Technical Field
The present invention relates to the lubrication of engines of vehicles with hybrid
5 engine and vehicles with micro-hybrid engine, in particular vehicles with micro-hybrid engine
equipped with the "Stop-and-Start" system.
Technical back~round
Environmental concerns and the search for savings in fossil energy resources have led
to the development of vehicles with electric motors. However, the latter are limited in terms of
10 power and range, and require a very long battery recharging time.
Hybrid engine systems remedy these drawbacks by utilizing an electric motor and a
standard thermal internal combustion engine in series, in parallel or in combination.
In a hybrid vehicle, starting is ensured by the electric motor. Up to a speed of the order
of 50 km/h, it is the electric motor which provides the driving power of the vehicle. From the
15 moment that a higher speed is reached or a high acceleration is required, the thermal internal
... combustion engine takes over. When the speed reduces or during vehicle"stops, the thermal
internal combustion engine stops and the electric motor takes over. Thus, the thermal internal
combustion engines of hybrid vehicles are subjected to a significant number of stops and
restarts compared to a thermal internal combustion engine of conventional vehicles.
20 Moreover, certain vehicles are equipped with the "Stop-and-Start" system, also
referred to as automatic stop and restart device. These vehicles are generally considered as
"micro-hybrid" vehicles. In fact, these vehicles are equipped with a thermal internal
combustion engine and a starter-alternator or a heavy-duty starter which ensures the stopping
and restarting of the thermal internal combustion engine when the vehicle is at a standstill. The
25 thermal internal combustion engines of micro-hybrid vehicles equipped with the "stop-andstart"
system, like the thermal internal combustion engines of hybrid vehicles, are therefore
subjected to a significant number of stops and restarts compared to thermal internal
combustion engines of conventional vehicles.
Thus, over its lifetime, the thermal internal combustion engine of a hybrid vehicle or
30 micro-hybrid vehicle is subjected to a much larger number of stops and starts than that of a
standard vehicle. This potentially produces specific wear problems for the thermal internal
combustion engines of hybrid and micro-hybrid vehicles, in particular over the long term. These
specific wear problems are in particular visible on the connecting rod bearings.
Cabinet Hirsch 33804 Application FR12/54151
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PPQ DELHH 2 7 - f 3 1 - L . O P 5 14: 32
There is therefore a need for the development of lubricant compositions allowing
reliable operation of the thermal internal combustion engines of hybrid and micro-hybrid
vehicles equipped with the Stop-and-Start system, and in particular capable of reducing wear,
in particular the wear of the bearings, in particular the wear of the connecting rod bearings, in
5 the thermal internal combustion engines of said vehicles.
Surprisingly, the Applicant has found that the use, in the thermal internal combustion
engines of vehicles with hybrid and micro-hybrid engines equipped with the Stop-and-Start
system, of polyalkylene glycols, in particular polyalkylene glycols obtained par copolymerization
of ethylene oxides and of propylene oxides or of polyalkylene glycols obtained par
10 homopolymerization of propylene oxides in lubricant compositions makes it possible to
considerably reduce the wear of the bearings present in said engines. This use advantageously
makes it possible to increase the lifetime of the engine, and in particular to increase the time
between changes of engine parts.
15 Brief description
.' . . An dbje'ct of the invention is the use of a lubricant composition comprising at least one
base oil and at least one polyalkylene glycol obtained by copolymerization of ethylene oxides
and of propylene oxides or obtained by homopolymerization of propylene oxides, for
lubricating metal surfaces, polymeric surfaces and/or amorphous carbon surfaces, of the
20 thermal internal combustion engines of vehicles with hybrid and/or micro-hybrid engines.
Preferably, the vehicles with micro-hybrid engines are equipped with a starteralternator
or a heavy-duty starter.
Preferably, the use makes it possible to reduce the wear of the thermal internal
combustion engine, in particular the wear of the bearings of the thermal internal combustion
25 engine, in particular the wear of the connecting rod bearings of the thermal internal
combustion engine.
Preferably, the use makes it possible to increase the lifetime of the thermal internal
combustion engine, in particular the lifetime of the bearings of the thermal internal
combustion engine, in particular the lifetime of the connecting rod bearings of the thermal
30 internal combustion engine.
Preferably, the use makes it possible to increase the time between changes of thermal
internal combustion engine parts, in particular the time between changes of the bearings of the
thermal internal combustion engine, in particular the time between changes of the connecting
rod bearings of the thermal internal combustion engine.
Cabinet Hirsch 33804 Application FR12/54151
FR2990214
Preferably, the lubricant composition comprises from 0.1 to 20% by mass with respect
to the total mass of lubricant composition of polyalkylene glycol, preferably from 0.2 to 15%)
more preferably from 0.5 to lo%, even more preferably from 1 to 5%) even more preferably
from 2 to 4%.
5 According to a first embodiment, the polyalkylene glycol originates from the
homopolymerization of propylene oxides.
According to a second embodiment, the polyalkylene glycol originates from the
copolymerization of ethylene oxide and propylene oxide and comprises at least 60% by mass of
propylene oxide, with respect to the total mass of polyalkylene glycol.
According to a first embodiment, the metal surface is an alloy.
Preferably, the alloy is steel.
Preferably, the alloy comprises as base element tin (Sn), lead (Pb), copper (Cu),
aluminium (Al), cadmium (Cd), silver (Ag) or zinc (Zn).
Preferably, the alloy comprises lead (Pb) and copper (Cu).
15 According to a second embodiment, the polymeric surface comprises
polytetrafluoroethylene.
Preferably, the kinematic viscosity at 100°C of the lubricating composition, measured
according to the standard ASTM D445, is comprised between 5.6 and 12.5 cSt.
Detailed description
20 The present invention relates to the field of the lubrication of thermal internal
combustion engines of vehicles with hybrid or micro-hybrid engine.
By vehicles with hybrid engine is meant here vehicles using two distinct energy
storages capable of moving said vehicles. In particular, hybrid vehicles combine a thermal
internal combustion engine and an electric motor, said electric motor participating in the
25 driving power of the vehicle. The operating principle of hybrid vehicles is the following:
- during the stationary phases (where the vehicle is immobile), both engines are
stopped,
- on starting, it is the electric motor which ensures the setting in motion of the vehicle,
up to higher speeds (25 or 30 kmlh),
- when higher speeds are reached, the thermal internal combustion engine takes over,
- in the event of high acceleration, both the engines are started up simultaneously,
which makes it possible to have accelerations equivalent to that of the engine of the
same power, or even greater,
Cabinet H~rsch3 3804
P P 8 D E L H I 2 7 . - O X - 2015 14 13.2
Application FR12/54151
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- optionally, during the'deceleration and braking phase, the kinetic energy is used to
recharge the batteries.
Thus, in hybrid vehicles, in the course of its lifetime the thermal internal combustion
engine is subjected to a much more significant number of stops and starts than in a
5 conventional vehicle ("Stop-and-Start" phenomenon).
By vehicles with micro-hybrid engine is meant here vehicles comprising a thermal
internal combustion engine but no electric motor like the hybrid vehicles, the "hybrid"
character being supplied by the presence of the Stop-and-Start system provided by a starteralternator
or a heavy-duty starter which ensure the stopping and starting of the thermal engine
10 when the vehicle is stopped then restarted.
The present invention more preferentially relates to the lubrication of the thermal
internal combustion engines of vehicles equipped with hybrid or micro-hybrid systems
operating in an urban environment, where the Stop-and-Start phenomenon and the resultant
wear are increased.
15 The wear caused by these frequent stops and restarts can be seen on the different
parts in contact with the lubricant: piston, piston ring, piston pin, piston pin boss, small end, big
end, connecting rod bearings, crankpin, journal, crankshaft bearing, crank bearings or journal
bearings or main bearings, chain pin, oil pump gears, gear system, camshaft, camshaft bearing,
cam followers, rocker arm roller, hydraulic valve lifters, turbocharger shaft, turbocharger
20 bearing.
In a motor vehicle engine there is a static portion comprising the engine block, the
cylinder head, the cylinder head gasket, the liner and various parts ensuring the assembly and
tightness of these different parts. There is also a mobile part comprising the crankshaft, the
connecting rod and its bearings, the piston and its rings.
2 5 The role of the connecting rod is to transmit to the crankshaft the forces received by
the piston, by converting a reciprocating rectilinear motion into a circular motion in a single
direction.
A connecting rod comprises two circular bores, one with a small diameter, called the
small end, and the other with a large diameter, called the big end. The body of the connecting
30 rod which connects the small end and the big end is situated between these two bores.
The small end is engaged around the piston pin, the friction between the small end and
the piston pin being reduced by the interposition between the two mobile parts of a circular
ring covered with or constituted by anti-friction metal (bronze for example), or roller bearings
(usually needle roller bearings) .
Cabinet Hirsch 33804 Application FR12/54151
,FR2990214
The big end encloses the crankpin of the crankshaft. The friction between the big end
and crankpin assembly is reduced by the existence of a film of oil and the interposition of
bearings between the big end and the crankpin. In this case the term big end bearings is used.
The crankshaft is a rotating part. It is put into position and held by a certain number of
5 bearings, called journals. There is therefore a fixed part, the crankshaft bearing, which encloses
a mobile part, the crankshaft journal. Lubrication between these two parts is imperative and
bearings are put in place in order to make it possible to withstand the forces applied to these
bearings. In this case the term journal bearings is used (or crank bearings or main bearings).
The role of the bearing in the case of a big end or of a journal, is to allow the crankshaft
10 to rotate properly. The bearings are thin shells in the form of a half cylinder. These are parts
which are severely affected by the lubrication conditions. If there is contact between the
bearing and the turning shaft, crankpin or journal, the energy released systematically results in
significant wear or engine breakdown. The wear produced can moreover have the effect of
amplifying the phenomenon and the severity of the contact.
15 Within the context of frequent stops and restarts, as is the case for vehicles with hybrid
or micro-hybrid engine, the bearings are subjected to frequent rupture and re-formation of the
film of oil. Thus at each stop/restart contact occurs between the metal interfaces and it is the
frequency of occurrence of these contacts which is problematic for the bearings.
The bearings are subjected to several types of wear in the engines. The different types
20 of wear encountered in the engines are: adhesive wear or wear by metal-metal contact,
abrasive wear,' corrosive wear, fatigue wear, or complex forms of wear (contact corrosion,
cavitation erosion, wear of electric origin). The bearings are in particular subjected to adhesive
wear, the invention is more particularly useful for reducing this type of wear but the invention
can nevertheless be applied to the other types of wear mentioned above.
2 5 The surfaces which are susceptible to wear, in particular the surfaces of bearings, are
metallic-type surfaces, or metallic-type surfaces coated with another layer which can be either
a polymer, or a layer of amorphous carbon. The wear is produced at the interface between said
surfaces which come into contact when the film of oil becomes insufficient.
The metallic-type surface can be a surface constituted by a pure metal such as tin (Sn)
30 or lead (Pb). Most of the time, the metallic-type surface is a metallic-type alloy, based on a
metal and at least one other metallic or non-metallic element. A frequently-used alloy is steel,
an alloy of iron (Fe) and carbon (C). The bearings used in the automobile industry, are mostly
bearings the support of which is made of steel, a support coated or not coated with another
metallic alloy.
Cabinet Hirsch 33804 Application FR12/54151
FR2990214
The other metallic alloys constituting the metallic surfaces according to the invention,
are alloys comprising as basic element, tin (Sn), lead (Pb), copper (Cu) or aluminium (Al).
cadmium (Cd), silver (Ag) or zinc (Zn) can also be basic elements of the metallic alloys
constituting the metallic surfaces according to the invention. To these basic elements other
5 elements chosen from antimony (Sb), arsenic (As), chromium (Cr), indium (In), magnesium
(Mg), nickel (Ni), platinum (Pt) or silicon (Si) will be added.
Preferred alloys are based on the following combinations AI/Sn, AI/Sn/Cu, Cu/Sn, Cu/AI,
Sn/Sb/Cu, Pb/Sb/Sn, Cu/Pb, Pb/Sn/Cu, AI/Pb/Si, Pb/Sn, Pb/ln, AI/Si, AI/Pb. The preferred
combinations are the combinations Sn/Cu, Sn/AI, Pb/Cu or Pb/AI.
10 Copper- and lead-based alloys are preferred alloys, they are also called copper-lead or
white metal alloys.
According to another embodiment, the surfaces affected by wear are polymeric type
surfaces. Most of the time, the bearings are made of steel and also comprise this polymeric
surface. The polymers which can be used are either thermoplastic materials such as
15 polyamides, polyethylenes, fluoropolymers such as the tetrafluoroethylenes, in particular the
polytetrafluoroethylenes (PTFE), or thermosetting materials such as the polyimides, phenolic
plastics (or phenol-formaldehyde (PF) resins).
According to another embodiment, the su'rfaces affected by wear are amorphous
carbon type surfaces. Most of the time, the bearings are made of steel and also comprise this
20 amorphous carbon type surface. The amorphous carbon type surfaces are also called DLC, or
Diamond Like Carbon or Diamond Like Coating, the carbons of which are sp2 and sp3
hybridizations.
Polyalkylene glycols
The lubricant compositions used in the invention comprise at least one polyalkylene
25 glycol (PAG). This polyalkylene glycol is either obtained by copolymerization of ethylene oxides
and propylene oxides, or obtained by homopolymerization of propylene oxides. When it is a
polyalkylene glycol obtained by homopolymerization of propylene oxide units only, this
polyalkylene glycol is called a polypropylene glycol.
The polyalkylene glycols of the compositions according to the invention are ethylene
30 oxide and propylene oxide polymers or copolymers (random or block), which can be prepared
according to the known methods described in the application WO 2009/134716, page 2 line 26
to page 4 line 12, for example by attack of an alcohol initiator on the epoxy bond of an ethylene
or propylene oxide and propagation of the reaction.
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The polyalkylene glycols that can be used according to the invention are commercially
available under the name SYNALOX~~.
Preferably, the PAG is a propylene oxide homopolymer.
When the polyalkylene glycol is an ethylene oxide and propylene oxide copolymer, said
5 polyalkylene glycol comprises at least 60% by mass of units originating from propylene oxides,
with respect to the total mass of polyalkylene glycol, preferentially at least 70%, even more
preferentially at least 80%) even more preferentially at least 90%.
In fact, the polyalkylene glycols (PAG) obtained mainly from ethylene oxides do not
have a sufficiently lipophilic character for use in engine oil formulae. In particular, they cannot
10 be used in combination with other mineral, synthetic or natural base oils.
Preferentially, the viscosity index VI (measured according to standard ASTM D2270) of
the PAGs according to the invention is greater than or equal to 30, preferentially greater than
or equal to 65, even more preferentially greater than or equal to 150, even more preferentially
greater than or equal to 300.
15 Preferentially, the viscosity at 40°C (KV40) measured according to standard ASTM
0445, is comprised between 20 and 800 cSt, preferably between 30 and 400 cSt, more
preferentially between 140 and 350 cSt.
Preferentially, the viscosity at 100°C (KV100) measured according to standard ASTM
0445 is comprised between 5 and 150 cSt, preferably between 10 and 100 cSt, more
20 preferentially between 20 and 60 kt.
Preferentially, the weight-average molecular weight M, measured according to the
standard ASTM D4274 is comprise between 200 and 6000 g/mol, preferably between 400 and
4000 g/mol, more preferentially between 1100 and 2600 g/mol.
Lubricant composition
2 5 The lubricant compositions according to the invention can comprise between 0.1 and
20% by mass, with respect to the total mass of lubricant composition, of polyalkylene glycol,
preferably between 0.2 et 15%) more preferentially between 0.5 and lo%, even more
preferentially between 1 and 5%) even more preferentially between 2 and 4%.
Surprisingly, the Applicant has demonstrated that the use of these polyalkylene glycols,
30 in a lubricant composition, in particular in a composition for engines, makes it possible to
considerably reduce the wear of the connecting rod bearings in the engines of hybrid or microhybrid
vehicles equipped with the Stop-and-Start system, without modifying fuel consumption
or advantageously while reducing fuel consumption.
Cabinet Hirsch 33804 Application FR12/54151
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I P Q DELWI 2 7 - Q l - 2 0 1 5 1 4 : ~ 2
Base oils
The lubricant compositions used according to the present invention comprise one or
more base oils, generally representing from 50% to 90% by mass with respect to the total mass
of the lubricant composition, preferably from 60% to 85%, more preferentially from 65 to 80%,
5 even more preferentially from 70 to 75%.
The base oil(s) used in the lubricant compositions according to the present invention
can be oils of mineral or synthetic origin from Groups I to V 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.
Saturates content
Group I Mineral oils
Grou~II Hvdrocracked oils
Group IV I Polyalphaolefins (PAO)
I
Sulphur Content
Group Ill
Hydrocracked or hydroisomerized
oils
I Group V I Esters and other bases not included in base Groups I to IV I
Viscosity index (VI)
~ 9 0 %
2 90 %
10 These oils can be oils of vegetable, animal, or mineral origin. The mineral base oils
according to the invention include all types of bases obtained by atmospheric and vacuum
distillation of crude oil, followed by refining operations such as solvent extraction,
deasphalting, solvent dewaxing, hydrotreatment, hydrocracking and hydroisomerization,
hydrofinishing.
15 The base oils of the compositions according to the present invention can also be
synthetic oils, such as certain esters of carboxylic acids and of alcohols, or polyalphaolefins. The
polyalphaolephins used as base oils are for example obtained from monomers having from 4 to
32 carbon atoms (for example octene, decene), and a viscosity at 100°C comprised between 1.5
and 15 cSt (measured according to the standard ASTM D 445). Their weight-average molecular
20 weight is typically comprised between 250 and 3000 g/mol (ASTM D5296).
Mixtures of synthetic and mineral oils can also be used, for example when multigrade
lubricant compositions are formulated making it possible to prevent cold-start problems.
Other additives
The lubricant compositions can moreover comprise viscosity index (VI) improver
25 polymers such as for example the polymeric esters, Olefin Copolymers (OCP), styrene,
butadiene or isoprene homopolymers or copolymers, polymethacrylates (PMA).
2 90 %
Cabinet Hirsch 33804
> 0.03 %
10.03 %
Application FR12/54151
FR2990214
80 I VI c 120
80 I VI c 120
10.03 % 1120
The lubricant compositions according to the present invention can contain of the order
of from 0 to 20 %, or also from 5 to 15 % , or from 7 to 10 % by mass, with respect to the total
mass of the lubricant composition, of viscosity index improver polymers, for example chosen
from the polymeric esters, Olefin Copolymers (OCP), styrene, butadiene or isoprene
5 homopolymers or copolymers, polymethacrylates (PMA).
The lubricant compositions according to the invention preferentially have a viscosity
index or VI value, measured according to ASTM 02270 greater than 130, preferentially greater
than 140, preferentially greater than 150.
Preferentially, the lubricant compositions according to the invention have a kinematic
10 viscosity (KV100) at 100°C according to the standard ASTM 0445, comprised between 3.8 cSt
and 26.1 cSt, preferably between 5.6 and 12.5 cSt which, according to the SAE J 300
classification, corresponds to grades 20 (5.6 to 9.3 cSt) or 30 (9.3 to 12.5 cSt) at
high-temperature.
Preferentially, the lubricant compositions according to the invention are in particular
15 multigrade engine lubricant compositions of grade OW or 5W at low temperature, and 20 or 30
at high temperature according to the SAE J 300 classification.
The lubricant compositions for engines used according to the invention can moreover
contain all types of additives suitable for use as engine oil.
These additives can be introduced in isolation and/or included in additive packages used
20 in commercial lubricant formulations, with performance levels as defined by the ACEA
(Association des Constructeurs Europeens d'Automobiles [European Automobile
Manufacturers' Association]) and/or the API (American Petroleum Institute). These additive
packages (or additive compositions) are concentrates comprising approximately 30% by weight
of dilution base oil.
25 Thus, the lubricant compositions according to the invention can contain in particular and
non-limitatively anti-wear and extreme-pressure additives, antioxidants, detergents that are
overbased or not, pour-point improvers, dispersants, anti-foam additives, thickeners etc.
The anti-wear and extreme-pressure additives protect the friction surfaces by formation
of a protective film adsorbed on these surfaces. The most commonly used additive is zinc
30 dithiophosphate or ZnDTP. Various phosphorus-, sulphur-, nitrogen-, chlorine- and boroncontaining
compounds are also found in this category.
A great variety of anti-wear additives exists, but the category most frequently used in
lubricant compositions used as engine oils is that of the phospho sulphur-containing additives
such as metal alkylthiophosphates, in particular zinc alkylthiophosphates, and more specifically
Cabinet Hirsch 33804
IPQ DELClI Z T - Q I . - Z 0 - ? . 5 14132
zinc dialkyldithiophosphates or ZnDTP. The preferred compounds have the formula
Zn((SP(S)(OR9)(0Rlo)),, where R9 and Rlo are linear or branched, saturated or unsaturated alkyl
groups, preferably comprising 1 to 18 carbon atoms. The ZnDTP is typically present at levels of
the order of 0.1 to 2% by mass, with respect to the total mass of the lubricant composition.
5 The amine phosphates and polysulphides, in particular sulphur-containing olefins, are
also commonly used anti-wear additives.
The anti-wear and extreme-pressure additives are generally present in the engine
lubricant compositions at levels comprised between 0.5 and 6% by mass, preferably comprised
between 0.7 and 2%, preferably between 1 and 1.5% with respect to the total mass of the
10 lubricant composition.
The antioxidants delay the degradation of the oils in service, degradation which can lead
to the formation of deposits, the presence of sludge, or an increase in the viscosity of the
lubricant composition. They act as radical inhibitors or hydroperoxide destroyers. Among the
commonly used antioxidants, phenolic and amino-type antioxidants are found.
15 The phenolic antioxidants can be ash-free, or be in the form of neutral or basic metal
salts. Typically, these are compounds containing a sterically hindered hydroxyl group, for
example when two hydroxyl groups are in each other's ortho or para position, or the phenol is
substituted by an alkyl group comprising at least 6 carbon atoms.
The amino compounds are another class of antioxidants which can be used alone or
20 optionally in combination with the phenolic antioxidants. Typical examples are the aromatic
amines of formula R,,R12R13N, where R,, is an aliphatic group, or an optionally substituted
aromatic group, R,, is an optionally substituted aromatic group, R13 is hydrogen, or an alkyl or
aryl group, or a group of formula R14S(0),R,,, where R14 and R,, are alkylene, alkenylene, or
aralkylene groups, and x is an integer equal to 0,1 or 2.
2 5 Sulphurized alkyl phenols or their alkali or alkaline-earth metal salts are also used as
antioxidants.
Another class of antioxidants is that of the oil-soluble copper compounds, for example
copper thio- or dithiophosphates, copper and carboxylic acid salts, copper dithiocarbamates,
sulphonates, phenates and acetylacetonates. Copper I and I1 salts of succinic acid or anhydride
30 are used.
These compounds, alone or in a mixture, are typically present in engine lubricant
compositions in quantities comprised between 0.1 and 5% by mass, preferentially between
0.3 and 2%, even more preferentia'lly between 0.5 and 1.5%, with respect to the total mass of
the lubricant composition.
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Detergents reduce the formation of deposits on the surface of metal parts by dissolving
oxidation and combustion by-products, and allow the neutralization of certain acid impurities
originating from the combustion and found in the lubricant composition.
The detergents commonly used in the formulation of lubricant compositions are typically
5 anionic compounds comprising a long lipophilic hydrocarbon chain and a hydrophilic head. The
associated cation is typically a metal cation of an alkali or alkaline-earth metal.
The detergents are preferably chosen from the alkali or alkaline-earth metal salts of
carboxylic acids, sulphonates, salicylates, naphthenates, as well as the salts of phenates,
preferably of calcium, magnesium, sodium or barium.
10 These metal salts can contain the metal in an approximately stoichiometric quantity or in
excess (in a quantity greater than the stoichiometric quantity). In the latter case, we are dealing
with so-called overbased detergents.
The excess metal providing the detergent with its overbased character is present in the
form of metal salts which are insoluble in oil, for example carbonate, hydroxide, oxalate,
15 acetate, glutamate, preferably carbonate, preferably of calcium, magnesium, sodium or
barium.
The lubricant compositions according to the present invention can contain all types of
detergents known to a person skilled in the art, neutral or overbased. The more or less
overbased character of the detergents is characterized by the BN (base number), measured
20 according to the standard ASTM D2896, and expressed in mg of KOH per gram. The neutral
detergents have a BN comprised approximately between 0 and 80 mg KOH/g. The overbased
detergents, for their part, have BN values typically of the order of 150 mg KOH/g and more, or
even 250 mg KOH/g or 450 mg KOH/g or more. The BN of the lubricant composition containing
the detergents is measured according to the' standard ASTM D2896 and expressed in mg of
25 KOH per gram of lubricant composition.
Preferentially, the quantities of detergents included in the lubricant compositions
according to the invention are adjusted such that the BN of said oils, measured according to
the standard ASTM D2896, is comprised between 5 and less than or equal to 20 mg of KOH per
gram of lubricant composition, preferentially between 8 and 15 to mg of KOH per gram of
30 lubricant composition.
The pour point-depressant additives improve the low-temperature behaviour of the
lubricant compositions, by slowing down the formation of paraffin crystals. These are for
example alkyl polymethacrylates, polyacrylates, polyarylamides, polyalkylphenols,
polyalkylnaphthalenes, alkylated polystyrene. They are generally present in the lubricant
Cabinet Hirsch 33804 Application FR12/54151
FR2990214
compositions according to the invention at levels comprised between 0.1 and 0.5% by mass,
with respect to the mass of lubricant composition.
The dispersants such as for example succinimides, PIB (polyisobutene) succinimides,
Mannich bases ensure that the insoluble solid contaminants constituted by the oxidation by-
5 products formed when the lubricant composition is in service, are maintained in suspension
and removed. The dispersant level is typically comprised between 0.5 and 10% by mass,
preferentially between 1 and 5% with respect to the total mass of the lubricant composition.
The lubricant compositions according to the invention can also comprise friction
modifiers, for example friction modifiers chosen from the organomolybdenum compounds.
10 These compounds are, as their name indicates, molybdenum-, carbon- and hydrogen-based
compounds, but sulphur and phosphorus, and also oxygen and nitrogen are also found in these
compounds.
The organomolybdenum compounds used in the lubricant compositions according to
the invention are, for example, the molybdenum dithiophosphates, molybdenum
15 dithiocarbamates, molybdenum dithiophosphinates, molybdenum xanthates, molybdenum
thioxanthates, and various organic molybdenum complexes such as molybdenum carboxylates,
molybdenum esters, molybdenum amides, which can be obtained by reaction of molybdenum
oxide or ammonium molybdates with fats, glycerides or fatty acids, or'fatty acid derivatives
(esters, amines, amides etc.).
20 Organomolybdenum compounds used in the lubricant compositions according to the
present invention are for example described in the application EP2078745, from paragraph
[0036] to paragraph [062].
The preferred organomolybdenum compounds are the molybdenum dithiophosphates
and/or molybdenum dithiocarbamates.
2 5 In particular, the molybdenum dithiocarbamates have proved very effective in
combination with the polyalkylene glycols for reducing the wear of the bearings. The general
formula of these molybdenum dithiocarbamates is general formula (I) below in which R,, R,, R,
or R, are independently of each other saturated or unsaturated, linear or branched alkyl
groups, comprising from 4 to 18 carbon atoms, preferentially from 8 to 13.
3 0 0 0
R1\ s - l l / s \ l l s /R3
Mo Mo '\.-/ \ / \-7'C- N (1 ) /N-C '
R2 S S S
R4
Cabinet Hirsch 33804 Application FR12154151
FR2990214
The same applies to the molybdenum dithiophosphates. The general formula of these
molybdenum dithiophosphates is general formula (It) below, in which R,, R,, R, or R, are
independently of each other saturated or unsaturated, linear or branched alkyl groups,
comprising from 4 to 18 carbon atoms, preferentially from 8 to 13.
The lubricant compositions according to the invention can comprise between 0.1 and
10 10% by mass, with respect to the total mass of lubricant composition, of organomolybdenum
compound, preferably between 0.5 and 8%, more preferentially between 1 and 5%) even more
preferentially between 2 and 4%.
The organomolybdenum compounds used in the lubricant compositions according to the
invention comprise from 1 to 30% by mass of molybdenum with respect to the total mass of
15 organomolybdenum compound, preferably from 2 to 20%, more preferentially from 4 to lo%,
even more preferentially from 8 to 5%.
The organomolybdenum compounds that can be used according to the invention
comprise from 1 to 30% by mass of sulphur with respect to the total mass of
organomolybdenum compound, preferably from 2 to 20%, more preferentially from 4 to lo%,
20 even more preferentially from 8 to 5%.
The organomolybdenum compounds used in the lubricant compositions according to the
invention comprise from 1 to 10% by mass of phosphorus with respect to the total mass of
organomolybdenum compound, preferably from 2 to 8%, more preferentially from 3 to 6%)
even more preferentially from 4 to 5%.
25
Examples
Aggravated wear on the bearings of an engine equipped with a Stop-and-Start system
was simulated by a test consisting of a succession of 12,000 stop/start cycles over 150 hours:
1) Start engine,
3 0 2) 10 seconds' operation at idling speed,
3) Stop engine
Repeat sequence 1 to 3.
The tested system comprises a 4-cylinder diesel engine with maximum torque of 200
Nm at 1750 to 2500 rpm. It is of the Stop-and-Start type and comprises a starter-alternator
Cabinet Hirsch 33804 Application FR12/54151
FR2990214
. -
14
between the vehicle's clutch and gear box. The engine lubricant composition is maintained at
I approximately 100°C in these tests. The wear is monitored by a conventional radiotracer
I technique, consisting of irradiating the surface of the connecting rod bearings' the wear of
I which is to be tested and, during the test, measuring the increase in radioactivity of the engine
I 5 lubricant composition for engine, i.e. the rate at which the lubricant composition is loaded with
I irradiated metal particles. This rate is directly proportional to the rate of wear on the bearings.
I The results are based on comparative analysis of these rates of damage (reference
lubricant composition and lubricant composition to be tested) and are validated by comparison
with a reference lubricant composition in order to incorporate elements of positive or negative
10 surface adaptation to the damage rate.
The damage rates of the tested lubricant compositions are all compared with the
damage rate of the reference lubricant composition and quantified in the form of a % ratio of
the rate denoted Wear in Table I below.
Lubricant composition A is a reference lubricant composition of grade 5W30.
15 Lubricant composition B is a lubricant composition with a polyalkylene glycol
originating from the homopolymerization of propylene oxides (100% PO). The molecular mass
of this polyalkylene glycol is 400 g/mol (ASTM D4274), its viscosity index is 65 (ASTM D2270), its
KV40 is 30 cSt (ASTM D445), its KVlOO is 5 cSt (ASTM D445):
The compositions by mass and properties of the lubricant compositions tested are
20 summarized in Table I below:
Cabinet Hirsch 33804 Application FR12/54151
FR2990214
Table I
1 Base oil 1 * 1 70% 168% I
I Viscosity index improving polymer 1 16.6 % 1 16.6 % 1
I I
I PPD 1 0.3 % 1 0.3% 1
Additive package 12.3 %
I I
12.3 %
Antioxidant
I HTHS (High Temperature High Shear), mPa.s, ASTM D4741 1 3.5 1 3.5 I
I I
0.8 %
PAG 100% PO
I CCS (Cold Crank Simulator) -30°C, mPa.s, ASTM D5293 1 6360 1 6400 1
0.8 %
2%
I I
* excluding base oil for dilution of the additive package
The base oil used is a mixture of base oils of Group Ill, with a viscosity index equal to
171.
5 The.viscosity index improving polymer used is a linear styrenelbutadiene polymer of
mass Mw equal to 139,700 (measured according to the standard ASTM D5296), of mass M,
equal to 133,000 (measured according to the standard ASTM D5296), with a polydispersity
index equal to 1.1, with 8% of active material in a base oil of Group Ill.
The antioxidant is an amine-containing antioxidant of alkylarylamine structure.
10 The PPD or Pour Point Depressant is of polymethacrylate type.
The additive package used comprises anti-wear additives, antioxidants, dispersants and
standard detergents.
It is noted that the use of a polyalkylene glycol in lubricant composition B makes it
possible to reduce wear in comparison with lubricant composition A.
15
KV100, cSt, ASTM D445 11.8
SAE Grade
Wear
Cabinet Hirsch 33804
12.04
Application FR12154151
FR2990214
5W30
100%
5W30
46%
Claims:
1. Use of a lubricant composition comprising at least one base oil and at least one
polyalkylene glycol obtained by copolymerization of ethylene oxides and of propylene oxides or
5 obtained by homopolymerization of propylene oxides for lubricating metal surfaces, polymeric
surfaces and/or amorphous carbon surfaces of the thermal internal combustion engines of
vehicles with hybrid and/or micro-hybrid engines.
2. Use according to claim 1 in which the vehicles with micro-hybrid engines are equipped
with a starter-alternator or heavy-duty starter.
10 3. Use according to claim 1 or 2 for reducing the wear of the thermal internal combustion
engine, in particular the wear of the bearings of the thermal internal combustion engine, in
particular the wear of the connecting rod bearings of the thermal internal combustion engine.
4. Use according to any one of claims 1 to 3 for increasing the lifetime of the thermal
internal combustion engine, in particular the lifetime of the bearings of the thermal internal
15 combustion engine, in particular the lifetime of the connecting rod bearings of the thermal
internal combustion engine.
5. Use according to any one of claims 1 to 4 for increasing the time between changes of
thermal internal combustion engine parts, in particular the time between changes of the
'bearings of the thermal internal combustion engine, in particular the time between changes of
20 the connecting rod bearings of the thermal internal combustion engine. . '
6. Use according to any one of claims 1 to 5 in which the lubricant composition comprises
from 0.1 to 20% by mass, with respect to the total mass of lubricant composition, of
polyalkylene glycol, preferably from 0.2 to 15%, more preferentially from 0.5 to lo%, even
more preferentially from 1 to 5%, even more preferentially from 2 to 4%.
25 7. Use according to any one of claims 1 to 6 in which the polyalkylene glycol originates
from the homopolymerization of propylene oxides.
8. Use according to any one of claims 1 to 6 in which the polyalkylene glycol originates
from the copolymerization of ethylene oxide and of propylene oxide and comprises at least
60% by mass of propylene oxide, with respect to the total mass of polyalkylene glycol.
9. Use according to any one of claims 1 to 8, in which the metal surface is an alloy.
10. Use according to claim 9 in which the alloy is steel.
11. Use according to claim 9 in which the alloy comprises as base element tin (Sn), lead
(Pb), copper (Cu), aluminium (Al), cadmium (Cd), silver (Ag) or zinc (Zn).
12. Use according to claim 11 in which the alloy comprises lead (Pb) and copper (Cu).
13. Use according to any one of claims 1 to 8 in which the polymeric surface comprises
polytetrafluoroethylene.
14. Use according to any one of claims 1 to 13 in which the kinematic viscosity at 100°C of
the lubricant composition, measured according to the standard ASTM D445, is comprised
between 5.6 and 12.5 cSt.