Coating composition and coated article

Abstract

To provide a coating composition excellent in coatability and having good water vapor resistance and corrosion resistance of a formed coating film. The coating composition comprises an aqueous dispersion containing a water-soluble polyamide-imide resin (P), a polyethersulfone resin (Q), and a fluoropolymer (R) containing a non-melt-processable fluoropolymer (S) and a melt-processable perfluoropolymer (T) having a melting point of 200-350° C, in which coating composition the mass ratio of the water-soluble polyamide-imide resin (P) and the polyethersulfone resin (Q) is 10 / 90 to 40 / 60.

Description

Coating composition and coated article

[0001] The present disclosure relates to coating compositions and coated articles.

[0002] Fluorine-containing polymers such as polytetrafluoroethylene (PTFE) have excellent properties such as heat resistance and electrical insulation, and their molded articles have a low coefficient of friction and excellent non-stick properties. These surface properties also provide chemical resistance, water and oil repellency, mold releasability, and sliding properties.

[0003] Because the fluorine-containing polymer has such properties, it can be used in a wide range of applications, for example, by preparing it into a coating composition and applying it to an article to be coated to provide a coating film made of the fluorine-containing polymer, such as mold release materials for molding dies, rolls for office automation (OA) equipment, household items such as irons, kitchen utensils such as frying pans and hot plates, and in the fields of food industry, electrical industry, and machinery industry.

[0004] On the other hand, fluorine-containing polymers have a problem in that they have poor adhesion to the object to be coated due to their non-stickiness. In order to improve this adhesion, a primer containing a fluorine-containing polymer and a binder resin such as a heat-resistant resin is applied as an undercoat to the object to be coated in advance.

[0005] As the primer, a primer composition has been proposed in which polyethersulfone, polyamideimide and / or polyimide, fluororesin, and metal powder are dissolved or dispersed in an organic solvent (Patent Document 1).

[0006] An example of an aqueous primer composition is an aqueous dispersion containing a water-soluble polyamideimide resin (P), a heat-resistant resin (Q) different from the water-soluble polyamideimide resin, and a fluorine-containing polymer (R) (Patent Document 2).

[0007] Furthermore, as an aqueous primer composition, there is a coating composition containing a polyethersulfone resin, a polyimide resin, a non-melt-processible fluorine-containing polymer, and a melt-processible fluorine-containing polymer (Patent Document 3).

[0008] In addition, an aqueous fluororesin coating composition has been proposed which contains a water-soluble polyamideimide resin, polyetherimide, polyethersulfone, and a fluororesin, and the fluororesin contains non-thermofusible polytetrafluoroethylene and a thermofusible fluororesin (Patent Document 4).

[0009] Japanese Patent Application Laid-Open No. 6-264000 Japanese Patent Application Laid-Open No. 2007-63482 Japanese Patent Application Laid-Open No. 2020-176216 Japanese Patent Application Laid-Open No. 2021-21013

[0010] An object of the present disclosure is to provide a coating composition that has excellent coatability and provides a coating film that has good water vapor resistance and corrosion resistance.

[0011] The present disclosure relates to a coating composition comprising an aqueous dispersion containing a water-soluble polyamideimide resin (P), a polyethersulfone resin (Q), and a fluorine-containing polymer (R) comprising a non-melt-processable fluorine-containing polymer (S) and a melt-processable perfluoropolymer (T) having a melting point of 200 to 350°C, wherein the mass ratio of the water-soluble polyamideimide resin (P) to the polyethersulfone resin (Q) is 10 / 90 to 40 / 60.

[0012] The aqueous dispersion contains particles made of the polyethersulfone resin (Q) and particles made of the fluoropolymer (R), and it is preferred that the particles made of the polyethersulfone resin (Q) are particles dispersed in the aqueous dispersion and have an average particle size of 0.1 to 10 μm.

[0013] The perfluoropolymer (T) is preferably a tetrafluoroethylene / hexafluoropropylene copolymer, and the melt flow rate (MFR) of the tetrafluoroethylene / hexafluoropropylene copolymer is preferably 1 to 50 g / 10 min.

[0014] The perfluoropolymer (T) is preferably a tetrafluoroethylene / perfluoro(alkyl vinyl ether) copolymer, and the melt flow rate (MFR) of the tetrafluoroethylene / perfluoro(alkyl vinyl ether) copolymer is preferably 1 to 50 g / 10 min.

[0015] The water-soluble polyamide-imide resin (P) preferably has a number-average molecular weight of 5,000 to 50,000 and an acid value, calculated as the total equivalent of the carboxyl groups and the carboxyl groups obtained by ring-opening the imide bonds, of 10 to 100. The mass ratio of the non-melt-processible fluorine-containing polymer (S) to the perfluoropolymer (T) is preferably 5 / 95 to 95 / 5.

[0016] The ratio of the total mass of the water-soluble polyamideimide resin (P) and polyethersulfone resin (Q) to the total mass of the non-melt-processible fluorine-containing polymer (S) and perfluoropolymer (T) is preferably 15 / 85 to 40 / 60. The viscosity of the water-soluble polyamideimide resin (P) at 25°C is preferably 1000 to 10,000 mPa·s. The coating composition of the present disclosure preferably has a viscosity of 50 to 1000 mPa·s at 25°C. The water-soluble polyamideimide resin (P) preferably has a number average molecular weight of 1500 to 25,000, an acid value of the combined carboxyl groups and carboxyl groups resulting from ring-opening of imide bonds of 30 to 60 equivalents, and a viscosity of the coating composition at 25°C of 1200 to 8,000 mPa·s. The aqueous medium preferably contains at least one organic liquid selected from the group consisting of N-ethyl-2-pyrrolidone, N-butyl-2-pyrrolidone, 3-alkoxy-N,N-dimethylpropanamide, 1,3-dimethyl-2-imidazolidinone, 3-methyl-2-oxazolidinone, N-formylmorpholine, N-acetylmorpholine, and dimethylpropylene urea.

[0017] The present disclosure also relates to a coated article comprising a substrate and a layer formed from the coating composition. The present disclosure also relates to a coated article having a substrate, a primer layer formed from the coating composition, and a fluorine-containing topcoat layer containing a fluorine-containing polymer. The present disclosure also relates to a coated article having a substrate, a primer layer containing a heat-resistant resin, an intermediate layer formed from the coating composition, and a fluorine-containing topcoat layer containing a fluorine-containing polymer.

[0018] The coating composition of the present disclosure has excellent coatability. Furthermore, the coating film of a coated article obtained by applying the coating composition of the present disclosure has good water vapor resistance and corrosion resistance, and is less prone to cissing and uneven coating.

[0019] The present disclosure will be described in detail below. The coating composition of the present disclosure comprises an aqueous dispersion containing a water-soluble polyamideimide resin [PAI] (P), a polyethersulfone resin [PES] (Q), and a fluoropolymer (R) comprising a non-melt-processible fluoropolymer (S) and a melt-processible perfluoropolymer (T) having a melting point of 200 to 350° C. The coating composition of the present disclosure also contains the water-soluble PAI (P) and PES (Q) in a specific ratio.

[0020] When a coating composition contains water-soluble PAI (P), the water-soluble PAI (P) has a carboxyl group, and therefore the corrosion resistance of the coating film obtained by applying the coating composition to an object to be coated is reduced. However, the present disclosure provides a coating composition as described above, which not only has excellent coatability on the object to be coated, but also provides a coating film that has excellent water vapor resistance and corrosion resistance by applying the coating composition to an object to be coated.

[0021] The coating composition of the present disclosure can form a coating film on an object to be coated by applying it to the object to be coated. In this specification, the term "applying" with respect to the coating composition refers to a process of applying the coating composition, drying it as needed, and then baking it.

[0022] In the coating film, since the PES resin (Q) and the fluoropolymer (R) have different surface tensions, the fluoropolymer (R) rises to the surface during baking, with the fluoropolymer (R) being mainly located on the surface side of the coating film and the PES resin (Q) being mainly located on the side of the substrate. The coating film can have excellent adhesion to the substrate because the PES resin (Q) has adhesive properties with the substrate.

[0023] If necessary, a topcoat coating film may be laminated on the coating film. The topcoat coating film is usually formed by applying a topcoat paint comprising a fluorine-containing topcoat polymer. When a topcoat coating film is laminated on the coating film, the coating film also has excellent adhesion to the topcoat coating film because the fluorine-containing polymer (R) has affinity for the fluorine-containing topcoat polymer.

[0024] In this specification, an article having the above-mentioned substrate and coating film is referred to as a coated article. The coated article may further have the above-mentioned topcoat coating film.

[0025] In this specification, the method for producing the coated article is referred to as a one-coat method when the topcoat film is not laminated on the coating film, which comprises applying the coating composition to the substrate, drying it if necessary, and then baking it.

[0026] In this specification, the method for producing the coated article is referred to as a two-coat method when the topcoat coating film is laminated on the coating film. The two-coat method typically involves applying the coating composition to the substrate, drying it if necessary, and then applying the topcoat paint without baking it, drying it if necessary, and then baking it. In the two-coat method, the coating composition is used as an undercoat paint for the topcoat coating film and functions as a primer.

[0027] In the coating composition of the present disclosure, the aqueous dispersion contains a fluoropolymer (R). The fluoropolymer (R) is a polymer having fluorine atoms directly bonded to carbon atoms constituting the main chain or side chain. The fluoropolymer (R) contains a non-melt-processible fluoropolymer (S) and a melt-processible perfluoropolymer (T) having a melting point of 200 to 350°C.

[0028] "Non-melt processable" means that the melt flow rate cannot be measured at a temperature higher than the crystallization melting point according to ASTM D-1238 and D-2116.

[0029] The non-melt-processible fluoropolymer (S) is preferably at least one selected from the group consisting of tetrafluoroethylene homopolymer (hereinafter also referred to as "homo-PTFE") and modified polytetrafluoroethylene (hereinafter also referred to as "modified PTFE").

[0030] The modified PTFE is a modified PTFE made of tetrafluoroethylene (TFE) and a monomer other than TFE (hereinafter also referred to as "modified monomer").

[0031] The above-mentioned modified monomer is not particularly limited as long as it can be copolymerized with TFE, and for example, can be listed perfluoroolefin such as hexafluoropropylene (HFP); chlorofluoroolefin such as chlorotrifluoroethylene (CTFE); hydrogen-containing fluoroolefin such as trifluoroethylene, vinylidene fluoride (VDF); perfluorovinyl ether; perfluoroalkylethylene, ethylene etc. In addition, the modified monomer used can be one kind or multiple kinds.

[0032] The perfluorovinyl ether is not particularly limited, and examples thereof include perfluorovinyl ethers represented by the following general formula (1): CF ２ =CF-ORf １ (1) (wherein, Rf １ represents a perfluoroorganic group.) Examples include perfluorounsaturated compounds represented by the following formula: In this specification, the "perfluoroorganic group" refers to an organic group in which all hydrogen atoms bonded to carbon atoms are substituted with fluorine atoms. The perfluoroorganic group may have an ether oxygen.

[0033] The perfluorovinyl ether may be, for example, a compound represented by the general formula (1) in which Rf １ is a perfluoroalkyl group having 1 to 10 carbon atoms. The number of carbon atoms in the perfluoroalkyl group is preferably 1 to 5.

[0034] Examples of the perfluoroalkyl group in the PAVE include perfluoromethyl, perfluoroethyl, perfluoropropyl, perfluorobutyl, perfluoropentyl, and perfluorohexyl groups, but the perfluoroalkyl group is preferably a perfluoropropyl group. That is, the PAVE is preferably perfluoropropyl vinyl ether (PPVE).

[0035] The modifying monomer in the modified PTFE is preferably at least one selected from the group consisting of HFP, CTFE, VDF, PAVE, PFAE, and ethylene, more preferably PAVE, and even more preferably PPVE.

[0036] The homo-PTFE is preferably one that is substantially composed of TFE units only, and is obtained without using any modified monomer, for example.

[0037] The modified PTFE preferably contains the modified monomer unit in an amount of 0.001 to 2 mol %, more preferably 0.001 to 1 mol %.

[0038] The content of each monomer unit in the non-melt-processible fluoropolymer (S) can be calculated by an appropriate combination of NMR, FT-IR, elemental analysis and X-ray fluorescence analysis depending on the type of monomer.

[0039] The fluoropolymer (R) further contains a perfluoropolymer (T) which is melt-processable and has a melting point of 200 to 350°C (hereinafter also referred to as melt-processable fluoropolymer (T)). The term "melt-processable" means that the polymer can be melted and processed using conventional processing equipment such as an extruder or an injection molding machine. Therefore, the melt-processable fluoropolymer (T) usually has a melt flow rate (MFR) of 1.0 to 50 g / 10 min.

[0040] In this specification, the MFR is a value obtained in accordance with ASTM D 1238 using a melt indexer (manufactured by Yasuda Seiki Seisakusho Co., Ltd.) as the mass (g / 10 min) of polymer flowing out per 10 min from a nozzle with an inner diameter of 2 mm and a length of 8 mm at a measurement temperature determined depending on the type of fluoropolymer (for example, 372°C for PFA and FEP, and 297°C for ETFE) and a load (for example, 5 kg for PFA, FEP and ETFE).

[0041] The melt-processible fluoropolymer (T) has a melting point of 200 to 350° C. The melting point is preferably 210° C. or higher, particularly preferably 220° C. or higher. The melting point is preferably 340° C. or lower, particularly preferably 330° C. or lower.

[0042] In this specification, the melting point of the melt-processible fluoropolymer (T) is the temperature corresponding to the maximum value on the heat of fusion curve when the temperature is raised at a rate of 10°C / min using a differential scanning calorimeter [DSC].

[0043] As the melt-processable fluorine-containing polymer (T), at least one selected from the group consisting of low molecular weight PTFE, TFE / PAVE copolymer (PFA), TFE / HFP copolymer (FEP), ethylene (Et) / TFE copolymer (ETFE), Et / TFE / HFP copolymer, polychlorotrifluoroethylene (PCTFE), CTFE / TFE copolymer, Et / CTFE copolymer and polyvinylidene fluoride (PVDF) can be enumerated.The melt-processable fluorine-containing polymer (T) is preferably at least one selected from the group consisting of FEP and PFA, more preferably FEP, in that it can obtain a coating film with more excellent corrosion resistance.

[0044] The FEP is not particularly limited, but a copolymer in which the molar ratio of TFE units to HFP units (TFE units / HFP units) is 70 / 30 or more and less than 99 / 1 is preferred. A more preferred molar ratio is 70 / 30 or more and 98.9 / 1.1 or less, and an even more preferred molar ratio is 80 / 20 or more and 98.9 / 1.1 or less. When the molar ratio of TFE units is above the above range, the mechanical properties do not deteriorate, and when the molar ratio of TFE units is below the above range, the melting point does not become too high and moldability does not deteriorate. The FEP is also preferably a copolymer in which the monomer units derived from monomers copolymerizable with TFE and HFP are 0.1 to 10 mol %, and the total of TFE units and HFP units is 90 to 99.9 mol %. Monomers copolymerizable with TFE and HFP include PAVE, CF ２ =CF-OCH ２ -Rf ２ (wherein, Rf ２ represents a perfluoroalkyl group having 1 to 5 carbon atoms.

[0045] The melting point of the FEP is preferably 200 to less than 350°C, more preferably 210 to 340°C, and even more preferably 220 to 330°C.

[0046] The FEP preferably has an MFR of 1 to 50 g / 10 min, more preferably 2 to 40 g / 10 min, and even more preferably 3 to 30 g / 10 min.

[0047] The FEP preferably has a thermal decomposition starting temperature of 360° C. or higher, more preferably 380° C. or higher, and even more preferably 390° C. or higher.

[0048] In this specification, the thermal decomposition onset temperature is the temperature at which a 10 mg sample loses 1 mass % when heated from room temperature at a heating rate of 10°C / min using a differential thermal / thermogravimetric analyzer [TG-DTA] (trade name: TG / DTA6200, manufactured by Seiko Electronics Co., Ltd.).

[0049] The PFA is not particularly limited, but is preferably a copolymer in which the molar ratio of TFE units to PAVE units (TFE units / PAVE units) is 70 / 30 or more and less than 99 / 1. A more preferred molar ratio is 70 / 30 or more and 98.9 / 1.1 or less, and an even more preferred molar ratio is 80 / 20 or more and 98.9 / 1.1 or less. When the molar ratio of TFE units is above the above range, the mechanical properties do not deteriorate, and when the molar ratio of TFE units is below the above range, the melting point does not become too high and moldability does not deteriorate. The PFA is also preferably a copolymer in which the monomer units derived from monomers copolymerizable with TFE and PAVE are 0.1 to 10 mol %, and the total of TFE units and PAVE units is 90 to 99.9 mol %. Monomers copolymerizable with TFE and PAVE include HFP, CZ １ Z ２ =CZ ３ (CF ２ ) ｎ Z ４ (In the formula, Z １ , Z ２ and Z ３ are the same or different and represent a hydrogen atom or a fluorine atom; Z ４ represents a hydrogen atom, a fluorine atom, or a chlorine atom, and n represents an integer of 2 to 10. ２ =CF-OCH ２ -Rf ２ (wherein, Rf ２ represents a perfluoroalkyl group having 1 to 5 carbon atoms.

[0050] The melting point of the PFA is preferably 200 to less than 350°C, more preferably 210 to 340°C, and even more preferably 220 to 330°C.

[0051] The PFA preferably has a melt flow rate (MFR) of 1 to 50 g / 10 min, more preferably 5 to 45 g / 10 min, and even more preferably 10 to 40 g / 10 min.

[0052] The PFA preferably has a thermal decomposition starting temperature of 380° C. or higher, more preferably 400° C. or higher, and even more preferably 410° C. or higher.

[0053] The content of each monomer unit in the melt-processible fluoropolymer (T) can be calculated by an appropriate combination of NMR, FT-IR, elemental analysis and X-ray fluorescence analysis depending on the type of monomer.

[0054] The aqueous dispersion contains particles made of the fluoropolymer (R). From the viewpoints of dispersion stability in the coating composition and surface smoothness of the resulting coating film, the non-melt-processible fluoropolymer (S) and the melt-processible fluoropolymer (T) each preferably have an average particle size of 0.01 to 40 μm. The average particle size is more preferably 0.05 μm or more, more preferably 20 μm or less, even more preferably 10 μm or less, and particularly preferably 5 μm or less. The average particle size can be measured by a laser light scattering method.

[0055] In order to obtain a coating film having even more excellent corrosion resistance, the mass ratio of the non-melt-processible fluorine-containing polymer (S) to the melt-processible fluorine-containing polymer (T) is preferably 5 / 95 to 95 / 5. The mass ratio is more preferably 20 / 80 or more, even more preferably 30 / 70 or more, even more preferably 40 / 60 or more, and particularly preferably 50 / 50 or more, and is more preferably 90 / 10 or less, even more preferably 80 / 20 or less, and particularly preferably 70 / 30 or less.

[0056] The coating composition of the present disclosure is in a form in which particles of the above-mentioned fluorine-containing polymer (R) are dispersed in an aqueous medium.

[0057] In the coating composition of the present disclosure, the aqueous dispersion contains a water-soluble polyamide-imide resin [PAI] (P). The water-soluble PAI (P) is preferably represented by the following general formula (i):

[0058]

[0059] (In the formula, R５ represents a trivalent organic group, R ６ represents a divalent organic group).

[0060] The water-soluble PAI (P) can be obtained, for example, by reacting a diisocyanate compound or a diamine compound with a polybasic acid anhydride or a polybasic acid anhydride chloride.

[0061] The water-soluble PAI (P) has the following general formula (ii):

[0062]

[0063] (wherein → means isomerization, G is a hydrogen atom or a carboxyl group, and R ７ represents a tetravalent organic group, R ８ represents a divalent organic group.) and may also have a carboxyl group at the polymer chain end. These polyamic acids are preferably neutralized with a stoichiometric amount of a basic compound in order to enhance the water solubility of the PAI. ５ ~R ８ As the group, an organic group having 6 to 20 carbon atoms and an aromatic ring is preferred.

[0064] Examples of the diisocyanate compound include 4,4'-diphenylmethane diisocyanate, xylylene diisocyanate, 3,3'-diphenylmethane diisocyanate, and paraphenylene diisocyanate.

[0065] Examples of the diamine compound include phenylenediamine, xylylenediamine, bis-(4-aminophenyl)ether, benzidine, 2,2'-(4'-aminophenyl)propane, bis-(4-aminophenyl)methane, bis-(4-aminophenyl)sulfone, bis-(4-aminophenyl)sulfide, and 2,2'-hexamethylenediamine.

[0066] Examples of the polybasic acid anhydride include pyromellitic dianhydride, trimellitic dianhydride, 2,2'-bis(3',4'-dicarboxyphenyl)propane dianhydride, and bis(3,4-dicarboxyphenyl)ether dianhydride.

[0067] Examples of the polybasic acid anhydride chloride include trimellitic acid anhydride chloride.

[0068] Examples of the basic compound include ammonia and caustic alkalis such as sodium hydroxide and potassium hydroxide; alkylamines such as trimethylamine, triethylamine, tributylamine, triethylenediamine, pyridine, N-methylpyrrole, and N-methylmorpholine; alkylanilines such as methylaniline, dimethylaniline, and N,N-dimethylaniline; and alkanolamines such as diethyl 2-hydroxyethylamine, tris(2-hydroxyethyl)amine, ethylbis(2-hydroxyethyl)amine, and N,N-dimethylethanolamine, and two or more of these may be used in combination.

[0069] The basic compound is preferably used in an amount of 1 to 20 equivalents relative to the total acid value of the carboxyl groups contained in the polyamideimide obtained by the reaction in the reaction medium and the carboxyl groups resulting from the ring-opening of the imide bonds. If the amount is less than 1 equivalent, it may be difficult to make the resin water-soluble, and if the amount is more than 20 equivalents, hydrolysis of the resin may be accelerated.

[0070] The water-soluble PAI (P) preferably has a number-average molecular weight of 5,000 to 50,000. When the number-average molecular weight is 5,000 or more, the heat resistance and mechanical properties of the resulting film are not reduced, and when the number-average molecular weight is 50,000 or less, the viscosity of the coating composition is not too high, resulting in good coatability. The number-average molecular weight is more preferably 10,000 to 30,000, and even more preferably 15,000 to 25,000.

[0071] The number average molecular weight is a value measured by gel permeation chromatography (GPC) and converted to polystyrene. In this specification, gel permeation chromatography (GPC) is performed using a sample prepared by passing a 0.1 to 0.2 wt % solution of a fluoropolymer in tetrahydrofuran (THF) through a disposable membrane filter unit DISMIC-25HP (hydrophilic polytetrafluoroethylene (PTFE), manufactured by Advantec). The GPC apparatus used is HLC-8020 (manufactured by Tosoh Corporation), and the column used is TSKgel G2000H. ＨＲ , G3000H ＨＲ , G4000H ＨＲ , G5000H ＨＲ During the measurement, the sample was introduced into the column at a rate of 1.0 ml / min, and the pressure was 55 kg / cm. ２ The temperature is maintained at 40° C. A differential refractometer (RI) is used as a detector.

[0072] The water-soluble PAI (P) preferably has an acid value of 10 to 100 equivalents, including the total acid value of the carboxyl groups and the carboxyl groups formed by ring-opening the imido bond [-CO-N-CO-] (imido). If the acid value is 10 equivalents or more, there will be no shortage of carboxyl groups to react with the polybasic acid anhydride or polybasic acid anhydride chloride, making it possible to make the PAI water-soluble. If the acid value is 100 equivalents or less, the resulting coating composition is less likely to gel. The acid value is preferably 20 to 80 equivalents, and more preferably 30 to 60 equivalents.

[0073] The acid value is a value obtained by the following method. Approximately 0.5 g of water-soluble PAI (P) is taken, to which approximately 0.15 g of 1,4-diazabicyclo[2.2.2]octane is added, and then approximately 60 g of N-methyl-2-pyrrolidone and approximately 1 ml of ion-exchanged water are added, followed by stirring until the water-soluble PAI (P) is completely dissolved. This is then titrated with a 0.05 mol / L ethanolic potassium hydroxide solution using a potentiometric titrator to obtain the acid value of the water-soluble PAI (P).

[0074] The water-soluble PAI (P) is usually used in the form of a solution for preparing a coating composition, and the water-soluble PAI (P) solution can be easily obtained by dissolving the water-soluble PAI (P) in water containing an organic solvent.

[0075] Examples of the organic solvent include N-methyl-2-pyrrolidone (NMP), N-ethyl-2-pyrrolidone, N-butyl-2-pyrrolidone, 3-alkoxy-N,N-dimethylpropanamide, γ-butyrolactone, dimethyl sulfoxide, 1,3-dimethyl-2-imidazolidinone, 3-methyl-2-oxazolidinone, dimethylacetamide, dimethylformamide, N-formylmorpholine, N-acetylmorpholine, dimethylpropylene urea, anisole, diethyl ether, ethylene glycol, acetophenone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, cyclopentanone, xylene, toluene, ethanol, and 2-propanol, and these can be used alone or in combination.

[0076] The organic solvent is preferably at least one selected from the group consisting of N-ethyl-2-pyrrolidone, N-butyl-2-pyrrolidone, 3-alkoxy-N,N-dimethylpropanamide, γ-butyrolactone, dimethyl sulfoxide, 1,3-dimethyl-2-imidazolidinone, 3-methyl-2-oxazolidinone, dimethylacetamide, dimethylformamide, N-formylmorpholine, N-acetylmorpholine, dimethylpropylene urea, anisole, diethyl ether, ethylene glycol, acetophenone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, cyclopentanone, xylene, toluene, ethanol, and 2-propanol, and more preferably N-ethyl-2-pyrrolidone, N-butyl-2-pyrrolidone , 3-alkoxy-N,N-dimethylpropanamide, γ-butyrolactone, dimethyl sulfoxide, 1,3-dimethyl-2-imidazolidinone, 3-methyl-2-oxazolidinone, dimethylacetamide, dimethylformamide, N-formylmorpholine, N-acetylmorpholine, and dimethylpropylene urea, and even more preferably at least one selected from the group consisting of N-ethyl-2-pyrrolidone, N-butyl-2-pyrrolidone, 3-alkoxy-N,N-dimethylpropanamide, 1,3-dimethyl-2-imidazolidinone, 3-methyl-2-oxazolidinone, N-formylmorpholine, N-acetylmorpholine, and dimethylpropylene urea.

[0077] The 3-alkoxy-N,N-dimethylpropanamide is N(CH ３ ) ２ COCH ２ CH ２ OR １１ (R １１ is an alkyl group). １１ The 3-alkoxy-N,N-dimethylpropanamide (N(CH 2 O group) is not particularly limited, but is preferably an alkoxy group containing a lower alkyl group having about 1 to 6 carbon atoms, and more preferably a methoxy group, an ethoxy group, a propoxy group, or a butoxy group. Examples of the 3-alkoxy-N,N-dimethylpropanamide include 3-methoxy-N,N-dimethylpropanamide (N(CH 2 O group)).３ ) ２ COCH ２ CH ２ OCH ３ ) is particularly preferred.

[0078] The organic solvent preferably has a boiling point of 150°C or higher, more preferably 170°C or higher, and even more preferably 200°C or higher. This can slow the drying rate during coating and improve the surface smoothness of the coating film. The boiling point is a value measured at 1 atmosphere (atm).

[0079] The viscosity of the water-soluble PAI (P) at 25°C is preferably 1000 to 10,000 mPa·s, more preferably 1100 to 9,000 mPa·s, and particularly preferably 1200 to 8,000 mPa·s. When the viscosity of the water-soluble PAI (P) is 1000 mPa·s or higher, the viscosity of the coating composition is sufficient, making it less likely to cause sagging or the like during application. When the viscosity of the water-soluble PAI (P) is 10,000 mPa·s or lower, the viscosity of the coating composition does not become too high, allowing for good application. The above viscosity is a value obtained by measurement using a BM-type single-cylinder rotational viscometer (manufactured by Tokyo Keiki Co., Ltd.).

[0080] In view of the above-mentioned viscosity, the water-soluble PAI(P) is preferably present at a concentration of 1 to 50% by mass, more preferably 5 to 40% by mass, of the water-soluble PAI(P) solution. The water-soluble PAI(P) is thought to be dispersed in a molecular state in the solvent in the water-soluble PAI(P) solution, and is thought to be similarly dispersed in a molecular state in the coating composition of the present disclosure prepared using the water-soluble PAI(P) solution, and to exist in a dissolved state in the aqueous medium.

[0081] In the coating composition of the present disclosure, the aqueous dispersion contains a polyethersulfone resin (PES) (Q).

[0082] The PES (Q) has excellent adhesion to the object to be coated, and has sufficient heat resistance even at the temperature during baking when forming the coating film, and the resulting coating film has excellent corrosion resistance and water vapor resistance.

[0083] PES can be, for example, a compound represented by the following general formula:

[0084] The resin is a polymer having a repeating unit represented by the formula:

[0085] There are no particular limitations on the PES, and examples thereof include resins made of polymers obtained by polycondensation of dichlorodiphenyl sulfone and bisphenol.

[0086] The aqueous dispersion contains particles made of the PES(Q). The particles made of the PES(Q) are preferably particles dispersed in the aqueous medium with an average particle size of 0.1 to 10 μm. When the average particle size of the PES(Q) is within the above range, the corrosion resistance of a coating film obtained from the coating composition is good. The average particle size is a value obtained by measurement using a laser light scattering method. In the coating composition of the present disclosure, the PES(Q) is dispersed in the aqueous medium described below as particles.

[0087] In the coating composition of the present disclosure, the mass ratio of the water-soluble PAI resin (P) to the PES resin (Q) in the aqueous dispersion is 10 / 90 to 40 / 60. By setting the mass ratio within this range, the corrosion resistance and water vapor resistance of the coating film are good. The range is preferably 15 / 85 to 35 / 65. When the mass ratio of the PES resin (Q) is above the above range, the water vapor resistance of the coating film obtained from the coating composition is not reduced, and when the mass ratio of the PES resin (Q) is below the above range, the corrosion resistance of the coating film is not reduced.

[0088] Furthermore, in order to obtain a coating film having even more excellent corrosion resistance, the ratio of the total mass of the water-soluble PAI (P) and the PES (Q) to the total mass of the non-melt-processible fluorine-containing polymer (S) and the melt-processible fluorine-containing polymer (T) is preferably 15 / 85 to 40 / 60, more preferably 20 / 80 or more, and more preferably 30 / 70 or less.

[0089] In the coating composition of the present disclosure, the above-mentioned aqueous dispersion may contain, as necessary, other resins in addition to the water-soluble PAI (P), PES (Q), and fluoropolymer (R). By blending the above-mentioned other resins, the film-forming properties, corrosion resistance, etc. of the coating film obtained from the coating composition can be improved.

[0090] The other resins are not particularly limited, and examples thereof include phenol resins, urea resins, epoxy resins, urethane resins, melamine resins, polyester resins, polyether resins, acrylic resins, acrylic silicone resins, silicone resins, and silicone polyester resins.

[0091] In the coating composition of the present disclosure, the aqueous dispersion contains particles of the fluoropolymer (R) as a main dispersoid and an aqueous medium as a dispersion medium. The aqueous medium is not particularly limited as long as it contains water, and examples thereof include water, a mixture of water and an organic liquid, and water.

[0092] The organic liquid is not particularly limited, and examples thereof include aromatic hydrocarbon solvents such as toluene, xylene, trimethylbenzene, methylethylbenzene, propylbenzene, and butylbenzene; saturated hydrocarbon solvents having 6 to 12 carbon atoms; nitrogen-containing solvents such as N-methyl-2-pyrrolidone, 2-pyrrolidone, and N,N-dimethylacetamide; lactones such as γ-butyrolactone; acyclic esters such as butyl acetate; ketones such as methyl isobutyl ketone and methyl ethyl ketone; glycol ethers such as butyl cellosolve; glycols such as ethylene glycol, triethylene glycol, and propylene glycol; and monoalcohols such as 1-butanol and diacetone alcohol.

[0093] In the coating composition of the present disclosure, the total content of the organic solvent that may be contained in the water-soluble PAI (P) solution and the organic liquid that may be contained in the aqueous dispersion is preferably 40 to 500 parts by mass, and more preferably 80 to 300 parts by mass, per 100 parts by mass of the water-soluble PAI (P).

[0094] As the aromatic hydrocarbon solvent, commercially available products such as Solvesso 100, Solvesso 150, and Solvesso 200 (all trade names, manufactured by Exxon Chemical Co.) may be used. As the saturated hydrocarbon solvent, commercially available products such as mineral spirits (Japan Industrial Standards, Industrial Gasoline No. 4) may be used. The organic liquids may be used alone or in combination of two or more. As the organic liquid, it is preferable to use at least one selected from the group consisting of N-ethyl-2-pyrrolidone, N-butyl-2-pyrrolidone, 3-alkoxy-N,N-dimethylpropanamide, 1,3-dimethyl-2-imidazolidinone, 3-methyl-2-oxazolidinone, N-formylmorpholine, N-acetylmorpholine, and dimethylpropylene urea.

[0095] The aqueous medium may be, for example, one in which various additives described below are dissolved or dispersed. The aqueous medium may be the aqueous medium used in the polymerization of the fluoropolymer (R), or may be one prepared separately from the aqueous medium used in the polymerization, but when the fluoropolymer (R) is obtained by emulsion polymerization or suspension polymerization, the aqueous medium used in the polymerization of the fluoropolymer (R) can be used as it is.

[0096] The solids concentration of the coating composition is preferably 5 to 70% by mass, more preferably 10% by mass or more, more preferably 60% by mass or less, even more preferably 50% by mass or less, and particularly preferably 40% by mass or less.

[0097] The coating composition of the present disclosure may further contain various additives, which are not particularly limited and examples thereof include fillers, leveling agents, solid lubricants, anti-settling agents, moisture absorbers, surfactants, surface conditioners, thixotropy-imparting agents, viscosity modifiers, anti-gelling agents, UV absorbers, light stabilizers, plasticizers, anti-color separation agents, anti-skinning agents, anti-scratch agents, anti-fungal agents, antibacterial agents, antioxidants, antistatic agents, silane coupling agents, colorants (iron oxide, titanium dioxide, etc.), etc.

[0098] The coating composition of the present disclosure may contain a filler as the additive for the purpose of imparting characteristics to the resulting coated article, improving physical properties, increasing the amount, etc. Examples of the characteristics and physical properties include strength, durability, weather resistance, flame retardancy, and designability.

[0099] The filler is not particularly limited, and examples thereof include wood flour, quartz sand, carbon black, clay, talc, diamond, fluorinated diamond, corundum, silica stone, boron nitride, boron carbide, silicon carbide, fused alumina, tourmaline, jade, germanium, zirconium oxide, zirconium carbide, chrysoberyl, topaz, beryl, garnet, extender pigments, lustrous flat pigments, scaly pigments, glass, glass powder, mica powder, metal powder (gold, silver, copper, platinum, stainless steel, aluminum, etc.), various reinforcing materials, various extenders, conductive fillers, and the like.

[0100] The content of the additive is preferably 0.01 to 10.0% by mass, more preferably 0.1 to 5.0% by mass, based on the coating composition.

[0101] The coating composition of the present disclosure preferably has a viscosity at 25°C of 50 to 1000 mPa·s. A viscosity of 50 mPa·s or higher prevents sagging during application onto the substrate, making it possible to obtain the desired film thickness, while a viscosity of 1000 mPa·s or lower improves leveling during application, resulting in a uniform coating film thickness and improved surface smoothness. A more preferred lower limit is 60 mPa·s, and a more preferred upper limit is 800 mPa·s. The above viscosity is a value obtained by measurement using a BM-type single-cylinder rotational viscometer (manufactured by Tokyo Keiki Inc.).

[0102] When the coating composition of the present invention is used as a primer composition, the total solid content mass (total mass) (W) of the water-soluble PAI (P) and PES (Q) is preferably 15 to 50 mass% of the total solid content mass (total mass) of (W) and the fluorinated polymer (R).

[0103] In this specification, the above "total solids mass of (W) and the fluoropolymer (R)" means the total mass of the water-soluble PAI (P), PES (Q), and the fluoropolymer (R) in the residue obtained after applying the coating composition of the present invention to an object to be coated, drying at a temperature of 80 to 100°C, and baking at 380 to 400°C for 45 minutes.

[0104] When the W is 15% by mass or more of the total solid content of W and the fluoropolymer (R), the water-soluble PAI (P) and the PES (Q) exert their effects, and sufficient adhesion is obtained between the coating film obtained from the coating composition and the substrate. When the W is 50% by mass or less, the fluoropolymer (R) exerts its effects, and sufficient adhesion is obtained between the coating film and the topcoat coating. A more preferred lower limit is 20% by mass, and a more preferred upper limit is 35% by mass.

[0105] The coating composition of the present disclosure can be prepared by a conventionally known method, for example, by appropriately mixing the water-soluble PAI (P) dissolved in a molecularly dispersed state in water containing an organic solvent, PES (Q), the fluoropolymer (R), and other resins to be blended as needed, and dispersing or dissolving the mixture in the aqueous medium to obtain an aqueous dispersion, adjusting the viscosity to an easy-to-apply viscosity using a viscosity modifier or the like as needed, and blending various additives other than the viscosity modifier as desired. The coating composition of the present disclosure may also be prepared by previously preparing dispersions of the PES (Q), the fluoropolymer (R), the pigment, etc., and then mixing the resulting dispersions.

[0106] The coating composition of the present invention has excellent coating properties, and even when used in spray coating, it is less likely to cause cissing or uneven coating when the atomized coating reaches the substrate. The mechanism behind this effect is unclear, but it is thought to be due to the inclusion of water-soluble PAI (P), which dissolves in a molecularly dispersed state in the aqueous dispersion, resulting in smaller coating particles during spraying than conventional products. Furthermore, the high viscosity of the water-soluble PAI eliminates the need to add a methylcellulose-based thickener when preparing the coating composition, thereby suppressing foaming caused by the methylcellulose-based thickener. Therefore, the spray-applied coating film is uniform and less likely to develop pinholes.

[0107] Although the coating composition of the present disclosure further contains a water-soluble PAI (P), by using a non-melt-processible fluoropolymer (S) in combination with a melt-processible fluoropolymer (T), the coating composition has good corrosion resistance and water vapor resistance, and can maintain corrosion resistance even if the water-soluble PAI (P) has a relatively large number of carboxyl groups. This is thought to be due to the effect of the melt viscosities of the melt-processible fluoropolymer (T) and the melt-processible fluoropolymer of the top coat being similar. The corrosion resistance in the present disclosure can also be maintained at least to the same extent as when a water-insoluble PAI is used instead of the water-soluble PAI (P).

[0108] The coating composition of the present disclosure contains a fluorine-containing polymer (R). When the coating composition is a paint composition used in the one-coat method, it can impart non-stickiness, lubricity, etc. to the object to be coated. When the coating composition is a primer composition used in the two-coat method, it can improve the adhesion between the paint film obtained by painting and the topcoat paint film. An intermediate coat layer may be further provided between the primer layer and the topcoat layer. The intermediate coat layer is not particularly limited and can be formed using a known intermediate coat paint.

[0109] The coating composition of the present invention is also composed of water-soluble PAI and PES, and since the PAI and PES have adhesive properties with the substrate as described above, the coating film obtained by coating has excellent adhesion to the substrate.

[0110] The coating composition of the present disclosure has the above-mentioned configuration and can therefore be suitably used as a paint composition for producing coated articles.

[0111] The coated article of the present disclosure can be obtained by applying the coating composition of the present disclosure to an object to be coated and drying it as needed. The present disclosure also provides a coated article comprising an object to be coated and a layer formed from the coating composition.

[0112] The coated article of the present disclosure may comprise at least the substrate and the coating film, and may further comprise the topcoat coating film. When the topcoat coating film is comprised, the layer formed from the coating composition serves as a primer layer. The present disclosure also relates to a coated article comprising a substrate, a primer layer formed from the coating composition, and a fluorine-containing topcoat layer containing a fluorine-containing polymer.

[0113] The coated article of the present invention can be obtained by applying the coating composition of the present invention to an object to be coated, drying it if necessary, and then baking it. The object to be coated can be, for example, an object made of a metal or a non-metallic inorganic material, but an object made of a metal is preferred, and an object made of aluminum or stainless steel is more preferred.

[0114] Examples of the metals include simple metals such as iron, aluminum, and copper, as well as alloys thereof. Examples of the alloys include stainless steel. Examples of the non-metallic inorganic materials include enamel, glass, and ceramics. The object to be coated may contain other materials in addition to the metal or non-metallic inorganic material.

[0115] The above-mentioned object to be coated may be subjected to a surface treatment such as degreasing or roughening, as necessary. The method of the above-mentioned roughening treatment is not particularly limited, and examples thereof include chemical etching using an acid or alkali, anodizing (anodizing), sandblasting, etc. The above-mentioned surface treatment may be appropriately selected depending on the type of the above-mentioned object to be coated and the above-mentioned coating composition, etc., but for example, sandblasting is preferred.

[0116] The above-mentioned substrate may be one that has been subjected to a degreasing treatment in which oil and other impurities are thermally decomposed and removed by baking at 380° C. Alternatively, an aluminum substrate may be used that has been subjected to a surface roughening treatment using an alumina abrasive after surface treatment.

[0117] The above-mentioned object to be coated may be previously subjected to a surface treatment such as degreasing or roughening depending on the type of object. The method of the above-mentioned roughening treatment is not particularly limited, and examples thereof include chemical etching with an acid or alkali, anodizing (anodizing), sandblasting, etc. The above-mentioned surface treatment is preferably performed because it allows the coating composition to be applied uniformly without causing cissing and improves adhesion between the object to be coated and the coating film.

[0118] The coating method is not particularly limited, and examples thereof include spray coating, roll coating, coating with a doctor blade, dip coating, impregnation coating, spin flow coating, curtain flow coating, etc., of which spray coating is preferred. The drying method is not particularly limited, and examples thereof include conventionally known methods, and is preferably carried out at a temperature of 60 to 300°C for 5 to 60 minutes.

[0119] In the case of the one-coat method described above, in which no topcoat film is laminated on the coating film, the coated article of the present disclosure is produced by obtaining the coating film and then baking the coating film. The baking method is not particularly limited, and for example, a conventionally known method is used. The baking is usually carried out at 260 to 410°C for 10 to 30 minutes, depending on the type of the water-soluble PAI (P), PES (Q), fluoropolymer (R), etc.

[0120] In the case of the above-mentioned two-coat method in which a topcoat coating film is laminated on the coating film, the coated article of the present disclosure is produced by applying a topcoat paint onto the coating film after the coating film is obtained, drying the topcoat paint as necessary, and then baking the topcoat paint to obtain a coating film (primer layer) made of the coating composition and a topcoat coating film (fluorine-containing layer) made of the topcoat paint.

[0121]

[0013] In this specification, the "top coat paint" refers to a paint to be applied onto the coating film, and is composed of a fluorine-containing top coat polymer. The fluorine-containing top coat polymer is a polymer having fluorine atoms directly bonded to carbon atoms constituting the main chain or side chain. The fluorine-containing top coat polymer is similar to the fluorine-containing polymer (R) in that it is a polymer having fluorine atoms directly bonded to carbon atoms constituting the main chain or side chain, but is conceptually different from the fluorine-containing polymer (R) incorporated in the coating composition of the present disclosure in that it is incorporated in the top coat paint. The fluorine-containing top coat polymer, when present in the top coat paint film, can impart non-stick properties, lubricity, etc. to the object to be coated, and because it has affinity with the fluorine-containing polymer (R), it can also improve adhesion to the coating film.

[0122] The fluorine-containing polymer for the top coat is not particularly limited, and examples include PTFE, PFA, FEP, etc., but melt-processable fluorine-containing polymers are preferred from the viewpoint of improving interlayer adhesion between the coating film and the top coat. Examples of the top coat paint include PFA-based paints whose main component is PFA and FEP-based paints whose main component is FEP. PFA, which has excellent heat resistance, is particularly preferred. PFAs having an MFR of 1 to 50 g / 10 min close to the MFR of the melt-processable fluorine-containing polymer contained in the coating composition of the present disclosure are preferred, and PFAs of 2 to 40 g / 10 min are even more preferred.

[0123] The top coat paint may be one which further contains, together with the fluorine-containing top polymer, additives similar to the various additives which can be used in the above-mentioned coating compositions, for the purpose of improving coatability, the properties of the resulting coating film, etc. Examples of the top coat paint include liquid paints such as aqueous dispersion paints and solvent-based paints when the main component is PTFE, PFA or FEP, and powder paints when the main component is PFA or FEP.

[0124] The coating film is usually not baked before the top coat paint is applied, but may be baked if necessary. It is preferable not to bake the coating film before the top coat paint is applied, as this simplifies the process and reduces energy, labor, time, etc.

[0125] The method for applying the top coat paint is not particularly limited, and for example, when the top coat paint is a liquid paint, examples thereof include the same method as the method for applying the coating composition of the present disclosure, and when the top coat paint is a powder paint, examples thereof include electrostatic spray coating, fluidized bed coating, rotolining, etc. Drying and baking after application of the top coat paint can be carried out under the same conditions as the drying and baking carried out after application of the above-mentioned coating composition, respectively.

[0126] In the case of producing the coated article of the present disclosure by the above-mentioned two-coat method, the topcoat coating film may be obtained by using a film instead of the topcoat paint. In this specification, the film is mainly composed of the above-mentioned fluorine-containing polymer for topcoat coating and is formed into a film shape. When the film is used to form the topcoat coating film, a conventionally known method can be used, such as placing the film on the coating film and bonding it under heat and pressure to adhere the coating film and the film together.

[0127] The film thickness of the coating film and the topcoat coating film after baking of the coated article are not particularly limited and depend on the use of the coated article, but it is preferable that the film thickness of the primer coating film is 1 to 100 μm and the film thickness of the topcoat coating film is 10 to 200 μm.

[0128] When the coating film is formed on the substrate by the one-coat method described above, it can impart to the substrate the non-adhesive properties, lubricity, etc. that are possessed by the fluoropolymer (R), and when a topcoat coating film is laminated on the coating film by the two-coat method described above, it has excellent adhesion both to the substrate and to the topcoat coating film.

[0129] The coated article of the present disclosure may have a substrate, a primer layer containing a heat-resistant resin, an intermediate layer formed from the above-mentioned coating composition, and a fluorine-containing top-coat layer containing a fluorine-containing polymer. The present disclosure also provides a coated article having a substrate, a primer layer containing a heat-resistant resin, an intermediate layer formed from the above-mentioned coating composition, and a fluorine-containing top-coat layer containing a fluorine-containing polymer. Such a coated article also has excellent corrosion resistance.

[0130] Note that this method of use is similar to that disclosed in Japanese Patent Application Laid-Open No. 2020-176216 filed by the present applicant, and the method of use can be similar to that described in the prior document.

[0131] The coated article of the present disclosure can be used in applications that utilize the properties of the fluoropolymer (R) used in the above-mentioned one-coat method or the fluoropolymer for top coating used in the above-mentioned two-coat method or the like.

[0132] The coating composition of the present disclosure can provide a coating film having excellent corrosion resistance and water vapor resistance, and the coated article of the present disclosure has excellent corrosion resistance and water vapor resistance. Therefore, the coating composition of the present disclosure and the coated article of the present disclosure can be suitably used in any field where corrosion resistance and water vapor resistance are required. Applicable applications are not particularly limited, and examples include applications that utilize the non-stick properties, heat resistance, slip properties, etc., of the fluoropolymer. Examples of products that utilize non-adhesive properties include cooking utensils such as frying pans, pressure cookers, pots, grill pans, rice cookers, ovens, hot plates, bread pans, knives, and gas stoves; kitchen utensils such as electric kettles, ice trays, molds, and range hoods; food industry parts such as kneading rolls, rolling rolls, conveyers, and hoppers; industrial products such as office automation (OA) rolls, OA belts, OA separation claws, papermaking rolls, and film production calendar rolls; molds and casting dies for polystyrene foam molding, etc.; mold release dies for molding such as release plates for producing plywood and decorative panels; industrial containers (particularly for the semiconductor industry); and examples of products that utilize slipperiness include medical guide wires, catheters, sheaths, sheath introducers, and other tools such as saws and files; household products such as irons, scissors, and knives; metal foils; electric wires; sliding bearings for food processing machines, packaging machines, spinning and weaving machines, etc.; sliding parts for cameras and watches; automotive parts such as pipes, valves, and bearings; snow shovels; plows; and chutes.

[0133] The coating composition of the present disclosure and the coated article of the present disclosure are preferably used in cooking utensils or kitchenware, more preferably in cooking utensils, and even more preferably in rice cookers. The coated article of the present disclosure is also preferably a cooking utensil, kitchenware, or a component thereof, more preferably a cooking utensil or a component thereof, and even more preferably a rice cooker or a component thereof.

[0134] The present disclosure will be specifically described below with reference to examples, but the present disclosure is not limited to these examples. Hereinafter, "%" and "parts" represent % by mass and parts by mass, respectively.

[0135] Preparation Example 1: Preparation of Water-Soluble Polyamideimide Resin Solution (1) 111.1 parts of polyamideimide resin [PAI] having a number-average molecular weight of 20,000 and an acid value of 80 mg (KOH) per gram, 156.36 parts of N-methyl-2-pyrrolidone (hereinafter referred to as NMP) (boiling point 202°C), 17.37 parts of furfuryl alcohol, 44.92 parts of diethanolamine, 3.57 parts of aqueous ammonia (28%), and 333.33 parts of ion-exchanged water were stirred to dissolve the PAI, yielding a water-soluble PAI solution. The PAI concentration in the water-soluble PAI solution was 15%, the viscosity at 25°C was 1,800 mPa s, the number-average molecular weight was 21,000, and the acid value was 46 equivalents.

[0136] Preparation Example 2: Preparation of Polyethersulfone Resin Aqueous Dispersion (1) 60 parts of a polyethersulfone resin (PES) having a number-average molecular weight of approximately 24,000 and 60 parts of deionized water were stirred in a ceramic ball mill for approximately 10 minutes until the PES particles were completely pulverized. Next, 180 parts of NMP was added, and the mixture was further pulverized for 48 hours to obtain a dispersion. The resulting dispersion was further pulverized in a sand mill for 1 hour to obtain a PES aqueous dispersion with a PES concentration of approximately 20% (average particle size: 2 μm).

[0137] Production Example 3: Preparation of Polyamideimide Resin Aqueous Dispersion (1) A polyamideimide resin (PAI) varnish (containing 71% NMP) with a solids content of 29% was poured into water to precipitate PAI. This was ground in a ball mill for 48 hours to obtain a PAI aqueous dispersion (average particle size: 2 μm). The solids content of the resulting PAI aqueous dispersion was 20%.

[0138] Preparation Example 4: Preparation of Water-Soluble Polyamideimide Resin Solution (2) 111.1 parts of polyamideimide resin [PAI] having a number-average molecular weight of 20,000 and an acid value of 80 mg (KOH) per gram, 156.36 parts of N-ethyl-2-pyrrolidone (hereinafter referred to as NEP), 17.37 parts of furfuryl alcohol, 44.92 parts of diethanolamine, 3.57 parts of aqueous ammonia (28%), and 333.33 parts of ion-exchanged water were stirred to dissolve the PAI, yielding a water-soluble PAI solution. The PAI concentration in the water-soluble PAI solution was 15%, the viscosity at 25°C was 1,800 mPa s, the number-average molecular weight was 21,000, and the acid value was 46 equivalents.

[0139] Preparation Example 5: Preparation of Polyethersulfone Resin Aqueous Dispersion (2) 60 parts of a polyethersulfone resin (PES) having a number-average molecular weight of approximately 24,000 and 60 parts of deionized water were stirred in a ceramic ball mill for approximately 10 minutes until the PES particles were completely pulverized. Next, 180 parts of NEP were added, and the mixture was further pulverized for 48 hours to obtain a dispersion. The resulting dispersion was further pulverized in a sand mill for 1 hour to obtain a PES aqueous dispersion with a PES concentration of approximately 20% (average particle size: 2 μm).

[0140] Preparation Example 6: Preparation of Water-Soluble Polyamideimide Resin Solution (3) 111.1 parts of polyamideimide resin [PAI] having a number-average molecular weight of 20,000 and an acid value per gram of 80 mg (KOH), 156.36 parts of 3-methoxy-N,N-dimethylpropanamide (hereinafter referred to as NDPA), 17.37 parts of furfuryl alcohol, 44.92 parts of diethanolamine, 3.57 parts of aqueous ammonia (28%), and 333.33 parts of ion-exchanged water were stirred to dissolve the PAI, yielding a water-soluble PAI solution. The PAI concentration in the water-soluble PAI solution was 15%, the viscosity at 25°C was 1700 mPa s, the number-average molecular weight was 20,000, and the acid value was 46 equivalents.

[0141] Preparation Example 7: Preparation of Polyethersulfone Resin Aqueous Dispersion (3) 60 parts of a polyethersulfone resin (PES) having a number-average molecular weight of approximately 24,000 and 60 parts of deionized water were stirred in a ceramic ball mill for approximately 10 minutes until the PES particles were completely pulverized. Next, 180 parts of NDPA was added, and the mixture was further pulverized for 48 hours to obtain a dispersion. The resulting dispersion was further pulverized in a sand mill for 1 hour to obtain a PES aqueous dispersion with a PES concentration of approximately 20% (average particle size: 2 μm).

[0142] Preparation Example 8: Preparation of Water-Soluble Polyamideimide Resin Solution (4) 111.1 parts of polyamideimide resin [PAI] having a number average molecular weight of 20,000 and an acid value per gram of 80 mg (KOH), 156.36 parts of N-formylmorpholine, 17.37 parts of furfuryl alcohol, 44.92 parts of diethanolamine, 3.57 parts of aqueous ammonia (28%), and 333.33 parts of ion-exchanged water were stirred to dissolve the PAI, yielding a water-soluble PAI solution. The PAI concentration in the water-soluble PAI solution was 15%, the viscosity at 25°C was 1600 mPa s, the number average molecular weight was 19,000, and the acid value was 44 equivalents.

[0143] Production Example 9: Preparation of Polyetherimide Resin Aqueous Dispersion 60 parts of a polyetherimide resin [PEI] having a weight-average molecular weight of approximately 55,000 and 60 parts of deionized water were stirred in a ceramic ball mill for approximately 10 minutes until the PEI particles were completely pulverized. Next, 180 parts of N-formylmorpholine was added, and the mixture was further pulverized for 48 hours to obtain a dispersion. The resulting dispersion was further pulverized in a sand mill for 1 hour to obtain an aqueous PEI dispersion with a PEI concentration of approximately 20% (average particle size: 2 μm).

[0144] Production Example 10: Preparation of Polyethersulfone Resin Aqueous Dispersion (4) 60 parts of a polyethersulfone resin [PES] having a number-average molecular weight of approximately 24,000 and 60 parts of deionized water were stirred in a ceramic ball mill for approximately 10 minutes until the PES particles were completely pulverized. Next, 180 parts of N-formylmorpholine was added, and the mixture was further pulverized for 48 hours to obtain a dispersion. The resulting dispersion was further pulverized in a sand mill for 1 hour to obtain a PES aqueous dispersion with a PES concentration of approximately 20% (average particle size: 2 μm).

[0145] Example 1 The PES aqueous dispersion (1) obtained in Production Example 2 and the water-soluble PAI solution (1) obtained in Production Example 1 were mixed so that the PES accounted for 75% of the total solid content of the PES and PAI, and this was mixed with an aqueous dispersion of tetrafluoroethylene homopolymer (TFE homopolymer, hereinafter referred to as PTFE) (average particle size 0.28 μm, solid content 60%, containing 6% of a polyether-based nonionic surfactant as a dispersant relative to PTFE) and an aqueous dispersion of tetrafluoroethylene-hexafluoropropylene copolymer (hereinafter referred to as FEP). (average particle size 0.20 μm, solid content 60%, containing 5% by weight of polyether-based nonionic surfactant as a dispersant relative to FEP) was added so that FEP accounted for 50% of PTFE in terms of solid mass ratio, and PES and PAI accounted for 25% of the total solid mass of PES, PAI, PTFE, and FEP, and a polyether-based nonionic surfactant was added as a dispersion stabilizer in an amount of 6% relative to the solid mass of PTFE, to obtain an aqueous dispersion (undercoat coating composition) with a polymer solid content of 30% and a viscosity at 25° C. of 190 mPa s.

[0146] Examples 2 to 17 Undercoat coating compositions were obtained in the same manner as in Example 1, adjusting the amounts of each component so as to obtain the coating compositions (mass composition ratios of resin solids) shown in Tables 1 and 2.

[0147] Example 18 A primer coating composition was obtained in the same manner as in Example 1, except that the PES aqueous dispersion (2) obtained in Production Example 5 and the water-soluble PAI solution (2) obtained in Production Example 4 were used.

[0148] Example 19 A coating composition for undercoat coating was obtained in the same manner as in Example 1, except that the PES aqueous dispersion (3) obtained in Production Example 7 and the water-soluble PAI solution (3) obtained in Production Example 6 were used.

[0149] Comparative Examples 1, 2, 4 to 7 Undercoat coating compositions were obtained in the same manner as in Example 1, adjusting the amounts of each component so as to obtain the coating compositions (mass composition ratios of resin solids) shown in Tables 3 and 4.

[0150] Comparative Example 3 A coating composition for undercoat coating was obtained in the same manner as in Example 1, except that the aqueous polyamideimide resin dispersion (1) obtained in Production Example 3 was used instead of the water-soluble polyamideimide resin solution (1).

[0151] Comparative Example 8 A primer coating composition was prepared in the same manner as in Example 1, except that the aqueous polyamideimide resin dispersion (4) obtained in Production Example 8 was used instead of the water-soluble polyamideimide resin solution (1), and the aqueous polyetherimide resin dispersion (1) was used instead of the aqueous polyethersulfone resin dispersion (1) with the aqueous polyetherimide resin dispersion (4) obtained in Production Example 9, and the amounts of each component were adjusted to obtain the coating composition (mass composition ratio of resin solids) shown in Table 5.

[0152] Comparative Example 9 An undercoat coating composition was obtained in the same manner as in Example 1, except that the aqueous polyamideimide resin dispersion (4) obtained in Production Example 8 was used instead of the water-soluble polyamideimide resin solution (1), the aqueous polyethersulfone resin dispersion (4) obtained in Production Example 10 was used instead of the aqueous polyethersulfone resin dispersion (1), and the aqueous polyetherimide resin dispersion (4) obtained in Production Example 9 was also used instead, and the amounts of each component were adjusted so as to obtain the coating composition (mass composition ratio of resin solids) shown in Table 6.

[0153] (Preparation of Coated Plates for Evaluation) The surface of an aluminum plate (A-1050) measuring 2.0 mm in thickness and 5 × 10 cm in size was degreased with acetone and then sandblasted to roughen the surface so that the surface roughness Ra value measured in accordance with JIS B 1982 was 2.5 to 3.5 μm. After removing dust from the surface with an air blower, the resulting coating composition was sprayed as a primer coating using a gravity-type spray gun W-101 (trade name, manufactured by Anest Iwata Corporation, nozzle diameter 1.0 mm) at a spray pressure of 0.2 MPa to achieve a dry film thickness of 10 to 15 μm. The resulting coating film was dried at 80 to 100°C for 15 minutes and cooled to room temperature. Onto the obtained coating film, a PFA powder coating (trade name: Neoflon PFA ACX34 manufactured by Daikin Industries, Ltd.) was electrostatically coated as a topcoat coating under conditions of an applied voltage of 40 kV and a pressure of 0.08 MPa, and baked at 380°C for 20 minutes to produce a topcoat coating film with a thickness of approximately 40 μm, and a coated plate for evaluation was obtained.

[0154] The resulting coating composition and the coated plate for evaluation were evaluated as follows.

[0155] (Coatability) The obtained coating composition was applied to an aluminum plate using a gravity spray gun W-101 type (trade name, manufactured by Anest Iwata Corporation, gun diameter 2 mm) at an atomization pressure of 0.1 MPa, and the occurrence of bubbles and cissing was visually checked immediately after application. If no bubbles or cissing occurred, the result was rated as good, and if bubbles or cissing occurred, the result was rated as poor.

[0156] (Water vapor resistance) The obtained coated plate for evaluation was placed in water vapor at 165°C and 0.6 MPa, and after 100 hours, it was removed and cooled to room temperature. The coated plate for evaluation was placed on a hot plate and reheated to 200°C in 60 seconds, and visually inspected for the occurrence of blistering in the coating film. The period up to reheating after 100 hours was considered one cycle. A plate that did not blister after 5 or more cycles was evaluated as passing.

[0157] (Corrosion Resistance) The obtained coated plates for evaluation were immersed in salt water (5.0 mass%) at 98°C, and the coating film was visually inspected every 50 hours for blistering. A plate that did not blister for 250 hours or more was rated as passing.

[0158] The evaluation results are shown in Tables 1 to 6.

[0159]

[0160]

[0161]

[0162]

[0163]

[0164]

[0165] The coating composition of the present disclosure is resistant to cissing and uneven coating and has excellent coatability, and therefore can be widely used in the manufacture of various coated articles. The coated articles of the present disclosure are formed by coating the coating composition, and therefore have no uneven coating, good corrosion resistance and water vapor resistance, and can be suitably used as various food and drink containers, etc.

Claims

1. A coating composition comprising an aqueous dispersion containing a water-soluble polyamideimide resin (P), a polyethersulfone resin (Q), and a fluorine-containing polymer (R) comprising a non-melt-processable fluorine-containing polymer (S) and a melt-processable perfluoropolymer (T) having a melting point of 200 to 350°C, wherein the mass ratio of the water-soluble polyamideimide resin (P) to the polyethersulfone resin (Q) is 10 / 90 to 40 / 60.

2. The coating composition according to claim 1, wherein the aqueous dispersion contains particles made of polyethersulfone resin (Q) and particles made of fluorine-containing polymer (R), and the particles made of polyethersulfone resin (Q) are particles dispersed in the aqueous dispersion and have an average particle size of 0.1 to 10 μm.

3. The coating composition according to claim 1 or 2, wherein the perfluoropolymer (T) is a tetrafluoroethylene / hexafluoropropylene copolymer.

4. The coating composition according to claim 3, wherein the melt flow rate (MFR) of the tetrafluoroethylene / hexafluoropropylene copolymer is 1 to 50 g / 10 min.

5. The coating composition according to claim 1 or 2, wherein the perfluoropolymer (T) is a tetrafluoroethylene / perfluoro(alkyl vinyl ether) copolymer.

6. The coating composition according to claim 5, wherein the melt flow rate (MFR) of the tetrafluoroethylene / perfluoro(alkyl vinyl ether) copolymer is 1 to 50 g / 10 min.

7. The coating composition according to any one of claims 1 to 6, wherein the water-soluble polyamide-imide resin (P) has a number average molecular weight of 5,000 to 50,000 and an acid value of the combined carboxyl groups and carboxyl groups resulting from ring-opening of imide bonds of 10 to 100 equivalents.

8. The coating composition according to any one of claims 1 to 7, wherein the mass ratio of the non-melt-processible fluorine-containing polymer (S) to the perfluoropolymer (T) is from 5 / 95 to 95 / 5.

9. The coating composition according to any one of claims 1 to 8, wherein the ratio of the total mass of the water-soluble polyamideimide resin (P) and the polyethersulfone resin (Q) to the total mass of the non-melt-processible fluorine-containing polymer (S) and the perfluoropolymer (T) is 15 / 85 to 40 / 60.

10. The coating composition according to any one of claims 1 to 9, wherein the viscosity of the water-soluble polyamideimide resin (P) at 25°C is 1,000 to 10,000 mPa·s.

11. The coating composition according to any one of claims 1 to 10, characterized in that the viscosity at 25°C is 50 to 1,000 mPa·s.

12. The coating composition according to any one of claims 1 to 11, wherein the water-soluble polyamide-imide resin (P) has a number average molecular weight of 1,500 to 25,000, an acid value of the combined carboxyl groups and carboxyl groups resulting from ring-opening of imide bonds of 30 to 60 equivalents, and a viscosity at 25°C of 1,200 to 8,000 mPa·s.

13. The coating composition according to any one of claims 1 to 12, which contains as an aqueous medium at least one organic liquid selected from the group consisting of N-ethyl-2-pyrrolidone, N-butyl-2-pyrrolidone, 3-alkoxy-N,N-dimethylpropanamide, 1,3-dimethyl-2-imidazolidinone, 3-methyl-2-oxazolidinone, N-formylmorpholine, N-acetylmorpholine, and dimethylpropyleneurea.

14. A coated article comprising an object to be coated and a layer formed from the coating composition according to any one of claims 1 to 13.

15. A coated article comprising an object to be coated, a primer layer formed from the coating composition according to any one of claims 1 to 13, and a fluorine-containing layer comprising a fluorine-containing topcoat polymer.

16. A coated article comprising an object to be coated, a primer layer containing a heat-resistant resin, an intermediate layer formed from the coating composition according to any one of claims 1 to 13, and a fluorine-containing layer containing a fluorine-containing topcoat polymer.

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