Lubricant composition for automotive transmissions

Abstract

A lubricant composition includes at least one base oil; at least one additive having the formula (I):wherein R and R1 are selected independently of each other from among a hydrogen atom; or saturated or unsaturated, linear hydrocarbon groups containing from 8 to 20 carbon atoms; with at least one of the two radicals R or R1 being a saturated or unsaturated, linear hydrocarbon group containing from 8 to 20 carbon atoms.

Description

TECHNICAL FIELD

[0001] The present invention relates to the field of lubricant compositions, in particular for motor vehicles, especially for lubricating the transmission components of motor vehicles, in particular the gears of internal combustion engine or electric motor transmissions.STATE OF THE ART

[0002] Motor vehicle transmission components operate under high loads and at high speeds. The oils (also referred to as “lubricant compositions” or “lubricants”) for these transmissions must therefore be particularly effective in protecting the parts against wear and tear, and in particular protect the gear teeth against the phenomenon of gear seizure (or scoring / scuffing).

[0003] Seizure occurs under conditions of high loads and may be assessed by monitoring visible deterioration.

[0004] The prevention of this phenomenon involves reducing contact stresses by means of ensuring the appropriate geometry for the parts, and reducing friction by avoiding adhesion. The lubricant composition plays a key role in this prevention process, mainly through the physico-chemical reactivity of its additives.

[0005] Anti-wear and extreme pressure additives containing sulphur, phosphorus or borates are generally added in order to impart protective anti-seizing properties to transmission oils. Other additives present in the lubricant composition may also have an impact, either positive or negative, on this phenomenon.

[0006] Another advantage to be provided by the subject matter covered by the invention is to avoid the need to introduce any additive, and more particularly any extreme pressure anti-wear additive, which comprises sulphur. It is desirable to limit, or indeed completely eliminate sulphur from oils for transmissions, in particular for electric vehicle transmissions, in order to limit the occurrence of the phenomenon of corrosion and to limit the conductivity values to the required levels.

[0007] Advantageously, the object of the present invention relates to a composition that moreover also comprises no zinc-based anti-wear additive.

[0008] The document EP3546550A1 discloses a composition comprising the reaction product from the reaction between an acid phosphate and a nitrogen compound.

[0009] The document EP3812445A1 discloses a composition comprising an acid phosphate that contains hydrocarbon groups with 1 to 6 carbon atoms.

[0010] The compounds described in these documents do not always offer satisfactory lubricating properties, particularly in terms of durability and load carrying capacity.

[0011] It is therefore an object of the present invention to provide a composition that serves to lubricate manual or automatic transmission components, in particular the transmission gears of internal combustion vehicles or, preferably, electric vehicles, the said composition exhibiting good durability and being free of any sulphur-based additives.SUMMARY OF THE INVENTION

[0012] More precisely, the present invention relates to a lubricant composition comprising:

[0013] at least one base oil;

[0014] at least one additive having the formula (I):wherein,

[0016] R and R1 are selected independently of each other from among: a hydrogen atom; or saturated or unsaturated, linear hydrocarbon groups containing from 8 to 20 carbon atoms; with at least one of the two radicals R or R1 being a saturated or unsaturated, linear hydrocarbon group containing from 8 to 20 carbon atoms.

[0017] According to one embodiment, the hydrocarbon groups are selected from among alkyl groups and alkenyl groups.

[0018] Preferably, R and R1 are selected independently of each other from among linear alkyl groups containing from 8 to 18 carbon atoms.

[0019] Preferably, the lubricant composition comprises:

[0020] from 250 to 1300 ppm by weight of phosphorus, with preferably from 400 to 1400 ppm by weight of phosphorus provided by the one or more additive(s) having the formula (I); and / or

[0021] less than 10 ppm by weight of sulphur, preferably less than 5 ppm by weight of sulphur, more preferably less than 1 ppm by weight of sulphur.

[0022] According to one preferred embodiment, the lubricant composition according to the invention additionally also comprises at least one additive selected from among phosphites containing from 1 to 24 carbon atoms; preferably from among phosphites containing from 4 to 12 carbon atoms; preferably from among phosphites containing two alkyl groups each having from 2 to 6 carbon atoms.

[0023] Preferably, the lubricant composition comprises from 0.01 to 10% by weight, preferably from 0.05 to 5% by weight, more preferably from 0.1 to 3% by weight, of one or more additive(s) having the formula (I), relative to the total weight of the lubricant composition.

[0024] According to one preferred embodiment, the lubricant composition according to the invention comprises:

[0025] from 0.01 to 5% by weight, preferably from 0.02 to 2% by weight, of one or more additive(s) having the formula (I); and

[0026] from 0.05 to 5% by weight, preferably from 0.1 to 2% by weight, of one or more additive(s) selected from among phosphites containing two alkyl groups each having from 2 to 6 carbon atoms.

[0027] According to one embodiment of the invention, the lubricant composition additionally also comprises at least one dispersant, preferably a borated dispersant, even more preferably a borated dispersant selected from among borated succinimides, even more preferably from among borated polyisobutene succinimides.

[0028] According to one embodiment of the invention, the lubricant composition according to the invention comprises:

[0029] at least 70% by weight, preferably from 75 to 99.5% by weight, of one or more non-aqueous base oil(s);

[0030] from 0.01 to 5% by weight, in particular from 0.02 to 2% by weight, of one or more additive(s) having the formula (I);

[0031] from 0.05 to 5% by weight, preferably from 0.1 to 2% by weight, of one or more additive(s) selected from among phosphites containing from 1 to 24 carbon atoms;

[0032] optionally from 0.1 to 15% by weight, preferably from 1 to 10% by weight, of one or more functional additive(s), preferably selected from among dispersants, antioxidants, pour point depressants, antifoam agents or defoamers, and mixtures thereof;

[0033] relative to the total weight of the lubricant composition.

[0034] Preferably, the one or more base oil(s) have a kinematic viscosity at 100° C. ranging from 1.5 to 35 cSt.

[0035] The invention also relates to the use of the lubricant composition according to the invention for lubricating at least one mechanical part of a motor vehicle, that is preferably present in a transmission component of a motor vehicle, preferably a gear of a motor vehicle.

[0036] The invention also relates to the use of an additive in a lubricant composition comprising at least one base oil, in order to improve the load carrying capacity of the lubricant composition, said additive having the formula (I):wherein,

[0038] R and R1 are selected independently of each other from among: a hydrogen atom; or saturated or unsaturated, linear hydrocarbon groups containing from 8 to 20 carbon atoms; with at least one of the two radicals R and R1 being a saturated or unsaturated, linear hydrocarbon group containing from 8 to 20 carbon atoms.

[0039] Preferably, the additive having the formula (I) is used in the lubricant composition, in combination with an additive selected from among phosphites containing from 1 to 24 carbon atoms, preferably with the following proportions:

[0040] from 0.01 to 5% by weight, preferably from 0.02 to 2% by weight, of one or more additive(s) having the formula (I);

[0041] from 0.05 to 5% by weight, preferably from 0.1 to 2% by weight, of one or more additive(s) selected from among phosphites containing from 1 to 24 carbon atoms; relative to the total weight of the lubricant composition.

[0042] Preferably, the lubricant composition implemented in the use of the additive according to the invention is as defined in the invention. In particular, the lubricant composition implemented in the use of the additive according to the invention presents one or more of the following characteristic features:

[0043] the hydrocarbon groups are selected from among alkyl groups and alkenyl groups, and / or

[0044] R and R1 are selected independently of each other from among the linear alkyl groups containing from 8 to 18 carbon atoms, and / or

[0045] the lubricant composition comprises:

[0046] from 250 to 1300 ppm by weight of phosphorus, with preferably from 400 to 1400 ppm by weight of phosphorus provided by the one or more additive(s) having the formula (I); and / or

[0047] less than 10 ppm by weight of sulphur, preferably less than 5 ppm by weight of sulphur, more preferably less than 1 ppm by weight of sulphur; and / or

[0048] the lubricant composition additionally also comprises at least one additive selected from among phosphites containing from 1 to 24 carbon atoms;

[0049] preferably from among phosphites containing from 4 to 12 carbon atoms; preferably from among phosphites containing two alkyl groups, each having from 2 to 6 carbon atoms; and / or

[0050] the lubricant composition comprises from 0.01 to 10% by weight, preferably from 0.05 to 5% by weight, more preferably from 0.1 to 3% by weight, of one or more additive(s) having the formula (I), relative to the total weight of the lubricant composition; and / or

[0051] the lubricant composition comprises, relative to the total weight of the lubricant composition:

[0052] 0.01 to 5% by weight, preferably 0.02 to 2% by weight, of one or more additive(s) having the formula (I); and

[0053] 0.05 to 5% by weight, preferably 0.1 to 2% by weight, of one or more additive(s) selected from among phosphites containing two alkyl groups each having from 2 to 6 carbon atoms; and / or

[0054] the lubricant composition additionally also comprises at least one dispersant, preferably a borated dispersant, even more preferably a borated dispersant selected from among borated succinimides, even more preferably from among borated polyisobutene succinimides; and / or

[0055] the lubricant composition comprises, relative to the total weight of the lubricant composition:

[0056] at least 70% by weight, preferably from 75 to 99.5% by weight, of one or more non-aqueous base oil(s);

[0057] from 0.01 to 5% by weight, in particular from 0.02 to 2% by weight, of one or more additive(s) having the formula (I);

[0058] from 0.05 to 5% by weight, preferably from 0.1 to 2% by weight, of one or more additive(s) selected from among phosphites containing from 1 to 24 carbon atoms;

[0059] optionally from 0.1 to 15% by weight, preferably from 1 to 10% by weight, of one or more functional additive(s), preferably selected from among dispersants, antioxidants, pour point depressants, antifoam agents or defoamers, and mixtures thereof;

[0060] the one or more base oil(s) have a kinematic viscosity at 100° C. ranging from 1.5 to 35 cSt.

[0061] The lubricant composition according to the invention offers the advantage of having very good properties for reducing the phenomenon of gear seizure (scoring / scuffing).

[0062] The lubricant composition according to the invention also exhibits good durability.

[0063] The lubricant composition exhibits particularly satisfactory performance levels for reducing wear even under heavy loads, this being so even in the absence of sulphur-based additives and / or in the absence of zinc-based additives.

[0064] In the remainder of the text, the terms ‘between . . . and . . . ’, ‘ranging from . . . to . . . ’ and ‘varying from . . . to . . . ’ are used interchangeably and are intended to indicate that the limits are included, unless otherwise stated.

[0065] Unless otherwise indicated, the quantities in a product are expressed by weight, relative to the total weight of the product.DETAILED DESCRIPTION

[0066] The present invention relates to a lubricant composition comprising:

[0067] at least one base oil;

[0068] at least one anti-wear additive having the formula (I).Acid Phosphate Type Anti-Wear Additive Having the Formula (I)

[0069] The lubricant composition according to the invention comprises at least one acid phosphate type additive having the formula (I):wherein:

[0071] R and R1 are selected independently of each other from among: a hydrogen atom; or saturated or unsaturated, linear hydrocarbon groups containing from 8 to 20 carbon atoms; with at least one of the two radicals R and R1 being a saturated or unsaturated, linear hydrocarbon group containing from 8 to 20 carbon atoms.

[0072] For the purposes of this invention the term ‘linear hydrocarbon groups’ is understood to refer to a linear hydrocarbon chain (comprising carbon and hydrogen atoms) optionally comprising one or more heteroatom(s), such as oxygen or nitrogen atoms.

[0073] Preferably, the hydrocarbon groups are selected from among alkyl groups and alkenyl groups.

[0074] According to one embodiment, R and R1 are selected independently of each other from among a hydrogen atom or linear alkyl group containing from 8 to 20 carbon atoms, preferably, R and R1 are selected independently of each other from among linear alkyl groups containing from 8 to 18 carbon atoms, it being understood that at least one of the R or R1 groups is a linear alkyl group.

[0075] The lubricant composition may optionally comprise a mixture of compounds having the formula (I).

[0076] Preferably, the anti-wear product(s) having the formula (I) provide(s) 250 to 1300 ppm by weight of phosphorus.

[0077] Preferably, the anti-wear additive(s) having the formula (I) represent(s) from 0.01 to 10% by weight, preferably from 0.05 to 5% by weight, more preferably from 0.1 to 3% by weight, of the total weight of the lubricant composition according to the invention.Phosphite Type Anti-Wear Additive

[0078] According to one advantageous embodiment of the invention, the lubricant composition according to the invention comprises at least one anti-wear additive selected from phosphites containing from 1 to 24 carbon atoms, preferably from phosphites containing from 4 to 12 carbon atoms.

[0079] Advantageously, the phosphite type anti-wear additive is selected from among phosphites containing two alkyl groups, each having 2 to 6 carbon atoms.

[0080] In a particularly advantageous manner, the phosphite type anti-wear additive is dibutyl hydrogen phosphite.

[0081] According to one embodiment, the phosphite type anti-wear additive represents from 0.05 to 5% by weight, preferably from 0.1 to 2% by weight, of the total weight of the lubricant composition according to the invention.

[0082] According to one embodiment of the invention, the lubricant composition comprises:

[0083] from 0.01 to 5% by weight, preferably from 0.02 to 2% by weight, of one or more anti-wear additive(s) having the formula (I), where R and R1 are selected independently of each other from among: a hydrogen atom; or saturated or unsaturated, linear hydrocarbon groups containing from 8 to 20 carbon atoms; with at least one of the two radicals R or R1 being a saturated or unsaturated, linear hydrocarbon group containing from 8 to 20 carbon atoms; and

[0084] from 0.05 to 5% by weight, preferably from 0.1 to 2% by weight, of one or more anti-wear additive(s) selected from among phosphites containing from 1 to 24 carbon atoms;

[0085] relative to the total weight of the lubricant composition.

[0086] According to one embodiment of the invention, the lubricant composition comprises:

[0087] from 0.01% to 5% by weight, preferably from 0.02% to 2% by weight, of one or more anti-wear additive(s) having the formula (I), where R and R1 are selected independently of each other from among saturated or unsaturated, alkyl or alkenyl, linear groups containing from 8 to 20 carbon atoms, and

[0088] from 0.05 to 5% by weight, preferably from 0.1 to 2% by weight, of one or more anti-wear additive(s) selected from among phosphites containing from 1 to 24 carbon atoms,

[0089] relative to the total weight of the lubricant composition.

[0090] According to one embodiment of the invention, the lubricant composition comprises:

[0091] from 0.01 to 5% by weight, preferably from 0.02 to 2% by weight, of one or more anti-wear additive(s) having the formula (I), where R and R1 are selected independently of each other from among linear alkyl groups containing from 8 to 18 carbon atoms;

[0092] and

[0093] from 0.05 to 5% by weight, preferably from 0.1 to 2% by weight, of one or more anti-wear additive(s) selected from among phosphites containing two alkyl groups, each having from 2 to 6 carbon atoms, relative to the total weight of the lubricant composition.Base Oil(s)

[0094] The lubricant composition according to the invention comprises one or more base oil(s), preferably in a content of at least 70% by weight, preferably ranging from 75 to 99.5% by weight, preferably ranging from 80 to 99% by weight, preferentially ranging from 85 to 98% by weight, relative to the total weight of the lubricant composition.

[0095] Preferably, the lubricant composition according to the invention comprises at least one base oil having a kinematic viscosity at 100° C. according to the standard ASTM D445 ranging from 1.5 to 35 cSt. Advantageously, the base oils of the lubricant composition according to the invention have a kinematic viscosity at 100° C. ranging from 1.5 to 35 cSt.

[0096] These base oils may be selected from among the base oils conventionally used in the field of lubricating oils, such as mineral, synthetic or natural, animal or plant oils, or mixtures thereof. Typically, the base oil or oils are non-aqueous base oils.

[0097] It may be a mixture of multiple base oils, for example a mixture of two, three or four base oils.

[0098] The base oils of the lubricant compositions considered according to the invention may in particular be oils of mineral or synthetic origin belonging to Groups I to V according to the categories defined in the American Petroleum Institute (API) classification (or equivalents thereof according to the classification of the ATIEL-Technical Association of the European Lubricants Industry) and presented in Table 1 below, or mixtures thereof.TABLE 1Saturates ContentSulphur ContentViscosity Index (VI)Group I <90% >0.03%80 ≤ VI < 120Mineral OilsGroup II≥90%≤0.03%80 ≤ VI < 120Hydrocracked OilsGroup III≥90%≤0.03%≥120Hydrocracked orHydro-isomerised OilsGroup IVPolyalphaolefins (PAO)Group VEsters and other bases not included in Groups I to IV

[0099] Mineral base oils include all types of base oils obtained by atmospheric and vacuum distillation of crude oil, followed by refining operations such as solvent extraction, deasphalting, solvent dewaxing, hydrotreating, hydrocracking, hydroisomerisation and hydrofining.

[0100] Blends of synthetic and mineral oils, which may be bio-sourced, may also be used.

[0101] There are generally no restrictions as to the use of different base oils in order to produce the compositions operationally implemented according to the invention, other than that they must have properties—particularly in terms of viscosity, viscosity index, or resistance to oxidation—that are suitable for use in propulsion systems of electric or hybrid vehicles.

[0102] The base oils of the compositions operationally implemented according to the invention may also be selected from among synthetic oils, such as certain esters of carboxylic acids and alcohols; polyalphaolefins (PAO); and polyalkylene glycols (PAG) obtained by polymerisation or copolymerisation of alkylene oxides containing from 2 to 8 carbon atoms, in particular from 2 to 4 carbon atoms.

[0103] The PAOs used as base oils are for example obtained from monomers containing from 4 to 32 carbon atoms, for example from octene or decene. The weight-average molecular weight of the PAO may vary quite widely. Preferably, the weight-average molecular weight of the PAO is less than 600 Da. The weight-average molecular weight of the PAO may also range from 100 to 600 Da, from 150 to 600 Da, or indeed even from 200 to 600 Da.

[0104] Advantageously, the one or more base oil(s) of the lubricant composition according to the invention may be selected from among the base oils of Groups II or III. According to an alternative embodiment, the one or more base oil(s) of the composition operationally implemented according to the invention are selected from among polyalphaolefins (PAO), polyalkylene glycol (PAG,) and esters of carboxylic acids and alcohols.Other Complementary Additives

[0105] The lubricant composition according to the invention may also comprise all types of functional additives, that are distinct from both the anti-wear additive having the formula (I) and the phosphite-type anti-wear additive as defined in the present invention, and that are suitable for use in a lubricant for motor vehicles, in particular for manual or automatic transmissions of motor vehicles.

[0106] Such additives, known to the person skilled in the art in the field of motor vehicle lubrication, may be selected from among detergents, dispersants, antioxidants, pour point depressants, antifoam agents or defoamers, viscosity index improvers (or viscosity modifiers), and mixtures thereof.

[0107] Advantageously, the composition according to the invention comprises at least one functional additive selected from among detergents, dispersants, antioxidants, pour point depressants, antifoam agents or defoamers, viscosity index improvers (or viscosity modifiers), and mixtures thereof.

[0108] Typically, when present, these additional, functional additives represent (in total) from 1 to 30% by weight, preferably from 1.5 to 25% by weight, preferentially from 2 to 20% by weight, of the total weight of the lubricant composition.

[0109] These additives may be introduced individually and / or in the form of a mixture similar to those already available on the market for commercial lubricant formulations for vehicle engines, with performance levels as defined by the ACEA (Association des Constructeurs Européens d′Automobiles / European Automobile Manufacturers' Association) and / or the API (American Petroleum Institute), which are well known to the person skilled in the art.

[0110] The lubricant composition according to the invention may comprise at least one antioxidant additive.

[0111] The antioxidant additive generally serves to delay degradation of the composition while in use in operation. This degradation may result in particular in the formation of deposits, in the presence of sludge, or in an increase in the viscosity of the composition.

[0112] Antioxidant additives act in particular as radical inhibitors or hydroperoxide destroyers (or scavengers). Commonly used antioxidant additives that may be mentioned include antioxidant additives of the phenol type and antioxidant additives of the amine type. The phenolic antioxidant additives may be ash-free or else be in the form of neutral or basic metal salts. The antioxidant additives may in particular be selected from among sterically hindered phenols; sterically hindered phenol esters; sterically hindered phenols comprising a thioether bridge; diphenylamines; diphenylamines substituted by at least one C1-C12 alkyl group; N,N′-dialkyl-aryl-diamines; and mixtures thereof.

[0113] Preferably according to the invention, the sterically hindered phenols are selected from among the compounds comprising a phenol group in which at least one vicinal carbon adjacent to the carbon bearing the alcohol functional group is substituted by at least one C1-C10 alkyl group, preferably a C1-C6 alkyl group, preferably a C4 alkyl group, preferably by the tert-butyl group.

[0114] Amino compounds are another class of antioxidant additives that may be used, possibly in combination with phenolic antioxidant additives. Examples of amine compounds include aromatic amines, for example aromatic amines having the formula NR10R11R12, wherein: R10 represents an aliphatic group or an aromatic group, optionally substituted; R11 represents an aromatic group, optionally substituted; and R12 represents a hydrogen atom, an alkyl group, an aryl group, or a group having the formula R13S(O)zR14 wherein: R13 represents an alkylene group or an alkenylene group, R14 represents an alkyl group, an alkenyl group or an aryl group, and z represents 0, 1 or 2.

[0115] Sulphurised alkyl phenols or alkali metal and alkaline earth metal salts thereof may also be used as antioxidant additives.

[0116] Copper compounds constitute another class of antioxidant additives, for example salts of copper and carboxylic acids, copper phenates, and copper acetylacetonates. Copper I and II salts, salts of succinic acid or succinic anhydride may also be used.

[0117] The lubricant composition according to the invention may contain all types of antioxidant additives known to the person skilled in the art.

[0118] In an advantageous manner, the lubricant composition according to the invention comprises at least one ash-free antioxidant additive.

[0119] The lubricant composition according to the invention may comprise from 0.5 to 2% by weight of at least one antioxidant additive, relative to the total weight of the composition.

[0120] The lubricant composition according to the invention may also comprise at least one detergent additive.

[0121] Detergent additives generally provide the means for reducing the formation of deposits on the surface of metal parts by dissolving the byproducts of oxidation and combustion.

[0122] The detergent additives that may be used in the lubricant composition according to the invention are generally known to the person skilled in the art. The detergent additives may be anionic compounds comprising a long lipophilic hydrocarbon chain and a hydrophilic head. The associated cation may be a metal cation of an alkali or alcaline earth metal.

[0123] The detergent additives are preferentially selected from among alkali metal or alkaline earth metal salts of carboxylic acids; salicylates; naphthenates; as well as phenate salts. The alkali and alkaline earth metals are preferentially calcium, magnesium, sodium, or barium.

[0124] These metal salts generally contain the metal in a stoichiometric quantity or indeed in an excess quantity, i.e. in a quantity greater than the stoichiometric quantity. These are therefore overbased detergent additives; the excess metal that imparts the overbased nature to the detergent additive is thus generally in the form of an oil insoluble metal salt, for example a carbonate, a hydroxide, an oxalate, an acetate, a glutamate, preferentially a carbonate.

[0125] The lubricant composition that conforms with the invention may, for example, comprise from 0.5 to 4% by weight of detergent additive, relative to the total weight of the composition.

[0126] As well, the lubricant composition according to the invention may comprise at least one dispersant. Typically, the dispersant serves to ensure the maintaining in suspension and the removal of insoluble solid contaminants consisting of oxidation byproducts which are formed when the lubricant composition is used in operation.

[0127] The dispersing agent may be selected from among Mannich bases; succinimide type compounds, such as polyisobutylene succinimide (PIBSI), optionally borated; or borated dispersants other than succinimides; preferably from among borated dispersants; even more preferably from among borated succinimide dispersants, in particular borated PIBSI.

[0128] The lubricant composition according to the invention may, for example, comprise from 0.2 to 10% by weight, relative to the total weight of the composition, of one or more dispersing agent(s).

[0129] The lubricant composition according to the invention may additionally also comprise at least one antifoaming agent.

[0130] The antifoaming agent may be selected from among silicones.

[0131] The lubricant composition according to the invention 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 antifoam agent, relative to the total weight of the composition.

[0132] The lubricant composition according to the invention may also comprise at least one pour point depressant (PPD) additive.

[0133] By slowing down the formation of paraffin crystals, pour point depressant additives generally improve the cold behaviour of the composition. Examples that may be cited by way of pour point depressant additives include alkyl polymethacrylates, polyacrylates, polyarylamides, polyalkylphenols, polyalkylnaphthalenes, and alkylated polystyrenes.

[0134] The lubricant composition according to the invention may also comprise at least one viscosity index improver (or VI modifier). Examples that may be cited by way of VI improvers include polymethacrylates, polyisobutenes, or fatty acid esters. When present, these additives may represent from 1 to 25% by weight of the total weight of the lubricant composition.

[0135] Preferably, the lubricant composition according to the invention does not comprise anti-wear additives containing zinc.

[0136] In terms of the formulation of such a lubricant composition, the one or more anti-wear additive(s) according to the invention may be added to a base oil or mixture of base oils, followed by the adding of any other complementary additive(s).

[0137] Alternatively, the one or more anti-wear additive(s) according to the invention may be added to a pre-existing conventional lubricant formulation, which comprises in particular one or more base oil(s), and optionally other complementary additives.

[0138] Alternatively, the one or more anti-wear additive(s) according to the invention may be combined with one or more additional additives where present, and with the ‘additive package’ thus formed being added to a base oil or mixture of base oils.

[0139] Advantageously, the lubricant composition according to the invention has a kinematic viscosity, measured at 40° C. in accordance with the standard ASTM D445, ranging from 5 to 300 mm2 / s, in particular from 10 to 25 mm2 / s.

[0140] Advantageously, the lubricant composition according to the invention has a kinematic viscosity, measured at 100° C. in accordance with the standard ASTM D445, ranging from 1 to 20 mm2 / s, in particular from 2 to 15 mm2 / s.

[0141] Preferably, the lubricant composition comprises from 400 to 1400 ppm by weight of phosphorus, whereof advantageously from 250 to 1300 ppm by weight of phosphorus is provided by the anti-wear agent(s) having the formula (I).

[0142] Preferably, the lubricant composition is substantially sulphur-free, preferably totally sulphur-free.

[0143] In particular, the lubricant composition according to the invention preferably does not comprise any sulphur-containing additives.

[0144] Thus, the lubricant composition according to the invention typically comprises less than 10 ppm by weight of sulphur, or indeed even less than 5 ppm by weight of sulphur, or even less than 1 ppm by weight of sulphur.

[0145] According to one particular embodiment, the lubricant composition according to the invention comprises, or indeed is constituted of:

[0146] a base oil or mixture of base oils;

[0147] an anti-wear additive having the formula (I);

[0148] optionally an anti-wear additive selected from among phosphites containing from 1 to 24 carbon atoms;

[0149] optionally one or more additional additive(s) selected from among dispersants, antioxidants, pour point depressants, antifoam agents or defoamers, and mixtures thereof.

[0150] According to one particular embodiment, the lubricant composition according to the invention comprises, or indeed is constituted of:

[0151] at least 70% by weight, preferably from 75 to 99.5% by weight, of one or more base oil(s);

[0152] from 0.01 to 10% by weight, in particular from 0.05 to 5% by weight, of one or more anti-wear additive(s) having the formula (I);

[0153] optionally from 0.05 to 5% by weight, in particular from 0.1 to 2% by weight, of one or more anti-wear additive(s) selected from among phosphites containing from 1 to 24 carbon atoms;

[0154] optionally from 0.1 to 15% by weight, preferably from 1 to 10% by weight, of one or more functional additive(s), preferably selected from among dispersants, antioxidants, pour point depressants, antifoam agents or defoamers, and mixtures thereof;

[0155] relative to the total weight of the lubricant composition.

[0156] According to one particular embodiment of the lubricant composition, the lubricant composition according to the invention comprises, or indeed is constituted of:

[0157] at least 70% by weight, preferably from 75 to 99.5% by weight, of one or more base oil(s);

[0158] from 0.01 to 5% by weight, in particular from 0.02 to 2% by weight, of one or more anti-wear additive(s) having the formula (I);

[0159] from 0.05 to 5% by weight, preferably from 0.1 to 2% by weight, of one or more anti-wear additive(s) selected from among phosphites containing from 1 to 24 carbon atoms;

[0160] optionally from 0.1 to 15% by weight, preferably from 1 to 10% by weight, of one or more functional additive(s), preferably selected from among dispersants, antioxidants, pour point depressants, antifoam agents or defoamers, and mixtures thereof;

[0161] relative to the total weight of the lubricant composition.

[0162] According to one particular embodiment, the lubricant composition according to the invention comprises:

[0163] at least 70% by weight, preferably from 75 to 99.5% by weight, of one or more base oil(s);

[0164] from 0.01 to 5% by weight, in particular from 0.02 to 2% by weight, of one or more additive(s) having the formula (I);

[0165] from 0.05 to 5% by weight, preferably from 0.1 to 2% by weight, of one or more additive(s) selected from among phosphites containing from 1 to 24 carbon atoms, preferably from 4 to 12 carbon atoms, preferably from among phosphites containing two alkyl groups each having 2 to 6 carbon atoms;

[0166] optionally from 0.1 to 15% by weight, preferably from 1 to 10% by weight, of one or more functional additive(s), preferably selected from among dispersants, antioxidants, pour point depressants, antifoam agents or defoamers, and mixtures thereof;

[0167] relative to the total weight of the lubricant composition.

[0168] According to one particular embodiment, the lubricant composition according to the invention comprises, or indeed is constituted of:

[0169] at least 70% by weight, preferably from 75 to 99.5% by weight, of one or more base oil(s);

[0170] from 0.01 to 5% by weight, in particular from 0.02 to 2% by weight, of one or more anti-wear additive(s) having the formula (I);

[0171] from 0.05 to 5% by weight, preferably from 0.1 to 2% by weight, of one or more anti-wear additive(s) selected from among phosphites containing from 1 to 24 carbon atoms;

[0172] optionally from 0.1 to 15% by weight, preferably from 1 to 10% by weight, of one or more functional additive(s), preferably selected from among dispersants, antioxidants, pour point depressants, antifoam agents or defoamers, and mixtures thereof;

[0173] said composition comprising less than 10 ppm by weight of sulphur;

[0174] relative to the total weight of the lubricant composition.

[0175] According to one particular embodiment, the lubricant composition according to the invention comprises, or indeed is constituted of:

[0176] at least 70% by weight, preferably from 75 to 99.5% by weight, of one or more base oil(s);

[0177] from 0.01 to 5% by weight, preferably from 0.02 to 2% by weight, of one or more anti-wear additive(s) having the formula (I), where R and R1 are selected independently of each other from among linear alkyl groups containing from 8 to 18 carbon atoms;

[0178] from 0.05 to 5% by weight, preferably from 0.1 to 2% by weight, of one or more anti-wear additive(s) selected from among phosphites containing two alkyl groups, each having 2 to 6 carbon atoms;

[0179] optionally from 0.1 to 15% by weight, preferably from 1 to 10% by weight, of one or more functional additive(s), preferably selected from among dispersants, antioxidants, pour point depressants, antifoam agents or defoamers, and mixtures thereof;

[0180] relative to the total weight of the lubricant composition.

[0181] According to one particular embodiment, the lubricant composition according to the invention comprises, or indeed is constituted of:

[0182] at least 70% by weight, preferably from 75 to 99.5% by weight, of one or more base oil(s);

[0183] from 0.01 to 5% by weight, in particular from 0.02 to 2% by weight, of one or more anti-wear additive(s) having the formula (I);

[0184] from 0.05 to 5% by weight, preferably from 0.1 to 2% by weight, of one or more anti-wear additive(s) selected from among phosphites containing from 1 to 24 carbon atoms;

[0185] from 0.5 to 5% by weight, preferably from 0.1 to 2% by weight, of one or more dispersant(s), preferably selected from among borated dispersants;

[0186] optionally from 0.1 to 10% by weight, preferably from 0.5 to 5% by weight, of one or more functional additive(s), preferably selected from among antioxidants, pour point depressants, antifoam agents or defoamers, and mixtures thereof;

[0187] relative to the total weight of the lubricant composition.

[0188] The object of the present invention also relates to the use of the lubricant composition according to the invention for lubricating the transmissions of motor vehicles, in particular the gears of transmissions. The transmissions may be manual or automatic transmissions.

[0189] Preferably, the lubricant composition according to the invention is used to reduce wear on a mechanical part of a motor vehicle transmission, in particular a motor vehicle gear. Thus, according to this embodiment, the lubricant composition according to the invention provides the means for reducing wear on transmission gears.

[0190] Preferably, the lubricant composition according to the invention is used for reducing the spalling or scoring that occurs on a mechanical part of a motor vehicle transmission, in particular a motor vehicle gear.

[0191] According to one advantageous embodiment, the lubricant composition according to the invention is used both to reduce wear and to reduce spalling or scoring on a mechanical part of a motor vehicle transmission, in particular a motor vehicle gear.

[0192] According to another aspect thereof, the invention also relates to a lubrication method for lubricating at least one part of a motor vehicle transmission, in particular a motor vehicle gear, which comprises at least one contacting step of the at least said part with the lubricant composition as described above.

[0193] According to another aspect thereof, the invention also relates to a process for enhancing the durability of a lubricant composition, said process comprising a step of mixing at least one anti-wear additive having the formula (I) as defined in the present invention, with at least one base oil, preferably the said anti-wear additive having the formula (I) is also mixed with an anti-wear additive selected from among phosphites containing from 1 to 24 carbon atoms.

[0194] The entirety of the characteristic features and preferences described for the lubricant composition according to the invention and for the uses thereof are also applicable to the said methods and processes.

[0195] In accordance with the invention, the particular, advantageous or preferred characteristic features of the composition according to the invention make it possible to define uses according to the invention that are also particular, advantageous or preferred.

[0196] The invention will be described below by means of the following examples, which are obviously provided by way of illustration and without limitation with respect to the invention.EXAMPLESExample 1: Preparation of the Lubricant Compositions

[0197] The lubricant compositions were prepared by mixing the ingredients at a temperature of about 40° C., according to methods well known to the person skilled in the art. The lubricant compositions that were prepared and tested are detailed in Tables 2 and 3 below.

[0198] The elemental phosphorus and sulphur contents were calculated on the basis of the elemental contents in the ingredients and are also indicated in Table 2 in ppm by weight.

[0199] The lubricant compositions tested have a viscosity at 100° C. of approximately 4.5 cSt as measured in accordance with the standard ASTM D445.TABLE 2CC1CC2CI1CI2CI3CI4Base Oils94.65% 94.65% 94.65% 95.15% 95.4%94.75% Anti-wear I1  1% 0.5%0.25%  1%Anti-wear P1 0.1% 0.1% 0.1% 0.1% 0.1%Anti-wear C1  1%Anti-wear C2  1%Antioxidant 1.4% 1.4% 1.4% 1.4% 1.4% 1.4%Anti-corrosion0.05%0.05%0.05%0.05%0.05%0.05%Dispersant2.25%2.25%2.25%2.25%2.25%2.25%Additive Package0.55%0.55%0.55%0.55%0.55%0.55%Total (% weight) 100% 100% 100% 100% 100% 100%Total P Content (ppm)1120146013807704651220P Content from: (I) or C1 or 970131012306203151070C2 (ppm)S Content (ppm)  0  0  0 0 0  0

[0200] In the compositions in Table 2:

[0201] the base oils are Group III base oils;

[0202] the anti-wear agent I1 has the formula (I), where R and R1 are two linear C8 alkyl chains;

[0203] the anti-wear agent P1 is dibutyl hydrogen phosphite;

[0204] the anti-wear agent C1 does not have the formula (I) since it is an acid phosphate with branched chains containing 8 carbon atoms;

[0205] the anti-wear agent C2 does not have the formula (I) since it is an acid phosphate with chains containing 5 carbon atoms;

[0206] the dispersant is a borated PIBSI dispersant capable of providing approximately 85 ppm of boron;

[0207] the antioxidant comprises a phenolic antioxidant and / or an amine antioxidant;

[0208] the anti-corrosion agent is a triazole derivative;

[0209] the additive package contains a pour point improver and an anti-foam agent / defoamer.Example 2: Test Studies on the Performance of the Lubricant Compositions

[0210] The scuffing load-carrying capacity of the lubricant compositions described in Table 2 was tested using the FZG A10 / 16.6R / 90 method (in accordance with the amended standard CEC-L-84-02). The results are indicated in Table 4 below.

[0211] The average coefficient of friction was determined on a Mini Traction Machine (MTM) under the following conditions:-load=5⁢N,-rolling⁢ speed / drive⁢ speed=3⁢ mm / s,-temperature=90⁢ °C,-duration=10⁢ minutes,-SSR⁢ (slide-roll⁢ ratio)=330⁢%.TABLE 4CC1CC2CI1CI2CI3CI4FZG458777Coefficient of Friction0.1300.1220.1080.1070.1120.098The compositions according to the invention CI1 to CI4 exhibit very good load carrying capacity. These load carrying capacity values (FZG) demonstrate the very high durability of the lubricant composition, particularly for deployment for use in transmissions.

[0213] The compositions according to the invention CI1 to CI4 also present a lower average coefficient of friction, thus demonstrating superior lubricating properties.

[0214] The anti-wear agents having the formula (I) as defined in the present invention provide the means for enhancing the performance levels of the lubricant composition. More particularly, the anti-wear agents having the formula (I) as defined in the present invention offer superior properties as compared to the anti-wear agents C1 and C2 of the state of the art.

Claims

1. A lubricant composition comprising:at least one base oil;at least one additive having the formula (I):wherein,R and R1 are selected independently of each other from among: a hydrogen atom; orsaturated or unsaturated, linear hydrocarbon groups containing from 8 to 20 carbon atoms, and optionally comprising one or more heteroatom(s); with at least one of the two radicals R or R1 being a saturated or unsaturated, linear hydrocarbon group containing from 8 to 20 carbon atoms.

2. The lubricant composition according to claim 1, wherein the hydrocarbon groups are selected from among alkyl groups and alkenyl groups.

3. The lubricant composition according to claim 1, wherein R and R1 are selected independently of each other from among linear alkyl groups containing from 8 to 18 carbon atoms.

4. The lubricant composition according to claim 1, comprising:from 250 to 1300 ppm by weight of phosphorus provided by the one or more additive(s) having the formula (I); and / orless than 10 ppm by weight of sulphur.

5. The lubricant composition according to claim 1, further comprising at least one additive selected from among phosphites containing from 1 to 24 carbon atoms.

6. The lubricant composition according to claim 5, comprising from 0.01 to 10% by weight of one or more additive(s) having the formula (I), relative to the total weight of the lubricant composition.

7. The lubricant composition according to claim 1, comprising, relative to the total weight of the lubricant composition:from 0.01 to 5% by weight of one or more additive(s) having the formula (I); andfrom 0.05 to 5% by weight of one or more additive(s) selected from among phosphites containing two alkyl groups, each having from 2 to 6 carbon atoms.

8. The lubricant composition according to claim 1, further comprising at least one dispersant.

9. The lubricant composition according to claim 1, comprising:at least 70% by weight of one or more base oil(s);from 0.01 to 5% by weight of one or more additive(s) having the formula (I);from 0.05 to 5% by weight of one or more additive(s) selected from among phosphites containing from 1 to 24 carbon atoms;relative to the total weight of the lubricant composition.

10. The lubricant composition according to claim 1, comprising:at least 70% by weight of one or more non-aqueous base oil(s);from 0.01 to 5% by weight of one or more additive(s) having the formula (I);from 0.05 to 5% by weight of one or more additive(s) selected from among phosphites containing from 1 to 24 carbon atoms;optionally from 0.1 to 15% by weight of one or more functional additive(s);relative to the total weight of the lubricant composition.

11. The lubricant composition according to claim 1, wherein the one or more base oil(s) have a kinematic viscosity at 100° C. ranging from 1.5 to 35 cSt.

12. A lubrication method for lubricating at least one mechanical part of a motor vehicle, the method comprising contacting the mechanical part of a motor vehicle with the composition according to claim 1.

13. A method to improve the load carrying capacity of a lubricant composition, the method comprising the addition of an additive in the lubricant composition comprising at least one base oil, said additive having the formula (I):wherein,R and R1 are selected independently of each other from among: a hydrogen atom; or saturated or unsaturated, linear hydrocarbon groups containing from 8 to 20 carbon atoms, and optionally comprising one or more heteroatom(s); with at least one of the two radicals R or R1 being saturated or unsaturated, linear hydrocarbon group containing from 8 to 20 carbon atoms.

14. The method according to claim 13, wherein the additive having the formula (I) is added in the lubricant composition, in combination with an additive selected from among phosphites containing from 1 to 24 carbon atoms.

15. The method according to claim 13, wherein the lubricant composition has one or more of the following features:the hydrocarbon groups are selected from among alkyl groups and alkenyl groups;R and R1 are selected independently of each other from among linear alkyl groups containing from 8 to 18 carbon atoms;the lubricant comprises:from 250 to 1300 ppm by weight of phosphorus provided by the one or more additive(s) having the formula (I); and / orless than 10 ppm by weight of sulphur, preferably less than 5 ppm by weight of sulphur;the lubricant composition further comprises at least one additive selected from among phosphites containing from 1 to 24 carbon atoms;the lubricant composition comprises from 0.01 to 10% by weight of one or more additive(s) having the formula (I), relative to the total weight of the lubricant composition;the lubricant composition comprises, relative to the total weight of the lubricant composition:from 0.01 to 5% by weight of one or more additive(s) having the formula (I); andfrom 0.05 to 5% by weight of one or more additive(s) selected from among phosphites containing two alkyl groups, each having from 2 to 6 carbon atoms;the lubricant composition further comprises at least one dispersant;the lubricant composition comprises, relative to the total weight of the lubricant composition:at least 70% by weight of one or more base oil(s);from 0.01 to 5% by weight of one or more additive(s) having the formula (I);from 0.05 to 5% by weight of one or more additive(s) selected from among phosphites containing from 1 to 24 carbon atoms;the lubricant composition comprises, relative to the total weight of the lubricant composition:at least 70% by weight of one or more non-aqueous base oil(s);from 0.01 to 5% by weight of one or more additive(s) having the formula (I);from 0.05 to 5% by weight of one or more additive(s) selected from among phosphites containing from 1 to 24 carbon atoms;optionally from 0.1 to 15% by weight of one or more functional additive(s);one or more base oil(s) have a kinematic viscosity at 100° C. ranging from 1.5 to 35 cSt.

16. The lubricant composition according to claim 1, further comprising at least one additive selected from among phosphites containing two alkyl groups, each having from 2 to 6 carbon atoms.

17. The lubricant composition according to claim 1, further comprising at least one borated dispersant.

18. The method according to claim 12, wherein the mechanical part of a motor is a transmission component of a motor vehicle.

19. The method according to claim 12, wherein the mechanical part of a motor is a gear of a motor vehicle.

20. The method according to claim 13, wherein the additive having the formula (I) is added in the lubricant composition, in combination with an additive selected from among phosphites containing from 1 to 24 carbon atoms, with the following proportions:from 0.01 to 5% by weight of one or more additive(s) having the formula (I);from 0.05 to 5% by weight of one or more additive(s) selected from among phosphites containing from 1 to 24 carbon atoms;relative to the total weight of the lubricant composition.

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