JP2023009821A - Precoat fin material and its manufacturing method - Google Patents

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

The present invention relates to a precoated fin material and its manufacturing method.

A so-called fin-and-tube heat exchanger, which has a large number of fins and tubes intersecting the fins, is often used as a heat exchanger mounted on air conditioners, refrigerators, and the like. The fin is produced by pressing a pre-coated fin material having a substrate made of aluminum (including pure aluminum and aluminum alloy; the same shall apply hereinafter) and a resin film provided on the substrate.

The resin film of the pre-coated fin material is configured so that it can impart various properties to the fins, such as corrosion resistance to suppress corrosion due to condensed water, and hydrophilicity to avoid clogging between fins due to condensed water. It is For example, in Patent Document 1, a corrosion-resistant film is formed on an aluminum base material, the corrosion-resistant film having one or more selected from acrylic resin, epoxy resin, and urethane resin as a constituent material, and an acrylic resin is formed on the upper layer of the corrosion-resistant film and a water-soluble lubricant layer containing polyethylene glycol as a constituent material is formed on the upper layer of the hydrophilic film. ing.

JP 2013-130320 A

However, in the precoated fin material of Patent Document 1, a plurality of types of resin coatings having different functions are provided on the base material in order to impart the properties required for the fin. Therefore, the manufacturing process of the precoated fin material tends to be complicated, and the processing cost tends to increase.

The present invention has been made in view of such a background, and an object thereof is to provide a precoated fin material that can be manufactured by a simple process and has excellent corrosion resistance and hydrophilicity, and a method for manufacturing the same.

One aspect of the present invention is a precoated fin material having a substrate made of aluminum 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 or more and 2.5 g/m ² or less,
The average value of the self-potential for one hour after the precoated fin material was immersed in the pH 3 5% by mass NaCl aqueous solution was 1 hour after the substrate was immersed in the pH 3 5% by mass NaCl aqueous solution. +0.040 V or more and +0.2 V or less with respect to the average value of the self-potential until the time has passed, and
Having a property that the contact angle of water after immersing the precoated fin material in running water for 10 minutes is 20° or more and 40° or less,
The resin film contains a hydrophilic polymer (A) and a cross-linking agent (B) capable of cross-linking 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 with respect to a total of 100 parts by mass of the hydrophilic polymer (A) and the cross-linking agent (B),
In the hydrophilic polymer (A),
a structural unit derived from a hydrophilic monomer (a1) having one polymerizable double bond and a polyoxyalkylene chain in one 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,
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): 0% by mass A precoated fin material containing at least 50% by mass or less.

However, m and n in the general formula (1) are each independently either 0 or 1, R ¹ represents a hydrogen atom or a methyl group, R ² and R ³ are each independently a hydrogen atom or the number of carbon atoms It represents an alkyl group of 1 to 5, and R ⁴ and R ⁵ each independently represents a methylene group or an ethylene group.

Another aspect of the present invention is a method for manufacturing a precoated fin material according to the aspect described above,
applying a paint containing the hydrophilic polymer (A) and the cross-linking agent (B) onto at least one surface of the base material;
Precoating, wherein the base material coated with the paint is heated in a heating furnace at a temperature of 240° C. or higher and 300° C. or lower for 4 seconds or more and 20 seconds or less to bake the paint, thereby forming the resin film on the base material. It is in the manufacturing method of the fin material.

The precoated fin material is provided with a resin film containing the specific hydrophilic polymer (A) and the cross-linking agent (B). Further, the precoated fin material has characteristics such that the difference in the average value of the natural potential with respect to the base material and the contact angle when measured under the specific conditions are within the specific ranges. By having such a configuration, the precoated fin material can improve both corrosion resistance and hydrophilicity in a well-balanced manner.

In addition, the precoated fin material can achieve both excellent corrosion resistance and hydrophilicity with a single resin film. Therefore, the precoated fin material can be produced by a simple process, and the production cost can be easily reduced.

In the method for producing a precoated fin material, after applying the paint containing the specific hydrophilic polymer (A) and the cross-linking agent (B) onto the substrate, the paint is baked under the specific conditions. , the resin film is formed on the substrate. As described above, in the manufacturing method, a precoated fin material excellent in corrosion resistance and hydrophilicity can be easily obtained by a simple process of applying the paint and baking the paint once.

As described above, according to the above aspect, it is possible to provide a precoated fin material which can be manufactured by a simple process and has excellent corrosion resistance and hydrophilicity, and a method for manufacturing the same.

FIG. 1 is a cross-sectional view of a precoated fin material in an example. FIG. 2 is an explanatory diagram of the self-potential measuring device in the embodiment.

(pre-coated fin material)
The precoated fin material has a base material and a resin film provided on one side or both sides of the base material. The configuration of each part of the precoated fin material will be described below.

A. Substrate In the precoated fin material, the aluminum constituting the substrate may be pure aluminum or an aluminum alloy. For example, the substrate may be composed of pure aluminum with chemical compositions represented by alloy numbers such as A1200 and A1050.

B. Undercoat Film An undercoat film made of an inorganic substance is provided on the surface of the substrate, and the resin film may be laminated on the undercoat film. By providing the base film between the substrate and the resin film, the adhesion of the resin film can be further improved, and the corrosion resistance of the substrate can be further improved.

The undercoating may be, for example, a chemical conversion coating formed by chemical conversion treatment. The chemical conversion film may be formed by a reactive chemical conversion treatment, or may be formed by a coating-type chemical conversion treatment. More specifically, the underlying film includes a chromium-containing film formed by chromate treatment using chromate phosphate or the like, and chromium such as titanium phosphate, zirconium phosphate, molybdenum phosphate, zinc phosphate and zirconium oxide. A chromium-free film or the like formed by non-chromate treatment using a non-containing compound can be employed.

C. Resin Coating At least one surface of the precoated fin material is provided with a resin coating. The resin coating may be directly laminated on the substrate, or may be laminated on the base film. Further, the resin film may be exposed on the outermost surface of the precoated fin material. Since the resin film has excellent corrosion resistance and hydrophilicity, and also has excellent lubricity during press molding, the press moldability of the precoated fin material is improved by providing the resin film on the outermost surface. can also

The resin film contains a hydrophilic polymer (A) and a cross-linking agent (B) capable of cross-linking the hydrophilic polymer (A).

C-1. Hydrophilic polymer (A)
The hydrophilic polymer (A) comprises a structural unit derived from the hydrophilic monomer (a1), a structural unit derived from the (meth)acrylamide-based monomer (a2), and a carboxyl group-containing polymerizable unsaturated monomer (a3). It is a copolymer containing a structural unit derived from. In the hydrophilic polymer (A), in addition to structural units derived from the monomers (a1) to (a3) described above, a polymerizable unsaturated monomer (a4) other than the monomers (a1) to (a3) A derived structural unit may be included.

- Hydrophilic monomer (a1)
The hydrophilic monomer (a1) has one polymerizable double bond and a polyoxyalkylene chain in one 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). may be included. The content of the structural unit derived from the hydrophilic monomer (a1) in the hydrophilic polymer (A) is 2% by mass or more relative to the total 100% by mass of the structural units derived from the monomers (a1) to (a4). It is 50% by mass or less. 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 with respect to the total 100% by mass of the structural units derived from the monomers (a1) to (a4). .

The hydrophilic monomer (a1) may have, for example, a chemical structure represented by general formula (2) below.

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

Hydrophilic monomers having such a structure (a1) include, for example, "FA-1000MW" and "FA-2000MW" manufactured by Hitachi Chemical Co., Ltd., "Blenmer PME-100" manufactured by NOF Corporation, "Blenmer PME-400”, “Blenmer PME-1000”, “Blenmer PME-4000” and “Blenmer PLE-200”. "Blemmer" is a registered trademark of NOF Corporation.

The structural unit derived from the hydrophilic monomer (a1) maintains the hydrophilicity of the precoated fin material for a long period of time and allows water droplets adhering to the surface of the precoated fin material to slide off easily.

- (meth) acrylamide-based monomer (a2)
The (meth)acrylamide-based monomer (a2) has a chemical structure represented by the following general formula (1). Incidentally, 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 two or more types of (meth)acrylamide-based monomers (a2). may contain a structural unit derived from. The content of structural units derived from the (meth)acrylamide-based monomer (a2) in the hydrophilic polymer (A) is 1 per 100% by mass of the total structural units derived from the monomers (a1) to (a4). It is more than mass % and below 70 mass %. The content of the structural unit derived from the (meth)acrylamide-based monomer (a2) is 5% by mass or more and 60% by mass or less with respect to the total 100% by mass of the structural units derived from the monomers (a1) to (a4). is preferred.

However, m and n in the general formula (1) are each independently either 0 or 1, R ¹ represents a hydrogen atom or a methyl group, R ² and R ³ are each independently a hydrogen atom or the number of carbon atoms It represents an alkyl group of 1 to 5, and R ⁴ and R ⁵ each independently represents a methylene group or an ethylene group.

The (meth)acrylamide-based monomer (a2) includes, for example, N-methylol(meth)acrylamide; N-methoxymethyl(meth)acrylamide, N-ethoxymethyl(meth)acrylamide, N-propoxymethyl(meth)acrylamide, N - N-alkoxymethyl (meth)acrylamides such as 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, etc. .

-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 in one molecule. The hydrophilic polymer (A) may contain structural units derived from one type of carboxyl group-containing polymerizable unsaturated monomer (a3), or two or more types of carboxyl group-containing polymerizable unsaturated monomers. A structural unit derived from the monomer (a3) may be included. The content of structural units derived from the carboxyl group-containing polymerizable unsaturated monomer (a3) in the hydrophilic polymer (A) is based on a total of 100% by mass of the structural units derived from the monomers (a1) to (a4). is 1% by mass or more and 50% by mass or less. The content of the structural unit derived from the carboxyl group-containing polymerizable unsaturated monomer (a3) is 5% by mass or more and 35% by mass or less with respect to the total 100% by mass of the structural units derived from the monomers (a1) to (a4). is preferably

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

- Other polymerizable unsaturated monomers (a4)
In the hydrophilic polymer (A), in addition to the structural units derived from the monomers (a1) to (a3) described above, as an optional component, polymerizable unsaturated monomers other than these monomers (a1) to (a3) A structural unit derived from the monomer (a4) may be included. The hydrophilic polymer (A) may contain a structural unit derived from one type of polymerizable unsaturated monomer (a4), or derived from two or more types of polymerizable unsaturated monomers (a4). may contain a structural unit that The content of structural units derived from the polymerizable unsaturated monomer (a4) in the hydrophilic polymer (A) is 0 mass relative to the total 100 mass% of the structural units derived from the monomers (a1) to (a4). % or more and 50 mass % or less. The content of the structural unit derived from the polymerizable unsaturated monomer (a4) is 5% by mass or more and 45% by mass or less with respect to the total 100% by mass of the structural units derived from the monomers (a1) to (a4). is preferred.

As the polymerizable unsaturated monomer (a4), for example, a hydroxyl group-containing polymerizable unsaturated monomer having a hydroxyl group and a polymerizable unsaturated group in one molecule can be used. Examples of hydroxyl group-containing polymerizable unsaturated monomers include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate and 4-hydroxybutyl (meth) acrylate, (Meth)acrylic acid hydroxyalkyl esters having 2 to 8 carbon atoms, and the like.

Further, as the polymerizable unsaturated monomer (a4), methylenebis(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, pentaerythritol trimethacrylate, pentaerythritol tetramethacrylate, dipentaerythritol pentamethacrylate, neo Polymerizable unsaturated monomers having two or more polymerizable unsaturated bonds in one molecule, such as pentyl glycol diacrylate, 1,6-hexanediol diacrylate, divinylbenzene and allyl (meth)acrylate; methyl (meth) C1-24 (meth)acrylics such as acrylates, ethyl (meth)acrylate, butyl (meth)acrylate, hexyl (meth)acrylate, octyl (meth)acrylate, lauryl (meth)acrylate and cyclohexyl (meth)acrylate acid alkyl esters and (meth)acrylic acid cycloalkyl esters; polymerizable unsaturated nitriles such as acrylonitrile and methacrylonitrile; aromatic vinyl compounds such as styrene, α-methylstyrene, vinyltoluene and α-chlorostyrene; - Nitrogen-containing alkyl esters of (meth)acrylic acid having 2 to 8 carbon atoms, such as dimethylaminoethyl (meth)acrylate and N,N-dimethylaminopropyl (meth)acrylate; α-olefins such as ethylene and propylene; butadiene and Diene compounds such as isoprene; vinyl esters such as vinyl acetate and vinyl propionate; vinyl ethers such as ethyl vinyl ether and n-propyl vinyl ether; γ-methacryloyloxypropyltrimethoxysilane, γ-acryloyloxypropyltrimethoxysilane, vinyltriethoxysilane unsaturated compounds having a hydrolyzable silyl group, such as vinyltrimethoxysilane, 2-styrylethyltrimethoxysilane and vinyltris(methoxyethoxy)silane; epoxy compounds such as glycidyl (meth)acrylate and allyl glycidyl ether; An unsaturated compound having a oxy group can be mentioned. Incidentally, the aforementioned "(meth)acrylic acid" includes acrylic acid and methacrylic acid.

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

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

Copolymerization of the monomer mixture is usually carried out in the presence of a radical polymerization initiator. The amount of the radical polymerization initiator to be used can be appropriately set, for example, within the range of 0.2 parts by mass or more and 5 parts by mass or less with respect to a total of 100 parts by mass of the monomers (a1) to (a4).

Moreover, the temperature at which the monomer mixture is copolymerized may be appropriately set according to the type of the radical polymerization initiator to be used. The temperature at which the monomer mixture is copolymerized may range, for example, from about 50°C to about 160°C. The reaction time for copolymerizing the monomer mixture can be, for example, about 0.5 to 10 hours.

- Form of hydrophilic polymer (A) The hydrophilic polymer (A) may or may not be particulate. When the hydrophilic polymer (A) is particulate, the hydrophilic polymer (A) preferably has 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. In this case, in the process of forming the resin film, it is possible to further improve the stability of the hydrophilic polymer (A) in the paint and more effectively suppress the aggregation of the hydrophilic polymer (A). can. From the viewpoint of enhancing such effects, the hydrophilic polymer (A) more preferably has a particle size distribution in which the cumulative 50% particle diameter on a volume basis is 10 nm or more and 500 nm or less.

For measuring the particle size distribution of the hydrophilic polymer (A), a particle size measuring device (for example, "Coulter Model N4MD" manufactured by Beckman Coulter, Inc.) or the like may be used.

- 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. It is more preferably 250,000 or less, and even more preferably 50,000 or more and 250,000 or less.

The weight-average molecular weight of the hydrophilic polymer (A) is a value obtained by converting the weight-average molecular weight measured using gel permeation chromatography (GPC) based on the molecular weight of standard polystyrene. As a GPC measuring device, for example, "HLC8120GPC" manufactured by Tosoh Corporation may be used. To this measurement device, four columns of Tosoh Corporation "TSKgelG-4000HXL", "TSKgelG-3000HXL", "TSKgelG-2500HXL" and "TSKgelG-2000HXL" are attached, using tetrahydrofuran at a temperature of 40 ° C. as a mobile phase, moving A chromatogram can be obtained by measuring the refractive index difference of the eluate with a phase flow rate of 1 mL/min and using an RI detector.

- Content of the hydrophilic polymer (A) The content of the hydrophilic polymer (A) is 60 parts by mass or more per 100 parts by mass in total of the hydrophilic polymer (A) and the cross-linking agent (B) 97 Part by mass or less. 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 well-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 decrease, which may lead to a decrease in hydrophilicity. Further, if the content of the hydrophilic polymer (A) is more than the specific range, cross-linking of the hydrophilic polymer (A) in the resin film becomes insufficient, which may lead to a decrease in corrosion resistance. .

From the viewpoint of improving the hydrophilicity and corrosion resistance of the precoated fin material in a well-balanced manner, the content of the hydrophilic polymer (A) is set to 100 parts by mass in total for the hydrophilic polymer (A) and the cross-linking agent (B). On the other hand, it is preferably 76 parts by mass or more and 97 parts by mass or less, more preferably 78 parts by mass or more and 95 parts by mass or less.

C-2. Crosslinking agent (B)
The hydrophilic polymer (A) in the resin film is crosslinked by the crosslinking agent (B). As the cross-linking agent (B), a compound capable of cross-linking the hydrophilic polymer (A) can be used. More specifically, the cross-linking agent (B) includes amino resins, phenol resins, polyisocyanate compounds, blocked polyisocyanate compounds, oxazoline group-containing resins, polyepoxy compounds, carbodiimide compounds, and the like. These cross-linking agents (B) may be used alone, or two or more cross-linking agents (B) may be used in combination.

The cross-linking agent (B) is preferably one or more resins selected from the group consisting of amino resins and phenol resins. In this case, the water resistance of the resin film can be further improved, and the elution of the components of the resin film upon contact with water can be suppressed over a longer period of time.

Examples of amino resins include melamine resins, urea resins and benzoguanamine resins. The melamine resin may be, for example, an etherified melamine resin obtained by etherifying the methylol group of a methylolated melamine resin with a monohydric alcohol having 1 to 8 carbon atoms. The etherified melamine resin may be a fully etherified melamine resin in which all methylol groups of the methylolated melamine resin are etherified. Moreover, the etherified melamine resin may be a partially etherified melamine resin in which a part of the methylol groups is etherified and the methylol groups and imino groups remain.

The melamine resin may be a fully alkyl methyl/butyl mixed etherified melamine resin. Examples of the fully alkyl-type methyl/butyl mixed etherified melamine resins include "Cymel 232", "Cymel 232S", "Cymel 235", "Cymel 236", "Cymel 238" and "Cymel 266" manufactured by Daicel Allnex Co., Ltd. ”, “Cymel 267” and “Cymel 285”.

The melamine resin may be a methylol group type methyl/butyl mixed etherified melamine resin. Examples of the methylol group type methyl/butyl mixed etherified melamine resin include "Cymel 272" manufactured by Daicel-Ornex Co., Ltd., and the like.

The melamine resin may be an imino-type methyl/butyl mixed etherified melamine resin. Examples of imino-type methyl/butyl mixed etherified melamine resins include "Cymel 202", "Cymel 207", "Cymel 212", "Cymel 253" and "Cymel 254" manufactured by Daicel-Ollnex.

The melamine resin may be a fully alkylated methylated melamine resin. Examples of fully alkyl-methylated melamine resins include "Cymel 300", "Cymel 301", "Cymel 303" and "Cymel 350" manufactured by Daicel-Ornex Co., Ltd.

The melamine resin may be an imino group-type methylated melamine resin. Examples of imino group-type methylated melamine resins include "Cymel 325", "Cymel 327", "Cymel 701", "Cymel 703", "Cymel 712", "Cymel 254" and "Cymel 253”, “Cymel 212” and “Cymel 1128”.

The melamine resin may be a butyl etherified melamine resin. Examples of the butyl-etherified melamine resin include “Uban 20SE60” manufactured by Mitsui Cytec Co., Ltd., and the like.

The urea resin may be, for example, a methylated urea resin, a butylated urea resin, or the like. Examples of methylated urea resins include "Cymel U-65" manufactured by Daicel-Ornex Co., Ltd., "Nikalac MX-270", "Nikalac MX-280" and "Nikalac MX-290" manufactured by Sanwa Chemical Co., Ltd. mentioned. Examples of butylated urea resins include "Nikalac MX-279" manufactured by Sanwa Chemical Co., Ltd., "Uvan 10S60" and "Uvan 10R" manufactured by Mitsui Cytec Co., Ltd., and "Beckamin P-138" and "Beckamin" manufactured by DIC Corporation. P-196-M" and "Beckamin G-1850".

The benzoguanamine resin may be, for example, a methylated benzoguanamine resin, a butylated benzoguanamine resin, or the like. Examples of the methylated benzoguanamine resin include "Nikalac BL-60" manufactured by Sanwa Chemical Co., Ltd., and the like. Examples of butylated benzoguanamine resins include "Super Beccamine TD-126" and "Super Beccamine 15-594" manufactured by DIC Corporation.

These amino resins may be used alone, or two or more amino resins may be used in combination. “Cymel” is a registered trademark of Allnex Netherlands, “Uvan” is a registered trademark of Mitsui Chemicals, Inc., “Nikalac” is a registered trademark of Nippon Carbide Industries Co., Ltd., and “Beccamin” is a DIC stock. It is a registered trademark of the company.

The phenolic resin may be, for example, a novolak 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. may be Moreover, a methylol group may be introduced into the phenol resin. Furthermore, some or all of the methylol groups introduced into the phenol resin may be alkyl-etherified with an alcohol having 6 or less carbon atoms.

Examples of phenolic resins include "SUMILITERESINPR-HF-3", "SUMILITERESINPR-HF-6", "SUMILITERESINPR-53194", "SUMILITERESINPR-53195", "SUMILITERESINPR-54869" and "SUMILITERESINPR-16382" manufactured by Sumitomo Bakelite Co., Ltd. ”, “SUMILITERESINPR-51939”, “SUMILITERESINPR-53153”, “SUMILITERESINPR-53364”, “SUMILITERESINPR-53365”, “SUMILITERESINPR-50702”, DIC Corporation “PHENOLITETD-2131”, “PHENOLITETD-2106” -2093", "PHENOLITETD-2091", "PHENOLITETD-2090", "PHENOLITEVH-4150", "PHENOLITEVH-4170", "PHENOLITEVH-4240", "PHENOLITEKH-1160", "PHENOLITEKH-1163", "PHENOLITEKH-1163" ”, “PHENOLITETD-2093-60M”, “PHENOLITETD-2090-60M”, “PHENOLITELF-4711”, “PHENOLITELF-6161”, “PHENOLITELF-4871”, “PHENOLITELA-7052”, “PHENOLITELA-7054”, “PHENOLITELTD-2093-60M” -7751", "PHENOLITELA-1356", "PHENOLITELA-3018-50P", Showa Polymer Co., Ltd. "Showol BKM-262", "Shownol BRG-555", "Shownol BRG-556", "Show Noll BRG-558", "Shownol CKM-923", "Shownol CKM-983", "Shownol BKM-2620", "Shownol BRL-2854", "Shownol BRG-5590M", "Shownol CKS -3898”, “Shaunol CKS-3877A” and “Shaunol CKM-937”.

These phenol resins may be used alone, or two or more phenol resins may be used in combination. "SUMILITERESIN" is a registered trademark of Sumitomo Bakelite Co., Ltd., "PHENOLITE" is a registered trademark of DIC Corporation, and "Shownol" is a registered trademark of Aica Kogyo Co., Ltd.

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 isocyanate), isophorone diisocyanate, methylcyclohexane diisocyanate, cyclohexane diisocyanate and cyclopentane diisocyanate; biuret type adducts and isocyanuric ring type adducts of these polyisocyanates; A free isocyanate group-containing prepolymer obtained by reacting an excess of isocyanate groups with a polyol compound (eg, acrylic polyol, polyester polyol, polyether polyol, etc.) may be mentioned.

These polyisocyanate compounds may be used alone, or two or more polyisocyanate compounds may be used in combination.

Blocking polyisocyanate compounds convert free isocyanate groups of polyisocyanate compounds into phenol compounds, oxime compounds, active methylene compounds, lactam compounds, alcohol compounds, mercaptan compounds, acid amide compounds, imide compounds, amine compounds, and imidazole compounds. , urea-based compounds, carbamic acid-based compounds, imine-based compounds, and other blocking agents. A single blocked polyisocyanate compound may be used, or two or more blocked polyisocyanate compounds may be used in combination.

C-3. Other Components The resin film may be composed of a hydrophilic polymer (A) and a cross-linking agent (B). In addition, the resin film may contain additives for coating as long as the effects described above are not impaired. Examples of additives include pigments, antirust agents, water-based organic resins, surfactants, rheology control agents, surface control agents, ionic liquids, antifoaming agents, and film-forming aids.

Also, the resin film may 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 the compound (C) is preferably 1 part by mass or more and 10 parts by mass or less with respect to a total of 100 parts by mass of the hydrophilic polymer (A) and the cross-linking agent (B). It is more preferably not more than parts by mass. In this case, the stability of the paint in the process of forming the resin film can be further improved, and the corrosion resistance and water resistance of the precoated fin material can be further improved.

C-4. Mass per Unit Area of Resin Coating The mass per unit area of the resin coating in the precoated fin material is 0.2 g/m ² or more and 2.5 g/m ² or less. Since the resin film contains the specific hydrophilic polymer (A) and the cross-linking agent (B), even a very thin thickness of 0.2 g/m ² with a mass per unit area of the pre-coated fin can be obtained. The corrosion resistance and hydrophilicity of the material can be improved.

If the mass per unit area of the resin film is less than 0.2 g/m ² , the thickness of the resin film becomes too thin, which may lead to deterioration in corrosion resistance of the precoated fin material. On the other hand, if the mass per unit area of the resin film exceeds 2.5 g/m ² , the amount of paint used in the process of manufacturing the precoated fin material increases, which may lead to an increase in manufacturing cost.

The mass per unit area of the resin film in the precoated fin material is preferably 0.2 g/m ² or more and 1.0 g/m ² or less, and 0.2 g/m ² or more and 0.9 g/m ² or less. is more preferable. In this case, it is possible to further reduce the amount of paint used in the process of manufacturing the precoated fin material while ensuring the corrosion resistance and hydrophilicity of the precoated fin material. As a result, the effect of further reducing the manufacturing cost of the precoated fin material can be expected.

D. Characteristics of precoated fin material The precoated fin material has an average self-potential value of 5% by mass NaCl aqueous solution of pH 3 for one hour after the precoated fin material is immersed in a 5% by mass NaCl aqueous solution of pH 3. It has a characteristic of being +0.040 V or more and +0.2 V or less with respect to the average value of the self-potential from the time when the base material is immersed in the water to the time when one hour has passed. Further, the precoated fin material has a property that the contact angle of water after immersing the precoated fin material in running water for 10 minutes is 20° or more and 40° or less.

A precoated fin material in which the potential difference between the precoated fin material and the base material and the contact angle of water are within the above specific ranges can achieve both high corrosion resistance and high hydrophilicity. If the average self-potential value of the precoated fin material is less than +0.040 V with respect to the average self-potential value of the substrate, the corrosion resistance of the precoated fin material may be insufficient. Further, when the contact angle of water on the precoated fin material after being immersed in running water exceeds 40°, the hydrophilicity of the precoated fin material may be insufficient.

(Manufacturing method of precoated fin material)
In producing the precoated fin material,
applying a paint containing the hydrophilic polymer (A) and the cross-linking agent (B) onto at least one surface of the base material;
The resin film may be formed on the substrate by heating the substrate coated with the paint in a heating furnace at a temperature of 240° C. or more and 300° C. or less for 4 seconds or more and 20 seconds or less to bake the paint. .

As the substrate, for example, an aluminum plate can be used. The thickness of the substrate may be, for example, within the range of 0.05 to 0.30 mm. In addition, the base material may be subjected to surface treatment such as chemical conversion treatment before the coating is applied. By subjecting the surface of the substrate to a chemical conversion treatment in advance, it is possible to form a base film on the substrate and improve the adhesion of the resin film.

The paint contains a hydrophilic polymer (A) and a cross-linking agent (B). In addition to these, the paint may contain the above-described additives, solvents, and the like. The method of applying the coating material to the substrate is not particularly limited, and various methods such as bar coater and roll coater can be employed.

After coating the base material with the paint, the base material is heated in a heating furnace at a temperature of 240° C. or higher and 300° C. or lower for 4 seconds or more and 20 seconds or less to bake the paint. Thereby, the resin film can be formed. If the temperature in the heating furnace is lower than the specific range, or if the baking time is shorter than the specific range, the coating will be insufficiently heated and the hydrophilic polymer (A) will not be crosslinked. may be sufficient. As a result, the corrosion resistance of the precoated fin material may deteriorate. Further, when the temperature in the heating furnace is higher than the specific range, the paint is excessively heated, which may lead to deterioration of the resin film.

In paint baking, it is preferable to convect the atmosphere in the heating furnace using a fan with a wind speed of 1 m/s or more and 5 m/s or less. In this case, the paint on the base material can be heated more uniformly, and a resin film excellent in corrosion resistance and hydrophilicity can be more reliably formed.

In the paint baking, it is preferable to heat the base material so that the maximum temperature (Peak Metal Temperature, PMT) of the base material in a dry state is within the range of 170°C or higher and 220°C or lower. In this case, the hydrophilic polymer (A) can be more reliably crosslinked, and a precoated fin material having excellent corrosion resistance and hydrophilicity can be obtained more reliably.

An embodiment of the precoated fin material and its manufacturing method will be described with reference to FIGS. 1 and 2. FIG. The specific aspects of the precoated fin material and the method of manufacturing the same according to the present invention are not limited to the aspects of the examples, and the configuration can be changed as appropriate without departing from the gist of the present invention.

The precoated fin material 1 of this example has a substrate 2 made of aluminum and resin films 3 provided on both sides of the substrate 2, as shown in FIG. A base film 21 is interposed between the substrate 2 and the resin film 3 . The resin film 3 contains a hydrophilic polymer (A) and a cross-linking agent (B).

A. Base material 2
The substrate 2 of this example is an aluminum plate made of A1050 aluminum and having a thickness of 0.1 mm. The surface of the base material 2 is covered with an undercoat film 21 . Specifically, the undercoat film 21 of this example is a chromate film formed by chromate treatment using chromate phosphate. The amount of the chromate film deposited was 20 mg/m ² as the mass of Cr atoms per side of the substrate.

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

The hydrophilic polymer (A1) comprises 30% by mass of the hydrophilic monomer (a1), 42% by mass of the (meth)acrylamide-based monomer (a2), and 20% by mass of the carboxyl group-containing polymerizable unsaturated monomer (a3). ) and 8% by mass of a polymerizable unsaturated monomer (a4). The hydrophilic monomer (a1) in the hydrophilic polymer (A1) is specifically "Blenmer 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 weight of 2-hydroxyethyl acrylate and 2 parts by weight of methylenebisacrylamide.

The hydrophilic polymer (A2) comprises 20% by mass of the hydrophilic monomer (a1), 52% by mass of the (meth)acrylamide-based monomer (a2), and 20% by mass of the carboxyl group-containing polymerizable unsaturated monomer. It is a copolymer of a monomer mixture consisting of (a3) and 8% by mass of a polymerizable unsaturated monomer (a4). The hydrophilic monomer (a1), the carboxyl group-containing polymerizable unsaturated monomer (a3) and the 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. there is

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 volume-based particle size distribution is 50 nm. Moreover, the polystyrene equivalent weight average molecular weights of the hydrophilic polymer (A1) and the hydrophilic polymer (A2) are both 200,000.

The cross-linking agent (B) is an imino group-type methylated melamine resin (“Cymel 701” manufactured by Daicel-Ornex Co., Ltd.).

In this example, as shown in Table 1, nine types of precoated fin materials (test materials S1 to S9) having different mass per unit area of the resin film 3 and different paint baking conditions were prepared. Evaluate the characteristics. The method for producing the test materials S1 to S9 shown in Table 1 is as follows.

C. Production Method First, the hydrophilic polymer (A1) or the hydrophilic polymer (A2) and the cross-linking agent (B) are mixed at the mass ratio shown in Table 1. A paint is prepared by adding pure water to this mixture so that the solid content, that is, the total amount of the hydrophilic polymer (A1), the hydrophilic polymer (A2) and the cross-linking agent (B) is 7% by mass. .

After the coating is applied using a bar coater on the base film 21 of the base material 2 prepared in advance, the coating is pre-dried. After that, the substrate 2 is 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 in the heating furnace is forcibly convected by a fan. Table 1 shows the maximum temperature (PMT) of the substrate in a dry state, which is calculated from the temperature in the furnace and the wind speed of the fan.

After the paint baking is completed, the precoated fin material 1 is taken out from the heating furnace and cooled to room temperature. As described above, the test materials S1 to S9 shown in Table 1 can be obtained.

The test materials R1 to R3 shown in Table 1 are test materials for comparison with the test materials S1 to S9. Test material R1 and test material R2 can be produced in the same manner as test materials S6 to S9, except that the paint baking conditions are changed as shown in Table 1. The test material R3 has the same structure as the test materials S6 to S9, except that it has a resin film consisting only of the hydrophilic polymer (A2). Test material R3 should be prepared in the same manner as test materials S6 to S9 except that the paint was prepared without adding the cross-linking agent (B) and the conditions for baking the paint were changed as shown in Table 1. can be done.

D. Evaluation/Measurement of Potential Difference Between Precoated Fin Material and Base Material A measuring device 4 shown in FIG. 2 is used for measuring the natural potential of the precoated fin material and the base material. The measurement device 4 includes a first container 41 containing a solution for immersing the test piece 5, a second container 42 containing a solution for immersing the reference electrode 6, and the solution in the first container 41. a salt bridge 43 for electrically connecting the solution in the second container 42; a potentiostat 44 for measuring the potential of the test strip 5 with respect to the reference electrode 6; and a recording device 45 .

In measuring the self-potential, first, a rectangular test piece 5 having a length of 40 mm and a width of 10 mm is taken from a test material or base material. A connecting portion 51 to the potentiostat 44 is provided at one end of the test piece 5 in the longitudinal direction, and a square potential measuring portion 52 having a side of 5 mm is provided at the other end. Then, as shown in FIG. 2, an insulating paint 53 is applied to the portions other than the connecting portion 51 and the potential measuring portion 52 .

Separately, a 5% NaCl aqueous solution adjusted to pH 3 using acetic acid is prepared in the first container 41 , and a saturated NaCl aqueous solution is prepared in the second container 42 . Then, the solution in the first container 41 and the solution in the second container 42 are electrically connected via the salt bridge 43 .

Next, the connecting portion 51 of the test strip 5 and the reference electrode 6 are connected to the potentiostat 44, respectively. As the reference electrode 6, for example, an Ag/AgCl electrode can be used.

In this state, the potential measuring part 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 The self-potential of the test piece 5 with reference to 6 can be measured. In this example, the natural potential of the test piece 5 is measured every 3 minutes and recorded in the recording device 45 .

The self-potential of the test piece shows a tendency to gradually decrease with the passage of time from the start of measurement, and reach a generally constant value after 10 hours have passed. In this example, the average value of the self-potential from the start of measurement to the time when one hour has passed is taken as the value of the self-potential of the test material. Table 2 shows the self-potential value of each test material.

Further, the same measurement as described above is performed using the base material 2 before forming the resin film 3 thereon. Then, the average value of the self-potential from the start of the measurement to the time when one hour has passed is taken as the value of the self-potential of the substrate 2 . The natural potential of the base material 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.

For the measurement of the natural potential of the base material 2, the base material 2 prepared by polishing the surface of the precoated fin material 1 and removing the resin film 3 and the base film 21 can also be used.

- Water contact angle A test piece is taken from each test material, and then immersed in running water at a temperature of 25°C and a flow rate of 5 L/min for 10 minutes. 2 μL of pure water is dropped on the surface of the test material taken out from the running water, and the contact angle of water is measured 30 seconds after dropping. Table 2 shows the water contact angle of each test material.

- Mass per unit area of resin film 3 A square test piece with a side of 100 mm is taken from each test material. After measuring the mass W1 (unit: g) of this test piece, the test piece is heated in an electric furnace at 500° C. for 15 minutes. After measuring the mass W2 (unit: g) of the test piece taken out from the electric furnace, the mass reduction amount W1-W2 (unit: g) from before heating is calculated. The mass per unit area of the resin film 3 can be calculated by dividing this mass decrease W1-W2 by the total area S (unit: cm ² ) of the resin film 3 formed on the test piece. . Table 1 shows the mass per unit area of the resin film 3 in each test material.

· Corrosion resistance A rectangular test piece of 100 mm long and 50 mm wide is taken from the test material so that the rolling direction and the longitudinal direction of the base material 2 are parallel. Using this test piece, a salt spray test is carried out by a method conforming to JIS Z2371:2000. The test time shall be 1000 hours. The corrosion area ratio of the test material after the test is calculated, and the rating number is determined by the rating number method of JIS Z2371:2000. A higher rating number indicates better corrosion resistance. Table 2 shows the rating number of each test material.

- Appearance The surface of the test material is visually observed to evaluate the properties of the resin film 3 .

As shown in Table 1, the test materials S1 to S9 had a resin film made of a hydrophilic polymer (A) and a cross-linking agent (B) provided on a substrate. In addition, as shown in Tables 1 and 2, the mass per unit area of the resin film in these test materials, the potential difference with the substrate, and the contact angle of water after immersion in flowing water are within the above-mentioned specific ranges, respectively. . Therefore, these test materials have excellent corrosion resistance and hydrophilicity as shown in Table 2.

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

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

As shown in Table 1, the resin film of test material R3 did not contain the cross-linking agent (B). Therefore, as shown in Table 2, the potential difference between the test material R3 and the substrate is smaller than the specific range. As a result, the corrosion resistance of test material R3 is inferior to that of test materials S1 to S9.

REFERENCE SIGNS LIST 1 precoated fin material 2 base material 3 resin film

Claims (7)

A precoated fin material having a substrate made of aluminum and a resin film provided on at least one surface of the substrate,
The mass per unit area of the resin film is 0.2 g/m ² or more and 2.5 g/m ² or less,
The average value of the self-potential for one hour after the precoated fin material was immersed in the pH 3 5% by mass NaCl aqueous solution was 1 hour after the substrate was immersed in the pH 3 5% by mass NaCl aqueous solution. +0.040 V or more and +0.2 V or less with respect to the average value of the self-potential until the time has passed, and
Having a property that the contact angle of water after immersing the precoated fin material in running water for 10 minutes is 20° or more and 40° or less,
The resin film contains a hydrophilic polymer (A) and a cross-linking agent (B) capable of cross-linking 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 with respect to a total of 100 parts by mass of the hydrophilic polymer (A) and the cross-linking agent (B),
In the hydrophilic polymer (A),
a structural unit derived from a hydrophilic monomer (a1) having one polymerizable double bond and a polyoxyalkylene chain in one 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,
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): 0% by mass A precoated fin material containing at least 50% by mass or less.

(where m and n in the general formula (1) are each independently 0 or 1, R ¹ represents a hydrogen atom or a methyl group, R ² and R ³ each independently represent a hydrogen atom or carbon represents an alkyl group of numbers 1 to 5, and R ⁴ and R ⁵ each independently represent a methylene group or an ethylene group.) 2. The precoated fin material according to claim 1, wherein the hydrophilic polymer (A) is fine particles having a particle size distribution such that the cumulative 50% particle size on a volume basis is 5 nm or more and 1 μm or less. 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. The precoated fin material according to any one of claims 1 to 3, wherein the cross-linking agent (B) is one or more resins selected from the group consisting of amino resins and phenol resins. In the hydrophilic polymer (A), a structural unit derived from the hydrophilic monomer (a1): 5% by mass or more and 45% by mass or less, and a structural unit derived from the (meth)acrylamide-based monomer (a2): 5% by mass or more and 60% by mass or less and a structural unit derived from the carboxyl group-containing polymerizable unsaturated monomer (a3): 5% by mass or more and 35% by mass or less and a structural unit derived from the polymerizable unsaturated monomer (a4) The precoated fin material according to any one of claims 1 to 4, which contains a structural unit of 5% by mass or more and 45% by mass or less. A method for manufacturing a precoated fin material according to any one of claims 1 to 5,
applying a paint containing the hydrophilic polymer (A) and the cross-linking agent (B) onto at least one surface of the base material;
Precoating, wherein the base material coated with the paint is heated in a heating furnace at a temperature of 240° C. or higher and 300° C. or lower for 4 seconds or more and 20 seconds or less to bake the paint, thereby forming the resin film on the base material. A method of manufacturing a fin material. 7. The method of manufacturing a precoated fin material according to claim 6, wherein the atmosphere in the heating furnace is caused to convect using a fan with a wind speed of 1 m/s or more and 5 m/s or less in the paint baking.

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