JP7502232B2 - 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 of air conditioners and the like.

Heat exchangers are used in a variety of products, including room air conditioners, packaged air conditioners, freezer showcases, refrigerators, oil coolers, and radiators. Aluminum and aluminum alloys, which have 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 with narrow intervals.

When the surface temperature of the fin material of a heat exchanger falls below the dew point, condensed water adheres to the fin material. If the fin material has low hydrophilicity, the contact angle of the condensed water increases, causing it to splash around in the living environment, a phenomenon known as water splashing. When the condensed water combines and grows large, it forms a bridge between adjacent fin materials, blocking the ventilation passage between the fin materials and increasing ventilation resistance.
For the purpose of preventing such water splashing and reducing ventilation resistance, for example, Patent Document 1 proposes a technique of applying and forming a hydrophilic coating on the surface of the fin material.

On the other hand, when the air conditioner is operated in heating mode, the surface temperature of the heat exchanger drops below the freezing point, and the condensed water on the surface of the fin material turns into frost or ice, resulting in frost formation. If the hydrophilicity is made too high, the frost formation described above is more likely to occur. If the fin material becomes clogged with frost, the heat exchange efficiency of the heat exchanger will decrease significantly, making defrosting operation necessary.

Therefore, various techniques for suppressing the formation of ice and frost on fin materials have been studied. For example, Patent Document 2 discloses that fluoroalkoxysilane with a critical surface tension of 20 dyn/cm or less is chemically adsorbed on the surface of the air-side heat transfer surface, and a coating having a structure in which _CF3 groups are oriented on the outermost surface is formed to impart high water repellency and make the frost phenomenon less likely to occur. Patent Document 3 also discloses that a water-repellent coating is formed on the surface and the surface average roughness Ra is set to 20 μm or more, thereby reducing the area of water droplets (snow, ice) and 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 having a first layer and a second layer located closer to the air than the first layer as a heat transfer part, the second layer being composed of a polymer layer having a plurality of polymer chains, and the roots of the main chains of adjacent polymer chains on the first layer side being bonded to each other with a metal oxide network structure. According to this, the polymer chains of the second layer can be bonded at high density in the direction perpendicular to the first layer, so that the hydrophilicity of the surface of the heat transfer part can be reliably improved, and even if condensed water occurs on the surface of the heat transfer part, the growth of frost can be sufficiently delayed.

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

However, no specific study has been done on the suppression of frost formation for the heat exchanger in Patent Document 4. Also, it cannot be said that improving hydrophilicity necessarily improves the suppression of frost formation, and it is necessary to conduct separate tests on the suppression of frost formation.

The present invention aims to provide an aluminum fin material having an anti-frost coating layer that has excellent anti-frost properties.

The present invention relates to the following [1] to [6].
[1] An aluminum plate and a coating layer formed on a surface of the aluminum plate,
The coating layer includes an anti-frost coating layer containing an amphoteric polyacrylamide resin,
In an infrared absorption spectrum of the amphoteric polyacrylamide resin by an ATR method using an infrared spectrophotometer, the ratio D anion/D _amide of a peak intensity D anion corresponding to an anionic group of the amphoteric polyacrylamide resin observed at 1730 to 1710 cm ^-1 and a peak intensity D _amide corresponding to an amide group of the amphoteric polyacrylamide resin observed at ₁₆₆₀ to 1640 _cm ^-1 is 0.30 or less.
[2] The aluminum fin material described in [1], wherein the frost-preventing coating layer further contains an inorganic material.
[3] The aluminum fin material according to [2], wherein the inorganic material is a compound containing silicon.
[4] The aluminum fin material according to any one of [1] to [3], wherein the frost-preventing coating layer further contains a crosslinking agent.
[5] The coating layer further comprises at least one selected from the group consisting of a corrosion-resistant coating layer, a hydrophilic coating layer, and a lubricating coating layer. The aluminum fin material according to any one of [1] to [4].
[6] The aluminum fin material according to any one of [1] to [5], further comprising a base treatment layer between the aluminum plate and the coating layer.

According to the present invention, the interaction between the condensed water adhering to the fin material surface and the anti-frost coating layer can suppress the formation of ice nuclei. As a result, it is possible to provide an aluminum fin material in which the freezing of the condensed water is delayed and the formation of frost on the surface is suitably suppressed.

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 is a detailed description of an embodiment of the aluminum fin material according to the present invention. Note that the use of "to" to indicate a range of values means that the values before and after the range are included as the lower and upper limits.

<Aluminum fin material>
As shown in Fig. 1, the aluminum fin material 10 (hereinafter, sometimes simply referred to as "fin material") according to this embodiment has an aluminum plate 1 and a coating layer 2 formed on the surface of the aluminum plate 1. The coating layer 2 includes an icing/frosting suppression coating layer 2a containing an amphoteric polyacrylamide resin.

The coating layer 2 may further include at least one selected from the group consisting of a corrosion-resistant coating layer, a hydrophilic coating layer, and a lubricating coating layer. When all of these coating layers are included, for example, as shown in FIG. 2, the layers are provided in the order of corrosion-resistant coating layer 2b, hydrophilic coating layer 2c, and lubricating coating layer 2d from the aluminum plate 1 side.

In FIG. 2, the ice/frost suppression coating layer 2a is located between the hydrophilic coating layer 2c and the lubricating coating layer 2d, but the location of the ice/frost suppression coating layer 2a is not limited to this. That is, the ice/frost suppression coating layer 2a may be provided between the aluminum plate 1 and the corrosion-resistant coating layer 2b, between the corrosion-resistant coating layer 2b and the hydrophilic coating layer 2c, between the hydrophilic coating layer 2c and the lubricating coating layer 2d, or as the outermost layer.

The ice/frost suppression coating layer 2a may also function as the hydrophilic coating layer 2c. Details will be described later, but for example, by further including a crosslinking agent in the ice/frost suppression coating layer 2a, the hydrophilic effect can be more suitably obtained, resulting in an ice/frost suppression coating layer that combines the functions of a hydrophilic coating layer and the function of suppressing ice/frost.

A base treatment layer may further be provided between the aluminum plate 1 and the coating layer 2 .
Furthermore, it is sufficient that at least one surface of the aluminum plate 1 has the above-mentioned configuration, and both surfaces of the aluminum plate 1 may have the above-mentioned configuration. Furthermore, when both surfaces of the aluminum plate 1 have the above-mentioned configuration, both surfaces do not need to have the same configuration.

(Ice and frost prevention coating layer)
The frost-suppressing coating layer 2a includes an amphoteric polyacrylamide resin. The amphoteric polyacrylamide resin is an amphoteric polymer having a cationic group and an anionic group. Only one type of amphoteric polyacrylamide resin may be used, or two or more types of amphoteric polyacrylamide resins may be used.

Amphoteric polyacrylamide resins are composed of cationic groups that carry a positive charge in the molecule and anionic groups that carry a negative charge.

The polar group portion of the cationic group of the amphoteric polyacrylamide 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 is a hydrogen atom, a linear or branched alkyl group having 1 to 5 carbon atoms, a salt, etc.

The polar group portion of the anionic group of the amphoteric polyacrylamide resin includes unsaturated monocarboxylic acids, unsaturated dicarboxylic acids, unsaturated tricarboxylic acids, unsaturated tetracarboxylic acids, unsaturated sulfonic acids, unsaturated phosphonic acids, and salts thereof.

The method for producing the amphoteric polyacrylamide resin is not particularly limited, and a conventionally known method can be applied. For example, it can be obtained by a polymerization reaction of acrylamide with a cationic monomer having a cationic group and an anionic monomer having an anionic group. In addition, other monomers may be added as necessary.
These polymerization reactions can be initiated, for example, by the addition of an initiator, and if necessary, a chain transfer agent, etc. may be added. Furthermore, the amphoteric polyacrylamide resin may be a commercially available product.

In the frost-preventing coating layer containing the amphoteric polyacrylamide resin, a peak corresponding to the anionic group of the amphoteric polyacrylamide resin is observed near 1720 cm ⁻¹ , i.e., in the range of 1730 to 1710 cm ⁻¹ , in an infrared absorption spectrum measured by an attenuated total reflection (ATR) method using an infrared spectrophotometer. Also, a peak corresponding to the amide group of the amphoteric polyacrylamide resin is observed near 1650 cm ⁻¹ , i.e., in the range of 1660 to 1640 cm ⁻¹ .
By setting the ratio of the peak intensity D _anion , which corresponds to the anionic group of the amphoteric polyacrylamide resin observed at 1730 to 1710 cm ^-1 , to the peak intensity D _amide , which corresponds to the amide group of the amphoteric polyacrylamide resin observed at 1660 to 1640 cm ^-1 , (D _anion /D _amide) to 0.30 or less, good icing and frosting inhibition properties can be obtained.
The reason for this is unclear, but the inhibition of ice nucleation of condensed water attached to the fin material surface is related to the strength of the interaction between the frost-inhibiting coating layer and the condensed water, and if the peak intensity ratio represented by D _anion /D _amide is too high, ice nucleation due to the interaction between the frost-inhibiting coating layer and the condensed water cannot be inhibited, and by setting the ratio to 0.30 or less, ice nucleation is inhibited by the interaction between the frost-inhibiting coating layer and the condensed water. As a result, it is believed that good frost-inhibiting properties can be obtained.

The peak intensity ratio represented by D _anion /D _amide may be 0.30 or less, preferably 0.27 or less, and more preferably 0.25 or less. The lower limit of the peak intensity ratio is not particularly limited, but is preferably 0.05 or more, and more preferably 0.10 or more, from the viewpoint of retarding frost formation.

The frost-preventing coating layer preferably contains a crosslinking agent in addition to the amphoteric polyacrylamide resin from the viewpoint of enhancing hydrophilicity.
Any conventionally known crosslinking agent can be used, and examples of such crosslinking agents include crosslinking agents containing an oxazoline group, an oxiranyl group (1,2-epoxy structure), an oxetanyl group (1,3-epoxy structure), an isocyanate group, a blocked isocyanate group, and the like. Of these, an oxazoline group and an oxiranyl group are more preferred. When sufficient hydrophilicity is obtained by containing a crosslinking agent, the frost-preventing coating layer can also serve as a hydrophilic coating layer without providing a separate hydrophilic coating layer on the fin material.

In order to enhance hydrophilicity, it is preferable that the anti-frost coating layer further contains a surfactant in addition to the amphoteric polyacrylamide resin. By containing a surfactant, even if the fin material further comprises a lubricating coating layer, it is possible to more preferably achieve both processability due to the lubricating coating layer and hydrophilicity. This is thought to be due to the exposing action of the surfactant.

Any of anionic, cationic, or nonionic surfactants can be used, but nonionic surfactants are preferred from the viewpoint of ease of dispersion in the anti-frost coating layer.

Examples of anionic surfactants include polyoxyethylene alkyl ethers, polyoxyethylene alkyl ether phosphates, polyoxyethylene alkyl ether sulfates, polyoxyethylene alkyl sulfosuccinates, polyoxyethylene polyoxypropylene block copolymers, etc.

Examples of nonionic surfactants include ethylenediamine polyoxypropylene-polyoxyethylene condensates, polyoxyethylene sorbitan monolaurate, polyoxyethylene polyoxypropylene block polymers, polyoxyethylene sorbitan monostearate, etc.

The anti-frost coating layer preferably further contains an inorganic material from the viewpoint of increasing hydrophilicity. Examples of the inorganic material include compounds containing silicon and compounds containing titanium, such as colloidal silica, sodium silicate, silicone oligomers, silane coupling agents, titanium alkoxides, and titanium oxide.

The icing/frost-suppressing coating layer can be formed by applying a paint composition containing an amphoteric polyacrylamide resin onto an aluminum plate or layer on which the icing/frost-suppressing coating layer is to be formed, and solidifying the composition by drying or the like.
The content of the amphoteric polyacrylamide resin in the frost-preventing coating layer is preferably 60% by mass or more, more preferably 70% by mass or more, even more preferably 75% by mass or more, and most preferably 80% by mass or more, in terms of solid content ratio. The upper limit of the content is not particularly limited, and the frost-preventing coating layer may be 100% by mass in terms of solid content ratio, i.e., it may be composed only of the amphoteric polyacrylamide resin.

When the anti-frost coating layer contains a crosslinking agent, the content of the crosslinking agent per 100 parts by mass of amphoteric polyacrylamide resin is preferably 1 part by mass or more, more preferably 3 parts by mass or more, and is preferably 20 parts by mass or less, more preferably 10 parts by mass or less, in terms of solid content composition ratio.

When the anti-frost coating layer contains a surfactant, the content of the surfactant per 100 parts by mass of amphoteric polyacrylamide 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 solid content composition ratio.

When the anti-frost coating layer contains an inorganic material, the content of the inorganic material per 100 parts by mass of amphoteric polyacrylamide resin is preferably 1 part by mass or more, more preferably 5 parts by mass or more, and is preferably 35 parts by mass or less, more preferably 30 parts by mass or less, in terms of solid content composition ratio.

From the viewpoint of obtaining a sufficient ice/frost suppression effect, the coating amount of the ice/frost suppression coating layer is preferably 0.01 g/m ² or more, more preferably 0.02 g/m ² or more, even more preferably 0.05 g/m ² or more, and even more preferably 0.1 g/m ² or more. From the viewpoint of suppressing a decrease in the heat exchange efficiency of the fin, the coating amount of the ice/frost suppression coating layer is preferably 5.0 g/m ² or less, and more preferably 2.5 g/m ² or less.

The anti-frost coating layer may contain other optional components within the scope of the present invention, such as various water-based solvents and paint additives for improving the paintability, workability, and physical properties of the coating layer.
Examples of paint additives include water-soluble organic solvents, surface conditioners, wetting and dispersing agents, anti-settling agents, antioxidants, defoamers, rust inhibitors, antibacterial agents, anti-fungal agents, etc. These paint additives may be contained alone or in combination of two or more.

The thickness of the anti-icing/frosting coating layer is not particularly limited, but assuming that the density of the anti-icing/frosting coating layer is 1 g/ ^cm3 , 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 terms of obtaining good anti-icing/frosting properties. Also, from the viewpoint of obtaining good coating workability when forming the coating layer, the thickness is preferably 5 μm or less, and more preferably 2.5 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.

(Aluminum plate)
The aluminum plate is a concept that includes a plate made of aluminum and a plate made of an aluminum alloy, and an aluminum plate that has 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 preferable because of its excellent thermal conductivity and workability. More specifically, aluminum having alloy numbers 1050, 1070, and 1200 is more preferable as the aluminum plate. However, the above description does not exclude the use of 2000 series to 9000 series aluminum alloys or other aluminum plates as the aluminum plate.

The aluminum plate is of 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 standpoint of fin strength, etc. On the other hand, the thickness is preferably 0.3 mm or less, and more preferably 0.2 mm or less, from the standpoint of workability into fins and heat exchange efficiency, etc.

(Corrosion-resistant coating layer)
The corrosion-resistant coating layer may be formed on the aluminum plate mainly for the purpose of enhancing the corrosion resistance of the aluminum plate, and preferably contains a hydrophobic resin.
When a base treatment layer is formed on the surface of the aluminum plate, the corrosion-resistant film layer is formed on the base treatment layer. Also, when an anti-icing/frosting film layer is formed on the aluminum plate or on the base treatment layer, the corrosion-resistant film layer may be formed on the anti-icing/frosting film layer.
The corrosion-resistant coating layer can be formed, for example, by applying a coating composition containing a hydrophobic resin onto an aluminum plate or layer, drying and baking the coating.

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

The hydrophobic resin in the corrosion-resistant coating layer may be any known resin. Examples include polyester, polyolefin, melamine, epoxy, urethane, and acrylic resins, and one or a mixture of two or more of these resins may 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 water-based solvents and paint additives for improving the coatability, workability, and 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, defoamers, rust inhibitors, antibacterial agents, anti-fungal agents, etc. These paint additives may be contained alone or in combination of two or more.

The coating amount of 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 coating amount of the corrosion-resistant coating layer 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 film layer and the amount of the hydrophobic resin attached can be adjusted by the concentration of the coating composition used to form the corrosion-resistant film layer and the selection of the bar coater number.

(Hydrophilic Coating Layer)
The hydrophilic coating layer is a coating layer that imparts hydrophilicity to the surface of the fin material, and contains a conventionally known hydrophilic resin.
The hydrophilic resin may contain one type of resin or two or more types of resins as long as it has a hydrophilic group. Examples of the hydrophilic group include a hydroxyl group, a carboxyl group, a sulfonic acid group, and a polyether group.

Examples of those having a hydroxyl group include polyethylene glycol (PEG) and polyvinyl alcohol (PVA). Examples of those having a carboxyl group include polyacrylic acid (PAA). Examples of those having both a hydroxyl group and a carboxyl group include carboxymethyl cellulose (CMC). Examples of those having a sulfonic acid group include sulfoethyl acrylate. Examples of those having a polyether group include polyethylene glycol (PEG) and modified compounds thereof.

Among these, from the viewpoint of more suitably expressing the desired hydrophilicity even when a lubricating coating layer is formed on the surface of the hydrophilic coating layer, the hydrophilic resin is preferably one containing a sulfonic acid group or a polyether group, i.e., one containing an ether bond, more preferably one containing a sulfonic acid group and an ether bond, and particularly preferably an acrylic acid resin containing a sulfonic acid group and an ether bond.

An acrylic acid resin containing sulfonic acid and an ether bond is an acrylic acid resin that contains an unsaturated double bond group and a sulfonic acid group, and examples thereof include polyvinyl ether-sulfonic acid acrylic copolymer, benzyl ether-sulfonic acid acrylic copolymer, etc. However, the acrylic acid resin containing sulfonic acid and an ether bond is not limited to these.

In addition to the above, the hydrophilic resin may also be a copolymer of two or more types of monomers having hydrophilic groups. For example, a copolymer of acrylic acid and sulfoethyl acrylate may be used. The copolymer may be an alternating copolymer, a block copolymer, a graft copolymer, a random copolymer, etc., and there is no particular limitation on the arrangement of the monomers.

It is preferable that the hydrophilic coating layer further contains a surfactant in addition to the hydrophilic resin. This allows for better hydrophilicity to be achieved along with the processability provided by the lubricating coating layer formed on the hydrophilic coating layer. This is believed to be due to the exposing action of the surfactant.

Any of anionic, cationic, and nonionic surfactants can be used, but nonionic surfactants are preferred from the viewpoint of ease of dispersion in the hydrophilic coating layer.

Examples of nonionic surfactants include ethylenediamine polyoxypropylene-polyoxyethylene condensates, polyoxyethylene sorbitan monolaurate, polyoxyethylene polyoxypropylene block polymers, polyoxyethylene sorbitan monostearate, etc.

The hydrophilic coating layer can be formed by applying a coating composition containing a hydrophilic resin onto a corrosion-resistant coating layer, if one is formed, and then drying and solidifying by baking or the like. If an anti-icing/frosting coating layer is formed on a corrosion-resistant coating layer, the hydrophilic coating layer can be formed by applying a coating composition onto the anti-icing/frosting coating layer, then drying and solidifying by baking or the like.

The amount of the hydrophilic coating is preferably 0.01 g/m ² or more, more preferably 0.1 g/m ² or more, and even more preferably 0.2 g/m ² or more, from the viewpoint of obtaining sufficient hydrophilicity. In addition, from the viewpoint of preventing the effect of the lubricating coating layer from being hindered by the hydrophilic resin being eluted when the surface of the fin material is wetted with water, the amount of the hydrophilic coating layer is preferably 5 g/m ² or less, more preferably 3 g/m ² or less, and even more preferably 1 g/m ² or less.

In addition to the hydrophilic resin and surfactant, the hydrophilic coating layer may contain other optional components within the range that does not impair the effects of the present invention. Examples of the optional components include various water-based solvents and paint additives for improving the coatability, workability, and physical properties of the coating layer.
Examples of paint additives include water-soluble organic solvents, crosslinking agents, surface conditioners, wetting and dispersing agents, antisettling agents, antioxidants, defoamers, rust inhibitors, antibacterial agents, antifungal agents, etc. These paint additives may be contained alone or in combination of two or more.

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 , the thickness is preferably 0.05 μm or more, more preferably 0.1 μm or more, and even more preferably 0.2 μm or more in terms of obtaining good hydrophilicity. Also, from the viewpoint of obtaining good coating workability when forming the hydrophilic coating layer, the thickness is preferably 5 μm or less, more preferably 3 μm or less, and even more preferably 1 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.

In addition, if the fin material has a hydrophilic coating layer and a lubricating coating layer in addition to the frost-preventing coating layer, the total thickness of these layers is preferably 5 μm or less in order to prevent a decrease in the heat exchange efficiency of the fin material.

(Lubricating coating layer)
The lubricating coating layer is a layer intended to obtain good processability by increasing the lubricity of the fin material surface, and contains a conventionally known resin that increases lubricity. This reduces the friction coefficient of the fin material surface, making it lubricated, and improves press formability when processing the fin material into a fin.

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

Examples of resins having hydroxyl groups include polyethylene glycol (PEG) and polyvinyl alcohol (PVA). Examples of resins having carboxyl groups include polyacrylic acid (PAA). Examples of resins having hydroxyl and carboxyl groups include carboxymethyl cellulose (CMC). Examples of resins having sulfonic acid groups include sulfoethyl acrylate. Examples of resins having polyether groups include polyethylene glycol (PEG) and modified compounds thereof. In addition to these, copolymers of two or more types of monomers having hydrophilic groups can also be used.

In addition to the above, the lubricating coating layer may contain other optional components within the scope of the invention, such as various water-based solvents and paint additives for improving the coatability, workability, and physical properties of the coating layer.
Examples of paint additives include water-soluble organic solvents, crosslinking agents, surfactants, surface conditioners, wetting and dispersing agents, antisettling agents, antioxidants, defoamers, antifouling agents, rust inhibitors, antibacterial agents, antifungal agents, etc. These paint additives may be contained alone or in combination of two or more.

The lubricating coating layer can be formed by applying a coating composition containing a resin that enhances lubricity, such as a resin having a hydroxyl group, onto the hydrophilic coating layer, drying it, and solidifying it by baking, etc. Also, if there is no hydrophilic coating layer or if an anti-icing/frosting coating layer is formed on the hydrophilic coating layer, the lubricating coating layer is formed on the layer directly below or on the anti-icing/frosting coating layer.

The coating amount of the lubricating coating layer is preferably 0.05 g/ ^m2 or more, more preferably 0.1 g/ ^m2 or more, and even more preferably 0.2 g/ ^m2 or more, from the viewpoint of obtaining sufficient lubricity. On the other hand, from the viewpoint of suppressing a decrease in the heat exchange efficiency of the fin when the surface of the fin material is wetted with water, the coating amount 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 lubricating coating layer is not particularly limited, but from the viewpoint of obtaining good lubricity, assuming that the density of the coating layer is 1 g/cm ³ , the thickness is preferably 0.05 μm or more, more preferably 0.1 μm or more, and even more preferably 0.2 μm or more. Also, from the viewpoint of obtaining good coating workability during the coating layer formation, the thickness is preferably 5 μm or less, more preferably 3 μm or less, and even more preferably 1 μm or less.
The thickness of the lubricating coating layer can be adjusted by the concentration of the coating composition used to form the lubricating coating layer, the selection of the bar coater number, and the like.

(Base treatment layer)
A primer layer may optionally be provided on the aluminum plate.
By providing a base treatment layer, the corrosion resistance of the aluminum plate can be increased, and when a corrosion-resistant coating layer is further provided, the adhesion between the aluminum plate and the corrosion-resistant coating layer can be increased.

The undercoat treatment layer may be any layer that can impart corrosion resistance to the aluminum plate, and may be any layer known in the art, 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 layer made of inorganic oxide that serves as the undercoat treatment layer can be formed, for example, by subjecting an aluminum plate to chromate phosphate treatment, zirconium phosphate treatment, zirconium oxide treatment, chromate chromate treatment, zinc phosphate treatment, titanic acid phosphate treatment, etc. 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 appropriately, but it is preferable that the deposition amount per unit area is 1 to 100 mg/ ^m2 in terms of metal (Cr, Zr, 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 in forming the undercoat treatment layer and the film formation treatment time.

Before forming the base treatment layer, the surface of the aluminum plate may be degreased in advance using an alkaline degreasing solution, which improves the reactivity of the base treatment and also improves the adhesion of the formed base treatment layer.

(Characteristics of aluminum fin material)
In the aluminum fin material according to the present embodiment, even if condensed water adheres to the surface, the interaction between the condensed water and the frost-suppressing 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 suitably suppressed.

A copper plate equipped with a refrigerant flow path, a Peltier element, and an air flow path is disposed in the upper part of the inside of an acrylic cylinder, and the device is placed in an environment of a temperature of 10° C. and a relative humidity of 55%. A fin material is disposed on the copper plate at a position in contact with the air inside the cylinder. Then, air is 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 condensation water is intentionally caused to adhere to the surface of the fin material.
A digital microscope is installed on the side of the fin material where the condensation water adheres, and the state of the 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 according to the above method is preferably 10 minutes or more, more preferably 12 minutes or more, even more preferably 20 minutes or more, and even more preferably 30 minutes or more.

Hydrophilicity is also an important parameter when using fin materials in heat exchangers. Therefore, when a fin material is provided with a hydrophilic coating layer or when a crosslinking agent is added to an anti-frost coating layer to improve hydrophilicity, the hydrophilicity can be evaluated by the contact angle when pure water is dropped on the surface of the fin material.
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 using a contact angle meter. The contact angle of the droplet (pure water) is preferably 50° or less, more preferably 30° or less. The lower limit is not particularly limited, but is usually 5° or more.

<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.
In addition, the following example describes a case where a base treatment layer, a corrosion-resistant film layer, a hydrophilic film layer, an anti-icing/frosting film layer, and a lubricating film layer are formed in this order on the surface of an aluminum plate, but the formation of the base treatment layer, the corrosion-resistant film layer, the hydrophilic film layer, and the lubricating film layer is not essential but is optional. In addition, the position where the anti-icing/frosting film layer is formed is not limited to between the hydrophilic film layer and the lubricating film layer, and it can be formed at any position.

A base treatment layer is formed on the surface of the aluminum plate by a known method. A corrosion-resistant coating layer is then formed on the surface by a known method, after which a coating composition containing a hydrophilic resin is applied, dried, and baked to form a hydrophilic coating layer.

Next, a coating composition containing an amphoteric polyacrylamide resin is applied onto the hydrophilic coating layer, dried, and baked to form an anti-frost coating layer.
The coating composition containing the amphoteric polyacrylamide resin may contain other components such as a crosslinking agent, a surfactant, an inorganic material, etc. By containing a crosslinking agent or an inorganic material, better hydrophilicity can be achieved in addition to the effect of suppressing frost formation. Furthermore, by containing a surfactant, even if the fin material further comprises a lubricating coating layer, the workability due to the lubricating coating layer, the frost formation suppression property, and the hydrophilicity can be more preferably achieved at the same time.

The solvent of the coating composition containing the amphoteric polyacrylic resin is not particularly limited, and examples thereof include water, alcohol, aliphatic ketones, etc. Among them, 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.

The solids concentration in the coating composition containing the amphoteric polyacrylic resin is preferably 0.5% by mass or more, more preferably 1.0% by mass or more, and even more preferably 5.0% by mass or more, from the viewpoint of coatability on the substrate. The solids concentration is preferably 20% by mass or less, more preferably 15% by mass or less, and even more preferably 10% by mass or less, from the viewpoint of coatability on the substrate.

When a coating composition containing an amphoteric polyacrylic resin is applied, the film thickness is preferably 1 μm or more, more preferably 5 μm or more, from the viewpoint of coatability on the substrate. In addition, the film thickness is preferably 40 μm or less, more preferably 20 μm or less, from the viewpoint of the volatility of the solvent. Note that the film thickness here is the film thickness before drying, and when the coating composition is applied using a bar coater, for example, the film thickness can be adjusted by selecting the bar coater number, etc.

Next, a paint composition containing, for example, a resin with hydrophilic groups is applied to the surface of the frost-preventing coating layer, dried, and baked to form a lubricating coating layer.

The application of the corrosion-resistant coating layer, hydrophilic coating layer, anti-icing and anti-frost coating layer, and lubricating coating layer is carried out by a bar coater, roll coating method, or the like. In particular, if the aluminum plate is in a coil shape, it is preferable in terms of productivity to use a roll coater or the like to continuously perform degreasing, painting, heating, winding, etc. Furthermore, the baking temperatures for the corrosion-resistant coating layer, hydrophilic coating layer, anti-icing and anti-frost coating layer, and lubricating coating layer may be set according to the components of the resin, etc., used, and are preferably in the range of, for example, 120 to 270°C.

The present invention will be explained in more detail below with reference to examples and comparative examples. However, the present invention is not limited to these examples, and can be modified within the scope of the invention, and all such modifications are within the technical scope of the present invention.

Example 1
An aluminum plate having a thickness of 0.1 mm and conforming to the alloy number 1070 standard specified in JIS H 4000:2014 was used, and a phosphate chromate treatment was performed on the aluminum plate as a base treatment layer.
Next, a coating composition containing amphoteric polyacrylamide resin A-1 (T-MP183, manufactured by Seiko PMC Corporation) was prepared using water as a solvent, and applied to the surface of the aluminum plate on which the undercoat treatment layer was applied using a bar coater. The coating was then dried and baked to form an anti-frost coating layer, resulting in an aluminum fin material. The coating amount of the anti-frost coating layer was 0.29 g/ ^m2 .

Example 2
An aluminum fin material was obtained in the same manner as in Example 1, except that the coating amount of the frost-preventing coating layer was 0.02 g/ ^m2.

(Examples 3 to 9)
An aluminum fin material was obtained in the same manner as in Example 1, except that the amphoteric polyacrylamide resin used in the anti-icing and frosting coating layer and the coating amount of the anti-icing and frosting coating layer were changed to those shown in Table 2.
The amphoteric polyacrylamide resins A-1 to A-8 in Table 2 are as shown in Table 1.

Example 10
An aluminum fin material was obtained in the same manner as in Example 1, except that the icing and frost-suppressing coating layer was added to the amphoteric polyacrylamide resin A-1, colloidal silica (Snowtex (registered trademark) PS-S, manufactured by Nissan Chemical Industries, Ltd.) was added as an inorganic material, and the coating amount of the icing and frost-suppressing coating layer was changed to that shown in Table 2. As shown in the "Solid content weight ratio" in Table 2, the solid content ratio of the inorganic material to 100 parts by mass of the amphoteric polyacrylamide resin A-1 was 25 parts by mass.

(Example 11)
An aluminum fin material was obtained in the same manner as in Example 1, except that a corrosion-resistant coating layer was formed between the aluminum plate and the ice-frost-inhibiting coating layer, and the total coating amount of the ice-frost-inhibiting coating layer and the corrosion-resistant coating layer was 1.54 g/m ^2. The corrosion-resistant coating layer was formed by applying a coating composition containing a modified urethane resin onto the aluminum plate, drying it, and baking it.

(Comparative Example 1)
An aluminum fin material was obtained in the same manner as in Example 1, except that the amphoteric polyacrylamide resin used in the anti-icing and frosting coating layer and the coating amount of the anti-icing and frosting coating layer were changed to those shown in Table 2.

(Comparative Example 2)
An aluminum fin material was obtained in the same manner as in Comparative Example 1, except that the icing and frost-suppressing coating layer was added to the amphoteric polyacrylamide resin A-8, glyoxal was added as the aldehyde compound, and the coating amount of the icing and frost-suppressing coating layer was changed to that shown in Table 2. As shown in the "Solid content weight ratio" in Table 2, the solid content ratio of the aldehyde compound to 100 parts by mass of the amphoteric polyacrylamide resin A-8 was 200 parts by mass.

(Comparative Example 3)
An aluminum fin material was obtained in the same manner as in Example 1, except that no amphoteric polyacrylamide resin was used for the frost-preventing coating layer, and sodium silicate was used as the inorganic material.

(D _anion /D _amide )
The infrared absorption spectrum of the frost-suppressing coating layer of the aluminum fin material was measured using an infrared spectrophotometer (Nicoret iS50 FT-IR, manufactured by Thermo Fisher Scientific). The measurement was performed by the ATR method (built-in diamond ATR module, manufactured by Thermo Fisher Scientific), and the measurement conditions were: number of integrations: 36, wave number resolution: 4, measurement area: 4000 cm ^-1 to 400 cm ^-1 , detector: DGTS ^KBr . The ratio D anion / D _amide of the peak intensity D _anion corresponding to the anionic group of the amphoteric polyacrylamide resin observed at 1730 to 1710 cm ^-1 and the peak intensity D _amide corresponding to the amide group of the amphoteric polyacrylamide _resin observed at 1660 to 1640 cm -1 was obtained. The results are shown in Table 2.

(Evaluation: frost suppression)
A copper plate equipped with a refrigerant flow path, a Peltier element, and an air flow path was placed in the upper part of the inside of an acrylic cylinder, and the device was placed in an environment of a temperature of 10° C. and a relative humidity of 55%. A fin material was placed on the copper plate at a position in contact with the air inside the cylinder. Then, air was blown into the cylinder at a speed of 1.5 m/s.
After the above process, the copper plate was cooled while continuing to blow air into the tube at the same air speed, the surface temperature was set to −7.5° C., 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 the condensation water adhered, and the state of the condensation water and frost on the fin material surface was observed. The time from the start of cooling to when frost began to form 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 Table 2 under "Ice and frost suppression."
A Best (pass): frost formation delay time is 30 minutes or more B Very good (pass): frost formation delay time is 20 minutes or more and less than 30 minutes C Very good (pass): frost formation delay time is 12 minutes or more and less than 20 minutes D Good (pass): frost formation delay time is 10 minutes or more and less than 12 minutes E Poor (fail): frost formation delay time is less than 10 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 meter (Model CA-05, manufactured by Kyowa Interface Science Co., Ltd.). The evaluation criteria are as follows, and the results are shown in "Contact angle" in Table 2.
A: Very good (pass): Contact angle is 30° or less. B: Good (pass): Contact angle is more than 30° and 50° or less. C: Poor (fail): Contact angle is 50° or more.

From the above results, it was found that the formation of frost-suppressing coating layer containing a specific amphoteric polyacrylamide resin can effectively suppress the formation of frost. In Comparative Example 1, in which the ratio D anion/D amide of the peak intensity D _anion corresponding to the anionic group of the amphoteric polyacrylamide resin observed at 1730 to 1710 cm ^-1 and the peak intensity D _amide corresponding to the amide group of the amphoteric _{polyacrylamide} resin observed at 1660 to 1640 cm ^-1 was 0.33, the _effect of the present invention could not be confirmed.
In addition, while a delay time for icing/frost formation of 10 minutes or more is considered good, and a delay time of 30 minutes or more is best, results were also obtained which significantly exceeded the time considered to be the best for icing/frost formation inhibition, for example, 60 minutes in Example 1, 39 minutes in Example 4, 74 minutes in Example 7, and 47 minutes in Example 9.
The above effect was not impaired even when an inorganic material was added to the anti-frost coating layer or a corrosion-resistant coating layer was provided. Specifically, in Example 10, in which an inorganic material was added, the anti-frost delay time was 74 minutes, and in addition to realizing better hydrophilicity, the anti-frost inhibition properties were also improved. In addition, in Example 11, in which a corrosion-resistant coating layer was provided, the anti-frost delay time was 61 minutes, and it was confirmed that the anti-frost inhibition properties were not lost.

Reference Signs List 1 Aluminum plate 2 Coating layer 2a Anti-icing/frosting coating layer 2b Corrosion-resistant coating layer 2c Hydrophilic coating layer 2d Lubricating coating layer 10 Aluminum fin material

Claims (6)

The aluminum plate has a coating layer formed on a surface of the aluminum plate.
The coating layer includes an anti-frost coating layer containing an amphoteric polyacrylamide resin,
In an infrared absorption spectrum of the amphoteric polyacrylamide resin by an ATR method using an infrared spectrophotometer, the ratio D anion/D _amide of a peak intensity D anion corresponding to an anionic group of the amphoteric polyacrylamide resin observed at 1730 to 1710 cm ^-1 and a peak intensity D _amide corresponding to an amide group of the amphoteric polyacrylamide resin observed at ₁₆₆₀ to 1640 _cm ^-1 is 0.30 or less. The aluminum fin material according to claim 1, wherein the anti-frost coating layer further contains an inorganic material. The aluminum fin material according to claim 2, wherein the inorganic material is a compound containing silicon. The aluminum fin material according to any one of claims 1 to 3, wherein the anti-frost coating layer further contains a crosslinking agent. The aluminum fin material according to any one of claims 1 to 4, wherein the coating layer further comprises at least one selected from the group consisting of a corrosion-resistant coating layer, a hydrophilic coating layer, and a lubricating coating layer. The aluminum fin material according to any one of claims 1 to 5, further comprising a base treatment layer between the aluminum plate and the coating layer.

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