Grease composition

Abstract

The present invention provides a grease composition which contains (A) a base oil, (B) a urea-based thickening agent and (C) a fat or oil curing agent, wherein: particles containing the urea-based thickening agent (B) in the grease composition satisfy requirement (I); the grease composition is liquefied if heated to a certain temperature or higher, and is returned to a solid state if cooled to room temperature after being heated to the certain temperature or higher; and the grease composition is highly responsive to the application of a shear stress, and is likely to be softened when a shear stress is applied thereto. Requirement (I): The area-based arithmetic mean particle diameter of the particles is 2.0 μm or less as determined by a laser diffraction / scattering method.

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, and therefore have been widely used for the lubrication of various sliding parts in automobiles, electrical equipment, industrial machinery, and other machinery.

[0003] Furthermore, with the recent increase in awareness of energy saving, low torque properties are also being sought for grease compositions. For example, Patent Document 1 proposes a grease composition containing a base oil, a thickener, and an amino acid-based gelling agent as a grease composition having low torque properties. Furthermore, Patent Document 2 proposes a grease composition containing a saturated fatty acid triglyceride as a base oil and a glycerin fatty acid ester as a thickener as a grease composition having low torque properties.

[0004] JP 2010-209129 A JP 2017-036363 A

[0005] Incidentally, for example, in factory robots, filling of unit-type devices such as reducers, servo motors, controllers, and torches with grease compositions is mainly carried out by drum pumping, in which the grease composition contained in a drum is filled via a hose using a pump. However, drum pumping is a method of supplying and filling the grease composition in its characteristic solid state, and therefore, when injecting the grease composition into the unit-type devices, it is difficult for the grease composition to reach the gaps and corners of the device. Furthermore, in order to inject an appropriate amount of grease composition without insufficient filling, it is necessary to supply an amount of grease composition that is in excess of the amount that should actually be filled, which results in a lot of waste.

[0006] Therefore, the present inventors have conducted extensive research to solve the above problems and have come up with the following idea: Namely, the present inventors have come up with the idea that by heating a solid grease composition to a certain temperature or higher to liquefy it, immersing a device in the liquefied grease composition, removing it and returning it to room temperature to return the grease composition to its solid state, it is possible to fill the device with an appropriate amount of solid grease composition without waste while spreading the solid grease composition throughout the gaps in the device.

[0007] Therefore, in order to realize the above idea, the present inventors conducted extensive research, focusing on grease compositions containing a grease hardener, as described in Patent Documents 1 and 2. However, it was found that grease compositions containing a grease hardener have insufficient responsiveness to the application of shear stress and are difficult to soften when shear stress is applied. As described above, there has been increasing awareness of energy saving in recent years. Therefore, grease compositions are required to have high responsiveness to the application of shear stress and to easily soften when shear stress is applied.

[0008] Therefore, an object of the present invention is to provide a grease composition that liquefies when heated to a certain temperature or above, but returns to a solid state when heated to a certain temperature or above and then returned to room temperature, and that is highly responsive to the application of shear stress and easily softens when shear stress is applied.

[0009] In the course of intensive research to solve the above-mentioned problems, the present inventors came up with the idea of ​​using a combination of an oil-based hardening agent and a urea-based thickener. Furthermore, the present inventors also focused on the particle size of particles containing the urea-based thickener and conducted extensive research. As a result, they found that a grease composition containing an oil-based hardening agent and having an area-based arithmetic mean particle size measured by a laser diffraction / scattering method adjusted to a predetermined range can solve the above-mentioned problems, thereby completing the present invention.

[0010] That is, the present invention provides the following [1]: [1] A grease composition containing a base oil (A), a urea-based thickener (B), and an oil / fat hardener (C), 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.

[0011] According to the present invention, it is possible to provide a grease composition that liquefies when heated to a certain temperature or above, but returns to a solid state when heated to a certain temperature or above and then returned to room temperature, and that is highly responsive to the application of shear stress and easily softens when shear stress is applied.

[0012] Fig. 1 is a schematic cross-sectional view of a grease production apparatus used in one embodiment of the present invention. Fig. 2 is a schematic cross-sectional view of a first concave-convex portion on the container body side of the grease production apparatus in Fig. 1, taken in a direction perpendicular to the rotation axis. Fig. 3 is a schematic cross-sectional view of a grease production apparatus used in Comparative Example 2. Fig. 4 shows rheometer measurement results for Examples 1 and 2 and Comparative Example 1. Fig. 5 shows rheometer measurement results for Comparative Examples 2 to 4.

[0013] In this specification, for preferred numerical ranges (e.g., ranges of content, etc.), the lower limit and upper limit values ​​described in stages can be independently combined. For example, the description "preferably 10 to 90, more preferably 30 to 60" can be combined with the "preferable lower limit (10)" and the "more preferable upper limit (60)" to form "10 to 60." Furthermore, in this specification, the numerical values ​​in the examples are numerical values ​​that can be used as upper or lower limits.

[0014] In the present invention, normal temperature means 20°C to 30°C. In the present invention, room temperature means 25°C. Furthermore, in the present invention, heating means heating to a temperature higher than normal temperature, specifically, heating to 60°C to 80°C.

[0015] [Grease Composition] The grease composition of the present invention is a grease composition containing a base oil (A), a urea-based thickener (B), and a fat / oil hardener (C), in which 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. In the following description, the "base oil (A)," the "urea-based thickener (B)," and the "fat / oil hardener (C)" will also be referred to as "component (A)," "component (B)," and "component (C)," respectively.

[0016] In the grease composition of one embodiment of the present invention, the total content of components (A), (B), and (C) is preferably 60% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, and even more preferably 90% by mass or more, based on the total amount (100% by mass) of the grease composition. Furthermore, it is usually 100% by mass or less, preferably less than 100% by mass, more preferably 99% by mass or less, and even more preferably 98% by mass or less. The grease composition of one embodiment of the present invention may contain components other than components (A), (B), and (C) as long as the effects of the present invention are not impaired.

[0017] <Requirement (I)> In the grease composition of the present invention, the 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 becomes one that softens when shear stress is applied.

[0018] 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. When the grease composition contains an additive other than the urea-based thickener (B), the particle size specified by the above requirement (I) can be obtained by measuring a grease composition prepared under the same conditions but without the additive by the laser diffraction / scattering method. However, when the additive is liquid at room temperature (25°C) or dissolves in the base oil (A), the grease composition containing the additive may also be used as the measurement target.

[0019] Urea-based thickeners (B) are typically obtained by reacting an isocyanate compound with a monoamine. However, because the reaction rate is extremely 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 when the particle diameter specified in the above requirement (I) exceeds 2.0 μm, the grease composition has insufficient responsiveness to shear stress and is difficult to soften even when shear stress is applied. On the other hand, by reducing the particle diameter specified in the above requirement (I) to 2.0 μm or less, a grease composition is obtained that is highly responsive to shear stress and easily softens when shear stress is applied. This effect is presumably due to the fact that by reducing the particle diameter specified in the above requirement (I) to 2.0 μm or less, the grease itself is composed of fine bundles with a narrow distribution of thickness and length, which makes it more likely to change to liquid-like properties with small strain. Furthermore, by miniaturizing the particle diameter specified in the above requirement (I) to 2.0 μm or less, the retention force of the base oil (A) by the particles is improved. Therefore, it is presumed that the effect of spreading the base oil (A) well and, concomitantly, spreading the oil hardener (C) well to the lubricated parts is improved. From the above viewpoint, in the grease composition of one embodiment of the present invention, the particle diameter 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.

[0020] <Requirement (II)> Here, it is preferable that the grease composition of one embodiment of the present invention further satisfies 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 ３That's all. The specific surface area specified in the above requirement (II) is a secondary index that indicates 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 the above requirement (I) and also the above requirement (II), the state of fineness of particles containing the urea-based thickener (B) in the grease composition is better, and the presence of large particles (lumps) is further suppressed. Therefore, it is possible to obtain a grease composition that is more responsive to shear stress and more likely to soften when shear stress is applied. From the above viewpoint, the specific surface area specified in the above requirement (II) is preferably 0.7 × 10 ５ cm ２ / cm ３ 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.

[0021] 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).

[0022] <Base oil (A)> As the base oil (A) contained in the grease composition of the present invention, any base oil conventionally used as a lubricating base oil can be used without particular limitation, and examples thereof include one or more types selected from mineral oils and synthetic oils.

[0023] Examples of mineral oils include distillates obtained by atmospheric or vacuum distillation of paraffinic crude oil, intermediate crude oil, or naphthenic crude oil, and refined oils obtained by refining these distillates according to conventional methods. Examples of refining methods include solvent dewaxing, hydroisomerization, hydrofinishing, clay treatment, etc. One type of mineral oil may be used alone, or two or more types may be used in combination.

[0024] As the mineral oil, for example, a base oil of Group II or III in the base oil category of the American Petroleum Institute (API) can be used. Also suitable is a GTL (Gas To Liquids) base oil obtained by isomerizing wax produced from natural gas by the Fischer-Tropsch process or the like.

[0025] Furthermore, bright stock, for example, can be used as the mineral oil. Bright stock refers to a high-viscosity base oil produced from the vacuum distillation residue of crude oil through a process selected from solvent deasphalting, solvent extraction, solvent dewaxing, hydrorefining, etc. The crude oil used to produce bright stock is not particularly limited, and examples thereof include paraffinic crude oil and naphthenic crude oil.

[0026] In the grease composition of one embodiment of the present invention, the mineral oil content is preferably 60% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, and even more preferably 90% by mass or more, based on the total amount (100% by mass) of base oil (A), and is usually 100% by mass or less, preferably less than 100% by mass, more preferably 99% by mass or less, and even more preferably 98% by mass or less.

[0027] Examples of synthetic oils include hydrocarbon oils, aromatic oils, ester oils, ether oils, and synthetic oils obtained by isomerizing wax (GTL wax) produced by the Fischer-Tropsch process, etc. One type of synthetic oil may be used alone, or two or more types may be used in combination.

[0028] Examples of hydrocarbon oils include normal paraffin, isoparaffin, polybutene, polyisobutylene, 1-decene oligomer, 1-decene and ethylene co-oligomer and other poly-α-olefins (PAO), and hydrogenated products thereof.

[0029] Examples of aromatic oils include alkylbenzenes such as monoalkylbenzenes and dialkylbenzenes; alkylnaphthalenes such as monoalkylnaphthalenes, dialkylnaphthalenes, and polyalkylnaphthalenes; and the like.

[0030] Examples of ester oils include diester oils such as dibutyl sebacate, di-2-ethylhexyl sebacate, dioctyl adipate, diisodecyl adipate, ditridecyl adipate, ditridecyl glutarate, and methyl acetyl ricinoleate; aromatic ester oils such as trioctyl trimellitate, tridecyl trimellitate, and tetraoctyl pyromellitate; polyol ester oils such as trimethylolpropane caprylate, trimethylolpropane bellargonate, pentaerythritol-2-ethylhexanoate, and pentaerythritol bellargonate; and complex ester oils such as oligoesters of polyhydric alcohols and mixed fatty acids of dibasic and monobasic acids.

[0031] 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.

[0032] The base oil (A) of this embodiment preferably has a kinematic viscosity at 40°C of 10 mm ２ / s or more, more preferably 25 mm ２ / s or more, more preferably 40 mm ２ The kinematic viscosity of the base oil (A) at 40°C is 40 mm / s or more. ２ The base oil (A) of this embodiment preferably has a kinematic viscosity at 40°C of 415 mm / s or more. ２ / s or less, more preferably 300 mm ２ / s or less, more preferably 200 mm ２ / s or less, and even more preferably 100 mm ２ / s or less, and even more preferably 80 mm ２ The kinematic viscosity of the base oil (A) at 40°C is 80 mm / s or less. ２ The effect of the present invention is more easily achieved when the value is equal to or less than 100 mm / s. The upper and lower limits of these numerical ranges can be arbitrarily combined. Specifically, it is preferably 10 to 300 mm ２ / s, more preferably 25 to 200 mm ２ / s, more preferably 40 to 100 mm ２ The base oil (A) used in one embodiment of the present invention may be a mixed base oil obtained by combining a high-viscosity base oil and a low-viscosity base oil to adjust the kinematic viscosity within the above range.

[0033] The base oil (A) of this embodiment preferably has a kinematic viscosity at 100°C of 1.0 to 50.0 mmHg, from the viewpoint of more easily achieving the effects of the present invention. ２ / s, more preferably 5.0 to 20.0 mm ２ / s.

[0034] 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.

[0035] In the grease composition of one embodiment of the present invention, the content of 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, and still more preferably 62 mass% or more, and is preferably 98.5 mass% or less, more preferably 97 mass% or less, even more preferably 95 mass% or less, still more preferably 93 mass% or less, even more preferably 92 mass% or less, even more preferably 90 mass% or less, and even more preferably 85 mass% or less.

[0036] <Urea-based thickener (B)> The urea-based thickener (B) contained in the grease composition of the present invention may be any compound having a urea bond, but a diurea compound having two urea bonds is preferred, and a diurea compound represented by the following general formula (b1) is more preferred. 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.

[0037] 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.

[0038] 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.

[0039] 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, and even more preferably 40 / 60 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 the general formula (b1). The values ​​of the requirements (a) and (b) above represent average values ​​relative to the total amount of the compounds represented by the general formula (b1) contained in the grease composition. By using a compound represented by the general formula (b1) that satisfies the requirements (a) and (b), it is easy to obtain a grease composition with excellent low-temperature properties. The values ​​of X, Y, and Z can be calculated from the molar equivalents of each amine used as a raw material.

[0040] Examples of the monovalent saturated chain hydrocarbon group include linear or branched alkyl groups having 6 to 24 carbon atoms, and specific examples thereof include a hexyl group, a heptyl group, an octyl group, a nonyl group, a decyl group, an undecyl group, a dodecyl group, a tridecyl group, a tetradecyl group, a pentadecyl group, a hexadecyl group, a heptadecyl group, an octadecyl group, an octadecenyl group, a nonadecyl group, and an icosyl group. 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.

[0041] Examples of the monovalent saturated alicyclic hydrocarbon group include cycloalkyl groups such as a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, and a cyclononyl group; and cycloalkyl groups substituted with an alkyl group having 1 to 6 carbon atoms, such as a methylcyclohexyl group, a dimethylcyclohexyl group, an ethylcyclohexyl group, a diethylcyclohexyl group, a propylcyclohexyl group, an isopropylcyclohexyl group, a 1-methyl-propylcyclohexyl group, a butylcyclohexyl group, a pentylcyclohexyl group, a pentyl-methylcyclohexyl group, and a hexylcyclohexyl group (preferably a cyclohexyl group substituted with an alkyl group having 1 to 6 carbon atoms).

[0042] 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).

[0043] 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.

[0044] 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.

[0045] In the grease composition of one embodiment of the present invention, the content of component (B) is, based on the total amount (100 mass%) of the grease composition, preferably 0.5 mass% or more, more preferably 0.6 mass% or more, even more preferably 0.7 mass% or more, even more preferably 0.8 mass% or more, and even more preferably 1.0 mass% or more. Furthermore, the content of component (B) is, based on the total amount (100 mass%) of the grease composition, preferably 15.0 mass% or less, more preferably 13.0 mass% or less, even more preferably 10.0 mass% or less, even more preferably 8.0 mass% or less, and even more preferably 6.0 mass% or less. When the content of component (B) is within the above range, it is easy to adjust the worked penetration of the resulting grease composition to an appropriate range. On the other hand, when the content of component (B) is 20.0 mass% or less, the grease composition is easily liquefied when heated (in other words, more fluid), resulting in a grease composition that is easy to handle when immersing an apparatus in the grease composition and filling the apparatus with the grease composition.

[0046] <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:

[0047] 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.

[0048] 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.

[0049] 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 grease raw materials are 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 materials inside the container body 2. This produces 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.

[0050] 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.

[0051] 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.

[0052] 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.

[0053] 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.

[0054] 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.

[0055] 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.

[0056] 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.

[0057] 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.

[0058] 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.

[0059] 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.

[0060] 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.

[0061] 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.

[0062] 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.

[0063] 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.

[0064] 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.

[0065] 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. 1 is provided with scrapers 15, the apparatus may not be provided with scrapers 15, or may be provided with scrapers 15 intermittently.

[0066] To produce a grease containing a urea-based thickener (B) using the grease production apparatus 1, the above-mentioned grease raw materials, solutions α and 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). Then, even when the oil hardener (C) and the additive (D) are blended into the grease base material thus obtained, the urea-based thickener (B) in the grease composition can be made fine so as to satisfy the above requirement (I) and further the above requirement (II).

[0067] 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 －１ More preferably, 10４ s －１ and usually 10 ７ s －１ The following is the result.

[0068] 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.

[0069] 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.

[0070] 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.

[0071] 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.

[0072]

[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.

[0073] <Oil Hardener (C)> The grease composition of the present invention contains an oil hardener (C) in addition to components (A) and (B). By including the oil hardener (C) in the grease composition of the present invention, it is possible to obtain a grease composition that is solid at room temperature and liquefies when heated. Furthermore, it is possible to improve the filling (adhesion) of the device. In the present invention, an oil hardener is a substance that, when added to and dissolved in liquid oils and fats, can thicken, solidify, and / or sol-gel the oils and fats at room temperature, and has the property of solidifying the grease composition at room temperature. Furthermore, the above-mentioned "liquefied" refers to a state in which the viscosity at 70°C is about 5,000 mPa s or less.

[0074] Examples of the oil / fat hardener (C) include glycerin fatty acid esters (C1), amino acid-based oil gelling agents (C2), amine-based hardeners (C3), and sorbitol-based hardeners (C4). These may be used alone or in combination of two or more. Among these, it is preferable to use glycerin fatty acid esters (C1) from the viewpoint of the effects of the present invention and ease of availability.

[0075] -Glycerin Fatty Acid Ester (C1)- Examples of the glycerin fatty acid ester (C1) include glycerin fatty acid esters and polyglycerin fatty acid esters.

[0076] The polyglycerol fatty acid ester contains fatty acids and polyglycerol as constituent components. It is preferable that, of all the constituent fatty acids of the polyglycerol fatty acid ester (hereinafter referred to as "constituent fatty acids"), linear fatty acids having 16 to 18 carbon atoms account for 45% or more in terms of the number of molecules.

[0077] The polyglycerin constituting the polyglycerin fatty acid ester preferably has an average degree of polymerization based on the hydroxyl value of 10 or more. More preferably, the average degree of polymerization of the polyglycerin is 20 or more, even more preferably 30 or more, and still more preferably 40 or more.

[0078] The average degree of polymerization of polyglycerol based on its hydroxyl value is a value calculated by end group analysis. The hydroxyl value used in calculating the average degree of polymerization by end group analysis can be calculated in accordance with "Standard Methods for Analysis of Fats, Oils and Related Compounds (I) 1996 Edition, Established by the Japan Oil Chemists' Society."

[0079] The esterification rate of the polyglycerol fatty acid ester is preferably 70% or more, more preferably 80% or more, and even more preferably 90% or more.

[0080] The esterification rate is a value calculated by the following formula: esterification rate (%) = (M / (n+2)) × 100, where n is the average degree of polymerization of a polyglycerol calculated from the hydroxyl value obtained by terminal group analysis, n is the number of hydroxyl groups in the polyglycerol, and M is the number of moles of fatty acid added to the polyglycerol.

[0081] In the present invention, the polyglycerol fatty acid ester can be one produced according to a conventional method, and more specifically, one produced by charging the above-mentioned components in a composition that satisfies the above-mentioned conditions, adding a catalyst such as sodium hydroxide, and subjecting the mixture to an esterification reaction under normal pressure or reduced pressure can be used. In addition, in the present invention, commercially available polyglycerol fatty acid esters can be used, and for example, TAISET AD (manufactured by Taiyo Kagaku Co., Ltd.), TAISET 50 (manufactured by Taiyo Kagaku Co., Ltd.), Ryoto Polyglycerol B-100D (manufactured by Mitsubishi Chemical Corporation), etc. can be suitably used.

[0082] In the grease composition of the present invention, the melting point of the oil / fat curing agent (C) is preferably 50°C or higher, more preferably 60°C or higher, from the viewpoint of being solid at room temperature and liquefying when heated. The melting point of the oil / fat curing agent (C) is higher than room temperature, specifically, preferably 20°C or higher than room temperature, more preferably 30°C or higher than room temperature. The melting point of the oil / fat curing agent (C) is preferably 100°C or lower, more preferably 80°C or lower. In this specification, the melting point of the oil / fat curing agent (C) means a value measured in accordance with JIS K0064.

[0083] In the grease composition of the present invention, the content of the oil / fat hardener (C) is preferably 0.1 to 10.0% by mass, more preferably 0.5 to 8.0% by mass, and even more preferably 1.0 to 6.0% by mass based on the total amount (100% by mass) of the grease composition, from the viewpoint of making the grease composition solid at room temperature and liquefied when heated.

[0084] The content ratio of the urea-based thickener (B) to the oil / fat hardener (C) [(B) / (C)] is preferably 0.3 to 10, more preferably 0.4 to 5, and even more preferably 0.5 to 3 by mass, from the viewpoint of being solid at room temperature, liquefying when heated, and softening when shear stress is applied.

[0085] <Additive (D)> The grease composition of one embodiment of the present invention may contain an additive (D) other than component (B) and component (C) that is typically blended into grease, as long as the effects of the present invention are not impaired. Examples of additive (D) include extreme pressure agents, antioxidants, rust inhibitors, dispersants, and metal deactivators. Each of the additives (D) may be used alone, or two or more may be used in combination.

[0086] Examples of the extreme pressure agent include one or more selected from organometallic extreme pressure agents, sulfur-based extreme pressure agents, phosphorus-based extreme pressure agents, and sulfur-phosphorus-based extreme pressure agents.

[0087] As the organometallic extreme pressure agent, for example, one or more compounds selected from organomolybdenum compounds such as molybdenum dialkyldithiocarbamate (MoDTC) and molybdenum dialkyldithiophosphate (MoDTP), and organozinc compounds such as zinc dialkyldithiocarbamate (ZnDTC) and zinc dialkyldithiophosphate (ZnDTP) can be used.

[0088] As the sulfur-based extreme pressure agent, for example, one or more selected from sulfurized fats and oils, sulfurized fatty acids, sulfurized esters, sulfurized olefins, monosulfides, polysulfides, dihydrocarbyl polysulfides, thiadiazole compounds, alkylthiocarbamoyl compounds, thiocarbamate compounds, thioterpene compounds, and dialkylthiodipropionate compounds can be used.

[0089] Examples of phosphorus-based extreme pressure agents that can be used include 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; acidic phosphite esters such as monoalkyl acid phosphite, dialkyl acid phosphite, monoalkenyl acid phosphite, and dialkenyl acid phosphite; and amine salts thereof.

[0090] As the sulfur-phosphorus based extreme pressure agent, for example, one or more selected from monoalkylthiophosphate, dialkyldithiophosphate, trialkyltrithiophosphate, and amine salts thereof, and zinc dialkyldithiophosphate (Zn-DTP) can be used.

[0091] Examples of antioxidants include amine-based antioxidants such as diphenylamine compounds and naphthylamine compounds, and phenol-based antioxidants such as monocyclic phenol compounds and polycyclic phenol compounds. Examples of rust inhibitors include carboxylic acid-based rust inhibitors such as alkenyl succinic acid polyhydric alcohol esters, zinc stearate, thiadiazole and its derivatives, and benzotriazole and its derivatives. Examples of dispersants include ashless dispersants such as succinimide and boron-based succinimide. Examples of metal deactivators include benzotriazole-based compounds.

[0092] In the grease composition of one embodiment of the present invention, the content of the additive (D) is set appropriately depending on the type of additive, but each additive is independently present in an amount of 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.

[0093] <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 220 to 430, more preferably 240 to 360, even more preferably 250 to 350, and still more preferably 255 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).

[0094] (Worked Penetration) From the viewpoint of softening when shear stress is applied, the worked penetration at 25°C of the grease composition of one embodiment of the present invention is preferably 220 or more, more preferably 250 or more, even more preferably 300 or more, still more preferably 330 or more, and is preferably 500 or less, more preferably 450 or less, even more preferably 440 or less, and still more preferably 430 or less. 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).

[0095] (Difference between Worked Penetration and Unworked Penetration) In one embodiment of the grease composition of the present invention, the difference obtained by subtracting the unworked penetration value from the worked penetration value at 25°C is, from the viewpoint of fluidity due to softening when shear stress is applied, preferably 10 to 150, more preferably 30 to 130, even more preferably 40 to 120, and still more preferably 50 to 110. The larger the difference obtained by subtracting the unworked penetration value from the worked penetration value, the more the grease composition is sheared upon mixing, and the softer the grease composition becomes.

[0096] (Dropping Point) From the viewpoint of grease fluidity, the dropping point of the grease composition of one embodiment of the present invention is preferably 50 to 300, more preferably 120 to 280, even more preferably 150 to 270, still more preferably 180 to 260, and even more preferably 190 to 250. In this specification, the dropping point of the grease composition means a value measured in accordance with JIS K2220:2013 (Clause 8).

[0097] (Solid at room temperature, liquefied when heated) It can be confirmed that the grease composition of one embodiment of the present invention is solid at room temperature and liquefied when heated, using the method described in the examples below.

[0098] (Rheological Properties) The grease composition of one embodiment of the present invention was tested to determine whether the strain was 1×10 －３ % to 1 x 10 ３ %, the storage modulus is measured against strain, and the absolute value of the maximum slope at which the storage modulus decreases is calculated, thereby enabling evaluation of the rheological properties (in the present invention, the property of softening and becoming fluid due to shear). The larger the absolute value of the slope, the higher the responsiveness to strain (shear stress) of the grease composition, and the more likely it is to soften when shear stress is applied.

[0099] <Method for Producing Grease Composition> The grease composition of the present invention can be produced by mixing a grease (base grease) containing a base oil (A), a urea-based thickener (B), an oil-hardening agent (C), and, if necessary, an additive (D). For example, the grease composition can be produced by mixing the base oil (A) and the grease (base grease) containing the urea-based thickener (B), adding and mixing the additive (D) if necessary, allowing the mixture to cool naturally to about 70°C to 80°C, and then adding and mixing the oil-hardening agent (C).

[0100] <Uses of Grease Composition> The grease composition of the present invention is solid at room temperature, liquefies when heated, and softens when subjected to shear stress. Therefore, the grease composition of one embodiment of the present invention can be used for lubrication of bearings, sliding parts, gears, joints, and other lubricating parts of devices requiring such properties. More specifically, it is preferably used for bearing parts of hub units, electric power steering, electric drive motor flywheels, ball joints, wheel bearings, spline parts, constant velocity joints, clutch boosters, servo motors, blade bearings, or generators. Furthermore, the grease composition of the present invention can be suitably used in fields such as automobiles, office equipment, machine tools, wind turbines, construction equipment, agricultural machinery, and industrial robots. Lubricated parts in automotive equipment for which the grease composition of the present invention can be suitably used include, for example, bearing parts in devices such as radiator fan motors, fan couplings, alternators, idler pulleys, hub units, water pumps, power windows, wipers, electric power steering, drive electric motor flywheels, ball joints, wheel bearings, spline parts, and constant velocity joints; bearing parts in devices such as door locks, door hinges, and clutch boosters; bearing parts, gear parts, and sliding parts of servo motors, blade bearings, or generators. Lubricated parts in office equipment for which the grease composition of the present invention can be suitably used include, for example, fuser rolls in devices such as printers, and bearings and gear parts in devices such as polygon motors. Lubricated parts in machine tool equipment for which the grease composition of the present invention can be suitably used include, for example, bearing parts in reducers of spindles, servo motors, and machine tool robots. Lubricated parts in wind turbine equipment for which the grease composition of the present invention can be suitably used include, for example, bearing parts in blade bearings and generators. Parts to be lubricated in equipment in the fields of construction or agricultural machinery, for which the grease composition of the present invention can be suitably used, include, for example, bearing parts such as ball joints and spline parts, gear parts, and sliding parts.The grease composition of the present invention can also be suitably used in reducers used in industrial robots and speed-up gears used in wind power generation facilities. Examples of such reducers and speed-up gears include reducers made of gear mechanisms and speed-up gears made of gear mechanisms. However, the application of the grease composition of one embodiment of the present invention is not limited to reducers made of gear mechanisms and speed-up gears made of gear mechanisms, but can also be applied to, for example, traction drives. Examples of reducers include RV type, harmonic type, and cyclo type, and the grease composition can be suitably used in any of these. Another embodiment of the present invention provides a device, preferably a reducer or speed-up gear, having the grease composition of the present invention in a lubrication site such as a bearing, sliding part, gear part, or joint. Another embodiment of the present invention provides a lubrication method for lubricating a lubrication site (e.g., a bearing, sliding part, gear part, or joint) of a device such as a reducer or speed-up gear with the grease composition of the present invention.

[0101] According to one aspect of the present invention, the following items [1] to [9] are provided. [1] A grease composition containing a base oil (A), a urea-based thickener (B), and an oil / fat hardener (C), 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. [2] The grease composition according to item [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 content of the oil / fat hardener (C) is 0.1 mass % to 10 mass % based on the total amount of the grease composition. [4] The grease composition according to any one of [1] to [3] above, wherein the melting point of the oil / fat hardener (C) is 100°C or lower. [5] The grease composition according to any one of [1] to [4] above, wherein the content of the urea-based thickener (B) is 1.0 mass % to 15.0 mass % based on the total amount of the grease composition. [6 ... kinematic viscosity at 40°C of the base oil (A) is 10 mm ２ / s~80mm ２ [7] The grease composition according to any one of [1] to [5] above, having a worked penetration of 300 to 500. [8] The grease composition according to any one of [1] to [7] above, which is used to lubricate lubricated parts of a reducer or a speed-up gear. [9] A lubrication method, comprising lubricating lubricated parts of a reducer or a speed-up gear with the grease composition according to any one of [1] to [8] above.

[0102] The present invention will be specifically described with reference to the following examples, but the present invention is not limited to these examples.

[0103] [Various physical properties] The methods for measuring various physical properties were as follows. (1) 40°C kinematic viscosity, 100°C kinematic viscosity, and viscosity index of base oil (A) Measured and calculated in accordance with JIS K2283:2000. (2) Melting point of oil / fat curing agent (C) Measured in accordance with JIS K0064. (3) Unworked penetration (1 / 4) of grease composition Measured at 25°C in accordance with JIS K2220:2013 (Clause 7). (4) Worked penetration (1 / 4) of grease composition Measured at 25°C in accordance with JIS K2220:2013 (Clause 7). (5) Difference between worked and unworked penetration of grease composition The difference was calculated by subtracting the unworked penetration value in (3) from the worked penetration value in (4). (6) Dropping point of grease composition: Measured in accordance with JIS K2220:2013 (Clause 8).

[0104] [Raw Materials] In Examples 1 and 2 and Comparative Examples 1 to 4, the base oils (A) and oil-hardening agents (C) used as raw materials for preparing the grease compositions were as follows.

[0105] <Base oil (A)> Base oil (A1): a base oil classified as Group III in the API classification (kinematic viscosity at 40°C: 19 mm ２ / s, 100℃ kinematic viscosity: 4.2mm ２ / s, viscosity index: 126) Base oil (A2): Bright stock (40°C kinematic viscosity: 409 mm ２ / s, 100℃ kinematic viscosity: 30.9mm ２ / s, viscosity index: 107) <Oil and fat hardener (C)> Glycerin fatty acid ester (C1): Glycerin fatty acid ester (trade name: TAISET AD, manufactured by Taiyo Kagaku Co., Ltd., melting point: 60°C)

[0106] Example 1 (1) Synthesis of Urea Grease Solution α was prepared by adding 2.47 parts by mass of diphenylmethane-4,4'-diisocyanate (MDI) to 48.00 parts by mass of base oil (A), a mixed base oil of base oil (A1) and base oil (A2) heated to 70°C. Separately, solution β was prepared by adding 1.51 parts by mass of cyclohexylamine and 1.03 parts by mass of octadecylamine (stearylamine) to 47.00 parts by mass of base oil (A), a mixed base oil of base oil (A1) and base oil (A2) heated to 70°C. Then, 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. Thereafter, this mixture was heated to 160°C using the stirring device shown in FIG. 3, stirred for 1 hour, and then homogenized by roll mill treatment 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) at this time was 10,500 s －１The 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 (b1) is 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 cyclohexylamine 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 In the above (1), the urea grease (b1) discharged from the grease production apparatus 1 shown in FIG. 1 was stirred and then allowed to cool naturally to 70°C. Next, the glycerin fatty acid ester (C1) was added to the urea grease (b1) that had been allowed to cool naturally to 70°C in the amount shown in Table 1 and mixed, thereby obtaining the grease composition of Example 1.

[0107] Example 2, Comparative Example 1 Grease compositions of Example 2 and Comparative Example 1 were obtained in the same manner as the grease composition of Example 1, except that the blending amounts were changed as shown in Table 1.

[0108] Comparative Example 2 (1) Synthesis of Urea Grease Solution α was prepared by adding 2.47 parts by mass of diphenylmethane-4,4'-diisocyanate (MDI) to 48.00 parts by mass of base oil (A), a mixed base oil of base oil (A1) and base oil (A2), heated to 70°C. Separately, solution β was prepared by adding 1.51 parts by mass of cyclohexylamine and 1.03 parts by mass of octadecylamine (stearylamine) to 47.00 parts by mass of a mixed base oil of base oil (A1) and base oil (A2), heated to 70°C. Then, using the grease production apparatus 1 shown in FIG. 3, solution β heated to 70°C was added to solution α heated to 70°C, and the stirring blade was rotated. While continuing stirring, the temperature was raised to 160°C and maintained at this temperature for 1 hour to synthesize urea grease (b2). The maximum shear rate (Max) was approximately 100 s －１ and the minimum shear rate is 1.23 s －１The ratio (Max / Min) of the maximum shear rate (Max) to the minimum shear rate (Min) was about 81. The urea-based thickener (B2) contained in the urea grease (b2) is 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 cyclohexylamine 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 In the above (1), the urea grease (b2) discharged from the grease production apparatus 1 shown in FIG. 3 was stirred and then allowed to cool naturally to 70°C. Next, glycerin fatty acid ester (C1) was added to the urea grease (b2) that had been allowed to cool naturally to 70°C in the amount shown in Table 1 and mixed, thereby obtaining the grease composition of Comparative Example 2.

[0109] Comparative Examples 3 and 4 Grease compositions of Comparative Examples 3 and 4 were obtained in the same manner as the grease composition of Comparative Example 2, except that the blending amounts were changed as shown in Table 1.

[0110] [Requirements] The following calculations were carried out for the urea greases synthesized in Examples 1 and 2 and Comparative Examples 1 to 4.

[0111] (1) Calculation of particle size of particles containing a urea-based thickener: Requirement (I) The particle size of particles containing a urea-based thickener in a grease composition was evaluated. Specifically, the urea grease synthesized in Example 1 and the urea grease synthesized in Comparative Example 1 were used as measurement samples, and the 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 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):

[0112] 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.

[0113] (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 )

[0114] The composition and physical properties of the grease composition are shown in Table 1.

[0115]

[0116] The following tests were carried out on the grease compositions obtained in Examples 1 and 2 and Comparative Examples 1 to 4 to confirm that they were solid at room temperature and liquefied when heated.

[0117] [Confirmation that the grease composition of Example 1 is solid at room temperature and liquefied when heated] The grease composition of Example 1 was heated to 70°C at room temperature to liquefy the grease composition. A bearing was placed in the grease composition, and the state of filling of the gaps in the bearing with the grease composition was visually confirmed. The filling state after returning to room temperature was also visually confirmed, and the retention of the grease composition was confirmed by inverting the bearing so that the open surface was facing downwards and determining whether or not there was any dripping. In addition, in Comparative Example 1, the filling state into the gaps in the bearing, the filling state after returning to room temperature, and the retention of the grease composition were confirmed in the same manner as in Example 1.

[0118] As a result of this test, it was confirmed that the grease composition of Example 1 was solid at room temperature and liquefied when heated to 70°C, and that the grease composition was easily filled into the gaps of the bearing. Furthermore, after returning to room temperature, the grease composition solidified and was sufficiently retained in the gaps of the bearing. On the other hand, the grease composition of Comparative Example 1, which did not contain the oil hardener (C), remained liquefied even after being heated to 70°C and then returned to room temperature, and the grease composition did not fill the gaps of the bearing, and dripping from the bearing was confirmed. In other words, the grease composition of Comparative Example 1, which did not contain the oil hardener (C), did not return to a solid state after being heated to 70°C and then returned to room temperature, and therefore no longer exhibited its performance as a grease composition.

[0119] Next, the rheological properties of Examples 1 and 2 and Comparative Examples 1 to 4 were evaluated.

[0120] [Evaluation of Rheological Properties] At room temperature (25°C), a strain of 1 × 10 was measured using an Anton-Paar MCR302 instrument. －３ % to 1 x 10 ３The storage modulus was measured in the range of 100%. The storage modulus was plotted against the strain, and the maximum slope (negative number) of the decrease in the storage modulus was compared.

[0121] The rheometer measurement results for Examples 1 and 2 and Comparative Example 1 are shown in Figure 4. The rheometer measurement results for Comparative Examples 2 to 4 are shown in Figure 5. The rheology curves (change in storage modulus with strain) for Examples 1 and 2 had a larger maximum slope (negative number) when the storage modulus decreased than the rheology curves for Comparative Examples 1 to 4. That is, the degree of decrease in storage modulus with strain (response to decrease) was high, and it was found that the composition was more likely to become fluid with strain. These results indicate that a urea-based thickener (B) that satisfies requirement (I) is highly responsive to the application of shear stress and is easily softened. The results of Comparative Example 1 revealed that a urea grease that does not contain an oil / fat hardener (C) can be liquefied by heating but does not return to a solid state when returned to room temperature. However, the grease compositions of Examples 1 and 2 could be liquefied by heating and became solid when returned to room temperature. From this, it can be said that the grease composition containing the urea-based thickener (B) and the oil-hardening agent (C) is a grease composition in which the properties exhibited by the oil-hardening agent (C) (the property of being able to be liquefied by heating and becoming solid when returned to room temperature) are not inhibited by the urea-based thickener (B), and which has excellent rheological properties (high responsiveness to the application of shear stress and easy softening).

[0122] 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 comprising a base oil (A), a urea-based thickener (B), and an oil hardener (C), The oil / fat hardener (C) is capable of thickening, solidifying, and / or sol-gelling oils and fats that are liquid at room temperature, A grease composition, 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 size of 2.0 μm or less when measured by a laser diffraction / scattering method.

2. 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 particles measured by a laser diffraction / scattering method is 0.5×10 ５ cm ２ / cm ３ That's all.

3. The content of the oil hardener (C) is 0.1 mass% to 10 mass% based on the total amount of the grease composition. The grease composition according to claim 1 or 2.

4. The grease composition according to claim 1 or 2, wherein the melting point of the oil / fat hardener (C) is 100° C. or lower.

5. The grease composition according to claim 1 or 2, wherein the content of the urea-based thickener (B) is 1.0 mass % to 15.0 mass % based on the total amount of the grease composition.

6. The base oil (A) has a kinetic viscosity of 10 mm at 40°C. ２ / s ~ 80mm ２ The grease composition according to claim 1 or 2, wherein

7. The grease composition according to claim 1 or 2, having a worked penetration of 300 to 500.

8. The grease composition according to claim 1 or 2, which is used for lubricating a lubricated portion of a reducer or a speed increaser.

9. A lubrication method, comprising lubricating a lubricated portion of a reducer or a speed increaser with the grease composition according to claim 1 or 2.