Lubricant composition having improved emulsion stability

Abstract

Disclosed is a lubricant composition comprising: - at least one base oil, - from 0.1% to 13% by weight of at least one viscosity index improver, - at least one organomolybdenum compound, the content of molybdenum element being at least 400 ppm by weight, - at least a first detergent additive chosen from magnesium salts of carboxylic acids, of sulfonates, of salicylates, of naphthenates, of phenates and any mixture thereof, - optionally, at least a second detergent additive chosen from calcium salts of carboxylic acids, of sulfonates, of salicylates, of naphthenates, of phenates and any mixture thereof, wherein the combined content of magnesium element and of calcium element, relative to the total weight of the lubricant composition, is at least 1000 ppm by weight.

Description

[0001] Lubricating composition with improved emulsion stability

[0002] The present invention relates to the lubrication of a vehicle comprising at least one combustion engine. In particular, the present invention relates to the lubrication of a hybrid vehicle engine of the plug-in hybrid vehicle type and a hybrid vehicle comprising a range extender.

[0003] Hybrid vehicles consist of two engines: a combustion engine and an electric motor. In most hybrid vehicles, the combustion engine drives the wheels and is assisted by an electric motor. A battery provides the electricity needed to operate the electric motor. In conventional hybrid vehicles, this battery is recharged during braking and deceleration by a kinetic energy recovery system (KERS) integrated into the vehicle.

[0004] There are different hybrid vehicle technologies. These hybrid technologies include:

[0005] - micro-hybrid vehicles (also called mild hybridization), these vehicles, equipped with the “stop&start” system, recover the energy generated by braking to charge a battery which can temporarily assist the thermal engine;

[0006] - mild-hybrid vehicles which include electric assistance during acceleration;

[0007] - Full hybrid vehicles are vehicles with total hybridization. At low speeds, when the battery is charged, the electric motor takes care of starting and locomotion. At high speeds, or when the battery is discharged, the combustion engine takes over; when increased power is needed (for example, acceleration), the two engines work together. It is thus possible to drive with the combustion engine switched off for a few kilometers.

[0008] Other complementary technologies have recently been developed: plug-in hybrid vehicles and hybrid vehicles with a range extender. Plug-in hybrid vehicles include a combustion engine and an electric motor. The battery can be recharged from the electricity network. These vehicles can therefore run in 100% electric mode for a distance of several dozen kilometers, for example 50 kilometers. In hybrid vehicles with a range extender, only the electric motor drives the wheels. This electric motor is powered by a battery for a few dozen kilometers.When the battery reaches a certain charge threshold (for example around 30%), the thermal engine starts and drives a current generator to produce the electricity needed to recharge the battery and maintain the operation of the electric motor.

[0009] Lubricating compositions, and in particular those used for the lubrication of combustion engines, generally contain small amounts of water resulting in particular from the direct adsorption by the lubricant of water contained in the air or from the condensation of ambient water vapor. A lubricating composition thus typically contains 0 to 10% water. Although present in trace amounts, water in lubricating compositions is the cause of cold start problems, corrosion and also premature wear of the combustion engine. In order to prevent these phenomena, it is then necessary to maintain this water in the form of an emulsion.

[0010] However, in hybrid vehicle engines, particularly plug-in hybrid vehicles or those incorporating a range extender, the combustion engine is used less frequently, which in particular has the consequence of promoting problems with the demixing of the lubricating composition. As the lubricating composition remains stationary, the emulsion becomes unstable, the water separates from the oil phase and forms a continuous phase.

[0011] Similar problems are also observed with conventional vehicles equipped only with a combustion engine (non-hybrid vehicles) and operated occasionally, particularly with gasoline engines. Since the lubricating composition is not regularly circulated in the engine, the water present tends to separate from the rest of the lubricating composition and form a continuous phase.

[0012] It is therefore necessary to provide a specific lubricating composition allowing the lubrication of such motorization systems, while preventing demixing problems.

[0013] An objective of the present invention is to provide a lubricating composition allowing the lubrication of an internal combustion engine, in particular a plug-in hybrid vehicle engine or one comprising a range extender.

[0014] Another objective of the present application is to provide a lubricating composition having improved emulsion stability. In particular, the objective of the invention is to provide a lubricating composition making it possible to maintain the water present in the form of stable emulsions. These objectives are fulfilled by the present application which relates to a lubricating composition comprising:

[0015] - at least one base oil,

[0016] - from 0.1% to 13% by mass, relative to the total mass of the lubricating composition, of at least one additive making it possible to improve the viscosity index,

[0017] - at least one organomolybdenum compound, the molybdenum element content being at least 400 ppm by mass, relative to the total mass of the lubricating composition,

[0018] - at least one first detergent additive chosen from magnesium salts of carboxylic acids, sulfonates, salicylates, naphthenates, phenates and any of their mixtures,

[0019] - optionally, at least one second detergent additive chosen from calcium salts of carboxylic acids, sulfonates, salicylates, naphthenates, phenates and any of their mixtures, in which the cumulative content of magnesium element and calcium element, relative to the total mass of the lubricating composition, is at least 1000 ppm by mass.

[0020] The base oil

[0021] The base oils used in the lubricating compositions according to the invention may be oils of mineral or synthetic origin, possibly regenerated, belonging to groups I to V according to the classes defined in the API classification (or their equivalents according to the ATIEL classification) (table A) or their mixtures.

[0022] Table 1 The mineral base oils according to the invention include all types of bases obtained by atmospheric and vacuum distillation of crude oil, followed by refining operations such as solvent extraction, deasphalting, solvent dewaxing, hydrotreating, hydrocracking, hydroisomerization and hydrofinishing.

[0023] Mixtures of synthetic and mineral oils, possibly regenerated, can also be used.

[0024] There is generally no limitation on the use of different lubricating bases to produce the lubricating compositions according to the invention, except that they must have properties, in particular viscosity, viscosity index, sulfur content, resistance to oxidation, suitable for use for engines or for vehicle transmissions.

[0025] The base oils of the lubricating compositions according to the invention may also be chosen from synthetic oils, such as certain esters of carboxylic acids and alcohols, and from polyalphaolefins. The polyalphaolefins used as base oils are for example obtained from monomers comprising from 4 to 32 carbon atoms, for example from octene or decene, and whose viscosity at 100°C is between 1.5 and 15 mm 2 . s -1according to ASTM D445. Their average molecular weight is generally between 250 and 3,000 according to ASTM D5296.

[0026] The lubricating composition according to the invention may comprise at least 50% by mass of base oils relative to the total mass of the composition. More advantageously, the lubricating composition according to the invention comprises at least 60% by mass, or even at least 70% by mass, of base oils relative to the total mass of the composition. More particularly advantageously, the lubricating composition according to the invention comprises from 75 to 95% by mass of base oils relative to the total mass of the composition.

[0027] The additive to improve the viscosity index

[0028] The lubricating composition according to the invention comprises at least one additive making it possible to improve the viscosity index of the lubricating composition (in English “viscosity index improver”).

[0029] For the purposes of the invention, the term "additive for improving the viscosity index" means a chemical compound for ensuring good cold resistance and minimum viscosity at high temperature of the lubricating composition. Examples of viscosity index improving polymers include polymer 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).

[0030] The lubricating composition according to the invention typically comprises from 0.1% to 13% by mass of additive(s) improving the viscosity index, relative to the total weight of the lubricating composition.

[0031] Preferably, the lubricating composition according to the invention comprises from 0.5% to 12% by mass of additive(s) improving the viscosity index, relative to the total weight of the lubricating composition, more preferably from 1% to 10% by mass, even more preferably from 5% to 10% by mass.

[0032] The organomolybdenum compound

[0033] The lubricating composition according to the invention comprises at least one organomolybdenum compound.

[0034] By organomolybdenum compound according to the invention is meant any liposoluble organomolybdenum compound.

[0035] The organomolybdenum compound according to the present invention may be chosen from organic molybdenum complexes comprising at least one molybdenum (Mo) chemical element, preferably at least two molybdenum (Mo) chemical elements, and at least one ligand such as a carboxylate ligand, an ester ligand, an amide ligand, a dithiophosphate ligand, a dithiocarbamate ligand.

[0036] For example, organic complexes of molybdenum with carboxylates, esters, amides can be obtained by reaction of molybdenum oxide or ammonium molybdates with fatty substances, glycerides, fatty acids or fatty acid derivatives (esters, amines, amides, etc.).

[0037] For the purposes of the invention, the carboxylate ligands, the ester ligands and the amide ligands are free of sulfur and phosphorus.

[0038] In one embodiment, the organomolybdenum compound of the invention is chosen from molybdenum complexes with amide ligands, mainly prepared by reaction of a molybdenum source, which may be for example molybdenum trioxide, and an amine derivative, and fatty acids comprising for example from 4 to 36 carbon atoms such as for example the fatty acids contained in vegetable or animal oils. The synthesis of such compounds is for example described in patents US4889647, EP0546357, US5412130 or EP1770153.

[0039] According to a preferred embodiment, the organomolybdenum compound is chosen from dinuclear organomolybdenum compounds.

[0040] For the purposes of the invention, the term "dinuclear organomolybdenum compound" means organomolybdenum compounds whose nucleus contains two molybdenum atoms. Dimeric organomolybdenum compounds are also referred to.

[0041] In a preferred embodiment of the invention, the organomolybdenum compound is chosen from organic complexes of molybdenum with amide ligands obtained by reaction:

[0042] (i) a fatty substance of mono, di or tri glyceride type, or fatty acid,

[0043] (ii) an amino source of formula (A): in which:

[0044] - X 1 represents an oxygen atom or a nitrogen atom,

[0045] - X 2 represents an oxygen atom or a nitrogen atom,

[0046] - n or m represents 1 when respectively X 1 or X 2 represents an oxygen atom, n or m represents 2 when respectively X 1 or X 2 represents a nitrogen atom,

[0047] (iii) and a source of molybdenum chosen from molybdenum trioxide or molybdates, preferably ammonium molybdate.

[0048] In one embodiment of the invention, the organomolybdenum compound may comprise from 0.1 to 30% by weight, preferably from 0.1 to 20%, more preferably from 2 to 8.5% by weight of molybdenum relative to the total weight of the organomolybdenum complex.

[0049] Preferably, the organomolybdenum compound comprises at least one organic molybdenum complex of formula (I) or (II), alone or as a mixture: in which:

[0050] - X 1 represents an oxygen atom or a nitrogen atom;

[0051] - X 2 represents an oxygen atom or a nitrogen atom;

[0052] - n represents 1 when X 1 represents an oxygen atom and m represents 1 when X 2 represents an oxygen atom;

[0053] - n represents 2 when X 1 represents a nitrogen atom and m represents 2 when X 2 represents a nitrogen atom;

[0054] Ri represents a linear or branched, saturated or unsaturated alkyl group, comprising from 4 to 36 carbon atoms, preferably from 4 to 20 carbon atoms, advantageously from 6 to 18 carbon atoms; in which:

[0055] - X 1 represents an oxygen atom or a nitrogen atom;

[0056] -X 2 represents an oxygen atom or a nitrogen atom;

[0057] -n represents 1 when X 1 represents an oxygen atom and m represents 1 when X 2 represents an oxygen atom;

[0058] - n represents 2 when X 1 represents a nitrogen atom and m represents 2 when X 2 represents a nitrogen atom;

[0059] - Ri represents a linear or branched, saturated or unsaturated alkyl group, comprising from 4 to 36 carbon atoms, preferably from 4 to 20 carbon atoms, advantageously from 6 to 18 carbon atoms;

[0060] -R2 represents a linear or branched, saturated or unsaturated alkyl group comprising from 4 to 36 carbon atoms, preferably from 4 to 20 carbon atoms, advantageously from 6 to 18 carbon atoms. Advantageously, the organic molybdenum complex of formula (I) or (II) is prepared by reaction:

[0061] (i) a fatty substance of mono, di or tri glyceride type, or fatty acid,

[0062] (ii) diethanolamine or 2-(2-aminoethyl)aminoethanol,

[0063] (iii) and a source of molybdenum chosen from molybdenum trioxide or molybdates, preferably ammonium molybdate.

[0064] More advantageously, the organic molybdenum complex of formula (I) consists of at least one compound of formula (Ia) or (Ib), alone or in a mixture: in which Ri represents a linear or branched, saturated or unsaturated alkyl group, comprising from 4 to 36 carbon atoms, preferably from 4 to 20 carbon atoms, advantageously from 6 to 18 carbon atoms, in which Ri represents a linear or branched, saturated or unsaturated alkyl group, comprising from 4 to 36 carbon atoms, preferably from 4 to 20 carbon atoms, advantageously from 6 to 18 carbon atoms.

[0065] As an example of sulfur-free molybdenum complexes according to the invention, mention may be made of Molyvan 855® marketed by the company Vanderbilt.

[0066] In another embodiment of the invention, the organomolybdenum compound is selected from organic complexes of molybdenum with dithiophosphate ligands or organic complexes of molybdenum with dithiocarbamate ligands.

[0067] For the purposes of the invention, organic complexes of molybdenum with dithiophosphate ligands are also called molybdenum dithiophosphates or Mo-DTP compounds and organic complexes of molybdenum with dithiocarbamate ligands are also called molybdenum dithiocarbamates or Mo-DTC compounds. In a more preferred embodiment of the invention, the organomolybdenum compound is selected from molybdenum dithiocarbamates.

[0068] Mo-DTC compounds are complexes formed of a molybdenum metal core bound to one or more ligands, the ligand being an alkyl dithiocarbamate group. These compounds are well known to those skilled in the art.

[0069] In one embodiment of the invention, the Mo-DTC compound may comprise from 1 to 40%, preferably from 2 to 30%, more preferably from 3 to 28%, advantageously from 4 to 15% by weight of molybdenum, relative to the total weight of the Mo-DTC compound.

[0070] In another embodiment of the invention, the Mo-DTC compound may comprise from 1 to 40%, preferably from 2 to 30%, more preferably from 3 to 28%, advantageously from 4 to 15% by weight of sulfur, relative to the total weight of the Mo-DTC compound.

[0071] In a preferred embodiment of the invention, the Mo-DTC compound is a dimeric Mo-DTC compound.

[0072] Examples of dimeric Mo-DTC compounds include compounds and their preparation processes as described in EP 0757093, EP 0719851, EP 0743354 or EP 1013749.

[0073] Dimeric Mo-DTC compounds generally correspond to compounds of formula (III): in which:

[0074] R3, R4, R5, Re, identical or different, independently represent a hydrocarbon group chosen from alkyl, alkenyl, aryl, cycloalkyl or cycloalkenyl groups,

[0075] X3, X4, X5 and X6, which may be identical or different, independently represent an oxygen atom or a sulfur atom. For the purposes of the invention, the term “alkyl group” means a linear or branched, saturated or unsaturated hydrocarbon group comprising from 1 to 24 carbon atoms, preferably from 4 to 18 carbon atoms.

[0076] In one embodiment of the invention, the alkyl group is selected from the group consisting of methyl, ethyl, propyl, isopropyl, n-butyl, iso-butyl, tert-butyl, n-pentyl, iso-pentyl, neopentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, isotridecyl, tetradecyl, hexadecyl, stearyl, icosyl, docosyl, tetracosyl, triacontyl, 2-ethylhexyl, 2-butyloctyl, 2-butyldecyl, 2-hexyloctyl, 2-hexyldecyl, 2-octyldecyl, 2-hexyldodecyl, 2- octyldodecyl, 2-decyltetradecyl, 2-dodecylhexadecyl, 2-hexadecyloctadecyl, 2-tetradecyloctadecyl, myristyl, palmityl and stearyl.

[0077] For the purposes of the present invention, an alkenyl group is understood to mean a linear or branched hydrocarbon group comprising at least one double bond and comprising from 2 to 24 carbon atoms. The alkenyl group may be chosen from vinyl, allyl, propenyl, butenyl, isobutenyl, pentenyl, isopentenyl, hexenyl, heptenyl, octenyl, nonenyl, decenyl, undecenyl, dodecenyl, tetradecenyl and oleic.

[0078] For the purposes of the present invention, the term aryl group means a polycyclic aromatic hydrocarbon or an aromatic group, substituted or not by an alkyl group. The aryl group may comprise from 6 to 24 carbon atoms.

[0079] In one embodiment, the aryl group may be selected from the group consisting of phenyl, toluyl, xylyl, cumenyl, mesityl, benzyl, phenethyl, styryl, cinnamyl, benzhydryl, trityl, ethylphenyl, propylphenyl, butylphenyl, pentylphenyl, hexylphenyl, heptylphenyl, octylphenyl, nonylphenyl, decylphenyl, undecylphenyl, dodecylphenyl, phenylphenyl, benzylphenyl, phenyl-styrene, p-cumylphenyl and naphthyl.

[0080] By cycloalkyl group within the meaning of the present invention, we mean a polycyclic or cyclic hydrocarbon, substituted or not by an alkyl group.

[0081] By cycloalkenyl group for the purposes of the present invention, we mean a polycyclic or cyclic hydrocarbon, substituted or not by an alkyl group, and comprising at least one unsaturation.

[0082] Cycloalkyl groups and cycloalkenyl groups may comprise from 3 to

[0083] 24 carbon atoms. For the purposes of the present invention, the cycloalkyl groups and the cycloalkenyl groups may be chosen, in a non-limiting manner, from the group consisting of cyclopentyl, cyclohexyl, cycloheptyl, methylcyclopentyl, methylcyclohexyl, methylcycloheptyl, cyclopentenyl, cyclohexenyl, cycloheptenyl, methylcyclopentenyl, methylcyclohexenyl.

[0084] In a preferred embodiment of the invention, R3, R4, R5 and Re, identical or different, independently represent an alkyl group comprising from 1 to 24 carbon atoms, preferably from 4 to 18 carbon atoms or an alkenyl group comprising from 2 to 24 carbon atoms.

[0085] In one embodiment of the invention, X3, X4, X5 and Xe may be the same and may represent a sulfur atom.

[0086] In another embodiment of the invention, X3, X4, X5 and Xe may be the same and may be an oxygen atom.

[0087] In another embodiment of the invention, X3 and X4 may represent a sulfur atom and X5 and X6 may represent an oxygen atom.

[0088] In another embodiment of the invention, X3 and X4 may represent an oxygen atom and Xs and Xe may represent a sulfur atom.

[0089] In another embodiment of the invention, the ratio of sulfur atoms to oxygen atoms (S / O) in the Mo-DTC compound may vary from (1 / 3) to (3 / 1).

[0090] In another embodiment of the invention, the Mo-DTC compound of formula (III) may be selected from a symmetrical Mo-DTC compound, an asymmetrical Mo-DTC compound and their combination.

[0091] By symmetrical Mo-DTC compound according to the invention is meant a Mo-DTC compound of formula (V) in which the groups R3, R4, R5 and Re are identical.

[0092] By asymmetric Mo-DTC compound according to the invention is meant a Mo-DTC compound of formula (V) in which the groups R3 and R4 are identical, the groups R5 and Re are identical and the groups R3 and R4 are different from the groups R5 and Re. In a preferred embodiment of the invention, the Mo-DTC compound is a mixture of at least one symmetric Mo-DTC compound and at least one asymmetric Mo-DTC compound.

[0093] In one embodiment of the invention, R3 and R4, which are identical, represent an alkyl group comprising from 5 to 15 carbon atoms, preferably from 8 to 13 carbon atoms, and R5 and Re, which are identical, represent an alkyl group comprising from 5 to 15 carbon atoms, preferably from 8 to 13 carbon atoms, and the groups R3 and R4 are identical to or different from the groups R5 and Re.

[0094] In another preferred embodiment of the invention, R3 and R4, which are identical, represent an alkyl group comprising from 6 to 10 carbon atoms and R5 and Re, which are identical, represent an alkyl group comprising from 10 to 15 carbon atoms, and the R3 and R4 groups are different from the R5 and Re groups.

[0095] In another preferred embodiment of the invention, R3 and R4, which are identical, represent an alkyl group comprising from 10 to 15 carbon atoms and R5 and Re, which are identical, represent an alkyl group comprising from 6 to 10 carbon atoms, and the R3 and R4 groups are different from the R5 and Re groups.

[0096] In another preferred embodiment of the invention, R3, R4, R5 and Re, which are identical, represent an alkyl group comprising from 5 to 15 carbon atoms, preferably from 8 to 13 carbon atoms.

[0097] Advantageously, the Mo-DTC compound is chosen from the compounds of formula (III) in which:

[0098] - X3 and X4 represent an oxygen atom,

[0099] - X5 and X6 represent a sulfur atom,

[0100] - R3 represents an alkyl group comprising 8 carbon atoms or an alkyl group comprising 13 carbon atoms,

[0101] - R4 represents an alkyl group comprising 8 carbon atoms or an alkyl group comprising 13 carbon atoms,

[0102] - R5 represents an alkyl group comprising 8 carbon atoms or an alkyl group comprising 13 carbon atoms, - Re represents an alkyl group comprising 8 carbon atoms or an alkyl group comprising 13 carbon atoms.

[0103] Thus, advantageously, the Mo-DTC compound is chosen from the compounds of formula (II la)

[0104] (lll-a) in which the groups R3, R4, R5 and Re are as defined for formula (III).

[0105] More advantageously, the Mo-DTC compound is a mixture:

[0106] - a Mo-DTC compound of formula (III-a) in which R3, R4, R5 and Re represent an alkyl group comprising 8 carbon atoms,

[0107] - a Mo-DTC compound of formula (III-a) in which R3, R4, R5 and Re represent an alkyl group comprising 13 carbon atoms, and / or

[0108] - a Mo-DTC compound of formula (III-a) in which R3, R4 represent an alkyl group comprising 8 carbon atoms and R5 and Re represent an alkyl group comprising 13 carbon atoms.

[0109] Examples of Mo-DTC compounds include the products Molyvan L®, Molyvan 807® or Molyvan 822® marketed by RT Vanderbilt Compagny® or the products Sakura-lube 200®, Sakura-lube 165®, Sakura-lube 525® or Sakura-lube 600® marketed by Adeka.

[0110] The lubricating composition according to the invention typically comprises at least 400 ppm by mass of molybdenum element, relative to the total mass of the lubricating composition.

[0111] Preferably, the lubricating composition according to the invention comprises at most 1,500 ppm by mass of molybdenum element, relative to the total mass of the lubricating composition, more preferably from 500 ppm to 1,200 ppm, even more preferably from 750 ppm to 1,000 ppm.

[0112] The first detergent additive (magnesium-based)

[0113] The lubricating composition according to the invention also comprises at least one first detergent additive. Detergent additives generally make it possible to reduce the formation of deposits on the surface of metal parts by dissolving secondary oxidation and combustion products.

[0114] The detergent additives that can be used in the lubricating compositions according to the invention are generally known to those skilled in the art. The detergent additives may be anionic compounds comprising a long lipophilic hydrocarbon chain and a hydrophobic head. The associated cation may be a metal cation of an alkali or alkaline earth metal.

[0115] The first detergent additive is typically selected from magnesium salts of carboxylic acids, sulfonates, salicylates, naphthenates, phenates and any mixtures thereof.

[0116] According to a preferred embodiment, the first detergent additive is chosen from magnesium sulfonates.

[0117] The detergents used will be non-overbased (or neutral) or overbased. We speak of non-overbased or "neutral" detergents when the metal salts contain the metal in an approximately stoichiometric quantity. We speak of overbased detergents when the metal is in excess (in an amount greater than the stoichiometric quantity). The excess metal providing the overbased character to the detergent is in the form of oil-insoluble metal salts. Overbased detergents are thus in the form of micelles composed of insoluble metal salts held in suspension in the lubricating composition by the detergents in the form of oil-soluble metal salts. These micelles may contain one or more types of insoluble metal salts, stabilized by one or more types of detergents.Overbased detergents will be said to be of mixed type if the micelles include several types of detergents, differing from each other by the nature of their hydrophobic chain.

[0118] Advantageously, the first detergent additive(s) represent from 0.5 to 8% by mass, preferably from 2% to 4% by mass, relative to the total mass of the lubricating composition.

[0119] The second detergent additive (calcium-based)

[0120] According to a preferred embodiment, the composition according to the invention further comprises at least one second detergent additive.

[0121] The second detergent additive is typically chosen from calcium salts.

[0122] Preferably, the second detergent additive is selected from calcium salts of carboxylic acids, sulfonates, salicylates, naphthenates, phenates and any mixture thereof. Advantageously, the second detergent additive is selected from calcium carboxylates, preferably from calcium salicylates.

[0123] The detergents used will be non-overbased (or neutral) or overbased. We speak of non-overbased or "neutral" detergents when the metal salts contain the metal in an approximately stoichiometric quantity. We speak of overbased detergents when the metal is in excess (in an amount greater than the stoichiometric quantity). The excess metal providing the overbased character to the detergent is in the form of oil-insoluble metal salts. Overbased detergents are thus in the form of micelles composed of insoluble metal salts held in suspension in the lubricating composition by the detergents in the form of oil-soluble metal salts. These micelles may contain one or more types of insoluble metal salts, stabilized by one or more types of detergents.Overbased detergents will be said to be of mixed type if the micelles include several types of detergents, differing from each other by the nature of their hydrophobic chain.

[0124] Advantageously, when present, the second detergent additive represents from 0.5 to 8% by mass, preferably from 2% to 4% by mass, relative to the total mass of the lubricating composition.

[0125] According to one embodiment, the composition according to the invention is free of second detergent additive.

[0126] Preferably, according to this embodiment, the content of magnesium element is at least 1000 ppm by mass, relative to the total mass of the lubricating composition, more preferably from 1100 ppm to 3000 ppm, even more preferably from 1400 ppm to 2800 ppm, typically from 1600 ppm to 2650 ppm.

[0127] According to a preferred embodiment, the composition according to the invention comprises at least one first detergent additive and at least one second detergent additive.

[0128] Preferably, according to this preferred embodiment, the cumulative content of magnesium element and calcium element, relative to the total mass of the lubricating composition, is at least 1000 ppm by mass, more preferably from 1100 ppm to 3000 ppm, even more preferably from 1400 ppm to 2800 ppm, typically from 1600 ppm to 2650 ppm.

[0129] For the purposes of the invention, the term "cumulative content of magnesium element and calcium element" means the sum of the content of magnesium element present in the lubricating composition and the content of calcium element present in the lubricating composition. Preferably, the ratio between the content of calcium element (from the first detergent additive) and the content of magnesium element (from the second detergent additive) ranges from 10:1 to 1:10.

[0130] Advantageously, the ratio between the calcium element content and the magnesium element content ranges from 5:1 to 1:5, preferably from 5:2 to 5:2, more preferably from 5:2 to 1:1.

[0131] The BN (Base Number measured according to ASTM D-2896) of the lubricating compositions according to the present invention is totally or partly provided by neutral or overbased detergents based on alkali or alkaline earth metals, in particular by the first and second detergent additives.

[0132] The BN value of the lubricating compositions according to the present invention, measured according to ASTM D-2896, can vary from 1 to 140 mg of KOH / g, preferably from 3 to 80 mg of KOH / g, more preferably from 5 to 50 mg of KOH / g, typically from 5 to 20 mg of KOH / g. The BN value will be chosen according to the conditions of use of the lubricating compositions and in particular according to the sulfur content of the fuel used.

[0133] Other additives

[0134] Many optional additives may also be present in the lubricating compositions according to the invention.

[0135] The preferred additives for the lubricating composition according to the invention are chosen from detergent additives different from the first and second detergent additives defined above, friction modifying additives different from the molybdenum compounds defined above, extreme pressure additives, dispersants, pour point activators, anti-foaming agents, thickeners and mixtures thereof.

[0136] Preferably, the lubricating compositions according to the invention comprise at least one extreme pressure additive, or a mixture.

[0137] Anti-wear additives and extreme pressure additives protect surface friction by forming a protective film adsorbed on its surfaces.

[0138] There are a wide variety of anti-wear additives. Preferably, for the lubricating compositions of the invention, the anti-wear additives are chosen from additives comprising phosphorus and sulfur such as alkylthiophosphate metals, in particular zinc alkylthiophosphate, and more precisely zinc dialkyldithiophosphate or ZnDTP. The preferred compounds are of formula Zn((SP(S)(OR)(OR'))2, in which R and R', identical or different, independently represent an alkyl group, preferably an alkyl group comprising from 1 to 18 carbon atoms. Amine phosphates are also anti-wear additives that can be used in the lubricating compositions of the invention. However, the phosphorus atoms provided by these additives can act as a poison for the catalytic systems of automobiles since they generate ash.These effects can be minimized by substituting some of the amine phosphates with non-phosphorus-containing additives, such as polysulfides, especially sulfur-containing olefins.

[0139] Advantageously, the lubricating compositions according to the invention may comprise from 0.01 to 6% by mass, preferably from 0.05 to 4% by mass, more preferably from 0.1 to 2% by mass relative to the total mass of lubricating composition, of anti-wear and extreme pressure additives.

[0140] Advantageously, the lubricating compositions according to the invention comprise from 0.01 to 6% by mass, preferably from 0.05 to 4% by mass, more preferably from 0.1 to 2% by mass relative to the total mass of lubricating composition, of anti-wear additives (or anti-wear compound).

[0141] Advantageously, the compositions according to the invention may comprise at least one friction-modifying additive different from the molybdenum compounds of the invention. The friction-modifying additives may in particular be chosen from compounds providing metallic elements and ashless compounds. Among the compounds providing metallic elements, mention may be made of transition metal complexes such as Mo, Sb, Sn, Fe, Cu, Zn for which the ligands may be hydrocarbon compounds comprising oxygen, nitrogen, sulfur or phosphorus atoms. The ashless friction-modifying additives are generally of organic origin or may be chosen from fatty acid monoesters and polyols, alkoxylated amines, alkoxylated fatty amines, fatty epoxides, fatty epoxide borates, fatty amines or glycerol acid esters.According to the invention, the fatty compounds comprise at least one hydrocarbon group comprising from 10 to 24 carbon atoms.

[0142] Advantageously, the lubricating composition according to the invention may comprise from 0.01 to 2% by mass or from 0.01 to 5% by mass, preferably from 0.1 to 1.5% by mass or from 0.1 to 2% by mass relative to the total mass of the lubricating composition, of friction modifying additive other than the molybdenum compounds according to the invention.

[0143] Advantageously, the lubricating composition according to the invention may comprise at least one antioxidant additive. Antioxidant additives generally delay the degradation of the lubricating composition. This degradation is most often expressed by the formation of deposits, by the presence of sludge or by an increase in the viscosity of the lubricating composition.

[0144] Antioxidant additives generally act as free radical inhibitors or hydroperoxide destructive inhibitors. Commonly used antioxidants include phenolic antioxidants, amine antioxidants, sulfur- and phosphorus-containing antioxidants. Some of these antioxidants, for example those comprising sulfur and phosphorus, may generate ash. Phenolic antioxidant additives may be ash-free or in the form of neutral or basic metal salts. Antioxidant additives may include, but are not limited to, sterically hindered phenols, sterically hindered phenol esters, sterically hindered phenols comprising a thioether bridge, diphenylamines, diphenylamines substituted with at least one C1-C12 alkyl group, N,N'-dialkylaryldiamines, and mixtures thereof.

[0145] Preferably according to the invention, the sterically hindered phenols are chosen from compounds comprising a phenol group for which at least one of the carbon atoms in the vicinity of the carbon atom carrying the alcohol function is substituted by at least one C1 to C10 alkyl group, preferably a C1 to C6 alkyl group, preferably a C4 alkyl group, preferably a tert-butyl group.

[0146] Amine 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 NRaRbRc in which Ra represents an aliphatic group or an aromatic group, optionally substituted, Rb represents an aromatic group, optionally substituted, Rc represents a hydrogen atom, an alkyl group, an aryl group or a group of the formula RdS(O)zRe in which Rd represents an alkylene or alkenylene group, Re represents an alkyl group, an alkenyl group or an aryl group and z represents 0, 1 or 2.

[0147] Sulfur-containing alkylphenols or their alkali or alkaline earth metal salts can also be used as antioxidant additives.

[0148] Other classes of antioxidant additives are compounds comprising copper, for example copper thio- or dithio-phosphate, copper salts and carboxylic acids, dithiocarbamates, sulfonates, phenates, copper acetylacetonates. Copper I and II salts, succinic acid or anhydride salts may also be used. The lubricating compositions according to the invention may also comprise any type of antioxidant known to those skilled in the art.

[0149] Advantageously, the lubricating composition comprises at least one ash-free antioxidant additive.

[0150] Also advantageously, the lubricating composition according to the invention comprises from 0.1 to 2% by mass relative to the total mass of the composition, of at least one antioxidant additive.

[0151] The lubricating composition according to the invention may also comprise at least one detergent additive distinct from the first and second detergent additives defined above.

[0152] The detergent additives are preferably selected from alkali or alkaline earth metal salts of carboxylic acid, sulfonates, salicylates, naphthenates, and phenate salts. The alkali and alkaline earth metals are preferably sodium or barium.

[0153] These metal salts generally comprise the metal in stoichiometric or excess amount, i.e. in a content greater than the stoichiometric content. These are then overbased detergents; the excess metal implying the overbased nature of the detergent additive is generally in the form of an oil-insoluble metal salt, e.g. carbonate, hydroxide, oxalate, acetate, glutamate, preferably carbonate.

[0154] Advantageously, the lubricating composition according to the invention may comprise from 0.2% to 8% or from 0.5% to 3% by mass of additional detergent additives (distinct from the first and second detergent additives defined above), relative to the total mass of the lubricating composition.

[0155] Also advantageously, the lubricating composition according to the invention may also comprise a pour point lowering additive.

[0156] By slowing the formation of paraffin crystals, the pour point lowering additive generally improves the cold behavior of the lubricating composition according to the invention.

[0157] Examples of pour point depressants include alkyl polymethacrylates, polyacrylates, polyarylamides, polyalkylphenols, polyalkylnaphthalenes, and alkyl polystyrenes.

[0158] Advantageously, the lubricating composition according to the invention may also comprise a dispersing agent.

[0159] The dispersing agents may be chosen from Mannich bases, succinimides and their derivatives. Also advantageously, the lubricating composition according to the invention may comprise from 0.2 to 10% by mass of dispersing agent relative to the total mass of lubricating composition.

[0160] The lubricating composition according to the invention may also comprise at least one thickening agent.

[0161] The lubricating composition according to the invention may also comprise an antifoaming agent and a demulsifying agent.

[0162] The lubricating composition

[0163] Preferably, the lubricating composition comprises, relative to the total mass of the lubricating composition:

[0164] - from 50% to 95% by mass of at least one base oil,

[0165] - from 0.1% to 13% by mass of at least one additive to improve the viscosity index,

[0166] - at least one organomolybdenum compound, the molybdenum element content ranging from 400 ppm to 1500 ppm by mass,

[0167] - at least one first detergent additive chosen from magnesium salts of carboxylic acids, sulfonates, salicylates, naphthenates, phenates and any of their mixtures,

[0168] - optionally, at least one second detergent additive chosen from calcium salts of carboxylic acids, sulfonates, salicylates, naphthenates, phenates and any of their mixtures, in which the cumulative content of magnesium element and calcium element, relative to the total mass of the lubricating composition, ranges from 1000 ppm to 3000 ppm by mass.

[0169] Advantageously, the lubricating composition comprises, relative to the total mass of the lubricating composition:

[0170] - from 60% to 95% by mass of at least one base oil,

[0171] - from 0.5% to 12% by mass of at least one additive to improve the viscosity index,

[0172] - at least one organomolybdenum compound, the molybdenum element content ranging from 500 ppm to 1500 ppm by mass,

[0173] - at least one first detergent additive chosen from magnesium sulfonates,

[0174] - optionally, at least one second detergent additive chosen from salicylates, calcium, in which the cumulative content of magnesium element and calcium element, relative to the total mass of the lubricating composition, ranges from 1400 ppm to 2800 ppm by mass.

[0175] More advantageously, the lubricating composition comprises, relative to the total mass of the lubricating composition:

[0176] - from 75% to 95% by mass of at least one base oil,

[0177] - from 5% to 10% by mass of at least one additive to improve the viscosity index,

[0178] - at least one organomolybdenum compound, the molybdenum element content ranging from 750 ppm to 100 ppm by mass,

[0179] - at least one first detergent additive chosen from magnesium sulfonates,

[0180] - optionally, at least one second detergent additive chosen from salicylates, calcium, in which the cumulative content of magnesium element and calcium element, relative to the total mass of the lubricating composition, ranges from 1600 ppm to 2650 ppm by mass.

[0181] Uses and methods

[0182] The invention also relates to the use of a lubricating composition as defined above for the lubrication of a combustion engine.

[0183] Preferably, the engine is selected from gasoline engines and diesel engines, preferably the combustion engine is a gasoline engine.

[0184] According to a preferred embodiment, the engine is a plug-in hybrid vehicle engine or a hybrid vehicle engine comprising a range extender.

[0185] In the context of the present invention, a rechargeable hybrid vehicle (also called plug-in in English) is understood to mean a vehicle comprising a thermal engine and an electric motor, the battery being able to be recharged on the electrical network, this vehicle can thus drive in 100% electric mode over a distance of several tens of kilometers, such as for example for 50 kilometers.

[0186] In the context of the present invention, a hybrid vehicle comprising a range extender is understood to mean a hybrid vehicle in which only the electric motor drives the wheels. This electric motor is powered by a battery for a few dozen kilometers. When the battery reaches a certain charge threshold (for example of the order of 30%), the thermal engine starts and drives a current generator making it possible to produce the electricity necessary to recharge the battery and maintain the operation of the electric motor. According to a first embodiment, the invention relates to the use of the lubricating composition according to the invention to prevent and / or prevent and / or slow down cold start problems of the engine.

[0187] According to a second embodiment, the invention relates to the use of the lubricating composition according to the invention to prevent and / or prevent and / or slow down corrosion phenomena likely to occur in the engine.

[0188] According to a third embodiment, the invention relates to the use of the lubricating composition according to the invention for preventing and / or preventing and / or slowing down the wear of said engine.

[0189] According to a fourth embodiment, the invention relates to the use of the lubricating composition according to the invention to prevent and / or prevent and / or slow down the phenomena of demixing of the lubricating composition.

[0190] For the purposes of the invention, the term "demixing" means the phenomenon during which the water present in the lubricating composition, initially in the form of emulsions, spontaneously separates from the mixture to form a continuous aqueous phase.

[0191] The capacity of a lubricating composition to prevent demixing phenomena can, for example, be evaluated according to the following protocol:

[0192] 1) prepare a 100mL mixture comprising 60mL of the lubricating composition to be tested, 20mL of water and 20mL of fuel, for example E10 type gasoline fuel,

[0193] 2) stir the mixture to make it homogeneous,

[0194] 3) place the mixture in an oven at 60°C for 18 hours in a closed truncated flask.

[0195] After 18 hours of storage, the capacity of the lubricating composition to prevent demixing phenomena is visually assessed by an operator.

[0196] If the mixture is in the form of a single phase, this means that the emulsion is stable. The rating "PASS" is then assigned to the lubricating composition, indicating that the lubricating composition is not very sensitive to demixing phenomena.

[0197] Conversely, if the mixture is not homogeneous, particularly due to the formation of an oily supernatant phase, the lubricant composition is given a "FAIL" rating. The emulsion is not sufficiently stable and the lubricant composition does not adequately prevent demixing phenomena.

[0198] The invention also relates to a method for lubricating a combustion engine, in particular a plug-in hybrid vehicle engine or a hybrid vehicle engine comprising a range extender, this method comprising bringing at least one part of the engine into contact with the lubricating composition according to the invention.

[0199] The variants and embodiments detailed below for the viscosity index improving additive, the orgnomolybdenum compound, the first detergent additive and the second detergent additive also apply to the various uses defined above.

[0200] The particular, advantageous or preferred characteristics of the combined use according to the invention define particular, advantageous or preferred combinations usable according to the invention.

[0201] The various aspects of the invention can be illustrated by the following examples.

[0202] Example:

[0203] Example 1: Preparation of lubricating compositions

[0204] Lubricating compositions C1, C2, C3* and C4* are prepared from the following components:

[0205] - Base oil 1: Group III base oil with a kinematic viscosity at 40°C, measured according to ASTM D445, equal to 19.57 mm 2 / s; a kinematic viscosity at 100°C, measured according to ASTM D445, equal to 4.23 mm 2 / s; a viscosity index, measured according to the ASTM D2270 standard, equal to 122; a NOACK volatility, measured according to the DIN 51581 standard, equal to 15% by mass;

[0206] - Additive Vil: additive for improving the viscosity index (“viscosity index improver” in English), which is a conventional olefin polymer;

[0207] - MoDTC compound: molybdenum dialkyldithiocarbamate compound, commercially available under the reference “Sakuralube 525®” from the company Adeka;

[0208] - PPD: Pour Point Depressant; - Additive Package 1: Conventional additive package comprising 5% by mass of a first detergent additive of magnesium sulfonate type and 15% by mass of a second detergent additive of calcium salicylate type. Additive Package 1 does not comprise any other detergent additives. - Additive Package 2: Conventional additive package. Additive Package 2 differs from Additive Package 1 in that it does not comprise a magnesium-based detergent additive. In particular, Additive Package 2 comprises only, as a detergent additive, 15% by mass of a calcium salicylate-type detergent additive. Additive Package 2 does not comprise any other detergent additives, in particular no magnesium-based detergent additives.

[0209] - Additional detergent additive: conventional detergent additive of the magnesium sulfonate type.

[0210] More particularly, compositions C1, C2, C3* and C4* are prepared by mixing the compounds described in Table 2, at a temperature of the order of 60°C. The percentages indicated correspond to percentages by mass relative to the total mass of the composition.

[0211] Table 2

[0212] Compositions C1 and C2 are according to the invention.

[0213] Composition C3* is comparative in that it does not include an organomolybdenum compound.

[0214] Composition C4* is comparative in that it does not include a magnesium-based detergent additive.

[0215] Example 2: Ability to prevent demixing phenomena

[0216] The ability of the lubricating compositions prepared above to prevent demixing phenomena was evaluated according to the following protocol: A 100mL composition is prepared by mixing 60mL of the lubricating composition to be tested, 20mL of water and 20mL of E1O type gasoline fuel. The composition is then mixed with an ultraturax (10,000 rpm) for 1 minute. The composition is poured into a closed truncated cone flask, then placed in an oven at 60°C for 18 hours.

[0217] After 18 hours of storage, the vials are recovered and the capacity of the lubricating composition to prevent demixing phenomena is visually assessed by an operator.

[0218] If the mixture is in the form of a single phase, this means that the emulsion is stable. The rating "PASS" is then assigned to the lubricating composition, indicating that the lubricating composition is not very sensitive to demixing phenomena.

[0219] Conversely, if the mixture is not homogeneous, particularly due to the formation of an oily supernatant phase, the lubricant composition is given a "FAIL" rating. The emulsion is not sufficiently stable and the aqueous phase separates from the oil phase. The lubricant composition does not sufficiently prevent demixing phenomena.

[0220] The results obtained are presented in Table 3.

[0221] Table 3

[0222] Compositions C1 and C2 according to the invention make it possible to prevent demixing phenomena.

[0223] Conversely, emulsions obtained from C3* and C4* lubricating compositions are not stable. These lubricating compositions therefore do not prevent demixing phenomena.

Claims

DEMANDS 1. Lubricating composition comprising: - at least one base oil, - from 0.1% to 13% by mass, relative to the total mass of the lubricating composition, of at least one additive to improve the viscosity index, - at least one organomolybdenum compound, the molybdenum content being at least 400 ppm by mass, relative to the total mass of the lubricating composition, - at least one first detergent additive chosen from magnesium salts of carboxylic acids, sulfonates, salicylates, naphthenates, phenates and any mixture thereof, - optionally, at least one second detergent additive selected from calcium salts of carboxylic acids, sulfonates, salicylates, naphthenates, phenates and any mixture thereof, wherein the cumulative content of element magnesium and element calcium, relative to the total mass of the lubricating composition, is at least 1000 ppm by mass.

2. Lubricating composition according to claim 1, wherein the molybdenum content is less than or equal to 1500 ppm by mass, relative to the total mass of the lubricating composition.

3. Lubricating composition according to claim 1 or according to claim 2, wherein the first detergent additive is selected from magnesium sulfonates.

4. Lubricating composition according to any one of claims 1 to 3, comprising at least one second detergent additive selected from calcium salts of carboxylic acids, sulfonates, salicylates, naphthenates, phenates and any mixture thereof, and wherein the ratio between the content of the element calcium and the content of the element magnesium ranges from 10:1 to 1:

10.

5. Lubricating composition according to claim 4, wherein the ratio between the content of element calcium and the content of element magnesium ranges from 5:1 to 1:5, preferably from 5:2 to 5:2, more preferably from 5:2 to 1:

1.

6. Lubricating composition according to any one of the preceding claims, wherein the second detergent additive is selected from calcium carboxylates, preferably from calcium salicylates.

7. Lubricating composition according to any one of the preceding claims, wherein the organomolybdenum compound is selected from molybdenum dithiocarbamates 8. Use of a lubricating composition according to any one of the preceding claims, for the lubrication of an internal combustion engine.

9. Use according to claim 8, for the lubrication of an internal combustion engine of a plug-in hybrid vehicle or of a hybrid vehicle engine including a range extender.

10. Use according to claim 8 or claim 9, for: - to prevent and / or inhibit and / or slow down cold start problems with said engine, and / or - to prevent and / or inhibit and / or slow down corrosion phenomena that may occur in said engine, and / or - to prevent and / or inhibit and / or slow down the wear of said engine, and / or - to prevent and / or inhibit and / or slow down the phenomena of demixing of the lubricating composition.

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