Use of an Anti-wear additive for improving the thermal conductivity of a cooling fluid for an electric vehicle

Abstract

The present invention relates to the use of at least one anti-wear additive for improving the thermal conductivity of a fluid containing at least one base oil.

Description

[0001] Description

[0002] Title: Use of an anti-wear additive to improve the thermal conductivity of a coolant for an electric vehicle

[0003] Technical field

[0004] The present invention relates to the field of lubricating compositions for electric vehicles. More particularly, the present invention relates to the field of lubricating and cooling compositions for electric vehicles, in particular for cooling the battery of an electric vehicle.

[0005] State of the art

[0006] 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.

[0007] One solution 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 several car companies.

[0008] Generally speaking, it is necessary to use lubricating compositions, also known as "lubricating fluids", in vehicles for the main purpose of reducing the friction forces between the various parts of the vehicle's propulsion system, particularly between the moving metal parts in engines. These lubricating compositions are also effective in preventing premature wear or even damage to these parts, and in particular to their surface.

[0009] Electric motors generate heat during operation. If the amount of heat generated is greater than the amount of heat normally dissipated to the environment, it is necessary to ensure motor cooling. Generally, cooling is carried out on one or more heat-generating parts of the motor and / or heat-sensitive parts of the motor, in order to avoid reaching dangerous temperatures.

[0010] This cooling can be achieved through direct cooling or indirect cooling. Due to the ever-increasing power density of electric motors, it will be necessary to develop and improve the direct cooling method of the electric motor where the lubricating fluid from the transmission part will also be used to cool the hot parts of the electric motor. An example is the Tesla Model S vehicle, in which the lubricant from the gearbox also circulates in the hollow rotor of the electric motor to cool the stator coil heads via several oil jets.

[0011] To do this, a lubricating composition is classically composed of one or more base oils, to which are generally associated several additives dedicated to stimulating the lubricating performance of the base oil, such as for example friction modifying additives.

[0012] For reasons of economy and ease of implementation, it would be advantageous to have a composition that could simultaneously meet the lubrication and cooling needs of a propulsion system (engine, battery, etc.) of an electric vehicle. Unfortunately, these two properties, lubrication and cooling, impose opposing constraints at first glance.

[0013] A particularly useful type of performance for a lubricating composition in electric vehicle propulsion systems is to have good wear resistance properties, properties that are systematically part of the prerogatives to be respected in the manufacturers' specifications.

[0014] In addition, this type of lubricating composition must be able to cool the propulsion systems of electric vehicles.

[0015] It is therefore an object of the present invention to provide a single fluid (single lubricating composition) which can be used in all the components of a propulsion system of an electric vehicle.

[0016] Summary of the invention

[0017] More specifically, the present invention relates to the use of at least one anti-wear additive to improve the thermal conductivity of a fluid comprising at least one base oil.

[0018] According to the invention, said anti-wear additive is chosen from phosphorus anti-wear agents, phospho-sulfur anti-wear agents, phospho-amine anti-wear agents, sulfur anti-wear agents, borate anti-wear agents, and mixtures thereof. According to one embodiment, the anti-wear additive is used to improve the heat transfer properties of the fluid.

[0019] According to one embodiment, the fluid is used to cool the battery of an electric vehicle.

[0020] According to one embodiment, the anti-wear additive is used to prepare a single fluid used to lubricate and cool the propulsion system of an electric vehicle. Thus, according to this embodiment, the single fluid (the same fluid) circulates throughout the cooling and lubrication system of the propulsion system of an electric vehicle.

[0021] Preferably, the anti-wear additive is chosen from phosphorus anti-wear agents, phospho-sulfur anti-wear agents, phospho-amine anti-wear agents, and mixtures thereof, preferably from phosphorus anti-wear agents.

[0022] Preferably, the anti-wear additive is a phosphite polymer, preferably corresponding to formula (I):

[0023] [Chem 1] in which,

[0024] - each of R1, R2, R3 and R4 can be chosen independently of each other from C1-C20 alkyl, C3-C22 alkenyl, C6-C40 cycloalkyl, C7-C40 cycloalkenyl, Cl-20 methoxy alkyl glycol ethers and Y-OH groups;

[0025] - Y is chosen from C2-C40 alkylene, C2-C40 alkyl lactone groups, - R7-N(R8)-R9-, in which R7, R8 and R9 are independently of each other chosen from hydrogen, C1-C20 alkyl, C3-C22 alkenyl, C6-C40 cycloalkyl, C7-C40 cycloalkenyl, Cl -20 methoxy alkyl glycol ethers,

[0026] - m is an integer ranging from 2 to 100,

[0027] - n is an integer ranging from 1 to 1000.

[0028] According to one embodiment, the phosphite polymer, preferably corresponding to formula (I), has a weight-average molecular mass of less than 30,000 g / mol, preferably ranging from 5,000 to 20,000 g / mol. According to one embodiment, the anti-wear additive represents from 0.01 to 10% by weight of the total weight of the fluid.

[0029] According to one embodiment, the anti-wear additive comprises from 5 to 9150 ppm by weight of phosphorus, preferably from 5 to 4500 ppm by weight of phosphorus, relative to the total weight of fluid.

[0030] According to one embodiment, the fluid comprises at least 70% by weight, preferably at least 80% by weight, more preferably at least 85% by weight, of base oil(s), relative to the total weight of the fluid.

[0031] According to one embodiment, the fluid comprises:

[0032] - from 70 to 99.99% by weight of one or more base oils, and

[0033] - from 0.01 to 10% by weight of anti-wear additive(s), preferably chosen from phosphorus anti-wear agents, preferably chosen from phosphite polymers,

[0034] - optionally from 1 to 30% by weight of one or more functional additives, preferably chosen from viscosity index improving additives, antioxidant additives, antifoam additives, dispersants, detergents, viscosity modifying additives, and their mixture, relative to the total weight of the fluid.

[0035] The fluid used according to the invention has the advantage of being able to be used both to lubricate the parts of a propulsion system of an electric vehicle and to cool the parts of a propulsion system of an electric vehicle.

[0036] Unless otherwise indicated, quantities in a product are expressed by weight, relative to the total weight of the product.

[0037] Detailed description

[0038] The present invention relates to the use of at least one anti-wear additive: to improve the thermal conductivity of a fluid comprising at least one base oil and / or to improve the heat transfer properties of a fluid comprising at least one base oil and / or in a fluid comprising at least one base oil for cooling the battery of an electric vehicle.

[0039] For the purposes of the present invention, the term "electric vehicle" means a vehicle comprising an electric motor as the sole means of propulsion, unlike a hybrid vehicle which comprises a combustion engine and an electric motor as combined means of propulsion.

[0040] For the purposes of the present invention, the term "propulsion system" means a system comprising the mechanical parts necessary for the propulsion of a vehicle. In the context of an electric vehicle, the propulsion system thus more particularly encompasses an electric motor, the rotor-stator assembly of the power electronics (dedicated to speed regulation), a transmission (also called a reducer) and a battery.

[0041] Thermal conductivity may be determined according to ASTM D7896-19. It is preferably determined at 30°C for the purposes of the present invention.

[0042] Anti-wear additive

[0043] The anti-wear additive implemented in the lubricating composition is an additive known for its wear reducing properties when added to a base oil.

[0044] According to the invention, the anti-wear additive is chosen from phosphorus anti-wear agents, phospho-sulfur anti-wear agents, phospho-amine anti-wear agents, sulfur anti-wear agents, borate anti-wear agents, and mixtures thereof.

[0045] Preferably, the anti-wear additive is chosen from phosphorus anti-wear agents, phospho-sulfur anti-wear agents, phospho-amine anti-wear agents, and mixtures thereof.

[0046] For the purposes of the present invention, a “phosphorus anti-wear” will designate an anti-wear comprising at least one phosphorus atom and not comprising sulfur or nitrogen.

[0047] For the purposes of the present invention, a “sulfur-containing anti-wear agent” will designate an anti-wear agent comprising at least one sulfur atom and not comprising phosphorus or nitrogen.

[0048] For the purposes of the present invention, a "phospho-sulfur anti-wear" will designate an anti-wear comprising at least one phosphorus atom and at least one sulfur atom and not comprising a nitrogen atom. For the purposes of the present invention, a "phospho-amine anti-wear" will designate an anti-wear comprising at least one phosphorus atom and at least one nitrogen atom and not comprising a sulfur atom.

[0049] For the purposes of the present invention, a “sulfur-containing anti-wear agent” will designate an anti-wear agent comprising at least one sulfur atom and not comprising a phosphorus or nitrogen atom.

[0050] For the purposes of the present invention, a “borated anti-wear” will designate an anti-wear comprising at least one boron atom and not comprising a phosphorus, nitrogen or sulfur atom.

[0051] Anti-wear additives of the phosphorus anti-wear, phospho-sulfur anti-wear, phospho-amine anti-wear, sulfur anti-wear, borate anti-wear type are commercially available.

[0052] Phosphorus-containing anti-wear additives include phosphates, phosphites, and phosphonates. These terms refer to phosphoric, phosphorous, and phosphonic acids, their mono-, di-, and triesters, for example, alkyl phosphates, alkyl phosphonates, and their salts.

[0053] The phospho-sulfur anti-wear additives optionally used in the present invention may be (mono or di) thiophosphates and thiophosphites, these terms including thiophosphoric and thiophosphorous acids, the esters of these acids, their salts, dithiophosphites and dithiophosphates.

[0054] Examples of phospho-sulfur anti-wear additives include monobutylthiophosphate, monooctylthiophosphate, monolaurylthiophosphate, dibutylthiophosphate, dilaurylthiophosphate, tributylthiophosphate, trioctylthiophosphate, triphenylthiophosphate, monooctylthiophosphite, trilaurylthiophosphate, monolaurylthiophosphite, monobutylthiophosphite, dibutylthiophosphite, dilaurylthiophosphite, tributylthiophosphite, trioctylthiophosphite, triphenylthiophosphite, trilaurylthiophosphite and their salts.

[0055] Among the phospho-sulfur anti-wear agents in the form of salts, mention may be made of metal dithiophosphate anti-wear agents, for example zinc, cobalt or nickel dithiophosphates. Among the sulfur anti-wear agents, mention may be made of sulfurized olefins, sulfurized esters, polysulfides, in particular disulfides, thiocarbamates and dithiocarbamates and their salts.

[0056] Among the sulfur anti-wear agents in the form of salts, we can cite the metal dithiocarbamate type anti-wear agents, for example zinc, cobalt or nickel dithiocarbamates.

[0057] Among the borated anti-wear agents, we can cite borated esters, calcium borates and potassium borates.

[0058] According to one embodiment, the anti-wear additive is chosen from phosphite polymers, preferably corresponding to formula (I):

[0059] [Chem 1] in which,

[0060] - each of the Rs 1 , R 2 , R 3 and R 4 can be chosen independently of each other from C1-C20 alkyl, C3-C22 alkenyl, C6-C40 cycloalkyl, C7-C40 cycloalkenyl, C1-20 methoxy alkyl glycol ethers and Y-OH (serving as terminal group);

[0061] - Y is chosen from C2-C40 alkylene, C2-C40 alkyl lactone, -R7 -N(R 8 )- R 9 -, in which R 7 , R 8 and R 9 are independently of each other selected from hydrogen, C1-C20 alkyl, C3-C22 alkenyl, C6-C40 cycloalkyl, C7-C40 cycloalkenyl, C1-20 methoxy alkyl glycol ethers,

[0062] - m is an integer ranging from 2 to 100,

[0063] - n is an integer ranging from 1 to 1000.

[0064] For the purposes of the present invention, the term "alkyl" means a saturated, non-cyclic, linear or branched hydrocarbon chain, optionally comprising one or more heteroatoms, such as oxygen, nitrogen or sulfur atoms. Preferably, the alkyls consist of carbon and hydrogen atoms. For the purposes of the present invention, the term "alkenyl" means a saturated, non-cyclic, linear or branched hydrocarbon chain, optionally comprising one or more heteroatoms, such as oxygen, nitrogen or sulfur atoms. Preferably, the alkenyls consist of carbon and hydrogen atoms.

[0065] For the purposes of the present invention, the term "cycloalkyl" means a saturated monocyclic or polycyclic group optionally having one or more alkyl or alkenyl substituents, said ring(s) may themselves be substituted by one or more heteroatoms, such as oxygen, nitrogen or sulfur atoms. Preferably, the cycloalkyls consist of carbon and hydrogen atoms.

[0066] For the purposes of the present invention, the term "cycloalkenyl" means an unsaturated monocyclic or polycyclic group optionally having one or more alkyl or alkenyl substituents, said ring(s) may themselves be substituted by one or more heteroatoms, such as oxygen, nitrogen or sulfur atoms. Preferably, the cycloalkenyls consist of carbon and hydrogen atoms.

[0067] For the purposes of the present invention, a “C1-C1j” group is a group comprising from i to j carbon atoms.

[0068] According to a preferred embodiment, the group Y is chosen from alkylene comprising from 2 to 20 carbon atoms, preferably from 2 to 12 carbon atoms, more preferably from 2 to 8 carbon atoms.

[0069] According to one embodiment, m ranges from 4 to 100.

[0070] According to one embodiment, the phosphite polymer, preferably corresponding to formula (I), has a weight-average molecular mass of less than 30,000 g / mol, preferably ranging from 3,000 to 20,000 g / mol. The weight-average molecular mass can be measured by size exclusion chromatography.

[0071] According to one embodiment, the phosphite polymer, preferably corresponding to formula (I), has a number-average molecular mass of less than 10,000 g / mol, preferably ranging from 1,000 to 5,000 g / mol. The number-average molecular mass can be measured by size exclusion chromatography. According to one embodiment, the phosphite polymer, preferably corresponding to formula (I), has a polydispersity index ranging from 1 to 5, preferably ranging from 2 to 4.

[0072] Preferably, the phosphite polymer, preferably corresponding to formula (I), contains less than 2% by weight, preferably less than 1% by weight, or even less than 0.7% by weight of (alkyl)phenol group, relative to the total weight of the phosphite polymer of formula (I).

[0073] Preferably, the phosphite polymer, preferably corresponding to formula (I), is completely free of aromatic groups other than (alkyl)phenol groups.

[0074] Typically, the phosphite polymer, preferably having formula (I), is in liquid form.

[0075] According to one embodiment, the phosphite polymer, preferably corresponding to formula (I), has a phosphorus content ranging from 0.5 to 20% by weight, preferably from 1 to 10% by weight, relative to the total weight of the phosphite polymer.

[0076] The phosphite polymer that can be used in the invention can be obtained according to the method described in document WO2011102861. In particular, the polymer can be obtained according to the method described in paragraphs 27 to 32 of this document.

[0077] The synthesis of polymers of formula (I) generally involves transesterification in which the triphenyl phosphite (or any other suitable alkyl or aryl phosphite) may be reacted with a saturated or unsaturated alcohol or polyethylene or polypropylene glycol ether and a diol or polymer diol H(OY) m0H where Y and m are as defined above with a suitable basic catalyst at a temperature between 20°C and 250°C, and preferably at a temperature between 50°C and 185°C. Non-limiting examples of saturated or unsaturated alcohols include decyl, isodecyl, lauryl, tridecyl, isotridecyl, tetradecyl, pentadecyl, hexadecyl, stearyl, isostearyl, oleic alcohols, monohydroxylated glycol ethers. Preferably, the fluid used according to the invention comprises from 0.01 to 10% by weight of anti-wear additives, preferably from 0.01 to 5% by weight of anti-wear additive(s), relative to the total weight of the fluid.

[0078] The quantity of anti-wear additives may be adapted in order to obtain a phosphorus content ranging from 5 to 9150 ppm by weight in the fluid. Preferably, the phosphorus content in the fluid used according to the invention ranges from 5 to 4500 ppm by weight, relative to the total weight of the fluid.

[0079] Base oil(s)

[0080] The fluid used according to the invention comprises one or more base oils, preferably in a content of at least 70% by weight, preferably ranging from 70 to 99% by weight, more preferably from 80 to 98% by weight, preferentially from 85 to 95% by weight, relative to the total weight of the fluid.

[0081] These base oils can be chosen from base oils conventionally used in the field of lubricating oils, such as mineral, synthetic or natural, animal or vegetable oils or their mixtures.

[0082] It can be a mixture of several base oils, for example a mixture of two, three, or four base oils.

[0083] The base oils of the fluids 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.

[0084] [Table 1]

[0085] 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, de-alphatting, solvent dewaxing, hydrotreating, hydrocracking, hydroisomerization and hydrofinishing.

[0086] Blends of synthetic and mineral oils, which can be bio-sourced, can also be used.

[0087] There is generally no limitation on the use of different base oils to produce the compositions used according to the invention, except that they must have properties, in particular in terms of viscosity, viscosity index, or resistance to oxidation, suitable for use in propulsion systems of an electric or hybrid vehicle.

[0088] The base oils of the fluids used according to the invention can also be chosen from synthetic oils, such as certain esters of carboxylic acids and alcohols, polyalphaolefins (PAO), and polyalkylene glycols (PAG) obtained by polymerization or copolymerization of alkylene oxides comprising from 2 to 8 carbon atoms, in particular from 2 to 4 carbon atoms.

[0089] PAOs used as base oils are, for example, obtained from monomers comprising 4 to 32 carbon atoms, for example from octene or decene. The weight-average molecular mass of the PAO can vary quite widely. Preferably, the weight-average molecular mass of the PAO is less than 600 Da. The weight-average molecular mass of the PAO can also range from 100 to 600 Da, from 150 to 600 Da, or from 200 to 600 Da.

[0090] Advantageously, the base oil or oils of the fluid used according to the invention may be chosen from base oils of group II or III.

[0091] According to an alternative embodiment, the base oil or oils of the fluid used according to the invention are chosen from polyalphaolefins (PAO), polyalkylene glycol (PAG) and esters of carboxylic acids and alcohols.

[0092] Additional additives

[0093] The fluid used according to the invention may also further comprise all types of functional additives, distinct from the anti-wear additives defined in the context of the present invention, suitable for use in a lubricant for electric vehicles.

[0094] Such additives, known to those skilled in the art in the field of lubrication of electric vehicles, may be chosen from detergents, dispersants, antioxidants, pour point depressants, anti-foaming agents, viscosity index improvers, and mixtures thereof.

[0095] Advantageously, the fluid used according to the invention comprises at least one functional additive chosen from detergents, dispersants, antioxidants, pour point depressants, anti-foaming agents, viscosity index improvers, and mixtures thereof.

[0096] 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 fluid.

[0097] These additives can be introduced in isolation and / or in the form of a mixture like those already available for sale for commercial lubricant formulations for vehicle engines, with performance levels as defined by ACEA (Association of European Automobile Manufacturers) and / or TAPI (American Petroleum Institute), well known to those skilled in the art. The fluid used according to the invention can comprise at least one antioxidant additive.

[0098] The antioxidant additive generally helps to delay the degradation of the composition in service. This degradation can notably result in the formation of deposits, the presence of sludge or an increase in the viscosity of the composition.

[0099] Antioxidant additives act in particular as radical inhibitors or hydroperoxide destroyers. Among the commonly used antioxidant additives, mention may be made of phenolic antioxidant additives, amine antioxidant additives, and phosphosulfur antioxidant additives. Some of these antioxidant additives, for example phosphosulfur antioxidant additives, may be ash-generating. Phenolic antioxidant additives may be ash-free or in the form of neutral or basic metal salts. The antioxidant additives may in particular be chosen from sterically hindered phenols, sterically hindered phenol esters and sterically hindered phenols comprising a thioether bridge, diphenylamines, diphenylamines substituted by at least one C1-C12 alkyl group, N,N'-dialkylaryldiamines and mixtures thereof.

[0100] Preferably according to the invention, the sterically hindered phenols are chosen from compounds comprising a phenol group of which at least one vicinal carbon of the carbon carrying 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.

[0101] Amino compounds are another class of antioxidant additives that can be used, possibly in combination with phenolic antioxidant additives. Examples of amino compounds are aromatic amines, for example aromatic amines of the formula NR 10 R n R 12 in which R 10 represents an aliphatic group or an aromatic group, optionally substituted, R 11 represents an aromatic group, optionally substituted, R 12represents a hydrogen atom, an alkyl group, an aryl group or a group of formula R 13 S(O) Z R 14 in which R 13 represents an alkylene group or an alkenylene group, R 14 represents an alkyl group, an alkenyl group or an aryl group and z represents 0, 1 or 2. Sulphurized alkyl phenols or their alkali and alkaline earth metal salts can also be used as antioxidant additives.

[0102] Another class of antioxidant additives is copper compounds, e.g. copper thio- or dithio-phosphates, copper salts of carboxylic acids, dithiocarbamates, sulphonates, phenates, copper acetylacetonates. Copper I and II salts, succinic acid or anhydride salts can also be used.

[0103] The fluid used according to the invention may contain all types of antioxidant additives known to those skilled in the art.

[0104] Advantageously, the fluid used according to the invention comprises at least one ash-free antioxidant additive.

[0105] The fluid used 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 fluid.

[0106] The fluid used according to the invention may also comprise at least one detergent additive.

[0107] Detergent additives generally reduce the formation of deposits on the surface of metal parts by dissolving secondary oxidation and combustion products.

[0108] The detergent additives that can be used in the fluid used according to the invention are generally known to those 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 alkaline earth metal.

[0109] The detergent additives are preferably chosen from alkali metal or alkaline earth metal salts of carboxylic acids, sulfonates, salicylates, naphthenates, as well as phenate salts. The alkali and alkaline earth metals are preferably calcium, magnesium, sodium or barium.

[0110] These metal salts generally contain the metal in a stoichiometric quantity or in excess, i.e. in a quantity greater than the narrow stoichiometric quantity. These are then overbased detergent additives; the excess metal providing the overbased character to the detergent additive is then generally in the form of an oil-insoluble metal salt, for example a carbonate, a hydroxide, an oxalate, an acetate, a glutamate, preferably a carbonate.

[0111] The fluid used according to the invention may, for example, comprise from 0.5 to 4% by weight of detergent additive, relative to the total weight of the composition.

[0112] Also, the fluid used according to the invention may comprise at least one dispersing agent. Typically, the dispersant will ensure the maintenance in suspension and the evacuation of insoluble solid contaminants consisting of secondary oxidation products which form when the fluid is in service.

[0113] The dispersing agent may be selected from Mannich bases or succinimide-type compounds, such as polyisobutylene succinimide (PIBSI).

[0114] The fluid used according to the invention may, for example, comprise from 0.2 to 10% by weight of dispersing agent(s), relative to the total weight of the fluid.

[0115] The fluid used according to the invention may further comprise at least one antifoaming agent.

[0116] The antifoam agent can be chosen from silicones.

[0117] The fluid used according to the invention may comprise from 0.01 to 2% by mass or from 0.01 to 5% by mass, preferably from 0.1 to 1.5% by mass or from 0.1 to 2% by mass of antifoam agent, relative to the total weight of the fluid.

[0118] The fluid used according to the invention may also comprise at least one pour point lowering additive (also known as “PPD” agents for “Pour Point Depressant” in English).

[0119] By slowing the formation of paraffin crystals, pour point depressants generally improve the cold behavior of the fluid. Examples of pour point depressants include polyalkyl methacrylates, polyacrylates, polyarylamides, polyalkylphenols, polyalkylnaphthalenes, and alkylated polystyrenes.

[0120] The fluid used according to the invention may also comprise at least one viscosity index improving additive (VI improver). Examples 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 fluid.

[0121] In terms of formulating such a fluid, the anti-wear additive(s) may be added to a base oil or blend of oils, and then any other additional additives added.

[0122] Alternatively, the anti-wear additive(s) may be added to a pre-existing conventional lubricant formulation, including in particular one or more base oils, and possibly additional additives.

[0123] Alternatively, the anti-wear additive(s) may be combined with one or more additional additives when present, and the resulting additive "package" added to a base oil or blend of oils.

[0124] Advantageously, the fluid used according to the invention has a kinematic viscosity, measured at 40°C according to the ASTM D445 standard, ranging from 5 to 300 mm 2 / s, especially from 10 to 25 mm 2 / s.

[0125] Advantageously, the fluid used according to the invention has a kinematic viscosity, measured at 100°C according to the ASTM D445 standard, ranging from 1 to 20 mm 2 / s, especially from 2 to 15 mm 2 / s.

[0126] According to a particular embodiment, the fluid used according to the invention comprises, or even consists of:

[0127] - a base oil or mixture of base oils;

[0128] - one or more anti-wear;

[0129] - optionally one or more additional additives chosen from viscosity index modifiers, detergents, dispersants, antioxidants, pour point depressants, anti-foaming agents and mixtures thereof.

[0130] According to a particular embodiment, the fluid used according to the invention comprises, or even consists of:

[0131] - from 70 to 99.99% by weight of one or more base oils, and

[0132] - from 0.01 to 10% by weight of anti-wear additive(s), preferably chosen from phosphorus anti-wear agents, preferably chosen from phosphite polymers,

[0133] - optionally from 1 to 30% by weight of one or more functional additives, preferably chosen from viscosity index improving additives, antioxidant additives, antifoam additives, dispersants, detergents, viscosity modifying additives, and their mixture, relative to the total weight of the fluid.

[0134] According to a particular embodiment, the fluid used according to the invention comprises, or even consists of:

[0135] - from 70 to 99% by weight of one or more base oil(s), and

[0136] - from 0.01 to 10% by weight of anti-wear additive(s), preferably chosen from phosphorus anti-wear agents, preferably chosen from phosphite polymers,

[0137] - optionally from 1 to 30% by weight of one or more functional additives, preferably chosen from viscosity index improving additives, antioxidant additives, antifoam additives, dispersants, detergents, viscosity modifying additives, and their mixture, relative to the total weight of the fluid.

[0138] According to a particular embodiment, the fluid used according to the invention comprises, or even consists of:

[0139] - at least 70% by weight, preferably from 70 to 99% by weight of base oil(s);

[0140] - from 0.05% to 10% by weight, in particular from 0.1% to 7% by weight, and more particularly from 1% to 5% by weight, of phosphite polymer(s) corresponding to formula (I);

[0141] - optionally from 1 to 20% by weight, preferably from 1.5 to 10% by weight, and more particularly from 2 to 5% by weight, of one or more functional additives, preferably chosen from viscosity index modifiers, detergents, dispersants, antioxidants, pour point depressants, anti-foaming agents and mixtures thereof, relative to the total weight of the fluid.

[0142] According to one embodiment, the fluid used according to the invention comprises from 5 to 9150 ppm by weight of phosphorus, preferably from 5 to 4500 ppm by weight of phosphorus, relative to the total weight of the fluid. According to one embodiment, the fluid used according to the invention comprises from 5 to 4000 ppm by weight of sulfur, preferably from 7 to 1000 ppm by weight of sulfur, more preferably from 10 to 800 ppm by weight of sulfur, relative to the total weight of the fluid.

[0143] The present invention also relates to the use of at least one anti-wear additive to improve the heat transfer properties of a fluid comprising at least one base oil.

[0144] Preferably, the anti-wear additive(s) exhibit one or more of the characteristics defined in the present invention.

[0145] Preferably, the fluid has one or more of the characteristics defined in the present invention.

[0146] The present invention also relates to the use of at least one anti-wear additive in a fluid comprising at least one base oil, said fluid being used to cool the battery of an electric vehicle.

[0147] Preferably, the anti-wear additive(s) exhibit one or more of the characteristics defined in the present invention.

[0148] Preferably, the fluid has one or more of the characteristics defined in the present invention.

[0149] The present invention also relates to the use of a fluid comprising at least one base oil and at least one anti-wear additive to improve the thermal conductivity of a fluid comprising at least one base oil and / or to improve the heat transfer properties of the fluid and / or to cool the battery of an electric vehicle.

[0150] Preferably, the anti-wear additive(s) exhibit one or more of the characteristics defined in the present invention.

[0151] Preferably, the fluid has one or more of the characteristics defined in the present invention.

[0152] The invention further relates, according to another of its aspects, to a method for lubricating and cooling a propulsion system of an electric vehicle, said method comprising circulating a single fluid in the lubrication and cooling system of the entire propulsion system of an electric vehicle, said fluid comprising a base oil and at least one anti-wear additive.

[0153] Preferably, the anti-wear additive(s) exhibit one or more of the characteristics defined in the present invention.

[0154] Preferably, the fluid has one or more of the characteristics defined in the present invention.

[0155] Typically, the electric vehicle propulsion system includes an electric motor, the rotor-stator assembly of the power electronics (dedicated to speed regulation), a transmission (also called a reducer) and a battery.

[0156] The invention also relates, according to another of its aspects, to a method for improving the thermal conductivity of a fluid comprising at least one base oil, said method comprising a step of mixing at least one anti-wear additive as defined in the present invention, with at least one base oil, preferably said anti-wear additive is chosen from phosphorus-containing anti-wear additives, preferably chosen from phosphite polymers preferably corresponding to formula (I).

[0157] Preferably, the anti-wear additive(s) exhibit one or more of the characteristics defined in the present invention.

[0158] Preferably, the fluid has one or more of the characteristics defined in the present invention.

[0159] 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.

[0160] Examples

[0161] Example 1

[0162] In this example, a phosphite polymer type anti-wear agent was used. It is a phosphite polymer corresponding to the formula (I) described in the present invention. It comprises 4.50% by weight of phosphorus and zero sulfur, it has a weight-average molecular mass of approximately 10,000 g / mol and a number-average molecular mass of approximately 3,000 g / mol, it can be obtained for example according to the method described in example 2 of document WO 2011 / 102861.

[0163] In this example, a Group III base oil was used. The base oil has a viscosity at 40°C of 7.62 cSt measured according to ASTM D445.

[0164] In this example, fluid 1 comprises 99% by weight of the base oil and 1% by weight of the antiwear and fluid 2 comprises 95% by weight of the base oil and 5% by weight of the antiwear.

[0165] Table 2 lists the thermal conductivities at 30°C, 60°C, and 90°C of the tested compositions. Thermal conductivity was measured according to ASTM D7896-19.

[0166] [Table 2]

[0167] The results in Table 2 show that the anti-wear additive improves the thermal conductivity at 30°C, 60°C and 90°C of the lubricating composition.

[0168] Example 2

[0169] Lubricating compositions were prepared by mixing the ingredients at a temperature of about 40°C, according to methods well known to those skilled in the art. The lubricating compositions that were prepared and tested are detailed in Table 3 below. The elemental contents of phosphorus and sulfur were calculated based on the elemental contents in the ingredients and are also shown in Table 3 in ppm by weight.

[0170] Finally, the kinematic viscosities at 40°C and 100°C were determined by the ASTM D445 method and are shown in Table 3.

[0171] [Table 3]

[0172] In the compositions of table 3: - the base oils are group III base oils,

[0173] - the phosphite polymer is identical to the phosphite polymer used in the example

[0174] 1,

[0175] - the phosphorus anti-wear is a tert-butylphenyl phosphate (not corresponding to the formula

[0176] (I)), comprising 8.10% by weight of phosphorus and zero sulfur and marketed as an anti-wear additive,

[0177] - T antioxidant is an alkylated diphenylamine antioxidant,

[0178] - The anti-corrosion agent is a tolytriazine, - the detergent is a calcium sulfonate overbased detergent,

[0179] - the additive package contains a pour point improver and an antifoam.

[0180] The anti-wear properties of the additive of formula (I) were determined by the FZG A / 8.3 / 90 method with a low load.

[0181] The lubricating compositions described in Table 3 were subjected to the FZG A / 8.3 / 90 method (according to ISO 14635-1). The results are shown in Table 3 above. At the same phosphorus content, the composition Cil according to the invention has better anti-wear properties than the composition CCI.

Claims

Claims 1. Use of at least one anti-wear additive to improve the thermal conductivity of a fluid comprising at least one base oil, said anti-wear additive being chosen from phosphorus anti-wear agents, phospho-sulfur anti-wear agents, phospho-amine anti-wear agents, sulfur anti-wear agents, borate anti-wear agents, and mixtures thereof.

2. Use of at least one anti-wear additive according to claim 1, to improve the heat transfer properties of the fluid.

3. Use of at least one anti-wear additive according to claim 1 or 2, wherein the fluid is used to cool the battery of an electric vehicle.

4. Use of at least one anti-wear additive according to one of claims 1 to 3, for preparing a single fluid used to lubricate and cool the propulsion system of an electric vehicle.

5. Use of at least one anti-wear additive according to one of claims 1 to 4, in which the anti-wear additive is chosen from phosphorus anti-wear agents, phospho-sulfur anti-wear agents, phospho-amine anti-wear agents, and mixtures thereof, preferably from phosphorus anti-wear agents.

6. Use of at least one anti-wear additive according to any one of claims 1 to 5, in which the anti-wear additive is a phosphite polymer, preferably corresponding to formula (I): [Chem 1] in which, - each of the Rs 1 , R 2 , R 3 and R 4 may be chosen independently of each other from C1-C20 alkyl, C3-C22 alkenyl, C6-C40 cycloalkyl, C7-C40 cycloalkenyl, Cl -20 methoxy alkyl glycol ethers and Y-OH groups; - Y is chosen from C2-C40 alkylene, C2-C40 alkyl lactone, -R groups 7 -N(R 8 )-R 9- , in which R 7 , R 8 and R 9 are independently of each other selected from hydrogen, C1-C20 alkyl, C3-C22 alkenyl, C6-C40 cycloalkyl, C7-C40 cycloalkenyl, Cl -20 methoxy alkyl glycol ethers, - m is an integer ranging from 2 to 100, - n is an integer ranging from 1 to 1000.

7. Use of at least one anti-wear additive according to claim 6, in which the phosphite polymer, preferably corresponding to formula (I), has a weight-average molecular mass of less than 30,000 g / mol, preferably ranging from 5,000 to 20,000 g / mol.

8. Use of at least one anti-wear additive according to any one of claims 1 to 7, in which the anti-wear additive represents from 0.01 to 10% by weight of the total weight of the fluid.

9. Use of at least one anti-wear additive according to any one of claims 1 to 8, wherein the anti-wear additive comprises from 5 to 9150 ppm by weight of phosphorus, preferably from 5 to 4500 ppm by weight of phosphorus, relative to the total weight of fluid.

10. Use of at least one anti-wear additive according to any one of claims 1 to 9, in which the fluid comprises at least 70% by weight, preferably at least 80% by weight, more preferably at least 85% by weight, of base oil(s), relative to the total weight of the fluid.

11. Use of at least one anti-wear additive according to any one of claims 1 to 10, in which the fluid comprises: from 70 to 99.99% by weight of one or more base oils, and from 0.01 to 10% by weight of anti-wear additive(s), preferably chosen from phosphorus anti-wear additives, preferably chosen from phosphite polymers, optionally from 1 to 30% by weight of one or more functional additives, preferably chosen from viscosity index improving additives, antioxidant additives, antifoam additives, dispersants, detergents, viscosity modifying additives, and their mixture, relative to the total weight of the fluid.

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