Lubricating oil composition

Abstract

There has been a need for the development of a lubricating oil composition that reduces oil evaporation at lower temperatures and improves both fuel efficiency and oil film retention. [Solution] A lubricating oil composition comprising a base oil (A) and a viscosity index improver (B), wherein the base oil (A) contains a fraction (a1) having fewer than 28 carbon atoms in an amount of 60.0 to 80.0% by mass on a basis of the total amount of the base oil (A), and the viscosity index improver (B) contains a comb-shaped polymer (B1) with a mass average molecular weight of 450,000 or more.

Description

Technical Field

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

Background Art

[0002] As an index of oil volatility, the NOACK test at 250 °C defined in ASTM D5800 is widely used. However, with the advancement of engines, there are cases where the correlation between the NOACK value and the oil evaporation amount (consumption amount) in the actual use environment cannot be obtained. Under such circumstances, it has been reported that the value of oil volatility at a lower temperature correlates with the actual oil consumption amount (Non-Patent Document 1).

Prior Art Documents

Non-Patent Documents

[0003]

Non-Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Under such circumstances, the development of a lubricating oil composition with a reduced oil evaporation amount at a lower temperature and improved fuel efficiency and oil film retention has been desired.

Means for Solving the Problems

[0005] As a result of intensive research, the inventors of the present invention have found that by containing a base oil of a specific fraction in a predetermined amount and a comb polymer having a specific mass average molecular weight, the above problems can be solved, and the present invention has been completed. That is, the present invention provides, for example, the following aspects. [1] A lubricating oil composition comprising a base oil (A) and a viscosity index improver (B), ​​Base oil (A) contains a fraction (a1) containing a hydrocarbon group having less than 28 carbon atoms in an amount of 60.0 to 80.0% by mass based on the total amount of base oil (A). The viscosity index improver (B) is a lubricating oil composition containing a comb-shaped polymer (B1) having a mass average molecular weight of 450,000 or more. [2] The base oil (A) contains a fraction (a2) containing a hydrocarbon group having 28 or more and less than 32 carbon atoms in an amount of 15.0 to 25.0% by mass based on the total amount of base oil (A), and the lubricating oil composition according to [1]. [3] The lubricating oil composition according to [1] or [2], wherein the molecular weight distribution (Mw / Mn) of the comb-shaped polymer (B1) is 3.0 or less. [4] The lubricating oil composition according to any one of [1] to [3], wherein the base oil (A) contains mineral oil. [5] The lubricating oil composition according to any one of [1] to [4], wherein the viscosity index of the base oil (A) is 200 or less. [6] The lubricating oil composition according to any one of [1] to [5], wherein the viscosity index of the lubricating oil composition is 250 or more. [7] The lubricating oil composition according to any one of [1] to [6], wherein the kinematic viscosity of the lubricating oil composition at 100 °C is 5.0 mm 2 / s or more. [Advantages of the Invention]

[0006] A preferred embodiment of the present invention provides a lubricating oil composition with low oil evaporation at temperatures lower than 250 °C. Also, a preferred embodiment of the present invention provides a lubricating oil composition that has a low kinematic viscosity at 40 °C, a high viscosity index, and an appropriate high-temperature shear viscosity (HTHS viscosity), and can improve fuel efficiency and oil film retention. [[ID=3故]] [Embodiments for Carrying Out the Invention]

[0007] The numerical ranges described herein can be any combination of upper and lower limits. For example, if the numerical range is described as "preferably 30 to 100, more preferably 40 to 80," then the ranges of "30 to 80" and "40 to 100" are also included in the numerical range described herein. Similarly, if the numerical range is described as "preferably 30 or more, more preferably 40 or more, and also preferably 100 or less, more preferably 80 or less," then the ranges of "30 to 80" and "40 to 100" are also included in the numerical range described herein. In addition, as a numerical range described in this specification, for example, "60 to 100" means a range of "60 or more (60 or greater than 60) and 100 or less (100 or less than 100)." Furthermore, in the provisions for upper and lower limits described herein, the numerical range from the lower limit to the upper limit can be defined by appropriately selecting and combining options from each set of choices as appropriate. In addition, several of the requirements described as preferred embodiments in this specification can be combined.

[0008] [Composition of the lubricating oil composition] A lubricating oil composition according to one aspect of the present invention is a lubricating oil composition comprising a base oil (A) (hereinafter also referred to as "component (A)") and a viscosity index improver (B) (hereinafter also referred to as "component (B)"), wherein the base oil (A) contains a fraction (a1) having hydrocarbon groups with fewer than 28 carbon atoms in an amount of 60.0 to 80.0% by mass on a basis of the total amount of base oil (A), and the viscosity index improver (B) contains a comb-shaped polymer (B1) with a mass average molecular weight of 450,000 or more. This configuration allows the NOACK value at 150°C to be below the specified value, thus enabling the creation of a lubricating oil composition with low oil consumption even under actual operating conditions. Furthermore, this configuration makes it possible to obtain a lubricating oil composition with low kinematic viscosity at 40°C, a high viscosity index, and excellent fuel efficiency. Furthermore, this configuration allows for a lubricating oil composition that exhibits excellent fuel efficiency and oil film retention, as the ratio of the HTHS viscosity at 80°C to the HTHS viscosity at 150°C (hereinafter also referred to as HTHS80 / 150) is within an appropriate range. In this specification, the NOACK value at 150°C refers to 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 a lubricating oil composition according to one embodiment of the present invention will be described below.

[0009] <Ingredients (A): Base oil> In one embodiment of the present invention, a lubricating oil composition is used in which a fraction (a1) containing hydrocarbon groups with fewer than 28 carbon atoms is present in an amount of 60.0 to 80.0% by mass on a basis of the total amount of base oil (A) as the base oil (A). By setting the fraction (a1) of base oil (A) to below the upper limit of the above numerical range, the NOACK 150℃ value can be adjusted to 5.00 mass% or less, improving oil consumption under actual engine operating conditions. Furthermore, by setting the fraction (a1) of base oil (A) to above the lower limit of the above numerical range, the kinematic viscosity at 40℃ can be set to 25.0 mmHg. 2 A lubricating oil composition with excellent fuel efficiency of less than / s can be obtained. Furthermore, by setting the fraction (a1) of the base oil (A) within the above numerical range, a lubricating oil composition with excellent oil film retention, where HTHS80 / 150 is 2.00 or higher, can be obtained. The fraction (a1) containing hydrocarbon groups with fewer than 28 carbon atoms is preferably in an amount of 61.0% by mass or more, 61.5% by mass or more, 62.0% by mass or more, 62.5% by mass or more, or 63.0% by mass or more, from the viewpoint of providing a lubricating oil composition that can improve fuel efficiency and oil film retention, and may also be 64.0% by mass or more, 65.0% by mass or more, 66.0% by mass or more, 67.0% by mass or more, 68.0% by mass or more, 69.0% by mass or more, or 70.0% by mass or more. Furthermore, the fraction (a1) containing hydrocarbon groups with fewer than 28 carbon atoms is preferably in an amount of 79.5% by mass or less, 79.0% by mass or less, 78.5% by mass or less, 78.0% by mass or less, or 77.5% by mass or less, from the viewpoint of providing a lubricating oil composition that has a low oil evaporation rate and can improve oil film retention, and may also be 77.0% by mass or less, 76.0% by mass or less, 75.0% by mass or less, 74.0% by mass or less, 73.0% by mass or less, 72.0% by mass or less, 71.0% by mass or less, or 70.0% by mass or less.

[0010] In one embodiment of the present invention, a lubricating oil composition may be used in which, as the base oil (A), together with the above-mentioned fraction (a1), a fraction (a2) containing hydrocarbon groups having 28 or more and less than 32 carbon atoms is present in an amount of 15.0 to 25.0% by mass based on the total amount of the base oil (A). By setting the fraction (a2) of the base oil (A) to below the upper limit of the above numerical range, the oil consumption performance under actual engine operating conditions can be improved. Furthermore, by setting the fraction (a2) of the base oil (A) to above the lower limit of the above numerical range, a lubricating oil composition with superior fuel efficiency can be obtained. In addition, by setting the fraction (a2) of the base oil (A) to within the above numerical range, a lubricating oil composition with superior oil film retention can be obtained. The fraction (a2) containing hydrocarbon groups with 28 or more carbon atoms and less than 32 carbon atoms is preferably in an amount of 15.5% by mass or more, 16.0% by mass or more, or 16.5% by mass or more, from the viewpoint of providing a lubricating oil composition that can further improve fuel efficiency and oil film retention, and may also be 17.0% by mass or more, 17.5% by mass or more, 18.0% by mass or more, 18.5% by mass or more, 19.0% by mass or more, 19.5% by mass or more, or 20.0% by mass or more. Furthermore, the fraction (a2) containing hydrocarbon groups with 28 or more carbon atoms but less than 32 carbon atoms is preferably 24.9% by mass or less, 24.8% by mass or less, 24.7% by mass or less, or 24.6% by mass or less, from the viewpoint of providing a lubricating oil composition that has less oil evaporation and can further improve oil film retention, and may also be 24.5% by mass or less, 24.0% by mass or less, 23.5% by mass or less, 23.0% by mass or less, 22.5% by mass or less, 22.0% by mass or less, 21.5% by mass or less, or 21.0% by mass or less.

[0011] The base oil (A) described above can be adjusted to the range of hydrocarbon groups containing the above number of carbon atoms, based on the measurement results of each fraction measured by the method described in the examples below. Furthermore, the base oil (A) can be obtained, for example, by combining mineral oils, synthetic oils, or a combination of mineral oil and synthetic oil as described below, and adjusting the range of hydrocarbon groups containing the above number of carbon atoms while considering the measurement results of each fraction measured by the method described in the examples below.

[0012] Examples of mineral oils constituting a fraction (a1) containing hydrocarbon groups having less than 28 carbon atoms and a fraction (a2) containing hydrocarbon groups having 28 or more carbon atoms but less than 32 carbon atoms in a lubricating oil composition according to one embodiment of the present invention include atmospheric residue obtained by atmospheric distillation of crude oil such as paraffinic crude oil, intermediate crude oil, and naphthenic crude oil; distillate obtained by vacuum distillation of these atmospheric residues; and refined oil obtained by subjecting the distillate to one or more refining treatments such as solvent delamination, solvent extraction, hydrocracking, solvent dewaxing, catalytic dewaxing, and hydrorefining. The base oil (A) used in a lubricating oil composition according to one embodiment of the present invention may be a single mineral oil or a mixed oil using multiple mineral oils in combination.

[0013] The synthetic oils constituting the fraction (a1) containing hydrocarbon groups having less than 28 carbon atoms and the fraction (a2) containing hydrocarbon groups having 28 or more carbon atoms, contained in a lubricating oil composition according to one embodiment of the present invention, include, for example, poly-α-olefins such as α-olefins and their 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; ether-based oils such as polyphenyl ethers; ester-based oils such as polyol esters, dibasic acid esters, and monoesters; alkylbenzenes; alkylnaphthalenes; synthetic oils (GTL) obtained by isomerizing wax (GTL wax (Gas To Liquids Wax)) produced from natural gas by the Fischer-Tropsch process, etc.; and synthetic oils (Ethylene To) obtained by oligomerizing olefins produced using gas as a raw material. Liquid (ETL) oils include CTL base oils obtained by direct liquefaction methods (such as the Bergius process) in which coal is crushed, mixed with a solvent, and reacted directly with hydrogen under high temperature and pressure; and CTL base oils obtained by indirect liquefaction methods (such as the Fischer-Tropsch process) in which coal is first gasified (coal gasification), and the resulting gas is separated and purified and then reacted with the raw materials to liquefy the mixture. These synthetic oils may also be produced from renewable resources. The base oil (A) used in a lubricating oil composition according to one embodiment of the present invention may be a single synthetic oil or a mixed oil using multiple synthetic oils in combination. Furthermore, as described above, the base oil (A) used in the lubricating oil composition according to one embodiment of the present invention may be a mixed oil obtained by using both mineral oil and synthetic oil.

[0014] Among these, the base oil (A) used in one aspect of the present invention preferably includes at least one selected from mineral oils classified into groups 2 and 3 of the API (American Petroleum Institute) base oil categories, and synthetic oils.

[0015] The kinematic viscosity of the base oil (A) used in one aspect of the present invention at 100°C is 2.0 mm, from the viewpoint of providing a lubricating oil composition with superior oil film retention. 2 / s or more, 2.1mm 2Above / s, 2.2 mm 2 Above / s, 2.3 mm 2 Above / s, 2.4 mm 2 Above / s, 2.5 mm 2 Above / s, 2.6 mm 2 Above / s, or 2.8 mm 2 Above / s is preferable, and also 3.0 mm 2 Above / s, 3.2 mm 2 Above / s, 3.4 mm 2 Above / s, 3.6 mm 2 Above / s, 3.8 mm 2 Above / s, or 4.0 mm 2 It may be above / s. Also, from the viewpoint of obtaining a lubricating oil composition with better fuel economy, the kinematic viscosity at 100 °C of the base oil (A) used in one aspect of the present invention is 5.0 mm 2 / s or less, 4.9 mm 2 / s or less, 4.8 mm 2 / s or less, 4.7 mm 2 / s or less, 4.6 mm 2 / s or less, or 4.5 mm 2 / s or less is preferable, and also 4.3 mm 2 / s or less, 4.1 mm 2 / s or less, 4.0 mm<o000025> / s or less, 3.8 mm 2 / s or less, 3.6 mm 2 / s or less, 3.4 mm 2 / s or less, 3.2 mm 2 / s or less, or 3.0 mm 2 It may be / s or less. In one aspect of the present invention, when a mixed oil is used as the base oil (A), it is preferable that the kinematic viscosity at 100 °C of the mixed oil is within the above range.

[0016] Furthermore, the viscosity index of the base oil (A) used in one aspect of the present invention is preferably 80 or higher, more preferably 90 or higher, even more preferably 100 or higher, and even more preferably 110 or higher, from the viewpoint of suppressing viscosity changes due to temperature changes and further improving fuel efficiency and oil film retention, and may also be 200 or lower, 190 or lower, 180 or lower, 170 or lower, 160 or lower, 150 or lower, 140 or lower, or 130 or lower. The base oil (A) used in one aspect of the present invention has the above-mentioned fractions (a1) and (a2) adjusted, and has the limitation that the viscosity index will be low as a base oil composition. However, by combining it with the viscosity index improver (B) described later, the viscosity index is improved, and by adjusting the ratio of the HTHS viscosity at 80°C to the HTHS viscosity at 150°C (HTHS80 / 150) to a predetermined range, fuel efficiency and oil film retention are improved. In this specification, kinematic viscosity and viscosity index mean values ​​measured or calculated in accordance with ASTM D455.

[0017] In a lubricating oil composition according to one aspect of the present invention, the base oil (A) content is 60% by mass or more, 65% by mass or more, 70% by mass or more, 75% by mass or more, 80% by mass or more, or 85% by mass or more, based on the total amount (100% by mass) of the lubricating oil composition, and is also 99% by mass or less, 98% by mass or less, 95% by mass or less, or 90% by mass or less.

[0018] <Component (B): Viscosity index improver> A lubricating oil composition according to one aspect of the present invention contains a viscosity index improver (B) comprising a comb-shaped polymer (B1) with a mass-average molecular weight of 450,000 or more. By including the above-mentioned comb-shaped polymer (B1) as the viscosity index improver (B), the viscosity index of the lubricating oil composition is significantly increased, thereby improving the fuel efficiency and oil film retention of the lubricating oil composition. The comb-shaped polymer (B1) is preferably a polymer having a structure in which the main chain has many tridentation points from which high molecular weight side chains emerge. The comb-shaped polymer (B1) used in one aspect of the present invention is more preferably a polymer having at least one constituent unit (X1) derived from a macromonomer (x1). This constituent unit (X1) corresponds to the "high molecular weight side chain" mentioned above. In this invention, the above-mentioned "macromonomer (x1)" refers to a high molecular weight monomer having a polymerizable functional group, and it is preferable that the high molecular weight monomer has a polymerizable functional group at its terminus.

[0019] The comb-shaped polymer (B1) used in one aspect of the present invention may be a homopolymer consisting only of constituent units (X1) derived from one type of macromonomer (x1), or it may be a copolymer containing constituent units (X1) derived from two or more types of macromonomers (x1). Furthermore, the comb-shaped polymer (B1) used in one aspect of the present invention may be a copolymer containing structural units derived from a macromonomer (x1) as well as structural units (X2) derived from other monomers other than the macromonomer (x1). As for the specific structure of such comb-shaped polymers, a copolymer having a main chain containing a constituent unit (X2) derived from a monomer (x2) and side chains containing a constituent unit (X1) derived from a macromonomer (x1) is preferred.

[0020] Examples of monomers (x2) include (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, aromatic hydrocarbon vinyl monomers, and the like. Among these, the comb-shaped polymer (B1) used in one aspect of the present invention is preferably a comb-shaped poly(meth)acrylate (b1) having poly(meth)acrylate as the main chain.

[0021] The mass-average molecular weight of the comb-shaped polymer (B1) used in one aspect of the present invention is preferably 460,000 or more, 470,000 or more, 480,000 or more, 490,000 or more, or 500,000 or more, from the viewpoint of further improving the fuel efficiency and oil film retention of the lubricating oil composition, and may also be 520,000 or more, 540,000 or more, 560,000 or more, 580,000 or more, or 600,000 or more. Furthermore, the mass-average molecular weight of the comb-shaped polymer (B1) used in one aspect of the present invention is preferably 2 million or less, 1.5 million or less, 1 million or less, 800,000 or less, 750,000 or less, or 700,000 or less, from the viewpoint of obtaining a lubricating oil composition with good shear stability, and may also be 680,000 or less, 660,000 or less, 640,000 or less, 620,000 or less, or 600,000 or less.

[0022] In one aspect of the present invention, the molecular weight distribution (Mw / Mn) (Mw: mass-average molecular weight of the comb-shaped polymer (B1), Mn: number-average molecular weight of the comb-shaped polymer (B1)) of the comb-shaped polymer (B1) used is preferably 3.0 or less, 2.9 or less, or 2.8 or less, and also preferably 2.0 or more, greater than 2.0, 2.1 or more, 2.2 or more, 2.3 or more, or 2.4 or more, from the viewpoint of further improving the fuel efficiency and oil film retention of the lubricating oil composition. In this specification, the mass-average molecular weight (Mw) and number-average molecular weight (Mn) are values ​​calculated on a standard polystyrene basis by gel permeation chromatography (GPC).

[0023] In a lubricating oil composition according to one embodiment of the present invention, the content of the comb-shaped polymer (B1) in terms of resin content is preferably 2.0% by mass or more, 2.2% by mass or more, 2.4% by mass or more, or 2.5% by mass or more, based on the total amount (100% by mass) of the lubricating oil composition, from the viewpoint of further improving the fuel efficiency and oil film retention of the lubricating oil composition, and is preferably 5.0% by mass or less, 4.5% by mass or less, 4.0% by mass or less, or 3.5% by mass or less, from the viewpoint of maintaining good lubrication performance.

[0024] Furthermore, the viscosity index improver (B) used in one aspect of the present invention may contain, or may not contain, a viscosity index improver made of a polymer other than the comb-shaped polymer (B1) described above, as long as it does not impair the effects of the present invention. Other polymers that fall under the category of comb-type polymers include, for example, dispersed poly(meth)acrylates, olefin copolymers (e.g., ethylene-propylene copolymers), dispersed olefin copolymers, and styrene copolymers (e.g., styrene-diene copolymers, styrene-isoprene copolymers).

[0025] In one aspect of the present invention, the content ratio of component (B1) in component (B) used is preferably 50% by mass or more, 60% by mass or more, 70% by mass or more, 80% by mass or more, 90% by mass or more, 95% by mass or more, 98% by mass or more, 99% by mass or more, or 100% by mass, based on the total amount (100% by mass) of component (B).

[0026] <Various additives> A lubricating oil composition according to one aspect of the present invention may contain various additives as needed, as long as they do not impair the effects of the present invention. Examples of such additives include pour point depressants, antioxidants, metal-based detergents, ashless dispersants, friction modifiers, wear inhibitors, rust inhibitors, defoamers, metal deactivators, and extreme pressure additives. These lubricating oil additives may be used individually or in combination of two or more. Furthermore, compounds possessing multiple additive functions (for example, compounds functioning as anti-wear agents and extreme-pressure additives) may also be used.

[0027] 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 on a basis of the total amount (100% by mass) of the lubricating oil composition, the content of each additive is usually 0.001 to 15% by mass, preferably 0.005 to 10% by mass, and more preferably 0.01 to 5% by mass for each additive independently.

[0028] [Pour point depressant] A lubricating oil composition according to one embodiment of the present invention may further contain a pour point depressant. The pour point depressant may be used alone or in combination of two or more types. Examples of pour point depressants used in one aspect of the present invention include ethylene-vinyl acetate copolymers, condensates of chlorinated paraffin and naphthalene, condensates of chlorinated paraffin and phenol, and polyalkylstyrene.

[0029] [Antioxidant] A lubricating oil composition according to 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 antioxidants used in one aspect 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.

[0030] [Metal-based cleaning agent] A lubricating oil composition according to one aspect of the present invention may further contain a metal-based detergent. The metal-based detergent may be used alone or in combination of two or more types. Examples of metal-based detergents used in one aspect of the present invention include metal salts such as metal sulfonates, metal salicylates, and metal phenates. Furthermore, the metal atoms constituting the metal salt are preferably selected from alkali metals and alkaline earth metals, more preferably sodium, calcium, magnesium, or barium, and even more preferably calcium and magnesium. In one aspect of the present invention, the metal-based cleaning agent used is preferably a metal salicylate, and most preferably one or more selected from calcium salicylate and magnesium salicylate.

[0031] [Ashless Dispersant] A lubricating oil composition according to 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 types. In one aspect of the present invention, alkenyl succinimide is preferred as the ashless dispersant, and may also be a modified alkenyl succinimide obtained by reacting with one or more selected from boron compounds, alcohols, aldehydes, ketones, alkylphenols, cyclic carbonates, epoxy compounds, and organic acids.

[0032] [Friction modifier] A lubricating oil composition according to one aspect of the present invention may further contain a friction modifier. The friction modifier may be used alone or in combination of two or more types. Examples of friction modifiers used in one aspect of the present invention include molybdenum-based friction modifiers such as molybdenum dithiocarbamate (MoDTC), molybdenum dithiophosphate (MoDTP), and amine salts of molybdenum acid; and ashless friction modifiers such as aliphatic amines, fatty acid esters, fatty acid amides, fatty acids, aliphatic alcohols, and aliphatic ethers, which have at least one alkyl group or alkenyl group with 6 to 30 carbon atoms in their molecule.

[0033] [Abrasion-resistant agent] A lubricating oil composition according to 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 types. Examples of wear-resistant agents used in one aspect of the present invention include sulfur-containing compounds such as zinc dialkyldithiophosphate (ZnDTP), zinc phosphate, zinc dithiocarbamate, disulfides, sulfurized olefins, sulfurized oils and fats, sulfurized esters, thiocarbonates, thiocarbamates, and polysulfides; phosphorus-containing compounds such as phosphite esters, phosphate esters, phosphonic acid esters, and their amine salts or metal salts; and sulfur and phosphorus-containing wear-resistant agents such as thiophosphite esters, thiophosphate esters, thiophosphonic acid esters, and their amine salts or metal salts.

[0034] [Rust inhibitor] A lubricating oil composition according to one aspect of the present invention may further contain a rust inhibitor. The rust inhibitor may be used alone or in combination of two or more types. Examples of rust inhibitors used in one aspect of the present invention include fatty acids, alkenyl succinate half esters, fatty acid soaps, alkyl sulfonates, polyhydric alcohol fatty acid esters, fatty acid amines, oxidized paraffins, alkyl polyoxyethylene ethers, and the like.

[0035] [Antifoaming agent] A lubricating oil composition according to 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 types. Examples of defoaming agents used in one aspect of the present invention include alkyl silicone-based defoaming agents, fluorosilicone-based defoaming agents, and fluoroalkyl ether-based defoaming agents.

[0036] [Metal deactivator] A lubricating oil composition according to one embodiment of the present invention may further contain a metal deactivator. The metal deactivator may be used alone or in combination of two or more types. Examples of metal deactivators used in one aspect of the present invention include benzotriazole, imidazoline, pyrimidine derivatives, and thiadiazole.

[0037] [Extreme pressure additives] A lubricating oil composition according to one embodiment of the present invention may further contain extreme pressure additives. The extreme pressure additives may be used alone or in combination of two or more types. Examples of extreme pressure additives used in one aspect of the present invention include sulfur-containing compounds such as zinc dialkyldithiophosphate (ZnDTP), zinc phosphate, zinc dithiocarbamate, disulfides, sulfurized olefins, sulfurized oils and fats, sulfurized esters, thiocarbonates, thiocarbamates, and polysulfides; phosphorus-containing compounds such as phosphite esters, phosphate esters, phosphonic acid esters, and their amine salts or metal salts; and sulfur and phosphorus-containing abrasion-resistant agents such as thiophosphite esters, thiophosphate esters, thiophosphonic acid esters, and their amine salts or metal salts.

[0038] [Method for producing a lubricating oil composition] The method for producing a lubricating oil composition according to one embodiment of the present invention is not particularly limited, but it is preferable to have a step of blending a base oil (A) and a viscosity index improver (B) with various other additives as needed. The order in which each component is blended can be set as appropriate.

[0039] [Properties of the lubricating oil composition] The kinematic viscosity at 100°C of a lubricating oil composition according to one aspect of the present invention is 5.0 mm, from the viewpoint of providing a lubricating oil composition that balances fuel efficiency and lubricity. 2 / s or more, 5.2mm 2 / s or more, 5.4mm 2 / s or more, 5.6mm 2 / s or more, 5.8mm 2 / s or more, 6.0mm 2 / s or more, 6.2mm 2 / s or more, or 6.4mm 2 A value of 10.0 mm or more is preferred, and 10.0 mm 2 / s or less, 9.5mm 2 / s or less, 9.0mm 2 / s or less, 8.8mm 2 / s or less, 8.6mm 2 / s or less or 8.4mm 2 A value of / s or less is preferable.

[0040] The kinematic viscosity of a lubricating oil composition according to one embodiment of the present invention at 40°C is 25.0 mm, from the viewpoint of providing a lubricating oil composition with excellent fuel efficiency. 2 / s or less, 24.8mm 2 / s or less, or 24.6mm 2 A value of / s or less is preferred, and the lower limit is not particularly limited, but for example, 10.0 mm. 2 / s or more, 12.0mm 2 / s or more, or 14.0mm 2 / s or longer is also acceptable.

[0041] The viscosity index of the lubricating oil composition according to one embodiment of the present invention is preferably 280 or higher, from the viewpoint of providing a lubricating oil composition with excellent fuel efficiency and oil film retention properties, and may also be 290 or higher, 300 or higher, 310 or higher, 320 or higher, 330 or higher, 340 or higher, or 350 or higher. The upper limit of the viscosity index of the lubricating oil composition is not particularly limited, but may be, for example, 500 or less, 400 or less, 390 or less, or 380 or less.

[0042] The HTHS viscosity at 150°C of a lubricating oil composition according to one embodiment of the present invention is preferably 2.00 mPa·s or higher, 2.10 mPa·s or higher, or 2.20 mPa·s or higher, from the viewpoint of providing a lubricating oil composition with excellent oil film retention properties. The lower limit is not particularly limited, but may be, for example, 3.00 mPa·s or lower, 2.90 mPa·s or lower, or 2.80 mPa·s or lower.

[0043] In a lubricating oil composition according to one embodiment of the present invention, the ratio of the HTHS viscosity at 80°C to the HTHS viscosity at 150°C (HTHS80 / 150) is preferably 2.00 or higher, 2.05 or higher, or 2.10 or higher, and also preferably 2.50 or lower, 2.45 or lower, or 2.40 or lower, from the viewpoint of providing a lubricating oil composition with excellent oil film retention properties.

[0044] In one embodiment of the present invention, from the viewpoint of providing a lubricating oil composition with improved oil evaporation, the NOACK value measured at 150°C for 12 hours in accordance with ASTM D5800 is preferably 5.00% by mass or less, or 4.50% by mass or less, and the lower limit is not particularly limited, but for example, it is 3.00% by mass or more.

[0045] [Uses of lubricating oil compositions] The lubricating oil composition of the present invention exhibits low oil evaporation, as indicated by the NOACK value at 150°C, and also has excellent fuel efficiency and oil film retention properties, making it suitable for use in lubricating internal combustion engines. Therefore, the present invention also provides the internal combustion engine described in [I] below and a method for using the lubricating oil composition described in [II] below. [I] An internal combustion engine filled with a lubricating oil composition according to one embodiment of the present invention described above. [II] A method of using a lubricating oil composition according to one aspect of the present invention described above for the lubrication of an internal combustion engine. [Examples]

[0046] Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited in any way by these examples. The various physical properties of each component used in the examples and comparative examples and the obtained lubricating oil compositions were measured in accordance with the following methods.

[0047] (1) Kinematic viscosity and viscosity index Measurements and calculations were performed in accordance with ASTM D455. The kinematic viscosity at 40°C was 25.0 mmHg. 2 We judged samples with a viscosity index of 280 or less to be acceptable. (2) Mass average molecular weight (Mw), number average molecular weight (Mn) A Waters 1515 isocratic HPLC pump and a 2414 differential refractive index (RI) detector were used, with one TSKguardcolumn SuperHZ-L and two TSKSuperMultipore HZ-M columns from Tosoh Corporation installed in that order from upstream. Measurements were taken at a temperature of 40°C, with tetrahydrofuran as the mobile phase, a flow rate of 0.35 mL / min, and a sample concentration of 1.0 mg / mL. The results were then calculated in terms of standard polystyrene equivalents. (3) Amount of fraction (a1) and fraction (a2) Using the following measuring apparatus and under the following measurement conditions, the peak area of ​​fractions containing hydrocarbon groups for each carbon number range was calculated, starting from 8 to less than 10 carbon numbers, then 10 to less than 12 carbon numbers, and continuing up to 36 to less than 38 carbon numbers, increasing by 2 each time. Fractions containing hydrocarbon groups with 36 or more carbon numbers were calculated as the residue of fractions containing hydrocarbon groups with fewer than 36 carbon numbers. In addition, the proportion of fractions containing hydrocarbon groups to all peak areas in each carbon number range was calculated. Furthermore, the cumulative amount up to 28 carbon numbers was calculated from the proportions of the fractions. (Measuring device) Equipment: 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℃ Detector temperature: 360℃ Heating conditions: Initial temperature 60°C Heating rate: 10℃ / min Final heating temperature: 350℃ Final temperature holding time: 5 min Gas flow rate: N245 mL / min (4) NOACK 150℃ Measurements were taken at 150°C for 12 hours, in accordance with ASTM D5800. Samples with a NOACK 150°C value of 5.00% by mass or less were deemed acceptable. (5)HTHS viscosity In accordance with ASTM D4683, a TBS (Tapered Bearing Simulator Viscometer) was used to measure the shear rate at 10°C under temperature conditions of 80°C and 150°C. 6 Measurements were taken in seconds. A score of 2.00 or higher and 2.50 or lower for HTHS80 / 150 was considered acceptable.

[0048] Examples 1-8, Comparative Examples 1-18 Lubricant compositions were prepared by adding and mixing the various components and other additives shown in Tables 1-4 in the amounts indicated in Tables 1-4. Note that the amounts of viscosity index improvers in Tables 1-4 are listed as amounts equivalent to resin content. Furthermore, the viscosity index improver content varied from sample to sample to ensure consistent viscosity grade. The details of each component used in the preparation of the lubricating oil composition are as follows: <Ingredients (A): Base oil> Using the following mineral oils A1 to A7, the fractions containing hydrocarbon groups with fewer than 28 carbon atoms (a1) and fractions containing hydrocarbon groups with 28 or more carbon atoms but less than 32 carbon atoms (a2) were adjusted to the values ​​shown in Tables 1 to 4. • Mineral oil A1: Kinematic viscosity at 100℃ is 4.5 mm 2Mineral oil with a viscosity index of 127 (API base oil category group 3) at / s. ·Mineral oil A2: 100℃ kinematic viscosity is 4.3mm 2 / s, mineral oil with a viscosity index of 122 (API base oil category group 3). • Mineral oil A3: Kinematic viscosity at 100°C is 4.1 mm² 2 / s, mineral oil with a viscosity index of 121 (API base oil category group 3). • Mineral oil A4: Kinematic viscosity at 100°C is 2.7 mm 2 / s, mineral oil with a viscosity index of 112 (API base oil category group 2). • Mineral oil A5: Kinematic viscosity at 100°C is 2.7 mm 2 / s, mineral oil with a viscosity index of 113 (API base oil category group 2). • Mineral oil A6: Kinematic viscosity at 100°C is 2.9 mm 2 Mineral oil with a viscosity index of 119 (API base oil category group 2) at 1 / s. • Mineral oil A7: Kinematic viscosity at 100°C is 2.8 mm 2 / s, mineral oil with a viscosity index of 123 (API base oil category group 3).

[0049] <Component (B): Viscosity index improver> • Comb-shaped polymer b1: A non-dispersible comb-shaped poly(meth)acrylate (Mw=520,000, Mw / Mn=2.8) with a structure that has many tridental branching points in the main chain from which high molecular weight side chains emerge. • Comb-shaped polymer b2: A non-dispersible comb-shaped poly(meth)acrylate (Mw=600,000, Mw / Mn=2.4) with a structure that has many tridental branching points in the main chain from which high molecular weight side chains emerge.

[0050] <Viscosity index improver (not applicable to component (B))> • Comb-shaped polymer (1): Non-dispersible poly(meth)acrylate (Mw=400,000, Mw / Mn=1.7) • Comb-shaped polymer (2): A non-dispersible comb-shaped poly(meth)acrylate (Mw=310,000, Mw / Mn=2.0) with a structure that has many tridental branching points in the main chain from which high molecular weight side chains emerge.

[0051] <Other additives> • An additive mixture comprising a pour point depressant, detergent, ashless dispersant, ZnDTP, antioxidant, metal deactivator, defoamer, and friction modifier. In the following tables, the amount of diluent oil for the viscosity index improver is included in "other additives." Since the amount of diluent oil differs depending on the type of viscosity index improver, the content of "other additives" differs for each sample oil.

[0052] [Table 1] [Table 2] [Table 3] [Table 4]

[0053] From the results in Table 1, the lubricating oil compositions of Examples 1 to 8, which contained a fraction (a1) with fewer than 28 carbon atoms as the base oil (A) in an amount of 60.0 to 80.0% by mass on a total basis of the base oil (A), and a comb-shaped polymer (B1) with a mass-average molecular weight of 450,000 or more, had a NOACK value of 5.00% by mass or less at 150°C and exhibited low oil evaporation. Furthermore, the lubricating oil compositions of Examples 1 to 8 had a kinematic viscosity of 25.0 mm at 40°C. 2 The viscosity index was less than or equal to / s, the viscosity index was 280 or higher, and the HTHS80 / 150 was between 2.00 and 2.50, resulting in excellent fuel efficiency and oil film retention.

[0054] On the other hand, as shown in Table 2, the lubricating oil compositions of Comparative Examples 1 to 6, in which the proportion of fraction (a1) in base oil (A) was 60.0% by mass or less, did not meet the acceptance criteria for kinematic viscosity and viscosity index at 40°C. Furthermore, as shown in Table 3, the lubricating oil compositions of Comparative Examples 7 to 14, in which the proportion of fraction (a1) in base oil (A) was 80.0% by mass or more, did not meet the acceptance criteria for NOACK value and / or HTHS80 / 150 at 150°C. Furthermore, as shown in Table 4, the lubricating oil compositions of Comparative Examples 15-18, which used viscosity index improvers that did not meet the requirements for comb-shaped polymers (B1), did not meet the viscosity index standards.

Claims

1. A lubricating oil composition comprising a base oil (A) and a viscosity index improver (B), The base oil (A) contains a fraction (a1) containing hydrocarbon groups with fewer than 28 carbon atoms in an amount of 60.0 to 80.0% by mass on a basis of the total amount of base oil (A). The viscosity index improver (B) is a lubricating oil composition containing a comb-shaped polymer (B1) with a mass-average molecular weight of 450,000 or more.

2. The lubricating oil composition according to claim 1, wherein the base oil (A) contains a fraction (a2) having hydrocarbon groups with 28 or more and less than 32 carbon atoms in an amount of 15.0 to 25.0% by mass on a basis of the total amount of base oil (A).

3. The lubricating oil composition according to claim 1 or 2, wherein the molecular weight distribution (Mw / Mn) of the comb-shaped polymer (B1) is 3.0 or less.

4. A lubricating oil composition according to any one of claims 1 to 3, wherein the base oil (A) contains mineral oil.

5. The lubricating oil composition according to any one of claims 1 to 4, wherein the viscosity index of the base oil (A) is 200 or less.

6. The lubricating oil composition according to any one of claims 1 to 5, wherein the viscosity index of the lubricating oil composition is 250 or higher.

7. The kinematic viscosity of the lubricating oil composition at 100°C is 5.0 mm. ２ A lubricating oil composition according to any one of claims 1 to 6, wherein the ratio is 1 / s or more.

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