WO2016150950A1

WO2016150950A1 - Lubricating composition

Info

Publication number: WO2016150950A1
Application number: PCT/EP2016/056237
Authority: WO
Inventors: Goulven BOUVIER; Alder DA COSTA D'AMBROS
Original assignee: Total Marketing Services
Priority date: 2015-03-23
Filing date: 2016-03-22
Publication date: 2016-09-29
Also published as: US20180112148A1; EP3274432A1; FR3034100B1; JP2018509512A; CN107466315A; EP3274432B1; FR3034100A1

Abstract

The invention relates to the field of lubricating compositions, specifically of lubricating compositions for motor vehicles, and in particular to the field of lubricating compositions for a transmission, a gearbox or an axle. The lubricating composition according to the invention includes at least 30 wt.% of the composition of at least one monoester, at least one polyalphaolefin oil (PAO) with a kinematic viscosity, measured at 100°C, of 40 to 3,000 mm².s^-1, and at least one polyalphaolefin oil (PAO) with a kinematic viscosity, measured at 100°C, of 1 to 10 mm².s^-1. The invention also relates to the use of said lubricating composition to reduce the fuel consumption of a vehicle provided with a transmission, in particular with an axle or a gearbox, lubricated by means of said lubricating composition.

Description

LUBRICANT COMPOSITION

DESCRIPTION The invention relates to the field of lubricating compositions, especially lubricating compositions for motor vehicles, in particular the field of lubricating compositions for transmission, gearbox or bridge. The lubricating composition according to the invention comprises at least 30% by weight of the composition of at least one monoester, at least one polyalphaolefinic (PAO) oil whose kinematic viscosity measured at 100 ° C. ranges from 40 to 3000 mm ² . s ^"1 and at least one polyalphaolefinic oil (PAO) whose kinematic viscosity measured at 100 ° C ranges from 1.5 to 10 mm ² s ^-1 . The invention also relates to the use of this lubricant composition for reducing the fuel consumption of a vehicle equipped with a transmission, in particular a bridge or a gearbox, lubricated with this lubricating composition.

Oils for gearboxes or for axles, and more generally for gear oils, must satisfy many requirements, notably related to driving comfort (perfect gearshift, quiet running, trouble-free operation, high reliability), at the same time. lifetime of the assembly (reduction of wear during cold passage, no deposits and high thermal stability and oxidation, safety of lubrication at high temperatures, stable viscosity situation and absence of shear loss, long service life) as well as taking into account environmental aspects (lower fuel consumption, reduced oil consumption, low noise, easy evacuation).

These are usually the requirements for manual gearbox oils and axle gears.

Concerning the requirements imposed on automatic gearbox oils (ATF oils for automatic transmission fluids), because of their use, it appears for ATF oils very specific requirements which are a great constancy of the coefficient of friction throughout the stay for optimal gear change, excellent aging stability for long oil change intervals, good viscosity-temperature performance to ensure perfect operation with a hot engine and a cold engine and sufficient sealing compatibility with different elastomers used in transmission seals so that they do not swell, shrink or embrittle.

Moreover, in the automotive field, the search for the reduction of C0 ₂ emissions requires the development of lubricant products that reduce friction in gearboxes and bridge differentials. This reduction of friction in the gearboxes and in the bridge differentials must be obtained for different operating conditions. These friction reductions must concern the internal friction of the lubricant but also the friction of the elements constituting the gearboxes or bridge differentials, in particular the metal elements.

The nature of automotive engine lubricating compositions has an influence on pollutant emissions and fuel consumption. Vehicle lubricant compositions for energy saving are often referred to as "fuel-eco" (FE) in English terminology. Such "fuel-eco" oils have been developed to meet these new needs. The reduction of energy losses is therefore a constant search in the field of lubricant compositions for vehicles.

The lubricating vehicle compositions must therefore have improved properties and performance. In particular, it is necessary to provide alternative lubricating compositions, in particular lubricant compositions having a high viscosity index (VI) and a low tensile coefficient.

The desired lubricating compositions must have a high viscosity index in order to avoid cold energy losses due to friction but also to keep a sufficient lubricant film on the lubricated elements hot. A high viscosity index thus guarantees a lower drop in viscosity when the temperature increases.

It is also necessary to provide alternative lubricating compositions with good oxidation resistance.

There is therefore a need for lubricating compositions for vehicle transmission which can provide a solution to all or part of the problems of the lubricant compositions of the prior art. Thus, the invention provides a lubricating composition comprising

(a) at least 30% by weight of the composition of at least one monoester of formula (I)

in which

^■ R ¹ represents a hydrocarbon group, saturated or unsaturated, linear or branched, comprising from 14 to 24 carbon atoms;

^■ R ² represents a hydrocarbon group, saturated or unsaturated, linear or branched, comprising 2 to 18 carbon atoms;

(b) at least one polyalphaolefinic (PAO) oil whose kinematic viscosity measured at 100 ° C according to ASTM D445 is from 40 to 3000 mm ² .s ^-1 ;

(c) at least one polyalphaolefinic (PAO) oil whose kinematic viscosity measured at 100 ° C. according to ASTM D445 is from 1.5 to 10 mm ² . s ^"1 .

The composition according to the invention comprises at least one monoester (a), at least one polyalphaolefinic oil (b) and at least one polyalphaolefinic oil (c). It may comprise only one monoester (a), one polyalphaolefinic oil (b) and one polyalphaolefinic oil (c). It may also comprise one, two or three monoesters (a) but also one, two or three polyalphaolefinic oils (b) or a two or three polyalphaolefinic oils (c).

The monoester (a) present in the lubricant composition according to the invention is a monoester of formula (I). Preferably, for the monoester (a) of formula (I) according to the invention, R ¹ represents a hydrocarbon group, saturated or unsaturated, linear or branched, comprising from 14 to 20 carbon atoms, preferentially from 14 to 18 carbon atoms. carbon, more preferably from 16 to 18 carbon atoms. Also preferably for the monoester (a) of formula (I) according to the invention, R ² represents a hydrocarbon group, saturated or unsaturated, linear or branched, comprising from 3 to 14 carbon atoms, preferentially from 4 to 12 atoms carbon, more preferably from 4 to 10 carbon atoms.

Advantageously, the monoester (a) present in the lubricant composition according to the invention is a monoester of formula (I) in which

^■ R ¹ is a linear group and R ² is a branched group; or ^■ R ¹ is a branched group and R ² is a linear array; or

^■ R ¹ and R ² are linear arrays; or

^■ R ¹ and R ² are branched groups.

Preferably, the monoester (a) present in the lubricant composition according to the invention is a monoester of formula (I) in which R ¹ and R ² are linear groups.

In a particularly preferred manner, the monoester (a) present in the lubricating composition according to the invention is a monoester of formula (I) in which R ¹ and R ² independently represent a group chosen from

A linear saturated group;

^■ a branched saturated group containing from 1 to 5 branching chains;

^■ a saturated branched group whose branching chains comprise from 1 to 5 carbon atoms;

^■ a branched saturated group containing from 1 to 5 ranges of branching and whose branching chains comprise from 1 to 5 carbon atoms.

Also preferably, the monoester (a) present in the lubricating composition according to the invention is a monoester of formula (I) in which R ¹ and R ² are chosen from

^■ a linear saturated group;

A branched saturated group comprising from 1 to 5 branching chains;

^■ a branched saturated group containing from 1 to 5 ranges of branching and whose branching chains comprise from 1 to 5 carbon atoms. Also preferably, only R ¹ or only R ² is chosen from one or other of these groups.

Preferably, the monoester (a) is of formula (I) in which

^■ R ¹ is a saturated group and R ² is an unsaturated group; or

^■ R ¹ is an unsaturated group and R ² is a saturated group; or

R ¹ and R ² are saturated groups; or

^■ R ¹ and R ² are unsaturated groups.

A monoester (a) of formula (I) in which R ¹ is a saturated group and R ² is a saturated group is particularly preferred. A monoester (a) of formula (I) in which R ¹ is an unsaturated group and R ² is a saturated group is more particularly preferred. The monoester (a) of formula (I) according to the invention may be chosen from numerous monoesters. Preferably, it is chosen from stearates, preferably alkyl stearates and alkenyl stearates, more preferentially C ₄ -C ₁₀ alkyl stearates, in particular butyl stearate, pentyl stearate, hexyl stearate, heptyl stearate, octyl stearate, nonyl stearate, decyl stearate. Also preferably, it is chosen from oleates, preferably alkyl oleates and alkenyl oleates, more preferentially C ₄ -C ₁₀ alkyl oleates, in particular butyl oleate, oleate of pentyl, hexyl oleate, heptyl oleate, octyl oleate, nonyl oleate, decyl oleate.

Other monoesters that may be suitable according to the invention include linoleate, preferably alkyl linoleate and alkenyl linoleate, more preferably C ₄ -C ₁₀ -alkyl linoleate, in particular butyl linoleate, pentyl linoleate, hexyl linoleate, heptyl linoleate, octyl linoleate, nonyl linoleate, decyl linoleate. Mention may also be made of palmitoleates; palmitates; linolenates; eicosenoates; erucic acid esters; the nervonic acid esters. The monoester (a) of formula (I) according to the invention may also be chosen from alkenes monoesters and alkyl monoesters, preferably C ₂ -C ₁₀ alkyl monoesters, in particular ethyl monoesters, propylene monoesters, butyl monoesters, pentyl monoesters, hexyl monoesters, heptyl monoesters, octyl monoesters, nonyl monoesters, decyl monoesters.

Advantageously, the lubricant composition according to the invention comprises from 30 to 70% by weight of the monoester composition of formula (I). Also advantageously, the lubricating composition according to the invention comprises from 30 to 60% by weight of the composition or from 30 to 50% by weight of the monoester composition of formula (!) ^■

In addition to the monoester (a), the lubricating composition according to the invention comprises at least two polyalphaolefinic oils (b) and (c). These are hydrogenated PAOs. The polyalphaolefinic oil (b) is a heavy PAO. It has a kinematic viscosity measured at 100 ° C. according to ASTM D445 ranging from 40 to 3000 mm ² .s ^-1 . The polyalphaolefinic oil (c) is a light PAO It has a kinematic viscosity measured at 100 ° C. C according to ASTM D445 ranging from 1.5 to 10 mm ² .s ^-1 . Preferably, the kinematic viscosity of the polyalphaolefinic oil (b), measured at 100 ° C. according to ASTM D445, ranges from 40 to 1500 mm ² .s- ^1, more preferably, the kinematic viscosity of the Polyalphaolefinic oil (b), measured at 100 ° C. according to ASTM D445, ranges from 40 to 300 mm ² .s ^-1 .

Also preferably, the weight average molecular weight of the polyalphaolefinic oil (b) is greater than 2500 Da or ranges from 2500 to 80 000 Da. More preferably, the weight average molecular weight of the polyalphaolefinic oil (b) is from 4000 to 50,000 Da.

Particularly preferably, the polyalphaolefinic oil (b) has a kinematic viscosity, measured at 100 ° C according to ASTM D445, ranging from 40 to 1500 mm ² .s ^-1 and a weight average molecular weight of 2 500 to 80,000 Da or 4,000 to 50,000 Da. More preferably, the polyalphaolefinic oil (b) has a kinematic viscosity, measured at 100 ° C according to ASTM D445, ranging from 40 to 300 mm ² . s ^"1 and an average molecular weight ranging from 2 500 to 80 000 Da, or from 4 000 to 50 000 Da.

Preferably, the kinematic viscosity of the polyalphaolefin oil (c), measured at 100 ° C according to ASTM D445, is from 1 5 to 10 mm ² .s ^"1 or 2 to 10 mm ² ^{.s" 1} . More preferably, the kinematic viscosity of the polyalphaolefinic oil (c), measured at 100 ° C. according to ASTM D445, ranges from 1.5 to 8 mm ² · s ^-1 or from 2 to 8 mm ² · s. ^"1 .

Also preferably, the weight average molecular weight of the polyalphaolefinic oil (c) is less than 500 Da or is from 50 to 500 Da. More preferably, the weight average molecular weight of the polyalphaolefinic oil (c) is 50 to 350 Da or 50 to 300 Da.

Particularly preferably, the polyalphaolefinic oil (c) has a kinematic viscosity, measured at 100 ° C. according to ASTM D445, ranging from 1.5 to 8 mm ² .s ^-1 and a weight average molecular weight ranging from 50 to 500 Da or 50 to 350 Da or 50 to 300 Da or a kinematic viscosity, measured at 100 ° C according to ASTM D445, ranging from 2 to 8 mm ² s ^-1 and an average molecular weight of weight ranging from 50 to 500 Da or 50 to 350 Da or 50 to 300 Da.

More preferably, the polyalphaolefinic oil (c) has a kinematic viscosity, measured at 100 ° C. according to ASTM D445, ranging from 1.5 to 6 mm ² .s ^-1 and a weight average molecular weight ranging from 50 to 500 Da or 50 to 350 Da or 50 to 300 Da or a kinematic viscosity, measured at 100 ° C according to the ASTM D445 standard, ranging from 2 to 6 mm ² . s ^"1 and an average molecular weight ranging from 50 to 500 Da, or from 50 to 350 Da, or from 50 to 300 Da.

As a particular polyalphaolefinic oil (c) according to the invention, mention may also be made of an oil with a kinematic viscosity at 100 ° C., measured according to the ASTM D445 standard, ranging from 3 to 4 mm ² · s ^-1 , comprising more than 50% by weight of 9-methyl-1-octyl-henicosane, 1-decene trimer.

The respective proportions of polyalphaolefinic oils (b) and (c) within the lubricating composition according to the invention may vary. Preferably, the lubricating composition according to the invention comprises from 5 to 30%, preferably from 5 to 25%, by weight of the polyalphaolefinic oil composition (b). Also preferably, the lubricating composition according to the invention comprises from 5 to 70%, preferably from 30 to 70%, by weight of the polyalphaolefinic oil composition (c). The respective proportions of polyalphaolefinic oils (b) and (c) in the lubricant composition according to the invention may also vary according to the intended application for the lubricant composition according to the invention. Thus, for use as a gearbox lubricant, the lubricant composition according to the invention may comprise from 1 to 40% by weight of the polyalphaolefinic oil composition (b) and from 30 to 69% by weight of the composition of polyalphaolefinic oil (c).

In general, besides the monoester (a) and polyalphaolefinic oils (b) and (c), the lubricating composition according to the invention may comprise other oils as well as additives. The lubricating composition according to the invention may comprise any type of mineral lubricating base oil, synthetic or natural, animal or vegetable adapted to its use.

The base oils used in the lubricant compositions according to the invention may be oils of mineral or synthetic origins belonging to groups I to V according to the classes defined in the API classification (or their equivalents according to the ATIEL classification) (Table A) or their mixtures.

Content Content in Saturated Sulfur Viscosity Index (VI)

Group I

<90%> 0.03% 80 <VI <120 Mineral oils

Group II

> 90% <0.03% 80 <VI <120 Hydrocracked oils Group III

Hydrocracked oils> 90% <0,03%> 120 or hydro-isomerized

Group IV polyalphaolefins (PAO) esters and other bases not included in groups 1

Group V

at IV

Table A

The mineral base oils useful according to the invention include all types of bases obtained by atmospheric and vacuum distillation of crude oil, followed by refining operations such as solvent extraction, desalphating, solvent dewaxing, hydrotreatment, hydrocracking, hydroisomerization and hydrofinishing. Mixtures of synthetic and mineral oils can also be used.

There is generally no limitation on the use of different lubricating bases to make the lubricating compositions according to the invention, except that they must have properties, in particular viscosity, viscosity index, sulfur content. , oxidation resistance, suitable for use for engines or for vehicle transmissions.

The base oils of the lubricating compositions according to the invention may also be chosen from synthetic oils, such as certain carboxylic acid esters and alcohols, as well as from polyalphaolefins. The other polyalphaolefins used as base oils are, for example, obtained from monomers comprising from 4 to 32 carbon atoms, for example from octene or decene, and whose viscosity at 100 ° C. is between 1 and 5. and 15 mm ² . s ^"1 according to ASTM D445. Their weight average molecular weight is generally between 250 and 3000 Da according to ASTM D5296.

Advantageously, the lubricant composition according to the invention comprises at least 50% by weight of base oils relative to the total mass of the composition. More advantageously, the lubricating composition according to the invention comprises at least 60% by weight, or even at least 70% by weight, of base oils relative to the total mass of the composition. Also advantageously, the lubricating composition according to the invention comprises from 75 to 99.9% by weight of base oils relative to the total mass of the composition. Many additives can be used for the lubricant composition according to the invention. The preferred additives for the lubricant composition according to the invention are chosen from detergent additives, anti-wear additives, friction modifying additives, extreme pressure additives, dispersants, pour point improvers, anti-wear agents and anti-wear agents. foam, thickeners and mixtures thereof.

Preferably, the lubricant composition according to the invention comprises at least one pour point depressant additive or PPD agent (depressant point or pour point reducing agent). By slowing down the formation of paraffin crystals, the pour point reducing agents generally improve the cold behavior of the lubricant composition according to the invention. Examples of pour point reducing agents include alkyl polymethacrylates, polyacrylates, polyarylamides, polyalkylphenols, polyalkylnaphthalenes, alkylated polystyrenes. The lubricant composition according to the invention may also comprise at least one anti-wear additive, at least one extreme pressure additive or their mixtures.

Anti-wear additives and extreme pressure additives protect friction surfaces by forming a protective film adsorbed on these surfaces. There is a wide variety of anti-wear additives. In a preferred manner for the lubricating composition according to the invention, the anti-wear additives are chosen from phosphosulfur additives such as metal alkylthiophosphates, in particular zinc alkylthiophosphates, and more specifically zinc dialkyldithiophosphates or ZnDTPs. The preferred compounds have the formula Zn ((SP (S) (OR ³ ) (OR ⁴ )) ₂ , in which R ³ and R ⁴ , which may be identical or different, independently represent an alkyl group, preferably an alkyl group containing from 1 to 18 carbon atoms Amine phosphates are also anti-wear additives which can be used in the lubricating composition according to the invention However, the phosphorus provided by these additives can act as a poison for the catalytic systems of automobiles because these additives These effects can be minimized by partially substituting the amine phosphates with additives which do not add phosphorus, such as, for example, polysulfides, especially sulfur-containing olefins, and advantageously the lubricating composition according to the invention. the invention 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. mass relative to the total mass of lubricating composition, antiwear additives and extreme pressure additives.

Advantageously, the lubricant composition according to the invention may comprise at least one friction-modifying additive. The friction modifying additive may be chosen from a compound providing metal elements and an ash-free compound. Among the compounds providing metal elements, mention may be made of transition metal complexes such as Mo, Sb, Sn, Fe, Cu and Zn, the ligands of which may be hydrocarbon compounds comprising oxygen, nitrogen, sulfur or phosphorus. The ashless friction modifier additives are generally of organic origin and may be selected from monoesters of fatty acids and polyols, alkoxylated amines, alkoxylated fatty amines, fatty epoxides, borate fatty epoxides; fatty amines or fatty acid glycerol esters. According to the invention, the fatty compounds comprise at least one hydrocarbon group comprising from 10 to 24 carbon atoms. Advantageously, the lubricant composition according to the invention may comprise from 0.01 to 2% by weight or from 0.01 to 5% by weight, preferably from 0.1 to 1.5% by weight or 0.1 at 2% by weight relative to the total mass of the lubricant composition, friction modifier additive.

Advantageously, the lubricant composition according to the invention may comprise at least one antioxidant additive. The antioxidant additive generally serves to retard the degradation of the lubricating 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 lubricant composition. Antioxidant additives act in particular as radical inhibitors or destroyers of hydroperoxides. Among the antioxidant additives commonly used, mention may be made of antioxidant additives of phenolic type, antioxidant additives of amine type, antioxidant phosphosulfur additives. Some of these antioxidant additives, for example phosphosulfur antioxidant additives, can be ash generators. Phenolic antioxidant additives may be ash-free or may be in the form of neutral or basic metal salts. The antioxidant additives may especially be chosen from sterically hindered phenols, sterically hindered phenol esters and sterically hindered phenols comprising a thioether bridge, diphenylamines, diphenylamines substituted with at least one alkyl group and CrC ₁₂ , Ν, Ν'-dialkyl-aryl diamines and mixtures thereof. Preferably, according to the invention, the sterically hindered phenols are chosen from compounds comprising a phenol group in which at least one vicinal carbon of the carbon bearing the alcohol function is substituted with at least one alkyl group containing ₁₀ carbon atoms, preferably an alkyl group containing CrC ₆ , preferably a C ₄ alkyl group, preferably by the ter-butyl group. Amino compounds are another class of antioxidant additives that can be used, optionally in combination with phenolic antioxidant additives. Examples of amine compounds are aromatic amines, for example aromatic amines of formula NR ⁵ R ⁶ R ⁷ in which R ⁵ represents an optionally substituted aliphatic or aromatic group, 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 may also be used as antioxidant additives. Another class of antioxidant additives is copper compounds, for example copper thio- or dithio-phosphates, copper and carboxylic acid salts, dithiocarbamates, sulphonates, phenates, copper acetylacetonates. Copper salts I and II, succinic acid or anhydride salts can also be used. The lubricant composition according to the invention may contain all types of antioxidant additives known to those skilled in the art. Advantageously, the lubricating composition comprises at least one ash-free antioxidant additive. Also advantageously, the lubricating composition according to the invention comprises from 0.5 to 2% by weight relative to the total weight of the composition, of at least one antioxidant additive.

The lubricant composition according to the invention may also comprise at least one detergent additive. The detergent additives generally make it possible to reduce the formation of deposits on the surface of the metal parts by dissolving the secondary oxidation and combustion products. The detergent additives that can be used in the lubricant composition according to the invention are generally known to those skilled in the art. The detergent additives may be anionic compounds comprising a long lipophilic hydrocarbon chain and a hydrophilic head. The associated cation may be a metal cation of an alkali metal or alkaline earth metal. The detergent additives are preferentially chosen from alkali metal or alkaline earth metal salts of carboxylic acids, sulphonates, salicylates, naphthenates, as well as phenate salts. The alkali and alkaline earth metals are preferably calcium, magnesium, sodium or barium. These metal salts generally comprise the metal in stoichiometric amount or in excess, therefore in an amount greater than the stoichiometric amount. It is then overbased detergent additives; the excess metal bringing the overbased character to the detergent additive is then generally in the form of an oil insoluble metal salt, for example a carbonate, a hydroxide, an oxalate, an acetate, a glutamate, preferably a carbonate . Advantageously, the lubricant composition according to the invention may comprise from 2 to 4% by weight of detergent additive relative to the total mass of the lubricating composition.

Advantageously, the lubricant composition according to the invention may also comprise at least one dispersing agent. The dispersing agent may be chosen from Mannich bases, succinimides and their derivatives. Also advantageously, the lubricating composition according to the invention may comprise from 0.2 to 10% by weight of dispersing agent relative to the total mass of the lubricating composition.

Advantageously, the lubricating composition may also comprise at least one viscosity index improving polymer. Examples of viscosity index improver polymers include polymeric esters, homopolymers or copolymers, hydrogenated or non-hydrogenated, of styrene, butadiene and isoprene, polymethacrylates (PMA). Also advantageously, the lubricating composition according to the invention may comprise from 1 to 15% by weight relative to the total weight of the viscosity index improving lubricant composition.

The invention also relates to the use as a lubricant of the lubricating composition according to the invention. Preferably, the lubricant composition according to the invention is useful for lubricating a gear system, in particular a vehicle transmission, in particular a bridge or a gearbox.

The composition according to the invention is also advantageously used to reduce the fuel consumption of an engine, in particular a vehicle engine. Preferably, the composition according to the invention is used to reduce the fuel consumption of a vehicle equipped with a transmission, in particular a bridge or a gearbox, lubricated with this composition. The invention also relates to the use of at least one lubricant composition according to the invention for reducing the traction coefficient of a transmission oil, preferably for reducing the traction coefficient of a gearbox oil. in particular a gearbox of a vehicle.

The invention also relates to the use for decreasing the tensile coefficient of a lubricating composition comprising at least one heavy PAO (b) and at least one light PAO (c) and at least 30% by weight of composition of a monoester (a) of formula (I) defined according to the invention.

The uses of the lubricant composition according to the invention comprise contacting at least one element of the transmission, in particular the gearbox or the bridge, with a lubricant composition according to the invention.

By analogy, the particular, advantageous or preferred characteristics of the lubricating composition according to the invention, as well as the monoester (a) and the polyalphaolefinic oils (b) and (c), define particular, advantageous or preferred uses according to the invention. . The various aspects of the invention will be the subject of the following examples. They are provided for illustration.

Example 1 Preparation of Lubricating Compositions According to the Invention

Decyl oleate (Stéarinerie Dubois) was mixed with a heavy PAO (Spectrasyn mPAO150 product from Exxon - KV100 of about 150 mm ² sec ^-1 ), a first light PAO (Spectrasyn 6 product from Exxon - KV100 of about 6 mm ² .s ^"1 ) and a second light PAO (Spectrasyn 8 product of the company Exxon - KV100 about 8 mm ² .s ^{" 1} ).

In a similar manner, a second composition according to the invention is prepared in which the decyl oleate is replaced by butyl stearate (Stéarinerie Dubois). The respective amounts of the various constituents are presented in Table 1 and are expressed in weight% relative to the weight of the final composition. The viscosity index (Viscosity Index in English or VI) is measured according to the ASTM D2270 standard. Composition (1) according to Composition (2) according to the invention (%) the invention (%) decyl oleate 30 0

butyl stearate 0 30

Heavy PAO (b) 8 10

Light PAO (d) (Spectrasyn 6) 30 4

Light PAO (c2) (Spectrasyn 8) 32 56

Viscosity index (VI) 174 176

Table 1

Comparative Example 1: Preparation of Comparative Lubricating Compositions

In a similar manner to Example 1, 3 comparative lubricating compositions are prepared by replacing the decyl oleate respectively with methyl oleate (Stéarinerie Dubois), methyl stearate (Stéarinerie Dubois) and isononanoate. isononyl (Stéarinerie Dubois). The respective amounts of the various constituents are presented in Table 2 and are expressed in weight% relative to the weight of the final composition.

Table 2

Example 2 Comparison of the Traction Coefficient of the Compositions According to the Invention and Comparative Lubricating Compositions

The tensile coefficient of the lubricating compositions prepared is evaluated and the results obtained are shown in Table 3. £ i

o o .2 .≥

O ≡ O ≡ 6 8

tensile coefficient (MTM:

T = 40 ° C, V _e = 1 m. ^"1 , 0.034 0.033 0.048

SRR = 20% load = 75 N)

Table 3

The lubricating compositions according to the invention have a better coefficient of traction than the comparative lubricating compositions.

l ^it seon ^D m ^p os

i ^{t i} eno ^r v

Example 3 Comparison of the Oxidation Resistance Properties of the Composition

l ^it seon ^D m ^p os

lubricant (1) according to the invention and the comparative lubricating composition (1)

i ^{t i} eno ^r v

Oxidation resistance properties of the prepared lubricating compositions are ^t ^D i m ^p os

assessed according to the CEC-L48-A-00 A method and results are presented in Table 4. More variation KV 100 (KV R 100) e ^t m ^p a ^r ⁱ st important, the lower the resistance to oxidation. The greater the variation of KV 40 (R KV 40), the lower the resistance to oxidation.

The greater the variation of TAN (Total Acid Number in English, R TAN), the lower the resistance to oxidation. The higher the PAI (Peak Area Increase in English), the lower the resistance to oxidation.

Lubricating composition (1) Lubricating composition according to the comparative invention (1)

Duration (h) 192,192

KV 100 initial (mm .s ^{~ 1} ) 6.68 6.79

KV 100 final (mm ² .s ^{~ 1} ) 7.88 1 1, 08

R KV 100 (%) 18.01 63.18

KV 40 initial (mm .s ^{~ 1} ) 31, 13 30.44

KV 40 initial (mm .s ^{~ 1} ) 37.79 60.15

R KV 40 (%) 21, 39 97.60

Insoluble compounds 0 4 cm at the bottom

Initial TAN 1, 87 1, 46 Final TAN 3.48 4.12

R TAN (%) 1, 6 2.7

PAI <20 34

Table 4

The lubricating composition according to the invention has an oxidation resistance which is greater than that of the comparative lubricating composition. No deposit of insoluble compounds occurs with the lubricating composition according to the invention.

These results also show that the lubricant compositions according to the invention retain a high viscosity index and are therefore compatible with applications as transmission lubricants or motor lubricants.

Claims

1. Lubricating composition comprising

in which

2. Lubricating composition according to claim 1 comprising from 30 to 70% by weight of the composition, preferably from 30 to 60% by weight, preferably from 30 to 50% by weight of the monoester composition of formula (I).

3. Lubricating composition according to one of claims 1 and 2 wherein R ¹ is a saturated group and R ² is an unsaturated group.

4. Lubricating composition according to one of claims 1 and 2 wherein R ¹ is an unsaturated group and R ² is a saturated group.

5. Lubricating composition according to one of claims 1 and 2 wherein R ¹ and R ² are saturated groups.

6. Lubricating composition according to one of claims 1 and 2 wherein R ¹ and R ² are unsaturated groups.

7. Lubricating composition according to one of claims 1 to 6 for which ^■ R ¹ represents a hydrocarbon group, saturated or unsaturated, linear or branched, comprising from 14 to 20 carbon atoms, preferably 14 to 1 8 carbon atoms, more preferably 16 to 1 8 carbon atoms; or

^■ R ² represents a hydrocarbon group, saturated or unsaturated, linear or branched, comprising from 3 to 14 carbon atoms, preferably from 4 à 1 2 carbon atoms, more preferably from 4 A 1 0 carbon atoms; or

^■ R ¹ is a linear group and R ² is a branched group; or

^■ R ¹ is a branched group and R ² is a linear array; or

^■ R ¹ and R ² are linear arrays; or

^■ R ¹ and R ² are branched groups.

8. Lubricating composition according to one of claims 1 to 7 for which only R ¹ , only R ² or R ¹ and R ² are chosen from

^■ a linear saturated group;

^■ a branched saturated group containing from 1 to 5 branching chains;

9. Lubricating composition according to one of claims 1 to 8 for which the monoester is selected from

^■ stearates, preferably alkyl stearates and stearates alkenyl, more preferably stearates C ₄ -C _{1 0} alkyl, particularly butyl stearate, pentyl stearate, hexyl stearate, heptyl stearate, octyl stearate, nonyl stearate, decyl stearate;

^■ oleates, preferably alkyl oleates and alkenyl oleates, more preferably oleates of C ₄ -Ci ₀ alkyl, especially oleate, butyl oleate, pentyl oleate hexyl, heptyl oleate, octyl oleate, nonyl oleate, decyl oleate.

10. Lubricating composition according to one of claims 1 to 8 wherein the monoester is selected from alkenes monoesters and alkyl monoesters, preferably C ₂ -C ₁₀ monoesters-alkyl.

1 1. Lubricating composition according to one of claims 1 to 10 for which the kinematic viscosity of the polyalphaolefinic oil (b), measured at 100 ° C according to ASTM D445, ranges from 40 to 1500 mm ² .s ^"1 , of preferably from 40 to 300 mm ² .s ^-1 .

12. Lubricating composition according to one of claims 1 to 1 1 wherein the weight average molecular weight of the polyalphaolefinic oil (b) is greater than

2500 Da, preferably from 2500 to 80 000 Da, preferably from 4000 to 50 000 Da.

13. Lubricating composition according to one of claims 1 to 12 for which the kinematic viscosity of the polyalphaolefinic oil (c), measured at 100 ° C according to ASTM standard

D445 is from 1.5 to 10 mm ² .s ^-1 , preferably from 1.5 to 6 mm ² .s ^-1 , preferably from 2 to 8 mm ² . s ^"1 .

14. Lubricating composition according to one of claims 1 to 13 wherein the weight average molecular weight of the polyalphaolefinic oil (c) is less than 500 Da, preferably from 50 to 500 Da, preferably from 50 to 500 Da 350 Da is preferably from 50 to 300 Da.

15. Lubricating composition according to one of claims 1 to 14 comprising from 5 to 30% by weight, preferably from 5 to 25% by weight, of the polyalphaolefinic oil composition (b).

16. Lubricating composition according to one of claims 1 to 15 comprising from 5 to 70% by weight, preferably from 30 to 70% by weight, of the polyalphaolefinic oil composition (c).

17. Lubricating composition according to one of claims 1 to 16 comprising

^■ one, two or three monoesters (a); or

^■ one, two or three polyalphaolefinic oils (b); or

■ one, two or three polyalphaolefinic oils (c); or comprising a single monoester (a), a single polyalphaolefinic oil (b) and a single polyalphaolefinic oil (c).

18. Lubricating composition according to one of claims 1 to 17 also comprising at least one additive, preferably a PPD agent (for depressant point or pour point reducing agent).

19. Use of at least one lubricant composition according to one of claims 1 to 18 for lubricating a gear system, in particular a vehicle transmission, in particular a bridge or a gearbox.

20. Use of at least one lubricant composition according to one of claims 1 to 18 for reducing the fuel consumption of an engine, in particular a vehicle engine.

21. Use of at least one lubricant composition according to one of Claims 1 to 18 for reducing the fuel consumption of a vehicle equipped with a transmission, in particular a gearbox or transmission, lubricated by means of this composition.

22. Use of at least one lubricant composition according to one of claims 1 to 18 for reducing the traction coefficient of a transmission oil, in particular of a gearbox oil, in particular a gearbox. a vehicle.

23. Use for reducing the tensile coefficient of a lubricating composition comprising at least one heavy PAO (b) and at least one light PAO (c) and at least 30% by weight of composition of a monoester (a) of formula (I) defined according to one of claims 1 to 18.