CARBODIIMIDE FOR USE AS AN ADDITIVE IN LUBRICANTS INTENDED FOR DRIVE DEVICE SYSTEMS FOR IMPROVED ELASTOMER COMPATIBILITY

Abstract

Carbodiimide for use as an additive in lubricants intended for drive device systems for improved elastomer compatibility

The present invention relates to a lubricant composition intended for a drive system, comprising at least one or more base oils, at least one carbodiimide additive and at least one basic organic additive improving TBN; as well as a process for lubricating a drive system using such a lubricating composition.

It also relates to the use of at least one carbodiimide additive in a lubricant composition intended for a drive system, to improve its compatibility with elastomers.

Claims

1-15. (canceled)

16. A lubricant for a drive system, the lubricant comprising: at least one base oil; at least one carbodiimide additive; and at least one basic organic additive that increases the total base number (TBN) of the lubricant, as measured according to the standard ASTM D2896.

17. The lubricant of claim 16, wherein the carbodiimide additive is represented by formula (I):
X(NCNY).sub.qNCNY(I), wherein: each X and Y independently represent a saturated or unsaturated, linear, branched or cyclic, aromatic or nonaromatic, optionally substituted hydrocarbon-based radical comprising from 6 to 60 carbon atoms; and q is 0 or an integer ranging from 1 to 100.

18. The lubricant of claim 17, wherein: X and Y each comprise from 9 to 15 carbon atoms; and q is an integer ranging from 1 to 40.

19. The lubricant of claim 16, wherein the carbodiimide additive is a mono-carbodiimide represented by formula (I):
XNCNY(I), wherein X and Y are independently represented by formula (i): ##STR00027## wherein: * represents the site of bonding to a nitrogen atom of the carbodiimide function; R.sub.1 represents a substituted or unsubstituted, saturated or unsaturated, linear, branched or cyclic aliphatic group, or a substituted or unsubstituted aromatic group; R.sub.2 represents a hydrogen atom, a substituted or unsubstituted, saturated or unsaturated, linear, branched or cyclic aliphatic group, or a substituted or unsubstituted aromatic group; and R.sub.3 represents a hydrogen atom, a substituted or unsubstituted, saturated or unsaturated, linear, branched or cyclic aliphatic group, or a substituted or unsubstituted aromatic group.

20. The lubricant of claim 19, wherein R.sub.1, R.sub.2, and R.sub.3 each comprise from 2 to 20 carbon atoms.

21. The lubricant of claim 16, wherein X and Y are independently represented by formula (i): ##STR00028## wherein: R.sub.1 and R.sub.2 independently represent C.sub.3 to C.sub.20 branched alkyl groups; and R.sub.3 represents a hydrogen atom or a C.sub.3 to C.sub.20 branched alkyl group.

22. The lubricant of claim 21, wherein: R.sub.1 and R.sub.2 independently represent C.sub.3 to C.sub.6 isopropyl groups; and R.sub.3 represents a hydrogen atom.

23. The lubricant of claim 16, wherein the carbodiimide additive is chosen from N,N-bis(2,6-diisopropylphenyl)carbodiimide, N,N-bis(2,4,6-triisopropylphenyl)carbodiimide or mixtures thereof.

24. The lubricant of claim 16, wherein the carbodiimide additive is N, N-bis(2,6-diisopropylphenyl)carbodiimide.

25. The lubricant of claim 16, wherein the basic organic additive has a base number (BN) ranging from greater than 10 mg KOH/g to 1200 mg KOH/g of additive, as measured according to the standard ASTM D2896.

26. The lubricant of claim 25, wherein the basic organic additive has a base number of greater than or equal to 100 mg KOH/g of additive.

27. The lubricant of claim 16, wherein the basic organic additive is chosen from: (a) polyalkylamine additives; (b) guanidinium, ammonium, or phosphonium-based ionic liquid additives; (c) additives produced by reaction between i) a boron compound, ii) an amine compound, and iii) a hydroxybenzoic acid or an alkali metal or alkaline-earth metal salt thereof; or (d) mixtures thereof.

28. The lubricant of claim 16, wherein the basic organic additive is chosen from polyalkylamines of formula (II): ##STR00029## wherein: R.sub.4 and R.sub.5 independently represent a hydrogen atom or a linear or branched alkyl or alkenyl group comprising from 1 to 22 carbon atoms; R.sub.6 and R.sub.7 independently represent a linear or branched alkyl or alkenyl group comprising from 1 to 30 carbon atoms; A1 and A2 independently represent a C.sub.1 to C.sub.6 alkylene groups; and m is 0, 1, 2, or 3.

29. The lubricant of claim 28, wherein: R.sub.6 and R.sub.7 independently represent a linear or branched alkyl or alkenyl group comprising from 1 to 22 carbon atoms; and A1 and A2 independently represent (CH.sub.2).sub.3 propylene groups; and m is 1 or 2.

30. The lubricant of claim 16, wherein the basic organic additive is chosen from polyalkylamines of formula (II-a): ##STR00030## wherein: R.sub.4 and R.sub.5 independently represent a hydrogen atom or a C.sub.1 to C.sub.6 alkyl group; and R.sub.6 and R.sub.7 independently represent a C.sub.1 to C.sub.6 alkyl group.

31. The lubricant of claim 30, wherein R.sub.4, R.sub.5, R.sub.6, and R.sub.7, represent methyl groups.

32. The lubricant of claim 16, wherein the basic organic additive is chosen from polyalkylamines of formula polyalkylamines of formula (II-b): ##STR00031## wherein: R.sub.4 and R.sub.5 represent hydrogen atoms; and R.sub.6 and R.sub.7 independently represent a C.sub.8 to C.sub.22 alkyl group.

33. The lubricant of claim 32, wherein R.sub.6 and R.sub.7 independently represent represent a C.sub.16 to C.sub.18 alkyl group.

34. The lubricant of claim 16, wherein the lubricant comprises at least 0.1% by mass of the basic organic additive, relative to the total mass of the lubricant.

35. The lubricant of claim 16, wherein: the lubricant comprises from 1% to 5% by mass of the basic organic additive, relative to the total mass of the lubricant; and the lubricant composition further comprises at least one additional additive chosen from metallic detergent additives, friction-modifying additives, anti-wear additives, extreme-pressure additives, antioxidants, viscosity index improvers, pour point depressants, dispersants, antifoams, thickeners, corrosion inhibitors, copper passivators, or mixtures thereof.

Description

DETAILED DESCRIPTION

Carbodiimide Additive

[0080] As indicated previously, the invention is based on the use, in a lubricant for a drive system, of one or more carbodiimide additives, to improve the compatibility of the lubricant with elastomers.

[0081] It is understood that the invention may involve a single carbodiimide additive or a mixture of at least two different carbodiimide additives, notably two, three or more different carbodiimide additives, in particular as defined below.

[0082] The term carbodiimide additive is intended to denote an additive comprising at least one NCN unit.

[0083] The carbodiimide additive under consideration according to the invention may be a mono-carbodiimide additive comprising a single carbodiimide unit, or else a poly-carbodiimide additive comprising at least two carbodiimide units.

[0084] Preferably, the carbodiimide additives used according to the invention are of formula (I) below:

[Chem 1]

X(NCNY).sub.qNCNY(I) [0085] in which: [0086] X and Y represent, independently of each other, a saturated or unsaturated, linear, branched or cyclic, aromatic or nonaromatic, optionally substituted hydrocarbon-based radical preferably comprising from 6 to 60 carbon atoms, in particular from 8 to 20 carbon atoms, and more particularly from 9 to 15 carbon atoms; and [0087] q is 0 or an integer ranging from 1 to 100, in particular from 1 to 50 and more particularly from 1 to 40.

[0088] Said radicals X and Y, which are preferably aromatic, may bear aromatic, aliphatic and/or cycloaliphatic substituents, preferably at least in the ortho position relative to the carbodiimide group, for example alkyl groups comprising at least two carbon atoms.

[0089] According to a particular embodiment, the carbodiimide additive under consideration according to the invention is a mono-carbodiimide.

[0090] It more particularly corresponds to the abovementioned formula (I) in which q is 0.

[0091] In other words, the carbodiimide additive under consideration according to the invention may be of formula (I) below:

[Chem 2]

XNCNY(I), [0092] in which X and Y are as defined previously.

[0093] In particular, X and Y, which may be identical or different, in particular identical, may represent a phenyl group, preferably substituted at at least one of the ortho positions relative to the carbodiimide function, preferably at both ortho positions, and optionally in the para position relative to the carbodiimide function, with a group chosen from linear, branched or cyclic, substituted or unsubstituted, saturated or unsaturated aliphatic groups and substituted or unsubstituted aromatic groups, said aliphatic and/or aromatic groups preferably comprising from 2 to 20 carbon atoms.

[0094] In other words, X and Y in the abovementioned formula (I), which may be identical or different, in particular identical, may represent radicals of formula:

##STR00001## [0095] in which: [0096] * represents the site of bonding to a nitrogen atom of the carbodiimide function; [0097] at least one from among R.sub.1 and R.sub.2 represents a substituted or unsubstituted, saturated or unsaturated, linear, branched or cyclic aliphatic group, or a substituted or unsubstituted aromatic group, preferably comprising from 2 to 20 carbon atoms; [0098] the other from among R.sub.1 and R.sub.2 represents a hydrogen atom, a substituted or unsubstituted, saturated or unsaturated, linear, branched or cyclic aliphatic group, or a substituted or unsubstituted aromatic group, preferably comprising from 2 to 20 carbon atoms; and [0099] R.sub.3 represents a hydrogen atom, a substituted or unsubstituted, saturated or unsaturated, linear, branched or cyclic aliphatic group, or a substituted or unsubstituted aromatic group, preferably comprising from 2 to 20 carbon atoms; said aromatic group being optionally condensed with the phenyl ring bearing it.

[0100] Preferably, at least one from among R.sub.1 and R.sub.2, in particular R.sub.1 and R.sub.2, which may be identical or different, represents(s) a linear or branched C.sub.2 to C.sub.20 alkyl group, such as ethyl, propyl, isopropyl, butyl or tert-butyl groups; a C.sub.3 to C.sub.20 cycloalkyl group, for example a cyclohexyl group; or an aryl or aralkyl group comprising from 6 to 15 carbon atoms, such as a phenyl, tolyl or benzyl group.

[0101] According to a particularly preferred embodiment, R.sub.1 and R.sub.2, which may be identical or different, in particular identical, represent C.sub.3 to C.sub.20, in particular C.sub.3 to C.sub.10, notably C.sub.3 to C.sub.6, branched alkyl groups such as isopropyl groups. Preferably, R.sub.3 represents a hydrogen atom or a C.sub.3 to C.sub.20, in particular C.sub.3 to C.sub.10, notably C.sub.3 to C.sub.6, branched alkyl group such as an isopropyl group; more preferentially, R.sub.3 represents a hydrogen atom.

[0102] According to a particular embodiment, the carbodiimide additive used according to the invention corresponds to formula (Ia) below:

##STR00002##

[0103] in which the groups R.sub.1, which may be identical or different, and the groups R.sub.2, which may be identical or different, are as defined previously, and in particular represent C.sub.3 to C.sub.6 branched alkyl groups, preferably isopropyl groups.

[0104] By way of example, the carbodiimide additive may be chosen from N,N-bis(2,6-diisopropylphenyl)carbodiimide, N,N-bis(2,4,6-triisopropylphenyl)carbodiimide and mixtures thereof.

[0105] According to a particularly preferred embodiment, the carbodiimide additive is N,N-bis(2,6-diisopropylphenyl)carbodiimide.

[0106] The carbodiimide additives may also be chosen from carbodiimide dimers, oligomers and polymers, known as poly-carbodiimide additives.

[0107] Such poly-carbodiimide additives more particularly correspond to the abovementioned formula (I), in which q is greater than or equal to 1, the groups X and Y possibly being as defined previously for mono-carbodiimides.

[0108] The carbodiimide additives used according to the invention, preferably mono-carbodiimides, may be commercially available or prepared according to synthetic methods known to those skilled in the art.

[0109] Said carbodiimide additive(s) are advantageously used in a content sufficient to achieve the desired effect in terms of the lubricant's compatibility with elastomers, in particular to reach the required specifications for the lubricant in terms of compatibility with elastomers, for example as assessed according to the standard CEC L-112-16.

[0110] The amount of carbodiimide additive(s) used thus varies more particularly as a function of the nature of the lubricant, and notably with regard to the nature and amount of basic organic additives, notably amine additives, present in the lubricant and which may adversely affect the lubricant's compatibility with elastomers.

[0111] Said carbodiimide additive(s) may thus be advantageously used in an adjusted amount to mitigate/compensate for the adverse effect associated with the use of basic organic additives, in particular as described in the text hereinbelow, on the lubricant's compatibility with elastomers.

[0112] Generally speaking, said carbodiimide additive(s) under consideration according to the invention, in particular as defined previously, may be used in a proportion of from 0.1% to 8% by mass of commercial product, in particular from 0.5% to 5% by mass and more particularly from 1% to 3% by mass of commercial product, relative to the total mass of said lubricant composition.

[0113] According to a particular embodiment, a lubricant composition according to the invention may comprise from 0.01% to 0.8% by mass of carbodiimide active material, in particular from 0.05% to 0.5% by mass and more particularly from 0.1% to 0.3% by mass of carbodiimide active material, relative to the total mass of said lubricant composition.

[0114] The mass content of carbodiimide active material is intended to denote the mass content of said carbodiimide compound, without any compounds, in particular solvents, with which it is formulated.

Lubricant Composition

[0115] A lubricant composition under consideration according to the invention thus comprises one or more base oils, and also other additives conventionally considered in lubricant compositions.

[0116] It is understood that the nature and amount of the other compounds are suitable for the intended purpose of the lubricant, and more particularly for the type of drive system for which it is intended, for example depending on whether it is intended for use in a vehicle engine, marine engine, etc.

Base Oil

[0117] Conventionally, a lubricant composition comprises one or more base oils.

[0118] These base oils may be chosen from the base oils conventionally used in the field of lubricant oils, such as mineral, synthetic or natural, animal or plant oils or mixtures thereof.

[0119] It may be a mixture of several base oils, for example a mixture of two, three, four or even more than four base oils.

[0120] The base oils of the lubricant compositions under consideration 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 equivalents thereof according to the ATIEL classification) and presented in the table below or mixtures thereof.

TABLE-US-00001 TABLE 1 Saturates Sulfur Viscosity content content index (VI) Group I <90% >0.03% 80 VI < 120 Mineral oils Group II 90% 0.03% 80 VI < 120 Hydrocracked oils Group III 90% 0.03% 120 Hydrocracked or hydro- isomerized oils Group IV Poly--olefins (PAO) Group V Esters and other bases not included in Groups I to IV

[0121] The 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, deasphalting, solvent deparaffinning, hydrotreating, hydrocracking, hydroisomerization and hydrofinishing.

[0122] The synthetic base oils may be esters of carboxylic acids and of alcohols, poly--olefins or polyalkylene glycols (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 poly--olefins used as base oils are obtained, for example, from monomers comprising 4 to 32 carbon atoms, for example from decene, octene or dodecene, and with a viscosity at 100 C. of between 1.5 and 15 mm.sup.2.Math.s.sup.1 according to the standard ASTM D445. Their average molecular mass is generally between 250 and 3000 according to the standard ASTM D5296. Mixtures of synthetic and mineral oils, which may be biobased, may also be used.

[0123] There is generally no limit as regards the use of different base oils in the lubricant composition, apart from the fact that they must have properties, measured according to the standards in force, notably in terms of viscosity, viscosity index, sulfur content or resistance to oxidation, that are suitable for use in drive systems, for example for vehicle engines.

[0124] According to one particular embodiment, a lubricant composition under consideration according to the invention comprises at least one mineral base oil (group I).

[0125] According to another particular embodiment, a lubricant composition under consideration according to the invention comprises at least one base oil chosen from group II, III and IV oils of the API classification, and mixtures thereof, in particular at least one group III base oil.

[0126] A lubricant composition under consideration according to the invention may comprise at least 50% by mass of base oil(s) relative to its total mass, in particular at least 60% by mass of base oil(s), and more particularly between 70% and 99% by mass of base oil(s), relative to its total mass.

Additives

TBN Booster Basic Organic Additive

[0127] As indicated previously, the use of one or more carbodiimide additives according to the invention proves to be particularly advantageous for countering the adverse effect associated with the use of basic organic additives improving the TBN, in particular amine additives, on the compatibility of the lubricant with elastomers.

[0128] The lubricant composition under consideration according to the invention, supplemented with one or more carbodiimide additives, in particular as defined previously, may thus advantageously comprise one or more basic organic additives that are capable of increasing the TBN of the lubricant composition, in particular one or more amine additives.

[0129] Basic organic TBN booster additives are known to those skilled in the art. They are different from metallic detergents. These TBN booster additives have the advantage of generating little or even no ash, unlike metallic detergents. They are also said to be ashless compounds or additives.

[0130] Preferably, the TBN booster additives used according to the invention have a base number (BN), measured according to the standard ASTM D2896, of greater than 10 mg KOH/g and up to 1200 mg KOH/g of additive, in particular greater than or equal to 50 mg KOH/g of additive and more particularly greater than or equal to 100 mg KOH/g of additive.

[0131] Advantageously, by virtue of the use of one or more carbodiimide additives according to the invention, the amount of said basic organic additive(s) improving the TBN, in particular amine additive(s), for example of the polyalkylamine type, as described in the text hereinbelow, which can be incorporated into said lubricant composition, is not limited in view of the incompatibility considerations of said bases with respect to elastomers.

[0132] Consequently, the amount of basic organic additives, in particular amine additives, for example of the polyalkylamine type, may be adjusted in such a way as to achieve the desired TBN for the lubricant composition.

[0133] The TBN target value may vary according to the lubricant's intended application.

[0134] In an advantageous manner, the presence of at least one carbodiimide additive thus allows the use of an increased amount of basic organic additive(s) without having an impact on the compatibility of the lubricant with elastomers, to achieve a lubricant with the desired TBN, and thus to reduce the presence of undesirable metallic detergents in view of the ash they generate.

[0135] In particular, said basic organic TBN booster additive(s), in particular amines, for example of the polyalkylamine type, can be used in a content of greater than or equal to 0.1% by mass, relative to the total mass of said lubricant composition, in particular in a content of between 0.1% and 10% by mass, more particularly between 0.5% and 7% by mass, preferably between 1% and 5% by mass.

[0136] Preferably, said basic organic TBN booster additive(s), in particular amines, for example of the polyalkylamine type, can be used in a content such that their presence, in the lubricant composition, contributes at least 1 mg KOH/g of the total TBN of said composition, in particular from 1 to 40 mg KOH/g, in particular from 1 to 15 mg KOH/g, in particular at least 3 mg KOH/g of the TBN of the lubricant composition.

[0137] In particular, said basic organic TBN booster additive(s), in particular amines, for example of the polyalkylamine type, may be used in a content such that the BN of said basic organic additive(s) represents at least 3%, in particular at least 5% and preferably from 10% to 50% of the TBN of the lubricant composition.

[0138] According to a particular embodiment, said basic organic TBN booster additive(s), in particular amines, for example of the polyalkylamine type, and said carbodiimide compound(s), are present in a lubricant composition according to the invention in a TBN booster/carbodiimide mass ratio greater than or equal to 0.3, in particular greater than or equal to 0.8 and more particularly between 1 and 10.

[0139] Said basic organic TBN booster additive(s) used in a composition according to the invention may preferably be chosen from: [0140] (a) polyalkylamine additives, in particular as described in the text hereinbelow; [0141] (b) guanidinium-, ammonium- or phosphonium-based ionic liquid additives, in particular as described in the text hereinbelow; [0142] (c) additives produced by reaction between at least: [0143] a hydroxybenzoic acid, optionally substituted with a hydrocarbon-based group; or an alkali metal or alkaline-earth metal salt thereof, optionally overbased; [0144] a boron compound; and [0145] an amine compound, in particular as described in the text hereinbelow; [0146] and mixtures thereof.

[0147] In particular, the TBN booster additives under consideration according to the invention are not amine antioxidant additives, in particular aromatic amine antioxidant additives. Aromatic amine antioxidants are generally of formula NR.sup.8R.sup.9R.sup.10 in which R.sup.8 represents an optionally substituted aliphatic or aromatic group, R.sup.9 represents an optionally substituted aromatic group, R.sup.10 represents a hydrogen atom, an alkyl group, an aryl group or a group of formula R.sup.11S(O).sub.2R.sup.12 in which R.sup.11 represents an alkylene group or an alkenylene group, R.sup.12 represents an alkyl group, an alkenyl group or an aryl group and z represents 0, 1 or 2.

[0148] It is understood that a lubricant composition according to the invention may comprise a single basic organic TBN booster additive or a mixture of at least two basic organic TBN booster additives, in particular two, three or more basic organic TBN booster additives, chosen from the amine compounds detailed in the text hereinbelow.

(a) Polyalkylamine Additives

[0149] The basic organic TBN booster additives used in a lubricant composition according to the invention may more particularly comprise polyalkylamine-type additives.

[0150] According to a particular embodiment, a lubricant composition according to the invention comprises at least one polyalkylamine additive, more particularly chosen from dialkylene triamines and trialkylene tetramines.

[0151] The polyalkylamine additives may more particularly be of formula (II) below:

##STR00003## [0152] in which: [0153] R.sub.4 and R.sub.5 represent, independently of each other, a hydrogen atom or a linear or branched alkyl or alkenyl group in particular comprising from 1 to 22 carbon atoms; [0154] R.sub.6 and R.sub.7 represent, independently of each other, a linear or branched alkyl or alkenyl group in particular comprising from 1 to 30 carbon atoms, in particular from 1 to 22 carbon atoms; [0155] A1 and A2 represent, independently of each other, a C.sub.1 to C.sub.6, in particular C.sub.1 to C.sub.4, notably C.sub.1 to C.sub.3 alkylene group; preferably, A1 and A2 represent (CH.sub.2).sub.3 propylene groups; and [0156] m is 0, 1, 2 or 3; preferably, m is 1 or 2.

[0157] Preferably, A1 and A2 are identical. In particular, they may represent methylene (CH.sub.2), ethylene (CH.sub.2CH.sub.2), methylethylene (CH.sub.2CH(CH.sub.3) or CH(CH.sub.3)CH.sub.2) or propylene ((CH.sub.2).sub.3) groups. Preferably, A1 and A2 represent (CH.sub.2).sub.3 propylene (or trimethylene) groups.

[0158] Preferably, R.sub.4 and R.sub.5 are identical. In particular, R.sub.4 and R.sub.5 may represent hydrogen atoms.

[0159] According to a particular embodiment, the polyalkylamine additive may be of formula (II) in which: [0160] R.sub.4 and R.sub.5 represent hydrogen atoms; and [0161] R.sub.6 and R.sub.7, which may be identical or different, represent linear or branched alkyl groups comprising from 8 to 22 carbon atoms, preferably from 14 to 18 carbon atoms and more preferentially from 16 to 18 carbon atoms.

[0162] According to another implementation variant, the polyalkylamine additive may be of formula (II) in which: [0163] R.sub.4 and R.sub.5 represent, independently of each other, a hydrogen atom or a linear or branched C.sub.1 to C.sub.6, in particular C.sub.1 to C.sub.3, alkyl group, notably a methyl group; preferably, R.sub.4 and R.sub.5, which are identical, represent hydrogen atoms or methyl groups; preferably, R.sub.4 and R.sub.5, which are identical, represent hydrogen atoms; [0164] R.sub.6 and R.sub.7 represent, independently of each other, a linear or branched C.sub.1 to C.sub.6, in particular C.sub.1 to C.sub.3, alkyl group, notably a methyl group; preferably, R.sub.6 and R.sub.7, which are identical, represent methyl groups.

[0165] According to a particular embodiment, a lubricant composition according to the invention may comprise at least one polyalkylamine additive of the abovementioned formula (II) in which m is 1 and A1 and A2 are propylene groups.

[0166] In particular, the polyalkylamine additive may be of formula (II-a) below:

##STR00004## [0167] in which: [0168] R.sub.4 and R.sub.5 represent, independently of each other, a hydrogen atom or a C.sub.1 to C.sub.6, in particular [0169] C.sub.1 to C.sub.3, alkyl group and more particularly a methyl group; [0170] preferably, R.sub.4 and R.sub.5 are identical and more preferentially represent hydrogen atoms or methyl groups; and even more preferentially R.sub.4 and R.sub.5 are identical and represent hydrogen atoms; [0171] R.sub.6 and R.sub.7 represent, independently of each other, a C.sub.1 to C.sub.6, in particular C.sub.1 to C.sub.3 alkyl group and more particularly a methyl group; preferably R.sub.6 and R.sub.7 are identical and more preferentially represent methyl groups.

[0172] By way of example, mention may be made of N,N-dimethyldipropylenetriamine (DMAPAPA) (CAS: 10563-29-8) and N,N,N,N-tetramethyldipropylenetriamine (TMDPT) CAS: 6711-48-4).

[0173] According to another particular embodiment, a lubricant composition according to the invention may comprise at least one polyalkylamine additive of the abovementioned formula (II) in which m is 2 and A1 and A2 are propylene groups.

[0174] In particular, the polyalkylamine additive may be of formula (II-b) below:

##STR00005## [0175] in which: [0176] R.sub.4 and R.sub.5 represent hydrogen atoms; and [0177] R.sub.6 and R.sub.7 represent, independently of each other, a C.sub.8 to C.sub.22, preferably C.sub.14 to C.sub.18 and more preferentially C.sub.16 to C.sub.18 alkyl group.

[0178] By way of example, mention may be made of the compound having the IUPAC name N-{3-[(3-aminopropyl)amino]propyl}-N,N-di-C16-C18 (even-numbered) alkyl propane-1,3-diamine (CAS 1623405-26-4).

[0179] Other polyalkylamine additives may also be considered. The lubricant composition according to the invention may thus comprise a mixture of polyalkylamines incorporating one or more branched polyalkylamines, as described in patent application WO 2017/148816. In particular, the lubricant composition according to the invention may use one or more polyalkylamines chosen from the polyalkylamines of formula (III) or (IV) below:

##STR00006## [0180] in which: [0181] R.sub.6 and R.sub.7 are as defined previously and in particular represent, independently of each other, a linear or branched alkyl or alkenyl group comprising from 8 to 22 carbon atoms, in particular from 14 to 18 carbon atoms and more particularly from 16 to 18 carbon atoms; [0182] n and z represent, independently of each other, 0, 1, 2 or 3; and [0183] when z is other than 0, o and p are, independently of each other, 0, 1, 2 or 3; [0184] and derivatives thereof.

[0185] The polyalkylamine derivatives correspond more particularly to polyalkylamines of formula (III) or (IV) in which one or more NH functions are methylated and/or alkoxylated.

[0186] In particular, a composition according to the invention may use at least one branched polyalkylamine of formula (III) or (IV), in other words being of formula (III) in which at least one from among n and z is greater than or equal to 1, or of formula (IV) in which n is greater than or equal to 1.

[0187] According to a particular embodiment, the lubricant composition comprises a mixture of polyalkylamines of formulae (III) and/or (IV) of which at least 3% by mass, in particular at least 5% by mass, notably at least 10% by mass and more particularly at least 20% by mass, are branched polyalkylamines of formulae (III) and/or (IV), relative to the total mass of the mixture of polyalkylamines of formulae (III) and (IV).

(b) Ionic Liquids

[0188] According to a particular embodiment, a lubricant composition according to the invention may comprise, as basic organic TBN booster additives, one or more ionic liquid-type additives chosen from guanidinium-based ionic liquids, ammonium-based ionic liquids, phosphonium-based ionic liquids and mixtures thereof.

[0189] Such additives are notably described in patent application WO 2020/216655 and in the patent applications filed under EP 20315181.6, EP 20315180.8 and EP 20315182.4.

[0190] The guanidinium-based ionic liquid additives may more particularly be of formula (V) below:

[Chem 9]

[CAT.sub.1.sup.+][X.sub.1.sup.](V) [0191] in which [CAT.sub.1.sup.+] represents a guanidinium ion and [X.sub.1.sup.] represents one or more anionic species.

[0192] Preferably, [CAT.sub.1.sup.+] represents a cation of formula (Va):

##STR00007## [0193] in which: [0194] R1 and R2 are chosen, independently of each other, from a hydrogen atom, a linear or branched C.sub.1-C.sub.30 alkyl group, a C.sub.3-C.sub.8 cycloalkyl group, a C.sub.6-C.sub.12 aryl group, or a C.sub.7-C.sub.12 aralkyl group, optionally substituted with a functional group comprising an oxygen and/or nitrogen atom; [0195] R3, R4, R5 and R6 are chosen, independently of each other, from a linear or branched C.sub.1-C.sub.30 alkyl group, a C.sub.3-C.sub.8 cycloalkyl group, a C.sub.6-C.sub.12 aryl group or a C.sub.7-C.sub.12 aralkyl group, optionally substituted with a functional group comprising an oxygen and/or nitrogen atom; or two from among (R3,R4) or (R5,R6) together form a methylene chain (CH.sub.2)p.sub.1- with p.sub.1 an integer from 2 to 5.

[0196] According to a particularly preferred embodiment, in formula (Va): [0197] R.sub.1 and R.sub.2 represent, independently of each other, a hydrogen atom or a linear or branched C.sub.1-C.sub.6, in particular C.sub.1-C.sub.3, alkyl group, notably methyl or ethyl.

[0198] Preferably, R1=R2. [0199] R3, R4, R5 and R6 are chosen, independently of each other, from linear or branched C.sub.1-C.sub.6, in particular C.sub.1-C.sub.3, alkyl groups, notably methyl and ethyl groups.

[0200] Preferably, R3=R4=R5=R6, and in particular represents CH.sub.3 or CH.sub.2CH.sub.3.

[0201] Preferably, [CAT.sub.1.sup.+] is chosen from:

##STR00008##

[0202] In formula (V), [X.sub.1.sup.] represents a counterion that is compatible with the intended application according to the invention.

[0203] In particular, [X.sub.1.sup.] may comprise one or more anions chosen from halides, perhalides, pseudohalides, sulfates, sulfites, sulfonates, sulfonimides, phosphates, phosphites, phosphonates, methides, carboxylates, hydroxycarboxylates, alkoxides, azolates, carbonates, carbamates, thiophosphates, thiocarboxylates, thiocarbamates, thiocarbonates, xanthates, thiosulfonates, thiosulfates, nitrate, nitrite, perchlorate, halometallates, amino acids and borates.

[0204] According to a particular embodiment, the counterion [X.sub.1.sup.] is chosen from: [0205] a) carboxylates RaCOO.sup., with Ra chosen from alkyl and alkenyl groups comprising from 1 to 30 carbon atoms, preferably from 6 to 15 carbon atoms; aryl groups comprising from 6 to 30 carbon atoms, preferably from 6 to 15 carbon atoms; aralkyl groups comprising from 7 to 30 carbon atoms, in particular from 7 to 20 carbon atoms, optionally substituted with a functional group comprising an oxygen and/or nitrogen atom. For example, [X.sub.1.sup.] may represent 2-ethylhexanoate. [0206] b) alkoxides RaRbHCO.sup. with Ra chosen from alkyl and alkenyl groups comprising from 1 to 30 carbon atoms, aryl groups comprising from 6 to 30 carbon atoms, aralkyl groups comprising from 7 to 30 carbon atoms; Rb is chosen from H, alkyl and alkenyl groups comprising from 1 to 30 carbon atoms, aryl groups comprising from 6 to 30 carbon atoms, aralkyl groups comprising from 7 to 30 carbon atoms, optionally substituted with a functional group comprising an oxygen and/or nitrogen atom.

[0207] Preferably, [X.sub.1.sup.] is chosen from alkyl phenoxides, in particular comprising from 7 to 20 carbon atoms; aminophenoxides, in particular in which the amine group is substituted with at least one alkyl group comprising from 1 to 18, in particular from 2 to 12, carbon atoms; and mixtures thereof.

[0208] For example, [X.sub.1.sup.] may represent tert-amylphenoxide, isooctylphenoxide or dioctylaminophenoxide. [0209] c) hydroxycarboxylates HO-Rc-COO.sup., with Rc a divalent radical chosen from alkyl and alkenyl groups, comprising from 1 to 30 carbon atoms, in particular from 1 to 15 carbon atoms; aryl groups comprising from 6 to 30 carbon atoms, in particular from 6 to 15 carbon atoms; aralkyl groups comprising from 7 to 30 carbon atoms, in particular from 7 to 20 carbon atoms, optionally substituted with a functional group comprising an oxygen and/or nitrogen atom. For example, [X.sub.1.sup.] may represent 2-hydroxypropanoic acid.

[0210] According to a particularly preferred embodiment, [X.sub.1.sup.] is chosen from: 2-ethylhexanoate, 2-hydroxypropanoate, tert-amylphenoxide, isooctylphenoxide or dioctylaminophenoxide.

[0211] According to another variant, the guanidinium-based ionic liquid is of the abovementioned formula (V), in which [CAT.sub.1.sup.+] represents 1,1,3,3-tetramethylguanidinium, of formula (Vb)

##STR00009## [0212] and [X.sub.1.sup.] represents one or more counterions chosen from the compounds of formula (VI)

##STR00010## [0213] in which: [0214] A represents an aryl group comprising from 6 to 12 carbon atoms; in particular a phenyl or naphthyl group; [0215] R.sub.1 is chosen from a hydrogen atom, a linear or branched alkyl or alkenyl group comprising from 1 to 30 carbon atoms, an aryl group comprising from 6 to 30 carbon atoms; [0216] Y.sub.1 represents a linear or branched alkylene group comprising from 1 to 6 carbon atoms; and [0217] n.sub.1 represents an integer ranging from 1 to 20, in particular from 1 to 15 and more particularly from 1 to 12, preferably from 4 to 12 and more preferentially from 6 to 10.

[0218] According to a preferred embodiment, [X.sub.1.sup.] corresponds to formula (VIA):

##STR00011## [0219] in which: [0220] R.sub.1 is chosen from a hydrogen atom, a linear or branched alkyl or alkenyl group comprising from 1 to 30 carbon atoms and an aryl group comprising from 6 to 30 carbon atoms; R.sub.1 may be in the ortho, para or meta position, preferably in the para position; [0221] Y.sub.1 is a linear or branched alkylene group comprising from 1 to 6 carbon atoms, preferably from 1 to 3 carbon atoms, and more preferentially Y.sub.1 is CH.sub.2CH.sub.2; and [0222] n.sub.1 is an integer ranging from 1 to 15; preferably from 1 to 12.

[0223] Preferably, in formula (VI) or (VIA), R.sup.1 is chosen from a hydrogen atom and a linear or branched alkyl or alkenyl group comprising from 1 to 30 carbon atoms, preferably from 1 to 24, notably from 1 to 18 carbon atoms, more preferentially from 1 to 12 carbon atoms; R.sup.1 being in the ortho, para or meta position. Advantageously, R.sup.1 represents a linear or branched alkyl group comprising from 1 to 18 carbon atoms, in particular from 1 to 12 carbon atoms, R.sup.1 preferably being in the para position.

[0224] For example, R.sup.1 may be chosen from an isopropyl, n-propyl, iso-butyl, tert-butyl, n-butyl, tert-pentyl, n-pentyl, n-hexyl, tert-hexyl, n-heptyl, tert-heptyl, n-octyl, tert-octyl, 2-ethylhexyl, n-nonyl, tert-nonyl and dodecyl group.

[0225] According to a preferred embodiment, [X.sub.1.sup.] corresponds to formula (VIB):

##STR00012## [0226] in which n.sub.1 is between 4 and 10, in particular between 6 and 10.

[0227] Advantageously, [X.sub.1.sup.] is tert-octylphenylpolyethoxyethoxide of formula (VIB) with n1=8 or 9.

[0228] The ammonium-based ionic liquid additives may more particularly be of formula (VII) below:

[Chem 16]

[CAT.sub.2.sup.+][X.sub.2.sup.](VII) [0229] in which: [0230] [CAT.sub.2.sup.+] represents a tri-n-octylmethylammonium cation; and [0231] [X.sub.2.sup.] represents one or more anionic species chosen from the carboxylates of formula (VIIA):

##STR00013## [0232] in which R.sub.2 is a linear or branched alkyl or alkenyl group comprising from 2 to 8 carbon atoms; preferably a linear or branched alkyl group comprising from 2 to 8 carbon atoms, in particular from 4 to 8 carbon atoms and more particularly from 5 to 7 carbon atoms.

[0233] According to a preferred embodiment, [X.sub.2.sup.] is 2-ethylhexanoate.

[0234] According to a preferred embodiment, the ammonium-based ionic liquid is tri-n-octylmethylammonium 2-ethylhexanoate.

[0235] The phosphonium-based ionic liquid additives may more particularly be of formula (VIII) below:

[Chem 18]

[CAT.sub.3.sup.+][X.sub.3.sup.](VIII) [0236] in which: [0237] [CAT.sub.3.sup.+] represents a phosphonium cation and [X.sub.3.sup.] represents one or more anionic species.

[0238] Preferably, [CAT.sub.3.sup.+] is chosen from cations of formula (VIIIA):

##STR00014## [0239] in which: [0240] R7, R8, R9 and R10 are linear or branched, saturated or unsaturated hydrocarbon-based groups comprising from 1 to 12 carbon atoms; [0241] at least one of the groups R7, R8, R9, R10 is chosen from linear or branched C.sub.1 to C.sub.3 alkyl or alkenyl groups; [0242] at least two of the groups R7, R8, R9, R10 are chosen, independently of each other, from linear or branched C.sub.8 to C.sub.12 alkyl or alkenyl groups.

[0243] Advantageously, in formula (VIIIA): [0244] R7 represents a linear or branched C.sub.1 to C.sub.3 alkyl or alkenyl group, preferably an alkyl group; and [0245] R8, R9, R10 represent, independently of each other, alkyl or alkenyl groups, preferably linear or branched C.sub.8 to C.sub.12 alkyl groups; preferably R7, R8 and R9 are identical and represent linear or branched C.sub.8 to C.sub.12 alkyl groups.

[0246] Advantageously, in formula (VIIIA), R7=CH.sub.3; and R8=R9=R10=CH.sub.3(CH.sub.2).sub.p3, with p3 representing an integer between 6 and 8; preferably R8=R9=R10=CH.sub.3(CH.sub.2).sub.7.

[0247] In formula (VIII), [X.sub.3.sup.] represents a counterion chosen from the compounds of formula (VIIIB):

##STR00015## [0248] in which R.sub.3 is chosen from linear or branched alkyl or alkenyl groups comprising from 5 to 7 carbon atoms.

[0249] According to a particularly advantageous embodiment, [X.sub.3.sup.] represents 2-ethylhexanoate.

[0250] According to a preferred embodiment, [CAT.sub.3.sup.+] is tri-n-octylmethylphosphonium and [X.sub.3.sup.] is 2-ethylhexanoate. In other words, the phosphonium-based ionic liquid is tri-n-octylmethylphosphonium 2-ethylhexanoate.

[0251] The guanidinium-, ammonium- or phosphonium-based ionic liquids are preferably soluble in the base oil(s) used in the lubricant composition. A compound is said to be soluble in a base oil if it can be dissolved at a concentration of at least 0.01% by weight relative to the weight of the base oil, at room temperature.

(c) Additives Bearing Amine, Boron and Acid or Carboxylate Functionalities

[0252] According to a particular embodiment, a lubricant composition according to the invention may comprise, as a basic organic TBN booster additive, one or more additives bearing amine, boron and acid or carboxylate functionalities.

[0253] Such additives are notably described in patent applications WO 2018/220007, WO 2018/220009, WO 2019/229173, WO 2020/094796, WO 2020/094800 and WO 2021/089671.

[0254] These additives may more particularly be chosen from the products of reaction between at least: [0255] a hydroxybenzoic acid, optionally substituted with a hydrocarbon-based group; or an alkali metal or alkaline-earth metal salt thereof, optionally overbased; [0256] a boron compound; and [0257] an amine compound, in particular chosen from the compounds detailed below.

Hydroxybenzoic Acid Type Compound and Hydroxybenzoate Salt Thereof

[0258] Hydroxybenzoic acid compounds, optionally substituted with a hydrocarbon-based group, are molecules which comprise at least one benzoic acid fragment, and in which the aromatic ring bears at least one hydroxyl function, and optionally an alkyl, alkenyl, aryl or aralkyl substituent. When it is present, the hydrocarbon-based substituent and the hydroxyl function may be in the ortho, meta or para position relative to the acid function and relative to each other. The hydrocarbon-based substituent may comprise from 1 to 50 carbon atoms. Hydroxybenzoic compounds notably comprise salicylic acid (2-hydroxybenzoic acid), 3-hydroxybenzoic acid, 4-hydroxybenzoic acid, preferably salicylic acid.

[0259] Hydroxybenzoic acid compounds substituted with a hydrocarbon-based group may be chosen, for example, from mono-(alkyl or alkenyl)-substituted salicylic acids, di-(alkyl and/or alkenyl)-substituted salicylic acids, acid-functionalized calixarenes, notably salicylic acid calixarenes, and mixtures thereof.

[0260] Preferably, compounds of the hydroxybenzoic acid type, optionally substituted with a hydrocarbon-based group, may correspond to formula (IX) below:

##STR00016## [0261] in which: [0262] R represents a linear, branched or cyclic hydrocarbon-based group of 1 to 50 carbon atoms; [0263] R may optionally comprise one or more heteroatoms; [0264] a is 0, 1 or 2; preferably, a is 1.

[0265] When a is 2, the hydrocarbon-based groups may be identical or different.

[0266] The hydrocarbon-based groups comprise alkyl, alkenyl, aryl and aralkyl groups, and optionally comprise one or more heteroatoms. The heteroatoms in the hydrocarbon-based groups R may be chosen from O, N, S, for example may be chosen from: OH, NH.sub.2 or SH, or O, NH, N or S.

[0267] Preferably, R does not comprise a heteroatom. Preferably, R represents a linear or branched alkyl or alkenyl group, preferably a linear alkyl group, comprising from 1 to 50 carbon atoms, in particular from 12 to 40 and more particularly from 18 to 30 carbon atoms. Preferably, the hydroxybenzoic acid compound of formula (IX) is salicylic acid or a salicylic acid derivative of formula (IXA).

##STR00017## [0268] in which R and a have the abovementioned definitions.

[0269] According to an implementation variant, the hydroxybenzoic acid-type compounds, optionally substituted with a hydrocarbon-based group, may be chosen from the calixarene structures.

[0270] The calixarene structures according to the invention more particularly denote cyclic structures comprising m hydroxybenzoic acid units substituted with a hydrocarbon-based group of formula (X) and n phenol units of formula (XI) which are linked together to form a ring.

##STR00018## [0271] in which: [0272] G.sub.1 represents a linear, branched or cyclic hydrocarbon-based group of 1 to 50 carbon atoms, and G.sub.1 may comprise one or more heteroatoms, in particular chosen from O, N and S; preferably, G.sub.1 is chosen from alkyl and alkenyl groups, in particular a linear alkyl group notably comprising from 12 to 40 carbon atoms, in particular from 18 to 30 carbon atoms; [0273] b is 0, 1 or 2; [0274] Q represent, independently of each other, divalent bonding groups, [0275] G.sub.2, G.sub.3, G.sub.4 and G.sub.5 are chosen from: OH, H or a hydrocarbon-based group of 1 to 50 carbon atoms which comprises one or more heteroatoms, on condition that one or two from among G.sub.2, G.sub.3, G.sub.4 and G.sub.5 is OH, [0276] m and n are integers which satisfy: m is between 1 and 8, n is at least 3, m+n is between 4 and 20, preferably between 5 and 12.

[0277] When b=2, the hydrocarbon-based groups G.sub.1 may be identical or different.

[0278] Preferably, the units (X) are chosen from units of formula (XA) below:

##STR00019## [0279] in which G.sub.1, Q and b are as defined for formula (X).

[0280] Preferably, in formula (XI), G.sub.5 is a hydroxyl group.

[0281] Advantageously, G.sub.2, G.sub.3, G.sub.4 in formula (XI) represent, independently of each other, H or an alkyl or alkenyl group of 1 to 50 carbon atoms; in particular H or a linear alkyl group of 1 to 40 carbon atoms, in particular of 1 to 30 carbon atoms and more particularly of 4 to 25 carbon atoms.

[0282] When more than one unit (X) is present, the units (X) may be identical or different. The units (XI) may be identical or different in a calixarene molecule.

[0283] The groups Q may be chosen, independently of each other, from S and groups of formula (CHG.sub.6) in which G.sub.6 is chosen from a hydrogen atom and a hydrocarbon-based group of 1 to 10 carbon atoms and c is an integer of 1 to 4 carbon atoms; notably, each G.sub.6 is H.

[0284] The alkali metal and/or alkaline-earth metal hydroxybenzoate compounds, optionally substituted with a hydrocarbon-based group, are the alkali metal and/or alkaline-earth metal salts of the abovementioned hydroxybenzoic acid-type compounds.

[0285] Preferably, the alkali metal is lithium, sodium or potassium, in particular potassium. Preferably, the alkaline-earth metal is calcium, barium, magnesium or strontium, preferably calcium.

[0286] According to a particular embodiment, in the reaction with the boron compound and the amine compound, the hydroxybenzoic acid-type compound, optionally substituted with a hydrocarbon-based group, or an alkali metal and/or alkaline-earth metal salt thereof, may be used as a mixture with an alkylphenol. The mixture may comprise, for example, up to 50 mol % of alkylphenol, relative to the total number of moles of the mixture of alkylphenol and alkali metal and/or alkaline-earth metal hydroxybenzoic acid or hydroxybenzoate compound.

Boron Compound

[0287] The boron compound (in other words, the boron-based compound) may notably be chosen from boric acid (B(OH).sub.3), hydrocarbon-based boronic acids, boric esters and hydrocarbon-based boronic esters, boron oxide and boric acid complexes.

[0288] In particular, the boron compound may be chosen from boric acid; boron oxide; boric acid complexes; trialkyl borates, in particular in which the alkyl groups independently of each other comprise from 1 to 4 carbon atoms; boronic acids containing a C.sub.1 to C.sub.12 alkyl group; boric acids substituted with two alkyl groups, in particular C.sub.1 to C.sub.12 groups; boric acids substituted with two aryl groups, in particular C.sub.6 to C.sub.12 groups; boric acids substituted with one or two aralkyl groups, in particular C.sub.7 to C.sub.12 groups, and derivatives thereof obtained by substitution of at least one alkyl group with one or more alkoxy groups.

[0289] The alkyl and alkoxy groups may be linear, branched or cyclic.

[0290] The boric acid complexes are notably complexes of boron with one or more molecules comprising one or more alcohol functions.

[0291] According to a particular embodiment, the boron compound is boric acid.

Amine Compound

[0292] According to a first implementation variant, the amine compound may be a polyalkylamine compound, as described in patent application WO 2021/089671, of formula (XII):

##STR00020## [0293] in which: [0294] a1 represents 0 or 1; [0295] x1, y1 and z1 represent, independently of each other, an integer chosen from 1, 2 and 3; [0296] preferably 2 or 3; [0297] when a1=0, R.sub.8 and R.sub.9 represent, independently of each other, a C.sub.1-C.sub.3-alkyl group; [0298] when a1=1, R.sub.8 and R.sub.9 represent, independently of each other, a group chosen from: a hydrogen atom and a C.sub.1-C.sub.3-alkyl group.

[0299] Preferably, in formula (XII), x1=y1.

[0300] Preferably, in formula (XII), when a1=1, x1=y1=z1.

[0301] According to a first embodiment, the polyalkylamine compound is of formula (XII) in which a1=0 (triamine compounds).

[0302] More particularly, the polyalkylamine compound may be of formula (XIIA):

##STR00021## [0303] in which: [0304] R.sub.8 and Ry represent, independently of each other, a C.sub.1-C.sub.3-alkyl group; preferably, R.sub.8=R.sub.9; [0305] x1 and y1 are, independently of each other, an integer chosen from 1, 2 and 3; preferably 2 or 3; preferably, x1=y1; [0306] the total number of carbon atoms in formula (XIIA) being between 4 and 10, preferably 8.

[0307] Preferably, x1=y1=3.

[0308] Preferably, R.sub.8=R.sub.9=CH.sub.3.

[0309] The dialkylaminopolyalkylamine of formula (XIIA) may thus be dimethylaminopropylaminopropylamine (DMAPAPA).

[0310] According to another embodiment, the polyalkylamine compound is of formula (XII) in which a1=1 (tetramine compounds).

[0311] More particularly, the polyalkylamine compound may be of formula (XIIB):

##STR00022## [0312] in which: [0313] R.sub.8 and R.sub.9 represent, independently of each other, a hydrogen atom or a C to C.sub.3 alkyl group; [0314] preferably, R.sub.8=R.sub.9; in particular, R.sub.8=R.sub.9=H; [0315] x1, y1 and z1 are integers, independently of each other, equal to 1, 2 or 3; preferably x1=y1=z1, and notably equal to 2 or 3, in particular 2.

[0316] The trialkylaminopolyalkylamine of formula (XIIB) may notably be triethylenetetramine.

[0317] According to another implementation variant, the amine compound may be a quaternary ammonium salt, as described in patent applications WO 2019/229173 and WO 2020/094796. Preferably, the amine compound may be chosen from quaternary ammonium salts comprising four hydrocarbon-based groups, advantageously chosen from C.sub.1-C.sub.40 alkenyl and alkyl groups.

[0318] According to a particularly preferred embodiment, the amine compound is chosen from the quaternary ammonium salts corresponding to formula (XIII):

##STR00023## [0319] in which: [0320] W.sup. represents a counterion, in particular chosen from halogens, for example Cl.sup.; [0321] R.sub.10, R.sub.11, R.sub.12 and R.sub.13 are chosen, independently of each other, from hydrocarbon-based groups comprising from 1 to 40 carbon atoms, advantageously from linear, branched or cyclic alkenyl and alkyl groups comprising from 1 to 40 carbon atoms.

[0322] According to a first embodiment, R.sub.10, R.sub.11, R.sub.12 and R.sub.13 are chosen, independently of each other, from linear alkyl and alkenyl groups comprising from 1 to 8 carbon atoms, preferably from 2 to 6 carbon atoms.

[0323] According to another embodiment, R.sub.10, R.sub.11, R.sub.12 and R.sub.13 are chosen, independently of each other, from linear alkyl and alkenyl groups comprising from 14 to 22 carbon atoms, preferably from 14 to 18 carbon atoms and more preferentially from 16 to 18 carbon atoms. Compounds of formula (XIII) are, for example, commercially available from Akzo under the references Arquad and Ethoquad.

[0324] According to another variant, the amine compound may be chosen from compounds comprising two or three amine functions, at least one amine function being substituted with at least one hydrocarbon-based group and, optionally, one or more amine functions being substituted with at least one monoalkoxy or polyalkoxy group, as described in patent applications WO 2018/220007 and WO 2020/0947966.

[0325] According to this variant, preferably, the amine compound is chosen from compounds comprising two or three amine functions, at least one amine function being substituted with at least one hydrocarbon-based group comprising from 1 to 40 carbon atoms, advantageously a C.sub.1-C.sub.40 alkyl or alkenyl group, and in which one or more amine functions are optionally substituted with a C.sub.2-C.sub.4 monoalkoxy or polyalkoxy group.

[0326] In a particularly preferred embodiment, the amine compound is chosen from the diamines of formula (XIV)

[Chem 29]

R.sub.10NX.sub.1RdNZ.sub.1Z.sub.2(XIV) [0327] or the triamines of formula (XV)

[Chem 30]

R.sub.10NX.sub.1-Rd-NYReNZ.sub.1Z.sub.2(XV) [0328] in which [0329] X1 represents a group chosen from a hydrogen atom, an alkyl group or an alkenyl group R.sub.11; [0330] Y represents a group chosen from a hydrogen atom, an alkyl group or an alkenyl group R.sub.13; [0331] Z.sub.1 and Z.sub.2 represent, independently of each other, a hydrogen atom, an alkyl group or an alkenyl group R.sub.12; [0332] R.sub.10, R.sub.11, R.sub.12 and R.sub.13 represent, independently of each other, hydrocarbon-based groups comprising from 1 to 40 carbon atoms, advantageously alkyl or alkenyl groups comprising from 1 to 40 carbon atoms, [0333] Rd and Re represent, independently of each other, alkyl or alkenyl groups comprising from 1 to 20 carbon atoms; [0334] when Z.sub.1 and Z.sub.2 both represent alkyl or alkenyl groups R.sub.12, they may be different.

[0335] Preferably, in formulae (XIII), (XIV) and (XV), R.sub.10, R.sub.11, R.sub.12 and R.sub.13 are chosen, independently of each other, from alkyl and alkenyl groups, which are preferably linear, comprising from 4 to 30 carbon atoms, in particular from 8 to 22 carbon atoms, notably from 14 to 22 carbon atoms, preferably from 14 to 18 carbon atoms and more preferentially from 16 to 18 carbon atoms.

[0336] According to a particular embodiment, the groups R.sub.10, R.sub.11, R.sub.12 and R.sub.13 are identical.

[0337] In formulae (XIV) and (XV), Rd and Re are preferably chosen from linear alkyl and alkenyl groups, preferably linear alkyl groups, in particular comprising 2 to 4 carbon atoms. Advantageously, Rd and Re are chosen from CH.sub.2CH.sub.2, CH(CH.sub.3)CH.sub.2 and CH.sub.2CH.sub.2CH.sub.2.

[0338] According to a particular embodiment, the amine compound of formula (XIV) is of formula (XIVA):

##STR00024## [0339] in which R.sub.10 and X1 are as defined previously for formula (XIV) and x2 is 2, 3 or 4.

[0340] According to a particular embodiment, the amine compound of formula (XV) is of formula (XVB):

##STR00025## [0341] in which: [0342] R.sub.10 and X.sub.1 are as defined previously for formula (XV); [0343] x2 is 2, 3, 4; y2 is 2, 3 or 4.

[0344] According to another implementation variant, the amine compound may be chosen from mixtures of polyalkylamines substituted with two alkyl and/or alkenyl fatty chains, as described in patent applications WO 2018/220009 and WO 2020/094800.

[0345] The polyalkylamine mixture more particularly comprises one or more polyalkylamines of formula (III) or (IV) as described previously.

##STR00026## [0346] in which: [0347] R.sub.6 and R.sub.7 represent, independently of each other, linear or branched, preferably linear, alkyl or alkenyl groups comprising from 4 to 30 carbon atoms, preferably from 8 to 22 carbon atoms and more particularly from 14 to 18 carbon atoms, preferably from 16 to 18 carbon atoms; [0348] n and z represent, independently of each other, 0, 1, 2 or 3; and [0349] when z is other than 0, o and p are, independently of each other, 0, 1, 2 or 3; [0350] or derivatives thereof; [0351] in which the mixture of polyalkylamines comprises at least 3% by mass, in particular at least 5% by mass, notably at least 7% by mass, preferably at least 10% by mass and more particularly at least 20% by mass, of branched polyalkylamines of formula (III) and/or (IV) relative to the total mass of the mixture of polyalkylamines of formulae (III) and (IV).

[0352] The term branched means that, for a polyalkylamine of formula (III), at least one from among n and z is greater than or equal to 1, and for a polyalkylamine of formula (IV), n is greater than or equal to 1.

[0353] Preferably, the mixture of polyalkylamines comprises, or even consists of, compounds of formula (III) or (IV) in which n, o, p and z are, independently of each other, 0, 1 or 2, preferably 0 or 1.

[0354] In formulae (III) and (IV), R.sub.6 and R.sub.7, which are preferably identical, may be derived from animal and plant oils and fats, in particular as described previously, and in particular tallow oil, coconut oil and palm oil, preferably tallow oil.

[0355] Such amines may be commercially available from the company Akzo, for example under the trade name Tetrameen 2HBT.

Reaction Product

[0356] As indicated previously, the compound used as a TBN booster additive in a lubricant composition according to the invention may thus be the product of reaction of at least one hydroxybenzoic acid, optionally substituted with a hydrocarbon-based group or an alkali metal and/or alkaline-earth metal salt thereof, at least one boron compound and at least one amine compound, as described above.

[0357] The reaction may be performed, for example, by combining the hydroxybenzoic acid or hydroxybenzoate compound and the boron compound in the desired ratio and in the presence of a suitable solvent. Suitable solvents may be, for example, naphtha and polar solvents such as water and alcohols, for example methanol, ethanol, propanol or butanol.

[0358] Advantageously, the reaction is performed with a mole ratio of hydroxybenzoic acid compound to boron compound ranging from 30:1 to 1:30, preferably from 15:1 to 1:5, notably from 10:1 to 1:5, more particularly from 5:1 to 1:2 and even more preferentially from 4:1 to 1:1.

[0359] After a sufficient time, the boron compound is dissolved. The amine compound is then slowly added to the mixture to bring about neutralization and the formation of the desired reaction product.

[0360] Advantageously, the amine compound is added in an amount such that the mole ratio of hydroxybenzoic acid compound to amine compound is between 30:1 and 1:30, notably between 10:1 and 1:5, preferably between 15:1 and 1:5, more preferentially between 5:1 and 1:2 and more preferentially between 4:1 and 1:1.

[0361] Advantageously, the amine compound is added in an amount such that the boron compound/amine compound mole ratio is between 20:1 and 1:20, preferably between 10:1 and 1:10, more preferentially between 5:1 and 1:5 and more preferentially between 2:1 and 1:2.

[0362] The reaction may be performed by maintaining the reaction medium at a temperature of between about 20 C. and about 100 C., for example between about 50 C. and about 75 C., generally for a time of between 0.5 and 5 hours, and more preferentially between 1 and 4 hours.

[0363] The resulting product contains a complex mixture of compounds which may be used as such in the lubricant composition according to the invention.

[0364] Preferably, the product results from the reaction of a mixture of reagents (not including solvent(s)) consisting of at least one alkali metal or alkaline-earth metal hydroxybenzoic acid or hydroxybenzoate compound optionally substituted with a hydrocarbon-based group, at least one boron compound and at least one amine compound, and optionally an alkylphenol.

[0365] Other basic organic additives improving the TBN may also be considered according to the invention, for instance succinimide-type dispersants or else nitrogen-based organic dispersants.

[0366] According to a particular embodiment, the TBN booster additive(s) used in a lubricant composition according to the invention consist of one or more polyalkylamines. Alternatively, according to a particular embodiment, a lubricant composition according to the invention comprises no TBN booster additives other than polyalkylamine-type additives, in particular as described above.

[0367] According to a particular embodiment, a lubricant composition according to the invention may comprise, or even consist of: [0368] from 60% to 99.8% by mass, in particular from 70% to 90% by mass, of one or more base oils; [0369] from 0.01% to 0.8% by mass, in particular from 0.05% to 0.5% by mass, of one or more carbodiimide additives, in particular as defined previously; [0370] from 0.1% to 10% by mass, preferably from 0.5% to 7% by mass and more particularly from 1% to 5% by mass, of at least one basic organic additive for improving the total base number (TBN) of said composition, in particular amine additive(s), preferably comprising one or more polyalkylamines as described previously;
the contents being expressed relative to the total mass of said lubricant composition.

Other Additives

[0371] A lubricant composition according to the invention may comprise any type of additive that is suitable for the intended use of the lubricant, as detailed in the following text, for example for use in gas-powered drive systems, for mobile and stationary application, heavy-duty drive systems, four-stroke marine drive systems, etc.

[0372] In particular, in the case where it is sought to formulate a lubricant with a low sulfated ash content, the additives are chosen in such a way as not to have a significant impact on the lubricant composition's sulfated ash content.

[0373] These additives may be introduced individually and/or in the form of an additive mixture such as those already available for sale for commercial lubricant formulations for vehicle engines, with a performance level as defined by the ACEA (Association des Constructeurs

[0374] Europens dAutomobiles) and/or the API (American Petroleum Institute), which are well known to those skilled in the art.

[0375] These additives, which are different from said basic organic additive(s) improving the TBN and from said carbodiimide additive(s), may notably be chosen from metallic detergents, friction-modifying additives, anti-wear additives and extreme-pressure additives, antioxidants, viscosity index (VI) improvers, pour point depressants (PPD), dispersants, antifoams, thickeners, corrosion inhibitors, copper passivators, and mixtures thereof.

[0376] Advantageously, a lubricant composition according to the invention comprises one or more additives chosen from viscosity index improvers, pour point depressants, anti-wear additives, antioxidants and mixtures thereof.

Metallic Detergent Additives

[0377] Metallic detergents are known to those skilled in the art. In general, they are anionic compounds comprising a long lipophilic hydrocarbon-based chain and a hydrophilic head, the associated cation possibly being a metal cation of an alkali metal or alkaline-earth metal. They are generally chosen from alkali metal or alkaline-earth metal salts of carboxylic acids, sulfonates, salicylates and naphthenates, and also phenoxide salts. The alkali metals and alkaline-earth metals are preferentially calcium, magnesium, sodium or barium.

[0378] These metal salts generally comprise the metal in a stoichiometric amount (they are then referred to as non-overbased or neutral detergents), or else in excess, thus in an amount greater than the stoichiometric amount. They are then overbased detergent additives; the excess metal giving the overbased nature to the detergent additive is then generally in the form of a metal salt that is insoluble in the base oil, for example a carbonate, a hydroxide, an oxalate, an acetate or a glutamate, preferentially a carbonate.

[0379] According to a particular embodiment, the lubricant composition according to the invention comprises at least one metallic detergent additive chosen from overbased and/or neutral detergents.

[0380] In particular, the overbased detergent and/or neutral detergent are metal-based compounds chosen from calcium, magnesium, sodium and barium, preferentially calcium- or magnesium-based.

[0381] Preferably, the overbased detergent is overbased with insoluble metal salts chosen from the group of alkali metal and alkaline-earth metal carbonates, preferentially calcium carbonate. The overbased detergent used in a lubricant composition according to the invention may be chosen in particular from phenoxides, sulfonates, salicylates and mixed detergents (phenoxides-sulfonates-salicylates) overbased with calcium carbonate, more particularly from sulfonates and phenoxides overbased with calcium carbonate.

[0382] A lubricant composition according to the invention may comprise less than 15% by mass of metallic detergent(s), notably less than 10% by mass, and more particularly from 0.5% to 5%, notably less than 2% by mass, of metallic detergent(s), relative to the total mass of said lubricant composition.

[0383] Lowering the metallic detergent(s) content advantageously allows the specifications of LOW SAPS lubricant compositions to be met.

[0384] Advantageously, a lubricant composition according to the invention thus has a sulfated ash content, determined according to the standard ASTM D-874, of less than or equal to 1.3% by mass, in particular less than or equal to 1% by mass and more particularly less than or equal to 0.8% by mass.

[0385] According to a particular embodiment, a lubricant composition according to the invention may comprise, or even consist of: [0386] from 60% to 99% by mass, in particular from 70% to 90% by mass, of one or more base oils; [0387] from 0.01% to 0.8% by mass, in particular from 0.05% to 0.5% by mass, of one or more carbodiimide additives, in particular as defined previously; [0388] from 0.1% to 10% by mass, preferably from 0.5% to 7% by mass and more particularly from 1% to 5% by mass, of at least one basic organic additive for improving the total base number (TBN) of said composition, in particular comprising one or more polyalkylamines as described previously; [0389] from 0.5% to 10% by mass; in particular from 0.5% to 5% by mass, of one or more metallic detergent additives, in particular chosen from the overbased detergents and/or neutral detergents as described previously;
the contents being expressed relative to the total mass of said lubricant composition.

[0390] A lubricant composition under consideration according to the invention may comprise at least one friction-modifying additive.

[0391] The friction-modifying additives may be chosen from compounds providing metal elements and ash-free compounds, preferably from ash-free compounds.

[0392] Among the compounds providing metal elements, mention may be made of complexes of transition metals such as Mo, Sb, Sn, Fe, Cu or Zn, the ligands of which may be hydrocarbon-based compounds comprising oxygen, nitrogen, sulfur or phosphorus atoms.

[0393] Advantageously, the friction-modifying additives are chosen from ash-free compounds, generally of organic origin, and which may be chosen more particularly from fatty acid monoesters of polyols, alkoxylated amines, alkoxylated fatty amines, fatty epoxides, borate fatty epoxides, fatty amines or fatty acid esters of glycerol. According to the invention, the fatty compounds comprise at least one hydrocarbon-based group comprising 10 to 24 carbon atoms.

[0394] According to an advantageous variant, a lubricant composition comprises at least one friction-modifying additive, in particular based on molybdenum.

[0395] In particular, the molybdenum-based compounds may be chosen from molybdenum dithiocarbamates (Mo-DTC), molybdenum dithiophosphates (Mo-DTP), and mixtures thereof.

[0396] Advantageously, a lubricant composition under consideration according to the invention may comprise from 0.01% to 5% by mass, preferably from 0.1% to 5% by mass, more particularly from 0.1% to 2% by mass or even more particularly from 0.1% to 1.5% by mass, relative to the total mass of the lubricant composition, of friction-modifying additives, advantageously including at least one molybdenum-based friction-modifying additive.

[0397] A lubricant composition under consideration according to the invention may comprise at least one antioxidant additive. The antioxidant additives are essentially dedicated toward retarding the degradation of the lubricant composition in service. This degradation may notably be reflected by the formation of deposits, by the presence of sludges, or by an increase in the viscosity of the lubricant composition. They act notably as free-radical inhibitors or hydroperoxide destroyers.

[0398] Among the commonly used antioxidant additives, mention may be made of antioxidants of phenolic type, antioxidant additives of amine type and phospho-sulfur-based antioxidant additives. Some of these antioxidant additives, for example the phospho-sulfur-based antioxidant additives, may be ash generators. The phenolic antioxidants additives may be ash-free or may be in the form of neutral or basic metal salts. The antioxidants additives may notably 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.sub.1-C.sub.12 alkyl group, N,N-dialkyl-aryl-diamines, and mixtures thereof.

[0399] Preferably, the sterically hindered phenols are chosen from compounds comprising a phenol group, in which at least one carbon vicinal to the carbon bearing the alcohol function is substituted with at least one C.sub.1-C.sub.10 alkyl group, preferably a C.sub.1-C.sub.6 alkyl group, preferably a C.sub.4 alkyl group, preferably with a tert-butyl group.

[0400] Amine compounds are another class of antioxidant additives that may be used, optionally in combination with the phenolic antioxidants additives. Examples of amine compounds are aromatic amines, for example the aromatic amines of formula NR.sup.8R.sup.9R.sup.10 in which R.sup.8 represents an optionally substituted aliphatic or aromatic group, R.sup.9 represents an optionally substituted aromatic group, R.sup.10 represents a hydrogen atom, an alkyl group, an aryl group or a group of formula R.sup.11S(O).sub.2R.sup.12 in which R.sup.11 represents an alkylene group or an alkenylene group, R.sup.12 represents an alkyl group, an alkenyl group or an aryl group and z represents 0, 1 or 2.

[0401] Sulfurized alkylphenols or the alkali metal and alkaline-earth metal salts thereof may also be used as antioxidant additives.

[0402] A lubricant composition under consideration according to the invention may contain any type of antioxidant additive known to those skilled in the art. Advantageously, the lubricant composition comprises at least one ash-free antioxidant additive.

[0403] Advantageously also, a lubricant composition under consideration according to the invention may comprise from 0.1% to 2% by mass, relative to the total mass of the composition, of at least one antioxidant additive.

[0404] A lubricant composition under consideration according to the invention may comprise at least one pour-point depressant (PPD). By slowing down the formation of paraffin crystals, the pour-point depressant additives generally improve the cold-temperature behavior of the lubricant composition.

[0405] Examples of pour-point depressants that may be mentioned include polyalkyl methacrylates, polyacrylates, polyarylamides, polyalkylphenols, polyalkylnaphthalenes and polyalkylstyrenes.

[0406] A lubricant composition under consideration according to the invention may also comprise at least one dispersant. The dispersants ensure the holding in suspension and the removal of insoluble solid contaminants constituted by the oxidation byproducts that are formed when the lubricant composition is in service. They may be chosen from Mannich bases, succinimides and derivatives thereof.

[0407] In particular, a lubricant composition under consideration according to the invention may comprise from 0.2% to 10% by mass of dispersant(s) relative to the total mass of the composition.

[0408] A lubricant composition under consideration according to the invention may also comprise at least one viscosity index (VI) enhancer. The viscosity index (VI) enhancers, in particular the viscosity index-enhancing polymers, make it possible to ensure good cold-weather behavior and a minimal viscosity at high temperature. Examples of viscosity index-enhancing polymers that may be mentioned include polymeric esters, hydrogenated or non-hydrogenated homopolymers or copolymers of styrene, butadiene and isoprene, homopolymers or copolymers of olefins, such as ethylene or propylene, polyacrylates and polymethacrylates (PMA).

[0409] In particular, a lubricant composition under consideration according to the invention may comprise from 1% to 15% by mass of viscosity index-enhancing additive(s), relative to the total mass of the lubricant composition.

[0410] A lubricant composition under consideration according to the invention may also comprise at least one antifoam additive. The antifoam additives may be chosen from polar polymers such as polymethylsiloxanes or polyacrylates.

[0411] In particular, a lubricant composition under consideration according to the invention may comprise from 0.01% to 3% by mass of antifoam additive(s), relative to the total mass of the lubricant composition.

[0412] According to a particular embodiment, a lubricant composition according to the invention may comprise, or even consist of: [0413] a base oil or a mixture of base oils; [0414] one or more carbodiimide additives, in particular as defined previously; [0415] one or more basic organic additives for improving the total base number (TBN) of said composition, in particular comprising one or more polyalkylamines as described previously; [0416] optionally one or more additives, different from said basic organic additive(s) improving the TBN and from said carbodiimide additive(s), chosen from metallic detergent additives, friction modifiers, anti-wear additives, extreme-pressure additives, antioxidants, viscosity index (VI) improvers, pour point depressants (PPD), dispersants, antifoams, thickeners, corrosion inhibitors, copper passivators, and mixtures thereof.

[0417] Preferably, a lubricant composition formulated according to the invention comprises, or even consists of: [0418] from 60% to 99% by mass of one or more base oils; [0419] from 0.01% to 0.8% by mass, in particular from 0.05% to 0.5% by mass, of one or more carbodiimide additives, in particular as defined previously; [0420] from 0.1% to 10% by mass, preferably from 0.5% to 7% by mass and more particularly from 1% to 5% by mass, of at least one basic organic additive for improving the total base number (TBN) of said composition, in particular comprising one or more polyalkylamines as described previously; [0421] optionally from 1% to 30% by mass, preferably from 5% to 20% by mass, of one or more other additives, different from said basic organic additive(s) improving the TBN and from said carbodiimide additive(s), chosen from metallic detergent additives, friction-modifying additives, anti-wear additives, extreme-pressure additives, antioxidants, viscosity index (VI) improvers, pour point depressants (PPD), dispersants, antifoams, thickeners, corrosion inhibitors, copper passivators, and mixtures thereof;
the contents being expressed relative to the total mass of said lubricant composition.

[0422] According to a particular embodiment, a lubricant composition according to the invention may have a kinematic viscosity, measured at 40 C. according to the standard ASTM D445, of between 20 mm.sup.2/s and 50 mm.sup.2/s, preferably between 25 mm.sup.2/s and 40 mm.sup.2/s. More advantageously, a lubricant composition according to the invention has a kinematic viscosity, measured at 100 C. according to the standard ASTM D445, of between 2 mm.sup.2/s and 20 mm.sup.2/s, preferably between 4 mm.sup.2/s and 15 mm.sup.2/s.

[0423] All the particular features and embodiments relating to the use of a carbodiimide compound according to the invention and to the lubricant composition comprising it, also apply to the uses, processes and methods targeted according to the invention.

Application

[0424] As indicated previously, the lubricant compositions under consideration according to the invention may be intended for a variety of mobile or stationary drive systems.

[0425] In particular, the invention proves to be particularly advantageous for use in drive systems comprising an elastomeric material, for example elastomeric seals, exposed to said lubricant.

[0426] According to another of its aspects, the invention thus relates to the use of a composition as defined previously, incorporating one or more carbodiimide additives, as an additive for improving the compatibility of the lubricant composition with elastomers, for lubricating a drive system, in particular a mobile or stationary drive system.

[0427] The lubricant compositions according to the invention may notably be intended for drive systems including an internal combustion engine, for example a diesel or gas engine.

[0428] The drive system may notably comprise a diesel engine, typically a heavy-duty diesel engine, a marine engine, a gasoline engine, a gas engine or an ammonia engine.

[0429] These may be drive systems for light vehicles, heavy duty vehicles or boats.

[0430] In particular, the lubricant composition under consideration according to the invention may be a lubricant for mobile or stationary gas drive systems, notably for natural gas (LNG or CNG) engines, hydrogen engines, but also gas/gasoline dual fuel or gas/diesel dual fuel engines.

[0431] It may be used for four-stroke heavy-duty drive systems or marine drive systems.

[0432] In particular, a lubricant composition according to the invention is used for drive systems different from two-stroke marine engines.

[0433] It may find particularly advantageous application for drive systems with a gas engine, notably operating with gases of renewable origin, for example gases charged with impurities, and for which it is important to use a lubricant with a high level of TBN.

[0434] It may also be particularly suitable for lubricating heavy-duty drive systems, for example trucks. It is also suitable for heavy-duty diesel engines fitted with exhaust gas recirculation (EGR) systems. Such systems may be used in efforts to reduce the environmental emissions of these engines.

[0435] Diesel engines with EGR can experience higher loads of acidic combustion products, transmitted to the lubricant from the exhaust gases, so lubricants with high levels of TBN are often desirable to perform the neutralization of these acids.

[0436] The invention will now be described by means of the following examples, which are given as nonlimiting illustrations of the invention.

Example

[0437] The compatibility of engine lubricants with elastomers is evaluated according to the standard CEC L-112-16. This test explores the performance of four types of elastomer materials (RE6: fluoroelastomer; RE7: polyacrylate; RE8: nitrile and RE9: ethylene acrylic) when exposed to a lubricant.

[0438] The reference lubricant is a lubricant sold under the reference NATERIA MJ 40, intended for the lubrication of stationary gas engines.

[0439] Formulations C1, I1, I2 and I3 are prepared by supplementing the reference lubricant with: [0440] a basic organic additive of the polyalkylamine type: [0441] N,N-dimethyldipropylenetriamine, known as DMAPAPA (formulations C1, I1 and I2), in a mass content of 0.5% relative to the mass of the reference lubricant; or [0442] N,N,N,N-tetramethyldipropylenetriamine, known as TMDPT (formulation I3), in a mass content of 0.7% relative to the mass of the reference lubricant; and [0443] for formulations I1, I2 and I3, also with a carbodiimide additive according to the invention (N,N-bis(2,6-diisopropylphenyl)carbodiimide), introduced in the form of two commercial products, Carbodiimide 1 and Carbodiimide 2, in a commercial product mass content of 1% or 2% by mass relative to the total mass of the reference lubricant.

[0444] The results obtained in terms of volumetric variation, variation in tensile strength and elongation at break, according to the tests performed according to the standard CEC L-112-16, on the various elastomer materials, when exposed to the reference lubricant and to each of the lubricant compositions C1, I1, I2 and I3, are collated in the table below.

TABLE-US-00002 TABLE 2 Ref. C1 I1 I2 I3 Test Target +0.5 wt % +0.5 wt % +0.5 wt % +0.7 wt % value DMAPAPA DMAPAPA + 1% DMAPAPA + 2% TMDPT + 2% Carbodiimide 1 Carbodiimide 2 Carbodiimide 2 RE6 Volumetric % 5.5/+2.1 0 1.1 0.4 0.3 0.2 variation Tensile % Report 18 74 68 63 69 strength variation Elongation % 70/+20 31 82 70 62 68 at break RE7 Volumetric % 1.8/+8.9 0.1 0.7 1.4 ND ND variation Tensile % Report 5 26 17 ND ND strength variation Elongation % 65/+15 25 64 25 ND ND at break RE8 Volumetric % +1.0/+12.0 2.1 4.1 4.4 ND ND variation Tensile % Report 5 27 26 ND ND strength variation Elongation % 51/+9 26 13 19 ND ND at break RE9 Volumetric % 2.5/+16.0 1.4 1.6 5.7 6.5 8.8 variation Tensile % Report 24 62 6 1 23 strength variation Elongation % 65/+19 34 83 38 28 42 at break

[0445] The results show that the addition of a carbodiimide additive to the lubricant allows the adverse effect of polyalkylamine addition on elastomer compatibility to be counteracted, notably with regard to the lubricant's impact on the elongation-at-break properties of the elastomer material.

[0446] Thus, the addition of a carbodiimide additive according to the invention to a lubricant affords good lubricant compatibility with the various elastomers, and similarly does so in the presence of an amine additive.