WO2024223792A1 - Composition for cooling and/or lubricating at least one element of a moving or stationary system - Google Patents

Abstract

The invention relates to a lubricating and/or cooling composition comprising one or more diester(s) of formula (1), in which R represents a linear or branched divalent alkylene or alkenylene radical comprising from 2 to 8 carbon atoms; R¹ and R² represent, independently of one another, a monovalent hydrocarbon radical optionally comprising one or more heteroatoms, it being understood that at least one of R¹ and R² comprises at least one ether function, said diester(s) of formula (1) having a kinematic viscosity at 100°C ranging from 1 to 6 mm²/s The invention further relates to the use of the composition for cooling and/or lubricating at least one element of a moving or stationary system.

Description

Cooling and/or lubricating composition for at least one element of a mobile or stationary system

Technical field

The present invention relates to the field of compositions for cooling and/or lubricating at least one element of a mobile or stationary system. The present invention relates in particular to compositions for cooling and/or lubricating a heavy or light vehicle, a public works machine, stationary systems such as energy storage systems, charging stations, chargers, data centers, 5G antennas, photovoltaic panels, wind turbines, turbines, switching devices, inverters and medical devices. It aims in particular to propose a cooling and/or lubricating composition compatible with its implementation at the level of transmissions in thermal engines and/or reducers in electric motors.

Previous technique

Improving the performance of lubricants is a constant concern. In particular, to meet increasing environmental requirements, manufacturers of mobile or stationary systems are seeking to improve the performance of lubricant compositions. This issue concerns both manufacturers of mobile systems, such as automobile manufacturers, particularly those of new generation vehicles, including electric vehicles, and manufacturers of stationary systems, such as energy storage systems, charging stations, chargers, data centers, 5G antennas, photovoltaic panels, wind turbines, turbines, switching devices, inverters and medical devices.

A battery is an electricity-generating device in which chemical energy is converted into electrical energy. The chemical energy consists of electrochemically active compounds deposited on at least one face of electrodes arranged in the electrochemical generator. The electrical energy is produced by electrochemical reactions during a discharge of an electrochemical cell. A battery consists of several electrochemical cells. A lithium-ion electrochemical cell is based on the principle of reversible insertion of lithium into a host structure in an electrochemically active manner.

In the field of electrochemical cells such as lithium-ion cells, the temperature of the cells must be managed in order to maintain the temperature within an adequate range of the cell.

In the automotive sector, the evolution of international standards for the reduction of CO2 emissions, but also for the reduction of 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 vehicles by a number of car companies.

For the purposes of the present invention, the term “electric vehicle” means a vehicle comprising an electric motor as the sole means of propulsion, whereas a hybrid vehicle comprises a combustion engine and an electric motor as combined means of propulsion.

For the purposes of the present invention, the term “propulsion system” means a system comprising the mechanical parts required for the propulsion of an electric vehicle. The propulsion system thus more particularly includes an electric motor comprising the rotor-stator assembly of the power electronics (dedicated to speed regulation), a transmission (also called a reducer, and when the reducer is attached to the motor, it is then referred to as a geared motor) and a battery. The battery itself is generally made up of a set of electrical accumulators, called cells.

Generally speaking, it is necessary to implement, in mobile or stationary systems, compositions to meet the lubrication and/or cooling constraints of the different elements of these systems. Particularly in the field of electric vehicles, electric drive systems generate heat during operation via the electric motor, power electronics and batteries. Since the amount of heat generated is greater than the amount of heat normally dissipated to the environment, it is necessary to ensure cooling of the motor, power electronics and batteries. In general, cooling is carried out on several parts of the drive 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.

Traditionally, it is known to cool electric motors with air or water, possibly combined with glycol. However, with the advent of increasingly smaller and more powerful motors, these cooling methods are no longer sufficient. In addition, the heat that a battery can generate, especially during rapid charging, cannot be extracted by the methods traditionally used.

Thus, alternative methods of cooling and lubricating propulsion systems, especially batteries, have recently been proposed.

In this respect, lubricating compositions have been proposed to ensure the dual function of lubrication and cooling. Lubricating compositions are conventionally composed of one or more base oils, to which are generally associated several additives dedicated to boosting the lubricating performance of the base oils, such as for example friction modifier additives.

By way of example, document WO 2018/078290 proposes to implement, for cooling and/or lubricating a motorization system of an electric vehicle, a composition comprising at least one polyalkylene glycol obtained by polymerization or copolymerization of alkylene oxides comprising from 2 to 8 carbon atoms.

The invention aims specifically to propose a new composition, suitable for its implementation for the cooling and/or lubrication of at least one element of a mobile or stationary system, of the propulsion systems of electric or hybrid vehicles, in particular to reduce the fuel consumption of a vehicle equipped with a transmission member.

Summary of the invention The present invention thus relates to a lubricating and/or cooling composition comprising one or more diester(s) of formula (1),

dans laquelle [Chem 1]

in which

R represents a divalent alkylene or alkenylene radical, linear or branched, containing from 2 to 8 carbon atoms;

R ¹ and R ² represent, independently of each other, a monovalent hydrocarbon radical optionally comprising one or more heteroatoms, it being understood that at least one of R ¹ and R ² comprises at least one ether function, said diester(s) of formula (1) having a kinematic viscosity at 100°C ranging from 1 to 6 mm ² /s.

According to one embodiment, R ¹ and R ² have one or more of the following characteristics:

- R ¹ and/or R ² comprise(s) from 1 to 6 ether functions, preferably from 1 to 4 ether functions, even more preferably from 1 to 3 ether functions;

- R ¹ and/or R ² contain(s) from 2 to 20 carbon atoms, preferably from 3 to 16 carbon atoms, even more preferably from 8 to 10 carbon atoms;

- R ¹ and/or R ² are chosen from a radical of formula (CHR ³ CH2O) _n R ⁴ , where R ³ represents a hydrogen atom or a methyl, preferably a hydrogen atom; R ⁴ represents an alkyl having from 1 to 10 carbon atoms, preferably from 1 to 6 carbon atoms, preferably chosen from a methyl, an ethyl, a propyl or a butyl; and n is an integer ranging from 1 to 4, preferably from 1 to 3;

- R ¹ and/or R ² are chosen from CH3(CH2)3O(CH2)2-, CH3(CH2)3(OCH2CH2)2-, CH3(OCH ₂ CH ₂ )3- and CH3(CH2)3(OCH ₂ CH ₂ )3-.

According to one embodiment, the radical R is chosen from the radicals -(Cfkjx-, x ranging from 2 to 8, even more preferably x ranging from 4 to 7. According to one embodiment, at least one of said diesters of formula (1) is formed between:

- two alcohols R ¹ -OH and R ² -OH, identical or different, at least one of said alcohols comprising at least one ether function, and

- a dicarboxylic acid R[C(O)OH]2 comprising a linear or branched alkylene or alkenylene chain comprising 4 to 8 carbon atoms.

According to one embodiment, said diester(s) is (are) chosen from:

- a diester formed from a mono-, di- or tri-ethylene glycol monoalkyl ether and succinic acid,

- a diester formed from a mono-, di- or tri-ethylene glycol monoalkyl ether and adipic acid,

- a diester formed from a mono-, di- or tri-ethylene glycol monoalkyl ether and glutaric acid,

- a diester formed from a mono-, di- or tri-ethylene glycol monoalkyl ether and pimelic acid,

- a diester formed from a mono-, di- or tri-ethylene glycol monoalkyl ether and suberic acid,

- a diester formed from a mono-, di- or tri-ethylene glycol monoalkyl ether and azelaic acid,

- a diester formed from a mono-, di- or tri-ethylene glycol monoalkyl ether and sebacic acid, said alkyl group preferably having from 1 to 10 carbon atoms, preferably from 1 to 6 carbon atoms, more preferably from 1 to 4 carbon atoms.

According to one embodiment, said diester(s) of formula (1) are formed with at least one alcohol chosen from monoethylene glycol monobutyl ether, diethylene glycol monobutyl ether, triethylene glycol monomethyl ether and triethylene glycol monobutyl ether. According to one embodiment, the composition comprises at least 5% by mass, preferably at least 10% by mass, more preferably from 10% to 100% of said diester(s), relative to the total mass of the composition.

According to one embodiment, the composition according to the invention comprises, in addition to said diester(s), at least one additive chosen from antioxidants, pour point lowering additives, anti-foaming agents, anti-corrosion agents, anti-wear and/or extreme pressure additives, friction modifiers, detergents, dispersing agents, viscosity index improvers, thickeners, copper passivators and mixtures thereof, preferably said at least one additive is chosen from viscosity index improvers, pour point lowering additives, anti-wear additives, antioxidants and mixtures thereof.

According to one embodiment, the composition comprises:

- from 5 to 90% by mass, preferably from 10 to 70% by mass, more preferably from 10 to 50% by mass, of said diester(s) of formula (1),

- one or more base oils different from said diester(s) and/or one or more additives distinct from said diester(s) and distinct from the base oil(s), the base oil(s) preferably representing a proportion of 10 to 95% by mass, preferably 30 to 90% by mass, more preferably 50 to 90% by mass, the additive(s) preferably representing a proportion of up to 20% by mass, preferably 0.05 to 15% by mass, more preferably 0.1 to 10% by mass, even more preferably 0.5 to 7% by mass, or even 1 to 5% by mass, relative to the total mass of the composition.

The applicant has surprisingly discovered that when the diester according to the invention is formed between a dicarboxylic acid chosen from succinic acid, adipic acid, glutaric acid, pimelic acid, suberic acid, azelaic acid, sebacic acid and mixtures thereof, and a mono-, di- or tri-ethylene glycol monoalkyl ether, in particular when said diester of formula (1) is formed with at least one alcohol chosen from monoethylene glycol monobutyl ether, diethylene glycol monobutyl ether, triethylene glycol monomethyl ether and triethylene glycol monobutyl ether, the composition comprising the diester exhibit both very good thermal properties and very good lubricating properties (in friction and traction) compared to the diesters of the prior art.

The applicant has also discovered that the diesters according to the invention make it possible to simultaneously obtain a pour point below -20°C (or even below -30°C) and a thermal conductivity at 30°C of at least 150 mW.m'fK' ¹ (or even at least 155 mW.m'hK' ¹ ), while having improved lubrication properties (lower coefficients of friction and traction).

The invention also relates to a use of a composition according to the invention for cooling and/or lubricating at least one element of a mobile or stationary system.

According to one embodiment, the composition according to the invention is a lubricating and/or cooling composition comprising one or more diester(s) of formula (1),

dans laquelle [Chem 1]

in which

R represents a divalent alkylene or alkenylene radical, linear or branched, containing from 2 to 8 carbon atoms;

dans laquelle R ¹ and R ² represent, independently of each other, a monovalent hydrocarbon radical optionally comprising one or more heteroatoms, it being understood that at least one of R ¹ and R ² comprises at least one ether function, said diester(s) of formula (1) having a kinematic viscosity at 100°C ranging from 1 to 6 mm ² /s, said diester(s) of formula (1) being formed with at least one alcohol chosen from monoethylene glycol monobutyl ether, diethylene glycol monobutyl ether, triethylene glycol monomethyl ether and triethylene glycol monobutyl ether. According to one embodiment, the invention relates to the use of a composition for lubricating and/or cooling transmissions in thermal engines and/or reducers in electric motors of a mobile system, said lubricating and/or cooling composition comprising one or more diester(s) of formula (1), [Chem 1]

in which

R represents a divalent alkylene or alkenylene radical, linear or branched, containing from 2 to 8 carbon atoms;

R ¹ and R ² represent, independently of each other, a monovalent hydrocarbon radical optionally comprising one or more heteroatoms, it being understood that at least one of R ¹ and R ² comprises at least one ether function, said diester(s) of formula (1) having a kinematic viscosity at 100°C ranging from 1 to 6 mm ² /s.

According to one embodiment, the invention relates to the use of a composition for lubricating and/or cooling transmissions in thermal engines and/or reducers in electric motors of a mobile system, said lubricating and/or cooling composition comprising one or more diester(s) of formula (1), [Chem 1]

. f

H '• ¹ H'

C R G in which

R represents a divalent alkylene or alkenylene radical, linear or branched, containing from 2 to 8 carbon atoms;

R ¹ and R ² represent, independently of each other, a monovalent hydrocarbon radical optionally comprising one or more heteroatoms, it being understood that at least one of R ¹ and R ² comprises at least one ether function, said diester(s) of formula (1) having a kinematic viscosity at 100°C ranging from 1 to 6 mm ² /s, said diester(s) of formula (1) being formed with at least one alcohol chosen from monoethylene glycol monobutyl ether, diethylene glycol monobutyl ether, triethylene glycol monomethyl ether and triethylene glycol monobutyl ether.

According to one embodiment, the mobile or stationary system is selected from heavy or light vehicles, public works machinery, energy storage systems, charging stations, chargers, data centers, 5G antennas, photovoltaic panels, wind turbines, turbines, switching devices, inverters and medical devices, or a combination of these systems.

According to one embodiment, the composition according to the invention is used to lubricate and/or cool transmissions in thermal engines and/or reducers in electric motors of a mobile system.

According to one embodiment, the mobile system is a vehicle with a thermal engine, the composition being used to reduce the fuel consumption of said vehicle equipped with a transmission member, in particular a gearbox and/or an axle, lubricated using this composition.

According to one embodiment, the mobile system is an electric or hybrid vehicle, the composition being used to improve the efficiency of reducers in electric motors.

According to one embodiment, the mobile system is an electric or hybrid vehicle, the composition being used to extend the battery life of the electric or hybrid vehicle and/or to cool the battery and/or the power electronics of the electric or hybrid vehicle, in particular a lithium-ion or nickel-cadmium battery.

The present invention makes it possible to provide diesters having excellent properties, in particular the diesters according to the invention having both very good thermal properties and very good lubricating properties (in friction and traction). Other characteristics, variants and advantages of the implementation of a diester according to the invention will emerge more clearly upon reading the description and examples which follow, given as an illustration and not as a limitation of the invention.

In the remainder of the text, the expressions “between ... and ...”, “ranging from ... to . . .” and “varying from ... to . . .” are equivalent and are intended to mean that the limits are included, unless otherwise stated.

Unless otherwise indicated, the expression “comprising a” must be understood as “comprising at least one”.

Brief description of the drawings

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

Detailed description

First, the invention relates to a lubricating and/or cooling composition comprising one or more diester(s) of formula (1), formula (1) being the following formula:

dans laquelle [Chem 1]

in which

R represents a divalent alkylene or alkenylene radical, linear or branched, containing from 2 to 8 carbon atoms;

R ¹ and R ² represent, independently of each other, a monovalent hydrocarbon radical optionally comprising one or more heteroatoms, it being understood that at least one of R ¹ and R ² comprises at least one ether function, said diester(s) have a kinematic viscosity at 100°C ranging from 1 to

6 mm ² /s. The invention also relates to the use of a composition comprising one or more diester(s) of formula (1) for cooling and/or lubricating at least one element of a mobile or stationary system.

The invention can use one or more diesters, each of said diesters being formed between: two alcohols R ¹ -OH and R ² -OH, identical or different, at least one of said alcohols comprising at least one ether function, and a dicarboxylic acid R[C(O)OH]2 comprising a linear or branched alkylene or alkenylene chain, comprising from 4 to 8 carbon atoms.

In particular, it is possible to prepare a mixture of diesters used according to the invention by reacting a dicarboxylic acid with a mixture of alcohols, preferably chosen from mono-alcohols and diols.

By "mono-alcohol" we mean a compound containing (exactly) one hydroxyl function (-OH).

By "diol" we mean a compound containing (exactly) two hydroxyl (-OH) functions.

By “alcohol comprising at least one ether function” is meant a compound comprising at least one hydroxyl function (-OH) and at least one ether function (-O-).

By “compound comprising at least one ether function” is meant that the compound comprises at least one oxygen atom linked by single bonds to two carbon atoms.

For the purposes of the present invention, the term “diester formed between two alcohols and a dicarboxylic acid” means a compound obtained by two esterification reactions, each esterification reaction being carried out between one of the two carboxylic functions of the diacid and a hydroxyl function of one of the two alcohols.

According to the invention, at least one of the two alcohols comprises at least one ether function, the other alcohol being able to be an aliphatic alcohol or an alcohol comprising at least one ether function. The alcohols comprising at least one ether function may be identical or different.

By "aliphatic alcohol" is meant an alcohol devoid of heteroatoms except for the oxygen atom forming the hydroxyl function. For example, it is possible to react a dicarboxylic acid and three monoalcohols A1, A2 and A3. Thus, according to this example, the mixture of diesters falling within the scope of the present invention is likely to comprise:

- a diester formed between the dicarboxylic acid and two monoalcohols Al,

- a diester formed between the dicarboxylic acid and two monoalcohols A2,

- a diester formed between the dicarboxylic acid and two monoalcohols A3,

- a diester formed between the dicarboxylic acid and a monoalcohol Al and a monoalcohol A2,

- a diester formed between the dicarboxylic acid and a monoalcohol Al and a monoalcohol A3,

- a diester formed between the dicarboxylic acid and a monoalcohol A2 and a monoalcohol A3.

Diester implemented according to the invention

As mentioned above, at least one of said diester(s) used according to the invention is (are) typically formed between two alcohols and a dicarboxylic acid, at least one alcohol comprising at least one ether function.

A diester according to the invention is defined by the formula (1):

dans laquelle [Chem 1]

in which

R represents a divalent alkylene or alkenylene radical, linear or branched, containing from 2 to 8 carbon atoms;

R ¹ and R ² represent, independently of one another, a monovalent hydrocarbon radical optionally comprising one or more heteroatoms, it being understood that at least one of R ¹ and R ² comprises at least one ether function.

For the purposes of the invention, the term “monovalent hydrocarbon radical” means a linear or branched alkyl or alkenyl chain, optionally comprising one or more heteroatoms, in particular one or more oxygen atoms. According to one embodiment, R ¹ or R ² do not contain any heteroatom.

According to one embodiment, R ¹ and/or R ² comprise at least one heteroatom, preferably from 1 to 6 heteroatoms, preferentially from 1 to 4 heteroatoms, even more preferentially from 1 to 3 heteroatoms.

Preferably, R ¹ and/or R ² comprise at least one oxygen atom, preferably from 1 to 6 oxygen atoms, preferentially from 1 to 4 oxygen atoms, even more preferentially from 1 to 3 oxygen atoms,

Preferably, R ¹ and/or R ² comprise(s) from 1 to 6 ether functions, preferably from 1 to 4 ether functions, even more preferably from 1 to 3 ether functions.

According to one embodiment, R ¹ and/or R ² comprise a hydroxyl function. Preferably, according to this embodiment, the hydroxyl function of R ¹ and/or R ² is carried by a primary carbon atom. A carbon atom is said to be primary when it is linked to only one other carbon atom.

According to one embodiment, the radicals R ¹ and/or R ² are chosen independently of one another from a radical of formula -(CHR ³ CH2O) _n R ⁴ , where R ³ represents a hydrogen atom or a methyl, preferably a hydrogen atom; R ⁴ represents an alkyl having from 1 to 10 carbon atoms, preferably from 1 to 6 carbon atoms, preferably chosen from a methyl, an ethyl, a propyl or a butyl; and n is an integer ranging from 1 to 4, preferably from 1 to 3.

Preferably R ¹ and/or R ² are independently selected from CH ₃ (CH ₂ ) 3 O (CH 2 ) 2 -, CH ₃ (CH 2 ) 3 (OCH ₂ CH 2 ) 2 -, CH 3 (OCH ₂ CH ₂ ) 3 - and CH ₃ (CH 2 ) 3 (OCH ₂ CH 2 ) 3 -.

According to a particular embodiment, R ¹ and R ² are identical.

Typically, the radicals R ¹ and R ² are radicals resulting from the reaction of two alcohols of formula R ¹ -OH and R ² -OH, identical or different, with a diacid, at least one alcohol among R ¹ -OH and R ² -OH comprises at least one ether function. Said alcohols R ¹ -OH and R ² -OH, identical or different, can be chosen from monoalcohols and diols, preferably monoalcohols.

Preferably, said at least one alcohol comprising an ether function is chosen from a monoethylene glycol monoalkyl ether, a diethylene glycol monoalkyl ether or a triethylene glycol monoalkyl ether, preferably from a diethylene glycol monoalkyl ether or a triethylene glycol monoalkyl ether, said alkyl groups preferably having from 1 to 10 carbon atoms, preferably from 1 to 6 carbon atoms, more preferably from 1 to 4 carbon atoms. Preferably, said at least one alcohol is chosen from a diethylene glycol monoalkyl ether or a triethylene glycol monoalkyl ether, the alkyl groups are from 1 to 10 carbon atoms, preferably from 1 to 6 carbon atoms, more preferably from 1 to 4 carbon atoms.

Preferably, at least one alcohol is selected from monoethylene glycol monobutyl ether, diethylene glycol monobutyl ether, triethylene glycol monomethyl ether and triethylene glycol monobutyl ether.

The alcohols used according to the invention may be commercially available or synthesized according to any method known to those skilled in the art.

For the purposes of the invention, the term “divalent alkylene radical” means a saturated, linear or branched hydrocarbon chain, consisting of carbon and hydrogen atoms (therefore not containing any heteroatoms).

For the purposes of the invention, the term “divalent alkenylene radical” means an unsaturated, linear or branched hydrocarbon chain, consisting of carbon and hydrogen atoms (therefore not containing any heteroatoms).

According to the invention, the radical R contains from 2 to 8 carbon atoms, more preferably from 3 to 8 carbon atoms, even more preferably from 4 to 7 carbon atoms.

Preferably, R is chosen from the radicals -(CH2) _X -, x being an integer ranging from 2 to 8, even more preferably x ranges from 4 to 7.

Preferably, when the invention uses a mixture of diesters corresponding to formula (1), said diesters are formed from the same dicarboxylic acid. According to this embodiment, all the radicals R of the diesters of formula (1) are identical.

By "dicarboxylic acid" is meant an acid comprising (exactly) 2 carboxyl functions -(C(O)OH).

According to one embodiment of the invention, the dicarboxylic acid comprises a linear or branched alkylene or alkenylene chain comprising from 4 to 8 carbon atoms, preferably a linear or branched alkylene chain comprising from 4 to 8 carbon atoms, more preferably a linear alkylene chain comprising from 4 to 8 carbon atoms.

Preferably, the dicarboxylic acid is chosen from succinic acid, adipic acid, glutaric acid, pimelic acid, suberic acid, azelaic acid, sebacic acid and mixtures thereof, preferentially from azelaic acid and adipic acid.

The dicarboxylic acids used according to the invention may be commercially available or synthesized according to any method known to those skilled in the art.

According to one embodiment, the composition according to the invention comprises at least one diester of formula (1) in which:

- the radicals R ¹ and/or R ² are chosen from a radical of formula -(CHR ³ CH2O) _n R ⁴ , where R ³ represents a hydrogen atom or a methyl, preferably a hydrogen atom; R ⁴ represents an alkyl having from 1 to 10 carbon atoms, preferably from 1 to 6 carbon atoms, preferably chosen from a methyl, an ethyl, a propyl or a butyl; and n is an integer ranging from 1 to 4, preferably from 1 to 3, and

- the radical R contains from 2 to 8 carbon atoms, more preferably from 3 to 8 carbon atoms, even more preferably from 4 to 7 carbon atoms.

Typically, the invention uses at least one diester of formula (1) formed between: two alcohols R ¹ -OH and R ² -OH, identical or different, at least one of said alcohols comprising at least one ether function, and a dicarboxylic acid R[C(O)OH]2 comprising a linear or branched alkylene or alkenylene chain, comprising from 4 to 8 carbon atoms.

Preferably, the diester(s) used according to the invention is (are) saturated.

For the purposes of the invention, the term "saturated diester" means a diester comprising saturated hydrocarbon chains where the carbon-carbon bonds are single carbon-carbon bonds. Thus, preferably, the alcohols used according to the invention each comprise a saturated hydrocarbon chain and the dicarboxylic acids used according to the invention comprise a saturated hydrocarbon chain, preferably, said hydrocarbon chain is made up of carbon and hydrogen atoms. Preferably, the diester of formula (1) used according to the invention consists of carbon atoms, oxygen atoms and hydrogen atoms.

According to one embodiment, the diester comprises from 12 to 60 carbon atoms, preferably from 16 to 50 carbon atoms.

According to one embodiment, the diester used in the invention is a linear or branched diester.

For the purposes of the invention, the term “branched diester” means a diester comprising a branched hydrocarbon chain, said branching being able to be located between the two ester functions and/or at one or both ends of the diester.

According to a preferred embodiment, the diester used in the invention is a linear diester.

According to a preferred embodiment, the diester used in the invention is saturated and linear.

According to one embodiment, at least one diester of formula (1) used according to the invention is chosen from:

- a diester formed from a monoethylene glycol monoalkyl ether and succinic acid,

- a diester formed from a monoethylene glycol monoalkyl ether and adipic acid,

- a diester formed from a monoethylene glycol monoalkyl ether and glutaric acid,

- a diester formed from a monoethylene glycol monoalkyl ether and pimelic acid,

- a diester formed from a monoethylene glycol monoalkyl ether and suberic acid,

- a diester formed from a monoethylene glycol monoalkyl ether and azelaic acid,

- a diester formed from a monoethylene glycol monoalkyl ether and sebacic acid,

- a diester formed from a diethylene glycol monoalkyl ether and succinic acid,

- a diester formed from a diethylene glycol monoalkyl ether and adipic acid,

- a diester formed from a diethylene glycol monoalkyl ether and glutaric acid,

- a diester formed from a diethylene glycol monoalkyl ether and pimelic acid,

- a diester formed from a diethylene glycol monoalkyl ether and suberic acid,

- a diester formed from a diethylene glycol monoalkyl ether and azelaic acid,

- a diester formed from a diethylene glycol monoalkyl ether and sebacic acid,

- a diester formed from a triethylene glycol monoalkyl ether and succinic acid,

- a diester formed from a triethylene glycol monoalkyl ether and adipic acid,

- a diester formed from a triethylene glycol monoalkyl ether and glutaric acid, - a diester formed from a triethylene glycol monoalkyl ether and pimelic acid,

- a diester formed from a triethylene glycol monoalkyl ether and suberic acid,

- a diester formed from a triethylene glycol monoalkyl ether and azelaic acid,

- a diester formed from a triethylene glycol monoalkyl ether and sebacic acid, and mixtures thereof, said alkyl group preferably having from 1 to 10 carbon atoms, preferably from 1 to 6 carbon atoms, more preferably from 1 to 4 carbon atoms.

Preferably, at least one diester of formula (1) used according to the invention is chosen from:

- a diester formed from monoethylene glycol monobutyl ether and azelaic acid,

- a diester formed from diethylene glycol monobutyl ether and succinic acid,

- a diester formed from a diethylene glycol monobutyl ether and adipic acid,

- a diester formed from a diethylene glycol monobutyl ether and azelaic acid,

- a diester formed from a diethylene glycol monobutyl ether and glutaric acid,

- a diester formed from a diethylene glycol monobutyl ether and pimelic acid,

- a diester formed from a diethylene glycol monobutyl ether and suberic acid,

- a diester formed from a diethylene glycol monobutyl ether and sebacic acid,

- a diester formed from a triethylene glycol monomethyl ether and succinic acid,

- a diester formed from a triethylene glycol monomethyl ether and adipic acid,

- a diester formed from a triethylene glycol monomethyl ether and glutaric acid,

- a diester formed from a triethylene glycol monomethyl ether and pimelic acid,

- a diester formed from a triethylene glycol monomethyl ether and suberic acid,

- a diester formed from a triethylene glycol monomethyl ether and azelaic acid,

- a diester formed from a triethylene glycol monomethyl ether and sebacic acid,

- a diester formed from a triethylene glycol monobutyl ether and succinic acid,

- a diester formed from a triethylene glycol monobutyl ether and adipic acid,

- a diester formed from a triethylene glycol monobutyl ether and glutaric acid,

- a diester formed from a triethylene glycol monobutyl ether and pimelic acid,

- a diester formed from a triethylene glycol monobutyl ether and suberic acid, a diester formed from a triethylene glycol monobutyl ether and azelaic acid, a diester formed from a triethylene glycol monobutyl ether and sebacic acid, and mixtures thereof.

Preferably, at least one diester of formula (1) used according to the invention is chosen from:

- a diester formed from monoethylene glycol monobutyl ether and azelaic acid,

- a diester formed from diethylene glycol monobutyl ether and succinic acid,

- a diester formed from diethylene glycol monobutyl ether and adipic acid,

- a diester formed from diethylene glycol monobutyl ether and azelaic acid,

- a diester formed from diethylene glycol monobutyl ether and glutaric acid,

- a diester formed from triethylene glycol monomethyl ether and azelaic acid,

- a diester formed from triethylene glycol monobutyl ether and azelaic acid, and mixtures thereof.

Preferably, at least one diester of formula (1) used according to the invention is chosen from:

- a diester formed from monoethylene glycol monobutyl ether and azelaic acid,

- a diester formed from diethylene glycol monobutyl ether and succinic acid,

- a diester formed from diethylene glycol monobutyl ether and adipic acid,

- a diester formed from diethylene glycol monobutyl ether and azelaic acid,

- a diester formed from diethylene glycol monobutyl ether and glutaric acid,

- a diester formed from triethylene glycol monomethyl ether and azelaic acid,

- a diester formed from triethylene glycol monobutyl ether and azelaic acid.

The diester used according to the invention typically has a kinematic viscosity, measured at 100°C, ranging from 1 to 6 mm ² /s, preferably from 1 to 5 mm ² /s.

Within the scope of the invention, kinematic viscosity may be measured according to ASTM D445. Preferably, when the invention uses a mixture of diesters corresponding to formula (1), the mixture of diesters has a kinematic viscosity, measured at 100°C, ranging from 1 to 6 mm ² /s, preferably from 1 to 5 mm ² /s.

According to one embodiment, the diester used according to the invention has a kinematic viscosity, measured at 40°C, ranging from 5 to 20 mm ² /s, preferably from 8 to 18 mm ² /s.

Preferably, when the invention uses a mixture of diesters of formula (1), each diester of the composition according to the invention has a kinematic viscosity, measured at 40°C, ranging from 5 to 20 mm ² /s, preferably from 8 to 18 mm ² /s.

It is understood that the definitions given above for the dicarboxylic acid and the alcohol may be combined, to the extent possible, to define other particular embodiments.

The diester(s) according to the invention can be prepared according to synthesis methods known to those skilled in the art. These synthesis methods more particularly implement two esterification reactions.

Of course, it is up to the person skilled in the art to adjust the synthesis conditions to obtain a diester according to the invention.

It is understood that, within the framework of the present invention, a diester according to the invention may be in the form of a mixture of at least two diesters of formula (1), in particular as defined above.

The diester or mixture of diesters of formula (1) may represent at least 5% by mass, preferably at least 10% by mass, more preferably from 10% to 100% by mass, of the total mass of the composition according to the invention.

According to a particular embodiment, a cooling and/or lubricating composition according to the invention can be formed at more than 95% by mass, in particular at more than 98% by mass, of one or more diester(s) of formula (1), or even with 100% by mass of one or more diester(s) of formula (1). Annex base oil(s)

A cooling and/or lubricating composition according to the invention may comprise, in addition to one or more diesters of formula (1), one or more additional base oils, distinct from the diesters according to the invention (also called co-bases).

Said base oil(s), optionally present in a cooling and/or lubricating composition according to the invention, are chosen appropriately, with regard to their compatibility with said diester(s) used according to the invention.

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

Preferably, the base oil or mixture of additional base oils, used in a cooling composition according to the invention, may have a kinematic viscosity, measured at 100°C according to the ASTM D445 standard, ranging from 1.5 to 8 mm ² /s, in particular from 1.5 to 6.1 mm ² /s, more particularly from 1.5 to 4.1 mm ² /s, even more particularly from 1.5 to 2.1 mm ² /s.

Base oils may be chosen from oils of mineral or synthetic origin belonging to groups I to V according to the classes defined in the API classification (or their equivalents according to the ATIEL classification) and presented in table 1 below or their mixtures.

[Table 1]

Mineral base oils include all types of base oils obtained by atmospheric and vacuum distillation of crude oil, followed by refining operations. such as solvent extraction, de-alphatting, solvent dewaxing, hydrotreating, hydrocracking, hydroisomerization and hydrofinishing.

Mixtures of synthetic and mineral oils, which can be bio-sourced, can also be used.

According to one embodiment, the base oils are at least partly re-refined or recycled oils, i.e. originating from at least one used lubricant having been subjected to one or more prior steps of dehydration, distillation, filtration, hydrogenation, liquid/liquid extraction, decantation and/or passage of the used lubricant over an adsorbent material.

There are generally no limitations on the use of additional different base oils to make cooling and/or lubricating compositions, except that they must have properties, such as viscosity index, sulfur content or oxidation resistance, suitable for use in propulsion systems of an electric or hybrid vehicle.

The base oils may also be chosen from synthetic oils, such as certain esters of carboxylic acids and alcohols, other than the diester defined according to the invention, from polyalphaolefins (PAOs), and from polyalkylene glycols (PAGs) obtained by polymerization or copolymerization of alkylene oxides comprising from 2 to 8 carbon atoms, in particular from 2 to 4 carbon atoms.

PAOs used as base oils are, for example, obtained from monomers comprising 4 to 32 carbon atoms, for example from octene or decene.

The mass average molecular mass of PAO can vary quite widely. Preferably, the mass average molecular mass of PAO is less than 600 Da. The mass average molecular mass of PAO can also range from 100 to 600 Da, from 150 to 600 Da, or from 200 to 600 Da.

For example, the PAOs used in the context of the invention, having a kinematic viscosity, measured at 100°C according to the ASTM D445 standard, ranging from 1.5 to 8 mm ² /s are sold commercially by Ineos under the brands Durasyn® 162, Durasyn® 164, Durasyn® 166 and Durasyn® 168.

Advantageously, the additional base oil or oils are chosen from polyalphaolefins (PAOs). It is up to the person skilled in the art to adjust the content of additional base oil(s) present in a cooling and/or lubricating composition according to the invention.

According to one embodiment, a composition according to the invention may comprise from 10 to 95% by mass, preferably from 30 to 90% by mass, more preferably from 50 to 90% by mass, of one or more base oils different from said diester(s) according to the invention, relative to the total mass of said composition.

According to this embodiment, preferably, the composition will comprise: from 5 to 90% by mass, preferably from 10 to 70% by mass, more preferably from 10 to 50% by mass, of said diester(s) of formula (1), one or more base oils different from said diester(s), preferably in a proportion of 10 to 95% by mass, preferably from 30 to 90% by mass, more preferably from 50 to 90% by mass, relative to the total mass of said diester(s) of formula (1) and base oils different from said diester(s).

According to a particular embodiment, a cooling composition implemented according to the invention will comprise 100% by mass of a mixture of diester(s) of formula (1) and of ancillary base oil(s), preferably in a proportion such that the composition comprises:

- from 5 to 90% by mass, preferably from 10 to 70% by mass, more preferably from 10 to 50% by mass, of said diester(s),

- one or more base oils different from said diester(s), preferably in a proportion of 10 to 95% by mass, preferably 30 to 90% by mass, more preferably 50 to 90% by mass, relative to the total mass of the composition.

Additives

The diester(s) used according to the invention can be used with one or more additives. A cooling and/or lubricating composition according to the invention may further comprise one or more additives known to those skilled in the art in the field of lubrication and in particular in the field of lubrication and/or cooling of mobile and/or stationary systems.

The additives that can be incorporated into a composition according to the invention can be chosen from friction modifying additives, anti-wear additives, extreme pressure additives, detergents, antioxidants, viscosity index (VI) improvers, pour point depressants (PPD), dispersants, anti-foaming agents, thickeners, corrosion inhibitors, copper passivators, and mixtures thereof.

According to one embodiment, said additive(s) distinct from said diester(s) and distinct from the base oil(s), is (are) present in a proportion of up to 20% by mass, preferably from 0.05 to 15% by mass, more preferably from 0.1 to 10% by mass, even more preferably from 0.5 to 7% by mass, or even from 1 to 5% by mass relative to the total mass of the composition.

Preferably, a cooling and/or lubricating composition according to the invention may further comprise one or more additives chosen from antioxidants, anti-foams, pour point improvers and anti-corrosion agents.

The addition of one or more additives chosen from anti-wear additives, friction modifiers, detergents, extreme pressure additives and dispersants may also prove advantageous in the context of the implementation of the cooling composition according to the invention as a multifunctional fluid, for example for cooling the battery and/or the power electronics, and for lubricating parts of the propulsion system, for example the transmission, in an electric or hybrid vehicle.

It is understood that the nature and quantity of additives used are chosen so as not to affect the properties of the cooling and/or lubricating composition conferred by the diester according to the invention.

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

Said additive(s) may be present in the cooling and/or lubricating composition according to the invention in a content of less than or equal to 20% by mass, in particular ranging from 0.05 to 15% by mass, preferably from 0.1 to 10% by mass, more preferably from 0.5 to 7% by mass, relative to the total mass of said composition.

A cooling and/or lubricating composition according to the invention can thus comprise at least one antioxidant additive.

The invention thus relates, according to another of its aspects, to a cooling and/or lubricating composition, in particular capable of cooling a propulsion system, in particular the engine or the geared motor, the battery and/or the power electronics of an electric or hybrid vehicle, said composition comprising (i) at least one diester as defined above, and (ii) at least one antioxidant additive.

The antioxidant additive generally makes it possible to delay the degradation of the composition in service. This degradation can notably result in the formation of deposits, the presence of sludge or an increase in the viscosity of the composition.

Antioxidant additives act in particular as radical inhibitors or hydroperoxide destroyers. Among the commonly used antioxidant additives, mention may be made of phenolic antioxidant additives, amine antioxidant additives, and phosphosulfur antioxidant additives. Some of these antioxidant additives, for example phosphosulfur antioxidant additives, may be ash-generating. Phenolic antioxidant additives may be ash-free or in the form of neutral or basic metal salts. Antioxidant additives may in particular be chosen from sterically hindered phenols, sterically hindered phenol esters and sterically hindered phenols comprising a thioether bridge, diphenylamines, diphenylamines substituted by at least one C 1 -C 12 alkyl group, N,N'-dialkyl-aryl-diamines and mixtures thereof.

Preferably according to the invention, the sterically hindered phenols are chosen from compounds comprising a phenol group of which at least one vicinal carbon of the carbon carrying the alcohol function is substituted by at least one C 1 -C 2 alkyl group. Cio, preferably a C1-C6 alkyl group, preferably a C4 alkyl group, preferably by the tert-butyl group.

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

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

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

Advantageously, a cooling and/or lubricating composition comprises at least one ash-free antioxidant additive.

Said additive(s) may be used, in a cooling composition according to the invention, at a rate of 0.1 to 2% by mass, relative to the total mass of the composition.

A cooling and/or lubricating composition according to the invention may comprise at least one anti-wear and/or extreme pressure additive.

Anti-wear additives and extreme pressure additives protect friction surfaces by forming a protective film adsorbed on these surfaces.

There are a wide variety of anti-wear additives. Preferably, the anti-wear additives are selected from phosphosulfur additives such as metal alkylthiophosphates, in particular zinc alkylthiophosphates, and more specifically zinc dialkyldithiophosphates or ZnDTP. The preferred compounds are of formula Zn((SP(S)(OQ ² )(OQ ³ ))2, in which Q ² and Q ³ , identical or different, independently represent an alkyl group, preferably an alkyl group comprising from 1 to 18 carbon atoms.

Amine phosphates are also anti-wear additives that can be used in a composition according to the invention. However, the phosphorus provided by these additives can act as a poison for automobile catalytic systems because these additives generate ash. These effects can be minimized by partially substituting the amine phosphates with additives that do not provide phosphorus, such as, for example, polysulfides, in particular sulfur-containing olefins.

A cooling and/or lubricating composition may comprise from 0.01 to 6% by mass, preferably from 0.05 to 4% by mass, more preferably from 0.1 to 2% by mass of anti-wear additives and extreme pressure additives, by mass relative to the total mass of the composition.

A cooling and/or lubricating composition according to the invention may also comprise at least one additive improving the viscosity index (VI).

Viscosity index improvers, particularly viscosity index improver polymers, help ensure good cold resistance and minimal viscosity at high temperatures.

Examples of viscosity index improving polymers include polymeric esters, homopolymers or copolymers, hydrogenated or non-hydrogenated, of styrene, butadiene and isoprene, homopolymers or copolymers of olefins, such as ethylene or propylene, polyacrylates and polymethacrylates (PMA), preferably homopolymers or copolymers of olefins, such as ethylene or propylene.

In particular, a cooling and/or lubricating composition according to the invention may comprise from 1 to 15% by mass of additive(s) improving the viscosity index, preferably from 5% to 10% by mass, relative to the total mass of the cooling and/or lubricating composition.

A cooling and/or lubricating composition according to the invention may further comprise an antifoaming agent. The antifoaming agent can be chosen from silicones.

A cooling and/or lubricating composition may comprise from 0.01 to 2% by mass or from 0.01 to 5% by mass, preferably from 0.1 to 1.5% by mass or from 0.1 to 2% by mass of antifoaming agent, relative to the total mass of the composition.

A cooling and/or lubricating composition according to the invention may comprise at least one friction modifying additive.

The friction-modifying additive may be chosen from a compound providing metallic elements and an ash-free compound. Among the compounds providing metallic elements, mention may be made of transition metal complexes such as Mo, Sb, Sn, Fe, Cu, Zn, the ligands of which may be hydrocarbon compounds comprising oxygen, nitrogen, sulfur or phosphorus atoms. The ash-free friction-modifying additives are generally of organic origin and may be chosen from fatty acid and polyol monoesters, alkoxylated amines, alkoxylated fatty amines, fatty epoxides, borate fatty epoxides; fatty amines or fatty acid glycerol esters. According to the invention, the fatty compounds comprise at least one hydrocarbon group comprising from 10 to 24 carbon atoms.

A cooling and/or lubricating composition may comprise from 0.01 to 2% by mass or from 0.01 to 5% by mass, preferably from 0.1 to 1.5% by mass or from 0.1 to 2% by mass of friction modifying additive, relative to the total mass of the composition.

Advantageously, a cooling and/or lubricating composition is free of friction modifying additive, in particular for use in cooling the battery part.

A cooling and/or lubricating composition according to the invention may comprise at least one detergent additive.

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

Detergent additives usable in a cooling and/or lubricating composition are generally known to those skilled in the art. Detergent additives may be anionic compounds comprising a lipophilic hydrocarbon group and a hydrophilic head. The associated cation may be a metal cation of an alkali or alkaline earth metal.

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

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

A cooling and/or lubricating composition may for example comprise from 2 to 4% by weight of detergent additive, relative to the total weight of the composition.

A cooling and/or lubricating composition may also include at least one pour point depressant additive.

By slowing the formation of paraffin crystals, pour point depressant additives generally improve the cold behavior of the composition. Examples of pour point depressant additives include polyalkyl methacrylates, polyacrylates, polyarylamides, polyalkylphenols, polyalkylnaphthalenes, alkylated polystyrenes.

The cooling and/or lubricating composition according to the invention may, for example, comprise from 0.05 to 2% by mass of pour point lowering additive, relative to the total mass of the composition.

Also, the cooling and/or lubricating composition according to the invention may comprise at least one dispersing agent. The dispersing agent may be selected from Mannich bases, succinimides and their derivatives. A cooling composition may for example comprise from 0.2 to 10% by weight of dispersing agent, relative to the total weight of the composition.

According to a particular embodiment, the cooling and/or lubricating composition according to the invention comprises, or even consists of (i) at least one diester corresponding to formula (I) as defined above and (ii) at least one additive chosen from antioxidants, anti-foaming agents, pour point lowering additives, anti-corrosion agents, anti-wear and/or extreme pressure additives, friction modifiers, detergents, dispersing agents and mixtures thereof, preferably from antioxidants, pour point lowering additives, anti-foaming agents and anti-corrosion agents, and mixtures thereof.

Advantageously, a cooling and/or lubricating composition according to the invention is formed (i) from at least one diester corresponding to formula (I) as defined above and (ii) from at least one antioxidant additive.

Cooling and/or lubricating composition

The diester(s) used according to the invention may be used with one or more additional base oils and/or one or more additives. According to this embodiment, the composition will preferably comprise: from 5 to 90% by mass, preferably from 10 to 70% by mass, more preferably from 10 to 50% by mass, of diester(s) corresponding to formula (1),

- one or more base oils different from said diester(s) and/or one or more additives distinct from said diester(s) and distinct from the base oil(s), the base oil(s) preferably representing a proportion of 10 to 95% by mass, preferably 30 to 90% by mass, more preferably 50 to 90% by mass, the additive(s) preferably representing a proportion of up to 20% by mass, preferably 0.05 to 15% by mass, more preferably 0.1 to 10% mass, even more preferably from 0.5 to 7% by mass, or even from 1 to 5% by mass, relative to the total mass of the composition.

According to one embodiment, the composition comprises: from 5 to 90% by mass, preferably from 10 to 70% by mass, more preferably from 10 to 50% by mass, of diester(s) corresponding to formula (1),

- one or more base oils different from said diester(s), preferably in a proportion of 10 to 95% by mass, preferably 30 to 90% by mass, more preferably 50 to 90% by mass,

- one or more additives distinct from said diester(s) and distinct from the base oil(s), preferably in a proportion of up to 20% by mass, preferably from 0.05 to 15% by mass, more preferably from 0.1 to 10% by mass, even more preferably from 0.5 to 7% by mass, or even from 1 to 5% by mass, relative to the total mass of the composition.

According to one embodiment, the composition according to the invention comprises, or even consists of: from 5 to 90% by mass, preferably from 10 to 70% by mass, more preferably from 10 to 50% by mass, of diester(s) corresponding to formula (1) in which: the radicals R ¹ and/or R ² are chosen independently of one another from -(CHR ³ CH2O) _n R ⁴ , where R ³ represents a hydrogen atom or a methyl, preferably a hydrogen atom; R ⁴ represents an alkyl having from 1 to 10 carbon atoms, preferably from 1 to 6 carbon atoms, preferably chosen from a methyl, an ethyl, a propyl or a butyl; and n is an integer ranging from 1 to 4, preferably from 1 to 3, the radical R contains from 2 to 8 carbon atoms, more preferably from 3 to 8 carbon atoms, even more preferably from 4 to 7 carbon atoms;

- one or more base oils different from said diester(s), preferably in a proportion of 10 to 95% by mass, preferably 30 to 90% by mass, more preferably 50 to 90% by mass; - one or more additives distinct from said diester(s) and distinct from the base oil(s), preferably in a proportion of up to 20% by mass, preferably from 0.05 to 15% by mass, more preferably from 0.1 to 10% by mass, even more preferably from 0.5 to 7% by mass, or even from 1 to 5% by mass, relative to the total mass of the composition.

According to a particular embodiment, a cooling and/or lubricating composition according to the invention comprises, or even consists of:

- at least 5% by mass, preferably at least 10% by mass, preferably at least 30% by mass, preferably at least 50% by mass, more preferably at least 70% by mass, or even at least 90% by mass, of diester(s) corresponding to formula (1);

- optionally from 0.01 to 20% by mass, preferably from 0.05 to 15% by mass, more preferably from 0.1 to 10% by mass, even more preferably from 0.5 to 7% by mass, or even from 1 to 5% by mass, of one or more additives chosen from friction modifying additives, anti-wear additives, extreme pressure additives, detergents, antioxidants, viscosity index (VI) improvers, pour point depressants (PPD), dispersants, anti-foaming agents, thickeners, corrosion inhibitors, copper passivators, and mixtures thereof, the contents being expressed relative to the total mass of said composition.

According to a particular embodiment, a cooling and/or lubricating composition according to the invention comprises, or even consists of: from 5 to 90% by mass, preferably from 10 to 70% by mass, more preferably from 10 to 50% by mass, of diester(s) corresponding to formula (1),

- one or more base oils different from said diesters, preferably in a proportion of 10 to 95% by mass, preferably 30 to 90% by mass, more preferably 50 to 90% by mass; optionally up to 20% by mass, preferably 0.05 to 15% by mass, more preferably 0.1 to 10% by mass, even more preferably 0.5 to 7% by mass, or even 1 to 5% by mass, of one or more additives chosen from friction modifying additives, anti-wear additives, extreme pressure additives, detergents, antioxidants, viscosity index (VI) improvers, pour point depressants (PPD), dispersants, anti-foaming agents, thickeners, corrosion inhibitors, copper passivating agents, and mixtures thereof, the contents being expressed relative to the total mass of said composition.

According to a particular embodiment, a cooling and/or lubricating composition according to the invention comprises, or even consists of:

- from 5 to 95% by mass, preferably from 10 to 90% by mass, more preferably from 20 to 80% by mass, even more preferably from 30 to 70% by mass, or even from 40 to 60% by mass, of diester(s) corresponding to formula (1);

- optionally from 5 to 95% by mass, preferably from 10 to 90% by mass, more preferably from 20 to 80% by mass, even more preferably from 30 to 70% by mass, or even from 40 to 60% by mass of one or more base oils different from said diesters;

- optionally from 0.01 to 20% by mass, preferably from 0.05 to 15% by mass, more preferably from 0.1 to 10% by mass, even more preferably from 0.5 to 7% by mass, or even from 1 to 5% by mass of one or more additives distinct from the diester and distinct from the base oil(s), among friction modifying additives, anti-wear additives, extreme pressure additives, detergents, antioxidants, viscosity index (VI) improvers, pour point depressants (PPD), dispersants, anti-foaming agents, thickeners, corrosion inhibitors, copper passivators, and mixtures thereof, the contents being expressed relative to the total mass of said composition.

A cooling and/or lubricating composition according to the invention advantageously has a kinematic viscosity, measured at 100°C, ranging from 1 to 6 mm ² /s, preferably from 1 to 5 mm ² /s.

A cooling and/or lubricating composition according to the invention advantageously has a kinematic viscosity, measured at 40°C, ranging from 5 to 20 mm ² /s, preferably from 8 to 18 mm ² /s. The cooling and/or lubricating composition according to the invention can be prepared by mixing the ingredients according to any method known to those skilled in the art.

Application

As indicated above, a composition according to the invention can be implemented as a cooling and/or lubricating fluid for a mobile and/or stationary system.

The mobile or stationary system can be chosen from a heavy or light vehicle, public works machinery, an energy storage system, charging stations, chargers, data centers, 5G antennas, photovoltaic panels, wind turbines, turbines, switching devices, inverters and medical devices, or a combination of these systems.

The composition can be used to lubricate and/or cool transmissions in thermal engines and/or reducers in electric motors of a mobile system.

According to one embodiment, the mobile system is a vehicle with a thermal engine, the cooling and/or lubricating composition then preferably being used to reduce the fuel consumption of said vehicle equipped with a transmission member, in particular a gearbox and/or an axle, lubricated using this composition.

According to one embodiment, the composition according to the invention is implemented in an electric vehicle as a single fluid in the entire lubrication system in said electric vehicle. Thus, according to this embodiment, the lubricating composition is implemented to lubricate and cool all the components of the propulsion system of the electric vehicle.

A system according to the invention may be a propulsion system of an electric or hybrid vehicle, the composition then preferably being used to improve the efficiency of the reducers in the electric motors and/or to extend the autonomy of the battery of the electric or hybrid vehicle and/or to cool the battery and/or power electronics, electric or hybrid vehicle, in particular a lithium-ion or nickel-cadmium battery.

For information purposes, as shown schematically in Figure 1, the propulsion system of an electric or hybrid vehicle includes in particular the electric motor part (1), an electric battery (2) and a transmission, and in particular a speed reducer (3).

The electric motor typically comprises power electronics (11) connected to a stator (13) and a rotor (14). The stator comprises coils, in particular copper coils, which are alternately supplied with an electric current. This makes it possible to generate 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), stator (13) and 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 rotation speed at the output of the electric motor and to adapt the speed transmitted to the wheels, allowing at the same time to control the speed of the vehicle.

Advantageously, a composition according to the invention can be used to cool the battery of an electric or hybrid vehicle or the batteries of an energy storage system. In particular, according to this embodiment, it is intended to be placed in direct contact with the battery or batteries.

As batteries suitable for the propulsion systems of an electric or hybrid vehicle, we can cite in particular Li-ion batteries or nickel-cadmium batteries.

The invention also relates, according to another of its aspects, to a method of cooling and/or lubricating at least one element of a mobile and/or stationary system, said method comprising at least one step of bringing into contact at least said element with a composition comprising one or more diester(s) of formula (1) according to the invention.

The composition implemented within the framework of the methods according to the invention may comprise one or more of the characteristics described within the framework of the lubricating and/or cooling composition according to the invention.

The mobile or stationary system can be chosen from heavy or light vehicles, public works machinery, energy storage systems, charging stations, chargers, data centers, 5G antennas, photovoltaic panels, wind turbines, turbines, switching devices, inverters and medical devices, or a combination of these systems.

The invention also relates, according to another of its aspects, to a method for cooling at least one part of a propulsion system of an electric or hybrid vehicle, in particular the battery, comprising at least one step of bringing at least said part, in particular said battery, for example a lithium-ion or nickel-cadmium battery, into contact with a composition comprising at least one diester of formula (1) according to the invention, as defined above.

Bringing the cooling composition according to the invention into contact with the battery may consist of immersion or semi-immersion of the battery in said composition or even injection of said composition onto the surface of the battery.

By “immersion” is meant that the entire battery is surrounded by the cooling composition according to the invention. By “semi-immersion” is meant that only a portion of the battery is in contact with said composition.

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.

Examples of direct contact include cooling by injection, jet, spraying, immersion or semi-immersion in a bath, or by forming a mist from the composition according to the invention under pressure and by gravity on the battery.

Advantageously, the composition is injected by jet under fairly high pressure into the areas to be cooled of the propulsion system. Advantageously, the shear resulting from this injection makes it possible to reduce the viscosity of the fluid at the injection zone, compared to the kinematic viscosity at rest, and thus, to further increase the cooling potential of the composition.

Additionally, oil circulation systems commonly used in electric motors may be employed, as for example described in WO 2015/116496.

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 and/or the geared motor.

The cooling composition according to the invention has in particular electrical insulation properties which are particularly satisfactory for use in electric or hybrid vehicles.

It is possible to take advantage, in addition to the cooling properties of a composition according to the invention, of its lubricating properties.

Thus, a composition according to the invention can simultaneously be used to lubricate the various parts of a stationary or mobile system such as a propulsion system of an electric or hybrid vehicle, in particular bearings located between the rotor and the stator of an electric motor, or even the transmission, in particular the reducer, in an electric or hybrid vehicle.

In the case of such an application, a cooling composition according to the invention advantageously further comprises one or more additives chosen from anti-wear additives, friction modifiers, detergents, dispersants, extreme pressure additives, and mixtures thereof.

The invention will now be described by means of the following examples, given of course as illustrations and not as limitations of the invention.

Examples

Example 1: Preparation of the test compounds The following compounds were prepared:

- Diester A: diester formed from succinic acid and a diethylene glycol monobutyl ether with the following molar proportions: 2 moles of diethylene glycol monobutyl ether and 1 mole of succinic acid;

- Diester B: diester formed from adipic acid and a diethylene glycol monobutyl ether with the following molar proportions: 2 moles of diethylene glycol monobutyl ether and 1 mole of adipic acid;

- Diester C: diester formed from azelaic acid and a diethylene glycol monobutyl ether with the following molar proportions: 2 moles of diethylene glycol monobutyl ether and 1 mole of azelaic acid;

- Diester D: diester formed from glutaric acid and a diethylene glycol monobutyl ether with the following molar proportions: 2 moles of diethylene glycol monobutyl ether and 1 mole of glutaric acid;

- Diester E: diester formed from azelaic acid and a triethylene glycol monomethyl ether with the following molar proportions: 2 moles of triethylene glycol monomethyl ether and 1 mole of azelaic acid;

- Diester F: mixture of diesters formed from azelaic acid and a triethylene glycol monobutyl ether with the following molar proportions: 2 moles of triethylene glycol monobutyl ether and 1 mole of azelaic acid;

- Diester G: diester formed from azelaic acid and a monoethylene glycol monobutyl ether with the following molar proportions: 2 moles of monoethylene glycol monobutyl ether and 1 mole of azelaic acid;

- Diester H: diester formed from succinic acid and a triethylene glycol monobutyl ether with the following molar proportions: 2 moles of triethylene glycol monobutyl ether and 1 mole of succinic acid;

- Diester I: diester formed from adipic acid and a monoethylene glycol monohexyl ether with the following molar proportions: 2 moles of monoethylene glycol monohexyl ether and 1 mole of adipic acid; monoester formed from a monocarboxylic acid comprising a saturated hydrocarbon chain of 3 to 14 carbon atoms; and a monoalcohol comprising a saturated hydrocarbon chain of 3 to 14 carbon atoms. The diesters and monoester were prepared according to known methods of ester preparation.

The compositions tested in the following examples comprise 100% of each ester (diester or monoester) defined in this example 1.

Example 2: Viscosity measurement

The kinematic viscosity at 100°C (KV100) and the kinematic viscosity at 40°C (KV40) of the compounds of Example 1 were determined according to ASTM D445.

Viscosities are shown in Table 2.

[Table 2]

All the diesters used according to the invention have a viscosity at 100°C of less than 5 mm ² /s.

Example 3: Measuring thermal conductivity

The thermal conductivity of the compounds described in Example 1 was determined according to ASTM D7896-19 at 30°C.

The results are shown in Table 3. [Table 3]

These results show that the diesters used according to the invention have good thermal properties, which allows their use as a cooling fluid. Indeed, the diesters have a thermal conductivity greater than 150 mW. m' ¹ . K' ¹ or even at least 155 mW.m'hK' ¹ .

Example 4: Measuring the mini flash point

The mini flash point is measured according to ASTM D93Ac (Cleaveland open cup method).

The values are shown in Table 4.

[Table 4]

As shown by the values in Table 4, the flash point of the diesters used in the invention is particularly high, in particular the flash point is greater than 150°C. Example 5: Measurement of the mini pour point

The mini pour point is measured according to ASTM D7346.

The values are shown in Table 5.

Les résultats du tableau 5 montrent que les diesters mis en œuvre dans l’invention présentent un point d’écoulement très faible, pouvant être inférieur à -20°C ou même inférieur à -25°C pour les diesters formés avec au moins un alcool choisi parmi le monoéthylène glycol monobutyl éther, le diéthylène glycol monobutyl éther, le triéthylène glycol monométhyl éther et le triéthylène glycol monobutyl éther. Les diesters A à F et H ont un point d’écoulement plus faible que le monoester. [Table 5]

The results in Table 5 show that the diesters used in the invention have a very low pour point, which may be less than -20°C or even less than -25°C for the diesters formed with at least one alcohol chosen from monoethylene glycol monobutyl ether, diethylene glycol monobutyl ether, triethylene glycol monomethyl ether and triethylene glycol monobutyl ether. Diesters A to F and H have a lower pour point than the monoester.

The diesters according to the invention thus exhibit excellent cold properties.

Example 6: Measuring volatility

NOACK volatility was measured according to ASTM D6375. The values are shown in Table 6.

[Table 6]

The results in Table 6 show that the diesters used in the invention have a particularly low NOACK volatility, in particular lower than the monoester.

The diesters according to the invention thus exhibit excellent resistance to high temperatures.

Example 7: Measuring the coefficient of friction

Tribological properties can be assessed by a test on a rotating ball-disc tribometer (also called a ball-plate) of the Linear Reciprocating Tribometer type. This test makes it possible in particular to assess the performance of lubricants in terms of friction in mixed/limit regime according to the load, pressure or speed conditions applied.

The coefficient of friction of the lubricating compositions tested is determined at 100°C by using a hardened steel ball of approximately 2 cm in diameter, for example 1.905 cm in diameter, on a hardened steel plane.

The tribometer may be a device for setting a steel ball and a steel plane in relative motion in order to determine the friction coefficients for a given lubricating composition, while varying various properties such as the speed, load, and temperature. The hardened steel plane is AISI 52100 with a mirror finish and the ball is also AISI 52100 made of hardened steel.

The applied load is 25 N respectively and the drive speed varies from 20 mm/s to 2500 mm/s. The friction coefficient is determined in particular at a rotation speed of 10 mm/s. The coefficient is determined at a sliding speed/drive speed ratio ("Slide-to-Roll Ratio" or %SRR) of 5% to 100%.

Approximately 50 ml of the tested lubricating composition was introduced into the device. The ball is engaged face against plane, said ball and said plane being actuated independently so as to create a mixed rolling/sliding contact.

The coefficient of friction is measured and recorded using a force sensor.

The results with a feed speed of 225 mm/s are shown in Table 7.

The lubricating compositions tested comprise 100% ester as defined in Example 1.

[Table 7]

These results show that the diesters used according to the invention have very low coefficients of friction, in particular a lower coefficient of friction than the monoester. The diesters according to the invention thus have excellent lubricating properties, thus making it possible in particular to reduce fuel consumption or to extend the battery life.

Example 8: Measuring the traction coefficient

The coefficient of traction (COT) was measured using the PCS instrument MTM tribometer. It is used to evaluate the performance of lubricants in terms of friction in mixed/hydrodynamic conditions. This test consists of putting a steel ball and a steel plane in relative motion, at different speeds, to define the %SSR (Slide-to-Roll Ratio) which corresponds to the sliding speed/drive speed. This test aims to reproduce electrohydrodynamic (EHD) lubrication conditions.

The measurement conditions were 25 N load, a disk speed of 1.4 m/s for an estimated temperature of 100 °C and an SRR of 20%, 40%, 60%, 80% and 100%.

The lower the traction coefficient for a lubricating composition, the more friction between metal parts is reduced, thus resulting in a greater gain in terms of fuel economy.

The results obtained are shown in Table 8.

[Table 8]

These results show that the diesters defined in the invention have a good traction coefficient and in particular a better traction coefficient than the monoester. All of these results demonstrate that when the diester is obtained from at least one alcohol among monoethylene glycol monobutyl ether, diethylene glycol monobutyl ether, triethylene glycol monomethyl ether and triethylene glycol monobutyl ether, then said diester will exhibit better resistance to high temperatures, better cold properties, improved thermal properties as well as improved lubrication performance.

Indeed, diesters B and I are obtained from the same dicarboxylic acid, namely adipic acid, but from a different alcohol. The results in the tables above show that the NOACK volatility is lower for ester B, indicating better resistance to high temperatures, that the pour point is also lower for ester B, thus presenting better cold properties, and that the conductivity is higher for ester B, proving that the thermal properties are better.

Also, concerning lubrication performance (traction/friction), diester B has a lower coefficient of friction than diester I which implies better lubrication properties, thus making it possible in particular to reduce fuel consumption or extend battery life, but also a lower coefficient of traction than diester I and this whatever the SRR implying that the friction between the metal parts is further reduced which results in a greater gain in terms of fuel economy.

Claims

Claims 1. Lubricating and/or cooling composition comprising one or more diester(s) of formula (1), [Chem 1]

in which R represents a divalent alkylene or alkenylene radical, linear or branched, containing from 2 to 8 carbon atoms; R ¹ and R ² represent, independently of each other, a monovalent hydrocarbon radical optionally comprising one or more heteroatoms, it being understood that at least one of R ¹ and R ² comprises at least one ether function, said diester(s) of formula (1) having a kinematic viscosity at 100°C ranging from 1 to 6 mm ² /s. 2. Composition according to claim 1, in which R ¹ and R ² have one or more of the following characteristics: - R ¹ and/or R ² comprise(s) from 1 to 6 ether functions, preferably from 1 to 4 ether functions, even more preferably from 1 to 3 ether functions; - R ¹ and/or R ² contain(s) from 2 to 20 carbon atoms, preferably from 3 to 16 carbon atoms, even more preferably from 8 to 10 carbon atoms; - R ¹ and/or R ² are chosen from a radical of formula -(CHR ³ CH2O) _n R ⁴ , where R ³ represents a hydrogen atom or a methyl, preferably a hydrogen atom; R ⁴ represents an alkyl having from 1 to 10 carbon atoms, preferably from 1 to 6 carbon atoms, preferably chosen from a methyl, an ethyl, a propyl or a butyl; and n is an integer ranging from 1 to 4, preferably from 1 to 3; - R ¹ and/or R ² are chosen from CH3(CH2)3O(CH2)2-, CH3(CH2)3(OCH2CH2)2-, CH ₃ (OCH ₂ CH2)3- and CH3(CH2)3(OCH ₂ CH2)3- 3. Composition according to one of claims 1 or 2, in which the radical R is chosen from the radicals -(CH2) _X -, x ranging from 2 to 8, even more preferably x ranges from 4 to 7. 4. Composition according to any one of claims 1 to 3, in which at least one of said diesters of formula (1) is formed between: two alcohols R^OH and R ² -OH, identical or different, at least one of said alcohols comprising at least one ether function, and - a dicarboxylic acid R[C(O)OH]2 comprising a linear or branched alkylene or alkenylene chain comprising 4 to 8 carbon atoms. 5. Composition according to any one of claims 1 to 4, characterized in that said diester(s) is (are) chosen from: - a diester formed from a mono-, di- or tri-ethylene glycol monoalkyl ether and succinic acid, - a diester formed from a mono-, di- or tri-ethylene glycol monoalkyl ether and adipic acid, - a diester formed from a mono-, di- or tri-ethylene glycol monoalkyl ether and glutaric acid, - a diester formed from a mono-, di- or tri-ethylene glycol monoalkyl ether and pimelic acid, - a diester formed from a mono-, di- or tri-ethylene glycol monoalkyl ether and suberic acid, - a diester formed from a mono-, di- or tri-ethylene glycol monoalkyl ether and azelaic acid, - a diester formed from a mono-, di- or tri-ethylene glycol monoalkyl ether and sebacic acid, said alkyl group preferably having from 1 to 10 carbon atoms, preferably from 1 to 6 carbon atoms, more preferably from 1 to 4 carbon atoms. 6. Composition according to any one of claims 1 to 5, said diester(s) of formula (1) are formed with at least one alcohol chosen from monoethylene glycol monobutyl ether, diethylene glycol monobutyl ether, triethylene glycol monomethyl ether and triethylene glycol monobutyl ether. 7. Composition according to any one of claims 1 to 6, in which the composition comprises at least 5% by mass, preferably at least 10% by mass, more preferably from 10% to 100% of said diester(s), relative to the total mass of the composition. 8. Composition according to any one of claims 1 to 7, characterized in that it comprises, in addition to said diester(s), at least one additive chosen from antioxidants, pour point lowering additives, anti-foaming agents, anti-corrosion agents, anti-wear and/or extreme pressure additives, friction modifiers, detergents, dispersing agents, viscosity index improvers, thickeners, copper passivators and mixtures thereof, preferably said at least one additive is chosen from viscosity index improvers, pour point lowering additives, anti-wear additives, antioxidants and mixtures thereof. 9. Composition according to any one of claims 1 to 8, comprising: from 5 to 90% by mass, preferably from 10 to 70% by mass, more preferably from 10 to 50% by mass, of said diester(s) of formula (1), - one or more base oils different from said diester(s) and/or one or more additives distinct from said diester(s) and distinct from the base oil(s), the base oil(s) preferably representing a proportion of 10 to 95% by mass, preferably 30 to 90% by mass, more preferably 50 to 90% by mass, the additive(s) preferably representing a proportion of up to 20% by mass, preferably 0.05 to 15% by mass, more preferably 0.1 to 10% by mass, even more preferably 0.5 to 7% by mass, or even 1 to 5% by mass, relative to the total mass of the composition. 10. Use of a composition according to any one of claims 1 to 9 for cooling and/or lubricating at least one element of a mobile or stationary system. 11. Use according to claim 10, in which the mobile or stationary system is chosen from heavy or light vehicles, public works machinery, energy storage systems, charging stations, chargers, data centers, 5G type antennas, photovoltaic panels, wind turbines, turbines, switching devices, inverters and medical devices, or a combination of these systems. 12. Use according to one of claims 10 or 11, for lubricating and/or cooling transmissions in thermal engines and/or reducers in electric motors of a mobile system. 13. Use according to any one of claims 10 to 12, in which the mobile system is a vehicle with a thermal engine, the composition being used to reduce the fuel consumption of said vehicle equipped with a transmission member, in particular a gearbox and/or an axle, lubricated using this composition. 14. Use according to any one of claims 10 to 13, in which the mobile system is an electric or hybrid vehicle, the composition being used to improve the efficiency of reducers in electric motors. 15. Use according to any one of claims 10 to 14, in which the mobile system is an electric or hybrid vehicle, the composition being used to extend the battery life of the electric or hybrid vehicle and/or to cool the battery and/or the power electronics of the electric or hybrid vehicle, in particular a lithium-ion or nickel-cadmium battery.