Technical field
The present invention is applicable to the field of lubricants, and more
5 particularly to the field of lubricants for motor vehicles, in particular to the field of
lubricants for motor vehicle transmission components. The invention relates to a
lubricant composition comprising metal nanoparticles. More particularly, the
invention relates to a lubricant composition coniprising a dispersant with a high
weight-average molecular weight and metal nanoparticles. The lubricant
10 composition according to the invention simultaneously has good stability and good
anti-flaking properties.
The present invention also relates to a method for reducing the flaking of a
mechanical part utilizing this lubricant composition.
The present invention also relates to a composition of the additive-
15 concentrate type comprising a dispersant with a high weight-average molecular
weight and metal nanoparticles.
Prior art
Motor vehicle transmission components operate under a high load and high
20 speeds. The oils for these transmission components must therefore be particularly
efficient at protecting parts against wear and fatigue, and in particular protect the
gear teeth against the flaking phenomenon.
The phenomenon of wear corresponds to the abrasion and fretting of metal
at the surface during friction between the moving parts.
25 As for the flaking phenomenon, it differs from the phenomenon of wear. It
corresponds to a degradation of the parts due to fatigue and is produced after a long
period of ageing, preceding visible deterioration. It is known that this phenomenon
starts by the initiation of cracks at a certain depth under the surface, these cracks
propagate, and when normal cracks are created at the surface, flakes suddenly
30 break off.
This phenomenon is prevented by reducing the contact stresses by means of
an appropriate geometry of the parts, and by reducing friction, while avoiding
adhesion. The lubricant is involved in this prevention process, mainly due to the
physico-chemical reactivity of its additives.
The sulphur-, phosphorus-, phosphorus/sulphur-, or borate-containing antiwear
and extreme-pressure additives are known to give the transmission oils .
protection properties against flaking. The other additives present in the lubricant can
also have a positive or negative impact on the propagation of the cracks inside the
5 parts and therefore on the flaking phenomenon.
In manual gearboxes, the presence of synchronizers leads to additional
stresses. In fact, these components comprise a cone and ring device betweer1 whlch
friction must be precisely controlled. Thus, the friction should be sufficient for
synchronization of the gears, but the cone and the ring must then be able to
10 disengage, otherwise there is a risk of blocking the synchronizer.
Moreover, if the friction level is not adapted to the geometry of the parts,
wear occurs on the cone-ring assembly.
The friction level can be adjusted by adding friction modifiers in these oils for
gear boxes.
15 Thus, in oils for manual gear boxes, anti-wear, extreme-pressure additives
and friction modifiers can co-exist, all having an action at the surface of the parts
and potentially an effect on both the friction level and the flaking phenomenon.
It is known to formulate lubricant compositions comprising friction modifier
compounds of the organomolybdenum type with organophosphorus- and/or
20 organosulphur- andlor organophosphorus/sulphur-containing anti-wear and
extreme-pressure compounds, in particular in order to improve the anti-wear
properties of these oils.
Other compounds have been described as possibly being useful in the
lubrication of mechanical parts, in particular of the parts of an engine.
25 The use of nanoparticles, in particular of metal nanoparticles, in a lubricant
composition, has been described. Thus, the document WO 20071035626 describes
a lubricant composition comprising metal nanoparticles, in particular based on
lithium, potassium, sodium, copper, magnesium, calcium, barium or mixtures
thereof.
30 Document US201 1/01 521 42 A1 discloses a composition comprising at least
l
one base oil, at least one dispersant and nanoparticles of metal hydroxides in the
form of crystals. These compositions are used for lubricating combustion engines
and for neutralizing the acids formed during combustion.
Document US2006/0100292 A1 describes a method for manufacturing a
35 grease in which at least one base oil, at least one dispersant and nanoparticles of
metal hydroxides in the form of crystals are mixed. This method has the advantage
of reducing the formation of foam, reducing environmental risks and reducing
reaction time.
Document US2009/0203563 describes a method for manufacturing an
ovebased or neutral .detergent. This method utilizes a surfactant and an organic
medium with a composition comprising at least one base oil, at least one dispersant
and nanoparticles of metal hydroxides in the form of crystals.
Document W02011/081538 A1 describes a method for manufacturiny
particles of molybdenum disulphide and tungsten disulphide, the method consisting
of passing and pressing a mixture of molybdenum disulphide and tungsten
disulphide between plates covered with glue. This document does not describe
lubricant compositions.
As for document CN 101691 517, it describes an engine oil comprising a
dispersant and tungsten disulphide nanoparticles, making it possible to improve the
service life of the engine and reduce fuel consumption. However, the content of
tungsten disulphide nanoparticles ranges from 15 to 34%. Such a content can lead
to instability of the composition and is therefore incompatible with a lubricant
composition, in particular for transmissions. Furthermore, no indication is given in
this document as to any anti-flaking properties of the oil, in particular vis-a-vis the
transmission components of a motor vehicle.
Document EP 1 953 196 describes a dispersion of metal nanoparticles, in
particular of metal oxides based on zinc, zirconium, cerium, titanium, aluminium,
indium or tin in a organic solvent and in the presence of a polymeric dispersant of
PlBSA (polyisobutenyl succinic anhydride) type. However, this document does not
relate to the field of lubricant compositions and in particular discloses no lubricant
composition comprising at least one base oil and metal nanoparticles. The organic
solvents mentioned in this document have no lubricant properties. Furthermore, they
have a flash point of less than 100°C which makes them incompatible with use in
lubricant applications in which the implementation temperature is greater than or
equal to 100°C. Moreover, no indication is given in this document of any anti-flaking
properties of mechanical parts, in particular vis-a-vis the transmission components
of a motor vehicle.
It would therefore be desirable to have available a lubricant composition, in
particular for motor vehicles, which is both stable and makes it possible to reduce, or
even eliminate the flaking phenomenon, in particular in transmission components,
and more particularly in gearboxes.
It would also be desirable to have available a lubricant composition, in
particular for motor vehicles having good anti-flaking properties while retaining
satisfactory friction properties.
5 An objective of the present invention is to provide a lubricant composition
overcoming some or all of the abovementioned drawbacks.
Another objective of the invention is to provide a lubricant compositiun Illat is
stable and easy to utilize.
Another objective of the present invention is to provide a lubrication method
10 making it possible in particular to reduce the flaking phenomena of mechanical
parts, and more particularly of transmission components of motor vehicles.
Summarv of the invention
A subject of the invention is thus a lubricant composition comprising at least
15 one base oil, at least one dispersant having a weight-average molecular weight
greater than or equal to 2000 Daltons and metal nanoparticles in a content by
weight ranging from 0.01 to 2% with respect to the total weight of the lubricant
composition, said metal nanoparticles being concentric polyhedrons with a
multilayer structure or in sheets.
20 According to the invention, the weight-average molecular weight of the
dispersant is assessed according to the standard ASTM D5296.
Surprisingly, the Applicant found that the presence of a dispersant having a
weight-average molecular weight greater than or equal to 2000 Daltons in a
lubricant composition comprising at least one base oil and metal nanoparticles
25 makes it possible both to improve the stability of the lubricant composition, and to
give said composition very good anti-flaking properties.
Thus, the present invention makes it possible to formulate lubricant
compositions comprising a reduced content of metal nanoparticles and having,
30 however, remarkable anti-flaking properties.
Advantageously, by the use of lubricant compositions according to the
invention, the risk of residual deposition of metal nanoparticles on mechanical parts,
and more particularly on transmission components of motor vehicles, is significantly
35 reduced or even eliminated.
Advantageously, the lubricant compositions according to the invention have
an improved storage stability as well as a viscosity that does not: vary, or only very
slightly.
5 Advantageously, the lubricant compositions according to the invention retain
satisfactory friction properties.
In an embodiment, the lubricant composition essentially consists of at least
one base oil, at least one dispersant having a weight-average molecular weight
10 greater than or equal to 2000 Daltons and at least a content by weight of metal
nanoparticles ranging from 0.01 to 2% with respect to the total weight of the
lubricant composition.
The invention also relates to a transmission oil comprising a lubricant
15 composition as defined above.
The invention also relates to the use of a lubricant composition as defined
above for the lubrication of gearboxes or axles, preferentially of the gearboxes of
motor vehicles, advantageously for the lubrication of manual gearboxes.
20
The invention also relates to the use of a lubricant composition as defined
above for reducing the flaking of a mechanical part, preferentially of a transmission
component, more preferentially of a gearbox, even more preferentially of a manual
gearbox.
25
The invention also relates to a process for reducing the flaking of a
mechanical part, preferentially of a transmission component, advantageously of a
gearbox or of an axle, comprising at least bringing the mechanical part into contact
with a lubricant composition as defined above.
3 0
The invention also relates to a composition of the additive-concentrate type
- comprising at least one dispersant having a weight-average molecular weight
greater than or equal to 2000 Daltons and tungsten disulphide nanoparticles.
35 Detailed description
The percentages given below correspond to percentages by mass of active
ingredient.
Metal nanoparticles
5 The lubricant composition according to the invention comprises metal
nanoparticles in a content by weight ranging from 0.01 to 2% with respect to the
total weight of the lubricant composition.
By metal nanoparticles, is meant in particular metal particles, generally solid,
10 the average size of which is less than or equal to 600 nm.
Advantageously, the metal nanoparticles are constituted by at least 80% by
mass of at least one metal, or by at least 80% by mass of at least one metal alloy or
by at least 80% by mass of at least one metal, in particular transition metal,
15 chalcogenide with respect to the total mass of the nanoparticle.
Advantageously, the metal nanoparticles are constituted by at least 90% by
mass of at least one metal, or by at least 90% by mass of at least one metal alloy or
by at least 90% by mass of at least one metal, in particular transition metal,
20 chalcogenide with respect to the total mass of the nanoparticle.
Advantageously, the metal nanoparticles are constituted by at least 99% by
mass of at least one metal, or by at least 99% by mass of at least one metal alloy or
by at least 99% by mass of at least one metal, in particular transition metal,
25 chalcogenide with respect to the total mass of the nanoparticle, the remaining 1%
being constituted by impurities.
Advantageously, the metal of which the metal nanoparticle is constituted can
be selected from the group formed by tungsten, molybdenum, zirconium, hafnium,
30 platinum, rhenium, titanium, tantalum, niobium, zinc, cerium, aluminium, indium and
tin.
The metal nanoparticles can have the form of spheres, lamellas, fibres,
tubes, and fullerene-type structures.
3 5 Advantageously, the metal nanoparticles used in the compositions according
to the invention are solid metal nanoparticles having a fullerene-type (or fullerene-
- f g > : ~ . ~ : ~ c : Q ~ * . t i . " ~ : ~ . : : :- 1 p 'fJ E. L H.1. ' ' ~5
like) structure and are represented by the formula MX, 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.
5 Preferably, M is selected from the group formed by tungsten, molybdenum,
zirconium, hafnium, platinum, rhenium, titanium, tantalum and niobium.
More preferably, M is selected from the group formed by molybdenurr~ and
tungsten.
Even more preferably, M is tungsten.
10
Preferably, X is selected from the group formed by oxygen, sulphur,
selenium and tellurium.
Preferably, X is selected from sulphur or tellurium.
Even more preferably, X is sulphur.
15
Advantageously, the metal nanoparticles according to the invention are
selected from the group formed 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.
20 Preferably, the metal nanoparticles according to the invention are selected
from the group formed by WS2, WSe2, MoS2 and MoSe2, preferentially WS2 and
MoS2, preferentially WS2.
The nanoparticles according to the invention advantageously have a
fullerene-type structure.
25 Initially, the term fullerene denotes a closed convex polyhedron
nanostructure, composed of carbon atoms. The fullerenes are similar to graphite,
composed of sheets of linked hexagonal rings, but they contain pentagonal, and
sometimes heptagonal rings, which prevent the structure from being flat.
Studies of the fullerene-type structures have shown that this structure was
30 not limited to the carbon-containing materials, but was capable of being produced in
all the nanoparticles of materials in the form of sheets, in particular in the case of the
nanoparticles comprising chalcogens and transition metals. These structures are
analogous to that of the carbon fullerenes and are called inorganic fullerenes or
fullerene-type structures (or "Inorganic Fullerene-like materials", also denoted "IF).
35 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 synthesis process.
The metal nanoparticles are closed structures, of the spherical type, more or
less perfect depending on the synthesis processes used. The nanoparticles
5 according to the invention are concentric polyhedrons with a multilayer or sheet
structure. This is referred to as an "onion" or "nested polyhedron" structure.
By concentric polyhedron having a multilayer or sheet structure, is meant
more particularly substantially spherical polyhedrons, the different layers of which
coiistitute several spheres having the same centre.
10 The multilayer or sheet structure of the nanoparticles according to the
invention can in particular be determined by transmission electron microscopy
(TEM).
In an embodiment of the invention, the metal nanoparticles are multilayer
metal nanoparticles comprising from 2 to 500 layers, preferably from 20 to 200
15 layers, advantageously from 20 to 100 layers.
The number .of layers of the nanoparticles according to the invention can in
particular be determined by transmission electron microscopy.
The average size of the metal nanoparticles according to the invention
20 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 microscopy or by high
resolution transmission electron microscopy. It is possible to determine the average
size of the particles from measurement of the size of at least 50 solid particles
25 visualized on transmission electron microscopy photographs. The median value of
the distribution histogram of the measured sizes of the solid particles is the average
size of the solid particles used in the lubricant composition according to the
invention.
3 0 In an 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.
The average diameter of the nanoparticles according to the invention can in
particular be determined by transmission electron microscopy.
3 5
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% with respect
to the total weight of the lubricant composition.
5 As an example of metal nanoparticles according to the invention, the product
NanoLub Gear Oil Concentrate marketed by the company Nanomaterials may be
mentioned, being presented in the form of a dispersion of multilclyer nanopa~ticlesu f
tungsten disulphide in a mineral oil or oil of the PA0 (Poly Alfa Olefin) type.
10
Dispersant
The lubricant composition according to the invention comprises at least one
dispersant having a weight-average molecular weight greater than or equal to 2000
Daltons.
15 According to the invention, the weight-average molecular weight of the
dispersant is assessed according to the standard ASTM D5296.
By dispersant within the meaning of the present invention, is meant more
particularly any compound which ensures the maintenance in suspension of the
20 metal nanoparticles.
In an embodiment of the invention, the dispersant can be selected from the
compounds comprising at least one succinimide group, the polyolefins, the olefin
copolymers (OCP), the copolymers comprising at least one styrene unit, the
25 polyacrylates or their derivatives.
By derivatives, is meant any compound comprising at least one group or a
polymer chain as defined above.
-
Advantageously, the dispersant according to the invention is selected from
30 the compounds comprising at least one succinimide group.
In a preferred embodiment of the invention, the dispersant can be selected
from the compounds comprising at least one substituted succinimide group or the
compounds comprising at least two substituted succinimide groups, the succinimide
35 groups being linked at their vertex bearing a nitrogen atom by a polyamine group.
By substituted succinimide group within the meaning of the present
invention, is meant a succinimide group at least one of the carbon-containing
vertices of which is substituted with a hydrocarbon-containing group comprising from
8 to 400 carbon atoms.
In a preferred embodiment of the invention, the dispersant is selected from
the polyisobutylene succinimide-polyamines
Advantageously, the dispersant is a substituted succinimide of formula (I) or
a substituted succinimide of formula (11):
in which:
x represents an integer ranging from 1 to 10, preferably 2, 3, 4, 5 or
6;
y represents an integer ranging from 2 to 10;
R, represents a hydrogen atom, a linear or branched alkyl group
comprising from 2 to 20 carbon atoms, a heteroalkyl group
comprising from 2 to 20 carbon atoms and at least one heteroatom
selected from the group formed by 0, N and S, a hydroxyalkyl group
25 comprising from 2 to 20 carbon atoms or a -(CH2),-0-(CH2),-OH
grou *
XPE) DELHI. ; . T ~ Q ''. Pbl h- s- 1% 1 Q,B L
R2 represents a linear or branched alkyl group comprising from 8 to
400 carbon atoms, preferably from 50 to 200 carbon atoms, an aryl
group comprising from 8 to 400 carbon atoms, preferably from 50 to
200 carbon atoms, a linear or branched arylalkyl group comprising
from 8 to 400 carbon atoms, preferably from 50 to 200 carbon atoms
or a linear or branched alkylaryl group comprising from 8 to 400
carbon atoms, preferably from 58 to 200 carbon atoms;
R3 and R4, identical or different, represent independently a hydrogen
atom, a linear or branched alkyl group comprising from 1 to 25
carbon atoms, an alkoxy group comprising from 1 to 12 carbon
atoms, an alkylene group comprising from 2 to 6 carbon atoms, a
hydroxylated alkylene group comprising from 2 to 12 carbon atoms or
an aminated alkylene group comprising from 2 to 12 carbon atoms.
15
Advantageously, the dispersant is a substituted succinimide of formula (I) or
a substituted succinimide of formula (11) in which Rp represents a polyisobutylene
group.
Even more advantageously, the dispersant is a substituted succinimide of
20 formula (11) in which R2 represents a polyisobutylene group.
Even more advantageously, the dispersant is a substituted succinimide of
formula (11) in which:
R, represents a -(CH2),-0-(CH2),-OH group, .
R2 represents a polyisobutylene group,
25 x represents 2,
y represents 5.
Advantageously, the dispersant according to the invention has a weightaverage
molecular weight ranging from 2000 to 15000 Daltons, preferably ranging
30 from 2500 to 10000 Daltons, advantageously from. 3000 to 7000 Daltons.
Advantageously, the dispersant also has, moreover, a number-average
molecular weight greater than or equal to 1000 Daltons, preferably ranging from
1000 to 5000 Daltons, more preferentially from 1800 to 3500 Daltons,
35 advantageously from 1800 to 3000 Daltons.
According to the invention, the number-average molecular weight of the
dispersant is assessed according to the standard ASTM D5296.
In a preferred embodiment of the invention, the content by weight of
5 dispersant having a weight-average molecular weight greater than or equal to 2000
Daltons ranges from 0.1 to lo%, preferably from 0.1 to 5%, advantageously from 0.1
to 3% with respect to the total weight of the lubricant composition.
As an example of a dispersant according to the invention, OLOA 13000 from
10 the company Oronite may be mentioned.
Other compounds
Base oils
15 The lubricant compositions according to the invention can contain any type of
lubricant base, mineral, synthetic or natural, animal or vegetable suited to their use.
The base oil or oils used in the lubricant compositions according to the
present invention can be oils of mineral or synthetic origin, of groups I to V
20 according to the classes defined in the API classification (or their equivalents
according to the ATlEL classification) as summarized below, alone or in a mixture.
Moreover, base oil or oils used in the lubricant compositions according to the
invention can be selected from the oils of synthetic origin of group VI according to
the ATlEL classification. The API classification is defined in American Petroleum
25 Institute 1509 "Engine oil Licensing and Certification System" 17th edition,
September 201 2.
Viscosity index
('.'I)
80 I Group I Mineral oils V I< 120
Group II Hydrocracked
oils
I
Group V I Esters and other bases not included in bases of Groups I
Group Ill
Hydrocracked or hydroisomerized
oils
Group IV
I
Group VI* I Poly Internal Olefins (PIO)
Saturates content
< 90 %
2 90 %
I I I
*only for the ATIEL classification
Sulphur content
> 0.03 %
:, 00 %
The mineral base oils according to the invention include any type of bases
obtained by atmospheric and vacuum distillation of crude oil, followed by refining
5 operations such as solvent extraction, deasphalting, solvent dewaxing,
hydrotreatment, hydrocracking and hydroisomerization, hydrofinishing.
I 0.03 %
The base oils of the lubricant compositions according to the present
invention can also be synthetic oils, such as the poly alpha olefins (PAO) or certain
10 esters of carboxylic acids and alcohols, in particular polyol esters.
The poly alpha olefins used as base oils, are for example obtained from
monomers having from 4 to 32 carbon atoms (for example octene, decene), and
have a viscosity at 100°C comprised between 1.5 and 15 cSt measured according
to the standard ASTM D445. Mixtures of synthetic and mineral oils can also be
15 used.
There is no limitation on the use of any particular lubricant base for
producing the lubricant compositions according to the invention, except that they
must have properties, in particular viscosity, viscosity index, sulphur content,
oxidation resistance, suited to use in a gearbox, in particular in a motor vehicle
20 gearbox, in particular in a manual gearbox.
80 I VI < 120
Poly Alpha Olefins (PAO)
5 0.03 %
Advantageously, the base oil has a flash point greater than or equal to
150°C, preferably greater than or equal to 17O0C, even more preferentially greater
1120
than or equal to 1 9 0 " ~ .
I P O D E L H I 16 -.&El;.-a2azX5 16 a@ - .
Advantageously, the base oil is selected from the group formed by the bases
of group I, the bases of group II, the bases of group Ill, the bases of group IV, the
bases of group V of the API classification (or their equivalents according to the
5 ATlEL classification) and mixtures thereof. Moreover, the base oil can be sclected
from the bases of group VI of the ATlEL classification.
In an embodiment of the invention the base oil is selected from the group
formed by the bases of group Ill, the bases of group IV, the bases of group V of the
10 API classification and mixtures thereof.
In a preferred embodiment of the invention, the base oil is a mixture of bases
of group IV and group V of the API classification.
15 In a preferred embodiment of the invention, the base oil is selected from the
poly alph aolefins (PAO) and the esters, preferably the polyol esters or mixtures
thereof.
In a more preferred embodiment of the invention, the base oil is a mixture of
20 at least one poly alpha olefin and at least one ester, preferably a polyol ester.
In an embodiment of the invention, the base oil or the base oils can
represent at least 50% by mass, with respect to the total mass of the lubricant
composition, preferentially at least 60%, or also at least 70%. Typically, it (they)
25 represent(s) between 75 and 99.89% by weight, with respect to the total weight of
the lubricant compositions according to the invention.
Preferentially, the lubricant compositions according to the invention have a
kinematic viscosity at 100°C measured according to the standard ASTM D445
30 comprised between 4 and 41 cSt, according to the classification SAE J 306,
preferably between 4.1 and 32.5 cSt.
The preferred grades are all the grades comprised between the grades SAE
75W and SAE 140, in particular the grades SAE 75W, SAE 75W-80 and SAE 75W-
90.
35
Preferentially, the lubricant compositions according to the invention have a
viscosity index (VI) greater than 95 (measured according to the standard ASTM
2270).
5 In a preferred embodiment, a subject of the invention is a transmission oil
comprising a lubricant composition according to the invention.
All of the characteristics and preferences presented for the lubricant
composition also apply to the transmission oil according to the invention.
10 Additional additives
The lubricant compositions according to the invention can also contain any
type of additives suitable for use in the formulations of transmission oils, for example
one or more additives selected from the additional dispersants, polymeric viscosity
index improvers, antioxidants, corrosion inhibitors, friction modifiers or anti-foaming
15 agents, used alone or in mixtures, present in the usual contents required for the
application.
The additional dispersants are selected from dispersants different from the
dispersants having a weight-average molecular weight greater than or equal to 2000
20 Daltons.
These additional dispersants can in particular ensure the maintenance in
suspension and the removal of the insoluble solid contaminants constituted by the
by-products of oxidation and combustion residues (soots) which are formed when a
25 lubricant composition is in service.
In an embodiment of the invention, the additional dispersants can be
selected from the groups formed by the succinimides that are different from the
compounds of formula (I) or (11) having a weight-average molecular weight greater
than or equal to 2000 Daltons or the Mannich bases.
30
In an embodiment, the lubricant composition according to the invention can
also comprise at least one additional additive selected from the polymeric viscosity
index improvers, the antioxidants and mixtures thereof.
35 The polymeric viscosity index improvers can be selected from polymers other
than the dispersant according to the invention.
The polymeric viscosity index improvers can be selected from the group of
the shear-stable polymers, preferably from the group constituted by the ethylene
and alpha-olefin copolymers, in particular the ethylenelpropylene copolymers.
5 In a preferred embodiment of the invention, the additional additive is a
polymeric viscosity index improver selected from the ethylene and alpha-olefin
copolymers.
The antioxidants can be selected from the amine-containing antioxidants,
10 preferably the diphenylamines, in particular the dialkylphenylamines, such as the
octadiphenylamines, phenyl-alpha-naphthyl amines, the phenolic antioxidants
(dibutylhydroxytoluene BHT and derivatives) or sulphur-containing antioxidants
(sulphurized phenates).
15 In a preferred embodiment of the invention, the additional additive is an
antioxidant selected from the dialkyphenylamines, the phenolic antioxidants, used
alone and mixtures thereof.
The friction modifiers can be compounds providing metallic elements that are
20 different from the metal nanoparticles according to the invention, or an ash-free
compound. Among the compounds providing metallic elements, the complexes of
transition metals such as Mo, Sb, Sn, Fe, Cu, Zn, the ligands of which can be
hydrocarbon-containing compounds containing oxygen, nitrogen, sulphur or
phosphorus atoms, such as molybdenum dithiocarbamates or dithiophosphates may
25 be mentioned. The ash-free friction modifiers are of organic origin and can be
selected from the monoesters of fatty acids and polyols, alkoxylated amines,
alkoxylated fatty amines, amine phosphates, fatty alcohols, fatty epoxides, borated
fatty epoxides, fatty amines or glycerol esters of fatty acid. By "fatty" is meant within
the meaning of the present invention a hydrocarbon-containing group comprising
30 from 8 to 24 carbon atoms.
In a preferred embodiment of the invention, the additional additive is a friction
modifier selected from the molybdenum dithiocarbamates, amine phosphates and
fatty alcohols, used alone or in a mixture.
3 5
The anti-corrosion additives can be selected from the phenol derivatives, in
particular ethoxylated phenol derivatives and substituted with alkyl groups in the
ortho position. The corrosion inhibitors can be dimercaptothiadiazole derivatives.
5 In another preferred embodiment of the invention, the additional additive
comprises a mixture of an anti-oxidant and a polymeric viscosity index improver
selected from the group formed by the ethylenelalpha-olefin copolymers, in
particular the ethylenelpropylene copolymers.
10 In another preferred embodiment of the invention, the additional additive
comprises a mixture of an amine-containing antioxidant, a phenolic antioxidant and
a polymeric viscosity index improver selected from the ethylene and alpha-olefin
copolymers.
15 In an embodiment of the invention, the mass ratio (metal
nanopartic1es:dispersant) ranges from 1150 to 1011, preferably from 1/50 to 511,
more preferentially from 1/30 to 511, advantageously from 1/10 to 511.
A subject of the invention is also a lubricant composition comprising:
20 - from 50 to 99.89% of at least one base oil,
- from 0.01 to 2% of metal nanoparticles,
- from 0.1 to 10% of at least one dispersant having a weight-average
molecular weight greater than or equal to 2000 Daltons.
All of the characteristics and preferences presented above for the base oil, for
25 the metal nanoparticles and for the dispersant also apply to the above lubricant
composition.
In an embodiment, a subject of the invention is also a lubricant composition
comprising:
3 0 - from 50 to 99.79% of at least one base oil,
- from 0.01 to 2% of metal nanoparticles,
- from 0.1 to 10% of at least one dispersant having a weight-average
molecular weight greater than or equal to 2000 Daltons,
- from 0.1 to 10% of at least one additional additive, preferentially from 2 to
3 5 5%, specifically 3.5%.
All of the characteristics and preferences presented above for the base oil,
for the metal nanoparticles, for the dispersant and for the additional additive also
apply to the above lubricant composition.
5 A subject of the invention is also a lubricant composition consisting
essentially of:
- 50 to 99.9% of at least one base oil,
- 0.01 to 2% of metal nanoparticles,
- 0.1 to 10% of at least one dispersant having a weight-average molecular
10 weight greater than or equal to 2000 Daltons.
All of the characteristics and preferences presented above for the base oil,
for the metal nanoparticles and for the dispersant also apply to the above lubricant
composition.
15 In an embodiment, a subject of the invention is also a lubricant composition
essentially consisting of:
- 50 to 99.79% of at least one base oil,
- 0.01 to 2% of metal nanoparticles,
- 0.1 to 10% of at least one dispersant having a weight-average molecular
20 weight greater than or equal to 2000 Daltons,
-- 0.1 to 10% of at least one additional additive, preferentially from 2 to 5%,
specifically 3.5%.
All of the characteristics and preferences presented above for the base oil, for
the metal nanoparticles, for the .dispersant and for the additional additive also apply
25 to the above lubricant composition.
A subject of the invention is also a composition of the additive-concentrate
type comprising:
- from 1 to 15% of tungsten disulphide nanoparticles,
30 - from 5 to 99% of at least one dispersant having a weight-average molecular
weight greater than or equal to 2000 Daltons.
All of the characteristics and preferences presented above for the tungsten
disulphide nanoparticles and for the dispersant also apply to the above composition.
Advantageously, the tungsten disulphide nanoparticles have a fullerene-type
35 structure.
In an embodiment, the invention relates to a composition of the additiveconcentrate
type comprising:
- from 1 to 15% of tungsten disulphide nanoparticles,
- from 15 to 89% of at least one dispersant having a weight-average molecular
5 weight greater than or equal to 2000 Daltons,
- from 10 to 59% of at least one additional additive.
All of the characteristics and preferences presented above for the tungsten
disulphide nanoparticles, for the dispersant and for the additional additive also apply
to the above composition. Advantageously, the tungsten disulphide nanoparticles
10 have a fullerene-type structure.
In an embodiment of the invention, at least one base oil can be added to the
composition of the additive-concentrate type according to the invention in order to
obtain a lubricant composition according to the invention. Advantageously, the base
15 oil is a base selected from the group formed by the bases of group Ill, the bases of
group IV, the bases of group V of the API classification and mixtures thereof.
In a preferred embodiment of the invention, the base oil is a mixture of bases
of group IV and group V of the API classification, preferably the base oil is selected
from the poly alpha olefins (PAO) and the esters and a mixture thereof. In a more
20 preferred embodiment of the invention, the base oil is a mixture of at least one poly
alpha olefin and at least one ester, preferably a polyol ester.
The parts
The lubricant composition according to the invention can lubricate at least
25 one mechanical part or mechanical component, in particular bearings, gears,
universal joints, transmissions, the pistons/rings/liners system, camshafts, clutch,
manual or automatic gearboxes, axles, rocker arms, housings etc.
In a preferred embodiment, the lubricant composition according to the
30 invention can lubricate a mechanical part or a metal component of the transmission,
clutch, manual or automatic gearboxes, preferably manual.
A subject of the invention is also a process for reducing the flaking of a
mechanical part, preferentially of a transmission component, advantageously of a
35 gearbox or an axle, comprising at least bringing the mechanical part into contact
with a lubricant composition as defined above or obtained from the composition of
the additive-concentrate type as defined above.
All of the characteristics and preferences presented for the lubricant
5 composition also apply to the process for reducing the flaking of a mechanical part
according to the invention.
A subject of the invention is also the use of a lubricant composition according
to the ir~vention for the lubrication of gearboxes or axles, preferentially the
10 gearboxes of motor vehicles.
In a preferred embodiment, the invention relates to the use of a lubricant
composition according to the invention for the lubrication of manual gearboxes of
motor vehicles.
15
All of the characteristics and preferences presented for the lubricant
composition also apply to the use for lubricating gearboxes according to the
invention.
20 A subject of the invention is also the use of a lubricant composition according
to the invention for reducing the flaking of a mechanical part, preferentially of a
transmission component, more preferentially of a gearbox or an axle.
In a preferred embodiment, the invention relates to the use of a lubricant
25 composition according to the invention for reducing the flaking of a manual gearbox.
All of the characteristics and preferences presented for the lubricant
composition also apply to the use for reducing the flaking according to the invention.
30 The different subjects of the present invention and their implementations will
be better understood on reading the following examples. These examples are given
as an indication, without being limitative in nature.
Fiaures:
Figure 1 shows a closed-loop power circulation bench comprising a
simulated gearbox (1 1 I), an electric motor (1 12), a torque meter (1 13), a torque
5 producing device (114), a gearbox comprising the torque to be tested (115), a
differential (1 16), a output shaft (1 17), an input shaft (1 18), a system for detecting
the formation of flakes (1 19), fifth gear (120), reverse gear (121), fourth gear (122),
third gear (123), second gear (124), first gear (125) and a drive belt (126).
10 Figure 2 is a photograph of a gearbox housing after 600h of testing on a
closed-loop power circulation bench with a composition according to the invention.
Figure 3 is a photograph of a gearbox housing after 400h of testing on a
closed-loop power circulation bench with a composition not according to the
invention.
15
Examples:
Example 1: assessment of the stabilitv of lubricant compositions accordina to
the invention
20 The stability of lubricant compositions according to the invention is assessed
by monitoring, over time, the concentration of tungsten disulphide nanoparticles in
the supernatant phase of the composition.
To this end, different lubricant compositions were prepared from the following
25 compounds:
- a base oil of group Ill,
- a mixture of 20% tungsten disulphide nanoparticles in active material in an
oil (NanoLub Gear Oil Concentrate marketed by the company Nanomaterials),
- dispersant 1: dispersant of the PIB succinimide type with a weight-average
30 molecular weight measured according to the standard ASTM D5296 equal to 1921
Da and a number-average molecular weight measured according to the standard
ASTM D5296 equal to 1755 Da,
- dispersant 2: dispersant of the PIB succinimide type with a weight-average
molecular weight measured according to the standard ASTM D5296 equal to 1514
35 Da and a number-average molecular weight measured according to the standard
ASTM D5296 equal to 1328 Da,
- dispersant 3: dispersant of the succinimide ester type with a weightaverage
molecular weight measured according to the standard ASTM D5296 equal
to 1132 Da and a number-average molecular weight measured according to the
standard ASTM D5296 equal to 1046 Da,
5 - dispersant 4: dispersant according to the invention of the PI6 succinimide
type with a weight-average molecular weight measured according to the standard
ASTM D5296 equal to 6370 Da and a number-average molecular weight mcasured
according to the standard ASTM D5296 equal to 2850 Da (OLOA 13000 from the
company Oronite),
10 - dispersant 5: dispersant according to the invention of the PI6 succinimide
type with a weight-average molecular weight measured according to the standard
ASTM D5296 equal to 3085 Da and a number-average molecular weight measured
according to the standard ASTM D5296 equal to 1805 Da.
The different compositions L, to L5 are described in Table I; the percentages
15 indicated correspond to percentages by mass.
Table I
Each of the compositions L1 to L5 was prepared according to the procedure
20 below:
- addition of the dispersant,
- addition of the dispersion of tungsten disulphide nanoparticles,
- magnetic stirring for 1 h,
- addition of the base oil,
. X ~ ; D ~ E L - + E, 1- 1~0- ZB1.5-. 16 1
Compositions
Base oil of
group Ill
Tungsten
disulphide
nanoparticles
(NanoLub
Gear Oil
L 1
(comparative)
89
1
L4
(invention)
89
1
L5
(invention)
89
1
L2
(comparative)
89
1
L3
(comparative)
89
1
- stirring with heating at 60-70°C for 1 h,
- stirring without heating overnight (approximately 16h),
- ultrasound bath for 15 min.
5 The protocol for monitoring, over time, the concentration of tungsten
disulphide nanoparticles in the supernatant phase for each of the compositions L1 to
L5 is defined as follows:
i) Calibration curve at t = Oh, giving the absorbance as a function of the
content of tungsten disulphide nanoparticles,
10 ii) 3 to 4 samples of different masses of the composition after stirring in the
ultrasound bath for 15 min,
iii) Addition of 20 ml of cyclohexane,
iv) Measurement of the absorbance (wavelength fixed at 490 nm),
v) Plotting the absorbance curve as a function of the concentration of
15 tungsten disulphide nanoparticles (calculated from the sampled mass, the initial
concentration of nanoparticles in the composition, the volume of cyclohexane added
and density of the cyclohexane); the curve thus formed is a straight line representing
the standard straight line characteristic of the composition tested,
vi) Placing in a test-tube, 100 ml of composition and storage at ambient
20 temperature,
vii) Sampling a mass to be weighed and adding 20 ml of cyclohexane,
viii) Measurement of the absorbance (wavelength fixed at 490 nm),
ix) Calculation of the concentration of nanoparticles in the supernatant phase
based on the standard straight line,
25 x) Repetition of stages vi) to ix) at regular time intervals thus making it
possible to determine the concentration of tungsten disulphide nanoparticles in the
supernatant phase as a function of time.
The results are summarized in Table II and correspond to the mass
30 concentration of tungsten disulphide nanoparticles in the supernatant phase; they
are expressed as a percentage by mass.
The higher the percentage and the closer it is to 1, the better the dispersion
of the tungsten disulphide nanoparticles in the lubricant composition and thus the
better the stability of the lubricant composition.
35
$&.
Table II
d = day
The results show that the lubricant compositions according to the invention
5 L4 and L5, comprising 0.2% by weight of tungsten disulphide nanoparticles and a
dispersant having a weight-average molecular weight greater than or equal to 2000
Daltons, have an improved stability with respect to lubricant compositions
comprising 0.2% by weight of tungsten disulphide nanoparticles and a dispersant
having a weight-average molecular weight less than 2000 Daltons.
10
It should be noted that this stability persists over time for the lubricant
compositions according to the invention L4 and L5, which is not at all the case for the
other compositions L,, L2 and LS.
.
15
Example 2: assessment of the friction properties of the lubricant
compositions accordinq to the invention
The impact of the combination of tungsten disulphide nanoparticles and a
dispersant having a weight-average molecular weight greater than or equal to 2000
20 Daltons on the friction properties of a lubricant composition is assessed by a
Cameron Plint Friction laboratory test using a reciprocating tribometer of the
Cameron-Plint TE-77 type.
L1
L2
L3
L4
L5
To this end, two lubricant compositions were prepared from the following
25 compounds:
- base oil 1: base oil of the poly-alpha-olefin PA0 8 type with a kinematic
viscosity measured at 100°C of 8 mm2/s,
- base oil 2: polyol ester ('s Priolube 3970 from the company Croda),
- polymer 1': ethylenelpropylene copolymer (Lucant HC600 from the
30 company Mitsui Chemicals),
- polymer 2: Poly Alpha Olefin (Spectrasyn 1000 from the company Exxon),
9 to 15d
0.01
0.06
0.14
0.77
0.96
29 to35d
0.01
0.03
0.01
0.75
0.69
49to55 d
0
0.01
0.02
0.61
0.79
Morethan 100d
0
0.01
0.01
0.34
0.28
- silicone-containing anti-foaming agent,
- a mixture of 20% tungsten disulphide nanoparticles as active ingredient in
an oil (NanoLub Gear Oil Concentrate marketed by Nanomaterials),
- dispersant: dispersant according to the invention of the PIB succinimide
5 type having a weight-average molecular weight measured according to the standard
ASTM D5296 equal to 6370 Da and a number-average molecular weight measured
according to the standard ASTM 05296 equal to 2850 Da (OLOA 13000 from the
company Oronite),
- Friction modifier: molybdenum dithiocarbamate (Molyvan 855 from the
10 company Vanderbilt),
-Additive package 1 (Anglamol 2198 from the company Lubrizol) also
containing a mixture of an aminated anti-oxidant and a phenolic anti-oxidant.
The different lubricant compositions L6 to L7 are described in Table Ill; the
percentages indicated correspond to percentages by mass.
15
Table Ill
The composition L6 is a lubricant composition conventionally used for
lubricating transmissions, and in particular motor vehicle gearboxes.
20 The kinematic viscosity at 100°C of the compositions L6 and L7 was adjusted
in order to be identical, in particular by the content of base oils 1, so as to be able to
compare these two compositions.
Compositions
Base oil 1
Base oil 2
Polymer 1
Polymer 2
Anti-foaming agent
Tungsten disulphide
nanoparticles (NanoLub Gear
Oil Concentrate marketed by
Nanomaterials)
Dispersant
Friction modifier
Additive package 1
Kinematic viscosity at 100°C
measured according to the
standard ASTM D445 (mm2/s)
L6
(comparative)
62.95
15
10
5
0.05
0.5
6.5
14.5
L7
(invention)
61.95
15
10
5
0.05
2
2
0.5
3.5
14.5
The coefficient of friction of each composition was assessed by means of a
Cameron Plint Friction laboratory test using a reciprocating tribometer of the
Cameron-Plint TE-77 type. The test bench is constituted by a cylinder-on-flat
tribometer immersed in the lubricant composition to be tested. The coefficient of
5 - friction is monitored throughout the test by measuring the tangential force over the
normal force. A cylinder (SKF 100C6) having a length of 10 mm and diameter of 7
mm is applied to the steel flat immersed in the lubricant composition to be tested,
the temperature of the lubricant composition is set at each test. A sinusoidal
reciprocating movement is: applied with a defined frequency. Each measurement is
10 carried out over a period of 100 seconds during the test.
The values of the average coefficient of friction taken at different
temperatures, loads and speeds, for each of the compositions L6 and L7 are
indicated in Table IV.
15 Table IV
The average coefficient of friction at 60°C was measured under different
loads ranging from 300 MPa to 650 MPa and at different speeds ranging from 70
mmls to 550 mmls.
20.
The average coefficient of friction at 100°C was measured under different
loads ranging from 300 MPa to 650 MPa and at different speeds ranging from 70
mmls to 550 mmls.
Average coefficient of friction at 60°C
Average coefficient of friction at 100°C
Average coefficient of friction under a
load of 650 MPa
25 The average coefficient of friction under a load of 640 MPa was measured at
different temperatures ranging from 60°C to 140°C and at different speeds ranging
from 70 mmls to 550 mmls.
The results show that the presence of the combination of tungsten disulphide
30 nanoparticles and a dispersant having a weight-average molecular weight greater
L6
(comparative)
0.087
0.089
0.072
L7
(invention)
0.082
0.104
0.078
than or equal to 2000 Daltons according to the invention in a lubricant composition
do not alter, or only slightly alter, the friction properties of this composition.
Example 3: assessment of the anti-flakinq properties of the lubricant
5 compositions accordinq to the invention
The anti-flaking properties of a lubricant composition according to the
invention are assessed by implementing a test on a closed-loop power circulation
bench.
10 To this end, the lubricant composition according to the invention L8 and the
composition L9 not according to the invention, the com.positions of which are
described in Table V, were prepared; the percentages indicated correspond to
percentages by mass.
15 Table V
The base oils 1 and 2, the polymers 1 and 2, the anti-foaming agent,
dispersant and additive package 1 are identical to those described in Example 2.
The additive package 2 (Anglamol 2190 from the company Lubrizol) comprises a
20 zinc dithiophosphate as friction modifier.
The closed-loop power circulation bench is represented in Figure 1.
A Renault JR5 gearbox is installed in a power recirculation loop and placed
under load by means of a torsion system, the gearbox being engaged in 3rd gear.
25 The machine is put into operation using an electric motor in order to obtain a
rotation speed of 3000 rpm under a torque of 148 N.m at the gearbox input.
* .-.- I P ~D E L ~ I 1 6-1 8-z ,a!1.%&. .b-.-. .= a O
Lg
(comparative)
62.45
15
10
5
0.05
3.5
4
Compositions
Base oil 1
Base oil 2
Polymer 1
Polymer 2
Anti-foaming agent
Tungsten disulphide
nanoparticles (NanoLub Gear
Oil Concentrate marketed by
Nanomaterials)
Dispersant
Additive package 1
Additive package 2
L8
(invention)
62.45
15
10
5
0.05
2
2
3.5
The assessment criterion, and therefore the critical part to be assessed
(because of the load supported), is the drive pinion of the output shaft.
The gearbox is inspected at regular intervals of approximately 150h after
5 dismantling and visual scoring. The visual scoring is carried out using the "Chrysler"
scoring system for monitoring the presence of flakes on the teeth of the drive pinion
with, moreover, continuous vibration monitoring in order to detect the appearance of
flaking in the gearbox during operation.
The "Chrysler" scoring system consists of noting the state of the teeth nf the
10 drive pinion after testing. Each tooth of the pinion is thus examined in order to
monitor any presence of flaking(s) and a score is assigned to each flaking level.
The scoring system is defined as follows:
- Score = 0 if the Flaking Surface (FS) on a tooth is equivalent to 0
mm2
15 - Score = 0.4 if FS I 1 mm2
- Score = 1.3 if 1 cFS13mm2
- Score = 4 if 3 c FS I 7 mm2
- Score = 12 if 7 c F S I 16mm2
- Score = 36 if 16c FSc36 mm2
20 - Score = 108 if FS 1 36 mm2
The total score is based on the following formula: 0.4 x A + 1.3 x B + 4 x C +
12 x D + 36 x E + 108 x F in which A, B, C, Dl E and F represent the number of
teeth with the same level of degradation, on one and the same pinion.
25 Vibration monitoring consists of placing an accelerometer close to the test
piece and noting the intensity of the vibrations during operation. In the case of
degradation of a part, the intensity of the vibrations increases. It is sufficient to set a
threshold for stopping the device and verifying the appearance of flakes on the
teeth.
3 0 In order to prevent untimely degradation of the pinion which would not be
linked to the lubricant (but to metallic debris caused by the degradation of the other
parts), the shaft bearings and the 3rd gear pinion are normally replaced every 150h.
The test is stopped when a flake of 12mm2 maximum is observed and/or
when 80 mm2 of flaked surface in total is observed and/or at 312h when no flaking
35 has appeared after this period.
The results of the test obtained with the lubricant composition L8 are the
following:
-the test has been running for 600h without any replacement of parts in the
gearbox and without observing the slightest flaking either on the drive pinion or on
5 the 3rd gear pinion,
- no excessive deposit of tungsten disulphide nanoparticles has been
observed in the housing.
As for the lubricant composition L9, the test had to be stopped after 125h,
several flakes having been observed.
10
Example 4: assessment of the stabilitv properties after use of the lubricant
compositions accordinq to the invention
The risk of deposit of nanoparticles contained in a composition according to
15 the invention after the implementation of testing on a closed-loop power circulation
bench is assessed.
To this end, the lubricant composition according to the invention Llo and the
composition LI1 not according to the invention, the compositions of which are
20 described in Table VI were prepared; the percentages indicated correspond to
percentages by mass.
Table VI
25 The base oils 1 and 2, the polymers 1 and 2, the anti-foaming agent, the
dispersant and the additive package 1 are identical to those described in Example 2.
Compositions
Base oil 1
Base oil 2
Polymer 1
Polymer 2
Anti-foaming agent
Tungsten disulphide
nanoparticles (NanoLub Gear
Oil Concentrate marketed by
Nanomaterials)
Dispersant
Additive package 1
I Q O DELHI 3.6-16-LQ315.16:OQ
Llo
(invention)
60.45
15
10
5
0.05
4
2
3.5
LII
(comparative)
62.45
15
10
5
0.05
4
3.5
3 0
The test conditions are identical to those described in Example 3.
Figure 2 shows that no excessive deposit (200) of tungsten disulphide
nanoparticles was observed in the housing after testing with the composition
5 according to the invention Llo.
As for the composition LI1, Figure 3 shows an excessive deposit (300) of
tungsten disulphide nanoparticles in the housing after testing with the composition
Lll, which can thus give rise to a risk of obstructing the lubricating holes of the
bearings or also of the synchronizers.
10
Thus, the examples above show that the lubricant compositions according to
the invention have both good stability over time and good anti-flaking properties,
while retaining satisfactory friction reduction properties.

Claims
1. Lubricant composition comprising at least one base oil, at least one
dispersant having a weight-average molecular weight greater than or equal to 2000
5 Daltons and metal nanoparticles in a content by weight ranging from 0.01 to 2% with
respect to the total weight of the lubricant composition, the metal nanoparticles
being concentric polyhedrons with a multilayer or sheet structure.
2. Lubricant composition according to claim 1 in which the metal of which the
10 metal nanoparticle is constituted is selected from the group formed by tungsten,
molybdenum, zirconium, hafnium, platinum, rhenium, titanium, tantalum, niobium,
zinc, cerium, aluminium, indium and tin.
3. Lubricant composition according to claim 1 or 2 in which the metal
15 nanoparticles are selected from the group formed 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, preferentially from MoS2, MoSe2, WS2,
WSe2, advantageously WS2.
20 4. Lubricant composition according to any one of the preceding claims in
which the content by weight of metal nanoparticles ranges from
0.05 to 2%, preferably from 0.1 to I%, advantageously from 0.1 to 0.5% with respect
to the total weight of the lubricant composition.
25 5. Lubricant composition according to any one of the preceding claims in
which the average size of the metal nanoparticles ranges from
5 to 600 nm, preferably from 20 to 400 nm, advantageously from 50 to 200 nm.
6. Lubricant composition according to any one of the preceding claims in
30 which the dispersant is selected from the compounds comprising at least one
succinimide group, the polyolefins, the olefin copolymers, the copolymers
comprising at least one styrene unit, the polyacrylates or derivatives thereof.
7. Composition according to any one of the preceding claims in which the
35 dispersant is selected from the compounds comprising at least one substituted
succinimide group or the compounds comprising at least two substituted
succinimide groups, the succinimide groups being linked at their carbon-containing
vertex bearing a nitrogen atom by a polyamine group.
8. Lubricant composition according to any one of the preceding claims in
which the dispersant has a weight-average molecular weight ranging from 2000 to
15000 Daltons, preferably ranging from 2500 to 10000 Daltons, advantageously
from 3000 to 7000 Daltons.
5
9. Composition according to any one of the preceding claims in which the
dispersant also has a number-average molecular weight oreater than or equal to
1000 Daltons, preferably ranging from 1000 to 5000 Daltons, more preferentially
from 1800 to 3500 Daltons, advantageously trom 1800 to 3000 Daltons.
10
10. Lubricant composition according to any one of the preceding claims in
which the content by weight of dispersant ranges from 0.1 to 10% with respect to the
total weight of the lubricant composition.
15 11. Composition according to any one of the preceding claims in which the
base oil is selected from the poly alpha olefins or the esters, preferably the polyol
esters or mixtures thereof.
12. Lubricant composition according to any one of the preceding claims also
20 comprising at least one additional additive selected from the polymeric viscosity
index improvers and the antioxidants or mixtures thereof, the polymeric viscosity
index improvers being selected from the ethylene and alpha-olefin copolymers, in
particular the ethylene and propylene copolymers.
25 13. Lubricant composition according to claim 12 in which the additional
additive is an antioxidant selected from the dialkylphenylamines, phenolic
antioxidants or mixtures thereof.
14. Transmission oil comprising a lubricant composition according to any one
30 of claims 1 to 13.
15. Use of a lubricant composition according to any one of claims 1 to 13 for
the lubrication of gearboxes or axles, preferentially motor vehicle gearboxes.
3 5 16. Use of a lubricant composition according to the preceding claim for which
the gearbox is a manual gearbox.
I Q O DELHI 16- 10-
17. Use of a lubricant composition according to any one of claims 1 to 13 for
reducing the flaking of a mechanical part, preferentially a transmission component,
more preferentially a gearbox or an axle.
5 18. Use of a lubricant composition according to the preceding claim for which
the gearbox is a manual gearbox.
19. Composition of the additive-concentrate type comprising tungsten
disulphide nanoparticles and at least one dispersant having a weight-average
10 molecular weight greater than or equal to 2000 Daltons.