Lubricating coating composition and lubricating coating

Abstract

To provide a composition for a lubricating coating film and a lubricating coating film that use an alternative material to PFAS and have high lubricity.SOLUTION: A composition for a lubricating coating film comprises a first polyethylene having a weight-average molecular weight of 1,000,000 or more and a second polyethylene having a density of 0.94 g / cm3 or more. A total amount of the first polyethylene and the second polyethylene is 15 mass% or more to 40 mass% or less with respect to a total amount of the composition for a lubricating coating film.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a lubricating coating composition and a lubricating coating. [Background technology]

[0002] In a sliding device having a sliding surface, it is preferable to provide a lubricating coating film on the sliding surface to improve lubricity, from the viewpoint of reducing the coefficient of friction during sliding.

[0003] For example, Patent Document 1 discloses a paint composition for forming a lubricating coating, which contains a phenolic resin, an epoxy resin, and a solid lubricant. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Special Publication No. 2017-514928 Summary of the Invention [Problem to be solved by the invention]

[0005] In recent years, restrictions on fluorinated organic compounds (PFAS) have been considered and implemented in various countries around the world. As a result, PFASs, such as polytetrafluoroethylene (PTFE), which have traditionally been used in lubricating coatings to achieve low friction coefficients, may become unusable or their usage may be restricted. Therefore, alternative materials to PFASs in lubricating coatings are being investigated. Lubricating coatings using alternative materials to PFASs are expected to have high lubricity, similar to that of lubricating coatings using PFASs.

[0006] The present invention has been made in view of the above circumstances, and aims to provide a lubricating coating composition and a lubricating coating that use an alternative material to PFAS and have high lubricity. [Means for solving the problem]

[0007] The present inventors have conducted extensive research to solve the above problems. As a result, they have discovered a first polyethylene having a weight-average molecular weight of 1,000,000 or more and a second polyethylene having a density of 0.94 g / cm. 3 The present inventors have found that the above-mentioned problems can be solved by a lubricating coating composition comprising the above-mentioned second polyethylene, wherein the total amount of the first polyethylene and the second polyethylene is 15% by mass or more and 40% by mass or less, based on the total amount of the lubricating coating composition, and have completed the present invention.

[0008] That is, the present invention includes the following aspects. [1] A first polyethylene having a weight average molecular weight of 1 million or more and a density of 0.94 g / cm 3 A lubricating coating composition comprising the above second polyethylene, the total amount of the first polyethylene and the second polyethylene is 15% by mass or more and 40% by mass or less, based on the total amount of the lubricating coating composition; Composition for lubricating coatings. [2] The median diameter of the first polyethylene is 70 μm or less, The median diameter of the second polyethylene is 70 μm or less. [1] The lubricating coating composition according to [1]. [3] The lubricating coating composition contains 5% by mass or more and 10% by mass or less of an amide-modified polyethylene wax relative to the total amount of the lubricating coating composition. [1] or [2]. A lubricating coating composition according to the present invention. [4] The median diameter of the amide-modified polyethylene wax is 70 μm or less. [3] The lubricating coating composition according to [3]. [5] The lubricating coating composition contains 50% by mass or more and 70% by mass or less of engineering plastics based on the total amount of the lubricating coating composition. The lubricating coating composition according to any one of [1] to [4]. [6] Substantially free of organic fluorine compounds, The lubricating coating composition according to any one of [1] to [5]. [7] A lubricating coating comprising the lubricating coating composition according to any one of [1] to [6], the first polyethylene and the second polyethylene are present in an island-like pattern on the surface of the lubricating coating; Lubricating coating. [8] A method for producing a lubricating coating, comprising the step of producing a lubricating coating using the lubricating coating composition according to any one of [1] to [6], wherein the step of producing the lubricating coating comprises a baking step of baking the lubricating coating composition at a temperature equal to or higher than the melting points of the first polyethylene and the second polyethylene. A method for producing a lubricating coating. [Effects of the Invention]

[0009] According to the present invention, it is possible to provide a lubricating coating composition and a lubricating coating that use an alternative material to PFAS and have high lubricity. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a cross-sectional view of a base material having a lubricating coating film formed thereon. [Figure 2] FIG. 2 is a diagram showing an example of the composition of a lubricating coating film according to the present embodiment. [Figure 3] FIG. 1 is a diagram showing the results of an example. DETAILED DESCRIPTION OF THE INVENTION

[0011] Below, we will explain in detail the embodiment of the present invention (hereinafter referred to as the ``present embodiment''), but the present invention is not limited to this and various modifications are possible within the scope of the gist of the present invention.

[0012] 1. Composition for lubricating coating film 1.1.Polyethylene The lubricating coating composition of this embodiment contains multiple types of polyethylene. The content of the polyethylene relative to the total amount of the lubricating coating composition is preferably 0.2 to 100 mass%, 0.5 to 95 mass%, 1 to 90 mass%, 2 to 80 mass%, 3 to 70 mass%, 4 to 60 mass%, 5 to 55 mass%, 10 to 50 mass%, or 15 to 40 mass%. The lower limit of the polyethylene content relative to the total amount of the lubricating coating composition may be 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, or 60 mass%. The upper limit of the polyethylene content relative to the total amount of the lubricating coating composition may be 100, 95, 90, 85, 80, 75, 70, 65, or 60 mass%. The lower limit and the upper limit may be combined in any combination.

[0013] The polyethylene contained in the lubricating coating composition of this embodiment is not particularly limited, but may include, for example, one or more selected from the group consisting of ultra-high molecular weight polyethylene (UHMW-PE), high density polyethylene (HDPE), medium density polyethylene (MDPE), linear low density polyethylene (LLDPE), low density polyethylene (LDPE), very low density polyethylene (VLDPE), and polyethylene oxide, or may be one or more selected from these groups. UHMW-PE is polyethylene with a weight average molecular weight of 1 million or more. HDPE has a density of 0.94 g / cm. 3 MDPE is polyethylene with a density of 0.93 g / cm 3 More than 0.94g / cm 3 LDPE is polyethylene with a density of 0.91 g / cm 3 More than 0.93g / cm 3 VLDPE is polyethylene with a density of 0.91 g / cm 3 LLDPE is polyethylene with a density of 0.910 g / cm 3 More than 0.925g / cm 3 The polyethylene is as follows: The weight average molecular weight can be determined, for example, by a GPC measurement method using polystyrene equivalent.

[0014] The lubricating coating composition of this embodiment comprises a first polyethylene having a weight average molecular weight of 1,000,000 or more and a polyethylene terephthalate having a density of 0.94 g / cm 3 and the second polyethylene, wherein the total amount of the first polyethylene and the second polyethylene is 15% by mass or more and 40% by mass or less of the total amount of the lubricating coating composition, where the first polyethylene is UHMW-PE and the second polyethylene is HDPE.

[0015] Polyethylenes tend to have weak intermolecular forces and a low coefficient of friction. Among these, HDPE has an even lower coefficient of friction, but its molecular weight is low, resulting in poor wear resistance. UHMW-PE also tends to have a higher coefficient of friction than HDPE, but its molecular weight is high, resulting in high wear resistance. The lubricating coating composition of this embodiment contains HDPE and UHMW-PE. When the composition is baked at or above the melting points of both polyethylenes to produce a lubricating coating, the two polyethylenes melt and mix within the lubricating coating. When melted, HDPE has high fluidity due to its low molecular weight, while UHMW-PE has low fluidity due to its high molecular weight, resulting in HDPE flowing and clinging to the UHMW-PE. Therefore, in the lubricating coating formed by solidifying the molten composition, the region containing HDPE (hereinafter also referred to as the "HDPE region") tends to cover the region containing UHMW-PE (hereinafter also referred to as the "UHMW-PE region"). As a result, HDPE, which has a smaller coefficient of friction, is more likely to appear on the surface of the lubricating coating, and the coefficient of friction is reduced when a member slides on the surface of the lubricating coating. In other words, the lubricating coating of this embodiment has excellent lubricity. Furthermore, in the lubricating coating provided on the base material, a UHMW-PE region with higher wear resistance is present inside (on the base material side of) the HDPE region, so the HDPE region is less likely to peel off even when a member repeatedly slides on the lubricating coating. Even after the HDPE region peels off, the UHMW-PE region appears on the surface of the lubricating coating that slides against the member, preventing a decrease in the lubricity of the lubricating coating. In other words, the lubricating coating of this embodiment tends to have excellent lubrication durability. Furthermore, in the lubricating coating, the UHMW-PE regions are scattered, and HDPE regions tend to be present between these regions. In this way, the UHMW-PE regions are bonded to each other via the HDPE regions, and the UHMW-PE regions and the HDPE regions are bonded to each other within the lubricating coating, so that even when members repeatedly slide on the lubricating coating, the UHMW-PE regions and the HDPE regions are less likely to peel off, and the lubricating properties of the lubricating coating tend to be maintained. In other words, the lubricating coating of this embodiment tends to have excellent lubricity and lubrication durability.

[0016] Furthermore, when the total amount of the first polyethylene and the second polyethylene is 15% by mass or more and 40% by mass or less of the total amount of the lubricating coating composition, the lubricity and lubrication durability of the lubricating coating tend to be further improved.

[0017] The lubricating coating composition of this embodiment is preferably substantially free of PFAS, and more preferably does not contain any PFAS. "Substantially free of PFAS" is not particularly limited, but refers to, for example, a PFAS content of 0 to 2.0 mass%, 0 to 1.5 mass%, 0 to 1.0 mass%, 0 to 0.5 mass%, or 0 to 0.1 mass% relative to the total amount of the lubricating coating composition. When a lubricating coating composition is substantially free of PFAS or does not contain any PFAS, it tends to have improved lubrication durability and environmental compatibility. PFAS is not particularly limited as long as it is an organic fluorine compound, which is an organic compound in which some or all of the hydrogen atoms bonded to carbon in a hydrocarbon are substituted with fluorine. Examples of PFAS include polyfluoroalkyl compounds such as polytetrafluoroethylene (PTFE); and perfluoroalkyl compounds such as perfluorooctanesulfonic acid and perfluorooctanoic acid.

[0018] The total amount of the first polyethylene and the second polyethylene is preferably 17.5 to 35.0 mass%, or 20.0 to 30.0 mass%, of the total amount of the lubricating coating composition. When the total amount of the first polyethylene and the second polyethylene is within this range, the lubricity and lubrication durability of the lubricating coating tend to be further improved.

[0019] The content of the first polyethylene is preferably 2.5 to 20.0 mass%, 5.0 to 15.0 mass%, or 7.5 to 12.5 mass%, relative to the total amount of the lubricating coating composition. When the content of the first polyethylene is within the above range, the lubricity and lubrication durability of the lubricating coating tend to be further improved.

[0020] The content of the second polyethylene is preferably 10.0 to 30.0 mass%, 12.5 to 27.5 mass%, or 15.0 to 25.0 mass%, relative to the total amount of the lubricating coating composition. When the content of the second polyethylene is within the above range, the lubricity and lubrication durability of the lubricating coating tend to be further improved.

[0021] In the lubricating coating composition, the ratio (W2 / W1) of the second polyethylene content (W2) to the first polyethylene content (W1) is preferably 1.1 to 3.0, 1.3 to 2.8, or 1.5 to 2.5. When this ratio is within the above range, the lubricity and lubrication durability of the lubricating coating tend to be further improved.

[0022] The weight-average molecular weight of the first polyethylene is preferably 1,000,000 to 7,000,000, 1,100,000 to 6,000,000, 1,200,000 to 5,000,000, 1,300,000 to 4,000,000, or 1,500,000 to 3,000,000. When the weight-average molecular weight of the first polyethylene is within the above range, the lubricity and lubrication durability of the lubricating coating film tend to be further improved.

[0023] The density of the second polyethylene is preferably 0.94 to 1.10 g / cm 3 and 0.95 to 1.00 g / cm 3 When the density of the second polyethylene is within the above range, the lubricity and lubrication durability of the lubricating coating film tend to be further improved.

[0024] The melting point of the first polyethylene is preferably 110 to 200° C., 115 to 175° C., or 120 to 150° C. When the melting point of the first polyethylene is within the above range, it tends to be possible to melt the lubricating coating composition at an appropriate temperature and obtain a lubricating coating.

[0025] The melting point of the second polyethylene is preferably 100 to 150° C., 105 to 140° C., or 110 to 130° C. When the melting point of the second polyethylene is within the above range, it tends to be possible to melt the lubricating coating composition at an appropriate temperature and obtain a lubricating coating.

[0026] The first polyethylene is preferably in the form of solid particles, and the median diameter (D50) thereof is preferably 70 μm or less, 1 to 70 μm, 2 to 50 μm, 3 to 25 μm, or 5 to 20 μm. When the median diameter (D50) of the first polyethylene is within the above range, the lubricity of the lubricating coating tends to be further improved.

[0027] The second polyethylene is preferably in the form of solid particles, and the median diameter (D50) thereof is preferably 70 μm or less, 1 to 70 μm, 2 to 50 μm, 3 to 25 μm, or 5 to 20 μm. When the median diameter (D50) of the second polyethylene is within the above range, the lubricity of the lubricating coating tends to be further improved.

[0028] The median diameter (D50) is the particle diameter corresponding to a cumulative degree of 50% in the particle size distribution measured by a laser diffraction / scattering method, and is determined so that the number of particles larger than the median diameter is the same as the number of particles smaller than the median diameter.

[0029] The median diameter is not particularly limited, but can be measured using, for example, a laser diffraction particle size distribution analyzer "MT3300EXII" manufactured by Microtrac.

[0030] 1.2.Wax The lubricating coating composition of this embodiment may contain a substance other than the first polyethylene and the second polyethylene. Examples of such substances include, but are not limited to, wax. Examples of waxes include, but are not limited to, one or more selected from the group consisting of amide-modified polyethylene wax, carboxyl-modified polyethylene wax, hydroxyl-modified polyethylene wax, polyolefin wax (solid paraffin), monoamide, and bisamide. Of these, it is preferred that the lubricating coating composition contain amide-modified polyethylene wax. The term "amide-modified polyethylene wax" refers to polyethylene wax in which hydrogen atoms in polyethylene have been substituted with amide groups.

[0031] The wax content is not particularly limited, but may be, for example, 15% by mass or less, 0 to 15% by mass, 1 to 14% by mass, 2 to 13% by mass, 3 to 12% by mass, 4 to 11% by mass, or 5 to 10% by mass, relative to the total amount of the lubricating coating composition. The lubricating coating composition does not have to contain wax. When the lubricating coating composition of this embodiment contains wax, the lubricity of the lubricating coating tends to be further improved.

[0032] The wax is preferably in the form of solid particles, and the median diameter thereof is preferably 70 μm or less, 1 to 70 μm, 2 to 50 μm, 3 to 25 μm, 4 to 20 μm, or 5 to 10 μm. When the median diameter of the wax is within the above range, the lubricity of the lubricating coating tends to be further improved.

[0033] 1.3.Binder The lubricating coating composition of this embodiment may contain a binder. Examples of binders include one or more selected from the group consisting of engineering plastics such as epoxy resins, melamine resins, triazine resins, phenolic resins, polyamideimides (PAI), polyethersulfones (PES), and polyimides (PI). Here, engineering plastics refers to resins with a heat resistance temperature of 100°C or higher, a tensile strength of 49 MPa or higher, and a flexural modulus of 2.4 GPa or higher. The binder content is not particularly limited, but may be, for example, 10 to 80 mass%, 20 to 75 mass%, 30 to 70 mass%, 40 to 65 mass%, or 50 to 60 mass% of the total lubricating coating composition. Alternatively, the binder content may be, for example, 50 to 70 mass% of the total lubricating coating composition. Having the binder content within the above range tends to further improve the lubricity of the lubricating coating.

[0034] When the lubricating coating composition of this embodiment contains a binder, the binder preferably contains an epoxy resin or a phenol resin, which are engineering plastics, and more preferably contains an epoxy resin and a phenol resin, which are engineering plastics.

[0035] 1.4. Other Additives The lubricating coating composition of this embodiment may contain additives other than the above-mentioned substances. Examples of such additives include, but are not limited to, one or more selected from the group consisting of molybdenum disulfide, graphite, tungsten disulfide, boron nitride, calcium carbonate, talc, mica, melamine cyanurate (MCA), metal oxides, inorganic oxides, and oils (polyalphaolefins (PAO), silicones, polyalkylene glycols (PAG), esters, and mineral oils). The amount of the additives contained is, but is not limited to, 30% by mass or less, 0 to 30% by mass, 1 to 25% by mass, 2 to 22% by mass, 3 to 19% by mass, 4 to 17% by mass, or 5 to 15% by mass, based on the total amount of the lubricating coating composition. The inclusion of molybdenum disulfide or the like tends to further improve the lubricity of the lubricating coating.

[0036] 2.Lubricating coating film The lubricating coating of this embodiment is a coating containing the lubricating coating composition of this embodiment described above. The lubricating coating is a coating that imparts lubricity to the base material on which the coating is provided.

[0037] The lubricating coating of the present embodiment is not particularly limited, but can be obtained, for example, by containing the lubricating coating composition of the present embodiment and baking it at a temperature higher than the melting points of all the polyethylenes contained in the lubricating coating composition.

[0038] The lubricating coating of this embodiment contains multiple types of polyethylene. The content of the polyethylene relative to the total mass of the lubricating coating is preferably 0.2 to 100 mass%, 0.5 to 95 mass%, 1 to 90 mass%, 2 to 80 mass%, 3 to 70 mass%, 4 to 60 mass%, 5 to 55 mass%, 10 to 50 mass%, or 15 to 40 mass%. The lower limit of the polyethylene content relative to the total mass of the lubricating coating may be any of 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, and 60 mass%. The upper limit of the polyethylene content relative to the total mass of the lubricating coating may be any of 100, 95, 90, 85, 80, 75, 70, 65, and 60 mass%. The above lower and upper limits may be combined in any combination.

[0039] The polyethylene contained in the lubricating coating of this embodiment includes ultra-high molecular weight polyethylene (UHMW-PE, first polyethylene) and high density polyethylene (HDPE, second polyethylene). The polyethylene contained in the lubricating coating is not particularly limited, and may include, for example, one or more selected from the group consisting of medium density polyethylene (MDPE), linear low density polyethylene (LLDPE), low density polyethylene (LDPE), very low density polyethylene (VLDPE), and polyethylene oxide.

[0040] The lubricating coating of this embodiment is preferably substantially free of PFAS, and more preferably free of PFAS. "Substantially free of PFAS" is not particularly limited, but refers to, for example, a PFAS content of 0 to 2.0 mass%, 0 to 1.5 mass%, 0 to 1.0 mass%, 0 to 0.5 mass%, or 0 to 0.1 mass% relative to the total amount of the lubricating coating. When a lubricating coating is substantially free of PFAS or free of PFAS, the lubrication durability tends to improve and environmental compatibility tends to improve. PFAS is an organic compound in which some or all of the hydrogen atoms bonded to carbon in a hydrocarbon are substituted with fluorine, and is not particularly limited as long as it is an organic fluorine compound. Examples of PFAS include polyfluoroalkyl compounds such as polytetrafluoroethylene (PTFE); and perfluoroalkyl compounds such as perfluorooctanesulfonic acid and perfluorooctanoic acid.

[0041] The total amount of the first polyethylene and the second polyethylene in the lubricating coating is preferably 15.0 to 40.0 mass%, 17.5 to 35.0 mass%, or 20.0 to 30.0 mass%, relative to the total amount of the lubricating coating. When the total amount of the first polyethylene and the second polyethylene is within the above range, the lubricity and lubrication durability of the lubricating coating tend to be further improved.

[0042] The content of the first polyethylene in the lubricating coating is preferably 2.5 to 20.0 mass%, 5.0 to 15.0 mass%, or 7.5 to 12.5 mass%, relative to the total amount of the lubricating coating. When the content of the first polyethylene is within the above range, the lubricity and lubrication durability of the lubricating coating tend to be further improved.

[0043] The content of the second polyethylene in the lubricating coating is preferably 10.0 to 30.0 mass%, 12.5 to 27.5 mass%, or 15.0 to 25.0 mass%, relative to the total amount of the lubricating coating. When the content of the second polyethylene is within the above range, the lubricity and lubrication durability of the lubricating coating tend to be further improved.

[0044] The ratio (W2 / W1) of the second polyethylene content (W2) to the first polyethylene content (W1) in the lubricating coating is preferably 1.1 to 3.0, 1.3 to 2.8, or 1.5 to 2.5. When this ratio is within the above range, the lubricity and lubrication durability of the lubricating coating tend to be further improved.

[0045] The lubricating coating of this embodiment may contain a substance other than the first polyethylene and the second polyethylene. Examples of such substances include, but are not limited to, wax. Examples of waxes include, but are not limited to, one or more selected from the group consisting of amide-modified polyethylene wax, carboxyl-modified polyethylene wax, hydroxyl-modified polyethylene wax, polyolefin wax (solid paraffin), monoamide, and bisamide. Of these, it is preferable that the lubricating coating contain amide-modified polyethylene wax. The wax content is not particularly limited, but is, for example, 15% by mass or less, 0 to 15% by mass, 1 to 14% by mass, 2 to 13% by mass, 3 to 12% by mass, 4 to 11% by mass, or 5 to 10% by mass, relative to the total mass of the lubricating coating. The lubricating coating does not necessarily need to contain wax.

[0046] The lubricating coating of this embodiment may contain a binder. Examples of binders include one or more selected from the group consisting of engineering plastics such as epoxy resins, melamine resins, triazine resins, phenolic resins, polyamideimides (PAI), polyethersulfones (PES), and polyimides (PI). The content of the binder is not particularly limited, but may be, for example, 10 to 80 mass%, 20 to 75 mass%, 30 to 70 mass%, 40 to 65 mass%, or 50 to 60 mass% relative to the total mass of the lubricating coating. Alternatively, the content of the binder may be, for example, 50 to 70 mass% relative to the total mass of the lubricating coating.

[0047] When the lubricating coating of this embodiment contains a binder, the binder preferably contains an epoxy resin or a phenol resin, which are engineering plastics, and more preferably contains an epoxy resin and a phenol resin, which are engineering plastics.

[0048] The lubricating coating of this embodiment may contain additives other than the above-mentioned substances. Examples of such additives include, but are not limited to, one or more selected from the group consisting of molybdenum disulfide, graphite, tungsten disulfide, boron nitride, calcium carbonate, talc, mica, MCA, metal oxides, inorganic oxides, and oils (PAO, silicone, PAG, ester, mineral oil). The content of the additives is, but is not limited to, 30% by mass or less, 0 to 30% by mass, 1 to 25% by mass, 2 to 22% by mass, 3 to 19% by mass, 4 to 17% by mass, or 5 to 15% by mass, based on the total mass of the lubricating coating. The inclusion of molybdenum disulfide or the like tends to further improve the lubricity of the lubricating coating.

[0049] The lubricating coating of this embodiment may contain multiple types of polyethylene as described above. Alternatively, the lubricating coating of this embodiment may be a coating containing multiple types of polyethylene as described above and baked at a temperature higher than the melting points of these polyethylenes.

[0050] The lubricating coating of this embodiment may contain UHMW-PE, HDPE, and amide-modified polyethylene wax. Furthermore, the lubricating coating of this embodiment is not particularly limited, and may be, for example, a coating containing UHMW-PE, HDPE, and amide-modified polyethylene wax and baked at a temperature higher than the melting points of the UHMW-PE, HDPE, and amide-modified polyethylene wax.

[0051] In the lubricating coating of this embodiment, the polyethylene may be present in an islands-in-a-sea pattern on the surface of the coating. Furthermore, in the lubricating coating of this embodiment, UHMW-PE and HDPE may be present in an islands-in-a-sea pattern on the surface of the coating. The lubricating coating of this embodiment comprises the lubricating coating composition of this embodiment described above, and the first polyethylene and the second polyethylene may be present in an islands-in-a-sea pattern on the surface of the lubricating coating. This lubricating coating tends to have better lubricity. In this case, the islands correspond to, for example, the regions where the first polyethylene and the second polyethylene are present, and the remaining regions (for example, the regions where the binder is present) correspond to the sea.

[0052] 3. Manufacturing method of lubricating coating film The method for producing a lubricating coating of this embodiment includes a step of producing a lubricating coating using the lubricating coating composition of this embodiment, and the step of producing a lubricating coating includes a baking step of baking the lubricating coating composition at a temperature equal to or higher than the melting points of the first polyethylene and the second polyethylene. By baking the lubricating coating composition at a temperature equal to or higher than the melting points of the first polyethylene and the second polyethylene, the first polyethylene and the second polyethylene melt and mix together. The lubricating coating obtained by cooling and solidifying after baking tends to have excellent lubricity and lubrication durability. Furthermore, the first polyethylene and the second polyethylene tend to exist in an island-like structure on the surface of the lubricating coating. In other words, the lubricating coating tends to have excellent lubricity and lubrication durability.

[0053] The lubricating coating composition and lubricating coating of this embodiment tend to provide a coating with a low friction coefficient even without containing PFAS. Furthermore, the lubricating coating composition and lubricating coating of this embodiment tend to have excellent lubrication durability (friction resistance) even without containing PFAS. Furthermore, the lubricating coating composition and lubricating coating of this embodiment tend to have excellent one or more of rust prevention, water repellency, and oil repellency even without containing PFAS.

[0054] FIG. 1 shows an example of a cross-sectional view of a lubricating coating provided on a base material. In FIG. 1, a lubricating coating 100 is provided on a base material 200, and the lubricating coating 100 includes a mixture 130 of polyethylene and wax, an additive 120, and a binder 110. The polyethylene and wax may be partially mixed, with the remainder existing independently, or may all be mixed together to form the mixture 130. In FIG. 1, the first polyethylene and the second polyethylene are present in a sea-island pattern on the surface of the lubricating coating 100. Specifically, on the surface of the lubricating coating 100, the areas where the mixture 130 exists are islands, and the areas where the binder 110 exists are seas.

[0055] The lubricating coating of this embodiment includes the following aspects. 1. A lubricating coating containing multiple types of polyethylene (UHMW-PE, HDPE) that has been baked at a temperature higher than the melting point of these materials. 2. A lubricating coating containing UHMW-PE, HDPE and amide-modified polyethylene waxes, baked at a temperature higher than their melting points. 3. A lubricating coating having the composition shown in FIG. 4. A lubricating coating film in which dissolved UHMW-PE and HDPE exist in an island-like pattern on the surface of the coating film. 5. A lubricating coating film containing, as a wax, one or more selected from the group consisting of amide-modified polyethylene wax, carboxyl-modified polyethylene wax, hydroxyl-modified polyethylene wax, polyolefin wax (solid paraffin), monoamide and bisamide. 6. A lubricating coating containing, as an additive, one or more selected from the group consisting of molybdenum disulfide, graphite, tungsten disulfide, boron nitride, calcium carbonate, talc, mica, MCA, metal oxides, inorganic oxides, and oils (PAO, silicone, PAG, ester, mineral oil). 7. A lubricating coating film containing, as a binder, one or more selected from the group consisting of engineering plastics (epoxy resin, melamine resin, triazine resin, phenolic resin, PAI, PES, PI, etc.).

[0056] 4.Sliding device The lubricating coating composition of this embodiment is applied to the surface of a substrate to form a lubricating coating. The substrate is configured so that components slide on its surface. The material of the substrate is not particularly limited, but examples thereof include synthetic resins such as phenolic resin, melamine resin, urea resin, alkyd resin, epoxy resin, polyester resin, polyurethane resin, polyethylene resin, polypropylene resin, polystyrene resin, polyvinyl acetate resin, polyurethane resin, polylactic acid resin, Teflon resin, acrylonitrile butadiene styrene resin, acrylonitrile styrene resin, acrylic resin, polyvinyl chloride resin, polyamide resin, glass fiber reinforced polyamide resin, polyacetal resin, polycarbonate resin, and modified polyphenylene ether resin; metals such as aluminum, magnesium, iron, copper, tin, zinc, and lead, and alloys thereof; and inorganic materials such as glass.

[0057] The material of the member is not particularly limited, but may be the same as those exemplified for the base material.

[0058] The base material and the member may be made of the same material or different materials.

[0059] The sliding device has a base material and a member, and the member slides on the base material. Examples of the sliding device include, but are not limited to, a door lock mechanism, a window regulator, a seat rail, a sunroof, a suspension, a brake, a seat belt mechanism, or a gear part of a steering system. [Example]

[0060] The present invention will be described in more detail below using examples. The present invention is not limited to the following examples. Unless otherwise specified, the experiments were carried out at room temperature (25°C) and 1 atmosphere.

[0061] The lubricating coating compositions for each experimental example were obtained by mixing and stirring the compounds to obtain the compositions shown in Figure 3. The lubricating coating compositions for each experimental example were then applied to a substrate and baked at 200°C to obtain the lubricating coatings for each experimental example.

[0062] The abbreviations and product ingredients shown in Figure 3 are as follows: Note that blank spaces in Figure 3 indicate that the ingredient was not used. Binder: Epoxy resin / phenolic resin (engineering plastic) Additive: Molybdenum disulfide powder UHMW-PE: Molecular weight: 1.8 million, Melting point: 136°C, Median diameter: 10 μm HDPE A: Density: 0.94 or more, Melting point: 125°C HDPE B: Density: 1.06, Melting point: 125°C HDPE C: Density: 0.98, Melting point: 125°C HDPE D: Density: 0.97, Melting point: 122°C, Median diameter: 8 μm PA12 A: Polyamide 12 powder, melting point: 170℃ PA12 B: Polyamide 12 powder, melting point: 170℃ PA12 C: Polyamide 12 powder, melting point: 177°C PA12 D: Polyamide 12 powder, melting point: 177°C Biopolymer A: Modified biopolymer, melting point: 175°C Biopolymer B: Modified biopolymer, melting point: 175°C Amide-modified polyethylene wax: Median diameter: 6 μm

[0063] In the table of Figure 3, μs represents the static friction coefficient, and μd represents the dynamic friction coefficient. The static friction coefficient and dynamic friction coefficient were measured under the following conditions. Equipment used: Shinto Scientific TRIBOGEAR Type 14 special Test piece: A lubricating coating film of each experimental example was formed to a thickness of 20 μm on a SUS301 test piece (thickness t = 0.3 mm). Counterpart material: SPCC-SB flat plate 25 x 25 mm Speed: 0.4mm / sec Stroke width: 5 mm (The mating material was reciprocated at this stroke width on the lubricating coating film of each experimental example formed on the base material.) Load: 24N (surface pressure: 0.0384MPa) Evaluation: Static friction coefficient and dynamic friction coefficient after 5 sliding strokes

[0064] The μs was evaluated based on the following evaluation criteria. A was the most excellent, followed by A, B, C, and D. Lubricating coatings rated B or higher can be suitably used in sliding devices. A: μs≦0.10 B: 0.10<μs≦0.15 C:0.15<μs≦0.30 D:0.30<μs

[0065] μd was evaluated based on the following evaluation criteria. A was the most excellent, followed by A, B, C, and D. Lubricating coatings rated B or higher can be suitably used in sliding devices. A: μd≦0.10 B: 0.10<μd≦0.15 C: 0.15<μd≦0.30 D: 0.30<μd

[0066] The lubrication durability was evaluated for the lubricating coatings prepared using the lubricating coating composition of Experimental Example 1 and the lubricating coatings prepared using the lubricating coating compositions of Experimental Examples 12 to 15. Specifically, the wear depth (μm) of the test specimens was measured under the same conditions as those for measuring the static and dynamic friction coefficients, except that sliding was performed 20,000 times.

[0067] The wear depth of the lubricating coatings produced using the lubricating coating compositions of Experimental Examples 12 to 15 was smaller than the wear depth of the lubricating coating produced using the lubricating coating composition of Experimental Example 1. This shows that the lubricating coatings produced using the lubricating coating compositions of Experimental Examples 12 to 15 have excellent lubrication durability.

[0068] Furthermore, when the cross sections of the lubricating coatings prepared using the lubricating coating compositions of Experimental Examples 12 to 15 were observed with a scanning electron microscope (SEM), it was confirmed that the first polyethylene and the second polyethylene were present in an island-like pattern on the surface of the lubricating coating. [Explanation of symbols]

[0069] 100...lubricating coating, 110...binder, 120...additive, 130...mixture of polyethylene and wax, 200...base material

Claims

1. A first polyethylene having a weight average molecular weight of 1,000,000 or more and a second polyethylene having a density of 0.94 g / cm 3 A lubricating coating composition comprising the above second polyethylene, the total amount of the first polyethylene and the second polyethylene is 15% by mass or more and 40% by mass or less, based on the total amount of the lubricating coating composition; Composition for lubricating coatings.

2. The median diameter of the first polyethylene is 70 μm or less, The median diameter of the second polyethylene is 70 μm or less. The lubricating coating composition of claim 1.

3. The lubricating coating composition contains 5% by mass or more and 10% by mass or less of an amide-modified polyethylene wax relative to the total amount of the lubricating coating composition. The lubricating coating composition of claim 1.

4. The median diameter of the amide-modified polyethylene wax is 70 μm or less. The lubricating coating composition of claim 3.

5. The lubricating coating composition contains 50% by mass or more and 70% by mass or less of engineering plastics based on the total amount of the lubricating coating composition. The lubricating coating composition of claim 1.

6. The lubricating coating composition does not contain any organic fluorine compound, or contains the organic fluorine compound and the content of the organic fluorine compound is more than 0 mass % and 2.0 mass % or less relative to the total amount of the lubricating coating composition. The lubricating coating composition of claim 1.

7. A lubricating coating comprising the lubricating coating composition according to any one of claims 1 to 6, the first polyethylene and the second polyethylene are present in an island-like pattern on the surface of the lubricating coating; Lubricating coating.

8. A method for producing a lubricating coating, comprising the step of producing a lubricating coating using the lubricating coating composition according to any one of claims 1 to 6, wherein the step of producing the lubricating coating comprises a baking step of baking the lubricating coating composition at a temperature equal to or higher than the melting points of the first polyethylene and the second polyethylene. A method for producing a lubricating coating.

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