Lubricant oil composition

Abstract

To provide a lubricant oil composition excellent in separability with respect to water (anti-emulsification property).SOLUTION: The lubricating oil composition to be used in an internal combustion engine operated by hydrogen as fuel, comprises base oil (A), a calcium-based detergent (B), a polyoxyalkylene glycol compound (C) represented by the following general formula (1), and one or more species of imide compounds (D) selected from the group consisting of compounds represented by the following general formulae (2) and (3), with the content of the EO unit and the PO unit relative to the total amount of polyoxyalkylene glycol compound (C) being 65 mol% or less, and the content of the imide compound (D) being 1.50 mass% or more.SELECTED DRAWING: None

Description

[Technical Field]

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

[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 (for example, Patent Document 1). In hydrogen-fueled engines, water is generated because hydrogen is used as fuel. It is conceivable that the generated water could be discharged outside the vehicle, but if this water gets mixed into a lubricating oil composition, the lubricating oil composition may become emulsified, making it difficult to discharge the water. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2008-137505 Summary of the Invention [Problem to be solved by the invention]

[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"). [Means for solving the problem]

[0005] As a result of 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] The present invention relates to a lubricating oil composition 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), The polyoxyalkylene glycol compound (C) has an EO unit content of 65 mol% or less based on the total amount of EO units and PO units, A lubricating oil composition for use in an internal combustion engine that runs on hydrogen as fuel, which contains an imide compound (D) in an amount of 1.50 mass % or more. [ka] (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.) [ka] (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 according to [1], wherein the calcium-based detergent (B) comprises 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% by mass to 0.1% by 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): [ka] (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 represents an alkyl group having 1 to 10 carbon atoms or a group represented by -(AO)nH (wherein A represents an alkylene group having 2 to 4 carbon atoms, and n represents 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. [Effects of the Invention]

[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. DETAILED DESCRIPTION OF THE INVENTION

[0007] The upper and lower limits of the numerical ranges described herein can be combined in any combination. For example, if 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 herein. 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 specifying the upper and lower limits described in this specification, the numerical range from the lower limit to the upper limit can be specified by appropriately selecting from the respective options and combining them as desired. Furthermore, as a numerical range described in this specification, for example, "60 to 100" means a range of "60 or more (60 or more) and 100 or less (100 or less)." In addition, the various features described as preferred embodiments in this specification can be combined in multiple ways.

[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, the problem of emulsification of lubricating oil compositions caused by the inclusion of water generated in hydrogen fuel engines is addressed by blending a polyoxyalkylene glycol compound (C) having a specific structure and blending a predetermined amount of an imide compound (D) having a specific structure, thereby improving the demulsification performance. Therefore, the lubricating oil composition of the present invention can expel water and does not significantly impair lubricity even if water is mixed in and emulsified, making it suitable for use in hydrogen fuel engines. The lubricating oil composition of one embodiment of the present invention may further contain other lubricating oil additives in addition to components (B) to (D) as needed, provided that the effects of the present invention are not impaired. 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 may 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 (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 base oil (A) used in one embodiment of the present invention has a kinematic viscosity at 100°C of 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 90 or more, more preferably 100 or more, and even more preferably 110 or more. 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 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), which 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, calcium salicylate (B1) is preferred as the calcium-based detergent (B) from the viewpoint of obtaining a lubricating oil composition with improved demulsibility.

[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 refers to 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)> 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]

[0019] In the 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 includes 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 these may be used in combination. 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 may be 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, or may be 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% by mass or more, 1.00% by mass or more, or 1.50% 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.

[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 %, by blending 5.0 mass % or more of neutral calcium salicylate (B12), a lubricating oil composition with excellent demulsibility can be obtained.

[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% by mass or more, 1.50% by mass or more, or 2.00% 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 good lubricity, the content of calcium salicylate (B1) may be 10.0% by mass or less, 8.00% by mass or less, or 6.00% by mass or less.

[0026] <Calcium sulfonate (B2)> An example of the calcium sulfonate (B2) used in one embodiment of the present invention is a compound represented by the following general formula (b-2). [ka]

[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 mg KOH / g or more, or a neutral calcium sulfonate (B22) having a base number of less than 100 mg KOH / 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) 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]

[0032] In the general formula (b-3), each 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% 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 may be 10.0% by mass or less, 5.00% by mass or less, or 3.00% by 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 metallic detergent other than the calcium-based detergent (B) described above. Examples of such metallic detergents include magnesium-based detergents. In the lubricating oil composition of one embodiment of the present invention, the content of metal-based detergents 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> A lubricating oil composition according to 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%, it may be difficult to obtain a lubricating oil composition with excellent demulsibility. 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, it is possible to impart excellent demulsibility to the lubricating oil composition. [ka] In the general formula (1), E represents an ethylene group, and P represents a propylene group. a and c are each independently a number equal to or greater than 0. b is a number equal to or greater than 1. Here, E is preferably -CH2CH2-, and P is preferably -CH2CH(CH3)-. The polyoxyalkylene glycol compound (C) is a block copolymer formed by block-bonding 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 %. However, from the viewpoint of suppressing cloudiness of the lubricating oil composition and improving the appearance, the content of EO units relative to the total amount of EO units and PO units is preferably greater 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 4000. If the number average molecular weight of the polyoxyalkylene glycol compound (C) is 4000 or less, it may be difficult to obtain a lubricating oil composition with excellent demulsibility properties. 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. 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 refers to the number average molecular weight in terms of polystyrene, measured by the method described in the examples below.

[0040] Furthermore, from the viewpoint of further improving the demulsibility of the lubricating oil composition, 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 solubility in the base oil and preventing cloudiness of the lubricating oil composition to improve its appearance, the 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 from more than 0 mol% to 65 mol%, more preferably from 1 to 50 mol%, even more preferably from 10 to 30 mol%, and still more preferably from 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 of them 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 suppression of cloudiness of the lubricating oil composition to improve 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 of 1 or more. 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 not be possible to obtain a lubricating oil composition with excellent demulsibility properties. The imide compound (D) is represented by the following general formulas (2) and (3): B -NH- or -R B1 The imide compound (D) 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. [ka] 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 as include polybutenyl groups, polyisobutenyl groups, and ethylene-propylene copolymers. Among these, polybutenyl groups and polyisobutenyl groups are preferred, and polyisobutenyl groups are more preferred. The weight average molecular weight of the alkenyl group 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 RB2 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.

[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, or 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 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 non-capped imide compound (D) having -R 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 [ka] 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)nH (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 as include polybutenyl groups, polyisobutenyl groups, and ethylene-propylene copolymers. Among these, polybutenyl groups and polyisobutenyl groups are preferred, and polyisobutenyl groups are more preferred. The weight average molecular weight of the alkenyl group 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)nH (wherein A is an alkylene group having 2 to 4 carbon atoms, and n is an integer of 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 an ethylene group, a trimethylene group, and various butylene groups, with an ethylene group being preferred. n is an integer of 1 to 10, preferably an integer of 1 to 5, and more preferably an integer of 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 set to 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 improved demulsibility; and may be set to 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] <Lubricant additives> The lubricating oil composition of one embodiment of the present invention may further contain other lubricating oil additives in addition to components (B) to (D) as needed, provided 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 improvers may be used alone or in combination of two or more. 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 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. 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.

[0067] [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. Examples of antioxidants used in one embodiment of the present invention include amine-based antioxidants and phenol-based antioxidants. Examples of amine-based antioxidants include diphenylamine-based antioxidants such as alkylated diphenylamines having an alkyl group with 3 to 20 carbon atoms. Examples of phenol-based antioxidants 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. [Anti-wear or extreme pressure agents] The lubricating oil composition of one embodiment of the present invention may further contain an anti-wear agent or an extreme pressure agent. The anti-wear agent or extreme pressure agent may be used alone or in combination of two or more types. Examples of anti-wear agents or extreme pressure agents include sulfur-containing compounds such as zinc dialkyldithiophosphate (ZnDTP), zinc phosphate, zinc dithiocarbamate, disulfides, sulfurized olefins, sulfurized fats and oils, sulfurized esters, thiocarbonates, thiocarbamates, and polysulfides; phosphorus-containing compounds such as phosphites, phosphate esters, phosphonate esters, and amine salts or metal salts thereof; and sulfur- and phosphorus-containing anti-wear agents such as thiophosphites, thiophosphate esters, thiophosphonate esters, and amine salts or metal salts thereof. Of 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 types. Examples of friction modifiers 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 molybdic 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 agents may be used alone or in combination of two or more. Examples of the defoaming agent used in one embodiment of the present invention include alkylsilicone-based defoaming agents, fluorosilicone-based defoaming agents, and fluoroalkyl ether-based defoaming 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, etc. 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 that includes a step of blending various other additives with the base oil (A) as needed. The order of blending the components can be determined as appropriate.

[0073] [Properties of lubricating oil composition] The lubricating oil composition of one embodiment of the present invention has a kinematic viscosity at 100°C of 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, which allows water to be easily discharged and prevents deterioration of the lubricity of the lubricating oil composition. The lubricating oil composition of one embodiment of the present invention can be applied to various devices that can exhibit the above-mentioned properties, but it can also be suitably used for lubricating the components of internal combustion engines, and more suitably used for lubricating the components of internal combustion engines that run on hydrogen as fuel.

[0076] Furthermore, in consideration of the above-mentioned 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 according to one embodiment of the present invention is applied to lubricate a hydrogen fuel engine. [Example]

[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 Measurement was performed in accordance with ASTM D445. (2) Viscosity index Calculations were made 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 Measurement was performed 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: 0.3mL / 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 of 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 and a Ca content of 8.0% by mass. "Ca salicylate (2)": Calcium salicylate with a base number (perchloric acid method) of 226 mg KOH / g and a Ca content of 7.9% by mass. "Ca salicylate (3)": Calcium salicylate with a base number (perchloric acid method) of 64 mg KOH / g and a Ca content of 2.9% by mass. "Ca sulfonate (1)": Calcium sulfonate with a base number (perchloric acid method) of 300 mg KOH / g and a Ca content of 11.6% by mass "Ca sulfonate (2)": Calcium sulfonate with a base number (perchloric acid method) of 307 mg KOH / g and a Ca content of 11.9% by mass "Ca phenate": Calcium phenate with a base number (perchloric acid method) of 250 mg KOH / g, and a 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 (imide compound in which the ethylene group is present). Uncapped imide compound (2): a non-boron-modified polybutenyl succinic acid bisimide having an uncapped structure (N content = 2.1 mass %, R A1 and R A2 is a polybutenyl group, R B1 and R B2 (imide compound in which the ethylene group is present).

[0083] <Component (E): Imide compound> Capped imide compound (1): a 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 is an imide compound in which the group is represented by -(C2H4O)2-H. Capped imide compound (2): a boron-modified polybutenyl succinic acid bisimide having a capped structure (N content = 1.23 mass %, R A1 and R A2is a polybutenyl group, R B1 and R B2 is an ethylene group, and R C is a boric acid group (an imide compound in which a group represented by -(C2H4O)2-H is modified with boric acid).

[0084] Other additives: including antioxidants, anti-wear agents (ZnDTP), metal deactivators, pour point depressants and anti-foam agents. The prepared lubricating oil compositions were subjected to the following water resistance test, and the test results are shown in Tables 1 and 2.

[0085] [Water resistance test] The prepared lubricating oil composition was used as a sample and tested 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 container was heated to 93°C and held for 48 hours while rotating. The container was then 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 using the following four-point scale. Evaluation results of A and B were considered acceptable. A: The oil layer and water layer are completely separated, and the water layer is clear. B: The oil and water layers are completely separated, and the water layer is slightly cloudy. C: Separation into two layers: oil layer and emulsion layer C: No separation into oil and water layers, forming an emulsion layer

[0086] [Table 1] [Table 2]

[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, showed 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), showed 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), showed 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 generated emulsions as a result of the water resistance test, and were inferior in demulsibility to 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 %, a lubricating oil composition with excellent demulsibility was obtained by blending 5.0 mass % or more of neutral calcium salicylate (B12).

Claims

1. The present invention comprises 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), The polyoxyalkylene glycol compound (C) has an EO unit content of 65 mol% or less based on the total amount of EO units and PO units, A lubricating oil composition for use in an internal combustion engine that runs on hydrogen as fuel, the lubricating oil composition having an imide compound (D) content of 1.50 mass % or more. 【Chemical 1】 (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.) 【Chemistry 2】 (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. 2. The lubricating oil composition of claim 1, wherein the calcium-based detergent (B) comprises calcium salicylate (B1).

3. 3. The lubricating oil composition according to claim 1, 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% by mass to 0.1% by 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): 【Chemistry 3】 (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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