Composition, coating film, and sliding member

Abstract

Provided are: a composition capable of improving friction characteristics, durability, and sealability by using a solid lubricant having a proper particle size and aspect ratio; a coating composition; a coating film thereof; and a sliding member. Specifically, the composition contains a solid lubricant (A). The solid lubricant (A) contains molybdenum disulfide particles (a1) in which the aspect ratio, which is the ratio of the median diameter D50 (nm) and the thickness (nm) of the primary particles, is in the range of 2-110, and the median diameter D50 is 50-500 nm.

Description

Composition, coating film and sliding member

[0001] The present invention relates to a composition, a coating film, and a sliding member containing a solid lubricant.

[0002] Molybdenum disulfide is used as a solid lubricant in a wide range of applications. For example, Patent Document 1 discloses a sliding coating structure suitable for sliding parts such as piston skirts, ring grooves, and pin holes of internal combustion engines such as gasoline engines. This sliding coating structure has a lubricating coating covering the surface of a metal substrate. The lubricating coating is composed of a heat-resistant resin containing polyamide-imide resin and molybdenum disulfide particles. The weight percentage of the heat-resistant resin in the lubricating coating is 52 to 84 wt %, the weight percentage of the molybdenum disulfide particles is 48 to 16 wt %, and the average particle size of the molybdenum disulfide particles is in the range of 0.7 to 2.7 μm, as measured by a laser diffraction / scattering particle size distribution analyzer.

[0003] Also disclosed is a resin composition for forming a lubricating coating on the surface of a sliding member, the resin composition containing a polyamideimide resin as a binder, a solid lubricant, and an organic solvent, the polyamideimide resin having a weight average molecular weight of 10,000 to 50,000, the blending amounts of each component excluding the organic solvent being 89.0 to 97.5% by volume of polyamideimide resin, 1 to 7% by volume of fluorine-based solid lubricant, 1 to 5% by volume of sulfur-containing compound-based solid lubricant, and 0.5 to 5% by volume of carbon-based solid lubricant, with the total amount of solid lubricants being 2.5 to 11% by volume (Patent Document 2).

[0004] Furthermore, in a sealed sliding member having a sliding surface that slides against another member and seals a fluid through the sliding surface, it is disclosed that by providing the sliding surface with a sliding material containing a solid lubricant and a thermosetting resin that fixes it, friction during sliding can be reduced and leakage from the sealing surface can be prevented (Patent Document 3).Alternatively, a sliding member that achieves both sealing properties and sliding properties by using a liquid lubricant and a solid lubricant in combination has also been provided (Patent Document 4).

[0005] JP 2009-068584 A JP 2011-213761 A JP 2015-10689 A JP 8-100860 A Japanese Patent No. 6614471 A

[0006] Molybdenum disulfide particles used to improve lubricity are generally obtained by cutting and pulverizing natural molybdenum disulfide ore. Inexpensive powders obtained by crushing natural molybdenum disulfide ore and then classifying them according to application have a size on the order of μm, as shown in Patent Document 1, and a very high specific gravity of about 5, resulting in a low lubricating effect per mass added. Furthermore, when conventional molybdenum disulfide particles such as those described above are contained in coatings, the large particle size results in a rough coating surface, and the molybdenum disulfide protruding from the coating surface is prone to fracture or detachment during sliding, resulting in poor friction characteristics and durability. Particularly in sealed sliding components, the presence of protruding μm-order molybdenum disulfide particles on the surface can impair sealing properties, and their high specific gravity makes it difficult to ensure sufficient presence on the outermost surface of the lubricating layer. Furthermore, when a liquid lubricant is applied to the coating film, the rough surface of the coating film makes it difficult to retain the liquid lubricant on the coating film, making it difficult to obtain the friction and wear reducing effect of the liquid lubricant.Furthermore, natural molybdenum disulfide minerals contain a large amount of impurities derived from mineral deposits, such as copper and lead, which reduces the lubricating effect.

[0007] The applicant holds a patent for a manufacturing method for synthesizing nm-sized molybdenum disulfide particles by heating molybdenum oxide in the presence of a sulfur source (Patent Document 5). There is room for further study and improvement regarding whether the application of nm-sized molybdenum disulfide particles to coatings contributes to improved friction properties and durability. Furthermore, the nm-sized molybdenum disulfide particles independently developed by the applicant have not only a 2H crystal structure but also a rare 3R (rhombohedral) structure. This technology, by producing molybdenum disulfide particles using the applicant's proprietary "nm-sized molybdenum trioxide microparticles" as a raw material, makes it possible to synthesize "nm-scale molybdenum disulfide containing a 3R structure, which is lightweight and advantageous for achieving a large surface area," something that is difficult to achieve by crushing mine products or synthesizing from general-purpose molybdenum trioxide.

[0008] An object of the present invention is to provide a composition, a coating film and a sliding member that have an appropriate particle size and aspect ratio and are capable of improving friction characteristics, durability and sealing properties.

[0009] As a result of extensive research, the present inventors have focused on the aspect ratio and particle size of molybdenum disulfide particles contained in coating compositions and the like, and have found that the appropriate aspect ratio and median diameter D of the primary particles in the composition are ５０ The present inventors have found that the inclusion of molybdenum disulfide particles having the above formula improves the surface smoothness of a coating film, which is a cured product of a coating composition, or a lubricating layer made of the composition, reducing the occurrence of defects that could cause the coating film or lubricating layer to break down when sliding surfaces slide against each other. Furthermore, when the amount added is the same as that of conventional molybdenum disulfide particles, the small particle size of the molybdenum disulfide particles allows them to be more uniformly distributed within the surface, allowing loads to be received by area contact rather than point contact, resulting in improved friction properties and durability of the coating film or lubricating layer. Furthermore, the present inventors have found that when the molybdenum disulfide particles have an appropriate particle size and aspect ratio, the molybdenum disulfide particles are less likely to protrude from the surface of the coating film or lubricating layer and therefore less likely to detach, thereby reducing frictional wear that occurs between the coating film or lubricating layer and the sliding surface. Furthermore, they found that when a liquid lubricant is applied to the coating, the smoothing of the lubricating coating surface makes it easier to retain the liquid lubricant on the lubricating coating, making it easier to demonstrate the effect of reducing friction and wear due to the liquid lubricant; and that in a lubricating layer used in combination with a liquid lubricant, molybdenum disulfide particles can be uniformly distributed within the layer, resulting in excellent uniformity in the sliding parts.

[0010] Furthermore, we found that molybdenum disulfide particles with the appropriate particle size and aspect ratio can reduce the gap between the coating film and the sliding member in the sliding area, thereby improving the sealing performance of the sliding area in addition to reducing friction and wear. Molybdenum disulfide particles generally have a layered crystal structure. Each layer is a single-layer, two-dimensional sheet structure of molybdenum disulfide, and when an external force is applied in the two-dimensional in-plane direction, the layers shift. This property is thought to be the reason why molybdenum disulfide exhibits the effect of reducing friction and wear. When an external force is applied to molybdenum disulfide particles in the sliding area by a sliding member, the external force cleaves the surface layer of the molybdenum disulfide particle, in particular. The cleaved molybdenum disulfide pieces intervene to better fill the gap between the coating film and the sliding member, and the labyrinth effect also works, resulting in excellent sealing performance. The applicant has found that molybdenum disulfide particles produced by the technology he possesses have the 3R crystal structure as described above, and therefore cleavage occurs more easily than with molybdenum disulfide particles having a 1H or 2H crystal structure, making it easier to achieve the above-mentioned effects.

[0011] That is, the present invention provides the following configuration: [1] A solid lubricant (A) is contained, and the solid lubricant (A) has a median diameter D of primary particles of ５０ The aspect ratio, which is the ratio of the diameter (nm) of the nanoparticles to the thickness (nm), is in the range of 2 to 110, and the median diameter D ５０ A composition comprising molybdenum disulfide particles (a1) having a particle size of 50 nm or more and 500 nm or less.

[0012] [2] A resin and a solid lubricant (A), wherein the solid lubricant (A) has a median diameter D of primary particles. ５０ The aspect ratio, which is the ratio of the diameter (nm) of the nanoparticles to the thickness (nm), is in the range of 2 to 110, and the median diameter D ５０ A composition comprising molybdenum disulfide particles (a1) having a particle size of 50 nm or more and 500 nm or less.

[0013] [3] The solid lubricant (A) is a molybdenum disulfide particle (a1) having a median diameter D of a primary particle ５０and molybdenum disulfide particles (a2) having a particle size of 600 nm or more and 500 μm or less, wherein the content ratio ((a1):(a2)) of the molybdenum disulfide particles (a1) to the molybdenum disulfide particles (a2) is 1:0 to 1:20 in mass ratio.

[0014] [4] Median diameter D of primary particles of molybdenum disulfide particles (a2) ５０ The composition according to [3], wherein the particle size is 1 μm or more and 50 μm or less.

[0015] [5] The composition according to [1] or [2], wherein the solid lubricant (A) comprises the molybdenum disulfide particles (a1).

[0016] [6] The composition according to any one of [1] to [5], wherein the content of the solid lubricant (A) is 0.5% by mass or more and 30% by mass or less when the total mass of the composition is 100% by mass.

[0017] [7] The composition according to any one of [2] to [5], wherein the resin comprises one or more selected from the group consisting of epoxy resins, phenolic resins, polyamide resins, polyimide resins, and polyamideimide resins.

[0018] [8] The composition according to any one of [1] to [7], further comprising a solid lubricant (B), wherein the solid lubricant (B) comprises one or more selected from a carbon-based solid lubricant and a fluorine-based solid lubricant.

[0019] [9] The composition according to any one of [1] to [8], further comprising a solvent, wherein the solvent comprises one or more selected from the group consisting of N-methyl-2-pyrrolidone, γ-butyrolactone, cyclopentanone, N-ethyl-2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone, dimethyl sulfoxide, butyl cellosolve, and methyl ethyl ketone.

[0020]

[10] The composition according to any one of [1] to [9], which contains antimony trioxide as an antioxidant.

[0021]

[11] The composition according to any one of [2] to

[10] , which is a coating composition.

[0022]

[12] A coating film that is a cured product of the composition according to any one of [1] to

[11] .

[0023]

[13] A sliding member having the coating film according to

[10] .

[0024]

[14] At least a part of the sliding surface has a median diameter D of primary particles. ５０ The aspect ratio, which is the ratio of the diameter (nm) of the nanoparticles to the thickness (nm), is in the range of 2 to 110, and the median diameter D ５０ A sliding member having a solid lubricant (A) containing molybdenum disulfide particles (a1) having a particle size of 50 nm or more and 500 nm or less.

[0025]

[15] The sliding member according to

[13] or

[14] , which is a molded article.

[0026] According to the present invention, it is possible to provide a composition, a coating film and a sliding member which have an appropriate particle size and aspect ratio and can improve friction characteristics, durability and sealing properties.

[0027] Fig. 1 is a cross-sectional view showing an example of the configuration of a coating film according to the present embodiment; Fig. 2 is a cross-sectional view showing an example of the configuration of a coating film according to the present embodiment; Fig. 3 is a graph showing the results of a paper vertical sliding test in the examples; Fig. 4 is a graph showing the results of a FALEX sliding test in the examples; Fig. 5 is a graph showing the results of a Kawamura type reciprocating friction test in the examples.

[0028] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

[0029] <Composition> The composition according to this embodiment contains a solid lubricant (A), and the solid lubricant (A) has a median diameter D of primary particles of ５０ The aspect ratio, which is the ratio of the thickness to the surface area, is 2 or more and 110 or less, and the median diameter D ５０ The particle size of the molybdenum disulfide particles (a1) is 50 nm or more and 500 nm or less.

[0030] The composition may contain resins, organic solvents, various additives, etc., as described below. In particular, due to its small particle size, it can be easily dispersed in liquid lubricants conventionally used for sliding members, such as silicone oil, fluorine oil, polyalkylene glycol, white oil, mineral oil, white petrolatum (petrolatum), liquid paraffin, paraffin wax, olefin polymerized oil, alkylated aromatic oil, coal tar, hydrogenated oil, polyether oil, ester oil, and halogenated hydrocarbon oil, thereby improving lubrication and sliding properties without impairing sealing properties. It can also be easily dispersed in organic solvents, reactive monomers, and liquid resins. When dispersing in these media, various dispersants may be used in combination, or various dispersants may be used to first disperse the solid lubricant (A) containing the molybdenum disulfide particles (a1) in a medium at a high concentration, and then the solid lubricant (A) may be dispersed in the same or different target medium at a desired concentration.

[0031] <Coating composition> The coating composition according to this embodiment contains a resin and a solid lubricant (A), and the solid lubricant (A) has a median diameter D of primary particles of ５０ The aspect ratio, which is the ratio of the thickness to the surface area, is 2 or more and 110 or less, and the median diameter D ５０ The particle size of the molybdenum disulfide particles (a1) is 50 nm or more and 500 nm or less.

[0032] [Molybdenum disulfide particles (a1)] In this embodiment, the aspect ratio of the molybdenum disulfide particles (a1) is determined by the ratio of the median diameter D to the thickness (nm) of the primary particles. ５０ (nm) ratio ((median diameter D ５０) / thickness (height)), and the average of five particles is 2 or more and 110 or less. When the aspect ratio of the molybdenum disulfide particles (a1) is within the above range, the molybdenum disulfide particles (a1) are easily oriented so that their longitudinal direction is aligned with the in-plane direction of the coating film or lubricating layer. This allows the surface of the coating film or lubricating layer to be efficiently covered, sufficiently reducing wear and seizure due to friction. The larger the aspect ratio, the more the above-mentioned effects can be enjoyed. The aspect ratio is preferably 3 or more, more preferably 5 or more, and particularly preferably 8 or more. Furthermore, from a manufacturing standpoint, it is easy to obtain particles having an aspect ratio of 80 or less, and even more easily to obtain particles having an aspect ratio of 60 or less.

[0033] In addition, assuming that the aspect ratio of the primary particles of the molybdenum disulfide particles (a1) is within the above range, the median diameter D of the primary particles of the molybdenum disulfide particles (a1) is ５０ The median diameter D of the molybdenum disulfide particles (a1) is 50 nm or more and 500 nm or less. ５０ By making the particle size 500 nm or less, the particles are less likely to protrude from the surface of the coating film or lubricating layer, and the surface of the coating film or lubricating layer is smoothed. Therefore, when an external force is applied due to sliding or the like, the molybdenum disulfide particles (a1) are less likely to detach, and sealing properties are improved. Furthermore, even when the gap between the coating film or lubricating layer and the sliding material is as small as less than 1000 nm, the molybdenum disulfide particles (a1) tend to remain in the gap without detaching from the coating film or lubricating layer, and lubricating properties can be maintained for a long period of time.

[0034] Median diameter D of primary particles of molybdenum disulfide particles (a1) ５０ From the viewpoint of the above-mentioned effects, the median diameter D of the primary particles of the molybdenum disulfide particles (a1) is more preferably 400 nm or less, and even more preferably 300 nm or less. ５０ The median diameter D of the primary particles of the molybdenum disulfide particles (a1) may be 100 nm or more, or 150 nm or more. ５０is measured using, for example, a dynamic light scattering particle size distribution analyzer (Nanotrac Wave II, manufactured by Microtrackbell Co., Ltd.) or a laser diffraction particle size distribution analyzer (SALD-7000, manufactured by Shimadzu Corporation).

[0035] The shape of the primary particles of the molybdenum disulfide particles (a1) is not particularly limited, but preferably has a thin layer shape such as a disk, ribbon, or sheet. When the molybdenum disulfide particles (a1) have the above shape, they can more efficiently cover the surface of a coating film or lubricating layer even at a small content, and can further improve friction and wear properties.

[0036] Molybdenum disulfide (MoS ２ ) particles (a1) may contain a 2H crystal structure and a 3R crystal structure. When molybdenum disulfide particles (a1) having a 3R crystal structure abundance ratio of 10% or more in the crystalline phase of molybdenum disulfide are used as a coating material or a lubricating layer component, they not only reduce the occurrence of seizure even under heavy loads, but also exhibit excellent friction properties, reducing the friction coefficient by 20 to 30%. The abundance ratio of the 3R crystal structure in the crystalline phase of molybdenum disulfide is preferably 20% or more, more preferably 30% or more, even more preferably 50% or more, and particularly preferably 60% or more.

[0037] The fact that the molybdenum disulfide particles (a1) have a 2H crystal structure and a 3R crystal structure can be confirmed, for example, by using an extended Rietveld analysis software (High Score Plus, manufactured by Malvern Panalytical) that can take into account the crystallite size. In this Rietveld analysis software, the entire XRD diffraction profile is simulated using a crystal structure model including the crystallite size, and compared with the XRD diffraction profile obtained experimentally. The residual between the diffraction profile obtained experimentally and the diffraction profile obtained by calculation is minimized by the least squares method, and the crystal lattice constants of the crystal structure model, crystal structure factors such as atomic coordinates, weight fraction (abundance ratio), etc. are optimized, and each phase of the 2H crystal structure and the 3R crystal structure is identified and quantified with high precision, and in addition to the crystal structure type and its ratio calculated by normal Rietveld analysis, the crystallite size can be calculated. Hereinafter, in this patent, the analysis method using the above-mentioned High Score Plus is referred to as "extended Rietveld analysis".

[0038] Furthermore, in the molybdenum disulfide particles (a1) of this embodiment, the crystallite size of the 3R crystal structure calculated by extended Rietveld analysis based on the analytical formula L = Kλ / (β cos θ) using a profile obtained from powder X-ray diffraction (XRD) using Cu-Kα radiation as an X-ray source may be 1 nm or more and 150 nm or less. In the above formula, K is an instrument constant dependent on the XRD optical system (incident side and detector side) and settings, L is the crystallite size [m], λ is the measured X-ray wavelength [m], K is a constant, β is the half-width [rad], and θ is the Bragg angle [rad] of the diffraction line. When the crystallite size of the 3R crystal structure is 1 nm or more and 150 nm or less, slippage between layers occurs more easily when subjected to shear force, which can reduce the friction coefficient of the dispersion system and improve frictional properties. The crystallite size of the 3R crystal structure is preferably a value obtained by extended Rietveld analysis. The coefficient of friction can be measured, for example, from a Stribeck curve using a ball-on-disk tester or a four-ball tester.

[0039] From the viewpoint of the above-mentioned effects, the 3R crystal structure obtained by the extended Rietveld analysis is preferably a crystalline phase composed of crystallites having a crystallite size calculated based on the analytical formula of 1 nm to 100 nm, more preferably 1 nm to 50 nm, and even more preferably 1 nm to 40 nm. Furthermore, in the molybdenum disulfide particles (a1) of this embodiment, the crystallite size of the 2H crystal structure is preferably 1 nm to 150 nm. When the crystallite size of the 2H crystal structure is 1 nm to 150 nm, the friction coefficient can be reduced and the friction characteristics can be improved. The crystallite size of the 2H crystal structure is preferably a value obtained according to extended Rietveld analysis. The 2H crystal structure obtained by the Rietveld analysis is preferably a crystalline phase composed of crystallites having a crystallite size calculated based on the analytical formula of 1 nm to 150 nm, more preferably 5 nm to 150 nm.

[0040] The 2H crystal structure obtained by extended Rietveld analysis preferably consists of a single crystalline phase composed of crystallites having a predetermined crystallite size. In the manufacturing method described below, a 2H crystal structure composed of a single crystalline phase can be obtained by setting the heating temperature in the heat treatment to a relatively low temperature. In this case, the crystallite size of the 2H crystal structure is more preferably 1 nm or more and 20 nm or less, and more preferably 5 nm or more and 15 nm or less.

[0041] The crystallite size of the 2H crystal structure and the crystallite size of the 3R crystal structure can also be calculated using, for example, the peak half width of an XRD diffraction profile.

[0042] The abundance ratio (2H:3R) of the 2H crystal structure and the 3R crystal structure in the crystalline phase, obtained by extended Rietveld analysis using the profile obtained from the XRD, is preferably 10:90 to 90:10. When the abundance ratio of the 3R crystal structure in the crystalline phase is 10% to 90%, when the molybdenum disulfide particles (a1) are used as a coating material or a lubricating layer component, seizure is less likely to occur under high load, and the friction coefficient can be reduced by 20 to 30%.

[0043] From the viewpoint of the above-mentioned effects, the abundance ratio (2H:3R) of the 2H crystal structure and the 3R crystal structure in the crystal phase obtained by extended Rietveld analysis using the profile obtained from the above-mentioned XRD is more preferably 10:90 to 80:20, and even more preferably 40:60 to 80:20.

[0044] Furthermore, the 2H crystal structure obtained by the extended Rietveld analysis may consist of a first crystal phase composed of crystallites having a predetermined crystallite size and a second crystal phase having a smaller crystallite size than the first crystal phase. In the manufacturing method described below, a 2H crystal structure composed of a first crystal phase and a second crystal phase can be obtained by further heating the molybdenum disulfide particles (a1) as a post-treatment. The crystallite size of the first crystal phase of the 2H crystal structure is, for example, greater than 20 nm and less than 150 nm, and may be 50 nm to 150 nm, or 100 nm to 150 nm. However, in order to reduce the friction coefficient, it is preferable that the first crystal phase is not present in the crystalline phase of the 2H crystal structure, or that its abundance ratio is low. Furthermore, the crystallite size of the second crystal phase of the 2H crystal structure is preferably 1 nm to 20 nm, and may be 1 nm to 10 nm, or 5 nm to 15 nm.

[0045] The crystallite size of the first crystalline phase of the 2H crystalline structure, the crystallite size of the 3R crystalline structure, and the crystallite size of the second crystalline phase of the 2H crystalline structure can also be calculated using, for example, the peak half-width of the XRD diffraction profile, as described above.

[0046] The abundance ratio of the first crystalline phase of the 2H crystalline structure, the 3R crystalline structure, and the second crystalline phase of the 2H crystalline structure in the crystalline phase (2H (first crystalline phase):3R:2H (second crystalline phase)) obtained by extended Rietveld analysis using the profile obtained from the XRD is preferably 30 to 0:10 to 70:80 to 15. When the abundance ratio of the first crystalline phase of the 2H crystalline structure, the 3R crystalline structure, and the second crystalline phase of the 2H crystalline structure in the crystalline phase is 30 to 10:10 to 70:80 to 15, when the molybdenum disulfide particles (a1) are used as a coating material or a lubricating layer component, seizure is less likely to occur when a high load is applied, and the friction coefficient can be reduced by 20 to 30%.

[0047] From the viewpoint of the above-mentioned effects, the abundance ratio of the first crystalline phase of the 2H crystalline structure, the 3R crystalline structure, and the second crystalline phase of the 2H crystalline structure obtained by extended Rietveld analysis using the profile obtained from the XRD is more preferably 30-0:10-70:80-15, and even more preferably 25-0:20-60:75-20.

[0048] In a profile obtained by powder X-ray diffraction (XRD) of the molybdenum disulfide particles (a1) using Cu-Kα radiation as an X-ray source, the peaks near 39.5° and 49.5° are derived from a 2H crystal structure, and the peaks near 32.5°, 39.5°, and 49.5° are derived from a 3R crystal structure, and the half widths of the peaks near 39.5° and 49.5° are preferably 1° or more. Furthermore, the molybdenum disulfide particles (a1) may contain a crystal structure other than the 2H crystal structure and 3R crystal structure of molybdenum disulfide, such as a 1H crystal structure.

[0049] The molybdenum disulfide particles (a1) can be distinguished from the molybdenum disulfide particles by the fact that, in a profile obtained by powder X-ray diffraction (XRD) using Cu-Kα radiation as an X-ray source, a peak at about 39.5° and a peak at about 49.5° are both composed of composite peaks of a 2H crystal structure and a 3R crystal structure.

[0050] In practice, by using the profile obtained from the above-mentioned powder X-ray diffraction (XRD), the abundance ratio of 2H crystal structure is determined by the peak around 39.5 ° and the broad peak around 49.5 °.In addition, by optimizing the difference between the peak around 39.5 ° and the broad peak around 49.5 ° with two peaks around 32.5 ° and two peaks around 39.5 °, the abundance ratio of 3R crystal structure is determined.That is, the peak around 39.5 ° and the peak around 49.5 ° are both the composite wave derived from 2H crystal structure and 3R crystal structure, and these composite waves can be used to calculate the abundance ratio of 2H crystal structure and 3R crystal structure in molybdenum disulfide particle (a1).

[0051] The molybdenum disulfide particles (a1) may also contain an amorphous phase. The ratio of the amorphous phase in the molybdenum disulfide particles (a1), expressed as 100(%) - (crystallinity (%)), is preferably 5% or more, more preferably 15% or more, and even more preferably 20% or more. When the ratio of the amorphous phase in the molybdenum disulfide particles (a1) is 5% or more, the coefficient of friction is further reduced, and friction characteristics can be improved.

[0052] The specific surface area of ​​the molybdenum disulfide particles (a1) measured by the BET method is 10 m ２ / g or more, and ２ / g or more is more preferable, and 40m ２ The specific surface area of ​​the molybdenum disulfide particles (a1) measured by the BET method is more preferably 300 m / g or more. ２ / g or less, and ２ / g or less.

[0053] The primary particles of the molybdenum disulfide particles (a1) have layers that are close to each other due to relatively weak interactions, and can be easily displaced by external forces such as friction. Therefore, when the primary particles of the molybdenum disulfide particles (a1) are sandwiched between metals as sliding materials, for example, the layers that make up the primary particles are displaced by the frictional force, reducing the apparent friction coefficient and preventing contact between sliding materials. When the specific surface area of ​​the molybdenum disulfide particles (a1) measured by the BET method is 10 m ２ / g or more, when the primary particles are present between sliding materials, the contact area between the sliding materials can be further reduced, which is thought to contribute to both improving the performance of the coating film or lubricating layer and preventing seizure.

[0054] In the radial distribution function obtained from the extended X-ray absorption fine structure (EXAFS) profile of the molybdenum K absorption edge of the molybdenum disulfide particles (a1), the ratio (I / II) of the peak intensity I attributable to Mo—S to the peak intensity II attributable to Mo—Mo is preferably greater than 1.0, more preferably 1.1 or greater, and particularly preferably 1.2 or greater.

[0055] Whether the crystal structure of molybdenum disulfide is a 2H crystal structure or a 3R crystal structure, the distance between Mo and S is approximately the same due to covalent bonding, and therefore the intensity of the peak due to Mo—S is the same in the extended X-ray absorption fine structure (EXAFS) profile at the molybdenum K absorption edge. On the other hand, because the 2H crystal structure of molybdenum disulfide is hexagonal, the same hexagon is located 90° directly below the hexagon of Mo atoms, thereby shortening the distance between Mo-Mo atoms and increasing the peak intensity II due to Mo-Mo. Conversely, because the 3R crystal structure of molybdenum disulfide is rhombohedral, the hexagon is located halfway down from the hexagon rather than directly below it, thereby increasing the distance between Mo-Mo atoms and decreasing the peak intensity II due to Mo-Mo. In the pure 2H crystal structure of molybdenum disulfide, the ratio (I / II) is small, but as the 3R crystal structure is included, the ratio (I / II) becomes larger. In the 3R crystal structure, the hexagons of Mo atoms in each of the three layers are offset from each other by half a hexagon, so the interaction between each layer is smaller and it is expected that sliding will be easier compared to the 2H crystal structure in which the hexagons of Mo atoms in two layers are aligned perpendicularly and regularly. Even in the 2H crystal structure, if the crystallite size is small, it is expected that sliding will be easier to occur at the contact surface.

[0056] The conversion rate R from the molybdenum oxide precursor compound to molybdenum disulfide particles (a1) described below Ｃ The conversion rate R of the molybdenum disulfide particles (a1) is preferably 70% or more, more preferably 80% or more, and even more preferably 90% or more, because the presence of molybdenum trioxide is thought to adversely affect lubrication performance. Ｃ Since the lubricating oil exhibits a value close to 100%, the lubricating oil has superior lubricating properties to other molybdenum disulfide materials or their precursors that may contain molybdenum trioxide as a by-product.

[0057] Conversion rate R to molybdenum disulfide particles (a1) Ｃ can be determined by the RIR (reference intensity ratio) method from profile data obtained by subjecting the molybdenum disulfide particles (a1) to X-ray diffraction (XRD).２ ) RIR value K Ａ and molybdenum disulfide (MoS ２ ) The integrated intensity I of the peak at about 2θ = 14.4 ° ± 0.5 °, which is attributed to the (002) or (003) plane of Ａ , and each molybdenum oxide (the raw material MoO ３ , and the reaction intermediate Mo ９ O ２５ , Mo ４ O １１ , MoO ２ RIR value K Ｂ and each molybdenum oxide (the raw material MoO ３ , and the reaction intermediate Mo ９ O ２５ , Mo ４ O １１ , MoO ２ The integrated intensity I of the strongest line peak of Ｂ Using the following formula (1), MoS ２ Conversion rate R Ｃ can be obtained. R Ｃ (%) = (I Ａ / K Ａ ) / (Σ(I Ｂ / K Ｂ )) × 100 (1) Here, the RIR values ​​can be those listed in the Inorganic Crystal Structure Database (ICSD) (manufactured by the Japan Chemical Information Association), and the analysis can be performed using integrated powder X-ray analysis software (PDXL2, manufactured by Rigaku Corporation).

[0058] The composition of the present embodiment only needs to contain the molybdenum disulfide particles (a1), which are an essential component. ｘ (X=1 to 3) or MoS ｘ The molybdenum sulfide particles may contain one or more types of molybdenum sulfide particles represented by (X=1 to 3).

[0059] [Molybdenum disulfide particles (a2)] The solid lubricant (A) is a mixture of the molybdenum disulfide particles (a1) and a molybdenum disulfide particle (a2) having a median diameter D ５０The molybdenum disulfide particles (a2) may be, for example, natural molybdenum disulfide (MoS ２ ) crushed natural molybdenum disulfide (MoS ２ The crushed particles of molybdenum disulfide (a2) contain many particles with particle sizes exceeding 1 μm, and the lubricating effect per added weight is small when only molybdenum disulfide particles (a2) are used. However, the median diameter D of the primary particle size ５０ Molybdenum disulfide particles (a1) having a small median diameter D ５０ By using the molybdenum disulfide particles (a1) in combination with the molybdenum disulfide particles (a2) having a larger particle size, the small molybdenum disulfide particles (a1) penetrate between the relatively large molybdenum disulfide particles (a2), smoothing the surface of the coating film or sliding member. Therefore, when an external force is applied due to sliding or the like, separation of the molybdenum disulfide particles (a1) and the molybdenum disulfide particles (a2) can be suppressed.

[0060] Median diameter D of primary particles of molybdenum disulfide particles (a2) ５０ is not particularly limited, and may be, for example, 600 nm or more and 500 μm or less, 1 μm or more and 50 μm or less, or 1 μm or more and 20 μm or less.

[0061] The shape of the primary particles of the molybdenum disulfide particles (a2) is not particularly limited, and may be, for example, spherical, polygonal, irregular, etc. The primary particles of the molybdenum disulfide particles (a2) may have a different shape from the primary particles of the molybdenum disulfide particles (a1) which have a lamellar shape.

[0062] Furthermore, molybdenum disulfide, which is generally used as a lubricant, is a hexagonal solid lubricant and has a crystalline structure that is substantially composed of a 2H crystalline structure. The molybdenum disulfide particles (a2) of this embodiment may differ from the molybdenum disulfide particles (a1) in that they do not contain a 3R crystalline structure and are substantially composed of a 2H crystalline structure.

[0063] When the solid lubricant (A) contains molybdenum disulfide particles (a1) and molybdenum disulfide particles (a2), the content ratio ((a1):(a2)) of the molybdenum disulfide particles (a1) to the molybdenum disulfide particles (a2) is preferably 1:0 to 1:20, more preferably 1:1 to 1:15, by mass. When the content ratio of the molybdenum disulfide particles (a1) to the molybdenum disulfide particles (a2) is 1:0 to 1:20, the surfaces of the coating film and the sliding parts are made smoother, and high lubrication properties and sealing properties can be obtained.

[0064] The solid lubricant (A) may contain the molybdenum disulfide particles (a1) and the molybdenum disulfide particles (a2) as described above, or may consist of the molybdenum disulfide particles (a1). When the solid lubricant (A) consists of the molybdenum disulfide particles (a1), it is possible to increase the lubricating effect per added mass and maintain excellent lubricating properties and sealing performance over a long period of time.

[0065] When the total mass of the composition is taken as 100 mass%, the content of the solid lubricant (A) is preferably 0.5 mass% to 30 mass%, more preferably 0.5 mass% to 20 mass%, and even more preferably 0.5 mass% to 10 mass%. By having the content of the solid lubricant (A) be 0.5 mass% to 30 mass%, it is possible to ensure good manufacturability of the coating film and the sliding member while increasing the lubricating effect per added weight.

[0066] [Resin] The composition of this embodiment may contain a resin. The resin is not particularly limited as long as it has a binder function to disperse or fix the solid lubricant (A). For example, when forming a coating composition, it is preferable to contain one or more resins selected from epoxy resins, phenolic resins, polyamide resins, polyimide resins, and polyamideimide resins. Among these, from the viewpoints of heat resistance, chemical resistance, and adhesion to the coated member, it is more preferable to contain one or more resins selected from polyamide resins, polyimide resins, and polyamideimide resins, and polyamide resins are even more preferable. Furthermore, in this embodiment, the resin used for the sliding member may be, in addition to the above resins, one or more resins selected from fluorine-based resins such as polyester resins, polyether resins, polyphenylene sulfide resins, and polytetrafluoroethylene.

[0067] [Solid Lubricant (B)] The composition of this embodiment may further contain a solid lubricant (B). The solid lubricant (B) may contain, for example, one or more types selected from carbon-based solid lubricants and fluorine-based solid lubricants. Examples of carbon-based solid lubricants include graphite, fullerenes, carbon nanotubes, carbon nanofibers, graphite, and graphene, and one or more types of these may be used. Examples of fluorine-based solid lubricants include polytetrafluoroethylene, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymers, tetrafluoroethylene-hexafluoropropylene copolymers, tetrafluoroethylene-ethylene copolymers, polyvinylidene fluoride, and trichlorotrifluoroethylene, and one or more types of these may be used. When the solid lubricant (B) further contains one or more types selected from carbon-based solid lubricants and fluorine-based solid lubricants, the lubrication properties can be further improved.

[0068] [Antioxidant (C)] The composition of the present embodiment may further contain an antioxidant (C). The antioxidant (C) may contain a metal oxide-based antioxidant. Examples of the metal oxide-based antioxidant include antimony trioxide (Sb２ O ３ When the composition further contains a metal oxide antioxidant, particularly antimony trioxide, oxidation of the molybdenum disulfides (a1) and (a2) can be suppressed, and the friction coefficient can be stabilized even during long-term use.

[0069] [Solvent] The composition of the present embodiment may further contain a solvent. The solvent is not particularly limited, but preferably contains one or more solvents selected from the group consisting of NMP (N-methyl-2-pyrrolidone), GBL (γ-butyrolactone), CPN (cyclopentanone), NEP (N-ethyl-2-pyrrolidone), 1,3-dimethyl-2-imidazolidinone, dimethyl sulfoxide, butyl cellosolve, and MEK (methyl ethyl ketone). When the solvent contains one or more of the above-mentioned specific compounds, the solubility of the resin, particularly the polyamideimide resin, can be improved, and the drying property can be controlled to ensure film-forming properties.

[0070] When producing the composition, for example, the solid lubricant (a1) and various resins, solvents, liquid lubricants, and other media depending on the application are stirred and mixed with a stirrer, and the resulting mixture is dispersed using a dispersing machine such as a bead mill or a three-roll mill. A solid lubricant (B) may be further added, or either or both of the solid lubricant (B) and the antioxidant (C) may be further added. Furthermore, various commonly used additives such as dispersants and antifoaming agents may be blended as necessary.

[0071] The composition can be diluted with a diluting solvent such as a nitrogen-containing solvent, a hydrocarbon solvent, or a ketone solvent, as needed, and then applied or coated onto the surface of a sliding member to form a lubricating coating. The dilution ratio with the solvent can be adjusted to an appropriate viscosity depending on the method of application or coating onto the part. Alternatively, a sliding member can be obtained by impregnating a fibrous or porous molded body with a composition containing a liquid medium.

[0072] <Coating Film> The coating film of this embodiment is a cured product of the above composition. The coating film is formed on a sliding member, a member to be slid that is disposed opposite the sliding member, or both. FIG. 1 is a cross-sectional view showing an example of the configuration of a coating film that is a cured product of a coating composition. As shown in FIG. 1, coating film 100A has a base layer 10 formed on a substrate 101 and solid lubricants 20 dispersed in base layer 10. Base layer 10 corresponds to the resin in the coating composition, and solid lubricant 20 corresponds to solid lubricant (A) in the coating composition. In this embodiment, solid lubricant 20 includes solid lubricants 21 and 22. Solid lubricant 21 has a median primary particle diameter D ５０ The aspect ratio, which is the ratio of the thickness to the surface area, is 2 or more and 110 or less, and the median diameter D ５０ The solid lubricant 22 has a primary particle median diameter D ５０ The solid lubricant 21 corresponds to the solid lubricant (a1) in the coating composition, and the solid lubricant 22 corresponds to the solid lubricant (a2).

[0073] In the coating film 100A, some of the solid lubricants 21 and some of the solid lubricants 22 protrude from the surface of the base layer 10. Small particle size solid lubricants 21 are interspersed between the relatively large particle size solid lubricants 22, thereby forming minute irregularities on the surface of the base layer 10 and smoothing the surface of the coating film 100A. Therefore, when the sliding member 102 slides, the solid lubricants 21 protruding from the surface of the coating film 100A are less likely to come off due to the sliding, thereby sufficiently reducing frictional wear that occurs between the coating film 100A and the sliding member 102. Furthermore, when a liquid-based lubricant 103 is applied to the coating film 100A, the smooth surface of the coating film 100A makes it easier to retain the liquid-based lubricant 103 on the coating film 100A, making it easier to achieve the frictional wear reduction effect of the liquid-based lubricant 103.

[0074] The coating film 100A is obtained by applying or coating the coating composition to one or both sliding surfaces of members that slide against each other due to relative movement. As the application or coating method, known methods such as spray application, roll coating, pad coating, dip coating, screen printing, offset printing, bar coating, and spin coating can be used, but spray application or screen printing is preferred from an industrial perspective.

[0075] FIG. 2 is a cross-sectional view showing another example of the configuration of a coating film that is a cured product of a coating composition. As shown in FIG. 2, coating film 100B has a base layer 10 formed on a substrate 101 and solid lubricants 20 dispersed in base layer 10. In this embodiment, solid lubricant 20 contains solid lubricant 21 but does not contain solid lubricant 22. Coating film 100B is similar to coating film 100A in other configurations except for solid lubricant 20. When solid lubricant 20 is composed of solid lubricant 21 in this manner, in coating film 100B, a portion of solid lubricant 21 protrudes from the surface of base layer 10. The small particle size solid lubricant 21 protruding from the surface of base layer 10 forms minute irregularities on the surface of base layer 10, thereby smoothing the surface of coating film 100B. Therefore, when the sliding member 102 slides, the solid lubricant 21 protruding from the surface of the coating film 100B is unlikely to come off due to the sliding, and it is possible to sufficiently reduce frictional wear that occurs between the coating film 100B and the sliding member 102. Furthermore, when the liquid-based lubricant 103 is applied onto the coating film 100B, the smoothed surface of the coating film 100B makes it easy to retain the liquid-based lubricant 103 on the coating film 100B, making it easier to obtain the effect of reducing frictional wear due to the liquid-based lubricant 103.

[0076] <Sliding Member> The sliding member has the coating film on one or more portions. There are no particular limitations on the sliding member, as long as it is a member that slides against each other by relative movement and has a portion on the sliding surface where a coating film can be formed. Typical sliding members are pistons of internal combustion engines such as gasoline engines, cylinders in engine blocks, and intake and exhaust valves in cylinder heads. When the sliding member is a piston, the portion on which the coating film is formed is, for example, a skirt portion, a ring groove, or a pin hole. Furthermore, the sliding member may be a member other than an internal combustion engine, and may be, for example, a mechanical element such as a bearing mechanism or a fastening member. When the sliding member is a bearing mechanism, the coating film can be formed on either or both of the shaft and the bearing. When the sliding member is a fastening member such as a bolt or a nut, the coating film can be formed on, for example, either the male thread or the female thread of the threaded portion, or both.

[0077] The molybdenum disulfide particles (a1) can be prepared as a coating composition and then applied to a sliding part to form a coating film, which can then be used as a sliding member. They can also be used for sliding members where sealing properties are required for moving parts. Due to their characteristic shape, the molybdenum disulfide particles (a1) are less likely to protrude from the coating surface, as described above, and their ability to smooth the coating surface can reduce the gap between the coating film and the sliding member at the sliding part, thereby improving both lubricity and sealing properties. This characteristic makes them particularly suitable for use as sliding members for moving parts where prevention of liquid or gas leakage and pressure loss is required. In such cases, it is more preferable that such sliding members are not liquid or oily, but rather are molded bodies with a fixed shape. Examples of such sliding members include rotating shaft sealing devices, more specifically, components and devices such as mechanical seals and gland packings. When the molybdenum disulfide particles (a1) are used in such a sliding member, they may be used in a manner of forming a coating film on the surface of the sliding portion as described above, or may be used as a constituent component that is uniformly present inside the sliding member. ５０The aspect ratio, which is the ratio of the diameter (nm) of the nanoparticles to the thickness (nm), is in the range of 2 to 110, and the median diameter D ５０ A solid lubricant (A) is present, which contains molybdenum disulfide particles (a1) having a particle size of 50 nm or more and 500 nm or less.

[0078] When a solid lubricant (A) containing molybdenum disulfide particles (a1) is present inside the sliding member, lubrication and sealing properties can be maintained even when the sliding member wears due to the presence of the molybdenum disulfide particles (a1) contained in the solid lubricant (A). The surface layer of the molybdenum disulfide (a1) present on or near the surface of the sliding part is cleaved by the external force of the sliding part so that the cleavage plane is parallel to the sliding direction, and the cleaved molybdenum disulfide pieces bleed out and intervene to further fill the gap between the coating film and the sliding member, and the labyrinth effect also works, thereby exhibiting good sealing properties. Such a sliding member can be prepared by previously mixing the solid lubricant (A) of the present application with a resin or the like that forms a molded body, pelletizing the mixture as necessary, and then injection-molding the mixture into a desired shape. Alternatively, if the molded body is one that can be impregnated with a liquid component, such as a fibrous or porous one, the molded body can be immersed in a liquid composition, and the liquid medium can be entrained in the molded body to impregnate the molded body, thereby forming a sliding member.

[0079] <Method for Producing Molybdenum Disulfide Particles> Next, a method for producing the molybdenum disulfide particles (a1) according to this embodiment will be described. The molybdenum disulfide particles (a1) can be produced, for example, by heating molybdenum trioxide particles having an average primary particle size of 2 nm to 1000 nm in the presence of a sulfur source at a temperature of 200 to 1000°C.

[0080] The average particle size of the primary particles of molybdenum trioxide particles refers to the average primary particle size of 50 randomly selected primary particles, when the molybdenum trioxide particles are photographed with a scanning electron microscope (SEM) or a transmission electron microscope (TEM), the major axis (the Feret diameter of the longest observed part) and minor axis (the shorter Feret diameter in the direction perpendicular to the Feret diameter of the longest part) of the smallest unit particle (i.e., primary particle) constituting the aggregate in the two-dimensional image are measured, and the average value is taken as the primary particle size.

[0081] In the method for producing molybdenum disulfide particles, the molybdenum trioxide particles preferably have an average primary particle size of 1 μm or less. From the viewpoint of reactivity with sulfur, the average primary particle size is more preferably 600 nm or less, even more preferably 400 nm or less, and particularly preferably 200 nm or less. The average primary particle size of the molybdenum trioxide particles may be 2 nm or more, 5 nm or more, or 10 nm or more.

[0082] The molybdenum trioxide particles used in the production of the molybdenum disulfide particles are preferably composed of an aggregate of primary particles containing the β crystal structure of molybdenum trioxide. The molybdenum trioxide particles have a better reactivity with sulfur than conventional molybdenum trioxide particles that are composed only of α crystals, and because they contain the β crystal structure of molybdenum trioxide, they react with a sulfur source to form MoS ２ Conversion rate R Ｃ can be made larger.

[0083] The β crystal structure of molybdenum trioxide is shown by the profile obtained from powder X-ray diffraction (XRD) using Cu-Kα radiation as an X-ray source. ３ The α-crystal structure of molybdenum trioxide can be confirmed by the presence of a peak (2θ: around 23.01°, No. 86426 (Inorganic Crystal Structure Database (ICSD))) which is assigned to the (011) plane of the β-crystal of MoO. ３ This can be confirmed by the presence of a peak on the (021) plane of the α-crystal (2θ: around 27.32°, No. 166363 (Inorganic Crystal Structure Database (ICSD))).

[0084] The molybdenum trioxide particles have a profile obtained by powder X-ray diffraction (XRD) using Cu-Kα radiation as an X-ray source, which profile is MoO ３ The peak intensity attributed to the (011) plane of the β crystal of MoO ３ It is preferable that the ratio (β(011) / α(021)) of the peak intensity of the α-crystal (2θ: around 27.32°_No. 166363 (Inorganic Crystal Structure Database (ICSD))) assigned to the (021) plane of the α-crystal is 0.1 or more.

[0085] MoO ３ The peak intensity attributed to the (011) plane of the β crystal of MoO ３ For the peak intensities attributable to the (021) plane of the α crystal, the maximum intensity of each peak is read, and the ratio (β(011) / α(021)) is calculated.

[0086] In the molybdenum trioxide particles, the ratio (β(011) / α(021)) is preferably 0.1 to 10.0, more preferably 0.2 to 10.0, and particularly preferably 0.4 to 10.0.

[0087] The β crystal structure of molybdenum trioxide is determined by Raman spectroscopy at wave numbers of 773 and 848 cm －１ and 905 cm －１ The α-crystalline structure of molybdenum trioxide can also be confirmed by the presence of peaks at wavenumbers 663 and 816 cm. －１ and 991 cm －１ This can be confirmed by the presence of a peak at

[0088] The molybdenum trioxide powder may have an average primary particle size of 5 nm or more and 2000 nm or less.

[0089] Examples of sulfur sources include sulfur and hydrogen sulfide, which may be used alone or in combination.

[0090] The method for producing molybdenum disulfide particles may include heating molybdenum trioxide particles comprising an aggregate of primary particles having a β crystal structure of molybdenum trioxide at a temperature of 100 to 800°C in the absence of a sulfur source, and then heating at a temperature of 200 to 1000°C in the presence of a sulfur source.

[0091] The heating time in the presence of the sulfur source may be any time that allows the sulfurization reaction to proceed sufficiently, and may be 1 to 20 hours, 2 to 15 hours, or 3 to 10 hours.

[0092] In the method for producing the molybdenum disulfide particles, the molybdenum trioxide particles are ３The ratio of the amount of S in the sulfur source to the amount of MoO of the molybdenum trioxide particles is preferably set to a value that satisfies the condition for the sulfurization reaction to proceed sufficiently. ３ The amount of S in the sulfur source is preferably 450 mol% or more, more preferably 600 mol% or more, and even more preferably 700 mol% or more, relative to 100 mol% of the amount of MoO in the molybdenum trioxide particles. ３ The amount of S in the sulfur source may be 3000 mol % or less, 2000 mol % or less, or 1500 mol % or less, relative to 100 mol % of the amount of S.

[0093] In the method for producing molybdenum disulfide particles, the heating temperature in the presence of the sulfur source may be any temperature at which the sulfurization reaction proceeds sufficiently, and is preferably 320° C. or higher, more preferably 340° C. or higher, and even more preferably 360° C. or higher. The heating temperature may be 320 to 1000° C., 340 to 1000° C., or 360 to 500° C. By lowering the heating temperature, the crystallinity of the molybdenum disulfide particles decreases, and the proportion of amorphous phases present can be increased.

[0094] In the method for producing molybdenum disulfide particles, the obtained molybdenum disulfide particles may be cooled and then heated as a post-treatment, if necessary. In this heat treatment, it is preferable to calcinate the molybdenum disulfide particles, for example, in an inert atmosphere. Heating and calcining the obtained molybdenum disulfide particles promotes crystallization of the amorphous phase, improving the crystallinity. Furthermore, as the crystallinity improves, new 2H crystal structures and 3R crystal structures are generated, changing the abundance ratio of the 2H crystal structure and the 3R crystal structure. When reheating is performed as a post-treatment in this way, the crystallinity of the molybdenum disulfide particles increases, reducing the ease of peeling due to lubrication to some extent, but the abundance ratio of the 3R crystal structure, which contributes to improving frictional properties, increases, thereby improving frictional properties compared to when only the 2H crystal structure is used. Furthermore, by changing the temperature when heating the obtained molybdenum disulfide particles, the abundance ratio of the 2H crystal structure and the 3R crystal structure can be adjusted.

[0095] When the obtained molybdenum disulfide particles are heated and fired at a predetermined temperature or higher to change the amorphous phase to a 2H crystalline structure, a second crystalline phase composed of crystallites with a crystallite size of 20 nm or less, preferably 10 nm or less, is newly generated. In this case, if crystallites with a crystallite size of 10 nm or less existed in the 2H crystalline structure before heating the molybdenum disulfide particles, these crystallites will grow to a crystallite size of 100 nm or more after heating the molybdenum disulfide particles, and a first crystalline phase composed of these grown crystallites will be generated.

[0096] As described above, it is presumed that, among the crystal structures of molybdenum disulfide particles, the crystal phase constituting the 3R crystal structure contributes to improving frictional characteristics, while the first crystal phase constituting the 2H crystal structure does not contribute to frictional characteristics or may be a factor in deteriorating frictional characteristics. Therefore, from the viewpoint of increasing the abundance ratio of the crystal phase of the 3R crystal structure while minimizing the abundance ratio of the first crystal phase of the 2H crystal structure, the heating temperature of the molybdenum disulfide particles in the post-treatment is preferably 500 to 900°C, and more preferably 500 to 800°C.

[0097] The heating rate of the molybdenum disulfide particles in the post-treatment is preferably 1° C. / min or more and 50° C. / min or less, and more preferably 2° C. / min or more and 10° C. / min or less.

[0098] In the method for producing molybdenum disulfide particles, the molybdenum trioxide particles are MoO measured by X-ray fluorescence (XRF). ３ It is preferable that the content of MoS is 99.5% or more. ２ Conversion rate R Ｃ Therefore, it is possible to obtain high-purity molybdenum disulfide that is free from the risk of producing disulfides derived from impurities and has good storage stability.

[0099] The molybdenum trioxide particles have a specific surface area of ​​10 m as measured by the BET method. ２ / g~150m ２ / g.

[0100] In the molybdenum trioxide particles, the specific surface area is 10 m because the reactivity with sulfur is improved. ２ / g or more, and ２ / g or more is more preferable, and 30m ２ In the molybdenum trioxide particles, it is more preferable that the molybdenum trioxide particle has a particle size of 150 m / g or more because it is easy to produce the particles. ２ / g or less, and ２ / g or less, ２ / g or less.

[0101] The molybdenum trioxide particles preferably have a ratio (I / II) of a peak intensity I attributable to Mo—O to a peak intensity II attributable to Mo—Mo in a radial distribution function obtained from an extended X-ray absorption fine structure (EXAFS) profile at the molybdenum K absorption edge of greater than 1.1.

[0102] The maximum intensities of the peak intensity I due to Mo—O and the peak intensity II due to Mo—Mo are read, and the ratio (I / II) is calculated. The ratio (I / II) is determined based on the ratio of MoO ３ The larger the ratio (I / II), the better the reactivity with sulfur.

[0103] In the molybdenum trioxide particles, the ratio (I / II) is preferably 1.1 to 5.0, may be 1.2 to 4.0, or may be 1.2 to 3.0.

[0104] (Method for Producing Molybdenum Trioxide Powder) The method for producing molybdenum trioxide powder used in the production method of this embodiment includes vaporizing a molybdenum oxide precursor compound to form molybdenum trioxide vapor, and cooling the molybdenum trioxide vapor. For example, the production methods disclosed in the following Patent Documents A and B can be mentioned. [Patent Document A] WO 2021 / 060375 [Patent Document B] WO 2022 / 202757

[0105] The molybdenum disulfide particles (a1) of this embodiment can be produced by the above-described method for producing molybdenum disulfide particles. Furthermore, the molybdenum trioxide powder production method can be used to produce molybdenum trioxide particles suitable for producing the molybdenum disulfide particles (a1) of this embodiment.

[0106] Examples of the present invention will be described below, but the present invention is not limited to the following examples.

[0107] Synthesis Example 1 A calcination furnace equivalent to a heat-resistant container, a cooling pipe provided with an outside air supply port, and a dust collector for recovering molybdenum oxide were prepared. A mixture of 1 kg of molybdenum trioxide (manufactured by Taiyo Koko Co., Ltd.) and 2 kg of aluminum hydroxide (manufactured by Wako Pharmaceutical Co., Ltd.) was charged into a sheath. The calcination furnace, cooling pipe, and dust collector were connected. The temperature in the calcination furnace was raised to 1,300°C and maintained at that temperature for 10 hours to obtain α-alumina, and molybdenum trioxide was vaporized in the calcination furnace. Next, air in a large excess relative to the amount of molybdenum trioxide was blown through the outside air supply port of the cooling pipe to the molybdenum trioxide vaporized from the exhaust port of the incinerator at a cooling rate of 2,000°C / sec, rapidly cooling the mixture to 200°C or below to powderize it, and 890 g of molybdenum trioxide was obtained in the dust collector.

[0108] Synthesis Example 2: 10.00 g (69.4 mmol) of the molybdenum trioxide prepared in Synthesis Example 1 and 11.11 g (347 mmol) of sulfur powder (Kanto Chemical) were added to a porcelain crucible and mixed with a stirrer until the powder was uniform. After mixing, the crucible was capped and placed in a high-temperature tubular furnace (Yamada Electric, TSS model) for firing. The firing conditions were as follows: the temperature was raised from room temperature (25°C) at a rate of 5°C / min, and after reaching 500°C, the temperature was maintained for 4 hours. Nitrogen gas was blown in at 0.2 ml / min during the firing process. The furnace was then allowed to cool naturally, yielding molybdenum disulfide particles.

[0109] The specific surface area of ​​the molybdenum disulfide particles obtained in Synthesis Example 2 was measured by the BET method using a high-precision gas adsorption measurement device (MICROTRAC, BELSORP-MINI). ２The particle size distribution of the molybdenum disulfide particles was measured using a nanoparticle size measuring device (MICROTRAC WAVE II, manufactured by MICROTRAC Corporation), and the median diameter D ５０ The thickness was measured using an atomic force microscope (Cypher-ES, manufactured by Oxford Instruments). The thickness measurement result was 2.7 nm. The aspect ratio was calculated to be 95.7 from the median diameter D50 and thickness.

[0110] [Example 1] 8.0 mass% of the molybdenum disulfide particles (a1) obtained in Synthesis Example 2, 4.0 mass% of antimony trioxide (Wako Pure Chemical Industries, Ltd.) reagent, 60.0 mass% of NMP (Wako Pure Chemical Industries, Ltd.) reagent, and 20.0 mass% of MEK (Wako Pure Chemical Industries, Ltd.) reagent were added to 8.0 mass% of polyamideimide resin (Viromax HR11NN, manufactured by Toyobo Co., Ltd.), and then a dispersion treatment was performed to obtain a coating composition (1) containing the molybdenum disulfide particles (a1). The obtained coating composition (1) was spray-coated onto a steel plate to a thickness of 1.0 mm, and then sintered at 230 ° C. for 1 hour to obtain a coating film (1A) for evaluation.

[0111] [Example 2] 8.0 mass% of polyamideimide resin was mixed with 4.0 mass% of the molybdenum disulfide particles (a1) obtained in Synthesis Example 2 and 4.0 mass% of dry-ground molybdenum disulfide particles (a2) (manufactured by Climax, median diameter D ５０ To the mixture (a1, a2, a3, a4, a5, a6, a7, a8, a9, a10, a11, a12, a13, a14, a15, a16, a17, a18, a19 ...

[0112] [Example 3] 0.5% by mass of the molybdenum disulfide particles (a1) obtained in Synthesis Example 2, 7.5% by mass of molybdenum disulfide particles (a2), 4.0% by mass of antimony trioxide, 60.0% by mass of NMP, and 20.0% by mass of MEK were added to 8.0% by mass of polyamideimide resin, and the mixture was then subjected to a dispersion treatment to obtain a coating composition (3) containing the molybdenum disulfide particles (a1) and the molybdenum disulfide particles (a2). The obtained coating composition (3) was applied to a steel plate and dried in the same manner as in Example 1 to obtain a coating film (3A) for evaluation.

[0113] [Comparative Example 1] 8.0% by mass of molybdenum disulfide particles (a2), 4.0% by mass of antimony trioxide, 60.0% by mass of NMP, and 20.0% by mass of MEK were added to 8.0% by mass of polyamideimide resin, and then the mixture was subjected to a dispersion treatment to obtain a coating composition (4) containing molybdenum disulfide particles (a2). The obtained coating composition (4) was spray-coated onto a steel plate to a thickness of 1.0 mm, and then sintered at 230°C for 1 hour to obtain a coating film (4A) for evaluation.

[0114] [Example 4] A steel plate having the evaluation coating film (1A) obtained in Example 1 formed thereon was placed on the moving side of a ball-on-disk tester, and an SUJ2-7 / 32 inch ball was placed on the stationary side. The number of slides until the terminal friction reached μ = 0.3 was measured at a sliding speed of 300 rpm in a dry atmosphere at room temperature, with a sliding diameter of 24.5 mm and a load of 1 kgf. The number of slides was 9,670. The results are shown in Table 1 and FIG. 3.

[0115] [Example 5] The number of sliding strokes was measured in the same manner as in Example 4, except that the steel plate on which the evaluation coating film (2A) obtained in Example 2 was formed was placed on the moving side of the ball-on-disk tester. The number of sliding strokes was 7,260. The results are shown in Table 1 and FIG. 3.

[0116] [Example 6] The number of sliding strokes was measured in the same manner as in Example 4, except that the steel plate on which the evaluation coating film (3A) obtained in Example 3 was formed was placed on the moving side of the ball-on-disk tester. The number of sliding strokes was 6,908. The results are shown in Table 1 and Figure 3.

[0117] [Comparative Example 2] The number of sliding strokes was measured in the same manner as in Example 4, except that the steel plate on which the evaluation coating film (4A) obtained in Comparative Example 1 was formed was placed on the moving side of the ball-on-disk tester. The number of sliding strokes was 2,227. The results are shown in Table 1 and Figure 3. The results of the paper vertical sliding test for Examples 4 to 6 and Comparative Example 2 are shown in Table 1 and Figure 3.

[0118]

[0119] As shown in Table 1 and FIG. 3, in all of Examples 4 to 6, the solid lubricant (A) of the coating films (1A) to (3A) contained molybdenum disulfide particles (a1), and the molybdenum disulfide particles (a1) had a median diameter of primary particles D ５０ The aspect ratio, which is the ratio of the diameter (nm) of the crystal to the thickness (nm), is in the range of 2 to 110, and the median diameter D ５０ When the particle size is 50 nm or more and 500 nm or less, the number of sliding cycles until the terminal friction reaches μ = 0.3 in a paper vertical sliding test is 6,500 or more, and it has been found that this shows excellent friction characteristics and durability. In particular, in Example 1, when the solid lubricant (A) of the coating film (1A) is made of molybdenum disulfide particles (a1), the number of sliding cycles until the terminal friction reaches μ = 0.3 in a paper vertical sliding test is 9,500 or more, and it has been found that this shows extremely excellent friction characteristics and durability.

[0120] On the other hand, in Comparative Example 2, the solid lubricant (A) of the coating film (4A) was composed of molybdenum disulfide particles (a2) and did not contain molybdenum disulfide particles (a1). Therefore, in the paper vertical sliding test, the number of sliding cycles until the terminal friction reached μ = 0.3 was less than 2,500, and the friction characteristics and durability were poor.

[0121] Example 7: A pin coated with the coating composition (1) prepared in Example 1 after SB#220 manganese phosphate treatment and then dried in the same manner as in Example 1 to a thickness of 12 μm was mounted on a FALEX sliding tester. A block coated with the coating composition (1) prepared in Example 1 after SB#220 manganese phosphate treatment and then dried in the same manner as in Example 1 to a thickness of 12 μm was mounted on the pin. The time until the terminal friction reached μ = 0.2 was measured. The pin was clamped by the block with a load of 1.2 kN for 180 seconds, then 1.8 kN for 60 seconds, and then 2.6 kN for 60 seconds, resulting in a final load of 765 lbs. The endurance time was 510 minutes. The results are shown in Table 2 and Figure 4.

[0122] [Example 8] A FALEX test was carried out in the same manner as in Example 7, except that the coating composition (2) prepared in Example 2 was used in the FALEX sliding tester. The durability time was 537 minutes. The results are shown in Table 2 and Figure 4.

[0123] [Comparative Example 3] A FALEX test was carried out in the same manner as in Example 7, except that the coating composition (4) prepared in Comparative Example 1 was used in the FALEX sliding tester. The durability time was 347 minutes. The results are shown in Table 2 and Figure 4.

[0124]

[0125] As shown in Table 2 and FIG. 4, in all of Examples 7 and 8, the solid lubricant (A) of the coating films (1B) to (2B) contained molybdenum disulfide particles (a1), and the molybdenum disulfide particles (a1) had a median diameter of primary particles D ５０ The aspect ratio, which is the ratio of the diameter (nm) of the crystal to the thickness (nm), is in the range of 2 to 110, and the median diameter D ５０ When the thickness is 50 nm or more and 500 nm or less, the time required for the terminal friction to reach μ=0.2 in the FALEX sliding test is 500 minutes or more, and it has been found that excellent friction characteristics and durability are exhibited.

[0126] On the other hand, in Comparative Example 3, the solid lubricant (A) of the coating film (4B) was composed of molybdenum disulfide particles (a2) and did not contain molybdenum disulfide particles (a1). Therefore, in the FALEX sliding test, the time until the terminal friction reached μ = 0.2 was less than 350 minutes, and the friction characteristics and durability were poor.

[0127] Example 9 8.0% by mass of polyamideimide resin was mixed with 8.0% by mass of molybdenum disulfide particles (a1), 2.0% by mass of graphite (Wako Pure Chemical Industries, Ltd.), 1.5% by mass of PTFE (Daikin Corporation, Polyflon PTFE D-310), 0.5% by mass of antimony trioxide, 60% by mass of NMP, and 20% by mass of MEK, followed by a dispersion treatment to obtain a coating composition (5) containing molybdenum disulfide particles (a1). The obtained coating composition (5) was spray-coated onto a steel plate to a thickness of 1.0 mm, and then sintered at 230°C for 1 hour to obtain a coating film (5A) for evaluation.

[0128] [Example 10] 4.0% by mass of molybdenum disulfide particles (a1), 4.0% by mass of molybdenum disulfide particles (a2), 2.0% by mass of graphite, 2.0% by mass of PTFE, 60% by mass of NMP, and 20% by mass of MEK solvent were added to 8.0% by mass of polyamideimide resin, and then the mixture was subjected to a dispersion treatment to obtain a coating composition (6) containing molybdenum disulfide particles (a1) and molybdenum disulfide particles (a2). The obtained coating composition (6) was applied to a steel plate and dried in the same manner as in Example 9 to obtain a coating film (6A) for evaluation.

[0129] Example 11 To 8.0% by mass of polyamideimide resin, 0.5% by mass of molybdenum disulfide particles (a1), 7.5% by mass of molybdenum disulfide particles (a2), 2.0% by mass of graphite, 1.5% by mass of PTFE, 0.5% by mass of antimony trioxide, 60% by mass of NMP, and 20% by mass of MEK were added, followed by a dispersion treatment to obtain a coating composition (7) containing molybdenum disulfide particles (a1) and molybdenum disulfide particles (a2). The obtained coating composition (7) was applied to a steel plate and dried in the same manner as in Example 9 to obtain a coating film (7A) for evaluation.

[0130] [Comparative Example 4] 8.0 mass% of molybdenum disulfide particles (a2), 2.0 mass% of graphite, 1.5 mass% of PTFE, 0.5 mass% of antimony trioxide, 60 mass% of NMP, and 20 mass% of MEK were added to 8.0 mass% of polyamideimide resin, and then the mixture was subjected to a dispersion treatment to obtain a coating composition (8) containing molybdenum disulfide particles (a2). The obtained solution was applied to a steel plate and dried in the same manner as in Example 9 to obtain a coating film (8A) for evaluation.

[0131] [Example 12] The steel plate on which the evaluation coating film (5A) obtained in Example 9 was formed was placed on the moving side of a Kawamura-type reciprocating friction tester, and an SUJ2-7 / 32 inch ball was placed on the stationary side. The number of sliding strokes until the terminal friction reached μ = 0.3 was measured under conditions of an initial speed of 9 rpm, a sliding speed of 240 rpm, a stroke of 10 mm, a load of 3 kgf, and a room temperature, dry atmosphere. The number of sliding strokes was 1,801. The results are shown in Table 3 and FIG. 5.

[0132] [Example 13] The number of sliding strokes was measured in the same manner as in Example 12, except that the steel plate on which the evaluation coating film (6A) obtained in Example 10 was formed was placed on the moving side of the Kawamura-type reciprocating friction tester. The number of sliding strokes was 2,789. The results are shown in Table 3 and Figure 5.

[0133] [Example 14] The number of sliding strokes was measured in the same manner as in Example 12, except that a steel plate on which the evaluation coating film (7A) obtained in Example 11 was formed was placed on the moving side of the Kawamura-type reciprocating friction tester. The number of sliding strokes was 2,513. The results are shown in Table 3 and Figure 5.

[0134] [Comparative Example 5] The number of sliding strokes was measured in the same manner as in Example 12, except that the steel plate coated with the evaluation coating film (8A) obtained in Comparative Example 4 was placed on the moving side of the Kawamura-type reciprocating friction tester. The number of sliding strokes was 1,292. The results are shown in Table 3 and Figure 5.

[0135]

[0136] As shown in Table 3 and FIG. 5, in all of Examples 12 to 14, the solid lubricant (A) of the coating films (5A) to (7A) contained molybdenum disulfide particles (a1), and the molybdenum disulfide particles (a1) had a median diameter of primary particles D ５０The aspect ratio, which is the ratio of the diameter (nm) of the crystal to the thickness (nm), is in the range of 2 to 110, and the median diameter D ５０ When the thickness is 50 nm or more and 500 nm or less, the number of sliding cycles until the terminal friction reaches μ=0.3 in a Kawamura type reciprocating friction test is 1800 or more, and it has been found that the film exhibits excellent friction characteristics and durability.

[0137] On the other hand, in Comparative Example 5, the solid lubricant (A) of the coating film (8A) was composed of molybdenum disulfide particles (a2) and did not contain molybdenum disulfide particles (a1). Therefore, in the Kawamura-type reciprocating friction test, the number of sliding cycles until the terminal friction reached μ = 0.3 was 1,300 or less, and the friction characteristics and durability were poor.

[0138] Example 15 Three parts by mass of the molybdenum disulfide particles (a1) obtained in Synthesis Example 2 and 97 parts by mass of UBE NYLON POLYAMIDE 6 1013NW8 manufactured by UBE Corporation were used to produce a 50 mm × 90 mm × 2 mm plate in an injection molding machine PNX-603-5A manufactured by Nissei Plastic Industrial Co., Ltd. under molding conditions of a kneading temperature of 280°C, a mold temperature of 70°C, a filling rate of 100 mm / s, and a pressure of 40 MPa. The obtained plate was sandwiched between a Separoth 55Z manufactured by Kiriyama Manufacturing Co., Ltd. connected to an aspirator, and the pressure was reduced. The aspirator was stopped when the pressure had reached its lowest possible pressure, and the pressure was measured after 1 minute and 2 minutes. The plate was then pressed against a biscuit plate made by firing high-purity alumina (surface roughness Ra = 7.2 μm, maximum 9.4 μm, minimum 4.4 μm, standard deviation 1.3 μm) and rubbed 100 times in a circular motion (scratch treatment). After that, the plate was clamped in a Kiriyama Seisakusho Separot 55Z connected to an aspirator in the same manner as above, and the pressure was reduced. The aspirator was stopped when the pressure had reached its lowest point, and the pressure was measured after 1 minute and 2 minutes. The results are shown in Table 4.

[0139] Comparative Example 6 The pressure before and after the scratch treatment was measured in the same manner as in Example 15, except that molybdenum disulfide particles (a2) were used instead of the molybdenum disulfide particles (a1) in Example 15. The results are shown in Table 4.

[0140]

[0141] As shown in Table 4, it can be seen that the plate of Example 15 maintains high airtightness even after scratching. On the other hand, it can be seen that the airtightness after scratching is inferior in Comparative Example 6. From this, it can be seen that the molded body using molybdenum disulfide particles (a1) is excellent as a sliding member that exhibits high sealing properties against pressure even when subjected to sliding movement.

[0142] REFERENCE SIGNS LIST 10 base layer 20 solid lubricant 21 solid lubricant 22 solid lubricant 100A coating film 100B coating film 101 substrate 102 sliding member 103 liquid lubricant

Claims

1. A solid lubricant (A) is contained, and the solid lubricant (A) has a median diameter D of primary particles. ５０ The aspect ratio, which is the ratio of the diameter (nm) of the nanotube to the thickness (nm), is in the range of 2 to 110, and the median diameter D ５０ The composition comprises molybdenum disulfide particles (a1) having a particle size of 50 nm or more and 500 nm or less.

2. A resin and a solid lubricant (A) are included, and the solid lubricant (A) has a median diameter D of primary particles. ５０ The aspect ratio, which is the ratio of the diameter (nm) of the nanotube to the thickness (nm), is in the range of 2 to 110, and the median diameter D ５０ The composition comprises molybdenum disulfide particles (a1) having a particle size of 50 nm or more and 500 nm or less.

3. The solid lubricant (A) has a median diameter D of the primary particles of the molybdenum disulfide particles (a1). 50 and molybdenum disulfide particles (a2) having a particle size of 600 nm or more and 500 μm or less, and a content ratio ((a1):(a2)) of the molybdenum disulfide particles (a1) to the molybdenum disulfide particles (a2) is 1:0 to 1:20 in terms of mass ratio.

4. Median diameter D of primary particles of molybdenum disulfide particles (a2) ５０ The composition according to claim 3, wherein the average particle size is 1 μm or more and 50 μm nm or less.

5. The composition according to claim 1 or 2, wherein the solid lubricant (A) consists of the molybdenum disulfide particles (a1).

6. The composition according to claim 1 or 2, wherein the content of the solid lubricant (A) is 0.5% by mass or more and 30% by mass or less when the total mass of the composition is 100% by mass.

7. The composition of claim 2, wherein the resin comprises one or more selected from epoxy resins, phenolic resins, polyamide resins, polyimide resins, and polyamideimide resins.

8. The composition according to claim 1 or 2, further comprising a solid lubricant (B), wherein the solid lubricant (B) comprises one or more solid lubricants selected from the group consisting of carbon-based solid lubricants and fluorine-based solid lubricants.

9. The composition of claim 1 or 2, further comprising a solvent, said solvent comprising one or more selected from N-methyl-2-pyrrolidone, gamma-butyrolactone, cyclopentanone, N-ethyl-2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone, dimethylsulfoxide, butyl cellosolve, and methyl ethyl ketone.

10. The composition of claim 1 or 2, which contains antimony trioxide as an antioxidant.

11. The composition of claim 2 which is a coating composition.

12. A coating film which is a cured product of the composition according to claim 11.

13. A sliding member having the coating film according to claim 10.

14. At least a part of the sliding surface has a median diameter D of primary particles. ５０ The aspect ratio, which is the ratio of the diameter (nm) of the nanotube to the thickness (nm), is in the range of 2 to 110, and the median diameter D ５０ A sliding member having a solid lubricant (A) containing molybdenum disulfide particles (a1) having a particle size of 50 nm or more and 500 nm or less.

15. The sliding member according to claim 14, which is a molded article.

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