Grease composition containing particles

Abstract

Provided is a particulate-containing grease composition that can efficiently improve friction and wear resistance characteristics with a small addition amount and exhibits excellent friction and wear resistance characteristics even when the clearance of the sliding part and the surface roughness of the friction surface are extremely small. The particulate-containing grease composition is a particulate-containing grease composition containing a base oil, a thickener, and molybdenum disulfide particles, and the median particle size D 50 of the molybdenum disulfide particles determined by dynamic light scattering is 10 nm or more and less than 450 nm.

Description

Technical Field

[0001] The present invention relates to a grease composition containing particles, and more particularly to a grease composition containing particles and molybdenum disulfide.

[0002] This application claims priority based on Japanese Patent Application No. 2021-050498 filed in Japan on March 24, 2021, the content of which is incorporated herein by reference. Background Art

[0003] Molybdenum disulfide is widely known as a lubricant for reducing friction and wear and has been used in various countries. In fact, it is compounded and used in lubricating oils such as engine oil (long-chain aliphatic low-polarity solvent system), coating paints (low-boiling-point polar solvents), greases (substances obtained by adding thickeners such as Li soap to long-chain aliphatic low-polarity solvents), etc.

[0004] As a conventional grease composition containing particles, for example, a grease composition for constant velocity joints has been proposed, which contains a base oil, a diurea thickener, molybdenum disulfide, molybdenum sulfide dialkyldithiocarbamate, 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 also contains zinc dialkyldithiocarbamate as an additive (Patent Document 1).

[0005] In addition, a lubricant composition in a semi-solid state at normal temperature has been proposed, which contains 10 to 99.9% by mass of a liquid base oil, 0.1 to 90% by mass of an amide compound, and 1.0 to 20% by mass of a solid lubricant or an organomolybdenum compound in an amount of 0.0005 to 5% by mass in terms of molybdenum (Mo) (Patent Document 2).

[0006] In addition, a grease composition for constant velocity joints has been proposed, which contains a base oil comprising 10 to 95% of an ester synthetic oil produced from an aliphatic alcohol and an aromatic carboxylic acid and 90 to 5% of a synthetic hydrocarbon oil, a thickener, molybdenum disulfide, molybdenum sulfide dialkyldithiocarbamate, and zinc dithiophosphate (Patent Document 3); and a grease composition for constant velocity joints, which contains a diurea thickener, an ester synthetic oil, a mineral oil and / or a synthetic hydrocarbon oil, molybdenum dialkyldithiocarbamate, molybdenum disulfide, polytetrafluoroethylene, and a zinc dithiophosphate compound (Patent Document 4).

[0007] In addition, a grease for constant velocity universal joints is proposed, which contains an alkali metal salt of molybdic acid and a layered compound as essential components in a base grease prepared by blending a thickener into a base oil (Patent Document 5); a grease to which molybdenum disulfide is added as a solid lubricant for density adjustment (Patent Document 6); or an application method in which a composition containing 0.1 to 40% by mass of surface-modified nanoparticles and 99.9 to 60% by mass of a loading material, and the above surface modification includes a mercapto group, is added to the grease (Patent Document 7).

[0008] As a grease composition containing particles in which the particle size of molybdenum disulfide is specified, a grease composition for constant velocity universal joints is disclosed, which contains a base oil, a diurea-based thickener, molybdenum dialkyldithiocarbamate insoluble in the base oil, molybdenum dialkyldithiocarbamate soluble in the base oil, molybdenum disulfide, calcium phenolate or calcium sulfonate, and a sulfur-based extreme pressure additive containing no phosphorus component. In the examples, the particle size of the above molybdenum disulfide is 0.45 μm (Patent Document 8).

[0009] Prior art documents

[0010] Patent documents

[0011] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2010-90243

[0012] Patent Document 2: Japanese Unexamined Patent Application Publication No. 2008-231293

[0013] Patent Document 3: Japanese Unexamined Patent Application Publication No. 2008-163201

[0014] Patent Document 4: Japanese Unexamined Patent Application Publication No. 2007-138110

[0015] Patent Document 5: Japanese Unexamined Patent Application Publication No. 2006-298963

[0016] Patent Document 6: Japanese Unexamined Patent Application Publication No. 2003-301188

[0017] Patent Document 7: Japanese Patent Application Laid-Open No. 2014-518932

[0018] Patent Document 8: Japanese Unexamined Patent Application Publication No. 2006-16481 Summary of the invention

[0019] Problems to be Solved by the Invention

[0020] However, commercially available molybdenum disulfide particles added to the above-mentioned conventional grease compositions are submicron-sized or larger obtained by pulverizing natural molybdenum disulfide minerals, and have a very large specific gravity of about 5. Therefore, there is a problem that the anti-friction and anti-wear characteristic effect is low relative to the unit weight added. In addition, in recent years, with technological innovation, the surface roughness of the friction surface of the sliding part is extremely small, and the above-mentioned commercially available molybdenum disulfide particles cannot enter the minute recesses of the friction surface, and the manifestation of the above effect is insufficient. Furthermore, there is no opinion on the relationship between the crystal structure of molybdenum disulfide particles and the anti-friction and anti-wear characteristics in a grease-containing system.

[0021] An object of the present invention is to provide a grease composition containing particles, which can efficiently improve the anti-friction and anti-wear characteristics with a small addition amount, and can exhibit excellent anti-friction and anti-wear characteristics even when the gap of the sliding part and the surface roughness of the friction surface are extremely small.

[0022] Solutions for Solving the Problems

[0023] The present inventors repeatedly conducted in-depth studies and found that when molybdenum disulfide particles having a specified median particle diameter D 50 are used as an additive for a grease composition containing particles, the molybdenum disulfide particles can easily enter the gap between the friction surfaces of the sliding part and the minute recesses of the friction surface, and the number of effective particles per unit weight added becomes large. As a result, even with a small addition amount, the effect of improving the anti-friction and anti-wear characteristics is high, and the anti-friction and anti-wear characteristics can be efficiently improved.

[0024] In addition, when molybdenum disulfide particles are manufactured using the technology "nanosized molybdenum oxide fine particles" held by the present applicant as a raw material, as its crystal structure, it has not only 2H but also a rare 3R (rhombohedral) structure. According to this technology, by using the technology "nanosized molybdenum trioxide fine particles" held by the present applicant as a raw material to manufacture molybdenum disulfide particles, it is possible to synthesize "molybdenum disulfide having a 3R structure, being nanoscale, having a large specific surface area per unit weight, and having a plate-like structure" which is difficult to achieve by pulverizing ore products and synthesizing from general molybdenum trioxide (μm size) in a grease composition containing particles. Thus, it was found that when the molybdenum disulfide particles are used as an additive for a grease composition containing particles, excellent anti-friction and anti-wear characteristics can be exhibited due to the large specific surface area of the molybdenum disulfide particles.

[0025] That is, the present invention provides the following constitution.

[0026] [1] A grease composition containing particles, which contains a base oil, a thickener, and molybdenum disulfide particles,

[0027] The median particle diameter D of the above-mentioned molybdenum disulfide particles determined by the dynamic light scattering method 50is 10 nm or more and less than 450 nm.

[0028] [2] The grease composition containing particles according to [1] above, wherein the shape of the primary particles of the molybdenum disulfide particles is disc-shaped, strip-shaped or flake-shaped, and the thickness is in the range of 3 to 100 nm.

[0029] [3] The grease composition containing particles according to [1] or [2] above, wherein the specific surface area of the molybdenum disulfide particles measured by the BET method is 10 m 2 / g or more.

[0030] [4] The grease composition containing particles according to any one of [1] to [3] above, wherein the bulk density of the molybdenum disulfide particles is 0.1 g / cm 3 or more and 1.0 g / cm 3 or less.

[0031] [5] The grease composition containing particles according to any one of [1] to [4] above, wherein in the radial distribution function of the molybdenum disulfide particles obtained from the extended X-ray absorption fine structure (EXAFS) spectrum of the K absorption edge of molybdenum, the ratio (I / II) of the intensity I of the peak derived from Mo-S to the intensity II of the peak derived from Mo-Mo is greater than 1.0.

[0032] [6] The grease composition containing particles according to any one of [1] to [5] above, wherein the molybdenum disulfide particles have a 2H crystal structure and a 3R crystal structure of molybdenum disulfide,

[0033] In the spectrum obtained by powder X-ray diffraction (XRD) using Cu-Kα rays as the X-ray source of the molybdenum disulfide particles, the peaks near 39.5° and 49.5° are derived from the above 2H crystal structure, and the peaks near 32.5°, 39.5° and 49.5° are derived from the above 3R crystal structure,

[0034] The full width at half maximum of the peaks near 39.5° and 49.5° is 1° or more.

[0035] [7] The grease composition containing particles according to [6] above, wherein the crystallite size of the above 3R crystal structure calculated by extended Rietveld analysis based on the spectrum obtained by powder X-ray diffraction (XRD) using Cu-Kα rays as the X-ray source is 1 nm or more and 150 nm or less based on the analytical formula L = Kλ / (βcosθ).

[0036] (In the above formula, L is the size of the microcrystal [m], K is an apparatus constant that depends on the XRD optical system (incident side and detector side) and settings, λ is the wavelength of the X-ray to be measured [m], β is the half-value width [rad], and θ is the Bragg angle of the diffraction line [rad].)

[0037] [8] The grease composition containing particles according to [6] or [7] above, wherein the abundance ratio of the above-mentioned 2H crystal structure and the above-mentioned 3R crystal structure obtained by extended Rietveld analysis using the spectrogram obtained by the above-mentioned XRD is 10:90 to 90:10.

[0038] [9] The grease composition containing particles according to any one of [1] to [8] above, wherein, based on 100% by mass of the total mass of the grease composition containing particles, it contains 0.0001% by mass or more and 10% by mass or less of the above-mentioned molybdenum disulfide particles.

[0039] Effects of the Invention

[0040] According to the present invention, it is possible to provide a grease composition containing particles that can efficiently improve the friction and wear resistance characteristics with a small addition amount and exhibits excellent friction and wear resistance characteristics even when the clearance of the sliding part and the surface roughness of the friction surface are extremely small. Description of the Drawings

[0041] Figure 1 It is a schematic diagram showing an example of the apparatus used when producing molybdenum trioxide particles that are raw materials for molybdenum disulfide particles of the present embodiment.

[0042] Figure 2 It is a graph showing the results of the X-ray diffraction (XRD) spectrogram of the molybdenum sulfide powder obtained in Synthesis Example 1 together with the diffraction spectrograms of the 3R crystal structure of molybdenum disulfide (MoS2), the diffraction spectrogram of the 2H crystal structure of molybdenum disulfide (MoS2), and the diffraction spectrogram of molybdenum dioxide (MoO2) Figure 1 It is a graph showing.

[0043] Figure 3 It is an AFM image of the synthesized molybdenum disulfide particles.

[0044] Figure 4 It is for showing Figure 3 It is a cross-sectional curve graph of the molybdenum disulfide particles shown.

[0045] Figure 5 It is an extended X-ray absorption fine structure (EXAFS) spectrogram of the K absorption edge of molybdenum measured using the molybdenum sulfide powder obtained in Synthesis Example 1.

[0046] Figure 6A graph showing the X-ray diffraction (XRD) spectrum of the molybdenum disulfide particles of Synthesis Example 1 and the reference peaks of the 2H crystal structure and 3R crystal structure of molybdenum disulfide.

[0047] Figure 7 A graph showing the ratio of the 2H crystal structure and 3R crystal structure obtained by Rietveld analysis from the X-ray diffraction (XRD) spectrum of the molybdenum disulfide particles of Synthesis Example 1 and the calculation results of the crystallite size.

[0048] Figure 8 A graph showing the results of comparing the X-ray diffraction (XRD) spectrum of the molybdenum sulfide powder of Comparative Example 1 with the diffraction spectrum of the 2H crystal structure of molybdenum disulfide (MoS2) Figure 1 presented.

[0049] Figure 9 A graph showing the results obtained by performing a friction and wear test on the grease composition containing particles of Example 1 using a vibration friction and wear tester and observing the sliding surface with a microscope.

[0050] Figure 10 A graph showing the results obtained by performing a friction and wear test on the grease composition containing particles of Comparative Example 1 using a vibration friction and wear tester and observing the sliding surface with a microscope.

[0051] Figure 11 A graph showing the results obtained by performing a friction and wear test on the grease composition of Comparative Example 3 using a vibration friction and wear tester and observing the sliding surface with a microscope. Detailed Description of the Invention

[0052] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0053] <Grease Composition Containing Particles>

[0054] The grease composition containing particles of the present embodiment is a grease composition containing particles containing a base oil, a thickener, and molybdenum disulfide particles, and the median particle size D of the above molybdenum disulfide particles determined by dynamic light scattering method 50 is 10 nm or more and less than 450 nm.

[0055] Commercially available molybdenum disulfide particles are crushed products of ores and contain many particles with a particle size exceeding 0.45 μm. Therefore, for example, when 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 number of particles per unit weight of the added molybdenum disulfide particles is small. On the other hand, by making the above median particle size D as in the present embodiment 50When the particle size is less than 450 nm, the molybdenum disulfide particles can fully enter the gaps, the number of effective particles per unit weight of the added molybdenum disulfide particles increases, and the particles are not easily ground, abraded or sintered even when a high load is applied, thereby effectively improving the friction and wear characteristics.

[0056] Commercially available MoS2 is a crushed product of ore, and contains a large number of particles with a particle size of more than 0.45 μm, so the efficiency per unit weight for covering the area between the contact surfaces becomes low. On the other hand, by making the median particle size D 50 The molybdenum disulfide particles are less than 450nm, so that even when the surface roughness of the friction surface is extremely small, for example, hundreds of nanometers, the molybdenum disulfide particles can easily enter the tiny recesses of either or both of the friction surfaces of the two components. Usually, molybdenum disulfide infiltrates into the gap between the contact surfaces, and the layer of molybdenum disulfide is easily staggered in the direction perpendicular to the load, so the layered compound containing molybdenum disulfide exhibits good function as a lubricant. Therefore, when subjected to the shear force peculiar to the layered compound, sliding properties are generated between the crystal planes, and the friction coefficient between the contact surfaces is also reduced. Therefore, compared with the conventional grease composition containing particles, grinding, wear, etc. can be prevented, and as a result, it can contribute to the extension of the life of the friction surface.

[0057] (Molybdenum disulfide particles)

[0058] The median particle size D of the molybdenum disulfide particles in the particle-containing grease composition of the present embodiment determined by the dynamic light scattering method is 50 The median particle size D of the molybdenum disulfide particles is preferably 10 nm or more and less than 450 nm, and is particularly preferably 400 nm or less from the viewpoint of the above-mentioned effects. 50 The median particle size D of the molybdenum disulfide particles may be greater than 10 nm, greater than 20 nm, or greater than 40 nm. 50 For example, the measurement can be performed using a dynamic light scattering particle size distribution measuring apparatus (manufactured by Microtrac BEL, Nanotrac Wave II), a laser diffraction particle size distribution measuring apparatus (SALD-7000 manufactured by Shimadzu Corporation), or the like.

[0059] The molybdenum disulfide particles in the particle-containing grease composition of the present embodiment preferably include a 3R crystal structure of molybdenum disulfide. It is believed that the 3R crystal structure, which forms a rhombohedral structure by staggering the six-membered ring unit lattice of an arbitrary layer with the six-membered ring unit lattice of an adjacent layer, has a weak interaction (SS contact) between sulfur atoms between layers compared to the 2H crystal structure in which the six-membered ring unit lattice of an adjacent layer exists right below the 90 degrees of the six-membered ring unit lattice of an arbitrary layer and forms a regular hexagonal columnar hexagonal crystal, and the layers of the 3R structure are easily staggered by external force, thereby contributing to further improvement of the friction and wear resistance.

[0060] Commercially available molybdenum disulfide particles generally contain relatively many particles with a particle size exceeding 0.45 μm. Additionally, they are hexagonal solids and, as a crystal structure, basically have a 2H crystal structure. In contrast, the molybdenum disulfide particles produced via the "method for manufacturing molybdenum trioxide particles" and the "method for manufacturing molybdenum disulfide particles" described below contain both 2H and 3R crystal structures, and it is easy to adjust the median particle size D 50 to be 10 nm or more and less than 450 nm.

[0061] The fact that the molybdenum disulfide particles have both 2H and 3R crystal structures can be confirmed, for example, using extended Rietveld analysis software (manufactured by Malvern Panalytical, HighScore Plus) that can take into account the crystallite size. This Rietveld analysis software uses a crystal structure model containing the crystallite size to simulate the entire XRD diffraction pattern, and compares it with the XRD diffraction pattern obtained through experiments. In order to minimize the residual between the diffraction pattern obtained through experiments and the diffraction pattern obtained through calculations, the crystal structure factors such as the lattice constants and atomic coordinates of the crystal structure model, and the weight fraction (presence ratio), etc. are optimized by the least squares method, and each phase of the 2H and 3R crystal structures is identified and quantified with high precision. Thus, based on the crystal structure type and its ratio calculated by the usual Rietveld analysis, the crystallite size can also be calculated. In this patent, the analysis method using the above-mentioned HighScore Plus will hereinafter be referred to as "extended Rietveld analysis".

[0062] In the molybdenum disulfide particles of this embodiment, the crystallite size of the above-mentioned 3R crystal structure is preferably 1 nm or more and 150 nm or less. When the crystallite size of the above-mentioned 3R crystal structure is 1 nm or more and 150 nm or less, when used as a solid lubricant contained in a grease composition, the friction coefficient of the grease composition containing the particles can be reduced, and the friction and wear resistance characteristics can be improved. The crystallite size of the above-mentioned 3R crystal structure is preferably the value calculated by the above-mentioned extended Rietveld analysis based on the analysis formula described below. The friction coefficient can be measured, for example, from the Stribeck curve using a ball-on-disk tester or a four-ball tester, or can also be measured by an SRV tester accompanied by reciprocating vibration.

[0063] The crystallite size of the 3R crystal structure calculated by the extended Rietveld analysis based on the spectrum obtained by powder X-ray diffraction (XRD) using Cu-Kα rays as the X-ray source is preferably 1 nm or more and 150 nm or less, more preferably 1 nm or more and 50 nm or less, and still more preferably 1 nm or more and 15 nm or less, according to the analytical formula L = Kλ / (βcosθ). In the above formula, L is the size of the crystallite [m], K is the instrument constant depending on the XRD optical system (incident side and detector side) and the setup, λ is the wavelength of the measured X-ray [m], β is the full width at half maximum [rad], and θ is the Bragg angle of the diffracted ray [rad]. The constant K is a value optimized for the instrument used for the extended Rietveld analysis using the above HighScore Plus. In this embodiment, for example, K = 1.00 is adopted.

[0064] From the viewpoint of the above effects, the 3R crystal structure obtained by the above extended Rietveld analysis is preferably a crystal phase composed of crystallites with a crystallite size of 1 nm or more calculated according to the analytical formula described below. The crystallite size is more preferably 1 nm or more. In addition, from the viewpoint of the above effects, the 3R crystal structure obtained by the above extended Rietveld analysis is preferably a crystal phase composed of crystallites with a crystallite size of 50 nm or less obtained according to the analytical formula described below. The crystallite size is more preferably 15 nm or less. Furthermore, from the viewpoint of the above effects, the 3R crystal structure obtained by the above extended Rietveld analysis is preferably a crystal phase composed of crystallites with a crystallite size of 1 nm or more and 50 nm or less obtained according to the above analytical formula. The crystallite size is more preferably 1 nm or more and 15 nm or less.

[0065] In addition, in the molybdenum disulfide particles of this embodiment, the crystallite size of the above 2H crystal structure is preferably 1 nm or more. In addition, the crystallite size of the above 2H crystal structure is preferably 150 nm or less. Furthermore, the crystallite size of the above 2H crystal structure is preferably 1 nm or more and 150 nm or less. When the crystallite size of the above 2H crystal structure is 1 nm or more and 150 nm or less, when used as a solid lubricant contained in a grease composition, the friction coefficient of the grease composition containing the particles can be reduced, and the friction and wear resistance characteristics can be improved.

[0066] The crystallite size of the above-mentioned 2H crystal structure is preferably the value calculated by the extended Rietveld analysis. The above-mentioned 2H crystal structure obtained by the above-mentioned extended Rietveld analysis is preferably a crystal phase composed of crystallites with a crystallite size of 1 nm or more obtained according to the following analysis formula. In addition, the above-mentioned 2H crystal structure obtained by the above-mentioned extended Rietveld analysis is preferably a crystal phase composed of crystallites with a crystallite size of 150 nm or less obtained according to the above analysis formula. Furthermore, the above-mentioned 2H crystal structure obtained by the above-mentioned extended Rietveld analysis is preferably a crystal phase composed of crystallites with a crystallite size of 1 nm or more and 150 nm or less obtained according to the above analysis formula.

[0067] The crystallite size of the above-mentioned 2H crystal structure and the crystallite size of the above-mentioned 3R crystal structure can also be calculated using, for example, the full width at half maximum of the peaks in the XRD diffraction pattern.

[0068] The ratio of the above-mentioned 2H crystal structure to the above-mentioned 3R crystal structure in the crystal phase (2H:3R) obtained by the extended Rietveld analysis using the spectrum obtained from the above-mentioned XRD 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 using molybdenum disulfide particles as an inorganic lubricant.

[0069] From the viewpoint of the above effects, the ratio of the above-mentioned 2H crystal structure to the above-mentioned 3R crystal structure (2H:3R) obtained by the extended Rietveld analysis using the spectrum obtained from the above-mentioned XRD is more preferably 10:90 to 80:20, and further preferably 40:60 to 80:20.

[0070] Preferably, in the spectrum obtained by powder X-ray diffraction (XRD) using Cu-Kα rays as the X-ray source for the above-mentioned molybdenum disulfide particles, the peaks near 39.5° and near 49.5° originate from the 2H crystal structure, and the peaks near 32.5°, near 39.5°, and near 49.5° originate from the 3R crystal structure. The full width at half maximum of the peaks near 39.5° and near 49.5° is 1° or more. Furthermore, the above-mentioned molybdenum disulfide particles may contain crystal structures other than the 2H crystal structure and 3R crystal structure of molybdenum disulfide, such as the 1H crystal structure.

[0071] The fact that the above-mentioned molybdenum disulfide particles contain a metastable 3R crystal structure can be distinguished by the following method: in the spectrum obtained by powder X-ray diffraction (XRD) using Cu-Kα rays as the X-ray source, the peaks near 39.5° and near 49.5° are both composed of composite peaks of the 2H crystal structure and the 3R crystal structure.

[0072] Actually, using the spectrum obtained from the above powder X-ray diffraction (XRD), the presence ratio of the 2H crystal structure is determined by the peak near 39.5° and the broad peak near 49.5°. In addition, the presence ratio of the 3R crystal structure is determined by optimizing the difference between the peak near 39.5° and the broad peak near 49.5° with two peaks near 32.5° and two peaks near 39.5°. That is, the peaks near 39.5° and the peaks near 49.5° are both composite waves from the 2H crystal structure and the 3R crystal structure, and the presence ratios of the 2H crystal structure and the 3R crystal structure in the molybdenum disulfide particles can be calculated from these composite waves.

[0073] In addition, the molybdenum disulfide particles may contain an amorphous phase. The presence ratio of the amorphous phase of the molybdenum disulfide particles is expressed as 100 (%) - (crystallinity (%)), preferably 5% or more, more preferably 15% or more, and further preferably 20% or more. When the presence ratio of the amorphous phase of the molybdenum disulfide particles is 5% or more, the friction coefficient further decreases, and the friction characteristics can be improved.

[0074] In a two-dimensional image taken with a transmission electron microscope (TEM), the shape of the primary particles of the molybdenum disulfide particles described above can be granular, spherical, plate-like, needle-like, rope-like, ribbon-like, or flake-like, or can include these shapes in combination. The shape of the primary particles of the molybdenum disulfide particles described above is preferably disc-shaped, ribbon-like, or flake-like. Additionally, the shape of 50 primary particles of the molybdenum disulfide particles preferably has a size in the range of length (longitudinal) × width (transverse) = 50 to 1000 nm × 50 to 1000 nm on average, more preferably has a size in the range of 100 to 500 nm × 100 to 500 nm, and particularly preferably has a size in the range of 50 to 200 nm × 50 to 200 nm. Further, the thickness measured by an atomic force microscope (AFM) in the shape of the primary particles of the molybdenum disulfide particles described above preferably has a size in the range of 3 nm or more, more preferably has a size in the range of 5 nm or more. Additionally, the thickness measured by an atomic force microscope (AFM) in the shape of the primary particles of the molybdenum disulfide particles described above preferably has a size in the range of 100 nm or less, more preferably has a size in the range of 50 nm or less, and particularly preferably has a size in the range of 20 nm or less. Moreover, the thickness measured by an atomic force microscope (AFM) in the shape of the primary particles of the molybdenum disulfide particles described above can have a size in the range of 40 mn or less and can have a size in the range of 30 mn or less. By making the shape of the primary particles of the molybdenum disulfide particles disc-shaped, ribbon-like, or flake-like, the specific surface area of the molybdenum disulfide particles can be increased. Additionally, it is preferable that the shape of the primary particles of the molybdenum disulfide particles is disc-shaped, ribbon-like, or flake-like and the thickness is in the range of 3 to 100 nm. Here, being disc-shaped, ribbon-like, or flake-like means being in a thin layer shape. There is no clear distinction between disc-shaped, ribbon-like, and flake-like. For example, when the thickness is 10 nm or less, it can be regarded as flake-like; when the thickness is 10 nm or more and length ÷ width ≥ 2, it can be regarded as ribbon-like; when the thickness is 10 nm or more and length ÷ width < 2, it can be regarded as disc-shaped. The aspect ratio of the primary particles of the molybdenum disulfide particles, that is, the value of (length (size in the vertical and horizontal directions)) / (thickness (height)) is preferably 1.2 to 1200 on average for 50 particles, more preferably 2 to 800, further preferably 5 to 400, and particularly preferably 10 to 200. The shape of 50 primary particles of molybdenum disulfide can be measured for shape, length, width, and thickness under observation with an atomic force microscope (AFM), and the aspect ratio can also be calculated from the measurement results.

[0075] It is considered that the shape of the primary particles of the molybdenum disulfide particles described above is not a simple sphere but a disc-shaped, ribbon-like, or flake-like shape with a large aspect ratio, so that it can more efficiently intervene between the grease composition containing the particles and the friction surface of the sliding part, and it is possible to expect to reduce the contact probability (or contact area × time) between the friction surfaces and suppress surface wear.

[0076] The specific surface area of the molybdenum disulfide particles measured by the BET method is preferably 10 m 2 / g or more, more preferably 30m 2 / g or more, particularly preferably 40m 2 The specific surface area of the molybdenum disulfide particles measured by the BET method can be 300 m 2 / g or less, can be 200m 2 / g or less.

[0077] In the primary particles of the molybdenum disulfide particles, the layers constituting the primary particles are close to each other due to weak interactions, and external forces such as friction easily cause the layers to be offset from each other. Therefore, when the primary particles of the molybdenum disulfide particles are interposed between the friction surfaces of the sliding part and frictional force is generated, the layers constituting the primary particles are offset due to the frictional force, which can reduce the apparent friction coefficient and prevent contact between the friction surfaces.

[0078] The specific surface area of the molybdenum disulfide particles measured by the BET method is 10 m 2 When the primary particles are present between the friction surfaces of the sliding portion, the contact area with the friction surfaces can be increased and the contact area between the friction surfaces of the sliding portion can be further reduced, thereby exhibiting excellent friction and wear resistance.

[0079] The specific surface area measured by the BET method is as large as 10m 2 The particle-containing grease composition of the present embodiment having molybdenum disulfide particles in an amount of 100 g or more can increase the contact area between the molybdenum disulfide particles and the friction surface, and thus can exhibit excellent anti-friction and wear characteristics.

[0080] The bulk density of the molybdenum disulfide particles is preferably 0.1 g / cm 3 More preferably 0.2 g / cm 3 More preferably 0.4 g / cm 3 In addition, the bulk density of the molybdenum disulfide particles is preferably 1.0 g / cm 3 Below, more preferably 0.9 g / cm 3 Below, more preferably 0.7 g / cm 3 Furthermore, the bulk density of the molybdenum disulfide particles is preferably 0.1 g / cm 3 Above and 1.0g / cm 3 Below, more preferably 0.2g / cm 3 Above 0.9g / cm 3 The volume density of molybdenum disulfide particles is 0.1 g / cm 3 Above and 1.0g / cm 3When the following conditions are met, compared with the case where molybdenum disulfide particles with a relatively high bulk density are contained in the same content as the grease composition, the molybdenum disulfide particles are more likely to be exposed on the surface of the grease composition containing the particles, and the coefficient of friction of the grease composition containing the particles can be further reduced. In addition, compared with the case where molybdenum disulfide particles with a relatively high bulk density as described above are contained, the desired anti-friction and anti-wear characteristics can be obtained with a smaller content, and the molded product using the grease composition containing the particles can be made lighter in weight.

[0081] In the radial distribution function obtained from the extended X-ray absorption fine structure (EXAFS) spectrum at the K absorption edge of molybdenum in the above molybdenum disulfide particles, the ratio (I / II) of the peak intensity I derived from Mo-S to the peak intensity II derived from Mo-Mo is preferably greater than 1.0, more preferably 1.1 or more, and particularly preferably 1.2 or more.

[0082] Regardless of whether the crystal structure of molybdenum disulfide is the 2H crystal structure or the 3R crystal structure, the distance between Mo-S is basically the same due to covalent bonds. Therefore, in the extended X-ray absorption fine structure (EXAFS) spectrum at the K absorption edge of molybdenum, the peak intensity derived from Mo-S is the same. On the other hand, the 2H crystal structure of molybdenum disulfide is hexagonal, so the same hexagon is located directly below the hexagon of the Mo atom at 90°, so the distance between Mo-Mo becomes closer and the peak intensity II derived from Mo-Mo becomes stronger.

[0083] Conversely, the 3R crystal structure of molybdenum disulfide is rhombohedral, so the hexagon is not located directly below the hexagon at 90°, but is offset by half, so the distance between Mo-Mo becomes farther and the peak intensity II derived from Mo-Mo becomes weaker.

[0084] In the pure 2H crystal structure of molybdenum disulfide, the above ratio (I / II) becomes smaller, but as the 3R crystal structure is included, the above ratio (I / II) becomes larger.

[0085] In the 3R crystal structure, the hexagons of each Mo atom in the three layers are offset from each other by only half of the hexagon. Therefore, compared with the 2H crystal structure in which the hexagons of the Mo atoms in the two layers are regularly arranged perpendicular to each other, the interaction between the layers is small, and the anti-friction and anti-wear characteristics can be improved by the sliding between crystal planes based on shear force.

[0086] It should be noted that for the 2H crystal structure, it can also be expected that if the crystallite size is small, sliding of the contact surface is likely to occur.

[0087] It is considered that the presence of molybdenum trioxide will have an adverse effect on the anti-friction and anti-wear characteristics. Therefore, the conversion rate R of the above molybdenum trioxide particles to MoS2 CPreferably 70% or more, more preferably 80% or more, particularly preferably 90% or more.

[0088] For the above molybdenum disulfide particles, by making the conversion rate R to MoS2 C show a number close to 100%, although the lubricating performance is exerted by the heating generated by friction, compared with other molybdenum disulfide raw materials and their precursors that may by-produce or contain molybdenum trioxide, the friction and wear resistance characteristics can be made excellent.

[0089] The conversion rate R of molybdenum trioxide particles to MoS2 C can be obtained from the spectral data obtained by X-ray diffraction (XRD) measurement of the molybdenum disulfide particles and calculated according to the RIR (reference intensity ratio) method. Using the RIR value K of molybdenum disulfide (MoS2) A and the integrated intensity I of the peak near 2θ = 14.4° ± 0.5° belonging to the (002) plane or (003) plane of molybdenum disulfide (MoS2) A , and the RIR values K of each molybdenum oxide (MoO3 as the raw material and Mo9O as the reaction intermediate 25 , Mo4O 11 , MoO2, etc.) B and the integrated intensity I of the strongest ray peak of each molybdenum oxide (MoO3 as the raw material and Mo9O as the reaction intermediate 25 , Mo4O 11 , MoO2, etc.), the conversion rate R to MoS2 can be calculated from the following formula (1) B . C .

[0090] RC(%) = (I A / K A ) / (Σ(I B / K B )) × 100 ··· (1)

[0091] Here, the RIR values can be the values described in the Inorganic Crystal Structure Database (ICSD) (manufactured by the Chemical Information Association, Incorporated Administrative Agency) respectively, and the comprehensive powder X-ray analysis software (PDXL2) (manufactured by Rigaku Corporation) can be used in the analysis.

[0092] It should be noted that the grease composition containing particles of the present embodiment preferably contains molybdenum disulfide particles (MoS2), but is not limited thereto, and may also contain molybdenum sulfide particles represented by MoS x (X = 1 to 3), and may contain one or more of the molybdenum sulfide particles represented by MoS x (X = 1 to 3).

[0093] The grease composition containing particles of the present embodiment preferably contains 0.0001% by mass or more, more preferably 0.01% by mass or more, and still more preferably 1% by mass or more of the molybdenum disulfide particles with respect to 100% by mass of the total mass of the grease composition containing particles. Further, the grease composition containing particles preferably contains 50% by mass or less, more preferably 20% by mass or less, and still more preferably 10% by mass or less of the molybdenum disulfide particles with respect to 100% by mass of the total mass of the grease composition containing particles. Furthermore, the grease composition containing particles preferably contains 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, and still more preferably 1% by mass or more and 10% by mass or less of the molybdenum disulfide particles with respect to 100% by mass of the total mass of the grease composition containing particles.

[0094] (Base oil)

[0095] There is no particular limitation on the base oil used in the grease composition containing particles of the present embodiment, and known base oils can be used. Examples include one or more selected from naphthenic and / or paraffinic mineral oils (spindle oils, turbine oils, engine oils, bright oils, etc.), synthetic oils (diesters, polyol esters, silicone oils, PFPE (perfluoropolyether), PAO (polyalphaolefin), PAG (polyalkylene glycol), alkyl diphenyl ethers, polyphenyl ethers, etc.).

[0096] The grease composition containing particles may contain 50% by mass or more, more preferably 70% by mass or more, preferably 99% by mass or less, and still more preferably 95% by mass or less of the base oil with respect to 100% by mass of the total mass of the grease composition containing particles. Further, with respect to 100% by mass of the total mass of the grease composition containing particles, it may contain 50% by mass or more and 99% by mass or less, preferably 70% by mass or more and 95% by mass or less of the base oil.

[0097] (Thickener)

[0098] There is no particular limitation on the thickener used in the grease composition containing particles of the present embodiment, and soap-based or non-soap-based thickeners can be used.

[0099] Examples of the soap-based thickeners include one or more selected from Ca soaps (tallow-based or castor oil-based), Li complex soaps, Ba complex soaps, Al soaps, Ca complexes, Li complexes, Al complexes, etc. Examples of the non-soap-based thickeners include one or more selected from urea compounds (aromatic diureas, aliphatic or alicyclic diureas, triureas, tetraureas, sodium terephthalate, PTFE, bentonite, silica gel, carbon black, etc.).

[0100] The above grease composition containing particles may contain 2% by mass or more, and may contain 5% by mass or more of the above thickener based on 100% by mass of the total mass of the above grease composition containing particles. Further, the above grease composition containing particles may contain 60% by mass or less, and may contain 30% by mass or less of the above thickener based on 100% by mass of the total mass of the above grease composition containing particles. Furthermore, the above grease composition containing particles may contain the above thickener in an amount of 2% by mass or more and 60% by mass or less, and may contain the above thickener in an amount of 5% by mass or more and 30% by mass or less based on 100% by mass of the total mass of the above grease composition containing particles.

[0101] (Anti-wear additive)

[0102] From the viewpoint of reducing frictional wear between friction surfaces and preventing sintering, the grease composition containing particles of the present embodiment may further contain an anti-wear additive. Examples of the anti-wear additive include one or more selected from lead naphthenate, chlorinated paraffin, SP series, various metal compounds, phosphorus-based and sulfur-based compounds such as MoDTP and ZnDTP.

[0103] The above grease composition containing particles may contain 0.01% by mass or more, may contain 0.1% by mass or more, and may contain 1% by mass or more of the above anti-wear additive based on 100% by mass of the total mass of the above grease composition containing particles. The above grease composition containing particles may contain 50% by mass or less, may contain 20% by mass or less, and may contain 10% by mass or less of the above anti-wear additive based on 100% by mass of the total mass of the above grease composition containing particles. Furthermore, the above grease composition containing particles may contain the above anti-wear additive in an amount of 0.01% by mass or more and 50% by mass or less, may contain the above anti-wear additive in an amount of 0.1% by mass or more and 20% by mass or less, and may contain the above anti-wear additive in an amount of 1% by mass or more and 10% by mass or less based on 100% by mass of the total mass of the above grease composition containing particles.

[0104] (Other additives)

[0105] The grease composition containing particles of the present embodiment may contain other additives other than the above according to the use and specifications. As other additives, antioxidants (sulfur, phosphorus, amine, phenolic), rust inhibitors (carboxylic acids, metal sulfonates, etc.), corrosion inhibitors (benzotriazole, etc.), oiliness agents (fatty acids, fatty acid esters, etc.), anti-wear agents (phosphate esters, phosphite esters, thiophosphates, amine salts of phosphate esters, zinc dialkyldithiocarbamate, etc.), extreme pressure agents (sulfurized oils and fats, sulfurized esters, polysulfides, chlorine compounds, lead naphthenate, alkyl thiophosphoric acid amines, chloroalkyl xanthates, etc.), solid lubricants (graphite, MoS2, soft metals, etc.), viscosity index improvers (alkyl polymethacrylates, etc.), detergent-dispersants (metal sulfonates, succinimides, etc.), etc. may be used alone or in combination of two or more thereof.

[0106] The above grease composition containing particles may contain 0.01% by mass or more, may contain 0.1% by mass or more, and may contain 0.2% by mass or more of the above additives based on 100% by mass of the total mass of the grease composition containing particles. In addition, the above grease composition containing particles may contain 50% by mass or less, may contain 10% by mass or less, and may contain 5% by mass or less of the above additives based on 100% by mass of the total mass of the grease composition containing particles. Further, the above grease composition containing particles may contain 0.01% by mass or more and 50% by mass or less, may contain 0.1% by mass or more and 10% by mass or less, and may contain 0.2% by mass or more and 5% by mass or less of the above additives based on 100% by mass of the total mass of the grease composition containing particles.

[0107] <Manufacturing method of grease composition containing particles>

[0108] Regarding the manufacturing method of the grease composition containing particles of the present embodiment, it can be manufactured by uniformly mixing a base oil, a thickener, and molybdenum disulfide particles obtained by the manufacturing method of molybdenum disulfide particles described below at the above blending ratio. In addition, an extreme pressure agent and other additives may be further added to the raw materials as needed and mixed uniformly. The molybdenum disulfide particles can be added together with the raw materials containing the base oil and the thickener as described above. From the viewpoint of uniformly dispersing the molybdenum disulfide particles, the raw materials containing the base oil and the thickener may be mixed in advance to manufacture a grease composition, and then the molybdenum disulfide particles are added to the semi-solid grease composition. In this case, for example, the molybdenum disulfide particles can be uniformly dispersed in the grease composition by kneading using a Hoover automatic flat grinder, a rotation-revolution kneader, a three-roll mill, a Charlotte colloid mill, a Manton-Gaulin homogenizer, etc.

[0109] The grease composition containing particles according to this embodiment is in a semi-solid (gel-like) state at normal temperature in the present invention. When applied to the sliding part of a mechanical element, it turns into a liquid (lubricating composition) state due to frictional heat during sliding and penetrates into the sliding part, forming a thin film on the surface (friction surface) of the solid constituting the sliding part, such as metal and resin, to lubricate the sliding part. In addition, at this time, the molybdenum disulfide particles contained in the grease composition containing particles or the above liquid are supplied to the minute recesses of the sliding part and the friction surface, thereby reducing the frictional wear of the sliding part. When the sliding stops and the temperature drops, the liquid lubricating composition returns to the semi-solid grease composition containing particles again.

[0110] The grease composition containing particles according to this embodiment has excellent friction and wear resistance characteristics such as low wear, high seizure load, and high welding load, especially by containing the above molybdenum disulfide particles, and can maintain excellent friction and wear resistance characteristics for a long time. In addition, the grease composition containing particles according to this embodiment can reconstruct the gel (semi-solid) structure even when repeatedly subjected to the temperature rise and cooling stress associated with use and non-use, so that pollution caused by oil leakage can be avoided.

[0111] (Manufacturing method of molybdenum disulfide particles in the grease composition containing particles)

[0112] The molybdenum disulfide particles in the grease composition containing particles according to this embodiment can be manufactured, for example, by heating molybdenum trioxide particles at a temperature of 200 to 1150 °C in the presence of a sulfur source.

[0113] 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 means that when the molybdenum trioxide particles are photographed with a scanning electron microscope (SEM) or a transmission electron microscope (TEM), and the major axis (Feret diameter of the longest part observed) and the minor axis (short Feret diameter in the direction perpendicular to the Feret diameter of the longest part) of the particles (i.e., primary particles) constituting the aggregate on the two-dimensional image are measured and their average value is taken as the primary particle size, the average value of the primary particle sizes of 50 randomly selected primary particles.

[0114] In the manufacturing method of the molybdenum sulfide powder according to this embodiment, the content ratio of MoO3 measured by fluorescent X-ray (XRF) of the above molybdenum trioxide particles is preferably 99.5% or more, whereby the conversion rate R to MoS2 can be increased C , and molybdenum disulfide with high purity, free from disulfide derived from impurities and having good storage stability can be obtained.

[0115] The average particle diameter of the primary particles of the molybdenum trioxide particles described above can be 5 nm or more and 2000 nm or less. Additionally, the average particle diameter of the primary particles of the molybdenum trioxide particles can be set to 1000 nm or less, and from the perspective of reactivity with sulfur, it is more preferably 600 nm or less, further preferably 400 nm or less, and particularly preferably 200 nm or less. The average particle diameter of the primary particles of the molybdenum trioxide particles can be 2 nm or more, can be 5 nm or more, and can be 10 nm or more.

[0116] Examples of the sulfur source include sulfur, hydrogen sulfide, etc. They can be used alone or in combination of two.

[0117] The specific surface area of the above molybdenum trioxide particles measured by the BET method is preferably 10 m 2 / g or more and 100 m 2 / g or less.

[0118] In the above molybdenum trioxide particles, from the perspective of good reactivity with sulfur, the specific surface area is preferably 10 m 2 / g or more, preferably 20 m 2 / g or more, preferably 30 m 2 / g or more. In the above molybdenum trioxide particles, from the perspective of easier manufacturing, it is preferably 100 m 2 / g or less, can be 90 m 2 / g or less, and can be 80 m 2 / g or less.

[0119] The molybdenum trioxide particles used in the production of molybdenum disulfide particles preferably contain an aggregate of primary particles having a β crystal structure containing molybdenum trioxide. Compared with the existing molybdenum trioxide particles composed only of α crystals as the crystal structure, the molybdenum trioxide particles have good reactivity with sulfur. Since they contain the β crystal structure of molybdenum trioxide, in the reaction with the sulfur source, the conversion rate R to MoS2 can be increased. C .

[0120] The β crystal structure of molybdenum trioxide can be confirmed by the presence of a peak attributed to the (011) plane of the β crystal of MoO3 (2θ: near 23.01°, No. 86426 (Inorganic Crystal Structure Database (ICSD))) in the spectrum obtained by powder X-ray diffraction (XRD) using Cu-Kα rays as the X-ray source. The α crystal structure of molybdenum trioxide can be confirmed by the presence of a peak of the (021) plane (2θ: near 27.32° - No. 166363 (Inorganic Crystal Structure Database (ICSD))) of the α crystal of MoO3.

[0121] In the method for manufacturing the molybdenum disulfide particles described above, in the X-ray diffraction (XRD) pattern of the molybdenum trioxide particles obtained using Cu-Kα rays as the X-ray source, the peak intensity of the (011) plane of the β crystal attributed to MoO3 (2θ: near 23.01°, No. 86426 (Inorganic Crystal Structure Database (ICSD))) relative to the peak intensity of the (021) plane of the α crystal attributed to MoO3 (2θ: near 27.32°, No. 166363 (Inorganic Crystal Structure Database (ICSD))), the ratio (β(011) / α(021)) is preferably 0.1 or more.

[0122] For the peak intensity of the (011) plane of the β crystal attributed to MoO3 and the peak intensity of the (021) plane of the α crystal attributed to MoO3, the maximum intensity of the peak is read respectively, and the above ratio (β(011) / α(021)) is obtained.

[0123] In the above molybdenum trioxide particles, the above 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.

[0124] The β crystal structure of molybdenum trioxide can also be confirmed by the presence of peaks at wavenumbers 773 cm -1 , 848 cm -1 and 905 cm -1 in the Raman spectrum obtained by Raman spectroscopy measurement. The α crystal structure of molybdenum trioxide can also be confirmed by the presence of peaks at wavenumbers 663 cm -1 , 816 cm -1 and 991 cm -1 in the Raman spectrum.

[0125] For the above molybdenum trioxide particles, it is preferable that the ratio (I / II) of the peak intensity I derived from Mo-O to the peak intensity II derived from Mo-Mo in the radial distribution function obtained from the extended X-ray absorption fine structure (EXAFS) spectrum at the K absorption edge of molybdenum is greater than 1.1.

[0126] For the intensity I of the peak derived from Mo-O and the intensity II of the peak derived from Mo-Mo, the maximum intensity of the peak is read respectively, and the above ratio (I / II) is obtained. It is considered that the above ratio (I / II) is a criterion for obtaining the β crystal structure of MoO3 in the molybdenum trioxide particles, and the larger the above ratio (I / II), the more excellent the reactivity with sulfur.

[0127] In the above molybdenum trioxide particles, the above ratio (I / II) is preferably 1.1 to 5.0, can be 1.2 to 4.0, and can be 1.2 to 3.0.

[0128] The method for manufacturing molybdenum disulfide for use in the grease composition of the present embodiment may include the following steps: heating molybdenum trioxide particles containing an aggregate of primary particles having a β crystal structure containing molybdenum trioxide at a temperature of 100 to 800 °C in the absence of a sulfur source, and then heating in the presence of a sulfur source at a temperature of 200 to 1000 °C.

[0129] The heating time in the presence of the sulfur source may be any time as long as the sulfidation reaction proceeds sufficiently, and may be 1 h to 20 h, may be 2 h to 15 h, may be 3 h to 10 h.

[0130] In the method for manufacturing the molybdenum disulfide particles, the input ratio of the S amount of the sulfur source to the MoO3 amount of the molybdenum trioxide particles is preferably a condition under which the sulfidation reaction proceeds sufficiently. Relative to 100 mol% of the MoO3 amount of the molybdenum trioxide particles, the S amount of the sulfur source is preferably 450 mol% or more, preferably 600 mol% or more, preferably 700 mol% or more. Relative to 100 mol% of the MoO3 amount of the molybdenum trioxide particles, the S amount of the sulfur source may be 3000 mol% or less, may be 2000 mol% or less, may be 1500 mol% or less.

[0131] In the method for manufacturing the molybdenum disulfide particles, the heating temperature in the presence of the sulfur source may be any temperature as long as the sulfidation reaction proceeds sufficiently, preferably 320 °C or higher, more preferably 340 °C or higher, particularly preferably 360 °C or higher. It may be 320 to 1000 °C, may be 340 to 1000 °C, may be 360 to 500 °C.

[0132] In the method for manufacturing the molybdenum disulfide particles, as a post-treatment, the obtained molybdenum disulfide particles may be heated as needed after cooling. In this heat treatment, it is preferable to calcine the molybdenum disulfide particles, for example, in an inert atmosphere. By heating and calcining the obtained molybdenum disulfide particles, the crystallization of the amorphous part is promoted and the crystallinity is improved. In addition, as the crystallinity increases, the 2H crystal structure and the 3R crystal structure are newly formed respectively, and the ratio of the existence of the 2H crystal structure and the 3R crystal structure changes. If reheating is performed as a post-treatment as described above, the crystallinity of the molybdenum disulfide particles becomes high. Although the peelability due to the lubrication of each layer is reduced to a certain extent, the ratio of the existence of the 3R crystal structure that contributes to improving the friction characteristics increases, so the friction characteristics can be improved compared with the case of only the 2H crystal structure. In addition, by changing the temperature when heating the obtained molybdenum disulfide particles, the ratio of the existence of the 2H crystal structure and the 3R crystal structure can be adjusted.

[0133] Through the method for manufacturing the molybdenum disulfide particles described above, the molybdenum disulfide particles contained in the grease composition containing particles of the present embodiment can be manufactured.

[0134] (Method for manufacturing molybdenum trioxide particles)

[0135] The above-mentioned molybdenum trioxide particles can be manufactured as follows: vaporize the molybdenum trioxide precursor compound to form molybdenum trioxide vapor, and cool the above-mentioned molybdenum trioxide vapor, whereby they can be manufactured.

[0136] The method for manufacturing the above-mentioned molybdenum trioxide particles includes the following steps: roasting a raw material mixture containing a molybdenum trioxide precursor compound and a metal compound other than the above-mentioned molybdenum trioxide precursor compound to vaporize the above-mentioned molybdenum trioxide precursor compound to form molybdenum trioxide vapor. The ratio of the above-mentioned metal compound in terms of oxide conversion relative to 100% by mass of the above-mentioned raw material mixture is preferably 70% by mass or less.

[0137] The method for manufacturing the above-mentioned molybdenum trioxide particles can be suitably implemented using Figure 1 the manufacturing apparatus 1 shown.

[0138] Figure 1 It is a schematic diagram of an example of the apparatus used for manufacturing the above-mentioned molybdenum trioxide particles which are the raw materials for the molybdenum disulfide particles of the present embodiment.

[0139] As Figure 1 shown, the manufacturing apparatus 1 has: a roasting furnace 2 for roasting the molybdenum trioxide precursor compound or the above-mentioned raw material mixture to vaporize the above-mentioned molybdenum trioxide precursor compound; a cross-shaped cooling pipe 3 connected to the above-mentioned roasting furnace 2 for pulverizing the molybdenum trioxide vapor vaporized by the above-mentioned roasting; and a recovery machine 4 as a recovery mechanism for recovering the molybdenum trioxide particles pulverized in the above-mentioned cooling pipe 3. At this time, the above-mentioned roasting furnace 2 and the cooling pipe 3 are connected via an exhaust port 5. In addition, an opening degree adjustment damper 6 is arranged at the left end of the above-mentioned cooling pipe 3 at an external gas suction port (not shown), and an observation window 7 is arranged at the upper end. A ventilation device 8 as a first air supply mechanism is connected to the recovery machine 4. The ventilation device 8 performs ventilation, thereby sucking the recovery machine 4 and the cooling pipe 3, and external gas is supplied to the cooling pipe 3 from the opening degree adjustment damper 6 provided in the cooling pipe 3. That is, by the ventilation device 8 exerting a suction function, air supply is passively generated in the cooling pipe 3. That is, the ventilation device 8 exerts a suction function, thereby generating air supply in the cooling pipe 3 without a power source. It should be noted that the manufacturing apparatus 1 can have an external cooling device 9, whereby the cooling conditions of the molybdenum trioxide vapor generated from the roasting furnace 2 can be arbitrarily controlled.

[0140] Air is drawn in from the external gas intake port by adjusting the damper 6, and the molybdenum trioxide vapor vaporized in the roasting furnace 2 is cooled in an air atmosphere to form molybdenum trioxide particles. Thus, the above ratio (I / II) can be set to be greater than 1.1, and it is easy to obtain the β crystal structure of MoO3 in the molybdenum trioxide particles. When the molybdenum trioxide vapor is cooled using liquid nitrogen or the like, the cooling of the molybdenum trioxide vapor in a nitrogen atmosphere with a low oxygen concentration easily increases the oxygen defect density and reduces the above ratio (I / II).

[0141] As the above molybdenum trioxide precursor compound, as long as it is a substance that forms molybdenum trioxide vapor by roasting, there is no particular limitation. Examples 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 to 3)), sodium molybdate (Na2Mo n O 3n+1 (n = 1 to 3)), titanium molybdate, iron molybdate, potassium molybdate (K2Mo n O 3n+1 (n = 1 to 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 trioxide precursor compounds can be used alone or in combination of two or more. The form of the molybdenum trioxide precursor compound is not particularly limited. For example, it can be in the form of powder such as molybdenum trioxide, and powder form with good processability and energy efficiency is preferred.

[0142] As the molybdenum trioxide precursor compound, commercially available α-crystal molybdenum trioxide is particularly preferably used. In addition, when ammonium molybdate is used as the molybdenum trioxide precursor compound, it is converted to thermodynamically stable molybdenum trioxide by roasting, and the vaporized molybdenum trioxide precursor compound is the above molybdenum trioxide.

[0143] It is also possible to form molybdenum trioxide vapor by roasting a raw material mixture containing a molybdenum trioxide precursor compound and a metal compound other than the above molybdenum trioxide precursor compound. Among these, from the viewpoint of easily controlling the purity, average particle size of primary particles, and crystal structure of the obtained molybdenum trioxide particles, the molybdenum trioxide precursor compound preferably contains molybdenum trioxide.

[0144] The calcination temperature varies depending on the molybdenum trioxide precursor compound, metal compound, and desired molybdenum trioxide particles used, etc., and is generally preferably set to a temperature at which the intermediate can decompose. For example, when using a molybdenum compound as the molybdenum trioxide precursor compound and an aluminum compound as the metal compound, aluminum molybdate can be formed as an intermediate. Therefore, the calcination temperature is preferably 500 to 1500 °C, more preferably 600 to 1550 °C, and further preferably 700 to 1600 °C.

[0145] There is no particular limitation on the calcination time either. For example, it can be set to 1 minute to 30 hours, can be set to 10 minutes to 25 hours, or can be set to 100 minutes to 20 hours.

[0146] The heating rate also varies depending on the molybdenum trioxide precursor compound, the above-mentioned metal compound, and the characteristics of the desired molybdenum trioxide particles, etc. From the viewpoint of manufacturing efficiency, it is preferably 0.1 °C / minute to 100 °C / minute, more preferably 1 °C / minute to 50 °C / minute, and further preferably 2 °C / minute to 10 °C / minute.

[0147] Then, the above-mentioned molybdenum trioxide vapor is cooled to form a powder.

[0148] The cooling of the molybdenum trioxide vapor is carried out by keeping the cooling pipe at a low temperature. At this time, as the cooling mechanism, cooling based on the blowing of gas into the cooling pipe as described above, cooling using the cooling mechanism of the cooling pipe, cooling using an external cooling device, etc. can be cited.

[0149] The cooling of the molybdenum trioxide vapor is preferably carried out in an air atmosphere. By cooling the molybdenum trioxide vapor in an air atmosphere to form molybdenum trioxide particles, the above ratio (I / II) can be set to be greater than 1.1, and it is easy to obtain the β crystal structure of MoO3 in the molybdenum trioxide particles.

[0150] The cooling temperature (the temperature of the cooling pipe) is not particularly limited, and is preferably -100 to 600 °C, more preferably -50 to 400 °C.

[0151] There is no particular limitation on the cooling rate of the molybdenum trioxide vapor, and it is preferably 100 °C / s or more and 100000 °C / s or less, more preferably 1000 °C / s or more and 50000 °C / s or less. It should be noted that there is a tendency that the faster the cooling rate of the molybdenum trioxide vapor, the smaller the particle size and the larger the specific surface area of the obtained molybdenum trioxide particles.

[0152] When the cooling mechanism is cooling based on the blowing of gas into the cooling pipe, the temperature of the blowing gas is preferably -100 to 300 °C, more preferably -50 to 100 °C.

[0153] The powder obtained by cooling molybdenum trioxide vapor is transported to a recovery machine for recovery.

[0154] In the method for manufacturing the molybdenum trioxide particles described above, the powder obtained by cooling the molybdenum trioxide vapor can also be calcined again at a temperature of 100 to 320°C.

[0155] That is, the molybdenum trioxide particles obtained by the method for manufacturing the molybdenum trioxide particles described above can be calcined again at a temperature of 100 to 320°C. The calcination temperature for the second calcination can be 120 to 280°C, and can be 140 to 240°C. The calcination time for the second calcination can be set to, for example, 1 minute to 4 hours, can be set to 10 minutes to 5 hours, and can be set to 100 minutes to 6 hours. Among them, by performing the second calcination, a part of the β crystal structure of molybdenum trioxide disappears. If it is calcined at a temperature of 350°C or higher for 4 hours, the β crystal structure in the molybdenum trioxide particles disappears, and the above ratio (β(011) / α(021)) becomes 0, and the reactivity with sulfur is impaired.

[0156] By the method for manufacturing the molybdenum trioxide particles described above, molybdenum trioxide particles suitable for manufacturing the molybdenum disulfide particles contained in the grease composition containing particles of the present embodiment can be manufactured.

[0157] Examples

[0158] Examples are shown below to further illustrate the present invention in detail, but the present invention is not limited by the following examples. In addition, in the following examples, unless otherwise specified, "parts by mass" means "mass %".

[0159] [Method for measuring the average particle size of the primary particles of molybdenum trioxide particles]

[0160] The molybdenum trioxide particles constituting the molybdenum trioxide powder are photographed with a transmission electron microscope (TEM). For the particles (i.e., primary particles) that are the smallest units constituting the aggregates on the two-dimensional image, the major axis (Feret diameter of the longest part observed) and the minor axis (short Feret diameter in the direction perpendicular to the Feret diameter of the longest part) are measured, and their average value is used as the primary particle size. The same operation is performed on 50 randomly selected primary particles, and the average particle size of the primary particles is calculated from the average value of the primary particle sizes of the primary particles.

[0161] [Determination of the purity of molybdenum trioxide: XRF analysis]

[0162] Using a fluorescent X-ray analyzer Primus IV (manufactured by Rigaku Co., Ltd.), approximately 70 mg of the recovered molybdenum trioxide particle sample was taken onto a filter paper, covered with a PP film, and subjected to compositional analysis. The amount of molybdenum obtained from the XRF analysis results was determined by converting it to molybdenum trioxide in terms of mass percentage relative to 100% by mass of the molybdenum trioxide particles.

[0163] [Specific surface area measurement: BET method]

[0164] For a sample of molybdenum trioxide particles or molybdenum sulfide powder particles, measurement was carried out using a specific surface area meter (MicrotracBEL Corporation, BELSORP-mini). The surface area of the measured average 1 g sample was calculated from the nitrogen adsorption amount based on the BET method and used as the specific surface area (m 2 / g).

[0165] [Identification and analysis of crystal structure (1)]

[0166] A sample of molybdenum disulfide particles was filled into a specimen holder for measurement with a depth of 0.5 mm and set in a wide-angle X-ray diffractometer (XRD) (Ultima IV manufactured by Rigaku Co., Ltd., using a parallel beam method on the incident side in the optical system + scintillation counter detector, rotating stage). Measurement was carried out under the conditions of Cu / Kα ray; 40 kV / 40 mA, scanning speed 2° / min, step size 0.02°, and scanning range of 5° or more and 70° or less ( Figure 2 , Figure 4 and Figure 6 ). The XRD spectrum was plotted and compared with the reference peaks using XRD spectrum analysis software (PDXL Version 2) manufactured by Rigaku Co., Ltd.

[0167] [Identification and analysis of crystal structure (2)]

[0168] A sample of molybdenum disulfide particles was filled into a SUS specimen holder for measurement in such a way that the thickness became 2.4 mm and the inner diameter became 27 mm, and the measurement surface was made smooth. It was set in a multi-purpose X-ray diffractometer (XRD) (Empyrean 3 manufactured by Malvern Panalytical Ltd.). Measurement was carried out under the conditions of Cu / Kα ray, 45 kV / 40 mA, a monochromator on the incident side, using a semiconductor high-speed detector (1D mode), focusing method, using a rotating stage, measurement time 8 minutes (Examples 1 and 2), step size 0.066 degrees (Examples 1 and 2), and scanning range of 5° or more and 100° or less to obtain a diffraction spectrum ( Figure 5 ).

[0169] The Rietveld analysis including the evaluation of the microcrystalline size was carried out using software (manufactured by Malvern Panalytical, HighScore Plus).

[0170] The crystallinity of the molybdenum disulfide particles was calculated as follows: (1) The background A from the instrument and the boundary line of the obtained diffraction pattern were determined in the range of 10 to 95°, and the background A was subtracted from the obtained diffraction pattern; (2) In the range of 10 to 95°, a broad peak B called the amorphous halo originating from the amorphous phase was determined, and the background B was further subtracted from the obtained diffraction pattern; (3) The sum of the peak intensities from the crystal, which is higher than the background A and the amorphous halo B, was divided by the sum of the intensities in the XRD pattern except for the background A. The maximum value of the crystallinity is 99.95%, indicating the state where all the molybdenum disulfide particles are crystallized.

[0171] Regarding the abundance ratios of the 2H crystal structure and the 3R crystal structure in the molybdenum disulfide particles, specifically, in Example 1, they were obtained by performing the following operations: The microcrystalline size and abundance ratio of the 2H crystal structure were determined through the broad peaks near 40° and 50°, and for the difference, the 3R crystal structure parameters were optimized with two peaks near 33° and two peaks near 40°, thereby reproducing the overall measured XRD pattern.

[0172] [Evaluation basic formula and calculation of microcrystalline size]

[0173] Using the diffraction pattern, the microcrystalline sizes of the 2H crystal structure and the 3R crystal structure were obtained based on the analytical formula L = Kλ / βcosθ. In the above formula, K is the instrument constant depending on the XRD optical system (incident side and detector side) and the settings, L is the size of the microcrystal [m], λ is the wavelength of the measured X-ray [m], β is the half-value width [rad], and θ is the Bragg angle of the diffracted ray [rad].[[]END]]

[0174] [Conversion rate R to MoS2 C

[0175] By the RIR (reference intensity ratio) method, using the RIR value K of molybdenum sulfide (MoS2) A and the integrated intensity I of the peak near 2θ = 14.4° ± 0.5° belonging to the (002) plane or (003) plane of molybdenum sulfide (MoS2) A 、and the RIR values K of each molybdenum oxide (MoO3 as the raw material and Mo9O as the reaction intermediate 25 、Mo4O 11 、MoO2, etc.) B and the RIR values K of each molybdenum oxide (MoO3 as the raw material and Mo9O as the reaction intermediate 25 、Mo4O 11 ​, the integrated intensity I of the strongest ray peak of (such as MoO2, etc.) B , the conversion rate R to MoS2 is obtained from the following formula (1) C .

[0176] R C (%) = (I A / K A ) / (Σ(I B / K B )) × 100 ··· (1)

[0177] Here, the RIR values are respectively the values recorded in the Inorganic Crystal Structure Database (ICSD), and the analysis is performed using the comprehensive powder X-ray analysis software (PDXL2) (manufactured by Rigaku Co., Ltd.).

[0178] [Extended X-ray Absorption Fine Structure (EXAFS) Measurement]

[0179] 36.45 mg of molybdenum sulfide powder and 333.0 mg of boron nitride were mixed in a mortar. 123.15 mg of this mixture was weighed and compression-molded into tablets to obtain a measurement sample. Using this measurement sample, the extended X-ray absorption fine structure (EXAFS) was measured by the transmission method through BL5S1 of the Aichi Synchrotron Radiation Center. Athena (Internet <URL: https: / / bruceravel.github.io / demeter / >) was used in the analysis.

[0180] [Measurement of the median particle size D 50 of the molybdenum disulfide particles constituting the molybdenum sulfide powder]

[0181] 0.1 g of molybdenum sulfide powder was added to 20 cc of acetone, and after subjecting it to ultrasonic treatment in an ice bath for 4 hours, the concentration was further appropriately adjusted with acetone to a range where it could be measured by a dynamic light scattering type particle size distribution measuring device (manufactured by Microtrac BEL Corporation, Nanotrac Wave II) to obtain a measurement sample. Using this measurement sample, the particle size distribution in the range of 0.0001 to 10 μm of particle size was measured by the above-mentioned dynamic light scattering type particle size distribution measuring device, and the median particle size D 50 was calculated.

[0182] [Observation Method of the Particle Shape of Molybdenum Disulfide Particles]

[0183] The molybdenum disulfide particles were measured with an atomic force microscope (AFM) (Oxford Cypher-ES), and the particle shape was observed.

[0184] <Synthesis Example 1>

[0185] (Manufacture of Molybdenum Trioxide Particles)

[0186] 1.5 kg of aluminum hydroxide (manufactured by Nippon Light Metal Company) and 1 kg of molybdenum trioxide (manufactured by Nippon Inorganic Co., Ltd.) were mixed, and then put into a crucible, and calcined in the calcination furnace 2 in the manufacturing apparatus 1 shown in Figure 1 at a temperature of 1100 °C for 10 hours. During the calcination, external gas was introduced from the side and bottom of the calcination furnace 2 (blowing speed: 50 L / minute, external gas temperature: 25 °C). After molybdenum trioxide evaporated in the calcination furnace 2, it was cooled near the recovery machine 4 and precipitated in the form of particles. As the calcination furnace 2, an RHK simulation device (manufactured by NORITAKE CO., LIMITED) was used, and as the recovery machine 4, a VF-5N dust collector (manufactured by AMANO Corporation) was used.

[0187] After calcination, 1.0 kg of alumina as a blue powder and 0.85 kg of molybdenum trioxide particles recovered in the recovery machine 4 were taken out from the crucible. The average particle size of the primary particles of the recovered molybdenum trioxide particles was 80 nm, and it was confirmed by fluorescence X-ray (XRF) measurement that the purity of molybdenum trioxide was 99.7%. The specific surface area (SA) of the molybdenum trioxide particles measured by the BET method was 44.0 m 2 / g.

[0188] (Manufacture of Molybdenum Disulfide Powder)

[0189] In a magnetic crucible, 40.0 g (277.9 mmol) of the molybdenum trioxide particles recovered in the above recovery machine 4 and 40.0 g (1250 mmol) of sulfur powder (manufactured by Kanto Chemical Co., Inc.) were mixed with a stirring rod to make the powder uniform, and added to a high-temperature atmosphere calcination furnace (manufactured by Motoyama Corporation, SKM-2030P-OP). After evacuating the inside of the furnace, nitrogen replacement was carried out, and then calcination was carried out at 500 °C for 4 hours to obtain a black powder. Here, based on 100 mol% of the MoO3 amount of the above molybdenum trioxide particles, the S amount of the above sulfur was 450 mol%. The results of the X-ray diffraction (XRD) pattern of the black powder (molybdenum disulfide powder used in Example 1) were compared with the diffraction patterns of the 3R crystal structure of molybdenum disulfide (MoS2), the diffraction pattern of the 2H crystal structure of molybdenum disulfide (MoS2), and the diffraction pattern of molybdenum dioxide (MoO2) included in the inorganic crystal structure database (ICSD) Figure 1 are shown in Figure 2 . Molybdenum dioxide (MoO2) is a reaction intermediate.

[0190] The specific surface area of the molybdenum disulfide powder manufactured in Synthesis Example 1 was measured by the BET method, and the result was 49.6 m 2 / g. In addition, the bulk density was measured using a bulk density measuring instrument (manufactured by Ito Seisakusho, based on JIS-K-5101) and an electromagnetic balance type balance (manufactured by A&T Corporation, GX-4000R), and the result was 0.283 g / cm 3 .

[0191] The particle size distribution of the molybdenum disulfide powder produced in Synthesis Example 1 was measured using a dynamic light scattering type particle size distribution measuring device, and the median diameter D 50 was obtained, and the result was 250 nm.

[0192] The AFM image of the synthesized molybdenum disulfide particles is shown in Figure 3 . Figure 3 The AFM image obtained for the measurement shows the upper surface of the molybdenum disulfide particles. The length (vertical) × width (horizontal) was obtained from this AFM image, and the result was 180 nm × 80 nm. Figure 4 To show Figure 3 The curve graph of the cross section of the molybdenum disulfide particles shown. The thickness (height) was obtained from this cross-sectional view, and the result was 16 nm. Therefore, the aspect ratio (length (vertical) / thickness (height)) of the primary particles of the molybdenum disulfide particles was 11.25.

[0193] Including Figure 3 The average value of 50 molybdenum disulfide particles including the molybdenum disulfide particles shown was length (vertical) × width (horizontal) × thickness (height) = 198 nm × 158 nm × 19 nm.

[0194] In addition, a representative example of the AFM measurement results of the molybdenum disulfide particles is shown in Table 1. In the table, "molybdenum disulfide particle (1)" is Figure 3 The molybdenum disulfide particles described. "Molybdenum disulfide particle (2)" is the particle with the longest length among the measured molybdenum disulfide particles, and "molybdenum disulfide particle (3)" is the particle with the shortest length. "Molybdenum disulfide particle (4) is a particle with a relatively thick thickness, and "molybdenum disulfide particle (5)" is the particle with the thinnest thickness. "Molybdenum disulfide particle (6)" is the particle with the largest aspect ratio. "Molybdenum disulfide particle (7)" is the particle with the thickest thickness and also the particle with the smallest aspect ratio.

[0195] [Table 1]

[0196]

[0197] The extended X-ray absorption fine structure (EXAFS) of the molybdenum disulfide powder produced in Synthesis Example 1 was measured. The extended X-ray absorption fine structure (EXAFS) spectrum of the K absorption edge of molybdenum is shown in Figure 3 . In the radial distribution function obtained from this spectrum, the ratio (I / II) of the intensity I of the peak derived from Mo-S to the intensity II of the peak derived from Mo-Mo was 1.26.

[0198] First, a part of the X-ray diffraction (XRD) pattern of the molybdenum disulfide particles obtained in Synthesis Example 1 is shown in Figure 6 . As shown in this figure, the main peak (A in the figure) of the molybdenum disulfide particles in Synthesis Example 1 is consistent around 2θ: 14°, and is also consistent with the main peaks of the 3R crystal structure and 2H crystal structure as references. On the other hand, the broad peaks (B in the figure) around 2θ: 32.5°, around 2θ: 39.5°, and around 2θ: 49.5° are almost consistent with the peak positions of the 3R crystal structure and 2H crystal structure as references, but the peaks around 2θ: 39.5° and around 2θ: 49.5° are the composite waves of the peaks of each crystal structure of the 3R crystal structure and 2H crystal structure, indicating that both the 3R crystal structure and 2H crystal structure are included.

[0199] Therefore, an attempt was made to perform Rietveld analysis on each diffraction pattern of Synthesis Example 1, and it was confirmed from Figure 5 the results that there are two types, namely the 3R crystal structure and the 2H crystal structure. The calculated results of the existence ratios of the respective crystal structures are that in the crystal phase of Example 1, the existence ratio of the 2H crystal structure is 71.5%, and the existence ratio of the 3R crystal structure is 28.5%. In addition, the crystallite size of the 2H crystal structure (crystal phase) can be evaluated as 9.6 nm, and the crystallite size of the 3R crystal structure (crystal phase) can be evaluated as 11.8 nm.

[0200] (Manufacture of grease composition containing particles)

[0201] <Example 1>

[0202] To 11.3 parts by mass of a grease composition (manufactured by Kyodo Yushi Co., Ltd., MARUTEMP PS No2) using diester and synthetic hydrocarbon oil as base oils and Li soap as a thickener, 3 parts by mass of the obtained molybdenum disulfide powder (molybdenum disulfide particles) was added and mixed to prepare a particle-containing grease composition precursor containing 21% by mass of molybdenum disulfide. The particle-containing grease composition precursor was kneaded 3 times with a Hoover automatic grinding machine (manufactured by Toyo Seiki Co., Ltd.) at a load of 6 kgf and a rotation speed of 30 rpm. To 14.3 parts by weight of the kneaded particle-containing grease composition precursor, 85.7 parts by weight of a grease composition (manufactured by Kyodo Yushi Co., Ltd., MARUTEMP PS No2) was added and mixed evenly, and finally kneaded with a planetary mixer (manufactured by THINKY Corporation, awatori rentaro) at a rotation speed of 2000 rpm for 30 seconds to obtain the particle-containing grease composition of Example 1 containing 3% by mass of molybdenum disulfide.

[0203] <Example 2>

[0204] 1.43 parts by mass of the particulate-containing grease composition precursor containing 21% by mass of molybdenum disulfide after kneading with the Hoover automatic surface grinder of Example 1 was allowed to act on 98.57 parts by weight of the grease composition (manufactured by Kyodo Yushi Co., Ltd., MARUTEMP PS No2), and the same procedure as in Example 1 was carried out except for this, to obtain a particulate-containing grease composition containing 0.3% by mass of molybdenum disulfide.

[0205] (Commercially available molybdenum disulfide particles)

[0206] The results of the X-ray diffraction pattern of the commercially available molybdenum disulfide powder (M-5 powder manufactured by DAIZO NICHIMOLY Co., Ltd.) were compared with the diffraction pattern of molybdenum disulfide with a 2H crystal structure. Figure 1 are shown in Figure 6 . It was found that the commercially available molybdenum disulfide reagent is molybdenum disulfide with a 2H crystal structure having a presence ratio of 99% or more. The half-value widths of the peaks around 39.5° and 49.5° are 0.23° and 0.22°, respectively, which are narrower than those in Synthesis Example 1.

[0207] For the commercially available molybdenum disulfide powder, the ratio (I / II) of the intensity I of the peak derived from Mo-S to the intensity II of the peak derived from Mo-Mo obtained by measuring the specific surface area (SA) and the extended X-ray absorption fine structure (EXAFS) at the K absorption edge of molybdenum was 0.72. The specific surface area of the commercially available molybdenum disulfide powder was measured by the BET method, and the result was 9.1 m 2 / g.

[0208] In addition, the particle size distribution of the commercially available molybdenum disulfide powder was measured using a dynamic light scattering type particle size distribution measuring device, and the median diameter D 50 was determined, and the result was 602 nm.

[0209] (Manufacture of particulate-containing grease composition)

[0210] <Comparative Example 1>

[0211] Using the commercially available molybdenum disulfide powder (molybdenum disulfide particles), the same procedure as in Example 1 was carried out except for this, to obtain a particulate-containing grease composition of Comparative Example 1 containing 3% by mass of molybdenum disulfide.

[0212] <Comparative Example 2>

[0213] Using the commercially available molybdenum disulfide powder (molybdenum disulfide particles), the same procedure as in Example 2 was carried out except for this, to obtain a particulate-containing grease composition of Comparative Example 2 containing 0.3% by mass of molybdenum disulfide.

[0214] <Comparative Example 3>

[0215] As Comparative Example 3, a grease composition (manufactured by Kyodo Yushi Co., Ltd., MARUTEMP PS No2) containing no molybdenum disulfide powder (molybdenum disulfide particles) was prepared.

[0216] [Friction and Wear Evaluation 1]

[0217] For Examples 1 to 2 and Comparative Examples 1 to 3, a friction and wear test (based on ASTM D2266, load 40 kgf, rotational speed 1200 rpm, time 1 h, starting temperature 20 °C) was conducted using a high-speed four-ball EP testing machine, and the scar diameter, maximum non-sintering load, and welding load were measured.

[0218] Three SUJ2 special stainless steel balls were fixed, and 2 g of the obtained grease composition containing particles was evenly applied. While applying torque to each 1 / 2-inch SUJ2 special stainless steel ball from above, it was rotated while applying a specified load in the vertical direction. The rotational speed of the SUJ2 ball was set to 1200 rpm, the load was set to 40 kgf, and after 1 hour, the diameter (mm) of the scar on the fixed SUJ2 ball was recorded.

[0219] In addition, based on ASTM D2596, the rotational speed of the SUJ2 ball was set to 1770 rpm and the rotation time was set to 10 seconds, and the load (kgf) just before sintering and the welding load (kgf) of the 1 / 2-inch SUJ2 ball were recorded respectively. The results are shown in Table 2.

[0220] [Table 2]

[0221]

[0222] As a result, in Example 1, the average value of the scar diameter was 0.58 mm, the scar diameter was small, and it was found that the friction surface was not easily ground. In addition, the maximum non-sintering load was 100 kgf, and it was found that even when the load was increased, the friction surface was not easily deteriorated and sintering did not easily occur. The welding load was 350 kgf, and it was found that even when the load was increased, the friction surface was not easily heated and welding between the metal balls did not easily occur.

[0223] On the other hand, in Comparative Example 1, the average value of the scar diameter was 0.63 mm, which was larger than that in Example 1, and it was found that the friction surface was easily ground. In addition, the maximum non-sintering load was 80 kgf and the welding load was 225 kgf, and the load at which sintering and welding occurred was smaller than that in Example 1, and the friction and wear characteristics were poor.

[0224] In addition, in Example 2, the average value of the wear scar diameter is 0.64 mm. Since the wear scar diameter is small, it can be seen that the friction surface is not easily ground. In addition, the maximum non-sintering load is 63 kgf, indicating that even when the load is increased, the friction surfaces are not easily deteriorated and sintering does not easily occur. The welding load is 225 kgf, indicating that even when the load is increased, the friction surfaces are not easily heated and welding between the metal balls does not easily occur.

[0225] On the other hand, in Comparative Example 2, the average value of the wear scar diameter is 0.68 mm. Compared with Example 2, the wear scar diameter is larger, indicating that the friction surface is easily ground. In addition, the maximum non-sintering load is 63 kgf and the welding load is 200 kgf. Compared with Example 2, the load at which welding occurs is small, and the friction and wear characteristics are poor.

[0226] In addition, in Comparative Example 3, the average value of the wear scar diameter is 0.67 mm. Compared with Example 1, the friction scar diameter is larger, indicating that the friction surface is easily ground. In addition, the maximum non-sintering load is 63 kgf and the welding load is 170 kgf. Compared with Examples 1 and 2, the loads at which sintering and welding occur are small, and the friction and wear characteristics are poor.

[0227] Here, the differences in friction and wear performance between Example 1 and Comparative Example 1, and between Example 2 and Comparative Example 2 were examined. The molybdenum disulfide powder used in Examples 1 and 2 is molybdenum disulfide containing a 2H crystal structure and a 3R crystal structure. In addition, the specific surface area measured by the BET method is 49.6 m 2 / g, and the median particle diameter D 50 measured by a dynamic light scattering type particle size distribution measuring device is 250 nm. On the other hand, the commercially available molybdenum disulfide powder used in Comparative Examples 1 and 2 is molybdenum disulfide with a 2H crystal structure of 99% or more. In addition, the specific surface area measured by the BET method is 9.1 m 2 / g, and the median particle diameter D 50 measured by a dynamic light scattering type particle size distribution measuring device is 602 nm. It is speculated that the reasons why the friction and wear characteristics of Example 1 are superior to those of Comparative Example 1 and the friction and wear characteristics of Example 2 are superior to those of Comparative Example 2 are as follows: The fact that the median particle diameter D 50 of the molybdenum disulfide powder used in Examples 1 and 2 is about 250 nm is very helpful. On this premise, the inclusion of a 2H crystal structure and a 3R crystal structure and a specific surface area of 49.6 m 2 / g are also helpful. Therefore, it is considered that, for example, molybdenum disulfide powder with a median particle diameter D 50 of about 250 nm, a 2H crystal structure with a presence ratio of 99% or more, and a specific surface area of about 9.1 m 2 / g will also exhibit relatively excellent friction and wear performance. Similarly, it is considered that the median particle diameter D 50Molybdenum disulfide powder with a median particle size of about 250 nm, a proportion of the 2H crystal structure of 99% or more, and a specific surface area of about 49.6 m 2 / g also exhibits relatively excellent friction and wear performance. Alternatively, it is considered that the median particle size D 50 is about 250 nm, contains both 2H and 3R crystal structures, and has a specific surface area of about 9.1 m 2 / g, and such molybdenum disulfide powder also shows relatively excellent friction and wear performance.

[0228] [Friction and Wear Evaluation 2]

[0229] For Example 1, Comparative Example 1, and Comparative Example 3, a friction and wear test was conducted using a vibratory friction and wear testing machine (based on ASTM D5707, load 200 N, amplitude 1.0 mm, temperature 80 °C, frequency 50 Hz, test time 120 minutes), and the friction coefficient was measured.

[0230] A disk and a ball made of SUJ2 special stainless steel were fixed, and 10 g of the obtained grease composition containing particles was evenly applied. A specified load was applied vertically from above the ball to vibrate the ball at a specified frequency and amplitude. The friction coefficient during 120 minutes (2 hours) of vibration was measured, and the friction coefficient at the 30-minute mark (f30) was recorded. In addition, after 120 minutes of vibration, the wear scar generated on the sliding surface was observed using a laser microscope (Keyence Corporation, VK-200), and the depth of the wear scar and the surface roughness of the wear scar were measured. The surface roughness was obtained in the form of arithmetic mean roughness (Ra). These measurement results are shown in Table 3. In addition, the results of observing the sliding surface with a microscope are shown in Figures 9 - 11 .

[0231] [Table 3]

[0232]

[0233] In Example 1, f30 was 0.15, confirming excellent friction coefficient. In addition, as Figure 9 shown, the depth of the wear scar was shallow, and the depth and surface roughness of the wear scar were 12.9 μm and 2.0 μm, respectively, confirming less wear and small surface roughness.

[0234] On the other hand, in Comparative Example 1, f30 was 0.15, which was the same as that in Example 1. However, as Figure 10 shown, the depth of the wear scar was deep, and the depth and surface roughness of the wear scar were 19.8 μm and 3.1 μm, respectively. It can be seen that the wear amount and surface roughness were larger than those in Example 1. Therefore, the wear resistance characteristics were poor compared with Example 1.

[0235] In addition, in Comparative Example 3, f30 was 0.16, and the friction coefficient was poor compared with Example 1. Furthermore, as Figure 11The depth of the shown abrasion mark is deeper, and the depth and surface roughness of the abrasion mark are 34.7 μm and 7.1 μm respectively, and the abrasion resistance characteristics are significantly worse than those of Example 1.

[0236] Industrial Applicability

[0237] The grease composition containing particles of the present invention is suitable for use in sliding parts between metal members, between resin members, or between a resin member and a metal member, and can be used for equipment, components, etc. in various industrial fields. For example, it can be widely used in transmission devices such as speed reducers, speed increasers, gears, chains, and electric motors; control system components such as driving system components; steering system components; drive system components such as transmissions; automotive enhancement components such as electric window motors, electric seat motors, and sunroof motors; components for office equipment such as copiers and printers; hinge components for electronic information devices, mobile phones, etc.; various components in the food / drug industry, steel, construction, glass industry, cement industry, film stretching machines, chemical / rubber / resin industry, environmental / power equipment, paper / printing industry, wood industry, fiber / apparel industry, mechanical components performing relative motion, etc., and is particularly suitably used for transmission elements that may generate high loads. In addition, the grease composition containing particles of the present invention can also be applied to bearings such as rolling bearings, thrust bearings, hydrodynamic bearings, resin bearings, and linear motion devices.

[0238] Explanation of Reference Numerals

[0239] 1 Manufacturing apparatus

[0240] 2 Roaster

[0241] 3 Cooling pipe

[0242] 4 Recovery machine

[0243] 5 Exhaust port

[0244] 6 Opening adjustment damper

[0245] 7 Observation window

[0246] 8 Exhaust device

[0247] 9 External cooling device

Claims

1. A grease composition containing particles, which contains a base oil, a thickener, and molybdenum disulfide particles, The molybdenum disulfide particles are sulfides of molybdenum trioxide particles, and the molybdenum trioxide particles contain an aggregate of primary particles having a β crystal structure, The median particle size D of the molybdenum disulfide particles obtained by dynamic light scattering method 50 is 10 nm or more and less than 450 nm, The primary particles of the molybdenum disulfide particles are in the shape of a disc, a strip or a sheet and have a thickness in the range of 3 to 100 nm, The specific surface area of the molybdenum disulfide particles measured by the BET method is 10 m 2 / g or more, The bulk density of the molybdenum disulfide particles is 0.1 g / cm 3 or more and 1.0 g / cm 3 or less.

2. The grease composition containing particles according to claim 1, wherein, The molybdenum disulfide particles have a 2H crystal structure and a 3R crystal structure of molybdenum disulfide.

3. The grease composition containing particles according to claim 1, wherein, In the radial distribution function of the molybdenum disulfide particles obtained from the extended X-ray absorption fine structure (EXAFS) spectrum at the K absorption edge of molybdenum, the ratio (I / II) of the intensity I of the peak derived from Mo-S to the intensity II of the peak derived from Mo-Mo is greater than 1.

0.

4. The grease composition containing particles according to claim 1, wherein, The molybdenum disulfide particles have a 2H crystal structure and a 3R crystal structure of molybdenum disulfide. In the spectrum of the molybdenum disulfide particles obtained by powder X-ray diffraction (XRD) using Cu-Kα rays as the X-ray source, the peaks near 39.5° and near 49.5° are derived from the 2H crystal structure, and the peaks near 32.5°, near 39.5° and near 49.5° are derived from the 3R crystal structure, The half-value widths of the peaks near 39.5° and near 49.5° are 1° or more.

5. The grease composition containing particles according to claim 4, wherein, The crystallite size of the 3R crystal structure calculated by extended Rietveld analysis based on the spectrum obtained by powder X-ray diffraction (XRD) using Cu-Kα rays as the X-ray source according to the analytical formula L = Kλ / (βcosθ) is 1 nm or more and 150 nm or less, In the formula, L is the size of the crystallite [m], K is a device constant depending on the XRD optical system (incident side and detector side) and settings, λ is the measurement X-ray wavelength [m], β is the half-value width [rad], and θ is the Bragg angle of the diffracted ray [rad].

6. The grease composition containing particles according to claim 4, wherein, The abundance ratio of the 2H crystal structure and the 3R crystal structure obtained by extended Rietveld analysis using the spectrum obtained by the XRD is 10:90 to 90:

10.

7. The grease composition containing particles according to any one of claims 1 to 6, wherein, Relative to 100% by mass of the total mass of the grease composition containing particles, 0.0001% by mass or more and 10% by mass or less of the molybdenum disulfide particles are contained.

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