WO2023202998A1

WO2023202998A1 - Aqueous composition for lubricating and/or cooling a propulsion system of an electric or hybrid vehicle

Info

Publication number: WO2023202998A1
Application number: PCT/EP2023/059957
Authority: WO
Inventors: Benoît THIEBAUT; Hakim EL-BAHI
Original assignee: Totalenergies Onetech
Priority date: 2022-04-20
Filing date: 2023-04-18
Publication date: 2023-10-26
Also published as: FR3134815A1

Abstract

Aqueous composition for lubricating and/or cooling a propulsion system of an electric or hybrid vehicle. The present application relates to the use, for cooling and/or lubricating a propulsion system of an electric or hybrid vehicle, of an aqueous lubricant composition comprising at least water and a polyalkylene glycol; said aqueous lubricant composition having a phosphate ester salt content of strictly less than 0.1% by weight, relative to the total weight of said composition. It also relates to the use of such an aqueous lubricant composition for reducing pitting, due to mechanical fatigue, of the mechanical part(s) of an electric or hybrid vehicle propulsion system in contact with said composition. Finally, the invention relates to an aqueous lubricant composition for lubricating and/or cooling an electric or hybrid propulsion system, comprising at least 45% by weight of water, relative to the total weight of the composition and a polyalkylene glycol; said composition having a phosphate ester salt content of strictly less than 0.1% by weight, relative to the total weight of said composition.

Description

Title: Aqueous composition for the lubrication and/or cooling of a propulsion system of an electric or hybrid vehicle

Technical area

The present invention relates to the field of lubricating compositions intended for a propulsion system of an electric or hybrid vehicle. It aims more particularly to propose an aqueous-based lubricating composition, endowed with both lubricating and cooling properties with respect to the various organs of a propulsion system of an electric or hybrid vehicle, such as the transmission. , the motor and the battery.

Prior art

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

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

By “electric vehicle” within the meaning of the present invention, is meant a vehicle comprising an electric motor as the sole means of propulsion and, by “hybrid vehicle”, a vehicle which comprises a combustion engine and an electric motor as means of propulsion. combined.

By “propulsion system” within the meaning of the present invention, we mean a system comprising the mechanical parts necessary for the propulsion of an electric vehicle. The propulsion system thus includes more particularly an electric motor, the rotor-stator assembly of the power electronics (dedicated to speed regulation), a transmission and a battery.

Generally speaking, it is necessary to implement, in electric or hybrid vehicles, compositions to meet the double constraint of lubrication and cooling of the different parts of the propulsion system recalled above. On the one hand, lubricating compositions, also called "lubricants", are commonly used in engines for the purpose of reducing friction forces between the different metal parts moving in engines, and thus protecting the parts against 'wear. In addition to wear phenomena, friction can oppose the relative movement of the parts in contact and induce energy losses detrimental to optimal operation of the propulsion system.

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

On the other hand, electric propulsion systems generate heat during operation via the electric motor, power electronics and batteries. As the quantity of heat generated is greater than the quantity of heat normally dissipated to the environment, it is necessary to ensure cooling of the motor, power electronics and batteries. Generally speaking, cooling is carried out on several parts of the propulsion system generating heat and/or the 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 for example air, an aqueous fluid, such as water or even by a mixture of water and a glycol.

For obvious reasons of economy and ease of implementation, it would be advantageous to be able to have a composition making it possible to simultaneously meet the lubrication and cooling needs of a propulsion system of an electric or hybrid vehicle.

The most common lubricants are hydrocarbon-based lubricants. However, these hydrocarbon oils generally do not lead to sufficient heat dissipation allowing their joint use as cooling fluids.

More recently, and to meet growing expectations to eliminate the use of toxic solvents and reduce the impact of products on the environment, studies have focused on the development of aqueous-based lubricants. Although water is an excellent cooling fluid, it does not, however, have the tribological properties required for a lubricant, particularly in terms of reducing friction and protecting parts against wear. Additivation systems making it possible to give the aqueous fluid satisfactory lubrication performance have thus been proposed.

For example, in application WO 2021/259853, an aqueous lubricating composition comprising a polyalkylene glycol, an antifreeze compound and a phosphorus compound has been described. However, this aqueous lubricant does not give complete satisfaction, in particular with regard to the phenomenon of pitting by mechanical fatigue (“pitting” in the English language) that it is likely to cause. Indeed, it could be observed that this lubricating composition can generate this type of failure in mechanical contacts, in particular depending on the formulation protocol of the composition.

Presentation of the invention

The present invention aims precisely to propose a new aqueous-based composition, having tribological and cooling properties, adapted to its implementation for the lubrication and/or cooling of an electric or hybrid vehicle propulsion system, while reducing , or even by avoiding pitting phenomena due to mechanical fatigue.

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

- water, preferably deionized water; And

- at least one polyalkylene glycol; said aqueous lubricating composition comprising a content of salt(s) of phosphate ester(s), in particular chosen from alkali metal salts of phosphate esters, strictly less than 0.1% by weight, relative to to the total mass of said composition.

Preferably, an aqueous lubricating composition according to the invention comprises less than 0.05% by weight, in particular less than 0.01% by weight, of phosphate ester salt(s), in particular chosen from alkali metal salts of phosphate esters, or even is completely free of phosphate ester salts.

Advantageously, the aqueous lubricating composition according to the invention comprises less than 0.1% by weight of sulfur-containing fatty acid(s), preferably less than 0.01% by weight, in particular is completely free of acid. sulfur fat.

By “aqueous composition” within the meaning of the present invention, is meant a composition comprising water as base fluid, in other words as the majority solvent. Water, preferably deionized, advantageously represents more than 35% by weight, in particular more than 40% by weight, and in particular more than 50% by weight, of the total mass of the lubricating composition.

In the remainder of the text, the term “aqueous lubricating composition” or “aqueous lubricant” will be designated as a lubricating composition required according to the invention as defined above and detailed in the remainder of the text. Due to its cooling properties, such a composition can also be designated “aqueous cooling composition” or “aqueous cooling composition”.

Advantageously, a lubricating composition used according to the invention, formed mainly of water, has little toxicological impact, particularly for people using this lubricant.

Furthermore, even though water is the majority solvent, a composition according to the invention has good properties in terms of lubrication.

Thus, an aqueous lubricating 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 ensure the dual function of lubricating and cooling the engine system of the electric or hybrid vehicle, in particular the electric motor, the power electronics, the transmission and/or the battery of an electric or hybrid vehicle.

The invention thus relates, according to another of its aspects, to a method of lubricating and/or cooling a propulsion system of an electric or hybrid vehicle. comprising at least one step of bringing at least one mechanical part of said propulsion system into contact with an aqueous lubricating composition as defined above. Thus, an aqueous composition according to the invention advantageously makes it possible to avoid the use of two distinct fluids, on one side a cooling fluid, on the other, a lubricating fluid.

In particular, an aqueous lubricating composition according to the invention makes it possible to ensure effective cooling of the motor, the power electronics and the battery, as well as the lubrication of the electric motor, the transmission, in particular the reduction gear, in an electric or hybrid vehicle.

In particular, an aqueous lubricating composition according to the invention can be used to lubricate and/or cool the reduction gear and/or the motor and/or the power electronics of an electric vehicle.

Also, as illustrated in the examples which follow, the inventors have discovered that an aqueous lubricant according to the invention as described previously, in particular in which the content of salt(s) of phosphate esters, if present(s) , remains strictly less than 0.1% by mass, makes it possible to reduce or even eliminate phenomena known as pitting by mechanical fatigue (or “pitting” in Anglo-Saxon terminology).

An aqueous lubricating composition according to the invention thus proves suitable for use for the lubrication and/or cooling of propulsion systems of electric or hybrid vehicles, but also for reducing pitting by mechanical fatigue, in these systems.

The present application thus concerns the use of an aqueous lubricating composition intended to lubricate and/or cool a propulsion system of an electric or hybrid vehicle, comprising at least:

- water, preferably deionized water; And

- at least one polyalkylene glycol; said aqueous lubricating composition comprising a content of phosphate ester salt(s), in particular chosen from alkali metal salts of phosphate esters, strictly less than 0.1% by weight, relative to the mass total composition, to reduce pitting by mechanical fatigue, of the mechanical part(s) of said propulsion system brought into contact with said composition. The invention also relates, according to another of its aspects, to an aqueous lubricating composition for the lubrication and/or cooling of an electric or hybrid propulsion system, comprising at least:

- at least 45% by weight of water, in particular at least 50% by weight of water, preferably deionized water, relative to the total mass of the composition; And

- at least one polyalkylene glycol; said aqueous lubricating composition comprising a content of salt(s) of phosphate ester(s), in particular chosen from alkali metal salts of phosphate esters, strictly less than 0.1% by weight, relative to to the total mass of the composition.

Furthermore, an aqueous lubricating composition according to the invention advantageously makes it possible to act effectively on fuel consumption via its impact on the friction forces generated between the different components of hybrid vehicles. In particular, an aqueous lubricating composition proves particularly advantageous for reducing friction in gearboxes, in axle differentials and/or in the cylinder head. By thus reducing friction between the moving parts at the vehicle propulsion system, a lubricating composition according to the invention makes it possible not only to reduce wear, but also to limit energy losses responsible for overconsumption of fuel.

An aqueous lubricating composition according to the invention thus advantageously has good properties in terms of reducing the fuel consumption of hybrid vehicles, also known as “Fuel Eco” properties.

The invention thus relates, according to another of its aspects, to the use of an aqueous lubricating composition according to the invention to reduce the fuel consumption of a combustion engine of a hybrid vehicle lubricated by means of this composition, or a hybrid vehicle equipped with a transmission, in particular a bridge or a gearbox, said transmission being lubricated by means of this composition.

Other characteristics, variants and advantages of an aqueous lubricating composition according to the invention and its use for lubricating and/or cooling a propulsion system of an electric or hybrid vehicle will become clearer on reading the description. and the examples which follow, given by way of illustration and not limitation of the invention. The expressions “between ... and ...”, “ranging from ... to ...”, “formed from ... to ...”, and “varying from ... to …” , must be understood inclusive, unless otherwise stated.

In the description and examples, unless otherwise indicated, percentages are weight percentages. The percentages are therefore expressed in mass relative to the total mass of the composition. Temperature is expressed in degrees Celsius unless otherwise noted, and pressure is atmospheric pressure unless otherwise noted.

Brief description of the drawings

[Fig 1] schematically represents a propulsion system for an electric or hybrid vehicle.

detailed description

AQUEOUS COMPOSITION

As mentioned previously, an aqueous lubricating composition used according to the invention, also called an aqueous lubricant, is a formulation comprising water as the majority solvent.

For the purposes of the invention, by “majority solvent” is meant that water is present in a greater quantity than any other solvent possibly present in the composition. Preferably, an aqueous lubricating composition according to the invention comprises at least 20% by weight of water, in particular deionized water, preferably at least 30% by weight, in particular between 35% and 90% by weight, more preferably between 40%. and 75% by weight, in particular between 40 and 60% by weight, relative to the total mass of the composition.

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

Advantageously, in addition to its role as a solvent, water provides access to a lubricating composition having good cooling properties, and which can be used as a cooling fluid for the various organs in an electric vehicle propulsion system or hybrid. By “cooling fluid” within the meaning of the present invention is meant a fluid capable of dissipating the heat generated by a propulsion system of an electric or hybrid vehicle. More precisely, such a fluid is characterized by an increased thermal absorption capacity during its contact with a heating part.

According to a particular embodiment, the water used in an aqueous lubricating composition required according to the invention is demineralized or osmosis water, in particular deionized water.

By “osmosis water” within the meaning of the present invention, is meant water having undergone purification, in particular by a reverse osmosis process, in order to reduce the content of organic and/or mineral compounds, for example to a lower content. at 5.0% by weight, preferably less than 1.0% by weight. In the remainder of the text, the expressions “demineralized water” or even “ultrapure water” will be considered equivalent or synonymous with the expression “osmosis water”. In particular, reverse osmosis water can be “deionized water”, in other words water having undergone purification in order to reduce the content of ions, such as Ca ²⁺ and HCO3' ions generally present in water. Preferably deionized water does not include ions.

The use of deionized water is therefore particularly advantageous in the context of the use of the aqueous lubricant according to the invention for the organs of the propulsion system of an electric or hybrid vehicle requiring a fluid that conducts little, if at all, electricity, such as the electric motor or the battery.

An aqueous lubricating composition used according to the invention differs from lubricants conventionally used in vehicle propulsion systems, which comprise a majority proportion of one or more base oils not soluble in water.

By “oil not soluble in water”, we mean in particular an oil which does not dissolve substantially in water at room temperature (at approximately 25°C). In particular, an oil that is not soluble in water has a solubility in water of less than 0.2 g/L, at room temperature.

These include lubricating base oils belonging to groups I to V according to the classes defined in the API classification (or their equivalents according to the ATIEL classification) and their mixtures. Preferably, an aqueous lubricating composition used according to the present invention comprises less than 5% by weight of base oil(s) not soluble in water, preferably less than 2% by weight, more preferably less than 1% by mass, relative to the total mass of the composition.

Advantageously, an aqueous lubricating composition used according to the invention is completely free of oil not soluble in water.

POLYALKYLENE GLYCOL

As indicated previously, an aqueous lubricating composition used according to the invention comprises at least one polyalkylene glycol.

Polyalkylene glycols (denoted “PAG”) are chosen from water-soluble polyalkylene glycols.

By “soluble in water” is meant a polyalkylene glycol having a solubility in water of at least 10 g/L, preferably at least 500 g/L, in water at room temperature (approximately 25°C).

The polyalkylene glycols can be more particularly formed of C1-C4 alkylene oxide units, preferably C1-C3, more particularly C2-C3.

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

Preferably, a polyalkylene glycol used in an aqueous lubricating composition according to the invention has a weight average molecular mass (Mw) of between 100 and 50,000 g. mol' ¹ , preferably between 5,000 and 25,000 g.mol ¹ .

Weight average molecular mass can be measured by gel permeation chromatography (GPC).

Preferably, a polyalkylene glycol used in an aqueous lubricating composition according to the invention has a kinematic viscosity measured at 100°C (KV100), according to the ASTM D445 standard, of between 100 and 25,000 mm ² /s, in particular between 150 and 10,000 mm ² /s. Preferably, a polyalkylene glycol used in an aqueous lubricating composition according to the invention has a kinematic viscosity measured at 40°C (KV40), according to the ASTM D445 standard, of between 500 and 100,000 mm ² /s, more particularly between

I 000 and 95 000 mm ² /s.

The flash point of a polyalkylene glycol used in an aqueous lubricating composition according to the invention is preferably greater than or equal to 160°C, in particular greater than or equal to 220°C. Flash point can be measured by ISO 2592 or ASTM D92.

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

In particular, said polyalkylene glycol compound(s) can be used in an aqueous lubricating composition required according to the invention in a content of at least 5.0% by weight, preferably between 5.0% and 50% by weight, more preferably between 10% and 40% by weight, in particular between 10% and 20% by weight, relative to the total mass of the composition.

Preferably, an aqueous lubricating composition used according to the invention comprises less than 17% of polyalkylene glycol compound(s), more preferably between 10% and 15% by weight of polyalkylene glycol compound(s).

It is understood that an aqueous lubricating composition used according to the invention may comprise a single polyalkylene glycol or a mixture of several different polyalkylene glycols.

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

It is within the general skills of those skilled in the art to adjust the nature and content of polyalkylene glycols of low and high weight average molecular mass of the mixture of polyalkylene glycols, particularly with regard to the viscosity targeted for the final lubricating composition. The combination of at least one polyalkylene glycol of low weight average molecular mass and at least one polyalkylene glycol of high weight average molecular mass is particularly advantageous in order to obtain good solubilization of the different compounds introduced into the composition. aqueous lubricant.

According to an alternative embodiment, it is possible to use, alternatively to the polyalkylene glycol(s) or in conjunction with them, one or more vinylpyrrolidone polymer(s).

By “polymer” we mean, in the broad sense, both homopolymers of vinylpyrrolidone and copolymers formed from vinylpyrrolidone and one or more other monomers.

Thus, more generally, an aqueous lubricating composition used according to the invention may comprise one or more vinylpyrrolidone polymer(s), in particular chosen from polyvinylpyrrolidones (denoted PVPs).

Polyvinylpyrrolidones correspond more particularly to the following formula:

in which n represents the average number of constituent units of the polymer.

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

Polyvinylpyrrolidones which are more particularly suitable for the invention have a weight average molecular mass (Mw) of between 20,000 and 50,000 g.mol' ¹ , preferably between 25,000 and 45,000 g.mol' ¹ .

In particular, said vinylpyrrolidone polymer(s), in particular chosen from polyvinylpyrrolidones, may be present in an aqueous lubricating composition according to the invention in a content of at least 5.0% by weight, preferably between 5.0%. and 50% by weight, more preferably between 10% and 40% by weight, in particular between 10% and 20% by weight, relative to the total mass of the composition. ADDITIVES

Phosphorus compounds

As indicated above, the content of phosphorus compound(s) such as phosphate ester salts, if present, in an aqueous lubricating composition used according to the invention, is strictly less than 0.1 % by mass, relative to the total mass of the composition.

Generally speaking, a “phosphorus compound” within the meaning of the present invention is intended to designate a compound comprising at least one phosphorus atom. Preferably, such phosphorus compounds do not provide sulfur.

Said phosphorus compound(s) can be used in aqueous compositions in a form that is soluble or emulsifiable in water, in particular in the form of ionic salts.

As examples of phosphate ester salts, mention may be made of the salts of alkyl, alkenyl or aryl phosphate esters, in particular of alkyl or dialkyl phosphate esters. Cs. These salts are found in particular in the form of phosphate ions neutralized by an appropriate counterion.

The salts may be salts of alkali or alkaline earth metals, of ammonium, of alkanolamines, in particular C2-C8, or of alkaneamines, in particular C2-C8 of phosphate esters.

Advantageously, the phosphate ester salt(s) are alkali metal salts of phosphate esters.

When the aqueous lubricating composition according to the invention comprises one or more salts of phosphate esters, for example as described above, these are used in a content strictly less than 0.1% by weight, relative to to the total mass of said composition.

Advantageously, an aqueous lubricating composition used according to the invention comprises less than 0.05% by weight of phosphate ester salt(s), in other words comprises a content of ester salt(s). ) of phosphate ranging from 0.0% to 0.05% by mass, in particular less than 0.01% by mass and more particularly less than 0.001% by mass, relative to the total mass of composition. According to a particularly preferred embodiment, an aqueous lubricating composition used according to the invention is completely free of phosphate ester salts.

An aqueous lubricating composition used according to the invention may comprise one or more other phosphorus compounds distinct from phosphate ester salts, called “additional phosphorus compound(s)”.

As examples of additional phosphorus compounds, amine phosphates can be cited; polyphosphates; phosphonates such as phosphonate esters, in particular alkyl, alkenyl or aryl phosphonates; polyphosphonates; carbamyl phosphates; phosphinates; and their mixtures.

The latter can be found in the form of salts, in particular in the form of phosphonate or phosphinate ions neutralized by an appropriate counterion.

The salts may be salts of alkali or alkaline earth metals, of ammonium, of alkanolamines, in particular C2-C8, or of alkaneamines, in particular of C2-C8, of phosphonate or phosphinate.

When the aqueous lubricating composition according to the invention comprises one or more additional phosphorus compound(s), for example as described above, these can be used in a content ranging from 0.01% to 5.0% by weight, in particular ranging from 0.1% to 3.0% by weight, relative to the total mass of composition.

According to one embodiment, when the aqueous lubricating composition according to the invention comprises one or more additional phosphorus compound(s), in particular as described above, these are used in a strictly lower content. at 0.1% by weight, relative to the total mass of said composition.

Advantageously, the overall content of phosphorus compound(s), including salts of phosphate esters or any other annexed phosphorus compound, may be strictly less than 0.1% by weight, relative to the total mass of said composition. , in particular less than 0.05% by mass.

In other words, an aqueous lubricating composition used according to the invention preferably comprises a content of phosphorus compound(s) strictly less than 0.1% by weight, in particular ranging from 0.0% to 0.05%. mass, in particular less than 0.01 % by mass and more particularly less than 0.001% by mass, relative to the total mass of composition.

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

- water, preferably deionized water;

- at least one polyalkylene glycol; and said aqueous lubricating composition comprising a content of phosphorus compound(s) strictly less than 0.1% by weight, in particular ranging from 0.0% to 0.05% by weight, in particular less than 0.01% by weight and more particularly less than 0.001% by weight, relative to the total mass of the composition,

According to a particularly preferred embodiment, an aqueous lubricating composition used according to the invention is completely free of phosphorus compounds.

According to a particular embodiment, an aqueous lubricating composition required according to the invention may comprise a phosphorus content less than or equal to 0.05% by mass, in particular less than or equal to 0.02% by mass and more particularly less than or equal to 0.01% by weight. The phosphorus content can be measured by ICP (for “Inductively Coupled Plasma” in English). Advantageously, an aqueous lubricating composition required according to the invention is completely free of phosphorus.

Antifreeze compound

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

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

- water, preferably deionized water;

- at least one polyalkylene glycol; And

- at least one antifreeze compound chosen from glycols, preferably alkylene glycols; glycerol; diglycerol; triglycerol, and mixtures thereof; said aqueous lubricating composition comprising a content of phosphate ester salt(s), in particular chosen from alkali metal salts of phosphate esters, strictly less than 0.1% by weight, relative to the total mass of the composition, preferably being free of phosphate ester salts.

These compounds are known for their antifreeze action, in other words for reducing the freezing temperature of the composition.

Glycols are diols in which the two hydroxyl groups are carried by different carbon atoms, preferably by vicinal carbon atoms.

Preferably, the glycols are alkylene glycols, in particular having from 2 to 10 carbon atoms, in particular from 2 to 6 carbon atoms. As examples, monoethylene glycol, diethylene glycol and propylene glycol can be cited.

The antifreeze compound can also be chosen from glycerol, diglycerol, triglycerol and mixtures thereof.

Preferably the antifreeze compound used according to the invention is chosen from monoethylene glycol, diethylene glycol, propylene glycol, glycerol and their mixtures. Preferably, the antifreeze compound is diethylene glycol.

In particular, said antifreeze compound(s), in particular as defined above, for example diethylene glycol, can be used in an aqueous lubricating composition according to the invention in a content of at least 1.0% by weight, of preferably between 5.0% and 50% by weight, more preferably between 10% and 45% by weight, in particular between 20% and 40% by weight, relative to the total mass of the composition.

Preferably, an aqueous lubricating composition used according to the invention comprises a content of antifreeze compound(s), in particular as defined above, for example diethylene glycol, greater than or equal to 33%, in particular between 33.5% and 40% by weight, relative to the total mass of said composition.

According to a particular embodiment, the invention relates to the use, to cool and/or lubricate a propulsion system of an electric or hybrid vehicle, of an aqueous lubricating composition comprising at least:

- some water ;

- at least one polyalkylene glycol; And - at least one antifreeze compound chosen from glycols in a content greater than or equal to 33% by weight, relative to the total mass of the composition; said aqueous lubricating composition comprising a content of salt(s) of phosphate ester(s), in particular chosen from alkali metal salts of phosphate esters, strictly less than 0.1% by weight, relative to to the total mass of said composition.

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

- at least 45% by weight of water, relative to the total mass of the composition;

- at least one polyalkylene glycol; And

- at least one antifreeze compound chosen from glycols in a content greater than or equal to 33% by weight, relative to the total mass of the composition; said aqueous lubricating composition comprising a content of salt(s) of phosphate ester(s), in particular chosen from alkali metal salts of phosphate esters, strictly less than 0.1% by weight, relative to to the total mass of said composition.

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

- at least 35% by weight of water, in particular deionized water, preferably 40 to 60% by weight of water; in particular from 45 to 60% by weight of water;

- at least 10% by weight, in particular between 10 and 20% by weight, of at least one polyalkylene glycol, in particular as defined above;

- at least 5.0% by weight, in particular between 20 and 40% by weight, of at least one antifreeze compound chosen from glycols, preferably alkylene glycols; glycerol; diglycerol; triglycerol, and mixtures thereof, said antifreeze compound preferably being diethylene glycol.

According to a particular embodiment, the assembly consisting of water, said polyalkylene glycol(s), and optionally said antifreeze compound(s) represent more than 90% of the total mass of said aqueous lubricating composition, in particular more 95%, in particular more than 96%, or even more than 97%, of the total mass of said aqueous lubricating composition. Other additives

An aqueous lubricating composition according to the invention may further comprise various additives.

It is understood that said additive(s) are compatible with their use in an aqueous medium. Advantageously, the additives are used in a form that is soluble or emulsifiable in water, for example in the form of salts or ionic liquids.

Said additive(s) are of course chosen with regard to the intended application for the aqueous lubricant.

Of course, those skilled in the art will take care to choose any additives and/or their quantity in such a way that the advantageous properties of the aqueous lubricating composition according to the invention, in particular the properties in terms of reduction of pitting by mechanical fatigue ( “pitting”), and cooling, are not altered by the planned addition.

Such additives may be more particularly chosen from anti-foam agents, biocides, pH regulators, corrosion inhibitors, anti-wear and/or extreme pressure additives, sequestering agents, metal passivating agents, dyes, dispersants, emulsifying agents, and mixtures thereof.

Advantageously, an aqueous lubricating composition according to the invention may comprise one or more additives chosen from anti-foaming agents, extreme pressure agents, corrosion inhibitors, pH regulators, metal passivating agents, dyes, and their mixtures.

An aqueous lubricating composition according to the invention may more particularly comprise from 0.1 to 10% by weight of additives, in particular from 1.0 to 8.0% by weight of additives, relative to the total mass of the composition.

pH regulator

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

The said pH regulator(s), by ensuring that the pH of the aqueous lubricating composition is maintained between 8 and 15, makes it possible in particular to prevent corrosion of the surfaces. metallic, but also to promote the solubilization of the different compounds in the lubricating composition, in particular of the polyalkylene glycol(s), in particular as defined above.

The pH regulator can be chosen from the family of amines, in particular alkanolamines and amino alcohols.

It may in particular be a pH regulating additive chosen from alkanolamines, such as dimethylethanolamine (DMEA), ethanolamines, such as monoethanolamine (MEA), diethanolamine (DEA), triethanolamine (TEA), isopropanolamines, such as mono-isopropanolamine (MIPA), diisopropanolamine (DIPA) and triisopropanolamine (TIPA); diglycolamine (DGA); ethylene amines, such as ethylene diamine (EDA), diethylene triamine (DETA), triethylene tetramine (TETA) and tetraethylene pentamine (TEPA); cyclamines, such as cyclohexylamine; 2-amino-2-ethyl-1,3-propanediol; 2-amino-2-methyl-l-propanol; and their mixtures.

An aqueous lubricating composition according to the invention may in particular comprise from 0.1% to 10% by weight of pH regulating additive(s), preferably from 0.5% to 5% by weight, relative to the mass total composition.

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

Thus, in a particular embodiment, an aqueous lubricating composition required according to the invention comprises at least:

- water, in particular deionized water;

- at least one polyalkylene glycol, in particular as defined above; And

- at least one pH regulating additive making it possible to maintain the pH of said lubricating composition between 8 and 15, in particular chosen from alkanolamines, said aqueous lubricating composition comprising a content of phosphate ester salt(s), in particular chosen from alkali metal salts of phosphate esters, strictly less than 0.1% by weight, relative to the total mass of the composition, preferably being free of phosphate ester salts.

Corrosion inhibitor

An aqueous lubricating composition according to the invention may comprise at least one corrosion inhibitor agent. Corrosion inhibitors advantageously make it possible to reduce or even prevent corrosion of metal parts. The nature of said corrosion inhibitor(s) can be chosen with regard to the metal to be protected against corrosion, such as aluminum, steel, galvanized steel, yellow metals, for example copper or brass. Among the inorganic corrosion inhibitors may be mentioned nitrites, sulphites, silicates, borates, sodium, potassium, calcium or magnesium phosphates, alkali metal phosphates, hydroxides, molybdates, zinc sulphates, magnesium or nickel.

Among the organic corrosion inhibitors may be mentioned alkanolamines such as triethanolamine, aliphatic monocarboxylic acids, in particular having from 4 to 15 carbon atoms, for example octanoic acid, aliphatic dicarboxylic acids having from 4 to 15 carbon atoms. carbon, for example decane dioic acid, undecane dioic acid, dodecane dioic acid or mixtures thereof, polycarboxylic acids optionally neutralized by triethanolamine, such as 1,3,5-triazine-2,4 acid ,6-tri-(6-aminocaproic), alkanoylamidocarboxylic acids, in particular isononanoylamidocaproic acid, and mixtures thereof. Borated amides, products of the reaction of amines or amino alcohols with boric acid, can also be used.

Preferably, the corrosion inhibitor(s) are distinct from the pH regulating additive(s), in particular making it possible to maintain the pH of the lubricating composition between 8 and 15, and defined previously.

An aqueous lubricating composition according to the invention may in particular comprise from 0.1% to 5% by weight of corrosion inhibitor(s), in particular as defined above, preferably from 0.5% to 4% by weight, more preferably from 1% to 2.5% by weight, relative to the total mass of the composition.

In a particular embodiment, an aqueous lubricating composition required according to the invention comprises at least: - water, in particular deionized water;

- at least one polyalkylene glycol, in particular as defined above; And

- at least one corrosion inhibitor, in particular chosen from organic corrosion inhibitors, more particularly from aliphatic monocarboxylic acids, said aqueous lubricating composition comprising a content of phosphate ester salt(s), in particular chosen (s) among the alkali metal salts of phosphate esters, strictly less than 0.1% by weight, relative to the total mass of the composition, preferably being free of salts of phosphate esters.

Anti-wear/extreme pressure additive

An aqueous lubricating composition according to the invention may comprise at least one anti-wear and/or extreme pressure additive. Their function is to reduce wear and the coefficient of friction, or to prevent metal-metal contact by forming a protective film adsorbed on these surfaces.

There is a wide variety of anti-wear additives, among which can be cited those chosen from phosphosulfur additives such as metal alkylthiophosphates or their salts.

Additives which do not provide phosphorus are preferred, such as, for example, poly sulphides, in particular sulfur olefins.

According to a particular embodiment, an 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 used in their neutralized form, in particular by inorganic alkalizing agents or alkanolamines, emulsifiable or soluble in water.

Advantageously, an aqueous lubricating composition used according to the invention comprises less than 0.1% by weight of extreme pressure additive of the sulfur fatty acid type, in particular in a neutralized form, preferably less than 0.01% by weight, more particularly less than 0.001% by weight, relative to the total mass of the composition, or even is completely free of extreme pressure additive of the sulfur fatty acid type.

Sulfur-containing fatty acids can comprise from 8 to 22 carbon atoms, in particular

12 to 18 carbon atoms. The quantity of sulfur according to the ASTM D2622 standard provided by said sulfurized fatty acid(s) may be between 5% and 30% by weight, in particular between 10% and 20% by weight, relative to the total mass of the composition.

Preferably, the quantity of sulfur active at 150°C according to the ASTM D 1662 standard provided by said sulfur-containing fatty acid(s) in the aqueous lubricating composition according to the invention is less than or equal to 2% by weight, in particular less than or equal to 1% by weight, more particularly less than 0.1% by weight, relative to the total mass of the lubricating composition.

The term “active sulfur” within the meaning of the present invention is understood to mean the sulfur that a chemical compound is capable of giving up or releasing when this compound is placed under the conditions of the ASTM D1662 standard. The ASTM D-1662 standard defines an active sulfur level of a compound at a given temperature as a difference expressed as a weight percentage of sulfur content before and after reaction of a sample of this sulfur compound with a given quantity of copper for a fixed time.

As mentioned above, said sulfur fatty acid(s) are generally used in an aqueous lubricating composition in their form neutralized by an alkalizing agent, such as sodium hydroxide, potassium hydroxide, or an alkanolamine, such as monoethanolamine. , triethanolamine, monoisopropanolamine, diisopropanolamine and triisopropanolamine.

An aqueous lubricating composition required according to the invention may comprise between 0.01% and 10% by weight of anti-wear and/or extreme pressure additive(s), preferably between 0.2% and 5% by weight, relative to to the total mass of the composition.

Anti-foam

An aqueous lubricating composition according to the invention may comprise at least one anti-foam additive. Antifoams prevent the lubricating fluid from foaming.

This may be, for example, an anti-foaming agent based on polysiloxanes or acrylate polymers. Preferably, the anti-foaming agent is chosen from three-dimensional siloxanes.

Also, the anti-foam agents can be polar polymers such as polymethylsiloxanes or poly acrylates. In particular, an aqueous lubricating composition according to the invention may comprise from 0.001% to 3.0% by weight of anti-foam additive(s), preferably from 0.005% to 1.5% by weight, more preferably 0.01 % to 1.0% by weight, relative to the total mass of the lubricating composition.

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

- water, in particular deionized water;

- at least one polyalkylene glycol, in particular as defined above; And

- at least one anti-foam additive, in particular chosen from three-dimensional siloxanes, said aqueous lubricating composition comprising a content of phosphate ester salt(s), in particular chosen from alkali metal salts of phosphate esters, strictly less than 0.1% by weight, relative to the total mass of the composition, preferably being free of phosphate ester salts.

Metal passivating agents

An aqueous lubricating composition according to the invention may comprise at least one metal passivating agent. Metal passivating agents help protect metal parts by promoting the formation of metal oxide on their surface.

The metal passivating agents can for example be chosen from triazole derivatives, such as tetrahydrobenzotriazole (THBTZ), tolyltryazole (TTZ), benzotriazole (BTZ), amines substituted by a triazole group, such as N,N -bis(2- ethylhexyl)-1,2,4-triazol-l-yl methanamine, N'-bis(2 ethylhexyl)-4-methyl-lH- benzotriazol- 1-methyl-amine, N,N- bis(heptyl)-ar-methyl- IH-benzotriazole- 1 - methanamine, N,N-bis(nonyl)-ar-methyl- IH-benzo triazole- 1 -methanamine, N,N- bis(decyl)-ar- methyl- IH-benzotriazole-1-methanamine, N,N-bis(undecyl)-ar-methyl-1H-benzotriazole-1-methanamine, N,N-bis(dodecyl)-ar-methyl-1H-benzotriazole-l - methanamine, N,N-bis(2-ethylhexyl)-ar-methyl-lH-benzotriazole-l-methanamine, 1,2,4-triazoles, benzimidazoles, 2-alkyldithiobenzimidazoles, 2-alkyldithiobenzo thiazoles, 2-(N,N-dialkyldithiocarbamoyl)benzothiazoles, 2,5-bis(alkyldithio)-1,3,4-thiadiazoles, such as 2,5-bis(tert-octyldithio)-1,3,4- thiadiazole, 2.5-bis(tert-nonyldithio)-1,3,4-thiadiazole, 2,5-bis(tert-decyldithio)-1,3,4-thiadiazole,

2.5-bis(tert-undecyldithio)-1,3,4-thiadiazole, 2,5-bis(tert-dodecyldithio)-1,3,4-thiadiazole, 2,5-bis(tert-tridecyldithio)-l ,3,4-thiadiazole, 2,5-bis(tert-tetradecyldithio)-1,3,4-thiadiazole, 2,5-bis(tert-pentadecyldithio)-l,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)-l ,3,4-thiadiazole, 2,5-bis(N,N-dialkyldithiocarbamoyl)-1,3,4-thiadiazoles, 2-alkyldithio-5-mercaptothiadiazoles, and mixtures thereof.

Preferably the metal passivating agents are chosen from tetrahydrobenzotriazole (THBTZ), tolyltriazole (TTZ), benzotriazole (BTZ), and their salts, taken alone or in mixtures.

An aqueous lubricating composition according to the invention may in particular comprise from 0.01% to 2.0% by weight of metal passivating agent(s), preferably from 0.1% to 1.0% by weight, more preferably from 0 .2% to 0.8% by weight, relative to the total mass of the composition.

- water, in particular deionized water;

- at least one polyalkylene glycol, in particular as defined above; And

- at least one metal passivating agent, in particular chosen from triazole derivatives, more particularly chosen from tetrahydrobenzotriazole (THBTZ), tolyltriazole (TTZ), benzotriazole (BTZ), and their salts, taken alone or in mixtures, said aqueous lubricating composition comprising a content of phosphate ester salt(s), in particular selected alkali metal salts of phosphate esters, strictly less than 0.1% by weight, relative to the total mass of the composition, preferably being free of phosphate ester salts.

Dyes

An aqueous lubricating composition according to the invention may comprise one or more dyes. Colors can be natural or synthetic, usually organic. The dyes which can be used in an aqueous lubricating composition can be more particularly chosen from natural or synthetic water-soluble dyes, for example the dyes 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), xanthenes, carmine, chlorophyllin, methylene blue , anthocyanins (enocianin, black carrot and hibiscus), caramel and riboflavin.

An aqueous lubricating composition according to the invention may comprise between 0.01% and 2.0% by weight of dye(s), preferably between 0.01% and 1.5% by weight, more preferably between 0.02% and 1 .0% by mass, relative to the total mass of the composition.

- water, in particular deionized water;

- at least one polyalkylene glycol, in particular as defined above; And

- at least one dye, in particular chosen from xanthenes, said aqueous lubricating composition comprising a content of phosphate ester salt(s), in particular chosen from alkali metal salts of phosphate esters phosphate, strictly less than 0.1% by weight, relative to the total mass of the composition, preferably being free of phosphate ester salts.

Emulsifying agents

An aqueous lubricating composition according to the invention may comprise one or more emulsifying agents, also called emulgators. Their function is to generate stable emulsions in water.

The emulsifying agents may be more particularly non-ionic, such as for example ethoxylated fatty alcohols, ethoxylated fatty acids, ethoxylated fatty amides; anionic, for example KOH, NaOH soaps; sulfonates; cationic, such as quaternary ammonium compounds; or even carboxylic acid esters that are soluble or emulsifiable in water. In particular, an aqueous lubricating composition according to the invention may comprise from 0.01% to 10% by weight of emulsifying agent(s), preferably from 0.1% to 5.0% by weight, relative to the total mass. of the lubricating composition.

Sequestering agents

An aqueous lubricating composition according to the invention may comprise at least one sequestering agent. Sequestering agents, also called chelating agents, make it possible to limit the encrustation of metal ions in the composition.

As examples of sequestering agents, mention may be made of those derived from phosphonic acids and phosphonates, such as diethylenetriaminepentamethyl phosphonic acid (DTPMPA), amino tri(methylene phosphonic) acid (ATMP), acid hydroxyethane-diphosphonic acid (HEDP), 1,1-hydroxyethylidene 1,1-diphosphonate, 2-hydroxyethylamine di(methylene phosphonic) acid (HEAMBP), diethylene triamino penta(methylene phosphonic) acid (DTMP), multifunctional organic acids and hydroxy acids, such as ethylene diamine tetraacetic acid (EDTA), pteroyl-L-glutamic acid (PGLU), polyorganic acids, such as maleic acid and polyaspartic acid , polysaccharides and carbohydrates, such as inulin, carboxymethylinulin and carboxymethylchitosan.

An aqueous lubricating composition according to the invention may comprise from 0.001% to 2.0% by weight of sequestering agent(s), preferably from 0.01% to 1.0% by weight, relative to the total mass of the composition. .

Biocides and fungicides

An aqueous lubricating composition according to the invention may comprise at least one biocidal and/or fungicidal agent. Biocides and fungicides can be used to improve the biological stability of the composition by limiting the proliferation of bacteria, fungi and yeasts in the lubricating fluid.

Such biocides can be chosen from parabens, aldehydes, reactive acetylacetone compounds, isothiazolinones, phenolic compounds, acid salts, halogenated compounds, quaternary ammoniums, certain alcohols and their mixtures.

Preferably, the biocides can be chosen from optionally substituted benzisothiazolinones (BIT), such as N-butyl-1,2-benzisothiazolin-3-one, methylisothiazolinones (MIT), mixtures of methylisothiazolinone and chloromethylisothiazolinone (MIT/CMIT), orthophenyl-phenol (OPP) or its sodium salt, 3-iodo-2-propynylbutylcarbamate (IPBC), chloro-cresol and N,N-methylene-bis-morpholine (MBM); sorbic acid; preferably from orthophenyl-phenol (OPP) or its sodium salt, 3-iodo-2-propynylbutylcarbamate, chloro-cresol, benzisothiazolinones and N,N-methylene-isomorpholine.

An aqueous lubricating composition according to the invention may in particular comprise between 0.01% and 10% by weight of biocide(s) and/or fungicide(s), preferably between 0.5% and 5.0% by weight, relative to the total mass of the composition.

- water, in particular deionized water;

- at least one polyalkylene glycol, in particular as defined above; And

- one or more additives chosen from anti-foaming agents, corrosion inhibitors, pH regulators, metal passivating agents, dyes, in particular as defined above, said aqueous lubricating composition comprising a salt content (s) of phosphate ester(s), in particular chosen from alkali metal salts of phosphate esters, strictly less than 0.1% by mass, relative to the total mass of the composition, of preferably being free of phosphate ester salts.

- water, in particular deionized water;

- at least one polyalkylene glycol, in particular as defined above;

- at least one antifreeze compound chosen from glycols, preferably alkylene glycols; glycerol; diglycerol; triglycerol, and mixtures thereof; And

- one or more additives chosen from anti-foaming agents, corrosion inhibitors, pH regulators, metal passivating agents, dyes, in particular as defined above, said aqueous lubricating composition comprising a salt content ester(s) ZI phosphate, in particular chosen from alkali metal salts of phosphate esters, strictly less than 0.1% by weight, relative to the total mass of the composition, preferably being free of salts of esters of phosphate.

According to a particular embodiment, an aqueous lubricating composition used according to the invention comprises:

- at least 35% by weight of water, in particular from 40 to 60% by weight, in particular at least 50% by weight of water, preferably deionized water;

- from 5.0% to 50% by weight, in particular from 10 to 20% by weight, of at least one polyalkylene glycol, in particular as defined above;

- optionally from 5.0% to 45%, in particular from 20 to 40% by weight, of at least one antifreeze compound, chosen from glycols, preferably alkylene glycols; glycerol; diglycerol; triglycerol, and mixtures thereof; preferably diethylene glycol; And

- optionally from 0.1% to 10% by weight of one or more additives chosen from anti-foaming agents, extreme pressure agents, corrosion inhibitors, pH regulators, metal passivating agents, dyes, emulsifying agents, sequestering agents, and mixtures thereof, said aqueous lubricating composition comprising a content of phosphate ester salt(s), in particular chosen from alkali metal salts of phosphate esters , strictly less than 0.1% by weight, preferably being free of phosphate ester salts; the contents being expressed in relation to the total mass of the lubricating composition.

In particular, an aqueous lubricating composition used according to the invention may consist of:

- optionally from 0.1% to 10% by weight of one or more additives chosen from anti-foam agents, extreme pressure agents, corrosion inhibitors, pH regulators, metal passivating agents, dyes, emulsifying agents, sequestering agents, and mixtures thereof, said aqueous lubricating composition comprising a content of phosphate ester(s) salt(s), in particular chosen ( s) among the alkali metal salts of phosphate esters, strictly less than 0.1% by weight, in particular being free of phosphate ester salts; the contents being expressed relative to the total mass of the lubricating composition, the remainder consisting of water, preferably deionized water.

It is understood that the different particular embodiments described above can be combined, as far as possible, to define other particular embodiments.

In particular, each of the additives specifically described above can be introduced alone, or in combination with at least one other of the additives specifically described, which defines different embodiments of an aqueous lubricating composition according to the invention. In other words, particular embodiments of the invention are defined by an aqueous lubricating composition according to the invention, comprising at least water; and one or more polyalkylene glycol(s), in particular as defined above, preferably in the proportions indicated above, and further comprising one or more of the additives specifically detailed in the text.

- from 40 to 55% by weight of water, in particular deionized water, in particular more than 45% by weight of water;

- from 10 to 15% by weight of one or more polyalkylene glycols;

- optionally from 30 to 40% by weight of an antifreeze compound chosen from glycols, preferably alkylene glycols; glycerol; diglycerol; triglycerol, and mixtures thereof; preferably diethylene glycol;

- optionally from 0.1% to 10% by weight of one or more additives chosen from anti-foaming agents, corrosion inhibitors, pH regulators, metal passivating agents, dyes, emulsifying agents, agents sequestering, and their mixtures, said composition being free of phosphate ester salts and, more preferably free of phosphorus compounds, said composition being free of extreme pressure additives of sulfur fatty acid type.

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

More generally, an aqueous lubricating composition used according to the invention comprises one or more polycyclic dianthraquinone type compound(s) in a content strictly less than 0.1% by weight, preferably less than or equal to 0.01% by weight, more preferably less than or equal to 0.01% by weight, relative to the total weight of the composition. In particular, an aqueous lubricating composition used according to the invention is completely free of polycyclic dianthraquinone type compounds.

APPLICATION

As indicated previously, an aqueous lubricating composition can be 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 vehicle or hybrid, in particular of the engine, the power electronics, the transmission and/or the battery, in an electric or hybrid vehicle, preferably in an electric vehicle.

As shown schematically in Figure 1, the propulsion system of an electric or hybrid vehicle comprises in particular the electric motor part (1), an electric battery (2) and a transmission, and in particular a speed reducer (3). As batteries suitable for the propulsion systems of an electric or hybrid vehicle, we can cite in particular Li-ion batteries or even nickel-cadmium batteries. 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 powered by an electric current. This generates a rotating magnetic field. The rotor itself comprises coils, permanent magnets or other magnetic materials, and is rotated by the rotating magnetic field.

The power electronics (11), the stator (13) and the rotor (14) of a propulsion system (1) are parts whose structure is complex and generates a large amount of heat during operation of the engine . It is therefore imperative to ensure cooling of the electric motor and the power electronics.

A bearing (12) is generally integrated between the stator (13) and the rotor (14). A transmission, and in particular a speed reducer (3), makes it possible to reduce the rotational speed at the output of the electric motor and to adapt the speed transmitted to the wheels, at the same time making it possible to control the speed of the vehicle.

Advantageously, an aqueous lubricating 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. In particular, it is intended to be placed in direct contact with the battery.

Cooling can be implemented by any method known to those skilled in the art. The battery can be immersed or semi-immersed, static or circulating, in said composition.

As examples of direct contact, we can cite cooling by injection, jet, spraying or even by formation of a mist from the composition required according to the invention under pressure and by gravity on the battery.

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.

An aqueous lubricating composition according to the invention can simultaneously be used to lubricate the different parts of a propulsion system of an electric or hybrid vehicle, in particular of the engine, the power electric, the transmission and/or there battery, more particularly bearings located between the rotor and the stator of an electric motor, or the transmission, in particular the reduction gear, in an electric or hybrid vehicle.

More particularly, an aqueous lubricating composition according to the invention makes it possible to cool and lubricate an electric motor of an electric or hybrid vehicle. It is particularly effective for cooling the power electronics and/or the rotor and/or the stator of an electric motor. It also provides lubrication of the bearings located between the rotor and the stator of an electric motor of an electric or hybrid vehicle.

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

Thus, advantageously, it is for example possible, by implementing a single composition according to the invention, to ensure both the cooling of the battery and the lubrication of the transmission, in particular the reduction gear, in a electric or hybrid vehicle.

Advantageously, the present invention relates to the use of an aqueous lubricating composition as defined according to the invention, to lubricate and/or cool the reduction gear and/or the motor and/or the power electronics of an electric vehicle.

The particular, advantageous or preferred characteristics relating to the uses and methods of implementing an aqueous lubricating composition according to the invention, make it possible to define particular, advantageous or preferred modes of an aqueous lubricating composition according to the invention.

Example

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

Measuring pitting by mechanical fatigue

Pitting by mechanical fatigue (or “pitting” in English) is evaluated by a test on an MPR tribometer (for “Micro Pitting Rig” in English).

The MPR tribometer is a machine bringing a central roller (diameter 12 mm) into contact with three rings (diameter 54 mm) arranged around the roller. This configuration geometry allows the test roller to be subjected to a large number of rolling contact cycles over a short test period, thereby encouraging pitting by mechanical fatigue.

The test is carried out for a period of 20 hours. The fatigue pitting phenomenon is detected by an accelerometer connected to a vibration monitor. When the vibration setpoint is exceeded due to the occurrence of tapping, the test is stopped.

The performance of the compositions in terms of stitching by mechanical fatigue is described as insufficient if the stitching time is less than 10 hours, average if the stitching time is between 10 hours and 20 hours and good in the absence of stitching after 20 hours of testing.

EXAMPLE 1

Preparation of lubricating compositions

Two aqueous lubricating compositions (Il and 12) according to the invention, and a comparative lubricating composition (Cl) comprising a phosphorus compound content greater than 0.1

% by weight, were formulated by simple mixing, at room temperature, of the following components, in the mass percentages indicated in Table 1 below. The percentages are therefore expressed in mass relative to the total mass of the composition

[Table 1]

Additive mixture comprising one or more anti-corrosion additives, one or more metal passivating agents, one or more anti-foam additives and/or one or more colorants.

EXAMPLE 2 Characterization of the compositions according to the invention and comparative in terms of pitting by mechanical fatigue

The performances in terms of pitting by mechanical fatigue of composition 12, according to the invention, and of the comparative composition Cl, were evaluated according to the protocol detailed above. The results are presented in Table 2 below:

[Table 2]

As emerges from these results, composition 12, in accordance with the invention, presents resistance performances to pitting by mechanical fatigue which are much higher than those obtained for the comparative composition Cl, characterized in particular by the presence of a phosphorus compound in a content greater than 0.1% by weight, relative to the total weight of the composition. Furthermore, compositions II and 12 according to the invention have excellent performance in terms of cooling in an electric or hybrid vehicle propulsion system, in particular cooling of the electric motor. Consequently, an aqueous lubricating composition according to the invention can be used for the lubrication and/or cooling of an electric or hybrid vehicle propulsion system, without having a detrimental effect on mechanical fatigue pitting of the parts. lubricated and/or cooled using said composition.

Claims

1. Use, to cool and/or lubricate a propulsion system of an electric or hybrid vehicle, of an aqueous lubricating composition comprising at least:

- some water ; And

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

3. Use according to the preceding claim, in which the aqueous lubricating composition comprises at least 1.0% by weight of antifreeze compound(s), preferably between 5.0% and 50% by weight, more preferably between 10% and 45% by weight , in particular between 20% and 40% by weight, relative to the total mass of said composition.

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

5. Use according to any one of the preceding claims, in which the aqueous lubricating composition comprises at least 20% by weight of water, in particular deionized water, preferably between 35% and 90% by weight, more preferably between 40%. and 75% by weight, in particular between 40 and 60% by weight, relative to the total mass of said composition.

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

7. Use according to any one of the preceding claims, characterized in that said polyalkylene glycol(s) have a kinematic viscosity measured at 100 °C (KV100), according to ASTM D445, between 100 and 25,000 mm ² /s, in particular between 150 and 10,000 mm ² /s.

8. Use according to any one of the preceding claims, in which the aqueous lubricating composition comprises at least 5.0% by weight of polyalkylene glycol(s), preferably between 5.0% and 50% by weight, more preferably between 10%. and 40% by weight, in particular between 10% and 20% by weight, relative to the total mass of the composition.

9. Use according to any one of the preceding claims, in which the aqueous lubricating composition comprises less than 0.05% by weight of salt(s) of phosphate ester(s), in particular chosen from salts of alkali metals of phosphate esters, preferably less than 0.01% by weight, more particularly less than 0.001% by weight, relative to the total mass of the composition, the aqueous lubricating composition being more preferably completely free of ester salts phosphate, in particular alkali metal salts of phosphate esters.

10. Use according to any one of the preceding claims, in which the aqueous lubricating composition further comprises at least one additive chosen from anti-foaming agents, biocides, pH regulators, corrosion inhibitors, anti-foam additives. wear and/or extreme pressure, sequestering agents, metal passivating agents, dyes, dispersants, emulsifying agents, and mixtures thereof, preferably chosen from anti-foam agents, extreme pressure agents, inhibitors corrosion protection, pH regulators, metal passivating agents, dyes, and mixtures thereof.

11. Use according to any one of the preceding claims, in which the aqueous lubricating composition further 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. Use according to any one of the preceding claims, in which the aqueous lubricating composition comprises less than 0.1% by weight of extreme pressure additive of the sulfur fatty acid type, preferably less than 0.01% by weight, more particularly less than 0.001% by weight, relative to the total mass of the composition, more preferably is completely free of extreme pressure additive of the sulfur fatty acid type.

13. Use of an aqueous lubricating composition as defined according to any one of the preceding claims, to lubricate and/or cool the reduction gear and/or the motor and/or the power electronics of an electric vehicle.

14. Use of an aqueous lubricating composition intended to lubricate and/or cool a propulsion system of an electric or hybrid vehicle, comprising at least:

- some water ; And

- at least one polyalkylene glycol; said aqueous lubricating composition comprising a content of salt(s) of phosphate ester(s), in particular chosen from alkali metal salts of phosphate esters, strictly less than 0.1% by weight, relative to to the total mass of said composition, to reduce pitting by mechanical fatigue, of the mechanical part(s) of said propulsion system, brought into contact with said composition.

15. Aqueous lubricating composition for the lubrication and/or cooling of an electric or hybrid propulsion system, comprising at least:

- at least 45% by weight of water, relative to the total mass of the composition; And

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