Fluororesin solvent-based primer composition, coating film, fluorine-containing resin laminate and article

Abstract

The present invention provides a fluorine-containing resin solvent-based primer composition, a coating film, a fluorine-containing resin laminate and an article, wherein the fluorine-containing resin solvent-based primer composition comprises a fluorine-containing resin and a binder resin dispersed in a liquid medium, wherein the fluorine-containing resin comprises a tetrafluoroethylene [TFE] / perfluoro(alkyl vinyl ether) [PAVE] copolymer [PFA] having a melt flow rate (MFR) of 10 to 30 (g / 10min) and a tetrafluoroethylene [TFE] / hexafluoropropylene copolymer having a melt flow rate (MFR) of 10 to 30 (g / 10min). The invention relates to a polyolefin [HFP] copolymer [FEP], wherein the mass ratio of [PFA] / [FEP] is in the range of 10 / 90 to 90 / 10, the binder resin comprises polyamideimide [PAI] and polyethersulfone [PES], and the mass ratio of [PAI] / [PES] is in the range of 1 / 99 to 60 / 40, the composition comprises 1% by mass to 30% by mass of a liquid medium (A) having a boiling point of less than 100° C., and the composition comprises 1% by mass to 30% by mass of a liquid medium (B) having a boiling point of 100° C. to 150° C.

Description

Technical Field

[0001] The present invention relates to a fluorine-containing resin solvent-based primer composition, a coating film, a fluorine-containing resin laminate and an article. Background Art

[0002] Fluororesins are widely used in the following aspects: they are prepared into coating compositions and applied to substrates of objects such as bread molds and rice cookers that require corrosion resistance, non-adhesiveness, and heat resistance to form fluororesin layers. However, fluororesins also have the problem of poor adhesion to substrates composed of metals, ceramics, etc. due to their non-adhesiveness.

[0003] Therefore, when coating fluororesin on the surface of a substrate such as metal, ceramic, or glass, the following method is generally widely used: after forming physical irregularities on the surface of these substrates by sandblasting, etching, or the like, a primer composition having adhesive properties is applied to the surface of the substrate to form a primer layer, and the substrate and the fluororesin as a top coat are bonded by the primer layer. In this method, the following anchoring effect is utilized in the bonding between the substrate surface and the primer layer: the unevenness of the substrate surface increases the bonding area between the primer layer and the substrate surface, thereby improving the bonding strength.

[0004] In addition, the primer layer must be bonded to the surface of the substrate such as metal, ceramic, glass, etc., and also to the fluororesin as the top coating layer. Therefore, the following method is used to form the primer layer: fluororesin powder, which is the same material as the top coating layer, and a substance with adhesive properties called a binder resin are uniformly dispersed in a liquid medium, and the resulting primer composition is applied to the substrate surface. As the fluororesin powder used in the primer composition, fluororesin fine powder with an average particle size of less than 1 μm has been widely used in the past from the perspectives of dispersibility and adhesion to the fluororesin powder of the top coating layer.

[0005] Patent document 1 discloses an article having a fluororesin coating film composed of a primer layer formed on a substrate and a top coat layer formed on the primer layer, wherein the primer layer has a fluororesin coating film formed from a primer composition, the primer composition being obtained by uniformly dispersing at least one fluororesin powder (A) having an average particle size greater than the film thickness and at least one fluororesin powder (B) having an average particle size less than the film thickness in a liquid medium at a weight ratio of (A):(B) of 10 to 100:90 to 0, and discloses that at least one of the above-mentioned fluororesin powders (A) and (B) is preferably polytetrafluoroethylene, a tetrafluoroethylene / perfluoro(alkyl vinyl ether) copolymer, a tetrafluoroethylene / hexafluoropropylene copolymer, a tetrafluoroethylene / ethylene copolymer, polyvinylidene fluoride, polychlorotrifluoroethylene, or a mixture thereof.

[0006] In addition, Patent Document 2 discloses a coating composition, characterized in that it contains a fluorine-containing polymer, a heat-resistant resin and a water-soluble inorganic salt, the fluorine-containing polymer is at least one selected from the group consisting of polytetrafluoroethylene, tetrafluoroethylene / hexafluoropropylene copolymer and tetrafluoroethylene / perfluoro (alkyl vinyl ether) copolymer, and the average particle size is 0.01 μm to 5 μm, the average particle size of the heat-resistant resin is 0.1 μm to 10.0 μm, the solid content mass ratio of the heat-resistant resin to the fluorine-containing polymer is 15:85 to 50:50, and the water-soluble inorganic salt is 0.0001 mass% to 10 mass% relative to the total solid content of the fluorine-containing polymer and the heat-resistant resin.

[0007] Prior art literature

[0008] Patent Literature

[0009] Patent Document 1: Japanese Patent Application Publication No. 2001-219122

[0010] Patent Document 2: Japanese Patent Application Publication No. 2009-242711 Summary of the invention

[0011] Problems to be solved by the invention

[0012] The object of the present invention is to provide a fluororesin solvent-based primer composition suitable as a primer for a fluororesin layer and capable of achieving high adhesion between a substrate and a fluororesin layer. More specifically, to provide a fluororesin laminate having excellent adhesion obtained by providing a primer layer having sufficient adhesion to the fluororesin layer.

[0013] Means for solving problems

[0014] The present invention relates to a fluorine-containing resin solvent-based primer composition, which is a fluorine-containing resin solvent-based primer composition in which a fluorine resin and a binder resin are dispersed in a liquid medium, and is characterized in that:

[0015] The fluororesin comprises a tetrafluoroethylene [TFE] / perfluoro(alkyl vinyl ether) [PAVE] copolymer [PFA] having a melt flow rate (MFR) of 10 to 30 (g / 10 min) and a tetrafluoroethylene [TFE] / hexafluoropropylene [HFP] copolymer [FEP] having a melt flow rate (MFR) of 10 to 30 (g / 10 min),

[0016] The mass ratio of [PFA] / [FEP] is in the range of 10 / 90 to 90 / 10,

[0017] The binder resin comprises polyamideimide [PAI] and polyethersulfone [PES], wherein the mass ratio of [PAI] / [PES] is in the range of 1 / 99 to 60 / 40,

[0018] Furthermore, the composition contains 1 to 30% by mass of a liquid medium (A) having a boiling point of less than 100°C, and 1 to 30% by mass of a liquid medium (B) having a boiling point of 100 to 150°C.

[0019] The fluorine-containing resin solvent-based primer composition may contain less than 1% by mass of N-methyl-2-pyrrolidone in the composition.

[0020] The present invention also relates to a coating film formed from the above-mentioned fluorine-containing resin solvent-based primer composition.

[0021] The present invention also relates to a fluororesin laminate, characterized in that it is composed of an object to be coated, the coating film and a fluororesin layer containing PFA, wherein the object to be coated, the coating film and the fluororesin layer are laminated in this order.

[0022] The present invention also relates to an article comprising the above-mentioned fluorine-containing resin laminate.

[0023] Effects of the Invention

[0024] The fluorine-containing resin solvent-based primer composition of the present invention can form a primer layer having excellent adhesion to a metal substrate and excellent adhesion to a fluorine-containing resin layer. DETAILED DESCRIPTION

[0025] Next, the present invention will be described in detail.

[0026] The present invention relates to a fluorine-containing resin solvent-based primer composition, which is a fluorine-containing resin solvent-based primer composition in which a fluorine resin and a binder resin are dispersed in a liquid medium, and is characterized in that:

[0027] The fluororesin comprises a tetrafluoroethylene [TFE] / perfluoro(alkyl vinyl ether) [PAVE] copolymer [PFA] having a melt flow rate (MFR) of 10 to 30 (g / 10 min) and a tetrafluoroethylene [TFE] / hexafluoropropylene [HFP] copolymer [FEP] having a melt flow rate (MFR) of 10 to 30 (g / 10 min),

[0028] The mass ratio of [PFA] / [FEP] is in the range of 10 / 90 to 90 / 10,

[0029] The binder resin comprises polyamideimide [PAI] and polyethersulfone [PES], wherein the mass ratio of [PAI] / [PES] is in the range of 1 / 99 to 60 / 40,

[0030] The composition contains a liquid medium (A) having a boiling point of less than 100°C in an amount of 1 to 30% by mass, and further contains a liquid medium (B) having a boiling point of 100 to 150°C in an amount of 1 to 30% by mass.

[0031] The fluorinated solvent-based primer composition of the present invention (hereinafter referred to as the primer composition) comprises PFA and FEP having MFRs within a specific range in a specific mass ratio, PAI and PES as binder resins within a specific mass ratio, and further comprises a liquid medium (A) having a boiling point of less than 100° C. and a liquid medium (B) having a boiling point of 100° C. to 150° C. in specific amounts, thereby forming a coating film having excellent adhesion to a coated object and improved adhesion to a fluororesin layer.

[0032] When a primer coating composition containing a fluororesin and a binder resin is applied, the fluororesin floats up during firing due to the difference in surface tension between the fluororesin and the binder resin, thereby forming a coating film in which the fluororesin is mainly arranged on the surface side of the coating film and the binder resin is mainly arranged on the side of the object to be coated. In the conventional primer coating composition, as described above, the fluororesin oriented on the surface side of the coating film shows affinity with the fluororesin in the upper coating film, and thus the property of showing excellent adhesion with the upper coating film is utilized.

[0033] The primer composition of the present invention further limits the MFR of the fluororesin to a specific range, thereby controlling the fluidity of the fluororesin. The fluororesin having an MFR in the above range can float rapidly during firing, so that a coating film having the fluororesin disposed on the coating film surface can be effectively formed.

[0034] In addition, the primer composition of the present invention contains a low-boiling liquid medium with a boiling point of 150°C or less. So far, primer compositions mixed with liquid media with relatively low boiling points have been studied, but mainly liquid media with a boiling point of about 160°C to 180°C, and liquid media with a boiling point of 150°C or less have not been studied. The present invention can form a coating film with better adhesion by using a liquid medium (A) with a boiling point of less than 100°C and a liquid medium (B) with a boiling point of 100°C to 150°C. It is believed that this effect may be due to the fact that when the coating film is fired, the above-mentioned two liquid media are transferred to the surface of the coating film in sequence, so that the above-mentioned fluororesin can also rise to the surface of the coating film more quickly.

[0035] (Fluororesin)

[0036] The primer composition of the present invention comprises PFA having a melt flow rate (MFR) of 10 to 30 (g / 10 min) and FEP having a melt flow rate (MFR) of 10 to 30 (g / 10 min) as fluororesins.

[0037] In the above FEP, the HFP unit in the copolymer exceeds 2% by mass, preferably 20% by mass or less, and more preferably 10% by mass to 15% by mass.

[0038] As the PAVE in the above-mentioned PFA, a substance having an alkyl group having 1 to 6 carbon atoms is preferred, and perfluoro(methyl vinyl ether) [PMVE], perfluoro(ethyl vinyl ether) [PEVE] or perfluoro(propyl vinyl ether) [PPVE] is more preferred. In the above-mentioned PFA, the PAVE unit in the copolymer exceeds 2% by mass, preferably 5% by mass or less, and more preferably 2.5% by mass to 4.0% by mass.

[0039] In the present specification, the "monomer unit" such as the HFP unit mentioned above refers to a part derived from a corresponding monomer which is a part of the molecular structure of the fluororesin.

[0040] As long as the PFA and FEP have the above-mentioned compositions, other monomers may be further polymerized. As the other monomers, for example, in the case of the FEP, PAVE may be further cited, and in the case of the PFA, HFP may be further cited. One or more of the other monomers may be used.

[0041] The other monomers described above vary depending on their types, but are generally preferably 1% by mass or less based on the mass of the fluororesin, with a more preferred upper limit being 0.5% by mass, and a further preferred upper limit being 0.3% by mass.

[0042] The MFR of the above-mentioned PFA and FEP is in the range of 10 to 30 (g / 10min). If the MFR is less than 10 (g / 10min), the transfer to the coating surface may be insufficient. If the MFR exceeds 30 (g / 10min), the molecular weight is low and the coating strength is reduced, which is not preferred.

[0043] In this specification, MFR is a value measured under the conditions of a temperature of 372° C. and a load of 5.0 kg in accordance with ASTM D3307 and D2116.

[0044] The MFR is more preferably 15 to 28 (g / 10 min).

[0045] The average particle diameter of the above-mentioned PFA and FEP is preferably 0.01 μm to 5 μm, respectively. If it is less than 0.01 μm, the mechanical stability of the particles composed of the fluororesin is poor, and the mechanical stability and storage stability of the obtained primer composition may be poor. If it exceeds 5 μm, the particles composed of the fluororesin lack uniform dispersibility, and when the obtained primer composition is used for coating, sometimes a smooth coating film cannot be obtained, and the coating film has poor physical properties. A more preferred upper limit is 0.5 μm, and a more preferred lower limit is 0.05 μm.

[0046] The mechanical stability refers to a property that during liquid transport / redispersion, even when strong stirring or shearing force is applied by a homogenizer or the like, aggregates that cannot be redispersed are unlikely to be generated.

[0047] In this specification, the average particle size of the fluororesin is measured by observation under a transmission electron microscope.

[0048] The total content of the above-mentioned PFA and FEP is preferably in the range of 10% to 40% by mass of the composition. If the above-mentioned total content is less than 10% by mass, the adhesion between the primer and the top coat may be reduced. If the above-mentioned total content exceeds 40% by mass, the strength of the primer is easily reduced, and the adhesion to the substrate may also be reduced. The total content of the above-mentioned PFA and FEP is more preferably in the range of 15% to 35% by mass of the composition.

[0049] In addition, the mass ratio of [PFA] / [FEP] is in the range of 10 / 90 to 90 / 10.

[0050] The mass ratio is more preferably in the range of 20 / 80 to 80 / 20.

[0051] The primer coating composition of the present invention may contain other fluororesins such as polytetrafluoroethylene [PTFE] within a range not impairing the effects of the present invention. In addition, it may contain PFA and FEP having MFR outside the above range within a range not impairing the effects of the present invention.

[0052] (Binder resin)

[0053] The primer composition of the present invention contains a binder resin, so that a coating film having excellent adhesion to a coating object and good corrosion resistance and water vapor resistance can be obtained.

[0054] The binder resin exhibits heat resistance at a temperature of 150° C. or higher. The binder resin generally has a molecular structure or a functional group such as an amide bond or an imide bond that exhibits adhesion to the object to be coated, and thus exhibits adhesion to the object to be coated.

[0055] The primer composition of the present invention necessarily contains polyamideimide [PAI] and polyethersulfone [PES] as binder resins.

[0056] The PAI is a resin composed of a polymer having an amide bond and an imide bond in the molecular structure. The PAI is not particularly limited, and examples thereof include a resin composed of a high molecular weight polymer obtained by the reaction of an aromatic diamine having an amide bond in the molecule with an aromatic tetracarboxylic acid such as pyromellitic acid; a reaction of an aromatic tricarboxylic acid such as trimellitic anhydride with a diamine such as 4,4-diaminophenyl ether or a diisocyanate such as diphenylmethane diisocyanate; a reaction of a dibasic acid having an aromatic imide ring in the molecule with a diamine, etc. As the PAI, it is preferably composed of a polymer having an aromatic ring in the main chain from the perspective of excellent heat resistance.

[0057] The above PES has the following formula:

[0058]

Chemistry 1

[0059]

[0060] The repeating units of the polymers shown constitute the resin.

[0061] The PES is not particularly limited, and examples thereof include resins composed of a polymer obtained by polycondensation of dichlorodiphenyl sulfone and bisphenol.

[0062] The total content of the PAI and PES is preferably 10% by mass to 40% by mass of the composition, and more preferably 15% by mass to 35% by mass.

[0063] In addition, the mass ratio of PAI / PES is 1 / 99 to 60 / 40. If the mass ratio is less than 1 / 99, the adhesion between the coating film obtained from the primer composition and the substrate may be reduced; if the mass ratio exceeds 60 / 40, the adhesion between the coating film and the top coating layer may be reduced.

[0064] The average particle size of the binder resin is preferably 0.1 μm to 10 μm. When the average particle size of the binder resin is within the above range, the corrosion resistance of the obtained coating film is good. The average particle size of the binder resin is more preferably 0.2 μm to 8 μm.

[0065] In the present specification, the average particle size of the binder resin is measured using an ultracentrifugal automatic particle size distribution measuring apparatus CAPA-700 manufactured by Horiba, Ltd.

[0066] The primer composition of the present invention may also contain other binder resins, such as polyimide resins [PI], polyetherimide resins, polyetheretherketone resins, aromatic polyester resins, polyarylene sulfide resins represented by polyphenylene sulfide [PPS], and the like.

[0067] In the primer composition of the present invention, the solid content mass ratio of the fluororesin to the binder resin is preferably binder resin:fluororesin = 15:85 to 85:15. If the binder resin is less than 15% by mass of the total solid content mass of the fluororesin and the binder resin, the binder resin is insufficient, so the adhesion of the obtained coating film to the coated object is insufficient. If it exceeds 50% by mass, the fluororesin is insufficient, so the adhesion of the above coating film to the top coating film is insufficient.

[0068] The solid content mass ratio is more preferably binder resin:fluororesin = 25:75 to 75:25, and even more preferably binder resin:fluororesin = 35:65 to 65:35.

[0069] The solid content mass ratio is calculated from the amounts of the fluororesin and the binder resin mixed during preparation.

[0070] (Liquid medium (A))

[0071] The liquid medium (A) has a boiling point of less than 100° C. The liquid medium (A) is not particularly limited as long as it has wettability with the fluororesin.

[0072] Specific examples of the liquid medium (A) include methyl ethyl ketone, ethanol, acetone, benzene, and the like, and one or more kinds thereof may be used.

[0073] The content of the liquid medium (A) is 1% to 30% by mass in the composition. If the content is less than 1% by mass, the transfer of the fluororesin may be insufficient. If the content exceeds 30% by mass, the transfer of the fluororesin is too much, and cohesion failure in the primer layer is likely to occur, so it is not preferred. The content of the liquid medium (A) is more preferably 3% to 25% by mass in the composition.

[0074] (Liquid medium (B))

[0075] The liquid medium (B) has a boiling point of 100° C. to 150° C. The liquid medium (B) is not particularly limited as long as it has wettability to the fluororesin similarly to the liquid medium (A).

[0076] Specific examples of the liquid medium (B) include 1-butanol, methyl isobutyl ketone, butyl acetate, toluene, and xylene, and one or more of these may be used.

[0077] The content of the liquid medium (B) is 1% to 30% by mass in the composition. If the content is less than 1% by mass, the transfer of the fluororesin may be insufficient. If the content exceeds 30% by mass, the transfer of the fluororesin is too much, and cohesion failure in the primer layer is likely to occur, so it is not preferred. The content of the liquid medium (B) is more preferably 3% to 25% by mass in the composition.

[0078] When two or more of the liquid media (A) and (B) are used in combination, the content thereof shall be the total content.

[0079] The primer composition of the present invention preferably uses an organic solvent other than the liquid medium (A) (B) as a dispersion medium. The organic solvent as the dispersion medium is preferably a compound having excellent dispersibility of the fluororesin and dispersibility or solubility of the binder resin. Such an organic solvent is not particularly limited, but specifically, it is preferably an organic solvent that can dissolve and disperse the binder resin and has a boiling point of 200° C. or above.

[0080] Specifically, for example, lower alcohols such as diacetone alcohol; ketones; esters; amides such as N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, N-butyl-2-pyrrolidone, N,N-dimethylacetamide, N,N-dimethylformamide, 3-methoxy-N,N-dimethylpropionamide; aromatic hydrocarbons such as trimethylbenzene, methylethylbenzene, propylbenzene, butylbenzene, etc., and one or more kinds can be used.

[0081] As the above-mentioned dispersion medium, a mixed solvent of water and the above-mentioned organic solvent may be used.

[0082] It should be noted that the “organic solvent other than the liquid medium (A) (B)” should be treated as an organic solvent not belonging to any of the above-mentioned liquid mediums (A) (B) in the blending amount.

[0083] The content of the organic solvent other than the liquid medium (A) (B) is preferably 20% to 50% by mass in the composition. If the content is less than 20% by mass, the dissolution and dispersion of the binder resin may be insufficient. If the content exceeds 50% by mass, the proportion of the fluororesin decreases, which is not preferred.

[0084] The primer composition of the present invention may be substantially free of N-methyl-2-pyrrolidone. In this specification, substantially free of N-methyl-2-pyrrolidone means that the content of N-methyl-2-pyrrolidone is less than 1% by mass of the composition. N-methyl-2-pyrrolidone is a solvent with excellent solubility, but the surface tension is too high, and the wettability to the substrate is insufficient, and there is also a problem of being difficult to obtain good adhesion. By making a primer composition that does not substantially use N-methyl-2-pyrrolidone, better adhesion can be obtained, which is preferred from this aspect.

[0085] In addition, by using a solvent with a lower surface tension than N-methyl-2-pyrrolidone as the main solvent, such as 3-methoxy-N,N-dimethylpropionamide, the fluororesin can be well wetted and coagulation in the coating can be prevented, thereby improving storage stability. If coagulation of the fluororesin occurs, the fluororesin is difficult to transfer to the surface of the coating film during firing, and the peel strength is reduced.

[0086] The primer composition of the present invention may contain other resins as required. By blending the other resins, the film-forming property, corrosion resistance, etc. of the coating film obtained from the primer composition can be improved.

[0087] 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.

[0088] The primer composition of the present invention may further contain additives used in conventional coating compositions in order to improve coating properties and properties of a coating film obtained from the primer composition, within a range that does not impair the characteristics of the present invention.

[0089] The additives are not particularly limited and can be selected according to the purpose of the obtained coated article. For example, leveling agents, solid lubricants, wood flour, quartz sand, carbon black, diamond, tourmaline, germanium, aluminum oxide, silicon nitride, fluorite, clay, talc, extender pigments, various fillers, conductive fillers, bright materials, pigments, fillers, pigment dispersants, anti-settling agents, moisture absorbers, surface conditioners, thixotropy imparting agents, viscosity modifiers, anti-gelling agents, ultraviolet absorbers, light stabilizers, plasticizers, anti-floating agents, anti-skinning agents, anti-scratch agents, mildew inhibitors, antibacterial agents, antioxidants, antistatic agents, silane coupling agents, etc.

[0090] Examples of the bright material include mica, metal powder, glass beads, glass bubbles, glass flakes, and glass fibers.

[0091] The metal powder is not particularly limited, and examples thereof include powders of metal elements such as aluminum, iron, tin, zinc, gold, silver, and copper; powders of alloys such as aluminum alloys and stainless steel; and the like. The shape of the metal powder is not particularly limited, and examples thereof include granular and flake shapes. The primer composition of the present invention can form a coating film having an excellent appearance when containing such a bright material. The content of the bright material is preferably 0.1% to 10.0% by mass relative to the solid content of the primer composition.

[0092] Examples of the viscosity modifier include methylcellulose and alumina sol.

[0093] The primer composition of the present invention can be obtained, for example, by (1) preparing a dispersion liquid composed of a fluororesin, a liquid medium (A), a liquid medium (B) and a dispersion medium, and (2) adding a binder resin and, if necessary, additives to the obtained dispersion liquid. It should be noted that the binder resin is preferably used in a state dissolved in the above-mentioned "organic solvent other than the liquid medium (A) (B)".

[0094] The primer composition of the present invention can form a coating film on the object by coating it on the object. In this specification, "coating" with respect to the primer composition refers to a process consisting of: coating the primer composition, drying it as needed, and then firing it.

[0095] The primer composition of the present invention can form a coating film having good adhesion to not only the object to be coated but also good adhesion to the top coating film.

[0096] As the top coating applied to the coating film obtained from the primer composition of the present invention, a coating containing a fluororesin is preferred. In this case, in the above-mentioned coating film, as described above, the fluororesin oriented on the surface side of the coating film shows affinity with the fluororesin in the top coating film, and thus shows excellent adhesion with the top coating film.

[0097] The coating film obtained from the primer composition of the present invention can be formed by applying the primer composition onto a coating object, drying the resulting coating film, and then firing the resulting coating film as necessary.

[0098] The object to be coated is not particularly limited, and examples thereof include metals such as iron, aluminum, copper and their alloys; and non-metallic inorganic materials such as enamel, glass, and ceramics. Examples of the alloys include stainless steel.

[0099] From the aspect that the above-mentioned primer composition can be evenly applied and the aspect that the adhesion with the coating film obtained by the above-mentioned primer composition is improved, the above-mentioned object to be coated is preferably subjected to a surface treatment such as a degreasing treatment and a surface roughening treatment in advance. The method for the above-mentioned surface roughening treatment is not particularly limited, and chemical etching using acid or alkali, anodizing (acid-resistant aluminum treatment), sandblasting, etc. can be cited.

[0100] The coating method is not particularly limited, and examples thereof include spray coating, roll coating, coating with a doctor blade, impregnation (immersion) coating, immersion coating, swirl coating, curtain coating, and the like.

[0101] The drying can be performed by a conventionally known method, and is preferably performed at a temperature of 60° C. to 200° C. for 5 to 60 minutes.

[0102] The coating film is usually not fired before the top coating is applied, but may be fired as required. It is preferred not to fire before the top coating is applied in order to simplify the process and reduce energy, labor, time, etc.

[0103] The top coating film can be formed, for example, by applying a top coating paint on the coating film or on the coating film, followed by firing.

[0104] The fluororesin in the above-mentioned top coating is not particularly limited, and examples thereof include PTFE, PFA, FEP, etc. From the perspective of improving the interlayer adhesion between the above-mentioned coating film and the top coating film, it is preferably a substance that is the same as the above-mentioned fluororesin in the base coating composition of the present invention, or a substance with similar properties such as the presence or absence of melt processability.

[0105] Examples of the top coating material include PTFE-based coating materials whose main component is PTFE, PFA-based coating materials whose main component is PFA, and FEP-based coating materials whose main component is FEP. Among them, PFA-based coating materials are preferred.

[0106] The top coating composition may further contain additives similar to the various additives that can be used in the base coating composition for the purpose of improving coating properties, properties of the resulting coating film, and the like.

[0107] In the case where the main component is PFA or FEP, the top coating material can be made into a powder coating material.

[0108] As a coating method of the above-mentioned top coating material, in the case of a powder coating material, electrostatic spray coating, flow dip coating, spin coating method, etc. are mentioned.

[0109] The firing after applying the top coating composition can be carried out under the same conditions as those for the firing after applying the base coating composition and drying.

[0110] The thickness of the coating film obtained from the primer composition of the present invention and the top coating film are not particularly limited, but the coating film preferably has a thickness of 1 μm to 100 μm and the top coating film preferably has a thickness of 10 μm to 200 μm.

[0111] The fluororesin laminate of the present invention is composed of an object to be coated, a coating film and a fluororesin layer. As described above, the coating film is obtained by coating the primer composition of the present invention, and in the fluororesin laminate, the primer composition of the present invention is applied to the object to be coated. The fluororesin layer is obtained by coating a top coating containing the fluororesin. In the fluororesin laminate of the present invention, the object to be coated, the coating film and the fluororesin layer are laminated in this order.

[0112] The use of the fluorine-containing resin laminate of the present invention is not particularly limited, and it can be used, for example, as a product requiring heat resistance, non-stickiness, sliding properties, etc. on the surface of a substrate.

[0113] Examples of such uses include cooking utensils such as frying pans, baking pans, pressure cookers, various other pots, rice cookers, rice cake machines, ovens, heating plates, bread baking molds, kitchen knives, and gas stoves; food containers such as electric kettles and ice trays; food industry parts such as mixing rollers, calender rollers, conveyors, and hoppers; industrial products such as rollers for office automation equipment [OA], OA belts, OA separation claws, papermaking rollers, and calender rollers for film manufacturing; mold release for forming molds such as molds for foamed styrene molding, and stripper plates for plywood and decorative board manufacturing; kitchen products such as range hoods; frozen food manufacturing equipment such as conveyor belts; tools such as saws and files; household products such as irons and scissors; metal foil; sliding bearings for food processing machines, packaging machines, textile equipment, etc.; sliding parts for cameras and watches; and automotive parts.

[0114] The coated article having the fluorine-containing resin laminate exemplified above is also one of the present invention.

[0115] Example

[0116] Hereinafter, the present invention will be specifically described based on Examples.

[0117] In the following examples, "part" and "%" mean "part by mass" and "mass %", respectively, unless otherwise specified.

[0118] The fluororesin powders used are shown below.

[0119] PFA Pellets A:

[0120] MFR: 7 (g / 10min), melting point: 306°C, average particle size: 23 μm

[0121] PFA Pellets B:

[0122] MFR: 28 (g / 10min), melting point: 301°C, average particle size: 24 μm

[0123] PFA Granules C

[0124] MFR: 37 (g / 10min), melting point: 298°C, average particle size: 20 μm

[0125] PFA Granules D

[0126] MFR: 29 (g / 10min), melting point: 301°C, average particle size: 0.3 μm

[0127] FEP Granule A

[0128] MFR: 22 (g / 10min), melting point: 256°C, average particle size: 20 μm

[0129] FEP Granules B

[0130] MFR: 9 (g / 10min), melting point: 254°C, average particle size: 0.3 μm

[0131] FEP Granules C

[0132] MFR: 20 (g / 10min), melting point: 258°C, average particle size: 0.3 μm

[0133] FEP Granules D

[0134] MFR: 35 (g / 10min), melting point: 256°C, average particle size: 0.2 μm

[0135] Examples 1 to 8, Comparative Examples 1 to 13

[0136] Any one of PFA particles A to D and any one of FEP particles A to D as fluororesins, polyamideimide (PAI) varnish A (manufactured by Showa Denko Materials Co., Ltd., solid content 28%, N-methylpyrrolidone solution) as a binder resin, and polyethersulfone (PES) powder (manufactured by Sumitomo Chemical Co., Ltd., number average molecular weight 24000), N-methylpyrrolidone, methyl isobutyl ketone, 1-butanol, methyl ethyl ketone, ethanol, and diacetone alcohol are mixed in the prescribed mass ratios shown in Tables 1 to 3 to obtain a fluorinated solvent-based primer composition.

[0137] An iron plate (SS400, surface roughness Ra: 2 μm to 3 μm) was sandblasted with alumina powder (TOSA Emery #40 manufactured by Uji Denka Kogyo Co., Ltd.) at a spray pressure of 1.0 MPa, and the above-mentioned fluorinated solvent-based primer composition was spray-coated on the iron plate and dried at 150° C. for 30 minutes. PFA powder (ACX-34 manufactured by Daikin Industries, Ltd.) was then electrostatically coated on the upper layer and fired at 380° C. for 20 minutes to obtain a laminate with a total film thickness of 40 μm.

[0138] The boiling points of the solvents used are shown below.

[0139]

[0140] Embodiments 9-10

[0141] PFA particles B and FEP particles C as fluororesins, polyamideimide (PAI) varnish B (manufactured by ELANTAS, solid content 36%, 3-methoxy-N,N-dimethylpropionamide solution) as binder resin, and polyethersulfone (PES) powder (manufactured by Sumitomo Chemical Co., Ltd., number average molecular weight 24000), 3-methoxy-N,N-dimethylpropionamide, methyl isobutyl ketone, and methyl ethyl ketone are mixed in the specified mass ratio shown in Table 3 to obtain a fluorine-containing solvent-type primer composition.

[0142] Thereafter, the same steps as in Example 1 were carried out to obtain a laminate.

[0143] (Peel Strength)

[0144] The peel strength of the laminate obtained above was measured by the following method.

[0145] The peel strength was measured in a direction at 90° with respect to the test piece at a tensile speed of 50 mm / min using a Tensilon universal testing machine in accordance with JIS K 6854-1.

[0146] In addition, the locations where peeling occurred are shown below.

[0147] A: Damage to the top coating

[0148] B: Destruction of base coating

[0149] C: Peeling between topcoat and basecoat

[0150] (Peel strength of coating after storage)

[0151] Furthermore, the fluorinated solvent-based primer compositions obtained in Examples 5, 6, 9 and 10 were allowed to stand at 50°C for 1 month and then subjected to the same procedures as in Example 1 to evaluate the adhesiveness of the laminate.

[0152]

Table 1

[0153]

[0154]

Table 2

[0155]

[0156]

Table 3

[0157]

[0158] The results in Tables 1 to 3 show that the fluorine-containing resin laminates obtained in the examples have sufficient peel strength. In addition, it can be seen that the fluorine-containing resin laminates obtained in the examples have a top coating layer destroyed, while in the comparative examples, the primer layer is destroyed or peeling between the top coating layer and the primer layer occurs, so the primer composition of the present invention has sufficient coating film strength and adhesion.

[0159] Furthermore, for the primer compositions of Examples 5, 6, 9 and 10, the fluorine-containing resin laminates obtained after standing at 50° C. for 1 month also had good peel strength, indicating that the primer compositions of the present invention have excellent storage stability.

[0160] Industrial Applicability

[0161] The primer composition of the present invention is a coating composition capable of forming a coating film having both adhesion to a coating object and adhesion to a fluororesin layer, and can be suitably used as a primer for a fluororesin layer.

Claims

1. A fluorine-containing resin solvent-based primer composition, wherein a fluorine-containing resin and a binder resin are dispersed in a liquid medium, characterized in that: The fluororesin comprises a tetrafluoroethylene / perfluoro(alkyl vinyl ether) copolymer PFA having a melt flow rate MFR of 10 g / 10 min to 30 g / 10 min and a tetrafluoroethylene / hexafluoropropylene copolymer FEP having a melt flow rate MFR of 10 g / 10 min to 30 g / 10 min, The mass ratio of PFA / FEP is in the range of 10 / 90 to 90 / 10. The binder resin comprises polyamideimide PAI and polyethersulfone PES, and the mass ratio of PAI / PES is in the range of 1 / 99 to 60 / 40. Furthermore, the composition contains 1% to 30% by mass of a liquid medium (A) having a boiling point of less than 100° C., and the composition contains 1% to 30% by mass of a liquid medium (B) having a boiling point of 100° C. to 150° C., The total content of PFA and FEP is in the range of 10% to 40% by mass of the composition. The solid content mass ratio of the fluororesin to the binder resin is binder resin:fluororesin = 15:85 to 85:15, The MFR is a value measured under the conditions of a temperature of 372° C. and a load of 5.0 kg in accordance with ASTM D3307 and D2116.

2. The fluorine-containing resin solvent-based primer composition according to claim 1, wherein The total content of PAI and PES is 10 to 40% by mass of the composition.

3. The fluorine-containing resin solvent-based primer composition according to claim 1, wherein The MFR of each of PFA and FEP is in the range of 15 g / 10 min to 28 g / 10 min.

4. The fluorine-containing resin solvent-based primer composition according to claim 1, wherein The mass ratio of PFA / FEP is in the range of 20 / 80 to 80 / 20.

5. The fluorine-containing resin solvent-based primer composition according to claim 1, wherein The content of N-methyl-2-pyrrolidone in the composition is less than 1% by mass.

6. The fluorine-containing resin solvent-based primer composition according to claim 1, wherein The total content of PFA and FEP is 10% to 40% by mass of the composition. The total content of PAI and PES is 10% to 40% by mass of the composition. The MFR of PFA and FEP is in the range of 15g / 10min to 28g / 10min. The mass ratio of PFA / FEP is in the range of 20 / 80 to 80 / 20. The solid content mass ratio of the fluororesin to the binder resin is binder resin:fluororesin = 15:85 to 85:15, The content of N-methyl-2-pyrrolidone in the composition is less than 1% by mass. 7 . A coating film formed from the fluorine-containing resin solvent-based primer composition according to claim 1 .

8. A fluorine-containing resin laminate, characterized in that: The coating film comprises an object to be coated, the coating film according to claim 7 and a fluororesin layer containing PFA, wherein the object to be coated, the coating film and the fluororesin layer are laminated in this order. 9 . An article comprising the fluorine-containing resin laminate according to claim 8 .

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