JPH073317B2 - Fine material - Google Patents

Description

TECHNICAL FIELD The present invention relates to a fin material for a heat exchanger, and more particularly to an aluminum fin material having improved wettability.

(Prior Art) Aluminum fins with anticorrosion properties are used in heat exchangers of general room air conditioners and package air conditioners.
When the aluminum fin surface is cooled to a temperature below the dew point of the atmosphere during the cooling operation of the air conditioner, moisture in the atmosphere adheres to the fin surface as condensed water. In this case, if the fin surface is water-repellent, condensed water will form water droplets and form a bridge between the fins, narrowing the air ventilation path, which increases ventilation resistance, resulting in problems such as power loss, noise, and water splashes. Occurs. This problem is particularly noticeable when the thickness of the aluminum fins is reduced and the heat exchanger is downsized, and the distance between the aluminum fins is further reduced.

Condensed water adhering to the surface of the fins does not easily become water drops,
The fin surface has hydrophilicity (water wettability) to increase heat exchange efficiency by reducing ventilation resistance and increasing air volume.
Has been attempted. For example, (1) A hydrophilic film (eg, silicate treatment, boehmite treatment, hydrophilic acrylic resin, etc.) is formed on the surface of an aluminum alloy, and a surface-active agent layer is provided thereon (JP-A-60-
However, the disadvantage of this is that the initial water wettability is not so high, and the water wettability deteriorates during long-term use. Moreover,
There was a problem in the durability of the hydrophilic film, and the chemical conversion treatment had a manufacturing problem. For example, boehmite treatment is performed at 90 ° C or higher for 10
It is necessary to treat for more than a minute, and the alkali silicate treatment must be baked at a high temperature after the treatment.

(2) Form a corrosion resistant chemical film (chromate treatment, boehmite treatment, phosphoric acid treatment, etc.) on the surface of the aluminum alloy,
Some of them have a hydrophilic coating layer (silica sol, silicate, etc.) on their surface, but they have good corrosion resistance and hydrophilicity, but this coating is very hard and cracks occur in the fin bends during processing. However, there are drawbacks such as poor moldability and easy wear of the molding die. Furthermore, there is a problem that the hydrophilicity of the surface deteriorates after long-term use.

(3) There is a method of applying a water-based paint containing a surfactant and synthetic silica on the surface of the aluminum alloy as a hydrophilic film treatment, but the film thickness is thick and it is necessary to bake at high temperature. In addition, there is a problem that the hydrophilicity of the surface deteriorates after long-term use.

(Problems to be Solved by the Invention) An object of the present invention is to solve the drawbacks of the prior art and provide an aluminum fin material having excellent hydrophilicity (water wettability).

(Means for Solving Problems) The aluminum fin material provided by the present invention forms an anodized film on the surface of a foil or a thin plate of aluminum or an alloy thereof, and ultraviolet rays or electron beams are formed on the outer surface of the anodized film. It has a structure having a hydrophilic film formed by applying and impregnating a surface treatment agent comprising a curable coating material and a surfactant.

The foil or the thin plate 1 on which the anodized film is formed may be made of aluminum or its alloy that constitutes the conventional aluminum fin material. The thickness of the foil or thin plate made of aluminum or an alloy (hereinafter, abbreviated as aluminum (alloy) foil) is appropriately set in consideration of moldability, heat exchange efficiency, strength and the like.

The anodized film 2 is formed on the surface of the aluminum (alloy) foil 1. The anodized film is formed on one side or both sides of the aluminum (alloy) foil depending on the quality required for the aluminum fin material. Since the anodic oxide coating 2 is formed to impart particularly excellent corrosion resistance to the aluminum fin material, it is desirable that the thickness thereof be 0.5 μm or more in consideration of the corrosion resistance. The thicker the anodized film is, the more excellent the corrosion resistance of the aluminum fin material can be obtained, but if it is too thick, cracks may occur in the film during deformation processing of the aluminum fin material, and the corrosion resistance may decrease.
A thickness not exceeding μm is preferred.

The anodized film 2 is formed on the surface of the aluminum (alloy) foil by electrolysis in a solution of sulfuric acid, oxalic acid, phosphoric acid or a mixture thereof according to any conventionally known method.

Then, a surface treatment agent composed of an ultraviolet ray or electron beam curable coating material and a surfactant is applied and impregnated on the outer surface of the thus formed anodic oxide coating 2 to form the hydrophilic coating 4.

The UV-curable coating used as one component of the surface treatment agent is composed of three main components of a prepolymer having a polymerizable functional group, a reactive diluent (monomer) and a photopolymerization initiator. , Additives such as stabilizers, leveling agents, defoamers, and colorants may be added. The electron beam curable coating material has substantially the same composition as the ultraviolet curable coating material except that no photopolymerization initiator is added. Explaining each main component of the ultraviolet (electron beam) curable coating material in detail by taking an acrylic coating material as an example, typical prepolymers include polyester acrylate, polyether acrylate, urethane acrylate, epoxy acrylate, polyacetal acrylate, and the like. Reactive monomers include 2-ethylhexyl acrylate, n-stearyl acrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, butoxyethyl acrylate, cyclohexyl acrylate,
Tetrahydrofurfuryl acrylate, 2,2-hydroxyethyl acryloyl phosphate, ethoxyethoxyethyl acrylate, 1,6-hexanediol diacrylate, neopentyl glycol diacrylate, diethylene glycol diacrylate, polyethylene glycol diacrylate, hydroxypivalate neopentyl Glycol diacrylate, trimethylolpropane diacrylate, pentaerythritol diacrylate, dipentaerythritol hexaacrylate and the like are exemplified, and as the photopolymerization initiator, ethyl 2-dimethylaminobenzoate, methyl 4-dimethylaminobenzoate, 2,2 −
Diethoxyacetophenone, benzyl dimethyl ketal, 1-fanyl-1,2-propanedione-2- (α-ethoxycarbonyl) oxime, benzophenone, methyl 0-benzoylbenzoate, 4,4′-bisdimethylaminobenzophenone, 4, 4'-bisdiethylaminobenzophenone, benzyl, benzoin, benzoin ethyl ether, benzoin isobutyl ether, 4'-isopropyl-2-hydroxy-2-methyl-propiophenone, 2-
Examples thereof include hydroxy-2-methyl-propiophenone, 2-methylthioxanthone, chlorothioxanthone, α, α-dichloro-4-phenoxyacetophenone, and 1-hydroxycyclohexylphenyl ketone.

The surfactant used as the other component of the surface treatment agent is not particularly limited, but includes perfluoroalkyl sulfonate, perfluoroalkyl carboxylate, perfluoroalkyl ethylene oxide adduct, perfluoroalkyl trimethyl ammonium salt, Fluorocarbon-based surfactants such as perfluoroalkyl polyoxyethylene ethanol and fluorinated alkyl esters, and organic dibasic acids (malonic acid, succinic acid, glutaric acid, adipic acid, maleic acid, fumaric acid, phthalic acid, Anionic surfactants represented by C _1-24 alkyl ester sulfonates of isophthalic acid, terephthalic acid, etc.) can be preferably used. You may mix and use these surfactants.

The mixing ratio of the ultraviolet (electron beam) curable paint and the surfactant in the surface treatment agent is adjusted according to the required film characteristics, and when the corrosion resistance is strongly required, many ultraviolet (electron beam) curable paints are used. When a high hydrophilicity is required, a large amount of surfactant may be added.

Even if the surface treatment agent is applied to the outer surface of the anodic oxide coating after sealing the numerous small holes 3 extending vertically from the surface of the anodic oxide coating 2, sufficient hydrophilicity can be imparted. However, in order to maintain the hydrophilicity thus imparted and to impart higher corrosion resistance, the treatment may be interrupted by a slight sealing treatment, or the surface treatment agent may be anodized without sealing treatment. It is preferable to apply so as to impregnate the small holes 3 of the oxide film. By doing so, excellent hydrophilicity can be retained continuously, and corrosion resistance and lubricity during press molding can be increased. In order to impregnate the surface treatment agent deeply into the small holes of the anodized film, do not simply immerse the aluminum (alloy) foil with the anodized film in the tank containing the surface treatment agent. It is preferable to keep the tank in a reduced pressure state during the dipping process, or to subject the aluminum (alloy) foil and the tank to shock such as vibration. The temperature of the liquid in the bath may be room temperature, but heating and heating is preferable because the viscosity of the surface treatment agent decreases and the treatment agent can be impregnated deep into the small holes of the anodized film.

The coating amount of the surface treatment agent is appropriately adjusted so as to obtain a coating film thickness as necessary, but the outer surface of the anodic oxide film in a dry state is 0.
The coating amount is preferably such that a film having a thickness of 05 to 5 g / m ² is formed. Coating thickness can not be obtained the desired curing is less than 0.05 g / m ^2, since the thermal conductivity of the opposite to 5 g / m ² greater than the resulting aluminum fin material is deteriorated undesirably.

In the present invention, a suitable amount of a surface treatment agent is applied to the outer surface of the anodized film, and then a hydrophilic film is formed using a conventionally known ultraviolet or electron beam curing device.

(Examples) Examples of the fin material of the present invention will be shown below, but these are merely non-limiting examples and can be modified without departing from the spirit and idea of the present invention.

Example 1 An aluminum alloy foil (JIS H4160, 3004 soft) having a thickness of 80 μm was anodized under the following conditions to form an anodized film having a thickness of 1 μm on each side of the foil.

Treatment bath 15% by volume H ₂ SO ₄ , 25 ° C Cathode carbon plate Distance between electrodes 5 cm Voltage 15V Current density 2A / dm ² Akumi alloy foil coil with anodic oxide film formed was perpendicular and dried, and then multiple foil samples were prepared. . The sample was dipped in a closed tank of a solution of a surface treatment agent consisting of a polyester acrylate UV-curable coating [PV-2 varnish, Toka Dye Chemical Industry Co., Ltd.] and an anionic surfactant (sodium dialkyl sulfonate). , 5 mm under reduced pressure of 60 mmHg
After holding for a minute, the surface treatment agent was applied and impregnated on the outer surface of the anodized film and inside the small holes. Then, the sample was irradiated with ultraviolet rays for 1 to 3 seconds by an ultraviolet curing device equipped with a high pressure mercury lamp of 80 to 160 W / cm to form a hydrophilic film.

The experiment was repeated a plurality of times while changing the amount of the surfactant added (based on 100% by weight of the paint) as shown in Table 1.

The following tests were performed on the obtained aluminum alloy foil on which the anodized film and the hydrophilic film were sequentially formed.

Test items and method 1) Initial hydrophilicity: The contact angle (unit: degree) of water on the surface after the foil was formed was measured.

2) Water resistance: The contact angle of water on the surface was measured after the foil was wetted for 2 minutes and dried for 1/6 cycle by repeating 500 cycles.

3) Weather resistance: A change in the coating film of the foil after irradiation with the sunshine weather meter was examined according to JIS-D-0205.

4) Corrosion resistance: A change in the coating film of the foil after the salt spray test was examined according to JIS-Z-2371.

The test results are shown in Table 1.

Example 2 Example 1 was repeated. However, the thickness of each side of the alloy foil is 3 μm by changing the winding speed of the foil during anodizing.
Of the anodic oxide film was formed.

The performance of the obtained aluminum alloy foil on which the anodized film and the hydrophilic film were sequentially formed was measured in the same manner as in Example 1.
The results are shown in Table 2.

Example 3 The aluminum alloy foil having the anodized film of 1 μm formed in Example 1 was sealed with deionized water at pH 6 and a temperature of 98 ° C. for 10 minutes.

The sealing-treated aluminum alloy foil obtained was heated to 50 to 60 ° C, and a polyester acrylate-based ultraviolet curable coating (PV
-2 varnish, Toka Dye Chemicals Co., Ltd.) and an anionic surfactant (sodium dialkyl sulfonate) are immersed in a closed tank containing a solution of a surface treatment agent, and the anode is kept for 5 minutes under a reduced pressure of 60 mmHg. The oxide film was applied and impregnated on the outer surface and inside the small holes. Then, the performance of the aluminum alloy foil obtained by the same treatment as in Example 1 was examined. The results are shown in Table 3.

Example 4 Example 1 was repeated. However, instead of holding the tank containing the surface treatment agent in a depressurized state, the surface treatment agent solution is placed in a tank heated to 50 to 60 ° C and the foil is immersed in this tank, and the frequency is 26 kHz in this tank. 5 while applying ultrasonic vibration of output 150W
Hold for minutes.

The results of measuring the performance of the obtained foil in the same manner as in Example 1 are shown in Table 4.

(Function) The fin material of the present invention has excellent corrosion resistance and hydrophilicity due to the function of the anodized film.

Since the fin material of the present invention has a film containing a surfactant formed on the surface, it has excellent hydrophilicity and water resistance.

The fin material of the present invention is free from pinholes, that is, excellent in corrosion resistance, because the ultraviolet ray or electron beam curable coating material used for forming the hydrophilic film has a high solid content but low viscosity. It has a film of. In addition, when conventional surface treatment agents such as solvent-type polymer resins and water-soluble polymer resins are used to produce fin materials that require corrosion resistance, pinholes are likely to occur when the coating film is made thinner However, since the coating material having the above-mentioned characteristics is used in the present invention, it is possible to form an ultrathin film without pinholes. In addition, in the present invention, a thin film can be formed by using an ultraviolet or electron beam curable coating material, and the resulting film is flexible, so that the aluminum fin material of the present invention can be used. Is also excellent in terms of formability during press working.

In the present invention, when the surface treatment agent is impregnated deep into the small holes of the anodized film, the corrosion resistance is further improved and the excellent hydrophilicity can be maintained for a long time.

Conventional aluminum fin material uses relatively thick aluminum foil with a thickness of about 100 to 150 μm, so when baking resin is applied to form a hydrophilic film on the surface of this foil, a very large amount of heat is required for production. In addition to the decrease in the property, there was a drawback that the difference in the physical properties of the coating film is likely to occur due to the variation of the baking temperature, but since the ultraviolet or electron beam curing method is used to form the hydrophilic film in the present invention, Compared with this, an extremely thin uniform film is formed in an extremely short time, and it is excellent in productivity.

[Brief description of drawings]

Figure 1 shows aluminum (alloy) with anodic oxide coating on both sides.
FIG. 2 is a sectional view of a foil, and FIG. 2 is a sectional view of an aluminum fin material of the present invention in which an anodized film and a hydrophilic film are sequentially formed on the surface of an aluminum (alloy) foil. 1 ... Aluminum (alloy) foil, 2 ... Anodized film, 3 ...
Small holes, 4 ... Hydrophilic coating.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP 59-105877 (JP, A) JP 59-196782 (JP, A) JP 60-134198 (JP, A)

Claims (2)

[Claims] 1. A anodic oxide film is formed on the surface of a foil or a thin plate of aluminum or its alloy, and the surface of the anodic oxide film is coated with a surface-treating agent composed of an ultraviolet or electron beam curable coating material and a surfactant. Aluminum fin material for heat exchangers, which is formed by irradiating ultraviolet rays or electron beams to form a hydrophilic film. 2. The fin material according to claim 1, wherein the surface treatment agent is impregnated into the small holes of the anodized film.