Use of diester compounds as detergent additives in a lubricant composition for a motorization system

Abstract

The use, as a detergent additive in a lubricant composition, of a diester compound of formula (I): Ra-C(O)-O-([C(R)2]n-O)s-C(O)-Rb (I) wherein: R represent a hydrogen atom or a C1-C5 alkyl group; s is equal to 1 or 2; n is equal to 1, 2 or 3; it being understood that, when s is different from 1, n may be identical or different; and Ra and Rb represent hydrocarbon groups having a linear chain with 2 to 11 carbon atoms; provided that, when s has a value of 2 and n, which are identical, have a value of 2, at least one of the groups R represents a C1-C5 alkyl group; and provided that, when s=1 and n=3, at least one of the groups R bound to the carbon in the beta position of the oxygen atoms of the ester functions represents a hydrogen atom.

Description

[0001] Use of diester compounds as detergent additives in a lubricant composition for a motorization system

[0002] The invention relates to the field of lubricating compositions, notably of compositions for the lubrication of motorization systems, whether mobile or stationary, in particular gasoline, diesel, gas (liquefied natural gas, compressed natural gas or hydrogen) or dual fuel engines, in particular light and heavy-duty motor vehicles. More particularly, the invention relates to lubricant compositions for motorcycle engines. It relates more particularly to the use of specific diester compounds as detergent additives in lubricating compositions intended for the lubrication of these motorization systems.

[0003] Prior art

[0004] Lubricating compositions, also called "lubricants", are commonly used in engines for the main purpose of reducing the friction forces between the various metal parts in motion in engines. They are also effective in preventing premature wear or even damage to these parts, and in particular to their surfaces.

[0005] For this purpose, a lubricant composition is typically composed of a base oil with which several additives, such as friction modifying additives, are generally associated, dedicated to stimulate the lubricating performances of the base oil, but also to provide additional performances.

[0006] In fact, lubricants intended for the lubrication of engines, for example diesel engines, must meet several requirements. They must combine good anti-wear and anti-corrosion performances with good detergency and dispersion properties to reduce deposit formation.

[0007] In particular, it is essential that lubricants, especially for gasoline, diesel, gas (liquefied natural gas, compressed natural gas or hydrogen) or dual fuel engines, have good detergent properties. The incomplete combustion of fuel produces soot which can lead to sludge, carbon and varnish deposits. In the case of diesel or gasoline fuels, the residual sulfur in the fuel burns in the combustion chamber to produce sulfur acids. These acids are responsible for corrosion and wear in the engine and accelerate oil degradation.

[0008] Detergent additives are therefore added to base oils to prevent the formation of deposits on the surface of metal parts, which are harmful to the engine, by dissolving the by-products of oxidation and combustion, and thus increase the life of the engine. The detergent additives commonly used are metal salts, in particular sulfonates, phenates, salicylates of alkali metals, in particular calcium or magnesium, overbased or not.

[0009] There is still a need to provide alternative detergent additives for engines lubricant compositions, more particularly for motorcycle engines lubricant compositions. In particular, there is a need of alternative detergent additives that may be used in a lubricant composition to keep-clean and / or to clean-up the internal parts of a motorization system, notably of a motorcycle engine.

[0010] There is also a need of a detergency booster additive that may be used in combination with a commonly used a detergent additive to further increase the detergency performances of the commonly used detergent additive.

[0011] Therefore, research has been directed towards the development of new additives that may be used as detergent additive and / or as detergent booster additive in a lubricant composition.

[0012] Summary of the invention

[0013] The purpose of the present invention is to provide an alternative detergent additive that may be used in a lubricant composition, intended for use in mobile or stationary power systems, particularly in light and heavy-duty vehicles.

[0014] The purpose of the present invention is also to provide a detergent booster additive that may be used to improve the efficiency of a detergent additive present in a lubricant composition, intended for use in mobile or stationary power systems, particularly in light and heavy-duty vehicles.

[0015] The inventors have surprisingly discovered that specific diester compounds have detergent properties when used in a lubricant composition. The inventors have also discovered that the same diester compounds, when used in a lubricant composition already comprising a further detergent additive (that is distinct for the diester compounds of the invention), allow improving the detergent performances of the lubricant composition, compared to the same composition comprising said further detergent additive but that is free from diester compounds according to the invention.

[0016] Therefore, the invention firstly relates to the use, as a detergent additive in a lubricant composition, of at least one diester compound of formula (I):

[0017] Ra-C(O)-O-([C(R)2]n-O)s-C(O)-Rb(I) wherein: each R represents, independently of one another, a hydrogen atom or a (Ci-C5)alkyl group, linear or branched, in particular a methyl, ethyl or propyl group, notably methyl; s has a value of 1 or 2; n has a value of 1 , 2 or 3; it being understood that, when s is different from 1 , n may be identical or different; and

[0018] Raand Rb, which may be identical or different, represent independently of one another, hydrocarbon groups, saturated or unsaturated, linear or branched, having a linear chain with 2 to 1 1 carbon atoms, preferably with 3 to 8 carbon atoms; provided that, when s has a value of 2 and n, which are identical, have a value of 2, at least one of the groups R represents a (Ci-C5)alkyl group, linear or branched; and provided that, when s has a value of 1 and n has a value of 3, at least one of the groups R bound to the carbon in the beta position of the oxygen atoms of the ester functions represents a hydrogen atom.

[0019] Preferably, said at least one diester compound of formula (I) is a diester of formula (I’):

[0020] Ra-C(O)-O-([C(R)2]n-O)-([C(R’)2]m-O)s.i-C(O)-Rb(I ) wherein:

[0021] R and R’ represent, independently of one another, a hydrogen atom or a (Ci-C5)alkyl group, linear or branched, in particular a methyl, ethyl or propyl group, notably methyl; s has a value of 1 or 2; n is equal to 2; and

[0022] Raand Rb, which may be identical or different, represent independently of one another, hydrocarbon groups, saturated or unsaturated, linear or branched, having a linear chain with 2 to 1 1 carbon atoms, preferably with 3 to 8 carbon atoms; provided that, when s has a value of 2, at least one of the R or R’ groups represents a (Ci-C5)alkyl group, linear or branched.

[0023] Advantageously, the diester compound(s) of formula (I) are used in an amount of from 1 % to 30% by weight, based on the total weight of the lubricant composition, in particular, from 5% to 25% by weight, preferably from 7% to 20% by weight, and more particularly from 7.5% to 15 % by weight.

[0024] According to an embodiment, the lubricant composition further comprises at least one further detergent additive, that is distinct from the diester compound(s) of formula (I), preferably chosen from metal detergent additives, preferably chosen from the salts of alkali metals or alkaline-earth metals, overbased or not, in particular from the calcium salts, the magnesium salts and mixtures thereof.

[0025] Preferably, said further detergent additive(s) are present in a content of less than or equal to 15% by weight, relative to the total weight of the lubricant composition, in particular less than or equal to 10% by weight, and more particularly from 0.5% to 5.0% by weight, advantageously from 0.5% to 2.0% by weight.

[0026] According to a preferred embodiment, the diester compound(s) of formula (I) and the further detergent additive(s) are present in the lubricant composition according to a weight ratio ranging from 10:1 to 1 :10, preferably from 10:1 to 1 :1 , more preferably from 10:1 to 5:1 , advantageously from 5:1 to 7:1. According to a particular embodiment, the lubricant composition further comprises one or more other additives, distinct from said diester compound(s), selected from friction modifying additives, anti-wear additives, extreme pressure additives, antioxidants, viscosity index improvers, pour point depressants, dispersants, antifoam agents, thickeners, corrosion inhibitors, and mixtures thereof.

[0027] Preferably, the lubricant composition is used in a motorization system, preferably in a mobile or stationary engine system, more preferably in an internal combustion engine, typically in a diesel engine, a gasoline engine, a gas engine or dual-fuel engine, in particular in a light or heavy duty motor vehicle.

[0028] More preferably, the motorization system is a motorcycle engine.

[0029] Advantageously, the lubricant composition is used to clean up and / or to keep clean at least one internal part of the motorcycle engine system, preferably the pistons.

[0030] The invention also relates to the use as a detergency booster additive in a lubricant composition comprising at least one detergent additive, of at least one diester compound of formula (I):

[0031] Ra-C(O)-O-([C(R)2]n-O)s-C(O)-Rb(I) wherein: each R represents, independently of one another, a hydrogen atom or a (Ci-C5)alkyl group, linear or branched, in particular a methyl, ethyl or propyl group, notably methyl; s has a value of 1 or 2; n has a value of 1 , 2 or 3; it being understood that, when s is different from 1 , n may be identical or different; and

[0032] Raand Rb, which may be identical or different, represent independently of one another, hydrocarbon groups, saturated or unsaturated, linear or branched, having a linear chain with 2 to 1 1 carbon atoms, preferably with 3 to 8 carbon atoms; provided that, when s has a value of 2 and n, which are identical, have a value of 2, at least one of the groups R represents a (Ci-C5)alkyl group, linear or branched; and provided that, when s has a value of 1 and n has a value of 3, at least one of the groups R bound to the carbon in the beta position of the oxygen atoms of the ester functions represents a hydrogen atom.

[0033] Preferably, the lubricant composition comprising said at least one detergent additive and said at least one diester compound of formula (I) has improved detergent performances, with respect to a same lubricant composition comprising said at least one detergent additive and that is free from said at least one diester compound of formula (I). Detailed description of the invention

[0034] The invention firstly relates to the use of one or more specific diester compound(s) in a lubricant composition to improve the detergency properties of a lubricant composition, intended to lubricate a motorization system

[0035] In particular, the invention relates to the use, as detergent additive, of one or more specific diester compound(s) in a lubricant composition.

[0036] By “detergent additive”, we refer in the context of the invention to an additive which, when incorporated in a small amount into a lubricant composition, allows preventing the formation of deposits on the surface of the metal parts of an engine, as compared to said the lubricant composition that is free from said detergent additive.

[0037] The invention is also relates to the use of one or more specific diester compound(s) as an additive to further improve and / or boost the detergency properties of a lubricant composition further comprising an further detergent additive.

[0038] In particular, the invention relates to the use, as detergent booster additive, of one or more specific diester compound(s) in a lubricant composition further comprising an further detergent additive.

[0039] By “detergent booster additive”, we refer in the context of the invention to an additive which, when incorporated in a small amount into a lubricant composition already comprising a detergent additive, allows improving and / or boosting the detergency performances of the lubricant composition. The lubricant composition comprising both the detergent additive and the detergent booster additive has improved detergent properties, as compared to the same lubricant composition comprising said detergent additive but that is free from said detergent booster additive.

[0040] It is understood that the invention may involve a single diester compound or a mixture of at least two distinct diester compounds, in particular three or four distinct diester compounds, in particular as defined below.

[0041] The diester compound(s)

[0042] According to the invention, the diester compound used in the lubricant composition is a diester of general formula (I):

[0043] Ra-C(O)-O-([C(R)2]n-O)s-C(O)-Rb(I) in which :

[0044] - R represent, independently of each other, a hydrogen atom or a (Ci-C5)alkyl group, linear or branched, in particular a methyl, ethyl or propyl group, especially methyl;

[0045] - 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

[0046] - Raand Rb, which may be identical or different, represent, independently of one another, saturated or unsaturated, linear or branched hydrocarbon groups having a linear chain of 2 to 1 1 carbon atoms, preferably of 3 to 8 carbon atoms; with the proviso that, when s is 2 and n, which are identical, are 2, at least one of the groups R is a linear or branched (Ci-C5)alkyl group; and with the proviso 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.

[0047] According to a mode of realization, Raand Rb, which may be identical or different, represent, independently of one another, saturated or unsaturated, linear or branched hydrocarbon groups comprising from 2 to 11 carbon atoms, preferably from 3 to 8 carbon atoms.

[0048] In the following, a diester of formula (I) required according to the invention will be referred to more simply as a diester of the invention.

[0049] Preferably, in the context of the invention, it is meant by:

[0050] - "Ct-z" where t and z are integers, a carbon chain which may have from t to z carbon atoms; for example C1-4 a carbon chain which may have from 1 to 4 carbon atoms ;

[0051] - "alkyl" means a saturated, linear or branched aliphatic group; for example a C1-4- alkyl group represents a carbon chain of 1 to 4 carbon atoms, linear or branched, more particularly methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl.

[0052] Preferably, in the aforementioned formula (I), when s is different from 1 , all n are identical.

[0053] In particular, n in the above formula (I) is 2 or 3, and more particularly n is 2.

[0054] Preferably, at least one of the groups R represents a (Ci-C5)alkyl, in particular (C1- C4)alkyl, linear or branched, more preferably methyl, ethyl or propyl; advantageously methyl.

[0055] According to a particularly preferred embodiment, the diester of formula (I) is a diester of the following formula (I'):

[0056] Ra-C(O)-O-([C(R)2]n-O)-([C(R’)2]m-O)s-i-C(O)-Rb(I ) in which:

[0057] - R and R' represent, independently of each other, a hydrogen atom or a (Ci-C5)alkyl group, linear or branched, in particular a methyl, ethyl or propyl group; - s is 1 or 2;

[0058] - n is 2;

[0059] - m is 2;

[0060] - Raand Rb, which may be identical or different, represent, independently of one another, saturated or unsaturated, linear or branched hydrocarbon groups having a linear chain of 2 to 1 1 carbon atoms, preferably of 3 to 8 carbon atoms; with the proviso that, when s is 2, at least one of the groups R or R' represents a linear or branched (Ci-C5)alkyl group.

[0061] Preferably, according to this particularly preferred embodiment, the diester is a diester of formula (I') in which at least one of R or R' represents a (Ci-C5)alkyl group, in particular (Ci-C4)alkyl, linear or branched, more preferably methyl, ethyl or propyl; advantageously methyl.

[0062] According to an alternative embodiment, s in the aforementioned formula (I) or (I') is equal to 2.

[0063] In particular, according to this an alternative embodiment, the diester is of the following formula (I'a):

[0064] Ra-C(O)-O-([C(R)2]n-O)-([C(R’)2]m-O)-C(O)-Rb(I'a) in which:

[0065] - R and R' represent, independently of each other, a hydrogen atom or a (Ci-C5)alkyl group, linear or branched, in particular a methyl, ethyl or propyl group, advantageously methyl;

[0066] - n is 2;

[0067] - m is 2;

[0068] - Raand Rb, which may be identical or different, represent, independently of one another, saturated or unsaturated, linear or branched hydrocarbon groups having a linear chain of 2 to 1 1 carbon atoms, preferably of 3 to 8 carbon atoms; with the proviso that at least one of the groups R or R' represents a linear or branched (Ci-C5)alkyl group, in particular methyl, ethyl or propyl, advantageously methyl.

[0069] Preferably, at least one of the groups R represents a linear or branched (Ci-C5)alkyl group, in particular a methyl, ethyl or propyl group, advantageously methyl; and at least one of the groups R' represents a linear or branched (Ci-C5)alkyl group, in particular a methyl, ethyl or propyl group, advantageously methyl.

[0070] Even more preferably, the diester of the invention is of formula (I'a) in which one of the groups R represents a linear or branched (Ci-C5)alkyl group, in particular a methyl, ethyl or propyl group, advantageously methyl; and one of the groups R' represents a linear or branched (Ci-C5)alkyl group, in particular a methyl, ethyl or propyl group, advantageously methyl; the other groups R and R' representing hydrogen atoms.

[0071] In other words, according to a particular embodiment, the diester of the invention may be of the following formula (l"

[0072] Ra-C(O)- in which :

[0073] - one of the groups Ri and R2 represents a linear or branched (Ci-C5)alkyl group, the other representing a hydrogen atom ;

[0074] - one of the groups R3 and R4 represents a linear or branched (Ci-C5)alkyl group, the other representing a hydrogen atom; and

[0075] - Raand Rb, which are identical or different, are as defined above.

[0076] In particular, the diester of the invention may be of formula (l"a) in which:

[0077] - one of the groups R1and R2represents a methyl, ethyl or propyl group, advantageously methyl, the other representing a hydrogen atom; and

[0078] - one of the groups R3and R4represents a methyl, ethyl or propyl group, advantageously methyl, the other representing a hydrogen atom.

[0079] According to another embodiment, s in the aforementioned formula (I) or (I') is 1 .

[0080] In other words, according to this another embodiment, the diester is a diester of the following formula (I'b):

[0081] Ra-C(O)-O-([C(R)2]n-O)-C(O)-Rb(I'b) in which:

[0082] - R represent, independently of each other, a hydrogen atom or a (Ci-C5)alkyl group, linear or branched, in particular a methyl, ethyl or propyl group, advantageously methyl;

[0083] - n is 2;

[0084] - Raand Rb, which may be identical or different, represent, independently of one another, saturated or unsaturated, linear or branched hydrocarbon groups having a linear chain of 2 to 1 1 carbon atoms, preferably of 3 to 8 carbon atoms.

[0085] Preferably, in the above formula (I'b), at least one of the R represents a linear or branched (Ci-C5)alkyl group, in particular a methyl, ethyl or propyl group, advantageously methyl.

[0086] In particular, the diester is a diester of formula (I'b) in which one of the groups R represents a linear or branched (Ci-C5)alkyl group, in particular a methyl, ethyl or propyl group, advantageously methyl, the others representing hydrogen atoms. As previously indicated, Raand Rbin the above-mentioned formula (I), (I'), (I'a), (l"a) or (I'b), which may be identical or different, represent saturated or unsaturated, linear or branched hydrocarbon groups having a linear chain of 2 to 1 1 carbon atoms, preferably of 3 to 8 carbon atoms.

[0087] By "hydrocarbon" group is meant any group having a carbon atom directly attached to the rest of the molecule and having mainly an aliphatic hydrocarbon character.

[0088] Preferably, Raand Rbin the above-mentioned formula (I), (I'), (I'a), (l"a) or (I'b) have a linear chain of 3 to 6 carbon atoms.

[0089] According to an alternative embodiment, Raand Rbin the above-mentioned formula (I), (I'), (I'a), (l"a) or (I'b) have a linear chain of 8 to 1 1 carbon atoms.

[0090] By "linear chain of t to z carbon atoms" is meant a saturated or unsaturated, preferably saturated, carbon chain comprising from t to z carbon atoms in succession, the carbon atoms possibly present at the level of the branches of the carbon chain not being taken into account in the number of carbon atoms (t-z) constituting the linear chain.

[0091] According to a particular mode of realization, in the above-mentioned formula (I), (I'), (I'a), (l"a) or (I'b), Raand Rb, which may be identical or different, are of plant, animal or petroleum origin.

[0092] According to a particular embodiment, in the above-mentioned formula (I), (I'), (I'a), (l"a) or (I'b), Raand Rb, which are identical or different, represent saturated groups.

[0093] According to another particularly preferred embodiment, in the aforesaid formula (I), (I'), (I'a), (l"a) or (I'b), Raand Rb, which may be identical or different, represent linear groups.

[0094] According to another particular embodiment, in the aforementioned formula (I), (I'), (I'a), (l"a) or (I'b), Raand Rbrepresent linear saturated hydrocarbon groups with Cs to Cn, in particular with Cs to C .

[0095] In particular, Raand Rbare identical.

[0096] Preferably, Raand Rbare both n-octyl or n-undecyl groups, preferably n-octyl.

[0097] According to another particular embodiment, in the above-mentioned formula (I), (I'), (I'a), (l"a) or (I'b), Raand Rbrepresent branched hydrocarbon groups comprising from 2 to 11 carbon atoms, preferably from 3 to 8 carbon atoms.

[0098] According to this variant, Raand Rbin the above-mentioned formula (I), (I'), (I'a), (l"a) or (I'b) preferably have a linear chain of 3 to 7 carbon atoms branched by at least one, preferably one, Ci to C& hydrocarbon group, preferably methyl or ethyl.

[0099] In particular, Raand Rbare identical.

[0100] Preferably, Raand Rbare both 2-methylheptyl or 2-ethylhexyl groups.

[0101] The diesters of formula (I) may be commercially available or prepared according to synthetic methods described in the literature and known to the person skilled in the art. More particularly, these synthetic methods involve an esterification reaction between a diol compound of formula HO-([C(R)2]n-O)s-OH and compounds of formula Ra-COOH and Rb- COOH, with Raand Rb, which are identical or different, being as defined above.

[0102] Of course, it belongs to the person skilled in the art to adjust the synthesis conditions to obtain the required diesters according to the invention.

[0103] By way of example, diesters of the above-mentioned formula (I), in particular of the above-mentioned formula (I'), can be obtained by esterification reaction between a mono- or polypropylene glycol, in particular monopropylene glycol (MPG) or dipropylene glycol (DPG), diethylene glycol (DEG), neopentyl glycol (NPG), preferably between dipropylene glycol or diethylene glycol, and one or more suitable carboxylic acids Ra-COOH and Rb-COOH suitable, in particular selected from nonanoic acid, dodecanoic acid, isononanoic acid, 2-ethylhexanoic acid, and mixtures thereof.

[0104] By way of example, a diester or mixture of diesters of formula (I') as defined above, where:

[0105] - s is 2,

[0106] - one of the groups R representing a linear or branched (Ci-Csjalkyl group, in particular a methyl, ethyl or propyl group, advantageously methyl, the others representing hydrogen atoms; and

[0107] - one of the groups R' representing a linear or branched (Ci-Csjalkyl group, 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 carboxylic acids Ra-COOH and Rb-COOH.

[0108] A diester of formula (I') as defined above, wherein

[0109] - s is 1 ,

[0110] - one of the groups R representing a linear or branched (Ci-Csjalkyl group, 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 carboxylic acids Ra-COOH and Rb-COOH.

[0111] In particular, in the case where Raand Rbboth 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 dodecanoic acid. According to one embodiment, a diester or diester mixture required according to the invention may be obtained by esterification reaction between dipropylene glycol and nonanoic acid, dodecanoic acid and mixtures thereof.

[0112] According to another embodiment, a diester or diester mixture required according to the invention may be obtained by esterification reaction between diethylene glycol and nonanoic acid.

[0113] According to another embodiment, a diester or diester mixture required according to the invention can be obtained by esterification reaction between neopentyl glycol and nonanoic acid, isononanoic acid, 2-ethylhexanoic acid and mixtures thereof.

[0114] The diester of formula (I) required according to the invention advantageously has a kinematic viscosity measured at 40°C according to ASTM D445 of between 5 and 18 mm2 / s, preferably between 8 and 15 mm2 / s, and / or a kinematic viscosity measured at 100°C according to ASTM D445 of between 1 .5 and 9.3 mm2 / s, preferably between 2 and 4 mm2 / s.

[0115] The diester of formula (I) required according to the invention advantageously has a thermal conductivity measured at 30°C according to ASTM D7896, greater than or equal to 100 mW / Km, preferably between 110 and 180 mW / Km and / or a thermal conductivity measured at 130°C according to ASTM D7896, greater than or equal to 90 mW / Km, preferably between 95 and 160 mW / Km.

[0116] The diester of formula (I) required according to the invention advantageously has a heat capacity measured at 20°C according to ASTM E1269, greater than or equal to 1.5 J / K, preferably between 1 .8 and 2.1 J / K and / or a heat capacity measured at 80°C according to ASTM E1269, greater than or equal to 2 J / K, preferably between 2.0 and 2.8 J / K.

[0117] The diester of formula (I) advantageously has an evaporation time of 20% by weight of said ester, measured according to ASTM D6375, greater than or equal to 400 seconds, preferably between 410 and 600 seconds.

[0118] Preferably, the diester is distinct from the base oil.

[0119] It is understood in the context of the present invention that the diester of formula (I) as defined above may be in the form of a mixture of diesters of formula (I) as defined above.

[0120] According to the present invention, the diester(s) of formula (I) may be present in a content of from 1 % to 30% by weight, based on the total weight of the lubricant composition, in particular, from 5% to 25% by weight, preferably from 7% to 20% by weight, and more particularly from 7.5% to 15 % by weight. The lubricant composition

[0121] A lubricant composition as considered according to the invention more particularly comprises one or more base oils and, optionally, other additives conventionally considered in lubricant compositions.

[0122] It is understood that the nature and quantity of the other additives are adapted with respect to the destination of the lubricant, and more particularly with respect to the type of motorization system for which it is intended, for example depending on whether it is intended for use in a light vehicle engine, a heavy vehicle engine, a diesel or gasoline engine, etc.

[0123] Base oil

[0124] Conventionally, a lubricant composition comprises one or more base oils.

[0125] These base oils may be selected from base oils conventionally used in the field of lubricant oils, such as mineral, synthetic or natural, animal or vegetable oils or mixtures thereof.

[0126] It may be a mixture of several base oils, for example a mixture of two, three or four base oils.

[0127] The base oils of the lubricant 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 (or their equivalents according to the ATIEL classification) and presented in Table 1 below or mixtures thereof.

[0128] Table 1

[0129] Mineral base oils include all types of base oils obtained by atmospheric and vacuum distillation of crude oil, followed by refining operations such as solvent extraction, dealkalization, solvent dewaxing, hydrotreating, hydrocracking, hydroisomerization and hydrofining. Synthetic base oils can be esters of carboxylic acids and alcohols, polyalphaolefins or polyalkylene glycol (PAG) obtained by polymerization or copolymerization of alkylene oxides comprising from 2 to 8 carbon atoms, in particular from 2 to 4 carbon atoms. The 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 mm2.s-1 according to ASTM D445. Their average molecular weight is generally between 250 and 3000 according to ASTM D5296.

[0130] Mixtures of synthetic and mineral oils, which may be biobased, can also be used.

[0131] There is generally no limitation on the use of different base oils in the lubricant composition, except that they must have properties, such as viscosity, viscosity index, sulfur content, or oxidation resistance, suitable for use in engine systems, especially vehicle engines.

[0132] Preferably, the lubricant composition under consideration according to the invention comprises at least one base oil selected from group II, III and IV oils of the API classification, and mixtures thereof.

[0133] More preferably, the lubricant composition under consideration according to the invention comprises at least one base oil selected from group II and III oils of the API classification, and mixtures thereof.

[0134] In particular, such a lubricating composition may comprise at least one group III base oil, in particular a mixture of at least two group III base oils.

[0135] The base oils suitable for the invention may have a kinematic viscosity measured at 40 °C according to ASTM D445 (KV40) ranging from 10 mm2 / s to 100 mm2 / s, in particular from 12 mm2 / s to 50 mm2 / s, more particularly from 15 mm2 / s to 40 mm2 / s.

[0136] Base oils suitable for the invention may have a kinematic viscosity measured at 100 °C in accordance with ASTM D445 (KV100) of from 1 mm2 / s to 15 mm2 / s, in particular from 2 mm2 / s to 10 mm2 / s, more particularly from 4 mm2 / s to 8 mm2 / s.

[0137] The base oil(s) may be present in a lubricant composition according to the invention in a content of at least 50% by weight, based on its total weight, in particular of at least 60% by weight, more particularly ranging from 60% to 99% by weight and preferably from 70% to 90% by weight, typically ranging from 75% to 85% by weight.

[0138] Preferably, the oil or oils of group II and III represents at least 50% by mass, in particular at least 60% by mass, more particularly between 70 and 100% by mass, for example between 80 and 100% by mass, of the total mass of the base oils of the composition. Additive(s)

[0139] A lubricant composition according to the invention may comprise any type of additives suitable for the intended use of the lubricant, as detailed hereafter, for example for use in engine systems for light or heavy vehicles, especially diesel engines.

[0140] These additives can be introduced alone and / or in the form of a mixture, or "additive package", like those already available for sale in commercial lubricant formulations for vehicle engines, with performance levels as defined by the ACEA “Association des Constructeurs Europeens dAutomobiles”) and / or the API (American Petroleum Institute), which are well known to the man of the trade.

[0141] These additives, distinct from said diester compound(s), may be selected from other detergent additives, distinct from said diester compound(s), in particular metallic detergent additives, friction modifiers, anti-wear additives, extreme pressure additives, antioxidants, viscosity index (VI) improvers, pour point depressant (PPD) additives, dispersants, antifoam agents, thickeners, corrosion inhibitors, and mixtures thereof.

[0142] According to a particular embodiment, the lubricant composition according to the invention further comprises at least one viscosity index (VI) improvers, preferably selected from

[0143] Advantageously, a lubricant composition according to the invention comprises one or more additives selected from other detergent additives, distinct from said diester compound(s), viscosity index improvers, pour point depressants, anti-wear additives, antioxidants and mixtures thereof.

[0144] Further detergent additive(s)

[0145] The lubricant composition under consideration according to the invention, supplemented with one or more diester compound(s) according to the invention may comprise one or more detergent additives, different from said one or more diester compound(s). These detergent additives which are different from the diester(s) compounds of the invention are designated hereafter as “further detergent additive”.

[0146] According to an embodiment, the lubricant composition under consideration according to the invention does not comprise further detergent additive, that is different from the diester compound(s) according to the invention.

[0147] Thus, according to this first embodiment, the diester compound(s) according to the invention act(s) as a detergent additive in the lubricant composition. According to an alternative embodiment, the lubricant composition according to the invention further comprises at least one further detergent additive that different from the diester compound(s) according to the invention.

[0148] Thus, according to this alternative embodiment, the diester compound(s) according to the invention act(s), in the lubricant composition, as a detergent booster additive.

[0149] Preferably, the (further) detergent additives are chosen from metallic detergent additives.

[0150] As mentioned above, metallic detergents are known to the person skilled in the art for providing high levels of detergency.

[0151] They are generally anionic compounds comprising a long lipophilic hydrocarbon chain and a hydrophilic head, and the associated cation may be a metal cation of an alkali or alkaline earth metal.

[0152] They are generally selected from alkali metal or alkaline earth metal salts of carboxylic acids, including sulfonates, salicylates, naphthenates, phenates, carboxylates and mixtures thereof. Alkali and alkaline earth metals are preferably calcium, magnesium, sodium or barium.

[0153] These metal salts generally contain the metal in a stoichiometric quantity or in excess, i.e. in a quantity greater than the stoichiometric quantity. These are then called 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, preferably a carbonate.

[0154] According to a particular embodiment, a lubricant composition according to the invention comprises at least one metal detergent additive, in particular chosen from overbased or unbased alkali metal or alkaline earth metal salts, in particular from calcium salts, magnesium salts and mixtures thereof.

[0155] Thus, according to a particular embodiment, a lubricating composition according to the invention, intended for a motorization system, in particular for a light or heavy motor vehicle, comprises at least:

[0156] - one or more base oils;

[0157] - at least one diester compound according to the invention; and

[0158] - at least one further detergent additive (distinct from the said diester compound), notably chosen from metallic detergent additives, in particular chosen from calcium and magnesium salts and mixtures thereof. In particular, a lubricant composition according to the invention may comprise at least one magnesium-based detergent additive, such as a magnesium sulfonate, salicylate, naphthenate, phenate, carboxylate or a mixture thereof, in particular an overbased magnesium-based detergent additive, for example by magnesium carbonate.

[0159] According to a particular embodiment, the lubricating composition according to the invention comprises less than 15% by weight, in particular less than 10% by weight and more particularly from 0.1 to 5% by weight, in particular from 0.5% to 2.0% by weight, of further detergent additive(s) (which are distinct from the diester compounds according to the invention), relative to the total weight of said composition.

[0160] In particular, when the further detergent additive(s) are chosen from metallic detergent additive(s), they may be present in the lubricant composition so as to provide a content of metallic element(s), in particular magnesium, of less than or equal to 6000 ppm, in particular ranging from 100 ppm to 4000 ppm, preferably from 250 ppm to 3000 ppm.

[0161] Preferably, the diester compound(s) of formula (I) and the further detergent additive(s) are present in the lubricant composition according to a weight ratio ranging from 10:1 to 1 :10, preferably from 10:1 to 1 :1 , more preferably from 10:1 to 5:1 , advantageously from 5:1 to 7:1.

[0162] According to a particular embodiment, a lubricating composition according to the invention may comprise:

[0163] - from 60% to 99.8% by weight, preferably from 70% to 90% by weight, of one or more base oils;

[0164] - from 1 % to 30% by weight, in particular from 5 to 25% by weight, more particularly from 5 to 20% by weight and typically from 7.5% to 15% by weight of at least one diester compound according to the invention, as defined above; and

[0165] - from 0.1 to 10% by weight, in particular from 0.5 to 5% by weight, more preferably from 0.5% to 2.0% by weight, of one or more further detergent additives (distinct from the said diester compound according to the invention), notably chosen from metallic detergent additives, especially chosen from calcium and magnesium salts and mixtures thereof; with respect to the total weight of the lubricating composition.

[0166] Other additives

[0167] A lubricant composition considered according to the invention may also comprise one or more other additives, distinct from said diester compound(s), selected from friction modifying additives, anti-wear additives, extreme pressure additives, antioxidants, viscosity index improvers, pour point depressant additives, dispersants, antifoam agents, thickeners, corrosion inhibitors, and mixtures thereof.

[0168] Thus, a lubricant composition under consideration according to the invention may also comprise at least one viscosity index improver (VI). Viscosity index improvers (VI), in particular viscosity index improver polymers, ensure good cold-holding properties and minimum viscosity at high temperatures.

[0169] Examples of viscosity index improvers include polymeric esters, hydrogenated or nonhydrogenated homopolymers or copolymers of styrene, butadiene and isoprene, olefin homopolymers or copolymers, such as ethylene or propylene, polyacrylates and polymethacrylates (PMA).

[0170] Advantageously, a lubricant composition according to the invention comprises at least one viscosity index improver selected from linear, grafted, comb or star, preferably star, polymethacrylates (PMA) and hydrogenated polyisoprene-styrene (PISH).

[0171] In particular, the viscosity index improving additive(s) may be present in a lubricant composition according to the invention in a content ranging from 1 to 20% by weight, in particular from 10 to 15% by weight, based on the total weight of the lubricant composition.

[0172] According to one embodiment, a lubricant composition according to the invention is free of viscosity index improving additive.

[0173] A lubricant composition considered according to the invention may comprise at least one friction modifying additive.

[0174] The friction modifying additives may be selected from compounds providing metallic elements and ash-free compounds, preferably from ash-free compounds.

[0175] Among the compounds providing metallic elements, mention may be made of transition metal complexes such as Mo, Sb, Sn, Fe, Cu, Zn whose ligands may be hydrocarbon compounds comprising oxygen, nitrogen, sulfur or phosphorus atoms.

[0176] Advantageously, the friction-modifying additives are selected from ash-free compounds, generally of organic origin and which may be more particularly 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.

[0177] According to an advantageous embodiment, a lubricant composition comprises at least one friction-modifying additive, in particular molybdenum-based. In particular, the molybdenum-based compounds may be selected from molybdenum dithiocarbamates (Mo-DTC), molybdenum dithiophosphates (Mo-DTP), and mixtures thereof.

[0178] Advantageously, a lubricant composition considered according to the invention may comprise from 0.01 to 5% by weight, preferably from 0.01 to 5% by weight, more preferably from 0.1 to 2% by weight or even more preferably from 0.1 to 1 .5% by weight, based on the total weight of the lubricant composition, of friction modifying additives.

[0179] A lubricant composition according to the invention may comprise at least one antiwear and / or extreme pressure additive.

[0180] Anti-wear additives and extreme pressure additives protect rubbing surfaces by forming a protective film adsorbed on these surfaces.

[0181] There is a wide variety of anti-wear additives. Preferably for the lubricant composition according to the invention, the anti-wear additives are selected from phospho-sulphur additives such as metal alkylthiophosphates, in particular zinc alkylthiophosphates, and more specifically zinc dialkyldithiophosphates or ZnDTP. Preferred compounds are of the formula Zn((SP(S)(ORs)(OR4))2, wherein R3and R4, which may be the same or different, independently represent an alkyl group, preferably an alkyl group having from 1 to 18 carbon atoms.

[0182] Amine phosphates are also anti-wear additives which can be employed in the lubricant composition according to the invention. However, the phosphorus provided by these additives can act as a poison to automotive catalytic systems because these additives are ash generators. These effects can be minimized by partially substituting the amine phosphates with additives that do not contribute phosphorus, such as, for example, polysulfides, in particular sulfur-containing olefins. Advantageously, the extreme-pressure and / or anti-wear additive(s) may be present in a lubricant composition according to the invention in a content ranging 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 total mass of lubricant composition.

[0183] A lubricant composition considered according to the invention may comprise at least one antioxidant additive. The antioxidant additives are essentially dedicated to delaying the degradation of the lubricant composition in service. This degradation may result in particular 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 radical inhibitors or hydroperoxide destroyers. Among the antioxidant additives commonly used, we can mention the phenolic type antioxidant additives, the amino type antioxidant additives, the phosphosulphur antioxidant additives. Some of these antioxidant additives, for example phosphosulfur antioxidant additives, can be ash generating. Phenolic antioxidant additives may be ashless or may be in the form of neutral or basic metal salts. In particular, the antioxidant additives may be selected from sterically hindered phenols, sterically hindered phenol esters and sterically hindered phenols comprising a thioether bridge, diphenylamines, diphenylamines substituted with at least one C1 -C12 alkyl group, N,N'-dialkyl-aryl-diamines and mixtures thereof.

[0184] Preferably, the sterically hindered phenols are selected from compounds comprising a phenol group in which at least one vicinal carbon of the carbon bearing the alcohol function is substituted by at least one C1 -C10 alkyl group, preferably a C1 -C6 alkyl group, preferably a C4 alkyl group, preferably by the ter-butyl group.

[0185] 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 the formula NR5R6R7 wherein R5 represents an aliphatic group or an aromatic group, optionally substituted, R6 represents an aromatic group, optionally substituted, R7 is a hydrogen atom, an alkyl group, an aryl group or a group of the formula R8S(O)zRg in which R8is an alkylene group or an alkenylene group, Rg is an alkyl group, an alkenyl group or an aryl group and z is 0, 1 or 2.

[0186] Sulfurized alkyl phenols or alkali and alkaline earth metal salts thereof may also be used as antioxidant additives.

[0187] A lubricant composition considered according to the invention may contain any type of antioxidant additives known to the skilled person. Advantageously, the lubricant composition comprises at least one ash-free antioxidant additive.

[0188] Also advantageously, a lubricant composition considered 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.

[0189] A lubricant composition considered according to the invention may comprise at least one pour point depressant additive (also known as "PPD" agents). By slowing down the formation of kerosene crystals, pour point depressant additives generally improve the cold behavior of the lubricant composition.

[0190] Examples of pour point depressants include alkyl polymethacrylates, polyacrylates, polyarylamides, polyalkylphenols, polyalkylnaphthalenes and alkylated polystyrenes. In particular, the pour point depressant additive(s) may be present in a lubricant composition according to the invention in a content ranging from 0.01% to 1% by weight, in particular from 0.1 % to 0.5% by weight, based on the total weight of the lubricant composition.

[0191] A lubricating composition considered according to the invention may also include at least one dispersing agent. The dispersing agents ensure the suspension and removal of insoluble solid contaminants consisting of oxidation by-products that are formed when the lubricant composition is in use. They may be selected from Mannich bases, succinimides and derivatives thereof.

[0192] In particular, a lubricant composition considered according to the invention may comprise from 0.2% to 10% by weight of dispersing agent(s), based on the total weight of the composition.

[0193] A lubricating composition under consideration according to the invention may also comprise at least one antifoam additive. The antifoam additives may be selected from polar polymers such as polymethylsiloxanes or polyacrylates.

[0194] In particular, a lubricant composition considered according to the invention may comprise from 0.01 % to 3% by weight of antifoam additive(s), relative to the total weight of the lubricant composition.

[0195] As mentioned above, all of the additives detailed above can be introduced in the form of a mixture or "package" of additives.

[0196] According to this embodiment, the additive package may represent from 1% to 30% by weight with respect to the total mass of the composition, in particular from 1% to 20% by weight, in particular from 3% to 15% by weight and more particularly from 5% to 15% by weight.

[0197] According to a particular embodiment, a lubricating composition according to the invention may comprise or even consist of:

[0198] - a base oil or a mixture of base oils;

[0199] - one or more diester compounds according to the invention, in particular as defined above; and

[0200] - optionally one or more additives, distinct from said diester compound(s), selected from further detergent additives, in particular metallic detergent additives, friction modifiers, anti-wear additives, extreme pressure additives, antioxidants, viscosity index (VI) improvers, pour point depressant (PPD) additives, dispersants, antifoam agents, thickeners, corrosion inhibitors, and mixtures thereof.

[0201] Preferably, a lubricant composition formulated according to the invention comprises or consists of:

[0202] - from 60% to 98.9% by weight, in particular from 70% to 90% by weight, of one or more base oils;

[0203] - from 0.%1 to 20% by weight, preferably from 0.5% to 10% by weight, of one or more diester compounds according to the invention as defined above; and

[0204] - from 1% to 30% by weight, preferably from 3% to 20% by weight, of one or more additive(s) chosen from further detergent additives, distinct from the said diester compound(s), in particular chosen from metal detergent additives; anti-wear agents; antioxidants; dispersants; viscosity index improvers and mixtures thereof; the contents being expressed with respect to the total mass of said lubricant composition.

[0205] In particular, a lubricant composition formulated according to the invention may comprise or even consist of:

[0206] - from 60% to 99.8% by weight, in particular from 70% to 90% by weight, of one or more base oils;

[0207] - from 0.1 % to 20% by weight, preferably from 0.5% to 10% by weight, of one or more diester compounds according to the invention as defined above;

[0208] - from 0.1 % to 10% by weight, in particular from 0.5% to 5% by weight, of one or more metallic detergent additives distinct from the said diester compound(s), in particular as defined above, especially chosen from calcium and magnesium salts and mixtures thereof; and

[0209] - optionally from 1% to 30% by weight, preferably from 3% to 20% by weight, of one or more other additives chosen from pour point depressants, anti-wear agents, antioxidants, viscosity index improvers and mixtures thereof, the contents being expressed with respect to the total mass of said lubricant composition.

[0210] More particularly, a lubricant composition formulated according to the invention may comprise or even consist of:

[0211] - from 60% to 99.8% by weight, in particular from 70% to 90% by weight, of one or more base oils; - from 0.1 % to 20% by weight, preferably from 0.5% to 10% by weight, of one or more diester compounds according to the invention as defined above;

[0212] - from 0.1 % to 10% by weight, in particular from 0.5% to 5% by weight, of one or more metallic detergent additives distinct from the said diester compound(s), in particular as defined above, especially chosen from calcium and magnesium salts and mixtures thereof; and

[0213] - optionally from 1% to 20% by weight, in particular from 10% to 15% by weight, of one or viscosity index improvers,

[0214] - optionally, from 0.01 % to 1% by weight, in particular from 0.1 % to 0.5% by weight, of one or more pour point depressant additive(s), the contents being expressed with respect to the total mass of said lubricant composition.

[0215] According to a particular embodiment, a lubricating composition according to the invention may have a kinematic viscosity, measured at 40°C according to ASTM D445, of between 50 mm2 / s and 200 mm2 / s, preferably between 100 mm2 / s and 150 mm2 / s.

[0216] Advantageously still, a lubricant composition according to the invention has a kinematic viscosity, measured at 100°C according to ASTM D445, of between 10 mm2 / s and 50 mm2 / s, preferably between 15 mm2 / s and 20 mm2 / s.

[0217] Applications

[0218] As previously indicated, the lubricating compositions considered according to the invention can be intended for mobile or stationary motorization systems, in particular for gasoline, diesel, gas or dual-fuel engines.

[0219] The invention thus relates, according to another of its aspects, to the use of a composition as defined above, incorporating one or more diester compound(s) as defined above as detergent additive or as detergent booster additive, to lubricate a mobile or stationary motorization system.

[0220] The lubricating compositions according to the invention can be intended in particular for motorization systems including an internal combustion engine, and more particularly a diesel or gasoline engine, preferably a diesel engine.

[0221] According to a particular embodiment, they are implemented for the lubrication of a motorization system of a vehicle, more particularly of a light or heavy vehicle, for example trucks. In particular, they can be adapted for the lubrication of gasoline or diesel engine systems, equipped with exhaust gas after-treatment systems, in particular diesel particulate filters (DPF).

[0222] According to preferred embodiment, the lubricating compositions according to the invention can be intended for motorcycle engines.

[0223] The detergency performances of the lubricant compositions according to the invention may be evaluated by any method known from the skilled person. In particular, the detergency performances of the lubricant composition may be evaluated by rating the level of deposits and / or varnish formed in an engine after a specific period of running.

[0224] All of the particular features and modes relating to the diester compound(s) of formula (I) and the lubricating composition comprising it, also apply to the intended uses, processes and methods according to the invention.

[0225] The invention will now be described by means of the following examples, which are given by way of illustration and are not limiting of the invention.

[0226] EXAMPLES

[0227] In the following examples, lubricant compositions according to the invention, and comparative composition have been prepared and evaluated regarding their detergency performances in a motorcycle engine.

[0228] Unless explicitly stated otherwise, the component contents for each lubricant composition are shown as percentages by weight based on the total weight of the lubricant composition.

[0229] Preparation of the lubricant compositions

[0230] Table 2 below shows the details of lubricating compositions according to the invention and of comparative compositions as well as their physicochemical characteristics.

[0231] The lubricating compositions are obtained by simply mixing at room temperature, the following components:

[0232] - Base oil 1 is a group III base oil (kinematic viscosity at 100°C measured according to ASTM D-556 = 7.5 mm2 / s),

[0233] - Base oil 2 is a group II base oil (kinematic viscosity at 100°C measured according to ASTM D-556 = 10.93 mm2 / s),

[0234] - Base oil 3 is a group II base oil (kinematic viscosity at 100°C measured according to ASTM D-556 = 15.174 mm2 / s), - An additive package (designated hereafter as “Package”) comprising notably from 10% to 20% by weight of an alkali metal sulfonate detergent dispersant,

[0235] - A viscosity index improver (VII) which is a conventional olefin polymer commercially available,

[0236] - A pour point depressant additive (PPD) which is a conventional polymethacrylate polymer,

[0237] - A diester compound obtained by esterification reaction between a dipropylene glycol molecule and two lauric acid (or dodecanoic acid) molecules and having a kinematic viscosity at 100°C measured according to ASTM D445-97 = 3.91 mm2 / s).

[0238] Table 2

[0239] The nature of the base oil is adapted in order to obtain final lubricant compositions with a similar viscosity both at 40°C and 100°C.

[0240] Composition C1 * is comparative since it does not comprise any diester compound of formula (I).

[0241] Composition C2 is according to the invention.

[0242] Evaluation of the detergency performances of the lubricant compositions

[0243] The detergency performances of the lubricant compositions have been evaluated by running a motor with the lubricant composition to be tested and by rating the levels of carbon or varnish deposits formed on the internal parts of the engine.

[0244] The engine used is a 4-Stroke engine with a single cylinder. Engine specifications are reported in Table 3 below. Table 3

[0245] Each lubricant composition is tested in a new engine. For each lubricant, the engine is run for 20 hours by repeating 5 times the following 4 hours cycle:

[0246] - 15 min at 1600 rpm,

[0247] - 165 min at 8,650 rpm,

[0248] - 35 min at 7,000 rpm, and

[0249] - 25 min at 9,000 rpm.

[0250] At the end of the 20 hours run, the engine parts are rated to determine the levels of carbon or varnish deposits as per ASTM manual no. 20 on merit basis. Merit Rating defines the amount of distress or deposits in numerical term on a descending scale from 10, which represents the absence of distress or deposits. The engine parts rated are: the top groove filling, the piston top, the crown land, the 2ndland, the 3rdland, the top groove, the second groove, the 3rdgroove, the under crown and the crown cutting..

[0251] A Total merits value are finally obtained by summing the Merit Ratings determined for each component. The higher the Total merits value is, the cleaner the engine.

[0252] The results are presented in Table 4 below.

[0253] Table 4

[0254] We observe that the Total merits value associated to the lubricant composition C2 according to the invention is higher than the Total merits value associated to the comparative lubricant composition C1 *. The lubricant composition C2 according to the invention has therefore improved detergency performances with respect to the comparative lubricant composition C1 *.

Claims

CLAIMS1 . Use, as a detergent additive in a lubricant composition, of at least one diester compound of formula (I):Ra-C(O)-O-([C(R)2]n-O)s-C(O)-Rb(I)Wherein: each R represents, independently of one another, a hydrogen atom or a (Ci-C5)alkyl group, linear or branched, in particular a methyl, ethyl or propyl group, notably methyl; s has a value of 1 or 2; n has a value of 1 , 2 or 3; it being understood that, when s is different from 1 , n may be identical or different; andRaand Rb, which may be identical or different, represent independently of one another, hydrocarbon groups, saturated or unsaturated, linear or branched, having a linear chain with 2 to 1 1 carbon atoms, preferably with 3 to 8 carbon atoms; provided that, when s has a value of 2 and n, which are identical, have a value of 2, at least one of the groups R represents a (Ci-C5)alkyl group, linear or branched; and provided that, when s has a value of 1 and n has a value of 3, at least one of the groups R bound to the carbon in the beta position of the oxygen atoms of the ester functions represents a hydrogen atom.

2. The use according to claim 1 , wherein said at least one diester compound of formula (I) is a diester of formula (I’):Ra-C(O)-O-([C(R)2]n-O)-([C(R’)2]m-O)s.i-C(O)-Rb(I )Wherein:R and R’ represent, independently of one another, a hydrogen atom or a (Ci-C5)alkyl group, linear or branched, in particular a methyl, ethyl or propyl group, notably methyl; s has a value of 1 or 2; n is equal to 2; andRaand Rb, which may be identical or different, represent independently of one another, hydrocarbon groups, saturated or unsaturated, linear or branched, having a linear chain with 2 to 1 1 carbon atoms, preferably with 3 to 8 carbon atoms; provided that, when s has a value of 2, at least one of the R or R’ groups represents a (Ci-C5)alkyl group, linear or branched.

3. The use according to claim 1 or to claim 2, wherein said diester compound(s) of formula (I) are used in an amount of from 1% to 30% by weight, based on the total weightof the lubricant composition, in particular, from 5% to 25% by weight, preferably from 7% to 20% by weight, and more particularly from 7.5% to 15 % by weight.

4. The use according to any of claims 1 to 3, said lubricant composition further comprising at least one further detergent additive, distinct from the diester compound(s) of formula (I), preferably chosen from metal detergent additives, preferably chosen from the salts of alkali metals or alkaline-earth metals, overbased or not, in particular from the calcium salts, the magnesium salts and mixtures thereof.

5. The use according to claim 4, wherein said further detergent additive(s) are present in a content of less than or equal to 15% by weight, relative to the total weight of the lubricant composition, in particular less than or equal to 10% by weight, and more particularly from 0.5% to 5.0% by weight, advantageously from 0.5% to 2.0% by weight.

6. The use according to claim 4 or to claim 5, wherein the diester compound(s) of formula (I) and the further detergent additives are present in the lubricant composition according to a weight ratio ranging from 10:1 to 1 :10, preferably from 10:1 to 1 :1 , more preferably from 10:1 to 5:1 , advantageously from 5:1 to 7:1 .

7. The use according to any one of the preceding claims, said lubricant composition comprising one or more other additives, distinct from said diester compound(s), selected from friction modifying additives, anti-wear additives, extreme pressure additives, antioxidants, viscosity index improvers, pour point depressants, dispersants, antifoam agents, thickeners, corrosion inhibitors, and mixtures thereof.

8. The use according to any of the preceding claims, in a motorization system, preferably in a mobile or stationary engine system, more preferably in an internal combustion engine, typically in a diesel engine, a gasoline engine, a gas engine or dualfuel engine, in particular in a light or heavy duty motor vehicle.

9. The use according to the preceding claim, wherein the motorization system is a motorcycle engine.

10. The use according to claim 8, to clean up and / or to keep clean at least one internal part of the motorcycle engine system, preferably the pistons.1 1 . Use as detergency booster additive in a lubricant composition comprising at least one detergent additive, of at least one diester compound of formula (I):Ra-C(O)-O-([C(R)2]n-O)s-C(O)-Rb(I) wherein: each R represents, independently of one another, a hydrogen atom or a (Ci-C5)alkyl group, linear or branched, in particular a methyl, ethyl or propyl group, notably methyl; s has a value of 1 or 2; n has a value of 1 , 2 or 3; it being understood that, when s is different from 1 , n may be identical or different; andRaand Rb, which may be identical or different, represent independently of one another, hydrocarbon groups, saturated or unsaturated, linear or branched, having a linear chain with 2 to 1 1 carbon atoms, preferably with 3 to 8 carbon atoms; provided that, when s has a value of 2 and n, which are identical, have a value of 2, at least one of the groups R represents a (Ci-C5)alkyl group, linear or branched; and provided that, when s has a value of 1 and n has a value of 3, at least one of the groups R bound to the carbon in the beta position of the oxygen atoms of the ester functions represents a hydrogen atom.

12. The use according to claim 1 1 , wherein the lubricant composition comprising said at least one detergent additive and said at least one diester compound of formula (I) has improved detergent performances, with respect to a same lubricant composition comprising said at least one detergent additive and that is free from said at least one diester compound of formula (I).

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