Coating film, molded article, and method for manufacturing the molded article

Abstract

To provide a coating film with excellent resistance to the adhesion of foreign matter. [Solution] The coating film of the present disclosure contains polyimide and fluororesin, wherein the content of the fluororesin is 15% by volume or more and 55% by volume or less.

Description

[Technical Field]

[0001] This disclosure relates to a coating film, a molded article, and a method for manufacturing a molded article. [Background technology]

[0002] During the molding, processing, transportation, and storage of various industrial products, food products, etc., coating films are used to prevent foreign substances such as sticky materials and contaminants from adhering to the various substrates.

[0003] As an example of such a coating film, in the prior art, a functional film consisting of a cured product of a coating composition containing inorganic particles and titanium alkoxide or a partially hydrolyzed condensate thereof has been proposed (see Patent Document 1). Because the above coating composition contains inorganic particles, irregularities are formed on the surface of the functional film, reducing the contact area for fiber contamination and resulting in a functional film with excellent dustproof properties. Furthermore, because the above coating composition contains titanium alkoxide or a partially hydrolyzed condensate thereof, it can exhibit dustproof properties against fiber contamination in the functional film. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2022-156229 [Overview of the project]

[0005] The coating film of this disclosure contains polyimide and fluororesin, wherein the content of the fluororesin is 15% by volume or more and 55% by volume or less. [Brief explanation of the drawing]

[0006] [Figure 1] Figure 1 is a schematic partial cross-sectional view of a molded body according to one embodiment of the present disclosure. [Modes for carrying out the invention]

[0007] [Issues this disclosure aims to address] The conventional functional films described above contain inorganic particles, which creates an uneven surface that reduces the contact area for fiber contaminants and provides excellent dust protection. However, fluid foreign matter, concrete containing large amounts of moisture, and mud can easily get trapped in the surface irregularities, resulting in insufficient adhesion prevention. Consequently, handling and subsequent processing of objects containing these foreign matter becomes difficult, and if these foreign matter gets caught in the components of various devices, stable operation becomes impossible.

[0008] This disclosure aims to provide a coating film that exhibits excellent resistance to the adhesion of foreign matter.

[0009] [Effects of this disclosure] The coating film of this disclosure exhibits excellent resistance to the adhesion of foreign matter.

[0010] [Description of Embodiments in this Disclosure] First, the embodiments of this disclosure will be listed and described.

[0011] (1) The coating film of the present disclosure contains polyimide and fluororesin, wherein the content of the fluororesin is 15% by volume or more and 55% by volume or less.

[0012] The coating film, by containing polyimide and fluororesin, increases the water contact angle on its surface, thereby improving its release properties. Furthermore, it increases the hardness of the coating film, improving its scratch resistance and reducing the likelihood of foreign matter entering surface depressions. Additionally, a fluororesin content of 15% to 55% by volume enhances both the release properties and hardness of the coating film. Therefore, the coating film exhibits excellent resistance to foreign matter adhesion.

[0013] (2) In (1) above, the fluororesin may be polytetrafluoroethylene, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, or tetrafluoroethylene-hexafluoropropylene copolymer. By using polytetrafluoroethylene (PTFE), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), or tetrafluoroethylene-hexafluoropropylene copolymer (FEP) as the fluororesin, the water contact angle of the coating film can be increased and the release properties of the coating film can be improved, thereby improving the ability to prevent foreign matter from adhering. In addition, the hardness of the coating film can be maintained well and the scratch resistance can be improved, thereby improving the ability to prevent foreign matter from adhering.

[0014] (3) In (1) or (2) above, the ratio of fluorine atoms to carbon atoms in the near-surface region of the coating film may be 1.9 or more. A ratio of fluorine atoms to carbon atoms in the near-surface region of the coating film of 1.9 or more increases the water contact angle of the surface of the coating film, thereby improving the release properties of the coating film and thus improving the ability to prevent the adhesion of foreign matter. The "ratio of fluorine atoms to carbon atoms in the near-surface region of the coating film" can be measured by elemental analysis of the surface of the coating film by X-ray photoelectron spectroscopy (XPS). The "near-surface region" refers to the region on the surface of the coating film in which elemental analysis using X-ray photoelectron spectroscopy can be performed under the following conditions after irradiating the surface with X-rays. X-ray source: MONO AlKα Beam conditions: 100 μmφ, 100 W, 20 kV Transmission energy: 55 eV, 280 eV Analysis elements: C, N, O, F, Ca

[0015] (4) In any of (1) to (3) above, the area occupied by the fluororesin in a cross section perpendicular to the surface of the coating film, from the surface to a depth of 1 μm, may be 75% or more and 95% or less. By having the area occupied by the fluororesin in the cross section from the surface to a depth of 1 μm of the coating film be 75% or more and 95% or less, the release properties of the coating film can be improved, thereby further improving the ability to prevent the adhesion of foreign matter and maintaining sufficient hardness. The "area occupied by the fluororesin in the cross section from the surface to a depth of 1 μm" can be measured by using a fluorine mapping image obtained by scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDX) of a cross section perpendicular to the surface of the coating film, with the fluorine mapping image being binarized based on the average value of the brightness.

[0016] (5) In any of (1) to (4) above, the arithmetic mean curvature Spc of the peaks on the surface is 10,000 μm -1 More than 26000μm -1 The following may also apply. The ability of the coating film to prevent the adhesion of foreign matter can be improved if the arithmetic mean curvature Spc of the peaks on the surface is within the above range. The "arithmetic mean curvature Spc" represents the average of the principal curvatures of the peaks on the surface and serves as an indicator of the sharpness of the tips of the convex parts on the surface. The arithmetic mean curvature Spc is a value measured according to the method compliant with ISO 25178-2:2012.

[0017] (6) The molded article of the present disclosure further comprises a substrate and a coating film according to any one of (1) to (5) above, which is laminated on at least a portion of the surface of the substrate. Since the molded article comprises a substrate and the above-described coating film, it has excellent resistance to the adhesion of foreign matter.

[0018] (7) Further, the method for manufacturing a molded body according to the present disclosure is the method for manufacturing a molded body described in (6) above, which includes a step of coating at least a part of the surface of the substrate with a composition for a coating film containing a polyimide precursor and a fluororesin, and a step of heating the coating film formed after the coating step, and the heating temperature in the heating step is not less than the melting point of the fluororesin. In the method for manufacturing the molded body, it is considered that the fluororesin is likely to be dispersed toward the surface of the coating film because the heating temperature in the heating step is not less than the melting point of the fluororesin. Thereby, the water contact angle of the surface of the coating film can be increased, and the mold release property of the coating film can be made better, so that the adhesion prevention property of foreign matters can be improved.

[0019] [Details of Embodiments of the Present Disclosure] Hereinafter, the coating film, the molded body, and the method for manufacturing the molded body according to the embodiments of the present disclosure will be described in detail with reference to the drawings.

[0020] <Coating Film> The coating film contains a polyimide and a fluororesin. The coating film can be suitably used as a coating film for coating various industrial products, molding equipment, processing equipment, transportation pipes and members, storage containers, etc. in foods and the like.

[0021] [[ID=十六]]The coating film contains polyimide, which can increase the hardness of the coating film, reduce the scratch resistance of the surface, and improve the adhesion prevention property of foreign matters. The lower limit of the polyimide content in the coating film may be 45% by volume, 50% by volume, or 55% by volume. When the polyimide content is 45% by volume or more, the coating film can obtain sufficient hardness. On the other hand, the upper limit of the polyimide content in the coating film may be 85% by volume, 80% by volume, or 75% by volume. When the polyimide content is 85% by volume or less, the fluororesin content can be made sufficient, the coating film can obtain sufficient mold release property, and the adhesion prevention property of foreign matters is improved.

[0022] The coating film contains a fluororesin, which improves its release properties and enhances its ability to prevent the adhesion of foreign substances. The fluororesin may be polytetrafluoroethylene, tetrafluoroethylene-perfluoroalkoxyethylene copolymer, or tetrafluoroethylene-hexafluoropropylene copolymer. By using polytetrafluoroethylene (PTFE), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), or tetrafluoroethylene-hexafluoropropylene copolymer (FEP) as the fluororesin, the water contact angle of the coating film can be increased, improving its release properties and thus enhancing its ability to prevent the adhesion of foreign substances. Furthermore, the hardness of the coating film can be maintained well, improving its scratch resistance and thus enhancing its ability to prevent the adhesion of foreign substances.

[0023] The lower limit of the fluororesin content in the coating film is 15% by volume, but it may also be 20% by volume or 25% by volume. A fluororesin content of 15% by volume or more increases the water contact angle on the surface of the coating film, improving release properties and thus providing better protection against foreign matter adhesion. On the other hand, the upper limit of the fluororesin content is 55% by volume, but it may also be 50% by volume or 45% by volume. A fluororesin content of 55% by volume or less improves the surface properties of the coating film, enhances release properties, and provides better protection against foreign matter adhesion.

[0024] In a cross-section perpendicular to the surface of the coating film, the lower limit of the area occupied by the fluororesin in the cross-section from the surface to a depth of 1 μm may be 65%, 75%, or 80%. A ratio of 65% or more for the fluororesin improves the release properties of the coating film, and a ratio of 75% or more for the fluororesin improves the water contact angle on the surface of the coating film, further improving its release properties and thus enhancing its ability to prevent the adhesion of foreign matter. On the other hand, the upper limit of the area occupied by the fluororesin may be 95%, 90%, or 87% or less. A ratio of 95% or less for the fluororesin maintains sufficient hardness in the coating film.

[0025] The lower limit of the ratio of fluorine atoms to carbon atoms in the near-surface region of the coating film is 1.9, but may also be 2.0. A ratio of fluorine atoms to carbon atoms in the near-surface region of the coating film of 1.9 or higher increases the water contact angle on the surface of the coating film, improving its release properties and thus enhancing its ability to prevent the adhesion of foreign matter. On the other hand, the upper limit of the ratio of fluorine atoms to carbon atoms in the near-surface region of the coating film may be 2.2, or may also be 2.1. A ratio of fluorine atoms to carbon atoms in the near-surface region of the coating film of 2.2 or lower maintains sufficient hardness on the surface of the coating film.

[0026] The coating film may contain other additive components besides those mentioned above, as needed. Examples of additives include anti-settling agents, dispersants, defoaming agents, coloring pigments, antioxidants, UV absorbers, antistatic agents, surfactants, leveling agents, rheology control agents, and inorganic particles.

[0027] The lower limit of the average thickness of the coating film may be 5 μm or 10 μm. On the other hand, the upper limit of the average thickness may be 70.0 μm or 50.0 μm. Having an average thickness of 5 μm or more and 70.0 μm or less allows for good durability and elasticity. Here, "average thickness" refers to the average value of the thickness measured at any ten points.

[0028] The lower limit of the arithmetic mean height Sa of the surface of the coating film may be 0.1 μm, 0.3 μm, or 0.4 μm. The upper limit of the arithmetic mean height Sa of the surface of the coating film may be 1.0 μm, 0.8 μm, or 0.7 μm. By having the arithmetic mean height Sa of the surface of the coating film within the above range, the ability to prevent the adhesion of foreign matter can be improved. The arithmetic mean height Sa represents the average of the absolute values ​​of the height differences of each point relative to the average plane of the surface, and the arithmetic mean height Sa is an indicator of the overall protruding length of the convex parts on the surface of the coating film. The arithmetic mean height Sa is a value measured by a method compliant with JIS-B0681-2:2018.

[0029] The lower limit of the arithmetic mean curvature Spc of the peaks on the surface of the coating film is 10,000 μm. -1 It may also be 10500 μm -1 It may also be 11000 μm -1 This may also be the case. The upper limit of the arithmetic mean curvature Spc of the peaks on the surface of the coating film is 26,000 μm. -1 It may also be 25,000 μm -1 This may also be the case. The smaller the arithmetic mean curvature Spc of the peaks on the surface, the more rounded the tips of the protrusions on the surface of the coating film will be. On the other hand, the larger the arithmetic mean curvature Spc of the peaks on the surface, the sharper the tips of the protrusions on the surface of the coating film will be. The arithmetic mean curvature Spc of the peaks on the surface of the coating film is 10,000 μm. -1By being as described above, the contact area between the surface of the coating film and foreign matter is reduced, and the adhesion prevention property of foreign matter can be improved. The arithmetic mean curvature Spc of the peak points on the surface of the coating film is 26,000 μm -1 By being as described below, the sharpness of the convex portions on the surface of the coating film is reduced, and the deterioration of the adhesion prevention property due to foreign matter piercing the convex portions can be reduced.

[0030] According to the coating film, the adhesion prevention property of foreign matter is excellent.

[0031] <Formed body> The formed body of the present disclosure includes a substrate and a coating film laminated on at least a part of the surface of the substrate. The formed body has the coating film formed from the above-described coating film. Specifically, the coating film contains polyimide and a fluororesin.

[0032] FIG. 1 is a schematic partial cross-sectional view showing a formed body 1 according to an embodiment of the present disclosure. The formed body 1 includes a substrate 2 and a coating film 3 laminated on at least a part of the surface of the substrate 2.

[0033] [Substrate] The main component of substrate 2 is not particularly limited and includes, for example, metals, super engineering plastics, ceramics, and carbon materials. Examples of metals include iron alloys such as stainless steel, nickel, aluminum, aluminum alloys, copper, and copper alloys. Among these, stainless steel or nickel may be used because they have excellent malleability and heat resistance. The metals may be used individually or in combination of two or more. Examples of super engineering plastics include polyimide, polyamide-imide, polyetherimide, polyetheretherketone, polyphenylene sulfide, polyarylate, liquid crystal polymer, polysulfone, and polyethersulfone. Examples of ceramics include alumina, aluminum nitride, silicon nitride, boron nitride, silicon carbide, zirconia, cordierite, sialon, steatite, sapphire, and cermet. Examples of carbon materials include diamond, graphite, C / C composite, and C / SiC composite. The term "main component" refers to the component with the highest mass content, for example, a component with a content of 60% by mass or more.

[0034] The shape of the base 2 described above is not particularly limited and can be changed as appropriate depending on the application. For example, it is not limited to plate-shaped, tubular, cylindrical, cylindrical, conical, elliptical conical, pyramidal, gourd-shaped, elliptical prism-shaped, and prismatic shapes, and various molded body shapes such as rotors can be adopted.

[0035] The average thickness of the substrate 2 is not particularly limited and can be changed as appropriate depending on the application. Furthermore, the surface of the substrate 2 does not need to be flat; it may have patterns such as grooves or dimples (indentations). The substrate 2 may also have through holes.

[0036] [Coating film] The coating film 3 does not need to be laminated over the entire surface of the substrate 2; it is sufficient if it is laminated over at least a portion of the surface of the substrate 2. The coating film 3 contains polyimide and fluororesin. Because the coating film 3 contains polyimide and fluororesin, it has excellent resistance to the adhesion of foreign matter.

[0037] The molded body comprises a substrate and the aforementioned coating film, and therefore exhibits excellent resistance to the adhesion of foreign matter.

[0038] <Method for manufacturing molded articles> A method for manufacturing the molded article according to one embodiment comprises the steps of applying a coating film composition containing a polyimide precursor and a fluororesin to at least a portion of the surface of a substrate, and heating the coating film formed after the coating step. The coating step and the step of heating the coating film formed after the coating step are usually performed multiple times to obtain the coating film of the desired thickness.

[0039] (The coating process) In this process, a coating film composition containing a polyimide precursor and a fluororesin is applied to at least a portion of the surface of the substrate. The coating film composition may also contain a solvent.

[0040] As the solvent, amide solvents such as N-methyl-2-pyrrolidone, 2-pyrrolidone, dimethylacetamide, N,N-dimethylformamide, and N,N-diethylformamide can be used individually, or mixtures of the above amide solvents with other solvents such as water, alcohols, ketones, ethers, esters, amines, or combinations thereof can be used. The coating film composition can be prepared by preparing the above-mentioned predetermined amounts of each component contained in the coating film, using an appropriate organic solvent as a solvent, and uniformly stirring and mixing using mechanical force.

[0041] The lower limit of the solid content concentration of the coating film composition may be 5% by mass, 25% by mass, or 40% by mass. On the other hand, the upper limit of the solid content concentration of the coating film composition may be 60% by mass, 50% by mass, or 45% by mass. By setting the solid content concentration of the coating film composition within the above ranges, the applicability can be improved, and as a result, a coating film with fewer coating defects can be easily and reliably formed.

[0042] <Polyimide precursor> Polyimide precursors refer to resins that are converted to polyimide through heat treatment or chemical treatment with acids or bases. Polyimide precursors are reaction products obtained by the polymerization condensation reaction of aromatic tetracarboxylic dianhydrides and aromatic diamines. Polyimide precursors are also known as polyamic acids. Polyimide precursors form cyclic imides through polymerization condensation reactions.

[0043] A known method can be used for the polymerization condensation reaction described above. A specific method for the polymerization condensation reaction is, for example, a method of mixing an aromatic tetracarboxylic dianhydride and an aromatic diamine in an organic solvent. By this method, the aromatic tetracarboxylic dianhydride and the aromatic diamine polymerize, and a solution in which the polyimide precursor is dissolved in the organic solvent can be obtained. Furthermore, the degree of polymerization (weight-average molecular weight) can be controlled by carrying out the polymerization condensation reaction in the presence of a reaction control agent.

[0044] The lower limit of the polyimide precursor content in the coating film composition may be 5% by mass or 8% by mass. The upper limit of the above content may be 40% by mass or 20% by mass. By setting the above content to 5% by mass or more, the amount of coating film composition required throughout the entire manufacturing process to obtain a coating film of the desired thickness when forming the coating film using the coating film composition can be reduced, and the number of steps for applying and heating the coating film composition can be reduced. By setting the polyimide precursor content to 40% by mass or less, the viscosity of the coating film composition can be appropriately adjusted while maintaining good properties of the coating film, thereby improving the coatability.

[0045] Examples of the above coating methods include dip coating, electrostatic coating, air spray coating, inkjet coating, dispenser coating, electrodeposition coating, screen printing, wire bar coating, spin coating, die coating, roll coating, blade coating, or gravure coating.

[0046] (The heating process) In the heating step, the coating film formed after the coating step is heated. Specifically, the substrate on which the coating film is formed is placed in a heating furnace and heated to bake the coating film. This heating allows the solvent in the coating film composition to evaporate. The heating temperature in the heating step is above the melting point of the fluororesin. In this method of manufacturing the molded article, it is believed that the fluororesin is more easily dispersed toward the surface of the coating film because the heating temperature in the heating step is above the melting point of the fluororesin. This increases the water contact angle on the surface of the coating film and improves the release properties of the coating film, thereby improving the ability to prevent the adhesion of foreign matter.

[0047] The heating temperature for firing the coating film can be, for example, 360°C to 450°C. The heating time for firing the coating film can be, for example, 10 minutes to 60 minutes. By setting the heating temperature and time within the above range, a film with excellent density can be formed while reducing the decomposition of polyimide. Subsequently, the coating film is cooled, causing it to be laminated onto at least a portion of the substrate surface.

[0048] The method for manufacturing the molded article increases the water contact angle on the surface of the coating film and improves the release properties of the coating film, thereby improving the ability to prevent foreign matter from adhering to it.

[0049] [Other embodiments] The embodiments disclosed herein should be considered in all respects to be illustrative and not restrictive. The scope of the present invention is not limited to the configurations of the embodiments described above, but is indicated by the claims, and all modifications within the meaning and scope equivalent to the claims are intended to be included.

[0050] In the above embodiment, the coating film was directly laminated on the surface of the substrate, but an intermediate layer such as a primer layer or an organic glass layer may be further provided between the substrate and the coating film. [Examples]

[0051] The present disclosure will be further described below with reference to examples, but the present disclosure is not limited to the following examples.

[0052] <Coating films No. 1 to No. 7> At room temperature, a fluororesin listed in Table 1 was added to a polyimide precursor solution to which a surfactant had been added. The mixture was then stirred using a Thinky "Awatori Rentaro ARE-310" in MIX mode (2000 RPM) for 3 minutes and in DEFORM mode (2200 RPM) for 30 seconds to prepare a coating film composition as a coating liquid. Next, the coating liquid was applied to an aluminum plate with an average thickness of 3 mm, which served as a substrate, using the wire bar coating method. Subsequently, the plate was heated in an air-fired furnace at 100°C for 20 minutes, then the temperature was raised to the heating temperature listed in Table 1, and heating was continued for 20 minutes to obtain a coating film containing polyimide and fluororesin. The average thickness of the coating film was 20 μm. The content of each component in coating films No. 1 to No. 7 is shown in Table 1.

[0053] The materials used are as follows: (Polyimide (Polyimide precursor solution)) Polyimide A varnish manufactured by Ube Industries, Ltd. (Surfactants) Neos "Futergent 710FL" (Fluoropolymer: PTFE) Kitamura Co., Ltd. "KTL500f"

[0054] [Table 1]

[0055] <Rating> Next, coating films No. 1 through No. 7 were evaluated against the following evaluation criteria.

[0056] [Percentage of the area occupied by fluororesin in a cross-section with a depth of 1 μm or less from the surface] The percentage of the area occupied by fluororesin in the cross-section perpendicular to the surface of each coating film, from the surface to a depth of 1 μm, was measured by using a fluorine mapping image obtained by scanning electron microscopy-energy-dispersive X-ray spectroscopy of the cross-section from the surface to a depth of 1 μm (depth of 1 μm or less), with the average brightness value used as the basis for the binarized fluorine mapping image.

[0057] [Ratio of fluorine atoms to carbon atoms in the near-surface region of the coating film] The ratio of fluorine atoms to carbon atoms in the near-surface region of the coating film was measured by elemental analysis of the coating film surface using X-ray photoelectron spectroscopy (XPS). (XPS measurement conditions) Measurement equipment: Scanning dual X-ray photoelectron spectroscopy analyzer, ULVAC-PHI "PHI Quantes" X-ray source: MONO AlKα Beam conditions: 100 μmφ, 100 W, 20 kV Transmission energy: 55 eV, 280 eV Analysis elements: C, N, O, F, Ca

[0058] [Contact angle] The contact angle [°] was evaluated using the following procedure. Two μL of deionized water was dropped onto the surface of each coating film, and the contact angle of the droplet was measured using a "Portable Contact Angle Meter ST-2" manufactured by Surfgauge Instruments. A larger contact angle [°] is better, and a contact angle of 100° or more is even better.

[0059] [Wet slip angle] The rag sliding angle [°] was evaluated using the following procedure. A piece of absorbent cotton, "Cutmen 3.5cm x 3.5cm," manufactured by Osaki Medical Co., Ltd., was placed on the surface of each layered coating film on the surface of an aluminum substrate. A 50g weight was then placed on top of the cotton to apply pressure between the coating film and the absorbent cotton. In this state, one end of the aluminum substrate was fixed, and the other end was lifted by hand. The angle at which the absorbent cotton began to slide across the coating film was measured. A smaller angle of rag sliding [°] is better, and an angle of 40° or less is even better.

[0060] [Water rag sliding angle] The sliding angle of the wet cloth [°] was evaluated using the following procedure. On the surface of each coating film layered on the surface of an aluminum substrate, a piece of absorbent cotton ("Cutmen 3.5cm x 3.5cm") soaked in 10g of deionized water was placed, and a 50g weight was placed on top to apply pressure between the coating film and the absorbent cotton. In this state, one end of the aluminum substrate was fixed, and the other end was lifted by hand, and the angle at which the absorbent cotton began to slide on the coating film was measured. A smaller sliding angle of the water-soaked cotton [°] is better, and an angle of 50° or less is even better.

[0061] [Anti-adhesion properties against mud] The adhesion prevention performance against mud [°] was evaluated using mud with a moisture content of 20% according to the following procedure. Deionized water was added to Akagi Gardening's "Arakida Soil" to create a mud mixture with a moisture content of 20%. Then, 10g of the mud was dropped from a height of 15cm onto the surface of each coating film layered on the surface of an aluminum substrate, causing the mud to adhere to each coating film. With one end of the aluminum substrate fixed, the other end was lifted by hand, and the angle at which the attached mud began to slide across the coating film was measured. The anti-adhesion property of the mud [°] is considered good if it is small, and 45° or less is even better.

[0062] (Dispersibility of fluororesins) The dispersibility of the fluororesin was evaluated using the following procedure. At room temperature, a surfactant was added to the polyimide precursor solution, and the fluororesin listed in Table 1 was added. The mixture was then stirred using a Thinky "Awatori Rentaro ARE-310" in MIX mode (2000 RPM) for 3 minutes and in DEFORM mode (2200 RPM) for 30 seconds to prepare a coating film composition for use as a coating liquid. Next, the coating liquid was applied to a substrate using the wire bar coating method so that the average thickness of the coating film after firing was 20 μm. After that, the condition of the coated film was visually inspected to determine whether there were any powder clumps of 0.5 cm or larger. Dispersibility was evaluated in three stages according to the following criteria. If the evaluation is B or higher, it can be judged that the dispersibility is good. A: Disperses without creating clumps. B: If you increase the stirring time (3 minutes in MIX mode (2000 RPM), then 30 seconds twice in DEFORM mode (2200 RPM)), the lumps will disappear. C: Increasing the number of stirring cycles (stirring for 3 minutes in MIX mode (2000 RPM) and 30 seconds in DEFORM mode (2200 RPM) three or more times) will eliminate lumps.

[0063] (Arithmetic mean height Sa) A shape analysis laser microscope "VK-X1100" manufactured by Keyence Corporation was used as the measurement device. Under the standard eyepiece type CF IC EPI Plan Apo50X, each coating film was measured over an area of ​​282.8 μm × 212.3 μm. Height data for 1024 points × 768 points was obtained. Subsequently, reference plane correction was performed using the multi-analysis application software included with the laser microscope, based on the measurement data for the entire surface. After reference plane correction, the Sa [μm] at the surface was calculated.

[0064] (Arithmetic mean curvature of the mountain peak Spc) A shape analysis laser microscope "VK-X1100" manufactured by Keyence Corporation was used as the measurement device. Under the standard eyepiece type CF IC EPI Plan Apo50X, each coating film was measured over an area of ​​282.8 μm × 212.3 μm, obtaining 1024 × 768 height data points. Subsequently, reference plane correction was performed using the multi-analysis application software attached to the laser microscope, based on the measurement data of the entire surface. After reference plane correction, the arithmetic mean curvature Spc[μm] of the peaks across the entire surface was calculated. -1 The result was calculated.

[0065] [Pencil hardness] Pencil hardness was measured using a pencil hardness tester under conditions of a 45° angle and a 750g load, in accordance with JIS-K-5600-5-4 (1999). A higher pencil hardness is better, and a hardness of 5H or higher indicates that the surface is less prone to scratching and is of higher quality.

[0066] (Ring-on-disc abrasion test) A ring-on-disk abrasion test is a test in which the tip of a metal ring, for example, is pressed perpendicularly against the sliding surface of the test member while the sliding surface is rotated, thereby causing rotational sliding. The limit PV value [MPa·m / min] of the outer surface of the coating film was measured by ring-on-disk abrasion using the following procedure. The measurement was performed under the conditions of temperature control at 23±2℃, a constant load of 10MPa, and increasing the speed by one step every 3 minutes. Specifically, a ring-shaped mating material made of S45C (carbon steel for machine structures) with ring dimensions (outer diameter / inner diameter) of φ11.6mm / φ7.4mm was used. Then, with a load (surface pressure: P) of 10MPa applied to the mating material under dry lubrication conditions, the test piece was rotated at a predetermined speed (rotational speed: V), and the coefficient of dynamic friction was measured by the reaction torque generated in the mating material. In this process, the speed was increased starting at 1 m / min in step (1), then to 5 m / min in step (2), and to 10 m / min in step (3). Thereafter, the speed was increased by 10 m / min with each subsequent step, and the limit PV value was defined as the value obtained by multiplying the surface pressure P just before the substrate was exposed by the rotational speed V. The AND Corporation "EFM-3-1010-S" was used as the test apparatus for the above measurements. A higher limit PV value [MPa·m / min] is better, and a value of 1000 or higher indicates better wear resistance.

[0067] Table 1 above shows the evaluation results for coating films No. 1 to No. 7.

[0068] As shown in Table 1, a coating film containing polyimide and fluororesin, with a fluororesin content of 15% to 55% by volume, exhibited good resistance to mud adhesion.

[0069] From the above, it was demonstrated that the coating film exhibits excellent resistance to the adhesion of foreign matter. [Explanation of Symbols]

[0070] 1 Molded body 2 Base 3. Coating film

Claims

1. Polyimide and Fluororesin and It contains, A coating film having a fluororesin content of 15% by volume or more and 55% by volume or less.

2. The coating film according to claim 1, wherein the fluororesin is polytetrafluoroethylene, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, or tetrafluoroethylene-hexafluoropropylene copolymer.

3. The coating film according to claim 1, wherein the ratio of the number of fluorine atoms to the number of carbon atoms in the region near the surface of the coating film is 1.9 or more.

4. The coating film according to claim 1, wherein, in a cross section perpendicular to the surface of the coating film, the proportion of the area occupied by the fluororesin in the cross section from the surface to a depth of 1 μm is 75% or more and 95% or less.

5. The arithmetic mean curvature Spc of the peaks on the surface is 10,000 μm. －１ 26000 μm or more －１ The coating film according to claim 1, which is as follows:

6. Substrate and, A coating film according to any one of claims 1 to 5 is laminated on at least a portion of the surface of the above substrate. A molded body comprising the following features.

7. A method for manufacturing a molded article according to claim 6, A step of coating a coating film composition containing a polyimide precursor and a fluororesin onto at least a portion of the surface of the substrate, A step of heating the coating film formed after the above coating step, Equipped with, A method for manufacturing a molded article, wherein the heating temperature in the heating step is equal to or greater than the melting point of the fluororesin.

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