WO2024056827A1

WO2024056827A1 - Use of a monoester in a lubricant composition for vehicle transmissions

Info

Publication number: WO2024056827A1
Application number: PCT/EP2023/075352
Authority: WO
Inventors: Gaël ROBINEAU; Alice LIMOGES; Delphine CROZET
Original assignee: Totalenergies Onetech
Priority date: 2022-09-15
Filing date: 2023-09-14
Publication date: 2024-03-21
Also published as: FR3139828A1; FR3139828B1

Abstract

The present invention relates to the use of a composition comprising 1-methylheptyl laurate as a lubricant composition for transmissions.

Description

Use of a monoester in a lubricating composition for vehicle transmissions

Technical area

The present invention relates to the field of lubricating compositions, more particularly the field of lubricating compositions of transmissions in thermal engine vehicles (gearboxes and/or axles) as well as transmissions, in particular the reduction gear, in propulsion systems of electric or hybrid vehicles. It concerns more particularly the use of a monoester in order to improve the efficiency performances of transmissions in thermal engines as well as the efficiency performances for the reduction gears of electric motors.

Prior art

Lubricating compositions, also called "lubricants", are commonly used in the various components of motor vehicles for the main purposes of reducing the friction forces between the different metal parts moving in these components, in particular the engine, the transmission and the hydraulic circuit. They are also effective in preventing premature wear or even damage to these parts, and in particular to their surface. To do this, a lubricating composition is conventionally composed of a base oil to which are generally associated several additives dedicated to stimulating the lubricating performance of the base oil, such as for example friction modifier additives, but also to providing additional performance.

Lubricating compositions for transmissions (for example, gearboxes or axles) must meet numerous requirements, particularly with regard to the strict specifications imposed by automobile manufacturers. In particular, they must have satisfactory properties in terms of viscosity, viscosity-temperature resistance, cold performance, etc. adapted to their implementation at the level of a transmission member, in particular at the level of the gearbox or the bridges, in a vehicle.

The evolution of international standards for reducing CO2 emissions, but also for reducing energy consumption, is pushing car manufacturers to offer alternative solutions to combustion engines. One of the solutions identified by car manufacturers is to replace combustion engines with electric motors. Research into reducing CO2 emissions has therefore led to the development of electric vehicles by a number of automobile companies.

By “electric vehicle” within the meaning of the present invention, we mean a vehicle comprising an electric motor as the sole means of propulsion while a hybrid vehicle comprises a combustion engine and an electric motor as combined means of propulsion.

By “propulsion system” within the meaning of the present invention, we mean a system comprising the mechanical parts necessary for the propulsion of an electric vehicle. The propulsion system thus encompasses more particularly an electric motor comprising the rotor-stator assembly of the power electronics (dedicated to speed regulation), a transmission (also called a reduction gear, and when the gearbox is attached to the motor, we then speak of a gear motor) and a battery. The battery itself is generally made up of a set of electrical accumulators, called cells.

There is a need to provide lubricating compositions of renewable plant origin with a low impact on the environment.

Furthermore, current environmental concerns, particularly with a view to reducing carbon dioxide emissions, induce an urgent need to reduce the fuel consumption of motor vehicles. As such, it is known that lubricating compositions represent an effective means of acting on fuel consumption via their impact on the friction forces generated between the different components of motor vehicles. Thus, there is a need to develop lubricants to reduce friction in gearboxes and axle differentials.

Improving the “Fuel Eco” properties of transmission lubricants, while otherwise maintaining the high levels of performance required, remains a challenge.

The invention aims precisely to propose a monoester which can be entirely biosourced capable of improving the efficiency performance of transmissions in thermal engines as well as the efficiency performance for the reduction gears of electric motors. Summary of the invention

The subject of the present invention is thus the use of a composition comprising 1-methylheptyl laurate, as a lubricating composition for transmissions.

According to one embodiment, the lubricating composition comprising 1-methylheptyl laurate is used for transmissions in heat engines and/or for reduction gears in electric motors.

According to one embodiment, the lubricating composition comprising 1-methylheptyl laurate is used to improve the efficiency of transmissions.

According to one embodiment, the lubricating composition comprising 1-methylheptyl laurate is used to reduce the fuel consumption of a vehicle equipped with a transmission member, in particular a gearbox and/or a bridge. , lubricated by means of said lubricating composition.

According to one embodiment, the lubricating composition comprising 1-methylheptyl laurate is used to improve the efficiency of reduction gears in electric motors.

According to one embodiment, the lubricating composition comprising 1-methylheptyl laurate is used to extend the battery life of an electric or hybrid vehicle.

Preferably, the lubricating composition comprises 5 to 50% by weight of 1-methylheptyl laurate, preferably 10 to 40% by weight of 1-methylheptyl laurate, relative to the total mass of the lubricating composition.

Preferably, the lubricating composition comprises: from 5 to 50% by weight, preferably from 10 to 40% by weight, of 1-methylheptyl laurate, and from 50 to 95% by weight, preferably from 60 to 90% by weight. mass, of one or more base oils other than 1-methylheptyl laurate, relative to the total mass of the lubricating composition.

Preferably, the lubricating composition has a kinematic viscosity at 100°C ranging from 1 to 6 mm ² /s, preferably ranging from 1 to 4 mm ² /s.

Preferably, 1-methylheptyl laurate has a carbon content of biological origin of at least 90% by weight relative to the total weight of the carbon atoms. According to one embodiment, the lubricating composition comprises, in addition to 1-methylheptyl laurate, at least one additive chosen from antioxidants, additives improving the viscosity index, pour point depressant additives, agents anti-foam, anti-corrosion agents, anti-wear and/or extreme pressure additives, friction modifiers, detergents, dispersing agents and their mixtures, in particular among anti-oxidants, additives depressing point of flow, anti-foam agents and anti-corrosion agents.

Preferably, the additive(s) represent from 0.01 to 20% by mass, preferably from 0.1 to 15% by mass, more preferably from 0.5 to 10% by mass, relative to the total mass of the lubricating composition.

The invention aims precisely to improve the efficiency performances of transmissions in thermal engines as well as the efficiency performances for the reduction gears of electric motors.

The present invention thus aims to improve the “fuel eco” properties for thermal engines and to extend the battery life for electric motors.

Other characteristics, variants and advantages of the use of a monoester according to the invention will become clearer on reading the description and examples which follow, given by way of illustration and not limitation of the invention.

In the remainder of the text, the expressions “between ... and ...”, “ranging from ... to . . . » and “varying from ... to ...” are equivalent and are intended to mean that the limits are included, unless otherwise stated.

Unless otherwise indicated, the expression “comprising a(n)” must be understood as “comprising at least one(e)”.

Brief description of the drawings

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

Firstly, the invention relates to the use of 1-methylheptyl laurate in a lubricating composition for transmissions.

The invention relates to the use of a composition comprising 1-methylheptyl laurate as a lubricating composition for transmissions.

1-Methylheptyl laurate can be obtained by esterification reaction between lauric acid and octane-2-ol.

Preferably, lauric acid and/or octane-2-ol are of biosourced origin. Octan-2-ol of biosourced origin can be obtained by cracking ricinoleic acid.

Thus, preferably, the 1-methylheptyl laurate has a carbon content of biological origin of at least 90% by weight, preferably at least 95% by weight, advantageously 100% by weight, relative to the total weight of carbon atoms.

In the context of the present invention, the carbon content of biological origin can be measured according to the ASTM D6866 standard.

1-methylheptyl laurate, also called the monoester of the invention, is used in a lubricating composition for transmissions.

Annex base oil(s)

The lubricating composition used according to the invention may comprise, in addition to the monoester according to the invention, one or more base oils distinct from the monoester according to the invention.

Said base oil(s), possibly present in a lubricating composition according to the invention, are chosen adequately, with regard to their compatibility with the monoester used according to the invention.

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

Preferably, the base oil or mixture of additional base oils, used in a lubricating composition according to the invention, may have a kinematic viscosity, measured at 100°C according to the ASTM D445 standard, ranging from 1, 5 to 8 mm ² /s, in particular 1.5 to 6.1 mm ² /s, more particularly 1.5 to 4.1 mm ² /s, even more particularly 1.5 to 2.1 mm ² /s. The base oils can be chosen from oils of mineral or synthetic origin belonging to groups I to V according to the classes defined in the API classification (or their equivalents according to the ATIEL classification) and presented in table 1 below or their mixtures.

[Table 1]

Mineral base oils include all types of base oils obtained by atmospheric and vacuum distillation of crude oil, followed by refining operations such as solvent extraction, desalphating, solvent dewaxing, hydrotreating, hydrocracking, hydroisomerization and hydrofinishing .

Blends of synthetic and mineral oils, which can be biosourced, can also be used.

There is generally no limitation as to the use of different additional base oils to produce lubricating compositions, except that they must preferably have properties, in particular viscosity index, content in sulfur or resistance to oxidation, suitable for use for propulsion systems of an electric or hybrid vehicle.

The base oils can also be chosen from synthetic oils, such as certain esters of carboxylic acids and alcohols, distinct from the diester defined according to the invention, from polyalphaolefins (PAO), and from polyalkylene glycol (PAG) obtained by polymerization or copolymerization of alkylene oxides comprising from 2 to 8 carbon atoms, in particular from 2 to 4 carbon atoms. The PAOs used as base oils are for example obtained from monomers comprising 4 to 32 carbon atoms, for example from octene or decene.

The weight average molecular weight of PAO can vary quite widely. Preferably, the mass average molecular weight of the PAO is less than 600 Da. The mass average molecular mass of the PAO can also range from 100 to 600 Da, from 150 to 600 Da, or even from 200 to 600 Da.

For example, the PAOs implemented in the context of the invention, having a kinematic viscosity, measured at 100 ° C according to the ASTM D445 standard, ranging from 1.5 to 8 mm ² /s are sold commercially by Ineos under the brands Durasyn® 162, Durasyn® 164, Durasyn® 166 and Durasyn® 168.

Advantageously, the additional base oil or oils are chosen from polyalphaolefins (PAO).

It is up to those skilled in the art to adjust the content of additional base oil(s) present in a lubricating composition according to the invention.

According to one embodiment, a composition used according to the invention may comprise from 5 to 95% by mass, preferably from 50 to 95% by mass, more preferably from 60 to 90% by mass, of one or more several base oils different from the monoester according to the invention, relative to the total mass of said composition.

Additives

A lubricating composition according to the invention may further comprise one or more additives known to those skilled in the art in the field of transmission lubrication, in particular for thermal engines and for propulsion systems of electric or hybrid vehicles.

The additives, which can be incorporated into a composition according to the invention, can be chosen from antioxidants, pour point depressant additives, anti-foam agents, anti-corrosion agents, anti-wear additives and/or extreme pressure, friction modifiers, detergents, dispersing agents and mixtures thereof, in particular among anti-oxidants, pour point depressant additives, anti-foaming agents and anti-corrosion agents. Preferably, a lubricating composition according to the invention may further comprise one or more additives chosen from antioxidants, anti-foams, pour point improvers, viscosity index improvers, and anti-corrosion agents.

The addition of one or more additives chosen from anti-wear additives, friction modifiers, detergents, extreme pressure additives and dispersants, can also prove advantageous in the context of the implementation of the lurifying composition according to the invention as a multifunctional fluid, for example for cooling the battery and/or the power electronics, and for lubricating parts of the propulsion system, for example the transmission, in an electric or hybrid vehicle.

It is understood that the nature and quantity of additives used are chosen so as not to affect the properties of the lubricating composition conferred by the monoester according to the invention.

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

Said additive(s) may be present in the lubricating composition according to the invention in a content less than or equal to 20% by mass, in particular ranging from 0.01 to 20% by mass, preferably from 0.1 to 15% by mass. , more preferably from 0.5 to 10% by mass, relative to the total mass of said composition.

A lubricating composition used according to the invention can thus comprise at least one antioxidant additive.

The invention thus relates, according to another of its aspects, to a lubricating composition, in particular capable of lubricating a transmission, in particular of a heat engine or of a propulsion system of an electric or hybrid vehicle, said composition comprising (i) at least one monoester according to the invention, and (ii) at least one antioxidant additive. The antioxidant additive generally makes it possible to delay the degradation of the composition in service. This degradation can notably result in the formation of deposits, the presence of sludge or an increase in the viscosity of the composition.

Antioxidant additives act in particular as free radical inhibitors or hydroperoxide destroyers. Among the commonly used antioxidant additives, mention may be made of phenolic-type antioxidant additives, amine-type antioxidant additives and phosphosulfur-containing antioxidant additives. Some of these antioxidant additives, for example phosphosulfur antioxidant additives, can generate ash. Phenolic antioxidant additives can be ash-free or in the form of neutral or basic metal salts. The antioxidant additives may in particular be chosen from sterically hindered phenols, sterically hindered phenol esters and sterically hindered phenols comprising a thioether bridge, diphenylamines, diphenylamines substituted by at least one alkyl group in Ci-Ci2, N,N '-dialkyl-aryl-diamines and mixtures thereof.

Preferably according to the invention, the sterically hindered phenols are chosen from compounds comprising a phenol group of which at least one vicinal carbon of the carbon carrying the alcohol function is substituted by at least one alkyl group in Ci-Cio, preferably an alkyl group in CI-CÔ, preferably a C4 alkyl group, preferably by the tert-butyl group.

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

Sulfurized alkyl phenols or their alkali and alkaline earth metal salts can also be used as antioxidant additives. Another class of antioxidant additives is that of copper compounds, for example copper thio- or dithio-phosphates, copper salts and carboxylic acids, dithiocarbamates, sulphonates, phenates, copper acetylacetonates. Copper I and II salts, succinic acid or anhydride salts can also be used.

Advantageously, a lubricating composition comprises at least one ash-free antioxidant additive.

Said additive(s) can be used, in a lubricating composition according to the invention, at a rate of 0.1 to 2% by weight, relative to the total mass of the composition.

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

Anti-wear additives and extreme pressure additives protect rubbing surfaces by forming a protective film adsorbed on these surfaces.

There is a wide variety of anti-wear additives. Preferably, the anti-wear additives are chosen from phosphosulfur additives such as metal alkylthiophosphates, in particular zinc alkylthiophosphates, and more specifically zinc dialkyldithiophosphates or ZnDTP. The preferred compounds are of formula Zn((SP(S)(OQ ² )(OQ ³ ))2, in which Q ² and Q ³ , identical or different, independently represent an alkyl group, preferably an alkyl group comprising from 1 to 18 carbon atoms.

Amine phosphates are also anti-wear additives which can be used in a composition according to the invention. However, the phosphorus provided by these additives can act as a poison in the catalytic systems of automobiles because these additives generate ash. These effects can be minimized by partially substituting the amine phosphates with additives which do not provide phosphorus, such as, for example, polysulphides, in particular sulfur-containing olefins.

A lubricating composition may comprise from 0.01 to 6% by weight, preferably from 0.05 to 4% by weight, more preferably from 0.1 to 2% by weight of anti-wear additives and extreme pressure additives, by weight per relative to the total mass of composition. A lubricating composition according to the invention may further comprise an anti-foaming agent.

The anti-foaming agent can be chosen from silicones.

A lubricating composition may comprise from 0.01 to 2% by weight or from 0.01 to 5% by weight, preferably from 0.1 to 1.5% by weight or from 0.1 to 2% by weight of antifoaming agent, relative to to the total mass of the composition.

A lubricating composition according to the invention may comprise at least one friction modifier additive.

The friction modifier additive can be chosen from a compound providing metallic elements and an ash-free compound. Among the compounds providing metallic elements, mention may be made of transition metal complexes such as Mo, Sb, Sn, Fe, Cu, Zn whose ligands can be hydrocarbon compounds comprising atoms of oxygen, nitrogen, sulfur or phosphorus. The ash-free friction modifier additives are generally of organic origin and can be chosen from monoesters of fatty acids and polyols, alkoxylated amines, alkoxylated fatty amines, fatty epoxides, fatty borate epoxides; fatty amines or glycerol esters of fatty acids. According to the invention, the fatty compounds comprise at least one hydrocarbon group comprising from 10 to 24 carbon atoms.

A lubricating composition may comprise from 0.01 to 2% by weight or from 0.01 to 5% by weight, preferably from 0.1 to 1.5% by weight or from 0.1 to 2% by weight of friction modifier additive, relative to the total mass of the composition.

A lubricating composition according to the invention may comprise at least one additive making it possible to improve the viscosity index of the lubricating composition (in English “viscosity index improver”).

By “additive making it possible to improve the viscosity index”, within the meaning of the invention is meant a chemical compound making it possible to guarantee good cold resistance and a minimum viscosity at high temperature of the lubricating composition.

As examples of polymers improving the viscosity index, mention may be made of polymer esters; homopolymers or copolymers, hydrogenated or non-hydrogenated, styrene, butadiene and isoprene; olefin homopolymers or copolymers, such as ethylene or propylene; polyacrylates and polymethacrylates (PMA).

The lubricating composition according to the invention typically comprises from 0.1% to 15% by mass of additive(s) improving the viscosity index, relative to the total mass of the lubricating composition.

A lubricating composition according to the invention may comprise at least one detergent additive.

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

The detergent additives which can be used in a lubricating composition are generally known to those skilled in the art. The detergent additives can be anionic compounds comprising a lipophilic hydrocarbon group and a hydrophilic head. The associated cation may be a metallic cation of an alkali or alkaline earth metal.

The detergent additives are preferably chosen from alkali metal or alkaline earth metal salts of carboxylic acids, sulfonates, salicylates, naphthenates, as well as phenate salts. The alkali and alkaline earth metals are preferably calcium, magnesium, sodium or barium.

These metal salts generally include the metal in stoichiometric quantity or in excess, therefore in quantity greater than the stoichiometric quantity. These are then overbased detergent additives; the excess metal providing the overbased character to the detergent additive is then generally in the form of a metal salt insoluble in oil, for example a carbonate, a hydroxide, an oxalate, an acetate, a glutamate, preferably a carbonate .

A lubricating composition used according to the invention can for example comprise from 2 to 4% by weight of detergent additive, relative to the total mass of the composition.

A lubricating composition used according to the invention may also comprise at least one pour point depressant additive. By slowing the formation of paraffin crystals, pour point depressant additives generally improve the cold behavior of the composition. As an example of pour point depressant additives, mention may be made of polyalkyl methacrylates, polyacrylates, polyarylamides, polyalkylphenols, polyalkylnaphthalenes and alkylated polystyrenes.

A lubricating composition used according to the invention may for example comprise from 0.05 to 2% by weight of pour point depressant additive, relative to the total mass of the composition.

Also, a lubricating composition used according to the invention may comprise at least one dispersing agent.

The dispersing agent can be chosen from Mannich bases, succinimides and their derivatives. A lubricating composition used according to the invention can for example comprise from 0.2 to 10% by weight of dispersing agent, relative to the total mass of the composition.

According to a particular embodiment, a lubricating composition used according to the invention comprises, or even is formed of (i) the monoester according to the invention and (ii) at least one additive chosen from antioxidants, agents anti-foam, pour point depressant additives, anti-corrosion agents, anti-wear and/or extreme pressure additives, friction modifiers, detergents, dispersing agents and mixtures thereof, preferably among anti-foam oxidants, pour point depressant additives, anti-foaming agents, anti-corrosion agents, and mixtures thereof.

Advantageously, a lubricating composition used according to the invention comprises (i) the monoester according to the invention and (ii) at least one antioxidant additive.

According to a particular embodiment, a lubricating composition used according to the invention comprises, or even consists of:

- from 5 to 50% by weight, preferably from 10 to 40% by weight, of 1-methylheptyl laurate; - from 50 to 95% by weight, preferably from 60 to 90% by weight, of one or more base oils other than 1-methylheptyl laurate;

- optionally from 0.01 to 20% by mass, preferably from 0.1 to 15% by mass, more preferably from 0.5 to 10% by mass, of one or more additives chosen from additives friction modifiers, anti-wear additives, extreme pressure additives, detergents, antioxidants, viscosity index (VI) improvers, pour point depressant (PPD) additives, dispersants, agents defoamers, thickeners, corrosion inhibitors, copper passivators, and mixtures thereof; and the contents being expressed in relation to the total mass of said composition.

- from 5 to 45% by weight, preferably from 10 to 40% by weight, of 1-methylheptyl laurate;

- from 50 to 95% by weight, preferably from 55 to 90% by weight, of one or more base oils other than 1-methylheptyl laurate;

- from 0.01 to 20% by mass, preferably from 0.1 to 15% by mass, more preferably from 0.5 to 10% by mass, of one or more additives chosen from modifying additives friction, anti-wear additives, extreme pressure additives, detergents, antioxidants, viscosity index (VI) improvers, pour point depressant (PPD) additives, dispersants, anti-wear agents -foam, thickeners, corrosion inhibitors, copper passivating agents, and mixtures thereof; and the contents being expressed in relation to the total mass of said composition.

- from 5 to 50% by weight, preferably from 10 to 40% by weight, of 1-methylheptyl laurate;

- from 50 to 95% by weight, preferably from 55 to 90% by weight, of one or more base oils other than esters; - optionally from 0.01 to 20% by mass, preferably from 0.1 to 15% by mass, more preferably from 0.5 to 10% by mass, of one or more additives chosen from additives friction modifiers, anti-wear additives, extreme pressure additives, detergents, antioxidants, viscosity index (VI) improvers, pour point depressant (PPD) additives, dispersants, agents defoamers, thickeners, corrosion inhibitors, copper passivators, and mixtures thereof; and the contents being expressed in relation to the total mass of said composition.

- from 50 to 95% by weight, preferably from 55 to 90% by weight, of one or more base oils other than esters;

- from 0.01 to 20% by mass, preferably from 0.1 to 15% by mass, more preferably from 0.5 to 10% by mass, of one or more additives chosen from anti- oxidants, pour point depressant additives, anti-foaming agents, anti-corrosion agents, and mixtures thereof; and the contents being expressed in relation to the total mass of said composition.

- from 50 to 95% by mass, preferably from 55 to 90% by mass, of one or more mineral or synthetic base oils chosen from group I oils, group II oils, group III oils and group IV oils, and their mixtures;

- from 0.01 to 20% by mass, preferably from 0.1 to 15% by mass, more preferably from 0.5 to 10% by mass, of one or more additives chosen from modifying additives friction, anti-wear additives, extreme pressure additives, detergents, antioxidants, viscosity index (VI) improvers, pour point depressant (PPD) additives, dispersants, anti-wear agents -foam, the thickeners, corrosion inhibitors, copper passivating agents, and mixtures thereof; and the contents being expressed in relation to the total mass of said composition.

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

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

Application

As indicated previously, the lubricating composition according to the invention can be used as a lubricating fluid for transmission.

In particular, the lubricating composition defined in the present invention makes it possible to improve the efficiency of transmissions.

1-methylheptyl laurate makes it possible to improve the performance of transmissions when it is incorporated into a lubricating composition used to lubricate transmissions. 1-methylheptyl laurate also makes it possible to improve the fuel economy properties, so-called “Fuel -Eco” properties of the lubricating composition comprising said 1-methylheptyl laurate. Indeed, 1-methylheptyl laurate makes it possible to reduce the traction coefficient of the lubricating composition comprising said 1-methylheptyl laurate.

The transmissions may be transmissions for thermal vehicle engines and/or transmissions for electric or hybrid vehicle propulsion systems.

The transmission of a propulsion system of an electric or hybrid vehicle more specifically includes a speed reducer. Thus, the monoester according to the invention particularly makes it possible to improve the efficiency of reduction gears in the propulsion systems of electric or hybrid vehicles.

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

The electric motor typically comprises power electronics (11) connected to a stator (13) and a rotor (14). The stator comprises coils, in particular copper coils, which are alternately powered by an electric current. This generates a rotating magnetic field. The rotor itself comprises coils, permanent magnets or other magnetic materials, and is rotated by the rotating magnetic field.

The power electronics (11), the stator (13) and the rotor (14) of a propulsion system (1) are parts whose structure is complex and generates a large amount of heat during operation of the engine .

A bearing (12) is generally integrated between the stator (13) and the rotor (14). A transmission, and in particular a speed reducer (3), makes it possible to reduce the rotational speed at the output of the electric motor and to adapt the speed transmitted to the wheels, at the same time making it possible to control the speed of the vehicle.

Advantageously, a lubricating composition defined in the present invention can be used to improve the efficiency of transmissions, in particular for the engine of thermal vehicles and for the propulsion system of a vehicle. electric or hybrid. In particular, a lubricating composition defined in the present invention can be used to improve the efficiency of propulsion system reduction gears of an electric or hybrid vehicle.

The invention also relates, according to another of its aspects, to a method of lubricating at least one mechanical part of a transmission member of motor vehicles, in particular light or heavy vehicles, for example gearboxes, bridges, preferably manual gearbox and heavy goods vehicle axles, or even reduction gear for electric or hybrid vehicles, said method comprising at least one step in which said mechanical part is brought into contact with at least one lubricating composition according to the invention.

The invention also relates to the use of the monoester according to the invention, as defined above, to reduce the traction coefficient of a lubricating composition for transmission in a motor vehicle, in particular of a gearbox lubricant and/or or an axle lubricant, particularly heavy goods vehicle axles, or even electric or hybrid vehicle reduction gears.

Also, as mentioned previously, a lubricating composition according to the invention has excellent properties in terms of reducing fuel consumption (“Fuel Eco” properties).

Advantageously, a lubricating composition according to the invention thus has low traction coefficients.

A lubricating composition defined in the invention can also be used to cool the electric motor of an electric or hybrid vehicle, in particular to cool the power electronics and/or the rotor and/or the stator of the electric motor and /or the gear motor.

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

The properties of the monoester of the invention (El), ester of lauric acid and 2-octanol, were compared to another monoester, ester of lauric acid and 2-ethylhexanol (E2).

2-ethylhexanol is not of biosourced origin whereas the 2-octanol used in this example is of biosourced origin.

The kinematic viscosity was measured at 40°C (KV40) and at 100°C (KV100) according to the ASTM D445 standard.

The mini pour point (mini PE) is measured according to ASTM D7346.

Viscosity index (VI) is measured according to ASTM D2270.

The tribological properties can be evaluated by a test on a MTM type tribometer (Mini Traction Machine also called ball-plane), from the PCS Instruments brand. This test makes it possible in particular to evaluate the performance of lubricants in terms of friction in mixed/limit mode depending on the load, pressure or speed conditions applied.

The traction coefficient of the lubricating compositions tested is determined at 40°C and 100°C and 140°C by placing a hardened steel ball of approximately 2 cm in diameter, for example 1.905 cm in diameter, on a plane made of hardened steel.

This device makes it possible to put a steel ball and a steel plane into relative motion in order to determine the coefficients of friction/friction for a given lubricating composition, while varying various properties such as speed, load, and temperature. The hardened steel surface is reference AISI 52100 with a mirror finish and the ball is also reference AISI 52100 made from hardened steel.

The applied load is respectively 25 N and the rotation speed varies from 20 mm/s to 2500 mm/s. (SRR (slide-roll-ratio =5%))

Approximately 50 ml of tested lubricating composition was introduced into the device. The ball is engaged face against plane, said ball and said plane being actuated independently so as to create a mixed rolling/sliding contact.

The traction coefficient is measured and recorded via a force sensor.

Table 2 brings together the results of measurements of tribological properties at 40°C (40°C SRR 5%), 100°C (100°C SRR 5%) and 140°C (140°C SRR 5%). [table 2]

As shown by the results in this table, the monoester according to the invention has a better traction coefficient, i.e. a lower traction coefficient, than the comparative monoester of the state of the art. This lower traction coefficient will provide a better gain in terms of fuel economy (Fuel -Eco) for a thermal engine and a better gain in terms of battery autonomy for an electric or hybrid vehicle.

Claims

1. Use of a composition comprising 1-methylheptyl laurate, as a lubricating composition for transmissions.

2. Use according to claim 1, for transmissions in heat engines and/or for reduction gears in electric motors.

3. Use according to any one of claims 1 to 2, to improve the efficiency of transmissions.

4. Use according to any one of claims 1 to 3, to reduce the fuel consumption of a vehicle equipped with a transmission member, in particular a gearbox and/or a bridge, lubricated by means of said lubricating composition.

5. Use according to any one of claims 1 to 3, to improve the efficiency of reduction gears in electric motors.

6. Use according to any one of claims 1 to 3 or 5, to extend the autonomy of the battery of an electric or hybrid vehicle.

7. Use according to any one of claims 1 to 6, in which the lubricating composition comprises 5 to 50% by weight of 1-methylheptyl laurate, preferably from 10 to 40% by weight of 1-methylheptyl laurate, for example relative to the total mass of the lubricating composition.

8. Use according to any one of claims 1 to 7, in which the composition comprises:

- from 5 to 50% by weight, preferably from 10 to 40% by weight, of 1-methylheptyl laurate, and

- from 50 to 95% by weight, preferably from 60 to 90% by weight, of one or more base oils other than 1-methylheptyl laurate, relative to the total mass of the lubricating composition.

9. Use according to any one of claims 1 to 8, in which the lubricating composition has a kinematic viscosity at 100°C ranging from 1 to 6 mm ² /s, preferably ranging from 1 to 4 mm ² /s.

10. Use according to any one of claims 1 to 9, in which the 1-methylheptyl laurate has a carbon content of biological origin of at least 90% by weight relative to the total weight of the carbon atoms.

11. Use according to any one of claims 1 to 10, characterized in that said lubricating composition comprises, in addition to 1-methylheptyl laurate, at least one additive chosen from antioxidants, additives improving the viscosity index , pour point depressant additives, anti-foaming agents, anti-corrosion agents, anti-wear and/or extreme pressure additives, friction modifiers, detergents, dispersing agents and mixtures thereof, in particular among anti-oxidants, pour point depressant additives, anti-foaming agents and anti-corrosion agents.

12. Use according to claim 11, in which the additive(s) represent from 0.01 to 20% by mass, preferably from 0.1 to 15% by mass, more preferably from 0.5 to 10% by mass, relative to the total mass of the lubricating composition.