Lubricating oil composition

Abstract

There has been a demand for a lubricating oil composition that exhibits excellent separability with respect to water (emulsification resistance).　This lubricating oil composition is for use in an internal combustion engine that operates using hydrogen as a fuel. The lubricating oil composition comprises: a base oil (A); a calcium-based detergent (B); a polyoxyalkylene glycol compound (C) represented by general formula (1); and at least one imide compound (D) selected from the group consisting of compounds represented by general formulae (2) and (3). The polyoxyalkylene glycol compound (C) contains EO units in an amount of 65 mol% or less with respect to the total amount of EO units and PO units. The contained amount of the imide compound (D) is 1.50 mass% or more.

Description

lubricating oil composition

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

[0002] Technological development of internal combustion engines that run on hydrogen as fuel (hereinafter also referred to as "hydrogen-fueled engines") for use in automobiles and the like is progressing (see, for example, Patent Document 1). In hydrogen-fueled engines, water is generated because hydrogen is used as fuel. While it is conceivable that the generated water could be discharged outside the vehicle, if this water gets mixed into a lubricating oil composition, the lubricating oil composition may become emulsified, making it difficult to discharge the water.

[0003] Japanese Patent Application Laid-Open No. 2008-137505

[0004] In view of these circumstances, there is a demand for lubricating oil compositions that have excellent water separation properties (hereinafter also referred to as "anti-emulsification properties").

[0005] After extensive research, the present inventors have found that the above-mentioned problems can be solved by blending a calcium-based detergent, a polyoxyalkylene glycol compound having a specific structure, and a predetermined amount of an imide compound having a specific structure into a lubricating oil composition. Specifically, the present invention discloses the following aspects. [1] A lubricating oil composition for use in an internal combustion engine running on hydrogen fuel, comprising: a base oil (A), a calcium-based detergent (B), a polyoxyalkylene glycol compound (C) represented by the following general formula (1), and one or more imide compounds (D) selected from the group consisting of compounds represented by the following general formulas (2) and (3), wherein the polyoxyalkylene glycol compound (C) has an EO unit content of 65 mol % or less relative to the total amount of EO units and PO units, and the imide compound (D) content is 1.50 mass % or more. (In the general formula (1), E represents an ethylene group, P represents a propylene group, a and c each independently represent a number of 0 or more, and b represents a number of 1 or more.) (In the general formulas (2) and (3), R Ａ , R Ａ１ and R Ａ２ are each independently an alkenyl group having a weight average molecular weight of 500 to 4,000. Ｂ , R Ｂ１and R Ｂ２ are each independently an alkylene group having 2 to 5 carbon atoms. X1 and X2 are each independently an integer of 1 to 10.) [2] The lubricating oil composition according to [1], wherein the calcium-based detergent (B) contains calcium salicylate (B1). [3] The lubricating oil composition according to [1] or [2], wherein the calcium-based detergent (B) is substantially free of calcium sulfonate (B2) and calcium phenate (B3). [4] The lubricating oil composition according to any one of [1] to [3], wherein the content of the calcium-based detergent (B) is 0.10 to 10.0 mass%. [5] The lubricating oil composition according to any one of [1] to [4], wherein the content of the polyoxyalkylene glycol compound (C) is 0.001 mass% to 0.1 mass%. [6] The lubricating oil composition according to any one of [1] to [5], wherein the content of the imide compound (D) is 10.0 mass% or less. [7] The lubricating oil composition according to any one of [1] to [6], further comprising one or more imide compounds (E) selected from the group consisting of compounds represented by the following general formulas (4) and (5): (In the general formulas (4) and (5), R Ａ , R Ａ１ and R Ａ２ are each independently an alkenyl group having a weight average molecular weight of 500 to 4,000. Ｂ , R Ｂ１ and R Ｂ２ are each independently an alkylene group having 2 to 5 carbon atoms. Ｃis an alkyl group having 1 to 10 carbon atoms, or a group represented by -(AO)n-H (wherein A is an alkylene group having 2 to 4 carbon atoms, and n is an integer of 1 to 10). X1 and X2 each independently represent an integer of 1 to 10. [8] The lubricating oil composition according to any one of [1] to [7], wherein the content ratio of the calcium-based detergent (B) to the polyoxyalkylene glycol compound (C) [component (C) / component (B)] is 0.15 or less, in mass ratio. [9] The lubricating oil composition according to any one of [1] to [8], wherein the content ratio of the polyoxyalkylene glycol compound (C) to the imide compound (D) [component (C) / component (D)] is 0.10 or less, in mass ratio.

[10] The lubricating oil composition according to any one of [1] to [9], wherein the content ratio of the imide compound (D) to the imide compound (E) [component (D) / component (E)] is 10.0 or less in mass ratio.

[0006] A preferred embodiment of the present invention provides a lubricating oil composition having excellent demulsibility, and therefore, the lubricating oil composition of a preferred embodiment of the present invention can be suitably used in, for example, an internal combustion engine that runs on hydrogen as fuel.

[0007] Regarding the numerical ranges described herein, the upper and lower limits can be arbitrarily combined. For example, when a numerical range is described as "preferably 30 to 100, more preferably 40 to 80," the ranges "30 to 80" and "40 to 100" are also included in the numerical ranges described herein. Furthermore, 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 ranges "30 to 80" and "40 to 100" are also included in the numerical ranges described herein. In other words, when specifying the upper and lower limits described herein, the numerical range from the lower limit to the upper limit can be specified by appropriately selecting from the respective options and combining them arbitrarily. Furthermore, as a numerical range described herein, for example, "60 to 100" means a range of "60 or more (60 or more) and 100 or less (100 or less)." In addition, multiple combinations of the various requirements described as preferred aspects described herein can be used.

[0008] [Constitution of Lubricating Oil Composition] The lubricating oil composition of the present invention contains a base oil (A) (hereinafter also referred to as "component (A)"), a calcium-based detergent (B) (hereinafter also referred to as "component (B)"), a polyoxyalkylene glycol compound (C) (hereinafter also referred to as "component (C)") represented by general formula (1), and one or more imide compounds (D) (hereinafter also referred to as "component (D)") selected from the group consisting of compounds represented by general formulas (2) and (3). In the present invention, to address the problem of emulsification of lubricating oil compositions caused by water contamination in hydrogen fuel engines, the polyoxyalkylene glycol compound (C) having a specific structure is blended, and a predetermined amount of an imide compound (D) having a specific structure is blended, thereby improving demulsification performance. Therefore, the lubricating oil composition of the present invention can discharge water and does not significantly impair lubricity even if water is mixed in and emulsifies, making it suitable for use in hydrogen fuel engines. Note that the lubricating oil composition of one embodiment of the present invention may further contain other lubricating oil additives other than components (B) to (D) as necessary, within a range that does not impair the effects of the present invention. Hereinafter, each component contained in the lubricating oil composition of one embodiment of the present invention will be described in detail.

[0009] <Component (A): Base Oil> The base oil (A) used in one embodiment of the present invention can be one or more selected from mineral oils and synthetic oils. Examples of mineral oils include atmospheric residues obtained by atmospheric distillation of crude oils such as paraffinic crude oil, intermediate crude oil, and naphthenic crude oil; distillates obtained by vacuum distillation of these atmospheric residues; and refined oils obtained by subjecting the distillates to one or more refining treatments such as solvent deasphalting, solvent extraction, hydrocracking, solvent dewaxing, catalytic dewaxing, and hydrorefining.

[0010] 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; monoesters, diesters; ethers; alkylbenzenes; alkylnaphthalenes; 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)), and synthetic oils (Ethylene to Liquid (ETL)) obtained by oligomerizing olefins produced using gas as a raw material. These synthetic oils are preferably produced from renewable resources.

[0011] The kinematic viscosity at 100°C of the base oil (A) used in one embodiment of the present invention is 10.0 mm ２ / s or more, 11.0mm ２ / s or more, or 12.0 mm ２ / s or more, and the upper limit is not particularly limited, but for example, 16.5 mm ２ / s or less, 15.5mm ２ / s, or 15.0 mm ２ / s or less.

[0012] The viscosity index of the base oil (A) used in one embodiment of the present invention is preferably at least 90, more preferably at least 100, and even more preferably at least 110. In this specification, kinematic viscosity refers to a value measured or calculated in accordance with ASTM D445, and viscosity index refers to a value measured or calculated in accordance with ASTM D2270.

[0013] 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 kinematic viscosity and viscosity index of the mixed oil are preferably within the above-mentioned ranges.

[0014] In the lubricating oil composition of one embodiment of the present invention, the content of base oil (A) may be 60.00 mass% or more, 65.00 mass% or more, 70.00 mass% or more, 75.00 mass% or more, or 80.00 mass% or more, based on the total amount (100 mass%) of the lubricating oil composition, and may be 99.90 mass% or less, 99.50 mass% or less, 99.00 mass% or less, 97.00 mass% or less, 95.00 mass% or less, or 92.00 mass% or less.

[0015] <Component (B): Calcium-Based Detergent> The lubricating oil composition of one embodiment of the present invention contains a calcium-based detergent (B). The calcium-based detergent is an essential component for obtaining a lubricating oil composition with good demulsibility. Examples of the calcium-based detergent (B) used in one embodiment of the present invention include calcium salicylate (B1), calcium sulfonate (B2), and calcium phenate (B3). Among these, from the viewpoint of obtaining a lubricating oil composition with improved demulsibility, it is preferable to contain calcium salicylate (B1) as the calcium-based detergent (B).

[0016] In the lubricating oil composition of one embodiment of the present invention, the content of the calcium-based detergent (B) in terms of calcium atoms may be, for example, 900 ppm by mass or more, 1100 ppm by mass or more, or 1200 ppm by mass or more, or 1600 ppm by mass or less, based on the total amount of the lubricating oil composition. In this specification, the calcium atom content means the value measured in accordance with ASTM D5185.

[0017] In the lubricating oil composition of one embodiment of the present invention, the content of the calcium-based detergent (B) may be, for example, 0.10 mass % or more, 0.50 mass % or more, or 1.00 mass % or more, based on the total amount (100 mass %) of the lubricating oil composition, and may be 10.0 mass % or less, 8.00 mass % or less, or 6.00 mass % or less.

[0018] <Calcium Salicylate (B1)> Examples of the calcium salicylate (B1) used in one embodiment of the present invention include compounds represented by the following general formula (b-1).

[0019] In the general formula (b-1), each R is independently 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.

[0020] 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 mgKOH / g or more, or a neutral calcium salicylate (B12) having a base number of less than 100 mgKOH / g, or a combination of these. In this specification, the base number of the calcium-based detergent (B) means a value measured by the perchloric acid method in accordance with ASTM D2896.

[0021] 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 400 mgKOH / g or less, or 350 mgKOH / g or less. 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, and 70 mgKOH / g or less.

[0022] In the lubricating oil composition of one embodiment of the present invention, the content of the overbased calcium salicylate (B11) may be 0.50 mass % or more, 1.00 mass % or more, or 1.50 mass % or more, based on the total amount (100 mass %) of the lubricating oil composition, from the viewpoint of obtaining a lubricating oil composition with improved demulsibility; and may be 10.0 mass % or less, 5.00 mass % or less, or 3.00 mass % or less, from the viewpoint of obtaining a lubricating oil composition with good lubricity.

[0023] In the lubricating oil composition of one embodiment of the present invention, the content of neutral calcium salicylate (B12) may be 1.00% by mass or more, 1.50% by mass or more, 3.00% by mass or more, or 5.00% 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 improved demulsibility; and may be 10.0% by mass or less, 8.00% by mass or less, or 6.00% by mass or less, from the viewpoint of obtaining a lubricating oil composition with good lubricity.

[0024] Even when the content of EO units in the polyoxyalkylene glycol compound of component (C) relative to the total amount of EO units and PO units exceeds 65 mol %, a lubricating oil composition with excellent demulsibility can be obtained by blending 5.0 mass % or more of neutral calcium salicylate (B12).

[0025] In the lubricating oil composition of one embodiment of the present invention, when an overbased calcium salicylate (B11) and a neutral calcium salicylate (B12) are used in combination, the content of calcium salicylate (B1) may be 1.00 mass % or more, 1.50 mass % or more, or 2.00 mass % or more based on the total amount (100 mass %) of the lubricating oil composition; and from the viewpoint of obtaining a lubricating oil composition with good lubricity, it may be 10.0 mass % or less, 8.00 mass % or less, or 6.00 mass % or less.

[0026] <Calcium Sulfonate (B2)> Examples of the calcium sulfonate (B2) used in one embodiment of the present invention include compounds represented by the following general formula (b-2):

[0027] In the general formula (b-2), each R is independently a hydrocarbon group having 8 to 30 carbon atoms. Examples of hydrocarbon groups that can be selected as R include alkyl groups having 8 to 30 carbon atoms.

[0028] The calcium sulfonate (B2) used in one embodiment of the present invention may be an overbased calcium sulfonate (B21) having a base number of 100 mgKOH / g or more, or a neutral calcium sulfonate (B22) having a base number of less than 100 mgKOH / g, but is preferably an overbased calcium sulfonate (B21).

[0029] The base number of the overbased calcium sulfonate (B21) used in one embodiment of the present invention may be 150 mgKOH / g or more, 200 mgKOH / g or more, 225 mgKOH / g or more, or 300 mgKOH / g or more, and may be 400 mgKOH / g or less, or 350 mgKOH / g or less.

[0030] In the lubricating oil composition of one embodiment of the present invention, the content of the overbased calcium sulfonate (B21) may be 0.50% by mass or more, 0.80% by mass or more, or 1.00% 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 improved demulsibility; and from the viewpoint of obtaining a lubricating oil composition with good lubricity, the content may be 10.0% by mass or less, 5.00% by mass or less, or 3.00% by mass or less.

[0031] <Calcium Phenate (B3)> Examples of the calcium phenate (B3) used in one embodiment of the present invention include compounds represented by the following general formula (b-3).

[0032] In the general formula (b-3) above, R is independently a hydrocarbon group having 8 to 30 carbon atoms, and y is an integer of 0 or greater. Examples of hydrocarbon groups that can be selected as R include alkyl groups having 8 to 30 carbon atoms.

[0033] The calcium phenate (B3) used in one embodiment of the present invention may be an overbased calcium phenate (B31) having a base number of 100 mgKOH / g or more, or a neutral calcium phenate (B32) having a base number of less than 100 mgKOH / g, but is preferably an overbased calcium phenate (B31).

[0034] The base number of the overbased calcium phenate (B31) used in one embodiment of the present invention may be 150 mgKOH / g or more, 170 mgKOH / g or more, 200 mgKOH / g or more, or 220 mgKOH / g or more, and may be 400 mgKOH / g or less, or 350 mgKOH / g or less.

[0035] In the lubricating oil composition of one embodiment of the present invention, the content of the overbased calcium phenate (B31) may be 0.50 mass % or more, 0.80 mass % or more, or 1.00 mass % or more, based on the total amount (100 mass %) of the lubricating oil composition, from the viewpoint of obtaining a lubricating oil composition with improved demulsibility; and may be 10.0 mass % or less, 5.00 mass % or less, or 3.00 mass % or less, from the viewpoint of obtaining a lubricating oil composition with good lubricity.

[0036] The lubricating oil composition of one embodiment of the present invention may be substantially free of calcium sulfonate (B2) and calcium phenate (B3). Specifically, the contents of calcium sulfonate (B2) and calcium phenate (B3) may be less than 0.01 mass%, less than 0.005 mass%, or less than 0.001 mass%, based on the total amount of the lubricating oil composition.

[0037] The lubricating oil composition of one embodiment of the present invention may or may not contain a metal-based detergent other than the calcium-based detergent (B) described above. Examples of such metal-based detergents include magnesium-based detergents. In the lubricating oil composition of one embodiment of the present invention, the content of the metal-based detergent other than the calcium-based detergent (B) may be less than 0.01 mass%, less than 0.005 mass%, or less than 0.001 mass%, based on the total amount of the lubricating oil composition.

[0038] <Component (C): Polyoxyalkylene Glycol Compound> The lubricating oil composition of one embodiment of the present invention contains a polyoxyalkylene glycol compound (C) represented by the following general formula (1). In the polyoxyalkylene glycol compound (C), the content of EO units relative to the total amount of EO units and PO units is 65 mol% or less. If the content of EO units relative to the total amount of EO units and PO units exceeds 65 mol%, a lubricating oil composition with excellent demulsibility may not be obtained. As mentioned above, if water generated in a hydrogen fuel engine is mixed into the lubricating oil composition, the lubricating oil composition may become emulsified, making it difficult to discharge the water. In the present invention, by blending a polyoxyalkylene glycol compound (C) having a specific structure as a demulsifier into the lubricating oil composition, excellent demulsibility can be imparted to the lubricating oil composition. In the general formula (1), E represents an ethylene group, and P represents a propylene group. a and c are each independently a number of 0 or more. b is a number of 1 or more. Here, E is preferably —CH ２ CH ２ -, and P is preferably -CH ２ CH (CH ３ )-. The polyoxyalkylene glycol compound (C) is a block copolymer formed by block bonding of EO units and PO units. The content of EO units relative to the total amount of EO units and PO units may be 0 mol %, but from the viewpoint of suppressing cloudiness of the lubricating oil composition and improving its appearance, the content of EO units relative to the total amount of EO units and PO units is preferably more than 0 mol %.

[0039] The polyoxyalkylene glycol compound (C) used in one embodiment of the present invention may have a number average molecular weight of more than 4,000. If the number average molecular weight of the polyoxyalkylene glycol compound (C) is 4,000 or less, there is a risk that a lubricating oil composition with excellent demulsibility cannot be obtained. From the viewpoint of further improving the demulsibility of the lubricating oil composition, the number average molecular weight of the polyoxyalkylene glycol compound (C) is preferably 4,500 or more, more preferably 5,000 or more, and even more preferably 5,300 or more. Furthermore, from the viewpoint of solubility in the base oil and suppressing cloudiness of the lubricating oil composition to improve its appearance, the number average molecular weight of the polyoxyalkylene glycol compound (C) is preferably 10,000 or less, more preferably 9,500 or less, and even more preferably 9,000 or less. In this specification, the number average molecular weight means the number average molecular weight in terms of polystyrene, measured by the method described in the Examples below.

[0040] The weight average molecular weight of the polyoxyalkylene glycol compound (C) is preferably more than 5,000, more preferably 5,500 or more, and even more preferably 6,000 or more, from the viewpoint of further improving the demulsibility of the lubricating oil composition. Furthermore, from the viewpoint of solubility in the base oil and suppressing cloudiness of the lubricating oil composition to improve its appearance, the weight average molecular weight is preferably 12,000 or less, more preferably 11,500 or less, and even more preferably 11,000 or less. In this specification, the weight average molecular weight refers to the weight average molecular weight in terms of polystyrene, measured by the method described in the Examples below.

[0041] In one embodiment of the present invention, from the viewpoint of further improving the demulsibility of the lubricating oil composition while suppressing haze and improving the appearance of the lubricating oil composition, the content of EO units in the polyoxyalkylene glycol compound (C) relative to the total amount of EO units and PO units is preferably more than 0 mol % and up to 65 mol %, more preferably 1 to 50 mol %, even more preferably 10 to 30 mol %, and still more preferably 15 to 25 mol %.

[0042] In the above general formula (1), a and c are each independently a number greater than or equal to 0. That is, both a and c may be 0, or only one may be 0, but from the viewpoint of suppressing cloudiness of the lubricating oil composition and improving its appearance, it is preferable that a+c is a number greater than or equal to 1. Furthermore, from the viewpoint of further improving the demulsibility of the lubricating oil composition, the solubility in the base oil, and the viewpoint of suppressing cloudiness of the lubricating oil composition and improving its appearance, a and c are each independently preferably a number from 4 to 27, more preferably a number from 10 to 25, and even more preferably a number from 12 to 24.

[0043] In the above general formula (1), b is a number equal to or greater than 1. From the viewpoint of further improving the demulsibility of the lubricating oil composition, the solubility in the base oil, and suppressing cloudiness of the lubricating oil composition to improve its appearance, b is preferably a number from 64 to 129, more preferably a number from 66 to 125, even more preferably a number from 67 to 120, and still more preferably a number from 70 to 116.

[0044] The polyoxyalkylene glycol compound (C) can be appropriately produced by a known method, for example, using propylene glycol as an initiator, polymerizing oxypropylene in the presence of a catalyst such as a potassium hydroxide catalyst, and then polymerizing oxyethylene, and the production method is not particularly limited.

[0045] In one embodiment of the present invention, the content of the polyoxyalkylene glycol compound (C) is preferably 0.001 to 0.50 mass%, more preferably 0.005 to 0.30 mass%, and even more preferably 0.01 to 0.10 mass%, based on the total amount (100 mass%) of the lubricating oil composition, from the viewpoint of further improving the demulsibility of the lubricating oil composition.

[0046] In one embodiment of the present invention, the content ratio of the calcium-based detergent of component (B) to the polyoxyalkylene glycol compound of component (C) [component (C) / component (B)] may be set to 0.15 or less, 0.10 or less, or 0.08 or less by mass, from the viewpoint of obtaining a lubricating oil composition with improved demulsibility, and the lower limit is not particularly limited, but may be, for example, 0.0001 or more, 0.001 or more, or 0.005 or more.

[0047] <Component (D): Imide Compound> The lubricating oil composition of one embodiment of the present invention contains at least 1.50 mass% of one or more imide compounds (D) selected from the group consisting of compounds represented by the following general formulas (2) and (3). If the content of imide compound (D) is less than 1.50 mass%, it may be difficult to obtain a lubricating oil composition with excellent demulsibility properties. The imide compound (D) is an imide compound represented by the following general formulas (2) and (3), which is a -R Ｂ -NH- or -R Ｂ１ It has a structure called an "uncapped type" in which the nitrogen atom in the structural unit represented by -NH- is bonded to a hydrogen atom. In the present invention, by blending an imide compound (D) having such a specific structure as a dispersant together with the polyoxyalkylene glycol compound (C) in a lubricating oil composition, it is possible to impart excellent emulsification resistance to the lubricating oil composition. In the general formulas (2) and (3), R Ａ , R Ａ１ and R Ａ２ are each independently an alkenyl group having a weight average molecular weight of 500 to 4,000. Ｂ , R Ｂ１ and R Ｂ２ are each independently an alkylene group having 2 to 5 carbon atoms. X1 and X2 are each independently an integer of 1 to 10.

[0048] R Ａ , R Ａ１ and R Ａ２ Examples of alkenyl groups that can be selected include polybutenyl groups, polyisobutenyl groups, and ethylene-propylene copolymers. Of these, polybutenyl groups and polyisobutenyl groups are preferred, with polyisobutenyl groups being more preferred. The weight-average molecular weight of the alkenyl groups is 500 to 4,000, preferably 900 to 3,000, more preferably 1,300 to 2,800, and even more preferably 1,800 to 2,600.

[0049] R Ｂ , R Ｂ１ and R Ｂ２Examples of alkylene groups that can be selected as include a methylene group, an ethylene group, a trimethylene group, various butylene groups, various pentylene groups, etc. In this specification, the term "various" in various butylene groups, etc. means that straight-chain, branched, and isomers thereof are included.

[0050] 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 1 to 10, preferably an integer of 3 to 7, and more preferably 5 or 6.

[0051] Furthermore, the monoimide compound (D1) represented by the general formula (2) and the bisimide compound (D2) represented by the general formula (3) may be boron-modified or non-boron-modified, or a combination of these.

[0052] In one embodiment of the present invention, the content of the imide compound (D), calculated as nitrogen atoms, based on the total amount (100 mass%) of the lubricating oil composition may be 0.08 mass% or more, 0.09 mass% or more, 0.10 mass% or more, or 0.12 mass% or more, from the viewpoint of obtaining a lubricating oil composition with improved demulsibility; and may be 0.155 mass% or less, 0.15 mass% or less, 0.145 mass% or less, or 0.14 mass% or less, from the viewpoint of obtaining a lubricating oil composition with good lubricity.

[0053] In one embodiment of the present invention, the content of the imide compound (D) may be 2.00 mass % or more, 3.00 mass % or more, or 4.00 mass % or more, based on the total amount (100 mass %) of the lubricating oil composition, from the viewpoint of obtaining a lubricating oil composition with improved demulsibility; and may be 10.0 mass % or less, 9.00 mass % or less, or 8.00 mass % or less, from the viewpoint of obtaining a lubricating oil composition with good lubricity.

[0054] In one embodiment of the present invention, the content ratio of the polyoxyalkylene glycol compound of component (C) to the imide compound of component (D) [component (C) / component (D)] may be set to a mass ratio of 0.10 or less, 0.05 or less, or 0.03 or less, from the viewpoint of obtaining a lubricating oil composition with improved demulsibility, and the lower limit is not particularly limited, but may be, for example, 0.0001 or more, 0.001 or more, or 0.005 or more.

[0055] <Component (E): Imide Compound> The lubricating oil composition of one embodiment of the present invention may further contain, in addition to one or more imide compounds (D) selected from the group consisting of compounds represented by the above general formulas (2) and (3), one or more imide compounds (E) selected from the group consisting of compounds represented by the following general formulas (4) and (5): The imide compound (E) is a compound selected from the group consisting of -R in the uncapped imide compound (D). Ｂ -NH- or -R Ｂ１ The hydrogen atom in the structural unit represented by -NH- is R Ｃ It has a structure called a "cap type" in which In the general formulas (4) and (5), R Ａ , R Ａ１ and R Ａ２ are each independently an alkenyl group having a weight average molecular weight of 500 to 4,000. Ｂ , R Ｂ１ and R Ｂ２ are each independently an alkylene group having 2 to 5 carbon atoms. Ｃ is an alkyl group having 1 to 10 carbon atoms, or a group represented by -(AO)n-H (wherein A is an alkylene group having 2 to 4 carbon atoms, and n is an integer of 1 to 10). X1 and X2 each independently represent an integer of 1 to 10.

[0056] R Ａ , R Ａ１ and R Ａ２Examples of alkenyl groups that can be selected include polybutenyl groups, polyisobutenyl groups, and ethylene-propylene copolymers. Of these, polybutenyl groups and polyisobutenyl groups are preferred, with polyisobutenyl groups being more preferred. The weight-average molecular weight of the alkenyl groups is 500 to 4,000, preferably 900 to 3,000, more preferably 1,300 to 2,800, and even more preferably 1,800 to 2,600.

[0057] R Ｂ , R Ｂ１ and R Ｂ２ Examples of alkylene groups that can be selected as include a methylene group, an ethylene group, a trimethylene group, various butylene groups, various pentylene groups, etc. In this specification, the term "various" in various butylene groups, etc. means that straight-chain, branched, and isomers thereof are included.

[0058] R Ｃ is an alkyl group having 1 to 10 carbon atoms, or a group represented by -(AO)n-H (wherein A is an alkylene group having 2 to 4 carbon atoms, and n is an integer from 1 to 10). Examples of the alkyl group include linear or branched alkyl groups such as methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, 1,1-dimethylhexyl, 2-ethylhexyl, nonyl, 1,1-dimethylheptyl, and decyl. Examples of the alkylene group having 2 to 4 carbon atoms represented by A include ethylene, trimethylene, and various butylene groups, with ethylene being preferred. n is an integer from 1 to 10, preferably an integer from 1 to 5, and more preferably an integer from 1 to 3.

[0059] 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 1 to 10, preferably an integer of 3 to 7, and more preferably 5 or 6.

[0060] Furthermore, the monoimide compound (E1) represented by the general formula (4) and the bisimide compound (E2) represented by the general formula (5) may be boron-modified or non-boron-modified, or a combination of these.

[0061] In one embodiment of the present invention, the content of the imide compound (E), calculated as nitrogen atoms, based on the total amount (100 mass%) of the lubricating oil composition may be 0.05 mass% or more, 0.07 mass% or more, 0.08 mass% or more, or 0.09 mass% or more, from the viewpoint of obtaining a lubricating oil composition with improved demulsibility; and may be 0.13 mass% or less, 0.12 mass% or less, 0.11 mass% or less, or 0.10 mass% or less, from the viewpoint of obtaining a lubricating oil composition with good lubricity.

[0062] In one embodiment of the present invention, the content of the imide compound (E) may be 0.10 mass % or more, 0.50 mass % or more, 1.00 mass % or more, or 1.50 mass % or more, based on the total amount (100 mass %) of the lubricating oil composition, from the viewpoint of obtaining a lubricating oil composition with further improved demulsibility; and may be 5.00 mass % or less, 4.00 mass % or less, or 3.00 mass % or less, from the viewpoint of obtaining a lubricating oil composition with good lubricity.

[0063] In one embodiment of the present invention, the content ratio of the imide compound of component (D) to the imide compound of component (E) [component (D) / component (E)] may be set to a mass ratio of 10.0 or less, 7.00 or less, or 5.00 or less, from the viewpoint of obtaining a lubricating oil composition with improved demulsibility, and the lower limit is not particularly limited, but may be, for example, 0.10 or more, 0.50 or more, or 1.00 or more.

[0064] <Lubricating Oil Additives> The lubricating oil composition of one embodiment of the present invention may further contain other lubricating oil additives besides components (B) to (D), as necessary, to the extent that the effects of the present invention are not impaired. Examples of such lubricating oil additives include viscosity index improvers, pour point depressants, antioxidants, antiwear or extreme pressure agents, friction modifiers, metal deactivators, antifoaming agents, and demulsifiers other than component (C). These lubricating oil additives may be used alone or in combination of two or more.

[0065] [Viscosity Index Improver] The lubricating oil composition of one embodiment of the present invention may further contain a viscosity index improver. The viscosity index improver may be used alone or in combination of two or more types. Examples of viscosity index improvers used in one embodiment of the present invention include polymers such as non-dispersant polymethacrylate, dispersant polymethacrylate, olefin copolymers (e.g., ethylene-propylene copolymers), dispersant olefin copolymers, and styrene copolymers (e.g., styrene-diene copolymers, styrene-isoprene copolymers).

[0066] [Pour Point Depressant] 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. 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, with polymethacrylates having a weight average molecular weight of 40,000 to 200,000 being preferred.

[0067] [Antioxidant] The lubricating oil composition of one embodiment of the present invention may further contain an antioxidant. The antioxidant may be used alone or in combination of two or more types. Examples of the antioxidant used in one embodiment of the present invention include amine-based antioxidants and phenol-based antioxidants. Examples of the amine-based antioxidant include diphenylamine-based antioxidants such as alkylated diphenylamines having an alkyl group containing 3 to 20 carbon atoms. Examples of the phenol-based antioxidant include 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. [Antiwear Agent or Extreme Pressure Agent] The lubricating oil composition of one embodiment of the present invention may further contain an antiwear agent or an extreme pressure agent. Anti-wear agent or extreme pressure agent may be used alone or in combination of two or more.As anti-wear agent or extreme pressure agent, for example, zinc dialkyldithiophosphate (ZnDTP), zinc phosphate, zinc dithiocarbamate, disulfides, sulfurized olefins, sulfurized fats and oils, sulfurized esters, thiocarbonates, thiocarbamates, polysulfides and other sulfur-containing compounds; phosphorus-containing compounds such as phosphites, phosphates, phosphonates, and their amine salts or metal salts; sulfur and phosphorus-containing anti-wear agents such as thiophosphites, thiophosphates, thiophosphonates, and their amine salts or metal salts.Among these, zinc dialkyldithiophosphate (ZnDTP) is preferred.

[0068] [Friction Modifier] The lubricating oil composition of one embodiment of the present invention may further contain a friction modifier. The friction modifier may be used alone or in combination of two or more. Examples of the friction modifier 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; and ashless friction modifiers such as aliphatic amines, fatty acid esters, fatty acid amides, fatty acids, fatty alcohols, and aliphatic ethers, each having at least one alkyl or alkenyl group having 6 to 30 carbon atoms in the molecule.

[0069] [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. Examples of the metal deactivator used in one embodiment of the present invention include benzotriazole, benzotriazole derivatives, and thiadiazole derivatives.

[0070] [Antifoaming Agent] The lubricating oil composition of one embodiment of the present invention may further contain an antifoaming agent. The antifoaming agent may be used alone or in combination of two or more. Examples of the antifoaming agent used in one embodiment of the present invention include alkylsilicone-based antifoaming agents, fluorosilicone-based antifoaming agents, and fluoroalkyl ether-based antifoaming agents.

[0071] [Demulsifier] The lubricating oil composition of one embodiment of the present invention may further contain a demulsifier other than component (C). Examples of the demulsifier used in one embodiment of the present invention include polyoxypolyalkylene alkyl ethers. These may be used alone or in combination of two or more.

[0072] [Method for Producing Lubricating Oil Composition] The method for producing the lubricating oil composition of one embodiment of the present invention is not particularly limited, and is preferably a method including a step of blending various other additives, as necessary, with the base oil (A). The order of blending the components can be appropriately determined.

[0073] [Properties of Lubricating Oil Composition] The kinematic viscosity at 100°C of the lubricating oil composition of one embodiment of the present invention is 10.0 mm ２ / s or more, 11.0mm ２ / s or more, 12.0mm ２ / s or more, and the upper limit is not particularly limited, but for example, 16.5 mm ２ / s or less, 15.5mm ２ / s or less, or 15.0 mm ２ / s or less.

[0074] The base number (perchloric acid method) of the lubricating oil composition of one embodiment of the present invention is not particularly limited, but may be 4.0 mgKOH / g or more, or 5.0 mgKOH / g or more, and may be 8.0 mgKOH / g or less, or 9.0 mgKOH / g or less.

[0075] [Uses of Lubricating Oil Composition] The lubricating oil composition of one embodiment of the present invention has excellent demulsibility and good water separation properties. Therefore, the lubricating oil composition can easily drain water and prevent the lubrication properties of the lubricating oil composition from deteriorating. The lubricating oil composition of one embodiment of the present invention can be applied to various devices that can exhibit the above properties, but can be suitably used for lubricating the components of internal combustion engines. In particular, it can be suitably used for lubricating the components of internal combustion engines that run on hydrogen as fuel.

[0076] In consideration of the above-described properties 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, in which the lubricating oil composition of one embodiment of the present invention is applied to lubricate a hydrogen-fueled engine.

[0077] 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.

[0078] (1) Kinematic viscosity: Measured in accordance with ASTM D445. (2) Viscosity index: Calculated in accordance with ASTM D2270. (3) Base number (perchloric acid method): Measured by the perchloric acid method in accordance with ASTM D2896. (4) Calcium atom (Ca) content: Measured in accordance with ASTM D5185. (5) Number average molecular weight (Mn), weight average molecular weight (Mw): The number average molecular weight (Mn) and weight average molecular weight (Mw) of the polyoxyalkylene glycol compound and the imide compound were measured using a gel permeation chromatography (GPC) device under the following conditions, and the values ​​measured in terms of standard polystyrene were used. (Measurement conditions) Column: KF-G (guard column) x 1 + KF 402.5HQ x 2 Developing solvent: Chloroform Flow rate: 0.3 mL / min

[0079] Examples 1 to 9, Comparative Examples 1 to 12, Reference Example 1 The components shown in Tables 1 and 2 were added in the amounts shown in the tables and mixed thoroughly to prepare lubricating oil compositions. The base oils and various additives used in the examples and comparative examples are as follows. <Component (A): Base oil> "Base oil": Mineral oil classified as Group II in the API base oil category, kinematic viscosity at 40°C = 90.51 mm ２ / s, 100℃ kinematic viscosity = 10.89mm ２ / s, viscosity index=107.

[0080] <Component (B): Calcium-based detergent> "Ca salicylate (1)": calcium salicylate with a base number (perchloric acid method) of 225 mg KOH / g, Ca content of 8.0 mass%. "Ca salicylate (2)": calcium salicylate with a base number (perchloric acid method) of 226 mg KOH / g, Ca content of 7.9 mass%. "Ca salicylate (3)": calcium salicylate with a base number (perchloric acid method) of 64 mg KOH / g, Ca content of 2.9 mass%. "Ca sulfonate (1)": calcium sulfonate with a base number (perchloric acid method) of 300 mg KOH / g, Ca content of 11.6% by mass. "Ca sulfonate (2)": calcium sulfonate with a base number (perchloric acid method) of 307 mg KOH / g, Ca content of 11.9% by mass. "Ca phenate": calcium phenate with a base number (perchloric acid method) of 250 mg KOH / g, Ca content of 9.25% by mass.

[0081] <Component (C): Polyoxyalkylene glycol compound (PAG compound)> PAG compound (1): Polyoxyethylene polyoxypropylene glycol formed by block bonding of EO units and PO units (number average molecular weight = 8,500, content of EO units relative to the total amount of EO units and PO units = 23 mol%). PAG compound (2): Polyoxyethylene polyoxypropylene glycol formed by block bonding of EO units and PO units (number average molecular weight = 5,700, content of EO units relative to the total amount of EO units and PO units = 29 mol%). PAG compound (3): Polyoxyethylene polyoxypropylene glycol formed by block bonding of EO units and PO units (number average molecular weight = 1,900, content of EO units relative to the total amount of EO units and PO units = 71 mol%). PAG compound (4): Polyoxyethylene polyoxypropylene glycol formed by random bonding of EO units and PO units (number average molecular weight = 980, content of EO units relative to the total amount of EO units and PO units = 70 mol%). PAG compound (5): Polyoxyethylene polyoxypropylene glycol formed by random bonding of EO units and PO units (number average molecular weight = 1360, content of EO units relative to the total amount of EO units and PO units = 90 mol%). PAG compound (6): Polyoxyethylene polyoxypropylene glycol formed by random bonding of EO units and PO units (number average molecular weight = 1600, content of EO units relative to the total amount of EO units and PO units = 90 mol%).

[0082] <Component (D): Imide Compound> Uncapped imide compound (1): a non-boron-modified polybutenyl succinic acid bisimide having an uncapped structure (N content = 1.08 mass%, R Ａ１ and R Ａ２ is a polybutenyl group, R Ｂ１ and R Ｂ２ is an ethylene group). Uncapped imide compound (2): a non-boron-modified polybutenyl succinic acid bisimide having an uncapped structure (N content = 2.1% by mass, R Ａ１ and R Ａ２ is a polybutenyl group, R Ｂ１ and RＢ２ is an ethylene group).

[0083] <Component (E): Imide Compound> Capped imide compound (1): Non-boron-modified polybutenyl succinic acid bisimide having a capped structure (N content = 1.0 mass %, R Ａ１ and R Ａ２ is a polybutenyl group, R Ｂ１ and R Ｂ２ is an ethylene group, and R Ｃ But-(C ２ H ４ O) ２ - Capped imide compound (2): a boron-modified polybutenyl succinic acid bisimide having a capped structure (N content = 1.23 mass %, in the above general formula (5), R Ａ１ and R Ａ２ is a polybutenyl group, R Ｂ１ and R Ｂ２ is an ethylene group, and R Ｃ is a boric acid group (-(C ２ H ４ O) ２ an imide compound in which a group represented by —H is modified with boric acid);

[0084] Other additives: antioxidant, anti-wear agent (ZnDTP), metal deactivator, pour point depressant, and anti-foaming agent. The prepared lubricating oil compositions were subjected to the following water resistance test. The test results are shown in Tables 1 and 2.

[0085] [Water Resistance Test] Using the prepared lubricating oil composition as a sample, the test method was carried out in accordance with 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 added to a container containing 75 mL of sample, and the temperature was raised to 93°C. The container was then rotated while being held for 48 hours. After that, the container was cooled to room temperature (25°C), and the liquid in the container was transferred to a measuring cylinder and allowed to stand for 24 hours. After standing, the separation of the oil layer, water layer, and emulsion layer was visually evaluated according to the following four-point scale. Evaluation results of A and B were evaluated as passing. A: The oil layer and water layer were completely separated, and the water layer was not cloudy. B: The oil layer and water layer were completely separated, and the water layer was slightly cloudy. C: Separation into two layers, an oil layer and an emulsion layer. D: No separation into an oil layer and a water layer, and an emulsion layer was formed.

[0086]

[0087] As can be seen from Tables 1 and 2, the lubricating oil compositions of Examples 1 to 9, which contained a calcium-based detergent (B), a polyoxyalkylene glycol compound (C) having a specific structure, and a predetermined amount of an imide compound (D) having a specific structure, exhibited good results in the water resistance test and excellent demulsification properties. In particular, Examples 1 to 6, which used calcium salicylate (B1) as the calcium-based detergent (B), exhibited extremely good results in the water resistance test. The lubricating oil compositions of Examples 7 to 9, which used calcium sulfonate (B2) or calcium phenate (B3) as the calcium-based detergent (B), exhibited generally acceptable results, but their demulsification properties were inferior to those of Examples 1 to 6. On the other hand, the lubricating oil compositions of Comparative Examples 1 to 12 all exhibited emulsions in the water resistance test and exhibited inferior demulsification properties to those of Examples 1 to 9. As shown in Reference Example 1, even when the content of EO units in the polyoxyalkylene glycol compound of component (C) relative to the total amount of EO units and PO units exceeds 65 mol %, by blending 5.0 mass % or more of neutral calcium salicylate (B12), a lubricating oil composition with excellent demulsibility properties was obtained.

Claims

1. A lubricating oil composition for use in an internal combustion engine that uses hydrogen as fuel, comprising: a base oil (A); a calcium-based detergent (B); a polyoxyalkylene glycol compound (C) represented by the following general formula (1); and one or more imide compounds (D) selected from the group consisting of compounds represented by the following general formulas (2) and (3), wherein the polyoxyalkylene glycol compound (C) has an EO unit content of 65 mol% or less relative to the total amount of EO units and PO units; and the imide compound (D) content is 1.50 mass% or more. (In the general formula (1), E represents an ethylene group, P represents a propylene group, a and c each independently represent a number of 0 or more, and b represents a number of 1 or more.) (In the general formulas (2) and (3), R Ａ , R Ａ１ and R Ａ２ are each independently an alkenyl group having a weight average molecular weight of 500 to 4,000. Ｂ , R Ｂ１ and R Ｂ２ are each independently an alkylene group having 2 to 5 carbon atoms. X1 and X2 are each independently an integer of 1 to 10.

2. The lubricating oil composition of claim 1, wherein the calcium-based detergent (B) comprises calcium salicylate (B1).

3. The lubricating oil composition according to claim 1 or 2, wherein the calcium-based detergent (B) is substantially free of calcium sulfonate (B2) and calcium phenate (B3).

4. The lubricating oil composition according to any one of claims 1 to 3, wherein the content of the calcium-based detergent (B) is 0.10 to 10.0 mass %.

5. The lubricating oil composition according to any one of claims 1 to 4, wherein the content of the polyoxyalkylene glycol compound (C) is 0.001 to 0.1 mass %.

6. The lubricating oil composition according to any one of claims 1 to 5, wherein the content of the imide compound (D) is 10.0 mass% or less.

7. The lubricating oil composition according to any one of claims 1 to 6, further comprising one or more imide compounds (E) selected from the group consisting of compounds represented by the following general formulas (4) and (5): (In the general formulas (4) and (5), R Ａ , R Ａ１ and R Ａ２ are each independently an alkenyl group having a weight average molecular weight of 500 to 4,000. Ｂ , R Ｂ１ and R Ｂ２ are each independently an alkylene group having 2 to 5 carbon atoms. Ｃ is an alkyl group having 1 to 10 carbon atoms, or a group represented by -(AO)n-H (wherein A is an alkylene group having 2 to 4 carbon atoms, and n is an integer of 1 to 10. X1 and X2 each independently represent an integer of 1 to 10.) 8. The lubricating oil composition according to any one of claims 1 to 7, wherein the content ratio of the calcium-based detergent (B) to the polyoxyalkylene glycol compound (C) [component (C) / component (B)] is 0.15 or less in mass ratio.

9. The lubricating oil composition according to any one of claims 1 to 8, wherein the content ratio of the polyoxyalkylene glycol compound (C) to the imide compound (D) [component (C) / component (D)] is 0.10 or less in mass ratio.

10. The lubricating oil composition according to any one of claims 1 to 9, wherein the content ratio of the imide compound (D) to the imide compound (E) [component (D) / component (E)] is 10.0 or less in mass ratio.

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