Grease composition

Abstract

To provide a grease composition exhibiting a high traction coefficient and superior shear stability.SOLUTION: A grease composition comprising a base oil having a traction coefficient of 0.07-0.14 at 40°C, and a thickener which is a calcium sulfonate complex.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present disclosure relates to a grease composition. [Background technology]

[0002] A traction drive device is a power transmission device that utilizes rolling and sliding friction. In a traction drive device, the oil film sandwiched between a cylindrical or conical rotor loses its fluidity and hardens under high pressure, creating resistance to shear and generating rolling and sliding friction.

[0003] Grease is considered to be an advantageous alternative to conventional liquid oil (lubricant) for use in such traction drive devices, from the viewpoints of power transmission and device size and weight reduction. A high traction coefficient, which represents the capacity of power transmission occurring when rollers or the like are pressed against each other, is also required.

[0004] For example, Patent Document 1 discloses a traction grease composition that has a large torque capacity and is suitable for use in traction drives under severe operating conditions, has a high traction coefficient over a wide temperature range, and also has excellent low-temperature properties.

[0005] Furthermore, Patent Document 2 discloses a grease composition for food machinery that is excellent in low torque and extreme pressure properties. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 2020-8067 [Patent Document 2] Japanese Patent Application Publication No. 2019-94504 Summary of the Invention [Problem to be solved by the invention]

[0007] However, conventional grease compositions are subject to shear stress during use in traction mechanisms, which can cause temporary or permanent viscosity loss. This reduced shear stability leads to a decrease in consistency, i.e., the grease composition becomes hard, making it more susceptible to torque loss in the traction mechanisms.

[0008] The present disclosure has been made in view of the above, and relates to providing a grease composition that has a high traction coefficient and excellent shear stability. [Means for solving the problem]

[0009] The present disclosure includes the following aspects. <1> A grease composition comprising a base oil having a traction coefficient of 0.07 to 0.14 at 40°C and a thickener which is a calcium sulfonate complex. <2> The base oil has a traction coefficient of 0.06 to 0.12 at 120°C. <1> The grease composition according to claim 1. <3> The traction coefficient of the grease composition is 0.13 to 0.16. <1> or <2> The grease composition according to claim 1. <4> The base oil is at least one selected from the group consisting of an α-alkylstyrene base oil, a polybutene base oil, and an ester base oil. <1> ~ <3> 1. The grease composition according to claim 1 . <5> The α-alkylstyrene base oil is (A) containing at least one selected from the group consisting of hydrogenated α-alkylstyrene dimers and trimers represented by any one of general formulas (1) to (3) in an amount of 25% by mass to 100% by mass based on the total mass of the α-alkylstyrene base oil; <4> The grease composition according to claim 1.

[0010] [ka]

[0011] (In general formulas (1) to (3), R1 to R19 each independently represent a hydrogen atom, an alkyl group having 1 to 3 carbon atoms, or a cyclohexyl group; Q1 to Q7 each independently represent an alkyl group having 1 to 3 carbon atoms or a cyclohexyl group, n1 to n7 each independently represent an integer of 0 to 5, and when n1 to n7 are integers of 2 to 5, each of the multiple groups Q1 to Q7 is independently selected. <6> The polybutene base oil has a traction coefficient of 0.07 to 0.14 at 40°C. <4> or <5> The grease composition according to claim 1. <7> The ester-based base oil has a traction coefficient of 0.07 to 0.14 at 40°C. <4> ~ <6> 1. The grease composition according to claim 1 . <8> The content of the thickener is 30% by mass to 80% by mass relative to the total mass of the grease composition. <1> ~ <7> 1. The grease composition according to claim 1 . [Effects of the Invention]

[0012] According to the present disclosure, a grease composition having a high traction coefficient and excellent shear stability is provided. DETAILED DESCRIPTION OF THE INVENTION

[0013] An embodiment of the present disclosure will be described in detail below. However, the present disclosure is not limited to the following embodiment. In the following disclosure, components (including element steps, etc.) are not essential unless otherwise specified. The same applies to numerical values ​​and their ranges, and do not limit the present disclosure.

[0014] In the present disclosure, numerical ranges indicated using "to" include the numerical values ​​before and after "to" as the lower and upper limits, respectively. In the numerical ranges described in stages in this disclosure, the upper or lower limit value described in one numerical range may be replaced with the upper or lower limit value of another numerical range described in stages. Furthermore, in the numerical ranges described in this disclosure, the upper or lower limit value of that numerical range may be replaced with a value shown in the examples. In the present disclosure, when a composition contains multiple substances corresponding to each component, the content of each component in the composition means the total content of the multiple substances present in the composition, unless otherwise specified. In the present disclosure, when multiple elements are listed using "or" or "or," unless otherwise expressly stated, it does not exclude the selection of a combination of the multiple elements unless a technical contradiction arises. In the present disclosure, even if an element is referred to in the singular, unless expressly stated otherwise, it does not exclude the presence of a plurality insofar as it does not create a technical contradiction. In the present disclosure, multiple exemplary aspects described separately may be combined with each other to form a new aspect, unless they contradict each other.

[0015] <Grease composition> The grease composition of the present disclosure contains a base oil having a traction coefficient of 0.07 to 0.14 at 40°C and a thickener that is a calcium sulfonate complex.

[0016] The grease composition of the present disclosure has a high traction coefficient and excellent shear stability. The action of the grease composition of the present disclosure is not clear, but is presumed to be as follows. The base oil contained in the grease composition of the present disclosure has a traction coefficient of 0.07 to 0.14 at 40° C. When the traction coefficient of the base oil is 0.07 or more, the traction coefficient of the grease composition containing that base oil also becomes high, and when that grease composition is used in a traction mechanism, a greater traction force can be obtained. On the other hand, it is preferable that the traction coefficient of the base oil at 40° C. is 0.14 or less from the viewpoint of achieving both torque transmission and lubricity.

[0017] Furthermore, the thickener contained in the grease composition of the present disclosure is a calcium sulfonate complex. Generally, overbased calcium sulfonate, the raw material for calcium sulfonate complexes, contains amorphous calcium carbonate, which is believed to transform into crystalline calcite during the manufacturing process of the grease composition. This calcite, like solid lubricants such as molybdenum disulfide and graphite, can impart wear resistance and load-bearing performance to the grease composition. That is, the calcium sulfonate complex exhibits excellent extreme pressure properties (the property of preventing seizure of sliding surfaces when metal members slide against each other via the grease composition).

[0018] Therefore, the grease composition of the present disclosure is likely to harden and turn into solid crystals when pressure is applied due to the combination of the chemical structures of the base oil and thickener contained in the grease composition, enabling high power transmission. Therefore, the present disclosure provides a grease composition with a high traction coefficient and excellent shear stability. It should be noted that the present disclosure is in no way limited to the above-mentioned presumed mechanism.

[0019] [traction coefficient] In the present disclosure, the traction coefficient of a base oil is measured by the following method. Specifically, a traction measuring device (product name: MTM Traction Measurement System, manufactured by PCS Instruments) is used to measure the traction coefficient under the following conditions. A 3 / 4-inch standard holed steel ball and a standard steel disk for 3 / 4-inch balls (material: conforming to the AISI 52100 standard) are used as test specimens. The measurement conditions are a rotation speed of 3900 mm / s, a load of 63 N, and a slip ratio of 5%.

[0020] In the present disclosure, the traction coefficient of a grease composition is measured by the following method. Specifically, an MPR tester manufactured by PCS Instruments is used to measure at a rotation speed of 1 mm / s, a sliding ratio of 1%, a load of 100 N, and room temperature (25° C.).

[0021] <Base oil> The base oil contained in the grease composition of the present disclosure has a traction coefficient at 40°C of 0.07 to 0.14. In order for the grease composition to have excellent power transmission properties, the traction coefficient of the base oil at 40°C is preferably 0.08 to 0.13, and more preferably 0.09 to 0.12.

[0022] From the viewpoint of the grease composition having excellent power transmission properties, the base oil contained in the grease composition of the present disclosure preferably has a traction coefficient at 80°C of 0.07 to 0.13, and more preferably 0.08 to 0.12.

[0023] From the viewpoint of the grease composition having excellent power transmission properties, the base oil contained in the grease composition of the present disclosure preferably has a traction coefficient at 100°C of 0.06 to 0.12, and more preferably 0.07 to 0.11.

[0024] From the viewpoint of the grease composition having excellent power transmission properties, the base oil contained in the grease composition of the present disclosure preferably has a traction coefficient at 120°C of 0.05 to 0.11, and more preferably 0.06 to 0.10.

[0025] The traction coefficient of the base oil can be adjusted by appropriately selecting the type of base oil used. Furthermore, when the grease composition contains two or more base oils, the traction coefficient of the base oil at 40°C is a weighted average of the traction coefficients of the base oils contained, and this value is 0.07 to 0.14. Similarly, for the traction coefficients at other temperatures, it is preferable that the weighted average of the traction coefficients of the base oils contained is each within the above-mentioned preferred range.

[0026] [Type of base oil] The base oil of the present disclosure is preferably at least one selected from the group consisting of an α-alkylstyrene-based base oil, a polybutene-based base oil, and an ester-based base oil. The base oil of the present disclosure may be any one of an α-alkylstyrene-based base oil, a polybutene-based base oil, or an ester-based base oil, or may be at least two selected from the group consisting of an α-alkylstyrene-based base oil, a polybutene-based base oil, and an ester-based base oil, or may include an α-alkylstyrene-based base oil, a polybutene-based base oil, and an ester-based base oil. The α-alkylstyrene base oils of the present disclosure are preferred because they have high traction coefficients and low torque loss.

[0027] (α-Alkylstyrene base oil) -(A)- The α-alkylstyrene base oil of the present disclosure preferably contains 25% by mass to 100% by mass of at least one selected from the group consisting of hydrogenated α-alkylstyrene dimers and trimers represented by any one of general formulas (1) to (3) (hereinafter also referred to as "component (A)"), based on the total mass of the α-alkylstyrene base oil.

[0028] [ka]

[0029] In general formulas (1) to (3), R1 to R19 each independently represent a hydrogen atom, an alkyl group having 1 to 3 carbon atoms, or a cyclohexyl group; Q1 to Q7 each independently represent an alkyl group having 1 to 3 carbon atoms or a cyclohexyl group, n1 to n7 each independently represent an integer of 0 to 5, and when n1 to n7 are an integer of 2 to 5, each of the multiple groups Q1 to Q7 is independently selected.

[0030] In the compounds represented by general formulas (1) to (3) that are component (A) of the present disclosure, examples of the alkyl group having 1 to 3 carbon atoms for R1 to R19 and Q1 to Q7 include a methyl group, an ethyl group, an n-propyl group, and an i-propyl group.

[0031] R1 to R19 are preferably a hydrogen atom, a methyl group, or an ethyl group, more preferably a hydrogen atom or a methyl group, and particularly preferably a group in which the carbon atom adjacent to the cyclohexyl group is alkylated. In addition, in consideration of the ease of availability of raw materials and costs, n1 to n7 are preferably integers of 0 to 2. When Q1 to Q7 are present, Q1 to Q7 are preferably methyl groups.

[0032] As the hydrogenated α-alkylstyrene dimer-trimer represented by the general formulas (1) to (3), the compounds represented by any of the general formulas (1) to (3) may be used alone, or the compounds represented by any of the general formulas (1) to (3) may be mixed in any combination and ratio and used.

[0033] Preferred examples of the general formulas (1) and (2) include 1,2-dicyclohexylpropane, 1,2-dicyclohexyl-2-methylpropane, 2,3-dicyclohexylbutane, 2,3-dicyclohexyl-2-methylbutane, 2,3-dicyclohexyl-2,3-dimethylbutane, 1,3-dicyclohexylbutane, 1,3-dicyclohexyl-3-methylbutane, 2,4-dicyclohexylpentane, 2,4-dicyclohexyl-2-methylpentane, 2,4-dicyclohexyl-2,4-dimethylpentane, 1,3-dicyclohexyl-2-methylbutane, 2,4-dicyclohexyl-2,3-dimethylbutane, and 2,4-dicyclohexyl-2,3-dimethylpentane.

[0034] Preferred examples of the general formula (3) include 2,4,6-tricyclohexyl-2,4-dimethylheptane, 2,4,6-tricyclohexyl-2-methylhexane, and 2,4,6-tricyclohexyl-2,4,6-trimethylheptane.

[0035] The method for producing the compounds represented by general formulas (1) to (3) is not particularly limited, and any appropriate method may be used. One example of a method for producing the compounds represented by general formulas (1) and (2) is a method of dimerizing styrene or an α-alkylstyrene such as α-methylstyrene, followed by hydrogenation. One example of a method for producing the compounds represented by general formula (3) is a method of trimerizing styrene or an α-alkylstyrene such as α-methylstyrene, followed by hydrogenation.

[0036] The above-mentioned dimerization, trimerization, and hydrogenation methods are not particularly limited and can be carried out appropriately using known methods. For example, the dimerization of α-methylstyrene can be carried out in the presence of a catalyst, generally an acidic catalyst, with the addition of a solvent, a reaction modifier, and the like, as necessary. Specific examples of acidic catalysts include white clays such as activated clay and acid clay; mineral acids such as sulfuric acid, hydrochloric acid, and hydrofluoric acid; organic acids such as p-toluenesulfonic acid and triflic acid; Lewis acids such as aluminum chloride, ferric chloride, stannic chloride, boron trifluoride, boron tribromide, aluminum bromide, gallium chloride, and gallium bromide; and solid acids such as zeolites, silica, alumina, silica-alumina, cation exchange resins, and heteropolyacids. The amount of this acidic catalyst used is preferably 0.1% to 100% by mass, more preferably 1% to 20% by mass, relative to the amount of α-methylstyrene, but is not particularly limited.

[0037] As the solvent, saturated hydrocarbons may be used, and specific examples include n-pentane, n-hexane, heptane, octane, nonane, decane, cyclopentane, cyclohexane, methylcyclohexane, decalin, and the like.

[0038] In addition, it is preferable to use a reaction modifier for the purpose of increasing the selectivity of the dimer produced in the reaction. Specific reaction modifiers include carboxylic acids such as acetic acid, acid anhydrides such as acetic anhydride and phthalic anhydride, cyclic esters such as γ-butyrolactone and valerolactone, glycols such as ethylene glycol, mononitro compounds such as nitromethane and nitrobenzene, esters such as ethyl acetate, ketones such as mesityl oxide, aldehydes such as formalin and acetaldehyde, cellosolves, and polyalkylene glycol alkyl ethers such as diethylene glycol monoethyl ether.

[0039] The temperature for the dimerization reaction is preferably from -30°C to 180°C, more preferably from 0°C to 160°C.

[0040] The hydrogenation of the α-methylstyrene dimer obtained as described above can also be carried out generally in the presence of a catalyst, using a solvent as needed. The catalyst may be what is known as a hydrogenation catalyst, containing one or more metals such as nickel, ruthenium, palladium, platinum, rhodium, iridium, copper, chromium, molybdenum, cobalt, and tungsten. The amount of the catalyst used is not particularly limited, but is preferably 0.1% by mass to 100% by mass, more preferably 1% by mass to 20% by mass, based on the polymer.

[0041] Examples of the solvent include liquid saturated hydrocarbons such as n-pentane, n-hexane, heptane, octane, nonane, decane, and dodecane, as well as cyclopentane, cyclohexane, and methylcyclohexane.

[0042] This hydrogenation reaction is carried out, similarly to a conventional hydrogenation reaction, at a temperature of preferably 20°C to 300°C, more preferably 40°C to 200°C, and preferably at atmospheric pressure to 200 kg / cm 2 (G), more preferably 20 kg / cm 2 (G) ~ 100kg / cm 2 (G) can be carried out under hydrogen pressure.

[0043] The hydrogenation of a dimer of α-methylstyrene has been described above, but the hydrogenation of dimers and trimers of styrene and α-alkylstyrenes substituted with an alkyl group or cycloalkyl group other than a methyl group can also be carried out in a similar manner.

[0044] The hydrogenated α-alkylstyrene dimer-trimer of the present disclosure preferably has a high proportion of linear units. To produce such α-alkylstyrene dimer-trimer with a high proportion of linear units, it is preferable to employ the following method already proposed by the present inventors. That is, α-alkylstyrene is subjected to the following reaction according to the description in JP-A-7-242575: i) dimerization or trimerization is carried out in a solvent-free, solid-liquid heterogeneous system at 80°C to 140°C using a heteropolyacid in an amount of 1% by mass to 100% by mass based on the raw material α-alkylstyrene as a catalyst, or ii) Dimerization or trimerization is carried out in a solid-liquid heterogeneous system at 30°C to 140°C in the presence of a solvent that does not dissolve the catalyst, using a heteropolyacid in an amount of 1% by mass to 200% by mass based on the raw material α-alkylstyrene as a catalyst, or Or, according to the description of JP-A-7-242573, iii) A method in which a heteropoly acid is used as a catalyst to carry out dimerization or trimerization in the presence of water. The reaction products obtained by these methods and hydrogenating them by the above-mentioned known methods have an extremely high proportion of linear compounds, which has the advantage that the difficult step of separating cyclic compounds can be omitted.

[0045] -Traction coefficient- The α-alkylstyrene base oil of the present disclosure preferably has a traction coefficient of 0.07 to 0.14 at 40° C. The α-alkylstyrene base oil more preferably has a traction coefficient of 0.08 to 0.13, and even more preferably 0.09 to 0.12 at 40° C.

[0046] -Content- In the base oil of the present disclosure, the content of the α-alkylstyrene base oil may be 30% by mass to 100% by mass, 50% by mass to 100% by mass, or 80% by mass to 100% by mass. The α-alkylstyrene base oils may be used alone or in combination of two or more.

[0047] (Polybutene base oil) The polybutene base oil may be a polybutene base oil commonly used in the field of lubricating oils. Specific examples of the polybutene base oil include polybutene obtained by polymerizing butene-1 monomer, and polybutene obtained by low-temperature selective polymerization of isobutene and normal butene from the BB fraction produced by naphtha cracking. Among these, a base oil having a branched carbon chain structure and a large steric hindrance structure is preferred.

[0048] The polybutene base oil of the present disclosure preferably has a traction coefficient of 0.07 to 0.14 at 40° C. The polybutene base oil more preferably has a traction coefficient of 0.08 to 0.13, and even more preferably 0.09 to 0.12 at 40° C.

[0049] The content of polybutene base oil in the base oil of the present disclosure may be 30% by mass to 100% by mass, 50% by mass to 100% by mass, or 80% by mass to 100% by mass. The polybutene base oil may be used alone or in combination of two or more.

[0050] (ester base oil) The ester-based base oil may be any ester-based base oil commonly used in the field of lubricating oils. Specific examples of the ester-based base oil include monoesters, diesters, and polyol esters. Among these, base oils with a branched carbon chain structure and a large steric hindrance are preferred.

[0051] The ester base oil of the present disclosure preferably has a traction coefficient of 0.07 to 0.14 at 40° C. The ester base oil more preferably has a traction coefficient of 0.08 to 0.13 at 40° C., and even more preferably has a traction coefficient of 0.09 to 0.12.

[0052] The content of the ester-based base oil in the base oil of the present disclosure may be 30% by mass to 100% by mass, 50% by mass to 100% by mass, or 80% by mass to 100% by mass. The ester-based base oils may be used alone or in combination of two or more.

[0053] <Other base oils> The grease composition of the present disclosure may contain base oils other than the above-mentioned α-alkylstyrene-based base oil, polybutene-based base oil, and ester-based base oil, such as fatty acid esters, mineral oils, polyalphaolefins, alkylnaphthalenes, and perfluoroalkyl polyethers. Examples of fatty acid esters include fatty acid esters extracted from animal and vegetable oils such as beef tallow, lard, fish oil, rapeseed oil, soybean oil, olive oil, coconut oil, salad oil, menhaden oil, etc. There are no particular limitations on the fatty acid ester as long as it is an ester of an alcohol and a fatty acid. Examples of mineral oils include those refined by an appropriate combination of refining methods such as vacuum distillation, solvent refining, hydrorefining, solvent stripping, solvent deasphalting, sulfuric acid washing-clay treatment, and the like. Examples of polyalphaolefins include linear α-olefins obtained by low polymerization of ethylene, which are further polymerized or whose terminal double bonds are hydrogenated.

[0054] <Base oil content> From the viewpoint of lubricity, the content of the base oil is preferably 20% by mass to 80% by mass, and more preferably 20% by mass to 60% by mass, relative to the total mass of the grease composition. From the viewpoint of low torque, the content of the base oil may be 20% by mass to 40% by mass relative to the total mass of the grease composition. From the viewpoint of achieving both power transmission efficiency and wear resistance, the content of the base oil is preferably 45% by mass to 60% by mass relative to the total mass of the grease composition.

[0055] <Thickener> The thickener contained in the grease composition of the present disclosure is a calcium sulfonate complex.

[0056] Examples of calcium sulfonate complexes include complexes (complex soaps) that combine calcium sulfonate with a calcium salt other than calcium sulfonate.

[0057] The calcium sulfonate is not particularly limited, and examples thereof include calcium salts of alkylbenzenesulfonic acids such as dodecylbenzenesulfonic acid and octadecylbenzenesulfonic acid, and calcium salts of petroleum sulfonic acids.

[0058] The calcium salts other than calcium sulfonate are not particularly limited, and examples thereof include calcium carbonate, calcium borate, calcium salts of higher fatty acids such as calcium dibehenate, calcium distearate, and calcium dihydroxystearate, and calcium salts of lower fatty acids such as calcium acetate.

[0059] The calcium salts may be used alone or in combination of two or more.

[0060] The content of the thickener is preferably 30% by mass to 60% by mass, more preferably 35% by mass to 55% by mass, and even more preferably 40% by mass to 50% by mass, relative to the total mass of the grease composition. When the content of the thickener is within the above range, it becomes possible to adjust the worked penetration to within the range of 140 to 420. The calcium sulfonate complex may be used alone or in combination of two or more.

[0061] The ratio of the thickener to the base oil is preferably 0.25 to 4.0 by mass, and more preferably 0.42 to 3.0 by mass. When the ratio of the thickener to the base oil is within the above range, the extreme pressure properties and low torque tend to be excellent.

[0062] <Other additives> In addition to the base oil and thickener, the grease composition of the present disclosure can use additives (hereinafter also referred to as "other additives") registered in the HX-1 grade specified by the NSF (National Sanitation Foundation) or used in raw materials certified by NSF as other components used in ordinary grease compositions, and can contain other additives as appropriate within the content range specified by NSF. Examples of other additives include antioxidants, extreme pressure agents, and rust inhibitors.

[0063] The antioxidant may include a phenol-based antioxidant, an amine-based antioxidant, a phosphorus-based antioxidant, or the like. The extreme pressure agent includes, for example, tricresyl phosphate. Examples of the rust inhibitor include alkenyl succinic acid and its derivatives, esters such as oleyl sarcosine, wax oxides, neutral barium sulfonate, sorbitan triol, and paraffin.

[0064] There are no particular restrictions on the content of the above additives as long as the effects of the present disclosure are obtained within the range, and the total content of the additives is usually preferably 0.1 mass % to 5 mass %, and more preferably 0.3 mass % to 4 mass %, relative to the total mass of the grease composition.

[0065] <Traction coefficient of grease composition> From the viewpoint of the grease composition having excellent power transmission properties, the grease composition of the present disclosure preferably has a traction coefficient at 25°C of 0.13 to 0.16.

[0066] The traction coefficient of the grease composition can be adjusted by the type or combination of base oils, the type or combination of thickeners, or the type or combination of additives.

[0067] <Worked penetration of grease composition> The grease composition of the present disclosure preferably has a worked penetration of 140 to 420, more preferably 200 to 400, even more preferably 250 to 350, and particularly preferably 290 to 320. A small worked penetration value indicates that the grease is hard, and a large value indicates that the grease is soft.

[0068] In the present disclosure, the worked penetration can be determined based on the JIS K 2220 (2023) penetration test method (ISO 2137:2020).

[0069] <Method for producing grease composition> The method for producing the grease composition of the present disclosure is not particularly limited. The grease composition of the present disclosure can be produced, for example, by the following method. At least the base oil, thickener, and other additives as required are placed in a stirring vessel, and the mixture is stirred and mixed to obtain a grease composition. For stirring and mixing, a known stirrer or the like can be used.

[0070] In the method for producing a grease composition, when other additives are added, the additives need only be stirred for a period of time sufficient to dissolve or disperse the additives, and the additives may be added to the stirring vessel together with the specific base oil and specific thickener, or may be added thereafter.

[0071] <Applications of grease composition> The grease composition of the present disclosure can be suitably used in food processing machinery, traction drive mechanisms (for example, planetary roller traction drive mechanisms used as transmissions in machine tools and various other devices and equipment), and automobiles (for example, devices with large torque capacities and operating conditions that are severe, such as automobile continuously variable transmissions). [Example]

[0072] Hereinafter, the present disclosure will be described more specifically with reference to examples, but the present disclosure is not limited to the following examples as long as it does not deviate from the gist of the disclosure.

[0073] <Preparation of grease composition> The base oils and thickeners used in the grease compositions of Examples 1 to 3 and Comparative Examples 1 to 4 were prepared as follows.

[0074] [Base oil] (α-Alkylstyrene base oil) -Step 1: Preparation of component (A) of the present disclosure 1- 300 g of α-methylstyrene and 33 g of 12-tungstic acid (Kanto Chemical Co., Ltd.) as a catalyst were placed in a glass reaction vessel, heated at 130°C for 5 minutes with stirring to cause a reaction, then cooled in a water bath at 20°C, and the solid catalyst was filtered off. To the filtrate, 30 g of palladium carbon (containing 5% by mass of palladium) as a catalyst and 3 liters (hereinafter, liter is abbreviated as "L") of cyclohexane were added, and the mixture was stirred under a hydrogen pressure of 40 kg / cm. 2 (G) was hydrogenated at 120°C for 3 hours and then at 180°C for 5 hours to obtain 302 g of hydrogenated α-methylstyrene dimer (component (A1)) containing linear units at a ratio of 96 mass%. The kinematic viscosity of this hydrogenated α-methylstyrene dimer at 40°C was 15.7 mm 2 / s.

[0075] -Step 2: Preparation of component (A) of the present disclosure 2- 1000 g of α-methylstyrene dimer, 5000 g of cyclohexane, and 10 g of a hydrogenation catalyst (5% by mass Pd supported; manufactured by Wako Pure Chemical Industries, Ltd.) containing Pd on an activated carbon carrier (hereinafter referred to as "Pd / C hydrogenation catalyst") were placed in a 10 L autoclave equipped with a stirrer and sealed. The autoclave was maintained at 0.1 MPa with H2, and the contents were stirred at room temperature (25°C) for 18 hours. The autoclave was then opened, the Pd / C hydrogenation catalyst was filtered off, and the cyclohexane was distilled off to obtain 1008 g of 2-methyl-2,4-diphenylpentane.

[0076] Next, 1008 g of this 2-methyl-2,4-diphenylpentane and 100.8 g of AlCl3 were placed in a 10 L three-necked reactor equipped with a calcium chloride tube, a condenser, and a dropping funnel. While stirring, 2016 g of diisobutylene was added dropwise from the dropping funnel over 30 minutes, and the mixture was then heated to 60°C and stirred for 3 hours. While cooling the reactor in an ice bath, 3000 g of distilled water was added dropwise over 30 minutes to decompose the AlCl3. The mixture was then allowed to stand, the organic layer was separated, and dehydrated with anhydrous Na2SO4 to obtain 3000 g of a mixture containing alkylated 2-methyl-2,4-diphenylpentane and diisobutylene dimers and multimers.

[0077] The entire reaction mixture, 30,000 g of cyclohexane, and 300 g of N-113 nickel-based hydrogenation catalyst (manufactured by Nikki Chemical Co., Ltd.) were placed in an autoclave, sealed, and subjected to nuclear hydrogenation at a hydrogen pressure of 6.1 MPa and 200°C for 2 hours. After cooling, the catalyst was filtered off and the cyclohexane was distilled off. The reaction mixture was distilled under reduced pressure at 2 mmHg and 165-180°C to obtain 1,600 g of a fraction (component (A2)).

[0078] -Preparation of α-Alkylstyrene Base Oil- As the component (A), 50% by mass of the component (A1) and 50% by mass of the component (A2) were mixed to prepare an α-alkylstyrene base oil.

[0079] (Polybutene base oil) As a polybutene-based base oil, NOF Polybutene 06N (trade name, manufactured by NOF Corporation) was prepared.

[0080] (ester base oil) As an ester-based base oil, a product name: SR800 (manufactured by New Japan Chemical Co., Ltd.) was prepared.

[0081] (mineral oil) As the mineral oil, a product name: YUBASE6 (manufactured by SK Lubricants, viscosity grade: ISO VG32) was prepared.

[0082] [Thickener] (Calcium sulfonate complex) Overbased calcium sulfonate, sulfonic acid, propylene glycol, acetic acid, and various base oils were placed in a heat-resistant container and heated to 80°C with stirring. Water was then added, and the mixture was stirred while maintaining the temperature at around 90°C. The mixture was further heated to a maximum temperature of 150°C and cooled to room temperature to obtain a mixture of calcium sulfonate complex and base oil.

[0083] (Urea compounds) A heat-resistant container was charged with base oil and diphenylmethane-4,4'-diisocyanate, and the mixture was heated to approximately 90°C with stirring. Next, a solution of the base oil and cyclohexylamine was added, and the mixture was further reacted at approximately 90°C for approximately 60 minutes. The resulting reaction liquid was heated to 140°C with stirring, and then cooled to 60°C to obtain a mixture of the urea compound and base oil.

[0084] (lithium soap) Various base oils and lithium-12-hydroxystearate (product name: "S7000H", manufactured by Sakai Chemical Industry Co., Ltd.) were placed in a heat-resistant container and heated to dissolve at approximately 200°C, and various base oils were further added and cooled. After that, a milling process was performed to optimize the crystallization of lithium-12-hydroxystearate, and a mixture of lithium soap and base oil was obtained.

[0085] [mixture] The base oil and thickener were mixed together in the amounts and components shown in Table 1 below, and milled to obtain the grease compositions of Examples 1 to 3 and Comparative Examples 1 to 4.

[0086] <Traction coefficient> The traction coefficient of the base oil was measured by the following method. Specifically, the traction coefficient was measured under the following conditions using a traction measuring device (product name: MTM Traction Measurement System, manufactured by PCS Instruments). For the measurement, a combination of a 3 / 4-inch standard holed steel ball and a standard steel disk for 3 / 4-inch balls (material: conforming to the AISI 52100 standard) was used as the test specimen. The measurement conditions were a rotation speed of 3900 mm / s, a load of 63 N, and a slip ratio of 5%.

[0087] The traction coefficient of the grease composition was measured by the following method. Measurements were carried out at room temperature (25°C) using an MPR tester manufactured by PCS Instruments, with a rotation speed of 1 mm / s, a sliding ratio of 1%, and a load of 100 N. The results are shown in Table 1. A grease composition having a traction coefficient of 0.13 or more can be said to be excellent in power transmission.

[0088] <Shear stability> The shear stability was evaluated by measuring the worked penetration, which was determined based on the JIS K 2220 (2023) penetration test method. Specifically, the grease composition was subjected to roller processing four times using a three-roller mill at a roller processing rate of 60 g / min. The more times the roller processing was performed, the lower the consistency became, i.e., the harder the grease composition became. The amount of change between the consistency before and after the treatment was calculated. A smaller amount of change indicates a smaller change in consistency when pressure is applied to the grease composition, i.e., indicates that the grease composition has excellent shear stability. The results are shown in Table 1. In the table, "-" indicates that the measurement was not performed.

[0089] [Table 1]

[0090] As shown above, the grease compositions of Examples 1 to 3 had higher traction coefficients than the grease composition of Comparative Example, i.e., were grease compositions with better power transmission. Furthermore, the grease compositions of Examples 1 to 3 showed a small change in consistency before and after roller treatment, i.e., were excellent in shear stability.

Claims

1. A grease composition comprising a base oil having a traction coefficient of 0.07 to 0.14 at 40°C and a thickener which is a calcium sulfonate complex.

2. 2. The grease composition according to claim 1, wherein the base oil has a traction coefficient at 120°C of 0.06 to 0.

12.

3. 3. The grease composition according to claim 1, wherein the grease composition has a traction coefficient of 0.13 to 0.

16.

4. 3. The grease composition according to claim 1, wherein the base oil is at least one selected from the group consisting of an α-alkylstyrene base oil, a polybutene base oil, and an ester base oil.

5. The α-alkylstyrene base oil is 5. The grease composition according to claim 4, comprising (A) at least one selected from the group consisting of hydrogenated α-alkylstyrene dimers, α-alkylstyrene trimers, and α-alkylstyrene trimers represented by any one of general formulas (1) to (3) in an amount of 25% by mass to 100% by mass based on the total mass of the α-alkylstyrene base oil. 【Chemical 1】 (In general formulas (1) to (3), R1 to R19 each independently represent a hydrogen atom, an alkyl group having 1 to 3 carbon atoms, or a cyclohexyl group; Q1 to Q7 each independently represent an alkyl group having 1 to 3 carbon atoms or a cyclohexyl group; n1 to n7 each independently represent an integer of 0 to 5, and when n1 to n7 are integers of 2 to 5, each of the multiple Q1 to Q7 groups is independently selected.

6. 5. The grease composition according to claim 4, wherein the polybutene base oil has a traction coefficient at 40°C of 0.07 to 0.

14.

7. 5. The grease composition according to claim 4, wherein the ester-based base oil has a traction coefficient at 40°C of 0.07 to 0.

14.

8. 3. The grease composition according to claim 1, wherein the content of the thickener is 30% by mass to 80% by mass relative to the total mass of the grease composition.

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