JP7715686B2 - Aluminum fin material - Google Patents

Description

The present invention relates to aluminum fin materials, and in particular to aluminum fin materials suitable for use in heat exchangers for air conditioners and the like.

Heat exchangers are used in a variety of products, including room air conditioners, packaged air conditioners, refrigerated showcases, refrigerators, oil coolers, and radiators. Aluminum and aluminum alloys, which offer excellent thermal conductivity, workability, and corrosion resistance, are commonly used as materials for heat exchanger fins. Plate-fin and plate-and-tube heat exchangers have a structure in which the fin material is arranged in parallel at close intervals.

When the surface temperature of a heat exchanger's fin material drops below the dew point, condensation water adheres to it. If the fin material's surface is not hydrophilic, the contact angle of the condensation water increases, causing it to splash around in the living environment, a phenomenon known as water splashing. Furthermore, when the condensation water combines and grows, it forms bridges between adjacent fin materials, blocking the ventilation passages between the fin materials and increasing ventilation resistance.
In order to prevent such water splashing and reduce ventilation resistance, for example, Patent Document 1 proposes a technique of applying a hydrophilic surface treatment agent to the surface of the fin material to form a hydrophilic coating.

On the other hand, when an air conditioner is operating in heating mode, the surface temperature of the heat exchanger drops below freezing, and the condensation on the surface of the fin material turns into frost or ice, resulting in frost formation. If the hydrophilicity of the fin material surface is made too high, this frost formation becomes more likely. If the frost forms and blocks the spaces between the fin materials, the heat exchange efficiency of the heat exchanger drops significantly, necessitating defrosting operations, etc.

Therefore, various technologies for suppressing frost formation on fin materials have been studied. For example, Patent Document 2 discloses that frost formation is prevented by chemically adsorbing a fluoroalkoxysilane having a critical surface tension of 20 dyn/cm or less onto the surface of the air-side heat transfer surface, and forming a water-repellent coating having a structure in which _CF3 groups are oriented on the outermost surface. Furthermore, Patent Document 3 discloses that by forming a water-repellent coating on the surface and setting the average surface roughness Ra to 20 μm or more, the area of water droplets, snow, and ice that come into contact with the surface of the component is reduced, thereby reducing their adhesive force.

However, there are concerns that the water repellency may deteriorate over time, and that the durability may decrease due to a decrease in the strength of the water repellent coating when the average surface roughness Ra is increased.
Therefore, Patent Document 4 discloses a heat exchanger equipped with a specific heat transfer section. This heat transfer section has a first layer and a second layer located closer to the air than the first layer, and the second layer is composed of a polymer layer having multiple polymer chains. The roots of the main chains of adjacent polymer chains on the first layer side are bonded to each other through a metal oxide network structure. This allows the polymer chains in the second layer to be densely bonded in a direction perpendicular to the first layer, thereby reliably improving the hydrophilicity of the surface of the heat transfer section. Therefore, even if condensed water occurs on the surface of the heat transfer section, it is said that the growth of frost can be sufficiently delayed.

Patent No. 2520308 Japanese Patent Application Publication No. 10-281690 Japanese Patent Application Publication No. 9-228073 Japanese Patent Application Laid-Open No. 2019-158247

However, Patent Document 4 does not specifically consider the suppression of frost formation in heat exchangers. Furthermore, it cannot be said that improving hydrophilicity necessarily improves the suppression of frost formation, and separate testing is required to suppress frost formation.

In response to this, the inventors have discovered that frost formation on aluminum fin materials can be effectively suppressed by providing an anti-frost coating layer containing an amphoteric polymer that has both positively charged cationic groups and negatively charged anionic groups.
However, further investigation revealed that the hydrophilicity of the surface of the aluminum fin material is initially good, but decreases over time. This decrease in hydrophilicity causes condensation water to form bridges between adjacent fin materials, reducing heat exchange performance. Furthermore, if the condensation water remains on the surface, it can cause freezing.

The present invention aims to provide an aluminum fin material that has excellent frost suppression effects while maintaining good stability over time in the hydrophilic properties of its surface.

The present invention relates to the following [1] to [7].
[1] An aluminum fin material comprising an aluminum plate and an anti-frost coating layer and a hydrophilic coating layer, in this order, on at least one surface of the aluminum plate, wherein the anti-frost coating layer contains an amphoteric (meth)acrylamide resin, and the hydrophilic coating layer contains hydrophilic inorganic particles.
[2] The aluminum fin material according to [1], wherein the hydrophilic coating layer further contains at least one of polyethylene glycol and a modified polyethylene glycol.
[3] The aluminum fin material according to [1] or [2], wherein the amphoteric (meth)acrylamide resin is an amphoteric acrylamide resin.
[4] The aluminum fin material according to [1] or [2], wherein the hydrophilic coating layer has a coating amount of 0.01 to 1.0 g / m ² .
[5] The aluminum fin material according to [1] or [2], wherein the hydrophilic inorganic particles are hydrophilic silica particles.
[6] The aluminum fin material according to [1] or [2], further comprising a corrosion-resistant coating layer between the aluminum plate and the anti-frost coating layer.
[7] The aluminum fin material according to [1] or [2], further comprising a base treatment layer between the aluminum plate and the anti-frost coating layer.

According to the present invention, ice nucleation can be suppressed through the interaction between the condensed water adhering to the fin material surface and the anti-frost coating layer. As a result, the freezing of the condensed water is delayed, providing an aluminum fin material in which frost formation on the surface is suitably suppressed. Furthermore, the excellent hydrophilicity of the fin material surface can be maintained for an extended period of time. This prevents the formation of bridges due to the condensed water, and prevents a decrease in heat exchange performance and freezing.

FIG. 1 is a schematic cross-sectional view showing one embodiment of the configuration of an aluminum fin material. FIG. 2 is a schematic cross-sectional view showing one embodiment of the configuration of an aluminum fin material.

The following provides a detailed description of embodiments of the aluminum fin material and frost inhibitor of the present invention. Note that the use of "to" to indicate a range of values means that the values before and after it are included as both the lower and upper limits.

<Aluminum fin material>
As shown in Figure 1, the aluminum fin material 10 (hereinafter sometimes simply referred to as "fin material") of this embodiment comprises an aluminum plate 1, an anti-icing and frosting coating layer 2 and a hydrophilic coating layer 3 formed on at least one surface of the aluminum plate 1, in this order.
The anti-icing and frosting coating layer 2 contains an amphoteric (meth)acrylamide resin, and the hydrophilic coating layer 3 contains hydrophilic inorganic particles.

The aluminum fin material 10 may further include other layers, such as a base treatment layer 4 and a corrosion-resistant coating layer 5. If all of these layers are included, it is preferable to include the base treatment layer 4 and the corrosion-resistant coating layer 5 between the aluminum plate 1 and the anti-icing and frosting coating layer 2. In this case, as shown in Figure 2, it is preferable to include the base treatment layer 4, the corrosion-resistant coating layer 5, the anti-icing and frosting coating layer 2, and the hydrophilic coating layer 3 in this order from the aluminum plate 1 side. However, the hydrophilic coating layer 3 is preferably the outermost layer. Furthermore, other layers with other functions may be included as long as they do not impair the effects of the present invention.

In Figures 1 and 2, the hydrophilic coating layer 3 is provided directly on the surface of the anti-icing and frosting coating layer 2, but other layers may also be provided between these layers. In order to achieve both the anti-icing and frosting effect of the partially exposed anti-icing and frosting coating layer 2 and the high level of sustained hydrophilicity obtained by covering most of the upper layer, it is preferable that the hydrophilic coating layer 3 be provided directly on the anti-icing and frosting coating layer 2.

In Figures 1 and 2, the hydrophilic coating layer 3 is located on the outermost surface of the aluminum fin material 10, but other layers may be provided on the surface of the hydrophilic coating layer 3. In order to achieve high hydrophilicity in the initial state, it is preferable that the hydrophilic coating layer 3 be located on the outermost surface.

It is sufficient that at least one surface of the aluminum plate 1 has the above configuration, and both surfaces of the aluminum plate 1 may have the above configuration. Furthermore, if both surfaces of the aluminum plate 1 have the above configuration, both surfaces do not need to have the same configuration.

(Ice and frost prevention coating layer)
The anti-icing/frosting coating layer 2 contains an amphoteric (meth)acrylamide resin. The amphoteric (meth)acrylamide resin refers to at least one of an amphoteric methacrylamide resin and an amphoteric acrylamide resin.
The term "amphoteric" means that the amino group of (meth)acrylamide is composed of a cationic group that bears a positive charge, and an anionic group that bears a negative charge by introducing an anionic group into the amino group.
The use of an amphoteric (meth)acrylamide resin having an anionic group and a cationic group in one molecule is preferred from the viewpoint of solution stability, since it does not precipitate compared to a mixture of an anionic compound and a cationic compound.

By providing an anti-frost coating layer, water adhering to the fin material surface interacts with the anti-frost coating layer, suppressing the formation of ice nuclei and delaying the freezing of the water. As a result, the formation of frost can be suppressed.

The anti-frost coating layer can be formed, for example, by applying a paint composition containing an amphoteric (meth)acrylamide resin onto an aluminum plate, a substrate treatment layer, or a corrosion-resistant coating layer, and then solidifying it by drying or other means.

The amphoteric (meth)acrylamide resin contained in the anti-frost coating layer is an amphoteric polymer having cationic and anionic groups in its molecule. Only one type of amphoteric (meth)acrylamide resin may be used, or two or more types may be used.

The polar group portion of the cationic group of the amphoteric (meth)acrylamide resin is represented by -NR ₃ ⁺ , and examples of the structure include a primary amino group, a secondary amino group, a tertiary amino group, and a quaternary ammonium salt, where R represents a hydrogen atom, a linear or branched alkyl group having 1 to 5 carbon atoms, or a salt.

Examples of the polar group portion of the anionic group in amphoteric (meth)acrylamide resins include unsaturated monocarboxylic acids, unsaturated dicarboxylic acids, unsaturated tricarboxylic acids, unsaturated tetracarboxylic acids, unsaturated sulfonic acids, unsaturated phosphonic acids, and salts thereof.

The anti-frost coating layer preferably contains a crosslinking agent in addition to the amphoteric (meth)acrylamide resin, from the viewpoint of enhancing hydrophilicity.
Conventional crosslinking agents can be used, including, for example, crosslinking agents containing an oxazoline group, an oxiranyl group (1,2-epoxy structure), an oxetanyl group (1,3-epoxy structure), an isocyanate group, or a blocked isocyanate group. Of these, an oxazoline group or an oxiranyl group is more preferred. When sufficient hydrophilicity is achieved by including a crosslinking agent, the anti-frost coating layer can also serve as a hydrophilic coating layer, without the need to provide a separate hydrophilic coating layer on the fin material.

It is also preferable for the anti-frost coating layer to contain a surfactant in addition to the amphoteric (meth)acrylamide resin, as this enhances hydrophilicity. By including a surfactant, the hydrophilic coating layer can more effectively achieve both processability and hydrophilicity. This is thought to be due to the exposing effect of the surfactant.

Anionic, cationic, and nonionic surfactants are all applicable, and amphoteric surfactants are also applicable.

Examples of anionic surfactants include alkyl sulfate salts such as sodium lauryl sulfate, ethanolamine lauryl sulfate, and ammonium lauryl sulfate; polyoxyethylene alkyl ether sulfate salts such as polyoxyethylene lauryl ether sodium sulfate and polyoxyethylene alkyl ether sodium sulfate; alkyl benzene sulfonates and other sulfonates such as alkyl benzene sulfonates, sodium dodecyl benzene sulfonate, alkyl naphthalene sulfonates, sodium dialkyl sulfosuccinate, sodium alkyl diphenyl ether disulfonate, and sodium alkanesulfonate; reactive surfactants such as polyoxyalkylene alkenyl ether ammonium sulfate; fatty acid salts such as sodium stearate soap and potassium oleate soap; and other anionic surfactants such as potassium polyoxyethylene alkyl ether phosphate and dipotassium alkenyl succinate.

Examples of nonionic surfactants include polyoxyethylene alkyl ethers such as polyoxyethylene lauryl ether; polyoxyalkylene derivatives such as polyoxyethylene alkylene alkyl ethers, reactive surfactants such as polyoxyalkylene alkenyl ethers; sorbitan fatty acid esters such as sorbitan monolaurate; polyoxyethylene sorbitan fatty acid esters such as polyoxyethylene sorbitan monolaurate; polyoxyethylene sorbitol fatty acid esters such as polyoxyethylene sorbit tetraoleate; glycerin fatty acid esters such as glycerol monostearate, polyoxyethylene alkylamines, and alkyl alkanolamides .

Examples of cationic surfactants include alkylamine salts such as stearylamine acetate; and quaternary ammonium salts such as lauryltrimethylammonium chloride.

Examples of amphoteric surfactants include carboxybetaines, aminocarboxylic acids, sulfobetaines, aminosulfuric acid esters, and imidazolines .

The content of amphoteric (meth)acrylamide resin in the anti-frost coating layer is preferably 80% by mass or more, more preferably 85% by mass or more, and even more preferably 90% by mass or more, in terms of solid content. There is no particular upper limit to the content, and the anti-frost coating layer may be 100% by mass in terms of solid content, i.e., it may consist solely of amphoteric (meth)acrylamide resin.

When the anti-frost coating layer contains a crosslinking agent, the content of the crosslinking agent per 100 parts by mass of amphoteric (meth)acrylamide resin is preferably 1 part by mass or more, more preferably 3 parts by mass or more, and preferably 10 parts by mass or less, more preferably 8 parts by mass or less, in terms of solids content.

When the anti-frost coating layer contains a surfactant, the content of the surfactant per 100 parts by mass of amphoteric (meth)acrylamide resin is preferably 0.1 parts by mass or more, more preferably 0.5 parts by mass or more, and is preferably 2 parts by mass or less, more preferably 1.5 parts by mass or less, in terms of solids content.

The coating amount of the anti-icing and frosting coating layer is preferably 0.01 g/ ^m2 or more, more preferably 0.1 g/ ^m2 or more, from the viewpoint of obtaining a sufficient anti-icing and frosting effect. Although there is no particular upper limit, the coating amount of the anti-icing and frosting coating layer is preferably 5 g/ ^m2 or less, more preferably ³ g/m2 or less.

The anti-icing and frosting coating layer may contain other optional components within the range that does not impair the effects of the present invention. Examples of other optional components include various paint additives for improving the physical properties of the coating layer. In addition, in the process of forming the anti-icing and frosting coating layer, an aqueous solvent or a water-soluble organic solvent may be used from the viewpoints of paintability, workability, etc.
Examples of paint additives include surface conditioners, wetting and dispersing agents, anti-settling agents, antioxidants, anti-foaming agents, rust inhibitors, antibacterial agents, anti-fungal agents, etc. One type of these paint additives may be contained, or two or more types may be contained.

The thickness of the anti-icing and frosting coating layer is not particularly limited, but assuming that the density of the anti-icing and frosting coating layer is 1 g/cm ³ , the thickness is preferably 0.01 μm or more, more preferably 0.1 μm or more, and even more preferably 0.3 μm or more in order to obtain good anti-icing and frosting properties. Furthermore, the upper limit is not particularly limited, but is preferably 5 μm or less, and more preferably 3 μm or less.
The thickness of the anti-icing/frosting coating layer can be adjusted by the concentration of the coating composition used to form the anti-icing/frosting coating layer, the selection of the bar coater number, and the like.

(Hydrophilic film layer)
The hydrophilic coating layer contains hydrophilic inorganic particles.
The hydrophilic inorganic particles refer to inorganic particles whose surfaces have not been subjected to a hydrophobic treatment or inorganic particles whose surfaces have been subjected to a hydrophilic treatment. Hydrophilic inorganic particles have superior dispersibility in aqueous media compared to hydrophobic inorganic particles.

The hydrophilic inorganic particles are preferably such that when a hydrophilic coating layer consisting only of the hydrophilic inorganic particles is formed so as to have a coating amount of 0.05 g/m ² or more, the initial contact angle of water is 25° or less. When the hydrophilic coating layer contains polyethylene glycol or the like, which will be described later, the polyethylene glycol or the like may be washed away with water to form a hydrophilic coating layer consisting only of the hydrophilic inorganic particles, and the initial contact angle of water may be measured.
The above coating amount is not an essential amount for obtaining the effect of the hydrophilic coating layer, but is a coating amount that can be used as a guide when determining whether or not the inorganic particles are hydrophilic.

The hydrophilic coating layer can be formed, for example, by applying a coating composition containing hydrophilic inorganic particles onto the anti-frost coating layer or the corrosion-resistant coating layer, and then solidifying it by drying or other means.

Examples of inorganic materials that can be used as hydrophilic inorganic particles include silica (SiO ₂ ), titanium oxide (TiO ₂ ), alumina (Al ₂ O ₃ ), etc. Inorganic materials containing two or more of these may also be used, such as zeolite (aluminosilicate). One type of hydrophilic inorganic particle or two or more types may be used.

The shape of the hydrophilic inorganic particles is not particularly limited and may be spherical, plate-like, flat, needle-like, disc-like, etc. They may also be in the shape of a pearl necklace, where spherical particles are bonded together.

The size of the hydrophilic inorganic particles is not particularly limited, but from the perspective of dispersibility, the median diameter (D50) of the primary particles determined by dynamic light scattering is preferably 1 μm or less, and more preferably 300 nm or less. There is also no particular lower limit to the median diameter (D50), but it is, for example, 1 nm or more.

From the viewpoint of high hydrophilic stability over time, the content of hydrophilic inorganic particles in the hydrophilic coating layer is preferably 50% by mass or more, more preferably 55% by mass or more, and even more preferably 60% by mass or more, in terms of solid content ratio. There is no particular upper limit, and the hydrophilic coating layer may be 100% by mass, i.e., composed solely of hydrophilic inorganic particles. When the hydrophilic coating layer also contains components other than hydrophilic inorganic particles, the content of hydrophilic inorganic particles is preferably, for example, 95% by mass or less.

In addition to hydrophilic inorganic particles, the hydrophilic coating layer may contain a resin that enhances lubricity. This reduces the coefficient of friction on the fin material surface, improving lubrication and improving press formability when processing the fin material into fins.

Examples of resins that enhance lubricity include resins with hydrophilic groups. Examples of hydrophilic groups include hydroxyl groups, carboxyl groups, sulfonic acid groups, and polyether groups.

Resins with hydroxyl groups include polyethylene glycol (PEG) and polyvinyl alcohol (PVA). Resins with carboxyl groups include polyacrylic acid (PAA). Resins with both hydroxyl and carboxyl groups include carboxymethyl cellulose (CMC). Resins with sulfonic acid groups include sulfoethyl acrylate. Resins with polyether groups include polyethylene glycol (PEG) and modified compounds thereof. Copolymers of two or more types of monomers with hydrophilic groups can also be used.

Among the above, it is preferable that the composition further contains at least one of polyethylene glycol (PEG) and a modified polyethylene glycol (modified PEG).
Examples of modified PEG include those having a urethane bond in the molecule, those containing a glycidyl ether group in the molecule, methyl ethers in which one or both of the terminal -OH groups of the molecule are substituted with _-CH3 groups, and those having an amine in the molecule.

From the viewpoint of good lubricity, the total content of PEG and modified PEG in the hydrophilic coating layer is preferably 5% by mass or more, more preferably 8% by mass or more, and even more preferably 10% by mass or more, in terms of solids composition. Furthermore, from the viewpoint of effectively exerting the effects of the hydrophilic inorganic particles, the above total content is preferably 50% by mass or less, and more preferably 40% by mass or less.

The hydrophilic coating layer may contain a water-soluble thickener along with the resin that enhances lubricity. The water-soluble thickener helps to fix the resin that enhances lubricity. There are no particular restrictions on the water-soluble thickener, and conventionally known thickeners can be used, such as carboxymethyl cellulose (CMC).

The total content of water-soluble thickeners in the hydrophilic coating layer is preferably 0.5% by mass or more, preferably 1% by mass or more, and preferably 5% by mass or less, in terms of solid content.

The hydrophilic coating layer may contain hydrophilic inorganic particles, an optional resin for enhancing lubricity, such as PEG or a modified PEG, and a water-soluble thickener, as long as the effects of the present invention are not impaired. Examples of other optional components include various paint additives for improving the physical properties of the coating layer. Examples of paint additives include crosslinkers, surfactants, surface conditioners, wetting and dispersing agents, anti-settling agents, antioxidants, defoamers, antifouling agents, rust inhibitors, antibacterial agents, and anti-fungal agents. These paint additives may be used alone or in combination with other additives. Furthermore, in the process of forming the hydrophilic coating layer, aqueous solvents or water-soluble organic solvents may be used from the perspectives of paintability, workability, etc.

From the viewpoint of obtaining sufficient stability of hydrophilicity over time, the coating amount of the hydrophilic coating layer is preferably 0.01 g/ ^m2 or more, more preferably 0.03 g/ ^m2 or more, and even more preferably 0.05 g/ ^m2 or more. There is no particular upper limit to the coating amount of the hydrophilic coating layer, but it is preferably 5 g/m2 or ^less , more preferably 3 g/ ^m2 or less, and even more preferably 1 g/ ^m2 or less.

The thickness of the hydrophilic coating layer is not particularly limited, but assuming that the density of the hydrophilic coating layer is 1 g/ ^cm3 , in order to obtain good stability of hydrophilicity over time, the thickness is preferably 0.01 μm or more, more preferably 0.1 μm or more, and even more preferably 0.3 μm or more. The upper limit is not particularly limited, but is preferably 5 μm or less, and more preferably 3 μm or less.
The thickness of the hydrophilic coating layer can be adjusted by the concentration of the coating composition used to form the hydrophilic coating layer, the selection of the bar coater number, etc.

(aluminum plate)
The aluminum plate is a concept that includes a plate made of aluminum and a plate made of an aluminum alloy, and aluminum plates that have conventionally been used for aluminum fin materials can be used.
As the aluminum plate, 1000 series aluminum as specified in JIS H 4000:2014 is preferred because of its excellent thermal conductivity and workability. More specifically, aluminum of alloy numbers 1050, 1070, and 1200 are more preferred as the aluminum plate. However, the above description does not in any way exclude the use of 2000 series to 9000 series aluminum alloys or other aluminum plates as the aluminum plate.

The aluminum plate is cut to a desired thickness depending on the application and specifications of the fin material. For fin materials for heat exchangers, the thickness is preferably 0.08 mm or more, and more preferably 0.1 mm or more, from the perspective of fin strength. On the other hand, the thickness is preferably 0.3 mm or less, and more preferably 0.2 mm or less, from the perspective of workability into fins and heat exchange efficiency.

(Corrosion-resistant coating layer)
The corrosion-resistant coating layer is not essential, but is a layer formed on the aluminum plate, if desired, to enhance the corrosion resistance of the aluminum plate, and preferably contains a hydrophobic resin.
When a substrate treatment layer is formed on the surface of the aluminum plate, the corrosion-resistant coating layer is preferably formed on the substrate treatment layer. Also, when an anti-icing/frosting coating layer is formed on the aluminum plate or the substrate treatment layer, the corrosion-resistant coating layer may be formed on the anti-icing/frosting coating layer.

The corrosion-resistant coating layer can be formed, for example, by applying a coating composition containing a hydrophobic resin onto an aluminum plate, a substrate treatment layer, or an anti-frost coating layer, and then solidifying it by drying or other means.

The corrosion-resistant coating layer makes it difficult for moisture such as condensation, oxygen, chloride ions, and other ionic species to penetrate the aluminum plate, thereby suppressing corrosion of the aluminum plate and the formation of odor-causing aluminum oxides.

The hydrophobic resin in the corrosion-resistant coating layer can be any conventionally known resin. Examples include polyester, polyolefin, melamine, epoxy, urethane, and acrylic resins, and one or a mixture of two or more of these can be used.

In addition to the above, the corrosion-resistant coating layer may contain other optional components within the range that does not impair the effects of the present invention. Examples of optional components include various paint additives for improving the physical properties of the coating. Examples of paint additives include water-soluble organic solvents, crosslinking agents, surfactants, surface conditioners, wetting and dispersing agents, anti-settling agents, antioxidants, antifoaming agents, rust inhibitors, antibacterial agents, and anti-fungal agents. These paint additives may be contained alone or in combination of two or more.
In the process of forming the corrosion-resistant coating layer, an aqueous solvent or a water-soluble organic solvent may be used from the viewpoint of paintability, workability, etc.

The amount of the hydrophobic resin coating in the corrosion-resistant coating layer is not particularly limited, but from the viewpoint of imparting sufficient corrosion resistance to the aluminum plate, it is preferably 0.05 g/ ^m2 or more, and more preferably 0.2 g/m2 or ^more . On the other hand, from the viewpoint of suppressing a decrease in the heat exchange efficiency of the fin, the amount of the hydrophobic resin coating is preferably 15 g/m2 ^or less, and more preferably 3 g/ ^m2 or less.

The thickness of the corrosion-resistant coating layer is preferably 0.05 μm or more from the viewpoint of obtaining good corrosion resistance, and is preferably 15 μm or less from the viewpoints of good film-forming properties, reduced defects such as cracks, low heat transfer resistance of the corrosion-resistant coating layer, and good heat exchange efficiency of the fin.
The thickness of the corrosion-resistant coating layer and the amount of the hydrophobic resin applied can be adjusted by selecting the concentration of the coating composition used to form the corrosion-resistant coating layer and the bar coater number.

(Base treatment layer)
The primer treatment layer is not essential, but is a layer that is formed on the aluminum plate as desired. The primer treatment layer can improve the corrosion resistance of the aluminum plate, and when the fin material has a corrosion-resistant coating layer, providing the primer treatment layer between the aluminum plate and the corrosion-resistant coating layer can improve the adhesion between the two layers.

The undercoat treatment layer may be any known layer that can impart corrosion resistance to the aluminum plate, such as a layer made of an inorganic oxide or an inorganic-organic composite compound.
As the inorganic material constituting the inorganic oxide or inorganic-organic composite compound, chromium (Cr), zirconium (Zr), or titanium (Ti) is preferred as the main component.

The inorganic oxide layer that serves as the base treatment layer can be formed, for example, by subjecting the aluminum plate to chromate phosphate treatment, zirconium phosphate treatment, zirconium oxide treatment, chromate chromate treatment, zinc phosphate treatment, or titanic acid phosphate treatment. However, the type of inorganic oxide is not limited to those formed by these treatments.

The layer made of an inorganic-organic composite compound that serves as the undercoat treatment layer can be formed, for example, by subjecting an aluminum plate to a coating-type chromate treatment or a coating-type zirconium treatment. Specific examples of such inorganic-organic composite compounds include acrylic-zirconium composites.

The thickness of the undercoat treatment layer is not particularly limited and may be set as appropriate, but it is preferable that the deposition amount per unit area is 1 to 100 mg/ ^m2 in terms of metals such as Cr, Zr, and Ti, and the thickness is preferably 1 to 100 nm.
The deposition amount and film thickness of the undercoat treatment layer can be adjusted by adjusting the concentration of the chemical conversion treatment solution used to form the undercoat treatment layer and the film formation treatment time.

Before forming the primer layer, the surface of the aluminum plate may be degreased using an alkaline degreasing solution. This improves the reactivity of the primer and also improves the adhesion of the formed primer layer.

(Characteristics of aluminum fin material)
Even if condensed water adheres to the surface of the aluminum fin material according to this embodiment, the interaction between the condensed water and the anti-frost coating layer can suppress ice nucleation. As a result, the freezing of the condensed water is delayed, and frost formation on the surface of the fin material can be effectively suppressed. Furthermore, since good hydrophilicity can be achieved not only initially but also with stability over time, the formation of bridges due to condensed water can be prevented, and deterioration of heat exchange performance and freezing can be prevented.

The frost-suppressing effect of the fin material can be evaluated by the following method.
A copper plate equipped with a refrigerant flow path, a Peltier element, and an air flow path was placed inside the upper part of an acrylic cylinder, and the device was placed in an environment with a temperature of 10°C and a relative humidity of 55%. Fin materials were placed on the copper plate in a position that came into contact with the air inside the cylinder. Next, air was blown into the cylinder at a speed of 1.5 m/s.
After the above process, the copper plate is cooled while continuing to blow air into the tube at the same air speed, the surface temperature is set to −7.5° C., and condensed water is intentionally deposited on the surface of the fin material.
A digital microscope is installed on the side of the fin material where condensation water adheres, and the state of condensation water and frost on the fin material surface is observed. The time from the start of cooling to the start of frost formation is measured as the "frost formation delay time" and the frost formation suppression effect is evaluated.
The frost formation delay time by the above method is preferably more than 20 minutes, more preferably more than 30 minutes.

Hydrophilicity is also an important parameter when using fin materials in heat exchangers. Therefore, hydrophilicity can be evaluated by the initial contact angle when pure water is dropped on the fin material surface.
Specifically, about 2 μL of pure water is dropped onto the surface of the fin material at room temperature, and the contact angle of the droplet (pure water) is measured as the initial contact angle using a contact angle measuring device.
The initial contact angle of the droplet (pure water) is preferably 30° or less, more preferably 25° or less, even more preferably 20° or less, and particularly preferably 10° or less. The lower limit is not particularly limited, but is usually 2° or more.

The stability of the hydrophilicity of the fin material over time can be evaluated by the contact angle when pure water is dropped onto the surface of the fin material after it has been subjected to a dry-wet cycle.
Specifically, the wet-dry cycle involves applying processing oil to the surface of the fin material, heating it at 200°C for 10 minutes, and then returning it to room temperature. Next, (i) the fin material is exposed to ion-exchanged water at a flow rate of 0.1 mL/min for 8 hours, and (ii) drying it at 80°C for 16 hours. This process is repeated 14 times. After that, the temperature is returned to room temperature, and approximately 2 μL of pure water is dropped onto the surface of the fin material. The contact angle of the droplet (pure water) is measured as the time-dependent contact angle using a contact angle meter.

The contact angle of a droplet (pure water) over time is preferably 30° or less, more preferably 25° or less, even more preferably 20° or less, and particularly preferably 10° or less. There is no particular lower limit, but it is usually 2° or more.

Drainage is also important for fin materials. Drainage can be evaluated by dropping a drop of water (pure water) onto the surface of the fin material, lifting one end of the fin material and tilting it, and measuring the angle (sliding angle) between the fin material and the horizontal plane when the drop begins to fall.
As with the contact angle, it can be evaluated by the initial sliding angle and the sliding angle over time after undergoing a dry-wet cycle. However, for both the initial sliding angle and the sliding angle over time, it is preferable that sliding occurs regardless of the angle, and the sliding angle is more preferably 50° or less, even more preferably 30° or less, even more preferably 20° or less, and particularly preferably 10° or less.

The coefficient of friction can be used as an index of the workability of fin material. A high coefficient of friction can cause wear of the mold when pressing the aluminum fin material with a mold during heat exchanger manufacturing. The fin material is subjected to three reciprocating strokes at a load of 200 g while changing the position using a Bowden tester, and the average value of the values obtained is used as the coefficient of friction.
The coefficient of friction is preferably 0.25 or less, more preferably 0.2 or less, even more preferably 0.15 or less, and particularly preferably 0.1 or less.
The coefficient of friction can be reduced by adding a component that enhances lubricity, such as PEG or modified PEG, to the hydrophilic coating layer.

<Method of manufacturing aluminum fin material>
An example of a manufacturing method for the aluminum fin material according to this embodiment will be described, but the present invention is not limited to this embodiment, and other manufacturing methods can also be used as long as they do not interfere with the effects of this embodiment.
Although the following example describes a case where a substrate treatment layer, a corrosion-resistant coating layer, an anti-icing/frosting coating layer, and a hydrophilic coating layer are formed in this order on the surface of an aluminum plate, the formation of the substrate treatment layer and the corrosion-resistant coating layer is optional, and the order of the layers can also be changed as appropriate.

A primer layer is formed on the surface of the aluminum plate using a known method. A corrosion-resistant coating layer is then formed on that surface using a known method.

Next, a coating composition containing an amphoteric (meth)acrylamide resin is applied onto the corrosion-resistant coating layer, dried, and baked to form an anti-icing/frosting coating layer.
The baking temperature is not particularly limited as long as the corrosion-resistant coating layer does not peel off, but is preferably 100° C. or higher, more preferably 200° C. or higher. In order to prevent oxidation of the resin of the corrosion-resistant coating layer, the baking temperature is preferably 400° C. or lower, more preferably 300° C. or lower. The baking temperature is the temperature of the oven in which baking is performed.

The baking time is not particularly limited as long as the corrosion-resistant coating layer does not peel off, but for example, 3 seconds or more is preferable, and 10 seconds or more is more preferable. Furthermore, from the perspective of preventing oxidation of the resin in the corrosion-resistant coating layer, the baking time is preferably 2 hours or less, and more preferably 1 hour or less.

A coating composition containing an amphoteric (meth)acrylamide resin may also contain other components, such as a surfactant. By including a surfactant, the surface tension can be adjusted as desired, improving coatability.

The solvent for the coating composition containing the amphoteric (meth)acrylamide resin is not particularly limited, but examples thereof include water, alcohol, aliphatic ketones, etc. Among these, water and alcohol are preferred, and as the alcohol, butanol, ethanol, etc. are preferred.
The solvent may be used alone or in combination of two or more. For example, in the case of a mixed solvent of water and alcohol, it is preferable from the viewpoint of coatability onto a substrate that the amount of alcohol is 1 to 20 parts by mass per 100 parts by mass of water.

From the viewpoint of paint stability, the solids concentration in a paint composition containing an amphoteric (meth)acrylamide resin is preferably 1% by mass or more, and more preferably 3% by mass or more. Furthermore, from the viewpoint of coatability onto substrates, the solids concentration is preferably 40% by mass or less, more preferably 20% by mass or less, and even more preferably 10% by mass or less.

When a coating composition containing an amphoteric (meth)acrylamide resin is applied, the film thickness is preferably 1 μm or more, more preferably 5 μm or more, from the standpoint of coatability. Furthermore, from the standpoint of solvent volatility, the film thickness is preferably 40 μm or less, more preferably 20 μm or less. Note that the film thickness here refers to the film thickness before drying. For example, when applying the coating composition using a bar coater, the film thickness can be adjusted by selecting the bar coater number, etc.

Next, a coating composition containing hydrophilic inorganic particles is applied to the surface of the anti-frost coating layer, dried, and baked to form a hydrophilic coating layer.
The baking temperature is not particularly limited as long as the anti-icing and frosting coating layer does not peel off, but is preferably 100° C. or higher, and more preferably 200° C. or higher. From the viewpoint of preventing oxidation of the anti-icing and frosting coating layer, the baking temperature is preferably 400° C. or lower, and more preferably 300° C. or lower. The baking temperature is the temperature of the oven in which baking is performed.

The baking time is not particularly limited as long as the anti-icing and frosting coating layer does not peel off, but for example, 3 seconds or more is preferable, and 10 seconds or more is more preferable. Furthermore, from the perspective of preventing oxidation of the resin in the anti-icing and frosting coating layer, the baking time is preferably 2 hours or less, and more preferably 1 hour or less.

The corrosion-resistant coating layer, anti-icing and anti-frosting coating layer, and hydrophilic coating layer are applied using a bar coater, roll coating, or similar method. In particular, if the aluminum plate is in a coiled form, it is preferable from a productivity perspective to use a roll coater or similar device to continuously degrease, paint, heat, wind, and perform other processes. The baking temperatures for the corrosion-resistant coating layer, anti-icing and anti-frosting coating layer, and hydrophilic coating layer can be set according to the components of the resin or other material used, and are preferably in the range of 120 to 270°C, for example.

The present invention will be explained in more detail below using examples and comparative examples, but the present invention is not limited to these examples and can be implemented with modifications within the scope of the invention, all of which are within the technical scope of the present invention.

Example 1
The aluminum plate used was an aluminum plate having a thickness of 0.1 mm and conforming to alloy number 1070 specified in JIS H 4000:2014. A primer layer was formed on one surface of the aluminum plate by phosphate chromate treatment.
Next, an amphoteric polyacrylamide resin was dissolved in water to prepare a coating composition. The solids concentration of the amphoteric polyacrylamide resin in this coating composition was 5 mass %, and the compound solids weight ratio of the amphoteric polyacrylamide resin, i.e., the proportion of the amphoteric polyacrylamide resin in the solids, was 100 mass %.
The coating composition was applied to the surface of the primer layer using a bar coater. The coating was then dried and baked at 225°C to form an anti-icing/frosting coating layer. The coating weight of the anti-icing/frosting coating layer was 0.2 to 0.3 g/ ^m² .
Next, a coating composition was prepared by dispersing the hydrophilic silica particles in water, in which the solid content of the hydrophilic silica particles was 2% by mass, and the weight ratio of the hydrophilic silica particles to the solid content of the compound, i.e., the proportion of the hydrophilic silica particles in the solid content, was 100% by mass.
The coating composition was applied to the surface of the anti-frost coating layer using a bar coater. The coating was then dried and baked at 225°C to form a hydrophilic coating layer, resulting in an aluminum fin material. The coating weight of the hydrophilic coating layer was 0.08 g/ ^m² .

Example 2
An aluminum plate having a thickness of 0.1 mm and conforming to alloy number 1070 as specified in JIS H 4000:2014 was used. A primer layer was formed on one surface of the aluminum plate by phosphate chromate treatment. Next, a corrosion-resistant coating layer 1 containing ammonium polyacrylate was formed on the surface of the primer layer.
Next, an anti-frost coating layer and a hydrophilic coating layer were formed on the surface of the corrosion-resistant coating layer 1 in the same manner as in Example 1 to obtain an aluminum fin material. However, the solid content concentration of the hydrophilic silica particles in the coating composition forming the hydrophilic coating layer was 1 mass %, and the coating amount of the hydrophilic coating layer was 0.04 g/ ^m2 .

(Examples 3 to 5)
Aluminum fin material was obtained in the same manner as in Example 2, except that the solid content concentration of the hydrophilic silica particles in the coating composition forming the hydrophilic coating layer was changed to the concentration shown in Table 1 and the coating amount of the hydrophilic coating layer was changed to the amount shown in Table 1.

(Examples 6 to 15)
The process up to the formation of the anti-frost coating layer was carried out in the same manner as in Example 2. Next, a coating composition was prepared by dispersing hydrophilic silica particles, polyethylene glycol (PEG), and carboxymethyl cellulose (CMC) in water to obtain the compound solid content weight ratio shown in Table 1. The solid content concentration of this coating composition is as shown in Table 1.
The coating composition was applied to the surface of the anti-frost coating layer using a bar coater. The coating was then dried and baked at 160°C to form a hydrophilic coating layer, yielding an aluminum fin material. The coating amount of the hydrophilic coating layer is shown in Table 1.

Example 16
An aluminum fin material was obtained in the same manner as in Example 7, except that the corrosion-resistant coating layer 1 was changed to a corrosion-resistant coating layer 2 containing sodium silicate.

(Example 17)
An aluminum fin material was obtained in the same manner as in Example 16, except that the corrosion-resistant coating layer 2 was changed to a corrosion-resistant coating layer 3 containing an epoxy-based resin, and the paint composition forming the frost-preventing coating layer was changed to an amphoteric polyacrylamide resin and a surfactant, sodium dialkyl sulfosuccinate, in a solids weight ratio of 100/0.3.

(Comparative Example 1)
An aluminum fin material was obtained in the same manner as in Example 1, except that a hydrophilic coating layer was not formed.

(Comparative Example 2)
The coating composition for forming the anti-frost coating layer was prepared by dissolving and dispersing amphoteric polyacrylamide resin and hydrophilic silica particles in water in a solids weight ratio of 80/20. Aluminum fin material was obtained in the same manner as in Example 1, except that no hydrophilic coating layer was formed.

The compositions of the corrosion-resistant coating layer, anti-frost coating layer, and hydrophilic coating layer of the aluminum fin material obtained above are summarized in Table 1. In Table 1, a "-" indicates that the corresponding coating layer was not formed.

(Evaluation: frost suppression)
A copper plate equipped with a refrigerant flow path, a Peltier element, and an air flow path was placed inside the upper part of an acrylic cylinder, and the device was placed in an environment of 10°C and 55% relative humidity. Fin materials were placed on the copper plate in a position that would come into contact with the air inside the cylinder. Next, air was blown into the cylinder at a speed of 1.5 m/s.
After the above process, the copper plate was cooled to a surface temperature of −7.5° C. while continuing to blow air into the tube at the same air speed, and condensed water was intentionally deposited on the surface of the fin material.
A digital microscope was placed on the side of the fin material where condensation water adhered, and the state of condensation water and frost on the fin material surface was observed. The time from the start of cooling to the start of frost formation was measured as the "frost formation delay time," and the frost formation suppression effect was evaluated.
The evaluation criteria are as follows, and the results are shown in "Ice and frost suppression" in Table 1. In the table, "-" means that the measurement was not performed.
◎ Very good (pass): Delay time for frost formation is more than 30 minutes. ○ Good (pass): Delay time for frost formation is more than 20 minutes and less than 30 minutes. △ Poor (fail): Delay time for frost formation is less than 20 minutes.

(Evaluation: Hydrophilicity)
At room temperature, about 2 μL of pure water was dropped onto the surface of the aluminum fin material, and the contact angle of the droplet (pure water) was measured using a contact angle measuring instrument (manufactured by Kyowa Interface Science Co., Ltd., Model CA-05).
The results are shown in Table 1 under "hydrophilicity, contact angle, initial". An angle of 30° or less is good and can be said to pass, an angle of 25° or less is very good, and an angle of 20° or less is extremely good.

To evaluate the stability of hydrophilicity over time, the surface of the fin material was coated with processing oil, heated at 200 ° C for 10 minutes, and then returned to room temperature. Next, (i) the fin material was exposed to ion-exchanged water at a flow rate of 0.1 mL / min for 8 hours, and (ii) then dried at 80 ° C for 16 hours. This process was repeated 14 times. After that, the temperature was returned to room temperature, and approximately 2 μL of pure water was dropped on the surface of the fin material. The contact angle of the droplet (pure water) was measured using a contact angle meter as the contact angle over time.
The results are shown in "Hydrophilicity, Contact Angle, Time" in Table 1, where a value of 30° or less is considered good and acceptable, a value of 25° or less is considered very good, and a value of 20° or less is considered extremely good. In "Hydrophilicity, Evaluation" in Table 1, a contact angle of 10° or less in "Hydrophilicity, Contact Angle, Time" is considered particularly good and is indicated by "◎", a value of more than 10° and 30° or less is indicated by "◯", and a value of more than 30° is considered unacceptable and is indicated by "△".

(Evaluation: Water sliding)
At room temperature, a drop of water (pure water) was dropped onto the surface of the fin material, and when one end of the fin material was lifted and tilted, the angle between the fin material and the horizontal plane at the time when the drop of water began to fall was measured as the sliding angle.
The results are shown in Table 1 under "Water sliding property, sliding angle, initial stage." If the sample slid regardless of the angle, it was deemed to pass, and the smaller the sliding angle, the better.

In addition, to evaluate the stability of water sliding over time, the same process as when measuring the contact angle over time (evaluation: hydrophilicity) was repeated 14 times, and then the temperature was returned to room temperature, pure water was dropped onto the surface of the fin material, and the sliding of the droplet (pure water) was measured as the contact angle over time.
The results are shown in Table 1 under "Water sliding property, sliding angle, time elapsed." A sliding angle of more than 10° and sliding was deemed acceptable and indicated by a "◯." A sliding angle of 10° or less was deemed a "◎." In addition, a sample that did not slide over time or at the initial stage was deemed unacceptable and indicated by an "×.""-" indicates that no measurement was performed.

(Evaluation: Workability)
The fin material was subjected to three reciprocating slides using a Bowden testing machine while changing the position under a load of 200 g to determine the coefficient of friction, and the average value was taken as the coefficient of friction of the fin material.
The results are shown in "Processability, Friction Coefficient" in Table 1. A friction coefficient of more than 0.1 and not more than 0.25 is considered good and passed, indicated by "◯", and a friction coefficient of 0.1 or less is considered particularly good and indicated by "◎". A friction coefficient of more than 0.25 is considered unsatisfactory and indicated by "△", and "-" means that it was not measured.

The above results show that by providing the aluminum fin material of this embodiment with an anti-icing and frosting coating layer containing an amphoteric (meth)acrylamide resin and a hydrophilic coating layer containing hydrophilic inorganic particles, it is possible to effectively suppress the formation of anti-icing and frosting while also achieving good stability over time in the hydrophilicity of the surface. Furthermore, by adding a component that enhances lubricity, such as PEG, to the hydrophilic coating layer of the aluminum fin material of this embodiment, the coefficient of friction can be reduced without compromising the excellent anti-icing and frosting properties or hydrophilicity. As a result, wear on the mold used to press the fin material during heat exchanger manufacturing can be prevented.

1 Aluminum plate 2 Ice and frost prevention coating layer 3 Hydrophilic coating layer 4 Base treatment layer 5 Corrosion-resistant coating layer 10 Aluminum fin material

Claims (7)

An aluminum plate and an anti-frost coating layer and a hydrophilic coating layer are provided in this order on at least one surface of the aluminum plate;
The anti-frost coating layer contains an amphoteric (meth)acrylamide resin,
The aluminum fin material, wherein the hydrophilic coating layer contains hydrophilic inorganic particles. The aluminum fin material according to claim 1, wherein the hydrophilic coating layer further contains at least one of polyethylene glycol and a modified polyethylene glycol. The aluminum fin material according to claim 1 or 2, wherein the amphoteric (meth)acrylamide resin is an amphoteric acrylamide resin. The aluminum fin material according to claim 1 or 2, wherein the hydrophilic coating layer has a coating amount of 0.01 to 1.0 g/ ^m2 . The aluminum fin material according to claim 1 or 2, wherein the hydrophilic inorganic particles are hydrophilic silica particles. The aluminum fin material according to claim 1 or 2, further comprising a corrosion-resistant coating layer between the aluminum plate and the anti-frost coating layer. The aluminum fin material according to claim 1 or 2, further comprising a base treatment layer between the aluminum plate and the anti-frost coating layer.