Grease composition

Abstract

Provided is a grease composition excellent in reduction of friction coefficient under low speed and low load conditions, which contains base oil (A), a urea-based thickening agent (B), and a high molecular compound (C), the particles containing the aforementioned urea-based thickening agent (B) in the aforementioned grease composition satisfy the following requirement (I), the number average molecular weight (Mn) of the aforementioned high molecular compound (C) is 30,000 or greater, and the molecular weight distribution (Mw / Mn) of the aforementioned high molecular compound (C) is 2.20 or less. Requirement (I): the arithmetic average particle diameter on an area basis when the aforementioned particles are measured by a laser diffraction / scattering method is 2.0 μm or less.

Description

Technical Field

[0001] This invention relates to lubricating grease compositions. Background Technology

[0002] Grease compositions are easier to seal than lubricating oils, enabling the miniaturization and weight reduction of the machinery used. Therefore, they have long been widely used for lubrication of various sliding parts in automobiles, electrical equipment, industrial machinery, and other industrial equipment.

[0003] In recent years, from the perspectives of lightweighting and quiet operation, resin materials have been studied for use as components in sliding parts.

[0004] For example, in the worm gear of an automotive electric power steering (EPS) system, the worm is generally made of metal from a strength perspective. On the other hand, the worm wheel is mostly made of resin from the perspectives of lightweight automotive components, preventing unpleasant noises such as impact noise and vibration noise caused by contact with the worm (quietness), and preventing seizing with the worm. Furthermore, the resin used is, for example, known polyamide-based resins.

[0005] EPS is a steering mechanism that assists in steering the car at low speeds. On the other hand, at high speeds, centrifugal force is applied to the car when it is about to turn, allowing it to be turned with slight steering wheel adjustments. Therefore, at high speeds, control is achieved by means of EPS-based assistance not being active.

[0006] In this case, the operation of the worm gear without the auxiliary lubricant is at a lower speed and under lower load compared to when the auxiliary lubricant is active. Therefore, a grease composition is required that can lubricate the sliding parts made of metal materials such as worms and resin materials such as worm wheels, even under low speed and low load conditions.

[0007] For example, Patent Document 1 discloses a grease composition aimed at reducing steering torque when EPS is not assisted.

[0008] Existing technical documents

[0009] Patent documents

[0010] Patent Document 1: International Publication No. 2016 / 104812 Summary of the Invention

[0011] The problem that the invention aims to solve

[0012] Worm gears also aim to improve the lifespan of resin materials. Therefore, during the sliding between the metal and resin materials, it is necessary to suppress the phenomenon of increased strain (creep) in the resin material caused by long-term applied loads. In particular, resin materials are more prone to deformation at higher temperatures.

[0013] Therefore, in order to suppress creep and improve the lifespan of resin materials, it is important to suppress frictional heat, that is, to reduce the coefficient of friction.

[0014] In addition, in recent years, in order to improve the lifespan of resin materials, resins that are mixed with glass fiber and have increased strength are used as the material for worm gears.

[0015] Reinforced resins containing glass fibers tend to have the glass fibers vertically oriented on the resin surface and other areas. This causes the glass fibers to scrape against the metal contact surface of the worm gear, increasing the coefficient of friction. Therefore, there is a need for a grease composition suitable for lubricating sliding parts made of metal materials and resin materials with properties different from conventional lubricants.

[0016] However, the grease composition in Patent Document 1 did not conduct any research on the lubrication performance of resin materials and metal materials that are different from those in the past, such as reinforced resin materials containing glass fibers. As the resin materials changed, the friction characteristics sometimes became insufficient.

[0017] Therefore, the object of the present invention is to provide a grease composition that effectively reduces the coefficient of friction under low speed and low load conditions.

[0018] Methods for solving problems

[0019] The inventors of this invention focused on the particle size of the urea-based thickener particles in a grease composition containing a base oil and a urea-based thickener. Furthermore, they discovered that by adjusting the arithmetic mean particle size (measured by laser diffraction and scattering) to a predetermined range, a grease composition containing a specific polymer compound could solve the aforementioned problem, thus completing this invention.

[0020] That is, the present invention provides the following [1].

[0021] [1] A grease composition comprising a base oil (A), a urea-based thickener (B), and a polymeric compound (C),

[0022] The particles containing the aforementioned urea-based thickener (B) in the aforementioned grease composition meet the following requirement (I).

[0023] • Requirement (I): The arithmetic mean particle size, measured by laser diffraction and scattering method, is less than 2.0 μm based on area.

[0024] The aforementioned polymer compound (C) has a number-average molecular weight (Mn) of 30,000 or higher.

[0025] The molecular weight distribution (Mw / Mn) of the aforementioned polymer compound (C) is below 2.20.

[0026] The effects of the invention

[0027] According to the present invention, a grease composition is provided that can provide excellent reduction of the coefficient of friction under low speed and low load conditions. Attached Figure Description

[0028] Figure 1 This is a schematic cross-sectional view of a grease manufacturing apparatus used in one embodiment of the present invention.

[0029] Figure 2 yes Figure 1 A schematic diagram of a cross-section perpendicular to the rotation axis in the first concave-convex portion on the container body side of the grease manufacturing apparatus.

[0030] Figure 3 This is a schematic diagram of the cross-section of the grease manufacturing apparatus used in Comparative Example 3. Detailed Implementation

[0031] In this specification, the lower limit and upper limit values ​​recorded in stages for the preferred numerical range (e.g., the range of content) can be combined independently. For example, based on the record "preferably 10 to 90, more preferably 30 to 60", the "preferable lower limit (10)" and the "more preferably upper limit (60)" can be combined to set "10 to 60".

[0032] Furthermore, in this specification, the numerical values ​​in the embodiments are values ​​that can be used as upper or lower limits.

[0033] In this specification, the mass-average molecular weight (Mw) and number-average molecular weight (Mn) of each component are values ​​converted from standard polystyrene determined by gel permeation chromatography (GPC), specifically the values ​​determined by the methods described in the examples.

[0034] In this specification, for example, "(meth)acrylate" refers to the word used to refer to both "acrylate" and "methacrylate", and the same applies to other similar terms and the same markings.

[0035] [Lubricating Grease Composition]

[0036] The grease composition of the present invention contains a base oil (A), a urea-based thickener (B), and a polymer compound (C). The particles containing the urea-based thickener (B) in the grease composition satisfy the following requirement (I): the number average molecular weight (Mn) of the polymer compound (C) is 30,000 or more, and the molecular weight distribution (Mw / Mn) of the polymer compound (C) is 2.20 or less.

[0037] • Requirement (I): The arithmetic mean particle size based on area when the aforementioned particles are measured by laser diffraction and scattering method is less than 2.0 μm.

[0038] In the following description, “base oil (A)”, “urea thickener (B)”, and “polymer (C)” are also referred to as “component (A)”, “component (B)”, and “component (C)”, respectively.

[0039] In one embodiment of the grease composition of the present invention, the total content of components (A), (B), and (C), based on the total amount (100% by mass) of the grease composition, is preferably 60% by mass or more, more preferably 70% by mass or more, further preferably 80% by mass or more, and even more preferably 90% by mass or more. Furthermore, it is typically 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.

[0040] It should be noted that, without impairing the effects of the invention, the grease composition of one aspect of the present invention may also contain other components besides components (A), (B), and (C).

[0041] In order to solve the above-mentioned problems, the inventors conducted in-depth research and found that when the number average molecular weight (Mn) of the polymer (C) in the grease composition is 30,000 or more and the molecular weight distribution (Mw / Mn) of the polymer (C) is 2.20 or less, a grease composition with excellent friction coefficient reduction is obtained.

[0042] Specifically, the inventors discovered the following.

[0043] Depending on the degree of polymerization, polymers are mixtures of substances with various molecular weights, ranging from low to high. Furthermore, the smaller the molecular weight distribution (Mw / Mn) of a polymer, the higher the proportion of molecules with a specific molecular weight, and the lower the proportion of compounds with other molecular weights. In other words, the smaller the molecular weight distribution (Mw / Mn) of a polymer, the more it is confined to a specific molecular weight, resulting in molecules with nearly uniform size.

[0044] The inventors hypothesize that when the number average molecular weight (Mn) of the polymer in the grease composition is 30,000 or more, and the molecular weight distribution (Mw / Mn) of the polymer is 2.20 or less, the large molecular weight polymers in the grease composition loosely overlap (in other words, the large molecular weight polymers overlap in a rough state containing a large number of voids), and the polymers generate elastic force. Furthermore, it is hypothesized that the elastic force of these polymers in the grease composition compresses the frictional boundary surfaces, thereby increasing the oil film thickness of the base oil. Moreover, the inventors have found that this results in a reduction of the coefficient of friction.

[0045] On the other hand, when the molecular weight distribution (Mw / Mn) of the polymer is greater than 2.20, a mixture of substances with various molecular weights, ranging from low to high, exists. Therefore, it is speculated that small particles can easily enter the gaps between large particles, resulting in the polymers overlapping in a compact state, insufficient oil film thickness in the base oil, and inadequate frictional properties.

[0046] Furthermore, even when the molecular weight distribution (Mw / Mn) of the polymer is below 2.20 and the number average molecular weight (Mn) of the polymer is below 30,000, it is presumed that small particles overlap, resulting in insufficient oil film thickness and inadequate friction characteristics of the base oil.

[0047] <Requirement (I)>

[0048] In the grease composition of the present invention, the particles containing the aforementioned urea-based thickener (B) in the grease composition satisfy the following requirement (I).

[0049] • Requirement (I): The arithmetic mean particle size based on area when the aforementioned particles are measured by laser diffraction and scattering method is less than 2.0 μm.

[0050] By satisfying the above requirement (I), a grease composition with excellent friction coefficient reduction is formed.

[0051] The above-mentioned element (I) can also be referred to as a parameter indicating the aggregation state of the urea-based thickener (B) in the grease composition.

[0052] Here, "particles containing urea-based thickener (B)" that are the objects measured by laser diffraction and scattering method refer to particles formed by the aggregation of urea-based thickener (B) contained in the grease composition.

[0053] It should be noted that when the grease composition contains additives other than the urea-based thickener (B), the particle size specified in requirement (I) above shall be obtained by laser diffraction and scattering method on a grease composition prepared under the same conditions without the additive. However, if the additive is liquid at room temperature (25°C) or if the additive is dissolved in the base oil (A), the grease composition containing the additive may also be used as the test subject.

[0054] Urea-based thickeners (B) are typically obtained by reacting isocyanate compounds with monoamines, but the reaction is very fast, causing urea-based thickeners (B) to agglomerate, and large particles (micelle particles, so-called "agglomerates") are easily produced in excess. Through in-depth research, the inventors discovered that if the particle size specified in requirement (I) above is greater than 2.0 μm, it is impossible to ensure the frictional properties of the grease composition while increasing its working cone penetration. That is, it was found that if the particle size specified in requirement (I) above is greater than 2.0 μm, it is difficult to produce a grease composition with excellent frictional properties even when using a specific polymer compound (C).

[0055] In this regard, the inventors have conducted in-depth research and discovered that by miniaturizing the particle size specified in the above-mentioned element (I) to below 2.0 μm, and by combining it with a specific polymer compound (C), a grease composition with excellent frictional properties can be prepared.

[0056] This effect is presumably achieved by refining the particle size specified in requirement (I) to below 2.0 μm, making it easier for particles containing the urea-based thickener (B) to enter lubrication points (friction surfaces) such as worm gears, while also making them difficult to remove from these lubrication points, thereby improving the retention of the grease composition in these lubrication points. Furthermore, by refining the particle size specified in requirement (I) to below 2.0 μm, the retention of the base oil (A) by these particles is improved. Therefore, the ability to effectively deliver the base oil (A) to lubrication points (friction surfaces) such as worm gears, along with the accompanying high molecular weight compound (C), is enhanced, resulting in improved frictional characteristics.

[0057] Based on the above viewpoints, in one embodiment of the grease composition of the present invention, the particle size specified in element (I) is preferably 1.5 μm or less, more preferably 1.0 μm or less, further preferably 0.9 μm or less, even more preferably 0.8 μm or less, even more preferably 0.7 μm or less, even more preferably 0.6 μm or less, further preferably 0.5 μm or less, and even more preferably 0.4 μm or less. Furthermore, it is generally 0.01 μm or more.

[0058] <Requirements (II)>

[0059] Here, the grease composition of one aspect of the present invention preferably further satisfies the following requirement (II).

[0060] • Requirement (II): The specific surface area of ​​the aforementioned particles, as determined by laser diffraction and scattering, is 0.5 × 10⁻⁶. 5 cm 2 / cm 3 above.

[0061] The specific surface area specified in requirement (II) above is a secondary indicator representing the fineness of the particles containing the urea-based thickener (B) in the grease composition and the presence of large particles (agglomerates). That is, by satisfying requirement (I) above and further satisfying requirement (II) above, the fineness of the particles containing the urea-based thickener (B) in the grease composition is better, and the presence of large particles (agglomerates) is further suppressed. Therefore, a grease composition with excellent frictional properties and which easily exerts the effects based on the polymer compound (C) can be produced.

[0062] Based on the above viewpoint, the preferred specific surface area specified in requirement (II) is 0.7 × 10⁻⁶. 5 cm 2 / cm 3 The above, and more preferably 0.8×10 5 cm 2 / cm 3 The above, and more preferably 1.2×10 5 cm 2 / cm 3 The above, and even more preferably, is 1.5 × 10 5 cm 2 / cm 3 The above, and even more preferably 1.8 × 10 5 cm 2 / cm 3 The above, and more preferably 2.0×10 5 cm 2 / cm 3 That's all. It should be noted that the specific surface area is typically 1.0 × 10⁻⁶. 6 cm 2 / cm 3 the following.

[0063] In this specification, the values ​​specified in requirement (I) above and further requirement (II) above are values ​​measured by the method described in the embodiments described later.

[0064] Furthermore, the values ​​specified in the above requirement (I) and further above requirement (II) can be adjusted primarily by the manufacturing conditions of the urea-based thickener (B).

[0065] Hereinafter, we will focus on specific means for adjusting the values ​​specified in the above-mentioned requirement (I) and further requirement (II), and at the same time, we will describe in detail the components contained in the grease composition of the present invention.

[0066] <Base Oil (A)>

[0067] The base oil (A) included in the lubricating grease composition of the present invention may be selected from one or more mineral oils and synthetic oils.

[0068] As mineral oils, examples include distillates obtained by atmospheric or vacuum distillation of paraffinic crude oil, intermediate-base crude oil, or cycloalkane crude oil, and refined oils obtained by refining these distillates using conventional methods.

[0069] Examples of refining methods include solvent dewaxing, hydroisomerization, hydrorefining, and clay treatment.

[0070] Examples of synthetic oils include hydrocarbon oils, aromatic oils, ester oils, ether oils, and synthetic oils obtained by isomerization of waxes (GTL waxes) produced by the Fischer-Tropsch process, etc.

[0071] Examples of hydrocarbon-based oils include n-alkanes, isoalkanes, polybutene, polyisobutene, 1-decene oligomers, 1-decene and ethylene copolymer oligomers, and poly-α-olefins (PAOs) and their hydrides.

[0072] As aromatic oils, examples include alkylbenzenes such as monoalkylbenzenes and dialkylbenzenes; and alkylnaphthalenes such as monoalkylnaphthalenes, dialkylnaphthalenes, and polyalkylnaphthalenes.

[0073] Examples of ester-based oils include dibutyl sebacate, di-2-ethylhexyl sebacate, dioctyl adipate, diisodecyl adipate, di(tetrazyl) adipate, di(tetrazyl) glutarate, and methylacetyl castor oil ester; aromatic ester-based oils such as trioctyl trimellitate, tridecyl trimellitate, and tetraoctyl pyromellitic acid; polyol ester-based oils such as trimethylolpropane octanoate, trimethylolpropane nonanoate, pentaerythritol-2-ethylhexanoate, and pentaerythritol nonanoate; and complex ester-based oils such as low-polyester blends of polyols with diacids and monocarboxylic acids.

[0074] Examples of ether-based oils include polyethylene glycol, polypropylene glycol, polyethylene glycol monoether, polypropylene glycol monoether, etc.; and phenyl ether oils such as monoalkyl triphenyl ether, alkyl diphenyl ether, dialkyl diphenyl ether, pentaphenyl ether, tetraphenyl ether, monoalkyl tetraphenyl ether, dialkyl tetraphenyl ether, etc.

[0075] The kinematic viscosity of the base oil (A) in this embodiment is preferably 10 mm at 40°C. 2 / s or higher, more preferably 15mm 2 / s or higher, more preferably 20mm 2 / s or more. If the kinematic viscosity of base oil (A) at 40°C is 10 mm. 2 If the speed is above / s, the effects of the present invention will be more easily achieved.

[0076] Furthermore, the kinematic viscosity of the base oil (A) in this embodiment at 40°C is preferably 150 mm. 2 / s or less, more preferably 130mm 2 / s or less, more preferably 110mm 2 / s or less, more preferably 100mm 2 / s or less. If the kinematic viscosity of base oil (A) at 40°C is 150 mm... 2 The effect of the present invention is more easily achieved when the speed is below / s.

[0077] The upper and lower limits of these numerical ranges can be combined arbitrarily. Specifically, a range of 10–150 mm is preferred. 2 / s, more preferably 10 to 130 mm 2 / s, further preferably 15-110mm 2 / s, more preferably 20-100mm 2 / s.

[0078] It should be noted that the base oil (A) used in one embodiment of the present invention can be a combination of high-viscosity base oil and low-viscosity base oil, using a mixed base oil with a kinematic viscosity prepared in the range described above.

[0079] The viscosity index of the base oil (A) used in one aspect of the present invention is preferably 80 or more, more preferably 100 or more, and even more preferably 120 or more.

[0080] It should be noted that in this specification, kinematic viscosity and viscosity index refer to values ​​measured or calculated in accordance with JIS K2283:2000.

[0081] In one embodiment of the grease composition of the present invention, the content of base oil (A) is preferably 50% or more, more preferably 55% or more, further preferably 60% or more, and even more preferably 65% ​​or more, based on the total amount (100% by mass) of the grease composition. In addition, it is preferably 98.5% or less, more preferably 97% or less, further preferably 95% or less, and even more preferably 93% or less.

[0082] <Urea-based thickener (B)>

[0083] As the urea-based thickener (B) included in the grease composition of the present invention, any compound having urea bonds is acceptable, preferably a diurea compound having two urea bonds, and more preferably a diurea compound represented by the following general formula (b1).

[0084] R 1 -NHCONH-R 3 -NHCONH-R 2 (b1)

[0085] It should be noted that the urea-based thickener (B) used in one embodiment of the present invention may comprise one type or a mixture of two or more types.

[0086] In the above general formula (b1), R 1 and R 2 Each group independently represents a monovalent hydrocarbon group with 6 to 24 carbon atoms. R 1 and R 2 They can be the same, or they can be different from each other. R 3 It represents a divalent aromatic hydrocarbon group with 6 to 18 carbon atoms.

[0087] As R can be selected as the aforementioned general formula (b1) 1 and R 2 The number of carbon atoms in the monovalent hydrocarbon group is 6 to 24, preferably 6 to 20, and more preferably 6 to 18.

[0088] In addition, as an option that can be selected as R 1 and R 2 The monovalent hydrocarbon group can be categorized as saturated or unsaturated monovalent chain hydrocarbon groups, saturated or unsaturated monovalent alicyclic hydrocarbon groups, and monovalent aromatic hydrocarbon groups.

[0089] Here, R in the aforementioned general formula (b1) 1 and R 2 When the content of chain hydrocarbon groups is denoted as X molar equivalent, the content of alicyclic hydrocarbon groups is denoted as Y molar equivalent, and the content of aromatic hydrocarbon groups is denoted as Z molar equivalent, the following conditions (a) and (b) are preferably satisfied.

[0090] • Requirement (a): The value of [(X+Y) / (X+Y+Z)]×100 is 90 or more (preferably 95 or more, more preferably 98 or more, and even more preferably 100).

[0091] • 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).

[0092] It should be noted that the aforementioned alicyclic hydrocarbon group, the aforementioned chain hydrocarbon group, and the aforementioned aromatic hydrocarbon group are all possible alternatives to R in the above general formula (b1). 1 and R 2 The group, therefore, the sum of the values ​​of X, Y, and Z is 2 molar equivalents relative to 1 mole of the compound represented by the above general formula (b1). Furthermore, the values ​​of the above requirements (a) and (b) refer to the average value relative to the total amount of the compound group represented by the above general formula (b1) contained in the grease composition.

[0093] By using the compound represented by the above general formula (b1) that satisfies the above requirements (a) and (b), a grease composition with excellent low-temperature properties can be easily prepared.

[0094] It should be noted that the values ​​of X, Y, and Z can be calculated from the molar equivalents of the various amines used as raw materials.

[0095] Examples of monovalent saturated chain hydrocarbon groups include straight-chain or branched alkyl groups with 6 to 24 carbon atoms. Specifically, examples include hexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecanyl, octadecyl, octadecenyl, nonadecanyl, and eicosyl.

[0096] Examples of monovalent unsaturated chain hydrocarbon groups include straight-chain or branched alkenyl groups with 6 to 24 carbon atoms. Specifically, examples include hexenyl, heptenyl, octenyl, nonenyl, decenyl, undecenyl, dodecenyl, tridecenyl, tetradecenyl, pentadecenyl, hexadecenyl, heptadecenyl, octadecenyl, nonadecenyl, eicoseneyl, oleyl, geranyyl, farnesyl, and linoleyl.

[0097] It should be noted that monovalent saturated chain hydrocarbon groups and monovalent unsaturated chain hydrocarbon groups can be straight-chain or branched.

[0098] Examples of monovalent saturated alicyclic hydrocarbon groups include cyclohexyl, cycloheptyl, cyclooctyl, cyclononyl, and other cycloalkyl groups; cycloalkyl groups substituted with alkyl groups having 1 to 6 carbon atoms, such as methylcyclohexyl, dimethylcyclohexyl, ethylcyclohexyl, diethylcyclohexyl, propylcyclohexyl, isopropylcyclohexyl, 1-methyl-propylcyclohexyl, butylcyclohexyl, pentylcyclohexyl, pentyl-methylcyclohexyl, and hexylcyclohexyl (preferably cyclohexyl groups substituted with alkyl groups having 1 to 6 carbon atoms).

[0099] Examples of monovalent unsaturated alicyclic hydrocarbon groups include cyclohexenyl, cycloheptenyl, cyclooctenyl, and other cycloalkenyl groups; cycloalkenyl groups substituted with alkyl groups having 1 to 6 carbon atoms, such as methylcyclohexenyl, dimethylcyclohexenyl, ethylcyclohexenyl, diethylcyclohexenyl, and propylcyclohexenyl (preferably cyclohexenyl groups substituted with alkyl groups having 1 to 6 carbon atoms).

[0100] Examples of monovalent aromatic hydrocarbon groups include phenyl, biphenyl, terphenyl, naphthyl, diphenylmethyl, diphenylethyl, diphenylpropyl, methylphenyl, dimethylphenyl, ethylphenyl, propylphenyl, etc.

[0101] As R can be selected as the aforementioned general formula (b1) 3 The number of carbon atoms in the divalent aromatic hydrocarbon group is 6 to 18, preferably 6 to 15, and more preferably 6 to 13.

[0102] As can be selected as R 3 Examples of divalent aromatic hydrocarbon groups include phenylene, diphenylmethylene, diphenylethylene, diphenylpropylene, methylphenylene, dimethylphenylene, and ethylphenylene.

[0103] Among these, phenylene, diphenylmethylene, diphenylethylene, or diphenylpropylene are preferred, and diphenylmethylene is more preferred.

[0104] In one embodiment of the grease composition of the present invention, the content of component (B), based on the total amount (100% by mass) of the grease composition, is preferably 1.0 to 15.0% by mass, more preferably 1.5 to 13.0% by mass, further preferably 2.0 to 10.0% by mass, even more preferably 2.5 to 8.0% by mass, and even more preferably 4.0% to 7.0% by mass.

[0105] If the content of component (B) is 1.0% by mass or more, it is easy to prepare the working cone penetration of the resulting grease composition to a suitable range.

[0106] On the other hand, if the content of component (B) is less than 15.0% by mass, the resulting grease composition can be flexibly adjusted, thus making it easy to set the lubricity to good and easily improve the friction characteristics.

[0107] <Manufacturing Method of Urea Thickener (B)>

[0108] Urea-based thickeners (B) are typically obtained by reacting an isocyanate compound with a monoamine. This reaction is preferably carried out by dissolving the isocyanate compound in the aforementioned base oil (A), and then adding a solution β obtained by dissolving the monoamine in the base oil (A) to the resulting heated solution α.

[0109] For example, in the case of synthesizing the compound shown in the aforementioned general formula (b1), as an isocyanate compound, a compound having R as in the aforementioned general formula (b1) is used. 3 The diisocyanate corresponding to the divalent aromatic hydrocarbon group shown is used as a monoamine, employing a group having the same characteristic as R. 1 and R 2 The amine corresponding to the monovalent hydrocarbon group shown can be used to synthesize the desired urea-based thickener (B) through the method described above.

[0110] It should be noted that, from the viewpoint of miniaturizing the urea-based thickener (B) in the grease composition, in order to satisfy the above requirements (I) and further the above requirements (II), it is preferable to use a grease manufacturing apparatus as shown below [1] to manufacture a grease composition containing components (A) and (B).

[0111] [1] A grease manufacturing apparatus, comprising:

[0112] The container body has an inlet for introducing lubricating grease and an outlet for spraying lubricating grease to the outside; and

[0113] The rotor has a rotating shaft in the axial direction on the inner circumference of the aforementioned container body, and is configured to rotate inside the aforementioned container body.

[0114] The aforementioned rotor has a first uneven portion, the first uneven portion

[0115] (i) Along the surface of the aforementioned rotor, alternating concave and convex shapes are provided, which are inclined relative to the aforementioned rotation axis.

[0116] (ii) It has the ability to convey from the aforementioned inlet section to the aforementioned ejection section.

[0117] Hereinafter, the grease manufacturing apparatus described above[1] will be explained, but the following description of the "preferred" provisions, without particular limitation, is based on the viewpoint of miniaturizing the urea-based thickener (B) in the grease composition in a manner that satisfies the above-mentioned requirement (I) and further the above-mentioned requirement (II).

[0118] Figure 1 This is a schematic cross-sectional view of the grease manufacturing apparatus described above [1] that can be used in one aspect of the present invention.

[0119] Figure 1 The grease manufacturing apparatus 1 shown has a container body 2 for introducing grease raw materials into the container body 2, 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.

[0120] Rotor 3 rotates at high speed around the central axis 12, applying high shear force to the grease material inside the container body 2. This produces a grease containing a urea-based thickener (B).

[0121] Container body 2 as Figure 1 As shown, from the upstream side, it is divided into an inlet section 4, a retention section 5, a first inner circumferential surface 6, a second inner circumferential surface 7, and an ejection section 8.

[0122] Container body 2 as Figure 1 As shown, it has a truncated conical inner circumferential surface with the inner diameter gradually increasing from the inlet portion 4 to the outlet portion 8.

[0123] The inlet section 4 at one end of the container body 2 has multiple solution inlet tubes 4A and 4B for introducing lubricating grease material from the outside of the container body 2.

[0124] The retention section 5 is located downstream of the inlet section 4 and serves as a space for temporarily retaining the grease material introduced from the inlet section 4. If the grease material remains in the retention section 5 for an extended period, large clumps of grease will form on the inner circumferential surface of the retention section 5. Therefore, it is preferable to transport the grease to the first inner circumferential surface 6 downstream as quickly as possible. More preferably, the grease will not pass through the retention section 5 and will be transported directly to the first inner circumferential surface 6.

[0125] The first inner circumferential surface 6 is disposed in the downstream portion adjacent to the retention portion 5, and the second inner circumferential surface 7 is disposed in the downstream portion adjacent to the first inner circumferential surface 6. As detailed below, the first inner circumferential surface 6 is provided with a first concave-convex portion 9, and the second inner circumferential surface 7 is provided with a second concave-convex portion 10, so that the first inner circumferential surface 6 and the second inner circumferential surface 7 function as high-shear portions that impart high shear force to the grease material or grease, and are therefore preferred.

[0126] The ejector section 8, which forms the other end of the container body 2, is the part from which the grease stirred by the first inner circumferential surface 6 and the second inner circumferential surface 7 is ejected, and has an ejector nozzle 11 for ejecting the grease. The ejector nozzle 11 is formed in a direction perpendicular to or approximately perpendicular to the rotation axis 12. Thus, the grease is ejected from the ejector nozzle 11 in a direction perpendicular to or approximately perpendicular to the rotation axis 12. However, the ejector nozzle 11 may not necessarily be perpendicular to the rotation axis 12, and may also be formed in a direction parallel to or approximately parallel to the rotation axis 12.

[0127] The rotor 3 is rotatably mounted with the central axis of the truncated conical inner circumferential surface of the container body 2 as the rotation axis 12, such as... Figure 1 When viewing the container body 2 from the upstream to the downstream as shown, rotate it counterclockwise.

[0128] The rotor 3 has an outer circumferential surface that is enlarged according to the enlargement of the inner diameter of the truncated cone of the container body 2, and the outer circumferential surface of the rotor 3 maintains a certain distance from the inner circumferential surface of the truncated cone of the container body 2.

[0129] On the outer peripheral surface of the rotor 3, there is a first concave-convex part 13 of the rotor, which is provided with concave and convex alternating along the surface of the rotor 3.

[0130] The first protrusion 13 of the rotor is inclined relative to the rotation axis 12 of the rotor 3 in the direction from the inlet 4 to the outlet 8, and has the ability to convey materials from the inlet 4 to the outlet 8. That is, the first protrusion 13 of the rotor is inclined relative to the rotation axis 12 of the rotor 3 in the direction from the inlet 4 to the outlet 8. Figure 1 When rotating in the direction shown, it tilts in the direction that squeezes the solution downstream.

[0131] The height difference between the concave portion 13A and the convex portion 13B of the first concave-convex 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 concave portion 13A on the outer peripheral surface of the rotor 3 is set to 100.

[0132] The number of protrusions 13B of the first concave-convex portion 13 of the rotor in the circumferential direction is preferably 2 to 1000, more preferably 6 to 500, and even more preferably 12 to 200.

[0133] The ratio of the width of the convex portion 13B to the width of the concave portion 13A of the first concave-convex portion 13 of the rotor in a cross section perpendicular to the rotation axis 12 of the rotor 3 (width of the convex portion / width of the concave portion) is preferably 0.01 to 100, more preferably 0.1 to 10, and even more preferably 0.5 to 2.

[0134] The tilt angle of the first concave-convex portion 13 of the rotor relative 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.

[0135] Preferably, the first inner circumferential surface 6 of the container body 2 has a first protrusion 9 forming a plurality of protrusions and concavities along the inner circumferential surface.

[0136] Furthermore, the protrusions and depressions of the first protrusions and depressions 9 on the side of the container body 2 are preferably inclined in the opposite direction to the first protrusions and depressions 13 of the rotor.

[0137] That is, the multiple protrusions and concave parts 9 on the first protrusion and convex part 9 on the side of the container body 2 are aligned with the rotation axis 12 of the rotor 3. Figure 1 When rotating in the indicated direction, it is preferable to tilt in the direction that squeezes the solution downstream. The stirring and ejection capabilities are further enhanced by the first protrusions 9 with multiple irregularities on the first inner circumferential surface 6 of the container body 2.

[0138] When the inner diameter (diameter) of the container is denoted as 100, the depth of the first concave-convex portion 9 on the side of the container body 2 is preferably 0.2 to 30, more preferably 0.5 to 15, and even more preferably 1 to 5.

[0139] The number of protrusions and concavities in the first protrusion and concavity portion 9 on the two sides of the container body is preferably 2 to 1000, more preferably 6 to 500, and even more preferably 12 to 200.

[0140] The ratio of the width of the concave portion of the first concave-convex portion 9 on the 2nd side of the container body to the width of the convex portion between the grooves [width of the concave portion / width of the convex portion] is preferably 0.01 to 100, more preferably 0.1 to 10, and even more preferably 0.5 to 2 or less.

[0141] The tilt angle of the first concave-convex portion 9 on the side of the container body 2 relative to the rotation axis 12 is preferably 2 to 85 degrees, more preferably 3 to 45 degrees, and even more preferably 5 to 20 degrees.

[0142] It should be noted that by having a first protrusion 9 on the first inner circumferential surface 6 of the container body 2, the first inner circumferential surface 6 can function as a shearing part that imparts high shear force to the grease material or grease, but it is not necessary to provide the first protrusion 9.

[0143] On the outer peripheral surface of the downstream portion of the first protrusion 13 of the rotor, a second protrusion 14 of the rotor is preferably provided, which is alternately arranged along the surface of the rotor 3.

[0144] The second concave-convex portion 14 of the rotor is inclined relative to the rotation axis 12 of the rotor 3, and has the ability to suppress the flow of the solution from the inlet portion 4 to the ejection portion 8 back to the upstream side.

[0145] The height difference of the second concave-convex 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 concave portion on the outer peripheral surface of the rotor 3 is denoted as 100.

[0146] The number of protrusions in the second concave-convex portion 14 of the rotor in the circumferential direction is preferably 2 to 1000, more preferably 6 to 500, and even more preferably 12 to 200.

[0147] The ratio of the width of the convex portion to the width of the concave portion of the second concave-convex portion 14 of the rotor 3 in the cross section perpendicular to the rotation axis [width of convex portion / width of concave portion] is preferably 0.01 to 100, more preferably 0.1 to 10, and even more preferably 0.5 to 2.

[0148] The tilt angle of the second concave-convex portion 14 of the rotor relative 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.

[0149] On the second inner peripheral surface 7 of the container body 2, there is preferably a second protrusion 10 that is adjacent to the downstream portion of the protrusion in the first protrusion 9 on the side of the container body 2 and forms a plurality of protrusions.

[0150] Multiple protrusions and depressions are formed on the inner circumferential surface of the container body 2, and each protrusion and depression is preferably inclined in the opposite direction to the inclination direction of the second protrusion and depression portion 14 of the rotor.

[0151] That is, the multiple protrusions and concave parts 10 on the second protrusion and convex part 10 on the rotation axis 12 of the rotor 3 are located at... Figure 1 When rotating in the indicated direction, it is preferable to tilt in the direction that pushes the solution back to the upstream side. The stirring capability is further enhanced by the irregularities of the second irregularity 10 in the second inner circumferential surface 7 of the container body 2. Furthermore, the second inner circumferential surface 7 of the container body can function as a shearing section that imparts high shear force to the grease material or grease.

[0152] The depth of the recess of the second concave-convex portion 10 on the side of the container body 2 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 denoted as 100.

[0153] The number of recesses in the second concave-convex portion 10 on the two sides of the container body is preferably 2 to 1000, more preferably 6 to 500, and even more preferably 12 to 200.

[0154] The ratio of the width of the convex portion to the width of the concave portion of the second concave-convex portion 10 on the side of the container body 2 in the cross section perpendicular to the rotation axis 12 of the rotor 3 (width of the convex portion / width of the concave portion) is preferably 0.01 to 100, more preferably 0.1 to 10, and even more preferably 0.5 to 2 or less.

[0155] The tilt angle of the second concave-convex portion 10 on the side of the container body 2 relative to the rotation axis 12 is preferably 2 to 85 degrees, more preferably 3 to 45 degrees, and even more preferably 5 to 20 degrees.

[0156] The ratio of the length of the first concave-convex portion 9 on the side of the container body 2 to the length of the second concave-convex portion 10 on the side of the container body 2 [length of the first concave-convex portion / length of the second concave-convex portion] is preferably 2 / 1 to 20 / 1.

[0157] Figure 2 It is a cross-sectional view of the first concave-convex portion 9 on the side of the container body 2 of the grease manufacturing apparatus 1 in a direction perpendicular to the rotation axis 12.

[0158] Figure 2In the first concave-convex portion 13 of the rotor shown, a plurality of scrapers 15 are provided, the front ends of which protrude toward the inner circumferential surface of the container body 2 compared to the protruding front ends of the protrusions 13B of the first concave-convex portion 13. Furthermore, although not shown in the figure, the second concave-convex portion 14, similarly to the first concave-convex portion 13, is also provided with a plurality of scrapers, the front ends of which protrude toward the inner circumferential surface of the container body 2.

[0159] The scraper 15 scrapes the grease adhering to the inner circumferential surfaces of the first concave-convex portion 9 and the second concave-convex portion 10 on the side of the container body 2.

[0160] With respect to the protrusion of the protrusion 13B of the first concave-convex portion 13 of the rotor, the protrusion of the front end of the scraper 15 is preferably such that the ratio of the radius (R2) of the front end of the scraper 15 to the radius (R1) of the front end of the protrusion 13B [R2 / R1] is greater than 1.005 and less than 2.0.

[0161] The number of scraper blades 15 is preferably 2 to 500 parts, more preferably 2 to 50 parts, and even more preferably 2 to 10 parts.

[0162] It should be explained that Figure 2 The grease manufacturing apparatus 1 shown is equipped with a scraper 15, but it may not be equipped with a scraper 15, or the scraper 15 may be provided intermittently.

[0163] In the process of manufacturing grease containing urea-based thickener (B) using grease manufacturing apparatus 1, solutions α and β, which are the raw materials for the grease, are introduced from the solution inlet pipes 4A and 4B of the inlet section 4 of container body 2, respectively. By rotating rotor 3 at high speed, a grease base material containing urea-based thickener (B) can be manufactured.

[0164] Furthermore, in the grease base material obtained in this way, even when combined with sulfur-phosphorus extreme pressure agent (C) and other additives (D), the urea thickener (B) in the grease composition can be micronized in a manner that satisfies the above-mentioned requirements (I) and further the above-mentioned requirements (II).

[0165] As a condition for the high-speed rotation of rotor 3, the shear rate applied to the lubricating grease material is preferably 10. 2 s -1 The above, or more preferably 10 3 s -1 The above, and more preferably 10 4 s -1 In addition, it is usually 10. 7 s -1 the following.

[0166] Furthermore, the ratio (Max / Min) of the highest shear rate (Max) to the lowest shear rate (Min) during the high-speed rotation of the rotor 3 is preferably 100 or less, more preferably 50 or less, and even more preferably 10 or less.

[0167] By making the shear rate of the mixture as uniform as possible, it is easier to refine the urea-based thickener (B) and its precursor in the grease composition, thus forming a more uniform grease structure.

[0168] Here, the maximum shear rate (Max) refers to the highest shear rate applied to the mixture, and the minimum shear rate (Min) refers to the lowest shear rate applied to the mixture, as defined below.

[0169] • Maximum shearing speed (Max) = (Linear velocity of the front end of the protrusion 13B of the first concave-convex part 13 of the rotor) / (Gap A1 between the front end of the protrusion 13B of the first concave-convex part 13 of the rotor and the protrusion of the first concave-convex part 9 of the first inner circumferential surface 6 of the container body 2)

[0170] • Minimum shear rate (Min) = (Linear velocity of the recess 13A of the first concave-convex part 13 of the rotor) / (Gap A2 between the recess 13A of the first concave-convex part 13 of the rotor and the recess of the first concave-convex part 9 of the first inner circumferential surface 6 of the container body 2)

[0171] It should be noted that gaps A1 and A2 are as follows: Figure 2 As shown.

[0172] The grease manufacturing apparatus 1 has a scraper 15, which can scrape the grease adhering to the inner circumferential surface of the container body 2, thereby preventing agglomeration during mixing and enabling the continuous production of grease that micronizes the urea-based thickener (B) in a short time.

[0173] Furthermore, the scraper 15 scrapes off the attached grease, thereby preventing the grease residue from forming resistance to the rotation of the rotor 3. This reduces the rotational torque of the rotor 3, reduces the power consumption of the drive source, and enables the continuous production of grease with high efficiency.

[0174] The inner circumferential surface of the container body 2 is a truncated cone shape with an increased inner diameter as it moves from the inlet 4 to the outlet 8. Therefore, the centrifugal force has the effect of discharging the grease or grease raw material downstream, which can reduce the rotational torque of the rotor 3 and enable continuous production of grease.

[0175] On the outer peripheral surface of the rotor 3, a first concave-convex portion 13 of the rotor is provided. The first concave-convex portion 13 of the rotor is inclined relative to the rotation axis 12 of the rotor 3 and has the ability to convey from the inlet portion 4 to the outlet portion 8. The second concave-convex portion 14 of the rotor is inclined relative to the rotation axis 12 of the rotor 3 and has the ability to inhibit the conveying from the inlet portion 4 to the outlet portion 8. Therefore, it is possible to impart high shear force to the solution. After the addition of additives, it is also possible to micronize the urea thickener (B) in the grease composition in a manner that satisfies the above-mentioned requirement (I) and further the above-mentioned requirement (II).

[0176] A first protrusion 9 is formed on the first inner circumferential surface 6 of the container body 2, which is inclined in the opposite direction to the first protrusion 13 of the rotor. Therefore, in addition to the effect of the first protrusion 13 of the rotor, it is also possible to fully stir the grease material while extruding the grease or grease material downstream. Even after the addition of additives, the urea thickener (B) in the grease composition can be micronized in a manner that satisfies the above-mentioned requirement (I) and further the above-mentioned requirement (II).

[0177] Furthermore, a second protrusion 10 is provided on the second inner peripheral surface 7 of the container body 2, and a second protrusion 14 of the rotor is provided on the outer peripheral surface of the rotor 3. This prevents the lubricating grease material from flowing out of the first inner peripheral surface 6 of the container body as necessary. Therefore, a high shear force is applied to the solution to highly disperse the lubricating grease material. Even after the addition of additives, the urea thickener (B) can be micronized in a manner that satisfies the above-mentioned requirement (I) and further requirement (II).

[0178] <Polymer Compound (C)>

[0179] The lubricating grease composition of the present invention, together with components (A) and (B), includes a polymer compound (C). Furthermore, the number-average molecular weight (Mn) of the polymer compound (C) is 30,000 or more, and the molecular weight distribution (Mw / Mn) of the polymer compound (C) is 2.20 or less.

[0180] The grease composition of the present invention comprises a polymer compound (C), wherein the number-average molecular weight (Mn) and molecular weight distribution (Mw / Mn) of the polymer compound (C) satisfy the above-mentioned range, thereby reducing the coefficient of friction in the grease composition.

[0181] When the molecular weight distribution (Mw / Mn) of the polymer (C) is greater than 2.20, or when the number average molecular weight (Mn) of the polymer (C) is less than 30,000, sufficient friction reduction effect cannot be obtained.

[0182] From the viewpoint of tribological properties, the mass-average molecular weight (Mw) of the polymer compound (C) is preferably 50,000 or more, and more preferably 100,000 or more. Furthermore, from the viewpoint of the availability of the polymer compound (C), the mass-average molecular weight (Mw) of the polymer compound (C) is preferably 1,000,000 or less.

[0183] The upper and lower limits of their numerical ranges can be combined arbitrarily. Specifically, it is preferably 50,000 to 1,000,000, more preferably 100,000 to 1,000,000.

[0184] From the viewpoint of tribological properties, the number average molecular weight (Mn) of the polymer (C) is 30,000 or more, preferably 50,000 or more, and more preferably 80,000 or more. Furthermore, from the viewpoint of the availability of the polymer (C), the number average molecular weight (Mn) of the polymer (C) is preferably 500,000 or less.

[0185] The upper and lower limits of their numerical ranges can be combined arbitrarily. Specifically, it is preferably 30,000 to 500,000, more preferably 50,000 to 500,000, and even more preferably 80,000 to 500,000.

[0186] From the viewpoint of tribological properties, the molecular weight distribution (Mw / Mn) of the polymer (C) is preferably 2.20 or less, more preferably 2.00 or less, more preferably 1.90 or less, and even more preferably 1.85 or less. Furthermore, from the viewpoint of the availability of the polymer (C), the molecular weight distribution (Mw / Mn) of the polymer (C) is preferably 1.10 or more.

[0187] The upper and lower limits of their numerical ranges can be combined arbitrarily. Specifically, it is preferred to be 1.10 to 2.20, more preferably 1.10 to 2.00, further preferably 1.10 to 1.90, and even more preferably 1.10 to 1.85.

[0188] As a polymer (C), there are no special restrictions as long as the number average molecular weight (Mn) is above 30,000 and the molecular weight distribution (Mw / Mn) is below 2.20, and conventionally used polymers can be used.

[0189] Examples of polymers (C) include non-dispersed poly(meth)acrylates, dispersed poly(meth)acrylates, star polymers, olefin copolymers, dispersed olefin copolymers, polyalkylstyrene, and styrene copolymers.

[0190] Examples of olefin copolymers include ethylene-propylene copolymers and ethylene-butene copolymers.

[0191] Examples of styrene-based copolymers include styrene-diene copolymers and styrene-isoprene copolymers.

[0192] They can be used individually or in combination of two or more. Furthermore, they can be either random copolymers or block copolymers.

[0193] Among these, ethylene-propylene copolymer and ethylene-butene copolymer are preferred.

[0194] When the polymer (C) is a polymer containing ethylene, such as an ethylene-propylene copolymer or an ethylene-butene copolymer, the ethylene content is preferably 30% to 70% by mass, more preferably 40% to 60% by mass, based on the total amount of the polymer containing ethylene.

[0195] It should be noted that the ethylene content in polymers containing ethylene can be determined by the method described in the examples described later.

[0196] From the viewpoint of reducing the coefficient of friction, the content of the resin equivalent component of the polymer compound (C) is preferably 0.1 to 10.0% by mass, more preferably 0.1 to 5.0% by mass, further preferably 0.1 to 3.7% by mass, even more preferably 0.5 to 2.5% by mass, and even more preferably 1.0 to 2.3% by mass, based on the total amount (100% by mass) of the grease composition.

[0197] From the viewpoint of frictional properties, the content ratio [(B) / (C)] of the urea-based thickener (B) and the polymer compound (C) is preferably 0.5 to 5.0 by mass, more preferably 1.0 to 4.5, further preferably 2.0 to 4.0, even more preferably 2.5 to 3.8, and even more preferably 2.8 to 3.4.

[0198] <Additives (D)>

[0199] One embodiment of the grease composition of the present invention may contain additives (D) other than components (B) and (C) that are commonly used in lubricants, without impairing the effects of the present invention.

[0200] Examples of additives (D) include antioxidants, rust inhibitors, extreme pressure agents, solid lubricants, detergents and dispersants, corrosion inhibitors, and metal inertizers.

[0201] Each additive (D) can be used alone or in combination of two or more.

[0202] Examples of antioxidants include phenolic antioxidants.

[0203] Examples of rust inhibitors include carboxylic acid-based rust inhibitors such as alkenyl succinic acid polyol ester, zinc stearate, thiadiazole and its derivatives, benzotriazole and its derivatives, etc.

[0204] Examples of extreme pressure agents include zinc dialkyl dithiophosphate, molybdenum dialkyl dithiophosphate, ashless dithiocarbamates, zinc dithiocarbamate, molybdenum dithiocarbamate, and other thiocarbamates; sulfur compounds such as sulfurized oils, sulfurized olefins, polysulfides, thiophosphates, thioterpenes, and dialkyl thiodipropionates; phosphate esters such as tri(tolyl) phosphate; and phosphites such as triphenyl phosphite.

[0205] Examples of solid lubricants include polyimide, PTFE, graphite, metal oxides, boron nitride, melamine cyanurate (MCA), and molybdenum disulfide.

[0206] Examples of cleaning and dispersing agents include ashless dispersants such as succinic acid imide and boron-based succinic acid imide.

[0207] Examples of corrosion inhibitors include benzotriazole compounds and thiazole compounds.

[0208] Examples of metal inertizers include benzotriazole compounds.

[0209] In one aspect of the grease composition of the present invention, the content of these additives (D) is appropriately set according to the type of additive, and each is independently based on the total amount (100% by mass) of the grease composition, 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.

[0210] <Physical Properties of Lubricating Grease Compositions>

[0211] (Working cone penetration)

[0212] The working cone depth of the grease composition at 25°C, as an aspect of the present invention, is preferably 220–430, more preferably 240–360, further preferably 250–350, and even more preferably 260–330, from the viewpoint of producing excellent frictional properties.

[0213] It should be noted that, in this specification, the working cone penetration of the grease composition refers to the value measured at 25°C in accordance with JIS K2220:2013 (item 7).

[0214] (Effect of reducing the coefficient of friction)

[0215] The rate of reduction in the coefficient of friction of a grease composition according to one aspect of the present invention can be determined by the method described in the examples described later, and thus evaluated.

[0216] The reduction rate of the friction coefficient obtained by the method described in the following embodiments is preferably 45% or more.

[0217] <Method for manufacturing grease composition>

[0218] The grease composition of the present invention can be manufactured by mixing a base oil (A), a grease containing a urea-based thickener (B) (base grease), a polymer compound (C), and an additive (D) as needed.

[0219] For example, it can be manufactured by mixing base oil (A) and additive (D), then mixing it with a grease (base grease) containing a urea-based thickener (B), and then further mixing it with a polymer compound (C).

[0220] <Uses of Lubricating Grease Compositions>

[0221] The grease composition of the present invention exhibits excellent reduction in the coefficient of friction. Particularly when used for lubrication of sliding parts made of metallic and resin materials, it demonstrates excellent reduction in the coefficient of friction under low-speed and low-load conditions.

[0222] Therefore, the grease composition of one aspect of the present invention can be suitably used for lubrication of sliding parts of various devices, and is particularly preferred for lubrication of devices having sliding parts made of metallic and resin materials.

[0223] The preferred metallic materials are carbon steel, stainless steel, various steels, aluminum alloys, and copper. It should be noted that metallic materials can be replaced with high-strength materials (such as ceramic materials).

[0224] The resin material can be a natural resin or a synthetic resin, preferably a general-purpose plastic (polyethylene, polystyrene, polypropylene, polyvinyl chloride, etc.) or an engineering plastic, and more preferably an engineering plastic from the viewpoint of heat resistance and mechanical strength.

[0225] Engineering plastics include synthetic resins such as polyamide resin, polyacetal resin, polycarbonate resin, polysulfone resin, polyphenylene sulfide resin, polyamide-imide resin, polyether ether ketone resin, phenol resin, polyester resin, and epoxy resin.

[0226] Furthermore, fiber-reinforced resin materials are preferred as resin materials.

[0227] Examples of fiber-reinforced resin materials include glass fiber reinforced resin materials.

[0228] Examples of suitable applications for devices using the grease composition of the present invention include the automotive industry, office machinery industry, machine tool industry, windmill industry, construction industry, agricultural machinery industry, and industrial robot industry.

[0229] Examples of lubrication components suitable for use in automotive applications include bearing components in devices such as radiator fan motors, fan cascades, alternators, idler gears, hub units, water pumps, power windows, windshield wipers, electric power steering, drive motor flywheels, ball joints, wheel hub bearings, splines, and constant velocity joints; and bearing components, gear components, and sliding components in devices such as door locks, door hinges, and clutch accelerators.

[0230] More specifically, examples include hub units, electric power steering, drive motor flywheels, ball joints, wheel hub bearings, splines, constant velocity joints, clutch accelerators, servo motors, blade bearings, or bearing sections of generators.

[0231] Examples of lubrication components in devices in the field of office machinery that are suitable for using the grease composition of the present invention include, for example, the stationary roller in a device such as a printer, and the bearing and gear components in a device such as a polygonal motor.

[0232] Examples of suitable lubrication components in working machinery that utilize the grease composition of the present invention include, for example, the bearing portion in a speed reducer of a spindle, servo motor, or working robot.

[0233] Examples of lubrication components in windmill devices suitable for using the grease composition of the present invention include, for example, blade bearings and bearing components of generators.

[0234] Examples of lubrication components in devices used in the construction or agricultural machinery fields where the grease composition of the present invention can be used include, for example, bearing portions, gear portions, and sliding portions such as ball joints and splines.

[0235] One preferred method for applying the lubricating grease composition of the present invention to an apparatus is as a reduction gear (worm gear) for electric power steering, comprising a metal worm and a resin worm wheel. By configuring the apparatus in this way, the coefficient of friction is significantly reduced under low speed and low load conditions, thus resulting in excellent frictional characteristics even during high-speed driving when controlled by EPS assistance without its function.

[0236] [Lubrication methods for sliding mechanisms]

[0237] The grease composition of the present invention can be applied to a lubrication method for a sliding mechanism in which a sliding mechanism in which a metal material and a resin material slide are lubricated by the grease composition of the present invention described above.

[0238] According to the lubrication method of the sliding mechanism applicable to the grease composition of the present invention, the dynamic friction in the lubricated part can be appropriately maintained. The effect is that, in the case of an electric power steering reducer (worm gear) having a metal worm and a resin worm wheel, the coefficient of friction is excellently reduced under low speed and low load conditions, thus maintaining excellent frictional characteristics even during high-speed driving when the EPS assistance is not in effect.

[0239] According to one aspect of the present invention, the following [1] to

[11] are provided.

[0240] [1] A grease composition comprising a base oil (A), a urea-based thickener (B), and a polymeric compound (C),

[0241] The particles containing the aforementioned urea-based thickener (B) in the aforementioned grease composition meet the following requirement (I).

[0242] • Requirement (I): The arithmetic mean particle size, measured by laser diffraction and scattering method, is less than 2.0 μm based on area.

[0243] The aforementioned polymer compound (C) has a number-average molecular weight (Mn) of 30,000 or more;

[0244] The molecular weight distribution (Mw / Mn) of the aforementioned polymer compound (C) is below 2.20.

[0245] [2] According to the grease composition described in [1] above, wherein the particles containing the aforementioned urea-based thickener (B) in the aforementioned grease composition further satisfy the following requirement (II),

[0246] • Requirement (II): The specific surface area of ​​the aforementioned particles, as determined by laser diffraction and scattering, is 0.5 × 10⁻⁶. 5 cm 2 / cm 3 above.

[0247] [3] According to the grease composition described in [1] or [2] above, the content of the resin equivalent component of the aforementioned polymer compound (C) is 0.1% to 10.0% by mass, based on the total amount of the grease composition.

[0248] [4] The grease composition according to any one of [1] to [3] above, wherein the aforementioned polymer compound (C) comprises an ethylene-propylene copolymer.

[0249] [5] According to the grease composition described above [4], the ethylene content in the ethylene-propylene copolymer is 40% to 60% by mass, based on the total amount of the ethylene-propylene copolymer.

[0250] [6] The grease composition according to any one of [1] to [5] above, wherein the kinematic viscosity of the base oil (A) at 40°C is 10 mm. 2 / s~150mm 2 / s.

[0251] [7] The grease composition according to any one of [1] to [6] above, wherein the ratio of the aforementioned urea thickener (B) to the aforementioned polymer compound (C) [(B) / (C)] is 1.0 to 4.5 by mass.

[0252] [8] The grease composition according to any one of [1] to [7] above, wherein the content of the aforementioned urea thickener (B) is 1.0% to 15.0% by mass based on the total amount of the grease composition.

[0253] [9] The grease composition according to any one of [1] to [8] above, wherein the working penetration is 250 to 350.

[0254]

[10] The grease composition according to any one of [1] to [9] above is used for lubrication of sliding mechanisms in which metal materials and resin materials slide together.

[0255]

[11] A lubrication method wherein a sliding mechanism in which metal materials and resin materials slide is lubricated by the grease composition described in any one of [1] to

[10] above.

[0256] Example

[0257] The present invention will be specifically described through the following embodiments, but the present invention is not limited to the following embodiments.

[0258] [Various physical property values]

[0259] The methods for determining various physical properties are as follows.

[0260] (1) Kinematic viscosity and viscosity index of base oil (A) at 40°C

[0261] Measured and calculated according to JIS K2283:2000.

[0262] (2) Mass-average molecular weight (Mw), number-average molecular weight (Mn), and molecular weight distribution (Mw / Mn) of polymer (C)

[0263] Using a gel permeation chromatography apparatus (manufactured by Agilent Corporation, apparatus name "Type 1260 HPLC"), the values ​​were determined using the conversion from standard polystyrene under the following determination conditions.

[0264] -Determination Conditions-

[0265] • Column: Connect the two “Shodex LF404” columns in sequence.

[0266] Column temperature: 35℃

[0267] Elution solvent: chloroform

[0268] • Flow rate: 0.3 mL / min

[0269] (3) Ethylene content of polymer compound (C)

[0270] right 13 The C-NMR quantitative spectra were analyzed and calculated.

[0271] (4) Working cone penetration of the grease composition

[0272] According to JIS K2220:2013 (entry 7), the determination was performed at 25°C.

[0273] [raw material]

[0274] In Examples 1-6 and Comparative Examples 1-4, the base oil (A) and polymer compound (C) used as raw materials for preparing the lubricating grease composition are as follows.

[0275] It should be noted that the contents in Tables 1 and 2 are contents converted from resin components.

[0276] <Base Oil (A)>

[0277] • Base oil (A1) (poly-α-olefin (PAO), kinematic viscosity at 40°C: 30 mm) 2 (S / s, viscosity index: 135)

[0278] • Base oil (A2) (poly-α-olefin (PAO), kinematic viscosity at 40°C: 63 mm) 2 (Viscosity index: 140)

[0279] <Polymer Compound (C)>

[0280] • Polymer compounds (C1)

[0281] Ethylene-propylene copolymer, weight-average molecular weight (Mw): 172,000, number-average molecular weight (Mn): 93,500, molecular weight distribution (Mw / Mn): 1.84, ethylene content: 58.6% by mass

[0282] • Polymer compounds (C2)

[0283] Ethylene-propylene copolymer, weight-average molecular weight (Mw): 270,000, number-average molecular weight (Mn): 149,000, molecular weight distribution (Mw / Mn): 1.81, ethylene content: 52.5% by mass

[0284] • Polymer compounds (C3)

[0285] Ethylene-propylene copolymer, weight-average molecular weight (Mw): 284,000, number-average molecular weight (Mn): 166,000, molecular weight distribution (Mw / Mn): 1.71, ethylene content: 51.6% by mass

[0286] • Polymer compounds (C4)

[0287] Ethylene-butene copolymer, weight-average molecular weight (Mw): 258,000, number-average molecular weight (Mn): 148,000, molecular weight distribution (Mw / Mn): 1.74, ethylene content: 67.3% by mass

[0288] • Polymer compounds (C')

[0289] Ethylene-propylene copolymer, weight-average molecular weight (Mw): 109,000, number-average molecular weight (Mn): 47,800, molecular weight distribution (Mw / Mn): 2.28, ethylene content: 53.2% by mass

[0290] (Example 1)

[0291] (1) Synthesis of urea grease

[0292] Solution α was prepared by adding 10.74 parts by mass of diphenylmethane-4,4'-diisocyanate (MDI) to 89.26 parts by mass of base oil (A1) heated to 70°C.

[0293] In addition, 3.40 parts by weight of cyclohexylamine and 13.88 parts by weight of octadecylamine (stearylamine) were added to 82.72 parts by weight of a separately prepared base oil (A1) heated to 70°C to prepare solution β.

[0294] And, using Figure 1 The grease manufacturing apparatus 1 shown introduces a solution α heated to 70°C from solution inlet pipe 4A and a solution β heated to 70°C from solution inlet pipe 4B, both simultaneously and in equal amounts into container body 2. While rotor 3 is rotating, solutions α and β are continuously introduced into container body 2. Subsequently, the mixture is... Figure 3The stirring device shown is heated to 160°C and stirred for 1 hour. Then, it is homogenized by roller milling to synthesize urea grease (b1).

[0295] It should be noted that the rotor 3 of the grease manufacturing apparatus 1 is set to a rotational speed of 8,000 rpm. Furthermore, the maximum shear rate (Max) at this time is 10,500 s. -1 The ratio of the maximum shear rate (Max) to the minimum shear rate (Min) [Max / Min] is set to 3.5, and stirring is performed.

[0296] It should be noted that the urea-based thickener (B1) contained in the obtained urea grease is equivalent to R in the aforementioned general formula (b1). 1 and R 2 Cyclohexyl or octadecyl (stearyl), R 3 It is a compound that is diphenylmethylene.

[0297] In addition, the molar ratio of cyclohexylamine to octadecylamine used as raw material (cyclohexylamine / octadecylamine) is 40 / 60.

[0298] (2) Preparation of grease composition

[0299] The urea grease obtained in (1) above was stirred at 120°C while a polymer compound (C1) was added. After stirring for 0.5 hours, it was cooled to 25°C by natural cooling to obtain the grease composition of Example 1.

[0300] It should be noted that the content of each component in the grease composition of Example 1 is shown in Table 1.

[0301] (Example 2)

[0302] In the synthesis of (1) urea grease in Example 1, the content of each component was changed as described below. Otherwise, the grease composition of Example 2 was obtained in the same manner as in Example 1.

[0303] • 87.29 parts by weight of base oil (A1) heated to 70°C

[0304] 12.71 parts by weight of diphenylmethane-4,4'-diisocyanate (MDI)

[0305] • 86.51 parts by weight of base oil (A1) prepared separately and heated to 70°C

[0306] 8.03 parts by weight of cyclohexylamine

[0307] · Octadecylamine (stearylamine) 5.46 parts by weight

[0308] It should be noted that the urea-based thickener (B2) contained in the obtained urea grease is equivalent to R in the aforementioned general formula (b1). 1 and R 2 Cyclohexyl or octadecyl (stearyl), R 3 It is a compound that is diphenylmethylene.

[0309] In addition, the molar ratio of cyclohexylamine to octadecylamine used as raw material (cyclohexylamine / octadecylamine) is 80 / 20.

[0310] (Example 4)

[0311] In the synthesis of (1) urea grease in Example 1, octylamine was used instead of cyclohexylamine, and the content of each component was changed as described below. Otherwise, the grease composition of Example 4 was obtained in the same manner as in Example 1.

[0312] · 89.91 parts by weight of base oil (A1) heated to 70°C

[0313] 10.09 parts by weight of diphenylmethane-4,4'-diisocyanate (MDI)

[0314] • 83.87 parts by weight of base oil (A1) prepared separately and heated to 70°C

[0315] 5.24 parts by weight of octylamine

[0316] · 10.90 parts by weight of octadecylamine (stearylamine)

[0317] It should be noted that the urea-based thickener (B3) contained in the obtained urea grease is equivalent to R in the aforementioned general formula (b1). 1 and R 2 Octyl or octadecyl (stearyl), R 3 It is a compound that is diphenylmethylene.

[0318] In addition, the molar ratio of octylamine to octadecylamine used as raw materials (octylamine / octadecylamine) is 50 / 50.

[0319] (Comparative Example 3)

[0320] Solution α was prepared by adding 10.74 parts by mass of diphenylmethane-4,4'-diisocyanate (MDI) to 89.26 parts by mass of base oil (A1) heated to 70°C.

[0321] In addition, 3.40 parts by weight of cyclohexylamine and 13.88 parts by weight of octadecylamine (stearylamine) were added to 82.72 parts by weight of a separately prepared base oil (A1) heated to 70°C to prepare solution β.

[0322] And, using Figure 3 The grease manufacturing apparatus 1 shown introduces a solution α heated to 70°C into the container body through a solution inlet tube. Then, while stirring, a solution β heated to 70°C is introduced into the container body containing solution α through the solution inlet tube. After all solution β has been introduced into the container body, the stirring blades are rotated, and while continuously stirring, the temperature is raised to 160°C and maintained for 1 hour to synthesize urea grease (b2), which is designated as the grease composition of Comparative Example 3.

[0323] It should be noted that the maximum shear rate at this point is approximately 100 s. -1 The minimum shear rate is 1.23 s. -1 Furthermore, the ratio of the maximum shear rate (Max) to the minimum shear rate (Min) (Max / Min) is approximately 81.

[0324] It should be noted that the urea-based thickener contained in the urea grease (b2) is equivalent to R in the aforementioned general formula (b1). 1 and R 2 Cyclohexyl or octadecyl (stearyl), R 3 It is a compound that is diphenylmethylene.

[0325] In addition, the molar ratio of cyclohexylamine to octadecylamine used as raw material (cyclohexylamine / octadecylamine) is 40 / 60.

[0326] (Comparative Example 4)

[0327] In Comparative Example 3, a polymer compound (C1) was further added and mixed to obtain the grease composition of Comparative Example 4.

[0328] (Examples 3, 5-6, Comparative Examples 1-2)

[0329] The components and contents are changed to those shown in Tables 1 and 2. Otherwise, each grease composition is prepared in the same manner as the grease compositions described above.

[0330] [Requirements]

[0331] The following calculations were performed on the urea greases synthesized in Examples 1-6 and Comparative Examples 1-4.

[0332] (1) Calculation of particle size of particles containing urea-based thickeners: Requirement (I)

[0333] The particle size of particles containing urea-based thickeners in the grease composition was evaluated. Specifically, urea greases synthesized in Examples 1-6 and urea greases synthesized in Comparative Examples 1-4 were used as test samples, and the particle size of particles containing urea-based thickener (B) was determined by the following procedure.

[0334] First, the test sample is vacuum degassed and filled into a 1 mL syringe. 0.10–0.15 mL of the sample is extruded from the syringe and placed on the surface of a plate-shaped unit of the paste unit's fixing clamp. Next, another plate-shaped unit is overlapped on top of the sample, and the sample is clamped between the two units to obtain the test unit. Then, the arithmetic mean particle size of the particles in the test unit's sample is measured using a laser diffraction particle size analyzer (manufactured by Horiba Manufacturing Co., Ltd., trade name: LA-920).

[0335] Here, "arithmetic mean particle size based on area" refers to the value obtained by arithmetically averaging the particle size distribution based on area. The particle size distribution based on area is a distribution of the frequency of particle sizes in the entire set of particles being measured, based on the area calculated from that particle size (more specifically, the cross-sectional area of ​​particles having that particle size). Furthermore, the value obtained by arithmetically averaging the particle size distribution based on area can be calculated using the following formula (1).

[0336] [Number 1]

[0337] Arithmetic mean particle size = Σ{q(J)×X(J)}÷Σ{qJ)}…((1)

[0338] In equation (1) above, J refers to the particle size division number. q(J) refers to the frequency distribution value (unit: %). X(J) refers to the representative diameter of the J-th particle size range (unit: μm).

[0339] (2) Calculation of the specific surface area of ​​particles containing urea-based thickeners: Requirement (II)

[0340] The specific surface area is calculated using the particle size distribution of the thickener-containing particles in the grease composition determined in section (I) above. Specifically, the specific surface area is calculated using this particle size distribution. 3 Surface area of ​​particles (unit: cm) 2 The total of ) is recorded as the specific surface area (unit: cm²). 2 / cm 3 ).

[0341] Next, the reduction in the coefficient of friction was evaluated using Examples 1 to 6 and Comparative Examples 1 to 4 described above.

[0342] [Evaluation of the effect of reducing the coefficient of friction]

[0343] According to JIS K7218-A, a sliding test was conducted under the following test conditions to determine the coefficient of friction between the sliding parts of the metal and resin materials. (When conducting the test under high-speed and high-load conditions using this method, for example, a sliding speed of 1.0 m / s and a load of 350 N can be used. In contrast, in this embodiment, to evaluate the friction characteristics under low-speed and low-load conditions, a sliding test was conducted under the test conditions shown below.)

[0344] Furthermore, the percentage reduction in friction coefficient (the rate of reduction in friction coefficient) is calculated from the friction coefficient of the comparative example, which is set as the baseline value. The effect of reducing friction coefficient is evaluated according to the evaluation criteria below. It should be noted that in the evaluation criteria below, "B" and above are feasible levels.

[0345] It should be noted that Examples 1-6 and Comparative Example 2 are based on Comparative Example 1, which contains a urea-based thickener (B) but does not contain a polymeric compound (C). Furthermore, Comparative Example 4 is based on Comparative Example 3, which contains a thickener (B') but does not contain a polymeric compound (C).

[0346] -Test Conditions-

[0347] • Test apparatus: Thrust-type sliding test machine (Apparatus name: EFM-III-F-ADX-S, manufactured by A. And. Day Co., Ltd.)

[0348] • Metal test piece: Roller shape, 10mm diameter, material S45C

[0349] • Resin test piece: ring shape, outer diameter 25.6 mm, inner diameter 20 mm, material is polyamide 66 mixed with 15% by mass of glass fiber.

[0350] • Sliding speed: 0.2m / s

[0351] • Load capacity: 50N

[0352] • Test duration: 5 minutes

[0353] • Test temperature: Room temperature (25℃)

[0354] -Evaluation criteria for the effect of reducing the coefficient of friction-

[0355] A: The reduction in friction coefficient from the baseline value (the rate of reduction in friction coefficient) is over 50%.

[0356] B: The percentage reduction in the coefficient of friction from the baseline value (the rate of reduction in the coefficient of friction) is 45% or more but less than 50%.

[0357] C: The percentage reduction in friction coefficient from the baseline value (the rate of reduction in friction coefficient) is less than 45%.

[0358] The evaluation results are shown in Tables 1 and 2.

[0359] [Table 1]

[0360] Table 1

[0361]

[0362] [Table 2]

[0363] Table 2

[0364]

[0365] According to the results shown in Tables 1 and 2, the grease compositions of Examples 1 to 6 exhibited excellent reduction in the coefficient of friction (reduction rate of the coefficient of friction) of more than 45% from the reference value, under test conditions of low speed and low load.

[0366] On the other hand, the grease compositions of Comparative Example 2, which contains a polymer compound (C') with a molecular weight distribution (Mw / Mn) of 2.28, and Comparative Example 4, which contain particles in a thickener (B') that do not meet requirement (I), have a friction coefficient reduction rate (the rate of friction coefficient reduction) of less than 45% from the reference value. Under test conditions of low speed and low load, the friction coefficient is not sufficiently reduced.

[0367] Explanation of reference numerals in the attached figures

[0368] 1. Grease manufacturing apparatus

[0369] 2. Container body

[0370] 3 rotors

[0371] 4. Import section

[0372] 4A and 4B solution inlet tubes

[0373] 5. Detention Area

[0374] 6 First concave-convex part

[0375] 7 Second concave-convex part

[0376] 8. Ejection section

[0377] 9. The first protrusion / recess on the side of the container body

[0378] 10. The second concave-convex part on the side of the container body

[0379] 11 Spray outlet

[0380] 12 Rotation axis

[0381] 13 The first concave-convex part of the rotor

[0382] 13A recess

[0383] 13B convex part

[0384] 14 The second concave and convex part of the rotor

[0385] 15 Scrapers

[0386] A1, A2 gap

Claims

1. A grease composition comprising a base oil (A), a urea-based thickener (B), and a polymeric compound (C), The aforementioned base oil (A) is selected from at least one of poly-α-olefins and their hydrides. The particles containing the aforementioned urea-based thickener (B) in the aforementioned grease composition meet the following requirement (I). • Requirement (I): The arithmetic mean particle size, measured by laser diffraction and scattering method, is less than 2.0 μm based on area. The aforementioned urea-based thickener (B) is a diurea compound represented by the following general formula (b1). R 1 -NHCONH-R 3 -NHCONH-R 2 (b1) In the above general formula (b1), R 1 and R 2 Each independently represents a monovalent hydrocarbon group with 6 to 18 carbon atoms, R 1 and R 2 They can be the same or different from each other, R 3 It is diphenylmethylene. The content of the aforementioned urea-based thickener (B), based on the total amount of the aforementioned grease composition, is 4.0 to 7.0% by mass. The number-average molecular weight Mn of the aforementioned polymer compound (C) is 80,000 to 500,000. The molecular weight distribution (Mw / Mn) of the aforementioned polymer (C) is 1.10~1.

85. The aforementioned polymeric compound (C) is selected from at least one of ethylene-propylene copolymers and ethylene-butene copolymers. The resin-converted content of the aforementioned polymer compound (C), based on the total amount of the aforementioned lubricating grease composition, is 1.0 to 2.3% by mass. The ratio of the aforementioned urea-based thickener (B) to the aforementioned polymer compound (C) by mass is 2.8 to 3.

4.

2. The grease composition according to claim 1, wherein, The total content of the aforementioned base oil (A), the aforementioned urea-based thickener (B), and the aforementioned polymeric compound (C), based on the total amount of the aforementioned grease composition, is 60% by mass or more.

3. The grease composition according to claim 1 or 2, wherein, The total content of the aforementioned base oil (A), the aforementioned urea-based thickener (B), and the aforementioned polymeric compound (C), based on the total amount of the aforementioned grease composition, is 70% by mass or more.

4. The grease composition according to claim 1 or 2, wherein, The particle size specified in the aforementioned requirement (I) is less than 1.5 μm.

5. The grease composition according to claim 1 or 2, wherein, The particles containing the aforementioned urea-based thickener (B) in the aforementioned grease composition further satisfy the following requirement (II). • Requirement (II): The specific surface area of ​​the aforementioned particles, as determined by laser diffraction and scattering, is 0.5 × 10⁻⁶. 5 cm 2 / cm 3 above.

6. The grease composition according to claim 5, wherein, The specific surface area specified in requirement (II) above is 0.7 × 10⁻⁶. 5 cm 2 / cm 3 above.

7. The grease composition according to claim 1 or 2, wherein, R in the aforementioned general formula (b1) 1 and R 2 When the content of chain hydrocarbon groups is denoted as X molar equivalent, the content of alicyclic hydrocarbon groups as Y molar equivalent, and the content of aromatic hydrocarbon groups as Z molar equivalent, the following conditions (a) and (b) must be met. • Requirement (a): The value of [(X+Y) / (X+Y+Z)]×100 is 90 or higher. • Requirement (b): The X / Y ratio is 0 / 100 (X=0, Y=100) to 100 / 0.

8. The grease composition according to claim 1 or 2, wherein, The mass-average molecular weight (Mw) of the aforementioned polymer compound (C) is 50,000 to 1,000,000.

9. The grease composition according to claim 1 or 2, wherein, The mass-average molecular weight (Mw) of the aforementioned polymer compound (C) is 100,000 to 1,000,000.

10. The grease composition according to claim 1 or 2, wherein, The aforementioned polymer compound (C) is an ethylene-propylene copolymer.

11. The grease composition according to claim 10, wherein, In the aforementioned ethylene-propylene copolymer, the ethylene content, based on the total amount of the aforementioned ethylene-propylene copolymer, is 40% to 60% by mass.

12. The grease composition according to claim 1 or 2, wherein, The kinematic viscosity of the aforementioned base oil (A) at 40°C is 10 mm. 2 / s~150mm 2 / s.

13. The grease composition according to claim 1 or 2, wherein, The kinematic viscosity of the aforementioned base oil (A) at 40°C is 10 mm. 2 / s~130mm 2 / s.

14. The grease composition according to claim 1 or 2, wherein, The viscosity index of the aforementioned base oil (A) is above 80.

15. The grease composition according to claim 1 or 2, wherein, The viscosity index of the aforementioned base oil (A) is above 100.

16. The grease composition according to claim 1 or 2, wherein, The content of the aforementioned base oil (A) is 50% by mass or more, based on the total amount of the aforementioned grease composition.

17. The grease composition according to claim 1 or 2, wherein, The content of the aforementioned base oil (A) is 55% by mass or more, based on the total amount of the aforementioned grease composition.

18. The grease composition according to claim 1 or 2, wherein, As an additive (D), it also contains one or more selected from antioxidants, rust inhibitors, extreme pressure agents, solid lubricants, detergents and dispersants, corrosion inhibitors, and metal inert agents.

19. The grease composition according to claim 18, wherein, The content of each of the aforementioned additives (D) is 0.01 to 20% by mass, based independently on the total amount of the aforementioned grease composition.

20. The grease composition according to claim 1 or 2, wherein, The working cone penetration is 250~350.

21. The grease composition according to claim 1 or 2, wherein, The working cone penetration is 260~330.

22. The grease composition according to claim 1 or 2, used for lubrication of sliding mechanisms in which metal materials and resin materials slide together.

23. The grease composition according to claim 22, wherein, The aforementioned sliding mechanism is a speed reducer for electric power steering, consisting of a metal worm gear and a resin worm wheel.

24. A lubrication method for lubricating a sliding mechanism in which a metal material and a resin material slide, using the grease composition according to any one of claims 1 to 23.

25. The lubrication method according to claim 24, wherein, The aforementioned sliding mechanism is a speed reducer for electric power steering, consisting of a metal worm gear and a resin worm wheel.

26. A method for manufacturing a grease composition according to any one of claims 1 to 23, comprising the step of mixing a base oil (A), a grease containing a urea-based thickener (B), and a polymeric compound (C).

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