WO2024013127A1 - Diester-based lubricant composition - Google Patents

Abstract

The present invention relates to a lubricant composition comprising: one or more diesters, each of said diesters being formed between - a diol chosen from 1,2-propanediol, 1,2-decanediol and 1,3-diol having 3 to 10 carbon atoms, and - two monocarboxylic acids, identical or different, comprising a linear or branched hydrocarbon chain having 4 to 10 carbon atoms; and at least one base oil distinct from the diester and/or at least one additive distinct from the diester, said additive being chosen from friction-modifying additives, anti-wear additives, extreme pressure additives, detergents, antioxidants, viscosity index improvers (VI), pour point depressant additives (PPD), dispersants, anti-foaming agents, thickeners, corrosion inhibitors, copper passivating agents, and mixtures thereof.

Description

Lubricating composition based on diester

Technical area

The present invention relates to the field of compositions for lubricating and/or cooling parts of mobile or stationary systems, such as heavy or light vehicles, public works machinery, or energy storage devices. It concerns more particularly the use of new compounds of the diester type in cooling and/or lubricating compositions, particularly used in heavy or light vehicles, public works machinery, or energy storage devices.

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.

Lubricating compositions, also called cooling compositions, can also be used in energy storage devices, such as data centers. There is a need to provide lubricating and/or cooling compositions of renewable plant origin having 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.

As examples of lubricants for transmissions, we can cite document WO 2010/038147 which proposes, to generate fuel savings, to formulate lubricating compositions for gearboxes, using at least 30% by weight of a or several methyl esters of fatty acids of formula RCOOCH3, where R is a paraffinic or olefinic group containing from 11 to 23 carbon atoms, in combination with one or more anti-wear and/or extreme pressure additives phosphorus, sulfur or phosphosulfur and polyalphaolefins.

We can also cite document US 2017/0145337 which describes lubricating compositions for transmissions, presenting a gain in “Fuel Eco”, based on a base oil having a kinematic viscosity at 100°C ranging from 1.5 mm ² /s to 3.5 mm ² /s, and comprising from 3% to 10% of a monoester type oil with kinematic viscosity at 100°C ranging from 2 mm ² /s to 10 mm ² /s, as well as a phosphite type ester providing sulfur.

The present invention aims to provide a new lubricating composition, having improved properties in terms of friction reduction or cooling properties.

The present invention also aims to propose a new lubricating composition, having improved properties in terms of fuel economy (“Fuel Eco” properties), while satisfying the properties required for its implementation for the lubrication of transmission components of motor vehicles, light or heavy, for example gearbox and axles, and in particular having good performance in terms of cold properties.

Summary of the invention

The subject of the present invention is thus a lubricating composition comprising: One or more diesters, each of said diesters being formed between: o a diol chosen from 1,2-propanediol, 1,2-decanediol and 1,3-diol comprising from 3 to 10 carbon atoms, and o two monocarboxylic acids, identical or different, comprising a linear or branched hydrocarbon chain comprising from 4 to 10 carbon atoms, and at least one base oil distinct from the diester and/or at least one additive distinct from the diester, said additive being chosen from friction modifier additives, anti-wear additives, extreme pressure additives, detergents, antioxidants, viscosity index (VI) improvers, point lowering additives (PPD), dispersants, anti-foaming agents, thickeners, corrosion inhibitors, copper passivating agents, and mixtures thereof.

According to one embodiment, the lubricating composition according to the invention comprises: from 5 to 95% by weight, preferably from 10 to 90% by weight, more preferably from 20 to 80% by weight, even more preferably from 30 to 70% by weight , or even from 40 to 60% by weight of said diester(s), from 1 to 95% by weight, preferably from 10 to 90% by weight, more preferably from 20 to 80% by weight, even more preferably from 30 to 70% by weight, or even from 40 to 60% by weight of one or more base oils different from said diesters, optionally from 0.01 to 20% by weight, preferably from 0.05 to 15% by weight, more preferably from 0.1 to 10% by weight , even more preferably from 0.5 to 7% by weight, or even from 1 to 5% by weight of one or more additives distinct from the diester and distinct from the base oil(s), relative to the total mass of the composition.

According to one embodiment, the lubricating composition according to the invention comprises: at least 5% by weight, preferably at least 10% by weight, preferably at least 30% by weight, preferably at least 50% by weight, more preferably at least 70% by weight, or even at least 90% by weight, of one or more diesters; from 0.01 to 20% by weight, preferably from 0.05 to 15% by weight, more preferably from 0.1 to 10% by weight, even more preferably from 0.5 to 7% by weight, or even from 1 to 5% mass, of one or more additives chosen from friction modifier additives, anti-wear additives, extreme pressure additives, detergents, antioxidants, viscosity index (VI) improvers, additives pour point depressants (PPDs), dispersants, antifoaming agents, thickeners, corrosion inhibitors, copper passivating agents, and mixtures thereof; And

- optionally from 5 to 94% by weight, preferably from 10 to 94% by weight, preferably from 15 to 90% by weight of base oil(s) distinct from the diester according to the invention, relative to the mass total composition.

Preferably, said diester contains from 13 to 25 carbon atoms, preferably from 13 to 24 carbon atoms.

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

Preferably, the diol is chosen from 1,2-propanediol, 1,2-decanediol and 1,3-alkanediol containing from 3 to 7 carbon atoms, preferably from 1,2-propanediol and 1, 3-propanediol, more preferably the diol is 1,2-propanediol.

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

Preferably, said diester(s) is(are) chosen from: a diester formed from 1,2-decanediol and two heptanoic acids, a diester formed from 1,2-decanediol and two pentanoic acids, a diester formed from 1,2-propanediol and two heptanoic acids, a diester formed from 1,2-propanediol and two nonanoic acids, a diester formed from 1,3-propanediol and two heptanoic acids, a diester formed from 1,2-propanediol and two octanoic acids, a diester formed from 1,2-propanediol and two decanoic acids, a diester formed from 1,2-propanediol and an octanoic acid and a decanoic acid, and mixtures thereof.

Preferably, the lubricating composition according to the invention comprises:

- One or more diesters chosen from: o The diesters formed between:

• a diol chosen from 1,2-decanediol and 1,3 propanediol, and

• two monocarboxylic acids, identical or different, comprising a linear or branched hydrocarbon chain comprising 4 to 10 carbon atoms, o a diester formed from 1,2-propanediol and two heptanoic acids, o a diester formed from 1,2-propanediol and two octanoic acids, o a diester formed from 1,2-propanediol and two decanoic acids, o a diester formed from 1,2-propanediol and an octanoic acid and a decanoic acid, and mixtures thereof, and at least one base oil distinct from the diester and/or at least one additive distinct from the diester, said additive being chosen from friction modifier additives, anti-wear additives, extreme pressure additives , detergents, antioxidants, viscosity index (VI) improvers, pour point depressant (PPD) additives, dispersants, anti-foaming agents, thickeners, corrosion inhibitors, anti-foaming agents, copper passivant, and mixtures thereof.

The invention also relates to the use of at least one diester in a lubricating composition, said diester being formed between: a diol chosen from 1,2-propanediol, 1,2-decanediol and 1,3-diol comprising from 3 to 10 carbon atoms, and two monocarboxylic acids, identical or different, comprising a linear or branched hydrocarbon chain comprising from 4 to 10 carbon atoms, said lubricating composition further comprising at least one base oil distinct from the diester and/or at least one additive distinct from the diester, said additive being chosen from friction modifier additives, anti-wear additives, extreme pressure additives, detergents , antioxidants, viscosity index (VI) improvers, pour point depressant (PPD) additives, dispersants, anti-foaming agents, thickeners, corrosion inhibitors, copper passivating agents , and their mixtures.

According to one embodiment, said at least one diester is used to lubricate and/or cool at least one element of a mobile or stationary system, chosen for example from a heavy or light vehicle, a public works machine, and a energy storage system.

Preferably, the mobile system is a vehicle, the lubricating composition being used to reduce the fuel consumption of a vehicle equipped with a transmission member, in particular a gearbox and/or a bridge, lubricated with means of this composition.

Preferably, the diester used in the use according to the invention is as defined in the context of the lubricating composition according to the invention and/or the lubricating composition used in the use according to the invention is such as defined in the context of the lubricating composition according to the invention.

According to one embodiment, the invention relates to the use of at least one diester in a lubricating composition for lubricating and/or cooling at least one element of a mobile or stationary system chosen from a public works machine and a energy storage system, said diester being formed between:

- a diol chosen from 1,2-propanediol, 1,2-decanediol and 1,3-diol comprising 3 to 10 carbon atoms, and two monocarboxylic acids, identical or different, comprising a linear or branched hydrocarbon chain comprising from 4 to 10 carbon atoms, said lubricating composition further comprising at least one base oil distinct from the diester and/or at least one additive distinct from the diester, said additive being chosen from friction modifier additives, anti- wear, extreme pressure additives, detergents, antioxidants, viscosity index (VI) improvers, pour point depressant (PPD) additives, dispersants, anti-foaming agents, thickeners, corrosion inhibitors, passivating agents copper, and their mixtures.

According to one embodiment, the invention relates to the use of at least one diester in a lubricating composition for lubricating and/or for cooling at least one element of a mobile system, said mobile system being a vehicle, said diester being formed between:

- a diol chosen from 1,2-propanediol, 1,2-decanediol and 1,3-diol comprising 3 to 10 carbon atoms, and two monocarboxylic acids, identical or different, comprising a linear or branched hydrocarbon chain comprising from 4 to 10 carbon atoms, said lubricating composition further comprising at least one base oil distinct from the diester and/or at least one additive distinct from the diester, said additive being chosen from friction modifier additives, anti- wear, extreme pressure additives, detergents, antioxidants, viscosity index (VI) improvers, pour point depressant (PPD) additives, dispersants, anti-foaming agents, thickeners, corrosion inhibitors, copper passivating agents, and mixtures thereof, said lubricating composition being used to reduce the fuel consumption of a vehicle equipped with a transmission member, in particular a gearbox and/or a bridge, lubricated using this composition.

In the rest of the text, the expressions “between ... and ...”, “ranging from. . . has . . . » 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)”.

detailed description

Firstly, the invention relates to a lubricating composition comprising: at least one diester formed between: o a diol chosen from 1,2-propanediol, 1,2-decanediol and 1,3-diol comprising from 3 to 10 carbon atoms, and o two monocarboxylic acids, identical or different, comprising a linear hydrocarbon chain or branched comprising from 4 to 10 carbon atoms, and at least one ingredient chosen from base oils distinct from the diester, additives distinct from the diester, and mixtures thereof, when present said additive being chosen from friction modifier additives , anti-wear additives, extreme pressure additives, detergents, antioxidants, viscosity index (VI) improvers, pour point depressant (PPD) additives, dispersants, anti-foaming agents , thickeners, corrosion inhibitors, copper passivators, and mixtures thereof.

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

In particular, it is possible to prepare a mixture of diesters by reacting a diol and a mixture of monocarboxylic acids.

For example, it is possible to react a diol and three monocarboxylic acids Al, A2 and A3. Thus, according to this example, the mixture of diesters falling within the scope of the present invention is likely to comprise:

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

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

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

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

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

- a diester formed between the diol and an A2 acid and an A3 acid. Diester used according to the invention

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

By “diester formed between a diol and two monocarboxylic acids” within the meaning of the present invention, is meant a compound obtained by two esterification reactions, each esterification reaction being carried out between one of the two alcohol functions of the diol and the acid function of one of the two monocarboxylic acids.

According to one embodiment, the diester contains from 13 to 25 carbon atoms, preferably from 15 to 24 carbon atoms.

The diol used in the invention is among 1,2-propanediol, 1,2-decanediol and 1,3-diol containing 3 to 10 carbon atoms.

By “diol” we mean a compound comprising (exactly) two hydroxyl functions (-OH).

By “1,3-diol comprising from X to Y carbon atoms”, we mean a diol whose alcohol functions are located respectively in position 1 and in position 3 of a hydrocarbon chain comprising from X to Y carbon atoms.

By “hydrocarbon chain” within the meaning of the invention, we mean an alkyl or alkylene chain, linear or branched, saturated or unsaturated. The hydrocarbon chain can optionally be interrupted by one or more heteroatoms, in particular by one or more oxygen atoms. Preferably the hydrocarbon chain is an alkyl or alkylene chain, linear or branched, saturated or unsaturated, consisting of carbon and hydrogen atoms.

According to one embodiment, the 1,3-diol comprising 3 to 10 carbon atoms is chosen from 1,3-alkanediol comprising 3 to 10 carbon atoms.

By “1,3-alkanediol comprising from X to Y carbon atoms” is meant a diol whose alcohol functions are located respectively in position 1 and in position 3 of an alkane chain comprising from

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

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

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

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

The diester used according to the invention is obtained from two identical or different monocarboxylic acids.

By “monocarboxylic acid” is meant a compound comprising a single carboxyl function (-COOH).

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

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

According to one embodiment, the monocarboxylic acids, identical or different, comprise a linear and saturated hydrocarbon chain comprising from 5 to 10 carbon atoms, preferably from 5 to 9 carbon atoms, more preferably from 5 to 8 carbon atoms . The monocarboxylic acids used according to the invention may be commercially available or synthesized according to any method known to those skilled in the art.

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

Preferably, the diester used according to the invention is saturated.

By “saturated diester” within the meaning of the invention is meant a diester comprising saturated hydrocarbon chains. Thus, preferably, the diol used according to the invention comprises a saturated hydrocarbon chain and the monocarboxylic acids used according to the invention each comprise a saturated hydrocarbon chain, preferably, said hydrocarbon chain consists of atoms carbon and hydrogen.

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

By “branched diester” within the meaning of the invention is meant a diester comprising a branched hydrocarbon chain which can be located between the two ester functions and/or at one or both ends of the diester.

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

According to one embodiment, the diester used according to the invention 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.

According to one embodiment, the diester used according to the invention 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. It is understood that the definitions given above for carboxylic acid and alcohol may be combined, where possible, to define other particular embodiments.

dans lesquelles : A diester used according to the invention may correspond more particularly to one of the following formulas (I), (II) or (III): [Chem 1]

in which :

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

° R ² represents a hydrocarbon chain, linear or branched, saturated or unsaturated, preferably saturated, having from 3 to 9 carbon atoms, preferably from 4 to 8 carbon atoms, preferably from 5 to 7 carbon atoms, said hydrocarbon chain being optionally interrupted by one or more heteroatoms, such as oxygen atoms, preferably the hydrocarbon chain is made up of carbon and hydrogen atoms. Preferably, the diester(s) corresponding to formula (I), (II) or (III) contain from 13 to 25 carbon atoms, preferably from 15 to 24 carbon atoms.

In the diesters of formulas (I), (II) or (III), R ¹ and R ² may be identical or different.

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

The diesters according to the invention can be prepared according to synthesis methods known to those skilled in the art. These synthesis methods more particularly implement two esterification reactions, each esterification reaction being implemented between an alcohol function of the diol and the acid function of the monocarboxylic acid.

Of course, it is up to those skilled in the art to adjust the synthesis conditions to obtain a diester according to the invention.

It is understood that, in the context of the present invention, a diester according to the invention can be in the form of a mixture of at least two diesters according to the invention, in particular as defined above. Preferably, the diester used according to the invention comprises a carbon content of biological origin of at least 60% by mass, preferably at least 70% by mass, more preferably at least 80%. by mass, even more preferably at least 90% by mass, relative to the total mass of the carbon atoms of the diester.

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

The diester or mixture of diesters according to the invention may represent at least 5% by weight of the composition according to the invention, preferably at least 10% by weight, preferably at least 30% by weight, more preferably at least 50% by weight. , even more preferably at least 70% by weight, in particular at least 80% by weight, more particularly at least 90% by weight, or even at least 95% by weight, of the total mass of the composition according to the invention.

The diester(s) according to the invention can be used with one or more additional base oils (also called co-bases). According to this embodiment, preferably, the composition will comprise: from 5 to 95% by weight, preferably from 5 to 50% by weight, more preferably 10 to 40% by weight, of the diester(s) according to the invention, and from 5 to 95% by mass, preferably from 50 to 95% by mass, preferably from 60 to 90% by mass, of one or more base oils different from the diesters according to the invention, relative to the mass total of diester(s) and base oils other than diesters.

According to one embodiment, a lubricating composition according to the invention may comprise at least 30% by weight of a diester or mixture of diesters according to the invention, more particularly between 50% and 99.5% by weight, preferably between 70%. and 99% by weight, more preferably between 80% and 99% by weight, or even between 80% and 95% by weight, relative to the total mass of said composition. According to a particular embodiment, a lubricating composition according to the invention can be formed at more than 95% by weight, in particular at more than 98% by mass, of one or more diesters according to the invention.

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

This embodiment is particularly advantageous when the composition is used for cooling, as a cooling fluid.

Additional base oil(s) (co-base(s))

The lubricating composition according to the invention may comprise, in addition to one or more diesters according to the invention, one or more base oils distinct from the diesters according to the invention, called “additional base oil”.

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

The base oils can also be chosen from synthetic oils, such as certain esters of carboxylic acids and alcohols, distinct from Tester 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 600Da. 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 the composition according to the invention.

In particular, a composition according to the invention may comprise from 5 to 95% by weight, preferably from 50 to 95% by weight, more preferably from 60 to 90% by weight, of one or more base oils different from the diesters according to the invention, relative to the total mass of said composition.

Additives

The lubricating composition according to the invention may optionally also comprise one or more additives known to those skilled in the art in the field of lubrication, in particular for vehicle transmissions, in particular for transmissions of light or heavy vehicles.

These additives may be chosen in particular from friction modifier additives, anti-wear additives, extreme pressure additives, detergents, antioxidants, viscosity index (VI) improvers, pour point depressant additives. (PPD), dispersants, anti-foaming agents, thickeners, corrosion inhibitors, copper passivating agents, and mixtures thereof.

Preferably, the lubricating composition according to the invention may further comprise one or more additives chosen from antioxidants, anti-foaming agents, pour point improvers and anti-corrosion agents. 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 diester 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 10% by weight, in particular less than or equal to 5% by weight, and more particularly ranging from 0.01 to 3% by weight, for example relative to the total mass of said composition.

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

The invention thus relates, according to one of its aspects, to a lubricating composition comprising (i) at least one diester as defined above, 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 we can cite phenolic-type antioxidants, 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 C1-C12 alkyl group, N,N'-dialkyl-aryl-diamines and their mixtures. Preferably, the sterically hindered phenols are chosen from compounds comprising a phenol group of which at least one vicinal carbon of the carbon carrying the alcohol function is substituted by at least one C1-C10 alkyl group, preferably a CI-C6 alkyl group. , preferably a C4 alkyl group, preferably 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 ⁵ R ⁶ R ⁷ in which R ⁵ represents an aliphatic group or an aromatic group, optionally substituted, R ⁶ represents an aromatic group, optionally substituted, R ⁷ represents a hydrogen atom, an alkyl group, an aryl group or a group of formula R ⁸ S(O) _Z R ⁹ in which R ⁸ represents an alkylene group or an alkenylene group, R ⁹ 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.

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 additive, an extreme pressure additive or mixtures thereof.

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, represent independently an alkyl group, preferably an alkyl group comprising from 1 to 18 carbon atoms.

Preferably, the lubricating composition according to the invention is free from phosphite type esters containing sulfur of formula

dans laquelle R est un groupe hydrocarboné en C4 à C20 contenant du soufre et R¹ est un hydrogène, un groupe hydrocarboné en C4 à C20 ou un groupe hydrocarboné en C4 à C20 contenant du soufre. [Chem 4]

wherein R is a C4 to C20 hydrocarbon group containing sulfur and R ¹ is hydrogen, a C4 to C20 hydrocarbon group or a C4 to C20 hydrocarbon group containing sulfur.

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.

Friction modifier additives make it possible to limit friction by forming monolayers adsorbed on the surfaces of metals in contact with them. They can be chosen from compounds providing metallic elements and compounds free of ash. Among the compounds providing metallic elements, we can cite transition metal complexes such as Mo, Sb. Sn, Fe, Cu, Zn whose ligands can be hydrocarbon compounds comprising oxygen, nitrogen, sulfur or phosphorus atoms. The ash-free friction modifier additives are generally of organic origin and can be chosen from esters of fatty acids and polyols, distinct from the monoester required according to the invention, 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. In particular, the molybdenum-based compounds can be chosen from molybdenum dithiocarbamates (Mo-DTC), molybdenum dithiophosphates (Mo-DTP), and mixtures thereof. A lubricating composition may in particular comprise a molybdenum content of between 1000 and 2500 ppm.

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

When used at too high a content, molybdenum compounds can negatively impact the cold properties of the lubricating composition in which they are used. Thus, a lubricating composition according to the invention preferably comprises less than 1.5% by weight of molybdenum, more preferably less than 1% by weight, relative to the total mass of the composition, or is even free from molybdenum.

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

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

A lubricating composition may also comprise at least one pour point depressant additive (also called “PPD” agent for “Pour Point Depressant” in English).

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, alkylated polystyrenes.

A lubricating composition according to the invention may comprise from 0.1% to 2%, preferably from 0.2% to 1% by weight of pour point depressant additive(s), relative to the mass. total composition. Also, a lubricating composition may comprise at least one dispersing agent.

The dispersing agent can be chosen from Mannich bases, succinimides and their derivatives, such as polyisobutylene succinic anhydride derivatives.

A lubricating composition can for example comprise from 0.2 to 10% by weight of dispersing agent, relative to the total mass of the composition.

A lubricating composition according to the invention may also comprise at least one additive improving the viscosity index (VI).

Viscosity index improvers, in particular viscosity index improving polymers, make it possible to guarantee good cold resistance and minimum viscosity at high temperatures.

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

In particular, a lubricating composition according to the invention may comprise from 1 to 15% by weight of additive(s) improving the viscosity index, preferably from 5% to 10% by weight, relative to the total mass of the composition. lubricating.

A lubricating composition may also comprise at least one antifoam additive, for example chosen from polar polymers such as polymethylsiloxanes or polyacrylates.

In particular, a lubricating composition according to the invention may comprise from 0.01 to 3% by weight of anti-foam additive(s), relative to the total mass of the lubricating composition.

It may also include at least one anti-corrosion agent or copper passivating agent, for example compounds such as polyisobutenes succinic anhydrides, thiadiazole sulfonates or mercaptobenzothiazoles. They are typically present in a lubricating composition according to the invention at contents of between 0.01% and 1% by weight, relative to the total mass of the composition.

Advantageously, a lubricating composition according to the invention comprises one or more additives chosen from viscosity index improving agents, pour point lowering agents, anti-wear agents and antioxidant agents.

According to a particular embodiment, a lubricating composition according to the invention comprises, or even is formed of (i) at least one diester according to the invention and (ii) at least one additive chosen from antioxidants, viscosity index improving additives, pour point depressant additives, anti-wear and/or extreme pressure additives, antifoams, detergents, dispersants, and mixtures thereof, preferably among anti-oxidants, viscosity index improving additives, pour point depressant additives, anti-wear and/or extreme pressure additives, and mixtures thereof.

Advantageously, a lubricating composition according to the invention is formed of (i) at least one diester corresponding to one of formulas (I), (II) or (III) as defined above and (ii) at least an antioxidant additive.

Advantageously, a lubricating composition according to the invention is formed of (i) at least one diester corresponding to one of formulas (I) or (II) as defined above and (ii) at least one anti- oxidant.

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

- at least 5% by weight, preferably at least 10% by weight, preferably at least 30% by weight, preferably at least 50% by weight, more preferably at least 70% by weight, or even at least 90% by weight, of diester(s) ) corresponding to one of formulas (I), (II) or (III);

- from 0.01 to 20% by mass, preferably from 0.05 to 15% by mass, more preferably from 0.1 to 10% by mass, even more preferably from 0.5 to 7% by mass, or even from 1 to 5 % by mass, of one or more additives chosen from the 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

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

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

- from 5 to 95% by weight, preferably from 10 to 90% by weight, more preferably from 20 to 80% by weight, even more preferably from 30 to 70% by weight, or even from 40 to 60% by weight, of diester(s) corresponding to one of formulas (I), (II) or (III);

- from 5 to 95% by weight, preferably from 10 to 90% by weight, more preferably from 20 to 80% by weight, even more preferably from 30 to 70% by weight, or even from 40 to 60% by weight of one or more oils different bases of said diesters;

- optionally from 0.01 to 20% by weight, preferably from 0.05 to 15% by weight, more preferably from 0.1 to 10% by weight, even more preferably from 0.5 to 7% by weight, or even from 1 to 5% by weight of one or more additives distinct from the diester and distinct from the base oil(s), the contents being expressed in relation to the total mass of said composition.

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

- at least 5% by weight, preferably from 10% to 40%, more preferably from 15% to 30% by weight, of one or more diesters according to the invention defined previously, preferably chosen from diesters corresponding to the formula ( I);

- from 50% to 95% by weight of base oil(s) distinct from the diesters defined according to the invention, preferably chosen from group II and/or III base oils according to the API classification ; - optionally from 5% to 15% by weight of at least one additive improving the viscosity index;

- optionally from 0.1% to 1% by weight of at least one pour point depressant additive;

- optionally from 0.01% to 6% by weight of at least one anti-wear additive; And

- optionally from 0.1% to 2% by weight of at least one antioxidant additive, the contents being expressed in relation to the total mass of said composition.

Preferably, a lubricating composition according to the invention comprises, or even consists of:

- less than 30% by weight, in particular 1 and 30% by weight, in particular 5 to 30% by weight, preferably 10 to 30% by weight and more particularly 15 to 30% by weight, of one or more diesters depending on invention defined above, preferably chosen from diesters of formula (I) or (II);

- from 50% to 85% by weight of base oil(s) distinct from the diesters defined according to the invention, preferably chosen from group II and/or III base oils according to the API classification ;

- optionally from 5% to 15% by weight of at least one additive improving the viscosity index;

- optionally from 0.1% to 1% by weight of at least one pour point depressant additive;

- optionally from 0.01% to 6% by weight of at least one anti-wear additive; And

- optionally from 0.1% to 2% by weight of at least one antioxidant additive, the contents being expressed in relation to the total mass of said composition.

According to a particular embodiment, a composition according to the invention comprises, or even consists of: from 5 to 95% by mass, preferably from 5 to 50% by mass, more preferably 10 to 40% by mass, of said or said diesters corresponding to formula (I) or (II); from 5 to 95% by weight, preferably from 50 to 95% by weight, preferably from 60 to 90% by weight, of one or more base oils different from said diesters; optionally from 0.01 to 20% by weight, preferably from 0.05 to 15% by weight, more preferably from 0.1 to 10% by weight, even more preferably from 0.5 to 7% by weight, or even from 1 to 5 % by mass, of one or more additives chosen from friction modifier additives, anti-wear additives, extreme pressure additives, detergents, antioxidants, viscosity index (VI) improvers, pour point depressant (PPD) additives, dispersants, anti-foaming agents, thickeners, corrosion inhibitors, copper passivating agents, and mixtures thereof, the contents being expressed relative to the total mass of said composition.

A composition according to the invention advantageously has a kinematic viscosity, measured at 100°C according to the ASTM D445 standard, ranging from 1 to 20 mm ² /s, preferably from 2 to 15 mm ² /s.

A composition according to the invention advantageously has a kinematic viscosity, measured at 40°C according to the ASTM D445 standard, ranging from 20 to 50 mm ² /s, preferably from 25 to 40 mm ² /s.

The composition according to the invention has good lubricating properties.

The composition according to the invention also has good properties in terms of cold resistance.

The composition according to the invention also has good cooling properties.

The present invention also relates to the use of a diester in a composition for lubricating and/or cooling at least one part of a mobile or stationary system, said diester being formed between: a diol chosen from 1,2- propanediol, 1,2-decanediol and 1,3-diol comprising 3 to 10 carbon atoms, and two monocarboxylic acids, identical or different, comprising a linear or branched hydrocarbon chain comprising 4 to 10 carbon atoms.

Preferably, the composition for lubricating and/or cooling further comprises at least one base oil distinct from the diester and/or at least one additive distinct from the diester, said additive being chosen from anti-oxidants, pour point depressant additives, anti-foam agents, anti-corrosion agents, anti-wear and/or extreme pressure additives, friction modifiers, detergents, agents dispersants and mixtures thereof, in particular among anti-oxidants, pour point depressant additives, anti-foaming agents and anti-corrosion agents.

The characteristic(s) of the diester presented in the context of the composition according to the invention are also applicable to the diester used according to the invention.

According to one embodiment of the use according to the invention, the lubricated and/or cooled part is a part of a heavy or light vehicle, a public works machine, or an energy storage device (e.g. data center).

The diester defined in the present invention makes it possible to reduce the friction coefficients of the lubricating composition.

The diester defined in the present invention makes it possible to cool the elements of a mobile or stationary system, such as a heavy or light vehicle, a public works machine, an energy storage device.

The composition formulated according to the invention, in particular as described above, has excellent tribological properties, particularly in terms of reducing friction, which makes it particularly well suited to use as a lubricating fluid.

The composition formulated according to the invention, in particular as described above, has excellent thermal properties, particularly in terms of thermal conductivity, which makes it particularly well suited to use as a cooling fluid.

A composition of the invention is suitable for the lubrication of transmission members of motor vehicles, in particular transmissions for light or heavy vehicles, for example gearboxes and/or axles.

In particular, it can be used to lubricate the manual gearbox and/or the axles of a light or heavy vehicle. Advantageously, a lubricating composition according to the invention has performances in particular in terms of cold properties, particularly well suited to its use for the transmission of heavy goods vehicles, in particular for lubricating the manual gearbox and/or the weight axles. heavy. The present invention also relates to a method of lubricating and/or cooling at least one part of a mobile or stationary system, comprising bringing the composition according to the invention into contact with said part.

According to one embodiment, the mobile or stationary system is chosen from a heavy or light vehicle, a public works machine, an energy storage device such as a data center.

The present invention also relates to a method of lubricating and/or cooling at least one mechanical part, in particular a motor vehicle transmission member, comprising bringing the lubricating composition according to the invention into contact with said mechanical part. , in particular said motor vehicle transmission member.

The diesters defined in the invention can be added to lubricating compositions used in vehicle transmissions in order to improve their “Fuel-Eco” properties, namely their ability to limit the fuel consumption of motor vehicles, without affect their performance, particularly in terms of cold properties.

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

des composé testés Example 1:

compounds tested

The following compounds were prepared:

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

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

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

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

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

- Diester F: mixture of diesters formed from 1,2-propanediol and a biosourced cut of C8-C10 acids monoester formed from a monocarboxylic acid comprising a saturated hydrocarbon chain of 3 to 14 carbon atoms; and a monoalcohol comprising a saturated hydrocarbon chain of 3 to 14 carbon atoms.

The diesters and monoester were prepared according to known ester preparation methods.

The compositions tested in the following examples comprise 100% of each ester (diester or monoester) defined in this example 1.

Example 2: Viscosity measurement

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

The viscosities are presented in Table 2.

[Table 2]

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

Example 3: Measuring friction coefficients

The tribological properties can be evaluated by a test on a rotating ball-disc tribometer (also called ball-plane) of the Linear reciprocating tribometer type. This test makes it possible in particular to evaluate the performance of lubricants in terms of friction in mixed/limit regime depending on the load, pressure or speed conditions applied.

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

The tribometer can be a device allowing a steel ball and a steel plane to be put 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 driving speed varies from 10 mm/s to 2500 mm/s. The coefficient of friction is in particular determined at a rotation speed of 10 mm/s. The coefficient is determined at a sliding speed/drive speed ratio (“Slide-to-Roll Ratio” or %SRR) of 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 coefficient of friction is measured and recorded via a force sensor.

The results with a drive speed of 225 mm ² /s are shown in Table 3.

The lubricating compositions tested comprise 100% of each ester defined in Example 1.

[Table 3]

These results show that the diesters used according to the invention have very low friction coefficients, in particular a lower friction coefficient than the monoester.

Example 4: Mini flash point measurement

The mini flash point is measured according to the ASTM D93Ac standard (Cl eaveland open cup method).

The values are shown in Table 4.

[Table 4]

As shown by the values in Table 4, the flash point is better if the diester is a branched diester. Indeed, the diester formed from type 1,2 propanediol has a lower flash point than the diester formed from type 1,3 propanediol, with the same number of carbon atoms in total.

Example 5: Measuring the mini pour point

Mini pour point is measured according to ASTM D7346.

The values are shown in Table 5. [Table 5]

The results in Table 5 show that the diesters used in the lubricating composition according to the invention have a low pour point, in particular lower than the monoester.

Example 6: Measurement of the traction coefficient

The coefficient of traction (COT) was measured using the PCS instrument MTM tribometer. It makes it possible to evaluate the performance of lubricants in terms of friction in mixed/hydrodynamic conditions. This test consists of putting a steel ball and a steel plane into relative motion, at different speeds, making it possible to define the %SSR (Sliding speed/drive speed ratio or “Slide-to-Roll Ratio” in English language) which corresponds to the sliding speed/drive speed.

The measurement conditions were 25 N load, a disk speed of 1.4 m/s for a rated temperature of 100 °C and an SRR of 20%.

The lower the traction coefficient for a lubricating composition, the more friction between metal parts is reduced, thus resulting in a greater gain in fuel economy.

The results obtained are shown in Table 6.

[Table 6]

These results show that the diesters used according to the invention have very low traction coefficients, in particular a lower traction coefficient than the monoester.

Example 7: Measurement of thermal conductivity

The thermal conductivity of the compounds described in Example 1 was determined according to standard ASTM D7896-19 at different temperatures.

The results are shown in Table 7.

[Table 7]

These results show that the diesters defined in the invention have good thermal properties, which allows their use as a cooling fluid.

Claims

Claims 1. Lubricating composition comprising: - One or more diesters, each of said diesters being formed between: o a diol chosen from 1,2-propanediol, 1,2-decanediol and 1,3-diols comprising from 3 to 10 carbon atoms, and o two monocarboxylic acids, identical or different, comprising a linear or branched hydrocarbon chain comprising from 4 to 10 carbon atoms, said hydrocarbon chain optionally being interrupted by one or more heteroatoms and at least one base oil distinct from the diester and/or at least one additive distinct from the diester, said additive being chosen from friction modifier additives, anti-wear additives, extreme pressure additives, detergents, antioxidants, viscosity index (VI) improvers, point lowering additives (PPD), dispersants, anti-foaming agents, thickeners, corrosion inhibitors, copper passivating agents, and mixtures thereof. 2. Lubricating composition according to claim 1, in which the linear or branched hydrocarbon chain comprising 4 to 10 carbon atoms is an alkyl or alkylene chain, linear or branched, saturated or unsaturated, consisting of carbon and hydrogen atoms . 3. Lubricating composition according to claim 1 or 2, comprising: from 5 to 95% by weight, preferably from 10 to 90% by weight, more preferably from 20 to 80% by weight, even more preferably from 30 to 70% by weight, or even from 40 to 60% by weight of said diester(s), from 1 to 95% by weight, preferably from 10 to 90% by weight, more preferably from 20 to 80% by weight, even more preferably from 30 to 70% by weight, or even from 40 at 60% by weight of one or more base oils different from said diesters, optionally from 0.01 to 20% by weight, preferably from 0.05 to 15% by weight, more preferably from 0.1 to 10% by weight, again more preferably from 0.5 to 7% by weight, or even 1 to 5% by weight of one or more additives distinct from the diester and distinct from the base oil(s), relative to the total mass of the composition. 4. Lubricating composition according to one of claims 1 to 3, comprising: at least 5% by weight, preferably at least 10% by weight, preferably at least 30% by weight, preferably at least 50% by weight, more preferably at least 70% by weight, or even at least 90% by weight, of one or more diesters; from 0.01 to 20% by weight, preferably from 0.05 to 15% by weight, more preferably from 0.1 to 10% by weight, even more preferably from 0.5 to 7% by weight, or even from 1 to 5% mass, of one or more additives chosen from friction modifier additives, anti-wear additives, extreme pressure additives, detergents, antioxidants, viscosity index (VI) improvers, additives pour point depressants (PPDs), dispersants, antifoaming agents, thickeners, corrosion inhibitors, copper passivating agents, and mixtures thereof; And - optionally from 5 to 94% by weight, preferably from 10 to 94% by weight, preferably from 15 to 90% by weight of base oil(s) distinct from the diester according to the invention, relative to the mass total composition. 5. Lubricating composition according to any one of the preceding claims, in which said diester comprises from 13 to 25 carbon atoms, preferably from 13 to 24 carbon atoms. 6. Lubricating composition according to any one of the preceding claims, in which said diester has a kinematic viscosity at 100°C ranging from 1 to 6 mm ² /s, preferably ranging from 1 to 4 mm ² /s. 7. Lubricating composition according to any one of the preceding claims, in which the diol is chosen from 1,2-propanediol, 1,2-decanediol and 1,3-alkanediol comprising from 3 to 7 carbon atoms, preferably from 1,2-propanediol and 1,3-propanediol, more preferably the diol is 1,2-propanediol. 8. Lubricating composition according to any one of the preceding claims, in which said monocarboxylic acids, identical or different, comprise a linear hydrocarbon chain comprising from 4 to 10 carbon atoms, preferably from 5 to 9 carbon atoms. 9. Lubricating composition according to any one of the preceding claims, in which said diester(s) is(are) chosen from: - the diesters formed between: • a diol chosen from 1,2-decanediol and 1,3 propanediol, and • two monocarboxylic acids, identical or different, comprising a linear or branched hydrocarbon chain comprising from 4 to 10 carbon atoms, said hydrocarbon chain possibly being interrupted by one or more heteroatoms, - a diester formed from 1,2-propanediol and two heptanoic acids, - a diester formed from 1,2-propanediol and two octanoic acids, - a diester formed from 1,2-propanediol and two decanoic acids, - a diester formed from 1,2-propanediol and an octanoic acid and a decanoic acid, and their mixtures. 10. Lubricating composition according to any one of the preceding claims, in which said diester(s) is(are) chosen from: - a diester formed from 1,2-decanediol and two heptanoic acids, - a diester formed from 1,2-decanediol and two pentanoic acids, - a diester formed from 1,2-propanediol and two heptanoic acids, - a diester formed from 1,2-propanediol and two nonanoic acids, - a diester formed from 1,3-propanediol and two heptanoic acids, - a diester formed from 1,2-propanediol and two octanoic acids, - a diester formed from 1,2-propanediol and two decanoic acids, - a diester formed from 1,2-propanediol and an octanoic acid and a decanoic acid, and their mixtures. 11. Use of at least one diester in a lubricating composition, said diester being formed between: - a diol chosen from 1,2-propanediol, 1,2-decanediol and 1,3-diol comprising 3 to 10 carbon atoms, and two monocarboxylic acids, identical or different, comprising a linear or branched hydrocarbon chain comprising from 4 to 10 carbon atoms, said hydrocarbon chain being optionally interrupted by one or more heteroatoms, said lubricating composition further comprising at least one base oil distinct from the diester and/or at least one additive distinct from the diester, said additive being chosen from friction modifier additives, anti-wear additives, extreme pressure additives, detergents, antioxidants, viscosity index (VI) improvers, pour point depressant (PPD) additives, dispersants, anti-foaming agents, thickeners, corrosion inhibitors, copper passivating agents, and mixtures thereof. 12. Use according to claim 11, for lubricating and/or cooling at least one element of a mobile or stationary system, chosen for example from a heavy or light vehicle, a public works machine, and a storage system. energy. 13. Use according to claim 12, in which the mobile system is a vehicle, the lubricating composition being used to reduce the fuel consumption of a vehicle equipped with a transmission member, in particular a gearbox and/or of a bridge, lubricated by means of this composition. 14. Use according to any one of claims 11 to 13, in which the diester is as defined in any one of claims 2.5 to 9 and/or the lubricating composition is as defined in claim 3 or 4 .