JP7503449B2 - Pre-coated fin material - Google Patents

Description

The present invention relates to precoated fin materials.

The so-called cross fin tube type heat exchanger, which has many fins and tubes that cross these fins, is widely used as a heat exchanger installed in air conditioners, refrigerators, etc. The fins are made by pressing a precoated fin material that has a substrate made of aluminum (including pure aluminum and aluminum alloys; the same applies below) and a resin coating formed on the substrate.

When the surface temperature of the fins falls below the dew point of the air while an air conditioner or other device is operating, condensation may form on the surface of the fins, causing the gaps between the fins to become blocked by the condensed water. If the gaps between the fins become blocked, this may lead to a decrease in the heat exchange efficiency of the heat exchanger.

To address this problem, a technique is known that increases the hydrophilicity of the fin surface to prevent the gaps between the fins from being blocked by condensed water. For example, Patent Document 1 describes a hydrophilic treatment composition for heat exchanger fin materials that contains (A) at least one polymer selected from polyglycerin and polyvinyl alcohol, (B) a high acid value acrylic resin having a resin acid value of 300 mgKOH/g or more, and (C) a water-soluble resin other than the polymer (A) and the high acid value acrylic resin (B), and that is characterized in that the resin solid content of the hydrophilic treatment composition has a resin acid value of 200 mgKOH/g or more and a hydroxyl value of 100 mgKOH/g or more.

JP 2002-38134 A

However, if condensation water adheres to the surface of the fins while the heat exchanger is in use, the hydrophilic substances in the resin film are washed away by the condensation water, gradually reducing the hydrophilicity of the fin surface. Furthermore, as the heat exchanger is used, oily contaminants present in the environment, such as higher fatty acids and higher alcohols, adhere to the fin surface. These contaminants may reduce the hydrophilicity of the fin surface.

As such, conventional fins have the problem that their hydrophilicity gradually decreases during use of the heat exchanger due to the reduction of hydrophilic substances caused by condensation water and the adhesion of oily contaminants.

The present invention was made in view of this background, and aims to provide a precoated fin material that can maintain excellent hydrophilicity for a long period of time and from which oily contaminants adhering to the surface can be easily removed.

One aspect of the present invention is a substrate made of aluminum;
A resin coating film formed on the substrate and exposed on the surface,
The resin coating film is
A modified polyvinyl alcohol (A) having a molecular structure represented by the following general formula (1),
An acrylamide polymer (B),
the total content of the modified polyvinyl alcohol (A) and the acrylamide-based polymer (B) is 85 parts by mass or more relative to 100 parts by mass of the entire resin coating film,
The content of the modified polyvinyl alcohol (A) is, in terms of mass ratio, 0.5 to 2.0 times the content of the acrylamide-based polymer (B).
Found in pre-coated fin material.

In the general formula (1), R ¹ is an organic group having a linear structure and having 5 to 10 carbon atoms, and m and n are positive integers satisfying the relationship 0.005≦n/m≦0.025.

The surface of the precoated fin material is provided with a resin coating containing the specific modified polyvinyl alcohol (A) and an acrylamide-based polymer (B). The resin coating uses the specific modified polyvinyl alcohol (A) and has a mass ratio of the polyvinyl alcohol (A) to the acrylamide-based polymer (B) within the specific range, thereby increasing the hydrophilicity of the surface of the precoated fin material and maintaining excellent hydrophilicity for a long period of time.

In addition, the surface of the precoated fin material is not only hydrophilic but also oil-repellent, which makes it possible to suppress adhesion of oily contaminants to the surface of the precoated fin material. Furthermore, since the precoated fin material is both hydrophilic and oil-repellent, condensed water and the like can easily get between the surface of the precoated fin material and the contaminants attached to the surface. Therefore, even if oily contaminants adhere to the surface of the precoated fin material, the contaminants can be washed away by moisture such as condensed water and easily removed from the surface of the fin.

As described above, the precoated fin material can maintain excellent hydrophilicity for a long period of time, and oily contaminants adhering to the surface can be easily removed.

A partially enlarged cross-sectional view showing the main parts of test materials 1 to 3 in the examples. A partially enlarged cross-sectional view showing the main parts of test material 4 and test material 5 in the examples.

In the precoated fin material, the aluminum constituting the substrate can be appropriately selected from pure aluminum and aluminum alloys depending on the desired mechanical properties, corrosion resistance, etc. The substrate may be made of pure aluminum having a chemical composition represented by an alloy number such as 1200 or 1050 in JIS H4000, for example.

A resin coating film containing modified polyvinyl alcohol (A) and an acrylamide polymer (B) is formed on the substrate. The resin coating film may be laminated directly on the substrate, or another film or coating film may be interposed between the substrate and the resin coating film.

For example, the precoated fin material may further have a base coating laminated on the substrate. Depending on the material, the base coating can have the effect of improving the adhesion between the substrate and the corrosion-resistant coating, improving the corrosion resistance of the substrate, etc.

As the base coating, for example, a coating obtained by chemical coating treatment such as a chromate treatment such as chromate phosphate, or a non-chromate treatment using compounds other than chromium compounds such as titanium phosphate, zirconium phosphate, molybdenum phosphate, zinc phosphate, or zirconium oxide, a so-called chemical conversion treatment, can be used.

The above-mentioned chemical conversion treatment method includes a reactive type and a coating type, and either method may be used. The amount of the base coating can be appropriately selected from a range of, for example, 100 mg/ ^m2 or less in terms of the metal content. The amount of the base coating can be measured by a fluorescent X-ray analyzer.

The precoated fin material may further have a corrosion-resistant coating film interposed between the substrate and the resin coating film. The corrosion-resistant coating film may contain, for example, one or more resins selected from the group consisting of acrylic resins, epoxy resins, urethane resins, and ester resins. Corrosion-resistant coating films containing these resins can further improve the corrosion resistance of the fin.

The thickness of the corrosion-resistant coating can be set appropriately, for example, within the range of 0.3 μm to 5.0 μm. By setting the thickness of the corrosion-resistant coating within the above-mentioned specific range, it is possible to fully obtain the effect of improving the corrosion resistance of the fin while avoiding the deterioration of heat dissipation performance due to the corrosion-resistant coating.

The resin coating film provided on the surface of the precoated fin material contains modified polyvinyl alcohol (A) and an acrylamide-based polymer (B). The resin coating film may have a hydrophilic layer that contains modified polyvinyl alcohol (A) and an acrylamide-based polymer (B) and is interposed between the lubricating layer and the substrate. By forming such a hydrophilic layer within the resin coating film, the hydrophilicity and oil repellency of the surface of the precoated fin material can be increased and these properties can be maintained for a long period of time.

The thickness of the resin coating can be set appropriately, for example, within the range of 0.3 μm or more and 2.0 μm or less. By making the thickness of the resin coating 0.3 μm or more, the hydrophilicity of the surface of the precoated fin material is increased, and contaminants adhering to the surface of the fin can be more easily removed from the surface of the fin. In addition, by making the thickness of the resin coating 2.0 μm or less, the applicability of the paint when forming the resin coating can be improved.

The modified polyvinyl alcohol (A) in the resin coating has a molecular structure in which some of the hydroxyl groups in the polyvinyl alcohol are modified by an organic group having a hydroxyl group at the end. Specifically, the modified polyvinyl alcohol (A) has a molecular structure represented by the following general formula (1).

In the general formula (1), R ¹ is an organic group having a linear structure and having 5 to 10 carbon atoms, and m and n are positive integers satisfying the relationship 0.005≦n/m≦0.025.

The modified polyvinyl alcohol (A) modified with the specific organic group has a relatively bulky organic group introduced into the side chain, so it is less likely to crystallize than unmodified polyvinyl alcohol. Therefore, by blending modified polyvinyl alcohol (A) into the resin coating, it is possible to suppress the formation of hydrogen bonds and maintain the hydrophilicity and oil repellency of the surface of the precoated fin material for a long period of time.

From the viewpoint of further enhancing the above-mentioned action and effect, R ¹ in the general formula (1) is preferably an organic group containing a plurality of methylene groups and one or more carbonyl groups, and more preferably an organic group containing a plurality of methylene groups and two or more carbonyl groups.

When R ¹ in the general formula (1) is an organic group containing a carbonyl group, the position of the carbonyl group may take various forms. For example, the carbonyl group may form an ester bond (-O-CO-) together with an oxygen atom bonded to the main chain of the polyvinyl alcohol. The carbonyl group may be present between methylene groups (-CH ₂ -CO-CH ₂ -). Furthermore, the carbonyl group may form a carboxyl group (-CO-OH) together with a hydroxyl group at the end of the side chain.

The content of polyvinyl alcohol (A) in the resin coating is 0.5 to 2.0 times that of the acrylamide polymer (B) in terms of mass ratio. By setting the ratio of polyvinyl alcohol (A) to acrylamide polymer (B) within the above-mentioned specific range, the hydrophilicity and oil repellency of the surface of the precoated fin material can be maintained for a long period of time. If the ratio of polyvinyl alcohol (A) to acrylamide polymer (B) is outside the above-mentioned specific range, the resin coating may deteriorate relatively early during use of the heat exchanger, resulting in a decrease in hydrophilicity and oil repellency.

From the viewpoint of maintaining excellent hydrophilicity and oil repellency for a long period of time, the content of polyvinyl alcohol (A) is preferably 0.7 to 1.9 times the content of acrylamide polymer (B), and more preferably 1.0 to 1.6 times.

As the acrylamide-based polymer (B) in the resin coating film, for example, a homopolymer such as polyacrylamide or polymethacrylamide, in which (meth)acrylamide or its derivatives are used as monomers, a copolymer in which two or more compounds selected from the group consisting of (meth)acrylamide and its derivatives are used as monomers, or a copolymer in which one or more compounds selected from the group consisting of (meth)acrylamide and its derivatives are used as monomers with other compounds, can be used. The resin coating film may contain one or more of these homopolymers and copolymers as the acrylamide-based polymer (B).

As the acrylamide-based polymer (B), it is preferable to use a homopolymer of a primary amide or a secondary amide, or a copolymer containing a primary amide or a secondary amide as a monomer. These homopolymers and copolymers contain a primary amide group or a secondary amide group that has high polarity. Therefore, by using these homopolymers and copolymers as the acrylamide-based polymer (B), the hydrophilicity of the resin coating film can be increased, and contaminants can be more easily removed from the fin surface. From this perspective, it is particularly preferable to use polyacrylamide as the acrylamide-based polymer (B).

The acid value of the acrylamide polymer (B) is preferably 20 mgKOH/g or more and 100 mgKOH/g or less. By using an acrylamide polymer (B) having an acid value in the above-mentioned specific range, it is possible to maintain excellent hydrophilicity and oil repellency for a longer period of time. As a result, contaminants adhering to the surface of the fin can be easily removed from the surface of the fin, and the ability to remove contaminants can be maintained for a longer period of time.

From the viewpoint of maintaining the ability to remove pollutants for a longer period of time, it is more preferable that the acid value of the acrylamide-based polymer (B) is 40 mgKOH/g or more. On the other hand, from the viewpoint of further enhancing the ability to remove pollutants, it is more preferable that the acid value of the acrylamide-based polymer (B) is 90 mgKOH/g or less.

In addition to the essential components polyvinyl alcohol (A) and acrylamide polymer (B), the resin coating may contain other optional components. When the resin coating contains optional components, the total content of the modified polyvinyl alcohol (A) and the acrylamide polymer (B) can be appropriately set within a range of, for example, 85 parts by mass or more when the mass of the entire resin coating is 100 parts by mass. In this case, the amount of polyvinyl alcohol (A) and acrylamide polymer (B) in the resin coating can be sufficiently large. As a result, the effects of the optional components can be obtained while maintaining excellent hydrophilicity and oil repellency.

The resin coating may contain polyethylene glycol as an optional component.

Polyethylene glycol floats to the surface of the hydrophilic layer during the formation of the resin coating film, and can form a lubricating layer. The polyethylene glycol exposed on the surface of the resin coating film functions as a lubricant that reduces friction between the precoated fin material and the press die when the precoated fin material is press-processed, and can improve processability during press processing.

The content of polyethylene glycol in the resin coating is preferably 1.5 parts by mass or more and 8 parts by mass or less per 100 parts by mass of the resin coating. By making the content of polyethylene glycol 1.5 parts by mass or more, it is possible to further reduce friction between the precoated fin material and the mold during press processing. From the viewpoint of further reducing friction between the precoated fin material and the mold during press processing, it is preferable to make the content of polyethylene glycol 2.0 parts by mass or more, and more preferably 2.5 parts by mass or more.

In addition, by setting the polyethylene glycol content to 8 parts by mass or less, the surface roughness of the precoated fin material can be reduced, making it more difficult for contaminants to adhere to the fin surface. From the viewpoint of making the surface of the precoated fin material smoother and more effectively suppressing the adhesion of contaminants to the fin surface, it is preferable to set the polyethylene glycol content to 7 parts by mass or less, and more preferably to 5 parts by mass or less.

The number average molecular weight of the polyethylene glycol is preferably within the range of 1,000 to 20,000. In this case, the lubricity during press processing can be improved and adhesion of contaminants to the fin surface can be more effectively suppressed.

The resin coating may contain, as an optional component, a crosslinking agent for making the crystal structure of the modified polyvinyl alcohol (A) denser. By adding a crosslinking agent to the resin coating, the hardness of the resin coating can be increased and adhesion of dust can be more effectively suppressed. As the crosslinking agent, for example, a melamine resin or a blocked isocyanate compound can be used. These compounds may be used alone or in combination of two or more kinds.

The resin coating may further contain at least one of an antibacterial agent and an antifungal agent as an optional component, or both may be added. An antibacterial/antifungal agent having both antibacterial and antifungal properties may also be added to the resin coating. By adding a compound having at least one of an antibacterial and antifungal property to the resin coating, corrosion of the resin coating can be suppressed, and the effect of the resin coating can be maintained for a longer period of time.

Examples of compounds with antibacterial and antifungal properties include organic antibacterial and antifungal agents such as isothiazolinone-based antibacterial and antifungal agents, aldehyde-based antibacterial and antifungal agents, benzimidazole-based antibacterial and antifungal agents, halogen-based antibacterial and antifungal agents, carboxylic acid-based antibacterial and antifungal agents, sulfamide-based antibacterial and antifungal agents, thiazole-based antibacterial and antifungal agents, triazole-based antibacterial and antifungal agents, phenol-based antibacterial and antifungal agents, phthalimide-based antibacterial and antifungal agents, naphthenic acid-based antibacterial and antifungal agents, and pyridine-based antibacterial and antifungal agents, as well as inorganic antibacterial and antifungal agents such as Ag, Cu, and Zn.

As the antibacterial and antifungal agent, it is preferable to use at least one of zinc pyrithione, 2,3,5,6-tetrachloro-4-(methylsulfonyl)-pyridine, and 2-(4-thiazolyl)benzimidazole. These compounds have little effect on the physical properties of the resin coating film, are insoluble in water, and are highly stable against heat. Therefore, by adding these compounds to the resin coating film, the antibacterial and antifungal effects can be maintained for a long period of time.

The resin coating may contain, as an optional component, fluororesin particles made of a fluororesin having a perfluoroalkyl group and having a median diameter of 1 μm or more and 4 μm or less on a volume basis. At least a portion of the fluororesin particles in the resin coating are disposed on the surface of the hydrophilic layer described above, and function as a lubricant together with polyethylene glycol during press processing. By setting the median diameter of the fluororesin particles within the specific range, it is possible to further reduce the lubricity during press processing. From the viewpoint of more reliably achieving such an effect, it is preferable that the content of the fluororesin particles is 2 parts by mass or more and 5 parts by mass or less per 100 parts by mass of the resin coating.

The median diameter of the fluororesin particles on a volume basis is specifically the cumulative 50% diameter in the particle size distribution obtained by the laser diffraction/scattering method.

The fluororesin particles may be made of, for example, fully fluorinated resins such as polytetrafluoroethylene (i.e., PTFE), partially fluorinated resins such as polyvinylidene fluoride (i.e., PVDF) and polyvinyl fluoride (i.e., PVF), and fluorinated resin copolymers such as tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (i.e., PFA) and ethylene-tetrafluoroethylene copolymer (i.e., ETFE). The fluororesin particles may be made of one type of particles made of these fluororesins, or two or more types may be used in combination.

The fluororesin particles are preferably made of a fluororesin having perfluoroalkyl groups. In this case, the lubricity during press processing can be improved.

The precoated fin material can be produced, for example, by applying a paint containing modified polyvinyl alcohol (A) and an acrylamide-based polymer (B) onto a substrate, and then heating and drying the paint. In the process of drying the paint, the modified polyvinyl alcohol (A) and the acrylamide-based polymer (B) settle to the substrate side, forming a hydrophilic layer. At this time, since the modified polyvinyl alcohol (A) has low compatibility with the acrylamide-based polymer (B), a phase containing modified polyvinyl alcohol (A) and a phase containing acrylamide-based polymer (B) are formed in the hydrophilic layer in a phase-separated state. Both of these phases are exposed on the surface of the hydrophilic layer.

The phase containing modified polyvinyl alcohol (A) can exhibit excellent oil repellency derived from modified polyvinyl alcohol (A). Furthermore, in the phase containing modified polyvinyl alcohol (A), the formation of hydrogen bonds between hydroxyl groups contained in modified polyvinyl alcohol (A) is suppressed due to steric hindrance of the organic group introduced into the side chain. Therefore, a relatively large number of hydroxyl groups that have not formed hydrogen bonds can be exposed on the surface of the phase containing modified polyvinyl alcohol (A), thereby increasing the hydrophilicity of the surface of the hydrophilic layer.

In addition, in the phase containing the acrylamide-based polymer (B), excellent hydrophilicity derived from the acrylamide-based polymer (B) can be expressed. Therefore, the hydrophilic layer containing the modified polyvinyl alcohol (A) and the acrylamide-based polymer (B) can achieve both excellent hydrophilicity and oil repellency.

The precoated fin material is used, for example, in the manufacture of a heat exchanger as follows. First, the precoated fin material is cut to the desired dimensions to produce fins. The obtained fins are subjected to an appropriate combination of slit processing, louver molding, and collar processing using a press machine to form slits, louvers, and collars. Then, multiple fins are arranged at a predetermined interval from each other, and a metal tube is attached so as to pass through the multiple fins and allow the refrigerant to flow. Then, an expansion plug is inserted into the metal tube to expand the outer diameter of the metal tube, thereby bringing the metal tube and the fins into close contact with each other. In this way, a heat exchanger can be obtained. The heat exchanger can be incorporated, for example, into an indoor unit or outdoor unit of an air conditioner.

An example of the precoated fin material will be described with reference to FIG. 1. As shown in FIG. 1, the precoated fin material 1 of this example has a substrate 2 made of aluminum and a resin coating film 3 formed on the substrate 2 and exposed on the surface. The resin coating film 3 contains a modified polyvinyl alcohol (A) having a molecular structure represented by the general formula (1) above, and an acrylamide polymer (B). The content of the modified polyvinyl alcohol (A) is 0.5 to 2.0 times the content of the acrylamide polymer (B) in terms of mass ratio. Below, a more specific example of the precoated fin material of this example will be described together with its manufacturing method.

Test material 1 to test material 3
Test materials 1 to 3 shown in Table 1 can be prepared by the following method. First, a substrate 2 is prepared. As the substrate 2, a plate material made of aluminum may be used as it is, or a plate material on which a base coating has been formed in advance by chemical conversion treatment may be used. Specifically, the substrate 2 used for the test materials 1 to 3 is an aluminum plate having a thickness of 0.1 mm, which is made of aluminum having a chemical composition represented by alloy number 1050 in JIS H4000 and has been subjected to tempering represented by quality symbol H26 in JIS H0001. The substrate 2 has been subjected to chemical conversion treatment using a chromate phosphate solution, and both sides of the substrate 2 are provided with a base coating 21 made of chromate phosphate.

Next, prepare a paint containing modified polyvinyl alcohol (A) and acrylamide polymer (B) in the mass ratio shown in Table 1. In Table 1, "polyvinyl alcohol" is abbreviated to "PVA" and "acrylamide polymer" is abbreviated to "PAM."

The modified polyvinyl alcohol (A) used in test materials 1 to 3 has a molecular structure represented by the following structural formula (2).

In the structural formula (2), ^R2 is a linear organic group having 7 carbon atoms and containing both a methylene group and a carbonyl group, and m and n are positive integers satisfying the relationship 0.005≦n/m≦0.025.

The acid value of the acrylamide polymer (B) used in test materials 1 to 3 is 50 mg KOH/g, and the weight average molecular weight in polystyrene equivalent is 300,000.

After applying the aforementioned paint to the substrate 2 using a bar coater, the paint is heated at a temperature of 225°C for 10 seconds to dry. In this manner, a resin coating film 3 is formed on the substrate 2, and test materials 1 to 3 can be obtained. The thickness of the resin coating film 3 is 1 μm.

As shown in FIG. 1, the resin coating film 3 of test materials 1 to 3 has a hydrophilic layer 31 that includes a phase 311 containing modified polyvinyl alcohol (A) and a phase 312 containing an acrylamide-based polymer (B).

Test material 4 and test material 5
Test materials 4 and 5 have the same configuration as test materials 1 to 3, except that polyethylene glycol is contained in the resin coating film 3. The manufacturing method of test materials 4 and 5 is the same as that of Examples 1 to 3, except that polyethylene glycol is added to the paint in the amount shown in Table 1. The number average molecular weight of the polyethylene glycol used in test materials 4 and 5 is 6000. In Table 1, "polyethylene glycol" is abbreviated to "PEG".

When the paint contains polyethylene glycol, as in test materials 4 and 5, the modified polyvinyl alcohol (A) and acrylamide polymer (B) in the paint settle to the substrate 2 side during the process of heating and drying the paint on the substrate. As a result, as shown in FIG. 2, a hydrophilic layer 31 having a phase 311 containing modified polyvinyl alcohol (A) and a phase 312 containing acrylamide polymer (B) is formed on the base coating 21 of test materials 4 and 5.

On the other hand, since polyethylene glycol has a lower viscosity than the modified polyvinyl alcohol (A) and the acrylamide polymer (B), it floats to the surface as the paint dries. As a result, a lubricating layer 32 containing polyethylene glycol is formed on the hydrophilic layer 31. In this way, the resin film 302 of the test material 4 and the test material 5 has the lubricating layer 32 exposed on the surface and the hydrophilic layer 31 interposed between the lubricating layer 32 and the substrate 2.
Test material 6 and test material 7
Test materials 6 and 7 have the same configuration as test materials 1 to 3, except that the ratio of the modified polyvinyl alcohol (A) to the acrylamide polymer (B) is outside the specific range.
Test material 8
Test material 8 has the same structure as test material 4 and test material 5, except that the content of polyethylene glycol is higher than the specific range.

Test material 9
Test material 9 was prepared by the same manufacturing method as test materials 1 to 3, except that unmodified polyvinyl alcohol (number average molecular weight 6000) was used instead of the modified polyvinyl alcohol (A).

The properties of test materials 1 to 9 can be evaluated using the following methods.

Hydrophilicity The hydrophilicity of the test material can be evaluated based on the contact angle of water. In this example, the contact angle of water on each test material immediately after preparation and the contact angle of water on the test material after the deterioration test are measured. The contact angle of water on each test material immediately after preparation is as shown in Table 1.

After measuring the water contact angle immediately after preparation, a degradation test is conducted. In the degradation test, the test material is immersed in ion-exchanged water for 2 minutes, and then air is blown onto each test material for 6 minutes to dry the resin coating film 3. This cycle is repeated 300 times. After the degradation test is completed, water is dropped onto the test material and the water contact angle is measured. The water contact angle of the test material after the degradation test is as shown in Table 1.

Oil repellency The oil repellency of the test material can be evaluated based on the results of the cleaning test shown below. First, a square with sides of 15 mm is drawn on the resin coating film 3 of the test material using an oil-based dye marker, and the inside of the square is filled in with the oil-based dye marker to adhere an ink layer onto the resin coating film 3. As the oil-based dye marker, for example, "Twin Marker MFN-15FB-B" manufactured by Pilot Corporation can be used.

Next, the test material is set up vertically, and water is sprayed 150 times using a spray bottle onto the portion of the test material that is located above the ink layer. In this case, care is taken to ensure that the water sprayed from the spray bottle does not directly hit the squares. After spraying is completed, the area of the ink layer that has been removed by spraying is measured. The ratio of the area of the ink layer that has been removed by spraying to the area of the ink layer before spraying, expressed as a percentage, is taken as the ink layer removal rate (unit: %).

The results of the above cleaning tests performed on the test materials immediately after preparation and on the test materials after the deterioration test described above are shown in the "Oil repellency" column of Table 1. In the "Oil repellency" column of Table 1, the following symbols are used to indicate the ink layer removal rate: "A" if it is greater than 80%, "B" if it is greater than 60% and less than 80%, "C" if it is greater than 40% and less than 60%, "D" if it is greater than 20% and less than 40%, and "E" if it is less than 20%.

Adhesion The adhesion between the substrate 2 and the resin coating film 3 can be evaluated by a method conforming to the cross-cut method specified in JIS K5600-5-6:1999. Specifically, the resin coating film 3 is first cut into a lattice shape using a cutter knife, and 100 square pieces with sides of 2 mm are formed on the resin coating film 3. Cellophane tape is attached to these square pieces as an adhesive tape. The cellophane tape is then peeled off at an angle of 45° to the substrate 2, and the number of square pieces remaining on the substrate 2 is counted. In the "Adhesion" column of Table 1, "Good" is written when all the square pieces remain on the substrate 2, and "Bad" is written when one or more square pieces are peeled off from the substrate 2.

As shown in Table 1, test materials 1 to 5 have a resin coating having a composition within the specific range on a substrate. Therefore, these test materials have a water contact angle of 20° or less immediately after preparation, and exhibit excellent hydrophilicity immediately after preparation. Furthermore, these test materials have a water contact angle of 30° or less after a degradation test, and can maintain high hydrophilicity for a long period of time. Furthermore, these test materials have excellent oil repellency immediately after preparation and after a degradation test.

On the other hand, the mass ratio of modified polyvinyl alcohol (A) to acrylamide polymer (B) in test material 6 is smaller than the specific range. Therefore, the hydrophilicity and oil repellency of test material 6 after the deterioration test are lower than those of test materials 1 to 5.

The mass ratio of modified polyvinyl alcohol (A) to acrylamide polymer (B) in test material 7 is greater than the specific range as shown in Table 1. Therefore, the oil repellency of test material 7 after the deterioration test is lower than that of test materials 1 to 5.

The content of polyethylene glycol in the test material 8 is greater than the above-mentioned specific range. Therefore, the adhesion of the resin coating film 3 of the test material 8 is lower than those of the test materials 1 to 5.

Test material 9 contains unmodified polyvinyl alcohol instead of modified polyvinyl alcohol (A), so the structure of the hydrophilic layer of test material 9 is different from test materials 1 to 5. The hydrophilicity of test material 9 after the deterioration test is lower than that of test materials 1 to 5.

The specific aspects of the precoated fin material according to the present invention are not limited to those of the above-mentioned examples, and can be modified as appropriate within the scope of the present invention. For example, in the above-mentioned examples and experimental examples, an example of a precoated fin material 1 in which a base coating 21 is formed on a substrate 2 is shown, but it is also possible to omit the chemical conversion treatment for forming the base coating 21 and form the resin coating 3 directly on the substrate 2. In addition, the chemical conversion treatment for forming the base coating 21 may be omitted, and the corrosion-resistant coating and the resin coating 3 may be formed on the substrate 2 in sequence.

1 Precoated fin material 2 Substrate 3 Resin coating film

Claims (7)

A substrate made of aluminum;
A resin coating film formed on the substrate and exposed on the surface,
The resin coating film is
A modified polyvinyl alcohol (A) having a molecular structure represented by the following general formula (1),
An acrylamide polymer (B),
the total content of the modified polyvinyl alcohol (A) and the acrylamide-based polymer (B) is 85 parts by mass or more relative to 100 parts by mass of the entire resin coating film,
The content of the modified polyvinyl alcohol (A) is, in terms of mass ratio, 0.5 to 2.0 times the content of the acrylamide-based polymer (B).
Pre-coated fin material.

(In the above general formula (1), R ¹ is an organic group having a linear structure and a carbon number of 5 to 10, and m and n are positive integers satisfying the relationship 0.005≦n/m≦0.025.) The precoated fin material according to claim 1, wherein R ¹ in the general formula (1) is an organic group containing a plurality of methylene groups and one or more carbonyl groups. The precoated fin material according to claim 1 or 2, wherein the resin coating further contains polyethylene glycol. The precoated fin material according to any one of claims 1 to 3, wherein the resin coating further contains one or more compounds selected from the group consisting of blocked isocyanate compounds and melamine resins. The precoated fin material according to any one of claims 1 to 4, wherein the resin coating further contains at least one of an antibacterial agent and an antifungal agent. The precoated fin material according to any one of claims 1 to 5, wherein the resin coating contains fluororesin particles made of a fluororesin having perfluoroalkyl groups and having a median diameter on a volume basis of 1 μm or more and 4 μm or less. The precoated fin material according to any one of claims 1 to 6, which has a corrosion-resistant coating film interposed between the substrate and the resin coating film, and the corrosion-resistant coating film contains one or more resins selected from the group consisting of acrylic resins, epoxy resins, urethane resins, and ester resins.

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