Grease composition

Abstract

Provided is a grease composition containing: a base oil (A), a urea-based thickening agent (B), and melamine cyanurate (C). Particles including the urea-based thickening agent (B) in the grease composition satisfy requirement (I). The grease composition has superior wear resistance. Requirement (I): The area-based arithmetic average particle diameter of the particles is 2.0 μm or less as measured by a laser diffraction / scattering method. The particles including the urea-based thickening agent (B) in the grease composition preferably further satisfy requirement (II). Requirement (II): The specific surface area of the particles is 0.5×105 cm2 / cm3 or more as measured by the laser diffraction / scattering method.

Description

Technical Field

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

Background Art

[0002] Grease compositions are easier to seal than lubricating oils and enable miniaturization and weight reduction of the machines to which they are applied. Therefore, they have been widely used conventionally for lubricating various sliding parts such as automobiles, electric equipment, industrial machines, and industrial machinery. In recent years, from the viewpoints of weight reduction and quietness, etc., the use of resin materials as members of sliding parts has been studied. For example, in the worm gear of an electric power steering (EPS) of an automobile, the material of the worm is generally metal from the viewpoint of strength. On the other hand, the material of the worm wheel is often resin from the viewpoints of weight reduction of automobile parts, prevention of generation of unpleasant sounds such as tooth meshing sounds and vibration sounds due to contact with the worm (quietness), prevention of seizure with the worm, etc. And, as the resin used, for example, polyamide-based resins etc. are known. Thus, there is a demand for a grease composition that can be suitable for lubricating sliding parts composed of a metal material such as a worm and a resin material such as a worm wheel.

[0003] Here, in order to enhance lubrication performance, adding melamine cyanurate, which is a solid lubricant, to a lubricant composition has been studied. For example, Patent Document 1 discloses a resin-metal sliding lubricant composition containing a base oil containing a fluorine-based polyether oil and melamine cyanurate as a lubricant composition suitable for lubricating a sliding part composed of a metal material and a resin material. Also, Patent Document 2 discloses a grease composition containing a base oil composed of a synthetic hydrocarbon oil, a thickener composed of lithium soap, and melamine cyanurate as a grease composition containing melamine cyanurate.

Prior Art Documents

Patent Documents

[0004] [Patent Document 1] Japanese Patent Publication No. 2012-102157 [Patent Document 2] Japanese Patent Publication No. 2009-13350 [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] However, the resin-metal sliding lubricant composition disclosed in Patent Document 1 is not a grease composition containing a base oil and a thickener. Furthermore, the base oil is not a commonly used mineral oil or hydrocarbon-based synthetic oil. Furthermore, the grease composition disclosed in Patent Document 2 improves the frictional properties at sliding points between rubber members, or between rubber members and resin members. Therefore, grease compositions containing melamine cyanurate that are suitable for lubricating sliding parts composed of metal and resin materials have not been investigated.

[0006] In recent years, EPS (Electric Power Steering) has been increasingly adopted in large vehicles. Because large vehicles experience greater forces than conventional vehicles, conventional worm wheels made from resin materials sometimes lacked sufficient strength. Therefore, resins mixed with glass fiber to improve strength are now being used as the material for worm wheels.

[0007] In reinforced resins containing glass fibers, the glass fibers tend to be vertically oriented on the resin surface, making it easy for defects to occur on the resin surface when the metal contact surface of the worm gear scratches and breaks the glass fibers. Furthermore, prolonged exposure to high loads on the resin material accelerates these defects, increasing wear. Therefore, there is a need for a grease composition that can reduce wear even in sliding parts composed of metal and resin materials with different properties than conventional materials. However, neither the resin-metal sliding lubricant composition in Patent Document 1 nor the grease composition in Patent Document 2 have considered the wear resistance between the metal and resin materials.

[0008] Therefore, the present invention aims to provide a grease composition that exhibits excellent wear resistance. [Means for solving the problem]

[0009] The 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. They found that a grease composition containing melamine cyanurate, while adjusting the arithmetic mean particle size based on area measured by laser diffraction and scattering to a predetermined range, can solve the above problem, and thus completed the present invention.

[0010] In other words, the present invention provides the following [1]. [1] A grease composition containing a base oil (A), a urea-based thickener (B), and melamine cyanurate (C), A grease composition wherein the particles containing the urea-based thickener (B) in the grease composition satisfy the following requirement (I). Requirement (I): The arithmetic mean particle diameter based on area, when the particles are measured by laser diffraction and scattering, is 2.0 μm or less. [Effects of the Invention]

[0011] According to the present invention, it is possible to provide a grease composition with excellent wear resistance. [Brief explanation of the drawing]

[0012] [Figure 1] This is a schematic cross-sectional view of a grease manufacturing apparatus used in one aspect of the present invention. [Figure 2] Figure 1 is a schematic diagram of the cross-section of the first uneven portion on the container body side of the grease manufacturing apparatus, in a direction perpendicular to the axis of rotation. [Modes for carrying out the invention]

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

[0014] In this specification, the mass-average molecular weight (Mw) and number-average molecular weight (Mn) of each component are values ​​on a standard polystyrene basis measured by gel permeation chromatography (GPC), and specifically refer to the values ​​measured by the method described in the Examples. In this specification, for example, "(meth)acrylate" is used to refer to both "acrylate" and "methacrylate," and the same applies to other similar terms and similar notations.

[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 melamine cyanurate (C), wherein the particles containing the urea-based thickener (B) in the grease composition satisfy the following requirement (I). Requirement (I): The arithmetic mean particle diameter based on area, when the particles are measured by laser diffraction and scattering, is 2.0 μm or less. In the following explanation, "base oil (A)", "urea-based thickener (B)", and "melamine cyanurate (C)" will also be referred to as "component (A)", "component (B)", and "component (C)", respectively.

[0016] In a grease composition according to one aspect of the present invention, the total content of component (A), component (B), and component (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. Also, 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. Furthermore, a grease composition according to one embodiment of the present invention may contain other components other than components (A), (B), and (C), as long as they do not impair the effects of the present invention.

[0017] A grease composition according to one embodiment of the present invention may optionally contain an oily agent (D), an anti-wear agent (E), a friction reducer (F), and an additive (G). In the following explanation, "oil-based agent (D)", "anti-wear agent (E)", and "friction-reducing agent (F)" will also be referred to as "component (D)", "component (E)", and "component (F)", respectively.

[0018] If components (D), (E), and (F) are included as needed, the total content of components (A), (B), (C), (D), (E), and (F) 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. Also, 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.

[0019] In order to solve the above problems, the inventors of this invention conducted diligent research and found that when the grease composition contains melamine cyanurate (C), a grease composition with excellent wear resistance can be obtained.

[0020] Specifically, the inventors have found the following: As mentioned above, in reinforced resins containing glass fibers, the glass fibers tend to be vertically oriented on the resin surface, so contact metal surfaces such as worms can scratch the glass fibers, causing them to break and resulting in defects on the resin surface. Here, we hypothesized that when the resin material comes into contact with a grease composition containing melamine cyanurate, the melamine cyanurate, a solid lubricant, penetrates into defects on the surface of the resin material, and plays a role in sealing these defects. Furthermore, we hypothesized that even when the resin material is subjected to high loads for a long period of time, the progression of defects in the resin material is suppressed. Therefore, we concluded that a grease composition containing melamine cyanurate can reduce the amount of wear.

[0021] <Requirement(I)> The grease composition of the present invention satisfies the following requirement (I) in the particles containing the urea-based thickener (B) in the grease composition. Requirement (I): The arithmetic mean particle diameter based on area, when the particles are measured by laser diffraction and scattering, is 2.0 μm or less. By satisfying the above requirement (I), a grease composition with excellent wear resistance is obtained.

[0022] 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 urea-based thickener (B)" that are measured by laser diffraction and scattering refer to particles formed by the aggregation of 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 requirement (I) above can be obtained by measuring a grease composition prepared under the same conditions without the additive using laser diffraction / scattering. However, if the additive is liquid at room temperature (25°C) or dissolves in the base oil (A), the grease composition containing the additive may be used as the measurement target.

[0023] Urea-based thickeners (B) are usually obtained by reacting an isocyanate compound with a monoamine, but because the reaction rate is very fast, the urea-based thickener (B) tends to aggregate, and large particles (micelle particles, so-called "clumps") are easily generated in excess. As a result of diligent research by the present inventors, it was found that if the particle size specified in requirement (I) above exceeds 2.0 μm, the wear resistance of the grease composition cannot be ensured when the consistency of the grease composition is increased. In other words, it was found that if the particle size specified in requirement (I) above exceeds 2.0 μm, it is difficult to obtain a grease composition with excellent wear resistance even when using melamine cyanurate (C). In response to this, the present inventors conducted thorough research and found that by reducing the particle size specified in requirement (I) above to 2.0 μm or less, a grease composition with excellent wear resistance can be obtained in combination with melamine cyanurate (C). This effect is presumed to be achieved by reducing the particle size specified in requirement (I) above to 2.0 μm or less, which makes it easier for particles containing the urea-based thickener (B) to penetrate into lubrication parts (friction surfaces) such as worm gears, and also makes it more difficult for them to be removed from said lubrication parts, thereby improving the retention capacity of the grease composition in said lubrication parts. Furthermore, reducing the particle size specified in requirement (I) above to 2.0 μm or less improves the retention capacity of the base oil (A) by said particles. Therefore, it is presumed that the base oil (A) is distributed well to lubrication parts (friction surfaces) such as worm gears, and consequently, the distribution of melamine cyanurate (C) to the lubrication parts is also improved, resulting in improved wear resistance. From the above viewpoint, in a grease composition according to one embodiment of the present invention, the particle size defined in requirement (I) above is preferably 1.5 μm or less, more preferably 1.0 μm or less, even more preferably 0.9 μm or less, even more preferably 0.8 μm or less, still 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.

[0024] <Requirement (II)> Here, the grease composition of one aspect of the present invention preferably further satisfies the following requirement (II). · Requirement (II): The specific surface area of the particles measured by the laser diffraction / scattering method is 0.5×10 5 cm 2 / cm 3 or more. The specific surface area defined in the above requirement (II) is a secondary index indicating the state of refinement of the particles containing the urea-based thickener (B) in the grease composition and the presence of large particles (lumps). That is, by satisfying the above requirement (I) and further satisfying the above requirement (II), it means that the state of refinement of the particles containing the urea-based thickener (B) in the grease composition is better, and the presence of large particles (lumps) is more suppressed. Therefore, it is possible to obtain a grease composition having excellent wear resistance and in which the effect of melamine cyanurate (C) is easily exerted. From the above viewpoints, the specific surface area defined in the above requirement (II) is preferably 0.7×10 5 cm 2 / cm 3 or more, more preferably 0.8×10 5 cm 2 / cm 3 or more, still more preferably 1.2×10 5 cm 2 / cm 3 or more, even more preferably 1.5×10 5 cm 2 / cm 3 or more, still even more preferably 1.8×10 5 cm 2 / cm 3 or more, still more preferably 2.0×10 5 cm 2 / cm 3 or more. Note that the specific surface area is usually 1.0×10 6 cm 2 / cm 3 or less.

[0025] In this specification, the values defined in the above requirement (I), and further the above requirement (II), are values measured by the method described in the examples described later. Furthermore, the values ​​specified in requirement (I) and requirement (II) above can be adjusted mainly by the manufacturing conditions of the urea-based thickener (B). The details of each component included in the grease composition of the present invention will be described below, focusing on specific means for adjusting the values ​​specified in requirement (I) and further in requirement (II) above.

[0026] <Base oil (A)> The base oil (A) contained in the grease composition of the present invention may be one or more selected from mineral oil and synthetic oil. 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 purification methods include solvent dewaxing, hydrogenation isomerization, hydrogenation finishing, and clay treatment.

[0027] Examples of synthetic oils include hydrocarbon oils, aromatic oils, ester oils, ether oils, and synthetic oils obtained by isomerizing waxes (GTL waxes) produced by the Fischer-Tropsch process, etc. Examples of hydrocarbon oils include normal paraffins, isoparaffins, polybutenes, polyisobutylenes, 1-decene oligomers, poly-α-olefins (PAOs) such as 1-decene and ethylene co-oligomers, and their hydrogenated products.

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

[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 methylacetyl ricinolate; aromatic ester oils such as trioctyl trimellitate, tridecyl trimellitate, and tetraoctyl pyromelitate; polyol ester oils such as trimethylolpropane caprylate, trimethylolpropane veralgonate, pentaerythritol-2-ethylhexanoate, and pentaerythritol veralgonate; 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 monoalkyltriphenyl ether, alkyldiphenyl ether, dialkyldiphenyl ether, pentaphenyl ether, tetraphenyl ether, monoalkyltetraphenyl ether, and dialkyltetraphenyl ether.

[0031] The base oil (A) of this embodiment preferably has a kinematic viscosity of 10 mm at 40°C. 2 / s or more, more preferably 20 mm 2 / s or more, more preferably 30mm 2 The kinematic viscosity of the base oil (A) at 40°C is 10 mm². 2 When the value is 1 / s or higher, the effects of the present invention can be more easily achieved. Furthermore, the base oil (A) of this embodiment preferably has a kinematic viscosity of 420 mmHg at 40°C. 2 / s or less, more preferably 300mm 2 / s or less, more preferably 200 mm 2 It is less than / s. The kinematic viscosity of base oil (A) at 40°C is 420 mmHg. 2 When the value is less than or equal to / s, the effects of the present invention can be more easily realized. The upper and lower limits of these numerical ranges can be combined in any way. Specifically, preferably 10 to 420 mm. 2 / s, more preferably 20-300mm 2 / s, more preferably 30-200mm 2 It is / s. In one aspect of the present invention, the base oil (A) used 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 to the above range.

[0032] The viscosity index of the base oil (A) used in one aspect of the present invention is preferably 90 or higher, more preferably 110 or higher, and even more preferably 130 or higher. In this specification, kinematic viscosity and viscosity index refer to values ​​measured or calculated in accordance with JIS K2283:2000.

[0033] In a grease composition according to one aspect of the present invention, the base oil (A) content is preferably 50% by mass or more, more preferably 55% by mass or more, even more preferably 60% by mass or more, and even more preferably 62% by mass or more, based on the total amount (100% by mass) of the grease composition, and also preferably 98.5% by mass or less, more preferably 97% by mass or less, even more preferably 95% by mass or less, and even more preferably 93% by 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) In one embodiment of the present invention, the urea-based thickener (B) may consist of one type or a mixture of two or more types.

[0035] In the above general formula (b1), R 1and R 2 Each of these independently represents a monovalent hydrocarbon group having 6 to 24 carbon atoms. 1 and R 2 They may be the same or they may be different from each other. 3 This represents a divalent aromatic hydrocarbon group having 6 to 18 carbon atoms.

[0036] In the above general formula (b1) R 1 and R 2 The number of carbon atoms in the monovalent hydrocarbon group that can be selected is 6 to 24, but preferably 6 to 20, and more preferably 6 to 18. Also, R 1 and R 2 Examples of monovalent hydrocarbon groups that can be selected include saturated or unsaturated monovalent chain hydrocarbon groups, saturated or unsaturated monovalent alicyclic hydrocarbon groups, and monovalent aromatic hydrocarbon groups.

[0037] Here, in the general formula (b1) above, R 1 and R 2 In the above, 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) are met. Requirement (a): The value of [(X+Y) / (X+Y+Z)] × 100 is 90 or greater (preferably 95 or greater, more preferably 98 or greater, 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). Furthermore, the alicyclic hydrocarbon group, the chain hydrocarbon group, and the aromatic hydrocarbon group are R in the general formula (b1) above. 1 and R 2Since it is a group selected as such, 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) above. Furthermore, the values ​​of requirements (a) and (b) above represent the average value of the total amount of the compound group represented by the general formula (b1) above contained in the grease composition. By using a compound represented by the general formula (b1) above that satisfies the above 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 monovalent saturated hydrocarbon groups include linear or branched alkyl groups having 6 to 24 carbon atoms. Specifically, these include hexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl, octadecyl, octadecenyl, nonadecyl, and eicosyl groups. Examples of monovalent unsaturated chain hydrocarbon groups include straight-chain or branched alkenyl groups having 6 to 24 carbon atoms. Specifically, these include hexenyl, heptenyl, octenyl, nonenyl, decenyl, undecenyl, dodecenyl, tridecenyl, tetradecenyl, pentadecenyl, hexadecenyl, heptadecenyl, octadecenyl, nonadecenyl, icocenyl, oleyl, geranyl, farnesyl, and linoleyl groups. Furthermore, the monovalent saturated-chain hydrocarbon group and the monovalent unsaturated-chain hydrocarbon group may be linear or branched.

[0039] Examples of monovalent saturated alicyclic hydrocarbon groups include cycloalkyl groups such as cyclohexyl, cycloheptyl, cyclooctyl, and cyclononyl groups; and cycloalkyl groups substituted with C1-C6 alkyl groups such as methylcyclohexyl, dimethylcyclohexyl, ethylcyclohexyl, diethylcyclohexyl, propylcyclohexyl, isopropylcyclohexyl, 1-methylpropylcyclohexyl, butylcyclohexyl, pentylcyclohexyl, pentyl-methylcyclohexyl, and hexylcyclohexyl groups (preferably cyclohexyl groups substituted with C1-C6 alkyl groups).

[0040] Examples of monovalent unsaturated alicyclic hydrocarbon groups include cycloalkenyl groups such as cyclohexenyl, cycloheptenyl, and cyclooctenyl groups; and cycloalkenyl groups substituted with C1-C6 alkyl groups such as methylcyclohexenyl, dimethylcyclohexenyl, ethylcyclohexenyl, diethylcyclohexenyl, and propylcyclohexenyl groups (preferably cyclohexenyl groups substituted with C1-C6 alkyl groups).

[0041] Examples of monovalent aromatic hydrocarbon groups include phenyl, biphenyl, terphenyl, naphthyl, diphenylmethyl, diphenylethyl, diphenylpropyl, methylphenyl, dimethylphenyl, ethylphenyl, and propylphenyl groups.

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

[0043] In a grease composition according to one aspect of the present invention, the content of component (B) is preferably 1.0 to 20.0% by mass, more preferably 1.5 to 15.0% by mass, even more preferably 2.0 to 13.0% by mass, even more preferably 2.5 to 10.0% by mass, and still more preferably 4.0% to 9.0% by mass, based on the total amount (100% by mass) of the grease composition. If the content of component (B) is 1.0% by mass or more, it is easier to adjust the consistency of the resulting grease composition to an appropriate range. On the other hand, if the content of component (B) is 20.0% by mass or less, the resulting grease composition can be made softer, making it easier to achieve good lubricity and improve wear resistance.

[0044] <Method for producing urea-based thickener (B)> Urea-based thickeners (B) can usually be obtained by reacting an isocyanate compound with a monoamine. This reaction is preferably carried out by adding a solution β, in which a monoamine is dissolved in the base oil (A), to a heated solution α obtained by dissolving the isocyanate compound in the base oil (A) as described above. For example, when synthesizing the compound represented by the general formula (b1), the isocyanate compound is R in the general formula (b1). 3 A diisocyanate having a group corresponding to the divalent aromatic hydrocarbon group shown is used, and as the monoamine, R 1 and R 2 Using an amine having a group corresponding to the monovalent hydrocarbon group shown, the desired urea-based thickener (B) can be synthesized by the above method.

[0045] Furthermore, in order to satisfy the above requirement (I), and moreover, the above requirement (II), it is preferable to manufacture a grease composition containing component (A) and component (B) using a grease manufacturing apparatus as shown in [1] below, from the viewpoint of micronizing the urea-based thickener (B) in the grease composition. [1] A container body having an introduction section into which grease raw material is introduced, and a discharge section for discharging grease to the outside, The container body comprises a rotor having a rotation axis in the axial direction of the inner circumference of the container body and rotatably mounted inside the container body, The rotor is, (i) Along the surface of the rotor, irregularities are provided alternately, and the irregularities are inclined with respect to the rotation axis, (ii) Having the ability to feed from the introduction section toward the discharge section A grease manufacturing apparatus equipped with a first uneven surface.

[0046] The grease manufacturing apparatus described in [1] above will be described below, but unless otherwise specified, the "preferred" provisions described below refer to embodiments from the viewpoint of micronizing the urea-based thickener (B) in the grease composition in order to satisfy requirement (I) above, and furthermore, requirement (II) above.

[0047] Figure 1 is a schematic cross-sectional view of the grease manufacturing apparatus described in [1] above, which may be used in one aspect 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 about the rotating shaft 12 as its central axis. The rotor 3 rotates at high speed around the rotating shaft 12, applying a high shear force to the grease raw material inside the container body 2. This produces grease containing a urea-based thickener (B). The container body 2 is preferably divided 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 Figure 1. The container body 2 preferably has a frustoconical inner surface, as shown in Figure 1, where the inner diameter gradually widens from the inlet 4 towards the discharge 8. The inlet section 4, which forms one end of the container body 2, is equipped with a plurality of solution inlet tubes 4A and 4B for introducing grease raw material from outside 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 surface of the retention section 5 will form large clumps, so it is preferable to transport it to the first inner surface 6 downstream as quickly as possible. More preferably, it is preferable to transport it directly to the first inner surface 6 without passing through the retention section 5. The first inner surface 6 is located downstream of the retention area 5, and the second inner surface 7 is located downstream of the first inner surface 6. As will be described in more detail later, it is preferable to provide the first uneven surface 9 on the first inner surface 6 and the second uneven surface 10 on the second inner surface 7 in order to make the first inner surface 6 and the second inner surface 7 function as high-shear sections that impart high shear force to the grease raw material or grease. The discharge section 8, which is the other end of the container body 2, is the part that discharges the grease that has been agitated on the first inner surface 6 and the second inner surface 7, and is equipped with a discharge port 11 for discharging the grease. The discharge port 11 is formed in a direction perpendicular to or approximately perpendicular to the rotation axis 12. As a result, the grease is discharged from the discharge port 11 in a direction perpendicular to 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 to or approximately parallel to the rotation axis 12.

[0049] The rotor 3 is rotatably mounted on the central axis of the frustoconical inner surface of the container body 2, with the rotation axis 12 being the axis of rotation, and rotates counterclockwise when the container body 2 is viewed from upstream to 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 frustum 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 frustum of the container body 2. The outer circumferential surface of the rotor 3 is provided with a first uneven portion 13 of the rotor, which has alternating irregularities arranged along the surface of the rotor 3.

[0050] The first protrusions 13 of the rotor are inclined with respect to the rotation axis 12 of the rotor 3 in the direction from the inlet 4 to the discharge 8, and have the ability to feed in the direction from the inlet 4 to the discharge 8. That is, the first protrusions 13 of the rotor are inclined in a direction that pushes the solution downstream when the rotor 3 rotates in the direction shown in Figure 1.

[0051] The difference in height between the recess 13A and the protrusion 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 recess 13A on the outer surface of the rotor 3 is 100. The number of protrusions 13B of the first concave 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 protrusion 13B to the width of the recess 13A of the first uneven portion 13 of the rotor [width of protrusion / width of recess] in a cross section perpendicular to the rotation axis 12 of the rotor 3 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 grooved portion 13 of the rotor with respect to the rotating shaft 12 is preferably 2 to 85 degrees, more preferably 3 to 45 degrees, and even more preferably 5 to 20 degrees.

[0053] Preferably, the first inner circumferential surface 6 of the container body 2 is provided with a first uneven portion 9, which has multiple irregularities formed along the inner circumferential surface. Furthermore, it is preferable that the protrusions of the first protrusions 9 on the container body 2 side are inclined in the opposite direction to the first protrusions 13 of the rotor. In other words, it is preferable that the multiple protrusions of the first protrusion portion 9 on the container body 2 side are inclined in a direction that pushes the solution downstream when the rotation axis 12 of the rotor 3 rotates in the direction shown in Figure 1. The stirring capacity and discharge capacity are further enhanced by the first protrusion portion 9 having multiple protrusions on the first inner circumferential surface 6 of the container body 2.

[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 100. The number of protrusions on the first protrusion portion 9 on the container body 2 side is preferably 2 to 1000, more preferably 6 to 500, and even more preferably 12 to 200.

[0055] The ratio of the width of the recesses in 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 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. Furthermore, 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 be made to function as a shearing portion that imparts high shear force to the grease raw material or grease; however, the first uneven portion 9 is not necessarily required.

[0056] Preferably, a second uneven portion 14 of the rotor is provided on the outer circumferential surface of the rotor downstream of the first uneven portion 13, with alternating unevenness arranged along the surface of the rotor 3. 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 the flow of the solution, pushing it back to the upstream side from the inlet portion 4 towards the discharge portion 8.

[0057] The step difference 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, when the diameter of the recess on the outer surface of the rotor 3 is taken as 100. The number of protrusions in the second uneven 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 protrusions to the width of the recesses [width of protrusions / width of recesses] of the second uneven portion 14 of the rotor in a cross section perpendicular to the rotation axis of the rotor 3 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 grooved portion 14 of the rotor with respect to the rotating shaft 12 is preferably 2 to 85 degrees, more preferably 3 to 45 degrees, and even more preferably 5 to 20 degrees.

[0059] Preferably, the second inner circumferential surface 7 of the container body 2 is provided with a second uneven portion 10, which has multiple uneven surfaces formed adjacent to the downstream portion of the unevenness in the first uneven portion 9 on the container body 2 side. Preferably, multiple irregularities are formed on the inner circumferential surface of the container body 2, and each irregularity is inclined in the opposite direction to the inclination direction of the second irregular portion 14 of the rotor. In other words, it is preferable that the multiple irregularities of the second irregularity portion 10 on the container body 2 side are inclined in a direction that pushes the solution back upstream when the rotation axis 12 of the rotor 3 rotates in the direction shown in Figure 1. The irregularities of the second irregularity portion 10 provided on the second inner circumferential surface 7 of the container body 2 further enhance the stirring capacity. In addition, the second inner circumferential surface 7 of the container body can function as a shearing section that imparts a high shear force to the grease raw material or grease.

[0060] The depth of the recess in 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 in the second uneven portion 10 on the container body 2 side is preferably 2 to 1000, more preferably 6 to 500, and even more preferably 12 to 200.

[0061] The ratio of the width of the protrusions to the width of the recesses [width of protrusions / width of recesses] 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 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 uneven 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 protrusion 9 on the container body 2 side to the length of the second protrusion 10 on the container body 2 side [length of the first protrusion / length of the second protrusion] is preferably 2 / 1 to 20 / 1.

[0062] Figure 2 is a cross-sectional view of the first uneven portion 9 on the container body 2 side of the grease manufacturing apparatus 1, in a direction perpendicular to the rotation axis 12. As shown in Figure 2, the first uneven portion 13 of the rotor is provided with multiple scrapers 15 whose tips protrude further toward the inner circumferential surface of the container body 2 than the tip of the protrusion 13B of the first uneven portion 13. Although not shown in the figure, the second uneven portion 14 is also provided with multiple scrapers, similar to the first uneven portion 13, whose tips protrude toward the inner circumferential surface of the container body 2. The scraper 15 scrapes off the grease adhering to the inner circumferential surface of the first uneven portion 9 and the second uneven portion 10 on the container body 2. The amount of protrusion of the tip of the scraper 15 relative to the amount of protrusion of the convex portion 13B of the first concave portion 13 of the rotor is preferably such that the ratio [R2 / R1] of the radius of the tip of the scraper 15 (R2) to the radius of the tip of the convex portion 13B (R1) is greater than 1.005 and less than 2.0.

[0063] The number of scrapers 15 is preferably 2 to 500, more preferably 2 to 50, and even more preferably 2 to 10. In the grease manufacturing apparatus 1 shown in Figure 2, a scraper 15 is provided, but it is also possible to omit the scraper 15, or to provide the scraper 15 intermittently.

[0064] To produce grease containing a urea-based thickener (B) using the grease manufacturing 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 a sulfur-phosphorus extreme pressure agent (C) and other additives (D) are blended into the grease base material obtained in this manner, the urea-based thickener (B) in the grease composition can be refined to satisfy requirement (I) and even requirement (II) above.

[0065] As a condition for high-speed rotation of the rotor 3, the shear rate applied to the grease raw material is preferably 10 2 s -1 The above is more comfortable 10 3 s -1 More preferably 10 4 s -1 That's all, and also, usually 10 7 s -1 The following applies:

[0066] Furthermore, the ratio (Max / Min) of the maximum shear rate (Max) to the minimum shear rate (Min) during high-speed rotation of the rotor 3 is preferably 100 or less, more preferably 50 or less, and even more preferably 10 or less. By ensuring that the shear rate is as uniform as possible with respect to the mixture, the urea-based thickener (B) and its precursor in the grease composition can be more easily refined, resulting in a more uniform grease structure.

[0067] Here, the maximum shear rate (Max) is the highest shear rate applied to the mixture, and the minimum shear rate (Min) is the lowest shear rate applied to the mixture, and are defined as follows. • Maximum shear rate (Max) = (Linear velocity at the tip of the protrusion 13B of the first protrusion 13 of the rotor) / (Gap A1 between the tip of the protrusion 13B of the first protrusion 13 of the rotor and the protrusion 9 of the first protrusion 9 of the first inner surface 6 of the container body 2) * Minimum shear rate (Min) = (linear velocity of the recess 13A of the first protrusion 13 of the rotor) / (gap A2 between the recess 13A of the first protrusion 13 of the rotor and the recess of the first protrusion 9 of the first inner surface 6 of the container body 2) Gap A1 and Gap A2 are as shown in Figure 2.

[0068] Because the grease manufacturing apparatus 1 is equipped with a scraper 15, grease adhering to the inner surface of the container body 2 can be scraped off, preventing lumps from forming during mixing, and enabling the continuous production of finely textured grease containing urea-based thickener (B) in a short time. Furthermore, the scraper 15 scrapes off the adhering grease, preventing the stagnant grease from becoming resistance to the rotation of the rotor 3. This reduces the rotational torque of the rotor 3, thereby reducing the power consumption of the drive source and enabling efficient continuous production of grease.

[0069] Since the inner circumferential surface of the container body 2 is frustoconical in shape, with the inner diameter increasing from the inlet 4 to the discharge 8, centrifugal force has the effect of discharging grease or grease raw material downstream, reducing the rotational torque of the rotor 3 and enabling continuous grease production. The rotor 3 has a first uneven portion 13 on its outer circumferential surface, and the first uneven portion 13 is inclined with respect to the rotation axis 12 of the rotor 3, providing a feeding capability from the introduction portion 4 to the discharge portion 8. The second uneven portion 14 of the rotor is also inclined with respect to the rotation axis 12 of the rotor 3, providing a feeding suppression capability from the introduction portion 4 to the discharge portion 8. As a result, a high shear force can be imparted to the solution, and even after the additive is blended, the urea-based thickener (B) in the grease composition can be micronized to satisfy requirement (I) and further requirement (II) above.

[0070] A first uneven portion 9 is formed on the first inner circumferential surface 6 of the container body 2, and since it 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, it is possible to further sufficiently stir the grease raw material while pushing the grease or grease raw material downstream, and even after the additive is blended, the urea-based thickener (B) in the grease composition can be made finer so as to satisfy the above requirement (I) and further requirement (II). Furthermore, since a second uneven portion 10 is provided on the second inner circumferential surface 7 of the container body 2, and a second uneven portion 14 is provided on the outer circumferential surface of the rotor 3, it is possible to prevent the grease raw material from flowing out of the first inner circumferential surface 6 of the container body more than necessary. This imparts a high shear force to the solution, highly dispersing the grease raw material, and even after the additive is blended, the urea-based thickener (B) can be finely milled to satisfy the above requirement (I), and furthermore, requirement (II).

[0071] <Melamine cyanurate (C)> The grease composition of the present invention comprises melamine cyanurate (C) along with components (A) and (B). The grease composition of the present invention contains melamine cyanurate (C), which allows for a grease composition with excellent wear resistance. Melamine cyanurate is an organic salt composed of melamine and cyanuric acid, and it has a graphite structure.

[0072] The particle size of melamine cyanurate (C) is preferably 5.0 μm or less, more preferably 4.0 μm or less, even more preferably 3.0 μm or less, even more preferably 2.5 μm or less, and still more preferably 2.0 μm or less. There is no particular lower limit for the particle size of melamine cyanurate (C), but it is usually 0.005 μm or more. The smaller the particle size of melamine cyanurate (C), the easier it is for the solid lubricant melamine cyanurate (C) to penetrate into defects on the surface of the resin material that the grease composition comes into contact with. As a result, the melamine cyanurate (C) seals the defects, suppressing the progression of defects in the resin material and reducing wear, even when subjected to high loads for extended periods. Therefore, a smaller particle size of melamine cyanurate (C) is preferable. In this specification, the particle size of melamine cyanurate (C) refers to the average particle size measured by the following method. Furthermore, the particle size of melamine cyanurate (C) alone is maintained at a similar level within the grease composition. (That is, the particle size of melamine cyanurate (C) contained in the grease composition is approximately the same as the particle size of melamine cyanurate (C) itself.)

[0073] [Particle size of melamine cyanurate (C)] The particle size (average particle size) of melamine cyanurate (C) was measured at 25°C using dynamic light scattering (photon correlation method), and the 50% particle size (volume median particle size, D) was calculated from the dispersed particle size distribution analyzed by the CONTIN method, based on the scattering intensity. 50 ) can be used.

[0074] In the grease composition of the present invention, the melamine cyanurate (C) content is preferably 0.2% by mass or more, more preferably 0.3% by mass or more, and even more preferably 0.5% by mass or more, based on the total amount (100% by mass) of the grease composition, from the viewpoint of wear resistance. Furthermore, in the grease composition of the present invention, the melamine cyanurate (C) content is preferably 10.0% by mass or less, more preferably 5.0% by mass or less, even more preferably 3.0% by mass or less, and even more preferably 2.0% by mass or less, based on the total amount (100% by mass) of the grease composition, from the viewpoint of reducing wear.

[0075] From the viewpoint of abrasion resistance, the content ratio of the urea-based thickener (B) to melamine cyanurate (C) [(B) / (C)] is preferably 1.0 to 18.0, more preferably 3.0 to 15.0, and even more preferably 5.0 to 12.0 by mass.

[0076] <Oily-based agent (D)> The grease composition of the present invention preferably contains an oily agent (D) along with components (A), (B), and (C). A grease composition according to one aspect of the present invention can be made to have a lower coefficient of friction by including an oily agent (D).

[0077] As the oily agent (D), at least one selected from, for example, sarcosine derivatives (D1), amine compounds (D2), polyamide compounds (D3), and ether compounds (D4) is preferred. These may be used individually or in combination of two or more.

[0078] <<Sarcosine derivative (D1)>> The sarcosine derivative (D1) is an α-amino acid in which a secondary or tertiary amino group having a methyl group is bonded to the carbon atom to which a carboxyl group is bonded, and it can be an aliphatic amino acid having an N-methylglycine or N-methylglycine skeleton. Examples of sarcosine derivatives (D1) include N-oleoylsarcosine, N-methyl-oleylsarcosine, N-methyl-stearylsarcosine, N-octyl-oleylsarcosine, N-lauryl-oleylsarcosine, and N-lauryl-stearylsarcosine. Among these, N-oleoylsarcosine is preferred. These sarcosine derivatives (D1) may be used individually or in combination of two or more.

[0079] In one aspect of the present invention, the sarcosine derivative (D1) is preferably a compound represented by the following general formula (d-1). [ka]

[0080] In the above general formula (d-1), R is an alkyl group having 1 to 30 carbon atoms, or an alkenyl group having 1 to 30 carbon atoms. The number of carbon atoms in the alkyl and alkenyl groups is 1 to 30, preferably 6 to 27, more preferably 10 to 24, and even more preferably 12 to 20. The alkyl group may be a linear alkyl group or a branched alkyl group. Furthermore, the alkenyl group may be a linear alkenyl group or a branched alkenyl group.

[0081] <<Amine compound (D2)>> The amine compound (D2) can be any compound having an amino group, such as monoamines, diamines, and triamines. The amine compound (D2) may be used alone or in combination of two or more types. Among these, monoamines are preferred as the amine compound (D2) used in one aspect of the present invention, and aliphatic monoamines are more preferred.

[0082] Examples of aliphatic monoamines used in one aspect of the present invention include primary aliphatic monoamines represented by the following general formula (d2-i), secondary aliphatic monoamines represented by the following general formula (d2-ii), and tertiary aliphatic monoamines represented by the following general formula (d2-iii). [ka]

[0083] In the above general formulas (d2-i) to (d2-iii), R 11 ~R 13 Each of these is independently an alkyl group or an alkenyl group, and an alkenyl group is preferred. R 11 ~R 13 The number of carbon atoms in the alkyl and alkenyl groups that can be selected is preferably 8 to 22, more preferably 10 to 20, and even more preferably 12 to 18. The alkyl group may be a linear alkyl group or a branched alkyl group. Furthermore, the alkenyl group may be a linear alkenyl group or a branched alkenyl group.

[0084] Examples of primary aliphatic monoamines represented by the general formula (d2-i) include octylamine, laurylamine, stearylamine, and oleylamine. Among these, oleylamine is preferred. Examples of secondary aliphatic monoamines represented by the general formula (d2-ii) include dioctylamine, dilaurylamine, distearylamine, and dioleylamine. Examples of tertiary aliphatic monoamines represented by the general formula (d2-iii) include trioctylamine, trilaurylamine, tristearylamine, and trioleylamine.

[0085] In one aspect of the present invention, the amine compound (D2) used is preferably a primary aliphatic monoamine represented by the general formula (d2-i), wherein the R in the general formula (i) 1 A primary aliphatic monoamine is more preferable, in which the alkenyl group has 8 to 22 carbon atoms.

[0086] <<Polyamide compound (D3)>> The polyamide compound (D3) can be any compound having multiple amide bonds, but it is preferably an acid amide obtained by reacting carboxylic acids with amines, and more preferably a fatty acid amide obtained by reacting fatty acids with amines. The polyamide compound (D3) may be used alone or in combination of two or more types.

[0087] Examples of carboxylic acids include linear or branched saturated or unsaturated monocarboxylic acids, specifically saturated fatty acids such as heptanoic acid, octanoic acid, nonanoic acid, decanoic acid, undecanoic acid, dodecanoic acid, tridecanoic acid, tetradecanoic acid, pentadecanoic acid, hexadecanoic acid, heptadecanoic acid, octadecanoic acid, isostearic acid, nonadecanoic acid, eicosanoic acid, henicosanoic acid, docosanoic acid, tricosanoic acid, and tetracosanoic acid; and unsaturated fatty acids such as heptenoic acid, octenoic acid, nonenic acid, decenoic acid, undecenoic acid, dodecenoic acid, tridecenoic acid, tetradecenoic acid, pentadecenoic acid, hexadecenoic acid, heptadecenoic acid, octadecenoic acid (including oleic acid), nonadecenoic acid, eicosenoic acid, henicosenoic acid, docosenoic acid, tricosenoic acid, and tetracosenoic acid. Among these, isostearic acid is preferred. These saturated and unsaturated fatty acids may be either straight-chain or branched-chain. Furthermore, the position of the double bond in an unsaturated fatty acid is arbitrary.

[0088] The number of carbon atoms in the carboxylic acids is preferably 7 to 30, more preferably 8 to 24, and even more preferably 10 to 22.

[0089] Examples of amines include alkylamines, alkanolamines, and polyalkylene polyamines. Among these, polyalkylene polyamines are preferred.

[0090] Examples of alkylamines include primary aliphatic alkylamines such as monomethylamine, monoethylamine, monopropylamine, monobutylamine, monopentylamine, monohexylamine, and monoheptylamine; and secondary aliphatic alkylamines such as dimethylamine, methylethylamine, diethylamine, methylpropylamine, ethylpropylamine, dipropylamine, methylbutylamine, ethylbutylamine, propylbutylamine, dibutylamine, dipentylamine, dihexylamine, and diheptylamine. Furthermore, the alkyl group in the alkylamine may be either a straight chain or a branched chain.

[0091] Examples of alkanolamines include monomethanolamine, monoethanolamine, monopropanolamine, monobutanolamine, monopentanolamine, monohexanolamine, dimethanolamine, methanolethanolamine, diethanolamine, methanolpropanolamine, ethanolpropanolamine, dipropanolamine, methanolbutanolamine, ethanolbutanolamine, propanolbutanolamine, dibutanolamine, dipentanolamine, and dihexanolamine. Furthermore, the alkanol group in the alkanolamine may be either linear or branched.

[0092] Examples of polyalkylene polyamines include diethylenetriamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, hexaethyleneheptamine, tetrapropylenepentamine, and hexasubtileneheptamine. Among these, tetraethylenepentamine is preferred.

[0093] <<Ether compound (D4)>> Any compound containing an ether bond can be used as the ether compound (D4), such as aliphatic ethers. Examples of aliphatic ethers include monoalkylglyceryl ethers. The alkyl group in the monoalkylglyceryl ether preferably has 1 to 20 carbon atoms, more preferably 4 to 10. The alkyl group in the monoalkylglyceryl ether may be a straight chain or a branched chain. Examples of alkyl groups included in monoalkylglyceryl ethers include methyl group, ethyl group, propyl group, n-butyl group, isobutyl group, n-pentyl group, 2-methylbutyl group, isopentyl group, n-hexyl group, isohexyl group, n-heptyl group, n-octyl group, 2-ethylhexyl group, n-decyl group, and isodecyl group. Examples of monoalkylglyceryl ethers include 1-methylglyceryl ether, 2-methylglyceryl ether, 1-ethylglyceryl ether, 1-pentylglyceryl ether, 2-pentylglyceryl ether, and 1-octylglyceryl ether.

[0094] In the grease composition of the present invention, the content of the oily agent (D) is preferably 0.1 to 5.0% by mass, more preferably 0.5 to 3.0% by mass, and even more preferably 0.8 to 1.5% by mass, based on the total amount (100% by mass) of the grease composition, from the viewpoint of reducing the coefficient of friction.

[0095] The content ratio of melamine cyanurate (C) to oily agent (D) [(C) / (D)] is preferably 0.3 to 3.0, more preferably 0.4 to 2.0, and even more preferably 0.6 to 1.5 by mass, from the viewpoint of wear resistance and friction characteristics.

[0096] <Abrasion-resistant agent (E)> The grease composition of the present invention preferably contains an anti-wear agent (E) along with components (A), (B), and (C). A grease composition according to one embodiment of the present invention can be made to have improved wear resistance by including an anti-wear agent (E).

[0097] Examples of the wear-resistant agent (E) include at least one selected from ester compounds (E1) and bisamide compounds (E2). These may be used individually or in combination of two or more.

[0098] There are no particular restrictions on the ester compound (E1), and examples include fatty acid esters. The fatty acids that make up the fatty acid ester may be saturated fatty acids or unsaturated fatty acids. The number of carbon atoms in the fatty acid constituting the fatty acid ester is preferably 10 to 24, more preferably 12 to 22, and even more preferably 16 to 20. There are no particular restrictions on the fatty acid esters, and examples include methyl stearate, methyl laurate, methyl myristate, methyl palmitate, methyl oleate, methyl erucate, methyl behenate, butyl laurate, butyl stearate, isopropyl myristate, isopropyl palmitate, and octyl palmitate. These may be used individually or in combination of two or more. Among these, methyl stearate is preferred.

[0099] The bisamide compound (E2) is not particularly limited, and examples include fatty acid bisamides. There are no particular restrictions on the fatty acid bisamide; for example, ethylenebisstearate, methylenebiscaprylate, methylenebiscaprate, methylenebislaurate, methylenebismyristicate, methylenebispalmitate, methylenebisstearate, methylenebisisostearate, methylenebisbehenate, methylenebisoleamide, methylenebiserucate, ethylenebiscaprylate, ethylenebiscaprate, ethylenebislaurate, ethylenebismyristicate, ethylenebispalmitate, ethylenebisisostearate, ethylenebisbehenate, ethylenebisoleamide, ethylenebisoleamide, ethylenebis Examples include lenbis-erucic acid amide, butylene bis-stearic acid amide, butylene bis-behenic acid amide, butylene bis-oleic acid amide, butylene bis-erucic acid amide, hexamethylene bis-stearic acid amide, hexamethylene bis-behenic acid amide, hexamethylene bis-oleic acid amide, hexamethylene bis-erucic acid amide, m-xylylene bis-stearic acid amide, m-xylylene bis-12-hydroxystearic acid amide, p-xylylene bis-stearic acid amide, p-phenylene bis-stearic acid amide, methylene bis-hydroxystearic acid amide, ethylene bis-hydroxystearic acid amide, butylene bis-hydroxystearic acid amide, and hexamethylene bis-hydroxystearic acid amide. These may be used individually or in combination of two or more. Among these, ethylene bis-stearic acid amide is preferred.

[0100] The content ratio of melamine cyanurate (C) to abrasion resistant agent (E) [(C) / (E)] is preferably 0.1 to 2.0, more preferably 0.2 to 1.0, and even more preferably 0.3 to 0.5 by mass, from the viewpoint of abrasion resistance.

[0101] <Friction reducing agent (F)> The grease composition of the present invention preferably contains a friction reducer (F) along with components (A), (B), and (C). In one embodiment of the present invention, the grease composition can be made to further improve the frictional properties of the grease composition by including a friction reducing agent (F).

[0102] Examples of friction-reducing agents (F) include polymer compounds (F1).

[0103] Examples of polymer compounds (F1) include non-dispersible poly(meth)acrylates, dispersed poly(meth)acrylates, star-shaped polymers, olefin copolymers, dispersed olefin copolymers, polyalkylstyrenes, and styrene copolymers. Examples of olefin copolymers include ethylene-propylene copolymers and ethylene-butylene copolymers. Examples of styrene-based copolymers include styrene-diene copolymers and styrene-isoprene copolymers. These can be used individually or in combination of two or more types. Furthermore, they may be either random copolymers or block copolymers. Among these, ethylene-propylene copolymer and ethylene-butylene copolymer are preferred.

[0104] The mass-average molecular weight (Mw) of the polymer compound (F1) is preferably 50,000 or more, and more preferably 100,000 or more, from the viewpoint of wear resistance. Furthermore, the mass-average molecular weight (Mw) of the polymer compound (F1) is preferably 1,000,000 or less, from the viewpoint of the availability of the polymer compound.

[0105] The number-average molecular weight (Mn) of the polymer compound (F1) is preferably 30,000 or more, more preferably 50,000 or more, and even more preferably 80,000 or more, from the viewpoint of wear resistance. Furthermore, the number-average molecular weight (Mn) of the polymer compound (F1) is preferably 500,000 or less, from the viewpoint of the availability of the polymer compound.

[0106] From the viewpoint of wear resistance, the molecular weight distribution (Mw / Mn) of the polymer compound (F1) is preferably 2.20 or less, more preferably 2.00 or less, even more preferably 1.90 or less, and even more preferably 1.85 or less. Furthermore, from the viewpoint of the availability of the polymer compound, the molecular weight distribution (Mw / Mn) of the polymer compound (F1) is preferably 1.10 or more.

[0107] The content of the polymer compound (F1) in terms of resin equivalent is preferably 0.1 to 35.0% by mass, more preferably 1.0 to 30.0% by mass, even more preferably 5.0 to 27.0% by mass, and even more preferably 8.0 to 26.0% by mass, based on the total amount (100% by mass) of the grease composition, from the viewpoint of reducing the coefficient of friction.

[0108] <Additive (G)> A grease composition according to one aspect of the present invention may contain additives (G) other than components (B), (C), (D), (E), and (F) that are commonly used in greases, as long as they do not impair the effects of the present invention. Examples of additives (G) include antioxidants, rust inhibitors, extreme pressure agents, thickeners, solid lubricants, detergent dispersants, corrosion inhibitors, and metal deactivators. Each additive (G) may be used individually or in combination of two or more types.

[0109] Examples of antioxidants include phenolic antioxidants. Examples of rust inhibitors include carboxylic acid-based rust inhibitors such as alkenyl succinic acid polyhydric alcohol esters. Examples include zinc stearate, thiadiazole and its derivatives, and benzotriazole and its derivatives. Examples of extreme pressure agents include thiocarbamates such as zinc dialkyldithiophosphate, molybdenum dialkyldithiophosphate, ashless dithiocarbamates, zinc dithiocarbamates, and molybdenum dithiocarbamates; sulfur compounds such as sulfurized oils and fats, sulfurized olefins, polysulfides, thiophosphates, thioterpenes, and dialkylthiodipyropionates; phosphate esters such as tricresyl phosphate; and phosphite esters such as triphenylphosphite. Examples of solid lubricants include polyimide, PTFE, graphite, metal oxides, boron nitride, and molybdenum disulfide. Examples of cleaning dispersants include ashless dispersants such as succinimide and boron-based succinimide. Examples of corrosion inhibitors include benzotriazole compounds and thiazole compounds. Examples of metal deactivators include benzotriazole compounds.

[0110] In a grease composition according to one aspect of the present invention, the content of these additives (G) is appropriately set according to the type of additive, but each is independently typically 0.01 to 20% by mass, preferably 0.01 to 15% by mass, more preferably 0.01 to 10% by mass, and even more preferably 0.01 to 7% by mass, based on the total amount (100% by mass) of the grease composition.

[0111] <Physical properties of the grease composition> (Consistency of mixing) The consistency of the grease composition according to one embodiment of the present invention at 25°C is preferably 220 to 430, more preferably 240 to 360, even more preferably 250 to 350, and even more preferably 260 to 330, from the viewpoint of providing excellent wear resistance. In this specification, the consistency of the grease composition refers to the value measured at 25°C in accordance with JIS K2220:2013 (Clause 7).

[0112] (Abrasion resistance) The wear resistance of a grease composition according to one aspect of the present invention can be evaluated by measuring the rate of reduction in wear amount using the method described in the examples below.

[0113] <Method for producing grease composition> The grease composition of the present invention can be manufactured by mixing a grease (base grease) containing a base oil (A), a urea-based thickener (B), melamine cyanurate (C), and optionally an oiliness agent (D), an anti-wear agent (E), a friction reducer (F), and an additive (G). For example, it can be manufactured by mixing a grease (base grease) containing a base oil (A) and a urea-based thickener (B), and then adding melamine cyanurate (C), and optionally an oiliness agent (D), an anti-wear agent (E), a friction reducer (F), and an additive (G), mixing and homogenizing the mixture.

[0114] <Applications of grease compositions> The grease composition of the present invention exhibits excellent wear resistance. In particular, it exhibits excellent wear resistance when used for lubricating sliding parts composed of metal and resin materials. Therefore, a grease composition according to one aspect of the present invention can be suitably used for lubrication of sliding parts of various devices, but it is particularly preferable to use it for lubrication of devices having sliding parts made of metal and resin materials. The metal material is preferably various types of steel such as carbon steel and stainless steel, various alloys such as aluminum alloys, or copper. However, the metal material may be replaced with a material with high strength (for example, 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 viewpoint of heat resistance and mechanical strength. Examples of engineering plastics include synthetic resins such as polyamide resins, polyacetal resins, polycarbonate resins, polysulfone resins, polyphenylene sulfide resins, polyamide-imide resins, polyetheretherketone resins, phenolic resins, polyester resins, and epoxy resins. Furthermore, fiber-reinforced resin materials are preferred as the resin material. Examples of fiber-reinforced resin materials include glass fiber-reinforced resin materials.

[0115] Fields in which the grease composition of the present invention can be suitably used include the automotive industry, office equipment industry, machine tool industry, wind turbine industry, construction industry, agricultural machinery industry, or industrial robot industry. Examples of lubrication parts in automotive devices that can suitably use the grease composition of the present invention 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, drive motor flywheels, ball joints, wheel bearings, spline sections, and constant velocity joints; and bearing parts, gear sections, and sliding parts in devices such as door locks, door hinges, and clutch boosters. More specifically, examples include hub units, electric power steering, drive electric motor flywheels, ball joints, wheel bearings, spline sections, constant velocity joints, clutch boosters, servo motors, blade bearings, or generator bearing sections.

[0116] Examples of lubrication parts in office equipment that can suitably use the grease composition of the present invention include, for example, the fixing rolls in printers and other devices, and the bearings and gear parts in polygon motors and other devices. Examples of lubrication parts in machine tool equipment that can suitably use the grease composition of the present invention include spindles, servo motors, bearing parts in reduction gears of machine robots, and the like. Examples of lubrication parts in wind turbine equipment that can suitably use the grease composition of the present invention include blade bearings and bearing parts of generators, etc. Examples of lubrication parts in devices for construction or agricultural machinery that can suitably use the grease composition of the present invention include bearing parts such as ball joints and spline sections, gear sections, and sliding parts.

[0117] In one embodiment of an apparatus to which the grease composition of the present invention can be applied, it is preferable that the sliding mechanism is a reduction gear (worm gear) for electric power steering, having a metal worm and a resin worm wheel. By configuring the apparatus in this way, excellent wear resistance is achieved.

[0118] [Lubrication methods for sliding mechanisms] A method for lubricating a sliding mechanism applicable to the grease composition of the present invention is a method for lubricating a sliding mechanism in which a metal material and a resin material slide against each other using the grease composition of the present invention described above.

[0119] The lubrication method for sliding mechanisms applicable to the grease composition of the present invention can reduce the amount of wear in the lubricated parts. This effect is particularly pronounced when the sliding mechanism is a reduction gear (worm gear) for electric power steering, having a metal worm and a resin worm wheel, resulting in excellent wear resistance.

[0120] According to one aspect of the present invention, the following [1] to

[16] are provided. [1] A grease composition containing a base oil (A), a urea-based thickener (B), and melamine cyanurate (C), A grease composition wherein the particles containing the urea-based thickener (B) in the grease composition satisfy the following requirement (I). Requirement (I): The arithmetic mean particle diameter based on area, when the particles are measured by laser diffraction and scattering, is 2.0 μm 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 particle measured by laser diffraction and scattering is 0.5 × 10⁻⁶. 5 cm 2 / cm 3 That's all. [3] The grease composition according to [1] or [2], wherein the content of melamine cyanurate (C) is 0.2% by mass or more on a basis of the total amount of the grease composition. [4] The grease composition according to any one of [1] to [3], wherein the particle size of the melamine cyanurate (C) is 5.0 μm or less. [5] The grease composition according to any one of [1] to [4], further comprising one or more oily agents (D) selected from the group consisting of sarcosine derivatives (D1), amine compounds (D2), polyamide compounds (D3), and ether compounds (D4). [6] The grease composition according to [5], wherein the ratio of the melamine cyanurate (C) content to the oily agent (D) content [(C) / (D)] is 0.3 to 3.0 by mass. [7] The grease composition according to any one of [1] to [6], further comprising one or more anti-wear agents (E) selected from the group consisting of ester compounds (E1) and bisamide compounds (E2). [8] The grease composition according to [7], wherein the ratio of the content of melamine cyanurate (C) to the content of the wear-resistant agent (E) [(C) / (E)] is 0.1 to 2.0 by mass. [9] The grease composition according to any one of [1] to [8], wherein the content of the urea-based thickener (B) is 1.0% by mass to 20.0% by mass on a basis of the total amount of the grease composition.

[10] The grease composition according to any one of [1] to [9], wherein the content ratio [(B) / (C)] of the urea-based thickener (B) to the melamine cyanurate (C) is 1.0 to 18.0 by mass.

[11] The kinematic viscosity of the base oil (A) at 40°C is 30 mm 2 / s~200mm 2A grease composition according to any one of the above [1] to

[10] , wherein the value is / s.

[12] A grease composition according to any one of [1] to

[11] , wherein the consistency of the mixture is 260 to 330.

[13] A grease composition according to any one of [1] to

[12] above, used for lubricating a sliding mechanism in which a metal material and a resin material slide against each other.

[14] The grease composition according to

[13] , wherein the resin material is a glass fiber reinforced resin material.

[15] A lubrication method for lubricating a sliding mechanism in which a metal material and a resin material slide against each other using the grease composition described in any one of [1] to

[12] above.

[16] The lubrication method according to

[15] , wherein the resin material is a glass fiber reinforced resin material. [Examples]

[0121] The present invention will be specifically described by the following examples, but the present invention is not limited to the following examples.

[0122] [Various physical properties] The measurement methods for various physical properties were as follows: (1) Kinematic viscosity and viscosity index of base oil (A) at 40°C Measurements and calculations were performed in accordance with JIS K2283:2000. (2) Average particle size of melamine cyanurate (C) The 50% particle size (volume median particle size, D) was calculated from the dispersion particle size distribution, which was measured at 25°C using dynamic light scattering (photon correlation method) and analyzed by the CONTIN method, based on the scattering intensity. 50 ) was used. (3) Mass-average molecular weight (Mw), number-average molecular weight (Mn), and molecular weight distribution (Mw / Mn) of the polymer compound (F1) The values ​​used were measured using a gel permeation chromatograph (Agilent HPLC, model number "1260") under the following measurement conditions, and converted to standard polystyrene equivalents. -Measurement conditions- • Column: Two "Shodex LF404" columns connected sequentially. • Column temperature: 35℃ • Developing solvent: Chloroform ·Flow rate: 0.3mL / min (4) Consistency of the grease composition Measurements were taken at 25°C in accordance with JIS K2220:2013 (Clause 7).

[0123] [Raw materials] In Examples 1-4 and Comparative Examples 1-2, the base oil (A), melamine cyanurate (C), oiliness agent (D), wear inhibitor (E), friction reducer (F), and additive (G) used as raw materials for preparing the grease composition were as follows. Note that the content figures in Table 1 are calculated based on resin content.

[0124] <Base oil (A)> • Base oil (A1) (Poly-α-olefin (PAO), kinematic viscosity at 40°C: 30 mm) 2 / s, viscosity index: 130) • Base oil (A2) (poly-α-olefin (PAO), kinematic viscosity at 40°C: 400 mm) 2 / s, viscosity index: 150)

[0125] <Melamine cyanurate (C)> • Melamine cyanurate (C1) (average particle size: approximately 4.5 μm) • Melamine cyanurate (C2) (average particle size: approximately 3.0 μm) • Melamine cyanurate (C3) (average particle size: approximately 1.5 μm)

[0126] <Oily-based agent (D)> • Sarcosine derivative (D1): N-oleoyl sarcosine • Amine compound (D2): Oleylamine • Polyamide compound (D3): Reaction product of isostearic acid and tetraethylenepentamine

[0127] <Abrasion-resistant agent (E)> • Ester compound (E1): Methyl stearate • Bisamide compound (E2): Ethylene bis-stearic acid amide

[0128] <Friction reducing agent (F)> • Polymer compound (F1): Ethylene-propylene copolymer (Mass-average molecular weight (Mw): 172,000, Number-average molecular weight (Mn): 93,500, Molecular weight distribution (Mw / Mn): 1.84)

[0129] <Additive (G)> • Antioxidant: Phenolic antioxidant

[0130] (Example 1) (1) Synthesis of urea grease Solution α was prepared by adding 3.25 parts by mass of diphenylmethane-4,4'-diisocyanate (MDI) to a mixed base oil of 13.00 parts by mass of base oil (A1) and 26.45 parts by mass of base oil (A2) heated to 70°C. In addition, solution β was prepared by adding 1.03 parts by mass of cyclohexylamine and 4.20 parts by mass of octadecylamine (stearylamine) to a mixed base oil consisting of 13.00 parts by mass of base oil (A1) and 25.00 parts by mass of base oil (A2), which had been prepared separately and heated to 70°C. Then, using the grease manufacturing apparatus 1 shown in Figure 1, equal amounts of solution α heated to 70°C were simultaneously introduced into the container body 2 through the solution introduction pipe 4A, and equal amounts of solution β heated to 70°C were introduced through the solution introduction pipe 4B. The rotor 3 was rotated while the solutions α and β were continuously introduced into the container body 2. After that, the mixture was heated to 160°C using a stirring device, stirred for 1 hour, and then homogenized by roll milling to synthesize urea grease (b1). The rotational speed of the rotor 3 of the grease manufacturing device 1 used was set to 8,000 rpm. The maximum shear speed (Max) at this time was 10,500 s. -1 The mixture was stirred with a ratio of the maximum shear rate (Max) to the minimum shear rate (Min) [Max / Min] of 3.5. Furthermore, the urea-based thickener (B1) contained in the obtained urea grease is R in the general formula (b1) above. 1 and R 2However, it is a cyclohexyl group or an octadecyl group (stearyl group), R 3 This corresponds to a compound in which the group is a diphenylmethylene group. Furthermore, the molar ratio (cyclohexylamine / octadecylamine) of cyclohexylamine and octadecylamine used as raw materials was 40 / 60. (2) Preparation of grease composition In (1) above, the urea grease (b1) discharged from the grease manufacturing apparatus 1 shown in Figure 1 was stirred and then cooled by natural cooling. Next, the urea grease (b1), which had been cooled to 25°C by natural cooling, was mixed with each component from melamine cyanurate (C2) to the phenolic antioxidant shown in Table 1, in the amounts shown in Table 1. After that, it was homogenized using a three-roll mill to obtain the grease composition of Example 1.

[0131] (Example 4) The grease composition of Example 4 was obtained in the same manner as in Example 1, except that the content of each component was changed as follows in the synthesis of urea grease (1) of Example 1. 30.00 parts by mass of base oil (A1) heated to 70°C • Diphenylmethane-4,4'-diisocyanate (MDI) 4.10 parts by mass • 29.95 parts by mass of base oil (A1) heated to 70°C, prepared separately. 2.60 parts by mass of cyclohexylamine Octadecylamine (stearylamine) 1.77 parts by mass Furthermore, the urea-based thickener (B2) contained in the obtained urea grease is R in the general formula (b1) above. 1 and R 2 However, it is a cyclohexyl group or an octadecyl group (stearyl group), R 3 This corresponds to a compound in which the group is a diphenylmethylene group. Furthermore, the molar ratio (cyclohexylamine / octadecylamine) of cyclohexylamine and octadecylamine used as raw materials is 80 / 20.

[0132] (Examples 2-3, Comparative Examples 1-2) Each grease composition was prepared in the same manner as described above, except that the content was changed as shown in Table 1.

[0133] [Requirements] The following calculations were performed for the urea grease synthesized in Examples 1-4 and Comparative Examples 1-2.

[0134] (1) Calculation of particle size of particles containing urea-based thickeners: Requirement (I) The particle size of particles containing a urea-based thickener in the 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 the urea-based thickener (B) was determined by the following procedure. First, the sample was degassed under vacuum and then filled into a 1 mL syringe. 0.10–0.15 mL of the sample was extruded from the syringe and placed on the surface of a plate-shaped cell of a paste cell fixing jig. Next, another plate-shaped cell was placed on top of the sample to obtain a measurement cell in which the sample was sandwiched between two cells. Then, the arithmetic mean particle size of the particles in the sample within the measurement cell was measured using a laser diffraction particle size analyzer (manufactured by Horiba, Ltd., product name: LA-920) based on area. Here, "arithmetic mean particle diameter based on area" refers to the value obtained by arithmetic mean of the particle diameter distribution based on area. The particle diameter distribution based on area represents the frequency distribution of particle diameters among all particles being measured, based on the area calculated from the particle diameter (more specifically, the cross-sectional area of ​​the particle having that particle diameter). Furthermore, the value obtained by arithmetic mean of the particle diameter distribution based on area can be calculated using the following formula (1).

[0135]

number

[0136] (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 thickener-containing particles in the grease composition, as measured in the above requirement (I). Specifically, the specific surface area was calculated using the said particle size distribution, per unit volume (1 cm³). 3 ) Surface area of ​​particles per unit (unit: cm 2 The total of ) is calculated and this is used as the specific surface area (unit: cm²). 2 / cm 3 )

[0137] Next, the wear resistance will be evaluated based on Examples 1-4 and Comparative Examples 1-2 described above.

[0138] [Evaluation of abrasion resistance] In accordance with JIS K7218-A, a sliding test was conducted under the following test conditions to measure the amount of wear of the resin material at the sliding portion between the metal material and the resin material. The amount of wear obtained from the following test is the sum of the change in the resin due to creep deformation and the change in the resin due to wear. Furthermore, the ratio of the amount of wear to the amount of wear of a comparative example (the rate of reduction in wear) was calculated, and the wear resistance was evaluated according to the evaluation criteria below. In the evaluation criteria below, a score of "B" or higher indicates a feasible level. For Examples 1-4 and Comparative Example 2, Comparative Example 1, which contained only base oil (A), urea-based thickener (B1), and phenol-based antioxidant, was used as the baseline value. -Test Conditions- • Test equipment: Thrust-type sliding tester (Equipment name: EFM-III-F-ADX-S, manufactured by A&D Company, Limited) • Metal test piece: Roller shape, 1.8 mm diameter, material: S45C • Resin test specimen: Ring shape, outer diameter 25.6 mm, inner diameter 20 mm, material is polyamide 66 mixed with 15% by mass of glass fiber. • Sliding speed: 1.0 m / s • Load: 350N • Exam duration: 45 minutes • Test temperature: Room temperature (25℃) - Criteria for evaluating wear resistance - A: The percentage of wear reduction from the standard wear amount (wear reduction rate) is 75% or more. B: The percentage of wear reduction from the standard wear amount (wear reduction rate) is 50% or more but less than 75%. C: The percentage of wear reduction from the standard wear value (wear reduction rate) is less than 50%.

[0139] The evaluation results are shown in Table 1.

[0140] [Table 1]

[0141] The results shown in Table 1 indicate that the grease compositions of Examples 1 to 4 exhibited excellent wear resistance, with a reduction in wear amount from the standard value (amount of wear reduction) of 50% or more. On the other hand, the grease composition of Comparative Example 2, which did not contain melamine cyanurate (C), showed a reduction in wear amount from the standard value (amount of wear reduction) of less than 50%, indicating that the amount of wear was not sufficiently reduced.

[0142] Next, we investigated the abrasion resistance of melamine cyanurate (C) with respect to particle size.

[0143] (Comparative Example 3) A grease composition was prepared by removing the phenolic antioxidant from the composition of Comparative Example 1, and this was designated as Comparative Example 3.

[0144] (Example 5) To 99 parts by mass of the grease composition of Comparative Example 3, 1 part by mass of melamine cyanurate (C1) was added and mixed. Then, it was homogenized using a three-roll mill to obtain the grease composition of Example 5.

[0145] (Examples 6-7) The grease compositions of Examples 6 and 7 were prepared in the same manner as in Example 5, except that melamine cyanurate (C1) was replaced with melamine cyanurate (C2) and (C3), respectively.

[0146] [Evaluation of abrasion resistance of melamine cyanurate (C) with respect to particle size] For Examples 5 to 7, Comparative Example 3 was used as the baseline value, and the ratio of the amount of wear to the amount of wear of Comparative Example 3 (the rate of reduction in the amount of wear) was calculated in the same manner as the wear resistance evaluation described above, and the wear resistance was evaluated according to the evaluation criteria below. In the evaluation criteria below, a score of "B" or higher is considered a feasible level. - Criteria for evaluating wear resistance - A: The percentage of wear reduction from the standard wear amount (wear reduction rate) is 30% or more. B: The percentage of wear reduction from the standard wear amount (wear reduction rate) is 20% or more but less than 30%. C: The percentage of wear reduction from the standard wear value (wear reduction rate) is less than 20%.

[0147] The evaluation results are shown in Table 2.

[0148] [Table 2]

[0149] As shown in Table 2, the grease compositions of Examples 5 and 6 showed a reduction in wear amount from the standard value (abrasion reduction rate) of 20% or more and less than 30%. The grease composition of Example 7 showed a reduction in wear amount from the standard value (abrasion reduction rate) of 30% or more. From these results, it was found that the smaller the average particle size of melamine cyanurate (C) in the grease composition, the better the abrasion resistance. [Explanation of symbols]

[0150] 1. Grease manufacturing equipment 2. Container body 3 rotors 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 axes 13 First uneven portion of the rotor 13A Recess 13B protrusion 14. Second uneven section of the rotor 15 Scrapers A1, A2 gap

Claims

1. Base oil (A), urea-based thickener (B), melamine cyanurate (C), One or more components (D) selected from the group consisting of sarcosine derivatives (D1), amine compounds (D2), and polyamide compounds (D3), and A grease composition containing one or more components (E) selected from the group consisting of ester compounds (E1) and bisamide compounds (E2), The sarcosine derivative (D1) includes N-oleoylsarcosine, The amine compound (D2) includes oleylamine, The polyamide compound (D3) is a fatty acid amide obtained by reacting a saturated fatty acid containing isostearic acid with a polyalkylene polyamine containing tetraethylenepentamine. The ester compound (E1) comprises methyl stearate, The bisamide compound (E2) comprises ethylenebisstearamide, It is used for lubricating worm gears where metal and resin materials slide against each other. The particle size of the melamine cyanurate (C) is 5.0 μm or less. The content ratio of the urea-based thickener (B) to the melamine cyanurate (C) [(B) / (C)] is 1.0 to 18.0 by mass. The ratio of the content of melamine cyanurate (C) to the content of component (D) [(C) / (D)] is 0.3 to 3.0 by mass. A grease composition wherein the particles containing the urea-based thickener (B) in the grease composition satisfy the following requirement (I). Requirement (I): The arithmetic mean particle diameter based on area, when the particles are measured by laser diffraction / scattering, is 2.0 μm or less.

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

3. The grease composition according to claim 1 or 2, wherein the content of melamine cyanurate (C) is 0.2% by mass or more based on the total amount of the grease composition.

4. The grease composition according to any one of claims 1 to 3, wherein the base oil (A) comprises poly-α-olefin (PAO).

5. The grease composition according to any one of claims 1 to 4, comprising the sarcosine derivative (D1), the amine compound (D2), and the polyamide compound (D3).

6. The grease composition according to any one of claims 1 to 5, wherein the content of the base oil (A) is 50% by mass or more and 98.5% by mass or less on a basis of the total amount of the grease composition.

7. The grease composition according to any one of claims 1 to 6, comprising the ester compound (E1) and the bisamide compound (E2).

8. The grease composition according to any one of claims 1 to 7, wherein the ratio of the content of melamine cyanurate (C) to the content of component (E) [(C) / (E)] is 0.1 to 2.0 by mass.

9. The grease composition according to any one of claims 1 to 8, wherein the content of the urea-based thickener (B) is 1.0% by mass to 20.0% by mass on a basis of the total amount of the grease composition.

10. The kinematic viscosity of the base oil (A) at 40°C is 30 mm ２ / s ~ 200mm ２ A grease composition according to any one of claims 1 to 9, wherein the ratio is / s.

11. A grease composition according to any one of claims 1 to 10, wherein the consistency is 260 to 330.

12. The grease composition according to any one of claims 1 to 11, wherein the resin material is a glass fiber reinforced resin material.

13. A lubrication method for lubricating a sliding mechanism in which a metal material and a resin material slide against each other, using the grease composition according to any one of claims 1 to 12.

14. The lubrication method according to claim 13, wherein the resin material is a glass fiber reinforced resin material.

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