JP2014199152A - Aluminum fin material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an aluminum fin material capable of inhibiting the formation of low molecular carboxylic acid not only during manufacturing heat exchangers but also at a time of using an air conditioner while applying polyethylene glycol or the like biodegradable to form the low molecular carboxylic acid such as formic acid that is a substance causing ant nest-like corrosion in a copper tube to a hydrophilic film.SOLUTION: An aluminum fin material 10 according to the present invention comprises: an aluminum-based substrate 1; and a hydrophilic film 4 formed on surfaces and containing a compound with an ethylene oxide group as a structural unit. The hydrophilic film 4 further contains an alkaline metal or alkaline earth metal compound that exhibits alkaline property during hydrolysis so that water extracted from the hydrophilic film 4 has a pH 5 or higher.

Description

  The present invention relates to an aluminum fin material for a heat exchanger used for an indoor unit or the like of an air conditioner.

  Heat exchangers are used in various fields such as room air conditioners, packaged air conditioners, refrigeration showcases, refrigerators, oil coolers, and radiators. The heat exchanger is configured, for example, by passing a copper pipe (referring to a pipe made of copper or a copper alloy) through which a heat medium passes through plate-like fins. Generally, aluminum or an aluminum alloy (hereinafter collectively referred to as aluminum) is applied to the fins of the heat exchanger because of its excellent thermal conductivity and workability.

  In the heat exchanger, if dew condensation water during cooling operation accumulates between the fins, it becomes a resistance during blowing and deteriorates the heat exchanger characteristics. Therefore, in order to impart hydrophilicity or water repellency so that condensed water does not accumulate on the fin surface, such fins made of aluminum are subjected to surface treatment before coating the fin (such as a coating film). Hereinafter, it is applied to the fin material). That is, the surface of the fin is made hydrophilic to increase the fluidity of the condensed water, or it is made water-repellent and dropped before the water droplets of the condensed water become large, depending on the use of the heat exchanger and the like. For example, for a heat exchanger mounted on an indoor unit of an air conditioner such as a room air conditioner, it is preferable to use a hydrophilic property in which water uniformly spreads on the fin surface, rather than water repellency in which condensed water is easily scattered. is there. As one of coating film materials imparting hydrophilicity, compounds having an ethylene oxide group as a structural unit, such as polyethylene glycol, are widely used because they also have an effect of imparting lubricity to the surface.

  Here, the coating material is formed by being applied to an aluminum plate as a substrate and baked at a temperature corresponding to the material. However, a compound having an ethylene oxide group as a structural unit decomposes at a high temperature to produce a low molecular carboxylic acid such as formic acid or acetic acid. In the heat exchanger, the low molecular carboxylic acid is added to the copper tube contacting the fin. There is a problem that nesting corrosion occurs, and crazing occurs when it flows out to the drain pan. Therefore, for example, Patent Document 1 discloses an aluminum fin material provided with a hydrophilic film to which a thermal decomposition inhibitor is added so that a low molecular carboxylic acid is not generated even by baking at a high temperature during coating film formation.

JP 2011-208813 A

  In heat exchangers, low-molecular carboxylic acids such as formic acid may be generated when formaldehyde or the like adheres to the fin surface as a VOC and oxidizes in a use environment such as indoors as an air conditioner. Prior art document 1 is not effective for the source.

  The present invention has been made in view of the above-mentioned problems, and has a hydrophilic film to which a compound such as polyethylene glycol having an ethylene oxide group as a structural unit is applied on the fin surface. Aluminum for heat exchangers that can suppress corrosion of copper tubes not only when manufacturing heat exchangers but also when formaldehyde adheres when used as an air conditioner for the purpose of suppressing nest corrosion It is an object to provide a fin material.

  In order to solve the above problems, the present inventors have reached the idea of controlling the pH value of the surface of the aluminum fin material so that the low-molecular carboxylic acid is neutralized. Then, it discovered that the ant nest-like corrosion of the copper pipe was suppressed.

  That is, the aluminum fin material according to the present invention includes a substrate made of aluminum or an aluminum alloy, and a hydrophilic film formed on the surface containing a compound having an ethylene oxide group as a structural unit. The aluminum fin material further contains an alkali metal or alkaline earth metal compound that exhibits alkalinity during hydrolysis so that the water extracted from the hydrophilic film has a pH of 5 or more. It is characterized by.

  In this way, the hydrophilic film is formed by adding a compound that exhibits alkalinity during hydrolysis to control the pH value of the surface, so that low-molecular carboxylic acid is formed by oxidation of formaldehyde and the like attached to the surface. However, even if it adheres as VOC, it is neutralized, so that ant nest corrosion of the copper pipe is suppressed.

  In the aluminum fin material, the hydrophilic film preferably further contains a thermal decomposition inhibitor.

  Thus, the hydrophilic film contains a thermal decomposition inhibitor, so that the generation of low-molecular carboxylic acids is suppressed in high-temperature treatment such as baking during formation or when an aluminum fin material is processed into fins. .

  Moreover, it is preferable that the aluminum fin material according to the present invention further includes a hydrophobic coating on the surface of the substrate.

  Thus, the corrosion resistance of a board | substrate (aluminum) improves by forming a hydrophobic membrane | film | coat on the board | substrate surface.

  In addition, the aluminum fin material according to the present invention may further include an intermediate hydrophilic film whose component is different from that of the hydrophilic film, and at this time, the hydrophilic film is formed on the intermediate hydrophilic film.

  Thus, by providing an intermediate hydrophilic film, the hydrophilicity is compensated, and the hydrophilic film on the outermost surface is a film for mainly imparting lubricity by a compound having an ethylene oxide group as a structural unit. Can do.

  According to the aluminum fin material of the present invention, only a high-temperature treatment at the time of manufacturing the aluminum fin material or assembling the heat exchanger is provided on the surface with a hydrophilic film to which a compound having an ethylene oxide group as a structural unit is applied. In addition, even when used as an air conditioner, a heat exchanger capable of preventing corrosion of a copper pipe even if low molecular carboxylic acid such as formaldehyde or formic acid adheres can be provided.

It is sectional drawing explaining the structure of the aluminum fin material which concerns on this invention, (a), (b), (c), (d) is a schematic diagram of embodiment of this invention.

[Aluminum fin material]
Hereinafter, the form for implement | achieving the aluminum fin material which concerns on this invention is demonstrated.
The aluminum fin material is a plate material before being formed into a fin, and is cut into a predetermined size and formed by press working to be manufactured into a heat exchanger fin. As shown to Fig.1 (a), the aluminum fin material 10 which concerns on this invention is equipped with the hydrophilic film | membrane 4 which is formed in the board | substrate 1 and both surfaces and coat | covers the outermost surface. Hereinafter, for the aluminum fin material and the substrate, the surface on which the hydrophilic film is formed is simply referred to as the surface.

(substrate)
The substrate 1 is formed of aluminum or an aluminum alloy (hereinafter collectively referred to as aluminum) that is applied to a fin material for a normal heat exchanger, and 1000 series aluminum defined by JIS H4000 from the viewpoint of thermal conductivity and workability. Is preferably used, and more preferably, aluminum having an alloy number of 1200 is used. These materials are produced into a plate material having a desired thickness by a known method such as casting, hot rolling, cold rolling, and tempering. The thickness of the substrate 1 is not particularly specified, and may be a thickness that can meet the required thermal conductivity, strength, corrosion resistance, etc. according to the specifications of the heat exchanger to be manufactured. For this, a plate material having a plate thickness of about 0.06 to 0.3 mm is preferably used.

It is preferable that a chemical conversion treatment film (not shown) is formed on the surface of the substrate 1 by chemical conversion treatment. The substrate 1 made of aluminum is given corrosion resistance and improved adhesion with the hydrophilic coating 4 by the chemical conversion coating. The chemical conversion treatment film is made of an inorganic oxide or an organic-inorganic composite compound containing chromium (Cr), zirconium (Zr), or titanium (Ti) as an inorganic substance, and is formed by chemical conversion treatment of the substrate. The chemical conversion treatment film is not particularly limited as long as it imparts corrosion resistance to the substrate 1, and may be appropriately set according to the purpose of use, but the adhesion amount per area is metal (Cr, Zr, Ti) is preferably in the range of 1 to 100 mg / m ² in terms, it is preferable to 1~100nm in thickness.

  The inorganic oxide film applied to the chemical conversion coating is applied to a substrate such as a phosphate chromate treatment, a zirconium phosphate treatment, a zirconium oxide treatment, a chromate chromate treatment, a zinc phosphate treatment, or a phosphate titanate treatment. It is processed and formed on the surface. The organic-inorganic composite compound film is formed by applying a coating type chromate treatment or a coating type zirconium treatment to the substrate, and examples thereof include an acrylic-zirconium composite. Before forming these chemical conversion coatings, it is preferable to degrease the surface of the substrate in advance with an alkaline degreasing solution, thereby improving the reactivity of the chemical conversion treatment and further improving the adhesion of the formed chemical conversion coating. To do.

(Hydrophilic film)
The hydrophilic film 4 contains a hydrophilic resin and is a film that imparts hydrophilicity to the surface of the aluminum fin material 10 according to the present invention, or a film that gradually elutes into water and mainly imparts lubricity. . The hydrophilic film 4 is preferably formed in the aluminum fin material 10 so that the adhesion amount per area is 0.01 to 3 g / m ^2, and the specific gravity of the resin forming the hydrophilic film 4 is 1 Considering the degree, the film thickness is preferably in the range of 0.01 to 3 μm on average. If the hydrophilic coating 4 is too thin, sufficient hydrophilicity or lubricity cannot be obtained. On the other hand, if the hydrophilic coating 4 is too thick, the coating workability at the time of formation is lowered. In particular, the substrate 1 is a coiled aluminum plate (strip material). When it is, formation of a coating film becomes difficult. In addition, since the heat exchange efficiency is reduced when the hydrophilic film 4 mainly made of resin is thick, the aluminum film 10 is formed thin as long as sufficient hydrophilicity and lubricity can be obtained. It is preferable.

Examples of the hydrophilic resin material include polyethylene glycol (PEG, PEO), polyvinyl alcohol (PVA), polyacrylic acid (PAA), carboxymethyl cellulose (CMC), sulfoethyl acrylate, and two or more kinds of single monomers For example, a copolymer of acrylic acid and sulfoethyl acrylate can be used. Furthermore, the hydrophilic film 4 of the aluminum fin material 10 according to the present invention contains a compound (— [CH ₂ —CH ₂ —O] _n —) having an ethylene oxide group as a structural unit as a hydrophilic resin material. Specific examples of such compounds (hereinafter referred to as EO group-containing compounds) include polyalkylene glycol alkyl ethers, polyalkylene glycol aryl ethers, or polyoxyalkylene alkyl ethers in addition to the above polyalkylene glycols such as polyethylene glycol. (AE) or its acetate or sulfate (AES). Since the EO group-containing compound imparts lubricity as well as hydrophilicity, the aluminum fin material 10 according to the present invention may use only the EO group-containing compound as the hydrophilic resin material according to the required properties. One or more hydrophilic resin materials can be mixed and applied to the hydrophilic film 4. In particular, in order to impart lubricity to the surface of the aluminum fin material 10, the hydrophilic film 4 contains 1% by mass of EO group-containing compound (1% by mass ratio (in terms of solid content) in the hydrophilic film 4). Similarly, it is preferable to contain the above.

  In the aluminum fin material 10 according to the present invention, the hydrophilic film 4 is provided with hydrophilicity and lubricity, and the EO group-containing compound contained in the hydrophilic film 4 is thermally decomposed or used as a heat exchanger. When used, formaldehyde and the like adhere and oxidize, thereby neutralizing low molecular carboxylic acids such as formic acid and acetic acid produced. For this purpose, the hydrophilic film 4 is prepared such that it further contains a compound that is hydrolyzed to show alkalinity, and the water extracted from the hydrophilic film 4 has a pH of 5 or more. Thereby, since the aluminum fin material 10 is neutralized even if formaldehyde or a low molecular weight carboxylic acid adheres to the surface as a fin of a heat exchanger in a use environment, it is difficult to cause corrosion in the copper tube.

Examples of such a compound exhibiting alkalinity include alkali metal or alkaline earth metal hydroxides, carbonates, hydrogencarbonates, and phosphates. Alkali metals and alkaline earth metals are Na, K, Li, Ca, Ba, Mg, etc., and these compounds (hereinafter collectively alkali metal compounds) are, for example, sodium hydrogen carbonate (NaHCO ₃ ), phosphoric acid Sodium (Na ₃ PO ₄ ), calcium carbonate (CaCO ₃ ), lithium carbonate (Li ₂ CO ₃ ), barium hydroxide (Ba (OH) ₂ ), and magnesium hydroxide (Mg (OH) ₂ ). These alkali metal compounds hydrolyze and show weak alkalinity. In the hydrophilic film 4, it is particularly effective to apply a neutralized salt of a weak acid having a buffering action as described above. Further, the hydrophilic film 4 may be added by mixing two or more kinds of alkali metal compounds. An amine compound such as ammonia also has a neutralizing action, but it may cause a problem of stress corrosion cracking with respect to the copper pipe, so it is not desirable to apply it to the fin material.

The hydrophilic film 4 only needs to contain a content of alkali metal compound such that the extraction water has a pH of 5 or more. As the hydrophilic film 4 is added in a large amount, the pH can be controlled to a high value, and the neutralizing action is increased. The effect of suppressing corrosion of the copper pipe is improved. On the other hand, the hydrophilic coating 4 contains an alkali metal compound, depending on the processing conditions of the aluminum fin material 10 because the hygroscopicity increases and press workability decreases when an excessive amount of the alkali metal compound is added. The amount is preferably 1 g / m ² or less in terms of the amount of adhesion per area in the aluminum fin material 10. In addition, about the upper limit of the adhesion amount of this alkali metal compound, when the aluminum fin material 10 is provided with the below-mentioned intermediate | middle hydrophilic membrane | film | coat 3 (refer FIG.1 (b)), it manages by the sum total with the intermediate | middle hydrophilic membrane | film | coat 3. To do.

The added amount of the alkali metal compound in the actual hydrophilic film 4 may be prepared, for example, by cutting a test piece from the aluminum fin material 10 and collecting extracted water so that the pH value can be 5 or more. Specifically, the aluminum fin material 10 having the hydrophilic film 4 formed on both sides is cut out into 10 cm × 10 cm (surface area 200 cm ² of the hydrophilic film 4) to make a test piece, and this test piece is subjected to a heat degreasing process of the heat exchanger. After carrying out the assumed heat treatment at 160 ° C. for 10 minutes, it is immersed in 50 ml of ion exchange water at 25 ° C. for 10 minutes, and 30 ml of the supernatant of this ion exchange water can be used as extraction water. Although the upper limit of the pH value of extraction water is not specifically limited, According to the alkali metal compound added, it can rise to about pH12. The pH value of the extracted water is the same even when the hydrophilic film 4 contains other than the hydrophilic resin and the alkali metal compound such as the following thermal decomposition inhibitor.

  In the heat exchanger, the neutralization action of the hydrophilic film 4 of the aluminum fin material 10 according to the present invention is manifested particularly at a site where the fin contacts the copper tube. Condensed water is extremely difficult to enter into this part, and even if the amount of alkali metal compound in the hydrophilic film 4 is very small, the amount of condensed alkali metal compound increases because the amount of condensed water is small. In addition, an environment where it is easy to maintain a pH of 5 or higher can be maintained, and a sufficient neutralizing action can be exhibited over a long period of time.

  The hydrophilic film 4 may further contain a thermal decomposition inhibitor (see Patent Document 1), and particularly contains a thermal decomposition inhibitor when the content of the EO group-containing compound is 75% by mass or more. Is preferred. Since the hydrophilic film 4 contains a thermal decomposition inhibitor, the EO group-containing compound is hardly decomposed during high-temperature treatment such as baking during formation or when the aluminum fin material 10 is processed into fins. Acid generation is suppressed. When the content of the EO group-containing compound exceeds 99.9% by mass, the hydrophilic film 4 is prone to thermal decomposition of the EO group-containing compound, so that a large amount of low-molecular carboxylic acid is generated, resulting in a heat exchanger. In this case, it is particularly preferable to contain a thermal decomposition inhibitor, since it tends to cause ant nest corrosion in the copper tube and may cause crazing in the drain pan. Examples of the thermal decomposition inhibitor include sulfur-based compounds such as diphenyl monosulfide and diphenyl disulfide, phenol-based compounds having a phenol skeleton such as BHT (dibutylhydroxytoluene), and carbazide compounds. Two or more of these may be added. . In the hydrophilic film 4, it is preferable that the content of the thermal decomposition inhibitor is 0.1% by mass or more in order to make the effect sufficient. On the other hand, if the thermal decomposition inhibitor is added excessively, the hydrophilicity of the hydrophilic coating 4 is lowered, so the content is preferably 25% by mass or less.

  As shown in FIG. 1B, the aluminum fin material 10 according to the present invention may further include a hydrophilic film (intermediate hydrophilic film 3) made of another component as a base of the hydrophilic film 4, In other words, the hydrophilic film can have a two-layer structure. In this way, the aluminum fin material 10 is provided with the intermediate hydrophilic film 3 separately from the hydrophilic film 4 on the base, so that the hydrophilic film 4 on the outermost surface is specialized for imparting lubricity, while having intermediate hydrophilicity. The coating 3 also provides sufficient hydrophilicity.

(Intermediate hydrophilic film)
In the aluminum fin material 10 shown in FIG. 1B, the hydrophilic resin material in the hydrophilic film 4 can be applied to the intermediate hydrophilic film 3. The intermediate hydrophilic film 3 may contain an EO group-containing compound. In this case, a thermal decomposition inhibitor may be further added to the extent that the hydrophilicity is not inhibited. An alkali metal compound may be added. In addition, the intermediate hydrophilic film 3 has a film thickness and an adhesion amount per area according to the range for the hydrophilic resin 4 described above, but the total with the hydrophilic resin 4, that is, two layers should be 5 μm or less. Is preferable in terms of heat exchange efficiency. Furthermore, when the aluminum fin material 10 includes the intermediate hydrophilic film 3, the film thickness of the outermost hydrophilic film 4 is set so that the effect (hydrophilicity) is easily exhibited on the surface of the aluminum fin material 10. It is more preferable to reduce the thickness within the aforementioned range.

  Furthermore, when the aluminum fin material 10 according to the present invention includes an intermediate hydrophilic film 3 on the surface of the substrate 1, that is, between the substrate 1 and the hydrophilic film 4, as shown in FIGS. 1 (c) and (d). It is preferable to provide a hydrophobic film 2 made of a hydrophobic resin between the substrate 1 and the intermediate hydrophilic film 3. The substrate 1 made of aluminum is not only formed with a chemical conversion treatment film, but is further coated with a hydrophobic film 2 to further improve the corrosion resistance of the aluminum fin material 10.

(Hydrophobic film)
The hydrophobic film 2 is a film made of a hydrophobic resin that coats the surface of the substrate 1 in order to impart corrosion resistance to the substrate 1 (aluminum fin material 10) made of aluminum. It is formed by applying to the material surface. Examples of the hydrophobic resin used in the paint include various resins such as polyester, polyolefin, epoxy, and urethane, and a mixture of one or more of these resins is used. The thickness of the hydrophobic coating 2 is not particularly limited, but in order to give the substrate 1 sufficient corrosion resistance, the amount of adhesion per area is preferably 0.01 g / m ² or more, and 0.05 g / m ^2. The above is more preferable. On the other hand, like the hydrophilic film 4, since the hydrophobic coating 2 made of resin is reduced the efficiency of a thick heat exchange, preferably 8 g / m ² or less at a coverage, 4g / m ² or less is more preferable. The film thickness is preferably 0.1 to 3 μm.

[Method of manufacturing aluminum fin material]
The aluminum fin material 10 according to the present invention is manufactured by applying a coating for forming the hydrophilic film 4 on the surface of the substrate 1 subjected to the chemical conversion treatment, and drying it by natural drying or warm air (by baking treatment). can do. Further, before forming the hydrophilic film 4, the intermediate hydrophilic film 3 may be formed in the same manner, or the hydrophobic film 2 may be formed by applying a hydrophobic resin paint to the surface of the substrate 1. Good. In the case of providing the intermediate hydrophilic film 3, the aluminum fin material 10, after the intermediate hydrophilic film 3 is formed (baked), the surface is washed with water, and then the outermost hydrophilic film 4 is formed. It is preferable to form (apply paint). When a hydrophilic undercoat such as the intermediate hydrophilic coat 3 is provided, it is easy to form a coated surface uniformly in the top coat by washing with water and removing the water-soluble component of the undercoat. The adhesion of the top coat film (hydrophilic film 4) is improved. Furthermore, when the intermediate hydrophilic film 3 is baked and a low molecular organic acid is generated by thermal decomposition, it has an effect of removing it as a water-soluble component.

  For the hydrophilic film 4, or further, the intermediate hydrophilic film 3 and the hydrophobic film 2, a paint for forming the film is prepared, applied to the object to be coated (substrate 1) by a bar coater, a roll coating method, or the like, and baked. Formed. In particular, if the substrate 1 is a coiled aluminum plate, it is preferable in terms of productivity to apply a roll coater or the like and continuously perform degreasing, painting, heating, winding, and the like.

  The coating material that forms each of the hydrophilic film 4 and the intermediate hydrophilic film 3 is not limited to the above components such as the resin, and various water-based coatings are used to improve paintability, workability, and coating film properties. Solvents and paint additives may be added, for example, water-soluble organic solvents, crosslinking agents, surfactants, surface conditioners, wetting and dispersing agents, anti-settling agents, antioxidants, antifoaming agents, rust inhibitors, Various solvents and additives such as antibacterial agents and fungicides may be added alone or in combination.

  As mentioned above, although the form for implementing this invention was described, the Example which confirmed the effect of this invention is demonstrated concretely compared with the comparative example which does not satisfy | fill the requirements of this invention below. In addition, this invention is not limited to this Example.

[Production of test materials]
(Substrate, chemical conversion treatment)
A JIS H4000 A1200 aluminum plate having a thickness of 0.10 mm was applied as a substrate in the test material of the aluminum fin material. The surface of this substrate is degreased with an alkaline agent (Surf Cleaner (registered trademark) EC370, manufactured by Nippon Paint Co., Ltd.), and Alsurf (registered trademark) 401KB-2 / 45KB manufactured by Nippon Paint Co., Ltd. is used as a chemical conversion treatment solution. An acid chromate treatment was applied to form a chemical conversion coating. The Cr conversion value of the chemical conversion film measured with a wavelength dispersive X-ray fluorescence apparatus (manufactured by Shimadzu Corporation, LAB CENTER XRF-1800) was 20 mg / m ² , and the film thickness was about 20 nm.

  A hydrophobic film, an intermediate hydrophilic film, and a hydrophilic film are formed on both surfaces of the substrate in the types and combinations shown in Table 1 to provide the aluminum fin material shown in FIGS. A sample was prepared. The specimens not provided with the hydrophobic film and the intermediate hydrophilic film are indicated by “-” in each column of Table 1.

(Formation of hydrophobic film)
The following resin paint, which is appropriately diluted so that the solid content concentration becomes 10%, is applied to the substrate with a bar coater, baked at a substrate reaching temperature of about 220 ° C. in a hot air drying furnace, air-cooled, A hydrophobic film having a thickness of about 1 μm was formed.

(Hydrophobic resin)
Urethane: Urethane-modified resin emulsion, manufactured by Toho Chemical Co., Ltd., Hitech (registered trademark) S-6254
Epoxy system: Water-based epoxy resin, heat curing type, anion system, manufactured by ADEKA CORPORATION, Ajika Resin (registered trademark) EM series EM-0434AN
Acrylic: Polyacrylic acid ester copolymer, manufactured by Nippon Pure Chemical Co., Ltd., Jurimer (registered trademark) AT-210

(Formation of intermediate hydrophilic film)
A resin coating of the type shown in Table 1 was mixed with the formulation shown in Table 1 so that the total solid content concentration was 10%, and appropriately diluted with a bar coater in the same manner as in the formation of the hydrophobic resin. It was applied to the substrate, baked at a substrate reaching temperature of about 220 ° C. in a hot air drying furnace, washed with water, and the elution was removed while cooling to form an intermediate hydrophilic film having a thickness of about 0.5 μm.

(Formation of hydrophilic film)
As a resin coating for the hydrophilic film, a hydrophilic resin aqueous solution was prepared as follows. First, sodium polyacrylate and sodium carboxymethyl cellulose are based on an aqueous solution having an equal solid content (each solid content concentration of 10%), and the EO group-containing compounds of the types shown in Table 1 are added to the aqueous solution. To 1%. To this aqueous solution, an alkali metal compound having the type shown in Table 1 and a solid content concentration in the aqueous solution was added. Furthermore, about the test material which described the kind of thermal decomposition inhibitor in Table 1, the kind of thermal decomposition inhibitor is made into hydrophilic resin aqueous solution so that content in a hydrophilic membrane | film | coat may be 0.5 mass%. Added.

  The prepared hydrophilic resin aqueous solution was applied to the substrate with a bar coater in the same manner as the formation of the hydrophobic resin and the like, baked at a substrate reaching temperature of 200 ° C. in a hot air drying furnace, air-cooled, and a film thickness of about 0. A 5 μm hydrophilic film was formed to prepare a test material.

  The following were used for the hydrophilic resin material of the hydrophilic film and the intermediate hydrophilic film, the EO group-containing compound of the hydrophilic film, and the thermal decomposition inhibitor.

(Hydrophilic resin)
Sodium polyacrylate (PAANA): manufactured by Toa Gosei Co., Ltd., Aron A-20L (registered trademark)
Sodium carboxymethyl cellulose (CMCNa): Serogen 7A (registered trademark), manufactured by Daiichi Kogyo Seiyaku Co., Ltd.
Acrylic acid / sulfonic acid monomer copolymer salt (AASF): manufactured by Nippon Shokubai Co., Ltd., Aquaric (registered trademark) GL
Polyethylene glycol (PEG): manufactured by Sanyo Chemical Industries, PEG-6000S (registered trademark)

(EO group-containing compound)
Polyethylene glycol (PEG): manufactured by Sanyo Chemical Industries, PEG-6000S (registered trademark)
Polyoxyethylene alkyl ether (AE): Nippon Emulsifier Co., Ltd., New Coal NT-12 (registered trademark)
Polyoxyalkylene ether sulfate (AES): manufactured by Lion Corporation, Sannol (registered trademark) PP-2030

(Pyrolysis inhibitor)
Carbazide compound: MS-3000 (registered trademark), manufactured by Meisei Chemical Co., Ltd.
Phenol compound: Dibutylhydroxytoluene, manufactured by Kanto Chemical Co., Inc.

(PH value of extracted water from hydrophilic film)
The specimen was cut into 10 cm × 10 cm to form a test piece, and this test piece was subjected to a heat treatment at 160 ° C. for 10 minutes assuming a heat degreasing process of a heat exchanger. The heat-treated test piece was immersed in 50 ml of ion exchange water at 25 ° C. for 10 minutes, and 30 ml of the supernatant was used as extraction water. The pH of this extracted water was measured and shown in Table 1.

[Evaluation]
About the produced test material, the surface hydrophilicity, corrosion resistance, and the inhibitory effect of the ant nest-like corrosion with respect to copper were evaluated.

(Hydrophilic)
As a hydrophilic index, the water contact angle at room temperature was measured. The test material was heated at 160 ° C. for 10 minutes and subjected to heat treatment equivalent to heat degreasing, and then immersed in ion-exchanged water for 24 hours and dried at room temperature. This test material was placed horizontally with the evaluation surface on top, about 0.5 μL of pure water was dropped on the surface, and the contact angle was measured with a goniometer. A contact angle of 50 ° or less is shown in Table 1, with “合格” indicating that the hydrophilicity is acceptable, 20 ° or less being excellent, and “◯” indicating that the contact angle exceeds 20 ° and 50 ° or less is good. Those with a contact angle exceeding 50 ° are shown as “x” in Table 1 as rejected.

(Corrosion resistance)
Corrosion resistance was evaluated based on the degree of corrosion of the specimen after a salt spray test according to JIS Z2371 for 480 hours. A 5 mass% sodium chloride aqueous solution was used as the spray solution, the spray environment temperature was 35 ° C., the spray amount was 80 cm ² , and the amount was 1.5 ml per hour. The numerical value is quantified in accordance with the rating number method for quantifying the degree of corrosion by the corrosion area ratio. The rating number is 9.0 or higher, and 9.5 or higher is excellent. Table 1 shows that less than 5 is good and is “◯”. Moreover, it shows in Table 1 by "x" by making less than 9.0 disqualified.

(Inhibiting effect of ant nest corrosion on copper)
In order to evaluate the inhibitory effect of ant nest-like corrosion on copper, ion-exchanged water (extracted water) immersed in a test material used for measurement of the pH value of extracted water from the hydrophilic film was used. A phosphorus deoxidized copper tube (smooth tube O material) having a diameter of 9.52 mm, a wall thickness of 0.23 mm, and a length of 100 mm is immersed in the extracted water, and a container containing these is further sealed in a sealed container having a volume of 1 liter. And stored at room temperature (20 ° C.) for 20 days. Then, the gas-liquid boundary part cross section of a copper pipe is observed, and what has a through-hole is set as "x" as a rejection, and what passed through a through-hole is set as "(circle)" in Table 1.

  As shown in Table 1, the test material No. In Nos. 1 to 11, the outermost hydrophilic film was prepared such that the pH value of the extracted water was 5 or more by addition of an alkali metal compound. Since 5, 6 and 10 were added with a thermal decomposition inhibitor, in addition to the original hydrophilicity, an inhibitory effect of ant nest corrosion on the copper tube was obtained. The test material No. No. 5 had a relatively small amount of alkali metal compound (sodium hydrogen carbonate) added, but the pH value was also increased by the carbazide compound added as a thermal decomposition inhibitor, so the range of the present invention was satisfied. Furthermore, sample No. 6-8, 10 and 11 showed particularly excellent hydrophilicity by providing an intermediate hydrophilic film. In addition, the sample No. provided with a hydrophobic coating on the substrate surface. 9 to 11 were particularly excellent in corrosion resistance.

  On the other hand, the hydrophilic film does not contain an alkali metal compound, or the content is small, and the test sample No. Nos. 12 to 22 have good hydrophilicity and corrosion resistance, but lead to generation of through-holes in the copper pipe with the respective extracted water, and it can be said that the effect of suppressing ant nest corrosion of the copper pipe is insufficient.

10 Aluminum fin material 1 Substrate 2 Hydrophobic film 3 Intermediate hydrophilic film 4 Hydrophilic film

Claims (4)

An aluminum fin material comprising a substrate made of aluminum or an aluminum alloy, and a hydrophilic film formed on the surface and containing a compound having an ethylene oxide group as a structural unit,
The hydrophilic film further contains an alkali metal or alkaline earth metal compound that exhibits alkalinity during hydrolysis so that the water extracted from the hydrophilic film has a pH of 5 or more. .   The aluminum fin material according to claim 1, wherein the hydrophilic film further contains a thermal decomposition inhibitor.   The aluminum fin material according to claim 1, further comprising a hydrophobic film on a surface of the substrate.   The component according to any one of claims 1 to 3, further comprising an intermediate hydrophilic film whose component is different from the hydrophilic film, wherein the hydrophilic film is formed on the intermediate hydrophilic film. Aluminum fin material.

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