Additive composition for hybrid vehicles

Abstract

The present invention relates to an additive composition for lubricants comprising a carboxylate detergent and one or more sulphonate detergent(s), as well as to a lubricant composition containing the additive composition, in particular intended for hybrid vehicle engines.

Description

[0001] COMPOSITION OF ADDITIVES FOR HYBRID VEHICLES

[0002] The present invention relates to an additive composition, in particular for hybrid vehicles, as well as a lubricating composition comprising said additive composition and its use for lubricating in particular hybrid vehicle engines.

[0003] Hybrid vehicles consist of two engines: a combustion engine and an electric motor. In most hybrid vehicles, the combustion engine drives the wheels and is assisted by an electric motor. A battery provides the electricity needed to operate the electric motor. In conventional hybrid vehicles, this battery is recharged during braking and deceleration by a kinetic energy recovery system (KERS) integrated into the vehicle.

[0004] There are different hybrid vehicle technologies. These hybrid technologies include:

[0005] - micro-hybrid vehicles (also called mild hybridization), these vehicles, equipped with the “stop&start” system, recover the energy generated by braking to charge a battery which can temporarily assist the thermal engine;

[0006] - mild-hybrid vehicles which include electric assistance during acceleration; and

[0007] - Full hybrid vehicles are vehicles with total hybridization. At low speeds, when the battery is charged, the electric motor takes care of starting and locomotion. At high speeds, or when the battery is discharged, the combustion engine takes over; when increased power is needed (for example, acceleration), the two engines work together. It is thus possible to drive with the combustion engine switched off for a few kilometers.

[0008] Other complementary technologies have recently been developed: plug-in hybrid vehicles and hybrid vehicles with a range extender. Plug-in hybrid vehicles include a combustion engine and an electric motor. The battery can be recharged from the electricity grid. These vehicles can therefore run in 100% electric mode for a distance of several dozen kilometers, for example 50 kilometers. In hybrid vehicles with a range extender, only the electric motor drives the wheels. This electric motor is powered by a battery for a few dozen kilometers.When the battery reaches a certain charge threshold (for example around 30%), the thermal engine starts and drives a current generator to produce the electricity needed to recharge the battery and maintain the operation of the electric motor.

[0009] In both types of hybrid vehicles, the combustion engine is used less frequently and therefore operates at lower temperatures (around, or even below, 40°C) than the engines of other types of hybrid vehicles. However, at low temperatures, conventional lubricant compositions are more viscous and the additives are not as active as in a conventional application at higher temperatures. Current lubricants have been optimized to achieve fuel consumption gains when hot.

[0010] The operation of the internal combustion engine in a hybrid vehicle involves changes in the stresses that the lubricant endures. The temperature of the lubricant in hybrid engines is lower than that of conventional internal combustion vehicles, which results in greater dilution of the lubricant by the fuel as well as water accumulation. The presence of water and gasoline induces the formation of water-oil emulsions in the field and raises the question of its impact on the corrosion performance of the lubricant in operation.

[0011] Currently, to reduce corrosion in the presence of water and gasoline, anti-corrosion additives are used, which are added to the lubricant composition. However, this solution has several disadvantages, particularly in terms of cost and effectiveness.

[0012] There is therefore a need to reduce corrosion in hybrid engines.

[0013] The present invention therefore aims to provide a composition exhibiting a reduction in corrosion in hybrid engines.

[0014] The present invention also aims to provide a lubricating composition improving corrosion performance for hybrid vehicles.

[0015] Thus, the present invention relates to a lubricant additive composition comprising a carboxylate detergent and one or more sulfonate detergent(s).

[0016] Detergent additives are generally used to reduce the formation of deposits on the surface of metal parts by dissolving secondary oxidation and combustion products. The present invention also relates to a lubricating composition comprising at least one base oil and the aforementioned additive composition.

[0017] According to the invention, the term "additive composition" means a composition before the addition of the base oil to form a lubricating composition.

[0018] The additive composition according to the invention is a binary mixture comprising a carboxylate detergent and a sulfonate detergent or an at least ternary mixture comprising a carboxylate detergent and several sulfonate detergents.

[0019] "Carboxylate detergent" means a carboxylate compound with an associated cation which may be a metal cation of an alkali or alkaline earth metal.

[0020] The carboxylates according to the invention are, for example, aliphatic carboxylates (for example, stearates). In particular, they can be prepared by reacting a carboxylic acid with a suitable metal compound such as an oxide or a hydroxide.

[0021] "Sulfonate detergent" means a sulfonate compound with an associated cation which may be a metal cation of an alkali or alkaline earth metal.

[0022] The sulfonates of the invention may be prepared from sulfonic acids which are typically obtained by sulfonation of alkyl-substituted aromatic hydrocarbons such as those obtained from petroleum fractionation or by alkylation of aromatic hydrocarbons. Examples include those obtained by alkylation of benzene, toluene, xylene, naphthalene, diphenyl or their halogenated derivatives. This alkylation may be carried out in the presence of a catalyst with alkylating agents having from 3 to more than 70 carbon atoms. Alkaryl sulfonates usually contain from 9 to 80 or more carbon atoms (e.g., from 16 to 60 carbon atoms) per alkyl-substituted aromatic residue.

[0023] The alkali and alkaline earth metals of the above-mentioned carboxylates and sulfonates are preferably calcium, magnesium, sodium or barium.

[0024] These metal salts generally contain the metal in stoichiometric quantity or in excess, i.e. in a quantity greater than the stoichiometric quantity. These are then overbased detergent additives; the excess metal providing the overbased character to the detergent additive is then generally in the form of a metal salt insoluble in oil.

[0025] Detergent additives include overbased detergent additives, and in particular low overbased (LOB), medium overbased (MOB) or high overbased (HOB). These overbased detergent additives are defined in particular by their total base number or TBN.

[0026] The term "total base number" (or TBN) refers to the amount of bases, equivalent to milligrams of KOH in one gram of a sample of said detergent. Thus, higher TBN values ​​correspond to more alkaline products, and therefore to greater alkalinity. The TBN value is determined according to ASTM D2896.

[0027] According to the invention, a LOB detergent generally has a TBN of less than 100 mg KOH / g and a HOB detergent generally has a TBN of greater than 200 mg KOH / g.

[0028] According to one embodiment, the additive composition according to the invention comprises a carboxylate detergent and two sulfonate detergents. According to one embodiment, the additive composition according to the invention comprises a carboxylate detergent, in particular MOB, a sulfonate detergent LOB and a sulfonate detergent HOB.

[0029] According to one embodiment, in the additive composition according to the invention, the carboxylate detergent is chosen from alkali metal or alkaline earth metal salts of carboxylate, and is preferably calcium carboxylate.

[0030] According to one embodiment, the carboxylate detergent of the additive composition according to the invention is calcium carboxylate. Preferably, the carboxylate detergent of the additive composition according to the invention is calcium carboxylate MOB.

[0031] According to one embodiment, in the additive composition according to the invention, the sulfonate detergents are chosen from alkali metal or alkaline earth metal sulfonate salts, preferably calcium sulfonate, magnesium sulfonate or a mixture thereof. According to one embodiment, the sulfonate detergents of the additive composition according to the invention are a mixture of calcium sulfonate and magnesium sulfonate. Preferably, the sulfonate detergents of the additive composition according to the invention are a mixture of calcium sulfonate LOB and magnesium sulfonate HOB.

[0032] In one embodiment, the carboxylate detergent has a total base number TBN of 120 to 200 mg KOH / g, as measured according to ASTM D-2896, as noted above.

[0033] Preferably, the carboxylate detergent of the additive composition according to the invention is calcium carboxylate having a total base number TBN of from 120 to 200 mg KOH / g, as measured according to ASTM D-2896.

[0034] In one embodiment, the additive composition of the invention comprises a mixture of two sulfonate detergents, the first sulfonate detergent, preferably calcium sulfonate, having a total TBN base number of less than 100 mg KOH / g, and the second sulfonate detergent, preferably magnesium sulfonate, having a total TBN base number of greater than 200 mg KOH / g, as measured according to ASTM D-2896.

[0035] According to one embodiment, the additive composition according to the invention comprises calcium carboxylate, calcium sulfonate and magnesium sulfonate, preferably calcium carboxylate with a total number of TBN bases of from 120 to 200 mg KOH / g, calcium sulfonate with a total number of TBN bases of less than 100 mg KOH / g and magnesium sulfonate with a total number of TBN bases of greater than 200 mg KOH / g.

[0036] According to a preferred embodiment, the additive composition according to the invention comprises calcium carboxylate, calcium sulfonate and magnesium sulfonate. Preferably, the additive composition according to the invention comprises calcium carboxylate with a TBN of from 120 to 200 mg KOH / g, calcium sulfonate TBN strictly less than 200 mg KOH / g and magnesium sulfonate TBN strictly greater than 200 mg KOH / g, the TBNs being measured according to ASTM D-2896. According to one embodiment, the additive composition according to the invention comprises from 1% to 30%, preferably from 5% to 20%, preferentially from 8% to 15%, by weight of carboxylate detergent, relative to the total weight of said additive composition.

[0037] According to one embodiment, the additive composition according to the invention comprises from 1% to 20%, preferably from 5% to 10%, by weight of sulfonate detergent(s), relative to the total weight of said additive composition.

[0038] According to one embodiment, the additive composition according to the invention comprises from 1% to 30%, preferably from 5% to 20%, preferentially from 8% to 15%, by weight of carboxylate detergent and from 1% to 20%, preferably from 5% to 10%, by weight of sulfonate detergent(s), relative to the total weight of said additive composition.

[0039] According to one embodiment, the additive composition according to the invention comprises from 1% to 30%, preferably from 5% to 15% by weight of calcium carboxylate and from 1% to 20%, preferably from 5% to 10%, by weight of calcium sulfonate, preferably LOB, and magnesium sulfonate, preferably HOB, relative to the total weight of said additive composition.

[0040] According to one embodiment, the total content of carboxylate detergent and sulfonate detergent(s) in the additive composition according to the invention is from 1% to 30%, in particular from 2% to 30%, preferably from 5% to 20%, by weight relative to the total weight of said additive composition.

[0041] According to one embodiment, the total content of calcium carboxylate and calcium sulfonate and magnesium sulfonate in the additive composition according to the invention is from 1% to 30%, preferably from 5% to 20%, by weight relative to the total weight of said additive composition.

[0042] According to one embodiment, the additive composition according to the invention comprises from 1% to 10%, preferably from 2% to 5%, by weight of a first sulfonate detergent having a total number of TBN bases of less than 100 mg KOH / g, and from 1% to 10%, preferably from 2% to 5%, by weight of a second sulfonate detergent having a total number of TBN bases of greater than 200 mg KOH / g, relative to the total weight of said additive composition. An additive composition according to the invention may also comprise at least one dispersing agent, borated or not. Such dispersing agents ensure the maintenance in suspension and the removal of insoluble solid contaminants constituted by the secondary oxidation products which form when the lubricating composition is in service. They may be chosen from Mannich bases, succinimides and their derivatives, such as derivatives of polyisobutylene succinic anhydride.

[0043] According to one embodiment, the additive composition comprises one or more dispersant(s) in a content of 10% to 50% by weight, preferably 15% to 40%, and preferentially 20% to 30% by weight relative to the total weight of said additive composition.

[0044] In particular, a lubricating composition according to the invention may comprise from 0.2% to 10% by mass of dispersing agent(s), relative to the total weight of the composition.

[0045] The additive composition according to the invention may also comprise other usual additives, different from the aforementioned detergent additives.

[0046] According to one embodiment, the additive composition according to the invention further comprises one or more additional additive(s) chosen from the group consisting of anti-wear additives, antioxidant additives, viscosity index improving additives, pour point lowering additives, friction modifying additives, and mixtures thereof.

[0047] Preferably, the additive composition according to the invention further comprises at least one anti-wear additive.

[0048] There is a wide variety of anti-wear additives. Preferably, for the lubricating compositions used according to the invention, the anti-wear additives are chosen from additives comprising phosphorus and sulfur such as alkylthiophosphate metals, in particular zinc alkylthiophosphate, and more precisely zinc dialkyldithiophosphate or ZnDTP. The preferred compounds are of formula Zn((SP(S)(OR)(OR'))2, in which R and R', identical or different, independently represent an alkyl group, preferably an alkyl group comprising from 1 to 18 carbon atoms.

[0049] Amine phosphates are also anti-wear additives that can be used in the additive compositions according to the invention. However, the phosphorus atoms provided by these additives can act as a poison for automobile catalytic systems since they generate ash. It is possible to minimize these effects by substituting a portion of the amine phosphates with additives that do not provide phosphorus, such as, for example, polysulfides, in particular sulfur-containing olefins.

[0050] Advantageously, the additive compositions according to the invention comprise from 0.1% to 20% by weight, preferably from 1% to 15% by weight, more preferably from 5% to 12% by weight of anti-wear additives (or anti-wear compound), in particular ZnDTP, relative to the total weight of the additive composition according to the invention.

[0051] Advantageously, the additive compositions according to the invention comprise from 0.01% to 2% by weight, preferably from 0.05% to 1.5% by weight, more preferably from 0.1% to 1.2% by weight of anti-wear additives (or anti-wear compound), in particular ZnDTP, relative to the total weight of the lubricating composition.

[0052] Advantageously, the additive composition according to the invention may comprise at least one antioxidant additive.

[0053] Antioxidant additives generally delay the degradation of the lubricating composition. This degradation is most often expressed by the formation of deposits, by the presence of sludge or by an increase in the viscosity of the lubricating composition.

[0054] Antioxidant additives generally act as free radical inhibitors or hydroperoxide destructive inhibitors. Commonly used antioxidants include phenolic antioxidants, amine antioxidants, sulfur- and phosphorus-containing antioxidants. Some of these antioxidants, for example those comprising sulfur and phosphorus, may generate ash. Phenolic antioxidant additives may be ash-free or in the form of neutral or basic metal salts. Antioxidant additives may include, but are not limited to, sterically hindered phenols, sterically hindered phenol esters, sterically hindered phenols comprising a thioether bridge, diphenylamines, diphenylamines substituted with at least one C1-C12 alkyl group, N,N'-dialkylaryldiamines, and mixtures thereof.

[0055] Preferably according to the invention, the sterically hindered phenols are chosen from compounds comprising a phenol group for which at least one of the carbon atoms in the vicinity of the carbon atom carrying the alcohol function is substituted by at least one C1 to C10 alkyl group, preferably a C1 to C6 alkyl group, preferably a C4 alkyl group, preferably a tert-butyl group.

[0056] Amine compounds are another class of antioxidant additives that can be used, optionally in combination with phenolic antioxidant additives. Examples of amine compounds are aromatic amines, for example aromatic amines of the formula NRaRbRc in which Ra represents an aliphatic group or an aromatic group, optionally substituted, Rb represents an aromatic group, optionally substituted, Rc represents a hydrogen atom, an alkyl group, an aryl group or a group of the formula RdS(O)zRe in which Rd represents an alkylene or alkenylene group, Re represents an alkyl group, an alkenyl group or an aryl group and z represents 0, 1 or 2.

[0057] Sulfur-containing alkylphenols or their alkali or alkaline earth metal salts can also be used as antioxidant additives.

[0058] Other classes of antioxidant additives are compounds containing copper, e.g. copper thio- or dithio-phosphate, copper salts of carboxylic acids, dithiocarbamates, sulfonates, phenates, copper acetylacetonates. Copper I and II salts, succinic acid or anhydride salts may also be used.

[0059] The additive compositions according to the invention may also comprise any type of antioxidant known to those skilled in the art.

[0060] Advantageously, the lubricating composition used according to the invention comprises at least one ash-free antioxidant additive.

[0061] Also advantageously, the additive composition according to the invention comprises from 1% to 20% by weight of at least one antioxidant additive, relative to the total weight of said additive composition.

[0062] Also advantageously, the lubricating composition according to the invention comprises from 0.1% to 2% by weight relative to the total weight of the composition, of at least one antioxidant additive.

[0063] The additive composition according to the invention may also comprise at least one viscosity index improving additive of the hydrogenated butylene and styrene polymer type, of the ethylene propylene copolymer type, or of the polymethacrylate polymer type, preferably a hydrogenated butylene and styrene polymer. The additive composition according to the invention may therefore also comprise at least one viscosity index improving additive chosen from the group consisting of hydrogenated butylene and styrene polymers, ethylene propylene copolymers and polymethacrylate polymers, said viscosity index improving additive preferably being a hydrogenated butylene and styrene polymer. The additive composition according to the invention may comprise from 20% to 60% by weight of viscosity index improving additive, relative to the total weight of said additive composition.

[0064] The lubricating composition according to the invention may comprise from 0.1% to 15% by weight of viscosity index improving additive, relative to the total weight of lubricating composition.

[0065] Also advantageously, the lubricating composition used according to the invention may also comprise a pour point lowering additive.

[0066] By slowing the formation of paraffin crystals, the pour point lowering additive generally improves the cold behavior of the lubricating composition according to the invention.

[0067] Examples of pour point depressant additives include alkyl polymethacrylates, polyacrylates, polyarylamides, polyalkylphenols, polyalkylnaphthalenes, and alkyl polystyrenes.

[0068] According to one embodiment, the additive composition according to the invention further comprises a friction modifying additive, preferably based on molybdenum.

[0069] Preferably, the additive composition according to the invention comprises at least one friction-modifying additive. The friction-modifying additives make it possible to limit friction by forming adsorbed monolayers on the surfaces of the metals in contact with them. They may be chosen from compounds providing metallic elements and ash-free compounds. Among the compounds providing metallic elements, mention may be made of transition metal complexes such as Mo, Sb, Sn, Fe, Cu, Zn, the ligands of which may be hydrocarbon compounds comprising oxygen, nitrogen, sulfur or phosphorus atoms.The ash-free friction modifying additives are generally of organic origin and may be chosen from fatty acid esters and polyols, distinct from the monoester required according to the invention, alkoxylated amines, alkoxylated fatty amines, fatty epoxides, borate fatty epoxides, fatty amines or fatty acid glycerol esters. According to the invention, the fatty compounds comprise at least one hydrocarbon group comprising from 10 to 24 carbon atoms. In particular, the molybdenum-based compounds may be chosen from molybdenum dithiocarbamates (Mo-DTC), molybdenum dithiophosphates (Mo-DTP), and mixtures thereof.Advantageously, the lubricating composition according to the invention may comprise from 0.01 to 10% by mass or from 0.01 to 5% by mass, preferably from 0.01 to 2% by mass, preferably from 0.1 to 1.5% by mass or from 0.1 to 2% by mass relative to the total mass of the lubricating composition, of friction modifying additive.

[0070] The Molybdenum (Mo) in the lubricating composition of the invention is provided by an organomolybdenum compound, in particular a compound chosen from a molybdenum dithiocarbamate derivative (MoDTC), a molybdenum dithiophosphate derivative (MoDTP) or a sulfur-free molybdenum complex, preferably a molybdenum dithiocarbamate derivative (MoDTC).

[0071] Molybdenum dithiocarbamate compounds (MoDTC compound) are complexes formed of a metal core bound to one or more ligands independently selected from alkyl dithiocarbamate groups. The MoDTC compound of the compositions used according to the invention may comprise from 0.01 to 5%, preferably from 0.1 to 1.5% by mass of molybdenum, relative to the total mass of the MoDTC compound.

[0072] Preferably, the composition according to the invention comprises a molybdenum-based friction modifying additive and preferably comprises (in active content) from 1 to 1,000 ppm of Mo, preferably from 400 to 600 ppm relative to the weight of lubricating composition.

[0073] The present invention also relates to a lubricating composition comprising at least one base oil and an additive composition as defined above.

[0074] The base oils used in the lubricating compositions of the invention may be oils of mineral or synthetic origin belonging to groups I to V according to the classes defined by the API classification (or their equivalents according to the ATIEL classification (Table 1) or their mixtures. Table 1

[0075] The mineral base oils of the invention include any type of base oil obtained by atmospheric and vacuum distillation of crude oil, followed by refining operations such as solvent extraction, deasphalting, solvent dewaxing, hydrotreating, hydrocracking, hydroisomerization and hydrofinishing.

[0076] The base oils of the lubricating compositions according to the invention may also be chosen from synthetic oils, such as certain esters of carboxylic acids and alcohols, and polyalphaolefins. The polyalphaolefins used as base oils are, for example, obtained from monomers comprising from 4 to 32 carbon atoms, for example from octene or decene, and for which the viscosity at 100°C is between 1.5 and 15 mm 2 . s -1 according to ASTM D445.

[0077] As base oil, according to the present invention, mention may also be made of re-refined oils, or even oils of biological origin.

[0078] According to one embodiment, the lubricating composition according to the invention comprises a base oil content of from 75% to 95%, preferably from 80% to 90%, by weight relative to the weight of said lubricating composition. According to one embodiment, the lubricating composition according to the invention comprises less than 2.5%, preferably from 1% to 2.5%, preferentially from 1.5% to 2%, by weight of carboxylate detergent relative to the total weight of said lubricating composition.

[0079] According to one embodiment, the lubricating composition according to the invention comprises from 0.02% to 2%, preferably from 0.8% to 1.5%, by weight of sulfonate detergent(s), relative to the total weight of said lubricating composition.

[0080] According to one embodiment, the lubricating composition according to the invention comprises less than 2.5%, preferably from 1% to 2.5%, preferentially from 1.5% to 2%, by weight of carboxylate detergent relative to the total weight of said lubricating composition and from 0.02% to 2%, preferably from 0.8% to 1.5%, by weight of sulfonate detergent(s), relative to the total weight of said lubricating composition.

[0081] According to one embodiment, in the lubricating composition according to the invention, the total content of carboxylate detergent and sulfonate detergent(s) is from 0.05% to 3%, preferably from 1.1% to 2%, by weight relative to the total weight of said lubricating composition.

[0082] According to one embodiment, the lubricating composition according to the invention comprises from 0.1% to 1%, preferably from 0.5% to 0.8%, by weight of a first sulfonate detergent having a total number of TBN bases of less than 100 mg KOH / g, and from 0.1% to 1%, preferably from 0.5% to 0.8%, by weight of a second sulfonate detergent having a total number of TBN bases of greater than 200 mg KOH / g, relative to the total weight of said lubricating composition.

[0083] Preferably, the lubricating composition according to the invention further comprises one or more dispersant(s), preferably in a content of from 2% to 5% by weight, preferably from 3% to 4.5% by weight, and preferentially from 3.5% to 4% by weight, relative to the total weight of said lubricating composition. The present invention also relates to a method for lubricating a plug-in hybrid vehicle engine or a hybrid vehicle engine comprising a range extender, comprising bringing at least one mechanical part of said engine into contact with a lubricating composition as defined above.

[0084] The present invention also relates to the use of the additive composition according to the invention in a lubricating composition for reducing corrosion in a plug-in hybrid vehicle engine or one comprising a range extender.

[0085] EXAMPLES

[0086] Example 1: Preparation of lubricating compositions

[0087] The lubricating compositions are prepared by mixing the compounds described in Table 2 below.

[0088] The percentages indicated correspond to percentages by mass relative to the total mass of the composition.

[0089] Table 2

[0090] The additive package includes, among other things, an antioxidant, two anti-wear agents, a viscosity index improver and / or a friction modifier and / or a pour point depressant additive. Example 2: Evaluation of lubricant compositions

[0091] The lubricating compositions are evaluated for their anti-corrosion performance in PEHV (“Plug-In Hybrid Electric Vehicle”) hybrid engines.

[0092] The evaluation method is adapted from ASTM D1748-22 and is intended to evaluate the anti-corrosive properties of a lubricating composition.

[0093] This method evaluates the anti-corrosion properties of metal protection products in high humidity conditions. The test consists of positioning steel plates previously immersed in oil in a humidity cabinet at 49°C, with air circulation, for 72 hours (Humidity cabinet Linetronic LT / HC- 250000M).

[0094] Materials used

[0095] • Plates measuring 102x51x3.2mm, steel according to ASTM A109

[0096] • Plates measuring 102x51x3mm in PMMA •

[0097] • Solvents: heptane, ethanol

[0098] Preparation of the plates a) Sandblasted face.

[0099] • Sandblast a batch of plates under the following conditions: a pressure of 5 bars and the sandblaster nose positioned at a distance of 51 mm to 76 mm.

[0100] • For each sandblasting series, check the roughness obtained by profilometry. b) Sanded face.

[0101] • Polish the plate lengthwise using sandpaper (240 grit (number of grains / unit of surface area)).

[0102] • Always keep the plate clean and dry.

[0103] • Following the usual precautions, polish the four rounded edges with regular strokes in the direction of each edge. Ream the two holes used for suspension and clean them using a tissue moistened with the selected solvent.

[0104] • Never move the plate while sanding. Continue polishing the plate until a uniform surface is obtained. Examine the plate and if there are any scratches or imperfections, continue polishing until they disappear. • A profilometer can be used to check that the plate is well polished (Ra=0.25 to 0.51 pm). c) Sanded and sanded plates

[0105] • Leave the plates to soak in heptane for approximately 30 minutes, drain the solvent and dry in an oven for approximately 30 minutes.

[0106] • Remove any dirt from the plate using a tissue moistened with the chosen solvent.

[0107] • Clean until there are no more black marks on the tissue.

[0108] • Use the prepared plates the same day.

[0109] Preparing the enclosure

[0110] • Start the device, open the air inlet valve located at the top behind the device and allow the enclosure to stabilize according to the following operating conditions:

[0111] - Air temperature

[0112] ■ In the cabin: 48.9 ± 1.1°C

[0113] ■ Outside the cabin: 24.1 ± 5.5°C

[0114] ■ Cabin air ratio 0.878 ± 0.028 m 3 / h

[0115] - Water in the cabin

[0116] ■ Level: 203 mm ± 6.4 mm

[0117] ■ pH: 5.5 to 7.5

[0118] ■ Rotation speed: 0.33 r / min ± 0.03 r / min

[0119] Course of the test

[0120] • Place the plate in the oil at 23.3 ± 0.5°C (submerge the plate completely) and shake for 10s and drain for 10s.

[0121] • Place the plate back in the oil for 1 minute with gentle stirring.

[0122] • Hang the plate on the support and leave to drain at room temperature for 2 hours ± 20 minutes.

[0123] It is also possible to hang the plates on the appropriate support and soak them with oil by sprinkling with a pipette, then let them drain.

[0124] • At the end of the draining period, hang the plates in the humidity cabinet and open the cabinet twice a day at 7 to 8 hour intervals between the two, for 15 minutes for the first inspection, and for 5 minutes for the second inspection. • Remove the plates, rinse them with ethanol then with heptane and leave them to dry on the support.

[0125] Expression of results

[0126] • Visually assess the percentage of corrosion on each side of the plates.

[0127] • Oils (or lubricating compositions) are PASS or FAIL depending on the number and size of corrosion spots visible on the surface of the plate.

[0128] • The result will be PASS: If the plate does not contain more than 3 rust spots, and the size does not exceed 1 mm.

[0129] • The result will be FAIL: If the plate contains one or more rust spots larger than 1 mm or more than 3 spots of any size.

[0130] The results obtained for the composition CL1 according to the invention and the comparative composition CC1 are indicated in Table 3 below.

[0131] Table 3

[0132] In conclusion, it appears that the combination of additives according to the invention, comprising both a carboxylate detergent and two sulfonate detergents, makes it possible to obtain good anti-corrosion properties for the lubricating composition, in particular in comparison with an additive composition comprising other types of detergents.

Claims

CLAIMS 1. Use of a lubricant additive composition in a lubricating composition, for reducing corrosion in a plug-in hybrid vehicle engine or one comprising a range extender, said composition comprising a carboxylate detergent and one or more sulfonate detergent(s).

2. Use according to claim 1, wherein the additive composition comprises a carboxylate detergent and two sulfonate detergents.

3. Use according to claim 1 or 2, wherein the carboxylate detergent is selected from alkali metal or alkaline earth metal salts of carboxylate, and is preferably calcium carboxylate.

4. Use according to any one of claims 1 to 3, in which the sulfonate detergents are chosen from alkali metal or alkaline earth metal sulfonate salts, preferably calcium sulfonate, magnesium sulfonate or their mixture.

5. Use according to any one of claims 1 to 4, wherein the carboxylate detergent has a total base number TBN of from 120 to 200 mg KOH / g, as measured according to ASTM D-2896.

6. Use according to any one of claims 1 to 5, wherein the additive composition comprises a mixture of two sulfonate detergents, the first sulfonate detergent, preferably calcium sulfonate, having a total base number TBN of less than 100 mg KOH / g, and the second sulfonate detergent, preferably magnesium sulfonate, having a total base number TBN of greater than 200 mg KOH / g, as measured according to ASTM D-2896.

7. Use according to any one of claims 1 to 6, wherein the additive composition comprises calcium carboxylate, calcium sulfonate and magnesium sulfonate, preferably calcium carboxylate with a total base number TBN of 120 to 200 mg KOH / g, calcium sulfonate calcium with a total base number TBN less than 100 mg KOH / g and magnesium sulfonate with a total base number TBN greater than 200 mg KOH / g.

8. Use according to any one of claims 1 to 7, wherein the additive composition comprises from 1% to 30%, preferably from 5% to 20%, preferentially from 8% to 15%, by weight of carboxylate detergent relative to the total weight of said additive composition.

9. Use according to any one of claims 1 to 8, wherein the additive composition comprises from 1% to 20%, preferably from 5% to 10%, by weight of sulfonate detergent(s), relative to the total weight of said additive composition.

10. Use according to any one of claims 1 to 9, wherein the additive composition comprises from 1% to 10%, preferably from 2% to 5%, by weight of a first sulfonate detergent having a total TBN base number of less than 100 mg KOH / g, and from 1% to 10%, preferably from 2% to 5%, by weight of a second sulfonate detergent having a total TBN base number of greater than 200 mg KOH / g, relative to the total weight of said additive composition.

11. Use according to any one of claims 1 to 10, in which the total content of carboxylate detergent and sulfonate detergent(s) is from 2% to 30%, preferably from 5% to 20%, by weight relative to the total weight of said additive composition.

12. Use according to any one of claims 1 to 11, in which the additive composition further comprises one or more dispersant(s), preferably in a content of from 10% to 50% by weight, preferably from 15% to 40% by weight, and preferentially from 20% to 30% by weight, relative to the total weight of said additive composition.

13. Use according to any one of claims 1 to 12, wherein the additive composition further comprises one or more additional additive(s) selected from the group consisting of anti-wear additives, antioxidant additives, viscosity index improving additives, pour point depressant additives, friction modifying additives, and mixtures thereof.

14. A lubricant additive composition comprising a carboxylate detergent and two sulfonate detergents, the first sulfonate detergent, preferably calcium sulfonate, having a total base number (TBN) of less than 100 mg KOH / g, and the second sulfonate detergent, preferably magnesium sulfonate, having a total base number (TBN) of greater than 200 mg KOH / g, as measured according to ASTM D-2896.

15. A lubricating composition comprising at least one base oil and an additive composition according to claim 14.

16. Lubricating composition according to claim 15, wherein the base oil content is from 75% to 95%, preferably from 80% to 90%, by weight relative to the weight of said lubricating composition.

17. A method of lubricating a plug-in hybrid vehicle engine or a hybrid vehicle engine comprising a range extender, comprising bringing at least one mechanical part of said engine into contact with a lubricating composition according to claim 15 or 16.

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