Coating composition and coated article

Abstract

To provide a coating composition which has excellent coatability and forms a coating film good in steam resistance and corrosion resistance.SOLUTION: The coating composition comprises an aqueous dispersion containing: a water-soluble polyamide-imide resin (P); a polyethersulfone resin (Q); and a fluorine-containing polymer (R) which contains a non-melt-processable fluorine-containing polymer (S) and a melt-processable perfluoropolymer (T) having a melting point of 200-350°C. The mass ratio of the water-soluble polyamide-imide resin (P) to the polyethersulfone resin (Q) is 10 / 90-40 / 60.SELECTED DRAWING: None

Description

[Technical field]

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

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

[0003] Since the fluorine-containing polymer has such properties, for example, by preparing it into a coating composition and applying it onto an object to be coated to provide a coating film made of the fluorine-containing polymer, the fluorine-containing polymer can be used in a wide range of applications, such as 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, the food industry, the electrical industry, the machinery industry, and the like.

[0004] On the other hand, the fluoropolymer has a problem of poor adhesion to the object to be coated due to its non-stickiness. In order to improve this adhesion, a primer containing a binder resin such as a heat-resistant resin and a fluoropolymer 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, a fluororesin, and a 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, a polyetherimide, a polyethersulfone, and a fluororesin, and is characterized in that the fluororesin contains non-thermofusible polytetrafluoroethylene and a thermofusible fluororesin (Patent Document 4). [Prior art documents] [Patent documents]

[0009] [Patent Document 1] Japanese Patent Application Publication No. 6-264000 [Patent Document 2] JP 2007-63482 A [Patent Document 3] JP 2020-176216 A [Patent Document 4] Patent Publication No. 2021-21013 Summary of the Invention [Problem to be solved by the invention]

[0010] An object of the present disclosure is to provide a coating composition which has excellent coatability and which forms a coating film having good water vapor resistance and corrosion resistance. [Means for solving the problem]

[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 above-mentioned aqueous dispersion contains particles made of a polyethersulfone resin (Q) and particles made of a fluoropolymer (R), and it is preferable 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. The tetrafluoroethylene / hexafluoropropylene copolymer preferably has a melt flow rate (MFR) of 1 to 50 g / 10 min.

[0014] The perfluoropolymer (T) is preferably a tetrafluoroethylene / perfluoro(alkyl vinyl ether) copolymer. 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 polyamideimide resin (P) preferably has a number average molecular weight of 5,000 to 50,000 and an acid value of 10 to 100 equivalents, calculated as the total of the carboxyl groups and the carboxyl groups resulting from ring-opening of the imide bonds. The mass ratio of the non-melt-processible fluoropolymer (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 the polyethersulfone resin (Q) to the total mass of the non-melt-processible fluorine-containing polymer (S) and the perfluoropolymer (T) is preferably 15 / 85 to 40 / 60. The water-soluble polyamideimide resin (P) preferably has a viscosity at 25° C. of 1,000 to 10,000 mPa·s. The coating composition of the present disclosure preferably has a viscosity at 25°C of 50 to 1000 mPa·s. The water-soluble polyamideimide resin (P) preferably 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 the imide bonds of 30 to 60 equivalents, and a viscosity of the coating composition at 25°C of 1,200 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 dimethylpropyleneurea.

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

[0018] The coating composition of the present disclosure has excellent paintability. In addition, 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 susceptible to cissing and uneven coating. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[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) containing a non-melt-processable fluoropolymer (S) and a melt-processable perfluoropolymer (T) having a melting point of 200 to 350° C. The coating composition of the present disclosure 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 objects 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 coating the composition on the object to be coated. In this specification, the term "coating" of the coating composition means a process of applying the coating composition, drying it as necessary, and then baking it.

[0022] In the above coating film, since the PES resin (Q) and the fluoropolymer (R) have a difference in surface tension, the fluoropolymer (R) rises to the surface during baking, and the fluoropolymer (R) is mainly disposed on the surface side of the coating film, and the PES resin (Q) is mainly disposed on the side of the substrate. Since the PES resin (Q) has adhesive properties with the substrate, the above coating film can have excellent adhesion to the substrate.

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

[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 called a one-coat method when the topcoat film is not laminated on the coating film, which comprises applying the coating composition onto the substrate, drying it if necessary, and then baking it.

[0026] In this specification, the method for producing the coated article is called a two-coat method when the topcoat coating film is laminated on the coating film. The two-coat method usually involves applying the coating composition onto 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 case of 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 fluorine-containing polymer (R) is a polymer having fluorine atoms directly bonded to carbon atoms constituting the main chain or side chain. The fluorine-containing polymer (R) contains a non-melt-processable fluorine-containing polymer (S) and a melt-processable perfluoropolymer (T) having a melting point of 200 to 350°C.

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

[0029] The non-melt-processible fluorine-containing polymer (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 a "modified monomer").

[0031] The above-mentioned modified monomer is not particularly limited as long as it is copolymerizable with TFE, and examples thereof include perfluoroolefins such as hexafluoropropylene (HFP), chlorofluoroolefins such as chlorotrifluoroethylene (CTFE), hydrogen-containing fluoroolefins such as trifluoroethylene and vinylidene fluoride (VDF), perfluorovinyl ethers, perfluoroalkylethylenes, ethylene, etc. The modified monomer used may be one type or multiple types.

[0032] The perfluorovinyl ether is not particularly limited, and examples thereof include perfluorovinyl ethers represented by the following general formula (1): CF2=CF-ORf 1 (1) (In the formula, Rf 1 represents a perfluoro organic group. In the present specification, the term "perfluoro organic group" refers to an organic group in which all hydrogen atoms bonded to carbon atoms are replaced with fluorine atoms. The perfluoro organic group may have an ether oxygen.

[0033] The perfluorovinyl ether may be, for example, a compound represented by the general formula (1), where Rf 1 and perfluoro(alkyl vinyl ether) (PAVE), which 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] The perfluoroalkyl group in the above PAVE may be, for example, a perfluoromethyl group, a perfluoroethyl group, a perfluoropropyl group, a perfluorobutyl group, a perfluoropentyl group, a perfluorohexyl group, etc., and the perfluoroalkyl group is preferably a perfluoropropyl group. That is, the above 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 composed substantially of TFE units only, and is preferably obtained without using any modified monomer, for example.

[0037] The modified PTFE preferably contains the modified monomer unit at 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 and an injection molding machine. Therefore, the melt-processable fluoropolymer (T) usually has a melt flow rate (MFR) of 1.0 to 50g / 10min.

[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 of polymer flowing out per 10 minutes 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 (e.g., 372°C for PFA and FEP, and 297°C for ETFE) and a load (e.g., 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, and more preferably 340° C. or lower, particularly preferably 330° C. or lower.

[0042] In this specification, the melting point of the above 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] The melt-processible fluorine-containing polymer (T) may be 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). The melt-processible fluoropolymer (T) is preferably at least one selected from the group consisting of FEP and PFA, and more preferably FEP, in that a coating film having even more excellent corrosion resistance can be obtained.

[0044] The FEP is not particularly limited, but is preferably 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. 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 the above range or more, the mechanical properties are not deteriorated, and when the molar ratio of TFE units is the above range or less, the melting point is not too high and the moldability is not deteriorated. The FEP is also preferably a copolymer containing 0.1 to 10 mol % of monomer units derived from monomers copolymerizable with TFE and HFP, and 90 to 99.9 mol % of TFE units and HFP units in total. Examples of monomers copolymerizable with TFE and HFP include PAVE, CF2=CF-OCH2-Rf 2 (In the formula, Rf 2 represents a perfluoroalkyl group having 1 to 5 carbon atoms.)

[0045] The melting point of the FEP is preferably from 200 to less than 350°C, more preferably from 210 to 340°C, and even more preferably from 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 further preferably 3 to 30 g / 10 min.

[0047] The FEP preferably has a thermal decomposition onset temperature of 360° C. or higher. The thermal decomposition onset temperature is 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) (product 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 the above range or more, the mechanical properties are not deteriorated, and when the molar ratio of TFE units is the above range or less, the melting point is not too high and the moldability is not deteriorated. The PFA is also preferably a copolymer containing 0.1 to 10 mol % of monomer units derived from monomers copolymerizable with TFE and PAVE, and 90 to 99.9 mol % of TFE units and PAVE units in total. Examples of monomers copolymerizable with TFE and PAVE include HFP, CZ, 1 Z 2 =CZ 3 (CF2) n Z 4 (In the formula, Z 1 , Z 2 and Z 3 are the same or different and each represents 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 (In the formula, Rf 2 represents a perfluoroalkyl group having 1 to 5 carbon atoms.)

[0050] The melting point of the PFA is preferably from 200 to less than 350°C, more preferably from 210 to 340°C, and even more preferably from 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 further preferably 10 to 40 g / 10 min.

[0052] The PFA preferably has a thermal decomposition onset temperature of 380° C. or higher. The thermal decomposition onset temperature is 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 above aqueous dispersion contains particles made of the above fluoropolymer (R). From the viewpoint of dispersion stability in the coating composition and surface smoothness of the resulting coating film, the non-melt-processible fluorine-containing polymer (S) and the melt-processible fluorine-containing polymer (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, particularly preferably 50 / 50 or more, and more preferably 90 / 10 or less, even more preferably 80 / 20 or less, 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 fluoropolymer (R) are dispersed in an aqueous medium.

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

[0058] [ka]

[0059] (In the formula, R 5 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] [ka]

[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 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 increase 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 preferable.

[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] The polybasic acid anhydride chloride may, for example, be trimellitic anhydride chloride.

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

[0069] The basic compound is preferably used in an amount of 1 to 20 equivalents based on 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 is difficult to make the resin water-soluble, and if the amount is more than 20 equivalents, hydrolysis of the resin may be promoted.

[0070] The water-soluble PAI (P) preferably has a number average molecular weight of 5000 to 50000. When the number average molecular weight is 5000 or more, the heat resistance and mechanical properties of the resulting film are not reduced, and when the number average molecular weight is 50000 or less, the viscosity of the coating composition is not too high, resulting in good coatability. The number average molecular weight is more preferably 10000 to 30000, and further preferably 15000 to 25000.

[0071] The number average molecular weight is a value measured by gel permeation chromatography [GPC] and converted into polystyrene equivalent. In this specification, gel permeation chromatography [GPC] is performed using a sample obtained by passing a tetrahydrofuran [THF] solution of a fluoropolymer prepared to a concentration of 0.1 to 0.2% by weight 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 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 the detector.

[0072] The water-soluble PAI (P) preferably has an acid value of 10 to 100 equivalents, which is the sum of the carboxyl groups and the carboxyl groups obtained by ring-opening the imide bond [-CO-N-CO-] (imido). When the acid value is 10 equivalents or more, there is no shortage of carboxyl groups to react with the polybasic acid anhydride or polybasic acid anhydride chloride, making it possible to make it water-soluble, and when 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. That is, take about 0.5 g of water-soluble PAI (P), add about 0.15 g of 1,4-diazabicyclo[2.2.2]octane, add about 60 g of N-methyl-2-pyrrolidone and about 1 ml of ion-exchanged water, and stir until the water-soluble PAI (P) is completely dissolved. This is titrated with a potentiometric titrator using a 0.05 mol / L ethanolic potassium hydroxide solution 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. 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 one or more of these may be used.

[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, dimethylsulfoxide, 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 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 above 3-alkoxy-N,N-dimethylpropanamide is N(CH3)2COCH2CH2OR 11 (R 11 is an alkyl group). 11 The 3-alkoxy-N,N-dimethylpropanamide 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. As the 3-alkoxy-N,N-dimethylpropanamide, 3-methoxy-N,N-dimethylpropanamide (N(CH3)2COCH2CH2OCH3) is particularly preferable.

[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, which can slow down the drying rate during coating and improve the surface smoothness of the coating film. The above boiling points are values ​​measured at 1 atmosphere (atm).

[0079] The viscosity of the water-soluble PAI (P) at 25°C is preferably 1000 to 10000 mPa·s, more preferably 1100 to 9000 mPa·s, and particularly preferably 1200 to 8000 mPa·s. When the viscosity of the water-soluble PAI (P) is 1000 mPa·s or more, the viscosity of the coating composition is sufficient, so that sagging is unlikely to occur during coating. When the viscosity of the water-soluble PAI (P) is 10000 mPa·s or less, the viscosity of the coating composition does not become too high, and coating can be performed well. 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 believed to be dispersed in a molecular state in a solvent in a water-soluble PAI (P) solution, and is believed 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 an aqueous medium.

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

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

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

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

[0085] There is no particular limitation on the PES, and examples thereof include resins made of polymers obtained by polycondensation of dichlorodiphenylsulfone and bisphenol.

[0086] The aqueous dispersion contains particles made of the PES(Q). The particles made of the PES(Q) are preferably particles having an average particle size of 0.1 to 10 μm when dispersed in the aqueous medium. When the average particle size of the PES(Q) is within the above range, the coating film obtained from the coating composition has good corrosion resistance. 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 as particles in an aqueous medium described below.

[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 it within this range, the corrosion resistance and water vapor resistance of the coating film are good. The above range is preferably 15 / 85 to 35 / 65. When the mass ratio of the PES resin (Q) is the above-mentioned or more, 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 the above-mentioned or less, 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. The mass ratio is 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 other resins, if necessary, in addition to the above-mentioned water-soluble PAI (P), PES (Q) and fluoropolymer (R). By blending the above-mentioned other resins, the film-forming property, 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 made of a fluoropolymer (R) as the main dispersoid, and an aqueous medium as the dispersion medium. The aqueous medium is not particularly limited as long as it contains water, and examples thereof include 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 kinds. 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 dimethylpropyleneurea.

[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. The additives are not particularly limited, and examples thereof include fillers, leveling agents, solid lubricants, anti-settling agents, moisture absorbents, surfactants, surface conditioners, thixotropic agents, viscosity regulators, gelling inhibitors, ultraviolet absorbers, light stabilizers, plasticizers, color separation inhibitors, anti-skinning agents, anti-scratch agents, anti-fungal agents, antibacterial agents, antioxidants, antistatic agents, silane coupling agents, colorants (iron oxide, titanium dioxide, etc.), and the like.

[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, design, etc.

[0099] The above-mentioned 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 powders (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, and 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. If the viscosity is 50 mPa·s or more, no sagging occurs when applied to an object to be coated, and it becomes possible to obtain a desired film thickness, and if the viscosity is 1000 mPa·s or less, the leveling property during application is improved, the thickness of the resulting coating film is uniform, and the surface smoothness, etc. are improved. A more preferable lower limit is 60 mPa·s, and a more preferable 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 Co., Ltd.).

[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 fluorine-containing polymer (R).

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

[0104] When the above W is 15% by mass or more of the total solid content of W and the fluoropolymer (R), the water-soluble PAI (P) and PES (Q) exert their effects, and sufficient adhesion is obtained between the coating film obtained from the coating composition and the substrate. When the above 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 molecular dispersion state in water containing an organic solvent, PES (Q), fluoropolymer (R), and other resins to be added as necessary, 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 necessary, and adding various additives other than the viscosity modifier as desired. In the coating composition of the present disclosure, the PES (Q), fluoropolymer (R), pigment, etc. may be prepared by previously preparing dispersions thereof and mixing the obtained dispersions.

[0106] The coating composition of the present invention has excellent coating properties, and even when used for spray coating, it is unlikely to cause cissing or uneven coating when the mist of coating reaches the object to be coated. The mechanism by which this effect is achieved is not clear, but it is believed that the water-soluble PAI (P) is dissolved in the aqueous dispersion in a molecular dispersion state, and the coating particles during spraying are smaller than those of conventional products. In addition, since the viscosity of the water-soluble PAI is high, it is no longer necessary to add a methylcellulose-based thickener when preparing the coating composition, and foaming caused by the methylcellulose-based thickener can be suppressed. Therefore, the spray-coated coating film is uniform and pinholes are unlikely to occur.

[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 considered to be due to the similarity in melt viscosity between the melt-processible fluoropolymer (T) and the melt-processible fluoropolymer of the topcoat. In the present disclosure, the corrosion resistance can 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 above-mentioned one-coat method, it can impart non-adhesiveness, lubricity, etc. to the object to be coated. When the coating composition is a primer composition used in the above-mentioned two-coat method, it can improve the adhesion between the coating film obtained by painting and the above-mentioned topcoat coating film. An intermediate coating layer may be further provided between the primer layer and the top coating layer. The intermediate coating layer is not particularly limited and may be formed from a known intermediate coating material.

[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 respect to the substrate as described above, the coating film obtained by coating has excellent adhesion to the substrate.

[0110] Since the coating composition of the present disclosure has the above-mentioned configuration, it can 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 onto an object to be coated, and then drying it as necessary. The present disclosure also relates to a coated article comprising an object to be coated and a layer formed from the above-mentioned coating composition.

[0112] The coated article of the present disclosure may be any article that comprises at least the above-mentioned substrate and the above-mentioned coating film, and may further comprise the above-mentioned topcoat coating film. In the case where the above-mentioned topcoat coating film is present, the layer formed from the above-mentioned coating composition serves as a primer layer. The present disclosure also relates to a coated article having a substrate, a primer layer formed from the above-mentioned coating composition, and a fluorine-containing layer comprising a topcoat fluorine-containing polymer.

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

[0114] The metals include metals such as iron, aluminum, copper, and alloys thereof. The alloys include stainless steel. Examples of the non-metallic inorganic material include enamel, glass, and ceramics. The substrate may include metal or non-metallic inorganic materials as well as other materials.

[0115] The above-mentioned object to be coated may be subjected to a surface treatment such as degreasing treatment or surface roughening treatment, if necessary. The method of the surface roughening treatment is not particularly limited, and examples thereof include chemical etching using an acid or alkali, anodizing (alumite treatment), 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 preferable.

[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 that has been subjected to a surface roughening treatment using an alumina abrasive after surface treatment may be used.

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

[0118] The coating method is not particularly limited, and examples thereof include spray coating, roll coating, coating with a doctor blade, dip (immersion) coating, impregnation coating, spin flow coating, curtain flow coating, etc., with spray coating being preferred. The drying method is not particularly limited, and for example, a conventionally known method may be used, and is preferably performed at a temperature of 60 to 300° C. for 5 to 60 minutes.

[0119] In the case of the one-coat method 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 to obtain a coating film. The baking is not particularly limited, and for example, a conventionally known method is used, and is usually performed at 260 to 410°C for 10 to 30 minutes depending on the type of the water-soluble PAI (P), PES (Q), fluorine-containing polymer (R), etc.

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

[0121] In this specification, the "topcoat paint" is a paint applied on the coating film, and is made of a fluorine-containing polymer for topcoat. The fluorine-containing polymer for topcoat is a polymer having fluorine atoms directly bonded to carbon atoms constituting the main chain or side chain. The fluorine-containing polymer for topcoat is a polymer having fluorine atoms directly bonded to carbon atoms constituting the main chain or side chain in common with 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) blended in the coating composition of the present disclosure in that it is blended in the topcoat paint. The fluorine-containing polymer for topcoat can impart non-adhesiveness, lubricity, etc. to the coated object by being present in the topcoat coating film, and has affinity with the fluorine-containing polymer (R), so that the adhesion with the coating film can also be improved.

[0122] The above-mentioned topcoat fluorine-containing polymer is not particularly limited, and examples thereof include PTFE, PFA, FEP, etc., but from the viewpoint of improving the interlayer adhesion between the above-mentioned coating film and the topcoat coating film, a melt-processable fluorine-containing polymer is preferred. The above-mentioned topcoat paint includes a PFA-based paint whose main component is PFA, an FEP-based paint whose main component is FEP, etc. PFA having excellent heat resistance is particularly preferred. PFA 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, is preferred, and PFA having an MFR of 2 to 40 g / 10 min is more preferred.

[0123] The above-mentioned topcoat paint may further contain, together with the above-mentioned fluorine-containing polymer for topcoat coating, additives similar to the various additives usable in the above-mentioned coating composition for the purpose of improving coatability, properties of the coating film to be obtained, etc. Examples of the topcoat 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 topcoat paint is applied, but may be baked if necessary. It is preferable not to bake the coating film before the topcoat paint is applied, since this simplifies the process and reduces energy, labor, time, etc.

[0125] The method for applying the topcoat paint is not particularly limited, and for example, when the topcoat paint is a liquid paint, a method similar to the method for applying the coating composition of the present disclosure may be used. When the topcoat paint is a powder paint, electrostatic spray coating, fluidized bed coating, roto-lining, etc. may be used. The drying and baking after application of the above-mentioned topcoat paint can be carried out under the same conditions as those for the drying and baking after application of the above-mentioned coating composition.

[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 the present 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 above-mentioned topcoat coating film, a conventionally known method can be used, such as placing the film on the coating film and bonding the coating film and the film together by heating and pressing.

[0127] The thickness of the coating film and the topcoat coating film after the coated article has been baked is not particularly limited and depends on the application of the coated article, but it is preferable that the thickness of the primer coating film is 1 to 100 μm and the thickness of the topcoat coating film is 10 to 200 μm.

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

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

[0130] In addition, such a method of use is similar to that of JP 2020-176216 filed by the present applicant, and the method of use may be similar to the method of use 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, etc.

[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. There are no particular limitations on the applicable uses, and examples of the uses include uses that utilize the non-adhesive property, heat resistance, slipperiness, etc. of the fluorine-containing polymer. Examples of products that utilize the non-adhesiveness include cooking utensils such as frying pans, pressure cookers, pots, grill pans, rice cookers, ovens, hot plates, bread baking molds, knives, and gas stoves; kitchen supplies such as electric kettles, ice trays, molds, and range hoods; food industry parts such as kneading rolls, rolling rolls, conveyers, and hoppers; industrial supplies such as office automation (OA) rolls, OA belts, OA separation claws, papermaking rolls, and film manufacturing calendar rolls; molds and casting dies for polystyrene foam molding; mold release dies such as release plates for plywood and decorative panel manufacturing; industrial containers (especially for the semiconductor industry); and examples of products that utilize the 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, and textile machines; 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 for cooking utensils or kitchen supplies, more preferably for cooking utensils, and even more preferably for rice cookers. The coated article of the present disclosure is preferably a cooking utensil, kitchen utensil or a component thereof, more preferably a cooking utensil or a component thereof, and even more preferably a rice cooker or a component thereof. EXAMPLES

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

[0135] Production Example 1 Preparation of Water-Soluble Polyamideimide Resin Solution (1) 111.1 parts of polyamideimide resin [PAI] with a number average molecular weight of 20000 and an acid value of 80mg (KOH) per gram, 156.36 parts of N-methyl-2-pyrrolidone (hereinafter referred to as NMP) (boiling point 202℃), 17.37 parts of furfuryl alcohol, 44.92 parts of diethanolamine, 3.57 parts of ammonia water (28%), and 333.33 parts of ion-exchanged water were stirred to dissolve the PAI, obtaining a water-soluble PAI solution. The concentration of PAI in the water-soluble PAI solution was 15%, the viscosity at 25℃ was 1800mPa·s, the number average molecular weight was 21000, and the acid value was 46 equivalents.

[0136] Production Example 2 Preparation of polyethersulfone resin aqueous dispersion (1) 60 parts of polyethersulfone resin [PES] having a number average molecular weight of about 24000 and 60 parts of deionized water were stirred in a ceramic ball mill for about 10 minutes until the particles made of PES were completely pulverized. Then, 180 parts of NMP were added, and the mixture was further pulverized for 48 hours to obtain a dispersion. The obtained dispersion was further pulverized in a sand mill for 1 hour to obtain a PES aqueous dispersion with a PES concentration of about 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 solid 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 solid content of the resulting PAI aqueous dispersion was 20%.

[0138] Production Example 4 Preparation of Water-Soluble Polyamideimide Resin Solution (2) 111.1 parts of polyamideimide resin [PAI] with a number average molecular weight of 20000 and an acid value of 80mg (KOH) per gram, 156.36 parts of N-ethyl-2-pyrrolidone (hereafter referred to as NEP), 17.37 parts of furfuryl alcohol, 44.92 parts of diethanolamine, 3.57 parts of ammonia water (28%), and 333.33 parts of ion-exchanged water were stirred to dissolve the PAI, obtaining a water-soluble PAI solution. The concentration of PAI in the water-soluble PAI solution was 15%, the viscosity at 25℃ was 1800mPa·s, the number average molecular weight was 21000, and the acid value was 46 equivalents.

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

[0140] Production Example 6 Preparation of Water-Soluble Polyamideimide Resin Solution (3) 111.1 parts of polyamideimide resin [PAI] with a number average molecular weight of 20000 and an acid value of 80mg (KOH) per gram, 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 ammonia water (28%), and 333.33 parts of ion-exchanged water were stirred to dissolve the PAI, obtaining a water-soluble PAI solution. The concentration of PAI in the water-soluble PAI solution was 15%, the viscosity at 25℃ was 1700mPa·s, the number average molecular weight was 20000, and the acid value was 46 equivalents.

[0141] Production Example 7 Preparation of polyethersulfone resin aqueous dispersion (3) 60 parts of polyethersulfone resin [PES] having a number average molecular weight of about 24000 and 60 parts of deionized water were stirred in a ceramic ball mill for about 10 minutes until the particles made of PES were completely pulverized. Then, 180 parts of NDPA were added, and the mixture was further pulverized for 48 hours to obtain a dispersion. The obtained dispersion was further pulverized in a sand mill for 1 hour to obtain a PES aqueous dispersion with a PES concentration of about 20% (average particle size 2 μm).

[0142] Production Example 8 Preparation of Water-Soluble Polyamideimide Resin Solution (4) 111.1 parts of polyamideimide resin [PAI] with a number average molecular weight of 20000 and an acid value of 80mg (KOH) per gram, 156.36 parts of N-formylmorpholine, 17.37 parts of furfuryl alcohol, 44.92 parts of diethanolamine, 3.57 parts of ammonia water (28%), and 333.33 parts of ion-exchanged water were stirred to dissolve the PAI, obtaining a water-soluble PAI solution. The concentration of PAI in the water-soluble PAI solution was 15%, the viscosity at 25℃ was 1600mPa s, the number average molecular weight was 19000, and the acid value was 44 equivalents.

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

[0144] Production Example 10 Preparation of polyethersulfone resin aqueous dispersion (4) 60 parts of polyethersulfone resin [PES] having a number average molecular weight of about 24000 and 60 parts of deionized water were stirred in a ceramic ball mill for about 10 minutes until the particles made of PES were completely pulverized. Then, 180 parts of N-formylmorpholine was added, and the mixture was further pulverized for 48 hours to obtain a dispersion. The obtained dispersion was further pulverized in a sand mill for 1 hour to obtain a PES aqueous dispersion with a PES concentration of about 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 relative to PTFE as a dispersant) and an aqueous dispersion of tetrafluoroethylene-hexafluoropropylene copolymer (hereinafter referred to as FEP). (average particle size 0.20 μm, solids content 60%, containing 5% polyether-based nonionic surfactant as a dispersant relative to FEP) was added so that FEP was 50% of PTFE in terms of solids mass ratio, and PES and PAI were 25% of the total solids content of PES, PAI, PTFE and FEP, and a polyether-based nonionic surfactant was added at 6% relative to the PTFE solids content as a dispersion stabilizer to obtain an aqueous dispersion (undercoat coating composition) with a polymer solids content of 30% and a viscosity of 190 mPa s at 25°C.

[0146] Examples 2 to 17 The amount of each component was adjusted so as to obtain the coating composition shown in Tables 1 and 2 (mass composition ratio of resin solid content), and an undercoat coating composition was obtained in the same manner as in Example 1.

[0147] Example 18 An undercoat 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 An undercoat coating composition 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 The amounts of each component were adjusted so as to obtain the coating compositions shown in Tables 3 and 4 (mass composition ratios of resin solids), and an undercoat coating composition was obtained in the same manner as in Example 1.

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

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

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

[0153] (Preparation of coated panels for evaluation) The surface of an aluminum plate (A-1050) having a thickness of 2.0 mm and a size of 5×10 cm was degreased with acetone, and then sandblasted and roughened so that the surface roughness Ra value measured according to JIS B 1982 was 2.5 to 3.5 μm. After removing dust from the surface with an air blower, the obtained coating composition was sprayed as an undercoat paint using a gravity type spray gun W-101 type (trade name, manufactured by Anest Iwata Corporation, nozzle diameter 1.0 mm) at a spray pressure of 0.2 MPa so that the dry film thickness was 10 to 15 μm. The obtained 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 paint (product name: Neoflon PFA ACX34 manufactured by Daikin Industries, Ltd.) was electrostatically applied as a topcoat paint under conditions of an applied voltage of 40 KV and a pressure of 0.08 MPa, and then baked at 380°C for 20 minutes to produce a topcoat coating film with a thickness of approximately 40 μm, and a coated panel for evaluation was obtained.

[0154] The resulting coating composition and the coated plate for evaluation were subjected to the following evaluations.

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

[0156] (Water vapor resistance) The obtained coated plate for evaluation was placed in steam 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 the time of reheating after 100 hours was counted as one cycle. A plate that did not experience blistering for 5 cycles or more was deemed to have passed the test.

[0157] (Corrosion resistance) The obtained coated plates for evaluation were immersed in salt water (5.0 mass%) at 98°C and visually inspected every 50 hours to see if any blisters had occurred in the coating. If no blisters had occurred for 250 hours or more, the plate was deemed to have passed the test.

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

[0159] [Table 1]

[0160] [Table 2]

[0161] [Table 3]

[0162] [Table 4]

[0163] [Table 5]

[0164] [Table 6] [Industrial Applicability]

[0165] The coating composition of the present disclosure is less prone to cissing or uneven coating and has excellent coatability, and can therefore be widely used in the manufacture of various coated articles. The coated article of the present disclosure is formed by coating the above-mentioned coating composition, and therefore has no coating unevenness, 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, and the melt flow rate (MFR) of the perfluoropolymer (T) is 2 to 50 g / 10 min.

2. The coating composition according to claim 1, wherein the aqueous dispersion contains particles made of the polyethersulfone resin (Q) and particles made of the fluorine-containing polymer (R), and 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.

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

4. 4. The coating composition according to claim 3, wherein the melt flow rate (MFR) of the tetrafluoroethylene / hexafluoropropylene copolymer is 2 to 50 g / 10 min.

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

6. 6. The coating composition according to claim 5, wherein the melt flow rate (MFR) of the tetrafluoroethylene / perfluoro(alkyl vinyl ether) copolymer is 2 to 50 g / 10 min.

7. The coating composition according to claim 1 or 2, 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 is 10 to 100 mg (KOH) equivalent.

8. 3. The coating composition according to claim 1, 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 claim 1 or 2, 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-processable fluorine-containing polymer (S) and the perfluoropolymer (T) is 15 / 85 to 40 / 60.

10. The coating composition according to claim 1 or 2, 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 30 / 70.

11. The coating composition according to claim 1 or 2, wherein the viscosity of the water-soluble polyamideimide resin (P) measured in a 15% solution at 25° C. is 1,000 to 10,000 mPa·s.

12. 3. The coating composition according to claim 1, wherein the viscosity at 25° C. is 50 to 1,000 mPa·s.

13. The coating composition according to claim 1 or 2, 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 total of the carboxyl groups and the carboxyl groups resulting from ring-opening of the imide bonds of 30 to 60 mg (KOH) equivalents, and a viscosity of 1,200 to 8,000 mPa·s at 25°C measured in a 15% solution.

14. 3. The coating composition according to claim 1 or 2, 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.

15. A coated article comprising an object to be coated and a layer formed from the coating composition according to claim 1 or 2.

16. 3. A coated article comprising an object to be coated, a primer layer formed from the coating composition according to claim 1 or 2, and a fluorine-containing layer comprising a fluorine-containing topcoat polymer.

17. 3. 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 claim 1 or 2, and a fluorine-containing layer containing a fluorine-containing topcoat polymer.

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