JPH0718017B2 - Method of manufacturing heat exchange medium material - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a heat exchanger medium such as a fin material for a heat exchanger made of aluminum or an aluminum alloy used for a heat exchanger of an automobile or a cooling and heating device for home appliances. The present invention relates to a method for manufacturing a material.

[Prior Art and Its Problems] A medium material for a heat exchanger made of aluminum or an aluminum alloy (hereinafter simply referred to as “aluminum”) usually has an organic, inorganic, or a composite-type film thereof having good wettability on its surface. Has been formed. This fin material for heat exchange medium is press-molded to form fins. After that, the lubricating oil such as the press oil adhered to the fin surface or the like in the press working step is degreased with an organic solvent or an aqueous solution of a neutral or weak alkaline detergent to manufacture the heat exchanger.

And, in recent years, there is a tendency to reduce the fin pitch of the heat exchanger in order to improve the heat exchange efficiency and reduce the size, and in such a case, in the evaporator, the moisture in the atmosphere is condensed into the fins, and the ventilation resistance and the Since the dry-humidity ratio increases, noise is generated, condensed water is blown out into the room, and the defrosting energy increases outdoors in the winter,
It is extremely important that the fin surface has good water wettability and oil stain resistance.

Therefore, the present inventors have already proposed a heat exchange medium manufacturing method (Japanese Patent Publication No. 60-1558) as a method for solving these problems. By this method, that is, after the surface of an aluminum thin plate (usually having a plate thickness of 0.05 to 0.2 mm) is treated with sodium hypochlorite or the like to form a hydrated oxide film on the surface, for example, alkali silicic acid is used. It is industrially mass-produced as a heat exchanger medium material excellent in moldability, water wettability, corrosion resistance, etc. by forming a silicon compound on the film by dipping treatment with salt (water glass) or the like.

However, even when these heat exchange medium materials are actually assembled and used as a heat exchanger, they are not without problems. For example, one of those problems is that the heat exchanger medium is used in the atmosphere. In the state in which the pollutants and the like are easily adsorbed, so-called "cement odor", "mold odor", etc. are expressed (for example, Japanese Patent Laid-Open No. 61-
As shown in 253390. ) A problem has been raised that it produces an extremely faint offensive odor.

DISCLOSURE OF THE INVENTION The present inventor has conducted extensive studies to clarify the above-mentioned problems, and after forming a hydrated oxide film of 0.4 to 0.6 g / m ^{2 on} the surface of an aluminum thin plate, 1) A step of forming a silicon compound in an amount of 0.01 to 0.04 g / m ^{2 in} terms of silicon on the surface of the hydrated oxide film by immersion treatment with an aqueous solution containing a silicate.

2) A step of applying a water-based paint containing a surfactant to form a coating film having a coating film weight after drying of 0.3 to 0.8 g / m ² on the surface of the hydrated oxide film.

When the aluminum heat exchanger medium material is manufactured by sequentially performing the above steps 1) and 2), even when assembled as a heat exchanger after molding, there is no strange odor such as so-called "mold odor". The present invention has been completed with good workability in that the surface of the fin has good wettability before and after use (that is, a small air-drying resistance dry / wet ratio), excellent white rust resistance, and good workability.

Incidentally, the hydrated oxide film referred to in the present invention, boehmite film formed on the surface by immersing an aluminum thin plate in boiling pure water, or triethanolamine, ammonia, and caustic soda, various basic By substance
Boehmite-based film formed by treatment with a pure water-based aqueous solution adjusted to pH 9 to 12, a film formed with a basic aqueous solution of PH 9 to 12 to which an oxidizing agent disclosed in JP-A-59-211578 is added, etc. Can be mentioned.

The silicon compound is, for example, a concentration of 0.05 to 10%, preferably 0.5 to 5% of water glass, sodium silicate,
Using an aqueous solution or suspension of potassium silicate or the like, an immersion treatment is performed to form a silicon compound of about 0.01 to 0.04 g / m ^{2 in} terms of silicon on the surface of the hydrated oxide film, and As the surfactant contained in the water-based paint in an amount of about 1 to 5%, any of a nonionic type, anionic type, cationic type and amphoteric type can be used, and a nonionic type is particularly preferable.

Examples of nonionic surfactants include polyoxyethylene alkyl ether type (polyoxyethylene nonylphenyl ether, polyoxyethylene octyl phenyl ether), alkyl ether type (polyoxyethylene lauryl ether), alkyl ester type (polyoxyethylene lauryl ether). Oxyethylene oleate), alkylamine type (polyoxyethylene laurylamine), sorbitan derivative ester type (sorbitan laurate, sorbitan palmitate), sorbitan derivative complex type (polyoxyethylene sorbitan laurate, polyoxyethylene sorbitan stearate) Etc.

Further, as the water-based paint, for example, acrylic acid ester-based, alkyd-based, acrylic alkyd-based,
Various paints such as polyester-based, epoxy-based, amino-based, polyamide-based and the like are used in the form of water-soluble or water-dispersed solutions.

Next, the reason for limiting the manufacturing method of the present invention will be described in detail.

1) Amount of hydrated oxide film.

The amount of hydrated oxide film formed on the surface of the aluminum sheet is 0.
When the amount is less than 4 g / m ² , the adhesion between the aluminum substrate and the hydrated oxide film is poor, and the hydrated oxide film may peel off due to press working, etc.
If it exceeds 0.6 g / m ² , abnormalities are likely to occur during press working of the heat exchange medium material.

2) Amount of silicon compound formed on the hydrated oxide film.

When the amount of silicon compound is less than 0.01 g / m ^{2 in} terms of silicon,
Since the hydrated oxide film is not completely covered, the effect of surface modification such as improvement of adhesion and hydrophilicity of the coating film is not sufficient. Further, when the silicon compound is formed in excess of 0.04 g / m ^{2 in} terms of silicon, an excessive silicon compound is formed on the hydrated oxide film, which not only deteriorates the adhesiveness, but also Problems such as so-called "moldy smell" tend to occur after the application of the water-based paint.

3) Amount of water-based paint applied.

The solid content of the water-based or water-dispersible coating is preferably 1 to 20%, more preferably 2 to 10% by weight. It is preferable that these coating films have a thickness of 0.3 to 0.8 g / m ² after drying. That is 0.3g
If it is less than / m ² , as shown in FIG. 2, the hydrated oxide film cannot be completely covered, and there is a portion left as a hydrated oxide film. Due to the adsorption of pollutants, problems such as so-called "moldy smell" remain. In addition, if the weight of the coating after drying exceeds 0.8 g / m ² , water wetting persistence deteriorates, the coating adheres to the mold during press working, causing mold damage, and accelerating wear. It is not preferable.

Next, specific examples of the present invention will be described.

[Example 1] A JIS1050 H24 aluminum thin plate was degreased by weak alkaline etching, and then immersed in an aqueous solution of sodium hypochlorite (NaOCl solution concentration 200 ppm; PH10.5) by heating to about 85 ° C, A hydrated oxide film of 0.6 g / m ² is formed. Then, a 1.5% water glass solution (PH: 11.4) was heated to 60 ° C and immersed. Further, it was washed with shower water to remove excess water glass, and about 0.03 g / m ² of silicon compound in terms of silicon was formed on the surface of the aluminum thin plate.

Then, on the surface of the aluminum thin plate, about 3 g / m ² roll coating of a polyamide-based water-based paint (Nippon Paint Co., Ltd., trade name NP Alcoat 112, resin solid content 20%) containing nonionic and anionic surfactants Apply by 230
After heating and drying at 60 ° C. for 60 seconds, a coating film having a coating amount of 0.6 g / m ^{2 was} applied to the surface of the aluminum thin plate. Then, the pre-coated fin material was draw-pressed to form fins.
Then, after degreasing with a trichloroethylene solvent at 80 ° C. for 1 minute, a heat exchanger was obtained.

[Comparative Example 1] A heat exchanger was obtained through the same steps as in Example 1, except that the coating amount of the polyamide-based aqueous coating material containing a surfactant after drying was 0.2 g / m ² .

[Comparative Example 2] In Example 1, the coating amount of the water-based paint after drying was about 1.
A heat exchanger was obtained through the same steps except that the amount was 0 g / m ² .

[Example 2] A heat exchanger was obtained through the same steps as in Example 1, except that the silicon compound on the surface of the hydrated oxide film was applied in an amount of about 0.01 g / m ² in terms of silicon.

[Example 3] A heat exchanger was assembled through the same steps as in Example 1, except that a draw press process was performed instead of the drawless press process.

[Comparative Example 3] A heat exchanger was obtained through the same steps as in Example 1, except that the amount of the hydrated oxide film was about 0.9 g / m ² .

[Comparative Example 4] A heat exchanger was obtained through the same steps as in Example 1, except that the amount of the hydrated oxide film was about 0.3 g / m ² .

[Comparative Example 5] In Example 1, a water-soluble acrylic melamine-based paint containing no surfactant was applied and dried to give an applied amount of about 0.8 g.
A heat exchanger was obtained after going through the same steps except that the rate was changed to / m ² .

[Comparative Example 6] A heat exchanger was obtained through the same steps as in Example 1, except that the coating of the polyamide-based paint containing a surfactant was omitted.

[Comparative Example 7] A heat exchanger was obtained through the same steps as in Example 1, except that the silicon compound was not formed on the surface of the hydrated oxide film.

[Comparative Example 8] A heat exchanger was obtained through the same steps except that the silicon compound on the surface of the hydrated oxide film in Example 1 was coated at about 0.05 g / m ² in terms of silicon.

[Test Method] With respect to the aluminum heat exchanger medium material obtained as described above, a weak offensive odor such as so-called "mold odor",
Initial water wettability (ventilation resistance dry / wet ratio in wind speed 1m / min, 30 ℃, 60% RH), water wettability (water wettability of fin material after immersion in running water for 500 hours), corrosion resistance (JIS Z2371 The salt spray test based on the above, the corrosion state after 336 hours is shown.) The press workability (the state of the coating film and the hydrated oxide film on the surface after the pressing work) was examined, and the results are shown in the table.

[Effect of the invention] As can be seen from the table, the heat exchanger medium material according to the production method of the present invention does not have a problem of a slight offensive odor such as so-called "mold odor", and has an initial water wettability, a water wettability persistence, and a corrosion resistance. In terms of press workability and the like, when used as a heat exchanger, various excellent effects are exhibited, and the effects are very large in industrial production.

[Brief description of drawings]

FIG. 1 is an enlarged photograph of a metal surface structure of a fin material for an aluminum heat exchanger according to an embodiment of the present invention, taken with an electron microscope and having a magnification of 50,000. FIG. ^{2 is} a comparative example with a coating amount of 0.2 g / m ² , which is an enlarged photograph of a metal surface structure of a fin material for an aluminum heat exchanger by an electron microscope, at a magnification of 50,000 times.

Claims (1)

[Claims] 1. A hydrated oxide film is formed on the surface of an aluminum or aluminum alloy thin plate in a range of 0.4 to 0.6 g / m ² , and then 1) treated with an aqueous solution containing a silicate to form silicon on the surface of the hydrated oxide film. A step of forming 0.01 to 0.04 g / m ² of a silicon compound in terms of conversion. 2) A step of applying a surfactant and an aqueous resin coating material to form a coating film having a coating film weight after drying of 0.3 to 0.8 g / m ^{2 on} the surface of the hydrated oxide film. A method for manufacturing a heat exchange medium material made of aluminum or aluminum alloy, which comprises sequentially performing the above steps 1) and 2).