Lubricating oil composition

Abstract

To provide a lubricant composition capable of improving life performance, reliability, and efficiency.SOLUTION: A lubricant composition of the present invention is characterized by including (A) a poly-α-olefin-containing synthetic base oil having a kinematic viscosity at 100°C of 5 mm2 / s or over and 30 mm2 / s or under and a group III base oil as a lubricant base oil, and (B) a performance improvement additive.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a lubricating oil composition, and more particularly to a lubricating oil composition for a gas engine.

Background Art

[0002] A gas engine cogeneration system is a system that generates electricity using a gas engine and utilizes waste heat as energy. Here, the "gas" refers to natural gas or city gas. In recent years, there has been an urgent need to improve the efficiency (compactification and high output) of gas cogeneration systems. Therefore, countermeasures have been studied not only on the hardware side but also on the lubricating oil (engine oil) side. Specifically, reduction of viscous resistance (low friction) by reducing the product viscosity (low viscosity) and improvement of traction performance (low friction under high pressure) can be mentioned.

[0003] In Patent Document 1, in order to improve traction performance and fuel efficiency, two different base oils: a kinematic viscosity of 2 mm 2 / s or more and 12 mm 2 / s or less at 100 °C, and a first base oil which is one or more oils selected from the group consisting of Group I, Group II, Group III, Group IV or Group V base oils, and a kinematic viscosity of at least 38 mm 2 / s at 100 °C, and a base oil containing a bimodal blend of a second base oil selected from Group IV base oils, wherein the difference in kinematic viscosity between the first base oil and the second base oil is at least 30 mm 2 / s has been proposed. However, in order to reduce the product viscosity of the lubricating oil composition, a low-viscosity base oil has to be used, which may lead to an increase in oil consumption and a decrease in reliability.

[0004] Furthermore, since lubricating oil compositions are exposed to a constant high-temperature environment, their lifespan is often limited by their oxidation stability. Additionally, because lubricating oil compositions operate with high emissions of nitrogen oxides (NOx), their lifespan may be limited by their nitrification resistance. Therefore, lubricating oil compositions with superior lifespan performance are required. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Special Publication No. 2013-518937 [Overview of the project] [Problems that the invention aims to solve]

[0006] Currently, there is a need for a lubricating oil composition that can improve lifespan, reliability, and efficiency in a balanced manner while reducing the viscosity of the product. Therefore, the object of the present invention is to provide a lubricating oil composition that can improve lifespan, reliability, and efficiency in a balanced manner. [Means for solving the problem]

[0007] The present inventors conducted diligent studies to solve the above problems and have found that in a lubricating oil composition, (A) as a lubricating oil base oil, the kinematic viscosity at 100°C is 5 mm 2 / s or more 30mm 2 We have found that the above problems can be solved by blending a poly-α-olefin-containing synthetic base oil with a viscosity of 1 / s or less, a Group III base oil, and (B) a performance-enhancing additive, and have thus completed the present invention.

[0008] In other words, the present invention provides the following invention. [1] (A) Lubricating oil base oil with a kinematic viscosity of 5 mm at 100°C 2 / s or more 30mm 2 A synthetic base oil containing poly-α-olefins with a viscosity of / s or less, and a Group III base oil, (B) Performance improver, and a lubricating oil composition containing the same. [2] The kinematic viscosity of the Group III base oil at 100 °C is 3.0 mm 2 / s or more and 9.0 mm 2 / s or less. The lubricating oil composition according to [1]. [3] The blending ratio of the synthetic base oil containing polyalphaolefin and the Group III base oil is 10:90 to 90:10. The lubricating oil composition according to [1] or [2]. [4] The kinematic viscosity of the lubricating oil composition at 100 °C is 9.3 mm 2 / s or more and less than 12.5 mm 2 / s. The lubricating oil composition according to any one of [1] to [3]. [5] The viscosity index of the lubricating oil composition is 120 or more and 160 or less. The lubricating oil composition according to any one of [1] to [4]. [6] The (B) performance improver contains (B1) a metal detergent. The lubricating oil composition according to any one of [1] to [5]. [7] The (B) performance improver contains (B2) an ashless dispersant. The lubricating oil composition according to any one of [1] to [6]. [8] The (B) performance improver contains (B3) an antioxidant. The lubricating oil composition according to any one of [1] to [7]. [9] The (B) performance improver contains (B4) an antiwear agent. The lubricating oil composition according to any one of [1] to [8].

[10] For a gas engine. The lubricating oil composition according to any one of [1] to [9]. [Advantages of the Invention]

[0009] The lubricating oil composition according to the present invention can improve the life performance, reliability performance, and efficiency performance in a balanced manner. Such a lubricating oil composition can be suitably used for a gas engine that requires these performances. [Embodiments for Carrying Out the Invention]

[0010] [Lubricating Oil Composition] The lubricating oil composition according to the present invention comprises at least (A) a lubricating oil base oil and (B) a performance-enhancing additive, and may further contain other additives. The lubricating oil composition according to the present invention can improve lifespan, reliability, and efficiency in a balanced manner. Such a lubricating oil composition can be suitably used for gas engines.

[0011] [Physical properties of lubricating oil compositions] The kinematic viscosity of the lubricating oil composition at 100°C is preferably 9.3 mm. 2 / s or more 12.5mm 2 Less than / s, more preferably 9.4mm 2 / s or more 12.0mm 2 / s or less, and more preferably 9.5 mm 2 / s or more 11.5mm 2 It is less than or equal to / s. If the kinematic viscosity of the lubricating oil composition at 100°C is within the above numerical range, the product viscosity can be made lower than that of conventional lubricating oils for gas cogeneration, and sufficient fuel efficiency can be obtained. In this specification, "kinematic viscosity at 100°C" refers to the kinematic viscosity at 100°C measured in accordance with JIS K 2283-2010.

[0012] The kinematic viscosity of the lubricating oil composition at 40°C is preferably 40 mm². 2 / s or more 100mm 2 / s or less, more preferably 45mm 2 / s or more 90mm 2 / s or less, and more preferably 50mm 2 / s or more 80mm 2 It is less than or equal to / s. If the kinematic viscosity of the lubricating oil composition at 40°C is within the above numerical range, the product viscosity can be made lower than that of conventional lubricating oils for gas cogeneration, and sufficient fuel efficiency can be obtained. In this specification, "kinematic viscosity at 40°C" refers to the kinematic viscosity at 40°C measured in accordance with JIS K 2283-2010.

[0013] The viscosity index of the lubricating oil composition is preferably 120 to 160, more preferably 125 to 155, and even more preferably 130 to 150. If the viscosity index of the lubricating oil composition is within the above numerical range, the viscosity in the actual operating temperature range can be lower than that of conventional lubricating oils for gas cogeneration, and sufficient fuel efficiency can be obtained. In this specification, "viscosity index" refers to the viscosity index measured in accordance with JIS K 2283-2010.

[0014] The following describes in detail each component constituting the lubricating oil composition according to the present invention.

[0015] [(A) Lubricant base oil] The lubricating oil composition according to the present invention comprises a poly-α-olefin-containing synthetic base oil and a group III base oil according to the API base oil classification as the lubricating oil base oil.

[0016] (Synthetic base oil containing poly-alpha-olefin (PAO)) Typical examples of poly-α-olefin-containing synthetic base oils include α-olefin oligomers or co-oligomers (1-octene oligomers, decene oligomers, ethylene-propylene co-oligomers, etc.) having 2 to 32 carbon atoms, preferably 6 to 16 carbon atoms, and their hydrogenation products. The method for producing poly-α-olefins is not particularly limited, but examples include polymerizing α-olefins in the presence of a polymerization catalyst, such as a catalyst containing a complex of aluminum trichloride or boron trifluoride with water, alcohol (ethanol, propanol, butanol, etc.), carboxylic acid, or ester. Poly-α-olefin (PAO)-containing synthetic base oils may be used alone or in combination of two or more types.

[0017] The kinematic viscosity of the poly-α-olefin-containing synthetic base oil at 100°C is 5 mm². 2 / s or more 30mm 2 / s or less, more preferably 6mm 2 / s or more 25mm 2 / s or less, and more preferably 7mm2 / s or more 20mm 2 The kinematic viscosity at 100°C of the poly-α-olefin-containing synthetic base oil is within the above numerical range. If the use of this base oil allows for both reduced traction and reduced viscosity, sufficient fuel efficiency can be achieved.

[0018] The kinematic viscosity of the poly-α-olefin-containing synthetic base oil at 40°C is preferably 20 mmHg. 2 / s or more 500mm 2 / s or less, more preferably 30mm 2 / s or more 450mm 2 / s or less, and more preferably 40mm 2 / s or more 400mm 2 The kinematic viscosity of the poly-α-olefin-containing synthetic base oil at 40°C is within the above numerical range. If the use of this base oil allows for both reduced traction and reduced viscosity, sufficient fuel efficiency can be achieved.

[0019] The viscosity index of the poly-α-olefin-containing synthetic base oil is preferably 100 or higher, more preferably 110 or higher, even more preferably 120 or higher, and may also be 200 or lower, 180 or lower, or 160 or lower. If the viscosity index of the poly-α-olefin-containing synthetic base oil is within the above numerical range, the viscosity-temperature characteristics of the lubricating oil composition will be good, enabling both low traction and low viscosity when using the base oil, and sufficient fuel efficiency can be obtained.

[0020] (Group III base oil) According to the API classification, Group III base oils are mineral oil-based base oils with a sulfur content of 0.03% by mass or less, a saturation content of 90% by mass or more, and a viscosity index of 120 or higher. In the present invention, the Group III base oil is not particularly limited, and conventionally known Group III base oils can be used. Group III base oils may be used alone or in combination of two or more types.

[0021] Examples of mineral oil-based base oils in Group III include paraffinic or naphthenic base oils obtained by applying one or more refining methods, such as solvent delamination, solvent extraction, hydrocracking, solvent dewaxing, catalytic dewaxing, hydrorefining, sulfuric acid washing, and clay treatment, to lubricating oil fractions obtained by atmospheric and vacuum distillation of crude oil. API Group III base oils are usually produced through a hydrocracking process.

[0022] The kinematic viscosity of Group III base oil at 100°C is 3.0 mm². 2 / s or more 9.0mm 2 / s or less, more preferably 3.5 mm 2 / s or more 8.5mm 2 The value is less than or equal to / s, and more preferably 4.0 mm 2 / s or more 8.0mm 2 It is less than / s. If the kinematic viscosity of the Group III base oil at 100°C is within the above numerical range, the product viscosity can be lower than that of conventional gas cogeneration lubricants, and sufficient fuel efficiency can be obtained.

[0023] The kinematic viscosity of the Group III base oil at 40°C is preferably 10 mmHg. 2 / s or more 100mm 2 / s or less, more preferably 12mm 2 / s or more 80mm 2 / s or less, and more preferably 15mm 2 / s or more 60mm 2 It is less than / s. If the kinematic viscosity of the Group III base oil at 40°C is within the above numerical range, the product viscosity can be lower than that of conventional lubricating oils for gas cogeneration, and sufficient fuel efficiency can be obtained.

[0024] The viscosity index of the Group III base oil is preferably 100 or higher, more preferably 110 or higher, even more preferably 120 or higher, and may also be 200 or lower, 180 or lower, or 160 or lower. If the viscosity index of the Group III base oil is within the above numerical range, the viscosity-temperature characteristics of the lubricating oil composition will be good, and sufficient fuel efficiency can be obtained.

[0025] The blending ratio of the above poly-α-olefin-containing synthetic base oil to the above Group III base oil is preferably 10:90 to 90:10 by mass, more preferably 20:80 to 80:20, and even more preferably 30:70 to 70:30. If the above blending ratio is within the above numerical range, both low traction and low viscosity can be achieved, and sufficient fuel efficiency can be obtained.

[0026] The content of lubricating oil base oil in the lubricating oil composition is preferably 70% by mass or more, more preferably 75% by mass or more, even more preferably 80% by mass or more, and preferably 98% by mass or less, based on the total amount of the lubricating oil composition.

[0027] [(B) Performance-enhancing additives] Examples of performance-enhancing additives include (B1) metal-based detergents, (B2) ashless dispersants, (B3) antioxidants, and (B4) anti-wear agents. These performance-enhancing additives may be used individually or in combination of two or more types.

[0028] The content of the performance-enhancing additive in the lubricating oil composition is preferably 1 to 20 parts by mass, and more preferably 2 to 15 parts by mass, per 100 parts by mass of the lubricating oil base oil.

[0029] [(B1) Metal-based cleaner] As a metal-based cleaning agent, it is preferable to use an alkaline earth metal-based cleaning agent. Examples of alkaline earth metal-based cleaning agents include phenate-based cleaning agents, sulfonate-based cleaning agents, and salicylate-based cleaning agents. These cleaning agents can be used individually or in combination of two or more. In this specification, "alkaline earth metal" also includes magnesium.

[0030] Examples of phenate-based cleaning agents include overbasic salts of alkaline earth metal salts of compounds having the structure shown in the following general formula (1). Examples of alkaline earth metals include calcium, magnesium, and barium, with calcium or magnesium being preferred among them.

[0031] [ka] In general formula (1), R 1 represents a linear or branched alkyl or alkenyl group, saturated or unsaturated; m is the degree of polymerization; A represents a sulfide (-S-) group or a methylene (-CH2-) group; and x is an integer between 1 and 3. 1 R may be a combination of two or more different groups. 1 The number of carbon atoms is 6 to 21, preferably 9 to 18, and more preferably 9 to 15. 1 By having the number of carbon atoms within the above numerical range, solubility and heat resistance can be improved. Furthermore, the degree of polymerization m in general formula (1) is an integer between 1 and 10, preferably between 1 and 4. By having the degree of polymerization m within the above numerical range, heat resistance can be improved.

[0032] Examples of sulfonate-based detergents include alkaline earth metal salts or basic or overbasic salts of alkyl aromatic sulfonic acids obtained by sulfonating alkyl aromatic compounds, i.e., basic or overbasic salts of compounds having the structure shown in the following general formula (2). Examples of alkaline earth metals include calcium, magnesium, and barium, with calcium or magnesium being preferred among them.

[0033] [ka] In the above general formula (2), R 2 Each of these independently represents an alkyl or alkenyl group having 23 to 102 carbon atoms, and M represents an alkaline earth metal. The weight-average molecular weight of the alkyl aromatic compound is preferably 400 to 1500, and more preferably 700 to 1300.

[0034] Examples of alkyl aromatic sulfonic acids include so-called petroleum sulfonic acids and synthetic sulfonic acids. Examples of petroleum sulfonic acids include alkyl aromatic compounds obtained by sulfonating the lubricating oil fraction of mineral oil, and so-called mahogany acid, which is a by-product during the production of white oil. An example of a synthetic sulfonic acid is obtained by sulfonating alkylbenzenes having linear or branched alkyl groups, which are obtained by recovering by-products in alkylbenzene production plants that are raw materials for detergents, or by alkylating benzene with polyolefins. Another example of a synthetic sulfonic acid is obtained by sulfonating alkylnaphthalenes such as dinonylnaphthalene. Furthermore, there are no particular restrictions on the sulfonating agent used when sulfonating these alkyl aromatic compounds; for example, fuming sulfuric acid or anhydrous sulfuric acid can be used.

[0035] Examples of salicylate-based cleaning agents include alkaline earth metal salicylates or their basic or overbasic salts. Examples of alkaline earth metal salicylates include compounds represented by the following general formula (3). Examples of alkaline earth metals include calcium, magnesium, and barium, with calcium or magnesium being preferred among these.

[0036] [ka] In the above general formula (3), R 3 Each of these independently represents an alkyl or alkenyl group having 14 to 30 carbon atoms, and M represents an alkaline earth metal.

[0037] The method for producing alkaline earth metal salicylates is not particularly limited, and known methods for producing monoalkyl salicylates can be used. For example, alkaline earth metal salicylates can be obtained by reacting monoalkyl salicylic acid, obtained by alkylating with an olefin using phenol as a starting material and then carboxylating with carbon dioxide, or by reacting monoalkyl salicylic acid, obtained by alkylating with an equivalent amount of the above olefin using salicylic acid as a starting material, with an alkaline earth metal base such as an alkaline earth metal oxide or hydroxide, or by first converting these monoalkyl salicylic acids into alkali metal salts such as sodium salts or potassium salts and then performing metal exchange with an alkaline earth metal salt.

[0038] Alkaline earth metal-based cleaning agents may be over-basicated with alkaline earth metal carbonates or over-basicated with alkaline earth metal borates.

[0039] There are no particular limitations on the method for obtaining an alkaline earth metal-based detergent that has been over-basified with an alkaline earth metal carbonate. For example, it can be obtained by reacting a neutral salt of an alkaline earth metal-based detergent (alkaline earth metal phenate, alkaline earth metal sulfonate, alkaline earth metal salicylate, etc.) with an alkaline earth metal base (alkaline earth metal hydroxide, oxide, etc.) in the presence of carbon dioxide.

[0040] There are no particular limitations on the method for obtaining an alkaline earth metal-based detergent that has been overbased with an alkaline earth metal borate. It can be obtained by reacting a neutral salt of an alkaline earth metal-based detergent (alkaline earth metal phenate, alkaline earth metal sulfonate, alkaline earth metal salicylate, etc.) with an alkaline earth metal base (alkaline earth metal hydroxide, oxide, etc.) in the presence of boric acid, boric anhydride, or a borate.

[0041] As alkaline earth metal-based cleaning agents, alkaline earth metal phenates, alkaline earth metal sulfonates, alkaline earth metal salicylates, or combinations thereof can be used, with alkaline earth metal sulfonates being preferred.

[0042] The total base number of the alkaline earth metal-based detergent is not particularly limited and may be 0, but is preferably 10 mg KOH / g or more and 500 mg KOH / g or less, more preferably 50 mg KOH / g or more and 500 mg KOH / g or less, and even more preferably 100 mg KOH / g or more and 500 mg KOH / g or less. If the total base number of the alkaline earth metal-based detergent is within the above numerical range, the acid neutralization properties necessary for lubricating oil can be maintained, and wear resistance and seizure resistance can be further improved. When two or more alkaline earth metal-based detergents are used in mixture, it is preferable that the base number obtained from the mixture is within the above range. The total base number is a value measured according to ASTM D2896.

[0043] The content of the metal-based detergent is preferably 1 to 10 parts by mass, more preferably 2 to 9 parts by mass, and even more preferably 3 to 8 parts by mass, per 100 parts by mass of lubricating oil base oil. If the content of the metal-based detergent is within the above numerical range, sufficient base number maintenance performance and engine combustion chamber cleaning effect can be obtained.

[0044] [(B2) Ashless Dispersant] The ashless dispersant (hereinafter sometimes referred to as "component (B2)") is not particularly limited, and for example, one or more compounds selected from (B2-1) to (B2-3) below can be used. (B2-1) Succinimide or a derivative thereof having at least one alkyl group or alkenyl group in the molecule (hereinafter sometimes referred to as "component (B2-1)"), (B2-2) Benzylamine or its derivative having at least one alkyl group or alkenyl group in the molecule (hereinafter sometimes referred to as "component (B2-2)"), (B2-3) Polyamines or derivatives thereof having at least one alkyl group or alkenyl group in the molecule (hereinafter sometimes referred to as "component (B2-3)").

[0045] As component (B2), component (B2-1) can be used particularly preferably. Examples of succinimides among component (B2-1) that have at least one alkyl group or alkenyl group in their molecule include compounds represented by the following general formula (4) or general formula (5).

[0046] [ka] [ka] In general formula (4), R 4 R represents an alkyl group or alkenyl group, and h represents an integer between 1 and 5, preferably between 2 and 4. 4The number of carbon atoms is preferably 60 or more, and more preferably 350 or less.

[0047] In general formula (5), R 5 and R 6 Each of these independently represents an alkyl group or an alkenyl group, and may be a different combination of groups. 5 and R 6 The group is particularly preferably a polybutenyl group. Also, i is an integer between 0 and 4, preferably between 1 and 3. 5 and R 6 The number of carbon atoms is preferably 60 or more, and more preferably 350 or less.

[0048] R in general formulas (4) and (5) 4 ~R 6 By having a carbon number equal to or greater than the above lower limit, good solubility in the lubricating oil base oil can be obtained. On the other hand, R 4 ~R 6 By keeping the number of carbon atoms below the above upper limit, the low-temperature fluidity of the lubricating oil composition can be improved.

[0049] The alkyl or alkenyl group (R) in general formulas (4) and (5) 4 ~R 6 The group may be linear or branched, and preferably, for example, branched alkyl groups or branched alkenyl groups derived from olefin oligomers such as propylene, 1-butene, and isobutene, or from co-oligomers of ethylene and propylene. Among these, branched alkyl groups or alkenyl groups derived from isobutene oligomers, commonly called polyisobutylene, or polybutenyl groups are most preferred.

[0050] The alkyl or alkenyl group (R) in general formulas (4) and (5) 4 ~R 6 The number-average molecular weight of ) is preferably 800 to 3500.

[0051] Succinimides having at least one alkyl or alkenyl group in the molecule include so-called monotype succinimides represented by general formula (4), in which succinic anhydride is attached to only one end of the polyamine chain, and so-called bistype succinimides represented by general formula (5), in which succinic anhydride is attached to both ends of the polyamine chain. The lubricating oil composition of the present invention may contain either monotype succinimides or bistype succinimides, or both may be contained as a mixture.

[0052] The method for producing succinimides having at least one alkyl or alkenyl group in the molecule is not particularly limited. For example, alkyl succinic acid or alkenyl succinic acid obtained by reacting a compound having an alkyl or alkenyl group with 40 to 400 carbon atoms with maleic anhydride at 100°C to 200°C can be obtained by reacting the resulting mixture with a polyamine. Examples of polyamines include diethylenetriamine, triethylenetetramine, tetraethylenepentamine, and pentaethylenehexamine.

[0053] Examples of benzylamines among component (B2-2) that have at least one alkyl group or alkenyl group in their molecule include compounds represented by the following general formula (6).

[0054] [ka] In general formula (6), R 7 R represents an alkyl or alkenyl group having 40 to 400 carbon atoms, and j represents an integer between 1 and 5, preferably between 2 and 4. 7 The number of carbon atoms is preferably 60 or more, and more preferably 350 or less.

[0055] The method for producing component (B2-2) is not particularly limited. For example, one method involves reacting a polyolefin such as propylene oligomer, polybutene, or ethylene-α-olefin copolymer with phenol to form an alkylphenol, and then reacting this alkylphenol with formaldehyde and a polyamine such as diethylenetriamine, triethylenetetramine, tetraethylenepentamine, or pentaethylenehexamine by a Mannich reaction.

[0056] Examples of polyamines among components (B2-3) that have at least one alkyl group or alkenyl group in their molecule include compounds represented by the following formula (7).

[0057] [ka] In general formula (7), R 8 R represents an alkyl or alkenyl group having 40 to 400 carbon atoms, and k represents an integer between 1 and 5, preferably between 2 and 4. 8 The number of carbon atoms is preferably 60 or more, and more preferably 350 or less.

[0058] The method for producing components (B2-3) is not particularly limited. For example, one method involves chlorinating a polyolefin such as propylene oligomer, polybutene, or ethylene-α-olefin copolymer, and then reacting it with ammonia or a polyamine such as ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, or pentaethylenehexamine.

[0059] Examples of derivatives in components (B2-1) to (B2-3) include (i) succinimide, benzylamine, or polyamine having at least one alkyl or alkenyl group in the molecule (hereinafter referred to as "the above nitrogen-containing compound"), which is reacted with a monocarboxylic acid having 1 to 30 carbon atoms such as fatty acids, a polycarboxylic acid having 2 to 30 carbon atoms (e.g., oxalic acid, phthalic acid, trimellitic acid, pyromellitic acid, etc.), their anhydrides or ester compounds, alkylene oxide having 2 to 6 carbon atoms, or a hydroxy(poly)oxyalkylene carbonate, thereby neutralizing or amidating some or all of the remaining amino and / or imino groups, and is acid-containing. Examples of modified compounds include: (i) boron-modified compounds obtained by reacting the above-mentioned nitrogen-containing compound with boric acid, thereby neutralizing or amidating some or all of the remaining amino and / or imino groups; (iii) phosphorylated compounds obtained by reacting the above-mentioned nitrogen-containing compound with phosphoric acid, thereby neutralizing or amidating some or all of the remaining amino and / or imino groups; (iv) sulfur-modified compounds obtained by reacting the above-mentioned nitrogen-containing compound with a sulfur compound; and (v) modified compounds obtained by combining two or more modifications selected from modification with an oxygen-containing organic compound, boron modification, phosphoric acid modification, and sulfur modification on the above-mentioned nitrogen-containing compound. Among these derivatives of (i) to (v), the use of a boron-modified compound of alkenyl succinimide can further improve electrical insulation properties.

[0060] There are no particular restrictions on the molecular weight of component (B2), but the weight-average molecular weight of component (B2-1) is preferably 1000 to 20000, and more preferably 2000 to 10000.

[0061] The content of the ashless dispersant is preferably 1 to 10 parts by mass, more preferably 2 to 9 parts by mass, and even more preferably 3 to 8 parts by mass, per 100 parts by mass of lubricating oil base oil. If the content of the ashless dispersant is within the above numerical range, a sufficient sludge dispersion effect can be obtained.

[0062] [(B3) Antioxidant] The antioxidant is not particularly limited, and compounds commonly used as antioxidants for lubricating oils can be used. Examples of antioxidants include amine-based antioxidants and phenol-based antioxidants. As amine-based antioxidants, known amine-based antioxidants such as alkylated diphenylamine, alkylated phenyl-α-naphthylamine, phenyl-α-naphthylamine, and phenyl-β-naphthylamine can be used. As phenol-based antioxidants, known phenol-based antioxidants such as 2,6-di-tert-butyl-4-methylphenol (DBPC) and 4,4'-methylenebis(2,6-di-tert-butylphenol) can be used.

[0063] The antioxidant content is preferably 0.01 parts by mass to 5 parts by mass, and more preferably 0.1 parts by mass to 3 parts by mass, per 100 parts by mass of lubricating oil base oil. A sufficient antioxidant effect can be obtained if the antioxidant content is within the above numerical range.

[0064] [(B4) Anti-wear agent] The anti-wear agent is not particularly limited, and compounds commonly used as anti-wear agents for lubricating oils can be used. Examples of anti-wear agents include sulfur-based, phosphorus-based, and sulfur-phosphorus-based anti-wear agents. Specifically, examples of anti-wear agents include phosphite esters, thiophosphite esters, dithiophosphite esters, trithiophosphite esters, phosphate esters, thiophosphate esters, dithiophosphate esters, trithiophosphate esters, amine salts thereof, metal salts thereof, derivatives thereof, dithiocarbamates, zinc dithiocarbamates, disulfides, polysulfides, sulfurized olefins, and sulfurized oils and fats.

[0065] Among these anti-wear agents, phosphorus-based anti-wear agents are preferred, and in particular, zinc dialkyldithiophosphate (ZnDTP), represented by the following formula (8), is preferred. [ka]

[0066] In formula (8), R 9 ~R 12 Each of these independently represents a linear or branched alkyl group having 1 to 24 carbon atoms, and may be a combination of different groups. Also, R 9 ~R 12 The number of carbon atoms is preferably 3 or more, preferably 12 or less, and more preferably 8 or less. Also, R 9 ~R 12 The alkyl group may be a primary alkyl group, a secondary alkyl group, or a tertiary alkyl group, but it is preferably a primary alkyl group, a secondary alkyl group, or a combination thereof. Furthermore, the molar ratio of primary alkyl group to secondary alkyl group (primary alkyl group:secondary alkyl group) is preferably 0:100 to 30:70. This ratio may be the combination ratio of alkyl chains within the molecule, or it may be the mixed ratio of ZnDTP having only primary alkyl groups and ZnDTP having only secondary alkyl groups. The presence of a secondary alkyl group improves fuel efficiency.

[0067] The above method for producing zinc dialkyldithiophosphate is not particularly limited. For example, R 9 ~R 12 It can be synthesized by reacting an alcohol having the corresponding alkyl group with phosphorus pentasulfide to synthesize dithiophosphate, and then neutralizing it with zinc oxide.

[0068] The amount of anti-wear agent is preferably 0.01 parts by mass or more and 5 parts by mass or less, and more preferably 0.1 parts by mass or more and 3 parts by mass or less, per 100 parts by mass of lubricating oil base oil. If the amount of anti-wear agent is within the above numerical range, a sufficient anti-wear effect can be obtained.

[0069] [Other ingredients] In addition to components (A) and (B) described above, the lubricating oil composition may further contain other components commonly used in lubricating oil compositions, such as thickeners, rust inhibitors, pour point depressants, anti-emulsifiers, metal deactivators, and antifoaming agents.

[0070] As the thickener, any known thickener used in lubricating oils can be used without particular limitation. Examples include polymethacrylate, ethylene-α-olefin copolymer and its hydride, copolymer of α-olefin and an ester monomer having a polymerizable unsaturated bond, polyisobutylene and its hydride, styrene-diene copolymer hydride, styrene-maleic anhydride copolymer, and polyalkylstyrene. Among these, polymethacrylate, ethylene-α-olefin copolymer or its hydride, or a combination thereof can be preferably used. The thickener may be dispersed or non-dispersed. The weight-average molecular weight of the thickener may be, for example, 2000 to 30000. The lubricating oil composition does not need to contain a thickener, but if the lubricating oil contains a thickener, the content is preferably 0.01 parts by mass or more and 10 parts by mass or less, and more preferably 0.05 parts by mass or more and 5 parts by mass or less, per 100 parts by mass of lubricating oil base oil.

[0071] Examples of rust inhibitors include petroleum sulfonates, alkylbenzene sulfonates, dinonylnaphthalene sulfonates, alkenyl succinate esters, and polyhydric alcohol esters. Lubricating oil compositions do not need to contain rust inhibitors, but if a lubricating oil composition contains a rust inhibitor, the amount is preferably 0.01 parts by mass or more and 1 part by mass or less, and more preferably 0.05 parts by mass or more and 0.5 parts by mass or less, per 100 parts by mass of lubricating oil base oil.

[0072] As a pour point depressant, for example, a polymethacrylate-based polymer that is compatible with the lubricating oil base oil used can be used. The lubricating oil composition does not have to contain a pour point depressant, but if the lubricating oil composition contains a pour point depressant, the content is preferably 0.01 parts by mass or more and 1 part by mass or less, and more preferably 0.05 parts by mass or more and 0.5 parts by mass or less, per 100 parts by mass of the lubricating oil base oil.

[0073] Examples of anti-emulsifiers include polyalkylene glycol-based nonionic surfactants such as polyoxyethylene alkyl ethers, polyoxyethylene alkylphenyl ethers, and polyoxyethylene alkylnaphthyl ethers. The lubricating oil composition does not need to contain an anti-emulsifier, but if it does, the amount is preferably 0.01 parts by mass or more and 5 parts by mass or less, and more preferably 0.05 parts by mass or more and 3 parts by mass or less, per 100 parts by mass of the lubricating oil base oil.

[0074] Examples of metal deactivators include imidazoline, pyrimidine derivatives, alkylthiadiazole, mercaptobenzothiazole, 1,3,4-thiadiazole polysulfide, 1,3,4-thiadiazolyl-2,5-bisdialkyldithiocarbamate, 2-(alkyldithio)benzimidazole, and β-(o-carboxybenzylthio)propionnitrile. The lubricating oil composition does not need to contain a metal deactivator, but if the lubricating oil composition does contain a metal deactivator, the content is preferably 0.01 parts by mass or more and 1 part by mass or less, and more preferably 0.05 parts by mass or more and 0.5 parts by mass or less, per 100 parts by mass of the lubricating oil base oil.

[0075] As an antifoaming agent, for example, one with a kinematic viscosity of 1,000 mm at 25°C. 2 / s or more 1,000,000mm 2Examples include silicone oils with a viscosity of 0.0001 or less, alkenyl succinic acid derivatives, esters of polyhydroxyaliphatic alcohols and long-chain fatty acids, methyl salicylates, and o-hydroxybenzyl alcohol. The lubricating oil composition does not need to contain an antifoaming agent, but if the lubricating oil composition contains an antifoaming agent, the amount is preferably 0.0001 parts by mass or more and 0.5 parts by mass or less, and more preferably 0.0005 parts by mass or more and 0.1 parts by mass or less, per 100 parts by mass of the lubricating oil base oil. [Examples]

[0076] The present invention will be specifically described below with reference to examples and comparative examples, but the present invention is not limited to these examples.

[0077] [(A) Lubricant base oil] Base oils A to J, as shown in Table 1 below, were prepared. In Table 1 below, the kinematic viscosity (100°C, 40°C) and viscosity index were measured in accordance with JIS K 2283-2010. [Table 1]

[0078] [(B) Performance-enhancing additives] Various additives, shown in Table 1 below (B1) to (B4), were prepared. (B1) Metal-based cleaning agent: Calcium salicylate (B2) Ashless dispersant: Polyalkenyl succinate imide (B3) Antioxidant: Diphenylamine + Hindered phenol (B4) Anti-wear agent: ZnDTP (zinc dialkyldithiophosphate) ((a mixture of compounds represented by general formula (8))

[0079] The following additives were prepared for comparative analysis. Viscosity index improver: Olefin copolymer (average molecular weight: approximately 130,000)

[0080] [Preparation of lubricating oil composition] Using the lubricating oil base oil and various additives prepared above, lubricating oil compositions of the present invention (Examples 1-5) and comparative lubricating oil compositions (Comparative Examples 1-4) were prepared according to the formulations shown in Table 2. In Table 2, the amount of each component is expressed in parts by mass.

[0081] [Physical properties of lubricating oil compositions] The following physical properties were measured for each lubricating oil composition in Examples 1-5 and Comparative Examples 1-4. The measurement results for the lubricating oil compositions are shown in Table 2. • Kinematic viscosity (100°C, 40°C): Values ​​measured in accordance with JIS K 2283-2010. • Viscosity index: The value was measured in accordance with JIS K 2283-2010.

[0082] [Performance evaluation of lubricating oil compositions] The following performance evaluations were performed on each lubricating oil composition in Examples 1-5 and Comparative Examples 1-4. The evaluation results are shown in Table 2.

[0083] [Life characteristics] (NOx blowing test) A NOx injection test was conducted on each lubricating oil composition. In this test, a heat-resistant glass container containing the oil sample was heated in an oil bath, and oxygen and NOx were injected into the glass container. x This is an accelerated oxidation degradation test that simulates oil degradation in the engine combustion chamber by injecting (NO+NO2). The test conditions are as follows. After the test, the residual base number and acid value increase of each lubricating oil composition were measured by the hydrochloric acid method in accordance with JIS K2501. A higher residual base number indicates better lifespan performance, and a lower acid value increase also indicates better lifespan performance. In particular, a residual base number of 0.70 or higher and an acid value increase of 1.00 or lower indicates excellent lifespan performance. <Test Conditions> Mixed gas: A mixture of oxygen (85%), NO2 (1000 ppm), and nitrogen (remainder). Test temperature: 140℃ Exam duration: 48 hours

[0084] [Reliability] (Abrasion mark diameter) Each lubricating oil composition was tested according to ASTM D417-82 (Shell high-speed four-ball abrasion test) under conditions of 294N, 1800 rpm, 80°C, and 30 min, and the abrasion mark diameter was measured. A smaller abrasion mark diameter indicates better reliability. In particular, an abrasion mark diameter of 0.50 or less indicates excellent reliability.

[0085] (Oil consumption: NOACK evaporation) Each lubricating oil composition was tested in accordance with ASTM D5800. Specifically, the percentage of mass loss after thermal degradation by heating at 250°C for 1 hour was measured. A smaller percentage of mass loss indicates lower oil consumption and superior performance in suppressing sludge formation in the combustion chamber. In particular, a percentage of mass loss of 6.0 or less indicates excellent performance as a lubricating oil for gas cogeneration systems where long service life is required.

[0086] [Efficiency Performance] (Coefficient of friction between metals) For each lubricating oil composition, friction tests were conducted using a reciprocating friction tester (SRV; Schwingungs Reihungund Verschleiss tester @ Optimol Instruments) to measure the intermetallic friction coefficient. The test conditions are as follows: The sliding condition was a cylinder-on-disk type (test piece material: steel (according to ASTM D5706)), the test time was 30 minutes, and the average value between 25 and 30 minutes was used as the friction coefficient data. In this test, a smaller value of the intermetallic friction coefficient indicates better friction characteristics, i.e., better fuel efficiency. In particular, an intermetallic friction coefficient of 0.140 or less indicates excellent fuel efficiency. <Test Conditions> Load: 170N Frequency: 50Hz Test temperature: 80℃ Exam duration: 30 minutes

[0087] (Traction coefficient) The traction coefficient of each lubricating oil composition was evaluated using an EHD oil film thickness tester (manufactured by PCS Instruments). The test conditions were room temperature, a load of 20N (surface pressure 0.44GPa / average Hertz pressure (steel ball vs. glass disk)), a peripheral speed of 0.5m / s, and the traction coefficient was measured while varying the slip ratio (2-5%). The value at a slip ratio of 3% (average value of n=2) was adopted as the traction data. A smaller traction coefficient value indicates better traction performance. In particular, a traction performance value of 0.015 or less indicates excellent traction performance.

[0088] [Table 2]

[0089] The lubricating oil compositions of Examples 1 to 5 showed good results in terms of lifespan, reliability, and efficiency. On the other hand, (A) as a lubricating oil base oil, the kinematic viscosity at 100°C is 5 mm 2 / s or more 30mm 2 Comparative Example 1, which did not use any poly-α-olefin-containing synthetic base oil or group III base oil with a viscosity of 0.0 or less, showed inferior results in terms of lifespan and traction coefficient. (A) As a lubricating oil base oil, the kinematic viscosity at 100°C is 5 mm². 2 / s or more 30mm 2 Comparative Example 2, which did not use a poly-α-olefin-containing synthetic base oil with a viscosity of 1 / s or less, showed inferior results in terms of lifespan, reliability, and traction coefficient. (A) Comparative examples 3 and 4, which used a poly-α-olefin-containing synthetic base oil with excessively high kinematic viscosity at 100°C as the lubricating oil base oil, showed inferior results in terms of oil consumption and intermetallic friction coefficient.

Claims

1. (A) As a lubricating oil base oil, the kinematic viscosity at 100°C is 8.0 mm. ２ / s or more 30mm ２ Poly-α-olefin-containing synthetic base oils with a coefficient of 1 / s or less, and Group III base oils, (B) Performance-enhancing additives, A lubricating oil composition comprising, The content of the lubricating oil base oil (A) is 80% by mass or more and 98% by mass or less on a total basis of the lubricating oil composition. A lubricating oil composition in which the blending ratio of the poly-α-olefin-containing synthetic base oil and the group III base oil is 20:80 to 80:

20.

2. The kinematic viscosity of the aforementioned Group III base oil at 100°C is 3.0 mm². ２ / s or more 9.0mm ２ The lubricating oil composition according to claim 1, wherein the value is less than or equal to / s.

3. The lubricating oil composition according to claim 1, wherein the blending ratio of the poly-α-olefin-containing synthetic base oil and the group III base oil is 30:70 to 70:

30.

4. The kinematic viscosity of the aforementioned lubricating oil composition at 100°C is 9.3 mm. ２ / s or more 12.5mm ２ The lubricating oil composition according to claim 1, wherein the value is less than / s.

5. The lubricating oil composition according to claim 1, wherein the viscosity index of the lubricating oil composition is 120 or more and 160 or less.

6. The lubricating oil composition according to claim 1, wherein the content of the performance-enhancing additive (B) is 1 part by mass or more and 20 parts by mass or less per 100 parts by mass of the lubricating oil base oil (A).

7. (B) The lubricating oil composition according to claim 1, wherein the performance-enhancing additive comprises (B1) a metal-based detergent.

8. (B) The lubricating oil composition according to claim 1, wherein the performance-enhancing additive comprises (B2) an ashless dispersant.

9. (B) The lubricating oil composition according to claim 1, wherein the performance-enhancing additive comprises (B3) an antioxidant.

10. (B) The lubricating oil composition according to claim 1, wherein the performance-enhancing additive comprises (B4) an anti-wear agent.

11. A lubricating oil composition according to any one of claims 1 to 10, for use in a gas engine.

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