Use of a Diester in a Cooling And/Or Lubricating Composition for an Electric or Hybrid Vehicle

The present application is a national entry of PCT Application no. PCT/EP2023/069115, filed on Jul. 11, 2023, which claims priority under the Paris Convention to French Application FR FR2207203, filed on Jul. 13, 2022. The entire contents of such prior applications are incorporated by reference herein.

The present invention relates to the field of compositions for cooling and/or lubricating a propulsion system of an electric or hybrid vehicle, and more particularly for cooling the battery and the motor reduction gear, the battery and/or the power electronic components of an electric or hybrid vehicle. More particularly, the invention aims at proposing a cooling composition compatible with the implementation thereof in motor or a motor reduction gear, a battery and power electronic components.

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

One of the solutions identified by car manufacturers is to replace internal combustion engines with electric motors. Research to reduce CO2 emissions has thus led a number of automotive companies to the development of electric vehicles.

“Electric vehicle” as defined by the present invention refers to a vehicle including an electric motor as the only means of propulsion, whereas a hybrid vehicle comprises an internal combustion engine and an electric motor as combined means of propulsion.

“Propulsion system” as defined by the present invention, refers to a system comprising the mechanical parts required for the propulsion of an electric vehicle. The propulsion system thereby encompasses more particularly an electric motor comprising the rotor-stator assembly of power electronic systems (dedicated to speed regulation), a transmission (also called reduction gear and when the reduction gear is joined to the motor, one talks about a motor reduction gear) and a battery. The battery as such usually consists of a set of electric accumulators, called cells.

In general, in electric or hybrid vehicles, it is necessary to use compositions so as to meet the lubrication and/or cooling requirements of the different parts of the aforementioned propulsion system.

More particularly, electric propulsion systems generate heat during the operation thereof, via the electric motor, the power electronic systems and the batteries. Since the amount of heat generated is greater than the amount of heat normally dissipated into the environment, cooling must be provided for the engine, the electronic systems and the batteries. In general, cooling is performed on several of heat-generating parts of the propulsion system and/or heat-sensitive parts of said system, in particular power electronic systems and batteries, so as to prevent dangerous temperatures from being reached.

Conventionally, it is known how to cool electric motors by air or water, optionally combined with glycol. However, with the emergence of increasingly smaller engines with increasingly higher power, such cooling methods are no longer sufficient. In addition, the heat that a battery can generate, in particular during a quick charging, cannot be extracted by the methods conventionally used.

Thereby, alternative methods of cooling and of lubrication of the propulsion systems, more particularly batteries, have recently been proposed.

As such, lubricating compositions have been proposed to perform the double function of lubrication and cooling. The lubricating compositions are conventionally composed of one or a plurality of base oils, with which are generally associated a plurality of additives dedicated to stimulating the lubricating performance the base oils, such as e.g. friction modifier additives.

As an example, document WO 2018/078290 proposes to use, for cooling and/or lubricating a motor 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 precisely at proposing a novel composition suitable for the implementation thereof for cooling and/or lubricating propulsion systems of electric or hybrid vehicles, more particularly for cooling the motor or the motor reduction gear, the batteries and/or the power electronic components, or in particular for the lubrication of the motor or of the motor reduction gear, or even of the reduction gear alone.

The subject matter of the present invention is thereby the use, for cooling and/or lubricating a propulsion system of an electric or hybrid vehicle, of a composition comprising one or a plurality of diesters, each of said diesters being formed between a diol having from 3 to 12 carbon atoms and two monocarboxylic acids, identical or different, including a linear or branched hydrocarbon chain having from 4 to 10 carbon atoms.

According to one embodiment, the composition comprises at least 5% by weight, preferably at least 10% by weight, else preferably at least 30% by weight, even more preferentially at least 50% by weight, or even at least 70% by weight of said diester(s) or 100% by weight of said diester(s), relative to the total weight of the composition.

Preferably, the composition comprises:

According to one embodiment, the composition is used to cool the battery and/or the power electronic components of an electric or hybrid vehicle, more particularly a lithium-ion or nickel-cadmium battery.

Preferably, said diester included 13 to 25 carbon atoms; preferably from 15 to 24 carbon atoms,

Preferably, said diester has a kinematic viscosity at 100° C. ranging from 1 to 6 mm/s, preferably ranging from 1 to 4 mm/s.

Preferably, at least one of the two hydroxyl functions of the diol is supported by a primary carbon atom.

Preferably, the diol is chosen from 1,2-propanediol, 1,2-decanediol and 1,3-alkanediols having from 3 to 10 carbon atoms.

Preferably, said diol is chosen from 1,2-propanediol and 1,3-propanediol, preferably the diol is 1,2-propanediol.

Preferably, said monocarboxylic acids, either identical or different, include a linear hydrocarbon chain having from 4 to 10 carbon atoms, preferably from 5 to 9 carbon atoms.

Preferably, said composition comprises, in addition to said diester(s), at least one additive chosen from antioxidants, pour point depressants, anti-foam agents, anticorrosion agents, anti-wear and/or extreme-pressure additives, friction modifiers, detergents, dispersants and mixtures thereof, more particularly from antioxidants, pour point depressants, anti-foam agents and anticorrosion agents.

According to one embodiment of the invention, the invention relates to the use, for cooling and/or lubricating a propulsion system of an electric or hybrid vehicle, of a composition comprising one or a plurality of diesters chosen from:

Other features, variants and advantages of the implementation of a diester according to the invention will become clearer upon reading the following description and the examples, given as an illustration of the invention, but not limited to.

Hereinafter in the text, the expressions “comprised between . . . and . . . ”, “ranging from . . . to . . . ” and “varying from . . . to . . . ” are equivalent and mean that the limits are included, unless otherwise stated.

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

Firstly, the invention relates to the use, for cooling and/or lubricating a propulsion system of an electric or hybrid vehicle, of a composition comprising one or a plurality of diesters, each of said diesters being formed between a diol having from 3 to 12 carbon atoms and two monocarboxylic acids, identical or different, including a linear or branched hydrocarbon chain having from 4 to 10 carbon atoms.

The invention further relates to the use, for cooling and/or lubricating a propulsion system of an electric or hybrid vehicle, of one or a plurality of diesters, each of said diesters being formed between a diol having from 3 to 12 carbon atoms and two monocarboxylic acids, identical or different, including a linear or branched hydrocarbon chain having from 4 to 10 carbon atoms.

The invention can use one or a plurality of diesters, each of said diesters being formed between:

More particularly, it is possible to prepare a mixture of diesters by reacting a diol with a mixture of monocarboxylic acids.

For example, it is possible to react a diol and three monocarboxylic acids A1, A2 and A3. Thereby, according to such example, the mixture of diesters falling within the scope of the present invention can comprise:

As mentioned hereinabove, the diester(s) used according to the invention is (are) formed between a diol and two monocarboxylic acids.

“Diester formed between a diol and two monocarboxylic acids”, as defined by the present invention, refers to a compound obtained by two esterification reactions, each esterification reaction being carried out between one of the two alcohol functions of the diol and the acid function of one of the two monocarboxylic acids.

According to a preferred embodiment, the diester has 13 to 25 carbon atoms, preferably from 15 to 24 carbon atoms.

The diol used in the invention has from 3 to 12 carbon atoms. Preferably, at least one of the two hydroxyl functions of the diol is carried by a primary carbon atom.

A carbon atom is called primary when same is bonded to only one other carbon atom.

According to an embodiment, the diol is chosen from 1,2-propanediol, 1,2-decanediol and 1,3-diols having from 3 to 12 carbon atoms.

“Diol” refers to a compound including (exactly) two hydroxyl functions (—OH).

“1,3-diol including X to Y carbon atoms” means a diol the alcohol functions of which are located in position 1 and in position 3, respectively, of a hydrocarbon chain including X to Y carbon atoms.

Preferably, the 1,3-diol is chosen from the 1,3-diol having from 3 to 10 carbon atoms, preferably from 3 to 7 carbon atoms.

“Hydrocarbon chain”, as defined by the invention, refers to a linear or branched, saturated or unsaturated alkyl or alkylene chain. The hydrocarbon chain may optionally be interrupted by one or a plurality of heteroatoms, more particularly by one or a plurality of oxygen atoms. Preferably, the hydrocarbon chain is a linear or branched, saturated or unsaturated alkyl or alkylene chain consisting of carbon and hydrogen atoms.

According to one embodiment, the 1,3-diol having from 3 to 12 carbon atoms is chosen from 1,3-alkanediols having from 3 to 12 carbon atoms

“1,3-alkanediol having X to Y carbon atoms'” means a diol the alcohol functions of which are located in position 1 and in position 3, respectively, of an alkane chain having X to Y carbon atoms.

According to one embodiment, the diol is chosen from 1,2-propanediol, 1,2-decanediol and 1,3-diol having from 3 to 7 carbon atoms, preferably from 1,2-propanediol and 1,3-alkanediol having from 3 to 7 carbon atoms, more preferably from 1,2-propanediol and 1,3-propanediol, advantageously the diol is 1,2-propanediol.

The diol used according to the invention may be available commercially or synthesized according to any method well known to a person skilled in the art.

Preferably, the diol used according to the invention comprises a content of carbon of biological origin of at least 60% by weight, preferably of at least 70% by weight, else preferably of at least 80% by weight, else more preferentially of at least 90% by weight, relative to the total weight of the carbon atoms of the diol.

Within the framework of the present invention, the content of carbon of biological origin can be measured as per the standard ASTM D6866.

The diester used according to the invention is obtained from two identical or different monocarboxylic acids.