Powdery composition, coating film, multilayer object, coated article, and molding method

Abstract

Provided is a primer for use in forming fluororesin coating films by rotational molding, the primer being capable of forming coating films by rotational molding. This powdery composition comprises a meltable fluororesin powder having an average particle diameter of 100-1,000 μm and a binder resin powder.

Description

Powder composition, coating, laminate, coated article and molding method

[0001] The present disclosure relates to powder compositions, coatings, laminates, coated articles, and molding methods.

[0002] Methods for processing powder compositions containing fluororesin by rotational molding are known (Patent Documents 1 to 4). In these methods, in order to improve adhesion between the substrate and the coating film, it is necessary to apply a primer. Such primer application often uses a liquid primer composition (Patent Documents 1 to 3). Furthermore, the use of powder primers is also known, but such powder primer application has generally been carried out by electrostatic coating (Patent Document 4).

[0003] JP 2010-43283 JP 2005-335185 JP 2008-45140 JP 2022-137848

[0004] The present disclosure aims to provide a primer for use in processing a fluororesin coating by rotational molding, which allows the coating to be processed by rotational molding.

[0005] The present disclosure relates to a powder composition comprising a melt processable fluororesin powder and a binder resin powder, the average particle size of which is 100 to 1000 μm. The present disclosure also relates to a powder composition comprising a melt processable fluororesin powder and a binder resin powder, the powder composition being characterized in that the average particle size of the entire powder composition is 100 to 1000 μm.

[0006] The melt processable fluororesin may be a perfluoropolymer. The melt processable fluororesin may be a tetrafluoroethylene / perfluoro(alkyl vinyl ether) copolymer. The melt processable fluororesin may be a non-perfluoropolymer. The melt processable fluororesin may be an ethylene / tetrafluoroethylene copolymer.

[0007] The binder resin preferably contains at least one selected from the group consisting of polyamideimide, polyphenylene sulfide, polyethersulfone, aromatic polyetherketones, and polyetherimide. The binder resin powder preferably has an average particle size of 100 to 3000 μm. The mass ratio of the melt processable fluororesin powder to the binder resin powder is preferably 50:50 to 95:5. It is preferred that the melt processable fluororesin powder has an average particle size of 200 to 600 μm, the melt processable fluororesin has a melt flow rate of 10 to 30 g / 10 min, the melt processable fluororesin is a tetrafluoroethylene / perfluoro(alkyl vinyl ether) copolymer or an ethylene / tetrafluoroethylene copolymer, the binder resin powder has an average particle size of 100 to 3000 μm, the binder resin comprises at least one resin selected from the group consisting of polyamideimide, polyphenylene sulfide, polyethersulfone, aromatic polyether ketone resin, and polyetherimide, the content of the melt processable fluororesin powder is 50 to 90 mass% relative to the total amount of the melt processable fluororesin powder and the binder resin powder, and the total content of the melt processable fluororesin powder and the binder resin powder is 98 to 100 mass% relative to the total amount of the powdery composition.

[0008] The powder composition is preferably a primer composition. The present disclosure also relates to a coating formed from the powder composition. The present disclosure also relates to a laminate having a coating containing a melt processable fluororesin provided on the coating. The present disclosure also relates to a coated article having the laminate provided on a metal substrate.

[0009] The present disclosure also relates to a molding method comprising: a step (1) of processing the powder composition by rotational molding; and a step (2) of processing a top coat, which is a powder composition containing a melt processable fluororesin, on the coating formed by the step (1) by rotational molding.

[0010] The composition of the present disclosure is a powder composition that can be processed by rotational molding, and can therefore be used as a primer for fluororesin powder coatings, and has excellent adhesion.

[0011] The present disclosure will be described in detail below. The powdery composition of the present disclosure relates to a powdery composition that can be suitably used as a primer when processing a powdery composition containing a fluorine-containing resin by rotational molding.

[0012] When processing primers using the conventional methods described above, there are issues with foaming and poor adhesion when processing the topcoat layer using rotational molding. Processing clear types, in particular, that do not contain heat stabilizers or fillers to suppress shrinkage can be extremely time-consuming and require repair of foamed areas, resulting in extremely low yields. While this problem can be solved by adding heat stabilizers to the topcoat, as described above, this can also lead to practical issues such as reduced coating life due to mechanical strength and leaching issues.

[0013] On the other hand, if the primer could also be processed by rotational molding, the primer and top coat molding processes could be performed on the same equipment. Also, if sufficient performance could be achieved without adding a heat stabilizer to the top coat, the practical issues mentioned above could be overcome by using a clear powder paint.

[0014] The powder composition of the present disclosure has been perfected from the above-mentioned viewpoints and can be suitably used as a primer that can be processed by rotational molding. The use of such a powder composition can solve the above-mentioned problem of achieving both foam suppression and adhesive strength. Furthermore, the powder composition of the present disclosure has the advantage of being able to form a sufficiently smooth coating.

[0015] (First Present Disclosure) The first present disclosure is a powder composition comprising a melt processable fluororesin powder having an average particle size of 100 to 1000 μm and a binder resin powder. That is, a melt processable fluororesin powder having a relatively large average particle size is used in combination with a binder resin powder. This makes it possible to achieve the above-mentioned object. When the average particle size of the melt processable fluororesin powder is 100 μm or more, foaming can be sufficiently suppressed. Furthermore, when the average particle size of the melt processable fluororesin powder is 100 μm or more, the flowability of the powder composition tends to be improved. On the other hand, when the average particle size of the melt processable fluororesin powder is 1000 μm or less, a sufficiently smooth coating can be formed.

[0016] The lower limit of the average particle size is more preferably 150 μm, and even more preferably 200 μm, and the upper limit of the average particle size is more preferably 800 μm, and even more preferably 600 μm.

[0017] The average particle size of the melt processible fluororesin powder here is a value measured using particle analysis software from an image of the powder composition observed under an electron microscope. An example of particle analysis software is MultiImageTool from SIF. By using this method and the element identification function of the device, it is also possible to measure the average particle size of only the melt processible fluororesin powder from a powder composition containing a melt processible fluororesin powder and a binder resin powder.

[0018] (Second Disclosure) The second disclosure relates to a powder composition comprising a melt processable fluororesin powder and a binder resin powder, wherein the average particle size of the entire powder composition is 100 to 1000 μm. That is, the powder composition has a relatively large average particle size of the entire powder composition, and the average particle size here refers to the average particle size of the melt processable fluororesin powder and the binder resin powder as a whole. When the average particle size of the entire powder composition is 100 μm or more, foaming can be sufficiently suppressed. Furthermore, when the average particle size of the entire powder composition is 100 μm or more, the flowability of the powder composition tends to be improved. On the other hand, when the average particle size of the entire powder composition is 1000 μm or less, a sufficiently smooth coating can be formed.

[0019] The lower limit of the average particle size is more preferably 150 μm, and even more preferably 200 μm, and the upper limit of the average particle size is more preferably 900 μm, and even more preferably 800 μm.

[0020] The average particle size of the powder composition in the second present disclosure is measured by image analysis particle size measurement.

[0021] The powder composition of the present disclosure is of these two types, but in either case, the effect when used as a primer is similar, and the elements other than the average particle size are substantially identical, so they will be described below without distinguishing between them.

[0022] (Melt processible fluororesin powder) The melt processible fluororesin used in the present disclosure may be obtained by polymerizing, as a monomer component, one or more of the following: a chlorofluorovinyl monomer such as chlorotrifluoroethylene; a fluorovinyl monomer such as vinylidene fluoride or trifluoroethylene; or a perfluoromonomer such as tetrafluoroethylene, hexafluoropropylene, or perfluoro(alkyl vinyl ether). The monomer component may further contain one or more vinyl monomers such as ethylene or propylene. The perfluoromonomer has a main chain composed of carbon atoms, fluorine atoms, and optionally oxygen atoms, and is preferably CH or CH. ２ and includes perfluorovinyl monomers and perfluoro(alkyl vinyl ether) monomers. The oxygen atom is usually an ether oxygen.

[0023] The melt processible fluororesin may also use a monomer having a functional group such as a hydroxyl group or a carbonyl group, or a monomer having a cyclic structure, as a comonomer to be copolymerized in small amounts with the monomer component. Examples of the cyclic structure include those having a cyclic ether structure such as a cyclic acetal structure, and preferably at least two carbon atoms constituting the cyclic ether structure form part of the main chain of the melt processible fluororesin.

[0024] Examples of the above-mentioned melt processable fluororesin include alkylene / fluoroalkylene copolymers such as ethylene / tetrafluoroethylene copolymer (ETFE), ethylene / chlorotrifluoroethylene copolymer (ECTFE), and propylene / tetrafluoroethylene copolymer; and perfluoropolymers such as tetrafluoroethylene / hexafluoropropylene copolymer (FEP), tetrafluoroethylene / perfluoro(alkyl vinyl ether) copolymer (PFA).The above-mentioned perfluoropolymers contain the above-mentioned perfluoromonomer as a monomer component.

[0025] The melt processible fluororesin varies depending on the application, but in the case of the perfluoropolymer, it is more preferable to use one copolymerized with tetrafluoroethylene, and the above perfluoromonomers can be used as other comonomers. Among these copolymers, FEP or PFA are particularly suitable from the viewpoint of protecting the substrate due to their advantages such as high heat resistance and chemical resistance.

[0026] The melt processable fluororesin may be a non-perfluoropolymer. When the non-perfluoropolymer is used, it is particularly preferably ETFE.

[0027] The melt processible fluororesin must be melt-soluble, so that it can be melted and processed by baking, as described below.

[0028] The meltability of the melt processible fluororesin is generally expressed as MFR, which is an index of flowability. MFR is expressed as the weight extruded from a nozzle with a diameter of 2 mm under a load of 5 kg in 10 minutes according to ASTM D3159. MFR is measured at 372°C when the melt processible fluororesin is a perfluoropolymer such as PFA or FEP, and at 297°C when it is ETFE.

[0029] The melt processable fluororesin preferably has an MFR of 0.1 to 50 g / 10 min. If the melt flow rate is within this range, the adhesion between the resulting primer coating and the melt processable perfluoropolymer coating is further improved due to the flow characteristics of the melt processable fluororesin.

[0030] In particular, the MFR of the perfluoropolymer is preferably 1 to 40 g / 10 min. A more preferred lower limit is 5 g / 10 min, and an even more preferred lower limit is 10 g / 10 min. A more preferred upper limit is 30 g / 10 min. Within the above melt flow rate range, it is possible to achieve both interlayer adhesion and corrosion resistance.

[0031] The melt processible fluororesin can be made to have a melt flow rate within the above range by adjusting the molecular weight as described above.

[0032] In the first present disclosure, the melt processible fluororesin powder has an average particle size of 100 to 1000 μm. Having an average particle size within this range is preferable in that good processability can be obtained during rotational molding. A preferred lower limit of the average particle size is 100 μm, a more preferred lower limit is 150 μm, and an even more preferred lower limit is 200 μm. A preferred upper limit is 600 μm. In the second present disclosure as well, the melt processible fluororesin powder preferably has an average particle size within the above-mentioned range.

[0033] The method for producing the melt processible fluororesin powder is not particularly limited, and for example, it can be obtained by copolymerization using a conventionally known polymerization method such as emulsion polymerization. The melt processible fluororesin obtained by copolymerization is pulverized as necessary to obtain a melt processible fluororesin powder having an average particle size within the above-mentioned range. The pulverization method is not particularly limited, and for example, a conventionally known method can be used. For example, there is a method in which the melt processible fluororesin dry powder obtained by the above-mentioned emulsion polymerization method is compressed into a sheet using a roll, pulverized using a pulverizer, and classified.

[0034] The binder resin powder can be made of a resin that has melting properties, has a higher affinity with metal substrates than fluororesins, contributes to adhesion to metal substrates, and has heat resistance that can withstand the processing temperatures of fluororesins.

[0035] The resin that can be used as such a binder resin powder is preferably at least one type (e.g., 1 to 5 types) selected from the group consisting of polyamideimide, polyphenylene sulfide, polyethersulfone, aromatic polyetherketones (aromatic polyetherketones), and polyetherimide. These resins are preferred because they have high heat resistance and excellent physical properties. While the melt processable fluororesin that can be used for the melt processable fluororesin powder is a fluororesin, the binder resin that can be used for the binder resin powder may be, for example, a non-fluororesin.

[0036] The binder resin powder preferably has an average particle size of 20 to 3000 μm. Using such a binder resin powder is preferable in that it can achieve both good coating film formation and adhesion to the metal substrate by rotational molding. The preferred lower limit of the average particle size is 100 μm, more preferably 150 μm, and even more preferably 200 μm. The preferred upper limit is 2000 μm.

[0037] The polyamideimide (PAI) is a resin made of a polymer having an amide bond and an imide bond in its molecular structure. The PAI is not particularly limited, and examples thereof include a resin made of a high molecular weight polymer obtained by a reaction between an aromatic diamine having an amide bond in the molecule and an aromatic tetracarboxylic acid such as pyromellitic acid; a reaction between an aromatic tricarboxylic acid such as trimellitic anhydride and a diamine such as 4,4-diaminophenyl ether or a diisocyanate such as diphenylmethane diisocyanate; or a reaction between a dibasic acid having an aromatic imide ring in the molecule and a diamine. From the viewpoint of excellent heat resistance, the PAI is preferably made of a polymer having an aromatic ring in the main chain.

[0038] Examples of the polyphenylene sulfide resin include those having a repeating unit represented by the following formula: -(Ar-S)- (wherein Ar represents an arylene group and S represents sulfur). Examples of the arylene group include p-phenylene, m-phenylene, o-phenylene, alkyl-substituted phenylene, phenyl-substituted phenylene, halogen-substituted phenylene, amino-substituted phenylene, amido-substituted phenylene, p,p'-diphenylene sulfone, p,p'-biphenylene, and p,p'-biphenylene ether. The polyphenylene sulfide resin preferably has a p-phenylene content of 70 mol% or more as the arylene group of the repeating unit in the resin. Furthermore, polyphenylene sulfide resins can be broadly classified into resins having a crosslinked or branched structure (crosslinked type) and resins having substantially no crosslinked or branched structure (linear type). In the present disclosure, either the crosslinked type or the linear type may be used.

[0039] The MFR (melt flow rate) of the polyphenylene sulfide resin is preferably 10 to 2500 g / 10 min, more preferably 400 to 1800 g / 10 min. By using a resin in this range, the resin's physical properties can be maintained while achieving resin fluidity. The MFR is a value that indicates the amount of resin extruded from the bottom opening of a cylindrical extrusion plastometer within a certain period of time when the resin is heated and pressurized at a constant temperature and pressure, and is a known parameter that serves as an indicator of resin fluidity. Specifically, the MFR is a value measured in accordance with the measurement method described in ISO 1133 (ASTM D1238-86) (316°C, 5 kg load).

[0040] If the MFR is less than 10 g / 10 min, the flowability during processing is poor, and processing conditions tend to be more restricted.If the MFR is more than 2,500 g / 10 min, the molecular weight of the resin is relatively low, and this tends to result in a deterioration in the quality of the molded product, such as a deterioration in mechanical properties.

[0041] Generally, by adjusting the molecular weight to a high molecular weight region, a polyphenylene sulfide resin having a desired MFR can be obtained.

[0042] As the polyphenylene sulfide resin having the above-mentioned physical properties, commercially available products can be used, such as DIC PPS (trade name), Toray Torelina (trade name), Solvay Ryton (trade name), Tosoh Susteal (trade name), Celanese® PPS (trade name), and NHU-PPS (trade name).

[0043] The polyethersulfone resin (PES) has the following general formula:

[0044]

[0045] The PES is not particularly limited, and examples thereof include resins made of polymers obtained by polycondensation of dichlorodiphenyl sulfone and bisphenol.

[0046] The aromatic polyether ketone resin is not particularly limited as long as it contains a repeating unit composed of an arylene group, an ether group [—O—], and a carbonyl group [—C(═O)—], and may contain, for example, a repeating unit represented by any of the following formulas (a1) to (a5): [—Ar—O—Ar—C(═O)—] (a1) [—Ar—O—Ar—C(═O)—Ar—C(═O)—] (a2) [—Ar—O—Ar—O—Ar—C(═O)—] (a3) ​​[—Ar—O—Ar—C(═O)—Ar—O—Ar—C(═O)—Ar—C(═O)—] (a4) [—Ar—O—Ar—O—Ar—C(═O)—Ar—C(═O)—] (a5) (wherein Ar represents a divalent aromatic hydrocarbon ring group which may have a substituent). Examples of the divalent aromatic hydrocarbon ring group represented by Ar include arylene groups having 6 to 10 carbon atoms, such as a phenylene group (e.g., an o-, m-, or p-phenylene group) and a naphthylene group; biarylene groups (each arylene group having 6 to 10 carbon atoms), such as a biphenylene group (e.g., a 2,2'-biphenylene group, a 3,3'-biphenylene group, or a 4,4'-biphenylene group); and terarylene groups (each arylene group having 6 to 10 carbon atoms), such as an o-, m-, or p-terphenylene group. These aromatic hydrocarbon ring groups may have a substituent such as a halogen atom, an alkyl group (e.g., a linear or branched alkyl group having 1 to 4 carbon atoms, such as a methyl group), a haloalkyl group, a hydroxyl group, an alkoxy group (e.g., a linear or branched alkoxy group having 1 to 4 carbon atoms, such as a methoxy group), a mercapto group, an alkylthio group, a carboxyl group, a sulfo group, an amino group, an N-substituted amino group, or a cyano group. In the repeating units (a1) to (a5), the types of Ar may be the same or different. Preferred examples of Ar include phenylene groups (e.g., p-phenylene groups) and biphenylene groups (e.g., 4,4'-biphenylene groups).

[0047] Examples of resins having the repeating unit (a1) include polyether ketone (e.g., "PEEK-HT" manufactured by Victrex), and examples of resins having the repeating unit (a2) include polyether ketone ketone (e.g., "PEKK" manufactured by Arkema+Oxford Performance Material). Examples of resins having the repeating unit (a3) ​​include polyether ether ketone (for example, "VICTREX PEEK" manufactured by Victrex, "Vestakeep (registered trademark)" manufactured by Evonik, "Vestakeep-J" manufactured by Daicel-Evonik, and "KetaSpire (registered trademark)" manufactured by Solvay Specialty Polymers), and polyether-diphenyl-ether-phenyl-ketone-phenyl (for example, "Kadel (registered trademark)" manufactured by Solvay Specialty Polymers). Examples of resins having the repeating unit (a4) include polyether ketone ether ketone ketone (for example, "VICTREX ST" manufactured by Victrex). Examples of resins having the repeating unit (a5) include polyether ether ketone ketone. In the repeating unit composed of an arylene group, an ether group, and a carbonyl group, the ratio of the ether segment (E) to the ketone segment (K) is, for example, E / K=0.5 to 3, and preferably about 0.5 to 2.0. The ether segment imparts flexibility to the molecular chain, and the ketone segment imparts rigidity to the molecular chain. Therefore, the more ether segments there are, the faster the crystallization rate and the higher the ultimately achievable crystallinity, and the more ketone segments there are, the higher the glass transition temperature and melting point tend to be. These aromatic polyether ketone resins can be used alone or in combination of two or more.

[0048] Among these aromatic polyetherketone resins, aromatic polyetherketone resins having any of the repeating units (a1) to (a4) are preferred. For example, the aromatic polyetherketone resin is preferably at least one resin (e.g., 1 to 4 types) selected from the group consisting of polyetherketone, polyetheretherketone, polyetherketoneketone, and polyetherketoneetherketoneketone. Furthermore, it is more preferably at least one resin (e.g., 1 to 3 types) selected from the group consisting of polyetherketone, polyetheretherketone, and polyetherketoneketone. In particular, polyetherketoneketone is preferred because it improves thin-wall processability and increases tensile elongation.

[0049] The aromatic polyether ketone resin preferably has a melting point of 300°C or higher. More preferably, it is 320°C or higher. A melting point within the above range can improve the heat resistance of the resulting molded article. Furthermore, the melting point is preferably 380°C or lower. When an aromatic polyether ketone resin having a melting point higher than this is kneaded, the fluorocopolymer may be severely thermally deteriorated during kneading, and the physical properties may not be maintained. The melting point is the temperature corresponding to the maximum value in the heat of fusion curve when the temperature is increased at a rate of 10°C / min using a differential scanning calorimetry (DSC) device.

[0050] The aromatic polyether ketone resin preferably has a melt flow rate (MFR) measured under conditions of 380°C and a load of 5,000 g of 1 to 150 g / 10 min, more preferably 5 to 130 g / 10 min, and even more preferably 10 to 100 g / 10 min. Having an MFR within the above range improves thin-wall processability and enables the production of an insulating layer (B) with a high tensile elongation. The MFR of the aromatic polyether ketone resin is measured using a melt indexer in accordance with ASTM D1238.

[0051] The aromatic polyether ketone resin preferably has a glass transition temperature of 130°C or higher, more preferably 135°C or higher, and even more preferably 140°C or higher. A glass transition temperature within the above range enables an insulated electric wire with excellent heat resistance to be obtained. The upper limit of the glass transition temperature is not particularly limited, but from the viewpoint of moldability, it is preferably 220°C or lower, and more preferably 180°C or lower. The glass transition temperature is measured in accordance with JIS K7121 using a differential scanning calorimetry (DSC) device under measurement conditions consisting of a heating rate of 20°C / min.

[0052] (Polyetherimide Resin) Polyetheretherimide resin is a resin represented by the following general formula:

[0053]

[0054] The resin is a polymer having a repeating unit represented by the formula: As such a resin, commercially available resins can be used.

[0055] In the powder composition of the present disclosure, the binder resin may be used alone or in combination of two or more. The upper limit of the number of types of binder resins is not particularly limited, but may be, for example, 10 types.

[0056] The binder resin is used in a powder state, and the method for producing the binder resin powder is not particularly limited, and it can be obtained by a known method.

[0057] The binder resin powder preferably has an average particle size of 100 to 3000 μm. A particle size within this range is preferable in that it can be suitably applied to rotational molding. The lower limit of the average particle size is more preferably 150 μm, and even more preferably 200 μm. The upper limit of the average particle size is more preferably 2500 μm, and even more preferably 2000 μm.

[0058] In the powder composition of the present disclosure, the mass ratio of the melt processable fluororesin powder to the binder resin powder is preferably 50:50 to 95:5. That is, the powder composition of the present disclosure preferably contains 50 to 95 mass% of the melt processable fluororesin powder relative to the total amount of the melt processable fluororesin powder and the binder resin powder. Amounts within the above range are preferable in that they can achieve both adhesion between the substrate and the primer layer and adhesion between the top coat layer and the primer layer. The lower limit of the content of the melt processable fluororesin powder is more preferably 60 mass%, and even more preferably 70 mass%. The upper limit of the content of the melt processable fluororesin powder is more preferably 90 mass%, and even more preferably 80 mass%.

[0059] The powder composition of the present disclosure may contain components other than the melt processable fluororesin powder and binder resin powder, as needed, to the extent that the effects of the present disclosure are not impaired. Examples of such other components include color pigments, antioxidants, heat stabilizers, fillers, leveling agents, etc. These other components may be contained in the melt processable fluororesin powder and binder resin powder.

[0060] When components other than the melt processible fluororesin and binder resin are used, the content thereof is preferably 5% by mass or less, more preferably 3% by mass or less, and even more preferably 2% by mass or less, based on the total amount of the powder composition.

[0061] The total content of the melt processable fluororesin powder and the binder resin powder is preferably 95% by mass or more and 100% by mass or less, based on the total amount of the powder composition. The total content is more preferably 97% by mass or more, and even more preferably 98% by mass or more. The total content may be less than 100% by mass or may be 99.9% by mass or less.

[0062] (Primer composition) The powder composition of the present disclosure is preferably used as a primer composition. That is, it is preferable that after the powder composition of the present disclosure is applied to a substrate, a top coat (a composition for forming a top coat film) is further applied thereto.

[0063] When the powder composition of the present disclosure is used as a binder composition, the substrate is not particularly limited and examples thereof include simple metals such as iron, aluminum, copper, and nickel, and alloys thereof. Examples of the alloys include metals such as stainless steel (SUS), and non-metallic inorganic materials such as enamel, glass, and ceramics.

[0064] When the powder composition of the present disclosure is used as a primer composition, the top coat is not particularly limited, but is preferably a powder coating containing a fluororesin.

[0065] The fluororesin contained in the top coat is not particularly limited, and any of the melt-soluble fluororesins exemplified as the fluororesin in the powder composition of the present disclosure can be used.

[0066] The average particle size of the fluororesin contained in the top coat is preferably 100 to 1000 μm, and the lower limit of the average particle size is more preferably 100 μm, even more preferably 150 μm, and even more preferably 200 μm. The upper limit of the average particle size is more preferably 800 μm, and even more preferably 600 μm.

[0067] The MFR of the fluororesin contained in the top coat is preferably 1 to 40 g / 10 min. The lower limit is more preferably 5 g / 10 min, and even more preferably 10 g / 10 min. The upper limit is more preferably 30 g / 10 min.

[0068] When using the above-mentioned primer composition and top coat to process a multi-layer film, the fluororesin contained in these two compositions is preferably the same.That is, when used as a primer for a top coat containing ETFE, the powder composition of the present disclosure preferably contains ETFE.When used as a primer for a top coat containing PFA, the powder composition of the present disclosure preferably contains PFA.

[0069] It is preferable that the top coat is substantially free of heat stabilizers. Conventionally, top coats used in rotational molding processes have been made to contain heat stabilizers to suppress foaming. When the powder composition of the present disclosure is used as a primer, problems such as foaming are unlikely to occur, so even if the top coat does not contain a heat stabilizer, it is preferable in that it does not cause the conventional problems.

[0070] If the top coat contains a heat stabilizer, the heat stabilizer may discolor the coating or leach out the heat stabilizer components. Therefore, using a top coat that is substantially free of heat stabilizers has the advantage of preventing such problems.

[0071] The heat stabilizer herein refers to a heat stabilizer commonly used in the coating field, specifically, for example, an amine-based antioxidant, an organic sulfur-containing compound, a metal powder, etc. In the present disclosure, "substantially" not containing a heat stabilizer means that the amount of the heat stabilizer is 0.001 mass % or less relative to the total amount of the top coat.

[0072] It is preferable that the top coat is substantially free of pigment. Conventionally, top coats used in rotational molding processes have been made to contain pigment to adjust the film color tone derived from the heat stabilizer. When the powder composition of the present disclosure is used as a primer, problems such as foaming are unlikely to occur, and therefore the top coat is preferable in that it does not require the inclusion of pigment as well as pigment heat stabilizer.

[0073] If the top coat contains a pigment, the pigment component may leach out, so the use of a top coat that is substantially free of pigments has the advantage of preventing such problems.

[0074] The term "pigment" used herein refers to pigments commonly used in the field of paints, specifically, for example, carbon black, titanium oxide, etc. In the present disclosure, "substantially" not containing a pigment means that the amount of the pigment is 0.001% by mass or less relative to the total amount of the top coat.

[0075] The content of components other than the fluororesin in the top coat is preferably 0.1% by mass or less. When the top coat contains a fluororesin, the content of the fluororesin is preferably 99.9% by mass or more and 100.0% by mass or less, based on the total amount of the top coat. The lower limit is more preferably 99.99% by mass, and even more preferably 99.999% by mass.

[0076] (Molding method) The molding method of the present disclosure is characterized by comprising: a step (1) of processing the above-described powder composition by rotational molding; and a step (2) of processing, by rotational molding, a top coat that is a powder composition containing a melt processable fluororesin on the coating processed in the step (1).

[0077] That is, after processing by rotational molding using the powder composition of the present disclosure in step (1), in step (2) the powder composition as a top coat containing a melt processable fluororesin is processed by rotational molding, thereby making it possible to form a top coat film with sufficient adhesive strength without problems such as foaming.

[0078] In the molding method of the present disclosure, the substrate to be processed is not particularly limited, but it must have a tubular shape, because rotational molding is a processing method in which a resin film is formed inside a tubular substrate while the tubular substrate is rotated.

[0079] The substrate is not particularly limited, and examples thereof include tanks, pipes, joints, valves, and the like.

[0080] In the above step (1), the powder composition of the present disclosure is processed by rotational molding to form a primer coating on a substrate. Specifically, step (1) is a step in which the powder composition is placed in a tube and heated while rotating the tube to form a coating. In this step, the processing temperature is preferably 250 to 400°C. By maintaining the temperature within this range, good processing can be achieved.

[0081] The coating formed in step (1) preferably has a thickness of 100 to 10,000 μm. By achieving a thickness within this range, good physical properties can be obtained. The thickness is measured using a magnetic / eddy current film thickness meter. The lower limit of the thickness is more preferably 300 μm, and even more preferably 500 μm. The upper limit of the thickness is more preferably 8,000 μm, and even more preferably 6,000 μm.

[0082] In the above step (2), the top coat is rotationally molded to form a top coat film on the primer film. Specifically, step (2) is a step in which the top coat, which is a powder composition, is placed in a tube and heated while rotating the tube to form a film on the substrate on which the film was formed in step (1). This step allows the top coat film to be formed. In step (2), the processing temperature is preferably 250 to 400°C. By maintaining the temperature within this range, good processing can be achieved.

[0083] The coating formed in step (2) preferably has a thickness of 100 to 10,000 μm. By achieving a thickness within this range, good physical properties can be obtained. The thickness is measured using an electromagnetic / eddy current film thickness meter. The lower limit of the thickness is more preferably 300 μm, and even more preferably 500 μm. The upper limit of the thickness is more preferably 8,000 μm, and even more preferably 6,000 μm.

[0084] The molding method of the present disclosure can be suitably applied in the fields of chemicals, medicines, pharmaceuticals, food, semiconductors, etc.

[0085] (Coating) The present disclosure also relates to a coating. The coating of the present disclosure is formed from the powder composition of the present disclosure described above. The coating of the present disclosure can be produced, for example, by performing the above-mentioned step (1).

[0086] (Laminate) The present disclosure also relates to a laminate. The laminate of the present disclosure has a coating containing a melt processable fluororesin provided on the coating of the present disclosure described above. The coating containing a melt processable fluororesin can be produced, for example, by using a powder coating containing a melt processable fluororesin as a top coat and performing the above step (2).

[0087] (Coated Article) The present disclosure also relates to a coated article. The coated article of the present disclosure comprises a metal substrate on which the laminate of the present disclosure is provided. The metal substrate is not particularly limited, and examples thereof include metal tanks, metal piping, metal joints, and metal valves. The coated article of the present disclosure is not particularly limited in its application, and can be used in fields such as chemicals, medicines, pharmaceuticals, food, and semiconductors.

[0088] The present disclosure will be specifically described below based on examples. In the following examples, unless otherwise specified, "parts" and "%" represent "parts by mass" and "% by mass", respectively.

[0089] The components used in the following examples are as follows: Fluorine-containing copolymer A: PFA: PFA (MFR 15 g / 10 min) manufactured by Daikin Industries, Ltd. Fluorine-containing copolymer B: ETFE: ETFE (MFR 28 g / 10 min) manufactured by Daikin Industries, Ltd. Binder resin A: PAI: Torlon PAI manufactured by Solvay Binder resin B: PPS: Ryton PPS manufactured by Solvay Binder resin C: PES: Sumikaexcel PES manufactured by Sumitomo Chemical Co., Ltd. Binder resin D: PEEK: KetaSpire PEEK manufactured by Solvay Binder resin E: PEI: ULTEM PEI manufactured by Sabic Heat stabilizer A: Nocrac White manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Heat stabilizer B: Noccela MZ manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Heat stabilizer C: Copper oxide II powder manufactured by Kanto Chemical Co., Ltd.

[0090] (Preparation of powdery composition containing melt processible fluororesin) A polymerized raw powder of melt processible fluororesin was compacted using a roller compactor manufactured by Freund Turbo Corporation and pulverized using an ACM pulverizer manufactured by Hosokawa Micron Corporation to obtain a powder of the melt processible fluororesin.

[0091] (Preparation of Powdery Composition Containing Binder Resin) A binder resin raw material (pellet or flake form) was pulverized in an atomizer-type pulverizer to obtain a powder.

[0092] (Preparation of Powder Composition) The pulverized particles were mixed using an FM mixer manufactured by Nippon Coke Corporation to obtain a powder composition.

[0093] (Molding method) The obtained powder composition was processed by the following method. Alumina powder (Ujiden Chemical Industry Co., Ltd., Tosa Emery #40) was used to blast a stainless steel plate (SUS403, surface roughness Ra: 2-3 μm) at a spray pressure of 1.0 MPa. The powder composition was processed so that the film thickness after firing would be 1000 μm, and the PFA system was fired at 350 ° C. for 60 minutes, and the ETFE system was fired at 300 ° C. for 60 minutes. Then, PFA powder (MFR: 17 g / 10 min, average particle size: 210 μm) or ETFE powder (MFR: 28 / 10 min, average particle size 198 μm) was applied to the obtained coating so that the total film thickness after firing would be 3000 μm, and the coating was fired at 350 ° C. for 60 minutes or 300 ° C. for 60 minutes to obtain a laminate.

[0094] (Evaluation Method) (Average Particle Size) The average particle size was measured from 500 random particles in an image of the powder composition observed under an electron microscope using particle analysis software (MultiImageTool manufactured by SIF Corporation).

[0095] (Angle of repose) The angle of repose was measured as an index of the fluidity of the mixed powder. Approximately 5 g of powder was filled into a conical jig (exit diameter φ20 mm) and the powder was dropped from a height of 40 mm. The angle between the slope of the hill made by the powder and the horizontal plane was measured and used as the angle of repose.

[0096] (Smoothness) Appearance evaluation was carried out using the processed plate used for peel strength measurement. Regarding the surface smoothness after processing, the surface roughness Ra (arithmetic mean roughness) was calculated by averaging the measured values ​​at five measurement points using a surface roughness profiler (Mitutoyo Corporation SJ-210) in accordance with JIS B 0601-1994.

[0097] (Foaming state) Foaming after processing was visually inspected on the coating film after processing and judged on a scale of 1 to 5 according to the degree of foaming: 5: no foaming, 4: foaming 1 point, 3: foaming 2-4 points, 2: foaming 5-9 points, 1: foaming 10 points or more.

[0098] (Peel strength) Alumina powder (Ujiden Chemical Industry Co., Ltd., Tosa Emery #40) was used to blast a stainless steel plate (SUS403, surface roughness Ra: 2-3 μm) at a spray pressure of 1.0 MPa. The powder composition was processed so that the film thickness after firing was 1000 μm, and the PFA system was fired at 350 ° C. for 60 minutes, and the ETFE system was fired at 300 ° C. for 60 minutes. Then, PFA powder (MFR: 17 g / 10 min, average particle size: 210 μm) or ETFE powder (MFR: 28 / 10 min, average particle size 198 μm) was applied to the resulting coating so that the total film thickness after firing was 3000 μm, and the coating was fired at 350 ° C. for 60 minutes or 300 ° C. for 60 minutes to obtain a laminate. After making a 10 mm wide cut in this laminate, the peel strength was measured in a direction 90° to the test piece at a pulling rate of 50 mm / min using a Tensilon universal testing machine in accordance with JIS K 6854-1. The measurement results are shown in Tables 1 to 3.

[0099]

[0100]

[0101]

[0102] The results of the above examples demonstrate that a suitable coating film can be formed by using the powder composition of the present disclosure as a primer.

[0103] The powder composition of the present disclosure can be suitably used as a primer when coating a fluororesin by rotational molding.

Claims

1. A powder composition comprising a melt processable fluororesin powder having an average particle size of 100 to 1000 μm and a binder resin powder.

2. A powder composition comprising a melt processable fluororesin powder and a binder resin powder, characterized in that the average particle size of the entire powder composition is 100 to 1000 μm.

3. The powder composition according to claim 1 or 2, wherein the melt processable fluororesin is a perfluoropolymer.

4. The powder composition according to any one of claims 1 to 3, wherein the melt processible fluororesin is a tetrafluoroethylene / perfluoro(alkyl vinyl ether) copolymer.

5. The powder composition according to claim 1 or 2, wherein the melt processable fluororesin is a non-perfluoropolymer.

6. A powder composition according to claim 1, 2 or 5, wherein the melt processable fluororesin is an ethylene / tetrafluoroethylene copolymer.

7. The powder composition according to any one of claims 1 to 6, wherein the binder resin comprises at least one selected from the group consisting of polyamideimide, polyphenylene sulfide, polyethersulfone, aromatic polyetherketones, and polyetherimide.

8. The powder composition according to any one of claims 1 to 7, wherein the binder resin powder has an average particle size of 100 to 3,000 μm.

9. The powder composition according to any one of claims 1 to 8, wherein the mass ratio of the melt processible fluororesin powder to the binder resin powder is 50:50 to 95:

5.

10. The powder composition according to any one of claims 1 to 9, wherein the average particle size of the melt processable fluororesin powder is 200 to 600 μm, the melt processable fluororesin has a melt flow rate of 10 to 30 g / 10 min, the melt processable fluororesin is a tetrafluoroethylene / perfluoro(alkyl vinyl ether) copolymer or an ethylene / tetrafluoroethylene copolymer, the average particle size of the binder resin powder is 100 to 3000 μm, the binder resin comprises at least one resin selected from the group consisting of polyamideimide, polyphenylene sulfide, polyethersulfone, aromatic polyetherketone, and polyetherimide, the content of the melt processable fluororesin powder is 50 to 90 mass% based on the total amount of the melt processable fluororesin powder and the binder resin powder, and the total content of the melt processable fluororesin powder and the binder resin powder is 98 to 100 mass% based on the total amount of the powder composition.

11. The powder composition according to any one of claims 1 to 10, which is a primer composition.

12. A coating formed from the powder composition according to any one of claims 1 to 11.

13. A laminate comprising the coating of claim 12 and a coating containing a melt processable fluororesin provided on the coating.

14. A coated article comprising a metal substrate and the laminate of claim 13 provided thereon.

15. A molding method comprising: step (1) of processing the powder composition according to any one of claims 1 to 11 by rotational molding; and step (2) of processing, by rotational molding, a top coat which is a powder composition containing a melt processable fluororesin on the coating formed by step (1).

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