JPH07316835A - Aluminum fin material for heat exchanger excellent in workability - Google Patents

Abstract

PURPOSE:To reduce the wear of tools in drawless working to assemble a heat exchanger by dispersing the relatively coarse grains of the polysiloxane of Si-OH-Si in the baked film of a hydrophilic org. resin to be formed on the surface of a fin material. CONSTITUTION:The baked film layer of the hydrophilic org. resin contg. a colloidal silica having 40-60nm average grain diameter in 50-80% weight ratio is formed at 0.4-0.8g/m<2> on the surface of an aluminum can with a chromate substrate film layer. The adhesion of the baked film is improved by the chromate substrate treatment, and a chromic acid-chromate film or a phosphoric acid-chromate film is preferably provided at 5-30g/m<2> as Cr. An acrylic resin is preferably used as the hydrophilic org. resin from the standpoint of its stability to colloidal silica, and a nonionic or anionic surfactant can be added to improve its degreasing property.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aluminum fin material for a heat exchanger provided with an inorganic baking coating having good hydrophilicity and less tool wear.

[0002]

2. Description of the Related Art Generally, in heat exchangers, particularly evaporators of air conditioners, the surface temperature of the fins is below the dew point of the atmosphere, so that water drops adhere to the surfaces of the fins. In this way, when water drops adhere to the fins, the ventilation resistance increases and the air volume decreases, so that the heat exchange efficiency decreases. The heat exchange efficiency is greatly affected by the wettability (hydrophilicity) of the fin surface. Therefore, if the water wettability of the fin surface is good, the adhered water is less likely to become water droplets, which reduces ventilation resistance, increases air volume, and increases heat exchange efficiency. As such a hydrophilic treatment, it has been considered to perform surface treatment on an aluminum strip in advance before assembling it into a heat exchanger, and a silicate, a silica sol, a mixed liquid of a hydrophilic organic polymer and a silicate. Surface treatments such as At present, the mainstream is a coating treatment with an inorganic film having a good hydrophilicity.

[0003]

However, the fin material for the heat exchanger coated with the above inorganic coating is the first punched pierce in the drawless processing when the fin is formed and assembled into the heat exchanger. The wear on the punch was severe. Further, since the burring punch ironing punch, the die tool, and the like during ironing are also worn, the tools have to be changed frequently, resulting in poor workability and expensive maintenance costs for the tools. In the present invention, as a result of earnestly researching a surface treatment method with less wear of tools, as a colloidal silica, a large particle size silica having an average particle size of 40-60 nm is used.
Moreover, it was found that tool wear can be significantly improved without impairing the hydrophilicity of the obtained coating by defining the proportion of the inorganic substance and the coating amount, respectively, and the present invention has been completed. An object of the present invention is to provide an improved aluminum fin material for a heat exchanger, which does not impair the hydrophilicity of the hydrophilic baking coating on the aluminum fin material and has less tool wear.

[0004]

That is, in the aluminum fin material for a heat exchanger of the present invention, colloidal silica having an average particle diameter of 40 to 60 nm is contained in a weight ratio of 50 to 50 through a chromate film layer on the surface of an aluminum strip. The baking amount of the hydrophilic organic resin containing 80% is 0.4 to 0.8 g / m ^{2 in} terms of the coating amount.
It is characterized by being provided.

[0005]

In the present invention, the hydrophilic baking coating provided on the surface of the aluminum material is made of a mixture of colloidal silica and a hydrophilic organic resin. In addition, prior to the formation of the hydrophilic baking film, in order to impart corrosion resistance and improve the adhesion of the hydrophilic baking film, a chromic acid chromate film, a phosphoric acid chromate film, or the like is used as a base in a Cr amount. It is desirable to provide about 5 to 30 mg / m ² . In the present invention, the colloidal silica used in forming the hydrophilic baking coating is used for imparting hydrophilicity to the obtained baking coating, and the colloidal silica is dried from the sol state by the baking treatment to remove water. , A siloxane bond of Si-OH-Si is strongly formed on the surface of the aluminum material to exert hydrophilicity. Then, the film is more excellent in adhesion, water resistance and corrosion resistance than the alkali silicate which is usually used as silica. The average particle size is 40 to 60 nm, and the mixing ratio in the mixture with the hydrophilic organic resin is 5 by weight.
The reason for defining 0 to 80% is that the silica particles are sparsely distributed in the baking film to be formed, and if a fine particle size is used, a dense and hard silica film is formed,
This is because the piercing punch hits this directly at the time of punching, and wear of the piercing punch increases. Regarding the blending ratio, the content of colloidal silica in the mixture with the hydrophilic organic resin is 50% by weight.
If it is less than 80%, the obtained baked coating will be inferior in workability and tool wearability, and if it exceeds 80% in a large amount, the obtained baked coating will be inferior in hydrophilicity.

The hydrophilic organic resin used in the present invention is used for imparting hydrophilicity to the obtained baked film and improving processability. For example, acrylic resin,
Urea resins and cellulose resins can be used, but acrylic resins are preferable because of their stability with colloidal silica. A nonionic or anionic surfactant may be added to enhance hydrophilicity and degreasing property. In addition, the amount of the hydrophilic baking coating layer is 0.4 to
Was defined as 0. 8 g / m ² is 0. If it is less than 4g / m ^2, press oil immersion, now poor hydrophilicity degreased,
On the other hand, if it exceeds 0.8 g / m ² , the hydrophilicity is not further improved, and the workability and tool wear are rather deteriorated.

The aluminum fin material for a heat exchanger of the present invention is covered with a hydrophilic baking coating layer containing silica having an average particle size of 40 to 60 nm in a weight ratio of 50 to 80%, and therefore the aluminum fin material has a hydrophilic property. Excellent and less tool wear.

[0008]

EXAMPLES Examples of the present invention will be shown below. (Example 1) An industrial pure aluminum strip having a plate thickness of 0.105 mm is continuously subjected to degreasing and chemical conversion treatment to obtain a Cr content of 20 m.
A chromate chromate film of g / m ² was provided. On the other hand, as colloidal silica, silica having an average particle size of 40 to 60 nm (trade name Snowtex XL: manufactured by Nissan Chemical Co., Ltd.,
ST-XL) and a hydrophilic acrylic resin containing anionic and nonionic surfactants (trade name FC510: manufactured by Toho Kagaku Co., Ltd.) as a hydrophilic resin, and the silica content is 70% by solid content weight ratio. The paint prepared by blending
On the chromate chromate film on the aluminum strip,
It was baked at 260 ° C. for 15 seconds. The amount of the baked film was 0.6 g / m ² . With respect to the obtained sample, tool wear resistance and hydrophilicity were examined by the methods described below. The obtained results are also shown in Table 1.

Tool wearability = 300,000 continuous drawless fin forming is performed using a drawless fin die (7 mmφ) manufactured by Hidaka Seiki Co., Ltd. Tool wear was judged by cracking flare. A crack defect rate of 20% or less after 300,000 shots is ◎,
20 to 40% is shown as ◯, and 60% or more is shown as x. Hydrophilicity = Samples are immersed in press oil (Idemitsu AF8) at room temperature for 3 minutes, then at room temperature in triethane for 1 minute and at 70 ° C in triethane for 5 minutes. After that, the contact angle is measured and 15 °
Less than is indicated by ◯, 15 or more and less than 30 ° is indicated by Δ, and 30 ° or more is indicated by x.

Comparative Example 1 An industrial pure aluminum strip having a plate thickness of 0.105 mm was continuously subjected to degreasing and chemical conversion treatment to form a chromate chromate film having a Cr content of 20 mg / m ² . On the other hand, the colloidal silica has an average particle size of 10 to 2
Hydrophilic acrylic resin containing 0 nm silica (trade name Snowtex 40: Nissan Chemical Co., Ltd., hereinafter referred to as ST-40) and anionic and nonionic surfactant as hydrophilic resin (trade name FC510: Toho Kagaku). (Manufactured by Co., Ltd.) was prepared by mixing so that the silica content was 70% by weight in terms of solid content, and the coating material was applied onto the chromate chromate film on the aluminum strip and dried and baked at 260 ° C. for 15 seconds. The amount of the baked film was 0.6 g / m ² . With respect to the obtained sample, its tool wear property and hydrophilicity were examined in the same manner as in Example 1. The obtained results are also shown in Table 1.

(Examples 2 to 5, Comparative Examples 2 to 5) Plate thickness:
A 105 mm industrial pure aluminum strip was continuously subjected to degreasing and chemical conversion treatment to prepare a test sample in which a chromate chromate film with a Cr content of 20 mg / m ² was provided. On the other hand, as colloidal silica, the average particle size is 40 to 60 nm.
Silica (Product name Snowtex XL: Nissan Chemical Co., Ltd.)
And a hydrophilic acrylic resin containing anionic and nonionic surfactants (trade name FC510: manufactured by Toho Kagaku Co., Ltd.) as hydrophilic resins, with various solid content weight ratios and coating amounts varied as shown in Table 1. Was prepared, each coating was applied on the chromate chromate film of the test sample,
It was baked at 260 ° C. for 15 seconds. With respect to each of the obtained test samples, the tool wear resistance and hydrophilicity were examined in the same manner as in Example 1. The results obtained are shown in Table 1.
Also described in.

[0011]

[Table 1]

As is apparent from Table 1, the hydrophilic baking coating on the surface of the aluminum strip has an average particle size of 40 to 60 nm.
Examples 1 to 5, which contain the colloidal silica in the range of 50 to 80% by weight and the coating amount is in the range of 0.4 to 0.8 g / m ² , all have excellent tool wear resistance, The hydrophilicity was also good. On the other hand, the average particle size is 10 to 20n
In Comparative Example 1 in which m and fine colloidal silica were used, the compounding amount was 70% by weight and the amount was within the range specified by the present invention, and the coating amount was 0.60 g / m ² , but the tool wear The sex was extremely poor. The average particle size is 40
Comparative Example 2 in which colloidal silica having a particle size of -60 nm was used, but the content of the colloidal silica was 40% by weight, which was outside the scope of the present invention.
The tool wearability was good, but the hydrophilicity was remarkably reduced, and the blending amount was 90% by weight, which was more than the amount specified in the present invention, and Comparative Example 3 had good hydrophilicity. However, the tool wear property was significantly reduced. Further, colloidal silica having an average particle diameter of 40 to 60 nm is used, and the compounding amount is 70% by weight, which is within the range specified in the present invention, but the coating amount is too small as 0.30 g / m ^2. Comparative Example 4 was inferior in hydrophilicity, and the film amount was 1.0.
In Comparative Example 5, which was too much as 0 g / m ² , the tool wear resistance was deteriorated.

[0013]

As is apparent from the above examples, the aluminum fin material for a heat exchanger of the present invention has excellent hydrophilicity and an excellent baking film with little tool wear, and is excellent in workability. And its industrial value is extremely high.

Claims (1)

[Claims] 1. A baked film of a hydrophilic organic resin containing 50-80% by weight of colloidal silica having an average particle size of 40-60 nm through a chromate film layer on the surface of an aluminum strip and having a film amount of 0. An aluminum fin material for a heat exchanger, which is excellent in workability, characterized by being provided in an amount of 4 to 0.8 g / m ² .