Powder coating composition

Abstract

The objective of this invention is to provide a hot-melt fluoropolymer powder coating composition containing filler, which has a large film thickness that can be coated in one pass, a large limited film thickness for coating, and the ability to be thickly coated. This invention is a powder coating composition, which is a powder mixture containing: first hot-melt fluoropolymer particles having an average particle diameter of 2µm to 100µm, wherein filler is dispersed in the particles; second hot-melt fluoropolymer particles having an average particle diameter of 10µm to 200µm; and charge control agent particles.

Description

Technical Field

[0001] Cross-referencing of related applications

[0002] This application claims priority to Japanese Patent Application No. 2021-26033, filed on February 22, 2021, the disclosure of which is incorporated herein by reference in its entirety.

[0003] This invention relates to a hot-melt fluororesin powder coating composition containing fillers, which can be thickly coated on a vertical surface by electrostatic powder coating. Prior Technology

[0004] In addition to its very low coefficient of friction and non-stickiness, fluoropolymers possess excellent heat resistance, chemical resistance, electrical properties, and mechanical properties, leading to their widespread use in all types of industrial fields, such as chemical, mechanical, electrical devices, and the like. Specifically, hot-melt fluoropolymers exhibit fluidity at temperatures above their melting point, and therefore, the formation of pinholes in coatings can be suppressed, thereby allowing the use of fluoropolymers in coating compositions.

[0005] Patent document 1 discloses an aqueous liquid coating of fluoropolymers. These aqueous liquid coatings are used as so-called slurry coatings with high concentration and viscosity, allowing for a thick coating. However, unlike powder coatings, slurry coatings are prone to foaming when the solvent (dispersion medium) evaporates. To prevent this, various solvents are used, requiring multi-stage baking and drying processes, resulting in environmental problems such as solvent volatility, longer drying times for slurries, greater difficulty in storing and managing slurries compared to powder coatings, difficulty in coating materials with complex shapes using slurries, and similar issues.

[0006] On the other hand, hot-melt fluoropolymer powder coatings have advantages, including the ability to achieve thick coatings without volatile liquid media, reusability, and no VOC (volatile organic compounds) generation. Electrostatic coating is commonly used as a powder coating method for hot-melt fluoropolymer powder coatings, wherein the material to be coated and the powder coating are charged and coated. Furthermore, when fillers are used to impart various properties to the hot-melt fluoropolymer powder coating, such as conductivity, abrasion resistance, wear resistance, and the like, or to adjust appearance, such as color, brightness, and the like, the hot-melt fluoropolymer powder coating and filler particles can be mixed and used. However, from the perspectives of thick coating properties, coating film durability, prevention of filler detachment from the coating film, prevention of coating film changes, and the like, it is preferable that the filler particles are dispersed within the hot-melt fluoropolymer powder particles (e.g., Patent Documents 2 and 3).

[0007] On the other hand, in recent years, there has been a growing demand for coatings with high durability and corrosion resistance, as well as for thicker coatings to improve productivity and reduce processing costs. Furthermore, to increase productivity, it is preferable to achieve a larger film thickness in a single coating application to reduce the number of overcoatings. However, hot-melt fluoropolymer powder coatings containing fillers, particularly conductive fillers, exhibit poorer thick-coating properties compared to those without fillers. This is believed to be because even when fillers are dispersed internally as described above, including conductive fillers, it is difficult to apply charge to the powder particles during electrostatic coating, thus leading to easy particle desorption. On the other hand, conductive coatings are used to prevent charging, but thick coatings are also required to provide corrosion resistance. Moreover, to date, conductive coatings typically only provide conductivity to the surface layer, but it is necessary to provide conductivity throughout the entire thick coating film.

[0008] Furthermore, hot-melt fluoropolymer powder coatings (such as PFA and the like) are known to be able to achieve thicker coatings compared to liquid coatings. Although thicker coatings can be obtained by rotational lining, the application is limited to the inner surface of structures with a circular cross-section having grooves or pipes, in which rotational lining can be applied (Non-Patent Document 1). [Previous Technical Documents] []

[0009] Patent Document 1: Japanese Patent Publication No. 3321805 Patent Document 2: Japanese Publication Examination Application H5-73147 Patent Document 3: Japanese Publication Examination Application S52-44576 Non-patent documents

[0010] Non-Patent Document 1: Guide to Corrosion-Resistant Linings and Coatings (Published by JAPAN FLUOROPOLYMERS INDUSTRY ASSOCIATION), Page 9, Table 1 Summary of the Invention

[0011] The problem that this invention aims to solve

[0012] The objective of this invention is to provide a hot-melt fluororesin powder coating composition containing fillers that can be thickly coated, having a high film thickness that can be coated in one pass and a high limiting film thickness for coating. means of solving problems

[0013] The present invention relates to a powder coating composition, which is a powder mixture containing: first hot-melt fluororesin particles having an average particle diameter of 2µm to 100µm, wherein filler is dispersed in the particles; second hot-melt fluororesin particles having an average particle diameter of 10µm to 200µm; and charge control agent particles.

[0014] In the powder coating composition of the present invention, the ratio of the first hot-melt fluoropolymer particles to the second hot-melt fluoropolymer particles is preferably 1 wt% to 60 wt%: 40 wt% to 99 wt%, and the amount of charge control agent particles is 0.01 wt% to 5 wt% of the total amount of the powder coating composition. The average particle diameter of the second hot-melt fluoropolymer particles is preferably larger than the average particle diameter of the first hot-melt fluoropolymer particles. Furthermore, the filler is preferably a conductive filler, and more preferably a carbon material having a graphene structure. Furthermore, the charge control agent particles are preferably graphite. Furthermore, the hot-melt fluoropolymer is preferably a perfluorinated resin.

[0015] Another embodiment of the present invention is a coating film made from a powder coating composition, and the film thickness is preferably 100µm or greater. [Effects of the Invention] []

[0016] The present invention provides a hot-melt fluororesin powder coating composition containing filler, which has a large film thickness that can be coated in one step, a large limiting film thickness for coating, and can be thickly coated. Simple Explanation of the Diagram

[0017] none Implementation

[0018] The powder coating composition of the present invention is a powder coating composition containing the following powder mixture: (1) first hot melt fluororesin particles, (2) second hot melt fluororesin particles, and (3) charge control agent particles. (1) First hot-melt fluororesin particles

[0019] The first hot-melt fluororesin particle is described below. The first hot-melt fluororesin particle of the present invention is a particle having an average particle diameter of 2 to 100 µm, wherein the filler is dispersed in the hot-melt fluororesin, and the first hot-melt fluororesin particle is manufactured from the hot-melt fluororesin and the filler.

[0020] The hot-melt fluoropolymer used in this invention may suitably be selected from resins known as hot-melt fluoropolymers. Examples include polymers or copolymers of monomers selected from tetrafluoroethylene, trifluorochloroethylene, hexafluoropropylene, perfluoro(alkyl vinyl ether), difluoroethylene, and vinyl fluoride; copolymers of these monomers with ethylene, propylene, butene, pentene, and hexene; or copolymers with another monomer having a double bond, or acetylene and propylene; or copolymers with another monomer having a triple bond, and the like. Specific examples of hot-melt fluoropolymers include low molecular weight hot-melt polytetrafluoroethylene (hot-melt PTFE), tetrafluoroethylene / perfluoro(alkyl vinyl ether) copolymer (PFA), tetrafluoroethylene / hexafluoropropylene copolymer (FEP), tetrafluoroethylene / hexafluoropropylene / perfluoro(alkyl vinyl ether) copolymer, tetrafluoroethylene / ethylene copolymer, polyvinylidene fluoride, polychlorotrifluoroethylene, chlorotrifluoroethylene / ethylene copolymer, and the like.

[0021] Among these hot-melt fluoropolymers, perfluoropolymers, such as hot-melt PTFE, PFA, FEP, tetrafluoroethylene, hexafluoropropylene, and perfluoro(alkyl vinyl ether) copolymers, are particularly preferred from the viewpoint of non-stickiness and heat resistance of the coating film. In these cases, PFA is preferred from the viewpoint of heat resistance. When using PFA, the alkyl group of the perfluoro(alkyl vinyl ether) in PFA preferably has 1 to 5 carbon atoms, and more preferably 1 to 3 carbon atoms. Furthermore, the amount of perfluoro(alkyl vinyl ether) in PFA is preferably in the range of 1 to 50 wt%.

[0022] Furthermore, the hot-melt fluoropolymer used in this invention, from the viewpoint of good formability during high-temperature melting, is preferably a hot-melt fluoropolymer that has fluidity at temperatures above its melting point. Specifically, the melt flow rate (MFR) of the hot-melt fluoropolymer is preferably 0.1 g / 10 min or higher, and more preferably 0.5 g / 10 min or higher. Examples of resins include PFA, FEP, and tetrafluoroethylene, hexafluoropropylene, and perfluoro(alkyl vinyl ether) copolymers. PFA, which has a high melting point and excellent thermal fluidity, is particularly preferred. On the other hand, if the MFR is too high (melt viscosity is too low), appearance defects may easily occur during repeated coating and baking due to sagging or shrinkage (groove marks), and it becomes difficult to form a thick film, which is not preferred. Specifically, the MFR of the hot-melt fluoropolymer is preferably 15 g / 10 min or lower, more preferably 10 g / 10 min or lower, and particularly preferably 5 g / 10 min or lower.

[0023] Depending on the desired properties, the hot-melt fluoropolymer in this invention can be mixed with two or more hot-melt fluoropolymers. Additionally, non-hot-melt polytetrafluoroethylene may also be included.

[0024] In the first hot-melt fluoropolymer particles of the present invention, the filler is dispersed within the particles. Preferably, the filler material is uniformly dispersed within the particles. Whether the filler is uniformly dispersed within the particles can be confirmed by observing the particle surface using an electron microscope or similar means to ensure uniform dispersion. Furthermore, although it depends on the physical properties of the filler used, when a conductive filler is used, it can be confirmed by measuring the volume resistivity. The volume resistivity is the value measured according to the measurement method (7) described in the specification, and when a conductive filler is used, the volume resistivity is preferably 10⁶ Ω·cm or lower. Therefore, to uniformly disperse the filler in the hot-melt fluoropolymer to manufacture resin particles, the method described in Patent Document 2 can be used, for example.

[0025] Various types of fillers can be used as fillers dispersed in particles. Examples include metal powders, metal oxides (alumina, zinc oxide, tin oxide, titanium oxide, and the like), glass, ceramics, silicon carbide (SiC), silicon oxide, boron nitride, calcium fluoride, carbon black, graphite, mica, barium sulfate, various resin particles, and the like. Fillers in various shapes can be used (such as particulate fillers, fibrous fillers, sheet fillers, and the like).

[0026] Specifically, this invention is effective when using conductive fillers, and examples of conductive fillers include metals, metal oxides (zinc oxide, tin oxide, titanium oxide, indium oxide, and the like), titanium carbide, titanium nitride, carbon fibers, carbon black, graphite, carbon nanotubes (CNTs), and other carbon materials having a graphene structure, particles coated thereon, and composite particles. To achieve high conductivity, a combination of carbon black and carbon fibers is preferred. Furthermore, in this invention, materials with relatively low insulating properties (such as silicon carbide (SiC)) and, in particular, materials with a volume resistivity of 10⁸ Ω·cm or lower can also be used as conductive fillers. Silicon carbide (SiC) is preferred to improve the wear resistance of the coating film.

[0027] Furthermore, thick coatings are difficult to achieve when using polar particles with hydrophilic surfaces (such as mica, alumina, boron nitride, and silicon oxide) (fluoropolymers and fillers have different electrical properties, and therefore changes in charge are expected to occur during electrostatic coating), but this filler can be used. Mica provides a bright appearance to the coating film and is therefore preferred for use.

[0028] Fillers of various shapes (such as particulate fillers, fibrous fillers, flake fillers, and similar) can be used as particle shapes. The preferred mixing amount depends on the desired properties, the type of filler, and the particle size, but is preferably 0.1 to 30 wt%, more preferably 1 to 10 wt%, and especially preferably 2 to 5 wt%. If the filler amount is low, the filler effect is reduced. Furthermore, if the filler amount is high, there is a problem of not being able to obtain a smooth and uniform coating film due to the easy aggregation of filler particles or high melt viscosity.

[0029] The average particle diameter of the first hot-melt fluoropolymer particles is in the range of 2 to 100 µm, more preferably 3 to 75 µm, more preferably 5 to 50 µm, and particularly preferably 8 to 35 µm. If the average particle diameter is small, electrostatic powder coating becomes difficult due to wind influence, and the process is not only difficult to manufacture but also prone to aggregation during storage, resulting in defects. Furthermore, if the average particle diameter is too large, it becomes difficult to apply charge, and desorption easily occurs. Therefore, electrostatic coating becomes difficult, and the surface of the resulting coating film becomes uneven.

[0030] It should be noted that in this specification, "average particle diameter" refers to the particle diameter (d50) of the 50% integral value (based on volume) of the particle diameter distribution obtained by laser diffraction / scattering. (2) Second hot melt fluororesin particles

[0031] The second hot-melt fluoropolymer particles of the present invention contain particles of hot-melt fluoropolymer and have an average particle diameter of 10 to 200 µm.

[0032] The second hot-melt fluoropolymer particles can be manufactured from the resin used in the first hot-melt fluoropolymer particles described above. The second hot-melt fluoropolymer particles differ from the first hot-melt fluoropolymer particles described above in that they do not contain fillers. In hot-melt fluoropolymers, from the viewpoint of the non-stickiness and heat resistance of the coating film, perfluoropolymers such as PFA and FEP, tetrafluoroethylene, hexafluoropropylene, and perfluoro(alkyl vinyl ether) copolymers are particularly preferred. In these cases, PFA is preferred from the viewpoint of heat resistance.

[0033] The average particle diameter is between 10 and 200 µm, preferably 15 to 150 µm, more preferably 20 to 100 µm, and particularly preferably 25 to 70 µm. When compared with the average particle diameter of the first hot-melt fluoropolymer particles described above, the average particle diameter of the second hot-melt fluoropolymer particles is preferably larger than that of the first hot-melt fluoropolymer particles. Commercially available hot-melt fluoropolymer powder coatings can be used. It should be noted that the particles do not contain fillers, but may contain small amounts of additives, such as defoamers or the like, on the exterior of the particles (under powder mixing conditions). (3) Charge control agent particles

[0034] Various types of conductive particles can be used as the charge control particles of this invention. Examples include metal powders, carbon fibers, carbon black, graphite, carbon nanotubes (CNTs), and other carbon materials with graphene structures, metal oxides (zinc oxide, tin oxide, titanium oxide, indium oxide, and the like), titanium carbide, titanium nitride, and the like. Among these, carbon materials with graphene structures are preferred, and graphite is particularly preferred. The function of the charge control particles is believed to be that the charge control particles adhere to and coat particles with different electrostatic properties between a first hot-melt fluoropolymer particle containing filler and a second hot-melt fluoropolymer particle without filler, in order to homogenize the electrostatic properties of the surfaces and provide uniform mixing without aggregation and separation when these particles are mixed together. Graphite is preferred in this invention because the dry mixing is carried out at high speed, and brittle graphite is pulverized into fine flakes, which can adhere to and coat the particles. (4) Optional components

[0035] The powder coating composition of this invention may also contain organic / inorganic additives as optional components, within a range that does not affect the physical properties of the powder coating composition. Examples include polyarylene sulfides, polyetheretherketones, polyamides, polyimides, and other engineering plastics, metal powders, metal oxides (alumina, zinc oxide, tin oxide, titanium oxide, and the like), glass, ceramics, silicon carbide, silicon oxide, calcium fluoride, carbon black, graphite, mica, barium sulfate, and the like. Additives in various shapes (such as particulate additives, fibrous additives, flake additives, and the like) can be used as the form of the additive. Based on the total amount of the powder coating composition, this amount is preferably 10 wt% or less, and more preferably 5 wt% or less. (5) The composition ratio of the powder coating composition of the present invention

[0036] In the powder coating composition of the present invention, the ratio of the first hot-melt fluoropolymer particles to the second hot-melt fluoropolymer particles is preferably in the range of 1 wt% to 60 wt%: 40 wt% to 99 wt%, more preferably 5 wt% to 50 wt%: 50 wt% to 95 wt%, and even more preferably in the range of 10 wt% to 45 wt%: 55 wt% to 90 wt%. Furthermore, the amount of charge control agent particles is preferably 0.01 to 5 wt% of the entire powder coating composition, more preferably 0.1 to 3.0 wt%, and even more preferably 0.2 to 2.0 wt%. Additionally, the proportion of fluoropolymer in the entire powder coating composition is 80 wt% or higher, and preferably 90 wt% or higher. If the proportion of fluoropolymer increases, the properties of the fluoropolymer (such as release properties, slip properties, chemical resistance, weather resistance, and the like) can be suitably achieved. However, if the proportion of fluoropolymer decreases, the properties of the fluoropolymer cannot be sufficiently achieved. (6) Manufacturing method

[0037] The method for manufacturing the powder coating composition of the present invention is described below.

[0038] The powder coating composition of the present invention is obtained by mixing first hot-melt fluoropolymer particles, second hot-melt fluoropolymer particles, and charge control agent particles. Examples of possible mixing methods include methods of mixing particles under dry conditions (dry blending / dry mixing), and fluid mixing methods using a turbine mixer or similar, which agitates the particles by means of a rolling container for self-mixing. Examples of apparatus for dry blending include, but are not limited to, a cutting mixer, a Henschel mixer, a V-type mixer with a shredder, a double-cone mixer with a shredder, a rocking mixer, and the like. The mixed resin composition is molded into a predetermined shape according to the intended use. (7) Coating film prepared by means of the powder coating composition of the present invention

[0039] The "coating film" of this invention is a coating film obtained by applying the powder coating composition of this invention. Preferably, a primer layer containing a fluororesin is provided for adhesion to the substrate. The coating method of the powder coating composition of this invention can be any known powder coating method, but electrostatic powder coating is preferred. After coating, a coating film free of pinholes and other defects is obtained by heating to a temperature above the melting point of the hot-melt fluororesin. The powder coating composition of this invention is preferably used in: stoves, such as electric frying pans, electric cookers, and the like; heat-releasing trays in factory production lines or the like (such as bread baking processes and the like); office equipment related products, such as stationary rollers / belts / inkjet nozzles and the like; industrial equipment related products in chemical plants, such as pipelines and the like; and other products requiring non-sticky properties and water- and oil-repellent properties. Preparation of aluminum test pieces (A) Substrate surface treatment (sandblasting)

[0040] The surface of the aluminum substrate (a product conforming to JIS A1050, 95mm × 150mm, 1mm thick) was degreased using isopropanol, and then the surface was roughened by sandblasting using a sandblasting machine (Numablaster SGF-4(A)S-E566, manufactured by Fuji Manufacturing Co., Ltd.) with #60 alumina (Showa Blaster, manufactured by Showa Denko KK). (2) Primer application

[0041] A liquid primer coating (Teflon fluoropolymer coating, water-based primer PJ-BN910, manufactured by Chemours-Mitsui Fluoroproducts Co., Ltd.) was applied to the substrate treated in (A) above using an air spray gun (W-88-10E2 φ1mm nozzle (manufactured by Anest Iwata Corporation) at an air pressure of 3 to 4 kgf / cm². The coating was performed such that the liquid weight applied to each substrate was approximately 0.9 to 1.4 g, and then dried in a forced-draft oven at 120°C for 15 minutes to form a coating film with a thickness of 8 to 12 µm. The coating environment was at a temperature of 25°C and a humidity of 60% RH. Evaluation methods (1) Appearance of the coating film

[0042] Using an electrostatic powder coating machine (Hand Gun System GX7500CS, manufactured by Nihon Parkerizing Co., Ltd.), the aluminum substrates treated in (A) and (B) above were placed horizontally under ground conditions. Powder was electrostatically coated from a distance of approximately 25 cm at a coating voltage of 20 to 40 kV (negative) and a discharge rate of approximately 50 g / min, achieving a coating weight of approximately 2.8 g (corresponding to a film thickness of 100 µm). After baking at 390 °C for 30 minutes, the appearance of the resulting coating film was observed. A uniform appearance without any abnormalities was considered acceptable (○). (2) Concealment

[0043] Observe the appearance of the coating film obtained in (1) above to confirm whether the color of the primer is hidden. If the color of the substrate is not visible, it is considered to pass (○). (3) Thick coating properties 1

[0044] Using an electrostatic powder coating machine (Hand Gun System GX7500CS, manufactured by Nihon Parkerizing Co., Ltd.), the aluminum substrates treated in (A) and (B) above were placed in both vertical and floor-mounted conditions. Powder was then electrostatically coated from a distance of approximately 25 cm at a coating voltage of 20 to 40 kV (negative) and a discharge rate of approximately 50 g / min until the powder no longer adhered. The coating environment was 25°C with 60% RH humidity. The coated aluminum substrate was then baked in a forced-draft circulating oven at 390°C for 30 minutes to form a coating film. The coating amount, the presence or absence of powder shedding, the presence or absence of electrostatic reaction, and the appearance of the obtained coating film were examined. Coating films with a coating amount of 2.8 g (corresponding to a film thickness of 100 µm) or higher, no powder shedding, no electrostatic reaction, foaming, or other defects were considered acceptable (○). (4) Thick coating properties 2

[0045] Electrostatic powder coating was performed on a horizontally mounted glass substrate (float glass, 95mm × 150mm, 2mm thick) using a Hand Gun System GX7500CS powder coating machine (manufactured by Nihon Parkerizing Co., Ltd.), resulting in a film thickness of 100 to 120µm each time. The film was baked at a specified temperature for 30 minutes, repeated five times (390°C for the first time, 360°C for the second and third times, and 340°C for the fourth and fifth times). The thickness of the baked film was observed to be 500µm or higher, and the presence of defects due to foaming was checked. If the thickness was 500µm and no defects due to foaming were observed, the film was considered passed (○). (5) Conductivity 1

[0046] Electrostatic coating was applied to a glass substrate (float glass, 95mm × 150mm, 2mm thick) to achieve a film thickness of 100 to 120µm. After baking at 390°C for 30 minutes, the coating was peeled off in boiling water to obtain the final film. Surface resistivity was measured using a UA probe, Hiresta UX manufactured by Nittoseiko Analytech Co., Ltd., at an applied voltage of 100V. Surface resistivity below 10⁹ Ω indicates pass (○), between 10¹⁰ and 12 Ω indicates Δ, and above 10¹² Ω indicates ×. (6) Conductivity 2

[0047] Under the same conditions as in Thick Coating 2, a coating film with a thickness of 300 µm or greater was prepared and peeled off in boiling water to obtain a thin film. Surface resistivity was measured using a UA probe, a Hiresta UX manufactured by Nittoseiko Analytech Co., Ltd., at an applied voltage of 100 V. A surface resistivity below 10⁹ Ω indicates pass (○), between 10¹⁰ and 12 Ω indicates Δ, and above 10¹² Ω indicates ×. (7) Volume resistivity

[0048] Electrostatic coating was applied to a glass substrate (float glass, 95mm × 150mm, 2mm thick) to achieve a film thickness of 50 to 100µm. After baking at 390°C for 30 minutes, the coating was peeled off in boiling water to obtain the final film. The film was then peeled off, and the volume resistivity was calculated by measuring the resistance along the thickness direction (front and back surfaces) of the coating using a UA probe from a Hiresta UX manufactured by Nittoseiko Analytech Co., Ltd., under an applied voltage of 100V. A volume resistivity below 10⁶ Ω·cm was considered advantageous for the particle system used. raw material • Carbon Black 1: "Asahi Thermal" manufactured by Asahi Carbon Co., Ltd., with an average primary particle diameter of 80 nm (oil furnace black). • Carbon Black 2: Carbon ECP (KETJENBLACK) manufactured by Lion Specialty Chemicals Co., Ltd., with an average primary particle diameter of 25 nm. • Carbon fiber (Torayca Milled Fiber MLD-30 manufactured by Toray Industries, Inc., average length: 30µm) • Graphite (UF-G5 manufactured by Showa Denko KK, average particle diameter: 3µm) PFA aqueous dispersion

[0049] Aqueous dispersions of PFA were prepared as follows. The dispersion of tetrafluoroethylene / perfluoropropyl vinyl ether (TFE / PPVE) copolymer was prepared by the method described in Examples 1 to 3 of Japanese Patent Publication No. 5588679. (MFR of solid resin = 16.6 [g / 10 min], average particle diameter: 0.186 µm, comonomer (PPVE) ratio: 3.3 wt%, PFA content in dispersion: 30.6 wt%) • PFA powder coating: Fluorine Resin Teflon (registered trademark) coating powder topcoat MJ-508 manufactured by Chemours-Mitsui Fluoroproducts Co., Ltd., with an average particle diameter d50 of approximately 50µm (a mixture of pulverized amorphous particles and 3% PPS particles (to suppress foaming)). • 2H,3H-Decafluoropentane (Vertrel XF, a registered trademark manufactured by Chemours-Mitsui Fluoroproducts Co., Ltd.) • 60% Nitric Acid (manufactured by FUJIFILM Wako Pure Chemical Corporation) • Silicon carbide (SiC) (a powder with spherical particles having an average particle diameter of approximately 25 µm) • Mica (IRIODIN 355 manufactured by MERCK KGAA, with a particle size of 10 to 100 µm) [Example] [] Comparative Example 1 Example of preparation of the first hot-melt fluororesin particle 1

[0050] 1000g of pure water was collected in a 2L stainless steel beaker, and 29.5g of carbon black 2 (KETJENBLACK) and 9.0g of graphite were added. The mixture was then ultrasonically dispersed for five minutes using an ultrasonic generator (UE-100Z28S-8A, manufactured by Ultrasonic Engineering Co., Ltd.). The resulting dispersion was further added to a stainless steel container containing 4200g of PFA aqueous dispersion and stirred at 600rpm for 3 minutes using a downflow propeller-type 4-blade stirrer. Next, 88g of a 60% nitric acid aqueous solution was added, and after confirming a rapid increase in viscosity, 1000g of 2H,3H-decafluoropentane was added to generate coarse particles of aggregates in the liquid. The coarse particles of the aggregate removed by filtration were washed with pure water, and 2H,3H-decafluoropentane was volatilized and removed by raising the temperature to 50°C to 60°C and holding it for 30 minutes. The obtained dry coarse particles were pulverized using a pulverizer (RP-6-K115 manufactured by Rietz Manufacturing) to obtain pulverized powder. The pulverized powder of the aggregate was sprayed and baked in the baking oven described in Patent Document 3. The particles cooled below the melting point were collected and then used as the first hot melt fluoropolymer particles 1. The average particle diameter of the obtained particles was d50: 31.4µm. The volume resistivity of particle 1 was measured according to evaluation method (7) and found to be 10⁵ to 10⁶ Ω·cm. The particles (powder) were used as the composition of the powder coating for the above various evaluations. Comparative Example 2

[0051] 40.0 g of the first hot-melt fluoropolymer particles 1 (average particle diameter d50: 31.4 µm) and 60.0 g of PFA powder coating (MJ-508 manufactured by Chemours-Mitsui Fluoroproducts Co., Ltd., average particle diameter d50: 55.0 µm) as the second hot-melt fluoropolymer were placed in a high-speed mixer (KSMAX manufactured by TANINAKA) and then mixed and stirred at 12,000 rpm for 30 seconds to obtain the powder coating composition. [Example] [1]

[0052] 20.0 g of the first hot-melt fluoropolymer particles (average particle diameter d50: 31.4 µm), 79.4 g of PFA powder coating (MJ-508 manufactured by Chemours-Mitsui Fluoroproducts Co., Ltd., average particle diameter d50: 51.2 µm), which were prepared in the aforementioned preparation example 1, and 0.6 g of graphite were placed in a high-speed mixer (KSMAX manufactured by TANINAKA), and then mixed and stirred at 12,000 rpm for 30 seconds to obtain the powder coating composition. [Example] [2]

[0053] The powder coating composition was obtained by a method similar to that described in Example 1 above, except that 79.1 g (instead of 79.4 g) of PFA powder coating (second hot melt fluoropolymer) and 0.9 g (instead of 0.6 g) of graphite were used. Example of the preparation of the first hot-melt fluororesin particle 2

[0054] The first hot-melt fluoropolymer particles 2 were manufactured by a similar method to that described in Comparative Example 1 (Preparation Example of First Hot-melt Fluoropolymer Particles 1) above, except that carbon black 1 was used instead of carbon black 2 (KETJENBLACK) and graphite. The average particle diameter of the obtained particles was d50: 22.2 µm. The volume resistivity of particles 2 was measured according to evaluation method (7) and found to be 10¹² Ω·cm or higher. [Example] [3]

[0055] The powder coating composition was obtained by a similar method as described in Example 2 above, except that 20.0 g of the first hot melt fluoropolymer particles 2 (average particle diameter d50: 22.2 µm) manufactured in the aforementioned preparation example was used instead of the first hot melt fluoropolymer particles manufactured in Preparation Example 1 above, and a PFA powder coating (MJ-508 manufactured by Chemours-Mitsui Fluoroproducts Co., Ltd., average particle diameter d50: 42.8 µm) was used as the second hot melt fluoropolymer. [Example] [4]

[0056] The powder coating composition was obtained by a similar method as described in Example 3 above, except that 79.5 g (instead of 79.1 g) of PFA powder coating and 0.5 g (instead of 0.9 g) of graphite were used. [Example] [5]

[0057] The powder coating composition was obtained by a similar method as described in Example 3 above, except that 79.7 g (instead of 79.1 g) of PFA powder coating and 0.3 g (instead of 0.9 g) of graphite were used. Results of Comparative Example 1, Comparative Example 2, and Examples 1 to 5

[0058] Tables 1 and 2 show the composition ratios of the powder coating compositions of Comparative Examples 1 and 2 and Examples 1 to 5 and the evaluation results of the coating films. Table 1 summarizes the composition ratios of the powder coating compositions of the present invention. Table 2 shows the evaluation results measured according to evaluation methods (1) to (6). Comparative Example 1 provides a coating film from the first hot-melt fluoropolymer particles 1. However, (1) coating appearance (uniform appearance and no abnormalities: ○), (2) concealment (whether the substrate color is not visible: ○), and (3) coating thickness 1 (whether a coating film of 100µm or more can be formed by coating once on a vertical surface: ○) are sufficient, but (4) coating thickness 2 (whether a coating film of 500µm or more can be formed by repeated coating: ○) are not satisfied.

[0059] On the other hand, Comparative Example 2 provides a coating film obtained from the first hot melt fluoropolymer particles 1 and the second hot melt fluoropolymer particles. However, although the coating thickness 2 (forming a coating film of 500µm or more by repeated coating) is sufficient, items (1) to (3) are not satisfied.

[0060] In contrast, Examples 1 and 2, in which graphite was included in the powder coating composition of Comparative Example 2 as a charge control agent particle used as a third component, achieved favorable results in all items (1) to (4). In Examples 3 to 5, only the conductive particles dispersed in the first hot-melt fluoropolymer particles 2 were changed to carbon black 1, but the same favorable results as in Examples 1 and 2, which included graphite and carbon black 2 (KETJENBLACK), were obtained. [Table 1] []] Composition of powder coatings in Comparative Examples 1 and 2 and Examples 1 to 5 Comparative Example 1 Comparative Example 2 Example 1 Example 2 Example 3 Example 4 Example 5 First particle composition PFA 97.0wt% 97.0wt% 97.0wt% 97.0wt% 97.0wt% 97.0wt% 97.0wt% graphite 0.7wt% 0.7wt% 0.7wt% 0.7wt% Carbon Black 2 2.3wt% 2.3wt% 2.3wt% 2.3wt% Carbon Black 1 3.0wt% 3.0wt% 3.0wt% Average particle diameter d50 31.4µm 31.4µm 31.4µm 31.4µm 22.2µm 22.2µm 22.2µm Mixing ratio (wt%) 100 40.0 20.0 20.0 20.0 20.0 20.0 Second particle composition PFA 97.0wt% 97.0wt% 97.0wt% 97.0wt% 97.0wt% 97.0wt% PPS 3.0wt% 3.0wt% 3.0wt% 3.0wt% 3.0wt% 3.0wt% Average particle diameter d50 55.0µm 51.2µm 51.2µm 42.8µm 42.8µm 42.8µm Mixing ratio (wt%) 60.0 79.4 79.1 79.1 79.5 79.7 Charge control agent graphite Mixing ratio (wt%) 0.6 0.9 0.9 0.5 0.3 [, , ] [] [Table 2] []] Evaluation results of Comparative Examples 1 and 2 and Examples 1 to 5 Evaluation Project Evaluation criteria Comparative Example 1 Comparative Example 2 Example 1 Example 2 Example 3 Example 4 Example 5 Coating appearance Uniformity ○ × ○ ○ ○ ○ ○ Concealment Background color not visible ○ × ○ ○ ○ ○ ○ Thick coating properties 1 A 100µm coating film is formed on the vertical surface. ○ × ○ ○ ○ ○ ○ Thick coating properties 2 500µm probability × ○ ○ ○ ○ ○ ○ Electrical conductivity 1 100µm thick ○ (≤10 6Ω) × (>10 12Ω) × (>10 12Ω) × (>10 12Ω) × (>10 12Ω) × (>10 12Ω) × (>10 12Ω) Conductivity 2 300µm thick (Thick film formation: NG) × (10 12Ω) × (>10 12Ω) × (>10 12Ω) × (>10 12Ω) × (>10 12Ω) × (>10 12Ω) Example of the preparation of the first hot-melt fluororesin particle 3

[0061] 1000g of pure water was collected in a 2L stainless steel beaker, and 18g of carbon black 2 (KETJENBLACK) and 26g of carbon fiber were added. The mixture was then ultrasonically dispersed for five minutes using an ultrasonic generator (UE-100Z28S-8A, manufactured by Ultrasonic Engineering Co., Ltd.). The resulting dispersion was added to a stainless steel container containing 4200g of PFA aqueous dispersion and stirred at 600rpm for 3 minutes using a downflow propeller-type 4-blade stirrer. Next, 88g of a 60% nitric acid aqueous solution was added, and after confirming a rapid increase in viscosity, 1000g of 2H,3H-decafluoropentane was added to generate coarse particles of aggregates in the liquid. The coarse particles of the aggregate removed by filtration were washed with pure water, and 2H,3H-decafluoropentane was volatilized and removed by raising the temperature to 50°C to 60°C and holding it for 30 minutes. The obtained dry coarse particles were pulverized using a pulverizer (RP-6-K115 manufactured by Rietz Manufacturing) to obtain pulverized powder. The pulverized powder of the aggregate was sprayed and baked in the baking oven described in Patent Document 3. The particles cooled below the melting point were collected and then used as the first hot melt fluoropolymer particles 3. The average particle diameter of the obtained particles was d50: 17.6µm. The volume resistivity of particles 3 was measured according to evaluation method (7) and found to be 10⁵ to 10⁶ Ω·cm. [Example] [6]

[0062] 10.0 g of the first hot-melt fluoropolymer particles 3 (average particle diameter d50: 17.6 µm), 89.1 g of PFA powder coating (MJ-508 manufactured by Chemours-Mitsui Fluoroproducts Co., Ltd., average particle diameter d50: 49.2 µm), which was prepared in the aforementioned preparation example, and 0.9 g of graphite were placed in a high-speed mixer (KSMAX manufactured by TANINAKA), and then mixed and stirred at 12,000 rpm for 30 seconds to obtain the powder coating composition. [Example] [7]

[0063] The powder coating composition was obtained by a method similar to that in Example 6, except that 20.0 g (instead of 10.0 g) of the first hot melt fluoropolymer particles 3 was used, and 79.1 g (instead of 89.1 g) of PFA powder coating (second hot melt fluoropolymer) was used. [Example] [8]

[0064] The powder coating composition was obtained by a method similar to that in Example 6, except that 40.0 g (instead of 10.0 g) of the first hot melt fluoropolymer particles 3 was used, and 59.1 g (instead of 89.1 g) of PFA powder coating (second hot melt fluoropolymer) was used. Example of preparation of the first hot-melt fluororesin particle 4

[0065] The first hot-melt fluoropolymer particles 4 were manufactured by a similar method to that used in the preparation example of the first hot-melt fluoropolymer particles 3, except that the amounts of carbon black 2 and PFA aqueous dispersion were changed. The average particle diameter of the obtained particles was d50: 18.4 µm. The volume resistivity of particles 4 was measured according to evaluation method (7) and found to be 10⁵ to 10⁶ Ω·cm. [Example] [9]

[0066] The powder coating composition was obtained by a method similar to that in Example 6, except that the first hot melt fluoropolymer particles 4 (average particle diameter d50: 18.4µg) replaced the first hot melt fluoropolymer particles 3. [Example]

[10]

[0067] The powder coating composition was obtained by a method similar to that in Example 7, except that the first hot melt fluoropolymer particles 4 (average particle diameter d50: 18.4µg) replaced the first hot melt fluoropolymer particles 3. [Example]

[11]

[0068] The powder coating composition was obtained by a method similar to that in Example 8, except that the first hot melt fluoropolymer particles 4 (average particle diameter d50: 18.4µg) replaced the first hot melt fluoropolymer particles 3. Results of Examples 6 to 11

[0069] Tables 3 and 4 show the composition ratios of the powder coating compositions of Examples 6 to 11 and the evaluation results of the coating films. Table 3 summarizes the composition ratios of the powder coating compositions of the present invention. Table 4 shows the evaluation results measured according to evaluation methods (1) to (6). In Examples 6 to 11, carbon black 2 (KETJENBLACK) and carbon fiber particles dispersed therein were used as the first hot-melt fluoropolymer particles 3. In Example 6, (1) for thick coating 1, it was confirmed that a coating of more than 2.8 g could be applied without powder falling onto a vertical surface and without causing an electrostatic reaction, and no abnormalities were confirmed in the appearance of the coating film. (2) for thick coating 2, after the powder was electrodeposited and subjected to repeated coating and baking, a film with a thickness of 500 µm or more was obtained, and no bubbling was observed even after baking. (3) for conductivity 1, a film with a thickness of approximately 100 µm exhibited a surface resistivity of 106 to 7 Ω. (4) For conductivity 2, a surface resistivity of 10⁶ to 7 Ω is exhibited in a film with a thickness of 300 µm or greater. (5) For the appearance of the coating film, a smooth and uniform coating film is obtained. (6) For concealment, a coating film that adequately conceals the primer is obtained. As in Examples 7 to 11, favorable results are obtained in almost all projects, similar to Example 6.

[0070] In Examples 6 to 11, compared with Examples 1 to 5, by using carbon black 2 (KETJENBLACK) and carbon fiber dispersed therein as the first hot melt fluoropolymer particles, a favorable conductivity of approximately 10 6 Ω was exhibited for both (5) conductivity 1 (resistance value of 100 µm coating film) and (6) conductivity 2 (resistance value of 300 µm coating film). Table 3 []] Composition of powder coating components in Examples 6 to 11 Example 6 Example 7 Example 8 Example 9 Example 10 Example 11 First particle composition PFA 96.6wt% 96.6wt% 96.6wt% 96.9wt% 96.9wt% 96.9wt% graphite Carbon Black 2 1.4wt% 1.4wt% 1.4wt% 1.1wt% 1.1wt% 1.1wt% Carbon Black 1 carbon fiber 2.0wt% 2.0wt% 2.0wt% 2.0wt% 2.0wt% 2.0wt% Average particle diameter d50 17.6µm 17.6µm 17.6µm 18.4µm 18.4µm 18.4µm Mixing ratio (wt%) 10.0 20.0 40.0 10.0 20.0 40.0 Second particle composition PFA 97.0wt% 97.0wt% 97.0wt% 97.0wt% 97.0wt% 97.0wt% PPS 3.0wt% 3.0wt% 3.0wt% 3.0wt% 3.0wt% 3.0wt% Average particle diameter d50 49.2µm 49.2µm 49.2µm 49.2µm 49.2µm 49.2µm Mixing ratio (wt%) 89.1 79.1 59.1 89.1 79.1 59.1 Charge control agent graphite Mixing ratio (wt%) 0.9 0.9 0.9 0.9 0.9 0.9 Table 4 []] Evaluation results of Examples 6 to 11 Evaluation Project Evaluation criteria Example 6 Example 7 Example 8 Example 9 Example 10 Example 11 Coating appearance Uniformity ○ ○ ○ ○ ○ ○ Concealment Background color not visible ○ ○ ○ ○ ○ ○ Thick coating properties 1 A 100µm coating film is formed on the vertical surface. ○ ○ ○ ○ ○ ○ Thick coating properties 2 500µm probability ○ ○ ○ ○ ○ ○ Electrical conductivity 1 100µm thick ○ (≤10 6Ω) ○ (≤10 6Ω) ○ (≤10 6Ω) ○ (≤10 6Ω) ○ (≤10 6Ω) ○ (≤10 6Ω) Conductivity 2 300µm thick ○ (≤10 6Ω) ○ (≤10 6Ω) ○ (≤10 6Ω) ○ (≤10 6Ω) Example of preparation of the first hot-melt fluororesin particles 5

[0071] The first hot-melt fluoropolymer particle 5 was manufactured by a similar method as in the preparation example of the first hot-melt fluoropolymer particle 3, except that the amounts of carbon black 2 and PFA aqueous dispersion were changed. The average particle diameter of the obtained particles was d50: 20.2 µm. The volume resistivity of the particles 5 was measured according to the evaluation method (7) and found to be 10⁵ to 10⁶ Ω·cm. [, , ] [] [Example]

[12]

[0072] The powder coating composition was obtained by a method similar to that in Example 6, except that the first hot melt fluoropolymer particles 5 (average particle diameter d50: 20.2µg) replaced the first hot melt fluoropolymer particles 3. [Example]

[13]

[0073] The powder coating composition was obtained by a method similar to that in Example 7, except that the first hot melt fluoropolymer particles 5 (average particle diameter d50: 20.2µg) replaced the first hot melt fluoropolymer particles 3. [Example]

[14]

[0074] The powder coating composition was obtained by a method similar to that in Example 12, except that 30.0 g (instead of 10.0 g) of the first hot melt fluoropolymer particles 5 (average particle diameter d50: 20.2 µm) was used, and 69.1 g (instead of 89.1 g) of PFA powder coating (second hot melt fluoropolymer) was used. [Example]

[15]

[0075] A powder coating composition was obtained by a method similar to that in Example 8, except that the first hot melt fluoropolymer particles 5 (average particle diameter d50: 20.2µg) replaced the first hot melt fluoropolymer particles 3. [Example]

[16]

[0076] The powder coating composition was obtained by a method similar to that in Example 13, except that 78.65 g (instead of 79.1 g) of PFA powder coating (second hot melt fluoropolymer) and 1.35 g (instead of 0.9 g) of graphite were used. Results of Examples 12 to 16

[0077] Tables 5 and 6 show the composition ratios of the powder coating compositions of Examples 12 to 16 and the evaluation results of the coating films. Table 5 summarizes the composition ratios of the powder coating compositions of the present invention. Table 6 shows the evaluation results measured according to evaluation methods (1) to (6). For all Examples 12 to 16, favorable results were obtained with respect to all of the following items: (1) coating appearance, (2) concealment, (3) coating thickness 1, (4) coating thickness 2, (5) conductivity 1, and (6) conductivity 2. However, with respect to (6) conductivity 2, the surface resistance showed a tendency to increase when the ratio of the first particle to the second particle increased (a tendency to increase in Examples 12 to 15). Table 5 []] Composition of powder coating components in Examples 12 to 16 Example 12 Example 13 Example 14 Example 15 Example 16 First particle composition PFA 97.2wt% 97.2wt% 97.2wt% 97.2wt% 97.2wt% graphite Carbon Black 2 0.8wt% 0.8wt% 0.8wt% 0.8wt% 0.8wt% Carbon Black 1 carbon fiber 2.0wt% 2.0wt% 2.0wt% 2.0wt% 2.0wt% Average particle diameter d50 20.2µm 20.2µm 20.2µm 20.2µm 20.2µm Mixing ratio (wt%) 10.0 20.0 30.0 40.0 20.0 Second particle composition PFA 97.0wt% 97.0wt% 97.0wt% 97.0wt% 97.0wt% PPS 3.0wt% 3.0wt% 3.0wt% 3.0wt% 3.0wt% Average particle diameter d50 49.2µm 49.2µm 49.2µm 49.2µm 49.2µm Mixing ratio (wt%) 89.1 79.1 69.1 59.1 78.65 Charge control agent graphite Mixing ratio (wt%) 0.9 0.9 0.9 0.9 1.35 [, , ] [] Table 6 []] Evaluation results of Examples 12 to 16 Evaluation Project Evaluation criteria Example 12 Example 13 Example 14 Example 15 Example 16 Coating appearance Uniformity ○ ○ ○ ○ ○ Concealment Background color not visible ○ ○ ○ ○ ○ Thick coating properties 1 A 100µm coating film is formed on the vertical surface. ○ ○ ○ ○ ○ Thick coating properties 2 500µm probability ○ ○ ○ ○ ○ Electrical conductivity 1 100µm thick ○ (≤10 6Ω) ○ (≤10 6Ω) ○ (≤10 7Ω) ○ (≤10 6Ω) ○ (≤10 6Ω) Conductivity 2 300µm thick ○ (≤10 6Ω) ○ (≤10 7Ω) ○ (≤10 9Ω) ○ (≤10 11Ω) ○ (≤10 6Ω) Example of the preparation of the first hot-melt fluororesin particles 6

[0078] The first hot-melt fluoropolymer particles 6 (containing 5 wt% SiC) were manufactured by a similar method to that used in the preparation example of the first hot-melt fluoropolymer particles 2, except that SiC was used instead of carbon black 1, and the amount of SiC and the amount of PFA aqueous dispersion were changed. The average particle diameter of the obtained particles was d50: 21.0 µm. [Example]

[17]

[0079] The powder coating composition (PFA powder coating: 79.7 wt%, graphite: 0.3 wt%, particles 6: 20.0 wt%) was obtained by a method similar to that in Example 5, except that first hot melt fluoropolymer particles 6 (average particle diameter d50: 21.0 µm) were used instead of first hot melt fluoropolymer particles 2. [Comparative Example] [3]

[0080] The powder coating composition (PFA powder coating: 80 wt%, particles 6: 20 wt%) was obtained by a similar method to that described in Example 17 above, except that graphite was removed from the powder coating composition. [Comparative Example] [4]

[0081] A powder coating composition prepared solely from first hot-melt fluororesin particles 6. Example of the preparation of the first hot-melt fluororesin particles 7

[0082] The first hot-melt fluoropolymer particles 7 (containing 1 wt% mica) were manufactured by a similar method to that used in the preparation example of the first hot-melt fluoropolymer particles 6, except that mica was used instead of SiC, and the amount of mica and the amount of PFA aqueous dispersion were changed. The average particle diameter of the obtained particles was d50: 21.1 µm. [Example]

[18]

[0083] The powder coating composition (PFA powder coating: 79.7 wt%, graphite: 0.3 wt%, particles 7: 20 wt%) was obtained by a method similar to that in Example 5, except that the first hot melt fluoropolymer particles 7 (average particle diameter d50: 21.1 µm) were used instead of the first hot melt fluoropolymer particles 2. [Comparative Example] [5]

[0084] The powder coating composition (PFA powder coating: 80 wt%, particles 7: 20 wt%) was obtained using a method similar to that described in Example 18 above, except that graphite was removed from the powder coating composition. [Comparative Example] [6]

[0085] A powder coating composition prepared solely from first hot-melt fluororesin particles 7. Results of Examples 17 and 18 and Comparative Examples 3 to 6

[0086] Tables 7 and 8 show the composition ratios of the powder coating compositions of Examples 17 and 18 and Comparative Examples 3 to 6 and the coating film evaluation results. Table 7 summarizes the composition ratios of the powder coating compositions of the present invention. Table 8 shows the evaluation results measured according to evaluation methods (1) to (3). From the results of Examples 17 and 18, it can be confirmed that adding graphite as a third component improves (1) coating appearance, (2) concealment, and (3) thick coating properties in the same way as when using resin particles containing carbon black or the like, even when using first hot-melt fluoropolymer particles containing non-conductive fillers (such as SiC, mica, or the like). On the other hand, when graphite is not included as a third component (Comparative Examples 3 and 5), (1) the coating appearance is uneven and (2) the concealment is insufficient. Furthermore, when the powder coating composition is made only from hot melt fluoropolymer particles 6 and hot melt fluoropolymer particles 7 (Comparative Examples 4 and 6), it satisfies (1) coating appearance and (2) concealment, but (3) thick coating 1 is problematic. Table 7 []] Composition of powder coating compositions in Examples 17 and 18 and Comparative Examples 3 to 6 Example 17 Comparative Example 3 Comparative Example 4 Example 18 Comparative Example 5 Comparative Example 6 First particle composition PFA 95wt% 95wt% 95wt% 99wt% 99wt% 99wt% SiC 5 w% 5 w% 5 w% mica 1 w% 1 w% 1 w% Average particle diameter d50 21.0µm 21.0µm 21.0µm 21.1µm 21.1µm 21.1µm Mixing ratio (wt%) 20.0 20.0 100 20.0 20.0 100 Second particle Composition PFA 97.0wt% 97.0wt% 97.0wt% 97.0wt% Mixing ratio (wt%) PPS 3.0wt% 3.0wt% 3.0wt% 3.0wt% Average particle diameter d50 49.2µm 49.2µm 49.2µm 49.2µm Mixing ratio (wt%) 79.7 80.0 79.7 80.0 Charge control agent graphite Mixing ratio (wt%) 0.3 0.3 Table 8 []] Evaluation results of Examples 17 and 18 and Comparative Examples 3 to 6 Evaluation Project Evaluation criteria Example 17 Comparative Example 3 Comparative Example 4 Example 18 Comparative Example 5 Comparative Example 6 Coating appearance Uniformity ○ × ○ ○ × ○ Concealment Background color not visible ○ × ○ ○ × ○ Thick coating properties 1 A 100µm coating film is formed on the vertical surface. ○ ○ × ○ ○ ×

[0087] This invention is not limited to the examples disclosed in this specification or the embodiments of the invention disclosed in this specification, but also covers the invention with appropriate modifications based on the details disclosed in this specification, as long as the content does not conflict with the spirit of the invention. Industrial applicability

[0088] The hot-melt fluoropolymer powder coating composition of the present invention can be applied to a vertical surface by electrostatic powder coating, forming a relatively thick coating film on a wide range of industrial products and the like, and can provide properties (such as conductivity and the like) to the coating film through fillers included therein.

[0089] none

[0090] none

Claims

1. A powder coating composition, which is a powder mixture, comprising: first hot-melt fluororesin particles having an average particle diameter of 2µm to 100µm, wherein a filler is dispersed in the particles; second hot-melt fluororesin particles having an average particle diameter of 10µm to 200µm; and charge control particles; wherein the ratio of the first hot-melt fluororesin particles to the second hot-melt fluororesin particles is 1wt% to 60wt%: 40wt% to 99wt%, and the amount of the charge control particles is 0.01wt% to 5wt% of the total amount of the powder coating composition; the average particle diameter of the second hot-melt fluororesin particles is greater than the average particle diameter of the first hot-melt fluororesin particles; and wherein the charge control particles are graphite.

2. The powder coating composition of claim 1, wherein the filler is a conductive filler.

3. The powder coating composition of claim 2, wherein the conductive filler is a carbon material having a graphene structure.

4. The powder coating composition of claim 1, wherein the hot-melt fluoropolymer is a perfluorinated resin.

5. A coating film made from a powder coating composition as claimed in any one of claims 1 to 4, wherein the film thickness is 100 µm or higher.