Lubricants, materials having a lubricating film, and methods for manufacturing the same.

Abstract

To provide a lubricant capable of forming a lubricating coat that has low frictional coefficients and also ensures sufficient retention of the frictional coefficients.SOLUTION: A lubricant includes tungsten sulfide (component A) and at least one selected from bismuth sulfide, tin sulfide, chromium sulfide, and iron sulfide (component B) but is free of silver sulfide.SELECTED DRAWING: None

Description

[Technical Field]

[0001] This invention relates to lubricants. Furthermore, this invention relates to materials having a lubricating film and methods for producing the same. [Background technology]

[0002] In recent years, the electrification of automobiles and machinery has progressed, leading to a demand for further fuel efficiency, longer lifespan, and higher efficiency. Therefore, there is a need for lubricants that can form a low-friction lubricating film that can withstand damage such as frictional heat, wear, and seizure.

[0003] For example, Patent Document 1 discloses a graphene-containing film lubricant.

[0004] Furthermore, as described in Non-Patent Document 1, tungsten sulfide has a layered structure similar to molybdenum sulfide and is known as a solid lubricant with good lubricity (low coefficient of friction).

[0005] On the other hand, even among sulfides, bismuth, tin, chromium, and iron sulfides are generally often used as friction materials for brake pads (Patent Document 2). Brake pads are used for braking automobiles and the like, and depending on the temperature conditions, a friction coefficient of 0.25 or higher is generally required (JIS D4411-1993). [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Special Publication No. 2020-510121 [Patent Document 2] Japanese Patent Publication No. 2021-161342 [Non-patent literature]

[0007] [Non-Patent Document 1] Warren E. Jamison, "Crystalline Solid Lubricants," Lubrication, Vol. 31, No. 6, 369-373 (1986) [Overview of the project] [Problems that the invention aims to solve]

[0008] Tungsten sulfide is a good lubricant, but there is room for improvement in terms of forming a lubricating film with excellent friction coefficient retention performance.

[0009] In view of the above circumstances, one of the objectives of the present invention is to provide a lubricant capable of forming a lubricating film that has a low coefficient of friction and excellent friction coefficient retention performance. [Means for solving the problem]

[0010] As a result of extensive experimentation, the inventors discovered that when tungsten sulfide is used in combination with a predetermined metal sulfide that can form a film with a high coefficient of friction, which is commonly used as a friction material, it is possible to form a lubricating film that has a coefficient of friction of the same or lower than that formed by tungsten sulfide alone, and that also has excellent friction coefficient retention performance. This led to the completion of the present invention.

[0011] The present invention is exemplary as follows: [1] A lubricant containing tungsten sulfide (component A) and at least one selected from bismuth sulfide, tin sulfide, chromium sulfide, and iron sulfide (component B), but without silver sulfide. [2] Total number of moles of component A (A M The total number of moles of component B relative to (B M ) ratio (B M / A M The lubricant described in [1], wherein the value is in the range of 0.005 or more and 10 or less. [3] A method for producing a material having a lubricating film, comprising the step of bringing the lubricant described in [1] or [2] into contact with the material surface and then drying it. [4] As an element, in addition to W and S, it contains at least one selected from Bi, Sn, Cr, and Fe, and in terms of atomic ratio, 0.05 ≦ W / S ≦ 1.0 and 0.1 ≦ W / (Bi + Sn + Cr + Fe) ≦ 110, and it is a material having a lubricating film.

Advantages of the Invention

[0012] According to one embodiment of the present invention, it is possible to provide a lubricant capable of forming a lubricating film with a low friction coefficient and excellent retention performance of the friction coefficient. And by using the lubricant, it is possible to form a lubricating film that can effectively prevent damage to two or more moving surfaces such as those of automobiles and machines.

Modes for Carrying Out the Invention

[0013] Hereinafter, embodiments of the present invention including a lubricant and a material having a lubricating film will be described in detail. Note that the present invention can be arbitrarily changed without departing from the gist of the present invention and is not limited to the following embodiments.

[0014] [1. Lubricant] According to an embodiment of the present invention, there is provided a lubricant containing tungsten sulfide (component A) and at least one selected from bismuth sulfide, tin sulfide, chromium sulfide, and iron sulfide (component B), and not containing silver sulfide. As described above, tungsten sulfide as component A is known as a lubricant and can form a film with a low coefficient of friction. On the other hand, component B is known as a friction material and a film with a high coefficient of friction can be obtained. Therefore, it is predicted that a lubricant combining both will form a film with a higher coefficient of friction than component A. However, the inventor has surprisingly found that by combining component A that forms a film with a low coefficient of friction and component B that forms a film with a high coefficient of friction, a lubricating film having a coefficient of friction equal to or lower than that of component A can be obtained. In addition, it has been confirmed that the lubricating film obtained by the lubricant combining component A and component B is superior in the retention performance of the coefficient of friction to component A, that is, superior in durability. Therefore, according to the lubricant of the present invention, a lubricating film capable of effectively preventing damage to two or more moving surfaces such as those of an automobile or a machine can be provided, thereby achieving fuel savings and extended life of the automobile or machine.

[0015] The blending ratio of component A and component B is not particularly limited as long as the effects of the present invention are not inhibited. In terms of effects, the minimum value of the ratio (B M ) of the total number of moles of component B (B M ) to the total number of moles of component A (A M / A M ) is preferably 0.005, 0.1, 0.4 in this order, and the maximum value is preferably 10.0, 9.0, 8.0, 7.0, 6.0, 5.0 in this order. When only bismuth sulfide is used as component B, the minimum value of the ratio (B M / A M ) is preferably 0.005, 0.3, 0.4 in this order, and the maximum value is preferably 10.0, 9.0, 8.0, 7.0, 6.0, 5.0, 4.0, 3.0, 2.0, 1.5, 1.0 in this order. When only tin sulfide is used as component B, the ratio (B M / A MThe minimum value of (B) is preferably in the order of 0.005, 0.3, 1.0, and 1.4, and the maximum value is preferably in the order of 10.0, 9.0, 8.0, 7.0, 6.0, 5.0, 4.0, 3.0, 2.0, and 1.5. When only chromium sulfide is used as component B, the ratio (B) M / A M The minimum value of (B) is preferably 0.005, and the maximum value is preferably in the order of 10.0, 9.0, 8.0, 7.0, 6.0, 5.0, 4.0, 3.0, 2.0, 1.5, 1.0, 0.5, 0.2, 0.15, and 0.1. When only iron sulfide is used as component B, the ratio (B) M / A M The minimum value of ) is preferably in the order of 0.005, 0.01, 0.02, 0.3, 1.0, 1.5, 2.0, and 2.5, and the maximum value is preferably in the order of 10.0, 9.0, 8.0, 7.0, 6.0, 5.0, 4.0, 3.5, 3.0, and 2.9.

[0016] <Ingredient A> Component A is tungsten sulfide. Tungsten sulfide may be a natural or synthetic product. In this specification, tungsten sulfide means tungsten disulfide (WS2), which is a compound of tungsten and sulfur.

[0017] <Component B> Component B is at least one selected from bismuth sulfide, tin sulfide, chromium sulfide, and iron sulfide. These may be natural or synthetic products. One of these sulfides may be used, or two or more may be used in combination. In this specification, bismuth sulfide refers to a compound of bismuth and sulfur, and includes dibismuth trisulfide (Bi2S3), bismuth monosulfide (BiS), bismuth disulfide (BiS2), and the like. In this specification, tin sulfide refers to a compound of tin and sulfur, and includes tin monosulfide (SnS), tin disulfide (SnS2), tin trisulfide (Sn2S3), and the like. In this specification, chromium sulfide refers to a compound of chromium and sulfur, and includes chromium monosulfide (CrS), dichromium trisulfide (Cr2S3), and the like. In this specification, iron sulfide refers to a compound of iron and sulfur, including iron monosulfide (FeS), iron disulfide (FeS2), diferric trisulfide (Fe2S3), heptaferric octasulfide (Fe7S8), and nonaferric decasulfide (Fe9S2). 10 ), 11 iron dodeculfide (Fe 11 S 12 Examples include:

[0018] <Solvent> In one embodiment, the lubricant according to the present invention can be provided as a liquid in which components A and B are dispersed in a solvent. The solvent can be water (e.g., deionized water), but it is also possible to use water-miscible organic solvents such as ketone solvents such as acetone and methyl ethyl ketone; amide solvents such as N,N'-dimethylformamide and dimethylacetamide; alcohol solvents such as methanol, ethanol, and isopropanol; ether solvents such as ethylene glycol monobutyl ether and ethylene glycol monohexyl ether; and pyrrolidone solvents such as 1-methyl-2-pyrrolidone and 1-ethyl-2-pyrrolidone. From the viewpoint of easier handling of the lubricant, it is preferable to use water (e.g., deionized water).

[0019] <Other ingredients> In one embodiment, the lubricant according to the present invention may contain one or more additives in addition to component A, component B, and solvent. The additives are not limited to those listed above, but may include, for example, resin components, dispersants, surfactants, antifungal agents, and other additives used in existing lubricants, provided they do not impair the effects of the present invention. In one embodiment, the lubricant according to the present invention has a total content of component A and component B in the total mass of the lubricant excluding the solvent of 80% by mass or more, typically 85% by mass or more, and more typically 90% by mass or more.

[0020] [2. Method for manufacturing lubricants] The above lubricant can be manufactured by mixing component A, component B, and, if necessary, a desired additive with a solvent.

[0021] [3. Method for manufacturing a material having a lubricating film] According to one embodiment of the present invention, a method for manufacturing a material having a lubricating film is provided, which includes a step of drying after bringing a lubricant into contact with the material surface. By this manufacturing method, a material having a lubricating film, as described later, can be obtained.

[0022] <Material> The materials to which the lubricant according to the present invention is applied are not particularly limited, but examples include all metal materials (including metal materials and composite materials made of different metal materials), all plastic materials (including resin materials and composite materials made of different resin materials), composite materials made of metal materials and resin materials, and materials whose surfaces are formed of any of these materials (for example, plated metal materials). There are no particular restrictions on the shape of the material, but it may be molded products such as castings and forgings; components such as bearings; rods; strips; tubes; wires; foils; or plates. Typically, examples include sliding parts in automobiles and various machines where low friction is required, such as various bearings, drive parts such as speed increasers, reducers, and transmissions, drive parts of motors, various gears, various shafts, piston pins, piston skirts, cams and followers, cylinders, chains, connecting rods, valves, valve guides, hubs, springs, pins, couplings, etc., where rotational sliding, surface sliding, and sliding sliding occur. If the surface includes a metal material, the material may be one in which the surface of the metal material has undergone chemical conversion treatment. Examples of chemical conversion treatments include those using phosphates such as iron phosphate, zinc phosphate, zinc calcium phosphate, and manganese phosphate, as well as treatments using iron oxalate, aluminum fluoride, zirconium, titanium, hafnium, and vanadium.

[0023] <Pre-washing> Although not mandatory, prior to lubrication, pre-cleaning may be performed as appropriate, such as washing with an alkaline degreaser, hot water washing, acid washing, or solvent washing, to remove oil and dirt adhering to the material to be treated, including metal materials on the surface. If pre-cleaning is performed, it is preferable to rinse with water afterward to ensure that no cleaning solution remains on the material surface.

[0024] <Formation of a lubricating film> The method of contacting the material surface with the lubricant is not particularly limited, and examples include application methods such as roll coating, immersion, spraying, and bar coating. There are no particular restrictions on the lubricant temperature at contact, but 10°C to 80°C is preferred, and 15°C to 60°C is more preferred. After contacting the material with the lubricant, the lubricant is dried. Drying forms a highly durable lubricating film. Drying methods include heat drying treatment of the material that has come into contact with the lubricant and natural drying. Examples of heat drying treatments include dryers, hot air furnaces, high-frequency induction heating furnaces, infrared furnaces, etc., but there are no particular restrictions on the heat drying treatment method as long as the solvent contained in the lubricant evaporates. In addition, the drying time can be appropriately selected to the optimal conditions.

[0025] <Lubricating film> The lubricating film according to one embodiment of the present invention contains, as elements, W and S, as well as at least one selected from Bi, Sn, Cr, and Fe. The atomic ratio of W to S in the lubricating film (W / S) is preferably in the order of minimum values ​​of 0.05, 0.1, and 0.12, and in the order of maximum values ​​of 1.0, 0.7, 0.45, and 0.40. The atomic ratio of W, Bi, Sn, Cr, and Fe in the lubricating film [W / (Bi+Sn+Cr+Fe)] is preferably in the order of minimum values ​​of 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.15, 1.2, 1.4, 1.5, and 1.6, and in the order of maximum values ​​of 110, 105, 100, 80, 50, 30, 20, 10, 5.0, 3.5, and 2.0. Furthermore, the amount of each element in the lubricating film can be determined by elemental analysis using energy-dispersive X-ray fluorescence spectrometry.

[0026] The lubricating film according to one embodiment of the present invention may contain elements corresponding to the aforementioned additives in addition to the elements corresponding to components A and B. However, in one embodiment of the present invention, the total content of W, S, Bi, Sn, Cr, and Fe in the lubricating film is 80% by mass or more, typically 85% by mass or more, and more typically 90% by mass or more. Furthermore, the lubricating film according to one embodiment of the present invention does not contain Ag.

[0027] The amount of lubricating film deposited is not particularly limited and can be adjusted as needed. The amount can be adjusted by changing the lubricant composition (especially the solvent concentration), as well as the contact conditions between the material and the lubricant, such as the contact method, contact temperature, and contact time. For example, expressed as the mass of the lubricating film per unit area of ​​the material surface, it ranges from 0.5 to 20 g / m². 2 It can be set to 2-10 g / m², typically 2-10 g / m². 2 It can be done this way. [Examples]

[0028] Examples of the present invention and its advantages are shown below, along with comparative examples, to better illustrate the invention. However, the present invention is not limited by these examples.

[0029] (1. Preparation of lubricant) Component A was tungsten disulfide (WS2) powder, and component B was sulfide powders shown in Tables 1-1, 1-2, and 2. Lubricants for Examples 1-34 and Comparative Examples 1-6 were prepared by adding components A and B to deionized water in the molar percentages shown in Tables 1-1, 1-2, and 2, with their sum totaling 100%, and stirring at 25°C for 1 hour.

[0030] (2. Preparation of test plates with a lubricating coating) (1) Degreasing: A test plate (metal material; SPCC-SD, 70mm x 150mm x 0.8mm) was immersed for 10 minutes in a commercially available degreasing agent (Fine Cleaner E6400, manufactured by Nippon Parkerizing Co., Ltd., concentration 20g / L) heated to 60°C. (2) Washing: The degreased test plate was immersed in tap water at 20°C for 30 seconds. (3) Drying: The test plates were dried using an air blower after washing with water. (4) Lubrication treatment (contact process): Using a bar coater, lubricants from Examples 1 to 34 and Comparative Examples 1 to 6 (see Tables 1-1, 1-2, and 2) were applied to the test plates, respectively. (5) Drying: The test plate coated with lubricant was dried at 70°C for 3 minutes.

[0031] (3. Method for measuring the amount of film adhesion) The amount of lubricating film attached to the test plate prepared using the above procedure was determined by the following formula. The results are shown in Tables 1-1, 1-2, and 2. Film adhesion amount (g / m 2 ) = (Mass of test plate after lubrication treatment - Mass of test plate before lubrication treatment) / Surface area of ​​test plate

[0032] (4. Elemental analysis of the coating) The lubricating film on the test plate prepared using the above procedure was subjected to elemental analysis by energy-dispersive X-ray fluorescence spectrometry. The analysis conditions were as follows. The results are shown in Tables 1-1, 1-2, and 2. <Analysis conditions> Measuring device: Oxford Instruments, Model X-MaxN50 (Included with scanning electron microscope, JEOL JSM-IT100) Acceleration voltage: 15kV Spot size: 70 Measurement magnification: 100x Working distance: 10mm Analysis time: 90 seconds

[0033] (5. Coefficient of friction and durability) The friction coefficient and durability (number of sliding cycles) were measured using the Bowden test. A steel ball was brought into contact with the surface of a test plate with a lubricating film prepared according to the procedure described above, under a constant load. The test plate was then slid, and the friction coefficient and the number of sliding cycles were measured for evaluation. The average friction coefficient up to 100 sliding cycles was calculated and used as the baseline value. The measurement ended when the friction coefficient increased by 20% above the baseline value. The average friction coefficient from the start of sliding to the measurement end point was calculated as the average friction coefficient, and durability was evaluated based on the number of sliding cycles up to the measurement end point. For the average friction coefficient, evaluations S, A, and B were considered passing grades. For durability, evaluations of S and A based on the number of sliding cycles were considered passing grades. Specific test conditions and evaluation criteria are as follows. The evaluation results are shown in Tables 1-1, 1-2, and 2.

[0034] <Test Conditions> Measuring device: Shinto Scientific Tribogear TYPE14FW Load: 58.8N Indenter: 5mmφSUJ2 steel ball Sliding distance: 10mm Sliding speed: 10 mm / s Test temperature: 50℃

[0035] <Evaluation Criteria> Average coefficient of friction S: Less than 0.035 A: 0.035 or higher, less than 0.045 B: 0.045 or higher, less than 0.055 C: 0.055 or higher, less than 0.10 D:0.10 or more

[0036] Number of sliding movements S: Over 1000 times A: 500 times or more but less than 1000 times B: 250 times or more but less than 500 times C: 50 to less than 250 times D: Less than 50 cycles, or the coefficient of friction exceeds 0.3 within 20 sliding cycles.

[0037] [Table 1-1]

[0038] Table 1-2

[0039] Table 2

Claims

1. A lubricant containing tungsten sulfide (component A) and at least one selected from bismuth sulfide, tin sulfide, chromium sulfide, and iron sulfide (component B), but without silver sulfide.

2. Total number of moles of component A (A M The total number of moles of component B relative to (B M ) ratio (B M / A M The lubricant according to claim 1, wherein the value of ) is in the range of 0.005 or more and 10 or less.

3. A method for producing a material having a lubricating film, comprising the step of bringing the lubricant described in claim 1 or 2 into contact with the material surface and then drying it.

4. A lubricating film made from a lubricant that contains tungsten sulfide (component A) and at least one selected from bismuth sulfide, tin sulfide, chromium sulfide, and iron sulfide (component B), but does not contain silver sulfide, wherein the lubricating film contains, as an element, at least one selected from Bi, Sn, Cr, and Fe in addition to W and S, and the atomic ratio is 0.05 ≤ W / S ≤ 0.45 and 0.1 ≤ W / (Bi + Sn + Cr + Fe) ≤ 110.

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