Use of an aqueous lubricant composition for improving the energy efficiency of a powertrain of a vehicle

Abstract

The present invention relates to the use of an aqueous lubricant composition for improving the energy efficiency of a powertrain of a vehicle, said aqueous lubricant composition comprising at least: - water; - at least one polyalkylene glycol; and - at least one antifreeze compound. It also relates the use of this aqueous lubricant composition to reduce the energy consumption of an electric or hybrid vehicle. It also relates the use of this aqueous lubricant composition to increase the lifespan and / or the charging interval of the engine comprised in said powertrain.

Description

Technical field

[0001] The present invention relates to the field of lubricating compositions, more particularly the field of lubricating compositions for a powertrain of a vehicle, in particular an electric or hybrid vehicle. It relates more particularly to the use of an aqueous lubricant composition in a powertrain of a vehicle, in particular in propulsion systems, more particularly in mechanical systems, such as rolling bearings, gears, bearings or engines, of electric or hybrid vehicles, for improving the energy efficiency of such powertrains.Prior art

[0002] The evolution of international standards for reducing CO 2 emissions, but also for reducing energy consumption, are prompting vehicle manufacturers to propose alternative solutions to combustion engines.

[0003] One of the solutions identified by automobile manufacturers is to replace combustion engines with electric motors. Research into reducing CO 2 emissions has thus led to the development of electric or hybrid vehicles by a number of vehicle companies.

[0004] Generally, electric or hybrid vehicles require compositions to meet the dual requirements of lubricating and cooling the various parts of the powertrains of these vehicles.

[0005] Lubricant compositions, also referred to as "lubricants", are commonly used in powertains of a vehicle, in particular in mechanical systems of an electric or hybrid vehicle, to reduce friction between parts and thus protect parts against wear. In addition to wear phenomena, friction can oppose the relative motion between parts in contact and induce energy losses that are detrimental to the optimal operation of the mechanical system.

[0006] The most common lubricants are hydrocarbon-based lubricants. These hydrocarbon-based lubricants are conventionally composed of one or more base oils which are generally combined with several additives intended for stimulating the lubricant performance of the base oils, for instance friction-modifying additives.

[0007] Nowadays, the development of new lubricants must take into account new constraints aimed at avoiding the use of toxic or potentially toxic solvents, or else reducing their environmental impact and carbon dioxide emissions. As such, water-based formulations are of increasing interest.

[0008] Although water is an excellent coolant, it does not however have the tribological properties required for a lubricant, in particular in terms of reducing friction and protecting parts against wear.

[0009] Water-based lubricant compositions, supplemented by various additives, have already been studied. For example, document US 2012 / 0149616 proposes an aqueous lubricant comprising, in addition to water, water-soluble polyalkylene glycols, emulsifiers, antifreeze additives of alkylene glycol or glycerol type, anticorrosion additives, antifoam additives and friction-reducing additives.

[0010] Nevertheless, water-based lubricant compositions are not described as being suitable for specific issues of powertrain of a vehicle.

[0011] In particular, such specific issues comprise the optimization of the energy consumption of electric or hybrid vehicles which impacts the lifespan or the charging interval for an electric motor and must and is hence an important issue for their development.Summary of the invention

[0012] The present invention aims to provide a novel water-based composition, having properties suitable for its use for the lubrication of a powertrain of a vehicle, while improving performance in terms of energy savings.

[0013] Thus, according to a first of its aspects, the present invention relates to the use of an aqueous lubricant composition for improving the energy efficiency of a powertrain of a vehicle, said aqueous lubricant composition comprising at least: water; at least one polyalkylene glycol; and at least one antifreeze compound.

[0014] Surprisingly, as showed in the following examples, the inventors have discovered that the use of an aqueous lubricant composition according to the invention significantly improved the energy efficiency of a powertrain of a vehicle compared to the use of conventional hydrocarbon-based lubricant compositions, and advantageously allows to decrease the CO 2 emissions compared to conventional lubricants.

[0015] Advantageously, the use of an aqueous lubricant composition implies the smaller loss of dynamic energy efficiency as well as the higher static energy efficiency compared to the use of comparative hydrocarbon-based lubricant compositions.

[0016] It thus advantageously allows to save energy for electric and hybrid vehicles.

[0017] An "electric vehicle" in the sense of the present invention denotes a vehicle comprising an electric motor as its sole means of propulsion, whereas a "hybrid vehicle" comprises a combustion engine and an electric motor as combined means of propulsion.

[0018] A "powertrain" in the sense of the present invention denotes a system comprising an electric drive unit and a battery which generally consists of a set of electric accumulators.

[0019] A "electric drive unit" in the sense of the present invention denotes a system comprising mechanical components necessary to the propulsion of an electric or hybrid vehicle. The electric drive unit of an electric or hybrid vehicle thus encompasses more particularly an electric motor comprising the rotor-stator assembly of the power electronics (dedicated to regulating the speed), and a mechanical transmission.

[0020] In the remainder of the text, the expressions "aqueous lubricant composition" or "aqueous lubricant" will denote a lubricant composition used according to the invention, intended to lubricate a powertrain of a vehicle, in particular a mechanical system of a propulsion system, more particularly the moving parts in a mechanical system, and even more particularly intended to lubricate rolling bearing(s), gear(s), bearing(s) and / or engine.

[0021] For the purposes of the present invention, the expression "aqueous composition" is understood to denote a composition comprising water as base fluid, in other words as the major solvent. In particular, water, preferably deionized water, preferably represents more than 35% by weight, in particular more than 40% by weight, more particularly more than 50% by weight, of the total weight of the lubricant composition.

[0022] For the purposes of the present invention, the expression "osmosed water" is understood to denote water which has undergone purification, in particular by a reverse osmosis process, in order to reduce the content of organic and / or mineral compounds, for example to a content of less than 5.0% by weight, preferably less than 1.0% by weight. In the remainder of the text, the expressions "demineralized water" or else "ultrapure water" will be considered as equivalent or synonymous with the expression "osmosed water". In particular, the osmosed water may be "deionized water", in other words water that has undergone purification in order to reduce the content of ions, such as Ca 2+< and HCO 3 -< ions generally present in water. Preferably, a deionized water comprises no ions.

[0023] For the purposes of the present invention, the expression "Energy efficiency" refers to the ability of a lubricant composition to limit the energy consumption of a mobile or stationary, hybrid or electric, motorization system, in particular of a powertrain, more particularly such energy consumption being saved at the level of the motor itself, but also at the level of transmission components, such as the gearbox, gear(es), bridges and bearings. This energy efficiency translates, in particular, into longer service life or recharging intervals for an electric motor.

[0024] The present invention therefore also provides the use of an aqueous lubricant composition as described above to reduce the energy consumption of an electric or hybrid vehicle.

[0025] The present invention further provides the use of an aqueous lubricant composition as described above to increase the lifespan and / or the charging interval of the engine comprised in said powertrain.

[0026] The present invention also provides a method or a process for improving the energy efficiency of at least one component of a powertrain of a vehicle, in particular the rolling bearings situated between the rotor and the stator of an electric motor; and / or the transmission, more particularly the reduction gear, said method or process comprising at least one step of contacting said at least one component with an aqueous composition as described above.

[0027] Advantageously, the present invention also provides a method or a process for reducing the energy consumption or to improve the energy-saving properties of an electric or hybrid vehicle, said method or process comprising at least one step of contacting at least one component of a powertrain comprised in said electric or hybrid vehicle with an aqueous composition as described above.

[0028] The present invention further provides a method or a process to increase the lifespan and / or the charging interval of the engine comprised in said powertrain of a vehicle, said method or process comprising at least one step of contacting at least one component of a powertrain with an aqueous composition as described above.

[0029] The entirety of the features and preferences described for the use of an aqueous lubricant composition used according to the invention are also applicable to those methods or process.

[0030] Therefore, according to one particular embodiment, a composition according to the invention may exhibit good electrical insulation properties as well as lubrication properties.

[0031] Other features, variants and advantages of an aqueous lubricant composition used according to the invention will emerge more clearly on reading the description and the examples that follow, which are given as nonlimiting illustrations of the invention.

[0032] The terms "between... and...", "ranging from... to...", "formed from... to..." and "varying from... to..." should be understood as being limits included, unless otherwise mentioned.

[0033] In the description and the examples, unless otherwise indicated, the percentages are weight percentages. The percentages are therefore expressed by weight relative to the total weight of the composition. The temperature is expressed in degrees Celsius unless otherwise indicated, and the pressure is atmospheric pressure, unless otherwise indicated.Brief description of the drawings

[0034] Figure 1 represents a propulsion system of a powertrain of an electric or hybrid vehicle which comprises, in particular, the electric motor part (1), an electric battery (2) and a transmission, more particularly a speed reduction gear (3). Figure 2 represents specific profile of input speed over time from 0 second to 1800 seconds, used for the below-mentioned dynamic energy efficiency evaluation in the Worldwide Harmonized Light Vehicles Test Procedure (WLTP) class 3 cycle. Figure 3 represents specific profile of input torque over time from 0 second to 1800 seconds, used for the below-mentioned dynamic energy efficiency evaluation in the Worldwide Harmonized Light Vehicles Test Procedure (WLTP) class 3 cycle. Figure 4 represents the results of dynamic energy efficiency evaluated for lubricant compositions by using a test which involves specific profiles of input speed and input torque over time from 0 second to 1800 seconds, respectively represented in figures 2 and 3. Detailed description AQUEOUS COMPOSITION

[0035] As mentioned above, an aqueous lubricant composition used according to the invention, also referred to as an aqueous lubricant, is a formulation comprising water, in particular deionized water, as major solvent.

[0036] For the purposes of the invention, a "major solvent" is understood to mean that water is present in a greater amount than any other solvent possibly present in the composition. Preferably, an aqueous lubricant composition used according to the invention comprises at least 20% by weight, in particular at least 30% by weight, in particular ranging from 35% to 90% by weight, more particularly from 40% to 75% by weight, and even more particularly from 40% to 60% by weight, of water, preferably of deionized water, relative to the total weight of said composition.

[0037] Advantageously, in addition to its role as solvent, water provides access to a lubricant composition having good cooling properties, and which can be used as a cooling fluid for the moving parts in a mechanical system comprised in a powertrain of a vehicle.

[0038] For the purposes of this invention, the term "cooling fluid" refers to a fluid capable of dissipating the heat generated by a propulsion system comprised in a powertrain of a vehicle in an electric or hybrid vehicle. More precisely, such a fluid is characterized by an enhanced heat absorption capacity when in contact with a component that is heating up.

[0039] According to a particular embodiment, the water used in an aqueous lubricant composition used according to the invention is deionized water, also referred to as demineralized water.

[0040] For the purposes of this invention, "osmosed water" refers to water which has been subjected to a purification, in particular by a reverse osmosis process, to reduce the content of organic and / or mineral compounds, for example to a content less than 5.0% by weight, preferably less than 1.0% by weight, relative to the total weight of the osmosed water. In the text, the terms "demineralized water" or "ultrapure water" will be considered equivalent or synonymous with the term "reverse osmosis water". In particular, osmosis water can be "deionized water", i.e. water which has been subjected to a purification to reduce the content of ions, such as Ca 2+< and HCO 3 -< ions, generally present in water. Preferably, deionized water is free of ions.

[0041] The use of deionized water is therefore particularly advantageous in the context of the use of the aqueous lubricant according to the invention for applications requiring a fluid that conducts little or no electricity, such as for example for the use of the aqueous lubricant for the lubrication, and additionally the cooling, of mechanical systems comprising an electrical circuit, for example electric or hybrid motors comprised in a powertrain in electric or hybrid vehicles.

[0042] An aqueous lubricant composition used according to the invention therefore differs from the lubricants conventionally used in mechanical systems, in particular hydrocarbon-based lubricants, which comprise a major proportion of one or more water-insoluble base oils.

[0043] A "water-insoluble oil" is understood to mean in particular an oil which does not dissolve substantially in water at room temperature (at around 25°C). In particular, a water-insoluble oil has a solubility in water of less than 0.2 g / L, at room temperature.

[0044] These include in particular lubricating base oils belonging to groups I to V according to the classes defined in the API classification (or their equivalents according to the ATIEL classification) and mixtures thereof.

[0045] Preferably, an aqueous lubricant composition used according to the present invention comprises less than 5% by weight of water-insoluble base oil(s), preferably less than 2% by weight, more preferentially less than 1% by weight, relative to the total weight of the composition.

[0046] Advantageously, an aqueous lubricant composition used according to the invention is completely free of water-insoluble oil.POLYALKYLENE GLYCOL

[0047] As indicated above, an aqueous lubricant composition used according to the invention comprises at least one polyalkylene glycol.

[0048] The polyalkylene glycols (denoted "PAG") are chosen from water-soluble polyalkylene glycols.

[0049] The term "water-soluble" is understood to denote a polyalkylene glycol having a solubility in water of at least 10 g / L, preferably of at least 500 g / L, in water at room temperature (around 25°C).

[0050] The polyalkylene glycols can be more particularly formed from C 1 -C 4 , preferably C 1 -C 3 and more particularly C 2 -C 3 alkylene oxide units.

[0051] Advantageously, a polyalkylene glycol(s) used in an aqueous lubricant composition used according to the invention comprise(s) at least 50% by weight, in particular at least 80% by weight, more preferentially at least 90% by weight of propylene oxide and / or ethylene oxide units. It may be a copolymer, in particular a random copolymer, of ethylene oxide / propylene oxide.

[0052] Preferably, a polyalkylene glycol used in an aqueous lubricant composition used according to the invention has a weight-average molar mass (Mw) of between 100 and 50 000 g.mol -1< , preferably between 5 000 and 25 000 g.mol -1< .

[0053] The weight-average molar mass can be measured by gel permeation chromatography (GPC). Preferably, a polyalkylene glycol used in an aqueous lubricant composition used according to the invention has a kinematic viscosity measured at 100°C (KV100), according to the ASTM D445 standard, ranging from 100 to 25 000 mm 2< / s, and in particular from 150 to 3000 mm 2< / s.

[0054] Preferably, a polyalkylene glycol used in an aqueous lubricant composition used according to the invention has a kinematic viscosity measured at 40°C (KV40), according to the ASTM D445 standard, ranging from 500 to 100 000 mm 2< / s, and in particular from 1 000 to 95 000 mm 2< / s.

[0055] The flash point of a polyalkylene glycol used in an aqueous lubricant composition used according to the invention is preferably above or equal to 160°C, in particular above or equal to 220°C. The flash point can be measured by the ISO 2592 or ASTM D92 standard.

[0056] Preferably, a polyalkylene glycol used in an aqueous lubricant composition used according to the invention has a viscosity index measured according to the ASTM D2270 standard, ranginig from 100 to 800, and preferably from 250 to 550.

[0057] In particular, said polyalkylene glycol compound(s) can be implemented in an aqueous lubricant composition used according to the invention in a content of at least 5% by weight, preferably ranging from 5% to 50% by weight, more particularly from 10% to 40% by weight, and even more particularly from 10% to 20% by weight, relative to the total weight of the composition.

[0058] Preferably, an aqueous lubricant composition used according to the invention comprises less than 17 % by weight, more preferably ranging from 10 % to 15 % by weight of polyalkylene glycol compound(s), relative to the total weight of the composition.

[0059] It is understood that an aqueous lubricant composition used according to the invention may comprise a single polyalkylene glycol or a mixture of several distinct polyalkylene glycols.

[0060] In particular, an aqueous lubricant composition used according to the invention may comprise a mixture of at least two distinct polyalkylene glycols, more particularly at least one polyalkylene glycol of low weight-average molecular weight and at least one polyalkylene glycol of high weight-average molecular weight.

[0061] The combination of at least one polyalkylene glycol having a low weight-average molecular weight and at least one polyalkylene glycol having a high weight-average molecular weight is particularly advantageous for achieving good solubilization of the various compounds introduced into the aqueous lubricant composition.ANTIFREEZE COMPOUND

[0062] As indicated above, an aqueous lubricant composition used according to the invention comprises at least one antifreeze compound.

[0063] Preferably, the antifreeze compound is chosen from glycols, more preferably alkylene glycols, glycerol, diglycerol, triglycerol, and mixtures thereof.

[0064] These compounds are known for their antifreeze action, in other words for reducing the freezing temperature of the composition.

[0065] Glycols are diols in which the two hydroxyl groups are borne by different carbon atoms, preferably by vicinal carbon atoms.

[0066] Preferably, the glycols are alkylene glycols, in particular having from 2 to 10 carbon atoms, in particular from 2 to 6 carbon atoms. As examples, mention may be made of monoethylene glycol, diethylene glycol and propylene glycol.

[0067] The antifreeze compound can also be chosen from glycerol, diglycerol, triglycerol and mixtures thereof.

[0068] Preferably, the antifreeze compound used according to the invention is chosen from monoethylene glycol, diethylene glycol, propylene glycol, glycerol and mixtures thereof. Preferably, the antifreeze compound is diethylene glycol.

[0069] In particular, said antifreeze compound(s) can be implemented in an aqueous lubricant composition used according to the invention in a content of at least 1% by weight, in particular ranging from 5% to 50% by weight, more particularly from 10% to 45% by weight, and even more particularly from 20% to 40% by weight, of antifreeze compound(s), relative to the total weight of the aqueous lubricant composition.

[0070] Preferably, an aqueous lubricant composition used according to the invention comprises a content of antifreeze compound(s), more particularly comprising at one of the antifreeze compounds defined above, for example comprising at least diethylene glycol, greater than or equal to 20% by weight, in particular between 30% and 50% by weight, relative to the total weight of the aqueous lubricant composition.

[0071] According to a particular embodiment, an aqueous lubricant composition used according to the invention comprises: at least 30% by weight, in particular ranging from 40% to 75% by weight, more particularly from 40% to 60% by weight, of water, preferably of deionized water, relative to the total weight of said composition; at least 5% by weight, in particular ranging from 10% to 40% by weight, more particularly from 10% to 20% by weight, of polyalkylene glycol(s), preferably said polyalkylene glycol(s) comprising at least one polyalkylene glycol as defined above, relative to the total weight of said composition; and at least 1% by weight, in particular ranging from 5% to 50% by weight, more particularly from 20% to 40% by weight, of antifreeze compound(s), preferably said antifreeze compound(s) comprising at least one compound chosen from glycols, preferably from alkylene glycols, glycerol, diglycerol, triglycerol, and mixtures thereof, more preferably from monoethylene glycol, diethylene glycol, propylene glycol, glycerol and mixtures thereof, even more preferably comprising at least diethylene glycol, relative to the total weight of said composition. ADDITIVES

[0072] An aqueous lubricant composition used according to the invention may further comprise various additives.

[0073] It is understood that said additive(s) are compatible with their use in an aqueous medium. Advantageously, the additives are used in a water-soluble or water-emulsifiable form, for example in the form of ionic salts or liquids.

[0074] Said additive(s) are of course chosen with regard to the intended application for the aqueous lubricant.

[0075] Of course, those skilled in the art will take care to choose the possible additives and / or the amount thereof in such a way that the advantageous properties of the aqueous lubricant composition used according to the invention, in particular the lubrification properties as well as the improvement of energy efficiency and optionally cooling properties, are not adversely affected by the proposed addition.

[0076] Such additives can be more particularly chosen from antifoaming agents, biocides, pH regulators, corrosion inhibitors, antiwear and / or extreme-pressure additives, sequestrants, metal passivators, dyes, dispersants, emulsifiers, and mixtures thereof.

[0077] Advantageously, an aqueous lubricant composition used according to the invention may comprise one or more additives chosen from antifoaming agents, extreme-pressure agents, corrosion inhibitors, pH regulators, metal passivators, dyes, and mixtures thereof.

[0078] An aqueous lubricant composition used according to the invention may more particularly comprise from 0.1% to 10% by weight, more preferentially from 1.0% to 8.0% by weight of additives, relative to the total weight of the composition.pH regulator

[0079] An aqueous lubricant composition according to the invention may comprise at least one pH-regulating additive, in particular an alkaline buffer. The pH regulator makes it possible to maintain the desired pH of the lubricant composition, in particular in order to preserve an alkaline pH, advantageously between 8 and 15.

[0080] Said pH regulator(s), by maintaining the pH of the aqueous lubricant composition between 8 and 15, prevent corrosion of metal surfaces, but also promote solubilization of the various compounds in the lubricant composition, in particular polyalkylene glycol(s), in particular as defined above.

[0081] The pH regulator can be chosen from the family of amines, in particular alkanolamines and amino alcohols.

[0082] It may in particular be a pH-regulating additive chosen from ethanolamines, such as monoethanolamine (MEA), diethanolamine (DEA); triethanolamine (TEA), diglycolamine (DGA) isopropanolamines, such as monoisopropanolamine (MIPA), diisopropanolamine (DIPA) and triisopropanolamine (TIPA), ethyleneamines, such as ethylenediamine (EDA), diethylenetriamine (DETA), triethylenetetramine (TETA) and tetraethylenepentamine (TEPA), alkanolamines, such as methyldiethanolamine (MDEA), cyclamines, such as cyclohexylamine, 2-amino-2-ethyl-1,3-propanediol, 2-amino-2-methyl-1-propanol and mixtures thereof.

[0083] An aqueous lubricant composition according to the invention may in particular comprise from 0.1% to 10% by weight of pH-regulating additive(s), preferably from 0.5% to 5% by weight, relative to the total weight of the composition.

[0084] Preferably, an aqueous lubricant composition according to the invention may comprise at least one pH regulator enabling the pH of said lubricant composition to be maintained between 8 and 15, in particular between 8.5 and 14, more particularly between 9 and 13, said pH regulator being chosen in particular from alkanolamines, preferably ethanolamines, and more particularly from dimethylethanolamine (DMEA), triethanolamine (TEA) and mixtures thereof.Corrosion inhibitor

[0085] An aqueous lubricant composition according to the invention may comprise at least one corrosion inhibitor. Corrosion inhibitors advantageously make it possible to reduce or even prevent corrosion of metal parts. The nature of said corrosion inhibitor(s) can be chosen with regard to the metal to be protected against corrosion, such as aluminum, steel, galvanized steel, yellow metals, for example copper or brass.

[0086] Mention may be made, among the inorganic corrosion inhibitors, of nitrites, sulfites, silicates, borates, sodium, potassium, calcium or magnesium phosphates, alkali metal phosphates, hydroxides, molybdates, sulfates of zinc, magnesium or nickel.

[0087] Mention may be made, among the organic corrosion inhibitors, of alkanolamines, such as triethanolamine, aliphatic monocarboxylic acids, in particular having from 4 to 15 carbon atoms, for example octanoic acid, aliphatic dicarboxylic acids having from 4 to 15 carbon atoms, carbon, for example decanedioic acid, undecanedioic acid, dodecanedioic acid or mixtures thereof, polycarboxylic acids optionally neutralized with triethanolamine, such as 1,3,5-triazine-2,4,6-tri-(6-aminocaproic) acid, alkanoylamidocarboxylic acids, in particular isononanoylamidocaproic acid, and mixtures thereof. Borate amides, products of the reaction of amines or amino alcohols with boric acid, can also be used.

[0088] Preferably, the corrosion inhibitor(s) are distinct from the pH regulator(s), in particular for maintaining the pH of the lubricant composition between 8 and 15, as defined above.

[0089] An aqueous lubricant composition according to the invention may in particular comprise from 0.1% to 5% by weight of corrosion inhibitor(s), in particular as described above, preferably from 0.5% to 4% by weight, more preferentially from 1% to 2.5% by weight, relative to the total weight of the composition.Anti-wear / extreme-pressure additive

[0090] An aqueous lubricant composition according to the invention may comprise at least one anti-wear and / or extreme-pressure additive. Their function is to reduce wear and the coefficient of friction, or else to prevent metal-metal contact by forming an adsorbed protective film on these surfaces.

[0091] There is a wide variety of antiwear additives, among which mention may be made of those chosen from phosphorus-sulfur additives such as metal alkylthiophosphates or salts thereof. Additives that do not provide phosphorus may also be suitable, such as, for example, polysulfides, in particular sulfur-containing olefins.

[0092] According to a particular embodiment, an aqueous lubricant composition according to the invention may comprise at least one extreme-pressure additive chosen from sulfur-containing fatty acids, and dimercaptothiadiazoles, preferably used in the neutralized, water-emulsifiable or water-soluble form thereof, in particular neutralized by in particular by inorganic basifying agents or alkanolamines.

[0093] Advantageously, an aqueous lubricant composition according to the invention comprises at least 0.1% by weight of extreme-pressure additive of sulfur-containing fatty acid type, in particular in a neutralized form, preferably less than 0.01% by weight, more particularly less than 0.001% by weight, relative to the total weight of the lubricant composition, or even is completely free of extreme-pressure additive of sulfur-containing fatty acid type.

[0094] The sulfur-containing fatty acids can comprise from 8 to 22 carbon atoms, in particular from 12 to 18 carbon atoms.

[0095] The amount of sulfur according to the ASTM D2622 standard provided by said sulfur-containing fatty acid(s) can be between 5% and 30% by weight, in particular between 10% and 20% by weight, relative to the total weight of the lubricant composition.

[0096] Preferably, the amount of active sulfur at 150°C according to the ASTM D1662 standard provided by said sulfur-containing fatty acid(s) in the aqueous lubricant composition according to the invention is less than or equal to 2% by weight, in particular less than or equal to 1% by weight, more particularly less than or equal to 0.1% by weight, relative to the total weight of the lubricant composition.

[0097] For the purposes of the present invention, the expression "active sulfur" is understood to mean sulfur that a chemical compound is capable of yielding or releasing when this compound is placed under the conditions of the ASTM D1662 standard. The ASTM D-1662 standard defines an active sulfur content of a compound at a given temperature as a difference expressed as a weight percentage of sulfur content before and after reaction of a sample of this sulfur-containing compound with a given amount of copper over a fixed time.

[0098] As mentioned above, said sulfur-containing fatty acid(s) are generally used in an aqueous lubricant composition in their form neutralized by a basifying agent, such as sodium hydroxide, potassium hydroxide, or an alkanolamine, such as monoethanolamine, triethanolamine, monoisopropanolamine, diisopropanolamine and triisopropanolamine.

[0099] An aqueous lubricant composition according to the invention may comprise between 0.01% and 10% by weight of anti-wear and / or extreme-pressure additive(s), in particular of sulfur-containing fatty acid(s), as defined above, preferably between 0.2% and 5% by weight, relative to the total weight of the composition.Antifoam

[0100] An aqueous lubricant composition according to the invention may comprise at least one antifoam additive. Antifoams make it possible to prevent foaming of the lubricant fluid.

[0101] It may be, for example, an antifoaming agent based on polysiloxanes or on acrylate polymers. Preferably, the antifoaming agent is chosen from three-dimensional siloxanes.

[0102] Also, the antifoaming agents can be polar polymers such as polymethylsiloxanes or polyacrylates.

[0103] In particular, an aqueous lubricant composition according to the invention may comprise from 0.001% to 3.0% by weight of antifoam additive(s), preferably from 0.005% to 1.5% by weight, more preferentially from 0.01% to 1.0% by weight, relative to the total weight of the composition.

[0104] Preferably, an aqueous lubricant composition used according to the invention may further comprises at least one additive chosen from antifoam agents and mixtures thereof. Antifoams make it possible to prevent foaming of the lubricant fluid.

[0105] It may be, for example, an antifoaming agent based on polysiloxanes or on acrylate polymers. Preferably, the antifoaming agent is chosen from three-dimensional siloxanes.

[0106] Also, the antifoaming agents can be polar polymers such as polymethylsiloxanes or polyacrylates.

[0107] In particular, an aqueous lubricant composition used according to the invention may comprise from 0.001% to 3.0% by weight of antifoam additive(s), preferably from 0.005% to 1.5% by weight, more preferentially from 0.01% to 1.0% by weight, relative to the total weight of the composition.

[0108] Preferably, an aqueous lubricant composition used according to the invention may comprise less than 5% by weight, in particular less than or equal to 2% by weight, more particularly less than 1% by weight, even more particularly less than 0,1% by weight of antifoam agent(s) relative to the total weight of said composition.Metal passivators

[0109] An aqueous lubricant composition according to the invention may comprise at least one metal passivator. Metal passivators make it possible to protect metal parts by promoting the formation of metal oxide on their surface.

[0110] The metal passivators can be chosen, for example, from triazole derivatives, such as tetrahydrobenzotriazole (THBTZ), tolyltriazole (TTZ), benzotriazole (BTZ), amines substituted by a triazole group, such as N,N-bis(2-ethylhexyl)-1,2,4-triazol-1-ylmethanamine, N'-bis(2-ethylhexyl)-4-methyl-1H-benzotriazole-1-methylamine, N,N-bis(heptyl)-ar-methyl-1H-benzotriazole-1-methanamine, N,N-bis(nonyl)-ar-methyl-1H-benzotriazole-1-methanamine, N,N-bis(decyl)-ar-methyl -1H-benzotriazole-1-methanamine, N,N-bis(undecyl)-ar-methyl-1H-benzotriazole-1-methanamine, N,N-bis(dodecyl)-ar-methyl-1H-benzotriazole-1-methanamine, N,N-bis(2-ethylhexyl)-ar-methyl-1H-benzotriazole-1-methanamine, 1,2,4-triazoles, benzimidazoles, 2-alkyldithiobenzimidazoles, 2-alkyldithiobenzothiazoles, 2-(N,N-dialkyldithiocarbamoyl)benzothiazoles, 2,5-bis(alkyldithio)-1,3,4-thiadiazoles, such as 2,5-bis(tert-octyldithio)-1,3,4-thiadiazole, 2,5-bis(tert- nonyldithio)-1,3,4-thiadiazole, 2,5-bis(tert-decyldithio)-1,3,4-thiadiazole, 2,5-bis(tert-undecyldithio)-1,3,4-thiadiazole, 2,5-bis(tert-dodecyldithio)-1,3,4-thiadiazole, 2,5-bis(tert-tridecyldithio)-1,3,4-thiadiazole, 2,5-bis(tert- tetradecyldithio)-1,3,4-thiadiazole, 2,5-bis(tert-pentadecyldithio)-1,3,4-thiadiazole, 2,5-bis(tert-hexadecyldithio)-1,3,4-thiadiazole, 2,5-bis(tert-heptadecyldithio)-1,3,4-thiadiazole, 2,5-bis(tert-octadecyldithio)-1,3,4-thiadiazole, 2,5-bis(tert- nonadecyldithio)-1,3,4-thiadiazole, 2,5-bis(tert-eicosyldithio)-1,3,4-thiadiazole, 2,5-bis(N,N-dialkyldithiocarbamoyl)-1,3,4-thiadiazoles, 2-alkyldithio-5-mercaptothiadiazoles, and mixtures thereof.

[0111] Preferably, the metal passivators are chosen from tetrahydrobenzotriazole (THBTZ), tolyltriazole (TTZ), benzotriazole (BTZ), and salts thereof, taken alone or as mixtures.

[0112] An aqueous lubricant composition according to the invention may in particular comprise from 0.01% to 2.0% by weight of metal passivator(s), preferably from 0.1% to 1.0% by weight, more preferentially from 0.2% to 0.8% by weight, relative to the total weight of the composition.Dyes

[0113] An aqueous lubricant composition according to the invention may comprise one or more dyes. Dyes can be natural or synthetic, generally organic.

[0114] The dyes which can be used in an aqueous lubricant composition can be more particularly chosen from natural or synthetic water-soluble dyes, for example the dyes FDC Red 4, DC Red 6, DC Red 22, DC Red 28, DC Red 30, DC Red 33, DC Orange 4, DC Yellow 5, DC Yellow 6, DC Yellow 8, FDC Green 3, DC Green 5, FDC Blue 1, betanin (beet), xanthenes, carmine, chlorophyllin, methylene blue, anthocyanins (enocyanin, black carrot and hibiscus), caramel and riboflavin.

[0115] An aqueous lubricant composition according to the invention may comprise between 0.01% and 2.0% by weight of dye(s), preferably between 0.01% and 1.5% by weight, more preferentially between 0.02% and 1.0% by weight, relative to the total weight of the composition.Emulsifiers

[0116] An aqueous lubricant composition according to the invention may comprise one or more emulsifiers, also referred to as emulsifying agents. Their role is to generate stable emulsions in water.

[0117] The emulsifiers may more particularly be nonionic, such as for example ethoxylated fatty alcohols, ethoxylated fatty acids, ethoxylated fatty amides; anionic, for example soaps of KOH or NaOH; sulfonates; cationic, such as quaternary ammonium compounds; or else water-soluble or water-emulsifiable carboxylic acid esters.

[0118] In particular, an aqueous lubricant composition according to the invention may comprise from 0.01% to 10% by weight of emulsifier(s), preferably from 0.1% to 5.0% by weight, relative to the total weight of the lubricant composition.Sequestrants

[0119] An aqueous lubricant composition according to the invention may comprise at least one sequestrant. Sequestrants, also referred to as chelating agents, make it possible to limit the encrustation of metal ions in the composition.

[0120] As examples of sequestrants, mention may be made of those derived from phosphonic acids and phosphonates, such as diethylenetriamine pentamethyl phosphonic acid (DTPMPA), aminotri(methylene phosphonic) acid (ATMP), hydroxyethane diphosphonic acid (HEDP), 1-hydroxyethylidene 1,1-diphosphonate, 2-hydroxyethylamine di(methylene phosphonic acid) (HEAMBP), diethylene triaminopenta(methylene phosphonic acid) (DTMP), multifunctional organic acids and hydroxy acids, such as ethylenediaminetetraacetic acid (EDTA), pteroyl-L-glutamic acid (PGLU), organic polyacids, such as maleic acid and polyaspartic acid, polysaccharides and carbohydrates, such as inulin, carboxymethyl inulin and carboxymethyl chitosan.

[0121] An aqueous lubricant composition according to the invention may comprise from 0.001% to 2.0% by weight of sequestrant(s), preferably from 0.01% to 1.0% by weight, relative to the total weight of the lubricant composition.Biocides and fungicides

[0122] An aqueous lubricant composition according to the invention may comprise at least one biocidal and / or fungicidal agent. Biocides and fungicides can be used to improve the biological stability of the composition by limiting the proliferation of bacteria, fungi and yeasts in the lubricant fluid.

[0123] Such biocides can be chosen from parabens, aldehydes, reactive acetylacetone compounds, isothiazolinones, phenolic compounds, acid salts, halogenated compounds, quaternary ammoniums, certain alcohols and mixtures thereof.

[0124] Preferably, the biocides can be chosen from optionally substituted benzisothiazolinones (BIT), such as N-butyl-1,2-benzisothiazolin-3-one, methylisothiazolinones (MIT), mixtures of methylisothiazolinone and chloromethylisothiazolinone (MIT / CMIT), ortho-phenylphenol (OPP) or the sodium salt thereof, 3-iodo-2-propynyl butylcarbamate (IPBC), chlorocresol and N,N-methylenebismorpholine (MBM); sorbic acid; preferably from ortho-phenylphenol (OPP) or the sodium salt thereof, 3-iodo-2-propynyl butylcarbamate (IPBC), chlorocresol, benzisothiazolinones and N,N-methylenebismorpholine.

[0125] An aqueous lubricant composition according to the invention may in particular comprise between 0.01% and 10% by weight of biocide(s) and / or fungicide(s), preferably between 0.5% and 5.0% by weight, relative to the total weight of the lubricant composition.

[0126] According to a particular embodiment, an aqueous lubricant composition used according to the invention comprises: water, preferably deionized water; at least one polyalkylene glycol, in particular as defined previously; at least one antifreeze compound chosen from glycols, preferably from alkylene glycols, glycerol, diglycerol, triglycerol, and mixtures thereof, more preferably from monoethylene glycol, diethylene glycol, propylene glycol, glycerol and mixtures thereof, and even more preferably being diethylene glycol; and at least one antifoam agent, in particular as defined previously, preferably chosen among three-dimensional siloxanes.

[0127] According to one particular embodiment, the present invention also concerns the use of an aqueous lubricant composition for improving the energy efficiency of a powertrain of a vehicle, said aqueous lubricant composition comprising at least: from 35% to 90% by weight of water, preferably of deionized water, relative to the total weight of said composition; from 5% to 50% by weight of polyalkylene glycol(s) relative to the total weight of said composition, preferably said polyalkylene glycol(s) comprise(s) at least 50% by weight of propylene oxide and / or ethylene oxide units; and from 5% to 50% by weight of antifreeze compound(s), preferably chosen from glycols, relative to the total weight of said composition.

[0128] According to a particular embodiment, an aqueous lubricant composition used according to the invention comprises: from 40% to 60% by weight of deionized water, relative to the total weight of said composition; from 10% to 20% by weight of polyalkylene glycol(s), including at least one polyalkylene glycol as defined above, relative to the total weight of said composition; from 20% to 40% by weight of antifreeze compound(s), including at least one compound chosen from glycols as defined above, relative to the total weight of said composition; and less than or equal to 2% by weight of antifoam agent(s), preferably including at least one antifoam agent as defined above, relative to the total weight of said composition.

[0129] Advantageously, a lubricant composition used according to the invention has a kinematic viscosity, measured at 40°C (KV40), according to the standard ASTM D445 (ISO 3104), of between 10 and 1000 mm 2< / s, in particular between 20 and 300 mm 2< / s.

[0130] The kinematic viscosity, measured at 100°C (KV100), according to the standard ASTM D445 (ISO 3104), of a lubricant composition used according to the invention can advantageously be between 3 and 50 mm 2< / s, in particular between 4 and 25 mm 2< / s.APPLICATION

[0131] As indicated previously, an aqueous lubricant composition according to the invention, as described above, is used as a lubricant for a powertrain of a vehicle, in particular an electric or hybrid vehicle, more particularly for the propulsion systems, even more particularly for mechanical systems and the power electrics in an electric or hybrid vehicle.

[0132] As represented schematically in figure 1, the propulsion system comprises in a powertrain of an electric or hybrid vehicle comprises, in particular, the electric motor part (1), an electric battery (2) and a transmission, more particularly a speed reduction gear (3).

[0133] The electric motor typically comprises power electronics (11) connected to a stator (13) and a rotor (14). The stator comprises coils, more particularly copper coils, which are supplied with an alternating electric current. This enables the generation of a rotating magnetic field. The rotor in turn comprises coils, permanent magnets or other magnetic materials, and is made to rotate by the rotating magnetic field.

[0134] A rolling bearing (12) is generally incorporated between the stator (13) and the rotor (14). A transmission, and more particularly a speed reduction gear (3), allows the speed of rotation at the outlet of the electric motor to be reduced and the speed transmitted to the wheels to be adapted, so making it possible at the same time to control the speed of the vehicle.

[0135] The rolling bearing (12) is subject in particular to high mechanical stresses and gives rise to problems of wear by fatigue. It is therefore necessary for the rolling bearing to be lubricated in order to increase its working life. The reduction gear as well is subject to high frictional stresses and therefore requires appropriate lubrication so that it is not damaged too rapidly. As mentioned above, an aqueous lubricant composition formulated according to the invention, in particular as described above, has suitable tribological properties, while improved performances in terms of energy efficiency, which makes it particularly well suited for use as a lubricating fluid.

[0136] An aqueous lubricant composition used according to the invention find an advantageous application for the lubrication of a powertrain of an electric or hybrid vehicle, and more particularly of the engine, of the power electronics, of the transmission and / or of the battery. In particular, the composition according to the invention can thus be used for the lubrication of mechanical systems of a powertrain, in particular of gears, rolling bearings, bearings, such as rolling or sliding bearings.

[0137] By way of example, an aqueous lubricant composition according to the invention can be used to lubricate mobile powertrain, in particular for the lubrication of the various components of electric motor vehicles, in particular of the transmission of an electric engine, more particularly transmissions for light or heavy electric or hybrid vehicles, for example gearboxes and / or axles.

[0138] Advantageously, an aqueous lubricant composition according to the invention can further be used to reduce the friction between the parts of a powertrain of a vehicle, in particular of the propulsion system comprised in the electric drive unit, such as the transmission. More advantageously, the aqueous lubricant composition according to the invention can be used to reduce the coefficient of friction.

[0139] Preferably, an aqueous lubricant composition according to the invention may also be used both as a coolant and as a lubricant, in a powertrain of a vehicle, more particularly in electric or hybrid vehicle propulsion system. Advantageously, a composition according to the invention makes it possible to jointly achieve good properties in terms of cooling as well as suitable lubrication properties and improved energy efficiency of the powertrain of a vehicle, in particular of the parts of the electrical hybrid vehicle propulsion system.

[0140] More particularly, an aqueous lubricant composition according to the invention makes it possible to cool, lubricate and improve energy efficiency of an electric motor of an electric or hybrid vehicle. It is particularly effective for cooling the power electronics and / or the rotor and / or the stator of an electric motor. It also ensures lubrication and improved energy efficiency of the rolling bearings located between the rotor and the stator of an electric motor of an electric or hybrid vehicle.

[0141] Even more particularly, an aqueous lubricant composition according to the invention makes it possible to ensure the lubrication and the improvement of energy efficiency of the transmission, when it is present, in particular the reduction gear, of an electric or hybrid vehicle. Also, a composition according to the invention advantageously makes it possible, even more particularly, to cool the battery present in an electric or hybrid vehicle.

[0142] Thus, advantageously, it is for example possible, by using an aqueous lubricant composition according to the invention, to ensure the cooling of the battery and, the lubrication as well as of the improvement of energy efficiency of the transmission, in particular the reduction gear, in an electric or hybrid vehicle.

[0143] The invention will now be described by means of the examples that follow, which are, needless to say, given as nonlimiting illustrations of the invention.Examples Energy efficiency measurement

[0144] The performance of the lubricant compositions in terms of energy efficiency are measured using a test rig with a single-speed gearbox designed for electric vehicles mounted on it.

[0145] A single-speed gearbox comprises three shafts: input shaft, intermediate shaft, and output (also named "differential") shaft; two pairs of gears; and three pairs of bearings. The single-speed gearbox is mounted on a mechanical transmission test rig.

[0146] The test rig comprises several components: an input electric motor (input dyno), which injects energy into the system, with a rated power of 350 kW, capable of speeds up to 18000 rpm and a maximum torque of 490 Nm. This dyno emulates the electric motor of an electric drive unit comprised in a powertrain; Two output motors (output dynos), left and right, which recover energy from the system, each output dyno with a rated power of 200 kW, capable of speeds up to 3000 rpm and a torque of up to 3200 Nm. These dynos emulates the wheels of an electric vehicle; test table on which the single-speed gearbox is mounted; an input torque transducer and input speed encoder, positioned between the input electric motor and the input shaft of the single-speed gearbox, measuring the input torque and input speed and enabling the computation of input energy over time; left output torque transducer and left output speed encoder, positioned between the left output dyno and the left output shaft of the single-speed gearbox, measuring the left output torque and speed, and enabling the computation of the left output energy over time; right output torque transducer and right output speed encoder, positioned between the right output dyno and the right output shaft of the single-speed gearbox, measuring the right output torque and speed, and enabling the computation of the right output energy over time; An air blower directed at the single-speed gearbox to regulate the lubricant temperature within the single-speed gearbox.

[0147] The performance of the lubricant compositions in terms of energy efficiency, in particular in terms of dynamic energy efficiency or static energy efficiency, using the above-mentioned test rig with a single-speed gearbox designed for electric vehicles, is studied by two different measurement sets: one corresponding to dynamic efficiency measured in the Worldwide Harmonized Light Vehicles Test Procedure (WLTP) cycle, and the other corresponding to static efficiency. Both measurement sets are described hereafter.Dynamic energy efficiency evaluation

[0148] To evaluate the dynamic energy efficiency, specific profiles of input speed and input torque over time from 0 second to 1800 seconds, respectively represented in figures 2 and 3, are taken into account to measure the dynamic energy efficiency. Such profiles reproduce one of the conditions which can be present in an electric drive unit comprised in a powertrain of an electric vehicle, in particular in the Worldwide Harmonized Light Vehicles Test Procedure (WLTP) class 3 cycle.

[0149] The input energy is calculated by this equation (1): E in , Wh = 2 π 60 ∫ 0 1800 s Torque in ∗ Speed in dt wherein Torque in is torque value (in Nm) measured by the above-mentioned input torque transducer and Speed in is the speed value (in rpm) measured by the above-mentioned input speed encoder.

[0150] The output energy is calculated by this equation (2): E out , Wh = 2 π 60 ∫ 0 1800 s Torque out , left ∗ Speed out , left + Torque out , right ∗ Speed out , right dt wherein Torque out,left is the torque value (in Nm) measured by the above-mentioned left output torque transducer, Speed out,left is the speed value (in rpm) measured by the above-mentioned left output speed encoder, Torque out,right is the torque value (in Nm) measured by the above-mentioned right output torque transducer, and Speed out,right is the speed value (in rpm) measured by the above-mentioned right output speed encoder.

[0151] The loss of dynamic energy efficiency in WLTP cycle is calculated by this equation (3): loss Efficiency Wh , WLTP = E in , Wh − E out , Wh wherein E in,Wh is the input energy and E out,Wh is the output energy, both being calculated as described above.

[0152] An improvement of the dynamic energy efficiency means that a smaller value is obtained for the loss of dynamic energy efficiency described in equation (3), in particular that the output energy is closer to the input energy. In other words, the loss of dynamic energy efficiency described in equation (3) corresponds to a loss of energy during the WLTP cycle which has to be reduced to improve the energy efficiency.

[0153] In this example, the following conditions are set for one test: the input energy is 3406.5 ± 0.5 Wh ; and ten WLTP cycles are executed by the single-speed gearbox lubricating by a lubricant composition. the ten WLTPs cycles are performed consecutively, with a ten-minute interval between them. all ten WLTPs cycles start when the lubricant temperature achieves 23°C

[0154] Each test was performed five times for each lubricant composition. Flushes and lubricant changes in between the tests were performed to minimize any external bias. Thus, 50 values (10×5) of loss of dynamic energy efficiencies in WLTP cycle per lubricant composition are obtained. On the basis of this value, the average of these 50 values of each lubricant composition and corresponding standard deviations are calculated.Static energy efficiency evaluation

[0155] To evaluate the static energy efficiency, a set of 13 distinct combinations, as showed in table 1, of output speed value and input torque are used. For each of the 13 points showed in table 1, the input dynamometer is set to reach the specified "target input torque", while the left and right output dynamometers are set to reach the "target output speed". Table 1Point (number)Target output speed (rpm)Target input torque (Nm)145252455034515041822551825061821507364258364509364150105452511545501254515013118275

[0156] The input dynamometer and the two output dynamometers are programmed to operate each of these 13 points for a duration of 3 seconds, with a data acquisition frequency of 1000 Hz, which results in a total of 3000 data points for each point. The static energy efficiency (in %) is then computed for each of these 3000 points, each point being noted "ii" point, using the following equation (4): Efficiency % | ii = 100 ∗ Torque out , left ∗ Speed out , left + Torque out , right ∗ Speed out , right Torque in ∗ Speed in | ii wherein Torque out,left is the torque value (in Nm) measured by the above-mentioned left output torque transducer; Speed out,left is the speed value (in rpm) measured by the above-mentioned left output speed encoder; Torque out,right is the torque value (in Nm) measured by the above-mentioned right output torque transducer; Speed out,right is the speed value (in rpm) measured by the above-mentioned right output speed encoder; Torque in is torque value (in Nm) measured by the above-mentioned input torque transducer; and Speed in is the speed value (in rpm) measured by the above-mentioned input speed encoder. After the computing of the static energy efficiency for the 3000 "ii" points, only the static energy efficiency for the following "jj" points are selected and retained among these "ii" points. These "jj" points are selected only if they meet the following four conditions a) to d): a) the difference between the left and right output speed is lower than 10 rpm, being calculated by this equation (5): Speed out , left − Speed out , right ≤ 10 rpm b) the difference between the measured output speed being an average of left and right output speeds as calculated by the following equation (6), and target output speed for which the value is set and present in the table 1, as calculated by the following equation (7), is less than 4 rpm: Output Speed rpm = Speed out , left + Speed out , right 2 Target Output Speed rpm − Output Speed rpm ≤ 4 rpm c) the difference between the measured input torque and target torque for which the value is set and present in the table 1 is lower than 3 rpm, being calculated by this equation (8): Target Input Torque Nm − Torque in ≤ 3 Nm d) and the lubricant composition temperature inside the above-mentioned single-speed gearbox is in the range of 58 and 62°C, notably the lubricant composition temperature being equal to 60°C ± 2°C.

[0157] After the selection of the above-mentioned "jj" points, an average is calculated from those selected points giving the static energy efficiency (in %) for each 13 points which each correspond to a specific combination of target output speed and target input torque as showed in table 1.

[0158] The above conditions, computation and selection performed for the 13 points are repeated five times for each lubricant composition, giving an average and a standard deviation of static energy efficiency obtained for each point and each lubricant composition.Example 1 Preparation of lubricant compositions according to the invention and comparative compositions

[0159] An aqueous lubricant composition (I1) according to the invention, and comparative lubricant composition (C1) based on group II and group III base oils, and comparative lubricant composition (C2) based on group II and group III base oils, were formulated by simple mixing, at room temperature, of the following components, in the weight percentages indicated in table 2 below. The percentages are therefore expressed by weight relative to the total weight of the composition. Table 2CompositionComposition (I1) according to the invention Comparative composition (C1) Comparative composition (C2) Group III base oil n°1[%]-82.6518.85Group III base oil n°2 [%]--72.6Deionized water [%]51.94--Polyalkylene glycol [%]11.94--Polymère améliorant l'indice de viscosité-7.1-Diethylene glycol [%]33.52--pH-regulating additives [%]1.34--Additive package (*)< [%]1.2610.258.55 (*)< Additives mixture comprising at least of the following component: one or several corrosion inhibitors, one or several metal passivators, one or several antifoam agents, one or several dipersants, one or several detergents, one or several antiwear agents, one or several pour point depressant agents and / or one or several dyes. Example 2

[0160] The dynamic energy efficiency is evaluated for each lubricant composition by using the above-mentioned test.

[0161] The results are summarized in table 3 below and figure 4, and are expressed in Wh (dynamic energy efficiency). The lower the value obtained, the better the dynamic energy efficiency of the lubricant composition evaluated. Table 3Composition (I1) according to the invention Comparative composition (C1) Comparative composition (C2) Loss of dynamic energy efficiency (Wh)226 ± 7.9251 ± 0.0241 ± 2.9

[0162] It is apparent from these results that the aqueous lubricant composition (I1) according to the invention exhibits the smaller loss of dynamic energy efficiency compared to comparative hydrocarbon-based lubricant compositions (C1) and (C2), indicating an improved dynamic energy efficiency.

[0163] These results and the advantage of the aqueous lubricant composition regarding the improvement of the dynamic energy efficiency, can be reasonably generalized, by a person having ordinary skills in the art, to several other cycles, such as NEDC (New European Driving Cycle), EPA FTP-75 and CLTC (China light-duty vehicle test cycle).Example 3

[0164] The static energy efficiency is evaluated for each lubricant composition by using the above-mentioned test.

[0165] The results are summarized in table 4, and show the static energy efficiency (in %) for each composition measured for 1 to 13 points, each point corresponding to a combination of a given target output speed value (in rpm) and a given target input torque (Nm), both values being as defined above in table 1. The higher the value obtained, the better the static energy efficiency of the lubricant composition evaluated. Table 4Composition (I1) according to the invention Comparative composition (C1) Comparative composition (C2) Point (number)Measured static energy efficiency (%)197.28 ± 0.1197.26 ± 0.1796.79 ± 0.10297.49 ± 0.0797.43 ± 0.2296.91 ± 0.13397.25 ± 0.0797.10 ± 0.1996.62 ± 0.09497.64 ± 0.0397.59 ± 0.1197.39 ± 0.01598.12 ± 0.0597.83 ± 0.0997.59 ± 0.02698.25 ± 0.0697.61 ± 0.0897.42 ± 0.04797.37 ± 0.1697.17 ± 0.3197.04 ± 0.06898.18 ± 0.0597.68 ± 0.0897.63 ± 0.02998.65 ± 0.0497.77 ± 0.0597.66 ± 0.011096.75 ± 0.1196.54 ± 0.2396.34 ± 0.211197.77 ± 0.1397.45 ± 0.1597.25 ± 0.091298.72 ± 0.0497.84 ± 0.0697.75 ± 0.051397.83 ± 0.0897.19 ± 0.0597.14 ± 0.05Average of measured static energy efficiencies (%) 97.79 ± 0.08 97.42 ± 0.14 97.19 ± 0.07

[0166] The aqueous lubricant composition (I1) according to the invention has static energy efficiency values which are always higher for each of the 13 points than those obtained for comparative hydrocarbon-based lubricant compositions (C1) and (C2).

[0167] This demonstrates that the use of the aqueous lubricant composition (I1) according to the invention significantly improved the static energy efficiency compared to the use of comparative hydrocarbon-based lubricant compositions (C1) and (C2).

[0168] The previous results showed in examples 2 and 3 therefore imply that the aqueous lubricant composition (I1) according to the invention presents improved properties in terms of energy efficiency, in particular in term of dynamic energy efficiency and static energy efficiency, compared to hydrocarbon-based lubricant compositions.

Examples

example 1

Example 1

Preparation of lubricant compositions according to the invention and comparative compositions

[0159]An aqueous lubricant composition (I1) according to the invention, and comparative lubricant composition (C1) based on group II and group III base oils, and comparative lubricant composition (C2) based on group II and group III base oils, were formulated by simple mixing, at room temperature, of the following components, in the weight percentages indicated in table 2 below. The percentages are therefore expressed by weight relative to the total weight of the composition.

Table 2

CompositionComposition (I1) according to the invention Comparative composition (C1) Comparative composition (C2)

Group III base oil n°1[%]-82.6518.85

Group III base oil n°2 [%]--72.6

Deionized water [%]51.94--

Polyalkylene glycol [%]11.94--

Polymère améliorant l'indice de viscosité-7.1-

Diethylene glycol [%]33.52--

pH-regulating additives [%]1.34--

Additive package (*)1.2610.258.55

(*)

example 2

Example 2

[0160]The dynamic energy efficiency is evaluated for each lubricant composition by using the above-mentioned test.

[0161]The results are summarized in table 3 below and figure 4, and are expressed in Wh (dynamic energy efficiency). The lower the value obtained, the better the dynamic energy efficiency of the lubricant composition evaluated.

Table 3

Composition (I1) according to the invention Comparative composition (C1) Comparative composition (C2)

Loss of dynamic energy efficiency (Wh)226 ± 7.9251 ± 0.0241 ± 2.9

[0162]It is apparent from these results that the aqueous lubricant composition (I1) according to the invention exhibits the smaller loss of dynamic energy efficiency compared to comparative hydrocarbon-based lubricant compositions (C1) and (C2), indicating an improved dynamic energy efficiency.

[0163]These results and the advantage of the aqueous lubricant composition regarding the improvement of the dynamic energy efficiency, can be reasonably generalized, by...

example 3

Example 3

[0164]The static energy efficiency is evaluated for each lubricant composition by using the above-mentioned test.

[0165]The results are summarized in table 4, and show the static energy efficiency (in %) for each composition measured for 1 to 13 points, each point corresponding to a combination of a given target output speed value (in rpm) and a given target input torque (Nm), both values being as defined above in table 1. The higher the value obtained, the better the static energy efficiency of the lubricant composition evaluated.

Table 4

Composition (I1) according to the invention Comparative composition (C1) Comparative composition (C2)

Point (number)Measured static energy efficiency (%)

197.28 ± 0.1197.26 ± 0.1796.79 ± 0.10

297.49 ± 0.0797.43 ± 0.2296.91 ± 0.13

397.25 ± 0.0797.10 ± 0.1996.62 ± 0.09

497.64 ± 0.0397.59 ± 0.1197.39 ± 0.01

598.12 ± 0.0597.83 ± 0.0997.59 ± 0.02

698.25 ± 0.0697.61 ± 0.0897.42 ± 0.04

797.37 ± 0.1697.17 ± 0.3197.04 ± 0.06

898.18 ± 0.0597.68 ± 0.0897.63 ±...

Technical field

[0001] The present invention relates to the field of lubricating compositions, more particularly the field of lubricating compositions for a powertrain of a vehicle, in particular an electric or hybrid vehicle. It relates more particularly to the use of an aqueous lubricant composition in a powertrain of a vehicle, in particular in propulsion systems, more particularly in mechanical systems, such as rolling bearings, gears, bearings or engines, of electric or hybrid vehicles, for improving the energy efficiency of such powertrains.Prior art

[0002] The evolution of international standards for reducing CO 2 emissions, but also for reducing energy consumption, are prompting vehicle manufacturers to propose alternative solutions to combustion engines.

[0003] One of the solutions identified by automobile manufacturers is to replace combustion engines with electric motors. Research into reducing CO 2 emissions has thus led to the development of electric or hybrid vehicles by a number of vehicle companies.

[0004] Generally, electric or hybrid vehicles require compositions to meet the dual requirements of lubricating and cooling the various parts of the powertrains of these vehicles.

[0005] Lubricant compositions, also referred to as "lubricants", are commonly used in powertains of a vehicle, in particular in mechanical systems of an electric or hybrid vehicle, to reduce friction between parts and thus protect parts against wear. In addition to wear phenomena, friction can oppose the relative motion between parts in contact and induce energy losses that are detrimental to the optimal operation of the mechanical system.

[0006] The most common lubricants are hydrocarbon-based lubricants. These hydrocarbon-based lubricants are conventionally composed of one or more base oils which are generally combined with several additives intended for stimulating the lubricant performance of the base oils, for instance friction-modifying additives.

[0007] Nowadays, the development of new lubricants must take into account new constraints aimed at avoiding the use of toxic or potentially toxic solvents, or else reducing their environmental impact and carbon dioxide emissions. As such, water-based formulations are of increasing interest.

[0008] Although water is an excellent coolant, it does not however have the tribological properties required for a lubricant, in particular in terms of reducing friction and protecting parts against wear.

[0009] Water-based lubricant compositions, supplemented by various additives, have already been studied. For example, document US 2012 / 0149616 proposes an aqueous lubricant comprising, in addition to water, water-soluble polyalkylene glycols, emulsifiers, antifreeze additives of alkylene glycol or glycerol type, anticorrosion additives, antifoam additives and friction-reducing additives.

[0010] Nevertheless, water-based lubricant compositions are not described as being suitable for specific issues of powertrain of a vehicle.

[0011] In particular, such specific issues comprise the optimization of the energy consumption of electric or hybrid vehicles which impacts the lifespan or the charging interval for an electric motor and must and is hence an important issue for their development.Summary of the invention

[0012] The present invention aims to provide a novel water-based composition, having properties suitable for its use for the lubrication of a powertrain of a vehicle, while improving performance in terms of energy savings.

[0013] Thus, according to a first of its aspects, the present invention relates to the use of an aqueous lubricant composition for improving the energy efficiency of a powertrain of a vehicle, said aqueous lubricant composition comprising at least: water; at least one polyalkylene glycol; and at least one antifreeze compound.

[0014] Surprisingly, as showed in the following examples, the inventors have discovered that the use of an aqueous lubricant composition according to the invention significantly improved the energy efficiency of a powertrain of a vehicle compared to the use of conventional hydrocarbon-based lubricant compositions, and advantageously allows to decrease the CO 2 emissions compared to conventional lubricants.

[0015] Advantageously, the use of an aqueous lubricant composition implies the smaller loss of dynamic energy efficiency as well as the higher static energy efficiency compared to the use of comparative hydrocarbon-based lubricant compositions.

[0016] It thus advantageously allows to save energy for electric and hybrid vehicles.

[0017] An "electric vehicle" in the sense of the present invention denotes a vehicle comprising an electric motor as its sole means of propulsion, whereas a "hybrid vehicle" comprises a combustion engine and an electric motor as combined means of propulsion.

[0018] A "powertrain" in the sense of the present invention denotes a system comprising an electric drive unit and a battery which generally consists of a set of electric accumulators.

[0019] A "electric drive unit" in the sense of the present invention denotes a system comprising mechanical components necessary to the propulsion of an electric or hybrid vehicle. The electric drive unit of an electric or hybrid vehicle thus encompasses more particularly an electric motor comprising the rotor-stator assembly of the power electronics (dedicated to regulating the speed), and a mechanical transmission.

[0020] In the remainder of the text, the expressions "aqueous lubricant composition" or "aqueous lubricant" will denote a lubricant composition used according to the invention, intended to lubricate a powertrain of a vehicle, in particular a mechanical system of a propulsion system, more particularly the moving parts in a mechanical system, and even more particularly intended to lubricate rolling bearing(s), gear(s), bearing(s) and / or engine.

[0021] For the purposes of the present invention, the expression "aqueous composition" is understood to denote a composition comprising water as base fluid, in other words as the major solvent. In particular, water, preferably deionized water, preferably represents more than 35% by weight, in particular more than 40% by weight, more particularly more than 50% by weight, of the total weight of the lubricant composition.

[0022] For the purposes of the present invention, the expression "osmosed water" is understood to denote water which has undergone purification, in particular by a reverse osmosis process, in order to reduce the content of organic and / or mineral compounds, for example to a content of less than 5.0% by weight, preferably less than 1.0% by weight. In the remainder of the text, the expressions "demineralized water" or else "ultrapure water" will be considered as equivalent or synonymous with the expression "osmosed water". In particular, the osmosed water may be "deionized water", in other words water that has undergone purification in order to reduce the content of ions, such as Ca 2+< and HCO 3 -< ions generally present in water. Preferably, a deionized water comprises no ions.

[0023] For the purposes of the present invention, the expression "Energy efficiency" refers to the ability of a lubricant composition to limit the energy consumption of a mobile or stationary, hybrid or electric, motorization system, in particular of a powertrain, more particularly such energy consumption being saved at the level of the motor itself, but also at the level of transmission components, such as the gearbox, gear(es), bridges and bearings. This energy efficiency translates, in particular, into longer service life or recharging intervals for an electric motor.

[0024] The present invention therefore also provides the use of an aqueous lubricant composition as described above to reduce the energy consumption of an electric or hybrid vehicle.

[0025] The present invention further provides the use of an aqueous lubricant composition as described above to increase the lifespan and / or the charging interval of the engine comprised in said powertrain.

[0026] The present invention also provides a method or a process for improving the energy efficiency of at least one component of a powertrain of a vehicle, in particular the rolling bearings situated between the rotor and the stator of an electric motor; and / or the transmission, more particularly the reduction gear, said method or process comprising at least one step of contacting said at least one component with an aqueous composition as described above.

[0027] Advantageously, the present invention also provides a method or a process for reducing the energy consumption or to improve the energy-saving properties of an electric or hybrid vehicle, said method or process comprising at least one step of contacting at least one component of a powertrain comprised in said electric or hybrid vehicle with an aqueous composition as described above.

[0028] The present invention further provides a method or a process to increase the lifespan and / or the charging interval of the engine comprised in said powertrain of a vehicle, said method or process comprising at least one step of contacting at least one component of a powertrain with an aqueous composition as described above.

[0029] The entirety of the features and preferences described for the use of an aqueous lubricant composition used according to the invention are also applicable to those methods or process.

[0030] Therefore, according to one particular embodiment, a composition according to the invention may exhibit good electrical insulation properties as well as lubrication properties.

[0031] Other features, variants and advantages of an aqueous lubricant composition used according to the invention will emerge more clearly on reading the description and the examples that follow, which are given as nonlimiting illustrations of the invention.

[0032] The terms "between... and...", "ranging from... to...", "formed from... to..." and "varying from... to..." should be understood as being limits included, unless otherwise mentioned.

[0033] In the description and the examples, unless otherwise indicated, the percentages are weight percentages. The percentages are therefore expressed by weight relative to the total weight of the composition. The temperature is expressed in degrees Celsius unless otherwise indicated, and the pressure is atmospheric pressure, unless otherwise indicated.Brief description of the drawings

[0034] Figure 1 represents a propulsion system of a powertrain of an electric or hybrid vehicle which comprises, in particular, the electric motor part (1), an electric battery (2) and a transmission, more particularly a speed reduction gear (3). Figure 2 represents specific profile of input speed over time from 0 second to 1800 seconds, used for the below-mentioned dynamic energy efficiency evaluation in the Worldwide Harmonized Light Vehicles Test Procedure (WLTP) class 3 cycle. Figure 3 represents specific profile of input torque over time from 0 second to 1800 seconds, used for the below-mentioned dynamic energy efficiency evaluation in the Worldwide Harmonized Light Vehicles Test Procedure (WLTP) class 3 cycle. Figure 4 represents the results of dynamic energy efficiency evaluated for lubricant compositions by using a test which involves specific profiles of input speed and input torque over time from 0 second to 1800 seconds, respectively represented in figures 2 and 3. Detailed description AQUEOUS COMPOSITION

[0035] As mentioned above, an aqueous lubricant composition used according to the invention, also referred to as an aqueous lubricant, is a formulation comprising water, in particular deionized water, as major solvent.

[0036] For the purposes of the invention, a "major solvent" is understood to mean that water is present in a greater amount than any other solvent possibly present in the composition. Preferably, an aqueous lubricant composition used according to the invention comprises at least 20% by weight, in particular at least 30% by weight, in particular ranging from 35% to 90% by weight, more particularly from 40% to 75% by weight, and even more particularly from 40% to 60% by weight, of water, preferably of deionized water, relative to the total weight of said composition.

[0037] Advantageously, in addition to its role as solvent, water provides access to a lubricant composition having good cooling properties, and which can be used as a cooling fluid for the moving parts in a mechanical system comprised in a powertrain of a vehicle.

[0038] For the purposes of this invention, the term "cooling fluid" refers to a fluid capable of dissipating the heat generated by a propulsion system comprised in a powertrain of a vehicle in an electric or hybrid vehicle. More precisely, such a fluid is characterized by an enhanced heat absorption capacity when in contact with a component that is heating up.

[0039] According to a particular embodiment, the water used in an aqueous lubricant composition used according to the invention is deionized water, also referred to as demineralized water.

[0040] For the purposes of this invention, "osmosed water" refers to water which has been subjected to a purification, in particular by a reverse osmosis process, to reduce the content of organic and / or mineral compounds, for example to a content less than 5.0% by weight, preferably less than 1.0% by weight, relative to the total weight of the osmosed water. In the text, the terms "demineralized water" or "ultrapure water" will be considered equivalent or synonymous with the term "reverse osmosis water". In particular, osmosis water can be "deionized water", i.e. water which has been subjected to a purification to reduce the content of ions, such as Ca 2+< and HCO 3 -< ions, generally present in water. Preferably, deionized water is free of ions.

[0041] The use of deionized water is therefore particularly advantageous in the context of the use of the aqueous lubricant according to the invention for applications requiring a fluid that conducts little or no electricity, such as for example for the use of the aqueous lubricant for the lubrication, and additionally the cooling, of mechanical systems comprising an electrical circuit, for example electric or hybrid motors comprised in a powertrain in electric or hybrid vehicles.

[0042] An aqueous lubricant composition used according to the invention therefore differs from the lubricants conventionally used in mechanical systems, in particular hydrocarbon-based lubricants, which comprise a major proportion of one or more water-insoluble base oils.

[0043] A "water-insoluble oil" is understood to mean in particular an oil which does not dissolve substantially in water at room temperature (at around 25°C). In particular, a water-insoluble oil has a solubility in water of less than 0.2 g / L, at room temperature.

[0044] These include in particular lubricating base oils belonging to groups I to V according to the classes defined in the API classification (or their equivalents according to the ATIEL classification) and mixtures thereof.

[0045] Preferably, an aqueous lubricant composition used according to the present invention comprises less than 5% by weight of water-insoluble base oil(s), preferably less than 2% by weight, more preferentially less than 1% by weight, relative to the total weight of the composition.

[0046] Advantageously, an aqueous lubricant composition used according to the invention is completely free of water-insoluble oil.POLYALKYLENE GLYCOL

[0047] As indicated above, an aqueous lubricant composition used according to the invention comprises at least one polyalkylene glycol.

[0048] The polyalkylene glycols (denoted "PAG") are chosen from water-soluble polyalkylene glycols.

[0049] The term "water-soluble" is understood to denote a polyalkylene glycol having a solubility in water of at least 10 g / L, preferably of at least 500 g / L, in water at room temperature (around 25°C).

[0050] The polyalkylene glycols can be more particularly formed from C 1 -C 4 , preferably C 1 -C 3 and more particularly C 2 -C 3 alkylene oxide units.

[0051] Advantageously, a polyalkylene glycol(s) used in an aqueous lubricant composition used according to the invention comprise(s) at least 50% by weight, in particular at least 80% by weight, more preferentially at least 90% by weight of propylene oxide and / or ethylene oxide units. It may be a copolymer, in particular a random copolymer, of ethylene oxide / propylene oxide.

[0052] Preferably, a polyalkylene glycol used in an aqueous lubricant composition used according to the invention has a weight-average molar mass (Mw) of between 100 and 50 000 g.mol -1< , preferably between 5 000 and 25 000 g.mol -1< .

[0053] The weight-average molar mass can be measured by gel permeation chromatography (GPC). Preferably, a polyalkylene glycol used in an aqueous lubricant composition used according to the invention has a kinematic viscosity measured at 100°C (KV100), according to the ASTM D445 standard, ranging from 100 to 25 000 mm 2< / s, and in particular from 150 to 3000 mm 2< / s.

[0054] Preferably, a polyalkylene glycol used in an aqueous lubricant composition used according to the invention has a kinematic viscosity measured at 40°C (KV40), according to the ASTM D445 standard, ranging from 500 to 100 000 mm 2< / s, and in particular from 1 000 to 95 000 mm 2< / s.

[0055] The flash point of a polyalkylene glycol used in an aqueous lubricant composition used according to the invention is preferably above or equal to 160°C, in particular above or equal to 220°C. The flash point can be measured by the ISO 2592 or ASTM D92 standard.

[0056] Preferably, a polyalkylene glycol used in an aqueous lubricant composition used according to the invention has a viscosity index measured according to the ASTM D2270 standard, ranginig from 100 to 800, and preferably from 250 to 550.

[0057] In particular, said polyalkylene glycol compound(s) can be implemented in an aqueous lubricant composition used according to the invention in a content of at least 5% by weight, preferably ranging from 5% to 50% by weight, more particularly from 10% to 40% by weight, and even more particularly from 10% to 20% by weight, relative to the total weight of the composition.

[0058] Preferably, an aqueous lubricant composition used according to the invention comprises less than 17 % by weight, more preferably ranging from 10 % to 15 % by weight of polyalkylene glycol compound(s), relative to the total weight of the composition.

[0059] It is understood that an aqueous lubricant composition used according to the invention may comprise a single polyalkylene glycol or a mixture of several distinct polyalkylene glycols.

[0060] In particular, an aqueous lubricant composition used according to the invention may comprise a mixture of at least two distinct polyalkylene glycols, more particularly at least one polyalkylene glycol of low weight-average molecular weight and at least one polyalkylene glycol of high weight-average molecular weight.

[0061] The combination of at least one polyalkylene glycol having a low weight-average molecular weight and at least one polyalkylene glycol having a high weight-average molecular weight is particularly advantageous for achieving good solubilization of the various compounds introduced into the aqueous lubricant composition.ANTIFREEZE COMPOUND

[0062] As indicated above, an aqueous lubricant composition used according to the invention comprises at least one antifreeze compound.

[0063] Preferably, the antifreeze compound is chosen from glycols, more preferably alkylene glycols, glycerol, diglycerol, triglycerol, and mixtures thereof.

[0064] These compounds are known for their antifreeze action, in other words for reducing the freezing temperature of the composition.

[0065] Glycols are diols in which the two hydroxyl groups are borne by different carbon atoms, preferably by vicinal carbon atoms.

[0066] Preferably, the glycols are alkylene glycols, in particular having from 2 to 10 carbon atoms, in particular from 2 to 6 carbon atoms. As examples, mention may be made of monoethylene glycol, diethylene glycol and propylene glycol.

[0067] The antifreeze compound can also be chosen from glycerol, diglycerol, triglycerol and mixtures thereof.

[0068] Preferably, the antifreeze compound used according to the invention is chosen from monoethylene glycol, diethylene glycol, propylene glycol, glycerol and mixtures thereof. Preferably, the antifreeze compound is diethylene glycol.

[0069] In particular, said antifreeze compound(s) can be implemented in an aqueous lubricant composition used according to the invention in a content of at least 1% by weight, in particular ranging from 5% to 50% by weight, more particularly from 10% to 45% by weight, and even more particularly from 20% to 40% by weight, of antifreeze compound(s), relative to the total weight of the aqueous lubricant composition.

[0070] Preferably, an aqueous lubricant composition used according to the invention comprises a content of antifreeze compound(s), more particularly comprising at one of the antifreeze compounds defined above, for example comprising at least diethylene glycol, greater than or equal to 20% by weight, in particular between 30% and 50% by weight, relative to the total weight of the aqueous lubricant composition.

[0071] According to a particular embodiment, an aqueous lubricant composition used according to the invention comprises: at least 30% by weight, in particular ranging from 40% to 75% by weight, more particularly from 40% to 60% by weight, of water, preferably of deionized water, relative to the total weight of said composition; at least 5% by weight, in particular ranging from 10% to 40% by weight, more particularly from 10% to 20% by weight, of polyalkylene glycol(s), preferably said polyalkylene glycol(s) comprising at least one polyalkylene glycol as defined above, relative to the total weight of said composition; and at least 1% by weight, in particular ranging from 5% to 50% by weight, more particularly from 20% to 40% by weight, of antifreeze compound(s), preferably said antifreeze compound(s) comprising at least one compound chosen from glycols, preferably from alkylene glycols, glycerol, diglycerol, triglycerol, and mixtures thereof, more preferably from monoethylene glycol, diethylene glycol, propylene glycol, glycerol and mixtures thereof, even more preferably comprising at least diethylene glycol, relative to the total weight of said composition. ADDITIVES

[0072] An aqueous lubricant composition used according to the invention may further comprise various additives.

[0073] It is understood that said additive(s) are compatible with their use in an aqueous medium. Advantageously, the additives are used in a water-soluble or water-emulsifiable form, for example in the form of ionic salts or liquids.

[0074] Said additive(s) are of course chosen with regard to the intended application for the aqueous lubricant.

[0075] Of course, those skilled in the art will take care to choose the possible additives and / or the amount thereof in such a way that the advantageous properties of the aqueous lubricant composition used according to the invention, in particular the lubrification properties as well as the improvement of energy efficiency and optionally cooling properties, are not adversely affected by the proposed addition.

[0076] Such additives can be more particularly chosen from antifoaming agents, biocides, pH regulators, corrosion inhibitors, antiwear and / or extreme-pressure additives, sequestrants, metal passivators, dyes, dispersants, emulsifiers, and mixtures thereof.

[0077] Advantageously, an aqueous lubricant composition used according to the invention may comprise one or more additives chosen from antifoaming agents, extreme-pressure agents, corrosion inhibitors, pH regulators, metal passivators, dyes, and mixtures thereof.

[0078] An aqueous lubricant composition used according to the invention may more particularly comprise from 0.1% to 10% by weight, more preferentially from 1.0% to 8.0% by weight of additives, relative to the total weight of the composition.pH regulator

[0079] An aqueous lubricant composition according to the invention may comprise at least one pH-regulating additive, in particular an alkaline buffer. The pH regulator makes it possible to maintain the desired pH of the lubricant composition, in particular in order to preserve an alkaline pH, advantageously between 8 and 15.

[0080] Said pH regulator(s), by maintaining the pH of the aqueous lubricant composition between 8 and 15, prevent corrosion of metal surfaces, but also promote solubilization of the various compounds in the lubricant composition, in particular polyalkylene glycol(s), in particular as defined above.

[0081] The pH regulator can be chosen from the family of amines, in particular alkanolamines and amino alcohols.

[0082] It may in particular be a pH-regulating additive chosen from ethanolamines, such as monoethanolamine (MEA), diethanolamine (DEA); triethanolamine (TEA), diglycolamine (DGA) isopropanolamines, such as monoisopropanolamine (MIPA), diisopropanolamine (DIPA) and triisopropanolamine (TIPA), ethyleneamines, such as ethylenediamine (EDA), diethylenetriamine (DETA), triethylenetetramine (TETA) and tetraethylenepentamine (TEPA), alkanolamines, such as methyldiethanolamine (MDEA), cyclamines, such as cyclohexylamine, 2-amino-2-ethyl-1,3-propanediol, 2-amino-2-methyl-1-propanol and mixtures thereof.

[0083] An aqueous lubricant composition according to the invention may in particular comprise from 0.1% to 10% by weight of pH-regulating additive(s), preferably from 0.5% to 5% by weight, relative to the total weight of the composition.

[0084] Preferably, an aqueous lubricant composition according to the invention may comprise at least one pH regulator enabling the pH of said lubricant composition to be maintained between 8 and 15, in particular between 8.5 and 14, more particularly between 9 and 13, said pH regulator being chosen in particular from alkanolamines, preferably ethanolamines, and more particularly from dimethylethanolamine (DMEA), triethanolamine (TEA) and mixtures thereof.Corrosion inhibitor

[0085] An aqueous lubricant composition according to the invention may comprise at least one corrosion inhibitor. Corrosion inhibitors advantageously make it possible to reduce or even prevent corrosion of metal parts. The nature of said corrosion inhibitor(s) can be chosen with regard to the metal to be protected against corrosion, such as aluminum, steel, galvanized steel, yellow metals, for example copper or brass.

[0086] Mention may be made, among the inorganic corrosion inhibitors, of nitrites, sulfites, silicates, borates, sodium, potassium, calcium or magnesium phosphates, alkali metal phosphates, hydroxides, molybdates, sulfates of zinc, magnesium or nickel.

[0087] Mention may be made, among the organic corrosion inhibitors, of alkanolamines, such as triethanolamine, aliphatic monocarboxylic acids, in particular having from 4 to 15 carbon atoms, for example octanoic acid, aliphatic dicarboxylic acids having from 4 to 15 carbon atoms, carbon, for example decanedioic acid, undecanedioic acid, dodecanedioic acid or mixtures thereof, polycarboxylic acids optionally neutralized with triethanolamine, such as 1,3,5-triazine-2,4,6-tri-(6-aminocaproic) acid, alkanoylamidocarboxylic acids, in particular isononanoylamidocaproic acid, and mixtures thereof. Borate amides, products of the reaction of amines or amino alcohols with boric acid, can also be used.

[0088] Preferably, the corrosion inhibitor(s) are distinct from the pH regulator(s), in particular for maintaining the pH of the lubricant composition between 8 and 15, as defined above.

[0089] An aqueous lubricant composition according to the invention may in particular comprise from 0.1% to 5% by weight of corrosion inhibitor(s), in particular as described above, preferably from 0.5% to 4% by weight, more preferentially from 1% to 2.5% by weight, relative to the total weight of the composition.Anti-wear / extreme-pressure additive

[0090] An aqueous lubricant composition according to the invention may comprise at least one anti-wear and / or extreme-pressure additive. Their function is to reduce wear and the coefficient of friction, or else to prevent metal-metal contact by forming an adsorbed protective film on these surfaces.

[0091] There is a wide variety of antiwear additives, among which mention may be made of those chosen from phosphorus-sulfur additives such as metal alkylthiophosphates or salts thereof. Additives that do not provide phosphorus may also be suitable, such as, for example, polysulfides, in particular sulfur-containing olefins.

[0092] According to a particular embodiment, an aqueous lubricant composition according to the invention may comprise at least one extreme-pressure additive chosen from sulfur-containing fatty acids, and dimercaptothiadiazoles, preferably used in the neutralized, water-emulsifiable or water-soluble form thereof, in particular neutralized by in particular by inorganic basifying agents or alkanolamines.

[0093] Advantageously, an aqueous lubricant composition according to the invention comprises at least 0.1% by weight of extreme-pressure additive of sulfur-containing fatty acid type, in particular in a neutralized form, preferably less than 0.01% by weight, more particularly less than 0.001% by weight, relative to the total weight of the lubricant composition, or even is completely free of extreme-pressure additive of sulfur-containing fatty acid type.

[0094] The sulfur-containing fatty acids can comprise from 8 to 22 carbon atoms, in particular from 12 to 18 carbon atoms.

[0095] The amount of sulfur according to the ASTM D2622 standard provided by said sulfur-containing fatty acid(s) can be between 5% and 30% by weight, in particular between 10% and 20% by weight, relative to the total weight of the lubricant composition.

[0096] Preferably, the amount of active sulfur at 150°C according to the ASTM D1662 standard provided by said sulfur-containing fatty acid(s) in the aqueous lubricant composition according to the invention is less than or equal to 2% by weight, in particular less than or equal to 1% by weight, more particularly less than or equal to 0.1% by weight, relative to the total weight of the lubricant composition.

[0097] For the purposes of the present invention, the expression "active sulfur" is understood to mean sulfur that a chemical compound is capable of yielding or releasing when this compound is placed under the conditions of the ASTM D1662 standard. The ASTM D-1662 standard defines an active sulfur content of a compound at a given temperature as a difference expressed as a weight percentage of sulfur content before and after reaction of a sample of this sulfur-containing compound with a given amount of copper over a fixed time.

[0098] As mentioned above, said sulfur-containing fatty acid(s) are generally used in an aqueous lubricant composition in their form neutralized by a basifying agent, such as sodium hydroxide, potassium hydroxide, or an alkanolamine, such as monoethanolamine, triethanolamine, monoisopropanolamine, diisopropanolamine and triisopropanolamine.

[0099] An aqueous lubricant composition according to the invention may comprise between 0.01% and 10% by weight of anti-wear and / or extreme-pressure additive(s), in particular of sulfur-containing fatty acid(s), as defined above, preferably between 0.2% and 5% by weight, relative to the total weight of the composition.Antifoam

[0100] An aqueous lubricant composition according to the invention may comprise at least one antifoam additive. Antifoams make it possible to prevent foaming of the lubricant fluid.

[0101] It may be, for example, an antifoaming agent based on polysiloxanes or on acrylate polymers. Preferably, the antifoaming agent is chosen from three-dimensional siloxanes.

[0102] Also, the antifoaming agents can be polar polymers such as polymethylsiloxanes or polyacrylates.

[0103] In particular, an aqueous lubricant composition according to the invention may comprise from 0.001% to 3.0% by weight of antifoam additive(s), preferably from 0.005% to 1.5% by weight, more preferentially from 0.01% to 1.0% by weight, relative to the total weight of the composition.

[0104] Preferably, an aqueous lubricant composition used according to the invention may further comprises at least one additive chosen from antifoam agents and mixtures thereof. Antifoams make it possible to prevent foaming of the lubricant fluid.

[0105] It may be, for example, an antifoaming agent based on polysiloxanes or on acrylate polymers. Preferably, the antifoaming agent is chosen from three-dimensional siloxanes.

[0106] Also, the antifoaming agents can be polar polymers such as polymethylsiloxanes or polyacrylates.

[0107] In particular, an aqueous lubricant composition used according to the invention may comprise from 0.001% to 3.0% by weight of antifoam additive(s), preferably from 0.005% to 1.5% by weight, more preferentially from 0.01% to 1.0% by weight, relative to the total weight of the composition.

[0108] Preferably, an aqueous lubricant composition used according to the invention may comprise less than 5% by weight, in particular less than or equal to 2% by weight, more particularly less than 1% by weight, even more particularly less than 0,1% by weight of antifoam agent(s) relative to the total weight of said composition.Metal passivators

[0109] An aqueous lubricant composition according to the invention may comprise at least one metal passivator. Metal passivators make it possible to protect metal parts by promoting the formation of metal oxide on their surface.

[0110] The metal passivators can be chosen, for example, from triazole derivatives, such as tetrahydrobenzotriazole (THBTZ), tolyltriazole (TTZ), benzotriazole (BTZ), amines substituted by a triazole group, such as N,N-bis(2-ethylhexyl)-1,2,4-triazol-1-ylmethanamine, N'-bis(2-ethylhexyl)-4-methyl-1H-benzotriazole-1-methylamine, N,N-bis(heptyl)-ar-methyl-1H-benzotriazole-1-methanamine, N,N-bis(nonyl)-ar-methyl-1H-benzotriazole-1-methanamine, N,N-bis(decyl)-ar-methyl -1H-benzotriazole-1-methanamine, N,N-bis(undecyl)-ar-methyl-1H-benzotriazole-1-methanamine, N,N-bis(dodecyl)-ar-methyl-1H-benzotriazole-1-methanamine, N,N-bis(2-ethylhexyl)-ar-methyl-1H-benzotriazole-1-methanamine, 1,2,4-triazoles, benzimidazoles, 2-alkyldithiobenzimidazoles, 2-alkyldithiobenzothiazoles, 2-(N,N-dialkyldithiocarbamoyl)benzothiazoles, 2,5-bis(alkyldithio)-1,3,4-thiadiazoles, such as 2,5-bis(tert-octyldithio)-1,3,4-thiadiazole, 2,5-bis(tert- nonyldithio)-1,3,4-thiadiazole, 2,5-bis(tert-decyldithio)-1,3,4-thiadiazole, 2,5-bis(tert-undecyldithio)-1,3,4-thiadiazole, 2,5-bis(tert-dodecyldithio)-1,3,4-thiadiazole, 2,5-bis(tert-tridecyldithio)-1,3,4-thiadiazole, 2,5-bis(tert- tetradecyldithio)-1,3,4-thiadiazole, 2,5-bis(tert-pentadecyldithio)-1,3,4-thiadiazole, 2,5-bis(tert-hexadecyldithio)-1,3,4-thiadiazole, 2,5-bis(tert-heptadecyldithio)-1,3,4-thiadiazole, 2,5-bis(tert-octadecyldithio)-1,3,4-thiadiazole, 2,5-bis(tert- nonadecyldithio)-1,3,4-thiadiazole, 2,5-bis(tert-eicosyldithio)-1,3,4-thiadiazole, 2,5-bis(N,N-dialkyldithiocarbamoyl)-1,3,4-thiadiazoles, 2-alkyldithio-5-mercaptothiadiazoles, and mixtures thereof.

[0111] Preferably, the metal passivators are chosen from tetrahydrobenzotriazole (THBTZ), tolyltriazole (TTZ), benzotriazole (BTZ), and salts thereof, taken alone or as mixtures.

[0112] An aqueous lubricant composition according to the invention may in particular comprise from 0.01% to 2.0% by weight of metal passivator(s), preferably from 0.1% to 1.0% by weight, more preferentially from 0.2% to 0.8% by weight, relative to the total weight of the composition.Dyes

[0113] An aqueous lubricant composition according to the invention may comprise one or more dyes. Dyes can be natural or synthetic, generally organic.

[0114] The dyes which can be used in an aqueous lubricant composition can be more particularly chosen from natural or synthetic water-soluble dyes, for example the dyes FDC Red 4, DC Red 6, DC Red 22, DC Red 28, DC Red 30, DC Red 33, DC Orange 4, DC Yellow 5, DC Yellow 6, DC Yellow 8, FDC Green 3, DC Green 5, FDC Blue 1, betanin (beet), xanthenes, carmine, chlorophyllin, methylene blue, anthocyanins (enocyanin, black carrot and hibiscus), caramel and riboflavin.

[0115] An aqueous lubricant composition according to the invention may comprise between 0.01% and 2.0% by weight of dye(s), preferably between 0.01% and 1.5% by weight, more preferentially between 0.02% and 1.0% by weight, relative to the total weight of the composition.Emulsifiers

[0116] An aqueous lubricant composition according to the invention may comprise one or more emulsifiers, also referred to as emulsifying agents. Their role is to generate stable emulsions in water.

[0117] The emulsifiers may more particularly be nonionic, such as for example ethoxylated fatty alcohols, ethoxylated fatty acids, ethoxylated fatty amides; anionic, for example soaps of KOH or NaOH; sulfonates; cationic, such as quaternary ammonium compounds; or else water-soluble or water-emulsifiable carboxylic acid esters.

[0118] In particular, an aqueous lubricant composition according to the invention may comprise from 0.01% to 10% by weight of emulsifier(s), preferably from 0.1% to 5.0% by weight, relative to the total weight of the lubricant composition.Sequestrants

[0119] An aqueous lubricant composition according to the invention may comprise at least one sequestrant. Sequestrants, also referred to as chelating agents, make it possible to limit the encrustation of metal ions in the composition.

[0120] As examples of sequestrants, mention may be made of those derived from phosphonic acids and phosphonates, such as diethylenetriamine pentamethyl phosphonic acid (DTPMPA), aminotri(methylene phosphonic) acid (ATMP), hydroxyethane diphosphonic acid (HEDP), 1-hydroxyethylidene 1,1-diphosphonate, 2-hydroxyethylamine di(methylene phosphonic acid) (HEAMBP), diethylene triaminopenta(methylene phosphonic acid) (DTMP), multifunctional organic acids and hydroxy acids, such as ethylenediaminetetraacetic acid (EDTA), pteroyl-L-glutamic acid (PGLU), organic polyacids, such as maleic acid and polyaspartic acid, polysaccharides and carbohydrates, such as inulin, carboxymethyl inulin and carboxymethyl chitosan.

[0121] An aqueous lubricant composition according to the invention may comprise from 0.001% to 2.0% by weight of sequestrant(s), preferably from 0.01% to 1.0% by weight, relative to the total weight of the lubricant composition.Biocides and fungicides

[0122] An aqueous lubricant composition according to the invention may comprise at least one biocidal and / or fungicidal agent. Biocides and fungicides can be used to improve the biological stability of the composition by limiting the proliferation of bacteria, fungi and yeasts in the lubricant fluid.

[0123] Such biocides can be chosen from parabens, aldehydes, reactive acetylacetone compounds, isothiazolinones, phenolic compounds, acid salts, halogenated compounds, quaternary ammoniums, certain alcohols and mixtures thereof.

[0124] Preferably, the biocides can be chosen from optionally substituted benzisothiazolinones (BIT), such as N-butyl-1,2-benzisothiazolin-3-one, methylisothiazolinones (MIT), mixtures of methylisothiazolinone and chloromethylisothiazolinone (MIT / CMIT), ortho-phenylphenol (OPP) or the sodium salt thereof, 3-iodo-2-propynyl butylcarbamate (IPBC), chlorocresol and N,N-methylenebismorpholine (MBM); sorbic acid; preferably from ortho-phenylphenol (OPP) or the sodium salt thereof, 3-iodo-2-propynyl butylcarbamate (IPBC), chlorocresol, benzisothiazolinones and N,N-methylenebismorpholine.

[0125] An aqueous lubricant composition according to the invention may in particular comprise between 0.01% and 10% by weight of biocide(s) and / or fungicide(s), preferably between 0.5% and 5.0% by weight, relative to the total weight of the lubricant composition.

[0126] According to a particular embodiment, an aqueous lubricant composition used according to the invention comprises: water, preferably deionized water; at least one polyalkylene glycol, in particular as defined previously; at least one antifreeze compound chosen from glycols, preferably from alkylene glycols, glycerol, diglycerol, triglycerol, and mixtures thereof, more preferably from monoethylene glycol, diethylene glycol, propylene glycol, glycerol and mixtures thereof, and even more preferably being diethylene glycol; and at least one antifoam agent, in particular as defined previously, preferably chosen among three-dimensional siloxanes.

[0127] According to one particular embodiment, the present invention also concerns the use of an aqueous lubricant composition for improving the energy efficiency of a powertrain of a vehicle, said aqueous lubricant composition comprising at least: from 35% to 90% by weight of water, preferably of deionized water, relative to the total weight of said composition; from 5% to 50% by weight of polyalkylene glycol(s) relative to the total weight of said composition, preferably said polyalkylene glycol(s) comprise(s) at least 50% by weight of propylene oxide and / or ethylene oxide units; and from 5% to 50% by weight of antifreeze compound(s), preferably chosen from glycols, relative to the total weight of said composition.

[0128] According to a particular embodiment, an aqueous lubricant composition used according to the invention comprises: from 40% to 60% by weight of deionized water, relative to the total weight of said composition; from 10% to 20% by weight of polyalkylene glycol(s), including at least one polyalkylene glycol as defined above, relative to the total weight of said composition; from 20% to 40% by weight of antifreeze compound(s), including at least one compound chosen from glycols as defined above, relative to the total weight of said composition; and less than or equal to 2% by weight of antifoam agent(s), preferably including at least one antifoam agent as defined above, relative to the total weight of said composition.

[0129] Advantageously, a lubricant composition used according to the invention has a kinematic viscosity, measured at 40°C (KV40), according to the standard ASTM D445 (ISO 3104), of between 10 and 1000 mm 2< / s, in particular between 20 and 300 mm 2< / s.

[0130] The kinematic viscosity, measured at 100°C (KV100), according to the standard ASTM D445 (ISO 3104), of a lubricant composition used according to the invention can advantageously be between 3 and 50 mm 2< / s, in particular between 4 and 25 mm 2< / s.APPLICATION

[0131] As indicated previously, an aqueous lubricant composition according to the invention, as described above, is used as a lubricant for a powertrain of a vehicle, in particular an electric or hybrid vehicle, more particularly for the propulsion systems, even more particularly for mechanical systems and the power electrics in an electric or hybrid vehicle.

[0132] As represented schematically in figure 1, the propulsion system comprises in a powertrain of an electric or hybrid vehicle comprises, in particular, the electric motor part (1), an electric battery (2) and a transmission, more particularly a speed reduction gear (3).

[0133] The electric motor typically comprises power electronics (11) connected to a stator (13) and a rotor (14). The stator comprises coils, more particularly copper coils, which are supplied with an alternating electric current. This enables the generation of a rotating magnetic field. The rotor in turn comprises coils, permanent magnets or other magnetic materials, and is made to rotate by the rotating magnetic field.

[0134] A rolling bearing (12) is generally incorporated between the stator (13) and the rotor (14). A transmission, and more particularly a speed reduction gear (3), allows the speed of rotation at the outlet of the electric motor to be reduced and the speed transmitted to the wheels to be adapted, so making it possible at the same time to control the speed of the vehicle.

[0135] The rolling bearing (12) is subject in particular to high mechanical stresses and gives rise to problems of wear by fatigue. It is therefore necessary for the rolling bearing to be lubricated in order to increase its working life. The reduction gear as well is subject to high frictional stresses and therefore requires appropriate lubrication so that it is not damaged too rapidly. As mentioned above, an aqueous lubricant composition formulated according to the invention, in particular as described above, has suitable tribological properties, while improved performances in terms of energy efficiency, which makes it particularly well suited for use as a lubricating fluid.

[0136] An aqueous lubricant composition used according to the invention find an advantageous application for the lubrication of a powertrain of an electric or hybrid vehicle, and more particularly of the engine, of the power electronics, of the transmission and / or of the battery. In particular, the composition according to the invention can thus be used for the lubrication of mechanical systems of a powertrain, in particular of gears, rolling bearings, bearings, such as rolling or sliding bearings.

[0137] By way of example, an aqueous lubricant composition according to the invention can be used to lubricate mobile powertrain, in particular for the lubrication of the various components of electric motor vehicles, in particular of the transmission of an electric engine, more particularly transmissions for light or heavy electric or hybrid vehicles, for example gearboxes and / or axles.

[0138] Advantageously, an aqueous lubricant composition according to the invention can further be used to reduce the friction between the parts of a powertrain of a vehicle, in particular of the propulsion system comprised in the electric drive unit, such as the transmission. More advantageously, the aqueous lubricant composition according to the invention can be used to reduce the coefficient of friction.

[0139] Preferably, an aqueous lubricant composition according to the invention may also be used both as a coolant and as a lubricant, in a powertrain of a vehicle, more particularly in electric or hybrid vehicle propulsion system. Advantageously, a composition according to the invention makes it possible to jointly achieve good properties in terms of cooling as well as suitable lubrication properties and improved energy efficiency of the powertrain of a vehicle, in particular of the parts of the electrical hybrid vehicle propulsion system.

[0140] More particularly, an aqueous lubricant composition according to the invention makes it possible to cool, lubricate and improve energy efficiency of an electric motor of an electric or hybrid vehicle. It is particularly effective for cooling the power electronics and / or the rotor and / or the stator of an electric motor. It also ensures lubrication and improved energy efficiency of the rolling bearings located between the rotor and the stator of an electric motor of an electric or hybrid vehicle.

[0141] Even more particularly, an aqueous lubricant composition according to the invention makes it possible to ensure the lubrication and the improvement of energy efficiency of the transmission, when it is present, in particular the reduction gear, of an electric or hybrid vehicle. Also, a composition according to the invention advantageously makes it possible, even more particularly, to cool the battery present in an electric or hybrid vehicle.

[0142] Thus, advantageously, it is for example possible, by using an aqueous lubricant composition according to the invention, to ensure the cooling of the battery and, the lubrication as well as of the improvement of energy efficiency of the transmission, in particular the reduction gear, in an electric or hybrid vehicle.

[0143] The invention will now be described by means of the examples that follow, which are, needless to say, given as nonlimiting illustrations of the invention.Examples Energy efficiency measurement

[0144] The performance of the lubricant compositions in terms of energy efficiency are measured using a test rig with a single-speed gearbox designed for electric vehicles mounted on it.

[0145] A single-speed gearbox comprises three shafts: input shaft, intermediate shaft, and output (also named "differential") shaft; two pairs of gears; and three pairs of bearings. The single-speed gearbox is mounted on a mechanical transmission test rig.

[0146] The test rig comprises several components: an input electric motor (input dyno), which injects energy into the system, with a rated power of 350 kW, capable of speeds up to 18000 rpm and a maximum torque of 490 Nm. This dyno emulates the electric motor of an electric drive unit comprised in a powertrain; Two output motors (output dynos), left and right, which recover energy from the system, each output dyno with a rated power of 200 kW, capable of speeds up to 3000 rpm and a torque of up to 3200 Nm. These dynos emulates the wheels of an electric vehicle; test table on which the single-speed gearbox is mounted; an input torque transducer and input speed encoder, positioned between the input electric motor and the input shaft of the single-speed gearbox, measuring the input torque and input speed and enabling the computation of input energy over time; left output torque transducer and left output speed encoder, positioned between the left output dyno and the left output shaft of the single-speed gearbox, measuring the left output torque and speed, and enabling the computation of the left output energy over time; right output torque transducer and right output speed encoder, positioned between the right output dyno and the right output shaft of the single-speed gearbox, measuring the right output torque and speed, and enabling the computation of the right output energy over time; An air blower directed at the single-speed gearbox to regulate the lubricant temperature within the single-speed gearbox.

[0147] The performance of the lubricant compositions in terms of energy efficiency, in particular in terms of dynamic energy efficiency or static energy efficiency, using the above-mentioned test rig with a single-speed gearbox designed for electric vehicles, is studied by two different measurement sets: one corresponding to dynamic efficiency measured in the Worldwide Harmonized Light Vehicles Test Procedure (WLTP) cycle, and the other corresponding to static efficiency. Both measurement sets are described hereafter.Dynamic energy efficiency evaluation

[0148] To evaluate the dynamic energy efficiency, specific profiles of input speed and input torque over time from 0 second to 1800 seconds, respectively represented in figures 2 and 3, are taken into account to measure the dynamic energy efficiency. Such profiles reproduce one of the conditions which can be present in an electric drive unit comprised in a powertrain of an electric vehicle, in particular in the Worldwide Harmonized Light Vehicles Test Procedure (WLTP) class 3 cycle.

[0149] The input energy is calculated by this equation (1): E in , Wh = 2 π 60 ∫ 0 1800 s Torque in ∗ Speed in dt wherein Torque in is torque value (in Nm) measured by the above-mentioned input torque transducer and Speed in is the speed value (in rpm) measured by the above-mentioned input speed encoder.

[0150] The output energy is calculated by this equation (2): E out , Wh = 2 π 60 ∫ 0 1800 s Torque out , left ∗ Speed out , left + Torque out , right ∗ Speed out , right dt wherein Torque out,left is the torque value (in Nm) measured by the above-mentioned left output torque transducer, Speed out,left is the speed value (in rpm) measured by the above-mentioned left output speed encoder, Torque out,right is the torque value (in Nm) measured by the above-mentioned right output torque transducer, and Speed out,right is the speed value (in rpm) measured by the above-mentioned right output speed encoder.

[0151] The loss of dynamic energy efficiency in WLTP cycle is calculated by this equation (3): loss Efficiency Wh , WLTP = E in , Wh − E out , Wh wherein E in,Wh is the input energy and E out,Wh is the output energy, both being calculated as described above.

[0152] An improvement of the dynamic energy efficiency means that a smaller value is obtained for the loss of dynamic energy efficiency described in equation (3), in particular that the output energy is closer to the input energy. In other words, the loss of dynamic energy efficiency described in equation (3) corresponds to a loss of energy during the WLTP cycle which has to be reduced to improve the energy efficiency.

[0153] In this example, the following conditions are set for one test: the input energy is 3406.5 ± 0.5 Wh ; and ten WLTP cycles are executed by the single-speed gearbox lubricating by a lubricant composition. the ten WLTPs cycles are performed consecutively, with a ten-minute interval between them. all ten WLTPs cycles start when the lubricant temperature achieves 23°C

[0154] Each test was performed five times for each lubricant composition. Flushes and lubricant changes in between the tests were performed to minimize any external bias. Thus, 50 values (10×5) of loss of dynamic energy efficiencies in WLTP cycle per lubricant composition are obtained. On the basis of this value, the average of these 50 values of each lubricant composition and corresponding standard deviations are calculated.Static energy efficiency evaluation

[0155] To evaluate the static energy efficiency, a set of 13 distinct combinations, as showed in table 1, of output speed value and input torque are used. For each of the 13 points showed in table 1, the input dynamometer is set to reach the specified "target input torque", while the left and right output dynamometers are set to reach the "target output speed". Table 1Point (number)Target output speed (rpm)Target input torque (Nm)145252455034515041822551825061821507364258364509364150105452511545501254515013118275

[0156] The input dynamometer and the two output dynamometers are programmed to operate each of these 13 points for a duration of 3 seconds, with a data acquisition frequency of 1000 Hz, which results in a total of 3000 data points for each point. The static energy efficiency (in %) is then computed for each of these 3000 points, each point being noted "ii" point, using the following equation (4): Efficiency % | ii = 100 ∗ Torque out , left ∗ Speed out , left + Torque out , right ∗ Speed out , right Torque in ∗ Speed in | ii wherein Torque out,left is the torque value (in Nm) measured by the above-mentioned left output torque transducer; Speed out,left is the speed value (in rpm) measured by the above-mentioned left output speed encoder; Torque out,right is the torque value (in Nm) measured by the above-mentioned right output torque transducer; Speed out,right is the speed value (in rpm) measured by the above-mentioned right output speed encoder; Torque in is torque value (in Nm) measured by the above-mentioned input torque transducer; and Speed in is the speed value (in rpm) measured by the above-mentioned input speed encoder. After the computing of the static energy efficiency for the 3000 "ii" points, only the static energy efficiency for the following "jj" points are selected and retained among these "ii" points. These "jj" points are selected only if they meet the following four conditions a) to d): a) the difference between the left and right output speed is lower than 10 rpm, being calculated by this equation (5): Speed out , left − Speed out , right ≤ 10 rpm b) the difference between the measured output speed being an average of left and right output speeds as calculated by the following equation (6), and target output speed for which the value is set and present in the table 1, as calculated by the following equation (7), is less than 4 rpm: Output Speed rpm = Speed out , left + Speed out , right 2 Target Output Speed rpm − Output Speed rpm ≤ 4 rpm c) the difference between the measured input torque and target torque for which the value is set and present in the table 1 is lower than 3 rpm, being calculated by this equation (8): Target Input Torque Nm − Torque in ≤ 3 Nm d) and the lubricant composition temperature inside the above-mentioned single-speed gearbox is in the range of 58 and 62°C, notably the lubricant composition temperature being equal to 60°C ± 2°C.

[0157] After the selection of the above-mentioned "jj" points, an average is calculated from those selected points giving the static energy efficiency (in %) for each 13 points which each correspond to a specific combination of target output speed and target input torque as showed in table 1.

[0158] The above conditions, computation and selection performed for the 13 points are repeated five times for each lubricant composition, giving an average and a standard deviation of static energy efficiency obtained for each point and each lubricant composition.Example 1 Preparation of lubricant compositions according to the invention and comparative compositions

[0159] An aqueous lubricant composition (I1) according to the invention, and comparative lubricant composition (C1) based on group II and group III base oils, and comparative lubricant composition (C2) based on group II and group III base oils, were formulated by simple mixing, at room temperature, of the following components, in the weight percentages indicated in table 2 below. The percentages are therefore expressed by weight relative to the total weight of the composition. Table 2CompositionComposition (I1) according to the invention Comparative composition (C1) Comparative composition (C2) Group III base oil n°1[%]-82.6518.85Group III base oil n°2 [%]--72.6Deionized water [%]51.94--Polyalkylene glycol [%]11.94--Polymère améliorant l'indice de viscosité-7.1-Diethylene glycol [%]33.52--pH-regulating additives [%]1.34--Additive package (*)< [%]1.2610.258.55 (*)< Additives mixture comprising at least of the following component: one or several corrosion inhibitors, one or several metal passivators, one or several antifoam agents, one or several dipersants, one or several detergents, one or several antiwear agents, one or several pour point depressant agents and / or one or several dyes. Example 2

[0160] The dynamic energy efficiency is evaluated for each lubricant composition by using the above-mentioned test.

[0161] The results are summarized in table 3 below and figure 4, and are expressed in Wh (dynamic energy efficiency). The lower the value obtained, the better the dynamic energy efficiency of the lubricant composition evaluated. Table 3Composition (I1) according to the invention Comparative composition (C1) Comparative composition (C2) Loss of dynamic energy efficiency (Wh)226 ± 7.9251 ± 0.0241 ± 2.9

[0162] It is apparent from these results that the aqueous lubricant composition (I1) according to the invention exhibits the smaller loss of dynamic energy efficiency compared to comparative hydrocarbon-based lubricant compositions (C1) and (C2), indicating an improved dynamic energy efficiency.

[0163] These results and the advantage of the aqueous lubricant composition regarding the improvement of the dynamic energy efficiency, can be reasonably generalized, by a person having ordinary skills in the art, to several other cycles, such as NEDC (New European Driving Cycle), EPA FTP-75 and CLTC (China light-duty vehicle test cycle).Example 3

[0164] The static energy efficiency is evaluated for each lubricant composition by using the above-mentioned test.

[0165] The results are summarized in table 4, and show the static energy efficiency (in %) for each composition measured for 1 to 13 points, each point corresponding to a combination of a given target output speed value (in rpm) and a given target input torque (Nm), both values being as defined above in table 1. The higher the value obtained, the better the static energy efficiency of the lubricant composition evaluated. Table 4Composition (I1) according to the invention Comparative composition (C1) Comparative composition (C2) Point (number)Measured static energy efficiency (%)197.28 ± 0.1197.26 ± 0.1796.79 ± 0.10297.49 ± 0.0797.43 ± 0.2296.91 ± 0.13397.25 ± 0.0797.10 ± 0.1996.62 ± 0.09497.64 ± 0.0397.59 ± 0.1197.39 ± 0.01598.12 ± 0.0597.83 ± 0.0997.59 ± 0.02698.25 ± 0.0697.61 ± 0.0897.42 ± 0.04797.37 ± 0.1697.17 ± 0.3197.04 ± 0.06898.18 ± 0.0597.68 ± 0.0897.63 ± 0.02998.65 ± 0.0497.77 ± 0.0597.66 ± 0.011096.75 ± 0.1196.54 ± 0.2396.34 ± 0.211197.77 ± 0.1397.45 ± 0.1597.25 ± 0.091298.72 ± 0.0497.84 ± 0.0697.75 ± 0.051397.83 ± 0.0897.19 ± 0.0597.14 ± 0.05Average of measured static energy efficiencies (%) 97.79 ± 0.08 97.42 ± 0.14 97.19 ± 0.07

[0166] The aqueous lubricant composition (I1) according to the invention has static energy efficiency values which are always higher for each of the 13 points than those obtained for comparative hydrocarbon-based lubricant compositions (C1) and (C2).

[0167] This demonstrates that the use of the aqueous lubricant composition (I1) according to the invention significantly improved the static energy efficiency compared to the use of comparative hydrocarbon-based lubricant compositions (C1) and (C2).

[0168] The previous results showed in examples 2 and 3 therefore imply that the aqueous lubricant composition (I1) according to the invention presents improved properties in terms of energy efficiency, in particular in term of dynamic energy efficiency and static energy efficiency, compared to hydrocarbon-based lubricant compositions.

Examples

example 1

Example 1

Preparation of lubricant compositions according to the invention and comparative compositions

[0159]An aqueous lubricant composition (I1) according to the invention, and comparative lubricant composition (C1) based on group II and group III base oils, and comparative lubricant composition (C2) based on group II and group III base oils, were formulated by simple mixing, at room temperature, of the following components, in the weight percentages indicated in table 2 below. The percentages are therefore expressed by weight relative to the total weight of the composition.

Table 2

CompositionComposition (I1) according to the invention Comparative composition (C1) Comparative composition (C2)

Group III base oil n°1[%]-82.6518.85

Group III base oil n°2 [%]--72.6

Deionized water [%]51.94--

Polyalkylene glycol [%]11.94--

Polymère améliorant l'indice de viscosité-7.1-

Diethylene glycol [%]33.52--

pH-regulating additives [%]1.34--

Additive package (*)1.2610.258.55

(*)

example 2

Example 2

[0160]The dynamic energy efficiency is evaluated for each lubricant composition by using the above-mentioned test.

[0161]The results are summarized in table 3 below and figure 4, and are expressed in Wh (dynamic energy efficiency). The lower the value obtained, the better the dynamic energy efficiency of the lubricant composition evaluated.

Table 3

Composition (I1) according to the invention Comparative composition (C1) Comparative composition (C2)

Loss of dynamic energy efficiency (Wh)226 ± 7.9251 ± 0.0241 ± 2.9

[0162]It is apparent from these results that the aqueous lubricant composition (I1) according to the invention exhibits the smaller loss of dynamic energy efficiency compared to comparative hydrocarbon-based lubricant compositions (C1) and (C2), indicating an improved dynamic energy efficiency.

[0163]These results and the advantage of the aqueous lubricant composition regarding the improvement of the dynamic energy efficiency, can be reasonably generalized, by...

example 3

Example 3

[0164]The static energy efficiency is evaluated for each lubricant composition by using the above-mentioned test.

[0165]The results are summarized in table 4, and show the static energy efficiency (in %) for each composition measured for 1 to 13 points, each point corresponding to a combination of a given target output speed value (in rpm) and a given target input torque (Nm), both values being as defined above in table 1. The higher the value obtained, the better the static energy efficiency of the lubricant composition evaluated.

Table 4

Composition (I1) according to the invention Comparative composition (C1) Comparative composition (C2)

Point (number)Measured static energy efficiency (%)

197.28 ± 0.1197.26 ± 0.1796.79 ± 0.10

297.49 ± 0.0797.43 ± 0.2296.91 ± 0.13

397.25 ± 0.0797.10 ± 0.1996.62 ± 0.09

497.64 ± 0.0397.59 ± 0.1197.39 ± 0.01

598.12 ± 0.0597.83 ± 0.0997.59 ± 0.02

698.25 ± 0.0697.61 ± 0.0897.42 ± 0.04

797.37 ± 0.1697.17 ± 0.3197.04 ± 0.06

898.18 ± 0.0597.68 ± 0.0897.63 ±...

Claims

1. Use of an aqueous lubricant composition for improving the energy efficiency of a powertrain of a vehicle, said aqueous lubricant composition comprising at least: - water; - at least one polyalkylene glycol; and - at least one antifreeze compound.

2. The use as claimed in claim 1, wherein the composition comprises at least 20% by weight, in particular at least 30% by weight, in particular ranging from 35% to 90% by weight, more particularly from 40% to 75% by weight, and even more particularly from 40% to 60% by weight, of water, preferably of deionized water, relative to the total weight of said composition.

3. The use as claimed in claim 1 or 2, wherein the composition comprises at least 5% by weight, in particular ranging from 5% to 50% by weight, more particularly from 10% to 40% by weight, and even more particularly from 10% to 20% by weight of polyalkylene glycol(s) relative to the total weight of said composition.

4. The use as claimed in any one of the preceding claims, wherein said polyalkylene glycol(s) comprise(s) at least 50% by weight, in particular at least 80% by weight, more preferentially at least 90% by weight of propylene oxide and / or ethylene oxide units, in particular said polyalkylene glycol(s) is(are) a copolymer, more particularly a random copolymer, of ethylene oxide / propylene oxide.

5. The use as claimed in any one of the preceding claims, wherein said polyalkylene glycol has a kinematic viscosity measured at 100°C (KV100), according to the ASTM D445 standard, ranging from 100 to 25 000 mm2 / s, and in particular from 150 to 3000 mm2 / s.

6. The use as claimed in any one of the preceding claims, wherein the composition comprises at least 1% by weight, in particular ranging from 5% to 50% by weight, more particularly from 10% to 45% by weight, and even more particularly from 20% to 40% by weight of antifreeze compound(s) relative to the total weight of said composition.

7. The use as claimed in any one of the preceding claims, wherein said antifreeze compound(s) comprise(s) at least one compound chosen from glycols, preferably from alkylene glycols, glycerol, diglycerol, triglycerol, and mixtures thereof, and more preferably from monoethylene glycol, diethylene glycol, propylene glycol, glycerol and mixtures thereof.

8. The use as claimed in any one of the preceding claims, wherein the composition further comprises at least one additive chosen from antifoam agents, biocides, pH regulators, corrosion inhibitors, anti-wear and / or extreme-pressure additives, sequesterants, metal passivators, dyes, dispersants, emulsifiers, and mixtures thereof, in particular selected from antifoam agents, extreme-pressure agents, corrosion inhibitors, pH, metal passivators, dyes, and mixtures thereof.

9. The use as claimed in any one of the preceding claims, wherein the aqueous lubricant composition further comprises at least one additive chosen from antifoam agents and mixtures thereof.

10. The use as claimed in the preceding claim, wherein the composition comprises less than 5% by weight, in particular less than or equal to 2% by weight, more particularly less than 1% by weight, even more particularly less than 0,1% by weight of antifoam agent(s) relative to the total weight of said composition.

11. The use as claimed in any one of the preceding claims, to reduce the energy consumption of an electric or hybrid vehicle.

12. The use as claimed in any one of the preceding claims, to increase the lifespan and / or the charging interval of the engine comprised in said powertrain.

13. The use as claimed in any one of the preceding claims, said aqueous lubricant composition comprising at least: - from 35% to 90% by weight of water, preferably of deionized water, relative to the total weight of said composition; - from 5% to 50% by weight of polyalkylene glycol(s) relative to the total weight of said composition, preferably said polyalkylene glycol(s) comprise(s) at least 50% by weight of propylene oxide and / or ethylene oxide units; and - from 5% to 50% by weight of antifreeze compound(s), preferably chosen from glycols, relative to the total weight of said composition.

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