Lubricant composition

Abstract

To provide a lubricant composition that has properties, such as emulsification resistance, suitable for an internal combustion engine that operates using hydrogen as a fuel.SOLUTION: A lubricant composition used in an internal combustion engine that operates using hydrogen as a fuel comprises: a base oil (A) with a NOACK value of 6 mass% or less; and a Ca-based detergent (B) that contains at least Ca salicylate (B1) and may optionally contain one or more selected from neutral Ca sulfonate (B2) and Ca phenate (B3), wherein a ratio [(b2) / (b)] of a content (b2) in terms of Ca atoms of a component (B2) to a content (b) in terms of Ca atoms of a component (B) is 0 to 0.40, a ratio [(b3) / (b)] of a content (b3) in terms of Ca atoms of a component (B3) to the content (b) in terms of Ca atoms of the component (B) is 0 to 0.02, CCS viscosity at -25°C is 7,000 mPa*s or less, and HTHS viscosity at 150°C is 2.9 mPa*s or more.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to lubricating oil compositions and methods for lubricating internal combustion engines. [Background technology]

[0002] Various demands are placed on internal combustion engines used in automobiles and the like, such as compactness and high output, fuel efficiency, and compliance with exhaust gas regulations, and lubricating oil compositions for use in internal combustion engines are being developed to meet these demands. For example, Patent Document 1 discloses a lubricating oil composition for internal combustion engines that contains a lubricating oil base oil, a predetermined amount, calculated as boron, of a boron-containing alkenyl succinimide and / or a boron-containing alkyl succinimide, and a poly(meth)acrylate having a weight-average molecular weight and an average carbon number of the alkyl group within a predetermined range, for the purpose of providing a lubricating oil composition for internal combustion engines that can suppress the occurrence of coking and copper elution while suppressing a decrease in base number. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2015-196696 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, for example, hydrogen fuel engines use hydrogen as fuel, so water is generated. The inclusion of this water may emulsify the lubricating oil composition. Hydrogen fuel engines need to discharge the generated water to the outside of the vehicle, but once emulsified, it becomes difficult to discharge it. Furthermore, emulsification may cause the lubricating oil composition to thicken, which may cause engine equipment failure. For this reason, there is a demand for a lubricating oil composition that has properties suitable for internal combustion engines that run on hydrogen as fuel, such as resistance to emulsification. [Means for solving the problem]

[0005] As a result of intensive research, the present inventors have found that the above problems can be solved by including a calcium-based detergent containing at least calcium salicylate. Specifically, the present invention discloses the following aspects. [1] A base oil (A) having a NOACK value of 6 mass% or less as measured in a NOACK test conducted in accordance with ASTM D5800 at 250 °C for 1 hour; and a calcium-based detergent (B) which contains at least calcium salicylate (B1) and may optionally contain one or more selected from a neutral calcium sulfonate (B2) and a calcium phenate (B3) having a base number of 70 mgKOH / g or less, the ratio [(b2) / (b)] of the content (b2) of the neutral calcium sulfonate (B2) in terms of calcium atoms to the content (b) of the calcium-based detergent (B) in terms of calcium atoms is 0 to 0.40; the ratio [(b3) / (b)] of the content (b3) of the calcium phenate (B3) in terms of calcium atoms to the content (b) of the calcium-based detergent (B) in terms of calcium atoms is 0 to 0.02; The CCS viscosity at -25°C is 7000 mPa s or less, The HTHS viscosity at 150°C is 2.9 mPa s or more. A lubricating oil composition for use in an internal combustion engine that runs on hydrogen as fuel. [2] A method for lubricating an internal combustion engine, comprising applying the lubricating oil composition according to [1] above to lubricate the internal combustion engine that runs on hydrogen as fuel. Effect of the Invention

[0006] The lubricating oil composition according to a preferred embodiment of the present invention has properties, such as emulsification resistance, that make it suitable for use in an internal combustion engine that runs on hydrogen as fuel. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0007] 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, for example, when a numerical range is described as "preferably 30 or more, more preferably 40 or more, and preferably 100 or less, more preferably 80 or less," the range of "30 to 80" and the range of "40 to 100" are also included in the numerical range described in this specification. In other words, in defining the upper and lower limits described in this specification, the numerical range from the lower limit to the upper limit can be defined by appropriately selecting from each option and combining them in any way. 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." In addition, various features described as preferred embodiments in this specification may be combined in multiple ways.

[0008] [Constitution of lubricating oil composition] A lubricating oil composition according to one embodiment of the present invention comprises a base oil (A) and a specified calcium-based detergent (B), and satisfies the following requirements (I) and (II). Requirement (I): The CCS viscosity at -25°C is 7000 mPa·s or less. Requirement (II): The HTHS viscosity at 150°C is 2.9 mPa·s or more.

[0009] A lubricating oil composition that satisfies requirement (I) provides good engine startability at low temperatures. A lubricating oil composition having a CCS viscosity at -25°C of more than 7000 mPa s tends to provide insufficient engine startability in low temperature environments. In this specification, the CCS viscosity at -25°C means a value measured at -25°C in accordance with ASTM D5293.

[0010] By making the lubricating oil composition satisfy the requirement (II), the oil film is easily maintained even at high temperatures, and the wear resistance is good. A lubricating oil composition having an HTHS viscosity of less than 2.9 mPa s at 150°C tends to have poor wear resistance. From the viewpoint of improving oil film retention in high-temperature environments and providing a lubricating oil composition with excellent wear resistance, the HTHS viscosity at 150°C of the lubricating oil composition of one embodiment of the present invention is preferably 3.0 mPa s or more, and more preferably 3.2 mPa s or more. In this specification, the HTHS viscosity at 150°C means a value measured at 150°C in accordance with ASTM D4683.

[0011] The lubricating oil composition of one embodiment of the present invention may further contain a viscosity index improver (C). Furthermore, the lubricating oil composition of one embodiment of the present invention may further contain other lubricating oil additives in addition to the above components (B) to (C) to the extent that the effects of the present invention are not impaired.

[0012] Each component contained in the lubricating oil composition according to one embodiment of the present invention will now be described in detail.

[0013] <Component (A): Base oil> The base oil (A) used in one embodiment of the present invention can be one or more oils selected from mineral oils and synthetic oils. Examples of mineral oils include atmospheric residual oils obtained by atmospheric distillation of crude oils such as paraffinic crude oil, intermediate crude oil, and naphthenic crude oil; distillate oils obtained by vacuum distillation of these atmospheric residual oils; and refined oils obtained by subjecting the distillate oils to one or more refining treatments such as solvent deasphalting, solvent extraction, hydrocracking, solvent dewaxing, catalytic dewaxing, and hydrorefining.

[0014] Examples of synthetic oils include poly-α-olefins such as α-olefin homopolymers and α-olefin copolymers (e.g., α-olefin copolymers having 8 to 14 carbon atoms, such as ethylene-α-olefin copolymers); isoparaffins; polyalkylene glycols; ester-based oils such as polyol esters, dibasic acid esters, and phosphate esters; ether-based oils such as polyphenyl ether; alkylbenzenes; alkylnaphthalenes; and synthetic oils (GTL) obtained by isomerizing wax produced from natural gas by the Fischer-Tropsch process or the like (GTL wax (Gas To Liquids WAX)).

[0015] The base oil (A) used in one embodiment of the present invention has a NOACK value adjusted to 6% by mass or less. By using a base oil (A) with a NOACK value of 6% by mass or less, it is difficult to mist even when used in a high-temperature environment, and the amount of coking derived from the misted components can be suppressed. As a result, a lubricating oil composition having a high effect of suppressing the occurrence of coking in a high-temperature environment can be obtained, and it can be suitably used in an internal combustion engine that runs on hydrogen as fuel. On the other hand, if the NOACK value of the base oil (A) used is more than 6% by mass, the prepared lubricating oil composition tends to easily mist and easily cause coking in a high-temperature environment. The NOACK value of the base oil (A) used in one embodiment of the present invention may be 6 mass % or less, 5 mass % or less, less than 5 mass %, 4 mass % or less, less than 4 mass %, 3 mass % or less, or less than 3 mass %, from the viewpoint of obtaining a lubricating oil composition having further improved mist resistance and a higher effect of suppressing the occurrence of coking. The NOACK value of the base oil (A) can be adjusted, for example, by removing light fractions by distillation. In this specification, the NOACK value means a value measured at 250° C. for 1 hour in accordance with ASTM D5800.

[0016] The base oil (A) used in one embodiment of the present invention has a kinematic viscosity at 40° C. of preferably 20 to 120 mm 2 / s, more preferably 25 to 100 mm 2 / s, more preferably 30 to 80 mm2 / s, more preferably 35 to 60 mm 2 / s. In this specification, the kinematic viscosity refers to a value measured in accordance with ASTM D445.

[0017] The viscosity index of the base oil (A) used in one embodiment of the present invention is preferably 80 or more, more preferably 100 or more, even more preferably 110 or more, and still more preferably 120 or more. In this specification, viscosity index means a value calculated in accordance with ASTM D2270.

[0018] The base oil (A) used in one embodiment of the present invention may be a single base oil or a mixed oil of two or more base oils. When a mixed oil is used, the NOACK value of the mixed oil may be within the above range. Therefore, the mixture may be a combination of base oils having a NOACK value of 6 mass% or less, or a combination of a base oil having a NOACK value of 6 mass% or less and a base oil having a NOACK value of more than 6 mass%. In addition, it is preferable that the kinematic viscosity and viscosity index of the mixed oil are within the above range.

[0019] In the lubricating oil composition of one embodiment of the present invention, the content of base oil (A) may be, based on the total amount (100 mass%) of the lubricating oil composition, 60 mass% or more, 65 mass% or more, 70 mass% or more, 75 mass% or more, or 80 mass% or more, and may be 99.9 mass% or less, 99.5 mass% or less, 99.0 mass% or less, 97.0 mass% or less, 95.0 mass% or less, or 92.0 mass% or less.

[0020] <Component (B): Calcium-based detergent> The lubricating oil composition of one embodiment of the present invention contains at least a calcium salicylate (B1), and optionally contains a calcium-based detergent (B) which may contain one or more selected from a neutral calcium sulfonate (B2) and a calcium phenate (B3) having a base number of 70 mgKOH / g or less. By including calcium salicylate (B1) as the calcium-based detergent (B), it is possible to obtain a lubricating oil composition with improved emulsification resistance. An internal combustion engine that runs on hydrogen as fuel (hereinafter also referred to as a "hydrogen fuel engine") generates water because hydrogen is used as fuel. The inclusion of this water may emulsify the lubricating oil composition. Hydrogen fuel engines need to discharge the generated water to the outside of the vehicle, but once emulsified, it becomes difficult to discharge it. Furthermore, emulsification can cause the lubricating oil composition to thicken, which can lead to malfunctions of engine equipment. In contrast, the lubricating oil composition of one embodiment of the present invention contains calcium salicylate (B1) to improve emulsification resistance, and therefore has a high effect of suppressing thickening due to the inclusion of water, making it suitable for use in hydrogen fuel engines.

[0021] The lubricating oil composition of one embodiment of the present invention may contain, as the calcium-based detergent (B), a neutral calcium sulfonate (B2) having a base number of 70 mgKOH / g or less and / or a calcium phenate (B3) in addition to the calcium salicylate (B1).

[0022] In the lubricating oil composition of one embodiment of the present invention, the content (b) of the calcium-based detergent (B) in terms of calcium atoms, based on the total amount (100 mass%) of the lubricating oil composition, may be, for example, 1500 ppm by mass or more, 2000 ppm by mass or more, or 2300 ppm by mass or more, or may be 2800 ppm by mass or less. In this specification, the calcium atom content means a value measured in accordance with ASTM D5185.

[0023] <Calcium Salicylate (B1)> An example of the calcium salicylate (B1) used in one embodiment of the present invention is a compound represented by the following general formula (b-1). [ka]

[0024] In the above general formula (b-1), each R is independently a hydrocarbon group having 1 to 18 carbon atoms. The hydrocarbon group that can be selected as R is, for example, an alkyl group having 1 to 18 carbon atoms.

[0025] The calcium salicylate (B1) used in one embodiment of the present invention may be an overbased calcium salicylate (B11) having a base number of 100 mg KOH / g or more, or a neutral calcium salicylate (B12) having a base number of less than 100 mg KOH / g, or these may be used in combination. In this specification, the base number refers to a value measured by a perchloric acid method in accordance with ASTM D2896.

[0026] The base number of the overbased calcium salicylate (B11) used in one embodiment of the present invention may be 120 mgKOH / g or more, 150 mgKOH / g or more, 170 mgKOH / g or more, or 200 mgKOH / g or more, and may be 400 mgKOH / g or less, or 350 mgKOH / g or less.

[0027] The base number of the neutral calcium salicylate (B12) used in one embodiment of the present invention may be 0 mgKOH / g or more, 10 mgKOH / g or more, 20 mgKOH / g or more, 30 mgKOH / g or more, or 40 mgKOH / g or more, or may be 70 mgKOH / g or less.

[0028] In the lubricating oil composition of one embodiment of the present invention, the ratio [(b1) / (b)] of the content (b1) of the calcium salicylate (B1) calculated in terms of calcium atoms to the content (b) of the calcium-based detergent (B) calculated in terms of calcium atoms may be 0.60 or more, 0.65 or more, or 0.70 or more, and may be 1.00 or less, 0.95 or less, 0.90 or less, or 0.85 or less.

[0029] In the lubricating oil composition of one embodiment of the present invention, the content of the overbased calcium salicylate (B11) is, based on the total amount (100 mass%) of the lubricating oil composition, 0.1 mass% or more, 0.5 mass% or more, 1.0 mass% or more, 1.5 mass% or more, 1.7 mass% or more, and is 10.0 mass% or less, 7.0 mass% or less, 5.0 mass% or less, 4.0 mass% or less.

[0030] In the lubricating oil composition of one embodiment of the present invention, the content of neutral calcium salicylate (B12) is, based on the total amount (100 mass%) of the lubricating oil composition, 1.0 mass% or more, 3.0 mass% or more, 5.0 mass% or more, 7.0 mass% or more, or 9.0 mass% or more, and is 20.0 mass% or less, 17.0 mass% or less, 15.0 mass% or less, or 12.0 mass% or less.

[0031] <Neutral calcium sulfonate (B2)> The lubricating oil composition of one embodiment of the present invention may contain, as the calcium-based detergent (B), a neutral calcium sulfonate (B2) having a base number of 70 mgKOH / g or less. However, the ratio [(b2) / (b)] of the content (b2) of the neutral calcium sulfonate (B2) calculated in terms of calcium atoms to the content (b) of the calcium-based detergent (B) calculated in terms of calcium atoms is 0 to 0.40. A lubricating oil composition in which the ratio [(b2) / (b)] exceeds 0.40 exhibits reduced emulsification resistance and there is concern about thickening due to the inclusion of water.

[0032] In the lubricating oil composition of one embodiment of the present invention, from the viewpoint of obtaining a lubricating oil composition with further improved emulsification resistance, the ratio [(b2) / (b)] may be 0.40 or less, 0.35 or less, or 0.30 or less, or may be 0 or more, 0.05 or more, or 0.10 or more, and from the viewpoint of particularly improving emulsification resistance, the ratio is preferably 0.15 or more, more preferably 0.20 or more.

[0033] The base number of the neutral calcium sulfonate (B2) used in one embodiment of the present invention is 70 mgKOH / g or less, and may be 0 mgKOH / g or more, 10 mgKOH / g or more, 20 mgKOH / g or more, 30 mgKOH / g or more, or 40 mgKOH / g or more.

[0034] An example of the neutral calcium sulfonate used in one embodiment of the present invention is a compound represented by the following general formula (b-2) and having a base number of 70 mgKOH / g or less. [ka]

[0035] In the above general formula (b-2), each R is independently a hydrocarbon group having 8 to 30 carbon atoms. Examples of the hydrocarbon group that can be selected as R include alkyl groups having 8 to 30 carbon atoms.

[0036] In the lubricating oil composition of one embodiment of the present invention, from the viewpoint of providing a lubricating oil composition with good emulsification resistance, the content of the neutral calcium sulfonate (B2) is, based on the total amount (100 mass%) of the lubricating oil composition, 8.0 mass% or less, 6.0 mass% or less, 5.0 mass% or less, 4.0 mass% or less, or 3.5 mass% or less, or may be 0 mass% or more, 0.5 mass% or more, 1.0 mass% or more, or 1.5 mass% or more.

[0037] ≪Calcium phenate (B3)≫ The lubricating oil composition of one embodiment of the present invention may contain calcium phenate (B3) as the calcium-based detergent (B). However, the ratio [(b3) / (b)] of the content (b3) of the calcium phenate (B3) calculated in terms of calcium atoms to the content (b) of the calcium-based detergent (B) calculated in terms of calcium atoms is 0 to 0.02. A lubricating oil composition in which the ratio [(b3) / (b)] exceeds 0.02 exhibits reduced emulsification resistance and is susceptible to increased viscosity due to the inclusion of water.

[0038] The calcium phenate (B3) used in one embodiment of the present invention includes an overbased calcium phenate (B31) having a base number of 100 mgKOH / g or more.

[0039] The base number of the overbased calcium phenate (B31) used in one embodiment of the present invention may be 120 mgKOH / g or more, 150 mgKOH / g or more, 170 mgKOH / g or more, or 200 mgKOH / g or more, and may be 400 mgKOH / g or less, or 350 mgKOH / g or less.

[0040] An example of the calcium phenate (B3) used in one embodiment of the present invention is a compound represented by the following general formula (b-3). [ka]

[0041] In the above general formula (b-3), R is each independently a hydrocarbon group having 8 to 30 carbon atoms, and y is an integer of 0 or greater. Examples of the hydrocarbon group that can be selected as R include alkyl groups having 8 to 30 carbon atoms.

[0042] <Overbased calcium sulfonate (B4)> The lubricating oil composition of one embodiment of the present invention may contain an overbased calcium sulfonate (B4) having a base number of 120 mgKOH / g or more, provided that the effects of the present invention are not impaired. The base number of the overbased calcium sulfonate (B4) may be 120 mgKOH / g or more, 150 mgKOH / g or more, 170 mgKOH / g or more, or 200 mgKOH / g or more, and may be 500 mgKOH / g or less, 400 mgKOH / g or less, or 350 mgKOH / g or less. However, from the viewpoint of obtaining a lubricating oil composition with good emulsification resistance, the content of such other metal compounds is preferably as small as possible. In the lubricating oil composition of one embodiment of the present invention, from the viewpoint of providing a lubricating oil composition with good emulsification resistance, the ratio of the content (b4) of the overbased calcium sulfonate (B4), calculated in terms of calcium atoms, to the content (b) of the calcium-based detergent (B), calculated in terms of calcium atoms, [(b4) / (b)] is preferably less than 0.10.

[0043] <Component (C): Viscosity index improver> The lubricating oil composition of one embodiment of the present invention may further contain a viscosity index improver (C). By containing the viscosity index improver (C), it is possible to obtain a lubricating oil composition having good fuel economy properties. The viscosity index improver used in one embodiment of the present invention may be used alone or in combination of two or more kinds. Examples of the viscosity index improver (C) used in one embodiment of the present invention include polymers such as non-dispersed polymethacrylate, dispersed polymethacrylate, olefin copolymers (e.g., ethylene-propylene copolymers, etc.), dispersed olefin copolymers, and styrene copolymers (e.g., styrene-diene copolymers, styrene-isoprene copolymers, etc.). The viscosity index improver (C) used in one embodiment of the present invention may be a comb polymer having a structure in which the main chain has many three-way branching points from which high molecular weight side chains emerge, or it may be a star polymer having a structure in which one atom, such as a carbon atom, is bonded to three or more chain polymers.

[0044] In the lubricating oil composition of one embodiment of the present invention, the content of the viscosity index improver (C), calculated as the resin content, based on the total amount (100 mass%) of the lubricating oil composition, from the viewpoint of obtaining a lubricating oil composition that can suppress the amount of coking, is preferably 0.40 mass% or less, more preferably 0.35 mass% or less, even more preferably 0.30 mass% or less, and may also be 0.01 mass% or more, 0.02 mass% or more, or 0.04 mass% or more.

[0045] The viscosity index improver (C) used in one embodiment of the present invention and the pour point depressant and antifoaming agent described below are often commercially available in the form of a solution dissolved in a diluent oil such as a mineral oil or a synthetic oil, taking into consideration handling properties and solubility in the base oil (A). However, the content of the viscosity index improver mentioned above means the content calculated as the resin content (solid content) excluding the diluent oil.

[0046] <Lubricant additives> The lubricating oil composition of one embodiment of the present invention may further contain other lubricating oil additives other than components (B) to (C) as necessary, provided that the effects of the present invention are not impaired. Examples of such lubricating oil additives include pour point depressants, antioxidants, friction modifiers, antiwear agents, metal deactivators, ashless dispersants, metal deactivators, and antifoaming agents. These lubricating oil additives may be used alone, or two or more of them may be used in combination.

[0047] [Pour point depressants] The lubricating oil composition of one embodiment of the present invention may further contain a pour point depressant. The pour point depressants may be used alone or in combination of two or more kinds. Examples of pour point depressants used in one embodiment of the present invention include polymethacrylates, alkylated aromatic compounds, copolymers of fumarate and vinyl acetate, and copolymers of ethylene and vinyl acetate, and polymethacrylates having a weight average molecular weight of 40,000 to 200,000 are preferred.

[0048] [Antioxidants] The lubricating oil composition of one embodiment of the present invention may further contain an antioxidant. The antioxidants may be used alone or in combination of two or more kinds. Examples of the antioxidant used in one embodiment of the present invention include amine-based antioxidants such as alkylated diphenylamine, phenylnaphthylamine, and alkylated phenylnaphthylamine; phenol-based antioxidants such as 2,6-di-t-butylphenol, 4,4'-methylenebis(2,6-di-t-butylphenol), isooctyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate, and n-octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate; and sulfur-based antioxidants such as phenothiazine, dioctadecyl sulfide, dilauryl-3,3'-thiodipropionate, and 2-mercaptobenzimidazole.

[0049] [Friction modifiers and anti-wear agents] The lubricating oil composition of one embodiment of the present invention may further contain a friction modifier or an anti-wear agent. The friction modifier or anti-wear agent may be used alone or in combination of two or more kinds. Examples of the friction modifier and anti-wear agent used in one embodiment of the present invention include sulfur-based compounds such as sulfurized olefins, dialkyl polysulfides, diaryl alkyl polysulfides, and diaryl polysulfides; phosphorus-based compounds such as phosphate esters, thiophosphate esters, phosphites, alkyl hydrogen phosphites, amine salts of phosphate esters, and amine salts of phosphites; organic molybdenum-based compounds such as molybdenum dithiocarbamate (MoDTC), molybdenum dithiophosphate (MoDTP), and amine salts of molybdenum acid; organic zinc-based compounds such as zinc dithiophosphate (ZnDTP) and zinc dithiocarbamate (ZnDTC); ashless friction modifiers such as amine compounds, fatty acid esters, fatty acid amides, fatty acids, aliphatic alcohols, aliphatic ethers, urea-based compounds, and hydrazide-based compounds; and the like.

[0050] [Metal deactivator] The lubricating oil composition of one embodiment of the present invention may further contain a metal deactivator. The metal deactivators may be used alone or in combination of two or more kinds. Examples of the metal deactivator used in one embodiment of the present invention include benzotriazole, triazole derivatives, benzotriazole derivatives, and thiadiazole derivatives.

[0051] [Ashless dispersant] The lubricating oil composition of one embodiment of the present invention may further contain an ashless dispersant from the viewpoint of improving dispersibility. The ashless dispersant may be used alone or in combination of two or more kinds. The ashless dispersant used in one embodiment of the present invention is preferably an alkenyl succinimide, and examples thereof include an alkenyl succinic acid bisimide represented by the following general formula (f-1) and an alkenyl succinic acid monoimide represented by the following general formula (f-2).

[0052] [ka]

[0053] In the above general formulas (f-1) and (f-2), R f1 , R f2 and R f3 are each independently an alkenyl group having a number average molecular weight (Mn) of 900 to 2,500. R f1 , R f2 and R f3 Examples of the alkenyl group that can be selected as the alkyl group include a polybutenyl group and a polyisobutenyl group. A f1 , A f2 and A f3 each independently represents an alkylene group having 2 to 5 carbon atoms. x1 is an integer from 2 to 6. x2 is an integer from 2 to 6.

[0054] The compound represented by the general formula (f-1) or (f-2) may be a modified alkenyl succinimide reacted with one or more selected from a boron compound, an alcohol, an aldehyde, a ketone, an alkylphenol, a cyclic carbonate, an epoxy compound, and an organic acid.

[0055] [Antifoaming agent] The lubricating oil composition of one embodiment of the present invention may further contain an antifoaming agent. The antifoaming agents may be used alone or in combination of two or more kinds. Examples of the defoaming agent used in one embodiment of the present invention include alkyl silicone defoaming agents, fluoro silicone defoaming agents, and fluoroalkyl ether defoaming agents.

[0056] [Properties of the lubricating oil composition] The lubricating oil composition of one embodiment of the present invention preferably has a kinematic viscosity at 40° C. of 10 to 150 mm 2 / s, more preferably 20 to 120 mm 2 / s, more preferably 30 to 110 mm 2 / s, more preferably 40 to 100 mm 2 / s, and even more preferably 50 to 90 mm 2 / s, particularly preferably 55 to 85 mm 2 / s.

[0057] The lubricating oil composition of one embodiment of the present invention preferably has a kinematic viscosity at 100°C of 9.5 mm 2 / s or more, and the upper limit is not particularly limited, but is, for example, 16.3 mm 2 / s may be less.

[0058] The viscosity index of the lubricating oil composition of one embodiment of the present invention is preferably 80 or greater, more preferably 100 or greater, more preferably 110 or greater, even more preferably 120 or greater, and even more preferably 130 or greater.

[0059] The base number (perchloric acid method) of the lubricating oil composition of one embodiment of the present invention may be 5.0 mgKOH / g or more, 7.0 mgKOH / g or more, 9.0 mgKOH / g or more, or 9.2 mgKOH / g or more, and may be 15.0 mgKOH / g or less, 12.0 mgKOH / g or less, or 10.0 mgKOH / g or less.

[0060] Using the lubricating oil composition of one embodiment of the present invention as a sample, a copper catalyst and 25 mL of distilled water were placed in a container containing 75 mL of sample in accordance with the test method of ASTM D 2619 "Standard Test Method for Hydrolytic Stability of Hydraulic Fluids (Beverage Bottle Method)", and the volume fraction of the emulsion layer measured by the procedure described in the Examples below is preferably 30 vol% or less, more preferably 28 vol% or less, and even more preferably 26 vol% or less.

[0061] [Uses of the lubricating oil composition] The lubricating oil composition according to one embodiment of the present invention has excellent emulsification resistance, and therefore the lubricating oil composition can prevent thickening of the lubricating oil composition due to contamination with water, thereby preventing problems in the equipment in which the lubricating oil composition is used. The lubricating oil composition of one embodiment of the present invention can be applied to various devices that can exhibit the above-mentioned characteristics, but can be suitably used for lubrication between each part in an internal combustion engine. Among internal combustion engines, it can be more suitably used for lubrication between each part in an internal combustion engine (hydrogen fuel engine) that operates using hydrogen as fuel. Hydrogen fuel engines use hydrogen as fuel, so water is easily mixed into the lubricating oil composition. This mixing of water may cause the lubricating oil composition to emulsify. Hydrogen fuel engines need to discharge the generated water to the outside of the vehicle, but if the water emulsifies, it becomes difficult to discharge it. In addition, emulsification causes thickening of the lubricating oil composition, which can also cause defects in engine equipment. In contrast, the lubricating oil composition of one embodiment of the present invention exhibits excellent emulsification resistance and can suppress thickening due to mixing of water, so that troubles in hydrogen fuel engines can be prevented in advance.

[0062] In addition, the lubricating oil composition of one embodiment of the present invention can be suitably used for lubrication of hydrogen fuel engines equipped with turbochargers, among hydrogen fuel engines. In a hydrogen fuel engine equipped with a turbocharger, the inside of the combustion chamber becomes very hot because the fuel is hydrogen, and the environment is such that the lubricating oil composition is easily misted. The misted lubricating oil composition is discharged to the turbine wheel of the turbocharger installed on the exhaust passage side, but adheres to the turbine wheel and causes coking. In contrast, the lubricating oil composition of one embodiment of the present invention has excellent mist resistance in a high-temperature environment, so that even when used in a hydrogen fuel engine equipped with a turbocharger, the amount of the lubricating oil composition adhering to the turbine wheel can be suppressed, and the occurrence of coking can be effectively suppressed.

[0063] In consideration of the above-mentioned characteristics of the lubricating oil composition of one embodiment of the present invention, the present invention can also provide the following [I]. [I] A method for lubricating an internal combustion engine, comprising applying the lubricating oil composition according to one embodiment of the present invention to the lubrication of a hydrogen fuel engine. The hydrogen fuel engine described in [I] above is, for example, one equipped with a turbocharger. This makes it possible to prevent equipment trouble caused by water being mixed into the lubricating oil composition.

[0064] As described above, the present invention discloses the following aspects. [1] A base oil (A) having a NOACK value of 6 mass% or less as measured in a NOACK test conducted in accordance with ASTM D5800 at 250 °C for 1 hour; and a calcium-based detergent (B) which contains at least calcium salicylate (B1) and may optionally contain one or more selected from a neutral calcium sulfonate (B2) and a calcium phenate (B3) having a base number of 70 mgKOH / g or less, the ratio [(b2) / (b)] of the content (b2) of the neutral calcium sulfonate (B2) in terms of calcium atoms to the content (b) of the calcium-based detergent (B) in terms of calcium atoms is 0 to 0.40; the ratio [(b3) / (b)] of the content (b3) of the calcium phenate (B3) in terms of calcium atoms to the content (b) of the calcium-based detergent (B) in terms of calcium atoms is 0 to 0.02; The CCS viscosity at -25°C is 7000 mPa s or less, The HTHS viscosity at 150°C is 2.9 mPa s or more. A lubricating oil composition for use in an internal combustion engine that runs on hydrogen as fuel. [2] The lubricating oil composition according to the above item [1], further comprising a viscosity index improver (C), the content of which, calculated as a resin content, is 0.40 mass% or less based on the total amount of the lubricating oil composition. [3] The lubricating oil composition according to [1] or [2] above, which is used in an internal combustion engine equipped with a turbocharger and running on hydrogen as fuel. [4] A method for lubricating an internal combustion engine, comprising applying the lubricating oil composition according to any one of the above [1] to [3] to lubricate the internal combustion engine that runs on hydrogen as fuel. [5] The method for lubricating an internal combustion engine according to [4] above, wherein the internal combustion engine is equipped with a turbocharger. EXAMPLES

[0065] 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 various physical properties are as follows.

[0066] (1)Kinematic viscosity Measured in accordance with ASTM D445. (2) Viscosity index Calculations were made in accordance with ASTM D2270. (3) NOACK value Measured at 250°C for 1 hour in accordance with ASTM D5800. (4) Calcium atom (Ca) content Measured in accordance with ASTM D5185. (5) CCS viscosity (-25℃) Measured at -25°C according to ASTM D5293. (6)HTHS viscosity (150℃) Measured at 150°C according to ASTM D4683. (7) Base number (perchloric acid method) Measured by the perchloric acid method in accordance with ASTM D2896.

[0067] Examples 1 to 8, Comparative Examples 1 to 8 The components shown in Table 1 or 2 were added in the amounts shown in the same table and thoroughly mixed to prepare lubricating oil compositions. The base oils and various additives used in the examples and comparative examples are as follows. <Base oil> "Base oil": Mineral oil classified as Group III of API base oil category, kinematic viscosity at 40℃ = 41.58mm 2 / s, 100℃ kinematic viscosity=7.307mm 2 / s, viscosity index = 141, NOACK value = 2.9 mass%. <Various additives> "Overbased Ca salicylate (1)": Calcium salicylate with a base number (perchloric acid method) of 170 mg KOH / g, Ca content of 6.1 mass%. "Overbased Ca salicylate (2)": Calcium salicylate with a base number (perchloric acid method) of 225 mg KOH / g, Ca content of 8.0 mass%. "Overbased Ca salicylate (3)": Calcium salicylate with a base number (perchloric acid method) of 350 mg KOH / g, Ca content of 12.1% by mass. "Neutral Ca salicylate": Calcium salicylate with a base number (perchloric acid method) of 64 mg KOH / g, Ca content of 2.3 mass%. "Overbased Ca sulfonate (1)": Calcium sulfonate with base number (perchloric acid method) = 307 mg KOH / g, Ca content = 11.9 mass%. "Overbased Ca sulfonate (2)": Calcium sulfonate with base number (perchloric acid method) = 300 mg KOH / g, Ca content = 11.6 mass%. "Overbased Ca sulfonate (3)": Calcium sulfonate with a base number (perchloric acid method) of 425 mg KOH / g, Ca content of 16.0 mass%. "Neutral Ca sulfonate": Calcium sulfonate with base number (perchloric acid method) = 19 mg KOH / g, Ca content = 2.4 mass%. "Overbased Ca phenate": Calcium phenate with base number (perchloric acid method) = 250 mg KOH / g, Ca content = 9.3 mass%. - "Viscosity index improver": A solution of hydrogenated styrene-diene copolymer diluted with a diluent oil classified as Group I of the API base oil category, resin content = 10.7% by mass. "Pour point depressant": Polymethacrylate (VISCOPLEX 1-500 (EVONIK)) ·Additive Blend: JASO DH-2 additive package containing antioxidants, ashless dispersants, antiwear agents, and antifoam agents.

[0068] The lubricating oil compositions thus prepared were subjected to the following hydrolytic stability tests, the results of which are shown in Tables 1 and 2. [Hydrolytic stability test] The prepared lubricating oil composition was used as a sample, and in accordance with the test method of ASTM D 2619 "Standard Test Method for Hydrolytic Stability of Hydraulic Fluids (Beverage Bottle Method)", a copper catalyst and 25 mL of distilled water were placed in a container containing 75 mL of sample, and the temperature was raised to 93 ° C. and the container was rotated while being held for 48 hours. After that, it was cooled to room temperature (25 ° C.), and the liquid in the container was transferred to a graduated cylinder and left to stand for 24 hours. After standing, the total amount of the oil layer, water layer, and emulsion layer was set to 100 volume %, and the volume ratio of each layer was measured. The smaller the volume fraction of the emulsion layer, the more excellent the emulsification resistance of the lubricating oil composition. In this example, a lubricating oil composition having a volume fraction of the emulsion layer of 30 volume % or less was determined to have good emulsification resistance.

[0069] [Table 1]

[0070] [Table 2]

[0071] As can be seen from Table 1, the lubricating oil compositions prepared in Examples 1 to 8 had a low emulsion layer volume fraction in the hydrolysis stability test, resulting in excellent emulsification resistance. On the other hand, as can be seen from Table 2, the lubricating oil compositions prepared in Comparative Examples 1 to 8 had a high emulsion layer volume fraction in the hydrolysis stability test, resulting in poor emulsification resistance.

Claims

1. A base oil (A) having a NOACK value of 6 mass% or less as measured by a NOACK test performed in accordance with ASTM D5800 at 250°C for 1 hour; and a calcium-based detergent (B) which contains at least calcium salicylate (B1) and may optionally contain one or more selected from a neutral calcium sulfonate (B2) and a calcium phenate (B3) having a base number of 70 mgKOH / g or less, the ratio (b2) of the content (b2) of the neutral calcium sulfonate (B2), calculated in terms of calcium atoms, to the content (b) of the calcium-based detergent (B), calculated in terms of calcium atoms, [(b2) / (b)] is 0 to 0.40; the ratio [(b3) / (b)] of the content (b3) of the calcium phenate (B3) in terms of calcium atoms to the content (b) of the calcium-based detergent (B) in terms of calcium atoms is 0 to 0.02; The CCS viscosity at −25° C. is 7000 mPa s or less, The HTHS viscosity at 150°C is 2.9 mPa·s or more. A lubricating oil composition for use in an internal combustion engine that runs on hydrogen as fuel.

2. 2. The lubricating oil composition according to claim 1, further comprising a viscosity index improver (C), the content of which, calculated as a resin content, is 0.40 mass% or less based on the total amount of the lubricating oil composition.

3. 3. The lubricating oil composition according to claim 1, which is used in an internal combustion engine equipped with a turbocharger and running on hydrogen as fuel.

4. 3. A method for lubricating an internal combustion engine, comprising applying the lubricating oil composition according to claim 1 or 2 to lubricate the internal combustion engine which runs on hydrogen as fuel.

5. 5. The method of claim 4, wherein the engine comprises a turbocharger.