Use of esters in cooling compositions

Abstract

Use of an ester in a cooling composition. The present invention relates to a composition for cooling the drive system of an electric or hybrid vehicle, the composition having a 200mm saturation temperature measured at -25°C. 2 The present invention also relates to the use of a composition comprising at least one ester having a kinematic viscosity of 200 mm / s or less and an autoignition point of 350°C or more. The composition is also capable of cooling a drive system, in particular a battery and / or power electronics of an electric or hybrid vehicle, and the composition (i) has a kinematic viscosity of 200 mm / s or less measured at -25°C. 2 and an autoignition point of 350°C or greater; and (ii) at least one additive selected from antioxidants, friction modifiers, detergents, anti-wear additives, extreme pressure additives, dispersants, pour point depressants, anti-foaming agents, and mixtures thereof.

Description

[Technical Field]

[0001] The present invention relates to the field of compositions for cooling the propulsion systems of electric or hybrid vehicles, more particularly for cooling the batteries and / or power electronics of electric or hybrid vehicles. The invention is more particularly directed to proposing a cooling composition that is compatible with its use in batteries and / or power electronics and that has improved stability at high temperatures, in particular temperatures reached in the event of thermal runaway. [Background technology]

[0002] Changing international standards, not only to reduce CO2 emissions but also to lower energy consumption, are forcing car manufacturers to come up with alternative solutions to the combustion engine.

[0003] One of the solutions identified by car manufacturers consists of replacing combustion engines with electric motors. Research aimed at reducing CO2 emissions has therefore led to the development of electric vehicles by a number of car companies.

[0004] For purposes of this invention, the term "electric vehicle" means a vehicle that has an electric motor as its sole means of propulsion, while a hybrid vehicle has a combustion engine and an electric motor as a combined means of propulsion.

[0005] For the purposes of this invention, the term "propulsion system" refers to the system including the mechanical components necessary for the propulsion of an electric vehicle. The propulsion system therefore encompasses more particularly an electric motor with a rotor-stator assembly of power electronics (only for speed regulation), a transmission, and a battery, which itself generally consists of a set of accumulator cells known as cells.

[0006] Generally, electric or hybrid vehicles require the use of compositions to satisfy the constraints of lubricating and / or cooling the various components of the propulsion system envisaged above.

[0007] In particular, electric propulsion systems generate heat during their functioning due to the electric motor, power electronics, and batteries. Since the amount of heat generated is greater than the amount that is typically dissipated to the environment, it is necessary to ensure that the motor, power electronics, and batteries are cooled. Generally, cooling is provided to some heat-generating parts of the propulsion system and / or heat-sensitive parts of said system, and in particular the power electronics and batteries, to prevent them from reaching dangerous temperatures.

[0008] Conventionally, the practice of cooling electric motors with air or water, possibly in combination with glycol, is known. However, with the emergence of increasingly powerful and increasingly small motors, these cooling methods are no longer sufficient. Furthermore, the heat that can be generated by the battery, especially during fast charging, cannot be extracted by the conventional methods used.

[0009] Therefore, alternative methods for cooling propulsion systems, and in particular batteries, have recently been proposed.

[0010] In this regard, lubricant compositions are proposed to perform the dual function of lubricating and cooling. Lubricant compositions are conventionally composed of one or more base oils, generally combined with several additives intended to stimulate the lubrication performance of the base oil, e.g., friction-modifying additives. For example, WO 2018 / 078290 proposes the use of a composition comprising at least one polyalkylene glycol obtained by polymerization or copolymerization of alkylene oxides containing 2 to 8 carbon atoms to cool and / or lubricate the motorization system of an electric vehicle.

[0011] Despite the use of cooling systems, it is not possible to completely eliminate the risk of a battery overheating, for example in the event of a defective cell or otherwise, during which a cell may be punctured. This can lead to the battery exploding and even catching fire, known as the "runaway effect." Such overheating is particularly feared in the context of the functioning of Li-ion batteries. Therefore, safety tests (UN RE100 standard) must be carried out on the batteries before they can be placed on the market. [Prior art documents] [Patent documents]

[0012] [Patent Document 1] WO2018 / 078290 [Patent Document 2] WO2015 / 116496 Summary of the Invention [Problem to be solved by the invention]

[0013] Therefore, it is desirable for the coolant fluid used in the propulsion system of an electric or hybrid vehicle, particularly in the battery and / or power electronics, to have properties that protect even at the high temperatures that may be reached if the battery overheats. [Means for solving the problem]

[0014] The present invention is particularly directed to proposing novel compositions suitable for use in cooling the propulsion systems of electric or hybrid vehicles, in particular for cooling the batteries and / or power electronics, while remaining stable at the high temperatures that can be reached during system heating, up to temperatures of up to 350°C or even 400°C.

[0015] The subject of the present invention is therefore a 200 mm refrigerant cooling system, measured at −25° C. according to standard ASTM D445, for cooling the propulsion system of an electric or hybrid vehicle, in particular the battery and / or the power electronics. 2 1. Use of a composition comprising at least one ester having a kinematic viscosity of not more than 1000 kJ / s and an autoignition temperature of not less than 350° C., measured according to standard ASTM E659.

[0016] The term "ester" refers to a compound containing at least one ester functional group. The ester can be, inter alia, a monoester, a diester, or a triester.

[0017] In the remainder of the text, and unless otherwise indicated, the term "ester according to the invention" means an ester that satisfies the above criteria in terms of kinematic viscosity and autoignition temperature.

[0018] The autoignition temperature, known as "AIT," refers to the temperature at or above which combustion will self-initiate without any flame being applied.

[0019] Likewise, the terms "cooling composition" or "coolant composition" are used in the remainder of the text to mean a composition used according to the invention, comprising at least one ester according to the invention, as defined above.

[0020] Advantageously, the esters according to the invention have a viscosity of 20 mm, measured at 25° C. according to standard ASTM D445. 2 / s or less, preferably 15 mm 2 / s or less, especially 10mm 2 / s or less.

[0021] Furthermore, the esters according to the invention advantageously have a particularly high autoignition temperature, preferably above 360°C, more preferentially above 380°C and in particular above 400°C.

[0022] The composition according to the invention may be formed in whole or in part from one or more esters as defined above. Preferably, the cooling composition according to the invention is formed from at least 30% by weight, preferably at least 50% by weight, more preferentially at least 70% by weight, even more preferentially at least 80% by weight or even at least 90% by weight of one or more esters according to the invention, relative to the total weight of the composition.

[0023] Additives, preferably one or more antioxidants, can be added, provided that their presence does not affect the properties provided by the esters used according to the invention.

[0024] The esters used according to the invention are, in particular: - monoesters, preferably "branched" monoesters, formed between at least one saturated or unsaturated, preferably saturated, monocarboxylic acid containing a branched hydrocarbon-based chain and at least one linear or branched, saturated or unsaturated monoalcohol containing a hydrocarbon-based chain, and - esters containing at least one heteroatom, preferably an oxygen atom, other than the oxygen atom attached to the ester functional group of the ester, and A mixture of them may be selected from:

[0025] According to a particular embodiment, the esters used according to the invention are: - esters, referred to in the remainder of the text as "branched esters", formed between at least one carboxylic acid comprising at least one saturated or unsaturated, preferably saturated, branched hydrocarbon-based chain and at least one alcohol comprising at least one linear or branched, saturated or unsaturated hydrocarbon-based chain, preferably a branched monoester, - esters containing at least one heteroatom, preferably an oxygen atom, other than the oxygen atom attached to the ester functional group of the ester, and - A mixture of these is selected from.

[0026] Preferably, the branched esters according to the invention are formed from at least one carboxylic acid containing at least one branched hydrocarbon-based chain, preferably saturated, containing from 3 to 14 carbon atoms.

[0027] In particular, the branched esters according to the invention may be formed from at least one alcohol comprising at least one branched hydrocarbon-based chain, preferably saturated, containing in particular from 3 to 14 carbon atoms.

[0028] The ester according to the present invention, which comprises at least one heteroatom other than the oxygen atom attached to the ester functional group, can be formed from at least one alcohol comprising at least one heteroatom other than the oxygen atom of the hydroxyl functional group, and / or at least one carboxylic acid comprising at least one heteroatom other than the oxygen atom of the carboxyl functional group, wherein the heteroatom is selected from oxygen and nitrogen.

[0029] In particular, the esters according to the invention, which contain at least one heteroatom other than the oxygen atom attached to the ester function, are formed from at least one alcohol containing at least one ether function, preferably from at least one alcohol containing at least one linear or branched, preferably linear, saturated or unsaturated, preferably saturated, hydrocarbon-based chain, in particular containing from 3 to 14 carbon atoms, the hydrocarbon-based chain being interrupted by at least one oxygen atom.

[0030] The esters according to the invention are advantageously monoesters, diesters or triesters. The esters are preferably monoesters or diesters.

[0031] According to a particular embodiment, the esters according to the invention are monoesters, in particular branched monoesters as defined above.

[0032] According to another particular embodiment, the ester according to the invention is an ester comprising at least one heteroatom other than the oxygen atom attached to said ester functional group, which may be a monoester, a diester or a triester, preferably a diester.

[0033] Preferably, the ester according to the invention is a branched monoester, or a diester as defined above, which contains at least one heteroatom, preferably two heteroatoms, in particular two oxygen atoms, in addition to the oxygen atom attached to the ester functional group of the diester.

[0034] Thus, according to a particularly preferred embodiment variant, the cooling composition according to the invention comprises at least one monoester formed between a monocarboxylic acid comprising a preferably branched, saturated or unsaturated hydrocarbon-based chain, preferably containing from 3 to 14 carbon atoms, and a monoalcohol comprising a linear or branched, saturated or unsaturated hydrocarbon-based chain, preferably containing from 1 to 14 carbon atoms.

[0035] Advantageously, the monoester according to the invention may be a monoester formed between a branched saturated C9 monocarboxylic acid and a branched saturated C9 monoalcohol, such as 3,5,5-trimethylhexyl 3,5,5-trimethylhexanoate.

[0036] In particular, the composition according to the invention comprises a mixture of a branched saturated C9 monocarboxylic acid, such as 3,5,5-trimethylhexanoic acid, and a branched saturated C8-C 10 It may comprise a mixture of monoesters formed with a mixture of monoalcohols, preferably a mixture of branched saturated C9 monoalcohol isomers.

[0037] According to another variant of the invention, the cooling composition according to the invention comprises at least one diester formed between a dicarboxylic acid comprising a linear, saturated or unsaturated hydrocarbon-based chain, preferably containing from 3 to 14 carbon atoms, and a monoalcohol comprising a linear or branched, saturated or unsaturated hydrocarbon-based chain, preferably containing from 2 to 14 carbon atoms, interrupted by at least one heteroatom, preferably an oxygen atom.

[0038] Advantageously, the diesters according to the invention are linear saturated C4-C 10 Dicarboxylic acids and linear saturated C4-C chains interrupted by oxygen atoms 10 The diester may be formed between a monoalcohol containing a hydrocarbon-based chain, for example, dibutyl glycol adipate.

[0039] As will appear from the examples below, the inventors have found that the esters according to the invention advantageously combine good viscosity properties suitable for their use to cool batteries and / or power electronics with a particularly high autoignition temperature, which therefore ensures the stability of the cooling composition, making it resistant to ignition, in particular if the battery overheats.

[0040] Advantageously, therefore, the esters according to the invention have a viscosity of 20 mm, measured at 25° C. according to standard ASTM D445. 2 / s or less, preferably 15 mm 2 / s or less, especially 10mm 2 / s or less.

[0041] Furthermore, the esters according to the invention advantageously have a particularly high autoignition temperature, preferably above 360°C, more preferentially above 380°C and in particular above 400°C.

[0042] Advantageously, in particular by the use of one or more esters according to the invention as defined above, it is therefore possible to make available cooling compositions which at the same time have a viscosity suitable for their use, in particular in the propulsion systems of batteries and / or power electronics, of electric or hybrid vehicles, and an excellent resistance to fire.

[0043] The cooling composition according to the invention may more particularly be intended to be placed in direct contact with the battery pack of an electric vehicle, especially with Li-ion or nickel-cadmium (Ni-Cd) batteries.

[0044] The cooling composition according to the present invention can reduce or prevent thermal runaway in the battery pack by preventing the cells from reaching a critical temperature and therefore from undergoing thermal runaway.

[0045] The cooling compositions used according to the present invention also have excellent electrical insulating properties, which make them particularly suitable for use in hybrid and electric vehicles. The insulating properties can be evaluated by measuring the electrical resistance of the cooling composition, in particular according to standard ASTM D1169.

[0046] The present invention also relates to a method for cooling at least one component of an electric or hybrid vehicle, in particular of a battery and / or power electronics propulsion system, comprising at least one step of placing at least said component, in particular said battery, for example a lithium-ion battery or a nickel-cadmium battery, in contact with a composition comprising at least one ester according to the invention as defined above.

[0047] According to another of its aspects, the present invention also provides a composition capable of cooling the propulsion system, in particular the battery and / or power electronics, of an electric or hybrid vehicle, comprising: (i) at least one ester according to the invention, as defined above, and (ii) at least one additive selected from antioxidants, antifoaming agents, pour point improvers, corrosion inhibitors, antiwear additives, friction modifiers, detergents, extreme pressure additives, dispersants, and mixtures thereof; The present invention relates to a composition comprising:

[0048] Advantageously, the compositions according to the invention may combine cooling and lubricating properties.

[0049] Thus, according to a particular embodiment, the composition according to the invention used in the propulsion system of an electric or hybrid vehicle makes it possible to take advantage of its good properties for lubricating the components of the propulsion system, in addition to its cooling function, for example for lubricating the transmission in an electric or hybrid vehicle.

[0050] Other characteristics, variants and advantages of the use of the esters according to the invention will appear more clearly on reading the description and examples that follow, given as non-limiting examples of the invention.

[0051] In the remainder of this text, the expressions "between... and...," "ranging from... to...," and "varying from... to..." are intended to be equivalent and, unless otherwise expressly stated, to mean that a limitation is included.

[0052] Unless otherwise indicated, the phrase "comprising one of" is to be understood as "comprising at least one of." [Brief explanation of the drawings]

[0053] [Figure 1] 1 is a diagram showing a schematic of a propulsion system for an electric or hybrid vehicle. DETAILED DESCRIPTION OF THE INVENTION

[0054] Esters according to the invention As mentioned above, the esters used according to the invention have a viscosity of 200 mm measured at -25°C according to standard ASTM D445. 2 / s or less, and an autoignition temperature of 350°C or more, measured in accordance with standard ASTM E659.

[0055] Preferably, the esters according to the invention have a viscosity of 150 mm, measured at −25° C. according to standard ASTM D445. 2 / s or less, especially 120mm 2 / s, preferably less than 100 mm 2 / s or less, especially 20-100mm 2 / s range, more specifically 40-70mm 2 / s range of kinematic viscosity.

[0056] According to a particular embodiment, the esters according to the invention advantageously have a viscosity of 20 mm, measured at 25 ° C according to standard ASTM D445. 2 / s or less, preferably 15 mm 2 / s or less, especially 10mm 2 / s or less.

[0057] Likewise, the esters used according to the invention advantageously have an autoignition temperature, measured in accordance with standard ASTM E659, of greater than or equal to 360° C., in particular greater than or equal to 380° C., and more particularly greater than or equal to 400° C.

[0058] The ester according to the present invention is preferably a monoester, diester or triester, preferably a monoester or a diester. The ester may preferably be a monoester formed between a monocarboxylic acid and a monoalcohol. The ester may also be a diester formed between a dicarboxylic acid and a monoalcohol, or a diester formed between a monocarboxylic acid and a diol.

[0059] The esters used according to the present invention may be saturated or unsaturated, preferably saturated.

[0060] According to a particularly preferred embodiment, the esters used according to the invention are: - monoesters, preferably "branched" monoesters, formed between at least one saturated or unsaturated, preferably saturated, monocarboxylic acid containing a branched hydrocarbon-based chain and at least one linear or branched, saturated or unsaturated monoalcohol containing a hydrocarbon-based chain, and - esters containing at least one heteroatom, preferably an oxygen atom, other than the oxygen atom attached to the ester functional group of the ester, and A mixture of them is selected from.

[0061] According to a particular embodiment, the esters used according to the invention are: branched esters, in particular branched monoesters formed between at least one carboxylic acid containing at least one saturated or unsaturated, preferably saturated, branched hydrocarbon-based chain and at least one alcohol containing at least one linear or branched, saturated or unsaturated hydrocarbon-based chain, - esters containing at least one heteroatom, preferably an oxygen atom, other than the oxygen atom attached to the ester functional group of the ester, and - A mixture of these is selected from.

[0062] For the purposes of the present invention, the term "carboxylic acid" is intended to mean a compound containing at least one carboxyl functional group. The carboxylic acid may be a monocarboxylic acid or a polycarboxylic acid. The carboxylic acid is more preferentially a monocarboxylic acid, a dicarboxylic acid, a tricarboxylic acid or a tetracarboxylic acid. Preferably, the carboxylic acid is a monocarboxylic acid.

[0063] For the purposes of the present invention, the term "alcohol" is intended to mean a compound containing at least one hydroxyl functional group. The alcohol may be a monoalcohol or a polyol. Preferably, the alcohol is a monoalcohol, a diol, or a triol. Preferably, the alcohol is a monoalcohol.

[0064] For the purposes of the present invention, the term "hydrocarbon-based chain" is intended to mean a linear or branched, saturated or unsaturated alkyl or alkylene chain. The hydrocarbon-based chain may optionally be interrupted by one or more heteroatoms, in particular one or more oxygen atoms. Preferably, the hydrocarbon-based chain is a linear or branched, saturated or unsaturated alkyl or alkylene chain consisting of carbon and hydrogen atoms. The hydrocarbon-based chain preferably contains 1 to 14 carbon atoms, in particular 3 to 10 carbon atoms, and especially 4 to 9 carbon atoms.

[0065] According to a particular embodiment, the ester used according to the invention is a monoester formed between a monocarboxylic acid and a monoalcohol.

[0066] The monoesters according to the invention may be formed more particularly between monocarboxylic acids containing a linear or branched, saturated or unsaturated, preferably saturated, hydrocarbon-based chain, preferably containing 1 to 14 carbon atoms, in particular 3 to 14 carbon atoms, especially 5 to 12 carbon atoms, more particularly 6 to 10 carbon atoms, and monoalcohols containing a linear or branched, saturated or unsaturated, hydrocarbon-based chain, preferably containing 1 to 14 carbon atoms, in particular 3 to 14 carbon atoms, especially 5 to 12 carbon atoms, more particularly 6 to 10 carbon atoms.

[0067] Preferably, the monoesters according to the present invention are "branched" monoesters as defined below.

[0068] The monoester may in particular be a monoester formed between a saturated or unsaturated, preferably saturated, monocarboxylic acid comprising a branched hydrocarbon-based chain containing preferably 3 to 14 carbon atoms and a saturated or unsaturated, preferably saturated, monoalcohol comprising at least one linear or branched hydrocarbon-based chain containing preferably 1 to 14 carbon atoms.

[0069] In one particular embodiment, the monoester according to the invention is a saturated, preferably branched C-C 10 , preferably C9 monocarboxylic acids, in particular 3,5,5-trimethylhexanoic acid, and saturated, preferably branched C8-C 10 , preferably a C9 monoalcohol, such as 3,5,5-trimethylhexanol or an isomer thereof.

[0070] According to a particular embodiment, the esters used according to the invention are: at least one carboxylic acid containing at least one branched hydrocarbon-based chain, saturated or unsaturated, preferably saturated, preferably containing from 3 to 14 carbon atoms, and at least one alcohol containing at least one linear or branched hydrocarbon-based chain, saturated or unsaturated, preferably saturated, preferably containing from 1 to 14 carbon atoms; It is a "branched ester" formed between

[0071] The branched esters according to the invention are preferably monoesters, diesters or triesters.

[0072] According to a particular embodiment, the branched ester according to the present invention may be a monoester formed between a monocarboxylic acid and a monoalcohol.

[0073] According to another particular embodiment, the branched ester according to the present invention can be a diester formed between one diol compound and two monocarboxylic acids, or alternatively, a diester formed between one dicarboxylic acid (diacid) and two monoalcohols.

[0074] As previously mentioned, the branched esters used according to the present invention are derived from at least one carboxylic acid which is preferably saturated and contains at least one branched hydrocarbon-based chain.

[0075] The branched hydrocarbon-based chain of the carboxylic acid may more particularly contain from 3 to 14 carbon atoms, in particular from 5 to 12 carbon atoms, and even more particularly from 6 to 10 carbon atoms.

[0076] Preferably, the branched hydrocarbon-based chain of the carboxylic acid may be formed from a linear main chain containing 4 to 10 carbon atoms, in particular 5 to 8 carbon atoms, said main chain containing at least one alkyl side group, preferably at least two alkyl side groups, in particular at least three alkyl side groups, said alkyl groups being more particularly C1 to C4, preferably C1 to C3, especially C1 to C2, e.g. a methyl group.

[0077] According to one embodiment variant, the branched esters according to the invention are obtained in particular from monocarboxylic acids containing a hydrocarbon-based chain as defined above.

[0078] In one particular embodiment, the branched ester according to the present invention is a branched saturated C-C 10 and preferably derived from a C9 monocarboxylic acid, in particular 3,5,5-trimethylhexanoic acid.

[0079] The alcohols from which the branched esters according to the invention are formed may comprise preferably saturated, branched or unbranched (straight-chain) hydrocarbon-based chains.

[0080] The hydrocarbon-based chain of said alcohol may more particularly contain from 1 to 14 carbon atoms, in particular from 3 to 12 carbon atoms, more particularly from 6 to 10 carbon atoms.

[0081] According to a particular embodiment, the branched esters according to the invention are formed from at least one alcohol comprising a branched hydrocarbon-based chain, in particular containing from 3 to 14 carbon atoms, in particular from 5 to 12 carbon atoms, more particularly from 6 to 10 carbon atoms.

[0082] The branched hydrocarbon-based chains may be formed from a linear main chain containing 4 to 10 carbon atoms, in particular 5 to 8 carbon atoms, said main chain containing at least one alkyl side group, preferably at least two alkyl side groups, in particular at least three alkyl side groups, said alkyl groups being more particularly C1 to C4, preferably C1 to C3, especially C1 to C2, for example a methyl group.

[0083] According to one embodiment variant, the branched esters according to the invention are obtained in particular from monoalcohols containing a hydrocarbon-based chain as defined above, preferably a branched hydrocarbon-based chain.

[0084] In one particular embodiment, the branched ester according to the present invention is a branched saturated C-C 10 and preferably obtained from a C9 monoalcohol, such as 3,5,5-trimethylhexanol or an isomer thereof.

[0085] According to another particular embodiment, the esters used according to the invention are esters that contain at least one heteroatom, preferably an oxygen atom, other than the oxygen atom attached to the ester functional group of said ester.

[0086] The esters may be, inter alia, monoesters, diesters or triesters, and may be branched or unbranched esters, containing at least one heteroatom, preferably an oxygen atom, other than the oxygen atom attached to the ester functional group of the ester.

[0087] According to a particular embodiment, the esters used according to the invention are diesters, which contain at least one heteroatom, preferably an oxygen atom, other than the oxygen atom attached to the ester functional group of said ester.

[0088] Preferably, the esters according to the invention comprising at least one heteroatom, preferably an oxygen atom, other than the oxygen atom attached to the ester functional group of the ester are formed between at least one carboxylic acid and at least one alcohol comprising at least one ether functional group, preferably from at least one alcohol comprising at least one linear or branched, preferably linear, saturated or unsaturated, preferably saturated, hydrocarbon-based chain, in particular comprising from 2 to 14 carbon atoms, the hydrocarbon-based chain being interrupted by at least one oxygen atom.

[0089] The hydrocarbon-based chain of the alcohol may more particularly contain 4 to 10 carbon atoms, in particular 5 to 8 carbon atoms, optionally interrupted by one or more oxygen atoms, preferably one oxygen atom.

[0090] The carboxylic acids from which the esters according to the invention are formed, which contain at least one heteroatom other than the oxygen atom attached to the ester functional group of the ester, are at least one linear or branched, preferably linear, saturated or unsaturated, preferably saturated, in particular C3-C 14 , especially C4~C 10 and especially may comprise C4 to C8 hydrocarbon-based chains.

[0091] According to a particular embodiment, the ester containing at least one heteroatom other than the oxygen atom attached to the ester function is a diester formed between a dicarboxylic acid and at least one monoalcohol containing a linear or branched, saturated or unsaturated hydrocarbon-based chain, preferably containing from 2 to 14 carbon atoms, interrupted by at least one heteroatom, preferably an oxygen atom.

[0092] Preferably, the dicarboxylic acid is linear or branched, preferably linear, saturated or unsaturated, preferably saturated, in particular C3-C 14 , preferably C4 to C 10 and especially C6-C8 hydrocarbon-based chains. The dicarboxylic acid can be, for example, adipic acid.

[0093] Preferably, the monoalcohol comprising a hydrocarbon-based chain interrupted by at least one heteroatom has a linear, saturated hydrocarbon-based chain, in particular comprising 3 to 14 carbon atoms, preferably 4 to 10 carbon atoms, more particularly 4 to 8 carbon atoms, said chain being interrupted by one or more oxygen atoms, preferably one oxygen atom.

[0094] Such monoalcohols may more particularly comprise a C2 to C4 alkylene chain having at least one C2 to C6 and especially C4 alkoxy group.The monoalcohol may be, for example, butyl glycol.

[0095] In a particular embodiment, the ester used in accordance with the present invention is dibutyl glycol adipate.

[0096] It is understood that the definitions provided above for carboxylic acids and alcohols, where possible, can be combined to define other specific embodiments.

[0097] The esters according to the present invention have the following formula (I): [Chemical formula 1] G 1 -C(O)-OG 2 (I) (In the formula, ○ G 1 represents a linear or branched, preferably branched, saturated or unsaturated hydrocarbon-based chain, in particular containing 3 to 14 carbon atoms, said hydrocarbon-based chain optionally interrupted by one or more heteroatoms, such as oxygen atoms, and / or one or more R 1 -OC(O)- group, preferably one or two R 1 optionally having an —OC(O)— group, R 1 represents a linear or branched, saturated or unsaturated hydrocarbon-based chain, preferably containing 1 to 13 carbon atoms, optionally interrupted by one or more heteroatoms, such as oxygen atoms, ○ G 2 represents a saturated or unsaturated, linear or branched, preferably branched, hydrocarbon-based chain, in particular containing 1 to 14 carbon atoms, said hydrocarbon-based chain being optionally interrupted by one or more heteroatoms, such as oxygen atoms, and / or one or more -OC(O)-R 2 groups, preferably one or two -OC(O)-R 2 optionally having a group, R 2 represents a linear or branched, preferably branched, saturated or unsaturated hydrocarbon-based chain, preferably containing 3 to 13 carbon atoms, optionally interrupted by one or more heteroatoms, such as oxygen atoms) can correspond more specifically to:

[0098] According to a particular embodiment, the ester according to the invention has the following formula (I): [Chemical formula 1] G 1 -C(O)-OG 2 (I) (In the formula, ○ G 1represents a preferably branched, saturated or unsaturated hydrocarbon-based chain, in particular containing 3 to 14 carbon atoms, said hydrocarbon-based chain possibly containing one or more R 1 -OC(O)- group, preferably one or two R 1 -OC(O)- group, and R 1 represents a linear or branched, saturated or unsaturated hydrocarbon-based chain, preferably containing 1 to 13 carbon atoms, optionally interrupted by one or more heteroatoms, such as oxygen atoms, ○ G 2 represents a saturated or unsaturated, linear or branched, preferably branched, hydrocarbon-based chain, in particular containing 1 to 14 carbon atoms, said hydrocarbon-based chain being optionally interrupted by one or more heteroatoms, such as oxygen atoms, and / or one or more -OC(O)-R 2 groups, preferably one or two -OC(O)-R 2 optionally having a group, R 2 represents a linear or branched, preferably branched, saturated or unsaturated hydrocarbon-based chain, preferably containing 3 to 13 carbon atoms) can correspond more specifically to:

[0099] Preferably, G 1 In particular, C3~C 13 , especially C4~C 11 , more specifically, a C5 to C9 alkyl group, preferably a branched alkyl group, or R 1 -OC(O)-A 1 - group, and A 1 In particular, C2~C 12 , especially C3~C 10 represents an alkylene group consisting of 1 is as defined above.

[0100] Preferably, G 2 is optionally interrupted by one or more oxygen atoms, in particular C1-C 14 , especially C3~C 12, more specifically C6~C 10 or a linear or branched alkyl chain consisting of -A 2 -OC(O)-R 2 represents a group, and A 2 In particular, C1~C 13 represents an alkylene group consisting of 2 is as defined above, and R 2 is preferably C3 to C 13 Preferably, it represents a branched alkyl group consisting of the following:

[0101] According to a first embodiment variant, the ester according to the invention can be of formula (I) above, in which ○ G 1 Especially C3~C 13 , especially C4~C 11 More specifically, it represents a C5 to C9 alkyl group, preferably a branched alkyl group.

[0102] G 1 is preferably formed from a linear alkyl main chain, in particular of C3 to C9, especially C4 to C7, said main chain containing at least one alkyl side group, preferably at least two alkyl side groups, in particular at least three alkyl side groups, more particularly alkyl side groups of C1 to C4, preferably C1 to C3, especially C1 to C2, for example a methyl group.

[0103] Advantageously, G 1 can represent a 2,4,4-trimethylpentyl group.

[0104] ○ G 2 Especially C1~C 14 , especially C3~C 12 , more specifically C6~C 10 represents a linear or branched alkyl group consisting of:

[0105] According to a particularly advantageous variant, G 2 Especially C3~C 14 , especially C6~C 12 , more specifically C8~C 10represents a branched alkyl chain consisting of:

[0106] Such branched alkyl groups are particularly C4-C 10 , in particular formed from a linear alkyl backbone of C5 to C8, said backbone containing at least one alkyl side group, preferably at least two alkyl side groups, in particular at least three alkyl side groups, said alkyl side groups being more particularly C1 to C4, preferably C1 to C3, in particular C1 to C2, for example a methyl group.

[0107] Advantageously, G 2 may represent a branched C9 alkyl group, for example, 3,5,5-trimethylhexyl or an isomer thereof.

[0108] According to another embodiment variant, the ester according to the invention can be of formula (I) above, in which ○ G 1 Especially C3~C 13 , especially C4~C 11 More specifically, it represents a C5 to C9 alkyl group, preferably a branched alkyl group.

[0109] G 1 is preferably formed from a linear alkyl main chain, in particular of C3 to C9, especially C4 to C7, said main chain containing at least one alkyl side group, preferably at least two alkyl side groups, especially at least three alkyl side groups, more particularly alkyl side groups of C1 to C4, preferably C1 to C3, especially C1 to C2, for example a methyl group.

[0110] Advantageously, G 1 can represent a 2,4,4-trimethylpentyl group.

[0111] ○ G 2 -A 2 -OC(O)-R 2 represents a group, and A 2 and R 2 is as already defined.

[0112] Preferably, A 2 is C1~C 13 , especially C3~C 12 , more specifically C6~C 10 Represents an alkylene group.

[0113] According to a particular embodiment, R 2 is G 1 The groups can be as defined above, preferentially R 2 is G 1 is the same as

[0114] According to a particular embodiment, the ester according to the invention may be of formula (I) above, wherein ○ G 1 denotes in particular a linear or branched, saturated or unsaturated hydrocarbon-based chain containing from 3 to 14 carbon atoms, ○ G 2 -A 2 -OC(O)-R 2 Group(A 2 and R 2 is as previously defined); at least one hydrocarbon-based chain, in particular one or more heteroatoms, preferably one or more oxygen atoms, in particular one oxygen atom, interrupted by G 1 and R 2 Both represent hydrocarbon-based chains, represented by

[0115] According to yet another embodiment variant, the ester according to the invention can be of formula (I) above, in which ○ G 2 represents a linear or branched, saturated or unsaturated hydrocarbon-based chain, in particular containing 1 to 14 carbon atoms, said hydrocarbon-based chain optionally interrupted by one or more heteroatoms, preferably one or more oxygen atoms. 2may represent a preferably linear alkyl chain containing 1 to 14 carbon atoms, in particular 3 to 12 carbon atoms, more particularly 6 to 10 carbon atoms, which is interrupted by at least one oxygen atom, preferably one oxygen atom, ○ G 1 is R 1 -OC(O)-A 1 - group, and A 1 and R 1 is as already defined.

[0116] In particular, R 1 is G 2 The groups can be as defined above, preferentially R 1 is G 2 is the same as

[0117] Preferably, A 1 is a linear or branched C3-C 13 , and especially C4~C 11 represents an alkylene group, preferably at least one hydrocarbon-based chain, in particular G 2 and R 1 are interrupted by one or more heteroatoms, preferably one or more oxygen atoms, especially one oxygen atom.

[0118] According to a particularly preferred embodiment, the ester according to the invention is (i) a branched monoester comprising: - monocarboxylic acids containing a branched saturated hydrocarbon-based chain, preferably containing 3 to 14 carbon atoms, in particular as defined above, - monoalcohols containing saturated, preferably branched, hydrocarbon-based chains, preferably containing 3 to 14 carbon atoms, in particular as defined above; A branched monoester formed between or (ii) a diester: - dicarboxylic acids containing a linear saturated hydrocarbon-based chain, preferably containing from 3 to 14 carbon atoms, in particular from 4 to 10 carbon atoms, monoalcohols containing a linear saturated hydrocarbon-based chain interrupted by oxygen atoms, preferably containing 3 to 14 carbon atoms, in particular 4 to 10 carbon atoms; The diester formed between is selected from.

[0119] Advantageously, the ester according to the invention may be a monoester formed between 3,5,5-trimethylhexanoic acid and 3,5,5-trimethylhexanol or an isomer thereof, or else a diester formed between adipic acid and butyl glycol.

[0120] The esters according to the invention may be commercially available or may be prepared according to synthetic methods known to those skilled in the art, which more particularly involve an esterification reaction between at least one alcohol compound and at least one carboxylic acid compound.

[0121] It is of course up to the skilled artisan to adjust the synthesis conditions to obtain the esters according to the invention.

[0122] Advantageously, the branched esters according to the invention have a viscosity of 20 mm, measured at 25° C. according to standard ASTM D445. 2 / s or less, preferably 15 mm 2 / s or less, especially 10mm 2 / s or less.

[0123] Advantageously, the branched esters according to the invention have a viscosity of 150 mm, measured at −25° C. according to standard ASTM D445. 2 / s or less, especially 120mm 2 / s or less, especially 20-100mm 2 / s range, more specifically 40-70mm 2 / s range of kinematic viscosity.

[0124] Advantageously, the branched esters according to the invention have an autoignition temperature of 360°C or higher, in particular 380°C or higher, more particularly 400°C or higher.

[0125] In the context of the present invention, it is understood that the esters according to the invention, in particular the branched esters according to the invention, can be in the form of a mixture of at least two esters according to the invention, in particular as defined above.

[0126] The ester or mixture of esters according to the invention may represent more than 30% by weight, preferably more than 50% by weight, more preferentially more than 70% by weight, even more preferentially more than 80% by weight, in particular more than 90% by weight, more particularly more than 95% by weight, or even more than 98% by weight, relative to the total weight of the cooling composition according to the invention.

[0127] In particular, the cooling composition used according to the invention may comprise between 30% and 100% by weight, more particularly between 50% and 99.5% by weight, preferably between 70% and 99% by weight, more preferentially between 80% and 99% by weight, or even between 80% and 95% by weight of the ester or mixture of esters according to the invention, relative to the total weight of said composition.

[0128] According to a particular embodiment, the cooling composition according to the invention may be formed from more than 95% by weight, in particular more than 98% by weight, of one or more esters according to the invention, in particular one or more branched esters according to the invention.

[0129] Additional base oils The cooling compositions used according to the invention may contain, in addition to one or more esters according to the invention, one or more base oils other than the esters according to the invention.

[0130] The base oil that may be present in the cooling composition according to the invention is suitably selected with regard to its compatibility with the ester used according to the invention.

[0131] The base oil may be a mixture of several base oils, for example a mixture of two, three or four base oils.

[0132] Preferably, the base oil or mixture of further base oils used in the cooling composition according to the invention has a viscosity of 1.5 to 8 mm, measured at 100°C according to standard ASTM D445. 2 / s, especially 1.5~6.1mm 2 / s, more specifically 1.5 to 4.1 mm 2 / s and even more particularly 1.5 to 2.1 mm 2 The viscosity may be in the range of 1 / s.

[0133] The base oil may be selected from oils of mineral or synthetic origin, or mixtures thereof, belonging to groups I to V according to the classes defined by the API classification (or its equivalent according to the ATIEL classification) and represented in table 1 below.

[0134] [Table 1]

[0135] 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, deasphalting, solvent deparaffinization, hydrotreating, hydrocracking, hydroisomerization and hydrofinishing.

[0136] Mixtures of synthetic and mineral oils, which may be bio-based, may also be used.

[0137] There are generally no limitations regarding the use of various additional base oils to prepare the cooling compositions, except that the base oils must have properties, particularly with respect to viscosity index, sulfur content, or oxidation resistance, that are suitable for use in electric or hybrid vehicle propulsion systems.

[0138] The base oil may also be chosen from synthetic oils, such as certain esters of carboxylic acids and alcohols other than the esters defined by the present invention, from poly-α-olefins (PAO) and from polyalkylene glycols (PAG) obtained by polymerization or copolymerization of alkylene oxides containing from 2 to 8 carbon atoms, in particular from 2 to 4 carbon atoms.

[0139] The PAOs used as base oils are derived, for example, from monomers containing from 4 to 32 carbon atoms, for example from octene or decene.

[0140] The weight average molecular mass of the PAO can vary widely. Preferably, the weight average molecular mass of the PAO is less than 600 Da. The weight average molecular mass of the PAO can also be in the range of 100 to 600 Da, 150 to 600 Da, or 200 to 600 Da.

[0141] For example, 1.5 to 8 mm measured at 100°C according to standard ASTM D445 2 PAOs used in the context of the present invention having a kinematic viscosity in the range of 1 / s are marketed by Ineos under the trade names Durasyn® 162, Durasyn® 164, Durasyn® 166 and Durasyn® 168.

[0142] Advantageously, the additional base oil is chosen from poly-alpha-olefins (PAO).

[0143] It is left to the skilled artisan to adjust the content of additional base oil present in the cooling composition according to the invention.

[0144] In particular, the cooling composition according to the invention may comprise less than 70% by weight, in particular less than 50% by weight, in particular less than 30% by weight, or even less than 20% by weight, or less than 10% by weight, more particularly less than 5% by weight of additional base oil relative to the total weight of said composition.

[0145] additives Cooling compositions according to the present invention may also include one or more additives known to those skilled in the art of lubricating and / or cooling electric or hybrid vehicle propulsion systems.

[0146] The additives that may be incorporated in the compositions according to the invention may be chosen from antioxidants, pour point depressing additives, antifoam agents, corrosion inhibitors, antiwear and / or extreme pressure additives, friction modifiers, detergents, dispersants and mixtures thereof, in particular from antioxidants, pour point depressing additives, antifoam agents and corrosion inhibitors.

[0147] Preferably, the cooling composition according to the present invention may also contain one or more additives selected from antioxidants, antifoam agents, pour point improvers and corrosion inhibitors.

[0148] The addition of one or more additives selected from anti-wear additives, friction modifiers, detergents, extreme pressure additives and dispersants may also prove advantageous in the context of using the cooling composition according to the invention as a multi-purpose fluid, for example for cooling batteries and / or power electronics in electric or hybrid vehicles, and for lubricating parts of the propulsion system, e.g., the transmission.

[0149] It will be understood that the nature and amount of additives used will be selected so as not to affect the properties of the cooling composition imparted by the esters according to the invention.

[0150] These additives may be introduced individually and / or in the form of mixtures, such as those already sold for commercial lubricant formulations for automobile engines, with performance levels defined by ACEA (European Automobile Manufacturers Association) and / or API (American Petroleum Institute), which are well known to those skilled in the art.

[0151] The additives may be present in the cooling composition according to the invention in a content of less than or equal to 10% by weight, in particular less than or equal to 5% by weight, more particularly in the range from 0.01% to 3% by weight, relative to the total weight of the composition.

[0152] Thus, the cooling compositions used in accordance with the present invention may include at least one antioxidant additive.

[0153] Thus, according to another of its aspects, the present invention relates to a cooling composition particularly capable of cooling the propulsion system, in particular the battery and / or power electronics, of an electric or hybrid vehicle, said cooling composition comprising (i) at least one branched ester as defined above, and (ii) at least one antioxidant additive.

[0154] Antioxidant additives generally make it possible to inhibit the degradation of the composition during use, which degradation can be particularly affected by the formation of deposits, the presence of sludge, or by an increase in the viscosity of the composition.

[0155] Antioxidant additives act, inter alia, as free radical inhibitors or hydroperoxide destroyers. Among commonly used antioxidant additives, phenolic-type antioxidant additives, amine-type antioxidant additives, and phospho-sulfur-based antioxidant additives can be mentioned. Some of these antioxidant additives, such as phospho-sulfur-based antioxidant additives, can be ash generators. Phenolic antioxidant additives can be ash-free or in the form of neutral or basic metal salts. Antioxidant additives include sterically hindered phenols, sterically hindered phenol esters, and thioether bridges, diphenylamines, and at least one C1-C 12 They may especially be selected from sterically hindered phenols, including alkyl-substituted diphenylamines, N,N'-dialkyl-aryl-diamines and mixtures thereof.

[0156] Preferably, according to the present invention, the sterically hindered phenol has at least one C1-C vicinal carbon atom vicinal to the carbon bearing the alcohol functional group. 10It is selected from compounds containing a phenol group substituted by an alkyl group, preferably a C1-C6 alkyl group, preferably a C4 alkyl group, preferably a tert-butyl group.

[0157] Amine compounds are another class of antioxidant additives that can optionally be used in combination with phenolic antioxidant additives. Examples of amine compounds are aromatic amines, such as those of the formula NR 4 R 5 R 6 Aromatic amines (R 4 represents an optionally substituted aliphatic or aromatic group, R 5 represents an optionally substituted aromatic group, and R 6 represents a hydrogen atom, an alkyl group, or an aryl group), or a group represented by the formula R 7 S(O) z R 8 A group (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).

[0158] Sulfurized alkylphenols or their alkali metal and alkaline earth metal salts may also be used as antioxidant additives.

[0159] Another class of antioxidant additives is the class of copper compounds, such as copper thiophosphates or dithiophosphates, copper salts of carboxylic acids, and copper dithiocarbamates, copper sulfonates, copper phenolates, and copper acetylacetonates. Copper(I) and copper(II) salts, and succinate or anhydride salts may also be used.

[0160] Advantageously, the cooling composition includes at least one ashless antioxidant additive.

[0161] In the cooling composition according to the invention, the additives may be used in a proportion of 0.1% to 2% by weight relative to the total weight of the composition.

[0162] Coolant compositions according to the present invention may include at least one anti-wear and / or extreme pressure additive.

[0163] Anti-wear and extreme pressure additives protect friction surfaces by forming a protective film that is adsorbed onto these surfaces.

[0164] A wide range of anti-wear additives exists. Preferably, the anti-wear additive is selected from metal alkylthiophosphates, especially zinc alkylthiophosphates, more particularly zinc dialkyldithiophosphates or phospho-sulfur based additives such as ZnDTP. Preferred compounds have the formula Zn((SP(S)(OR 2 )(OR 3 ))2 and R 2 and R 3 may be the same or different and independently represent an alkyl group, preferentially an alkyl group containing from 1 to 18 carbon atoms.

[0165] Amine phosphates are also anti-wear additives that may be used in the compositions of the present invention. However, the phosphorus introduced by these additives can act as a poison to automotive catalyst systems because they are ash-generating. These effects can be minimized by partially replacing the amine phosphates with non-phosphorus-introducing additives, such as polysulfides, especially sulfur-based olefins.

[0166] The cooling composition may comprise from 0.01% to 6%, preferentially from 0.05% to 4%, and more preferentially from 0.1% to 2%, by weight of anti-wear and extreme pressure additives relative to the total weight of the composition.

[0167] Cooling compositions according to the present invention may also include an antifoaming agent.

[0168] The antifoaming agent may be selected from silicones.

[0169] The cooling composition may comprise from 0.01% to 2% by weight, or from 0.01% to 5% by weight, preferentially from 0.1% to 1.5% by weight or from 0.1% to 2% by weight of antifoaming agent relative to the total weight of the composition.

[0170] Cooling compositions according to the present invention may include at least one friction modifying additive.

[0171] The friction modifying additive may be selected from compounds that provide metallic elements and ashless compounds. Among the compounds that provide metallic elements, mention may be made of complexes of transition metals such as Mo, Sb, Sn, Fe, Cu, or Zn, whose ligands may be hydrocarbon-based compounds containing oxygen, nitrogen, sulfur, or phosphorus atoms. Ashless friction modifying additives are generally of organic origin and may be selected from fatty acid monoesters of polyols, alkoxylated amines, alkoxylated fatty amines, fatty epoxides, borate fatty epoxides, fatty amines, or fatty acid esters of glycerol. According to the present invention, the fatty compound contains at least one hydrocarbon-based group containing 10 to 24 carbon atoms.

[0172] The cooling composition may comprise from 0.01% to 2%, or from 0.01% to 5%, and preferentially from 0.1% to 1.5% or from 0.1% to 2%, by weight of friction modifying additive relative to the total weight of the composition.

[0173] Advantageously, the cooling composition does not include friction modifying additives, particularly for use towards cooling battery components.

[0174] The cooling composition according to the present invention may also comprise at least one detergent additive.

[0175] Detergent additives generally enable the reduction of deposit formation on the surfaces of metal parts by dissolving oxidation and combustion by-products.

[0176] Detergent additives that can be used in cooling compositions are generally known to those skilled in the art. The detergent additives can be anionic compounds containing a long, lipophilic hydrocarbon-based group and a hydrophilic head. The associated cation can be a metal cation of an alkali metal or alkaline earth metal.

[0177] The detergent additives are preferentially selected from alkali metal or alkaline earth metal salts of carboxylic acids, sulfonic acids, salicylic acids and naphthenic acids, and also phenolate salts. The alkali metals and alkaline earth metals are preferentially calcium, magnesium, sodium or barium.

[0178] These metal salts generally contain the metal in a stoichiometric amount or in excess, i.e., in an amount greater than stoichiometric. They are then overbased detergent additives. The excess metal, which then gives the detergent additive its overbased nature, is generally in the form of an oil-insoluble metal salt, such as a carbonate, hydroxide, oxalate, acetate, or glutamate, preferentially carbonate.

[0179] The cooling composition may contain, for example, 2% to 4% by mass of the detergent additive, based on the total mass of the composition.

[0180] The cooling composition may also include at least one pour point depressant additive.

[0181] By slowing down the formation of paraffin crystals, pour point depressant additives generally improve the low temperature behavior of the composition. Examples of pour point depressant additives that may be mentioned include polyalkyl methacrylates, polyacrylates, polyarylamides, polyalkylphenols, polyalkylnaphthalenes and polyalkylstyrenes.

[0182] Likewise, the cooling composition may include at least one dispersant.

[0183] The dispersant may be selected from Mannich bases, succinimides and their derivatives. The cooling composition may contain, for example, 0.2 to 10% by weight of the dispersant, based on the total weight of the composition.

[0184] According to a particular embodiment, the cooling composition used according to the invention comprises or may even be formed from (i) at least one ester according to the invention, in particular at least one branched ester as defined above, more particularly a branched monoester as defined above, and (ii) at least one additive chosen from antioxidants, antifoams, pour point depressants, corrosion inhibitors, antiwear and / or extreme pressure additives, friction modifiers, detergents, dispersants and mixtures thereof, preferably from antioxidants, pour point depressants, antifoams and corrosion inhibitors.

[0185] Advantageously, the cooling composition used according to the invention is formed from (i) at least one ester according to the invention, in particular at least one branched ester as defined above, more particularly a branched monoester as defined above, and (ii) at least one antioxidant additive.

[0186] According to a particular embodiment, the cooling composition used in accordance with the present invention comprises: - at least 30% by weight, preferably at least 50% by weight, preferably at least 70% by weight, preferably at least 80% by weight, more preferentially at least 90% by weight or even at least 95% by weight of one or more esters according to the invention, in particular one or more branched esters according to the invention - 0.01% to 10% by weight, preferably 0.05% to 5% by weight, of one or more additives chosen from antioxidants, antifoam agents, anti-wear and extreme pressure additives, friction modifiers, detergents, pour point depressant additives, dispersants and mixtures thereof, preferably chosen from antioxidants, antifoam agents, pour point depressant additives, corrosion inhibitors and mixtures thereof optionally 5% to 70%, preferably 10% to 50%, preferably 15% to 30% by weight of base oils other than esters according to the invention and the percentages are expressed relative to the total weight of the composition.

[0187] The cooling composition used according to the invention has a viscosity of 200 mm, measured at -25°C according to standard ASTM D445. 2 / s or less, especially 120mm 2 / s or less, especially 20-100mm 2 / s range, more specifically 40-70mm 2 Advantageously, the oil has a kinematic viscosity in the range of 1 / s.

[0188] Advantageously, the cooling composition used according to the invention also has a viscosity of 20 mm, measured at 25° C. according to standard ASTM D445. 2 / s or less, especially 15mm 2 / s or less, especially 2 to 12 mm 2 / s range, more specifically 5-10 mm 2 / s range of kinematic viscosity.

[0189] Furthermore, the cooling compositions used according to the invention have a particularly high autoignition temperature, in particular they advantageously have an autoignition temperature of 360°C or higher, in particular 380°C or higher, more particularly 400°C or higher.

[0190] Purpose As indicated above, the compositions according to the present invention may be used as cooling fluids for the propulsion systems of electric or hybrid vehicles.

[0191] As represented diagrammatically in FIG. 1, the propulsion system of an electric or hybrid vehicle comprises, inter alia, an electric motor part (1), a battery (2) and a transmission, and in particular a reduction gear (3).

[0192] An electric motor typically comprises power electronics 11 connected to a stator 13 and a rotor 14. The stator comprises coils, in particular copper coils, powered by an alternating current, which allows the generation of a rotating magnetic field. In terms of its components, the rotor comprises coils, permanent magnets or other magnetic material, which are set in rotation by the rotating magnetic field.

[0193] The power electronics 11, stator 13 and rotor 14 of the propulsion system 1 are complex components that generate a lot of heat while the motor is running, so ensuring cooling of the electric motor and power electronics is essential.

[0194] A rolling bearing (12) is generally incorporated between the stator (13) and the rotor (14). The transmission, and in particular the reduction gear (3), makes it possible to reduce the rotational speed at the outlet of the electric motor and to vary the speed transmitted to the wheels, thus simultaneously controlling the speed of the vehicle.

[0195] Advantageously, the compositions according to the invention may be used to cool the batteries of electric or hybrid vehicles, in particular those intended to be placed in direct contact with the batteries.

[0196] Suitable batteries for the propulsion systems of electric or hybrid vehicles include, in particular, Li-ion batteries or nickel-cadmium batteries.

[0197] According to another of its aspects, the present invention also relates to a method for cooling at least one component of the propulsion system of an electric or hybrid vehicle, in particular a battery, comprising at least one step of placing at least said component, in particular said battery, for example a lithium-ion battery or a nickel-cadmium battery, in contact with a composition comprising at least one branched ester according to the invention as defined above.

[0198] The step of placing a cooling composition according to the invention in contact with the battery may consist of immersing or semi-immersing the battery in said composition, or otherwise injecting said composition onto the surface of the battery.

[0199] The term "immersed" means that the entire cell is surrounded by the cooling composition according to the invention, while the term "semi-immersed" means that only a portion of the cell is in contact with said composition.

[0200] Cooling can be achieved by any method known to those skilled in the art. The cells can be present in the composition submerged or semi-submerged, stationary or circulating.

[0201] Examples of direct contact placement include cooling using a composition according to the invention under pressure, by injection, by spraying, by spraying or by forming a mist, and by gravity acting on the battery.

[0202] Advantageously, the composition is injected by jetting at relatively high pressure into the area of ​​the propulsion system to be cooled, and advantageously, the shear caused by this injection makes it possible to reduce the viscosity of the fluid in the injection area relative to its dynamic viscosity at rest, thus further increasing the coolability of the composition.

[0203] Furthermore, oil circulation systems commonly used in electric motors can be used, for example as described in WO2015 / 116496.

[0204] The compositions according to the invention may also be used to cool the electric motors of electric or hybrid vehicles, in particular to cool the power electronics and / or rotor and / or stator of the electric motor.

[0205] The cooling compositions according to the present invention have inter alia electrical insulating properties that make them particularly suitable for use in electric or hybrid vehicles.

[0206] In addition to the cooling properties of the composition according to the invention, it is possible to take advantage of its lubricating properties.

[0207] The compositions according to the invention may therefore be used to simultaneously lubricate various parts of the propulsion system of an electric or hybrid vehicle, in particular the rolling bearings located between the rotor and the stator of the electric motor, or else the transmission, in particular the reduction gear, in an electric or hybrid vehicle.

[0208] For such applications, the cooling composition according to the present invention also advantageously comprises one or more additives selected from anti-wear additives, friction modifiers, detergents, dispersants, extreme pressure additives and mixtures thereof.

[0209] The invention will now be described with the aid of the examples that follow, which, of course, are given as non-limiting illustrations of the invention. [Example]

[0210] Various compositions formed from the following compounds were evaluated: branched esters A according to the invention: 3,5,5-trimethylhexyl 3,5,5-trimethylhexanoate; - ester B according to the invention: dibutyl glycol adipate, which is a diester formed between a dicarboxylic acid containing an unbranched alkylene chain containing 6 carbon atoms and butyl glycol monoalcohol; - Poly-α-olefin C, a hydrogenated decene dimer type, customarily used in these battery cooling applications; - ester D not according to the invention: diisodecyl adipate, which is a diester formed between a dicarboxylic acid containing an unbranched linear alkylene chain containing 6 carbon atoms and a monoalcohol containing a branched alkyl chain containing 10 carbon atoms; an ester E not according to the invention, which is a diester formed between neopentyl glycol and 3,5,5-trimethylhexanoic acid; and Ester F not according to the invention, which is a triester formed between trimethylolpropane and 3,5,5-trimethylhexanoic acid.

[0211] The stability of a composition at high temperatures, in other words its resistance to ignition, is evaluated by determining its autoignition temperature in accordance with standard ASTM E659.

[0212] The viscosity of the composition at 25° C. and −25° C. is determined in accordance with standard ASTM D445.

[0213] The results of the viscosity measurements at autoignition temperature and cooling temperature are listed in Table 2 below.

[0214] [Table 2]

[0215] The branched esters A and B according to the present invention have low cooling temperature viscosities while simultaneously having high autoignition temperatures, which makes them suitable for use in batteries and / or power electronics of electric or hybrid vehicles, respectively.

[0216] Thus, the stability and resistance to fire of Esters A and B is ensured even if the battery overheats.

[0217] It is more particularly noted that the esters defined in the present invention have viscosity and autoignition properties that are particularly advantageous for their use in compositions for cooling electric or hybrid vehicle propulsion systems, in particular batteries and / or power electronics. [Explanation of symbols]

[0218] 1 Electric motor section, propulsion system 2 batteries 3 Transmission, reduction gear 11 Power Electronics 12 Rotating bearings 13 Stator 14 rotors

Claims

1. 200mm measured at -25°C according to standard ASTM D445 for cooling the propulsion systems of electric or hybrid vehicles 2 Use of a composition comprising at least one ester having a kinematic viscosity of not more than 1 / s and an autoignition temperature of not less than 350°C, measured according to standard ASTM E659, The use wherein the ester is a monoester formed between a branched saturated C9 monocarboxylic acid and a branched saturated C9 monoalcohol.

2. 2. The use according to claim 1, wherein the composition comprises at least 30% by weight of said ester relative to the total weight of the composition.

3. 3. Use according to claim 1 or 2 for cooling the battery and / or power electronics of an electric or hybrid vehicle.

4. The ester has a viscosity of 150 mm, measured at -25°C according to standard ASTM D445. 2 4. Use according to any one of claims 1 to 3, having a kinematic viscosity of not more than 1 / s and / or an autoignition temperature of not less than 360°C, measured in accordance with standard ASTM E659.

5. 5. Use according to any one of claims 1 to 4, characterized in that the ester is 3,5,5-trimethylhexyl 3,5,5-trimethylhexanoate.

6. 6. Use according to any one of claims 1 to 5, characterized in that the composition comprises, in addition to the ester, at least one additive chosen from antioxidants, pour point depressant additives, antifoam agents, corrosion inhibitors, anti-wear and / or extreme pressure additives, friction modifiers, detergents, dispersants and mixtures thereof.

7. 1. A composition capable of cooling a propulsion system of an electric or hybrid vehicle, comprising: (i) at least one ester as defined in claim 1, and (ii) at least one additive selected from antioxidants, pour point depressant additives, antifoam agents, corrosion inhibitors, antiwear and / or extreme pressure additives, friction modifiers, detergents, dispersants, and mixtures thereof; and comprising greater than 95% by weight of the ester.

8. 8. Composition according to claim 7, characterized in that the ester is as defined in claim 4 or 5.

9. 9. The composition of claim 7 or 8, wherein the composition is formed from the ester and one or more antioxidant additives.

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