Lubricating oil composition

Abstract

The present invention addresses the problem of providing a lubricating oil composition which, in a low-temperature range, is less apt to increase in viscosity and is highly effective in fuel saving and which, in a high-temperature range, is apt to increase in viscosity, is excellent in terms of wear resistance and hydraulic property, and is apt to form an oil film. The problem was solved with a lubricating oil composition comprising a base oil (A) and a viscosity-index improver (B), wherein the base oil (A) comprises a mineral oil (A1) and an oxygenic synthetic oil (A2), the viscosity-index improver (B) comprises a comb-shaped polymer (B1), the dynamic viscosity at 100°C is 9.3 mm2 / s or less, the viscosity index is 280 or greater, and the content Y [unit: mass%] of the oxygenic synthetic oil (A2) with respect to the whole lubricating oil composition satisfies relationship (1).　Relationship (1): α≤Y<-3.7ln(X)+β [In relationship (1), α=0.5, β=19, and X indicates the ratio (C / O) of the number of carbon atoms to the number of oxygen atoms per molecule of the oxygenic synthetic oil (A2).]

Description

[Technical Field]

[0001] This invention relates to a lubricating oil composition. [Background technology]

[0002] One fuel-saving measure for internal combustion engines is to reduce the viscosity of the engine oil. Reducing the viscosity of engine oil is effective in reducing stirring losses and the coefficient of friction in fluid lubrication parts. On the other hand, reducing the viscosity of engine oil causes problems such as increased evaporation due to the lighter base oil, or in other words, increased engine oil consumption. Taking these points into consideration, various lubricating oil compositions have been proposed (see, for example, Patent Documents 1 to 3). [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Special Publication No. 2018-514621 [Patent Document 2] Special Publication No. 2017-500426 [Patent Document 3] Japanese Patent Publication No. 2010-53252 [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] In recent years, hybrid vehicles, which combine electric motors and internal combustion engines in a wide variety of designs, have been gaining popularity as one way to improve the fuel efficiency of automobiles. Hybrid vehicles tend to have lower internal combustion engine operating rates than conventional engine vehicles, resulting in less oil temperature rise. Therefore, to improve fuel efficiency in hybrid vehicles, it is important to reduce the viscosity of the engine oil in the low-temperature range of around 40°C. On the other hand, in the high-temperature range of 80°C and above, reducing the viscosity of the engine oil at high temperatures increases boundary lubrication, which can worsen wear resistance and hydraulic characteristics, and may prevent the maintenance of sufficient oil film thickness. For this reason, it is necessary to increase the viscosity of the engine oil. Consequently, there is a demand for engine oil that does not easily increase viscosity at low temperatures but easily increases viscosity at high temperatures.

[0005] An effective solution to meet these demands is to improve the viscosity index of the lubricating oil composition by incorporating a viscosity index improver into the lubricating oil composition. However, generally speaking, viscosity index improvers increase their viscosity index improvement ability, which in turn increases their viscosity-enhancing effect at low temperatures. Therefore, it is necessary to set the viscosity of the base oil low to match this viscosity-enhancing effect. However, setting the viscosity of the base oil low leads to an increase in the evaporation rate of the lubricating oil composition, as mentioned above. Thus, measures such as using low-viscosity synthetic oils that can easily suppress the evaporation rate of the lubricating oil composition are necessary. Furthermore, if the thickening effect at low temperatures is reduced by using the low-viscosity base oil or viscosity index improver mentioned above, the thickening effect at high temperatures will be insufficient. Therefore, measures are also needed to ensure the thickening effect at high temperatures.

[0006] Patent documents 1 to 3 propose lubricating oil compositions that combine synthetic oil and viscosity index improvers. However, these lubricating oil compositions have not been sufficiently studied in terms of ensuring sufficient viscosity reduction at low temperatures of around 40°C while also maintaining a viscosity-enhancing effect at high temperatures.

[0007] Therefore, the object of the present invention is to provide a lubricating oil composition that is less prone to viscosity increase in low-temperature ranges, has excellent fuel efficiency, and is more prone to viscosity increase in high-temperature ranges, has excellent wear resistance and hydraulic properties, and is also easy to maintain an oil film. [Means for solving the problem]

[0008] As a result of diligent research, the inventors have found that a lubricating oil composition obtained by adding an oxygen-containing synthetic oil and a comb-shaped polymer to mineral oil, and by adjusting the content of the oxygen-containing synthetic oil to a specific range, can solve the above problem.

[0009] In other words, the present invention relates to the following [1] to [3]. [1] A lubricating oil composition containing a base oil (A) and a viscosity index improver (B), The base oil (A) comprises mineral oil (A1) and oxygenated synthetic oil (A2). The viscosity index improver (B) comprises a comb-shaped polymer (B1), The kinematic viscosity at 100°C is 9.3 mm 2 It is less than or equal to / s, The viscosity index is 280 or higher. A lubricating oil composition in which the content Y [unit: mass%] of the oxygen-containing synthetic oil (A2) on a basis of the total amount of the lubricating oil composition satisfies the following formula (1). α ≤ Y < -3.7ln(X) + β ···(1) [In formula (1) above, α = 0.5, β = 19, and X represents the ratio (C / O) of the number of carbon atoms to the number of oxygen atoms per molecule of the oxygen-containing synthetic oil (A2).] [2] A method of using the lubricating oil composition described in [1] above in an internal combustion engine of an automobile. [3] A step of mixing a base oil (A) and a viscosity index improver (B), The base oil (A) comprises mineral oil (A1) and oxygenated synthetic oil (A2). The viscosity index improver (B) comprises a comb-shaped polymer (B1), The kinematic viscosity at 100°C is 9.3 mm 2 Adjusted to / s or less. The viscosity index is adjusted to 280 or higher. A method for producing a lubricating oil composition, wherein the content Y [unit: mass%] of the oxygen-containing synthetic oil (A2) on a basis of the total amount of the lubricating oil composition is adjusted to satisfy the following formula (1). α ≤ Y < -3.7ln(X) + β ···(1) [In formula (1) above, α = 0.5, β = 19, and X represents the ratio (C / O) of the number of carbon atoms to the number of oxygen atoms per molecule of the oxygen-containing synthetic oil (A2).] [Effects of the Invention]

[0010] According to the present invention, a lubricating oil composition is possible that is less prone to viscosity increase in low-temperature ranges, has excellent fuel efficiency, and is more prone to viscosity increase in high-temperature ranges, has excellent wear resistance and hydraulic properties, and is also easy to maintain an oil film. [Modes for carrying out the invention]

[0011] In this specification, the lower and upper limits described in steps for a preferred numerical range (e.g., a range of content, etc.) can be combined independently. For example, from a numerical range description of "preferably A to B, more preferably C to D," the "preferred lower limit A" and the "more preferred upper limit D" can be combined to become "A to D." Furthermore, in this specification, unless otherwise specified, the numerical range "A to B" means "A or greater and B or less". Furthermore, in this specification, the numerical values ​​in the examples are values ​​that can be used as upper or lower limits.

[0012] In this specification, the kinematic viscosity at 40°C (hereinafter also referred to as "40°C kinematic viscosity") and the kinematic viscosity at 100°C (hereinafter also referred to as "100°C kinematic viscosity") are values ​​measured in accordance with JIS K2283:2000. Furthermore, in this specification, the viscosity index is a value calculated in accordance with JIS K2283:2000 from the measured kinematic viscosity at 40°C and the measured kinematic viscosity at 100°C.

[0013] [Aspects of the lubricating oil composition of the present invention] The lubricating oil additive of the present invention is a lubricating oil composition containing a base oil (A) and a viscosity index improver (B). The base oil (A) includes mineral oil (A1) and oxygenated synthetic oil (A2). The viscosity index improver (B) comprises a comb-shaped polymer (B1). The kinematic viscosity at 100°C is 9.3 mm 2 It is less than or equal to / s. The viscosity index is 280 or higher. Furthermore, the content Y [unit: mass%] of the oxygen-containing synthetic oil (A2) on a basis of the total amount of the lubricating oil composition satisfies the following formula (1). α ≤ Y < -3.7ln(X) + β ···(1) [In formula (1) above, α = 0.5, β = 19, and X represents the ratio (C / O) of the number of carbon atoms to the number of oxygen atoms per molecule of the oxygen-containing synthetic oil (A2).]

[0014] The inventors of this invention conducted thorough research to solve the above problems. First, after investigating viscosity index improvers, it was found that using comb-shaped polymers as viscosity index improvers is effective in obtaining a lubricating oil composition with the above-mentioned characteristics. Furthermore, considering that evaporation can be easily suppressed even at low viscosity, synthetic oils were investigated, and it was found that using oxygenated synthetic oil as the synthetic oil can improve the viscosity index of the lubricating oil composition. Based on the above findings, the inventors conducted various studies on lubricating oil compositions in which mineral oil is blended with oxygen-containing synthetic oil and comb-shaped polymer. However, cases were observed in which the lubricating oil compositions became highly viscous at low temperatures, or even if the viscosity could be reduced at low temperatures, the viscosity-enhancing effect at high temperatures was insufficient. In order to investigate the cause of this problem, the inventors conducted further intensive research and discovered that the above problem could be solved by adjusting the content of oxygen-containing synthetic oil to a specific range, thus completing the present invention.

[0015] In the following explanation, "base oil (A)" and "viscosity index improver (B)" will also be referred to as "component (A)" and "component (B)," respectively. A lubricating oil composition according to one aspect of the present invention may consist only of component (A) and component (B), or it may contain other components other than components (A) and component (B). In a lubricating oil composition according to one embodiment of the present invention, the total content of component (A) and component (B) is preferably 70% by mass or more, more preferably 75% by mass or more, and even more preferably 80% by mass or more, based on the total amount of the lubricating oil composition. Furthermore, it is preferably 100% by mass or less, more preferably less than 100% by mass, and even more preferably 95% by mass or less. The upper and lower limits of these numerical ranges can be combined in any way. Specifically, they are preferably 70% to 100% by mass, more preferably 75% to less than 100% by mass, and even more preferably 80% to 95% by mass. The components contained in the lubricating oil composition of the present invention will be described in detail below.

[0016] [Base oil (A)] The base oil (A) includes mineral oil (A1) and oxygenated synthetic oil (A2). If the base oil (A) does not contain oxygenated synthetic oil (A2), the viscosity index of the lubricating oil composition cannot be sufficiently improved. In a lubricating oil composition according to one aspect of the present invention, the base oil (A) may consist only of mineral oil (A1) and oxygenated synthetic oil (A2), but may also contain other base oils other than mineral oil (A1) and oxygenated synthetic oil (A2) without departing from the spirit of the present invention. In a lubricating oil composition according to one aspect of the present invention, the total content of mineral oil (A1) and oxygenated synthetic oil (A2) is preferably 70% to 100% by mass, more preferably 80% to 100% by mass, even more preferably 90% to 100% by mass, even more preferably 95% to 100% by mass, and still more preferably 99% to 100% by mass, based on the total amount of base oil (A).

[0017] <Mineral oil (A1)> As for mineral oil (A1), any mineral oil commonly used as a lubricating oil base oil can be used without any particular restrictions. Specific examples of the mineral oil (A1) include atmospheric residue obtained by atmospheric distillation of crude oils such as paraffinic crude oil, intermediate-base crude oil, naphthenic crude oil, etc.; distillate oil obtained by vacuum distillation of these atmospheric residues; mineral oil obtained by subjecting the distillate oil to one or more treatments selected from solvent deasphalting, solvent extraction, hydrocracking, solvent dewaxing, catalytic dewaxing, and hydrorefining; wax isomerized mineral oil, and the like. The mineral oil (A1) may be used alone or in combination of two or more.

[0018] Here, as the mineral oil (A1), a mineral oil classified into Group II or III of the American Petroleum Institute (API) base oil category is preferable, and a mineral oil classified into Group III is more preferable.

[0019] (Various physical properties of the mineral oil (A1)) From the viewpoints of suppressing the evaporation amount of the lubricating oil composition and oil film retention, the kinematic viscosity of the mineral oil (A1) at 100 °C is preferably 2.0 mm 2 / s or more, more preferably 2.5 mm 2 / s or more, still more preferably 3.0 mm 2 / s or more. Also, from the viewpoint of easily reducing the viscosity of the lubricating oil composition in a low temperature range, it is preferably 5.0 mm 2 / s or less, more preferably 4.7 mm 2 / s or less, still more preferably 4.5 mm 2 / s or less. The upper and lower limit values of these numerical ranges can be arbitrarily combined. Specifically, it is preferably 2.0 mm 2 / s to 5.0 mm 2 / s, more preferably 2.5 mm 2 / s to 4.7 mm 2 / s, still more preferably 3.0 mm 2 / s to 4.5 mm 2 / s. From the viewpoints of suppressing the evaporation amount of the lubricating oil composition and oil film retention, the kinematic viscosity of the mineral oil (A1) at 40 °C is preferably 10.0 mm 2 / s or more, more preferably 13.0 mm2 / s or more, more preferably 15.0 mm 2 It is 25.0 mm² or more. Furthermore, from the viewpoint of making it easier to reduce the viscosity of the lubricating oil composition in the low-temperature range, it is preferably 25.0 mm². 2 / s or less, more preferably 20.0 mm 2 / s or less, more preferably 18.0 mm 2 It is less than or equal to / s. The upper and lower limits of these numerical ranges can be combined in any way. Specifically, 10.0 mm is preferred. 2 / s~25.0mm 2 / s, more preferably 13.0 mm 2 / s~20.0mm 2 / s, more preferably 15.0 mm 2 / s~18.0mm 2 It is / s. The viscosity index of the mineral oil (A1) is preferably 90 or higher, more preferably 100 or higher, and even more preferably 110 or higher. The Noack evaporation rate of mineral oil (A1) is preferably less than 40% by mass, more preferably 30% by mass or less, and even more preferably 20% by mass or less, from the viewpoint of easily suppressing the evaporation rate of the lubricating oil composition. It is also usually 10% by mass or more. Furthermore, if the mineral oil (A1) is a mixture of two or more types, it is sufficient that the kinematic viscosity, viscosity index, and Noack evaporation rate of the mixture fall within the above range.

[0020] (Mineral oil (A1) content) From the viewpoint of making it easier to exhibit the effects of the present invention, the content of mineral oil (A1) is preferably 60% by mass or more, more preferably 65% ​​by mass or more, and even more preferably 68% by mass or more. Also, it is preferably 90% by mass or less, more preferably 87% by mass or less, and even more preferably 85% by mass or less. The upper and lower limits of these numerical ranges can be combined in any way. Specifically, they are preferably 60% to 90% by mass, more preferably 65% ​​to 87% by mass, and even more preferably 68% to 85% by mass.

[0021] <Oxygenated synthetic oil (A2)> As for oxygen-containing synthetic oil (A2), any mineral oil commonly used as a lubricating oil base oil can be used without any particular restrictions. In this specification, "oxygen-containing" in "oxygen-containing synthetic oil" means that oxygen atoms are present in the molecules that make up the synthetic oil.

[0022] In a lubricating oil composition according to one embodiment of the present invention, the oxygen-containing synthetic oil (A2) is preferably one or more selected from the group consisting of ester oil, ether oil, and alcohol oil, more preferably one or more selected from the group consisting of ester oil and ether oil, and even more preferably ester oil.

[0023] (Ester oil) As for the ester oil, any ester oil commonly used as a lubricating oil base oil can be used without any particular restrictions. In a lubricating oil composition according to one embodiment of the present invention, the ester oil is preferably one or more selected from the group consisting of monoester oil, diester oil, and polyol ester oil, from the viewpoint of making it easier to exhibit the effects of the present invention, and more preferably one or more selected from the group consisting of monoester oil and diester oil.

[0024] • Monoester oil Examples of monoester oils include monoesters of monohydric alcohols and monobasic acids. The number of oxygen atoms per molecule of a monoester can be determined by considering the number of oxygen atoms contained in the monohydric alcohol and monobasic acid that make up the monoester, and the number of oxygen atoms that are reduced by the esterification reaction, and is usually 2.

[0025] From the viewpoint of making it easier to exhibit the effects of the present invention, the monohydric alcohol constituting the monoester is preferably a monohydric aliphatic alcohol having 1 to 24 carbon atoms, more preferably a monohydric aliphatic alcohol having 1 to 12 carbon atoms, and even more preferably a monohydric aliphatic alcohol having 1 to 10 carbon atoms. The monohydric aliphatic alcohol may be linear or branched, and may be saturated or unsaturated. Specific examples of monohydric alcohols that constitute monoesters include methanol, ethanol, propanol, butanol, pentanol, hexanol, heptanol, octanol, 2-ethylhexanol, 3,5-dimethylhexanol, nonanol, decanol, undecanol, dodecanol, tridecanol, tetradecanol, pentadecanol, hexadecanol, heptadecanol, octadecanol, nonadecanol, eicosanol, henico Examples include sanol, docosanol, tricosanol, and tetracosanol, as well as butenol, pentenol, hexenol, heptenol, octenol, nonenol, decenol, undecenol, dodecenol, tridecenol, tetradecenol, pentadecenol, hexadecenol, heptadecenol, octadecenol, nonadecenol, icosenol, henicocenol, docosenol, tricosenol, and tetracosenol.

[0026] From the viewpoint of making it easier to exhibit the effects of the present invention, the monobasic acid constituting the monoester is preferably an aliphatic monocarboxylic acid having 2 to 24 carbon atoms, more preferably an aliphatic monocarboxylic acid having 4 to 22 carbon atoms, and even more preferably an aliphatic monocarboxylic acid having 6 to 20 carbon atoms. The aliphatic monocarboxylic acid may be linear or branched, and may be saturated or unsaturated. Specific examples of monobasic acids that make up monoesters include acetic acid, propionic acid, butanoic acid, pentanoic acid, hexanoic acid, heptanoic acid, octanoic acid, nonanoic acid, decanoic acid, undecanoic acid, dodecanoic acid, tridecanoic acid, tetradecanoic acid, pentadecanoic acid, hexadecanoic acid (palmitic acid), heptadecanoic acid, octadecanoic acid, nonadecanoic acid, eicosanic acid, henicosanoic acid, docosanic acid, tricosanic acid, Examples include tetracosanoic acid, as well as acrylic acid, methacrylic acid, butenoic acid, pentenoic acid, hexenoic acid, heptenic acid, octenic acid, nonenic acid, decenoic acid, undecenoic acid, dodecenoic acid, tridecenoic acid, tetradecenoic acid, pentadecenoic acid, hexadecenoic acid, heptadecenoic acid, octadecenoic acid, nonadecenoic acid, eicosenoic acid, henicosenoic acid, docosenoic acid, tricosenoic acid, and tetracosenoic acid.

[0027] Monoesters may be used individually or in combination of two or more types.

[0028] Furthermore, from the viewpoint of making it easier to exhibit the effects of the present invention, the monoester has a ratio [C / O] of carbon atoms to oxygen atoms of preferably 2 to 24, more preferably 3 to 20, and even more preferably 4 to 15.

[0029] • Diester oil Examples of diester oils include diesters of monohydric alcohols and dibasic acids. The number of oxygen atoms per molecule of a diester can be determined by considering the number of oxygen atoms contained in the monohydric alcohol and dibasic acid that make up the diester, as well as the number of oxygen atoms reduced by the esterification reaction, and is usually four.

[0030] From the viewpoint of making it easier to exhibit the effects of the present invention, the monohydric alcohol constituting the diester is preferably a monohydric aliphatic alcohol having 1 to 24 carbon atoms, more preferably a monohydric aliphatic alcohol having 1 to 12 carbon atoms, and even more preferably a monohydric aliphatic alcohol having 1 to 10 carbon atoms. The monohydric aliphatic alcohol may be linear or branched, and may be saturated or unsaturated. Specific examples of monohydric alcohols that constitute diesters include the same alcohols listed as specific examples of monohydric alcohols that constitute monoesters.

[0031] From the viewpoint of making it easier to exhibit the effects of the present invention, the dibasic acid constituting the diester is preferably an aliphatic dicarboxylic acid having 2 to 24 carbon atoms, more preferably an aliphatic dicarboxylic acid having 4 to 16 carbon atoms, and even more preferably an aliphatic dicarboxylic acid having 6 to 12 carbon atoms. The aliphatic dicarboxylic acid may be linear or branched, and may be saturated or unsaturated. Specific examples of dibasic acids that make up diesters include ethanedioic acid, propanedioic acid, butanedioic acid, pentanedioic acid, hexanedioic acid, heptanedioic acid, octanodioic acid, nonanedioic acid, decanedioic acid, undecanedioic acid, dodecanedioic acid, tridecanedioic acid, tetradecanedioic acid, pentadecanedioic acid, hexadecanedioic acid, heptadecanedioic acid, octadecanedioic acid, nonadecanedioic acid, eicosanedioic acid, henicosandioic acid, docosanedioic acid, and tricosanedioic acid. Acids, and tetracosendioic acid, as well as butenioic acid, pentenioic acid, hexenioic acid, heptenioic acid, octenioic acid, nonenioic acid, decenoic acid, undecenoic acid, dodecenoic acid, tridecenoic acid, tetradecenoic acid, pentadecenoic acid, hexadecenioic acid, heptadecenoic acid, octadecenoic acid, nonadecenioic acid, eicosendioic acid, henicosendioic acid, docosendioic acid, tricosendioic acid, and tetracosendioic acid, etc.

[0032] Diesters may be used individually or in combination of two or more types.

[0033] Furthermore, from the viewpoint of making it easier to exhibit the effects of the present invention, the ratio of the number of carbon atoms to the number of oxygen atoms [C / O] of the diester is preferably 1 to 18, more preferably 2 to 14, and even more preferably 3 to 10.

[0034] • Polyol ester oil Polyol ester oil is an ester which is a condensate of a polyol and a fatty acid. The number of oxygen atoms per molecule of polyol ester can be determined by considering the number of oxygen atoms contained in the polyol and fatty acid that make up the polyol ester and the number of oxygen atoms that are reduced by the esterification reaction, and is usually 4 to 12, and from the viewpoint of making it easier to exhibit the effects of the present invention, it is preferably 4 to 10, more preferably 4 to 8, and even more preferably 6.

[0035] From the viewpoint of making the effects of the present invention easier to achieve, the number of hydroxyl groups in the polyol constituting the polyol ester is preferably 2 to 6, more preferably 2 to 5, and even more preferably 2 to 4. Furthermore, from the viewpoint of making it easier to exhibit the effects of the present invention, the number of carbon atoms in the polyol is preferably 2 to 20, more preferably 2 to 15, and even more preferably 2 to 10.

[0036] Specific examples of polyols that make up polyol esters include ethylene glycol, 1,3-propanediol, propylene glycol, 1,4-butanediol, 1,2-butanediol, 2-methyl-1,3-propanediol, 1,5-pentanediol, neopentyl glycol, 1,6-hexanediol, 2-ethyl-2-methyl-1,3-propanediol, 1,7-heptanediol, 2-methyl-2-propyl-1,3-propanediol, 2,2-diethyl-1,3-propanediol, 1,8-octanediol, 1,9-nonanediol, 1, Examples include diols such as 10-decanediol, 1,11-undecanediol, and 1,12-dodecanediol; polyhydric alcohols such as trimethylolethane, trimethylolpropane, trimethylolbutane, ditrimethylolpropane, pentaerythritol, glycerin, glycerin dimer, 1,3,5-pentanetriol, sorbitol, sorbitan, adonitol, arabitol, xylitol, and mannitol; and sugars such as xylose, arabinose, ribose, rhamnose, glucose, fructose, galactose, mannose, and sorbose. Among these, neopentyl glycol, trimethylolethane, trimethylolpropane, trimethylolbutane, and pentaerythritol are preferred, trimethylolethane, trimethylolpropane, and trimethylolbutane are more preferred, and trimethylolpropane is even more preferred.

[0037] From the viewpoint of making it easier to exhibit the effects of the present invention, the fatty acids constituting the polyol ester are preferably aliphatic monocarboxylic acids having 2 to 14 carbon atoms, more preferably aliphatic monocarboxylic acids having 2 to 10 carbon atoms, and even more preferably aliphatic monocarboxylic acids having 2 to 8 carbon atoms. The aliphatic monocarboxylic acid may be linear or branched, and may be saturated or unsaturated.

[0038] Specific examples of fatty acids that constitute polyol esters include acetic acid, propionic acid, butanoic acid, pentanoic acid, hexanoic acid, heptanoic acid, octanoic acid, nonanoic acid, decanoic acid, undecanoic acid, dodecanoic acid, tridecanoic acid, and tetradecanoic acid, as well as acrylic acid, methacrylic acid, butenoic acid, pentenoic acid, hexenoic acid, heptenoic acid, octenic acid, nonenic acid, decenoic acid, undecenoic acid, dodecenoic acid, tridecenoic acid, and tetradecenoic acid.

[0039] Polyol esters may be used individually or in combination of two or more types.

[0040] Furthermore, from the viewpoint of making it easier to exhibit the effects of the present invention, the ratio of the number of carbon atoms to the number of oxygen atoms [C / O] of the diester is preferably 1 to 10, more preferably 2 to 8, and even more preferably 2 to 6.

[0041] (Ether oil) As for the ether oil, any ether oil commonly used as a lubricating oil base oil can be used without any particular restrictions. In a lubricating oil composition according to one aspect of the present invention, the ether oil is preferably a polyoxyalkylene glycol represented by the following general formula (I), from the viewpoint of making it easier to exhibit the effects of the present invention. R a1 O-(R a2 O) n -R a3 (I) In the above general formula (I), R a2 This represents an alkylene group with 2 to 6 carbon atoms. R a1 and R a3 Each of these independently represents a hydrogen atom, a C1-C10 alkyl group, a C1-C11 acyl group, or a C5-C18 saturated or unsaturated alicyclic hydrocarbon group or aromatic hydrocarbon group, which may have substituents. n is an integer greater than or equal to 2, preferably 6 to 30, more preferably 10 to 25, and even more preferably 15 to 25. The value of n is adjusted as appropriate according to the kinematic viscosity required for the ether oil. Furthermore, the number of oxygen atoms per molecule of polyoxyalkylene glycols can be determined by considering the number of oxygen atoms in the terminal alkoxy groups and polyoxyalkylene groups constituting the polyoxyalkylene glycols, and is usually n+1. (R a2 O) When there are multiple units, i.e., n≧2, each (R a2 O) The units may be the same or different from each other. (R a2 O) When the units are different, either random or block type is acceptable, but random type is preferred from the viewpoint of ease of handling. In this specification, among the compounds of general formula (I) described above, those with hydrogen atoms at both ends are referred to as polyoxyalkylene glycols, and those with at least one other end not containing hydrogen atoms are referred to as polyoxyalkylene glycol derivatives. Furthermore, "polyoxyalkylene glycols" is a concept that encompasses both polyoxyalkylene glycols and polyoxyalkylene glycol derivatives.

[0042] R a1 and R a3Examples of C1-C10 alkyl groups that can be selected include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, sec-butyl group, tert-butyl group, hexyl group, 2-ethylhexyl group, heptyl group, octyl group, nonyl group, and decyl group. R a1 and R a3 Examples of acyl groups having 1 to 11 carbon atoms that can be selected include those having an alkyl group having 1 to 10 carbon atoms and a carbonyl group. R a1 and R a3 Examples of saturated alicyclic hydrocarbon groups having 5 to 18 carbon atoms that can be selected include cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, cyclononyl, and cyclodecyl groups. R a1 and R a3 Examples of unsaturated alicyclic hydrocarbon groups having 5 to 18 carbon atoms that can be selected include cyclopentenyl and cyclohexenyl groups. R a1 and R a3 Examples of aromatic hydrocarbon groups having 5 to 18 carbon atoms that can be selected include aryl groups such as phenyl and naphthyl groups. Examples of substituents include C1-C6 alkyl groups, C1-C6 alkoxy groups, and C6-C 14 Examples include aryl groups.

[0043] Here, as polyoxyalkylene glycols, from the viewpoint of making it easier to exhibit the effects of the present invention, (R) of the above general formula (I) is used. a2 O) The unit is composed of one or more alkylene oxides selected from the group consisting of ethylene oxide, propylene oxide, and butylene oxide, R a1 and R a3 A polyoxyalkylene glycol derivative in which is an alkyl group having 1 to 10 carbon atoms is preferred. Also, from a similar viewpoint, (R of the above general formula (I) a2The O) unit is preferably ethylene oxide or propylene oxide, and more preferably ethylene oxide.

[0044] Polyoxyalkylene glycols may be used individually or in combination of two or more types.

[0045] Furthermore, from the viewpoint of making it easier to exhibit the effects of the present invention, the ratio of the number of carbon atoms to the number of oxygen atoms [C / O] of the polyoxyalkylene glycols is preferably 2 to 7, more preferably 2 to 5, and even more preferably 2 to 4.

[0046] (Alcohol oil) As for the alcohol oil, any alcohol oil commonly used as a lubricating oil base oil can be used without particular limitations. However, from the viewpoint of making it easier to exhibit the effects of the present invention, preferably a monohydric aliphatic alcohol having 10 to 24 carbon atoms is preferred, more preferably a monohydric aliphatic alcohol having 12 to 20 carbon atoms, and even more preferably a monohydric aliphatic alcohol having 14 to 20 carbon atoms. The monohydric aliphatic alcohol may be linear or branched, and may be saturated or unsaturated. Specific examples of monohydric alcohols that constitute monoesters include decanol, undecanol, dodecanol, tridecanol, tetradecanol, pentadecanol, hexadecanol, heptadecanol, octadecanol, isooctadecanol, nonadecanol, eicosanol, henicosanol, docosanol, tricosanol, and tetracosanol, as well as butenol, pentenol, hexenol, heptenol, octenol, nonenol, decenol, undecenol, dodecenol, tridecenol, tetradecenol, pentadecenol, hexadecenol, heptadecenol, octadecenol, nonadecenol, eicosenol, henicosenol, docosenol, tricosenol, and tetracosenol.

[0047] Alcohol may be used alone or in combination of two or more types.

[0048] Furthermore, from the viewpoint of making it easier to exhibit the effects of the present invention, the alcohol has a carbon atom to oxygen atom ratio [C / O] of preferably 1 to 40, more preferably 10 to 30, and even more preferably 15 to 25.

[0049] (Various physical properties of oxygenated synthetic oil (A2)) The kinematic viscosity of oxygen-containing synthetic oil (A2) at 100°C is preferably 1.5 mm, from the viewpoint of suppressing evaporation of the lubricating oil composition and maintaining oil film. 2 / s or more, more preferably 2.0 mm 2 / s or more, more preferably 2.5 mm 2 / s or more, more preferably 3.0 mm 2 It is 1 / s or more. Furthermore, from the viewpoint of making it easier to reduce the viscosity of the lubricating oil composition in the low-temperature range, it is preferably 5.0 mm. 2 / s or less, more preferably 4.5 mm 2 / s or less, more preferably 4.3 mm 2 It is less than or equal to / s. The upper and lower limits of these numerical ranges can be combined in any way. Specifically, 1.5 mm is preferred. 2 / s~5.0mm 2 / s, more preferably 2.0mm 2 / s~5.0mm 2 / s, more preferably 2.5 mm 2 / s~4.5mm 2 / s, more preferably 3.0 mm 2 / s~4.3mm 2 It is / s. The kinematic viscosity of oxygen-containing synthetic oil (A2) at 40°C is preferably 3.0 mm, from the viewpoint of suppressing evaporation of the lubricating oil composition and maintaining oil film. 2 / s or more, more preferably 4.0 mm 2 / s or more, more preferably 5.0 mm 2 It is 25.0 mm² or more. Furthermore, from the viewpoint of making it easier to reduce the viscosity of the lubricating oil composition in the low-temperature range, it is preferably 25.0 mm². 2 / s or less, more preferably 22.0 mm 2 / s or less, more preferably 20.0 mm 2 It is less than or equal to / s. The upper and lower limits of these numerical ranges can be combined in any way. Specifically, 3.0 mm is preferred. 2 / s~25.0mm 2 / s, more preferably 4.0 mm 2 / s~22.0mm 2 / s, more preferably 5.0 mm 2 / s~20.0mm 2 It is / s. The viscosity index of the oxygen-containing synthetic oil (A2) is preferably 100 or higher, more preferably 110 or higher, and even more preferably 120 or higher. The Noack evaporation rate of the oxygen-containing synthetic oil (A2) is preferably less than 40% by mass, more preferably 37% by mass or less, and even more preferably 35% by mass or less, from the viewpoint of easily suppressing the evaporation rate of the lubricating oil composition. It is also usually 1% by mass or more. Furthermore, if the oxygenated synthetic oil (A2) is a mixture of two or more types, it is sufficient that the kinematic viscosity and viscosity index of the mixture fall within the above range.

[0050] (Content of oxygenated synthetic oil (A2)) In the lubricating oil additive of the present invention, the content of oxygen-containing synthetic oil (A2) is adjusted to a specific range. Specifically, the content Y [unit: mass%] of oxygen-containing synthetic oil (A2) on a total basis of the lubricating oil composition is adjusted to satisfy the following formula (1). α ≤ Y < -3.7ln(X) + β···(1) [In formula (1) above, α = 0.5, β = 19, and X represents the ratio (C / O) of the number of carbon atoms to the number of oxygen atoms per molecule of the oxygen-containing synthetic oil (A2).] Note that ln(X) represents the natural logarithm of X. If Y < α, the viscosity index of the lubricating oil composition cannot be sufficiently improved. Furthermore, if Y ≥ -3.7ln(X) + β, the viscosity-enhancing effect of the comb-shaped polymer (B1) blended as a viscosity index improver (B) on the lubricating oil composition in the low-temperature range increases, making it impossible to reduce the viscosity of the lubricating oil composition in the low-temperature range. Here, from the viewpoint of making it easier to improve the viscosity index of the lubricating oil composition, the value of α is preferably 1.0, more preferably 2.0, even more preferably 3.0, even more preferably 4.0, and still most preferably 4.5. Furthermore, from the viewpoint of making it easier to reduce the viscosity of the lubricating oil composition at low temperatures, the value of β is preferably 18.5, more preferably 18, even more preferably 17.2, and particularly preferably 16.2.

[0051] Here, if the oxygen-containing synthetic oil (A2) is a monoester, the content of the oxygen-containing synthetic oil (A2) is preferably 0.5% by mass or more, more preferably 1.0% by mass or more, even more preferably 2.0% by mass or more, even more preferably 3.0% by mass or more, even more preferably 4.0% by mass or more, and even more preferably 4.5% by mass or more, based on the total amount of the lubricating oil composition. Also, it is preferably less than 15% by mass, more preferably 14% by mass or less, even more preferably 13% by mass or less, even more preferably 12% by mass or less, and even more preferably 11% by mass or less. The upper and lower limits of these numerical ranges can be combined in any way. Specifically, preferably 0.5% by mass or more and less than 15% by mass, more preferably 1.0% by mass to 14% by mass, even more preferably 2.0% by mass to 13% by mass, even more preferably 3.0% by mass to 12% by mass, still more preferably 4.0% by mass to 11% by mass, and even more preferably 4.5% by mass to 11% by mass.

[0052] Furthermore, when the oxygen-containing synthetic oil (A2) is a diester, the content of the oxygen-containing synthetic oil (A2) is preferably 0.5% by mass or more, more preferably 1.0% by mass or more, even more preferably 2.0% by mass or more, even more preferably 3.0% by mass or more, even more preferably 4.0% by mass or more, and even more preferably 4.5% by mass or more, based on the total amount of the lubricating oil composition. Also, it is preferably less than 15% by mass, more preferably 14% by mass or less, even more preferably 13% by mass or less, even more preferably 12% by mass or less, and even more preferably 11% by mass or less. The upper and lower limits of these numerical ranges can be combined in any way. Specifically, preferably 0.5% by mass or more and less than 15% by mass, more preferably 1.0% by mass to 14% by mass, even more preferably 2.0% by mass to 13% by mass, even more preferably 3.0% by mass to 12% by mass, still more preferably 4.0% by mass to 11% by mass, and even more preferably 4.5% by mass to 11% by mass.

[0053] Furthermore, when the oxygen-containing synthetic oil (A2) is a polyol ester, the content of the oxygen-containing synthetic oil (A2) is preferably 0.5% by mass or more, more preferably 1.0% by mass or more, even more preferably 2.0% by mass or more, even more preferably 3.0% by mass or more, even more preferably 4.0% by mass or more, and even more preferably 4.5% by mass or more, based on the total amount of the lubricating oil composition. Also, it is preferably less than 15% by mass, more preferably 14% by mass or less, even more preferably 13% by mass or less, even more preferably 12% by mass or less, and even more preferably 11% by mass or less. The upper and lower limits of these numerical ranges can be combined in any way. Specifically, preferably 0.5% by mass or more and less than 15% by mass, more preferably 1.0% by mass to 14% by mass, even more preferably 2.0% by mass to 13% by mass, even more preferably 3.0% by mass to 12% by mass, still more preferably 4.0% by mass to 11% by mass, and even more preferably 4.5% by mass to 11% by mass.

[0054] Furthermore, if the oxygenated synthetic oil (A2) is ether oil, the content of the oxygenated synthetic oil (A2) is preferably 0.5% by mass or more, more preferably 1.0% by mass or more, even more preferably 2.0% by mass or more, even more preferably 3.0% by mass or more, even more preferably 4.0% by mass or more, and even more preferably 4.5% by mass or more, based on the total amount of the lubricating oil composition. Also, it is preferably less than 15% by mass, more preferably 14% by mass or less, even more preferably 13% by mass or less, even more preferably 12% by mass or less, and even more preferably 11% by mass or less. The upper and lower limits of these numerical ranges can be combined in any way. Specifically, preferably 0.5% by mass or more and less than 15% by mass, more preferably 1.0% by mass to 14% by mass, even more preferably 2.0% by mass to 13% by mass, even more preferably 3.0% by mass to 12% by mass, still more preferably 4.0% by mass to 11% by mass, and even more preferably 4.5% by mass to 11% by mass.

[0055] Furthermore, when the oxygenated synthetic oil (A2) is an alcohol oil, the content of the oxygenated synthetic oil (A2) is preferably 0.5% by mass or more, more preferably 1.0% by mass or more, even more preferably 2.0% by mass or more, even more preferably 3.0% by mass or more, even more preferably 4.0% by mass or more, and even more preferably 4.5% by mass or more, based on the total amount of the lubricating oil composition. Also, it is preferably less than 15% by mass, more preferably 14% by mass or less, even more preferably 13% by mass or less, even more preferably 12% by mass or less, and even more preferably 11% by mass or less. The upper and lower limits of these numerical ranges can be combined in any way. Specifically, preferably 0.5% by mass or more and less than 15% by mass, more preferably 1.0% by mass to 14% by mass, even more preferably 2.0% by mass to 13% by mass, even more preferably 3.0% by mass to 12% by mass, still more preferably 4.0% by mass to 11% by mass, and even more preferably 4.5% by mass to 11% by mass.

[0056] <Content ratio of mineral oil (A1) and oxygenated synthetic oil (A2)> In a lubricating oil composition according to one embodiment of the present invention, the content ratio of mineral oil (A1) to oxygen-containing synthetic oil (A2) [(A1) / (A2)] is preferably 3.0 to 20.0, more preferably 4.0 to 20.0, even more preferably 5.0 to 18.0, and even more preferably 6.0 to 17.0 by mass, from the viewpoint of making it easier to exhibit the effects of the present invention.

[0057] <Base oils other than mineral oil (A1) and oxygenated synthetic oil (A2)> A lubricating oil composition according to one aspect of the present invention may contain base oils other than mineral oil (A1) and oxygen-containing synthetic oil (A2), to the extent that the effects of the present invention are not significantly impaired. Examples of such base oils include non-oxygen-containing synthetic oils (A2') such as poly-α-olefins. In this specification, "oxygen-free" in "oxygen-free synthetic oil" means that there are no oxygen atoms present in the molecules that make up the synthetic oil. In this context, in a lubricating oil composition according to one embodiment of the present invention, it is preferable that the content of non-oxygenated synthetic oil (A2') is low, from the viewpoint of easily improving the viscosity index of the lubricating oil composition. Specifically, the content of non-oxygenated synthetic oil (A2') is preferably 10 parts by mass or less, more preferably 5.0 parts by mass or less, even more preferably 1.0 part by mass or less, and even more preferably 0.1 parts by mass or less, per 100 parts by mass of oxygenated synthetic oil (A2).

[0058] [Viscosity index improver (B)] The lubricating oil composition of the present invention contains a viscosity index improver (B). The viscosity index improver (B) contains a comb-shaped polymer (B1). Furthermore, the content ratio of oxygen-containing synthetic oil (A2) to comb-shaped polymer (B1) [(A2) / (B1)] is preferably 10.0 or less by mass. Note that the content of comb-type polymer (B1) used to calculate [(A2) / (B1)] refers to the content of comb-type polymer (B) in terms of resin content. If [(A2) / (B1)] is 10.0 or less, the lubricating oil composition is more likely to have low viscosity at low temperatures. Here, the content ratio [(A2) / (B1)] of the oxygen-containing synthetic oil (A2) to the comb-shaped polymer (B1) is preferably 9.0 or less, more preferably 8.5 or less, even more preferably 8.0 or less, even more preferably 7.5 or less, even more preferably 7.0 or less, even more preferably 6.0 or less, and even more preferably 5.0 or less, from the viewpoint of making the lubricating oil composition more viscous in the low-temperature range. It is also preferably 1.0 or more.

[0059] In a lubricating oil composition according to one aspect of the present invention, the viscosity index improver (B) may consist solely of a comb-shaped polymer (B1), but may also contain other viscosity index improvers other than the comb-shaped polymer (B1) without departing from the spirit of the present invention. In a lubricating oil composition according to one aspect of the present invention, the resin content of the comb-shaped polymer (B1) is preferably 70% to 100% by mass, more preferably 80% to 100% by mass, even more preferably 90% to 100% by mass, even more preferably 95% to 100% by mass, and still more preferably 99% to 100% by mass, based on the total amount of resin content of the viscosity index improver (B).

[0060] However, in a lubricating oil composition according to one embodiment of the present invention, the content of one or more polymethacrylates (B2) selected from the group consisting of non-dispersible polymethacrylates and dispersed polymethacrylates is preferably small, from the viewpoint of suppressing the thickening effect of the viscosity index improver and making it easier to exhibit the effects of the present invention. Specifically, the resin content of polymethacrylate (B2) is preferably 10 parts by mass or less, more preferably 5.0 parts by mass or less, even more preferably 1.0 part by mass or less, and even more preferably 0.1 parts by mass or less, per 100 parts by mass of the resin content of the comb-shaped polymer (B1).

[0061] <Comb-shaped polymer (B1)> The following provides a detailed explanation of the comb-shaped polymer (B1). In this invention, "comb-shaped polymer (B1)" refers to a polymer having a structure in which the main chain has many tridental branching points from which high molecular weight side chains protrude. The mass-average molecular weight (Mw) of the comb-shaped polymer (B1) is preferably 100,000 to 1,000,000, more preferably 150,000 to 800,000, and even more preferably 200,000 to 700,000, from the viewpoint of improving fuel efficiency.

[0062] The molecular weight distribution (Mw / Mn) of the comb-shaped polymer (B1) (where Mw is the mass-average molecular weight of the comb-shaped polymer (B1) and Mn is the number-average molecular weight of the comb-shaped polymer (B1)) is preferably 8.00 or less, more preferably 7.00 or less, more preferably 6.50 or less, even more preferably 6.00 or less, even more preferably 5.00 or less, and even more preferably 3.00 or less, from the viewpoint of improving the fuel efficiency of the lubricating oil composition. Furthermore, the smaller the molecular weight distribution of the comb-shaped polymer (B1), the more the fuel efficiency of the lubricating oil composition containing the comb-shaped polymer (B1) together with the base oil (A) tends to improve. Furthermore, while there are no particular lower limits on the molecular weight distribution of the comb-shaped polymer (B1), it is usually 1.01 or higher, preferably 1.05 or higher, and more preferably 1.10 or higher.

[0063] In a lubricating oil composition according to one aspect of the present invention, the resin content of the comb-shaped polymer (B1) is not particularly limited as long as it satisfies the specified content ratio of oxygen-containing synthetic oil (A2) to comb-shaped polymer (B1) [(A2) / (B1)]. However, from the viewpoint of making it easier to exhibit the effects of the present invention, it is preferably 0.5% to 5.0% by mass, more preferably 0.8% to 4.0% by mass, and even more preferably 1.0% to 3.5% by mass, on a total basis of the lubricating oil composition.

[0064] The PSSI (Permanent Shear Stability Index) of the comb-shaped polymer (B1) is preferably 12.0 or less, more preferably 10.0 or less, even more preferably 5.0 or less, even more preferably 3.0 or less, and particularly preferably 1.0 or less. Furthermore, while there is no particular lower limit for the PSSI of the comb-shaped polymer (B1), it is usually 0.1 or higher, preferably 0.2 or higher.

[0065] In this specification, the PSSI (Permanent Shear Stability Index) of a viscosity index improver represents the percentage of viscosity reduction due to shear originating from the resin component in the viscosity index improver, and is a value calculated in accordance with ASTM D6022-06. More specifically, it is a value calculated using the following formula.

number

[0066] In the above calculation formula, Kv0 is the kinematic viscosity at 100°C of the sample oil, which is prepared by diluting a viscosity index improver containing resin in mineral oil, and Kv1 is the kinematic viscosity at 100°C after passing the sample oil, which is prepared by diluting the viscosity index improver containing resin in mineral oil, through a 30-cycle high-shear diesel injector according to the procedure of ASTM D6278. oil This is the kinematic viscosity at 100°C of the mineral oil used to dilute the viscosity index improver.

[0067] The PSSI value of comb-type polymer (B1) varies depending on its structure. Specifically, it tends to follow the trends shown below, and by considering these factors, the PSSI value of comb-type polymer (B1) can be easily adjusted. Note that the following factors are merely examples, and adjustments can also be made by considering other factors. Comb polymers in which the side chains of the comb-shaped polymer (B1) are composed of macromonomers (x1), and the content of constituent units (X1) derived from the macromonomers (x1) is 0.5 mol% or more based on the total amount of constituent units, tend to have a low PSSI value. The larger the molecular weight of the macromonomer (x1) constituting the side chain of the comb-shaped polymer (B1), the lower the PSSI value tends to be.

[0068] <Constituent units of comb-shaped polymer (B1)> The following describes the constituent units of the comb-shaped polymer (B1) used in one embodiment of the present invention. As the comb-shaped polymer (B1), a polymer having at least one constituent unit (X1) derived from a macromonomer (x1) is preferred. This constituent unit (X1) corresponds to the "high molecular weight side chain" mentioned above. In this invention, the term "macromonomer" 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.

[0069] Comb-shaped polymers (B1) with a relatively long main chain compared to the side chains exhibit lower shear stability. This property is thought to contribute to improved fuel efficiency even at low temperatures around 40°C.

[0070] In the comb-shaped polymer (B1) used in one aspect of the present invention, from the above viewpoint, the content of the constituent unit (X1) is preferably 0.1 mol% or more, more preferably 0.3 mol% or more, and even more preferably 0.5 mol% or more, based on the total amount of constituent units of the comb-shaped polymer (B1). Furthermore, it is preferably 20 mol% or less, more preferably 17 mol% or less, and even more preferably 15 mol% or less. The upper and lower limits of these numerical ranges can be combined in any way. Specifically, they are preferably 0.1 mol% to 20 mol%, more preferably 0.3 mol% to 17 mol%, and even more preferably 0.5 mol% to 15 mol%. In this specification, the content of each constituent unit in the comb-shaped polymer (B1) is as follows: 13 This refers to the value calculated by analyzing the 1C-NMR quantitative spectrum.

[0071] From the above viewpoint, the number-average molecular weight (Mn) of the macromonomer (x1) is preferably 300 or more, more preferably 500 or more, even more preferably 1,000 or more, even more preferably 2,000 or more, particularly preferably 4,000 or more, and also preferably 100,000 or less, more preferably 50,000 or less, even more preferably 20,000 or less, and even more preferably 10,000 or less.

[0072] Examples of polymerizable functional groups of the macromonomer (x1) include acryloyl group (CH2=CH-COO-), methacryloyl group (CH2=CCH3-COO-), ethenyl group (CH2=CH-), vinyl ether group (CH2=CH-O-), allyl group (CH2=CH-CH2-), allyl ether group (CH2=CH-CH2-O-), groups represented by CH2=CH-CONH-, and groups represented by CH2=CCH3-CONH-. Among these, acryloyl group (CH2=CH-COO-) or methacryloyl group (CH2=CCH3-COO-) is preferred, and methacryloyl group (CH2=CCH3-COO-) is more preferred.

[0073] In addition to the polymerizable functional group described above, the macromonomer (x1) may have one or more repeating units represented by the following general formulas (i) to (iii). [ka]

[0074] In the above general formula (i), R b1 This refers to a linear or branched alkylene group having 1 to 10 carbon atoms, specifically including methylene, ethylene, 1,2-propylene, 1,3-propylene, 1,2-butylene, 1,3-butylene, 1,4-butylene, pentylene, hexylene, heptylene, octylene, nonylene, desilene, and 2-ethylhexylene groups. In the above general formula (ii), R b2 This refers to a linear or branched alkylene group having 2 to 4 carbon atoms, specifically including ethylene, 1,2-propylene, 1,3-propylene, 1,2-butylene, 1,3-butylene, and 1,4-butylene groups. In the above general formula (iii), R b3 This represents a hydrogen atom or a methyl group. Also, R b4represents a linear or branched alkyl group having 1 to 10 carbon atoms, specifically, methyl group, ethyl group, n-propyl group, n-butyl group, n-pentyl group, n-hexyl group, n-heptyl group, n-octyl group, n-nonyl group, n-decyl group, isopropyl group, isobutyl group, sec-butyl group, t-butyl group, isopentyl group, t-pentyl group, isohexyl group, t-hexyl group, isoheptyl group, t-heptyl group, 2-ethylhexyl group, isooctyl group, isononyl group, and isodecyl group, etc. When there are a plurality of repeating units represented by the above general formulas (i) to (iii), respectively, R b1 , R b2 , R b3 , and R b4 may be the same as each other or different from each other.

[0075] In one aspect of the present invention, the macromonomer (x1) is preferably a polymer having a repeating unit represented by the general formula (i), and more preferably a polymer having a repeating unit (X1-1) in which R b1 in the general formula (i) is a 1,2-butylene group and / or a 1,4-butylene group.

[0076] The content of the repeating unit (X1-1) is preferably 1 to 100 mol%, more preferably 20 to 95 mol%, still more preferably 40 to 90 mol%, and even more preferably 50 to 80 mol% based on the total amount (100 mol%) of the constituent units of the macromonomer (x1).

[0077] When the macromonomer (x1) is a copolymer having two or more repeating units selected from the above general formulas (i) to (iii), the copolymerization form may be a block copolymer or a random copolymer.

[0078] 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). The comb-shaped polymer (B1) used in one aspect of the present invention may be a copolymer containing constituent units (X2) derived from other monomers (x2) other than macromonomers (x1) along with constituent units derived from macromonomers (x1). Here, from the viewpoint of making the lubricating oil composition easier to lower viscosity at low temperatures and easier to increase viscosity at high temperatures, it is preferable that the comb-shaped polymer (B1) is a copolymer that includes structural units derived from macromonomers (x1) as well as structural units (X2) derived from other monomers (x2) other than macromonomers (x1). A specific structure of such a comb-shaped polymer (B1) is preferably a copolymer having a main chain containing a structural unit (X2) derived from a monomer (x2), and side chains containing a structural unit (X1) derived from a macromonomer (x1). More preferably, the copolymer is one in which a structural unit (X1) derived from a macromonomer (x1) is also included as part of the main chain, in addition to the structural unit (X2) derived from a monomer (x2).

[0079] Examples of monomers (x2) include monomers represented by the following general formula (a1) (x2-a), alkyl (meth)acrylates (x2-b), nitrogen atom-containing vinyl monomers (x2-c), hydroxyl group-containing vinyl monomers (x2-d), phosphorus atom-containing monomers (x2-e), aliphatic hydrocarbon vinyl monomers (x2-f), alicyclic hydrocarbon vinyl monomers (x2-g), vinyl esters (x2-h), vinyl ethers (x2-i), vinyl ketones (x2-j), epoxy group-containing vinyl monomers (x2-k), halogen element-containing vinyl monomers (x2-l), esters of unsaturated polycarboxylic acids (x2-m), (di)alkyl fumarates (x2-n), (di)alkyl maleates (x2-o), and aromatic hydrocarbon vinyl monomers (x2-p).

[0080] Furthermore, as monomer (x2), monomers other than nitrogen atom-containing vinyl monomer (x2-c), phosphorus atom-containing monomer (x2-e), and aromatic hydrocarbon vinyl monomer (x2-p) are preferred. Furthermore, the monomer (x2) preferably contains one or more selected from monomers represented by the following general formula (a1) (x2-a), alkyl (meth)acrylate (x2-b), and hydroxyl group-containing vinyl monomer (x2-d), and more preferably contains at least hydroxyl group-containing vinyl monomer (x2-d). The monomer (x2) of the present invention preferably contains an alkyl (meth)acrylate (x2-b). Furthermore, from the viewpoint of making it easier to improve the effects of the present invention, it is preferable that the monomer represented by the following general formula (a1) (x2-a) and the hydroxyl group-containing vinyl monomer (x2-d) are present in small quantities. The content of constituent units derived from the monomer (x2-a) represented by the following general formula (a1) and the hydroxyl group-containing vinyl monomer (x2-d) is preferably 12 mol% or less, more preferably 10 mol% or less, even more preferably 5 mol% or less, even more preferably less than 1.0 mol%, even more preferably less than 0.5 mol%, even more preferably less than 0.1 mol%, even more preferably less than 0.01 mol%, and particularly preferably 0 mol%, based on the total amount of constituent units of the comb-shaped polymer (100 mol%).

[0081] (The monomer (x2-a) represented by the general formula (a1) below) [ka]

[0082] In the above general formula (a1), R b11 This represents a hydrogen atom or a methyl group. R b12 This represents a single bond, a linear or branched alkylene group having 1 to 10 carbon atoms, -O-, or -NH-. R b13 R represents a linear or branched alkylene group having 2 to 4 carbon atoms. n represents an integer of 1 or more (preferably an integer from 1 to 20, more preferably an integer from 1 to 5). If n is an integer of 2 or more, multiple R groups are used.b13 may be the same or different, and furthermore, the (R b13 O) n portion may be randomly bonded or block-bonded. R b14 represents a linear or branched alkyl group having 1 to 60 carbon atoms (preferably 10 to 50, more preferably 20 to 40). Specific examples of the above-mentioned "linear or branched alkylene group having 1 to 10 carbon atoms", "linear or branched alkylene group having 2 to 4 carbon atoms", and "linear or branched alkyl group having 1 to 60 carbon atoms" include the same groups as those exemplified in the descriptions regarding the general formulas (i) to (iii) above.

[0083] (alkyl (meth)acrylate (x2-b)) Examples of alkyl (meth)acrylate (x2-b) include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, t-butyl (meth)acrylate, pentyl (meth)acrylate, hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, heptyl (meth)acrylate, 2-t-butylheptyl (meth)acrylate, octyl (meth)acrylate, and 3-isopropylheptyl (meth)acrylate, etc. <x

[0084] The number of carbon atoms of the alkyl group in alkyl (meth)acrylate (x2-b) is preferably 4 to 30, more preferably 4 to 24, and still more preferably 4 to 18. Note that the alkyl group may be a linear alkyl group or a branched alkyl group.

[0085] The content ratio [(α) / (β)] of constituent units (α) derived from butyl (meth)acrylate and constituent units (β) derived from alkyl (meth)acrylate having an alkyl group with 12 to 20 carbon atoms is preferably 5.00 or more, more preferably 7.00 or more, even more preferably 8.50 or more, and even more preferably 10.00 or more, and also preferably 20 or less, and more preferably 15 or less, in molar ratio.

[0086] The content of the constituent unit (α) derived from butyl (meth)acrylate is preferably 40 to 95 mol%, more preferably 50 to 90 mol%, and even more preferably 60 to 85 mol%, based on the total amount (100 mol%) of the constituent units of the comb-shaped polymer.

[0087] The content of constituent units (β) derived from alkyl (meth)acrylates having an alkyl group with 12 to 20 carbon atoms is preferably 1 to 30 mol%, more preferably 3 to 25 mol%, and even more preferably 5 to 20 mol%, based on the total amount (100 mol%) of constituent units of the comb-shaped polymer.

[0088] (Nitrogen atom-containing vinyl monomer (x2-c)) Examples of nitrogen atom-containing vinyl monomers (x2-c) include amide group-containing vinyl monomers (x2-c1), nitro group-containing monomers (x2-c2), primary amino group-containing vinyl monomers (x2-c3), secondary amino group-containing vinyl monomers (x2-c4), tertiary amino group-containing vinyl monomers (x2-c5), and nitrile group-containing vinyl monomers (x2-c6).

[0089] Examples of amide group-containing vinyl monomers (x2-c1) include (meth)acrylamide; monoalkylamino(meth)acrylamides such as N-methyl(meth)acrylamide, N-ethyl(meth)acrylamide, N-isopropyl(meth)acrylamide, Nn-butyl(meth)acrylamide, and N-isobutyl(meth)acrylamide; monoalkylaminoalkyl(meth)acrylamides such as N-methylaminoethyl(meth)acrylamide, N-ethylaminoethyl(meth)acrylamide, N-isopropylamino-n-butyl(meth)acrylamide, Nn-butylamino-n-butyl(meth)acrylamide, and N-isobutylamino-n-butyl(meth)acrylamide; and N,N-dimethyl(meth)acrylamide. Examples include dialkylamino(meth)acrylamides such as amides, N,N-diethyl(meth)acrylamide, N,N-diisopropyl(meth)acrylamide, and N,N-di-n-butyl(meth)acrylamide; dialkylaminoalkyl(meth)acrylamides such as N,N-dimethylaminoethyl(meth)acrylamide, N,N-diethylaminoethyl(meth)acrylamide, N,N-dimethylaminopropyl(meth)acrylamide, and N,N-di-n-butylaminobutyl(meth)acrylamide; and N-vinyl carboxylic acid amides such as N-vinylformamide, N-vinylacetamide, N-vinyl-n-propionylamide, N-vinylisopropionylamide, and N-vinylhydroxyacetamide.

[0090] Examples of nitro group-containing monomers (x2-c2) include nitroethylene and 3-nitro-1-propene.

[0091] Examples of primary amino group-containing vinyl monomers (x2-c3) include alkenylamines having 3-6 C3 alkenyl groups such as (meth)allylamine and clotylamine; aminoalkyl (meth)acrylates having 2-6 C3 alkyl groups such as aminoethyl (meth)acrylate; and the like.

[0092] Examples of secondary amino group-containing vinyl monomers (x2-c4) include monoalkylaminoalkyl(meth)acrylates such as t-butylaminoethyl(meth)acrylate and methylaminoethyl(meth)acrylate; dialkenylamines having 6 to 12 carbon atoms such as di(meth)allylamine; and the like.

[0093] Examples of tertiary amino group-containing vinyl monomers (x2-c5) include dialkylaminoalkyl (meth)acrylates such as dimethylaminoethyl (meth)acrylate and diethylaminoethyl (meth)acrylate; alicyclic (meth)acrylates having a nitrogen atom such as morpholinoethyl (meth)acrylate; and their hydrochloride salts, sulfates, phosphates, or lower alkyl (C1-C8) monocarboxylic acid (acetic acid, propionic acid, etc.) salts; and the like.

[0094] Examples of nitrile group-containing vinyl monomers (x2-c6) include (meth)acrylonitrile. In addition, in the comb-shaped polymer used in one aspect of the present invention, it is preferable that the content of constituent units derived from nitrogen atom-containing vinyl monomers (x2-c) be as low as possible. Specifically, the content of constituent units derived from nitrogen atom-containing vinyl monomers (x2-c) is preferably less than 1.0 mol%, more preferably less than 0.5 mol%, even more preferably less than 0.1 mol%, even more preferably less than 0.01 mol%, and particularly preferably 0 mol%, based on the total amount of constituent units of the comb-shaped polymer (100 mol%).

[0095] (Hydroxyl group-containing vinyl monomer (x2-d)) Examples of hydroxyl group-containing vinyl monomers (x2-d) include hydroxyl group-containing vinyl monomers (x2-d1) and polyoxyalkylene chain-containing vinyl monomers (x2-d2).

[0096] Examples of hydroxyl group-containing vinyl monomers (x2-d1) include hydroxyalkyl (meth)acrylates having C2-6 alkyl groups such as 2-hydroxyethyl (meth)acrylate and 2- or 3-hydroxypropyl (meth)acrylate; mono- or di-hydroxyalkyl-substituted (meth)acrylamides having C1-4 alkyl groups such as N,N-dihydroxymethyl (meth)acrylamide, N,N-dihydroxypropyl (meth)acrylamide, and N,N-di-2-hydroxybutyl (meth)acrylamide; vinyl alcohols; and C3-12 alkyl groups such as (meth)allyl alcohol, clotyl alcohol, isoclotyl alcohol, 1-octenol, and 1-undecenol. Examples include: ols; C4-C12 alkene monools or alkene diols such as 1-buten-3-ol, 2-buten-1-ol, and 2-buten-1,4-diol; hydroxyalkyl alkenyl ethers having C1-C6 alkyl groups and C3-C10 alkenyl groups such as 2-hydroxyethylpropenyl ether; compounds obtained by introducing unsaturated groups such as alkenyl groups or the polymerizable functional groups of macromonomers (x1) into polyhydric alcohols such as glycerin, pentaerythritol, sorbitol, sorbitan, diglycerin, sugars, and sucrose; and compounds obtained by introducing unsaturated groups such as alkenyl groups or the polymerizable functional groups of macromonomers (x1) into glyceric acid or glycerin fatty acid esters. Among these, hydroxyl group-containing vinyl monomers having two or more hydroxyl groups are preferred, and compounds obtained by introducing the unsaturated group into a polyhydric alcohol or glyceric acid are more preferred.

[0097] Examples of polyoxyalkylene chain-containing vinyl monomers (x2-d2) include polyoxyalkylene glycols (alkylene group with 2-4 carbon atoms, degree of polymerization 2-50), polyoxyalkylene polyols (polyoxyalkylene ethers of the above-mentioned polyhydric alcohols (alkylene group with 2-4 carbon atoms, degree of polymerization 2-100)), and compounds obtained by introducing the aforementioned unsaturated group into compounds selected from alkyl (1-4 carbon atoms) ethers of polyoxyalkylene glycols or polyoxyalkylene polyols. Specifically, examples include polyethylene glycol (Mn: 100-300) mono(meth)acrylate, polypropylene glycol (Mn: 130-500) mono(meth)acrylate, methoxypolyethylene glycol (Mn: 110-310) (meth)acrylate, lauryl alcohol ethylene oxide adduct (2-30 mol) (meth)acrylate, and polyoxyethylene mono(meth)acrylic acid (Mn: 150-230) sorbitan.

[0098] (Phosphorus atom-containing monomer (x2-e)) Examples of phosphorus atom-containing monomers (x2-e) include phosphate ester group-containing monomers (x2-e1) and phosphono group-containing monomers (x2-e2).

[0099] Examples of phosphate ester group-containing monomers (x2-e1) include (meth)acryloyloxyalkyl phosphates having an alkyl group with 2 to 4 carbon atoms, such as (meth)acryloyloxyethyl phosphate and (meth)acryloyloxyisopropyl phosphate; and alkenyl phosphates having an alkenyl group with 2 to 12 carbon atoms, such as vinyl phosphate, allyl phosphate, propenyl phosphate, isopropenyl phosphate, butenyl phosphate, pentenyl phosphate, octenyl phosphate, decenyl phosphate, and dodecenyl phosphate.

[0100] Examples of phosphono group-containing monomers (x2-e2) include (meth)acryloyloxyalkylphosphonic acids having an alkyl group with 2 to 4 carbon atoms, such as (meth)acryloyloxyethylphosphonic acid; and alkenylphosphonic acids having an alkenyl group with 2 to 12 carbon atoms, such as vinylphosphonic acid, allylphosphonic acid, and octenylphosphonic acid.

[0101] In addition, in the comb-shaped polymer used in one aspect of the present invention, it is preferable that the content of constituent units derived from phosphorus atom-containing monomers (x2-e) be as low as possible. Specifically, the content of constituent units derived from phosphorus atom-containing monomers (x2-e) is preferably less than 1.0 mol%, more preferably less than 0.5 mol%, even more preferably less than 0.1 mol%, even more preferably less than 0.01 mol%, and particularly preferably 0 mol%, based on the total amount of constituent units of the comb-shaped polymer (100 mol%).

[0102] (Aliphatic hydrocarbon vinyl monomer (x2-f)) Examples of aliphatic hydrocarbon vinyl monomers (x2-f) include alkenes with 2 to 20 carbon atoms such as ethylene, propylene, butene, isobutylene, pentene, heptene, diisobutylene, octene, dodecene, and octadecene; and alkadienes with 4 to 12 carbon atoms such as butadiene, isoprene, 1,4-pentadiene, 1,6-heptadiene, and 1,7-octadiene. The aliphatic hydrocarbon vinyl monomer (x2-f) preferably has 2 to 30 carbon atoms, more preferably 2 to 20, and even more preferably 2 to 12 carbon atoms.

[0103] (Alicyclic hydrocarbon vinyl monomer (x2-g)) Examples of alicyclic hydrocarbon vinyl monomers (x2-g) include cyclohexene, (di)cyclopentadiene, pinene, limonene, vinylcyclohexene, and ethylidenebicycloheptene. The number of carbon atoms in the alicyclic hydrocarbon vinyl monomer (x2-g) is preferably 3 to 30, more preferably 3 to 20, and even more preferably 3 to 12.

[0104] (Vinyl esters (x2-h)) Examples of vinyl esters (x2-h) include vinyl acetate, vinyl propionate, vinyl butyrate, and vinyl octanoate, which are vinyl esters of saturated fatty acids having 2 to 12 carbon atoms.

[0105] (Vinyl ethers (x2-i)) Examples of vinyl ethers (x2-i) include C1-C12 alkyl vinyl ethers such as methyl vinyl ether, ethyl vinyl ether, propyl vinyl ether, butyl vinyl ether, and 2-ethylhexyl vinyl ether; and C1-C12 alkoxyalkyl vinyl ethers such as vinyl-2-methoxyethyl ether and vinyl-2-butoxyethyl ether.

[0106] (Vinyl ketones (x2-j)) Examples of vinyl ketones (x2-j) include alkyl vinyl ketones having 1 to 8 carbon atoms, such as methyl vinyl ketone and ethyl vinyl ketone.

[0107] (Epoxy group-containing vinyl monomer (x2-k)) Examples of epoxy group-containing vinyl monomers (x2-k) include glycidyl (meth)acrylate and glycidyl (meth)allyl ether.

[0108] (Halogen-containing vinyl monomer (x2-l)) Examples of halogen-containing vinyl monomers (x2-l) include vinyl chloride, vinyl bromide, vinylidene chloride, and (meth)allyl chloride.

[0109] (Esters (x2-m) of unsaturated polycarboxylic acids) Examples of esters (x2-m) of unsaturated polycarboxylic acids include alkyl esters of unsaturated polycarboxylic acids, cycloalkyl esters of unsaturated polycarboxylic acids, and aralkyl esters of unsaturated polycarboxylic acids. Examples of unsaturated carboxylic acids include maleic acid, fumaric acid, and itaconic acid.

[0110] In addition, in the comb-shaped polymer used in one aspect of the present invention, it is preferable that the content of constituent units derived from vinyl esters (x2-h), vinyl ethers (x2-i), vinyl ketones (x2-j), epoxy group-containing vinyl monomers (x2-k), and halogen-containing vinyl monomers (x2-l) be as low as possible. The specific content of the constituent units derived from these monomers is preferably less than 1.0 mol%, more preferably less than 0.5 mol%, even more preferably less than 0.1 mol%, even more preferably less than 0.01 mol%, and particularly preferably 0 mol%, based on the total amount (100 mol%) of the constituent units of the comb-shaped polymer.

[0111] ((di)alkyl fumarate (x2-n)) Examples of (di)alkyl fumarate (x2-n) include monomethyl fumarate, dimethyl fumarate, monoethyl fumarate, diethyl fumarate, methyl ethyl fumarate, monobutyl fumarate, dibutyl fumarate, dipentyl fumarate, and dihexyl fumarate.

[0112] ((di)alkylmaleate(x2-o)) Examples of (di)alkyl maleates (x2-o) include monomethyl maleate, dimethyl maleate, monoethyl maleate, diethyl maleate, methylethyl maleate, monobutyl maleate, and dibutyl maleate.

[0113] In addition, in the comb-shaped polymer (B1) used in one aspect of the present invention, it is preferable that the content of constituent units derived from (di)alkyl maleate (x2-o) and (di)alkyl fumarate (x2-n) be as low as possible. The specific content of the constituent units derived from these monomers is preferably less than 1.0 mol%, more preferably less than 0.5 mol%, even more preferably less than 0.1 mol%, even more preferably less than 0.01 mol%, and particularly preferably 0 mol%, based on the total amount (100 mol%) of the constituent units of the comb-shaped polymer.

[0114] (Aromatic hydrocarbon vinyl monomer (x2-p)) Examples of aromatic hydrocarbon vinyl monomers (x2-p) include styrene, α-methylstyrene, α-ethylstyrene, vinyltoluene, 2,4-dimethylstyrene, 4-ethylstyrene, 4-isopropylstyrene, 4-butylstyrene, 4-phenylstyrene, 4-cyclohexylstyrene, 4-benzylstyrene, p-methylstyrene, monochlorostyrene, dichlorostyrene, tribromostyrene, tetrabromostyrene, 4-clotylbenzene, indene, and 2-vinylnaphthalene. The number of carbon atoms in the aromatic hydrocarbon vinyl monomer (x2-p) is preferably 8 to 30, more preferably 8 to 20, and even more preferably 8 to 18.

[0115] In addition, in the comb-shaped polymer (B1) used in one aspect of the present invention, it is preferable that the content of constituent units derived from aromatic hydrocarbon vinyl monomers (x2-p) be as low as possible. The specific content of constituent units derived from aromatic hydrocarbon vinyl monomers (x2-p) is preferably less than 1.0 mol%, more preferably less than 0.5 mol%, even more preferably less than 0.1 mol%, even more preferably less than 0.01 mol%, and particularly preferably 0 mol%, based on the total amount (100 mol%) of constituent units of the comb-shaped polymer.

[0116] [Other additives] A lubricating oil composition according to one aspect of the present invention may further contain, as necessary, other components other than components (A) and (B), without departing from the spirit of the present invention. Other components include lubricant additives commonly used in lubricant compositions, such as one or more selected from the group consisting of metal-based detergents, anti-wear agents, ashless dispersants, extreme pressure agents, pour point depressants, antioxidants, defoaming agents, surfactants, anti-emulsifiers, friction modifiers, oiliness improvers, rust inhibitors, and metal deactivators. Furthermore, compounds having multiple functions as lubricating oil additives (for example, compounds having the functions of an anti-wear agent and an extreme pressure agent) may be used. These lubricating oil additives may be used individually or in combination of two or more types.

[0117] The content of each of these lubricating oil additives can be adjusted as appropriate without departing from the spirit of the present invention. In a lubricating oil composition according to one embodiment of the present invention, the content of each of these lubricating oil additives is preferably 0.001 to 15% by mass, more preferably 0.005 to 10% by mass, and even more preferably 0.01 to 8% by mass, based on the total amount of the lubricating oil composition. Furthermore, in a lubricating oil composition according to one embodiment of the present invention, if these lubricating oil additives are included, their total content is preferably more than 0% by mass and 30% by mass or less, more preferably 0.001 to 25% by mass, even more preferably 0.001 to 20% by mass, and even more preferably 0.001 to 15% by mass, based on the total amount of the lubricating oil composition.

[0118] <Metal-based cleaning agent> Examples of metal-based cleaning agents include organic acid metal salt compounds containing metal atoms selected from alkali metals and alkaline earth metals. Specifically, examples include metal salicylates, metal phenates, and metal sulfonates containing metal atoms selected from alkali metals and alkaline earth metals. In this specification, "alkali metals" refers to lithium, sodium, potassium, rubidium, cesium, and francium. Furthermore, "alkaline earth metals" refer to beryllium, magnesium, calcium, strontium, and barium. From the viewpoint of improving cleaning performance at high temperatures, the metal atoms included in the metal-based cleaning agent are preferably sodium, calcium, magnesium, or barium, with calcium being more preferred.

[0119] As the metal salicylate, a compound represented by the following general formula (MD1) is preferred; as the metal phenate, a compound represented by the following general formula (MD2) is preferred; and as the metal sulfonate, a compound represented by the following general formula (MD3) is preferred.

[0120] [ka]

[0121] In the general formulas (MD1) to (MD3) above, M is a metal atom selected from alkali metals and alkaline earth metals, and sodium, calcium, magnesium, or barium are preferred, with calcium being more preferred. E is an alkaline earth metal, preferably calcium, magnesium, or barium, with calcium being more preferred. q is the valence of M, which is 1 or 2. R 11 and R 12 Each of these is independently a hydrogen atom or a hydrocarbon group having 1 to 18 carbon atoms. S represents a sulfur atom. r is an integer of 0 or more, preferably an integer from 0 to 3. R 11 and R 12 Examples of hydrocarbon groups that can be selected include C1-C18 alkyl groups, C1-C18 alkenyl groups, C3-C18 cycloalkyl groups, C6-C18 aryl groups, C7-C18 alkylaryl groups, C7-C18 arylalkyl groups, and C7-C18 arylalkyl groups.

[0122] In one embodiment of the present invention, these metal-based detergents may be used individually or in combination of two or more. Among these, it is preferable that one or more are selected from calcium salicylate, calcium phenate, and calcium sulfonate, from the viewpoint of improving cleaning performance at high temperatures and solubility in base oil.

[0123] In one embodiment of the present invention, these metal-based cleaning agents may be neutral salts, basic salts, superbasic salts, or mixtures thereof. The total base number of the aforementioned metal-based detergent is preferably 0 to 600 mg KOH / g. In one embodiment of the present invention, when the metal-based detergent is a basic salt or an overbasic salt, the total base number of the metal-based detergent is preferably 10 to 600 mg KOH / g, more preferably 20 to 500 mg KOH / g. In this specification, "base number" refers to the base number measured by the perchloric acid method in accordance with JIS K2501:2003 "Petroleum products and lubricating oils - Neutralization number test method" 7.

[0124] In a lubricating oil composition according to one embodiment of the present invention, if a metal-based detergent is included as another component, the content of the metal-based detergent is preferably 0.01 to 10% by mass based on the total amount (100% by mass) of the lubricating oil composition. The aforementioned metal-based cleaning agents may be used alone or in combination of two or more types. The preferred total content when using two or more types is the same as the content described above.

[0125] <Abrasion-resistant agent> Examples of wear-resistant agents include sulfur-containing compounds such as zinc dialkyldithiophosphate (ZnDTP), zinc phosphate, 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. Among these, zinc dialkyldithiophosphate (ZnDTP) is preferred. In a lubricating oil composition according to one embodiment of the present invention, if an anti-wear agent is included as another component, the content of the anti-wear agent is preferably 0.05 to 5.0% by mass based on the total amount (100% by mass) of the lubricating oil composition. The abrasion-resistant agent may be used alone or in combination of two or more types. The preferred total content when using two or more types is the same as the content described above.

[0126] <Ashless Dispersant> Examples of ashless dispersants include succinimide, benzylamine, succinic acid esters, or boron-modified products thereof, but alkenyl succinimide and boron-modified alkenyl succinimide are preferred.

[0127] Examples of alkenyl succinimides include alkenyl succinate monoimides represented by the following general formula (i), or alkenyl succinate bisimides represented by the following general formula (ii). Furthermore, the alkenyl succinimide may be a modified alkenyl succinimide obtained by reacting a compound represented by the following general formula (i) or (ii) with one or more selected from alcohols, aldehydes, ketones, alkylphenols, cyclic carbonates, epoxy compounds, and organic acids. Furthermore, examples of boron-modified alkenyl succinimides include boron-modified compounds represented by the following general formulas (AD1) or (AD2).

[0128] [ka]

[0129] In the above general formulas (AD1) and (AD2), R A , R A1 and R A2 Each of these is an alkenyl group having a mass-average molecular weight (Mw) of 500 to 3,000 (preferably 1,000 to 3,000), and a polybutenyl group or a polyisobutenyl group is preferred. R B , R B1 and R B2 These are, independently, alkylene groups having 2 to 5 carbon atoms. x1 is an integer from 1 to 10, preferably from 2 to 5, more preferably 3 or 4. x2 is an integer between 0 and 10, preferably an integer between 1 and 4, more preferably 2 or 3.

[0130] In one embodiment of the present invention, the ratio of boron atoms to nitrogen atoms [B / N] constituting the boron-modified alkenyl succinimide is preferably 0.5 or higher, more preferably 0.6 or higher, even more preferably 0.8 or higher, and even more preferably 0.9 or higher, from the viewpoint of improving cleanliness. In a lubricating oil composition according to one embodiment of the present invention, if an ashless dispersant is included as another component, the content of the ashless dispersant is preferably 0.1 to 20% by mass based on the total amount (100% by mass) of the lubricating oil composition.

[0131] <Extreme pressure agent> Examples of extreme pressure agents include sulfur-based extreme pressure agents such as sulfides, sulfoxides, sulfones, and thiophosphinates, halogen-based extreme pressure agents such as chlorinated hydrocarbons, and organometallic extreme pressure agents. Furthermore, compounds that function as extreme pressure agents among the aforementioned wear-resistant agents can also be used. In one embodiment of the present invention, these extreme pressure agents may be used individually or in combination of two or more. In a lubricating oil composition according to one embodiment of the present invention, if an extreme pressure agent is included as another component, the content of the extreme pressure agent is preferably 0.1 to 10% by mass on a basis of the total amount of the lubricating oil composition.

[0132] <Antioxidant> As an antioxidant, any known antioxidant conventionally used in lubricating oils can be appropriately selected and used. Examples include amine-based antioxidants, phenol-based antioxidants, molybdenum-based antioxidants, sulfur-based antioxidants, phosphorus-based antioxidants, and the like. Examples of amine-based antioxidants include diphenylamine-based antioxidants such as diphenylamine and alkylated diphenylamine having an alkyl group with 3 to 20 carbon atoms; naphthylamine-based antioxidants such as α-naphthylamine, phenyl-α-naphthylamine, and substituted phenyl-α-naphthylamine having an alkyl group with 3 to 20 carbon atoms; and the like. Examples of phenolic antioxidants include monophenolic antioxidants such as 2,6-di-tert-butylphenol, 2,6-di-tert-butyl-4-methylphenol, 2,6-di-tert-butyl-4-ethylphenol, isooctyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, and octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate; diphenolic antioxidants such as 4,4'-methylenebis(2,6-di-tert-butylphenol) and 2,2'-methylenebis(4-ethyl-6-tert-butylphenol); and hindered phenolic antioxidants. Examples of molybdenum-based antioxidants include molybdenum amine complexes obtained by reacting molybdenum trioxide and / or molybdic acid with an amine compound. Examples of sulfur-based antioxidants include dilauryl-3,3'-thiodipropionate. Examples of phosphorus-based antioxidants include phosphites. When using a phosphorus-based antioxidant, it is preferable to use an amount that satisfies the suitable phosphorus atom content of the lubricating oil composition described later. In one embodiment of the present invention, these antioxidants can be included individually or in any combination of two or more, and are preferably phenolic antioxidants and / or amine antioxidants. In a lubricating oil composition according to one embodiment of the present invention, if an antioxidant is included as another component, the content of the antioxidant is preferably 0.05 to 7% by mass based on the total amount (100% by mass) of the lubricating oil composition.

[0133] <Pour point depressant> Examples of the pour point depressants include ethylene-vinyl acetate copolymers, condensates of chlorinated paraffin and naphthalene, condensates of chlorinated paraffin and phenol, polymethacrylates (PMA-based; polyalkyl(meth)acrylate, etc.), polyvinyl acetate, polybutene, polyalkylstyrene, etc., with polymethacrylates being preferred. These pour point depressants may be used individually or in combination of two or more. In a lubricating oil composition according to one embodiment of the present invention, if a pour point depressant is included as another component, the content of the pour point depressant is preferably 0.01 to 10% by mass based on the total amount (100% by mass) of the lubricating oil composition.

[0134] <Antifoaming agent> Examples of defoaming agents include silicone oils such as dimethylpolysiloxane, fluorosilicone oils, and fluoroalkyl ethers. These defoaming agents may be used individually or in combination of two or more. In a lubricating oil composition according to one embodiment of the present invention, if an antifoaming agent is included as another component, the content of the antifoaming agent is preferably 0.001 to 0.5% by mass based on the total amount (100% by mass) of the lubricating oil composition.

[0135] <Surfactants or anti-emulsifiers> Examples of surfactants or antiemulsifiers include polyalkylene glycol-based nonionic surfactants such as polyoxyethylene alkyl ethers, polyoxyethylene alkylphenyl ethers, and polyoxyethylene alkyl naphthyl ethers. These surfactants or antiemulsifiers can be included individually or in any combination of two or more. In a lubricating oil composition according to one embodiment of the present invention, if a surfactant or an anti-emulsifier is included as other components, the content of the surfactant or anti-emulsifier is preferably 0.01 to 3% by mass, based on the total amount (100% by mass) of the lubricating oil composition.

[0136] <Friction modifier> Examples of friction modifiers include molybdenum-based friction modifiers such as molybdenum dithiocarbamate (MoDTC), molybdenum dithiophosphate (MoDTP), and amine salts of molybdenum acid; ashless friction modifiers such as aliphatic amines, fatty acid esters, fatty acid amides, fatty acids, aliphatic alcohols, and aliphatic ethers having at least one alkyl or alkenyl group with 6 to 30 carbon atoms in the molecule; and oils and fats, amines, amides, sulfur esters, phosphate esters, phosphite esters, and phosphate ester amine salts. In a lubricating oil composition according to one embodiment of the present invention, if a friction modifier is included as another component, the content of the friction modifier is preferably 0.05 to 4% by mass based on the total amount (100% by mass) of the lubricating oil composition.

[0137] <Oiliness enhancer> Examples of oiliness improvers include aliphatic saturated or unsaturated monocarboxylic acids such as stearic acid and oleic acid; polymerized fatty acids such as dimer acid and hydrogenated dimer acid; hydroxy fatty acids such as ricinoleic acid and 12-hydroxystearic acid; aliphatic saturated or unsaturated monoalcohols such as lauryl alcohol and oleyl alcohol; aliphatic saturated or unsaturated monoamines such as stearylamine and oleylamine; aliphatic saturated or unsaturated monocarboxylic acid amides such as lauric acid amide and oleic acid amide; and partial esters of polyhydric alcohols such as glycerin and sorbitol with aliphatic saturated or unsaturated monocarboxylic acids. In a lubricating oil composition according to one embodiment of the present invention, if an oiliness improver is included as another component, the content of the oiliness improver is preferably 0.01 to 5% by mass based on the total amount (100% by mass) of the lubricating oil composition.

[0138] <Rust Inhibitor> Examples of rust inhibitors include fatty acids, alkenyl succinate half esters, fatty acid soaps, alkyl sulfonates, polyhydric alcohol fatty acid esters, fatty acid amines, oxidized paraffins, and alkyl polyoxyethylene ethers. In a lubricating oil composition according to one embodiment of the present invention, if a rust inhibitor is included as another component, the content of the rust inhibitor is preferably 0.01 to 3% by mass based on the total amount (100% by mass) of the lubricating oil composition.

[0139] <Metal deactivator> Examples of metal deactivators include benzotriazole compounds, toltriazole compounds, thiadiazole compounds, imidazole compounds, and pyrimidine compounds. In a lubricating oil composition according to one embodiment of the present invention, if a metal deactivator is included as another component, the content of the metal deactivator is preferably 0.01 to 5% by mass based on the total amount (100% by mass) of the lubricating oil composition.

[0140] [Properties of Lubricating Oil Compositions] <100℃ kinematic viscosity> The lubricating oil composition of the present invention has a kinematic viscosity of 9.3 mm at 100°C. 2 It is less than or equal to / s. The kinematic viscosity at 100°C is 9.3 mm². 2 If the viscosity exceeds / s, it becomes impossible to create a low-viscosity lubricant composition, resulting in reduced fuel efficiency. Furthermore, from the viewpoint of the above-mentioned aspects and the ability to retain oil film and suppress Noack evaporation, the lubricating oil composition according to one embodiment of the present invention preferably has a kinematic viscosity of 6.1 mm at 100°C. 2 / s~9.3mm 2 / s, more preferably 6.1mm 2 / s~9.0mm 2 / s, more preferably 6.1 mm 2 / s~8.8mm 2 It is / s.

[0141] <40℃ kinematic viscosity> One embodiment of the present invention provides a lubricating oil composition with a kinematic viscosity at 40°C of preferably 15.0 mm, from the viewpoint of improving fuel efficiency by reducing the viscosity of the lubricating oil composition, and from the viewpoint of oil film retention and suppression of Noack evaporation. 2 / s~35.0mm 2 / s, more preferably 17.0 mm 2 / s~30.0mm 2 / s, more preferably 18.0 mm 2 / s to 30.0 mm 2 / s, even more preferably 19.0 mm 2 / s to 29.0 mm 2 / s.

[0142] <Viscosity index> The lubricating oil composition of the present invention requires that the viscosity index be 280 or more. If the viscosity index is less than 280, the change in viscosity with respect to temperature cannot be sufficiently suppressed, and fuel efficiency may not be sufficiently ensured. The viscosity index is preferably 290 or more, more preferably 295 or more, and even more preferably 300 or more.

[0143] <HTHS (High Temperature High Shear) viscosity at 150 °C> The lubricating oil composition of one embodiment of the present invention preferably has an HTHS viscosity at 150 °C of 2.0 mPa·s to 2.8 mPa·s or less. When the HTHS viscosity at 150 °C is 2.0 mPa·s or more, it becomes easier to maintain an oil film. Also, when the HTHS viscosity at 150 °C is 2.8 mPa·s or less, it is easier to achieve good fuel efficiency. From such a viewpoint, the lubricating oil composition of one embodiment of the present invention preferably has an HTHS viscosity at 150 °C of more preferably 2.2 mPa·s or more, even more preferably 2.3 mPa·s or more. Also, more preferably 2.7 mPa·s or less, even more preferably 2.6 mPa·s or less. The upper and lower limit values of these numerical ranges can be arbitrarily combined. Specifically, more preferably 2.2 mPa·s to 2.7 mPa·s, even more preferably 2.3 mPa·s to 2.6 mPa·s or less. In this specification, the HTHS viscosity at 150 °C is in accordance with ASTM D4683 and is measured using a TBS high-temperature viscometer (Tapered Bearing Simulator Viscometer) under the temperature condition of 150 °C and a shear rate of 10 6 / s.

[0144] <Noack evaporation loss> In one embodiment of the present invention, the lubricating oil composition has a Noack evaporation rate (250°C, 1 hour) that is preferably 25% by mass or less, more preferably 24% by mass or less, and even more preferably 23% by mass or less, from the viewpoint of suppressing viscosity increase of the lubricating oil composition and making it easier to exhibit the effects of the present invention. It is also usually 0.1% by mass or more. In this specification, the Noack evaporation rate is a value measured in accordance with JPI-5S-41-2004 under conditions of 250°C for 1 hour.

[0145] [Method for producing a lubricating oil composition] The method for producing the lubricating oil composition of the present invention is not particularly limited. For example, a method for producing a lubricating oil composition according to one aspect of the present invention is a method for producing a lubricating oil composition containing a base oil (A) and a viscosity index improver (B), comprising the step of mixing the base oil (A) and the viscosity index improver (B), The base oil (A) comprises mineral oil (A1) and oxygenated synthetic oil (A2). The viscosity index improver (B) comprises a comb-shaped polymer (B1), The kinematic viscosity at 100°C is 9.3 mm 2 Adjusted to / s or less. The viscosity index is adjusted to 280 or higher. The method for producing a lubricating oil composition is to adjust the content Y [unit: mass%] of the oxygen-containing synthetic oil (A2) on a basis of the total amount of the lubricating oil composition so that it satisfies the following formula (1). α ≤ Y < -3.7ln(X) + β ···(1) [In formula (1) above, α = 0.5, β = 19, and X represents the ratio (C / O) of the number of carbon atoms to the number of oxygen atoms per molecule of the oxygen-containing synthetic oil (A2).] There are no particular restrictions on the method of mixing the above components, but for example, one method is to blend the viscosity index improver (B) with the base oil (A). Alternatively, the lubricating oil additive may be blended at the same time as the viscosity index improver (B), or at a different time from the viscosity index improver (B). In addition, each component may be blended after being made into a solution (dispersion) by adding a diluent oil or the like. After blending each component, it is preferable to stir and uniformly disperse it by a known method.

[0146] [Use of the Lubricating Oil Composition] The lubricating oil composition of the present invention is difficult to thicken in a low temperature range, is excellent in fuel efficiency, and is easy to thicken in a high temperature range, is excellent in wear resistance and hydraulic characteristics, and is easy to secure an oil film. Therefore, the lubricating oil composition of the present invention is suitable as a lubricating oil composition used for an internal combustion engine used in a vehicle such as an automobile, and is more suitable as a lubricating oil composition used for an internal combustion engine of a hybrid automobile. It is also suitable as a lubricating oil composition used for an internal combustion engine of an automobile equipped with an idling stop mechanism. Therefore, according to the present invention, the following methods are provided. (1) A method of using the lubricating oil composition of the present invention for an internal combustion engine of an automobile. (2) A method of using the lubricating oil composition of the present invention for an internal combustion engine of a hybrid automobile. (3) A method of using the lubricating oil composition of the present invention for an internal combustion engine of an automobile equipped with an idling stop mechanism.

[0147] [One Aspect of the Present Invention Provided] In one aspect of the present invention, the following [1] to

[14] are provided. [1] A lubricating oil composition containing a base oil (A) and a viscosity index improver (B), The base oil (A) includes a mineral oil (A1) and an oxygen-containing synthetic oil (A2), The viscosity index improver (B) includes a comb-shaped polymer (B1), The kinematic viscosity at 100 °C is 9.3 mm 2 / s or less, The viscosity index is 280 or more, A lubricating oil composition in which the content Y [unit: mass%] of the oxygen-containing synthetic oil (A2) based on the total amount of the lubricating oil composition satisfies the following formula (1). α ≦ Y < -3.7 ln(X) + β ···(1) [In formula (1) above, α = 0.5, β = 19, and X represents the ratio (C / O) of the number of carbon atoms to the number of oxygen atoms per molecule of the oxygen-containing synthetic oil (A2).] [2] The lubricating oil composition according to [1] above, wherein the content ratio of the oxygen-containing synthetic oil (A2) to the comb-shaped polymer (B1) [(A2) / (B1)] is 10.0 or less by mass ratio. [3] The lubricating oil composition according to [1] or [2] above, wherein the oxygenated synthetic oil (A2) is one or more selected from the group consisting of ester oil, ether oil, and alcohol oil. [4] The lubricating oil composition according to any one of [1] to [3] above, wherein the number of oxygen atoms per molecule of the oxygen-containing synthetic oil (A2) is 1 to 10. [5] The lubricating oil composition according to any one of [1] to [4] above, wherein the content ratio [(A1) / (A2)] of the mineral oil (A1) to the oxygen-containing synthetic oil (A2) is 3.0 to 20.0 by mass. [6] The kinematic viscosity of the oxygenated synthetic oil (A2) at 40°C is 3.0 mm 2 / s~20.0mm 2 A lubricating oil composition according to any of the above [1] to [5], wherein the ratio is / s. [7] The kinematic viscosity of the base oil (A) at 40°C is 3.0 mm 2 / s~20.0mm 2 A lubricating oil composition according to any of the above [1] to [6], wherein the ratio is / s. [8] The lubricating oil composition according to any one of [1] to [7] above, wherein the comb-shaped polymer (B1) contains a comb-shaped polymer (B1-1) that does not have polar groups in its side chains. [9] The kinematic viscosity at 100°C is 6.1 mm 2 A lubricating oil composition according to any of the above [1] to [8], wherein the value is 1 / s or more.

[10] The lubricating oil composition according to any one of [1] to [9] above, wherein the Noack evaporation rate is 25% by mass or less.

[11] A lubricating oil composition according to any of [1] to

[10] above, for use in an internal combustion engine of an automobile.

[12] A lubricating oil composition according to any one of [1] to

[10] above, for use in an internal combustion engine of a hybrid vehicle or a vehicle equipped with an idle stop mechanism.

[13] A method of using any of the lubricating oil compositions described in [1] to

[10] above in an internal combustion engine of an automobile.

[14] The process includes a step of mixing a base oil (A) and a viscosity index improver (B), The base oil (A) comprises mineral oil (A1) and oxygenated synthetic oil (A2). The viscosity index improver (B) comprises a comb-shaped polymer (B1), The kinematic viscosity at 100°C is 9.3 mm 2 Adjusted to / s or less. The viscosity index is adjusted to 280 or higher. A method for producing a lubricating oil composition, wherein the content Y [unit: mass%] of the oxygen-containing synthetic oil (A2) on a basis of the total amount of the lubricating oil composition is adjusted to satisfy the following formula (1). α ≤ Y < -3.7ln(X) + β ···(1) [In formula (1) above, α = 0.5, β = 19, and X represents the ratio (C / O) of the number of carbon atoms to the number of oxygen atoms per molecule of the oxygen-containing synthetic oil (A2).] [Examples]

[0148] The present invention will be specifically described by the following examples, but the present invention is not limited to the following examples.

[0149] [Methods for measuring various physical properties] The properties of each raw material used in each example and comparative example, as well as the properties of each lubricating oil composition in each example and comparative example, were measured according to the following procedure.

[0150] (1) Kinematic viscosity at 40°C, kinematic viscosity at 100°C, and viscosity index The kinematic viscosity at 40°C and 100°C was measured in accordance with JIS K2283:2000. Viscosity indices were calculated from measured kinematic viscosity at 40°C and 100°C, in accordance with JIS K2283:2000.

[0151] (2) HTHS viscosity at 150 °C The HTHS viscosity of the lubricant composition at 150 °C was measured in accordance with ASTM D4683 using a TBS high-temperature viscometer (Tapered Bearing Simulator Viscometer) at a shear rate of 10 6 / s under the temperature condition of 150 °C.

[0152] (3) Noack evaporation loss The Noack evaporation loss was measured in accordance with JPI-5S-41-2004 under the conditions of 250 °C for 1 hour.

[0153] (4) Weight-average molecular weight (Mw), number-average molecular weight (Mn) The weight-average molecular weight (Mw) was measured using a gel permeation chromatograph (manufactured by Agilent Technologies, "1260型HPLC") under the following conditions, and the value measured in terms of standard polystyrene conversion was used. (Measurement conditions) · Column: Two "Shodex LF404" columns connected in series. · Column temperature: 35 °C · Eluent: Chloroform · Flow rate: 0.3 mL / min

[0154] (5) PSSI (Shear stability index) PSSI indicates the percentage of viscosity reduction due to shear derived from the polymer and was calculated by the following formula defined in ASTM D6022-06(2012). [Number] In the above formula, Kv0 is the value of the kinematic viscosity at 100 °C of the mixture (before shear) obtained by adding the polymer to the base oil. Kv1 is the value of the kinematic viscosity at 100 °C of the mixture obtained by adding the polymer to the base oil, measured in accordance with ASTM D-6278 (after shear). Also, Kv oil is the value of the kinematic viscosity at 100 °C of the base oil, and Kv0 was adjusted to 7.5 mm 2 / s.

[0155] [Examples, comparative examples, reference examples] Each of the raw materials listed below was thoroughly mixed in the proportions (mass%) shown in Tables 2 to 6 to prepare the respective lubricating oil compositions. Details of the base oils and various additives used in the examples, comparative examples, and reference examples are as follows.

[0156] <Mineral oil (A1)> (1) Mineral oil 1 Mineral oil classified as Group III in the API category 40℃ kinematic viscosity: 18.5mm 2 / s, 100℃ kinematic viscosity: 4.0mm 2 / s, Viscosity index: 128, Noack evaporation rate: 12% by mass (2) Mineral oil 2 Mineral oil classified as Group II in the API category 40℃ kinematic viscosity: 10.4mm 2 / s, 100℃ kinematic viscosity: 3.0mm 2 / s, Viscosity index: 115, Noack evaporation rate: 40% by mass

[0157] <Oxygenated synthetic oil (A2)> (1) Ester oil 1 Trimethylolpropane trimethacrylate [ka] Number of carbon atoms (C): 18, Number of oxygen atoms (O): 6, C / O = 3 40℃ kinematic viscosity: 19.8mm 2 / s, 100℃ kinematic viscosity: 4.3mm 2 / s, Viscosity index: 126, Noack evaporation rate: 3% by mass, Ester oil corresponding to polyol ester oil (2) Ester oil 2 Diethyl sebacate (diethyl decandioate) [ka] Number of carbon atoms (C): 14, Number of oxygen atoms (O): 4, C / O = 3.5 40℃ kinematic viscosity: 11.5mm 2 / s, 100℃ kinematic viscosity: 3.2mm 2 / s, Viscosity index: 151, Noack evaporation rate: 15% by mass, Ester oil corresponding to diester oil (3) Ester oil 3 Methyl oleate (methyl octadecenoate) [ka] Number of carbon atoms (C): 19, Number of oxygen atoms (O): 2, C / O = 9.5 40℃ kinematic viscosity: 5.78mm 2 / s, 100℃ kinematic viscosity: 2.1mm 2 / s, Viscosity index: 221, Noack evaporation rate: 32% by mass, Ester oil corresponding to monoester oil (4) Ester oil 4 Isopropyl palmitate (Isopropyl hexadecanoate) [ka] Number of carbon atoms (C): 19, Number of oxygen atoms (O): 2, C / O = 9.5 40℃ kinematic viscosity: 5.03mm 2 / s, 100℃ kinematic viscosity: 1.9mm 2 / s, viscosity index: 179, ester oil corresponding to monoester oil. (5) Ether oil Polyoxyalkylene glycol methyl ether CH3-(CH2CH2O) n -O CH3 Number of carbon atoms (C): 4, Number of oxygen atoms (O): 2, C / O = 2 40℃ kinematic viscosity: 14.9mm 2 / s, 100℃ kinematic viscosity: 4.0mm 2 / s, Viscosity index: 193, Noack evaporation rate: 12% by mass In the above general formula (I), R a2 This is an alkylene group with 2 carbon atoms, and R a1 and Ra3 It is a polyoxyalkylene glycol derivative in which n is a methyl group and n is 20.

[0158] <Non-oxygenated synthetic oil (A2')> (1) PAO Poly-α-olefin 40℃ kinematic viscosity: 17.5mm 2 / s, 100℃ kinematic viscosity: 4.0mm 2 / s, Viscosity index: 125, Noack evaporation rate: 13% by mass

[0159] <Viscosity index improver> (1) Comb-shaped polymer 1 Comb-shaped PMA without polar groups Mw: 310,000, resin content: 23% by mass, PSSI: 1 (2) Comb-shaped polymer 2 Polar group-containing comb-shaped PMA Mw: 600,000, resin content: 20% by mass, PSSI: 1 (3) PMA Mw: 400,000, resin content: 20% by mass Details of comb-shaped polymers 1 and 2 are shown in Table 1. The content of each constituent unit is 13 The values ​​were analyzed by 13C-NMR quantitative spectroscopy. For the macromonomer, we used hydrogenated polybutadiene with one end methacrylated (Kuraray Co., Ltd., Kraton Liquid® L-1253), which has constituent units derived from hydrogenated butadiene with one end methacrylated. Its mass-average molecular weight is approximately 7,000, and its number-average molecular weight is approximately 6,800. For the butyl group-containing monomer, we used n-butyl methacrylate. For the butoxyethyl group-containing monomer, we used butoxyethyl methacrylate. For the long-chain alkyl group-containing monomer, we used a mixture of n-dodecyl methacrylate and n-tridecyl methacrylate.

[0160] [Table 1]

[0161] <Other additives> The additive package used conforms to API / ILSAC and SP / GF-6 standards. This additive package contains the following additives: Metal-based cleaning agents, dispersants, wear-resistant agents, antioxidants, friction modifiers, defoaming agents

[0162] [evaluation] To estimate the viscosity-enhancing effect of viscosity index improvers, specific viscosity was calculated. A higher specific viscosity indicates a greater temperature dependence of the lubricating oil's viscosity, making it easier to thicken. Conversely, a lower specific viscosity indicates a smaller temperature dependence of the lubricating oil's viscosity, making it less likely to thicken. The specific viscosity at 40°C was calculated using the following formula (X1). (Specific viscosity at 40°C) = (40KV) b -40KV a ) / (40KV a )···(X1) In formula (X1), “40KV b " is the kinematic viscosity at 40°C of the lubricating oil composition being evaluated, and "40KV a "40KV" is the kinematic viscosity at 40°C of a lubricating oil composition that is a mixture of the base oil to be evaluated and other additives, without any viscosity index improvers added. a " is the kinematic viscosity at 40°C of the mixture of base oil and other additives, excluding the viscosity index improver from the lubricating oil composition being evaluated.

[0163] Furthermore, the specific viscosity at 100°C was calculated using the following formula (X2). (Specific viscosity at 100°C) = (100KV) b -100KV a ) / (100KV a )···(X2) In formula (X2), “100KV b " is the kinematic viscosity at 100°C of the lubricating oil composition being evaluated, and "100KV a " is the kinematic viscosity at 100°C of a lubricating oil composition that is a mixture of the base oil to be evaluated and other additives, without any viscosity index improvers added. In other words, "100KV a" is the kinematic viscosity at 100°C of the mixture of base oil and other additives, excluding the viscosity index improver from the lubricating oil composition being evaluated.

[0164] Furthermore, a specific viscosity of 0.40 or less at 40°C was considered acceptable. A smaller value indicates less viscosity increase at low temperatures. Furthermore, a ratio of specific viscosity at 100°C to specific viscosity at 40°C of 2.6 or higher was considered acceptable. A higher value indicates that the substance is less likely to thicken at low temperatures, while ensuring sufficient thickening action at high temperatures.

[0165] The results are shown in Tables 2-6. Note that in Tables 2-6, the content of comb-shaped polymer (B1) and PMA is calculated based on resin content.

[0166] [Table 2]

[0167] [Table 3]

[0168] [Table 4]

[0169] [Table 5]

[0170] [Table 6]

[0171] The results shown in Table 2 indicate the following: First, as shown in Reference Example 1, when PMA is used as a viscosity index improver, the specific viscosity at 40°C is high, and it is clear that the viscosity of the lubricating oil composition cannot be reduced in the low-temperature range (40°C). In contrast, as shown in Reference Examples 2-3, when a comb-shaped polymer is used as a viscosity index improver, the specific viscosity at 40°C is small, indicating that the lubricating oil composition can be made less viscous in the low-temperature range (40°C). Furthermore, the ratio of the specific viscosity at 100°C to the specific viscosity at 40°C is large, indicating that it does not thicken easily in the low-temperature range, while sufficient thickening effect is ensured in the high-temperature range. However, it can be seen that in Reference Examples 2-3, the viscosity index of the lubricating oil composition cannot be sufficiently improved. Furthermore, it can be seen that in Comparative Examples 1 and 2, where a portion of mineral oil 1 was replaced with PAO, the viscosity index of the lubricating oil composition could not be sufficiently improved.

[0172] The results shown in Table 3 indicate the following: Table 3 uses a polyol ester with a C / O ratio of 3 as the oxygen-containing synthetic oil (A2). Therefore, the content Y [unit: mass%] of the oxygenated synthetic oil (A2) defined by the above formula (1) is 0.5 ≤ Y < 14.94. As shown in Examples 1 and 2, when the oxygen-containing synthetic oil (A2) content is less than 14.94% by mass, the specific viscosity at 40°C is low, indicating that the lubricating oil composition can be made low viscosity in the low-temperature range (40°C). Furthermore, because the ratio of the specific viscosity at 100°C to the specific viscosity at 40°C is large, it can be said that the oil does not thicken easily in the low-temperature range, while sufficient thickening effect is ensured in the high-temperature range. In contrast, as shown in Comparative Example 3, when the oxygen-containing synthetic oil (A2) content is 20% by mass, the specific viscosity at 40°C is high, indicating that it tends to thicken in the low-temperature range.

[0173] The results shown in Table 4 indicate the following: Table 4 uses a diester with a C / O ratio of 3.5 as the oxygen-containing synthetic oil (A2). Therefore, the content Y [unit: mass%] of the oxygenated synthetic oil (A2) defined by the above formula (1) is 0.5 ≤ Y < 14.36. As shown in Examples 3 to 6, when the content of oxygen-containing synthetic oil (A2) is less than 14.36% by mass, the specific viscosity at 40°C is low, indicating that the lubricating oil composition can be made low viscosity in the low temperature range (40°C). Furthermore, because the ratio of the specific viscosity at 100°C to the kinematic viscosity at 40°C is large, it can be said that the composition does not thicken easily in the low temperature range, while sufficient thickening effect is ensured in the high temperature range. In contrast, as shown in Comparative Examples 4-6, when the oxygen-containing synthetic oil (A2) content is 15% by mass or more, the specific viscosity at 40°C is high, indicating that it tends to thicken in the low-temperature range.

[0174] The results shown in Table 5 indicate the following: Table 5 uses a monoester with a C / O ratio of 9.5 as the oxygen-containing synthetic oil (A2). Therefore, the content Y [unit: mass%] of the oxygenated synthetic oil (A2) defined by the above formula (1) is 0.5 ≤ Y < 10.67. As shown in Examples 7-11, when the oxygen-containing synthetic oil (A2) content is less than 10.67% by mass, the specific viscosity at 40°C is low, and it can be said that it does not thicken easily in the low-temperature range. Furthermore, because the ratio of the specific viscosity at 100°C to the specific viscosity at 40°C is large, it can be said that it does not thicken easily in the low-temperature range, while sufficient thickening effect is ensured in the high-temperature range. In contrast, as shown in Comparative Examples 7-8, when the oxygenated synthetic oil (A2) content is 15% by mass or more, the specific viscosity at 40°C is high, indicating that it tends to thicken at low temperatures.

[0175] The results shown in Table 6 indicate the following: Table 6 uses ether with a C / O ratio of 2 as the oxygenated synthetic oil (A2). Therefore, the content Y [unit: mass%] of the oxygenated synthetic oil (A2) defined by the above formula (1) is 0.5 ≤ Y < 16.44. As shown in Examples 12 and 13, when the content of oxygenated synthetic oil (A2) is less than 16.44% by mass, the specific viscosity at 40°C is low, and it can be said that it does not thicken easily in the low-temperature range. Furthermore, because the ratio of the specific viscosity at 100°C to the specific viscosity at 40°C is large, it can be said that it does not thicken easily in the low-temperature range, while sufficient thickening effect is ensured in the high-temperature range.

Claims

1. A lubricating oil composition containing a base oil (A) and a viscosity index improver (B), The base oil (A) comprises mineral oil (A1) and oxygenated synthetic oil (A2). The viscosity index improver (B) comprises a comb-shaped polymer (B1), The kinematic viscosity at 100°C is 9.3 mm². ２ / s or less, The viscosity index is 280 or higher. The oxygen-containing synthetic oil (A2) has a kinematic viscosity of 1.5 to 4.5 mm² / s at 100°C and a viscosity index of 120 or higher. The content Y [unit: mass%] of the oxygen-containing synthetic oil (A2) on a basis of the total amount of the lubricating oil composition satisfies the following formula (1): α≦Y<-3.7ln(X)+β ...(1) [In formula (1) above, α = 0.5, β = 19, and X represents the ratio (C / O) of the number of carbon atoms to the number of oxygen atoms per molecule of the oxygen-containing synthetic oil (A2).] The comb-shaped polymer (B1) has a mass-average molecular weight (Mw) of 200,000 to 700,000, a molecular weight distribution (Mw / Mn) of 3.00 or less, and a PSSI (Permanent Shear Stability Index) of 0.2 to 3.

0. A lubricating oil composition in which the content of the comb-shaped polymer (B1) on a basis of the total amount of the lubricating oil composition is 1.0 to 3.5% by mass.

2. The lubricating oil composition according to claim 1, wherein the content ratio of the oxygen-containing synthetic oil (A2) to the comb-shaped polymer (B1) [(A2) / (B1)] is 10.0 or less by mass ratio.

3. The lubricating oil composition according to claim 1 or 2, wherein the oxygen-containing synthetic oil (A2) is one or more selected from the group consisting of ester oil, ether oil, and alcohol oil.

4. The lubricating oil composition according to any one of claims 1 to 3, wherein the number of oxygen atoms per molecule of the oxygen-containing synthetic oil (A2) is 1 to 10.

5. The lubricating oil composition according to any one of claims 1 to 4, wherein the content ratio [(A1) / (A2)] of the mineral oil (A1) to the oxygen-containing synthetic oil (A2) is 3.0 to 20.0 by mass.

6. The kinematic viscosity of the oxygenated synthetic oil (A2) at 40°C is 3.0 mm. ２ / s ~ 20.0 mm ２ A lubricating oil composition according to any one of claims 1 to 5, wherein the ratio is / s.

7. The kinematic viscosity of the base oil (A) at 40°C is 3.0 mm. ２ / s ~ 20.0 mm ２ A lubricating oil composition according to any one of claims 1 to 6, wherein the ratio is / s.

8. The lubricating oil composition according to any one of claims 1 to 7, wherein the comb-shaped polymer (B1) contains a comb-shaped polymer (B1-1) that does not have polar groups in its side chains.

9. The kinematic viscosity at 100°C is 6.1 mm. ２ A lubricating oil composition according to any one of claims 1 to 8, wherein the ratio is 1 / s or more.

10. A lubricating oil composition according to any one of claims 1 to 9, wherein the Noack evaporation rate is 25% by mass or less.

11. A lubricating oil composition according to any one of claims 1 to 10, for use in an internal combustion engine of an automobile.

12. A lubricating oil composition according to any one of claims 1 to 10, for use in an internal combustion engine of a hybrid vehicle or a vehicle equipped with an idle stop mechanism.

13. A method of using the lubricating oil composition according to any one of claims 1 to 11 in an internal combustion engine of an automobile.

14. The process includes a step of mixing a base oil (A) and a viscosity index improver (B), The base oil (A) comprises mineral oil (A1) and oxygenated synthetic oil (A2). The viscosity index improver (B) comprises a comb-shaped polymer (B1), The kinematic viscosity at 100°C is 9.3 mm². ２ Adjusted to / s or less. The viscosity index is adjusted to 280 or higher. The oxygen-containing synthetic oil (A2) has a kinematic viscosity of 1.5 to 4.5 mm² / s at 100°C and a viscosity index of 120 or higher. The content Y [unit: mass%] of the oxygen-containing synthetic oil (A2) on a basis of the total amount of the lubricating oil composition satisfies the following formula (1): α≦Y<-3.7ln(X)+β ...(1) [In formula (1) above, α = 0.5, β = 19, and X represents the ratio (C / O) of the number of carbon atoms to the number of oxygen atoms per molecule of the oxygen-containing synthetic oil (A2).] The comb-shaped polymer (B1) has a mass-average molecular weight (Mw) of 200,000 to 700,000, a molecular weight distribution (Mw / Mn) of 3.00 or less, and a PSSI (Permanent Shear Stability Index) of 0.2 to 3.

0. A method for producing a lubricating oil composition, wherein the content of the comb-shaped polymer (B1) on a basis of the total amount of the lubricating oil composition is adjusted to be 1.0 to 3.5% by mass.

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