Lubricating oil composition

Abstract

To provide a lubricant composition excellent in low-temperature characteristics and shear stability.SOLUTION: A lubricant composition comprises a plant-derived base oil that satisfies the following relational expression (1) when kinematic viscosity at 100°C is X and weight average molecular weight (Mw) obtained by gel permeation chromatography measurement of tetrahydrofuran soluble matter is Y. The relational expression (1) is represented by Y≥70X+305.SELECTED DRAWING: None

Description

[Technical Field] 【0001】 This disclosure relates to lubricating oil compositions. [Background technology] 【0002】 Lubricating oil compositions are used in various types of industrial machinery, including agricultural machinery, construction machinery, and transport machinery. For example, agricultural machinery includes tractors for land preparation, rice transplanters for cultivation management, and binders and combines for harvesting, with tractors being the most widely used of all agricultural machinery. 【0003】 In agricultural machinery, despite having numerous metal-to-metal contact points such as hydraulic pumps, transmissions, power take-off (PTO) clutches, differential gears, and wet brakes, a single type of agricultural lubricant is often used for all these contact points. Therefore, lubricant compositions applied to agricultural machinery are required to possess multiple functions, including friction characteristics, wear resistance, oxidation stability, rust prevention, and compatibility with organic materials. Various studies have been conducted to ensure and further enhance these performances (see, for example, Patent Documents 1-4). [Prior art documents] [Patent Documents] 【0004】 [Patent Document 1] Japanese Patent Application Publication No. 3-20396 [Patent Document 2] Japanese Patent Publication No. 2004-59930 [Patent Document 3] Japanese Patent Publication No. 2009-144097 [Patent Document 4] Japanese Patent Publication No. 2009-144098 [Overview of the project] [Problems that the invention aims to solve] 【0005】 Incidentally, since industrial machines such as agricultural machines are used even in cold regions in winter, the lubricating oil composition is required to have a property (hereinafter also referred to as "low-temperature property") in which lubricating performance is exhibited even in a low-temperature environment (for example, an environment of -40°C). However, conventional lubricating oil compositions may have a high viscosity (hereinafter also referred to as "low-temperature viscosity") in a low-temperature environment and are inferior in low-temperature properties. In particular, lubricating oil compositions using only mineral oil-based base oil tend to be inferior in low-temperature properties. The use of a lubricating oil composition with inferior low-temperature properties reduces the starting performance (low-temperature starting performance) of industrial machines to which the lubricating oil composition is applied in a low-temperature environment. 【0006】 As a measure to suppress the increase in low-temperature viscosity and exhibit low-temperature properties, there is a measure to increase the viscosity index and reduce the viscous resistance in a low-temperature environment. The viscosity index can be improved by blending a viscosity index improver (VII: Viscosity Index Improvers). However, the improvement of the viscosity index by a high blending of VII causes the viscosity to decrease when the lubricating oil composition is subjected to a shearing force in sliding parts and gear parts of a machine for a long time, and the oil film is not sufficiently retained in the lubricating part, and the antifriction and antiwear properties may deteriorate. That is, since the decrease in shear stability is considered to be due to the breakage of the molecular chain of VII and the decrease in molecular weight, an increase in the amount of the viscosity index improver may further decrease the shear stability. 【0007】 Thus, in a lubricating oil composition, the compatibility between low-temperature properties and shear stability is in a trade-off relationship, and a measure that does not depend on an increase in the amount of the viscosity index improver is desired, but such a lubricating oil composition has not yet been provided at present. 【0008】 This disclosure has been made in view of such circumstances, and the problem to be solved by one embodiment of this disclosure is to provide a lubricating oil composition excellent in low-temperature properties and shear stability. 【Means for Solving the Problem】 【0009】 This disclosure includes the following aspects. <1> A lubricating oil composition containing a plant-derived base oil that satisfies the following relationship (1), where X is the kinematic viscosity at 100°C and Y is the weight-average molecular weight (Mw) obtained by gel permeation chromatography of the tetrahydrofuran-soluble component. Relational equation (1): Y ≥ 70X + 305 <2> The content of the above-mentioned plant-derived base oil is 10% by mass or more of the total amount of base oil contained in the lubricating oil composition. <1> The lubricating oil composition described above. <3> Furthermore, it contains a base oil which is mineral oil. <1> or <2> The lubricating oil composition described above. <4> The ratio of the above-mentioned plant-derived base oil to the mineral oil base oil is in the range of 10:90 to 100:0 by mass. <3> The lubricating oil composition described above. <5> The lubricating oil composition contains a viscosity index improver, and when the content of the viscosity index improver is A% by mass and the content of the plant-derived base oil is B% by mass, the lubricating oil composition contains a plant-derived base oil that satisfies the following relationship (A1): <1> ~ <4> A lubricating oil product as described in any one of the following. Relation (A1): 0.01 ≤ A / (A+B) ≤ 0.50 <1> ~ <4> A lubricating oil product as described in any one of the following. <6> The BF viscosity at -40℃ is 18000 mPa·s or less. <1> ~ <5> A lubricating oil composition as described in any one of the following. <7> It is a lubricant for agricultural machinery. <1> ~ <6> A lubricating oil composition as described in any one of the following. [Effects of the Invention] 【0010】 According to one embodiment of the present disclosure, a lubricating oil composition with excellent low-temperature properties and shear stability can be provided. [Brief explanation of the drawing] 【0011】 [Figure 1] This is a correlation diagram between the kinematic viscosity at 100°C and the weight-average molecular weight (Mw) of the base oil used in each example. [Modes for carrying out the invention] 【0012】 The lubricating oil compositions relating to this disclosure will be described in detail below. The following description may be based on representative embodiments, but the lubricating oil compositions relating to this disclosure are not limited to such embodiments. 【0013】 In this disclosure, a numerical range indicated using "~" means a range that includes the numbers before and after "~" as the minimum and maximum values, respectively. In numerical ranges described in stages within this disclosure, the upper or lower limit of one numerical range may be replaced with the upper or lower limit of another numerical range described in stages. Furthermore, in numerical ranges described within this disclosure, the upper or lower limit of that range may be replaced with the values ​​shown in the examples. In this disclosure, the amount of each component in a composition means the total amount of multiple substances corresponding to each component present in the composition, unless otherwise specified. In this disclosure, "mass%" and "weight%" are synonymous. In this disclosure, a combination of two or more preferred embodiments is a more preferred embodiment. In this disclosure, "JIS" is used as an abbreviation for Japanese Industrial Standards. 【0014】 [Lubricating oil composition] The lubricating oil composition according to this disclosure is a lubricating oil composition that contains a plant-derived base oil that satisfies the following relational expression (1), where X is the kinematic viscosity at 100°C and Y is the weight-average molecular weight (Mw) obtained by gel permeation chromatography measurement of tetrahydrofuran-soluble components. 【0015】 Relational equation (1): Y ≥ 70X + 305 【0016】 In the following, "tetrahydrofuran-soluble matter" will be abbreviated as "THF-soluble matter," and "gel permeation chromatography measurement" will be abbreviated as "GPC measurement." 【0017】 The lubricating oil composition according to this disclosure exhibits excellent low-temperature properties and shear stability. Although the mechanism by which the lubricating oil composition according to this disclosure achieves the above effects is not entirely clear, it is thought that plant-derived base oils satisfying relation (1) have smaller interionic interactions or less entanglement of molecular chains compared to base oils that do not satisfy relation (1), resulting in a higher weight-average molecular weight (Mw) even at the same viscosity range. This is presumed to contribute to achieving both low-temperature properties and shear stability. 【0018】 (Base oil) The lubricating oil composition according to this disclosure contains a plant-derived base oil (hereinafter also referred to as "specified base oil") that satisfies the following relational expression (1), where X is the kinematic viscosity at 100°C and Y is the weight-average molecular weight (Mw) obtained by GPC measurement of THF-soluble components. Relational equation (1): Y ≥ 70X + 305 【0019】 The specific base oil contained in the lubricating oil composition relating to this disclosure may be used alone or in combination of two or more types. 【0020】 The specified base oil satisfies the following relationship (1), where X is the kinematic viscosity at 100°C and Y is the weight-average molecular weight (Mw) obtained by GPC measurement of THF-soluble components. From the viewpoint of superior low-temperature characteristics and shear stability, it is preferable that it satisfies the following relationship (2), and more preferably that it satisfies the following relationship (3). 【0021】 Relational equation (1): Y ≥ 70X + 305 Relational equation (2): Y ≥ 70X + 320 Relational equation (3): Y ≥ 70X + 335 【0022】 A specified base oil is a base oil derived from plants. A plant-derived base oil refers to a base oil that contains at least one selected from oil components extracted from plants and chemically synthesized oils obtained using plant-derived raw materials. The part of the plant used is not particularly limited and may be any of the following: seeds, fruits, wood, roots, etc. Examples of plant-derived raw materials include extracts from plants and decomposed plant products. A plant-derived base oil also includes those in which the above-mentioned oil components have been modified with stabilizers, etc. 【0023】 Examples of specific base oils include isoparaffins, poly-α-olefins, α-olefin oligomers, fatty acid ester compounds (such as dialkyldiesters), polyol compounds, alkylbenzene compounds, polyglycol compounds, phenyl ether compounds, saturated or unsaturated polyol esters, polyphenyl ethers, hydrocarbons, etc., and include chemically synthesized oils obtained using oil components extracted from plants and plant-derived raw materials. 【0024】 Examples of oil components extracted from plants include soybean oil, sunflower oil, safflower oil, corn oil, meadowfoam oil, rapeseed oil, castor oil, rice bran oil, olive oil, and palm oil. 【0025】 Whether or not the lubricating oil composition relating to this disclosure contains a plant-derived base oil depends on the radioactive carbon-14 (hereinafter referred to as " 14 This can be confirmed by measuring the concentration of (referred to as "C"). The atmosphere contains a certain proportion of 14 Since C is present, and this ratio is similar to that of carbon dioxide in the atmosphere, it is also present in plants that fix carbon dioxide through photosynthesis. 14 It contains C. Therefore, plant-derived base oils also contain C. 14 It contains C. On the other hand, 14 Since the half-life of carbon is 5730 years, the carbon contained in petroleum-derived components (for example, mineral oil, synthetic oil, additives such as viscosity index improvers, etc.) 14 C is hardly present in the lubricating oil composition. 14By measuring the concentration of C, it is possible to confirm whether the lubricating oil composition contains a plant-derived base oil. 【0026】 In the lubricating oil composition 14 The concentration of C can be confirmed by a method conforming to ASTM D6866. Examples of the test methods include liquid scintillation counting (LSC), accelerator mass spectrometry (AMS), and isotope ratio mass spectrometry (IRMS). 【0027】 The kinematic viscosity X at 100 °C of a specific base oil is a value measured by a method conforming to JIS K-2283-2000 (ASTM D445-19). 【0028】 From the viewpoint of further reducing the viscosity in a low-temperature environment, the kinematic viscosity X at 100 °C of the specific base oil is preferably 30 mm 2 / s or less, more preferably 2 mm 2 / s or more and 15 mm 2 / s or less, and even more preferably 3 mm 2 / s or more and 10 mm 2 / s or less. When the catalog value of the kinematic viscosity of the base oil can be confirmed, the catalog value shall be adopted. 【0029】 The weight average molecular weight (Mw) Y of a specific base oil is obtained by GPC measurement of the THF-soluble component. The measurement conditions of GPC are as follows. <Conditions> Apparatus: Shodex GPC-101 (manufactured by Showa Denko K.K.) Column: Three Shodex GPC LF-804 (manufactured by Showa Denko K.K.) Detector: Differential refractive index detector, Mobile phase: THF (tetrahydrofuran) Flow rate: 1 ml / min Sample concentration: Approximately 1.0 mass% / vol% THF Injection volume: 100 μL 【0030】 From the viewpoint of low-temperature characteristics, the weight-average molecular weight (Mw) Y of the specified base oil is preferably 2000 or less, more preferably 300 to 1500, and even more preferably 300 to 1200. 【0031】 From the viewpoint of further reducing the generation of wax in the lubricating oil composition, the specified base oil is preferably such that, in a chromatogram of the tetrahydrofuran-soluble components obtained by gel permeation chromatography (GPC) with the detected amount on the vertical axis and the elution time (minutes) on the horizontal axis, the full width at half maximum of the maximum peak is 0.9 or less, more preferably 0.8 or less, and even more preferably 0.3 to 0.7. 【0032】 The full width at half maximum (FWHM) of the maximum peak refers to the peak width at half maximum (FWHM) observed in a chromatogram obtained by GPC, where the vertical axis is the detection amount and the horizontal axis is the elution time (minutes). The elution time is defined as the time it takes for the molecular weight to reach 10⁴ when converted to polystyrene equivalent. 【0033】 The lubricating oil composition relating to this disclosure may contain a base oil that does not satisfy relational formula (1), to the extent that the effects of this disclosure are achieved. 【0034】 A base oil that does not satisfy relation (1) may be a plant-derived base oil that does not satisfy relation (1). Alternatively, a base oil that does not satisfy relation (1) may be a chemically synthesized oil obtained using mineral oil or petroleum resource-derived raw materials that do not satisfy relation (1). 【0035】 Examples of mineral oil base oils include those obtained by refining the lubricating oil fraction of crude oil using a combination of refining methods such as solvent refining, hydrorefining, hydrocracking, and hydrodewaxing. The mineral oil may also be a paraffinic mineral oil (i.e., a high viscosity index mineral oil-based lubricating oil base oil) that has been highly refined by subjecting hydrorefined oil, catalytic isomerized oil, etc., to solvent dewaxing or hydrodewaxing. The mineral oil may be used alone or in combination of two or more types. 【0036】 Examples of base oils that are chemically synthesized oils obtained using petroleum-derived raw materials include isoparaffins, poly-α-olefins, α-olefin oligomers, fatty acid esters (dialkyldiesters, etc.), polyol compounds, alkylbenzene compounds, polyglycol compounds, phenyl ether compounds, saturated or unsaturated polyol esters, polyphenyl ethers, hydrocarbons, etc., and are base oils obtained by chemical synthesis using petroleum-derived raw materials. Chemically synthesized oils may be used alone or in combination of two or more types. 【0037】 The content of the specified base oil is preferably 10% by mass or more, more preferably 15% by mass or more, and even more preferably 20% by mass or more, relative to the total amount of base oil contained in the lubricating oil composition, from the viewpoint of making it easier to satisfy the aforementioned relationships (1) to (3) and achieving both low-temperature characteristics and shear stability of the lubricating oil composition. The total amount of base oil contained in the lubricating oil composition (100% by mass) may be the specified base oil. The content of the specified base oil may be 100% by mass or less, 90% by mass or less, or 80% by mass or less, relative to the total amount of base oil contained in the lubricating oil composition. In one embodiment, the content of the specified base oil is preferably 10% by mass to 100% by mass, relative to the total amount of base oil contained in the lubricating oil composition. 【0038】 If the lubricating oil composition according to this disclosure contains a base oil other than the specified base oil, it is preferable from the viewpoint of supply stability that it further contains a mineral oil base oil. The content ratio of the specified base oil to the mineral oil base oil is preferably in the range of 10:90 to 100:0 by mass, more preferably in the range of 15:85 to 100:0, and even more preferably in the range of 20:80 to 100:0. 【0039】 (Viscosity index improver) The lubricating oil components relating to this disclosure may contain viscosity index improvers. The viscosity index improvers contained in the lubricating oil composition relating to this disclosure may be used alone or in combination of two or more types. 【0040】 There are no particular limitations on the viscosity index improver, and examples of known viscosity index improvers include polyalkyl (meth)acrylates, olefin copolymers, polyisobutylene, polyalkylstyrene, styrene-butadiene hydrogenated copolymers, styrene-isoprene hydrogenated copolymers, styrene-maleic anhydride ester copolymers, and those containing dispersion groups. 【0041】 When preparing a lubricating oil composition, the viscosity index improver may be used as a liquid containing the viscosity index improver as an active ingredient, a diluent, and other optional components, taking into consideration factors such as solubility in the base oil and reduction of manufacturing time during production. 【0042】 The above-mentioned styrene-butadiene hydrogenated copolymer refers to a styrene-butadiene copolymer that has been hydrogenated to replace the remaining double bonds with saturated bonds. The above-mentioned styrene-isoprene hydrogenated copolymer refers to a styrene-isoprene copolymer that has been hydrogenated to replace the remaining double bonds with saturated bonds. 【0043】 Among these, from the viewpoint of exhibiting good viscosity characteristics at low temperatures, olefin copolymers and polyalkyl (meth)acrylates are preferred as viscosity index improvers, polyalkyl (meth)acrylates are more preferred, and polyalkyl methacrylates are even more preferred. 【0044】 An olefin copolymer can be any copolymer that contains constituent units derived from an olefin in its main chain. Examples of olefin copolymers include copolymers of α-olefins with other monomers, and ethylene-propylene copolymers are preferred, for example. 【0045】 The weight-average molecular weight (Mw) of the viscosity index improver, which is an olefin copolymer, is preferably 10,000 or more, 1,200,000 or less, and 20,000 to 1,000,000, more preferably 20,000 to 800,000, and even more preferably 20,000 to 600,000. When the weight-average molecular weight (Mw) of the viscosity index improver, which is an olefin copolymer, is within the range of 20,000 to 600,000, it tends to be superior in low-temperature starting performance and shear stability. 【0046】 The polyalkyl (meth)acrylate is preferably a polyalkyl (meth)acrylate having an alkyl group having 1 to 100 carbon atoms, more preferably a polyalkyl (meth)acrylate having an alkyl group having 1 to 80 carbon atoms, and even more preferably a polyalkyl (meth)acrylate having an alkyl group having 1 to 50 carbon atoms. The alkyl group in the polyalkyl (meth)acrylate may be one type or two or more types. 【0047】 Examples of polyalkyl (meth)acrylates include polymethyl methacrylate, polymethyl acrylate, and methacrylate esters. In one embodiment, the viscosity index improver preferably contains polymethyl methacrylate. 【0048】 The weight-average molecular weight (Mw) of the viscosity index improver, which is a polyalkyl (meth)acrylate, is preferably 30,000 to 600,000, more preferably 30,000 to 550,000, and even more preferably 40,000 to 500,000. When the weight-average molecular weight (Mw) of the viscosity index improver, which is a polyalkyl (meth)acrylate, is in the range of 30,000 to 600,000, it tends to be superior in low-temperature starting performance and shear stability. 【0049】 In this disclosure, the weight-average molecular weight (Mw) of the viscosity index improver refers to the weight-average molecular weight in polystyrene equivalent as measured by GPC. The measurement conditions can be the same as those for the weight-average molecular weight (Mw) of the specific base oil. 【0050】 When the lubricating oil composition according to this disclosure contains a viscosity index improver, the content of the viscosity index improver is preferably 0.5% to 10.0% by mass, more preferably 1.0% to 10.0% by mass, and even more preferably 1.0% to 8.0% by mass, based on the total amount of the lubricating oil composition. When a liquid containing the viscosity index improver as an active ingredient is used in the preparation of the lubricating oil composition, the above content refers to the content of the active ingredient in the lubricating oil composition. 【0051】 The lubricating oil composition according to this disclosure can achieve both low-temperature properties and shear stability without increasing the viscosity index improver content. Furthermore, reducing the viscosity index improver content can contribute to further improvement of shear stability. For this reason, in one embodiment, when the lubricating oil composition according to this disclosure satisfies the following relation (A1) when the viscosity index improver content is A mass% and the plant-derived base oil content is B mass% relative to the total amount of the lubricating oil composition, it is preferable that it satisfies the following relation (A2) and more preferable that it satisfies the following relation (A3) from the viewpoint of being superior in both low-temperature properties and shear stability. Relation (A1): 0.01 ≤ A / (A+B) ≤ 0.50 Relational expression (A2): 0.01≦A / (A+B)≦0.47 Relation (A3): 0.01 ≤ A / (A + B) ≤ 0.45 【0052】 (Zinc dialkyldithiophosphate) The lubricating oil composition according to this disclosure may contain zinc dialkyldithiophosphate from the viewpoint of friction and wear resistance. Examples of zinc dialkyldithiophosphate include compounds represented by the following formula (A). 【0053】 [ka] 【0054】 In formula (A), R 9 , R 10 , R 11 and R 12Each of these independently represents an alkyl group with 3 to 24 carbon atoms. 9 , R 10 , R 11 and R 12 It is preferably an alkyl group having 3 to 12 carbon atoms, and more preferably an alkyl group having 6 to 12 carbon atoms. Also, R 9 , R 10 , R 11 and R 12 It may have only a primary alkyl group, or only a secondary alkyl group, or it may have both a primary alkyl group and a secondary alkyl group. From the viewpoint of friction coefficient stability, R 9 , R 10 , R 11 and R 12 It is preferable that it is a primary alkyl group. 【0055】 The zinc dialkyldithiophosphate content is preferably 0.05% to 0.2% by mass, more preferably 0.07% to 0.18% by mass, and even more preferably 0.08% to 0.15% by mass, based on the amount of zinc relative to the total amount of the lubricating oil composition. 【0056】 (Metal-type cleaning agent) The lubricating oil composition of this disclosure may further contain a metallic detergent. Examples of metallic detergents include alkaline earth metal salts such as alkaline earth metal sulfonates, alkaline earth metal phenates, and alkaline earth metal salicylates. 【0057】 From the viewpoint of achieving both suppression of emulsion formation and frictional properties, alkaline earth metal sulfonates can be suitably used as metal-type detergents. Metal-type detergents may be used alone or in combination of two or more types. 【0058】 The metal-type detergent is preferably an alkaline earth metal salt over-basicated with carbonic acid or boric acid. There are no particular restrictions on the alkaline earth metal contained in the metal-type detergent; calcium, barium, etc., can be used. Among these, calcium is preferred as the alkaline earth metal. 【0059】 The base number of the metal-type detergent is determined by the perchloric acid method according to JIS K2501:2003, preferably 150 mg KOH / g to 500 mg KOH / g, more preferably 200 mg KOH / g to 450 mg KOH / g, and even more preferably 250 mg KOH / g to 450 mg KOH / g. 【0060】 The content of the metallic detergent is preferably 0.05% to 0.5% by mass, and more preferably 0.15% to 0.45% by mass, based on the amount of alkaline earth metal relative to the total amount of the lubricating oil composition. 【0061】 (Ashless dispersant) The lubricating oil compositions of this disclosure may contain an ashless dispersant. Examples of ashless dispersants include succinimides having polyalkenyl groups and their boron derivatives. 【0062】 Examples of succinimides having a polyalkenyl group include compounds represented by the following formula (B). Examples of boron derivatives of succinimides having a polyalkenyl group include compounds obtained by acid treatment of the compound represented by the following formula (B) with boric acid or a boric acid derivative. 【0063】 [ka] 【0064】 In formula (B), R 13 and R 14 Each of these independently represents a polyalkenyl group, and q represents an integer from 0 to 4. Preferably, q is an integer from 2 to 4, and more preferably from 3 to 4. 【0065】 The number-average molecular weight of the polyalkenyl group is preferably 800 to 2600, more preferably 1200 to 2600, even more preferably 1250 to 2600, and particularly preferably 1300 to 2600. 【0066】 When the lubricating oil composition of this disclosure contains succinimide having a polyalkenyl group, the content of succinimide having a polyalkenyl group is preferably 0.001% to 0.04% by mass, and more preferably 0.002% to 0.02% by mass, based on nitrogen concentration relative to the total amount of the lubricating oil composition. 【0067】 (Other additives) The lubricating oil composition relating to this disclosure may contain known additives (hereinafter also referred to as "other additives") as necessary. 【0068】 Other additives include, for example, friction modifiers, lubricity agents, anti-wear agents other than zinc dialkyldithiophosphate, extreme pressure agents, rust inhibitors, antioxidants, metal deactivators, pour point depressants, defoamers, colorants, and other additives such as tractor hydraulic fluid package additives, as well as various lubricant package additives containing at least one selected from the other additives. 【0069】 Examples of friction modifiers include organic molybdenum compounds, ester compounds of polyhydric alcohols and fatty acids, amine compounds, amide compounds, ether compounds, sulfur esters, phosphate esters, acidic phosphate esters and their amine salts, and diols. 【0070】 Examples of oily agents include oleic acid, stearic acid, higher alcohols, aliphatic amine compounds, fatty acid amide compounds, fatty acid ester compounds, sulfurized oils and fats, acidic phosphate esters, and acidic phosphite esters. Furthermore, components contained in the base oil may also function as oily agents. 【0071】 Examples of anti-wear agents include sulfur compounds, phosphate esters, phosphite esters, acidic phosphate esters, and their amine salts. 【0072】 Examples of extreme pressure additives include hydrocarbon sulfides, sulfurized oils and fats, phosphate esters, phosphite esters, chlorinated paraffins, and chlorinated diphenyls. 【0073】 Examples of rust inhibitors include carboxylic acids and their amine salts, ester compounds, sulfonates, and boron compounds. 【0074】 Examples of antioxidants include amine-based antioxidants, phenol-based antioxidants, and sulfur-based antioxidants. 【0075】 Examples of metal deactivators include benzotriazole, thiadiazole, and alkenyl succinate esters. 【0076】 Examples of pour point depressants include polyalkyl methacrylates, chlorinated paraffin-naphthalene condensates, and alkylated polystyrenes. 【0077】 Examples of defoaming agents include silicone compounds such as dimethylpolysiloxane, fluorosilicone compounds, and ester compounds. 【0078】 [Properties of Lubricating Oil Compositions] The lubricating oil composition preferably has a Brookfield (BF) viscosity at -40°C of 18,000 mPa·s or less, and more preferably 17,500 mPa·s or less. 【0079】 When the BF viscosity of a lubricating oil composition at -40°C is 18,000 mPa·s or less, the lubricity in low-temperature environments tends to be adequately maintained. 【0080】 The lower limit of the BF viscosity of the lubricating oil composition at -40°C is, for example, 3000 mPa·s or higher. 【0081】 The BF viscosity of the lubricating oil composition at -40°C is a value measured according to the method in accordance with ASTM D 2983. 【0082】 The lubricating oil composition has a kinematic viscosity of 6.0 mm at 100°C. 2 / s~15.0mm 2 It is preferable that it be / s, and 7.0 mm2 / s~13.0mm 2 It is more preferable that it be / s, and 7.5mm 2 / s~11.0mm 2 It is even more preferable to use / s. 【0083】 The lubricating oil composition has a kinematic viscosity of 20 mm at 40°C. 2 / s~80mm 2 It is preferable that it be / s, which is 20mm 2 / s~70mm 2 It is more preferable that it be / s, which is 25mm 2 / s~60mm 2 It is even more preferable to use / s. 【0084】 The kinematic viscosity of the lubricating oil composition at 100°C and 40°C is measured according to the method conforming to JIS K-2283-2000 (ASTM D445-19). 【0085】 The viscosity index of the lubricating oil composition is preferably 150 or higher, more preferably 170 or higher, and even more preferably 190 or higher. 【0086】 When the kinematic viscosity and viscosity index of the lubricating oil composition at 100°C meet the above range, it maintains lubricity and also exhibits superior low-temperature characteristics. 【0087】 The viscosity index of the lubricating oil composition is a value measured according to the method conforming to JIS K 2283:2000. 【0088】 The density of the lubricating oil composition is not particularly limited, but for example, 0.75 g / cm³ 3 ~1.00g / cm 3 Preferably, it is 0.77 g / cm³. 3 ~1.00g / cm 3 It is more preferable that it be 0.80 g / cm³ 3 ~0.95g / cm 3 It is even more preferable that this be the case. 【0089】 The density of the lubricating oil composition is a value measured according to the method conforming to JIS K 2249-1:2011. 【0090】 [Method for preparing a lubricating oil composition] The method for preparing the lubricating oil composition according to this disclosure is not particularly limited, and a base oil containing a specific base oil may be appropriately mixed with the aforementioned components, which may be added as needed. The mixing order of the components is not particularly limited. 【0091】 [Uses of lubricating oil compositions] The lubricating oil composition according to this disclosure includes embodiments for use in agricultural machinery. That is, one embodiment of the lubricating oil composition according to this disclosure is a lubricating oil composition for agricultural machinery. Examples of agricultural machinery include tractors, which are land leveling implements; rice transplanters, which are cultivation management implements; and binders and combines, which are harvesting implements. In particular, the lubricating oil composition according to this disclosure can be suitably used in tractors and can be used as a common lubricant for hydraulic pumps, transmissions, PTO clutches, differential gears, wet brakes, etc. 【0092】 In addition to being used as a lubricating oil composition for agricultural machinery, the lubricating oil composition described herein can also be applied, for example, as a lubricating oil composition for internal combustion engines, hydraulic fluids, and gear oils. [Examples] 【0093】 The lubricating oil compositions relating to this disclosure will be described in more detail by reference to examples and comparative examples. However, the lubricating oil compositions relating to this disclosure are not limited in any way to the examples shown below. 【0094】 <Preparation of base oil and additives> (1) Base oil Five types of mineral oils and six types of plant-derived base oils (referred to as "vegetable oil" in the table) were prepared. For each base oil, the kinematic viscosity at 100°C (referred to as "100°C kinematic viscosity" in the table) and the weight-average molecular weight (Mw) (referred to as "Mw" in the table), measured using the measurement method described above, are shown in Table 1. 【0095】 (2) Viscosity index improver liquid X (active ingredient amount: 50% by mass) Active ingredient: Polymethyl methacrylate (weight-average molecular weight: 140,000, viscosity index improver) 【0096】 (3) Other additives Table 1 shows the total amount of all additives, including friction and wear inhibitors, dispersants, metal-type detergents, friction modifiers, antioxidants, pour point depressants, rust inhibitors, and silicone-based defoamers. 【0097】 <Examples 1-10 and Comparative Examples 1-5> Lubricating oil compositions for each example were prepared by mixing base oil, viscosity index improver, and other additives in the amounts (mass%) shown in Table 1. 【0098】 In Table 1, in the columns for "Relationship (1)", "Relationship (2)", and "Relationship (3)", those that satisfy relations (1) to (3) are indicated as "fulfilled", and those that do not satisfy are indicated as "not fulfilled". 【0099】 In Table 1, the column "Amount of viscosity index improver A / (Amount of viscosity index improver A + Amount of specific base oil B)" shows the calculated value of A / (A+B) when the viscosity index improver content is A [mass%] and the plant-derived base oil content is B [mass%]. "Amount of viscosity index improver A" corresponds to the amount of viscosity index improver contained in viscosity index improver liquid X, i.e., the amount of active ingredient [mass%]. "Amount of specific base oil B" corresponds to the total content [mass%] of vegetable oils 1 to 6 (specific base oils). 【0100】 <Measurement and Evaluation> The following measurements and evaluations were performed on each of the lubricating oil compositions obtained above. The results are shown in Table 1. 【0101】 (1) Density The density (15°C) of the lubricating oil composition was measured according to the method in accordance with JIS K 2249-1:2011. (2) Kinematic viscosity and viscosity index The kinematic viscosity and viscosity index of the lubricating oil composition were measured according to the method in accordance with JIS K 2283:2000. (3)BF viscosity The BF viscosity of the lubricating oil composition was measured according to the method compliant with ASTM D 2983. A BF viscosity value of 18,000 mPa or less is considered acceptable. An acceptable BF viscosity indicates excellent low-temperature characteristics. 【0102】 (4) Shear stability SONIC shear stability test: In accordance with JPI-5S-29 "Test method for shear stability of lubricating oil," the rate of change (decrease rate) of kinematic viscosity at 100°C compared to new oil after 30 minutes was calculated. Based on the results obtained, shear stability was evaluated according to the following evaluation criteria. -Evaluation Criteria- A: The viscosity efficiency is 9% or less. B: The viscosity efficiency is between 9% and 12%. C: The viscosity efficiency is over 12%. 【0103】 [Table 1] 【0104】 Figure 1 is a correlation diagram between the kinematic viscosity at 100°C and the weight-average molecular weight (Mw) of the base oils used in each example. In Figure 1, the values ​​applied to the plots of each base oil are those listed in Table 1 for kinematic viscosity at 100°C and Mw. 【0105】 As shown in Table 1 and Figure 1, the lubricating oil composition of the example containing a base oil that satisfies relation (1) is superior in both low-temperature characteristics and shear stability compared to the lubricating oil composition of the comparative example that does not contain a base oil that satisfies relation (1).

Claims

[Claim 1] When the kinematic viscosity at 100°C is X and the weight-average molecular weight (Mw) obtained by gel permeation chromatography of the tetrahydrofuran-soluble component is Y, the following relation (1) is satisfied for a plant-derived base oil and a viscosity index improver. The plant-derived base oil is isoparaffin, poly-α-olefin, α-olefin oligomer, fatty acid ester compound, polyol compound, alkylbenzene compound, polyglycol compound, phenyl ether compound, saturated or unsaturated polyol ester, polyphenyl ether, or hydrocarbon, and is at least one base oil selected from oil components extracted from plants such as soybean oil, sunflower oil, safflower oil, corn oil, meadowfoam oil, rapeseed oil, castor oil, rice bran oil, olive oil, or palm oil, and chemically synthesized oils obtained using plant-derived raw materials. A lubricating oil composition that satisfies the following relational expression (A1) when the content of the viscosity index improver is A% by mass and the content of the plant-derived base oil is B% by mass, relative to the total amount of the lubricating oil composition. Relational equation (1): Y ≥ 70X + 305 Relational expression (A1): 0.01 ≤ A / (A + B) ≤ 0.50 [Claim 2] The lubricating oil composition according to claim 1, wherein the content of the plant-derived base oil is 10% by mass or more with respect to the total amount of the lubricating oil composition. [Claim 3] Furthermore, the lubricating oil composition according to claim 1 or claim 2 further contains a base oil which is a mineral oil. [Claim 4] The lubricating oil composition according to claim 3, wherein the content ratio of the plant-derived base oil to the mineral oil base oil is in the range of 10:90 to 100:0 by mass. [Claim 5] The lubricating oil composition according to claim 1 or claim 2, wherein the BF viscosity at -40°C is 18,000 mPa·s or less. [Claim 6] A lubricating oil composition according to claim 1 or claim 2, which is a lubricating oil for agricultural machinery.

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