LUBRICATING COMPOSITION FOR 2-STROKE MARINE ENGINES

Abstract

LUBRICANT COMPOSITION FOR 2-STROKE MARINE ENGINE The present invention relates to a lubricating composition intended to be used as a system oil in a 2-stroke marine engine, said composition comprising: - one or more base oils, of which at least 5% to 98% by mass, relative to the total mass of said lubricating composition, of one or more base oils chosen from group II oils, group III oils and mixtures thereof; - from 0.3% to 3% by mass of at least one copolymer of styrene and hydrogenated diene(s) and / or at least one olefin copolymer, relative to the total mass of said lubricating composition, and - at least one detergent in a mass content strictly less than 10% relative to the total mass of said lubricating composition, and in which the kinematic viscosity at 100°C, measured according to standard ASTM D445, of the base oil or the mixture of base oils is strictly less than 7 mm2 / s.Figure for the abstract: none.

Description

Title of the invention: COMPOSITION 2-STROKE MARINE ENGINE LUBRICANT

[0001] The present invention relates to the field of lubricating compositions, and more particularly to the field of lubricating compositions for two-stroke marine engines. More particularly, the present invention relates to a lubricating composition intended for use in a 2-stroke marine engine, this composition making it possible to reduce fuel consumption (Fuel Eco or FE). The present invention also relates to a method for reducing the fuel consumption, in particular fuel oil, of a ship using this lubricating composition.

[0002] In the automotive field, due to environmental concerns, there is an increasing desire to reduce pollutant emissions and achieve fuel savings. The nature of automotive engine lubricants has an influence on these two phenomena, and so-called "fuel-eco" (in English terminology) automotive engine lubricants have emerged. It is mainly the quality of the lubricating bases, alone or in combination with viscosity index improving polymers and / or friction modifying additives, which gives the lubricant its "fuel-eco" properties. The fuel savings generated by "fuel-eco" engine lubricants are essentially achieved during cold start-up, when the engine is not yet in stabilized mode, and not at high temperature in stabilized mode.In general, consumption gains in the NEDC cycle (New European Driving Cycle) according to European directive 70 / 220 / EEC are 5% cold (urban cycle), 1.5% hot (extra-urban cycle), for average gains of 2.5%.

[0003] However, in the field of marine lubricants, marine engines operate at a stabilized speed, there are few cold starts. The "fuel-eco" solutions adapted to automobile engines are therefore not suitable for marine engines, in particular 2T marine engines. In particular, the consumption savings obtained in the automobile field cannot be obtained in the marine field.

[0004] Furthermore, the formulation of a “fuel-eco” marine lubricant must not be to the detriment of the other performances of the lubricant. In particular, the wear resistance, the demulsification and filterability properties, the neutralization capacity, the control of the formation of varnishes and deposits (engine cleanliness (piston skirt and / or crankcase)) must not be impaired.

[0005] Marine lubricants used in 2-stroke (or 2T) engines are of two types. Cylinder oils on the one hand, ensuring the lubrication of the cylinder piston ring assembly, and system oils on the other hand, ensuring the lubrication of all moving parts outside the cylinder piston ring assembly (bearing area, turbo, etc.). In addition, the system lubricant is used as a hydraulic fluid, in other words as a means of transmitting power in a hydraulic system. The formulation of a “fuel-eco” marine system lubricant must therefore not be to the detriment of its hydraulic performance.

[0006] There is therefore an interest in having a lubricating composition suitable as a system oil for a 2-stroke marine engine, which allows satisfactory reductions in fuel consumption, particularly fuel oil, while maintaining the other performances of the lubricating composition.

[0007] An objective of the present invention is therefore to provide a lubricating composition which overcomes all or part of the aforementioned drawbacks. In particular, an objective of the present invention is to provide a lubricating composition suitable as a system oil in a 2-stroke marine engine, allowing fuel savings, in particular Fuel Eco (FE) savings, while maintaining the other performances of the lubricating composition, in particular its hydraulic performances.

[0008] Another objective of the present invention is to provide a method for lubricating a 2-stroke marine engine allowing fuel savings, in particular fuel oil, while maintaining the other performances of the lubricating composition.

[0009] Still other objectives will appear on reading the description of the invention which follows.

[0010] For this purpose, the invention relates to a lubricating composition intended to be used as a system oil in a 2-stroke marine engine, said composition comprising:

[0011] - one or more base oils, of which at least 5% to 98% by mass, relative to the total mass of said lubricating composition, of one or more base oils chosen from group II oils, group III oils and their mixtures;

[0012] - from 0.3% to 3% by mass of one or more copolymer(s) of styrene and diene(s) hydrogenated and / or one or more olefin copolymer(s), relative to the total mass of said lubricating composition, and

[0013] - at least one detergent in a mass content strictly less than 10% per relative to the total mass of said lubricating composition, and

[0014] wherein the kinematic viscosity at 100°C, measured according to ASTM D445, of the base oil or mixture of base oils is strictly less than 7 mm2 / s.

[0015] Surprisingly, the applicant found that it was possible to formulate lubricating compositions for 2-stroke marine engines making it possible to reduce significantly reduce fuel consumption, particularly fuel oil (Fuel Eco), while maintaining the other performance characteristics of the lubricating composition, compared to conventional lubricating compositions for marine engines. This is made possible by a lubricating composition with the aforementioned characteristics.

[0016] Thus, the present invention makes it possible to formulate lubricating compositions of the system oil type for 2-stroke marine engines, making it possible to combine both fuel savings, in particular fuel (Fuel Eco), and maintenance of the other performances of the lubricating compositions.

[0017] In particular, the lubricating composition according to the invention has hydraulic performances of the same level as a non-FE system lubricant.

[0018] The present invention also relates to a composition as defined above, in which the copolymer of styrene and hydrogenated diene(s) is a non-linear copolymer, preferably a star-shaped copolymer.

[0019] The present invention also relates to a composition as defined above, in which the copolymer of styrene and hydrogenated diene(s) is a copolymer of styrene and at least two hydrogenated dienes.

[0020] The present invention also relates to a composition as defined above, in which the copolymer of styrene and hydrogenated diene(s) is a copolymer of hydrogenated styrene, isoprene and butadiene, preferably star-shaped.

[0021] The present invention also relates to a composition as defined above, having a kinematic viscosity at 100°C, measured according to the ASTM D445 standard, of less than 16.3 mm2 / s, preferably between 9.3 and 16.3 mm2 / s, and preferentially between 9.3 and 12.5 mm2 / s.

[0022] The present invention also relates to the use of a lubricating composition as defined above as a system oil for the lubrication of 2-stroke marine engines and / or for reducing the fuel consumption of a 2-stroke marine engine.

[0023] The present invention also relates to a method for lubricating a 2-stroke marine engine, comprising bringing at least one mechanical part of the 2-stroke marine engine, in particular moving parts other than the piston-cylinder ring assembly, into contact with a lubricating composition as defined above.

[0024] The present invention also relates to a method for reducing the fuel consumption of a 2-stroke marine engine comprising bringing at least one mechanical part of the 2-stroke marine engine, in particular moving parts other than the piston-cylinder ring assembly, into contact with a lubricating composition as defined above.

[0025] Other characteristics and variants of the lubricating composition according to the invention will become more apparent on reading the description and examples which follow, given by way of illustration and not limitation of the invention.

[0026] In the rest of the text, the expressions “between ... and ...”, “from ... to ...”, “ranging ... to ...” and “varying from ... to ...” are equivalent and are intended to mean that the limits are included, unless otherwise stated.

[0027] As indicated above, the present invention relates to a lubricating composition for use as a system oil in a 2-stroke marine engine, said composition comprising:

[0028] - one or more base oils, of which at least 5% to 98%, preferably 60% at 98%, preferably from 70% to 98%, by mass, relative to the total mass of said lubricating composition, of one or more base oils, chosen from group II oils, group III oils and their mixtures;

[0029] - from 0.3% to 3%, in particular from 0.5% to 2%, by mass of one or more copolymer(s) of styrene and hydrogenated diene(s) and / or one or more olefin copolymer(s), relative to the total mass of said lubricating composition, and

[0030] - at least one detergent in a mass content strictly less than 10% per relative to the total mass of said lubricating composition, and

[0031] wherein the kinematic viscosity at 100°C, measured according to ASTM D445, of the base oil or base oil mixture is strictly less than 7 mm2 / s.

[0032] A lubricating composition according to the invention is therefore suitable as a system oil for two-stroke marine engines, and more particularly as a system oil intended for the lubrication of the lower part of two-stroke marine engines, in particular the crankpins and the crankshaft bearings.

[0033] According to one embodiment, a lubricating composition according to the invention has a kinematic viscosity at 100°C, measured according to the ASTM D445 standard, of less than 16.3 mm2 / s, in particular between 6.1 mm2 / s and 16.3 mm2 / s, preferably between 9.3 mm2 / s and 16.3 mm2 / s, and preferentially between 9.3 and 12.5 mm2 / s.

[0034] In one embodiment of the invention, the lubricating compositions according to the invention have a viscometric grade ranging from SAE 16 to SAE 40 according to the SAEJ300 classification. In particular, a lubricating composition according to the invention may have a viscometric grade SAE 16, SAE 20, SAE 30 or SAE 40 according to the SAEJ300 classification, preferably SAE 30 or SAE 40, advantageously SAE 30.

[0035] Grade 16 (or SAE 16) oils have a kinematic viscosity at 100°C of between 6.1 and 8.2 mm2 / s. Grade 20 (or SAE 20) oils have a kinematic viscosity at 100°C of between 6.9 and 9.3 mm2 / s. Grade 30 (or SAE 30) oils have a kinematic viscosity at 100°C of between 9.3 and 12.5 mm2 / s. Grade 40 (or SAE 40) oils have a kinematic viscosity at 100°C of between 12.5 and 16.3 mm2 / s.

[0036] Kinematic viscosity is measured according to ASTM D445 at 100°C. Base oil(s)

[0037] A lubricating composition according to the invention comprises a base oil or a mixture of base oils including at least one or more oils chosen from group II oils, group III oils and mixtures thereof.

[0038] A lubricating composition according to the invention therefore comprises at least one group II base oil and / or at least one group III oil.

[0039] In other words, a lubricating composition according to the invention comprises one or more group II oils, or one or more group III oils or even a mixture of group II and group III oils.

[0040] A lubricating composition according to the invention comprises from 5% to 98% by mass of one or more group II and / or III base oils, relative to the total mass of said lubricating composition.

[0041] Preferably, a lubricating composition according to the invention comprises from 30% to 98%, in particular from 60% to 98%, preferably from 65% to 98%, and more preferably from 70% to 98%, by mass relative to the total mass of said lubricating composition of one or more base oils chosen from group II oils, group III oils and their mixtures.

[0042] According to one embodiment, a lubricating composition according to the invention comprises at least one group II oil, in particular in a mass content greater than or equal to 65%.

[0043] In a particular embodiment, a lubricating composition according to the invention comprises one or more group II oil(s) alone (in other words, does not comprise group III oil), in particular in a mass content greater than or equal to 60% by mass, in particular greater than or equal to 65%, relative to the total mass of said lubricating composition. In a particular embodiment, the mass content of group II oil(s), in particular in the case where the lubricating composition does not comprise group III oil, may be greater than or equal to 70% by mass, in particular greater than or equal to 75% by mass.

[0044] According to one embodiment, a lubricating composition according to the invention comprises at least one group III oil.

[0045] In another particular embodiment, a lubricating composition according to the invention comprises one or more group III oil(s) alone (in other words, does not comprise group II oil), in particular in a mass content greater than or equal to 60%, or even greater than or equal to 65%, or even greater than or equal to 70%, or even greater than or equal to 75%, relative to the total mass of said lubricating composition.

[0046] A lubricating composition may comprise, in addition to said group II base oil(s) and / or said group III oil(s), one or more additional base oil(s), in other words one or more base oils distinct from the group II and III oils.

[0047] According to one embodiment, a lubricating composition according to the invention may thus comprise one or more additional base oils chosen from group I base oils, group IV base oils and group V base oils, said additional base oil preferably being a group I base oil.

[0048] According to one embodiment, a lubricating composition according to the invention comprises at least one additional base oil chosen from group I base oils.

[0049] In this embodiment, the lubricating composition according to the invention thus comprises one or more group II and / or group III base oil(s), in combination with a group I base oil.

[0050] For example, a lubricating composition according to the invention may comprise at least one group II base oil, in combination with at least one group I base oil.

[0051] Preferably, the mass content of additional base oil(s), when present, in particular group I oil(s), is from 0.5% to 95%, in particular from 1% to 90%, in particular from 1% to 50%, in particular from 1.5% to 30%, and preferably from 2% to 15%, relative to the total mass of said lubricating composition.

[0052] The above-mentioned base oils may be chosen from base oils conventionally used in the field of lubricating oils, such as mineral, synthetic or natural, animal or vegetable oils or mixtures thereof.

[0053] It may be a mixture of several base oils, for example a mixture of two, three or four base oils.

[0054] The base oils used in the lubricating compositions according to the invention may in particular be 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 (table 1), or their mixtures.

[0055] [Tableauxl] Saturates content Sulphur content Viscosity index (VI) Group I Mineral oils <90% > 0.03% 80 <VI < 120 Groupe II Huiles hydrocraquées >90% <0.03% 80 <VI < 120 Groupe III Huiles hydrocraquées ou hydro-isomérisées >90% <0.03% >120 Group IV Polyalphaolefins (PAO) Group V Esters and other bases not included in groups I to IV

[0056] 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 extraction, de-alphatting, solvent dewaxing, hydrotreating, hydrocracking, hydroisomerization and hydrofinishing.

[0057] Group I mineral bases are for example the bases called Neutral Solvent (such as for example, 150NS, 330NS, 500NS or 600NS) or Brightstock.

[0058] Synthetic base oils may be esters of carboxylic acids and alcohols, polyalphaolefins or polyalkylene glycols (PAG) obtained by polymerization or copolymerization of alkylene oxides comprising from 2 to 8 carbon atoms, in particular from 2 to 4 carbon atoms. The polyalphaolefins used as base oils are for example obtained from monomers comprising 4 to 32 carbon atoms, for example from decene, octene or dodecene, and whose viscosity at 100°C is between 1.5 and 15 mm2.s 1 according to the ASTM D445 standard. Their average molecular mass is generally between 250 and 3000 g / mol according to the ASTM D5296 standard.

[0059] Mixtures of synthetic and mineral oils, which can be bio-sourced, can also be used.

[0060] The base oil or all of the base oils present in the lubricating composition according to the invention, including said group II and / or group III base oil(s), and optionally one or more additional oils, for example one or more group I oils, may represent from 50% to 99%, in particular from 50% to 98%, in particular from 55% to 98% by mass, in particular from 60% to 98% by mass, relative to the total mass of the composition.

[0061] A lubricating composition according to the invention can be characterized by its BOV (for “Base Oil Viscosity” in English) which is an indication of the viscosity of the base oil or of the mixture of all the base oils of the lubricating composition.

[0062] Thus, the base oil or the mixture of all the base oils of the lubricating composition according to the invention has a kinematic viscosity at 100°C, measured according to the ASTM D445 standard, strictly less than 7 mm2 / s.

[0063] According to one embodiment, the BOV of a lubricating composition according to the invention is less than or equal to 6.5 mm2 / s.

[0064] As indicated above, a lubricating composition according to the invention comprises at least one copolymer of styrene and hydrogenated diene(s) and / or at least one olefin copolymer.

[0065] According to one embodiment, a lubricating composition according to the invention comprises a copolymer of styrene and hydrogenated diene(s) and an olefin copolymer. According to this embodiment, the copolymer of styrene and hydrogenated diene(s) is preferably non-linear, preferably star-shaped.

[0066] According to another embodiment, the lubricating composition according to the invention comprises at least one copolymer of styrene and hydrogenated diene(s) but is free of olefin copolymer.

[0067] According to one embodiment, the lubricating composition according to the invention comprises at least one olefin copolymer but is free of copolymer of styrene and hydrogenated diene(s).

[0068] According to one embodiment, the total content of olefin copolymer(s) and copolymer(s) of styrene and hydrogenated diene(s) in a lubricating composition according to the invention is strictly greater than 0.8% by mass, preferably greater than or equal to 0.85% by mass, relative to the total mass of said composition. Copolymer of styrene and hydrogenated diene(s)

[0069] According to one embodiment, a lubricating composition of the invention comprises at least one copolymer of styrene and hydrogenated diene(s), alone or in combination with an olefin copolymer.

[0070] The copolymer of styrene and hydrogenated diene(s) (or styrene / hydrogenated diene(s) copolymer) according to the invention is a copolymer of styrene and one or more hydrogenated diene(s), and in particular a copolymer of styrene and several hydrogenated dienes.

[0071] According to one embodiment, the copolymer of styrene and hydrogenated diene(s) is a copolymer of styrene and two hydrogenated dienes.

[0072] According to one embodiment, a lubricating composition of the invention comprises at least one copolymer of styrene and several hydrogenated dienes, in particular a copolymer of styrene and two hydrogenated dienes, alone or in combination with an olefin copolymer.

[0073] Preferably, when a lubricating composition according to the invention comprises a copolymer of styrene and hydrogenated diene(s), in combination with an olefin copolymer, the copolymer of styrene and hydrogenated diene(s) is non-linear, in particular in star form.

[0074] The copolymer of styrene and hydrogenated diene(s) used according to the invention may be chosen from copolymers in linear or star form, preferably star-shaped.

[0075] In particular, the copolymer of styrene and hydrogenated diene(s) is a block copolymer.

[0076] According to one embodiment, the copolymer of styrene and hydrogenated diene(s) is a non-linear copolymer, in particular when used in combination with an olefin copolymer.

[0077] According to one embodiment, the copolymer of styrene and hydrogenated diene(s) is a star copolymer, in particular when used in combination with an olefin copolymer.

[0078] Preferably, the content of hydrogenated diene units is from 50% to 98%, preferably from 60% to 98%, more preferably from 70% to 98% or from 70% to 97%, even more preferably from 70% to 96%, in particular from 75% to 95%, by mass relative to the mass of the copolymer.

[0079] Preferably, the content of styrene units is from 2% to 50%, preferably from 2% to 40%, more preferably from 2% to 30%, or from 10% to 40%, even more preferably from 4% to 30%, by mass relative to the mass of the copolymer.

[0080] Preferably, the styrene / hydrogenated diene(s) copolymer is used in an amount of 0.1% to 3% by mass relative to the total mass of the lubricating composition. Preferably, the styrene / hydrogenated diene(s) copolymer is used in an amount of 0.1% to 2.5%, preferably 0.1% to 2%, by mass relative to the total mass of the lubricating composition.

[0081] Preferably, the styrene / hydrogenated diene(s) copolymer is used in an amount of 0.6% to 3%, preferably 0.8% to 2%, by mass relative to the total mass of the lubricating composition.

[0082] According to one embodiment, the lubricating composition according to the invention comprises more than 0.6% by mass of copolymer of styrene and hydrogenated diene(s) relative to the total mass of the lubricating composition.

[0083] This quantity is understood as the quantity of active polymer material (dry extract). In fact, the copolymer of styrene and hydrogenated diene(s) used in the context of the The present invention may be in the form of a dispersion in a mineral or synthetic oil, for example with a dilution rate of 5 to 20% by mass.

[0084] According to one embodiment, the copolymer of styrene and hydrogenated diene(s) comprises styrene units in a content of styrene units ranging from 2% to 50%, preferably from 2% to 40%, preferentially from 10% to 40%, by mass relative to the mass of copolymer, and hydrogenated diene(s) units in a content ranging from 50% to 98%, preferably from 60% to 98%, preferentially from 70% to 97%, and in particular from 70% to 96%, by mass relative to the mass of copolymer.

[0085] According to one embodiment, the hydrogenated diene unit(s) may be chosen from hydrogenated butadiene and hydrogenated isoprene units.

[0086] Preferably, the hydrogenated diene units are hydrogenated butadiene units and hydrogenated isoprene units.

[0087] According to one embodiment, the copolymer of styrene and hydrogenated dienes is a copolymer, preferably non-linear, of styrene and at least two hydrogenated dienes, in particular a non-linear copolymer of styrene and two hydrogenated dienes.

[0088] According to one embodiment, the copolymer of styrene and hydrogenated diene(s) used in lubricating compositions according to the invention is a copolymer of hydrogenated styrene, isoprene and butadiene, in other words is formed from styrene units, hydrogenated isoprene units and hydrogenated butadiene units, also called “styrene / butadiene / isoprene copolymer”.

[0089] In a particular embodiment, the styrene / butadiene / isoprene copolymer may comprise from 2% to 40%, preferably from 3% to 10%, by mass of styrene units, from 15% to 40%, preferably from 20% to 30%, by mass of hydrogenated butadiene units, and from 50% to 80%, preferably from 60% to 75%, by mass of hydrogenated isoprene units.

[0090] Preferably, the styrene / butadiene / isoprene copolymer is a star copolymer.

[0091] According to one embodiment, the copolymer of styrene and hydrogenated diene(s) is neither a hydrogenated styrene / butadiene polymer nor a hydrogenated styrene / isoprene polymer. Olefin copolymer

[0092] According to one embodiment, the lubricating composition according to the invention comprises at least one olefin copolymer, alone or in combination with a copolymer of styrene and hydrogenated diene(s) as defined above.

[0093] It is understood that an olefin copolymer according to the invention is distinct from copolymers of styrene and hydrogenated diene(s).

[0094] Preferably, the olefin copolymer is an ethylene-propylene copolymer.

[0095] These olefin copolymers may be copolymers based on ethylene units and propylene units, or copolymers based on ethylene units, propylene units and diene units (EPDM). Preferably, the olefin copolymer according to the invention is an ethylene / propylene copolymer.

[0096] The olefin copolymer used according to the invention is in linear or star form, preferably in linear form. The olefin copolymer used according to the invention is in block form or in random form.

[0097] The olefin copolymer used according to the invention advantageously has a content of ethylene units, ranging from 30% to 80% by mass, relative to the mass of olefin copolymer, preferably from 30% to 70%, more preferably from 40% to 70%.

[0098] The olefin copolymer used according to the invention advantageously has a content of propylene units, ranging from 20% to 70% by mass, relative to the mass of olefin copolymer, preferably from 30% to 70%, more preferably from 30% to 60%.

[0099] The amount of olefin copolymer in a lubricating composition according to the invention is from 0.1% to 3% by mass, preferably from 0.1% to 2%, by mass relative to the total mass of the lubricating composition. This amount is understood as the amount of dry matter of polymer. Indeed, the olefin copolymer used in the context of the present invention is sometimes found diluted in a mineral or synthetic oil (most often a group I, II or III oil according to the API classification). Additives

[0100] A lubricating composition according to the invention may comprise all types of additives usually used in marine lubricants.

[0101] It is understood that the nature of the other additives used is chosen so as not to negatively impact the properties sought for the marine lubricant.

[0102] These additives can be introduced in isolation and / or in the form of a mixture, or "additive package", similar to those already available for sale for commercial lubricant formulations for marine engines.

[0103] These additives may in particular be chosen from detergent additives, basic organic additives improving the total base number (TBN), anti-wear additives, extreme pressure additives, dispersant additives, anti-foaming agents, anti-oxidant additives, anti-rust additives, friction modifiers, and mixtures thereof. Detergent(s)

[0104] A lubricating composition according to the invention comprises one or more detergents.

[0105] The mass content of detergent(s) is strictly less than 10% relative to the total mass of the lubricating composition, in particular strictly less than 9% by mass.

[0106] According to one embodiment, the quantity of detergents is from 0.1% to 8%, preferably from 0.2% to 5%, by mass relative to the total mass of said lubricating composition.

[0107] According to one embodiment, the quantity of detergents is from 0.5% to 4%, preferably from 1% to 3%, by mass relative to the total mass of said lubricating composition.

[0108] The detergents used in the lubricating compositions according to the present invention may be chosen from detergents known to those skilled in the art.

[0109] Detergents commonly used in the formulation of lubricating compositions are typically 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.

[0110] The detergents may be chosen from alkali or alkaline earth metal salts of carboxylates, sulfonates, salicylates, naphthenates, and phenates taken alone or in mixture. The detergents are named according to the nature of the hydrophobic chain, carboxylate, sulfonate, salicylate, naphthenate or phenate.

[0111] The alkali and alkaline earth metals are preferably calcium, magnesium, sodium or barium, more preferably calcium.

[0112] The detergents used will be non-overbased (or neutral) or overbased. We speak of non-overbased or "neutral" detergents when the metal salts contain the metal in an approximately stoichiometric quantity. We speak of overbased detergents when the metal is in excess (in an amount greater than the stoichiometric quantity). The excess metal providing the overbased character to the detergent is in the form of oil-insoluble metal salts. Overbased detergents are thus in the form of micelles composed of insoluble metal salts held in suspension in the lubricating composition by the detergents in the form of oil-soluble metal salts. These micelles may contain one or more types of insoluble metal salts, stabilized by one or more types of detergents.Overbased detergents will be said to be of mixed type if the micelles include several types of detergents, differing from each other by the nature of their hydrophobic chain.

[0113] Preferred detergents are carboxylates, sulfonates and / or phenates, taken alone or in mixture, in particular calcium carboxylates, sulfonates and / or phenates.

[0114] The BN (Base Number measured according to ASTM D2896) of the lubricating compositions according to the present invention is totally or partly provided by neutral or overbased detergents based on alkali or alkaline earth metals.

[0115] The BN value of the lubricating compositions according to the present invention, measured according to ASTM D2896, can vary from 1 to 80 mg of KOH / g, preferably from 3 to 50 mg of KOH / g, more preferably from 4 to 20 mg of KOH / g. The BN value will be chosen according to the conditions of use of the lubricating compositions and in particular according to the sulfur content of the fuel oil used.

[0116] A lubricating composition according to the invention may further comprise one or more additives other than detergents.

[0117] According to one embodiment, a lubricating composition according to the invention comprises an anti-wear additive and / or an extreme pressure additive.

[0118] Anti-wear additives and extreme pressure additives protect friction surfaces by forming a protective film adsorbed on these surfaces.

[0119] There is a wide variety of anti-wear additives. Examples include phospho-sulfur additives, such as metal alkylthiophosphates, in particular zinc alkylthiophosphates, and more specifically zinc dialkyldithiophosphates (or ZnDTP). The alkyl groups of these zinc dialkyldithiophosphates preferably contain from 1 to 18 carbon atoms. The preferred compounds are of formula Zn((SP(S)(OR)(OR'))2, in which R and R', which may be identical or different, independently represent an alkyl group, preferably an alkyl group comprising from 1 to 18 carbon atoms.

[0120] Preferably, a lubricating composition according to the invention may comprise ZnDTP.

[0121] Amine phosphates, polysulfides, in particular sulfur-containing olefins, are also anti-wear additives which can be used in a lubricating composition according to the invention. Mention may also be made of nitrogen-containing and sulfur-containing anti-wear additives, such as, for example, metal dithiocarbamates, in particular molybdenum dithiocarbamates.

[0122] Advantageously, the extreme pressure and / or anti-wear additive(s) may be present in a lubricating composition according to the invention in a content ranging from 0.01% to 6% by mass, preferably from 0.05% to 4% by mass, more preferably from 0.1% to 2% by mass relative to the total mass of lubricating composition.

[0123] A lubricating composition considered according to the invention may also comprise at least one basic organic additive making it possible to increase the total base number, known as TBN, of the lubricating composition.

[0124] These basic organic additives, called “TBN boosters”, make it possible to increase the total base number of the composition; in other words, they are capable of neutralizing acids and provide improved detergent performance.

[0125] Basic organic additives improving TBN are known to those skilled in the art.

[0126] They may in particular be organic amino, alkyl or aromatic additives or even nitrogenous dispersants.

[0127] As basic organic additives improving TBN, fatty amines may be mentioned, for example.

[0128] In particular, said basic organic additive(s) improving the TBN may be used in a content greater than or equal to 0.1% by mass, relative to the total mass of said lubricating composition, in particular in a content of between 0.1% and 10% by mass, more particularly between 0.5% and 7% by mass, preferably between 1% and 5% by mass.

[0129] A lubricating composition according to the invention may also comprise at least one anti-foam additive, in particular used to counter the effect of metallic detergents. The anti-foam additives may be chosen from polar polymers such as polymethylsiloxanes or polyacrylates.

[0130] In particular, a lubricating composition according to the invention may comprise from 0.01% to 3% by mass of anti-foam additive(s), relative to the total mass of the lubricating composition.

[0131] A lubricating composition according to the invention may comprise at least one antioxidant additive. The antioxidant additives are essentially dedicated to delaying the degradation of the lubricating composition in service. This degradation may in particular result in the formation of deposits or in an increase in the viscosity of the lubricating composition. They act in particular as radical inhibitors or hydroperoxide destroyers.

[0132] Among the commonly used antioxidant additives, mention may be made of phenolic type antioxidant additives, amine type antioxidant additives, phosphosulfur antioxidant additives. The phenolic antioxidant additives may be in the form of neutral or basic metal salts. The antioxidant additives may in particular be chosen from sterically hindered phenols, sterically hindered phenol esters and sterically hindered phenols comprising a thioether bridge, diphenylamines, diphenylamines substituted by at least one C1-C12 alkyl group, N,N'-dialkyl-aryl-diamines and mixtures thereof.

[0133] Preferably, the sterically hindered phenols are chosen from compounds comprising a phenol group in which at least one vicinal carbon of the carbon carrying the alcohol function is substituted by at least one C1-C10 alkyl group, preferably a C1-C6 alkyl group, preferably a C4 alkyl group, preferably by the tert-butyl group.

[0134] Amino 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 formula N(R5)(R6)(R7) in which R5 represents an aliphatic group or an aromatic group, optionally substituted, R6 represents an aromatic group, optionally substituted, R7 represents a hydrogen atom, an alkyl group, an aryl group or a group of formula R8S(O)ZR9 in which R8 represents an alkylene group or an alkenylene group, R9 represents an alkyl group, an alkenyl group or an aryl group and z represents 0, 1 or 2.

[0135] Sulfurized alkyl phenols or their alkali and alkaline earth metal salts can also be used as antioxidant additives.

[0136] A lubricating composition according to the invention may contain all types of antioxidant additives known to those skilled in the art.

[0137] Advantageously, the antioxidant additive(s) may be present in a lubricating composition according to the invention in a content ranging from 0.01% to 10% by mass, preferably from 0.05% to 8% by mass, more preferably from 0.1% to 5% by mass, even more preferably from 0.1% to 2% by mass relative to the total mass of lubricating composition.

[0138] In one embodiment, the lubricating composition according to the invention may further comprise at least one dispersing agent.

[0139] The dispersing agents ensure the maintenance in suspension and the evacuation of insoluble solid contaminants constituted by the secondary oxidation products which are formed when the lubricating composition is in service or by combustion residues, unburned matter, or any other contaminant. They can be chosen from Mannich bases, succinimides and their derivatives, in particular from polyisobutylene succinimide (PIBSI) or polyisobutylene succinic anhydride (PIBSA).

[0140] In particular, a lubricating composition considered according to the invention may comprise from 0.2% to 10% by mass of dispersing agent(s), relative to the total mass of the composition.

[0141] A lubricating composition according to the invention may also comprise friction modifiers. Friction modifiers make it possible to reduce friction between engine parts as much as possible. These additives help to prevent engine damage, while increasing fuel economy. They can be chosen from organic molecules having a polar function at one end: carboxylic acid and derivatives, glycerol ester, imides, fatty amides, fatty amines and derivatives, phosphoric or phosphonic acid derivatives (phosphite or amine phosphate). They act by chemical reaction on the metal surface or by absorption on the metal surface (hydrogen bonding).

[0142] Another type of friction modifier can be selected from organometallic compounds: molybdenum dithiophosphate, molybdenum dithiocarbamate, copper oleate, copper salicylate.

[0143] Finally, the friction modifier can be a solid compound: the most common being molybdenum disulfide MoS2, boron nitride, polytetrafluoroethylene (PTFE).

[0144] The mass content of friction modifier in a lubricating composition according to the invention may range from 0.01% to 5%, preferably from 0.02% to 4%, more preferably from 0.02% to 2% relative to the total mass of the lubricating composition.

[0145] According to one embodiment, a composition of the invention does not comprise a glycerol ester.

[0146] According to one embodiment, a composition of the invention does not comprise a polyol ester(s).

[0147] A lubricating composition according to the invention is advantageously used as a system oil in 2-stroke marine engines.

[0148] The invention also relates to a system oil comprising a lubricating composition as defined above.

[0149] By system oil according to the invention is meant any lubricating composition intended for the lubrication of all moving parts in the 2-stroke marine engine excluding the piston-cylinder ring assembly, in particular the lower part of 2-stroke marine engines, in particular the crankpins and the crankshaft bearings. The system oil also protects the crankcase and cools the piston skirts.

[0150] The present invention also relates to the use of a lubricating composition as defined above, as a system oil for the lubrication of 2-stroke marine engines.

[0151] The invention also relates to the use of a lubricating composition as defined above, for reducing the fuel consumption, in particular fuel oil, of a 2-stroke marine engine.

[0152] The term "reduce fuel consumption" refers to a decrease in fuel consumption compared to the fuel consumption associated with a conventional lubricating composition.

[0153] The reduction in fuel consumption, particularly fuel oil, is notably evaluated by engine bench tests.

[0154] All of the characteristics and preferences presented for the lubricating composition apply to the above use.

[0155] The present invention also relates to a method for lubricating a 2-stroke marine engine, comprising bringing at least one mechanical part of the 2-stroke marine engine, in particular moving parts outside the piston ring cylinder assembly as described above, into contact with a lubricating composition as defined above.

[0156] The present invention also relates to a method for reducing the consumption of fuel, in particular fuel oil, of a 2-stroke marine engine comprising bringing at least one mechanical part of the 2-stroke marine engine, in particular moving parts other than the piston ring cylinder assembly as described above, into contact with a lubricating composition as defined above.

[0157] Preferably, the lubricating composition is a system oil, brought into contact with the parts of the lower part of the 2-stroke marine engine, as indicated above.

[0158] All of the characteristics and preferences presented for the lubricating composition also apply to the processes / methods according to the invention.

[0159] The various objects of the present invention and their implementations will be better understood upon reading the examples which follow. These examples are given for information purposes only, without limitation. EXAMPLES

[0160] Example 1: Formulation of a lubricating composition according to the invention Preparation of the composition

[0161] A lubricating composition according to the invention, CL1, was prepared by simple mixing, at temperatures between 60 and 70°C, of ​​the following components, in the mass proportions indicated in Table 2.

[0162] [Tables2] CL1 Compounds Additive package 1 (1) 2.42 Styrene / diene(s)(2) copolymer (10.7% active matter in a group el base oil) 8.40 Group II oil(3) 89.18

[0163] (1) Additive packages including in particular detergents in a content greater than 50% by mass, anti-wear additives, in particular phospho-sulfur, and anti-foam;

[0164] (2) Star isoprene / butadiene / styrene copolymer having the proportions following mass quantities: 70% hydrogenated isoprene, 23% hydrogenated butadiene and 7% styrene,

[0165] (3) Group II base oil, having a viscosity measured at 100°C according to ASTM D445 (KV100) standard of 4.4 mm2 / s and a Noack volatility, determined according to CEC L-040-093 standard, of 15.2% by mass.

[0166] Measurement of the rheological properties of the lubricating composition

[0167] The kinematic viscosity at 100°C (KV100) of the composition prepared above was measured according to ASTM D445.

[0168] The BOV or "Base Oil Viscosity" in English, corresponds to the viscosity KV100 of the base oil or mixture of base oils. In the case of a mixture of base oils, the KV100 of the mixture of base oils is calculated according to the following equation (Arrhenius rule), for a mixture of 2 base oils:

[0169] log (visco mixture) = Xi*log(viscol) +x2*log(visco2), with

[0170] visco mixture the viscosity of the mixture of oils 1 and 2,

[0171] viscol the viscosity of base oil 1, visco2 the viscosity of base oil 2,

[0172] xi and x2 the respective molar fractions of base oil 1 and base oil 2 (x1+x2=l),

[0173] the same equation can be implemented and extrapolated for a mixture of n base oils.

[0174] As detailed below, the fuel consumption saving properties of the lubricating composition according to the invention are compared to those of a 2T system oil marketed under the reference SHELL MELINA S30.

[0175] The rheological properties of the two lubricants are gathered in the following table 3.

[0176] [Tables3] CCI characteristics (commercial composition SHELL MELINA S3 0) CL1 (invention) Lubricant grade according to SAEJ300 SAE 30 SAE 30 KV100 in mm2 / s 11.53 10.14 (measured at 100°C according to ASTM D445) KV40 in mm2 / s (measured at 40°C according to ASTM D445) 98.60 55.73 Viscosity index (VI) (calculated according to standard I SO2908) 104 172 BOV in mm2 / s (measured at 100°C according to ASTM D445) - 4.4

[0177] Example 3: Evaluation of the fuel consumption saving properties of the lubricating composition according to the invention

[0178] The fuel saving properties of a lubricating composition according to the invention were validated by a test carried out on a bench equipped with a MAN B&W 6S35ME-B9 - Tier II - 2009.11 engine. The particular characteristics of this engine were described in the publication entitled "Experimental study on reducing BC emissions from a low-speed marine engine by using blended biodiesel and a nitro additive", by Y.Sun et al. in the journal Process Safety and Environmental Protection 185 (2024) 1232-1249.

[0179] A dedicated steady-state procedure has been developed to measure the “fuel eco” properties of lubricating compositions as described below. This procedure uses equipment normally found in engine bench test centers: • System oil change and engine crankcase inspection • Loading of the candidate oil • Engine warm-up at 80% load for 90 min • Measurement of distillate fuel oil consumption (Marine Diesel Oil - according to ISO8217 specification) at 80, 60 and 40% load for 90 min, after 30 min of stabilization at the load studied. The measurement sequence is repeated to ensure accuracy, • The fuel oil consumptions obtained with the candidate 2T system lubricant are compared with those obtained when a reference 2T system lubricant is tested under the same conditions, • The engine operating conditions are: • Speed: 142 rpm, • Cylinder oil: Sinopec BN40 • Power developed 3570 kW: 80% load, or 2850 kW, 60% load or 2150 kW and 40% load or 1430 kW, loads representative of low speed marine engine operation, • Bearing temperature: 36-42°C • System lubricant volume: 9,500 liters • In this case, the reference lubricant is a commercial 2T engine oil with a viscosity grade of SAE 30: SHELL MELINA S30.

[0180] The comparative CCI commercial composition SHELL MELINA S30 without polymer and the composition according to the invention CL1 were evaluated.

[0181] The results, representing the gain in fuel consumption, compared to the commercial composition, for the different engine loads tested, are grouped in table 4.

[0182] [Tables4] Fuel consumption gain (%) CL1 (invention) At 80% engine load +1.3 At 60% engine load +1.8 At 40% engine load +2.4

[0183] It is found that the CL1 lubricating composition according to the invention makes it possible to reduce fuel oil consumption by more than 1.3% compared to the commercial 2T system oil.

Claims

Claims

1. Lubricating composition for use as a system oil in a 2-stroke marine engine, said composition comprising: - one or more base oils, of which at least from 5% to 98% by mass, relative to the total mass of said lubricating composition, are one or more base oils chosen from group II oils, group III oils and mixtures thereof; - from 0.3% to 3% by mass of at least one copolymer of styrene and hydrogenated diene(s) and / or at least one olefin copolymer, relative to the total mass of said lubricating composition, and - at least one detergent in a mass content strictly less than 10% relative to the total mass of said lubricating composition, and in which the kinematic viscosity at 100°C, measured according to standard ASTM D445, of the base oil or mixture of base oils is strictly less than 7 mm2 / s.

2. A lubricating composition according to claim 1, wherein the copolymer of styrene and hydrogenated diene(s) is a non-linear copolymer, preferably a star copolymer.

3. A lubricating composition according to claim 1 or 2, wherein the copolymer of styrene and hydrogenated diene(s) is a copolymer of styrene and at least two hydrogenated dienes.

4. A lubricating composition according to any one of claims 1 to 3, wherein the copolymer of styrene and hydrogenated diene(s) is a copolymer of hydrogenated styrene, isoprene and butadiene.

5. Lubricating composition according to any one of claims 1 to 4, in which the copolymer of styrene and hydrogenated diene(s) comprises styrene units in a styrene unit content ranging from 2% to 50%, preferably from 2% to 40%, preferentially from 10% to 40%, by mass relative to the mass of copolymer, and hydrogenated diene units in a content ranging from 50% to 98%, preferably from 60% to 98%, preferentially from 70% to 97%, and in particular from 75% to 95%, by mass relative to the mass of copolymer.

6. A lubricating composition according to any one of claims 1 to 5, wherein the olefin copolymer is an ethylene-propylene copolymer.

7. Lubricating composition according to claim 6, in which the ethylene-propylene copolymer comprises a content of ethylene units ranging from 30% to 80% by mass relative to the mass of olefin copolymer, preferably from 30% to 70%, more preferably from 40% to 70%.

8. Lubricating composition according to any one of claims 1 to 7, having a kinematic viscosity at 100°C, measured according to standard ASTM D445, of less than 16.3 mm2 / s, preferably between 9.3 and 16.3 mm2 / s, and preferentially between 9.3 and 12.5 mm2 / s.

9. A lubricating composition according to any one of claims 1 to 8, wherein the amount of detergents is from 0.1% to 8%, preferably from 0.2% to 5%, by mass relative to the total mass of said lubricating composition.

10. A lubricating composition according to any one of claims 1 to 9, further comprising one or more additives selected from basic organic additives improving the total base number, anti-wear additives, extreme pressure additives, dispersant additives, anti-foaming agents, antioxidant additives, anti-rust additives, friction modifiers, and mixtures thereof.

11. Use of a lubricating composition according to any one of claims 1 to 10, as a system oil for the lubrication of 2-stroke marine engines.

12. Use of a lubricating composition according to any one of claims 1 to 10, for reducing the fuel consumption of a 2-stroke marine engine.

13. A method of lubricating a 2-stroke marine engine, comprising bringing at least one mechanical part of the 2-stroke marine engine, in particular moving parts in the 2-stroke marine engine excluding the piston-cylinder ring assembly, and more particularly the lower part of 2-stroke marine engines, in particular the crankpins and crankshaft bearings, into contact with a lubricating composition according to any one of claims 1 to 10.

14. A method of reducing the fuel consumption of a 2-stroke marine engine comprising contacting at least one mechanical part of the 2-stroke marine engine, in particular moving parts in the 2-stroke marine engine other than the piston-cylinder ring assembly, and more particularly the lower part of 2-stroke marine engines, in particular the crankpins and crankshaft bearings, with a lubricating composition according to any one of claims 1 to 10.