Lubricating oil composition

Abstract

To provide a lubricant composition that effectively suppresses occurrence of coking and is suitable for internal combustion engines.SOLUTION: A lubricant composition includes a base oil (A) wherein a NOACK value is 6 mass% or less as measured by a NOACK test at 250°C for 1 hour in accordance with ASTM D5800. The lubricant composition has CCS viscosity of 7000 mPa s or less at -25°C and HTHS viscosity of 2.9 mPa s or more at 150°C.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a lubricating oil composition and a method for lubricating an internal combustion engine. [Background technology]

[0002] Internal combustion engines used in automobiles and other vehicles are subject to various demands, such as miniaturization, increased power output, improved fuel efficiency, and compliance with exhaust gas regulations. Development is underway to meet these demands for lubricating oil compositions used in internal combustion engines. For example, Patent Document 1 discloses a lubricating oil composition for internal combustion engines that can suppress the occurrence of coking and copper leaching while suppressing a decrease in base number, and contains a lubricating oil base oil, a predetermined amount of boron-containing alkenyl succinimide and / or boron-containing alkyl succinimide in terms of boron, and a poly(meth)acrylate having a weight-average molecular weight and an average number of carbon atoms of alkyl groups within a predetermined range. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2015-196696 [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] In this situation, there is a need for a lubricating oil composition that, for example, is highly effective in suppressing coking in high-temperature environments and can be suitably used in internal combustion engines. [Means for solving the problem]

[0005] As a result of diligent research, the inventors have found that the above problems can be solved by using a base oil with a predetermined NOACK value and by adjusting the CCS viscosity at -25°C and the HTHS viscosity at 150°C to within predetermined ranges in the lubricating oil composition. Specifically, the present invention discloses the following aspects. [1] Contains base oil (A) with a NOACK value of 6% by mass or less as measured by a NOACK test conducted in accordance with ASTM D5800 under the conditions of 250°C for 1 hour. The CCS viscosity at -25℃ is 7000 mPa·s or less. The HTHS viscosity at 150°C is 2.9 mPa·s or higher. Lubricating oil composition. [2] A method for lubricating an internal combustion engine, wherein the lubricating oil composition described in [1] above is applied to the lubrication of the internal combustion engine. [Effects of the Invention]

[0006] A lubricating oil composition according to one preferred embodiment of the present invention is highly effective in suppressing the occurrence of coking in high-temperature environments. Therefore, a lubricating oil composition according to one embodiment of the present invention can be suitably used, for example, for lubricating internal combustion engines. [Modes for carrying out the invention]

[0007] The numerical ranges described herein can be any combination of upper and lower limits. For example, if the numerical range is described as "preferably 30 to 100, more preferably 40 to 80," then the ranges of "30 to 80" and "40 to 100" are also included in the numerical ranges described herein. Furthermore, for example, if the numerical range is described as "preferably 30 or more, more preferably 40 or more, and also preferably 100 or less, more preferably 80 or less," then the ranges of "30 to 80" and "40 to 100" are also included in the numerical range described herein. In other words, in the upper and lower limit provisions described herein, the numerical range from the lower limit to the upper limit can be defined by appropriately selecting and combining the options from each set of choices as appropriate. Furthermore, a numerical range described in this specification, such as "60 to 100," means a range of "60 or more and 100 or less." In addition, several of the requirements described as preferred embodiments in this specification can be combined.

[0008] [Composition of Lubricating Oil Composition] The lubricating oil composition according to one embodiment of the present invention contains a base oil (A) having a NOACK value of 6% by mass or less and satisfies the following requirements (I) and (II). · Requirement (I): The CCS viscosity at -25°C is 7000 mPa·s or less. · Requirement (II): The HTHS viscosity at 150°C is 2.9 mPa·s or more.

[0009] By making the lubricating oil composition satisfy Requirement (I), the starting performance of the engine at low temperatures is improved. A lubricating oil composition having a CCS viscosity at -25°C exceeding 7000 mPa·s tends to have insufficient starting performance of the engine in a low-temperature environment. In this specification, the CCS viscosity at -25°C means the value measured at -25°C in accordance with ASTM D5293.

[0010] By making the lubricating oil composition satisfy Requirement (II), it is easy to retain the oil film even at high temperatures, and the anti-wear property is improved. A lubricating oil composition having an HTHS viscosity at 150°C less than 2.9 mPa·s tends to have inferior anti-wear properties. From the viewpoint of improving the oil film retention property in a high-temperature environment and obtaining a lubricating oil composition having excellent anti-wear properties, the HTHS viscosity at 150°C of the lubricating oil composition according to one embodiment of the present invention is preferably 3.0 mPa·s or more, more preferably 3.2 mPa·s or more. In this specification, the HTHS viscosity at 150°C means the value measured at 150°C in accordance with ASTM D4683.

[0011] The lubricating oil composition according to one embodiment of the present invention may further contain a viscosity index improver (B). The lubricating oil composition according to one embodiment of the present invention may further contain other lubricating oil additives other than the above component (B) as long as the effects of the present invention are not impaired.

[0012] Hereinafter, the details of each component contained in the lubricating oil composition according to one embodiment of the present invention will be described.

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

[0014] Examples of synthetic oils include polyalphaolefins such as α-olefin homopolymers, α-olefin copolymers (e.g., α-olefin copolymers having 8 to 14 carbon atoms such as ethylene-α-olefin copolymers); isoparaffin; polyalkylene glycol; ester-based oils such as polyol ester, dibasic acid ester, and phosphate ester; ether-based oils such as polyphenyl ether; alkylbenzene; alkylnaphthalene; synthetic oils (GTL) obtained by isomerizing wax (GTL wax (Gas To Liquids WAX)) produced from natural gas by the Fischer-Tropsch method, etc.

[0015] The NOACK value of the base oil (A) used in one aspect of the present invention is 6% by mass or less. By using a base oil (A) with a NOACK value of 6% by mass or less, even when used in a high-temperature environment, it is difficult to be misted, and the amount of coking derived from the misted components can be suppressed. As a result, a lubricating oil composition with a high effect of suppressing the occurrence of coking in a high-temperature environment can be obtained. On the other hand, when the NOACK value of the base oil (A) used exceeds 6% by mass, the prepared lubricating oil composition tends to be easily misted and coking tends to occur in a high-temperature environment. From the viewpoint of further improving the mist resistance and obtaining a lubricating oil composition with a higher effect of suppressing the occurrence of coking, the NOACK value of the base oil (A) used in one aspect of the present invention may be 5% by mass or less, less than 5% by mass, 4% by mass or less, less than 4% by mass, 3% by mass or less, or less than 3% by mass.

[0016] Furthermore, the NOACK value of the base oil (A) can be adjusted, for example, by removing light fractions through distillation. Furthermore, in this specification, the NOACK value refers to the value measured at 250°C for 1 hour in accordance with ASTM D5800.

[0017] The kinematic viscosity of the base oil (A) used in one aspect of the present invention at 40°C is preferably 32 to 120 mm². 2 / s, more preferably 34-100mm 2 / s, more preferably 35-80 mm 2 / s, more preferably 35-60 mm 2 It is / s. In this specification, kinematic viscosity refers to the value measured in accordance with ASTM D445.

[0018] The viscosity index of the base oil (A) used in one aspect of the present invention is preferably 80 or higher, more preferably 100 or higher, even more preferably 110 or higher, and even more preferably 120 or higher. In this specification, viscosity index refers to a value calculated in accordance with ASTM D2270.

[0019] In one aspect of the present invention, the base oil (A) may be a single base oil or a mixed oil combining two or more base oils. When a mixed oil is used, the NOACK value of the mixed oil should be within the above range. Therefore, the mixture may be a combination of base oils with a NOACK value of 6% by mass or less, or a combination of a base oil with a NOACK value of 6% by mass or less and a base oil with a NOACK value greater than 6% by mass. Furthermore, it is preferable that the kinematic viscosity and viscosity index of the mixed oil are within the above range.

[0020] In a lubricating oil composition according to one aspect of the present invention, the content of base oil (A) may be 60% by mass or more, 65% by mass or more, 70% by mass or more, 75% by mass or more, or 80% by mass or more, based on the total amount (100% by mass) of the lubricating oil composition, or it may be 99.9% by mass or less, 99.5% by mass or less, 99.0% by mass or less, 97.0% by mass or less, 95.0% by mass or less, 92.0% by mass or less, or 90.0% by mass or less.

[0021] <Component (B): Viscosity index improver> A lubricating oil composition according to one embodiment of the present invention may contain a viscosity index improver (B). By including a viscosity index improver, a lubricating oil composition with good fuel efficiency can be obtained. In one embodiment of the present invention, the viscosity index improver (B) may be used alone or in combination of two or more types.

[0022] Examples of the viscosity index improver (B) used in one aspect of the present invention include polymers such as non-dispersible polymethacrylate, dispersed polymethacrylate, olefin copolymers (e.g., ethylene-propylene copolymer, etc.), dispersed olefin copolymers, and styrene copolymers (e.g., styrene-diene copolymer, styrene-isoprene copolymer, etc.). The viscosity index improver (B) used in one aspect of the present invention may be a comb-shaped polymer having a structure in which the main chain has many tridental branching points from which high molecular weight side chains protrude, or it may be a star-shaped polymer having a structure in which one atom such as a carbon atom is bonded to three or more chain-like polymers.

[0023] In a lubricating oil composition according to one aspect of the present invention, from the viewpoint of providing a lubricating oil composition that can suppress the amount of coking that occurs, the content of the viscosity index improver (B) in terms of resin content is preferably 0.40% by mass or less, more preferably 0.35% by mass or less, and even more preferably 0.30% by mass or less, based on the total amount (100% by mass) of the lubricating oil composition, and may also be 0.01% by mass or more, 0.03% by mass or more, or 0.05% by mass or more.

[0024] In one aspect of the present invention, the viscosity index improver, the pour point depressant, and the defoamer described later are usually commercially available in the form of a solution dissolved in a diluent such as mineral oil or synthetic oil, taking into consideration handling properties and solubility with the base oil (A). However, the content of the viscosity index improver (B) mentioned above refers to the content on a resin (solids) basis, excluding the diluent.

[0025] <Additives for lubricating oils> A lubricating oil composition according to one aspect of the present invention may, if necessary, further contain other lubricating oil additives other than component (B), as long as they do not impair the effects of the present invention. Examples of such additives for lubricating oils include metal-based detergents, pour point depressants, antioxidants, friction modifiers, wear inhibitors, metal deactivators, ashless dispersants, and defoamers. These lubricating oil additives may be used individually or in combination of two or more types.

[0026] [Metal-based cleaning agent] One embodiment of the lubricating oil composition of the present invention may further contain a metal-based detergent. Metal-based cleaning agents may be used alone or in combination of two or more types. Examples of metal-based detergents used in one aspect of the present invention include metal salts such as metal sulfonates, metal salicylates, and metal phenates. Furthermore, the metal atoms constituting the metal salt are preferably selected from alkali metals and alkaline earth metals, and more preferably sodium, calcium, or magnesium. In addition, the metal-based cleaning agent used in one aspect of the present invention may be a neutral metal-based cleaning agent or a hyperbasic metal-based cleaning agent.

[0027] [Pour point depressant] A lubricating oil composition according to one embodiment of the present invention may further contain a pour point depressant. The pour point depressant may be used alone or in combination of two or more types. Examples of pour point depressants used in one aspect of the present invention include polymethacrylate, alkylated aromatic compounds, copolymers of fumarate and vinyl acetate, and copolymers of ethylene and vinyl acetate, with polymethacrylate having a weight-average molecular weight of 40,000 to 200,000 being preferred.

[0028] [Antioxidant] A lubricating oil composition according to 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 antioxidants used in one aspect of the present invention include amine-based antioxidants such as alkylated diphenylamine, phenylnaphthylamine, and alkylated phenylnaphthylamine; phenol-based antioxidants such as 2,6-di-t-butylphenol, 4,4'-methylenebis(2,6-di-t-butylphenol), isooctyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate, and n-octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate; and sulfur-based antioxidants such as phenothiazine, dioctadecyl sulfide, dilauryl-3,3'-thiodipropionate, and 2-mercaptobenzimidazole.

[0029] [Friction modifiers and wear-resistant agents] A lubricating oil composition according to one embodiment of the present invention may further contain a friction modifier or an anti-wear agent. The friction modifier or anti-wear agent may be used alone or in combination of two or more types. Examples of friction modifiers and wear-resistant agents used in one aspect of the present invention include, for example, sulfur compounds such as sulfurized olefins, dialkyl polysulfides, diarylalkyl polysulfides, and diaryl polysulfides; phosphorus compounds such as phosphate esters, thiophosphate esters, phosphite esters, alkyl hydrogen phosphites, phosphate ester amine salts, and phosphite ester amine salts; organic molybdenum compounds such as molybdenum dithiocarbamate (MoDTC), molybdenum dithiophosphate (MoDTP), and amine salts of molybdenum acid; organic zinc compounds such as zinc dithiophosphate (ZnDTP) and zinc dithiocarbamate (ZnDTC); and ashless friction modifiers such as amine compounds, fatty acid esters, fatty acid amides, fatty acids, aliphatic alcohols, aliphatic ethers, urea compounds, and hydrazide compounds.

[0030] [Metal deactivator] A lubricating oil composition according to one embodiment of the present invention may further contain a metal deactivator. The metal deactivator may be used alone or in combination of two or more types. Examples of metal deactivators used in one aspect of the present invention include benzotriazole, triazole derivatives, benzotriazole derivatives, thiadiazole derivatives, and the like.

[0031] [Ashless Dispersant] A lubricating oil composition according to one aspect of the present invention may further contain an ashless dispersant from the viewpoint of improving dispersibility. The ashless dispersant may be used alone or in combination of two or more types. In one aspect of the present invention, alkenyl succinimides are preferred as ashless dispersants, and examples include alkenyl succinic acid bisimide represented by the following general formula (f-1), alkenyl succinic acid monoimide represented by the following general formula (f-2), and the like.

[0032] [ka]

[0033] In the above general formulas (f-1) and (f-2), R f1 , R f2 and R f3 are each independently an alkenyl group having a number average molecular weight (Mn) of 900 to 2500. R f1 , R f2 and R f3 As the alkenyl group that can be selected as, examples thereof include a polybutenyl group, a polyisobutenyl group, and the like. A f1 , A f2 and A f3 are each independently an alkylene group having 2 to 5 carbon atoms. x1 is an integer of 2 to 6. x2 is an integer of 2 to 6.

[0034] In addition, the compound represented by the general formula (f-1) or (f-2) may be a modified alkenyl succinimide obtained by reacting with one or more selected from boron compounds, alcohols, aldehydes, ketones, alkylphenols, cyclic carbonates, epoxy compounds, and organic acids.

[0035] [Defoaming agent] The lubricating oil composition of one embodiment of the present invention may further contain a defoaming agent. The defoaming agent 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 alkyl silicone-based defoaming agents, fluorosilicone-based defoaming agents, fluoroalkyl ether-based defoaming agents, and the like.

[0036] [Properties of lubricating oil composition] The kinematic viscosity at 40 °C of the lubricating oil composition of one embodiment of the present invention is preferably 10 to 150 mm 2 / s, more preferably 20 to 120 mm 2 / s, more preferably 30 to 110 mm 2 / s, still more preferably 40 to 100 mm 2 / s, even more preferably 50 to 90 mm 2 / s, particularly preferably 55 to 85 mm 2 / s.

[0037] The kinematic viscosity of a lubricating oil composition according to one embodiment of the present invention at 100°C is preferably 9.5 mm². 2 The value must be greater than or equal to / s, and there is no particular upper limit, but for example, 16.3 mm 2 It may be less than / s.

[0038] The viscosity index of the lubricating oil composition according to one embodiment of the present invention is preferably 80 or higher, more preferably 100 or higher, more preferably 110 or higher, even more preferably 120 or higher, and even more preferably 130 or higher.

[0039] For a lubricating oil composition according to one embodiment of the present invention, the atomization rate measured and calculated based on the method described in the examples below is preferably 0.90% by mass or less, more preferably 0.80% by mass or less, even more preferably 0.70% by mass or less, even more preferably 0.65% by mass or less, and particularly preferably 0.60% by mass or less.

[0040] When a panel caulking test was performed on a lubricating oil composition according to one embodiment of the present invention, based on the method described in the examples in accordance with Fed.TestMethodStd.791-3462, under conditions of oil temperature of 90°C and panel temperature of 300°C for 24 hours, the amount of caulking material adhering to the panel was preferably 150 mg or less, more preferably 110 mg or less, even more preferably 100 mg or less, and particularly preferably 80 mg or less.

[0041] [Uses of lubricating oil compositions] A lubricating oil composition according to one aspect of the present invention exhibits excellent mist resistance in high-temperature environments and a high caulking suppression effect. Therefore, the lubricating oil composition according to one aspect of the present invention can be applied to various devices that can exhibit the above characteristics, but it can be suitably used for lubrication between parts in an internal combustion engine. In particular, among internal combustion engines, it can be suitably used for lubrication between parts in an internal combustion engine equipped with a turbocharger and operating on hydrogen as fuel (hereinafter also referred to as a "hydrogen fuel engine"). In a hydrogen fuel engine equipped with a turbocharger, the combustion chamber becomes extremely hot because the fuel is hydrogen, creating an environment where the lubricating oil composition is easily atomized. The atomized lubricating oil composition is discharged to the turbine wheel of the turbocharger installed on the exhaust passage side, but it adheres to the turbine wheel and becomes a cause of coking. In contrast, the lubricating oil composition according to one aspect of the present invention has excellent resistance to misting in high-temperature environments, so even when used in a hydrogen fuel engine equipped with a turbocharger, it can suppress the amount of lubricating oil composition that adheres to the turbine wheel and effectively suppress the occurrence of coking.

[0042] Furthermore, considering the above-mentioned properties of a lubricating oil composition according to one embodiment of the present invention, the present invention may also provide the following [I]. [I] A method for lubricating an internal combustion engine, comprising applying the lubricating oil composition according to one aspect of the present invention described above to the lubrication of the internal combustion engine. Examples of internal combustion engines described in [I] above include hydrogen fuel engines equipped with turbochargers, and in particular, hydrogen fuel engines equipped with turbine wheels installed on the exhaust passage side of the turbocharger can effectively suppress the generation of coking.

[0043] As described above, the present invention discloses the following aspects. [1] Contains base oil (A) with a NOACK value of 6% by mass or less as measured by a NOACK test conducted in accordance with ASTM D5800 under the conditions of 250°C for 1 hour. The CCS viscosity at -25℃ is 7000 mPa·s or less. The HTHS viscosity at 150°C is 2.9 mPa·s or higher. Lubricating oil composition. [2] Furthermore, it contains a viscosity index improver (B), The lubricating oil composition according to [1] above, wherein the content of viscosity index improver (B) on a resin basis is 0.40% by mass or less on a total basis of the lubricating oil composition. [3] The lubricating oil composition according to [1] or [2] above, for use in an internal combustion engine equipped with a turbocharger and operating on hydrogen as fuel. [4] A method for lubricating an internal combustion engine, comprising applying the lubricating oil composition described in [1] or [2] above to the lubrication of the internal combustion engine. [5] The method for lubricating an internal combustion engine according to [4] above, wherein the internal combustion engine is an internal combustion engine equipped with a turbocharger and operating on hydrogen as fuel. [Examples]

[0044] Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited in any way by these examples. The methods for measuring various physical properties are as follows.

[0045] (1)Kinematic viscosity Measurements were taken in accordance with ASTM D445. (2) Viscosity index at 40°C and 100°C The calculation was performed in accordance with ASTM D2270. (3) NOACK value Measurements were taken at 250°C for 1 hour, in accordance with ASTM D5800. (4)CCS viscosity Measurements were taken at -25°C in accordance with ASTM D5293. (5)HTHS viscosity (150℃) Measurements were taken at 150°C in accordance with ASTM D4683.

[0046] The base oils and various additives used in the following examples and comparative examples are as follows. <Base oil (A)> Table 1 shows the API (American Petroleum Institute) base oil category classifications and properties of the base oils (a1-1) to (a1-5) and (a2-1) to (a2-5) used in the examples and comparative examples. [Table 1]

[0047] <Various additives> • Viscosity index improver (1): A solution of hydrogenated styrene-diene copolymer diluted with a diluent oil classified as Group III in the API base oil category, resin concentration = 6.5% by mass. • Viscosity index improver (2): A solution of hydrogenated styrene-diene copolymer diluted with a diluent oil classified as Group I of the API base oil category, resin concentration = 10.7% by mass. • Pour point depressant: Polymethacrylate (VISCOPLEX 1-500 (manufactured by EVONIK)) • Additive mixture: JASO DH-2 additive package containing antioxidants, metal-based detergents, dispersants, anti-wear agents, and defoamers.

[0048] Examples 1-6, Comparative Examples 1-2 The base oils and various additives described above were added in the amounts shown in Table 2 and thoroughly mixed to prepare the lubricating oil compositions. The properties of the base oils used (mixed base oils) and the properties of the prepared lubricating oil compositions are shown in Table 2. Furthermore, the following tests were conducted using the prepared lubricating oil composition. The results are also shown in Table 2.

[0049] (1) Mist resistance test Under the measurement conditions described below, each sample oil, which is a prepared lubricating oil composition, was mixed with compressed air to form a mist, and the amount of floating mist (mist mass, unit: g) was measured. (Measurement conditions) • Test equipment: TACO mist measuring device (Model number: C3-0807) • Air pressure: 0.2 MPa ·Sample oil amount: 40g Then, the misting rate was measured using the following formula (i). Formula (i): Atomization rate (mass%) = [Mass of atomized oil (g) / Mass of sample oil (=40g)] × 100 A lower atomization rate indicates less suspended mist and superior mist resistance, suggesting that the lubricating oil composition suppresses caulking. In this example, a atomization rate of 0.90% by mass or less was considered to indicate a lubricating oil composition with good mist resistance.

[0050] (2) Panel caulking test Measurements were taken in accordance with Fed.TestMethodStd.791-3462. Specifically, 300 mL of sample oil was placed in a test container equipped with a splasher, an aluminum panel was attached to the top, the sample oil was heated to 90°C and the panel to 300°C, and the splasher was rotated to continuously splash the oil onto the panel for 24 hours. After the test, the amount of caulking material adhering to the panel was weighed (in mg). The smaller the amount of adhesive, the better the lubricating oil composition is in terms of resistance to caulking. In this example, a lubricating oil composition was judged to have good resistance to caulking when the amount of adhesive was 150 mg or less.

[0051] [Table 2]

[0052] As shown in Table 2, the lubricating oil compositions prepared in Examples 1 to 6 exhibited superior mist resistance compared to the lubricating oil compositions of Comparative Examples 1 to 2, resulting in effective suppression of caulking.

Claims

1. It contains base oil (A) with a NOACK value of 6% by mass or less, as measured by a NOACK test conducted at 250°C for 1 hour in accordance with ASTM D5800. The CCS viscosity at -25°C is 7000 mPa·s or less. The HTHS viscosity at 150°C is 2.9 mPa·s or higher. A lubricating oil composition for use in an internal combustion engine equipped with a turbocharger and operating on hydrogen as fuel.

2. Furthermore, it contains a viscosity index improver (B), The lubricating oil composition according to claim 1, wherein the content of the viscosity index improver (B) on a resin basis is 0.40% by mass or less on a total basis of the lubricating oil composition.

3. A method for lubricating an internal combustion engine, comprising applying the lubricating oil composition according to claim 1 or 2 to the lubrication of an internal combustion engine equipped with a turbocharger and operating on hydrogen as fuel.

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