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 polymer compound, wherein: particles containing the urea-based thickening agent (B) in the grease composition satisfy the requirement (I) described below; the number average molecular weight (Mn) of the polymer compound (C) is 30,000 or more; and the molecular weight distribution (Mw / Mn) of the polymer compound (C) is 2.20 or less. This grease composition is excellent in terms of reduction of the coefficient of friction at a low velocity under a low load. Requirement (I): The area-based arithmetic average particle diameter of the particles is 2.0 μm or less as determined by a laser diffraction / scattering method.

Description

[Technical Field]

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

[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. In recent years, from the viewpoint of weight reduction and quietness, the use of resin materials as members for sliding parts has been considered. For example, in the worm gear of an automobile's electric power steering (EPS), the worm is generally made of metal from the viewpoint of strength. On the other hand, resin is often used as the material for the worm wheel from the viewpoints of reducing the weight of the automobile part, preventing unpleasant noises such as teeth rattles and vibrations due to contact with the worm (quietness), and preventing seizure with the worm. Polyamide resins, for example, are known as resins used.

[0003] EPS is a mechanism that assists steering force when a vehicle is traveling at low speeds. However, when a vehicle is traveling at high speeds, centrifugal force acts on the vehicle attempting to turn, allowing the vehicle to turn with slight steering movements of the steering wheel, so EPS assistance is controlled so that it does not apply when the vehicle is traveling at high speeds. As described above, the operation of a worm gear without assistance is slower and under a lower load than when assistance is applied, and therefore there is a demand for a grease composition that is suitable for lubricating sliding parts made of metal materials such as worms and resin materials such as worm wheels, even under low speed and low load conditions. For example, Patent Document 1 discloses a grease composition that aims to reduce steering torque when EPS is not assisted. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2016 / 104812 Summary of the Invention [Problem to be solved by the invention]

[0005] There is also a desire to improve the lifespan of resin materials used in worm gears. To achieve this, it is necessary to suppress creep, a phenomenon in which resin distortion increases due to the application of a load to the resin over a long period of time when the resin slides against metal. Resin materials are particularly prone to deformation in high-temperature environments. Therefore, in order to suppress creep and improve the life of the resin material, it is important to suppress frictional heat, that is, to reduce the coefficient of friction.

[0006] Furthermore, in recent years, in order to improve the lifespan of resin materials, resins that have glass fiber mixed in to improve strength have come to be used as the material for worm wheels.

[0007] In reinforced resins containing glass fibers, the glass fibers tend to be oriented perpendicularly on the surface of the resin, causing the glass fibers to scratch the contacting metal surface of the worm, increasing the coefficient of friction. Therefore, there is a need for a grease composition that can be used to lubricate sliding parts made of metal materials and resin materials with different performance than conventional materials. However, the grease composition of Patent Document 1 does not consider the lubrication performance between metal materials and resin materials that are different from conventional materials, such as reinforced resin materials containing glass fibers, and as a result, the friction characteristics have sometimes become insufficient as resin materials have changed.

[0008] Therefore, an object of the present invention is to provide a grease composition that is excellent in reducing the coefficient of friction under conditions of low speed and low load. [Means for solving the problem]

[0009] The present inventors focused on the particle size of particles containing a urea-based thickener in a grease composition containing a base oil and a urea-based thickener, and discovered that the above-mentioned problems can be solved by adjusting the arithmetic mean particle size based on area, as measured by a laser diffraction / scattering method, to a predetermined range and by using a grease composition containing a specific polymer compound, thereby completing the present invention.

[0010] That is, the present invention provides the following [1]. [1] A grease composition comprising a base oil (A), a urea-based thickener (B), and a polymer compound (C), 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 size of 2.0 μm or less when measured by a laser diffraction / scattering method. The number average molecular weight (Mn) of the polymer compound (C) is 30,000 or more, A grease composition, wherein the molecular weight distribution (Mw / Mn) of the polymer compound (C) is 2.20 or less. [Effects of the Invention]

[0011] According to the present invention, it is possible to provide a grease composition that is excellent in reducing the coefficient of friction under conditions of low speed and low load. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a schematic cross-sectional view of a grease production apparatus used in one embodiment of the present invention. [Figure 2] 2 is a schematic diagram of a cross section of a first concave-convex portion on the container body side of the grease production apparatus of FIG. 1, taken in a direction perpendicular to the rotation axis. [Figure 3] FIG. 1 is a schematic cross-sectional view of a grease production apparatus used in Comparative Example 3. DETAILED DESCRIPTION OF THE INVENTION

[0013] In this specification, for preferred numerical ranges (e.g., ranges of content, etc.), the lower and upper limits 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." In this specification, the numerical values ​​in the examples are numerical values ​​that can be used as upper or lower limit values.

[0014] In this specification, the mass average molecular weight (Mw) and number average molecular weight (Mn) of each component are values ​​calculated as standard polystyrene measured by gel permeation chromatography (GPC), and specifically mean values ​​measured by the method described in the examples. 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 labels.

[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 polymer compound (C), wherein particles containing the urea-based thickener (B) in the grease composition satisfy the following requirement (I), the number average molecular weight (Mn) of the polymer compound (C) is 30,000 or more, and the molecular weight distribution (Mw / Mn) of the polymer compound (C) is 2.20 or less. 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. In the following description, the "base oil (A)," the "urea-based thickener (B)," and the "polymer compound (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, based on the total amount (100 mass%) of the grease composition, 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. Also, it is usually 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 embodiment of the present invention may contain components other than components (A), (B), and (C) to the extent that the effects of the present invention are not impaired.

[0017] As a result of extensive research conducted by the present inventors to solve the above problems, it has been found that a grease composition that is excellent in reducing the coefficient of friction can be obtained when the number average molecular weight (Mn) of the polymer compound (C) in the grease composition is 30,000 or more and further the molecular weight distribution (Mw / Mn) of the polymer compound (C) is 2.20 or less.

[0018] Specifically, the present inventors have found the following. Polymer compounds contain a wide variety of molecular weights, ranging from low to high, depending on the degree of polymerization. The smaller the molecular weight distribution (Mw / Mn) of a polymer compound, the higher the proportion of molecules with a specific molecular weight and the lower the proportion of compounds with other molecular weights. In other words, the smaller the molecular weight distribution (Mw / Mn) of a polymer compound, the more closely it is aligned to a specific molecular weight, and the closer the molecular size is to being uniform.

[0019] The inventors have hypothesized that when the number-average molecular weight (Mn) of the polymeric compound in a grease composition is 30,000 or more and the molecular weight distribution (Mw / Mn) of the polymeric compound is 2.20 or less, the polymeric compound with a large molecular weight will bulk up and overlap in the grease composition (in other words, the polymeric compound with a large molecular weight will overlap in a coarse state containing many voids), and the polymeric compound will generate elastic force. Furthermore, the inventors have hypothesized that the elastic force of the polymeric compound in the grease composition will raise the friction boundary surface, thereby improving the oil film thickness of the base oil. The inventors have then discovered that this will result in a reduced coefficient of friction.

[0020] On the other hand, when the molecular weight distribution (Mw / Mn) of the polymer compound exceeds 2.20, a wide range of molecular weights, from low to high, are mixed together. Therefore, small particles tend to get into the gaps between larger particles, causing the polymer compounds to pile up in a dense state, resulting in an insufficient oil film thickness in the base oil and insufficient friction characteristics. Furthermore, even if the molecular weight distribution (Mw / Mn) of the polymer compound is 2.20 or less, if the number average molecular weight (Mn) of the polymer compound is less than 30,000, small particles will overlap, resulting in an insufficient oil film thickness in the base oil and insufficient friction characteristics.

[0021] <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 size of 2.0 μm or less when measured by a laser diffraction / scattering method. By satisfying the above requirement (I), the grease composition is excellent in reducing the coefficient of friction.

[0022] The above requirement (I) can also be said to be a parameter indicating the state of aggregation of the urea-based thickener (B) in the grease composition. Here, the "particles containing a 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. If the grease composition contains additives other than the urea-based thickener (B), the particle size specified in the above requirement (I) can be obtained by measuring a grease composition prepared under the same conditions but without the additives by a laser diffraction / scattering method. However, if the additives are liquid at room temperature (25°C) or dissolve in the base oil (A), the grease composition containing the additives may also be used for measurement.

[0023] 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 particle size specified by the above requirement (I) exceeds 2.0 μm, the friction properties of the grease composition cannot be ensured even when the worked penetration of the grease composition is increased. In other words, it has been found that if the particle size specified by the above requirement (I) exceeds 2.0 μm, it is difficult to obtain a grease composition with excellent friction properties, even if a specific polymer compound (C) is used. In response to this, the present inventors conducted extensive research and found that by reducing the particle size specified in the above requirement (I) to 2.0 μm or less, a grease composition with excellent friction properties can be obtained in combination with a specific polymer compound (C). This effect is presumably achieved by reducing the 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 lubricated parts (friction surfaces) such as worm gears and makes them less likely to be removed from the lubricated parts, thereby improving the retention of the grease composition at the lubricated parts. Furthermore, reducing the 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 effectively distributed over the lubricated parts (friction surfaces) such as worm gears, and the polymer compound (C) is also effectively distributed over the lubricated parts, thereby improving the friction characteristics. From the above viewpoints, in the grease composition of one embodiment of the present invention, the particle size specified by 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, still more preferably 0.6 μm or less, even more preferably 0.5 μm or less, and still more preferably 0.4 μm or less. Also, it is usually 0.01 μm or more.

[0024] <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 3 That'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 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 has excellent friction properties and is more likely to exhibit the effects of the polymer compound (C). 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 x 10 6 cm 2 / cm 3 The following is the result.

[0025] In this specification, the values ​​specified in the above requirement (I) and further the above requirement (II) are values ​​measured by the method described in the examples below. The values ​​specified by the above requirement (I) and furthermore the requirement (II) can be adjusted mainly by the production 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 the specific means for adjusting the values ​​specified in the above requirement (I) and further the above requirement (II).

[0026] <Base oil (A)> The base oil (A) contained in the grease composition of the present invention may be at least one oil selected from mineral oils and synthetic oils. Examples of mineral oils include distillate oils obtained by atmospheric or vacuum distillation of paraffinic crude oil, intermediate crude oil, or naphthenic crude oil, and refined oils obtained by refining these distillate oils according to conventional methods. Examples of refining methods include solvent dewaxing, hydroisomerization, hydrofinishing, and clay treatment.

[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 or the like. 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.

[0028] Examples of aromatic oils include alkylbenzenes such as monoalkylbenzenes and dialkylbenzenes; alkylnaphthalenes such as monoalkylnaphthalenes, dialkylnaphthalenes, and polyalkylnaphthalenes; and the like.

[0029] 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.

[0030] 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.

[0031] The base oil (A) of this embodiment preferably has a kinematic viscosity at 40°C of 10 mm 2 / s or more, preferably 15 mm 2 / s or more, more preferably 20 mm 2 / s or more. The kinematic viscosity of base oil (A) at 40°C is 10mm 2 / s or more, the effects of the present invention are more easily exhibited. The base oil (A) of this embodiment preferably has a kinematic viscosity at 40°C of 150 mm 2 / s or less, preferably 130 mm 2 / s or less, more preferably 110 mm 2 / s or less, and even more preferably 100 mm 2 / s or less. The kinematic viscosity of base oil (A) at 40°C is 150mm 2 / s or less, the effects of the present invention are more easily exhibited. The upper and lower limits of these numerical ranges can be arbitrarily combined. Specifically, the range is preferably 10 to 150 mm. 2 / s, preferably 10 to 130 mm 2 / s, more preferably 15 to 110 mm 2 / s, and even more preferably 20 to 100 mm 2 / s. 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.

[0032] The viscosity index of the base oil (A) used in one embodiment of the present invention is preferably 80 or more, more preferably 100 or more, and even more preferably 120 or more. In this specification, the kinematic viscosity and viscosity index refer to values ​​measured or calculated in accordance with JIS K2283:2000.

[0033] 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, 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.

[0034] <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. 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.

[0035] 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.

[0036] R in the general formula (b1) 1 and R 2 The monovalent hydrocarbon group that can be selected as has 6 to 24 carbon atoms, preferably 6 to 20 carbon atoms, and more preferably 6 to 18 carbon atoms. Also, R 1 and R 2Examples 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.

[0037] 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 80 / 20 to 20 / 80, and even more preferably 70 / 30 to 40 / 60). The alicyclic hydrocarbon group, the chain hydrocarbon group, and the aromatic hydrocarbon group are each independently represented by R 1 and R 2 Since X, Y, and Z are groups selected as the group represented by the general formula (b1), the sum of the values ​​of X, Y, and Z is 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 compound group represented by the general formula (b1) contained in the grease composition. By using the compound represented by the general formula (b1) above, which 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.

[0038] 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 the monovalent unsaturated chain hydrocarbon group include linear or branched alkenyl groups having 6 to 24 carbon atoms, such as 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, and a linoleyl group. The monovalent saturated chain hydrocarbon group and the monovalent unsaturated chain hydrocarbon group may be linear or branched.

[0039] 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).

[0040] 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).

[0041] 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.

[0042] R in the general formula (b1) 3 The divalent aromatic hydrocarbon group that can be selected as has 6 to 18 carbon atoms, preferably 6 to 15 carbon atoms, and more preferably 6 to 13 carbon atoms. R 3 Examples of the divalent aromatic hydrocarbon group that can be selected as include a phenylene group, a diphenylmethylene group, a diphenylethylene group, a diphenylpropylene group, a methylphenylene group, a dimethylphenylene group, and an ethylphenylene group. Among these, a phenylene group, a diphenylmethylene group, a diphenylethylene group, or a diphenylpropylene group is preferred, and a diphenylmethylene group is more preferred.

[0043] 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 1.0 to 15.0 mass%, more preferably 1.5 to 13.0 mass%, even more preferably 2.0 to 10.0 mass%, still more preferably 2.5 to 8.0 mass%, and even more preferably 4.0 mass% to 7.0 mass%. If the content of component (B) is 1.0% by 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 15.0 mass % or less, the resulting grease composition can be adjusted to be soft, which makes it easier to improve lubricity and friction characteristics.

[0044] <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 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 following formula:

[0045] 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 such as that shown in [1] below. [1] A container body having an introduction part into which a grease raw material is introduced and an ejection part that ejects the grease to the outside; a rotor having a rotation axis in the axial direction of the inner periphery of the container body and rotatably provided inside the container body, The rotor is (i) along the surface of the rotor, concaves and convexes are alternately provided, and the concaves and convexes are inclined with respect to the rotation axis; (ii) having a feeding capability from the introduction portion to the discharge portion A grease manufacturing device comprising a first uneven portion.

[0046] The grease production apparatus described in [1] above will be explained below. Unless otherwise specified, the "preferred" provisions described below are aspects 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).

[0047] 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 manufacturing apparatus 1 shown in Figure 1 comprises 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 circumference of the container body 2 and rotating around the rotating shaft 12 as its central axis. The rotor 3 rotates at high speed around the rotary shaft 12 as the central axis, and applies a high shear force to the grease raw material inside the container body 2. This produces grease containing the urea-based thickener (B). As shown in FIG. 1, the vessel body 2 is preferably partitioned into an introduction section 4, a retention section 5, a first inner circumferential surface 6, a second inner circumferential surface 7, and a discharge section 8 in this order from the upstream side. As shown in FIG. 1, the container body 2 preferably has a truncated conical inner peripheral surface whose inner diameter gradually increases from the introduction part 4 toward the discharge part 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 the grease raw material from the outside of the container body 2.

[0048] The retention section 5 is located downstream of the introduction section 4 and is a space for temporarily retaining the grease raw material introduced from the introduction section 4. If the grease raw material remains in this retention section 5 for a long time, the grease adhering to the inner circumferential surface of the retention section 5 will form large lumps, so it is preferable to transport the grease raw material downstream to the first inner circumferential surface 6 in as short a time as possible. It is even more preferable to transport the grease raw material directly to the first inner circumferential surface 6 without passing through the retention section 5. The first inner circumferential surface 6 is disposed in a downstream portion adjacent to the retention portion 5, and the second inner circumferential surface 7 is disposed in a downstream portion adjacent to the first inner circumferential surface 6. As will be described in detail later, providing a first uneven portion 9 on the first inner circumferential surface 6 and a second uneven portion 10 on the second inner circumferential surface 7 is preferable in order to make the first inner circumferential surface 6 and the second inner circumferential surface 7 function as high shear portions that apply high shear force to the grease raw material or the 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.

[0049] The rotor 3 is rotatably mounted with the central axis of the truncated cone-shaped inner surface of the container body 2 as the rotation axis 12, and rotates counterclockwise when the container body 2 is viewed from the upstream to the downstream as shown in Figure 1. The rotor 3 has an outer surface that expands in accordance with the expansion of the inner diameter of the truncated cone of the container body 2, and a constant distance is maintained between the outer surface of the rotor 3 and the inner surface of the truncated cone of the container body 2. The rotor 3 has a first uneven portion 13 on the outer circumferential surface thereof, in which unevenness is alternately provided along the surface of the rotor 3.

[0050] 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.

[0051] The step between the recessed portion 13A and the protruding portion 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 portion 13A on the outer peripheral surface of the rotor 3 is taken as 100. The number of convex portions 13B of the first concave-convex 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.

[0052] The ratio of the width of the convex portion 13B of the first uneven portion 13 of the rotor to the width of the concave portion 13A in a cross section perpendicular to the rotation axis 12 of the rotor 3 (width of convex portion / width of concave portion) 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 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.

[0053] The first inner circumferential surface 6 of the container body 2 is preferably provided with a first uneven portion 9 in which a plurality of unevennesses are formed along the inner circumferential surface. Moreover, it is preferable that the concaves and convexes of the first concave-convex portion 9 on the vessel body 2 side are inclined in the opposite direction to the first concave-convex portion 13 of the rotor. That is, the plurality of projections and recesses 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 Fig. 1. The first uneven portion 9 having a plurality of projections and recesses provided on the first inner circumferential surface 6 of the container body 2 further enhances the stirring capacity and discharge capacity.

[0054] The depth of the first uneven 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 in 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.

[0055] 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 [width of recesses / width of protrusions] 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 first concave-convex portion 9 on the container body 2 side relative 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. 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 shear portion that applies high shear force to the grease raw material or the grease, but the first uneven portion 9 does not necessarily have to be provided.

[0056] It is preferable that a second uneven portion 14 of the rotor is provided on the outer peripheral surface of the downstream portion of the first uneven portion 13 of the rotor, along the surface of the rotor 3, with unevenness being provided alternately. The second uneven portion 14 of the rotor is inclined with respect to the rotation axis 12 of the rotor 3, and has a feed suppression ability to push the solution back upstream from the inlet portion 4 toward the outlet portion 8.

[0057] The step 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 circumferential surface of the rotor 3 is 100. The number of convex portions of the second concave-convex portion 14 of the rotor in the circumferential direction is preferably 2 to 1000, more preferably 6 to 500, and even more preferably 12 to 200.

[0058] 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 (width of convex portion / width of concave portion) 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.

[0059] It is preferable that the second inner peripheral surface 7 of the container body 2 is provided with a second uneven portion 10 having a plurality of uneven portions formed adjacent to the downstream portion of the unevenness in the first uneven portion 9 on the container body 2 side. A plurality of irregularities are formed on the inner circumferential surface of the vessel body 2, and each of the irregularities is preferably inclined in the opposite direction to the inclination direction of the second irregular portion 14 of the rotor. That is, the multiple concave-convex portions of the second concave-convex 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 concave-convex portions of the second concave-convex portion 10 provided on the second inner circumferential surface 7 of the container body 2 further enhance the stirring ability. In addition, the second inner circumferential surface 7 of the container body can function as a shearing portion that applies a high shear force to the grease raw material or the grease.

[0060] 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 taken as 100. The number of recesses in 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.

[0061] The ratio of the width of the convex portion of the second uneven portion 10 on the container body 2 side in a cross section perpendicular to the rotation axis 12 of the rotor 3 to the width of the concave portion [width of convex portion / width of concave portion] 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 relative 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 uneven portion 9 on the container body 2 side to the length of the second uneven portion 10 on the container body 2 side [length of the first uneven portion / length of the second uneven portion] is preferably 2 / 1 to 20 / 1.

[0062] FIG. 2 is a cross-sectional view of the first concave-convex portion 9 on the container body 2 side of the grease production apparatus 1, taken in a direction perpendicular to the rotation axis 12. 2, the first uneven portion 13 of the rotor is provided with a plurality of scrapers 15 whose tips protrude further toward the inner circumferential surface of the container body 2 than the tips of the protruding portions 13B of the first uneven portion 13. In addition, 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 scraper 15 scrapes 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 of the tip of the scraper 15 relative to the protrusion of the convex portion 13B.

[0063] 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 the scraper 15, it may not be provided with the scraper 15, or the scraper 15 may be provided intermittently.

[0064] To produce grease containing a urea-based thickener (B) using the grease production apparatus 1, the aforementioned grease raw materials, solution α and solution β, are introduced from the solution introduction pipes 4A and 4B of the introduction section 4 of the container body 2, respectively, and the rotor 3 is rotated at high speed, thereby producing a grease base material containing a urea-based thickener (B). Furthermore, even when the sulfur-phosphorus extreme pressure agent (C) and other additives (D) are blended into the grease base material obtained in this manner, the urea thickener (B) in the grease composition can be made finer so as to satisfy the above requirement (I) and further the above requirement (II).

[0065] As a high speed rotation condition of the rotor 3, the shear rate applied to the grease raw material is preferably 10 2 s -1 More than 10, preferably 3 s -1 More preferably, 10 4 s -1 and usually 10 7 s -1 The following is the result.

[0066] 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 100 or less, more preferably 50 or less, and even more preferably 10 or less. By applying as uniform a shear rate to the mixed liquid 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.

[0067] 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 is 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 of the first inner circumferential surface 6 of the container body 2) Minimum shear rate (Min) = (linear velocity of recess 13A of first uneven portion 13 of rotor) / (gap A2 between recess 13A of first uneven portion 13 of rotor and recess of first uneven portion 9 of first inner circumferential surface 6 of container body 2) The gaps A1 and A2 are as shown in FIG.

[0068] Since the grease manufacturing apparatus 1 is equipped with the scraper 15, it is possible to scrape off the grease adhering to the inner surface of the container body 2, thereby preventing the formation of lumps during kneading, and making it possible to continuously manufacture grease with finely divided urea-based thickener (B) in a short time. Furthermore, by scraping off the adhering grease, the scraper 15 can prevent the remaining grease from becoming a 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.

[0069] The inner surface of the container body 2 is a truncated cone shape with the inner diameter expanding from the inlet 4 toward the outlet 8, so that centrifugal force has the effect of discharging the grease or grease raw materials downstream, reducing the rotational torque of the rotor 3 and enabling continuous production of grease. A first uneven portion 13 of the rotor is provided on the outer peripheral surface of the rotor 3, and the first uneven portion 13 of the rotor 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 uneven portion 14 of the rotor is inclined with respect to the rotation axis 12 of the rotor 3 and has the ability to suppress feeding 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.

[0070] A first uneven portion 9 is formed on the first inner peripheral surface 6 of the container body 2, and is inclined in the opposite direction to the first uneven portion 13 of the rotor. Therefore, in addition to the effect of the first uneven portion 13 of the rotor, the grease raw material can be sufficiently stirred while the grease or grease raw material is pushed downstream, and even after the additives are blended, 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). Furthermore, by providing the second uneven portion 10 on the second inner peripheral surface 7 of the container body 2 and the second rotor uneven portion 14 on the outer peripheral surface of the rotor 3, it is possible to prevent the grease raw material from flowing out of the first inner peripheral surface 6 of the container body more than necessary, and therefore it is possible to apply a high shear force to the solution to highly disperse the grease raw material, and to finely refine the urea-based thickener (B) so that the above requirement (I) and further the above requirement (II) are satisfied even after the additives are blended.

[0071] <High molecular compound (C)> The grease composition of the present invention contains a polymeric compound (C) in addition to components (A) and (B), wherein the number average molecular weight (Mn) of the polymeric compound (C) is 30,000 or more, and the molecular weight distribution (Mw / Mn) of the polymeric compound (C) is 2.20 or less. When the grease composition of the present invention contains a polymer compound (C) and the number average molecular weight (Mn) and molecular weight distribution (Mw / Mn) of the polymer compound (C) satisfy the above ranges, the coefficient of friction in the grease composition can be reduced. If the molecular weight distribution (Mw / Mn) of the polymer compound (C) exceeds 2.20, or if the number average molecular weight (Mn) of the polymer compound (C) is less than 30,000, a sufficient friction reducing effect cannot be obtained.

[0072] The mass average molecular weight (Mw) of the polymer compound (C) is preferably 50,000 or more, more preferably 100,000 or more, from the viewpoint of frictional properties, and is preferably 1,000,000 or less, from the viewpoint of availability of the polymer compound (C). The upper and lower limits of these numerical ranges can be combined arbitrarily. Specifically, the range is preferably 50,000 to 1,000,000, and more preferably 100,000 to 1,000,000.

[0073] The number average molecular weight (Mn) of the polymer compound (C) is 30,000 or more, preferably 50,000 or more, more preferably 80,000 or more, from the viewpoint of frictional properties. Also, the number average molecular weight (Mn) of the polymer compound (C) is preferably 500,000 or less, from the viewpoint of availability of the polymer compound (C). The upper and lower limits of these numerical ranges can be combined arbitrarily. Specifically, the range is preferably 30,000 to 500,000, more preferably 50,000 to 500,000, and even more preferably 80,000 to 500,000.

[0074] The molecular weight distribution (Mw / Mn) of the polymer compound (C) is 2.20 or less, preferably 2.00 or less, more preferably 1.90 or less, and even more preferably 1.85 or less, from the viewpoint of frictional properties. Also, the molecular weight distribution (Mw / Mn) of the polymer compound (C) is preferably 1.10 or more, from the viewpoint of availability of the polymer compound (C). The upper and lower limits of these numerical ranges can be combined arbitrarily. Specifically, the range is preferably 1.10 to 2.20, more preferably 1.10 to 2.00, even more preferably 1.10 to 1.90, and still more preferably 1.10 to 1.85.

[0075] The polymer compound (C) is not particularly limited as long as it satisfies the conditions of a number average molecular weight (Mn) of 30,000 or more and a molecular weight distribution (Mw / Mn) of 2.20 or less, and any commonly used polymer compound can be used. Examples of the polymer compound (C) include polymers such as non-dispersed poly(meth)acrylate, dispersed poly(meth)acrylate, star polymer, olefin copolymer, dispersed olefin copolymer, polyalkylstyrene, and styrene copolymer. Examples of the olefin copolymer include an ethylene-propylene copolymer and an ethylene-butylene copolymer. Examples of the styrene copolymer include a styrene-diene copolymer and a styrene-isoprene copolymer. These may be used alone or in combination of two or more, and may be either random copolymers or block copolymers. Among these, ethylene-propylene copolymer and ethylene-butylene copolymer are preferred.

[0076] When the polymer compound (C) is a polymer containing ethylene, such as an ethylene-propylene copolymer or an ethylene-butylene copolymer, the ethylene content is preferably 30% by mass to 70% by mass, more preferably 40% by mass to 60% by mass, based on the total amount of the ethylene-containing polymer. The ethylene content in the ethylene-containing polymer can be measured by the method described in the examples below.

[0077] From the viewpoint of reducing the coefficient of friction, the content of the polymer compound (C) converted into resin is preferably 0.1 to 10.0 mass%, more preferably 0.1 to 5.0 mass%, even more preferably 0.1 to 3.7 mass%, still more preferably 0.5 to 2.5 mass%, and even more preferably 1.0 to 2.3 mass%, based on the total amount (100 mass%) of the grease composition.

[0078] From the viewpoint of friction characteristics, the content ratio of the urea-based thickener (B) to the polymer compound (C) [(B) / (C)] is preferably 0.5 to 5.0 by mass, more preferably 1.0 to 4.5, even more preferably 2.0 to 4.0, still more preferably 2.5 to 3.8, and even more preferably 2.8 to 3.4.

[0079] <Additives (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 the additive (D) include antioxidants, rust inhibitors, extreme pressure agents, solid lubricants, detergents and dispersants, corrosion inhibitors, and metal deactivators. The additives (D) may be used singly or in combination of two or more kinds.

[0080] Examples of the antioxidant include phenol-based antioxidants. 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, and benzotriazole and its derivatives. Examples of extreme pressure agents include thiocarbamic acids such as zinc dialkyldithiophosphate, molybdenum dialkyldithiophosphate, ashless dithiocarbamate, zinc dithiocarbamate, and molybdenum dithiocarbamate; sulfur compounds such as sulfurized fats and oils, sulfurized olefins, polysulfides, thiophosphoric acids, thioterpenes, and dialkylthiodipropionates; phosphate esters such as tricresyl phosphate; and phosphite esters such as triphenyl phosphite. Examples of solid lubricants include polyimide, PTFE, graphite, metal oxides, boron nitride, melamine cyanurate (MCA), and molybdenum disulfide. Examples of detergent dispersants include ashless dispersants such as succinimide and boron-based succinimide. Examples of the corrosion inhibitor include benzotriazole compounds and thiazole compounds. Examples of the metal deactivator include benzotriazole compounds.

[0081] In the grease composition of one embodiment of the present invention, the content of these additives (D) is set appropriately depending on the type of additive, but each independently is 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.

[0082] <Properties of grease composition> (Worked penetration) The worked 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 260 to 330, from the viewpoint of achieving excellent friction properties. In this specification, the worked penetration of the grease composition refers to a value measured at 25°C in accordance with JIS K2220:2013 (Clause 7).

[0083] (friction coefficient reduction effect) The grease composition of one embodiment of the present invention can be evaluated by determining the reduction rate of the friction coefficient by the method described in the examples below. The reduction rate of the friction coefficient obtained by the method described in the examples below is preferably 45% or more.

[0084] <Method for producing grease composition> The grease composition of the present invention can be produced by mixing a base oil (A), a grease (base grease) containing a urea-based thickener (B), a polymer compound (C), and, if necessary, an additive (D). For example, the lubricating oil composition can be produced by mixing a base oil (A) with an additive (D), then mixing the mixture with a grease (base grease) containing a urea-based thickener (B), and then adding and mixing a polymer compound (C).

[0085] <Applications of grease composition> The grease composition of the present invention is excellent at reducing the coefficient of friction, particularly when used to lubricate sliding parts made of metal and resin materials, under conditions of low speed and low load. Therefore, the grease composition of one embodiment of the present invention can be suitably used for lubricating the sliding parts of various devices, and is particularly preferably used for lubricating devices having sliding parts made of metal materials and resin materials. The metal material is preferably various steels such as carbon steel and stainless steel, various alloys such as aluminum alloys, or copper. The metal material may be replaced with a material with high strength (for example, a ceramic material). The resin material may be a natural resin or a synthetic resin, but general-purpose synthetic plastics (polyethylene, polystyrene, polypropylene, polyvinyl chloride, etc.) and engineering plastics are preferred, and engineering plastics are more preferred from the standpoint of heat resistance and mechanical strength. Examples of engineering plastics include synthetic resins such as polyamide resin, polyacetal resin, polycarbonate resin, polysulfone resin, polyphenylene sulfide resin, polyamideimide resin, polyether ether ketone resin, phenol resin, polyester resin, and epoxy resin. The resin material is preferably a fiber reinforced resin material. An example of the fiber reinforced resin material is a glass fiber reinforced resin material.

[0086] Examples of equipment fields in which the grease composition of the present invention can be suitably used include the automotive field, office equipment field, machine tool field, wind turbine field, construction field, agricultural machinery field, and industrial robot field. Examples of lubricated parts in devices in the automotive field for which the grease composition of the present invention can be suitably used include bearing parts in devices such as radiator fan motors, fan couplings, alternators, idler pulleys, hub units, water pumps, power windows, wipers, electric power steering, electric drive motor flywheels, ball joints, wheel bearings, spline parts, and constant velocity joints; bearing parts, gear parts, and sliding parts in devices such as door locks, door hinges, and clutch boosters; and the like. More specifically, examples include hub units, electric power steering, drive electric motor flywheels, ball joints, wheel bearings, spline parts, constant velocity joints, clutch boosters, servo motors, blade bearings, and bearing parts of generators.

[0087] Examples of lubricating 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. Parts to be lubricated in equipment in the field of machine tools, for which the grease composition of the present invention can be suitably used, include, for example, bearing parts in reducers of spindles, servo motors, machine tool robots, and the like. Examples of lubricating parts in equipment in the wind turbine field that can be suitably used with the grease composition of the present invention include bearing parts such as 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.

[0088] In one embodiment of a device to which the grease composition of the present invention can be applied, the sliding mechanism is preferably a reducer (worm gear) for electric power steering, having a metal worm and a resin worm wheel. This configuration of the device provides excellent reduction in the coefficient of friction under low speed and low load conditions, and therefore excellent friction characteristics even during high-speed driving where EPS assistance is not applied.

[0089] [Lubrication method for sliding mechanism] A method for lubricating a sliding mechanism that can be applied to the grease composition of the present invention is a method in which a sliding mechanism in which a metal material slides on a resin material is lubricated with the above-mentioned grease composition of the present invention.

[0090] According to the method for lubricating a sliding mechanism applicable to the grease composition of the present invention, it is possible to appropriately maintain the dynamic friction force in the lubricated part. When the sliding mechanism is an electric power steering reducer (worm gear) having a metal worm and a resin worm wheel, this effect is excellent in reducing the friction coefficient under low speed and low load conditions, and therefore, it is possible to achieve excellent friction characteristics even during high-speed driving controlled so as not to apply EPS assistance.

[0091] According to one aspect of the present invention, the following [1] to

[11] are provided. [1] A grease composition comprising a base oil (A), a urea-based thickener (B), and a polymer compound (C), 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 size of 2.0 μm or less when measured by a laser diffraction / scattering method. The number average molecular weight (Mn) of the polymer compound (C) is 30,000 or more, A grease composition, wherein the molecular weight distribution (Mw / Mn) of the polymer compound (C) is 2.20 or less. [2] The 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 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 grease composition according to [1] or [2], wherein the content of the polymer compound (C) in terms of resin is 0.1% by mass to 10.0% by mass based on the total amount of the grease composition. [4] The grease composition according to any one of the above [1] to [3], wherein the polymer compound (C) contains an ethylene-propylene copolymer. [5] The grease composition according to [4], wherein the ethylene content in the ethylene-propylene copolymer is 40% by mass to 60% by mass based on the total amount of the ethylene-propylene copolymer. [6] The kinematic viscosity of the base oil (A) at 40°C is 10mm 2 / s~150mm 2 The grease composition according to any one of the above [1] to [5], wherein the grease composition is [7] The grease composition according to any one of [1] to [6], wherein the content ratio of the urea-based thickener (B) to the polymer compound (C) [(B) / (C)] is 1.0 to 4.5 by mass. [8] The grease composition according to any one of [1] to [7], 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. [9] The grease composition according to any one of the above [1] to [8], which has a worked penetration of 250 to 350.

[10] The grease composition according to any one of the above [1] to [9], which is used for lubricating a sliding mechanism in which a metal material slides on a resin material.

[11] A lubrication method, comprising lubricating a sliding mechanism in which a metal material slides on a resin material with the grease composition according to any one of the above [1] to

[10] . [Example]

[0092] The present invention will be specifically described with reference to the following examples, but the present invention is not limited to these examples.

[0093] [Various physical properties] The methods for measuring various physical properties were as follows. (1) 40°C kinematic viscosity and viscosity index of base oil (A) Measurements and calculations were made in accordance with JIS K2283:2000. (2) Mass average molecular weight (Mw), number average molecular weight (Mn), and molecular weight distribution (Mw / Mn) of polymer compound (C) The values ​​were measured using a gel permeation chromatograph (manufactured by Agilent, model 1260 HPLC) under the following measurement conditions, and converted into standard polystyrene values. -Measurement conditions- Column: Two Shodex LF404 columns connected in series. Column temperature: 35℃ Developing solvent: chloroform ·Flow rate: 0.3mL / min (3) Ethylene content of polymer compound (C) 13 The C-NMR quantitative spectrum was analyzed and calculated. (4) Worked consistency of the grease composition Measurement was performed at 25°C in accordance with JIS K2220:2013 (Clause 7).

[0094] [Raw materials] In Examples 1 to 6 and Comparative Examples 1 to 4, the base oil (A) and polymer compound (C) used as raw materials for preparing the grease compositions were as follows. The contents in Tables 1 and 2 are calculated as resin contents.

[0095] <Base oil (A)> Base oil (A1) (poly-α-olefin (PAO), kinematic viscosity at 40°C: 30 mm 2 / s, viscosity index: 135) Base oil (A2) (poly-α-olefin (PAO), kinematic viscosity at 40°C: 63 mm 2 / s, viscosity index: 140)

[0096] <High molecular compound (C)> ·High molecular compound (C1) Ethylene-propylene copolymer, mass average molecular weight (Mw): 172,000, number average molecular weight (Mn): 93,500, molecular weight distribution (Mw / Mn): 1.84, ethylene content: 58.6% by mass ·High molecular compound (C2) Ethylene-propylene copolymer, mass average molecular weight (Mw): 270,000, number average molecular weight (Mn): 149,000, molecular weight distribution (Mw / Mn): 1.81, ethylene content: 52.5% by mass ·High molecular compound (C3) Ethylene-propylene copolymer, mass average molecular weight (Mw): 284,000, number average molecular weight (Mn): 166,000, molecular weight distribution (Mw / Mn): 1.71, ethylene content: 51.6% by mass ·High molecular compound (C4) Ethylene-butylene copolymer, mass average molecular weight (Mw): 258,000, number average molecular weight (Mn): 148,000, molecular weight distribution (Mw / Mn): 1.74, ethylene content: 67.3% by mass ·High molecular compound (C') Ethylene-propylene copolymer, mass average molecular weight (Mw): 109,000, number average molecular weight (Mn): 47,800, molecular weight distribution (Mw / Mn): 2.28, ethylene content: 53.2% by mass

[0097] Example 1 (1) Synthesis of urea grease Solution α was prepared by adding 10.74 parts by mass of diphenylmethane-4,4′-diisocyanate (MDI) to 89.26 parts by mass of base oil (A1) heated to 70° C. Separately, 3.40 parts by mass of cyclohexylamine and 13.88 parts by mass of octadecylamine (stearylamine) were added to 82.72 parts by mass of base oil (A1) heated to 70°C to prepare a solution β. Then, using the grease production apparatus 1 shown in Fig. 1, equal amounts of solution α heated to 70°C were introduced into the vessel body 2 from the solution inlet pipe 4A, and equal amounts of solution β heated to 70°C were introduced into the vessel body 2 from the solution inlet pipe 4B, and while the rotor 3 was rotating, solutions α and β were continuously introduced into the vessel 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 milling to synthesize urea grease (b1). The rotation speed of the rotor 3 of the grease manufacturing device 1 used was 8,000 rpm. The maximum shear rate (Max) was 10,500 s -1 The stirring was carried out with the ratio of the maximum shear rate (Max) to the minimum shear rate (Min) [Max / Min] set to 3.5. The urea-based thickener (B1) contained in the obtained urea grease is represented by the 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 is a diphenylmethylene group. The molar ratio of cyclohexylamine to octadecylamine used as raw materials (cyclohexylamine / octadecylamine) was 40 / 60. (2) Preparation of grease composition The polymer compound (C1) was added to the urea grease obtained in (1) above while stirring at 120° C. After stirring for 0.5 hours, the mixture was allowed to cool naturally to 25° C., thereby obtaining the grease composition of Example 1. The content of each component in the grease composition of Example 1 is as shown in Table 1.

[0098] Example 2 A grease composition of Example 2 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. 87.29 parts by mass of base oil (A1) heated to 70°C Diphenylmethane-4,4'-diisocyanate (MDI) 12.71 parts by mass 86.51 parts by mass of base oil (A1) heated to 70°C 8.03 parts by mass of cyclohexylamine Octadecylamine (stearylamine) 5.46 parts by weight The urea-based thickener (B2) contained in the obtained urea grease is represented by the 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 is a diphenylmethylene group. The molar ratio of cyclohexylamine to octadecylamine used as raw materials (cyclohexylamine / octadecylamine) was 80 / 20.

[0099] Example 4 The grease composition of Example 4 was obtained in the same manner as in Example 1, except that in the synthesis of (1) urea grease in Example 1, octylamine was used instead of cyclohexylamine and the contents of each component were changed as follows: 89.91 parts by mass of base oil (A1) heated to 70°C Diphenylmethane-4,4'-diisocyanate (MDI) 10.09 parts by mass 83.87 parts by mass of base oil (A1) heated to 70°C 5.24 parts by weight of octylamine Octadecylamine (stearylamine) 10.90 parts by weight The urea-based thickener (B3) contained in the obtained urea grease is represented by the formula (b1) R 1 and R 2 is an octyl group or an octadecyl group (stearyl group), and R 3 corresponds to a compound in which is a diphenylmethylene group. The molar ratio of octylamine to octadecylamine used as raw materials (octylamine / octadecylamine) was 50 / 50.

[0100] (Comparative Example 3) Solution α was prepared by adding 10.74 parts by mass of diphenylmethane-4,4′-diisocyanate (MDI) to 89.26 parts by mass of base oil (A1) heated to 70° C. Separately, 3.40 parts by mass of cyclohexylamine and 13.88 parts by mass of octadecylamine (stearylamine) were added to 82.72 parts by mass of base oil (A1) heated to 70°C to prepare a solution β. Then, using the grease production apparatus 1 shown in Fig. 3, solution α heated to 70°C was introduced into the container body through the solution inlet pipe. Thereafter, while stirring, solution β heated to 70°C was introduced through the solution inlet pipe into the container body containing solution α. ​​After all of solution β was introduced into the container body, the stirring blade was rotated, and while continuing stirring, the temperature was raised to 160°C and maintained at this temperature for 1 hour to synthesize urea grease (b2), which was used as the grease composition of Comparative Example 3. The maximum shear rate (Max) was approximately 100 s -1 and the minimum shear rate is 1.23 s -1 The ratio (Max / Min) of the maximum shear rate (Max) to the minimum shear rate (Min) was approximately 81. The urea-based thickener contained in the urea grease (b2) is represented by the 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 is a diphenylmethylene group. The molar ratio of cyclohexylamine to octadecylamine used as raw materials (cyclohexylamine / octadecylamine) was 40 / 60.

[0101] Comparative Example 4 In Comparative Example 3, the polymer compound (C1) was further added and mixed to obtain the grease composition of Comparative Example 4.

[0102] (Examples 3, 5-6, Comparative Examples 1-2) Each grease composition was prepared in the same manner as the above-mentioned grease composition, except that the components and contents were changed as shown in Tables 1 and 2.

[0103] [Requirements] The following calculations were carried out for the urea greases synthesized in Examples 1 to 6 and Comparative Examples 1 to 4.

[0104] (1) Calculation of particle size of particles containing urea-based thickeners: Requirement (I) The particle size of particles containing a urea-based thickener in a grease composition was evaluated. Specifically, the urea greases synthesized in Examples 1 to 6 and the urea greases synthesized in Comparative Examples 1 to 4 were used as measurement samples, and the particle sizes of particles containing a urea-based thickener (B) were determined by 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 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, resulting in 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 on an area basis using a laser diffraction particle size analyzer (Horiba, Ltd., product name: LA-920). Here, "area-based arithmetic mean particle diameter" refers to the arithmetic mean of the area-based particle diameter distribution. The area-based particle diameter distribution indicates the frequency distribution of particle diameters for all particles being 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):

[0105]

number

[0106] (2) Calculation of the specific surface area of ​​particles containing urea-based thickeners: Requirement (II) The specific surface area was calculated using the particle size distribution of the particles, including the thickener, in the grease composition, measured in the section on requirement (I) above. Specifically, the specific surface area was calculated using the particle size distribution. 3 ) surface area of ​​particles per unit (unit: cm 2 ) and calculate the specific surface area (unit: cm 2 / cm 3 ) was decided.

[0107] Next, the reduction in the coefficient of friction will be evaluated using the above Examples 1 to 6 and Comparative Examples 1 to 4.

[0108] [Evaluation of the effect of reducing the friction coefficient] A sliding test was conducted in accordance with JIS K7218-A under the following test conditions to measure the coefficient of friction at the sliding portion between the metal material and the resin material. (When conducting a test under high speed and high load conditions using this test method, the test can be conducted, for example, at a sliding speed of 1.0 m / s and a load of 350 N. In contrast, in this example, the sliding test was conducted under the test conditions shown below to evaluate the friction characteristics under low speed and low load conditions.) The percentage of the friction coefficient reduced from the reference value of the comparative example (the reduction rate of the friction coefficient) was calculated, and the effect of reducing the friction coefficient was evaluated according to the following evaluation criteria, where a rating of "B" or higher is considered acceptable. In Examples 1 to 6 and Comparative Example 2, the reference value was set to Comparative Example 1, which did not contain the polymer compound (C) but contained the urea-based thickener (B). In Comparative Example 4, the reference value was set to Comparative Example 3, which did not contain the polymer compound (C) but contained the thickener (B'). -Test conditions- Testing equipment: Thrust-type sliding tester (equipment name: EFM-III-F-ADX-S, manufactured by A&D Co., Ltd.) Metallic test piece: Roller shape, diameter 10 mm, material S45C Resin test piece: Ring shape, outer diameter 25.6 mm, inner diameter 20 mm, material: Polyamide 66 mixed with 15% glass fiber by mass Sliding speed: 0.2m / s Load: 50N Test duration: 5 minutes Test temperature: Room temperature (25°C) -Evaluation criteria for friction coefficient reduction effect- A: The percentage of the friction coefficient that has decreased from the reference value (the reduction rate of the friction coefficient) is 50% or more. B: The percentage of the friction coefficient that has decreased from the reference value (the reduction rate of the friction coefficient) is 45% or more but less than 50% C: The percentage of the friction coefficient that has decreased from the reference value (decrease in friction coefficient) is less than 45%

[0109] The evaluation results are shown in Tables 1 and 2.

[0110] [Table 1]

[0111] [Table 2]

[0112] From the results shown in Tables 1 and 2, it was found that the grease compositions of Examples 1 to 6 had a friction coefficient reduction rate (friction coefficient reduction rate) of 45% or more from the reference value of the friction coefficient, and were excellent in reducing the friction coefficient under test conditions of low speed and low load. On the other hand, in the grease compositions of Comparative Example 2 containing a polymer compound (C') with a molecular weight distribution (Mw / Mn) of 2.28 and Comparative Example 4 in which the particles contained in the thickener (B') did not satisfy requirement (I), the percentage of the friction coefficient that was reduced from the reference value of the friction coefficient (reduction rate of the friction coefficient) was less than 45%, and the friction coefficient was not sufficiently reduced under the test conditions of low speed and low load. [Explanation of symbols]

[0113] 1. Grease manufacturing equipment 2 Container body 3 rotor 4 Introduction 4A, 4B Solution introduction tube 5 Retention part 6 First uneven part 7 Second uneven part 8 Discharge part 9. First uneven portion on the container body side 10 Second uneven portion on the container body side 11 Discharge port 12 Rotation axis 13 First uneven portion of rotor 13A Recess 13B Convex part 14 Second uneven portion of rotor 15 Scraper A1, A2 gap

Claims

1. A grease composition comprising a base oil (A), a urea-based thickener (B), and a polymer compound (C), the base oil (A) is at least one selected from the group consisting of poly-α-olefins and hydrogenated poly-α-olefins, 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 size of 2.0 μm or less when measured by a laser diffraction / scattering method. The urea-based thickener (B) is a diurea compound represented by general formula (b1), R 1 -NHCONH-R 3 -NHCONH-R 2 (b1) [In formula (b1), R 1 and R 2 are hydrocarbon groups having 6 to 18 carbon atoms, and R 3 is a diphenylmethylene group.] The content of the urea-based thickener (B) is 4.0 to 7.0 mass% based on the total amount of the grease composition, the number average molecular weight (Mn) of the polymer compound (C) is 80,000 to 500,000; the molecular weight distribution (Mw / Mn) of the polymer compound (C) is 1.10 to 1.85; the polymer compound (C) is at least one selected from an ethylene-propylene copolymer and an ethylene-butylene copolymer, the content of the polymer compound (C) in terms of resin is 1.0 to 2.3 mass% based on the total amount of the grease composition, A grease composition used for lubricating a sliding mechanism in which a metal material slides on a resin material, wherein a content ratio [(B) / (C)] of the urea-based thickener (B) to the polymer compound (C) is 2.8 to 3.4 by mass.

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. 3. The grease composition according to claim 1, wherein the polymer compound (C) comprises an ethylene-propylene copolymer.

4. 4. The grease composition according to claim 3, wherein the ethylene-propylene copolymer has an ethylene content of 40% by mass to 60% by mass based on the total amount of the ethylene-propylene copolymer.

5. The kinematic viscosity of the base oil (A) at 40°C is 10 mm ２ / s~150mm ２ The grease composition according to any one of claims 1 to 4, wherein the grease composition is:

6. The grease composition according to any one of claims 1 to 5, which has a worked penetration of 250 to 350.

7. A lubrication method comprising lubricating a sliding mechanism in which a metal material slides on a resin material with the grease composition according to any one of claims 1 to 6.

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