EP3662041B1 - Lubricating composition comprising a diester - Google Patents

Description

The present invention relates to the field of lubricating compositions for engines, in particular for motor vehicle engines. It aims in particular to propose a lubricating composition endowed with improved performance, in particular in terms of improved engine cleanliness and reduced fuel consumption.

Lubricating compositions, also called “lubricants”, are commonly used in engines for the main purposes of reducing the friction forces between the various moving metal parts in the engines. 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 with 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. For example, detergent additives are very often considered in order to avoid the formation of deposits on the surface of metal parts by dissolving secondary products of oxidation and combustion.

For obvious reasons, improving the performance of lubricants is a constant concern. In particular, to meet growing environmental requirements, there is an increasing effort to reduce the fuel consumption of vehicles.

As such, it is known that lubricating compositions represent an effective means for acting on fuel consumption via their impact on the friction forces generated between the various parts of an engine. It is known in particular that the quality of the base oils, alone or in combination with viscosity index improving polymers and friction modifier additives, is particularly decisive for obtaining a gain in fuel consumption.

Thus lubricating compositions, called "Fuel-Eco" (FE) (for "fuel economy" in Anglo-Saxon terminology), have already been developed. The more or less fluid grade of the base oil is particularly decisive for access to such "Fuel-Eco" lubricants.

Furthermore, some monoesters used in lubricants are solid at room temperature, which poses problems of cold pumpability of the lubricants and, moreover, such lubricants do not meet the SAEJ300 criteria.

We also know, from the patent application EP 2 913 386 , a lubricating composition comprising from 50 to 97% by weight of a base oil and from 3 to 50% by weight of 2-ethylhexyl sebacate having Fuel-Eco properties.

As far as engine failures are concerned, they are most often the result of engine fouling. It is in fact desirable to have lubricating compositions allowing an improvement in engine cleanliness.

The invention specifically aims to provide a lubricating composition, in particular dedicated to a vehicle engine, which combines both improved properties in terms of fuel economy and engine cleanliness.

Against all expectations, the inventors have discovered that it is possible to obtain lubricating compositions, the effectiveness of which is increased in terms of gain in engine cleanliness, subject to considering therein the implementation of a specific diester , and which have performances in terms of fuel consumption savings that are equivalent to, or even superior to, those of so-called “Fuel-Eco” lubricating compositions.

• R représentent, indépendamment les uns des autres, un atome d'hydrogène ou un groupe (C₁-C₅)alkyle, linéaire ou ramifié, en particulier un groupe méthyle, éthyle ou propyle, notamment méthyle ;
• s vaut 1, 2, 3, 4, 5 ou 6 ;
• n vaut 1, 2 ou 3 ; étant entendu que, lorsque s est différent de 1, n peuvent être identiques ou différents ; et
• R^a et R^b, identiques ou différents, représentent indépendamment les uns des autres, des groupements hydrocarbonés, saturés ou insaturés, linéaires ou ramifiés, présentant un enchaînement linéaire de 6 à 18 atomes de carbone ;

sous réserve que, lorsque s vaut 2 et n, identiques, valent 2, au moins l'un des groupe R représente un groupe (C₁-C₅)alkyle, linéaire ou ramifié ; et
sous réserve que, lorsque s vaut 1 et n vaut 3, au moins l'un des groupes R lié au carbone en position bêta des atomes d'oxygène des fonctions esters représente un atome d'hydrogène ; ladite composition lubrifiante comprenant de 5 à 30 % en poids de diester(s) de formule (I) par rapport au poids total de la composition.The present invention thus relates, according to a first of its aspects, to a lubricating composition of grade according to the SAEJ300 classification defined by the formula (X)W(Y), in which X represents 0 or 5; and Y represents an integer ranging from 4 to 20, said composition comprising at least one diester of formula (I):

R ^a -C(O)-O-([C(R) ₂ ] _n -O) _s -C(O)-R ^b (I)

in which :

• R represent, independently of each other, a hydrogen atom or a (C ₁ -C ₅ )alkyl group, linear or branched, in particular a methyl, ethyl or propyl group, in particular methyl;
• s is 1, 2, 3, 4, 5 or 6;
• n is 1, 2 or 3; it being understood that, when s is different from 1, n can be identical or different; and
• R ^a and R ^b , which are identical or different, represent independently of each other hydrocarbon groups, saturated or unsaturated, linear or branched, having a linear sequence of 6 to 18 carbon atoms;

provided that, when s equals 2 and n, which are identical, equals 2, at least one of the R groups represents a (C ₁ -C ₅ )alkyl group, linear or branched; and
provided that, when s is 1 and n is 3, at least one of the R groups linked to the carbon in the beta position of the oxygen atoms of the ester functions represents a hydrogen atom; said lubricating composition comprising from 5 to 30% by weight of diester(s) of formula (I) relative to the total weight of the composition.

Preferably, s is 1, 2 or 3, in particular s is 1 or 2.

Preferably, n is 2 or 3, in particular n is 2.

• R et R' représentent, indépendamment les uns des autres, un atome d'hydrogène ou un groupe (C₁-C₅)alkyle, linéaire ou ramifié, en particulier un groupe méthyle, éthyle ou propyle, notamment un groupe méthyle ;
• s vaut 1, 2 ou 3, en particulier s vaut 1 ou 2 ;
• n vaut 2 ;
• m vaut 2 ;
• R^a et R^b, identiques ou différents, représentent indépendamment les uns des autres, des groupements hydrocarbonés, saturés ou insaturés, linéaires ou ramifiés, présentant un enchaînement linéaire de 6 à 18 atomes de carbone ;

sous réserve que, lorsque s vaut 2, au moins l'un des groupes R ou R' représente un groupe (C₁-C₅)alkyle, linéaire ou ramifié.According to a particular embodiment, the diester of formula (I) according to the invention is a diester of the following formula (I'):

R ^a -C(O)-O-([C(R) ₂ ] _n -O)-([C(R') ₂ ] _m -O) _s-1 -C(O)-R ^b (I' )

in which :

• R and R′ represent, independently of each other, a hydrogen atom or a (C ₁ -C ₅ )alkyl group, linear or branched, in particular a methyl, ethyl or propyl group, in particular a methyl group;
• s is 1, 2 or 3, in particular s is 1 or 2;
• n is 2;
• m is 2;
• R ^a and R ^b , which are identical or different, represent independently of each other hydrocarbon groups, saturated or unsaturated, linear or branched, having a linear sequence of 6 to 18 carbon atoms;

provided that, when s is 2, at least one of the R or R' groups represents a (C ₁ -C ₅ )alkyl group, linear or branched.

Advantageously, at least one of the R or R' groups in the diester of formula (I') represents a (C ₁ -C ₅ )alkyl group, in particular (C ₁ -C ₄ )alkyl, linear or branched, plus preferentially methyl, ethyl or propyl; advantageously methyl.

The diesters of formula (I), in particular of formula (I′), are more precisely described in the remainder of the text.

Preferably, R ^a and R ^b in the aforementioned formulas (I) and (I') have a linear sequence of 7 to 14 carbon atoms, in particular of 8 to 12 carbon atoms. carbon, more particularly from 8 to 11 carbon atoms and in particular from 8 to 10 carbon atoms. In particular, R ^a and R ^b both represent n -octyl or n -dodecanoyl groups, preferably n -octyl.

The lubricating compositions, incorporating such a diester of formula (I), in particular of formula (I′) above, prove to be particularly effective for their use as a lubricant for an engine, in particular for a vehicle engine.

The present invention thus relates, according to another of its aspects, to the use of a composition as described above as a lubricant for an engine, in particular for a vehicle engine.

In particular, as emerges from the examples below, the inventors have observed that a lubricating composition of grade according to the SAEJ300 classification defined by the formula (X)W(Y), in which X represents 0 or 5; and Y represents an integer ranging from 4 to 20 and containing at least one diester in accordance with the invention manifests improved properties compared to those observed with lubricating compositions comprising mono-esters or di-esters other than those of the invention or tri-esters, both in terms of reducing fuel consumption (“Fuel-Eco” properties) and engine cleanliness.

Of course, the document GB 716 086 dated 1951 proposes to implement a diester in lubricating compositions. However, this use is considered in a very different context from that of the invention. First of all, the lubricating compositions considered in the patent GB 716 086 are not in accordance with those considered according to the invention and in particular intended for use in aircraft engines which are exposed to very large temperature variations. Synthetic esters are described there as being more advantageous than mineral oils insofar as they have high viscosity indices and flash points, and lower pour points than mineral oils of comparable viscosity.

In the context of the invention, the lubricating compositions considered are of a grade according to the SAEJ300 classification defined by the formula (X)W(Y), in which X represents 0 or 5; and Y represents an integer ranging from 4 to 20. This grade qualifies a selection of lubricating compositions specifically intended for a motor vehicle engine application and which notably satisfy quantified specificities with respect to different parameters such as cold viscosity at start-up, cold pumpability, kinematic viscosity at low shear rate and dynamic viscosity at high shear rate.

Advantageously, the implementation of a diester of formula (I) as defined above, and in particular of formula (I ') above, as an additive in a lubricating composition of grade considered according to the invention makes it possible to reduce the fuel consumption of an engine. In other words, the lubricating compositions of the invention meet the qualification of “Fuel-Eco”, in that they allow access to reduced fuel consumption.

Thus, according to another of its aspects, the invention also relates to the use of a diester of formula (I) as defined above, and in particular of formula (I') mentioned above, as an additive in a lubricating composition of grade according to the SAEJ300 classification defined by the formula (X)W(Y), in which X represents 0 or 5, and Y represents an integer ranging from 4 to 20, and dedicated to an engine, in particular a vehicle engine, to reduce engine fuel consumption.

Also, as illustrated in the examples which follow, the use of such a diester, having good detergency properties, in a lubricating composition according to the invention advantageously makes it possible to improve engine cleanliness.

Thus, the invention relates, according to yet another of its aspects, to the use of a diester of formula (I) as defined previously, and in particular of formula (I') mentioned above, as an additive in a lubricating composition of grade according to the SAEJ300 classification defined by the formula (X)W(Y), in which X represents 0 or 5, and Y represents an integer ranging from 4 to 20, and dedicated to an engine, in particular a vehicle engine , to improve engine cleanliness.

Other characteristics, variants and advantages of the lubricating compositions according to the invention will emerge better on reading the description and the examples which follow, given by way of non-limiting illustration of the invention.

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

Unless otherwise indicated, the expression "comprising a" must be understood as "comprising at least one".

DIESTER OF GENERAL FORMULA (I)

• R représentent, indépendamment les uns des autres, un atome d'hydrogène ou un groupe (C₁-C₅)alkyle, linéaire ou ramifié, en particulier un groupe méthyle, éthyle ou propyle, notamment méthyle ;
• s vaut 1, 2, 3, 4, 5 ou 6 ; en particulier s vaut 1, 2 ou 3 et plus particulièrement s vaut 1 ou 2 ;
• n vaut 1, 2 ou 3 ; en particulier n vaut 2 ou 3 et plus particulièrement n vaut 2, étant entendu que, lorsque s est différent de 1, n peuvent être identiques ou différents ; et
• R^a et R^b, identiques ou différents, représentent indépendamment les uns des autres, des groupements hydrocarbonés, saturés ou insaturés, linéaires ou ramifiés, présentant un enchaînement linéaire de 6 à 18 atomes de carbone ;

sous réserve que, lorsque s vaut 2 et n, identiques, valent 2, au moins l'un des groupe R représente un groupe (C₁-C₅)alkyle, linéaire ou ramifié ; et
sous réserve que, lorsque s vaut 1 et n vaut 3, au moins l'un des groupes R lié au carbone en position bêta des atomes d'oxygène des fonctions esters représente un atome d'hydrogène.As specified above, a lubricating composition according to the invention has the specificity of containing at least one diester of general formula (I)

R ^a -C(O)-O-([C(R) ₂ ] _n -O) _s -C(O)-R ^b (I)

in which :

• R represent, independently of each other, a hydrogen atom or a (C ₁ -C ₅ )alkyl group, linear or branched, in particular a methyl, ethyl or propyl group, in particular methyl;
• s is 1, 2, 3, 4, 5 or 6; in particular s is 1, 2 or 3 and more particularly s is 1 or 2;
• n is 1, 2 or 3; in particular n is 2 or 3 and more particularly n is 2, it being understood that, when s is different from 1, n can be identical or different; and
• R ^a and R ^b , which are identical or different, represent independently of each other hydrocarbon groups, saturated or unsaturated, linear or branched, having a linear sequence of 6 to 18 carbon atoms;

provided that, when s equals 2 and n, which are identical, equals 2, at least one of the R groups represents a (C ₁ -C ₅ )alkyl group, linear or branched; and
provided that, when s is 1 and n is 3, at least one of the R groups linked to the carbon in the beta position of the oxygen atoms of the ester functions represents a hydrogen atom.

In the rest of the text, a diester of formula (I) according to the invention will be designated more simply by diester of the invention.

• « C_t-z » où t et z sont des entiers, une chaîne carbonée pouvant avoir de t à z atomes de carbone ; par exemple C_1-4 une chaîne carbonée qui peut avoir de 1 à 4 atomes de carbone ;
• « alkyle », un groupe aliphatique saturé, linéaire ou ramifié ; par exemple un groupe C_1-4-alkyle représente une chaîne carbonée de 1 à 4 atomes de carbone, linéaire ou ramifiée, plus particulièrement un méthyle, éthyle, propyle, isopropyle, butyle, isobutyle, tert-butyle.

Preferably, in the context of the invention, the following terms mean:

• “C _tz ” where t and z are integers, a carbon chain that can have from t to z carbon atoms; for example C _1-4 a carbon chain which can have from 1 to 4 carbon atoms;
• "alkyl", a saturated, linear or branched aliphatic group; for example a C _1-4 -alkyl group represents a carbon chain of 1 to 4 carbon atoms, linear or branched, more particularly a methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert -butyl.

Preferably, in the aforementioned formula (I), when s is different from 1, all the n are identical.

In particular, n in the aforementioned formula (I) is 2 or 3, and more particularly n is 2.

Preferably, s in the aforementioned formula (I) is 1, 2 or 3, preferably s is 1 or 2.

Preferably, at least one of the R groups represents a (C ₁ -C ₅ )alkyl group, in particular (C ₁ -C ₄ )alkyl, linear or branched, more preferentially methyl, ethyl or propyl; advantageously methyl.

• R et R' représentent, indépendamment les uns des autres, un atome d'hydrogène ou un groupe (C₁-C₅)alkyle, linéaire ou ramifié, en particulier un groupe méthyle, éthyle ou propyle, notamment un groupe méthyle ;
• s vaut 1, 2 ou 3, en particulier s vaut 1 ou 2 ;
• n vaut 2 ;
• m vaut 2 ;
• R^a et R^b, identiques ou différents, représentent indépendamment les uns des autres, des groupements hydrocarbonés, saturés ou insaturés, linéaires ou ramifiés, présentant un enchaînement linéaire de 6 à 18 atomes de carbone ;

sous réserve que, lorsque s vaut 2, au moins l'un des groupes R ou R' représente un groupe (C₁-C₅)alkyle, linéaire ou ramifié.According to a particularly preferred embodiment, the diester of formula (I) according to the invention may more particularly be a diester of the following formula (I'):

R ^a -C(O)-O-([C(R) ₂ ] _n -O)-([C(R') ₂ ] _m -O) _s-1 -C(O)-R ^b (I' )

in which :

• R and R′ represent, independently of each other, a hydrogen atom or a (C ₁ -C ₅ )alkyl group, linear or branched, in particular a methyl, ethyl or propyl group, in particular a methyl group;
• s is 1, 2 or 3, in particular s is 1 or 2;
• n is 2;
• m is 2;
• R ^a and R ^b , which are identical or different, represent independently of each other hydrocarbon groups, saturated or unsaturated, linear or branched, having a linear sequence of 6 to 18 carbon atoms;

provided that, when s is 2, at least one of the R or R' groups represents a (C ₁ -C ₅ )alkyl group, linear or branched.

Preferably, a diester according to the invention is of formula (I') in which at least one of R or R' represents a (C ₁ -C ₅ )alkyl group, in particular (C ₁ -C ₄ )alkyl , linear or branched, more preferably methyl, ethyl or propyl; advantageously methyl.

• R et R' représentent, indépendamment les uns des autres, un atome d'hydrogène ou un groupe (C₁-C₅)alkyle, linéaire ou ramifié, en particulier un groupe méthyle, éthyle ou propyle, avantageusement méthyle ;
• n vaut 2 ;
• m vaut 2 ;
• R^a et R^b, identiques ou différents, représentent indépendamment les uns des autres, des groupements hydrocarbonés, saturés ou insaturés, linéaires ou ramifiés, présentant un enchaînement linéaire de 6 à 18 atomes de carbone ;

sous réserve qu'au moins l'un des groupes R ou R' représente un groupe (C₁-C₅)alkyle, linéaire ou ramifié, en particulier méthyle, éthyle ou propyle, avantageusement méthyle.According to a variant embodiment, s in the aforementioned formula (I) or (I') is equal to 2. In particular, the diester according to the invention may be of the following formula (I'a):

R ^a -C(O)-O-([C(R) ₂ ] _n -O)-([C(R') ₂ ] _m -O)-C(O)-R ^b (I'a)

in which :

• R and R′ represent, independently of each other, a hydrogen atom or a (C ₁ -C ₅ )alkyl group, linear or branched, in particular a methyl, ethyl or propyl group, advantageously methyl;
• n is 2;
• m is 2;
• R ^a and R ^b , which are identical or different, represent independently of each other hydrocarbon groups, saturated or unsaturated, linear or branched, having a linear sequence of 6 to 18 carbon atoms;

provided that at least one of the R or R' groups represents a (C ₁ -C ₅ )alkyl group, linear or branched, in particular methyl, ethyl or propyl, advantageously methyl.

Preferably, at least one of the R groups represents a (C ₁ -C ₅ )alkyl group, linear or branched, in particular a methyl, ethyl or propyl group, advantageously methyl; and at least one of R' represents a (C ₁ -C ₅ )alkyl group, linear or branched, in particular a methyl, ethyl or propyl group, advantageously methyl.

Even more preferably, the diester of the invention may be of formula (I'a) in which one of the R groups represents a (C ₁ -C ₅ )alkyl group, linear or branched, in particular a methyl, ethyl or propyl, advantageously methyl; and one of the R' groups represents a (C ₁ -C ₅ )alkyl group, linear or branched, in particular a methyl, ethyl or propyl group, advantageously methyl; the other groups R and R' representing hydrogen atoms.

• l'un des groupes R¹ et R² représente un groupe (C₁-C₅)alkyle, linéaire ou ramifié, l'autre représentant un atome d'hydrogène ;
• l'un des groupes R³ et R⁴ représente un groupe (C₁-C₅)alkyle, linéaire ou ramifié, l'autre représentant un atome d'hydrogène ; et
• R^a et R^b, identiques ou différents, sont tels que définis précédemment.

In other words, according to a particular embodiment, the diester of the invention may have the following formula (I"a):

R ^a -C(O)-O-CHR ¹ -CHR ² -O-CHR ³ -CHR ⁴ -OC(O)-R ^b (I"a)

in which :

• one of the R ¹ and R ² groups represents a (C ₁ -C ₅ )alkyl group, linear or branched, the other representing a hydrogen atom;
• one of the R ³ and R ⁴ groups represents a (C ₁ -C ₅ )alkyl group, linear or branched, the other representing a hydrogen atom; and
• R ^a and R ^b , identical or different, are as defined previously.

• l'un des groupes R¹ et R² représente un groupe méthyle, éthyle ou propyle, avantageusement méthyle, l'autre représentant un atome d'hydrogène ; et
• l'un des groupes R³ et R⁴ représente un groupe méthyle, éthyle ou propyle, avantageusement méthyle, l'autre représentant un atome d'hydrogène.

In particular, the diester of the invention may be of formula (I"a) in which:

• one of the R ¹ and R ² groups represents a methyl, ethyl or propyl group, advantageously methyl, the other representing a hydrogen atom; and
• one of the R ³ and R ⁴ groups represents a methyl, ethyl or propyl group, advantageously methyl, the other representing a hydrogen atom.

According to another embodiment variant, s in the aforementioned formula (I) or (I') is equal to 1.

• R représentent, indépendamment les uns des autres, un atome d'hydrogène ou un groupe (C₁-C₅)alkyle, linéaire ou ramifié, en particulier un groupe méthyle, éthyle ou propyle, avantageusement méthyle ;
• n vaut 2 ;
• R^a et R^b, identiques ou différents, représentent indépendamment les uns des autres, des groupements hydrocarbonés, saturés ou insaturés, linéaires ou ramifiés, présentant un enchaînement linéaire de 6 à 18 atomes de carbone.

In other words, the diester according to the invention may have the following formula (I'b):

R ^a -C(O)-O-([C(R) ₂ ] _n -O)-C(O)-R ^b (I'b)

in which :

• R represent, independently of each other, a hydrogen atom or a (C ₁ -C ₅ )alkyl group, linear or branched, in particular a methyl, ethyl or propyl group, advantageously methyl;
• n is 2;
• R ^a and R ^b , which are identical or different, represent independently of each other hydrocarbon groups, saturated or unsaturated, linear or branched, having a linear chain of 6 to 18 carbon atoms.

Preferably, in the aforementioned formula (I'b), at least one of the R represents a (C ₁ -C ₅ )alkyl group, linear or branched, in particular a methyl, ethyl or propyl group, advantageously methyl.

In particular, the diester of the invention may be of formula (I'b) in which one of the R groups represents a (C ₁ -C ₅ )alkyl group, linear or branched, in particular a methyl, ethyl or propyl group, advantageously methyl, the others representing hydrogen atoms.

According to yet another embodiment variant, the diester of the invention may be of formula (I) in which s is equal to 3.

Preferably, in the context of this variant embodiment, n, which are identical, are equal to 2. Preferably, for each of the -([C(R) ₂ ] _n -O)- groups, one of the R represents a group ( C ₁ -C ₅ )alkyl, linear or branched, in particular methyl, ethyl or propyl, advantageously methyl, the others representing hydrogen atoms.

As indicated previously, R ^a and R ^b in formula (I), (I'), (I'a), (I"a) and (I'b) above, identical or different, represent hydrocarbon groups, saturated or unsaturated, linear or branched, having a linear sequence of 6 to 18 carbon atoms.

The term "hydrocarbon" group means any group having a carbon atom directly attached to the rest of the molecule and having mainly an aliphatic hydrocarbon character.

Preferably, R ^a and R ^b have a linear sequence of 7 to 17 carbon atoms, in particular of 7 to 14 carbon atoms, in particular of 8 to 12 carbon atoms and more particularly of 8 to 11 carbon atoms, in particular 8 to 10 carbon atoms.

By “linear sequence of t to z carbon atoms”, is meant a saturated or unsaturated carbon chain, preferably saturated, comprising from t to z carbon atoms one after the other, the carbon atoms possibly present at the level ramifications of the carbon chain not being taken into account in the number of carbon atoms (t-z) constituting the linear sequence.

According to a particular embodiment, in the aforementioned formula (I), (I'), (I'a), (I"a) or (I'b), R ^a and R ^b , which are identical or different, are derived of vegetable, animal or petroleum origin.

According to a particular embodiment, in the aforementioned formula (I), (I'), (I'a), (I"a) or (I'b), R ^a and R ^b , which are identical or different, represent saturated groups.

According to another particularly preferred embodiment, in the aforementioned formula (I), (I'), (I'a), (I"a) or (I'b), R ^a and R ^b , identical or different, represent linear groupings.

In particular, R ^a and R ^b represent saturated linear hydrocarbon groups of C ₆ to C ₁₈ , in particular of C ₇ to C ₁₇ , in particular of C ₇ to C ₁₄ , preferably of C ₈ to C ₁₂ and more preferably of C ₈ to C ₁₁ , in particular C ₈ to C ₁₀ .

According to another particularly preferred embodiment, in the aforementioned formula (I), (I'), (I'a), (I"a) or (I'b), R ^a and R ^b represent linear alkyl groups C ₆ to C ₁₈ , in particular C ₇ to C ₁₇ , especially C ₇ to C ₁₄ , preferably C ₈ to C ₁₂ and more preferably C ₈ to C ₁₁ , especially C ₈ to C ₁₀ .

In particular, R ^a and R ^b are identical.

Preferably, R ^a and R ^b both represent n -octyl or n -undecyl groups, preferably n -octyl.

The diesters of formula (I) according to the invention may be commercially available or prepared according to synthetic methods described in the literature and known to those skilled in the art. These synthesis methods more particularly implement an esterification reaction between a diol compound of formula HO-([C(R) ₂ ] _n -O) _s -OH and compounds of formula R ^a -COOH and R ^b - COOH, with R ^a and R ^b , identical or different, being as defined previously.

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

By way of examples, diesters of formula (I) above, in particular of formula (I') above, can be obtained by esterification reaction between a mono- or poly-propylene glycol, in particular monopropylene glycol (MPG ) or dipropylene glycol (DPG), and one or more suitable R ^a -COOH and R ^b -COOH carboxylic acids.

• s vaut 2,
• l'un des groupes R représentant un groupe (C₁-C₅)alkyle, linéaire ou ramifié, en particulier un groupe méthyle, éthyle ou propyle, avantageusement méthyle, les autres représentant des atomes d'hydrogène ; et
• l'un des groupes R' représentant un groupe (C₁-C₅)alkyle, linéaire ou ramifié, en particulier un groupe méthyle, éthyle ou propyle, avantageusement méthyle, les autres représentant des atomes d'hydrogène,

peut être obtenu via une réaction d'estérification entre le dipropylène glycol (DPG) et un ou plusieurs acides carboxyliques R^a-COOH et R^b-COOH adéquats.By way of example, a diester or mixture of diesters of formula (I') as defined above, where:

• s is 2,
• one of the R groups representing a (C ₁ -C ₅ )alkyl group, linear or branched, in particular a methyl, ethyl or propyl group, advantageously methyl, the others representing hydrogen atoms; and
• one of the groups R' representing a (C ₁ -C ₅ )alkyl group, linear or branched, in particular a methyl, ethyl or propyl group, advantageously methyl, the others representing hydrogen atoms,

can be obtained via an esterification reaction between dipropylene glycol (DPG) and one or more suitable R ^a -COOH and R ^b -COOH carboxylic acids.

• s vaut 1,
• l'un des groupes R représentant un groupe (C₁-C₅)alkyle, linéaire ou ramifié, en particulier un groupe méthyle, éthyle ou propyle, avantageusement méthyle, les autres représentant des atomes d'hydrogène,

peut être obtenu via une réaction d'estérification entre le monopropylène glycol (MPG) et un ou plusieurs acides carboxyliques R^a-COOH et R^b-COOH adéquats.A diester of formula (I') as defined above, where

• s is 1,
• one of the R groups representing a (C ₁ -C ₅ )alkyl group, linear or branched, in particular a methyl, ethyl or propyl group, advantageously methyl, the others representing hydrogen atoms,

can be obtained via an esterification reaction between monopropylene glycol (MPG) and one or more suitable R ^a -COOH and R ^b -COOH carboxylic acids.

In particular, in the case where R ^a and R ^b both represent n -octyl or n -undecyl groups, such a diester or mixture of diesters can thus be obtained by esterification reaction between monopropylene glycol or dipropylene glycol and nonanoic acid or undecanoic acid.

LUBRICANT COMPOSITION

The diesters of formula (I) can be mixed with one or more base oils, in particular as defined below, to form a ready-to-use lubricating composition. Alternatively, they can be added alone, or mixed with one or more other additives, as defined below, as additives intended to be added to a mixture of base oils to improve the properties of the lubricating composition.

It is understood that a diester of formula (I) in accordance with the invention can be used in a lubricating composition alone or in combination with one or more other diesters of formula (I).

Advantageously, a lubricating composition according to the invention may thus comprise a mixture of diesters of formula (I) formed at least 50% by mass of one or more diesters of formula (I) for which R ^a and R ^b represent groups C ₈ to C ₁₀ saturated linear hydrocarbons, in particular C _8-10 -alkyl groups.

According to a particular embodiment, a lubricating composition according to the invention comprises at least as diester of formula (I) in accordance with the invention, a diester or mixture of diesters resulting from the esterification reaction between monopropylene glycol ( MPG) or dipropylene glycol (DPG) and a C ₇ to C ₁₉ carboxylic acid, in particular between MPG or DPG and nonanoic or undecanoic acid.

Preferably, a lubricating composition according to the invention comprises at least as diester of formula (I) in accordance with the invention, a diester or mixture of diesters resulting from the esterification reaction between MPG or DPG and nonanoic acid.

The lubricating composition according to the invention comprises from 5 to 30% by weight of diester(s) of formula (I), in particular from 5 to 25% by weight, more particularly from 10 to 25% by weight, even more particularly from 10 to 20% by weight.

A lubricating composition according to the invention may comprise, in addition to one or more diesters of formula (I) as defined above, one or more base oils, as well as additives, in particular as defined in the following text.

Base oils

A lubricating composition according to the invention may also comprise one or more base oils.

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

The base oils used in the lubricating compositions according to the invention may in particular be oils of mineral or synthetic origin belonging to groups I to V according to the classes defined in the API classification (table A), or their equivalents according to the classification ATIEL, or mixtures thereof. <u>Table A</u> Saturates content Sulfur content Viscosity Index (VI) Group I Mineral oils < 90% > 0.03% 80 ≤ IV < 120 Group II Hydrocracked oils ≥ 90% ≤0.03% 80 ≤ IV < 120 Group III Hydrocracked or hydroisomerized oils ≥ 90% ≤0.03% ≥ 120 Group IV Polyalphaolefins (PAO) Group V Esters and other bases not included in groups I to IV

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

Synthetic base oils can be esters of carboxylic acids and alcohols or even polyalphaolefins. The polyalphaolefins used as base oils are for example obtained from monomers comprising 4 to 32 carbon atoms, for example from decene, octene or dodecene, and whose viscosity at 100° C. is between 1, 5 and 15 mm ² .s ^-1 according to the ASTM D445 standard. Their average molecular mass is generally between 250 and 3000 according to the ASTM D5296 standard.

Blends of synthetic and mineral oils can also be used.

There is generally no limitation as to the use of different lubricating bases to produce the lubricating compositions according to the invention, except that they must have properties, in particular of viscosity, viscosity index, sulfur content , oxidation resistance, suitable for use in vehicle engines. Good Of course, they must also not affect the properties provided by the oil or the diesters of general formula (I) with which they are combined.

Preferably, a lubricating composition according to the invention comprises a base oil chosen from group II, III and IV oils of the API classification.

In particular, a lubricating composition according to the invention may comprise at least one group III base oil.

A lubricating composition according to the invention may comprise at least 50% by weight of base oil(s) relative to its total weight, in particular at least 60% by weight of base oil(s), and more particularly between 60 and 99% by weight of base oil(s).

Preferably, the oil or oils of group III represent(s) at least 50% by weight, in particular at least 60% by weight, of the total weight of the base oils of the composition.

Additives

A lubricating composition according to the invention may also comprise all types of additives suitable for use in a lubricant for a vehicle engine, in particular for a motor vehicle.

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

A lubricating composition according to the invention may thus comprise one or more additives chosen from friction modifier additives, anti-wear additives, extreme pressure additives, detergent additives, antioxidant additives, viscosity index improvers ( VI), pour point depressants (PPDs), dispersing agents, antifoaming agents, thickeners, and mixtures thereof.

As regards the friction modifier additives, they can be chosen from compounds providing metallic elements and compounds free of ash.

Among the compounds providing metallic elements, mention may be made of complexes of transition metals such as Mo, Sb. Sn, Fe, Cu, Zn whose ligands can be hydrocarbon compounds comprising oxygen, nitrogen, sulfur or phosphorus atoms.

Ash-free 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, fats 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.

According to an advantageous variant, a lubricating composition according to the invention comprises at least one friction modifier additive, in particular based on molybdenum.

In particular, the molybdenum-based compounds can be chosen from molybdenum dithiocarbamates (Mo-DTC), molybdenum dithiophosphates (Mo-DTP), and mixtures thereof.

According to one particular embodiment, a lubricating composition according to the invention comprises at least one Mo-DTC compound and at least one Mo-DTP compound. A lubricating composition may in particular comprise a molybdenum content of between 1000 and 2500 ppm.

Advantageously, such a composition makes it possible to achieve additional fuel savings.

Advantageously, a lubricating composition according to the invention may comprise from 0.01 to 5% by weight, preferably 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, relative to the total weight of the lubricating composition, of friction modifier additives, advantageously including at least one molybdenum-based friction modifier additive.

As regards the anti-wear additives and the extreme pressure additives, they are more particularly dedicated to protecting the surfaces in friction by forming a protective film adsorbed on these surfaces. There are a wide variety of anti-wear additives.

Particularly suitable for the lubricating compositions according to the invention are the anti-wear additives chosen from polysulphide additives, sulphur-containing olefin additives or even phospho-sulphur additives such as metal alkylthiophosphates, in particular zinc alkylthiophosphates, and more specifically dialkyldithiophosphates zinc or ZnDTP. The preferred compounds are of formula Zn((SP(S)(OR)(OR')) ₂ , in which R and R', which are identical or different, independently represent an alkyl group, preferably comprising from 1 to 18 carbon atoms.

Advantageously, a lubricating composition according to 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, relative to the weight total of the composition, anti-wear additives and extreme pressure additives.

As regards the antioxidant additives, they are essentially dedicated to delaying the degradation of the lubricating composition in service. This degradation can in particular result in the formation of deposits, in the presence of sludge or in an increase in the viscosity of the lubricating composition. They act in particular as free radical inhibitors or hydroperoxide destroyers. Among the antioxidant additives commonly employed, mention may be made of antioxidants of the phenolic type, antioxidant additives of the amine type, phosphosulfur antioxidant additives. Some of these antioxidant additives, for example phosphosulfur antioxidant additives, can be ash generators. The 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 with at least one C ₁ -C ₁₂ alkyl group, N ,N'-dialkyl-aryl-diamines and mixtures thereof.

Preferably, the sterically hindered phenols are chosen from compounds comprising a phenol group including at least one carbon vicinal to the carbon carrying the alcohol function is substituted by at least one C ₁ -C ₁₀ alkyl group, preferably a C ₁ -C ₆ alkyl group, preferably a C ₄ alkyl group, preferably by the ter-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 optionally substituted aromatic group, R ⁶ represents an optionally substituted aromatic group, 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.

The lubricating 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, a lubricating composition according to the invention may comprise from 0.1 to 2% by weight, relative to the total weight of the composition, of at least one antioxidant additive.

As regards so-called detergent additives, they generally make it possible to reduce the formation of deposits on the surface of metal parts by dissolving the secondary products of oxidation and combustion.

The detergent additives which can be used in a lubricating composition according to the invention are generally known to those skilled in the art. Detergent additives can be anionic compounds comprising a long lipophilic hydrocarbon chain and a hydrophilic head. The associated cation can be a metal 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 metallic salts generally comprise the metal in a stoichiometric quantity or else in excess, therefore in a quantity greater than the stoichiometric quantity. These are then overbased detergent additives; the excess metal providing the overbased character to the detergent additive is then generally in the form of a metal salt insoluble in the base oil, for example a carbonate, a hydroxide, an oxalate, an acetate, a glutamate, preferentially a carbonate.

A lubricating composition according to the invention may comprise from 0.5 to 8%, preferably from 0.5 to 4% by weight, relative to the total weight of the lubricating composition, of detergent additive.

Advantageously, a lubricating composition according to the invention may comprise less than 4% by weight of detergent additive(s), in particular less than 2% by weight, in particular less than 1% by weight, or even be free of detergent additive.

As regards the pour point depressant additives (also called “PPD” agents for “Pour Point Depressant” in English), they make it possible, by slowing the formation of paraffin crystals, to improve the cold behavior of the lubricating composition according to the invention.

As examples of pour point reducing agents, mention may be made of polyalkyl methacrylates, polyacrylates, polyarylamides, polyalkylphenols, polyalkylnaphthalenes and alkylated polystyrenes.

As regards the dispersing agents, they ensure the maintenance in suspension and the evacuation of the insoluble solid contaminants constituted by the secondary oxidation products which are formed when the lubricating composition is in service. They can be chosen from Mannich bases, succinimides and their derivatives.

In particular, a lubricating composition according to the invention may comprise from 0.2 to 10% by weight of dispersing agent(s), relative to the total weight of the composition.

Viscosity index (VI) improvers, in particular viscosity index improver polymers, ensure good cold behavior and minimum viscosity at high temperature. Examples of viscosity index improving polymer include polymer esters, homopolymers or copolymers, hydrogenated or non-hydrogenated styrene, butadiene and isoprene, olefin homopolymers or copolymers, such as ethylene or propylene, polyacrylates and polymethacrylates (PMA).

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

The antifoam additives can be 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 antifoam additive(s), relative to the total weight of the lubricating composition.

APPLICATION

The lubricating compositions according to the invention find a particularly advantageous application as lubricants for an engine, in particular for a vehicle engine and more particularly for a light vehicle.

A lubricating composition according to the invention has a particularly advantageous viscosity grade.

The viscosity grade of a lubricating composition according to the invention can be chosen in particular from:
- a grade according to the SAEJ300 classification defined by formulas (II) or (III) 0W (Y) 5W (Y) (II) (III) in which Y represents an integer ranging from 4 to 20, in particular ranging from 4 to 16 or from 4 to 12; Where
- a grade according to the SAEJ300 classification defined by the formulas (IV) or (V° (X)W8 (X) W 12 (IV) (V) where X represents 0 or 5.

According to a particular embodiment, the grade according to the SAEJ300 classification of a lubricating composition according to the invention is chosen from 0W4, 0W8, 0W12, 0W16, 0W20, 5W4, 5W8, 5W12, 5W16 and 5W20.

In particular, a lubricating composition according to the invention may have a grade according to the SAEJ300 classification of 0W20 or 0W16.

Advantageously, the kinematic viscosity measured at 100° C. according to the ASTM D445 standard of a lubricating composition according to the invention is between 3 and 15 mm ² .s ^-1 , in particular between 3 and 13 mm ² .s ^{- 1} .

Advantageously, the viscosity measured at high temperature and high shear, HTHS (for “high temperature high-shear viscosity measurement”), measured at 150° C., is equal to or greater than 1.7 mPa.s, of preferably between 1.7 and 3.7 mPa.s, advantageously between 2.3 and 3.7 mPa.s.

The HTHS measurement is carried out at high shear (10 ⁶ s ^-1 ) and at 150° C. according to standardized methods CEC-L-36-A-90, ASTM D4683 and ASTMD4741.

Advantageously, a lubricating composition according to the invention has a Noak volatility, determined according to the ASTM D5800 standard, of less than or equal to 15%, in particular less than or equal to 14%.

As indicated previously, a lubricating composition according to the invention, in particular by the use of a diester of formula (I) according to the invention, advantageously makes it possible to combine both good properties in terms of reduction of consumption fuel and engine cleanliness.

The invention thus relates to the use of a diester of formula (I) according to the invention in a lubricating composition of grade according to the SAEJ300 classification defined by the formula (X)W(Y), in which X represents 0 or 5 , and Y represents an integer ranging from 4 to 20, in particular dedicated to an engine, in particular a vehicle engine.

Engine cleanliness is measured by rating the engine piston fouling at the end of an engine test using a lubricating composition to be tested, in particular with respect to a Group III base oil.

The invention will now be described by means of the following examples given of course by way of non-limiting illustration of the invention.

EXAMPLES

In the examples below, lubricating compositions according to the invention, and comparative compositions, for example comprising monoesters or diesters other than those of the invention, replacing a diester in accordance with the invention, were formulated with the following components listed in Table 1:
- The esters according to the invention and outside the invention were obtained by esterification reaction between a compound having at least two alcohol functions and at least two fatty acids, said acids possibly being identical or different.
- The esters outside the invention were also obtained by esterification reaction between a fatty acid having at least two carboxylic acid functions and at least two compounds having at least one alcohol function, said alcohols possibly being identical or different. <u>TABLE 1</u> Ester Alcohol Acid 1 Acid 2 KV 100°C ASTM D445-97 (mm ² /s) ester Diester 1 (excluding invention) Neopentyl glycol octanoic acid Decanoic acid 2.51 Diester 2 (excluding invention) 2-ethylhexanol sebacic acid × 3.20 Diester 3 (according to the invention) Dipropylene glycol nonanoic acid × 2.66 Diester 4 (according to the invention) Dipropylene glycol Dodecanoic acid × 3.91 Diester 5 (according to the invention) Monopropylene glycol Dodecanoic acid × 3.36 Diester 6 (excluding invention) Neopentyl glycol nonanoic acid × 2.57 Diester 7 (excluding invention) Neopentyl glycol Dodecanoic acid × 4.33

EXAMPLE 1 Physico-chemical characterization of the lubricating compositions according to the invention and comparisons

Tables 2 and 3 below show the details of the lubricating compositions according to the invention and of the comparative compositions as well as their physico-chemical characteristics.

• Huile de base 1 est une huile de base de groupe III (viscosité cinématique à 100°C mesurée selon la norme ASTM D-556 = 4,11 mm²/s) disponible commercialement par exemple auprès de la société SK sous le nom commercial « Yubase 4+ »,
• Huile de base 2 est une huile de base de groupe III (viscosité cinématique à 100°C mesurée selon la norme ASTM D-556 = 6 mm²/s) disponible commercialement par exemple auprès de la société SK sous le nom commercial « Yubase 6 »,
• Un paquet d'additifs 1 conventionnel comprenant un dispersant, des détergents, un anti-usure,
• Un paquet d'additifs 2 conventionnel,
• Un paquet d'additifs 3 conventionnel,
• Un paquet d'additifs 4 conventionnel,
• Un améliorant de l'indice de viscosité 1 qui est un polymère conventionnel de polyisoprène styrène hydrogéné disponible commercialement auprès de la société Infineum sous le nom commercial «SV^®»,
• Un améliorant de l'indice de viscosité 2 qui est un polymère conventionnel de polyisoprène styrène hydrogéné disponible commercialement auprès de la société Infineum sous le nom commercial «SV^®»,
• Un améliorant de l'indice de viscosité 3 qui est un polymère conventionnel de polyméthacrylate disponible commercialement auprès de la société Evonik sous le nom commercial «Viscoplex^®»,
• Un modificateur de frottement qui est un composé conventionnel d'organomolybdène disponible commercialement auprès de la société Adeka sous le nom commercial «Sakuralube^®»,
• Un additif abaisseur de point d'écoulement qui est un polymère conventionnel de polyméthacrylate disponible commercialement auprès de la société Evonik sous le nom commercial «Viscoplex^®»,
• Un additif anti-oxydant aminé disponible commercialement auprès de la société BASF sous le nom commercial «Irganox^®»

The lubricating compositions are obtained by simple mixing, at room temperature, of the following components:

• Base oil 1 is a group III base oil (kinematic viscosity at 100° C. measured according to the ASTM D-556 standard = 4.11 mm ² /s) commercially available, for example from the company SK under the trade name “ Yubase 4+”,
• Base oil 2 is a group III base oil (kinematic viscosity at 100° C. measured according to the ASTM D-556 standard = 6 mm ² /s) commercially available, for example from the company SK under the trade name “Yubase 6 »,
• A conventional additive package 1 including dispersant, detergents, anti-wear,
• A conventional 2 additive package,
• A conventional 3 additive package,
• A conventional 4 additive package,
• A viscosity index 1 improver which is a conventional polymer of hydrogenated polyisoprene styrene commercially available from Infineum under the trade name " ^SV® ",
• A viscosity index 2 improver which is a conventional polymer of hydrogenated polyisoprene styrene commercially available from Infineum under the trade name " ^SV® ",
• A viscosity index 3 improver which is a conventional polymethacrylate polymer commercially available from Evonik under the trade name " ^Viscoplex® ",
• A friction modifier which is a conventional organomolybdenum compound commercially available from Adeka under the trade name " ^Sakuralube® ",
• A pour point depressant additive which is a conventional polymethacrylate polymer commercially available from Evonik under the trade name " ^Viscoplex® ",
• An amine antioxidant additive commercially available from BASF under the trade name “Irganox ^® ”

In Table 2, the component contents for each lubricating composition are indicated in percentages by weight relative to the total weight of the lubricating composition.

The properties of the lubricating compositions thus prepared are collated in Table 3 below. <u>TABLE 2</u> CC1 CC2 CC3 C1 CC4 C2 C3 CC5 CC6 C4 CC7 CC8 C5 Base oil 1 82.6 66.9 66.9 66.9 80.9 64.4 64.9 66.4 66.4 56.7 57.1 64.0 48.8 Base oil 2 × × × × × × × × × × × 15.0 15 Additive package 1 9.4 9.4 9.4 9.4 × × × × × × × × × Additive package 2 × × × × 10 10 10 10 10 × × × × Additive package 3 × × × × × × × × × 21.8 21.8 × × Additive package 4 × × × × × × × × × × × 14.8 14.8 Viscosity Index Improver 1 6.8 7.5 7.5 7.5 × × × × × × × 2.0 2.2 Viscosity Index Improver 2 × × × × 8.5 10 9.5 8 8 × × × × Viscosity Index Improver 3 × × × × × × × × × 6.0 6.61 3.5 3.5 Friction modifier 0.5 0.5 0.5 0.5 0.6 0.6 0.6 0.6 0.6 × × 0.5 0.5 Pour point depressant 0.2 0.2 0.2 0.2 × × × × × 0.3 0.3 0.2 0.2 Anti-oxidant additive 0.5 0.5 0.5 0.5 × × × × × × × × × Diester 1 (excluding invention) × 15 × × × × × × × × × × × Diester 2 × × × × × × × × 15 × 14.6 × × Diester 3 (invention) × × × 15 × 15 × × × 7.5 × × 15 Diester 4 (invention) × × × × × × × × × 7.5 × × × Diester 5 (invention) × × × × × × 15 × × × × × × Diester 6 (excluding invention) × × 15 × × × × × × × × × × Diester 7 (excluding invention) × × × × × × × 15 × × × × × Composition CC1 CC2 CC3 C1 CC4 C2 C3 CC5 CC6 C4 CC7 CC8 C5 KV 40°C ASTM ^D445-97 (mm2/s) 44.46 41.13 41.49 41.22 31.20 28.6 29.4 30.0 30.0 29.7 29.9 43.03 39.4 3 KV 100°C ASTM ^D445-97 (mm2/s) 8.83 8.65 8.63 8.65 6.85 6.94 7.01 6.95 6.87 8.18 8.50 8.78 8.96 Viscosity Index (VI) ASTM D2270-93 182 196 193 195 187 218 214 205 200 271 284 189 218 HTHS at 150°C ASTM D 4683 (cP) 2.60 2.64 2.60 2.57 2.29 2.30 2.31 2.31 2.30 2.62 2.65 2.90 2.92 Noack volatility ASTM D5800 (% by weight) 13.0 15.7 15.0 13.5 12.3 14.0 11.9 11.1 n/a n/a n/a 11.5 13.3

EXAMPLE 2 Characterization of the compositions according to the invention and comparisons in terms of fuel economy (“Fuel-Eco”)

The test is carried out using an EB 1.2 L Turbo engine, whose power is 81 kW at 5500 rpm, driven by an electric generator allowing a rotation speed of between 900 and 4500 to be imposed. revolutions/min while a torque sensor makes it possible to measure the frictional torque generated by the movement of the parts in the engine. The friction torque induced by the test lubricant is compared for each speed and each temperature with the torque induced by the reference lubricating composition (SAE 0W30).

The conditions of this test are as follows.

• rinçage du moteur avec une huile de rinçage comprenant des additifs détergent, suivi d'un rinçage avec une composition lubrifiante de référence ;
• mesure du couple de friction aux quatre températures différentes indiquées ci-dessous sur le moteur mettant en œuvre la composition lubrifiante de référence ;
• rinçage du moteur avec une huile de rinçage comprenant des additifs détergent, suivi d'un rinçage avec une composition lubrifiante à évaluer ;
• mesure du couple de friction à quatre températures différentes sur le moteur mettant en œuvre la composition lubrifiante à évaluer ;
• rinçage du moteur avec une huile de rinçage comprenant des additifs détergent, suivi d'un rinçage avec la composition lubrifiante de référence ; et
• mesure du couple de friction aux quatre températures différentes indiquées ci-dessous sur le moteur mettant en œuvre la composition lubrifiante de référence.

The tests are carried out according to the following sequence:

• rinsing the engine with a rinsing oil comprising detergent additives, followed by rinsing with a reference lubricating composition;
• measurement of the friction torque at the four different temperatures indicated below on the engine implementing the reference lubricating composition;
• flushing the engine with a flushing oil comprising detergent additives, followed by a flushing with a lubricating composition to be evaluated;
• measurement of the friction torque at four different temperatures on the engine implementing the lubricating composition to be evaluated;
• rinsing the engine with a rinsing oil comprising detergent additives, followed by rinsing with the reference lubricating composition; and
• measurement of the friction torque at the four different temperatures indicated below on the engine implementing the reference lubricating composition.

The rpm ranges, the rpm variation and the temperature have been chosen to cover, in the most representative way possible, the points of the NEDC certified cycle.

• Température de l'eau en sortie du moteur : 35°C/50°C/80°C/100°C ± 0,5°C,
• Rampe de température de l'huile : 35°C/50°C/80°C/110°C ± 0,5°C.

The instructions implemented are:

• Engine outlet water temperature: 35°C/50°C/80°C/100°C ± 0.5°C,
• Oil temperature ramp: 35°C/50°C/80°C/110°C ± 0.5°C.

The gain in friction is evaluated for each lubricating composition (C1, CC1 to CC3) as a function of the temperature and the speed of the engine and in comparison with the friction of the reference lubricating composition.

The results of the "Fuel Eco" test are summarized in the following table 4, and indicate the average percentage of friction gains for each composition at a given temperature over a speed range from 900 rpm to 4500 rpm . <u>TABLE 4</u> Average of the gains in friction in percentage at a temperature t of the lubricating composition CC1 CC2 CC3 C1 t = 35°C 2.2 2.9 3.9 5.0 t = 50°C 1.9 2.1 2.8 3.7 t= 80°C 0.8 0.2 1.4 1.6 t=110°C 0.9 0.3 0.5 1.0

These results demonstrate that the friction gains for the composition C1 comprising the ester according to the invention are much greater than the friction gains obtained with the comparative compositions CC1 not comprising any ester, CC2 and CC3 comprising an ester different from those of the invention.

It is understood that the greater the gains in friction, the greater the fuel economy or Fuel Eco. This therefore implies that the compositions according to the invention make it possible to increase the Fuel Eco, unlike the compositions not comprising an ester or esters different from the esters of the invention.

EXAMPLE 3 Characterization of the compositions according to the invention and comparisons in terms of fuel economy (“Fuel-Eco”)

The test is carried out using a Nissan HR12DDR engine, whose power is 180 kW at 6500 rpm, driven by an electric generator allowing a rotation speed of between 1000 and 4400 rpm to be imposed while that a torque sensor makes it possible to measure the frictional torque generated by the movement of the parts in the engine. The friction torque induced by the test lubricant is compared for each speed and each temperature at the average torque induced by the reference lubricating composition (SAE 0W16) which was evaluated before and after the test lubricant.

The conditions of this test are as follows.

• rinçage du moteur avec une huile de rinçage comprenant des additifs détergent, suivi d'un rinçage avec une composition lubrifiante de référence ;
• mesure du couple de friction aux quatre températures différentes indiquées ci-dessous sur le moteur mettant en œuvre la composition lubrifiante de référence ;
• rinçage du moteur avec une huile de rinçage comprenant des additifs détergent, suivi d'un rinçage avec une composition lubrifiante à évaluer ;
• mesure du couple de friction à quatre températures différentes sur le moteur mettant en œuvre la composition lubrifiante à évaluer ;
• rinçage du moteur avec une huile de rinçage comprenant des additifs détergent, suivi d'un rinçage avec la composition lubrifiante de référence ; et
• mesure du couple de friction aux quatre températures différentes indiquées ci-dessous sur le moteur mettant en œuvre la composition lubrifiante de référence.

The tests are carried out according to the following sequence:

• rinsing the engine with a rinsing oil comprising detergent additives, followed by rinsing with a reference lubricating composition;
• measurement of the friction torque at the four different temperatures indicated below on the engine implementing the reference lubricating composition;
• flushing the engine with a flushing oil comprising detergent additives, followed by a flushing with a lubricating composition to be evaluated;
• measurement of the friction torque at four different temperatures on the engine implementing the lubricating composition to be evaluated;
• rinsing the engine with a rinsing oil comprising detergent additives, followed by rinsing with the reference lubricating composition; and
• measurement of the friction torque at the four different temperatures indicated below on the engine implementing the reference lubricating composition.

The rpm ranges, the rpm variation and the temperature have been chosen to cover, in the most representative way possible, the points of the NEDC certified cycle.

• Température de l'eau en sortie du moteur : 30°C/50°C ± 0,5°C,
• Rampe de température de l'huile : 30°C/50°C ± 0,5°C,

The instructions implemented are:

• Engine outlet water temperature: 30°C/50°C ± 0.5°C,
• Oil temperature ramp: 30°C/50°C ± 0.5°C,

The gain in friction is evaluated for each lubricating composition (C2, C3, CC4 to CC6) as a function of the temperature and the speed of the engine and in comparison with the friction of the reference lubricating composition.

The results of the "Fuel Eco" test are summarized in the following table 5 and indicate the average percentage gains in friction for each composition at a given temperature over a speed range from 1000 rpm to 4400 rpm: <u>TABLE 5</u> Average of the gains in friction in percentage at a temperature t of the lubricating composition CC4 C2 C3 CC5 CC6 t = 30°C -0.14 1.8 1.30 -0.75 -0.07 t = 50°C 0.56 1.51 1.14 -0.77 0.39

These results demonstrate that the friction gains for the compositions C2 and C3 comprising an ester according to the invention are much greater than the friction gains obtained with the comparative compositions CC4 not comprising any ester as well as CC5 and CC6 comprising an ester different from those of the invention.

These results also demonstrate that the comparative compositions CC4 to CC6 do not show friction gains, but friction losses, which implies that the comparative compositions CC4 to CC6 do not make it possible to make Fuel Eco but on the contrary lead to a excess fuel consumption compared to the reference composition.

It is understood that the greater the gains in friction, the greater the fuel economy or Fuel Eco. This therefore implies that the compositions according to the invention make it possible to increase the Fuel Eco, unlike the compositions not comprising an ester or esters other than the esters of the invention, such as 2-ethylhexyl sebacate.

EXAMPLE 4 Characterization of the compositions according to the invention and comparisons in terms of fuel economy (“Fuel-Eco”)

The test is carried out using a Honda L13-B engine, whose power is 81 kW at 5500 rpm, driven by an electric generator allowing a rotation speed of between 650 and 5000 rpm to be imposed. min while a torque sensor measures the frictional torque generated by the movement of parts in the engine. The friction torque induced by the test lubricant is compared for each speed and each temperature with the torque induced by the reference lubricating composition (SAE 0W16).

The conditions of this test are as follows.

• rinçage du moteur avec une huile de rinçage comprenant des additifs détergent, suivi d'un rinçage avec une composition lubrifiante de référence ;
• mesure du couple de friction aux quatre températures différentes indiquées ci-dessous sur le moteur mettant en œuvre la composition lubrifiante de référence ;
• rinçage du moteur avec une huile de rinçage comprenant des additifs détergent, suivi d'un rinçage avec une composition lubrifiante à évaluer ;
• mesure du couple de friction à quatre températures différentes sur le moteur mettant en œuvre la composition lubrifiante à évaluer ;
• rinçage du moteur avec une huile de rinçage comprenant des additifs détergent, suivi d'un rinçage avec la composition lubrifiante de référence ; et
• mesure du couple de friction aux quatre températures différentes indiquées ci-dessous sur le moteur mettant en œuvre la composition lubrifiante de référence.

The tests are carried out according to the following sequence:

• rinsing the engine with a rinsing oil comprising detergent additives, followed by rinsing with a reference lubricating composition;
• measurement of the friction torque at the four different temperatures indicated below on the engine implementing the reference lubricating composition;
• flushing the engine with a flushing oil comprising detergent additives, followed by a flushing with a lubricating composition to be evaluated;
• measurement of the friction torque at four different temperatures on the engine implementing the lubricating composition to be evaluated;
• rinsing the engine with a rinsing oil comprising detergent additives, followed by rinsing with the reference lubricating composition; and
• measurement of the friction torque at the four different temperatures indicated below on the engine implementing the reference lubricating composition.

The rpm ranges, the rpm variation and the temperature have been chosen to cover, in the most representative way possible, the points of the NEDC certified cycle.

• Température de l'eau en sortie du moteur : 35°C/50°C ± 0,5°C,
• Rampe de température de l'huile : 35°C/50°C ± 0,5°C.

The instructions implemented are:

• Engine outlet water temperature: 35°C/50°C ± 0.5°C,
• Oil temperature ramp: 35°C/50°C ± 0.5°C.

The gain in friction is evaluated for each lubricating composition (C4 and CC7) as a function of the temperature and the speed of the engine and in comparison with the friction of the reference lubricating composition.

The results of the "Fuel Eco" test are summarized in the following table 5, and indicate the average percentage of friction gains for each composition at a given temperature over a speed range from 650 rpm to 5000 rpm : <u>TABLE 6</u> Average of the gains in friction in percentage at a temperature t of the lubricating composition C4 CC7 t = 35°C 1.4 0.8 t = 50°C 0.2 -0.2

These results demonstrate that the gains in friction for the composition C4 comprising a mixture of esters according to the invention are much greater than the gains in friction obtained with the comparative composition CC7 comprising as ester, 2-ethylhexyl sebacate, different from those of the invention.

It is understood that the greater the gains in friction, the greater the fuel economy or Fuel Eco. This therefore implies that the compositions according to the invention make it possible to increase the Fuel Eco, unlike the compositions not comprising an ester or esters other than the esters of the invention, such as 2-ethylhexyl sebacate.

EXAMPLE 5 Evaluation of the properties for improving the cleanliness of an engine of a lubricating composition according to the invention C5 and of a comparative lubricating composition CC8

The engine cleanliness performances on the C5 and CC8 lubricating compositions are evaluated according to the following method.

Each lubricating composition (10 kg) is evaluated during a cleanliness test of a common rail diesel engine (common rail) for motor vehicles. The engine has a displacement of 1.4 L for 4 cylinders. Its power is 80 kW. The test cycle time is 96 hours alternating between idling and 4000 rpm. The temperature of the lubricating composition is 145°C and the temperature of the cooling system water is 100°C. No draining or topping up of lubricating composition is carried out during the test. EN 590 fuel is used.

The test takes place in two phases for a total duration of 106 hours and according to a first step of rinsing and running-in for 10 hours, then according to a second step with the composition evaluated (4 kg), finally according to an endurance step of duration of 96 hours with the evaluated composition (4 kg).

After this test, the engine parts were analyzed and the 4 pistons rated according to European standard CEC M02A78. For each piston, its merit rating is performed and then an average of the total piston merit rating of the 4 pistons is calculated.

The results obtained are summarized in Table 6.

The regular passage of a reference oil has made it possible to show that a difference of 4 points between two candidates is significant.

The higher the value of the average merit rating, the more the cleanliness of the piston is improved and therefore the better the performance of the lubricating composition in improving engine cleanliness. <u>TABLE 7</u> Composition assessed Piston merit rating after test (%) C5 66.71 CC8 61.6

The results show that the use of an ester according to the invention in a lubricating composition makes it possible to improve the cleanliness of an engine (lubricating composition C5) compared to a comparative lubricating composition not comprising an ester according to invention (lubricating composition CC8).

Claims (15)

1. Lubricating composition of grade according to the SAE J300 classification defined by formula (X)W(Y), in which X represents 0 or 5; and Y represents an integer ranging from 4 to 20; said composition comprising at least one diester of formula (I):
   
           R^a-C(O)-O-([C(R)₂]_n-O)_s-C(O)-R^b     (I)
   
   in which:

   - R represent, independently of one another, a hydrogen atom or a linear or branched (C₁-C₅)alkyl group, in particular a methyl, ethyl or propyl group, notably methyl;

   - s is 1, 2, 3, 4, 5 or 6; in particular s is 1, 2 or 3, and more particularly s is 1 or 2;

   - n is 1, 2 or 3; in particular n is 2 or 3 and more particularly n is 2, it being understood that, when s is different from 1, n may be identical or different; and

   - R^a and R^b, which may be identical or different, represent, independently of one another, saturated or unsaturated, linear or branched hydrocarbon groups having a linear chain of 6 to 18 carbon atoms;

   provided that, when s is 2 and n, which are identical, are 2, at least one of the groups R represents a linear or branched (C₁-C₅)alkyl group; and

   provided that, when s is 1 and n is 3, at least one of the groups R bonded to the carbon in the beta position of the oxygen atoms of the ester functions represents a hydrogen atom;

   said lubricating composition comprising from 5 to 30 wt% of diester(s) of formula (I) based on the total weight of the composition.
2. Composition according to the preceding claim, characterized in that R^a and R^b, which may be identical or different, have a linear chain of 7 to 14 carbon atoms, in particular 8 to 12 carbon atoms and more particularly 8 to 11 carbon atoms.
3. Composition according to Claim 1 and or 2, characterized in that R^a and R^b, which may be identical or different, represent C₆ to C₁₈, in particular C₇ to C₁₇, notably C₇ to C₁₄, preferably C₈ to C₁₂ and more preferentially C₈ to C₁₁, notably C₈ to C₁₀, linear alkyl groups.
4. Composition according to any one of the preceding claims, characterized in that R^a and R^b both represent n-octyl or n-undecyl groups, preferably n-octyl.
5. Composition according to any one of the preceding claims, characterized in that the diester is of the following formula (I')
   
           R^a-C(O)-O-([C(R)₂]_n-O)-([C(R')₂]_m-O)_s-1-C(O)-R^b     (I')
   
   in which:

   - R and R' represent, independently of one another, a hydrogen atom or a linear or branched (C₁-C₅)alkyl group, in particular a methyl, ethyl or propyl group, notably a methyl group;

   - s is 1, 2 or 3, in particular s is 1 or 2;

   - n is 2;

   - m is 2;

   - R^a and R^b, which may be identical or different, represent, independently of one another, saturated or unsaturated, linear or branched hydrocarbon groups having a linear chain of 6 to 18 carbon atoms;

   provided that, when s is 2, at least one of the groups R or R' represents a linear or branched (C₁-C₅)alkyl group.
6. Composition according to the preceding claim, characterized in that the diester is of formula (I') in which:

   - s is 2,

   - one of the groups R represents a linear or branched (C₁-C₅)alkyl group, in particular a methyl, ethyl or propyl group, advantageously methyl; and

   - one of the groups R' represents a linear or branched (C₁-C₅)alkyl group, in particular a methyl, ethyl or propyl group, advantageously methyl; the other groups R and R' representing hydrogen atoms.
7. Composition according to Claim 5, characterized in that:

   - s is equal to 1;

   - one of the groups R represents a linear or branched (C₁-C₅)alkyl group, in particular a methyl, ethyl or propyl group, advantageously methyl, the others representing hydrogen atoms.
8. Composition according to any one of the preceding claims, characterized in that the diester is obtained by esterification reaction between a monopropylene or polypropylene glycol, in particular monopropylene glycol or dipropylene glycol; and one or more carboxylic acids R^a-COOH and R^b-COOH, in particular nonanoic or undecanoic acid.
9. Composition according to any one of the preceding claims, characterized in that it comprises from 5 to 25 wt% of diester(s) of formula (I) based on the total weight of the composition, more particularly from 10 to 25 wt%, still more particularly from 10 to 20 wt%.
10. Composition according to any one of the preceding claims, characterized in that it comprises one or more base oils selected from the oils of Groups II, III and IV of the API classification, in particular at least one Group III base oil.
11. Composition according to any one of the preceding claims, comprising one or more additives selected from friction-modifying additives, anti-wear additives, extreme pressure additives, detergent additives, antioxidant additives, viscosity index improvers, pour point depressants, dispersing agents, antifoam agents, thickeners, and mixtures thereof, in particular said composition comprising at least one friction-modifying additive, in particular based on molybdenum, notably selected from molybdenum dithiocarbamates, molybdenum dithiophosphates and mixtures thereof.
12. Composition according to any one of the preceding claims, of grade according to the SAE J300 classification selected from 0W4, 0W8, 0W12, 0W16,0W20, 5W4, 5W8, 5W12, 5W16 and 5W20.
13. Use of a composition according to any one of the preceding claims as lubricant for an engine, in particular a vehicle engine.
14. Use of a diester of formula (I) as defined in any one of Claims 1 to 8, as additive in a lubricating composition of grade according to the SAE J300 classification defined by the formula (X)W(Y), in which X represents 0 or 5, and Y represents an integer ranging from 4 to 20, and dedicated to an engine, in particular to a vehicle engine, for reducing the fuel consumption of the engine.
15. Use of a diester of formula (I) as defined in any one of Claims 1 to 8, as additive in a lubricating composition of grade according to the SAE J300 classification defined by the formula (X)W(Y), in which X represents 0 or 5, and Y represents an integer ranging from 4 to 20, and dedicated to an engine, in particular to a vehicle engine, for improving engine cleanliness.