Precoated fin material and its manufacturing method

Abstract

To provide a precoat fin material which can be manufactured by a simple process, and is excellent in corrosion resistance and hydrophilicity, and its manufacturing method.SOLUTION: A precoat fin material 1 has a base material 2 and a resin membrane 3 formed on the base material 2. A mass of the resin membrane 3 per unit area is equal to or larger than 0.2 g / m2 and equal to or smaller than 2.5 g / m2. The precoat fin material 1 has a feature that an average value up to a one-hour lapse time point from a natural potential measurement start point which is measured in a 5-mass% NaCl water solution of pH3 becomes equal to or larger than +0.040 V and equal to or smaller than +0.2 V with respect to an average value of the natural potential of the base material 2, and a water contact angle after being immersed in flowing water for 10 min becomes equal to or larger than 20° and equal to or smaller than 40°. The resin membrane 3 contains a specified hydrophilic polymer (A) and a cross-linking agent (B), and a content of the polymer (A) is equal to or larger than 60 parts by mass and equal to or smaller than 97 parts by mass with respect to total 100 parts by mass in a total of the hydrophilic polymer (A) and the cross-linking agent (B).SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a precoated fin material and a manufacturing method thereof. [Background technology]

[0002] Fin-and-tube heat exchangers, which have multiple fins and tubes intersecting these fins, are widely used as heat exchangers installed in air conditioners, refrigerators, etc. The fins are fabricated by pressing a pre-coated fin material that has a substrate made of aluminum (including pure aluminum and aluminum alloys; the same applies hereinafter) and a resin coating formed on the substrate.

[0003] The resin coating of the precoated fin material is configured to impart various properties to the fins, such as corrosion resistance to suppress corrosion caused by condensation water and hydrophilicity to prevent clogging of the spaces between the fins due to condensation water.For example, Patent Document 1 describes an aluminum fin material for heat exchangers, which is characterized in that a corrosion-resistant coating made of one or more components selected from acrylic resin, epoxy resin, and urethane resin is formed on an aluminum substrate, a hydrophilic coating made of acrylic resin is formed on the corrosion-resistant coating, and a water-soluble lubricant layer made of polyethylene glycol is formed on the hydrophilic coating. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-130320 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the precoated fin material of Patent Document 1, multiple types of resin coatings with different functions are provided on the substrate to impart the properties required of the fin. This makes the manufacturing process of the precoated fin material cumbersome and likely leads to an increase in processing costs.

[0006] The present invention has been made in view of the above background, and aims to provide a precoated fin material that can be manufactured through a simple process and has excellent corrosion resistance and hydrophilicity, and a method for manufacturing the same. [Means for solving the problem]

[0007] One aspect of the present invention is a precoated fin material having an aluminum substrate and a resin coating provided on at least one surface of the substrate, The mass per unit area of the resin film is 0.2 g / m 2 More than 2.5g / m 2 is as follows: The average value of the natural potential from the time when the precoated fin material is immersed in a 5 mass% NaCl aqueous solution of pH 3 until one hour has elapsed is +0.040 V or more and +0.2 V or less relative to the average value of the natural potential from the time when the base material is immersed in a 5 mass% NaCl aqueous solution of pH 3 until one hour has elapsed, and The precoated fin material has a characteristic that the contact angle of water after immersion in running water for 10 minutes is 20° or more and 40° or less, the resin film contains a hydrophilic polymer (A) and a crosslinking agent (B) capable of crosslinking the hydrophilic polymer (A); the content of the hydrophilic polymer (A) is 60 parts by mass or more and 97 parts by mass or less relative to 100 parts by mass of the total of the hydrophilic polymer (A) and the crosslinking agent (B), The hydrophilic polymer (A) includes Structural units derived from a hydrophilic monomer (a1) having one polymerizable double bond and a polyoxyalkylene chain per molecule: 2% by mass or more and 50% by mass or less; Structural units derived from a (meth)acrylamide-based monomer (a2) represented by the following general formula (1): 1% by mass or more and 70% by mass or less; Structural units derived from a carboxyl group-containing polymerizable unsaturated monomer (a3) containing a carboxyl group: 1% by mass or more and 50% by mass or less; The precoated fin material contains 0% by mass or more and 50% by mass or less of structural units derived from a polymerizable unsaturated monomer (a4) other than the hydrophilic monomer (a1), the (meth)acrylamide-based monomer (a2), and the carboxyl group-containing polymerizable unsaturated monomer (a3).

[0008] [ka]

[0009] In the general formula (1), m and n are each independently either 0 or 1, and R 1 represents a hydrogen atom or a methyl group, and R 2 and R 3 each independently represents a hydrogen atom or an alkyl group having 1 to 5 carbon atoms, and R 4 and R 5 each independently represents a methylene group or an ethylene group.

[0010] Another aspect of the present invention is a method for producing a precoated fin material of the above aspect, applying a coating material containing the hydrophilic polymer (A) and the crosslinking agent (B) onto at least one surface of the substrate; The method for producing a precoated fin material includes heating the base material to which the paint has been applied for 4 to 20 seconds in a heating furnace at a temperature of 240°C to 300°C to bake the paint, thereby forming the resin film on the base material. [Effects of the Invention]

[0011] The precoated fin material is provided with a resin film containing the specific hydrophilic polymer (A) and crosslinking agent (B). The precoated fin material also has the properties that the difference in average spontaneous potential with the substrate and the contact angle measured under the specific conditions are within the specific ranges. By having this configuration, the precoated fin material can improve both corrosion resistance and hydrophilicity in a balanced manner.

[0012] Furthermore, the precoated fin material can achieve both excellent corrosion resistance and hydrophilicity with a single resin coating. Therefore, the precoated fin material can be produced through a simple process, and manufacturing costs can be easily reduced.

[0013] In the method for producing the precoated fin material, a coating material containing the specific hydrophilic polymer (A) and the crosslinking agent (B) is applied to a substrate, and then the coating is baked under the specific conditions to form the resin film on the substrate. In this way, the production method makes it possible to easily obtain a precoated fin material with excellent corrosion resistance and hydrophilicity through the simple process of applying the coating material and baking the coating material once each.

[0014] As described above, according to the above-described aspect, it is possible to provide a precoated fin material that can be manufactured through a simple process and has excellent corrosion resistance and hydrophilicity, and a method for manufacturing the same. [Brief explanation of the drawings]

[0015] [Figure 1] FIG. 1 is a cross-sectional view of a precoated fin material in an embodiment. [Figure 2] FIG. 2 is an explanatory diagram of a device for measuring spontaneous potential in the examples. DETAILED DESCRIPTION OF THE INVENTION

[0016] (Pre-coated fin material) The precoated fin material has a substrate and a resin coating formed on one or both sides of the substrate. The configuration of each part of the precoated fin material will be described below.

[0017] A. Base material In the precoated fin material, the aluminum constituting the substrate may be pure aluminum or an aluminum alloy. For example, the substrate may be made of pure aluminum having a chemical composition represented by an alloy number such as A1200 or A1050.

[0018] B. Base Coat The surface of the substrate may be provided with an undercoat made of an inorganic material, and the resin coating may be laminated on the undercoat. By providing the undercoat between the substrate and the resin coating, it is possible to further improve the adhesion of the resin coating and further improve the corrosion resistance of the substrate.

[0019] The base coating may be, for example, a chemical conversion coating formed by chemical conversion treatment. The chemical conversion coating may be formed by a reactive chemical conversion treatment or a paint-type chemical conversion treatment. More specifically, the base coating may be a chromium-containing coating formed by a chromate treatment using chromate phosphate or the like, or a chromium-free coating formed by a non-chromate treatment using a chromium-free compound such as titanium phosphate, zirconium phosphate, molybdenum phosphate, zinc phosphate, or zirconium oxide.

[0020] C. Resin film A resin film is provided on at least one surface of the precoated fin material. The resin film may be laminated directly on the substrate or on an undercoat film. The resin film may also be exposed on the outermost surface of the precoated fin material. The resin film has excellent corrosion resistance and hydrophilicity, as well as excellent lubrication during press molding. Therefore, providing the resin film on the outermost surface can also improve the press moldability of the precoated fin material.

[0021] The resin film contains a hydrophilic polymer (A) and a crosslinking agent (B) capable of crosslinking the hydrophilic polymer (A).

[0022] C-1. Hydrophilic polymer (A) The hydrophilic polymer (A) is a copolymer containing structural units derived from a hydrophilic monomer (a1), structural units derived from a (meth)acrylamide-based monomer (a2), and structural units derived from a carboxyl group-containing polymerizable unsaturated monomer (a3). In addition to the structural units derived from the monomers (a1) to (a3), the hydrophilic polymer (A) may further contain structural units derived from a polymerizable unsaturated monomer (a4) other than the monomers (a1) to (a3).

[0023] Hydrophilic monomer (a1) The hydrophilic monomer (a1) has one polymerizable double bond and a polyoxyalkylene chain per molecule. The hydrophilic polymer (A) may contain structural units derived from one type of hydrophilic monomer (a1), or may contain structural units derived from two or more types of hydrophilic monomers (a1). The content of the structural units derived from the hydrophilic monomer (a1) in the hydrophilic polymer (A) is 2% by mass or more and 50% by mass or less, based on 100% by mass of the total structural units derived from the monomers (a1) to (a4). The content of the structural units derived from the hydrophilic monomer (a1) is preferably 5% by mass or more and 45% by mass or less, based on 100% by mass of the total structural units derived from the monomers (a1) to (a4).

[0024] The hydrophilic monomer (a1) may have, for example, a chemical structure represented by the following general formula (2).

[0025] [ka]

[0026] However, R in the general formula (2) 6 ~R 8 each independently represents a hydrogen atom or a methyl group, and R 9represents a hydrogen atom or an alkyl group having 1 to 12 carbon atoms, and p represents an integer of 2 to 200. In the general formula (2), p is preferably 9 to 120, and more preferably 20 to 100.

[0027] Examples of hydrophilic monomers (a1) having such a structure include "FA-1000MW" and "FA-2000MW" manufactured by Hitachi Chemical Co., Ltd., and "Blenmer PME-100," "Blenmer PME-400," "Blenmer PME-1000," "Blenmer PME-4000," and "Blenmer PLE-200" manufactured by NOF Corporation. "Blenmer" is a registered trademark of NOF Corporation.

[0028] The structural units derived from the hydrophilic monomer (a1) maintain the hydrophilicity of the precoated fin material for a long period of time and also allow water droplets adhering to the surface of the precoated fin material to slide off easily.

[0029] (Meth)acrylamide monomer (a2) The (meth)acrylamide-based monomer (a2) has a chemical structure represented by the following general formula (1): The aforementioned "(meth)acrylamide" includes acrylamide and methacrylamide. The hydrophilic polymer (A) may contain structural units derived from one type of (meth)acrylamide-based monomer (a2), or may contain structural units derived from two or more types of (meth)acrylamide-based monomers (a2). The content of the structural units derived from the (meth)acrylamide-based monomer (a2) in the hydrophilic polymer (A) is 1% by mass or more and 70% by mass or less, based on 100% by mass of the total structural units derived from the monomers (a1) to (a4). The content of the structural units derived from the (meth)acrylamide-based monomer (a2) is preferably 5% by mass or more and 60% by mass or less, based on 100% by mass of the total structural units derived from the monomers (a1) to (a4).

[0030] [ka]

[0031] In the general formula (1), m and n are each independently either 0 or 1, and R 1 represents a hydrogen atom or a methyl group, and R 2 and R 3 each independently represents a hydrogen atom or an alkyl group having 1 to 5 carbon atoms, and R 4 and R 5 each independently represents a methylene group or an ethylene group.

[0032] Examples of the (meth)acrylamide monomer (a2) include N-methylol(meth)acrylamide; N-alkoxymethyl(meth)acrylamides such as N-methoxymethyl(meth)acrylamide, N-ethoxymethyl(meth)acrylamide, N-propoxymethyl(meth)acrylamide, N-isopropoxymethyl(meth)acrylamide, N-butoxymethyl(meth)acrylamide, and N-isobutoxymethyl(meth)acrylamide; (meth)acrylamide, N-methyl(meth)acrylamide, N,N-dimethyl(meth)acrylamide, N-ethyl(meth)acrylamide, Nn-propyl(meth)acrylamide, N-isopropyl(meth)acrylamide, and Nn-butyl(meth)acrylamide.

[0033] Carboxyl group-containing polymerizable unsaturated monomer (a3) The carboxyl group-containing polymerizable unsaturated monomer (a3) has at least one carboxyl group and one polymerizable unsaturated group per molecule. The hydrophilic polymer (A) may contain structural units derived from one type of carboxyl group-containing polymerizable unsaturated monomer (a3), or may contain structural units derived from two or more types of carboxyl group-containing polymerizable unsaturated monomers (a3). The content of the structural units derived from the carboxyl group-containing polymerizable unsaturated monomer (a3) in the hydrophilic polymer (A) is 1% by mass or more and 50% by mass or less, based on 100% by mass of the total structural units derived from the monomers (a1) to (a4). The content of the structural units derived from the carboxyl group-containing polymerizable unsaturated monomer (a3) is preferably 5% by mass or more and 35% by mass or less, based on 100% by mass of the total structural units derived from the monomers (a1) to (a4).

[0034] Examples of the carboxyl group-containing polymerizable unsaturated monomer (a3) include acrylic acid, methacrylic acid, crotonic acid, itaconic acid, maleic acid, fumaric acid, etc. The structural unit derived from the carboxyl group-containing polymerizable unsaturated monomer (a3) can improve the water resistance of the precoated fin material.

[0035] Other polymerizable unsaturated monomers (a4) In addition to the structural units derived from the aforementioned monomers (a1) to (a3), the hydrophilic polymer (A) may optionally contain structural units derived from a polymerizable unsaturated monomer (a4) other than these monomers (a1) to (a3). The hydrophilic polymer (A) may contain structural units derived from one type of polymerizable unsaturated monomer (a4), or may contain structural units derived from two or more types of polymerizable unsaturated monomers (a4). The content of the structural units derived from the polymerizable unsaturated monomer (a4) in the hydrophilic polymer (A) is from 0% to 50% by mass, based on 100% by mass of the total structural units derived from the monomers (a1) to (a4). The content of the structural units derived from the polymerizable unsaturated monomer (a4) is preferably from 5% to 45% by mass, based on 100% by mass of the total structural units derived from the monomers (a1) to (a4).

[0036] The polymerizable unsaturated monomer (a4) may be, for example, a hydroxyl-containing polymerizable unsaturated monomer having a hydroxyl group and a polymerizable unsaturated group in one molecule. Examples of the hydroxyl-containing polymerizable unsaturated monomer include (meth)acrylic acid hydroxyalkyl esters having 2 to 8 carbon atoms, such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate.

[0037] Examples of the polymerizable unsaturated monomer (a4) include methylene bis(meth)acrylamide, ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, tetraethylene glycol dimethacrylate, 1,3-butylene glycol dimethacrylate, 1,4-butanediol diacrylate, glycerin dimethacrylate, glycerin trimethacrylate, trimethylolpropane dimethacrylate, trimethylolpropane trimethacrylate, pentaerythritol dimethacrylate, and the like. Polymerizable unsaturated monomers having two or more polymerizable unsaturated bonds in one molecule, such as acrylate, pentaerythritol trimethacrylate, pentaerythritol tetramethacrylate, dipentaerythritol pentamethacrylate, neopentyl glycol diacrylate, 1,6-hexanediol diacrylate, divinylbenzene, and allyl (meth)acrylate; methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, hexyl (meth)acrylate, octyl (meth)acrylate, lauric acid, methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, hexyl (meth)acrylate, octyl (meth)acrylate, lauric acid, methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, ethyl ... (meth)acrylic acid alkyl esters and (meth)acrylic acid cycloalkyl esters having 1 to 24 carbon atoms, such as acrylonitrile and methacrylonitrile; polymerizable unsaturated nitriles, such as acrylonitrile and methacrylonitrile; aromatic vinyl compounds, such as styrene, α-methylstyrene, vinyltoluene, and α-chlorostyrene; (meth)acrylic acid nitrogen-containing alkyl esters having 2 to 8 carbon atoms, such as N,N-dimethylaminoethyl (meth)acrylate and N,N-dimethylaminopropyl (meth)acrylate; α-olefins such as ethylene and propylene; diene compounds such as butadiene and isoprene; vinyl esters such as vinyl acetate and vinyl propionate; vinyl ethers such as ethyl vinyl ether and n-propyl vinyl ether; unsaturated compounds having a hydrolyzable silyl group such as γ-methacryloyloxypropyltrimethoxysilane, γ-acryloyloxypropyltrimethoxysilane, vinyltriethoxysilane, vinyltrimethoxysilane, 2-styrylethyltrimethoxysilane, and vinyltris(methoxyethoxy)silane;Examples of such unsaturated compounds include glycidyl (meth)acrylate and allyl glycidyl ether, which have an epoxy group. The term "(meth)acrylic acid" includes acrylic acid and methacrylic acid.

[0038] -Method for producing hydrophilic polymers To prepare the hydrophilic polymer (A), a monomer mixture containing a hydrophilic monomer (a1), a (meth)acrylamide-based monomer (a2), and a carboxyl group-containing polymerizable unsaturated monomer (a3) may be copolymerized in a suitable solvent. The monomer mixture may optionally contain a polymerizable unsaturated monomer (a4). Examples of the solvent that can be used include water and water-miscible organic solvents.

[0039] The content of each of the monomers (a1) to (a4) in the monomer mixture may be appropriately set depending on the desired content of each structural unit in the hydrophilic polymer (A). That is, the content of each of the monomers (a1) to (a4) in the monomer mixture may be appropriately set within the range of 2% by mass or more and 50% by mass or less of the hydrophilic monomer (a1), 1% by mass or more and 70% by mass or less of the (meth)acrylamide-based monomer (a2), 1% by mass or more and 50% by mass or less of the carboxyl group-containing polymerizable unsaturated monomer (a3), and 0% by mass or more and 50% by mass or less of the polymerizable unsaturated monomer (a4), relative to 100% by mass of the total of the monomers (a1) to (a4).

[0040] The copolymerization of the monomer mixture is usually carried out in the presence of a radical polymerization initiator. The amount of the radical polymerization initiator used can be appropriately set within the range of, for example, 0.2 to 5 parts by mass per 100 parts by mass of the total of the monomers (a1) to (a4).

[0041] The temperature at which the monomer mixture is copolymerized may be appropriately set depending on the type of radical polymerization initiator used, etc. The temperature at which the monomer mixture is copolymerized may be, for example, in the range of about 50° C. to about 160° C. The reaction time at which the monomer mixture is copolymerized may be, for example, about 0.5 to 10 hours.

[0042] Morphology of hydrophilic polymer (A) The hydrophilic polymer (A) may or may not be particulate. When the hydrophilic polymer (A) is particulate, it preferably has a particle size distribution in which the cumulative 50% particle size on a volume basis is 5 nm or more and 1 μm or less. In this case, in the process of forming a resin film, the stability of the hydrophilic polymer (A) in the coating material can be further improved and aggregation of the hydrophilic polymer (A) can be more effectively suppressed. From the viewpoint of further enhancing such effects, it is more preferable that the hydrophilic polymer (A) has a particle size distribution in which the cumulative 50% particle size on a volume basis is 10 nm or more and 500 nm or less.

[0043] The particle size distribution of the hydrophilic polymer (A) can be measured using a particle size measuring device (for example, "Coulter Model N4MD" manufactured by Beckman Coulter, Inc.).

[0044] Molecular weight of hydrophilic polymer (A) When the hydrophilic polymer (A) is not particulate, the weight average molecular weight of the hydrophilic polymer (A) is preferably 10,000 or more, more preferably 20,000 or more and 250,000 or less, and even more preferably 50,000 or more and 250,000 or less.

[0045] The weight-average molecular weight of the hydrophilic polymer (A) is a value obtained by converting the weight-average molecular weight measured using a gel permeation chromatograph (GPC) to the molecular weight of standard polystyrene. A GPC measuring device such as the "HLC8120GPC" manufactured by Tosoh Corporation can be used. This measuring device is equipped with four columns manufactured by Tosoh Corporation: "TSKgel G-4000HXL," "TSKgel G-3000HXL," "TSKgel G-2500HXL," and "TSKgel G-2000HXL." A chromatogram can be obtained by using tetrahydrofuran at a temperature of 40°C as the mobile phase, setting the mobile phase flow rate to 1 mL / min, and measuring the refractive index difference of the eluate using an RI detector.

[0046] Hydrophilic polymer (A) content The content of the hydrophilic polymer (A) is 60 to 97 parts by mass per 100 parts by mass of the total of the hydrophilic polymer (A) and the crosslinking agent (B). By setting the content of the hydrophilic polymer (A) in the resin film within the specific range, the hydrophilicity and corrosion resistance of the precoated fin material can be improved in a balanced manner. If the content of the hydrophilic polymer (A) is less than the specific range, the proportion of the hydrophilic polymer (A) in the resin film will be reduced, which may result in a decrease in hydrophilicity. On the other hand, if the content of the hydrophilic polymer (A) is more than the specific range, the crosslinking of the hydrophilic polymer (A) in the resin film will be insufficient, which may result in a decrease in corrosion resistance.

[0047] From the viewpoint of improving the hydrophilicity and corrosion resistance of the precoated fin material in a more balanced manner, the content of the hydrophilic polymer (A) is preferably 76 parts by mass or more and 97 parts by mass or less, and more preferably 78 parts by mass or more and 95 parts by mass or less, per 100 parts by mass of the total of the hydrophilic polymer (A) and the crosslinking agent (B).

[0048] C-2. Crosslinking agent (B) The hydrophilic polymer (A) in the resin film is crosslinked by a crosslinking agent (B). The crosslinking agent (B) may be a compound capable of crosslinking the hydrophilic polymer (A). More specifically, examples of the crosslinking agent (B) include amino resins, phenolic resins, polyisocyanate compounds, blocked polyisocyanate compounds, oxazoline group-containing resins, polyepoxy compounds, and carbodiimide compounds. These crosslinking agents (B) may be used alone, or two or more crosslinking agents (B) may be used in combination.

[0049] The crosslinking agent (B) is preferably one or more resins selected from the group consisting of amino resins and phenolic resins, which can further improve the water resistance of the resin film and prevent components from leaching out of the resin film when it comes into contact with water for a longer period of time.

[0050] Examples of amino resins include melamine resins, urea resins, and benzoguanamine resins. The melamine resin may be, for example, an etherified melamine resin in which the methylol groups of a methylolated melamine resin are etherified with a monohydric alcohol having 1 to 8 carbon atoms. The etherified melamine resin may be a fully etherified melamine resin in which all of the methylol groups of the methylolated melamine resin are etherified. Alternatively, the etherified melamine resin may be a partially etherified melamine resin in which some of the methylol groups are etherified, with methylol groups and imino groups remaining.

[0051] The melamine resin may be a fully alkylated methyl / butyl mixed etherified melamine resin, such as Cymel 232, Cymel 232S, Cymel 235, Cymel 236, Cymel 238, Cymel 266, Cymel 267, and Cymel 285, manufactured by Daicel-Allnex Corporation.

[0052] The melamine resin may be a methylol group-type methyl / butyl mixed etherified melamine resin, such as "Cymel 272" manufactured by Daicel-Allnex Corporation.

[0053] The melamine resin may be an imino-type methyl / butyl mixed etherified melamine resin, such as Cymel 202, Cymel 207, Cymel 212, Cymel 253, and Cymel 254 manufactured by Daicel-Allnex Corporation.

[0054] The melamine resin may be a fully alkylated methylated melamine resin, such as "Cymel 300," "Cymel 301," "Cymel 303," and "Cymel 350" manufactured by Daicel-Allnex Corporation.

[0055] The melamine resin may be an imino group-type methylated melamine resin, such as Cymel 325, Cymel 327, Cymel 701, Cymel 703, Cymel 712, Cymel 254, Cymel 253, Cymel 212, and Cymel 1128, manufactured by Daicel-Allnex Corporation.

[0056] The melamine resin may be a butyl-etherified melamine resin, such as "Yu-Ban 20SE60" manufactured by Mitsui Cytec Co., Ltd.

[0057] The urea resin may be, for example, a methylated urea resin or a butylated urea resin. Examples of methylated urea resins include "Cymel U-65" manufactured by Daicel-Allnex Corporation, and "Nicalac MX-270," "Nicalac MX-280," and "Nicalac MX-290" manufactured by Sanwa Chemical Co., Ltd. Examples of butylated urea resins include "Nicalac MX-279" manufactured by Sanwa Chemical Co., Ltd., "U-Ban 10S60" and "U-Ban 10R" manufactured by Mitsui Cytec Co., Ltd., and "Beckamine P-138," "Beckamine P-196-M," and "Beckamine G-1850" manufactured by DIC Corporation.

[0058] The benzoguanamine resin may be, for example, a methylated benzoguanamine resin or a butylated benzoguanamine resin. Examples of the methylated benzoguanamine resin include "Nicalac BL-60" manufactured by Sanwa Chemical Co., Ltd. Examples of the butylated benzoguanamine resin include "Super Beckamine TD-126" and "Super Beckamine 15-594" manufactured by DIC Corporation.

[0059] These amino resins may be used alone or in combination of two or more. "Cymel" is a registered trademark of Allnex Netherlands BV, "Uban" is a registered trademark of Mitsui Chemicals, Inc., "Nicalac" is a registered trademark of Nippon Carbide Industries Co., Ltd., and "Beckamin" is a registered trademark of DIC Corporation.

[0060] The phenolic resin may be, for example, a novolac-type phenolic resin obtained by condensing a phenolic compound and an aldehyde under an acidic catalyst, or a resol-type phenolic resin obtained by condensing a phenolic compound and an aldehyde under a basic catalyst. Furthermore, methylol groups may be introduced into the phenolic resin. Furthermore, some or all of the methylol groups introduced into the phenolic resin may be alkyl-etherified with an alcohol having 6 or less carbon atoms.

[0061] Examples of phenolic resins include "SUMILITERESINPR-HF-3", "SUMILITERESINPR-HF-6", "SUMILITERESINPR-53194", "SUMILITERESINPR-53195", "SUMILITERESINPR-54869", "SUMILITERESINPR-16382", "SUMILITERESINPR-51939", "SUMILITERESINPR-53153", and "SUMILITERESINPR-16382" manufactured by Sumitomo Bakelite Co., Ltd. "PHENOLITE TD-2131", "PHENOLITE TD-2106", "PHENOLITE TD-2093", "PHENOLITE TD-2091", "PHENOLITE TD-2090", "PHENOLITE VH-4150", "PHENOLITE VH-4170", "PHENOLITE VH-4240", "PHENOLITE K ... -1160", "PHENOLITEKH-1163", "PHENOLITEKH-1165", "PHENOLITETD-2093-60M", "PHENOLITETD-2090-60M", "PHENOLITELF-4711", "PHENOLITE LITELF-6161”, “PHENOLITELF-4871”, “PHENOLITELA-7052”, “PHENOLITELA-7054”, “PHENOLITELA-7751”, “PHENOLITELA-1356”, “PHENOLI TELA-3018-50P" manufactured by Showa Polymer Co., Ltd., and "Shounol BKM-262," "Shounol BRG-555," "Shounol BRG-556," "Shounol BRG-558," "Shounol CKM-923," "Shounol CKM-983," "Shounol BKM-2620," "Shounol BRL-2854," "Shounol BRG-5590M," "Shounol CKS-3898," "Shounol CKS-3877A," and "Shounol CKM-937" manufactured by Showa Polymer Co., Ltd.

[0062] These phenolic resins may be used alone or in combination of two or more. "SUMILITERESIN" is a registered trademark of Sumitomo Bakelite Co., Ltd., "PHENOLITE" is a registered trademark of DIC Corporation, and "SHONUL" is a registered trademark of AICA Kogyo Co., Ltd.

[0063] A polyisocyanate compound is a compound having two or more isocyanate groups in one molecule. Examples of polyisocyanate compounds include aromatic diisocyanates such as tolylene diisocyanate, diphenylmethane diisocyanate, xylylene diisocyanate, and naphthalene diisocyanate; aliphatic diisocyanates such as tetramethylene diisocyanate, hexamethylene diisocyanate, dimer acid diisocyanate, and lysine diisocyanate; alicyclic diisocyanates such as methylenebis(cyclohexyl isocyanate), isophorone diisocyanate, methylcyclohexane diisocyanate, cyclohexane diisocyanate, and cyclopentane diisocyanate; biuret-type adducts and isocyanuric ring-type adducts of these polyisocyanates; and free isocyanate group-containing prepolymers obtained by reacting these polyisocyanates with low- or high-molecular-weight polyol compounds (e.g., acrylic polyol, polyester polyol, polyether polyol, etc.) in an excess of isocyanate groups.

[0064] These polyisocyanate compounds may be used alone, or two or more kinds of polyisocyanate compounds may be used in combination.

[0065] A blocked polyisocyanate compound is a compound in which the free isocyanate groups of a polyisocyanate compound are blocked with a blocking agent such as a phenol compound, an oxime compound, an active methylene compound, a lactam compound, an alcohol compound, a mercaptan compound, an acid amide compound, an imide compound, an amine compound, an imidazole compound, a urea compound, a carbamic acid compound, an imine compound, etc. The blocked polyisocyanate compound may be used alone, or two or more types of blocked polyisocyanate compounds may be used in combination.

[0066] C-3. Other ingredients The resin film may be composed of a hydrophilic polymer (A) and a crosslinking agent (B). The resin film may also contain paint additives, provided that the aforementioned effects are not impaired. Examples of additives include pigments, rust inhibitors, aqueous organic resins, surfactants, rheology control agents, surface conditioners, ionic liquids, antifoaming agents, and film-forming aids.

[0067] The resin film may also contain one or more compounds (C) selected from the group consisting of tannic acid, gallic acid, ascorbic acid, and salts thereof. These compounds (C) have the effect of further improving the corrosion resistance of the precoated fin material. The content of compound (C) is preferably 1 to 10 parts by mass, and more preferably 1 to 5 parts by mass, per 100 parts by mass of the total of the hydrophilic polymer (A) and the crosslinking agent (B). In this case, the stability of the paint during the resin film formation process can be further improved, and the corrosion resistance and water resistance of the precoated fin material can be further improved.

[0068] C-4. Mass per unit area of resin film The mass per unit area of the resin film in the precoated fin material is 0.2 g / m 2 More than 2.5g / m 2 The resin film contains the specific hydrophilic polymer (A) and the crosslinking agent (B), and thus has a mass per unit area of 0.2 g / m or less. 2Even with such a very thin thickness, the corrosion resistance and hydrophilicity of the precoated fin material can be improved.

[0069] The mass per unit area of the resin film is 0.2 g / m 2 If the mass per unit area of the resin film is less than 2.5 g / m, the thickness of the resin film will be too thin, which may result in a deterioration in the corrosion resistance of the pre-coated fin material. 2 If the coating weight exceeds this value, the amount of paint used in the manufacturing process of the precoated fin material will increase, which may result in an increase in manufacturing costs.

[0070] The mass per unit area of the resin film in the precoated fin material is 0.2 g / m 2 More than 1.0g / m 2 Preferably, it is 0.2 g / m or less. 2 More than 0.9g / m 2 It is more preferable that the amount of paint used in the manufacturing process of the precoated fin material is less than 100%. In this case, the corrosion resistance and hydrophilicity of the precoated fin material can be ensured while the amount of paint used in the manufacturing process of the precoated fin material can be further reduced. This can be expected to have the effect of further reducing the manufacturing cost of the precoated fin material.

[0071] D. Characteristics of pre-coated fin materials The precoated fin material has a property that the average natural potential from the time the precoated fin material is immersed in a 5 mass % NaCl aqueous solution of pH 3 until one hour has elapsed is +0.040 V or more and +0.2 V or less relative to the average natural potential from the time the base material is immersed in a 5 mass % NaCl aqueous solution of pH 3 until one hour has elapsed.The precoated fin material also has a property that the water contact angle after the precoated fin material is immersed in running water for 10 minutes is 20° or more and 40° or less.

[0072] A precoated fin material in which the potential difference between the precoated fin material and the substrate and the water contact angle are each within the above-mentioned specific ranges can achieve both high corrosion resistance and high hydrophilicity. If the average natural potential of the precoated fin material is less than +0.040 V relative to the average natural potential of the substrate, the corrosion resistance of the precoated fin material may be insufficient. Furthermore, if the water contact angle of the precoated fin material after immersion in running water exceeds 40°, the hydrophilicity of the precoated fin material may be insufficient.

[0073] (Method of manufacturing pre-coated fin material) When producing the precoated fin material, applying a coating material containing the hydrophilic polymer (A) and the crosslinking agent (B) onto at least one surface of the substrate; The base material coated with the paint may be baked by heating it in a heating furnace at a temperature of 240° C. to 300° C. for 4 to 20 seconds, thereby forming the resin film on the base material.

[0074] The substrate may be, for example, an aluminum plate. The thickness of the substrate may be, for example, within a range of 0.05 to 0.30 mm. The substrate may be subjected to a surface treatment such as a chemical conversion treatment before the coating material is applied. By subjecting the surface of the substrate to a chemical conversion treatment in advance, a base film is formed on the substrate, which can improve the adhesion of the resin film.

[0075] The coating material contains a hydrophilic polymer (A) and a crosslinking agent (B). In addition to these, the coating material may also contain the above-mentioned additives, solvents, etc. The method for applying the coating material to the substrate is not particularly limited, and various methods such as using a bar coater or a roll coater can be used.

[0076] After applying the coating material to the substrate, the substrate is heated for 4 to 20 seconds in a heating furnace at a temperature of 240 to 300°C to bake the coating material. This allows the resin film to be formed. If the temperature in the heating furnace is lower than the specified range or if the baking time is shorter than the specified range, the coating material may not be heated sufficiently, resulting in insufficient crosslinking of the hydrophilic polymer (A). This may result in a deterioration in the corrosion resistance of the precoated fin material. Furthermore, if the temperature in the heating furnace is higher than the specified range, the coating material may be overheated, resulting in deterioration of the resin film.

[0077] During the paint baking process, it is preferable to use a fan with an air velocity of 1 m / s to 5 m / s to create convection in the atmosphere inside the heating furnace, which allows the paint on the substrate to be heated more uniformly and more reliably forms a resin film with excellent corrosion resistance and hydrophilicity.

[0078] In the paint baking, the substrate is preferably heated so that the maximum temperature reached in the dry state (Peak Metal Temperature, PMT) of the substrate is in the range of 170° C. to 220° C. In this case, the hydrophilic polymer (A) can be crosslinked more reliably, and a precoated fin material having excellent corrosion resistance and hydrophilicity can be obtained more reliably. [Example]

[0079] Examples of the precoated fin material and its manufacturing method will be described with reference to Figures 1 and 2. Note that the specific aspects of the precoated fin material and its manufacturing method according to the present invention are not limited to those of the examples, and the configurations can be changed as appropriate within the scope of the present invention.

[0080] As shown in Fig. 1, the precoated fin material 1 of this example has a substrate 2 made of aluminum and resin coatings 3 provided on both sides of the substrate 2. A base coating 21 is interposed between the substrate 2 and the resin coating 3. The resin coating 3 contains a hydrophilic polymer (A) and a crosslinking agent (B).

[0081] A. Base material 2 The substrate 2 in this example is an aluminum plate made of A1050 aluminum and having a thickness of 0.1 mm. The surface of the substrate 2 is covered with an undercoat 21. Specifically, the undercoat 21 in this example is a chromate film formed by a chromate treatment using chromate phosphate. The deposition amount of the chromate film is 20 mg / m2 in terms of the mass of Cr atoms per side of the substrate. 2 is.

[0082] B. Resin film 3 The resin film 3 in this example is composed of 80 parts by mass of a hydrophilic polymer (A) and 20 parts by mass of a crosslinking agent (B). Specifically, as shown in Table 1, either a hydrophilic polymer (A1) or a hydrophilic polymer (A2) is used as the hydrophilic polymer (A).

[0083] The hydrophilic polymer (A1) is a copolymer of a monomer mixture consisting of 30% by mass of hydrophilic monomer (a1), 42% by mass of (meth)acrylamide-based monomer (a2), 20% by mass of carboxyl group-containing polymerizable unsaturated monomer (a3), and 8% by mass of polymerizable unsaturated monomer (a4). Specifically, the hydrophilic monomer (a1) in the hydrophilic polymer (A1) is "Blemmer PME-1000" manufactured by NOF Corporation. The (meth)acrylamide-based monomer (a2) is composed of 20 parts by mass of acrylamide, 5 parts by mass of N-methylolacrylamide, and 27 parts by mass of N-methoxymethylacrylamide. The carboxyl group-containing polymerizable unsaturated monomer (a3) is acrylic acid. The polymerizable unsaturated monomer (a4) is composed of 6 parts by mass of 2-hydroxyethyl acrylate and 2 parts by mass of methylenebisacrylamide.

[0084] The hydrophilic polymer (A2) is a copolymer of a monomer mixture consisting of 20% by mass of hydrophilic monomer (a1), 52% by mass of (meth)acrylamide-based monomer (a2), 20% by mass of carboxyl-containing polymerizable unsaturated monomer (a3), and 8% by mass of polymerizable unsaturated monomer (a4). The hydrophilic monomer (a1), carboxyl-containing polymerizable unsaturated monomer (a3), and polymerizable unsaturated monomer (a4) in the hydrophilic polymer (A2) are the same as those in the hydrophilic polymer (A1). The (meth)acrylamide-based monomer (a2) in the hydrophilic polymer (A2) is composed of 20 parts by mass of acrylamide, 5 parts by mass of N-methylolacrylamide, and 27 parts by mass of N-methoxymethylacrylamide.

[0085] Both the hydrophilic polymer (A1) and the hydrophilic polymer (A2) are particulate and have a particle size distribution in which the 50% cumulative diameter in the volumetric particle size distribution is 50 nm. The hydrophilic polymer (A1) and the hydrophilic polymer (A2) both have a weight average molecular weight in terms of polystyrene of 200,000.

[0086] The crosslinking agent (B) is an imino group-type methylated melamine resin (Daicel-Allnex Corporation, "Cymel 701").

[0087] In this example, nine types of precoated fin materials (test materials S1 to S9) with different masses per unit area of the resin coating 3 and different paint baking conditions were prepared and used to evaluate various properties, as shown in Table 1. The test materials S1 to S9 shown in Table 1 were prepared as follows.

[0088] C. Manufacturing method First, the hydrophilic polymer (A1) or the hydrophilic polymer (A2) and the crosslinking agent (B) are mixed in the mass ratio shown in Table 1. Pure water is added to this mixture so that the solid content, i.e., the total amount of the hydrophilic polymer (A1), the hydrophilic polymer (A2), and the crosslinking agent (B) is 7 mass %, to prepare a coating material.

[0089] A paint is applied to the base coating 21 of the substrate 2 prepared in advance using a bar coater, and then the paint is pre-dried. The substrate 2 is then placed in a heating furnace maintained at the temperature shown in Table 1, and heated for the time shown in Table 1 to bake the paint. The atmosphere inside the heating furnace is forced by convection using a fan. The maximum temperature (PMT) of the substrate in a dry state, calculated from the temperature inside the furnace and the air speed of the fan, is as shown in Table 1.

[0090] After the paint baking is completed, the precoated fin material 1 is removed from the heating furnace and cooled to room temperature. In this manner, test materials S1 to S9 shown in Table 1 can be obtained.

[0091] Note that test materials R1 to R3 shown in Table 1 are test materials for comparison with test materials S1 to S9. Test materials R1 and R2 can be prepared in the same manner as test materials S6 to S9, except that the paint baking conditions are changed as shown in Table 1. Test material R3 has the same configuration as test materials S6 to S9, except that it has a resin film consisting only of the hydrophilic polymer (A2). Test material R3 can be prepared in the same manner as test materials S6 to S9, except that the paint is prepared without adding crosslinking agent (B) and the paint baking conditions are changed as shown in Table 1.

[0092] D. Evaluation Measurement of the potential difference between the pre-coated fin material and the substrate The natural potential of the precoated fin material and the substrate is measured using a measuring device 4 shown in Fig. 2. The measuring device 4 has a first container 41 for holding a solution in which the test piece 5 is immersed, a second container 42 for holding a solution in which the reference electrode 6 is immersed, a salt bridge 43 for electrically connecting the solution in the first container 41 with the solution in the second container 42, a potentiostat 44 for measuring the potential of the test piece 5 relative to the reference electrode 6, and a recording device 45 for recording the measured potential.

[0093] To measure the natural potential, first, a rectangular test piece 5 measuring 40 mm in length and 10 mm in width is taken from the test material or substrate. One longitudinal end of this test piece 5 is provided with a connection part 51 for connecting to the potentiostat 44, and the other end is provided with a square potential measurement part 52 with sides of 5 mm. Then, as shown in FIG. 2, insulating paint 53 is applied to the areas other than the connection part 51 and the potential measurement part 52.

[0094] Separately, a 5% NaCl aqueous solution whose pH has been adjusted to 3 using acetic acid is prepared in a first container 41, and a saturated NaCl aqueous solution is prepared in a second container 42. The solutions in the first container 41 and the second container 42 are then electrically connected via a salt bridge 43.

[0095] Next, the connection portion 51 of the test piece 5 and the reference electrode 6 are each connected to the potentiostat 44. As the reference electrode 6, for example, an Ag / AgCl electrode can be used.

[0096] In this state, the potential measuring portion 52 of the test piece 5 is immersed in the 5% NaCl aqueous solution in the first container 41, and the reference electrode 6 is immersed in the saturated NaCl aqueous solution in the second container 42, thereby measuring the natural potential of the test piece 5 relative to the reference electrode 6. In this example, the natural potential of the test piece 5 is measured every three minutes and recorded in the recording device 45.

[0097] The natural potential of the test piece gradually decreases as time passes from the start of measurement, and tends to reach a roughly constant value after 10 hours. In this example, the average natural potential value from the start of measurement to the point where 1 hour has passed is taken as the natural potential value of the test material. The natural potential values of each test material are shown in Table 2.

[0098] The same measurement as above is also performed using the substrate 2 before the resin film 3 is formed. The average value of the natural potential from the start of the measurement until one hour has elapsed is taken as the natural potential value of the substrate 2. The natural potential of the substrate 2 is -0.720 V vs Ag / AgCl. The "potential difference" column in Table 2 shows the value obtained by subtracting the natural potential of the substrate 2 from the natural potential of the test material.

[0099] For measuring the natural potential of the substrate 2, a substrate 2 prepared by polishing the surface of the precoated fin material 1 and removing the resin coating 3 and the base coating 21 can also be used.

[0100] Water contact angle After taking a test piece from each test material, it was immersed in running water at 25°C and a flow rate of 5 L / min for 10 minutes. After removing the test piece from the water, 2 μL of pure water was dropped onto the surface, and the water contact angle was measured 30 seconds after the drop. Table 2 shows the water contact angle of each test material.

[0101] Mass per unit area of resin film 3 A square test piece with a side length of 100 mm was taken from each test material. After measuring the mass W1 (unit: g) of this test piece, the test piece was heated in an electric furnace at 500°C for 15 minutes. After measuring the mass W2 (unit: g) of the test piece removed from the electric furnace, the amount of mass loss W1-W2 (unit: g) from before heating was calculated. This amount of mass loss W1-W2 was multiplied by the total area S (unit: cm) of the resin film 3 formed on the test piece. 2 ) to calculate the mass per unit area of the resin film 3. Table 1 shows the mass per unit area of the resin film 3 for each test material.

[0102] Corrosion resistance A rectangular test piece measuring 100 mm in length and 50 mm in width is taken from the test material so that the rolling direction of the substrate 2 is parallel to the longitudinal direction. This test piece is used to conduct a salt spray test in accordance with JIS Z2371:2000. The test time is 1000 hours. After the test, the corrosion area ratio of the test material is calculated, and a rating number is determined using the rating number method of JIS Z2371:2000. A higher rating number indicates better corrosion resistance. Table 2 shows the rating numbers for each test material.

[0103] ·exterior The surface of the test material is visually observed, and the properties of the resin film 3 are evaluated.

[0104] [Table 1]

[0105] [Table 2]

[0106] As shown in Table 1, test materials S1 to S9 have a resin film made of a hydrophilic polymer (A) and a crosslinking agent (B) formed on a substrate. Furthermore, as shown in Tables 1 and 2, the mass per unit area of the resin film, the potential difference with the substrate, and the contact angle of water after immersion in flowing water for these test materials are all within the specified ranges. Therefore, as shown in Table 2, these test materials have excellent corrosion resistance and hydrophilicity.

[0107] On the other hand, the resin film of test material R1 is formed by heating at a lower furnace temperature than test materials S1 to S9, as shown in Table 1. Therefore, the potential difference between test material R1 and the substrate is smaller than the specific range, as shown in Table 2. As a result, the corrosion resistance of test material R1 is inferior to that of test materials S1 to S9.

[0108] The resin film of test material R2 is formed by heating at a higher furnace temperature than test materials S1 to S9, as shown in Table 1. Therefore, as shown in Table 2, the resin film of test material R2 deteriorates and discolors during heating.

[0109] The resin film of test material R3 does not contain a crosslinking agent (B), as shown in Table 1. Therefore, the potential difference between test material R3 and the substrate is smaller than the specific range, as shown in Table 2. As a result, the corrosion resistance of test material R3 is inferior to that of test materials S1 to S9. [Explanation of symbols]

[0110] 1 Pre-coated fin material 2 Base material 3 Resin film

Claims

1. A precoated fin material having an aluminum substrate and a resin coating provided on at least one surface of the substrate, The mass per unit area of the resin film is 0.2 g / m ２ 2.5g / m or more ２ is as follows: The average value of the natural potential from the time when the precoated fin material is immersed in a 5 mass% NaCl aqueous solution of pH 3 until one hour has elapsed is +0.040 V or more and +0.2 V or less relative to the average value of the natural potential from the time when the base material is immersed in a 5 mass% NaCl aqueous solution of pH 3 until one hour has elapsed, and The precoated fin material has a characteristic that the contact angle of water after immersion in running water for 10 minutes is 20° or more and 40° or less, the resin film contains a hydrophilic polymer (A) and a crosslinking agent (B) capable of crosslinking the hydrophilic polymer (A); the content of the hydrophilic polymer (A) is 60 parts by mass or more and 97 parts by mass or less, relative to 100 parts by mass of the total of the hydrophilic polymer (A) and the crosslinking agent (B); The hydrophilic polymer (A) includes Structural units derived from a hydrophilic monomer (a1) having one polymerizable double bond and a polyoxyalkylene chain per molecule: 2% by mass or more and 50% by mass or less; Structural units derived from a (meth)acrylamide-based monomer (a2) represented by the following general formula (1): 1% by mass or more and 70% by mass or less; Structural units derived from a carboxyl group-containing polymerizable unsaturated monomer (a3) containing a carboxyl group: 1% by mass or more and 50% by mass or less; and structural units derived from the hydrophilic monomer (a1), the (meth)acrylamide-based monomer (a2), and a polymerizable unsaturated monomer (a4) other than the carboxyl group-containing polymerizable unsaturated monomer (a3): 0% by mass or more and 50% by mass or less. 【Chemical 1】 (However, m and n in the general formula (1) are each independently either 0 or 1, and R １ represents a hydrogen atom or a methyl group, R ２ and R ３ each independently represents a hydrogen atom or an alkyl group having 1 to 5 carbon atoms; R ４ and R ５ each independently represents a methylene group or an ethylene group.

2. 2. The precoated fin material according to claim 1, wherein the hydrophilic polymer (A) is a fine particle having a particle size distribution in which the cumulative 50% particle diameter on a volume basis is 5 nm or more and 1 μm or less.

3. The precoated fin material according to claim 1 or 2, wherein the hydrophilic polymer (A) has a weight average molecular weight of 10,000 or more.

4. The precoated fin material according to any one of claims 1 to 3, wherein the crosslinking agent (B) is one or more resins selected from the group consisting of amino resins and phenolic resins.

5. The precoated fin material according to any one of claims 1 to 4, wherein the hydrophilic polymer (A) contains structural units derived from the hydrophilic monomer (a1): 5% by mass or more and 45% by mass or less, structural units derived from the (meth)acrylamide-based monomer (a2): 5% by mass or more and 60% by mass or less, structural units derived from the carboxyl group-containing polymerizable unsaturated monomer (a3): 5% by mass or more and 35% by mass or less, and structural units derived from the polymerizable unsaturated monomer (a4): 5% by mass or more and 45% by mass or less.

6. A method for producing a precoated fin material according to any one of claims 1 to 5, applying a coating material containing the hydrophilic polymer (A) and the crosslinking agent (B) onto at least one surface of the substrate; The base material to which the paint has been applied is heated in a heating furnace at a temperature of 240°C or higher and 300°C or lower for 4 seconds or longer and 20 seconds or shorter to perform paint baking, thereby forming the resin coating on the base material.

7. The method for producing a precoated fin material according to claim 6, wherein during the paint baking, the atmosphere in the heating furnace is convected using a fan with a wind speed of 1 m / s or more and 5 m / s or less.

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