Fluororesin liquid coating composition

Abstract

To provide a fluororesin liquid coating composition for a fluororesin coating which strongly adheres to both of metal base materials and resin base materials and exhibits excellent steam resistance and corrosion resistance, a coating film including the composition, and an article including the coating film.SOLUTION: The present invention provides a fluororesin liquid coating composition containing a fluororesin and a polyetherketoneketone (PEKK), a coating film including the composition, and an article including the coating film.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a fluororesin liquid paint composition for fluororesin coatings that firmly adheres to both metal and resin substrates and has excellent water vapor resistance and corrosion resistance, a coating film formed by applying the same, and an article having the coating film. [Background technology]

[0002] Fluorine resins have excellent heat resistance, chemical resistance, electrical properties, and mechanical properties, as well as an extremely low coefficient of friction, non-stick properties, and water and oil repellency, making them widely used in a variety of industrial fields, including chemical, mechanical, and electrical.

[0003] In particular, taking advantage of the non-stick, water-repellent and oil-repellent properties of fluororesin, fluororesin coatings are used in a variety of fields, including painting cookware such as frying pans and rice cookers, and fixing rolls and belts that fix toner in office equipment.In recent years, the range of uses has expanded even further, to include inkjet nozzles and chemical plant equipment.

[0004] However, when coating various substrates with fluororesin, due to the non-stickiness of fluororesin, it is extremely difficult to paint the fluororesin directly onto the substrate, as this results in poor adhesion. Therefore, when applying a fluororesin coating, a primer paint composition that has adhesion to the substrate and also to the fluororesin coating to be applied on top of it has usually been used.

[0005] Such primer coating compositions use heat-resistant resins (so-called engineering plastics) that have adhesive properties to the substrate and can withstand high temperatures above the melting point of the fluororesin. For example, Patent Document 1 discloses precursors of polyimide, polyamideimide, polyethersulfone, etc., and fine particles of polyphenylene sulfide, etc. Furthermore, aromatic polyether ketones have also become known in recent years as similar heat-resistant resins, and for example, polyether ether ketone (PEEK) is used in Patent Document 2. Such heat-resistant resins are called binders.

[0006] On the other hand, organic solvents (solvent-based paints) or water (water-based paints) are used as the medium for fluororesin paint compositions, including primer paint compositions, and in recent years, water-based (water-based) paint compositions have been preferred in terms of environmental impact and harmfulness to the human body. In water-based paint compositions, the heat-resistant resin (binder) that imparts adhesion to the substrate is usually water-insoluble, so its particles are dispersed in the liquid of the paint composition.

[0007] Until now, metal substrates that can withstand heat treatment above the melting point of the fluororesin to melt and form a coating have often been used as substrates for coating with fluororesins, particularly PTFE and PFA, which have excellent water and oil repellency. However, there has recently been a demand for primer paint compositions that can be coated on heat-resistant engineering plastic substrates.

[0008] In this case, it is desirable that the primer coating composition can be suitably used on metal substrates in the same manner as conventional ones, from the viewpoint of productivity of the coating and convenience of use.

[0009] The role of a primer is to bond the substrate and the top coat together and maintain this bond for a long period of time. Therefore, it is considered best to form a coating that is as thin as possible while maintaining sufficient abrasion and corrosion resistance. Furthermore, in order to form a thin, smooth coating, it is preferable to use a liquid paint rather than a powder paint. Liquid paints are also preferred because they are easier to apply to fine structures, making them more versatile for the target product.

[0010] Depending on the desired performance, paint compositions containing fluororesin and binder, like primer paint compositions, can also be applied to a substrate in a single layer and used as is. Such paint compositions are called one-coat paints, and demand for them has been increasing in recent years.

[0011] To date, a fluororesin coating composition using a water-soluble polyamideimide and a polyethersulfone resin has been proposed as a liquid primer coating composition having excellent water vapor resistance and corrosion resistance (Patent Document 3).

[0012] Furthermore, Patent Document 4 proposes a fluororesin coating composition that uses a water-soluble polyamideimide containing 3,3'-dimethylbiphenyl-4,4'-diisocyanate and / or 3,3'-dimethylbiphenyl-4,4'-diamine as structural units, thereby improving the water vapor resistance of the coating film formed.

[0013] Furthermore, Patent Document 2 proposes a coating material that contains a water-soluble polyamideimide resin, polyether ether ketone, and a fluororesin, where the fluororesin is a perfluororesin, and that exhibits sufficient adhesion even to stainless steel (SUS) substrates.

[0014] However, with the binders used to date, it has not been possible to obtain a primer coating composition or one-coat coating that can be suitably used on both heat-resistant engineering plastic substrates and metal substrates. [Prior art documents] [Patent documents]

[0015] [Patent Document 1] Special Publication No. 4-71951 [Patent Document 2] Patent Publication No. 2021-91754 [Patent Document 3] Patent No. 4534916 [Patent Document 4] International Publication No. WO2016 / 175099 Summary of the Invention [Problem to be solved by the invention]

[0016] The object of the present invention is to provide a fluororesin liquid paint composition for fluororesin coatings that firmly adheres to both metal substrates and resin substrates and has excellent water vapor resistance and corrosion resistance, a coating film formed by applying the same, and an article having the coating film. [Means for solving the problem]

[0017] In order to achieve the above object, the fluororesin liquid coating composition of the present invention is characterized by containing a fluororesin and polyether ketone ketone (PEKK).

[0018] That is, the present invention is as follows. (1) A fluororesin liquid coating composition containing a fluororesin and polyether ketone ketone (PEKK). (2) The fluororesin liquid coating composition of (1), which is an aqueous coating composition. (3) A fluororesin liquid coating composition according to (1) or (2), wherein the fluororesin is 35 to 90 mass% of the total binder resin containing PEKK and other resins. (4) A fluororesin liquid coating composition according to any one of (1) to (3), wherein the fluororesin is polytetrafluoroethylene or a heat-meltable perfluororesin. (5) A fluororesin liquid coating composition according to any one of (1) to (4), which contains both polytetrafluoroethylene and a heat-meltable perfluororesin as the fluororesin. (6) A fluororesin liquid coating composition according to any one of (1) to (5), further comprising a filler. (7) A coating film comprising the fluororesin liquid coating composition of (1) to (6). (8) A coating film of (7) having a thickness of 8 to 20 μm. (9) Articles having a coating film of (7) or (8). [Effects of the Invention]

[0019] According to the present invention, there is provided a fluororesin liquid coating composition containing a fluororesin and polyetherketoneketone (PEKK), which adheres firmly to both metal and resin substrates, has excellent water vapor resistance and corrosion resistance, and is capable of forming a thin coating film.The present invention also provides a coating film made of the fluororesin liquid coating composition containing a fluororesin and polyetherketoneketone (PEKK), and an article having such a coating film. The fluororesin liquid coating composition of the present invention can use water as a medium, and therefore is excellent in terms of the environment, safety and hygiene. DETAILED DESCRIPTION OF THE INVENTION

[0020] The "fluororesin liquid coating composition" of the present invention is characterized by containing a fluororesin and polyether ketone ketone (PEKK). The present invention will be described in detail below.

[0021] <Fluororesin liquid coating composition> The liquid coating composition of the present invention containing a fluororesin and polyether ketone ketone (PEKK) is particularly suitable as a primer coating (undercoat) for bonding a fluororesin layer to a substrate, and is also preferably used as a one-coat coating.

[0022] <Fluoropolymer> The fluororesin constituting the coating composition of the present invention may include, but is not limited to, polytetrafluoroethylene (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, etc. As the fluororesin in the present invention, it is preferable to use a conventional fluororesin that does not have functional groups in the side chain, from the viewpoints of the non-stickiness of the coating film when used as a one-coat coating and compliance with legal regulations (particularly for food contact applications).

[0023] In the present invention, from the viewpoints of suppressing the occurrence of pinholes when a coating is formed and obtaining a uniform and smooth coating, it is preferable to use a hot melt fluororesin that exhibits melt fluidity at or above its melting point. Among these, from the viewpoints of non-stickiness and heat resistance of the coating, hot melt perfluororesins such as low-molecular-weight PTFE, PFA, FEP, and tetrafluoroethylene-hexafluoropropylene-perfluoro(alkyl vinyl ether) copolymers are preferably used.

[0024] The alkyl group of the perfluoro(alkyl vinyl ether) in PFA preferably has 1 to 5 carbon atoms, and among these, perfluoro(propyl vinyl ether) (PPVE), perfluoro(ethyl vinyl ether) (PEVE), and perfluoro(methyl vinyl ether) (PMVE) are particularly suitable. The amount of perfluoro(alkyl vinyl ether) in PFA is preferably in the range of 1 to 50% by weight.

[0025] In the present invention, it is also preferable to use non-thermoplastic polytetrafluoroethylene (PTFE) as the fluororesin. The non-thermoplastic polytetrafluoroethylene preferably used in the present invention is a high-molecular-weight polytetrafluoroethylene (PTFE) that does not exhibit melt fluidity above its melting point, and may be either a homopolymer of tetrafluoroethylene (TFE) (TFE homopolymer), a TFE copolymer (modified PTFE) containing 1% by mass or less of a monomer copolymerizable with TFE, or a combination of both. This reduces the stress remaining in the coating film after heating and also enables cost reduction. Furthermore, it is more preferable to use a heat-meltable perfluororesin and a non-heat-meltable polytetrafluoroethylene (PTFE) simultaneously, since the above-mentioned advantages of each can be obtained. If necessary, other fluororesins may be added.

[0026] The fluororesin of the present invention can be used by dispersing in a coating composition a powder obtained by separating and drying a resin obtained by a known polymerization method, a powder obtained by further pulverizing the powder, or a powder obtained by finely granulating the powder by a method such as that described in Japanese Patent Publication No. 52-44576. Furthermore, a fluororesin dispersion obtained by emulsion polymerization can be used as is, or a fluororesin dispersion stabilized by adding a surfactant, or a fluororesin dispersion concentrated by a known technique such as that described in U.S. Patent No. 3,037,953 to adjust the fluororesin concentration to a high level. A stabilized fluororesin dispersion is preferred because the fluororesin can remain dispersed for a long period of time without aggregation or sedimentation.

[0027] The concentration of the fluororesin dispersion used in the coating composition of the present invention is preferably 20 to 70 mass%, and it is preferable to use a concentrated dispersion of 40 to 70 mass%, as this makes it easier to adjust the fluororesin concentration in the coating composition. Examples of commercially available fluororesin dispersions used in the present invention include Teflon (registered trademark) PTFE 31-JR, PTFE 34-JR, PFA 334-JR, PFA 335-JR, and FEP 120-JR, manufactured by Mitsui-Chemours Fluoroproducts Co., Ltd.

[0028] <Polyetherketoneketone (PEKK)> The "polyetherketoneketone (PEKK)" used in the present invention is a polymer compound having at least the following repeating unit, and either a homopolymer or a copolymer thereof can be used. In the present invention, polyetherketoneketone (PEKK) serves as the main binder. [ka]

[0029] The polyether ketone ketone (PEKK) used in the present invention can be produced by reacting diphenyl ether with a benzenedicarboxylic acid halide in the presence of a Friedel-Crafts catalyst, as known from, for example, Japanese Patent Publication Nos. 47-31440 and 5-13967. PEKK is already commercially available, and examples of such products include KEPSTAN (registered trademark) from Arkema and KSTONE (registered trademark) from Shandong Kaishen New Materials Co., Ltd.

[0030] <Other ingredients> The fluororesin liquid coating composition of the present invention may contain various additives used in ordinary coatings depending on the desired properties such as dispersibility, conductivity, foam prevention, and wear resistance improvement, for example, surfactants (for example, polyoxyethylene alkyl ether and polyoxyethylene alkyl phenyl ether-based nonionic surfactants such as Leocol manufactured by Lion Corporation, TRITON and TERGITOL series manufactured by Dow Chemical Company, and Emulgen manufactured by Kao Corporation; sulfosuccinates, alkyl ether sulfonate sodium salts, and mono-long-chain alkyl sulfate-based anionic surfactants such as Repearl manufactured by Lion Corporation, Emal and Pelex manufactured by Kao Corporation; and Leoar manufactured by Lion Corporation). Other examples of surfactants that can be added include polycarboxylates such as OROTAN manufactured by The Dow Chemical Company, acrylate-based polymer surfactants, L-77 manufactured by Momentive, and the Surfynol series manufactured by EVONIK (Surfynol 420, Surfynol 440, Surfynol 465, Surfynol 485, etc.), film-forming agents (e.g., polymer film-forming agents such as polyamide, polyamideimide, acrylic, and acetate, higher alcohols, ethers, and polymer surfactants with film-forming properties), and thickeners (water-soluble celluloses, solvent-dispersed thickeners, sodium alginate, casein, sodium caseinate, xanthan gum, polyacrylic acid, and acrylic esters).

[0031] In addition, various organic and inorganic materials can be added as binders or fillers to the fluororesin liquid coating composition of the present invention depending on the desired properties. Examples of organic materials include engineering plastics such as polyphenylene sulfide, polyethersulfone, polyphenylsulfone, polyamide, polyimide, phenolic resin, urea resin, epoxy resin, urethane resin, melamine resin, polyester resin, polyether resin, acrylic resin, acrylic silicone resin, silicone resin, and silicone polyester resin. Examples of inorganic materials include metal powder, metal oxides (aluminum oxide, zinc oxide, tin oxide, titanium oxide, etc.), glass, ceramics, silicon carbide, silicon oxide, calcium fluoride, carbon black, graphite, mica, and barium sulfate. Fillers can be used in a variety of shapes, including particles, fibers, and flakes.

[0032] In the fluororesin liquid coating composition of the present invention, the binder that can be used together with PEKK includes polyphenylene sulfide, polyethersulfone, polyphenylsulfone, polyamide, polyimide, polyamideimide (PAI), phenolic resin, urea resin, and epoxy resin. In the case of an aqueous coating composition that uses water as the solvent / dispersion medium for the fluororesin liquid coating composition, water-soluble polyamideimide (PAI) is particularly preferred because it dissolves and is uniformly present in the coating film, allowing it to adhere to the substrate without defects. However, the ratio of binders other than PEKK to the total binder resins (other binders / PEKK+other binders) is preferably 0.5 or less, and more preferably 0.3 or less or 0.2 or less.

[0033] <Aqueous medium> The use of water as the solvent / dispersion medium for the fluororesin liquid coating composition of the present invention to form an aqueous coating composition is particularly preferable from an environmental and cost perspective. A water-compatible polar solvent can be added to the aqueous coating composition, or a water-incompatible organic solvent can be dispersed in the aqueous coating composition to appropriately adjust rheological properties such as liquid viscosity and improve the dispersibility of PEKK and fillers. Adding a polar solvent dissolves the heat-resistant resin (binder), making it more uniform during the drying process after application, resulting in a denser coating film. This also facilitates penetration of the heat-resistant resin (binder) into the recesses of the substrate's irregularities, which is expected to improve adhesion to the substrate.

[0034] In the fluororesin liquid coating composition of the present invention, the fluororesin is preferably 35 to 90 mass% of the total of the binder resin (PEKK and other resin) and the fluororesin, and particularly preferably 45 to 80 mass%. If the fluororesin is less than 35 mass%, the water vapor resistance and corrosion resistance of the coating film may decrease, and the adhesion of the top coat may also decrease. On the other hand, if the fluororesin is more than 90 mass%, the corrosion resistance of the coating film may decrease, and the adhesion to the substrate and strength of the coating film may also decrease.

[0035] <Base material> The fluororesin liquid coating composition of the present invention can be suitably used on both metal and plastic substrates. Examples of metal substrates include aluminum, stainless steel (SUS), copper, iron, and various other alloys. As the plastic substrate, engineering plastics are preferably used, which can withstand the heat treatment required to form the fluororesin coating and have long-term durability. These include so-called super engineering plastics, such as polyaryl ketone resins (PEK, PEEK, PEKK, PEEKK), polyarylene sulfone resins (PPS, etc.), polyimide (PI), polyetherimide (PEI), and polyamideimide (PAI).

[0036] <Fluororesin coating composition manufacturing process> The fluororesin coating composition of the present invention can be prepared by a conventionally known method, for example, by appropriately mixing a fluororesin (aqueous dispersion or powder), PEKK, and, if necessary, other additives and fillers. In the fluororesin coating composition of the present invention, dispersions (dispersions) of PEKK, fluororesin, fillers, etc. may be prepared in advance, and the resulting dispersions may be mixed together to prepare the composition.

[0037] The fluororesin coating composition of the present invention preferably has a viscosity at 25°C of 0.1 to 50,000 mPa·s. If the viscosity is less than 0.1 mPa·s, sagging may occur during application to the substrate, making it difficult to obtain the desired film thickness. If the viscosity exceeds 50,000 mPa·s, coating workability may be impaired, the resulting coating film may not be uniform in thickness, and surface smoothness may be poor. A more preferred lower limit is 1 mPa·s, and a more preferred upper limit is 30,000 mPa·s. The above viscosity is a value obtained by measurement using a BM-type single-cylinder rotational viscometer (manufactured by Tokyo Keiki Co., Ltd.).

[0038] <Coating film> The "coating film" of the present invention is a coating film obtained by applying the fluororesin liquid coating composition of the present invention, and can be a thin coating film of 20 μm or less, for example, 8 to 20 μm. Furthermore, the "coating film" of the present invention is smooth and has excellent appearance. The coating composition of the present invention may be used as a primer layer to adhere to a substrate, and a plurality of layers may be applied thereon to form a laminated coating film. The "coating film" of the present invention can be formed by various existing coating methods, for example, spray coating, dip coating, spin coating, or other commonly used methods, and it is preferable to heat the coating film to a temperature above the melting point of the fluororesin in order to melt and flow it and obtain a uniform coating film.

[0039] The coating films used for performance evaluation were prepared by the following procedure. <Creating test specimens for evaluation (for evaluating aluminum substrates)> First, a 100mm wide, 150mm long aluminum plate (JIS A1050 compliant, 1mm thick) was used as the substrate. The surface was degreased with isopropyl alcohol, and then masking tape was applied parallel to the long edge of the substrate from the edge to 30mm from the edge. The plate was then shot blasted with #60 alumina to achieve a surface roughness (Ra) of 1-5μm. Next, the fluororesin coating composition of each example and comparative example was spray-coated (0.6-0.7g of coating composition) using a spray gun (W-101-101G, manufactured by Anest Iwata Corporation). After removing the masking tape, the plate was dried at 120°C for 10 minutes and then at 300°C for 20 minutes to form a primer layer (fluororesin coating composition layer). The primer-coated substrate was electrostatically powder-coated (1.4-1.6 g) with PFA powder paint (Mitsui-Chemours Fluoroproducts Teflon® Paint MJ-102) using a powder spray gun (Parker Ionics GX355HW) and baked at 400°C (substrate temperature) for 15 minutes. The same PFA powder paint was then electrostatically powder-coated in the same manner and baked at 360°C (substrate temperature) for 10 minutes to form a topcoat layer (PFA layer). The resulting test specimens had a topcoat layer (PFA layer) thickness of 100-120 μm, and the edges were not coated with primer.

[0040] <Creating evaluation specimens (for PEEK substrate evaluation)> An aluminum substrate with a 20-30 μm thick PEEK coating was obtained by applying an aqueous dispersion of PEEK powder to an aluminum plate (JIS A3004, 1 mm thick) measuring 100 mm in width and 150 mm in length, followed by heat treatment at approximately 400°C for approximately 15 minutes.

[0041] Masking tape was applied to the resulting PEEK-coated aluminum substrate from its long edge to 120 mm from the edge, parallel to the long edge, and the unmasked 30 mm wide PEEK coating was removed by shot blasting to expose the aluminum. The masking tape on the protected PEEK portion was peeled off, and instead the exposed aluminum portion was protected with masking tape from its long edge to 30 mm from the edge, parallel to the long edge of the substrate. Next, the fluororesin coating composition of each Example and Comparative Example was spray-coated in the same manner as in the preparation procedure for test pieces for aluminum substrate evaluation, to form a topcoat layer (PFA layer), and test pieces were obtained.

[0042] (Performance evaluation method) <Water vapor resistance evaluation> The above evaluation test pieces were left in steam at 150°C and 0.4 MPa for 100 hours, then left to cool to room temperature, and the adhesive strength of the coating film was measured using the following method. Next, the substrate was heated to 200°C on a gas stove and then quenched with water, and the condition of the coating film was checked. If swelling or blisters were observed, the sample was deemed to have failed.

[0043] <Adhesive strength measurement method> A 1cm wide cut was made in the coating film with a cutter parallel to the short side of the above test piece, and about 1cm of the coating film at the end where the primer was not applied was peeled off to create a gripping area for measuring the adhesive strength. The test piece was placed on an electronic balance, both ends fixed with tape, and the scale was set to zero. The peeled coating film was clamped with pliers and pulled at a rate of 50 mm / min. The value that decreased on the scale was read to measure the adhesive strength (peel strength). The unit is kgf (kilogram-force). The adhesive strength was measured before and after the above-mentioned evaluation of water vapor resistance. [Example]

[0044] (Preparation of Fluororesin Liquid Coating Composition) The following reagents were used in the present examples and comparative examples. Polyetherketoneketone (PEKK) resin PEKK powder: KSTONE® CC5601 manufactured by Shandong Kaishen New Materials Co., Ltd. Other binder resins Water-soluble polyamide-imide (PAI) resin Hitachi Chemical Co., Ltd. HPC-2100D-28 (a solution containing approximately 28% by mass of PAI, 22-32% by mass of water, and 30-40% by mass of N-formylmorpholine) Polyetheretherketone (PEEK) resin PEEK powder: VICOTE (registered trademark) Coatings 704 manufactured by Victrex Polyethersulfone (PES) resin PES powder: Sumikaexcel (registered trademark) 4100MP manufactured by Sumitomo Chemical Co., Ltd. Polyetherimide (PEI) resin PEI powder: SABIC Ultem 1000F3SP-1000 Fluorine resin PFA aqueous dispersion: Teflon® PFA 335-JR (PFA concentration 60% by mass) manufactured by Mitsui-Chemours Fluoroproducts Co., Ltd. PTFE aqueous dispersion: Teflon (registered trademark) PTFE 34-JR (PTFE concentration 58% by mass) manufactured by Mitsui-Chemours Fluoroproducts Co., Ltd.

[0045] Example 1 192 g of pure water was placed in a 1-L stainless steel container, and 18 g of a nonionic surfactant aqueous solution (concentration 81% by mass) was added while stirring at 140 rpm using a mixer (YAMATO SCIENTIFIC CO., LTD.). 77 g of PEKK powder was added and stirred for 10 minutes to disperse. 17 g of a nonionic surfactant aqueous solution (concentration 90% by mass), 105 g of a carbon black aqueous dispersion (25% by mass), and 58 g of a titanium dioxide aqueous dispersion (55% by mass) were then added and stirred for 10 minutes. Next, a fluororesin aqueous dispersion (44 g of PFA aqueous dispersion, 259 g of PTFE aqueous dispersion, and 96 g of pure water) that had been mixed in a separate container was added and stirred for 10 minutes to obtain an aqueous fluororesin coating composition.

[0046] Example 2 244 g of pure water was placed in a 1-L stainless steel container, and 24 g of a nonionic surfactant aqueous solution (81% by weight) was added while stirring at 140 rpm using a mixer (YAMATO SCIENTIFIC CO., LTD.). 81 g of PEKK powder was added and stirred for 10 minutes to disperse. 14 g of a nonionic surfactant aqueous solution (90% by weight), 101 g of a carbon black aqueous dispersion (25% by weight), and 54 g of a titanium dioxide aqueous dispersion (55% by weight) were then added and stirred for 10 minutes. Next, a fluororesin aqueous dispersion (30 g of PFA aqueous dispersion, 223 g of PTFE aqueous dispersion, and 21 g of pure water) that had been mixed in a separate container was added and stirred for 10 minutes. After stirring for 10 minutes, 30 g of water-soluble PAI was added and stirred for another 10 minutes to obtain an aqueous fluororesin coating composition.

[0047] Examples 3 to 5 An aqueous fluororesin coating composition was obtained in the same manner as in Example 2, adjusting the amount of each component so as to obtain the coating composition (composition ratio (mass %) in the resin solid content) shown in Table 1 below.

[0048] Comparative Examples 1 to 4 The amount of each component was adjusted so as to obtain the coating composition (composition ratio (mass %) in the resin solid content) shown in Table 2 below, and a fluororesin coating composition was obtained in the same manner as in the Examples.

[0049] The evaluation results for the coating films produced in the examples and comparative examples are shown in Tables 1 and 2, respectively. Those for which no swelling or blisters occurred were given an evaluation result of ○, and all other cases were given an evaluation result of ×. Those for which the adhesive strength was greater than 1.5 kgf before steam pressure treatment and greater than 0.8 kgf after steam pressure treatment were rated as pass, and those for which all the above evaluations were good were given an overall evaluation of good, while those for which even one evaluation was poor or failed were given an ×.

[0050] [Table 1]

[0051] [Table 2]

[0052] The results in Tables 1 and 2 above show that the fluororesin liquid coating composition of the present invention containing PEKK as a binder exhibits good performance on both metal and resin substrates (Table 1), whereas the coating composition not containing PEKK as a binder may perform well on either metal or resin substrates, but is unable to exhibit sufficient performance on both (Table 2).

Claims

1. An aqueous fluororesin liquid coating composition comprising a fluororesin and polyether ketone ketone (PEKK), wherein the fluororesin comprises both polytetrafluoroethylene and a heat-meltable perfluororesin.

2. 2. The aqueous fluororesin liquid coating composition according to claim 1, wherein the fluororesin is 35 to 90 mass% of the total of the binder resins including PEKK and other resins.

3. The aqueous fluororesin liquid coating composition according to claim 1 or 2, further comprising a filler.

4. A coating film comprising the aqueous fluororesin liquid coating composition according to any one of claims 1 to 3.

5. The coating of claim 4, which has a thickness of 8 to 20 μm.

6. An article having the coating film according to claim 4 or 5.

Images