Lubricating oil composition

Abstract

There has been a need for development of a lubricating oil composition which is reduced in the oil evaporation amount at lower temperatures, and is capable of improving the fuel consumption saving.　Disclosed is a lubricating oil composition which includes a base oil (A) in which the content of a fraction containing hydrocarbon groups having not less than 14 but less than 16 carbon atoms is within the range of 0.10% by mass to 0.60% by mass based on the total amount of the base oil (A), and the content of a fraction containing hydrocarbon groups having not less than 16 but less than 18 carbon atoms is within the range of 0.35% by mass to 1.85% by mass based on the total amount of the base oil (A).

Description

lubricating oil composition

[0001] The present invention relates to a lubricating oil composition.

[0002] The NOACK test at 250°C specified in ASTM D5800 is widely used as an index of oil volatility, but as engines become more sophisticated, it is sometimes difficult to obtain a correlation between the NOACK value and the amount of oil evaporation (consumption) under actual operating conditions. In this context, it has been reported that oil volatility values ​​at lower temperatures are correlated with actual oil consumption (Non-Patent Document 1).

[0003] Proceedings of the Society of Automotive Engineers of Japan, Vol.52, No.6, November 2021

[0004] Under these circumstances, there has been a demand for the development of a lubricating oil composition that reduces oil evaporation at lower temperatures and that can improve fuel economy.

[0005] As a result of extensive research, the present inventors have found that the above-mentioned problems can be solved by using a predetermined amount of a base oil of a specific fraction, and have thus completed the present invention. That is, the present invention provides the following aspects: [1] A lubricating oil composition comprising, as base oil (A), a fraction containing hydrocarbon groups having 14 to 16 carbon atoms in an amount of 0.10 to 0.60 mass%, based on the total amount of base oil (A), and a fraction containing hydrocarbon groups having 16 to 18 carbon atoms in an amount of 0.35 to 1.85 mass%, based on the total amount of base oil (A).

[0006] A preferred embodiment of the present invention provides a lubricating oil composition that reduces the amount of oil evaporation at temperatures below 250° C. Another preferred embodiment of the present invention provides a lubricating oil composition that has a low kinematic viscosity at 40° C. and can improve fuel economy.

[0007] Regarding the numerical ranges described herein, the upper and lower limits can be arbitrarily combined. For example, when a numerical range is described as "preferably 30 to 100, more preferably 40 to 80," the ranges "30 to 80" and "40 to 100" are also included in the numerical ranges described herein. Furthermore, when a numerical range is described as "preferably 30 or more, more preferably 40 or more, and preferably 100 or less, more preferably 80 or less," the ranges "30 to 80" and "40 to 100" are also included in the numerical ranges described herein. Furthermore, as a numerical range described herein, for example, "60 to 100" means a range of "60 or more (greater than 60) and 100 or less (less than 100)." Furthermore, when specifying the upper and lower limits described herein, the numerical range from the lower limit to the upper limit can be specified by appropriately selecting from the respective options and combining them arbitrarily. In addition, multiple combinations of the various requirements described as preferred aspects of the present specification can be used.

[0008] [Configuration of Lubricating Oil Composition] The lubricating oil composition of one embodiment of the present invention comprises a base oil (A) (hereinafter also referred to as "component (A)") in which the fraction containing hydrocarbon groups having 14 to 16 carbon atoms is in the range of 0.10 to 0.60 mass% based on the total amount of base oil (A), and the fraction containing hydrocarbon groups having 16 to 18 carbon atoms is in the range of 0.35 to 1.85 mass% based on the total amount of base oil (A). According to this configuration, the NOACK value at 150°C can be made less than the specified value, thereby obtaining a lubricating oil composition with low oil consumption even under actual use conditions. Furthermore, according to this configuration, it is possible to obtain a lubricating oil composition with excellent fuel economy properties, having a low kinematic viscosity at 40°C. Note that, in this specification, the NOACK value at 150°C means the value measured at 150°C for 12 hours in accordance with ASTM D5800 (hereinafter also referred to as NOACK 150°C). The details of each component contained in the lubricating oil composition of one embodiment of the present invention will be described below.

[0009] <Component (A): Base Oil> The lubricating oil composition of the present invention uses as base oil (A) a fraction containing hydrocarbon groups having 14 or more but less than 16 carbon atoms in the range of 0.10 to 0.60 mass% based on the total amount of base oil (A), and a fraction containing hydrocarbon groups having 16 or more but less than 18 carbon atoms in the range of 0.35 to 1.85 mass% based on the total amount of base oil (A). By setting the individual fractions of base oil (A) within the above ranges, the NOACK 150°C value can be adjusted to 5 mass% or less, thereby improving oil consumption under actual engine operating conditions. Furthermore, by setting the individual fractions of base oil (A) within the above ranges, the kinematic viscosity at 40°C can be adjusted to 25 mm ２ A lubricating oil composition having excellent fuel economy of 0.10 mass% or less / s or less can be obtained. From the viewpoint of satisfying the NOACK 150°C value and improving fuel economy, it is preferable that the fraction containing hydrocarbon groups having from 14 to less than 16 carbon atoms is 0.10 mass% or more, 0.15 mass% or more, and 0.60 mass% or less. From the viewpoint of satisfying the NOACK 150°C value and improving fuel economy, it is preferable that the fraction containing hydrocarbon groups having from 16 to less than 18 carbon atoms is 0.35 mass% or more, 0.40 mass% or more, or 0.50 mass% or more, while being 1.85 mass% or less, 1.80 mass% or less, 1.70 mass% or less, or 1.60 mass% or less. The base oil (A) as described above can be selected based on the measurement results of each fraction measured by the method described in the Examples below, and adjusted to the range of each fraction containing hydrocarbon groups with the above carbon numbers. The base oil (A) of the present invention can be produced, for example, by combining mineral oils, synthetic oils, or mineral oils and synthetic oils as described below, and adjusting the range of each fraction containing a hydrocarbon group having the above carbon number while taking into consideration the measurement results of each fraction measured by the method described in the Examples below.

[0010] The fractions containing hydrocarbon groups having 14 to 16 carbon atoms and the fractions containing hydrocarbon groups having 16 to 18 carbon atoms contained in the lubricating oil composition of the present invention are obtained, for example, by blending mineral oils and / or synthetic oils so as to contain hydrocarbon groups with the above carbon numbers. Examples of mineral oils constituting these fractions 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 these distillates to one or more refining processes such as solvent deasphalting, solvent extraction, hydrocracking, solvent dewaxing, catalytic dewaxing, and hydrorefining. The base oil (A) used in one embodiment of the lubricating oil composition of the present invention may be one of these mineral oils alone, or a mixture of multiple mineral oils.

[0011] The base oil (A) used in the lubricating oil composition of one embodiment of the present invention may be a single synthetic oil or a mixed oil containing a combination of multiple synthetic oils.Furthermore, the base oil (A) used in the lubricating oil composition of one embodiment of the present invention may be a mixed oil containing a mineral oil and a synthetic oil. Examples of synthetic oils include poly-α-olefins such as α-olefins, homopolymers thereof, or α-olefin copolymers (for example, α-olefin copolymers having 8 to 14 carbon atoms, such as ethylene-α-olefin copolymers); isoparaffins; polyalkylene glycols; ether oils such as polyphenyl ethers; ester oils such as polyol esters, dibasic acid esters, and monoesters; alkylbenzenes; alkylnaphthalenes; synthetic oils (GTL) obtained by isomerizing wax produced from natural gas by the Fischer-Tropsch process (GTL wax (Gas To Liquids WAX)), and synthetic oils (Ethylene To Liquid (ETL)) obtained by oligomerizing olefins produced using gas as a raw material. These synthetic oils may be produced from renewable resources.

[0012] Among these, the base oil used in one embodiment of the present invention preferably contains at least one selected from mineral oils classified into Group 2 and Group 3 of the API (American Petroleum Institute) base oil category and synthetic oils.

[0013] Furthermore, the lubricating oil composition of one embodiment of the present invention preferably further contains one or more base oils selected from the group consisting of poly-α-olefins (A1) and ester-based oils (A2). By including these base oils, it is possible to obtain a lubricating oil composition that can improve fuel economy while satisfying the NOACK 150°C value. Specific examples of the poly-α-olefins (A1) include the above-mentioned α-olefins, homopolymers thereof, and α-olefin copolymers (e.g., α-olefin copolymers having 8 to 14 carbon atoms, such as ethylene-α-olefin copolymers). Specific examples of the ester-based oils (A2) include the above-mentioned polyol esters, dibasic acid esters, and monoesters. More specific examples of the ester-based oils (A1) include trimethylolpropane tridecanoate, 2-ethylhexyl palmitate, and bis(2-ethylhexyl) sebacate. In one embodiment of the present invention, when the base oil (A) contains one or more base oils selected from the group consisting of poly-α-olefins (A1) and ester-based oils (A2), the content of the contained poly-α-olefins (A1) or ester-based oils (A2), or a mixture thereof, is preferably 3.0% by mass or more, more preferably 5.0% by mass or more, and even more preferably 7.0% by mass or more, based on the total amount (100% by mass) of the lubricating oil composition, from the viewpoint of satisfying the NOACK 150°C value and improving fuel economy, and is preferably 10.0% by mass or less, more preferably 9.0% by mass or less, from the viewpoint of suppressing deterioration of rubber materials.

[0014] The kinematic viscosity at 100°C of the base oil (A) used in one embodiment of the present invention is preferably 2.5 mm ２ / s or more, more preferably 2.8 mm ２ / s or more, more preferably 3.0 mm ２ / s or more, and preferably 4.5 mm ２ / s or less, more preferably 4.1 mm ２ / s or less, more preferably 3.8 mm ２ The kinematic viscosity of the base oil at 100°C is 2.5 mm ２On the other hand, if the kinematic viscosity of the base oil at 100°C is 4.5 mm / s or more, it is preferable for maintaining the oil film. ２ In one embodiment of the present invention, when a mixed oil is used as the base oil (A), the kinematic viscosity at 100°C of the mixed oil is preferably in the above range.

[0015] Furthermore, from the viewpoint of suppressing viscosity changes due to temperature changes and improving fuel economy, the viscosity index of the base oil used in one embodiment of the present invention is preferably 80 or more, more preferably 90 or more, even more preferably 100 or more, and still more preferably 110 or more. In this specification, the kinematic viscosity and viscosity index refer to values ​​measured or calculated in accordance with ASTM D455.

[0016] In the lubricating oil composition of one embodiment of the present invention, the content of base oil (A) is, based on the total amount (100 mass%) of the lubricating oil composition, 70 mass% or more, 75 mass% or more, and 99.9 mass% or less, 98 mass% or less, or 95 mass% or less.

[0017] <Component (B): Viscosity Index Improver> The lubricating oil composition of one embodiment of the present invention further contains a viscosity index improver (B) containing a comb polymer (B1). By including the comb polymer (B1) as the viscosity index improver (B), the fuel economy of the lubricating oil composition can be improved. The comb polymer (B1) may be any polymer having a structure in which the main chain has many three-pronged branching points from which high-molecular-weight side chains protrude. The comb polymer (B1) used in one embodiment of the present invention is preferably a polymer having at least a structural unit (X1) derived from a macromonomer (x1). This structural unit (X1) corresponds to the above-mentioned "high-molecular-weight side chain." In the present invention, the above-mentioned "macromonomer (x1)" refers to a high-molecular-weight monomer having a polymerizable functional group, and is preferably a high-molecular-weight monomer having a polymerizable functional group at its terminal.

[0018] The comb polymer (B1) used in one embodiment of the present invention may be a homopolymer consisting of only structural units (X1) derived from one type of macromonomer (x1), or may be a copolymer containing structural units (X1) derived from two or more types of macromonomers (x1). Furthermore, the comb polymer (B1) used in one embodiment of the present invention may be a copolymer containing structural units derived from the macromonomer (x1) as well as structural units (X2) derived from a monomer other than the macromonomer (x1). A specific structure of such a comb polymer is preferably a copolymer having a main chain containing structural units (X2) derived from the monomer (x2) and a side chain containing structural units (X1) derived from the macromonomer (x1).

[0019] Examples of the monomer (x2) include alkyl(meth)acrylates, nitrogen atom-containing vinyl monomers, hydroxyl group-containing vinyl monomers, phosphorus atom-containing monomers, aliphatic hydrocarbon vinyl monomers, alicyclic hydrocarbon vinyl monomers, vinyl esters, vinyl ethers, vinyl ketones, epoxy group-containing vinyl monomers, halogen element-containing vinyl monomers, esters of unsaturated polycarboxylic acids, (di)alkyl fumarates, (di)alkyl maleates, and aromatic hydrocarbon vinyl monomers.

[0020] In this specification, the weight average molecular weight (Mw) and number average molecular weight (Mn) are values ​​calculated as standard polystyrene measured by gel permeation chromatography (GPC).

[0021] In the lubricating oil composition of one embodiment of the present invention, the content of comb polymer (B1) is, from the viewpoint of improving fuel economy, preferably 5.0 mass% or more, more preferably 5.5 mass% or more, and even more preferably 6.0 mass% or more, based on the total amount (100 mass%) of the lubricating oil composition, and preferably 14.0 mass% or less, more preferably 13.0 mass% or less, and even more preferably 12.5 mass% or less, based on the total amount (100 mass%) of the lubricating oil composition.

[0022] The viscosity index improver (B) used in one embodiment of the present invention may or may not contain a viscosity index improver made of a polymer other than the comb polymer (B1) described above, provided that the effects of the present invention are not impaired. Examples of such other polymers include polymers that do not fall under the category of comb polymers, such as polymethacrylate, dispersion-type polymethacrylate, olefin copolymers (e.g., ethylene-propylene copolymers), dispersion-type olefin copolymers, and styrene copolymers (e.g., styrene-diene copolymers, styrene-isoprene copolymers).

[0023] <Component (C): Friction Modifier> The lubricating oil composition of one embodiment of the present invention further contains at least one friction modifier (C) selected from the group consisting of ashless friction modifiers (C1) and molybdenum-based friction modifiers (C2). By containing the friction modifier (C), a lubricating oil composition having excellent friction properties can be obtained. From the viewpoint of further improving friction properties, the lubricating oil composition of one embodiment of the present invention contains both the ashless friction modifier (C1) and the molybdenum-based friction modifier (C2) as the friction modifiers (C).

[0024] <Ashless friction modifier (C1)> The ashless friction modifier (C1) used in one embodiment of the present invention is not particularly limited, and examples thereof include ashless friction modifiers (C1) such as amine compounds, fatty acid esters, fatty acid amides, fatty acids, aliphatic alcohols, aliphatic ethers, urea compounds, and hydrazide compounds. The ashless friction modifier (C1) may be used alone or in combination of two or more. By containing the ashless friction modifier (C1), a lubricating oil composition having excellent friction characteristics can be obtained. Furthermore, even if the lubricating oil composition of one embodiment of the present invention contains an ester oil (A2) as the base oil (A), by blending an ashless friction modifier (C1) having a specific weight average molecular weight (Mw), the friction characteristics can be maintained well, and as a result, fuel economy performance can be maintained well.

[0025] In one embodiment of the present invention, the weight average molecular weight (Mw) of the ashless friction modifier (C1) is, from the viewpoint of improving friction characteristics, preferably 100 or more and less than 50,000, 100 or more and less than 10,000, 100 or more and less than 10,000, or 10,000 or more and less than 50,000, and more preferably 1,000 or more and less than 50,000.

[0026] In one embodiment of the present invention, the total content of the ashless friction modifiers (C1) is, from the viewpoint of providing a lubricating oil composition with excellent friction properties, preferably 0.1 mass % or more, more preferably 0.2 mass % or more, and even more preferably 0.3 mass % or more, based on the total amount (100 mass %) of the lubricating oil composition, and may be 1.0 mass % or less, 0.8 mass % or less, or 0.5 mass % or less.

[0027] <Molybdenum-based friction modifier (C2)> Examples of the molybdenum-based friction modifier (C2) used in one embodiment of the present invention include molybdenum compounds such as molybdenum dithiocarbamate (MoDTC), molybdenum dithiophosphate (MoDTP), and amine salts of molybdic acid. The molybdenum-based friction modifier (C2) may be used alone or in combination of two or more. Among these, the lubricating oil composition of one embodiment of the present invention preferably contains molybdenum dithiocarbamate (MoDTC) as the molybdenum-based friction modifier (C2).

[0028] <<Molybdenum Dithiocarbamate (MoDTC)>> Examples of the molybdenum dithiocarbamate (MoDTC) used in one embodiment of the present invention include compounds represented by the following general formula (1).

[0029] In formula (1), R １ ~R ４ are each independently a hydrocarbon group having 4 to 18 carbon atoms, and are preferably an alkyl group having 5 to 18 carbon atoms, an alkenyl group having 5 to 18 carbon atoms, a cycloalkyl group having 5 to 18 carbon atoms, an aryl group having 6 to 18 carbon atoms, an alkylaryl group having 7 to 18 carbon atoms, or an arylalkyl group having 7 to 18 carbon atoms.

[0030] Examples of alkyl groups having 5 to 18 carbon atoms include pentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl, and octadecyl groups.

[0031] Examples of the alkenyl group having 5 to 18 carbon atoms include an octenyl group, a nonenyl group, a decenyl group, an undecenyl group, a dodecenyl group, a tridecenyl group, a tetradecenyl group, and a pentadecenyl group.

[0032] Examples of the cycloalkyl group having 5 to 18 carbon atoms include a cyclohexyl group, a dimethylcyclohexyl group, an ethylcyclohexyl group, a methylcyclohexylmethyl group, a cyclohexylethyl group, a propylcyclohexyl group, a butylcyclohexyl group, and a heptylcyclohexyl group.

[0033] Examples of the aryl group having 6 to 18 carbon atoms include a phenyl group, a naphthyl group, an anthracenyl group, a biphenyl group, and a terphenyl group.

[0034] Examples of the alkylaryl group having 7 to 18 carbon atoms include a tolyl group, a dimethylphenyl group, a butylphenyl group, a nonylphenyl group, a methylbenzyl group, and a dimethylnaphthyl group.

[0035] Examples of the arylalkyl group having 7 to 18 carbon atoms include a phenylmethyl group, a phenylethyl group, and a diphenylmethyl group.

[0036] In one embodiment of the present invention, the content of molybdenum dithiocarbamate (MoDTC) is, from the viewpoint of providing a lubricating oil composition with excellent friction properties, preferably 0.3 mass % or more, more preferably 0.5 mass % or more, and even more preferably 0.6 mass % or more, based on the total amount (100 mass %) of the lubricating oil composition, and may be 1.0 mass % or less, 0.9 mass % or less, or 0.8 mass % or less.

[0037] <Various Additives> The lubricating oil composition of one embodiment of the present invention may contain various additives as needed, as long as the effects of the present invention are not impaired. Examples of such various additives include pour point depressants, antioxidants, metal detergents, ashless dispersants, antiwear agents, rust inhibitors, antifoaming agents, and extreme pressure additives. These lubricating oil additives may be used alone or in combination of two or more.

[0038] The content of each of these various additives can be adjusted as appropriate within a range that does not impair the effects of the present invention, but is typically 0.001 to 15 mass %, preferably 0.005 to 10 mass %, and more preferably 0.01 to 5 mass %, for each additive independently, based on the total amount (100 mass %) of the lubricating oil composition.

[0039] Furthermore, a compound having multiple functions as the above additives (for example, a compound having functions as an anti-wear agent and an extreme pressure additive) may be used.

[0040] [Pour Point Depressant] The lubricating oil composition of one embodiment of the present invention may further contain a pour point depressant. The pour point depressants may be used alone or in combination of two or more. Examples of pour point depressants used in one embodiment of the present invention include ethylene-vinyl acetate copolymers, condensates of chlorinated paraffins and naphthalene, condensates of chlorinated paraffins and phenols, polymethacrylates, polyalkylstyrenes, etc.

[0041] [Antioxidant] The lubricating oil composition of one embodiment of the present invention may further contain an antioxidant. The antioxidant may be used alone or in combination of two or more types. Examples of the antioxidant used in one embodiment of the present invention include amine-based antioxidants such as alkylated diphenylamine, phenylnaphthylamine, and alkylated phenylnaphthylamine; phenol-based antioxidants such as 2,6-di-t-butylphenol, 4,4'-methylenebis(2,6-di-t-butylphenol), isooctyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate, and n-octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate; and sulfur-based antioxidants such as phenothiazine, dioctadecyl sulfide, dilauryl-3,3'-thiodipropionate, and 2-mercaptobenzimidazole.

[0042] [Metallic Detergent] The lubricating oil composition of one embodiment of the present invention may further contain a metallic detergent. The metallic detergent may be used alone or in combination of two or more. Examples of the metallic detergent used in one embodiment of the present invention include metal salts such as metal sulfonates, metal salicylates, and metal phenates. Furthermore, the metal atom constituting the metal salt is preferably a metal atom selected from alkali metals and alkaline earth metals, more preferably sodium, calcium, magnesium, or barium, and even more preferably calcium and magnesium.

[0043] [Ashless Dispersant] The lubricating oil composition of one embodiment of the present invention may further contain an ashless dispersant. The ashless dispersant may be used alone or in combination of two or more. The ashless dispersant used in one embodiment of the present invention is preferably an alkenyl succinimide, and may be a modified alkenyl succinimide reacted with one or more selected from boron compounds, alcohols, aldehydes, ketones, alkylphenols, cyclic carbonates, epoxy compounds, and organic acids.

[0044] [Anti-wear Agent] The lubricating oil composition of one embodiment of the present invention may further contain an anti-wear agent. The anti-wear agent may be used alone or in combination of two or more. Examples of the anti-wear agent used in one embodiment of the present invention include sulfur-containing compounds such as zinc dialkyldithiophosphate (ZnDTP), zinc phosphate, zinc dithiocarbamate, disulfides, sulfurized olefins, sulfurized fats and oils, sulfurized esters, thiocarbonates, thiocarbamates, and polysulfides; phosphorus-containing compounds such as phosphites, phosphates, phosphonates, and their amine salts or metal salts; and sulfur- and phosphorus-containing anti-wear agents such as thiophosphites, thiophosphates, thiophosphonates, and their amine salts or metal salts.

[0045] [Rust inhibitor] The lubricating oil composition of one embodiment of the present invention may further contain a rust inhibitor. The rust inhibitor may be used alone or in combination of two or more. Examples of the rust inhibitor used in one embodiment of the present invention include fatty acids, alkenyl succinic acid half esters, fatty acid soaps, alkyl sulfonates, polyhydric alcohol fatty acid esters, fatty acid amines, oxidized paraffins, and alkyl polyoxyethylene ethers.

[0046] [Antifoaming Agent] The lubricating oil composition of one embodiment of the present invention may further contain an antifoaming agent. The antifoaming agent may be used alone or in combination of two or more. Examples of the antifoaming agent used in one embodiment of the present invention include alkylsilicone-based antifoaming agents, fluorosilicone-based antifoaming agents, and fluoroalkyl ether-based antifoaming agents.

[0047] [Extreme Pressure Additive] The lubricating oil composition of one embodiment of the present invention may further contain an extreme pressure additive. The extreme pressure additive may be used alone or in combination of two or more. Examples of the extreme pressure additive used in one embodiment of the present invention include sulfur-containing compounds such as zinc dialkyldithiophosphate (ZnDTP), zinc phosphate, zinc dithiocarbamate, disulfides, sulfurized olefins, sulfurized fats and oils, sulfurized esters, thiocarbonates, thiocarbamates, and polysulfides; phosphorus-containing compounds such as phosphites, phosphates, phosphonates, and their amine salts or metal salts; and sulfur- and phosphorus-containing antiwear agents such as thiophosphites, thiophosphates, thiophosphonates, and their amine salts or metal salts.

[0048] [Method for Producing Lubricating Oil Composition] The method for producing the lubricating oil composition of one embodiment of the present invention is not particularly limited, and is preferably a method including a step of blending various other additives, as necessary, with the base oil (A). The order of blending the components can be appropriately determined.

[0049] [Properties of Lubricating Oil Composition] The kinematic viscosity at 100°C of the lubricating oil composition of one embodiment of the present invention is preferably 5.0 mm ２ / s or more, more preferably 5.5 mm ２ / s or more, more preferably 6.1 mm ２ / s or more, and preferably 12.5 mm ２ / s or less, more preferably 10.0 mm ２ / s or less, more preferably 9.3 mm ２ / s or less.

[0050] The lubricating oil composition of one embodiment of the present invention preferably has a NOACK value measured in accordance with ASTM D5800 at 150°C for 12 hours of 5% by mass or less, and although there is no particular limitation on the lower limit, it is, for example, 3% by mass or more.

[0051] The coefficient of friction measured using the lubricating oil composition of one embodiment of the present invention as a sample oil by the method described in the Examples below is preferably 0.110 or less, more preferably 0.106 or less, even more preferably less than 0.085, and even more preferably 0.084 or less. Lubricating oil compositions having a coefficient of friction within the above ranges can be said to have excellent friction properties.

[0052] [Uses of Lubricating Oil Composition] The lubricating oil composition of the present invention has a low oil evaporation rate, as indicated by the NOACK value at 150°C, and therefore can be suitably used for lubricating internal combustion engines. Therefore, the present invention also provides the following internal combustion engine [I] and the following method for using the lubricating oil composition [II]. [I] An internal combustion engine filled with the lubricating oil composition of one embodiment of the present invention described above. [II] A method for using the lubricating oil composition, in which the lubricating oil composition of one embodiment of the present invention described above is applied to the lubrication of an internal combustion engine.

[0053] The present invention may include the following aspects. [1] A lubricating oil composition comprising, as a base oil (A), a fraction containing hydrocarbon groups having from 14 to less than 16 carbon atoms in a range of 0.10 to 0.60 mass% based on the total amount of the base oil (A), and a fraction containing hydrocarbon groups having from 16 to less than 18 carbon atoms in a range of 0.35 to 1.85 mass% based on the total amount of the base oil (A). [2] The lubricating oil composition according to [1], which contains an ashless friction modifier (C1), wherein the ashless friction modifier (C1) has a weight average molecular weight (Mw) of from 100 to less than 50,000. [3] The lubricating oil composition according to [1], which contains an ashless friction modifier (C1), wherein the ashless friction modifier (C1) has a weight average molecular weight (Mw) of from 1,000 to less than 50,000. [4] The lubricating oil composition according to any one of [1] to [3], further comprising, as the base oil (A), one or more base oils selected from the group consisting of poly-α-olefins (A1) and ester-based oils (A2). [5] The lubricating oil composition according to [4], further comprising, as the base oil (A), an ester-based oil (A2). [6] The lubricating oil composition according to any one of [1] to [5], further comprising, as a viscosity index improver (B) comprising a comb polymer (B1). [7] The lubricating oil composition according to any one of [1] to [6], further comprising, as a molybdenum-based friction modifier (C2).

[0054] The present invention will now be described in more detail with reference to examples, but the present invention is not limited to these examples. The physical properties of the components used in the examples and comparative examples and the resulting lubricating oil compositions were measured according to the following methods.

[0055] (1) Kinematic viscosity and viscosity index: Measured and calculated in accordance with ASTM D455. ２ (2) Weight average molecular weight (Mw) and number average molecular weight (Mn) One column "TSKguard column Super HZ-L" and two columns "TSKSuper Multipore HZ-M" manufactured by Tosoh Corporation were attached to a "1515 isocratic HPLC pump" and a "2414 differential refractive index (RI) detector" manufactured by Waters Corporation in this order from the upstream side, and measurements were performed under the conditions of a measurement temperature of 40°C, a mobile phase of tetrahydrofuran, a flow rate of 0.35 mL / min, and a sample concentration of 1.0 mg / mL, and the values ​​were calculated in terms of standard polystyrene. (3) Amount of Fractions Containing Hydrocarbon Groups with a Carbon Number of 14 or More but Less than 16 and 16 or More but Less than 18 Using the following measuring apparatus and under the following measuring conditions, the peak areas of fractions containing hydrocarbon groups with each carbon number were calculated in the ranges of carbon numbers from 8 to less than 10, from 10 to less than 12, and thereafter increasing the carbon number by 2 in increments of 2 up to 36 to less than 38, and the proportions of the fraction containing hydrocarbon groups with a carbon number of 14 to less than 16 relative to the total peak area and the fraction containing hydrocarbon groups with a carbon number of 16 to less than 18 relative to the total peak area were calculated. (Measurement device) Device: Shimadzu Corporation GC-2014 Detector type: FID Column: Packed column Filler: Silicone OV-1 1.5% Shinwasorb-S 60 / 80 (Measurement conditions) Injector temperature: 360°C Detector temperature: 360°C Heating conditions: Initial temperature 60°C Heating rate: 10°C / min Final temperature: 350°C Final temperature holding time: 5 min Gas flow rate: N ２45 mL / min (4) NOACK 150°C Measured at 150°C for 12 hours in accordance with ASTM D5800. A NOACK 150°C value of 5% by mass or less was judged to be acceptable. (5) Friction Coefficient [Evaluation of Friction Coefficient] Using an SRV tester (manufactured by Optimol), the friction coefficient was measured when the prepared lubricating oil composition was used under the following conditions. First, the temperature was raised from 30°C to 140°C in 10°C increments, and a sliding test was carried out for 5 minutes at each temperature under the following conditions. In the final minute of the test at 30°C, the friction coefficient was measured every second, and the average value of the friction coefficient during the final minute was calculated. Cylinder: AISI52100 Mirror-finished disc: AISI52100 (maximum height roughness (Rz): less than 0.20 μm) Vibration frequency: 50 Hz Amplitude: 1.5 mm Load: 400 N Temperature: 30 to 140°C, temperature increased in 10°C increments Test time: 5 minutes at each temperature The coefficient of friction was evaluated using the coefficient of friction at 30°C measured using the sample oil of Example 1 as the reference, and the improvement rate calculated using the following formula as an index. Note that "-" in Tables 1 and 2 means that the coefficient of friction was not measured. Formula: Improvement rate = 100 - (friction coefficient at 30°C of each Example / friction coefficient at 30°C of Example 1 × 100)

[0056] Examples 1 to 18 and Comparative Examples 1 to 4 Lubricating oil compositions were prepared by adding and mixing the various components and other additives shown in Tables 1 and 2 in the amounts shown in Tables 1 and 2. The blending amounts of viscosity index improvers in Tables 1 and 2 are listed as blending amounts including diluent oil. Details of each component used in preparing the lubricating oil compositions are as follows:

[0057] <Component (A): Base oil> Base oil (A): Base oil prepared using base oils (1) to (22) shown in Tables 1 and 2 so that the fraction having 14 or more but less than 16 carbon atoms and the fraction having 16 or more but less than 18 carbon atoms have the values ​​shown in Tables 1 and 2. Base oils (1) to (22) have a kinematic viscosity at 100°C of 2.61 to 4.45 mm ２ / s, and the viscosity index was in the range of 111 to 164. <Component (B): Viscosity index improver> Comb polymer (B1): A comb polymer having a structure with many three-pronged branching points in the main chain from which high molecular weight side chains protrude (Mw = 260,000, Mw / Mn = 3.1, resin content = 23%) <Component (C): Friction modifier> Ashless friction modifier (C1) (1): Stearyl diethanolamine (Mw = 350, N content = 4.2 wt%, resin content = 99%) Ashless friction modifier (C1) (2) Polymethacrylate (Mw = 9,800, N content = 0.25 wt%, resin content = 78%) Ashless friction modifier (C1) (3): Polymethacrylate (Mw = 18,000, N content = 0.24 wt%, resin content = 67%). Ashless friction modifier (C1) (4): Polymethacrylate (Mw = 57,000, N content = 0.40 wt%, resin content = 33.2%) Molybdenum friction modifier (C2): Molybdenum dithiocarbamate (MoDTC) (R in formula (1) １ ~R ４ are each independently 8 or 13 hydrocarbon groups, and X １ ~X ４ is an oxygen atom. Molybdenum atom content = 10.0 mass%, sulfur atom content = 11.5 mass%. <Other additives> An additive mixture comprising a detergent, a dispersant, ZnDTP, an antioxidant, a metal deactivator, an antifoaming agent, and a friction modifier.

[0058]

[0059] From the results in Tables 1 and 2, the lubricating oil compositions of Examples 1 to 18, which contained as base oil (A) a fraction containing hydrocarbon groups having a carbon number of 14 or more but less than 16 in the range of 0.10 to 0.60 mass% based on the total amount of base oil (A) and a fraction containing hydrocarbon groups having a carbon number of 16 or more but less than 18 in the range of 0.35 to 1.85 mass% based on the total amount of base oil (A), had a NOACK value of 5 mass% or less at 150°C and a low amount of oil evaporation. ２On the other hand, the lubricating oil compositions of Comparative Examples 1 to 4 did not satisfy the pass criteria for the NOACK value at 150°C or the kinematic viscosity at 40°C.

Claims

1. A lubricating oil composition comprising, as a base oil (A), a fraction containing a hydrocarbon group having a carbon number of 14 or more and less than 16 in the range of 0.10 to 0.60 mass % based on the total amount of base oil (A), and a fraction containing a hydrocarbon group having a carbon number of 16 or more and less than 18 in the range of 0.35 to 1.85 mass % based on the total amount of base oil (A).

2. The lubricating oil composition according to claim 1, which contains an ashless friction modifier (C1), and the weight average molecular weight (Mw) of the ashless friction modifier (C1) is 100 or more and less than 50,000.

3. The lubricating oil composition according to claim 1, which contains an ashless friction modifier (C1), and the weight average molecular weight (Mw) of the ashless friction modifier (C1) is 1,000 or more and less than 50,000.

4. The lubricating oil composition according to any one of claims 1 to 3, further comprising, as base oil (A), one or more base oils selected from the group consisting of poly-α-olefins (A1) and ester-based oils (A2).

5. The lubricating oil composition according to claim 4, comprising an ester-based oil (A2) as the base oil (A).

6. The lubricating oil composition according to any one of claims 1 to 5, further comprising a viscosity index improver (B) comprising a comb polymer (B1).

7. The lubricating oil composition according to any one of claims 1 to 6, further comprising a molybdenum-based friction modifier (C2).

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