Lubricating oil composition and method of using the lubricating oil composition

Abstract

Provided is a lubricating oil composition which contains a mineral oil (A), succinimide (B) and a polymer (C). The mineral oil (A) satisfies requirements (a1) to (a3). Requirement (a1): the kinematic viscosity at 100ºC is less than 3.10 mm 2 / s. Requirement (a2): the NOACK value is 36.0 mass% or less. Requirement (a3): the CP value, as measured in accordance with ASTM D3238, is 75.0 or more. The content of the succinimide (B) is 0.008-0.060 mass% in terms of nitrogen atoms relative to the total amount of the lubricating oil composition. The content of the polymer (C) is 0.40-3.00 mass% in terms of resin relative to the total amount of the lubricating oil composition.

Description

[Technical field]

[0001] The present invention relates to a lubricating oil composition and a method of using the lubricating oil composition. [Background technology]

[0002] In recent years, for the purpose of effective use of petroleum resources and reduction of carbon dioxide emissions, there is a strong demand for fuel-saving vehicles such as automobiles. There is also a strong demand for fuel-saving lubricating oil compositions used in engines of vehicles such as automobiles. Therefore, in order to obtain lubricating oil compositions with good fuel-saving properties, reduction in the viscosity of lubricating oil compositions has been studied. For example, Patent Document 1 discloses a lubricating oil composition that contains a magnesium detergent and a zinc dialkylthiophosphate in predetermined amounts in a lubricating base oil, and has a boron content limited to less than 100 ppm by mass, for the purpose of providing a lubricating oil composition that can reduce friction even when the viscosity is reduced. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2019-85491 A Summary of the Invention [Problem to be solved by the invention]

[0004] Under these circumstances, there is a demand for new lubricating oil compositions that can be suitably used for engine lubrication. [Means for solving the problem]

[0005] The present invention provides a lubricating oil composition containing a specified amount of succinimide and polymer together with a mineral oil that meets specific requirements. Specific embodiments of the present invention are as follows [1] to

[14] . [1] A lubricating oil composition comprising a mineral oil (A), a succinimide (B), and a polymer (C), The mineral oil (A) satisfies the following requirements (a1) to (a3). Requirement (a1): Kinematic viscosity at 100℃ is 3.10mm 2 / s Requirement (a2): NOACK value is 36.0% by mass or less Requirement (a3): %C measured according to ASTM D3238 P is 75.0 or more Fulfilling The content of the succinimide (B) in terms of nitrogen atoms is 0.008 to 0.060 mass% based on the total amount of the lubricating oil composition; The content of the polymer (C) in terms of the resin content is 0.40 to 3.00 mass% based on the total amount of the lubricating oil composition. Lubricating oil composition. [2] The lubricating oil composition according to the above item [1], wherein the ratio [(B) / (C)] of the content (unit: mass%) of succinimide (B) calculated as nitrogen atoms to the content (unit: mass%) of polymer (C) calculated as a resin content is 0.001 to 5.00. [3] The lubricating oil composition according to the above [1] or [2], wherein the polymer (C) comprises a comb polymer (C1). [4] The lubricating oil composition according to the above [3], wherein the comb polymer (C1) has a weight average molecular weight (Mw) of 200,000 to 1,000,000 and a molecular weight distribution (Mw / Mn) (Mn is the number average molecular weight of the comb polymer (C1)) of 4.0 or less. [5] The lubricating oil composition according to any one of the above [1] to [4], wherein the mineral oil (A) further satisfies the following requirement (a4): Requirement (a4): %C measured according to ASTM D3238 N is between 3.0 and 25.0 [6] The lubricating oil composition according to any one of the above [1] to [5], wherein the mineral oil (A) further satisfies the following requirement (a5): Requirement (a5): The temperature at which the distillate amount of the light fraction becomes 10% by volume in the gas chromatography distillation test is 345°C or higher. [7] The lubricating oil composition has a kinetic viscosity of 5.1 mm at 100°C. 2The lubricating oil composition according to any one of the above [1] to [6], wherein the viscosity is less than 1 / s. [8] The lubricating oil composition according to any one of the above [1] to [7], wherein the lubricating oil composition has an HTHS viscosity at 150°C of 1.40 mPa s or more. [9] The lubricating oil composition has a kinematic viscosity of 2.45 mm at 140 ° C. 2 The lubricating oil composition according to any one of the above [1] to [8], wherein the viscosity is 100 / s or more.

[10] The lubricating oil composition according to any one of the above [1] to [9], wherein the lubricating oil composition has an HTHS viscosity at 80°C of 4.40 mPa s or less.

[11] The lubricating oil composition according to any one of the above [1] to

[10] , which is used for lubricating an engine mounted on a hybrid car or an engine mounted on a generator for an electric vehicle.

[12] The lubricating oil composition according to any one of the above [1] to

[11] , which is used for lubricating an engine mounted in a range extender for an electric vehicle.

[13] A method for using the lubricating oil composition according to any one of the above [1] to

[11] for lubricating an engine mounted on a hybrid car or an engine mounted on a generator for an electric vehicle.

[14] A method for using the lubricating oil composition according to any one of the above [1] to

[11] for lubricating an engine mounted in a range extender for an electric vehicle. Effect of the Invention

[0006] The lubricating oil composition of a preferred embodiment of the present invention has excellent properties such as hydraulic characteristics, fuel economy, and oil consumption suppression, and can be particularly suitably used for lubricating engines of hybrid cars and engines mounted on generators for electric vehicles. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0007] In this specification, the kinematic viscosity and viscosity index refer to values ​​measured or calculated in accordance with JIS K2283:2000. In this specification, the weight average molecular weight (Mw) and the number average molecular weight (Mn) are values ​​calculated as standard polystyrene measured by gel permeation chromatography (GPC), and specifically, they mean values ​​measured by the method described in the Examples.

[0008] The upper and lower limit values ​​of the numerical ranges described in this specification can be combined in any combination. For example, when a numerical range is described as "preferably 30 to 100, more preferably 40 to 80," the range "30 to 80" and the range "40 to 100" are also included in the numerical ranges described in this specification. Furthermore, as a numerical range described in this specification, for example, "60 to 100" means a range of "60 or more and 100 or less." Furthermore, in defining the upper and lower limits described in this specification, a numerical range from the lower limit to the upper limit can be defined by appropriately selecting from the respective options and combining them in any desired manner.

[0009] [Constitution of lubricating oil composition] The lubricating oil composition of the present invention contains a mineral oil (A), a succinimide (B), and a polymer (C), and preferably further contains a friction modifier (D). Furthermore, the lubricating oil composition of one embodiment of the present invention may further contain components other than components (A) to (D) as necessary, provided that the effects of the present invention are not impaired.

[0010] In the lubricating oil composition of one embodiment of the present invention, the total content of components (A), (B) and (C) is, based on the total amount (100 mass%) of the lubricating oil composition, preferably 45 mass% or more, more preferably 55 mass% or more, even more preferably 65 mass% or more, still more preferably 75 mass% or more, particularly preferably 85 mass% or more, and may even be 87 mass% or more, or 90 mass% or more.

[0011] Each component contained in the lubricating oil composition according to one embodiment of the present invention will now be described in detail.

[0012] <Component (A): Mineral oil> Examples of the mineral oil (A) used in one embodiment of the present invention include atmospheric residual oils obtained by atmospheric distillation of crude oils such as paraffinic crude oil, intermediate base crude oil, naphthenic crude oil, etc.; distillate oils obtained by vacuum distillation of these atmospheric residual oils; refined oils obtained by subjecting the distillate oils to one or more refining processes such as solvent deasphalting, solvent extraction, hydrocracking, solvent dewaxing, catalytic dewaxing, and hydrorefining; mineral oils (GTL) obtained by isomerizing wax produced from natural gas by the Fischer-Tropsch process or the like (GTL wax (Gas To Liquids WAX)); and the like. These mineral oils may be used alone or in combination of two or more kinds.

[0013] The mineral oil (A) used in the present invention satisfies the following requirements (a1) to (a3). Requirement (a1): Kinematic viscosity at 100℃ is 3.10mm 2 / s. Requirement (a2): The NOACK value is 36.0% by mass or less. Requirement (a3): %C measured according to ASTM D3238 P is 75.0 or higher. Furthermore, the mineral oil (A) used in one embodiment of the present invention preferably satisfies at least one of the following requirements (a4) and (a5) in addition to the above requirements (a1) to (a3), and more preferably satisfies both of the following requirements (a4) and (a5). Requirement (a4): %C measured according to ASTM D3238 N is 3.0 to 25.0. Requirement (a5): The temperature at which the distillate amount of the light fraction in the gas chromatography distillation test is 10% by volume or less is 345°C or higher.

[0014] (Requirement (a1)) When the mineral oil (A) satisfies the above requirement (a1), a lubricating oil composition with a low viscosity can be obtained, and the fuel economy of the lubricating oil composition can be improved. From the above viewpoint, the kinetic viscosity of the mineral oil (A) at 100°C specified in the above requirement (a1) is 3.10 mm 2 / s, but preferably less than 3.05 mm 2 / s, more preferably less than 3.00 mm 2 / s, more preferably less than 2.98 mm 2 / s, and even more preferably less than 2.97 mm 2 / s. The lower limit of the kinematic viscosity at 100° C. of the mineral oil (A) is appropriately set within a range that satisfies the other requirements described above, but it is preferably 2.00 mm 2 / s or more, preferably 2.10 mm 2 / s or more, more preferably 2.20 mm 2 / s or more, and even more preferably 2.30 mm 2 / s or more, and especially preferably 2.40 mm 2 / s or more. That is, the mineral oil (A) used in one embodiment of the present invention preferably has a kinematic viscosity at 100°C of 2.00 mm 2 / s or more 3.10mm 2 / s, preferably less than 2.10 mm 2 / s or more 3.05mm 2 / s, more preferably less than 2.20 mm 2 / s or more 3.00mm 2 / s, and even more preferably less than 2.30 mm 2 / s or more 2.98mm 2 / s, particularly preferably 2.40 mm 2 / s or more 2.97mm 2 / s.

[0015] (Requirement (a2)) When the mineral oil (A) satisfies the above requirement (a2), the evaporation loss of the mineral oil (A) is reduced, and a lubricating oil composition having excellent oil consumption suppression properties can be obtained. From the above viewpoint, the NOACK value of the mineral oil (A) specified in the above requirement (a2) is not more than 36.0 mass%, preferably not more than 35.5 mass%, more preferably not more than 35.0 mass%, even more preferably not more than 34.5 mass%, still more preferably not more than 34.0 mass%, and may even be not more than 33.5 mass%, not more than 33.0 mass%, not more than 32.5 mass%, or not more than 32.0 mass%. The lower limit of the NOACK value of the mineral oil (A) is appropriately set within a range that satisfies the other requirements described above, and is preferably 1.0 mass% or more, more preferably 5.0 mass% or more, even more preferably 10.0 mass% or more, still more preferably 15.0 mass% or more, and particularly preferably 20.0 mass% or more. That is, the NOACK value of the mineral oil (A) used in one embodiment of the present invention is preferably 1.0 to 36.0 mass%, more preferably 5.0 to 35.5 mass%, even more preferably 10.0 to 35.0 mass%, still more preferably 15.0 to 34.5 mass%, and particularly preferably 20.0 to 34.0 mass%. In this specification, the NOACK value means a value measured at 250° C. in accordance with JPI-5S-41-2004.

[0016] (Requirement (a3), requirement (a4)) When the mineral oil (A) satisfies the above requirement (a3), the mineral oil (A) has reduced evaporation loss even when it has a low viscosity, and therefore a lubricating oil composition having improved fuel economy and oil consumption suppression properties can be obtained. In view of the above, the %C of mineral oil (A) specified in the above requirement (a3) P is 75.0 or more, preferably 77.0 or more, more preferably 78.5 or more, even more preferably 80.0 or more, still more preferably 82.0 or more, and may further be 83.0 or more, 85.0 or more, 87.0 or more, or 90.0 or more. In addition, the %C of mineral oil (A) PThe upper limit is appropriately set within a range that satisfies the other requirements described above, but is preferably 99.0 or less, more preferably 98.0 or less, even more preferably 97.0 or less, still more preferably 96.0 or less, particularly preferably 95.0 or less, and may further be 94.0 or less, 93.0 or less, 92.0 or less, 91.0 or less, or 90.0 or less. That is, the %C of the mineral oil (A) used in one embodiment of the present invention P is preferably 75.0 to 99.0, more preferably 77.0 to 98.0, even more preferably 78.5 to 97.0, still more preferably 80.0 to 96.0, and particularly preferably 82.0 to 95.0.

[0017] The mineral oil (A) used in one embodiment of the present invention satisfies the above requirement (a4), thereby making it possible to provide a lubricating oil composition in which evaporation loss is suppressed even if the composition has a low viscosity. In view of the above, the %C of mineral oil (A) specified in the above requirement (a4) N is preferably 3.0 to 25.0, more preferably 4.0 to 22.0, even more preferably 5.0 to 20.0, still more preferably 6.0 to 19.0, and particularly preferably 6.5 to 18.0. In addition, the %C of mineral oil (A) N may further be 6.8 or more, 7.0 or more, 8.0 or more, 9.0 or more, or 10.0 or more, and may be 17.5 or less, 17.0 or less, 16.0 or less, 15.0 or less, or 14.0 or less.

[0018] In this specification, %C P and %C N means a value measured in accordance with ASTM D-3238 ring analysis (ndM method).

[0019] (Requirement (a5)) When the mineral oil (A) used in one embodiment of the present invention satisfies the above requirement (a5), the evaporation loss of the mineral oil (A) is reduced, and a lubricating oil composition having excellent oil consumption suppression properties can be obtained. From the above viewpoint, the temperature at which the distillation amount of the light fraction is 10% by volume is preferably 345°C or higher, more preferably 348°C or higher, even more preferably 350°C or higher, still more preferably 352°C or higher, and may further be 353°C or higher, 355°C or higher, 357°C or higher, or 360°C or higher. Furthermore, there is no particular upper limit to the temperature at which the distillation amount of the light fraction becomes 10% by volume, but it may be 600°C or less, 550°C or less, 500°C or less, 430°C or less, 420°C or less, or 400°C or less. In this specification, "the temperature at which the distillation amount of the light fraction is 10% by volume" means the temperature at which the distillation amount of the light fraction reaches 10% by volume when the distillation amount of the light fraction is measured in the process of increasing the temperature from room temperature by a gas chromatography distillation test in accordance with ASTM D6352.

[0020] (Other requirements for mineral oil (A) other than the above requirements (a1) to (a5)) The viscosity index of the mineral oil (A) used in one embodiment of the present invention is preferably 70 or more, more preferably 80 or more, even more preferably 90 or more, still more preferably 100 or more, and particularly preferably 110 or more, from the viewpoint of obtaining a lubricating oil composition with little temperature dependency.

[0021] The aniline point of the mineral oil (A) used in one embodiment of the present invention is preferably from 100 to 140°C, more preferably from 108 to 130°C, and even more preferably from 110 to 125°C. In this specification, the aniline point refers to a value measured in accordance with JIS K2256 (U-tube method).

[0022] The mineral oil (A) used in one embodiment of the present invention has a flash point of preferably 180°C or higher, more preferably 192°C or higher, even more preferably 194°C or higher, and preferably 400°C or lower, more preferably 350°C or lower, even more preferably 300°C or lower. In this specification, the flash point refers to a value measured by the Cleveland Open Cup (COC) method in accordance with JIS K2265-4.

[0023] The pour point of the mineral oil (A) used in one embodiment of the present invention is preferably -20°C or lower, more preferably -30°C or lower, even more preferably less than -35°C, and even more preferably -37.5°C or lower. In this specification, the pour point means a value measured in accordance with JIS K2269:1987.

[0024] In addition, when the mineral oil (A) used in one embodiment of the present invention is a mixed mineral oil obtained by mixing two or more kinds of mineral oils, the mixed mineral oil only needs to satisfy the above requirements (a1) to (a5), and the viscosity index, aniline point, flash point, and pour point only need to be within the above preferred ranges. In addition, if each mineral oil constituting the mixed mineral oil satisfies the above requirements (a1) to (a5), the mixed mineral oil can also be considered to satisfy these requirements. The same applies to the viscosity index, aniline point, flash point, and pour point.

[0025] In order to adjust the mineral oil to satisfy the above requirements (a1) to (a5), the mineral oil (A) should have a kinematic viscosity of 3.0 mm at 100°C. 2 / s and a low-viscosity mineral oil (α) with a kinematic viscosity of 3.0 mm at 100°C. 2 It may also be a mixed mineral oil with a high viscosity mineral oil (β) of 1 / s or more. When the above-mentioned mixed mineral oils are used as the mineral oil (A), the blending ratio [(α) / (β)] of the low-viscosity mineral oil (α) and the high-viscosity mineral oil (β) may be appropriately set so as to satisfy the above requirements (a1) to (a5) depending on the types and kinematic viscosities of the mineral oils (α) and (β) to be mixed. Specifically, the blending ratio [(α) / (β)] of the low-viscosity mineral oil (α) to the high-viscosity mineral oil (β), in mass ratio, is preferably 10 / 90 to 99 / 1, more preferably 30 / 70 to 95 / 5, even more preferably 50 / 50 to 90 / 10, still more preferably 55 / 45 to 85 / 15, and particularly preferably 60 / 40 to 80 / 20.

[0026] In the lubricating oil composition of one embodiment of the present invention, the content of the mineral oil (A) is preferably 40 to 99.5 mass%, more preferably 50 to 99.0 mass%, even more preferably 60 to 98.0 mass%, still more preferably 70 to 96.0 mass%, and particularly preferably 80 to 95.0 mass%, based on the total amount (100 mass%) of the lubricating oil composition.

[0027] <Synthetic oil> The lubricating oil composition of one embodiment of the present invention may contain a synthetic oil together with the mineral oil (A) as long as the effects of the present invention are not impaired. Examples of synthetic oils include poly-α-olefins such as α-olefin homopolymers or α-olefin copolymers (e.g., α-olefin copolymers having 8 to 14 carbon atoms, such as ethylene-α-olefin copolymers); isoparaffin; polyalkylene glycol; ester-based oils such as polyol esters, dibasic acid esters, and phosphate esters; ether-based oils such as polyphenyl ether; alkylbenzenes; and alkylnaphthalenes. These synthetic oils may be used alone or in combination of two or more kinds.

[0028] The kinetic viscosity at 100°C of the synthetic oil that can be used in one embodiment of the present invention may be approximately the same as that of the mineral oil (A), and is preferably 2.00 mm 2 / s or more 3.10mm 2 / s, preferably less than 2.10 mm 2 / s or more 3.05mm 2 / s, more preferably less than 2.20 mm 2 / s or more 3.00mm 2 / s, and even more preferably less than 2.30 mm 2 / s or more 2.98mm 2 / s, particularly preferably 2.40 mm 2 / s or more 2.97mm 2 / s.

[0029] The viscosity index of the synthetic oil that can be used in one embodiment of the present invention is preferably 70 or more, more preferably 80 or more, even more preferably 90 or more, still more preferably 100 or more, and particularly preferably 110 or more. When a mixed synthetic oil made by combining two or more synthetic oils is used as the synthetic oil, the mixed synthetic oil preferably has a kinematic viscosity and a viscosity index within the above ranges.

[0030] In the lubricating oil composition of one embodiment of the present invention, the content of the synthetic oil is preferably 0 to 50 parts by mass, more preferably 0 to 30 parts by mass, even more preferably 0 to 10 parts by mass, still more preferably 0 to 5 parts by mass, and particularly preferably 0 to 1 part by mass, relative to 100 parts by mass of the total amount of the mineral oil (A) contained in the lubricating oil composition.

[0031] <Component (B): Succinimide> The lubricating oil composition of the present invention contains a succinimide (B). By containing the succinimide (B), it is possible to obtain a lubricating oil composition having excellent fuel economy and hydraulic properties.

[0032] In the lubricating oil composition of the present invention, the content of succinimide (B) calculated as nitrogen atoms is adjusted to 0.008 to 0.060 mass% based on the total amount (100 mass%) of the lubricating oil composition. By adjusting the content of component (B) calculated as nitrogen atoms within this range, it is possible to obtain a lubricating oil composition that has good fuel economy while improving hydraulic properties.

[0033] In the lubricating oil composition of one embodiment of the present invention, the content of succinimide (B) calculated as nitrogen atoms is 0.008% by mass or more based on the total amount (100% by mass) of the lubricating oil composition; from the viewpoint of obtaining a lubricating oil composition with further improved hydraulic properties, the content is preferably 0.015% by mass or more, more preferably 0.020% by mass or more, even more preferably 0.025% by mass or more, still more preferably 0.030% by mass or more, particularly preferably 0.035% by mass or more, and may even be 0.037% by mass or more, 0.040% by mass or more, or 0.042% by mass or more. The content of succinimide (B) calculated as nitrogen atoms is 0.060 mass% or less based on the total amount (100 mass%) of the lubricating oil composition, but from the viewpoint of obtaining a lubricating oil composition with better fuel economy properties, it is preferably 0.057 mass% or less, more preferably 0.055 mass% or less, even more preferably 0.052 mass% or less, still more preferably 0.050 mass% or less, particularly preferably 0.048 mass% or less, and may even be 0.047 mass% or less, 0.046 mass% or less, or 0.045 mass% or less. That is, the content of succinimide (B) calculated as nitrogen atoms is preferably 0.015 to 0.057 mass%, more preferably 0.020 to 0.055 mass%, even more preferably 0.025 to 0.052 mass%, still more preferably 0.030 to 0.050 mass%, and particularly preferably 0.035 to 0.048 mass%, based on the total amount (100 mass%) of the lubricating oil composition. In this specification, the nitrogen atom content refers to a value measured in accordance with JIS K2609.

[0034] In the lubricating oil composition of one embodiment of the present invention, the blending amount (content) of the succinimide (B) may be adjusted so that the content calculated as nitrogen atoms falls within the above range, and is preferably 0.01 to 15.0 mass%, more preferably 0.1 to 12.0 mass%, even more preferably 0.5 to 10.0 mass%, and still more preferably 1.0 to 7.0 mass%, based on the total amount (100 mass%) of the lubricating oil composition.

[0035] The succinimide (B) used in one embodiment of the present invention may be a succinic acid monoimide, a succinic acid bisimide, or a combination thereof. The succinic acid monoimide is preferably an alkenyl succinic acid monoimide represented by the following general formula (b-1), and the succinic acid bisimide is preferably an alkenyl succinic acid bisimide represented by the following general formula (b-2). The succinimides (B) may be used alone or in combination of two or more kinds.

[0036] [ka]

[0037] In the above general formulas (b-1) and (b-2), R A , R A1 and R A2 are each independently an alkenyl group having a weight average molecular weight (Mw) of 500 to 3000 (preferably 1000 to 3000). Examples of the alkenyl group include a polybutenyl group, a polyisobutenyl group, and an ethylene-propylene copolymer, and a polybutenyl group or a polyisobutenyl group is preferred. R B , R B1 and R B2 are each independently an alkylene group having 2 to 5 carbon atoms. R C and R C1 are each independently a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, or -(AO) n A group represented by -H (wherein, each A is independently an alkylene group having 2 to 4 carbon atoms, and n is an integer of 1 to 10). x1 is an integer of 1 to 10, preferably an integer of 2 to 5, and more preferably 3 or 4. x2 is an integer of 0 to 10, preferably an integer of 1 to 5, and more preferably an integer of 2 to 4.

[0038] The succinimide (B) used in one embodiment of the present invention may be a non-modified succinimide or a modified succinimide. The modified succinimide may be a modified alkenyl succinimide obtained by reacting a non-modified alkenyl succinimide represented by the general formula (b-1) or (b-2) with one or more compounds selected from a boron compound, an alcohol, an aldehyde, a ketone, an alkylphenol, a cyclic carbonate, an epoxy compound, an organic acid, and the like.

[0039] From the viewpoint of obtaining a lubricating oil composition having improved hydraulic properties and better fuel economy, the succinimide (B) used in one embodiment of the present invention preferably contains an unmodified succinimide, more preferably contains an unmodified succinic bisimide (B1), and even more preferably contains an unmodified alkenyl succinic bisimide (B11) represented by the general formula (b-2) above. From the above viewpoints, the content of component (B1) (or component (B11)) in the succinimide (B) used in one embodiment of the present invention is preferably 50 to 100 mass%, more preferably 70 to 100 mass%, even more preferably 80 to 100 mass%, still more preferably 90 to 100 mass%, and particularly preferably 95 to 100 mass%, relative to 100 mass% of the total amount of component (B) contained in the lubricating oil composition.

[0040] Furthermore, from the viewpoint of adjusting the kinetic viscosity to a low level to obtain a lubricating oil composition with improved fuel economy, the content of boron-modified succinimide in the lubricating oil composition of one embodiment of the present invention is preferably as low as possible. The specific content of the boron-modified succinimide is preferably 0 to 30 parts by mass, more preferably 0 to 10 parts by mass, even more preferably 0 to 5 parts by mass, still more preferably 0 to 1 part by mass, and particularly preferably 0 to 0.1 part by mass, relative to 100 parts by mass of the total amount of component (B) contained in the lubricating oil composition.

[0041] <Other ashless dispersants> The lubricating oil composition of one embodiment of the present invention may contain an ashless dispersant other than component (B) to the extent that the effects of the present invention are not impaired. Examples of such other ashless dispersants include benzylamine, succinic acid esters, and boron or other modified versions of these.

[0042] In the lubricating oil composition of one embodiment of the present invention, the content of the other ashless dispersant is preferably 0 to 50 parts by mass, more preferably 0 to 30 parts by mass, even more preferably 0 to 10 parts by mass, still more preferably 0 to 5 parts by mass, and particularly preferably 0 to 1 part by mass, per 100 parts by mass of the total amount of component (B) contained in the lubricating oil composition.

[0043] <Component (C): Polymer> The lubricating oil composition of the present invention contains a polymer (C). By containing the polymer (C) together with the succinimide (B), it is possible to obtain a lubricating oil composition having improved hydraulic properties and fuel economy in a well-balanced manner. From the viewpoint of providing a lubricating oil composition that can suppress the formation of deposits while improving hydraulic properties and fuel economy in a well-balanced manner, the content of polymer (C) in the lubricating oil composition of the present invention, calculated as the resin content, is adjusted to 0.40 to 3.00 mass% based on the total amount of the lubricating oil composition.

[0044] In the lubricating oil composition of one embodiment of the present invention, the content of polymer (C) calculated as the resin content is 0.40% by mass or more based on the total amount (100% by mass) of the lubricating oil composition. From the viewpoint of obtaining a lubricating oil composition having improved hydraulic properties and fuel economy in a well-balanced manner, the content is preferably 0.45% by mass or more, more preferably 0.48% by mass or more, even more preferably 0.50% by mass or more, still more preferably 0.52% by mass or more, particularly preferably 0.55% by mass or more, and may further be 0.57% by mass or more, 0.60% by mass or more, 0.62% by mass or more, 0.65% by mass or more, 0.67% by mass or more, or 0.70% by mass or more. The content of polymer (C) calculated as the resin content is 3.00% by mass or less based on the total amount (100% by mass) of the lubricating oil composition. From the viewpoint of obtaining a lubricating oil composition that has a good balance between hydraulic properties and fuel economy and can suppress the formation of deposits, the content is preferably 2.50% by mass or less, more preferably 2.20% by mass or less, even more preferably 2.00% by mass or less, still more preferably 1.70% by mass or less, particularly preferably 1.55% by mass or less, and may further be 1.40% by mass or less, 1.30% by mass or less, 1.20% by mass or less, 1.10% by mass or less, 1.00% by mass or less, or 0.90% by mass or less. That is, the content of polymer (C) calculated as the resin content is preferably 0.45 to 2.50 mass%, more preferably 0.48 to 2.20 mass%, even more preferably 0.50 to 2.00 mass%, still more preferably 0.52 to 1.70 mass%, and particularly preferably 0.55 to 1.55 mass%, based on the total amount (100 mass%) of the lubricating oil composition.

[0045] In consideration of handling properties and solubility in mineral oil (A), polymer (C) is often commercially available in the form of a solution in which it is dissolved in a diluent oil. However, in this specification, the content of polymer (C) is the content converted into the resin content constituting polymer (C) in a solution diluted with diluent oil, excluding the mass of the diluent oil.

[0046] In addition, from the viewpoint of obtaining a lubricating oil composition having improved hydraulic properties and fuel economy, in one embodiment of the lubricating oil composition of the present invention, the ratio of the content (unit: mass %) of succinimide (B) calculated as nitrogen atoms to the content (unit: mass %) of polymer (C) calculated as a resin content is preferably 0.001 to 5.00, more preferably 0.005 to 3.00, even more preferably 0.010 to 1.00, still more preferably 0.015 to 0.15, and particularly preferably 0.020 to 0.10. The ratio of the content (unit: mass%) of succinimide (B) calculated as nitrogen atoms to the content (unit: mass%) of polymer (C) calculated as a resin component [(B) / (C)] may be 0.025 or more, 0.030 or more, 0.035 or more, 0.040 or more, 0.045 or more, 0.050 or more, or 0.055 or more, and may be 0.095 or less, 0.090 or less, 0.085 or less, 0.080 or less, 0.075 or less, 0.070 or less, or 0.065 or less.

[0047] Examples of the polymer (C) used in one embodiment of the present invention include non-dispersed polymethacrylate, dispersed polymethacrylate, olefin copolymer (e.g., ethylene-propylene copolymer, etc.), dispersed olefin copolymer, styrene copolymer (e.g., styrene-diene copolymer, styrene-isoprene copolymer, etc.), etc. The polymer (C) is not limited to a linear polymer, but may be a branched polymer, a comb polymer, a star polymer, etc. These polymers (C) may be used alone or in combination of two or more kinds. The polymer (C) used in one embodiment of the present invention includes not only polymers used as so-called viscosity index improvers but also polymers used as pour point depressants.

[0048] The weight average molecular weight (Mw) of the polymer (C) used in one embodiment of the present invention is usually 500 to 1,000,000, preferably 1,000 to 1,000,000, and more preferably 3,000 to 1,000,000, but is appropriately set depending on the type of polymer.

[0049] From the viewpoint of providing a lubricating oil composition which has improved hydraulic properties, excellent viscosity characteristics independent of temperature range, and can exhibit fuel economy properties independent of temperature range, it is preferred that the polymer (C) used in one embodiment of the present invention contains a comb polymer (C1). The comb polymer (C1) functions as a so-called viscosity index improver. The comb polymer (C1) used in one embodiment of the present invention may be any polymer having a structure in which the main chain has many three-way branching points from which high molecular weight side chains extend.

[0050] From the above viewpoints, the content of comb polymer component (C1) in polymer (C) used in one embodiment of the present invention is preferably 50 to 100 mass%, more preferably 70 to 100 mass%, even more preferably 80 to 100 mass%, still more preferably 90 to 100 mass%, and particularly preferably 95 to 100 mass%, relative to 100 mass% of the total amount of component (C) contained in the lubricating oil composition.

[0051] The weight average molecular weight (Mw) of the comb polymer (C1) used in one embodiment of the present invention is preferably 200,000 to 1,000,000, more preferably 300,000 to 900,000, even more preferably 400,000 to 800,000, still more preferably 450,000 to 700,000, and particularly preferably 500,000 to 650,000.

[0052] The molecular weight distribution (Mw / Mn) of the comb polymer (C1) used in one embodiment of the present invention (wherein Mn represents the number average molecular weight of the comb polymer (C1)) is preferably 4.0 or less, more preferably 3.5 or less, even more preferably 3.0 or less, still more preferably 2.7 or less, particularly preferably 2.5 or less, and is preferably 1.01 or more, more preferably 1.05 or more, even more preferably 1.1 or more, still more preferably 1.2 or more, particularly preferably 1.5 or more. That is, the molecular weight distribution (Mw / Mn) of the comb polymer (C1) is preferably from 1.01 to 4.0, more preferably from 1.05 to 3.5, even more preferably from 1.1 to 3.0, still more preferably from 1.2 to 2.7, and particularly preferably from 1.5 to 2.5.

[0053] The comb polymer (C1) used as component (C) in one embodiment of the present invention is preferably a polymer having at least a structural unit (X1) derived from a macromonomer (x1). This structural unit (X1) corresponds to the above-mentioned "high molecular weight side chain." In the present invention, the above-mentioned "macromonomer (x1)" means a high molecular weight monomer having a polymerizable functional group, and is preferably a high molecular weight monomer having a polymerizable functional group at its terminal.

[0054] In the comb polymer (C1) used in one embodiment of the present invention, the content of the structural unit (X1) is preferably 0.5 to 20 mol %, more preferably 0.7 to 10 mol %, and even more preferably 0.9 to 5 mol %, based on the total amount (100 mol %) of the structural units of the comb polymer (C1).

[0055] The number average molecular weight (Mn) of the macromonomer (x1) is preferably 300 or more, more preferably 400 or more, and even more preferably 500 or more, and is preferably 20,000 or less, more preferably 10,000 or less, and even more preferably 5,000 or less. That is, the number average molecular weight (Mn) of the macromonomer (x1) is preferably 300 to 20,000, more preferably 400 to 10,000, and further preferably 500 to 5,000.

[0056] The weight average molecular weight (Mw) of the macromonomer (x1) is preferably 1,000 or more, more preferably 2,000 or more, and even more preferably 4,000 or more, and is preferably 50,000 or less, more preferably 25,000 or less, and even more preferably 10,000 or less. That is, the weight average molecular weight (Mw) of the macromonomer (x1) is preferably from 1,000 to 50,000, more preferably from 2,000 to 25,000, and further preferably from 4,000 to 10,000.

[0057] Examples of the polymerizable functional group possessed by the macromonomer (x1) include an acryloyl group (CH2=CH-COO-), a methacryloyl group (CH2=CCH3-COO-), an ethenyl group (CH2=CH-), a vinyl ether group (CH2=CH-O-), an allyl group (CH2=CH-CH2-), an allyl ether group (CH2=CH-CH2-O-), a group represented by CH2=CH-CONH-, a group represented by CH2=CCH3-CONH-, and the like.

[0058] The macromonomer (x1) may have, in addition to the above polymerizable functional group, for example, one or more repeating units represented by the following general formulas (i) to (iii). [ka]

[0059] In the above general formula (i), R b1 is a straight or branched alkylene group having 1 to 10 carbon atoms. In the above general formula (ii), R b2 is a straight or branched alkylene group having 2 to 4 carbon atoms. In the above general formula (iii), R b3 R is a hydrogen atom or a methyl group. b4 is a straight or branched alkyl group having 1 to 10 carbon atoms. In addition, when the repeating units represented by the above general formulas (i) to (iii) are each present in a plurality of repeating units, the repeating units each represented by the above general formula (i) to (iii) are each present in a plurality of R b1 , R b2 , R b3 , and R b4 may be the same or different from each other.

[0060] In one embodiment of the present invention, the macromonomer (x1) is preferably a polymer having a repeating unit represented by the general formula (i), and R b1 It is more preferable that the repeating unit (X1-1) is at least one of a 1,2-butylene group and a 1,4-butylene group.

[0061] The content of the repeating unit (X1-1) is preferably 1 to 100 mol %, more preferably 20 to 95 mol %, even more preferably 40 to 90 mol %, and still more preferably 50 to 80 mol %, based on the total amount (100 mol %) of the constituent units of the macromonomer (x1).

[0062] When the macromonomer (x1) is a copolymer having two or more kinds of repeating units selected from the general formulae (i) to (iii), the form of the copolymerization may be a block copolymer or a random copolymer.

[0063] The comb polymer (C1) used in one embodiment of the present invention may be a homopolymer consisting of only structural units (X1) derived from one type of macromonomer (x1), or may be a copolymer having structural units (X1) derived from two or more types of macromonomers (x1). Furthermore, the comb polymer (C1) used in one embodiment of the present invention may be a copolymer having a structural unit (X1) derived from the macromonomer (x1) as well as a structural unit (X2) derived from a monomer other than the macromonomer (x1). A specific structure of such a comb polymer is preferably a copolymer having a main chain containing a structural unit (X2) derived from a monomer (x2) and a side chain containing a structural unit (X1) derived from a macromonomer (x1).

[0064] Examples of the monomer (x2) include alkyl (meth)acrylates, nitrogen atom-containing vinyl monomers, hydroxyl group-containing vinyl monomers, phosphorus atom-containing monomers, aliphatic hydrocarbon vinyl monomers, alicyclic hydrocarbon vinyl monomers, vinyl esters, vinyl ethers, vinyl ketones, epoxy group-containing vinyl monomers, halogen element-containing vinyl monomers, esters of unsaturated polycarboxylic acids, (di)alkyl fumarates, (di)alkyl maleates, and aromatic hydrocarbon vinyl monomers.

[0065] The monomer (x2) is preferably a monomer other than a phosphorus atom-containing monomer and an aromatic hydrocarbon vinyl monomer, more preferably includes one or more selected from a monomer represented by the following general formula (a1), an alkyl (meth)acrylate, and a hydroxyl group-containing vinyl monomer, and further preferably includes at least a hydroxyl group-containing vinyl monomer (x2-d). [ka]

[0066] In the above general formula (a1), R b11 is a hydrogen atom or a methyl group. R b12 is a single bond, a linear or branched alkylene group having 1 to 10 carbon atoms, -O-, or -NH-. R b13 is a linear or branched alkylene group having 2 to 4 carbon atoms. n is an integer of 1 or more (preferably an integer of 1 to 20, more preferably an integer of 1 to 5). When n is an integer of 2 or more, a plurality of R b13 may be the same or different, and (R b13 O) n The moieties may be randomly or block bonded. R b14 is a straight-chain or branched-chain alkyl group having 1 to 60 carbon atoms (preferably 10 to 50, more preferably 20 to 40).

[0067] The SSI (shear stability index) of the comb polymer (C1) used in one embodiment of the present invention is preferably 100 or less, more preferably 80 or less, even more preferably 70 or less, still more preferably 60 or less, and particularly preferably 50 or less. The SSI of the comb polymer (C1) has no particular lower limit, but is usually 0.1 or more.

[0068] In this specification, the term "shear stability index" (SSI) refers to a percentage of the viscosity reduction due to shear caused by a polymer component, and is a value measured in accordance with JPI-5S-29-06, and more specifically, is a value calculated by the following calculation formula (1). Calculation formula (1): SSI(%)=(Kv0-Kv1) / (Kv0-Kv oil ) x 100

[0069] In the above formula (1), Kv0 is the value of the kinetic viscosity at 100°C of the sample oil in which the polymer component is diluted in mineral oil, and Kv1 is the value of the kinetic viscosity at 100°C of the sample oil in which the polymer component is diluted in mineral oil after irradiating ultrasonic waves for 30 minutes in accordance with the output method in accordance with the procedure of JPI-5S-29-06. oil is the value of the kinetic viscosity at 100°C of the mineral oil used to dilute the polymer component.

[0070] The SSI value of the comb polymer (C1) varies depending on the structure of the comb polymer. Specifically, there are the following tendencies, and the SSI value of the comb polymer (C1) can be easily adjusted by taking these factors into consideration. The following factors are merely examples, and the SSI value can also be adjusted by taking other factors into consideration. Comb polymers in which the side chains are composed of a macromonomer (x1) and the content of structural units (X1) derived from said macromonomer (x1) is 0.5 mol % or more based on the total amount of structural units (100 mol %) tend to have a low SSI value. The larger the molecular weight of the macromonomer (x1) that constitutes the side chain of the comb polymer, the lower the SSI value tends to be.

[0071] <Component (D): Friction modifier> From the viewpoint of further improving fuel economy, the lubricating oil composition of one embodiment of the present invention preferably further contains a friction modifier (D). Examples of the friction modifier (D) used in one embodiment of the present invention include molybdenum-based friction modifiers such as molybdenum dithiocarbamate (MoDTC), molybdenum dithiophosphate (MoDTP), and amine salts of molybdenum acid; ashless friction modifiers having at least one alkyl or alkenyl group having 6 to 30 carbon atoms in the molecule, such as aliphatic amines, fatty acid esters, fatty acid amides, fatty acids, aliphatic alcohols, and aliphatic ethers; oils and fats, amines, amides, sulfur esters, phosphate esters, phosphites, and phosphate amine salts. These friction modifiers (D) may be used alone or in combination of two or more kinds. Among these, the friction modifier (D) used in one embodiment of the present invention preferably contains one or more selected from molybdenum dithiocarbamate (MoDTC) and molybdenum dithiophosphate (MoDTP), and more preferably contains molybdenum dithiocarbamate (MoDTC).

[0072] In the lubricating oil composition of one embodiment of the present invention, the content of the friction modifier (D), calculated as molybdenum atom, based on the total amount (100 mass%) of the lubricating oil composition is preferably 0.010 mass% or more, more preferably 0.050 mass% or more, even more preferably 0.080 mass% or more, still more preferably 0.090 mass% or more, and is preferably 0.200 mass% or less, more preferably 0.180 mass% or less, even more preferably 0.160 mass% or less, and still more preferably 0.140 mass% or less. That is, the content of the friction modifier (D) in terms of molybdenum atoms is preferably 0.010 to 0.200 mass%, more preferably 0.050 to 0.180 mass%, even more preferably 0.080 to 0.160 mass%, and still more preferably 0.090 to 0.140 mass%, based on the total amount (100 mass%) of the lubricating oil composition. In this specification, the molybdenum atom content refers to a value measured in accordance with JPI-5S-38-2003.

[0073] <Lubricant additives> The lubricating oil composition of one embodiment of the present invention may further contain lubricating oil additives other than components (B) to (D) as necessary, provided that the effects of the present invention are not impaired. Examples of such lubricating oil additives include anti-wear agents, extreme pressure agents, metal detergents, antioxidants, metal deactivators, rust inhibitors, and anti-foaming agents. These lubricating oil additives may be used alone, or two or more of them may be used in combination.

[0074] The content of each of these lubricating oil additives can be adjusted as appropriate within a range that does not impair the effects of the present invention, but is usually 0.001 to 15 mass%, preferably 0.005 to 10 mass%, and more preferably 0.01 to 5 mass%, for each additive independently, based on the total amount (100 mass%) of the lubricating oil composition.

[0075] In addition, as the lubricating oil additive, a commercially available additive package containing multiple additives that conforms to API / ILSAC SN / GF-5 standards or the like may be used. Furthermore, a compound having multiple functions as the above-mentioned additives (for example, a compound having functions as an antiwear agent and an extreme pressure agent) may be used.

[0076] (Anti-wear agent) Examples of anti-wear agents used in one embodiment of the present invention include sulfur-containing compounds such as zinc dialkyldithiophosphate (ZnDTP), zinc phosphate, zinc dithiocarbamate, molybdenum dithiocarbamate, molybdenum dithiophosphate, disulfides, sulfurized olefins, sulfurized oils and fats, sulfurized esters, thiocarbonates, thiocarbamates, and polysulfides; phosphorus-containing compounds such as phosphites, phosphates, phosphonates, and amine salts or metal salts thereof; and sulfur- and phosphorus-containing anti-wear agents such as thiophosphites, thiophosphates, thiophosphonates, and amine salts or metal salts thereof. Of these, zinc dialkyldithiophosphate (ZnDTP) is preferred.

[0077] (Extreme pressure agent) Examples of the extreme pressure agent used in one embodiment of the present invention 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. Of the above-mentioned antiwear agents, compounds having a function as an extreme pressure agent can also be used.

[0078] (Metal-based cleaning agents) Examples of the metal-based detergent used in one embodiment of the present invention include organic acid metal salt compounds containing a metal atom selected from alkali metals and alkaline earth metals. Specific examples of the metal detergent include metal salicylates, metal phenates, and metal sulfonates, each of which contains a metal atom selected from alkali metals and alkaline earth metals. As the metal atom contained in the metal-based detergent, from the viewpoint of improving the detergency at high temperatures, sodium, calcium, magnesium or barium is preferred, and calcium is more preferred.

[0079] The metal sulfonate is preferably a compound represented by the following general formula (1), the metal salicylate is preferably a compound represented by the following general formula (2), and the metal phenate is preferably a compound represented by the following general formula (3).

[0080] [ka]

[0081] In the above general formulas (1) and (2), M is a metal atom selected from alkali metals and alkaline earth metals, preferably sodium, calcium, magnesium, or barium, more preferably calcium. In the above general formula (3), M' is an alkaline earth metal, preferably calcium, magnesium or barium, and more preferably calcium. y is an integer of 0 or more, and preferably an integer of 0 to 3. In the above general formulas (1) to (3), p is the valence of M and is 1 or 2. R is a hydrogen atom or a hydrocarbon group having 1 to 18 carbon atoms. Examples of hydrocarbon groups that can be selected as R include alkyl groups having 1 to 18 carbon atoms, alkenyl groups having 1 to 18 carbon atoms, cycloalkyl groups having 3 to 18 ring carbon atoms, aryl groups having 6 to 18 ring carbon atoms, alkylaryl groups having 7 to 18 carbon atoms, and arylalkyl groups having 7 to 18 carbon atoms.

[0082] In one embodiment of the present invention, the metal-based detergent may be any one of a neutral salt, a basic salt, an overbased salt, and a mixture thereof. The total base number of the metallic detergent is preferably 0 to 600 mgKOH / g. In one embodiment of the present invention, when the metallic detergent is a basic salt or an overbased salt, the total base number of the metallic detergent is preferably 10 to 600 mgKOH / g, more preferably 20 to 500 mgKOH / g. In this specification, the term "base number" refers to the base number measured by the perchloric acid method in accordance with 7 of JIS K2501 "Petroleum products and lubricants - Test method for neutralization number".

[0083] (Antioxidants) The antioxidant used in one embodiment of the present invention can be appropriately selected from known antioxidants that have been conventionally used as antioxidants for lubricating oils, and examples thereof include amine-based antioxidants, phenol-based antioxidants, molybdenum-based antioxidants, sulfur-based antioxidants, and phosphorus-based antioxidants.

[0084] Examples of the amine-based antioxidants include diphenylamine-based antioxidants such as diphenylamine and alkylated diphenylamines having an alkyl group with 3 to 20 carbon atoms; naphthylamine-based antioxidants such as α-naphthylamine, phenyl-α-naphthylamine, and substituted phenyl-α-naphthylamines having an alkyl group with 3 to 20 carbon atoms; and the like. Examples of the phenol-based antioxidants include monophenol-based 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; diphenol-based antioxidants such as 4,4'-methylenebis(2,6-di-tert-butylphenol) and 2,2'-methylenebis(4-ethyl-6-tert-butylphenol); hindered phenol-based antioxidants; and the like. Examples of the molybdenum-based antioxidant include molybdenum amine complexes obtained by reacting molybdenum trioxide and / or molybdic acid with an amine compound. An example of the sulfur-based antioxidant is dilauryl-3,3'-thiodipropionate. Examples of phosphorus-based antioxidants include phosphites.

[0085] (metal deactivator) Examples of the metal deactivator used in one embodiment of the present invention include benzotriazole-based compounds, tolyltriazole-based compounds, thiadiazole-based compounds, imidazole-based compounds, and pyrimidine-based compounds.

[0086] (rust inhibitor) Examples of the rust inhibitor used in one embodiment of the present invention include fatty acids, alkenyl succinic acid half esters, fatty acid soaps, alkyl sulfonates, polyhydric alcohol fatty acid esters, fatty acid amines, paraffin oxide, and alkyl polyoxyethylene ethers.

[0087] (Antifoaming agent) Examples of the defoaming agent used in one embodiment of the present invention include silicone oil, fluorosilicone oil, and fluoroalkyl ether.

[0088] <Method of producing lubricating oil composition> The method for producing the lubricating oil composition of one embodiment of the present invention is not particularly limited, but from the viewpoint of productivity, it is preferable that the method comprises a step of blending the succinimide (B) and the polymer (C) with the mineral oil (A), and, as necessary, a synthetic oil, an ashless dispersant other than the succinimide (B), and the other lubricating oil additives described above. From the viewpoint of compatibility with the mineral oil (A), it is preferable that the resin components such as the polymer (C) are in the form of a solution dissolved in a diluent oil, and the solution is blended with the mineral oil (A).

[0089] [Properties of the lubricating oil composition] The lubricating oil composition of one embodiment of the present invention preferably has a kinematic viscosity at 100°C of 5.1 mmHg 2 / s, more preferably 3.0 to 5.0 mm 2 / s, more preferably 3.2 to 4.8 mm 2 / s, and even more preferably 3.5 to 4.6 mm 2 / s, particularly preferably 3.7 to 4.5 mm 2 / s.

[0090] The lubricating oil composition of one embodiment of the present invention preferably has a kinematic viscosity at 40°C of 5.0 to 60.0 mm 2 / s, more preferably 6.0 to 50.0 mm 2 / s, more preferably 7.0 to 40.0 mm 2 / s, and even more preferably 8.0 to 30.0 mm 2 / s, particularly preferably 10.0 to 25.0 mm 2 / s.

[0091] The viscosity index of the lubricating oil composition of one embodiment of the present invention is preferably 100 or more, more preferably 120 or more, even more preferably 140 or more, still more preferably 160 or more, and particularly preferably 180 or more.

[0092] The lubricating oil composition of one embodiment of the present invention can maintain a constant viscosity to such an extent that excellent hydraulic properties can be exhibited over a wide range of high temperature temperatures. For example, the kinematic viscosity at 140°C of the lubricating oil composition of one embodiment of the present invention is preferably 2.45 mm 2 / s or more, preferably 2.46 to 4.40 m 2 / s, and more preferably 2.48 to 4.20 m 2 / s, and even more preferably 2.50 to 4.00 m 2 / s, and particularly preferably 2.55 to 3.80 m 2 / s. In addition, when applied to engine lubrication, the kinetic viscosity at 140°C is an index of hydraulic characteristics during engine use. 2 / s or more, it can be said that the lubricating oil composition has excellent hydraulic properties during engine use.

[0093] The lubricating oil composition of one embodiment of the present invention preferably has a kinematic viscosity at 110°C of 2.8 to 5.0 mm 2 / s, more preferably 3.0 to 4.8 mm 2 / s, more preferably 3.2 to 4.6 mm 2 / s, and even more preferably 3.3 to 4.5 mm 2 / s, particularly preferably 3.5 to 4.4 mm 2 / s.

[0094] The lubricating oil composition of one embodiment of the present invention preferably has a kinematic viscosity at 120°C of 2.7 to 4.8 mmHg 2 / s, more preferably 2.9 to 4.6 mm 2 / s, more preferably 3.0 to 4.4 mm 2 / s, and even more preferably 3.1 to 4.2 mm 2 / s, and particularly preferably 3.2 to 4.0 mm 2 / s.

[0095] The lubricating oil composition of one embodiment of the present invention preferably has a kinematic viscosity at 130°C of 2.5 to 4.6 mmHg 2 / s, more preferably 2.6 to 4.5 mm 2 / s, more preferably 2.7 to 4.3 mm 2 / s, and even more preferably 2.75 to 4.1 mm 2 / s, particularly preferably 2.8 to 3.9 mm 2 / s.

[0096] The lubricating oil composition of one embodiment of the present invention preferably has a kinematic viscosity at 150°C of 2.00 to 4.00 mm 2 / s, more preferably 2.05 to 3.80 mm 2 / s, more preferably 2.10 to 3.60 mm 2 / s, and even more preferably 2.15 to 3.40 mm 2 / s, and particularly preferably 2.20 to 3.20 mm 2 / s.

[0097] The lubricating oil composition of one embodiment of the present invention can exhibit excellent fuel economy over a wide range of high temperature ranges. For example, fuel economy in the low temperature range can be evaluated by HTHS viscosity at 80°C. Specifically, the lubricating oil composition of one embodiment of the present invention preferably has an HTHS viscosity at 80° C. of 4.40 mPa·s or less, more preferably 2.40 to 4.35 mPa·s, even more preferably 2.50 to 4.32 mPa·s, and even more preferably 2.60 to 4.30 mPa·s.

[0098] The lubricating oil composition of one embodiment of the present invention has an HTHS viscosity at 100° C. of preferably 2.00 to 4.00 mPa·s, more preferably 2.10 to 3.90 mPa·s, even more preferably 2.20 to 3.80 mPa·s, and still more preferably 2.40 to 3.60 mPa·s.

[0099] The lubricating oil composition of one embodiment of the present invention preferably has an HTHS viscosity at 150° C. of 1.40 mPa·s or more, more preferably 1.45 to 3.80 mPa·s, even more preferably 1.50 to 3.60 mPa·s, and even more preferably 1.55 to 3.40 mPa·s. In this specification, the HTHS viscosity at each temperature is measured according to ASTM D 4741 at a shear rate of 10 6 This refers to the viscosity measured after shearing at 1000 / s.

[0100] The lubricating oil composition of one embodiment of the present invention preferably has an SAE viscosity grade of 0W-4 or 0W-8, more preferably 0W-4. With these SAE viscosity grades, various performance properties can be fully exhibited when the composition is used, for example, for lubricating engines mounted on hybrid cars or generators.

[0101] The NOACK value of the lubricating oil composition of one embodiment of the present invention is preferably 32 mass % or less, more preferably 31 mass % or less, and even more preferably 30.5 mass % or less. If the NOACK value is 32 mass % or less, oil consumption due to evaporation is suppressed, and the lubricating oil composition can be said to be excellent in suppressing oil consumption.

[0102] In the lubricating oil composition of one embodiment of the present invention, the content of molybdenum atoms, based on the total amount (100 mass%) of the lubricating oil composition, is preferably 0.010 mass% or more, more preferably 0.050 mass% or more, even more preferably 0.080 mass% or more, still more preferably 0.090 mass% or more, and is preferably 0.200 mass% or less, more preferably 0.180 mass% or less, even more preferably 0.160 mass% or less, and still more preferably 0.140 mass% or less. That is, the content of molybdenum atoms is preferably 0.010 to 0.200 mass%, more preferably 0.050 to 0.180 mass%, even more preferably 0.080 to 0.160 mass%, and still more preferably 0.090 to 0.140 mass%, based on the total amount (100 mass%) of the lubricating oil composition.

[0103] [Uses of the lubricating oil composition] As described above, the lubricating oil composition of one embodiment of the present invention is excellent in properties such as hydraulic properties, fuel economy, and oil consumption suppression. Therefore, the lubricating oil composition of one embodiment of the present invention can be suitably used for lubricating engines, and in particular, can be suitably used for lubricating engines mounted on hybrid cars or engines mounted on generators for electric vehicles, and can be even more suitably used for lubricating engines mounted on range extenders for electric vehicles. In other words, taking into consideration the above-mentioned properties of the lubricating oil composition of one embodiment of the present invention, the present invention can also provide the engines described in [1] and [2] below, and the methods of using the lubricating oil compositions described in [3] and [4] below. [1] An engine of a hybrid car or an engine mounted on a generator for an electric vehicle, to which the lubricating oil composition according to one embodiment of the present invention is applied. [2] An engine mounted in a range extender for an electric vehicle, to which the lubricating oil composition according to one embodiment of the present invention is applied. [3] A method for using the lubricating oil composition according to one embodiment of the present invention described above, which comprises applying the lubricating oil composition to the engine of a hybrid car or an engine mounted on a generator for an electric vehicle. [4] A method for using the lubricating oil composition according to one embodiment of the present invention described above, comprising applying the lubricating oil composition to the lubrication of an engine mounted in a range extender for an electric vehicle.

[0104] The fuel for the engines [1] to [4] above is not particularly limited, and examples thereof include gas, gasoline, and bio-methanol. In the above [1] and [3], the engine of the hybrid car may be a parallel type engine using both an internal combustion engine and an electric motor as the driving source of the vehicle, a split type engine, etc. In addition, the hybrid car may be an electric vehicle equipped with an internal combustion engine capable of self-propelling only by an electric motor (for example, a full hybrid vehicle such as a plug-in hybrid vehicle), or a mild hybrid vehicle using an electric motor (such as an alternator) as a driving assistance for the internal combustion engine.

[0105] In addition, the engine mounted on the generator for the electric vehicle in [1] and [3] above may be an engine used to generate electricity for an electric motor when the electric motor is the only driving source for the vehicle, specifically, an engine mounted on a range extender for an electric vehicle that supplements the power generation of the electric motor of the electric vehicle.

[0106] The range extender in the above [2] and [4] refers to a mechanism that generates electricity using the engine when power supply is required, such as when the remaining capacity of the battery is low or when a relatively large amount of power is required during acceleration or heating operation, and stops the engine when power generation is not required. The lubricating oil composition of the present invention can be suitably applied to the lubrication of engines mounted on hybrid car engines and generators for electric vehicles, and is particularly preferably used for engines mounted on range extenders for electric vehicles. The engine mounted on the range extender does not require as much power as a conventional gasoline engine, and is repeatedly started and stopped in a short period of time. On the other hand, there is a demand for improving fuel economy by lowering the viscosity of the lubricating oil composition, but lowering the viscosity causes increased oil consumption and insufficient oil pressure. However, as described above, the lubricating oil composition of one embodiment of the present invention has excellent properties such as hydraulic characteristics, fuel economy, and oil consumption suppression even with a low viscosity. Therefore, it can be suitably applied to the above embodiments [2] and [4]. EXAMPLES

[0107] The present invention will now be described in more detail with reference to examples, but the present invention is not limited to these examples. The methods for measuring or evaluating various physical properties are as follows.

[0108] (1)Kinematic viscosity, viscosity index Measurements and calculations were made in accordance with JIS K2283:2000. (2)%C P , %C N Measured in accordance with ASTM D-3238 ring analysis (ndM method). (3) NOACK value Measured at 250°C in accordance with JPI-5S-41-2004. (4) Aniline point Measurements were performed in accordance with JIS K2256 (U-tube method). (5) Flash point Measurements were performed using the Cleveland open cup (COC) method in accordance with JIS K2265-4. (6) Pour point Measurements were performed in accordance with JIS K2269:1987. (7) The temperature at which the distillate content of the light fraction becomes 10% by volume In accordance with ASTM D6352, a gas chromatographic distillation test was used to measure the amount of light fraction distilled as the temperature was increased from room temperature, and the temperature at which the distillate amount reached 10% by volume was measured. (8) Nitrogen atom content Measurements were performed in accordance with JIS K2609. (9) Molybdenum atom content Measurements were performed in accordance with JPI-5S-38-2003. (10) Weight average molecular weight (Mw), number average molecular weight (Mn), Measurements were carried out using a gel permeation chromatograph (Agilent Technologies, "1260 Model HPLC") under the conditions below, and values ​​measured in terms of standard polystyrene were used. (Measurement conditions) Column: Two Shodex LF404 columns connected in series. Column temperature: 35℃ Developing solvent: Chloroform ·Flow rate: 0.3mL / min The ratio [Mw / Mn] of the measured weight average molecular weight (Mw) to the number average molecular weight (Mn) was calculated as the molecular weight distribution. (11) SSI (Shear Stability Index) A sample oil was prepared by adding mineral oil as a diluent to the polymer to be measured, and the sample oil and the mineral oil were used to perform measurements in accordance with JPI-5S-29-06. Specifically, for the target polymer, Kv0, Kv1, and Kv oil Each value was measured and calculated using the formula (1). (12)HTHS viscosity According to ASTM D 4741, at each measurement temperature, the shear rate was 10 6 The viscosity was measured after shearing at 10000 / s.

[0109] Examples 1 to 2, Comparative Examples 1 to 4 Lubricating oil compositions were prepared by blending mineral oil, succinimide, polymer, and various additives in the amounts shown in Table 2. The blended amount of polymer shown in Table 2 is the blended amount converted into active ingredient (solid content equivalent) excluding the mass of diluent oil. When a mixed mineral oil made by combining two or more types of mineral oils was used as the mineral oil, the "Properties of mineral oil" in Table 2 indicates the properties of the mixed mineral oil. Details of the mineral oil, succinimide, polymer and various additives used in the preparation of each lubricating oil composition are as follows:

[0110] <Mineral oil> Mineral oils (A-1) to (A-4): Paraffinic mineral oils classified into Group 2 or 3 of the API base oil category shown in Table 1 below. [Table 1]

[0111] <Succinimide> Unmodified succinic acid bisimide: Unmodified succinic acid bisimide, nitrogen atom (N) content = 1.2 mass%. <Polymer> Comb polymer: A comb polymer with Mw=600,000, Mw / Mn=2.4, and SSI=49. <Various additives> Additive mixture: a mixture of additives including an anti-wear agent (ZnDTP), a friction modifier (MoDTC, formulated so that the content in terms of molybdenum is 0.10 mass% based on the total amount of the lubricating oil composition), a metal-based detergent, an antioxidant, and an antifoaming agent.

[0112] The kinematic viscosity at each temperature, the viscosity index, the HTHS viscosity at 80°C, 100°C, and 150°C, and the NOACK value of the prepared lubricating oil compositions were measured according to the methods described above. The results are shown in Table 2. In addition, regarding fuel economy, the following motoring torque test was further carried out, and the driving torque improvement rate was calculated and used as one of the indices for evaluating fuel economy.

[0113] [Calculation of drive torque improvement rate through motoring torque test] The lubricating oil compositions of the Examples and Comparative Examples were filled into an engine having the specifications shown below, and a motoring torque test was carried out under the test conditions shown below, measuring the torque (dB) at an oil temperature of 80°C and rotation speeds of 1500 rpm, 2000 rpm, or 2500 rpm. (Test conditions) Equipment used: Engine motoring equipment Engine: Water-cooled 1,500cc inline 4-cylinder engine for automobiles Valve type: DOHC (roller) Engine speed: 1,500 rpm, 2,000 rpm, and 2,500 rpm Oil pan temperature: 80℃ Then, using the torque value measured at each rotation speed for the lubricating oil composition of Comparative Example 1 as the standard, the driving torque improvement rate at each rotation speed was calculated according to the following formula. Driving torque improvement rate (%)=([Measured torque value measured using the lubricating oil composition of Comparative Example 1]−[Measured torque value measured using the target lubricating oil composition]) / [Measured torque value measured using the lubricating oil composition of Comparative Example 1]×100 It should be noted that the driving torque improvement rate calculated from the above formula is positive when the torque measurement value of the target lubricating oil composition is smaller than the torque measurement value measured using the lubricating oil composition of Comparative Example 1. Conversely, when the torque measurement value of the target lubricating oil composition is larger, the driving torque improvement rate calculated from the above formula is negative. The larger the value of the driving torque improvement rate, the more the driving torque is improved, and therefore the lubricating oil composition to be measured can be said to have high fuel economy. In this embodiment, a lubricating oil composition having a driving torque improvement rate of "0.50% or more" is judged to have high fuel economy, more preferably 0.55% or more, even more preferably 0.60% or more, and even more preferably 0.70% or more.

[0114] The hydraulic properties, fuel economy, and oil consumption suppression properties of each lubricating oil composition were evaluated based on the measured physical property values ​​and the driving torque improvement rate calculated as described above, according to the following criteria. The evaluation results are shown in Table 2.

[0115] <Evaluation criteria for hydraulic characteristics> A: The lubricating oil composition has a kinetic viscosity of 2.45 mm at 140°C. 2 / s or more, and has a viscosity sufficient to maintain oil pressure under the temperature environment when the engine is in use. F: The kinetic viscosity of the lubricating oil composition at 140°C is 2.45 mm 2 / s, and since the viscosity is low under the temperature environment when the engine is in use, there is a risk that oil pressure will not be sufficiently maintained.

[0116] <Fuel economy evaluation criteria> ·A: The driving torque improvement rate at rotation speeds of 1500 rpm, 2000 rpm, and 2500 rpm at an oil temperature of 80°C is 0.5% or more at all rotation speeds, and the HTHS viscosity at 80°C is 4.40 mPa s or less. ·F: The driving torque improvement rate at the rotation speeds of 1500 rpm, 2000 rpm, and 2500 rpm at an oil temperature of 80°C is less than 0.5% at at least one of the rotation speeds, and / or the HTHS viscosity at 80°C is more than 4.40 mPa·s.

[0117] <Evaluation criteria for oil consumption suppression> A: The NOACK value is 32 mass% or less, and it can be said that this is a lubricating oil composition in which oil consumption due to evaporation is suppressed. · F: The NOACK value is more than 32 mass%, which means that evaporation loss is large and oil consumption is not sufficiently suppressed.

[0118] [Table 2]

[0119] As can be seen from Table 2, the lubricating oil compositions prepared in Examples 1 and 2 were excellent in hydraulic properties, fuel economy, and oil consumption suppression, and showed a good balance of these properties. On the other hand, the lubricating oil compositions prepared in Comparative Examples 1 to 4 were inferior in at least one of hydraulic properties, fuel economy, and oil consumption suppression, and showed room for improvement in the balance of these properties.

Claims

1. A lubricating oil composition comprising a mineral oil (A), a succinimide (B), and a polymer (C), The mineral oil (A) satisfies the following requirements (a1) to (a3): Requirement (a1): Kinematic viscosity at 100°C is 3.10 mm ２ / s is less than Requirement (a2): NOACK value is 36.0% by mass or less Requirement (a3): % C measured in accordance with ASTM D3238 Ｐ is 75.0 or more Fulfilling the content of the succinimide (B) in terms of nitrogen atoms is 0.008 to 0.060 mass% based on the total amount of the lubricating oil composition; the content of the polymer (C) in terms of the resin content is 0.40 to 3.00 mass% based on the total amount of the lubricating oil composition; The polymer (C) is any one of a non-dispersed polymethacrylate, a dispersed polymethacrylate, an olefin-based copolymer, a dispersed olefin-based copolymer, and a styrene-based copolymer; The polymer (C) comprises a comb polymer (C1), Lubricating oil composition.

2. The lubricating oil composition according to claim 1, wherein the ratio [(B) / (C)] of the content (unit: mass%) of succinimide (B) calculated as nitrogen atoms to the content (unit: mass%) of polymer (C) calculated as a resin content is 0.001 to 5.

00.

3. The lubricating oil composition according to claim 1 or 2, wherein the comb polymer (C1) has a weight average molecular weight (Mw) of 200,000 to 1,000,000 and a molecular weight distribution (Mw / Mn) (Mn is the number average molecular weight of the comb polymer (C1)) of 4.0 or less.

4. The lubricating oil composition according to any one of claims 1 to 3, wherein the mineral oil (A) further satisfies the following requirement (a4): Requirement (a4): % C measured in accordance with ASTM D3238 Ｎ is 3.0 to 25.0

5. The lubricating oil composition according to any one of claims 1 to 4, wherein the mineral oil (A) further satisfies the following requirement (a5): Requirement (a5): The temperature at which the distillation amount of the light fraction becomes 10% by volume in a gas chromatography distillation test is 345° C. or higher.

6. The lubricating oil composition has a kinetic viscosity of 5.1 mm at 100°C. ２ The lubricating oil composition according to any one of claims 1 to 5, wherein the viscosity is less than 1000 s.

7. The lubricating oil composition according to any one of claims 1 to 6, wherein the lubricating oil composition has a HTHS viscosity at 150°C of 1.40 mPa·s or more.

8. The lubricating oil composition has a kinematic viscosity of 2.45 mm at 140°C. ２ The lubricating oil composition according to any one of claims 1 to 7, wherein the R 1 / s is greater than or equal to 1.

9. The lubricating oil composition according to any one of claims 1 to 8, wherein the lubricating oil composition has a HTHS viscosity at 80°C of 4.40 mPa·s or less.

10. The lubricating oil composition according to any one of claims 1 to 9, which is used to lubricate an engine mounted on a hybrid car or an engine mounted on a generator for an electric vehicle.

11. The lubricating oil composition according to any one of claims 1 to 10, which is used to lubricate an engine mounted in a range extender for an electric vehicle.

12. A method for using the lubricating oil composition according to any one of claims 1 to 11, comprising applying the lubricating oil composition to an engine mounted on a hybrid car or an engine mounted on a generator for an electric vehicle.

13. A method for using the lubricating oil composition according to any one of claims 1 to 11, comprising applying the lubricating oil composition to an engine mounted in a range extender for an electric vehicle.

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