Use of a diester in a cooling and / or lubricating composition for an electric or hybrid vehicle

Abstract

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

Description

[0001] Use of a diester in a cooling and / or lubricating composition for an electric or hybrid vehicle

[0002] Technical field

[0003] 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 motor or geared motor, the battery and / or the power electronics of an electric or hybrid vehicle. It aims in particular to propose a cooling composition compatible with its implementation at the level of a motor or geared motor, a battery and / or the power electronics.

[0004] Prior art

[0005] The evolution of international standards for reducing CO2 emissions, but also for reducing energy consumption, is pushing car manufacturers to offer alternative solutions to combustion engines.

[0006] One solution 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 several car companies.

[0007] 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.

[0008] For the purposes of the present invention, the term "propulsion system" is understood to mean a system comprising the mechanical parts necessary for the propulsion of an electric vehicle. The propulsion system thus more particularly encompasses 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 electric or hybrid vehicles, compositions to meet the lubrication and / or cooling constraints of the various parts of the propulsion system mentioned above.

[0009] In particular, electric propulsion 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. Generally, cooling is carried out on several parts of the propulsion system that generate heat and / or the parts of said system that are sensitive to heat, in order to avoid reaching dangerous temperatures, and in particular the power electronics and batteries.

[0010] Traditionally, electric motors have been cooled 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. Furthermore, the heat generated by a battery, particularly during rapid charging, cannot be extracted using conventional methods.

[0011] Thus, alternative methods of cooling and lubricating propulsion systems, particularly batteries, have recently been proposed.

[0012] 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 modifying additives.

[0013] By way of example, document WO 2018 / 078290 proposes to use, 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.

[0014] The invention specifically aims to propose a new composition, suitable for its use for the cooling and / or lubrication of the propulsion systems of electric or hybrid vehicles, in particular for the cooling of the motor or geared motor, the batteries and / or the power electronics, or in particular for the lubrication of the motor or geared motor, or even the reducer alone. Summary of the invention

[0015] The present invention thus relates to the use, for cooling and / or lubricating a propulsion system of an electric or hybrid vehicle, of a composition comprising one or more diester(s), each of said diesters being formed between a diol comprising from 3 to 12 carbon atoms and two monocarboxylic acids, identical or different, comprising a linear or branched hydrocarbon chain comprising from 4 to 10 carbon atoms.

[0016] According to one embodiment, the composition comprises at least 5% by mass, preferably at least 10% by mass, more preferably at least 30% by mass, even more preferably at least 50% by mass, or even at least 70% by mass of said diester(s) or 100% by mass of said diester(s), relative to the total mass of the composition.

[0017] Preferably, the composition comprises: from 5 to 95% by mass, preferably from 5 to 50% by mass, more preferably 10 to 40% by mass, of said diester(s), and from 5 to 95% by mass, preferably from 50 to 95% by mass, preferably from 60 to 90% by mass, of one or more base oils different from said diesters, relative to the total mass of the diester(s) and the base oils different from the diesters.

[0018] According to one embodiment, the composition is used for cooling the battery and / or the power electronics of an electric or hybrid vehicle, in particular a lithium-ion or nickel-cadmium battery.

[0019] Preferably, said diester comprises from 13 to 25 carbon atoms, preferably from 15 to 24 carbon atoms.

[0020] Preferably, said diester has a kinematic viscosity at 100°C ranging from 1 to 6 mm 2 / s, preferably ranging from 1 to 4 mm 2 / s.

[0021] Preferably, at least one of the two hydroxyl functions of the diol is carried by a primary carbon atom.

[0022] Preferably, said 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.

[0023] Preferably, said monocarboxylic acids, identical or different, comprise a linear hydrocarbon chain comprising from 4 to 10 carbon atoms, preferably from 5 to 9 carbon atoms.

[0024] Preferably, said composition comprises, in addition to said diester(s), at least one additive chosen from antioxidants, pour point depressant additives, antifoaming agents, anticorrosion agents, antiwear and / or extreme pressure additives, friction modifiers, detergents, dispersing agents and mixtures thereof, in particular from antioxidants, pour point depressant additives, antifoaming agents and anticorrosion agents.

[0025] 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 more diester(s) chosen from:

[0026] - one or more diester(s) formed between: a diol chosen from 1,2 decanediol and 1,3 propanediol, and two monocarboxylic acids, identical or different, comprising a linear or branched hydrocarbon chain comprising from 4 to 10 carbon atoms,

[0027] - a diester formed from 1,2-propanediol and two heptanoic acids,

[0028] - a diester formed from 1,2-propanediol and two octanoic acids,

[0029] - a diester formed from 1,2-propanediol and two decanoic acids,

[0030] - a diester formed from 1,2-propanediol and an octanoic acid and a decanoic acid, and mixtures thereof.

[0031] Other characteristics, variants and advantages of the implementation of a diester according to the invention will become more apparent upon reading the description and examples which follow, given for illustrative and non-limiting purposes of the invention.

[0032] In the following 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 stated, the expression "comprising a" must be understood as "comprising at least one".

[0033] Brief description of the drawings

[0034] [Fig 1] schematically represents an electric or hybrid vehicle propulsion system.

[0035] Detailed description

[0036] 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 more diesters, each of said diesters being formed between a diol comprising from 3 to 12 carbon atoms and two monocarboxylic acids, identical or different, comprising a linear or branched hydrocarbon chain comprising from 4 to 10 carbon atoms.

[0037] The invention also relates to the use, for cooling and / or lubricating a propulsion system of an electric or hybrid vehicle, of one or more diesters, each of said diesters being formed between a diol comprising from 3 to 12 carbon atoms and two monocarboxylic acids, identical or different, comprising a linear or branched hydrocarbon chain comprising from 4 to 10 carbon atoms.

[0038] The invention may use one or more diesters, each of said diesters being formed between: o a diol chosen from 1,2-propanediol, 1,2-decanediol and 1,3-diols comprising from 3 to 10 carbon atoms, and o two monocarboxylic acids, identical or different, comprising a linear or branched hydrocarbon chain comprising from 5 to 10 carbon atoms.

[0039] In particular, 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. Thus, according to this example, the mixture of diesters falling within the scope of the present invention is likely to comprise:

[0040] - a diester formed between the diol and two Al acids,

[0041] - a diester formed between the diol and two A2 acids,

[0042] - a diester formed between the diol and two A3 acids,

[0043] - a diester formed between the diol and an acid Al and an acid A2,

[0044] - a diester formed between the diol and an acid Al and an acid A3,

[0045] - a diester formed between the diol and an acid A2 and an acid A3.

[0046] Diester implemented according to the invention

[0047] As mentioned above, the diester(s) used according to the invention is (are) formed between a diol and two monocarboxylic acids.

[0048] For the purposes of the present invention, the term "diester formed between a diol and two monocarboxylic acids" means 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.

[0049] According to one embodiment, the diester comprises from 13 to 25 carbon atoms, preferably from 15 to 24 carbon atoms.

[0050] The diol used in the invention comprises 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.

[0051] A carbon atom is said to be primary when it is bonded to only one other carbon atom.

[0052] According to one embodiment, the diol is chosen from 1,2-propanediol, 1,2-decanediol and 1,3-diols comprising from 3 to 12 carbon atoms.

[0053] By "diol" we mean a compound containing (exactly) two hydroxyl (-OH) functions.

[0054] By "1,3-diol comprising from X to Y carbon atoms" is meant a diol whose alcohol functions are located respectively in position 1 and in position 3 of a hydrocarbon chain comprising from X to Y carbon atoms. Preferably, the 1,3-diol is chosen from 1,3-diols comprising from 3 to 10 carbon atoms, preferably from 3 to 7 carbon atoms.

[0055] For the purposes of the invention, the term "hydrocarbon chain" is intended to denote a linear or branched, saturated or unsaturated alkyl or alkylene chain. The hydrocarbon chain may optionally be interrupted by one or more heteroatoms, in particular by one or more oxygen atoms. Preferably, the hydrocarbon chain is a linear or branched, saturated or unsaturated alkyl or alkylene chain, consisting of carbon and hydrogen atoms.

[0056] According to one embodiment, the 1,3-diol comprising from 3 to 12 carbon atoms is chosen from 1,3-alkanediol comprising from 3 to 12 carbon atoms

[0057] By "1,3-alkanediol containing from X to Y carbon atoms" is meant a diol whose alcohol functions are located respectively in position 1 and in position 3 of an alkane chain containing from X to Y carbon atoms.

[0058] According to one embodiment, the diol is chosen from 1,2-propanediol, 1,2-decanediol and 1,3-diol comprising from 3 to 7 carbon atoms, preferably from 1,2-propanediol and 1,3-alkanediol comprising from 3 to 7 carbon atoms, more preferably from 1,2-propanediol and 1,3-propanediol, advantageously the diol is 1,2-propanediol.

[0059] The diol used according to the invention may be commercially available or synthesized according to any method known to those skilled in the art.

[0060] Preferably, the diol used according to the invention comprises a carbon content of biological origin of at least 60% by mass, preferably at least 70% by mass, more preferably at least 80% by mass, even more preferably at least 90% by mass, relative to the total mass of carbon atoms in the diol.

[0061] For the purposes of the present invention, the bio-based carbon content may be measured according to ASTM D6866.

[0062] The diester used according to the invention is obtained from two identical or different monocarboxylic acids. By "monocarboxylic acid" is meant a compound comprising a single carboxyl function (-COOH).

[0063] The carboxylic acids used to form the diester of the invention are chosen from monocarboxylic acids, comprising a linear or branched hydrocarbon chain comprising from 4 to 10 carbon atoms, preferably from 5 to 9 carbon atoms, more preferably from 5 to 8 carbon atoms. Preferably, the linear or branched hydrocarbon chain of the monocarboxylic acids is saturated.

[0064] According to one embodiment, the monocarboxylic acids, identical or different, comprise a linear hydrocarbon chain comprising from 4 to 10 carbon atoms, preferably from 5 to 9 carbon atoms, more preferably from 5 to 8 carbon atoms.

[0065] According to one embodiment, the monocarboxylic acids, identical or different, comprise a linear and saturated hydrocarbon chain comprising from 5 to 10 carbon atoms, preferably from 5 to 9 carbon atoms, more preferably from 5 to 8 carbon atoms.

[0066] The monocarboxylic acids used according to the invention may be commercially available or synthesized according to any method known to those skilled in the art.

[0067] Preferably, the monocarboxylic acids used according to the invention comprise a carbon content of biological origin of at least 60% by mass, preferably at least 70% by mass, more preferably at least 80% by mass, even more preferably at least 90% by mass, relative to the total mass of carbon atoms of the monocarboxylic acids.

[0068] For the purposes of the present invention, the bio-based carbon content may be measured according to ASTM D6866.

[0069] Preferably, the diester(s) used according to the invention is / are saturated.

[0070] For the purposes of the invention, the term "saturated diester" means a diester comprising saturated hydrocarbon chains. Thus, preferably, the diol used according to the invention comprises a saturated hydrocarbon chain and the monocarboxylic acids used according to the invention each comprise a saturated hydrocarbon chain, preferably said hydrocarbon chain is made up of carbon and hydrogen atoms.

[0071] According to a preferred embodiment, the diester used in the invention is a branched diester.

[0072] For the purposes of the invention, the term “branched diester” means a diester comprising a branched hydrocarbon chain which may be located between the two ester functions and / or at one or both ends of the diester.

[0073] According to a preferred embodiment, the diester used in the invention is saturated and branched.

[0074] According to one embodiment, the diester used according to the invention has a kinematic viscosity, measured at 100°C according to standard ASTM D445, ranging from 1 to 6 mm 2 / s, preferably 1 to 4 mm 2 / s.

[0075] According to one embodiment, the diester used according to the invention has a kinematic viscosity, measured at 40°C according to standard ASTM D445, ranging from 2 to 20 mm 2 / s, preferably 3 to 10 mm 2 / s.

[0076] It is understood that the definitions given above for carboxylic acid and alcohol may be combined, where possible, to define other particular embodiments.

[0077] A diester used according to the invention may more particularly correspond to the following formula (I):

[0078] [Chem 1] in which:

[0079] - R 1represents a hydrocarbon chain, linear or branched, saturated or unsaturated, preferably saturated, having from 3 to 9 carbon atoms, preferably from 4 to 8 carbon atoms, preferably from 5 to 7 carbon atoms, said hydrocarbon chain being optionally interrupted by one or more heteroatoms, such as oxygen atoms, preferably the hydrocarbon chain is made up of carbon and hydrogen atoms; and

[0080] - R 2 represents a hydrocarbon chain, linear or branched, saturated or unsaturated, preferably saturated, having from 4 to 9 carbon atoms, said hydrocarbon chain being optionally interrupted by one or more heteroatoms, such as oxygen atoms, preferably the hydrocarbon chain is made up of carbon and hydrogen atoms; and

[0081] - R 3represents a hydrocarbon chain, linear or branched, saturated or unsaturated, preferably saturated, having from 3 to 10 carbon atoms, said hydrocarbon chain being optionally interrupted by one or more heteroatoms, such as oxygen atoms, preferably the hydrocarbon chain is made up of carbon and hydrogen atoms.

[0082] Preferably, the diester(s) corresponding to formula (I) contain from 13 to 25 carbon atoms, preferably from 15 to 24 carbon atoms.

[0083] According to a particular embodiment, the radical R 3 represents the following grouping: -CH(G 1 )-CH(G 2 )- in which G 1 and G 2 represent, independently of one another, a hydrogen atom or a linear or branched, preferably linear, saturated or unsaturated, preferably saturated, hydrocarbon chain comprising from 1 to 8 carbon atoms, it being understood that G 1 and G2 cannot both be hydrogen.

[0084] Preferably, one of the two G groups 1 or G 2 is a hydrogen atom.

[0085] According to one embodiment, the diester(s) used according to the invention is (are) chosen from: a diester formed from 1,2-decanediol and two heptanoic acids, a diester formed from 1,2-decanediol and two pentanoic acids, a diester formed from 1,2-propanediol and two heptanoic acids, a diester formed from 1,2-propanediol and two nonanoic acids, a diester formed from 1,3-propanediol and two heptanoic acids, a diester formed from 1,2-propanediol and two octanoic acids, a diester formed from 1,2-propanediol and two decanoic acids, a diester formed from 1,2-propanediol and one octanoic acid and one acid decanoic, and their mixtures.

[0086] The diesters 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, each esterification reaction being implemented between an alcohol function of the diol and the acid function of the monocarboxylic acid.

[0087] 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.

[0088] 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 according to the invention, in particular as defined above.

[0089] Preferably, the diester used according to the invention comprises a carbon content of biological origin of at least 60% by mass, preferably at least 70% by mass, more preferably at least 80% by mass, even more preferably at least 90% by mass, relative to the total mass of carbon atoms in the diester.

[0090] For the purposes of the present invention, the bio-based carbon content may be measured according to ASTM D6866.

[0091] The diester or the mixture of diesters according to the invention may represent at least 5% by mass of the composition used according to the invention, preferably at least 10% by mass, preferably at least 30% by mass, more preferably at least 50% by mass, even more preferably at least 70% by mass, in particular at least 80% by mass, more particularly at least 90% by mass, or even at least 95% by mass, of the total mass of the composition used according to the invention. The diester(s) used according to the invention may be used with one or more additional base oils (also called co-bases).According to this embodiment, preferably, the composition will comprise: from 5 to 95% by mass, preferably from 5 to 50% by mass, more preferably 10 to 40% by mass, of the diester(s) according to the invention, and from 5 to 95% by mass, preferably from 50 to 95% by mass, preferably from 60 to 90% by mass, of one or more base oils different from the diesters according to the invention, relative to the total mass of the diester(s) and of the base oils different from the diesters.

[0092] According to one embodiment, a composition used according to the invention may comprise at least 30% by mass of a diester or mixture of diesters according to the invention, more particularly between 50% and 99.5% by mass, preferably between 70% and 99% by mass, more preferably between 80% and 99% by mass, or even between 80% and 95% by mass, relative to the total mass of said composition.

[0093] According to a particular embodiment, a cooling and / or lubricating composition according to the invention may be formed at more than 95% by mass, in particular at more than 98% by mass, of one or more diesters according to the invention, or even with 100% by mass of one or more diesters according to the invention.

[0094] According to a particular embodiment, a cooling composition implemented according to the invention will comprise 100% by mass of a mixture of diester(s) defined in the invention and of additional base oil(s), preferably in a proportion such that the composition comprises: from 5 to 95% by mass, preferably from 5 to 50% by mass, more preferably 10 to 40% by mass, of the diester(s) according to the invention, and from 5 to 95% by mass, preferably from 50 to 95% by mass, preferably from 60 to 90% by mass, of one or more base oils different from the diesters according to the invention, relative to the total mass of the cooling composition.

[0095] Additional base oil(s) A cooling and / or lubricating composition used according to the invention may comprise, in addition to one or more diesters according to the invention, one or more base oils distinct from the diesters according to the invention.

[0096] 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.

[0097] It can be a mixture of several base oils, for example a mixture of two, three or four base oils.

[0098] 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 standard ASTM D445, ranging from 1.5 to 8 mm 2 / s, especially 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.

[0099] Base oils can 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.

[0100] [Table 1]

[0101] 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, dealphating, solvent dewaxing, hydrotreating, hydrocracking, hydroisomerization, and hydrofinishing. Blends of synthetic and mineral oils, which may be bio-based, may also be used.

[0102] 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, in particular viscosity index, sulfur content or oxidation resistance, suitable for use in propulsion systems of an electric or hybrid vehicle.

[0103] The base oils may also be chosen from synthetic oils, such as certain esters of carboxylic acids and alcohols, distinct from the diester defined according to the invention, from polyalphaolefins (PAO), and from polyalkylene glycols (PAG) obtained by polymerization or copolymerization of alkylene oxides comprising from 2 to 8 carbon atoms, in particular from 2 to 4 carbon atoms.

[0104] PAOs used as base oils are, for example, obtained from monomers containing 4 to 32 carbon atoms, for example from octene or decene.

[0105] 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.

[0106] 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.

[0107] Advantageously, the additional base oil or oils are chosen from polyalphaolefins (PAOs).

[0108] It is up to a 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.

[0109] According to one embodiment, a composition implemented according to the invention may comprise from 5 to 95% by mass, preferably from 50 to 95% by mass, more preferably from 60 to 90% by mass, of one or more base oils different from the diesters according to the invention, relative to the total mass of said composition. Additives

[0110] 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 / or cooling of propulsion systems of electric or hybrid vehicles.

[0111] The additives that can be incorporated into a composition according to the invention can be 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 and mixtures thereof, in particular from antioxidants, pour point lowering additives, anti-foaming agents and anti-corrosion agents.

[0112] 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.

[0113] 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.

[0114] 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.

[0115] These additives can be introduced in isolation and / or in the form of a mixture similar to those already available for sale for formulations of commercial lubricants for vehicle engines, with performance levels as defined by the ACEA (Association of European Automobile Manufacturers) and / or the API (American Petroleum Institute), well known to those skilled in the art.

[0116] 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 10% by mass, in particular less than or equal to 5% by mass, and more particularly ranging from 0.01 to 3% by mass, relative to the total mass of said composition.

[0117] A cooling and / or lubricating composition used according to the invention may thus comprise at least one antioxidant additive.

[0118] 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 previously, and (ii) at least one antioxidant additive.

[0119] The antioxidant additive generally helps 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.

[0120] 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. The 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 C1-C12 alkyl group, N,N'-dialkylaryldiamines and mixtures thereof.

[0121] 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 C1-C10 alkyl group, preferably a C1-C6 alkyl group, preferably a C4 alkyl group, preferably by the tert-butyl group.

[0122] Amino compounds are another class of antioxidant additives that can be used, possibly in combination with phenolic antioxidant additives. Examples of amino 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 6represents a hydrogen atom, an alkyl group, an aryl group or a group of 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.

[0123] Sulfurized alkyl phenols or their alkali and alkaline earth metal salts can also be used as antioxidant additives.

[0124] Another class of antioxidant additives is copper compounds, e.g. 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.

[0125] Advantageously, a cooling and / or lubricating composition comprises at least one ash-free antioxidant additive.

[0126] 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.

[0127] A cooling and / or lubricating composition according to the invention may comprise at least one anti-wear and / or extreme pressure additive.

[0128] Anti-wear additives and extreme pressure additives protect friction surfaces by forming a protective film adsorbed on these surfaces.

[0129] There are a wide variety of anti-wear additives. Preferably, the anti-wear additives are chosen 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.

[0130] 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.

[0131] 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.

[0132] A cooling and / or lubricating composition according to the invention may further comprise an antifoaming agent.

[0133] The antifoam agent can be chosen from silicones.

[0134] 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.

[0135] A cooling and / or lubricating composition according to the invention may comprise at least one friction modifying additive.

[0136] 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 monoesters of fatty acids and polyols, 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.

[0137] 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 aimed at cooling the battery part.

[0138] A cooling and / or lubricating composition according to the invention may comprise at least one detergent additive.

[0139] Detergent additives generally reduce the formation of deposits on the surface of metal parts by dissolving secondary oxidation and combustion products.

[0140] Detergent additives usable in a cooling and / or lubricating composition are generally known to those skilled in the art. The 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.

[0141] 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.

[0142] These metal salts generally contain the metal in a stoichiometric quantity or in excess, i.e. 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 an oil-insoluble metal salt, for example a carbonate, a hydroxide, an oxalate, an acetate, a glutamate, preferably a carbonate.

[0143] A cooling and / or lubricating composition may, for example, comprise from 2 to 4% by mass of detergent additive, relative to the total mass of the composition.

[0144] A cooling and / or lubricating composition may also comprise at least one pour point depressant additive.

[0145] By slowing the formation of paraffin crystals, pour point depressants generally improve the cold behavior of the composition. Examples of pour point depressants include polyalkyl methacrylates, polyacrylates, polyarylamides, polyalkylphenols, polyalkylnaphthalenes, and alkylated polystyrenes.

[0146] Also, a cooling and / or lubricating composition may comprise at least one dispersing agent.

[0147] The dispersing agent may be chosen from Mannich bases, succinimides and their derivatives. A cooling composition may, for example, comprise from 0.2 to 10% by mass of dispersing agent, relative to the total mass of the composition.

[0148] According to a particular embodiment, a cooling and / or lubricating composition used according to the invention comprises, or is formed from (i) at least one diester according to the invention and (ii) at least one additive chosen from antioxidants, antifoaming agents, pour point depressant additives, anticorrosion agents, antiwear and / or extreme pressure additives, friction modifiers, detergents, dispersing agents and mixtures thereof, preferably from antioxidants, pour point depressant additives, antifoaming agents and anticorrosion agents.

[0149] Advantageously, a cooling and / or lubricating composition used 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.

[0150] According to a particular embodiment, a cooling and / or lubricating composition implemented according to the invention comprises, or even consists of:

[0151] - 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 (I);

[0152] - 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 passivating agents, and mixtures thereof; and

[0153] - optionally from 5 to 94% by mass, preferably from 10 to 94% by mass, preferably from 15 to 90% by mass of base oil(s) distinct from the diester according to the invention, the contents being expressed relative to the total mass of said composition.

[0154] According to a particular embodiment, a cooling and / or lubricating composition used according to the invention comprises, or even consists of: from 5 to 95% by mass, preferably from 5 to 50% by mass, more preferably 10 to 40% by mass, of said diester(s) corresponding to formula (I); from 5 to 95% by mass, preferably from 50 to 95% by mass, preferably from 60 to 90% 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 chosen from friction modifying additives, anti-wear additives, extreme pressure additives, detergents, antioxidants, viscosity index (VI) improvers, pour point depressant (PPD) additives, 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.;

[0155] According to a particular embodiment, a cooling and / or lubricating composition implemented according to the invention comprises, or even consists of:

[0156] - 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 (I);

[0157] - 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;

[0158] - 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 depressant (PPD) additives, 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.

[0159] A cooling and / or lubricating composition used according to the invention advantageously has a kinematic viscosity, measured at 100°C according to standard ASTM D445, ranging from 1 to 6 mm 2 / s, preferably 1 to 4 mm 2 / s.

[0160] A cooling and / or lubricating composition used according to the invention advantageously has a kinematic viscosity, measured at 40°C according to standard ASTM D445, ranging from 2 to 20 mm 2 / s, preferably 3 to 10 mm 2 / s.

[0161] Application

[0162] As indicated previously, a composition according to the invention can be used as a cooling and / or lubricating fluid for a propulsion system of an electric or hybrid vehicle.

[0163] 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).

[0164] The electric motor typically comprises power electronics (11) connected to a stator (13) and a rotor (14). The stator comprises coils, in particular copper coils, which are alternately supplied with an electric current. This generates a rotating magnetic field. The rotor itself comprises coils, permanent magnets or other magnetic materials, and is rotated by the rotating magnetic field. The power electronics (11), the stator (13) and the rotor (14) of a propulsion system (1) are parts whose structure is complex and generate a large amount of heat during operation of the motor. It is therefore imperative to ensure cooling of the electric motor, and the power electronics.

[0165] 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.

[0166] Advantageously, a composition according to the invention can be used to cool the battery of an electric or hybrid vehicle. In particular, according to this embodiment, it is intended to be placed in direct contact with the battery.

[0167] Batteries suitable for the propulsion systems of an electric or hybrid vehicle include, in particular, Li-ion batteries and nickel-cadmium batteries.

[0168] 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 according to the invention, as defined previously.

[0169] 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 of injection of said composition onto the surface of the battery.

[0170] 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.

[0171] Cooling may be implemented by any method known to those skilled in the art. The battery may be immersed or semi-immersed, static or circulating, in said composition.

[0172] 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.

[0173] 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.

[0174] Additionally, oil circulation systems commonly used in electric motors may be employed, as for example described in WO 2015 / 116496.

[0175] 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.

[0176] The cooling composition according to the invention has in particular electrical insulation properties which are particularly satisfactory for use in electric or hybrid vehicles.

[0177] It is possible to take advantage, in addition to the cooling properties of a composition according to the invention, of its lubricating properties.

[0178] Thus, a composition according to the invention can simultaneously be used to lubricate the various parts of a propulsion system of an electric or hybrid vehicle, in particular 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.

[0179] 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.

[0180] The invention will now be described by means of the following examples, given of course by way of illustration and not limitation of the invention. Examples

[0181] Example 1: Preparation of the test compounds

[0182] The following compounds were prepared:

[0183] - Diester A: diester formed from 1,2-decanediol and two heptanoic acids

[0184] - Diester B: diester formed from 1,2-decanediol and two pentanoic acids

[0185] - Diester C: diester formed from 1,2-propanediol and two heptanoic acids

[0186] - Diester D: diester formed from 1,2-propanediol and two nonanoic acids

[0187] - Diester E: diester formed from 1,3-propanediol and two heptanoic acids

[0188] - Diester F: mixture of diesters formed from 1,2-propanediol and a biosourced fraction of C8-C10 monoester acids 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.

[0189] The diesters and monoester were prepared according to known methods for preparing esters.

[0190] Example 2: Viscosity measurement

[0191] 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.

[0192] Viscosities are shown in Table 2.

[0193] [Table 2] All the diesters used according to the invention have a viscosity at 100°C of less than 4 mm 2 / s.

[0194] Example 3: Measurement of thermal conductivity

[0195] The thermal conductivity of the compounds described in Example 1 was determined according to ASTM D7896-19 at various temperatures.

[0196] The results are shown in Table 3.

[0197] [Table 3]

[0198] These results show that the diesters used according to the invention have good thermal properties, which allows their use as a cooling fluid for a propulsion system of an electric or hybrid vehicle.

[0199] Example 4: Measuring the mini flash point

[0200] The mini flash point is measured according to ASTM D93Ac (Cleaveland open cup method).

[0201] The values ​​are shown in Table 4.

[0202] [Table 4]

[0203] As shown in Table 4, the flash point is better when the diester is a branched diester. Indeed, the diester formed from 1,2-propanediol has a lower flash point than the diester formed from 1,3-propanediol, with the same total number of carbon atoms.

Claims

Claims 1. Use, for cooling and / or lubricating a propulsion system of an electric or hybrid vehicle, of a composition comprising one or more diester(s), each of said diesters being formed between a diol comprising from 3 to 12 carbon atoms and two monocarboxylic acids, identical or different, comprising a linear or branched hydrocarbon chain comprising from 4 to 10 carbon atoms, said hydrocarbon chain possibly being interrupted by one or more heteroatoms.

2. Use according to claim 1, in which the linear or branched hydrocarbon chain comprising from 4 to 10 carbon atoms is a linear or branched, saturated or unsaturated alkyl or alkylene chain, consisting of carbon and hydrogen atoms.

3. Use according to claim 1 or 2, in which the composition comprises at least 5% by mass, preferably at least 10% by mass, more preferably at least 30% by mass, even more preferably at least 50% by mass, or even at least 70% by mass of said diester(s) or 100% by mass of said diester(s), relative to the total mass of the composition.

4. Use according to claim 1 or 2, wherein the composition comprises: from 5 to 95% by mass, preferably from 5 to 50% by mass, more preferably 10 to 40% by mass, of said diester(s), and from 5 to 95% by mass, preferably from 50 to 95% by mass, preferably from 60 to 90% by mass, of one or more base oils different from said diesters, relative to the total mass of the diester(s) and the base oils different from the diesters.

5. Use according to any one of claims 1 to 4, for cooling the battery and / or the power electronics of an electric or hybrid vehicle, in particular a lithium-ion or nickel-cadmium battery.

6. Use according to any one of the preceding claims, wherein said diester comprises from 13 to 25 carbon atoms, preferably from 15 to 24 carbon atoms.

7. Use according to any one of the preceding claims, in which the diester(s) correspond to formula (I): [Chem 1] in which: - R 1represents a hydrocarbon chain, linear or branched, saturated or unsaturated, preferably saturated, having from 3 to 9 carbon atoms, preferably from 4 to 8 carbon atoms, preferably from 5 to 7 carbon atoms, said hydrocarbon chain being optionally interrupted by one or more heteroatoms, such as oxygen atoms, preferably the hydrocarbon chain is made up of carbon and hydrogen atoms; and - R 2 represents a hydrocarbon chain, linear or branched, saturated or unsaturated, preferably saturated, having from 4 to 9 carbon atoms, said hydrocarbon chain being optionally interrupted by one or more heteroatoms, such as oxygen atoms, preferably the hydrocarbon chain is made up of carbon and hydrogen atoms; and - R 3represents a hydrocarbon chain, linear or branched, saturated or unsaturated, preferably saturated, having from 3 to 10 carbon atoms, said hydrocarbon chain being optionally interrupted by one or more heteroatoms, such as oxygen atoms, preferably the hydrocarbon chain is made up of carbon and hydrogen atoms.

8. Use according to any one of the preceding claims, wherein said diester has a kinematic viscosity at 100°C ranging from 1 to 6 mm 2 / s, preferably ranging from 1 to 4 mm 2 / s.

9. Use according to any one of the preceding claims, in which at least one of the two hydroxyl functions of the diol is carried by a primary carbon atom.

10. Use according to any one of the preceding claims, in which said diol is chosen from 1,2-propanediol, 1,2-decanediol and 1,3-alkanediols comprising from 3 to 10 carbon atoms.

11. Use according to any one of the preceding claims, wherein said diol is chosen from 1,2-propanediol and 1,3-propanediol, preferably the diol is 1,2-propanediol.

12. Use according to any one of the preceding claims, in which said monocarboxylic acids, identical or different, comprise a linear hydrocarbon chain comprising from 4 to 10 carbon atoms, preferably from 5 to 9 carbon atoms.

13. Use according to any one of the preceding claims, in which the diester(s) are chosen from: - one or more diester(s) formed between: a diol chosen from 1,2 decanediol and 1,3 propanediol, and two monocarboxylic acids, identical or different, comprising a linear or branched hydrocarbon chain comprising from 4 to 10 carbon atoms, - a diester formed from 1,2-propanediol and two heptanoic acids, - a diester formed from 1,2-propanediol and two octanoic acids, - a diester formed from 1,2-propanediol and two decanoic acids, - a diester formed from 1,2-propanediol and an octanoic acid and a decanoic acid, and mixtures thereof.

14. Use according to any one of the preceding claims, in which the diester(s) are chosen from - a diester formed from 1,2-decanediol and two heptanoic acids, - a diester formed from 1,2-decanediol and two pentanoic acids, - a diester formed from 1,2-propanediol and two heptanoic acids, - a diester formed from 1,2-propanediol and two nonanoic acids, - a diester formed from 1,3-propanediol and two heptanoic acids, - a diester formed from 1,2-propanediol and two octanoic acids, - a diester formed from 1,2-propanediol and two decanoic acids, - a diester formed from 1,2-propanediol and an octanoic acid and a decanoic acid, and mixtures thereof.

15. Use according to any one of the preceding claims, characterized in that said composition comprises, in addition to said diester(s), at least one additive chosen from antioxidants, pour point depressant additives, antifoaming agents, anticorrosion agents, antiwear and / or extreme pressure additives, friction modifiers, detergents, dispersing agents and mixtures thereof, in particular from antioxidants, pour point depressant additives, antifoaming agents and anticorrosion agents.

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