Lubricants and aerosol lubricant compositions

Abstract

To improve quick drying property of a lubricant that employs tungsten disulfide as its lubricating component.SOLUTION: There is provided a lubricant for use in an aerosol lubricant composition, including tungsten disulfide, i.e., a lubricating component, a binder component, and an alcohol-based solvent, with an average particle diameter of the tungsten disulfide being 8 μm or less.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to the art of lubricant compositions for aerosols. [Background technology]

[0002] In recent years, there has been a demand for lubricant compositions that can be used in special environments such as low temperatures, high temperatures, high pressures, or high vacuums (hereinafter referred to as "special environments"). Among the various forms of lubricant compositions, there is a particularly high demand for aerosol lubricant compositions in which the lubricant is sprayed in a mist (aerosol form) using a propellant (e.g., liquefied gas). Aerosol lubricant compositions are widely used in manufacturing sites in various industries because of their high operability and low contamination with impurities.

[0003] For example, Patent Documents 1 and 2 disclose aerosol lubricant compositions containing lubricating grease as a lubricating component, while Patent Document 3 discloses an aerosol lubricant composition containing a solid lubricant component (polytetrafluoroethylene), an acrylic resin, a fluorocarbon solvent, and a propellant (hydrofluoroolefin).

[0004] However, the techniques of Patent Documents 1 and 2 have the problem of low quick-drying properties because they use lubricating oil as a lubricating component, while the technique of Patent Document 3 has the problem of difficulty in use in special environments because it uses an organic substance as a lubricating component.

[0005] As disclosed in Non-Patent Documents 1 and 2, among various solid lubricant components, tungsten disulfide is known to have excellent lubricating performance even under special environments. Therefore, an aerosol product using tungsten disulfide ("WS2 Spray" manufactured by Nippon Lubricant Co., Ltd.) is commercially available. This aerosol product uses lubricating grease and resin in addition to tungsten disulfide as lubricating components. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 2019-127544 [Patent Document 2] Japanese Patent Application Publication No. 2019-099702 [Patent Document 3] Japanese Patent Application Laid-Open No. 2017-155200 [Non-Patent Document 1] Ayaka Takahashi and Keizo Hashimoto, "Evaluation of Vacuum and High-Temperature Friction Properties of Tungsten Disulfide Baked Films," Journal of the Japan Institute of Metals, Vol. 80, No. 4 (2016) 289-296 [Non-patent document 2] "New Edition Solid Lubrication Handbook" (Compiled by the Solid Lubrication Research Group of the Japanese Society of Tribologists) Yokendo Co., Ltd. Published March 2, 2010 Summary of the Invention [Problem to be solved by the invention]

[0007] However, the above-mentioned aerosol products use lubricating grease and resin as lubricating components, so the problem of low quick-drying properties and difficulty in use in special environments remains unresolved. In consideration of the above circumstances, the object is to improve the quick-drying properties of aerosol lubricant compositions using tungsten disulfide. [Means for solving the problem]

[0008] The lubricant according to the present invention is a lubricant used in an aerosol lubricant composition, and contains tungsten disulfide as a lubricating component, a binder component, and an alcohol-based solvent, and the average particle size of the tungsten disulfide is 8 μm or less. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 2 is a graph showing the particle size distribution of tungsten disulfide particles (fine powder) used in the lubricants according to the examples. [Figure 2]1 is a scanning electron microscope photograph of tungsten disulfide particles used in a lubricant according to an example. [Figure 3] 1 is a photograph of an aerosol lubricant composition using a lubricant according to an example. [Figure 4] FIG. 1 is a graph showing the coefficient of friction for a film formed from an aerosol lubricant composition using a lubricant according to an example. DETAILED DESCRIPTION OF THE INVENTION

[0010] The aerosol lubricant composition according to the present invention can be filled into a spray container and sprayed in aerosol form. The aerosol lubricant composition sprayed from the container forms a coating having lubricating properties. Specifically, the aerosol lubricant composition contains a lubricant (A), a diluent (B), and a propellant (C).

[0011] The lubricant (A) contained in the aerosol lubricant composition contains tungsten disulfide (a1), a binder component (a2), and an alcohol-based solvent (a3).

[0012] Tungsten disulfide (a1) blended into lubricant (A) functions as a lubricating component. The use of tungsten disulfide (a1) as a lubricating component has the advantage of improving quick-drying properties and enabling use in special environments (high temperature, high pressure, vacuum, dry gas, and high load).

[0013] Tungsten disulfide (a1) can be blended into the lubricating component as a powder raw material containing, for example, tungsten disulfide at high purity (95% or more from the viewpoint of improving lubricating performance).

[0014] The average particle size of the tungsten disulfide (a1) (average particle size of the powder raw material) is, for example, 8 μm or less, preferably 6 μm or less, and more preferably 5 μm or less. The lower limit of the average particle size of the tungsten disulfide (a1) is arbitrary, but is, for example, 0.3 μm or more, preferably 0.6 μm or more, and more preferably 1.0 μm or more.

[0015] The average particle size of tungsten disulfide (a1) can be determined from the particle size distribution measured using a laser diffraction / scattering particle size distribution analyzer. The average particle size of tungsten disulfide (a1) is the median diameter (D50) when the cumulative volume distribution is 50% in the particle size distribution where the horizontal axis is particle size and the vertical axis is cumulative volume distribution (%).

[0016] By setting the average particle size of the tungsten disulfide (a1) within the above range, it is possible to prevent the tungsten disulfide (a1) from settling, form a uniform coating, and prevent the spray nozzle from clogging.

[0017] In the particle size distribution of tungsten disulfide (a1), the volume fraction of particles having a particle size of 15 μm or more is, for example, 8% or less, preferably 5% or less, and more preferably 3% or less. Also, in the particle size distribution of tungsten disulfide (a1), the volume fraction of particles having a particle size of 10 μm or less is, for example, 80% or more, preferably 90% or more, and more preferably 95% or more.

[0018] By setting the volume ratio of particles having a particle size of 15 μm or more and particles having a particle size of 10 μm or less in the tungsten disulfide (a1) within the above range, the effect of forming a uniform coating and the effect of preventing clogging of the spray nozzle become significant.

[0019] The content of tungsten disulfide (a1) in the lubricant (A) is, for example, 15 to 55 mass%, preferably 20 to 50 mass%, and more preferably 35 to 45 mass%. By keeping the content of tungsten disulfide within this range, it becomes possible to form a uniform coating without deteriorating the lubricating performance.

[0020] The binder component (a2) contained in the lubricant (A) functions not only as a binder in the formation of the coating but also as a dispersant to improve the dispersion stability of tungsten disulfide. Any organic polymeric compound that dissolves in an alcohol-based solvent can be used as the binder component (a2). For example, one or more polymeric organic compounds selected from various cellulose derivatives such as ethyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, and sodium carboxymethyl cellulose, (meth)acrylic acid copolymers, N-vinyl-2-pyrrolidone copolymers, polyvinylpyrrolidone, etc. can be used as the binder component (a2).

[0021] From the viewpoint of forming a uniform coating film and improving the dispersion stability of tungsten disulfide (a1), ethyl cellulose is suitable as the binder component (a2). When ethyl cellulose is contained as the binder component (a2), the content of ethyl cellulose in the binder component (a2) is, for example, 70 to 100 mass%, preferably 80 to 100 mass%, and more preferably 90 to 100 mass%.

[0022] The content of the binder component (a2) in the lubricant is, for example, 1 to 10 mass%, preferably 2 to 8 mass%, and more preferably 3 to 6 mass%. By setting the content of the binder component (a2) within this range, it is possible to improve lubrication performance without reducing the dispersion stability of the tungsten disulfide (a1).

[0023] The alcohol-based solvent (a3) contained in the lubricant is an alcohol that disperses tungsten disulfide (a1) and dissolves the binder component (a2). Any alcohol can be used as the alcohol-based solvent (a3) as long as it can disperse tungsten disulfide (a1) and dissolve the binder component (a2). The valence and series of the alcohol are not particularly limited. Examples of the alcohol-based solvent (a3) include methanol, ethanol, n-propanol, isopropyl alcohol, n-butanol, isobutyl alcohol, 2-butanol, tert-butyl alcohol, 1-pentanol, 3-methyl-1-butanol, 3-pentanol, n-hexanol, 2-ethylbutanol, n-heptanol, 2-heptanol, 3-heptanol, n-octanol, 2-ethylhexanol, n-nonanol, n-decanol, n-undecanol, n-dodecanol, butanediol, propylene glycol, and pentanediol. One or more alcohols selected from the group consisting of ethanol, cyclohexanol, 2-methylcyclohexanol, ethylene glycol, diethylene glycol, triethylene glycol, glycerin, cyclohexanol, cyclopentanol, 2-methylcyclohexanol, benzyl alcohol, phenol, 1-methoxy-2-propanol, 1-ethoxy-2-propanol, methoxybutanol, 3-methoxybutanol, and 3-methyl-3-methoxybutanol are used as the alcoholic solvent (a3).

[0024] The content of the alcohol-based solvent (a3) in the lubricant (A) is, for example, 40 to 85 mass %, preferably 50 to 70 mass %, and more preferably 55 to 65 mass %. By keeping the content of the alcohol-based solvent (a3) within this range, quick-drying properties can be improved.

[0025] The lubricant (A) according to the present invention may contain various other additives, provided that they do not affect quick-drying properties or safety. Examples of such additives include lubricity improvers such as extreme pressure agents, oiliness agents, and antifriction and antiwear agents, rust inhibitors, antioxidants, corrosion inhibitors, antifoaming agents, hard-cake inhibitors, and anti-settling agents.

[0026] From the viewpoint of quick drying, the lubricant (A) according to the present invention is preferably configured without using an oil (i.e., configured with an oil content of 0% by mass). When an oil is contained in the lubricant (A), the content is, for example, 2% by mass or less, preferably 1% by mass or less, and more preferably 0.1% by mass or less.

[0027] The diluent (B) contained in the aerosol lubricant composition is used to dilute the lubricant (A). The diluent (B) is not particularly limited as long as it is compatible with the lubricant (A) and is safe, but a low-boiling, fast-drying organic solvent is preferred. For example, one or more organic solvents selected from normal hexane, isohexane, normal heptane, isoheptane, cyclopentane, cyclohexane, xylene, toluene, etc. are used as the diluent (B). Among these, cyclopentane is preferred as the diluent (B).

[0028] In the aerosol lubricant composition, the mass ratio of the diluent (B) to the lubricant (A) ((B) / (A)) is appropriately set depending on the application and purpose, and is, for example, 0.2 to 2, preferably 0.3 to 1.5, and more preferably 0.4 to 1. Note that the diluent (B) is not essential in the present invention. The presence or absence of the diluent (B) is appropriately selected depending on the application and purpose.

[0029] The propellant (C) contained in the aerosol lubricant composition is used to spray the lubricant (A) in an aerosol form. The propellant (C) is not particularly limited and can be selected from known propellants. For example, LPG (liquefied petroleum gas), DME (dimethyl ether), carbon dioxide, nitrogen, nitrous oxide, fluorohydrocarbons, etc. are used as the propellant (C). Among these, LPG or DME is preferred as the propellant (C).

[0030] In the aerosol lubricant composition, the mass ratio of the propellant (C) to the lubricant (A) ((C) / (A)) is, for example, 1 to 7, preferably 2 to 6, and more preferably 2 to 5. By keeping the mass ratio of the propellant (C) to the lubricant (A) within this range, the lubricant (A) can be appropriately aerosolized.

[0031] If the content of tungsten disulfide (a1) in the aerosol lubricant composition is too low, the lubricating performance of the formed coating will decrease, and if it is too high, a uniform coating will not be formed. Therefore, the content of tungsten disulfide (a1) in the aerosol lubricant composition is, for example, 3 to 20 mass%, preferably 4 to 18 mass%, and more preferably 5 to 15 mass%.

[0032] If the content of the binder component (a2) in the aerosol lubricant composition is too low, the dispersion stability of the tungsten disulfide (a1) decreases, preventing the formation of a uniform coating, while if the content is too high, the lubricating performance of the coating decreases. Therefore, the content of the binder component (a2) in the aerosol lubricant composition is, for example, 0.3 to 2.0 mass%, preferably 0.4 to 1.8 mass%, and more preferably 0.5 to 1.5 mass%.

[0033] As can be understood from the above explanation, by appropriately setting the contents of tungsten disulfide (a1) and binder component (a2) in the aerosol lubricant composition, it is possible to improve the dispersion stability of the solid lubricant particles and form a uniform coating without reducing the lubricating performance of the coating (tungsten disulfide).

[0034] Aerosol lubricant compositions that use an oil as a lubricating component have poor drying properties, and may drip immediately after spraying onto a vertical surface, or the coating may attract surrounding dust. In contrast, the aerosol lubricant composition of the present invention uses lubricant (A) (i.e., lubricant (A) that uses tungsten disulfide (a1) as the lubricating component), which allows for improved drying properties. Furthermore, because it does not use an oil as a lubricating component, it can be used in places where the use of oil is prohibited or in special environments such as vacuums.

[0035] Furthermore, the aerosol lubricant composition of the present invention does not use organic substances such as resins as lubricating components, and therefore can be used even in special environments such as high pressure (high load).

[0036] When an aerosol lubricant composition containing an oil or resin as a lubricating component is used under special environments such as high temperatures, the oil or resin may decompose or oxidize, resulting in deterioration. In contrast, the aerosol lubricant composition of the present invention can be used under special environments without deterioration and has excellent lubricating properties.

[0037] Furthermore, by using tungsten disulfide (a1) having an average particle size of 8 μm or less as a lubricating component, a stable aerosol lubricant composition with high quick-drying properties and good dispersibility can be obtained. Note that the effects described above for the aerosol lubricant composition can also be achieved with the lubricant (A) alone. [Example]

[0038] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0039] <Lubricant> The lubricants were prepared according to the formulations in Table 1 as follows: (1) 2-propanol and 1- B An alcohol solvent is prepared by mixing ethanol and 1-methoxy-2-propanol. (2) Ethyl cellulose (Kanto Chemical, Grade 1, product number 14076-01), a binder component, is added to an alcohol-based solvent and completely dissolved until the entire mixture becomes a transparent gel. (3) Add tungsten disulfide powder, a lubricant component, and stir to disperse. The tungsten disulfide powder is a fine powder prepared by sieving tungsten disulfide powder (purity: 99%) manufactured by Japan Lubricant Co., Ltd. to remove large particles.

[0040] [Table 1]

[0041] The properties of the tungsten disulfide powder (fine powder) prepared in (3) were confirmed by particle size distribution and electron microscope.

[0042] [Particle size distribution] The particle size distribution was measured using a laser diffraction / scattering particle size distribution measuring device (LA-950V2 manufactured by Horiba Ltd.).

[0043] The specific measurement conditions are as follows: Dispersion medium: Purified water Pre-treatment dispersion treatment: ultrasonic irradiation for 3 minutes Measurement method: circulation type Solvent refractive index: 1.333 Sample refractive index: 2.000-0.000i Particle size basis: volume Number of repetitions: 15

[0044] Figure 1 is a diagram showing the particle size distribution of tungsten disulfide particles according to the example. As shown in Figure 1, it was confirmed that the average particle size (median diameter) was about 4.0 µm, and that no coarse particles with a particle size of 15 µm or more were included.

[0045] [Powder X-ray diffraction] The crystal structure of the tungsten disulfide particles (fine powder) according to the example was analyzed using a powder X-ray diffractometer (RINT, manufactured by Rigaku Corporation).

[0046] The specific measurement conditions are as follows: X-ray: Cu / 40 kV / 30 mA Counting time / scan speed: 2 deg / min Goniometer: Ultima+ horizontal goniometer Sampling width: 0.02 deg Scan axis: 2θ / θ Scanning range: 5~80 deg Length limit slit: 10 mm Entrance slit: 1° Receiving slit 1:1° Receiving slit 2: 0.3 mm Detector: Scintillation counter Scan Mode: Continuous

[0047] [Electron microscope observation] The surface of the tungsten disulfide particles according to the example was imaged using a scanning electron microscope (JEOL Ltd.: JSM-6610LA). As a pretreatment, the tungsten disulfide particles were fixed on carbon tape, and then gold was vapor-deposited. The accelerating voltage during measurement was 15 kV.

[0048] Figure 2 is an electron microscope photograph of the tungsten disulfide particles according to the example. From the electron microscope photograph in Figure 2, it was confirmed that the particle size of the tungsten disulfide particles (fine powder) according to the example was about 1 to 10 µm.

[0049] <Aerosol Lubricant Composition> The aerosol lubricant composition was filled into a pressure-resistant glass container (Tokyo Polymer Co., Ltd.: aerosol test bottle valve set product, capacity 100 ml) according to the formulation in Table 2. Figure 3 is a photograph of the aerosol lubricant composition filled into the pressure-resistant glass container.

[0050] [Table 2]

[0051] It was confirmed that the pressure-resistant glass container filled with the aerosol lubricant composition of the example could be sprayed simply by pressing a button. It was also confirmed that the aerosol lubricant composition of the example had good dispersibility of tungsten disulfide and did not clog the spray nozzle.

[0052] [Coating preparation] The aerosol lubricant composition was sprayed onto the surface of a stainless steel substrate (SUS304) to form a coating. The coating did not drip when sprayed onto a vertical surface, and 30 seconds after spraying, the coating was completely dry and did not come off even when rubbed with a finger.

[0053] [Measurement of friction coefficient] Using a friction and wear tester (FPR-2000 manufactured by Rhesca Corporation), the coefficient of friction was measured for the coating formed on the stainless steel substrate, the coating after heat treatment at 400°C in air for 10 minutes, and the underlying stainless steel substrate (SUS304).

[0054] The specific measurement conditions are as follows: Mating material: Pin (SUJ2: tip φ10 mm) Load: 50g Linear velocity: 0.5236 cm / sec (rotating circle diameter φ5 mm, rotation speed 10 rpm) Environmental temperature: 22~25℃ Relative humidity: 45-55% Measurement time: 50 minutes

[0055] Figure 4 shows the results of measuring the coefficient of friction. As shown in Figure 4, the coatings (before and after heat treatment) formed using the aerosol lubricant compositions of the examples exhibit good lubricity. It is empirically known that coatings formed using conventional aerosol lubricant compositions (e.g., aerosol lubricant compositions using oil as a lubricating component) have sufficiently good lubricity immediately after formation, but the coefficient of friction increases after heat treatment at high temperatures (e.g., 400°C). In contrast, it was confirmed that the coefficient of friction of the coatings formed using the aerosol lubricant compositions of the present invention further decreases (i.e., the lubrication performance improves) after heat treatment at high temperatures (e.g., 400°C).

Claims

1. 1. A lubricant for use in an aerosol lubricant composition, comprising: The lubricating agent contains tungsten disulfide as a lubricating component, a binder component, and an alcohol-based solvent, The average particle size of the tungsten disulfide is 8 μm or less, the binder component is a cellulose derivative, The alcohol-based solvent includes one or more selected from isopropyl alcohol, n-butanol, and 1-methoxy-2-propanol. Lubricant.

2. In the particle size distribution of the tungsten disulfide, the volume ratio of particles having a particle size of 15 μm or more is 8% or less. The lubricant of claim 1.

3. In the particle size distribution of the tungsten disulfide, the volume ratio of particles having a particle size of 10 μm or less is 80% or more. The lubricant of claim 1 or claim 2.

4. The binder component is ethyl cellulose. The lubricant according to any one of claims 1 to 3.

5. The content of the tungsten disulfide is 15 to 55 mass %. The lubricant according to any one of claims 1 to 4.

6. The content of the binder component is 1 to 10% by mass. The lubricant according to any one of claims 1 to 5.

7. The lubricant of any one of claims 1 to 6, a propellant, and 1. An aerosol lubricant composition comprising:

8. The content of the tungsten disulfide is 3 to 20 mass %. The aerosol lubricant composition of claim 7.

9. The content of the binder component is 0.3 to 2.0 mass %.

9. The aerosol lubricant composition of claim 7 or claim 8.

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