JPH0926287A - Metal member excellent in water repellency and frosting prevention and manufacturing method of it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily ensure with inexpensive mean a metal member having a uniform water repelling coating film and being excellent in water repellency and frosting prevention property. SOLUTION: A material having adhesive force of 5 to 500gf/cm is brought into contact with a water repelling coating film composed of a coating formed on the surface of the metal member in the amount of coating of 1 to 100mg/dm<2> , and is released. A contact angle of the coating film to water droplets is increased to improve water repellency and frosting prevention property. It is preferably applied to a fin material for an aluminum heat exchanger.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a metal member having excellent water repellency and frost-prevention property, particularly water repellency and adhesion suitable for use as a fin for a heat exchanger incorporated in a room air conditioner for both heating and cooling. The present invention relates to an aluminum member having excellent frost prevention properties and a method for manufacturing the same.

[0002]

2. Description of the Related Art Conventionally, a fin material for a heat exchanger of a room air conditioner has excellent thermal conductivity and moldability,
Mainly aluminum materials (including aluminum alloy materials)
It is manufactured by. Normally, this type of fin material is subjected to anticorrosion treatment to prevent corrosion, and at the same time, in order to prevent water that has condensed during cooling operation from accumulating between the fins and increasing ventilation resistance, a surface treatment is performed. To impart hydrophilicity to improve the water wettability of the fin surface.

In recent years, the number of room air conditioners for both air conditioning and heating has increased, but in the heat pump type heat exchanger used in this type of room air conditioner, the indoor unit becomes the evaporator and the outdoor unit becomes the condenser in the summer. Becomes On the other hand, in winter, the indoor unit becomes the condenser and the outdoor unit becomes the evaporator. In such a room air conditioner for both air conditioning and heating, when heating operation is performed indoors in the winter when the outdoor temperature is low, the water condensed on the fin surface of the heat exchanger provided in the outdoor unit freezes to generate frost. Cheap. In particular, when a fin material having hydrophilicity is used, the fin surface has good wettability with water, so that frost is likely to occur on the entire fin surface. When frost is generated on the fin surface of the outdoor unit, the frost blocks the spaces between the fins, which increases ventilation resistance and reduces heating capacity.

Therefore, a method of imparting water repellency to the fin surface so that the condensed water droplets fall on the fin surface before it grows large to obtain good water drainage property and to improve the anti-frosting property can be considered. When imparting water repellency to a member in this way, a water repellent coating (a coating having a contact angle of 90 ° or more when formed as a single film) is applied, but generally only a coating of the water repellent coating is used. The current problem is that sufficient water repellency and frost prevention cannot be obtained.

On the other hand, a method of forming a special fluorine-based film on the fin surface (Japanese Patent Laid-Open No. 30939/1993, 44485/1993) or a fluorine-based water-repellent film on the surface of the fin. After this, the surface of this film is mechanically polished,
A method for further improving water repellency by roughening the surface by sputter etching, shot blasting, etc. (JP-A-3-45)
No. 893), a method of improving water repellency by incorporating fine particles into a coating material (Japanese Patent Publication No. 3-244680).

[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, and a huge cost is required to introduce manufacturing equipment, resulting in an increase in manufacturing cost and an increase in product price. Further, since batch processing is required, productivity is low, which is not practical. After providing a fluorine-based water-repellent film on the surface of the fin, the method of roughening the film surface is
Phenomena such as peeling of the film due to strong mechanical processing occur, and the water repellency is extremely reduced in the peeled part of the film. Therefore, it is extremely difficult to obtain a water-repellent coating film having uniform water repellency. Further, in the method of improving water repellency by adding fine particles to a coating material, it is difficult to uniformly disperse the fine particles, and sometimes precipitation of the fine particles occurs, so that it is difficult to form a uniform coating film. That is, it is difficult to obtain a uniform water-repellent surface. Further, the fine particles have a weak binding force in the coating film, and if the resin binder component is increased in order to hold the fine particles in the coating film, the water repellency deteriorates, which is a difficult problem.

The present invention has been made in view of the above-mentioned problems of the prior art, and has a uniform water-repellent polymer coating film and is excellent in water repellency and frost-prevention property, especially heat resistance. It is an object of the present invention to obtain an aluminum member such as a fin material for an exchanger easily and at low cost.

[0008]

MEANS FOR SOLVING THE PROBLEMS A metal member excellent in water repellency and frost prevention related to the present invention is 1 to 100 on the surface.
A metal member having a water-repellent coating formed by a coating film formed with a coating amount of mg / dm ² is characterized in that a part or all of the non-polymeric polymer present on the surface of the water-repellent coating is removed. . Further, the method for producing a metal member having excellent water repellency and anti-frost property according to the present invention is applied to a water repellent film formed by a coating film formed on the surface of the metal member at a film amount of 1 to 100 mg / dm ^2. , An object having an adhesive force of 5 to 500 gf / cm is temporarily brought into contact with or separated from the object.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The inventors of the present invention investigated the cause of insufficient water repellency and frost prevention in a polymer polymer film of a water-repellent coating alone. It was found that the body or the low molecular weight polymer remained, which hindered the water repellency and the anti-frost property. Then, these non-high molecular weight polymers are concentrated on the film surface portion, and the non-high molecular weight polymer is removed by some means, and the water-repellent group of the high molecular weight polymer is made to appear on the surface. It has been found that water repellency and anti-frost property can be obtained.

Here, the non-polymeric polymer means a non-polymer (monomer) and a low-molecular polymer (dimer (dimer), trimer (trimer), ...). The molecular weight is considerably smaller than that of a high molecular weight polymer having a molecular weight of about 10,000 to several million, and they are present on the surface of the high molecular weight polymer film without directly binding to the base material. Also, it is eluted from the surface of the film by a polar solvent such as methanol or acetone.

The non-polymeric polymer on the surface of the film can be removed by temporarily contacting or leaving an object having an adhesive force on the surface of the film. The object having an adhesive force is not particularly limited, and examples thereof include adhesive films, adhesive sheets, cellophane tape, vinyl tape, gum tape, and other films, sheets, tapes, and rubber products and plastics with an adhesive substance. , Metal, ceramics, etc. can be used as long as they have adhesiveness, and the form can be any form such as film, sheet, tape, roll, spherical, square,
The width, length, and thickness can be arbitrarily determined. To temporarily make these objects come into contact with or separate from each other means, for example, to press or stick these objects to the surface of the film and then to separate them.

However, the adhesive strength is preferably 5 to 500 gf / cm, and particularly preferably 25 to 500 gf / cm. The reason is that if it is 5 gf / cm or less, the non-high molecular weight polymer is not sufficiently removed, so that the contact angle is not improved, and if it is 500 gf / cm or more, when the film is strong, This is because peeling of the film itself from the base material occurs. Incidentally, the adhesive strength in the present invention means that the adhesive substance is adhered to a tape or a sheet in accordance with JIS-Z023.
7. Adhesive tape / adhesive sheet
It is a value measured in accordance with "Testing method of 80-degree peeling adhesive strength". Further, the contact angle is a contact angle of the surface of the member with respect to the water droplet, and in FIG. 1, the angle θ from the contact surface between the surface of the member 2 and the water droplet 1 to the contact surface between the water droplet 1 and the gas.
Means The contact angle θ is an index of water repellency, and the larger the contact angle θ, the higher the water repellency.

The means for removing the non-high molecular weight polymer existing on the surface of the coating is not limited to the above-mentioned means for contacting / releasing an object having an adhesive force. It is also possible to remove with a polar solvent such as, and even in that case, the same effect can be obtained.

In the present invention, the amount of the water repellent film is 1
˜100 mg / dm ² is desirable. The reason is 1m
If it is less than g / dm ² , the film thickness is too thin and the surface coating is insufficient, resulting in insufficient water repellency and 100 mg.
This is because if it exceeds / dm ² , coating unevenness occurs or film formation becomes difficult. Among them, especially 5 to 50 mg /
When it is between dm ² , it is desirable because the frost formation time becomes long.

The water-repellent coating used in the present invention may be any coating having a water-repellent coating having a contact angle of 90 ° or more when formed as a single film. For example, fluorine-based paint containing ethylene tetrafluoride or a copolymer of ethylene tetrafluoride and ethylene, Si-based water repellent paint, paint containing a compound having a methyl group (—CH ₃ ) which is a hydrophobic group, and perfluoroalkyl group repellent coatings with _{{(-CF 2) n -CF 3} } can be used. Of these, tetrafluoroethylene-based paint and perfluoroalkylsilane-based paint are preferable. Any coating method such as spray coating, dip coating, roll coating, bar coating, brush coating, etc. may be used as long as a film having water repellency can be formed.

In the above water-repellent coating, if the non-polymeric polymer is present on the surface, the water-repellent groups are not aligned on the surface at that portion, so that the water repellency of the film is locally deteriorated. Then, the water repellency of the film decreases and the contact angle decreases. The reason why the contact angle is improved after treatment with an object having an adhesive force is that a part or all of the non-high molecular weight polymer is removed and the water-repellent group of the high molecular weight polymer appears on the surface. It should be noted that it is difficult to confirm the presence of the non-high molecular weight polymer by a usual analysis method in the material having a contact angle of more than 145 °, but the contact angle is improved after the treatment with an object having an adhesive force. The removal of non-high molecular weight polymer can be confirmed.

Aluminum or aluminum alloy is preferably used as the metal material as the base material in the present invention, but similar effects can be obtained with other metals or alloys. The surface is not treated, after degreasing, after forming aluminum oxide film (hydroxide film), after chromate treatment, after shot blasting, after electrolytic or immersion etching, any surface can be obtained by using the means according to the present invention. A member excellent in water repellency and frost prevention can be produced. However, when any one of the above or other roughening treatments is performed on the surface of the metal substrate, there is an advantage that the contact angle of the water repellent film can be increased, the water repellency can be further improved, and the frost formation time can be longer. .

The purpose of the present invention is mainly to improve the water repellency of a coating film in a fin material for a heat exchanger to improve the water drainage property, and also to improve the frost prevention property. It can also be applied to applications other than heat exchangers that require flippability and the like.

[0019]

【Example】

(Example 1) A pure aluminum-based material (A1330) that has been degreased is roughened by wire brush polishing, and a perfluoroalkylsilane-based coating material is applied to the material with a bar coater # 4 at 100 ° C for 10 minutes. A film was formed by baking. Here, contact angle meter (C
A-A type) was used to measure the contact angle θ using 1.8 μl of water droplets, and then a tape having an adhesive force was attached to the surface of the film, followed by peeling, and the contact angle θ was measured again. Nine kinds of tapes having different adhesive strengths were prepared, and the adhesive strength was measured by using a digital force gauge with output DPRS-2T type manufactured by Imada Co., Ltd. and performing a 180 degree peeling test.

The results are shown in Table 1. In Table 1, those having a remarkable effect in improving the contact angle θ were evaluated as ⊚, those having an effect were evaluated as ◯, and those having no effect were evaluated as ×.

[0021]

[Table 1]

As shown in Table 1, the effect of improving the contact angle θ of the film is seen at an adhesive force of 5 to 500 gf / cm, and particularly remarkable at an adhesive force of 25 to 500 gf / cm, When the adhesive force is 1 gf / cm, the contact angle θ is not improved. Further, when the adhesive strength was 750 gf / cm, peeling of the film occurred. In Table 1, test numbers 2 to 8
Is an example of the present invention, and test numbers 1 and 9 are comparative examples.

(Example 2) The degreased pure aluminum material (A1330) was subjected to electrolytic etching for 1 minute using a hydrochloric acid-oxalic acid electrolytic solution to roughen the surface,
Apply tetrafluoroethylene-based paint by changing the coating amount, and
A film was formed by baking at 0 ° C. for 5 minutes. After checking the film forming property, the contact angle θ was measured by the same method as in Example 1,
Stick cellophane tape with adhesive strength of 245 gf / cm,
After peeling, the contact angle θ was measured again. Furthermore, the frosting time was measured with this aluminum member.

The frost formation time was measured using the test apparatus shown in FIG. This test apparatus is composed of a cold water tank 11, a circulation pump 12, an aluminum container 13, and a pipe 14 connecting these components. The exam is
The temperature of the refrigerant stored in the cold water tank 11 is maintained at −10 ° C., and the refrigerant is circulated between the aluminum container 13 and the cold water tank 11 by the circulation pump 12, and the sample 10 is placed in the aluminum container 13 for its treatment surface. The outer surface of the sample 10 is covered with frost by investigating the occurrence of frost on the surface of the sample 10 in an atmosphere having a dry-bulb temperature of 2 ° C and a wet-bulb temperature of 1 ° C. The time until the frost formation was performed.

The above results are shown in Table 2. In Table 2,
The film forming property was judged by visual observation of the appearance, and when the film was formed uniformly, it was evaluated as ◯, when uneven coating was caused or when film formation was difficult, was evaluated as ×, and the middle thereof was evaluated as Δ. Regarding the anti-frosting property, ⊚ indicates that the frosting time exceeds 120 minutes and is remarkably excellent in frosting preventive property, and ○ if it is less than that but excellent in frosting preventive property. Those having poor anti-frost properties were evaluated as x.

[0026]

[Table 2]

As shown in Table 2, the coating amount is 1 to 100.
The contact angle θ is improved between mg / dm ² and the frost formation time is prolonged, and the frost formation prevention property is improved. In particular, when the coating amount is 5 to 50 mg / dm ² , excellent contact angle improvement and frost prevention are exhibited. Also, the film-forming property is 1
200 mg / dm ² or less in the range, in particular a uniform film free from coating unevenness by 50 mg / dm ² or less in the range obtained. In Table 2, test numbers 11 to 16 are examples of the present invention, and test numbers 10 and 17 are comparative examples.

(Example 3) Degreased A1330 rolled material, A5083 rolled material, and A6N01 extruded material were subjected to various surface treatments (surface treatment or surface treatment), and various coating materials were applied with a bar coater # 4 and baked. Then, the film was formed. Subsequently, the contact angle θ was measured by the same method as in Example 1, a cellophane tape having an adhesive force of 245 gf / cm was attached, peeled off, and then the contact angle θ was measured again. Further, the frosting time of this aluminum member was measured in the same manner as in Example 2.

The above results are shown in Table 3. In Table 3, the evaluation criteria for the frost prevention property are the same as in Example 2.
The coating materials A to G used in 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

[0030]

[Table 3]

As shown in Table 3, in Test No. 23, the non-water-repellent coating F was used, so that the contact angle θ after treatment with cellophane tape was reduced. Regardless of the above, good water repellency and frost prevention can be obtained. In particular, when the aluminum member is subjected to surface roughening treatment such as electrolytic etching, sputter etching, shot blasting, and wire brushing, excellent water repellency and frost prevention can be obtained. In Table 3, 18 to 22 and 24
˜33 are examples of the present invention, and test No. 23 is a comparative example.

[0032]

According to the present invention, it is possible to easily improve the contact angle of a metal member having a water-repellent coating using a water-repellent coating, which has been generally used in the past, and to provide uniform and sufficient water repellency and frost prevention. It is possible to inexpensively manufacture a metal member having properties.

[Brief description of drawings]

FIG. 1 is a schematic diagram for explaining a contact angle.

FIG. 2 is a schematic diagram of a test apparatus used for measuring a frost formation time.

[Explanation of symbols]

 1 Water Drop 2 Member 10 Specimen 11 Cold Water Tank 12 Pump 13 Aluminum Container 14 Piping

Claims (8)

[Claims] 1. A metal member having a water-repellent coating film formed by coating at a coating amount of 1 to 100 mg / dm ² on a surface thereof, wherein a part of the non-polymeric polymer present on the surface of the water-repellent coating film. Alternatively, a metal member excellent in water repellency and frost prevention, which is characterized by being removed entirely. 2. A metal excellent in water repellency and frost prevention as set forth in claim 1, wherein the water repellent film is formed on the surface of a metal base material having a roughened surface. Element. 3. The metal member excellent in water repellency and frost prevention as set forth in claim 1 or 2, wherein the metal member is made of aluminum or an aluminum alloy. 4. The metal member excellent in water repellency and frost prevention as set forth in claim 3, wherein the metal member is a fin material for a heat exchanger. 5. 1 to 100 mg / d on the surface of the metal member
Excellent in water repellency and anti-frost property, characterized by temporarily contacting and releasing an object having an adhesive force of 5 to 500 gf / cm with respect to a water repellent film formed by a coating film formed with a coating amount of m ² . Manufacturing method of metal member. 6. The aluminum member excellent in water repellency and frost prevention as set forth in claim 5, wherein a water repellent film is formed on the surface of a metal base material having a roughened surface. Production method. 7. The method for producing a metal member having excellent water repellency and frost prevention as set forth in claim 5 or 6, wherein the metal member is made of aluminum or an aluminum alloy. 8. The method for producing a metal member excellent in water repellency and frost prevention as set forth in claim 7, wherein the metal member is a fin material for a heat exchanger.