Grease composition

Abstract

Provided is a grease composition which contains a base oil (A), a urea-based thickening agent (B), a phosphoric acid ester amine salt (C), a sulfur-based extreme pressure agent (D), zinc dithiophosphate (E), melamine cyanurate (F) and an organic molybdenum compound (G). The base oil (A) is a mixed base oil containing: a high viscosity poly-α-olefin (PAO) (A1) having a kinematic viscosity at 40°C of 288 mm2 to 506 mm2 / s; a low viscosity poly-α-olefin (PAO) (A2) having a kinematic viscosity at 40°C of 61.2 to 74.8 mm2 / s; and an ester-based synthetic oil. Particles containing the urea-based thickening agent (B) in the grease composition satisfy requirement (I). The grease composition exhibits excellent extreme pressure properties, load bearing properties, seizure resistance and abrasion resistance in a broad range of temperature environments, and is excellent in terms of suppression of leakage caused by a reduction in viscosity of the base oil.

Description

Grease composition

[0001] The present invention relates to a grease composition.

[0002] Grease compositions are easier to seal than lubricating oils and allow for the miniaturization and weight reduction of machines to which they are applied. Therefore, they have long been widely used to lubricate various sliding parts in automobiles, electrical equipment, industrial machinery, and other machinery. In recent years, the use of strain wave gearing as a reducer has expanded from the viewpoints of high precision, lightweight, and compactness. Various grease compositions to be applied to the sliding surfaces of strain wave gearing have also been proposed.

[0003] For example, Patent Documents 1 and 2 disclose grease compositions that are applied to the sliding surfaces of strain wave gear devices.

[0004] JP-A-8-157846 JP-A-3-179094

[0005] Harmonic drive gears, especially reducers, are used under extremely harsh conditions. Therefore, grease compositions applied to the sliding surfaces of harmonic drive gears are required to have extreme pressure properties, load resistance, seizure resistance, and wear resistance. Furthermore, taking into account temperature rises inside harmonic drive gears, extreme pressure properties, load resistance, seizure resistance, and wear resistance are also required under a wide range of temperature environments. However, the grease compositions disclosed in Patent Documents 1 and 2 do not fully address extreme pressure properties, load resistance, seizure resistance, and wear resistance under a wide range of temperature environments. Furthermore, from the perspective of transmission efficiency of harmonic drive gears, the base oil contained in the grease composition is required to have a low viscosity. However, if the grease composition is too soft, leakage from the harmonic drive gears may occur. Furthermore, Patent Documents 1 and 2 do not address the issue of reducing the viscosity of the base oil to prevent leakage of the grease composition.

[0006] Therefore, an object of the present invention is to provide a grease composition that is excellent in extreme pressure properties, load resistance, seizure resistance, and wear resistance under a wide range of temperature environments, and that is also excellent in suppressing leakage of the grease composition due to the low viscosity of the base oil.

[0007] The present inventors have discovered that the above-mentioned problems can be solved by a grease composition containing a base oil and a urea-based thickener, which contains a phosphate ester amine salt, a sulfur-based extreme pressure agent, zinc dithiophosphate, melamine cyanurate, and molybdenum dithiocarbamate, wherein the base oil is a specific base oil and the particles containing the urea-based thickener satisfy specific requirements, and have completed the present invention.

[0008] That is, the present invention provides the following [1] and [2]: [1] A grease composition containing a base oil (A), a urea-based thickener (B), a phosphoric acid ester amine salt (C), a sulfur-based extreme pressure agent (D), a zinc dithiophosphate (E), melamine cyanurate (F), and an organic molybdenum compound (G), wherein the base oil (A) is a grease composition having a kinematic viscosity at 40°C of 288 mm ２ / s ~ 506 mm ２ High viscosity poly-α-olefin (PAO) (A1) having a kinematic viscosity of 61.2 to 74.8 mm / s at 40°C ２ A grease composition comprising a mixed base oil containing a low-viscosity poly-α-olefin (PAO) (A2) having a kinematic viscosity of 2.0 μm / s and an ester-based synthetic oil, and particles containing the urea-based thickener (B) in the grease composition satisfy the following requirement (I): Requirement (I): The particles have an area-based arithmetic mean particle diameter of 2.0 μm or less when measured by a laser diffraction / scattering method. [2] A method for producing a grease composition comprising: (1) a step of synthesizing the urea-based thickener (B) in a base oil (A); and (2) a step of blending a phosphate ester amine salt (C), a sulfur-based extreme pressure agent (D), zinc dithiophosphate (E), melamine cyanurate (F), and an organic molybdenum compound (G) with the product synthesized in step (1), wherein the base oil (A) has a kinematic viscosity at 40°C of 288 mm ２ / s ~ 506 mm ２ High viscosity poly-α-olefin (PAO) (A1) having a kinematic viscosity of 61.2 to 74.8 mm / s at 40°C ２and a mixed base oil containing a low-viscosity poly-α-olefin (PAO) (A2) having a viscosity of 1 / s and an ester-based synthetic oil, and particles containing the urea-based thickener (B) in the grease composition satisfy the following requirement (I): Requirement (I): The particles have an area-based arithmetic mean particle diameter of 2.0 μm or less when measured by a laser diffraction / scattering method.

[0009] According to the present invention, it is possible to provide a grease composition that is excellent in extreme pressure properties, load resistance, seizure resistance, and wear resistance over a wide range of temperature environments, and that is also excellent in suppressing leakage of the grease composition due to the low viscosity of the base oil.

[0010] 1 is a schematic cross-sectional view of a grease production apparatus used in one embodiment of the present invention, taken along a direction perpendicular to the rotation axis of a first concave-convex portion on the container body side of the grease production apparatus of FIG.

[0011] The upper and lower limits of the numerical ranges described herein can be combined in any way. For example, when "A to B" and "C to D" are described as numerical ranges, the numerical ranges "A to D" and "C to B" are also included in the scope of the present invention. Furthermore, the numerical range "lower limit to upper limit" described herein means that the range is equal to or greater than the lower limit and equal to or less than the upper limit, unless otherwise specified. Furthermore, in this specification, the numerical values ​​in the examples are numerical values ​​that can be used as upper or lower limits. Note that in this specification, for example, "(meth)acrylate" is used as a term indicating both "acrylate" and "methacrylate," and the same applies to other similar terms and similar notations.

[0012] [Grease Composition] The grease composition of the present invention is a grease composition containing a base oil (A), a urea-based thickener (B), a phosphate ester amine salt (C), a sulfur-based extreme pressure agent (D), a zinc dithiophosphate (E), melamine cyanurate (F), and an organic molybdenum compound (G), wherein the base oil (A) has a kinematic viscosity at 40°C of 288 mm ２ / s ~ 506 mm ２ High viscosity poly-α-olefin (PAO) (A1) having a kinematic viscosity of 61.2 to 74.8 mm / s at 40°C ２and a mixed base oil containing a low-viscosity poly-α-olefin (PAO) (A2) having a viscosity of 1 / s and an ester-based synthetic oil, wherein particles containing the urea-based thickener (B) in the grease composition satisfy the following requirement (I): Requirement (I): The particles have an area-based arithmetic mean particle diameter of 2.0 μm or less when measured by a laser diffraction / scattering method.

[0013] In order to solve the above problems, the present inventors have conducted extensive research and have found that a urea-based grease composition contains a phosphate ester amine salt (C), a sulfur-based extreme pressure agent (D), a zinc dithiophosphate (E), melamine cyanurate (F), and an organic molybdenum compound (G), and the base oil (A) has a kinematic viscosity at 40°C of 288 mm ２ / s ~ 506 mm ２ High viscosity poly-α-olefin (PAO) (A1) having a kinematic viscosity of 61.2 to 74.8 mm / s at 40°C ２ The present inventors have found that when a mixed base oil containing a low-viscosity poly-α-olefin (PAO) (A2) of 1 / s and an ester-based synthetic oil is used, and when particles containing a urea-based thickener satisfy certain requirements, it is possible to obtain a grease composition that is excellent in extreme pressure properties, load resistance, seizure resistance, and wear resistance over a wide range of temperature environments, and that is also capable of suppressing leakage of the grease composition by reducing the viscosity of the base oil.

[0014] Specifically, the present inventors have discovered the following. Generally, formulations centered on sulfur-based extreme-pressure agents and organic molybdenum compounds are commonly used to improve extreme-pressure properties and load-carrying capacity. These additives react with sliding surfaces to form a film when the lubricated area is at a high temperature of 80°C or higher, thereby providing high extreme-pressure properties and load-carrying capacity. On the other hand, when the lubricated area is at a low temperature of less than 80°C, the effects of these additives are not fully realized. The present inventors have discovered that when a phosphate ester amine salt (C), zinc dithiophosphate (E), and melamine cyanurate (F) are used in combination as additives in a grease composition, high extreme-pressure properties and load-carrying capacity can be achieved even in low-temperature environments below 80°C. Furthermore, the present inventors have discovered that when these additives are used in combination with a sulfur-based extreme-pressure agent (D) or an organic molybdenum compound (G), the performance of each additive is not impaired, and sufficient extreme-pressure properties and load-carrying capacity are achieved both at temperatures above 80°C and below 80°C, i.e., across a wide range of temperature environments, regardless of the temperature of the lubricated area. In the present invention, the term "wide temperature environment" refers to a temperature environment of 25°C to 100°C.

[0015] If a grease composition contains a high-viscosity base oil that has high oil film retention, excellent lubricity, and is less likely to leak, the penetration and low-temperature characteristics will be insufficient, resulting in a decrease in the transmission efficiency of a wave gear device, etc. On the other hand, if a grease composition contains a low-viscosity base oil that has excellent penetration and low-temperature characteristics, there is a concern that the grease composition will seep out and leak from a wave gear device, etc. Therefore, the present inventors have investigated whether a base oil (A) having a kinematic viscosity at 40°C of 288 mm ２ / s ~ 506 mm ２ High viscosity poly-α-olefin (PAO) (A1) having a kinematic viscosity of 61.2 to 74.8 mm / s at 40°C ２ The inventors have discovered that when the grease composition is a mixed base oil containing a low-viscosity poly-α-olefin (PAO) (A2) having a viscosity of 1 / s and an ester-based synthetic oil, and particles containing the urea-based thickener (B) in the grease composition satisfy specific requirement (I), leakage of the grease composition due to the low viscosity of the base oil can be suppressed without impairing the transmission efficiency of a strain wave gear device or the like. Based on this discovery, the inventors have conducted further studies and have completed the present invention.

[0016] In the following description, the “base oil (A),” “urea-based thickener (B),” “phosphate ester amine salt (C),” “sulfur-based extreme pressure agent (D),” “zinc dithiophosphate (E),” “melamine cyanurate (F),” and “organomolybdenum compound (G)” will also be referred to as “component (A),” “component (B),” “component (C),” “component (D),” “component (E),” “component (F),” and “component (G),” respectively.

[0017] In the grease composition of this embodiment, the total content of components (A), (B), (C), (D), (E), (F), and (G) is preferably 60 mass% or more, more preferably 70 mass% or more, even more preferably 80 mass% or more, and even more preferably 90 mass% or more, based on the total amount (100 mass%) of the grease composition. It is also typically 100 mass% or less, preferably less than 100 mass%, more preferably 99 mass% or less, and even more preferably 98 mass% or less. The grease composition of one aspect of the present invention may contain components other than components (A), (B), (C), (D), (E), (F), and (G) within a range that does not impair the effects of the present invention.

[0018] <Requirement (I)> In one embodiment of the grease composition of the present invention, particles containing the urea-based thickener (B) in the grease composition satisfy the following requirement (I): Requirement (I): The particles have an area-based arithmetic mean particle diameter of 2.0 μm or less when measured by a laser diffraction / scattering method. By satisfying the above requirement (I), the grease composition can simultaneously achieve extreme pressure properties, load resistance, seizure resistance, and wear resistance, as well as suppression of leakage of the grease composition due to the low viscosity of the base oil.

[0019] The above requirement (I) can also be considered a parameter indicating the state of aggregation of the urea-based thickener (B) in the grease composition. Here, the "particles containing the urea-based thickener (B)" to be measured by the laser diffraction / scattering method refer to particles formed by aggregation of the urea-based thickener (B) contained in the grease composition. Although the grease composition contains additives other than the urea-based thickener (B), the arithmetic mean particle size specified by the above requirement (I) can be obtained by measuring a grease composition prepared under the same conditions but without the additives by the laser diffraction / scattering method. However, if the additive is liquid at room temperature (25°C) or if the additive is soluble in the base oil (A), the grease composition containing the additive may also be used as the measurement target.

[0020] Urea-based thickeners (B) are usually obtained by reacting an isocyanate compound with a monoamine. However, because the reaction rate is very fast, the urea-based thickener (B) tends to aggregate, resulting in the formation of excessively large particles (micelle particles, so-called "lumps"). As a result of extensive research, the present inventors have found that if the arithmetic mean particle size specified in the above requirement (I) exceeds 2.0 μm, it is impossible to ensure both extreme-pressure properties, load-bearing properties, seizure resistance, and wear resistance, as well as the suppression of leakage of the grease composition due to the low viscosity of the base oil, over a wide temperature range. On the other hand, by reducing the arithmetic mean particle size specified in the above requirement (I) to 2.0 μm or less, it is possible to obtain a grease composition that can simultaneously achieve extreme-pressure properties, load-bearing properties, seizure resistance, and wear resistance, as well as the suppression of leakage of the grease composition due to the low viscosity of the base oil. This effect is presumably achieved by reducing the arithmetic mean particle size specified in the above requirement (I) to 2.0 μm or less, which makes it easier for particles containing the urea-based thickener (B) to penetrate into the lubricated parts (friction surfaces) of a wave gear device or the like and makes them less likely to be removed from the lubricated parts, thereby improving the retention of the grease composition in the lubricated parts. Furthermore, reducing the arithmetic mean particle size specified in the above requirement (I) to 2.0 μm or less improves the retention of the base oil (A) by the particles. Therefore, it is presumed that the base oil (A) is well distributed over the lubricated parts (friction surfaces) of a wave gear device or the like, and the accompanying effect of well distributing the phosphate ester amine salt (C), sulfur-based extreme pressure agent (D), zinc dithiophosphate (E), melamine cyanurate (F), and organic molybdenum compound (G) over the lubricated parts is improved, resulting in further improvements in extreme pressure properties, load resistance, seizure resistance, wear resistance, and suppression of leakage of the grease composition due to the low viscosity of the base oil. From the above perspective, in the grease composition of one embodiment of the present invention, the arithmetic mean particle size specified in the above requirement (I) is preferably 1.5 μm or less, more preferably 1.0 μm or less, even more preferably 0.9 μm or less, still more preferably 0.8 μm or less, even more preferably 0.7 μm or less, even more preferably 0.6 μm or less, even more preferably 0.5 μm or less, and even more preferably 0.4 μm or less. Also, it is usually 0.01 μm or more.

[0021] <Requirement (II)> In order to facilitate further improvement of the effects of the present invention, it is preferable that the particles containing the urea-based thickener (B) in the grease composition of this embodiment further satisfy the following requirement (II): Requirement (II): The specific surface area of ​​the particles measured by a laser diffraction / scattering method is 0.5 × 10 ５ cm ２ / cm ３ That's all.

[0022] The specific surface area specified by the above requirement (II) is a secondary index indicating the state of fineness of particles containing the urea-based thickener (B) in the grease composition and the presence of large particles (lumps). In other words, by satisfying both the above requirement (I) and the above requirement (II), the state of fineness of particles containing the urea-based thickener (B) in the grease composition is improved, and the presence of large particles (lumps) is further suppressed. Therefore, a grease composition can be obtained that is excellent in extreme pressure properties, load-bearing capacity, seizure resistance, wear resistance, and suppression of leakage of the grease composition due to low viscosity of the base oil, and that is more likely to exhibit the effects of the phosphate ester amine salt (C), sulfur-based extreme pressure agent (D), zinc dithiophosphate (E), melamine cyanurate (F), and organic molybdenum compound (G). From the above viewpoint, the specific surface area specified by the above requirement (II) is preferably 0.7 × 10 ５ cm ２ / cm ３ or more, more preferably 0.8 × 10 ５ cm ２ / cm ３ More preferably, 1.2 × 10 ５ cm ２ / cm ３ More preferably, 1.5 × 10 ５ cm ２ / cm ３ More preferably, 1.8×10 ５ cm ２ / cm ３ More preferably, 2.0×10 ５ cm ２ / cm ３ The specific surface area is usually 1.0 × 10 ６ cm ２ / cm ３ The following is the result.

[0023] In this specification, the values ​​specified in the above requirement (I) and further requirement (II) are values ​​measured by the method described in the Examples below. Furthermore, the values ​​specified in the above requirement (I) and further requirement (II) can be adjusted mainly by the manufacturing conditions of the urea-based thickener (B). Hereinafter, the details of each component contained in the grease composition of the present invention will be described, focusing on specific means for satisfying the above requirement (I) and further requirement (II).

[0024] <Base oil (A)> The grease composition of this embodiment contains a base oil (A). The base oil (A) has a kinematic viscosity at 40°C of 288 mm ２ / s ~ 506 mm ２ / s high viscosity poly-α-olefin (hereinafter also referred to as "high viscosity PAO") (A1), kinematic viscosity at 40°C of 61.2 to 74.8 mm ２ The mixed base oil contains a low-viscosity poly-α-olefin (hereinafter also referred to as "low-viscosity PAO") (A2) of 1 / s and an ester-based synthetic oil. When the base oil (A) contains the high-viscosity PAO (A1), the oil film becomes thicker and lubrication is improved. When the base oil (A) contains the low-viscosity PAO (A2), the permeability of the base oil is improved, improving the supply of the base oil to lubrication points and improving low-temperature characteristics. When the base oil (A) contains the ester-based synthetic oil, the solubility of additives is improved, making it easier for the additives to exert their effects.

[0025] High viscosity PAO (A1) has a kinematic viscosity of 288 mm at 40°C. ２ / s ~ 506 mm ２ / s. Examples of the high-viscosity PAO (A1) include polybutene, polyisobutylene, 1-decene oligomer, ethylene-propylene copolymer, and hydrogenated products thereof. One type of high-viscosity PAO (A1) may be used alone, or two or more types may be used in combination.

[0026] In the grease composition of this embodiment, the high-viscosity PAO (A1) has a kinematic viscosity at 40°C of 288 mm ２ / s or more 506mm２ The kinematic viscosity of the high-viscosity PAO (A1) at 40°C is 288 mm / s or less. ２ When the kinematic viscosity at 40°C of the high-viscosity PAO (A1) is 506 mm / s or more, a sufficient oil film thickness can be ensured. ２ In the grease composition of this embodiment, the kinematic viscosity at 40°C of the high-viscosity PAO (A1) is preferably 300 mm / s or less. ２ / s or more 500mm ２ / s or less, more preferably 320 mm ２ / s or more 480mm ２ / s or less, more preferably 350 mm ２ / s or more 450mm ２ The kinematic viscosity of the high-viscosity PAO (A1) at 40°C is 300 mm ２ / s or more 500mm ２ When the ratio is 1 / s or less, the effect of the present invention is more likely to be improved.

[0027] In the grease composition of this embodiment, the high viscosity PAO (A1) preferably has a kinematic viscosity at 100°C of 10 mm ２ / s or more 70mm ２ / s or less, more preferably 20 mm ２ / s or more 60mm ２ The kinematic viscosity of the high-viscosity PAO (A1) at 40°C is 10 mm ２ / s or more 70mm ２ / s or less, the effects of the present invention are more likely to be improved. In the grease composition of this embodiment, the viscosity index of the high-viscosity PAO (A1) is preferably 100 or more, more preferably 110 or more, and even more preferably 120 or more. When the viscosity index of the high-viscosity PAO (A1) is 100 or more, the effects of the present invention are more likely to be improved.

[0028] Low viscosity PAO (A2) has a kinematic viscosity of 61.2 to 74.8 mm at 40°C. ２ / s. Examples of the low-viscosity PAO (A2) include polybutene, polyisobutylene, 1-decene oligomer, ethylene-propylene copolymer, and hydrogenated products thereof. One type of low-viscosity PAO (A2) may be used alone, or two or more types may be used in combination. The repeating unit structure of the low-viscosity PAO (A2) may be the same as or different from that of the high-viscosity PAO (A1).

[0029] In the grease composition of this embodiment, the kinematic viscosity at 40°C of the low-viscosity PAO (A2) is 61.2 mm ２ / s or more 74.8mm ２ The kinematic viscosity of the low-viscosity PAO (A2) at 40°C is 61.2 mm / s or less. ２ When the kinematic viscosity at 40°C of the low-viscosity PAO (A2) is 74.8 mm / s or more, the leakage resistance is good. ２ In the grease composition of this embodiment, the kinematic viscosity at 40°C of the low-viscosity PAO (A2) is preferably 61.2 mm / s or less. ２ / s or more 74.0mm ２ / s or less, more preferably 62.0 mm ２ / s or more 72.0mm ２ / s or less, more preferably 62.5 mm ２ / s or more 70.0mm ２ The kinematic viscosity of the low-viscosity PAO (A2) at 40°C is 61.2 mm / s or less. ２ / s or more 74.0mm ２ When the ratio is 1 / s or less, the effect of the present invention is more likely to be improved.

[0030] In the grease composition of this embodiment, the kinematic viscosity at 100°C of the low-viscosity PAO (A2) is preferably 7.0 mm ２ / s or more 13.0mm ２ / s or less, more preferably 8.0 mm ２ / s or more 12.0mm ２ / s or less, more preferably 9.0 mm ２ / s or more 11.0mm ２ The kinematic viscosity of the low-viscosity PAO (A2) at 40°C is 7.0 mm / s or less. ２ / s or more 13.0mm ２ / s or less, the effects of the present invention are more likely to be improved. In the grease composition of this embodiment, the viscosity index of the low-viscosity PAO (A2) is preferably 100 or more, more preferably 120 or more, and even more preferably 130 or more. When the viscosity index of the low-viscosity PAO (A2) is 100 or more, the effects of the present invention are more likely to be improved.

[0031] Examples of ester-based synthetic oils include diester-based oils, aromatic ester-based oils, polyol ester-based oils, complex ester-based oils, etc. These may be used alone or in combination of two or more.

[0032] Examples of diester oils include dibutyl sebacate, di(2-ethylhexyl) sebacate, diisodecyl sebacate, ditri(n-decyl) sebacate, diisotridecyl sebacate, dibutyl adipate, di(2-ethylhexyl) adipate, diisodecyl adipate, ditri(n-decyl) adipate, diisotridecyl adipate, ditridecyl glutarate, and methyl acetyl ricinoleate. Examples of aromatic ester oils include tris(2-ethylhexyl) trimellitate, tri(n-decyl) trimellitate, and tetra(n-octyl) pyromellitate. Examples of polyol ester oils include trimethylolpropane caprylate, trimethylolpropane bellargonate, pentaerythritol-2-ethylhexanoate, and pentaerythritol bellargonate. Examples of complex ester oils include oligoesters of polyhydric alcohols and mixed fatty acids of dibasic and monobasic acids. These may be used alone or in combination of two or more. Among these, branched chain ester synthetic oils are preferred, and di(2-ethylhexyl) sebacate, diisodecyl sebacate, diisotridecyl sebacate, di(2-ethylhexyl) adipate, diisodecyl adipate, diisotridecyl adipate, and tris(2-ethylhexyl) trimellitate are more preferred.

[0033] In the grease composition of this embodiment, the kinematic viscosity at 40°C of the ester-based synthetic oil is preferably 4.0 mm ２ / s or more 40mm ２ / s or less, more preferably 7.0 mm ２ / s or more 30mm ２ / s or less, more preferably 9.0 mm ２ / s or more 25mm ２ / s or less. The kinematic viscosity of the ester synthetic oil at 40°C is 4.0 mm ２ / s or more 40mm ２ When the ratio is 1 / s or less, the effect of the present invention is more likely to be improved.

[0034] In the grease composition of this embodiment, the 100°C kinematic viscosity of the ester-based synthetic oil is preferably 1.5 mm ２ / s or more 6.0mm ２ / s or less, more preferably 2.0 mm ２ / s or more 5.0mm ２ / s or less, more preferably 2.5 mm ２ / s or more 4.0mm ２ / s or less. The kinematic viscosity of the ester synthetic oil at 40°C is 1.5 mm ２ / s or more 6.0mm ２ / s or less, the effects of the present invention are more likely to be improved. In the grease composition of this embodiment, the viscosity index of the ester-based synthetic oil is preferably 100 or more, more preferably 120 or more, and even more preferably 140 or more. When the viscosity index of the ester-based synthetic oil is 100 or more, the effects of the present invention are more likely to be improved.

[0035] The ester synthetic oil preferably contains a diester oil (A3) and an aromatic ester oil (A4). When the ester synthetic oil contains a diester oil (A3) and an aromatic ester oil (A4), lubricity can be easily improved.

[0036] When the ester-based synthetic oil contains a diester-based oil (A3) and an aromatic ester-based oil (A4), the content of the diester-based oil (A3) in the ester-based synthetic oil is, from the viewpoint of improving torque transmission efficiency by lowering the viscosity of the mixed base oil (also simply referred to herein as the "viewpoint of lowering viscosity"), preferably 60% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, and is preferably 95% by mass or less, more preferably 92% by mass or less, even more preferably 90% by mass or less, based on the total amount of the ester-based synthetic oil.

[0037] When the ester-based synthetic oil contains a diester-based oil (A3) and an aromatic ester-based oil (A4), the content of the aromatic ester-based oil (A4) in the ester-based synthetic oil is, from the viewpoint of reducing viscosity, preferably 5% by mass or more, more preferably 8% by mass or more, even more preferably 10% by mass or more, based on the total amount of the ester-based synthetic oil, and is preferably 30% by mass or less, more preferably 25% by mass or less, even more preferably 20% by mass or less.

[0038] When the ester-based synthetic oil contains a diester-based oil (A3) and an aromatic ester-based oil (A4), the content of the diester-based oil (A3) is, from the viewpoint of reducing viscosity, preferably 15% by mass or more, more preferably 18% by mass or more, even more preferably 20% by mass or more, based on the total amount of the base oil (A), and is preferably 30% by mass or less, more preferably 28% by mass or less, even more preferably 26% by mass or less.

[0039] When the ester-based synthetic oil contains a diester-based oil (A3) and an aromatic ester-based oil (A4), the content of the aromatic ester-based oil (A4), based on the total amount of the base oil (A), is, from the viewpoint of reducing viscosity, preferably 2.0% by mass or more, more preferably 3.0% by mass or more, even more preferably 4.0% by mass or more, and is preferably 7.0% by mass or less, more preferably 6.0% by mass or less, even more preferably 5.0% by mass or less.

[0040] When the ester-based synthetic oil contains a diester-based oil (A3) and an aromatic ester-based oil (A4), from the viewpoint of reducing viscosity, the content of the diester-based oil (A3) is preferably 5% by mass or more, more preferably 10% by mass or more, even more preferably 13% by mass or more, based on the total amount of the grease composition, and is preferably 30% by mass or less, more preferably 25% by mass or less, even more preferably 22% by mass or less.

[0041] When the ester-based synthetic oil contains a diester-based oil (A3) and an aromatic ester-based oil (A4), the content of the aromatic ester-based oil (A4) is, from the viewpoint of reducing viscosity, preferably 1.0 mass % or more, more preferably 2.0 mass % or more, even more preferably 2.5 mass % or more, based on the total amount of the grease composition, and is preferably 5.0 mass % or less, more preferably 4.5 mass % or less, even more preferably 4.0 mass % or less.

[0042] When the ester-based synthetic oil contains a diester-based oil (A3) and an aromatic ester-based oil (A4), the content ratio of the diester-based oil (A3) to the aromatic ester-based oil (A4) [(A3) / (A4)] is preferably 1 to 12, more preferably 2 to 10, and even more preferably 3 to 8, in terms of mass ratio, from the viewpoint of reducing viscosity.

[0043] In the grease composition of this embodiment, the base oil (A) may contain a base oil other than the high-viscosity PAO (A1), the low-viscosity PAO (A2), and the ester-based synthetic oil, such as one or more mineral oils and synthetic oils other than PAOs and ester-based synthetic oils.

[0044] Examples of mineral oils include atmospheric residues obtained by atmospheric distillation of crude oils such as paraffin-based crude oil, intermediate-based crude oil, and naphthene-based crude oil; distillates obtained by vacuum distillation of the atmospheric residues; and mineral oils obtained by subjecting the distillates to one or more refining treatments such as solvent deasphalting, solvent extraction, hydrofinishing, hydrocracking, advanced hydrocracking, solvent dewaxing, catalytic dewaxing, and hydroisomerization dewaxing.

[0045] Examples of synthetic oils other than the high-viscosity PAO (A1), low-viscosity PAO (A2), and ester-based synthetic oils include normal paraffins, isoparaffins, aromatic oils, ether-based oils, and GTL base oils obtained by isomerizing wax produced by the Fischer-Tropsch process (GTL wax (Gas To Liquids WAX)). These may be used alone or in combination of two or more.

[0046] Examples of aromatic oils include alkylbenzenes such as monoalkylbenzenes and dialkylbenzenes; alkylnaphthalenes such as monoalkylnaphthalenes, dialkylnaphthalenes, and polyalkylnaphthalenes; and the like.

[0047] Examples of ether-based oils include polyglycols such as polyethylene glycol, polypropylene glycol, polyethylene glycol monoether, and polypropylene glycol monoether; and phenyl ether-based oils such as monoalkyl triphenyl ether, alkyl diphenyl ether, dialkyl diphenyl ether, pentaphenyl ether, tetraphenyl ether, monoalkyl tetraphenyl ether, and dialkyl tetraphenyl ether.

[0048] The base oil (A) used in one embodiment of the present invention preferably has a kinematic viscosity at 40°C of 10 mm ２ / s or more, more preferably 20 mm ２ / s or more, more preferably 30 mm ２ / s or more, and even more preferably 40 mm ２ The kinematic viscosity of the base oil (A) at 40°C is 10 mm / s or more. ２ The base oil (A) of this embodiment preferably has a kinematic viscosity at 40°C of 120 mm / s or more. ２ / s or less, more preferably 100 mm ２ / s or less, more preferably 90 mm ２ / s or less, and even more preferably 80 mm ２ The kinematic viscosity of the base oil (A) at 40°C is 120 mm / s or less. ２The effect of the present invention is more easily achieved when the value is equal to or less than 10 mm / s. The upper and lower limits of these numerical ranges can be arbitrarily combined. Specifically, it is preferably 10 to 120 mm. ２ / s, more preferably 20 to 100 mm ２ / s, more preferably 30 to 90 mm ２ / s, and even more preferably 40 to 80 mm ２ / s.

[0049] The base oil (A) used in one embodiment of the present invention preferably has a kinematic viscosity at 100°C of 2.0 mm ２ / s or more, more preferably 3.0 mm ２ / s or more, more preferably 4.0 mm ２ The kinematic viscosity at 100°C of the base oil (A) is 2.0 mm / s or more. ２ The base oil (A) of the present embodiment preferably has a kinematic viscosity at 100°C of 20 mm / s or more. ２ / s or less, more preferably 18 mm ２ / s or less, more preferably 16 mm ２ The kinematic viscosity of the base oil (A) at 40°C is 20 mm / s or less. ２ The upper and lower limits of these numerical ranges can be arbitrarily combined. Specifically, it is preferably 2.0 to 20 mm ２ / s, more preferably 3.0 to 18 mm ２ / s, more preferably 4.0 to 16 mm ２ The base oil (A) used in one embodiment of the present invention may be a mixed base oil prepared by combining a high-viscosity base oil and a low-viscosity base oil to have a kinematic viscosity within the above range.

[0050] The viscosity index of the base oil (A) used in one embodiment of the present invention is preferably at least 90, more preferably at least 110, and even more preferably at least 130. In this specification, the kinematic viscosity and viscosity index refer to values ​​measured or calculated in accordance with JIS K2283:2000.

[0051] In the grease composition of one embodiment of the present invention, the content of the base oil (A) is, based on the total amount (100 mass%) of the grease composition, preferably 50 mass% or more, more preferably 55 mass% or more, even more preferably 60 mass% or more, still more preferably 65 mass% or more, and is preferably 98.5 mass% or less, more preferably 97 mass% or less, even more preferably 95 mass% or less, and still more preferably 93 mass% or less.

[0052] <Urea-based thickener (B)> The grease composition of one embodiment of the present invention contains a urea-based thickener (B). The urea-based thickener (B) contained in the grease composition of one embodiment of the present invention may be a compound having a urea bond, but a diurea compound having two urea bonds is preferred, and from the viewpoint of heat resistance, a diurea compound represented by the following general formula (b1) is more preferred. R １ -NHCONH-R ３ -NHCONH-R ２ (b1) The urea-based thickener (B) used in one embodiment of the present invention may consist of one type or may be a mixture of two or more types.

[0053] In the above general formula (b1), R １ and R ２ R each independently represents a monovalent hydrocarbon group having 6 to 24 carbon atoms. １ and R ２ may be the same or different from each other. ３ represents a divalent aromatic hydrocarbon group having 6 to 18 carbon atoms.

[0054] R in the general formula (b1) １ and R ２ The number of carbon atoms of the monovalent hydrocarbon group that can be selected as R is 6 to 24, preferably 6 to 20, and more preferably 6 to 18. １ and R ２ Examples of the monovalent hydrocarbon group that can be selected as include a saturated or unsaturated monovalent chain hydrocarbon group, a saturated or unsaturated monovalent alicyclic hydrocarbon group, and a monovalent aromatic hydrocarbon group.

[0055] Here, R in the general formula (b1)１ and R ２ When the content of chain hydrocarbon groups is X molar equivalents, the content of alicyclic hydrocarbon groups is Y molar equivalents, and the content of aromatic hydrocarbon groups is Z molar equivalents, it is preferable that the following requirements (a) and (b) be satisfied. Requirement (a): The value of [(X+Y) / (X+Y+Z)]×100 is 90 or more (preferably 95 or more, more preferably 98 or more, and even more preferably 100). Requirement (b): The X / Y ratio is 0 / 100 (X=0, Y=100) to 100 / 0 (X=100, Y=0) (preferably 10 / 90 to 90 / 10, more preferably 20 / 80 to 80 / 20). The alicyclic hydrocarbon groups, chain hydrocarbon groups, and aromatic hydrocarbon groups are each independently selected from R in the above general formula (b1). １ and R ２ Since the groups selected as X, Y, and Z are 2 molar equivalents per mole of the compound represented by general formula (b1). The values ​​of requirements (a) and (b) above represent average values ​​relative to the total amount of the compounds represented by general formula (b1) contained in the grease composition. By using a compound represented by general formula (b1) that satisfies requirements (a) and (b), it is easy to obtain a grease composition with excellent heat resistance. The values ​​of X, Y, and Z can be calculated from the molar equivalents of each amine used as a raw material.

[0056] Examples of the monovalent saturated chain hydrocarbon group include linear or branched alkyl groups having 6 to 24 carbon atoms, specifically hexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl, octadecyl, octadecenyl, nonadecyl, and icosyl groups. Of these, octadecyl is preferred. Examples of monovalent unsaturated chain hydrocarbon groups include straight-chain or branched-chain alkenyl groups having 6 to 24 carbon atoms, and specific examples include a hexenyl group, a heptenyl group, an octenyl group, a nonenyl group, a decenyl group, an undecenyl group, a dodecenyl group, a tridecenyl group, a tetradecenyl group, a pentadecenyl group, a hexadecenyl group, a heptadecenyl group, an octadecenyl group, a nonadecenyl group, an icosenyl group, an oleyl group, a geranyl group, a farnesyl group, a linoleyl group, etc. The monovalent saturated chain hydrocarbon groups and the monovalent unsaturated chain hydrocarbon groups may be straight-chain or branched.

[0057] Examples of monovalent saturated alicyclic hydrocarbon groups include cycloalkyl groups such as cyclohexyl, cycloheptyl, cyclooctyl, and cyclononyl; and cycloalkyl groups substituted with an alkyl group having 1 to 6 carbon atoms, such as methylcyclohexyl, dimethylcyclohexyl, ethylcyclohexyl, diethylcyclohexyl, propylcyclohexyl, isopropylcyclohexyl, 1-methyl-propylcyclohexyl, butylcyclohexyl, pentylcyclohexyl, pentyl-methylcyclohexyl, and hexylcyclohexyl (preferably, a cyclohexyl group substituted with an alkyl group having 1 to 6 carbon atoms). Of these, cyclohexyl is preferred.

[0058] Examples of the monovalent unsaturated alicyclic hydrocarbon group include cycloalkenyl groups such as a cyclohexenyl group, a cycloheptenyl group, and a cyclooctenyl group; and cycloalkenyl groups substituted with an alkyl group having 1 to 6 carbon atoms such as a methylcyclohexenyl group, a dimethylcyclohexenyl group, an ethylcyclohexenyl group, a diethylcyclohexenyl group, and a propylcyclohexenyl group (preferably a cyclohexenyl group substituted with an alkyl group having 1 to 6 carbon atoms).

[0059] Examples of the monovalent aromatic hydrocarbon group include a phenyl group, a biphenyl group, a terphenyl group, a naphthyl group, a diphenylmethyl group, a diphenylethyl group, a diphenylpropyl group, a methylphenyl group, a dimethylphenyl group, an ethylphenyl group, and a propylphenyl group.

[0060] R in the general formula (b1) ３ The carbon number of the divalent aromatic hydrocarbon group that can be selected as R is 6 to 18, preferably 6 to 15, and more preferably 6 to 13. ３ Examples of the divalent aromatic hydrocarbon group that can be selected as aryl include a phenylene group, a diphenylmethylene group, a diphenylethylene group, a diphenylpropylene group, a methylphenylene group, a dimethylphenylene group, an ethylphenylene group, etc. Among these, a phenylene group, a diphenylmethylene group, a diphenylethylene group, or a diphenylpropylene group is preferred, and a diphenylmethylene group is more preferred.

[0061] In the grease composition of one embodiment of the present invention, the content of component (B) is preferably 1.0 to 20.0 mass%, more preferably 1.5 to 15.0 mass%, even more preferably 2.0 to 13.0 mass%, still more preferably 4.0 to 12.0 mass%, and even more preferably 5.0 to 11.0 mass%, based on the total amount (100 mass%) of the grease composition. If the content of component (B) is 1.0 mass% or more, the worked penetration of the resulting grease composition can be easily adjusted to an appropriate range. On the other hand, if the content of component (B) is 20.0 mass% or less, the resulting grease composition can be adjusted to a softer value, which makes it easier to improve the transmission efficiency of wave gear devices and the like.

[0062] [Method for producing urea-based thickener (B)] The urea-based thickener (B) can usually be obtained by reacting an isocyanate compound with a monoamine. The reaction is preferably carried out by adding a solution β obtained by dissolving a monoamine in the base oil (A) to a heated solution α obtained by dissolving an isocyanate compound in the base oil (A). For example, when synthesizing a compound represented by the general formula (b1), the isocyanate compound may be a compound represented by the general formula (b1) R ３ A diisocyanate having a group corresponding to a divalent aromatic hydrocarbon group represented by the formula: １ and R ２ The desired urea-based thickener (B) can be synthesized by the above method using an amine having a group corresponding to the monovalent hydrocarbon group represented by the formula:

[0063] From the viewpoint of finely pulverizing the urea-based thickener (B) in the grease composition so as to satisfy the above requirement (I) and further the above requirement (II), it is preferable to produce a grease composition containing component (A) and component (B) using a grease production apparatus as shown in the following item [1]: [1] A grease production apparatus comprising: a container body having an inlet portion into which a grease raw material is introduced and a discharge portion from which the grease is discharged to the outside; and a rotor having a rotation axis in the axial direction of the inner circumference of the container body and rotatably provided inside the container body, wherein the rotor (i) has concave and convex portions formed alternately along the surface of the rotor, the concave and convex portions being inclined with respect to the rotation axis, and (ii) a first concave-convex portion having a feeding capacity from the inlet portion toward the discharge portion.

[0064] The grease production apparatus described in [1] above will be explained below, and the "preferred" provisions described below are aspects from the viewpoint of finely granulating the urea-based thickener (B) in the grease composition so as to satisfy the above requirement (I) and further the above requirement (II), unless otherwise specified.

[0065] FIG. 1 is a schematic cross-sectional view of the grease production apparatus [1] above, which can be used in one embodiment of the present invention. The grease production apparatus 1 shown in FIG. 1 includes a container body 2 into which a grease raw material is introduced, and a rotor 3 having a rotating shaft 12 on the central axis of the inner periphery of the container body 2 and rotating around the rotating shaft 12. The rotor 3 rotates at high speed around the rotating shaft 12, applying high shear force to the grease raw material inside the container body 2. This produces a grease containing a urea-based thickener (B). As shown in FIG. 1, the container body 2 is preferably partitioned into an inlet section 4, a retention section 5, a first inner circumferential surface 6, a second inner circumferential surface 7, and a discharge section 8, in that order from the upstream side. As shown in FIG. 1, the container body 2 preferably has a truncated conical inner circumferential surface whose inner diameter gradually increases from the inlet section 4 toward the discharge section 8. An introduction section 4 at one end of the container body 2 is provided with a plurality of solution introduction pipes 4A, 4B for introducing grease raw materials from the outside of the container body 2.

[0066] The retention section 5 is located downstream of the introduction section 4 and is a space in which the grease raw material introduced from the introduction section 4 temporarily remains. If the grease raw material remains in the retention section 5 for a long period of time, the grease adhering to the inner peripheral surface of the retention section 5 will form large clumps. Therefore, it is preferable to transport the grease raw material to the first inner peripheral surface 6 downstream in as short a time as possible. It is even more preferable to transport the grease directly to the first inner peripheral surface 6 without passing through the retention section 5. The first inner peripheral surface 6 is located downstream adjacent to the retention section 5, and the second inner peripheral surface 7 is located downstream adjacent to the first inner peripheral surface 6. As will be described in detail later, providing a first uneven portion 9 on the first inner peripheral surface 6 and a second uneven portion 10 on the second inner peripheral surface 7 is preferable for the first inner peripheral surface 6 and the second inner peripheral surface 7 to function as high shear sections that apply high shear force to the grease raw material or grease. The discharge part 8, which is the other end of the container body 2, is a part that discharges the grease stirred between the first inner circumferential surface 6 and the second inner circumferential surface 7, and is provided with a discharge port 11 that discharges the grease. The discharge port 11 is formed in a direction perpendicular or approximately perpendicular to the rotation axis 12. This allows the grease to be discharged from the discharge port 11 in a direction perpendicular or approximately perpendicular to the rotation axis 12. However, the discharge port 11 does not necessarily have to be perpendicular to the rotation axis 12, and may be formed in a direction parallel or approximately parallel to the rotation axis 12.

[0067] The rotor 3 is rotatably mounted with the central axis of the truncated cone-shaped inner peripheral surface of the vessel body 2 as the rotation axis 12, and rotates counterclockwise when the vessel body 2 is viewed from the upstream to the downstream as shown in Figure 1. The rotor 3 has an outer peripheral surface that expands in accordance with the expansion of the inner diameter of the truncated cone of the vessel body 2, and a constant gap is maintained between the outer peripheral surface of the rotor 3 and the inner peripheral surface of the truncated cone of the vessel body 2. The outer peripheral surface of the rotor 3 is provided with a first rotor uneven portion 13 in which unevenness is provided alternately along the surface of the rotor 3.

[0068] The first uneven portion 13 of the rotor is inclined with respect to the rotation axis 12 of the rotor 3 in the direction from the introduction portion 4 to the discharge portion 8, and has the ability to feed from the introduction portion 4 to the discharge portion 8. In other words, the first uneven portion 13 of the rotor is inclined in a direction that pushes the solution downstream when the rotor 3 rotates in the direction shown in FIG.

[0069] The step between the recessed portions 13A and the protruding portions 13B of the first uneven portion 13 of the rotor is preferably 0.3 to 30, more preferably 0.5 to 15, and even more preferably 2 to 7, when the diameter of the recessed portions 13A on the outer peripheral surface of the rotor 3 is taken as 100. The number of protruding portions 13B of the first uneven portion 13 of the rotor in the circumferential direction is preferably 2 to 1000, more preferably 6 to 500, and even more preferably 12 to 200.

[0070] The ratio of the width of the convex portions 13B of the first uneven portion 13 of the rotor to the width of the concave portions 13A in a cross section perpendicular to the rotation axis 12 of the rotor 3 [convex portion width / concave portion width] is preferably 0.01 to 100, more preferably 0.1 to 10, and even more preferably 0.5 to 2. The tilt angle of the first uneven portion 13 of the rotor with respect to the rotation axis 12 is preferably 2 to 85 degrees, more preferably 3 to 45 degrees, and even more preferably 5 to 20 degrees.

[0071] The first inner circumferential surface 6 of the container body 2 is preferably provided with a first uneven portion 9 having a plurality of unevennesses formed along the inner circumferential surface. Furthermore, the unevenness of the first uneven portion 9 on the container body 2 side is preferably inclined in the opposite direction to the first uneven portion 13 of the rotor. In other words, the plurality of unevennesses of the first uneven portion 9 on the container body 2 side are preferably inclined in a direction that pushes the solution downstream when the rotation shaft 12 of the rotor 3 rotates in the direction shown in Figure 1. The first uneven portion 9 having a plurality of unevennesses provided on the first inner circumferential surface 6 of the container body 2 further enhances the stirring capacity and discharge capacity.

[0072] The depth of the projections and recesses of the first projection and recess portion 9 on the container body 2 side is preferably 0.2 to 30, more preferably 0.5 to 15, and even more preferably 1 to 5, when the inner diameter (diameter) of the container is taken as 100. The number of projections and recesses of the first projection and recess portion 9 on the container body 2 side is preferably 2 to 1,000, more preferably 6 to 500, and even more preferably 12 to 200.

[0073] The ratio of the width of the recesses of the first uneven portion 9 on the container body 2 side to the width of the protrusions between the grooves [recess width / protrusion width] is preferably 0.01 to 100, more preferably 0.1 to 10, and even more preferably 0.5 to 2. The inclination angle of the recesses and protrusions of the first uneven portion 9 on the container body 2 side with respect to the rotation axis 12 is preferably 2 to 85 degrees, more preferably 3 to 45 degrees, and even more preferably 5 to 20 degrees. Incidentally, by providing the first uneven portion 9 on the first inner circumferential surface 6 of the container body 2, the first inner circumferential surface 6 can function as a shearing portion that applies a high shear force to the grease raw material or the grease, but the first uneven portion 9 is not necessarily provided.

[0074] A second rotor uneven portion 14 having alternating unevenness along the surface of the rotor 3 is preferably provided on the outer peripheral surface of the downstream portion of the first rotor uneven portion 13. The second rotor uneven portion 14 is inclined with respect to the rotation axis 12 of the rotor 3, and has the ability to suppress the feed of the solution by pushing it back upstream from the inlet portion 4 toward the outlet portion 8.

[0075] The step height of the second uneven portion 14 of the rotor is preferably 0.3 to 30, more preferably 0.5 to 15, and even more preferably 2 to 7, where the diameter of the recess on the outer peripheral surface of the rotor 3 is taken as 100. The number of protrusions of the second uneven portion 14 of the rotor in the circumferential direction is preferably 2 to 1,000, more preferably 6 to 500, and even more preferably 12 to 200.

[0076] The ratio of the width of the convex portion to the width of the concave portion of the second uneven portion 14 of the rotor in a cross section perpendicular to the rotation axis of the rotor 3 [convex portion width / concave portion width] is preferably 0.01 to 100, more preferably 0.1 to 10, and even more preferably 0.5 to 2. The inclination angle of the second uneven portion 14 of the rotor with respect to the rotation axis 12 is preferably 2 to 85 degrees, more preferably 3 to 45 degrees, and even more preferably 5 to 20 degrees.

[0077] The second inner circumferential surface 7 of the container body 2 preferably has a second uneven portion 10 formed with multiple unevennesses adjacent to the downstream portion of the unevennesses in the first uneven portion 9 on the container body 2 side. Multiple unevennesses are preferably formed on the inner circumferential surface of the container body 2, and each unevenness is preferably inclined in the opposite direction to the inclination direction of the second uneven portion 14 of the rotor. That is, the multiple unevennesses of the second uneven portion 10 on the container body 2 side are preferably inclined in a direction that pushes the solution back upstream when the rotation shaft 12 of the rotor 3 rotates in the direction shown in FIG. 1 . The unevenness of the second uneven portion 10 on the second inner circumferential surface 7 of the container body 2 further enhances the stirring ability. Furthermore, the second inner circumferential surface 7 of the container body can function as a shearing portion that applies high shear force to the grease raw material or grease.

[0078] The depth of the recesses of the second uneven portion 10 on the container body 2 side is preferably 0.2 to 30, more preferably 0.5 to 15, and even more preferably 1 to 5, when the inner diameter (diameter) of the container body 2 is 100. The number of recesses of the second uneven portion 10 on the container body 2 side is preferably 2 to 1,000, more preferably 6 to 500, and even more preferably 12 to 200.

[0079] The ratio of the width of the convex portions to the width of the concave portions of the second concave-convex portion 10 on the container body 2 side in a cross section perpendicular to the rotation axis 12 of the rotor 3 [convex portion width / concave portion width] is preferably 0.01 to 100, more preferably 0.1 to 10, and even more preferably 0.5 to 2 or less. The inclination angle of the second concave-convex portion 10 on the container body 2 side with respect to the rotation axis 12 is preferably 2 to 85 degrees, more preferably 3 to 45 degrees, and even more preferably 5 to 20 degrees. The ratio of the length of the first concave-convex portion 9 on the container body 2 side to the length of the second concave-convex portion 10 on the container body 2 side [first concave-convex portion length / second concave-convex portion length] is preferably 2 / 1 to 20 / 1.

[0080] 2 is a cross-sectional view of the first uneven portion 9 on the container body 2 side of the grease production apparatus 1, taken in a direction perpendicular to the rotation axis 12. The first uneven portion 13 of the rotor shown in FIG. 2 is provided with a plurality of scrapers 15 whose tips protrude toward the inner circumferential surface of the container body 2 beyond the tips of the protruding portions 13B of the first uneven portion 13. Although not shown, the second uneven portion 14 is also provided with a plurality of scrapers whose tips protrude toward the inner circumferential surface of the container body 2, similar to the first uneven portion 13. The scrapers 15 scrape off grease adhering to the inner circumferential surfaces of the first uneven portion 9 on the container body 2 side and the second uneven portion 10 on the container body 2 side. It is preferable that the ratio [R2 / R1] of the radius (R2) of the tip of the scraper 15 to the radius (R1) of the tip of the convex portion 13B of the rotor's first uneven portion 13 is greater than 1.005 and less than 2.0, with respect to the protrusion amount of the convex portion 13B of the first uneven portion 13 of the rotor.

[0081] The number of scrapers 15 is preferably 2 to 500, more preferably 2 to 50, and even more preferably 2 to 10. Although the grease production apparatus 1 shown in Fig. 2 is provided with scrapers 15, the apparatus may not be provided with scrapers 15, or may be provided with scrapers 15 intermittently.

[0082] To produce a grease containing a urea-based thickener (B) using the grease production apparatus 1, the above-mentioned grease raw materials, solution α and solution β, are introduced through solution inlet pipes 4A and 4B, respectively, of the inlet portion 4 of the container body 2, and the rotor 3 is rotated at high speed, thereby producing a grease base material containing the urea-based thickener (B). Even when the sulfur-phosphorus-based extreme pressure agent (C) and other additives (D) are blended into the grease base material thus obtained, the urea-based thickener (B) in the grease composition can be made finer so as to satisfy the above requirement (I) and further the above requirement (II).

[0083] As a condition for the high speed rotation of the rotor 3, the shear rate applied to the grease raw material is preferably 10 ２ s －１ More preferably, 10 ３ s －１More preferably, 10 ４ s －１ and usually 10 ７ s －１ The following is the result.

[0084] Furthermore, the ratio (Max / Min) of the maximum shear rate (Max) to the minimum shear rate (Min) during shear when the rotor 3 rotates at high speed is preferably not more than 100, more preferably not more than 50, and even more preferably not more than 10. By making the shear rate for the mixed liquid as uniform as possible, it becomes easier to micronize the urea-based thickener (B) and its precursor in the grease composition, resulting in a more uniform grease structure.

[0085] Here, the maximum shear rate (Max) is the highest shear rate applied to the mixed liquid, and the minimum shear rate (Min) is the lowest shear rate applied to the mixed liquid, and are defined as follows: Maximum shear rate (Max) = (Linear velocity of the tip of the convex portion 13B of the first uneven portion 13 of the rotor) / (Gap A1 between the tip of the convex portion 13B of the first uneven portion 13 of the rotor and the convex portion of the first uneven portion 9 on the first inner circumferential surface 6 of the container body 2) Minimum shear rate (Min) = (Linear velocity of the concave portion 13A of the first uneven portion 13 of the rotor) / (Gap A2 between the concave portion 13A of the first uneven portion 13 of the rotor and the concave portion of the first uneven portion 9 on the first inner circumferential surface 6 of the container body 2) Note that gap A1 and gap A2 are as shown in FIG.

[0086] The grease production apparatus 1 is provided with the scraper 15, which makes it possible to scrape off grease adhering to the inner peripheral surface of the container body 2, thereby preventing the formation of lumps during kneading and enabling the continuous production of grease with a finely divided urea-based thickener (B) in a short period of time. Furthermore, by scraping off the adhering grease, the scraper 15 prevents the remaining grease from acting as resistance to the rotation of the rotor 3, thereby reducing the rotational torque of the rotor 3 and reducing the power consumption of the drive source, enabling efficient continuous production of grease.

[0087] The inner peripheral surface of the container body 2 is frustoconical, with the inner diameter increasing from the introduction portion 4 toward the discharge portion 8, so that centrifugal force has the effect of discharging the grease or grease raw material downstream, reducing the rotational torque of the rotor 3 and enabling continuous production of grease. The outer peripheral surface of the rotor 3 is provided with a first rotor uneven portion 13, which is inclined with respect to the rotation axis 12 of the rotor 3 and has the ability to feed from the introduction portion 4 to the discharge portion 8, and the second rotor uneven portion 14 is inclined with respect to the rotation axis 12 of the rotor 3 and has the ability to inhibit feed from the introduction portion 4 to the discharge portion 8, so that a high shear force can be applied to the solution, and the urea-based thickener (B) in the grease composition can be finely divided so as to satisfy the above requirement (I) and further the above requirement (II) even after the additives are blended.

[0088]

[0023] The first inner circumferential surface 6 of the container body 2 is formed with a first uneven portion 9, which is inclined in the opposite direction to the first uneven portion 13 of the rotor. In addition to the effect of the first uneven portion 13 of the rotor, the grease raw material can be sufficiently stirred while being pushed downstream, and the urea-based thickener (B) in the grease composition can be finely divided so as to satisfy the above-mentioned requirement (I) and further the requirement (II) even after the additives are blended. Furthermore, the second inner circumferential surface 7 of the container body 2 is provided with the second uneven portion 10, and the rotor's second uneven portion 14 is provided on the outer circumferential surface of the rotor 3, so that the grease raw material can be prevented from flowing out of the first inner circumferential surface 6 of the container body more than necessary. This applies a high shear force to the solution, highly dispersing the grease raw material, and the urea-based thickener (B) can be finely divided so as to satisfy the above-mentioned requirement (I) and further the requirement (II) even after the additives are blended.

[0089] <Phosphate ester amine salt (C)> The grease composition of this embodiment contains a phosphoric acid ester amine salt (C). The phosphoric acid ester amine salt (C) is a salt of a phosphoric acid ester and an amine. By containing the phosphoric acid ester amine salt (C), the grease composition of this embodiment can be made to have excellent wear resistance even in a low-temperature environment of less than 80°C.

[0090] Examples of the phosphoric acid ester of the phosphoric acid ester amine salt (C) include neutral phosphoric acid esters such as aryl phosphate, alkyl phosphate, alkenyl phosphate, and alkylaryl phosphate; acidic phosphoric acid esters such as monoaryl acid phosphate, diaryl acid phosphate, monoalkyl acid phosphate, dialkyl acid phosphate, monoalkenyl acid phosphate, and dialkenyl acid phosphate; phosphite esters such as aryl hydrogen phosphite, alkyl hydrogen phosphite, aryl phosphite, alkyl phosphite, alkenyl phosphite, and aryl alkyl phosphite; and acidic phosphite esters such as monoalkyl acid phosphite, dialkyl acid phosphite, monoalkenyl acid phosphite, and dialkenyl acid phosphite. Among these, from the viewpoint of wear resistance, neutral phosphate esters such as aryl phosphate, alkyl phosphate, alkenyl phosphate, and alkylaryl phosphate; and acidic phosphate esters such as monoaryl acid phosphate, diaryl acid phosphate, monoalkyl acid phosphate, dialkyl acid phosphate, monoalkenyl acid phosphate, and dialkenyl acid phosphate are preferred, with monoalkyl acid phosphate and dialkyl acid phosphate being more preferred. The number of carbon atoms in the alkyl group contained in the phosphate ester of the phosphate amine salt (C) is preferably 1 to 18, more preferably 1 to 15. The alkyl group is preferably linear or branched, and more preferably branched.

[0091] Examples of the amine in the phosphoric acid ester amine salt (C) include octylamine, dioctylamine, trioctylamine, dimethyldodecylamine, dibutylethanolamine, and dodecyldiethanolamine. Among these, trioctylamine is preferred from the viewpoint of abrasion resistance. The number of carbon atoms in the alkyl group contained in the amine in the phosphoric acid ester amine salt (C) is preferably 1 to 15, and more preferably 3 to 12. The alkyl group is preferably linear or branched, and more preferably linear.

[0092] As the phosphate ester amine salt, monohexyl phosphate amine salt and dihexyl phosphate amine salt are preferred. These may be used alone or in combination of two or more.

[0093] In the grease composition of this embodiment, from the viewpoint of wear resistance, the content of phosphorus atoms derived from the phosphate ester amine salt (C) is preferably 0.01 to 0.30% by mass, more preferably 0.03 to 0.20% by mass, and even more preferably 0.05 to 0.15% by mass, based on the total amount (100% by mass) of the grease composition. Note that in this specification, the content of phosphorus atoms means the value measured in accordance with JPI-5S-38-03.

[0094] In the grease composition of the present embodiment, the content of the phosphate ester amine salt (C) is, from the viewpoint of wear resistance, preferably 0.5 to 5.0 mass %, more preferably 0.7 to 4.0 mass %, and even more preferably 1.0 to 3.0 mass %, based on the total amount (100 mass %) of the grease composition.

[0095] <Sulfur-based extreme pressure agent (D)> The grease composition of this embodiment contains a sulfur-based extreme pressure agent (D). By containing the sulfur-based extreme pressure agent (D), the grease composition of this embodiment can have excellent high extreme pressure properties even at high temperatures of 80°C or higher.

[0096] Examples of sulfur-based extreme pressure agents (D) include sulfurized fats and oils, sulfurized fatty acids, sulfurized esters, sulfurized olefins, monosulfides, polysulfides, dihydrocarbyl polysulfides, thiadiazole compounds, alkylthiocarbamoyl compounds, thiocarbamate compounds, dithiocarbamate compounds, thioterpene compounds, and dialkylthiodipropionate compounds. These may be used alone or in combination of two or more. Among these, sulfurized olefins are preferred from the viewpoint of improving extreme pressure properties. The sulfurized olefins are preferably sulfides of olefins having 2 to 10 carbon atoms, more preferably sulfides of branched olefins having 2 to 10 carbon atoms.

[0097] In the grease composition of this embodiment, the content of sulfur atoms derived from the sulfur-based extreme pressure agent (D) is, from the viewpoint of extreme pressure properties, preferably 0.25% by mass to 0.65% by mass, more preferably 0.30% by mass to 0.60% by mass, and even more preferably 0.35% by mass to 0.55% by mass, based on the total amount (100% by mass) of the grease composition. Note that, in this specification, the content of sulfur atoms means the value measured in accordance with JIS K 2541-2:2013.

[0098] In the grease composition of the present embodiment, the content of the sulfur-based extreme pressure agent (D) is, from the viewpoint of extreme pressure properties, preferably 0.5% by mass to 5.0% by mass, more preferably 0.7% by mass to 4.0% by mass, and even more preferably 0.9% by mass to 3.0% by mass, based on the total amount (100% by mass) of the grease composition.

[0099] <Zinc dithiophosphate (E)> The grease composition of this embodiment contains zinc dithiophosphate (E). By containing zinc dithiophosphate (E), the grease composition of this embodiment can be made to have excellent wear resistance even in a low-temperature environment of less than 80°C.

[0100] Preferred examples of the zinc dithiophosphate (E) include compounds represented by the following general formula (b-1):

[0101] In general formula (b-1), R ｂ１~R ｂ４ Each of R independently represents a monovalent hydrocarbon group. The hydrocarbon group is not particularly limited as long as it is a monovalent hydrocarbon group, and from the viewpoint of abrasion resistance, preferred examples thereof include alkyl groups, alkenyl groups, cycloalkyl groups, and aryl groups. Among these, alkyl groups are preferred. That is, zinc dialkyldithiophosphate is preferred as the zinc dithiophosphate (E) used in this embodiment. Note that R ｂ１ ~R ｂ４ The cycloalkyl group and aryl group that can be selected as R may be a polycyclic group such as a decaryl group or a naphthyl group. ｂ１ ~R ｂ４ The monovalent hydrocarbon group that can be selected as may have a substituent containing an oxygen atom and / or a nitrogen atom, such as a hydroxyl group, a carboxy group, an amino group, an amide group, a nitro group, or a cyano group, or may be partially substituted with a nitrogen atom, an oxygen atom, a halogen atom, or the like. When the monovalent hydrocarbon group is a cycloalkyl group or an aryl group, it may further have a substituent such as an alkyl group or an alkenyl group.

[0102] R ｂ１ ~R ｂ４ The alkyl group and alkenyl group that can be selected as may be either linear or branched, but from the viewpoint of abrasion resistance, primary and secondary groups are preferred, and among these, primary alkyl groups and secondary alkyl groups are preferred, and secondary alkyl groups are more preferred. That is, the zinc dialkyldithiophosphate used in this embodiment is preferably a primary alkyl group or a secondary alkyl group or a combination thereof, more preferably a primary zinc dialkyldithiophosphate or a secondary zinc dialkyldithiophosphate or a combination thereof, and even more preferably a secondary zinc dialkyldithiophosphate.

[0103] From the viewpoint of wear resistance, R ｂ１ ~R ｂ４When the monovalent hydrocarbon group is an alkyl group, the number of carbon atoms in the hydrocarbon group is preferably 1 or more, more preferably 2 or more, and even more preferably 3 or more, with the upper limit being preferably 24 or less, more preferably 18 or less, even more preferably 12 or less, and still more preferably 10 or less. When the monovalent hydrocarbon group is an alkenyl group, the number of carbon atoms is preferably 2 or more, more preferably 3 or more, with the upper limit being preferably 24 or less, more preferably 18 or less, even more preferably 12 or less, and still more preferably 10 or less. When the monovalent hydrocarbon group is a cycloalkyl group, the number of carbon atoms is preferably 5 or more, with the upper limit being preferably 20 or less. When the monovalent hydrocarbon group is an aryl group, the number of carbon atoms is preferably 6 or more, with the upper limit being preferably 20 or less.

[0104] The zinc dithiophosphate (E) may be used alone or in combination of two or more.

[0105] In the grease composition of this embodiment, the content of zinc atoms derived from the zinc dithiophosphate (E) is, from the viewpoint of wear resistance, preferably 0.05 to 0.35 mass %, more preferably 0.07 to 0.30 mass %, and even more preferably 0.10 to 0.25 mass %, based on the total amount (100 mass %) of the grease composition. Note that in this specification, the zinc atom content refers to the value measured in accordance with JPI-5S-38-03.

[0106] In the grease composition of the present embodiment, the content of the zinc dithiophosphate (E) is, from the viewpoint of wear resistance, preferably 0.5 to 5.0 mass %, more preferably 0.7 to 4.0 mass %, and even more preferably 1.0 to 3.0 mass %, based on the total amount (100 mass %) of the grease composition.

[0107] <Melamine cyanurate (F)> The grease composition of this embodiment contains melamine cyanurate (F). By containing melamine cyanurate (F), the grease composition of this embodiment can be made to have excellent wear resistance even in a low-temperature environment of less than 80°C. Furthermore, by containing melamine cyanurate (F), the grease composition of this embodiment can be made to have excellent seizure resistance in a high-temperature environment of 80°C or higher. Melamine cyanurate is an organic salt of melamine and cyanuric acid, and has a graphite structure.

[0108] The average particle size of the melamine cyanurate (F) is preferably 5.0 μm or less, more preferably 4.0 μm or less, even more preferably 3.0 μm or less, still more preferably 2.5 μm or less, and even more preferably 2.0 μm or less. There is no particular lower limit for the particle size of the melamine cyanurate (F), but it is usually 0.005 μm or more. The smaller the average particle size of the melamine cyanurate (F), the easier it is for the grease composition to penetrate into a wave gear device or the like, thereby reducing the amount of wear of the wave gear device or the like. Therefore, the smaller the average particle size of the melamine cyanurate (F), the more preferable it is. In this specification, the average particle size of the melamine cyanurate (F) refers to the average particle size measured by the following method. The particle size of the melamine cyanurate (F) alone maintains the same particle size even in the grease composition. (That is, the average particle size of the melamine cyanurate (F) contained in the grease composition is approximately the same as the particle size of the melamine cyanurate (F) itself.)

[0109] [Average particle size of melamine cyanurate (F)] The average particle size of melamine cyanurate (F) is the 50% particle size (volume median particle size, D) based on scattering intensity, which is measured at 25°C by dynamic light scattering (photon correlation method) and calculated from the dispersed particle size distribution analyzed by the CONTIN method. ５０ ) can be used.

[0110] In the grease composition of this embodiment, the content of melamine cyanurate (F) is, from the viewpoint of lubricity, preferably 0.2 mass% or more, more preferably 0.3 mass% or more, and even more preferably 0.5 mass% or more, based on the total amount (100 mass%) of the grease composition. Also, in the grease composition of the present invention, the content of melamine cyanurate (F) is, from the viewpoint of lubricity, preferably 10.0 mass% or less, more preferably 5.0 mass% or less, even more preferably 3.0 mass% or less, and even more preferably 2.0 mass% or less, based on the total amount (100 mass%) of the grease composition.

[0111] <Organic Molybdenum Compound (G)> The grease composition of this embodiment contains an organic molybdenum compound (G). By containing the organic molybdenum compound (G), the grease composition of this embodiment reacts with the sliding surface to form a film at high temperatures of 80°C or higher, and therefore the grease composition can have high extreme pressure properties and excellent load resistance.

[0112] Examples of the organic molybdenum compound (G) include molybdenum dithiophosphate (MoDTP) (G1) and molybdenum dithiocarbamate (MoDTC) (G2). These may be used alone or in combination of two or more. Among these, from the viewpoint of more easily achieving the effects of the present invention, it is preferable that the organic molybdenum compound (G) includes molybdenum dithiophosphate (G1).

[0113] <<Molybdenum Dithiophosphate (G1)>> Examples of the molybdenum dithiophosphate (G1) include molybdenum dithiophosphates containing two molybdenum atoms in one molecule, which are represented by the following general formula (g1-1) or (g1-2).

[0114]

[0115] R in the above general formula (g1-1) ４１ ~R ４４ , R in the above general formula (g1-2) ５１ ~R ５４Each of X in the general formula (g1-1) above independently represents a hydrocarbon group having 1 to 30 carbon atoms, and these may be the same or different. ４１ ~X ４８ , X in the above general formula (g1-2) ５１ ~X ５４ each independently represents an oxygen atom or a sulfur atom, which may be the same or different, and X ４３ and X ４４ , X ４５ and X ４６ , X ４７ and X ４８ , X ５３ and X ５４ At least one of these is a sulfur atom.

[0116] R ４１ ~R ４４ , R ５１ ~R ５４ Examples of the hydrocarbon group include an alkyl group, an alkenyl group, a cycloalkyl group, an aryl group, an alkylaryl group, and an arylalkyl group. From the viewpoint of improving extreme pressure properties, an alkyl group or an alkenyl group is preferred, and an alkyl group is more preferred.

[0117] From a similar perspective, R ４１ ~R ４４ , R ５１ ~R ５４ The number of carbon atoms in the hydrocarbon group is preferably 2 or more, more preferably 4 or more, and even more preferably 6 or more, and the upper limit is preferably 24 or less, more preferably 22 or less, even more preferably 20 or less, and still more preferably 18 or less.

[0118] X in formula (g1-1) ４１ ~X ４８ As mentioned above, at least two of them are sulfur atoms, and preferably X ４１ , X ４２ is an oxygen atom, and X ４３ ~X ４８ is preferably a sulfur atom. ５１ ~X ５４ is preferably an oxygen atom.

[0119] When the organic molybdenum compound (G) contains a molybdenum dithiophosphate (G1), the content of the molybdenum dithiophosphate (G1) is preferably 50 to 100 mass%, more preferably 60 to 100 mass%, and even more preferably 70 to 100 mass%, based on the total amount of the organic molybdenum compound (G).

[0120] <<Molybdenum Dithiocarbamate (G2)>> Examples of the molybdenum dithiocarbamate (G2) include binuclear molybdenum dithiocarbamates containing two molybdenum atoms in one molecule, and trinuclear molybdenum dithiocarbamates containing three molybdenum atoms in one molecule.

[0121] Examples of the dinuclear molybdenum dithiocarbamate include compounds represented by the following general formula (g2-1) and compounds represented by the following general formula (g2-2).

[0122]

[0123] In the above general formulae (g2-1) and (g2-2), R １１ ~R １４ Each of X independently represents a hydrocarbon group, and these may be the same or different. １１ ~X １８ each independently represents an oxygen atom or a sulfur atom, and may be the same as or different from each other. １１ ~X １８ At least two of R are sulfur atoms. １１ ~R １４ The hydrocarbon group that can be selected as the alkyl group preferably has 6 to 22 carbon atoms.

[0124] R in the above general formulas (g2-1) and (g2-2) １１ ~R １４Examples of the hydrocarbon group that can be selected as include alkyl groups, alkenyl groups, cycloalkyl groups, aryl groups, alkylaryl groups, and arylalkyl groups. Examples of the alkyl group include hexyl groups, heptyl groups, octyl groups, nonyl groups, decyl groups, undecyl groups, dodecyl groups, tridecyl groups, tetradecyl groups, pentadecyl groups, hexadecyl groups, heptadecyl groups, and octadecyl groups. Examples of the alkenyl group include hexenyl groups, heptenyl groups, octenyl groups, nonenyl groups, decenyl groups, undecenyl groups, dodecenyl groups, tridecenyl groups, tetradecenyl groups, and pentadecenyl groups. Examples of the cycloalkyl group include a cyclohexyl group, a dimethylcyclohexyl group, an ethylcyclohexyl group, a methylcyclohexylmethyl group, a cyclohexylethyl group, a propylcyclohexyl group, a butylcyclohexyl group, and a heptylcyclohexyl group. Examples of the aryl group include a phenyl group, a naphthyl group, an anthracenyl group, a biphenyl group, and a terphenyl group. Examples of the alkylaryl group include a tolyl group, a dimethylphenyl group, a butylphenyl group, a nonylphenyl group, and a dimethylnaphthyl group. Examples of the arylalkyl group include a methylbenzyl group, a phenylmethyl group, a phenylethyl group, and a diphenylmethyl group.

[0125] Among these, molybdenum dialkyldithiocarbamate represented by the following structural formula (g2-3) is preferred. [In the above structural formula (g2-3), R １ , R ２ , R ３ , and R ４ Each of X independently represents an aliphatic hydrocarbon group having 4 to 22 carbon atoms. １ and X ２ is a sulfur atom, and X ３ and X ４ is an oxygen atom.] １ , R ２ , R ３ , and R ４preferably each independently contain a short-chain substituent group which is an aliphatic hydrocarbon group having 4 to 12 carbon atoms, or a long-chain substituent group which is an aliphatic hydrocarbon group having 13 to 22 carbon atoms. Examples of the aliphatic hydrocarbon group having 4 to 12 carbon atoms that can be selected as the short-chain substituent group include alkyl groups having 4 to 12 carbon atoms and alkenyl groups having 4 to 12 carbon atoms. Specific examples include butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl, butenyl, pentenyl, hexenyl, heptenyl, octenyl, nonenyl, decenyl, undecenyl, and dodecenyl groups. These may be linear or branched. The number of carbon atoms in the aliphatic hydrocarbon group that can be selected as the short-chain substituent group is preferably 5 to 11, more preferably 6 to 10, and even more preferably 7 to 9, from the viewpoint of more easily achieving the effects of the present invention. Examples of the aliphatic hydrocarbon group having 13 to 22 carbon atoms that can be selected as the long-chain substituent group include alkyl groups having 13 to 22 carbon atoms and alkenyl groups having 13 to 22 carbon atoms. Specific examples include tridecyl group, tetradecyl group, pentadecyl group, hexadecyl group, heptadecyl group, octadecyl group, nonadecyl group, icosyl group, henicosyl group, docosyl group, tridecenyl group, tetradecenyl group, pentadecenyl group, hexadecenyl group, heptadecenyl group, octadecenyl group, oleyl group, nonadecenyl group, icosenyl group, henicosyl group, and docosenyl group. These may be linear or branched. The number of carbon atoms in the aliphatic hydrocarbon group that can be selected as the long-chain substituent group is preferably 13 to 20, more preferably 13 to 16, and even more preferably 13 to 14, from the viewpoint of more easily achieving the effects of the present invention. The molar ratio of the short-chain substituent group to the long-chain substituent group (short-chain substituent group:long-chain substituent group) in all molecules of molybdenum dialkyldithiocarbamate represented by structural formula (1) is preferably 10:90 to 90:10, more preferably 30:70 to 70:30, and even more preferably 40:60 to 60:40.

[0126] Examples of trinuclear molybdenum dithiocarbamate include compounds represented by the following general formula (g2-4): Mo ３ S ｋ E ｍ L ｎ A ｐ Q ｚ (g2-4)

[0127] In the general formula (g2-4), k is an integer of 1 or more, m is an integer of 0 or more, and k+m is an integer of 4 to 10, preferably an integer of 4 to 7. n is an integer of 1 to 4, and p is an integer of 0 or more. z is an integer of 0 to 5, including non-stoichiometric values. Each E is independently an oxygen atom or a selenium atom, and is capable of substituting, for example, sulfur in the core described below. Each L is independently an anionic ligand having an organic group containing a carbon atom, and the total number of carbon atoms in the organic group in each ligand is 14 or more, and the ligands may be the same or different. Each A is independently an anion other than L. Each Q is independently an electron-donating neutral compound, and is present to fill a vacant coordination position on the trinuclear molybdenum compound.

[0128] The molybdenum atom content in the trinuclear molybdenum dithiocarbamate is preferably 2.0% by mass or more, more preferably 4.0% by mass or more, and even more preferably 5.0% by mass or more, based on the total amount of the trinuclear molybdenum dithiocarbamate. It is also preferably 9.0% by mass or less, more preferably 7.0% by mass or less, and even more preferably 6.0% by mass or less. The upper and lower limits of these numerical ranges can be arbitrarily combined. Specifically, it is preferably 2.0% by mass to 9.0% by mass, more preferably 4.0% by mass to 7.0% by mass, and even more preferably 5.0% by mass to 6.0% by mass.

[0129] When the organic molybdenum compound (G) contains molybdenum dithiocarbamate (G2), the content of the molybdenum dithiocarbamate (G2) is preferably 50 to 100 mass%, more preferably 60 to 100 mass%, and even more preferably 70 to 100 mass%, based on the total amount of the organic molybdenum compound (G).

[0130] When the organic molybdenum compound (G) contains a molybdenum dithiophosphate (G1) and a molybdenum dithiocarbamate (G2), the total content of the molybdenum dithiophosphate (G1) and the molybdenum dithiocarbamate (G2) is preferably 70 to 100 mass%, more preferably 80 to 100 mass%, and even more preferably 90 to 100 mass%, based on the total amount of the organic molybdenum compound (G).

[0131] In the grease composition of this embodiment, the content of molybdenum atoms derived from the organic molybdenum compound (G) is, from the viewpoint of extreme pressure properties, preferably 0.05% by mass to 0.35% by mass, more preferably 0.07% by mass to 0.30% by mass, and even more preferably 0.10% by mass to 0.25% by mass, based on the total amount (100% by mass) of the grease composition. Note that, in this specification, the molybdenum atom content refers to the value measured in accordance with JPI-5S-38-03.

[0132] In the grease composition of the present embodiment, the content of the organic molybdenum compound (G) is, from the viewpoint of extreme pressure properties, preferably 0.5% by mass to 5.0% by mass, more preferably 0.7% by mass to 4.0% by mass, and even more preferably 0.9% by mass to 3.0% by mass, based on the total amount (100% by mass) of the grease composition.

[0133] <Other Additives (H)> The grease composition of one embodiment of the present invention may contain additives (H) other than components (B), (C), (D), (E), (F), and (G) that are typically blended into greases, as long as the effects of the present invention are not impaired. Examples of additives (H) include antioxidants, viscosity modifiers, rust inhibitors, solid lubricants, and detergent dispersants. Each of the additives (H) may be used alone, or two or more may be used in combination. Among these, it is preferable to contain one or more additives selected from the group consisting of antioxidants, viscosity modifiers, and rust inhibitors.

[0134] Examples of the antioxidant include phenol-based antioxidants.

[0135] Examples of viscosity modifiers include non-dispersed poly(meth)acrylate (PMA), dispersed poly(meth)acrylate, olefin copolymers (olefin copolymers (OCP); for example, ethylene-propylene copolymers, etc.), dispersed olefin copolymers, and styrene copolymers (for example, hydrogenated styrene-diene copolymers, etc.). These may be used alone or in combination of two or more. The mass average molecular weight (Mw) of these viscosity modifiers is preferably 5,000 to 50,000, more preferably 7,000 to 30,000, and even more preferably 10,000 to 20,000, from the viewpoint of maintaining the mass average molecular weight and preventing molecular cleavage even when subjected to high shear in a wave gear device or the like. In this specification, the mass average molecular weight (Mw) of each component is a value calculated in terms of standard polystyrene as measured by gel permeation chromatography (GPC).

[0136] Examples of the rust inhibitor include carboxylic acid-based rust inhibitors such as alkenyl succinic acid polyhydric alcohol esters, zinc stearate, thiadiazole and its derivatives, benzotriazole and its derivatives, etc. Examples of the solid lubricant include polyimide, PTFE, graphite, metal oxide, boron nitride, and molybdenum disulfide, etc. Examples of the detergent dispersant include ashless dispersants such as succinimide and boron-based succinimide.

[0137] In the grease composition of one embodiment of the present invention, the contents of these additives (H) are set appropriately depending on the types of additives, but are each independently typically 0.01 to 20 mass %, preferably 0.01 to 15 mass %, more preferably 0.01 to 10 mass %, and even more preferably 0.01 to 7 mass %, based on the total amount (100 mass %) of the grease composition.

[0138] <Preferred Combination of Additives> A preferred combination of the phosphoric acid ester amine salt (C), the sulfur-based extreme pressure agent (D), the zinc dithiophosphate (E), the melamine cyanurate (F), and the organic molybdenum compound (G) is a combination in which the phosphoric acid ester amine salt (C) is an amine salt of a monoalkyl acid phosphate and trioctylamine, the sulfur-based extreme pressure agent (D) is a sulfurized olefin, the zinc dithiophosphate (E) is a zinc dialkyldithiophosphate, the melamine cyanurate (F) is melamine cyanurate having an average particle size of 4.0 μm or less, and the organic molybdenum compound (G) is molybdenum dithiophosphate. Furthermore, a more preferred combination of the phosphoric acid ester amine salt (C), the sulfur-based extreme pressure agent (D), the zinc dithiophosphate (E), the melamine cyanurate (F), and the organic molybdenum compound (G) is a combination in which the phosphoric acid ester amine salt (C) is an amine salt of isotridecyl acid phosphate and trioctylamine, the sulfur-based extreme pressure agent (D) is a sulfide of 6-methyl-1-heptene, the zinc dithiophosphate (E) is a secondary zinc dialkyldithiophosphate, the melamine cyanurate (F) is melamine cyanurate having an average particle size of 3.0 μm or less, and the organic molybdenum compound (G) is 2-ethylhexyl molybdenum dithiophosphate.

[0139] <Physical Properties of Grease Composition> (Unworked Penetration) From the viewpoint of handling at room temperature, the unworked penetration at 25°C of the grease composition of one embodiment of the present invention is preferably 230 to 410, more preferably 260 to 380, even more preferably 270 to 360, and still more preferably 280 to 330. In this specification, the unworked penetration of the grease composition means a value measured at 25°C in accordance with JIS K2220:2013 (Clause 7).

[0140] (Worked Penetration) From the viewpoint of achieving both a low viscosity of the base oil and suppression of leakage of the grease composition, the worked penetration at 25°C of the grease composition of one embodiment of the present invention is preferably 250 to 430, more preferably 280 to 400, even more preferably 290 to 380, and still more preferably 300 to 350. In this specification, the worked penetration of the grease composition means a value measured at 25°C in accordance with JIS K2220:2013 (Clause 7).

[0141] (Difference between Worked Penetration and Unworked Penetration) From the viewpoint of achieving both a low viscosity of the base oil and suppression of leakage of the grease composition, the difference obtained by subtracting the unworked penetration value from the worked penetration value at 25°C of the grease composition of one embodiment of the present invention is preferably 0 to 45, more preferably 1 to 40, even more preferably 3 to 35, and still more preferably 5 to 30. The smaller the difference obtained by subtracting the unworked penetration value from the worked penetration value, the less likely the grease composition is to soften even when sheared by mixing, which means that the grease composition is less likely to leak.

[0142] [Shell Four-Ball Load-Carrying (EP) Test] When a grease composition according to one embodiment of the present invention is subjected to a Shell four-ball load-carrying (EP) test by the method described in the Examples below, the maximum non-seizure load (LNL) is preferably 618 N or more, more preferably 785 N or more, and even more preferably 981 N or more, from the viewpoint of extreme pressure properties. When a grease composition according to one embodiment of the present invention is subjected to a Shell four-ball load-carrying (EP) test by the method described in the Examples below, the weld load (WL) is preferably 1,961 N or more, more preferably 2,452 N or more, and even more preferably 3,089 N or more, from the viewpoint of extreme pressure properties. When a grease composition according to one embodiment of the present invention is subjected to a Shell four-ball load-carrying (EP) test by the method described in the Examples below, the load-wear index (LWI) is preferably 300 N or more, more preferably 400 N or more, and even more preferably 500 N or more, from the viewpoint of load-carrying properties.

[0143] [Serious Friction and Wear (SRV) Test] When a serious friction and wear (SRV) test is performed on the grease composition of one embodiment of the present invention by the method described in the Examples below, the seizure load is preferably more than 1,500 N, more preferably more than 1,800 N, and even more preferably more than 2,000 N, from the viewpoint of seizure resistance.

[0144] [Shell Four-Ball Wear Test] When a Shell four-ball wear test is performed on the grease composition of one embodiment of the present invention by the method described in the Examples below, the wear scar diameter is preferably 0.55 mm or less, more preferably 0.50 mm or less, and even more preferably 0.45 mm or less, from the viewpoint of wear resistance.

[0145] <Method for producing grease composition> The grease composition of the present invention is a method for producing a grease composition, comprising: (1) a step of synthesizing a urea-based thickener (B) in a base oil (A); and (2) a step of blending a phosphate ester amine salt (C), a sulfur-based extreme pressure agent (D), a zinc dithiophosphate (E), melamine cyanurate (F), and an organic molybdenum compound (G) with the product synthesized in step (1), wherein the base oil (A) is a grease composition having a kinematic viscosity at 40°C of 288 mm ２ / s ~ 506 mm ２ High viscosity poly-α-olefin (PAO) (A1) having a kinematic viscosity of 61.2 to 74.8 mm / s at 40°C ２ and a mixed base oil containing a low-viscosity poly-α-olefin (PAO) (A2) having a viscosity of 1 / s and an ester-based synthetic oil, and particles containing the urea-based thickener (B) in the grease composition satisfy the following requirement (I): Requirement (I): The particles have an area-based arithmetic mean particle diameter of 2.0 μm or less when measured by a laser diffraction / scattering method.

[0146] As an example of the synthesis method, the diurea compound represented by the general formula (b1) can usually be obtained by reacting a diisocyanate with a monoamine. The reaction is preferably carried out by blending a diisocyanate with the base oil (A) described above, dissolving the diisocyanate under heating, and then heating and stirring the resulting diisocyanate-containing base oil to which a base oil prepared by dissolving a monoamine in the base oil (A) is added. For example, when synthesizing the diurea compound represented by the general formula (b1), the diisocyanate may be selected from the group consisting of R ３ A diisocyanate having a group corresponding to a divalent aromatic hydrocarbon group represented by the formula: １ and R ２ The desired diurea compound can be synthesized by the above method using an amine having a group corresponding to the monovalent hydrocarbon group represented by the following formula: If necessary, other additives (H) may be added in the step (2).

[0147] In each of the steps (1) and (2), it is preferable to blend an ester-based synthetic oil.

[0148] It is preferable that the ester-based synthetic oil contains a diester-based oil (A3) and an aromatic ester-based oil (A4), and that the diester-based oil (A3) is blended in the step (1) and the aromatic ester-based oil (A4) is blended in the step (2).

[0149] <Uses of Grease Composition> The grease composition of the present invention has excellent extreme pressure properties, load resistance, seizure resistance, and wear resistance over a wide range of temperature environments, and is also excellent in suppressing leakage of the grease composition due to the low viscosity of the base oil. Therefore, the grease composition of one embodiment of the present invention can be suitably used for lubricating sliding parts of various devices.

[0150] Devices in which the grease composition of the present invention can be suitably used include strain wave gear devices among reducers used in the fields of industrial robots and space probes, as well as mechanical elements involved in power transmission in the fields of bicycles, automobiles, office equipment, machine tools, wind turbines, construction, agricultural machinery, and industrial robots.

[0151] Examples of lubricated parts in devices in the field of office equipment for which the grease composition of the present invention can be suitably used include fuser rolls in devices such as printers, and bearings and gear parts in devices such as polygon motors. Examples of lubricated parts in devices in the field of machine tools for which the grease composition of the present invention can be suitably used include bearing parts in reducers of spindles, servo motors, and machine tool robots. The grease composition of the present invention can also be suitably used in reducers equipped in industrial robots and speed-up gears equipped in wind power generation facilities. Examples of such reducers and speed-up gears include reducers consisting of gear mechanisms and speed-up gears consisting of gear mechanisms. However, the application of the grease composition of one embodiment of the present invention is not limited to reducers consisting of gear mechanisms and speed-up gears consisting of gear mechanisms, but can also be applied to, for example. Examples of reducers include traction drive, harmonic type, RV type, and cyclo type, and all of these can be suitably used, although harmonic type wave gear devices are preferred. In another aspect of the present invention, there is provided a device, preferably a reducer or a speed increaser, having the grease composition of the present invention in a lubrication portion such as a bearing portion, a sliding portion, a gear portion, or a joint portion.

[0152] [Method for Lubricating a Sliding Mechanism] A method for lubricating a sliding mechanism that can be applied to the grease composition of the present invention is a method for lubricating the sliding mechanism using the grease composition of the present invention described above. In one aspect of the present invention, a lubrication method is provided in which the grease composition of the present invention is used to lubricate parts to be lubricated (e.g., bearing parts, sliding parts, gear parts, joint parts, etc.) of a device such as a reducer or a speed-up gear. Examples of the reducer and speed-up gear include a reducer made of a gear mechanism and a speed-up gear mechanism. However, the application of the grease composition of one aspect of the present invention is not limited to reducers made of a gear mechanism and speed-up gears made of a gear mechanism, and can also be applied to, for example. Furthermore, examples of reducers include traction drive, harmonic type, RV type, and cyclo type, and the grease composition can be suitably used in any of these, although a harmonic type wave gear device is preferred.

[0153] According to the method for lubricating a sliding mechanism to which the grease composition of the present invention can be applied, for example, when the sliding mechanism is a wave gear device or the like, the method provides excellent extreme pressure properties, load resistance, seizure resistance, and wear resistance over a wide range of temperature environments, while also enabling the suppression of leakage of the grease composition by reducing the viscosity of the base oil.

[0154] According to one aspect of the present invention, the following items [1] to

[12] are provided: [1] A grease composition containing a base oil (A), a urea-based thickener (B), a phosphoric acid ester amine salt (C), a sulfur-based extreme pressure agent (D), a zinc dithiophosphate (E), melamine cyanurate (F), and an organic molybdenum compound (G), wherein the base oil (A) is a grease composition having a kinematic viscosity at 40°C of 288 mm ２ / s ~ 506 mm ２ High viscosity poly-α-olefin (PAO) (A1) having a kinematic viscosity of 61.2 to 74.8 mm / s at 40°C ２ [2] A grease composition according to [1], wherein the grease composition is a mixed base oil containing a low-viscosity poly-α-olefin (PAO) (A2) having a viscosity of 1 / s and an ester-based synthetic oil, and particles containing the urea-based thickener (B) in the grease composition satisfy the following requirement (I): Requirement (I): The particles have an area-based arithmetic mean particle diameter of 2.0 μm or less when measured by a laser diffraction / scattering method. [3] A grease composition according to [1], wherein the particles containing the urea-based thickener (B) in the grease composition further satisfy the following requirement (II): Requirement (II): The particles have a specific surface area of ​​0.5×10 or less when measured by a laser diffraction / scattering method. ５ cm ２ / cm ３or more. [3] The grease composition according to [1] or [2] above, wherein the ester-based synthetic oil comprises a diester-based oil (A3) and an aromatic ester-based oil (A4). [4] The grease composition according to [3] above, wherein the content ratio [(A3) / (A4)] of the diester-based oil (A3) to the aromatic ester-based oil (A4) is 1 to 12 by mass. [5] The grease composition according to any one of [1] to [4] above, further comprising one or more additives selected from the group consisting of antioxidants, viscosity modifiers, and rust inhibitors. [6] The grease composition according to any one of [1] to [5] above, wherein the content ratio [(C) / (E)] of the phosphoric acid ester amine salt (C) to the zinc dithiophosphate salt (E) is 0.5 to 1.5 by mass. [7] The grease composition according to any one of [1] to [6], wherein the content ratio [(F) / (G)] of the melamine cyanurate (F) to the organic molybdenum compound (G) is 0.1 to 1.0 by mass. [8] The grease composition according to any one of [1] to [7], wherein the worked penetration at 25°C is 250 to 430. [9] The grease composition according to any one of [1] to [8], which is used for lubricating lubricated parts of a reducer or a speed increaser.

[10] The grease composition according to [9], wherein the reducer is a wave gear device.

[11] A lubrication method, comprising lubricating lubricated parts of a wave gear device with the grease composition according to any one of [1] to [8].

[12] A method for producing a grease composition, comprising: (1) a step of synthesizing a urea-based thickener (B) in a base oil (A); and (2) a step of blending a phosphate ester amine salt (C), a sulfur-based extreme pressure agent (D), a zinc dithiophosphate (E), melamine cyanurate (F), and an organic molybdenum compound (G) with the product synthesized in the step (1), wherein the base oil (A) is a grease composition having a kinematic viscosity at 40°C of 288 mm ２ / s ~ 506 mm ２ High viscosity poly-α-olefin (PAO) (A1) having a kinematic viscosity of 61.2 to 74.8 mm / s at 40°C ２and a mixed base oil containing a low-viscosity poly-α-olefin (PAO) (A2) having a viscosity of 1 / s and an ester-based synthetic oil, and particles containing the urea-based thickener (B) in the grease composition satisfy the following requirement (I): Requirement (I): The particles have an area-based arithmetic mean particle diameter of 2.0 μm or less when measured by a laser diffraction / scattering method.

[0155] The present invention will be specifically described with reference to the following examples, but the present invention is not limited to these examples.

[0156] [Various Physical Properties] Various physical properties were measured as follows: (1) Average particle size of melamine cyanurate (C) Measured at 25°C by dynamic light scattering (photon correlation method), the 50% particle size (volume median particle size, D) based on scattering intensity was calculated from the dispersed particle size distribution analyzed by the CONTIN method. ５０ ) was used. (2) Unworked Penetration of Grease Composition Measured at 25°C in accordance with JIS K2220:2013 (Clause 7). (3) Worked Penetration of Grease Composition Measured at 25°C in accordance with JIS K2220:2013 (Clause 7). (4) Difference between Worked Penetration and Unworked Penetration of Grease Composition The difference was calculated by subtracting the unworked penetration value in (2) from the worked penetration value in (3). (5) Content of Phosphorus Atoms, Zinc Atoms, and Molybdenum Atoms The contents of phosphorus atoms, zinc atoms, and molybdenum atoms were measured in accordance with JPI-5S-38-03. (6) Content of Sulfur Atoms The content of sulfur atoms was measured in accordance with JIS K 2541-2:2013.

[0157] [Raw Materials] In Examples 1 to 3 and Comparative Examples 1 and 2, the base oil (A), phosphate ester amine salt (C), sulfur-based extreme pressure agent (D), zinc dithiophosphate (E), melamine cyanurate (F), organic molybdenum compound (G), and other additives used as raw materials for preparing the grease compositions were as follows:

[0158] <Base oil (A)> Base oil (A1): Poly-α-olefin (PAO) (kinematic viscosity at 40°C: 400 mm ２ / s, viscosity index: 149) Base oil (A2): poly-α-olefin (PAO) (40°C kinematic viscosity: 63 mm ２ / s, viscosity index: 139) Base oil (A3-1): Ester-based synthetic oil (di(2-ethylhexyl) sebacate, kinematic viscosity at 40°C: 11 mm ２ / s, viscosity index: 156) Base oil (A3-2): Ester-based synthetic oil (diisodecyl sebacate, kinematic viscosity at 40°C: 20 mm ２ / s, viscosity index: 164) Base oil (A4): Ester-based synthetic oil (tris(2-ethylhexyl) trimellitate, kinematic viscosity at 40°C: 90 mm ２ / s, viscosity index: 78)

[0159] <Phosphate ester amine salt (C)> Phosphate ester: isotridecyl acid phosphate (phosphorus atom content: 8.2% by mass) Amine: trioctylamine

[0160] <Sulfur-based extreme pressure agent (D)> 6-methyl-1-heptene sulfide (sulfur atom content: 36% by mass)

[0161] <Zinc dithiophosphate (E)> Zinc dialkyldithiophosphate (ZnDTP) (secondary) (zinc atom content: 9.0 mass%, alkyl group carbon number: 3 to 6)

[0162] <Melamine cyanurate (F)> Melamine cyanurate (average particle size: approximately 3.0 μm)

[0163] <Organomolybdenum Compound (G)> Molybdenum dithiophosphate (2-ethylhexyl) (MoDTP) (kinematic viscosity at 40°C: 60 mm ２ / s mineral oil, dilution ratio: 50 mass%, molybdenum atom content: 9.0 mass%)

[0164] <Other additives (H)> Phenolic antioxidant (6-methylheptyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate) Viscosity modifier (ethylene propylene oligomer, Mw: 14,400, Mn: 3,800) Rust inhibitor: benzotriazole Other components: amide compound, alkylamine, alkylphosphate, alkyldithiothiazole

[0165] Example 1 (1) Synthesis of Urea Grease Solution α was prepared by adding 5.8 parts by mass of diphenylmethane-4,4′-diisocyanate (MDI) to a mixed base oil of 10 parts by mass of base oil (A1), 30 parts by mass of base oil (A2), and 10 parts by mass of base oil (A3-1) heated to 70° C. Separately, solution β was prepared by adding 5.6 parts by mass of cyclohexylamine and 3.8 parts by mass of octadecylamine (stearylamine) to a mixed base oil of 10 parts by mass of base oil (A1), 30 parts by mass of base oil (A2), and 10 parts by mass of base oil (A3-1) heated to 70° C. Using the grease manufacturing apparatus 1 shown in FIG. 1, equal amounts of solution α heated to 70°C through the solution inlet pipe 4A and solution β heated to 70°C through the solution inlet pipe 4B were simultaneously introduced into the container body 2, and while the rotor 3 was rotating, solution α and solution β were continuously introduced into the container body 2. The mixture was then heated to 160°C using a stirring device, stirred for 1 hour, and then allowed to cool naturally to 100°C. Subsequently, 5.0 parts by mass of base oil (A4) and 0.5 parts by mass of an amide compound were added, and the mixture was homogenized by roll milling to synthesize urea grease (b1). The rotation speed of the rotor 3 of the grease manufacturing apparatus 1 used was 8,000 rpm. The maximum shear rate (Max) was 10,500 s －１ The ratio of the maximum shear rate (Max) to the minimum shear rate (Min) [Max / Min] was set to 3.5, and stirring was performed. The urea-based thickener (B1) contained in the obtained urea grease was represented by the general formula (b1) R １ and R ２ is a cyclohexyl group or an octadecyl group (stearyl group), and R ３ corresponds to a compound in which the aryl group is a diphenylmethylene group. The molar ratio of cyclohexylamine to octadecylamine used as raw materials (cyclohexylamine / octadecylamine) was 80 / 20. (2) Preparation of Grease Composition Next, the components from phosphate ester to rust inhibitor and other components shown in Table 1 were added to urea grease (b1) in the amounts shown in Table 1 and mixed. Thereafter, the mixture was homogenized using a triple roll mill to obtain the grease composition of Example 1.

[0166] Examples 2 and 3 Grease compositions were prepared in the same manner as the grease composition of Example 1, except that the contents were changed as shown in Table 1.

[0167] Comparative Example 1 A grease composition of Comparative Example 1 was obtained in the same manner as in Example 1, except that in the synthesis of (1) urea grease in Example 1, the contents of each component were changed as follows: 41 parts by mass of base oil (A2) heated to 70°C 4.6 parts by mass of diphenylmethane-4,4'-diisocyanate (MDI) 41 parts by mass of separately prepared base oil (A2) heated to 70°C 1.5 parts by mass of cyclohexylamine 6.0 parts by mass of octadecylamine (stearylamine) 5.0 parts by mass of base oil (A4) 0.5 parts by mass of amide compound The urea-based thickener (B2) contained in the obtained urea grease was a urea-based thickener represented by the general formula (b1) R １ and R ２ is a cyclohexyl group or an octadecyl group (stearyl group), and R ３ is a diphenylmethylene group. The molar ratio of cyclohexylamine to octadecylamine used as raw materials (cyclohexylamine / octadecylamine) was 40 / 60.

[0168] Comparative Example 2 A grease composition of Comparative Example 2 was prepared in the same manner as the grease composition of Comparative Example 1, except that the contents were changed to those shown in Table 1.

[0169] [Requirements] The following calculations were carried out for the urea greases synthesized in Examples 1 to 3 and Comparative Examples 1 and 2.

[0170] (1) Calculation of the arithmetic mean particle size of particles containing a urea-based thickener: Requirement (I) The arithmetic mean particle size of particles containing a urea-based thickener in a grease composition was evaluated. Specifically, the urea greases synthesized in Examples 1 to 3 and Comparative Examples 1 and 2 were used as measurement samples, and the arithmetic mean particle size of particles containing a urea-based thickener (B) was determined using the following procedure. First, the measurement sample was vacuum-degassed and then loaded into a 1 mL syringe. 0.10 to 0.15 mL of the sample was extruded from the syringe, and the extruded sample was placed on the surface of a plate-shaped cell of a paste cell fixture. Next, another plate-shaped cell was placed on top of the sample to obtain a measurement cell in which the sample was sandwiched between the two cells. Next, the arithmetic mean particle size of the particles in the sample in the measurement cell was measured based on the area of ​​the particles using a laser diffraction particle size analyzer (manufactured by Horiba, Ltd., product name: LA-920). Here, "area-based arithmetic mean particle diameter" means the arithmetic mean of the area-based particle diameter distribution. The area-based particle diameter distribution indicates the frequency distribution of particle diameters of all particles to be measured, based on the area calculated from the particle diameters (more specifically, the cross-sectional area of ​​particles having the particle diameters). The arithmetic mean of the area-based particle diameter distribution can be calculated using the following formula (1):

[0171] In the above formula (1), J represents the particle size division number, q(J) represents the frequency distribution value (unit: %), and X(J) represents the representative diameter (unit: μm) of the Jth particle size range.

[0172] (2) Calculation of the specific surface area of ​​particles containing a urea-based thickener: Requirement (II) The specific surface area was calculated using the particle size distribution of particles containing a thickener in the grease composition measured in the above-mentioned section on requirement (I). Specifically, the specific surface area was calculated using the particle size distribution. ３ ) surface area of ​​particles per ２ ) was calculated as the specific surface area (unit: cm ２ / cm ３ )

[0173] Next, the extreme pressure properties, load resistance, and wear resistance of the above-mentioned Examples 1 to 3 and Comparative Examples 1 and 2 are evaluated.

[0174] [Shell Four-Ball Load-Carrying (EP) Test] In accordance with ASTM D 2596, a Shell Four-Ball Load-Carrying (EP) test was conducted under the following test conditions, measuring the maximum non-seizure load (LNL) and the fusion load (WL), and calculating the load-wear index (LWI). The larger the values ​​of the maximum non-seizure load (LNL) and the fusion load (WL), the better the extreme-pressure properties. Note that if the maximum non-seizure load (LNL) is 618 N or more and the fusion load (WL) is 1,961 N or more, it was determined that the extreme-pressure properties were good. Furthermore, the larger the value of the load-wear index (LWI), the better the load-carrying properties. If the load-wear index (LWI) was 300 N or more, it was determined that the load-carrying properties were good. - Test Conditions - Rotational speed: 1,800 rpm - Sample temperature: Room temperature (25±5°C)

[0175] [Serious Friction and Wear (SRV) Test] A serious Friction and Wear (SRV) test was conducted in accordance with ASTM D5706 under the following test conditions. Specifically, the load was increased by 100 N, and then the specimen was slid for 2 minutes each time, and the load (seizure load) at which seizure occurred and the coefficient of friction increased significantly was measured. The larger the seizure load, the better the seizure resistance. Note that if the seizure load was more than 1,500 N, the seizure resistance was judged to be good. - Test Conditions - Ball: SUJ2 (diameter: 10 mm) Disk: SUJ2 Frequency: 50 Hz Amplitude: 1.5 mm Temperature: 80°C

[0176] [Shell Four-Ball Wear Test] A Shell four-ball wear test was conducted in accordance with ASTM D2266-2001 under the following test conditions, and the wear scar diameter at the metal ball contact point was measured. A wear scar diameter of 0.55 mm or less was determined to indicate good wear resistance. - Test conditions - Test ball: steel ball (diameter 1 / 2 inch) coated with grease composition; Rotation speed: 1,200 rpm; Load: 392 N; Test time: 60 minutes; Test temperature: 75°C

[0177] The compositions, physical properties, and evaluation results of the grease compositions of Examples 1 to 3 and Comparative Examples 1 and 2 are shown in Table 1.

[0178]

[0179] As shown in Table 1, the grease compositions of Examples 1 to 3 achieved favorable results in the Shell four-ball load-carrying (EP) test at room temperature (25±5°C), the vibration friction and wear (SRV) test at 80°C, and the Shell four-ball wear test at 75°C. This demonstrates that the grease compositions of Examples 1 to 3 are capable of achieving sufficient extreme pressure and load-carrying properties over a wide range of temperature environments, regardless of the temperature of the lubrication location. Furthermore, the grease compositions of Examples 1 to 3 have sufficiently small differences between their worked and unworked penetrations, ranging from 8 to 11, which means that they are less likely to soften when sheared by blending, and are also excellent at suppressing leakage of the grease compositions due to the low viscosity of the base oil.

[0180] DESCRIPTION OF SYMBOLS 1 Grease manufacturing device 2 Container body 3 Rotor 4 Inlet section 4A, 4B Solution inlet pipe 5 Retention section 6 First uneven section 7 Second uneven section 8 Discharge section 9 First uneven section on container body side 10 Second uneven section on container body side 11 Discharge port 12 Rotating shaft 13 First uneven section of rotor 13A Concave section 13B Convex section 14 Second uneven section of rotor 15 Scraper A1, A2 Gap

Claims

1. A grease composition containing a base oil (A), a urea-based thickener (B), a phosphate ester amine salt (C), a sulfur-based extreme pressure agent (D), zinc dithiophosphate (E), melamine cyanurate (F), and an organic molybdenum compound (G), The base oil (A) has a kinematic viscosity of 288 mmHg at 40°C. ２ / s ~ 506mm ２ High viscosity poly-α-olefin (PAO) (A1) with a viscosity of 0.5 / s, kinematic viscosity at 40°C is 61.2–74.8 mmHg. ２ A mixed base oil containing low viscosity poly-α-olefin (PAO) (A2) and ester-based synthetic oil, A grease composition wherein the particles containing the urea-based thickener (B) in the grease composition satisfy the following requirement (I). Requirement (I): The arithmetic mean particle diameter based on area, when the particles are measured by laser diffraction / scattering, is 2.0 μm or less.

2. The grease composition according to claim 1, wherein the particles containing the urea-based thickener (B) in the grease composition further satisfy the following requirement (II). Requirement (II): The specific surface area of ​​the particle measured by laser diffraction / scattering is 0.5 × 10 ５ cm ２ / cm ３ That's all.

3. The grease composition according to claim 1 or 2, wherein the ester-based synthetic oil comprises a diester-based oil (A3) and an aromatic ester-based oil (A4).

4. The grease composition according to claim 3, wherein the content ratio [(A3) / (A4)] of the diester oil (A3) to the aromatic ester oil (A4) is 1 to 12 by mass.

5. The grease composition according to claim 1 or 2, further comprising one or more additives selected from the group consisting of antioxidants, viscosity modifiers, and rust inhibitors.

6. The grease composition according to claim 1 or 2, wherein the content ratio [(C) / (E)] of the phosphate ester amine salt (C) to the zinc dithiophosphate (E) is 0.5 to 1.5 by mass.

7. The grease composition according to claim 1 or 2, wherein the content ratio of the melamine cyanurate (F) to the organic molybdenum compound (G) [(F) / (G)] is 0.1 to 1.0 by mass ratio.

8. The grease composition according to claim 1 or 2, wherein the miscible consistency at 25°C is 250 to 430.

9. A grease composition according to claim 1 or 2, used for lubricating the lubrication parts of a speed reducer or speed increaser.

10. The grease composition according to claim 9, wherein the reduction gear is a harmonic drive gear.

11. A lubrication method for lubricating a lubrication part of a harmonic drive gear using the grease composition described in claim 1 or 2.

12. (1) A step of synthesizing a urea-based thickener (B) in a base oil (A), and (2) A method for producing a grease composition, comprising the step of blending a phosphate ester amine salt (C), a sulfur-based extreme pressure agent (D), zinc dithiophosphate (E), melamine cyanurate (F), and an organic molybdenum compound (G) into the compound from step (1), The base oil (A) has a kinematic viscosity at 40°C of 288 mm ２ / s to 506 mm ２ / s high-viscosity poly-α-olefin (PAO) (A1), a low-viscosity poly-α-olefin (PAO) (A2) having a kinematic viscosity at 40°C of 61.2 to 74.8 mm ２ / s, and an ester-based synthetic oil, which is a mixed base oil, A method for producing a grease composition, wherein the particles containing the urea-based thickener (B) in the grease composition satisfy the following requirement (I). Requirement (I): The arithmetic mean particle diameter based on area, when the particles are measured by laser diffraction / scattering, is 2.0 μm or less.