JPH0673934B2 - Aluminum fin material for heat exchanger - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an aluminum fin material for a heat exchanger, which is made of aluminum or an aluminum alloy, and particularly has a hydrophilic property and is used for a heat exchanger excellent in corrosion resistance and press formability. The present invention relates to an aluminum fin material.

(Prior art and its problems) Conventionally, fins made of aluminum or its alloy have been used for the heat exchange part of the air conditioning equipment. However, the dew point of the refrigerant pipes and fins is the dew point when the evaporator of the air conditioner is operating. In the following cases, condensed water will adhere. Thus, the attachment of the water droplets increases the draft resistance of the air flow to be blown to the evaporator, and this reduces the draft amount in the entire evaporator,
The heat exchange efficiency is reduced.

Therefore, in order to secure the required air flow, the evaporator must be made large, but recently, miniaturization has been promoted from the viewpoint of resource saving, energy saving, or design.
In the fact that the fin pitch is narrowed in the finned tube heat exchanger. Therefore, conventionally, as a fin of a heat exchanger, from the viewpoint of heat exchange efficiency and rust prevention, a fin having a surface-treated coating on the surface thereof is generally used.

By the way, this surface treatment film is formed by processing aluminum material into fins of the desired shape and combining it with the tube,
Most of the heat exchangers are formed by post-coating treatment after the heat exchanger. Conventionally, such post-coating treatments include an organic resin coating method (JP-A-55-164264) and a boehmite method ( JP-A-53-14450), alkali silicate method (Japanese Patent Publication No. 53-48177), chromate method and the like have been proposed. However, what can be said in common with such a post-coating method is that (1) the fin shape and fin pitch are restricted from the viewpoint of processing workability, and (2) the complicated shape after the heat exchanger is formed. Because of this, and because of the combination of different materials, it is difficult to perform uniform treatment, (3) there is a risk of appearance defects and heat exchange efficiency deterioration due to the occurrence of liquid pool, and (4) carry-out of processing liquid. This is because there are inherent problems such as an increase in pollution load and an increase in cost due to the large number of items.

For this reason, a precoat method in which a surface treatment film is formed before forming the fins has been proposed as an alternative method to the postcoat treatment. According to this method, in the strip state, a film having uniform and good water wettability and excellent corrosion resistance is formed on the fin material, and the fin material having such a film has a desired shape. The fin will be processed.

However, in such a precoat method,
The precoat film is liable to be damaged during the forming process such as bulging, ironing or punching, and the water wettability of the film deteriorates due to the trichlene degreasing process used to remove the press oil used during the forming process. Easy to do,
Alternatively, during forming of the precoat material, especially in drawless press working (hole expanding + ironing), cracking of the ironing part and breakage of the flare part are likely to occur, and further wear of the tool of the press die is likely to occur. This causes new problems that are not found in the above post-coating treatment. The fact is that a fin material having a surface-treated film having hydrophilicity, corrosion resistance, and press moldability, which solves all of the various problems in the precoat method, has not yet been obtained.

(Structure of the Invention) Here, the inventors of the present invention have a precoat film that has high hydrophilicity and corrosion resistance, and does not cause cracks in the ironing part or breakage in the flare part in press moldability, and We have proceeded with the development of a surface treatment film that does not cause tool wear, and obtained the following findings.

That is, hydrophilicity (water wettability) is to cause condensed water to flow down along the fin surface as a thin water film by expansion wetting. This is because of the composition forming the film and the film formed by the composition. It was found that the corrosion resistance and the press formability are closely related to the amount of the film, which is related to the surface fine morphology, and the present invention was completed based on such knowledge. .

Therefore, the aluminum fin material for a heat exchanger according to the present invention is a composite of an alkali silicate and a water-soluble hydrophilic polymer compound having at least one polar group of a carboxyl group, a hydroxyl group and an amino group. The composition is crosslinked and cured with an ammonium zirconium carbonate salt, a zirconium complex compound, or a mixture thereof, and is coated with a formed cured film, and the cured film contains 5 to 150 mg / m ² . It is characterized by containing Si, and by doing so, the problems in the above-mentioned conventional precoating method have been solved completely.

(Detailed Description of Configuration) By the way, as a composition for forming a cured film that covers the surface of the fin material according to the present invention, an alkali silicate is used as the first component, and a water-soluble hydrophilic polymer is used as the second component. A film-forming composite composition containing a molecular compound, and such a composite composition is crosslinked by a predetermined crosslinking agent,
It will be cured.

And the alkali silicate as the first component constituting such a composite composition is usually one which gives a film forming composition known as water glass, and is generally represented by the formula: Me ₂ O.nSiO _2.
It is represented by aq (however, Me means lithium, potassium, sodium or amine). The hydrophilic polymer compound as the second component has at least one polar group of a carboxyl group, a hydroxyl group, and an amino group, and is, for example, acrylamide, methacrylamide, hydroxymethyl (meth) acrylamide, hydroxy. (Meth) acrylamides such as ethyl (meth) acrylamide; (meth) acrylates such as hydroxypropyl (meth) acrylate and hydroxyethyl (meth) acrylate; polymers such as unsaturated carboxylic acids such as acrylic acid and methacrylic acid; Alternatively, a copolymer of these unsaturated compounds, or a copolymer of these unsaturated compounds and other unsaturated compounds or by introducing the carboxyl group or hydroxyl group or amino group by hydrolysis, etc., hydrophilic Examples of the present invention include polymers Is a, so that the polymer is water-soluble is used therein.

Further, the cross-linking agent to be incorporated into the composite composition of the present invention is ammonium zirconium carbonate salt, zirconium complex compound, or a mixture thereof, and the addition of such cross-linking agent effectively improves the hydrophilic polymer compound. It is crosslinked to form an insoluble composite film that gives excellent properties.

In such a composite composition, by changing the ratio of the above-mentioned first component and second component, the characteristics of the obtained composite film will change significantly. The basic concept is that if the ratio of the first component that gives the film-forming composition is increased, the surface of the composite film after curing is roughened and the hydrophilicity is increased. In addition, regarding the relationship between the coating amount of the composite coating and the press formability, as the coating of the first component becomes thicker, in other words, when the amount of alkali silicate present in the composite coating increases, especially ironing cracks in drawless press forming Also, the flare portion is easily damaged.

Therefore, in the present invention, in order to obtain good surface fine morphology and hydrophilicity, the amount of Si in the composite coating (cured coating) coating the surface of the fin material is in the range of 5 to 150 mg / m ² . It was regulated within. If the amount of Si exceeds 150 mg / m ² , practical press formability will be affected, and
When the amount is less than 5 mg / m ² , the composite coating layer including the polymer resin layer also becomes thin, which causes a problem that hydrophilic durability is lost.

Further, in order to form a composite film having such a Si content, the alkali silicate as the first component and the hydrophilic polymer compound as the second component are 10/1 to 10/6 by weight. It will be compounded in proportions to form a composite composition. If this ratio is greater than 10/1, the composite coating will be too rough and will retain more press oil during press molding, and the degreasing property after heat exchanger assembly will decrease. When the ratio is smaller than 10/6 and the ratio of the polymer resin is high, the degree of roughening of the composite film is not sufficient, the receding contact angle becomes large, and the water wettability decreases. Like

In addition, the composite film formed on the surface of the fin material by the composite composition according to the present invention is specifically 0.03
The thickness is about μm to 1.5 μm, and if the film thickness is too thin, the hydrophilic durability is poor as understood from the above explanation. It easily remains in the composite film, and the contact angle of water: θ
There are problems such as variations in H ₂ O, and easy occurrence of unevenness in color tone at the residual oil spots.

In addition, in such a composition composed of the first component and the second component, a leveling agent, a stabilizer, a quenching agent and the like may be blended with the above-mentioned crosslinking agent, if necessary, to form a composite An object is prepared and applied to a fin material made of a predetermined aluminum or aluminum alloy,
A coating film having a predetermined thickness is formed, and thereafter, the coating film is cured, whereby the intended precoat fin material according to the present invention is formed.

When forming a film of the composite composition on the fin material, the coating method for the fin material in the strip state of the composite composition is basically a 1-coat 1-bake method. The film thickness can be controlled by performing a coat 1 bake method, and further, a dip (dipping) method or a spray method can be applied to achieve a predetermined film thickness.

Then, the coating film made of the composite composition formed on the surface of the fin material is preferably cured (crosslinked) by heating, and the heating temperature at that time is the hydrophilic property as the second component. It varies depending on the type of polymer compound, the type of cross-linking agent as a curing agent blended, and the like, and it is difficult to unambiguously specify. Thus, generally, the composite composition is prepared and applied to the fin material so that the material can be cured at a temperature of 160 ° C. or higher.

The pre-coated fin material according to the present invention thus obtained is a flat plate in a strip state,
This is subjected to various forming processes to be processed into a predetermined fin product, and then combined with a tube or the like to form a desired heat exchanger.

(Examples) Hereinafter, some examples of the present invention will be shown to clarify the present invention more specifically, but the present invention is construed to be limited to the description of the examples. It goes without saying that this is not the case. It should be noted that the present invention is, in addition to the following embodiments, and in addition to the above specific description, various changes, modifications, and improvements within the scope not departing from the spirit of the present invention based on the knowledge of those skilled in the art. It should be understood that it can be implemented in addition to the above.

First, using a commercially available weak alkaline degreasing agent for a 0.110 mm thick aluminum (A1100-H26) coil material,
Degreasing treatment was performed, and then a chemical conversion film mainly composed of phosphoric acid chromate was formed with a liquid containing chromic acid, phosphoric acid and hydrofluoric acid. The amount of Cr in the chemical conversion film at this time was 20 mg / m ² .

Next, this chemical conversion treatment coil material is coated with a bar coater using various coating (composite) compositions shown in Tables 1 and 2 below, and heat treatment is performed at 200 ° C. for 40 seconds. By performing the above, a predetermined coating film was baked and cured.

With respect to the fin materials (coil materials) thus formed with various precoat films, the properties (composite film amount, hydrophilicity, press formability) of each produced composite film are examined,
The results are also shown in Tables 1 and 2 below.

The dry / wet alternating test for evaluating water wettability among the properties of the produced composite film is a combination of immersion in running water for 2 minutes and forced drying for 6 minutes, which is taken as one cycle, and this is 100 The ironing process, which was a test repeated in cycles and was performed to evaluate the press formability, was performed by using a taper tool to perform a reduction rate of 45% (reduction).

As is clear from the results of Tables 1 and 2, a composite film formed using the composite composition of the present invention comprising an alkali silicate and a hydrophilic polymer compound,
And its Si content is in the range of 5 to 150 mg / m ² No. 1 to 3
The fin materials of Nos. 9 to 12 are all excellent in water wettability, and their performance is not changed even after the alternate dry-wet test, and the press moldability is remarkably improved. Is recognized.

On the other hand, the Si content in the composite coating is too small (N
o.4) or too much (No.5), there is a problem that water wettability deteriorates or flare cracks frequently occur during ironing, and only the first component, alkali silicate When a precoat film is formed by coating (No. 6) or when a precoat film is formed by using only the hydrophilic polymer compound as the second component (No. 7), both are wettable by water. However, it was confirmed that the properties of the fin material changed before and after the alternate dry-wet test, and the fin material having a film consisting of No. 6 alkali silicate only had poor press formability. Is recognized. In addition, in the fin material having a film of No. 7 hydrophilic polymer alone, the initial water wettability was variable, θH ₂ O was high, and θH ₂ O was high in terms of hydrophilic sustainability. It is recognized that the wettability is also poor.

(Effects of the Invention) As is clear from the above description, the fin material according to the present invention has a precoat film having high hydrophilicity and corrosion resistance, and the precoat film has a crack in the ironing part in press formability. Without causing damage to the flare part,
Further, it is an excellent surface-treated film that does not cause wear of the die tool, and is industrially highly significant as it solves the problem of the fin material in the conventional precoat method.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Akihiro Kiyotani 3-12-12, Minase-ku, Minato-ku, Nagoya, Aichi Sumitomo Light Metal Industries, Ltd., Nagoya Works (72) Toshinori Maeda 3 Minen-ku, Nagoya, Aichi 1-12, Sumitomo Light Metal Industries, Ltd., Nagoya Works (72) Inventor Shin Kondo, 3-1-1-12, Millennial, Minato-ku, Nagoya, Aichi Prefecture, Sumitomo Light Metal Industries, Ltd., Nagoya Works (56) Reference: Japanese Patent Laid-Open No. Sho 59 -196782 (JP, A) JP-A-59-202398 (JP, A)

Claims (3)

[Claims] 1. A composite composition comprising an alkali silicate and a water-soluble hydrophilic polymer compound having at least one polar group selected from a carboxyl group, a hydroxyl group and an amino group is an ammonium zirconium carbonate salt, A heat treatment characterized by being cross-linked and cured with a zirconium complex compound or a mixture thereof to form a cured film, and the cured film contains 5 to 150 mg / m ² of Si. Aluminum fin material for exchangers. 2. The aluminum for heat exchanger according to claim 1, wherein the ratio of alkali silicate / hydrophilic polymer compound in the composite composition is 10/1 to 10/6 by weight. Fin material. 3. The alkali silicate has the general formula: Me ₂ O.n.
The aluminum fin material for a heat exchanger according to claim 1, which is represented by SiO ₂ (where Me means lithium, potassium, sodium or amine).