Particle-containing grease composition

Abstract

To provide a particle-containing grease composition that is capable of improving friction and abrasion resistance and exhibits excellent friction and abrasion resistance even when a clearance between sliding sections and a surface roughness of the friction surface are very small.SOLUTION: A particle-containing grease composition includes a base oil, a thickener, a molybdenum disulfide particle having a specified size, and molybdenum dialkyldithiocarbamate.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a particle-containing grease composition, and more particularly to a particle-containing grease composition containing molybdenum sulfide and molybdenum dialkyldithiocarbamate (hereinafter referred to as MoDTC). [Background technology]

[0002] Molybdenum disulfide is widely known as a lubricant for reducing friction and wear, and is used in many countries. In practice, it is used in a variety of applications, including lubricating oils (long-chain aliphatic, low-polarity solvents) such as engine oils, coating paints (low-boiling-point polar solvents), and greases (long-chain aliphatic, low-polarity solvents with additives such as lithium soap).

[0003] As a conventional particle-containing grease composition, for example, a grease composition for constant velocity joints has been proposed, which contains a base oil, a diurea-based thickener, molybdenum disulfide, MoDTC, a calcium salt of petroleum sulfonic acid, a sulfur-based extreme pressure agent, and at least one vegetable oil selected from the group consisting of castor oil and rapeseed oil, and further contains zinc dialkyldithiocarbamate as an additive (Patent Document 1).

[0004] In addition, a lubricant composition has been proposed that contains 10 to 99.9 mass% of a liquid base oil, 0.1 to 90 mass% of an amide compound, and 1.0 to 20 mass% of a solid lubricant or 0.0005 to 5 mass% of an organic molybdenum compound in terms of molybdenum (Mo), and that is semi-solid at room temperature (Patent Document 2).

[0005] As a particle-containing grease composition in which the particle size of molybdenum disulfide is specified, a grease composition for constant velocity joints has been disclosed that contains a base oil, a diurea-based thickener, MoDTC that is insoluble in the base oil, MoDTC that is soluble in the base oil, molybdenum disulfide, calcium phenate or calcium sulfonate, and a sulfur-based extreme pressure additive that does not contain phosphorus, and in the examples, the molybdenum disulfide particle size is 0.45 μm (Patent Document 3). [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-90243 [Patent Document 2] Japanese Patent Application Laid-Open No. 2008-231293 [Patent Document 3] Japanese Patent Application Laid-Open No. 2006-16481 Summary of the Invention [Problem to be solved by the invention]

[0007] However, the commercially available molybdenum disulfide particles added to the conventional grease compositions described above are produced by pulverizing natural molybdenum disulfide ore. These particles are submicron-sized and have a very large specific gravity of approximately 5, resulting in a problem of low friction and wear resistance relative to the weight added. Furthermore, recent technological innovations have significantly reduced the surface roughness of friction surfaces in sliding parts, preventing the commercially available molybdenum disulfide particles from penetrating into minute recesses in the friction surface, resulting in insufficient expression of the above-mentioned effects. Furthermore, while friction modifiers, such as organic molybdenum, are dispersed at the molecular level and can penetrate into extremely minute recesses in sliding parts, in order to function as friction reducers, a tribofilm must be formed by the frictional heat of the sliding part. Therefore, a sufficient film is not formed in the early stages of sliding, resulting in poor friction and wear resistance in the early stages of sliding.

[0008] An object of the present invention is to provide a particle-containing grease composition that can efficiently improve friction and wear resistance from the initial stage of sliding, and that exhibits excellent friction and wear resistance even when the clearance between sliding parts or the surface roughness of the friction surface are extremely small. [Means for solving the problem]

[0009] As a result of extensive research, the present inventors have found that the predetermined median diameter D 50It has been discovered that a grease composition that uses molybdenum disulfide particles having the formula (I) in combination with MoDTC is highly effective in improving friction and wear resistance from the early stages of sliding, and can efficiently improve friction and wear resistance. In addition, after a certain time has passed since the start of sliding, MoDTC intervenes even in fine irregularities, forming a tribofilm, thereby improving friction and wear resistance throughout the entire sliding period. It has also been discovered that the presence of molybdenum disulfide assists the formation of a tribofilm in the early stages of sliding, improving friction and wear resistance from the very early stages of sliding.

[0010] That is, the present invention provides the following configurations. [1] Base oil, thickener, and median diameter D determined by dynamic light scattering 50 A particle-containing grease composition comprising molybdenum disulfide particles having a size of 10 nm or more and less than 450 nm and molybdenum dialkyldithiocarbamate.

[0011] [2] The specific surface area of ​​the molybdenum disulfide particles measured by the BET method is 10 m 2 / g or more of the particle-containing grease composition according to [1] above.

[0012] [3] The particle-containing grease composition according to the above [1] or [2], wherein the structure of the molybdenum dialkyldithiocarbamate is represented by the following general formula (1): [ka] (In the formula, R 1 ~R 4 are the same or different alkyl groups having 1 to 18 carbon atoms, and X 1 ~X 4 each independently represents an oxygen atom or a sulfur atom.

[0013] [4] The particle-containing grease composition according to any one of the above [1] to [3], wherein the molybdenum disulfide particles have a 2H crystal structure and a 3R crystal structure of molybdenum disulfide.

[0014] [5] The particle-containing grease composition according to any one of [1] to [4] above, containing 0.3 mass % or more and 3 mass % or less of the molybdenum disulfide particles relative to 100 mass % of the total mass of the particle-containing grease composition.

[0015] [6] The particle-containing grease composition according to any one of [1] to [5] above, containing 0.1 mass % or more and 10 mass % or less of the molybdenum dialkyldithiocarbamate relative to 100 mass % of the total mass of the particle-containing grease composition. [Effects of the Invention]

[0016] According to the present invention, it is possible to provide a particle-containing grease composition that can efficiently improve friction and wear resistance, that exhibits excellent friction and wear resistance even when the clearance between sliding parts or the surface roughness of the friction surface is extremely small, and that improves friction and wear resistance from the very early stage of sliding. [Brief explanation of the drawings]

[0017] [Figure 1] FIG. 1 is a schematic diagram showing an example of an apparatus used for producing molybdenum trioxide particles, which are the raw material for the molybdenum disulfide particles in this embodiment. [Figure 2] FIG. 2 is a diagram showing the results of an SRV test at 40° C. in this embodiment. [Figure 3] FIG. 3 is a diagram showing the results of an SRV test at 80° C. in this embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0018] Hereinafter, embodiments of the present invention will be described in detail.

[0019] <Particle-containing grease composition> The particle-containing grease composition according to this embodiment is a particle-containing grease composition containing a base oil, a thickener, molybdenum disulfide particles, and MoDTC, and the median diameter D of the molybdenum disulfide particles determined by dynamic light scattering is 50is 10 nm or more and less than 450 nm. Commercially available molybdenum disulfide particles are crushed ore products, and many of them have particle sizes exceeding 0.45 μm. Therefore, for example, if the gap between the friction surfaces of the sliding part is less than 0.45 μm (i.e., 450 nm), the molybdenum disulfide particles cannot enter the gap, and the effective particle number per unit weight of the molybdenum disulfide particles added is small. On the other hand, if the median diameter D 50 By having a particle size of less than 450 nm, the molybdenum disulfide particles can penetrate sufficiently into gaps, increasing the effective particle number per unit weight of the added molybdenum disulfide particles. This increases the resistance to scraping, wear, or seizure even under heavy loads, thereby efficiently improving friction and wear resistance. Furthermore, MoDTC penetrates into minute gaps that molybdenum disulfide cannot penetrate, triggering a tribochemical reaction in the sliding area to form a tribofilm, thereby improving friction and wear resistance from the middle to late stages of sliding. Furthermore, in the very early stages of sliding, the synergistic effect of the molybdenum disulfide particles and MoDTC accelerates tribofilm formation, allowing for a more rapid transition to a stable low-friction state compared to when molybdenum disulfide and MoDTC are used alone.

[0020] Median diameter D of molybdenum disulfide particles 50 By having a surface roughness of less than 450 nm, molybdenum disulfide particles can easily penetrate into the minute recesses on one or both of the friction surfaces of two components, even when the surface roughness is extremely small, for example, several hundred nanometers. Generally, molybdenum disulfide particles penetrate into the gaps between contacting surfaces, and the layers of these molybdenum disulfide particles easily shift in the direction perpendicular to the load. This allows layered compounds containing molybdenum disulfide particles to function well as lubricants. Therefore, when subjected to shear forces specific to layered compounds, slippage occurs between the crystal planes, reducing the coefficient of friction between the contacting surfaces. Therefore, compared to conventional particle-containing grease compositions, scraping, wear, etc. can be prevented, thereby contributing to a longer life for the friction surfaces.

[0021] (Molybdenum disulfide particles) The median diameter D of the molybdenum disulfide particles in the particle-containing grease composition of this embodiment, determined by dynamic light scattering, 50 The median diameter D of the molybdenum disulfide particles is 10 nm or more and less than 450 nm, and from the viewpoint of the above-mentioned effects, it is particularly preferable that it is 400 nm or less. 50 The median diameter D of the molybdenum disulfide particles may be 10 nm or more, 20 nm or more, or 40 nm or more. 50 is measured using, for example, a dynamic light scattering particle size distribution analyzer (Microtrack Bell, Nanotrac Wave II) or a laser diffraction particle size distribution analyzer (Shimadzu Corporation, SALD-7000).

[0022] The molybdenum disulfide particles in the particle-containing grease composition of this embodiment preferably have a 3R crystal structure of molybdenum disulfide. The 3R crystal structure, in which the six-membered ring unit cell of any layer is shifted from the six-membered ring unit cell of the adjacent layer to form a rhombohedral crystal, weakens the interaction between sulfur atoms between layers (SS contact) compared to a 2H crystal structure, in which the six-membered ring unit cell of any layer is positioned 90 degrees below the six-membered ring unit cell of the adjacent layer to form a hexagonal crystal in the shape of a regular hexagonal column, making the layers of the 3R structure more susceptible to shifting relative to each other due to external forces, which is thought to contribute to further improvement in friction and wear resistance.

[0023] Generally, commercially available molybdenum disulfide particles include many particles with particle sizes exceeding 0.45 μm, and are hexagonal solids with a crystalline structure that is approximately 2H. In contrast, molybdenum disulfide particles manufactured through the "manufacturing method for molybdenum trioxide particles" and "manufacturing method for molybdenum disulfide particles" described below contain both 2H and 3R crystalline structures and have a median diameter D 50 It can be easily adjusted from 10 nm to less than 450 nm.

[0024] The presence of 2H and 3R crystal structures in molybdenum disulfide particles can be confirmed, for example, using extended Rietveld analysis software (High Score Plus, manufactured by Malvern Panalytical) that takes into account crystallite size. These are described in detail, for example, in International Publication No. 2022 / 202751A1.

[0025] In the molybdenum disulfide particles of this embodiment, the crystallite size of the 3R crystal structure is preferably 1 nm or more and 150 nm or less. When the crystallite size of the 3R crystal structure is 1 nm or more and 150 nm or less, when used as a solid lubricant in a grease composition, the friction coefficient of the particle-containing grease composition can be reduced, and the friction and wear resistance properties can be improved. The crystallite size of the 3R crystal structure can be calculated using the method described in the aforementioned International Publication. The friction coefficient can be measured, for example, from a Stribeck curve using a ball-on-disk tester or a four-ball tester, or it can also be measured using an SRV tester that involves reciprocating vibration.

[0026] The crystallite size of the 3R crystal structure is preferably 1 nm or more and 150 nm or less, more preferably 1 nm or more and 50 nm or less, and even more preferably 1 nm or more and 15 nm or less.

[0027] In addition, in the molybdenum disulfide particles of this embodiment, the crystallite size of the 2H crystal structure is preferably 1 nm or more and 150 nm or less. When the crystallite size of the 2H crystal structure is 1 nm or more and 150 nm or less, when used as a solid lubricant in a grease composition, the friction coefficient of the particle-containing grease composition can be reduced, and the friction and wear resistance properties can be improved. The crystallite size is more preferably 1 nm or more and 15 nm or less.

[0028] The crystallite size of the 2H crystal structure and the crystallite size of the 3R crystal structure can also be calculated using, for example, the peak half width of an XRD diffraction profile.

[0029] The ratio of the 2H crystal structure to the 3R crystal structure in the crystal phase (2H:3R) is preferably 10:90 to 90:10. When the ratio of the 3R crystal structure in the crystal phase is 10% or more and 90% or less, surface wear can be further suppressed when the molybdenum disulfide particles are used as an inorganic lubricant.

[0030] From the viewpoint of the above-mentioned effects, the abundance ratio (2H:3R) of the 2H crystal structure and the 3R crystal structure is more preferably 10:90 to 80:20, and even more preferably 40:60 to 80:20.

[0031] Furthermore, the molybdenum disulfide particles may contain a crystal structure other than the 2H crystal structure and 3R crystal structure of molybdenum disulfide, such as a 1H crystal structure.

[0032] The fact that the molybdenum disulfide particles contain a metastable 3R crystal structure can be distinguished by the fact that in a profile obtained by powder X-ray diffraction (XRD) using Cu-Kα radiation as the X-ray source, the peaks at around 39.5° and 49.5° are both composed of composite peaks of the 2H crystal structure and the 3R crystal structure.

[0033] In practice, the abundance ratio of the 2H crystal structure is determined by the peak around 39.5° and the broad peak around 49.5° using the profile obtained from the powder X-ray diffraction (XRD). Furthermore, the abundance ratio of the 3R crystal structure is determined by optimizing the difference between the peak around 39.5° and the broad peak around 49.5° with two peaks around 32.5° and two peaks around 39.5°. That is, both the peak around 39.5° and the peak around 49.5° are composite waves derived from the 2H crystal structure and the 3R crystal structure, and these composite waves can be used to calculate the abundance ratio of the 2H crystal structure and the 3R crystal structure in the molybdenum disulfide particles.

[0034] The molybdenum disulfide particles may also contain an amorphous phase. The proportion of the amorphous phase in the molybdenum disulfide particles, expressed as 100(%) - (crystallinity(%)), is preferably 5% or more, more preferably 15% or more, and even more preferably 20% or more. When the proportion of the amorphous phase in the molybdenum disulfide particles is 5% or more, the friction coefficient can be further reduced, and friction characteristics can be improved.

[0035] The shape of the primary particles of the molybdenum disulfide particles in a two-dimensional image taken with a transmission electron microscope (TEM) may be particulate, spherical, plate-like, needle-like, string-like, ribbon-like, or sheet-like, or may include a combination of these shapes. The shape of the molybdenum sulfide is preferably disk-like, ribbon-like, or sheet-like, and the average size of 50 primary particles of molybdenum sulfide is preferably in the range of length (vertical) × width (horizontal) × thickness (height) = 50-1000 nm × 50-1000 nm × 3-100 nm, more preferably 100-500 nm × 100-500 nm × 5-50 nm, and particularly preferably 50-200 nm × 50-200 nm × 5-20 nm. The disk-like, ribbon-like, or sheet-like shape allows for a large specific surface area of ​​the molybdenum disulfide particles. Here, the term "disc-shaped, ribbon-shaped, or sheet-shaped" refers to a thin layer shape. The aspect ratio of the primary particles of molybdenum sulfide, i.e., the value of (length (length and width)) / (thickness (height)), is preferably 1.2 to 1200, more preferably 2 to 800, further preferably 5 to 400, and particularly preferably 10 to 200, on average for 50 particles.

[0036] The primary particle shape of the molybdenum disulfide particles is not simply spherical, but is disk-shaped, ribbon-shaped, or sheet-shaped with a large aspect ratio, which is expected to more efficiently intervene between the particle-containing grease composition and the friction surface of the sliding part, reducing the probability of contact between the friction surfaces (or contact area x time), and thus suppressing surface wear.

[0037] Furthermore, from the viewpoint of providing superior lubrication performance, i.e., remaining without being expelled from the gap even when the friction surfaces of sliding materials come close to each other and easily maintaining lubrication performance, the molybdenum disulfide particles are not perfectly spherical, and preferably have an aspect ratio (the ratio of the length (nm) in the longitudinal direction of the particle to the thickness (nm)) in the range of 2 to 130, more preferably in the range of 2 to 100, and most preferably in the range of 3 to 100. The thickness and length used in calculating the aspect ratio can be measured by observation with an atomic force microscope (AFM), and the aspect ratio can be calculated from the measurement results.

[0038] The specific surface area of ​​the molybdenum disulfide particles measured by the BET method is 10 m 2 / g or more is preferable, and 30m 2 / g or more is more preferable, and 40m 2 The specific surface area of ​​the molybdenum disulfide particles measured by the BET method is particularly preferably 300 m / g or more. 2 / g or less, and 2 / g or less.

[0039] The layers constituting the primary particles of the molybdenum disulfide particles are close to each other due to relatively weak interactions, and can be easily displaced from each other by external forces such as friction. Therefore, when the primary particles of the molybdenum disulfide particles are interposed between the friction surfaces of sliding parts and frictional force is generated, the layers constituting the primary particles are displaced from each other by the frictional force, thereby reducing the apparent friction coefficient and preventing contact between the frictional surfaces. The specific surface area of ​​the molybdenum disulfide particles measured by the BET method is 10 m 2 / g or more, when the primary particles are present between the friction surfaces of the sliding parts, the contact area with the friction surfaces can be increased and the contact area between the friction surfaces of the sliding parts can be further reduced, thereby enabling excellent friction and wear resistance to be exhibited.

[0040] The specific surface area measured by the BET method is 10 m 2The particle-containing grease composition of this embodiment, which contains molybdenum disulfide particles having a molecular weight of 1 / g or larger, can increase the contact area between the molybdenum disulfide particles and the friction surface, thereby exhibiting excellent friction and wear resistance.

[0041] The bulk density of the molybdenum disulfide particles is 0.1 g / cm 3 More than 1.0g / cm 3 It is preferable that the density is 0.2 g / cm or less. 3 More than 0.9g / cm 3 More preferably, it is 0.4 g / cm or less. 3 More than 0.7g / cm 3 It is more preferable that the bulk density of the molybdenum disulfide particles is 0.1 g / cm or less. 3 More than 1.0g / cm 3 When the molybdenum disulfide content is less than 100%, the molybdenum disulfide particles are more likely to be exposed on the surface of the particle-containing grease composition, and the friction coefficient of the particle-containing grease composition can be further reduced, compared with when the same amount of molybdenum disulfide particles with a relatively high bulk density are contained in the grease composition. Furthermore, the desired friction and wear resistance can be obtained with a smaller content than when the above-mentioned molybdenum disulfide particles with a relatively high bulk density are contained, and it becomes possible to reduce the weight of molded articles using the particle-containing grease composition.

[0042] In the radial distribution function obtained from the extended X-ray absorption fine structure (EXAFS) profile of the molybdenum K absorption edge of the molybdenum disulfide particles, the ratio (I / II) of the peak intensity I due to Mo-S to the peak intensity II due to Mo-Mo is preferably greater than 1.0, more preferably 1.1 or more, and particularly preferably 1.2 or more.

[0043] Whether the crystal structure of molybdenum disulfide is a 2H crystal structure or a 3R crystal structure, the distance between Mo and S is nearly the same due to the covalent bond, so the intensity of the peak due to Mo-S is the same in the extended X-ray absorption fine structure (EXAFS) profile at the K absorption edge of molybdenum. On the other hand, because the 2H crystal structure of molybdenum disulfide is hexagonal, the same hexagon is located directly below the hexagon of the Mo atoms at 90°, so the distance between Mo and Mo is shorter and the peak intensity II due to Mo-Mo is stronger. Conversely, because the 3R crystal structure of molybdenum disulfide is rhombohedral, the hexagon is not directly below the hexagon at 90° but is shifted halfway, which increases the distance between Mo-Mo atoms and weakens the peak intensity II due to Mo-Mo atoms. In the pure 2H crystal structure of molybdenum disulfide, the ratio (I / II) is small, but as the 3R crystal structure is included, the ratio (I / II) becomes larger. In the 3R crystal structure, the hexagons of the Mo atoms in each of the three layers are offset from each other by half a hexagon, which means that there is less interaction between the layers than in the 2H crystal structure, in which the hexagons of the Mo atoms in two layers are aligned regularly and perpendicular to each other. This means that sliding between the crystal planes due to shear force can improve friction and wear resistance. It is expected that even in the 2H crystal structure, if the crystallite size is small, slippage at the contact surface will occur more easily.

[0044] The particle-containing grease composition of this embodiment preferably contains molybdenum disulfide particles (MoS2), but is not limited thereto. x (X=1 to 3) or MoS x The molybdenum sulfide particles may contain one or more types of molybdenum sulfide particles represented by (X=1 to 3).

[0045] (MoDTC) The MoDTC in the particle-containing grease composition of this embodiment is represented by the following general formula (1).

[0046] [ka] R in general formula (1) 1 ~R 4 and each represent the same or different alkyl groups having 1 to 18 carbon atoms. Examples of alkyl groups having 1 to 18 carbon atoms include linear alkyl groups such as n-hexyl, n-heptyl, n-octyl, n-nonyl, n-decyl, n-undecyl, n-dodecyl, n-tridecyl, and n-tetradecyl groups, and branched alkyl groups such as secondary hexyl, secondary heptyl, secondary octyl, isooctyl, secondary nonyl, isononyl, secondary decyl, isodecyl, secondary undecyl, isoundecyl, secondary dodecyl, isododecyl, secondary tridecyl, isotridecyl, secondary tetradecyl, and isotetradecyl groups. From the viewpoint of frictional properties, R 1 ~R 4 In order to relatively increase the amount of Mo element in one molecule, it is preferable that the number of carbon atoms is small, but a certain number of carbon atoms is necessary to ensure adequate solubility in oil. Therefore, each of the groups is preferably a linear or branched alkyl group having 4 to 14 carbon atoms, and from the viewpoint of easy availability of raw materials, a linear or branched alkyl group having 4, 8, or 13 carbon atoms is particularly preferable, and from the viewpoint of friction and wear resistance when used in combination with molybdenum disulfide particles, a linear or branched alkyl group having 4 carbon atoms is even more preferable. In addition, from the viewpoint of friction characteristics, R 1 and R 2 are the same alkyl group, and R 3 and R 4 are preferably the same alkyl groups.

[0047] X in the general formula (1) 1 ~X 4 Each independently represents an oxygen atom or a sulfur atom. From the viewpoint of friction properties, X 1 ~X 4 Among these, it is preferred that two or three are sulfur atoms and the rest are oxygen atoms, and it is more preferred that two are sulfur atoms and two are oxygen atoms, and X 1 , X 2 is sulfur atom and X 3 , X 4is most preferably an oxygen atom. For example, the MoDTC used in the present invention is R 1 , R 2 , R 3 and R 4 has 4 carbon atoms, and X 1 , X 2 is sulfur atom and X 3 , X 4 It is particularly preferred that is an oxygen atom.

[0048] In the present invention, one or more types of MoDTC represented by the general formula (1) may be used. MoDTC may be a commercially available product or may be produced by a known production method (e.g., the methods described in JP-A-51-80825 and JP-A-08-217782).

[0049] The particle-containing grease composition of this embodiment preferably contains the molybdenum disulfide particles in an amount of 0.0001% by mass or more and 50% by mass or less, more preferably 0.01% by mass or more and 20% by mass or less, even more preferably 0.1% by mass or more and 10% by mass or less, and most preferably 0.3% by mass or more and 3% by mass or less, relative to the total mass of the particle-containing grease composition (100% by mass).

[0050] The particle-containing grease composition of this embodiment preferably contains 0.001 mass % or more and 30 mass % or less of the MoDTC, more preferably 0.01 mass % or more and 20 mass % or less, even more preferably 0.1 mass % or more and 10 mass % or less, and most preferably 1 mass % or more and 10 mass % or less, relative to the total mass of the particle-containing grease composition (100 mass %).

[0051] (base oil) The base oil used in the particle-containing grease composition of this embodiment is not particularly limited, and known base oils can be used. For example, one or more types selected from naphthenic and / or paraffinic mineral oils (spindle oil, turbine oil, motor oil, bright stock, etc.), synthetic oils (diesters, polyol esters, silicone oils, PFPEs (perfluoropolyethers), PAOs (polyalphaolefins), PAGs (polyalkylene glycols), alkyl diphenyl ethers, polyphenyl ethers, etc. can be used.

[0052] The particle-containing grease composition can contain 50% by mass or more of the base oil, more preferably 70% by mass or more, more preferably 99% by mass or less, and even more preferably 95% by mass or less, relative to the total mass of the particle-containing grease composition (100% by mass).

[0053] (thickener) The thickener used in the particle-containing grease composition of this embodiment is not particularly limited, and either a soap-based or non-soap-based thickener can be used. Examples of soap-based agents include one or more selected from Ca soap (beef tallow-based or castor oil-based), Li complex soap, Ba complex soap, Al soap, Ca complex, Li complex, Al complex, etc. Examples of non-soap-based agents include one or more selected from urea compounds (aromatic diurea, aliphatic or alicyclic diurea, triurea, tetraurea, Na terephthalate, PTFE, bentonite, silica gel, carbon black, etc.).

[0054] The particle-containing grease composition may contain the thickener in an amount of 2% by mass or more and 60% by mass or less, and may contain 5% by mass or more and 30% by mass or less, relative to the total mass of the particle-containing grease composition (100% by mass).

[0055] (load-bearing additive) The particle-containing grease composition of this embodiment may further contain a load-bearing additive from the viewpoint of reducing frictional wear between friction surfaces and preventing seizure. Examples of the load-bearing additive include one or more selected from the group consisting of Pb naphthenate, chlorinated paraffins, SP-based compounds, various metal compounds, phosphorus-based compounds such as MoDTP and ZnDTP, and sulfur-based compounds.

[0056] The particle-containing grease composition may contain the load-bearing additive in an amount of 0.01% by mass or more and 50% by mass or less, or 0.1% by mass or more and 20% by mass or less, or 1% by mass or more and 10% by mass or less, relative to the total mass of the particle-containing grease composition (100% by mass).

[0057] (Other additives) The particle-containing grease composition of this embodiment may contain additives other than those described above depending on the application and specifications. Examples of other additives that can be used include one or more of antioxidants (sulfur, phosphorus-based, amine-based, phenol-based), rust inhibitors (carboxylic acids, metal sulfonates, etc.), corrosion inhibitors (benzotriazole, etc.), oiliness agents (fatty acids, fatty acid esters, etc.), wear inhibitors (phosphate esters, phosphites, thiophosphates, amine salts of phosphate esters, zinc dialkyldithiocarbamate, etc.), extreme pressure agents (sulfurized oils and fats, sulfurized esters, polysulfides, chlorine compounds, lead naphthenate, alkylthioamine phosphates, chloroalkylxanthates, etc.), solid lubricants (graphite, MoS2 other than the molybdenum disulfide particles, soft metals, etc.), viscosity index improvers (polyalkyl methacrylates, etc.), and detergent-dispersants (metal sulfonates, succinimides, etc.).

[0058] The particle-containing grease composition may contain the additive in an amount of 0.01 mass % or more and 50 mass % or less, or 0.1 mass % or more and 10 mass % or less, or 0.2 mass % or more and 5 mass % or less, relative to the total mass of the particle-containing grease composition (100 mass %).

[0059] <Method for producing particle-containing grease composition> The particle-containing grease composition according to this embodiment can be produced by uniformly mixing the base oil, thickener, molybdenum disulfide particles, and MoDTC in the above-described proportions. If necessary, extreme pressure agents and other additives may be added to the raw materials and mixed uniformly. The molybdenum disulfide particles and MoDTC may be added together with the base oil and thickener-containing raw materials, as described above. Alternatively, to uniformly disperse the molybdenum disulfide particles and MoDTC, the base oil and thickener-containing raw materials may be mixed together to produce a grease composition, and the molybdenum disulfide particles and MoDTC may then be added to the semi-solid grease composition. In this case, the grease composition can be homogenized by kneading using, for example, a Huber-Muller, a planetary kneader, a three-roll mill, a Shallot colloid mill, or a Monton-Gaulin homogenizer.

[0060] The particle-containing grease composition according to this embodiment is semi-solid (gel-like) at room temperature, and when applied to the sliding parts of a mechanical element, it changes state to a liquid (lubricating composition) due to frictional heat during sliding, penetrates the sliding parts, and forms a thin film on the surface (friction surface) of the solid that constitutes the sliding part, such as metal or resin, thereby lubricating the sliding part. Furthermore, at this time, the molybdenum disulfide particles (MoDTC) contained in the particle-containing grease composition or the liquid are supplied to the sliding parts and micro-recesses on the friction surface, thereby reducing frictional wear of the sliding parts. When sliding stops, the temperature drops, and the lubricating composition, which was in a liquid state, returns to a semi-solid particle-containing grease composition. The particle-containing grease composition of this embodiment contains the molybdenum disulfide particles and MoDTC, and therefore has excellent friction and wear resistance, particularly low wear, high seizure load, and high welding load, and can maintain these excellent friction and wear resistance over a long period of time. Furthermore, the particle-containing grease composition of this embodiment reconstructs its gel (semi-solid) structure even when repeatedly subjected to heating and cooling stresses associated with use and non-use, thereby preventing contamination due to oil leakage.

[0061] (Method for producing molybdenum disulfide particles in particle-containing grease composition) The molybdenum disulfide particles in the particle-containing grease composition of this embodiment can be produced, for example, by heating molybdenum trioxide particles at a temperature of 200 to 1150°C in the presence of a sulfur source.

[0062] The average particle size of the primary particles of the molybdenum trioxide particles is preferably 2 nm or more and 2000 nm or less. The average particle size of the primary particles of the molybdenum trioxide particles refers to the average value of primary particle diameters of 50 randomly selected primary particles, when the molybdenum trioxide particles are photographed with a scanning electron microscope (SEM) or a transmission electron microscope (TEM), and the major axis (the Feret diameter of the longest observed part) and minor axis (the shorter Feret diameter perpendicular to the Feret diameter of the longest part) of the smallest unit particle (i.e., primary particle) constituting the aggregate in the two-dimensional image are measured, and the average value is defined as the primary particle diameter.

[0063] In the method for producing molybdenum sulfide powder of this embodiment, the molybdenum trioxide particles preferably have a MoO3 content of 99.5% or more as measured by X-ray fluorescence (XRF), thereby achieving a conversion rate R C Therefore, it is possible to obtain high-purity molybdenum disulfide that is free from the risk of producing disulfides derived from impurities and has good storage stability.

[0064] The molybdenum trioxide particles may have an average primary particle size of 5 nm or more and 2000 nm or less. The molybdenum trioxide particles may have an average primary particle size of 1000 nm or less, and from the viewpoint of reactivity with sulfur, the average primary particle size is preferably 600 nm or less, more preferably 400 nm or less, and particularly preferably 200 nm or less. The molybdenum trioxide particles may have an average primary particle size of 2 nm or more, 5 nm or more, or 10 nm or more.

[0065] Examples of sulfur sources include sulfur and hydrogen sulfide, which may be used alone or in combination.

[0066] The molybdenum trioxide particles have a specific surface area of ​​10 m as measured by the BET method. 2 / g or more 100m 2 / g or less is preferable.

[0067] In the molybdenum trioxide particles, the specific surface area is 10 m because the reactivity with sulfur is improved. 2 / g, and 20m 2 / g, and 30m 2 In the molybdenum trioxide particles, it is preferable that the particle size is 100 m / g because it is easy to produce. 2 / g, and 90m 2 / g, and 80m 2 / g.

[0068] The molybdenum trioxide particles used in the production of molybdenum disulfide particles are preferably composed of an aggregate of primary particles containing the β crystal structure of molybdenum trioxide. The molybdenum oxide particles have a better reactivity with sulfur than conventional molybdenum trioxide particles that are composed only of α crystals, and because they contain the β crystal structure of molybdenum trioxide, the conversion rate R to MoS2 in the reaction with a sulfur source is higher. C can be made larger.

[0069] The β-crystalline structure of molybdenum trioxide can be confirmed by the presence of a peak (2θ: around 23.01°, No. 86426 (Inorganic Crystal Structure Database, ICSD)) assigned to the (011) plane of the β-crystalline MoO3 in the profile obtained by powder X-ray diffraction (XRD) using Cu-Kα radiation as the X-ray source. The α-crystalline structure of molybdenum trioxide can be confirmed by the presence of a peak (2θ: around 27.32°, No. 166363 (Inorganic Crystal Structure Database, ICSD)) assigned to the (021) plane of the α-crystalline MoO3.

[0070] In the method for producing molybdenum disulfide particles, the molybdenum trioxide particles preferably have a profile obtained by powder X-ray diffraction (XRD) using Cu-Kα radiation as an X-ray source, in which the ratio (β(011) / α(021)) of the peak intensity attributable to the (011) plane of the β crystal of MoO3 (near 2θ: 23.01°, No. 86426 (Inorganic Crystal Structure Database (ICSD))) to the peak intensity attributable to the (021) plane of the α crystal of MoO3 (near 2θ: 27.32°, No. 166363 (Inorganic Crystal Structure Database (ICSD))) is 0.1 or more.

[0071] The maximum intensity of the peak attributable to the (011) plane of the β crystal of MoO3 and the maximum intensity of the peak attributable to the (021) plane of the α crystal of MoO3 are read, and the ratio (β(011) / α(021)) is calculated.

[0072] In the molybdenum trioxide particles, the ratio (β(011) / α(021)) is preferably 0.1 to 10.0, more preferably 0.2 to 10.0, and particularly preferably 0.4 to 10.0.

[0073] The β-crystalline structure of molybdenum trioxide is observed at a wavenumber of 773 cm in the Raman spectrum obtained by Raman spectroscopy. -1 , 848cm -1 and 905 cm -1 The α-crystalline structure of molybdenum trioxide can also be confirmed by the presence of a peak at a wavenumber of 663 cm. -1 , 816cm -1 and 991 cm -1 This can be confirmed by the presence of a peak at

[0074] In the molybdenum trioxide particles, the ratio (I / II) of the peak intensity I attributable to Mo-O to the peak intensity II attributable to Mo-Mo in a radial distribution function obtained from an extended X-ray absorption fine structure (EXAFS) profile at the molybdenum K absorption edge is preferably greater than 1.1.

[0075] The maximum intensities of the peak intensity I attributable to Mo-O and the peak intensity II attributable to Mo-Mo are read, and the ratio (I / II) is calculated. The ratio (I / II) is considered to be an indicator of whether a β-crystalline structure of MoO3 has been obtained in the molybdenum trioxide particles, and the larger the ratio (I / II), the better the reactivity with sulfur.

[0076] In the molybdenum trioxide particles, the ratio (I / II) is preferably 1.1 to 5.0, may be 1.2 to 4.0, or may be 1.2 to 3.0.

[0077] The method for producing molybdenum disulfide may include heating molybdenum trioxide particles comprising an aggregate of primary particles having a β crystal structure of molybdenum trioxide at a temperature of 100 to 800°C in the absence of a sulfur source, and then heating at a temperature of 200 to 1000°C in the presence of a sulfur source.

[0078] The heating time in the presence of the sulfur source may be any time that allows the sulfurization reaction to proceed sufficiently, and may be 1 hour to 20 hours, 2 hours to 15 hours, or 3 hours to 10 hours.

[0079] In the method for producing molybdenum disulfide particles, the ratio of the amount of S in the sulfur source to the amount of MoO in the molybdenum trioxide particles is preferably set to a value that satisfies the conditions for sufficient sulfurization reaction. For 100 mol% of the MoO in the molybdenum trioxide particles, the amount of S in the sulfur source is preferably 450 mol% or more, preferably 600 mol% or more, and preferably 700 mol% or more. For 100 mol% of the MoO in the molybdenum trioxide particles, the amount of S in the sulfur source may be 3000 mol% or less, 2000 mol% or less, or 1500 mol% or less.

[0080] In the method for producing molybdenum disulfide particles, the heating temperature in the presence of the sulfur source may be any temperature at which the sulfurization reaction proceeds sufficiently, and is preferably 320°C or higher, more preferably 340°C or higher, and particularly preferably 360°C or higher. The temperature may be 320 to 1000°C, 340 to 1000°C, or 360 to 500°C.

[0081] In the method for producing molybdenum disulfide particles, the obtained molybdenum disulfide particles may be cooled and then heated as a post-treatment, if necessary. In this heat treatment, for example, the molybdenum disulfide particles are preferably fired in an inert atmosphere. Heating and firing the obtained molybdenum disulfide particles promotes crystallization of the amorphous portion, improving the crystallinity. Furthermore, as the crystallinity improves, new 2H and 3R crystal structures are generated, changing the abundance ratio of the 2H and 3R crystal structures. Reheating as a post-treatment like this increases the crystallinity of the molybdenum disulfide particles, reducing the ease of peeling due to lubrication to some extent, but also increasing the abundance ratio of the 3R crystal structure, which contributes to improving frictional properties, thereby improving frictional properties compared to when the particles are made of only a 2H crystal structure. Furthermore, by changing the temperature at which the obtained molybdenum disulfide particles are heated, the abundance ratio of the 2H and 3R crystal structures can be adjusted.

[0082] By using the method for producing molybdenum disulfide particles described above, the molybdenum disulfide particles contained in the particle-containing grease composition of this embodiment can be produced efficiently.

[0083] (Method of manufacturing molybdenum trioxide particles) The molybdenum trioxide particles can be produced by vaporizing a molybdenum trioxide precursor compound to form molybdenum trioxide vapor and cooling the molybdenum trioxide vapor.

[0084] The method for producing molybdenum trioxide particles includes calcining a raw material mixture containing a molybdenum trioxide precursor compound and a metal compound other than the molybdenum trioxide precursor compound, and vaporizing the molybdenum trioxide precursor compound to form molybdenum trioxide vapor, and it is preferable that the proportion of the metal compound relative to 100% by mass of the raw material mixture is 70% by mass or less in terms of oxide.

[0085] The method for producing the molybdenum trioxide particles can be suitably carried out using a production apparatus 1 shown in FIG.

[0086] FIG. 1 is a schematic diagram of an example of an apparatus used for producing the molybdenum trioxide particles, which are the raw material for the molybdenum disulfide particles in this embodiment. As shown in FIG. 1, the manufacturing apparatus 1 includes a calcination furnace 2 that calcines a molybdenum trioxide precursor compound or the raw material mixture and vaporizes the molybdenum trioxide precursor compound; a cross-shaped cooling pipe 3 connected to the calcination furnace 2 and that powders the molybdenum trioxide vapor vaporized by the calcination; and a recovery machine 4, which serves as recovery means for recovering the molybdenum trioxide particles powdered in the cooling pipe 3. The calcination furnace 2 and the cooling pipe 3 are connected via an exhaust port 5. The cooling pipe 3 also has an opening-adjusting damper 6 at the left end of an outside air intake (not shown) and an observation window 7 at the top end. A ventilation device 8, which serves as a first ventilation means, is connected to the recovery machine 4. When the exhaust device 8 exhausts air, the recovery machine 4 and the cooling pipe 3 are sucked, and outside air is blown into the cooling pipe 3 through the opening-adjusting damper 6 of the cooling pipe 3. That is, the exhaust device 8 performs a suction function, thereby passively blowing air into the cooling pipe 3. The manufacturing apparatus 1 may also have an external cooling device 9, which makes it possible to arbitrarily control the cooling conditions for the molybdenum trioxide vapor generated from the firing furnace 2.

[0087] By using the opening adjustment damper 6 to take in air from the outside air intake and cooling the molybdenum trioxide vapor vaporized in the firing furnace 2 in an air atmosphere to form molybdenum trioxide particles, the ratio (I / II) can be made greater than 1.1, making it easier to obtain a β-crystalline structure of MoO3 in the molybdenum trioxide particles. Cooling molybdenum trioxide vapor in a nitrogen atmosphere with a low oxygen concentration, such as when liquid nitrogen is used to cool the molybdenum trioxide vapor, increases the oxygen vacancy density and tends to decrease the ratio (I / II).

[0088] The molybdenum trioxide precursor compound is not particularly limited as long as it can form molybdenum trioxide vapor by firing. Examples of the molybdenum trioxide precursor compound include metallic molybdenum, molybdenum trioxide, molybdenum dioxide, molybdenum sulfide, ammonium molybdate, phosphomolybdic acid (H3PMo 12 O 40 ), silicomolybdic acid (H4SiMo 12 O 40 ), aluminum molybdate, silicon molybdate, magnesium molybdate (MgMo n O 3n+1 (n=1-3)), sodium molybdate (Na2Mo n O 3n+1 (n=1-3)), titanium molybdate, iron molybdate, potassium molybdate (KMo n O 3n+1 (n=1-3)), zinc molybdate, boron molybdate, lithium molybdate (Li2Mo n O 3n+1 (n=1 to 3)), cobalt molybdate, nickel molybdate, manganese molybdate, chromium molybdate, cesium molybdate, barium molybdate, strontium molybdate, yttrium molybdate, zirconium molybdate, copper molybdate, etc. These molybdenum oxide precursor compounds may be used alone or in combination of two or more. The form of the molybdenum oxide precursor compound is not particularly limited and may be, for example, a powder such as molybdenum trioxide, but is preferably a powder that is easy to handle and energy efficient.

[0089] It is particularly preferable to use commercially available α-crystalline molybdenum trioxide as the molybdenum trioxide precursor compound. When ammonium molybdate is used as the molybdenum trioxide precursor compound, it is converted into thermodynamically stable molybdenum trioxide by calcination, and the vaporized molybdenum trioxide precursor compound becomes the molybdenum trioxide.

[0090] Molybdenum trioxide vapor can also be produced by firing a raw material mixture containing a molybdenum trioxide precursor compound and a metal compound other than the molybdenum trioxide precursor compound. Of these, the molybdenum trioxide precursor compound preferably contains molybdenum trioxide, in terms of ease of control of the purity, average primary particle size, and crystal structure of the resulting molybdenum trioxide particles.

[0091] The firing temperature varies depending on the molybdenum trioxide precursor compound and metal compound used, the desired molybdenum trioxide particles, etc., but is usually preferably a temperature at which the intermediate can be decomposed. For example, when a molybdenum compound is used as the molybdenum trioxide precursor compound and an aluminum compound is used as the metal compound, aluminum molybdate may be formed as an intermediate, so the firing temperature is preferably 500 to 1500°C, more preferably 600 to 1550°C, and even more preferably 700 to 1600°C.

[0092] The firing time is not particularly limited either, and can be, for example, 1 minute to 30 hours, 10 minutes to 25 hours, or 100 minutes to 20 hours.

[0093] The heating rate varies depending on the molybdenum trioxide precursor compound and the metal compound used, the properties of the desired molybdenum trioxide particles, and other factors, but from the viewpoint of production efficiency, it is preferably 0.1°C / min to 100°C / min, more preferably 1°C / min to 50°C / min, and even more preferably 2°C / min to 10°C / min.

[0094] Next, the molybdenum trioxide vapor is cooled and powdered. The molybdenum trioxide vapor is cooled by lowering the temperature of the cooling pipe. In this case, the cooling means may be, as described above, cooling by blowing gas into the cooling pipe, cooling by a cooling mechanism of the cooling pipe, or cooling by an external cooling device.

[0095] The molybdenum trioxide vapor is preferably cooled in an air atmosphere. By cooling the molybdenum trioxide vapor in an air atmosphere to form molybdenum trioxide particles, the ratio (I / II) can be made greater than 1.1, making it easier to obtain a β-crystalline structure of MoO in the molybdenum trioxide particles.

[0096] The cooling temperature (temperature of the cooling pipe) is not particularly limited, but is preferably from -100 to 600°C, and more preferably from -50 to 400°C.

[0097] The cooling rate of the molybdenum trioxide vapor is not particularly limited, but is preferably 100°C / s or more and 100,000°C / s or less, and more preferably 1,000°C / s or more and 50,000°C / s or less. Note that as the cooling rate of the molybdenum trioxide vapor increases, molybdenum trioxide particles with smaller particle size and larger specific surface area tend to be obtained.

[0098] When the cooling means is a method of cooling by blowing gas into a cooling pipe, the temperature of the blown gas is preferably -100 to 300°C, more preferably -50 to 100°C.

[0099] The powder obtained by cooling the molybdenum trioxide vapor is transported to a recovery machine and recovered.

[0100] In the method for producing the molybdenum trioxide particles, the powder obtained by cooling the molybdenum trioxide vapor may be fired again at a temperature of 100 to 320°C.

[0101] That is, the molybdenum trioxide particles obtained by the method for producing molybdenum trioxide particles may be calcined again at a temperature of 100 to 320°C. The calcination temperature for the second calcination may be 120 to 280°C, or 140 to 240°C. The calcination time for the second calcination may be, for example, 1 min to 4 hours, 10 min to 5 hours, or 100 min to 6 hours. However, the second calcination will cause a portion of the β crystal structure of the molybdenum trioxide to disappear, and if the molybdenum trioxide particles are calcined for 4 hours at a temperature of 350°C or higher, the β crystal structure in the molybdenum trioxide particles will disappear, the ratio (β(011) / α(021)) will become 0, and the reactivity with sulfur will be impaired.

[0102] By the method for producing molybdenum trioxide particles described above, it is possible to produce molybdenum trioxide particles suitable for producing molybdenum disulfide particles. [Example]

[0103] The present invention will now be described in more detail with reference to examples, but the present invention is not limited to the following examples. In the following examples, "parts by mass" refers to "% by mass" unless otherwise specified.

[0104] [Median diameter D of molybdenum disulfide particles that make up the molybdenum sulfide powder 50 Measurement of Molybdenum Sulfide Powder 0.1 g was added to 20 cc of acetone, and the mixture was subjected to ultrasonic treatment in an ice bath for 4 hours. The mixture was then further adjusted with acetone to a concentration within the measurable range of a dynamic light scattering particle size distribution analyzer (Microtrack Bell, Nanotrac Wave II) to obtain a measurement sample. Using this measurement sample, the particle size distribution in the particle size range of 0.0001 μm to 10 μm was measured using the dynamic light scattering particle size distribution analyzer. The median diameter D 50 was calculated.

[0105] <Synthesis Example 1> Molybdenum trioxide particles were produced in the same manner as in Synthesis Example 1 of WO 2022 / 202751A1. (Production of molybdenum trioxide particles) 1.5 kg of aluminum hydroxide (manufactured by Nippon Light Metal Co., Ltd.) and 1 kg of molybdenum trioxide (manufactured by Nippon Inorganic Co., Ltd.) were mixed and then charged into a sheath. The mixture was then fired at 1100°C for 10 hours in firing furnace 2 of the manufacturing apparatus 1 shown in Figure 1. During firing, outside air (air flow rate: 50 L / min, outside air temperature: 25°C) was introduced from the side and bottom of firing furnace 2. Molybdenum trioxide evaporated in firing furnace 2, then cooled near recovery machine 4 and precipitated as particles. An RHK simulator (manufactured by Noritake Company Limited) was used as firing furnace 2, and a VF-5N dust collector (manufactured by Amano Corporation) was used as recovery machine 4.

[0106] After calcination, 1.0 kg of blue powder aluminum oxide was extracted from the scabbard, and 0.85 kg of molybdenum trioxide particles were recovered by recovery machine 4. The recovered molybdenum trioxide particles had an average primary particle size of 80 nm, and X-ray fluorescence (XRF) measurement confirmed that the purity of the molybdenum trioxide was 99.7%. The specific surface area (SA) of these molybdenum trioxide particles, measured by the BET method, was 44.0 m 2 / g.

[0107] Similarly, molybdenum disulfide particles were produced using the same method as used to produce the molybdenum disulfide powder disclosed in the International Publication.

[0108] (Manufacturing molybdenum disulfide powder) In a magnetic crucible, 40.0 g (277.9 mmol) of molybdenum trioxide particles recovered by recovery machine 4 and 40.0 g (1250 mmol) of sulfur powder (Kanto Chemical Co., Ltd.) were mixed with a stirrer to homogenize the powder, and the mixture was placed in a high-temperature atmosphere firing furnace (SKM-2030P-OP, manufactured by Motoyama Corporation). The furnace was evacuated and replaced with nitrogen, and then fired at 500°C for 4 hours to obtain a black powder. Here, the amount of S in the sulfur was 450 mol% relative to 100 mol% of the MoO3 content of the molybdenum trioxide particles.

[0109] The particle size distribution of the molybdenum disulfide powder produced in Synthesis Example 1 was measured using a dynamic light scattering particle size distribution analyzer, and the median diameter D 50The specific surface area was measured by the BET method and found to be 49.6 m 2 / g.

[0110] Furthermore, the thickness was measured using an AFM (Cypher ES, manufactured by Oxford Instruments). The length (vertical) x width (horizontal) calculated from the AFM image was 180 nm x 80 nm. The thickness (height) was calculated to be 16 nm. Therefore, the aspect ratio (length (vertical) / thickness (height)) of the primary particle of the molybdenum disulfide particle was 11.25. A representative example of the AFM measurement results is shown in Table 1. The average value for 50 random particles was 11.25.

[0111] [Table 1]

[0112] Since the molybdenum disulfide particles were produced using the same method as in the International Publication, the resulting molybdenum disulfide particles contained both the 3R and 2H crystal structures, with the abundance ratios of the 2H crystal structure being 71.5% and the 3R crystal structure being 28.5%. The crystallite sizes were 9.6 nm for the 2H crystal structure and 11.8 nm for the 3R crystal structure.

[0113] (Production of particle-containing grease composition) Example 1 A grease composition (Multidia MP-2 manufactured by Daido Yushi Co., Ltd.) using refined mineral oil as the base oil and Li soap as the adjuster was mixed with 96.7 parts by mass of the molybdenum disulfide particles obtained in Synthesis Example 1 and a molybdenum disulfide compound represented by the general formula (1), R 1 ~R 4 The alkyl chain length of X is 4, 1 and X 2 S, X 3 and X 4 3 parts by mass of MoDTC, in which % is O, was added, and the mixture was mixed in a plastic cup for 30 minutes using a medicine spoon, to obtain composition 1.

[0114] <Example 2> Composition 2 was obtained in the same manner as in Example 1, except that 3 parts by mass of molybdenum disulfide particles and 3 parts by mass of MoDTC, the same as in Example 1, were added to 94 parts by mass of the grease composition.

[0115] (Production of particle-containing grease composition) <Comparative Example 1> Composition 3 was obtained in the same manner as in Example 1, except that 0.3 parts by mass of molybdenum disulfide particles were added to 99.7 parts by mass of the grease composition.

[0116] <Comparative Example 2> Composition 4 was obtained in the same manner as in Example 1, except that 3 parts by mass of molybdenum disulfide particles were added to 97 parts by mass of the grease composition.

[0117] <Comparative Example 3> Composition 5 was obtained in the same manner as in Example 1, except that 3 parts by mass of MoDTC, the same as in Example 1, was added to 97 parts by mass of the grease composition.

[0118] <Comparative Example 4> For 97 parts by mass of the grease composition, a commercially available grease with a specific surface area of ​​3.5 m 2 Composition 6 was obtained in the same manner as in Example 1, except that 3 parts by mass of MoS2 was added.

[0119] <Comparative Example 5> Composition 7 was obtained in the same manner as in Example 1, except that 100 parts by mass of the grease composition was used.

[0120] [Friction and wear test] For Composition 1 obtained in Example 1, the coefficient of friction was measured at 40° C. using an SRV tester (manufactured by Optimol, model: type 5), and the wear state of the target plate after the SRV test was evaluated. Composition 1 obtained in Example 1 was placed on a 24 mm diameter × 7.8 mm diameter SUJ2 target plate, and a 10 mm diameter SUJ2 ball was pressed against it with a load of 200 N. An SRV test was then performed at 40°C for 10 minutes with an amplitude of 1 mm and a frequency of 50 Hz. The minimum dynamic friction was 0.065. The average coefficient of friction during the first 30 seconds of break-in was <0.089>. The wear mark on the target plate was then observed using an optical microscope, and the wear mark density was determined to be "Good." The wear mark density is indicated as "Good: Thin wear mark," "Good: Slightly thin wear mark," or "Poor: Dark wear mark."

[0121] The coefficient of friction of Composition 1 obtained in Example 1 was similarly measured using the SRV test at 80°C, and the minimum coefficient of friction was 0.068. The average coefficient of friction during the first 30 seconds of break-in was <0.099>. The wear mark density on the target plate was then observed using an optical microscope. The wear mark density was rated "Good." The same evaluation was carried out for Example 2 and Comparative Examples 1 to 5. The results are shown in Table 2.

[0122] [Table 2]

[0123] Examples 1 and 2, which used both molybdenum disulfide particles and MoDTC, had a smaller minimum friction coefficient at any temperature than Comparative Examples 1 to 5, and were superior in lubrication performance.

[0124] In Examples 1 and 2, in which molybdenum disulfide particles and MoDTC were used in combination, the average friction coefficient from the start to 30 seconds was smaller at all temperatures than in Comparative Examples 1 to 5, and the initial break-in was excellent.

[0125] In Examples 1 and 2, in which molybdenum disulfide particles and MoDTC were used in combination, the wear marks were thinner and the wear resistance was superior compared to Comparative Examples 1 to 5. [Industrial Applicability]

[0126] The particle-containing grease composition of the present invention is suitable for use in sliding portions between metal members, between resin members, or between resin and metal members, and can be applied to equipment and parts in a variety of industrial fields. For example, it can be widely used in power transmission devices such as reducers, speed increasers, gears, chains, and motors; driving system components; control system components such as anti-lock braking systems (ABS); steering system components; drive system components such as transmissions; automotive reinforcement components such as power window motors, power seat motors, and sunroof motors; office equipment components such as copiers and printers; hinge components for electronic information devices and mobile phones; various parts and mechanical parts that move relative to one another in the food and pharmaceutical industries, steel, construction, glass, cement, film tenter, chemical, rubber, and resin industries, environmental and power equipment, paper and printing, wood, and textile and apparel industries, and is particularly suitable for use in transmission elements that are subject to high loads. The particle-containing grease composition of the present invention can also be used in bearings such as rolling bearings, thrust bearings, hydrodynamic bearings, resin bearings, and linear motion devices. [Explanation of symbols]

[0127] 1 Manufacturing equipment 2. Kiln 3 Cooling piping 4. Collection machine 5 exhaust port 6 Opening adjustment damper 7 Observation window 8 Ventilation device 9 External cooling device

Claims

1. Base oil, thickener, and median diameter D determined by dynamic light scattering ５０ A particle-containing grease composition comprising molybdenum disulfide particles having a size of 10 nm or more and less than 450 nm and molybdenum dialkyldithiocarbamate.

2. The specific surface area of ​​the molybdenum disulfide particles measured by the BET method is 10 m ２ 2. The particle-containing grease composition according to claim 1, wherein the grease composition has a viscosity of 1000 MPa or more.

3. 2. The particle-containing grease composition according to claim 1, wherein the structure of the molybdenum dialkyldithiocarbamate is represented by the following general formula (1): 【Chemical 1】 (In the formula, R １ ~R ４ are the same or different alkyl groups having 1 to 18 carbon atoms; X １ ~X ４ each independently represents an oxygen atom or a sulfur atom.

4. 2. The particle-containing grease composition according to claim 1, wherein the molybdenum disulfide particles have the 2H and 3R crystal structures of molybdenum disulfide.

5. 5. The particle-containing grease composition according to claim 1, wherein the molybdenum disulfide particles are contained in an amount of 0.3 mass % to 3 mass % relative to 100 mass % of the total mass of the particle-containing grease composition.

6. 5. The particle-containing grease composition according to claim 1, wherein the molybdenum dialkyldithiocarbamate is contained in an amount of 0.1 mass % or more and 10 mass % or less relative to 100 mass % of the total mass of the particle-containing grease composition.

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