, nitrogen, sulfur or phosphorus atoms. Ashless friction modifier additives are generally of organic origin and can be chosen from fatty acid and polyol monoesters, alkoxylated amines, alkoxylated fatty amines, fatty epoxides, fatty epoxide borates, fatty amines acid or fatty acid glycerol esters. According to the invention, fatty compounds comprise at least one hydrocarbon moiety comprising from 10 to 24 carbon atoms.

[0081] A lubricating composition may comprise from 0.01 to 2% by weight or from 0.01 to 5% by weight, preferentially from 0.1 to 1.5% by weight or from 0.1 to 2% by weight of friction modifier additive, with respect to the total weight of the composition.

[0082] A lubricating composition according to the invention may comprise at least one additive making it possible to improve the viscosity index of the lubricating composition (in English viscosity index improver).

[0083] Viscosity index improver, as defined by the invention, refers to a chemical compound serving to provide good cold resistance and a minimum viscosity at high temperature of the lubricating composition.

[0084] Examples of polymers improving the viscosity index include polymer esters; hydrogenated or non-hydrogenated homopolymers or copolymers of styrene, of butadiene and of isoprene; homopolymers or copolymers of olefin, such as ethylene or propylene; polyacrylates and polymethacrylates (PMA).

[0085] The lubricating composition according to the invention typically comprises from 0.1% to 15% by weight of viscosity index improvers, relative to the total weight of the lubricating composition.

[0086] A lubricating composition according to the invention can comprise at least one detergent additive.

[0087] Detergent additives generally reduce the formation of deposits on the surface of metal parts, by dissolving oxidation and combustion by-products.

[0088] The detergent additives which can be used in the lubricating compositions are generally known to a person skilled in the art. The detergent additives can be anionic compounds comprising a lipophilic hydrocarbon moiety and a hydrophilic head. The associated cation can be a metal cation of an alkali or alkaline earth metal.

[0089] Detergent additives are preferentially chosen from alkali metal salts or alkaline-earth metal salts of carboxylic acid, sulfonates, salicylates, naphthenates, as well as phenate salts. The alkali metals and alkaline earth metals are preferentially calcium, magnesium, sodium or barium.

[0090] Such metal salts generally include the metal in a stoichiometric amount or in an excess amount, i.e. in a concentration greater than the stoichiometric amount. Same are then overbased detergents; the metal in excess which gives the overbased character to the detergent additive is generally in the form of an oil-insoluble metal salt, e.g. a carbonate, a hydroxide, an oxalate, an acetate, a glutamate, preferentially a carbonate.

[0091] A lubricating composition used according to the invention can comprise e.g. from 2 to 4% by weight of detergent additive, with respect to the total weight of the composition.

[0092] A lubricating composition used according to the invention can further comprise at least one pour point depressant additive.

[0093] By slowing down the formation of paraffin crystals, the pour point depressant additive generally improves the behavior of the composition under cold conditions. Examples of pour point depressant additives include alkyl polymethacrylates, polyacrylates, polyarylamides, polyalkylphenols, polyalkylnaphthalene, alkyls polystyrenes.

[0094] The lubricating composition used according to the invention can e.g. comprise from 0.05 to 2% by weight of pour point depressant additive, with respect to the total weight of the composition.

[0095] Also, a lubricating composition used according to the invention can comprise at least one dispersant agent.

[0096] The dispersant agent can be chosen from Mannich bases, succinimides and derivatives thereof. A lubricating composition used according to the invention can comprise e.g. from 0.2 to 10% by weight of dispersant agent, with respect to the total weight of the composition.

[0097] According to a particular embodiment, a lubricating composition used according to the invention comprises, or even is formed (i) by at least one monoester according to the invention and (ii) by at least one additive chosen from antioxidants, anti-foam agents, pour point depressants, anti-corrosion agents, anti-wear and/or extreme pressure additives, friction modifiers, detergents, dispersants, and mixtures thereof, preferably from antioxidants, pour point depressants, anti-foam agents, anti-corrosion agents, and mixtures thereof.

[0098] Advantageously, a lubricating composition used according to the invention comprises (i) the monoester according to the invention and (ii) at least one antioxidant additive.

[0099] According to one particular embodiment, a lubricating composition used according to the invention comprises, or even consists of: [0100] from 5 to 50% by weight, preferably from 10 to 40% by weight, of 1-methylheptyl laurate; [0101] from 50 to 95% by weight, preferably from 60 to 90% by weight, of one or more base oils different from 1-methylheptyl laurate, [0102] optionally from 0.01 to 20% by weight, preferably from 0.1 to 15% by weight, else preferably from 0.5 to 10% by weight, of one or more additives chosen from friction modifier additives, anti-wear additives, extreme pressure additives, detergents, antioxidants, viscosity index (VI) improvers, pour point depressant additives (PPD), dispersants, anti-foam agents, thickeners, corrosion inhibitors, copper passivating agents, and mixtures thereof; and
the contents being expressed with respect to the total weight of said composition.

[0103] According to one particular embodiment, a lubricating composition used according to the invention comprises, or even consists of: [0104] from 5 to 45% by weight, preferably from 10 to 40% by weight, of 1-methylheptyl laurate; [0105] from 50 to 95% by weight, preferably from 55 to 90% by weight, of one or more base oils different from 1-methylheptyl laurate, [0106] from 0.01 to 20% by weight, preferably from 0.1 to 15% by weight, else preferably from 0.5 to 10% by weight, of one or more additives chosen from friction modifier additives, anti-wear additives, extreme pressure additives, detergents, antioxidants, viscosity index (VI) improvers, pour point depressant additives (PPD), dispersants, anti-foam agents, thickeners, corrosion inhibitors, copper passivating agents, and mixtures thereof; and
the contents being expressed with respect to the total weight of said composition.

[0107] According to one particular embodiment, a lubricating composition used according to the invention comprises, or even consists of: [0108] from 5 to 50% by weight, preferably from 10 to 40% by weight, of 1-methylheptyl laurate; [0109] from 50 to 95% by weight, preferably from 55 to 90% by weight, of one or more base oils different from esters; [0110] optionally from 0.01 to 20% by weight, preferably from 0.1 to 15% by weight, else preferably from 0.5 to 10% by weight, of one or more additives chosen from friction modifier additives, anti-wear additives, extreme pressure additives, detergents, antioxidants, viscosity index (VI) improvers, pour point depressant additives (PPD), dispersants, anti-foam agents, thickeners, corrosion inhibitors, copper passivating agents, and mixtures thereof; and
the contents being expressed with respect to the total weight of said composition.

[0111] According to one particular embodiment, a lubricating composition used according to the invention comprises, or even consists of: [0112] from 5 to 45% by weight, preferably from 10 to 40% by weight, of 1-methylheptyl laurate; [0113] from 50 to 95% by weight, preferably from 55 to 90% by weight, of one or more base oils different from esters; [0114] from 0.01 to 20% by weight, preferably from 0.1 to 15% by weight, else preferably from 0.5 to 10% by weight, of one or more additives chosen from friction modifier additives, anti-wear additives, extreme pressure additives, detergents, antioxidants, viscosity index (VI) improvers, pour point depressant additives (PPD), dispersants, anti-foam agents, thickeners, corrosion inhibitors, copper passivating agents, and mixtures thereof; and
the contents being expressed with respect to the total weight of said composition.

[0115] According to one particular embodiment, a lubricating composition used according to the invention comprises, or even consists of: [0116] from 5 to 45% by weight, preferably from 10 to 40% by weight, of 1-methylheptyl laurate; [0117] from 50 to 95% by weight, preferably from 55 to 90% by weight, of one or more base oils different from esters; [0118] 1 from 0.01 to 20% by weight, preferably from 0.1 to 15% by weight, else preferably from 0.5 to 10% by weight, of one or a plurality additives selected from antioxidants, pour point depressants, antifoaming agents, anticorrosion agents, and mixtures thereof; and
the contents being expressed with respect to the total weight of said composition.

[0119] According to one particular embodiment, a lubricating composition used according to the invention comprises, or even consists of: [0120] from 5 to 50% by weight, preferably from 10 to 40% by weight, of 1-methylheptyl laurate; [0121] from 50 to 95% by weight, preferably 55 to 90% by weight, of one or more mineral or synthetic base oils selected from group I oils, group II oils, group III oils and group IV oils, and mixtures thereof; [0122] optionally from 0.01 to 20% by weight, preferably from 0.1 to 15% by weight, else preferably from 0.5 to 10% by weight, of one or more additives chosen from friction modifier additives, anti-wear additives, extreme pressure additives, detergents, antioxidants, viscosity index (VI) improvers, pour point depressant additives (PPD), dispersants, anti-foam agents, thickeners, corrosion inhibitors, copper passivating agents, and mixtures thereof; and
the contents being expressed with respect to the total weight of said composition.

[0123] According to one particular embodiment, a lubricating composition used according to the invention comprises, or even consists of: [0124] from 5 to 45% by weight, preferably from 10 to 40% by weight, of 1-methylheptyl laurate; [0125] from 50 to 95% by weight, preferably 55 to 90% by weight, of one or more mineral or synthetic base oils selected from group I oils, group II oils, group III oils and group IV oils, and mixtures thereof; [0126] from 0.01 to 20% by weight, preferably from 0.1 to 15% by weight, else preferably from 0.5 to 10% by weight, of one or more additives chosen from friction modifier additives, anti-wear additives, extreme pressure additives, detergents, antioxidants, viscosity index (VI) improvers, pour point depressant additives (PPD), dispersants, anti-foam agents, thickeners, corrosion inhibitors, copper passivating agents, and mixtures thereof; and
the contents being expressed with respect to the total weight of said composition.

[0127] According to one particular embodiment, a lubricating composition used according to the invention comprises, or even consists of: [0128] from 5 to 45% by weight, preferably from 10 to 40% by weight, of 1-methylheptyl laurate; [0129] from 50 to 95% by weight, preferably 55 to 90% by weight, of one or more mineral or synthetic base oils selected from group I oils, group II oils, group III oils and group IV oils, and mixtures thereof; [0130] from 0.01 to 20% by weight, preferably from 0.1 to 15% by weight, else preferably from 0.5 to 10% by weight, of one or more additives selected from antioxidants, pour point depressants, antifoaming agents, anticorrosion agents, and mixtures thereof; and
the contents being expressed with respect to the total weight of said composition.

[0131] A lubricating composition used according to the invention advantageously has a kinematic viscosity, measured at 100 C. as per the standard ASTM D445, ranging from 1 to 6 mm.sup.2/s, preferably from 1 to 4 mm.sup.2/s.

[0132] A lubricating composition used according to the invention advantageously has a kinematic viscosity, measured at 40 C. as per the standard ASTM D445, ranging from 2 to 20 mm.sup.2/s, preferably from 3 to 10 mm.sup.2/s.

Application

[0133] As indicated hereinabove, the lubricating composition according to the invention can be used as a lubricating fluid for transmission.

[0134] More particularly, the lubricating composition defined in the present invention serves to improve the efficiency performance of transmissions.

[0135] 1-methylheptyl laurate improves the performance of transmissions when incorporated into a lubricating composition used to lubricate transmissions.

[0136] 1-methylheptyl laurate also improves the fuel-saving properties, so-called Fuel-Eco properties of the lubricating composition comprising said 1-methylheptyl laurate. Indeed, 1-methylheptyl laurate serves to reduce the traction coefficient of the lubricating composition comprising said 1-methylheptyl laurate.

[0137] The transmissions may be transmissions for engines of internal combustion vehicles and/or transmissions for propulsion systems of electric or hybrid vehicles.

[0138] The transmission of a propulsion system of an electric or hybrid vehicle more specifically includes a reduction gear. Thereby, the monoester according to the invention serves most particularly to improve the efficiency of the reduction gears in the propulsion systems of electric or hybrid vehicles.

[0139] As shown diagrammatically in FIG. 1, the propulsion system of an electric or hybrid vehicle comprises in particular the electric motor (1) part, an electric battery (2) and a transmission, and more particularly a speed reducer (3).

[0140] The electric motor typically comprises electronic power components (11) connected to a stator (13) and a rotor (14). The stator comprises coils, more particularly copper coils, which are alternately supplied with an electric current. In this way, a rotating magnetic field is generated. The rotor as such comprises coils or permanent magnets or other magnetic materials and is rotated by the rotating magnetic field.

[0141] The electronic power components (11), the stator (13) and the rotor (14) of a propulsion system (1) are parts which have a complex structure and generate a large amount of heat during the motor operation.

[0142] A bearing (12) is generally integrated between the stator (13) and the rotor (14). A transmission, and more particularly a reduction gear (3), serves to reduce the speed of rotation at the output of the electric motor and to adapt the speed transmitted to the wheels, making it possible at the same time to control the speed of the vehicle.

[0143] Advantageously, a lubricating composition defined in the present invention can be used to improve the efficiency of transmissions, more particularly for the engine of internal combustion engine vehicles and for the propulsion system of an electric or hybrid vehicle. More particularly, a lubricating composition defined in the present invention can be used to improve the efficiency of the reduction gears of the propulsion system of an electric or hybrid vehicle.

[0144] The invention further relates, according to another of the aspects thereof, to a method of lubrication of at least one mechanical part of a transmission member of motor vehicles, in particular of light or heavy vehicles, e.g. a gearbox, axles, preferably a manual gearbox and heavy vehicle axles, or else a reduction gear of electric or hybrid vehicles, said method comprising at least one step wherein said mechanical part is brought into contact with at least one lubricating composition according to the invention.

[0145] The invention further relates to the use of the monoester according to the invention, as defined hereinabove, for reducing the traction coefficient of a lubricating composition for transmission in a motor vehicle, more particularly of a lubricant for gearbox and/or of a lubricant for axles, in particular for heavy vehicle axles, or else for reduction gears in electric or hybrid vehicles.

[0146] Also, as mentioned hereinabove, a lubricating composition according to the invention has excellent properties in terms of reduction of the fuel consumption (Fuel Eco properties).

[0147] Advantageously, a lubricating composition according to the invention thereby has low traction coefficients.

[0148] A lubricating composition defined in the invention may also be used for cooling the electric motor of an electric or hybrid vehicle, more particularly for cooling the power electronics and/or the rotor and/or the stator of the electric motor and/or the motor reduction gear.

[0149] The invention will now be described by means of the following examples, given of course as an illustration of the invention, but not limited to.

Example

[0150] The properties of the monoester (E1) of the invention, lauric acid ester of 2-octanol, were compared with another monoester, lauric acid ester of 2-ethylhexanol (E2).

[0151] 2-ethylhexanol is not of bio-based origin whereas the 2-octanol used in the example is of bio-based origin.

[0152] The kinematic viscosity at 40 C. (KV40) and at 100 C. (KV100) were determined according to the standard ASTM D445.

[0153] The mini pour point (mini PP) is measured as per the standard ASTM D7346.

[0154] The viscosity index (VI) is measured as per ASTM D2270.

[0155] The tribological properties can be evaluated by a test on a tribometer of the MTM type (Mini Traction Machine also called ball-plane), of the brand PCs instruments. The test serves to evaluate the performance of lubricants in terms of friction in mixed/limit conditions according to the load, pressure or speed conditions applied.

[0156] The traction coefficient of the lubricating compositions tested is determined at 40 C., 100 C. and 140 C. by using a hardened steel ball of about 2 cm in diameter, e.g. 1.905 cm in diameter, on a hardened steel plane.

[0157] Such device serves for moving a steel ball and a steel plane relative to each other in order to determine friction coefficients for a given lubricating composition while varying various properties such as speed, load, and temperature. The hardened steel surface has an AISI 52100 reference with a mirror finish and the ball has also an AISI 52100 reference and is made of hardened steel.

[0158] The applied load is respectively 25 N and the speed of rotation varies from 20 mm/s to 2500 mm/s. (SRR (slide-roll ratio=5%))

[0159] Approximately 50 ml of lubricating composition tested were added into the device. The ball is engaged face-to-plane, said ball and said plane being actuated independently so as to create a mixed rolling/sliding contact.

[0160] The traction coefficient is measured and recorded by means of a force sensor.

[0161] Table 2 collates the results of the measurements of the tribological properties at 40 C. (40 C. SRR 5%), 100 C. (100 C. SRR 5%) and 140 C. (140 C. SRR 5%).

TABLE-US-00002 TABLE 2 E1 E2 KV40 (cSt) 1.855 1.801 KV100 (cSt) 5.31 5.086 mini PP ( C.) 36 33 VI 142 143 (40 C. SRR 5%) 0.01 0.021 (100 C. SRR 5%) 0.019 0.045 (140 C. SRR 5%) 0.019 0.038

[0162] As shown by the results of the table, the monoester according to the invention has a better traction coefficient, i.e. a lower traction coefficient, than the comparative monoester of the prior art. The lower traction coefficient will allow for a better gain in terms of fuel economy (Fuel-Eco) for an internal combustion engine and a better gain in terms of battery autonomy for an electric or hybrid vehicle.