EP3110929A1

EP3110929A1 - Lubricating composition based on metal nanoparticles

Info

Publication number: EP3110929A1
Application number: EP15706812.3A
Authority: EP
Inventors: Benoit Thiebaut; Fabrice DASSENOY; Paula USSA
Original assignee: Total Marketing Services SA
Current assignee: TotalEnergies Onetech SAS
Priority date: 2014-02-28
Filing date: 2015-02-26
Publication date: 2017-01-04
Anticipated expiration: 2035-02-26
Also published as: CN106103670A; JP2017506694A; KR20160127034A; WO2015128444A1; KR102308393B1; EP3110929B1; FR3018079A1; FR3018079B1; US11015141B2; US20170073612A1

Abstract

The present invention relates to a lubricating composition comprising an anti-wear additive and metal nanoparticles. The lubricating composition according to the invention simultaneously exhibits good stability and also good friction properties which last over time.

Description

Lubricating composition based on metal nanoparticles

Technical area

The present invention is applicable to the field of lubricants, and more particularly to the field of lubricants for motor vehicles. The invention relates to a lubricating composition comprising metal nanoparticles. More particularly, the invention relates to a lubricant composition comprising an antiwear additive and metal nanoparticles. The lubricant composition according to the invention simultaneously has a good stability as well as good friction properties and which persist over time.

The present invention also relates to a method of lubricating a mechanical part implementing this lubricant composition.

The present invention also relates to a concentrated type composition of additives comprising an antiwear additive and metal nanoparticles.

Prior art

The transmission components of motor vehicles operate under heavy load and high speeds. The oils for these transmission members must therefore be particularly effective in protecting the parts against wear, and in particular have good properties for reducing friction on the surface of the members.

Thus, if the level of friction is not adapted to the geometry of the parts, there is wear on the ring cone assembly.

The level of friction can be adjusted by the addition of friction modifiers in these gearbox oils.

Moreover, the globalization of the automobile world since the end of the last century poses problems with regard to global warming, pollution, security and the use of natural resources, particularly exhaustion. oil reserves.

Following the establishment of the Kyoto Protocol, new standards protecting the environment require the automotive sector to build vehicles with reduced emissions and reduced fuel consumption. It As a result, the engines of these vehicles are subjected to increasingly stringent technical constraints: they run in particular faster, at higher and higher temperatures and must consume less and less fuel.

The nature of automotive lubricants has an influence on pollutant emissions and fuel consumption. Engine lubricants for automobiles called energy saving or "fuel-eco" (in English terminology), have been developed to meet these new needs.

The improvement of the energetic performances of the lubricating compositions can be obtained in particular by mixing in base oils friction modifiers.

Among the friction modifiers, organometallic compounds comprising molybdenum are commonly used. In order to obtain good friction-reducing properties, a sufficient amount of molybdenum must be present within the lubricating composition.

However, these compounds have the disadvantage of inducing sediment formation when the lubricating composition has too much molybdenum content. The poor solubility of these compounds modifies or even deteriorates the properties of the lubricant composition, in particular its viscosity. However, too much or not enough viscous composition hinders the movement of moving parts, the good start of an engine, the protection of an engine when it has reached its operating temperature, and therefore ultimately causes an increase in fuel consumption.

In addition, these compounds contribute to increasing the level of ash, reducing their potential for use in a lubricant composition, especially in Europe.

It is also known to formulate lubricating compositions comprising organomolybdenum-type friction modifying compounds with organophosphorus and / or organosulfur and / or organophosphorus compounds, especially for improving the antiwear properties of these oils. engines or transmissions.

Other compounds for reducing friction have been described as being of interest in the lubrication of mechanical parts, in particular parts of an engine. CN 101 691517 discloses an engine oil comprising nanoparticles of tungsten disulfide, to improve the life of the engine and reduce fuel consumption. However, the nanoparticle content of tungsten disulfide ranges from 15 to 34%, which can lead to risks of instability of the oil over time.

Moreover, the combination of nanoparticles and anti-wear compounds in grease compositions has been described, for example in WO 2007/085643. However, this document only describes grease compositions and does not describe any engine lubricant or transmission.

It would therefore be desirable to have a lubricating composition, especially for motor vehicles, which is not a grease and which is both stable while having good friction reducing properties.

It would also be desirable to have a lubricating composition, particularly for motor vehicles, which is not a grease and whose performance lasts over time.

It would also be desirable to have a lubricating composition, especially for motor vehicles, which is not a grease while having good friction reducing properties and maintaining satisfactory anti-flaking properties.

An object of the present invention is to provide a lubricant composition overcoming all or in part the aforementioned drawbacks.

Another object of the invention is to provide a lubricating composition which is stable and easy to implement.

Another object of the present invention is to provide a lubrication process which in particular makes it possible to reduce the friction on the surface of mechanical parts, and more particularly of an engine or a transmission member of motor vehicles. Summary of the invention

The subject of the invention is thus a lubricating composition of kinematic viscosity at 100 ° C. measured according to ASTM D445 ranging from 4 to 50 cSt and comprising at least one base oil, at least one compound comprising a dithiophosphate group and metal nanoparticles. in a content by weight ranging from 0.01 to 2% relative to the total weight of the lubricant composition.

Surprisingly, the Applicant has found that the presence of a compound comprising a dithiophosphate group in a lubricant composition comprising at least one base oil and metal nanoparticles makes it possible to confer on said composition very good properties for reducing friction.

In addition, the Applicant has found that the combination of a compound comprising a dithiophosphate group and metal nanoparticles in a lubricant composition makes it possible to maintain this reduction in friction over time.

Without being bound by a particular theory, this maintenance over time of the friction-reducing efficiency could be explained by the protection against oxidation of metal nanoparticles by the compound comprising a dithiophosphate group, thus prolonging the action of metallic nanoparticles on the surface of a mechanical part, and more particularly of a transmission member or a motor vehicle engine.

Thus, the present invention makes it possible to formulate stable lubricating compositions comprising a reduced content of metal nanoparticles and which, however, have remarkable friction reducing properties.

Advantageously, the lubricant compositions according to the invention have remarkable friction reducing properties which persist over time.

Advantageously, the lubricant compositions according to the invention have a good stability as well as a viscosity that does not vary or very little. Advantageously, the lubricant compositions according to the invention exhibit satisfactory anti-scaling properties.

Advantageously, the lubricant compositions according to the invention have a reduced risk of oxidation.

Advantageously, the lubricant compositions according to the invention exhibit remarkable fuel economy properties. In one embodiment, the lubricant composition essentially consists of at least one base oil, at least one compound comprising a dithiophosphate group and at least nanoparticles. metal in a content by weight ranging from 0.01 to 2% relative to the total weight of the lubricating composition. The invention also relates to an engine oil comprising a lubricant composition as defined above.

The invention also relates to a transmission oil comprising a lubricating composition as defined above.

The invention also relates to the use of a lubricant composition as defined above for the lubrication of a mechanical part, preferably a transmission member or a vehicle engine, preferably motor vehicles.

The invention also relates to the use of a lubricant composition as defined above for the reduction of friction on the surface of a mechanical part, preferably of a transmission member or a vehicle engine, advantageously of motor vehicles.

The invention also relates to the use of a lubricant composition as defined above for reducing the fuel consumption of vehicles, particularly motor vehicles. The invention also relates to a method for lubricating a mechanical part, preferably a transmission member or a vehicle engine, advantageously motor vehicles, said method comprising at least one step of contacting the mechanical part with a lubricating composition as defined above.

The invention also relates to a method for reducing friction on the surface of a mechanical part, preferably a transmission member or a vehicle engine, advantageously motor vehicles, comprising at least the contacting of the workpiece mechanical with a lubricating composition as defined above.

The invention also relates to a method for reducing the fuel consumption of a vehicle, in particular of a motor vehicle, comprising at least one step of bringing a mechanical part of the vehicle engine into contact with a lubricating composition such that defined above.

The invention also relates to the use of a compound comprising a dithiophosphate group for reducing the oxidation of a lubricating composition comprising at least one base oil and metal nanoparticles.

The invention also relates to a composition of the additive concentrate type comprising at least one compound comprising a dithiophosphate group and nanoparticles of tungsten disulfide.

detailed description

The percentages given below correspond to percentages by mass of active ingredient. Metal nanoparticles

The lubricant composition according to the invention comprises metal nanoparticles in a content by weight ranging from 0.01 to 2% relative to the total weight of the lubricating composition. By metal nanoparticles is meant especially metal particles, generally solid, whose average size is less than or equal to 600 nm.

Advantageously, the metal nanoparticles consist of at least 80% by weight of at least one metal, or at least 80% by weight of at least one metal alloy or at least 80% by weight of at least one metal chalcogenide, especially transition metal, with respect to the total mass of the nanoparticle.

Advantageously, the metal nanoparticles consist of at least 90% by weight with at least one metal, or at least 90% by weight of at least one metal alloy or at least 90% by weight of at least one metal chalcogenide, especially transition metal, with respect to the total mass of the nanoparticle. Advantageously, the metal nanoparticles consist of at least 99% by weight with at least one metal, or at least 99% by weight of at least one metal alloy or at least 99% by weight of at least one metal chalcogenide, especially transition metal, relative to the total mass of the nanoparticle, the remaining 1% being impurities.

Advantageously, the metal of which the metallic nanoparticle is constituted can be chosen from the group formed by tungsten, molybdenum, zirconium, hafnium, platinum, rhenium, titanium, tantalum, niobium, cerium indium and tin, preferably molybdenum or tungsten, advantageously tungsten.

The metal nanoparticles can have the shape of spheres, lamellae, fibers, tubes, fullerene type structures.

Advantageously, the metal nanoparticles used in the compositions according to the invention are solid metal nanoparticles having a fullerene type structure (in English term fullerene-like) and are represented by the formula MX _n in which M represents a transition metal. , X a chalcogen, with n = 2 or n = 3 depending on the oxidation state of the transition metal M. Preferably, M is selected from the group consisting of tungsten, molybdenum, zirconium, hafnium, platinum, rhenium, titanium, tantalum and niobium.

More preferably, M is selected from the group consisting of molybdenum and tungsten.

Even more preferably, M is tungsten.

Preferably, X is selected from the group consisting of oxygen, sulfur, selenium and tellurium.

Preferably, X is selected from sulfur or tellurium.

Even more preferably, X is sulfur.

Advantageously, the metal nanoparticles according to the invention are chosen from the group formed by MoS ₂ , MoSe ₂ , MoTe ₂ , WS ₂ , WSe ₂ , ZrS ₂ , ZrSe ₂ , HfS ₂ , HfSe ₂ , PtS ₂ , ReS ₂ , ReSe ₂ , TiS ₃ , ZrS ₃ , ZrSe ₃ , HfS ₃ , HfSe ₃ , TiS ₂ , TaS ₂ , TaSe ₂ , NbS ₂ , NbSe ₂ and NbTe ₂ .

Preferably, the metal nanoparticles according to the invention are chosen from the group formed by WS ₂ , WSe ₂ , MoS ₂ and MoSe ₂ , preferentially WS ₂ and MoS ₂ , preferentially WS ₂ .

The nanoparticles according to the invention advantageously have a fullerene type structure.

Initially, the term fullerene denotes a closed convex polyhedron nanostructure composed of carbon atoms. Fullerenes are similar to graphite, composed of linked hexagonal ring sheets, but they contain pentagonal, and sometimes heptagonal rings, which prevent the structure from being flat.

Studies on fullerene-type structures have shown that this structure was not limited to carbonaceous materials, but was likely to occur in all nanoparticles of sheet-like materials, particularly for nanoparticles including chalcogen and transition. These structures are similar to that of carbon fullerenes and are called inorganic fullerenes or fullerene type structure (in English term "Inorganic Fullerene like materials", also referred to as "IF"). The fullerene type structures are described in particular by Tenne, R., Margulis, L., Genut M. Hodes, G. Nature 1992, 360, 444. The document EP 0580 019 describes in particular these structures and their method of synthesis.

In a preferred embodiment of the invention, the metal nanoparticles are closed structures, spherical type, more or less perfect according to the synthetic methods used. The nanoparticles according to the invention are concentric polyhedra with a multilayer structure or in sheets. We speak of structure in "onions" or "polyhedron nested". In one embodiment of the invention, the metal nanoparticles are multilayer metal nanoparticles comprising from 2 to 500 layers, preferably from 20 to 200 layers, advantageously from 20 to 100 layers.

The average size of the metal nanoparticles according to the invention ranges from 5 to 600 nm, preferably from 20 to 400 nm, advantageously from 50 to 200 nm. The size of the metal nanoparticles according to the invention can be determined using images obtained by transmission electron micrograph or by high resolution transmission electron microscopy. The average particle size can be determined from the measurement of the size of at least 50 solid particles visualized on transmission electron micrographs. The median value of the measured size distribution histogram of the solid particles is the average size of the solid particles used in the lubricating composition according to the invention.

In one embodiment of the invention, the average diameter of the primary metal nanoparticles according to the invention ranges from 10 to 100 nm, preferably from 30 to 70 nm.

Advantageously, the content by weight of metal nanoparticles ranges from 0.05 to 2%, preferably from 0.1 to 1%, advantageously from 0.1 to 0.5% relative to the total weight of the lubricating composition.

As an example of metallic nanoparticles according to the invention, mention may be made of the NanoLub Gear Oil Concentrate product marketed by Nanomaterials, in the form of a dispersion of multilayer nanoparticles of tungsten bisulphide in a mineral oil or of PAO (Poly Alfa Olefin) type.

Compound comprising a dithiophosphate group

The lubricating composition according to the invention comprises at least one compound comprising a dithiophosphate group.

For the sake of simplification of the description, the compound comprising a dithiophosphate group is called "dithiophosphate" in the following description.

The dithiophosphate, without being limiting, may be chosen from ammonium dithiophosphates, amine dithiophosphates, ester dithiophosphates and metal dithiophosphates, taken alone or as a mixture.

In one embodiment of the invention, the dithiophosphate is chosen from the ammonium dithiophosphates of formula (I):

R1- O

\ l l

P-S NH ₄

/

R ² - °

(I)

in which R1 and R2 represent, independently of one another, an optionally substituted hydrocarbon group comprising from 1 to 30 carbon atoms. In a preferred embodiment of the invention, R 1 and R 2 represent, independently of one another, an optionally substituted hydrocarbon group comprising from 2 to 24 carbon atoms, more preferably from 3 to 18 carbon atoms, advantageously from 5 to 12 carbon atoms. In another preferred embodiment of the invention, R1 and R2 represent, independently of one another, an unsubstituted hydrocarbon group, said hydrocarbon group possibly being an alkyl, alkenyl, alkynyl, phenyl or benzyl group. In another preferred embodiment of the invention, R1 and R2 represent, independently of one another, a linear or branched alkyl hydrocarbon group, more preferably a linear alkyl hydrocarbon group.

In another preferred embodiment of the invention, R 1 and R 2 represent, independently of one another, a hydrocarbon-based group optionally substituted with at least one oxygen, nitrogen, sulfur and / or phosphorus atom, preferably by at least one oxygen atom.

Examples of ammonium dithiophosphate include ammonium dimethyl dithiophosphates, ammonium diethyl dithiophosphates and ammonium dibutyl dithiophosphates.

In another embodiment of the invention, the dithiophosphate is chosen from amine dithiophosphates of general formula (II):

- R3 and R4 represent, independently of each other, an optionally substituted hydrocarbon group comprising from 1 to 30 carbon atoms,

- R5, R6 and R7 represent, independently of one another, a hydrogen atom or a hydrocarbon group of 1 to 30 carbon atoms, it being understood that at least one of the groups R5, R6 and R7 does not represent a hydrogen atom.

In a preferred embodiment of the invention, R3 and R4 represent, independently of one another, an optionally substituted hydrocarbon group, comprising from 2 to 24 carbon atoms, more preferably from 3 to 18 carbon atoms, preferably from 5 to 12 carbon atoms.

In another preferred embodiment of the invention, R 3 and R 4 represent, independently of one another, an unsubstituted hydrocarbon group, said hydrocarbon group possibly being an alkyl, alkenyl, alkynyl, phenyl or benzyl group.

In another preferred embodiment of the invention, R3 and R4 represent, independently of one another, a linear or branched alkyl hydrocarbon group, more preferably a linear alkyl hydrocarbon group.

In another preferred embodiment of the invention, R3 and R4 represent, independently of one another, a hydrocarbon group optionally substituted with at least one oxygen, nitrogen, sulfur and / or phosphorus atom, preferably by at least one oxygen atom.

In another preferred embodiment of the invention, R5, R6 and R7 represent, independently of one another, a hydrocarbon group comprising from 2 to 24 carbon atoms, more preferably from 3 to 18 carbon atoms, advantageously from 5 to 12 carbon atoms.

In another embodiment of the invention, the dithiophosphate is chosen from the ester dithiophosphates of general formula (III):

(III)

in which :

R8 and R9 represent, independently of each other, an optionally substituted hydrocarbon group comprising from 1 to 30 carbon atoms,

- R10 and R1 1 represent independently of one another a hydrocarbon group comprising 1 to 18 carbon atoms. In a preferred embodiment of the invention, R 8 and R 9 represent, independently of one another, an optionally substituted hydrocarbon group comprising from 2 to 24 carbon atoms, more preferably from 3 to 18 carbon atoms, advantageously from 5 to 12 carbon atoms.

In another preferred embodiment of the invention, R8 and R9 represent, independently of one another, an unsubstituted hydrocarbon group, said hydrocarbon group possibly being an alkyl, alkenyl, alkynyl, phenyl or benzyl group. In another preferred embodiment of the invention, R8 and R9 represent, independently of one another, a linear or branched alkyl hydrocarbon group, more preferably a linear alkyl hydrocarbon group.

In another preferred embodiment of the invention, R 8 and R 9 represent, independently of one another, a hydrocarbon group optionally substituted with at least one oxygen, nitrogen, sulfur and / or phosphorus atom, preferably by at least one oxygen atom.

In another preferred embodiment of the invention, R8 and R9 represent, independently of one another, a hydrocarbon group comprising from 2 to 6 carbon atoms.

In another preferred embodiment of the invention, R10 and R1 1 represent, independently of one another, a hydrocarbon group comprising from 2 to 6 carbon atoms.

In another embodiment, the dithiophosphate is chosen from metal dithiophosphates of general formula (IV):

(IV)

in which :

R12 represents a linear or branched, saturated or unsaturated, substituted or unsubstituted alkyl group comprising from 1 to 30 carbon atoms;

R13 represents a linear or branched, saturated or unsaturated, substituted or unsubstituted alkyl group comprising from 1 to 30 carbon atoms;

M represents a metal cation, preferably a Zn ²⁺ cation;

• n represents the valence of the metal cation.

In a preferred embodiment of the invention, the metal is selected from the group consisting of zinc, aluminum, copper, iron, mercury, silver, cadmium, tin, lead, antimony, bismuth, thallium, chromium, molybdenum, cobalt, nickel, tungsten, sodium, calcium, magnesium, manganese and arsenic. The preferred metals are zinc, molybdenum, antimony, preferably zinc and molybdenum.

In a preferred embodiment of the invention, the metal is zinc.

Mixtures of metals can be used. Metal dithiophosphates are neutral as exemplified in formula (IV) or basic when a stoichiometric excess of metal is present.

In a preferred embodiment of the invention, R12 and R13 represent, independently of one another, an optionally substituted hydrocarbon group comprising from 2 to 24 carbon atoms, more preferably from 3 to 18 carbon atoms, advantageously from 5 to 12 carbon atoms. In another preferred embodiment of the invention, R12 and R13 represent, independently of one another, an unsubstituted hydrocarbon group, said hydrocarbon group possibly being an alkyl, alkenyl, alkynyl, phenyl or benzyl group. In another preferred embodiment of the invention, R12 and R13 represent, independently of one another, a linear or branched alkyl hydrocarbon group, more preferably a linear alkyl hydrocarbon group.

In another preferred embodiment of the invention, R12 and R13 represent, independently of one another, a hydrocarbon group optionally substituted with at least one oxygen, nitrogen, sulfur and / or phosphorus atom, preferably by at least one oxygen atom.

Advantageously, the dithiophosphate according to the invention is a zinc dithiophosphate of formula (IV-a) or of formula (IV-b):

(IV-b)

wherein R12 and R13 are as defined above.

As dithiophosphate metal according to the invention include eg Additin ^® RC 3038, the Additin ^® RC 3045, the Additin ^® RC 3048, the Additin ^® RC 3058, the Additin ^® RC 3080 Additin ^® RC 3180, Additin ^® RC 3212, Additin ^® RC 3580, Kikulube ^® Z1 12, Lubrizol ^® 1371, Lubrizol ^® 1375, Lubrizol ^® 1395, Lubrizol ^® 5179, Oloa ^® 260, Oloa ^® 267. In one embodiment of the invention, the content by weight of compound comprising a dithiophosphate group ranges from 0.1 to 5%, preferably from 0.2 to 4%, more preferably from 0.5 to 2%, advantageously from 0.5 to 1.5% relative to the total weight of the lubricating composition.

Base oil

The lubricant compositions according to the invention may contain any type of mineral, synthetic or natural, animal or vegetable lubricating base oil adapted for their use.

The base oil or oils used in the lubricant compositions according to the present invention may be oils of mineral or synthetic origin of groups I to V according to the classes defined in the API classification (or their equivalents according to the ATI EL classification) such that summarized below, alone or as a mixture.

Table I

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, hydrotreatment, hydrocracking and hydroisomerization, hydrofinishing. The base oils of the lubricating compositions according to the invention may also be synthetic oils, such as certain carboxylic acid esters and alcohols, or polyalphaolefins. The polyalphaolefins used as base oils, for example, are obtained from monomers having from 4 to 32 carbon atoms (for example octene, decene), and a viscosity at 100 ° C. of between 1.5 and 15 cSt measured according to US Pat. ASTM D445 standard. Their weight average molecular weight is typically between 250 and 3000 measured according to ASTM D5296. Mixtures of synthetic and mineral oils can also be used.

There is no limitation as to the use of a particular lubricating base for producing the lubricating compositions according to the invention, except that they must have properties, in particular viscosity, viscosity index, sulfur, oxidation resistance, suitable for use in a gearbox, in particular in a gearbox of motor vehicles, especially in a manual gearbox.

In one embodiment of the invention, the lubricating bases represent at least 50% by weight, with respect to the total mass of the lubricating composition, preferably at least 60%, or at least 70%. Typically, they represent between 75 and 99.9% by weight, relative to the total mass of the lubricating compositions according to the invention.

The lubricant composition according to the invention has a kinematic viscosity at 100 ° C measured according to ASTM D445 ranging from 4 to 50 cSt.

In one embodiment, the kinematic viscosity at 100 ° C. measured according to ASTM D445 of the composition according to the invention ranges from 4 to 45 cSt, preferably from 4 to 30 cSt.

In a preferred embodiment of the invention, the lubricating compositions comprise at least one Group IV base.

In another preferred embodiment of the invention, the lubricating compositions have a viscosity index (VI) greater than 95 (ASTM 2270). Other additives

The lubricant compositions according to the invention may also contain any type of additive suitable for use in transmission oil formulations, for example one or more additives chosen from polymers, antioxidants, anti-corrosion additives, modifiers different friction of the metal nanoparticles according to the invention and the dispersants present at the usual contents required for the application.

In one embodiment of the invention, the additive is selected from dispersants having a weight average molecular weight greater than or equal to 2000 Daltons.

According to the invention, the weight average molecular weight of the dispersant is evaluated according to the ASTM D5296 standard. By dispersant within the meaning of the present invention is meant more particularly any compound which improves the suspension retention of metal nanoparticles.

In one embodiment of the invention, the dispersant may be chosen from compounds comprising at least one succinimide group, polyolefins, olefin copolymers (OCP), copolymers comprising at least one styrene unit, polyacrylates or their derivatives.

By derivatives is meant any compound comprising at least one group or a polymeric chain as defined above. Advantageously, the dispersant according to the invention is chosen from compounds comprising at least one succinimide group.

In a preferred embodiment of the invention, the dispersant is chosen from compounds comprising at least one substituted succinimide group or compounds comprising at least two substituted succinimide groups, the succinimide groups being linked at their apex carrying a hydrogen atom. nitrogen with a polyamine group. By substituted succinimide group in the sense of the present invention is meant a succinimide group of which at least one of the carbon peaks is substituted by a hydrocarbon group comprising from 8 to 400 carbon atoms.

In a preferred embodiment of the invention, the dispersant is chosen from polyisobutylene succinimide-polyamine.

Advantageously, the dispersant according to the invention has a weight average molecular weight ranging from 2000 to 15000 Daltons, preferably ranging from 2500 to 10,000 Daltons, advantageously from 3000 to 7000 Daltons.

Also advantageously, the dispersant has a number-average molecular mass greater than or equal to 1000 Daltons, preferably ranging from 1000 to 5000 Daltons, more preferably from 1800 to 3500 Daltons, advantageously from 1800 to 3000 Daltons.

According to the invention, the number-average molecular mass of the dispersant is evaluated according to the ASTM D5296 standard.

In a preferred embodiment of the invention, the content by weight of dispersant having a weight average molecular weight greater than or equal to 2000 Daltons ranges from 0.1 to 10%, preferably from 0.1 to 5%, advantageously from 0.1 to 3% relative to the total weight of the lubricating composition.

The polymers may be selected from the group of shear-stable polymers, preferably from the group consisting of copolymers of ethylene and alpha-olefin, polyacrylates such as polymethacrylates, copolymer olefins (OCP), ethylene propylene Diene Monomers (EPDM), polybutenes, copolymers of styrene and olefin, hydrogenated or not, or copolymers of styrene and acrylate. The antioxidants may be chosen from aminated antioxidants, preferably diphenylamines, in particular dialkylphenylamines, such as octadiphenylamines, phenyl-alpha-naphthylamines, phenolic antioxidants (dibutylhydroxytoluene BHT and derivatives) or sulfur-containing antioxidants (sulfurized phenates). . The friction modifiers may be compounds providing metal elements different from the metal nanoparticles according to the invention or an ashless compound. Among the compounds providing metal elements, mention may be made of transition metal complexes such as Mo, Sb, Sn, Fe, Cu, Zn, the ligands of which may be hydrocarbon compounds containing oxygen, nitrogen, sulfur or phosphorus, such as dithiocarbamates or dithiophosphates of molybdenum. The ashless friction modifiers are of organic origin and may be selected from monoesters of fatty acids and polyols, alkoxylated amines, fatty alkoxylated amines, amine phosphates, fatty alcohols, fatty epoxides, borate fatty epoxides, fatty amines or fatty acid glycerol esters. For the purposes of the present invention, the term "fatty" or "fatty (s)" is intended to mean a hydrocarbon group comprising from 8 to 24 carbon atoms. The anti-corrosion additives can be chosen from phenol derivatives, in particular ethoxylated and substituted alkyl phenol derivatives in the ortho position. The corrosion inhibitors may be derivatives of dimercaptothiadiazole. In one embodiment of the invention, the lubricant composition comprises:

from 75 to 99.89% of at least one base oil,

from 0.01 to 2% of metal nanoparticles,

from 0.1 to 5% of at least one compound comprising a dithiophosphate group.

In another embodiment of the invention, the lubricant composition consists essentially of:

- 75 to 99.89% of at least one base oil,

0.01 to 2% of metal nanoparticles,

0.1 to 5% of at least one compound comprising a dithiophosphate group. All the characteristics and preferences presented for the base oil, the metal nanoparticles and the compound comprising a dithiophosphate group also apply to the above lubricating compositions. In one embodiment of the invention, the lubricating composition is not an emulsion.

In another embodiment of the invention, the lubricant composition is anhydrous.

The invention also relates to an engine oil comprising a lubricant composition according to the invention.

The invention also relates to a transmission oil comprising a lubricant composition according to the invention.

All the characteristics and preferences presented for the lubricant composition also apply to the engine oil or the transmission oil according to the invention.

Rooms

The lubricant composition according to the invention can lubricate at least one mechanical part or a mechanical member, in particular bearings, gears, universal joints, transmissions, the piston / piston / sleeve system, the camshafts, the clutch , manual or automatic gearboxes, bridges, rockers, crankcases, etc.

In a preferred embodiment, the lubricant composition according to the invention can lubricate a mechanical part or a metallic member of transmissions, clutch, bridges, manual or automatic gearboxes, preferably manual. Thus, the subject of the invention is also the use of a lubricant composition as defined above for the lubrication of a mechanical part, preferably of a transmission member or of a vehicle engine, advantageously of vehicles automobiles.

The invention also for the use of a lubricant composition as defined above for the reduction of friction on the surface of a mechanical part, preferably of a transmission member or a vehicle engine, advantageously of motor vehicles.

The invention also relates to the use of a lubricant composition as defined above for reducing the fuel consumption of vehicles, particularly motor vehicles. The subject of the invention is also the use of a lubricant composition as defined above for reducing the spalling of a mechanical part, preferably of a transmission member or of a vehicle engine, advantageously of vehicles automobiles. All of the features and preferences presented for the lubricant composition also apply to the above uses.

The invention also relates to a method for lubricating a mechanical part, preferably a transmission member or a vehicle engine, preferably motor vehicles, said method comprising at least one step of contacting the mechanical part with a lubricating composition as defined above.

The invention also relates to a method for reducing friction on the surface of a mechanical part, preferably a transmission member or a vehicle engine, advantageously motor vehicles, comprising at least the contacting of the mechanical part with a lubricating composition as defined above. The invention also relates to a method for reducing the fuel consumption of a vehicle, in particular of a motor vehicle comprising at least one step of contacting a mechanical part of the engine of the vehicle with a lubricant composition such as as defined above.

The subject of the invention is also a process for reducing the peeling of a mechanical part preferably of a transmission member or of a motor of vehicles, advantageously of motor vehicles, comprising at least the contacting of the part mechanical with a lubricating composition as defined above.

The set of characteristics and preferences presented for the lubricating composition also applies to the above processes.

The invention also relates to a composition of the additive concentrate type comprising at least one compound comprising a dithiophosphate group and nanoparticles of tungsten bisulfide.

The set of characteristics and preferences presented for the tungsten disulfide nanoparticles and the compound comprising a dithiophosphate group also applies to the above additive concentrate type composition.

In one embodiment of the invention, the composition of the additive concentrate type according to the invention may be added at least one base oil to obtain a lubricant composition according to the invention.

All of the features and preferences presented for the base oil also apply to the embodiment above.

The subject of the invention is also the use of a compound comprising a dithiophosphate group for reducing the oxidation of a lubricating composition comprising at least one base oil and metal nanoparticles.

The set of characteristics and preferences presented for the base oil, the metal nanoparticles and the compound comprising a dithiophosphate group also applies to the above use. The various objects of the present invention and their implementations will be better understood on reading the examples which follow. These examples are given for information only, and are not limiting in nature. Examples

Lubricating compositions Nos. 1 to 4 were prepared from the following compounds:

a grade 6 PAO (Poly Alpha Olefin) base oil (viscosity at 100 ° C. at around 6 cSt measured according to the ASTM D445 standard),

a mixture of nanoparticles of tungsten bisulphide containing 20% of active material in an oil (NanoLub Gear Oil Concentrate marketed by Nanomaterials),

a compound comprising a dithiophosphate: zinc dithiophosphate group (Lz 1371 sold by the company Lubrizol).

Lubricating compositions Nos. 1 to 4 are described in Table II; the percentages given are percentages by mass.

Table II

Composition N ° 1 N ° 2 N ° 3 N ° 4

lubricant

Base oil 100 99 99 98

Compound 1 1

including a

group

dithiophosphate

Nanoparticles of 1 1

disulfide

tungsten

(NanoLub Gear Oil

Concentrate) Test 1: Evaluation of the friction properties of lubricating compositions

It is a question of evaluating the friction properties of the lubricating compositions Nos. 1 to 4 by measuring the coefficient of friction.

The coefficient of friction is evaluated using a linear pion / plane tribometer under the following conditions:

- type of steel: AISI 52100 (hardness = 800 HV),

roughness of the plane: 35 nm,

- temperature: 100 ° C,

calculated contact pressure: 1, 12 GPa,

- sliding speed: 3 mm / s

- humidity level: 35-45R (ambient atmosphere),

- duration of the test: 8h. Table III shows the average coefficient of friction of lubricant compositions No. 1 to No. 4; the average coefficient of friction representing the average of the values of the coefficient of friction obtained after 4 tests.

Table III

These results show that the lubricating composition according to the invention No. 4 has improved friction properties, with respect to a lubricating composition comprising a compound comprising a dithiophosphate group according to the invention but not comprising metal nanoparticles (composition No. 2 ) and with respect to a composition comprising metal nanoparticles according to the invention but not comprising a compound comprising a dithiophosphate group (composition No. 3).

These results thus show a synergy of activity of the combination between a compound comprising a dithiophosphate group and metal nanoparticles in a lubricating composition in order to significantly reduce the coefficient of friction, in particular for steel / steel contacts. These results also show that the friction reduction efficiency is maintained over time by the use of a lubricant composition according to the invention. Moreover, the lubricant composition No. 4 has a satisfactory stability.

Claims

claims

1. A lubricating composition having a kinematic viscosity at 100 ° C. measured according to ASTM D445 ranging from 4 to 50 cSt and comprising at least one base oil, at least one compound comprising a dithiophosphate group and metal nanoparticles in a content by weight ranging from 0 , 01 to 2% relative to the total weight of the lubricating composition.

2. lubricating composition according to claim 1 wherein the metal of which the metal nanoparticle is made is selected from the group consisting of tungsten, molybdenum, zirconium, hafnium, platinum, rhenium, titanium, tantalum, niobium, cerium, indium and tin, preferably tungsten.

3. Lubricating composition according to claim 1 or 2 wherein the metal nanoparticles are chosen from the group formed by MoS ₂ , MoSe ₂ ,

MoTe ₂ , WS ₂ , WSe ₂ , ZrS ₂ , ZrSe ₂ , HfS ₂ , HfSe ₂ , PtS ₂ , ReS ₂ , ReSe ₂ , TiS ₃ , ZrS ₃ , ZrSe ₃ , HfS ₃ , HfSe ₃ , TiS ₂ , TaS ₂ , TaSe ₂ , NbS ₂ , NbSe ₂ and NbTe ₂ , preferentially from MoS ₂ , MoSe ₂ , WS ₂ , WSe ₂ , advantageously MoS ₂ and WS ₂ .

4. Lubricating composition according to any one of the preceding claims wherein the metal nanoparticles are concentric polyhedra with a multilayer structure or in sheets.

A lubricating composition according to any one of the preceding claims wherein the weight content of metal nanoparticles ranges from

From 0.05 to 2%, preferably from 0.1 to 1%, advantageously from 0.1 to 0.5% relative to the total weight of the lubricating composition.

A lubricating composition according to any preceding claim wherein the average size of the metal nanoparticles is from

At 600 nm, preferably from 20 to 400 nm, advantageously from 50 to 200 nm.

A lubricating composition according to any preceding claim wherein the compound comprising a dithiophosphate moiety is selected from the group consisting of ammonium dithiophosphates, amine dithiophosphates, ester dithiophosphates and metal dithiophosphates, alone or in admixture.

A composition according to any one of the preceding claims wherein the compound comprising a dithiophosphate group is a compound of formula (IV)

in which :

M represents a metal cation, preferably a Zn ²⁺ cation;

• n represents the valence of the metal cation.

A lubricating composition according to any one of the preceding claims wherein the compound comprising a dithiophosphate group is a compound of formula (IV-a) or of formula (IV-b):

(IV-a)

in which :

R12 represents a linear or branched, saturated or unsaturated, substituted or unsubstituted alkyl group comprising from 1 to 30 carbon atoms; • R13 represents a linear or branched, saturated or unsaturated, substituted or unsubstituted alkyl group comprising from 1 to 30 carbon atoms.

10. Lubricating composition according to any one of the preceding claims wherein the content by weight of compound comprising a dithiophosphate group ranges from 0.1 to 5%, preferably from 0.2 to 4%, more preferably from 0.5 to 2. %, advantageously from 0.5 to 1.5% relative to the total weight of the lubricating composition.

1 1. A lubricating composition according to any one of the preceding claims further comprising an additive selected from polymers, antioxidants, anti-corrosion additives, friction modifiers different from metal nanoparticles and dispersants.

12. Use of a lubricant composition according to any one of claims 1 to 1 1 for the lubrication of a mechanical part, preferably a motor or a transmission member.

13. Use of a lubricant composition according to the preceding claim for the lubrication of a mechanical part of motor vehicles.

14. Use of a lubricant composition according to any one of claims 1 to 1 1 for reducing the fuel consumption of vehicles, particularly motor vehicles.

15. Use of a compound comprising a dithiophosphate group to reduce the oxidation of a lubricating composition comprising at least one base oil and metal nanoparticles.