Lubricant composition for internal combustion engines

Abstract

To provide an internal combustion engine lubricating oil composition which contains an organomolybdenum compound and is excellent in fuel saving performance, piston cleaning properties, wear resistance, and anticorrosion properties.SOLUTION: An internal combustion engine lubricating oil composition includes: a lubricating oil base oil; a metal-based cleaning agent which includes at least two selected from the group consisting of an alkaline-earth metal salicylate, an alkaline-earth metal phenate, an alkaline-earth metal sulfonate having a total base number of 250 mgKOH / g or more, and an alkaline-earth metal sulfonate having a total base number of 100 mgKOH / g or less; an ashless dispersant which includes a boron-containing succinimide dispersant and a boron-free succinimide dispersant; and an organomolybdenum compound. The composition has the content of the boron-containing succinimide dispersant in terms of boron of 0.025 to 0.050 mass% based on the total amount thereof and the content of a total of the boron-containing succinimide dispersant and the boron-free succinimide dispersant in terms of nitrogen of 0.10 to 0.20 mass% based on the total amount thereof.SELECTED DRAWING: None

Description

[Technical Field]

[0001] This disclosure relates to lubricating oil compositions for internal combustion engines.

[0002] In recent years, fuel efficiency improvements have been demanded due to stricter environmental regulations on automobiles and other vehicles. One way to improve fuel efficiency through engine oil is to reduce its viscosity or friction. However, excessively low viscosity of engine oil can lead to a decrease in oil film thickness, which can ultimately increase engine wear and reduce reliability. On the other hand, from the perspective of reducing engine oil friction, the application of friction modifiers such as organic molybdenum compounds has been conventionally practiced.

[0003] For example, Patent Document 1 describes "a lubricating oil composition for internal combustion engines, comprising a lubricating oil base oil, an organic molybdenum-based friction modifier in the form of 0.03% by mass or more of molybdenum element, based on the total amount of the lubricating oil composition, and at least one metallic detergent selected from the group consisting of alkali metal phenates and alkaline earth metal phenates in the form of 0.03% by mass or more of metal element." [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2017-145322 [Overview of the project] [Problems that the invention aims to solve]

[0005] As previously mentioned, organic molybdenum compounds are compounds that function as friction modifiers when incorporated into lubricant compositions for internal combustion engines, such as engine oil.

[0006] However, when an internal combustion engine lubricant composition containing organic molybdenum compounds is used, for example, as engine oil for a diesel engine, the inclusion of soot may reduce the expected effects of the organic molybdenum compounds (i.e., wear resistance). Furthermore, as part of environmental regulations for automobiles, when exhaust gas aftertreatment devices are installed, ash content restrictions are imposed. Therefore, the inclusion of organic molybdenum compounds may relatively reduce the amount of other components in the mixture, potentially reducing the expected effects of those other components (e.g., piston cleaning properties, corrosion prevention properties).

[0007] One embodiment of this disclosure aims to solve the problem of providing a lubricating oil composition for internal combustion engines that contains an organic molybdenum compound and exhibits excellent fuel efficiency, piston cleaning properties, wear resistance, and corrosion prevention properties. [Means for solving the problem]

[0008] This disclosure includes the following aspects: <1> Lubricating oil base oil, A metal-based cleaning agent X is at least two selected from the group consisting of alkaline earth metal salicylates, alkaline earth metal phenates, alkaline earth metal sulfonates with a total base number of 250 mg KOH / g or more, and alkaline earth metal sulfonates with a total base number of 100 mg KOH / g or less. A boron-free succinimide-based dispersant and a boron-containing succinimide-based dispersant are included in this ashless dispersant, It contains an organic molybdenum compound, The content of the boron-containing succinimide-based dispersant is 0.025% to 0.050% by mass in terms of boron, relative to the total amount of the lubricating oil composition, and The total content of boron-free succinimide-based dispersants and boron-containing succinimide-based dispersants is 0.10% to 0.20% by mass in terms of nitrogen relative to the total amount of the lubricating oil composition. Lubricating oil composition for internal combustion engines. <2> The lubricating oil composition for an internal combustion engine according to <1>, wherein the metal detergent X contains at least one of an alkaline earth metal salicylate and an alkaline earth metal sulfonate having a total base number of 250 mg KOH / g or more. <3> The lubricating oil composition for an internal combustion engine according to <1> or <2>, wherein the ratio of the total content of the alkaline earth metal salicylate and the alkaline earth metal sulfonate having a total base number of 250 mg KOH / g or more to the total amount of the metal detergent X in the lubricating oil composition is 0.75 or more in terms of alkaline earth metal. <4> The lubricating oil composition for an internal combustion engine according to any one of <1> to <3>, further comprising a phenolic antioxidant and an amine antioxidant as ashless antioxidants. <5> The lubricating oil composition for an internal combustion engine according to <4>, wherein the contents of the phenolic antioxidant and the amine antioxidant are each 0.5 mass% to 1.5 mass% based on the total amount of the lubricating oil composition. <6> The lubricating oil composition for an internal combustion engine according to any one of <1> to <5>, wherein the organic molybdenum compound is at least one selected from the group consisting of molybdenum dialkyldithiophosphate, molybdenum dialkyldithiocarbamate, alkylamine molybdate, and organic molybdenum amide. <7> The lubricating oil composition for an internal combustion engine according to any one of <1> to <7>, wherein the content of the organic molybdenum compound is 0.01 mass% to 0.05 mass% in terms of molybdenum based on the total amount of the lubricating oil composition. <8> The lubricating oil composition for an internal combustion engine according to any one of <第一項> to <7>, wherein the total content of the alkaline earth metal salicylate, the alkaline earth metal phenate, the alkaline earth metal sulfonate having a total base number of 250 mg KOH / g or more, and the alkaline earth metal sulfonate having a total base number of 100 mg KOH / g or less is 0.18 mass% to 0.24 mass% in terms of alkaline earth metal based on the total amount of the lubricating oil composition. <9> The lubricating oil composition for an internal combustion engine according to any one of <1> to <8>, wherein the sulfuric acid ash content is 0.9 mass% to 1.1 mass% based on the total amount of the lubricating oil composition. <10> The kinematic viscosity at 100 °C is 12.5 mm 2 It should be noted that in the provided text, there seems to be an incomplete expression in <10> where "12.5mm" is not a complete description. Also, in <12>, "<第一項>" should be replaced with the correct item number in the original Japanese text. You may want to double-check the accuracy of the original content for a more precise translation.The lubricating oil composition for an internal combustion engine according to any one of <1> to <9>, which is less than / s. <11> The lubricating oil composition for an internal combustion engine according to any one of <1> to <10>, wherein the high-temperature high-shear viscosity (HTHS100) at 100 °C is 6.5 mPa·s or less. <12> The lubricating oil composition for an internal combustion engine according to any one of <1> to <11>, wherein the high-temperature high-shear viscosity (HTHS150) at 150 °C is 2.6 mPa·s or more. <13> The lubricating oil composition for an internal combustion engine according to any one of <1> to <12>, wherein the ratio (HTHS150 / HTHS100) of the high-temperature high-shear viscosity (HTHS150) at 150 °C to the high-temperature high-shear viscosity (HTHS100) at 100 °C is 0.45 or more. <14> The lubricating oil composition for an internal combustion engine according to any one of <1> to <13>, which is for a diesel engine.

Advantages of the Invention

[0009] According to one embodiment of the present disclosure, there is provided a lubricating oil composition for an internal combustion engine containing an organic molybdenum compound and excellent in fuel economy, piston cleanliness, abrasion resistance, and corrosion prevention.

Modes for Carrying Out the Invention

[0010] Hereinafter, embodiments which are examples of the present disclosure will be described. These descriptions and examples are illustrative of the embodiments and do not limit the scope of the invention.

[0011] In the present disclosure, a numerical range indicated using "~" means a range including the numerical values described before and after "~" as the lower limit value and the upper limit value, respectively. In the numerical ranges described stepwise in the present disclosure, the upper limit value or the lower limit value described in a certain numerical range may be replaced with the upper limit value or the lower limit value of the numerical range described in other stepwise descriptions. Further, in the numerical ranges described in the present disclosure, the upper limit value or the lower limit value described in a certain numerical range may be replaced with the value shown in the examples.

[0012] In this disclosure, when referring to the amount of each component in a composition, if there are multiple substances corresponding to each component in the composition, it means the total amount of all multiple components present in the composition unless otherwise specified.

[0013] In this disclosure, "mass%" and "weight%" are synonymous. In this disclosure, a combination of two or more preferred embodiments is a more preferred embodiment. In this disclosure, "JIS" is used as an abbreviation for Japanese Industrial Standards.

[0014] [Lubricant composition for internal combustion engines] The lubricating oil composition for internal combustion engines relating to this disclosure (hereinafter also referred to as the "lubricating oil composition") is (A): Lubricating oil base oil, (B): A metal-based cleaning agent X consisting of two or more selected from the group comprising alkaline earth metal salicylates, alkaline earth metal phenates, alkaline earth metal sulfonates with a total base number of 250 mg KOH / g or more, and alkaline earth metal sulfonates with a total base number of 100 mg KOH / g or less, (C): A boron-free succinimide-based dispersant and an ashless dispersant containing a boron-containing succinimide-based dispersant, (D): Contains an organic molybdenum compound, The content of the boron-containing succinimide-based dispersant is 0.025% to 0.050% by mass in terms of boron, relative to the total amount of the lubricating oil composition, and the total content of the boron-free succinimide-based dispersant and the boron-containing succinimide-based dispersant is 0.10% to 0.20% by mass in terms of nitrogen, relative to the total amount of the lubricating oil composition.

[0015] The lubricating oil composition according to this disclosure preferably further contains an ash-free antioxidant including a phenolic antioxidant and an amine-based antioxidant, and may optionally contain other additives.

[0016] The lubricating oil composition according to this disclosure, having the above configuration, contains an organic molybdenum compound and exhibits excellent fuel efficiency, piston cleaning properties, wear resistance, and corrosion prevention properties.

[0017] [(A): Lubricant base oil] The lubricating oil base oil is not particularly limited, and any base oil used in the field of lubricating oils for internal combustion engines can be used. The lubricating oil base oil may be included alone, or two or more types may be included in combination.

[0018] Specifically, the lubricating oil base oil may be one or more base oils selected from mineral oil-based base oils and synthetic base oils. For example, the lubricating oil base oil may be a base oil consisting of one mineral oil-based base oil, a mixed base oil consisting of two or more mineral oil-based base oils, a base oil consisting of one synthetic base oil, a mixed base oil consisting of two or more synthetic base oils, or a mixed base oil consisting of one or more mineral oil-based base oils and one or more synthetic base oils.

[0019] Examples of mineral oil-based base oils include base oils classified as API (American Petroleum Institute) Group I, obtained by combining processes such as atmospheric distillation, vacuum distillation, solvent desalination, solvent extraction, hydrorefining, and solvent dewaxing from crude oil; base oils classified as API Group II, obtained by combining processes such as hydrocracking and catalytic dewaxing; and base oils classified as API Group III, obtained by combining advanced hydrotreatment processes such as hydrocracking and hydroisomerization dewaxing.

[0020] Examples of synthetic base oils include isoparaffins synthesized from natural gas such as methane, α-olefin oligomers, dialkyldiesters, polyols, alkylbenzenes, polyglycols, and phenyl ethers. When applied to diesel engine oil, a synthetic base oil having the properties of a lubricating oil base oil typically used in diesel engine oil should be used as appropriate.

[0021] The kinematic viscosity of the lubricating base oil at 100 °C is preferably 3.0 m 2 / s to 7.0 mm 2 / s, more preferably 3.0 m 2 / s to 6.0 mm 2 / s, still more preferably 3.0 mm 2 / s to 5.0 mm 2 / s.

[0022] The kinematic viscosity of the lubricating base oil at 40 °C is not particularly limited, but from the viewpoints of fuel economy and volatility, 10 m 2 / s to 40 mm 2 / s is preferable, 15 m 2 / s to 35 mm 2 / s is more preferable, 20 m 2 / s to 30 mm 2 / s is still more preferable.

[0023] The kinematic viscosity of the lubricating base oil at 40 °C and 100 °C is preferably the above kinematic viscosity in any case of the base oil alone or the mixed base oil.

[0024] The kinematic viscosity of the lubricating base oil at 40 °C and 100 °C is measured in accordance with JIS K2283:2000 (ASTM D445).

[0025] The viscosity index of the lubricating base oil is not particularly limited, but is preferably 100 or more, more preferably 110 or more, and still more preferably 120 or more. When the viscosity index is within the above range, the viscosity change of the lubricating oil composition due to temperature becomes small, so that fuel economy is likely to be exhibited even at low temperatures.

[0026] The viscosity index of the lubricating base oil is measured in accordance with JIS K2283:2000 (ASTM D2270).

[0027] [(B): Metal detergent] The lubricating oil composition according to the present disclosure contains a metal detergent. The metal-based cleaning agent includes two or more metal-based cleaning agents X selected from the group consisting of (B-1): alkaline earth metal salicylate, (B-2): alkaline earth metal phenate, (B-3): alkaline earth metal sulfonate with a total base number of 250 mg KOH / g or more, and (B-4): alkaline earth metal sulfonate with a total base number of 100 mg KOH / g or less. The lubricating oil composition relating to this disclosure may contain metal-based detergents other than metal-based detergent X to the extent that the effects relating to this disclosure are achieved.

[0028] In the following, for convenience, the four types of metal-based cleaning agents (B-1) to (B-4) included in metal-based cleaning agent X will be referred to as "specific metal-based cleaning agent (B-1)," etc., and the metal-based cleaning agents included in these four types will be collectively referred to as "specific metal-based cleaning agent X."

[0029] In other words, the metal-based cleaning agent X in this disclosure is selected from at least two of four types of metal-based cleaning agents consisting of specific metal-based cleaning agents (B-1), (B-2), (B-3), and (B-4).

[0030] The combination of specific metal-based cleaning agents X only needs to be selected from four types consisting of specific metal-based cleaning agents (B-1), (B-2), (B-3), and (B-4), and the form of the combination may be any of those shown below. A combination of specific metal-based cleaning agents (B-1) and (B-2). A combination of specific metal-based cleaning agents (B-1) and (B-3). A combination of specific metal-based cleaning agents (B-1) and (B-4). A combination of specific metal-based cleaning agents (B-2) and (B-3). A combination of specific metal-based cleaning agents (B-2) and (B-4). A combination of specific metal-based cleaning agents (B-3) and (B-4). A combination of specific metal-based cleaning agents (B-1), (B-2), and (B-3). A combination of specific metal-based cleaning agents (B-1), (B-3), and (B-4). A combination of specific metal-based cleaning agents (B-2), (B-3), and (B-4). A combination of specific metal-based cleaning agents (B-1), (B-2), (B-3), and (B-4).

[0031] In any of the above combinations, the metal-based cleaning agents included in the specified metal-based cleaning agents (B-1), (B-2), (B-3), or (B-4) may be one type or two or more types.

[0032] The following provides further details about the specific metal-based cleaning agent X. The base number of the specific metal-based cleaning agent X is measured in accordance with the perchloric acid method in accordance with JIS-K-2501-7:2003.

[0033] (Specific metal-based cleaning agent (B-1): Alkaline earth metal salicylate) Examples of alkaline earth metals included in the specific metal-based cleaning agent (B-1), which is an alkaline earth metal salicylate, include calcium, magnesium, and barium, with calcium being preferred.

[0034] The base number of the alkaline earth metal salicylate, which is a specific metal-based detergent (B-1), is preferably 50 mg KOH / g to 350 mg KOH / g, more preferably 90 mg KOH / g to 300 mg KOH / g, even more preferably 130 mg KOH / g to 300 mg KOH / g, and even more preferably 160 mg KOH / g to 270 mg KOH / g.

[0035] (Specific metal-based cleaning agent (B-2): Alkaline earth metal phenate) Examples of alkaline earth metals included in the specific metal-based cleaning agent (B-2), which is an alkaline earth metal phenate, include calcium, magnesium, and barium, with calcium being preferred.

[0036] The base number of the alkaline earth metal phenate, which is a specific metal-based cleaning agent (B-2), is preferably 50 mg KOH / g to 350 mg KOH / g, more preferably 100 mg KOH / g to 300 mg KOH / g, and even more preferably 140 mg KOH / g to 270 mg KOH / g.

[0037] (Specific metal-based cleaning agent (B-3): Alkaline earth metal sulfonates with a total base number of 250 mg KOH / g or higher) Examples of alkaline earth metals included in the specific metal-based cleaning agent (B-3), which is an alkaline earth metal sulfonate, include calcium, magnesium, and barium, with calcium being preferred.

[0038] The base number of the alkaline earth metal sulfonate, which is a specific metal-based cleaning agent (B-3), is 250 mg KOH / g or more, more preferably 250 g KOH / g to 400 mg KOH / g, and even more preferably 300 g KOH / g to 400 mg KOH / g.

[0039] (Specific metal-based cleaning agent (B-4): Alkaline earth metal sulfonates with a total base number of 100 mg KOH / g or less) Examples of alkaline earth metals included in the specific metal-based cleaning agent (B-4), which is an alkaline earth metal sulfonate, include calcium, magnesium, and barium, with calcium being preferred.

[0040] The base number of the alkaline earth metal sulfonate, which is a specific metal-based cleaning agent (B-4), is 100 mg KOH / g or less, more preferably 50 mg KOH / g or less, and even more preferably 30 mg KOH / g or less.

[0041] From the viewpoint of fuel efficiency, piston cleaning, wear resistance, and corrosion prevention, the specific metal cleaner X preferably contains at least one of an alkaline earth metal salicylate and an alkaline earth metal sulfonate with a total base number of 250 mg KOH / g or more (i.e., at least one of the specific metal-based cleaners (B-1) and (B-3)). It may also contain both the specific metal-based cleaners (B-1) and (B-3). It is more preferable that the specific metal-based cleaner X contains at least one of the specific metal cleaners (B-1) and (B-3) and at least one of the specific metal-based cleaners (B-2) and (B-4).

[0042] The ratio of the total content of specific metal-based detergents (B-1) and (B-3) to the total amount of specific metal-based detergent X [((B-1)+(B-3)) / ((B-1)+(B-2)+(B-3)+(B-4))] is preferably 0.75 or higher, and more preferably 0.8 or higher, in terms of alkaline earth metals, from the viewpoint of piston cleaning performance.

[0043] The total content of the specific metal-based detergent X is preferably 0.18% to 0.24% by mass, and more preferably 0.20% to 0.22% by mass, in terms of alkaline earth metals, relative to the total amount of the lubricating oil composition, from the viewpoint of ensuring piston cleanliness and limiting sulfated ash content.

[0044] The alkaline earth metal content shall be determined by analytical values ​​obtained from ICP emission spectroscopy in accordance with JPI-5S-38-92.

[0045] [(C): Ashless dispersant] The lubricating oil composition relating to this disclosure contains (C-1): a boron-free succinimide-based dispersant and (C-2): an ashless dispersant including a boron-containing succinimide-based dispersant.

[0046] (C-1): Boron-free succinimide-based dispersants, and (C-2): Boron-containing succinimide-based dispersants, should each be selected from the corresponding dispersants, with one or more types to be chosen.

[0047] <(C-1): Boron-free succinimide-based dispersant> As a boron-free succinimide-based dispersant, a boron-free succinimide-based dispersant that is used in the field of lubricating oils for internal combustion engines can be used.

[0048] Examples of boron-containing succinimide-based dispersants include succinimide represented by the following formula (1) and succinimide represented by the following formula (2).

[0049] [ka]

[0050] In equations (1) and (2), R 1 and R 3 Each of these independently represents an alkyl group or an alkenyl group, R 2 represents an alkylene group. n represents an integer between 0 and 10.

[0051] The boron-free succinimide-based dispersant may be either a monotype succinimide such as the succinimide represented by formula (1), or a bistype succinimide such as the succinimide represented by formula (2). However, a bistype succinimide such as the succinimide represented by formula (2) is preferred because it is easier to obtain one with a weight-average molecular weight within a predetermined range.

[0052] The weight-average molecular weight (Mw) of the boron-free succinimide-based dispersant is preferably 3,000 to 20,000, more preferably 4,000 to 10,000, and even more preferably 5,000 to 10,000. A weight-average molecular weight within the above range of the boron-free succinimide-based dispersant is preferable because it improves wear prevention performance and low-temperature viscosity characteristics. In one embodiment, the boron-free succinimide-based dispersant is preferably a polyalkenyl succinimide having the above weight-average molecular weight.

[0053] The weight-average molecular weight (Mw) in this disclosure is measured using a Shodex GPC-101 measuring instrument (manufactured by Showa Denko Corporation), three Shodex GPC LF-804 measuring columns (manufactured by Showa Denko Corporation), a differential refractive detector, THF (tetrahydrofuran) as the mobile phase, a flow rate of 1 ml / min, a sample concentration of 1.0 mass% / vol, and an injection volume of 100 μL. The weight-average molecular weight is calculated from these measurement results using a molecular weight distribution curve prepared from a monodisperse polystyrene standard sample.

[0054] When a lubricating oil composition contains two or more boron-free succinimide-based dispersants, the content of the boron-free succinimide-based dispersants is the total content of the two or more boron-free succinimide-based dispersants.

[0055] <(C-2): Boron-containing succinimide-based dispersant> As a boron-containing succinimide-based dispersant, a succinimide-based dispersant containing boron, which is an ashless dispersant used in the field of lubricating oils for internal combustion engines, can be used.

[0056] Examples of boron-containing succinimide-based dispersants include succinimide represented by formula (1) or succinimide represented by formula (2), modified with boron compounds such as boric acid, boric anhydride, boron halides, boric acid esters, boric acid amides, and boron oxide, preferably with boric acid. For boron-containing succinimide-based dispersants, succinimide represented by formula (2), modified with a boron compound, is preferred in terms of its high dispersibility.

[0057] The B / N ratio of the boron-containing succinimide-based dispersant is 0.05 to 1.50, preferably 0.10 to 1.00, more preferably 0.20 to 0.80, and most preferably 0.30 to 0.60, from the viewpoint of wear prevention and corrosion prevention. The B / N ratio of a boron-containing succinimide dispersant refers to the mass ratio of the boron content to the nitrogen content in the boron-containing succinimide dispersant.

[0058] The weight-average molecular weight (Mw) of the boron-containing succinimide dispersant is not particularly limited, but from the viewpoint of dispersibility and low-temperature viscosity characteristics, it is preferably 1500 to 10000, more preferably 2000 to 8000, and even more preferably 3000 to 7000. In one embodiment, the boron-containing succinimide dispersant is preferably a boric acid-modified polyalkenyl succinimide having the above weight-average molecular weight.

[0059] The content of the boron-containing succinimide-based dispersant is 0.025% to 0.050% by mass, more preferably 0.030% to 0.040% by mass, in terms of boron, relative to the total amount of the lubricating oil composition.

[0060] When a lubricating oil composition contains two or more boron-containing succinimide-based dispersants, the content of the boron-containing succinimide-based dispersants is the total content of the two or more boron-containing succinimide-based dispersants.

[0061] The total content of (C-1): boron-containing succinimide-based dispersant and (C-2): boron-free succinimide-based dispersant is 0.10% to 0.20% by mass, preferably 0.10% to 0.17% by mass, and more preferably 0.10% to 0.14% by mass, based on nitrogen equivalent, relative to the total amount of the lubricating oil composition, from the viewpoint of fuel efficiency, piston cleaning performance, and corrosion prevention performance.

[0062] [(D): Organomolybdenum compounds] The lubricating oil composition relating to this disclosure contains (D): an organic molybdenum compound. The organic molybdenum compound may function as a friction modifier.

[0063] The organic molybdenum compound may be a single compound or a combination of two or more compounds.

[0064] As the organic molybdenum compound, organic molybdenum compounds used in the field of lubricating oils for internal combustion engines can be used. From the viewpoint of fuel efficiency, it is preferable to use at least one selected from the group consisting of molybdenum dialkyldithiophosphate, molybdenum dialkyldithiocarbamate, alkylamine molybdate salts, and organic molybdenum amides. Furthermore, from the viewpoint of piston cleanliness, it is more preferable to use a combination of two or more organic molybdenum compounds.

[0065] The preferred organic molybdenum compound is a combination of molybdenum dialkyldithiocarbamate or molybdenum dialkyldithiophosphate and an alkylamine salt of molybdate or an organic molybdenum amide.

[0066] In one embodiment, examples of organic molybdenum compounds include compounds represented by the following formula (3).

[0067] [ka]

[0068] In formula (3), R 4 ~R 7 Each of these independently represents a linear or branched hydrocarbon group having 4 to 18 carbon atoms. 1 , X 2 , Y 1 and Y 2 Each of these independently represents either an oxygen atom or a sulfur atom.

[0069] From the viewpoint of wear prevention and corrosion prevention, the content of the organic molybdenum compound is preferably 0.01% to 0.05% by mass, and more preferably 0.02% to 0.04% by mass, in terms of molybdenum, relative to the total amount of the lubricating oil composition.

[0070] When a lubricating oil composition contains two or more organic molybdenum compounds, the content of the organic molybdenum compounds is the total content of the two or more organic molybdenum compounds.

[0071] [(E): Ash-free antioxidant] The lubricating oil composition relating to this disclosure preferably contains (E) an ash-free antioxidant, (E-1) a phenolic antioxidant, and (E-2) an amine-based antioxidant.

[0072] (E-1): For phenolic antioxidants and (E-2): for amine antioxidants, one or more types should be selected from the applicable antioxidants.

[0073] <(E-1): Phenolic antioxidants> Examples of phenolic antioxidants include phenolic compounds that are known as antioxidants.

[0074] Examples of phenolic antioxidants include alkylphenol compounds, bisphenol compounds, and hindered phenol compounds. These compounds may be isomers with different numbers of carbon atoms or structures of the alkyl group.

[0075] As a phenolic antioxidant, for example, a hindered phenol represented by the following formula (4) is preferred.

[0076] [ka]

[0077] In formula (4), R 8 R represents a straight-chain or branched-chain hydrocarbon group having 1 to 30 carbon atoms. 8 The number of carbon atoms in the hydrocarbon group represented is preferably 4 to 24, and more preferably 7 to 18.

[0078] Examples of hindered phenols represented by formula (4) include isooctyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate and n-octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate.

[0079] In addition to the above, other examples of phenolic antioxidants include alkylphenols such as 2,6-di-tert-butyl-p-cresol and bisphenols such as 4,4'-methylenebis-(2,6-di-t-butylphenol).

[0080] <(E-2): Amine-based antioxidants> Examples of amine-based antioxidants include amine-based antioxidants that are known as antioxidants. Examples of amine-based antioxidants include aromatic amine compounds such as naphthylamines and dialkyldiphenylamines. Examples include diphenylamine, 4-benzylamine, 2-aminobiphenyl, naphthylamine, allylaniline, 4-aminobinephenyl, o-toluidine, m-toluidine, p-toluidine, aniline, allylamine, their alkylated derivatives, hindered amine compounds, and their alkenylated derivatives. These compounds may be isomers with different numbers of carbon atoms or structures of alkyl groups.

[0081] From the viewpoint of achieving a good balance between fuel efficiency, piston cleaning, and corrosion prevention, the content of (E-1): phenolic antioxidant and (E-2): amine antioxidant in the lubricating oil composition is preferably 0.5% to 1.5% by mass, and more preferably 0.5% to 1.0% by mass, relative to the total amount of the lubricating oil composition.

[0082] If a lubricating oil composition contains two or more phenolic antioxidants, the content of phenolic antioxidants is the total content of the two or more phenolic antioxidants. If a lubricating oil composition contains two or more amine-based antioxidants, the content of amine-based antioxidants is the total content of the two or more amine-based antioxidants.

[0083] From the viewpoint of piston cleaning, it is more preferable that the phenolic antioxidant be contained in 1% by mass or more of the total amount of the lubricating oil composition.

[0084] Furthermore, the ratio of the content of (E-2) amine-based antioxidant to the content of (E-1) phenol-based antioxidant in the lubricating oil composition ((E-2) / (E-1)) is preferably 0.3 or more and 1 or less by mass, more preferably 0.4 or more and 1 or less, and even more preferably 0.4 or more and 0.6 or less.

[0085] [(F): Other additives] The lubricating oil composition relating to this disclosure may contain other additives as needed.

[0086] Other additives include anti-wear agents, viscosity index improvers, pour point depressants, metal deactivators, friction modifiers, and defoamers.

[0087] Examples of anti-wear agents include zinc compounds such as zinc dialkyldithiophosphate (i.e., zinc-based anti-wear agents), phosphate esters, and the like.

[0088] Examples of viscosity index improvers include non-dispersive and dispersed viscosity index improvers as described in JASO M355:2021. Examples include polymethacrylate-based viscosity index improvers, ethylene propylene copolymers, styrene-isoprene copolymers, styrene-isoprene copolymer hydrides, and polyisobutylene.

[0089] Examples of pour point depressants include olefin copolymers, polyalkyl methacrylates, copolymers thereof, and alkylated derivatives thereof.

[0090] Examples of metal deactivators include thiadiazole derivatives, benzotriazole derivatives, and imidazole derivatives. Examples of antifoaming agents include silicone oils such as polydimethylsiloxane, alkylated polydimethylsiloxane derivatives, and halogenated alkylated polydimethylsiloxane derivatives.

[0091] When other additives are used, the content of these additives is preferably 10% to 25% by mass relative to the total amount of the lubricating oil composition.

[0092] (Physical properties of lubricating oil compositions for internal combustion engines) -Kinematic viscosity- The kinematic viscosity of the lubricating oil composition relating to this disclosure at 40°C is 25 mm². 2 / ~90mm 2 / s is preferred, 30mm 2 / ~70mm 2 / s is more preferable, 35-50mm 2 / s is even more preferable. The kinematic viscosity of the lubricating oil composition relating to this disclosure at 100°C is 12.5 mm². 2 Preferably less than / s, 6.9mm 2 / s~12.5mm 2 / s is more preferable, 8.1mm 2 / s~11.5mm 2 / s is even more preferable, 9.3 mm 2 / s~10.5mm 2 / s is particularly preferred.

[0093] The kinematic viscosity of the lubricating oil composition at 40°C and at 100°C shall be measured in accordance with JIS K2283:2000 (ASTM D445).

[0094] -Viscosity index- The viscosity index of the lubricating oil composition according to this disclosure is not particularly limited, but is preferably 140 to 300, more preferably 160 to 280, and most preferably 180 to 260.

[0095] The viscosity index of the lubricating oil composition shall be measured in accordance with JIS K 2283:2000 (ASTM D2270).

[0096] ―High-Temperature High-Shear Viscosity (HTHS Viscosity)― The high-temperature high-shear viscosity (HTHS100) of the lubricating oil composition according to this disclosure at 100°C is preferably 6.5 mPa·s or less, and more preferably 6.2 mPa·s or less, from the viewpoint of fuel efficiency.

[0097] The high-temperature high-shear viscosity (HTHS150) of the lubricating oil composition according to this disclosure at 150°C is preferably 2.6 mPa·s or higher, and more preferably 2.9 mPa·s or higher, from the viewpoint of wear prevention.

[0098] From the viewpoint of fuel efficiency, the ratio of the high-temperature high-shear viscosity (HTHS150) at 150°C to the high-temperature high-shear viscosity (HTHS100) at 100°C (HTHS100) of the lubricating oil composition according to this disclosure (HTHS150 / HTHS100) is preferably 0.45 or higher, and more preferably 0.47 or higher.

[0099] The high-temperature high-shear viscosity (HTHS150) at 150°C is measured in accordance with ASTM D4683. The high-temperature high-shear viscosity (HTHS100) at 100°C is measured in accordance with ASTM D6616.

[0100] -Sulfated ash- The sulfated ash content of the lubricating oil composition according to this disclosure is preferably 0.9% to 1.1% by mass relative to the total amount of the lubricating oil composition, from the viewpoint of piston cleanliness and compatibility with exhaust gas aftertreatment devices. The amount of sulfated ash shall be measured according to the method compliant with JIS K2272:1998.

[0101] [Uses of lubricating oil compositions for internal combustion engines] The lubricating oil composition according to this disclosure can be used as a lubricant for internal combustion engines such as diesel engines, gasoline engines, and gas engines in four-wheeled vehicles, power generation equipment, and marine vehicles, and is preferably used for diesel engines. When used for diesel engines, the lubricating oil composition according to this disclosure, while containing an organic molybdenum compound, exhibits excellent fuel efficiency, piston cleaning properties, wear resistance, and corrosion prevention properties.

[0102] [Method for preparing lubricating oil compositions for internal combustion engines] The method for preparing the lubricating oil composition according to this disclosure is not particularly limited, and the lubricating oil base oil and other constituent components may be mixed as appropriate. The mixing method and mixing order are not particularly limited, and the other constituent components may be mixed sequentially with the lubricating oil base oil. [Examples]

[0103] Examples are described below, but this disclosure is not limited to these examples.

[0104] [Examples 1-3, Comparative Examples 1-5] Lubricating oil base oil and various additives consisting of a metal-based detergent, an ashless dispersant, an ashless antioxidant (phenol-based antioxidant and amine-based antioxidant), an organic molybdenum compound, and other additives were prepared in the types shown in Table 1. The base oil and each additive were then mixed to the content (mass%) shown in Table 1 to prepare a lubricating oil composition.

[0105] <Base oil and additives> (A): Lubricant base oil ·API GroupIII, 100℃ kinematic viscosity: 4.2mm 2 Base oil with viscosity index: 122, and API Group III, kinematic viscosity at 100°C: 6.5 mm². 2 A mixture of base oils with a viscosity index of 131.

[0106] (B): Metal-based cleaner • Specific metal-based cleaning agent (B-1); calcium salicylate, base number: 225 mg KOH / g • Specific metal-based cleaning agent (B-2); calcium phenate, base number: 255 mg KOH / g • Specific metal-based cleaning agent (B-3); calcium sulfonate, base number 305 mg KOH / g • Specific metal-based cleaning agent (B-4); calcium sulfonate, base number 0 mg KOH / g

[0107] (C): Ashless dispersant • Ashless dispersant (C-1): Boric acid-modified polyalkenyl succinimide Mw: 6000 • Ashless dispersant (C-2); polyalkenyl succinate imide Mw: 6000 • Ashless dispersant (C-3); polyalkenyl succinimide Mw; 5000

[0108] (D): Organomolybdenum compounds • Organomolybdenum compound (D-1); molybdenum dialkyldithiocarbamate • Organomolybdenum compounds (D-2); molybdenum dialkyldithiophosphate • Organomolybdenum compounds (D-3); alkylamine molybdate salts • Organomolybdenum compounds (D-4); organomolybdenum amides

[0109] (E): Ash-free antioxidant • Phenolic antioxidant (E-1); Hindered phenol alkyl ester • Amine-based antioxidant (E-2); alkylated diphenylamine (F): Other additives (additives listed below) • Anti-wear agent • Viscosity index improver • Pour point depressant • Antifoaming agent

[0110] <Properties of the lubricating oil composition> • Kinematic viscosity at 40°C, kinematic viscosity at 100°C, and viscosity index: The kinematic viscosity at 40°C, the kinematic viscosity at 100°C, and the viscosity index were measured as specified in JIS K2283:2000. • High-temperature high-shear viscosity at 150℃ (HTHS150): The high-temperature, high-shear viscosity at 150°C, as specified in ASTM D4683, was measured. • High-temperature, high-shear viscosity at 100℃ (HTHS100): The high-temperature, high-shear viscosity at 100°C, as specified in ASTM D6616, was measured. ·Sulfated ash: The sulfated ash content was measured according to JIS K2272:1998.

[0111] <Evaluation>: Engine Test Evaluation tests were conducted using the lubricating oil compositions of Examples 1-3 and Comparative Examples 1-5 for piston cleanliness, wear resistance, corrosion prevention, and fuel efficiency.

[0112] 1. Piston cleanliness Piston cleanliness was evaluated based on two criteria: a WTD (Weighted Total Demerit) score and an underside (piston back surface) merit score.

[0113] 1-1.WTD • Evaluation method The piston cleanliness test was performed according to the JASO M336 standard. • Evaluation criteria Lubricating oil compositions with a total load disadvantage score of 550 or less were evaluated as having excellent cleaning properties.

[0114] 1-2. Underside • Evaluation method The piston cleanliness test was performed according to the JASO M336 standard. • Evaluation criteria Lubricating oil compositions with a merit score of 8.0 or higher were evaluated as having excellent cleaning properties.

[0115] 2. Wear resistance (tappet wear amount) • Evaluation method The evaluation was conducted using the valve train wear test specified in JASO M354. • Evaluation criteria Lubricating oil compositions with tappet wear of 9 μm or less were evaluated as having excellent wear resistance.

[0116] 3. Corrosion prevention (Cu content in oil after testing) • Evaluation method The amount of Cu in the lubricating oil composition after the piston cleanliness test was measured by ICP emission spectrometry as specified in JPI-5S-44-11. • Evaluation criteria Lubricating oil compositions with a Cu content of 30 ppm by mass or less were evaluated as having excellent corrosion prevention properties.

[0117] 4. Fuel efficiency • Evaluation method Using the Hino Motors, Ltd. "N04C-VH engine," the fuel efficiency improvement rate (%) compared to a control product was measured at 60°C and 90°C using a simulation method similar to the fuel efficiency test specified in JASO M362, and the evaluation was based on the average value (%) of the obtained measurements. A commercially available lubricating oil composition with an SAE viscosity grade of 10W-30 was used as the control product. • Evaluation criteria Lubricant compositions that showed a fuel efficiency improvement of 3.0% or more compared to the comparison product were evaluated as having superior fuel efficiency. In Table 1, the fuel efficiency improvement rates and average values ​​for 60°C and 90°C are shown in the columns "Fuel efficiency improvement rate compared to commercially available 10W-30 (60°C)", "Fuel efficiency improvement rate compared to commercially available 10W-30 (90°C)", and "Fuel efficiency improvement rate compared to commercially available 10W-30 (average)", respectively.

[0118] The results are shown in Table 1.

[0119] [Table 1]

[0120] In Table 1, a "-" in the composition column indicates that the corresponding ingredient is not included. In Table 1, the "B equivalent content / N equivalent content" shown in the column for ashless dispersant (C-1) indicates that the amount of ashless dispersant (C-1) added to the lubricating oil composition is such that the boron equivalent content and nitrogen equivalent content are equal to the values ​​shown in Table 1. In Table 1, "remainder" indicates that the base oil was added so that the total amount was 100% by mass.

[0121] As shown in Table 1, the lubricating oil composition of this embodiment contains an organic molybdenum compound and exhibits excellent fuel efficiency, piston cleaning properties, wear resistance, and corrosion prevention properties.

Claims

1. Lubricating oil base oil, A metal-based cleaning agent X is at least two selected from the group consisting of alkaline earth metal salicylates, alkaline earth metal phenates, alkaline earth metal sulfonates with a total base number of 250 mg KOH / g or more, and alkaline earth metal sulfonates with a total base number of 100 mg KOH / g or less. A boron-free succinimide-based dispersant and a boron-containing succinimide-based dispersant are included in this ashless dispersant, It contains an organic molybdenum compound, The content of the boron-containing succinimide-based dispersant is 0.025% to 0.050% by mass in terms of boron, relative to the total amount of the lubricating oil composition, and The total content of the boron-free succinimide-based dispersant and the boron-containing succinimide-based dispersant is 0.10% to 0.20% by mass in terms of nitrogen relative to the total amount of the lubricating oil composition. The total content of the alkaline earth metal salicylate, the alkaline earth metal phenate, the alkaline earth metal sulfonate with a total base number of 250 mg KOH / g or more, and the alkaline earth metal sulfonate with a total base number of 100 mg KOH / g or less is 0.18% to 0.24% by mass in terms of alkaline earth metals, relative to the total amount of the lubricating oil composition. Lubricating oil composition for internal combustion engines.

2. The lubricating oil composition for internal combustion engines according to claim 1, wherein the metal-based detergent X comprises at least one of the alkaline earth metal salicylate and the alkaline earth metal sulfonate having a total base number of 250 mg KOH / g or more.

3. The lubricating oil composition for an internal combustion engine according to claim 1, wherein the ratio of the total content of the alkaline earth metal salicylate and the alkaline earth metal sulfonate having a total base number of 250 mg KOH / g or more to the total amount of the metal-based detergent X in the lubricating oil composition is 0.75 or more in terms of alkaline earth metal.

4. Furthermore, the lubricating oil composition for internal combustion engines according to claim 1 further comprises a phenolic antioxidant and an amine-based antioxidant as ash-free antioxidants.

5. The lubricating oil composition for internal combustion engines according to claim 4, wherein the content of the phenolic antioxidant and the amine antioxidant is 0.5% by mass to 1.5% by mass, respectively, based on the total amount of the lubricating oil composition.

6. The lubricating oil composition for internal combustion engines according to claim 1, wherein the organic molybdenum compound is at least one selected from the group consisting of molybdenum dialkyldithiophosphate, molybdenum dialkyldithiocarbamate, alkylamine molybdate salts, and organic molybdenamides.

7. The lubricating oil composition for an internal combustion engine according to claim 1, wherein the content of the organic molybdenum compound is 0.01% to 0.05% by mass in terms of molybdenum relative to the total amount of the lubricating oil composition.

8. The lubricating oil composition for an internal combustion engine according to claim 1, wherein the amount of sulfated ash is 0.9% by mass to 1.1% by mass based on the total amount of the lubricating oil composition.

9. The kinematic viscosity at 100°C is 12.5 mm ２ The lubricating oil composition for an internal combustion engine according to claim 1, wherein the value is less than / s.

10. The lubricating oil composition for internal combustion engines according to claim 1, wherein the high-temperature high-shear viscosity (HTHS100) at 100°C is 6.5 mPa·s or less.

11. The lubricating oil composition for internal combustion engines according to claim 1, wherein the high-temperature high-shear viscosity (HTHS150) at 150°C is 2.6 mPa·s or more.

12. The lubricating oil composition for an internal combustion engine according to claim 1, wherein the ratio of the high-temperature high-shear viscosity at 150°C (HTHS150) to the high-temperature high-shear viscosity at 100°C (HTHS100) (HTHS150 / HTHS100) is 0.45 or more.

13. A lubricating oil composition for an internal combustion engine according to any one of claims 1 to 12, for use in a diesel engine.

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