Aqueous composition for lubricating and / or cooling propulsion system of electric or hybrid vehicle

Abstract

An aqueous composition for lubricating and / or cooling a propulsion system of an electric or hybrid vehicle. The present application relates to the use of an aqueous lubricating composition for cooling and / or lubricating a propulsion system of an electric or hybrid vehicle, the aqueous lubricating composition comprising at least: water and a polyalkylene glycol; the aqueous lubricating composition comprises a salt of a phosphate ester in a content strictly less than 0.1% by mass relative to the total mass of the composition. The present application also relates to the use of such an aqueous lubricating composition for reducing pitting corrosion caused by mechanical fatigue of a mechanical component of a propulsion system of an electric or hybrid vehicle in contact with said composition. The present application finally also relates to an aqueous lubricating composition for lubricating and / or cooling an electric or hybrid propulsion system, comprising at least: at least 45% by mass of water, relative to the total mass of the composition, and a polyalkylene glycol; the composition comprises a salt of phosphate ester in a content strictly less than 0.1% by mass relative to the total mass of the composition.

Description

Technical Field

[0001] The present invention relates to the field of lubricating compositions intended for use in propulsion systems of electric or hybrid vehicles. The present invention more particularly aims to provide an aqueous-based lubricating composition having both lubricating and cooling properties for the various components of the propulsion system of an electric or hybrid vehicle, such as the transmission, the engine and the battery. Background Art

[0002] The evolution of international standards for reducing CO2 emissions and lowering fuel consumption is driving automakers to come up with alternative solutions to combustion engines.

[0003] One of the solutions identified by car manufacturers is to replace the combustion engine with an electric motor. Therefore, research aimed at reducing CO2 emissions has led some car companies to develop electric or hybrid vehicles.

[0004] An "electric vehicle" within the meaning of the present invention is understood to mean a vehicle comprising an electric motor as sole propulsion means, whereas a "hybrid vehicle" is understood to mean a vehicle comprising a combustion engine and an electric motor as combined propulsion means.

[0005] A "propulsion system" within the meaning of the present invention is understood to mean a system comprising the mechanical components necessary to propel an electric vehicle. The propulsion system thus comprises more particularly an electric motor, a rotor-stator assembly of power electronics (dedicated to speed regulation), a transmission and a battery.

[0006] Typically, in electric or hybrid vehicles it is necessary to use a composition that meets the dual constraints of lubricating and cooling the various components of the above-mentioned propulsion system.

[0007] On the one hand, lubricating compositions, also called "lubricants", are usually used in engines, with the main purpose of reducing the friction between the various metal parts moving in the engine and thus protecting the parts from wear. In addition to the phenomenon of wear, friction also hinders the relative movement between the parts in contact and causes energy losses that are detrimental to the optimal operation of the propulsion system.

[0008] For this purpose, lubricating compositions typically consist of one or more base oils to which are usually combined various additives designed to stimulate the lubricating properties of the base oils, such as friction modifying additives.

[0009] On the other hand, electric propulsion systems generate heat during their operation by means of the electric motor, power electronics and batteries. Since the heat generated is greater than the heat normally dissipated to the environment, it is necessary to ensure cooling of the motor, power electronics and batteries. Usually, cooling is performed on various components of the propulsion system that generate heat and / or on components of the propulsion system that are sensitive to heat, in particular the power electronics and batteries, in order to avoid reaching dangerous temperatures. This cooling is typically provided by a cooling fluid different from a hydrocarbon-based lubricant, such as air, an aqueous fluid such as water or a mixture of water and glycols.

[0010] For obvious reasons of economy and ease of use, it would be advantageous to provide a composition that could be used to simultaneously meet the lubrication and cooling requirements of a propulsion system for an electric or hybrid vehicle.

[0011] The most common lubricants are hydrocarbon-based lubricants. However, these hydrocarbon-based oils are generally unable to generate sufficient heat dissipation to allow them to be used as cooling fluids at the same time.

[0012] More recently, and in response to growing desires to eliminate the use of toxic solvents and reduce the environmental impact of products, water-based lubricants have been developed.

[0013] Although water is an excellent cooling fluid, it does not have the tribological properties required of a lubricant, especially in terms of reducing friction and protecting components from wear. Additive systems have therefore been proposed that are able to impart satisfactory lubricating properties to aqueous fluids.

[0014] For example, patent application WO 2021 / 259853 describes an aqueous lubricating composition comprising a polyalkylene glycol, an antifreeze compound and a phosphorus-containing compound.

[0015] However, this aqueous lubricant is not entirely satisfactory, especially in view of its susceptibility to mechanical fatigue pitting phenomena. In fact, it has been found that this lubricating composition can produce this type of failure in mechanical contacts, especially depending on the formulation of the composition. Summary of the invention

[0016] Disclosure of the Invention

[0017] The present invention specifically aims to provide a new aqueous-based composition having tribological and cooling properties suitable for use in lubricating and / or cooling the propulsion system of electric or hybrid vehicles, while reducing or even eliminating the pitting phenomenon caused by mechanical fatigue.

[0018] More particularly, the present invention relates, according to its first aspect, to the use of an aqueous lubricating composition for cooling and / or lubricating a propulsion system of an electric or hybrid vehicle, in particular an electric vehicle, the aqueous lubricating composition comprising at least:

[0019] - water, preferably deionized water; and

[0020] - at least one polyalkylene glycol;

[0021] The aqueous lubricating composition comprises a salt of a phosphoric acid ester, in particular an alkali metal salt selected from phosphoric acid esters, in an amount strictly less than 0.1% by mass relative to the total mass of the composition.

[0022] Preferably, the aqueous lubricating composition according to the present invention contains less than 0.05% by mass, in particular less than 0.01% by mass, of salts of phosphoric acid esters, in particular alkali metal salts of phosphoric acid esters, or even contains no phosphoric acid ester salts at all.

[0023] Advantageously, the aqueous lubricating composition according to the invention comprises less than 0.1% by mass, preferably less than 0.01% by mass, of sulphur-containing fatty acids, and in particular is completely free of sulphur-containing fatty acids.

[0024] The term "aqueous composition" in the meaning of the present invention is understood to mean a composition comprising water as base fluid (in other words as main solvent). Water (preferably deionized water) advantageously represents more than 35% by mass, in particular more than 40% by mass, in particular more than 50% by mass of the total mass of the lubricating composition.

[0025] In the remainder of this document, "aqueous lubricating composition" or "aqueous lubricant" refers to the lubricating composition required according to the present invention as defined above and described in detail in the remainder of this document. Due to its cooling properties, such a composition may also be referred to as an "aqueous composition for cooling" or "aqueous cooling composition".

[0026] Advantageously, the lubricating composition formed mainly of water used according to the present invention has little toxicological impact, especially on humans using such lubricants.

[0027] Furthermore, the composition according to the invention exhibits good performance in terms of lubrication even if water is the main solvent.

[0028] The aqueous lubricating composition according to the invention thus advantageously combines good cooling properties associated with the presence of water with good tribological properties, in particular friction reduction and anti-wear properties. The aqueous composition according to the invention thus ensures the dual function of lubrication and cooling of the motorization system of an electric or hybrid vehicle, in particular the electric motor, power electronics, transmission and / or battery of an electric or hybrid vehicle.

[0029] According to another of its aspects, the invention thus relates to a method for lubricating and / or cooling a propulsion system of an electric or hybrid vehicle, comprising at least one step of contacting at least one mechanical component of said propulsion system with an aqueous lubricating composition as defined above.

[0030] The aqueous composition according to the invention thus advantageously makes it possible to avoid the use of two different fluids: a cooling fluid on the one hand and a lubricating fluid on the other hand.

[0031] In particular, the aqueous lubricating composition according to the invention makes it possible to ensure effective cooling of the engine, power electronics and battery, and lubrication of the electric motor, the transmission, in particular the reduction gear, in electric or hybrid vehicles.

[0032] In particular, the aqueous lubricating composition according to the present invention can be used for lubricating and / or cooling a reducer and / or an engine and / or power electronics of an electric vehicle.

[0033] Furthermore, as shown in the following examples, the inventors have found that the aqueous lubricant according to the present invention as described above, in particular wherein the content of the salt of the phosphoric acid ester, if present, is kept strictly less than 0.1% by mass, makes it possible to reduce or even eliminate the phenomenon of so-called pitting corrosion (or "pitting" in English) caused by mechanical fatigue.

[0034] The aqueous lubricating composition according to the invention thus proves to be suitable for lubrication and / or cooling of propulsion systems of electric or hybrid vehicles, and also for reducing pitting corrosion caused by mechanical fatigue in these systems.

[0035] The present application therefore relates to the use of an aqueous lubricating composition intended for lubricating and / or cooling a propulsion system of an electric or hybrid vehicle, for reducing pitting corrosion caused by mechanical fatigue of mechanical parts of said propulsion system in contact with said composition, said aqueous lubricating composition comprising at least:

[0036] - water, preferably deionized water; and

[0037] - at least one polyalkylene glycol;

[0038] The aqueous lubricating composition comprises a salt of a phosphoric acid ester, in particular an alkali metal salt selected from phosphoric acid esters, in an amount strictly less than 0.1% by mass relative to the total mass of the composition.

[0039] According to another aspect thereof, the present invention also relates to an aqueous lubricating composition for lubricating and / or cooling an electric or hybrid propulsion system, comprising at least:

[0040] at least 45% by mass of water, in particular at least 50% by mass of water, preferably deionized water, relative to the total mass of the composition; and

[0041] - at least one polyalkylene glycol;

[0042] The aqueous lubricating composition comprises a salt of a phosphoric acid ester, in particular an alkali metal salt selected from phosphoric acid esters, in an amount strictly less than 0.1% by mass relative to the total mass of the composition.

[0043] Furthermore, the aqueous lubricating composition according to the invention advantageously makes it possible to effectively influence fuel consumption by influencing the friction forces generated between the various components of a hybrid vehicle. In particular, the aqueous lubricating composition has proven to be particularly advantageous for reducing friction in gearboxes, in axle differentials and / or in cylinder heads.

[0044] By thus reducing the friction between the moving parts in the propulsion system of the vehicle, the lubricating composition according to the invention not only makes it possible to reduce wear but also to limit energy losses that lead to excessive fuel consumption.

[0045] The aqueous lubricating composition according to the present invention therefore advantageously has good performance in reducing the fuel consumption of hybrid vehicles (performance also referred to as “Fuel Eco”).

[0046] According to another aspect of the invention, the present invention therefore relates to the use of an aqueous lubricating composition according to the invention for reducing the fuel consumption of a combustion engine of a hybrid vehicle lubricated with the aid of such a composition or for reducing the fuel consumption of a hybrid vehicle equipped with a transmission, in particular an axle or a gearbox, lubricated with the aid of such a composition.

[0047] Other characteristics, variants and advantages of the aqueous lubricating composition according to the invention will become more apparent on reading the following description and the examples, which are given by way of illustration and do not limit the invention.

[0048] The expressions “between ... and ...”, “from ... to ...”, “formed from ... to ...” and “varied from ... to ...” are to be understood as including the limit values, unless otherwise indicated.

[0049] In the description and examples, unless otherwise stated, percentages are percentages by weight. The percentages are therefore expressed in mass relative to the total mass of the composition. Unless otherwise stated, temperatures are expressed in degrees Celsius, and unless otherwise stated, pressures are atmospheric pressure. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] [ Figure 1 ] schematically represents the propulsion system of an electric or hybrid vehicle. DETAILED DESCRIPTION

[0051] Detailed description

[0052] Aqueous composition

[0053] As mentioned above, the aqueous lubricating composition (also referred to as aqueous lubricant) used according to the present invention is a formulation comprising water as a main solvent.

[0054] For the purposes of the present invention, "main solvent" is understood to mean that water is present in an amount greater than any other solvent that may be present in the composition. Preferably, the aqueous lubricating composition according to the invention comprises at least 20% by mass, preferably at least 30% by mass, in particular 35% to 90% by mass, more preferably 40% to 75% by mass, in particular 40 to 60% by mass of water, in particular deionized water, relative to the total mass of the composition.

[0055] According to one embodiment, the aqueous lubricating composition according to the invention comprises at least 45% by mass, in particular at least 50% by mass of water, in particular deionized water, preferably 50% to 90% by mass, more preferably 50% to 75% by mass of water, in particular 50% to 60% by mass of water, relative to the total mass of the composition.

[0056] Advantageously, in addition to its role as solvent, water makes it possible to obtain a lubricating composition having good cooling properties and which can be used as a cooling fluid for different components in the propulsion system of an electric or hybrid vehicle.

[0057] "Cooling fluid" within the meaning of the present invention is understood to mean a fluid capable of dissipating the heat generated by the propulsion system of an electric or hybrid vehicle. More particularly, such a fluid is characterized by an increased heat absorption capacity when it comes into contact with heated components.

[0058] According to a particular embodiment, the water used in the aqueous lubricating composition required according to the invention is demineralized water or osmotic water, in particular deionized water.

[0059] The term "permeate water" within the meaning of the present invention is understood to mean water which has been purified, in particular by reverse osmosis, to reduce the content of organic and / or mineral compounds, for example to a content below 5.0% by weight, preferably below 1.0% by weight. In the remainder of this text, the expressions "demineralized water" or "ultrapure water" will be considered as equivalent or synonymous with the expression "permeate water". In particular, permeate water may be "deionized water", in other words water which has been purified to reduce the content of ions such as Ca, Mg, Mg and Mg which are usually present in water. 2+ and HCO3 - Preferably, deionized water contains no ions.

[0060] Therefore, the use of deionized water is particularly advantageous when the aqueous lubricant according to the present invention is used for components of the propulsion system of electric or hybrid vehicles that require little or no electrical conductivity, such as electric motors or batteries.

[0061] The aqueous lubricating composition used in accordance with the present invention differs from the lubricants conventionally used in the propulsion systems of vehicles in that it comprises a major proportion of one or more water-insoluble base oils.

[0062] "Water-insoluble oil" is understood to mean in particular an oil which is substantially insoluble in water at ambient temperature (about 25° C.). In particular, a water-insoluble oil has a solubility in water of less than 0.2 g / L at ambient temperature.

[0063] This relates in particular to lubricating base oils belonging to groups I to V according to the categories defined in the API classification (or their equivalents according to the ATIEL classification), and mixtures thereof.

[0064] Preferably, the aqueous lubricating composition used according to the invention comprises less than 5% by mass, preferably less than 2% by mass and more preferably less than 1% by mass of water-insoluble base oil relative to the total mass of the composition.

[0065] Advantageously, the aqueous lubricating composition used according to the invention is completely free of water-insoluble oils.

[0066] Polyalkylene glycol

[0067] As mentioned above, the aqueous lubricating composition used according to the invention comprises at least one polyalkylene glycol.

[0068] The polyalkylene glycol (denoted as "PAG") is selected from water-soluble polyalkylene glycols.

[0069] The term "water-soluble" refers to a polyalkylene glycol having a solubility in water at ambient temperature (about 25°C) of at least 10 g / L, preferably at least 500 g / L.

[0070] The polyalkylene glycols may more particularly be formed from C1-C4, preferably C1-C3 and more particularly C2-C3 alkylene oxide units.

[0071] Advantageously, the polyalkylene glycol used in the aqueous lubricating composition required according to the invention comprises at least 50% by mass, in particular at least 80% by mass, more preferably at least 90% by mass of propylene oxide and / or ethylene oxide units. It may be a copolymer of ethylene oxide / propylene oxide, optionally a random copolymer.

[0072] Preferably, the polyalkylene glycol used in the aqueous lubricating composition according to the present invention has a weight average molecular weight (Mw) between 100 and 50000 g.mol -1 Between, preferably between 5000 and 25000 g.mol -1 between.

[0073] The weight average molecular weight can be measured by gel permeation chromatography (GPC).

[0074] Preferably, the polyalkylene glycol used in the aqueous lubricating composition according to the present invention has a kinematic viscosity (KV100) measured at 100° C. according to ASTM D445 standard between 100 and 25000 mm 2 / s, especially between 150 and 10000mm 2 / s.

[0075] Preferably, the polyalkylene glycol used in the aqueous lubricating composition according to the present invention has a kinematic viscosity (KV40) measured at 40° C. according to ASTM D445 standard between 500 and 100,000 mm 2 / s, more particularly between 1000 and 95000 mm 2 / s.

[0076] The flash point of the polyalkylene glycol used in the aqueous lubricating composition according to the invention is preferably higher than or equal to 160° C., in particular higher than or equal to 220° C. The flash point can be measured by ISO 2592 or ASTM D92 standards.

[0077] Preferably, the polyalkylene glycol used in the aqueous lubricating composition according to the invention has a viscosity index measured according to the ASTM D2270 standard of between 100 and 800, preferably between 250 and 550.

[0078] In particular, the one or more polyalkylene glycol compounds may be used in the aqueous lubricating composition required according to the present invention in an amount of at least 5.0% by mass, preferably 5.0% to 50% by mass, more preferably 10% to 40% by mass, in particular 10% to 20% by mass, relative to the total mass of the composition.

[0079] Preferably, the aqueous lubricating composition used according to the present invention comprises less than 17% by mass of polyalkylene glycol compounds, more preferably 10% to 15% by mass of polyalkylene glycol compounds.

[0080] It will be appreciated that the aqueous lubricating composition used in accordance with the present invention may comprise a single polyalkylene glycol or a mixture of a plurality of different polyalkylene glycols.

[0081] In particular, the aqueous lubricating composition according to the invention may comprise a mixture of at least two different polyalkylene glycols, more particularly a mixture of at least one polyalkylene glycol of low weight average molecular weight and at least one polyalkylene glycol of high weight average molecular weight.

[0082] It is within the ordinary skill of those skilled in the art to adjust the nature and amount of the low and high weight average molecular weight polyalkylene glycols in the polyalkylene glycol mixture, particularly taking into account the target viscosity of the final lubricating composition.

[0083] The combination of at least one polyalkylene glycol of low weight average molecular weight and at least one polyalkylene glycol of high weight average molecular weight is particularly advantageous in order to obtain good solubilization of the various compounds introduced into the aqueous lubricating composition.

[0084] According to one embodiment variant, one or more vinylpyrrolidone polymers can be used instead of or in addition to polyalkylene glycols.

[0085] The term "polymer" is to be understood in a broad sense to refer to homopolymers of vinylpyrrolidone, as well as copolymers formed from vinylpyrrolidone and one or more other monomers.

[0086] Thus, more generally, the aqueous lubricating composition used according to the invention may comprise one or more vinylpyrrolidone polymers, in particular chosen from polyvinylpyrrolidone (denoted PVP).

[0087] Polyvinylpyrrolidone corresponds more particularly to the following formula:

[0088]

[0089] Here n represents the average number of constituent units of the polymer.

[0090] Such compounds can be synthesized according to any method known to the person skilled in the art, in particular by polymerization of N-vinylpyrrolidone, and may also be commercially available.

[0091] More particularly suitable polyvinyl pyrrolidone for use in the present invention has a weight average molecular weight (Mw) of 20,000-50,000 g.mol -1 , preferably 25000-45000 g.mol -1 .

[0092] In particular, the vinylpyrrolidone polymer (particularly selected from polyvinylpyrrolidone) may be present in the aqueous lubricating composition according to the present invention in an amount of at least 5.0% by mass, preferably 5.0% to 50% by mass, more preferably 10% to 40% by mass, in particular 10% to 20% by mass, relative to the total mass of the composition.

[0093] additive

[0094] Phosphorus compounds

[0095] As stated above, the content of phosphorus-containing compounds of the salt type of phosphoric esters, if present, in the aqueous lubricating composition used according to the invention is strictly less than 0.1% by mass relative to the total mass of the composition.

[0096] Generally, a "phosphorus-containing compound" within the meaning of the present invention is intended to mean a compound comprising at least one phosphorus atom. Preferably, such a phosphorus-containing compound does not provide sulfur.

[0097] The phosphorus-containing compounds can be used in aqueous compositions in a form that is soluble or emulsifiable in water, in particular in the form of ionic salts.

[0098] As examples of salts of phosphoric acid esters, mention may be made of salts of alkyl, alkenyl or aryl phosphoric acid esters, in particular salts of C1-C8 alkyl or dialkyl phosphoric acid esters. These salts are in particular in the form of phosphate ions neutralized by suitable counterions.

[0099] The salt may be an alkali metal or alkaline earth metal salt of a phosphoric acid ester, an ammonium salt, an alkanolamine salt, in particular a C2-C8 alkanolamine salt, or an alkaneamine salt, in particular a C2-C8 alkaneamine salt.

[0100] Advantageously, the salt of a phosphoric acid ester is an alkali metal salt of a phosphoric acid ester.

[0101] When the aqueous lubricating composition according to the invention comprises one or more salts of phosphoric esters, such as those described above, these salts are used in a content strictly less than 0.1% by mass relative to the total mass of the composition.

[0102] Advantageously, the aqueous lubricating composition used according to the invention contains less than 0.05% by mass of salt of phosphoric ester, in other words a content of 0.0% to 0.05% by mass of salt of phosphoric ester, in particular less than 0.01% by mass, more particularly less than 0.001% by mass, relative to the total mass of the composition.

[0103] According to a particularly preferred embodiment, the aqueous lubricating composition used according to the invention contains absolutely no salts of phosphoric esters.

[0104] The aqueous lubricating composition used according to the invention may contain one or more other phosphorus-containing compounds other than the salt of the phosphoric ester, referred to as "additional phosphorus-containing compounds".

[0105] As examples of additional phosphorus-containing compounds, mention may be made of amine phosphoric acids; polyphosphates; phosphonates such as esters of phosphonic acid, in particular alkyl, alkenyl or aryl phosphonates; polyphosphonates; carbamoylphosphonic acid; hypophosphites; and mixtures thereof.

[0106] They may be in the form of salts, in particular in the form of phosphonate or phosphinate ions neutralized by suitable counterions.

[0107] The salt may be an alkali metal or alkaline earth metal salt, an ammonium salt, an alkanolamine salt, in particular a C2-C8 alkanolamine salt, an alkaneamine salt, in particular a C2-C8 alkaneamine salt, a phosphonate salt or a phosphinate salt.

[0108] When the aqueous lubricating composition according to the invention comprises one or more additional phosphorus-containing compounds (eg as described above), said compounds may be used in a content of 0.01% to 5.0% by mass, in particular 0.1% to 3.0% by mass, relative to the total mass of the composition.

[0109] According to one embodiment, when the aqueous lubricating composition according to the invention comprises one or more additional phosphorus-containing compounds, in particular as described above, said compounds are used in a content strictly less than 0.1% by mass relative to the total mass of the composition.

[0110] Advantageously, the total content of phosphorus-containing compounds (including salts of phosphoric acid esters or any other additional phosphorus-containing compound) may be strictly less than 0.1% by mass, in particular less than 0.05% by mass, relative to the total mass of the composition.

[0111] In other words, the aqueous lubricating composition used according to the invention preferably contains a content of phosphorus-containing compounds strictly less than 0.1% by mass, in particular 0.0% to 0.05% by mass, particularly less than 0.01% by mass, more particularly less than 0.001% by mass, relative to the total mass of the composition.

[0112] Thus, according to one embodiment, the aqueous lubricating composition used according to the invention comprises at least:

[0113] - water, preferably deionized water;

[0114] - at least one polyalkylene glycol; and

[0115] The aqueous lubricating composition comprises phosphorus-containing compounds in an amount strictly less than 0.1% by mass, particularly 0.0% to 0.05% by mass, especially less than 0.01% by mass, more especially less than 0.001% by mass, relative to the total mass of the composition.

[0116] According to a particularly preferred embodiment, the aqueous lubricating composition used according to the invention contains absolutely no phosphorus-containing compounds.

[0117] According to a particular embodiment, the aqueous lubricating composition required according to the invention may contain a phosphorus content less than or equal to 0.05% by mass, in particular less than or equal to 0.02% by mass, more particularly less than or equal to 0.01% by mass. This phosphorus content can be measured by ICP (Inductively Coupled Plasma). Advantageously, the aqueous lubricating composition required according to the invention is completely free of phosphorus.

[0118] Antifreeze Compound

[0119] The aqueous lubricating composition used according to the invention may comprise at least one antifreeze compound selected from glycols, preferably alkylene glycols; glycerol; diglycerol; triglycerol, and mixtures thereof.

[0120] Thus, according to a preferred embodiment, the aqueous lubricating composition used according to the invention comprises at least:

[0121] - water, preferably deionized water;

[0122] - at least one polyalkylene glycol; and

[0123] - at least one antifreeze compound selected from glycols, preferably alkylene glycols; glycerol; diglycerol; triglycerol, and mixtures thereof;

[0124] The aqueous lubricating composition contains a salt of a phosphoric acid ester, in particular an alkali metal salt of a phosphoric acid ester, in an amount strictly less than 0.1% by mass, relative to the total mass of the composition, and preferably contains no phosphoric acid ester salt.

[0125] These compounds are known for their antifreeze effect, in other words they can be used to lower the freezing temperature of the composition.

[0126] Diols are diols in which the two hydroxyl groups are carried by different carbon atoms, preferably by adjacent carbon atoms.

[0127] Preferably, the diol is an alkylene glycol, in particular having 2 to 10 carbon atoms, in particular 2 to 6 carbon atoms. For example, mention may be made of monoethylene glycol, diethylene glycol and propylene glycol.

[0128] The antifreeze compound may also be selected from glycerol, diglycerol, triglycerol and mixtures thereof.

[0129] Preferably, the antifreeze compound used according to the invention is selected from monoethylene glycol, diethylene glycol, propylene glycol, glycerol and mixtures thereof. Preferably, the antifreeze compound is diethylene glycol.

[0130] In particular, the antifreeze compound, in particular as defined above, such as diethylene glycol, may be used in the aqueous lubricating composition according to the invention in a content of at least 1.0% by mass, preferably between 5.0% and 50% by mass, more preferably between 10% and 45% by mass, in particular between 20% and 40% by mass, relative to the total mass of the composition.

[0131] Preferably, the aqueous lubricating composition used according to the invention comprises a content of antifreeze compound greater than or equal to 33%, in particular 33.5% to 40% by mass relative to the total mass of the composition, in particular as defined above, such as diethylene glycol.

[0132] According to a particular embodiment, the invention relates to the use of an aqueous lubricating composition for cooling and / or lubricating a propulsion system of an electric or hybrid vehicle, the aqueous lubricating composition comprising at least:

[0133] -water;

[0134] - at least one polyalkylene glycol; and

[0135] - at least one antifreeze compound chosen from glycols, whose content is greater than or equal to 33% by mass relative to the total mass of the composition;

[0136] The aqueous lubricating composition comprises a salt of a phosphoric acid ester, in particular an alkali metal salt selected from phosphoric acid esters, in an amount strictly less than 0.1% by mass relative to the total mass of the composition.

[0137] According to a particular embodiment, the present invention relates to an aqueous lubricating composition for lubricating and / or cooling an electric or hybrid propulsion system, comprising at least:

[0138] - at least 45% by mass of water relative to the total mass of the composition;

[0139] - at least one polyalkylene glycol; and

[0140] - at least one antifreeze compound chosen from glycols, whose content is greater than or equal to 33% by mass relative to the total mass of the composition;

[0141] The aqueous lubricating composition comprises a salt of a phosphoric acid ester, in particular an alkali metal salt selected from phosphoric acid esters, in an amount strictly less than 0.1% by mass relative to the total mass of the composition.

[0142] According to a particular embodiment, the aqueous lubricating composition used according to the invention comprises at least:

[0143] - at least 35% by weight of water, in particular deionized water, preferably 40-60% by weight of water; in particular 45-60% by weight of water;

[0144] - at least 10% by mass, in particular 10 to 20% by mass, of at least one polyalkylene glycol, in particular as defined above;

[0145] - at least 5.0% by mass, in particular 20-40% by mass, of at least one antifreeze compound selected from glycols, preferably alkylene glycols; glycerol; diglycerol; triglycerol, and mixtures thereof, the antifreeze compound being preferably diethylene glycol.

[0146] According to a particular embodiment, the whole constituted by water, the polyalkylene glycol (s) and optionally the antifreeze compound (s) represents more than 90% of the total mass of the aqueous lubricating composition, in particular more than 95%, especially more than 96%, even more than 97% of the total mass of the aqueous lubricating composition.

[0147] Other additives

[0148] The aqueous lubricating composition according to the present invention may further contain various additives.

[0149] It will be appreciated that the additives are compatible with their use in aqueous media. Advantageously, the additives are used in a water-soluble or water-emulsifiable form, for example in the form of an ionic salt or a liquid.

[0150] The additives are of course selected for the intended application of the aqueous lubricant.

[0151] Of course, a person skilled in the art will note that possible additives and / or their amounts are selected so that the advantageous properties of the aqueous lubricating composition according to the invention (in particular the property of reducing pitting due to mechanical fatigue, and the cooling properties) are not adversely affected by the proposed addition of additives.

[0152] Such additives may more particularly be chosen from defoamers, biocides, pH regulators, corrosion inhibitors, antiwear and / or extreme pressure additives, chelating agents, metal deactivators, colorants, dispersants, emulsifiers and mixtures thereof.

[0153] Advantageously, the aqueous lubricating composition according to the invention may comprise one or more additives selected from defoamers, extreme pressure agents, corrosion inhibitors, pH regulators, metal deactivators, colorants and mixtures thereof.

[0154] The aqueous lubricating composition according to the invention may more particularly comprise 0.1% to 10% by mass, more preferably 1.0% to 8.0% by mass of additives relative to the total mass of the composition.

[0155] pH Adjusters

[0156] The aqueous lubricating composition according to the invention may comprise at least one pH regulating additive, in particular an alkaline buffer. The pH regulating agent makes it possible to maintain the desired pH of the lubricating composition, in particular in order to maintain an alkaline pH, advantageously between 8 and 15.

[0157] The pH regulator makes it possible in particular to prevent corrosion of metal surfaces by ensuring that the pH of the aqueous lubricating composition is maintained between 8 and 15, and it can also promote the solubilization of various compounds, in particular polyalkylene glycols, in particular as defined above, in the lubricating composition.

[0158] The pH adjuster may be selected from amines, in particular alkanolamines and amino alcohols.

[0159] It can in particular be a pH adjusting additive selected from the group consisting of alkanolamines, such as dimethylethanolamine (DMEA), ethanolamines, such as monoethanolamine (MEA), diethanolamine (DEA); triethanolamine (TEA), isopropanolamines, such as monoisopropanolamine (MIPA), diisopropanolamine (DIPA) and triisopropanolamine (TIPA), diglycolamine (DGA), ethyleneamines, such as ethylenediamine (EDA), diethylenetriamine (DETA), triethylenetetramine (TETA) and tetraethylenepentamine (TEPA); cyclic amines, such as cyclohexylamine, 2-amino-2-ethyl-1,3-propanediol, 2-amino-2-methyl-1-propanol and mixtures thereof.

[0160] The aqueous lubricating composition according to the invention may contain in particular 0.1% to 10% by mass, preferably 0.5% to 5% by mass, of a pH adjusting additive relative to the total mass of the composition.

[0161] Advantageously, the aqueous lubricating composition used according to the invention comprises at least one pH regulating additive making it possible to maintain the pH of the lubricating composition between 8 and 15, in particular between 8.5 and 14, more particularly between 9 and 13, the pH regulating additive being chosen in particular from alkanolamines, preferably ethanolamines, more particularly from dimethylethanolamine (DMEA), triethanolamine (TEA) and mixtures thereof.

[0162] Therefore, in a particular embodiment, the aqueous lubricating composition required according to the invention comprises at least:

[0163] - water, in particular deionized water;

[0164] - at least one polyalkylene glycol, in particular as defined above; and

[0165] - at least one pH regulating additive making it possible to maintain the pH of the lubricating composition between 8 and 15, in particular chosen from alkanolamines,

[0166] The aqueous lubricating composition contains a salt of a phosphoric acid ester, in particular an alkali metal salt of a phosphoric acid ester, in an amount strictly less than 0.1% by mass, relative to the total mass of the composition, and preferably contains no phosphoric acid ester salt.

[0167] Corrosion Inhibitors

[0168] The aqueous lubricating composition according to the invention may contain at least one corrosion inhibitor. Corrosion inhibitors advantageously make it possible to reduce or even prevent corrosion of metal parts. The nature of the corrosion inhibitor may be chosen according to the metal to be protected against corrosion, for example aluminum, steel, galvanized steel, yellow metals such as copper or brass.

[0169] Among the inorganic corrosion inhibitors, mention may be made of nitrites, sulfites, silicates, borates, sodium, potassium, calcium or magnesium phosphates, alkali metal phosphates, hydroxides, molybdates, zinc, magnesium or nickel sulfates.

[0170] Among the organic corrosion inhibitors, mention may be made of alkanolamines such as triethanolamine, aliphatic monocarboxylic acids having in particular 4 to 15 carbon atoms such as octanoic acid, aliphatic dicarboxylic acids having in particular 4 to 15 carbon atoms such as sebacic acid, undecanedioic acid, dodecanedioic acid or mixtures thereof, polycarboxylic acids optionally neutralized with triethanolamine such as 1,3,5-triazine-2,4,6-tris-(6-aminohexanoic acid), alkanoylamidocarboxylic acids, in particular isononanoylamidocaproic acid and mixtures thereof. Boric acid amides resulting from the reaction of amines or amino alcohols with boric acid may also be used.

[0171] Preferably, said corrosion inhibitor is different from said pH regulating additive, this additive notably enabling the pH of the lubricating composition to be maintained between 8 and 15, and as previously defined.

[0172] The aqueous lubricating composition according to the invention may in particular comprise 0.1% to 5% by mass, preferably 0.5% to 4% by mass, more preferably 1% to 2.5% by mass of corrosion inhibitors, in particular as defined above, relative to the total mass of the composition.

[0173] In a particular embodiment, the aqueous lubricating composition required according to the invention comprises at least:

[0174] - water, in particular deionized water;

[0175] - at least one polyalkylene glycol, in particular as defined above; and

[0176] - at least one corrosion inhibitor, in particular chosen from organic corrosion inhibitors, more particularly chosen from aliphatic monocarboxylic acids,

[0177] The aqueous lubricating composition contains a salt of a phosphoric acid ester, in particular an alkali metal salt of a phosphoric acid ester, in an amount strictly less than 0.1% by mass, relative to the total mass of the composition, and preferably contains no phosphoric acid ester salt.

[0178] Anti-wear / extreme pressure additives

[0179] The aqueous lubricating composition according to the invention may contain at least one antiwear and / or extreme pressure additive. Their function is to reduce the wear and friction coefficients or to prevent metal-metal contacts by forming an adsorbed protective film on these surfaces.

[0180] There is a wide variety of antiwear additives, among which mention may be made of those selected from phosphorus-sulfur additives such as metal alkylthiophosphates or their salts.

[0181] Additives that do not contribute phosphorus are preferred, such as polysulfides and particularly sulfur-containing olefins.

[0182] According to a particular embodiment, the aqueous lubricating composition used according to the invention may comprise at least one extreme pressure additive chosen from sulfur-containing fatty acids and dimercaptothiadiazoles, preferably in its neutralized (especially by inorganic alkalizing agents or alkanolamines), water-emulsifiable or water-soluble form.

[0183] Advantageously, the aqueous lubricating composition used according to the invention comprises less than 0.1% by mass, preferably less than 0.01% by mass, more preferably less than 0.001% by mass of extreme pressure additives of sulphur-containing fatty acid type, in particular in neutralized form, relative to the total weight of the composition.

[0184] The sulphur-containing fatty acids may contain 8 to 22 carbon atoms, in particular 12 to 18 carbon atoms.

[0185] The amount of sulfur provided by the sulfur-containing fatty acid according to ASTM D2622 standard may be 5% to 30% by mass, in particular 10% to 20% by mass, relative to the total weight of the composition.

[0186] Preferably, the amount of active sulfur at 150° C. provided by the sulfur-containing fatty acid in the aqueous lubricating composition according to the present invention according to the ASTM D1662 standard is less than or equal to 2% by mass, particularly less than or equal to 1% by mass, and more particularly less than 0.1% by mass, relative to the total mass of the lubricating composition.

[0187] The term "active sulfur" in the meaning of the present invention is understood to mean the sulfur that a compound is able to generate or release when it is subjected to the conditions of the ASTM D1662 standard. The ASTM D1662 standard defines the active sulfur content of a compound at a given temperature as the difference in weight percentage between the sulfur content before and after a sample of the sulfur-containing compound is reacted with a given amount of copper for a fixed time.

[0188] As mentioned above, the sulfur-containing fatty acid is generally used in the aqueous lubricating composition in a form in which it is neutralized with an alkalizing agent, such as sodium hydroxide, potassium hydroxide or an alkanolamine such as monoethanolamine, triethanolamine, monoisopropanolamine, diisopropanolamine and triisopropanolamine.

[0189] The aqueous lubricating composition required according to the invention may contain 0.01% to 10% by mass, preferably 0.2% to 5% by mass, of antiwear and / or extreme pressure additives relative to the total mass of the composition.

[0190] Defoaming agent

[0191] The aqueous lubricating composition according to the invention may contain at least one antifoaming agent additive.Antifoaming agents prevent the lubricating fluid from foaming.

[0192] It may for example be a defoamer based on polysiloxane or acrylate polymers.Preferably, the defoamer is selected from three-dimensional siloxanes.

[0193] Furthermore, the defoaming agent may be a polar polymer such as polymethylsiloxane or polyacrylate.

[0194] In particular, the aqueous lubricating composition according to the present invention may contain 0.001% to 3.0% by mass, preferably 0.005% to 1.5% by mass, more preferably 0.01% to 1.0% by mass of the defoamer additive relative to the total mass of the composition.

[0195] In a particular embodiment, the aqueous lubricating composition required according to the invention comprises at least:

[0196] - water, in particular deionized water;

[0197] - at least one polyalkylene glycol, in particular as defined above; and

[0198] - at least one antifoaming additive, in particular chosen from three-dimensional silicones,

[0199] The aqueous lubricating composition contains a salt of a phosphoric acid ester, in particular an alkali metal salt of a phosphoric acid ester, in an amount strictly less than 0.1% by mass, relative to the total mass of the composition, and preferably contains no phosphoric acid ester salt.

[0200] Metal passivator

[0201] The aqueous lubricating composition according to the present invention may contain at least one metal deactivator. Metal deactivators can protect metal parts by promoting the formation of metal oxides on their surfaces.

[0202] The metal deactivator can be selected, for example, from triazole derivatives, such as tetrahydrobenzotriazole (THBTZ), tolyltriazole (TTZ), benzotriazole (BTZ), amines substituted with triazole groups, such as N,N-bis(2-ethylhexyl)-1,2,4-triazol-1-ylmethylamine, N'-bis(2-ethylhexyl)-4-methyl-1H-benzotriazole-1-methylamine, N,N-bis(heptyl)-ar-methyl-1H-benzotriazole-1-methylamine, N,N-bis(nonyl)-ar-methyl-1H-benzotriazole-1-methylamine, N,N-bis(decyl)-ar-methyl-1H-benzotriazole-1-methylamine. Methyl-1H-benzotriazole-1-methylamine, N,N-bis(undecyl)-ar-methyl-1H-phenyltriazole-1-methylamine, N,N-bis(dodecyl)-ar-methyl-1H-benzotriazole-1-methylamine, N,N-bis(2-ethylhexyl)-ar-methyl-1H-benzotriazole-1-methylamine, 1,2,4-triazole, benzimidazole, 2-alkyldithiobenzimidazole, 2-alkyldithiobenzothiazole, 2-(N,N-dialkyldithiocarbamoyl)benzothiazole, 2,5-bis(alkyldithio)-1,3,4-thiadiazole , for example, 2,5-bis(tert-octyl disulfide)-1,3,4-thiadiazole, 2,5-bis(tert-nonyl disulfide)-1,3,4-thiadiazole, 2,5-bis(tert-decyl disulfide)-1,3,4-thiadiazole, 2,5-bis(tert-undecyl disulfide)-1,3,4-thiadiazole, 2,5-bis(tert-dodecyl disulfide)-1,3,4-thiadiazole, 2,5-bis(tert-tridecyl disulfide)-1,3,4-thiadiazole, 2,5-bis(tert-tetradecyl disulfide)-1,3,4-thiadiazole, 2,5-bis(tert-pentadecyl disulfide)-1,3,4-thiadiazole 1,3,4-thiadiazole, 2,5-bis(tert-hexadecyldithio)-1,3,4-thiadiazole, 2,5-bis(tert-heptadecyldithio)-1,3,4-thiadiazole, 2,5-bis(tert-octadecyldithio)-1,3,4-thiadiazole, 2,5-bis(tert-nonadecyldithio)-1,3,4-thiadiazole, 2,5-bis(tert-eicosyldithio)-1,3,4-thiadiazole, 2,5-bis(N,N-dialkyldithiocarbamoyl)-1,3,4-thiadiazole, 2-alkyldithio-5-mercaptothiadiazole, and mixtures thereof.

[0203] Preferably, the metal deactivator is selected from tetrahydrobenzotriazole (THBTZ), tolyltriazole (TTZ), benzotriazole (BTZ) and salts thereof, employed individually or as a mixture.

[0204] The aqueous lubricating composition according to the present invention may contain in particular 0.01% to 2.0% by mass, preferably 0.1% to 1.0% by mass, more preferably 0.2% to 0.8% by mass of a metal deactivator relative to the total mass of the composition.

[0205] In a particular embodiment, the aqueous lubricating composition required according to the invention comprises at least:

[0206] - water, in particular deionized water;

[0207] - at least one polyalkylene glycol, in particular as defined above; and

[0208] at least one metal deactivator, in particular chosen from triazole derivatives, more particularly chosen from tetrahydrobenzotriazole (THBTZ), tolyltriazole (TTZ), benzotriazole (BTZ) and their salts, used alone or in the form of a mixture,

[0209] The aqueous lubricating composition contains a salt of a phosphoric acid ester, in particular an alkali metal salt of a phosphoric acid ester, in an amount strictly less than 0.1% by mass, relative to the total mass of the composition, and preferably contains no phosphoric acid ester salt.

[0210] Colorants

[0211] The aqueous lubricating composition according to the invention may contain one or more colorants. The colorants may be natural or synthetic, typically organic.

[0212] The colorants that can be used in the aqueous lubricating composition can be more particularly chosen from natural or synthetic water-soluble colorants, such as the colorants FDC Red 4, DC Red 6, DC Red 22, DC Red 28, DC Red 30, DC Red 33, DC Orange 4, DC Yellow 5, DC Yellow 6, DC Yellow 8, FDC Green 3, DC Green 5, FDC Blue 1, betanin (beet), xanthene, carmine, chlorophyllin, methylene blue, anthocyanins (anthocyanin, black carrot and hibiscus), caramel and riboflavin.

[0213] The aqueous lubricating composition according to the present invention may contain 0.01% to 2.0% by mass, preferably 0.01% to 1.5% by mass, more preferably 0.02% to 1.0% by mass of the colorant relative to the total mass of the composition.

[0214] In a particular embodiment, the aqueous lubricating composition required according to the invention comprises at least:

[0215] - water, in particular deionized water;

[0216] - at least one polyalkylene glycol, in particular as defined above; and

[0217] - at least one coloring agent, in particular chosen from xanthenes,

[0218] The aqueous lubricating composition contains a salt of a phosphoric acid ester, in particular an alkali metal salt of a phosphoric acid ester, in an amount strictly less than 0.1% by mass, relative to the total mass of the composition, and preferably contains no phosphoric acid ester salt.

[0219] Emulsifier

[0220] The aqueous lubricating composition according to the invention may contain one or more emulsifiers, also called emulsifying agents, which function to form a stable emulsion in water.

[0221] The emulsifier may more particularly be nonionic, for example ethoxylated fatty alcohols, ethoxylated fatty acids, ethoxylated fatty amides; anionic, for example soaps of KOH or NaOH; sulfonates; cationic, for example quaternary ammonium compounds; or water-soluble or water-emulsifiable carboxylates.

[0222] In particular, the aqueous lubricating composition according to the present invention may contain 0.01% to 10% by mass, preferably 0.1% to 5.0% by mass of an emulsifier relative to the total mass of the lubricating composition.

[0223] Chelating agents

[0224] The aqueous lubricating composition according to the invention may comprise at least one chelating agent. Chelating agents (also called sequestering agents) make it possible to limit scaling of metal ions in the composition.

[0225] As examples of chelating agents, mention may be made of those derived from phosphonic acids and phosphonates, for example diethylenetriaminepentamethylphosphonic acid (DTPMPA), aminotri(methylenephosphonic acid) (ATMP), hydroxyethanediphosphonic acid (HEDP), 1-hydroxyethylene 1,1-diphosphonate, 2-hydroxyethylaminedi(methylenephosphonic acid) (HEAMBP), diethylenetriaminopenta(methylenephosphonic acid) (DTMP), polyfunctional organic acids and hydroxy acids, such as ethylenediaminetetraacetic acid (EDTA), pteroyl-L-glutamic acid (PGLU), organic polyacids, such as maleic acid and polyaspartic acid, polysaccharides and carbohydrates, such as inulin, carboxymethylinulin and carboxymethylchitosan.

[0226] The aqueous lubricating composition according to the present invention may contain 0.001% to 2.0% by mass, preferably 0.01% to 1.0% by mass of a chelating agent relative to the total mass of the composition.

[0227] Biocides and Fungicides

[0228] The aqueous lubricating composition according to the invention may comprise at least one biocide and / or fungicide.Biocides and fungicides may be used to increase the biological stability of the composition by limiting the proliferation of bacteria, fungi and yeasts in the lubricating fluid.

[0229] Such biocides may be selected from parabens, aldehydes, reactive acetylacetonate compounds, isothiazolinones, phenolic compounds, acid salts, halogenated compounds, quaternary ammonium, certain alcohols, and mixtures thereof.

[0230] Preferably, the biocide can be selected from optionally substituted benzisothiazolinone (BIT), such as N-butyl-1,2-benzisothiazolin-3-one, methylisothiazolinone (MIT), a mixture of methylisothiazolinone and chloromethylisothiazolinone (MIT / CMIT), o-phenylphenol (OPP) or its sodium salt, 3-iodo-2-propynylbutylcarbamate (IPBC), chlorocresol and N,N-methylenebismorpholine (MBM); sorbic acid; preferably selected from o-phenylphenol (OPP) or its sodium salt, 3-iodo-2-propynylbutylcarbamate, chlorocresol, benzisothiazolinone and N,N-methylenebismorpholine.

[0231] The aqueous lubricating composition according to the invention may in particular comprise 0.01% to 10% by mass, preferably 0.5% to 5.0% by mass, of biocides and / or fungicides relative to the total mass of the composition.

[0232] In a particular embodiment, the aqueous lubricating composition required according to the invention comprises at least:

[0233] - water, in particular deionized water;

[0234] - at least one polyalkylene glycol, in particular as defined above; and

[0235] - one or more additives selected from defoamers, corrosion inhibitors, pH regulators, metal deactivators, colorants, in particular as defined above,

[0236] The aqueous lubricating composition contains a salt of a phosphoric acid ester, in particular an alkali metal salt of a phosphoric acid ester, in an amount strictly less than 0.1% by mass, relative to the total mass of the composition, and preferably contains no phosphoric acid ester salt.

[0237] In a particular embodiment, the aqueous lubricating composition required according to the invention comprises at least:

[0238] - water, in particular deionized water;

[0239] - at least one polyalkylene glycol, in particular as defined above; and

[0240] - at least one antifreeze compound selected from glycols, preferably alkylene glycols; glycerol; diglycerol; triglycerol, and mixtures thereof; and

[0241] - one or more additives selected from defoamers, corrosion inhibitors, pH regulators, metal deactivators, colorants, in particular as defined above,

[0242] The aqueous lubricating composition contains a salt of a phosphoric acid ester, in particular an alkali metal salt of a phosphoric acid ester, in an amount strictly less than 0.1% by mass, relative to the total mass of the composition, and preferably contains no phosphoric acid ester salt.

[0243] According to a particular embodiment, the aqueous lubricating composition used according to the invention comprises:

[0244] - at least 35% by mass of water, in particular 40 to 60% by mass, especially at least 50% by mass of water, preferably deionized water;

[0245] - 5.0% to 50% by mass, in particular 10 to 20% by mass, of at least one polyalkylene glycol, in particular as defined above;

[0246] - optionally, 5.0% to 45% by mass, in particular 20 to 40% by mass, of at least one antifreeze compound selected from glycols, preferably alkylene glycols; glycerol; diglycerol; triglycerol, and mixtures thereof; preferably diethylene glycol; and

[0247] - Optionally, 0.1% to 10% by mass of one or more additives selected from defoamers, extreme pressure agents, corrosion inhibitors, pH regulators, metal passivators, colorants, emulsifiers, chelating agents and mixtures thereof,

[0248] The aqueous lubricating composition contains a salt of a phosphoric acid ester, in particular an alkali metal salt selected from phosphoric acid esters, in an amount strictly less than 0.1% by mass, and preferably contains no salt of a phosphoric acid ester;

[0249] The content is expressed relative to the total mass of the lubricating composition.

[0250] In particular, the aqueous lubricating composition used according to the invention may consist of:

[0251] - 5.0% to 50% by mass, in particular 10% to 20% by mass, of at least one polyalkylene glycol, in particular as defined above;

[0252] - optionally, 5.0% to 45% by mass, in particular 20 to 40% by mass, of at least one antifreeze compound selected from glycols, preferably alkylene glycols; glycerol; diglycerol; triglycerol, and mixtures thereof; preferably diethylene glycol; and

[0253] - Optionally, 0.1% to 10% by mass of one or more additives selected from defoamers, extreme pressure agents, corrosion inhibitors, pH regulators, metal passivators, colorants, emulsifiers, chelating agents and mixtures thereof,

[0254] The aqueous lubricating composition contains a salt of a phosphoric acid ester, in particular an alkali metal salt selected from phosphoric acid esters, in an amount strictly less than 0.1% by mass, and in particular contains no salt of a phosphoric acid ester;

[0255] The content is expressed relative to the total mass of the lubricating composition.

[0256] The balance consists of water, preferably deionized water.

[0257] It should be understood that the various specific embodiments described above can be combined as much as possible to define other specific embodiments.

[0258] In particular, each of the additives specifically described above may be introduced alone or in combination with at least one other of the additives specifically described, thereby defining different embodiment variants of the aqueous lubricating composition according to the invention.

[0259] In other words, a particular embodiment of the invention is defined by the aqueous lubricating composition according to the invention, comprising at least water; and one or more polyalkylene glycols, in particular as defined above, preferably in the proportions as indicated above, and also one or more additives particularly detailed herein.

[0260] According to a particular embodiment, the aqueous lubricating composition used according to the invention comprises:

[0261] - 40-55% by weight of water, in particular deionized water, in particular more than 45% by weight of water;

[0262] - 10-15% by mass of one or more polyalkylene glycols;

[0263] - Optionally, 30% to 40% by mass of an antifreeze compound selected from glycols, preferably alkylene glycols; glycerol; diglycerol; triglycerol, and mixtures thereof; preferably diethylene glycol;

[0264] - Optionally, 0.1% to 10% by mass of one or more additives selected from defoamers, corrosion inhibitors, pH regulators, metal passivators, colorants, emulsifiers, chelating agents and mixtures thereof,

[0265] The composition does not contain salts of phosphate esters, more preferably does not contain phosphorus-containing compounds,

[0266] The composition does not contain extreme pressure additives of the sulphur-containing fatty acid type.

[0267] According to a particular embodiment, the aqueous lubricating composition used according to the invention comprises hypericine in a content strictly less than 0.1% by mass, preferably less than or equal to 0.01% by mass, more preferably less than or equal to 0.01% by mass, relative to the total weight of the composition. In particular, the aqueous lubricating composition used according to the invention is completely free of hypericine.

[0268] More generally, the aqueous lubricating composition used according to the invention comprises one or more polycyclic anthraquinone type compounds in an amount strictly less than 0.1% by mass, preferably less than or equal to 0.01% by mass, more preferably less than or equal to 0.01% by mass, relative to the total weight of the composition. In particular, the aqueous lubricating composition used according to the invention is completely free of polycyclic anthraquinone type compounds.

[0269] application

[0270] As indicated above, the aqueous lubricating composition can be used simultaneously as a cooling fluid and a lubricating fluid due to its combined performance in terms of lubrication and cooling for use in the propulsion system of an electric or hybrid vehicle, in particular in an engine, power electronics, transmission and / or battery in an electric or hybrid vehicle, preferably an electric vehicle.

[0271] like Figure 1 As schematically shown in FIG. 1 , the propulsion system of an electric or hybrid vehicle comprises in particular an electric motor part (1), a battery (2) and a transmission device, and in particular a reducer (3). As batteries suitable for the propulsion system of an electric or hybrid vehicle, lithium-ion batteries or nickel-cadmium batteries may be mentioned in particular.

[0272] The electric motor typically comprises power electronics (11) connected to a stator (13) and a rotor (14). The stator comprises coils, particularly copper coils, which are supplied with alternating current. This generates a rotating magnetic field. The rotor itself comprises coils, permanent magnets or other magnetic material, and is rotated by the rotating magnetic field.

[0273] The power electronics (11), stator (13) and rotor (14) of the propulsion system (1) are components with complex structures and generate a lot of heat during the operation of the engine. It is therefore crucial to ensure the cooling of the electric motor and the power electronics.

[0274] The bearing (12) is usually integrated between the stator (13) and the rotor (14). The transmission, in particular the reducer (3), makes it possible to reduce the rotation speed of the motor output and adapt the speed transmitted to the wheels, making it possible to control the speed of the vehicle at the same time.

[0275] Advantageously, the aqueous lubricating composition according to the invention can be used to cool a battery present in an electric or hybrid vehicle, in particular in an electric vehicle. In particular, it is intended to be in direct contact with the battery.

[0276] Cooling may be achieved using any method known to those skilled in the art.The battery may be immersed or semi-immersed, static or cycling in the composition.

[0277] As an example of direct contact, mention may be made of cooling by injection, spraying, atomization or misting of the composition required according to the invention onto the battery under pressure and by gravity.

[0278] The composition according to the invention can also be used for cooling an electric motor of an electric or hybrid vehicle, in particular for cooling the rotor and / or stator and / or the power electronics of an electric motor, preferably in an electric vehicle.

[0279] The aqueous lubricating composition according to the invention can be used simultaneously for lubricating different components of the propulsion system of an electric or hybrid vehicle, in particular the engine, power electronics, transmission and / or battery, more particularly the bearings located between the rotor and the stator of the electric motor, or the transmission, in particular the reducer (in an electric or hybrid vehicle).

[0280] More particularly, the aqueous lubricating composition according to the invention enables cooling and lubrication of the electric motor of an electric or hybrid vehicle. It proves to be particularly effective in cooling the rotor and / or stator and / or the power electronics of the electric motor. It also ensures lubrication of the bearings situated between the rotor and the stator of the electric motor of the electric or hybrid vehicle.

[0281] Advantageously, the aqueous lubricating composition according to the invention makes it possible to ensure the lubrication of the transmission, when present, and in particular of the reduction gear, of an electric or hybrid vehicle.

[0282] Thus, advantageously, for example, cooling of the battery and lubrication of the transmission, in particular the reduction gear, in an electric or hybrid vehicle can be ensured simultaneously by using a single composition according to the invention.

[0283] Advantageously, the invention relates to the use of an aqueous lubricating composition as defined according to the invention for lubricating and / or cooling a retarder and / or an engine and / or power electronics of an electric vehicle.

[0284] The specific features, advantageous features or preferred features related to the method and use for using the aqueous lubricating composition according to the invention make it possible to define embodiments of the specific features, advantageous features or preferred features of the aqueous lubricating composition according to the invention.

[0285] Example

[0286] The invention will now be described by means of the following examples which are of course given as non-limiting illustrations of the invention.

[0287] Measuring pitting due to mechanical fatigue

[0288] Pitting corrosion (or “Pitting” in English) caused by mechanical fatigue was evaluated by testing on an MPR (“Micro Pitting Rig” in English) tribometer.

[0289] The MPR tribometer is a machine that brings a central roll (12 mm diameter) into contact with three rings (54 mm diameter) arranged around the roll. This geometric configuration allows the test roll to be subjected to a large number of rolling contact cycles in a short test period, which promotes pitting caused by mechanical fatigue.

[0290] The test was conducted for 20 hours. Fatigue pitting was detected using an accelerometer connected to a vibration monitor. The test was stopped when the vibration set point was exceeded due to the onset of pitting.

[0291] The performance of the composition in terms of pitting due to mechanical fatigue is determined as follows: if the pitting time is less than 10 hours, the performance is insufficient, if the pitting time is from 10 hours to 20 hours, the performance is fair, and if there is no pitting after 20 hours of testing, the performance is good.

[0292] Example 1

[0293] Preparation of lubricating composition

[0294] Two aqueous lubricating compositions according to the invention (I1 and I2) and a comparative lubricating composition (C1) comprising a phosphorus-containing compound content of greater than 0.1% by weight were formulated by simple mixing at ambient temperature the following components in the mass percentages indicated in the following Table 1. The percentages are therefore expressed in mass relative to the total mass of the composition.

[0295] [Table 1]

[0296]

[0297] (*) An additive mixture comprising one or more anti-corrosion additives, one or more metal deactivators, one or more anti-foam additives and / or one or more colorants.

[0298] Example 2

[0299] Characterization of the compositions according to the invention and comparative compositions with respect to pitting due to mechanical fatigue

[0300] The performance of the composition I2 according to the invention and the comparative composition C1 in terms of pitting due to mechanical fatigue was evaluated according to the protocol detailed above. The results are shown in the following Table 2:

[0301] [Table 2]

[0302] Composition I2 C1 Pitting performance good insufficient

[0303] From these results it can be seen that the mechanical fatigue pitting resistance exhibited by the composition I2 according to the invention is much better than that obtained by the comparative composition C1, which is characterized in particular by the presence of a phosphorus-containing compound in a content greater than 0.1% by weight relative to the total weight of the composition.

[0304] Furthermore, the compositions I1 and I2 according to the invention have excellent properties in the cooling of propulsion systems of electric or hybrid vehicles, in particular in the cooling of electric motors.

[0305] Therefore, the aqueous lubricating composition according to the present invention can be used to lubricate and / or cool the propulsion system of an electric or hybrid vehicle without adversely affecting pitting corrosion due to mechanical fatigue of the components lubricated and / or cooled using the composition.

Claims

1. Use of an aqueous lubricating composition for cooling and / or lubricating a propulsion system of an electric or hybrid vehicle, the aqueous lubricating composition comprising at least: - water; and - at least one polyalkylene glycol; The aqueous lubricating composition comprises a salt of a phosphoric acid ester, in particular an alkali metal salt selected from phosphoric acid esters, in an amount strictly less than 0.1% by mass relative to the total mass of the composition.

2. The use according to claim 1, wherein the aqueous lubricating composition further comprises at least one antifreeze compound selected from glycols, preferably alkylene glycols, glycerol, diglycerol, triglycerol, and mixtures thereof, more preferably selected from monoethylene glycol, diethylene glycol, propylene glycol, glycerol and mixtures thereof.

3. The use according to the preceding claim, wherein the aqueous lubricating composition comprises at least 1.0% by mass, preferably 5.0% to 50% by mass, more preferably 10% to 45% by mass, in particular 20% to 40% by mass of antifreeze compounds relative to the total mass of the composition.

4. Use according to any one of the preceding claims, wherein the water is permeate water, in particular deionized water.

5. The use according to any one of the preceding claims, wherein the aqueous lubricating composition comprises at least 20% by mass, preferably 35% to 90% by mass, more preferably 40% to 75% by mass, in particular 40 to 60% by mass of water, in particular deionized water, relative to the total mass of the composition.

6. Use according to any one of the preceding claims, characterized in that The polyalkylene glycol comprises at least 50% by mass, in particular at least 80% by mass, more preferably at least 90% by mass of propylene oxide and / or ethylene oxide units, in particular the polyalkylene glycol is an ethylene oxide / propylene oxide copolymer.

7. Use according to any one of the preceding claims, characterized in that The polyalkylene glycol has a kinematic viscosity (KV100) of 100-25 000 mm2 measured at 100°C according to ASTM D445. 2 / s, especially 150-10000mm 2 / s.

8. The use according to any one of the preceding claims, wherein the aqueous lubricating composition comprises at least 5.0% by mass, preferably 5.0% to 50% by mass, more preferably 10% to 40% by mass, in particular 10% to 20% by mass of polyalkylene glycol relative to the total mass of the composition.

9. The use according to any of the preceding claims, wherein the aqueous lubricating composition comprises less than 0.05% by mass, preferably less than 0.01% by mass, more particularly less than 0.001% by mass of salts of phosphoric acid esters, in particular selected from alkali metal salts of phosphoric acid esters, relative to the total mass of the composition, and the aqueous lubricating composition is more preferably completely free of salts of phosphoric acid esters, in particular alkali metal salts of phosphoric acid esters.

10. The use according to any one of the preceding claims, wherein the aqueous lubricating composition further comprises at least one additive selected from defoamers, biocides, pH regulators, corrosion inhibitors, antiwear and / or extreme pressure additives, chelating agents, metal passivators, colorants, dispersants, emulsifiers, and mixtures thereof, preferably selected from defoamers, extreme pressure agents, corrosion inhibitors, pH regulators, metal passivators, colorants, and mixtures thereof.

11. Use according to any one of the preceding claims, wherein the aqueous lubricating composition also comprises at least one pH regulating additive making it possible to maintain the pH of the lubricating composition between 8 and 15, in particular chosen from alkanolamines.

12. The use according to any one of the preceding claims, wherein the aqueous lubricating composition comprises less than 0.1% by mass, preferably less than 0.01% by mass, more particularly less than 0.001% by mass of extreme pressure additives of the sulphur-containing fatty acid type, relative to the total mass of the composition, and more preferably is completely free of extreme pressure additives of the sulphur-containing fatty acid type.

13. Use of an aqueous lubricating composition as defined in any one of the preceding claims for lubricating and / or cooling a retarder and / or a motor and / or power electronics of an electric vehicle.

14. Use of an aqueous lubricating composition intended for lubricating and / or cooling a propulsion system of an electric or hybrid vehicle for reducing pitting corrosion caused by mechanical fatigue of mechanical parts of said propulsion system in contact with said composition, said aqueous lubricating composition comprising at least: - water; and - at least one polyalkylene glycol; The aqueous lubricating composition comprises a salt of a phosphoric acid ester, in particular an alkali metal salt selected from phosphoric acid esters, in an amount strictly less than 0.1% by mass relative to the total mass of the composition.

15. An aqueous lubricating composition for lubricating and / or cooling an electric or hybrid propulsion system, comprising at least: - at least 45% by mass of water relative to the total mass of the composition; and - at least one polyalkylene glycol; The aqueous lubricating composition comprises a salt of a phosphoric acid ester, in particular an alkali metal salt selected from phosphoric acid esters, in an amount strictly less than 0.1% by mass relative to the total mass of the composition.

16. Aqueous lubricating composition according to the preceding claim, said composition being as defined in any one of claims 2-4 or 6-12.

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