USE OF A SUCCINIMIDE-TYPE COMPOUND AS A CORROSION ANTIFACT ADDITIVE IN A LUBRICANT COMPOSITION FOR A DRIVE SYSTEM OF AN ELECTRIC OR HYBRID VEHICLE

Description

[0001] The present invention relates to the field of lubricating compositions for a propulsion system of an electric or hybrid vehicle. It relates more particularly to the use of succinimide-type compounds to improve the anti-corrosion properties of a lubricating composition incorporating one or more amine and / or sulfur anti-wear additive(s). Technical field

[0002] The evolution of international standards for the reduction of CO2 emissions, but also for the reduction of energy consumption, is pushing car manufacturers to offer alternative solutions to combustion engines.

[0003] 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.

[0004] For the purposes of the present invention, the term "electric vehicle" means a vehicle comprising an electric motor as the sole means of propulsion, unlike a hybrid vehicle which comprises a combustion engine and an electric motor as combined means of propulsion.

[0005] For the purposes of the present invention, the term "propulsion system" means a system comprising the mechanical parts necessary for the propulsion of an electric vehicle. The propulsion system thus more particularly includes an electric motor, or the rotor-stator assembly of the power electronics (dedicated to speed regulation), a transmission and a battery.

[0006] Generally speaking, it is necessary to implement, in electric or hybrid vehicles, lubricating compositions, also called "lubricants", for the main purpose of reducing the friction forces between the different parts of the vehicle's propulsion system, in particular between the moving metal parts in the engines. These lubricating compositions are also effective in preventing premature wear or even damage to these parts, and in particular to their surface.

[0007] To do this, a lubricating composition is classically composed of one or more base oils, to which are generally associated several additives dedicated to stimulating the lubricating performance of the base oil, such as for example friction modifying additives, but also to provide additional performance.

[0008] In particular, so-called "anti-wear" additives are considered in order to reduce the wear of the mechanical parts of the engine, and thus prevent a deterioration in the durability of the engine. There is a wide variety of anti-wear additives, among which we can cite for example dimercaptothiadiazoles, polysulfides, in particular sulfur-containing olefins, amine phosphates, or even phospho-sulfur additives, such as metal alkylthiophosphates, in particular zinc alkylthiophosphates, and more specifically zinc dialkyldithiophosphates or ZnDTP.

[0009] Among these anti-wear additives, amine and / or sulfur anti-wear agents are particularly favored, such as dimercaptothiadiazoles, zinc dithiophosphate or polysulfides.

[0010] Unfortunately, these amine and / or sulfur-based anti-wear additives, such as dimercaptothiadiazoles, have the disadvantage of being corrosive. The corrosion problem is particularly critical in electric propulsion systems. In particular, corrosion can lead to a risk of deterioration in the stator and rotor windings, sensors in the propulsion system, solenoid valves in the hydraulic system, but also the bearings located between the rotor and stator of an electric motor, generally copper-based, and therefore particularly sensitive to corrosion, or the seals or varnishes present in the propulsion system.

[0011] Furthermore, to be able to cool the propulsion systems of electric or hybrid vehicles, it is imperative that the lubricant is insulating to avoid any failure of the electrical components. In particular, a conductive lubricant can lead to a risk of electrical current leakage in the stator and rotor windings, which reduces the efficiency of the propulsion systems, and creates possible overheating in the electrical components, even damaging the system. It is therefore crucial, when implementing lubricants for electric or hybrid vehicle powertrain systems, that the lubricants have good "electrical" properties in addition to non-corrosive properties.

[0012] The present invention aims precisely to overcome this drawback. Summary of the invention

[0013] The use of at least one succinimide-type compound is thus described, as an anti-corrosion additive in a lubricating composition, intended for a propulsion system of an electric or hybrid vehicle and comprising one or more amine and / or sulfur anti-wear additive(s).

[0014] More specifically, the present invention relates to the use of at least one succinimide-type compound, as an anti-corrosion additive in a lubricating composition, for a propulsion system of an electric or hybrid vehicle and comprising one or more amine and / or sulfur anti-wear additive(s); the amine and / or sulfur anti-wear additive being chosen from 2,5-dimercapto-1,3,4-thiadiazole derivatives of the following formulae taken alone or as a mixture: in which the R 1 group(s) represent, independently of one another, hydrogen atoms, linear or branched alkyl or alkenyl groups, comprising from 1 to 24 carbon atoms, preferably from 2 to 18, more preferably from 4 to 16, even more preferably from 8 to 12 or aromatic substituents, n being independently of one another integers equal to 1, 2, 3 or 4, preferably n being equal to 1; said succinimide-type compound being chosen from polyalkylene mono- or bis-succinimides; their borated derivatives and their mixtures.

[0015] Succinimide compounds, such as polyalkylene succinimides such as polyisobutylene succinimides (PIBSI), have already been proposed as dispersants, for example in lubricants for vehicle engines, as described for example in applications WO 2014 / 096328 and US 2008 / 194442 A1.

[0016] To the inventors' knowledge, however, it has never been proposed to use succinimide-type compounds, as an anti-corrosion additive, in the context of the use of a lubricant for a propulsion system of an electric or hybrid vehicle, to mitigate the corrosion effects caused by the use of amine and / or sulfur anti-wear additive(s).

[0017] Surprisingly, as illustrated in the following example, the inventors have found that such succinimide-type additives make it possible to effectively reduce the corrosion effects induced by amine and / or sulfur anti-wear additives.

[0018] Thus, the addition of at least one succinimide-type compound advantageously makes it possible to improve the anti-corrosion properties of a lubricant comprising one or more amine and / or sulfur anti-wear additive(s).

[0019] For the purposes of the present invention, the term "anti-corrosion additive" is intended to mean an additive that prevents or reduces the corrosion of metal parts. An anti-corrosion additive used in a composition thus makes it possible to improve the so-called "anti-corrosion" properties of this composition.

[0020] The use of one or more succinimide-type compound(s) according to the invention, together with one or more amine and / or sulfur anti-wear additives, advantageously provides a lubricating composition which jointly exhibits good anti-wear performance, while overcoming the corrosion problems discussed above. A composition according to the invention thus exhibits both good anti-wear and anti-corrosion properties.

[0021] The corrosive (or corroding) power of a compound can be evaluated according to a test implementing the study of the variation in the value of the electrical resistance of a copper wire of a pre-established diameter, as a function of the duration of immersion of this wire in a composition comprising, in a non-corrosive medium, for example in one or more base oils, said compound to be tested. The variation in the value of this electrical resistance is correlated directly with the variation in the diameter of the wire tested. Thus, in the context of the present invention, a compound is qualified as "non-corrosive" when the loss in diameter of the copper wire studied is less than or equal to 1.3 µm after immersion for 80 hours, in particular less than or equal to 0.8 µm after immersion for 40 hours in the composition comprising said compound.

[0022] The dielectric properties of a lubricant are represented in particular by the electrical resistivity and the dielectric loss (tan δ), and they can be measured according to the IEC 60247 standard.

[0023] Electrical resistivity represents the ability of the material to oppose the flow of electric current. It is expressed in ohm-meters (Ω.m). Resistivity must not be low to avoid electrical conduction.

[0024] The electrical dissipation factor or the tangent of the loss angle. The loss angle δ is the complementary angle of the phase shift between the applied voltage and the alternating current. This factor reflects energy losses due to the Joule effect. Heating is therefore directly related to the value of δ. A transmission oil typically has a tan δ value of around unity at room temperature. A good insulating lubricant must maintain a low level of tan δ.

[0025] The succinimide compound used according to the invention is chosen from polyalkylene mono- or bis-succinimides, such as polyisobutene (PIB) mono- or bis-succinimides; their borated derivatives and their mixtures. Also described but not covered by the scope of the claims are their succinic anhydride derivatives such as polyisobutylene succinic anhydrides (PIBSA); compounds obtained by opening such a succinic anhydride ring such as PIB pentaerythritol ester succinimides; and their mixtures.

[0026] Preferably, the succinimide compound is chosen from: polyalkylene bis-succinimides whose alkyl chain is optionally linked to the succinimide via a -(C=CH 2 )- group, in particular polyisobutylene (PIB) bis-succinimides whose alkyl chain is optionally linked to the succinimide via a -(C=CH 2 )- group, and their borated derivatives, the two succinimide groups being linked to each other by their respective nitrogen atom via an alkylene group or a polyamine group, in particular polyalkyleneamine; polyalkylene mono-succinimides whose alkyl chain is optionally linked to the succinimide via a -(C=CH 2 )- group, in particular polyisobutylene (PIB) mono-succinimides whose alkyl chain is optionally linked to the succinimide via a -(C=CH 2 )- group, and their borated derivatives, substituted on the nitrogen atom by a polyamine group, in particular polyalkyleneamine; and mixtures thereof.

[0027] The introduction, into a lubricating composition intended for a propulsion system of an electric or hybrid vehicle, of one or more succinimide-type compound(s) according to the invention thus advantageously allows the use, in the composition, of amine and / or sulfur anti-wear additive(s), such as dimercaptothiadiazoles, without causing an undesirable corrosive effect.

[0028] The amine and / or sulfur anti-wear additives used in a lubricating composition are described in more detail in the rest of the text. They are chosen from amine and sulfur anti-wear additives. More precisely, they are thia(di)azole type compounds, chosen from dimercaptothiadiazole derivatives.

[0029] Also, a composition suitable for the invention has the advantage of being easy to formulate. It has, in addition to good anti-wear and anti-corrosion performance, good stability, particularly to oxidation, as well as good properties in terms of electrical insulation.

[0030] Also described is the use, for lubricating a propulsion system of an electric or hybrid vehicle, in particular for the lubrication of the electric motor and the power electronics of an electric or hybrid vehicle, of a lubricating composition comprising: one or more succinimide-type compounds as defined in the invention, as anti-corrosion additive(s); and one or more amine and / or sulfur anti-wear additive(s) as defined in the invention.

[0031] Also described is a method for lubricating a propulsion system of an electric or hybrid vehicle, comprising at least one step of bringing at least one mechanical part of said system into contact with a lubricating composition comprising at least one succinimide-type compound as defined in the invention, as an anti-corrosion additive and at least one amine and / or sulfur anti-wear additive as defined in the invention.

[0032] Advantageously, a described lubricating composition is used to lubricate the electric motor itself, in particular the bearings located between the rotor and the stator of an electric motor, and / or the transmission, in particular the reducer in an electric or hybrid vehicle.

[0033] Other characteristics, variants and advantages of the use of succinimide-type compound(s) as anti-corrosion additives according to the invention will become more apparent upon reading the description and examples which follow, given as an illustration and not as a limitation of the invention.

[0034] In the rest of the text, the expressions "between ... and ...", "ranging from ... to ..." and "varying from ... to ..." are equivalent and are intended to mean that the limits are included, unless otherwise stated.

[0035] Unless otherwise indicated, the expression "comprising a(n)" must be understood as "comprising at least one(n)". Brief description of the drawings

[0036] [ Fig 1 ] schematically represents an electric or hybrid vehicle propulsion system. Detailed description

[0037] The present invention is described in and by the appended claims. SUCCINIMIDE TYPE ANTI-CORROSION ADDITIVES

[0038] As previously specified, the additive used as an anti-corrosion agent according to the invention, together with one or more amine and / or sulfur anti-wear additives, in a lubricating composition for the engine system of an electric or hybrid vehicle, is a succinimide type compound.

[0039] As mentioned above, many succinimide compounds have already been proposed for use as dispersing agents, such as, for example, polyalkylene mono- or bis-succinimides, such as polyisobutene (PIB) mono- or bis-succinimides and their borated derivatives; also, their succinic anhydride derivatives, such as, for example, polyisobutylene succinic anhydrides (PIBSA); compounds obtained by opening such a succinic anhydride ring, such as, for example, polyisobutylene pentaerythritol ester succinimides.

[0040] However, as previously indicated, such compounds have never been proposed as anti-corrosion additives in a lubricant for the powertrain system of an electric or hybrid vehicle, for the purpose of reducing, or even inhibiting, the corrosion effects induced by the use of one or more amine and / or sulfur anti-wear additives.

[0041] So-called “succinimide-type” compounds are compounds comprising at least one succinimide group, in other words a group of the following formula (i): or a borated derivative (BO bonds) thereof; or, described but not covered by the scope of the claims, a succinic anhydride derivative of such a succinimide group, or, described but not covered by the scope of the claims, a compound obtained by opening the succinic anhydride ring.

[0042] As already mentioned, succinimide compounds can be of various natures. They can be mono-succinimide or bis-succinimide compounds.

[0043] Preferably, the succinimide compound is chosen from compounds comprising at least one substituted succinimide group, in particular of the following formula (ii): or a borated derivative (BO bonds) of such a substituted succinimide group of formula (ii), or, described but not covered by the scope of the claims, a succinic anhydride derivative of such a substituted succinimide group of formula (ii), or, described but not covered by the scope of the claims, a compound obtained by opening the succinic anhydride ring, in which R 1< represents a hydrocarbon group, preferably comprising from 8 to 400 carbon atoms.

[0044] R 1< may be more particularly chosen from linear or branched C 8 to C 400 alkyl groups, in particular C 50 to C 200 , linear or branched C 8 to C 400 alkenyl groups, in particular C 50 to C 200 , C 6 to C 10 aryl groups, arylalkyl groups and alkylaryl groups.

[0045] Preferably, R 1< represents a long alkyl chain, preferably branched, from C 8 to C 400 , in particular from C 50 to C 200 or a long alkenyl chain, preferably branched, from C 8 to C 400 , in particular from C 50 to C 200 comprising a single double bond of which one of the two carbon atoms is directly linked to the succinimide ring.

[0046] Advantageously, R 1< represents a polyalkylene group, preferably having a mass-average molecular mass Mw of between 140 and 50,000, in particular between 2,000 and 30,000.

[0047] According to a particular embodiment, R 1< represents a polyisobutylene group, preferably with a number-average molecular mass of between 140 and 30,000, in particular between 2,000 and 20,000, or even 2,000 and 7,000 and in particular between 3,000 and 5,000.

[0048] According to another particular embodiment, R 1< represents a polyisobutylene group, preferably with a number-average molecular mass of between 140 and 30,000, in particular between 2,000 and 20,000, or even 2,000 and 7,000 and in particular between 3,000 and 5,000, linked to the succinimide group via a -(C=CH 2 )- group and is of formula (A) which follows: in which the symbol * indicates the point of attachment of this group to the succinimide group, and n represents an integer ranging from 6 to 500.

[0049] Thus, according to a particular embodiment, the succinimide compound comprises at least one substituted succinimide group of formula (ii), or a borate derivative of said group (ii), or, described but not covered by the scope of the claims, a succinic anhydride derivative of said group (ii), or, described but not covered by the scope of the claims, a compound obtained by opening the succinic anhydride ring, in which R 1< represents a hydrocarbon group, preferably comprising from 8 to 400 carbon atoms, in particular a polyalkylene group optionally connected to the succinimide group via a -(C=CH 2 )- group, preferably having a mass-average molecular weight Mw of between 140 and 50,000, in particular between 2,000 and 30,000, and more particularly a polyisobutylene group optionally connected to the succinimide group via a -(C=CH 2 )- group,preferably with a mass-average molecular mass Mw of between 140 and 30,000, in particular between 2,000 and 20,000 or even between 2,000 and 7,000 and in particular between 3,000 and 5,000.,

[0050] More particularly, the succinimide-type compound may be chosen from mono-succinimide compounds comprising a substituted succinimide group of formula (ii) above and bis-succinimide compounds comprising two substituted succinimide groups, in particular of formula (ii) above, said succinimide groups being more particularly linked at their top bearing a nitrogen atom by a polyamine group.

[0051] According to a particular embodiment, the succinimide-type compound used according to the invention corresponds to the following formula (I): or one of its borated derivatives, where A represents a linear or branched alkylene group, C 2 to C 24 , preferably C 2 to C 6 ; R 1< is as defined above, for example a polyisobutylene group optionally linked to the succinimide group via a -(C=CH 2 )- group; x represents 0 or an integer ranging from 1 to 6, preferably × is 2, 3 or 4; R 2< and R 3< are chosen, independently of each other, from a hydrogen atom, a linear or branched alkyl group, in particular C 1 to C 25 ; an alkoxy group, in particular C 1 to C 12 , an alkenyl group, in particular C 2 to C 12 , optionally carrying one or more hydroxyl and / or amine functions; or R 2< and R 3< together form, with the nitrogen atom carrying them, an optionally substituted succinimide group, preferably a succinimide group substituted by an R 1< group as defined above.

[0052] According to a first embodiment variant, a succinimide-type compound used according to the invention may be a mono-succinimide compound of formula (I) above in which R 2< and R 3< are chosen, independently of one another, from a hydrogen atom, a linear or branched alkyl group, in particular C 1 to C 25; an alkoxy group, in particular C 1 to C 12 , an alkenyl group, in particular C 2 to C 12 , optionally carrying one or more hydroxyl and / or amine functions.

[0053] Preferably, a succinimide-type compound used according to the invention is of the abovementioned formula (I) in which R 2< and R 3< represent hydrogen atoms. In other words, a succinimide-type compound used according to the invention may be of the following formula (II): or one of its borated derivatives, where: R 1< is as defined above, in particular R 1< represents a polyalkylene group optionally linked to the succinimide group via a -(C=CH 2 )- group, in particular polyisobutylene optionally linked to the succinimide group via a -(C=CH 2 )- group, A is as defined above, preferably represents at least one of the following segments -CH 2 -CH 2 -, -CH 2 -CH 2 -CH 2 -, -CH 2 -CH(CH 3 )-; and y represents an integer between 1 and 6, in particular y represents 2, 3 or 4. According to another embodiment variant, a succinimide compound used according to the invention may be a bis-succinimide compound of formula (I) above in which R 2< and R 3< together form, with the nitrogen atom carrying them, an optionally substituted succinimide group, preferably a succinimide group substituted by a group R 1< as defined above.

[0054] Advantageously, a bis-succinimide type compound used according to the invention may be of the following formula (III): or one of its borated derivatives, where: R 1< , identical or different, are as defined above; z represents an integer between 0 and 10, preferably between 2 and 6; s represents an integer between 2 and 6, preferably between 2 and 4.

[0055] Preferably, the bis-succinimide compound may be of formula (III) in which R 1< represent polyalkylene groups, in particular polyisobutylene groups, preferably with a molecular mass of between 150 and 15,000, in particular between 500 and 2,000 and in particular between 500 and 1,500.

[0056] The borated derivatives of the succinimide compounds of formula (I), (II) or (III) above can be obtained from the non-borated succinimide compounds, by reaction with borates, for example with boric acid, in particular to reach a concentration of 0.1 to 3% by mass, in particular 1 to 2% by mass of boron in the succinimide compound.

[0057] Among the succinic anhydride derivatives, described but not covered by the scope of the claims, mention may be made of polyisoalkylene succinic anhydrides, in particular polyisobutylene succinic anhydrides (called "PIBSA") such as the following compound, with a number-average molecular mass Mn of between 300 and 30,000 and a mass-average molecular mass Mw of between 300 and 30,000: in which R is a polyisobutylene group.

[0058] Among the compounds obtained by opening the succinic anhydride ring, described but not covered by the scope of the claims, mention may be made in particular of polyalkylene pentaerithritol ester succinimides such as, for example, polyisobutylene pentaerithritol ester succinimides of the following formulae, with a number-average molecular mass Mn of between 300 and 30,000 and a mass-average molecular mass Mw of between 300 and 30,000: in which PIB represents a polyisobutylene; in which PIB represents a polyisobutylene.

[0059] In the context of the invention, the following terms are understood to mean: alkyl, a saturated, linear or branched aliphatic group; for example, a Cx to Cz alkyl represents a hydrocarbon chain of x to z carbon atoms, linear or branched; alkylene represents a divalent alkyl group. For example, a Cx-Cz alkylene group represents a divalent hydrocarbon chain of x to z carbon atoms, linear or branched; alkenyl, an unsaturated, linear or branched aliphatic group; for example, a Cx to Cz alkenyl group represents an unsaturated carbon chain of x to z carbon atoms, linear or branched; alkoxy, an -O-alkyl radical, in which the alkyl group is as defined above; aryl, a mono- or polycyclic aromatic group, in particular comprising between 5 and 10 carbon atoms. Examples of aryl groups include phenyl, tolyl or naphthyl groups.

[0060] Advantageously, the succinimide-type additive (mono or bis-succinimide) is chosen from polyalkylene succinimides (in other words compounds comprising at least one group of formula (ii) above where R 1< is a polyalkylene group optionally linked to the succinimide group via a -(C=CH 2 )- group) and in particular polyisobutylene (PIB) succinimides of which the polyisobutylene part is optionally linked to the succinimide group via a -(C=CH 2 )- group, and their borated derivatives.

[0061] According to a particular embodiment, the succinimide-type additive is chosen from polyalkylene succinimides whose alkyl chain is optionally linked to the succinimide via a -(C=CH 2 )- group, in particular polyisobutylene (PIB) succinimides whose alkyl chain is optionally linked to the succinimide via a -(C=CH 2 )- group, and their borated derivatives, substituted on the nitrogen atom by a polyamine group, in particular polyalkyleneamine, for example polyethylene amine.

[0062] Preferably, the succinimide-type additive is chosen from the mono- or bis-succinimides of formula (I) above, in particular the mono-succinimides of formula (II) above, the bis-succinimides of formula (III) above, and their mixtures.

[0063] According to a particularly preferred embodiment, the succinimide-type additive is chosen from: polyalkylene bis-succinimides whose alkyl chain is optionally linked to the succinimide via a -(C=CH 2 )- group, in particular polyisobutylene (PIB) bis-succinimides whose alkyl chain is optionally linked to the succinimide via a -(C=CH 2 )- group, and their borated derivatives, the two succinimide groups being linked to each other by their respective nitrogen atom via an alkylene group or a polyamine group, in particular polyalkyleneamine or even polyethyleneamine; polyalkylene mono-succinimides whose alkyl chain is optionally linked to the succinimide via a -(C=CH 2 )- group, in particular polyisobutylene (PIB) mono-succinimides whose alkyl chain is optionally linked to the succinimide via a -(C=CH 2 )- group, and their borated derivatives, substituted on the nitrogen atom by a polyamine group, in particular polyalkyleneamine or even polyethyleneamine; and mixtures thereof.

[0064] According to an even more particularly preferred embodiment, the succinimide-type additive is chosen from the following compounds: wherein n ranges from 6 to 500, preferably is 90; and R is a linear or branched alkylene, C 2 to C 24 , preferably C 2 to C 6 or a group -R''-(NH-R')x- in which R' and R" represent, independently of each other, a linear or branched alkylene, C 2 to C 24 , preferably C 2 to C 6 and x is an integer ranging from 1 to 6, preferably x is 2, 3, 4 or 5. It is more precisely a bis-succinimide whose average molecular mass Mn is between 3000 and 4000, preferably 3410; the average molecular mass Mw is between 5000 and 6000, preferably 5225; the polydispersity index Ip is between 1.25 and 2, preferably 1.5; wherein n ranges from 10 to 350, preferably is 65; and R is a linear or branched alkyl, C 1 to C 24 , preferably C 2 to C 6 or a group -(R'-(NH)yH in which R' represents a linear or branched alkylene, C 2 to C 24 , preferably C 2 to C 6 , and y is an integer ranging from 1 to 6, preferably x is 2, 3 or 4. It is more precisely a PIB succinimide whose average molecular mass Mn is between 800 and 18,000, preferably 3519; the average molecular mass Mw is between 1,000 and 20,000, preferably 6220; the polydispersity index Ip is between 1.5 and 2.3, preferably 1.6; and mixtures thereof.

[0065] It is understood, within the framework of the present invention, that a succinimide-type compound considered according to the invention may be in the form of a mixture of at least two succinimide-type compounds, in particular as defined above.

[0066] The succinimide-type compounds used according to the invention may be commercially available, or prepared according to synthesis methods known to those skilled in the art.

[0067] For example, succinimide compounds may be synthesized by condensation of an optionally substituted succinic anhydride, for example, a succinic anhydride substituted by a polyisobutylene group, with a poly(alkyleneamine). The succinic anhydride substituted by a polyisobutylene (PIB) group may be previously obtained, for example, by reaction of maleic anhydride with methylvinylidene polyisobutene.

[0068] Other succinimide-type compounds, notably known as dispersants, can be used as anti-corrosion additives.

[0069] The succinimide-type compound(s) as defined above may be used in a lubricating composition according to the invention, in an amount of 0.01% to 10% by mass, in particular 0.1% to 10% by mass, and more particularly 0.5% to 8% by mass, relative to the total mass of the lubricating composition.

[0070] Advantageously, a lubricating composition considered according to the invention does not comprise other anti-corrosion additives other than succinimide-type compounds. According to a particular embodiment, a lubricating composition used according to the invention is free of anti-corrosion additives of triazole type or of compounds with amine function or sterically hindered phenolic function. LUBRICATING COMPOSITION Amine anti-wear additives and / or sulfurous

[0071] As indicated previously, a lubricating composition considered according to the invention comprises one or more amine and / or sulfur anti-wear additives.

[0072] “Amine and / or sulfur anti-wear additive” means an additive chosen from amine anti-wear additives, sulfur anti-wear additives and amine and sulfur anti-wear additives.

[0073] The term "anti-wear additive" means a compound which, when used in a lubricating composition, in particular a lubricating composition for a propulsion system of an electric or hybrid vehicle, makes it possible to improve the anti-wear properties of the composition.

[0074] The amine and / or sulfur anti-wear additive is selected from thia(di)azole type additives, more specifically dimercaptothiadiazole derivatives. Also described are polysulfide additives, in particular sulfur olefins, amine phosphates, phospho-sulfur additives such as alkylthiophosphates, and mixtures thereof. Thia(di)azole additives.

[0075] According to the invention, a lubricating composition comprises at least one anti-wear additive of the thia(di)azoles type.

[0076] Thia(di)azole compounds are compounds that contain both a sulfur atom and at least one nitrogen atom in a five-membered ring. Benzothiazoles are a special type of thia(di)azole. The term thia(di)azole includes, in addition to cyclic compounds containing one sulfur atom and one nitrogen atom per five-membered ring, also thiadiazoles that contain sulfur and two nitrogen atoms in such a ring.

[0077] In particular, the thia(di)azole type compounds are selected from benzothiazole derivatives, thiazole derivatives and thiadiazole derivatives.

[0078] According to the invention, the anti-wear additive is a thiadiazole derivative.

[0079] Thiadiazoles are heterocyclic compounds comprising two nitrogen atoms, one sulfur atom, two carbon atoms and two double bonds, of general formula C 2 N 2 SH 2 , which can exist in the following forms, respectively: 1,2,3-thiadiazole; 1,2,4-thiadiazole; 1,2,5-thiadiazole; 1,3,4-thiadiazole:

[0080] According to the invention, the thiadiazole derivative is a dimercaptothiadiazole derivative.

[0081] Thus, a lubricating composition according to the invention comprises at least one anti-wear additive chosen from dimercaptothiazole derivatives.

[0082] By dimercaptothiadiazole derivative according to the invention is meant chemical compounds derived from the following four dimercaptothiadiazole molecules, below: 4,5-dimercapto-1,2,3-thiadiazole, 3,5-dimercapto-1,2,4-thiadiazole, 3,4-dimercapto-1,2,5-thiadiazole, 2,5-dimercapto-1,3,4-thiadiazole, taken alone or in mixture:

[0083] Dimercaptothiadiazole derivatives are more particularly molecules or mixtures of molecules based on 4,5-dimercapto-1,2,3-thiadiazole, 3,5-dimercapto-1,2,4-thiadiazole, 3,4-dimercapto-1,2,5-thiadiazole or 2,5-dimercapto-1,3,4-thiadiazole, as represented above, in which at least one of the =S substitutions, or even both of the =S substitutions on the thiadiazole ring is replaced by a substituent: in which * represents the bond with a carbon atom of the 5-membered ring; n represents an integer equal to 1, 2, 3 or 4; and R 1 is chosen from a hydrogen atom, a linear or branched, saturated or unsaturated alkyl group, comprising from 1 to 24 carbon atoms, preferably from 2 to 18, more preferably from 4 to 16, even more preferably from 8 to 12 or an aromatic substituent.

[0084] Taking 2,5-dimercapto-1,3,4-thiadiazole as an example, 2,5-dimercapto-1,3,4-thiadiazole derivatives are molecules with the following formulae taken alone or in mixture: in which the R 1 group(s) represent, independently of one another, hydrogen atoms, linear or branched alkyl or alkenyl groups, comprising from 1 to 24 carbon atoms, preferably from 2 to 18, more preferably from 4 to 16, even more preferably from 8 to 12 or aromatic substituents, n being independently of one another integers equal to 1, 2, 3 or 4, preferably n being equal to 1.

[0085] Preferably, R 1 represent, independently of one another, linear alkyl groups, C 1 to C 24 , preferably C 2 to C 18 , in particular C 4 to C 16 , more particularly C 8 to C 12 and preferably C 12 .

[0086] The dimercaptothiadiazole derivatives used in the present invention may be commercially available, for example from the suppliers Vanderbilt, Rhein Chemie or Afton. Polysulfide additives

[0087] Described in the invention, the amine and / or sulfur anti-wear additive(s) used in a lubricating composition may be chosen from sulfur anti-wear additives of polysulfide type, in particular sulfur olefins.

[0088] The sulfur-containing olefins used in a lubricating composition may in particular be dialkyl sulfides represented by the general formula R a -S x -R b , where R a and R b are alkyl groups comprising from 3 to 15 carbon atoms, preferably from 1 to 5 carbon atoms, preferably 3 carbon atoms, and x is an integer between 2 and 6.

[0089] Preferably, the polysulfide additive is chosen from dialkyl trisulfides.

[0090] Preferably, the anti-wear additive present in a composition used according to the invention is chosen from amine and sulfur anti-wear additives, and advantageously from thia(di)azole compounds as described above, chosen from dimercaptothiadiazole derivatives.

[0091] A lubricating composition considered according to the invention may comprise from 0.01 to 10% by mass, in particular from 0.1 to 5% by mass and more particularly from 0.5 to 3% by mass of amine and / or sulfur anti-wear additive(s), of thia(di)azole type chosen from dimercaptothiadiazole derivatives, relative to the total mass of the lubricating composition.

[0092] The use of other anti-wear additives, known in particular for lubricants for propulsion systems, other than amine and / or sulphur additives, is conceivable, provided that they do not affect the properties conferred by the combination of said succinimide-type compound(s) and said amine and / or sulphur anti-wear additive(s) according to the invention.

[0093] A lubricating composition considered according to the invention may comprise from 0.01 to 15% by mass, in particular from 0.1 to 10% by mass and more particularly from 0.5 to 5% by mass of anti-wear additive(s), including one or more amine and / or sulfur additives, as described previously.

[0094] Preferably, a lubricating composition required according to the invention is free of anti-wear additive other than said amine and / or sulfur anti-wear additive(s) used according to the invention.

[0095] According to a particularly preferred embodiment, a lubricating composition considered according to the invention combines: one or more succinimide-type compounds, chosen from polyalkylene mono- or bis-succinimides and their borated derivatives, such as polyisobutene mono- or bis-succinimides and their borated derivatives, in particular chosen from the compounds of the abovementioned formula (I), preferably from the compounds of formula (II) and (III) as defined above; and one or more amine and sulfur anti-wear additives, chosen from dimercaptothiazole derivatives, as defined above.

[0096] A composition implemented according to the invention may comprise, in addition to one or more succinimide-type additives and one or more amine and / or sulfur anti-wear additives, in particular as defined above, one or more base oils, as well as other additives, conventionally considered in lubricating compositions. Base oils

[0097] A lubricating composition considered according to the invention can thus comprise one or more base oils.

[0098] These base oils can be chosen from base oils conventionally used in the field of lubricating oils, such as mineral, synthetic or natural, animal or vegetable oils or their mixtures.

[0099] It can be a mixture of several base oils, for example a mixture of two, three, or four base oils.

[0100] The base oils of the lubricating compositions considered according to the invention may in particular be oils of mineral or synthetic origin belonging to groups I to V according to the classes defined in the API classification (or their equivalents according to the ATIEL classification) and presented in table 1 below or their mixtures. [Table 1] Saturated content Sulfur content Viscosity index (VI) Group I < 90 % > 0,03 % 80 ≤VI < 120 Mineral oils Group II ≥90 % ≤0,03 % 80 ≤VI < 120 Hydrocracked oils Group III ≥90 % ≤0,03 % ≥120 Hydrocracked or hydroisomerized oils Group IV Polyalphaolefins (PAO) Group V Esters and other bases not included in groups I to IV

[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, de-alphatting, solvent dewaxing, hydrotreating, hydrocracking, hydroisomerization and hydrofinishing.

[0102] Blends of synthetic and mineral oils, which can be bio-sourced, can also be used.

[0103] There is generally no limitation on the use of different base oils to produce the compositions used according to the invention, except that they must have properties, in particular in terms of viscosity, viscosity index, or resistance to oxidation, suitable for use in propulsion systems of an electric or hybrid vehicle.

[0104] The base oils of the compositions used according to the invention can also be chosen from synthetic oils, such as certain esters of carboxylic acids and alcohols, polyalphaolefins (PAO), and 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.

[0105] PAOs used as base oils are, for example, obtained from monomers comprising 4 to 32 carbon atoms, for example from octene or decene. The weight-average molecular mass of the PAO can vary quite 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 range from 100 to 600 Da, from 150 to 600 Da, or from 200 to 600 Da.

[0106] Advantageously, the base oil or oils of the composition used according to the invention are chosen from polyalphaolefins (PAO), polyalkylene glycol (PAG) and esters of carboxylic acids and alcohols.

[0107] According to an alternative embodiment, the base oil or oils of the composition used according to the invention may be chosen from base oils of group II or III. It is up to a person skilled in the art to adjust the base oil content to be used in a composition suitable for the invention.

[0108] A lubricating composition considered according to the invention may comprise at least 50% by mass of base oil(s) relative to its total mass, in particular from 60 to 99% by mass of base oil(s), relative to its total mass. Additional additives

[0109] A lubricating composition suitable for the invention may also further comprise all types of additives, other than succinimide-type additives and amine and / or sulfur anti-wear additives defined in the context of the present invention, suitable for use in a lubricant for a propulsion system of an electric or hybrid vehicle. It is understood that the nature and quantity of additives used are chosen so as not to affect the properties in terms of anti-wear and anti-corrosion performance conferred by the combination of said succinimide-type compound(s) and said amine and / or sulfur additive(s) used according to the invention.

[0110] Such additives, known to those skilled in the art in the field of lubrication and / or cooling of propulsion systems of electric or hybrid vehicles, may be chosen from friction modifiers, detergents, extreme pressure additives, dispersants other than the succinimide-type compounds according to the invention, antioxidants, pour point depressants, anti-foaming agents and mixtures thereof. Advantageously, a composition suitable for the invention comprises at least one additional additive chosen from friction modifiers, viscosity index modifiers, detergents, extreme pressure additives, dispersants, antioxidants, pour point depressants, anti-foaming agents and mixtures thereof.

[0111] 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.

[0112] A lubricating composition suitable for the invention may comprise at least one friction-modifying additive. The friction-modifying additive may be chosen from a compound providing metallic elements and an ash-free compound. Among the compounds providing metallic elements, mention may be made of transition metal complexes such as Mo, Sb, Sn, Fe, Cu, Zn, the ligands of which may be hydrocarbon compounds comprising oxygen, nitrogen, sulfur or phosphorus atoms. The ash-free friction-modifying additives are generally of organic origin and may be chosen from 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.

[0113] A lubricating composition suitable for the invention may comprise from 0.01 to 2% by weight or from 0.01 to 5% by weight, preferably from 0.1 to 1.5% by weight or from 0.1 to 2% by weight of friction modifying additive, relative to the total weight of the composition.

[0114] A lubricating composition used according to the invention may comprise at least one antioxidant additive.

[0115] 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.

[0116] Antioxidant additives act in particular as radical inhibitors or hydroperoxide destroyers. Among the commonly used antioxidant additives, mention may be made of phenolic type antioxidant additives, amine type antioxidant additives, 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 C 1 -C 12 alkyl group, N,N'-dialkyl-aryl-diamines and mixtures thereof.

[0117] Preferably according to the invention, the sterically hindered phenols are chosen from compounds comprising a phenol group of which at least one vicinal carbon of the carbon carrying the alcohol function is substituted by at least one C 1 - C 10 alkyl group, preferably a C 1 - C 6 alkyl group, preferably a C 4 alkyl group, preferably by the tert-butyl group.

[0118] Amino compounds are another class of antioxidant additives that can be used, optionally in combination with phenolic antioxidant additives. Examples of amine compounds are aromatic amines, for example aromatic amines of the formula NR 4< R 5< R 6< in which R 4< represents an aliphatic group or an aromatic group, optionally substituted, R 5< represents an aromatic group, optionally substituted, R 6< represents a hydrogen atom, an alkyl group, an aryl group or a group of the formula R 7< S(O) z R 8< in which R 7< represents an alkylene group or an alkenylene group, R 8< represents an alkyl group, an alkenyl group or an aryl group and z represents 0, 1 or 2.

[0119] Sulfurized alkyl phenols or their alkali and alkaline earth metal salts can also be used as antioxidant additives.

[0120] Another class of antioxidant additives is that of copper compounds, for example copper thio- or dithio-phosphates, copper salts and carboxylic acids, dithiocarbamates, sulphonates, phenates, copper acetylacetonates. Copper I and II salts, succinic acid or anhydride salts can also be used. A lubricating composition used according to the invention can contain all types of antioxidant additives known to those skilled in the art.

[0121] Advantageously, a lubricating composition used according to the invention comprises at least one ash-free antioxidant additive.

[0122] A lubricating composition used according to the invention may comprise from 0.5 to 2% by weight of at least one antioxidant additive, relative to the total weight of the composition.

[0123] According to a particular embodiment, a lubricating composition used according to the invention is free of antioxidant additive of aromatic amine type or sterically hindered phenol type.

[0124] A lubricating composition suitable for the invention may also comprise at least one detergent additive.

[0125] Detergent additives generally reduce the formation of deposits on the surface of metal parts by dissolving secondary oxidation and combustion products.

[0126] The detergent additives that can be used in a lubricating composition used according to the invention are generally known to those skilled in the art. The detergent additives may be anionic compounds comprising a long lipophilic hydrocarbon chain and a hydrophilic head. The associated cation may be a metal cation of an alkali or alkaline earth metal.

[0127] 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.

[0128] These metal salts generally comprise the metal in a stoichiometric quantity or in excess, therefore in a quantity greater than the 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.

[0129] A lubricating composition suitable for the invention may, for example, comprise from 2 to 4% by weight of detergent additive, relative to the total weight of the composition.

[0130] Also, a lubricating composition implemented according to the invention may comprise at least one dispersing agent, distinct from the succinimide-type compounds defined according to the invention.

[0131] The dispersing agent can be chosen from Mannich bases.

[0132] A lubricating composition used according to the invention may, for example, comprise from 0.2 to 10% by weight of dispersing agent(s) other than the succinimide-type compounds defined according to the invention, relative to the total weight of the composition.

[0133] Advantageously, the lubricating composition used according to the invention does not comprise any dispersing agent(s), other than the succinimide-type compounds defined according to the invention.

[0134] A lubricating composition suitable for the invention may further comprise at least one antifoaming agent.

[0135] The antifoam agent can be chosen from silicones.

[0136] A lubricating composition suitable for the invention 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 weight of the composition.

[0137] A lubricating composition suitable for the invention may also comprise at least one pour point lowering additive (also known as “PPD” agents for “Pour Point Depressant” in English).

[0138] 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.

[0139] In particular, a lubricating composition used according to the invention may be free of anti-corrosion additive of triazole type and antioxidant additive of aromatic amine type or sterically hindered phenol type.

[0140] In terms of formulating such a lubricating composition, said succinimide compound(s) may be added to a base oil or mixture of oils, and then the other complementary additives, including the amine and / or sulfur anti-wear additive(s), added.

[0141] Alternatively, said succinimide-type compound(s) may be added to a pre-existing conventional lubricant formulation, comprising in particular one or more base oils, one or more amine and / or sulfur anti-wear additives, and possibly additional additives.

[0142] Alternatively, said succinimide-type anti-corrosion additive(s) according to the invention may be combined with one or more additional additives, and the "package" of additives thus formed added to a base oil or mixture of oils.

[0143] Advantageously, a lubricating composition used according to the invention has a kinematic viscosity, measured at 100°C according to the ASTM D445 standard, ranging from 1 to 15 mm 2 < / s, in particular ranging from 3 to 10 mm 2 < / s.

[0144] Advantageously, a lubricating composition used according to the invention has a kinematic viscosity, measured at 40°C according to the ASTM D445 standard, ranging from 3 to 80 mm 2 < / s, in particular from 15 to 70 mm 2 < / s.

[0145] According to an advantageous embodiment of the present invention, the electrical resistivity values ​​measured at 90°C of the lubricating compositions used according to the invention are between 5 and 10000 Mohm.m, more preferably between 6 and 5000 Mohm.m. According to an advantageous embodiment of the present invention, the dielectric loss values ​​measured at 90°C of the lubricating compositions used according to the invention are between 0.01 and 30, more preferably between 0.02 and 25, more preferably between 0.02 and 10.

[0146] Advantageously, a lubricating composition used according to the invention may be of grade according to the SAEJ300 classification defined by the formula (X)W(Y), in which X represents 0 or 5; and Y represents an integer ranging from 4 to 20, in particular ranging from 4 to 16 or from 4 to 12.

[0147] According to a particular embodiment, a lubricating composition implemented according to the invention comprises, or even consists of: a base oil or mixture of base oils, preferably chosen from polyalphaolefins (PAO), polyalkylene glycol (PAG) and esters of carboxylic acids and alcohols; one or more succinimide-type additives, chosen from polyalkylene mono- and bis-succinimides, such as polyisobutene mono- and bis-succinimides, and their borated derivatives; in particular chosen from the compounds of the abovementioned formula (I), preferably from the compounds of formula (II) and (III) as defined above; one or more amine and / or sulfur anti-wear additives, more precisely one or more amine and sulfur anti-wear additives, chosen from thia(di)azole-type compounds, more precisely from dimercaptothiazole derivatives as defined above;optionally one or more additional additives chosen from friction modifiers, viscosity index modifiers, detergents, extreme pressure additives, dispersants, antioxidants, pour point depressants, anti-foaming agents and mixtures thereof.;

[0148] According to a particular embodiment, a lubricating composition implemented according to the invention comprises, or even consists of: from 0.01% to 10% by mass, in particular from 0.1% to 10% by mass, and more particularly from 0.5% to 8% by mass, of one or more succinimide-type additives, chosen from polyalkylene mono- and bis-succinimides, such as polyisobutene mono- and bis-succinimides, and their borated derivatives; in particular chosen from the compounds of the abovementioned formula (I), preferably from the compounds of formula (II) and (III) as defined above; from 0.01 to 10% by mass, in particular from 0.1 to 5% by mass, and more particularly from 0.5 to 3% by mass, of one or more amine and / or sulfur anti-wear additives, more precisely one or more amine and sulfur anti-wear additives, chosen from thia(di)azole type compounds, more precisely dimercaptothiazole derivatives as defined above;from 60% to 99.9% by mass of base oil(s), preferably chosen from polyalphaolefins (PAO), polyalkylene glycol (PAG), esters of carboxylic acids and alcohols and mixtures thereof; optionally from 0.1% to 5% by mass of one or more additives chosen from friction modifiers, viscosity index modifiers, detergents, extreme pressure additives, dispersants, antioxidants, pour point depressants, anti-foaming agents and mixtures thereof; the contents being expressed relative to the total mass of said lubricating composition.; APPLICATION

[0149] As indicated previously, a lubricating composition as described previously is used as a lubricant for a propulsion system of an electric or hybrid vehicle, and more particularly of the engine and the power electronics.

[0150] Thus, also described is the use of a lubricating composition as defined above, combining one or more succinimide-type compounds, as defined above, and one or more amine and / or sulfur anti-wear additives, derived from dimercaptothiazole, for lubricating a propulsion system of an electric or hybrid vehicle, in particular for the lubrication of the electric motor and the power electronics of an electric or hybrid vehicle.

[0151] As schematically represented in Figure 1 , the propulsion system of an electric or hybrid vehicle, comprises in particular the electric motor part (1), an electric battery (2) and a transmission, and in particular a speed reducer (3).

[0152] 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.

[0153] 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.

[0154] The bearing (12) is particularly subject to high mechanical stresses and poses problems of fatigue wear. It is therefore necessary to lubricate the bearing in order to increase its service life. Also, the reducer is subject to high frictional stresses and therefore needs to be lubricated appropriately to prevent it from being damaged too quickly.

[0155] Thus, described is the use of a composition as described above for lubricating an electric motor of an electric or hybrid vehicle, in particular for lubricating the bearings located between the rotor and the stator of an electric motor.

[0156] It also relates to the implementation of a composition as described previously for lubricating the transmission, in particular the reducer, in an electric or hybrid vehicle.

[0157] Advantageously, a described composition can thus 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 and / or the transmission, in particular the reducer, in an electric or hybrid vehicle.

[0158] Advantageously, as previously discussed, a described lubricating composition exhibits excellent anti-wear and anti-corrosion performance.

[0159] Also described is a method of lubricating at least one part of a propulsion system of an electric or hybrid vehicle, in particular the bearings located between the rotor and the stator of an electric motor; and / or the transmission, in particular the reducer, comprising at least one step of bringing at least said part into contact with a composition as described previously.

[0160] Also described is a method for simultaneously reducing the wear and corrosion of at least one part of a propulsion system of an electric or hybrid vehicle, in particular the bearings located between the rotor and the stator of an electric motor; and / or the transmission, in particular the reducer, said method comprising at least one step of bringing at least said part into contact with a composition as described previously.

[0161] All of the characteristics and preferences described for the composition used and for its uses also apply to this method. According to a particular embodiment, a described composition may have, in addition to lubricating properties, good electrical insulation properties. According to this embodiment, a described composition may simultaneously be used to lubricate one or more parts of a propulsion system of an electric or hybrid vehicle, in particular for the lubrication of the sensors and solenoid valves of the motor, the bearings, but also the winding located at the rotor and stator of an electric motor, or even lubrication at the transmission, in particular the gears, the sensors, the solenoid valves, or the reducer found in an electric or hybrid vehicle, and to electrically insulate at least one part of said propulsion system, in particular the battery.

[0162] In the context of such an implementation variant, a lubricating composition considered advantageously has a kinematic viscosity, measured at 100°C according to the ASTM D445 standard, of between 2 and 8 mm 2 < / s, preferably between 3 and 7 mm 2 < / s. It is understood that the uses described above can be combined, a composition as described above being able to be used both as a lubricant, an electrical insulator and also as a cooling fluid for the engine, the battery and the transmission of an electric or hybrid vehicle.

[0163] 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. Example

[0164] Different compositions were evaluated: a composition C1 comprising an amine and sulfur anti-wear additive, of dimercaptothiadiazole type and devoid of succinimide type additive; a composition C2 comprising said anti-wear additive of dimercaptothiadiazole type, and a succinimide type dispersing additive, in accordance with the invention, more precisely a bis-succinimide of the following formula: as defined above, a composition C3 comprising said anti-wear additive of dimercaptothiadiazole type, and a succinimide-type dispersant additive, in accordance with the invention, more precisely a high molecular weight PIB succinimide, a composition C4 comprising said anti-wear additive of dimercaptothiadiazole type, and a succinimide-type dispersant additive, in accordance with the invention, more precisely a PIB succinimide of the following formula: as defined above.

[0165] Compositions C1 to C4 comprise, in addition to the aforementioned compounds, a group V base oil.

[0166] The compositions and quantities (expressed as a percentage by mass) are indicated in the following table 2. [Table 2] C1 C2 C3 C4 Base oil 99% 98% 98% 98% Anti-wear dimercaptothiadiazole 1% 1% 1% 1% Bis-succinimide - 1% - - PIB-succinimide - - 1% - PIB-succinimide - - - 1% Evaluation of anti-corrosion properties Evaluation method

[0167] The corrosive (or corroding) power of a composition can be evaluated according to a test implementing the study of the variation in the value of the electrical resistance of a copper wire having a pre-established diameter, as a function of the duration of immersion of this wire within the composition. The variation in the value of this electrical resistance is correlated directly with the variation in the diameter of the wire tested. In the context of the present invention, the diameter of the wire chosen is 70µm.

[0168] In the present case, a copper wire is immersed in a test tube containing a volume of 20 mL of a composition to be tested (compositions C2 to C4 being compositions according to the invention and composition C1 being a composition serving as a comparison).

[0169] The resistance of the wire is measured using an ohmmeter.

[0170] The measuring current is 1mA.

[0171] The temperature of the composition to be tested is brought to 150°C.

[0172] The resistance of copper wire is calculated by this equation (1): R = ρ × L S where R is the resistance, ρ is the resistivity of copper, L is the length of the wire, and S is the cross-sectional area.

[0173] In this equation (1), ρ and L are constant. Thus, the resistance R is inversely proportional to the cross-sectional area of ​​the immersed wire.

[0174] The wire diameter is calculated from the cross-sectional area (equation (2)): S = π 4 × D 2 where D is the diameter of the wire.

[0175] We inject equation (2) into equation (1) to have the relationship between resistance and diameter (equation (3)): R = ρ × L π 4 × D 2

[0176] This is how, when the wire is corroded by the compositions to be tested, the diameter of the wire decreases, thus causing an increase in the resistance value.

[0177] By monitoring the resistance, we can follow the change in the diameter of the wire, which is an image of the corrosion situation suffered by the immersed wire.

[0178] The wire diameter loss is therefore calculated directly from the measured resistance.

[0179] When the measured resistance is infinite, it is an open circuit. Therefore, the wire has broken, which defines very severe corrosion. Results

[0180] The results are summarized in the following table, and are expressed in µm (loss of diameter). The lower the value obtained, the better the anti-corrosion properties of the composition evaluated.

[0181] A composition is considered to be “non-corrosive” when the loss of diameter of the copper wire studied is less than or equal to 1.3 µm after immersion for 80 hours, in particular less than or equal to 0.8 µm after immersion for 40 hours in the composition comprising said compound. [Table 3] Compositions C1 C2 C3 C4 Diameter loss (µm) at 8 p.m. 0,28 0,55 0,44 0 Diameter loss (µm) at 40 h Broken wire 0,74 0,73 0,47 Diameter loss (µm) at 60 h Broken wire 0,70 1,03 0,82 Diameter loss (µm) at 80 hours Broken wire 0,82 1,28 1,19

[0182] It emerges from these results that the addition of a succinimide-type compound according to the invention makes it possible to reduce the corrosion effects induced by the amine and sulfur anti-wear additive.

Claims

1. Use of at least one succinimide compound, as an anticorrosion additive in a lubricant composition, for a propulsion system of an electric or hybrid vehicle and comprising one or more amine-based and / or sulfur-based antiwear additives; the amine-based and / or sulfur-based antiwear additive being chosen from the 2,5-dimercapto-1,3,4-thiadiazole derivatives having the following formulae, taken alone or as a mixture: in which the one or more R1 groups represent, independently of each other, hydrogen atoms, linear or branched alkyl or alkenyl groups comprising from 1 to 24, preferably from 2 to 18, more preferentially from 4 to 16 and even more preferentially from 8 to 12, carbon atoms, or aromatic substituents, n being, independently of each other, integers equal to 1, 2, 3 or 4, n preferably being equal to 1; said succinimide compound being chosen from polyalkylene mono- or bis-succinimides; borate derivatives thereof and mixtures thereof.

2. Use according to Claim 1, wherein the polyalkylene mono- or bis-succinimides are chosen from polyisobutene (PIB) mono- or bis-succinimides.

3. Use according to either one of the preceding claims, wherein said succinimide compound comprises at least one substituted succinimide group of the following formula (ii): or a borate derivative of said group (ii), in which R1 represents a hydrocarbon group, preferably comprising from 8 to 400 carbon atoms, in particular a polyalkylene group optionally linked to the succinimide group via a -(C=CH2)- group, preferably having a mass-average molecular mass Mw of between 140 and 50 000, in particular between 2000 and 30 000, and more particularly a polyisobutylene group optionally linked to the succinimide group via a -(C=CH2)- group, preferably with a mass-average molecular mass Mw of between 140 and 30 000, in particular between 2000 and 20 000 or even between 2000 and 7000 and especially between 3000 and 5000.

4. Use according to any one of the preceding claims, wherein said succinimide compound is a monosuccinimide of the following formula (II): or one of the borate derivatives thereof, in which: R1 is as defined in Claim 3, in particular R1 represents a polyalkylene group optionally linked to the succinimide group via a -(C=CH2)- group, in particular R1 represents a polyisobutylene group optionally linked to the succinimide group via a -(C=CH2)- group; A represents a linear or branched C2 to C24, preferably C2 to C6, alkylene group, and preferably represents at least one of the following segments: -CH2-CH2-, -CH2-CH2-CH2-, -CH2-CH(CH3)-; and y represents an integer between 1 and 6; in particular y represents 2, 3 or 4.

5. Use according to any one of Claims 1 to 3, wherein the succinimide compound is a bis-succinimide of the following formula (III): or one of the borate derivatives thereof, in which: R1, which may be identical or different, are as defined in Claim 3, in particular R1 represent polyalkylene groups optionally linked to the succinimide group via a -(C=CH2)-group, in particular polyisobutylene groups optionally linked to the succinimide group via a -(C=CH2)- group; z represents an integer between 0 and 10, preferably between 2 and 6; s represents an integer between 2 and 6, preferably between 2 and 4.

6. Use according to any one of the preceding claims, in which said one or more succinimide compounds are present in a content ranging from 0.01% to 10% by mass, in particular from 0.1% to 10% by mass, and more particularly from 0.5% to 8% by mass, relative to the total mass of the lubricant composition, and / or said one or more amine-based and / or sulfur-based antiwear additive are present in a content ranging from 0.01% to 10% by mass, in particular from 0.1% to 5% by mass and more particularly from 0.5% to 3% by mass, relative to the total mass of the lubricant composition.