JPH11293177A - Fin material for heat exchanger made of aluminum, and its surface treating agent - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a surface treating agent excellent in hydrophilic property, giving a soft film and capable of improving abrasion of a mold in molding an aluminum thin plate by compounding a specific polyvinyl alcohol with polyethylene glycol. SOLUTION: This treating agent comprises (A) a polyvinyl alcohol comprising (i) a vinyl alcohol unit, (ii) an amide group-containing vinyl unit and (iii) an aliphatic vinyl ester unit and (B) polyethylene glycol, and the component A has 300-3,300 polymerization degree and >=90 wt.% saponification degree and the content of the component (ii) is 2-12 mol.%, and the treating agent contains the component B having 600-20,000 molecular weight in an amount of 0.05-5 pts.wt. based on 100 pts.wt. component A. Furthermore, the component A is preferably obtained by copolymerizing, e.g. an aliphatic vinyl ester with an amide group-containing vinyl monomer and saponifying the resultant copolymer, and a metal chelate compound such as titanium may further be used as (C) a curing agent.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a fin material for an aluminum heat exchanger (hereinafter referred to as "aluminum fin material"), and the fin material is mainly used for an air conditioner. More specifically, a surface treatment agent mainly composed of a water-soluble polymer, which is characterized by imparting excellent hydrophilicity to the aluminum surface and preventing the formation of water droplets, and coating the surface with the surface treatment agent Aluminum fin material.

[0002]

2. Description of the Related Art A fin material for a heat exchanger of an air conditioner uses a thin aluminum plate having excellent heat conductivity. Is blocked by condensed water, a so-called bridge phenomenon occurs. For this reason, ventilation resistance has increased, causing problems such as loss of power, generation of noise, and scattering of water droplets into the room. Further, since the space between the fin materials has been remarkably narrowed with recent miniaturization of the heat exchanger, the above problem has become more prominent.

In order to solve these problems, a method of forming a hydrophilic film on an aluminum fin material to prevent water droplets from adhering has been studied. As a method for hydrophilizing the fin material 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 hydrophilic film on an aluminum fin material, 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). JP-A-62-1), a hydrophilic paint comprising a surfactant mixed with an organic compound comprising a water-soluble resin and a water-absorbent resin.
29366) and the like.

[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 coating. 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 surfaces of an aluminum thin plate, It has been found that the coating is soft because it is excellent in properties and does not contain a silica component, and that the wear of a mold is improved when a thin aluminum plate is molded.

That is, the present invention is 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, and a polyethylene glycol, The polyvinyl alcohol has a polymerization degree of 300 to 3300, a saponification degree of 90% or more, an amide group-containing vinyl unit of 2 to 12 mol%, and a molecular weight of 60 to 100 parts by weight of the polyvinyl alcohol.
0-20,000 polyethylene glycol 0.05-
A surface treating agent for an aluminum exchanger fin material containing 5 parts by weight, and an aqueous solution of the surface treating agent is applied to the surface of the aluminum fin material, dried and applied to the surface of the aluminum exchanger fin material. The present invention relates to a method for forming a coating, and further relates to a fin material for an aluminum heat exchanger having a coating of the surface treating agent on the surface of the fin material for a heat exchanger.

[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 coating film is reduced. Conversely, if the polymerization degree is large, 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 coating formed on the aluminum thin plate dissolves. Therefore, the above range is preferable.

The polyvinyl alcohol of the present invention can be produced by a known method. That is, it can be 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.

Polyethylene glycol has a molecular weight of 60
It is preferably in the range of 0 to 20,000, more preferably 40.
00 to 11000. When the molecular weight is large, the dispersibility is reduced, and when the molecular weight is small, the water resistance is reduced. The amount of polyethylene glycol added is 0.05 to 5
It is preferably 0.1 parts by weight, more preferably 0.1 to 3 parts by weight. If the amount of polyethylene glycol is too large, it bleeds on the surface of the coating film to cause poor appearance. If the amount is small, the effect of improving hydrophilicity is not exhibited.

In the surface treating agent of the present invention, 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. Examples of the surface treatment method include a chromate treatment, a titanate treatment, a zirconate treatment, and a boehmite treatment.

The coating of the aluminum sheet with the surface treating agent can be carried out by dipping in an aqueous solution of the surface treating agent, or by applying the aqueous solution by roll coating, spray coating, or the like. The conditions for drying the coating film are not particularly limited, but the drying is generally performed at 90 to 250 ° C. for 15 seconds to 30 minutes.

[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%. 0.2 parts of polyethylene glycol having a molecular weight of 4000 and 0.5 parts of zirconium ammonium carbonate were mixed with the obtained aqueous polyvinyl alcohol solution to obtain an aqueous solution of a surface treating agent.
After a 0.1 mm aluminum thin plate was degreased and subjected to chromate treatment, an aqueous solution of a surface treating agent was applied to the surface thereof to a thickness of about 1 μm. 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 2-5 An aqueous solution of a surface treating agent was prepared in the same manner as in Example 1 using polyvinyl alcohol and polyethylene glycol shown in Tables 1 to 3, and was immersed in running water for 100 hours. And the water resistance of the coating film were measured in the same manner as in Example 1. Table 2 shows the results.

Comparative Examples 1-4 An aqueous solution of a surface treating agent was prepared in the same manner as in Example 1 using polyvinyl alcohol and polyethylene glycol shown in f to i in Table 1, and was initially immersed in running water for 100 hours. And the water resistance of the coating film were 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 μL 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 surface treatment agent comprising a polyvinyl alcohol containing an amide group-containing vinyl monomer and polyethylene glycol is applied to the surface of an aluminum fin material and dried to form a film. In addition to improving the hydrophilicity of polyvinyl alcohol, the water-resistant adhesion to the aluminum thin plate becomes extremely good. 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 coating is soft, the fin material for a heat exchanger is less likely to wear the mold when pressing the aluminum fin material.

Claims (3)

[Claims] 1. A surface treating agent for an aluminum heat exchanger fin material comprising a polyvinyl alcohol and a polyethylene glycol containing a vinyl alcohol unit, an amide group-containing vinyl unit and an aliphatic vinyl ester unit, wherein the polyvinyl alcohol is polymerized. Degree 300-3
300, a saponification degree of 90% or more, an amide group-containing vinyl unit of 2 to 12 mol%, and the polyvinyl alcohol 1
The polyethylene glycol having a molecular weight of 600 to 20,000 is contained in an amount of 0.05 to 5 parts by weight with respect to 00 parts by weight.
Surface treatment agent for fin materials for aluminum heat exchangers. 2. A method for forming a film on the surface of a fin material for an aluminum heat exchanger, which comprises applying the aqueous solution of the surface treating agent according to claim 1 to the surface of a fin material of the aluminum heat exchanger and drying. . 3. A fin material for an aluminum heat exchanger, which has a film of the surface treating agent according to claim 1 on its surface.