JP6887366B2 - Pre-coated fin material - Google Patents

Description

The present invention relates to a precoated fin material.

As a heat exchanger mounted on an air conditioner, a refrigerator, or the like, a so-called plate fin tube type heat exchanger having a large number of fins and a tube intersecting these fins is often used. The fins are produced by pressing a precoated fin material having a substrate made of aluminum (including pure aluminum and an aluminum alloy; the same applies hereinafter) and a resin film provided on the substrate.

The resin film is composed of a hydrophilic resin or a hydrophobic resin. Further, a lubricating material is provided on the surface of the resin film for the purpose of improving lubricity during press working. As this type of lubricant, polyethylene glycol and the like are often used. The lubricant elutes with moisture adhering to the fin surface such as condensed water, and flows out from the fin surface as the heat exchanger is used for a longer period of time.

Contaminants present in the environment adhere to the surface of the fins with the use of heat exchangers. Known pollutants include, for example, dust such as sand and dust, and oily substances such as higher fatty acids and higher alcohols. When the surface of the fin is covered with these contaminants, the hydrophilicity or hydrophobicity of the resin film is reduced, and the discharge of condensed water adhering to the fin surface is hindered. As a result, the heat exchange performance may be deteriorated.

However, since the conventional resin film is relatively soft, dust in contact with the resin film is likely to be embedded in the resin film. Further, the surface roughness of the conventional resin film is roughened due to the presence of the lubricating material, and in some cases, a large number of pores are formed on the surface of the resin film, so that dust adhering to the surface of the resin film is collected. , Easy to be held on the surface due to the anchor effect.

As described above, the conventional fin has a problem that dust easily adheres to the surface and it is difficult to remove the contaminants adhering to the surface.

Therefore, in order to solve such a problem, for example, Patent Document 1 describes a technique for forming a coating film having a structure in which fluororesin particles are exposed in a silica film made of silica fine particles on the surface of fins. In Patent Document 1, the adhesion of dust is suppressed by increasing the hardness of the coating film.

Further, Patent Document 2 describes a technique for forming an antifouling film on the surface of fins, which includes conductive particles and a binder and has a film surface in which the surface of the conductive particles is covered with a fluororesin. In Patent Document 2, the conductive particles reduce the electrostatic attraction between the dust and the antifouling film, and the fluororesin makes it easy to separate the dust from the antifouling film.

Japanese Unexamined Patent Publication No. 2009-235338 International release WO2012 / 144121

However, the techniques of Patent Documents 1 and 2 have a low effect of suppressing the adhesion of oily substances to fins. Therefore, there is still room for improvement in the effect of suppressing the adhesion of contaminants to the fins.

The present invention has been made in view of this background, and an object of the present invention is to provide a precoated fin material capable of suppressing the adhesion of contaminants to the fin surface and easily removing the contaminants adhering to the fin surface. To do.

One aspect of the present invention is a substrate made of aluminum and
It has a resin coating film formed on the substrate and exposed on the surface.
The resin coating film is
Polyvinyl alcohol (A) having a saponification degree of 95.0 to 99.8% and
Acrylamide polymer (B) having an acid value of 20 to 100 mgKOH / g and
Polyethylene glycol (C) having a number average molecular weight of 1000 to 20000 and
Fluororesin particles (D) having an average particle diameter of 100 to 300 nm on a volume basis are contained.
When the mass of the resin coating film is 100 parts by mass, the content of the polyethylene glycol (C) is 1.0 to 13 parts by mass, and the content of the fluororesin particles (D) is 2. 0 to 5.0 parts by mass,
The content of the polyvinyl alcohol (A) is 0.3 to 0.6 times the content of the acrylamide polymer (B) in terms of mass ratio.
It is in the pre-coated fin material.

The pre-coated fin material has a resin coating film having the specific composition. The resin coating film has a high concentration of polyvinyl alcohol (A) on the substrate side and an acrylamide-based coating on the surface side by setting the mass ratio of polyvinyl alcohol (A) and acrylamide-based polymer (B) to the above-mentioned specific range. A concentration gradient in which the concentration of the polymer (B) is high can be formed.

The precoated fin material can increase the hydrophilicity of the resin coating film by increasing the concentration of the acrylamide polymer (B) on the surface side. As a result, when the surface of the fins condenses, the dew condensation water easily infiltrates between the resin coating film and the pollutants adhering to the surface of the resin coating film, that is, oily substances, dust, and the like. As a result, these pollutants can be washed away with water such as dew condensation water on the fins and easily removed from the surface of the fins.

Further, the hardness of the precoated fin material can be increased by increasing the concentration of polyvinyl alcohol (A) on the substrate side. Therefore, the dust that comes into contact with the surface of the fin is likely to be repelled by the resin coating film. As a result, it is possible to suppress the adhesion of dust to the surface of the fin.

Further, the precoated fin material uses polyethylene glycol (C) and fluororesin particles (D) in combination as a lubricating material, so that the lubricity during press working is higher than that in the case where the fluororesin particles (D) are not used. The content of polyethylene glycol (C) can be reduced without impairing the above. Then, by reducing the content of polyethylene glycol (C), the surface of the resin coating film can be smoothed, and dust adhering to the surface of the fin can be easily peeled off from the fin. As a result, the dust adhering to the surface of the fin can be easily removed from the surface of the fin.

As described above, according to the pre-coated fin material, it is possible to suppress the adhesion of contaminants and easily remove the contaminants adhering to the surface.

It is a partially enlarged sectional view which shows the main part of the pre-coated fin material in an Example. It is a partially enlarged sectional view which shows the main part of the pre-coated fin material after being immersed in running water in an experimental example.

In the precoated fin material, the aluminum constituting the substrate can be appropriately selected from pure aluminum and an aluminum alloy according to desired mechanical properties, corrosion resistance, and the like. The substrate may be made of, for example, pure aluminum such as JIS A1200 or JIS A1050.

A resin coating film containing polyvinyl alcohol (A), acrylamide-based polymer (B), polyethylene glycol (C), and fluororesin particles (D) is formed on the substrate. The resin coating film may be laminated directly on the substrate, or another film or coating film may be interposed between the substrate and the resin coating film.

For example, the precoated fin material may further have an undercoat film laminated on the substrate. Depending on the material of the undercoat film, for example, the adhesion between the substrate and the corrosion-resistant coating film can be improved, and the corrosion resistance of the substrate can be improved.

As the base film, for example, chemical film treatment such as chromate treatment such as chromate treatment with phosphoric acid, non-chromate treatment with titanium phosphate, zirconium phosphate, molybdenum phosphate, zinc phosphate, zirconium oxide, etc. other than chromium compounds, so-called chemical conversion. A film obtained by the treatment can be adopted.

The chemical conversion treatment method described above includes a reaction type and a coating type, and any method may be used. The amount of the base film adhered can be appropriately selected from the range ^{of 100 mg / m 2 or less as the metal content, for example.} Further, the amount of adhesion of the base film can be measured by a fluorescent X-ray analyzer.

Further, the pre-coated fin material may further have a corrosion-resistant coating film interposed between the substrate and the resin coating film. The corrosion-resistant coating film may contain, for example, one or more resins selected from the group consisting of acrylic resins, epoxy resins, urethane resins and ester resins. The corrosion-resistant coating film containing these resins can further improve the corrosion resistance of the fins.

The film thickness of the corrosion-resistant coating film can be appropriately set from, for example, in the range of 0.3 to 5.0 μm. By setting the film thickness of the corrosion-resistant coating film within the above-mentioned specific range, it is possible to sufficiently obtain the effect of improving the corrosion resistance of the fins while avoiding the deterioration of the heat dissipation performance due to the corrosion-resistant coating film.

The polyvinyl alcohol (A) and the acrylamide-based polymer (B) can form a hydrophilic layer containing them in the resin coating film by settling on the substrate side in the process of forming the resin coating film. Further, in the hydrophilic layer, a concentration gradient can be formed in which the concentration of polyvinyl alcohol (A) is high on the substrate side and the concentration of acrylamide polymer (B) is high on the surface side. By forming such a hydrophilic layer in the resin coating film, it is possible to impart a function to the fins to suppress the adhesion of contaminants to the surface and to remove the contaminants adhering to the surface.

Polyethylene glycol (C) is exposed on the surface of the resin coating film. Further, at least a part of the fluororesin particles (D) is arranged on the surface of the above-mentioned hydrophilic layer. The polyethylene glycol (C) exposed on the surface of the resin coating film and the fluororesin particles (D) arranged on the surface of the hydrophilic layer are used in the precoat fin material and the press die when the precoat fin material is pressed. It functions as a lubricant that reduces friction with and can improve lubricity during press working.

The film thickness of the resin coating film can be appropriately set from the range of 0.3 to 2.0 μm, for example. By setting the film thickness of the resin coating film to 0.3 μm or more, the hydrophilicity of the resin coating film can be increased, and contaminants adhering to the surface of the fin can be more easily removed from the surface of the fin. Further, by setting the film thickness of the resin coating film to 2.0 μm or less, the coatability of the paint when forming the resin coating film can be improved.

The saponification degree of polyvinyl alcohol (A) in the resin coating film is 95.0 to 99.8%. By using polyvinyl alcohol (A) having a saponification degree in the specific range, the polyvinyl alcohol (A) in the resin coating film can be crystallized and the hardness of the resin coating film can be increased. As a result, the adhesion of dust to the surface of the fin can be suppressed more effectively.

From the viewpoint of increasing the hardness of the resin coating film and more effectively suppressing the adhesion of dust to the surface of the fins, the saponification degree of polyvinyl alcohol (A) is preferably 97.0% or more. When the saponification degree of the polyvinyl alcohol (A) is less than 95.0%, the hardness of the resin coating film is lowered, so that dust may easily adhere to the surface of the fins.

On the other hand, polyvinyl alcohol (A) having a saponification degree of more than 99.8% is difficult to produce by a general method, which may lead to an increase in material cost. By setting the saponification degree of polyvinyl alcohol (A) to 99.8% or less, preferably 99.5% or less, the hardness of the resin coating film can be increased while suppressing an increase in material cost.

The content of polyvinyl alcohol (A) in the resin coating film is 0.3 to 0.6 times that of the acrylamide polymer (B) in terms of mass ratio. By setting the ratio of polyvinyl alcohol (A) to the acrylamide polymer (B) in the above-mentioned specific range, a resin coating film having excellent hydrophilicity and high hardness can be formed on the substrate. As a result, it is possible to suppress the adhesion of contaminants to the fin surface and easily remove the contaminants adhering to the fin surface from the fin surface.

When the content of polyvinyl alcohol (A) is less than 0.3 times that of the acrylamide polymer (B), the content of polyvinyl alcohol (A) in the resin coating film is insufficient, so that the hardness of the resin coating film is insufficient. May lead to a decrease in. Therefore, in this case, dust may easily adhere to the surface of the fin. From the viewpoint of further increasing the hardness of the resin coating film and more effectively suppressing the adhesion of dust to the fin surface, the content of polyvinyl alcohol (A) is 0.35 times or more that of the acrylamide polymer (B). It is preferable to do so.

When the content of polyvinyl alcohol (A) exceeds 0.6 times that of the acrylamide polymer (B), the content of the acrylamide polymer (B) in the resin coating film is insufficient, so that the resin coating film is hydrophilic. It may lead to deterioration of sex. Therefore, in this case, it may be difficult to remove contaminants adhering to the surface of the fins. From the viewpoint of increasing the hydrophilicity of the resin coating film and more easily removing contaminants adhering to the fin surface, the content of polyvinyl alcohol (A) should be 0.5 times or less that of the acrylamide polymer (B). Is preferable.

The acid value of the acrylamide polymer (B) in the resin coating film is 20 to 100 mgKOH / g. By using the acrylamide-based polymer (B) having an acid value in the specific range, excellent hydrophilicity can be maintained for a long period of time. As a result, the contaminants adhering to the surface of the fins can be easily removed from the surface of the fins, and the ability to remove the contaminants can be maintained for a long period of time.

When the acid value of the acrylamide polymer (B) is less than 20 mgKOH / g, the acrylamide polymer (B) is likely to elute into water such as condensed water adhering to the surface of the fin. Therefore, as the period of use of the fins becomes longer, the content of the acrylamide-based polymer (B) in the resin coating film may decrease, which may lead to a decrease in hydrophilicity. As a result, the ability to remove pollutants may decline prematurely. From the viewpoint of maintaining the ability to remove contaminants for a longer period of time, the acid value of the acrylamide polymer (B) is preferably 40 mgKOH / g or more.

When the acid value of the acrylamide polymer (B) exceeds 100 mgKOH / g, oily substances such as higher fatty acids and higher alcohols may adhere firmly to the resin coating film, making it difficult to remove the oily substances. .. From the viewpoint of further enhancing the ability to remove contaminants, the acid value of the acrylamide polymer (B) is preferably 90 mgKOH / g or less.

As the acrylamide-based polymer (B), for example, two or more kinds selected from the group consisting of a homopolymer having (meth) acrylamide or a derivative thereof as a monomer such as polyacrylamide and polymethacrylate, and (meth) acrylamide and a derivative thereof. It is possible to employ a copolymer having the above compound as a monomer, one or more compounds selected from the group consisting of (meth) acrylamide and derivatives thereof, and a copolymer having a compound other than these as a monomer. The resin coating film may contain one of these homopolymers and copolymers as the acrylamide-based polymer (B), or may contain two or more of these homopolymers and copolymers.

As the acrylamide polymer (B), it is preferable to use a homopolymer of a primary amide or a secondary amide, or a copolymer containing a primary amide or a secondary amide as a monomer. These homopolymers and copolymers contain highly polar primary or secondary amide groups. Therefore, by using these homopolymers and copolymers as the acrylamide-based polymer (B), the hydrophilicity of the resin coating film can be made higher, and contaminants can be more easily removed from the fin surface. From this point of view, it is particularly preferable to use polyacrylamide as the acrylamide-based polymer (B).

The total content of the polyvinyl alcohol (A) and the acrylamide polymer (B) in the resin coating film is not particularly limited, but for example, when the mass of the entire resin coating film is 100 parts by mass. The total mass of the polyvinyl alcohol (A) and the acrylamide polymer (B) can be appropriately set from the range of 85 to 97 parts by mass. In this case, the ratio of the total of the polyvinyl alcohol (A) and the acrylamide polymer (B) and the total of the polyethylene glycol (C) and the fluororesin particles (D) can be set in an appropriate range. As a result, the hydrophilicity of the resin coating film can be increased without impairing the lubricity during press working.

The resin coating film contains 1.0 to 13 parts by mass of polyethylene glycol (C). The number average molecular weight of polyethylene glycol (C) is in the range of 1000 to 20000. As described above, the polyethylene glycol (C) is exposed on the surface of the resin coating film and functions as a lubricant during press working. By setting the number average molecular weight and the content of polyethylene glycol (C) to the above-mentioned specific ranges, it is possible to suppress the adhesion of dust to the fin surface while avoiding deterioration of lubricity during press working.

When the content of polyethylene glycol (C) is less than 1.0 part by mass, the friction between the precoated fin material and the die during press working increases, which may lead to deterioration of lubricity. From the viewpoint of further reducing the friction between the precoated fin material and the mold during press working, the content of polyethylene glycol (C) is preferably 3.0 parts by mass or more.

When the content of polyethylene glycol (C) exceeds 13 parts by mass, the surface roughness of the resin coating film becomes rough, and dust may easily adhere to the surface of the fins. From the viewpoint of smoothing the surface of the resin coating film and more effectively suppressing the adhesion of dust to the surface of the fins, the content of polyethylene glycol (C) is preferably 8.0 parts by mass or less.

When the number average molecular weight of polyethylene glycol (C) is less than 1000, it may take a long time to dry the paint in the process of forming the resin coating film. Further, when the number average molecular weight of polyethylene glycol (C) exceeds 20,000, the production cost of the precoated fin material may increase.

The resin coating film contains 2.0 to 5.0 parts by mass of fluororesin particles (D). The average particle size of the fluororesin particles (D) on a volume basis is in the range of 100 to 300 nm. At least a part of the fluororesin particles (D) is arranged on the surface of the hydrophilic layer as described above, and functions as a lubricant during press working together with polyethylene glycol (C). By setting the average particle size and content of the fluororesin particles (D) within the above-mentioned specific ranges, it is possible to suppress the adhesion of dust to the fin surface while avoiding deterioration of lubricity during press working.

When the content of the fluororesin particles (D) is less than 2.0 parts by mass, the friction between the precoated fin material and the die during press working increases, which may lead to deterioration of lubricity. From the viewpoint of further reducing the friction between the precoated fin material and the mold during press working, the content of the fluororesin particles (D) is preferably 3.0 parts by mass or more.

When the content of the fluororesin particles (D) exceeds 5.0 parts by mass, the area ratio of the fluororesin particles (D) to the surface of the hydrophilic layer becomes excessively large, which may lead to a decrease in hydrophilicity. There is. From the viewpoint of improving the lubricity during press working while avoiding a decrease in hydrophilicity, the content of the fluororesin particles (D) is preferably 5.0 parts by mass or less.

When the average particle size of the fluororesin particles (D) is less than 100 nm, the fluororesin particles (D) are less likely to be exposed on the surface of the hydrophilic layer, which may lead to deterioration of lubricity during press working. When the average particle size of the fluororesin particles (D) exceeds 300 nm, the fluororesin particles (D) form relatively large irregularities on the surface of the hydrophilic layer, so that dust adheres to the fin surface. It may be easier to do.

The average particle size of the fluororesin particles (D) on a volume basis means a cumulative 50% diameter in a volume-based particle size distribution. Specifically, the average particle size of the fluororesin particles (D) can be calculated as a cumulative 50% diameter in the particle size distribution obtained by the laser diffraction / scattering method.

Examples of the fluororesin constituting the fluororesin particles (D) include a completely fluorinated resin such as polytetrafluoroethylene (that is, PTFE), polyvinylidene fluoride (that is, PVDF), polyvinyl fluoride (that is, PVF), and the like. Fluororesin copolymers such as partially fluorinated resin, tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer (that is, PFA), and ethylene-tetrafluoroethylene copolymer (that is, ETFE) can be used. .. The fluororesin particles (D) may be composed of one kind of particles made of these fluororesins, or two or more kinds may be used in combination.

The fluororesin particles (D) are preferably composed of a fluororesin having a perfluoroalkyl group. In this case, the content of polyethylene glycol (C) can be further reduced without impairing the lubricity during press working. As a result, it is possible to more reliably avoid an increase in the surface roughness of the resin coating film and more effectively suppress the adhesion of dust to the surface of the fins.

In the resin coating film, in addition to polyvinyl alcohol (A), acrylamide polymer (B), polyethylene glycol (C) and fluororesin particles (D) as essential components, components other than these are optional components. It may be included.

For example, the resin coating film may contain a cross-linking agent for making the crystal structure of polyvinyl alcohol (A) denser. By adding a cross-linking agent to the resin coating film, the hardness of the resin coating film can be further increased and the adhesion of dust can be suppressed more effectively. As the cross-linking agent, for example, a melamine resin, a blocked isocyanate compound, or the like can be used. These compounds may be used alone or in combination of two or more.

Further, at least one of the antibacterial agent and the antifungal agent may be further contained in the resin coating film, or both may be added. Further, an antibacterial / antifungal agent having both an antibacterial action and an antifungal action can be added to the resin coating film. By adding a compound having at least one of antibacterial action and antifungal action to the resin coating film, corrosion of the resin coating film can be suppressed and the action effect of the resin coating film can be maintained for a longer period of time. ..

Examples of compounds having antibacterial and antifungal effects include isothiazolin-based antibacterial / antifungal agents, aldehyde-based antibacterial / antifungal agents, benzimidazole-based antibacterial / antifungal agents, halogen-based antibacterial / antifungal agents, and carboxylic acids. Antibacterial / antifungal agent, sulfamide antibacterial / antifungal agent, thiazole antibacterial / antifungal agent, triazole antibacterial / antifungal agent, phenol antibacterial / antifungal agent, phthalimide antibacterial / antifungal agent, naphthenic acid Organic antibacterial and antifungal agents such as antibacterial and antifungal agents and pyridine antibacterial and antifungal agents, and inorganic antibacterial and antifungal agents such as Ag, Cu and Zn can be used.

As the antibacterial / antifungal agent, it is preferable to use at least one of zinc pyrithione, 2,3,5,6-tetrachloro-4- (methylsulfonyl) -pyridine and 2- (4-thiazolyl) benzimidazole. .. These compounds have little effect on the physical properties of the resin coating film, are insoluble in water, and have high heat stability. Therefore, by adding these compounds to the resin coating film, the antibacterial action and the antifungal action can be maintained for a long period of time.

When the hardness of the pre-coated fin material is measured by the pencil method using the pre-coated fin material after being immersed in running water at a flow rate of 2 L / min for 24 hours, graphite is attached to the surface of the resin coating film. It is preferable that the hardness of the pencil that can be made is 6H or more. Since the hardness of the resin coating film of the pre-coated fin material having such characteristics is sufficiently high, it is possible to more effectively suppress the adhesion of dust to the surface of the fins. The pencil method described above refers to the method specified in JIS K5600-5-4: 1999 (ISO / DIS 15184: 1996).

As a method for producing the precoated fin material, for example, a paint containing polyvinyl alcohol (A), an acrylamide polymer (B), polyethylene glycol (C) and fluororesin particles (D) is applied onto a substrate, and then the paint is applied. A method of heating and drying can be adopted. In the process of drying the paint, the polyvinyl alcohol (A) and the acrylamide polymer (B) settle on the substrate side to form a hydrophilic layer.

At this time, the viscosity of the polyvinyl alcohol (A) increases as the crystallization of the polyvinyl alcohol (A) proceeds in parallel with the drying of the paint. Therefore, polyvinyl alcohol (A) tends to settle on the substrate side of the hydrophilic layer. Therefore, in the resin coating film after drying, a concentration gradient is formed in which the concentration of polyvinyl alcohol (A) increases toward the substrate side and decreases toward the surface side.

Further, the polyethylene glycol (C) and the fluororesin particles (D) float on the surface side as the coating film dries, and at least a part of them is exposed on the surface of the resin coating film.

The pre-coated fin material is used in the manufacture of a heat exchanger, for example, as follows. First, fins are produced by cutting the precoated fin material to a desired size. Slit processing, louver molding, and color processing are appropriately combined and performed on the obtained fins using a press processing machine to form slits, louvers, and collars. After that, a plurality of fins are arranged at a predetermined distance from each other, and a metal pipe for allowing the refrigerant to flow is attached so as to penetrate the plurality of fins. After that, the expansion plug is inserted into the metal tube to expand the outer diameter of the metal tube, so that the metal tube and the fins are brought into close contact with each other. In this way, a heat exchanger can be obtained. The heat exchanger can be incorporated into, for example, an indoor unit or an outdoor unit of an air conditioner.

(Example)
An embodiment of the pre-coated fin material 1 will be described with reference to FIG. As shown in FIG. 1, the precoated fin material 1 of this example has a substrate 2 made of aluminum and a resin coating film 3 formed on the substrate 2 and exposed on the surface. Further, the resin coating film 3 has a number average molecular weight of polyvinyl alcohol (A) having a saponification degree of 95.0 to 99.8% and an acrylamide polymer (B) having an acid value of 20 to 100 mgKOH / g. It contains polyethylene glycol (C) having an average particle size of 6000 to 20000 and fluororesin particles (D) having an average particle size of 100 to 300 nm on a volume basis.

When the mass of the resin coating film 3 is 100 parts by mass, the content of polyethylene glycol (C) is 1.0 to 13 parts by mass, and the content of fluororesin particles (D) is 2.0 to 13 parts by mass. 5.0 parts by mass. The content of polyvinyl alcohol (A) is 0.3 to 0.6 times the content of the acrylamide polymer (B) in terms of mass ratio.

Hereinafter, a more detailed configuration of the pre-coated fin material 1 of this example will be described together with a manufacturing method. As the substrate 2 of the precoated fin material 1, an aluminum plate made of JIS A1050 aluminum and subjected to H26 tempering and having a plate thickness of 0.1 mm was used. The substrate 2 was immersed in a phosphoric acid chromate solution and subjected to chemical conversion treatment to form a base film 21 made of phosphoric acid chromate on both surfaces of the substrate 2.

Next, a coating material containing polyvinyl alcohol (A), acrylamide polymer (B), polyethylene glycol (C) and fluororesin particles (D) was applied onto the base film 21 using a bar coater. Then, the paint was heated at a temperature of 225 ° C. for 10 seconds to form the resin coating film 3 on the undercoat film 21. The film thickness of the resin coating film 3 was 1 μm.

In the process of heating and drying the paint, the polyvinyl alcohol (A) in the paint crystallizes due to hydrogen bonds between the hydroxyl groups, and the viscosity gradually increases. Therefore, the polyvinyl alcohol (A) settles toward the substrate 2 as the coating material dries. Further, polyethylene glycol (C) having a relatively low viscosity floats toward the surface as the coating material dries.

Since the acrylamide-based polymer (B) has a viscosity intermediate between that of polyvinyl alcohol (A) and polyethylene glycol (C), it tends to gather between the two. Further, the fluororesin particles (D) are uniformly dispersed in the paint during the drying process of the paint.

As a result of the above, the resin coating film 3 of this example has a two-layer structure consisting of a hydrophilic layer 31 laminated on the base film 21 and a lubricating layer 32 laminated on the hydrophilic layer 31 and exposed on the surface. Is formed. The hydrophilic layer 31 contains polyvinyl alcohol (A), an acrylamide polymer (B), and fluororesin particles (D). In the hydrophilic layer 31, a concentration gradient is formed such that the concentration of polyvinyl alcohol (A) is high on the substrate 2 side and the concentration of acrylamide polymer (B) is high on the surface side. Further, a part of the fluororesin particles (D) is exposed on the surface of the hydrophilic layer 31.

The lubricating layer 32 is made of polyethylene glycol (C).

Next, the action and effect of the pre-coated fin material 1 of this example will be described. Since the precoated fin material 1 has the resin coating film 3 having the specific composition, as described above, the concentration of polyvinyl alcohol (A) is high on the substrate 2 side, and the acrylamide polymer (acrylamide) is on the surface side. A concentration gradient with a high concentration of B) can be formed.

The precoated fin material 1 can increase the hydrophilicity of the resin coating film 3 by increasing the concentration of the acrylamide polymer (B) on the surface side. As a result, when the surface of the fins condenses, the dew condensation water easily infiltrates between the resin coating film 3 and the pollutants adhering to the surface of the resin coating film 3, that is, oily substances, dust, and the like. As a result, these contaminants can be washed away with the dew condensation water on the fins and easily removed from the surface of the fins.

Further, the hardness of the precoated fin material 1 can be increased by increasing the concentration of polyvinyl alcohol (A) on the substrate 2 side. Therefore, the dust that comes into contact with the surface of the fin is likely to be repelled by the resin coating film 3. As a result, it is possible to suppress the adhesion of dust to the surface of the fin.

Further, the precoated fin material 1 uses polyethylene glycol (C) and fluororesin particles (D) in combination as a lubricant, so that the lubricity during press working is higher than that in the case where the fluororesin particles (D) are not used. The content of polyethylene glycol (C) can be reduced without impairing the above. Then, by reducing the content of polyethylene glycol (C), the surface of the resin coating film 3 can be smoothed, and dust adhering to the surface of the fin can be easily peeled off from the fin. As a result, the dust adhering to the surface of the fin can be easily removed from the surface of the fin.

As described above, according to the precoated fin material 1, it is possible to suppress the adhesion of contaminants and easily remove the contaminants adhering to the surface.

(Experimental example)
This example is an example in which pre-coated fin materials in which the composition of the resin coating film is variously changed are produced and their performance is evaluated. In addition, among the codes used in this example and thereafter, the same codes as those used in the above-mentioned Examples indicate the same components and the like as those in the above-mentioned Examples unless otherwise specified.

In this example, the test materials 1 to 74 shown in Tables 1 to 8 were prepared. The test materials 1 to 59 and the test materials 63 to 74 have a structure in which a base film 21 made of phosphoric acid chromate and a resin coating film 3 having a film thickness of 1 μm are sequentially laminated on the substrate 2. These test materials were produced by the same method as the precoated fin material 1 of the examples, except that the composition of the resin coating film 3 was changed to the compositions shown in Tables 1 to 8.

Further, in the test materials 60 to 62, a corrosion-resistant coating film having a film thickness of 1 μm is interposed between the base film 21 and the resin coating film 3. The corrosion-resistant coating film was formed by applying a coating material containing the resin shown in Table 7 on the undercoat film 21 and then heating the coating material at a temperature of 225 ° C. for 10 seconds to dry it. The test materials 60 to 62 were produced by the same method as the pre-coated fin material 1 of the examples, except that a corrosion-resistant coating film was formed between the base film 21 and the resin coating film 3 by the method described above.

The test materials 1 to 74 obtained as described above were evaluated for hardness, hydrophilicity, dust adhesion, stain resistance, and lubricity during press working of the resin coating film 3 by the following methods.

-Hardness of resin coating film Each test material was immersed in running water at a flow rate of 2 L / min for 24 hours, and as shown in FIG. 2, polyethylene glycol (C) and fluororesin particles (D) exposed on the surface of the resin coating film 3 were exposed. ) Was removed from the test material S. Then, the pencil was reciprocated while pressing the pencil against the surface of the resin coating film 3 by the method specified in JIS K5600-5-4: 1999 (ISO / DIS 15184), and the graphite of the pencil adhered to the surface of the resin coating film 3. Whether or not it was confirmed by visual observation. When the graphite of the pencil did not adhere to the surface of the resin coating film 3, the same test was performed using a harder pencil, and the test was terminated when the graphite of the pencil adhered to the surface of the resin coating film 3. .. The hardness of the pencil at the end of the test was as shown in the "Hardness of resin coating film" column of Tables 1 to 8.

-Hydrophilicity In this example, the hydrophilicity of the test material was evaluated by measuring the water contact angle of the test material immediately after production and the water contact angle of the test material after the deterioration test. Specifically, the deterioration test was carried out by immersing the test material in ion-exchanged water for 2 minutes and then blowing air on the test material for 6 minutes to dry the test material as one cycle, and repeating this cycle for 300 cycles. The water contact angle of the test material immediately after production and the water contact angle of the test material after the deterioration test were as shown in the "hydrophilic" column of Tables 1 to 8.

-Dust adhesion In this example, the dust adhesion of the test material was evaluated by measuring the amount of hydrophilic powder attached to the test material and the amount of hydrophobic powder attached. As the hydrophilic powder, Kanto loam dust, which is the powder specified in JIS Z8901-2006, was used, and as the hydrophobic powder, carbon black, which is the powder specified in JIS Z8901-2006, was used. .. After spraying either the hydrophilic powder or the hydrophobic powder on the resin coating film with air for 5 seconds, the amount of the hydrophilic powder or the hydrophobic powder adhered to the test material was measured. The amount of hydrophilic powder adhered and the amount of hydrophobic powder adhered per 1 m ^{2 of the} test material were as shown in the “dust adhesion” column of Tables 1 to 8.

-Stain resistance In this example, the stain resistance of the test material was evaluated by measuring the water contact angle of the test material after the contamination test. Specifically, the contamination test was carried out by the following method. First, the test material and the higher fatty acid as a pollutant were placed in the container so that they would not come into direct contact with each other. After sealing the container, the container was kept at a temperature of 80 ° C. for 120 minutes to vaporize the higher fatty acid, and the test material was exposed to the atmosphere of the higher fatty acid. After cooling the container to room temperature while maintaining the sealed state, the test material was taken out from the container and the contamination test was completed. The water contact angle of the test material after the contamination test was as shown in the "contamination resistance" column of Tables 1 to 8.

-Lubricity during press working The dynamic friction coefficient of the surface of the test material was measured using a Bowden-Leben type wear tester. The coefficient of dynamic friction of the test material was as shown in the “Lubricity during press working” column of Tables 1 to 8.

As shown in Tables 1 to 7, the test materials 1 to 62 have a resin coating film having a composition in the specific range on the substrate. Therefore, these test materials had a water contact angle of 10 ° or less immediately after production, and exhibited excellent hydrophilicity immediately after production. Further, these test materials had a water contact angle of 20 ° or less after the deterioration test, and could maintain high hydrophilicity for a long period of time. Further, these test materials have a water contact angle of 40 ° or less after the contamination test, and even when an oily substance adheres to the surface of the resin coating film, the decrease in hydrophilicity can be suppressed.

From these results, the test materials 1 to 62 have excellent hydrophilicity and can maintain excellent hydrophilicity for a long period of time. Therefore, it is understood that by producing fins using these test materials, contaminants adhering to the surface of the fins can be washed away with moisture such as dew condensation water, and contaminants can be easily removed from the surface of the fins. it can.

In addition, the test materials 1 to 62 were able to suppress the adhesion amount of the hydrophilic powder and the adhesion amount of the hydrophobic powder to 0.4 g / m ^{2 or less.} Furthermore, these test materials were able to suppress the coefficient of dynamic friction to 0.1 or less. Therefore, it can be understood that by producing fins using these test materials, it is possible to suppress the adhesion of dust to the surface of the fins without impairing the lubricity during press working.

Further, among the test materials 1 to 62, the test materials 54 to 56 in which the blocked isocyanate compound was added to the resin coating film made the resin coating film harder and harder than the test materials 43 containing no blocked isocyanate compound. The adhesion of dust could be suppressed more effectively. Similarly, the test materials 57 to 59 in which the melamine resin is added to the resin coating film hardens the resin coating film and more effectively suppresses the adhesion of dust as compared with the test materials 43 containing no melamine resin. Was made.

Therefore, from the comparison between the test materials 54 to 59 and the test material 43, by adding the blocked isocyanate compound or the melamine resin to the resin coating film, the resin coating film is made harder and the adhesion of dust is more effective. It can be understood that it can be suppressed. Regarding the test materials 56 and 59 having a relatively high content of the blocked isocyanate compound and the melamine resin, the pot life of the paint was slightly shorter than that of the test materials 54 to 55 and the test materials 57 to 58.

On the other hand, as shown in Table 7, in the test material 63, the acid value of the acrylamide-based polymer (B) was lower than the above-mentioned specific range. Therefore, the acrylamide polymer (B) was eluted from the resin coating film during the deterioration test, and the hydrophilicity was lowered earlier than that of the test materials 1 to 62.
In the test material 64, the acid value of the acrylamide polymer (B) was higher than the above-mentioned specific range. Therefore, it was more difficult to remove the higher fatty acid adhering to the surface of the resin coating film from the surface of the resin coating film as compared with the test materials 1 to 62.

In the test material 65, the saponification degree of polyvinyl alcohol (A) was lower than the above-mentioned specific range. Therefore, the crystallization of polyvinyl alcohol (A) was insufficient, the hardness of the resin coating film was lower than that of the test materials 1 to 62, and dust was likely to adhere.
In the test material 66, the saponification degree of polyvinyl alcohol (A) was higher than the above-mentioned specific range. Therefore, the material cost has increased.
In the test material 67, the total content of the polyvinyl alcohol (A) and the acrylamide-based polymer (B) was less than the above-mentioned specific range. Therefore, the hydrophilicity of the resin coating film was lowered earlier than that of the test materials 1 to 62.

As shown in Table 8, in the test material 68, the total content of the polyvinyl alcohol (A) and the acrylamide-based polymer (B) was larger than the above-mentioned specific range. Therefore, polyethylene glycol (C) and fluororesin particles (D) were insufficient, and the lubricity during press working was lower than that of the test materials 1 to 62.
The test material 69 was deficient in polyvinyl alcohol (A) because the mass ratio of polyvinyl alcohol (A) to the acrylamide polymer (B) was less than the above-mentioned specific range. As a result, the hardness of the resin coating film was lower than that of the test materials 1 to 62, and dust was more likely to adhere.

In the test material 70, the mass ratio of polyvinyl alcohol (A) to the acrylamide polymer (B) was higher than the above-mentioned specific range, so that the acrylamide polymer (B) was insufficient. As a result, the higher fatty acids adhering to the surface of the resin coating film were less likely to be removed from the surface of the resin coating film as compared with the test materials 1 to 62.
The content of the fluororesin particles (D) in the test material 71 was less than the above-mentioned specific range. Therefore, the lubricity during press working was lower than that of the test materials 1 to 62.

The content of the fluororesin particles (D) in the test material 72 was higher than the specific range. Therefore, the hydrophilicity of the resin coating film was lowered earlier than that of the test materials 1 to 62.
In the test material 73, the average particle size of the fluororesin particles (D) was smaller than the specific range. Therefore, the lubricity during press working was lower than that of the test materials 1 to 62.

In the test material 74, the average particle size of the fluororesin particles (D) was larger than the specific range. Therefore, the unevenness of the surface of the resin coating film becomes large, and dust is more likely to adhere as compared with the test materials 1 to 62.

The specific embodiment of the precoated fin material according to the present invention is not limited to the embodiments described above in the examples and experimental examples, and can be appropriately changed as long as the gist of the present invention is not impaired. For example, in the above-mentioned Examples and Experimental Examples, an example of the precoated fin material 1 in which the base film 21 is formed on the substrate 2 is shown, but the chemical conversion treatment for forming the base film 21 is omitted and the substrate 2 is covered. It is also possible to directly form the resin coating film 3 on the surface. Further, the chemical conversion treatment for forming the undercoat film 21 may be omitted, and the corrosion-resistant coating film and the resin coating film 3 may be sequentially formed on the substrate 2.

Further, in the examples, the hydrophilic layer 31 is covered with the lubricating layer 32 made of polyethylene glycol (C), but the fluororesin particles (D) arranged on the surface of the hydrophilic layer 31 are present. It may protrude outward from the lubricating layer 32. If both the polyethylene glycol (C) and the fluororesin particles (D) are present on the surface of the resin coating film 3, the lubricity during press working can be improved by the action and effect of these.

1 Pre-coated fin material 2 Substrate 3 Resin coating film (A) Polyvinyl alcohol (B) Acrylamide polymer (C) Polyethylene glycol (D) Fluororesin particles

Claims (6)

A substrate made of aluminum and
It has a resin coating film formed on the substrate and exposed on the surface.
The resin coating film is
Polyvinyl alcohol (A) having a saponification degree of 95.0 to 99.8% and
Acrylamide polymer (B) having an acid value of 20 to 100 mgKOH / g and
Polyethylene glycol (C) having a number average molecular weight of 6000 to 20000 and
Fluororesin particles (D) having an average particle diameter of 100 to 300 nm on a volume basis are contained.
When the mass of the resin coating film is 100 parts by mass, the content of the polyethylene glycol (C) is 1.0 to 13 parts by mass, and the content of the fluororesin particles (D) is 2. 0 to 5.0 parts by mass,
The content of the polyvinyl alcohol (A) is 0.3 to 0.6 times the content of the acrylamide polymer (B) in terms of mass ratio.
Pre-coated fin material. The precoated fin material according to claim 1, wherein the fluororesin particles (D) are composed of a fluororesin having a perfluoroalkyl group. The precoated fin material according to claim 1 or 2, wherein the resin coating film further contains one or more compounds selected from the group consisting of a blocked isocyanate compound and a melamine resin. The precoated fin material according to any one of claims 1 to 3, wherein at least one of an antibacterial agent and an antifungal agent is further contained in the resin coating film. When the hardness is measured by the pencil method using the pre-coated fin material after being immersed in running water at a flow rate of 2 L / min for 24 hours, the hardness of the pencil capable of adhering graphite to the surface of the resin coating film. The precoated fin material according to any one of claims 1 to 4, wherein the material is 6H or harder than that. It has a corrosion-resistant coating film interposed between the substrate and the resin coating film, and the corrosion-resistant coating film is one or two selected from the group consisting of acrylic resin, epoxy resin, urethane resin and ester resin. The precoated fin material according to any one of claims 1 to 5, which contains the above resin.

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