Aqueous lubricant composition for electric or hybrid vehicles

Abstract

The present invention relates to the use of a lubricant composition for cooling and / or lubricating a propulsion system of an electric or hybrid vehicle, the lubricant composition comprising: - from 10 to 75% by weight of water, - from 2 to 50% by dry weight of at least one polyalkylene glycol (PAG1) having a kinematic viscosity at 40°C of at least 10000 cSt, - from 2 to 50% by dry weight of at least one polyalkylene glycol (PAG2) having a kinematic viscosity at 40°C of less than 10000 cSt, based on the total weight of the lubricant composition.

Description

FIELD OF THE INVENTION

[0001] The present invention concerns aqueous lubricant and / or cooling compositions for their use in electric or hybrid vehicles, in particular gears. In particular, the present invention concerns aqueous compositions for cooling and / or lubricating the propulsion system of an electric or hybrid vehicle.TECHNICAL BACKGROUND OF THE INVENTION

[0002] The evolution of international standards for the reduction of CO2 emissions, but also for the reduction of energy consumption, pushes car manufacturers to propose alternative solutions to internal combustion engines.

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

[0004] Generally, electric or hybrid vehicles require compositions to meet the twofold lubrication and cooling requirements of the various parts of the propulsion system mentioned above.

[0005] On the one hand, lubricating compositions, also known as "lubricants", are commonly used in engines to reduce the friction forces between the various metal parts in motion in engines, and thus protect the parts against wear. In addition to wear phenomena, friction can oppose the relative movement of parts in contact and induce energy losses that are detrimental to optimal operation of the propulsion system.

[0006] To this end, a lubricant composition is typically composed of one or more base oils, to which are generally associated a number of additives designed to boost the lubricating performance of the base oils, such as friction-modifying additives.

[0007] On the other hand, electric propulsion systems generate heat during operation via the electric motor, power electronics and batteries. As the amount of heat generated is greater than that normally dissipated to the environment, it is necessary to provide cooling for the motor, power electronics and batteries. Typically, cooling is carried out on several heat-generating parts of the propulsion system and / or parts of said system sensitive to heat, in order to avoid reaching dangerous temperatures, and in particular the power electronics and batteries. This cooling is typically provided by a cooling fluid, distinct from the hydrocarbon lubricant, such as air, an aqueous fluid, such as water, or a mixture of water and a glycol.

[0008] It would be advantageous to have a composition that could simultaneously meet the lubrication and cooling needs of an electric or hybrid vehicle propulsion system.

[0009] The most widely used lubricants are hydrocarbon-based lubricants. However, these hydrocarbon oils generally do not provide sufficient heat dissipation to enable them to be used together as coolants.

[0010] More recently, in response to a growing demand to avoid the use of toxic solvents and reduce the environmental impact of products, studies have focused on the development of water-based lubricants.

[0011] While water is an excellent coolant, it lacks the tribological properties required of a lubricant, particularly in terms of reducing friction and protecting parts against wear. Additivation systems have been proposed to give aqueous fluids satisfactory lubrication performance.

[0012] For example, WO 2021 / 259853 describes an aqueous lubricant composition comprising a polyalkylene glycol, an antifreeze compound and a phosphorus compound.

[0013] However, this aqueous lubricant is not entirely satisfactory, particularly with regard to the phenomenon of pitting caused by mechanical fatigue. Indeed, it has been found that this lubricant composition can generate this type of failure in mechanical contacts, particularly as a function of the composition's formulation protocol.

[0014] There is therefore an advantage in providing lubricant compositions which meet all the specific tests for lubricant compositions, that have a low carbon footprint.BRIEF DESCRIPTION OF FIGURES

[0015] Figure 1 represents a schematic view of a propulsion system of an electric or hybrid vehicle.SUMMARY OF THE INVENTION

[0016] The invention concerns the use of a lubricant composition for cooling and / or lubricating the propulsion system of an electric or hybrid vehicle, the lubricant composition comprising: from 10 to 75% by weight of water, from 2 to 50% by dry weight of at least one polyalkylene glycol (PAG1) having a kinematic viscosity at 40°C of at least 10000 cSt, from 2 to 50% by dry weight of at least one polyalkylene glycol (PAG2) having a kinematic viscosity at 40°C of less than 10000 cSt, based on the total weight of the lubricant composition.

[0017] Preferably, the lubricant composition is characterized by one or more of the following features: the ratio between the kinematic viscosity at 40°C of PAG1 and PAG2 is higher than 1.5, preferably higher than 2, more preferably higher than 2.5, even more preferably higher than 3.5, and / or PAG1 has a kinematic viscosity at 40°C ranging from 10000 to 35000 cSt and / or PAG2 has a kinematic viscosity at 40°C ranging from 100 to 5000 cSt, preferably from 100 to 1000 cSt, and / or the PAG1 has an average molecular weight ranging from 8000 g / mol to 50000 g / mol, preferably from 9000 to 40000 g / mol, more preferably from 10000 to 30000 g / mol, even more preferably from 11000 to 20000 g / mol, and / or the PAG2 has an average molecular weight ranging from 500 to 7500 g / mol, preferably from 700 to 6000 g / mol, more preferably from 1000 to 5000 g / mol, even more preferably from 2000 to 4000 g / mol, and / or the lubricant composition comprises: ∘ from 10 to 50% by weight, preferably from 20 to 40% by weight, of water, ∘ from 5 to 30% by dry weight, preferably from 10 to 25% by dry weight of at least one polyalkylene glycol PAG1, o from 10 to 50% by dry weight, preferably from 15 to 40% by dry weight, of at least one polyalkylene glycol PAG2, based on the total weight of the lubricant composition, and / or PAG1 and PAG2 comprises ethylene oxide units and optionally propylene oxide units. the lubricant composition comprises: ∘ from 10 to 50% by weight, preferably from 20 to 40% by weight, of water, o from 5 to 30% by dry weight, preferably from 10 to 25% by dry weight of at least one polyalkylene glycol PAG1, o from 10 to 50% by dry weight, preferably from 15 to 40% by dry weight, of at least one polyalkylene glycol PAG2, ∘ from 0.1 to 40% by weight, preferably from 1 to 30% by weight, of one or more functional additive(s) different from polyalkylene glycol, the additive(s) being preferably selected from anti-wear additives, extreme-pressure additives, metal deactivators, corrosion inhibitors, pH boosters, anti-freezing agents, anti-foam agents, lubricity enhancers, and mixtures thereof. based on the total weight of the lubricant composition, and / or the lubricant composition further comprises at least one functional additive selected from corrosion inhibitors, at least one corrosion inhibitor being preferably selected from carboxylic acids having less than 12 carbon atoms, and / or the lubricant composition has a kinematic viscosity at 40°C ranging from 5 cSt to 500 cSt, preferably from 10 to 200 cSt, more preferably from 10 to 100 cSt, and / or the lubricant composition comprises: ∘ from 10 to 50% by weight, preferably from 20 to 40% by weight, of water, ∘ from 5 to 30% by dry weight, preferably from 10 to 25% by dry weight of at least one polyalkylene glycol PAG1 comprising ethylene oxide units and propylene oxide units and having a kinematic viscosity at 40°C ranging from 10000 cSt to 35000 cSt, ∘ from 10 to 50% by dry weight, preferably from 15 to 40% by dry weight, of at least one polyalkylene glycol PAG2 comprising ethylene oxide units and propylene oxide units and having a kinematic viscosity at 40°C ranging from 100 to 5000 cSt, preferably from 100 to 1000 cSt, ∘ from 0.1 to 10% by weight, preferably from 1 to 5% by weight, of at least one carboxylic acid, wherein the carboxylic acid(s) have less than 12 carbon atoms, ∘ optionally from 0.1 to 40% by weight, preferably from 1 to 30% by weight, of one or more additive(s) selected from anti-wear and / or extreme-pressure additives, metal deactivators, pH boosters, anti-freezing agents, anti-foam agents, lubricity enhancers, and mixtures thereof, based on the total weight of the lubricant composition.

[0018] The invention also relates to the use of the lubricant composition defined in the invention to reduce frictions and / or to reduce abrasion and / or to reduce wear of mechanical part(s) of the propulsion system.

[0019] The invention also relates to the use of the lubricant composition defined in the invention, wherein the lubricant composition is coated onto gears of the propulsion system.

[0020] The invention also relates to the use of the lubricant composition defined in the invention to lubricate and / or cool the gearbox and / or motor and / or power electronics of an electric vehicle.

[0021] The invention also relates to the use of the lubricant composition defined in the invention to reduce pitting by mechanical fatigue, of mechanical part(s) of said propulsion system, brought into contact with said lubricant composition.

[0022] The invention also relates to a lubricating and / or cooling method comprising applying the lubricant composition as defined in the invention onto mechanical part(s) of a propulsion system of an electric or hybrid vehicle.

[0023] The aqueous lubricant compositions of the invention have less carbon footprint than oil-based lubricant compositions.

[0024] The lubricant compositions of the invention have good thermal properties.

[0025] The lubricant compositions of the invention have a very low coefficient of friction, and thus a high energy efficiency.

[0026] The present invention proposes an aqueous-based composition with tribological and cooling properties, suitable for use in lubricating and / or cooling an electric or hybrid vehicle propulsion system, while reducing or even eliminating mechanical fatigue pitting phenomena.

[0027] Advantageously, a lubricant composition used in accordance with the invention has little toxicological impact, particularly for people using this lubricant.

[0028] Moreover, even when water is the majority solvent, a composition according to the invention has good properties in terms of lubrication.

[0029] Thus, an aqueous lubricant composition according to the invention advantageously combines good cooling properties linked to the presence of water, and good tribological properties, in particular friction reduction and wear resistance. Thus, an aqueous composition according to the invention can perform the dual function of lubricating and cooling the propulsion system of an electric or hybrid vehicle, in particular the electric motor, power electronics, transmission and / or battery of an electric or hybrid vehicle.

[0030] Thanks to the aqueous composition as defined in the invention advantageously, there is no need to make use of two distinct fluids, on the one hand a cooling fluid and on the other hand a lubricating fluid. In particular, a lubricant composition according to the invention enables efficient cooling of the motor, power electronics and battery, as well as lubrication of the electric motor and of the transmission, in particular the gearbox, in an electric or hybrid vehicle.

[0031] In particular, an aqueous lubricant composition according to the invention can be used to lubricate and / or cool the gearbox and / or motor and / or power electronics of an electric vehicle.DETAILED DESCRIPTION OF THE INVENTION

[0032] The invention first concerns the use of a lubricant composition for cooling and / or lubricating a propulsion system of an electric or hybrid vehicle.

[0033] The lubricant composition used in the invention comprises: from 10 to 75% by weight of water, from 2 to 50% by dry weight of at least one polyalkylene glycol PAG1 having a kinematic viscosity at 40°C of at least 10000 cSt, from 2 to 50% by dry weight of at least one polyalkylene glycol PAG2 having a kinematic viscosity at 40°C of less than 10000 cSt, based on the total weight of the lubricant composition, the ratio between the kinematic viscosity at 40°C of PAG1 and the kinematic viscosity at 40°C of PAG2 being strictly greater than 1.

[0034] In the following, the term "aqueous lubricant composition" or "lubricant composition" will be used to designate a lubricating composition used according to the invention as defined above and detailed in the following. Because of its cooling properties, such a composition may also be referred to as an "aqueous cooling composition" or "cooling composition".

[0035] By "electric vehicle" in the sense of the present invention, we mean a vehicle comprising an electric motor as the sole means of propulsion, and by "hybrid vehicle", we mean a vehicle which comprises a combustion engine and an electric motor as combined means of propulsion.

[0036] By "propulsion system" in the sense of the present invention, we mean a system comprising the mechanical parts required to propel an electric vehicle. More specifically, the propulsion system comprises an electric motor, the rotor-stator assembly of the power electronics (dedicated to speed regulation), a transmission and a battery.

[0037] Within the present invention, the kinematic viscosity at 40°C of PAG (for example of PAG1 and of PAG2) can be measured according to ASTM D445.

[0038] The average molecular weight of PAG1 and PAG2 can be measured by methods well known for the skilled person, for example by size exclusion chromatography using polystyrene standard.

[0039] Typically, PAG1 and PAG2 used in the present invention are obtained by (co)polymerisation of alkylene glycol(s) comprising from 2 to 4 carbon atoms, for example by random copolymerisation.

[0040] The amount of water allows having both a low evaporation, a good thermal behaviour and low friction coefficient. The lubricant composition of the invention comprises from 10 to 75%wt of water, preferably from 10 to 50%wt, more preferably from 20 to 40%wt of water, based on the total weight of the lubricant composition.

[0041] The inventors found that the combination of PAG1 and PAG2 as defined in the invention allows to reach all grades of viscosities, from 5 to 500 cSt at 40°C.

[0042] According to an embodiment, the lubricant composition has a kinematic viscosity at 40°C from 10 to 200 cSt or even from 10 to 100 cSt.Polyalkylene glycol (PAG1)

[0043] The lubricant composition comprises at least one PAG1 having a kinematic viscosity at 40°C of at least 10000 cSt, preferably from 10000 to 35000 cSt.

[0044] According to an embodiment, the PAG1 has an average molecular weight of at least 7500 g / mol. Preferably, the PAG1 has an average molecular weight ranging from 8000 g / mol to 50000 g / mol, preferably from 9000 to 40000 g / mol, more preferably from 10000 to 30000 g / mol, even more preferably from 11000 to 20000 g / mol.

[0045] PAG1 can be a homopolymer or a copolymer.

[0046] According to an embodiment, PAG1 comprises ethylene oxide units and optionally propylene oxide units. Preferably, PAG1 consists of ethylene oxide units and optionally propylene oxide units.

[0047] According to an embodiment, PAG1 is a copolymer comprising ethylene units and propylene oxide units.

[0048] Within the meaning of the present invention, "ethylene oxide unit" is a unit of formula -CH 2 -CH 2 -O-.

[0049] Within the meaning of the present invention, "propylene oxide unit" is a unit of formula -(CH 3 )CH-CH 2 -O-.

[0050] Preferably, when PAG1 comprises ethylene oxide units and propylene oxide units, the molar ratio ethylene oxide units / propylene oxide units is higher than 1, preferably ranges from higher than 1 to 4, more preferably from higher than 1 to 3.

[0051] PAG1 can be synthetized according to processes known for the skilled person. PAG1 is also commercially available.

[0052] Preferably, PAG1 is selected from biodegradable polyalkylene glycol.

[0053] The lubricant composition comprises from 2 to 50% by dry weight of at least one PAG1. Preferably, the lubricant composition comprises from 2 to 50% by dry weight of one or more PAG1.

[0054] According to an embodiment, the lubricant composition comprises from 5 to 30% by dry weight, preferably from 10 to 25% by dry weight of at least one PAG1. Preferably, the lubricant composition comprises from 5 to 30% by dry weight, preferably from 10 to 25% by dry weight of one or more PAG1.Polyalkylene glycol (PAG2)

[0055] The lubricant composition comprises at least one PAG2 having a kinematic viscosity at 40°C of less than 10000 cSt, preferably from 100 to 5000 cSt, and more preferably from 100 to 1000 cSt.

[0056] According to an embodiment, the PAG2 has an average molecular weight of less than 7000 g / mol.

[0057] Preferably, the PAG2 has an average molecular weight ranging from 500 to 7500 g / mol, preferably from 700 to 6000 g / mol, more preferably from 1000 to 5000 g / mol, even more preferably from 2000 to 4000 g / mol.

[0058] PAG2 can be a homopolymer or a copolymer.

[0059] According to an embodiment, PAG2 comprises ethylene oxide units and optionally propylene oxide units. Preferably, PAG2 consists of ethylene oxide units and optionally propylene oxide units.

[0060] According to an embodiment, PAG2 is a copolymer comprising ethylene units and propylene oxide units.

[0061] Preferably, when PAG2 comprises ethylene oxide units and propylene oxide units, the molar ratio ethylene oxide units / propylene oxide units is higher than 1, preferably ranges from 1.5 to 5, more preferably from 2 to 4.

[0062] PAG2 can be synthetized according to processes known for the skilled person. PAG2 is also commercially available.

[0063] Preferably, PAG2 is selected from biodegradable polyalkylene glycol.

[0064] The lubricant composition comprises from 2 to 50% by dry weight of at least one PAG2. Preferably, the lubricant composition comprises from 2 to 50% by dry weight of one or more PAG2. '

[0065] According to an embodiment, the lubricant composition comprises from 10 to 50% by dry weight, preferably from 15 to 40% by dry weight of at least one PAG2. Preferably, the lubricant composition comprises from 10 to 50% by dry weight, preferably from 15 to 40% by dry weight of one or more PAG2.Lubricant composition

[0066] According to an embodiment of the lubricant composition, the ratio between the kinematic viscosity at 40°C of PAG1 and PAG2 is higher than 1.5, preferably higher than 2, more preferably higher than 2.5, even more preferably higher than 3.5.

[0067] According to an embodiment of the lubricant composition, the ratio between the molecular weight of PAG1 and PAG2 is higher than 1.5, preferably higher than 2, more preferably higher than 2.5, even more preferably higher than 3.5.

[0068] Preferably, the lubricant composition comprises: from 10 to 50% by weight, preferably from 20 to 40% by weight, of water, from 5 to 30% by dry weight, preferably from 10 to 25% by dry weight of PAG1, from 10 to 50% by dry weight, preferably from 15 to 40% by dry weight, of PAG2, based on the total weight of the lubricant composition.

[0069] The lubricant composition preferably comprises at least one additive, different from polyalkylene glycol, the at least one additive being preferably selected from anti-wear additives, extreme-pressure additives, metal deactivators, corrosion inhibitors, pH boosters, anti-freezing agents, anti-foam agents, lubricity enhancers, and mixtures thereof.

[0070] Typically, the additive(s) of the lubricant composition do not comprise carbon atom chains of more than 12 carbon atoms, the carbon atom chains can be linear or branched, being noted that according to this preferred embodiment, one additive can comprise several carbon atom chains having less than 12 carbon atoms.

[0071] According to an embodiment, the lubricant composition comprises, based on the total weight of the lubricant composition, from 0.1 to 40% by weight, preferably from 10 to 30% by weight, of one or more additive(s), the additive(s) being preferably selected from anti-wear additives, extreme-pressure additives, metal deactivators, corrosion inhibitors, pH boosters, anti-freezing agents, anti-foam agents, lubricity enhancers, and mixtures thereof.

[0072] According to an embodiment, the lubricant composition comprises at least one anti-wear additives and / or extreme-pressure additives.

[0073] Anti-wear additives and extreme-pressure additives protect surfaces against friction through the forming of a protective film adsorbed on these surfaces. There is a large variety of anti-wear additives. Preferably, some additives are both anti-wear and extreme-pressure additives.

[0074] Preferably, for the lubricant composition of the invention, the anti-wear and / or extreme-pressure additives are selected from among phosphorus-containing additives, sulfurous-containing additives, sulfur-phosphorous containing additives, and mixtures thereof.

[0075] Preferably, the anti-wear and / or extreme-pressure additives are selected from phosphates, phosphites, phosphorothionates, phosphonates, dithiophosphates, thiophosphates, dimercaptothiadiazoles, thiadiazoles, and mixtures thereof, more preferably from phosphates, phosphites, phosphonates, dimercaptothiadiazoles, thiadiazoles, and mixtures thereof. Within the meaning of the present invention, these anti-wear and / or extreme-pressure additives can be substituted by one or more aliphatic groups.

[0076] The anti-wear and / or extreme-pressure additive(s) may represent from 0.1 to 15%wt of the total weight of the lubricant composition, preferably from 0.5 to 10%wt of the total weight of the lubricant composition.

[0077] Within the meaning of the present invention, "aliphatic group" means a group that is not aromatic. The aliphatic group can be cyclic, linear or branched. Preferably, it is linear or branched.

[0078] The aliphatic group can be an alkyl or an alkenyl group. Preferably, the anti-wear and / or extreme-pressure additive(s) does not comprise alkyl group nor alkenyl group having more than 11 carbon atoms.

[0079] The low carbon atom chain length allows to improve the stability of the lubricant composition.

[0080] According to an embodiment, the lubricant composition comprises at least one anticorrosion additive.

[0081] Among anticorrosion additives that can be used in the lubricant composition of the invention, mention can be made of triazine-containing corrosion inhibitors, carboxylic acids comprising carbon atom chains having less than 12 carbon atoms and mixtures thereof.

[0082] The carboxylic acids may be selected from compounds of formula R1-COOH, wherein R1 is a linear or branched alkyl radical comprising less than 12 carbon atoms.

[0083] Preferably, the carboxylic acid(s) of the lubricant composition of the invention comprises from 4 to 10 carbon atoms. Among carboxylic acids, mention may be made of hexanoic acid, octanoic acid or decanoic acid.

[0084] The corrosion inhibitor(s) can represent from 0.1 to 10% by weight, preferably from 0.5 to 5% by weight, of the total weight of the lubricant composition.

[0085] According to an embodiment, the lubricant composition comprises from 0.5 to 10% by weight, preferably from 1 to 5% by weight, of at least one carboxylic acid having less than 12 carbon atoms, based on the total weight of the lubricant composition.

[0086] According to a specific embodiment, the carboxylic acid(s) of the lubricant composition represent from 1.4% to 4% by weight of the total weight of the lubricant composition.

[0087] The inventors surprisingly found that by adding carboxylic acid(s) having less than 12 carbon atoms in a composition comprising water and PAG(s), the stability of the composition is further improved, in particular the inventors found that the solubility of the ingredients, in particular of the PAG(s) is further improved thanks to the carboxylic acid(s) having less than 12 carbon atoms.

[0088] Among metal-deactivators, mention can be made of tolyltriazole, derivatives of tolyltriazole or dimercaptothiadiazoles. The metal-deactivator particularly allows neutralisation of the catalytic effect of metals such as copper and iron.

[0089] By « derivative of tolyltriazole » it is meant a tolyltriazole compound substituted preferably by one of more alkyl groups optionally comprising one or more heteroatoms.

[0090] the metal deactivator(s) can represent from 0.05 to 5% by weight, preferably from 0.1 to 2% by weight, of the total weight of the lubricant composition.

[0091] Among pH boosters, mention may be made of alkanolamines.

[0092] The pH booster(s) can represent from 0.1 to 15% by weight, preferably from 1 to 10% by weight, of the total weight of the lubricant composition.

[0093] Among anti-freeing agent(s), mention may be made of monoalkylene glycol.

[0094] The anti-freezing agent(s) can represent from 0.1 to 15% by weight, preferably from 1 to 10% by weight, of the total weight of the lubricant composition.

[0095] Among the anti-foam additives that can be used in the lubricant composition of the invention, mention can be made of silicone compounds and polyacrylate compounds.

[0096] The anti-foam agent(s) can represent from 0.001 to 2% by weight, preferably from 0.01 to 1% by weight, of the total weight of the lubricant composition.

[0097] Among lubricity enhancers, mention may be made of esters comprising carbon atom chains having less than 12 carbon atoms.

[0098] According to a preferred embodiment, the lubricant composition has a kinematic viscosity at 40°C ranging from 5 to 500 cSt, preferably from 10 to 200 cSt, and more preferably from 10 to 100 cSt.

[0099] The kinematic viscosity can be measured according to ASTM D445 standard.

[0100] According to a preferred embodiment, the lubricant composition comprises: from 10 to 50% by weight, preferably from 20 to 40% by weight, of water, from 5 to 30% by dry weight, preferably from 10 to 25% by dry weight of at least one polyalkylene glycol PAG1 comprising ethylene oxide units and optionally propylene oxide units, from 10 to 50% by dry weight, preferably from 15 to 40% by dry weight, of at least one polyalkylene glycol PAG2 comprising ethylene oxide units and optionally propylene oxide units, optionally from 0.1 to 40% by dry weight, preferably from 1 to 30% by dry weight, of one or more additive(s) selected from anti-wear additives, extreme-pressure additives, metal deactivators, corrosion inhibitors, pH boosters, anti-freezing agents, anti-foam agents, lubricity enhancers, and mixtures thereof, based on the total weight of the lubricant composition.

[0101] According to a preferred embodiment, the lubricant composition comprises: from 10 to 50% by weight, preferably from 20 to 40% by weight, of water, from 5 to 30% by dry weight, preferably from 10 to 25% by dry weight of at least one polyalkylene glycol PAG1 comprising ethylene oxide units and propylene oxide units and having a kinematic viscosity at 40°C ranging from 10000 to 35000 cSt, from 10 to 50% by dry weight, preferably from 15 to 40% by dry weight, of at least one polyalkylene glycol PAG2 comprising ethylene oxide units and propylene oxide units and having a kinematic viscosity at 40°C ranging from 100 to 5000 cSt, preferably from 100 to 1000 cSt, optionally from 0.1 to 40% by weight, preferably from 1 to 30% by weight, of one or more additive(s) selected from anti-wear additives, extreme-pressure additives, metal deactivators, corrosion inhibitors, pH boosters, anti-freezing agents, anti-foam agents, lubricity enhancers, and mixtures thereof, based on the total weight of the lubricant composition.

[0102] According to a preferred embodiment, the lubricant composition comprises: from 10 to 50% by weight, preferably from 20 to 40% by weight, of water, from 5 to 30% by dry weight, preferably from 10 to 25% by dry weight of at least one polyalkylene glycol PAG1 comprising ethylene oxide units and propylene oxide units and having a kinematic viscosity at 40°C ranging from 10000 to 35000 cSt, from 10 to 50% by dry weight, preferably from 15 to 40% by dry weight, of at least one polyalkylene glycol PAG2 comprising ethylene oxide units and propylene oxide units and having a kinematic viscosity at 40°C ranging from 100 to 5000 cSt, preferably from 100 to 1000 cSt, from 0.1 to 10% by weight, preferably from 1 to 5% by weight, of at least one carboxylic acid, wherein the carboxylic acid(s) have less than 12 carbon atoms, optionally from 0.1 to 40% by weight, preferably from 1 to 30% by weight, of one or more additive(s) selected from anti-wear and / or extreme-pressure additives, metal deactivators, pH boosters, anti-freezing agents, anti-foam agents, lubricity enhancers, and mixtures thereof, based on the total weight of the lubricant composition.

[0103] According to a preferred embodiment, the lubricant composition comprises: from 10 to 50% by weight, preferably from 20 to 40% by weight, of water, from 5 to 30% by dry weight, preferably from 10 to 25% by dry weight of at least one polyalkylene glycol PAG1 comprising ethylene oxide units and propylene oxide units and having a kinematic viscosity at 40°C ranging from 10000 to 35000 cSt, from 10 to 50% by dry weight, preferably from 15 to 40% by dry weight, of at least one polyalkylene glycol PAG2 comprising ethylene oxide units and propylene oxide units and having a kinematic viscosity at 40°C ranging from 100 to 5000 cSt, preferably from 100 to 1000 cSt, from 0.1 to 10% by weight, preferably from 1 to 5% by weight, of at least one carboxylic acid, wherein the carboxylic acid(s) have less than 12 carbon atoms, optionally from 0.1 to 40% by weight, preferably from 1 to 30% by weight, of one or more additive(s) selected from anti-wear and / or extreme-pressure additives, metal deactivators, pH boosters, anti-freezing agents, anti-foam agents, lubricity enhancers, and mixtures thereof, based on the total weight of the lubricant composition, wherein if the functional additive(s) comprise(s) aliphatic carbon chain(s), the aliphatic carbon chains have less than 12 carbon atoms.

[0104] The lubricant composition can be prepared according to processes well known by the skilled person to formulate lubricant compositions, for example by mixing ingredients at a temperature ranging from 20 to 60°C.Applications

[0105] As mentioned previously, the aqueous lubricant composition is advantageously used, due to its joint properties in terms of lubrication and cooling, both as a cooling fluid and as a lubricating fluid for a propulsion system of an electric or hybrid vehicle, in particular the motor, the power electronics, the transmission and / or the battery, in an electric or hybrid vehicle, preferably in an electric vehicle.

[0106] As shown schematically in Figure 1, the propulsion system of an electric or hybrid vehicle comprises in particular the electric motor (1), an electric battery (2) and a transmission, and in particular a reducer (3). Batteries suitable for electric or hybrid vehicle propulsion systems include Li-ion batteries and nickel-cadmium batteries.

[0107] The electric motor typically comprises power electronics (11) connected to a stator (13) and a rotor (14). The stator comprises coils, in particular copper coils, which are alternately supplied with 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.

[0108] The power electronics (11), stator (13) and rotor (14) of a propulsion system (1) are structurally complex parts that generate a large amount of heat during motor operation. It is therefore essential to ensure that the electric motor and power electronics are cooled.

[0109] A bearing (12) is generally integrated between the stator (13) and the rotor (14). A transmission, and in particular a reducer (3), is used to reduce the speed of rotation at the output of the electric motor and adapt the speed transmitted to the wheels, at the same time controlling the speed of the vehicle.

[0110] Advantageously, an aqueous lubricant composition according to the invention can be used to cool the battery present in an electric or hybrid vehicle, in particular in an electric vehicle. According to an embodiment, the lubricant composition is intended to be placed in direct contact with the battery.

[0111] Cooling can be carried out by any method known to the person skilled in the art. The battery may be immersed or semi-immersed, statically or in circulation, in the said composition.

[0112] Examples of direct contact include cooling by injection, jet, spray or even by forming a mist from the lubricant composition of the invention under pressure and by gravity on the battery.

[0113] A composition according to the invention can also be used to cool the electric motor of an electric or hybrid vehicle, in particular to cool the power electronics and / or the rotor and / or the stator of the electric motor, preferably in an electric vehicle.

[0114] An aqueous lubricant composition according to the invention can simultaneously be used to lubricate the various parts of a propulsion system of an electric or hybrid vehicle, in particular the motor, the electric power unit, the transmission and / or the battery, more particularly the bearings located between the rotor and the stator of an electric motor, or the transmission, in particular the gearbox, in an electric or hybrid vehicle.

[0115] More particularly, an aqueous lubricant composition according to the invention can be used to cool and lubricate an electric motor of an electric or hybrid vehicle. In particular, it is effective for cooling the power electronics and / or the rotor and / or the stator of an electric motor. It also lubricates the bearings located between the rotor and the stator of an electric motor of an electric or hybrid vehicle.

[0116] Advantageously, an aqueous lubricant composition according to the invention can be used to lubricate the transmission, when present, in particular the gearbox, of an electric or hybrid vehicle.

[0117] It is therefore advantageous, for example, to use a single composition according to the invention to ensure both cooling of the battery and lubrication of the transmission, in particular the gearbox, in an electric or hybrid vehicle.

[0118] Advantageously, the present invention relates to the use of an aqueous lubricating composition as defined according to the invention, for lubricating and / or cooling the gearbox and / or the motor and / or the power electronics of an electric vehicle.

[0119] The invention also relates to a lubricating and / or cooling method comprising applying the lubricant composition as defined in the invention onto mechanical part(s) of a propulsion system of an electric or hybrid vehicle, preferably an electric vehicle.

[0120] The mechanical part(s) can be one or several elements selected from the electric motor, the battery, and the transmission, preferably from the power electronics, the stator, the rotor, the battery, and the reducer.

Examples

Embodiment Construction

[0032]The invention first concerns the use of a lubricant composition for cooling and / or lubricating a propulsion system of an electric or hybrid vehicle.

[0033]The lubricant composition used in the invention comprises:

from 10 to 75% by weight of water, from 2 to 50% by dry weight of at least one polyalkylene glycol PAG1 having a kinematic viscosity at 40°C of at least 10000 cSt, from 2 to 50% by dry weight of at least one polyalkylene glycol PAG2 having a kinematic viscosity at 40°C of less than 10000 cSt,

based on the total weight of the lubricant composition, the ratio between the kinematic viscosity at 40°C of PAG1 and the kinematic viscosity at 40°C of PAG2 being strictly greater than 1.

[0034]In the following, the term "aqueous lubricant composition" or "lubricant composition" will be used to designate a lubricating composition used according to the invention as defined above and detailed in the following. Because of its cooling properties, such a composition may also be ref...

FIELD OF THE INVENTION

[0001] The present invention concerns aqueous lubricant and / or cooling compositions for their use in electric or hybrid vehicles, in particular gears. In particular, the present invention concerns aqueous compositions for cooling and / or lubricating the propulsion system of an electric or hybrid vehicle.TECHNICAL BACKGROUND OF THE INVENTION

[0002] The evolution of international standards for the reduction of CO2 emissions, but also for the reduction of energy consumption, pushes car manufacturers to propose alternative solutions to internal combustion engines.

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

[0004] Generally, electric or hybrid vehicles require compositions to meet the twofold lubrication and cooling requirements of the various parts of the propulsion system mentioned above.

[0005] On the one hand, lubricating compositions, also known as "lubricants", are commonly used in engines to reduce the friction forces between the various metal parts in motion in engines, and thus protect the parts against wear. In addition to wear phenomena, friction can oppose the relative movement of parts in contact and induce energy losses that are detrimental to optimal operation of the propulsion system.

[0006] To this end, a lubricant composition is typically composed of one or more base oils, to which are generally associated a number of additives designed to boost the lubricating performance of the base oils, such as friction-modifying additives.

[0007] On the other hand, electric propulsion systems generate heat during operation via the electric motor, power electronics and batteries. As the amount of heat generated is greater than that normally dissipated to the environment, it is necessary to provide cooling for the motor, power electronics and batteries. Typically, cooling is carried out on several heat-generating parts of the propulsion system and / or parts of said system sensitive to heat, in order to avoid reaching dangerous temperatures, and in particular the power electronics and batteries. This cooling is typically provided by a cooling fluid, distinct from the hydrocarbon lubricant, such as air, an aqueous fluid, such as water, or a mixture of water and a glycol.

[0008] It would be advantageous to have a composition that could simultaneously meet the lubrication and cooling needs of an electric or hybrid vehicle propulsion system.

[0009] The most widely used lubricants are hydrocarbon-based lubricants. However, these hydrocarbon oils generally do not provide sufficient heat dissipation to enable them to be used together as coolants.

[0010] More recently, in response to a growing demand to avoid the use of toxic solvents and reduce the environmental impact of products, studies have focused on the development of water-based lubricants.

[0011] While water is an excellent coolant, it lacks the tribological properties required of a lubricant, particularly in terms of reducing friction and protecting parts against wear. Additivation systems have been proposed to give aqueous fluids satisfactory lubrication performance.

[0012] For example, WO 2021 / 259853 describes an aqueous lubricant composition comprising a polyalkylene glycol, an antifreeze compound and a phosphorus compound.

[0013] However, this aqueous lubricant is not entirely satisfactory, particularly with regard to the phenomenon of pitting caused by mechanical fatigue. Indeed, it has been found that this lubricant composition can generate this type of failure in mechanical contacts, particularly as a function of the composition's formulation protocol.

[0014] There is therefore an advantage in providing lubricant compositions which meet all the specific tests for lubricant compositions, that have a low carbon footprint.BRIEF DESCRIPTION OF FIGURES

[0015] Figure 1 represents a schematic view of a propulsion system of an electric or hybrid vehicle.SUMMARY OF THE INVENTION

[0016] The invention concerns the use of a lubricant composition for cooling and / or lubricating the propulsion system of an electric or hybrid vehicle, the lubricant composition comprising: from 10 to 75% by weight of water, from 2 to 50% by dry weight of at least one polyalkylene glycol (PAG1) having a kinematic viscosity at 40°C of at least 10000 cSt, from 2 to 50% by dry weight of at least one polyalkylene glycol (PAG2) having a kinematic viscosity at 40°C of less than 10000 cSt, based on the total weight of the lubricant composition.

[0017] Preferably, the lubricant composition is characterized by one or more of the following features: the ratio between the kinematic viscosity at 40°C of PAG1 and PAG2 is higher than 1.5, preferably higher than 2, more preferably higher than 2.5, even more preferably higher than 3.5, and / or PAG1 has a kinematic viscosity at 40°C ranging from 10000 to 35000 cSt and / or PAG2 has a kinematic viscosity at 40°C ranging from 100 to 5000 cSt, preferably from 100 to 1000 cSt, and / or the PAG1 has an average molecular weight ranging from 8000 g / mol to 50000 g / mol, preferably from 9000 to 40000 g / mol, more preferably from 10000 to 30000 g / mol, even more preferably from 11000 to 20000 g / mol, and / or the PAG2 has an average molecular weight ranging from 500 to 7500 g / mol, preferably from 700 to 6000 g / mol, more preferably from 1000 to 5000 g / mol, even more preferably from 2000 to 4000 g / mol, and / or the lubricant composition comprises: ∘ from 10 to 50% by weight, preferably from 20 to 40% by weight, of water, ∘ from 5 to 30% by dry weight, preferably from 10 to 25% by dry weight of at least one polyalkylene glycol PAG1, o from 10 to 50% by dry weight, preferably from 15 to 40% by dry weight, of at least one polyalkylene glycol PAG2, based on the total weight of the lubricant composition, and / or PAG1 and PAG2 comprises ethylene oxide units and optionally propylene oxide units. the lubricant composition comprises: ∘ from 10 to 50% by weight, preferably from 20 to 40% by weight, of water, o from 5 to 30% by dry weight, preferably from 10 to 25% by dry weight of at least one polyalkylene glycol PAG1, o from 10 to 50% by dry weight, preferably from 15 to 40% by dry weight, of at least one polyalkylene glycol PAG2, ∘ from 0.1 to 40% by weight, preferably from 1 to 30% by weight, of one or more functional additive(s) different from polyalkylene glycol, the additive(s) being preferably selected from anti-wear additives, extreme-pressure additives, metal deactivators, corrosion inhibitors, pH boosters, anti-freezing agents, anti-foam agents, lubricity enhancers, and mixtures thereof. based on the total weight of the lubricant composition, and / or the lubricant composition further comprises at least one functional additive selected from corrosion inhibitors, at least one corrosion inhibitor being preferably selected from carboxylic acids having less than 12 carbon atoms, and / or the lubricant composition has a kinematic viscosity at 40°C ranging from 5 cSt to 500 cSt, preferably from 10 to 200 cSt, more preferably from 10 to 100 cSt, and / or the lubricant composition comprises: ∘ from 10 to 50% by weight, preferably from 20 to 40% by weight, of water, ∘ from 5 to 30% by dry weight, preferably from 10 to 25% by dry weight of at least one polyalkylene glycol PAG1 comprising ethylene oxide units and propylene oxide units and having a kinematic viscosity at 40°C ranging from 10000 cSt to 35000 cSt, ∘ from 10 to 50% by dry weight, preferably from 15 to 40% by dry weight, of at least one polyalkylene glycol PAG2 comprising ethylene oxide units and propylene oxide units and having a kinematic viscosity at 40°C ranging from 100 to 5000 cSt, preferably from 100 to 1000 cSt, ∘ from 0.1 to 10% by weight, preferably from 1 to 5% by weight, of at least one carboxylic acid, wherein the carboxylic acid(s) have less than 12 carbon atoms, ∘ optionally from 0.1 to 40% by weight, preferably from 1 to 30% by weight, of one or more additive(s) selected from anti-wear and / or extreme-pressure additives, metal deactivators, pH boosters, anti-freezing agents, anti-foam agents, lubricity enhancers, and mixtures thereof, based on the total weight of the lubricant composition.

[0018] The invention also relates to the use of the lubricant composition defined in the invention to reduce frictions and / or to reduce abrasion and / or to reduce wear of mechanical part(s) of the propulsion system.

[0019] The invention also relates to the use of the lubricant composition defined in the invention, wherein the lubricant composition is coated onto gears of the propulsion system.

[0020] The invention also relates to the use of the lubricant composition defined in the invention to lubricate and / or cool the gearbox and / or motor and / or power electronics of an electric vehicle.

[0021] The invention also relates to the use of the lubricant composition defined in the invention to reduce pitting by mechanical fatigue, of mechanical part(s) of said propulsion system, brought into contact with said lubricant composition.

[0022] The invention also relates to a lubricating and / or cooling method comprising applying the lubricant composition as defined in the invention onto mechanical part(s) of a propulsion system of an electric or hybrid vehicle.

[0023] The aqueous lubricant compositions of the invention have less carbon footprint than oil-based lubricant compositions.

[0024] The lubricant compositions of the invention have good thermal properties.

[0025] The lubricant compositions of the invention have a very low coefficient of friction, and thus a high energy efficiency.

[0026] The present invention proposes an aqueous-based composition with tribological and cooling properties, suitable for use in lubricating and / or cooling an electric or hybrid vehicle propulsion system, while reducing or even eliminating mechanical fatigue pitting phenomena.

[0027] Advantageously, a lubricant composition used in accordance with the invention has little toxicological impact, particularly for people using this lubricant.

[0028] Moreover, even when water is the majority solvent, a composition according to the invention has good properties in terms of lubrication.

[0029] Thus, an aqueous lubricant composition according to the invention advantageously combines good cooling properties linked to the presence of water, and good tribological properties, in particular friction reduction and wear resistance. Thus, an aqueous composition according to the invention can perform the dual function of lubricating and cooling the propulsion system of an electric or hybrid vehicle, in particular the electric motor, power electronics, transmission and / or battery of an electric or hybrid vehicle.

[0030] Thanks to the aqueous composition as defined in the invention advantageously, there is no need to make use of two distinct fluids, on the one hand a cooling fluid and on the other hand a lubricating fluid. In particular, a lubricant composition according to the invention enables efficient cooling of the motor, power electronics and battery, as well as lubrication of the electric motor and of the transmission, in particular the gearbox, in an electric or hybrid vehicle.

[0031] In particular, an aqueous lubricant composition according to the invention can be used to lubricate and / or cool the gearbox and / or motor and / or power electronics of an electric vehicle.DETAILED DESCRIPTION OF THE INVENTION

[0032] The invention first concerns the use of a lubricant composition for cooling and / or lubricating a propulsion system of an electric or hybrid vehicle.

[0033] The lubricant composition used in the invention comprises: from 10 to 75% by weight of water, from 2 to 50% by dry weight of at least one polyalkylene glycol PAG1 having a kinematic viscosity at 40°C of at least 10000 cSt, from 2 to 50% by dry weight of at least one polyalkylene glycol PAG2 having a kinematic viscosity at 40°C of less than 10000 cSt, based on the total weight of the lubricant composition, the ratio between the kinematic viscosity at 40°C of PAG1 and the kinematic viscosity at 40°C of PAG2 being strictly greater than 1.

[0034] In the following, the term "aqueous lubricant composition" or "lubricant composition" will be used to designate a lubricating composition used according to the invention as defined above and detailed in the following. Because of its cooling properties, such a composition may also be referred to as an "aqueous cooling composition" or "cooling composition".

[0035] By "electric vehicle" in the sense of the present invention, we mean a vehicle comprising an electric motor as the sole means of propulsion, and by "hybrid vehicle", we mean a vehicle which comprises a combustion engine and an electric motor as combined means of propulsion.

[0036] By "propulsion system" in the sense of the present invention, we mean a system comprising the mechanical parts required to propel an electric vehicle. More specifically, the propulsion system comprises an electric motor, the rotor-stator assembly of the power electronics (dedicated to speed regulation), a transmission and a battery.

[0037] Within the present invention, the kinematic viscosity at 40°C of PAG (for example of PAG1 and of PAG2) can be measured according to ASTM D445.

[0038] The average molecular weight of PAG1 and PAG2 can be measured by methods well known for the skilled person, for example by size exclusion chromatography using polystyrene standard.

[0039] Typically, PAG1 and PAG2 used in the present invention are obtained by (co)polymerisation of alkylene glycol(s) comprising from 2 to 4 carbon atoms, for example by random copolymerisation.

[0040] The amount of water allows having both a low evaporation, a good thermal behaviour and low friction coefficient. The lubricant composition of the invention comprises from 10 to 75%wt of water, preferably from 10 to 50%wt, more preferably from 20 to 40%wt of water, based on the total weight of the lubricant composition.

[0041] The inventors found that the combination of PAG1 and PAG2 as defined in the invention allows to reach all grades of viscosities, from 5 to 500 cSt at 40°C.

[0042] According to an embodiment, the lubricant composition has a kinematic viscosity at 40°C from 10 to 200 cSt or even from 10 to 100 cSt.Polyalkylene glycol (PAG1)

[0043] The lubricant composition comprises at least one PAG1 having a kinematic viscosity at 40°C of at least 10000 cSt, preferably from 10000 to 35000 cSt.

[0044] According to an embodiment, the PAG1 has an average molecular weight of at least 7500 g / mol. Preferably, the PAG1 has an average molecular weight ranging from 8000 g / mol to 50000 g / mol, preferably from 9000 to 40000 g / mol, more preferably from 10000 to 30000 g / mol, even more preferably from 11000 to 20000 g / mol.

[0045] PAG1 can be a homopolymer or a copolymer.

[0046] According to an embodiment, PAG1 comprises ethylene oxide units and optionally propylene oxide units. Preferably, PAG1 consists of ethylene oxide units and optionally propylene oxide units.

[0047] According to an embodiment, PAG1 is a copolymer comprising ethylene units and propylene oxide units.

[0048] Within the meaning of the present invention, "ethylene oxide unit" is a unit of formula -CH 2 -CH 2 -O-.

[0049] Within the meaning of the present invention, "propylene oxide unit" is a unit of formula -(CH 3 )CH-CH 2 -O-.

[0050] Preferably, when PAG1 comprises ethylene oxide units and propylene oxide units, the molar ratio ethylene oxide units / propylene oxide units is higher than 1, preferably ranges from higher than 1 to 4, more preferably from higher than 1 to 3.

[0051] PAG1 can be synthetized according to processes known for the skilled person. PAG1 is also commercially available.

[0052] Preferably, PAG1 is selected from biodegradable polyalkylene glycol.

[0053] The lubricant composition comprises from 2 to 50% by dry weight of at least one PAG1. Preferably, the lubricant composition comprises from 2 to 50% by dry weight of one or more PAG1.

[0054] According to an embodiment, the lubricant composition comprises from 5 to 30% by dry weight, preferably from 10 to 25% by dry weight of at least one PAG1. Preferably, the lubricant composition comprises from 5 to 30% by dry weight, preferably from 10 to 25% by dry weight of one or more PAG1.Polyalkylene glycol (PAG2)

[0055] The lubricant composition comprises at least one PAG2 having a kinematic viscosity at 40°C of less than 10000 cSt, preferably from 100 to 5000 cSt, and more preferably from 100 to 1000 cSt.

[0056] According to an embodiment, the PAG2 has an average molecular weight of less than 7000 g / mol.

[0057] Preferably, the PAG2 has an average molecular weight ranging from 500 to 7500 g / mol, preferably from 700 to 6000 g / mol, more preferably from 1000 to 5000 g / mol, even more preferably from 2000 to 4000 g / mol.

[0058] PAG2 can be a homopolymer or a copolymer.

[0059] According to an embodiment, PAG2 comprises ethylene oxide units and optionally propylene oxide units. Preferably, PAG2 consists of ethylene oxide units and optionally propylene oxide units.

[0060] According to an embodiment, PAG2 is a copolymer comprising ethylene units and propylene oxide units.

[0061] Preferably, when PAG2 comprises ethylene oxide units and propylene oxide units, the molar ratio ethylene oxide units / propylene oxide units is higher than 1, preferably ranges from 1.5 to 5, more preferably from 2 to 4.

[0062] PAG2 can be synthetized according to processes known for the skilled person. PAG2 is also commercially available.

[0063] Preferably, PAG2 is selected from biodegradable polyalkylene glycol.

[0064] The lubricant composition comprises from 2 to 50% by dry weight of at least one PAG2. Preferably, the lubricant composition comprises from 2 to 50% by dry weight of one or more PAG2. '

[0065] According to an embodiment, the lubricant composition comprises from 10 to 50% by dry weight, preferably from 15 to 40% by dry weight of at least one PAG2. Preferably, the lubricant composition comprises from 10 to 50% by dry weight, preferably from 15 to 40% by dry weight of one or more PAG2.Lubricant composition

[0066] According to an embodiment of the lubricant composition, the ratio between the kinematic viscosity at 40°C of PAG1 and PAG2 is higher than 1.5, preferably higher than 2, more preferably higher than 2.5, even more preferably higher than 3.5.

[0067] According to an embodiment of the lubricant composition, the ratio between the molecular weight of PAG1 and PAG2 is higher than 1.5, preferably higher than 2, more preferably higher than 2.5, even more preferably higher than 3.5.

[0068] Preferably, the lubricant composition comprises: from 10 to 50% by weight, preferably from 20 to 40% by weight, of water, from 5 to 30% by dry weight, preferably from 10 to 25% by dry weight of PAG1, from 10 to 50% by dry weight, preferably from 15 to 40% by dry weight, of PAG2, based on the total weight of the lubricant composition.

[0069] The lubricant composition preferably comprises at least one additive, different from polyalkylene glycol, the at least one additive being preferably selected from anti-wear additives, extreme-pressure additives, metal deactivators, corrosion inhibitors, pH boosters, anti-freezing agents, anti-foam agents, lubricity enhancers, and mixtures thereof.

[0070] Typically, the additive(s) of the lubricant composition do not comprise carbon atom chains of more than 12 carbon atoms, the carbon atom chains can be linear or branched, being noted that according to this preferred embodiment, one additive can comprise several carbon atom chains having less than 12 carbon atoms.

[0071] According to an embodiment, the lubricant composition comprises, based on the total weight of the lubricant composition, from 0.1 to 40% by weight, preferably from 10 to 30% by weight, of one or more additive(s), the additive(s) being preferably selected from anti-wear additives, extreme-pressure additives, metal deactivators, corrosion inhibitors, pH boosters, anti-freezing agents, anti-foam agents, lubricity enhancers, and mixtures thereof.

[0072] According to an embodiment, the lubricant composition comprises at least one anti-wear additives and / or extreme-pressure additives.

[0073] Anti-wear additives and extreme-pressure additives protect surfaces against friction through the forming of a protective film adsorbed on these surfaces. There is a large variety of anti-wear additives. Preferably, some additives are both anti-wear and extreme-pressure additives.

[0074] Preferably, for the lubricant composition of the invention, the anti-wear and / or extreme-pressure additives are selected from among phosphorus-containing additives, sulfurous-containing additives, sulfur-phosphorous containing additives, and mixtures thereof.

[0075] Preferably, the anti-wear and / or extreme-pressure additives are selected from phosphates, phosphites, phosphorothionates, phosphonates, dithiophosphates, thiophosphates, dimercaptothiadiazoles, thiadiazoles, and mixtures thereof, more preferably from phosphates, phosphites, phosphonates, dimercaptothiadiazoles, thiadiazoles, and mixtures thereof. Within the meaning of the present invention, these anti-wear and / or extreme-pressure additives can be substituted by one or more aliphatic groups.

[0076] The anti-wear and / or extreme-pressure additive(s) may represent from 0.1 to 15%wt of the total weight of the lubricant composition, preferably from 0.5 to 10%wt of the total weight of the lubricant composition.

[0077] Within the meaning of the present invention, "aliphatic group" means a group that is not aromatic. The aliphatic group can be cyclic, linear or branched. Preferably, it is linear or branched.

[0078] The aliphatic group can be an alkyl or an alkenyl group. Preferably, the anti-wear and / or extreme-pressure additive(s) does not comprise alkyl group nor alkenyl group having more than 11 carbon atoms.

[0079] The low carbon atom chain length allows to improve the stability of the lubricant composition.

[0080] According to an embodiment, the lubricant composition comprises at least one anticorrosion additive.

[0081] Among anticorrosion additives that can be used in the lubricant composition of the invention, mention can be made of triazine-containing corrosion inhibitors, carboxylic acids comprising carbon atom chains having less than 12 carbon atoms and mixtures thereof.

[0082] The carboxylic acids may be selected from compounds of formula R1-COOH, wherein R1 is a linear or branched alkyl radical comprising less than 12 carbon atoms.

[0083] Preferably, the carboxylic acid(s) of the lubricant composition of the invention comprises from 4 to 10 carbon atoms. Among carboxylic acids, mention may be made of hexanoic acid, octanoic acid or decanoic acid.

[0084] The corrosion inhibitor(s) can represent from 0.1 to 10% by weight, preferably from 0.5 to 5% by weight, of the total weight of the lubricant composition.

[0085] According to an embodiment, the lubricant composition comprises from 0.5 to 10% by weight, preferably from 1 to 5% by weight, of at least one carboxylic acid having less than 12 carbon atoms, based on the total weight of the lubricant composition.

[0086] According to a specific embodiment, the carboxylic acid(s) of the lubricant composition represent from 1.4% to 4% by weight of the total weight of the lubricant composition.

[0087] The inventors surprisingly found that by adding carboxylic acid(s) having less than 12 carbon atoms in a composition comprising water and PAG(s), the stability of the composition is further improved, in particular the inventors found that the solubility of the ingredients, in particular of the PAG(s) is further improved thanks to the carboxylic acid(s) having less than 12 carbon atoms.

[0088] Among metal-deactivators, mention can be made of tolyltriazole, derivatives of tolyltriazole or dimercaptothiadiazoles. The metal-deactivator particularly allows neutralisation of the catalytic effect of metals such as copper and iron.

[0089] By « derivative of tolyltriazole » it is meant a tolyltriazole compound substituted preferably by one of more alkyl groups optionally comprising one or more heteroatoms.

[0090] the metal deactivator(s) can represent from 0.05 to 5% by weight, preferably from 0.1 to 2% by weight, of the total weight of the lubricant composition.

[0091] Among pH boosters, mention may be made of alkanolamines.

[0092] The pH booster(s) can represent from 0.1 to 15% by weight, preferably from 1 to 10% by weight, of the total weight of the lubricant composition.

[0093] Among anti-freeing agent(s), mention may be made of monoalkylene glycol.

[0094] The anti-freezing agent(s) can represent from 0.1 to 15% by weight, preferably from 1 to 10% by weight, of the total weight of the lubricant composition.

[0095] Among the anti-foam additives that can be used in the lubricant composition of the invention, mention can be made of silicone compounds and polyacrylate compounds.

[0096] The anti-foam agent(s) can represent from 0.001 to 2% by weight, preferably from 0.01 to 1% by weight, of the total weight of the lubricant composition.

[0097] Among lubricity enhancers, mention may be made of esters comprising carbon atom chains having less than 12 carbon atoms.

[0098] According to a preferred embodiment, the lubricant composition has a kinematic viscosity at 40°C ranging from 5 to 500 cSt, preferably from 10 to 200 cSt, and more preferably from 10 to 100 cSt.

[0099] The kinematic viscosity can be measured according to ASTM D445 standard.

[0100] According to a preferred embodiment, the lubricant composition comprises: from 10 to 50% by weight, preferably from 20 to 40% by weight, of water, from 5 to 30% by dry weight, preferably from 10 to 25% by dry weight of at least one polyalkylene glycol PAG1 comprising ethylene oxide units and optionally propylene oxide units, from 10 to 50% by dry weight, preferably from 15 to 40% by dry weight, of at least one polyalkylene glycol PAG2 comprising ethylene oxide units and optionally propylene oxide units, optionally from 0.1 to 40% by dry weight, preferably from 1 to 30% by dry weight, of one or more additive(s) selected from anti-wear additives, extreme-pressure additives, metal deactivators, corrosion inhibitors, pH boosters, anti-freezing agents, anti-foam agents, lubricity enhancers, and mixtures thereof, based on the total weight of the lubricant composition.

[0101] According to a preferred embodiment, the lubricant composition comprises: from 10 to 50% by weight, preferably from 20 to 40% by weight, of water, from 5 to 30% by dry weight, preferably from 10 to 25% by dry weight of at least one polyalkylene glycol PAG1 comprising ethylene oxide units and propylene oxide units and having a kinematic viscosity at 40°C ranging from 10000 to 35000 cSt, from 10 to 50% by dry weight, preferably from 15 to 40% by dry weight, of at least one polyalkylene glycol PAG2 comprising ethylene oxide units and propylene oxide units and having a kinematic viscosity at 40°C ranging from 100 to 5000 cSt, preferably from 100 to 1000 cSt, optionally from 0.1 to 40% by weight, preferably from 1 to 30% by weight, of one or more additive(s) selected from anti-wear additives, extreme-pressure additives, metal deactivators, corrosion inhibitors, pH boosters, anti-freezing agents, anti-foam agents, lubricity enhancers, and mixtures thereof, based on the total weight of the lubricant composition.

[0102] According to a preferred embodiment, the lubricant composition comprises: from 10 to 50% by weight, preferably from 20 to 40% by weight, of water, from 5 to 30% by dry weight, preferably from 10 to 25% by dry weight of at least one polyalkylene glycol PAG1 comprising ethylene oxide units and propylene oxide units and having a kinematic viscosity at 40°C ranging from 10000 to 35000 cSt, from 10 to 50% by dry weight, preferably from 15 to 40% by dry weight, of at least one polyalkylene glycol PAG2 comprising ethylene oxide units and propylene oxide units and having a kinematic viscosity at 40°C ranging from 100 to 5000 cSt, preferably from 100 to 1000 cSt, from 0.1 to 10% by weight, preferably from 1 to 5% by weight, of at least one carboxylic acid, wherein the carboxylic acid(s) have less than 12 carbon atoms, optionally from 0.1 to 40% by weight, preferably from 1 to 30% by weight, of one or more additive(s) selected from anti-wear and / or extreme-pressure additives, metal deactivators, pH boosters, anti-freezing agents, anti-foam agents, lubricity enhancers, and mixtures thereof, based on the total weight of the lubricant composition.

[0103] According to a preferred embodiment, the lubricant composition comprises: from 10 to 50% by weight, preferably from 20 to 40% by weight, of water, from 5 to 30% by dry weight, preferably from 10 to 25% by dry weight of at least one polyalkylene glycol PAG1 comprising ethylene oxide units and propylene oxide units and having a kinematic viscosity at 40°C ranging from 10000 to 35000 cSt, from 10 to 50% by dry weight, preferably from 15 to 40% by dry weight, of at least one polyalkylene glycol PAG2 comprising ethylene oxide units and propylene oxide units and having a kinematic viscosity at 40°C ranging from 100 to 5000 cSt, preferably from 100 to 1000 cSt, from 0.1 to 10% by weight, preferably from 1 to 5% by weight, of at least one carboxylic acid, wherein the carboxylic acid(s) have less than 12 carbon atoms, optionally from 0.1 to 40% by weight, preferably from 1 to 30% by weight, of one or more additive(s) selected from anti-wear and / or extreme-pressure additives, metal deactivators, pH boosters, anti-freezing agents, anti-foam agents, lubricity enhancers, and mixtures thereof, based on the total weight of the lubricant composition, wherein if the functional additive(s) comprise(s) aliphatic carbon chain(s), the aliphatic carbon chains have less than 12 carbon atoms.

[0104] The lubricant composition can be prepared according to processes well known by the skilled person to formulate lubricant compositions, for example by mixing ingredients at a temperature ranging from 20 to 60°C.Applications

[0105] As mentioned previously, the aqueous lubricant composition is advantageously used, due to its joint properties in terms of lubrication and cooling, both as a cooling fluid and as a lubricating fluid for a propulsion system of an electric or hybrid vehicle, in particular the motor, the power electronics, the transmission and / or the battery, in an electric or hybrid vehicle, preferably in an electric vehicle.

[0106] As shown schematically in Figure 1, the propulsion system of an electric or hybrid vehicle comprises in particular the electric motor (1), an electric battery (2) and a transmission, and in particular a reducer (3). Batteries suitable for electric or hybrid vehicle propulsion systems include Li-ion batteries and nickel-cadmium batteries.

[0107] The electric motor typically comprises power electronics (11) connected to a stator (13) and a rotor (14). The stator comprises coils, in particular copper coils, which are alternately supplied with 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.

[0108] The power electronics (11), stator (13) and rotor (14) of a propulsion system (1) are structurally complex parts that generate a large amount of heat during motor operation. It is therefore essential to ensure that the electric motor and power electronics are cooled.

[0109] A bearing (12) is generally integrated between the stator (13) and the rotor (14). A transmission, and in particular a reducer (3), is used to reduce the speed of rotation at the output of the electric motor and adapt the speed transmitted to the wheels, at the same time controlling the speed of the vehicle.

[0110] Advantageously, an aqueous lubricant composition according to the invention can be used to cool the battery present in an electric or hybrid vehicle, in particular in an electric vehicle. According to an embodiment, the lubricant composition is intended to be placed in direct contact with the battery.

[0111] Cooling can be carried out by any method known to the person skilled in the art. The battery may be immersed or semi-immersed, statically or in circulation, in the said composition.

[0112] Examples of direct contact include cooling by injection, jet, spray or even by forming a mist from the lubricant composition of the invention under pressure and by gravity on the battery.

[0113] A composition according to the invention can also be used to cool the electric motor of an electric or hybrid vehicle, in particular to cool the power electronics and / or the rotor and / or the stator of the electric motor, preferably in an electric vehicle.

[0114] An aqueous lubricant composition according to the invention can simultaneously be used to lubricate the various parts of a propulsion system of an electric or hybrid vehicle, in particular the motor, the electric power unit, the transmission and / or the battery, more particularly the bearings located between the rotor and the stator of an electric motor, or the transmission, in particular the gearbox, in an electric or hybrid vehicle.

[0115] More particularly, an aqueous lubricant composition according to the invention can be used to cool and lubricate an electric motor of an electric or hybrid vehicle. In particular, it is effective for cooling the power electronics and / or the rotor and / or the stator of an electric motor. It also lubricates the bearings located between the rotor and the stator of an electric motor of an electric or hybrid vehicle.

[0116] Advantageously, an aqueous lubricant composition according to the invention can be used to lubricate the transmission, when present, in particular the gearbox, of an electric or hybrid vehicle.

[0117] It is therefore advantageous, for example, to use a single composition according to the invention to ensure both cooling of the battery and lubrication of the transmission, in particular the gearbox, in an electric or hybrid vehicle.

[0118] Advantageously, the present invention relates to the use of an aqueous lubricating composition as defined according to the invention, for lubricating and / or cooling the gearbox and / or the motor and / or the power electronics of an electric vehicle.

[0119] The invention also relates to a lubricating and / or cooling method comprising applying the lubricant composition as defined in the invention onto mechanical part(s) of a propulsion system of an electric or hybrid vehicle, preferably an electric vehicle.

[0120] The mechanical part(s) can be one or several elements selected from the electric motor, the battery, and the transmission, preferably from the power electronics, the stator, the rotor, the battery, and the reducer.

Examples

Embodiment Construction

[0032]The invention first concerns the use of a lubricant composition for cooling and / or lubricating a propulsion system of an electric or hybrid vehicle.

[0033]The lubricant composition used in the invention comprises:

from 10 to 75% by weight of water, from 2 to 50% by dry weight of at least one polyalkylene glycol PAG1 having a kinematic viscosity at 40°C of at least 10000 cSt, from 2 to 50% by dry weight of at least one polyalkylene glycol PAG2 having a kinematic viscosity at 40°C of less than 10000 cSt,

based on the total weight of the lubricant composition, the ratio between the kinematic viscosity at 40°C of PAG1 and the kinematic viscosity at 40°C of PAG2 being strictly greater than 1.

[0034]In the following, the term "aqueous lubricant composition" or "lubricant composition" will be used to designate a lubricating composition used according to the invention as defined above and detailed in the following. Because of its cooling properties, such a composition may also be ref...

Claims

1. Use of a lubricant composition for cooling and / or lubricating a propulsion system of an electric or hybrid vehicle, the lubricant composition comprising: - from 10 to 75% by weight of water, - from 2 to 50% by dry weight of at least one polyalkylene glycol (PAG1) having a kinematic viscosity at 40°C of at least 10000 cSt, - from 2 to 50% by dry weight of at least one polyalkylene glycol (PAG2) having a kinematic viscosity at 40°C of less than 10000 cSt, based on the total weight of the lubricant composition.

2. Use according to claim 1, wherein the ratio between the kinematic viscosity at 40°C of PAG1 and PAG2 is higher than 1.5, preferably higher than 2, more preferably higher than 2.5, even more preferably higher than 3.5.

3. Use according to claim 1 or 2, wherein PAG1 has a kinematic viscosity at 40°C ranging from 10000 to 35000 cSt and / or PAG2 has a kinematic viscosity at 40°C ranging from 100 to 5000 cSt, preferably from 100 to 1000 cSt.

4. Use according to any one of claims 1 to 3, wherein the PAG1 has an average molecular weight ranging from 8000 g / mol to 50000 g / mol, preferably from 9000 to 40000 g / mol, more preferably from 10000 to 30000 g / mol, even more preferably from 11000 to 20000 g / mol, and / or the PAG2 has an average molecular weight ranging from 500 to 7500 g / mol, preferably from 700 to 6000 g / mol, more preferably from 1000 to 5000 g / mol, even more preferably from 2000 to 4000 g / mol.

5. Use according to any one of claims 1 to 4, wherein the lubricant composition comprises: - from 10 to 50% by weight, preferably from 20 to 40% by weight, of water, - from 5 to 30% by dry weight, preferably from 10 to 25% by dry weight of at least one polyalkylene glycol PAG1, - from 10 to 50% by dry weight, preferably from 15 to 40% by dry weight, of at least one polyalkylene glycol PAG2, based on the total weight of the lubricant composition.

6. Use according to any one of claims 1 to 5, wherein PAG1 and PAG2 comprises ethylene oxide units and optionally propylene oxide units.

7. Use according to any one of claims 1 to 6, wherein the lubricant composition comprises: - from 10 to 50% by weight, preferably from 20 to 40% by weight, of water, - from 5 to 30% by dry weight, preferably from 10 to 25% by dry weight of at least one polyalkylene glycol PAG1, - from 10 to 50% by dry weight, preferably from 15 to 40% by dry weight, of at least one polyalkylene glycol PAG2, - from 0.1 to 40% by weight, preferably from 1 to 30% by weight, of one or more functional additive(s) different from polyalkylene glycol, the additive(s) being preferably selected from anti-wear additives, extreme-pressure additives, metal deactivators, corrosion inhibitors, pH boosters, anti-freezing agents, anti-foam agents, lubricity enhancers, and mixtures thereof. based on the total weight of the lubricant composition.

8. Use according to claim 7, wherein at least one functional additive is selected from corrosion inhibitors, at least one corrosion inhibitor being preferably selected from carboxylic acids having less than 12 carbon atoms.

9. Use according to any one of claims 1 to 8, wherein the lubricant composition has a kinematic viscosity at 40°C ranging from 5 cSt to 500 cSt, preferably from 10 to 200 cSt, more preferably from 10 to 100 cSt.

10. Use according to any one of claims 1 to 9, wherein the lubricant composition comprises: - from 10 to 50% by weight, preferably from 20 to 40% by weight, of water, - from 5 to 30% by dry weight, preferably from 10 to 25% by dry weight of at least one polyalkylene glycol PAG1 comprising ethylene oxide units and propylene oxide units and having a kinematic viscosity at 40°C ranging from 10000 cSt to 35000 cSt, - from 10 to 50% by dry weight, preferably from 15 to 40% by dry weight, of at least one polyalkylene glycol PAG2 comprising ethylene oxide units and propylene oxide units and having a kinematic viscosity at 40°C ranging from 100 to 5000 cSt, preferably from 100 to 1000 cSt, - from 0.1 to 10% by weight, preferably from 1 to 5% by weight, of at least one carboxylic acid, wherein the carboxylic acid(s) have less than 12 carbon atoms, - optionally from 0.1 to 40% by weight, preferably from 1 to 30% by weight, of one or more additive(s) selected from anti-wear and / or extreme-pressure additives, metal deactivators, pH boosters, anti-freezing agents, anti-foam agents, lubricity enhancers, and mixtures thereof, based on the total weight of the lubricant composition.

11. Use according to any one of the preceding claims, to reduce frictions and / or to reduce abrasion and / or to reduce wear of mechanical part(s) of the propulsion system.

12. Use according to any one of the preceding claims, wherein the lubricant composition is coated onto gears of the propulsion system.

13. Use according to any one of the preceding claims, to lubricate and / or cool the gearbox and / or motor and / or power electronics of an electric vehicle.

14. Use according to any one of the preceding claims, to reduce pitting by mechanical fatigue, of mechanical part(s) of said propulsion system, brought into contact with said lubricant composition.

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