Grease composition

Abstract

Provided is a grease composition containing a base oil (A), a thickener (B), and an organic molybdenum compound (C). The base oil (A) contains a synthetic oil (A1), and the thickener (B) contains a lithium complex soap (B1).

Description

Grease composition 【0001】 This invention relates to a grease composition. This application claims priority under Japanese Patent Application No. 2024-215385, filed in Japan on December 10, 2024, the contents of which are incorporated herein by reference. 【0002】 Grease is a lubricant made by dispersing a highly lipophilic solid thickener in a base oil to create a semi-solid substance. Compared to lubricating oil, grease adheres more easily to the lubricating part and is less likely to leak. Therefore, using grease can simplify the mechanical structure of the lubrication system. In addition, grease leaks less than lubricating oil, creating a cleaner environment, and the replenishment interval can be shortened. Grease is mainly used to lubricate mechanical elements such as rolling bearings, sliding bearings, ball screws, linear guides, and gears. Rolling bearings are widely used in machine tool spindles, railway vehicles, engine accessories such as alternators in automobiles, constant velocity joints, and wheels. 【0003】 For example, Patent Document 1 discloses a resin grease composition comprising (A) a lubricating oil base, (B) a thickener, and (C) at least one selected from the group consisting of organic molybdenum compounds and sulfur-based extreme pressure agents, wherein, when a sulfur-based extreme pressure agent is included, the content of the sulfur-based extreme pressure agent is 0.05% by mass or more and 2.5% by mass or less on a basis of the total amount of the composition, and substantially free of zinc dialkyldithiophosphate. It is disclosed that this resin grease composition does not degrade the resin it is in contact with, particularly acetal resin, even under high-temperature conditions. 【0004】 Japanese Patent Publication No. 2022-092773 【0005】The properties required for a grease composition vary depending on its intended use, and the optimal base oil, thickener, and additives are selected according to the application. Therefore, there is a need for grease compositions that exhibit excellent properties not only under high-temperature conditions, as described in Patent Document 1, but also under low-temperature conditions. Under low-temperature conditions, grease compositions tend to harden, and torque tends to increase. Therefore, grease compositions used under low-temperature conditions generally use base oils that have excellent low-temperature fluidity and low viscosity. However, grease compositions containing low-viscosity base oils tend to have a thin oil film, which can reduce load-bearing capacity and wear resistance. Therefore, it is difficult to achieve both low torque under low-temperature conditions and good load-bearing capacity and wear resistance. 【0006】 The present invention has been made in view of the above circumstances, and aims to provide a grease composition that has low torque under low temperature conditions without impairing load-bearing capacity and wear resistance. 【0007】 To solve the above problems, the present invention employs the following configuration: [1] A grease composition containing a base oil (A), a thickener (B), and an organic molybdenum compound (C), wherein the base oil (A) contains a synthetic oil (A1) and the thickener (B) contains a lithium complex soap (B1). [2] The grease composition according to [1], further containing an organic zinc compound (D). [3] The grease composition according to [1] or [2], wherein the content of synthetic oil (A1) in the total amount of base oil (A) is 99% by mass or more. [4] The grease composition according to any one of [1] to [3], used in a wind power generation device. [5] The grease composition according to any one of [1] to [4], wherein the organic zinc compound (D) contains zinc dialkyldithiophosphate. [6] The grease composition according to any one of [1] to [5], wherein the synthetic oil (A1) contains poly-α-olefin. 【0008】 According to the present invention, it is possible to provide a grease composition that exhibits low torque under low-temperature conditions without impairing load-bearing capacity and wear resistance. 【0009】(Grease Composition) The grease composition of this embodiment contains a base oil (A), a thickener (B), and an organic molybdenum compound (C). 【0010】 <Base Oil (A)> The grease composition of this embodiment contains a base oil (A). The kinematic viscosity of the base oil (A) at 40°C is preferably 100 mm ２ / s or more, more preferably 140 mm ２ / s or more, still more preferably 180 mm ２ / s or more, particularly preferably 200 mm ２ / s or more. The kinematic viscosity of the base oil (A) at 40°C is preferably 600 mm ２ / s or less, more preferably 550 mm ２ / s or less, still more preferably 500 mm ２ / s or less. 【0011】 When the kinematic viscosity of the base oil (A) of the grease composition of this embodiment at 40°C is 100 mm ２ / s or more, the torque under low-temperature conditions becomes low and the anti-wear property becomes high. Also, when the kinematic viscosity of the base oil (A) at 40°C is above the above-mentioned preferable lower limit value, the anti-wear property and load-carrying property become higher. When the kinematic viscosity of the base oil (A) of the grease composition of this embodiment at 40°C is above the above-mentioned preferable lower limit value, the torque under low-temperature conditions becomes lower. 【0012】 For example, the kinematic viscosity of the base oil (A) at 40°C is preferably 100 mm ２ / s or more and 600 mm ２ / s or less, more preferably 140 mm ２ / s or more and 550 mm ２ / s or less, still more preferably 180 mm ２ / s or more and 500 mm ２ / s or less, particularly preferably 200 mm ２ / s or more and 500 mm ２ / s or less. 【0013】 The kinematic viscosity of the base oil (A) at 100°C is preferably 17 mm ２ / s or more, more preferably 18 mm ２ / s or more, still more preferably 19 mm ２ / s or more is more preferable. The kinematic viscosity of base oil (A) at 100 °C is 65 mm ２ / s or less is preferable, 60 mm ２ / s or less is more preferable, 55 mm ２ / s or less is more preferably. 【0014】 When the kinematic viscosity of base oil (A) of the grease composition of this embodiment at 100 °C is at or above the above-mentioned preferable lower limit value, the anti-wear property and load-carrying property become higher. When the kinematic viscosity of base oil (A) of the grease composition of this embodiment at 100 °C is at or below the above-mentioned preferable upper limit value, the torque under low temperature conditions becomes lower. 【0015】 For example, the kinematic viscosity of base oil (A) at 100 °C is preferably 17 mm ２ / s or more and 65 mm ２ / s or less, more preferably 18 mm ２ / s or more and 60 mm ２ / s or less, even more preferably 19 mm ２ / s or more and 55 mm ２ / s or less is more preferably. 【0016】 The kinematic viscosities at 40 °C and 100 °C in this specification mean the kinematic viscosities measured in accordance with JIS K2283:2000. 【0017】 The base oil (A) of the grease composition of this embodiment contains a synthetic oil (A1). 【0018】 <<Synthetic oil (A1)>> Examples of the synthetic oil (A1) include polyolefins such as poly-α-olefins, ester base oils such as diesters and polyol esters, polyalkylene glycols, alkylbenzenes, and alkylnaphthalenes. Among the above, polyolefins are preferable as the synthetic oil (A1), and poly-α-olefins are more preferable. 【0019】 The base oil (A) of the grease composition of this embodiment may contain mineral oil. 【0020】<<Mineral Oil>> As the mineral oil, distillate oil obtained by atmospheric distillation of crude oil can be used. Further, a lubricating oil fraction obtained by subjecting this distillate oil to vacuum distillation and then refining it by various refining processes can also be used. As the refining processes, hydrorefining, solvent extraction, solvent dewaxing, hydrodewaxing, sulfuric acid washing, clay treatment, etc. can be appropriately combined. By treating these refining processes in an appropriate order in combination, mineral oil can be obtained. Further, a mixture of a plurality of refined oils having different properties obtained by subjecting different crude oils or distillate oils to different combinations of refining processes may be used. 【0021】 As the mineral oil, Group I base oil of API base oil classification (hereinafter referred to as "API Group I base oil"), Group II base oil (hereinafter referred to as "API Group II base oil"), or Group III base oil (hereinafter referred to as "API Group III base oil"), or a mixed base oil thereof can be used. API Group I base oil is a mineral oil-based base oil having a sulfur content of more than 0.03% by mass and / or a saturation of less than 90% by mass, and a viscosity index of 80 or more and less than 120. API Group II base oil is a mineral oil-based base oil having a sulfur content of 0.03% by mass or less, a saturation of 90% by mass or more, and a viscosity index of 80 or more and less than 120. API Group III base oil is a mineral oil-based base oil having a sulfur content of 0.03% by mass or less, a saturation of 90% by mass or more, and a viscosity index of 120 or more. 【0022】 As the base oil (A) of the grease composition of the present embodiment, one kind of mineral oil may be used alone, or a plurality of mineral oils may be mixed and used. In the mixed mineral oil containing a plurality of mineral oils, their API classifications may be the same or different from each other. 【0023】 The viscosity index of the mineral oil of the grease composition of the present embodiment is preferably 70 or more, more preferably 80 or more, and still more preferably 90 or more. The viscosity index of the mineral oil is preferably 150 or less, more preferably 120 or less, and still more preferably 100 or less. For example, the viscosity index of the mineral oil is preferably 70 or more and 150 or less, more preferably 80 or more and 120 or less, and still more preferably 90 or more and 100 or less. 【0024】 Viscosity indices as used herein refer to values ​​measured in accordance with JIS K 2283. 【0025】 The aniline point of the mineral oil in the grease composition of this embodiment is preferably 90°C or higher, more preferably 100°C or higher, and even more preferably 110°C or higher. The aniline point of the mineral oil is preferably 140°C or lower, more preferably 130°C or lower, and even more preferably 120°C or lower. For example, the aniline point of the mineral oil is preferably 90°C to 140°C, more preferably 100°C to 130°C, and even more preferably 110°C to 120°C. 【0026】 In this specification, the aniline point refers to the value measured in accordance with JIS K 2256. 【0027】 In the grease composition of this embodiment, the sulfur content of the mineral oil is preferably 0.40% by mass or more, more preferably 0.45% by mass or more, and even more preferably 0.50% by mass or more. The sulfur content of the mineral oil is preferably 0.70% by mass or less, more preferably 0.65% by mass or less, and even more preferably 0.60% by mass or less. For example, the density of the mineral oil at 20°C is preferably 1.30 to 1.60, more preferably 1.35 to 1.55, and even more preferably 1.40 to 1.50. 【0028】 In this specification, sulfur content refers to values ​​measured in accordance with JIS K 2541-6. 【0029】 In the grease composition of this embodiment, the sulfur content of the mineral oil is preferably 0.40% by mass or more, more preferably 0.45% by mass or more, and even more preferably 0.50% by mass or more. The sulfur content of the mineral oil is preferably 0.70% by mass or less, more preferably 0.65% by mass or less, and even more preferably 0.60% by mass or less. For example, the density of the mineral oil at 20°C is preferably 1.30 to 1.60, more preferably 1.35 to 1.55, and even more preferably 1.40 to 1.50. 【0030】 % C of mineral oil in the grease composition of this embodiment ＰIt is preferably 55 or higher, more preferably 60 or higher, and even more preferably 65 or higher. %C of mineral oil Ｐ It is preferably 80 or less, more preferably 75 or less, and even more preferably 70 or less. 【0031】 % C of mineral oil in the grease composition of this embodiment Ｎ It is preferably 10 or more, more preferably 15 or more, and even more preferably 20 or more. %C of mineral oil Ｎ It is preferably 35 or less, more preferably 30 or less, and even more preferably 25 or less. 【0032】 % C of mineral oil in the grease composition of this embodiment Ａ It is preferably 1 or more, more preferably 3 or more, and even more preferably 5 or more. %C of mineral oil Ｎ It is preferably 15 or less, more preferably 10 or less, and even more preferably 8 or less. 【0033】 For example, the mineral oil in the grease composition of this embodiment is %C Ｐ , %C Ｎ and %C Ａ Of the total of 100, %C Ｐ It is preferably 55 to 80, more preferably 60 to 75, and even more preferably 65 to 70. %C of mineral oil Ｎ It is preferably 10 to 35, more preferably 15 to 30, and even more preferably 20 to 25. %C of mineral oil Ａ It is preferably 1 to 15, more preferably 3 to 10, and even more preferably 5 to 8. 【0034】 In this specification, %C Ｐ , %C Ｎ and %C Ａ These are determined by methods (n-d-M ring analysis) in accordance with ASTM D 3238-85. %C ＮThis represents the percentage (mass ratio) of the number of naphthenic carbon atoms relative to the total number of carbon atoms. %C Ｐ This represents the percentage (mass ratio) of the number of carbon atoms in paraffin to the total number of carbon atoms. %C Ａ This represents the percentage of aromatic carbon atoms relative to the total number of carbon atoms. (See %C mentioned above.) Ｎ , %C Ｐ and %C Ａ The preferred range is based on the value obtained by the above method, and even for mineral oil-based base oils that do not contain naphthenes, the %C obtained by the above method is also applicable. Ｎ This can represent a value greater than 0. 【0035】 The parameters of the mineral oil described above can be controlled by precisely adjusting the pressure, temperature, reflux ratio, or the number of stages in the distillation column during the production of the mineral oil. 【0036】 The base oil (A) content of the grease composition of this embodiment is preferably 70% by mass or more, more preferably 75% by mass or more, and even more preferably 80% by mass or more, based on the total amount of the grease composition. The base oil (A) content of the grease composition of this embodiment is preferably 98% by mass or less, more preferably 95% by mass or less, and even more preferably 90% by mass or less, based on the total amount of the grease composition. For example, the base oil (A) content of the grease composition of this embodiment is preferably 70% by mass or more and 98% by mass or less, more preferably 75% by mass or more and 95% by mass or less, and even more preferably 80% by mass or more and 90% by mass or less, based on the total amount of the grease composition. 【0037】 In this embodiment, the proportion of synthetic oil (A1) in the total amount of base oil (A) of the grease composition is preferably 90% by mass or more, more preferably 95% by mass or more, and even more preferably 99% by mass or more. 【0038】 <Thickener (B)> The grease composition of this embodiment contains a thickener (B). The thickener (B) contains lithium complex soap (B1). 【0039】 ≪Lithium Complex Soap (B1)≫ Lithium complex soap (B1) is a metallic soap made by saponifying multiple fatty acids or oils with lithium hydroxide, etc. 【0040】 The fatty acid may be a fatty acid derivative having substituents such as a hydroxyl group. The fatty acid is preferably a monovalent or divalent fatty acid. The fatty acid is preferably a fatty acid having 6 to 20 carbon atoms, and more preferably a monovalent fatty acid having 12 to 20 carbon atoms or a divalent fatty acid having 6 to 14 carbon atoms. In this invention, "6 to 20 carbon atoms" means having 6 to 20 carbon atoms. 【0041】 Among the above, a monovalent fatty acid containing one hydroxyl group is preferred as the fatty acid. Examples of dibasic acids to be combined with fatty acids in lithium complex soap (B1) include acetic acid, azelaic acid, and sebacic acid. Examples of aromatic carboxylic acids to be combined with fatty acids in lithium complex soap (B1) include benzoic acid. 【0042】 Among the lithium complex soaps (B1) mentioned above, lithium complex soaps obtained by reacting lithium hydroxide with a monovalent fatty acid having 6 to 20 carbon atoms containing one hydroxyl group and a dibasic acid are preferred, lithium complex soaps obtained by reacting lithium hydroxide with a monovalent fatty acid having 12 to 20 carbon atoms containing one hydroxyl group and azelaic acid are more preferred, and lithium complex soaps obtained by reacting lithium hydroxide with 12-hydroxystearic acid and azelaic acid are even more preferred. 【0043】 Lithium complex soap (B1) may be used alone or in combination with other types. 【0044】The thickener (B) may contain other thickeners besides lithium complex soap (B1). Examples of other thickeners include single soaps; metal complex soaps other than lithium; urea-based thickeners; bentonite; and inorganic thickeners such as silica gel. Examples of urea-based thickeners include diurea compounds and polyurea compounds. Diurea compounds are compounds obtained by the reaction of diisocyanate with a monoamine and have two urea groups (-NH-CO-NH-). In this specification, polyurea compounds are compounds obtained by the reaction of diisocyanate with a monoamine or diamine and have three or more urea groups (-NH-CO-NH-). 【0045】 The thickener (B) may be used alone or in a mixture of several types. The content of the thickener (B) in the grease composition of this embodiment is preferably 1% by mass or more, more preferably 3% by mass or more, and even more preferably 5% by mass or more, based on the total amount of the grease composition. The content of the thickener (B) in the grease composition of this embodiment is preferably 18% by mass or less, more preferably 15% by mass or less, and even more preferably 12% by mass or less, based on the total amount of the grease composition. For example, the content of the thickener (B) in the grease composition of this embodiment is preferably 1% by mass or more and 18% by mass or less, more preferably 3% by mass or more and 15% by mass or less, and even more preferably 5% by mass or more and 12% by mass or less, based on the total amount of the grease composition. 【0046】 In this embodiment, the proportion of lithium complex soap (B1) in the total amount of thickener (B) of the grease composition is preferably 95% by mass or more, preferably 98% by mass or more, and more preferably 99% by mass or more. It is particularly preferable that the thickener (B) of the grease composition in this embodiment consists solely of lithium complex soap (B1). 【0047】<Organo-molybdenum compound (C)> The grease composition of this embodiment contains an organic-molybdenum compound (C). Examples of organic-molybdenum compound (C) include molybdenum dithiocarbamate (MoDTC), molybdenum dithiophosphate (MoDTP), and Mo-amine complex, with molybdenum dithiocarbamate (MoDTC) and molybdenum dithiophosphate (MoDTP) being preferred. Molybdenum dithiocarbamate is preferred as the organic-molybdenum compound, and molybdenum dithiocarbamate represented by the following formula (1) is more preferred. 【0048】 [In the formula, R1 to R4 may be the same or different, and each is a hydrocarbon group having 1 to 30 carbon atoms, X １ ~X ４ These may be the same or different, and are either S or O, respectively. 【0049】 In formula (1) above, the hydrocarbon groups in R1 to R4 have 1 to 30 carbon atoms, preferably 1 to 10 carbon atoms, more preferably 1 to 5 carbon atoms, and even more preferably 1 to 4 carbon atoms. 【0050】 In formula (1) above, the hydrocarbon groups in R1 to R4 are preferably cyclic alkyl groups or linear alkyl groups, and more preferably linear alkyl groups. 【0051】 The organic molybdenum compound (C) may be used alone or in a mixture of several. The content of the organic molybdenum compound (C) in the grease composition of this embodiment is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, and even more preferably 1.5% by mass or more, based on the total amount of the grease composition. The content of the organic molybdenum compound (C) in the grease composition of this embodiment is preferably 6% by mass or less, more preferably 4% by mass or less, and even more preferably 3% by mass or less, based on the total amount of the grease composition. For example, the content of the organic molybdenum compound (C) in the grease composition of this embodiment is preferably 0.1% by mass or more and 6% by mass or less, more preferably 0.5% by mass or more and 4% by mass or less, and even more preferably 1.5% by mass or more and 3% by mass or less, based on the total amount of the grease composition. 【0052】 In the grease composition of this embodiment, the proportion of molybdenum dithiocarbamate in the total amount of organic molybdenum compound (C) is preferably 95% by mass or more, preferably 98% by mass or more, and more preferably 99% by mass or more. In the grease composition of this embodiment, it is particularly preferable that the organic molybdenum compound (C) consists solely of molybdenum dithiocarbamate. 【0053】 <Optional Components> The grease composition of this embodiment may contain optional components other than the base oil (A), thickener (B), and organic molybdenum compound (C) described above. Examples of such optional components include organic zinc compounds (D), solid lubricants, anti-wear agents or extreme pressure agents, antioxidants, rust inhibitors, and corrosion inhibitors. 【0054】 <Organozinc Compound (D)> The grease composition of this embodiment may contain an organozinc compound (D). Examples of organozinc compound (D) include zinc dialkyldithiophosphate and zinc dialkyldithiocarbamate. Zinc dialkyldithiophosphate and zinc dialkyldithiocarbamate are preferred as organozinc compound (D), and zinc dialkyldithiophosphate represented by the following formula (2) is more preferred. 【0055】 [In the formula, R19 to R22 may be the same or different, and each independently represents a hydrocarbon group having one or more carbon atoms.] 【0056】 In formula (2) above, the hydrocarbon groups in R19 to R22 preferably have 1 to 30 carbon atoms, more preferably 1 to 10 carbon atoms, even more preferably 2 to 8 carbon atoms, and particularly preferably 3 to 6 carbon atoms. 【0057】 In formula (2) above, the hydrocarbon groups in R19 to R22 are preferably cyclic alkyl groups or linear alkyl groups, and more preferably linear alkyl groups. 【0058】The organozinc compound (D) may be used alone or in a mixture of several. When the grease composition of this embodiment contains organozinc compound (D), the content of organozinc compound (D) is preferably 0.5% by mass or more, more preferably 1% by mass or more, and even more preferably 1.5% by mass or more, based on the total amount of the grease composition. The content of organozinc compound (D) in the grease composition of this embodiment is preferably 5% by mass or less, more preferably 3% by mass or less, and even more preferably 2% by mass or less, based on the total amount of the grease composition. For example, the content of organozinc compound (D) in the grease composition of this embodiment is preferably 0.5% by mass or more and 5% by mass or less, more preferably 1% by mass or more and 3% by mass or less, and even more preferably 1.5% by mass or more and 2% by mass or less, based on the total amount of the grease composition. 【0059】 In the grease composition of this embodiment, the proportion of zinc dialkyldithiophosphate in the total amount of organozinc compound (D) is preferably 95% by mass or more, preferably 98% by mass or more, and more preferably 99% by mass or more. In particular, the organozinc compound (D) of the grease composition of this embodiment is preferably composed solely of zinc dialkyldithiophosphate. 【0060】 Examples of solid lubricants include graphite, graphite fluoride, melamine cyanurate, polytetrafluoroethylene, molybdenum disulfide, antimony sulfide, boron nitride, and alkali (earth) metal borates. When the grease composition contains a solid lubricant, its content is, for example, 0.1 to 20% by mass of the total amount of the grease composition. The solid lubricant may be used alone or in a mixture of multiple solid lubricants. 【0061】Examples of anti-wear agents or extreme pressure agents include sulfur-containing compounds such as dihydrocarbyl polysulfide, sulfur esters, thiazole compounds, and thiadiazole compounds; and phosphorus-based extreme pressure agents such as phosphate esters, acidic phosphate esters, amine salts of acidic phosphate esters, and phosphite esters. When a grease composition contains an anti-wear agent or extreme pressure agent, its content is, for example, 0.1 to 10% by mass of the total amount of the grease composition. The anti-wear agent or extreme pressure agent may be used alone, or multiple anti-wear agents or extreme pressure agents may be used in mixture form. 【0062】 Examples of antioxidants include phenolic compounds such as 2,6-di-t-butylphenol and 2,6-di-t-butyl-p-cresol; and amine compounds such as diphenylamine, dialkyldiphenylamine, phenyl-α-naphthylamine, and p-alkylphenyl-α-naphthylamine. When the grease composition contains an antioxidant, its content is, for example, 0.5 to 10% by mass of the total amount of the grease composition. The antioxidant may be used alone or in combination of multiple antioxidants. 【0063】 Examples of rust inhibitors include amines, neutral or overbasic petroleum-based or synthetic oil-based metal sulfonates, carboxylate metal salts, esters, phosphoric acid, phosphates, and ester-based rust inhibitors. Examples of neutral or overbasic petroleum-based or synthetic oil-based metal sulfonates include alkaline earth metal salts of sulfonic acids, specifically dinonylnaphthalene sulfonate calcium salt. Examples of ester-based rust inhibitors include partial esters of polyhydric alcohols, esterified oxide waxes, esterified lanolin fatty acids, alkyl or alkenyl succinate esters. Examples of partial esters of polyhydric alcohols include sorbitan isostearate. When the grease composition contains a rust inhibitor, its content is, for example, 0.005 to 5% by mass of the total amount of the grease composition. The rust inhibitor may be used alone or in combination of multiple rust inhibitors. 【0064】As corrosion inhibitors, known corrosion inhibitors such as benzotriazole compounds, toltriazole compounds, thiadiazole compounds, and imidazole compounds can be used. When the grease composition contains a corrosion inhibitor, its content is, for example, 0.01 to 10% by mass of the total amount of the grease composition. The corrosion inhibitor may be used alone or in a mixture of multiple corrosion inhibitors. 【0065】 The grease composition of this embodiment contains a base oil (A), a thickener (B), and an organic molybdenum compound (C), wherein the base oil (A) includes a synthetic oil (A1), and the thickener (B) includes a lithium complex soap (B1). The grease composition of this embodiment has relatively high viscosity and good low-temperature fluidity, and by combining a synthetic oil (A1) with a specific thickener (lithium complex soap (B1)) and a specific additive (organic molybdenum compound (C)), it exhibits low torque under low-temperature conditions and high load-bearing capacity and wear resistance. 【0066】 [Applications] The grease composition of this embodiment is particularly preferable for use in wind power generation equipment because it exhibits low torque under low temperature conditions and high load-bearing capacity and wear resistance. Specifically, the grease composition of this embodiment is used in yaw control bearings, pitch bearing races, open gears, main bearings, etc., of wind power generation equipment. Furthermore, because the grease composition of this embodiment exhibits low torque under low temperature conditions and high load-bearing capacity and wear resistance, it is also preferable for use in the applications shown in Table 1 below. 【0067】 【0068】 The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples. 【0069】 <Preparation of Grease Compositions> The grease compositions of Examples 1 to 16 and Comparative Examples 1 to 3 were prepared according to the blending ratios shown in Tables 3 to 6. The values ​​in Tables 3 to 6 represent the percentage (mass) of each component relative to the total grease composition. 【0070】(1) Base oil (A) ・(A)-1: Poly-α-olefin with parameters shown in Table 2 ・(A)-2: Poly-α-olefin with parameters shown in Table 2 ・(A)-3: Poly-α-olefin with parameters shown in Table 2 ・(a)-1: Mineral oil with parameters shown in Table 2 【0071】 【0072】 (2) Thickeners (B) ・(B)-1: Li complex soap (Li complex soap obtained by the reaction of lithium hydroxide, 12-hydroxystearic acid, and azelaic acid) ・(b)-1: Urea thickener (Urea thickener obtained by the reaction of an amine compound and an isocyanate compound) 【0073】 (3) Organic molybdenum compounds (C) ・(C)-1: MoDTC (Molybdenum dithiocarbamate represented by formula (1) below, where the hydrocarbon groups in R1-4 are chain alkyl groups having 4 carbon atoms, MoDTC) ・(C)-2: MoDTP (A mixture of 45-55% molybdenum dithiophosphate and 45-55% mineral oil) 【0074】 【0075】 (4) Organozinc compounds (D) ・(D)-1: ZnDTP (zinc dialkyldithiophosphate represented by formula (2) below, where the hydrocarbon group in R19-22 is a chain alkyl group having 3 or 6 carbon atoms) ・(D)-2: ZnDTC (mineral oil solution of zinc diamyldithiocarbamate) 【0076】 【0077】 (5) Additives: (X)-1: Thiadiazole, (X)-2: Sorbitan isostearate, (X)-3: Calcium dinonylnaphthalene sulfonate 【0078】 【0079】 【0080】 【0081】 【0082】 [Evaluation of Low-Temperature Characteristics] - Measurement of Low-Temperature Torque The low-temperature torque (-20°C and -40°C) (mN・m) of each example grease composition was measured in accordance with JIS K2220:2013. Specifically, each example grease composition was filled into a ball bearing, and the inner ring was rotated at a low speed (1 rpm) at -20°C or -40°C, and the torque applied to the outer ring was measured. The starting torque was defined as the maximum torque at the start of rotation, and the rotational torque was defined as the average torque for the last 30 seconds when the inner ring was rotated for 10 minutes, as shown in Tables 7 to 10. A smaller torque indicates better low-temperature characteristics. "Unmeasurable" means that the grease hardened and the torque did not rotate. 【0083】 [Evaluation of Load-Bearing Capacity] - High-Speed ​​Ball Test Following ASTM D2596, the maximum load that does not cause seizure (Last Non-Seizure Load: LNSL) when rotated at 1800 rpm for 10 seconds under a specified load was determined. The results are shown in Tables 7 to 10. A higher maximum load value indicates better load-bearing capacity. 【0084】 [Evaluation of wear resistance] A wear test was conducted using a high-speed four-ball tester under the following conditions, and the diameter of the wear marks (mm) after the test was measured. The results obtained are shown in Tables 7 to 10. Test piece: Steel ball for rolling bearings SUJ2 (1 / 2 inch) Grade 20 Test conditions: Rotation speed 1200 rpm, load 392 N, temperature 25 °C, test time 1 hour A lower value for the diameter of the wear marks indicates better wear resistance. 【0085】 【0086】 【0087】 【0088】 【0089】 As shown in Tables 7 to 10, the grease compositions of the examples can achieve lower torque under low-temperature conditions without compromising load-bearing capacity or wear resistance, compared to the grease compositions of the comparative examples. 【0090】 While preferred embodiments of the present invention have been described above, the present invention is not limited to these embodiments. Additions, omissions, substitutions, and other modifications are possible without departing from the spirit of the invention. The present invention is not limited by the foregoing description, but only by the scope of the appended claims.

Claims

1. A grease composition comprising a base oil (A), a thickener (B), and an organic molybdenum compound (C), wherein the base oil (A) comprises a synthetic oil (A1), and the thickener (B) comprises a lithium complex soap (B1).

2. The grease composition according to claim 1, further comprising an organozinc compound (D).

3. The grease composition according to claim 1 or 2, wherein the content ratio of synthetic oil (A1) in the total amount of base oil (A) is 99% by mass or more.

4. The grease composition according to claim 1 or 2, used in a wind power generation device.

5. The grease composition according to claim 2 or 3, wherein the organozinc compound (D) comprises zinc dialkyldithiophosphate.

6. The grease composition according to claim 1 or 2, wherein the synthetic oil (A1) comprises a poly-α-olefin.

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