JP7651361B2 - 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 such as air conditioners.

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 fins are arranged in parallel with narrow intervals.

When the surface temperature of the fins of a heat exchanger drops below the dew point, condensed water adheres to the fins. If the fins have low hydrophilicity, the contact angle of the condensed water increases, causing it to splash into the living environment. When the condensed water combines and grows large, it forms a bridge between adjacent fins, blocking the ventilation passage between the fins 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 surfaces of the fins.

Fins are manufactured through processes such as press molding, and processing oil is used during processing, such as press oil used in press molding. For example, Patent Document 2 discloses an aluminum fin material for heat exchangers in which a corrosion-resistant film, a hydrophilic film made of acrylic resin, and a water-soluble lubricant layer made of polyethylene glycol are formed in that order on an aluminum base material, in consideration of the fact that color skipping is likely to occur if an excessive amount of press oil is left on the surface.

Patent No. 2520308 JP 2013-130320 A

As described above, when processing a heat exchanger, heating is performed to volatilize the processing oil applied to the aluminum fin material. However, the coating film provided on the aluminum plate is deteriorated by the heat due to the high temperature and long time of heating, and the hydrophilicity is reduced.
Heating is also performed when copper pipes are inserted into the processed aluminum fin material and joined together, and the heating during this joining process also applies excessive heat to the aluminum fin material, reducing the hydrophilicity of the coating film.

Therefore, the present invention aims to provide an aluminum fin material that is excellent in heat resistance and in which the loss of hydrophilicity due to heating is suppressed.

The present invention relates to the following [1] to [5].
[1] An aluminum fin material having an aluminum plate and a coating layer, the coating layer comprising, in order from the aluminum plate side, a hydrophilic coating layer and a lubricating coating layer, the lubricating coating layer comprising a resin matrix containing polyethylene glycol as a main component and a hydrophilic component containing at least one of a sulfonic acid group and an ester group, the hydrophilic component exhibiting a change in the amount of functional groups contributing to hydrophilicity of 15% or less before and after heating under conditions of 200°C for 10 minutes.
[2] The aluminum fin material according to [1], wherein the content of the hydrophilic component per 100 parts by mass of the resin matrix is 2.0 to 4000 parts by mass.
[3] The aluminum fin material according to [1] or [2], wherein the coating amount of the lubricating coating layer is 0.05 to 3.0 mg / dm ² .
[4] The aluminum fin material according to any one of [1] to [3], wherein the hydrophilic coating layer contains an acrylic acid resin containing a sulfonic acid group and an ether bond.
[5] The aluminum fin material according to any one of [1] to [4], further comprising a base treatment layer between the aluminum plate and the coating layer.

According to the present invention, it is possible to suppress the decrease in hydrophilicity of the aluminum fin material surface even when the aluminum fin material is heated during processing of a heat exchanger or when copper tubes are inserted into the aluminum fin material and joined together. As a result, it is possible to provide an aluminum fin material that prevents water splashing and reduces ventilation resistance for a long period of time without losing the initial hydrophilic effect of the aluminum fin material during processing, etc.

FIG. 1 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>
The aluminum fin material (hereinafter, sometimes simply referred to as "fin material") 10 according to this embodiment has an aluminum plate 1 and a coating layer 2, as shown in Fig. 1. The coating layer 2 includes, in order from the aluminum plate 1 side, a hydrophilic coating layer 2b and a lubricating coating layer 2c. The coating layer 2 may further include a corrosion-resistant coating layer 2a, and when the corrosion-resistant coating layer 2a is included, it is located between the aluminum plate 1 and the hydrophilic coating layer 2b.
A base treatment layer (not shown) 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.

The lubricating coating layer 2c includes a resin matrix containing polyethylene glycol as a main component and a hydrophilic component containing at least one of a sulfonic acid group and an ester group, and the amount of functional groups that contribute to hydrophilicity of the hydrophilic component changes by 15% or less before and after heating at 200°C for 10 minutes.
The lubricating coating layer 2c is a layer intended to lubricate the surface of the fin material and obtain good processability. By providing the lubricating coating layer 2c with the above-mentioned configuration, the hydrophilic effect of the aluminum fin material 10 can be maintained without being lost by heating or the like, and the heat resistance is excellent. Furthermore, by setting the content of the hydrophilic component in the resin matrix in the lubricating coating layer 2c to an appropriate range, good processability can also be achieved. As a result, good processability and properties such as hydrophilicity related to preventing water splashing and reducing ventilation resistance can be achieved and improved without interfering with each other.

(Aluminum plate)
The aluminum plate 1 is a concept that includes a plate made of aluminum and a plate made of an aluminum alloy, and an aluminum plate that has been conventionally used for aluminum fin materials can be used.
As the aluminum plate 1, 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 1 has a thickness that is appropriately determined according to 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.

(Lubricating coating layer)
The lubricating coating layer 2c is a layer intended to obtain good processability by increasing the lubricity of the fin material surface. Specifically, by containing a resin that increases lubricity, the friction coefficient of the fin material surface is reduced, making it lubricated, and improving press formability when processing the fin material into a fin.

The lubricating coating layer 2c contains a resin matrix and a hydrophilic component.
The resin matrix is a resin component that is the base composition for forming the lubricating coating layer 2c. For example, the content of the resin matrix in the lubricating coating layer 2c is preferably 60% by mass or more based on the total amount of the components constituting the lubricating coating layer 2c. The upper limit of the content of the resin matrix is not particularly limited, but is, for example, 70% by mass or less.

The resin matrix contains polyethylene glycol (PEG) as a main component. In this specification, polyethylene glycol (PEG) also includes modified compounds thereof. A modified polyethylene glycol compound is a modified polyethylene glycol having one or more functional groups selected from the group consisting of a urethane bond, an ester bond, and an ether bond in its structure. Among these, modified polyethylene glycols having a urethane bond in their structure are preferred because they have functional groups with excellent elongation.

By including a resin matrix containing polyethylene glycol as the main component, when combined with a specific hydrophilic component described below, the deterioration of hydrophilic function due to heat can be suppressed, resulting in good heat resistance.

The resin constituting the resin matrix may be polyethylene glycol alone, or may contain other resins in addition to polyethylene glycol.
Examples of other resins include resins having a hydrophilic group, and examples of the hydrophilic group include a hydroxyl group, a carboxyl group, a sulfonic acid group, and a polyether group.

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

The resin matrix may contain resins other than polyethylene glycol, but containing polyethylene glycol as a main component means that the ratio of polyethylene glycol to the total amount of polyethylene glycol and other resins is 60 mass% or more. When the polyethylene glycol contains two or more types of polyethylene glycols with different molecular weights or structures, the total ratio of them may be 60 mass% or more.
The proportion of polyethylene glycol to the total amount of polyethylene glycol and other resins is preferably 70% by mass or more, more preferably 80% by mass or more, and the upper limit may be 100% by mass, that is, the resin may be composed only of polyethylene glycol.

The hydrophilic component contained in the lubricating coating layer 2c contains at least one of a sulfonic acid group and an ester group. This hydrophilic component exhibits a change in the amount of functional groups that contribute to hydrophilicity of 15% or less before and after heating at 200°C for 10 minutes. By including such a hydrophilic component, hydrophilicity with excellent heat resistance can be obtained.

Examples of hydrophilic components include sulfonic acid acrylic compounds, phosphate ester compounds, acrylic compounds, etc. However, as mentioned above, the change in the amount of functional groups that contribute to hydrophilicity before and after heating at 200°C for 10 minutes must be 15% or less.

The change in the amount of functional groups contributing to hydrophilicity before and after heating at 200° C. for 10 minutes may be 15% or less, preferably 10% or less, and more preferably 5% or less.
In this specification, the change in the amount of functional groups that contribute to hydrophilicity can be measured using a Fourier transform infrared spectrophotometer.

From the viewpoint of obtaining good hydrophilicity, the content of the hydrophilic component per 100 parts by mass of the resin matrix is preferably 2.0 parts by mass or more, more preferably 5.0 parts by mass or more, even more preferably 6.0 parts by mass or more, even more preferably 8.0 parts by mass or more, and particularly preferably 10 parts by mass or more. From the viewpoint of lubricity for obtaining good processability, the content of the hydrophilic component is preferably 6000 parts by mass or less, more preferably 5000 parts by mass or less, even more preferably 4000 parts by mass or less, and even more preferably 3000 parts by mass or less.

In addition to the above, the lubricating coating layer 2c may contain other optional components within the scope of the present 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.

For example, silicone components are one example of antifouling agents. Silicone components have low surface free energy and are thought to have low adhesion to substances. Therefore, by including silicone components, it is possible to suppress the adhesion of contaminants, mainly oil-based components.

The silicone component is a polymer of a silicon compound, and is a compound having a siloxane bond as a skeleton.The silicone component is preferably a modified polydimethylsiloxane derivative having one or more functional groups selected from polyether group, epoxy group, methacryl group, amino group, phenyl group, hydrogen group, and hydroxyl group in its structure, because it has high dispersibility in paint and high fixability in resin film, and more preferably a modified polydimethylsiloxane derivative having one or more functional groups selected from the group consisting of epoxy group, methacryl group, phenyl group, and hydrogen group in its structure.Also, silicone containing a long-chain alkyl group is also preferred.
Such modified polydimethylsiloxane derivatives and silicones containing long-chain alkyl groups may be nonionic, anionic, or cationic, with nonionic being preferred.

The lubricating coating layer 2c can be formed by applying a resin paint containing a resin matrix and a hydrophilic component onto the hydrophilic coating layer 2b, and solidifying it by drying, etc.

The amount of the lubricating coating layer 2c is preferably 0.05 mg/dm2 or ^more , more preferably 0.1 mg/dm2 or ^more , and even more preferably 0.2 mg/dm2 or ^more , from the viewpoint of obtaining sufficient lubricity and heat-resistant hydrophilicity. On the other hand, from the viewpoint of suppressing a decrease in hydrophilicity due to a part of the components constituting the lubricating coating layer 2c remaining on the surface when the surface of the fin material is wetted with water, the amount of the coating is preferably 3.0 mg/dm2 or ^less , more preferably 1.5 mg/dm2 or ^less , and even more preferably 1.0 mg/dm2 or ^less .

The thickness of the lubricating coating layer 2c is not particularly limited, but from the viewpoint of obtaining lubricity and heat-resistant hydrophilicity, assuming that the density of the coating layer is 1 g/cm ³ , the thickness is preferably 0.005 μm or more, more preferably 0.01 μm or more, and even more preferably 0.02 μm or more. Moreover, from the viewpoint of obtaining good coating workability when forming the lubricating coating layer 2c, the thickness is preferably 0.3 μm or less, more preferably 0.15 μm or less, and even more preferably 0.1 μm or less.
The thickness of the lubricating coating layer 2c can be adjusted by the concentration of the coating composition used to form the lubricating coating layer 2c, the selection of the bar coater number, and the like.

(Hydrophilic Coating Layer)
The hydrophilic coating layer 2b 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).

Among these, from the viewpoint of more suitably expressing the desired hydrophilicity even when the lubricating coating layer 2c is formed on the surface of the hydrophilic coating layer 2b, 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 be a copolymer of two or more monomers having a hydrophilic group. 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 2b 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 2c formed on the hydrophilic coating layer 2b. This is believed to be due to the surface-exposure effect of the surfactant.

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

From the viewpoint of improving hydrophilicity, it is more preferable that the anionic surfactant contains at least one compound selected from the group consisting of polyoxyethylene alkyl ether phosphate esters, polyoxyethylene alkyl ether sulfates, and polyoxyethylene alkyl sulfosuccinates.

The hydrophilic coating layer 2b can be formed by applying a resin paint containing a hydrophilic resin onto a layer that will be an underlying layer such as the corrosion-resistant coating layer 2a, and then solidifying the paint by drying or the like.
The amount of hydrophilic resin attached in the hydrophilic coating is preferably 0.2 mg/dm2 ^{or more} from the viewpoint of obtaining sufficient hydrophilicity, more preferably 1 mg/dm2 or ^more , and even more preferably 2 mg/dm2 or ^more . In addition, from the viewpoint of preventing the effect of the lubricating coating layer 2c from being impaired due to the hydrophilic resin being eluted when the surface of the fin material is wetted with water, the amount of hydrophilic resin attached is preferably 30 mg/dm2 or ^less , more preferably 20 mg/dm2 or ^less , and even more preferably 15 mg/dm2 or ^less .

In addition to the hydrophilic resin and surfactant, the hydrophilic coating layer 2b may contain other optional components within the scope of the present 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, 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 hydrophilic coating layer 2b is not particularly limited, but assuming that the density of the hydrophilic coating layer 2b is 1 g/ ^cm3 , the thickness is preferably 0.02 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 2b, the thickness is preferably 3 μm or less, more preferably 2 μm or less, and even more preferably 1.5 μm or less.
The thickness of the hydrophilic coating layer 2b can be adjusted by the concentration of the coating composition used to form the hydrophilic coating layer 2b, the selection of the bar coater number, etc.

In addition, the combined thickness of the hydrophilic coating layer 2b and the lubricating coating layer 2c is preferably 5 μm or less in order to prevent a decrease in the heat exchange efficiency of the fin material.

(Corrosion-resistant coating layer)
The corrosion-resistant coating layer 2a may be provided primarily for the purpose of increasing the corrosion resistance of the aluminum plate, and is preferably formed between the aluminum plate 1 and the hydrophilic coating layer 2b, and more preferably contains a hydrophobic resin.
When a base treatment layer (not shown) is formed on the surface of the aluminum plate 1, the corrosion-resistant coating layer 2a is formed on the base treatment layer.
The corrosion-resistant coating layer 2a can be formed, for example, by applying a resin paint containing a hydrophobic resin onto the aluminum plate 1 or onto the undercoat treatment layer, and then solidifying it by drying or the like.

The corrosion-resistant coating layer 2a makes it difficult for moisture such as condensation water, oxygen, chloride ions, and other ionic species to penetrate the aluminum plate 1, suppressing corrosion of the aluminum plate 1 and the generation of odor-causing aluminum oxides.

The hydrophobic resin in the corrosion-resistant coating layer 2a may be any known material. Examples include polyester, polyolefin, epoxy, urethane, and acrylic resins, and one or a mixture of two or more of these may be used.

In addition to the above, the corrosion-resistant coating layer 2a 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.
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 amount of the hydrophobic resin attached in the corrosion-resistant coating layer 2a is not particularly limited, but is preferably 1.0 mg/dm2 or ^more , and more preferably 3.0 mg/dm2 or ^more , from the viewpoint of imparting sufficient corrosion resistance to the aluminum plate 1. 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 attached is preferably 50 mg/dm2 ^{or less} , and more preferably 40 mg/dm2 or ^less .
The thickness of the corrosion-resistant coating layer 2a is preferably 0.05 μm or more from the viewpoint of obtaining good corrosion resistance, and the thickness is preferably 4 μm or less from the viewpoints of good film-forming properties, reduced defects such as cracks, and low heat transfer resistance of the corrosion-resistant coating layer 2a, thereby obtaining good heat exchange efficiency of the fin.
The thickness of the corrosion-resistant film layer 2a and the amount of the hydrophobic resin applied can be adjusted by the concentration of the coating composition used to form the corrosion-resistant film layer 2a and the selection of the bar coater number.

(Base treatment layer)
If desired, a base treatment layer may be provided between the aluminum plate 1 and the corrosion-resistant coating layer 2a.
By providing the undercoat treatment layer, the corrosion resistance of the aluminum plate 1 can be increased, and also the adhesion between the aluminum plate 1 and the corrosion-resistant coating layer 2a can be increased.

The undercoat treatment layer may be any known layer that can impart corrosion resistance to the aluminum plate 1. For example, a layer made of an inorganic oxide or an inorganic-organic composite compound may be used.
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 the aluminum plate 1 to a chromate phosphate treatment, a zirconium phosphate treatment, a zirconium oxide treatment, a chromate chromate treatment, a zinc phosphate treatment, a titanic acid phosphate treatment, or the like. 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 the aluminum plate 1 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 1 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)
The aluminum fin material 10 according to this embodiment can suppress the decrease in hydrophilicity on the fin material surface even after heating during processing, inserting a copper tube, etc. In addition, by setting the content of the hydrophilic component relative to the resin matrix in the lubricating coating layer 2c within an appropriate range, good processability can also be achieved.

The workability of the fin material 10 due to the lubricating coating layer 2c can be evaluated by the coefficient of friction.
The static friction coefficient measured by a horizontal linear reciprocating sliding method with processing oil applied to the surface of the fin material 10 is preferably 0.20 or less, more preferably 0.15 or less, and even more preferably 0.10 or less. The lower limit is not particularly limited, but is usually 0.01 or more.
When no processing oil is applied to the surface of the fin material 10, the static friction coefficient measured by a horizontal linear reciprocating sliding method is preferably 0.20 or less, more preferably 0.17 or less, even more preferably 0.15 or less, and even more preferably 0.12 or less. The lower limit is not particularly limited, but is usually 0.01 or more.

The heat resistance with respect to hydrophilicity of the fin material 10 can be evaluated by the contact angle when pure water is dropped onto the surface of the fin material 10 after the fin material 10 is heated.
The contact angle of pure water is measured using a contact angle meter. The surface of the fin material 10 is coated with processing oil, heated at 200° C. for 10 minutes, and then cooled to room temperature. After that, about 0.5 μL of pure water is dropped onto the surface. The contact angle of the droplet (pure water) is preferably 22° or less, more preferably 20° or less, and even more preferably 15° or less. The lower limit is not particularly limited, but is usually 5° or more.

In addition to the heat resistance related to the hydrophilicity of the fin material 10, the durability when the fin material 10 is used in a heat exchanger can be evaluated by the contact angle of pure water after undergoing a dry-wet cycle.
The surface of the fin material 10 is coated with processing oil, heated at 200°C for 10 minutes, and returned to room temperature. The fin material 10 is subjected to 14 cycles of the following steps (i) and (ii), which constitute one cycle. The temperature is then returned to room temperature, and about 0.5 μL of pure water is dropped onto the surface of the fin material 10. The contact angle of the droplet (pure water) is preferably 22° or less, more preferably 20° or less, and even more preferably 19° or less. The lower limit is not particularly limited, but is usually 5° or more.
(i) The fin material is exposed to ion-exchanged water at a flow rate of 0.1 mL/min for 8 hours.
(ii) Then dry at 80° C. for 16 hours.

The thickness of the fin material 10 varies depending on the application and is not particularly limited. For example, when used in a heat exchanger, the thickness is preferably 0.08 mm or more, more preferably 0.1 mm or more, in terms of the strength that can withstand processing. Also, in terms of processability and heat exchange efficiency, the thickness is preferably 0.3 mm or less, more preferably 0.2 mm or less.

<Method of manufacturing aluminum fin material>
An example of a manufacturing method for the aluminum fin material 10 according to this embodiment will be described, but the present invention is not limited to this embodiment, and the aluminum fin material 10 can also be manufactured by other manufacturing methods as long as the effects of this embodiment are not hindered.

After the corrosion-resistant coating layer 2a is formed on the aluminum plate 1 by a known method, a coating composition containing a hydrophilic resin is applied and dried to form the hydrophilic coating layer 2b. Before forming the corrosion-resistant coating layer 2a, a base treatment layer may be formed as desired.
Next, a resin coating material containing a resin matrix and a hydrophilic component is applied onto the hydrophilic coating layer 2b and dried to form a lubricating coating layer 2c.

The resin matrix contained in the resin paint used to form the lubricating coating layer 2c contains polyethylene glycol as a main component. The hydrophilic component contained in the resin paint contains at least one of a sulfonic acid group and an ester group. The change in the amount of functional groups that contribute to hydrophilicity of this hydrophilic component before and after heating at 200°C for 10 minutes is 15% or less.

When forming the hydrophilic coating layer 2b, by including an acrylic acid resin containing a sulfonic acid group and an ether bond in the paint composition, the desired hydrophilicity can be more suitably expressed even if the lubricating coating layer 2c is formed on the surface of the hydrophilic coating layer 2b.

The lubricating coating layer 2c, the hydrophilic coating layer 2b, and the corrosion-resistant coating layer 2a are formed by preparing a coating composition constituting each coating layer, applying it to the object to be coated using a bar coater or roll coating method, and then baking it. In particular, if the aluminum plate 1 is in a coil shape, it is preferable from the viewpoint of productivity to use a roll coater or the like to continuously perform degreasing, painting, heating, winding, etc. Furthermore, the baking temperatures for the lubricating coating layer 2c, the hydrophilic coating layer 2b, and the corrosion-resistant coating layer 2a 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 a standard of 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. The coating amount of the primer layer was 20 mg/ ^dm2 .
Next, a coating composition containing an epoxy resin was applied with a bar coater and baked at 200° C. to form a corrosion-resistant coating layer. The coating amount of the corrosion-resistant coating layer was 7.5 mg/dm ² .
Next, a resin composition containing a sulfonic acid group-containing ether-based acrylic compound as a main component as a hydrophilic resin was applied to the surface of the corrosion-resistant coating layer using a bar coater. The coating was then baked at 220°C to form a hydrophilic coating layer. The coating amount of the hydrophilic coating layer was 6 mg/ ^dm2 .
Finally, a resin coating material containing a sulfonic acid acrylic compound as a hydrophilic component (B) added to modified polyethylene glycol as a resin matrix (A) was applied to the surface of the obtained hydrophilic coating layer with a bar coater, and baked at 160°C to form a lubricating coating layer, thereby obtaining an aluminum fin material. The amount of the sulfonic acid acrylic compound added per 100 parts by mass of modified polyethylene glycol was 6 parts by mass. The coating amount of the lubricating coating layer was 1.0 mg/ ^dm2 .

(Examples 2 to 15)
In forming the lubricating coating layer, the amount of the sulfonic acid acrylic compound serving as the hydrophilic component (B) relative to 100 parts by mass of the modified polyethylene glycol serving as the resin matrix (A) was changed to the amount shown in Table 1. An aluminum fin material was obtained in the same manner as in Example 1.

(Example 16)
In forming the lubricating coating layer, an aluminum fin material was obtained in the same manner as in Example 1, except that a phosphate ester compound was added in the amount shown in Table 1 instead of the sulfonic acid acrylic compound as the hydrophilic component (B).

(Comparative Example 1)
An aluminum fin material was obtained in the same manner as in Example 1, except that the sulfonic acid acrylic compound, which is the hydrophilic component (B), was not added in forming the lubricating coating layer.

(Comparative Example 2)
In forming the lubricating coating layer, modified polyethylene glycol as the resin matrix (A) was not used, and a layer consisting only of a sulfonic acid acrylic compound as the hydrophilic component (B) was formed. An aluminum fin material was obtained in the same manner as in Example 1.

(Comparative Example 3)
In forming the lubricating coating layer, an aluminum fin material was obtained in the same manner as in Example 1, except that, as the hydrophilic component (B), instead of the sulfonic acid acrylic compound, a polyacrylic acid compound containing an ester group but not a sulfonic acid group was added in the amount shown in Table 1.

(Comparative Example 4)
An aluminum fin material was obtained in the same manner as in Example 1, except that in forming the hydrophilic coating layer, a sulfonic acid acrylic compound was used instead of the resin composition containing the sulfonic acid group-containing ether-based acrylic compound, and in forming the lubricating coating layer, the sulfonic acid acrylic compound, which is the hydrophilic component (B), was not added.

(Example 17)
An aluminum fin material was obtained in the same manner as in Example 1, except that in forming the lubricating coating layer, the coating amount of the lubricating coating layer was 0.2 mg/ ^dm2 .

(Examples 18 to 31)
In forming the lubricating coating layer, the amount of sulfonic acid acrylic compound, which is the hydrophilic component (B), added to 100 parts by mass of modified polyethylene glycol, which is the resin matrix (A), was changed to the amount shown in Table 2. An aluminum fin material was obtained in the same manner as in Example 17.

(Comparative Example 5)
An aluminum fin material was obtained in the same manner as in Example 17, except that the sulfonic acid acrylic compound, which is the hydrophilic component (B), was not added in forming the lubricating coating layer.

(Comparative Example 6)
In forming the lubricating coating layer, modified polyethylene glycol as the resin matrix (A) was not used, and a layer consisting only of a sulfonic acid acrylic compound as the hydrophilic component (B) was formed. An aluminum fin material was obtained in the same manner as in Example 17.

(Change in Functional Group of Hydrophilic Component)
The change in the amount of functional groups contributing to hydrophilicity before and after heating at 200°C for 10 minutes for the hydrophilic components contained in the lubricating coating layer of the aluminum fin material was measured using a Fourier transform infrared spectrophotometer (NICOLET iZ10, manufactured by Thermo Fisher Scientific Co., Ltd.). Specifically, the intensity ratio of the peak near 1510 cm ^-1 indicating the functional group contributing to hydrophilicity to the peak near 2900 cm ^-1 indicating the functional group not contributing to hydrophilicity was taken as the functional group amount A in the component, and the functional group amount A in the component before heating was taken as the standard (1). It was determined whether the change in the functional group amount A in the component after heating at 200°C for 10 minutes was 15% or less (0.85 or more).
The results are shown in Tables 1 and 2 under "Changes (%) in Functional Groups in Lubricating Coating Layer (B)."

(Evaluation: Workability)
The obtained aluminum fin material was evaluated for workability due to the lubricating coating layer in terms of the coefficient of friction as described below.
The surface of the fin material was oiled with processing oil and the static friction coefficient was measured using a horizontal linear reciprocating sliding method (TS-501 model, manufactured by Kyowa Interface Science Co., Ltd.). The evaluation criteria are as follows, and the results are shown in "Friction coefficient with oiling" in Tables 1 and 2. Note that blanks mean that the measurement was not performed.
A: Very good (pass): Static friction coefficient is 0.15 or less. B: Good (pass): Static friction coefficient is greater than 0.15 and less than 0.20. C: Poor (fail): Static friction coefficient is greater than 0.20.

Regarding the workability of the lubricating coating layer, the static friction coefficient was measured in the same manner as above, except that no processing oil was applied to the surface of the fin material. The evaluation criteria are as follows, and the results are shown in "friction coefficient without oil application" in Tables 1 and 2. Note that blanks mean that no measurement was performed.
A: Very good (pass): Static friction coefficient is 0.15 or less. B: Good (pass): Static friction coefficient is greater than 0.15 and less than 0.20. C: Poor (fail): Static friction coefficient is greater than 0.20.

(Evaluation: Heat resistance)
The obtained aluminum fin material was evaluated for heat resistance related to hydrophilicity as described below by measuring the contact angle when pure water was dropped on the surface.
The surface of the fin material was coated with processing oil, heated at 200°C for 10 minutes, and then cooled to room temperature. After that, about 0.5 μL of pure water was dropped onto the surface. The contact angle of the droplet (pure water) was measured using a contact angle meter (manufactured by Kyowa Interface Science Co., Ltd., CA-05 model). The evaluation criteria are as follows, and the results are shown in "Contact angle after heating" in Tables 1 and 2. Note that blanks mean that the measurement was not performed.
A Very good (pass): Contact angle is 15° or less B Good (pass): Contact angle is more than 15° and less than 22° C Poor (fail): Contact angle is more than 22°

(Rating: Durability)
The durability of the fin material when used in a heat exchanger was evaluated as follows based on the contact angle of pure water after a dry-wet cycle.
The surface of the fin material was coated with processing oil, heated at 200 ° C for 10 minutes, and 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, and this process was repeated 14 times. After that, the temperature was returned to room temperature, and about 0.5 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 (manufactured by Kyowa Interface Science Co., Ltd., CA-05 type). The evaluation criteria are as follows, and the results are shown in "Contact angle after dry-wet cycle" in Tables 1 and 2. Note that blanks mean that the measurement was not performed.
A Very good (pass): Contact angle is 20° or less B Good (pass): Contact angle is more than 20° and less than 22° C Poor (fail): Contact angle is more than 22°

From the above results, it was found that by containing a resin matrix containing polyethylene glycol in the lubricating coating layer and a hydrophilic component that contains at least one of sulfonic acid groups and ester groups and has a small change in the amount of functional groups before and after heating, the decrease in hydrophilicity due to heating is suppressed, and an aluminum fin material with excellent heat resistance can be obtained. If the change in the amount of functional groups in the hydrophilic component before and after heating is large, good hydrophilicity after heating cannot be achieved, as shown in Comparative Example 3, even if the hydrophilic component contains sulfonic acid groups or ester groups. Furthermore, by setting the content of the hydrophilic component relative to the resin matrix in the lubricating coating layer within an appropriate range, good processability can also be achieved.

Reference Signs List 1 Aluminum plate 2 Coating layer 2a Corrosion-resistant coating layer 2b Hydrophilic coating layer 2c Lubricating coating layer 10 Aluminum fin material (fin material)

Claims (5)

The present invention has an aluminum plate and a coating layer.
The coating layer includes, in order from the aluminum plate side, a hydrophilic coating layer and a lubricating coating layer,
the lubricating coating layer includes a resin matrix containing polyethylene glycol as a main component, and a hydrophilic component containing a sulfonic acid acrylic compound or a phosphate ester compound ,
The aluminum fin material, wherein the hydrophilic component exhibits a change in the amount of functional groups that contribute to hydrophilicity of 15% or less before and after heating at 200°C for 10 minutes. The aluminum fin material according to claim 1, wherein the content of the hydrophilic component per 100 parts by mass of the resin matrix is 2.0 to 4000 parts by mass. The aluminum fin material according to claim 1 or ² , wherein the coating amount of the lubricating coating layer is 0.05 to 3.0 mg/dm2. The aluminum fin material according to any one of claims 1 to 3, wherein the hydrophilic coating layer contains an acrylic acid resin containing a sulfonic acid group and an ether bond. The aluminum fin material according to any one of claims 1 to 4, further comprising a base treatment layer between the aluminum plate and the coating layer.

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