USE OF A PHOSPHORUS COMPOUND AS A NON-CORROSIVE EXTREME PRESSURE AND WEAR PROTECTION ADDITIVE IN A LUBRICANT FOR A DRIVE SYSTEM OF AN ELECTRIC OR HYBRID VEHICLE

Description

technical field

[0001] The present invention relates to the field of lubricating compositions, more particularly to the field of lubricating compositions for a propulsion system of an electric or hybrid vehicle. It relates more particularly to the use, in these lubricants, of sulfur-free and amine-free phosphorus compounds as anti-wear and extreme-pressure additives that are advantageously "non-corrosive".

[0002] The evolution of international standards for reducing CO2 emissions, but also for reducing energy consumption, is pushing car manufacturers to offer alternative solutions to combustion engines.

[0003] One of the solutions identified by car manufacturers is to replace combustion engines with electric motors. Research into reducing CO2 emissions has therefore led to the development of electric vehicles by a number of automotive companies.

[0004] For the purposes of this invention, "electric vehicle" means a vehicle comprising an electric motor as the sole means of propulsion, whereas a hybrid vehicle comprises a combustion engine and an electric motor as combined means of propulsion.

[0005] For the purposes of this invention, "propulsion system" means a system comprising the mechanical parts necessary for the propulsion of a vehicle. The propulsion system of an electric vehicle thus more specifically includes an electric motor comprising the rotor-stator assembly, the power electronics (dedicated to speed regulation), a transmission, and a battery.

[0006] Generally speaking, it is necessary to use lubricating compounds, also known as "lubricants," in vehicles primarily to reduce friction between the various components of the vehicle's propulsion system, particularly between the moving metal parts in engines. These lubricating compounds are also effective in preventing premature wear and even damage to these parts, especially their surfaces.

[0007] To achieve this, a lubricating composition is classically composed of one or more base oil(s) to which are generally associated several additives dedicated to stimulating the lubricating performance of the base oil, but also to provide it with additional performance.

[0008] In particular, so-called "anti-wear" additives are considered in order to reduce wear on propulsion system parts, especially mechanical engine parts, and thus prevent a degradation in engine durability.

[0009] There is a wide variety of anti-wear additives, among which we can mention for example dimercaptothiadiazoles, polysulfides, in particular sulfur olefins, amine phosphates, or even phospho-sulfur additives, such as metallic alkylthiophosphates, in particular zinc alkylthiophosphates, and more specifically zinc dialkyldithiophosphates or ZnDTP.

[0010] Unfortunately, anti-wear additives commonly used in vehicle engine lubricants, such as dimercaptothiadiazoles, zinc dithiophosphate, and polysulfides, have the drawback of being corrosive. Furthermore, ionic additives, such as metal dialkyldithiophosphates, reduce the electrical insulation properties of the fluid.

[0011] Corrosion can be a particularly critical problem in the propulsion systems of electric and hybrid vehicles. Specifically, corrosion can lead to damage to the stator-rotor windings, sensors in the propulsion system, solenoid valves in the hydraulic system, and bearings located between the rotor and stator of an electric motor. These bearings are generally copper-based and therefore particularly susceptible to corrosion. Seals and varnishes within the propulsion system can also be affected. Therefore, when using lubricants in the powertrain systems of electric and hybrid vehicles, it is crucial to prevent corrosion.

[0012] Furthermore, to effectively cool the propulsion systems of electric or hybrid vehicles, it is imperative that the lubricant be a good electrical insulator to prevent any failure of the electrical components. In particular, a conductive lubricant can lead to electrical current leakage in the stator and rotor windings, thus reducing the efficiency of the propulsion systems and potentially causing overheating of the electrical components, even leading to system damage. Therefore, when using lubricants for electric or hybrid vehicle powertrains, it is crucial that the lubricants possess good electrical insulation properties, in addition to being non-corrosive.

[0013] Document EP 1 405 897 relates to an oil for automotive transmission and electric motor comprising a mineral and / or synthetic base oil and 0.1 to 15% by mass of a phosphate compound selected from (A) zinc dithiophosphate, (B) triaryl phosphate and / or (C) triaryl thiophosphate; the composition having a volume resistivity measured at 80°C greater than or equal to 1.107 Ω.m. In particular, this document illustrates, in its example 9, a transmission composition comprising 97.9% by weight of a mixture of mineral oils, 0.6% by weight of tri(propylphenyl)phosphate compound and 1.5% by weight of additives comprising an amino antioxidant, benzotriazole (which is an anti-corrosion additive), a polymethacrylate and a dimethylsilicone.

[0014] Document EP 2 692 841 relates to a lubricating composition having properties necessary for the lubrication of a transmission, comprising (A) a base oil; (B) a phosphorus compound having at least one hydroxyl and / or thiol group; and less than 0.001 wt% of (C) ashless dispersant; the composition having a volume resistivity of 5.108 Ω.m or more. Summary of the invention

[0015] The present invention aims precisely to propose a means to improve the anti-wear properties of a lubricant intended for a propulsion system of an electric or hybrid vehicle, while avoiding the corrosion problems encountered with conventionally used anti-wear products.

[0016] More specifically, the inventors discovered that it is possible to obtain a lubricating composition for electric or hybrid vehicle propulsion systems, exhibiting improved anti-wear properties, without inducing a corrosive effect, by implementing, as anti-wear and extreme-pressure additives, certain sulfur-free and amine-free phosphorus compounds, said lubricating composition being free of anti-corrosion additives.

[0017] Thus, the present invention relates, according to a first of its aspects, to the use of at least one phosphorus compound, free of sulfur and of amine function, amine as defined below, as an anti-wear and extreme-pressure additive in a lubricating composition intended for a propulsion system of an electric or hybrid vehicle, said lubricating composition being free of anti-corrosion additives.

[0018] By "anti-wear and extreme-pressure additive" we mean a compound which, when used in a lubricating composition, particularly in a lubricating composition for the powertrain of an electric or hybrid vehicle, improves the anti-wear properties of the composition, even under severe pressure and / or temperature conditions.

[0019] The anti-wear properties of a composition can be more specifically evaluated according to the ASTM D2670 standard.

[0020] The invention further relates, according to another of its aspects, to the use of a lubricating composition comprising at least one phosphorus compound, free of sulfur and amine function as defined below, as an anti-wear and extreme-pressure additive, for lubricating and possibly cooling a propulsion system of an electric or hybrid vehicle, in particular for the lubrication and cooling of the electric motor and power electronics of an electric or hybrid vehicle, said lubricating composition being free of anti-corrosion additive.

[0021] As illustrated in the examples that follow, the inventors have found that such phosphorus-based anti-wear and extreme-pressure additives, free of sulfur and amine function, in particular of the triaryl phosphate ester type, do not induce corrosion when in contact with metallic surfaces, in particular those of a propulsion system in an electric or hybrid vehicle, unlike phosphorus-based amine and / or sulfur-based anti-wear additives.

[0022] The corrosive power of a compound can be evaluated by a test that involves studying the change in the electrical resistance of a copper wire of a predetermined diameter as a function of the immersion time of this wire in a composition containing, in a non-corrosive medium, for example, one or more base oils, the compound to be tested. The change in this electrical resistance is directly correlated with the change in the diameter of the wire tested. Thus, within the scope of the present invention, a compound is considered "non-corrosive" when the diameter loss of the copper wire studied is less than or equal to 0.5 µm after immersion for 80 hours, and in particular less than or equal to 0.2 µm after immersion for 20 hours in the composition containing said compound.

[0023] The dielectric properties of a lubricant are represented in particular by its electrical resistivity and dielectric loss (tan δ), which can be measured according to the IEC 60247 standard. Electrical resistivity represents the material's ability to oppose the flow of electric current. It is expressed in ohm-meters (Ω·m). The higher the electrical resistivity, the lower the lubricant's electrical conductivity.

[0024] The loss angle δ is the complementary angle of the phase shift between the applied voltage and the alternating current. This factor reflects energy losses due to the Joule effect. Heating is therefore directly related to the value of δ.

[0025] A lubricant intended for use in a vehicle transmission typically has a tan δ value on the order of unity at ambient temperature. The lower the tan δ value, the greater the electrical insulation of the lubricant.

[0026] The said phosphorus compound(s), used as anti-wear and extreme-pressure additives according to the invention, are chosen from triphenyl phosphate or triphenyl phosphite esters, preferably tri(alkyl-phenyl) phosphate or tri(alkyl-phenyl) phosphite esters.

[0027] The introduction, into a lubricant composition for electric or hybrid vehicle propulsion systems, of one or more sulfur-free phosphorus compounds with an amine functional group according to the invention advantageously improves the composition's anti-wear and extreme-pressure properties without causing corrosion, which could be particularly detrimental to the operation of the electric or hybrid vehicle. A composition according to the invention thus exhibits both good anti-wear and extreme-pressure properties while being non-corrosive. It is therefore particularly advantageous for the application considered according to the invention, in an electric or hybrid vehicle propulsion system, where it is crucial to prevent corrosion while maintaining good dielectric properties.

[0028] A composition according to the invention also has the advantage of being easy to formulate. In particular, the use, as an anti-wear and extreme-pressure additive, of one or more non-corrosive phosphorus compounds according to the invention, makes it possible to avoid the use, in these lubricants, of additional additives, known as "anti-corrosion" additives, intended to inhibit the effects of corrosion, generated in particular by the use of corrosive additives.

[0029] This disclosure also relates to a method for lubricating a propulsion system of an electric or hybrid vehicle, comprising at least one step of bringing at least one mechanical part of said system into contact with a lubricating composition comprising, as an anti-wear and extreme-pressure additive, at least one phosphorus compound, free of sulfur and amine function as defined below.

[0030] Advantageously, a lubricating composition according to the invention is implemented to lubricate the electric motor itself, in particular the bearings located between the rotor and the stator of an electric motor, and / or the transmission, in particular the reducer, in an electric or hybrid vehicle.

[0031] Other features, variations and advantages of implementing a sulfur-free and amine-free phosphorus compound according to the invention will become clearer from reading the description and examples that follow, given by way of illustration and not limitation of the invention.

[0032] In the following text, the expressions "between ... and ...", "ranging from ... to ..." and "varying from ... to ..." are equivalent and are meant to mean that the boundaries are included, unless otherwise stated. Brief description of the drawings

[0033] [ Fig 1] schematically represents a propulsion system for an electric or hybrid vehicle. Detailed description ANTI-WEAR AND EXTREME-PRESSURE PHOSPHORUS ADDITIVES ACCORDING TO THE INVENTION

[0034] As previously stated, the invention is based on the implementation, in a lubricant for the motorization system of an electric or hybrid vehicle, as an anti-wear and extreme-pressure additive, of one or more specific phosphorus compounds free of sulfur and amine function.

[0035] In the following text, and unless otherwise indicated, the term "phosphorus additive (or compound) according to the invention" will refer to the specific phosphorus compound(s), free of sulfur and amine function, implemented according to the invention as an anti-wear and extreme-pressure additive.

[0036] For the purposes of this invention, "sulfur-free" means that the anti-wear and extreme-pressure additive considered according to the invention does not contain any sulfur atoms.

[0037] By "free of amine function" in the sense of the invention, we mean to characterize the fact that the anti-wear and extreme-pressure additive considered according to the invention does not include an amine function, in other words does not include any primary, secondary, tertiary and quaternary amine group.

[0038] Furthermore, the anti-wear and extreme-pressure additive considered according to the invention does not include any nitrogen atoms.

[0039] The phosphorus compounds according to the invention, free of sulfur and amine function, make it possible to give the composition anti-wear and extreme-pressure properties.

[0040] Advantageously, the phosphorus-based anti-wear and extreme-pressure additives according to the invention are not corrosive, in other words, they do not induce a corrosion effect when they come into contact with metallic surfaces, in particular those of the parts of a propulsion system in an electric or hybrid vehicle.

[0041] The phosphorus-based anti-wear and extreme-pressure additives implemented according to the invention are chosen from phosphoric acid derivatives, and more particularly from phosphate esters and phosphite esters.

[0042] In general, the phosphorus-based anti-wear and extreme-pressure additives according to the invention have the following formula (I): in which s is either 0 or 1; and the radicals X represent, independently of each other, -OR' groups.

[0043] According to a particular embodiment, the phosphorus-coated anti-wear and extreme-pressure additive according to the invention is chosen from among the phosphite esters, and corresponds more particularly to the aforementioned formula (I), in which s is equal to 0.

[0044] According to another particular embodiment, the phosphorus-coated anti-wear and extreme-pressure additive according to the invention is chosen from among the phosphate esters, and corresponds more particularly to the aforementioned formula (I), in which s is equal to 1 and the three radicals X represent -OR' groups.

[0045] The hydrocarbon groups R' in the aforementioned formula (I) are chosen, independently of each other, from (alkyl)phenyl groups as defined below.

[0046] In the context of the invention, the following definitions apply: "Alkyl" means a saturated aliphatic group, linear or branched; for example, a Cx to Cz alkyl represents a saturated carbon chain of x to z carbon atoms, linear or branched; "alkenyl" means an unsaturated aliphatic group, linear or branched; for example, a Cx to Cz alkenyl group represents an unsaturated carbon chain of x to z carbon atoms, linear or branched; "alkoxy-alkyl" means an alkyl group bearing at least one alkoxy group. An alkoxy group is an -OR group where R represents an alkyl group; "cycloalkyl" means a cyclic alkyl group, for example, a Cx to Cz cycloalkyl represents a cyclic carbon group of x to z carbon atoms, for example, cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl; "Aryl" is a mono- or polycyclic aromatic group, in particular comprising between 6 and 10 carbon atoms. Examples of aryl groups include phenyl and naphthyl groups.

[0047] According to one embodiment, the phosphorus-containing anti-wear and extreme-pressure additives according to the invention can be chosen from triaryl phosphate esters, and in particular tri(alkyl-aryl) phosphate esters of the following formula (II): in which the R groups represent, independently of each other, alkyl groups, linear or branched in C1 to C10, in particular in C3 to C8, and n represent, independently of each other, 0, 1 or 2.

[0048] Preferably, n=1 and R represent para groups, preferably alkyl groups, preferably branched, at C3 to C6, such as an isopropyl group. Preferably, a phosphorus-coated anti-wear additive according to the invention has formula (II) in which the -(R)n groups are identical.

[0049] According to another embodiment, the phosphorus-containing anti-wear and extreme-pressure additives according to the invention can be selected from triaryl phosphite esters, and in particular tri(alkyl-aryl) phosphite esters of the following formula (II'): in which the R groups represent, independently of each other, alkyl groups, linear or branched in C1 to C10, in particular in C3 to C8, and n represent, independently of each other, 0, 1 or 2.

[0050] Preferably, n=1 and R represent para groups, preferably alkyl groups, preferably branched, at C3 to C6, such as an isopropyl group. Preferably, a phosphorus-coated anti-wear additive according to the invention has formula (II') in which the -(R)n groups are identical.

[0051] Advantageously, the phosphorus-based anti-wear additive according to the invention is selected from either tri(isopropylphenyl) phosphate (CAS 68937-41-7) and tris(2,4-ditert-butylphenyl)phosphite (CAS 31570-04-4).

[0052] It is understood, within the framework of the present invention, that the phosphorus-based anti-wear and extreme-pressure additive considered according to the invention may be in the form of a mixture of at least two phosphorus compounds, in particular as defined above.

[0053] The phosphorus compounds used according to the invention may be commercially available, or prepared according to synthesis methods known to those skilled in the art.

[0054] The phosphorus-based anti-wear and extreme-pressure additive(s) considered according to the invention, in particular as defined above, can be used in a lubricating composition for an electric or hybrid vehicle propulsion system, at a rate of 0.01% and 10% by mass, preferably between 0.1% and 5% by mass, more preferably between 0.5% and 3% by mass, relative to the total mass of the lubricating composition.

[0055] According to a particularly preferred embodiment, the phosphorus-based anti-wear and extreme-pressure additive(s) implemented according to the invention are triaryl phosphate esters of formula (II) as defined above, and preferably are implemented at a rate of 0.01% and 10% by mass, preferably between 0.1% and 5% by mass, more preferably between 0.5% and 3% by mass, relative to the total mass of the lubricating composition.

[0056] According to another particularly preferred embodiment, the phosphorus-based anti-wear and extreme-pressure additive(s) implemented according to the invention are triaryl phosphite esters of formula (II') as defined above, and preferably are implemented at a rate of 0.01% and 10% by mass, preferably between 0.1% and 5% by mass, more preferably between 0.5% and 3% by mass, relative to the total mass of the lubricating composition.

[0057] Preferably, a lubricating composition considered according to the invention comprises less than 10% by mass, in particular less than 5% by mass, or even is free of amine and / or sulfur anti-wear additive(s), in particular amine and / or sulfur phosphorus additive(s).

[0058] Advantageously, a lubricating composition considered according to the invention comprises less than 7.5% by mass, in particular less than 3% by mass, or even is free of anti-wear additive(s) other than the sulfur-free and amine-functional phosphorus additives considered according to the invention. LUBRICANT COMPOSITION

[0059] A composition implemented according to the invention may include, in addition to one or more phosphorus-coated anti-wear and extreme-pressure additives according to the invention, in particular as defined above, one or more base oils, as well as other additives, classically considered in lubricating compositions. Base oil

[0060] A suitable lubricating composition for the invention may therefore comprise one or more base oils.

[0061] These base oils can be chosen from among the base oils conventionally used in the field of lubricating oils, such as mineral, synthetic or natural, animal or vegetable oils or mixtures thereof.

[0062] It can be a mixture of several base oils, for example a mixture of two, three, or four base oils.

[0063] The base oils of the lubricating 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 classes defined in the API classification (or their equivalents according to the ATIEL classification) and presented in Table 1 below or their mixtures. [Table 1] Saturated fat content Sulfur content Viscosity index (VI) Group I Mineral Oils <90% > 0,03 % 80 ≤ VI < 120 Group II Hydrocracked Oils ≥90 % ≤0,03 % 80 ≤ VI < 120 Group III Hydrocracked or hydro-isomerized oils ≥90 % ≤0,03 % ≥120 Group IV Polyalphaolefins (PAO) Group V Esters and other bases not included in groups I to IV

[0064] 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, desalpha removal, solvent dewaxing, hydrotreating, hydrocracking, hydroisomerization and hydrofinishing.

[0065] Mixtures of synthetic and mineral oils, which may be bio-based, can also be used.

[0066] There are generally no limitations on the use of different base oils to produce the compositions implemented according to the invention, except that they must have properties, particularly in terms of viscosity, viscosity index, or resistance to oxidation, suitable for use in propulsion systems of an electric or hybrid vehicle.

[0067] The base oils of the compositions implemented according to the invention can also be chosen from synthetic oils, such as certain esters of carboxylic acids and alcohols, polyalphaolefins (PAO), and polyalkylene glycol (PAG) obtained by polymerization or copolymerization of alkylene oxides comprising 2 to 8 carbon atoms, in particular 2 to 4 carbon atoms.

[0068] The PAOs used as base oils are obtained, for example, from monomers comprising 4 to 32 carbon atoms, such as octene or decene. The weight-average molecular weight of the PAO can vary considerably. Preferably, the weight-average molecular weight of the PAO is less than 600 Da. The weight-average molecular weight of the PAO can also range from 100 to 600 Da, from 150 to 600 Da, or even from 200 to 600 Da.

[0069] Advantageously, the base oil or oils of the composition implemented according to the invention are chosen from polyalphaolefins (PAO), polyalkylene glycol (PAG), esters of carboxylic acids and alcohols, and mixtures thereof.

[0070] Preferably the base oil(s) of the composition implemented according to the invention is chosen from group III, IV or V oils, and their mixtures, preferably is a group III base oil.

[0071] According to an alternative embodiment, the base oil or oils of the composition implemented according to the invention can be chosen from the base oils of group II.

[0072] It is for a person skilled in the art to adjust the base oil content to be used in a composition suitable for the invention.

[0073] A lubricating composition considered according to the invention may comprise at least 50% by mass of base oil(s) relative to its total mass, in particular from 60 to 99% by mass of base oil(s), and more particularly between 70 and 98% by mass, preferably between 80 and 97% by mass. Additional additives

[0074] A lubricating composition suitable for the invention may also further comprise all types of additives, distinct from the phosphorus-based anti-wear and extreme-pressure additives considered according to the invention, suitable for use in a lubricant for the propulsion system of an electric or hybrid vehicle, provided that said lubricating composition is free of anti-corrosion additives.

[0075] It is understood that the nature and quantity of additives used are chosen so as not to affect the properties of the lubricating composition, in particular the properties conferred by the said anti-wear and extreme-pressure phosphorus additive(s) according to the invention.

[0076] Such additives, known to those skilled in the art in the field of lubrication and / or cooling of propulsion systems of electric or hybrid vehicles, can be chosen from friction modifiers, viscosity index modifiers, extreme-pressure additives other than anti-wear and phosphorus-containing extreme-pressure additives according to the invention, detergents, dispersants, antioxidants, pour point depressants, anti-foaming agents and mixtures thereof.

[0077] Advantageously, a composition suitable for the invention comprises at least one additional additive selected from antioxidants, detergents, dispersants, pour point lowering additives, antifoaming agents, and mixtures thereof.

[0078] These additives can be introduced individually and / or in the form of a mixture similar to those already available for sale for commercial lubricant formulations for vehicle engines, with performance levels as defined by ACEA (European Automobile Manufacturers' Association) and / or API (American Petroleum Institute), well known to those skilled in the art.

[0079] A lubricating composition suitable for the invention may include at least one friction-modifying additive. The friction-modifying additive may be selected from a compound containing metallic elements and an ash-free compound. Examples of compounds containing metallic elements include transition metal complexes such as Mo, Sb, Sn, Fe, Cu, and Zn, whose ligands may be hydrocarbon compounds comprising oxygen, nitrogen, sulfur, or phosphorus atoms. Ash-free friction-modifying additives are generally of organic origin and may be selected from fatty acid and polyol monoesters, alkoxylated amines, alkoxylated fatty amines, fatty epoxides, borate fatty epoxides, fatty amines, or fatty acid glycerol esters. According to the invention, the fatty compounds comprise at least one hydrocarbon group comprising 10 to 24 carbon atoms.

[0080] A suitable lubricant composition for the invention may comprise from 0.01 to 2% by weight or from 0.01 to 5% by weight, preferably from 0.1 to 1.5% by weight or from 0.1 to 2% by weight of friction modifier additive, relative to the total weight of the composition.

[0081] A lubricating composition implemented according to the invention may include at least one antioxidant additive.

[0082] The antioxidant additive generally helps to delay the degradation of the composition in service. This degradation can manifest itself in the formation of deposits, the presence of sludge, or an increase in the viscosity of the composition.

[0083] Antioxidant additives act primarily as radical scavengers or hydroperoxide scavengers. Commonly used antioxidant additives include phenolic antioxidants, amine antioxidants, and phosphosulfur antioxidants. Some of these antioxidants, such as phosphosulfur antioxidants, can generate ash. Phenolic antioxidants may be ash-free or in the form of neutral or basic metal salts. Antioxidant additives may include sterically hindered phenols, sterically hindered phenol esters, sterically hindered phenols containing a thioether bridge, diphenylamines, diphenylamines substituted with at least one C1-C12 alkyl group, N,N'-dialkylaryl diamines, and mixtures thereof.

[0084] Preferably according to the invention, sterically hindered phenols are selected from compounds comprising a phenol group in which at least one vicinal carbon of the carbon bearing the alcohol function 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.

[0085] Amino compounds are another class of antioxidant additives that can be used, possibly in combination with phenolic antioxidant additives. Examples of amine compounds are aromatic amines, for example aromatic amines of the formula NR 4< R 5< R 6< where R 4< represents an aliphatic or aromatic group, possibly substituted, R 5< represents an aromatic group, possibly substituted, R 6< represents a hydrogen atom, an alkyl group, an aryl group or a group of the formula R 7< S(O) z R 8< where R 7< represents an alkylene or alkenylene group, R 8< represents an alkyl, alkenyl or aryl group and z represents 0, 1 or 2.

[0086] Sulfurized alkyl phenols or their alkali and alkaline earth metal salts can also be used as antioxidant additives.

[0087] Another class of antioxidant additives consists of copper compounds, for example copper thio- or dithio-phosphates, copper salts of carboxylic acids, dithiocarbamates, sulfonates, phenates, and copper acetylacetonates. Copper I and II salts, and succinic acid or anhydride salts can also be used.

[0088] A lubricating composition implemented according to the invention may contain all types of antioxidant additives known to those skilled in the art.

[0089] Advantageously, a lubricating composition implemented according to the invention comprises at least one ash-free antioxidant additive.

[0090] A lubricating composition implemented 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.

[0091] A suitable lubricating composition for the invention may also include at least one detergent additive.

[0092] Detergent additives generally help to reduce the formation of deposits on the surface of metal parts by dissolving secondary oxidation and combustion products.

[0093] Detergent additives usable in a lubricating composition implemented according to the invention are generally known to those skilled in the art. These detergent additives may be anionic compounds comprising a long lipophilic hydrocarbon chain and a hydrophilic head group. The associated cation may be a metallic cation of an alkali or alkaline earth metal.

[0094] Detergent additives are preferably chosen from alkali metal or alkaline earth metal salts of carboxylic acids, sulfonates, salicylates, naphthenates, and phenate salts. The alkali and alkaline earth metals are preferably calcium, magnesium, sodium, or barium.

[0095] These metallic salts generally contain the metal in stoichiometric quantities or in excess, i.e., in a quantity greater than the stoichiometric amount. These are then called over-basic detergent additives; the excess metal that gives the detergent additive its over-basic character is then generally in the form of a metallic salt insoluble in oil, for example, a carbonate, a hydroxide, an oxalate, an acetate, a glutamate, preferably a carbonate.

[0096] A suitable lubricant composition for the invention may, for example, comprise 2 to 4% by weight of detergent additive, relative to the total weight of the composition.

[0097] Also, a lubricating composition implemented according to the invention may include at least one dispersing agent.

[0098] The dispersing agent can be chosen from Mannich bases, succinimides and their derivatives.

[0099] A lubricating composition implemented according to the invention may, for example, comprise from 0.2 to 10% by weight of dispersing agent, relative to the total weight of the composition.

[0100] A suitable lubricating composition for the invention may further comprise at least one antifoaming agent.

[0101] The antifoaming agent can be chosen from silicones.

[0102] A lubricating composition suitable for the invention may comprise from 0.01 to 5% by mass, preferably from 0.1 to 2% by mass of antifoaming agent, relative to the total weight of the composition.

[0103] A lubricating composition suitable for the invention may also include at least one pour point depressant additive (also called "PPD" agents for "Pour Point Depressant" in English).

[0104] By slowing down the formation of paraffin crystals, pour point lowering additives generally improve the cold behavior of the composition. Examples of pour point lowering additives include alkyl polymethacrylates, polyacrylates, polyarylamides, polyalkylphenols, polyalkylnaphthalenes, and alkylated polystyrenes.

[0105] In terms of formulation of such a lubricating composition, the said phosphorus-based anti-wear additive(s) according to the invention can be added to a base oil or mixture of base oils, and then the other complementary additives added.

[0106] Alternatively, the phosphorus-based anti-wear and extreme-pressure additive(s) according to the invention may be added to a pre-existing conventional lubricating formulation, including in particular one or more base oils, and possibly additional additives.

[0107] Alternatively, the said phosphorus-based anti-wear and extreme-pressure additive(s) according to the invention can be combined with one or more additional additives, and the "package" of additives thus formed added to a base oil or mixture of base oils.

[0108] Advantageously, a lubricating composition implemented according to the invention has a kinematic viscosity, measured at 100°C according to ASTM D445, ranging from 1 to 15 mm² / s, in particular ranging from 3 to 10 mm² / s.

[0109] Advantageously, a lubricating composition implemented according to the invention has a kinematic viscosity, measured at 40°C according to ASTM D445, ranging from 3 to 80 mm² / s, in particular from 15 to 70 mm² / s.

[0110] Advantageously, a lubricating composition implemented according to the invention can be of grade according to the SAEJ300 classification defined by the formula (X)W(Y), in which X represents 0 or 5; and Y represents an integer from 4 to 20, in particular from 4 to 16 or from 4 to 12.

[0111] Advantageously, a lubricating composition implemented according to the invention has an electrical resistivity measured at 90°C of between 5 and 10000 Mohm.m, preferably even more between 6 and 5000 Mohm.m.

[0112] Advantageously, a lubricating composition implemented according to the invention has a dielectric loss measured at 90°C of between 0.01 and 30, preferably between 0.02 and 25, more preferably between 0.02 and 10.

[0113] According to a preferred embodiment, a lubricating composition formulated according to the invention comprises, or is composed of: a base oil, or mixture of base oils, preferably selected from Group III base oils, Group IV or V base oils; one or more sulfur-free and amine-free phosphorus compounds as defined above, preferably of the triaryl phosphate ester type corresponding to formula (II) as defined above; optionally one or more additional additives, selected from antioxidants, detergents, dispersants, pour point depressants, antifoaming agents, and mixtures thereof, said lubricating composition being free from anti-corrosion additives.

[0114] Preferably, a lubricating composition formulated according to the invention comprises, or is even made up of: from 0.1% to 5% by mass, in particular from 0.5% to 3% by mass, of one or more sulfur-free and amine-free phosphorus compounds, selected from triaryl phosphate esters corresponding to formula (II) as defined above, and triaryl phosphite esters corresponding to formula (II') as defined above, more preferably selected from tri(isopropylphenyl) phosphate and Tris(2,4-ditert-butylphenyl) phosphite; from 50% to 99.5% by mass, in particular from 60% to 99% by mass, of one or more base oils, preferably selected from Group III base oils, Group IV or V base oils and mixtures thereof; and possibly 0.1 to 5% by mass of one or more additives chosen from antioxidants, detergents, dispersants, pour point depressants, antifoaming agents, and mixtures thereof, said lubricating composition being free of anti-corrosion additives; the contents being expressed in relation to the total mass of said lubricating composition. APPLICATION

[0115] As mentioned previously, a composition formulated according to the invention, as described above, is implemented as a lubricant for a propulsion system of an electric or hybrid vehicle, and more particularly of the motor and the power electrics in an electric or hybrid vehicle.

[0116] Thus, the present invention relates to the use of a composition as defined above, employing as an anti-wear and extreme-pressure additive, preferably as the sole anti-wear and extreme-pressure additive, one or more sulfur-free and amine-free phosphorus compounds, in particular as defined above, preferably of the triaryl phosphate ester type corresponding to formula (II) as defined above, to lubricate a propulsion system of an electric or hybrid vehicle, in particular for the lubrication of the electric motor and the power electrics of an electric or hybrid vehicle.

[0117] The present invention thus relates to the use, as an additive in a lubricating composition, of one or more sulfur-free and amine-free phosphorus compounds as defined above, to simultaneously reduce wear and not cause corrosion at the level of the parts of a propulsion system of an electric or hybrid vehicle, in particular at the level of the stator and rotor winding, the sensors in the propulsion system, the solenoid valves in the hydraulic system but also at the level of the bearings located between the rotor and the stator of an electric motor and / or the transmission, in particular the reducer, in an electric or hybrid vehicle, said lubricating composition being free of anti-corrosion additives.

[0118] As schematically represented in Figure 1The propulsion system of an electric or hybrid vehicle includes, in particular, the electric motor (1), an electric battery (2) and a transmission, in particular a speed reducer (3).

[0119] An electric motor typically comprises power electronics (11) connected to a stator (13) and a rotor (14). The stator includes coils, particularly copper coils, which are alternately energized by an electric current. This generates a rotating magnetic field. The rotor itself comprises coils, permanent magnets, or other magnetic materials, and is set in rotation by the rotating magnetic field.

[0120] A bearing (12) is generally integrated between the stator (13) and the rotor (14). A transmission, and in particular a speed reducer (3), makes it possible to reduce the rotational speed at the output of the electric motor and to adapt the speed transmitted to the wheels, thus allowing the speed of the vehicle to be controlled.

[0121] The bearing (12) is subjected to significant mechanical stress and is prone to fatigue wear. Therefore, it is necessary to lubricate the bearing to extend its service life. Similarly, the gearbox is subjected to high frictional stress and thus requires appropriate lubrication to prevent premature damage.

[0122] Thus, the invention relates in particular to the use of a composition as described above to lubricate an electric motor of an electric or hybrid vehicle, in particular to lubricate the bearings located between the rotor and the stator of an electric motor.

[0123] It also relates to the implementation of a composition such as described previously to lubricate the transmission, in particular the reduction gear, in an electric or hybrid vehicle.

[0124] Advantageously, a composition according to the invention can thus be used to lubricate the various parts of a propulsion system of an electric or hybrid vehicle, in particular the bearings located between the rotor and the stator of an electric motor and / or the transmission, in particular the reducer, in an electric or hybrid vehicle.

[0125] Advantageously, as mentioned previously, a lubricating composition according to the invention exhibits excellent anti-wear and extreme pressure performance while being non-corrosive.

[0126] This disclosure also relates, in another aspect, to a method of lubricating at least one part of a propulsion system of an electric or hybrid vehicle, in particular bearings located between the rotor and stator of an electric motor; and / or of the transmission, in particular the reducer, comprising at least one step of bringing at least said part into contact with a composition as described above.

[0127] This disclosure thus proposes a method to simultaneously reduce wear and not cause corrosion in at least one part of a propulsion system of an electric or hybrid vehicle, in particular bearings located between the rotor and stator of an electric motor; and / or the transmission, in particular the reducer, said method comprising at least one step of bringing at least said part into contact with a composition as described above.

[0128] All the characteristics and preferences described for the composition used according to the invention and for its uses also apply to this process.

[0129] It can also be advantageous to ensure electrical insulation of the different parts of the propulsion system.

[0130] Thus, according to a particular embodiment, a composition according to the invention can exhibit, in addition to lubrication properties, good electrical insulation properties.

[0131] According to this embodiment, a composition according to the invention can simultaneously be used to lubricate one or more parts of a propulsion system of an electric or hybrid vehicle, in particular for the lubrication of the sensors and solenoid valves of the motor, the bearings, but also the winding located at the rotor and stator of an electric motor, or the lubrication at the transmission level, in particular the gears, the sensors, the solenoid valves, or the reducer found in an electric or hybrid vehicle, and to electrically isolate at least one part of said propulsion system, in particular from the battery, the motor or the power electronics.

[0132] In such an embodiment, a lubricating composition considered according to the invention advantageously has a kinematic viscosity, measured at 100°C according to ASTM D445, of between 2 and 8 mm² / s, preferably between 3 and 7 mm² / s. It is understood that the uses described above can be combined, a composition such as described above being able to be used both as a lubricant, an electrical insulator, and also as a coolant for the motor, battery, and transmission of an electric or hybrid vehicle.

[0133] According to the invention, the particular, advantageous or preferred characteristics of the composition according to the invention make it possible to define uses according to the invention which are also particular, advantageous or preferred.

[0134] The invention will now be described by means of the following examples, given of course by way of illustration and not limitation of the invention. Example

[0135] Different compositions were evaluated: a composition C1 comprising a phosphorus compound A, according to the invention: tri(isopropylphenyl) phosphate; a composition C2 comprising a phosphorus compound B according to the invention: tris(2,4-ditert-butylphenyl) phosphite; a composition C3 comprising a phospho-sulfur compound C known as anti-wear and extreme-pressure, not according to the invention: tri-phenyl phosphorothionate; and a composition C4 comprising a mixture of amine phosphate compounds D known as anti-wear, not according to the invention, marketed under the reference Irgalube 349; a composition C5 comprising a mixture of dimercaptothiadiazole compounds E known as anti-wear, not according to the invention; a composition C6 comprising a mixture of zinc dialkyldithiophosphate compounds F known as anti-wear, not according to the invention.

[0136] Compositions C1 to C6 comprise, in addition to each of the aforementioned compounds, a group III base oil.

[0137] The compositions and quantities (expressed as mass percentages) are shown in the following table 2. [Table 2] Composition C1 C2 C3 C4 C5 C6 Base oil 98% 98% 98% 98% 98% 98% Phosphorus compound A 2% - - - - - Phosphorus compound B - 2% - - - - Phospho-sulfur compound C - - 2% - - - D-amine phosphate mixture - - - 2% - - Dimercaptothiadiazole mixture E - - - - 2% - Mixture of zinc dialkyldithiophosphates F - - - - - 2% Corrosive power assessment Evaluation method

[0138] The corrosive power of a composition can be evaluated by a test that studies the variation in the electrical resistance of a copper wire of a predetermined diameter as a function of the immersion time of this wire in the composition. The variation in this electrical resistance is directly correlated with the variation in the diameter of the wire tested. In the context of the present invention, the diameter of the wire chosen is 70 µm.

[0139] In the present case, a copper wire is immersed in a test tube containing a volume of 20 mL of a composition to be tested (compositions C1 and C2 being compositions according to the invention and compositions C3 to C6 being compositions used for comparison).

[0140] The resistance of the wire is measured using an ohmmeter.

[0141] The measurement current is 1 mA.

[0142] The temperature of the composition to be tested is raised to 150°C.

[0143] The resistance of the copper wire is calculated using this equation (1): R = ρ × L S where R is the resistance, ρ is the resistivity of copper, L is the length of the wire, and S is the cross-sectional area.

[0144] In equation (1), ρ and L are constants. Thus, the resistance R is inversely proportional to the cross-sectional area of ​​the immersed wire.

[0145] The wire diameter is calculated from the cross-sectional area (2): S = π 4 × D 2 where D is the diameter of the wire.

[0146] We substitute equation (2) into (1) to obtain the relationship between resistance and diameter (3): R = ρ × L π 4 × D 2

[0147] Thus, when the wire is corroded by the compositions to be tested, the diameter of the wire decreases, therefore causing an increase in the resistance value.

[0148] By monitoring the resistance, we can track the change in the diameter of the wire, which is a picture of the corrosion situation suffered by the immersed wire.

[0149] The wire diameter loss is therefore calculated directly from the measured resistance. When the measured resistance is infinite, it indicates an open circuit. This means the wire has broken, resulting in severe corrosion. Results

[0150] The results are summarized in Table 3 below and are expressed in µm (diameter loss). The lower the value obtained, the better the anti-corrosion properties of the evaluated composition.

[0151] A composition is considered "non-corrosive" when the diameter loss of the copper wire studied is less than or equal to 0.5 µm after immersion for 80 hours, and in particular less than or equal to 0.1 µm after immersion for 20 hours in the composition. [Table 3] Composition C1 C2 C3 C4 C5 C6 Diameter loss (in µm) at 20 hours 0 0.14 0,75 0,23 0,29 Broken wire Diameter loss (in µm) at 40 hours 0,10 0.21 1,80 0,58 Broken wire Broken wire Diameter loss (in µm) at 60 hours 0,23 0.26 2,00 0,99 Broken wire Broken wire Diameter loss (µm) at 80 hours 0,31 0.48 2,18 1,51 Broken wire Broken wire

[0152] It appears from these results that the addition of a sulfur-free phosphorus additive with no amine function according to the invention does not produce a corrosive effect, unlike sulfur- or amine-based phosphorus anti-wear additives.

Claims

1. Use of at least one phosphorus compound, free from sulfur and from amine function, as an extreme pressure and antiwear additive in a lubricating composition intended for a propulsion system of an electric or hybrid vehicle; said phosphorus compound free from sulfur and from amine function being selected from: phosphate esters of formula (II) below: in which the groups R represent, independently of one another, linear or branched C1 to C10, more particularly C3 to C8, alkyl groups, and n represents, independently at each occurrence, 0, 1 or 2; preferably n is 1 and R represents groups in para position, preferably C3 to C6 alkyl groups, more particularly branched; and phosphite esters of formula (II') below: in which the groups R represent, independently of one another, linear or branched C1 to C10, more particularly C3 to C8, alkyl groups, and n represents, independently at each occurrence, 0, 1 or 2; preferably n is 1 and R represents groups in para position, preferably C3 to C6 alkyl groups, more particularly branched; said lubricating composition being free from anticorrosion additive.

2. Use according to the preceding claim, wherein said phosphorus compound free from sulfur and from amine function is tri(isopropylphenyl) phosphate.

3. Use according to Claim 1, wherein said phosphorus compound free from sulfur and from amine function is tris(2,4-di-tert-butylphenyl) phosphite.

4. Use according to any one of the preceding claims, wherein said phosphorus compound or compounds free from sulfur and from amine function is or are present in an amount of between 0.01% and 10% by mass, preferably between 0.1% and 5% by mass, more preferably of between 0.5% and 3% by mass, relative to the total mass of the composition.

5. Use according to any one of the preceding claims, said lubricating composition comprising at least one base oil selected from polyalkylene glycols, polyalphaolefins, esters of carboxylic acids and alcohols, and mixtures thereof.

6. Use of a lubricating composition comprising at least one phosphorus compound, free from sulfur and from amine function, as extreme pressure and antiwear additive for lubricating and optionally cooling a propulsion system of an electric or hybrid vehicle, more particularly for lubricating and cooling the electric motor and the power electronics of an electric or hybrid vehicle; said phosphorus compound free from sulfur and from amine function being selected from: phosphate esters of formula (II) below: in which the groups R represent, independently of one another, linear or branched C1 to C10, more particularly C3 to C8, alkyl groups, and n represents, independently at each occurrence, 0, 1 or 2; preferably n is 1 and R represents groups in para position, preferably C3 to C6 alkyl groups, more particularly branched; and phosphite esters of formula (II') below: in which the groups R represent, independently of one another, linear or branched C1 to C10, more particularly C3 to C8, alkyl groups, and n represents, independently at each occurrence, 0, 1 or 2; preferably n is 1 and R represents groups in para position, preferably C3 to C6 alkyl groups, more particularly branched; said lubricating composition being free from anticorrosion additive.

7. Use according to the preceding claim, wherein the phosphorus compound is as defined according to Claim 2 or 3.

8. Use according to Claim 6 or 7, for lubricating the bearings situated between the rotor and the stator of an electric motor, and / or the transmission, more particularly the reduction gear, of an electric or hybrid vehicle.

9. Use according to any one of Claims 6 to 8, wherein the lubricating composition comprises, or even consists of: - from 0.1% to 5% by mass, more particularly from 0.5 to 3% by mass, of one or more phosphorus compounds free from sulfur and from amine function, preferably selected from tri(isopropylphenyl) phosphate and tris(2,4-di-tert-butylphenyl) phosphite; - from 50% to 99.5% by mass, more particularly from 60 to 99% by mass, of one or more base oils, preferably selected from group III base oils, group IV or V base oils, and mixtures thereof; and - optionally from 0.1 to 5% by mass of one or more additives selected from antioxidants, detergents, dispersants, pour point depressant additives, antifoams, and mixtures thereof; where the amounts are expressed relative to the total mass of said lubricating composition.