Lubricant composition

Abstract

To provide a lubricant composition having excellent shear stability and low viscosity.SOLUTION: In a lubricant composition comprising a base oil (A), a molybdenum dithiocarbamate (MoDTC) (B), and a viscosity index improver (C), the content of molybdenum atoms is 0.03 to 0.10 wt.% based on the total amount of the lubricant composition, the content of phosphorus atoms is 0.06 to 0.08 wt.% based on the total amount of the lubricant composition, the NOACK evaporation amount is 15 wt.% or less, and a viscosity reduction parameter X represented by the following formula is 1.00 or less. In the formula, KC represents the kinematic viscosity (mm2 / s) of the lubricant composition at 100°C, KA represents the kinematic viscosity (mm2 / s) of the base oil (A) contained in the lubricant composition at 100°C, and CVM represents the content (wt.%) of the viscosity index improver (C) in the lubricant composition.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a lubricating oil composition for internal combustion engines. [Background technology]

[0002] In recent years, from the viewpoint of environmental protection, improving fuel economy of automobiles and the like has become an important issue, and fuel economy is also being demanded for lubricating oils for internal combustion engines of automobiles and the like. Generally, lubricating oils for internal combustion engines prevent direct contact between sliding surfaces by forming a lubricating oil film between the sliding surfaces, thereby providing lubrication. Since the lower the viscosity of the lubricating oil, the less sliding resistance there is, leading to lower fuel economy, the lower the viscosity of lubricating oils for internal combustion engines has been promoted in order to improve fuel economy. However, since the lower the viscosity of the lubricating oil, the thinner the lubricating oil film formed on the sliding surfaces tends to be, simply lowering the viscosity of the lubricating oil can result in adverse effects such as increased wear at the sliding parts and reduced wear resistance. It is difficult to achieve both low viscosity and wear resistance in lubricating oils for internal combustion engines, and studies are being conducted to achieve both. For example, Patent Document 1 discloses a low-viscosity lubricating oil composition for internal combustion engines, which contains a specific metal-based detergent, an organic molybdenum compound, and a polyalkyl(meth)acrylate. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. WO2014 / 021350 Summary of the Invention [Problem to be solved by the invention]

[0004] In response to increasing demands for fuel economy, further reductions in viscosity are being pursued. On the other hand, in an environment where motorcycles are operated at high rotational speeds, high-speed shear stress causes a rapid decrease in viscosity, which can easily cause the lubricating oil film to break. In order to achieve both low viscosity and wear resistance even under such high shear stress, there is a demand for lubricating oil compositions that have excellent shear stability even when the viscosity is low. Under these circumstances, an object of the present invention is to provide a lubricating oil composition that has excellent shear stability and low viscosity. [Means for solving the problem]

[0005] The present invention includes, for example, the following embodiments. [1] A lubricating oil composition comprising a base oil (A), a molybdenum dithiocarbamate (MoDTC) (B), and a viscosity index improver (C), The content of molybdenum atoms is 0.03 to 0.10% by weight based on the total amount of the lubricating oil composition; the content of phosphorus atoms is 0.06 to 0.08 wt % based on the total amount of the lubricating oil composition; The NOACK evaporation amount is 15% by weight or less, The viscosity reduction parameter X is expressed by the following formula:

number

[10] A method for reducing wear in an internal combustion engine, the method comprising operating the internal combustion engine using the composition according to any one of [1] to [9]. [Effects of the Invention]

[0006] According to the present invention, a lubricating oil composition having low viscosity and excellent shear stability is provided. The lubricating oil composition of the present invention exhibits excellent fuel economy and wear resistance due to its low viscosity and excellent shear stability, and can be suitably used as a lubricating oil for internal combustion engines. In particular, the lubricating oil composition of this embodiment can be suitably used as a lubricating oil (engine oil) for motorcycle internal combustion engines that is excellent in fuel economy, and can suppress viscosity reduction under high-speed shear even when used as an engine oil for high-speed motorcycles. DETAILED DESCRIPTION OF THE INVENTION

[0007] Hereinafter, embodiments of the present invention will be described in detail. Note that the present invention is not limited to the following embodiments, and can be implemented by making any changes without departing from the spirit and scope of the present invention. The upper and lower limits of the numerical ranges described herein can be combined in any way. For example, if "A to B" and "C to D" are described, the ranges "A to D" and "C to B" are also included as numerical ranges in the scope of the present invention. Furthermore, the numerical range "lower limit to upper limit" described herein means a range equal to or greater than the lower limit and equal to or less than the upper limit.

[0008] [Lubricating oil composition] One aspect of the present invention relates to a lubricating oil composition. The lubricating oil composition comprises a base oil (A), a molybdenum dithiocarbamate (MoDTC) (B), a viscosity index improver (C), and, optionally, other components (D). In this specification, "combined with components (A) to (C)" means that the lubricating oil composition contains these components (components (A) to (C)) by blending the components (components (A) to (C)). It also means that at least a portion of the blended components (components (A) to (C)) has reacted. It also means that one or more of the components (A) to (C) has reacted with a portion of any blended component other than these components (components (A) to (C)). Therefore, the lubricating oil composition may contain other compounds resulting from the modification or reaction of at least a portion of the blended components. Such forms are also encompassed by the lubricating oil composition of the present invention.

[0009] (Viscosity reduction parameter X) The lubricating oil composition of this embodiment has a viscosity reduction parameter X, represented by the following formula, of 1.00 or less.

number

[0010] (NOACK evaporation amount) The lubricating oil composition of this embodiment has a NOACK evaporation rate of 15% by weight or less. If the NOACK evaporation rate exceeds 15% by weight, the high-temperature oxidation stability deteriorates, making the lubricating oil composition more likely to thicken. To improve fuel economy, the NOACK evaporation rate is preferably 8% by weight or more, more preferably 9.5% by weight or more, and even more preferably 9.5% by weight or more. In this specification, the "NOACK evaporation rate" is a value measured in accordance with JPI-5S-41-2004 at 250°C for 1 hour.

[0011] (Molybdenum atom (Mo) content) The content of molybdenum atoms (Mo content) in the lubricating oil composition is 0.03 to 0.10 wt % based on the total amount of the lubricating oil composition. If the Mo content is less than 0.03 wt %, the driving torque at low engine speeds may increase, making it difficult to improve fuel economy. If the Mo content exceeds 0.10 wt %, the solubility in oil (storage stability) may be poor. From the viewpoints of improving fuel economy and solubility in oil, the Mo content is preferably 0.03 to 0.10 wt %, more preferably 0.05 to 0.07 wt %.

[0012] (P atom content) The phosphorus atom content (P content) in the lubricating oil composition is 0.06 to 0.08 wt % based on the total amount of the lubricating oil composition. If the P content is less than 0.06 wt %, the driving torque at low engine speeds may increase, making it difficult to achieve low fuel consumption. On the other hand, if the P content exceeds 0.08 wt %, catalyst poisoning of the exhaust gas catalyst may occur. From the viewpoints of low fuel consumption and catalyst poisoning, the P content is preferably 0.06 to 0.08 wt %.

[0013] Each component will be described in detail below.

[0014] [Component (A): Base oil] The base oil can be selected from mineral oils and synthetic oils that have conventionally been used as base oils for lubricating oils.

[0015] Examples of mineral oils include atmospheric residues obtained by atmospheric distillation of crude oils such as paraffinic crude oil, intermediate crude oil, and naphthenic crude oil; distillates obtained by vacuum distillation of these atmospheric residues; and refined oils obtained by subjecting the distillates to one or more refining treatments such as solvent deasphalting, solvent extraction, hydrocracking, solvent dewaxing, catalytic dewaxing, and hydrorefining. These mineral oils may be used alone or in combination of two or more.

[0016] Examples of synthetic oils include poly-α-olefins such as α-olefin homopolymers or α-olefin copolymers (e.g., α-olefin copolymers having 8 to 14 carbon atoms, such as ethylene-α-olefin copolymers); isoparaffins; polyalkylene glycols; ester oils such as polyol esters, dibasic acid esters, and phosphate esters; ether oils such as polyphenyl ethers; alkylbenzenes; alkylnaphthalenes; and oils (GTL) obtained by isomerizing wax produced from natural gas by the Fischer-Tropsch process (GTL wax (Gas to Liquids Wax)). These synthetic oils may be used alone or in combination of two or more. As the base oil, one or more of the mineral oils mentioned above may be used in combination with one or more of the synthetic oils mentioned above.

[0017] There are no particular restrictions on the viscosity of the base oil, but the kinematic viscosity at 100°C is 2.0 to 6.0 mm 2 / s, and 2.5 to 5.5 mm 2 / s range is more preferable, 3.0 to 5.0 mm 2 By setting the kinematic viscosity at 100°C within this range, the viscosity of the lubricating oil composition can be reduced, making it easier to set the kinematic viscosity at 100°C of the lubricating oil composition within the specified range.

[0018] Furthermore, the viscosity index of the base oil is preferably at least 100, more preferably at least 120, and even more preferably at least 130. By increasing the viscosity index to 100 or more, the viscosity change that occurs with temperature changes in the lubricating base oil is reduced. In this specification, the kinematic viscosity and viscosity index values ​​at 100°C of the base oil and lubricating oil composition are measured in accordance with JIS K2283:2000.

[0019] In addition, the base oil is %C by ring analysis. p is preferably 75% or more, more preferably 80% or more, and even more preferably 85% or more. p By making the %C by ring analysis 75% or more, the high temperature oxidation stability of the lubricating oil composition can be improved. p indicates the proportion (percentage) of paraffin content calculated by ring analysis ndM method, measured in accordance with ASTM D-3238.

[0020] Among these, the base oil preferably contains a mineral oil classified as Group 3 of the API (American Petroleum Institute) base oil category.

[0021] The base oil is the main component of a lubricating oil composition, and the content of the base oil is usually preferably 60 to 99.5% by weight, more preferably 70 to 99.0% by weight, even more preferably 80 to 98.0% by weight, and particularly preferably 85 to 97.0% by weight, based on the total weight of the composition.

[0022] [Component (B): molybdenum dithiocarbamate (MoDTC)] The lubricating oil composition contains molybdenum dithiocarbamate (MoDTC), which has excellent lubricating oil film forming ability and is added to the lubricating oil composition for the purpose of imparting anti-friction properties to the lubricating oil composition. MoDTC is blended so that the content of molybdenum atoms in the lubricating oil composition falls within the above-mentioned range.

[0023] Examples of MoDTC include binuclear molybdenum dithiocarbamates containing two molybdenum atoms per molecule and trinuclear molybdenum dithiocarbamates containing three molybdenum atoms per molecule. These molybdenum dithiocarbamates may be used alone or in combination.

[0024] Examples of dinuclear molybdenum dithiocarbamates include molybdenum dithiocarbamates containing two molybdenum atoms per molecule, as described in JP 2017-149830 A. Preferred dinuclear molybdenum dithiocarbamates are, for example, compounds represented by the following general formula (i) and compounds represented by the following general formula (ii): [ka]

[0025] In the above general formulas (i) and (ii), X 11 ~X 18 Each of X independently represents an oxygen atom or a sulfur atom. 11 ~X 18 may be the same or different from each other, provided that X in formula (i) 11 ~X 18 In one embodiment of the present invention, at least two of X in formula (i) are sulfur atoms. 11 and X 12 is an oxygen atom, and X 13 ~X 18 is preferably a sulfur atom. X in formula (ii) 11 ~X 14 is preferably an oxygen atom.

[0026] In the above general formula (i), from the viewpoint of improving solubility in the base oil, X 11 ~X 18 The molar ratio of sulfur atoms to oxygen atoms therein (sulfur atoms / oxygen atoms) is preferably 1 / 4 to 4 / 1, and more preferably 1 / 3 to 3 / 1. In the above general formula (ii), from the same viewpoint as above, X 11 ~X 14 The molar ratio of sulfur atoms to oxygen atoms therein [sulfur atoms / oxygen atoms] is preferably 1 / 3 to 3 / 1, and more preferably 1.5 / 2.5 to 2.5 / 1.5.

[0027] In the above general formulas (i) and (ii), R 11 ~R14 each independently represents a hydrocarbon group, and may be the same as or different from each other. R 11 ~R 14 The hydrocarbon group as the alkyl group preferably has 7 to 22 carbon atoms, more preferably 7 to 18 carbon atoms, even more preferably 7 to 14 carbon atoms, and even more preferably 8 to 13 carbon atoms. R in the above formulas (i) and (ii) 11 ~R 14 Specific hydrocarbon groups that can be selected as the alkyl group include alkyl groups such as methyl, ethyl, propyl, butyl, benzyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl, and octadecyl; alkenyl groups such as octenyl, nonenyl, decenyl, undecenyl, dodecenyl, tridecenyl, tetradecenyl, and pentadecenyl; cycloalkyl groups such as cyclohexyl; and dimethylcyclohexyl. alkyl-substituted cycloalkyl groups such as ethylcyclohexyl group, methylcyclohexylmethyl group, cyclohexylethyl group, propylcyclohexyl group, butylcyclohexyl group, and heptylcyclohexyl group; aryl groups such as phenyl group, naphthyl group, anthracenyl group, biphenyl group, and terphenyl group; alkylaryl groups such as tolyl group, dimethylphenyl group, butylphenyl group, nonylphenyl group, methylbenzyl group, and dimethylnaphthyl group; and arylalkyl groups such as phenylmethyl group, phenylethyl group, and diphenylmethyl group.

[0028] Examples of trinuclear molybdenum dithiocarbamates include molybdenum dithiocarbamates containing three molybdenum atoms in one molecule, as described in paragraphs

[0052] to

[0066] of JP 2017-149830 A.

[0029] Among the above MoDTCs, those having a binuclear structure are preferred from the viewpoint of fuel economy.

[0030] [Component (C): Viscosity index improver] The lubricating oil composition contains a viscosity index improver. Examples of viscosity index improvers include polymers such as non-dispersant polymethacrylate, dispersant polymethacrylate, olefin copolymers (e.g., ethylene-propylene copolymers), dispersant olefin copolymers, and styrene copolymers (e.g., styrene-diene copolymers, styrene-isoprene copolymers). These may be used alone or in combination of two or more.

[0031] The type of viscosity index improver can affect the viscosity reduction parameter X. For example, when a hydrocarbon material is used, the viscosity reduction parameter X tends to increase because the alkyl group has a long chain, and when a polymethacrylate material is used, the molecule does not easily spread, so the viscosity reduction parameter X tends to decrease.

[0032] In some embodiments, the viscosity index improver comprises an olefin copolymer having an SSI of 25 or less. SSI stands for Shear Stability Index and indicates the ability of the polymer (component (C)) to resist degradation. The higher the SSI, the more unstable the polymer is to shear and the more susceptible it is to degradation. By blending an olefin copolymer having an SSI within the above range, it is possible to further reduce the viscosity reduction parameter of the lubricating oil composition, making it easier to adjust the viscosity reduction parameter X to a desired range. The lower limit of the SSI of the olefin copolymer is not particularly limited, and may be, for example, 1 or more.

[0033]

number

[0034] The content of the viscosity index improver (C) is not particularly limited, but is preferably 0.5 to 10 wt. % of the total weight of the lubricating oil composition, more preferably 1 to 8 wt. %, and even more preferably 1.5 to 7 wt. By adjusting the amount of component (C) to fall within these ranges, it becomes easier to achieve the desired viscosity and viscosity reduction parameter X of the lubricating oil composition. Generally, the greater the blend amount of viscosity index improver (C), the greater the viscosity (for example, kinematic viscosity at 100°C) of the lubricating oil composition.

[0035] [Component (D): Other components] The lubricating oil composition may further contain other components in addition to the above components (A) to (C) as necessary, provided that the effects of the present invention are not impaired. These other components include lubricating oil additives such as pour point depressants, friction modifiers that also function as antioxidants, such as zinc dialkyldithiophosphates, antioxidants, organomolybdenum compounds other than MoDTC, detergent dispersants, ashless dispersants, ashless friction modifiers, antifoaming agents, corrosion inhibitors, metal deactivators, and antistatic agents. These lubricating oil additives may be used alone or in combination of two or more.

[0036] (pour point depressants) The lubricating oil composition may also contain a pour point depressant, which can impart excellent low temperature and friction properties to the composition. Examples of pour point depressants include ethylene-vinyl acetate copolymers, condensates of chlorinated paraffins and naphthalene, condensates of chlorinated paraffins and phenols, poly(meth)acrylates, polyalkylstyrenes, etc., with polymethacrylates being particularly preferred. These pour point depressants may be used alone or in combination of two or more. The content of the pour point depressant is not particularly limited, but is preferably 0.01 to 5.0 wt % based on the total weight of the composition. When poly(meth)acrylate is used as a pour point depressant, its weight average molecular weight is usually less than 100,000 (for example, in the range of 30,000 to 90,000), and it is distinguished from viscosity index improvers, which will be described later.

[0037] (Zinc dialkyldithiophosphate) As the zinc dialkyldithiophosphate (ZnDTP), it is preferable to use a zinc dialkyldithiophosphate having an alkylaryl group substituted with a primary or secondary alkyl group having 3 to 22 carbon atoms or an alkyl group having 3 to 18 carbon atoms. These may be used alone or in combination of two or more kinds. By blending zinc dialkyldithiophosphate, functions such as oxidation prevention, corrosion prevention, wear prevention, and improved load carrying capacity can be imparted to the lubricating oil composition. When zinc dialkyldithiophosphate is contained, it is preferably blended so that the phosphorus atom content in the lubricating oil composition falls within the above-mentioned P content range.

[0038] (antioxidant) The antioxidant can be selected from known antioxidants that have been used as antioxidants in conventional lubricating oils. Examples include amine-based antioxidants, phenol-based antioxidants, sulfur-based antioxidants, and phosphorus-based antioxidants. These antioxidants can be used alone or in combination of two or more, but it is usually preferred to use two or more in combination. The content of the antioxidant is not particularly limited, but is preferably 0.01 to 10% by weight based on the total amount of the composition.

[0039] (Organo-molybdenum compounds other than MoDTC) Examples of organic molybdenum compounds other than MoDTC include at least one selected from molybdenum dithiophosphate (MoDTP), molybdenum amine complexes (Mo amine complexes), and molybdenum imide complexes (Mo imide complexes). The inclusion of these organic molybdenum compounds can impart anti-friction properties to the lubricating oil composition. When these organic molybdenum compounds are included, they are preferably incorporated so that the sum of the molybdenum atom content derived from these organic molybdenum compounds and the molybdenum atom content derived from molybdenum dithiophosphate (MoDTP) falls within the above-mentioned Mo content range. In some embodiments, the lubricating oil composition does not contain any organomolybdenum compound other than MoDTC. MoDTC is particularly excellent in terms of its ability to form a lubricating oil film, so by incorporating a sufficient amount of MoDTC, the lubricating oil composition can improve its ability to form a lubricating oil film even under high-speed shear stress, thereby improving wear resistance.

[0040] (detergent dispersant) Examples of detergent-dispersants include metal sulfonates, metal salicylates, metal phenates, succinimides, boronated succinimides, etc. These may be used alone or in combination of two or more. When the lubricating oil composition contains a detergent-dispersant, the content of the detergent-dispersant is preferably 0.01 to 10% by weight, more preferably 0.1 to 5% by weight, based on the total amount of the lubricating oil composition.

[0041] (Ashless dispersant) Examples of ashless dispersants include polybutenyl succinimides (such as polybutenyl succinic acid monoimides and polybutenyl succinic acid bisimides) having a number average molecular weight (Mn) of 900 to 3,500 and having a polybutenyl group, polybutenyl benzylamines, polybutenylamines, and derivatives thereof modified with boric acid (such as boronized polybutenyl succinimides). These may be used alone or in combination of two or more. The content of the ashless dispersant is not particularly limited, but is preferably 0.10 to 15 wt % based on the total weight of the composition.

[0042] (Ashless friction modifier) Ashless friction modifiers include ester-based friction modifiers such as partial ester compounds obtained by reacting a fatty acid with an aliphatic polyhydric alcohol. The fatty acid is preferably a fatty acid having a linear or branched hydrocarbon group with 6 to 30 carbon atoms, and the hydrocarbon group more preferably has 8 to 24 carbon atoms, and particularly preferably has 10 to 20 carbon atoms. The aliphatic polyhydric alcohol is a dihydric to hexahydric alcohol, such as ethylene glycol, glycerin, trimethylolpropane, pentaerythritol, or sorbitol. The content of the ashless friction modifier is not particularly limited, but is preferably 0.01 to 20% by weight based on the total amount of the composition.

[0043] (Antifoaming agent) Examples of antifoaming agents include dimethylpolysiloxane and polyacrylate. These antifoaming agents may be used alone or in combination of two or more. The content of the antifoaming agent is not particularly limited, but is preferably 0.0002 to 0.15% by weight based on the total amount of the composition.

[0044] (corrosion inhibitor) Examples of corrosion inhibitors that can be used include alkyl or alkenyl succinic acid derivatives such as dodecenyl succinic acid half ester, octadecenyl succinic anhydride, and dodecenyl succinamide; polyhydric alcohol partial esters such as sorbitan monooleate, glycerin monooleate, and pentaerythritol monooleate; amines such as rosin amine and N-oleyl sarcosine; and dialkyl phosphite amine salts. These may be used alone or in combination of two or more. The content of the corrosion inhibitor is not particularly limited, but is preferably 0.01 to 5.0 wt. % based on the total weight of the composition.

[0045] (metal deactivator) Examples of metal deactivators include benzotriazole, triazole derivatives, benzotriazole derivatives, and thiadiazole derivatives. These metal deactivators may be used alone or in combination of two or more. The content of the metal deactivator is not particularly limited, but is preferably 0.01 to 3.0 wt % based on the total amount of the composition.

[0046] [Properties of lubricating oil composition] The kinematic viscosity of the lubricating oil composition at 100°C is 5.0 to 12.0 mmHg. 2 The lubricating oil composition preferably has a kinematic viscosity of 5.0 mm / s at 100°C. 2 / s or more, it has excellent wear resistance, and 12.0 mm 2 From the viewpoint of wear resistance and fuel economy, the kinematic viscosity of the lubricating oil composition at 100°C is 5.5 to 10.0 mm / s or less. 2 / s is more preferable, 6.0 to 9.5 mm 2 / s is more preferable, and 6.1 to 9.3 mm 2 / s is more preferable, 6.2 to 8.0 mm 2 / s is particularly preferred.

[0047] The viscosity index of the lubricating oil composition is not particularly limited, but from the viewpoint of suppressing viscosity changes due to temperature changes and improving fuel economy, it is preferably 80 to 200, more preferably 90 to 180, even more preferably 100 to 180, and particularly preferably 110 to 160.

[0048] The lubricating oil composition has a high-temperature, high-shear viscosity (HTHS) at 150°C of 1.7 mPa·s or more but less than 3.7 mPa·s, preferably 2.0 mPa·s or more but less than 3.5 mPa·s, and more preferably 2.3 mPa·s or more but less than 3.0 mPa·s, from the viewpoint of fuel economy. "HTHS viscosity" is determined in accordance with ASTM D 4741 by measuring the viscosity of a lubricating oil composition at 150°C at a shear rate of 10 6 It is measured as viscosity after shear at 1500 kJ / s (HTHS150).

[0049] The lubricating oil composition preferably has an SAE viscosity grade of 16 or 20 as classified according to SAE J300:2015. SAE viscosity grade 16 has a kinematic viscosity of 6.1 mm at 100°C. 2 / s or more 8.2mm 2 / s, 150 °C, shear rate 10 6 The HTHS viscosity (high temperature high shear viscosity) at 1000kJ / s is 2.3 mPa·s or more. SAE viscosity grade 20 has a kinematic viscosity of 6.9 mm at 100°C. 2 / s or more 9.3mm 2 / s, 150 °C, shear rate 10 6 The HTHS viscosity (high temperature high shear viscosity) at 1000kJ / s is 2.6 mPa·s or more.

[0050] The lubricating oil composition has a kinematic viscosity of 5.0 to 12.0 mmHg at 100°C after a shear test under JPI 5S conditions. 2 / s, and 5.5 to 10.0 mm 2 / s is more preferable, 6.0 to 9.5 mm 2 / s is more preferable, and 6.1 to 9.3 mm 2 / s is particularly preferred.

[0051] [Method of manufacturing lubricating oil composition] The method for producing the lubricating oil composition is not particularly limited. Components (A), (B), (C), and, if necessary, component (D) may be blended by any method, and the method is not limited thereto. In one embodiment, the method for producing the lubricating oil composition includes a step of blending base oil (A) with molybdenum dithiocarbamate (MoDTC) (B), viscosity index improver (C), and, if necessary, other component (D).

[0052] [Uses of lubricating oil composition] The lubricating oil composition has low viscosity and excellent shear stability, and therefore can exhibit excellent fuel economy and wear resistance. Therefore, the lubricating oil composition of the embodiment can be preferably used as a lubricating oil (engine oil) for internal combustion engines such as gasoline engines, diesel engines, gas engines, and outboard motors of automobiles such as motorcycles and four-wheeled vehicles, generators, and ships, and can be used as a lubricating oil filled in the internal combustion engine to lubricate the various parts related to the internal combustion engine. In particular, the lubricating oil composition of this embodiment is preferably used in internal combustion engines for motorcycles. Because the lubricating oil composition of this embodiment has excellent shear stability, it can be suitably used as a lubricating oil (engine oil) for internal combustion engines of motorcycles used in high shear environments, and in particular, it is preferably used as a lubricating oil (engine oil) for internal combustion engines of motorcycles that contains a friction modifier (MoDTC) and is not used to lubricate the transmission.

[0053] In addition, in consideration of the above-mentioned properties of the lubricating oil composition, one embodiment of the present invention provides an internal combustion engine using the above-mentioned lubricating oil composition. Also, one embodiment of the present invention provides a method for reducing wear in an internal combustion engine, comprising operating the engine with the above-described lubricating oil composition. [Example]

[0054] The present invention will be described in detail below with reference to examples, but the technical scope of the present invention is not limited to these examples.

[0055] The physical properties of the raw materials used in the Examples and Comparative Examples and the lubricating oil compositions of the Examples and Comparative Examples were measured according to the procedures described below.

[0056] (1)Kinematic viscosity The kinematic viscosity at 100°C (KV100) was measured using a glass capillary viscometer in accordance with JIS K2283:2000.

[0057] (2) NOACK evaporation amount The value was measured in accordance with the method specified in ASTM D5800.

[0058] (3) Molybdenum atom content (Mo) and phosphorus atom content (P) The values ​​were measured by inductively coupled plasma atomic emission spectroscopy as described in ASTM D4951.

[0059] [Examples 1 to 4, Comparative Examples 1 to 4] The components shown in Tables 1 and 2 below were blended with the base oil to prepare lubricating oil compositions of Examples and Comparative Examples containing the base oil and these components.

[0060] The components used in Tables 1 and 2 are as follows: (1) Base oil (component (A)) a1: Mineral oil (paraffinic mineral oil; kinematic viscosity at 100°C: 4.3 mm) 2 / s, viscosity index: 124, %C by ring analysis p :81%) A2: Mineral oil (paraffinic mineral oil; kinematic viscosity at 100°C: 6.0 mm) 2 / s, viscosity index: 127, %C by ring analysis p :77%) A3: Mineral oil (paraffinic mineral oil; kinematic viscosity at 100°C: 4.3 mm) 2 / s, viscosity index: 130, %C by ring analysis p :84%) A4: Mineral oil (paraffinic mineral oil; kinematic viscosity at 100°C: 3.0 mm) 2 / s, viscosity index: 120, %C by ring analysis p :82%)

[0061] (2) MoDTC (component (B)) b: MoDTC (molybdenum dialkyldithiocarbamate, molybdenum atom content 10.0 wt%, sulfur atom content 10.9 wt%, product name "Sakuralube 515" (ADEKA))

[0062] (3) Viscosity index improver (component (C)) c1: OCP (olefin copolymer, structure: ethylene propylene copolymer, SSI=25, product name "PARATONE 8065" (manufactured by Chevron)) c2: OCP (olefin copolymer, structure: ethylene propylene copolymer, SSI=50, product name "HiTEC 5751" (manufactured by Afton))

[0063] (4) Other ingredients (ingredient (D)) d1: Additive package (type: SP performance additive, product name "HiTEC 2260" (manufactured by Afton)) d2: Pour point depressant (type: PMA, product name "Viscoplex 1-330" (manufactured by Evonik))

[0064] <Viscosity reduction parameter X> In the examples and comparative examples, the viscosity reduction parameter X was calculated. Specifically, the kinematic viscosity K of the base oil (A) contained in the lubricating oil composition at 100°C A (mm 2 / s), the kinematic viscosity K of the lubricating oil composition at 100°C C (mm 2 / s) and K A , K. C and the content C of the viscosity index improver (C) in the lubricating oil composition VM The viscosity reduction parameter X was calculated from the weight percent according to the following formula: The results are shown in Tables 1 and 2.

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[0065] <100°C kinematic viscosity of lubricating oil composition after shear test> Using the lubricating oil compositions prepared in the Examples and Comparative Examples as test oils, shear tests were carried out as follows. (shear test) The test was carried out in 30 cycles in accordance with the diesel injector method described in JPI-5S-29 Lubricating Oil Shear Stability Test Method. The kinematic viscosity (KV100) of the lubricating oil composition at 100°C after the shear test (K D The results are shown in Tables 1 and 2. [Table 1] [Table 2]

[0066] As shown in Tables 1 and 2, the lubricating oil compositions of the examples, which contain components (A) to (C), have specific NOACK evaporation amounts, Mo contents, and P contents, and have a viscosity reduction parameter X of 1.00 or less, exhibited a kinematic viscosity at 100°C (KV100) (K D ) was maintained at a high level, confirming that the material has excellent shear stability. On the other hand, the lubricating oil compositions of the comparative examples, which have a viscosity reduction parameter X exceeding 1.00, have a kinematic viscosity at 100°C (KV100) (K D ) and the 100°C kinematic viscosity (KV100) (KV) of the lubricating oil composition before the shear test C ) (the decrease in dynamic viscosity due to shear) was large, and the shear stability was poor. As shown in Tables 1 and 2, it is confirmed that the smaller the viscosity reduction parameter X, the more the reduction in kinematic viscosity of the lubricating oil composition after the shear test is suppressed. The above results show that by setting the viscosity reduction parameter X to 1.00 or less, it is possible to achieve both excellent shear stability and low viscosity, and to provide a lubricating oil composition that is excellent in fuel economy and wear resistance. [Industrial Applicability]

[0067] The lubricating oil composition of the embodiment has low viscosity and excellent shear stability, and therefore can exhibit excellent fuel economy and wear resistance, and can be suitably used as a lubricating oil for internal combustion engines (particularly, a lubricating oil (engine oil) for internal combustion engines of motorcycles). In particular, the lubricating oil composition of the embodiment is suitably used as a lubricating oil (engine oil) for internal combustion engines of motorcycles that are not used to lubricate the transmission.

Claims

1. A lubricating oil composition comprising a base oil (A), a molybdenum dithiocarbamate (MoDTC) (B), and a viscosity index improver (C), the content of molybdenum atoms is 0.03 to 0.10 wt % based on the total amount of the lubricating oil composition; the content of phosphorus atoms is 0.06 to 0.08 wt % based on the total amount of the lubricating oil composition; The NOACK evaporation amount is 15% by weight or less, Viscosity reduction parameter X represented by the following formula: [Equation 5] (In the formula, K Ｃ is the kinematic viscosity (mm ２ / s), K Ａ is the kinematic viscosity (mm ２ / s), C ＶＭ represents the content (wt%) of the viscosity index improver (C) in the lubricating oil composition) is 1.00 or less.

2. The kinematic viscosity of the base oil (A) at 100°C is 2.0 to 6.0 mm ２ 2. The lubricating oil composition of claim 1, wherein

3. The kinematic viscosity of the lubricating oil composition at 100°C is 5.0 to 12.0 mm ２ 3. The composition according to claim 1 or 2, wherein:

4. 4. The lubricating oil composition according to claim 1, wherein the content of the viscosity index improver (C) is 0.5 to 10% by weight based on the total amount of the lubricating oil composition.

5. 5. The lubricating oil composition according to claim 1, wherein the viscosity index improver (C) is an olefin copolymer having an SSI of 25 or less.

6. The lubricating oil composition of any one of claims 1 to 5, wherein the viscosity reduction parameter X is in the range of 0.50 to 0.

95.

7. The lubricating oil composition according to any one of claims 1 to 6, wherein the lubricating oil composition has a viscosity grade of 16 or 20 according to the classification according to SAE J300:2015.

8. The lubricating oil composition of any one of claims 1 to 7, further comprising a pour point depressant.

9. The lubricating oil composition according to any one of claims 1 to 8, which is used in an internal combustion engine for a motorcycle.

10. A method for reducing wear in an internal combustion engine, comprising operating the engine with a composition according to any one of claims 1 to 9.

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