Lubricant composition for a 4-stroke marine engine

Abstract

The present invention relates to a lubricant composition for a 4-stroke marine engine, comprising: - one or more base oils, including at least from 60% to 90% by weight, relative to the total weight of the lubricant composition, of one or more base oils chosen from group II oils, group III oils and mixtures thereof; - from 0.3% to 3%, in particular from 0.5% to 2%, by weight of a copolymer of styrene and hydrogenated diene(s), relative to the total weight of the lubricant composition; and - from 2% to 30% by weight of detergent(s), relative to the total weight of the lubricant composition, the lubricant composition being free from olefin copolymer, and wherein the kinematic viscosity at 100°C, measured according to standard ASTM D445, of the base oil or of the mixture of base oils is strictly less than 7 mm2 / s.

Description

[0001] LUBRICANT COMPOUND FOR 4-STROKE MARINE ENGINES

[0002] The present invention relates to the field of lubricating compositions, and more particularly to the field of lubricating compositions for four-stroke marine engines. More specifically, the present invention relates to a lubricating composition for use in a four-stroke marine engine, this composition enabling a reduction in fuel consumption (Fuel Eco or FE). The present invention also relates to a method for reducing fuel consumption, particularly fuel oil consumption, of a vessel using this lubricating composition.

[0003] In the automotive sector, due to environmental concerns, there is a growing focus on reducing polluting emissions and achieving fuel economy. The nature of automotive engine lubricants influences both of these phenomena, and so-called "fuel-eco" engine lubricants (in Anglo-Saxon terminology) have emerged. It is primarily the quality of the base lubricants, alone or in combination with viscosity-improving polymers and / or friction-modifying additives, that gives the lubricant its "fuel-eco" properties. The fuel savings generated by "fuel-eco" engine lubricants are mainly achieved during cold starts, when the engine is not yet at operating temperature, and not at high temperatures once it has reached operating temperature.In general, fuel consumption gains in the NEDC cycle (New European Driving Cycle) according to European Directive 70 / 220 / EEC are 5% when cold (urban cycle), 1.5% when hot (extra-urban cycle), for average gains of 2.5%.

[0004] However, in the field of marine lubricants, marine engines operate at a steady speed, with few cold starts. Therefore, "fuel-eco" solutions adapted for automotive engines are not suitable for marine engines. In particular, fuel consumption savings achieved in the automotive sector cannot be replicated in the marine sector.

[0005] Furthermore, the formulation of a "fuel-eco" lubricant must not compromise other lubricant performance characteristics. In particular, wear resistance, demulsification and filterability properties, neutralization capacity, and control of varnish and deposit formation (engine, piston and / or crankcase cleanliness) must not be impaired.

[0006] Therefore, there is an advantage to having a marine engine lubricant composition that allows for satisfactory reductions in fuel consumption, particularly fuel oil, while maintaining the other performance characteristics of the lubricant composition.

[0007] One objective of the present invention is therefore to provide a lubricating composition that overcomes, in whole or in part, the aforementioned drawbacks. In particular, one objective of the present invention is to provide a lubricating composition suitable for 4-stroke marine engines that allows for fuel savings, specifically an improvement in Fuel Eco (FE), while maintaining the other performance characteristics of the lubricating composition.

[0008] Another objective of the present invention is to provide a lubrication process that enables fuel savings, particularly of fuel oil, while maintaining the other performance characteristics of the lubricating composition.

[0009] Other objectives will become apparent upon reading the description of the invention that follows.

[0010] To this end, the invention relates to a lubricating composition for 4-stroke marine engines, comprising:

[0011] - one or more base oils, of which at least 5% to 95% by mass, relative to the total mass of said lubricating composition, of one or more base oils chosen from among group II oils, group III oils and their mixtures;

[0012] - from 0.3% to 3%, in particular from 0.5% to 2%, by mass of a copolymer of styrene and hydrogenated diene(s), relative to the total mass of said lubricating composition, and

[0013] - 2% to 30% by mass of detergent(s), relative to the total mass of said lubricating composition, said lubricating composition being free of olefin copolymer, and 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 mm 2Surprisingly, the applicant found that it was possible to formulate lubricant compositions for 4-stroke marine engines that significantly reduced fuel consumption, particularly fuel oil (Fuel Eco), while maintaining other performance characteristics of the lubricant composition, compared to conventional marine engine lubricant compositions. This is made possible by a lubricant composition with the aforementioned characteristics.

[0014] Thus, the present invention makes it possible to formulate lubricating compositions for 4-stroke marine engines that combine both fuel savings, particularly fuel (Fuel Eco), and maintenance of other performance levels.

[0015] In particular, a lubricating composition according to the invention exhibits good stability to thermo-oxidative aging during its use over time.

[0016] 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.

[0017] The present invention also relates to a composition as defined above, in which the copolymer of styrene and hydrogenated diene(s) is a star copolymer.

[0018] 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.

[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 hydrogenated styrene, isoprene and butadiene, preferably star-shaped.

[0020] The present invention also relates to a composition as defined above, having a kinematic viscosity at 100°C, measured according to ASTM D445, of less than 16.3 mm 2 / s, preferably between 9.3 and 16.3 mm 2 / s, and preferably between 12.5 and 16.3 mm 2 / s.

[0021] The present invention also relates to the use of a lubricating composition as defined above for the lubrication of 4-stroke marine engines and / or for reducing engine fuel consumption.

[0022] The present invention also relates to a method of lubricating a 4-stroke marine engine, comprising bringing at least one mechanical part of the 4-stroke marine engine into contact with a lubricating composition as defined above.

[0023] The present invention also relates to a method for reducing the fuel consumption of a 4-stroke marine engine comprising bringing at least one mechanical part of the 4-stroke marine engine into contact with a lubricating composition as defined above.

[0024] Other characteristics and variations of the lubricating composition according to the invention will become clearer from the description and examples that follow, given by way of illustration and not limitation of the invention.

[0025] In the following text, the expressions "between ... and ...", "from ... to ...", "ranging ... to ..." and "varying from ... to ..." are equivalent and are meant to mean that the boundaries are included, unless otherwise stated.

[0026] As mentioned above, the present invention relates to a lubricating composition (or lubricant) for a 4-stroke marine engine, comprising:

[0027] - one or more base oils, of which at least 5% to 95%, preferably 60% to 90%, preferably 70% to 85%, by mass, in relation to the total mass of said lubricating composition, of one or more base oils chosen from among Group II oils, Group III oils and their mixtures;

[0028] - from 0.3% to 3%, in particular from 0.5% to 2%, by mass of a copolymer of styrene and hydrogenated diene(s), relative to the total mass of said lubricating composition, and

[0029] - 2% to 30% by mass of detergent(s), relative to the total mass of said lubricating composition; said lubricating composition being free of olefin copolymer, and in which 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 mm 2 / s.

[0030] A lubricating composition according to the invention is therefore suitable for four-stroke marine engines.

[0031] A lubricating composition according to the invention is free of olefin copolymers distinct from hydrogenated styrene and diene copolymers, namely, free of ethylene-propylene copolymer. In one embodiment, a lubricating composition according to the invention has a kinematic viscosity at 100°C, measured according to ASTM D445, of less than 16.3 mm 2 / s, in particular between 6.9 mm 2 / s and 16.3 mm 2 / s, preferably between 9.3 mm 2 / s and 16.3 mm 2 / s, and preferably between 12.5 mm 2 / s and 16.3 mm 2 / s.

[0032] In one embodiment of the invention, the lubricating compositions according to the invention have a viscosity grade ranging from SAE 20 to SAE 40 according to the SAEJ300 classification. In particular, a lubricating composition according to the invention may have a viscosity grade of SAE 20, SAE 30 or SAE 40 according to the SAEJ300 classification, preferably SAE 30 or SAE 40, advantageously SAE 40.

[0033] Grade 20 (or SAE20) oils have a kinematic viscosity at 100°C between 6.9 and 9.3 mm 2 Grade 30 (or SAE 30) oils have a kinematic viscosity at 100°C between 9.3 and 12.5 mm 2 Grade 40 (or SAE 40) oils have a kinematic viscosity at 100°C between 12.5 and 16.3 mm 2 / s.

[0034] Kinematic viscosity is measured according to ASTM D445 at 100°C.

[0035] Base oil(s)

[0036] A lubricating composition according to the invention comprises a base oil or a mixture of base oils of which at least one or more oils are selected from Group II oils, Group III oils and mixtures thereof.

[0037] A lubricating composition according to the invention therefore comprises at least one group II base oil and / or at least one group III oil.

[0038] 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 a mixture of Group II and Group III oils.

[0039] A lubricating composition according to the invention comprises from 5% to 95% by mass of one or more base oils of group II and / or III, relative to the total mass of said lubricating composition.

[0040] Preferably, a lubricating composition according to the invention comprises from 30% to 90%, in particular from 50% to 90%, especially from 60% to 90%, preferably from 65% to 85%, and further preferably from 70% to 85%, by mass relative to the total mass of said lubricating composition, of one or more base oils selected from Group II oils, Group III oils, and mixtures thereof. In 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 60%, especially greater than or equal to 65%.

[0041] In a particular embodiment, a lubricating composition according to the invention comprises one or more Group II oils alone (in other words, does not comprise any Group III oil), in particular in a mass content greater than or equal to 60% by mass, and 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 any Group III oil, may be greater than or equal to 70% by mass, and in particular greater than or equal to 75% by mass.

[0042] According to one embodiment, a lubricating composition according to the invention comprises at least one group III oil.

[0043] 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 any 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.

[0044] A lubricating composition may include, in addition to the said Group II base oil(s) and / or the said Group III base 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.

[0045] According to one embodiment, a lubricating composition according to the invention may thus comprise one or more additional base oil(s) selected 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.

[0046] According to one embodiment, a lubricating composition according to the invention comprises at least one additional base oil selected from Group I base oils.

[0047] In this embodiment, a lubricating composition according to the invention thus comprises one or more base oil(s) of group II and / or group III, in combination with at least one base oil of group I. For example, a lubricating composition according to the invention may comprise at least one base oil of group II, in combination with at least one base oil of group I.

[0048] Preferably, the mass content of additional base oil(s), when present, in particular Group I oil(s), is between 0.5% and 90%, in particular between 1% and 50%, especially between 1.5% and 30%, and preferably between 2% and 15%, relative to the total mass of said lubricating composition.

[0049] The aforementioned base oils can be chosen from among the base oils conventionally used in the field of marine lubricants, such as mineral, synthetic or natural, animal or vegetable oils or mixtures thereof.

[0050] It can be a mixture of several base oils, for example a mixture of two, three or four base oils.

[0051] 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 mixtures thereof.

[0052] [Table 1]

[0053] 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, desalpha removal, solvent dewaxing, hydrotreating, hydrocracking, hydroisomerization and hydrofinishing.

[0054] Mineral bases in Group I include, for example, bases called Neutral Solvent (such as 150NS, 330NS, 500NS or 600NS) or Brightstock.

[0055] Synthetic base oils can be esters of carboxylic acids and alcohols, polyalphaolefins, or polyalkylene glycols (PAGs) obtained by polymerization or copolymerization of alkylene oxides containing 2 to 8 carbon atoms, particularly 2 to 4 carbon atoms. Polyalphaolefins used as base oils are, for example, obtained from monomers containing 4 to 32 carbon atoms, such as decene, octene, or dodecene, and have a viscosity at 100°C between 1.5 and 15 mm. 2 . s -1 according to ASTM D445. Their average molecular mass is generally between 250 and 3000 g / mol according to ASTM D5296.

[0056] Mixtures of synthetic and mineral oils, which may be bio-based, can also be used.

[0057] The base oil or set of base oils present in the lubricating composition according to the invention, including said Group II and / or Group III base oils, and possibly one or more additional oils, for example one or more Group I oils, may represent from 50% to 97% by mass, in particular from 55% to 95% by mass, notably from 60% to 90% by mass, relative to the total mass of the composition.

[0058] 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.

[0059] Thus, the base oil or the mixture of all the base oils in the lubricating composition according to the invention has a kinematic viscosity at 100°C, measured according to ASTM D445, strictly less than 7 mm 2 / s.

[0060] According to one embodiment, the BOV of a lubricating composition according to the invention is less than or equal to 6.5 mm 2 / s. Copolymer of styrene and hydrogenated diene(s)

[0061] A lubricating composition of the invention comprises at least one copolymer of styrene and hydrogenated diene(s).

[0062] The styrene and hydrogenated diene(s) copolymer (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.

[0063] According to one embodiment, the styrene and hydrogenated diene(s) copolymer is a styrene and two hydrogenated dienes copolymer.

[0064] The styrene and hydrogenated diene(s) copolymer used according to the invention can be chosen from linear or star-shaped copolymers, preferably star-shaped.

[0065] In particular, the copolymer of styrene and hydrogenated diene(s) is a block copolymer.

[0066] According to one embodiment, the copolymer of styrene and hydrogenated diene(s) is a non-linear copolymer.

[0067] According to one embodiment, the copolymer of styrene and hydrogenated diene(s) is a star copolymer.

[0068] Preferably, the content of hydrogenated diene motif(s) is 50% to 98%, preferably 60% to 98%, more preferably 70% to 98%, or 70% to 97%, even more preferably 70% to 96%, or 75% to 95%, by mass relative to the mass of the copolymer.

[0069] Preferably, the styrene motif content is 2% to 50%, preferably 2% to 40%, more preferably 2% to 30%, even more preferably 4% to 30%, or 10% to 40%, by mass relative to the mass of the copolymer.

[0070] Hydrogenated styrene / diene copolymer is used in an amount of 0.3% to 3% by mass relative to the total mass of the lubricating composition. Preferably, hydrogenated styrene / diene copolymer is used in an amount of 0.3% to 2.5%, preferably 0.5% to 2%, by mass relative to the total mass of the lubricating composition.

[0071] This quantity refers to the amount of active copolymer material (dry extract). Indeed, the styrene and hydrogenated diene(s) copolymer used in the context of the present invention can 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.

[0072] According to one embodiment, the styrene and hydrogenated diene(s) copolymer comprises styrene motifs in a styrene motif content of 2% to 50%, preferably 2% to 40%, preferably 2% to 30%, by mass relative to the mass of copolymer, and hydrogenated diene(s) motifs in a content of 50% to 98%, preferably 60% to 98%, preferably 70% to 98%, and in particular 70% to 96%, by mass relative to the mass of copolymer.

[0073] According to one embodiment, the hydrogenated diene motif(s) may be chosen from among the hydrogenated butadiene and hydrogenated isoprene motifs.

[0074] Preferably, hydrogenated diene motifs are hydrogenated butadiene motifs and hydrogenated isoprene motifs.

[0075] According to one embodiment, the styrene and hydrogenated diene copolymer 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.

[0076] According to one embodiment, the styrene and hydrogenated diene(s) copolymer used in lubricating compositions according to the invention is a hydrogenated styrene, isoprene and butadiene copolymer, in other words, is formed of styrene motifs, hydrogenated isoprene motifs and hydrogenated butadiene motifs, also called "styrene / butadiene / isoprene copolymer".

[0077] In a particular embodiment, the styrene / butadiene / isoprene copolymer may comprise from 2% to 40%, preferably from 3% to 10%, by mass of styrene motifs, from 15% to 40%, preferably from 20% to 30%, by mass of hydrogenated butadiene motifs, and from 50% to 80%, preferably from 60% to 75%, by mass of hydrogenated isoprene motifs.

[0078] Preferably, the styrene / butadiene / isoprene copolymer is a star copolymer.

[0079] 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. Additives

[0080] A lubricating composition according to the invention may include all types of additives commonly used in marine lubricants.

[0081] It is understood that the nature of the other additives used is chosen so as not to negatively impact the desired properties of the marine lubricant.

[0082] These additives can be introduced individually and / or in the form of a mixture, or "additive package", similar to those already available for sale for commercial marine engine lubricant formulations.

[0083] These additives can be chosen from among detergent additives, basic organic additives improving the total base index (TBN), anti-wear additives, extreme pressure additives, dispersant additives, anti-foaming agents, antioxidant additives, anti-rust additives, friction modifiers, and mixtures thereof.

[0084] Detergent(s)

[0085] A lubricating composition according to the invention comprises one or more detergents.

[0086] The mass content of detergent(s) is between 2% and 30% relative to the total mass of the lubricating composition.

[0087] The detergents used in the lubricating compositions according to the present invention can be chosen from detergents known to those skilled in the art.

[0088] Detergents commonly used in the formulation of lubricating compositions are typically anionic compounds with a long lipophilic hydrocarbon chain and a hydrophilic head group. The associated cation is typically a metallic cation of an alkali or alkaline earth metal.

[0089] Detergents can be chosen from alkali or alkaline earth metal salts of carboxylates, sulfonates, salicylates, naphthenates, and phenates, taken alone or in mixtures. Detergents are named according to the nature of the hydrophobic chain: carboxylate, sulfonate, salicylate, naphthenate, or phenate.

[0090] The alkali and alkaline earth metals are preferentially calcium, magnesium, sodium or barium, more preferentially calcium.

[0091] The detergents used will be either non-superbased (or neutral) or superbased. Non-superbased or "neutral" detergents are those whose metal salts contain the metal in approximately stoichiometric quantities. Superbased detergents are those where the metal is present in excess (in a quantity greater than the stoichiometric amount). The excess metal, which gives the detergent its superbased character, is in the form of oil-insoluble metal salts. Superbased detergents thus take the form of micelles composed of insoluble metal salts held in suspension within 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.Over-based detergents will be said to be of mixed type if the micelles include several types of detergents, different from each other by the nature of their hydrophobic chain.

[0092] The preferred detergents are carboxylates, sulfonates and / or phenates, taken alone or in mixtures, especially calcium carboxylates, sulfonates and / or phenates.

[0093] According to one embodiment, the quantity of detergents is from 2% to 25%, preferably from 2% to 20%, by mass relative to the total mass of said lubricating composition.

[0094] 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 over-based detergents based on alkali or alkaline earth metals.

[0095] The BN value of the lubricating compositions according to the present invention, measured according to ASTM D2896, can vary from 1 to 140 mg KOH / g, preferably from 3 to 80 mg KOH / g, and more preferably from 4 to 60 mg 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.

[0096] Thus, for fuel oils with a high sulfur content (of the order of 0.2% to 4.5% by weight), the BN value of the composition will be between 20 and 80 mg of KOH / g, more preferably between 30 and 65 mg of KOH / g.

[0097] For fuel oils with low sulfur content (in the order of 0.05% to 0.2% by weight), the BN value of the composition will be between 5 and 20 mg of KOH / g, more preferably between 10 and 15 mg of KOH / g.

[0098] A lubricating composition according to the invention may further comprise one or more additives other than detergents.

[0099] According to one embodiment, a lubricating composition according to the invention comprises an anti-wear additive and / or an extreme pressure additive. The anti-wear and extreme pressure additives protect the friction surfaces by forming a protective film adsorbed onto these surfaces.

[0100] There is a wide variety of anti-wear additives. These include phospho-sulfur additives, such as metallic alkylthiophosphates, particularly zinc alkylthiophosphates, and more specifically zinc dialkyldithiophosphates (or ZnDTP). The alkyl groups of these zinc dialkyldithiophosphates preferentially contain from 1 to 18 carbon atoms. Preferred compounds have the formula Zn((SP(S)(OR)(OR'))2, in which R and R', whether identical or different, independently represent an alkyl group, preferably an alkyl group comprising from 1 to 18 carbon atoms.

[0101] Preferably, a lubricating composition according to the invention may comprise ZnDTP.

[0102] Amine phosphates and polysulfides, particularly sulfur olefins, are also anti-wear additives that can be used in a lubricating composition according to the invention. Nitrogen and sulfur-containing anti-wear additives, such as metal dithiocarbamates, especially molybdenum dithiocarbamates, can also be mentioned.

[0103] 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 the lubricating composition.

[0104] A lubricating composition considered according to the invention may also include at least one basic organic additive to increase the total base index, known as TBN, of the lubricating composition.

[0105] These basic organic additives, known as "TBN boosters", increase the total base index of the composition; in other words, they are able to neutralize acids and allow for improved detergent performance.

[0106] Basic organic additives that improve TBN are known to those skilled in the art.

[0107] They can include, in particular, organic amine, alkyl or aromatic additives, or nitrogen dispersants.

[0108] Examples of basic organic additives that improve TBN include fatty amines. In particular, the aforementioned basic organic additive(s) that improve TBN may be used at a concentration of 0.1% or higher by mass, relative to the total mass of the lubricant composition, in particular at a concentration between 0.1% and 10% by mass, more particularly between 0.5% and 7% by mass, and preferably between 1% and 5% by mass.

[0109] A lubricating composition according to the invention may also include at least one antifoaming additive, particularly designed to counteract the effect of metallic detergents. Antifoaming additives may be selected from polar polymers such as polymethylsiloxanes or polyacrylates.

[0110] In particular, a lubricating composition according to the invention may comprise from 0.01% to 3% by mass of antifoaming additive(s), relative to the total mass of the lubricating composition.

[0111] A lubricating composition according to the invention may include at least one antioxidant additive. Antioxidant additives are primarily intended to delay the degradation of the lubricating composition during operation. This degradation can manifest itself in particular through the formation of deposits or an increase in the viscosity of the lubricating composition. They act, in particular, as radical inhibitors or hydroperoxide scavengers.

[0112] Commonly used antioxidant additives include phenolic antioxidants, amine antioxidants, and phosphosulfur antioxidants. Phenolic antioxidants can be in the form of neutral or basic metal salts. Antioxidant additives may be selected from among sterically hindered phenols, sterically hindered phenol esters, sterically hindered phenols containing a thioether bridge, diphenylamines, diphenylamines substituted with at least one C1-C12 alkyl group, N,N'-dialkylaryl diamines, and mixtures thereof.

[0113] Preferably, sterically hindered phenols are chosen from compounds comprising a phenol group in which at least one vicinal carbon of the carbon bearing 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 ter-butyl group.

[0114] Amino compounds are another class of antioxidant additives that can be used, possibly in combination with phenolic antioxidant additives. Examples of amine compounds are aromatic amines, for example, aromatic amines of the formula N(R5)(R6)(R7) in which R5 represents an aliphatic or aromatic group, possibly substituted, R6 represents an aromatic group, possibly substituted, and R7 represents a hydrogen atom, an alkyl group, an aryl group, or a group of the 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.

[0115] Sulfurized alkyl phenols or their alkali and alkaline earth metal salts can also be used as antioxidant additives.

[0116] A lubricating composition according to the invention may contain all types of antioxidant additives known to those skilled in the art.

[0117] 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 the lubricating composition.

[0118] In one embodiment, the lubricating composition according to the invention may further comprise at least one dispersing agent.

[0119] Dispersing agents ensure the suspension and removal of insoluble solid contaminants consisting of oxidation byproducts formed during the use of the lubricant composition, as well as combustion residues, unburned particles, or other contaminants. They can be selected from Mannich bases, succinimides and their derivatives, particularly polyisobutylene succinimide (PIBSI) or polyisobutylene succinic anhydride (PI BSA).

[0120] In particular, a lubricating composition considered according to the invention may comprise from 0.2% to 10% mass of dispersing agent(s), relative to the total mass of the composition.

[0121] A lubricating composition according to the invention may also include friction modifiers. Friction modifiers reduce friction between engine parts as much as possible. These additives help prevent engine damage while increasing fuel economy. They can be selected from organic molecules having a polar functional group at one end: carboxylic acids and derivatives, glycerol esters, imides, fatty amides, fatty amines and derivatives, and phosphoric or phosphonic acid derivatives (phosphite or amine phosphate). They act by chemical reaction with the metal surface or by absorption onto the metal surface (hydrogen bonding).

[0122] Another type of friction modifier can be selected from organo-metallic compounds: molybdenum dithiophosphate, molybdenum dithiocarbamate, copper oleate, copper salicylate.

[0123] Finally, the friction modifier can be a solid compound, the most common being molybdenum disulfide MoS2, boron nitride, polytetrafluoroethylene (PTFE).

[0124] The mass content of friction modifier(s) in a lubricating composition according to the invention can range from 0.01% to 5% by mass, preferably from 0.02% to 4%, more preferably from 0.02% to 2% by mass, relative to the total mass of the lubricating composition.

[0125] According to one embodiment, a composition of the invention does not comprise glycerol ester.

[0126] According to one embodiment, a composition of the invention does not comprise polyol(s) ester.

[0127] A lubricating composition according to the invention is advantageously used in 4-stroke marine engines.

[0128] In a preferred embodiment, a lubricating composition is used in high-speed or semi-high-speed 4-stroke engines, which operate respectively with distillates and bunker fuels or heavy fuel oil and also with gas.

[0129] In particular, a lubricating composition according to the invention is suitable for 4-stroke engines as a piston sleeve engine oil also called TPEO oil.

[0130] Thus, the invention also relates to a piston engine oil also called TPEO (Trunk Piston Engine Oil) comprising a lubricating composition as defined above.

[0131] Piston oil for piston sleeve engines, also referred to as TPEO oil according to the invention, is understood to mean any lubricating composition intended for the lubrication of 4-stroke marine engines, particularly the crankcase and cylinders. In particular, a lubricating composition according to the invention is distinct from a 2-stroke marine engine oil, especially a 2-stroke marine engine system oil.

[0132] The invention also relates to the use of a lubricating composition as defined above for the lubrication of 4-stroke marine engines.

[0133] The invention also relates to the use of a lubricating composition as defined above, to reduce fuel consumption, particularly fuel oil, of the engine.

[0134] The expression "reduce fuel consumption" refers to a decrease in fuel consumption compared to the fuel consumption associated with a usual lubricant composition, particularly without hydrogenated styrene / diene copolymer(s).

[0135] The reduction in fuel consumption, particularly fuel oil, is assessed in particular through engine bench tests.

[0136] All the characteristics and preferences presented for the lubricating composition apply to the above use.

[0137] The present invention also relates to a method of lubricating a 4-stroke marine engine, comprising bringing at least one mechanical part of the 4-stroke marine engine into contact with a lubricating composition as defined above.

[0138] The present invention also relates to a method for reducing fuel consumption, particularly fuel oil, of a 4-stroke marine engine comprising bringing at least one mechanical part of the 4-stroke marine engine into contact with a lubricating composition as defined above.

[0139] All the characteristics and preferences presented for the lubricating composition also apply to the processes / methods according to the invention.

[0140] The various objects of the present invention and their implementations will be better understood by reading the following examples. These examples are given for illustrative purposes only and are not intended to be limiting. EXAMPLES

[0141] Example 1: Formulation of lubricating compositions according to the invention

[0142] Preparation of compositions

[0143] Three lubricating compositions, CC1, CL1 and CL2, were prepared by simple mixing, at temperatures between 60 and 70°C, of ​​the following components, in the mass proportions indicated in Table 2.

[0144] [Table 2]

[0145] (1) Packages of additives including, in particular, detergents in a content exceeding 90% by mass, anti-wear additives, in particular phospho-sulfur additives, and anti-foaming agents; (2) Star isoprene / butadiene / styrene copolymer having the following mass proportions: 70% hydrogenated isoprene, 23% hydrogenated butadiene and 7% styrene,

[0146] (3) Linear hydrogenated styrene / butadiene copolymer having the following mass proportions: 71% hydrogenated butadiene by mass and 29% styrene by mass,

[0147] (4) Olefin copolymer: 58% by mass ethylene and 42% by mass propylene,

[0148] (5) Group II base oil, having a viscosity measured at 100°C according to ASTM D445 (KV100) of 4.4 mm 2 / s and a Noack volatility, determined according to CEC standard L-040-093, of 15.2% mass,

[0149] (6) Group II base oil blend, having a viscosity measured at 100°C according to ASTM D445 (KV100) of 4.1 mm 2 / s and 6.4 mm 2 / s and a Noack volatility, determined according to CEC standard L-040-093, of 15.2% and 9.0% mass,

[0150] (7) Group III base oil, having a viscosity measured at 100°C according to ASTM D445 (KV100) of 6.4 mm 2 / s and a Noack volatility, determined according to CEC standard L-040-093, of 6.5% mass,

[0151] (8) Inorganic Friction Modifier Additive of the Molybdenum dithiocarbamate type.

[0152] Measurement of the rheological properties of lubricant compositions

[0153] The kinematic viscosities at 100°C (KV100) of the above prepared compositions were measured according to ASTM D445.

[0154] The BOV, or "Base Oil Viscosity," corresponds to the KV100 viscosity of the base oil or base oil blend. In the case of a base oil blend, the KV100 of the base oil blend is calculated using the following equation (Arrhenius' rule) for a blend of two base oils: log(mixture visco) = x log(iscd) + x2*log(visco2), where viscomix is ​​the viscosity of the blend of oils 1 and 2, vised is the viscosity of base oil 1, visco2 is the viscosity of base oil 2, and x- and x2 are the respective mole fractions of base oil 1 and base oil 2 (x1+x2=1). The same equation can be applied and extrapolated for a blend of n base oils. The results are summarized in Table 3 below.

[0155] [Table 3]

[0156] Example 2: Evaluation of the fuel consumption saving properties of lubricating compositions according to the invention

[0157] The fuel economy properties of the lubricant compositions according to the invention were validated by a test carried out on a bench equipped with a MAN 5L16 / 24 engine. The particular characteristics of this engine were described in the publication entitled "INNOVATOR-4C, The cutting-edge MAN B&W 5L16 / 24 test engine", by D. Lançon, V. Doyen and J. Christensen, CIMAC Congress 2004, KYOTO (Paper 124).

[0158] A dedicated procedure under steady-state conditions has been developed to measure the "fuel eco" properties of lubricant compositions, as described below. This procedure uses equipment typically found in engine test bench facilities:

[0159] • Flushing the engine and lubrication circuits with the candidate lubricant,

[0160] • Engine break-in with the candidate lubricant

[0161] • Measurement of distillate-type fuel oil consumption (Marine Diesel Oil - according to ISO 8217 specification). Measurements are repeated to ensure accuracy.

[0162] • Fuel consumption obtained with the candidate lubricant is compared with that obtained when a reference lubricant is tested under the same conditions. • The engine operating conditions are: o Speed: 1000 rpm, o Power output 450 kW: 100% load (450 kW) and 75% load (337 kW), loads representative of marine engine operation, o Lubricant temperature at the engine inlet: 68-70°C, o Lubricant volume: 2 x 200 liters.

[0163] • The tests are organized according to a precise protocol which consists of placing any test carried out with a candidate lubricant between two tests carried out with the reference lubricant. This ensures the operational stability of the engine as well as the statistical significance of the differences in consumption measured between lubricants.

[0164] • In this case, the reference lubricant is a commercial 4-stroke semi-high-speed engine oil of SAE viscosity grade 40 and BN 30.

[0165] The comparative composition CC1 and the compositions according to the invention CL1 and CL2 were evaluated.

[0166] The results, representing the fuel consumption gain compared to the comparative composition, at the tested engine loads, are grouped in Table 4.

[0167] [Table 4]

[0168] It is observed that the use of a copolymer of styrene and hydrogenated diene(s) and base oil(s) according to the invention allows, in the CL1 and CL2 lubricating compositions, a reduction of more than 0.3% in fuel oil consumption (at 75% as at 100% engine load) compared to the CC1 composition (comparative). This result is all the more surprising given that the CL1 and CL2 lubricant compositions according to the invention are SAE 40 grade, while the comparative composition CC1 is SAE 30 grade. Indeed, it is known to those skilled in the art that fuel efficiency performance is partly related to the lubricant grade: typically, it is known that an SAE 30 grade lubricant offers better fuel economy than an SAE 40 grade lubricant. However, it is surprisingly observed here that the CL1 and CL2 compositions outperform the CC1 composition, even though they are SAE 40 grade and the CC1 (comparative) composition is SAE 30 grade.

[0169] Thus, the examples above show that the lubricating compositions according to the invention significantly reduce fuel consumption, particularly fuel oil.

[0170] Example 3: Formulation of other lubricating compositions according to the invention

[0171] Preparation of compositions

[0172] Four other lubricating compositions, CL3, CL4, CL5 and CL6, were prepared by simple mixing, at temperatures between 60 and 70°C, of ​​the following components, in the mass proportions indicated in Table 5.

[0173] [Table 5]

[0174] (1) Packages of additives including, in particular, detergents in a content exceeding 90% by mass, anti-wear additives, in particular phospho-sulfur additives, and anti-foaming agents; (2) Star isoprene / butadiene / styrene copolymer having the following mass proportions: 70% hydrogenated isoprene, 23% hydrogenated butadiene and 7% styrene,

[0175] (3) Group I base oil, having a viscosity measured at 100°C according to ASTM D445 (KV100) of 32 mm 2 / s,

[0176] (4) Group II base oil, having a viscosity measured at 100°C according to ASTM D445 (KV100) of 4.4 mm 2 / s and a Noack volatility, determined according to CEC standard L-040-093, of 15.2% mass.

[0177] Measurement of the rheological properties of lubricant compositions

[0178] As shown in Example 1, the kinematic viscosities at 100°C (KV100) of the above prepared compositions were measured according to ASTM D445 and the BOVs were also calculated as shown in Example 1.

[0179] The results are summarized in the following table 6.

[0180] [Table 6]

[0181] Example 4: Comparative Example

[0182] Preparation of the comparative composition

[0183] A lubricating composition, CC2, was prepared by simple mixing, at temperatures between 60 and 70°C, of ​​the following components, in the mass proportions indicated in Table 7.

[0184] This composition is compared to the CL1 composition according to the invention. [Table 7]

[0185] (1) Packages of additives including in particular detergents in a content exceeding 90% by mass, anti-wear additives, in particular phospho-sulfur, and anti-foaming;

[0186] (2) Star isoprene / butadiene / styrene copolymer having the following mass proportions: 70% hydrogenated isoprene, 23% hydrogenated butadiene and 7% styrene,

[0187] (3) Group II base oil, having a viscosity measured at 100°C according to ASTM D445 (KV100) of 4.4 mm 2 / s and a Noack volatility, determined according to CEC standard L-040-093, of 15.2% mass,

[0188] (4) Group I base oil, having a viscosity measured at 40°C according to ASTM D445 (KV100) of 29 to 32 mm 2 / s,

[0189] Measurement of the rheological properties of lubricant compositions

[0190] As shown in Example 1, the kinematic viscosities at 100°C (KV100) of the above prepared compositions were measured according to ASTM D445.

[0191] The results are summarized in the following table 8.

[0192] [Table 8] The fuel consumption economy properties of the two formulas were evaluated by evaluating the MTM machine traction coefficient using a method similar to that of Example 3 of WO 2014 / 135596.

[0193] The following conditions are applied: - load on the ball of 25N,

[0194] - training speed of 2m / s,

[0195] - SRR (sliding / rolling ratio) of 100M%, and

[0196] - temperature of 100°C.

[0197] The values ​​of the tensile strength coefficient at 100°C are as follows:

[0198] These results show that the traction coefficient for the lubricant according to the invention (CL1) is significantly lower than that obtained with the comparative composition CC2 which includes a group I oil. These results thus show that a lubricating composition according to the invention allows for a gain in fuel consumption.

Claims

1. DEMANDS 1. Lubricating composition for 4-stroke marine engines, comprising: - one or more base oils, of which at least 60% to 90% by mass, relative to the total mass of said lubricating composition, of one or more base oils chosen from among group II oils, group III oils and their mixtures; - from 0.3% to 3%, in particular from 0.5% to 2%, by mass of a copolymer of styrene and hydrogenated diene(s), relative to the total mass of said lubricating composition, and - 2% to 30% by mass of detergent(s), relative to the total mass of said lubricating composition, said lubricating composition being free of olefin copolymer, and 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 mm 2 / s.

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

3. Lubricating composition according to claim 1, wherein the copolymer of styrene and hydrogenated diene(s) is a star copolymer.

4. Lubricating composition according to any one of claims 1 to 3, wherein the copolymer of styrene and hydrogenated diene(s) comprises styrene motifs in a styrene motif content of 2% to 50%, preferably 2% to 40%, preferably 10% to 40%, by mass relative to the mass of copolymer, and hydrogenated diene(s) motifs in a content of 50% to 98%, preferably 60% to 98%, preferably 70% to 97%, and in particular 75% to 95%, by mass relative to the mass of copolymer.

5. Lubricating composition according to any one of claims 1 to 4, wherein the styrene and hydrogenated diene(s) copolymer is a styrene and at least two hydrogenated dienes copolymer.

6. Lubricating composition according to any one of claims 1 to 5, wherein the copolymer of hydrogenated styrene and diene(s) is a copolymer of hydrogenated styrene, isoprene and butadiene.

7. Lubricating composition according to any one of claims 1 to 6, wherein the copolymer of styrene and hydrogenated diene(s) comprises styrene motifs, hydrogenated isoprene motifs and hydrogenated butadiene motifs, for example from 2% to 40%, preferably from 3% to 10%, by mass of styrene motifs, from 15% to 40%, preferably from 20% to 30%, by mass of hydrogenated butadiene motifs, and from 50% to 80%, preferably from 60% to 75%, by mass of hydrogenated isoprene motifs.

8. Lubricating composition according to any one of claims 1 to 7, having a kinematic viscosity at 100°C, measured according to ASTM D445, of less than 16.3 mm 2 / s, preferably between 9.3 and 16.3 mm 2 / s, and preferably between 12.5 and 16.3 mm 2 / s.

9. Lubricating composition according to any one of claims 1 to 8, comprising one or more additional base oil(s) selected 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.

10. Lubricating composition according to any one of claims 1 to 9, wherein the amount of detergents is from 2% to 25%, preferably from 2% to 20%, by mass relative to the total mass of said lubricating composition.

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

12. Use of a lubricating composition according to any one of claims 1 to 11, for the lubrication of a 4-stroke marine engine.

13. Use of a lubricating composition according to any one of claims 1 to 11, to reduce the fuel consumption of a four-stroke marine engine.

14. Method of lubricating a four-stroke marine engine, comprising bringing at least one mechanical part of the four-stroke marine engine into contact with a lubricating composition according to any one of claims 1 to 11.

15. Method for reducing the fuel consumption of a 4-stroke marine engine comprising bringing at least one mechanical part of the 4-stroke marine engine into contact with a lubricating composition according to any one of claims 1 to 11.

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