WO2021162061A1

WO2021162061A1 - Aluminum fin material, heat exchanger, and method for producing aluminum fin material

Info

Publication number: WO2021162061A1
Application number: PCT/JP2021/005098
Authority: WO
Inventors: 亮介角田; 慶太館山
Original assignee: 株式会社神戸製鋼所
Priority date: 2020-02-13
Filing date: 2021-02-10
Publication date: 2021-08-19
Also published as: JP7409895B2; CN115003980A; JP2021127855A

Abstract

The present invention provides: an aluminum fin material which exhibits excellent hydrophilicity and excellent antifouling properties; a heat exchanger; and a method for producing an aluminum fin material. This aluminum fin material (10) comprises an aluminum plate (1), a hydrophobic coating layer (3) that is formed on the surface of the aluminum plate (1), and a hydrophilic coating layer (4) that is formed on the surface of the hydrophobic coating layer (3). The hydrophobic coating layer (3) contains an acrylic resin (3b) and polytetrafluoroethylene particles (3a); and at least some of the polytetrafluoroethylene particles (3a) protrude from the surface of the hydrophilic coating layer (4).

Description

Aluminum fin material, heat exchanger, and manufacturing method of aluminum fin material

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

Heat exchangers are used in products in various fields such as room air conditioners, packaged air conditioners, freezing showcases, refrigerators, oil coolers, and radiators.
The aluminum fin material used as the fins of these heat exchangers has a hydrophilic film formed on the surface from the viewpoint of reducing ventilation resistance and preventing water splashing.

However, if the heat exchanger is driven 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 such as an increase in ventilation resistance, mold generation originating from attached dust, and a decrease in comfort when the heat exchanger is installed in a living environment may occur.

Therefore, regarding the aluminum fin material, the following techniques have been proposed from the viewpoint of preventing the adhesion of dust.
For example, Patent Document 1 discloses an aluminum fin material in which fluororesin particles are contained in a baking coating film (hydrophilic film).

Japanese Patent Application Laid-Open No. 2016-90105

The technique according to Patent Document 1 is a configuration in which fluororesin particles are contained in a baked coating film (hydrophilic film). With such a configuration, the hydrophilicity of the hydrophilic film is due to the hydrophobicity of the fluororesin particles themselves. Is reduced, and it is difficult to secure a high level of hydrophilicity.

The present invention has been made in view of the above problems, and an object of the present invention is to provide an aluminum fin material, a heat exchanger, and a method for manufacturing the aluminum fin material, which exhibit excellent hydrophilicity and antifouling property. 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, and the hydrophobic film layer is provided. The sex film layer contains an acrylic resin and polytetrafluoroethylene particles, and at least a part of the polytetrafluoroethylene particles protrudes from the surface of the hydrophilic film layer.
Further, 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 producing 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 hydrophilicity on the surface of the hydrophobic film layer. In the step of forming the hydrophilic film layer, which includes the step of forming the film layer, at least a part of the polytetrafluoroethylene particles is in a state of protruding from the surface of the hydrophilic film layer.

The aluminum fin material and the heat exchanger according to the present invention can exhibit excellent hydrophilicity and antifouling property.
Further, the method for producing an aluminum fin material according to the present invention can produce an aluminum fin material capable of exhibiting excellent hydrophilicity and antifouling property.

FIG. 1A is a schematic cross-sectional view of an aluminum fin material in a state where a base treatment layer is formed on the surface of an aluminum plate. FIG. 1B is a schematic cross-sectional view of an aluminum fin material in a state where a hydrophobic film layer is formed on the surface of the base treatment layer. FIG. 1C is a schematic cross-sectional view of an aluminum fin material in which a hydrophilic film layer is formed on the surface of the hydrophobic film layer. FIG. 1D is a schematic cross-sectional view of an aluminum fin material in a state where a lubricating film layer is formed on the surface of the hydrophilic film layer. FIG. 2 is an image of the surface of an aluminum fin material (test material) obtained using a scanning electron microscope. FIG. 3 is a schematic view for explaining a method of measuring a contact angle in hydrophilicity evaluation.

Hereinafter, a mode for carrying out a method for manufacturing an aluminum fin material (hereinafter, appropriately referred to as “fin material”), a heat exchanger, and an 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 has an aluminum plate 1, a hydrophobic film layer 3 formed on the surface of the aluminum plate 1, and hydrophilicity formed on the surface of the hydrophobic film layer 3. It includes a sex film layer 4. Further, 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. Further, 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 the present embodiment contains polytetrafluoroethylene particles (hereinafter, appropriately referred to as “PTFE particles”) 3a. At least a part of the PTFE particles 3a protrudes from the surfaces of the hydrophilic film layer 4 and the lubricating film layer 5, as is clear from the scanning electron microscope image of FIG. That is, as shown in FIG. 1, it is presumed that the hydrophobic film layer 3 is composed of an undulating layer containing PTFE particles 3a and an acrylic resin 3b. Then, it is considered that the hydrophilic film layer 4 is formed on the hydrophobic film layer 3 so that at least a part of the PTFE particles 3a protrudes. In other words, it is considered that at least a part of the PTFE particles 3a penetrates the hydrophilic film layer 4 while being present in the hydrophobic film layer 3.
Each film layer of the fin material 10 according to the present embodiment is usually formed on both sides of the aluminum plate 1, but a part or all of the film layers are formed only on one side of the aluminum plate 1. You may.
Hereinafter, each configuration will be described in detail.

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

The thickness of the aluminum plate may be appropriately determined according to the application 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 appropriately ensuring the workability to the fins, the strength of the fins, the thermal conductivity, and the like. When the thickness of the aluminum plate is 0.08 mm or more, the strength required for a general fin material can be secured. On the other hand, when the thickness of the aluminum plate is 0.3 mm or less, the workability to the fin can be ensured.

[Hydrophobic film layer]
The hydrophobic film layer is a layer for enhancing the hydrophobicity of the fin material and exerting antifouling property. In addition, the hydrophobic film layer prevents water (condensation water, etc.), oxygen, ionic species such as chloride ions from entering the aluminum plate side, and causes corrosion and odor of the aluminum plate. It is a layer that plays a role of suppressing the formation of.
The hydrophobic film layer contains an acrylic resin and PTFE particles.

(Hydrophobic film layer: acrylic resin)
The acrylic resin contained in the hydrophobic film layer is a polymer of acrylic acid, methacrylic acid, and derivatives thereof.
The hydrophobic film layer is mainly composed of an acrylic resin except for the PTFE particles described later. The content of the acrylic resin in the hydrophobic film layer is, for example, preferably 80% by mass or more, and 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 resin of a polymer of tetrafluoroethylene.
Then, at least a part of the PTFE particles is in a state of protruding from the surface of the hydrophilic film layer described later.

(Hydrophobic film layer: protruding state of PTFE particles)
As shown in FIG. 1C, at least a part of the PTFE particles 3a protrudes from the surface of the hydrophilic film layer 4, so that the protruding portion prevents dust from adhering to the fin material 10. It can exhibit excellent antifouling properties.
As shown in FIG. 1D, the PTFE particles 3a may be in a state of protruding not only from the surface of the hydrophilic film layer 4 but also from the surface of the lubricating film layer 5, but the fins (heat exchanger). ), The lubricating film layer 5 has been removed. Therefore, if at least the PTFE particles 3a are in a state of protruding from the surface of the hydrophilic film layer 4, excellent antifouling property is 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 portion where the PTFE particles protrude in the top view of the surface of the hydrophilic film layer), more specifically, "the protruding area of the PTFE particles". / Surface area of hydrophilic film layer × 100 ”is preferably 0.1% or more, more preferably 0.3% or more, 0.8% or more, 1.0% or more, 1.2% or more. When the ratio of the protruding area of the PTFE particles is equal to or more than a predetermined value, the antifouling property can be improved.
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. When the ratio of the protruding area of the PTFE particles is equal to or less than a predetermined value, it is possible to avoid a decrease in hydrophilicity.
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 to be measured.

(Hydrophobic film layer: Content of PTFE particles)
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 0.30% by mass or more. When the content of the PTFE particles is at least a predetermined value, excellent antifouling property can be exhibited.
The content of PTFE particles in the hydrophobic film layer is preferably 10.00% by mass or less, preferably 8.00% by mass or less, 6.00% by mass or less, 4.00% by mass or less, and 2.50% by mass or less. , 1.50% by mass or less is preferable. If the content of the PTFE particles exceeds a predetermined value, the hydrophobicity based on the PTFE particles is excessively improved, and the hydrophilicity may be lowered.

The average particle size (particle size is equivalent to an area circle) of the PTFE particles is not particularly limited, but is preferably 0.1 μm or more and 5 μm or less, and more preferably 0.5 μm or more and 3 μm or less.
The particle size of the PTFE particles can be measured by a scanning electron microscope (SEM) or an electron probe microanalyzer (EPMA).

(Hydrophobic film layer: film amount)
The amount of the hydrophobic film 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 equal to or more than a predetermined value, more excellent antifouling property can be exhibited.
Further, the coating amount of the hydrophobic coating layer is preferably from 8.00 mg / dm ² or less, 6.00 mg / dm ² or less, 5.00 mg / dm ² or less is more preferable. If the amount of the hydrophobic film layer exceeds a predetermined value, the hydrophilicity may decrease, and a high level of hydrophilicity may not be ensured.
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 be rephrased as the amount of acrylic resin and PTFE particles formed.

The amount of the hydrophobic film layer is determined by the concentration of the coating composition used for forming the hydrophobic film layer and the bar coater No. 1 used for forming the film. It can be adjusted by selecting. Further, the amount of the hydrophobic film layer can be measured by fluorescent X-ray, an infrared film thickness meter, mass measurement by film peeling, or the like.
The method for adjusting the amount of the hydrophilic film layer and the lubricating film layer, which will be described later, and the measuring method are the same as those 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 the condensed water adhering to the surface of the fin material is reduced, and the heat exchange efficiency of the heat exchanger is less likely to deteriorate. Further, by increasing the hydrophilicity, the fluidity of the condensed water adhering to the surface of the fin material is also increased. Therefore, even if a pollutant adheres to the surface of the fin material, it can be easily washed off by the condensed water, and the removability of the pollutant 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, similarly to the acrylic resin in the hydrophobic film layer.
The hydrophilic film layer is mainly composed of an acrylic resin. The content of the acrylic resin in the hydrophilic film layer is, for example, preferably 80% by mass or more, and more preferably 90% by mass or more.

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

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

The lubricating film layer comprises a resin composition containing at least one 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 salt of carboxymethyl cellulose include sodium salt, potassium salt, calcium salt 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 preferable resin is a resin in which polyethylene glycol and sodium carboxymethyl cellulose are mixed. The mass ratio of polyethylene glycol to sodium carboxymethyl cellulose is preferably in the range of 5: 5 to 9: 1. According to the resin having such a composition, the film forming property and the lubricity are further improved.

(Lubricating film layer: film amount)
The amount of the lubricating film 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, and 0.8 mg / dm ² or more. Good lubricity can be obtained when the amount of the lubricating film layer is equal to or more than a predetermined value.
The amount of the lubricating film layer ^{is preferably 5 mg / dm 2} or less, preferably 3 mg / dm ² or less, 2 mg / dm ² or less, and 1.5 mg / dm ² or less. When the amount of the lubricating film layer is not more than a predetermined value, the heat transfer resistance can be suppressed low.

[Base treatment layer]
The base treatment layer is composed 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. In addition, the adhesion between the aluminum plate and the film layer arranged on the outside 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 phosphoric acid chromate treatment, zirconium phosphate treatment, chromic acid chromate treatment, zinc phosphate treatment, and titanium phosphate treatment. However, the types of inorganic oxides are not limited to those formed by these treatments.

Examples of the inorganic-organic composite compound include those formed by coating type chromate treatment and coating type zirconium treatment. Specific examples of such an inorganic-organic composite compound include an acrylic-zirconium complex and the like.

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, and more preferably 5 mg / m ² or more. When the amount of adhesion of the base treatment layer is equal to or more than a predetermined value, good corrosion resistance can be exhibited. The coating weight of the undercoating layer is preferably 100 mg / ^{m 2} or less, 80 mg / ^{m 2} or less is more preferable.
The thickness of the base treatment layer may be an appropriate thickness depending on the use of the fin material and the like, but is preferably 1 nm or more and 100 nm or less.

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

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

[Manufacturing method of aluminum fin material]
Next, a method for manufacturing the aluminum fin material according to the present embodiment will be described.
The method for manufacturing an aluminum fin material according to the present embodiment includes a substrate manufacturing step and a film layer forming step.

(Substrate manufacturing process)
In the substrate manufacturing process, an aluminum plate made of aluminum or an aluminum alloy is manufactured. For example, the metal is melted and the molten metal is solidified into an arbitrary shape to obtain an ingot containing a predetermined amount of a chemical component such as Al. Then, the ingot is chamfered as necessary and hot-rolled or cold-rolled to obtain an aluminum plate. In manufacturing the 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, tempering or the like.

(Film layer forming process)
In the film layer forming step, a film layer is formed on the surface of the aluminum plate. Specifically, after cleaning and degreasing the surface of the aluminum plate as necessary, each of the surface treatment layer, the hydrophobic film layer, the hydrophilic film layer, the lubricating film layer, etc. is applied to the surface of the clean aluminum plate. The film layers are formed in order.
1A to 1D show the flow of the film layer forming step, FIG. 1A shows a state in which the base treatment layer 2 is formed on the surface of the aluminum plate 1, and FIG. 1B shows hydrophobicity on the surface of the base treatment layer 2. A state in which the sex film layer 3 is formed, FIG. 1C shows a state in which the hydrophilic film layer 4 is formed on the surface of the hydrophobic film layer 3, and FIG. 1D shows a state in which the hydrophilic film layer 5 is formed on the surface of the hydrophilic film layer 4. It is in a state of being.

The steps of FIGS. 1B to 1C show a step of forming the hydrophilic film layer 4, and in this step, at least a part of the polytetrafluoroethylene particles 3a protrudes from the surface of the hydrophilic film layer 4. It will be in the state of
Here, as an embodiment in which "at least a part of the polytetrafluoroethylene particles 3a is in a state of protruding from the surface of the hydrophilic film layer 4", the amount of the hydrophilic film layer 4 formed is as shown in FIG. 1C. In addition to the embodiment in which the coating composition is applied by adjusting in advance, there is also an embodiment in which the hydrophilic film layer 4 is formed and then the state shown in FIG. 1C is ex post facto. That is, in the step of forming the hydrophilic film layer 4, the state as shown in FIG. 1C (a state in which at least a part of the polytetrafluoroethylene particles 3a protrudes from the surface of the hydrophilic film layer 4) is finally obtained. It should be.

The base treatment layer can be formed by applying a chemical conversion treatment liquid by a spray or the like, immersing an aluminum plate in the chemical conversion treatment liquid, and then heat-drying the base treatment layer.
Further, for the hydrophobic film layer, the hydrophilic film layer, and the lubricating film layer, a resin or the like for each film layer is dispersed in a solvent to obtain a coating composition, and then the coating composition is applied to a bar coater or a roll coater. A film can be formed by applying and baking using a coating device such as. In order to produce 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 of each film layer may normally be in the range of 100 ° C. or higher and 300 ° C. or lower. However, since PTFE particles are blended in the coating composition for the hydrophobic film layer, PTFE particles are used. A coating baking temperature (for example, 100 ° C. or higher and 280 ° C. or lower) that does not decompose is preferable.

The coating composition for forming each film used in the film layer forming step is not limited to the above-mentioned resins and particles, respectively, and various aqueous systems are considered in consideration of coatability, workability, coating property, etc. Solvents and paint additives may be added, for example, water-soluble organic solvents, cross-linking agents, surfactants, surface conditioners, wet dispersants, anti-settling agents, antioxidants, defoamers, rust preventives, etc. Various solvents and additives such as antibacterial agents and antifungal agents may be blended alone or in combination.
By going through the above steps, it is possible to manufacture the aluminum fin material according to the present embodiment.

Next, the aluminum fin material according to the present invention will be specifically described by comparing an example satisfying the requirements of the present invention with a comparative example not satisfying the requirements of the present invention. The present invention is not limited to this embodiment.

[Preparation of test material]
As the aluminum plate, an aluminum plate having a thickness of 0.1 mm, which is a standard of alloy number 1070 specified in JIS H 4000: 2014, was used. The surface of this aluminum plate was subjected to phosphoric acid chromate treatment to form a base treatment layer. 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 on the surface of the base treatment layer in this order.

For the hydrophobic film layer, a coating composition was applied to the surface of the base treatment layer with a bar coater and baked at 250 ° C. or lower to form a layer having ^{a film amount of 1 mg / dm 2.}
The test material No. The coating compositions of 1 to 3, 5 to 7 include an acrylic resin and each fluororesin particle (average particle diameter: about 0. 1 to 1.0 μm) and a mixture of the above were used. On the other hand, the test material No. The coating compositions of Nos. 4 and 8 are the test materials No. Compared with the coating compositions of 1 to 3, 5 to 7, it was different only in that it did not contain fluororesin particles.

For the hydrophilic film layer, the coating composition was applied to the surface of the hydrophobic film layer with a bar coater and baked at 250 ° C. to form a layer having ^{a film amount of 4 mg / dm 2.}
The test material No. As the coating compositions 1 to 7, a mixture of an acrylic resin and a solvent was used. On the other hand, the test material No. The coating composition of No. 8 is the test material No. Compared with the coating compositions 1 to 7, the only difference is that PTFE particles (average particle size: about 0.1 to 1.0 μm) are contained so that the content after layer formation is 0.35 wt%. rice field.

For the lubricating film layer, a coating composition was applied to the surface of the hydrophilic film layer with a bar coater and baked at 250 ° C. to form a layer having ^{a film amount of 1 mg / dm 2.}
The test material No. As the coating compositions 1 to 8, those obtained by mixing a resin containing polyethylene glycol with a solvent were used.

Next, the following measurements were carried out 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 acquired with 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 × 100".
Here, since the test material includes the 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 to the ratio of the protruding area of the fluororesin particles protruding from the hydrophilic film layer are substantially the same. It becomes a value.
The test material No. In No. 8, since the fluororesin particles were not contained in the hydrophobic film layer in the first place, the ratio of the protruding area was not measured.

Next, the prepared test materials were evaluated as follows.
[Hydrophilicity evaluation]
The prepared test material was immersed in a water tank overflowing with tap water at a flow rate of 0.1 L / min for 8 hours and then dried at 80 ° C. for 16 hours. This cycle was repeated for a total of 14 cycles. .. Then, after returning the test material to room temperature, it is placed horizontally so that the evaluation surface faces upward, and about 0.5 μL of pure water is dropped on the evaluation surface, and a contact angle measuring instrument (manufactured by Kyowa Interface Science Co., Ltd .: CA) is dropped. The contact angle was measured using -05 type).
As shown in FIG. 3, the contact angle θ is an angle formed by the test material T and the water droplet W.
Then, the hydrophilicity was determined according to the following evaluation criteria.

(Hydrophilicity: Evaluation criteria)
〇 Good: The contact angle is 40 ° or less.
Δ Generally good: The contact angle is more than 40 ° and less than 60 °.
× Defective: The contact angle is 60 ° or more.

[Anti-fouling property evaluation]
11 types (Kanto Loam) and 12 types (carbon black) of test powder specified in JISZ8901: 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 on a 5-point scale (5 points). : Adhesion amount is very large, 1 point: Adhesion amount is very small).
As for the antifouling property, those having a score of 3 or less for both carbon black and Kanto Loam were judged to be good (〇), and those other than that were judged to be defective (x).

Table 1 shows the composition of the prepared test materials and the evaluation results.
The amount of each film layer described above is a value measured by fluorescent X-rays. The content of the fluororesin particles shown in Table 1 is a value calculated from the addition amounts of the acrylic resin and the fluororesin particles used in the coating composition for each film layer. The particle size of the fluororesin particles used is a value measured by SEM.

Test material No.

Items

1, 5 to 7 satisfied the requirements specified by the present invention. Therefore, the test material No. For 1, 5 to 7, favorable results were obtained for both "hydrophilicity" and "antifouling property". Among them, the test material No. In 1, 5 to 6, very favorable results were obtained for both "hydrophilicity" and "antifouling property".

On the other hand, the test material No. As for 2 to 4 and 8, since the requirements specified in the present invention are not satisfied, unfavorable results were obtained for at least one of hydrophilicity and antifouling property.

Test material No. In No. 2, the fluororesin particles contained in the hydrophobic film layer were not predetermined, and the fluororesin particles did not protrude from the hydrophilic film layer, resulting in poor antifouling property.
Test material No. In No. 3, the fluororesin particles contained in the hydrophobic film layer were not predetermined, and the fluororesin particles did not protrude from the hydrophilic film layer, resulting in poor antifouling property.
Test material No. In No. 4, since the hydrophobic film layer did not contain the predetermined fluororesin particles, the result was that the antifouling property was poor.
Test material No. In No. 8, although the hydrophilic film layer contained predetermined fluororesin particles, the hydrophobic film layer did not contain the predetermined fluororesin particles. In other words, the hydrophilic film layer was close to the surface layer. Since it contained fluororesin particles, the result was poor hydrophilicity.

Then, the test material No. Comparing the results of 1 to 3, the following technical matters can be inferred.
Test material No. In No. 1, it is presumed that the PTFE particles were appropriately agglomerated to become agglomerated particles having a relatively large size by containing the "acrylic resin" and the "PTFE particles" as the hydrophobic film layer. As a result, large-sized PTFE particles 3a (aggregated particles) as shown in FIG. 1 are formed, and the PTFE particles 3a protrude from the surfaces of the hydrophilic film layer 4 and the lubricating film layer 5 (specifically, FIG. It is presumed that the condition is as shown in 2.
On the other hand, the test material No. In Nos. 2 and 3, "acrylic resin" and "polyvinylidene fluoride" or "polyvinylidene fluoride composite-polyvinylidene fluoride" were used as the hydrophobic film layer, but these fluororesin particles aggregate unlike PTFE particles. It is inferred that it remained small in size. As a result, the test material No. It is presumed that each of the fluororesin particles in Nos. 2 and 3 did not protrude from the hydrophilic film layer and the lubricating film layer, and the protruding area was 0% as shown in Table 1.
That is, the 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 in that the effect of the present invention (particularly, excellent antifouling property) is exhibited. It was confirmed that it is important for.

Although various embodiments have been described above with reference to the drawings, it goes without saying that the present invention is not limited to such examples. It is clear that a person skilled in the art can come up with various modifications or modifications within the scope of the claims, which naturally belong to the technical scope of the present invention. Understood. Further, each component in the above-described embodiment may be arbitrarily combined as long as the gist of the invention is not deviated.

Note that this application is based on a Japanese patent application (Japanese Patent Application No. 2020-022778) filed on February 13, 2020, the contents of which are incorporated herein by reference.

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

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 are provided.
The hydrophobic film layer contains an acrylic resin and polytetrafluoroethylene particles, and contains polytetrafluoroethylene particles.
An aluminum fin material characterized in that at least a part of the polytetrafluoroethylene particles protrudes from the surface of the hydrophilic film layer.
The ratio of the protruding area of the polytetrafluoroethylene particles protruding from the hydrophilic film layer (= the protruding area / the surface area of the hydrophilic film layer × 100) is 0.1 to 30.0%. The aluminum fin material according to claim 1, wherein the aluminum fin material is characterized by this.
The aluminum fin material according to claim 1 or 2, wherein the hydrophilic film layer contains an acrylic resin.
Further provided with a lubricating film layer formed on the surface of the hydrophilic film layer,
The first or second claim, wherein the lubricating film layer comprises a resin composition containing at least one selected from the group consisting of polyethylene glycol, carboxymethyl cellulose, and alkali metal salts of carboxymethyl cellulose. Aluminum fin material.
The aluminum fin material according to claim 1 or 2, wherein a base treatment layer is further provided between the aluminum plate and the hydrophobic film layer.
A heat exchanger comprising fins made of the aluminum fin material according to claim 1 or 2.
A process of forming a hydrophobic film layer containing an acrylic resin and polytetrafluoroethylene particles on the surface of an aluminum plate, and
Including a step of forming a hydrophilic film layer on the surface of the hydrophobic film layer.
A method for producing an aluminum fin material, characterized in that at least a part of the polytetrafluoroethylene particles protrudes from the surface of the hydrophilic film layer in the step of forming the hydrophilic film layer.