A lubricant composition especially to limit friction

The present application relates to novel lubricating compositions, particularly for internal combustion engine, in particular motor vehicle, in particular motor vehicle. Particularly preferably, the present invention relates to lubricating compositions to reduce friction between the parts.

It is known to use, in lubricating compositions, molybdenum compounds as friction modifier, in particular organomolybdènes compounds. These compounds form organomolybdènes tribochemical by decomposition in the presence of iron in the contacts during friction, MoS 2 which limits the friction between the parts. However, when this tribochemical decomposition, some of the compounds organomolybdènes turns into molybdenum oxide and molybdenum oxysulfide which have no effect on the limitation of friction. It is therefore generally necessary to use large amounts of organomolybdènes compounds (to optimize the amount of MoS 2 produced) in the lubricant compositions which may have adverse effects on lubricated parts including corrosion, fouling and deterioration of the coatings in the case of parts coated carbon.

It is known, in particular CN104450069, lubricating compositions comprising MoS 2 and titanium particles, in particular Ti0 2 , to allow to reduce the friction and wear of parts.

It is also known, in particular US5709936, parts of coatings comprising titanium, including titanium carbide or nitride and / or molybdenum to reduce friction.

It is also known from January 1 WO201 12372 lubricant compositions comprising organomolybdenum compounds and liposoluble compounds based on titanium.

There is an interest in providing lubricating compositions to reduce the friction between the parts and also to reduce the wear of these parts. There is also an interest in providing lubricating compositions to reduce the amount of compound introduced molybdenum.

An object of the present application is to provide lubricating compositions for reducing the friction between the parts.

An object of the present application also provide such lubricating compositions also reduces component wear.

An objective of this application is also to provide such compositions for a period of anti-friction action over a longer period.

Another object of the present application is also to provide a lubricating composition comprising a content reduce molybdenum compound.

Other goals become apparent on reading the description of the invention that follows.

These objectives are met by the present invention which provides a lubricating composition comprising:

- at least a base oil;

- from 0.05 to 1, 5% by weight of an organomolybdenum compound; and

- from 0.005 to 1% by weight of Ti0 particles 2 .

In the context of the present invention, the term compound organomolybdenum compound comprising molybdenum and an organic part, that is to say a part comprising carbon atoms. It should therefore be understood that molybdenum disulfide (MoS 2 ) is not an organomolybdenum compound of the invention.

Preferably, the particles of Ti0 2 have an average size between 10 nm and 1 μηι, preferably between 10 nm and 500 nm, more preferably between 10 nm and 250 nm, even more preferably between 10 nm and 150 nm. In the context of the present invention, the term average particle size, the average particle diameter. This average diameter can be measured by any method known to the skilled person such as a counting by optical or electron microscopy, measurement by light scattering or by laser diffraction. The measurement by light scattering may in particular be carried out using a device of Malvern Zetasizer (technique known as "Dynamic Light Scattering", measurement by laser diffraction may be made with a Mastersizer unit from Malvern.

The Ti0 particles 2 may especially come from rutile or anatase.

Preferably, the composition according to the invention comprises from 0.08 to 1% by weight of organomolybdenum compound relative to the total weight of the lubricating composition.

Preferably, the composition according to the invention comprises from 0.01 to 0.8% by weight of Ti0 particles 2 relative to the total weight of the lubricating composition.

Advantageously, the addition, in the lubricating composition, of particles of Ti0 2 reduces the amount of organomolybdenum compound typically used to reduce friction. Indeed, without being bound by theory, the inventors have surprisingly shown that the mixture of organomolybdenum compound and particles of Ti0 2 advantageously allowed to have an excellent organomolybdenum compound conversion rate MoS 2avoiding the generation molybdenum oxysulfide in the lubricating composition and thus the loss of active molybdenum to prevent chafing. This specific combination organomolybdenum and titanium particles according to the invention therefore allows to considerably reduce the friction at a lower content in organomolybdenum compound.

By organomolybdenum compound of the invention is meant any compound in an oil soluble organomolybdenum, especially in a base oil.

The organomolybdenum compound of the present invention can be selected from organic molybdenum complexes comprising at least one chemical element molybdenum (Mo) and at least one ligand such as a carboxylate ligand, a ligand ester, an amide ligand, a ligand dithiophosphate or a dithiocarbamate ligand.

For example, organic molybdenum complex with carboxylates, esters, amides may be obtained by reaction of molybdenum oxide or ammonium molybdate with fats, glycerides, fatty acids or fatty acid derivatives (esters , amines, amides, ...).

Within the meaning of the invention, the carboxylate ligands, the ligands esters and amides ligands are free of sulfur and phosphorus.

In one embodiment, the organomolybdenum compound of the invention is selected from molybdenum complexes with amide ligands, primarily prepared by reacting a molybdenum source, which may for example molybdenum trioxide, and a amine derivative, and fatty acids having for example 4 to 36 carbon atoms such as, for example, fatty acids contained in vegetable or animal oils.

The synthesis of such compounds is for example described in the US4889647 patent, EP0546357, US5412130 or EP1770153.

In a preferred embodiment of the invention, the organomolybdenum compound is selected from organic molybdenum complexes with ligands amide obtained by reacting:

(I) a fat monaural, di or tri glyceride or fatty acid,

(Ii) an amine source of the formula (A)

in which :

- X 1 represents an oxygen atom or a nitrogen atom,

- X 2 represents an oxygen atom or a nitrogen atom,

- 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,

(Iii) a molybdenum source selected from molybdenum trioxide or molybdate, preferably ammonium molybdate.

Advantageously, the molybdenum source is implemented in an amount sufficient to provide 0.1 to 30% molybdenum based on the total weight of the organic molybdenum complex with amide ligands, more preferably 0.1 to 20.0% molybdenum.

In one embodiment of the invention, the organomolybdenum compound may comprise from 2 to 8.5% by weight of molybdenum based on the total weight of the organic molybdenum complex with amide ligands.

Preferably the organomolybdenum compound comprises at least one organic molybdenum complex of the formula (III) or (IV), alone or mixed:

in which :

X 1 represents an oxygen atom or a nitrogen atom;

X 2 represents an oxygen atom or a nitrogen atom;

n represents 1 when X 1 represents an oxygen atom and m represents 1 when represents an oxygen atom;

n is 2 when X 1 represents a nitrogen atom, and m represents 2 when X 2 represents a nitrogen atom;

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

in which :

X 1 represents an oxygen atom or a nitrogen atom;

X 2 represents an oxygen atom or a nitrogen atom;

n represents 1 when X 1 represents an oxygen atom and m represents 1 when X 2 represents an oxygen atom;

n is 2 when X 1 represents a nitrogen atom, and m represents 2 when X 2 represents a nitrogen atom;

R Ï represents a linear or branched alkyl group, saturated or unsaturated, comprising from 4 to 36 carbon atoms, preferably from 4 to 20 carbon atoms, preferably from 6 to 18 carbon atoms;

R 2 represents a linear or branched alkyl group, saturated or unsaturated, comprising from 4 to 36 carbon atoms, preferably from 4 to 20 carbon atoms, preferably from 6 to 18 carbon atoms.

Advantageously, the organic molybdenum complex of the formula (III) or (IV) is prepared by reacting:

(I) a fat monaural, di or tri glyceride or fatty acid,

(Ii) diethanolamine or 2- (2-aminoethyl) aminoethanol,

(Iii) a molybdenum source selected from molybdenum trioxide or molybdate, preferably ammonium molybdate. More preferably, the organic molybdenum complex of the formula (I II) consists of at least one compound of formula (II) or (ll lb), alone or mixed:

wherein Ri represents a linear or branched alkyl group, saturated or unsaturated, comprising from 4 to 36 carbon atoms, preferably from 4 to 20 carbon atoms, preferably from 6 to 18 carbon atoms,

wherein Ri represents a linear or branched alkyl group, saturated or unsaturated, comprising from 4 to 36 carbon atoms, preferably from 4 to 20 carbon atoms, preferably from 6 to 18 carbon atoms.

Examples of sulfur-free molybdenum complexes according to the invention, mention may be made Molyvan 855® sold by the Vanderbilt company.

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

Within the meaning of the invention, organic molybdenum complexes with ligands are dithiophosphates also called molybdenum dithiophosphates or Mo-DTP compounds and organic molybdenum complexes with dithiocarbamate ligands are also known as dithiocarbamates or molybdenum compounds Mo-DTC .

In a more preferred embodiment of the invention, the organomolybdenum compound is selected from molybdenum dithiocarbamates.

Mo-DTC compounds are complexes of a metal of molybdenum core bonded to one or more ligands, the ligand being a group alkyl dithiocarbamate. These compounds are well known in the art.

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%, preferably 4 to 15% by weight of molybdenum, based on the total weight of the Mo-DTC compound.

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%, preferably 4 to 15% by weight sulfur , relative to the total weight of Mo-DTC compound.

In another embodiment of the invention, the Mo-DTC compound may be selected from those which present two atoms of molybdenum core (also called dimeric Mo-DTC) and those which present three carbon molybdenum core (also called Mo-DTC trimeric).

In another embodiment of the invention, the Mo-DTC trimeric compounds have the formula Mo 3 S k L n wherein:

k represents an integer at least equal to 4, preferably from 4 to 10, preferably 4 to 7,

n is an integer ranging from 1 to 4, and

L is an alkyl group of dithiocarbamate comprising from 1 to 100 carbon atoms, preferably 1 to 40 carbon atoms, preferably 3 to 20 carbon atoms.

Examples of Mo-DTC trimeric compounds of the invention include the compounds and methods of their preparation as described in WO 98/26030 and documents US 2003/022954.

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

Examples of Mo-DTC dimeric compounds include compounds and methods for their preparation as described in EP 0757093, EP15 0719851, EP 0743354 and EP 1013749.

The Mo-DTC dimeric compounds generally correspond to compounds of formula (V):

in which :

R 3, R 4 , R5, Re, identical or different, independently represent a hydrocarbon group selected from alkyl, alkenyl, aryl, cycloalkyl or cycloalkenyl,

X 3 , X 4, X 5 and X 6 , same or different, independently represent an oxygen atom or a sulfur atom.

Alkyl group within the meaning of the invention is meant a hydrocarbon group, linear or branched, saturated or unsaturated, comprising from 1 to 24 carbon atoms, preferably from 4 to 18 carbon atoms.

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 the, tetradecyl, l hexadecyl, stearyl, icosyl, docosyl, tetracosyl, triacontyl, 2-ethylhexyl, 2-butyloctyl, 2-butyldécyle, 2-hexyloctyle, 2-hexyldecyl, 2-octyldecyl, 2-hexyldodécyle , 2-octyldodecyl, 2-decyltetradecyl, 2-dodécylhexadécyle, 2-hexadécyloctadécyle, 2-tetradécyloctadécyle, myristyl, palmityl and stearyl.

Per alkenyl group within the meaning of the present invention, is meant a linear or branched hydrocarbon group comprising at least one double bond and having 2 to 24 carbon atoms. The alkenyl moiety may be selected from vinyl, allyl, propenyl, butenyl, isobutenyl, pentenyl, isopentenyl, hexenyl, heptenyl, octenyl, nonenyl, decenyl, the 'undecenyl, dodecenyl, the tetradecenyl and oleic.

An aryl group as defined in the present invention refers to a polycyclic aromatic hydrocarbon or an aromatic group, unsubstituted or substituted with an alkyl group. The aryl group may contain 6 to 24 carbon atoms.

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, the pentylphenyl hexylphenyl, heptylphenyl the on octylphenyl, nonylphenyl, the

decylphenyl, the undecylphenyl, dodecylphenyl, phenylphenyl the the benzylphenyl, phenyl styrene, p-cumylphenyl and naphthyl.

Cycloalkyl group as defined in the present invention means a polycyclic hydrocarbon or cyclic, unsubstituted or substituted with an alkyl group.

By cycloalkenyl group within the meaning of the present invention means a polycyclic hydrocarbon or cyclic, unsubstituted or substituted with an alkyl group, and comprising at least one unsaturation.

Cycloalkyl groups and cycloalkenyl groups may comprise 3 to 24 carbon atoms.

For the purposes of this invention, cycloalkyl groups and cycloalkenyl groups may be selected, without limitation, from the group consisting of cyclopentyl, cyclohexyl, cycloheptyl, methylcyclopentyl, methylcyclohexyl, the methylcycloheptyl, cyclopentenyl, cyclohexenyl, cycloheptenyl, the methylcyclopentenyl the methylcyclohexenyl.

In a preferred embodiment of the invention, R 3 , R 4 , R 5 and R 6 , 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.

In one embodiment of the invention, X 3 , X 4 , X 5 and X 6 may be identical and may represent a sulfur atom.

In another embodiment of the invention, X 3 , X 4 , X 5 and X 6 may be the same and may be an oxygen atom.

In another embodiment of the invention, X 3 and X 4 may represent a sulfur atom and X 5 and X 6 may represent an oxygen atom.

In another embodiment of the invention, X 3 and X 4 may represent an oxygen atom and X 5 and X 6 may represent a sulfur atom.

In another embodiment of the invention; the ratio in number of atoms of sulfur relative to the number of oxygen atoms (S / 0) of the Mo-DTC compound can range from (1/3) to (3/1).

In another embodiment of the invention, the Mo-DTC compound of formula (V) may be selected from a Mo-DTC symmetric compound, an asymmetric Mo-DTC compound and their combination.

Compound by Mo-DTC symmetrical according to the invention is meant a Mo-DTC compound of formula (V) wherein the groups R 3 , R 4 , R 5 and R 6 are identical.

Compound by Mo-DTC asymmetric according to the invention is meant a Mo-DTC compound of formula (V) wherein the groups R 3 and R 4 are identical, the groups R 5 and R 6 are identical and the groups R 3 and R 4 are different from the groups R 5 and R 6 .

In a preferred embodiment of the invention, the Mo-DTC compound is a mixture of at least one Mo-DTC symmetrical compound and at least one asymmetric Mo-DTC compound.

In one embodiment of the invention, R 3 and R 4 are identical and represent an alkyl group comprising from 5 to 15 carbon atoms, preferably from 8 to 13 carbon atoms, and R 5 and R 6 , identical, represent an alkyl group comprising from 5 to 15 carbon atoms, preferably from 8 to 13 carbon atoms, and the groups R 3 and R 4 are identical or different groups R 5 and R 6 .

In another preferred embodiment of the invention, R 3 and R 4 are identical and represent an alkyl group comprising from 6 to 10 carbon atoms and R 5 and R 6 , identical, represent an alkyl group comprising from 10 to 15 carbon atoms, and the groups R 3 and R 4 are different from the groups R 5 and R 6 .

In another preferred embodiment of the invention, R 3 and R 4 are identical and represent an alkyl group comprising from 10 to 15 carbon atoms and R 5 and R 6 , identical, represent an alkyl group comprising from 6 to 10 carbon atoms, and the groups R 3 and R 4 are different from the groups R 5 and R 6 .

In another preferred embodiment of the invention, R 3 , R 4 , R 5 and R 6 , identical, represent an alkyl group comprising from 5 to 15 carbon atoms, preferably from 8 to 13 carbon atoms.

Advantageously, the Mo-DTC compound is selected from compounds of formula (V) wherein:

- X 3 and X 4 represent an oxygen atom,

- X 5 and X 6 represent a sulfur atom,

- R 3 represents an alkyl group comprising 8 carbon atoms or an alkyl group containing 13 carbon atoms,

- R 4 represents an alkyl group comprising 8 carbon atoms or an alkyl group containing 13 carbon atoms,

- R 5 represents an alkyl group comprising 8 carbon atoms or an alkyl group containing 13 carbon atoms,

- R 6 represents an alkyl group comprising 8 carbon atoms or an alkyl group containing 13 carbon atoms.

Thus, advantageously, the Mo-DTC compound is chosen from compounds of

(Va)

wherein the groups R 3 , R 4 , R 5 and R 6 are as defined for formula (V).

More advantageously, Mo-DTC compound is a mixture:

- a Mo-DTC compound of formula (Va) wherein R 3 , R 4 , R 5 and R 6 represent an alkyl group comprising 8 carbon atoms,

- a Mo-DTC compound of formula (Va) wherein R 3 , R 4 , R 5 and R 6 represent an alkyl group containing 13 carbon atoms, and / or

- a Mo-DTC compound of formula (Va) wherein R 3 , R 4 represent an alkyl group comprising 8 carbon atoms and R 5 and R 6 represent an alkyl group containing 13 carbon atoms.

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

The lubricating composition according to the invention may further comprise at least one anti-wear additive selected from phospho-sulfurized additives such as metal alkylthiophosphates, especially zinc alkylthiophosphates, more specifically zinc dialkyldithiophosphates.

Generally, the lubricating composition according to the invention may comprise any type of mineral lubricating base oil, synthetic or natural, animal or plant, known to those skilled in the art.

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

Table A

mineral base oils according to the invention include all types of base oils obtained by atmospheric and vacuum distillation of crude oil, followed by refining operations such as extraction solvent, désalphatage, solvent dewaxing, hydrotreating, hydrocracking , hydroisomerization and hydrofinishing.

Mixtures of synthetic and mineral oils can also be used.

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

Oils bases lubricating compositions according to the invention may also be chosen from synthetic oils such certain carboxylic acid esters and alcohols, and from polyalphaolefins. 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 having a 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 3000 according to ASTM D5296. Preferably, the base oils of the present invention are selected from the base oils above whose aromatic content is between 0 and 45%, preferably between 0 and 30%. The oils of aromatic content is measured according to the UV Burdett method. Without being bound by any theory, the base oil is a character aromaticity to optimize the operation of the polymer depending on the temperature. The choice of an aromatic lean oil allows an optimum at higher temperature.

Advantageously, the lubricating composition according to the invention comprises at least 50% by weight of base oils relative to the total weight of the composition.

More advantageously, the lubricating composition according to the invention comprises at least 60 mass%, or even at least 70 wt%, base oil based on the total weight of the composition.

Of more advantageously, the lubricating composition according to the invention comprises from 60 to 99.5% by weight of base oil, preferably from 70 to 99.5% by weight base oil, based on the total weight of the composition.

Numerous additional additives may be used for the lubricant composition according to the invention.

Preferred additional additives for the lubricant composition according to the invention are selected from detergent additives, anti-wear different phospho-sulfurized additives additives, various additives friction modifiers organomolybdenum compounds, extreme pressure additives, dispersants, pour point improvers, anti-foaming agents, thickeners and mixtures thereof.

Amine phosphates are antiwear additives which may be employed in the lubricating composition according to the invention. However, phosphorus brought by these additives can act as a poison for automobile catalytic systems because these additives are generators of ashes. Can minimize these effects by partially substituting the amine phosphates by additives bringing no phosphorus, such as, for example, polysulfides including olefins sulfur.

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

Advantageously, the lubricating composition according to the invention may comprise at least one additional different friction modifier additive of organomolybdenum compounds. The additive of additional friction modifier may be selected from a compound supplying metal elements and a free compound of ashes. Among the compounds providing the metallic elements include transition metal complexes such as Sb, Sn, Fe, Cu, Zn whose ligands can be hydrocarbon compounds containing oxygen, nitrogen, sulfur or phosphorus. The friction modifier additives ashless are usually of organic origin and may be selected from monoesters of fatty acids and polyols, fatty epoxides, borated fatty epoxides; or fatty acid glycerol esters. According to the invention, the fatty compounds comprise at least one hydrocarbon group having from 10 to 24 carbon atoms.

Advantageously, the lubricating composition according to the invention may comprise at least one antioxidant additive.

The antioxidant additive generally used to delay the degradation of the lubricating composition in service. This degradation may especially result in the formation of deposits, the presence of sludge or by increasing the viscosity of the lubricant composition.

Antioxidants including additives act as inhibitors of free radical or destructive hydroperoxides. Among the additives commonly used antioxidants include phenolic antioxidants additives, antioxidants additives amine, antioxidants additives phosphorosulphur. Some of these antioxidant additives, such as antioxidants additives phosphorosulphur can be generators of ashes. Phenolic antioxidants additives may be ashless or be in the form of neutral or basic metal salts. The antioxidant additives

may especially be chosen from sterically hindered phenols, sterically hindered phenol esters and hindered phenols comprising a thioether bridge, the diphenylamines, the substituted diphenylamines at least one alkyl group in C 1 -C 12 , the Ν, Ν ' -dialkyle-aryl diamines and mixtures thereof.

Preferably according to the invention, sterically hindered phenols are selected from compounds comprising a phenol group having at least one vicinal carbon atoms bearing the alcohol function is substituted by at least one alkyl group dC 10 , preferably an alkyl group -C 6 , preferably an alkyl group C 4 , preferably by the t-butyl group.

Amine compounds are another class of antioxidant additives that can be used, optionally in combination with phenolic antioxidant additives. Examples of amino compounds are aromatic amines, for example, aromatic amines of the formula NR 7 R 8 R 9 wherein R 7 represents an aliphatic group or an aromatic group, optionally substituted, R 8 represents an aromatic group optionally substituted, R 9 represents a hydrogen atom, an alkyl group, an aryl group or a group of formula R 10 S (O) z R 11 wherein R 10represents an alkylene group or an alkenylene group, R 11 represents an alkyl group, an alkenyl group or an aryl group and z represents 0, 1 or 2.

Sulfurized alkylphenols or their alkali metal and alkaline earth salts may also be used as antioxidant additives.

Another class of antioxidant additives is that of copper compounds, for examples thio- or dithio-phosphates, copper salts of carboxylic acids, dithiocarbamates, sulphonates, phenates, copper acetylacetonates. copper salts I and II, acid salts or succinic anhydride can also be used.

The lubricating composition according to the invention can contain all types of antioxidant additives known to those skilled in the art.

Advantageously, the lubricant composition comprises at least one antioxidant ashless additive.

Also advantageously, the lubricating composition according to the invention comprises from 0.5 to 2% by weight relative to the total weight of the composition, of at least one antioxidant additive.

The lubricating composition according to the invention may also comprise at least one detergent additive.

The detergent additives generally reduce the formation of deposits on the surface of metal parts by dissolution of the oxidation by-products and combustion.

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

The detergent additives are preferably chosen from alkali metal salts or alkaline earth metals with carboxylic acids, sulfonates, salicylates, naphthenates, phenates and the salts. Alkali metal and alkaline earth metals are preferably calcium, magnesium, sodium or barium.

These metal salts generally include the metal in stoichiometric amount or in excess, so an amount greater than the stoichiometric amount. It is then overbased detergent additives; excess metal providing the character to the overbased detergent additive is then usually in the form of an insoluble metal salt in the oil, for example a carbonate, hydroxide, oxalate, acetate, glutamate, preferably a carbonate .

Advantageously, the lubricant composition of the invention may comprise from 2 to 4% by weight of additive detergent with respect to the total weight of the lubricating composition.

Also advantageously, the lubricating composition according to the invention may also comprise at least one additive pour point depressant.

By slowing down the formation of crystals of paraffin, pour point depressants additives generally improves cold behavior of the lubricant composition according to the invention.

Examples of additives of pour point depressants include alkyl polymethacrylates, polyacrylates, polyarylamides, the polyalkylphenols, the polyalkylnaphthalenes, alkylated polystyrenes.

Advantageously, the lubricating composition according to the invention may also comprise at least one dispersing agent.

The dispersant agent peut être parmi les choisis of Mannich bases, succinimides les et leurs derivates.

Also advantageously, the lubricating composition according to the invention may comprise from 0.2 to 10% by weight of dispersing agent relative to the total weight of the lubricating composition.

The lubricating composition of the present invention may also comprise at least one additional polymer improving the viscosity index. Examples of additional polymer improving the viscosity index, there may be mentioned polymeric esters, homopolymers or copolymers, hydrogenated or non-hydrogenated, styrene, butadiene and isoprene, polymethacrylates (PMA).

The present invention also relates to the use of the lubricant composition as defined above for the engine lubrication, in particular internal combustion engine, for example vehicle engine.

Advantageously, the lubricating composition according to the invention allows to reduce friction, particularly between two parts of an engine, in particular internal combustion engine, for example vehicle engine.

Thus, the invention relates to the use of the lubricating composition according to the invention to reduce wear of the engine parts, for example vehicle engine.

The present application also relates to a method of lubricating mechanical parts, in particular in a motor, in particular internal combustion engine, comprising at least one contacting step at least one part with a lubricating composition according to the invention.

The present invention will now be described by means of nonlimiting examples.

1 shows the X-ray photoelectron spectrum (the spectrum gives the binding energy (eV)) on the lubricant film (derived from compositions according to the invention) obtained at the end of tribological tests on steel parts / steel .

Example 1 Lubricating compositions

The compositions of Table 1 (CL: A lubricating composition according to the invention; CC: comparison composition) were prepared by mixing the particles of Ti0 2 and the organomolybdenum compound in a base oil at 60 ° C to obtain a good dispersion of particles in the composition.

Example 2: Results of tests triboloqiques

2.1 Tests on ball-plane tribometer alternative

Measurements of the coefficient of friction and wear of the balls μηι in diameter of the impression of the ball (Table 2) were carried out on alternative ball-plane tribometer. These tests were performed by changing for each test the mechanical parts flat surface. The parts used are:

- the balls have a diameter of 5 mm and are reference steel mechanical parts AISI52100 having a surface roughness (Ra) of 50 nm;

- the map is a mechanical part of selected planar surface from:

o PM1: a reference steel AISI52100; or

o PM2: steel having undergone a plasma treatment APS steel.

PM1 has a surface roughness (Ra) of 50 nm.

PM2 has a surface roughness (Ra) comprised between 170 and 200 nm.

The conditions of the test alternative ball-plane tribometer are:

- temperature: 100 ° C

- Frequency: 5 Hz

Maximum contact pressure: 700 MPa

- track length: 5 mm

Duration: 1 hour

- Volume of lubricant composition: 2-3 mL

The coefficients of friction and wear of the balls μηι in diameter of the impression of the ball shown in Table 2 were measured following contact with a smooth surface of ball (Ra = 50 nm) with a flat part respectively PM1 smooth surface (Ra = 50 nm) or a flat piece of PM2 rough surface (Ra = 170-200 nm), said parts are also in contact with a composition according to the invention or a comparative composition.

Table 2. Coefficients of friction and wear of the ball measured on the alternative ball-plane tribometer during contact between the ball and the parts PM1 and PM2 respectively, parts also being in contact with a composition according to the invention or a comparative composition

Nd: not determined

These results demonstrate that:

The coefficient of friction between ball / PM1 is decreased when the lubricant composition comprises an organomolybdenum compound and titanium, whatever the content of organomolybdenum compound and titanium. This coefficient of friction is measured between

two surface parts smooth, it determines the formation of MoS 2 from the organomolybdenum compound. However, PM1 parts having smooth surfaces, the contact friction are reduced compared to the friction contact between a smooth surface part and a roughened surface part such as PM2.

- wear of the balls is lower when there is a combination composition of the invention (CL1 or CL3) and the base oil in comparison with single base oil or with the comparative compositions (CC1, or CC3 CC4), for both types of surfaces (smooth or rough).

When the concentration of organomolybdenum compound is decreased (composition CL3), a significant decrease is observed in the friction coefficient and the wear of the balls at a time with respect to the oil alone and compared to comparative compositions.

The coefficient of friction between ball / PM2 (rough surface) is reduced when the lubricant composition comprises an organomolybdenum compound and titanium, whatever the content of organomolybdenum compound and titanium.

That there is a synergy between the molybdenum and the titanium particles in the lubricant composition to significantly reduce the friction coefficient and therefore to limit the friction between the parts.

Example 3: X-ray spectra

Photoelectron spectroscopy of X-ray were performed on the lubricant film (from the CL1 and CC3 compositions) obtained at the end of the tribological test ball / PM1.

Figure 1 shows the spectrum at the top of the composition and CC3 down the CL1 composition. This figure shows that in the absence of Ti0 particles 2 (CC3) decomposition MoDTC is not complete and results in the formation of MoS 2 and Mo MoOxSy oxysulfide in large quantities. On the contrary the presence of Ti0 2 permits a better decomposition of MoDTC and the formation of MoS 2 pure.

CLAIMS

1. - lubricating composition comprising:

- at least a base oil;

- from 0.05 to 1, 5% by weight of an organomolybdenum compound; and

- from 0.005 to 1% by weight of Ti0 particles 2 .

2. - A composition according to claim 1, wherein the particles have an average size between 10 nm and 1 μηι.

3. - A composition according to one of claims 1 or 2, comprising from 0.08 to 1% by weight of organomolybdenum compound relative to the total weight of said composition.

4.- Composition according to any one of claims 1 to 3, comprising from 0.01 to 0.8% by weight of titanium particles relative to the total weight of said composition.

5. - A composition according to any one of claims 1 to 4, wherein the organomolybdenum compound is selected from organic molybdenum complexes comprising at least one chemical element molybdenum (Mo) and at least one ligand selected from carboxylate ligands, ester , amide, dithiocarbamate or dithiophosphate.

6. - A composition according to any one of claims 1 to 5, wherein the organomolybdenum compound is selected from organic molybdenum complexes with ligands amide obtained by reacting:

(I) a fat monaural, di or tri glyceride or fatty acid,

(Ii) a source amine of formula (A):

in which :

- X 1 represents an oxygen atom or a nitrogen atom,

- X 2 represents an oxygen atom or a nitrogen atom,

- 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,

(Iii) a molybdenum source selected from molybdenum trioxide or molybdate, preferably ammonium molybdate.

7. A composition according to any one of claims 1 to 5, wherein the organomolybdenum compound comprises at least one organic molybdenum complex of the formula (III) or (IV), alone or in Mélan e:

in which :

X 1 represents an oxygen atom or a nitrogen atom;

X 2 represents an oxygen atom or a nitrogen atom;

n represents 1 when X 1 represents an oxygen atom and m represents 1 when X 2 represents an oxygen atom;

n is 2 when X 1 represents a nitrogen atom, and m represents 2 when X 2 represents a nitrogen atom;

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

in which :

X 1 represents an oxygen atom or a nitrogen atom;

X 2 represents an oxygen atom or a nitrogen atom;

n represents 1 when X 1 represents an oxygen atom and m represents 1 when X 2 represents an oxygen atom;

n is 2 when X 1 represents a nitrogen atom, and m represents 2 when X 2 represents a nitrogen atom;

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

R 2 represents a linear or branched alkyl group, saturated or unsaturated, comprising from 4 to 36 carbon atoms, preferably from 4 to 20 carbon atoms, preferably from 6 to 18 carbon atoms.

8. - A composition according to any one of claims 1 to 5, wherein the organomolybdenum compound is selected from organic molybdenum complexes with ligands dithiophosphates or organic complexes with molybdenum dithiocarbamate ligands.

9 - Composition according to any one of claims 1 to 5, wherein the organomolybdenum compound is a molybdenum dithiocarbamate compound (MoDTC).

10. - Use of the composition according to any one of claims 1 to 9 for the engine lubrication, in particular internal combustion engine, for example vehicle engine.

1 1 .- The use according to claim 10 to reduce friction.

12.- Use according to one of claims 9 or 10 to reduce wear of engine parts.

13. A method of lubricating mechanical parts, in particular in a motor, in particular internal combustion engine, comprising at least one contacting step at least one part with a lubricating composition according to any one of claims 1 to 9 .