extracted from wipo:
formulas and tables are not copied:
FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
& The Patent Rules, 2003
COMPLETE SPECIFICATION
1.TITLE OF THE INVENTION:
COMPOSITION FOR COOLING AND LUBRICATING A PROPULSION SYSTEM OF
AN ELECTRIC OR HYBRID VEHICLE
2. APPLICANT:
Name: TOTAL MARKETING SERVICES
Nationality: France
Address: 24 Cours Michelet, 92800 PUTEAUX, France.
3. PREAMBLE TO THE DESCRIPTION:
The following specification particularly describes the invention and the manner in which it
is to be performed:
2
The present invention relates 5 to the field of
lubricant compositions for a propulsion system of an electric
or hybrid vehicle. It thus aims to propose a composition
having both properties of lubrication with respect to the
transmission of the propulsion system, of cooling of the
10 power electronics and battery, and the two properties
combined with respect to the motor in a propulsion system of
an electric or hybrid vehicle.
The evolution of international standards for reducing
CO2 emissions, but also for lowering energy consumption, is
15 encouraging car manufacturers to propose solutions that are
alternatives to combustion engines.
One of the solutions identified by car manufacturers
consists of replacing combustion engines with electric
motors. Research for reducing CO2 emissions has therefore led
20 to the development of electric vehicles by a number of car
companies.
"Electric vehicle" means, in the sense of the present
invention, a vehicle comprising an electric motor as the sole
means of propulsion, in contrast to a hybrid vehicle, which
25 comprises a combustion engine and an electric motor as
combined means of propulsion.
"Propulsion system" means, in the sense of the
present invention, a system comprising the mechanical
components necessary for the propulsion of an electric
30 vehicle. The propulsion system thus includes more
particularly an electric motor, or the rotor-stator assembly
of the power electronics (dedicated to the regulation of
speed), a transmission and a battery.
Generally, it is necessary to employ, in electric or
35 hybrid vehicles, compositions for meeting the dual constraint
of lubrication and cooling of the various components of the
propulsion system mentioned above.
3
Regarding the electric motor itself, the lubricant
composition plays a combined role of lubrication and cooling.
Regarding the power electronics, the composition provides
cooling. The transmission is lubricated 5 by the composition
and finally the batteries are cooled by said composition.
A composition as defined according to the invention
plays a combined role of lubrication and cooling.
Lubricant compositions, also called "lubricants", are
10 commonly used in motors for the main purposes of reducing the
frictional forces between the various moving metal parts in
motors. They are in addition effective for preventing
premature wear or even damage of these parts, and in
particular of their surface.
15 For this purpose, a lubricant composition consists
conventionally of one or more base oils, which are generally
combined with several additives designed to stimulate the
lubrication performance of the base oils, for example such as
friction modifier additives.
20 Moreover, electric propulsion systems generate heat
during operation, from the electric motor, the power
electronics and the batteries. As the quantity of heat
generated is greater than the quantity of heat normally
dissipated to the environment, it is necessary to provide
25 cooling of the motor, the power electronics and the
batteries. Generally cooling is carried out on several parts
of the propulsion system generating heat and/or the parts of
said system that are sensitive to heat, in order to avoid
reaching dangerous temperatures, and notably the power
30 electronics and the batteries.
Furthermore, for obvious safety reasons, it is
important that the fluid for cooling an electric propulsion
system has low flammability.
Conventionally, it is known to cool electric motors
35 with air, with water optionally combined with glycol, or with
an oil jet.
4
Document WO 2011/113851 describes the use of a
lubricant composition comprising a base oil, preferably a
polyalphaolefin (PAO) or GTL, for cooling an electric motor
of a hybrid vehicle or of a vehicle equipped with a kinetic
energy recovery system (KERS). However, 5 the compositions
described are optimized for motors of hybrid vehicles or of
KERS systems, and their cooling properties will not be
adequate for use in a fully electric drive system. In fact, a
motor of an electric vehicle is subjected to much larger
10 stresses than an electric motor of a hybrid vehicle, owing to
a higher frequency of use, which requires the use of an oil
with enhanced cooling properties.
We may also cite document JP 2012/184360, which
describes a lubricant composition comprising a synthetic base
15 oil and a fluorinated compound for cooling an electric motor.
However, the hydrochlorofluorocarbons present in these
compositions are organic gases that have a significant
negative impact on the ozone layer and are powerful
greenhouse gases. The fluorinated gases are also subject to
20 several regulations that aim to limit their use
substantially.
It is true that document US 716 086 dating from 1951
proposes employing a diester in lubricant compositions.
However, this use is considered in a context that is very
25 different from that of the invention. Firstly, the lubricant
compositions considered in patent US 716 086 do not conform
to those considered according to the invention and are
notably intended to be used in aircraft engines, which are
exposed to very large temperature variations. The synthetic
30 esters are described there as being more useful than mineral
oils insofar as they possess higher viscosity indexes and
flash points, and lower pour points than the mineral oils of
comparable viscosity.
35 For obvious reasons of economy and ease of use, it
would be advantageous to have a composition allowing the
5
needs for lubrication and cooling of a propulsion system of
an electric or hybrid vehicle to be met simultaneously.
Unfortunately, these two properties, lubrication and
cooling, at first glance impose opposite constraints. In
fact, for optimal cooling of an electric 5 motor, it is known
to employ products, such as water, that are as fluid as
possible. Now, such fluids do not provide a good level of
lubrication. Conversely, compositions of high viscosity, able
to provide a good level of lubrication and protection of
10 parts in contact against wear, do not have a satisfactory
cooling potential.
The present invention precisely aims to propose a new
composition allowing the lubrication and cooling of the
15 aforementioned elements of the propulsion system to be
satisfied simultaneously.
More precisely, the inventors discovered that it is
possible to provide the multiple function of lubrication and
cooling of a propulsion system of an electric or hybrid
20 vehicle, using at least diester of formula (I) as defined
hereunder, in a lubricant composition.
The composition thus formed may thus be brought into
direct contact with the propulsion system, to cool the motor,
the power electronics and the battery by means of this direct
25 contact of said composition on these parts, while also
providing lubrication thereof.
The composition thus in direct contact with these
parts provides better cooling than conventional air cooling,
and water cooling with indirect contact. This bringing into
30 direct contact allows better heat dissipation.
In fact, air cooling allows direct cooling, but air
is a very poor fluid for heat dissipation. Conversely, water
is a high-performance fluid for cooling but is incompatible
with direct contact with the motor, the power electronics and
35 the battery.
6
Thus, according to a first aspect, the present
invention relates to the use, for cooling and lubricating a
propulsion system of an electric or hybrid vehicle, of a
composition comprising at least:
(i) at least 5 one base oil; and
(ii) at least one diester of formula (I), different
than the base oil (i):
Ra-C(O)-O-([C(R)2]n-O)s-C(O)-Rb (I)
in which:
10 - R represent, independently of one another, a hydrogen
atom or a (C1-C5)alkyl group, linear or branched, in
particular a methyl, ethyl or propyl group, notably methyl;
- s has a value of 1 or 2;
- n has a value of 1, 2 or 3; it being understood that,
15 when s is different from 1, n may be identical or
different; and
- Ra and Rb, which may be identical or different, represent
independently of one another, hydrocarbon groups, saturated
or unsaturated, linear or branched, having a linear chain
20 with 2 to 11 carbon atoms, preferably with 3 to 8 carbon
atoms;
provided that, when s has a value of 2 and n, which are
identical, have a value of 2, at least one of the groups R
represents a (C1-C5)alkyl group, linear or branched; and
25 provided that, when s has a value of 1 and n has a value of
3, at least one of the groups R bound to the carbon in the
beta position of the oxygen atoms of the ester functions
represents a hydrogen atom.
30 More particularly, the lubricant composition, with
said additives, is intended to be brought into direct contact
with the batteries of electric vehicles, notably Li-ion or
Ni-Cd batteries, which are notably immersed or semi-immersed,
static or circulating, in said lubricant composition with
35 additives, or composition employed according to the
invention, or else sprayed directly in the form of oil spray,
jet, or mist.
7
A composition as defined according to the invention
allows efficient cooling of the battery present in an
electric or hybrid vehicle.
The cooling properties of an ester required according
to the invention can be determined by measuring 5 the thermal
conductivity, denoted λ, and the heat capacity, denoted Cp,
of said ester.
The thermal conductivity characterizes the behavior
of a material during heat transfer by conduction. It
10 represents the energy (quantity of heat) transferred per unit
area and unit time under a temperature gradient of 1 kelvin
per meter. The higher the thermal conductivity, the more the
material is a conductor of energy and will have the capacity
to dissipate heat.
15 Thermal conductivity can be measured according to
standard ASTM D7896.
Heat capacity (or calorific capacity) makes it
possible to quantify the capacity of a body to absorb or
restore energy by heat exchange during a temperature change.
20 The higher the heat capacity, the more the body is a
conductor of energy and will have the capacity to dissipate
heat.
Heat capacity can be measured by differential
scanning calorimetry (DSC) according to standard ASTM E1269.
25 The inventors found, surprisingly, that the diesters
of formula (I) required according to the invention have high
values of conductivity and heat capacity, as demonstrated in
example 1 hereunder.
In fact, the values obtained demonstrate that a
30 diester of formula (I) as defined above has the capacity to
dissipate heat effectively. Its use in a composition
comprising at least one base oil thus makes it possible to
endow said composition with properties of cooling the parts
with which it is in contact, in particular a battery of an
35 electric or hybrid vehicle.
A composition employed according to the invention is
moreover able to provide lubrication of the propulsion system
8
of an electric or hybrid vehicle, and more particularly the
electric motor itself and the transmission.
Advantageously, a composition as defined according to
the invention makes it possible to provide lubrication of the
transmission, in particular the reduction 5 gearing, of an
electric or hybrid vehicle.
Thus, this single composition employed according to
the invention makes it possible to provide both cooling of
the motor, the power electronics and the battery, notably an
10 Li-ion or Ni-Cd battery, as well as lubrication of the
electric motor and transmission, in particular reduction
gearing, in an electric or hybrid vehicle.
Furthermore, the use of at least one diester of
formula (I) as defined above in at least one base oil
15 advantageously makes it possible to increase the flammability
temperature of the base oil.
Thus, a composition employed according to the
invention has a quite particularly advantageous hightemperature
flammability.
20 Also advantageously, the use of at least one diester
of formula (I) as defined above, in at least one base oil,
makes it possible to increase the life of said composition.
In fact, it is known that prolonged use of a
lubrication and/or cooling composition induces a reduction in
25 volume of composition due to its evaporation, and therefore
degradation of the properties of said composition over time.
Now, the inventors found, surprisingly, that, as
demonstrated in example 2 hereunder, a diester of formula (I)
required according to the invention has higher evaporation
30 times, and therefore a lower volatility, compared to those
observed for diesters not according to the invention, in
particular corresponding to formula (I) defined above for
which s would have a value of 3.
Volatility can be measured by thermogravimetric
35 analysis, or TGA, according to standard ASTM D6375.
Thus, a diester of formula (I) according to the
invention endows a composition, in which it is used, with
9
advantageous properties, in particular of lubrication and of
cooling, over a longer time of use, thereby extending the
oil-changing interval. This criterion is particularly
important for the parts of the propulsion system that are
difficultly accessible and for which oil 5 changes may prove
complex, such as batteries.
Therefore, according to another of its aspects, the
present invention relates to the use of a diester of formula
(I) as defined above, in a composition for cooling and
10 lubricating a propulsion system of an electric or hybrid
vehicle, comprising at least one base oil, to increase the
oil-changing interval of the propulsion system, in particular
the battery thereof.
15 The present invention further relates to a method of
cooling and lubricating a propulsion system of an electric or
hybrid vehicle, comprising at least one step of bringing at
least one mechanical component of said system into contact
with a composition as described according to the invention.
20 Other features, variants and advantages of using a
composition defined according to the invention will become
clearer on reading the description and the figure given
hereunder.
25 Hereinafter, the expressions "between … and …",
"ranging from … to …" and "varying from … to …" are
equivalent and are intended to signify that the limits are
included, unless stated otherwise.
Unless stated otherwise, the expression "comprising
30 a/one" is to be understood as "comprising at least a/one".
Fig. 1 is a schematic representation of an electric
or hybrid propulsion system.
COMPOSITION
35 As stated above, a composition employed according to
the invention comprises at least (i) a base oil or fluid base
10
as explained hereunder, and (ii) at least one diester of
formula (I) defined in detail hereunder.
More particularly, a composition employed according
to the invention may have a kinematic viscosity, measured at
100°C according to standard ASTM D445, between 5 2 and 8 mm²/s,
preferably between 3 and 7 mm²/s.
Advantageously, a lubricant composition employed
according to the invention may be of a grade according to the
SAEJ300 classification defined by the formula (X)W(Y), in
10 which X represents 0 or 5; and Y represents an integer from 4
to 20, in particular from 4 to 16 or from 4 to 12.
Base oil
15 A composition employed according to the invention
comprises at least one base oil, in particular a fluid base
formed from one or more base oils, having a kinematic
viscosity, measured at 100°C according to standard ASTM D445,
from 1.5 to 8 mm²/s, in particular from 1.5 to 6.1 mm²/s,
20 more particularly from 1.5 to 4.1 mm²/s, even more
particularly from 1.5 to 2.1 mm²/s.
This base oil may be a mixture of several base oils,
namely a mixture of 2, 3 or 4 base oils.
Hereinafter, the designation "fluid base" will denote
25 the oil or the mixture of base oils having a kinematic
viscosity measured at 100°C according to standard ASTM D445
from 1.5 to 8 mm²/s.
The base oil present in a lubricant composition
30 employed according to the invention may be selected from the
oils of mineral or synthetic origin belonging to groups I to
V according to the classes defined in the API classification
(or their equivalents according to the ATIEL classification)
and presented in Table A below or mixtures thereof, provided
35 that the oil or the mixture of oils has the desired viscosity
stated above.
11
Saturates
content
Sulfur
content
Viscosity
index (VI)
Group I
Mineral oils
< 90% > 0.03% 80 ≤VI < 120
Group II
Hydrocracked
oils
≥90% ≤0.03% 80 ≤VI < 120
Group III
Hydrocracked or
hydro-isomerized
oils
≥90% ≤0.03% ≥120
Group IV Polyalphaolefins (PAO)
Group V
Esters and other bases not included in
groups I to IV
Table A
The mineral base oils include all types of base oils
obtained by atmospheric and vacuum distillation of crude oil,
followed by refining operations such as solvent 5 extraction,
deasphalting, solvent dewaxing, hydrofining, hydrocracking,
hydroisomerization and hydrofinishing.
Mixtures of synthetic and mineral oils, which may be
biosourced, may also be used.
10 Generally there is no limitation regarding the use of
different base oils for preparing the compositions employed
according to the invention, except that they must, besides
meeting the aforementioned viscosity criterion, have
properties, notably of viscosity index, sulfur content or
15 resistance to oxidation, suitable for use for propulsion
systems of an electric or hybrid vehicle.
The base oils of the compositions employed according
to the invention may also be selected from synthetic oils,
such as certain esters of carboxylic acids and of alcohols,
20 polyalphaolefins (PAOs), and polyalkylene glycols (PAGs)
obtained by polymerization or copolymerization of alkylene
12
oxides comprising from 2 to 8 carbon atoms, in particular
from 2 to 4 carbon atoms.
The PAOs used as base oils are for example obtained
from monomers comprising from 4 to 32 carbon atoms, for
example from 5 octene or decene.
The weight-average molecular weight of the PAO may
vary quite widely. Preferably, the weight-average molecular
weight of the PAO is below 600 Da. The weight-average
molecular weight of the PAO may also range from 100 to 600
10 Da, from 150 to 600 Da, or from 200 to 600 Da.
For example, the PAOs used in the context of the
invention, having a kinematic viscosity, measured at 100°C
according to standard ASTM D445, from 1.5 to 8 mm²/s are sold
commercially by Ineos under the brands Durasyn® 162, Durasyn®
15 164, Durasyn® 166 and Durasyn® 168.
Advantageously, the base oil or oils of the
composition employed according to the invention are selected
from the polyalphaolefins (PAOs).
20 Preferably, a composition employed according to the
invention comprises a fluid base formed from one or more base
oils having a kinematic viscosity measured at 100°C according
to standard ASTM D445 between 1.5 and 8 mm²/s.
In other words, a composition employed according to
25 the invention may be free from base oil or mixture of base
oils not meeting the criterion of kinematic viscosity
measured at 100°C according to standard ASTM D445, in
particular free from oil or mixture of base oils having a
viscosity above 9 mm²/s.
30 A person skilled in the art is able to adjust the
content of fluid base to be used in a composition employed
according to the invention to achieve the viscosity desired
for the composition.
As stated above, the fluid base notably provides the
35 cooling potential of the composition employed according to
the invention. In particular, the fluidity of the base
notably ensures good cooling properties when using the
13
composition in contact with the batteries of a propulsion
system of an electric or hybrid vehicle.
The cooling properties of the composition employed
are further enhanced advantageously by the shearing applied
to the composition at the level of injection, 5 which brings
the fluid to a lower level of viscosity than at rest.
In particular, a composition employed according to
the invention comprises 60% to 99.5% by weight, preferably
from 70% to 98%, even more preferably from 80% to 98%,
10 advantageously from 90% to 97% by weight of base oil, or
mixture of base oils, notably having a kinematic viscosity
measured at 100°C according to standard ASTM D445 from 1.5 to
8 mm2/s, relative to the total weight of the composition.
15 Diester of formula (I)
As stated above, a lubricant composition employed
according to the invention has for specificity to contain at
least one diester of general formula (I), different than the
base oil defined above,
20 Ra-C(O)-O-([C(R)2]n-O)s-C(O)-Rb
(I)
in which:
- R represent, independently of one another, a
hydrogen atom or a (C1-C5)alkyl group, linear or branched, in
25 particular a methyl, ethyl or propyl group, notably methyl;
- s has a value of 1 or 2;
- n has a value of 1, 2 or 3; in particular n has a
value of 2 or 3 and more particularly n has a value of 2, it
being understood that, when s is different from 1, n may be
30 identical or different; and
- Ra and Rb, which may be identical or different,
represent independently of one another, hydrocarbon groups,
saturated or unsaturated, linear or branched, having a linear
chain with 2 to 11 carbon atoms, preferably with 3 to 8
35 carbon atoms;
14
provided that, when s has a value of 2 and n, which are
identical, have a value of 2, at least one of the groups R
represents a (C1-C5)alkyl group, linear or branched; and
provided that, when s has a value of 1 and n has a value of
3, at least one of the groups R bound to 5 the carbon in the
beta position of the oxygen atoms of the ester functions
represents a hydrogen atom.
According to one embodiment, Ra and Rb, which may be
10 identical or different, represent independently of one
another, hydrocarbon groups, saturated or unsaturated, linear
or branched, comprising from 2 to 11 carbon atoms, preferably
from 3 to 8 carbon atoms.
15 Hereinafter, a diester of formula (I) required
according to the invention will be designated more simply as
diester of the invention.
Preferably, in the context of the invention:
- "Ct-z" where t and z are integers, means a carbon
20 chain that may have from t to z carbon atoms; for example C1-4
a carbon chain that may have from 1 to 4 carbon atoms;
- "alkyl" means a linear or branched saturated
aliphatic group; for example a C1-4-alkyl group represents a
carbon chain from 1 to 4 carbon atoms, linear or branched,
25 more particularly a methyl, ethyl, propyl, isopropyl, butyl,
isobutyl, tert-butyl.
Preferably, in the aforementioned formula (I), when s
is different from 1, all the n are identical.
30 In particular, n in the aforementioned formula (I)
has a value of 2 or 3, and more particularly n has a value of
2.
Preferably, at least one of the groups R represents a
(C1-C5)alkyl group, in particular (C1-C4)alkyl, linear or
35 branched, more preferably methyl, ethyl or propyl;
advantageously methyl.
15
According to a particularly preferred embodiment, the
diester of formula (I) required according to the invention
may more particularly be a diester of the following formula
(I'):
Ra-C(O)-O-([C(R)2]n-O)-([C(R')2]m-5 O)s-1-C(O)-Rb (I')
in which:
- R and R' represent, independently of one another, a
hydrogen atom or a (C1-C5)alkyl group, linear or branched, in
particular a methyl, ethyl or propyl group, notably a methyl
10 group;
- s has a value of 1 or 2;
- n has a value of 2;
- m has a value of 2;
- Ra and Rb, which may be identical or different,
15 represent independently of one another, hydrocarbon groups,
saturated or unsaturated, linear or branched, having a linear
chain with 2 to 11 carbon atoms, preferably with 3 to 8
carbon atoms;
provided that, when s has a value of 2, at least one of the
20 groups R or R' represents a (C1-C5)alkyl group, linear or
branched.
Preferably, a diester required according to the
invention is of formula (I') in which at least one of the R
or R' represents a (C1-C5)alkyl group, in particular (C1-
25 C4)alkyl, linear or branched, more preferably methyl, ethyl
or propyl; advantageously methyl.
According to a variant embodiment, s in the
aforementioned formula (I) or (I') has a value of 2.
30 In particular, the diester required according to the
invention may be of the following formula (I'a):
Ra-C(O)-O-([C(R)2]n-O)-([C(R')2]m-O)-C(O)-Rb
(I'a)
in which:
35 - R and R' represent, independently of one another, a
hydrogen atom or a (C1-C5)alkyl group, linear or branched, in
16
particular a methyl, ethyl or propyl group, advantageously
methyl;
- n has a value of 2;
- m has a value of 2;
- Ra and Rb, which may be identical 5 or different,
represent independently of one another, hydrocarbon groups,
saturated or unsaturated, linear or branched, having a linear
chain with 2 to 11 carbon atoms, preferably with 3 to 8
carbon atoms;
10 provided that at least one of the groups R or R' represents a
(C1-C5)alkyl group, linear or branched, in particular methyl,
ethyl or propyl, advantageously methyl.
Preferably, at least one of the groups R represents a
(C1-C5)alkyl group, linear or branched, in particular a
15 methyl, ethyl or propyl group, advantageously methyl; and at
least one of the R' represents a (C1-C5)alkyl group, linear
or branched, in particular a methyl, ethyl or propyl group,
advantageously methyl.
20 Even more preferably, the diester of the invention
may be of formula (I'a) in which one of the groups R
represents a (C1-C5)alkyl group, linear or branched, in
particular a methyl, ethyl or propyl group, advantageously
methyl; and one of the groups R' represents a (C1-C5)alkyl
25 group, linear or branched, in particular a methyl, ethyl or
propyl group, advantageously methyl; the other groups R and
R' representing hydrogen atoms.
In other words, according to a particular embodiment,
the diester of the invention may be of the following formula
30 (I''a):
Ra-C(O)-O-CHR1-CHR2-O-CHR3-CHR4-O-C(O)-Rb
(I''a)
in which:
- one of the groups R1 and R2 represents a (C1-
35 C5)alkyl group, linear or branched, the other one
representing a hydrogen atom;
17
- one of the groups R3 and R4 represents a (C1-
C5)alkyl group, linear or branched, the other one
representing a hydrogen atom; and
- Ra and Rb, which may be identical or different, are
5 as defined above.
In particular, the diester of the invention may be of
formula (I''a) in which:
- one of the groups R1 and R2 represents a methyl,
ethyl or propyl group, advantageously methyl, the other one
10 representing a hydrogen atom; and
- one of the groups R3 and R4 represents a methyl,
ethyl or propyl group, advantageously methyl, the other one
representing a hydrogen atom.
15 According to another variant embodiment, s in the
aforementioned formula (I) or (I') has a value of 1.
In other words, the diester required according to the
invention may be of the following formula (I'b):
Ra-C(O)-O-([C(R)2]n-O)-C(O)-Rb
20 (I'b)
in which:
- R represent, independently of one another, a
hydrogen atom or a (C1-C5)alkyl group, linear or branched, in
particular a methyl, ethyl or propyl group, advantageously
25 methyl;
- n has a value of 2;
- Ra and Rb, which may be identical or different,
represent independently of one another, hydrocarbon groups,
saturated or unsaturated, linear or branched, having a linear
30 chain with 2 to 11 carbon atoms, preferably with 3 to 8
carbon atoms.
Preferably, in the aforementioned formula (I'b), at
least one of the R represents a (C1-C5)alkyl group, linear or
branched, in particular a methyl, ethyl or propyl group,
35 advantageously methyl.
In particular, the diester of the invention may be of
formula (I'b) in which one of the groups R represents a (C1-
18
C5)alkyl group, linear or branched, in particular a methyl,
ethyl or propyl group, advantageously methyl, the other one
representing hydrogen atoms.
As stated above, Ra and Rb in 5 the aforementioned
formula (I), (I'), (I'a), (I''a) or (I'b), which may be
identical or different, represent hydrocarbon groups,
saturated or unsaturated, linear or branched, having a linear
chain with 2 to 11 carbon atoms, preferably with 3 to 8
10 carbon atoms.
"Hydrocarbon-containing" group means any group having
a carbon atom fixed directly to the rest of the molecule and
having mainly an aliphatic hydrocarbon character.
Preferably, Ra and Rb in the aforementioned formula
15 (I), (I'), (I'a), (I''a) or (I'b) have a linear chain of 3 to
6 carbon atoms.
According to a variant embodiment, Ra and Rb in the
aforementioned formula (I), (I'), (I'a), (I''a) or (I'b) have
a linear chain of 8 to 11 carbon atoms.
20 "Linear chain of t to z carbon atoms" means a
saturated or unsaturated, preferably saturated, carbon chain
comprising from t to z carbon atoms one after another, the
carbon atoms optionally present at the level of the branches
of the carbon chain not being taken into account in the
25 number of carbon atoms (t-z) making up the linear chain.
According to a particular embodiment, in the
aforementioned formula (I), (I'), (I'a), (I''a) or (I'b), Ra
and Rb, which may be identical or different, are of
vegetable, animal or petroleum origin.
30 According to a particular embodiment, in the
aforementioned formula (I), (I'), (I'a), (I''a) or (I'b), Ra
and Rb, which may be identical or different, represent
saturated groups.
According to another particularly preferred
35 embodiment, in the aforementioned formula (I), (I'), (I'a),
(I''a) or (I'b), Ra and Rb, which may be identical or
different, represent linear groups.
19
According to another particular embodiment, in the
aforementioned formula (I), (I'), (I'a), (I''a) or (I'b), Ra
and Rb represent saturated linear C8 to C11, in particular C8
to C10, hydrocarbon groups.
In particular, Ra and 5 Rb are identical.
Preferably, Ra and Rb both represent n-octyl or nundecyl,
preferably n-octyl, groups.
According to another particular embodiment, in the
10 aforementioned formula (I), (I'), (I'a), (I''a) or (I'b), Ra
and Rb represent branched hydrocarbon groups comprising from
2 to 11 carbon atoms, preferably from 3 to 8 carbon atoms.
According to this variant, Ra and Rb in the
aforementioned formula (I), (I'), (I'a), (I''a) or (I'b)
15 preferably have a linear chain of 3 to 7 carbon atoms
branched by at least one, preferably one, C1 to C6
hydrocarbon group, preferably a methyl or an ethyl.
In particular, Ra and Rb are identical.
Preferably, Ra and Rb both represent 2-methylheptyl
20 or 2-ethylhexyl groups.
The diesters of formula (I) required according to the
invention may be commercially available or prepared by
methods of synthesis described in the literature and familiar
25 to a person skilled in the art. These methods of synthesis
more particularly employ an esterification reaction between a
diol compound of formula HO-([C(R)2]n-O)s-OH and compounds of
formula Ra-COOH and Rb-COOH, where Ra and Rb, which may be
identical or different, are as defined above.
30 Of course, it is up to a person skilled in the art to
adjust the synthesis conditions to obtain the diesters
required according to the invention.
As examples, diesters of the aforementioned formula
(I), in particular of the aforementioned formula (I'), may be
35 obtained by an esterification reaction between a mono- or
polypropylene glycol, in particular monopropylene glycol
(MPG) or dipropylene glycol (DPG), diethylene glycol (DEG),
20
neopentyl glycol (NPG), preferably between dipropylene glycol
or diethylene glycol, and one or more suitable carboxylic
acids Ra-COOH and Rb-COOH, in particular selected from
nonanoic acid, dodecanoic acid, isononanoic acid, 2-
ethylhexanoic acid, and 5 mixtures thereof.
As an example, a diester or mixture of diesters of
formula (I') as defined above, where:
- s has a value of 2,
- one of the groups R representing a (C1-C5)alkyl
10 group, linear or branched, in particular a methyl, ethyl or
propyl group, advantageously methyl, the other one
representing hydrogen atoms; and
- one of the groups R' representing a (C1-C5)alkyl
group, linear or branched, in particular a methyl, ethyl or
15 propyl group, advantageously methyl, the other one
representing hydrogen atoms,
may be obtained by an esterification reaction between
dipropylene glycol (DPG) and one or more suitable carboxylic
acids Ra-COOH and Rb-COOH.
20 A diester of formula (I') as defined above, where
- s has a value of 1,
- one of the groups R representing a (C1-C5)alkyl
group, linear or branched, in particular a methyl, ethyl or
propyl group, advantageously methyl, the other one
25 representing hydrogen atoms,
may be obtained by an esterification reaction between
monopropylene glycol (MPG) and one or more suitable
carboxylic acids Ra-COOH and Rb-COOH.
In particular, in the case when Ra and Rb both
30 represent n-octyl or n-undecyl groups, said diester or
mixture of diesters may thus be obtained by an esterification
reaction between monopropylene glycol or dipropylene glycol
and nonanoic acid or dodecanoic acid.
According to one embodiment, a diester or diester
35 mixture required according to the invention may be obtained
by an esterification reaction between dipropylene glycol and
nonanoic acid, dodecanoic acid and mixtures thereof.
21
According to another embodiment, a diester or diester
mixture required according to the invention may be obtained
by an esterification reaction between diethylene glycol and
nonanoic acid.
According to another embodiment, a 5 diester or diester
mixture required according to the invention may be obtained
by an esterification reaction between neopentyl glycol and
nonanoic acid, isononanoic acid, 2-ethylhexanoic acid and
mixtures thereof.
10
The diester of formula (I) required according to the
invention advantageously has a kinematic viscosity measured
at 40°C according to standard ASTM D445 between 5 and
18 mm²/s, preferably between 8 and 15 mm²/s, and/or a
15 kinematic viscosity measured at 100°C according to standard
ASTM D445 between 1.5 and 9.3 mm²/s, preferably between 2 and
4 mm²/s.
The diester of formula (I) required according to the
invention advantageously has a thermal conductivity measured
20 at 30°C according to standard ASTM D7896, greater than or
equal to 100 mW/Km, preferably between 110 and 180 mW/Km
and/or a thermal conductivity measured at 130°C according to
standard ASTM D7896, greater than or equal to 90 mW/Km,
preferably between 95 and 160 mW/Km.
25 The diester of formula (I) required according to the
invention advantageously has a heat capacity measured at 20°C
according to standard ASTM E1269, greater than or equal to
1.5 J/K, preferably between 1.8 and 2.1 J/K and/or a heat
capacity measured at 80°C according to standard ASTM E1269,
30 greater than or equal to 2 J/K, preferably between 2.0 and
2.8 J/K.
The diester of formula (I) required according to the
invention advantageously has an evaporation time of 20 wt% of
said ester, measured according to standard ASTM D6375,
35 greater than or equal to 400 seconds, preferably between 410
and 600 seconds.
22
It is understood in the context of the present
invention that the diester of formula (I) as defined above
may be in the form of a mixture of diesters of formula (I) as
defined above.
According to the present invention, 5 the diester or
diesters of formula (I) may be present in a content between 1
and 30 wt%, relative to the total weight of the composition
employed according to the invention, in particular between 5
and 30 wt%, preferably between 5 and 25 wt%, and more
10 particularly between 10 and 25 wt%.
In terms of formulation of a composition employed
according to the present invention, all the methods known by
a person skilled in the art may be used for this additive
treatment of oil with at least one ester of dipropylene
15 glycol.
The diester or diesters of formula (I) as defined
above may be incorporated directly in the base lubricant oil.
According to a variant embodiment, a composition
20 employed according to the invention is formed, in other words
consists of a mixture of:
- a base oil, or mixture of base oils, having a
kinematic viscosity measured at 100°C according to standard
ASTM D445 from 1.5 to 8 mm2/s; and
25 - a diester of formula (I) as defined above.
Alternatively, a composition employed according to
the invention may further comprise one or more additional
additives as defined more precisely hereinafter.
30
Additional additives
According to a variant of the invention, a lubricant
composition employed according to the present invention may
further comprise at least one additive modulating the
35 properties of the base oil.
It is understood that the nature and the amount of
additives used are selected so as not to affect the combined
23
properties of cooling and lubricant power of the composition
employed according to the invention.
Hydrocarbon-containing fluid
A composition employed according to 5 the invention may
moreover use at least one hydrocarbon-containing fluid having
a boiling point greater than or equal to 50°C.
A hydrocarbon-containing fluid of this kind
preferably has a boiling point between 50 and 350°C, in
10 particular between 60 and 250°C, and even more particularly
between 80 and 200°C.
Preferably, the hydrocarbon-containing fluid has a
content of carbon of biological origin greater than or equal
to 90 wt%, relative to the total weight of the hydrocarbon15
containing fluid.
In the sense of the present invention, "hydrocarboncontaining
fluid" means any fluid comprising molecules of
saturated or unsaturated, linear hydrocarbons, which may also
20 comprise aromatic or cyclic groups, or also heteroatoms.
Advantageously, the hydrocarbon-containing fluid is
fully saturated. Preferably, the components of the
hydrocarbon-containing fluid are selected from isoparaffins
comprising 12 to 30 carbon atoms, preferably 13 to 19 carbon
25 atoms and more preferably 14 to 18 carbon atoms.
According to one embodiment, the hydrocarboncontaining
fluid comprises alkanes, or linear molecules of
saturated hydrocarbons with a noncyclic chain, in particular
30 comprising between 12 and 30 carbon atoms, in a content
between 80 and 100 wt%, relative to the total weight of the
hydrocarbon-containing fluid, or even between 90 and 100 wt%,
and for example between 95 and 100 wt%.
In the context of the present invention, "paraffins"
35 denote straight-chain hydrocarbons (also called "normal
paraffins") and/or branched-chain hydrocarbons (also called
"isoparaffins").
24
As heteroatoms, in the context of the present
invention, we may notably mention nitrogen and oxygen.
According to a particular embodiment of the
invention, the hydrocarbon-containing fluid comprises from 90
to 100 wt% of isoparaffins, a content of 5 normal paraffins
from 0 to 10 wt% and a content of carbons of biological
origin greater than or equal to 90 wt% relative to the total
weight of the hydrocarbon-containing fluid.
The hydrocarbon-containing fluid advantageously
10 comprises a content greater than or equal to 90 wt%, in
particular greater than or equal to 95 wt%, and even more
advantageously greater than or equal to 98 wt% of
isoparaffins, relative to the total weight of hydrocarboncontaining
fluid.
15 According to one embodiment, the isoparaffins present
in the hydrocarbon-containing fluid comprise from 12 to 30
carbon atoms, preferably from 13 to 19 carbon atoms and even
more preferably from 14 to 18 carbon atoms.
The hydrocarbon-containing fluid advantageously
20 comprises a content of normal paraffins less than or equal to
10 wt%, preferably less than or equal to 5 wt% and even more
preferably less than or equal to 2 wt%, relative to the total
weight of the hydrocarbon-containing fluid.
The isoparaffins are advantageously noncyclic
25 isoparaffins. Preferably, the hydrocarbon-containing fluid
has a weight ratio of isoparaffins to normal paraffins of at
least 12:1, preferably at least 15:1 and more preferably at
least 20:1. According to an even more particular embodiment,
the hydrocarbon-containing fluid does not comprise normal
30 paraffins.
The hydrocarbon-containing fluid preferably comprises
a content by weight of isoparaffins from 90 to 100% and a
content of normal paraffins from 0 to 10%, preferably from 95
to 100% of isoparaffins selected from alkanes comprising from
35 12 to 30 carbon atoms, preferably from 12 to 24 carbon atoms,
more preferably from 12 to 22 carbon atoms.
25
According to a particular embodiment, the
hydrocarbon-containing fluid comprises a majority, i.e. more
than 90 wt%, of molecules having 14 to 18 carbon atoms, such
as isoparaffins.
According to another embodiment, 5 the hydrocarboncontaining
fluid comprises from 60 to 95 wt%, preferably from
80 to 98 wt%, of isoparaffins selected from the group
consisting of C15 isoparaffins, C16 isoparaffins, C17
isoparaffins, C18 isoparaffins and mixtures of two or more of
10 them.
According to one embodiment, the hydrocarbon-containing
fluid comprises:
- isoparaffins having 15 carbon atoms and isoparaffins
having 16 carbon atoms in a total amount from 80 to 98 wt%,
15 relative to the total weight of the hydrocarbon-containing
fluid, or
- isoparaffins having 16 carbon atoms, isoparaffins
having 17 carbon atoms and isoparaffins having 18 carbon
atoms in a total amount from 80 to 98 wt%, relative to the
20 total weight of the hydrocarbon-containing fluid, or
- isoparaffins having 17 carbon atoms and isoparaffins
having 18 carbon atoms in a total amount from 80 to 98 wt%,
relative to the total weight of the hydrocarbon-containing
fluid.
25 According to a preferred embodiment of the invention,
the hydrocarbon-containing fluid comprises isoparaffins
having 17 carbon atoms and isoparaffins having 18 carbon
atoms in a total amount from 80 to 98 wt%, relative to the
total weight of the hydrocarbon-containing fluid.
30 Examples of preferred hydrocarbon-containing fluids are
those comprising:
- from 30 to 70 wt% of C15 isoparaffins and from 30 to
70 wt% of C16 isoparaffins, preferably from 40 to 60 wt% of
C15 isoparaffins and from 35 to 55 wt% of C16 isoparaffins,
35 relative to the total weight of the hydrocarbon-containing
fluid,
26
- from 5 to 25% of C15 isoparaffins, from 30 to 70% of
C16 isoparaffins and from 10 to 40% of C17 isoparaffins,
preferably from 8 to 15% of C15 isoparaffins, from 40 to 60%
of C16 isoparaffins and from 15 to 25% of C17 isoparaffins,
relative to the total weight of the hydrocarbon-5 containing
fluid,
- from 5 to 30% of C17 isoparaffins and from 70 to 95%
of C18 isoparaffins, preferably from 10 to 25% of C17
isoparaffins and from 70 to 90% of C18 isoparaffins, relative
10 to the total weight of the hydrocarbon-containing fluid.
The hydrocarbon-containing fluid preferably comprises a
content by weight of naphthenic compounds less than or equal
to 3%, preferably less than or equal to 1%, more preferably
less than or equal to 0.5% and even more preferably less than
15 or equal to 500 ppm, or even 100 ppm or 50 ppm.
According to another embodiment, the hydrocarboncontaining
fluid comprises a content by weight of
isoparaffins from 90 to 100%, a content by weight of normal
paraffins from 0 to 10% and a content by weight of naphthenic
20 compounds less than or equal to 1%. Preferably the
hydrocarbon-containing fluid comprises a content by weight
from 95 to 100% of isoparaffins, from 0 to 5% of normal
paraffins and a content by weight of naphthenic compounds
less than or equal to 0.5%. More preferably it comprises a
25 content by weight from 98% to 100% of isoparaffins, from 0 to
2% of normal paraffins and a content by weight of naphthenic
compounds less than or equal to 100 ppm.
The hydrocarbon-containing fluid is advantageously free
from aromatic compounds. "Free from" means a content by
30 weight of aromatic compounds less than or equal to 500 ppm,
preferably less than or equal to 300 ppm, preferably less
than or equal to 100 ppm, more preferably less than or equal
to 50 ppm and advantageously less than or equal to 20 ppm
measured for example by UV spectrometry.
35 The content by weight of isoparaffins, normal paraffins,
naphthenic compounds and/or aromatics in the hydrocarboncontaining
fluid can be determined by methods familiar to a
27
person skilled in the art. We may mention, as a nonlimiting
example, a method using gas chromatography.
According to another embodiment, the hydrocarboncontaining
fluid comprises a content by weight of
isoparaffins from 90 to 100%, a content by 5 weight of normal
paraffins from 0 to 10%, a content by weight of naphthenic
compounds less than or equal to 1% and a content by weight of
aromatic compounds less than or equal to 500 ppm. Preferably
the hydrocarbon-containing fluid comprises a content by
10 weight from 95 to 100% of isoparaffins, from 0 to 5% of
normal paraffins, a content by weight of naphthenic compounds
less than or equal to 0.5% and a content by weight of
aromatic compounds less than or equal to 300 ppm, preferably
below 100 ppm, preferably below 50 ppm and advantageously
15 below 20 ppm. Also preferably, the hydrocarbon-containing
fluid comprises a content by weight from 95 to 100% of
isoparaffins, from 0 to 5% of normal paraffins and a content
by weight of aromatic compounds less than or equal to 100
ppm. More preferably it comprises a content by weight from
20 98% to 100% of isoparaffins, from 0 to 2% of normal
paraffins, a content by weight of naphthenic compounds less
than or equal to 100 ppm and a content by weight of aromatic
compounds less than or equal to 100 ppm.
The hydrocarbon-containing fluid also preferably has an
25 extremely low content by weight of sulfur-containing
compounds, typically less than or equal to 5 ppm, preferably
less than or equal to 3 ppm and more preferably less than or
equal to 0.5 ppm at a level too low to be detected with
conventional low sulfur content analyzers.
30 The hydrocarbon-containing fluid also preferably has a
flash point greater than or equal to 110°C, preferably
greater than or equal to 120°C and more preferably greater
than or equal to 140°C according to standard EN ISO 2719. A
high flash point, typically above 110°C, among other things
35 makes it possible on the one hand to overcome the problems of
safety during storage and transport by avoiding overly
sensitive flammability of the hydrocarbon-containing fluid.
28
The hydrocarbon-containing fluid also preferably has a
vapor pressure at 20°C less than or equal to 0.01kPa.
According to one embodiment, the hydrocarbon-containing
fluid also preferably has a flash point greater than or equal
to 110°C according to standard EN ISO 5 2719 and a vapor
pressure at 20°C less than or equal to 0.01kPa. Preferably
the hydrocarbon-containing fluid has a flash point greater
than or equal to 120°C and a vapor pressure at 20°C less than
or equal to 0.01kPa. More preferably, it has a flash point
10 greater than or equal to 140°C and a vapor pressure at 20°C
less than or equal to 0.01kPa.
The hydrocarbon-containing fluid has boiling points, a
flash point and a vapor pressure allowing the problems of
flammability, odor and volatility to be overcome.
15 Moreover, the hydrocarbon-containing fluid preferably
has a kinematic viscosity at 40°C less than or equal to 5
cSt, preferably less than or equal to 4 cSt and more
preferably less than or equal to 3.5 cSt according to
standard EN ISO 3104.
20
The hydrocarbon-containing fluid may be obtained by any
method known by a person skilled in the art.
Generally the hydrocarbon-containing fluid is a
hydrocarbon-containing cut that is obtained from biomass
25 conversion.
"Obtained from biomass conversion" means, in the context
of the present invention, a hydrocarbon-containing cut
produced from raw materials of biological origin.
30 According to one embodiment, the hydrocarbon-containing
fluid comprises:
- a content by weight of isoparaffins from 95 to 100%
and preferably from 98% to 100% relative to the total weight
of the hydrocarbon-containing fluid, and
35 - a content by weight of normal paraffins less than
or equal to 5% and preferably less than or equal to 2%
29
relative to the total weight of the hydrocarbon-containing
fluid; and
- a content by weight of naphthenic compounds less
than or equal to 0.5% and preferably less than or equal to
100 ppm relative to the total weight 5 of the hydrocarboncontaining
fluid; and
- a content by weight of aromatic compounds less than
or equal to 300 ppm, preferably less than or equal to 100
ppm, more preferably less than or equal to 50 ppm and
10 advantageously less than or equal to 20 ppm, relative to the
total weight of the hydrocarbon-containing fluid.
According to a particular embodiment, the hydrocarboncontaining
fluid comprises a content by weight of
15 isoparaffins from 98% to 100%, relative to the total weight
of the hydrocarbon-containing fluid, and a kinematic
viscosity at 40°C less than or equal to 5 cSt, preferably
less than or equal to 4 cSt and preferably less than or equal
to 3.5 cSt.
20
Radical inhibitor
A lubricant composition employed according to the
invention may further comprise at least one radical
inhibitor.
25 Said radical inhibitors are known per se by a person
skilled in the art and may have various chemical natures and
may in particular belong to different chemical classes.
Among the radical inhibitors, we may notably mention
the phosphorus-containing radical inhibitors.
30 Among the phosphorus-containing radical inhibitors, a
distinction is made between the compounds for which the
phosphorus is a P(V) or pentavalent phosphorus, in particular
phosphates such as triethyl phosphate, trimethyl phosphate,
alkyl phosphates optionally fluorinated or else aryl
35 phosphates, phosphazenes such as hexamethoxycyclotriphosphazene,
and the compounds for which the
30
phosphorus is a P(III) or trivalent phosphorus, in particular
phosphites such as tris(2,2,2-trifluoroethyl)phosphite.
Other additives
According to a variant of 5 the invention, a
composition employed according to the invention may further
comprise additives that modulate the properties of the base
oil.
Such additives may be selected from friction
10 modifiers, detergents, antiwear additives, extreme-pressure
additives, dispersants, antioxidants, pour-point improvers,
antifoaming agents and mixtures thereof.
These additives may be introduced individually and/or
in the form of a mixture like those already commercially
15 available for the formulations of commercial lubricants for
vehicle engines, with performance levels as defined by the
ACEA (European Automobile Manufacturers' Association) and/or
the API (American Petroleum Institute), which are familiar to
a person skilled in the art.
20
Antiwear additives and extreme-pressure additives
protect the rubbing surfaces by forming a protective film
that is adsorbed on said surfaces.
There is a great variety of antiwear additives.
25 Preferably, for the composition employed according to the
invention, the antiwear additives are selected from
thiophosphate additives such as metal alkylthiophosphates, in
particular zinc alkylthiophosphates, and more specifically
zinc dialkyldithiophosphates or ZnDTP. The preferred
30 compounds are of formula Zn((SP(S)(OR2)(OR3))2, in which R2
and R3, which may be identical or different, represent
independently an alkyl group, preferably an alkyl group
comprising from 1 to 18 carbon atoms.
The amine phosphates are also antiwear additives that
35 may be used in a composition employed according to the
invention. However, the phosphorus supplied by these
additives may act as a poison of automobile catalytic
31
systems, as these additives generate ash. These effects can
be minimized by partially replacing the amine phosphates with
additives that do not supply phosphorus, such as, for
example, polysulfides, notably sulfur-containing olefins.
A lubricant composition employed 5 according to the
invention may comprise from 0.01 to 6 wt%, preferably from
0.05 to 4 wt%, more preferably from 0.1 to 2 wt% of antiwear
additives and extreme-pressure additives, by mass relative to
the total weight of composition.
10 According to a particular embodiment, a lubricant
composition employed according to the invention is free from
antiwear additives and extreme-pressure additives. In
particular, a lubricant composition employed according to the
invention is advantageously free from phosphate-containing
15 additives.
A lubricant composition employed according to the
invention may comprise at least one friction modifying
additive. The friction modifying additive may be selected
20 from a compound supplying metallic elements and an ash-free
compound. Among the compounds supplying metallic elements, we
may mention complexes of transition metals such as Mo, Sb,
Sn, Fe, Cu, Zn whose ligands may be hydrocarbon compounds
comprising oxygen, nitrogen, sulfur or phosphorus atoms. The
25 ash-free friction modifying additives are generally of
organic origin and may be selected from monoesters of fatty
acids and polyols, alkoxylated amines, alkoxylated fatty
amines, fatty epoxides, borate fatty epoxides; fatty amines
or fatty acid glycerol esters. According to the invention,
30 the fatty compounds comprise at least one hydrocarbon group
comprising from 10 to 24 carbon atoms.
A lubricant composition employed according to the
invention may comprise from 0.01 to 2 wt% or from 0.01 to
5 wt%, preferably from 0.1 to 1.5 wt% or from 0.1 to 2 wt% of
35 friction modifying additive, relative to the total weight of
the composition.
32
Advantageously, a lubricant composition employed
according to the invention is free from friction modifying
additive.
A lubricant composition employed 5 according to the
invention may comprise at least one antioxidant additive.
The antioxidant additive generally makes it possible
to delay the degradation of the composition in service. This
degradation may notably be reflected in the formation of
10 deposits, the presence of sludge or an increase in viscosity
of the composition.
The antioxidant additives notably act as radical
inhibitors or destroyers of hydroperoxides. Among the
antioxidant additives commonly used, we may mention
15 antioxidant additives of the phenolic type, antioxidant
additives of the amino type, and thiophosphate antioxidants.
Certain of these antioxidant additives, for example the
thiophosphate antioxidants, may generate ash. The phenolic
antioxidants may be ash-free or may be in the form of neutral
20 or basic metal salts. The antioxidant additives may notably
be selected from sterically hindered phenols, sterically
hindered phenol esters and sterically hindered phenols
comprising a thioether bridge, diphenylamines, diphenylamines
substituted with at least one C1-C12 alkyl group, N,N'-dialkyl
25 aryl diamines and mixtures thereof.
Preferably, according to the invention, the
sterically hindered phenols are selected from compounds
comprising a phenol group, of which at least one carbon
vicinal of the carbon bearing the alcohol function is
30 substituted with at least one C1- C10 alkyl group, preferably
a C1-C6 alkyl group, preferably a C4 alkyl group, preferably
with the tert-butyl group.
The amine compounds are another class of antioxidant
additives that may be used, optionally in combination with
35 the phenolic antioxidants. Examples of amine compounds are
aromatic amines, for example aromatic amines of formula
NR4R5R6 in which R4 represents an aliphatic group or an
33
aromatic group, optionally substituted, R5 represents an
aromatic group, optionally substituted, R6 represents a
hydrogen atom, an alkyl group, an aryl group or a group of
formula R7S(O)zR8 in which R7 represents an alkylene group or
an alkenylene group, R8 represents an alkyl 5 group, an alkenyl
group or an aryl group and z represents 0, 1 or 2.
Sulfurized alkyl phenols or the alkali metal and
alkaline earth salts thereof may also be used as antioxidant
additives.
10 Another class of antioxidant additives is the copper
compounds, for example the copper thio- or dithiophosphates,
the salts of copper and carboxylic acids, copper
dithiocarbamates, sulfonates, phenolates, and
acetylacetonates. The salts of copper I and II, the salts of
15 succinic acid or anhydride may also be used.
A lubricant composition employed according to the
invention may contain all types of antioxidant additives
known by a person skilled in the art.
Advantageously, a lubricant composition employed
20 according to the invention comprises at least one ash-free
antioxidant additive.
A lubricant composition employed according to the
invention may comprise from 0.5 to 2 wt% of at least one
antioxidant additive, relative to the total weight of the
25 composition.
A lubricant composition employed according to the
invention may also comprise at least one detergent additive.
The detergents generally make it possible to reduce
30 the formation of deposits on the surface of metal parts by
dissolving the by-products of oxidation and combustion.
The detergents usable in a lubricant composition
employed according to the invention are generally familiar to
a person skilled in the art. The detergents may be anionic
35 compounds comprising a long lipophilic hydrocarbon chain and
a hydrophilic head. The associated cation may be a metal
cation of an alkali metal or alkaline-earth metal.
34
The detergents are preferably selected from the salts
of alkali metals or of alkaline-earth metals of carboxylic
acids, sulfonates, salicylates, naphthenates, as well as
phenolates. The alkali metals and alkaline-earth metals are
preferably calcium, magnesium, 5 sodium or barium.
These metal salts generally comprise the metal in
stoichiometric quantity or in excess, therefore in an amount
greater than the stoichiometric quantity. They are then
overbased detergents; the metal in excess giving the
10 detergent additive the overbased character is then generally
in the form of a metal salt that is insoluble in the oil, for
example a carbonate, a hydroxide, an oxalate, an acetate, a
glutamate, preferably a carbonate.
A lubricant composition employed according to the
15 invention may for example comprise from 2 to 4 wt% of
detergent, relative to the total weight of the composition.
A lubricant composition employed according to the
invention may also comprise at least one pour-point
20 depressant.
By slowing down the formation of paraffin crystals,
the pour-point depressants generally improve the
composition's low-temperature behavior.
As examples of pour-point depressants, we may mention
25 alkyl polymethacrylates, polyacrylates, polyaryl amides,
polyalkyl phenols, polyalkyl naphthalenes, alkylated
polystyrenes.
A lubricant composition employed according to the
30 invention may also comprise at least one dispersant.
The dispersant may be selected from Mannich bases,
succinimides and derivatives thereof.
A lubricant composition employed according to the
invention may for example comprise from 0.2 to 10 wt% of
35 dispersant, relative to the total weight of the composition.
35
It is up to a person skilled in the art to adjust the
proportions of the various constituents of the composition,
and the various additives defined above, to meet the
viscosity required according to the invention, and optionally
the density of 5 the composition.
APPLICATION
As stated above, a composition as defined according
to the invention may be employed, owing to its combined
10 properties in terms of lubrication and cooling, both as a
fluid for lubricating the motor and the transmission, and as
a cooling fluid for a propulsion system of an electric or
hybrid vehicle, and more particularly the motor, the power
electronics and the batteries.
15 Thus, according to one of its aspects, the present
invention relates to the use, as a lubrication fluid and
cooling fluid for a propulsion system of an electric or
hybrid vehicle, of a composition comprising:
(i) at least one base oil,
20 (ii) at least one diester of formula (I), different
than the base oil (i):
Ra-C(O)-O-([C(R)2]n-O)s-C(O)-Rb (I)
in which:
- R represent, independently of one another, a hydrogen
25 atom or a (C1-C5)alkyl group, linear or branched, in
particular a methyl, ethyl or propyl group, notably methyl;
- s has a value of 1 or 2;
- n has a value of 1, 2 or 3; it being understood that when
s is different from 1, n may be identical or different; and
30 - Ra and Rb, which may be identical or different, represent
independently of one another, hydrocarbon groups, saturated
or unsaturated, linear or branched, having a linear chain
with 2 to 11 carbon atoms, preferably with 3 to 8 carbon
atoms;
35 provided that when s has a value of 2 and n, which are
identical, have a value of 2, at least one of the groups R
represents a (C1-C5)alkyl group, linear or branched; and
36
provided that, when s has a value of 1 and n has a value of
3, at least one of the groups R bound to the carbon in the
beta position of the oxygen atoms of the ester functions
represents a hydrogen atom.
"Cooling fluid" means, in the sense 5 of the present
invention, a fluid able to dissipate the heat generated by a
propulsion system of an electric or hybrid vehicle. More
precisely, such a fluid is characterized by an enhanced
thermal absorption capacity while it is in contact with a
10 part that is being heated.
In particular, a composition employed according to
the invention makes it possible to optimize the heat
exchanges with the propulsion system of an electric or hybrid
vehicle. Advantageously, it has a heat capacity measured at
15 50°C and at atmospheric pressure above 1.8 kJ/kg/K,
preferably above 2 kJ/kg/K.
Advantageously, the composition employed according to
the invention is brought into contact with the battery by any
implementation that allows direct contact between the cells
20 of the battery and said composition, in particular by
immersion or semi-immersion.
Alternatively, the lubricant composition employed
according to the invention is advantageously brought into
direct contact with the batteries by methods described
25 hereunder.
As batteries suitable for the propulsion systems of
an electric or hybrid vehicle, we may mention Li-ion
batteries or nickel-cadmium batteries.
In particular, the invention relates to the use of a
30 composition as defined above for lubricating and cooling a
propulsion system of an electric or hybrid vehicle.
An electric motor is typically supplied by an
electric battery (2). Lithium-ion batteries are the most
widely used in the field of electric vehicles. The
35 development of batteries that are more and more powerful and
whose size is smaller and smaller leads to the problem of
cooling of said batteries. In fact, once the battery exceeds
37
temperatures of the order of 50 to 60°C, there is a high risk
of ignition, or even explosion, of the battery. There is also
a need to keep the battery at a temperature above about 0°C
for optimal operation of the battery.
As shown schematically in Fig. 5 1, the propulsion
system of an electric or hybrid vehicle notably comprises the
electric motor part (1). The latter typically comprises power
electronics (11) connected to a stator (13) and a rotor (14).
The stator comprises coils, in particular copper
10 coils, which are supplied alternately with an electric
current. This makes it possible to generate a rotating
magnetic field. The rotor itself comprises coils, permanent
magnets or other magnetic materials, and is caused to rotate
by the rotating magnetic field.
15 The power electronics (11), the stator (13) and the
rotor (14) of a propulsion system (1) are components of
complex structure that generate a large amount of heat during
operation of the motor. It is therefore imperative to provide
cooling of the electric motor and the power electronics.
20 Moreover, the bearing (12), generally incorporated
between the stator (13) and the rotor (14), is subjected to
high mechanical stresses and poses problems of fatigue wear.
It is therefore necessary to lubricate the bearing in order
to increase its service life.
25 Thus, a composition as described above makes it
possible to lubricate the transmission, in particular the
reduction gearing, in an electric or hybrid vehicle.
It will be understood that the uses described above
30 may be combined, and a composition as described above is
usable both as a lubricant and as a cooling fluid for the
motor, the battery and the transmission of an electric or
hybrid vehicle.
Thus, the invention relates to the use of a
35 composition as described above for cooling the battery, the
motor, and the power electronics, for lubricating the motor
and the transmission and for fire protection of a propulsion
38
system of an electric or hybrid vehicle, and notably the
battery.
In particular, such a composition makes it possible
to cool the power electronics and/or the rotor and/or the
stator of the electric motor. It can also provide 5 lubrication
of the bearings located between the rotor and the stator of
an electric motor of an electric or hybrid vehicle.
Thus, the invention offers the advantage of allowing
10 the use of a single composition combining the properties of
cooling and lubrication of the propulsion system of an
electric or hybrid vehicle as a whole.
Furthermore, the use of at least one diester of
formula (I) as defined above in at least one base oil makes
15 it possible to increase the flammability temperature of the
base oil.
Thus, the invention also relates to the use of at
least one diester of formula (I) in a composition comprising
at least one base oil, for improving the non-flammable
20 properties of the composition.
The invention further relates to a method of cooling
and lubricating a propulsion system of an electric or hybrid
vehicle comprising at least one step of bringing at least one
mechanical component of said system, notably at least one
25 battery cell, in particular a lithium-ion or nickel-cadmium
battery, into contact with a composition as defined above.
According to a particular embodiment, the contacting
step consists of immersion or semi-immersion, static or
circulating, of the battery in said composition or else
30 injection of said composition onto the surface of the
battery.
All of the features and preferences described for the
lubricant composition used according to the invention as well
as for the uses thereof also apply to this method.
35 The cooling by a lubricant composition defined
according to the invention may be implemented by any method
known by a person skilled in the art.
39
The battery may be immersed or semi-immersed, static
or circulating, in said composition.
As examples of bringing into direct contact, we may
mention cooling by injection, jet, by spraying or else by
formation of a mist from the composition 5 employed according
to the invention under pressure and by gravity on the
battery.
Advantageously, the composition is injected by jet at
quite high pressure in the zones of the propulsion system
10 that are to be cooled. Advantageously, the shearing resulting
from this injection makes it possible to reduce the viscosity
of the fluid at the level of the injection zone, relative to
the kinematic viscosity at rest, and thus further increase
the cooling potential of the composition.
15 Thus, the present invention also relates to a method
of cooling and lubricating a propulsion system of an electric
or hybrid vehicle as defined above in which the mechanical
component is at least one battery, in immersion or semiimmersion,
static or circulating, in said composition, or
20 said composition is brought into direct contact with the
batteries by injection, jet, by spraying or else by formation
of a mist from said composition under pressure and by gravity
on the battery.
Moreover, oil circulating systems commonly used in
25 electric motors may be used, for example as described in
document WO 2015/116496.
EXAMPLES
Example 1: Measurement of the rheological and thermal
30 properties of diesters according to the invention
Measurement of the rheological properties:
The rheological properties of the esters are
quantified by measuring their kinematic viscosities at 40°C
(KV40) and at 100°C (KV100), expressed in mm²/s, determined
35 according to standard ASTM D445.
Measurement of the thermal properties:
40
The thermal properties of the esters can be evaluated
by measuring their thermal conductivity and their heat
capacity (or calorific capacity).
Thermal conductivity is measured according to
standard 5 ASTM D7896.
Heat capacity is measured according to standard ASTM
E1269.
Nature of the diesters
The thermal and rheological properties were measured
10 for the diesters obtained by esterification between the
alcohols and the acids indicated in Table 1 below.
Ester Alcohol Acid
E1
Dipropylene glycol
(DPG)
Nonanoic acid / dodecanoic acid
(50/50)
E2 DPG Nonanoic acid
E3
Diethylene glycol
(DEG)
Nonanoic acid
E4
Neopentyl glycol
(NPG)
Nonanoic acid
E5 NPG Isononanoic acid
E6 NPG 2-Ethylhexanoic acid
Table 1 – Nature of the diesters tested
Results
The results obtained are presented in Table 2 below
Ester
KV40
(mm²/s)
KV100
(mm²/s)
λ at
30°C
(mW/Km)
λ at
130°C
(mW/Km)
Cp at
20°C
(J/K)
Cp at
80°C
(J/K)
E1 11.7 3.2 150.5 131.0 1.930 2.086
E2 9.1 2.7 147.1 127.0 1.900 2.070
E3 8.6 2.6 154.9 133.7 - 2.150
E4 8.7 2.6 141.8 123.2 1.970 2.180
E5 13.2 3.2 113.2 99.6 1.870 2.100
E6 7.5 2.1 128.2 111.2 1.837 2.040
15 Table 2 – Rheological and thermal properties of the
diesters
41
It is clear from the above results that the diesters
of formula (I) according to the invention have rheological
properties and values of thermal conductivity and of heat
capacity that allow them to be used in a lubricant
composition for purposes of lubrication 5 and cooling of the
parts of a propulsion system of an electric or hybrid
vehicle.
Example 2: Measurement of volatility of diesters
according to the invention and not according to the invention
10 Method of measurement
The volatility of the diesters is quantified by
thermogravimetric analysis (TGA), more particularly carried
out according to standard ASTM D6375.
The diester to be tested is heated quickly to a
15 temperature between 247°C and 249°C and then held at this
temperature. The apparatus for thermogravimetric measurement
records the percentage weight loss of the sample as a
function of time, connected with its evaporation.
The results obtained correspond to the time taken,
20 expressed in seconds, for 20% of the initial ester to be
evaporated. The longer the time, the slower the evaporation
of the product, and therefore the longer the life of the
lubricant.
Nature of the diester
25 The diesters E2 and E3 defined above, according to
the invention, were tested, as well as two diesters not
according to the invention, E8 and E9.
The diesters E8 and E9 are obtained by esterification
between triethylene glycol and heptanoic acid and 2-
30 ethylhexanoic acid, respectively.
Results
The results obtained are presented in Table 3 below
Ester Time taken for evaporation of
20% of product(s)
E2 (invention) 461
E3 (invention) 490
E8 (not 361
42
according to the
invention)
E9 (not
according to the
invention)
390
Table 3 – Volatility of the diesters
The diesters E2 and E3, according to the invention,
have longer evaporation times than the diesters E8 and E9 not
according to the invention.
These results demonstrate that a 5 diester of formula
(I) according to the invention endows the composition in
which it is used with advantageous properties, in particular
of lubrication and cooling, over a longer time of use,
thereby extending the oil-changing interval.
10
43
WE CLAIM:
1. The use, for cooling and lubricating a propulsion
system of an electric or hybrid vehicle, of a composition
comprising 5 at least:
(i) at least one base oil; and
(ii) at least one diester of formula (I), different
than the base oil (i):
Ra-C(O)-O-([C(R)2]n-O)s-C(O)-Rb (I)
10 in which:
- R represent, independently of one another, a
hydrogen atom or a (C1-C5)alkyl group, linear or branched, in
particular a methyl, ethyl or propyl group, notably methyl;
- s has a value of 1 or 2;
15 - n has a value of 1, 2 or 3; it being understood
that, when s is different from 1, n may be identical or
different; and
- Ra and Rb, which may be identical or different,
represent independently of one another, hydrocarbon groups,
20 saturated or unsaturated, linear or branched, having a linear
chain with 2 to 11 carbon atoms, preferably with 3 to 8
carbon atoms;
provided that, when s has a value of 2 and n, which
are identical, have a value of 2, at least one of the groups
25 R represents a (C1-C5)alkyl group, linear or branched; and
provided that, when s has a value of 1 and n has a
value of 3, at least one of the groups R bound to the carbon
in the beta position of the oxygen atoms of the ester
functions represents a hydrogen atom.
30 2. The use as claimed in the preceding claim,
characterized in that the base oil has a kinematic viscosity,
measured at 100°C according to standard ASTM D445, from 1.5
to 8 mm²/s, in particular from 1.5 to 6.1 mm²/s, more
particularly from 1.5 to 4.1 mm²/s, even more particularly
35 from 1.5 to 2.1 mm²/s.
3. The use as claimed in claim 1 or 2, in which the
base oil is selected from synthetic oils, such as certain
44
esters of carboxylic acids and alcohols, polyalphaolefins and
polyalkylene glycol obtained by polymerization or
copolymerization of alkylene oxides comprising from 2 to 8
carbon atoms, in particular from 2 to 4 carbon atoms.
4. The use as claimed in any one 5 of the preceding
claims, characterized in that the composition comprises from
60% to 99.5% by weight, preferably from 70% to 98%, even more
preferably from 80% to 98%, advantageously from 90% to 97% by
weight of base oil, or mixture of base oils.
10 5. The use as claimed in any one of the preceding
claims, in which the diester of formula (I) is a diester of
formula (I'):
Ra-C(O)-O-([C(R)2]n-O)-([C(R')2]m-O)s-1-C(O)-Rb (I')
in which:
15 - R and R' represent, independently of one another, a
hydrogen atom or a (C1-C5)alkyl group, linear or branched, in
particular a methyl, ethyl or propyl group, notably a methyl
group;
- s has a value of 1 or 2;
20 - n has a value of 2;
- m has a value of 2;
- Ra and Rb, which may be identical or different,
represent independently of one another, hydrocarbon groups,
saturated or unsaturated, linear or branched, having a linear
25 chain with 2 to 11 carbon atoms, preferably with 3 to 8
carbon atoms;
provided that, when s has a value of 2, at least one of the
groups R or R' represents a (C1-C5)alkyl group, linear or
branched.
30 6. The use as claimed in any one of the preceding
claims, in which the diester or diesters of formula (I) are
present in a content between 1 and 30 wt%, relative to the
total weight of the composition, in particular, between 5 and
30 wt%, preferably between 5 and 25 wt%, and more
35 particularly between 10 and 25 wt%.
7. The use as claimed in any one of the preceding
claims, in which the composition further comprises at least
45
one additive selected from hydrocarbon-containing fluids
having a boiling point greater than or equal to 50°C, radical
inhibitors, friction modifiers, detergents, antiwear
additives, extreme-pressure additives, dispersants,
antioxidants, pour-point improvers, antifoaming 5 agents and
mixtures thereof.
8. A method of cooling and lubricating a propulsion
system of an electric or hybrid vehicle comprising at least
one step of bringing at least one mechanical component of
10 said system, notably at least one battery cell, in particular
a lithium-ion or nickel-cadmium battery, into contact with a
composition as defined in any one of claims 1 to 7.
9. The method as claimed in the preceding claim,
characterized in that said at least one mechanical component
15 is at least one battery, immersed or semi-immersed, static or
circulating, in said composition, or said composition is
brought into direct contact with the batteries by injection,
jet, by spraying or else by formation of a mist from said
composition under pressure and by gravity on the battery.
20 10. The use of a diester of formula (I) as defined
in any one of claims 1, 5 and 6, in a composition for cooling
and lubricating a propulsion system of an electric or hybrid
vehicle, comprising at least one base oil, to extend the oilchanging
interval of the propulsion system, in particular of
25 its battery.