JP7409895B2 - Aluminum fin material, heat exchanger, and method for manufacturing aluminum fin material - Google Patents

Description

The present invention relates to an aluminum fin material, a heat exchanger, and a method for manufacturing the aluminum fin material.

Heat exchangers are used in products in a variety of fields, including room air conditioners, package air conditioners, refrigeration showcases, refrigerators, oil coolers, and radiators.
The aluminum fin materials used as the fins of these heat exchangers have a hydrophilic film formed on their surfaces in order to reduce ventilation resistance and prevent water splashing.

However, if the heat exchanger is operated for many years, dust floating in the atmosphere will adhere to the surface of the hydrophilic film of the aluminum fin material. As a result, various problems may occur, such as an increase in ventilation resistance, the growth of mold caused by attached dust, and a decrease in comfort when the heat exchanger is installed in a residential environment.

Therefore, with respect to aluminum fin materials, the following techniques have been proposed from the viewpoint of preventing dust from adhering.
For example, Patent Document 1 discloses an aluminum fin material in which fluororesin particles are contained in a baked coating (hydrophilic coating).

JP 2016-90105 Publication

The technology according to Patent Document 1 has a structure in which fluororesin particles are contained in a baked coating film (hydrophilic film), but with such a structure, the hydrophilic property of the hydrophilic film is decreases, making it difficult to ensure a high level of hydrophilicity.

The present invention has been made in view of the above problems, and an object thereof is to provide an aluminum fin material, a heat exchanger, and a method for manufacturing the aluminum fin material that exhibit excellent hydrophilicity and antifouling properties. do.

The aluminum fin material according to the present invention includes an aluminum plate, a hydrophobic film layer formed on the surface of the aluminum plate, and a hydrophilic film layer formed on the surface of the hydrophobic film layer, The hydrophilic film layer includes an acrylic resin and polytetrafluoroethylene particles, and at least a portion of the polytetrafluoroethylene particles protrude from the surface of the hydrophilic film layer.
Moreover, the heat exchanger according to the present invention includes fins made of the aluminum fin material according to the present invention.
Further, the method for manufacturing an aluminum fin material according to the present invention includes a step of forming a hydrophobic film layer containing an acrylic resin and polytetrafluoroethylene particles on the surface of an aluminum plate, and a step of forming a hydrophilic film layer on the surface of the hydrophobic film layer. forming a film layer, and in the step of forming the hydrophilic film layer, at least a portion of the polytetrafluoroethylene particles protrude from the surface of the hydrophilic film layer.

The aluminum fin material and heat exchanger according to the present invention can exhibit excellent hydrophilicity and antifouling properties.
Furthermore, the method for producing an aluminum fin material according to the present invention can produce an aluminum fin material that can exhibit excellent hydrophilicity and antifouling properties.

FIG. 2 is a schematic cross-sectional view of an aluminum fin material with a base treatment layer formed on the surface of the aluminum plate. FIG. 2 is a schematic cross-sectional view of an aluminum fin material with a hydrophobic film layer formed on the surface of a base treatment layer. FIG. 2 is a schematic cross-sectional view of an aluminum fin material in which a hydrophilic film layer is formed on the surface of a hydrophobic film layer. FIG. 2 is a schematic cross-sectional view of an aluminum fin material in which a lubricating film layer is formed on the surface of a hydrophilic film layer. It is an image of the surface of an aluminum fin material (test material) obtained using a scanning electron microscope. FIG. 2 is a schematic diagram for explaining a method of measuring a contact angle in hydrophilicity evaluation.

EMBODIMENT OF THE INVENTION Hereinafter, the form for carrying out the manufacturing method of the aluminum fin material (hereinafter suitably referred to as "fin material"), the heat exchanger, and the aluminum fin material according to the present invention will be described in detail.

[Aluminum fin material]
As shown in FIG. 1D, the fin material 10 according to the present embodiment includes an aluminum plate 1, a hydrophobic film layer 3 formed on the surface of the aluminum plate 1, and a hydrophilic film layer 3 formed on the surface of the hydrophobic film layer 3. and a sexual film layer 4. Furthermore, the fin material 10 according to the present embodiment may further include a lubricating film layer 5 formed on the surface of the hydrophilic film layer 4. Furthermore, the fin material 10 according to the present embodiment may further include a base treatment layer 2 between the aluminum plate 1 and the hydrophobic film layer 3.
The hydrophobic film layer 3 of the fin material 10 according to this embodiment includes polytetrafluoroethylene particles (hereinafter referred to as "PTFE particles" as appropriate) 3a. At least a portion of the PTFE particles 3a protrude from the surfaces of the hydrophilic film layer 4 and the lubricant film layer 5, as is clear from the scanning electron microscope image in FIG. That is, as shown in FIG. 1, the hydrophobic film layer 3 is presumed to be composed of an undulating layer containing PTFE particles 3a and acrylic resin 3b. It is considered that the hydrophilic film layer 4 is formed on the hydrophobic film layer 3 so that at least a portion of the PTFE particles 3a protrudes. In other words, it is considered that at least a portion of the PTFE particles 3 a penetrate through the hydrophilic film layer 4 while existing in the hydrophobic film layer 3 .
Each film layer of the fin material 10 according to the present embodiment is normally formed on both sides of the aluminum plate 10, but some or all of the film layers may be formed only on one side of the aluminum plate 10. You can.
Each configuration will be explained in detail below.

[Aluminum plate]
The aluminum plate is made of pure aluminum or aluminum alloy. As the aluminum plate, 1000 series aluminum specified in JIS H 4000:2014 can be suitably used from the viewpoint of thermal conductivity and workability. More specifically, aluminum with alloy numbers 1050, 1070, and 1200 is preferably used as the aluminum plate.
However, as the aluminum plate, a 2000 series to 9000 series aluminum alloy may be used as appropriate.

The thickness of the aluminum plate may be appropriately determined depending on the use and specifications of the fin material. Specifically, the thickness of the aluminum plate is preferably 0.08 mm or more and 0.3 mm or less from the viewpoint of ensuring appropriate workability into fins, fin strength, thermal conductivity, etc. If the thickness of the aluminum plate is 0.08 mm or more, it is possible to secure the strength required for a general fin material. On the other hand, if the thickness of the aluminum plate is 0.3 mm or less, workability into fins can be ensured.

[Hydrophobic film layer]
The hydrophobic film layer is a layer for increasing the hydrophobicity of the fin material and exhibiting antifouling properties. In addition, the hydrophobic film layer prevents moisture (such as condensed water), oxygen, and ionic species such as chloride ions from entering the aluminum plate, and prevents aluminum oxide from corroding the aluminum plate and causing odor. This layer plays the role of suppressing the production of.
The hydrophobic film layer includes an acrylic resin and PTFE particles.

(Hydrophobic film layer: acrylic resin)
The acrylic resin contained in the hydrophobic film layer is one obtained by polymerizing acrylic acid, methacrylic acid, and derivatives thereof.
The hydrophobic film layer is mainly composed of acrylic resin except for PTFE particles described later. The content of the acrylic resin in the hydrophobic film layer is, for example, preferably 80% by mass or more, more preferably 90% by mass or more.

(Hydrophobic film layer: PTFE particles)
The PTFE particles (polytetrafluoroethylene particles) contained in the hydrophobic film layer are particles made of a tetrafluoroethylene polymer resin.
At least a portion of these PTFE particles protrudes from the surface of the hydrophilic film layer, which will be described later.

(Hydrophobic film layer: protruding state of PTFE particles)
As shown in FIG. 1C, at least a portion of the PTFE particles 3a protrudes from the surface of the hydrophilic film layer 4, so that this protruding portion prevents dust from adhering to the fin material 10, It can exhibit excellent stain resistance.
As shown in FIG. 1D, the PTFE particles 3a may protrude not only from the surface of the hydrophilic film layer 4 but also from the surface of the lubricating film layer 5. ), the lubricating film layer 5 is removed. Therefore, as long as the PTFE particles 3a protrude from at least the surface of the hydrophilic film layer 4, excellent antifouling properties can be sufficiently ensured.

(Hydrophobic film layer: ratio of protruding area of PTFE particles)
The ratio of the protruding area of the PTFE particles protruding from the hydrophilic film layer (the ratio of the area of the part where the PTFE particles protrude when viewed from above on the surface of the hydrophilic film layer), more specifically, the "protruding area of PTFE particles" /surface area of the hydrophilic film layer x 100'' is preferably 0.1% or more, more preferably 0.3% or more, 0.8% or more, 1.0% or more, or 1.2% or more. When the ratio of the protruding area of the PTFE particles is at least a predetermined value, antifouling properties can be improved.
Further, the ratio of the protruding area of the PTFE particles is preferably 30.0% or less, more preferably 29.0% or less, 25.0% or less, 20.0% or less, 15.0% or less, and 14.0% or less. preferable. By setting the ratio of the protruding area of the PTFE particles to a predetermined value or less, a decrease in hydrophilicity can be avoided.
Note that the protruding area of the PTFE particles can be measured using a scanning electron microscope (SEM). Then, the ratio of the protruding area of the PTFE particles can be calculated based on the protruding area and the total area of the hydrophilic film layer that is the measurement target.

(Hydrophobic film layer: PTFE particle content)
The content of PTFE particles in the hydrophobic film layer is preferably 0.05% by mass or more, more preferably 0.10% by mass or more, 0.25% by mass or more, and more preferably 0.30% by mass or more. When the content of PTFE particles is at least a predetermined value, excellent antifouling properties can be exhibited.
Further, the content of PTFE particles in the hydrophobic film layer is preferably 10.00% by mass or less, 8.00% by mass or less, 6.00% by mass or less, 4.00% by mass or less, 2.50% by mass or less , preferably 1.50% by mass or less. If the content of PTFE particles exceeds a predetermined value, the hydrophobicity based on the PTFE particles may be improved too much, and the hydrophilicity may be reduced.

Although the average particle diameter (particle diameter is a diameter equivalent to an area circle) of the PTFE particles is not particularly limited, it is, for example, preferably 0.1 μm or more and 5 μm or less, and more preferably 0.5 μm or more and 3 μm or less.
Note that the particle diameter of the PTFE particles can be measured using a scanning electron microscope (SEM) or an electron beam microanalyzer (EPMA).

(Hydrophobic film layer: film amount)
The coating amount of the hydrophobic coating layer is preferably 0.05 mg/dm ² or more, more preferably 0.08 mg/dm ² or more, and more preferably 0.10 mg/dm ² or more. When the amount of the hydrophobic film layer is at least a predetermined value, more excellent antifouling properties can be exhibited.
Further, the coating amount of the hydrophobic coating layer is preferably 8.00 mg/dm ² or less, more preferably 6.00 mg/dm ² or less, and more preferably 5.00 mg/dm ² or less. If the amount of the hydrophobic coating layer exceeds a predetermined value, the hydrophilicity may decrease, and a high level of hydrophilicity may not be ensured.
Note that since most of the hydrophobic film layer is composed of the above-mentioned acrylic resin and PTFE particles, the amount of the hydrophobic film layer can also be translated as the amount of the acrylic resin and PTFE particles formed.

The amount of the hydrophobic film layer depends on the concentration of the coating composition used for forming the hydrophobic film layer and the bar coater No. used for film formation. It can be adjusted by selecting. Further, the amount of the hydrophobic film layer can be measured by fluorescent X-rays, infrared film thickness meter, mass measurement by peeling the film, or the like.
The method for adjusting and measuring the amount of the hydrophilic film layer and the lubricating film layer, which will be described later, is the same as that for the hydrophobic film layer described above.

[Hydrophilic film layer]
The hydrophilic film layer is a layer for increasing the hydrophilicity of the fin material. By providing the hydrophilic film layer, the contact angle of dew condensation water adhering to the surface of the fin material becomes small, making it difficult for the heat exchange efficiency of the heat exchanger to deteriorate. In addition, by increasing the hydrophilicity, the fluidity of condensed water adhering to the surface of the fin material also increases. Therefore, even if a contaminant adheres to the surface of the fin material, it can be easily washed off by the dew condensation water, and the removability of the contaminant is also improved.
The hydrophilic film layer preferably contains an acrylic resin.

(Hydrophilic film layer: acrylic resin)
The acrylic resin contained in the hydrophilic film layer is a polymer of acrylic acid, methacrylic acid, and derivatives thereof, similar to the acrylic resin in the hydrophobic film layer.
The hydrophilic film layer is mainly composed of acrylic resin. The content of the acrylic resin in the hydrophilic film layer is, for example, preferably 80% by mass or more, more preferably 90% by mass or more.

(Hydrophilic film layer: film amount)
The coating amount of the hydrophilic coating layer is preferably 0.5 mg/dm ² or more, more preferably 1 mg/dm ² or more, 2 mg/dm ² or more, or 3 mg/dm ^{2 or} more. When the coating amount of the hydrophilic coating layer is at least a predetermined value, good hydrophilicity can be ensured.
Further, the coating amount of the hydrophilic coating layer is preferably 10 mg/dm ² or less, more preferably 8 mg/dm ² or less, and more preferably 6 mg/dm ² or less. When the amount of the hydrophilic film layer is less than or equal to a predetermined value, film formability is good, defects such as cracks are reduced, and heat transfer resistance is kept low, so that the heat exchange efficiency of the fins is not easily impaired.
Note that, since most of the hydrophilic film layer is composed of acrylic resin, the amount of the hydrophilic film layer can also be referred to as the amount of film (formation amount) of the acrylic resin.

[Lubricating film layer]
The lubricating film layer is a layer for increasing the lubricity of the surface of the fin material. By providing the lubricating film layer, the coefficient of friction on the surface of the fin material is reduced, and press formability when processing the fin material into fins is improved.

The lubricating film layer is made of a resin composition containing one or more selected from the group consisting of polyethylene glycol, carboxymethyl cellulose, and alkali metal salts of carboxymethyl cellulose. However, the resin used for the lubricating film layer is not limited to these. Examples of the alkali metal salts of carboxymethylcellulose include sodium salts, potassium salts, calcium salts, and the like. These resins may be subjected to known modifications such as urethane modification and alkyl modification by copolymerization with other monomers. Among these, a particularly preferred resin is a hybrid resin of polyethylene glycol and carboxymethyl cellulose sodium. The mass ratio of polyethylene glycol to sodium carboxymethyl cellulose is preferably in the range of 5:5 to 9:1. A resin having such a composition provides even better film-forming properties and lubricity.

(Lubricating film layer: film amount)
The coating amount of the lubricating coating layer is preferably 0.1 mg/dm ² or more, preferably 0.3 mg/dm ² or more, 0.5 mg/dm ² or more, or 0.8 mg/dm ² or more. Good lubricity can be obtained when the amount of the lubricating film layer is at least a predetermined value.
Further, the coating amount of the lubricating coating layer is preferably 5 mg/dm ² or less, preferably 3 mg/dm ² or less, 2 mg/dm ² or less, or 1.5 mg/dm ² or less. By setting the film amount of the lubricating film layer to a predetermined value or less, heat transfer resistance can be kept low.

[Surface treatment layer]
The base treatment layer is made of an inorganic oxide or an inorganic-organic composite compound. By providing the base treatment layer on the aluminum plate, the corrosion resistance of the aluminum plate is enhanced. Furthermore, the adhesion between the aluminum plate and the outer coating layer is improved.

The inorganic oxide preferably contains chromium (Cr) or zirconium (Zr) as a main component. Specific examples of such inorganic oxides include those formed by chromate phosphate treatment, zirconium phosphate treatment, chromate chromate treatment, zinc phosphate treatment, titanate phosphate treatment, and the like. However, the type of inorganic oxide is not limited to those formed by these treatments.

Examples of the inorganic-organic composite compound include those formed by coating-type chromate treatment, coating-type zirconium treatment, and the like. Specific examples of such inorganic-organic composite compounds include, for example, acrylic-zirconium composites.

The amount of adhesion of the base treatment layer (the amount of adhesion converted to the mass of metal elements such as Cr and Zr) is preferably 1 mg/m ² or more, more preferably 5 mg/m ² or more. When the amount of the base treatment layer is equal to or greater than a predetermined value, good corrosion resistance can be exhibited. Moreover, the amount of adhesion of the base treatment layer is preferably 100 mg/m ² or less, more preferably 80 mg/m ² or less.
The thickness of the base treatment layer may be set as appropriate depending on the use of the fin material, but it is preferably 1 nm or more and 100 nm or less.

The adhesion amount of the base treatment layer can be adjusted by adjusting the concentration of the chemical conversion treatment liquid used for forming the base treatment layer and the film formation time. Further, the adhesion amount and thickness of the base treatment layer can be measured using fluorescent X-rays, an infrared film thickness meter, mass measurement by elution, and the like.

[Heat exchanger]
The heat exchanger according to this embodiment includes fins made of the fin material described above. The heat exchanger according to this embodiment can be applied to, for example, a room air conditioner, a package air conditioner, a freezer showcase, a refrigerator, an oil cooler, a radiator, and the like.
Note that the configuration of the heat exchanger according to the present embodiment other than the fins may be a configuration corresponding to each of the above-mentioned products and the same configuration as a conventionally known heat exchanger.

[Method for manufacturing aluminum fin material]
Next, a method for manufacturing an aluminum fin material according to this embodiment will be described.
The method for manufacturing an aluminum fin material according to this embodiment includes a substrate manufacturing process and a film layer forming process.

(Substrate manufacturing process)
In the substrate manufacturing process, an aluminum plate made of aluminum or an aluminum alloy is manufactured. For example, a base metal is melted and the molten metal is solidified into an arbitrary shape to obtain an ingot containing a predetermined amount of chemical components such as Al. Then, an aluminum plate is obtained by subjecting the ingot to face cutting as necessary and subjecting it to hot rolling or cold rolling. In addition, in manufacturing an aluminum plate, the ingot may be subjected to homogenization heat treatment, or intermediate annealing may be performed during rolling. Further, the rolled plate material may be subjected to solution heat treatment, thermal refining, etc.

(Film layer formation process)
In the film layer forming step, a film layer is formed on the surface of the aluminum plate. In detail, after cleaning and degreasing the surface of the aluminum plate as necessary, various layers such as a base treatment layer, a hydrophobic film layer, a hydrophilic film layer, and a lubricating film layer are applied to the surface of the clean aluminum plate. The film layers are deposited in sequence.
Note that FIGS. 1A to 1D show the flow of the film layer forming process, and FIG. 1A shows a state in which a base treatment layer 2 is formed on the surface of an aluminum plate 1, and FIG. 1B shows a state in which a hydrophobic layer is formed on the surface of the base treatment layer 2. FIG. 1C shows a state in which a hydrophilic film layer 4 is formed on the surface of the hydrophobic film layer 3, and FIG. 1D shows a state in which a lubricating film layer 5 is formed on the surface of the hydrophilic film layer 4. The situation is as follows.

The steps from FIG. 1B to FIG. 1C show the step of forming the hydrophilic film layer 4, and in this step, at least a part of the polytetrafluoroethylene particles 3a protrude from the surface of the hydrophilic film layer 4. The situation will be as follows.
Here, as an embodiment in which "at least a portion of the polytetrafluoroethylene particles 3a protrudes from the surface of the hydrophilic film layer 4", the amount of the hydrophilic film layer 4 formed is such that the state shown in FIG. 1C is achieved. In addition to an embodiment in which the coating composition is applied after adjusting the coating composition in advance, there is also an embodiment in which the state shown in FIG. 1C is obtained after the formation of the hydrophilic film layer 4. That is, in the step of forming this hydrophilic film layer 4, the final state is as shown in FIG. It is fine as long as it is.

The base treatment layer can be formed by applying a chemical conversion treatment liquid by spraying or the like, or by immersing an aluminum plate in the chemical conversion treatment liquid and then heating and drying it.
In addition, for the hydrophobic film layer, hydrophilic film layer, and lubricating film layer, the resin etc. for each film layer are dispersed in a solvent to obtain a coating composition, and then the coating composition is applied to a bar coater, a roll coater, etc. The film can be formed by coating using a coating device such as the following and baking. In order to manufacture the aluminum fin material having the above-mentioned structure, the coating composition for the hydrophobic film layer contains PTFE particles, while the coating composition for the hydrophilic film layer does not contain PTFE particles.
The coating baking temperature for each film layer should normally be in the range of 100°C or more and 300°C or less, but since the coating composition for the hydrophobic film layer contains PTFE particles, the PTFE particles It is preferable to set the coating baking temperature at which the paint does not decompose (for example, 100° C. or higher and 280° C. or lower).

The coating composition for forming each film used in the film layer forming process is not limited to the above-mentioned resins and particles, but also various water-based paint compositions, taking into consideration paintability, workability, physical properties of the film, etc. Solvents and paint additives may be added, such as water-soluble organic solvents, crosslinking agents, surfactants, surface conditioners, wetting and dispersing agents, antisettling agents, antioxidants, antifoaming agents, rust inhibitors, Various solvents and additives such as antibacterial agents and antifungal agents may be added alone or in combination.
Through the above steps, it is possible to manufacture the aluminum fin material according to this embodiment.

Next, the aluminum fin material according to the present invention will be specifically described by comparing examples that meet the requirements of the present invention and comparative examples that do not meet the requirements of the present invention. Note that the present invention is not limited to this example.

[Preparation of test material]
As the aluminum plate, an aluminum plate having alloy number 1070 specified in JIS H 4000:2014 and having a thickness of 0.1 mm was used. The surface of this aluminum plate was subjected to phosphoric acid chromate treatment to form a base treatment layer. In addition, the amount of adhesion of the base treatment layer was 30 mg/m ² .
Then, a hydrophobic film layer, a hydrophilic film layer, and a lubricating film layer were formed in this order on the surface of the base treatment layer.

The hydrophobic film layer was formed by coating the coating composition on the surface of the base treatment layer with a bar coater and baking it at 250° C. or lower to form a layer having a film amount of 1 mg/dm ² .
In addition, test material No. For the coating compositions 1 to 3 and 5 to 7, the acrylic resin and each fluororesin particle (average particle diameter: about 0.05 mm) were added to the solvent so that the content after layer formation would be the value shown in the table. 1 to 1.0 μm) was used. On the other hand, test material No. The coating compositions Nos. 4 and 8 were tested as test material No. When compared with coating compositions 1 to 3 and 5 to 7, the only difference was that they did not contain fluororesin particles.

The hydrophilic film layer was formed by coating the coating composition on the surface of the hydrophobic film layer with a bar coater and baking it at 250°C to form a layer with a film weight of 4 mg/dm ² .
In addition, test material No. The coating compositions Nos. 1 to 7 were prepared by mixing an acrylic resin with a solvent. On the other hand, test material No. The coating composition of No. 8 was the test material No. 8. Compared to coating compositions 1 to 7, the only difference is that PTFE particles (average particle diameter: about 0.1 to 1.0 μm) were included so that the content after layer formation was 0.35 wt%. Ta.

The lubricating film layer was formed by coating the coating composition on the surface of the hydrophilic film layer with a bar coater and baking it at 250°C to form a layer with a film weight of 1 mg/dm ² .
In addition, test material No. Coating compositions Nos. 1 to 8 were prepared by mixing a resin containing polyethylene glycol with a solvent.

Next, the following measurements were performed on the prepared test material.
[Measurement of protruding area ratio]
An image of the surface of the test material as shown in FIG. 2 was obtained using a scanning electron microscope (SEM), and the protruding area of the fluororesin particles was determined based on this image. Then, the ratio of the protruding area of the fluororesin particles protruding from the hydrophilic film layer was calculated by "protruding area of the fluororesin particles in the image/area of the entire image x 100".
Here, since the test material includes a lubricating film layer, strictly speaking, the ratio of the protruding area of the fluororesin particles protruding from the lubricating film layer is calculated. However, since the lubricating film layer is extremely thin, the ratio of the protruding area of the fluororesin particles protruding from the lubricating film layer and the ratio of the protruding area of the fluororesin particles protruding from the hydrophilic film layer are approximately the same. value.
In addition, test material No. In Sample No. 8, since the hydrophobic film layer did not contain fluororesin particles in the first place, the protrusion area ratio was not measured.

Next, the following evaluations were performed on the prepared test materials.
[Hydrophilicity evaluation]
One cycle of the prepared test material was immersing it in a water tank overflowing with tap water at a flow rate of 0.1 L/min for 8 hours, followed by drying it at 80°C for 16 hours, and this cycle was repeated for a total of 14 cycles. . After returning the test material to room temperature, it was placed horizontally with the evaluation surface facing upward, and about 0.5 μL of pure water was dropped onto the evaluation surface, and a contact angle measuring device (manufactured by Kyowa Interface Science Co., Ltd.: CA -05 type) was used to measure the contact angle.
Note that, as shown in FIG. 3, the contact angle θ is the angle between the test material T and the water droplet W.
Then, hydrophilicity was determined according to the following evaluation criteria.

(Hydrophilicity: evaluation criteria)
〇 Good: Contact angle is 40° or less.
△ Generally good: Contact angle is more than 40° and less than 60°.
× Poor: Contact angle is 60° or more.

[Fouling resistance evaluation]
Test powders of 11 types (Kanto loam) and 12 types (carbon black) specified in JIS Z8901:2006 were adhered to the surface of the prepared test material.
After adhering each powder to the surface of the test material, an image of the surface of each test material was taken, and based on the obtained image, the amount of adhesion between Kanto loam and carbon black was evaluated in five stages (5 points). : The amount of adhesion is very large; 1 point: The amount of adhesion is very small).
Regarding antifouling properties, those with a score of 3 or less for both carbon black and Kanto loam were judged to be good (○), and anything else was judged to be poor (x).

Table 1 shows the configuration of the test material prepared and the results of each evaluation.
Incidentally, the coating amount of each coating layer described above is a value measured by fluorescent X-rays. Furthermore, the content of fluororesin particles shown in Table 1 is a value calculated from the amounts of the acrylic resin and fluororesin particles added to the coating composition for each film layer. Moreover, the particle size of the fluororesin particles used is a value measured by SEM.

Test material No. 1, 5 to 7 met the requirements stipulated by the present invention. Therefore, test material No. Samples 1, 5 to 7 gave favorable results in both "hydrophilicity" and "antifouling property". Among them, test material No. 1, 5 and 6, very favorable results were obtained in both "hydrophilicity" and "antifouling property".

On the other hand, test material No. Regarding samples 2 to 4 and 8, unfavorable results were obtained with respect to at least one of hydrophilicity and antifouling property because they did not meet the requirements stipulated by the present invention.

Test material No. Sample No. 2 had poor stain resistance because the fluororesin particles contained in the hydrophobic coating layer were not as specified and the fluororesin particles did not protrude from the hydrophilic coating layer.
Test material No. Sample No. 3 had poor stain resistance because the fluororesin particles contained in the hydrophobic coating layer were not as specified and the fluororesin particles did not protrude from the hydrophilic coating layer.
Test material No. Sample No. 4 had poor antifouling properties because the hydrophobic film layer did not contain the specified fluororesin particles.
Test material No. No. 8 contained the prescribed fluororesin particles in the hydrophilic coating layer, but did not contain the prescribed fluororesin particles in the hydrophobic coating layer. In other words, the hydrophilic coating layer near the surface layer Since it contained fluororesin particles, the result was poor hydrophilicity.

And test material No. Comparing the results of 1 to 3, the following technical points can be inferred.
Test material No. In No. 1, it is presumed that by containing the "acrylic resin" and "PTFE particles" as a hydrophobic film layer, the PTFE particles were moderately aggregated and became aggregated particles of relatively large size. As a result, large-sized PTFE particles 3a (agglomerated particles) as shown in FIG. It is inferred that the situation was as shown in 2).
On the other hand, test material No. 2 and 3 used "acrylic resin" and "polyvinylidene fluoride" or "acrylic resin composite-polyvinylidene fluoride" as the hydrophobic film layer, but these fluororesin particles, unlike PTFE particles, aggregate. It is assumed that the size remained small without any problems. As a result, test material No. It is inferred that each of the fluororesin particles in Examples 2 and 3 did not protrude from the hydrophilic film layer and the lubricating film layer, resulting in a protrusion area of 0% as shown in Table 1.
In other words, test material No. Based on the results of 1 to 3, the combination of "acrylic resin" and "PTFE particles" as the composition of the hydrophobic film layer is extremely effective in exerting the effects of the present invention (especially excellent antifouling properties). was confirmed to be important.

1 Aluminum plate 2 Base treatment layer 3 Hydrophobic film layer 3a Polytetrafluoroethylene particles (PTFE particles)
3b Acrylic resin 4 Hydrophilic film layer 5 Lubricating film layer 10 Fin material

Claims (7)

An aluminum plate, a hydrophobic film layer formed on the surface of the aluminum plate, and a hydrophilic film layer formed on the surface of the hydrophobic film layer,
The hydrophobic film layer includes an acrylic resin and polytetrafluoroethylene particles,
At least a portion of the polytetrafluoroethylene particles contained in the hydrophobic film layer penetrate through the hydrophilic film layer and protrude from the surface of the hydrophilic film layer while existing in the hydrophobic film layer. An aluminum fin material characterized by: The ratio of the protruding area of the polytetrafluoroethylene particles protruding from the hydrophilic film layer (=protruding area/surface area of the hydrophilic film layer x 100) is 0.1 to 30.0%. The aluminum fin material according to claim 1, characterized in that: The aluminum fin material according to claim 1 or 2, wherein the hydrophilic film layer contains an acrylic resin. Further comprising a lubricating film layer formed on the surface of the hydrophilic film layer,
3. The lubricating film layer is made of a resin composition containing one or more selected from the group consisting of polyethylene glycol, carboxymethylcellulose, and an alkali metal salt of carboxymethylcellulose. Aluminum fin material. The aluminum fin material according to claim 1 or 2, further comprising a base treatment layer between the aluminum plate and the hydrophobic coating layer. A heat exchanger comprising fins made of the aluminum fin material according to claim 1 or 2. forming a hydrophobic film layer containing acrylic resin and polytetrafluoroethylene particles on the surface of the aluminum plate;
forming a hydrophilic film layer on the surface of the hydrophobic film layer,
A method for producing an aluminum fin material, characterized in that in the step of forming the hydrophilic film layer, at least a portion of the polytetrafluoroethylene particles protrude from the surface of the hydrophilic film layer.

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