JPH0665956B2 - 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) In general room air conditioners, aluminum fins with anticorrosion property are used in the heat exchanger of 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 forms water droplets and forms a bridge between the fins, narrowing the air ventilation path, which increases ventilation resistance and causes 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 fin surface is hard to be suitable for water,
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 coating (eg, silicate treatment, boehmite treatment, hydrophilic acrylic resin, etc.) is formed on the surface of an aluminum alloy, and a surfactant layer is provided on the hydrophilic coating (JP-A-60).
However, as a drawback of this,
There was a problem that the initial water-nulling property was not so high, and the water-draining property deteriorates after long-term use. Furthermore, there is a problem in durability of the hydrophilic film, and chemical conversion treatment has a problem in manufacturing. For example, the boehmite treatment needs to be performed at 90 ° C. or higher for 10 minutes or more, and the alkali silicate treatment needs to be baked at a high temperature after the treatment.

(2) Some aluminum alloys have a corrosion resistant chemical film (chromate treatment, boehmite treatment, phosphoric acid treatment, etc.) formed on the surface and a hydrophilic coating layer (silica sol, silicate, etc.) provided on the surface. And has good hydrophilicity,
This coating is very hard and has defects such as cracks in the bent portions of the fins during processing, 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 as a hydrophilic film treatment on the surface of an aluminum alloy, but the film thickness is thick and it is necessary to bake at a high temperature. or,
There is also 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 anodic oxide film on the surface of a foil or a thin plate of aluminum or its alloy, and has an interfacial activity in the small holes of the anodic oxide film. It has a constitution having a hydrophilic film formed by applying and impregnating the agent.

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. As the thickness of the anodic oxide film is thicker, an aluminum fin material having excellent corrosion resistance can be obtained, but if it is too thick, cracks may occur in the film during deformation processing of the aluminum fin material, and corrosion resistance may decrease.
A thickness not exceeding 5 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 surfactant is applied to the outer surface of the anodic oxide coating 2 thus formed to form the hydrophilic coating 4.

The surfactant used in the present invention must contain a long-chain fluorinated alkyl group. For example, perfluoroalkyl sulfonate, perfluoroalkyl carboxylate, perfluoroalkyl ethylene oxide adduct, perfluoroalkyl trimethyl ammonium salt, perfluoroalkyl polyoxyethylene ethanol, fluorinated alkyl ester, etc. are preferably used. Can be done. You may mix and use these surfactants.

Sufficient hydrophilicity can be imparted even if the surfactant is applied to the outer surface of the anodic oxide film 2 after sealing the numerous small holes 3 extending vertically from the surface of the anodic oxide film 2 after sealing treatment. However, in the present invention, in order to impart durability to the hydrophilicity thus imparted and to impart higher corrosion resistance, the treatment is interrupted with a mild sealing treatment or the surface treatment is performed without performing the sealing treatment. The agent is applied so as to impregnate the small holes of the anodized 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 of the anodized film into the small holes of the anodized film evenly, the aluminum (alloy) foil on which the anodized film is formed is not simply immersed in the tank containing the surfactant. 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 liquid temperature in the tank 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 surfactant is appropriately adjusted so as to obtain a coating film thickness as necessary, but the dry amount on the outer surface of the anodized film 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 effect 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.

(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.

Examples 1 to 3 and Comparative Examples 1 to 2 An aluminum alloy foil (JIS H4160, 3004 soft) having a thickness of 80 μm was subjected to anodizing treatment under the following conditions to form an anode having a thickness of 1 μm per side on both sides of the foil. An oxide film was formed.

Treatment bath 15% by volume H ₂ SO ₄ , 25 ° C Negative electrode carbon plate Distance between electrodes 5 cm Voltage 15V Current density 2A / dm ² Aluminum alloy foil coil with anodic oxide film formed on it was washed with water and dried. Created. The sample is immersed in a closed bath of a 10% by weight ethyl acetate solution of a fluorine-based surfactant (Florard FC-431, Sumitomo 3M Ltd.) heated to 30 to 40 ° C, and the pressure is reduced to 5 mm under a reduced pressure of 60 mmHg. After holding for a minute, the surface treatment agent was applied and impregnated into the small holes of the anodized film. Then, it was dried at 210 ° C. for 20 seconds to form a hydrophilic film.

The experiment was repeated a plurality of times by changing the winding speed of the foil during the anodizing treatment to change the thickness of the anodized film 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 Methods 1) Initial Hydrophilicity: The contact angle (unit: degree) of water on the surface of the foil was measured.

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

3) 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. Incidentally, in Comparative Example 1,
This is an example in which only the fluorine-based surfactant is applied without forming the anodized film, and Comparative Example 2 is an example in which only the anodized film having a thickness of 3 μm is formed without applying the fluorine-based surfactant.

Examples 1'-3 'and Comparative Examples 1'-2' Examples 1-3 and Comparative Examples 1-2 were repeated. However, instead of keeping the tank containing the surfactant solution under reduced pressure,
5 while applying ultrasonic vibration with a frequency of 2 kHz and an output of 150 W to the tank
Hold for minutes.

The results of measuring the performance of the obtained foil in the same manner as in the above example are shown in Table 2.

(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.

In the present invention, since the surfactant is impregnated deep into the small holes of the anodic oxide film, the corrosion resistance is further improved and excellent hydrophilicity can be connected for a long time. Moreover, since the obtained film has flexibility, the aluminum fin material of the present invention is also excellent in formability during press working.

[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.

Claims (1)

[Claims] 1. An anodized film is formed on the surface of a foil or a thin plate of aluminum or its alloy, and a small amount of pores of the anodized film is coated with and impregnated with a surfactant containing a fluorinated long-chain alkyl group. Aluminum fin material for heat exchangers that is formed by forming a hydrophilic film.