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

Abstract

A method for manufacturing an aluminum fin material, a heat exchanger, and an aluminum fin material with excellent hydrophilicity and antifouling properties is provided. The aluminum fin material (10) comprises: an aluminum plate (1); a hydrophobic film layer (3) formed on the surface of the aluminum plate (1); and a hydrophilic film layer (4) formed on the surface of the hydrophobic film layer (3), the hydrophobic film layer (3) comprising acrylic resin (3b) and polytetrafluoroethylene particles (3a), at least a portion of the polytetrafluoroethylene particles (3a) protruding from the surface of the hydrophilic film layer (4).

Description

Technical Field

[0001] This invention relates to aluminum fins, heat exchangers, and methods for manufacturing aluminum fins. Background Technology

[0002] Heat exchangers are used in various products such as indoor air conditioners, modular air conditioners, refrigerated display cases, refrigerators, oil coolers, and radiators.

[0003] Therefore, the aluminum fins used in these heat exchangers have a hydrophilic film formed on their surface, from the perspective of reducing ventilation resistance and preventing water splashing.

[0004] However, if the heat exchanger is operated for extended periods, dust floating in the atmosphere will adhere to the surface of the hydrophilic film on the aluminum fins. This can result in various problems, such as increased ventilation resistance, mold growth originating from the adhered dust, and reduced comfort when the heat exchanger is installed in a residential environment.

[0005] Therefore, regarding aluminum fins, from the perspective of preventing dust adhesion, the following technology is proposed.

[0006] For example, Patent Document 1 discloses an aluminum fin material in which a baked coating (hydrophilic film) contains fluororesin particles.

[0007] Existing technical documents

[0008] Patent documents

[0009] Patent Document 1: Japanese Patent Application Publication No. 2016-90105 Summary of the Invention

[0010] The problem that the invention aims to solve

[0011] The technology in Patent Document 1 involves a structure that contains fluoropolymer particles in the baked coating (hydrophilic film). However, if such a structure is used, the hydrophobicity of the fluoropolymer particles themselves will reduce the hydrophilicity of the hydrophilic film, making it difficult to ensure a high level of hydrophilicity.

[0012] The present invention addresses the aforementioned problems, and its objective is to provide an aluminum fin material, a heat exchanger, and a method for manufacturing the aluminum fin material that exhibits excellent hydrophilicity and antifouling properties.

[0013] Problem-solving methods

[0014] The aluminum fin material of the present invention comprises: 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, wherein the hydrophobic film layer comprises acrylic resin and polytetrafluoroethylene particles, and at least a portion of the polytetrafluoroethylene particles protrudes from the surface of the hydrophilic film layer.

[0015] Furthermore, the heat exchanger of the present invention includes fins formed from the aluminum fin material of the present invention.

[0016] In addition, the method for manufacturing aluminum fins of the present invention includes the following steps: forming a hydrophobic film layer comprising acrylic resin and polytetrafluoroethylene particles on the surface of an aluminum plate; forming a hydrophilic film layer on the surface of the hydrophobic film layer; wherein, 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.

[0017] Invention Effects

[0018] The aluminum fin material and heat exchanger of the present invention exhibit excellent hydrophilicity and antifouling properties.

[0019] Furthermore, the method for manufacturing aluminum fins of the present invention can produce aluminum fins that exhibit excellent hydrophilicity and antifouling properties. Attached Figure Description

[0020] Figure 1A This is a cross-sectional schematic diagram of an aluminum fin with a substrate treatment layer formed on the surface of an aluminum plate.

[0021] Figure 1B This is a cross-sectional schematic diagram of an aluminum fin with a hydrophobic film layer formed on the surface of the substrate treatment layer.

[0022] Figure 1C This is a cross-sectional schematic diagram of an aluminum fin with a hydrophilic film layer formed on the surface of a hydrophobic film layer.

[0023] Figure 1D This is a cross-sectional schematic diagram of an aluminum fin with a lubricating film layer formed on the surface of a hydrophilic film layer.

[0024] Figure 2 These are images of the surface of aluminum finned material (test material) obtained using a scanning electron microscope.

[0025] Figure 3 This is a schematic diagram illustrating the method for measuring the contact angle in hydrophilicity evaluation. Detailed Implementation

[0026] The following describes in detail the methods for manufacturing aluminum fins (hereinafter, appropriately referred to as "fins"), heat exchangers, and aluminum fins used in carrying out the present invention.

[0027] [Aluminum finned sheet]

[0028] like Figure 1DAs shown, the fin material 10 of this 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 4 formed on the surface of the hydrophobic film layer 3. Additionally, the fin material 10 of this embodiment may also include a lubricating film layer 5 formed on the surface of the hydrophilic film layer 4. Furthermore, the fin material 10 of this embodiment may also have a substrate treatment layer 2 between the aluminum plate 1 and the hydrophobic film layer 3.

[0029] Furthermore, the hydrophobic film layer 3 of the fin material 10 in this embodiment contains polytetrafluoroethylene particles (hereinafter, appropriately referred to as "PTFE particles") 3a. At least a portion of these PTFE particles 3a, such as Figure 2 Scanning electron microscope images show that the hydrophilic film layer 4 and the lubricating film layer 5 protrude from their surfaces. In other words, as shown in Figure 1, the hydrophobic film layer 3 is presumably composed of an undulating layer containing PTFE particles 3a and acrylic resin 3b. Furthermore, it is believed that the hydrophilic film layer 4 is formed on top of this hydrophobic film layer 3 with at least a portion of the PTFE particles 3a protruding. In other words, it is believed that at least a portion of the PTFE particles 3a is present both in the hydrophobic film layer 3 and penetrates the hydrophilic film layer 4.

[0030] Furthermore, in this embodiment, each film layer of the fin material 10 is typically formed on both sides of the aluminum plate 1, but some or all of the film layers may also be formed on only one side of the aluminum plate 1.

[0031] The following is a detailed description of each structure.

[0032] [Aluminum Plate]

[0033] The aluminum sheet is formed from pure aluminum or aluminum alloy. Furthermore, from the viewpoint of thermal conductivity and workability, aluminum of the 1000 series as specified in JIS H 4000:2014 can be used as the aluminum sheet. More specifically, aluminum with alloy numbers 1050, 1070, and 1200 is preferred as the aluminum sheet.

[0034] However, aluminum alloys from the 2000 series to the 9000 series can also be used as aluminum sheets.

[0035] The thickness of the aluminum sheet should be determined appropriately based on the intended use and specifications of the fin material. Specifically, from the viewpoint of ensuring processability, fin strength, and thermal conductivity, the aluminum sheet thickness is preferably 0.08 mm or more and 0.3 mm or less. If the aluminum sheet thickness is 0.08 mm or more, the required strength for general fin materials can be ensured. On the other hand, if the aluminum sheet thickness is 0.3 mm or less, the processability of the fin material can be ensured.

[0036] [Hydrophobic film layer]

[0037] The hydrophobic coating layer is used to improve the hydrophobicity of the fin material, thereby enhancing its anti-fouling properties. In addition, the hydrophobic coating layer also serves the following functions: preventing the penetration of moisture (condensation, etc.), oxygen, and ions, primarily chloride ions, into the aluminum plate; inhibiting aluminum plate corrosion; and preventing the formation of odorous aluminum oxides.

[0038] Furthermore, the hydrophobic film layer contains acrylic resin and PTFE particles.

[0039] (Hydrophobic film layer: acrylic resin)

[0040] The so-called acrylic resin contained in the hydrophobic film layer is made by polymerizing acrylic acid, methacrylic acid and their derivatives.

[0041] The hydrophobic film layer, excluding the PTFE particles described later, is mainly composed of acrylic resin. Furthermore, the content of acrylic resin in the hydrophobic film layer is preferably 80% by mass or more, and more preferably 90% by mass or more.

[0042] (Hydrophobic film layer: PTFE particles)

[0043] The so-called PTFE particles (polytetrafluoroethylene particles) contained in the hydrophobic film layer are particles composed of a polymer of tetrafluoroethylene.

[0044] Moreover, the PTFE particles are in a state where at least a portion protrudes from the surface of the hydrophilic film layer described later.

[0045] (Hydrophobic film layer: the protruding state of PTFE particles)

[0046] like Figure 1C As shown, by having at least a portion of the PTFE particles 3a protrude from the surface of the hydrophilic film layer 4, the protruding portion can prevent dust from adhering to the fin material 10, thus exhibiting excellent anti-fouling properties.

[0047] Also, such as Figure 1D As shown, although PTFE particles 3a can 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 when used as a fin (heat exchanger). 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 adequately ensured.

[0048] (Hydrophobic film layer: the proportion of the protruding area of ​​PTFE particles)

[0049] The ratio of the protruding area of ​​PTFE particles from the hydrophilic film layer (the ratio of the area of ​​the protruding PTFE particles on the surface of the hydrophilic film layer when viewed from above), more specifically, "the protruding area of ​​PTFE particles / the surface area of ​​the hydrophilic film layer × 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. By making the ratio of the protruding area of ​​PTFE particles a specified value or higher, the antifouling property can be improved.

[0050] Furthermore, 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, or 14.0% or less. By keeping the ratio of the protruding area of ​​the PTFE particles below a specified value, a decrease in hydrophilicity can be avoided.

[0051] Furthermore, the protruding area of ​​PTFE particles can be measured using a scanning electron microscope (SEM). Moreover, the proportion of the protruding area of ​​PTFE particles can be calculated based on their protruding area and the total area of ​​the hydrophilic membrane layer being measured.

[0052] (Hydrophobic film layer: PTFE particle content)

[0053] 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, or 0.30% by mass or more. By ensuring that the content of PTFE particles is at or above the specified value, excellent antifouling properties can be achieved.

[0054] Furthermore, the content of PTFE particles in the hydrophobic film layer is preferably 10.00% by mass or less, more preferably 8.00% by mass or less, 6.00% by mass or less, 4.00% by mass or less, 2.50% by mass or less, or 1.50% by mass or less. If the content of PTFE particles is higher than the specified value, the hydrophobicity of the PTFE particles may be excessively increased, and the hydrophilicity may be reduced.

[0055] While the average particle size (particle size is the area equivalent circle diameter) of PTFE particles is not particularly limited, it 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.

[0056] Furthermore, the particle size of PTFE particles can be measured using scanning electron microscopy (SEM) and electron probe microanalysis (EPMA).

[0057] (Hydrophobic film layer: film amount)

[0058] The preferred amount of hydrophobic film is 0.05 mg / dm³. 2The above, more preferably 0.08 mg / dm 2 Above, 0.10 mg / dm 2 In conclusion, by ensuring that the amount of hydrophobic film layer is above a specified value, superior antifouling properties can be achieved.

[0059] Furthermore, the preferred amount of hydrophobic film is 8.00 mg / dm³. 2 The preferred dosage is 6.00 mg / dm³. 2 Below, 5.00 mg / dm 2 The following applies. If the amount of hydrophobic film exceeds the specified value, the hydrophilicity may decrease, and a high level of hydrophilicity may not be guaranteed.

[0060] Furthermore, since the hydrophobic film layer is mostly composed of the acrylic resin and PTFE particles, the amount of the hydrophobic film layer can also be referred to as the amount of acrylic resin and PTFE particles formed.

[0061] The amount of hydrophobic film can be adjusted by factors such as the concentration of the coating composition used for film formation and the selection of the number of the doctor blade coater used for film formation. Furthermore, the amount of hydrophobic film can be measured using methods such as fluorescence X-rays, infrared thickness gauges, and mass measurements based on film peeling.

[0062] Furthermore, the methods for adjusting and measuring the amount of hydrophilic and lubricating film layers described later are the same as those for the hydrophobic film layer.

[0063] [Hydrophilic membrane layer]

[0064] The hydrophilic coating layer is used to enhance the hydrophilicity of the fin material. By applying this layer, the contact angle of condensation water adhering to the fin surface decreases, making it less likely for the heat exchanger's efficiency to deteriorate. Furthermore, the increased hydrophilicity also improves the fluidity of the condensation water adhering to the fin surface. Therefore, even if contaminants adhere to the fin surface, they are easily washed away by the condensation water, improving contaminant removal.

[0065] Furthermore, the hydrophilic film layer preferably contains acrylic resin.

[0066] (Hydrophilic film layer: acrylic resin)

[0067] The acrylic resin contained in the so-called hydrophilic film layer is the same as the acrylic resin in the hydrophobic film layer, and is made by polymerizing acrylic acid, methacrylic acid, and their derivatives.

[0068] The hydrophilic film layer is mainly composed of acrylic resin. Moreover, the content of acrylic resin in the hydrophilic film layer is preferably 80% by mass or more, and more preferably 90% by mass or more.

[0069] (Hydrophilic film layer: film amount)

[0070] The preferred amount of hydrophilic film is 0.5 mg / dm³. 2 The above, more preferably 1 mg / dm 2 Above, 2mg / dm 2 Above, 3mg / dm 2 The above. By ensuring that the amount of hydrophilic film layer is above a specified value, good hydrophilicity can be ensured.

[0071] In addition, the preferred amount of hydrophilic film is 10 mg / dm³. 2 The following is more preferably 8 mg / dm 2 The following 6mg / dm 2 The following applies. By keeping the amount of the hydrophilic film layer below a specified value, the film-forming properties are good, defects such as cracks can be reduced, and because the thermal resistance is suppressed to a low level, the heat exchange efficiency of the fins is less likely to be damaged.

[0072] Furthermore, since the hydrophilic film layer is mostly composed of acrylic resin, the amount of the hydrophilic film layer can also be referred to as the amount of acrylic resin film (formation amount).

[0073] [Lubricating film layer]

[0074] A lubricating film layer is a layer used to improve the lubricity of the fin surface. By setting a lubricating film layer, the coefficient of friction of the fin surface is reduced, improving the stamping formability when processing the fin into fins.

[0075] The lubricating film layer is composed of a resin composition containing one or more resins 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 this. Examples of alkali metal salts of carboxymethyl cellulose include sodium salts, potassium salts, and calcium salts. These resins can also be modified in a known manner, such as by copolymerization with other monomers, to achieve polyurethane modification or alkylation. A particularly preferred resin is a mixture of polyethylene glycol and sodium carboxymethyl cellulose. The mass ratio of polyethylene glycol to sodium carboxymethyl cellulose is preferably in the range of 5:5 to 9:1. A resin with such a composition exhibits better film-forming properties and lubricity.

[0076] (Lubricating film layer: film amount)

[0077] The preferred amount of lubricating film is 0.1 mg / dm³. 2The above, more preferably 0.3 mg / dm 2 Above, 0.5 mg / dm 2 Above, 0.8mg / dm 2 The above. By ensuring that the amount of lubricating film is above a specified value, good lubricity can be achieved.

[0078] In addition, the preferred amount of lubricating film is 5 mg / dm³. 2 The following is more preferably 3 mg / dm 2 Below, 2mg / dm 2 Below, 1.5 mg / dm 2 The following applies. By keeping the amount of the lubricating film layer below a specified value, thermal resistance can be reduced to a low level.

[0079] [Substrate Treatment Layer]

[0080] The substrate treatment layer is composed of inorganic oxides or inorganic-organic composite compounds. By applying a substrate treatment layer to the aluminum plate, the corrosion resistance of the aluminum plate can be improved. Furthermore, the aluminum plate exhibits good adhesion to the outer coating layer.

[0081] As an inorganic oxide, it is preferable that the main component contains chromium (Cr) or zirconium (Zr). Specific examples of such inorganic oxides include those formed by treatment with chromate phosphate, zirconium phosphate, chromate chromate, zinc phosphate, and titanate phosphate. However, the types of inorganic oxides are not limited to those formed by these treatments.

[0082] Examples of inorganic-organic composite compounds include those formed by coating-type chromate treatment and coating-type zirconium treatment. Specific examples of such inorganic-organic composite compounds include, for instance, acrylic-zirconium composites.

[0083] The amount of the substrate treatment layer (converted to the mass of metallic elements such as Cr or Zr) is preferably 1 mg / m³. 2 The above, more preferably 5 mg / m² 2 The above describes how good corrosion resistance can be achieved by ensuring that the adhesion amount of the substrate treatment layer is above a specified value. Furthermore, the adhesion amount of the substrate treatment layer is preferably 100 mg / m³. 2 The following is more preferably 80 mg / m² 2 the following.

[0084] Furthermore, the thickness of the substrate treatment layer can be appropriately determined according to the application of the fin material, but it is preferably 1 nm or more and 100 nm or less.

[0085] The amount of substrate treatment layer attached can be adjusted by regulating the concentration of the formation solution used for film formation and the film formation time. Furthermore, the amount and thickness of the substrate treatment layer can be measured using X-ray fluorescence, infrared film thickness gauges, or dissolution-based mass measurements.

[0086] [Heat Exchanger]

[0087] The heat exchanger of this embodiment includes fins made of the aforementioned fin material. Furthermore, the heat exchanger of this embodiment can be applied, for example, to indoor air conditioners, modular air conditioners, freezer display cases, refrigerators, oil coolers, radiators, etc.

[0088] Furthermore, the structure of the heat exchanger in this embodiment, other than the fins, is the same as that of the aforementioned products and can be the same as that of conventionally known heat exchangers.

[0089] [Manufacturing method of aluminum fins]

[0090] Next, the manufacturing method of the aluminum fin material according to this embodiment will be described.

[0091] The method for manufacturing aluminum fins in this embodiment includes a substrate manufacturing process and a film layer formation process.

[0092] (Substrate manufacturing process)

[0093] In the substrate manufacturing process, aluminum sheets made of aluminum or aluminum alloys are produced. For example, ingots are melted and the molten metal is solidified into an arbitrary shape to obtain an ingot containing a specified amount of chemical components such as Al. Then, the surface of the ingot is machined as needed, and an aluminum sheet is obtained by hot rolling and cold rolling. Furthermore, when manufacturing aluminum sheets, the ingot may be subjected to homogenization heat treatment, or intermediate annealing may be performed during rolling. Additionally, the rolled sheet may be subjected to solution heat treatment, quenching and tempering, etc.

[0094] (The process of forming the skin layer)

[0095] In the film layer formation process, a film layer is formed on the surface of the aluminum plate. Specifically, after cleaning and degreasing the surface of the aluminum plate as needed, various film layers are formed in sequence on the clean aluminum plate surface, including a film base treatment layer, a hydrophobic film layer, a hydrophilic film layer, and a lubricating film layer.

[0096] besides, Figures 1A-1D This shows the process flow of the film layer formation. Figure 1A It is a state in which a base treatment layer 2 is formed on the surface of aluminum plate 1. Figure 1B It is a state in which a hydrophobic film layer 3 is formed on the surface of the substrate treatment layer 2. Figure 1C It is a state in which a hydrophilic film layer 4 is formed on the surface of the hydrophobic film layer 3. Figure 1D It is a state in which a lubricating film layer 5 is formed on the surface of the hydrophilic film layer 4.

[0097] and, Figures 1B to 1C The process refers to the process of forming a hydrophilic film layer 4, but in the process, at least a portion of the polytetrafluoroethylene particles 3a are in a state of protruding from the surface of the hydrophilic film layer 4.

[0098] Here, as an example of "at least a portion of the polytetrafluoroethylene particle 3a being in a state protruding from the surface of the hydrophilic film layer 4", not only can be listed Figure 1C As shown, the method of applying the coating composition by adjusting the amount of hydrophilic film layer 4 beforehand can also be described as follows: after the hydrophilic film layer 4 is formed, it is then applied... Figure 1C The state shown is as described. In other words, in the process of forming this hydrophilic film layer 4, as long as it ultimately becomes... Figure 1C The state shown (where at least a portion of the polytetrafluoroethylene particles 3a protrude from the surface of the hydrophilic film layer 4) is acceptable.

[0099] The base treatment layer can be formed by applying a formation treatment solution through spraying or other methods, or by immersing the aluminum plate in a formation treatment solution and then drying it by heating.

[0100] Furthermore, the hydrophobic film layer, hydrophilic film layer, and lubricating film layer can be formed by dispersing the resin or the like for each film layer in a solvent to obtain a coating composition, then applying the coating composition using a coating apparatus such as a doctor blade coater or a roller coater, and baking it to form a film. Also, in order to manufacture the aluminum fin material with the aforementioned 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.

[0101] Furthermore, the coating baking temperature of each film layer can generally be carried out in the range of 100°C or higher and 300°C or lower. However, since PTFE particles are blended into the coating composition for the hydrophobic film layer, a coating baking temperature at which the PTFE particles will not decompose is preferred (e.g., 100°C or higher and 280°C or lower).

[0102] Furthermore, the coating compositions used in the film-forming process for forming each film are not limited to the aforementioned resins and particles. Considering factors such as coatability, workability, and film properties, various aqueous solvents and coating additives may be added. For example, water-soluble organic solvents, crosslinking agents, surfactants, surface modifiers, wetting and dispersing agents, anti-settling agents, antioxidants, defoamers, rust inhibitors, antibacterial agents, mildew inhibitors, and other solvents and additives may be added individually or in combination.

[0103] The aluminum fin material of this embodiment can be manufactured through the above processes.

[0104] Example

[0105] Next, by comparing embodiments that satisfy the requirements of the present invention with comparative examples that do not satisfy the requirements of the present invention, the aluminum fin material of the present invention will be specifically described. Furthermore, the present invention is not limited to these embodiments.

[0106] [Preparation of experimental materials]

[0107] The aluminum sheet used is alloy number 1070 as specified in JIS H 4000:2014, with a thickness of 0.1 mm. The surface of this aluminum sheet is treated with chromate phosphate to form a base treatment layer. Furthermore, the adhesion amount of the base treatment layer is 30 mg / m². 2 .

[0108] Then, a hydrophobic film layer, a hydrophilic film layer, and a lubricating film layer are formed sequentially on the surface of the substrate treatment layer.

[0109] The hydrophobic film layer is formed by applying a coating composition to the surface of a substrate treatment layer using a doctor blade coater and baking it at a temperature below 250°C, thereby creating a film with a thickness of 1 mg / dm³. 2 The layers.

[0110] Furthermore, the coating compositions for test materials No. 1 to 3, and 5 to 7 were prepared by mixing acrylic resin with solvent and various fluoropolymer particles (average particle size: approximately 0.1 to 1.0 μm), such that the content of fluoropolymer particles after layer formation was as shown in the table. On the other hand, the coating compositions for test materials No. 4 and 8 differ from those for test materials No. 1 to 3, and 5 to 7 only in that they do not contain fluoropolymer particles.

[0111] The hydrophilic film layer is formed by applying the coating composition to the surface of the hydrophobic film layer using a doctor blade coater and baking it at 250°C, thereby creating a film with a thickness of 4 mg / dm³. 2 The layers.

[0112] Furthermore, the coating compositions used in Test Materials No. 1 to 7 were made by mixing acrylic resin with a solvent. On the other hand, the coating composition of Test Material No. 8 differs from that of Test Materials No. 1 to 7 only in that it contains PTFE particles (average particle size: about 0.1 to 1.0 μm) in such a way that the content after layer formation is 0.35 wt%.

[0113] The lubricating film layer is formed by applying a coating composition to the surface of a hydrophilic film layer using a doctor blade coater and baking it at 250°C, thereby creating a film with a thickness of 1 mg / dm³.2 The layers.

[0114] Furthermore, the coating compositions used as test materials No. 1 to 8 were made by mixing a resin containing polyethylene glycol with a solvent.

[0115] Next, the following measurements were performed on the prepared test material.

[0116] [Measurement of the ratio of the protruding area]

[0117] Obtained using scanning electron microscopy (SEM). Figure 2 An image of the surface of the test material is shown, and based on this image, the protruding area of ​​the fluoropolymer particles is determined. Then, the ratio of the protruding area of ​​the fluoropolymer particles protruding from the hydrophilic film layer is calculated according to "protruding area of ​​fluoropolymer particles in the image / area of ​​the entire image × 100".

[0118] Here, since the test material has a lubricating film layer, strictly speaking, we calculate the ratio of the protruding areas of fluoropolymer particles protruding from the lubricating film layer. However, because the lubricating film layer is extremely thin, the ratio of the protruding areas of fluoropolymer particles protruding from the lubricating film layer is approximately the same as the ratio of the protruding areas of fluoropolymer particles protruding from the hydrophilic film layer.

[0119] Furthermore, since test material No. 8 does not contain any fluoropolymer particles in its hydrophobic film layer, the measurement of the outstanding area ratio was not performed.

[0120] Next, the following evaluation will be conducted on the prepared test materials.

[0121] [Hydrophilicity evaluation]

[0122] For the prepared test material, the following cycle was repeated for a total of 14 cycles: immersion in a water tank overflowing with tap water at a flow rate of 0.1 L / min for 8 hours, followed by drying at 80°C for 16 hours, constitutes one cycle. Afterward, the test material was allowed to return to room temperature, placed horizontally with the evaluation surface facing upward, and approximately 0.5 μL of pure water was dripped onto the evaluation surface. The contact angle was measured using a contact angle measuring instrument (Kyowa Surface Science Co., Ltd.: CA-05 type).

[0123] Also, such as Figure 3 As shown, the contact angle θ is the angle between the test material T and the water droplet W.

[0124] Then, hydrophilicity is determined according to the following evaluation criteria.

[0125] (Hydrophilicity: Evaluation Criteria)

[0126] Good: Contact angle is below 40°.

[0127] △ Overall good: Contact angle above 40° and below 60°.

[0128] ×Poor: Contact angle is above 60°.

[0129] [Fouling Resistance Evaluation]

[0130] The surfaces of the prepared test materials were coated with 11 types of test powders (Kanto loam) and 12 types of test powders (carbon black) as specified in JIS Z8901:2006.

[0131] After each powder adheres to the surface of the test material, an image of the surface of each test material is taken. Based on the obtained images, the adhesion amount of Kanto soil and carbon black is evaluated on a 5-point scale (5 points: very high adhesion amount, 1 point: very low adhesion amount).

[0132] Then, regarding antifouling properties, if the number of carbon black-related points and the number of Kanto soil-related points are both below 3, it is judged as good (○), and otherwise it is judged as poor (×).

[0133] Table 1 shows the composition of the test materials and the evaluation results.

[0134] Furthermore, the film content of each coating layer is a value measured by X-ray fluorescence. Additionally, the fluoropolymer particle content shown in Table 1 is a value calculated based on the amount of acrylic resin and fluoropolymer particles added to the coating composition used for each coating layer. Furthermore, the particle size of the fluoropolymer particles used is a value measured by SEM.

[0135] Table 1

[0136]

[0137] Regarding test materials No. 1, 5-7, they meet the requirements specified in this invention. Therefore, test materials No. 1, 5-7 can achieve satisfactory results in both "hydrophilicity" and "fouling resistance". Among them, test materials No. 1, 5-6 can achieve very satisfactory results in both "hydrophilicity" and "fouling resistance".

[0138] On the other hand, regarding test materials No. 2 to 4 and 8, since they do not meet the requirements specified in this invention, at least one of the hydrophilicity and antifouling properties yields unsatisfactory results.

[0139] Test material No. 2 showed poor antifouling properties because the fluoropolymer particles contained in the hydrophobic film layer were not specified and did not protrude from the hydrophilic film layer.

[0140] Test material No. 3 showed poor antifouling properties because the fluoropolymer particles contained in the hydrophobic film layer were not specified and did not protrude from the hydrophilic film layer.

[0141] Test material No. 4 showed poor antifouling properties because the hydrophobic film layer did not contain the specified fluoropolymer particles.

[0142] Test material No. 8 contains the specified fluoropolymer particles in the hydrophilic film layer, but not in the hydrophobic film layer. In other words, it contains fluoropolymer particles in the hydrophilic film layer near the surface, thus resulting in poor hydrophilicity.

[0143] Furthermore, by comparing the results of test materials No. 1 to 3, the following technical matters can be inferred.

[0144] Test material No. 1, as a hydrophobic film layer, contains "acrylic resin" and "PTFE particles." Based on this, it can be inferred that the PTFE particles moderately aggregate, becoming relatively large aggregated particles. As a result, it is inferred that they become large PTFE particles 3a (aggregated particles) as shown in Figure 1, protruding from the surfaces of the hydrophilic film layer 4 and the lubricating film layer 5 (specifically, that is...). Figure 2 (as shown in the image).

[0145] On the other hand, test materials No. 2 and 3, as hydrophobic coating layers, used "acrylic resin" and "polyvinylidene fluoride" or "acrylic resin composite-polyvinylidene fluoride." However, these fluoropolymer particles differ from PTFE particles, presumably because they do not aggregate and remain in a small-sized state. As a result, it is presumed that the fluoropolymer particles of test materials No. 2 and 3 do not protrude from the hydrophilic and lubricating coating layers, as shown in Table 1, resulting in a protrusion area of ​​0%.

[0146] In other words, based on the results of test materials No. 1 to 3, it can be confirmed that the combination of "acrylic resin" and "PTFE particles" as the structure of the hydrophobic film layer is very important in exerting the effects of the present invention (especially the excellent antifouling properties).

[0147] The above description, with reference to the accompanying drawings, outlines various embodiments, but the present invention is not limited to such examples. Those skilled in the art will undoubtedly conceive of various modifications and alterations within the scope of the patent claims, and these are naturally understood to fall within the technical scope of the present invention. Furthermore, the constituent elements of the above embodiments can be combined arbitrarily without departing from the spirit of the invention.

[0148] Furthermore, this application is based on Japanese Patent Application No. 2020-022778, filed on February 13, 2020, the contents of which are incorporated herein by reference.

[0149] Symbol Explanation

[0150] 1 Aluminum plate

[0151] 2. Substrate treatment layer

[0152] 3. Hydrophobic film layer

[0153] 3a Polytetrafluoroethylene (PTFE) particles

[0154] 3b Acrylic resin

[0155] 4. Hydrophilic membrane layer

[0156] 5. Lubricating film layer

[0157] 10 Finned Material

Claims

1. An aluminum fin material, characterized in that, It comprises: 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 comprises acrylic resin and polytetrafluoroethylene particles. At least a portion of the polytetrafluoroethylene particles protrude from the surface of the hydrophilic membrane layer.

2. The aluminum fin material according to claim 1, characterized in that, The ratio of the protruding area of ​​the polytetrafluoroethylene particles protruding from the hydrophilic film layer, i.e., the protruding area / the surface area of ​​the hydrophilic film layer × 100, is 0.1 to 30.0%.

3. The aluminum fin material according to claim 1 or claim 2, characterized in that, The hydrophilic film layer contains acrylic resin.

4. The aluminum fin material according to claim 1 or claim 2, characterized in that, It also has a lubricating film layer formed on the surface of the hydrophilic film layer. The lubricating film layer comprises a resin composition containing one or more resins selected from the group consisting of polyethylene glycol, carboxymethyl cellulose and alkali metal salts of carboxymethyl cellulose.

5. The aluminum fin material according to claim 1 or claim 2, characterized in that, A substrate treatment layer is also provided between the aluminum plate and the hydrophobic film layer.

6. A heat exchanger, characterized in that, It has fins formed from the aluminum fin material as described in claim 1 or claim 2.

7. A method for manufacturing aluminum fins, characterized in that, include: The process of forming a hydrophobic film layer containing acrylic resin and polytetrafluoroethylene particles on the surface of an aluminum plate. The process of forming a hydrophilic film layer on the surface of the hydrophobic film layer, In the process of forming the hydrophilic film layer, at least a portion of the polytetrafluoroethylene particles are formed to protrude from the surface of the hydrophilic film layer.

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