Lubricating oil composition

Abstract

To provide a lubricant composition that contains an oil-based friction modifier, having improved friction reducing performance in the lubrication of a gear.SOLUTION: A lubricant composition contains: (A) a lubricant base oil that contains one or more mineral base oils, one or more synthetic base oils, or a combination thereof, while having a kinematic viscosity at 40°C of 40 mm2 / s or less; and (B) a partial ester of (b1) one or more saturated or unsaturated monovalent fatty acids having 3 to 30 carbon atoms and (b2) one or more glycerol oligomers having a polymerization degree of 3 to 6 in an amount of 0.05-2.5 mass% based on the total amount of the composition.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a lubricating oil composition, and more particularly to a lubricating oil composition that can be suitably used for lubricating gears. [Background technology]

[0002] Lubricating oils are used to smooth the operation of internal combustion engines, automatic transmissions, bearings, etc. Generally, various additives are blended into lubricating oils to give them the performance required.

[0003] Among lubricating oil additives, additives that reduce frictional resistance (friction modifiers, hereafter sometimes referred to as "FM") are important components in reducing energy loss due to friction. Commonly used FMs can be classified into organomolybdenum-based FMs containing molybdenum and oiliness-based FMs (also called ashless FMs), which reduce friction by improving oiliness.

[0004] Widely known organic molybdenum-based FMs include molybdenum dithiocarbamate (MoDTC) and molybdenum dithiophosphate (MoDTP) (see, for example, Patent Document 1). While these organic molybdenum-based FMs offer excellent friction-reducing effects in the early stages of use, there are limitations to maintaining this friction-reducing effect over a long period of time. Furthermore, organic molybdenum-based FMs contain ash, which makes it difficult to reuse used lubricating oil. Therefore, there is a demand for reducing the amount of organic molybdenum-based FM added.

[0005] On the other hand, oil-based FMs have the potential to overcome the above-mentioned problems of organomolybdenum-based FMs, and therefore oil-based FMs are becoming increasingly important (see, for example, Patent Documents 2 and 3). [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-133453 [Patent Document 2] Japanese Patent Application Laid-Open No. 2009-235252 [Patent Document 3] Japanese Patent Application Laid-Open No. 2006-257383 [Patent Document 4] Special Publication No. 2016-540870 [Patent Document 5] Japanese Patent Application Laid-Open No. 2015-521685 [Patent Document 6] Japanese Patent Application Laid-Open No. 2011-140643 [Patent Document 7] International Publication No. 2003 / 031543 [Patent Document 8] Japanese Patent Application Publication No. 11-217577 [Patent Document 9] Japanese Patent Application Laid-Open No. 2005-061610 Summary of the Invention [Problem to be solved by the invention]

[0007] However, conventional oil-based FMs still have room for improvement in terms of gear friction coefficient. One example of a means to improve the energy efficiency of machinery is the use of low-viscosity lubricants made with low-viscosity base oils. Low-viscosity lubricants can reduce stirring resistance and improve energy efficiency. However, because low-viscosity base oils tend to reduce oil film thickness, the transition from hydrodynamic lubrication to mixed lubrication begins at a lower load than with conventional lubricants made with higher-viscosity base oils, and the friction coefficient begins to increase. This problem is particularly serious in the lubrication of gears, where the load on the lubricated surface increases in proportion to the driving force being transmitted.

[0008] An object of the present invention is to provide a lubricating oil composition containing an oiliness-based friction modifier that has improved friction-reducing performance in gear lubrication even when the composition has a low viscosity. [Means for solving the problem]

[0009] The present invention includes the following embodiments [1] to [6].

[0010] [1] (A) One or more mineral base oils or one or more synthetic base oils or a combination thereof, and having a kinematic viscosity of 40 mm at 40 ° C. 2 / s or less lubricating base oil; (B) A partial ester of one or more saturated or unsaturated monovalent fatty acids (b1) having 3 to 30 carbon atoms and one or more glycerin oligomers (b2) having a degree of polymerization of 3 to 6 is contained in an amount of 0.05 to 2.5% by mass based on the total amount of the composition. A lubricating oil composition comprising:

[0011] [2] The lubricating oil composition according to [1], wherein the fatty acid (b1) has 6 to 30 carbon atoms.

[0012] [3] (B') Contains or does not contain a partial ester of glycerin, a glycerin polymer other than the glycerin oligomer (b2), or a combination thereof with a fatty acid, The lubricating oil composition according to [1] or [2], wherein the content (unit: mass%) of the component (B') is not more than half the content (unit: mass%) of the component (B) based on the total amount of the composition.

[0013] [4] The lubricating oil composition according to any one of [1] to [3], further comprising one or more additives selected from a metallic detergent, an ashless dispersant, a phosphorus-containing antiwear agent, a sulfur-containing extreme pressure agent, an antioxidant, and a viscosity index improver.

[0014] [5] Kinematic viscosity at 40°C is 7.0 to 50 mm 2 The lubricating oil composition according to any one of [1] to [4], wherein the lubricating oil composition is a lubricating oil composition having a molecular weight of 1.0 or less.

[0015] [6] The lubricating oil composition according to any one of [1] to [5], which is used for lubricating gears. [Effects of the Invention]

[0016] The lubricating oil composition of the present invention is a lubricating oil composition containing a specific oily agent-based friction modifier, and can exhibit an improved friction reduction effect in the lubrication of gears while having a low viscosity.

Mode for Carrying Out the Invention

[0017] Hereinafter, the present invention will be described in detail. In this specification, unless otherwise specified, the notation "A to B" for numerical values A and B is equivalent to "A or more and B or less". In such a notation, when only the numerical value B is given a unit, the said unit is also applied to the numerical value A. In this specification, the words "or" and "or" mean a logical sum unless otherwise specified. In this specification, the notation "E1 and / or E2" for elements E1 and E2 is equivalent to "E1, or E2, or a combination thereof", and for N elements E1, …, E i , …, E N (N is an integer of 3 or more.) the notation "E1, …, and / or E N " is equivalent to "E1, …, or E i , …, or E N , or a combination thereof" (i is a variable that takes all integer values satisfying 1 < i < N). Also, in this specification, "alkaline earth metal" includes magnesium.

[0018] In this specification, unless otherwise specified, the content of each element of calcium, magnesium, zinc, phosphorus, sulfur, boron, barium, and molybdenum in the oil is measured by inductively coupled plasma optical emission spectrometry (intensity ratio method (internal standard method)) in accordance with JIS K0116. Also, the content of the nitrogen element in the oil is measured by chemiluminescence method in accordance with JIS K2609. Also, in this specification, "weight average molecular weight" means the weight average molecular weight in terms of standard polystyrene measured by gel permeation chromatography (GPC). The measurement conditions of GPC are as follows. [GPC Measurement Conditions] Equipment: Waters Corporation ACQUITY (registered trademark) APC UV RI system Columns: From the upstream side, two Waters Corporation ACQUITY® APC XT900A (gel particle size 2.5 μm, column size (inner diameter x length) 4.6 mm x 150 mm) and one Waters Corporation ACQUITY® APC XT200A (gel particle size 2.5 μm, column size (inner diameter x length) 4.6 mm x 150 mm) were connected in series. Column temperature: 40℃ Sample solution: tetrahydrofuran solution with a sample concentration of 1.0% by mass Eluent: tetrahydrofuran Solution injection volume: 20.0μL Detector: Differential refractive index detector Reference material: 8 standard polystyrenes (Agilent EasiCal (registered trademark) PS-1, manufactured by Agilent Technologies) (molecular weights: 2,698,000, 597,500, 290,300, 133,500, 70,500, 30,230, 9,590, 2,970) If the weight-average molecular weight measured under the above conditions is less than 10,000, change the column and standard substance to the following conditions and perform the measurement again. Columns: From the upstream side, one Waters Corporation ACQUITY® APC XT125A (gel particle size 2.5 μm, column size (inner diameter x length) 4.6 mm x 150 mm) and two Waters Corporation ACQUITY® APC XT45A (gel particle size 1.7 μm, column size (inner diameter x length) 4.6 mm x 150 mm) were connected in series. Reference material: 10 standard polystyrene samples (Agilent EasiCal (registered trademark) PS-1, manufactured by Agilent Technologies) (molecular weights: 30230, 9590, 2970, 890, 786, 682, 578, 474, 370, 266)

[0019] <(A) Lubricant base oil> The lubricating oil composition of the present invention (hereinafter sometimes referred to as "lubricating oil composition" or "composition") comprises a major amount of lubricating base oil and one or more additives other than the base oil. In the lubricating oil composition of the present invention, the lubricating base oil comprises one or more mineral base oils or one or more synthetic base oils, or a combination thereof, and has a kinematic viscosity at 40°C of 40mm 2 / s or less (hereinafter sometimes referred to as "component (A)").

[0020] The lubricant base oil may be one or more mineral base oils, one or more synthetic base oils, or a mixture thereof. In one embodiment, the lubricant base oil may be API Group I base oil (hereinafter referred to as "API Group I base oil"), Group II base oil (hereinafter referred to as "API Group II base oil"), Group III base oil (hereinafter referred to as "API Group III base oil"), Group IV base oil (hereinafter referred to as "API Group IV base oil"), or Group V base oil (hereinafter referred to as "API Group V base oil"), or a mixture thereof. API Group I base oils are mineral base oils having a sulfur content of more than 0.03 mass% and / or less than 90 mass% saturates and a viscosity index of 80 or greater but less than 120. API Group II base oils are mineral base oils having a sulfur content of 0.03 mass% or less, a saturates content of 90 mass% or greater, and a viscosity index of 80 or greater but less than 120. API Group III base oils are mineral base oils with a sulfur content of 0.03% by mass or less, a saturates content of 90% by mass or more, and a viscosity index of 120 or more. API Group IV base oils are poly-α-olefin base oils. API Group V base oils are base oils other than those in Groups I to IV, and preferred examples thereof include ester-based base oils.

[0021] In one embodiment, component (A) can be preferably one or more API Group II base oils, one or more API Group III base oils, one or more API Group IV base oils, or one or more API Group V base oils, or a combination thereof.

[0022] Examples of mineral base oils include paraffinic base oils, which are obtained by refining lubricating oil fractions obtained by atmospheric and / or vacuum distillation of crude oil through one or a combination of two or more refining processes selected from solvent deasphalting, solvent extraction, hydrocracking, solvent dewaxing, catalytic dewaxing, hydrorefining, sulfuric acid washing, clay treatment, etc., as well as normal paraffinic base oils, isoparaffinic base oils, and mixtures thereof. API Group II base oils and Group III base oils are usually produced through a hydrocracking process.

[0023] %C of mineral base oil P is preferably 60 or more, more preferably 65 or more, from the viewpoint of further improving the viscosity-temperature characteristics and fuel economy of the composition, and is preferably 99 or less, more preferably 95 or less, even more preferably 94 or less, from the viewpoint of improving the solubility of the additives, and in one embodiment, may be 60 to 99, or 60 to 95, or 65 to 95, or 65 to 94.

[0024] %C of mineral base oil A is preferably 2 or less, more preferably 1 or less, even more preferably 0.8 or less, and particularly preferably 0.5 or less, from the viewpoint of further improving the viscosity-temperature characteristics and fuel economy of the composition.

[0025] %C of mineral base oil N is preferably 1 or more, more preferably 4 or more, from the viewpoint of enhancing the solubility of the additive, and is preferably 40 or less, more preferably 35 or less, from the viewpoint of further enhancing the viscosity-temperature characteristics and fuel economy of the composition, and in one embodiment, may be 1 to 40, or 4 to 35.

[0026] In this specification, %C P , %C Nand %C A The percentages of paraffin carbon number to the total carbon number, naphthenic carbon number to the total carbon number, and aromatic carbon number to the total carbon number are determined by a method (ndM ring analysis) in accordance with ASTM D 3238-85. P , %C N and %C A The preferred range of %C is based on the value determined by the above method. For example, even in the case of a lubricating base oil that does not contain naphthenes, the %C determined by the above method is N can have a value greater than 0.

[0027] From the viewpoint of improving the viscosity-temperature characteristics of the composition, the content of saturated components in the mineral base oil is preferably 90% by mass or more, more preferably 95% by mass or more, and even more preferably 99% by mass or more, based on the total amount of the base oil. In this specification, saturated components refer to values ​​measured in accordance with ASTM D 2007-93.

[0028] The aromatic content of the mineral base oil is preferably 0 to 10% by mass, more preferably 0 to 5% by mass, and particularly preferably 0 to 1% by mass, based on the total amount of the base oil. In one embodiment, it may be 0.1% by mass or more. By having the aromatic content be equal to or less than the above upper limit, it is possible to improve the low-temperature viscosity characteristics and viscosity-temperature characteristics in a fresh oil state, further improve fuel economy, and reduce evaporation loss of the lubricating oil, thereby reducing lubricating oil consumption. Furthermore, when additives are blended into the lubricating base oil, the effects of the additives can be effectively exerted. Furthermore, although the lubricating base oil may be free of aromatics, by having the aromatic content be equal to or greater than the above lower limit, the solubility of the additives can be improved.

[0029] In this specification, the aromatic content refers to a value measured in accordance with ASTM D 2007-93. The aromatic content typically includes alkylbenzenes, alkylnaphthalenes, anthracene, phenanthrene, and alkylated products thereof, as well as compounds having four or more fused benzene rings, pyridines, quinolines, phenols, naphthols, and other aromatic compounds having heteroatoms.

[0030] Examples of API Group IV base oils include oligomers and cooligomers of α-olefins having 2 to 32 carbon atoms, preferably 6 to 16 carbon atoms, and hydrogenated products thereof, such as ethylene-propylene copolymers, polybutene, 1-octene oligomers, 1-decene oligomers, and hydrogenated products thereof.

[0031] Preferred examples of API Group V base oils include ester-based base oils such as monoesters (e.g., butyl stearate, octyl laurate, 2-ethylhexyl oleate, etc.), diesters (e.g., ditridecyl glutarate, di-2-ethylhexyl adipate, diisodecyl adipate, ditridecyl adipate, di-2-ethylhexyl sebacate, etc.), polyesters (e.g., trimellitic esters, etc.), and polyol esters (e.g., trimethylolpropane caprylate, trimethylolpropane pelargonate, pentaerythritol-2-ethylhexanoate, pentaerythritol pelargonate, etc.). Other examples of API Group V base oils include aromatic synthetic base oils such as alkylbenzenes, alkylnaphthalenes, polyoxyalkylene glycols, dialkyldiphenyl ethers, and polyphenyl ethers.

[0032] The kinematic viscosity of the lubricating base oil (all base oils) at 40°C is 40mm from the viewpoint of improving energy saving and low temperature viscosity characteristics of the lubricating oil composition. 2 / s or less, preferably 30 mm 2 / s or less, preferably 20 mm 2 / s or less, and from the viewpoint of improving the wear resistance and seizure resistance, it is preferably 6.0 mm2 / s or more, preferably 6.5 mm 2 / s or more, more preferably 7.0 mm 2 / s or more, and in one embodiment, 6.0 to 40 mm 2 / s, or 6.5 to 30 mm 2 / s, or 7.0 to 20 mm 2 In this specification, the term "kinematic viscosity at 40°C" refers to the kinematic viscosity at 40°C measured in accordance with JIS K 2283-2000 using an automatic viscometer (trade name "CAV-2100", manufactured by Cannon Instrument) as the measuring device.

[0033] The kinematic viscosity at 100°C of the lubricating base oil (all base oils) is preferably 5.0 mm from the viewpoint of further improving the energy saving and low temperature viscosity characteristics of the lubricating oil composition. 2 / s or less, preferably 4.0 mm 2 / s or less, more preferably 3.5 mm 2 / s or less, and from the viewpoint of improving the wear resistance and seizure resistance, it is preferably 1.9 mm 2 / s or more, preferably 2.0 mm 2 / s or more, more preferably 2.1 mm 2 / s or more, and in one embodiment, 1.9 to 5.0 mm 2 / s, or 2.0 to 4.0 mm 2 / s, or 2.1 to 3.5 mm 2 In this specification, the term "kinematic viscosity at 100°C" refers to the kinematic viscosity at 100°C measured in accordance with JIS K 2283-2000 using an automatic viscometer (trade name "CAV-2100", manufactured by Cannon Instrument) as the measuring device.

[0034] From the viewpoint of improving the viscosity-temperature characteristics of the composition and further improving fuel economy and wear resistance, the viscosity index of the lubricating base oil (total base oil) is preferably 100 or more, more preferably 105 or more, even more preferably 110 or more, particularly preferably 115 or more, and most preferably 120 or more. In this specification, viscosity index means a viscosity index measured in accordance with JIS K 2283-2000 using an automatic viscometer (trade name "CAV-2100", manufactured by Cannon Instrument) as the measuring device.

[0035] From the viewpoint of low-temperature fluidity of the entire lubricating oil composition, the pour point of the lubricating base oil (total base oil) is preferably −10° C. or lower, more preferably −12.5° C. or lower, even more preferably −15° C. or lower, particularly preferably −17.5° C. or lower, and most preferably −20.0° C. or lower. In this specification, pour point means the pour point measured in accordance with JIS K 2269-1987.

[0036] The sulfur content of a base oil depends on the sulfur content of the raw material. For example, when a raw material containing substantially no sulfur, such as a synthetic wax component obtained by the Fischer-Tropsch reaction, is used, a base oil containing substantially no sulfur can be obtained. Furthermore, when a raw material containing sulfur, such as slack wax obtained in the base oil refining process or microwax obtained in the refined wax process, is used, the sulfur content of the resulting base oil is usually 100 ppm by mass or more. The sulfur content of a lubricating base oil (total base oil) is usually 0.03% by mass or less, and preferably 0.01% by mass or less from the viewpoint of oxidation stability. In this specification, the sulfur content of a base oil refers to the amount of sulfur measured in accordance with JIS K 2541-2003.

[0037] The lubricating base oil has a kinematic viscosity of 40mm at 40°C as the entire base oil (total base oil). 2 As long as the viscosity of the base oil is not more than 1 / s, the base oil may consist of a single base oil component or may contain multiple base oil components.

[0038] In one embodiment, the lubricating base oil may contain 80 to 100 mass %, 90 to 100 mass %, 90 to 99 mass %, or 95 to 99 mass % of one or more API Group II base oils, one or more API Group III base oils, one or more API Group IV base oils, or one or more API Group V base oils, or a combination thereof, based on the total amount of base oil. The lubricating base oil may or may not contain API Group V base oil. In one embodiment, the content of one or more API Group V base oils in the lubricating base oil may be preferably 0 to 50 mass %, or 0 to 45 mass %, based on the total amount of base oil, from the viewpoint of improving oxidation stability, and 1 to 50 mass %, or 1 to 45 mass %, from the viewpoint of improving fatigue resistance. The lubricant base oil may or may not contain an API Group IV base oil. In one embodiment, the lubricant base oil may contain one or more API Group IV base oils in an amount of 0 to 70 mass %, or 0 to 65 mass %, or 1 to 70 mass %, or 1 to 65 mass %, based on the total mass of the base oil.

[0039] The content of lubricating base oil (total base oil) in the lubricating oil composition is 60 mass% or more, preferably 60 to 98.5 mass%, more preferably 70 to 98.5 mass%, and in one embodiment, 75 to 97 mass%, based on the total amount of the lubricating oil composition.

[0040] <(B) Fatty acid ester of glycerin oligomer> The lubricating oil composition of the present invention contains 0.05 to 2.5 mass% of a partial ester (hereinafter sometimes referred to as "component (B)") of one or more saturated or unsaturated monovalent fatty acids having 3 to 30 carbon atoms (hereinafter sometimes referred to as "fatty acid (b1)") and one or more glycerin oligomers having a degree of polymerization of 3 to 6 (hereinafter sometimes referred to as "glycerin oligomer (b2)"). In this specification, the term "partial ester" for an ester of glycerin oligomer (b2) and fatty acid (b1) means that the ester compound has one or more free hydroxy groups. That is, in component (B), at least one hydroxy group of the glycerin oligomer (b2) remains unesterified.

[0041] The fatty acid (b1) may be one type of fatty acid or a combination of two or more types of fatty acids. The fatty acid (b1) may be a saturated fatty acid or an unsaturated fatty acid. The fatty acid (b1) may be a straight-chain fatty acid or a branched-chain fatty acid, but is preferably a straight-chain fatty acid. Examples of the fatty acid (b1) include saturated fatty acids such as propionic acid, butanoic acid, pentanoic acid, hexanoic acid, heptanoic acid, octanoic acid, nonanoic acid, decanoic acid, undecanoic acid, dodecanoic acid, tridecanoic acid, tetradecanoic acid, pentadecanoic acid, hexadecanoic acid, heptadecanoic acid, octadecanoic acid, nonadecanoic acid, eicosanoic acid, heneicosanoic acid, docosanoic acid, tricosanoic acid, and tetracosanoic acid; Examples of unsaturated fatty acids include decenoic acid, butenoic acid, pentenoic acid, hexenoic acid, heptenoic acid, octenoic acid, nonenoic acid, decenoic acid, undecenoic acid, dodecenoic acid, tridecenoic acid, tetradecenoic acid, pentadecenoic acid, hexadecenoic acid, heptadecenoic acid, octadecenoic acid, nonadecenoic acid, eicosenoic acid, heneicosenoic acid, docosenoic acid, tricosenoic acid, and tetracosenoic acid; and mixtures thereof.

[0042] The number of carbon atoms in the fatty acid (b1) is 3 or more, preferably 6 or more, and in one embodiment 8 or more, from the viewpoint of enhancing the friction-reducing effect in gear lubrication, and from the same viewpoint, it is 30 or less, preferably 24 or less, and in one embodiment 18 or less, and in one embodiment, it may be 3 to 30, or 6 to 30, or 8 to 30, or 8 to 24, or 8 to 18. Preferred examples of the fatty acid (b1) include caprylic acid, 2-ethylhexanoic acid, pelargonic acid, capric acid, lauric acid, myristic acid, myristoleic acid, palmitic acid, palmitoleic acid, vaccenic acid, stearic acid, oleic acid, elaidic acid, linoleic acid, linolenic acid, eleostearic acid, stearidonic acid, arachidic acid, gadoleic acid, eicosenoic acid, eicosapentaenoic acid, behenic acid, erucic acid, sardine acid, docosahexaenoic acid, lignoceric acid, herring acid, and mixtures thereof. As a mixture containing two or more fatty acids, fatty acids derived from natural fats and oils or hydrogenated natural fats and oils may be used. Examples of fatty acids derived from natural fats and oils include coconut oil fatty acids, palm kernel oil fatty acids, palm oil fatty acids, tung oil fatty acids, tall oil fatty acids, corn oil fatty acids, rapeseed oil fatty acids, olive oil fatty acids, sesame oil fatty acids, soybean oil fatty acids, rice bran oil fatty acids, sunflower oil fatty acids, castor oil fatty acids, linseed oil fatty acids, fish oil fatty acids, beef tallow fatty acids, hydrogenated products thereof, and mixtures thereof. These fatty acids derived from natural fats and oils are mixtures of two or more fatty acids having 8 to 24 carbon atoms.

[0043] The glycerin oligomer (b2) can be produced, for example, by dehydration condensation of glycerin or ring-opening polymerization of glycidol. The glycerin oligomer (b2) may be an oligomer having a single degree of polymerization, or may be a combination of two or more oligomers having different degrees of polymerization. From the viewpoint of enhancing the effect of reducing gear friction, the polymerization degree of the glycerin oligomer (b2) is 3 or more, and from the same viewpoint, it is 6 or less, preferably 5 or less, and in one embodiment, it may be 4 or less, and in one embodiment, it may be 3 to 6, or 3 to 5, or 3 to 4.

[0044] Component (B) is an ester of a fatty acid (b1) and a glycerin oligomer (b2). In one embodiment, component (B) can be produced by a dehydration condensation reaction between the fatty acid (b1) and the glycerin oligomer (b2). Such a dehydration condensation reaction can be carried out, for example, by heating and refluxing the fatty acid (b1) and the glycerin oligomer (b2) in an organic solvent (e.g., toluene) that forms an azeotropic mixture with water in the presence of an acid catalyst (e.g., sulfuric acid, trifluoroacetic acid, etc.) while azeotropically removing the water produced as the condensation reaction proceeds. In another embodiment, component (B) can be produced by reacting the fatty acid (b1), the glycerin oligomer (b2), and a condensing agent in a solvent. Condensing agents include carbodiimide-based condensing agents such as N,N'-dicyclohexylcarbodiimide (DCC), N,N'-diisopropylcarbodiimide (DIC), and 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC); imidazole-based condensing agents such as N,N'-carbonyldiimidazole (CDI) and 1,1'-carbonyldi(1,2,4-triazole) (CDT); triazine-based condensing agents such as 4-(4,6-dimethoxy-1,3,5-triazin-2-yl)-4-methylmorpholinium chloride hydrate (DMT-MM); 2-chloro-1-methylpyridinium p-toluenesulfonate, and 2-fluoro-1-methylpyridinium Known condensing agents that can be used for esterification can be used without particular limitation, such as 2-halopyridinium salts such as p-toluenesulfonate; 2,4,6-trichlorobenzoyl chloride (TCBC); 2-methyl-6-nitrobenzoic anhydride (MNBA); a combination of diethyl azodicarboxylate (DEAD) and triphenylphosphine; a combination of a phosphine such as chlorodiphenylphosphine and 2,2'-dipyridyl disulfide; a combination of a p-benzoquinone such as 2,6-dimethyl-1,4-benzoquinone (DMBQ) or tetrafluoro-1,4-benzoquinone; and dimesitylammonium pentafluorobenzenesulfonate.The condensing agent may be used together with a catalyst such as 4-dimethylaminopyridine (DMAP), N-hydroxysuccinimide (NHS), 1-hydroxybenzotriazole (HOBt), or 1-hydroxy-7-azabenzotriazole (HOAt). In another embodiment, component (B) can be produced by reacting an acylating agent derived from a fatty acid (b1) with a glycerin oligomer (b2) in a solvent. Examples of the acylating agent derived from a fatty acid (b1) include acid halides of the fatty acid (b1) (e.g., acid chlorides, acid bromides, etc.), activated esters of the fatty acid (b1) (e.g., esters of the fatty acid (b1) and N-hydroxysuccinimide (NHS), esters of the fatty acid (b1) and 1-hydroxybenzotriazole (HOBt), esters of the fatty acid (b1) and 1-hydroxy-7-azabenzotriazole (HOAt), etc.), and acid anhydrides of the fatty acid (b1). The acylating agent derived from fatty acid (b1) may be used together with a catalyst such as 4-dimethylaminopyridine (DMAP). The solvent can be any organic solvent that does not interfere with the condensation reaction (e.g., aliphatic hydrocarbon solvents such as hexane and petroleum ether; aromatic hydrocarbon solvents such as benzene, toluene, and xylene; halogenated hydrocarbon solvents such as dichloromethane, 1,2-dichloroethane, chlorobenzene, and o-dichlorobenzene; pyridine, etc.). In the condensation reaction to produce component (B), if necessary, a suitable base (e.g., amines such as triethylamine, pyridine, and 2,6-lutidine; organolithium reagents such as butyllithium; inorganic bases such as potassium carbonate) may be added to the reaction mixture to promote the reaction or to capture the acid generated as the reaction proceeds (e.g., hydrogen halide is generated as the reaction proceeds in reactions using acid halides).

[0045] The glycerin oligomer (b2) has a plurality of hydroxy groups capable of reacting with the fatty acid (b1) (or an acylating agent derived from the fatty acid (b1)). In producing the component (B), the reaction molar ratio ((b2) / (b1)) of the fatty acid (b1) (or an acylating agent derived from the fatty acid (b1)) to the glycerin oligomer (b2) may be, for example, 1.0 to 10, preferably 1.0 to 5.0, more preferably 1.0 to 3.0, and in one embodiment, 1.0 to 2.0.

[0046] Component (B) has at least one free hydroxy group (hereinafter sometimes referred to as a "residual hydroxy group") derived from glycerin oligomer (b2). A glycerin oligomer (b2) with a degree of polymerization p (p is an integer of 2 or greater) has a maximum of p+2 hydroxy groups. Therefore, when component (B) has q ester bonds (q is an integer of 1 or greater), component (B) has a maximum of p+2-q residual hydroxy groups. The fact that glycerin oligomer (b2) with a degree of polymerization p has a "maximum" of p+2 hydroxy groups reflects the fact that glycerin oligomer (b2) can form a cyclic ether structure through a cyclization reaction involving intramolecular dehydration. A glycerin oligomer (b2) with r cyclic ether structures (where r is an integer of 0 or greater, and r=0 means no cyclic ether structure) loses 2r hydroxy groups due to the elimination of water during cyclization. That is, a glycerol oligomer (b2) having a degree of polymerization p and r cyclic ether structures has p+2-2r hydroxy groups. However, under normal conditions, the cyclic ether structure formed by such a cyclization reaction is a six-membered ring structure, and therefore the pair of two hydroxy groups involved in the intramolecular dehydration reaction is a pair of two hydroxy groups belonging to adjacent glycerol repeating units in the glycerol oligomer (b2). Since each glycerol repeating unit other than the terminal glycerol repeating unit of the glycerol oligomer has one or less hydroxy groups, typically, 0≦2r≦p, and therefore, p+2-2r≧2. Note that 2r is an even number, so when p is even, 0≦2r≦p, and when p is odd, 0≦2r≦p-1. Therefore, when p is even, p+2-2r≧2, and when p is odd, p+2-2r≧3. Such an intramolecular cyclization reaction can occur not only during the production of the glycerin oligomer (b2), but also during the condensation reaction between the glycerin oligomer (b2) and the fatty acid (b1). When the condensation reaction product between the glycerin oligomer (b2) and the fatty acid (b1) has s cyclic ether structures (where s is an integer of 0 or greater, and s=0 means that no cyclic ether structures are present), the condensation reaction product has p+2-q-2s residual hydroxy groups.Similarly to the above, normally, 0≦2s≦p (i.e., when p is an even number, 0≦2s≦p, and when p is an odd number, 0≦2s≦p−1), and therefore, when p is an even number, p+2−q−2s≧2−q, and when p is an odd number, p+2−q−2s≧3−q. In other words, even if one or more cyclic ether structures are formed by an intramolecular dehydration reaction, the monoester of the glycerin oligomer (b2) and the fatty acid (b1) has one or more free hydroxy groups (two or more when the degree of polymerization of the glycerin oligomer (b2) is odd).

[0047] After the condensation reaction between the fatty acid (b1) and the glycerin oligomer (b2) is complete, unreacted raw materials can be removed by known methods such as water washing, silica gel short-path column chromatography, and Celite filtration. The resulting product may contain one or more partial esters (which may have one or more cyclic ether structures) having one or more free hydroxy groups and one or more complete esters (which may have one or more cyclic ether structures) having no free hydroxy groups. The resulting product may be further purified by known purification methods such as column chromatography to remove or reduce the amount of complete esters in the product and increase the proportion of partial esters (component (B)).

[0048] Component (B) may contain (B1) a partial ester having only one free hydroxy group (hereinafter sometimes referred to as "component (B1)") and / or (B2) a partial ester having two or more free hydroxy groups (hereinafter sometimes referred to as "component (B2)"). The content of component (B2) in component (B) is preferably 70% by mass or more, 80% by mass or more, or 90% by mass or more, based on the total amount of component (B), from the viewpoint of further enhancing the friction-reducing effect under gear lubrication conditions, and is preferably 99% by mass or less from the viewpoint of ease of production. The content of component (B2) in component (B) can be adjusted, for example, by using an excess amount of glycerin oligomer (b2) relative to fatty acid (b1) in the condensation reaction, and further purifying the product obtained by the condensation reaction using a known purification method such as column chromatography.

[0049] The content of component (B) in the lubricating oil composition is 0.05% by mass or more, preferably 0.07% by mass or more, based on the total amount of the composition, from the viewpoint of enhancing the friction-reducing effect on metal surfaces that are prone to high loads, such as gears, and from the viewpoint of enhancing storage stability, it is 2.5% by mass or less, and in one embodiment, it may be 0.05 to 2.5% by mass or 0.07 to 2.5% by mass.

[0050] In addition to component (B), the lubricating oil composition may or may not further contain a partial ester (hereinafter sometimes referred to as "component (B')") of glycerin, a glycerin polymer (excluding those corresponding to the above-mentioned glycerin oligomer (b2)), or a combination thereof with a fatty acid (which may correspond to the above-mentioned fatty acid (b1)). In one embodiment, component (B') may be generated from impurities in the glycerin oligomer (b2). However, the content of component (B') (mass % based on the total amount of the composition) is preferably smaller than the content of component (B), and may be preferably ½ or less, ⅓ or less, or ¼ or less of the content of component (B) (mass % based on the total amount of the composition). In one embodiment, the content of component (B') may be 0 to 0.5 mass % based on the total amount of the composition. From the viewpoint of storage stability, the total content of components (B) and (B') in the lubricating oil composition is preferably 2.5 mass % or less based on the total amount of the composition.

[0051] In addition to component (B), the lubricating oil composition may or may not further contain a complete ester (hereinafter sometimes referred to as "component (B*)") of glycerin, a glycerin polymer (which may correspond to the above-mentioned glycerin oligomer (b2)), or a combination thereof with a fatty acid (which may correspond to the above-mentioned fatty acid (b1)). Component (B*) is a compound that does not have a free hydroxy group and may have one or more cyclic ether structures. In one embodiment, component (B*) may be generated as a by-product in the condensation reaction of glycerin oligomer (b2) with fatty acid (b1). However, the content of component (B*) (mass % based on the total amount of the composition) is preferably less than the content of component (B), and may be preferably 1 / 2 or less, 1 / 3 or less, or 1 / 4 or less of the content of component (B) (mass % based on the total amount of the composition). In one embodiment, the content of component (B*) may be 0 to 0.5 mass % based on the total amount of the composition.

[0052] <(C): Metallic detergent> In one preferred embodiment, the lubricating oil composition may further contain one or more metal-based detergents (hereinafter sometimes referred to as "component (C)"). Examples of component (C) include salicylate-based detergents, sulfonate-based detergents, and phenate-based detergents. Component (C) may contain only one type of metal-based detergent, or may contain two or more types of metal-based detergents. Generally, in the field of lubricating oils, the metal-based detergents used are organic acid metal salts capable of forming micelles in base oils (e.g., alkali or alkaline earth metal alkyl salicylates, alkali or alkaline earth metal alkyl benzene sulfonates, and alkali or alkaline earth metal alkyl phenates), or mixtures of such organic acid metal salts with basic metal salts (e.g., hydroxides, carbonates, borates, etc. of the alkali or alkaline earth metals that constitute the organic acid metal salts). Such organic acids usually have, in one molecule, at least one polar group (e.g., a carboxy group, a sulfo group, a phenolic hydroxy group, etc.) having a Bronsted acidity capable of forming a salt with a metal base (typically a metal oxide and / or a metal hydroxide), and at least one lipophilic group such as a linear or branched alkyl group (e.g., a linear or branched alkyl group having 6 or more carbon atoms, etc.).

[0053] Examples of salicylate detergents include metal salicylates or basic or overbased salts thereof. Preferred examples of metal salicylates include alkali or alkaline earth metal salicylates represented by the following general formula (1):

[0054] [ka]

[0055] In general formula (1), R 1each independently represents an alkyl or alkenyl group having 14 to 30 carbon atoms, M represents an alkali metal or alkaline earth metal, a represents 1 or 2, and n represents 1 or 2 corresponding to the valence of M. When M is an alkali metal, n is 1, and when M is an alkaline earth metal, n is 2. M is preferably an alkaline earth metal. As the alkali metal, sodium or potassium is preferred, and as the alkaline earth metal, calcium or magnesium is preferred. a is preferably 1. When a=2, R 1 may be a combination of different groups.

[0056] A preferred embodiment of the salicylate detergent is an alkaline earth metal salicylate, or a basic salt or overbased salt thereof, in which a=1 in the above general formula (1).

[0057] Preferred examples of sulfonate detergents include alkali or alkaline earth metal salts of alkyl aromatic sulfonic acids obtained by sulfonating alkyl aromatic compounds, or their basic salts or overbased salts, more preferably alkaline earth metal salts or their basic salts or overbased salts. The weight-average molecular weight of the alkyl aromatic compounds is preferably 400 to 1500, more preferably 700 to 1300. As the alkali metal, sodium or potassium is preferred, and as the alkaline earth metal, calcium or magnesium is preferred. Examples of alkyl aromatic sulfonic acids include so-called petroleum sulfonic acids and synthetic sulfonic acids. Examples of petroleum sulfonic acids include sulfonated alkyl aromatic compounds from the lubricating oil fraction of mineral oil, and so-called mahogany acid, which is a by-product produced during the production of white oil. Furthermore, an example of a synthetic sulfonic acid is sulfonated alkylbenzene having a linear or branched alkyl group, which is obtained by recovering by-products from an alkylbenzene production plant used as a raw material for detergents, or by alkylating benzene with polyolefin. Another example of a synthetic sulfonic acid is sulfonated alkylnaphthalene, such as dinonylnaphthalene. Furthermore, the sulfonating agent used to sulfonate these alkyl aromatic compounds is not particularly limited, and for example, fuming sulfuric acid or sulfuric anhydride can be used.

[0058] Preferred examples of phenate detergents include overbased salts of alkali or alkaline earth metal salts, more preferably overbased salts of alkaline earth metal salts, of compounds having a structure represented by the following general formula (2): The alkali metal is preferably sodium or potassium, and the alkaline earth metal is preferably calcium or magnesium.

[0059] [ka]

[0060] In general formula (2), R 2 represents a linear or branched, saturated or unsaturated alkyl or alkenyl group having 6 to 21 carbon atoms, m is the degree of polymerization and represents an integer of 1 to 10, A represents a sulfide (-S-) group or a methylene (-CH2-) group, and x represents an integer of 1 to 3. 2 may be a combination of two or more different groups.

[0061] R in general formula (2) 2 The number of carbon atoms is preferably 9 or more from the viewpoint of enhancing solubility in the base oil, and is preferably 18 or less, more preferably 15 or less, from the viewpoint of ease of production, and may be 9 to 18 or 9 to 15 in one embodiment.

[0062] The degree of polymerization m in the general formula (2) is preferably 1-4.

[0063] The metallic detergent may be overbased with a carbonate (e.g., an alkali metal carbonate such as sodium carbonate or potassium carbonate, or an alkaline earth metal carbonate such as calcium carbonate or magnesium carbonate), or with a borate (e.g., an alkali metal borate such as sodium borate or potassium borate, or an alkaline earth metal borate such as calcium borate or magnesium borate).

[0064] In one embodiment, component (C) may comprise one or more overbased calcium or magnesium sulfonate detergents, one or more overbased calcium or magnesium salicylate detergents, and / or one or more overbased calcium or magnesium phenate detergents, preferably one or more overbased calcium sulfonate detergents and / or one or more overbased calcium salicylate detergents. The calcium sulfonate detergents, calcium salicylate detergents, and calcium phenate detergents are each preferably overbased with calcium carbonate, and the magnesium sulfonate detergents, magnesium salicylate detergents, and magnesium phenate detergents are each preferably overbased with magnesium carbonate.

[0065] The base number of the metallic detergent can be appropriately determined depending on the application of the lubricating oil composition. For example, when the lubricating oil composition is used to lubricate gear devices such as transmissions (e.g., manual transmissions, automatic transmissions, continuously variable transmissions, etc.), the base number of the metallic detergent is preferably 200 mgKOH / g or more, more preferably 250 mgKOH / g or more, from the viewpoint of improving wear resistance, seizure resistance, and transmission torque capacity of wet clutches, and from the same viewpoint, is preferably 600 mgKOH / g or less, more preferably 550 mgKOH / g or less, and in one embodiment, may be 200 to 600 mgKOH / g, or 250 to 550 mgKOH / g. Furthermore, for example, when the lubricating oil composition is used for lubrication of an internal combustion engine, from the viewpoint of enhancing detergency and base number retention, it is preferably 0 mgKOH / g or more, more preferably 20 mgKOH / g or more, and from the viewpoint of suppressing ash content in the composition and extending the life of an exhaust gas aftertreatment device, it is preferably 500 mgKOH / g or less, more preferably 450 mgKOH / g or less, and in one embodiment it may be 0 to 500 mgKOH / g or 20 to 450 mgKOH / g. Note that, in this specification, the base number means the base number measured by the perchloric acid method in accordance with JIS K2501.

[0066] When the lubricating oil composition contains component (C), its content can be appropriately determined depending on the application of the lubricating oil composition. For example, when the lubricating oil composition is used to lubricate gear devices such as transmissions (e.g., manual transmissions, automatic transmissions, continuously variable transmissions, etc.), the content of component (C) in the lubricating oil composition is preferably 200 ppm by mass or more, more preferably 250 ppm by mass or more, in terms of the metal amount based on the total amount of the composition, from the viewpoints of improving wear resistance, seizure resistance, fatigue resistance, and the transmission torque capacity of wet clutches, and is preferably 600 ppm by mass or less, more preferably 550 ppm by mass or less, from the viewpoints of improving fuel economy and fatigue resistance, and in one embodiment, it may be 200 to 600 ppm by mass, or 250 to 550 ppm by mass. Furthermore, for example, when the lubricating oil composition is used to lubricate an internal combustion engine, the content of component (C) is preferably 500 ppm by mass or more, more preferably 1000 ppm by mass or more, in terms of the metal amount based on the total amount of the composition, from the viewpoint of enhancing cleaning performance and base number retention, and is preferably 10,000 ppm by mass or less, more preferably 5,000 ppm by mass or less, in terms of suppressing ash content in the composition and the life of exhaust gas aftertreatment devices, and in one embodiment may be 500 to 10,000 ppm by mass, or 1,000 to 5,000 ppm by mass.

[0067] <(D) Ashless Dispersant> In one preferred embodiment, the lubricating oil composition may further contain one or more ashless dispersants (hereinafter sometimes referred to as "component (D)"). In the field of lubricating oils, ashless dispersants generally used are nitrogen-containing compounds having at least one long-chain (e.g., 40 or more carbon atoms) linear or branched aliphatic hydrocarbon group and at least one polyamine chain (typically a polyethyleneamine chain) in one molecule, in which some of the nitrogen atoms in the polyamine chain may be acylated, or modified compounds (derivatives) thereof. Examples of modified compounds will be described later.

[0068] As the component (D), for example, one or more compounds selected from the following (D-1) to (D-3) can be used. (D-1) succinimide or a modified product (derivative) thereof having at least one alkyl group or alkenyl group in the molecule (hereinafter sometimes referred to as "component (D-1)"); (D-2) benzylamine or a modified product (derivative) thereof having at least one alkyl or alkenyl group in the molecule (hereinafter sometimes referred to as "component (D-2)"); (D-3) A polyamine having at least one alkyl or alkenyl group in the molecule, or a modified product (derivative) thereof (hereinafter sometimes referred to as "component (D-3)").

[0069] As the component (D), the component (D-1) can be particularly preferably used. Among the components (D-1), examples of succinimides having at least one alkyl or alkenyl group in the molecule include condensation reaction products of polyamines with alkyl or alkenyl succinic acids or anhydrides thereof having an alkyl or alkenyl group having 40 to 400 carbon atoms. Such condensation reaction products (condensation products) can be represented, for example, by the following general formula (3) or (4).

[0070] [ka]

[0071] In general formula (3), R 3 represents an alkyl or alkenyl group having 40 to 400 carbon atoms, and b represents an integer of 1 to 10, preferably 2 to 6. In one typical embodiment, the compound represented by general formula (3) is obtained as a mixture of compounds having different b's. 3 The carbon number of the alkyl group is 40 or more, preferably 60 or more, from the viewpoint of solubility in the base oil, and is 400 or less, preferably 350 or less, more preferably 250 or less, from the viewpoint of low-temperature fluidity of the composition, and in one embodiment, may be 40 to 400, or 60 to 350, or 60 to 250.

[0072] In general formula (4), R 4 and R5 R each independently represents an alkyl group or alkenyl group having 40 to 400 carbon atoms, and may be a combination of different groups. Furthermore, c represents an integer of 0 to 15, preferably 1 to 13, and more preferably 1 to 11. In one typical embodiment, the compound represented by general formula (4) is obtained as a mixture of compounds having different c's. 4 and R 5 The carbon number of the alkyl group is 40 or more, preferably 60 or more, from the viewpoint of solubility in the base oil, and is 400 or less, preferably 350 or less, more preferably 250 or less, from the viewpoint of low-temperature fluidity of the composition, and in one embodiment, may be 40 to 400, or 60 to 350, or 60 to 250.

[0073] The alkyl or alkenyl group (R 3 ~R 5 ) may be linear or branched. Preferred examples include branched alkyl groups and branched alkenyl groups derived from olefin oligomers such as propylene, 1-butene, and isobutene, and from ethylene-propylene co-oligomers. Among these, branched alkyl or alkenyl groups derived from isobutene oligomers commonly called polyisobutylene, and polybutenyl groups are most preferred. The alkyl or alkenyl group (R 3 ~R 5 The number average molecular weight of ) is preferably 800 to 3,500, and more preferably 900 to 3,500.

[0074] Succinimides having at least one alkyl or alkenyl group in the molecule include so-called mono-type succinimides represented by general formula (3), in which only one end of the polyamine chain is imidized, and so-called bis-type succinimides represented by general formula (4), in which both ends of the polyamine chain are imidized. The lubricating oil composition may contain either a mono-type succinimide or a bis-type succinimide, or may contain both as a mixture. The content of the bis-type succinimide or its modified product in component (D-1) is preferably 50 to 100 mass%, more preferably 70 to 100 mass%, based on the total amount of component (D-1) (100 mass%).

[0075] The weight average molecular weight of the component (D-1) is preferably 1,000 to 20,000, more preferably 2,000 to 20,000, even more preferably 3,000 to 15,000, and in one embodiment, it may be 4,000 to 15,000.

[0076] Examples of modified products (modified compounds, derivatives) of components (D-1) to (D-3) include (i) products modified with oxygen-containing organic compounds, (ii) products modified with boric acid, (iii) products modified with phosphoric acid, (iv) products modified with sulfur, and (v) products modified by a combination of two or more of these modifications. (i) The modified product with an oxygen-containing organic compound is a modified compound in which a part or all of the remaining amino groups and / or imino groups are neutralized or amidated by reacting a succinimide, benzylamine, or polyamine (hereinafter referred to as the "above-mentioned nitrogen-containing compound") having at least one alkyl or alkenyl group in the molecule with a monocarboxylic acid having 1 to 30 carbon atoms such as a fatty acid, a polycarboxylic acid having 2 to 30 carbon atoms (for example, oxalic acid, phthalic acid, trimellitic acid, pyromellitic acid, etc.), an anhydride or ester compound thereof, an alkylene oxide having 2 to 6 carbon atoms, or a hydroxy(poly)oxyalkylene carbonate. (ii) The boric acid modified product is a modified compound in which the remaining amino groups and / or imino groups are partially or entirely neutralized or amidated by reacting the nitrogen-containing compound with boric acid. (iii) Phosphoric acid-modified products are modified compounds in which the remaining amino groups and / or imino groups are partially or entirely neutralized or amidated by reacting phosphoric acid with the nitrogen-containing compounds described above. (iv) The sulfur-modified product is a modified compound obtained by reacting the above-mentioned nitrogen-containing compound with a sulfur compound. (v) A modified compound obtained by combining two or more types of modification can be obtained by subjecting the above-mentioned nitrogen-containing compound to a combination of two or more types of modification selected from modification with an oxygen-containing organic compound, boric acid modification, phosphoric acid modification, and sulfur modification. Among these modified compounds (derivatives) (i) to (v), boric acid modified compounds of alkenyl succinimides, particularly boric acid modified compounds of bis-type alkenyl succinimides, can be preferably used.

[0077] When the lubricating oil composition contains component (D), its content can be appropriately determined depending on the application of the lubricating oil composition. For example, when the lubricating oil composition is used to lubricate gear devices such as transmissions (e.g., manual transmissions, automatic transmissions, continuously variable transmissions, etc.), the content of component (D) in the lubricating oil composition is preferably 0.1 mass% or more based on the total amount of the composition to improve oxidation stability, and preferably 10 mass% or less, more preferably 5 mass% or less, to maintain energy saving properties. For example, when the lubricating oil composition is used to lubricate internal combustion engines, the content of component (D) is preferably 0.5 mass% or more, more preferably 1.0 mass% or more based on the total amount of the composition to improve coking resistance, and preferably 10.0 mass% or less, more preferably 5.0 mass% or less, to maintain fuel saving properties. In one embodiment, it can be 0.5 to 10.0 mass%, or 1.0 to 5.0 mass%.

[0078] Component (D-1) is preferably used as component (D), and a boric acid-modified component is preferably used as the modified component of component (D). In one embodiment, component (D) may be one or more unmodified components (D-1) (unmodified succinimide dispersants), one or more boric acid-modified components of component (D-1) (boric acid-modified succinimide dispersants), or a combination of one or more unmodified succinimide dispersants and one or more boric acid-modified succinimide dispersants. Component (D) may or may not contain a boric acid-modified component, but from the viewpoint of sludge dispersibility, the ratio (B / N) of the boron content (B) of component (D) to the nitrogen content (N) of component (D) is preferably 0 to 1.0 in one embodiment.

[0079] <(E) Phosphorus-containing anti-wear agent> In one preferred embodiment, the lubricating oil composition may contain one or more phosphorus-containing antiwear agents (hereinafter sometimes referred to as "component (E)"). As component (E), any phosphorus-containing antiwear agent used in lubricating oils can be used without particular limitation. Examples of phosphorus-containing antiwear agents include compounds represented by the following general formula (5), compounds represented by the following general formula (6), and metal salts and ammonium salts thereof.

[0080] [ka] (In general formula (5), X 1 , X 2 , and X 3 each independently represents an oxygen atom or a sulfur atom; R 6 represents a hydrocarbon group having 1 to 30 carbon atoms which may contain a sulfur atom; R 7 and R 8 each independently represents a hydrocarbon group having 1 to 30 carbon atoms which may contain a sulfur atom or a hydrogen atom; R 6 , R 7 , and R 8 may be the same or different from each other. 7 and / or R8 is a hydrogen atom, the compound of general formula (5) is intended to include any tautomer thereof.

[0081] [ka] (In general formula (6), X 4 , X 5 , X 6 , and X 7 each independently represents an oxygen atom or a sulfur atom; R 9 represents a hydrocarbon group having 1 to 30 carbon atoms which may contain a sulfur atom; R 10 and R 11 each independently represents a hydrocarbon group having 1 to 30 carbon atoms which may contain a sulfur atom or a hydrogen atom; R 9 , R 10 , and R 11 may be the same or different from each other.)

[0082] Examples of the hydrocarbon group having 1 to 30 carbon atoms in general formulas (5) and (6) include an alkyl group, a cycloalkyl group, an alkenyl group, an alkyl-substituted cycloalkyl group, an aryl group, an alkyl-substituted aryl group, and an arylalkyl group. The hydrocarbon group is preferably an alkyl group having 1 to 30 carbon atoms or an aryl group having 6 to 24 carbon atoms, and in one embodiment, is an alkyl group, aryl group, or alkylaryl group having 3 to 18 carbon atoms, more preferably 4 to 12 carbon atoms.

[0083] The hydrocarbon group having 1 to 30 carbon atoms in the general formulae (5) and (6) may be a hydrocarbon group containing a sulfur atom, or may be a hydrocarbon group containing no sulfur atom.

[0084] In one embodiment, preferred examples of the hydrocarbon group not containing a sulfur atom include a linear alkyl group having 4 to 18 carbon atoms. Examples of the linear alkyl group include a butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, a nonyl group, a decyl group, an undecyl group, a dodecyl group, a tridecyl group, a tetradecyl group, a pentadecyl group, a hexadecyl group, a heptadecyl group, and an octadecyl group.

[0085] Examples of hydrocarbon groups containing sulfur atoms include hydrocarbon groups functionalized with a sulfide bond. Preferred examples of hydrocarbon groups functionalized with a sulfide bond include groups having 4 to 20 carbon atoms and represented by the following general formula (7):

[0086] [ka] In general formula (7), R 12 R is a linear hydrocarbon group having 2 to 17 carbon atoms, preferably an ethylene group or a propylene group, and in one embodiment, an ethylene group. 13 is a straight chain hydrocarbon group having 2 to 17 carbon atoms, preferably a straight chain hydrocarbon group having 2 to 16 carbon atoms, and particularly preferably a straight chain hydrocarbon group having 6 to 10 carbon atoms.

[0087] Preferred examples of the group represented by general formula (7) include a 3-thiapentyl group, a 3-thiahexyl group, a 3-thiaheptyl group, a 3-thiaoctyl group, a 3-thianonyl group, a 3-thiadecyl group, a 3-thiaundecyl group, and a 4-thiahexyl group.

[0088] Examples of metals that form metal salts with the phosphorus compounds represented by general formula (5) or (6) include alkali metals such as lithium, sodium, potassium, and cesium, alkaline earth metals such as calcium, magnesium, and barium, and transition metals such as zinc, copper, iron, lead, nickel, silver, and manganese. Among these, alkaline earth metals such as calcium and magnesium, zinc, or a combination thereof is preferred.

[0089] Examples of nitrogen-containing compounds that form ammonium salts with the phosphorus compounds represented by general formula (5) or (6) include ammonia, monoamines, diamines, polyamines, and alkanolamines. More specifically, nitrogen-containing compounds represented by the following general formula (8): alkylenediamines such as methylenediamine, ethylenediamine, propylenediamine, and butylenediamine; polyamines such as diethylenetriamine, triethylenetetramine, tetraethylenepentamine, and pentaethylenehexamine; and combinations thereof.

[0090] [ka] (In general formula (8), R 14 ~R 16 each independently represents a hydrogen atom, a hydrocarbyl group having 1 to 8 carbon atoms, or a hydrocarbyl group having 1 to 8 carbon atoms and a hydroxyl group; R 14 ~R 16 At least one of the groups is a hydrocarbyl group having 1 to 8 carbon atoms or a hydrocarbyl group having 1 to 8 carbon atoms and a hydroxyl group.)

[0091] Preferred examples of the compound represented by the general formula (5) include compounds represented by the general formula (5) in which X 1 ~X 3 is an oxygen atom, and R 6 ~R 8 are each independently an alkyl group, aryl group (e.g., phenyl group, etc.), or alkylaryl group (e.g., alkylphenyl group, etc.) having 3 to 18 carbon atoms, which may contain a sulfur atom; 1 ~X 3 is an oxygen atom, and R 6 and R 7are each independently an alkyl group, aryl group (e.g., phenyl group), or alkylaryl group (e.g., alkylphenyl group) having 3 to 18 carbon atoms, which may contain a sulfur atom, and R 8 is hydrogen; a hydrogen phosphite compound in which X 1 ~X 3 Two of them are oxygen atoms and the remaining one is sulfur atom, and R 6 and R 7 are each independently an alkyl group, aryl group (e.g., phenyl group), or alkylaryl group (e.g., alkylphenyl group) having 3 to 18 carbon atoms, which may contain a sulfur atom, and R 8 is hydrogen; and a hydrogen thiophosphite compound in which X 1 ~X 3 One of them is an oxygen atom and the other two are sulfur atoms, and R 6 and R 7 are each independently an alkyl group, aryl group (e.g., phenyl group), or alkylaryl group (e.g., alkylphenyl group) having 3 to 18 carbon atoms, which may contain a sulfur atom, and R 8 and hydrogen dithiophosphite compounds in which R is hydrogen. Preferred examples of the compound represented by the general formula (6) include compounds represented by the general formula (6) in which X 4 ~X 7 Two of them are sulfur atoms and the other two are oxygen atoms, and R 9 ~R 11 are each independently an alkyl group, aryl group, or alkylaryl group having 3 to 18 carbon atoms (preferably 4 to 12) which may contain a sulfur atom. These compounds may be used alone or in combination of two or more.

[0092] One example of component (E) is zinc dialkyldithiophosphate (ZnDTP), which is a compound represented by the following general formula (9):

[0093] [ka] In general formula (9), R 17 ~R 20 Each of R independently represents a linear or branched alkyl group having 3 to 18 carbon atoms, and may be a combination of different groups. 17 ~R 20 The number of carbon atoms in R is preferably 3 to 12, more preferably 3 to 8. 17 ~R 20 may be any of a primary alkyl group, a secondary alkyl group, and a tertiary alkyl group, but is preferably a primary alkyl group, a secondary alkyl group, or a combination thereof.

[0094] When the lubricating oil composition contains component (E), its content can be appropriately determined depending on the application of the lubricating oil composition. For example, when the lubricating oil composition is used to lubricate gear devices such as transmissions (e.g., manual transmissions, automatic transmissions, continuously variable transmissions, etc.), the content of component (E) in the lubricating oil composition is, from the viewpoint of improving wear resistance, seizure resistance, bearing fatigue life, and prevention of gear shift shock, preferably 50 ppm by mass or more, more preferably 100 ppm by mass or more, in terms of phosphorus content based on the total amount of the composition, and from the same viewpoint, preferably 800 ppm by mass or less, more preferably 700 ppm by mass or less, and in one embodiment, may be 50 to 800 ppm by mass or 100 to 700 ppm by mass. Furthermore, for example, when the lubricating oil composition is used to lubricate an internal combustion engine, the content of component (E) is preferably 400 ppm by mass or more, more preferably 500 ppm by mass or more, in terms of phosphorus content based on the total amount of the composition, from the viewpoint of improving wear resistance, and is preferably 5000 ppm by mass or less, more preferably 3000 ppm by mass or less, in terms of reducing catalyst poisoning in exhaust gas aftertreatment devices, and in one embodiment may be 400 to 5000 ppm by mass, or 500 to 3000 ppm by mass.

[0095] <(F) Sulfur-containing extreme pressure agents> In one preferred embodiment, the gear oil composition may further contain one or more sulfur-containing extreme pressure agents other than component (E) (hereinafter sometimes referred to as "component (F)"). Examples of component (F) include known sulfur-containing extreme pressure agents such as thiadiazole compounds, dihydrocarbyl (poly)sulfides, sulfurized fats and oils, sulfurized fatty acids, sulfurized esters, sulfurized olefins, alkylthiocarbamoyl compounds, thiocarbamate compounds, thioterpene compounds, dialkylthiodipropionate compounds, sulfurized mineral oils, zinc dithiocarbamate compounds, and molybdenum dithiocarbamate compounds.

[0096] Preferred examples of the thiadiazole compound include a 1,3,4-thiadiazole compound represented by the following general formula (10), a 1,2,4-thiadiazole compound represented by the following general formula (11), and a 1,2,3-thiadiazole compound represented by the following general formula (12).

[0097] [ka]

[0098] [ka]

[0099] [ka] (In general formulas (10) to (12), R 21 and R 22 may be the same or different and each independently represent a hydrogen atom or a hydrocarbyl group having 1 to 20 carbon atoms; h and i may be the same or different and each independently represent an integer of 0 to 8.

[0100] Dihydrocarbyl (poly)sulfides are compounds represented by the following general formula (13): 23 and R 24 When is an alkyl group, it is sometimes called an alkyl sulfide.

[0101] [ka] (In general formula (13), R 23 and R 24 may be the same or different and each independently represent an alkyl group having 1 to 20 carbon atoms (which may be linear or branched, and may have a cyclic structure), an aryl group having 6 to 20 carbon atoms, an alkylaryl group having 7 to 20 carbon atoms, or an arylalkyl group having 7 to 20 carbon atoms, and j represents an integer of 1 to 8.

[0102] When the lubricating oil composition contains component (F), its content can be appropriately determined depending on the application of the lubricating oil composition. For example, when the lubricating oil composition is used to lubricate gear devices such as transmissions (e.g., manual transmissions, automatic transmissions, continuously variable transmissions, etc.), the content of component (F) in the lubricating oil composition is preferably 200 ppm by mass or more, more preferably 300 ppm by mass or more, in terms of sulfur content based on the total amount of the composition, from the viewpoint of improving extreme pressure properties and fatigue resistance, and is preferably 3000 ppm by mass or less, more preferably 2500 ppm by mass or less, from the viewpoint of improving wear resistance, fatigue resistance, and oxidation stability, and in one embodiment, it may be 200 to 3000 ppm by mass, or 300 to 2500 ppm by mass. Furthermore, for example, when the lubricating oil composition is used to lubricate an internal combustion engine, the content of component (F) is preferably 10 ppm by mass or more, more preferably 30 ppm by mass or more, in terms of sulfur content based on the total amount of the composition, from the viewpoint of improving extreme pressure properties and fatigue resistance, and is preferably 200 ppm by mass or less, more preferably 100 ppm by mass or less, from the viewpoint of reducing catalyst poisoning in exhaust gas aftertreatment devices, and in one embodiment may be 10 to 200 ppm by mass, or 30 to 100 ppm by mass.

[0103] <(G) Antioxidants> In one preferred embodiment, the lubricating oil composition may further contain one or more amine-based antioxidants and / or one or more phenol-based antioxidants as antioxidants (hereinafter sometimes referred to as "Component (G)").

[0104] Examples of the amine antioxidant include aromatic amine antioxidants and hindered amine antioxidants. Examples of the aromatic amine antioxidant include primary aromatic amine compounds such as alkylated α-naphthylamine; and secondary aromatic amine compounds such as alkylated diphenylamine, phenyl-α-naphthylamine, alkylated phenyl-α-naphthylamine, and phenyl-β-naphthylamine. As the aromatic amine antioxidant, alkylated diphenylamine, alkylated phenyl-α-naphthylamine, or a combination thereof can be preferably used.

[0105] Examples of hindered amine antioxidants include compounds having a 2,2,6,6-tetraalkylpiperidine skeleton (2,2,6,6-tetraalkylpiperidine derivatives). The 2,2,6,6-tetraalkylpiperidine derivative is preferably a 2,2,6,6-tetraalkylpiperidine derivative having a substituent at the 4-position. Two 2,2,6,6-tetraalkylpiperidine skeletons may be bonded via a substituent at the 4-position. The N-position of the 2,2,6,6-tetraalkylpiperidine skeleton may be unsubstituted or may be substituted with an alkyl group having 1 to 4 carbon atoms at the N-position. The 2,2,6,6-tetraalkylpiperidine skeleton is preferably a 2,2,6,6-tetramethylpiperidine skeleton.

[0106] The substituent at the 4-position of the 2,2,6,6-tetraalkylpiperidine skeleton is an acyloxy group (R 25 COO-), alkoxy group (R 25 O-), alkylamino group (R 25 NH-), acylamino group (R 25 CONH-), etc. 25 is a hydrocarbon group preferably having 1 to 30 carbon atoms, more preferably 1 to 24 carbon atoms, and even more preferably 1 to 20 carbon atoms. Examples of the hydrocarbon group include an alkyl group, an alkenyl group, a cycloalkyl group, an alkylcycloalkyl group, an aryl group, an alkylaryl group, and an arylalkyl group.

[0107] When two 2,2,6,6-tetraalkylpiperidine skeletons are bonded via a substituent at each 4-position, the substituent may be a hydrocarbylene bis(carbonyloxy) group (-OOC-R 25 -COO-), hydrocarbylenediamino group (-HN-R 25 -NH-), hydrocarbylene bis(carbonylamino) group (-HNCO-R 25 -CONH-), etc. 25 is preferably a hydrocarbylene group having 1 to 30 carbon atoms, and more preferably an alkylene group.

[0108] The substituent at the 4-position of the 2,2,6,6-tetraalkylpiperidine skeleton is preferably an acyloxy group. An example of a compound having an acyloxy group at the 4-position of the 2,2,6,6-tetraalkylpiperidine skeleton is an ester of 2,2,6,6-tetramethyl-4-piperidinol with a carboxylic acid. Examples of the carboxylic acid include linear or branched aliphatic carboxylic acids having 8 to 20 carbon atoms.

[0109] Examples of phenolic antioxidants include 4,4'-methylenebis(2,6-di-tert-butylphenol); 4,4'-bis(2,6-di-tert-butylphenol); 4,4'-bis(2-methyl-6-tert-butylphenol); 2,2'-methylenebis(4-ethyl-6-tert-butylphenol); 2,2'-methylenebis(4-methyl-6-tert-butylphenol); 4,4'-butylidenebis(3-methyl-6-tert-butylphenol); 4,4'-isopropylidenebis(2,6-di-tert-butylphenol); 2,2'-methylenebis(4-methyl-6-nonylphenol); 2,2'-isobutylidenebis(4,6-dimethylphenol); 2,2'-methylenebis(4-methyl-6-cyclohexylphenol); 2,6-di-tert-butyl-4-methylphenol; 2,6- Examples of hindered phenol compounds and bisphenol compounds include di-tert-butyl-4-ethylphenol; 2,4-dimethyl-6-tert-butylphenol; 2,6-di-tert-butyl-4-(N,N'-dimethylaminomethyl)phenol; 4,4'-thiobis(2-methyl-6-tert-butylphenol); 4,4'-thiobis(3-methyl-6-tert-butylphenol); 2,2'-thiobis(4-methyl-6-tert-butylphenol); bis(3-methyl-4-hydroxy-5-tert-butylbenzyl)sulfide; bis(3,5-di-tert-butyl-4-hydroxybenzyl)sulfide; 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid esters; and 3-methyl-5-tert-butyl-4-hydroxyphenol fatty acid esters.

[0110] When the lubricating oil composition contains component (G), its content can be appropriately determined depending on the intended use of the lubricating oil composition. For example, when the lubricating oil composition is used to lubricate gear devices such as transmissions (e.g., manual transmissions, automatic transmissions, continuously variable transmissions, etc.), the content of component (G) in the lubricating oil composition is preferably 0.1 mass% or more, more preferably 0.2 mass% or more, based on the total amount of the composition, from the viewpoint of enhancing thermo-oxidative stability. From the same viewpoint, it is preferably 2.0 mass% or less, more preferably 1.0 mass% or less, and in one embodiment, it can be 0.1 to 2.0 mass%, or 0.2 to 1.0 mass%. Furthermore, when the lubricating oil composition is used to lubricate internal combustion engines, the content of component (G) in the lubricating oil composition is preferably 0.1 mass% or more, more preferably 0.5 mass% or more, based on the total amount of the composition, from the viewpoint of enhancing thermo-oxidative stability. From the same viewpoint, it is preferably 5.0 mass% or less, more preferably 3.0 mass% or less, and in one embodiment, it can be 0.1 to 5.0 mass%, or 0.5 to 3.0 mass%.

[0111] <(H) Viscosity index improver> In one preferred embodiment, the lubricating oil composition may further contain one or more polymers having a viscosity index improving effect (hereinafter sometimes referred to as a "viscosity index improver" or "Component (H)"). Examples of Component (H) include non-dispersant or dispersant poly(meth)acrylate, (meth)acrylate-olefin copolymer, non-dispersant or dispersant ethylene-α-olefin copolymer or its hydrogenated product, polyisobutylene or its hydrogenated product, styrene-diene hydrogenated copolymer, styrene-maleic anhydride ester copolymer, and polyalkylstyrene. In this specification, "(meth)acrylate" means "acrylate and / or methacrylate." As Component (H), one type of polymer may be used alone, or two or more types of polymers may be used in combination.

[0112] In one embodiment, the component (H) can be preferably a dispersed poly(meth)acrylate, a non-dispersed poly(meth)acrylate, or a combination thereof. In one embodiment, a dispersed poly(meth)acrylate can be preferably used. In this specification, the dispersed poly(meth)acrylate compound has a functional group containing a nitrogen atom, whereas the non-dispersed poly(meth)acrylate compound does not have a functional group containing a nitrogen atom.

[0113] In one embodiment, the poly(meth)acrylate-based viscosity index improver is preferably a poly(meth)acrylate in which the proportion of structural units represented by the following general formula (14) in all monomer units in the polymer is 10 to 90 mol % (hereinafter, sometimes referred to as "poly(meth)acrylate (H1)" or simply "component (H1)").

[0114] [ka] (In general formula (14), R 26 represents hydrogen or a methyl group, and R 27 represents a linear or branched hydrocarbon group having 1 to 36 carbon atoms, preferably an alkyl group.

[0115] The weight-average molecular weight of component (H) can be appropriately determined depending on the application of the lubricating oil composition. For example, when the lubricating oil composition is used to lubricate gear devices such as transmissions (e.g., manual transmissions, automatic transmissions, continuously variable transmissions, etc.), the weight-average molecular weight of component (H) is preferably 10,000 or more, more preferably 20,000 or more, and even more preferably 30,000 or more, from the viewpoint of enhancing the viscosity index improving effect and improving low-temperature viscosity characteristics, and is preferably 200,000 or less, more preferably 150,000 or less, and even more preferably 100,000 or less, from the viewpoint of enhancing solubility in base oil, storage stability, and shear stability, and in one embodiment may be 10,000 to 200,000, or 20,000 to 150,000, or 30,000 to 100,000. Furthermore, for example, when the lubricating oil composition is used to lubricate an internal combustion engine, the weight average molecular weight of component (H) is preferably 100,000 or more, more preferably 200,000 or more, from the viewpoint of enhancing the viscosity index improving effect and improving low-temperature viscosity characteristics and fuel economy, and is preferably 1,000,000 or less, more preferably 700,000 or less, from the viewpoint of enhancing solubility in oil, storage stability, and shear stability, and in one embodiment may be 100,000 to 1,000,000, or 200,000 to 700,000.

[0116] When the lubricating oil composition contains component (H), its content can be appropriately determined as an amount that provides the desired kinematic viscosity and viscosity-temperature characteristics for the entire lubricating oil composition. For example, the viscosity index is an index for evaluating viscosity-temperature characteristics. For example, when the lubricating oil composition is used to lubricate gear devices such as transmissions (e.g., manual transmissions, automatic transmissions, continuously variable transmissions, etc.), the content of component (H) in the lubricating oil composition can be, for example, 0.1 mass % or more, or 0.5 mass % or more, as resin content based on the total amount of the composition, from the viewpoint of improving the viscosity-temperature characteristics and enhancing energy saving, and, from the viewpoint of enhancing shear stability, can be, for example, 22 mass % or less, or 12 mass % or less, and in one embodiment, 0.1 to 22 mass %, or 0.5 to 12 mass %. Furthermore, for example, when the lubricating oil composition is used to lubricate an internal combustion engine, the content of component (H) in the lubricating oil composition may be, for example, 0.1 mass % or more, or 0.5 mass % or more, in terms of resin content based on the total amount of the composition, from the viewpoint of improving fuel economy, and, from the viewpoint of improving shear stability, may be, for example, 20 mass % or less, or 15 mass % or less, and in one embodiment, 0.1 to 20 mass %, or 0.5 to 15 mass %. In this specification, resin content means a polymer component having a molecular weight of 1,000 or more.

[0117] (Other additives) The lubricating oil composition of the present invention may further contain one or more additives selected from (I) friction modifiers other than the above-mentioned components (B), (B'), (B*), and (F), (J) pour point depressants other than the above-mentioned component (H), (K) corrosion inhibitors other than the above-mentioned component (F), (L) metal deactivators other than the above-mentioned component (F), (M) rust inhibitors other than the above-mentioned components (B), (B'), and (B*), (N) demulsifiers, (O) antifoaming agents, and (P) colorants.

[0118] (I) The friction modifier other than the above components (B), (B'), (B*), and (F) (hereinafter sometimes referred to as "component (I)") can be an oil-soluble organomolybdenum compound or oiliness-based friction modifier used as a friction modifier in lubricating oils, and can be a compound other than the above components (B), (B'), (B*), and (F). Examples of such compounds include oil-soluble organomolybdenum compounds other than the molybdenum dithiocarbamate described above as an example of component (F), and oiliness-based friction modifiers other than the above components (B), (B'), and (B*). When the lubricating oil composition contains component (I), the content thereof may be, for example, 0.1 to 1.0 mass % based on the total amount of the composition.

[0119] (J) As a pour point depressant other than the above component (H) (hereinafter sometimes referred to as "component (J)"), known pour point depressants such as ethylene vinyl acetate can be used depending on the properties of the lubricating base oil used. When the lubricating oil composition contains component (J), its content can be, for example, 0.01 to 1.0 mass% based on the total amount of the composition.

[0120] (K) As a corrosion inhibitor other than the above component (F) (hereinafter sometimes referred to as "component (K)"), for example, known corrosion inhibitors such as benzotriazole-based compounds, tolyltriazole-based compounds, imidazole-based compounds, etc. When the lubricating oil composition contains component (K), its content may be, for example, 0.005 to 5.0 mass% based on the total amount of the composition.

[0121] (L) As a metal deactivator other than the above-mentioned component (F) (hereinafter sometimes referred to as "component (L)"), for example, known metal deactivators such as imidazoline, pyrimidine derivatives, mercaptobenzothiazole, benzotriazole and its derivatives, 2-(alkyldithio)benzimidazole, and β-(o-carboxybenzylthio)propionitrile can be used. When the lubricating oil composition contains component (L), its content can be, for example, 0.005 to 1.0 mass% based on the total amount of the composition.

[0122] (M) Rust inhibitors other than the above components (B), (B'), and (B*) (hereinafter sometimes referred to as "component (M)") can be known rust inhibitors such as petroleum sulfonates, alkylbenzene sulfonates, dinonylnaphthalene sulfonates, alkenyl succinic acid esters, and polyhydric alcohol esters (excluding those corresponding to the above components (B), (B'), or (B*)). When the lubricating oil composition contains component (M), its content can be, for example, 0.005 to 5.0 mass% based on the total amount of the composition.

[0123] As the (N) demulsifier, known demulsifiers such as polyalkylene glycol-based nonionic surfactants can be used. When the lubricating oil composition contains a demulsifier, the content thereof can be, for example, 0.005 to 5.0 mass% based on the total amount of the composition.

[0124] (O) Antifoaming agents that can be used include known antifoaming agents such as silicone, fluorosilicone, fluoroalkyl ether, etc. When the lubricating oil composition contains an antifoaming agent, the content thereof can be, for example, 0.0005 to 1.0 mass% based on the total amount of the composition.

[0125] As the colorant (P), known colorants such as azo compounds can be used.

[0126] <Lubricating oil composition> The kinematic viscosity of the lubricating oil composition at 100°C can be appropriately determined depending on the application of the lubricating oil composition. For example, when the lubricating oil composition is used to lubricate gear devices such as transmissions (e.g., manual transmissions, automatic transmissions, continuously variable transmissions, etc.), the kinematic viscosity of the lubricating oil composition at 100°C is preferably 2.0 mmHg from the viewpoint of enhancing wear resistance. 2 / s or more, preferably 2.5 mm 2 / s or more, and from the viewpoint of enhancing energy saving, it is preferably 8.0 mm 2 / s or less, preferably 7.0 mm 2 / s or less, and in one embodiment, 2.0 to 8.0 mm 2 / s, or 2.0 to 7.0 mm 2 / s, or 2.5 to 8.0 mm 2 / s, or 2.5 to 7.0 mm 2 For example, when the lubricating oil composition is used to lubricate an internal combustion engine, the kinematic viscosity of the lubricating oil composition at 100°C is preferably 2.0 mm / s from the viewpoint of enhancing wear resistance. 2 / s or more, preferably 4.0 mm 2 / s or more, and from the viewpoint of enhancing energy saving, it is preferably 12.5 mm 2 / s or less, preferably 9.3 mm 2 / s or less, and in one embodiment, 2.0 to 12.5 mm 2 / s, or 4.0 to 12.5 mm 2 / s, or 2.0 to 9.3 mm 2 / s, or 4.0 to 9.3 mm 2 / s.

[0127] The kinematic viscosity of the lubricating oil composition at 40°C can be appropriately determined depending on the application of the lubricating oil composition. For example, when the lubricating oil composition is used to lubricate gear devices such as transmissions (e.g., manual transmissions, automatic transmissions, continuously variable transmissions, etc.), the kinematic viscosity of the lubricating oil composition at 40°C is preferably 7.0 mmHg from the viewpoint of enhancing wear resistance. 2 / s or more, preferably 8.0 mm 2 / s or more, and from the viewpoint of enhancing energy saving, it is preferably 50 mm 2 / s or less, preferably 45 mm 2 / s or less, and in one embodiment, 7.0 to 50 mm 2 / s, or 7.0 to 45 mm 2 / s, or 8.0 to 50 mm 2 / s, or 8.0 to 45 mm 2 For example, when the lubricating oil composition is used to lubricate an internal combustion engine, the kinematic viscosity of the lubricating oil composition at 40°C is preferably 4.0 mm / s from the viewpoint of enhancing wear resistance. 2 / s or more, preferably 6.0 mm 2 / s or more, and from the viewpoint of enhancing energy saving, it is preferably 50 mm 2 / s or less, preferably 35 mm 2 / s or less, and in one embodiment, 4.0 to 50 mm 2 / s, or 6.0 to 50 mm 2 / s, or 4.0 to 35 mm 2 / s, or 6.0 to 35 mm 2 / s.

[0128] The viscosity index of the lubricating oil composition may be preferably 100 or greater, more preferably 110 or greater, and in one embodiment 115 or greater, or 120 or greater, from the viewpoint of further enhancing energy saving and anti-wear properties.

[0129] (Application) The lubricating oil composition of the present invention, due to the inclusion of component (B), has an enhanced friction-reducing effect under gear lubrication conditions, and is therefore particularly suitable as a lubricating oil with enhanced energy saving properties for lubricating gears, for example, for lubricating mechanical devices including gear mechanisms such as transmissions (e.g., manual transmissions, automatic transmissions, continuously variable transmissions, reducers for electric vehicles, etc.). [Example]

[0130] The present invention will be described in more detail below with reference to examples and comparative examples. Note that the following examples are intended to illustrate the present invention, but are not intended to limit the present invention.

[0131] Example Or reference example 1 to 42 and Comparative Examples 1 to 32> As shown in Tables 1 to 13, the lubricating oil compositions of the present invention (Examples Or reference example Lubricating oil compositions (Comparative Examples 1 to 32) for comparison were prepared. In the table, in the "Base Oil Composition" section, "% by mass" means % by mass based on the total amount of base oil (100% by mass), and in other sections, "% by mass" means % by mass based on the total amount of lubricating oil composition (100% by mass). Furthermore, "ppm by mass" means ppm by mass based on the total amount of lubricating oil composition, and the notation "ppm by mass / X" for element X means ppm by mass of the amount of element X based on the total amount of the composition. Details of each component are as follows:

[0132] ((A) Lubricant base oil) O-1: API Group III base oil (hydrocracked mineral oil base oil), kinematic viscosity (40°C): 12.7 mm 2 / s, kinematic viscosity (100℃): 3.3mm 2 / s, viscosity index: 135, saturated content: 99.8% by mass, sulfur content: less than 1 mass ppm O-2: API Group V base oil (bis(2-ethylhexyl)azelate), kinematic viscosity (40°C): 11.0 mm 2 / s, kinematic viscosity (100℃): 3.1mm 2 / s, viscosity index: 146 O-3: API Group IV base oil, kinematic viscosity (40℃): 63mm 2 / s, kinematic viscosity (100℃): 9.7mm 2 / s, viscosity index: 137 O-4: API Group IV base oil, kinematic viscosity (40℃): 396mm 2 / s, kinematic viscosity (100℃): 40mm 2 / s, viscosity index: 151 O-5: API Group V base oil (ester of mixed caprylic and capric acids with trimethylolpropane), kinematic viscosity (40°C): 19.8 mm 2 / s, kinematic viscosity (100℃): 4.3mm 2 / s, viscosity index: 126

[0133] ((B) Oil-based friction modifier) B-1 (C8s-G3-E1): Triglycerin monocaprylate (monoester of saturated monovalent fatty acid with 8 carbon atoms and glycerin trimer) B-2 (C8s-G4-E1): Tetraglycerin monocaprylate (monoester of saturated monovalent fatty acid with 8 carbon atoms and glycerin tetramer) B-3 (C8s-G6-E1): Hexaglycerin monocaprylate (monoester of saturated monovalent fatty acid with 8 carbon atoms and glycerin hexamer) B'-4 (C12s-G2-E1): Diglycerol monolaurate (monoester of saturated monovalent fatty acid with 12 carbon atoms and glycerol dimer) B-5 (C12s-G3-E1): Triglycerin monolaurate (monoester of saturated monovalent fatty acid with 12 carbon atoms and glycerin trimer) B-6 (C12s-G4-E1): Tetraglycerin monolaurate (monoester of saturated monovalent fatty acid with 12 carbon atoms and glycerin tetramer) B-7 (C12s-G4-E1): Hexaglycerin monolaurate (monoester of saturated monovalent fatty acid with 12 carbon atoms and glycerin hexamer) B'-8 (C12s-G10-E1): Decaglycerin monolaurate (monoester of saturated monovalent fatty acid with 12 carbon atoms and glycerin decamer) B'-9 (C18s-G2-E1): Diglycerol monostearate (monoester of saturated monovalent fatty acid with 18 carbon atoms and glycerol dimer) B'-10 (C18u-G2-E1): Diglycerol monooleate (monoester of unsaturated monovalent fatty acid with 18 carbon atoms and glycerol dimer) B-11 (C18s-G4-E1): Tetraglycerin monostearate (monoester of saturated monovalent fatty acid with 18 carbon atoms and glycerin tetramer) B-12 (C18u-G6-E1): Hexaglycerin monooleate (monoester of unsaturated monovalent fatty acid with 18 carbon atoms and glycerin hexamer) B-13 (C12s-G4-E2): Tetraglycerin dilaurate (a diester of saturated monovalent fatty acid with 12 carbon atoms and glycerin tetramer) B-14 (C12s-G4-E3): Tetraglycerin trilaurate (a triester of saturated monovalent fatty acid with 12 carbon atoms and glycerin tetramer) B-15 (C12s-G4-E4): Tetraglycerin tetralaurate (tetraester of saturated monovalent fatty acid with 12 carbon atoms and glycerin tetramer) B'-16 (C18u-G1-E1): Glycerin monooleate (monoester of glycerin and unsaturated monovalent fatty acid with 18 carbon atoms) Here, the expression "Ci(s or u)-Gj-Ek" (i, j, and k are each an integer of 1 or greater) means an ester of a monovalent fatty acid with carbon number i and a glycerin j-mer, in which k hydroxy groups of the glycerin j-mer are esterified with fatty acids. Furthermore, the "s" after "Ci" means saturated fatty acid, and the "u" after "Ci" means unsaturated fatty acid.

[0134] (Other additives) (C) Metallic detergent: calcium carbonate overbased calcium sulfonate, base number 300 mg KOH / g, Ca: 11.4 mass% (D) Ashless dispersant: boric acid modified polybutenyl succinimide dispersant, N: 2.2 mass%, B: 0.5 mass% (E) Phosphorus-containing anti-wear agent: diphenyl hydrogen phosphite, P: 13.2 mass% (F) Sulfur-containing extreme pressure agent: thiadiazole, S: 36% by mass (G) Antioxidants: Phenolic antioxidants (H) Viscosity index improver: Polymethacrylate-based viscosity index improver, weight average molecular weight: 3.5 x 10 4 Antifoaming agent: dimethyl silicone

[0135] [Table 1]

[0136] Table 2

[0137] Table 3

[0138] Table 4

[0139] Table 5

[0140] Table 6

[0141] Table 7

[0142] Table 8

[0143] Table 9

[0144] Table 10

[0145] Table 11

[0146] Table 12

[0147] [Table 13]

[0148] (MTM test) For each lubricating oil composition, a ball-on-disk friction test was carried out using an MTM traction measuring instrument (manufactured by PCS Instruments) to measure the friction coefficient (μ) under conditions simulating gear lubrication. The measurement conditions were as follows: Balls and discs: Standard specimens (AISI 52100 standard) Oil temperature: 115℃ Load: 50N Circumferential speed: 0.1m / s Slip rate: 5% The results are shown in Tables 1 to 13. The reduction rate (%) of the friction coefficient for Examples 1 to 39 relative to Comparative Example 1, the reduction rate (%) for Example 40 relative to Comparative Example 2, the reduction rate (%) for Example 41 relative to Comparative Example 3, the reduction rate (%) for Example 42 relative to Comparative Example 6, and the reduction rate (%) for Comparative Example 5 relative to Comparative Example 4 are shown in the tables.

[0149] (Storage stability) For each lubricating oil composition, the prepared composition was allowed to stand at 70°C for 10 hours, and then the state of the composition was visually observed to evaluate its storage stability on a three-point scale of 1 to 3. The state of the composition corresponding to the three-point scale is as follows: "3": The composition was transparent. "2": Cloudiness was observed in the composition, but no precipitation was observed. "1": Precipitation occurred in the composition. The results are shown in Tables 1 to 13. If the score in this test is 2 or higher, the composition has storage stability sufficient for practical use.

[0150] (Evaluation results) Example Or reference example The lubricating oil compositions Nos. 1 to 39 had sufficiently reduced friction coefficients under conditions simulating gear lubrication compared to the lubricating oil composition of Comparative Example 1, which did not contain an oiliness-based friction modifier.

[0151] The lubricating oil composition of Example 40 is a modified composition obtained by removing additives other than component (B) from the composition of Example 2. A fair comparison can be made between the composition of Example 40 and the composition of Comparative Example 2, which does not contain any additives other than component (B). The composition of Example 40 exhibited a significantly reduced coefficient of friction under conditions simulating gear lubrication compared to the composition of Comparative Example 2, which does not contain component (B).

[0152] reference The lubricating oil composition of Example 41 had a kinematic viscosity of 39.0 mmHg at 40°C for all base oils. 2 This is a composition obtained by modifying the composition of Example 2 by changing the composition of the base oil (A) so that the viscosity of the composition of Example 2 is 1 / s. reference The composition of Example 41 can be fairly compared with the composition of Comparative Example 3, which has the same base oil composition. reference The composition of Example 41 exhibited a reduced coefficient of friction under conditions simulating gear lubrication relative to the composition of Comparative Example 3, which did not contain component (B).

[0153] The lubricating oil composition of Example 42 is a modification of the composition of Example 2 by replacing the (A) base oil with an API Group V base oil. A fair comparison can be made between the composition of Example 42 and the composition of Comparative Example 6, which has the same base oil composition. The composition of Example 42 exhibited a significantly reduced coefficient of friction under conditions simulating gear lubrication relative to the composition of Comparative Example 6, which does not contain component (B).

[0154] The lubricating oil composition of Comparative Example 5 had a kinematic viscosity of 42.0 mmHg at 40°C for all base oils. 2 By changing the composition of the base oil (A) so that reference This is a composition obtained by further modifying the composition of Example 41. The composition of Comparative Example 5 is the same as the composition of Comparative Example 4, which has the same base oil composition. A fair comparison can be made between the compositions of Comparative Example 5 and Comparative Example 4. Although the composition of Comparative Example 5 exhibited a reduced coefficient of friction under conditions simulating gear lubrication compared to the composition of Comparative Example 4, which did not contain component (B), the reduction rate was insufficient.

[0155] The lubricating oil composition of Comparative Example 7 is a modified composition in which all of the friction modifier B-1 (triglycerol monocaprylate (C8s-G3-E1)) in the composition of Example 2 is replaced with friction modifier B'-16 (glycerol monooleate (C18u-G1-E1)). Under conditions simulating gear lubrication, the composition of Comparative Example 7 exhibited a reduced friction coefficient compared to the composition of Comparative Example 1, which did not contain component (B), but the rate of reduction was inferior to that of Example 2.

[0156] The lubricating oil compositions of Comparative Examples 11 to 13 were the same as those of Examples Or reference example These are modified compositions in which all of the friction modifier B-5 (triglycerin monolaurate (C12s-G3-E1)) in compositions 10 to 12 was replaced with friction modifier B'-4 (diglycerin monolaurate (C12s-G2-E1)). The compositions of Comparative Examples 11 to 13 exhibited reduced friction coefficients compared to the composition of Comparative Example 1, which did not contain component (B), under conditions simulating gear lubrication, but the reduction rate was less than that of the compositions of Examples 10 to 12. Or reference example were inferior to 10 to 12, respectively.

[0157] The lubricating oil compositions of Comparative Examples 17 to 19 were the same as those of Examples 17 to 19, respectively. Or reference example These are modified compositions in which the friction modifier B-7 (hexaglycerin monolaurate (C12s-G6-E1)) in compositions 16 to 18 was entirely replaced with friction modifier B'-8 (decaglycerin monolaurate (C12s-G10-E1)). The compositions of Comparative Examples 17 to 19 exhibited reduced friction coefficients compared to the composition of Comparative Example 1, which did not contain component (B), under conditions simulating gear lubrication, but the reduction rate was less than that of the compositions of Examples 16 to 18. Or reference example were inferior to 16 to 18, respectively.

[0158] The lubricating oil compositions of Comparative Examples 20 to 22 were reference These are modified compositions in which all of the friction modifier B-11 (tetraglycerin monostearate (C18s-G4-E1)) in the compositions of Examples 19 to 21 was replaced with friction modifier B'-9 (diglycerin monostearate (C18s-G2-E1)). The compositions of Comparative Examples 20 to 22 showed reduced friction coefficients compared to the composition of Comparative Example 1, which did not contain component (B), under conditions simulating gear lubrication, but the reduction rate was reference It was inferior to Examples 19 to 21, respectively.

[0159] The lubricating oil compositions of Comparative Examples 23 to 25 were reference These are modified compositions in which all of the friction modifier B-12 (hexaglycerin monooleate: C18u-G6-E1) in the compositions of Examples 22 to 24 was replaced with friction modifier B'-10 (diglycerin monooleate (C18u-G2-E1)). The compositions of Comparative Examples 23 to 25 showed reduced friction coefficients compared to the composition of Comparative Example 1, which did not contain component (B), under conditions simulating gear lubrication, but the reduction rate was reference It was inferior to Examples 22 to 24.

[0160] The lubricating oil compositions of Comparative Examples 8 to 10, 14 to 16, and 26 to 32, which contained an excessively large amount of component (B), were not suitable for practical use in terms of storage stability.

[0161] The above test results demonstrate that the lubricating oil composition of the present invention can exhibit an improved friction-reducing effect in gear lubrication. [Industrial Applicability]

[0162] The lubricating oil composition of the present invention exhibits an improved friction-reducing effect when lubricating metal surfaces that are subject to high loads, such as gears, and can therefore be suitably used for lubricating various mechanical devices that have metal surfaces that are subject to high loads, such as gear mechanisms, pistons, and connecting rod bearings, and can be particularly suitably used for lubricating transmissions and internal combustion engines.

Claims

1. (A) A mixture of one or more mineral base oils or one or more synthetic base oils, or a combination thereof, having a kinematic viscosity of 12.7 mm at 40°C. ２ / s or less, and a lubricating base oil; (B) A partial ester of one or more saturated or unsaturated monovalent fatty acids (b1) having 3 to 12 carbon atoms and one or more glycerin oligomers (b2) having a degree of polymerization of 3 to 6 is contained in an amount of 0.05 to 0.4 mass% based on the total amount of the composition. A lubricating oil composition comprising:

2. 2. The lubricating oil composition according to claim 1, wherein the fatty acid (b1) has 6 to 12 carbon atoms.

3. (B') contains or does not contain a partial ester of glycerin, a glycerin polymer other than the glycerin oligomer (b2), or a combination thereof with a fatty acid, 3. The lubricating oil composition according to claim 1, wherein the content (unit: mass%) of component (B') is not more than half the content (unit: mass%) of component (B) based on the total amount of the composition.

4. The lubricating oil composition according to any one of claims 1 to 3, further comprising one or more additives selected from a metal-based detergent, an ashless dispersant, a phosphorus-containing antiwear agent, a sulfur-containing extreme pressure agent, an antioxidant, and a viscosity index improver.

5. Kinematic viscosity at 40°C: 7.0 to 21.3 mm ２ The lubricating oil composition according to any one of claims 1 to 4, wherein

6. The lubricating oil composition according to any one of claims 1 to 5, which is used for lubricating gears.

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