JPH11199823A - Fin material for heat exchanger and surface treating agent therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the subject treating agent excellent in hydrophilic property and water resistant close adhesion by containing a specific polyvinyl alcohol. SOLUTION: This surface treating agent for a fin material of a heat exchanger made of aluminum contains a polyvinyl alcohol composed of a vinyl alcohol unit, a vinyl unit containing amide group and an aliphatic vinyl ester unit. The degree of polymerization of the above polyvinyl alcohol is 3,000-3,300, preferably 500-2,400, the degree of saponification is >=90%, preferably >=95%, and the content of the vinyl unit containing amide group is 2-12 mol.%, preferably 2.510 mol.%. The water soluble polymer of the above surface treating agent is used by applying the same on the surface of the fin material made of aluminum, and drying to form a film on the surface of the fin material for the heat exchanger made of aluminum.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a fin for an aluminum heat exchanger used for an air conditioner. More specifically, a surface treatment agent containing a water-soluble polymer as a main component, which is characterized by imparting excellent hydrophilicity to the aluminum surface to prevent the formation of water droplets, and a fin by the water-soluble polymer. The present invention relates to a fin material for a heat exchanger, the surface of which is coated.

[0002]

2. Description of the Related Art Aluminum fins for heat exchangers of air conditioners are made of aluminum sheets having excellent heat conductivity. Condensed water generated by the condensation of water during cooling adheres to the fin surface and condensed water is formed between the fins. This causes a so-called bridge phenomenon. This increases ventilation resistance and results in power loss,
Problems such as generation of noise and scattering of water droplets into the room have occurred. In addition, the above-mentioned problem has become more remarkable because the fin interval has been remarkably narrowed with the recent miniaturization of the heat exchanger.

[0003] In order to solve these problems, a method of forming a hydrophilic film on a fin material for a heat exchanger to prevent the attachment of water droplets has been studied. As a method for hydrophilizing the fin surface, various methods using a hydrophilic inorganic compound such as water glass or an organic compound such as a surfactant or a water-soluble resin have been proposed.

As a method for forming a film having hydrophilicity on aluminum fins, a method using a hydrophilic film-forming agent comprising an alkali silicate and a low molecular weight organic compound having a carbonyl group (Japanese Patent Application Laid-Open No. 60-101156). A hydrophilic paint comprising a surfactant mixed with an organic compound comprising a water-soluble resin and a water-absorbent resin (Japanese Patent Laid-Open No. 62-12936)
6) and the like are disclosed.

[0005]

However, the above-mentioned method using an alkali silicate has a problem that a mold is worn during press working, and a surfactant is added to an organic compound. Although the method improves the wear of the mold, there is a problem that the hydrophilicity is reduced due to the surfactant and the hydrophilic organic compound flowing out of the film. The present invention solves these problems.

[0006]

Means for Solving the Problems The present inventors have made intensive studies to solve the above-mentioned problems, and as a result, by forming a film of a resin composition of a specific composition on both sides of an aluminum thin plate, a hydrophilic film is formed. It has been found that since the film has excellent properties and does not contain a silica component, the film becomes soft and the wear of a mold is improved when a thin aluminum plate is molded.

That is, the present invention relates to a surface treating agent for a fin material for an aluminum heat exchanger, comprising a polyvinyl alcohol containing a vinyl alcohol unit, an amide group-containing vinyl unit and an aliphatic vinyl ester unit. Has a polymerization degree of 300 to 3300, a saponification degree of 90% or more, and an amide group-containing vinyl unit of 2 to 12
It is a surface treating agent for a fin material for an aluminum heat exchanger, which is a mol%, and a water-soluble polymer of the surface treating agent is applied to the surface of the aluminum fin material, and dried to be dried. A method of forming a film on the surface of a material, further comprising a film containing polyvinyl alcohol on the surface of the fin material for a heat exchanger, wherein the polyvinyl alcohol is a vinyl alcohol unit, an amide group-containing vinyl unit, or an aliphatic vinyl ester unit. And a degree of polymerization of 30
The present invention relates to a fin material for an aluminum heat exchanger having 0 to 3300, a saponification degree of 90% or more, and an amide group-containing vinyl unit of 2 to 12 mol%.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The polyvinyl alcohol of the present invention preferably contains 2 to 12 mol% of an amide group-containing vinyl unit, more preferably 2.5 to 10 mol%. When the amide group-containing vinyl unit is low, hydrophilicity decreases, and when it is high, water resistance decreases.

The degree of polymerization of the polyvinyl alcohol is 300 to 3300, preferably 500 to 2400. If the degree of polymerization is small, the water-resistant adhesion of the film is reduced. Conversely, if the degree of polymerization is high, the viscosity of the aqueous solution is increased, workability is reduced, and it becomes difficult to adjust the film thickness.

The degree of saponification of polyvinyl alcohol is 90%
And preferably 95% or more. When the degree of saponification is low, the solubility in water increases, and there is a disadvantage that the film formed on the aluminum thin plate dissolves. Therefore, the above range is preferable.

The polyvinyl alcohol of the present invention is produced by a known method. That is, it is obtained by copolymerizing an aliphatic vinyl ester and an amide group-containing vinyl monomer and saponifying the copolymer. As the aliphatic vinyl ester, for example, an aliphatic vinyl ester such as vinyl formate, vinyl acetate, vinyl propionate, and vinyl trifluoroacetate is subjected to amide group-containing vinyl polymerization by a known polymerization method such as solution polymerization, emulsion polymerization, suspension polymerization, or bulk polymerization. It can be obtained by copolymerizing with a monomer, dissolving the obtained polymer in an alcohol such as methanol, adding an alkali catalyst, saponifying and drying. As the amide group-containing vinyl monomer, acrylamide, methacrylamide and the like are preferable.

The above-mentioned polyvinyl alcohol includes carboxyl group-containing vinyl monomers such as itaconic acid, maleic anhydride and crotonic acid, glycidyl acrylate, glycidyl methacrylate, allyl glycidyl ether, 1, 3
An epoxy group-containing vinyl monomer such as diepoxy-2-propanol glycerol diglycidyl ether can be used in combination.

For the water-soluble polymer composed of polyvinyl alcohol, a chelating compound of a metal such as titanium, zirconium and vanadium can be used as a curing agent. Moreover, the aluminum thin plate which has been subjected to a surface treatment by a known method is used. As the surface treatment method, for example, chromate treatment, titanate treatment, zirconate treatment,
Boehmite treatment.

The water-soluble polymer is applied to the aluminum sheet by dipping, roll coating, spraying or the like. The conditions for drying the coating film are not particularly limited, but generally 9
The reaction is performed at 0 to 250 ° C. for 15 seconds to 30 minutes.

Conventional fin materials for heat exchangers have been found to have a short hydrophilicity duration or to be exposed to moisture for a long period of time to elute a hydrophilic coating film and become unable to maintain hydrophilicity. Is incorporated into polyvinyl alcohol to improve hydrophilicity and remarkably improve water-resistant adhesion to an aluminum thin plate.

[0016]

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. Note that “parts” and “%” are based on weight.

Example 1 20 parts of polyvinyl alcohol shown in Table 1a were added and dissolved in 380 parts of pure water heated to 60 ° C. to obtain 400 parts of an aqueous polyvinyl alcohol solution having a solid content of 5%. 0.5 parts of ammonium zirconium carbonate was mixed with the obtained aqueous polyvinyl alcohol solution to obtain a water-soluble polymer solution.
After a 0.1 mm aluminum thin plate was degreased and subjected to chromate treatment, a water-soluble polymer solution was applied to the surface thereof to a thickness of about 1 micron. A test plate was obtained by drying at a drying temperature of 200 ° C. for 1 minute. Initial hydrophilicity of the obtained test plate,
The hydrophilicity after immersion in running water for 100 hours and the water resistance of the coating film were measured. Table 2 shows the results.

Examples 2 to 4 Water-soluble polymer solutions were prepared in the same manner as in Example 1 using the polyvinyl alcohols shown in Tables 1 to 3, and had initial hydrophilicity and hydrophilicity after immersion in running water for 100 hours. The water resistance of the coating film was measured in the same manner as in Example 1. Table 2 shows the results.

Comparative Examples 1 to 3 Water-soluble polymer solutions were prepared in the same manner as in Example 1 using the polyvinyl alcohols shown in Tables 1 to g and hydrophilicity after immersion in running water for 100 hours. The water resistance of the coating film was measured in the same manner as in Example 1. Table 2 shows the results.

(Measurement method) Initial hydrophilicity: Dynamic contact angle absorption tester (FIBRO system ab)
10 μm of pure water was dropped on the test plate, and the contact angle and the diameter of the water droplet on the coating film after 20 seconds were measured. Hydrophilicity after immersion in running water: The test plate was immersed in running water for 100 hours and then dried, and the contact angle and the diameter of the water droplet on the coating film were measured in the same manner as the initial hydrophilicity measurement. Water resistance: The coating film of the test plate after immersion in running water was subjected to a tape peeling test to observe the change in appearance (degree of peeling).

(Determination method) Hydrophilic wettability ○: Water droplet diameter is 7 mm or more △: Water droplet diameter is 6 mm or more and less than 7 mm ×: Water droplet diameter is less than 6 mm Water-resistant adhesion ○: No change in appearance △: Slight peeling ×: Peeled

[0022]

[Table 1]

[0023]

[Table 2]

[0024]

According to the present invention, a water-soluble polymer composed of polyvinyl alcohol obtained by copolymerizing a vinyl alcohol unit with an amide group-containing vinyl monomer is applied to the surface of an aluminum fin and dried to form a film. In this method, the hydrophilicity of polyvinyl alcohol is improved, and the water-resistant adhesion to the aluminum thin plate is extremely improved. Therefore, even if the hydrophilic film is exposed to running water for a long time, the hydrophilic film does not peel off or elute.
Also, since the hydrophilic film is soft, it is a fin material for heat exchangers that causes less wear of the mold when pressing aluminum fins.

Claims (3)

[Claims] A surface treating agent for a fin material for an aluminum heat exchanger containing a polyvinyl alcohol containing a vinyl alcohol unit, an amide group-containing vinyl unit and an aliphatic vinyl ester unit, wherein the polyvinyl alcohol has a degree of polymerization of 1. 300-3300, degree of saponification is 90% or more,
A surface treating agent for a fin material for an aluminum heat exchanger, wherein the amide group-containing vinyl unit is 2 to 12 mol%. 2. A method of applying a water-soluble polymer of the surface treating agent according to claim 1 on the surface of an aluminum fin material and drying it to form a coating on the surface of the aluminum heat exchanger fin material. 3. A fin material for an aluminum heat exchanger, having a coating containing polyvinyl alcohol on the surface of the fin material, wherein the polyvinyl alcohol is a vinyl alcohol unit, an amide group-containing vinyl unit, or an aliphatic vinyl ester. And a polymerization degree of 300 to 3300, a saponification degree of 90% or more, and an amide group-containing vinyl unit of 2 to 12
Molar aluminum fin material for heat exchangers.