EP3110929B1 - Lubricating composition based on metal nanoparticles - Google Patents

Description

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 metallic nanoparticles. More particularly, the invention relates to a lubricating composition comprising an anti-wear additive and metallic nanoparticles. The lubricating composition according to the invention simultaneously exhibits good stability as well as good friction properties which last over time.

Also described is a process for lubricating a mechanical part using this lubricating composition.

Also described is an additive concentrate type composition comprising an anti-wear additive and metallic nanoparticles.

Prior art

Motor vehicle transmission components 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, wear occurs on the cone-ring assembly.

The level of friction can be adjusted by adding friction modifiers to these gear oils.

In addition, the generalization of the automobile on a planetary scale since the end of the last century poses problems with regard to global warming, pollution, safety and the use of natural resources, in particular the exhaustion oil reserves.

Following the establishment of the Kyoto Protocol, new standards protecting the environment require the automotive industry to build vehicles with reduced polluting emissions and fuel consumption. As a result, the engines of these vehicles are subject to increasingly severe technical constraints. In particular, they run faster, at increasingly high temperatures and need to consume less and less fuel.

The nature of automobile engine lubricants has an influence on the emission of pollutants and on fuel consumption. Engine lubricants for automobiles known as energy-saving or “fuel-eco” (in Anglo-Saxon terminology) have been developed to meet these new needs.

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

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

However, these compounds have the drawback of inducing the formation of sediments when the lubricating composition has too high a content of molybdenum element. The poor solubility of these compounds modifies or even deteriorates the properties of the lubricating composition, in particular its viscosity. However, a composition that is too viscous or not viscous enough is detrimental to the movement of moving parts, to the correct starting of an engine, to the protection of an engine when it has reached its operating temperature, and therefore ultimately causes in particular an increase in fuel consumption.

In addition, these compounds contribute to an increase in the ash content, reducing their potential for use in a lubricating composition, in particular in Europe.

It is also known to formulate lubricating compositions comprising organomolybdenum-type friction modifier compounds with organophosphorus and/or organosulfur and/or organophosphorus anti-wear and extreme pressure compounds, in particular to improve the anti-wear properties of these oils. engines or transmissions.

Other compounds for reducing friction have been described as being able to be of interest in the lubrication of mechanical parts, in particular parts of an engine.

The document CN 101691517 describes an engine oil comprising nanoparticles of tungsten disulphide, making it possible to improve engine life and reduce fuel consumption. However, the content of tungsten disulphide nanoparticles ranges from 15 to 34%, which can lead to risks of instability of the oil over time.

FR 2 910 911 discloses a lubricant composition comprising a base oil and metal-containing nanoparticles, the particles having an average diameter of 1 to 10 nm.

IZ Jenei et al., Tribology Letters, 51, 461-468 (2013 ) studies the impact of different additives on the properties of a lubricating composition comprising tungsten disulphide nanoparticles having a fullerene-like structure.

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

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

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

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

One objective of the present invention is to provide a lubricating composition which overcomes all or part of the aforementioned drawbacks.

Another objective 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 method of lubrication which makes it possible in particular to reduce 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 with a kinematic viscosity at 100° C. measured according to the ASTM D445 standard ranging from 4 to 50 cSt and comprising at least 70% by weight of at least one base oil, from 0.1 to 5% by weight of at least one anti-wear compound comprising a dithiophosphate group and metallic nanoparticles solids having a fullerene-like structure 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 in a content by weight ranging from 0.01 to 2% relative to the total weight of the lubricating composition. The metallic nanoparticles have an average size, determined using images obtained by transmission electron micrography or by high-resolution transmission electron microscopy, of 50 to 200 nm and are concentric polyhedra with a multilayer or sheet structure.

Surprisingly, the Applicant has found that the presence of an anti-wear compound comprising a dithiophosphate group in a lubricating composition comprising at least one base oil and metallic nanoparticles as defined above makes it possible to confer on said composition very good friction reducing properties.

In addition, the applicant has observed that the combination of an anti-wear compound comprising a dithiophosphate group and metallic nanoparticles as defined above in a lubricating 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 effectiveness of friction reduction could be explained by the protection against the oxidation of the metallic nanoparticles by the anti-wear compound comprising a dithiophosphate group, thus extending the action of metallic nanoparticles on the surface of a mechanical part, and more particularly of a transmission member or motor vehicle engine.

Thus, the present invention makes it possible to formulate stable lubricating compositions comprising a reduced content of metallic nanoparticles and yet exhibiting remarkable friction reduction properties.

Advantageously, the lubricating compositions according to the invention have remarkable friction reduction properties which last over time. Advantageously, the lubricating compositions according to the invention have good oil stability and a viscosity which does not vary or varies very little.

Advantageously, the lubricating compositions according to the invention have satisfactory anti-flaking properties.

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

Advantageously, the lubricating compositions according to the invention have remarkable fuel saving properties

In one embodiment, the lubricating composition consists essentially of at least one base oil, at least one anti-wear compound comprising a dithiophosphate group and at least metallic nanoparticles as defined above in a content by weight ranging from 0 0.01 to 2% relative to the total weight of the lubricating composition.

The application also describes an engine oil comprising a lubricating composition as defined above.

The application also describes a transmission oil comprising a lubricating composition as defined above.

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

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

The invention also relates to the use of a lubricating composition as defined above for reducing the fuel consumption of vehicles, in particular motor vehicles.

The application also describes a process for lubricating a mechanical part, preferably a transmission member or a vehicle engine, advantageously motor vehicles, said process comprising at least one step of bringing the mechanical part into contact with a lubricating composition as defined above.

The application also describes a method for reducing friction on the surface of a mechanical part, preferably of a transmission member or of a vehicle engine, advantageously of motor vehicles, comprising at least bringing the mechanical part into contact with a lubricating composition as defined above.

The application also describes 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 engine of the vehicle into contact with a lubricating composition as defined above.

The invention also relates to the use of an anti-wear compound comprising a dithiophosphate group to reduce the oxidation of a lubricating composition comprising at least one base oil and solid metallic nanoparticles having a fullerene-type structure represented by the formula MXn 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, the metallic nanoparticles having an average size, determined using images obtained by transmission electron micrography or by high resolution transmission electron microscopy, from 50 to 200 nm and being of concentric polyhedra with a multilayer or sheet structure.

The application also describes a composition of the concentrate type of additives comprising at least at least one compound comprising a dithiophosphate group and tungsten disulphide nanoparticles.

detailed description

The percentages indicated below correspond to percentages by mass of active material.

Metallic nanoparticles

The lubricating composition according to the invention comprises metallic nanoparticles in a content by weight ranging from 0.01 to 2% relative to the total weight of the lubricating composition.

By metallic nanoparticles is meant in particular metallic particles, generally solid, whose average size is less than or equal to 600 nm.

Advantageously, the metallic nanoparticles consist of at least 80% by mass of at least one metal, or else of at least 80% by mass of at least one metal alloy or else of at least 80% by mass of at least one metal chalcogenide, in particular of transition metal, with respect to the total mass of the nanoparticle. Advantageously, the metallic nanoparticles consist of at least 90% by mass of at least one metal, or else of at least 90% by mass of at least one metal alloy or else of at least 90% by mass of at least one metal chalcogenide, in particular of transition metal, with respect to the total mass of the nanoparticle.

Advantageously, the metallic nanoparticles consist of at least 99% by mass of at least one metal, or else of at least 99% by mass of at least one metal alloy or else of at least 99% by mass of at least one metal chalcogenide, in particular of transition metal, with respect to the total mass of the nanoparticle, the remaining 1% being constituted by impurities.

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

The metallic nanoparticles used in the compositions according to the invention are solid metallic nanoparticles having a structure of the fullerene type (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 chosen from the group formed by 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 chosen from the group formed by oxygen, sulfur, selenium and tellurium.

Preferably, X is chosen from sulfur or tellurium.

Even more preferably, X is sulfur.

Advantageously, the metallic nanoparticles according to the invention are chosen from the group formed by MoS2, 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 metallic 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 have a fullerene-type structure.

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

Studies on fullerene-like structures have shown that this structure is not limited to carbonaceous materials, but is likely to occur in all nanoparticles of materials in the form of sheets, especially for nanoparticles comprising chalcogens and metals of transition. These structures are analogous to that of carbon fullerenes and are called inorganic fullerenes or fullerene-like structures (in English terms “Inorganic Fullerene like materials”, also referred to as “IF”). Fullerene-like 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 metallic nanoparticles are closed structures, of the spherical type, more or less perfect depending on the synthesis methods used. The nanoparticles according to the invention are concentric polyhedrons with a multilayer or sheet structure. We speak of an "onion" or "nested polyhedron" structure.

In one embodiment of the invention, the metallic nanoparticles are multilayer metallic nanoparticles comprising from 2 to 500 layers, preferably from 20 to 200 layers, advantageously from 20 to 100 layers.

The average size of the metallic nanoparticles according to the invention ranges from 50 to 200 nm. The size of the metallic nanoparticles according to the invention can be determined using images obtained by transmission electron micrography or by electron microscopy. high resolution transmission. 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.

Advantageously, the content by weight of metallic 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 product NanoLub Gear Oil Concentrate marketed by the company Nanomaterials, which is in the form of a dispersion of multilayer nanoparticles of tungsten disulphide in a mineral or PAO type oil ( Poly Alfa Olefin).

Compound comprising a dithiophosphate group

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

For the sake of simplification of the description, the anti-wear compound comprising a dithiophosphate group is called “dithiophosphate” in the rest of the present description.

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

dans laquelle R1 et R2 représentent indépendamment l'un de l'autre un groupe hydrocarboné, éventuellement substitué, comprenant de 1 à 30 atomes de carbone.In one embodiment of the invention, the dithiophosphate is chosen from the ammonium dithiophosphates of formula (I):

in which R1 and R2 represent, independently of each other, an optionally substituted hydrocarbon group comprising from 1 to 30 carbon atoms.

In a preferred embodiment of the invention, R1 and R2 independently of each other represent a hydrocarbon group, optionally substituted, comprising from 2 to 24 carbon atoms, more preferentially from 3 to 18 carbon atoms, advantageously from 5 to 12 carbon atoms.

In another preferred embodiment of the invention, R1 and R2 independently represent 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 independently represent a linear or branched alkyl hydrocarbon group, more preferably a linear alkyl hydrocarbon group.

In another preferred embodiment of the invention, R1 and R2 independently represent a hydrocarbon group optionally substituted by at least one oxygen, nitrogen, sulfur and/or phosphorus atom, preferably by at least one oxygen atom.

As examples of ammonium dithiophosphate, mention may be made of ammonium dimethyl dithiophosphates, ammonium diethyl dithiophosphates and ammonium dibutyl dithiophosphates.

dans laquelle :

• R3 et R4 représentent indépendamment l'un de l'autre un groupe hydrocarboné, éventuellement substitué, comprenant de 1 à 30 atomes de carbone,
• R5, R6 et R7 représentent indépendamment l'un de l'autre un atome d'hydrogène ou un groupement hydrocarboné de 1 à 30 atomes de carbone, étant entendu qu'au moins un des groupes R5, R6 et R7 ne représente pas un atome d'hydrogène.

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

in which :

• 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 of hydrogen.

In a preferred embodiment of the invention, R3 and R4 independently of each other represent a hydrocarbon group, optionally substituted, comprising from 2 to 24 carbon atoms, more preferentially from 3 to 18 carbon atoms, advantageously from 5 to 12 carbon atoms.

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

In another preferred embodiment of the invention, R3 and R4 independently represent a hydrocarbon group optionally substituted by 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 independently represent 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.

dans laquelle :

• R8 et R9 représentent indépendamment l'un de l'autre un groupe hydrocarboné, éventuellement substitué, comprenant de 1 à 30 atomes de carbone,
• R10 et R11 représentent indépendamment l'un de l'autre un groupe hydrocarboné comprenant de 1 à 18 atomes de carbone.

In another embodiment of the invention, the dithiophosphate is chosen from the ester dithiophosphates of general formula (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 R11 represent, independently of each other, a hydrocarbon group comprising from 1 to 18 carbon atoms.

In a preferred embodiment of the invention, R8 and R9 independently represent an optionally substituted hydrocarbon group comprising from 2 to 24 carbon atoms, more preferentially from 3 to 18 carbon atoms, advantageously from 5 to 12 carbon atoms.

In another preferred embodiment of the invention, R8 and R9 independently represent 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 independently represent a linear or branched alkyl hydrocarbon group, more preferably a linear alkyl hydrocarbon group.

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

In another preferred embodiment of the invention, R10 and R11 independently represent a hydrocarbon group comprising from 2 to 6 carbon atoms.

dans laquelle :

• R12 représente un groupe alkyle linéaire ou ramifié, substitué ou non substitué comprenant de 1 à 30 atomes de carbone ;
• R13 représente un groupe alkyle linéaire ou ramifié, substitué ou non substitué comprenant de 1 à 30 atomes de carbone ;
• M représente un cation métallique, de préférence un cation Zn²⁺ ;
• n représente la valence du cation métallique.

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

in which :

• R12 represents a linear or branched, substituted or unsubstituted alkyl group comprising from 1 to 30 carbon atoms;
• R13 represents a linear or branched, 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. 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 independently represent an optionally substituted hydrocarbon group comprising from 2 to 24 carbon atoms, more preferentially from 3 to 18 carbon atoms, advantageously from 5 to 12 carbon atoms.

In another preferred embodiment of the invention, R12 and R13 independently represent 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 independently represent a linear or branched alkyl hydrocarbon group, more preferably a linear alkyl hydrocarbon group.

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

dans lesquelles R12 et R13 sont tels que définis ci-dessus.Advantageously, the dithiophosphate according to the invention is a zinc dithiophosphate of formula (IV-a) or of formula (IV-b):

wherein R12 and R13 are as defined above.

As metal dithiophosphate according to the invention, one can quote for example Additin ^® RC 3038, Additin ^® RC 3045, Additin ^® RC 3048, Additin ^® RC 3058, Additin° RC 3080, Additin° RC 3180, Additin° RC 3212, Additin° RC 3580, Kikulube° Z112, Lubrizol ^® 1371, Lubrizol ^® 1375, Lubrizol ^® 1395, Lubrizol ^® 5179, Oloa ^® 260, ^Oloa® 267.

The content by weight of anti-wear compound comprising a dithiophosphate group ranges from 0.1 to 5%, relative to the total weight of the lubricating composition.

In one embodiment of the invention, the content by weight of compound comprising a dithiophosphate group ranges from 0.2 to 4%, more preferably from 0.5 to 2%, advantageously from 0.5 to 1.5% per relative to the total weight of the lubricating composition.

base oil

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

The base oil(s) used in the lubricating 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 ATIEL classification) as summarized below, singly or in combination. Table I Content Saturates content Sulfur content Viscosity index (VI) Group I Mineral Oils < 90% > 0.03% 80 ≤ IV < 120 Group II Hydrocracked oils ≥ 90% ≤0.03% 80≤ IV <120 Group III Hydrocracked or hydroisomerized oils ≥ 90% ≤0.03% ≥ 120 Group IV Polyalphaolefins (PAO) Group V Esters and other bases not included in bases groups I to IV

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 and hydroisomerization, hydrofinishing.

The base oils of the lubricating compositions according to the invention can also be synthetic oils, such as certain esters of carboxylic acids and alcohols, or polyalphaolefins. The polyalphaolefins used as base oils are for example 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 the ASTM D445 standard. Their weight-average molecular weight is typically between 250 and 3000 measured according to standard ASTM D5296. Blends of synthetic and mineral oils can also be used.

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

In the invention, the lubricating bases represent at least 70% by mass, relative to the total mass of the lubricating composition, Typically, they represent between 75 and 99.9% by mass, relative to the total mass of the lubricating compositions according to the invention.

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

In one embodiment, the kinematic viscosity at 100° C. measured according to the ASTM D445 standard 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 standard).

Other additives

The lubricating compositions according to the invention may also contain any type of additive suitable for their use in the formulations of oils for transmissions, for example one or more additives chosen from polymers, antioxidants, anti-corrosion additives, modifiers different frictions of the metallic nanoparticles according to the invention and the dispersants, present at the usual levels required for the application. In one embodiment of the invention, the additive is chosen from dispersants having a weight-average molecular mass greater than or equal to 2000 Daltons.

According to the invention, the weight-average molecular mass 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 maintenance in suspension of the metallic nanoparticles.

In one embodiment of the invention, the dispersant can 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 one 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 top bearing a d atom. nitrogen by a polyamine group.

By substituted succinimide group within the meaning of the present invention, is meant a succinimide group of which at least one of the carbon vertices 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 mass ranging from 2000 to 15000 Daltons, preferably ranging from 2500 to 10000 Daltons, advantageously from 3000 to 7000 Daltons.

Also advantageously, the dispersant has a number 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 molecular weight 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 mass 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 can be chosen from the group of shear-stable polymers, preferably from the group consisting of copolymers of ethylene and alpha-olefin, polyacrylates such as polymethacrylates, olefin copolymers (OCP), Ethylene Propylene Diene Monomers (EPDM), polybutenes, copolymers of styrene and olefin, hydrogenated or not, or copolymers of styrene and acrylate.

The antioxidants can be chosen from amino antioxidants, preferably diphenylamines, in particular dialkylphenylamines, such as octadiphenylamines, phenyl-alpha-naphthyl amines, phenolic antioxidants (dibutylhydroxytoluene BHT and derivatives) or sulfur antioxidants (sulphurized phenates) .

The friction modifiers can be compounds providing metallic elements different from the metallic nanoparticles according to the invention or else an ashless compound. Among the compounds providing metallic elements, mention may be made of complexes of transition metals 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 molybdenum dithiophosphates. The ashless friction modifiers are of organic origin and can be chosen 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. By “fat” or “fat(s)” is meant within the meaning of the present invention a hydrocarbon group comprising from 8 to 24 carbon atoms.

The anti-corrosion additives can be chosen from phenolic derivatives, in particular ethoxylated phenolic derivatives substituted by alkyl groups in the ortho position. The corrosion inhibitors may be derivatives of dimercaptothiadiazole.

• de 75 à 99,89% d'au moins une huile de base,
• de 0,01 à 2% de nanoparticules métalliques telles que définies ci-dessus,
• de 0,1 à 5% d'au moins un composé anti-usure comprenant un groupement dithiophosphate.

In one embodiment of the invention, the lubricating composition comprises:

• from 75 to 99.89% of at least one base oil,
• from 0.01 to 2% of metallic nanoparticles as defined above,
• from 0.1 to 5% of at least one anti-wear compound comprising a dithiophosphate group.

• 75 à 99,89% d'au moins une huile de base,
• 0,01 à 2% de nanoparticules métalliques telles que définies ci-dessus,
• 0,1 à 5% d'au moins un composé anti-usure comprenant un groupement dithiophosphate.

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

• 75 to 99.89% of at least one base oil,
• 0.01 to 2% of metallic nanoparticles as defined above,
• 0.1 to 5% of at least one anti-wear compound comprising a dithiophosphate group.

All of the characteristics and preferences presented for the base oil, the metallic nanoparticles and the anti-wear compound comprising a dithiophosphate group also apply to the lubricating compositions above.

In one embodiment of the invention, the lubricating composition is not an emulsion.

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

The application also describes an engine oil comprising a lubricating composition according to the invention.

The application also describes a transmission oil comprising a lubricating composition according to the invention.

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

Rooms

The lubricating composition according to the invention can lubricate at least one mechanical part or one mechanical component, in particular bearings, gears, universal joints, transmissions, the piston/segment/liner system, the camshafts, the clutch , manual or automatic gearboxes, axles, rocker arms, crankcases, etc.

In a preferred embodiment, the lubricating composition according to the invention can lubricate a mechanical part or a metal component of the transmissions, of the clutch, of the axles, of manual or automatic, preferably manual, gearboxes.

Thus, the invention also relates to the use of a lubricating composition as defined above for lubricating a mechanical part, preferably a transmission member or a vehicle engine, advantageously vehicles automobiles.

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

A subject of the invention is also the use of a lubricating composition as defined above for reducing the fuel consumption of vehicles, in particular motor vehicles.

A subject of the invention is also the use of a lubricating 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 characteristics and preferences presented for the lubricating composition also apply to the above uses.

The application also describes a process for lubricating a mechanical part, preferably a transmission member or a vehicle engine, advantageously motor vehicles, said process comprising at least one step of bringing the mechanical part into contact with a lubricating composition as defined above.

The application also describes a method for reducing friction on the surface of a mechanical part, preferably of a transmission member or of a vehicle engine, advantageously of motor vehicles, comprising at least bringing the mechanical part into contact with a lubricating composition as defined above.

The application also describes a method for reducing the fuel consumption of a vehicle, in particular of a motor vehicle comprising at least one step of in contact with a mechanical part of the vehicle engine with a lubricating composition as defined above.

The application also describes a method for reducing the spalling of a mechanical part, preferably of a transmission member or of a vehicle engine, advantageously of motor vehicles, comprising at least bringing the mechanical part into contact with a lubricating composition as defined above.

All of the characteristics and preferences presented for the lubricating composition also apply to the above methods.

The application also describes a composition of the concentrate type of additives comprising at least one anti-wear compound comprising a dithiophosphate group and tungsten disulphide nanoparticles.

All of the characteristics and preferences presented for the tungsten disulphide nanoparticles and the anti-wear compound comprising a dithiophosphate group also apply to the composition of the concentrate type of additives above.

In one embodiment of the invention, to the composition of the concentrate type of additives can be added at least one base oil to obtain a lubricating composition according to the invention.

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

The invention also relates to the use of an anti-wear compound comprising a dithiophosphate group to reduce the oxidation of a lubricating composition comprising at least one base oil and solid metallic nanoparticles having a fullerene-type structure represented by the formula MXn 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, in which the metallic nanoparticles have an average size, determined using images obtained by transmission electron micrography or by transmission electron microscopy at high resolution, from 50 to 200 nm and are concentric polyhedra with a multilayer or sheet structure All of the characteristics and preferences presented for the base oil, the metallic nanoparticles and the anti-wear compound comprising a dithiophosphate group also apply 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, without limitation.

Examples

• une huile de base de type PAO (Poly Alpha Oléfine) de grade 6 (viscosité à 100°C aux environs de 6 cSt mesuré selon la norme ASTM D445),
• un mélange de nanoparticules de bisulfure de tungstène à 20% en matière active dans une huile (NanoLub Gear Oil Concentrate commercialisé par la société Nanomaterials),
• un composé comprenant un groupement dithiophosphate : dithiophosphate de zinc (Lz 1371 commercialisé par la société Lubrizol).

Lubricating compositions No. 1 to No. 4 were prepared from the following compounds:

• a grade 6 PAO (Poly Alpha Olefin) type base oil (viscosity at 100°C around 6 cSt measured according to the ASTM D445 standard),
• a mixture of tungsten disulphide nanoparticles with 20% active ingredient in an oil (NanoLub Gear Oil Concentrate marketed by the company Nanomaterials),
• a compound comprising a dithiophosphate group: zinc dithiophosphate (Lz 1371 marketed by the company Lubrizol).

Lubricating compositions No. 1 to No. 4 are described in Table II; the percentages indicated are percentages by mass. Table II Lubricant composition #1 #2 #3 #4 base oil 100 99 99 98 Compound comprising a dithiophosphate group 1 1 Tungsten Disulfide Nanoparticles (NanoLub Gear Oil Concentrate) 1 1

Test 1 : evaluation of the friction properties of lubricating compositions

This involves evaluating the friction properties of lubricating compositions No. 1 to No. 4 by measuring the coefficient of friction.

• nature de l'acier : AISI 52100 (dureté = 800 HV),
• rugosité du plan : 35 nm,
• température : 100°C,
• pression calculée de contact : 1,12 GPa,
• vitesse de glissement : 3 mm/s
• taux d'humidité : 35-45R (atmosphère ambiante),
• durée du test : 8h.

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

• type of steel: AISI 52100 (hardness = 800 HV),
• plane roughness: 35 nm,
• temperature: 100°C,
• calculated contact pressure: 1.12 GPa,
• sliding speed: 3 mm/s
• humidity: 35-45R (ambient atmosphere),
• duration of the test: 8 hours.

Table III shows the average coefficient of friction of lubricating 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 Composition #1 #2 #3 #4 Coefficient of friction 0.100 0.110 0.075 0.060

These results show that the lubricating composition according to the invention No. 4 has improved friction properties, compared to a lubricating composition comprising a compound comprising a dithiophosphate group according to the invention but does not not comprising metallic nanoparticles (composition No. 2) and relative to a composition comprising metallic 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 metallic nanoparticles in a lubricating composition to significantly reduce the coefficient of friction, in particular for steel/steel contacts.

These results also show that the effectiveness of reducing friction is maintained over time by the use of a lubricating composition according to the invention.

Furthermore, lubricating composition No. 4 exhibits satisfactory stability.

Claims (13)

1. Lubricant composition with kinematic viscosity at 100°C measured according to standard ASTM D445 ranging from 4 to 50 cSt and comprising, with respect to the total weight of the lubricant composition, at least 70% by weight of at least one base oil, from 0.1 to 5% by weight of one at least one anti-wear compound comprising a dithiophosphate group and from 0.01 to 2% by weight of solid metal nanoparticles having a fullerene-type structure 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, the metal nanoparticles having an average size, determined using images obtained by transmission electron microscopy or by high resolution transmission electron microscopy, ranging from 50 to 200 nm and being concentric polyhedrons with a multilayer or sheet structure.
2. Lubricant composition according to claim 1, wherein M is selected from the group constituted by tungsten, molybdenum, zirconium, hafnium, platinum, rhenium, titanium, tantalum and niobium.
3. Lubricant composition according to claim 1 or 2, wherein the metal nanoparticles are selected from the group constituted by MoS₂, MoSe₂, MoTe₂, WS₂, WSe₂, ZrS₂, ZrSe₂, HfS₂, HfSe₂, PtS₂, ReS₂, ReSe₂, TiS₃, ZrS₃, ZrSe₃, HfS₃, HfSe₃, TiS₂, TaS₂, TaSe₂, NbS₂, NbSe₂ and NbTe₂.
4. Lubricant composition according to any one of the preceding claims, wherein the content by weight of metal nanoparticles ranges from 0.05 to 2%, with respect to the total weight of the lubricant composition.
5. Lubricant composition according to any one of the preceding claims, wherein the the compound comprising a dithiophosphate group is selected from the group constituted by ammonium dithiophosphates, amine dithiophosphates, ester dithiophosphates and metal dithiophosphates, alone or in a mixture.
6. Composition according to any one of the preceding claims, wherein the compound comprising a dithiophosphate group is a compound of formula (IV)

   

   wherein:

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

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

   • M represents a metal cation,

   • n represents the valency of the metal cation.
7. Lubricant 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):

   

   

   

   wherein:

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

   • R13 represents a linear or branched, substituted or unsubstituted alkyl group comprising from 1 to 30 carbon atoms.
8. Lubricant composition according to any one of the preceding claims, wherein the content by weight of the compound comprising a dithiophosphate group ranges from 0.2 to 4%, with respect to the total weight of the lubricant composition.
9. Lubricant composition according to any one of the preceding claims, further comprising an additive selected from the shear-stable polymers, the antioxidants, the anti-corrosion additives, the friction modifiers different from metal nanoparticles, and the dispersants.
10. Use of a lubricant composition according to any one of claims 1 to 9 for the lubrication of a mechanical part.
11. Use of a lubricant composition according to the preceding claim for the lubrication of a mechanical part of motor vehicles.
12. Use of a lubricant composition according to any one of claims 1 to 9 for reducing the fuel consumption of vehicles.
13. Use of an anti-wear compound comprising a dithiophosphate group for decreasing the oxidation of a lubricant composition comprising at least one base oil and solid metal nanoparticles having a fullerene-type structure 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, the metal nanoparticles having an average size, determined using images obtained by transmission electron microscopy or by high resolution transmission electron microscopy, ranging from 50 to 200 nm and being concentric polyhedrons with a multilayer or sheet structure.