JP3274077B2 - Aluminum or aluminum alloy members with excellent water repellency and anti-frost properties - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aluminum or aluminum alloy member having excellent water repellency and anti-frosting property (hereinafter, aluminum and aluminum alloy are collectively referred to as aluminum members), and more particularly to a room air conditioner which is used for both cooling and heating. The present invention relates to an aluminum member having excellent water repellency and excellent anti-frosting properties suitable for use as a heat exchanger fin incorporated in an apparatus or the like.

[0002]

2. Description of the Related Art Conventionally, a fin material for a heat exchanger of a room air conditioner is mainly produced from an aluminum material (including an aluminum alloy material) because of its excellent heat conductivity and formability. Normally, this kind of fin material is subjected to anticorrosion treatment to prevent corrosion, and at the same time, to prevent water condensed during cooling operation from accumulating between the fins and increasing ventilation resistance. The treatment gives hydrophilicity and improves the water wettability of the fin surface.

[0003] In recent years, the number of room air conditioners that can be used for both cooling and heating has increased. However, in the heat pump type heat exchanger used for this type of room air conditioner, in summer, the indoor unit becomes an evaporator and the outdoor unit becomes an evaporator. Becomes a condenser. On the other hand, in winter, the indoor unit becomes a condenser and the outdoor unit becomes an evaporator. In such a room air conditioner that combines air conditioning and heating,
When the outside temperature in winter is low, heating operation indoors,
Water condensed on the fin surface of the heat exchanger provided in the outdoor unit freezes and frost is likely to occur. In particular, when a fin material having hydrophilicity is used, frost is easily generated on the entire fin surface because the fin surface has good water wettability. As described above, when frost is generated on the fin surface of the outdoor unit, the fins are blocked by the frost, so that the ventilation resistance increases and the heating capacity decreases.

[0004] Therefore, in order to prevent the performance degradation due to the frost, by imparting water repellency to the fin surface,
A method is conceivable in which water droplets condensed on the fin surface are dropped before becoming large, thereby obtaining good drainage properties and improving frost formation prevention properties. As described above, when imparting water repellency to an aluminum member, a water repellent paint (a paint having a water contact angle of 90 ° or more when a film is formed on a flat surface) is applied. The current problem is that sufficient water repellency and anti-frosting property cannot be obtained with only the film (1).

On the other hand, a method in which irregularities are directly added to the surface by chemical treatment and used as a base (Japanese Unexamined Patent Application Publication No.
No. 45894), a method of providing a special fluorine-based film on the fin surface (Japanese Patent Application Laid-Open Nos. 3-30939 and 3-44485), and a method of providing a fluorine-based water-repellent film on the surface of the fin. After this, this film surface is roughened,
Method for further improving water repellency (Japanese Patent Laid-Open No. 3-4589)
No. 3) and a method of improving water repellency by blending fine particles in a paint (Japanese Patent Publication No. 3-24468).
Etc. have been proposed.

[0006]

However, these conventional techniques have various problems as described below. That is, in the method of providing a special fluorine-based film, it is necessary to use a method such as plasma polymerization, which requires a large amount of cost for introducing a manufacturing facility, so that the manufacturing cost increases and the product price increases. Further, since batch processing is required, productivity is low, which is not practical.

In the method of providing a fluorine-based water-repellent film on the surface of the fin and then roughening the surface of the film, a phenomenon such as peeling of the film due to strong mechanical processing occurs. Extremely low water repellency. For this reason, it is extremely difficult to obtain a uniform water-repellent coating film.

Further, in the method of improving water repellency by incorporating fine particles into a coating material, it is difficult to uniformly disperse the fine particles, and sometimes fine particles precipitate, so that it is difficult to form a uniform coating film. is there. That is, it is difficult to obtain a surface having uniform water repellency. Further, the fine particles have a weak bonding force in the coating film, and when the amount of the resin binder component is increased in order to hold the fine particles in the coating film, there is a difficult problem that the water repellency decreases.

The present invention has been made in view of the above problems, and has a uniform and highly water-repellent water-repellent coating film.
It is an object of the present invention to provide an aluminum or aluminum alloy member having excellent water repellency and anti-frosting property, excellent in water repellency and anti-frosting property, low in production cost, and excellent in water repellency and anti-frosting property suitable as a material for heat exchanger fins and the like. I do.

[0010]

According to the present invention, there is provided an aluminum or aluminum alloy member having excellent water repellency and anti-frosting property, comprising a crystal in a film formed as a base treatment film on the surface of an aluminum or aluminum alloy substrate. 10 water
It is characterized by having a chemical conversion treatment film of not less than μg / cm ² , and a water-repellent film of a paint formed on the chemical conversion treatment film at a film amount of 0.1 to 20 mg / dm ² .

In the aluminum or aluminum alloy member having excellent water repellency and anti-frosting property, the surface of the substrate is preferably roughened. Furthermore,
This aluminum or aluminum alloy member having excellent water repellency and anti-frosting property is suitable as a fin material for a heat exchanger.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The present inventor has conducted various studies to improve the water repellency and anti-frosting property of an aluminum member. As a result, a chemical conversion treatment film was formed as a base treatment for the water repellent film. It has been found that the object of the present invention can be achieved by controlling the amount of water of crystallization in the chemical conversion coating. That is, as the amount of water of crystallization in the chemical conversion treatment film increases, the number of bonds between the non-water-repellent groups present at the ends of the linear chains having the water-repellent structure in the water-repellent film and the water of crystallization in the chemical conversion treatment film occur, As a result, the water repellency can be improved by increasing the number of water repellent groups on the surface. The present invention has been completed based on such new findings.

The chemical conversion coating film used as a base is easily formed by a treatment such as immersion using a treatment aqueous solution, so that a complicated and difficult surface roughening method such as machining which was conventionally required is not required, and the manufacturing process is not required. The process can be simplified. In addition, since the chemical conversion coating has a chemical bond with the substrate surface, there is no shortage of adhesion which is a problem in the fine particle dispersion method. Further, since the chemical conversion coating usually has an effect of improving corrosion resistance, the corrosion resistance of the chemical conversion coating is imparted to the aluminum member. Therefore, as compared with the conventional method of directly providing irregularities on the surface by chemical treatment, the present invention provides a material having remarkable corrosion resistance.

The method of preparing the chemical conversion coating is not particularly limited, and various methods such as a method of dipping in a processing solution and a method of spraying the processing solution by spraying can be used.

Therefore, it is necessary that the underlayer chemical conversion coating applied to the surface of the aluminum member contains crystal water of 10 μg / cm ² or more. Crystal water in the film is 10
When the amount is less than μg / cm ² , the water-repellent film formed on the surface has a water-repellent structure and a non-water-repellent group (portion involved in bonding) present at the end of the linear chain and the water of crystallization in the base film. This is because the number of unbonded non-water-repellent groups is increased in the water-repellent film because the number of bonds is reduced, and as a result, the water-repellent film cannot exhibit sufficient water repellency.

When the chemical conversion coating is used as a base, the thickness of the water-repellent coating to be formed is 0.1 to 20 mg / mg.
It needs to be in the range of dm ² . If the thickness of the water-repellent film is too thin, sufficient coating is not performed, and a portion of poor water-repellency is generated, so that the uniformity of water-repellency on the surface of the aluminum member is lost. On the other hand, if the water-repellent film is too thick, non-water-repellent groups present in the straight line having a water-repellent structure in the water-repellent film do not have a bond with the crystallization water in the chemical conversion treatment film. This is because they are present, and as a result, sufficient water repellency and anti-frosting property cannot be obtained.

As the water-repellent paint used for film formation, various materials can be used as long as they are water-repellent paints having a contact angle of 90 ° or more when formed as a single film. For example, a fluorine-based coating containing ethylene tetrafluoride or a copolymer of ethylene tetrafluoride and ethylene, an Si-based water-repellent coating, a coating containing a compound having a hydrophobic methyl group (—CH ₃ ), and perfluoroalkyl group _{{(-CF 2) n -CF 3} }
A water-repellent paint having the following can also be used. Among them, a tetrafluoroethylene-based paint and a perfluoroalkylsilane-based paint are desirable, and the coating method is any method such as spray coating, dip coating, roll coating, bar coating, brush coating, and the like.
Any material that can form a film having water repellency can be used.

In the present invention, the aluminum member includes, in addition to pure aluminum, an alloy containing 90% by weight or more of aluminum, and its surface is subjected to a method such as degreasing, shot blasting, sputter etching, wire brushing, electrolytic or immersion etching. Therefore, it is desirable to provide the substrate with a base chemical conversion treatment after cleaning the surface. In addition, when the surface of the aluminum member is roughened at the same time by these cleaning methods, the water repellency is further improved, so that there is an advantage that the anti-frosting property can be further improved.

The object of the present invention is mainly to improve the water repellency of a coating in a fin material for a heat exchanger so as to improve the water repellency and, at the same time, to improve the anti-frosting property. It is also applicable to applications other than heat exchangers that require resilience.

The evaluation of the water repellency was performed based on the contact angle. The contact angle is a contact angle of the surface of the member with respect to the water droplet, and as shown in FIG. 1, the contact surface between the surface of the member 2 and the water droplet 1 and the contact surface between the water droplet 1 and the gas are formed on both contact surfaces. The angle θ1 formed at the intersection position means that the larger the value of θ1, the higher the water repellency. Further, in order to have sufficient frost prevention performance, 15
A contact angle of 5 ° or more is required.

The thickness of the underlayer chemical conversion coating according to the present invention is not particularly limited, but if the thickness exceeds 3 μm, the processing time for preparing the chemical conversion coating increases. For this reason, the thickness of the underlayer chemical conversion treatment film is desirably about 3 μm or less. If more corrosion resistance is required, the treatment time may be increased to increase the film thickness.

The amount of water of crystallization was measured using a coulometric titration moisture analyzer (Model CA-06) and a moisture vaporizer (VA-22) manufactured by Mitsubishi Chemical Corporation at a temperature of 105 ° C. with a 20 cm ² sample as a pretreatment. After removing the adhering water by heating at 600 ° C., the water of crystallization was measured at 600 ° C. in nitrogen gas.

The bond between the non-water-repellent group present at the terminal of the linear chain having the water-repellent structure in the film and the water of crystallization actually depends on the paint, and is caused by reactions such as dehydration, dehydrochlorination and dealcoholation. Although it occurs, in the above description, it has been described that, for simplicity, it combines with water of crystallization in the film.

[0024]

EXAMPLES Examples of the present invention will be described below in comparison with comparative examples. Example 1 Aluminum plate material subjected to degreasing treatment (JIS 1100
H26, plate thickness 0.12 mm, 10 cm × 20 cm), a chemical conversion coating containing crystal water was grown in the coating, and a perfluoroalkylsilane-based coating was applied with a bar coater # 4. The film was formed by baking at a temperature of 10 ° C. for 10 minutes. Here, the contact angle was measured using a contact angle meter (CA-A type) manufactured by Kyowa Interface Science Co., Ltd. using a 1.8 μL water droplet. The results are shown in Table 1 below.

[0025]

[Table 1]

In the evaluation column of Table 1, those having a contact angle of 155 ° or more were indicated by “O”, and those having a contact angle of less than 155 ° were indicated by “X”.

Example No. Examples 1 to 8 satisfy the first aspect of the present invention, in which a contact angle of 155 ° or more was obtained and a coating film of a conventional water-repellent paint was formed (about 100 to 120 °). Is better than. Also,
Example No. As compared with Example Nos. 5 to 8, The reason why the contact angles of Nos. 1 to 4 are high is that fine irregularities are formed on the surface of the chemical conversion coating, which is the base of the water-repellent coating.

On the other hand, in Comparative Example No. In Nos. 9 to 11, since the amount of water of crystallization in the underlayer chemical conversion treatment film was less than 10 μg / cm ² , the contact angle was insufficient at less than 155 °. Thereby, the amount of water of crystallization in the underlayer chemical conversion treatment film was 10 μg /
It is understood that it is necessary to be not less than cm ² .

Example 2 A degreasing treated aluminum plate (JIS 1100)
H26, plate thickness 0.12 mm, 10 cm × 20 cm) was immersed in an aqueous solution containing each salt for 20 minutes to grow a chemical conversion coating, and then applied with a perfluoroalkylsilane-based paint with various thickness changes Then, baking was performed at 100 ° C. for 10 minutes to form a film. Then, the frosting time was measured in order to examine the anti-frosting property. The test apparatus shown in FIG. 2 was used for measuring the frosting time. The test apparatus includes a cold water tank 11, a circulation pump 12, an aluminum container 1
3 and pipes 14a and 14b connecting these members to circulate cold water. During the test, the temperature of the refrigerant stored in the cold water tank 11 was set to -1.
The temperature was maintained at 0 ° C., and the refrigerant was circulated between the aluminum container 13 and the cold water tank 11 by the circulation pump 12.
Then, the specimen 10 was attached to the aluminum container 13 such that the treated surface was on the outside, and the occurrence of frost was investigated in an atmosphere where the dry bulb temperature was 2 ° C and the wet bulb temperature was 1 ° C. That is, the frosting prevention property was evaluated by measuring the time until the entire surface of the specimen was covered with frost. The results are shown in Table 2 below.

[0030]

[Table 2]

In the evaluation column of Table 2, the total frosting time was 1
A sample of 20 minutes or more was indicated by ○, a sample of 60 minutes or more and less than 120 minutes was indicated by Δ, and a sample of less than 60 minutes was indicated by ×.

Example No. Examples 12 to 15 satisfy the requirements of the first aspect, and all of them have a total frosting time of 120 minutes or more, and show good anti-frosting properties.

On the other hand, in Comparative Example No. 16-19 are
The thickness of the film made of the water-repellent paint is as thin as less than 0.1 mg / dm ² and a uniform film is not formed, so that the frosting time is long. Also, in Comparative Example No. 20-23, the thickness of the coating by repelling the aqueous coating is above the 20 mg / dm ^2, those unbound among the non-water repellent groups present at the end of a straight with a water repellent structure of the water repellent film in Many chromium are present in the film, resulting in a long frosting time.

From the above points, the thickness of the water-repellent film is 0.1
mg / dm ² ~20mg / dm it can be seen that it is necessary to ² range.

Example 3 A surface-treated or surface-processed material was used as a degreased 1100H26 material, A5083 rolled material, and A6N01 extruded material, and this material was immersed in an aqueous solution containing lithium salts for 20 minutes. A chemical conversion coating was grown. The thickness of the chemical conversion coating was 3 μm, and the amount of water of crystallization in the coating was 7 μm.
3 μg / cm ² . Thereafter, various coatings were formed into a film having a thickness of 2 μm using a bar coater. The measurement of the contact angle and the frosting time was performed in the same manner as in Example 1 and Example 2.

The results are shown in Table 3 below. Table 3
Are as shown below, and all of them are commercially available. Paint A: tetrafluoroethylene-based water-repellent paint Paint B: fluorine-based water-repellent paint containing a copolymer of ethylene tetrafluoride and ethylene Paint C: silicon-based water-repellent paint Paint D: containing a compound having a methyl group Paint E: Perfluoroalkyl-based water-repellent paint Paint F: Acrylic non-water-repellent paint Paint G: Fluorine-based water-repellent paint with hydrophobic silica added

[0037]

[Table 3]

Example No. 24 to 28 and 30 to 36 are all examples of the present invention and satisfy claim 1. On the other hand, in Comparative Example No. Reference numeral 29 denotes a film formed by a non-water-repellent paint, which is outside the scope of the present invention.
In each of Examples 24 to 28 and 30 to 36, a contact angle of 160 ° or more was obtained and the frosting time on the entire surface was as good as 120 minutes or more even when any of the water-repellent paints was used. On the other hand, in the case of Comparative Example 29 in which a coating film of a non-water-repellent paint was formed, the contact angle was 60 °, the falling angle was 90 ° or more, and the entire frosting time was 1 hour.
It was bad for 5 minutes.

[0039]

As described above, according to the present invention,
The troublesome surface roughening process conventionally performed to obtain good water repellency and frost prevention properties is not required, and members having excellent corrosion resistance and adhesion, and excellent water repellency and frost prevention properties can be easily manufactured. Can be manufactured at low cost.

[Brief description of the drawings]

FIG. 1 is a schematic diagram illustrating a contact angle.

FIG. 2 is a schematic view showing a test device used for investigating the anti-frosting property.

[Explanation of symbols]

 1: Water droplet 2: Member θ1: Contact angle 10: Specimen 11: Cold water tank 12: Pump 13: Aluminum container 14a, 14b: Piping

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) F28F 13/18 B05D 7/14 B32B 1/00-35/00

Claims (3)

(57) [Claims] 1. A chemical conversion coating having an amount of water of crystallization of 10 μg / cm ² or more in a coating formed as a base coating on the surface of an aluminum or aluminum alloy substrate, and 0.1 to 20 mg on the chemical conversion coating. An aluminum or aluminum alloy member having excellent water repellency and anti-frosting properties, characterized by having a water-repellent film of a paint formed at a film amount of / dm ² . 2. The aluminum or aluminum alloy member according to claim 1, wherein the surface of the base material is roughened. 3. The aluminum or aluminum alloy member according to claim 1, wherein the aluminum or aluminum alloy member is used as a fin material for a heat exchanger.