JPH07268243A - Precoated fin material for heat exchanger and production thereof - Google Patents

Abstract

PURPOSE:To improve the adherence of a hydrophilic coating film to a primed fin material for use in a heat exchanger by using a specific hydrophilizing agent to form the coating film. CONSTITUTION:A hydrophilizing agent is obtained by adding to water glass 0.01-0.05wt.% nonionic surfactant which is an ethylene oxide adduct having 6-8 ethylene oxide units per molecule. An aluminum stripe to be fabricated into a fin material for a heat exchanger is primed with chromic acid or a chromate in an amount of 5-30mg/m<2> in terms of Cr amount or with a corrosion- resistant organic resin at a thickness of 0.5-1.5mum. The primed stripe is coated with the hydrophilizing agent and then press-molded.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a precoat fin material for a heat exchanger having a hydrophilic film having good adhesion and excellent productivity, and a method for producing the same.

[0002]

2. Description of the Related Art In a heat exchanger, particularly in an evaporator of an air conditioner, water drops adhere to the surface of the fin because the surface temperature of the fin falls below the dew point of the atmosphere. If water drops adhere, the ventilation resistance increases, the air volume decreases, and the heat exchange efficiency decreases. For this reason, the fin material for the heat exchanger is subjected to hydrophilic treatment so that water droplets are hard to occur. The hydrophilic treatment may be performed after fin formation or before fin formation. The former is called postcoat and the latter is called precoat. Precoating is advantageous because it simplifies the process and makes the coating layer uniform.

In the hydrophilic treatment by precoating, an aluminum strip to be a fin material is subjected to a base treatment, a hydrophilic treatment agent is applied onto the aluminum strip, and this is heated and baked to apply a hydrophilic film on the surface. A fin is formed by press-molding an aluminum strip coated with this hydrophilic film. The base treatment is performed to improve the corrosion resistance of the aluminum strip and the adhesion between the aluminum strip and the hydrophilic film. As the hydrophilic treatment agent, silicate, colloidal silica, a mixed liquid of a hydrophilic organic polymer and silicate, or the like is used. Further, the hydrophilic treatment agent usually contains a surfactant in an amount of 0.1 wt% or more for improving the coatability. As the surfactant, anionic or nonionic (eg, alkylphenol or higher alcohol) surfactants are used.

[0004]

When press-molding an aluminum strip on which a hydrophilic film is formed, the hydrophilic film peels off and adheres to the pinch roller of the press, or the release film mixes with aluminum powder. As a result, black powder adheres to the outside of the curl portion of the fins, which reduces the productivity of the heat exchanger.

[0005]

[Means for Solving the Problems] Under such circumstances, the cause of peeling of the hydrophilic film is that the surfactant is dispersed as a foreign substance in the hydrophilic film, which causes It is presumed that this is because the binding property is lowered, and further, various studies have been carried out on the amount and type of the surfactant that maintains the coating property and does not hinder the adhesion property, thereby completing the present invention. That is, in the invention of claim 1, in the precoat fin material for a heat exchanger coated with a hydrophilic treatment agent, water glass containing 0.01% by weight or more and 0.05% by weight or less of a surfactant in the hydrophilic treatment agent is used. A pre-coated fin material for a heat exchanger, which is characterized in that

A fourth aspect of the present invention is a method for producing a pre-coated fin material for a heat exchanger according to the first aspect of the invention, which has a constitution in which an aluminum strip to be a fin material for a heat exchanger is subjected to a surface treatment, and a hydrophilic treatment is applied thereon. In a method for producing a pre-coated fin material for a heat exchanger, in which a hydrophilic coating agent is applied and then an aluminum strip coated with the hydrophilic processing agent is press-molded, a hydrophilic treatment agent, a surfactant is added to water glass in an amount of 0.01 wt% or more and 0.05 wt% or more. % Or less is used for the hydrophilic treatment agent.

In the present invention, the surface treatment prior to the hydrophilic treatment is a usual treatment such as chromate chromate treatment, phosphoric acid chromate treatment, coating type chromate treatment, and corrosion resistant organic resin (acrylic resin, urethane resin, etc.) treatment. The method applies. If the film thickness of the base treatment is thin, the corrosion resistance effect decreases, and if it is thick, the workability decreases. In the case of chromate chromate treatment, the amount of chromium is preferably about 5 to 30 mg / m ² , and for the corrosion resistant organic resin, the thickness is preferably about 0.5 to 1.5 μm.

In the present invention, the water glass used as the hydrophilic treatment agent is applied to an aluminum strip, and after baking to evaporate the water content, a siloxane bond of Si-OH-Si is strongly formed, which exhibits hydrophilicity. To do. For water glass, SiO ₂
Those made in the range of 23 to 37 wt% and Na ₂ O 6 to 18 wt% are used. In particular, SiO ₂ 28-30 wt%, Na ₂ O 9
~ 10wt% water glass (Japanese Industrial Standard JIS3 equivalent) shows good hydrophilicity. Water glass in which Na ₂ O is replaced with K ₂ O or Li ₂ O can be similarly applied.

In the present invention, a surfactant is contained in order to improve the coating property of water glass. The amount is 0.01 wt% or more 0.05
The reason for limiting the content to less than 0.01% by weight is that if it is less than 0.01% by weight, the coating property of water glass is deteriorated, and if it exceeds 0.05% by weight, the hydrophilic film is easily peeled off.

As the surfactant, a nonionic surfactant is particularly effective for improving the coating property, and among them, those having an ethylene oxide addition mole number of 6 or more and 8 or less are preferable. When the number of moles of ethylene oxide added is less than 6 or more than 8, the coatability is slightly lowered. However, it is practically acceptable.
As the nonionic surfactant, linear alkyl polyoxyethylene ether, S-alkyl polyoxyethylene ether, alkylphenyl polyoxyethylene ether and the like are preferable. As the anionic surfactant, alkyl sulfate, alkylbenzene sulfonate,
An α-olefin sulfonate or the like is applied.

To the water glass, a hydrophilic organic resin such as a hydrophilic acrylic resin is added to enhance hydrophilicity and suppress odor, and an inorganic or organic gel is added to gelate the silicate to facilitate curing. It is desirable to add an agent (phosphoric acid, glyoxal, low molecular weight polymer, butyl lactone, etc.).
If the thickness of the hydrophilic film is less than 0.2 gr / m ² , sufficient hydrophilicity cannot be obtained, and if it exceeds 0.7 gr / m ² , not only the effect of improving hydrophilicity is saturated, but also the workability decreases, and Tool wear and press oil contamination are significant. Therefore, a film thickness of 0.2 to 0.7 gr / m ² is desirable.

[0012]

In the present invention, since the amount of the surfactant contained in the hydrophilic treatment agent is limited to 0.01 wt% or more and 0.05 wt% or less,
Hydrophilicity is maintained and peeling of the hydrophilic film is prevented.

[0013]

EXAMPLES The present invention will be described in detail below with reference to examples. Industrial pure aluminum strip with a plate thickness of 0.105 mm (JIS-1100, H-26)
Is continuously degreased and pretreated, coated with a water glass type hydrophilic treatment agent, heated to 230 ° C and baked to form an aluminum strip with a hydrophilic coating on the surface. It was made. In the surface treatment, a chromate phosphate film with a chromium content of 15 mg / m ² was formed. As the hydrophilic treatment agent, sodium silicate (JIS-3 product), hydrophilic acrylic resin, and low molecular weight acrylic resin were mixed in a weight ratio of 5: 3: 1, and various amounts of surfactant were added to this. Prepared. Nonionic surfactant nonipol (trade name, manufactured by Sanyo Kasei)
Alkylphenol type) and nonipolsoft SS (trade name, higher alcohol type) were used.

The paintability and adhesiveness of the above-mentioned aluminum strip having a hydrophilic film formed thereon were investigated. The results are shown in Table 1. In addition, the coatability is the uniformity of the coating film (whether there is uneven coating)
It was judged by. The adhesion was measured by a rubbing test and a press test. The rubbing test is a test method in which the surface is rubbed with moistened gauze. When the film was rubbed 30 times, the film with no film peeling was evaluated as ◯, the one partly peeled was evaluated as Δ, and the one with many peeled parts was evaluated as x. In the press test, after continuous drawless molding was performed 10,000 times, the number of curls adhered by the black powder was expressed as a percentage of the total number of curls.

[0015]

[Table 1]

As is clear from Table 1, the product of the present invention (N
o.1 to 9) were all excellent in coatability and adhesion of the hydrophilic film. In the case of containing a nonionic surfactant having an ethylene oxide addition mole number of 9 or 5 (No. 4, 5), a slight coating unevenness was observed, but there was no problem in practical use and the adhesion was It was good. On the other hand, in Comparative Example No. 10, the content of the surfactant was too small and uneven coating occurred. Further, No. 11 had too much content of the surfactant, and the adhesiveness decreased. A similar test was performed using Sandet Chemical's Sandet BL (trade name, which is the main component of sodium alkyldiphenyl ether sulfonate) for the anionic surfactant. It was almost as good as when the activator was used.

A heat exchanger was manufactured using various aluminum strips (Nos. 1 to 9 in Table 1) prepared in the examples and having a hydrophilic film formed on the surface thereof. In the press molding, the hydrophilic film was not peeled off in any case, and it could be manufactured with a high yield. Further, the fins were free from water drops during use, and the heat exchange efficiency was excellent.

[0018]

[Effect] As described above, the precoat fin material for a heat exchanger of the present invention has high adhesion of the hydrophilic film, and thus the hydrophilic film is not peeled off during fin processing, which is excellent in productivity.
In addition, the hydrophilicity is maintained well, the heat exchange efficiency is high, and the industrially remarkable effect is exhibited.

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Claims (5)

[Claims] 1. A precoat fin material for a heat exchanger coated with a hydrophilic treatment agent, wherein water glass containing 0.01 wt% to 0.05 wt% of a surfactant in the hydrophilic treatment agent is used. Pre-coated fin material for heat exchangers. 2. The precoat fin material for a heat exchanger according to claim 1, wherein the surfactant contained in the water glass is a nonionic surfactant. 3. The precoat fin material for a heat exchanger according to claim 2, wherein the surfactant contained in the water glass is a nonionic surfactant having an ethylene oxide addition mole number of 6 or more and 8 or less. . 4. A precoat for a heat exchanger in which an aluminum strip to be a fin material for a heat exchanger is subjected to a base treatment, a hydrophilic treatment agent is coated on the aluminum strip, and then an aluminum strip coated with the hydrophilic treatment agent is press-molded. In the fin material manufacturing method, 0.01 wt% of a nonionic surfactant is added to water glass as a hydrophilic treatment agent.
% Of 0.05 wt% or less is used, and a method for producing a pre-coated fin material for a heat exchanger, characterized by using a hydrophilic treatment agent. 5. A hydrophilic treatment agent comprising a nonionic surfactant having an ethylene oxide addition mole number of 6 or more and 8 or less in water glass of 0.01 wt% or more and 0.05 wt% or less is used as the hydrophilic treatment agent. The method for producing a pre-coated fin material for a heat exchanger according to claim 4.