JP3274044B2 - Surface treated fin material for heat exchanger and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fin material for a heat exchanger made of aluminum or an aluminum alloy material having a film formed on the surface thereof, and more particularly to a fin material for a heat exchanger suitable as a fin for a home air conditioner. About. Hereinafter, in this specification, the term “aluminum” includes an aluminum alloy.

[0002]

2. Description of the Related Art Conventionally, aluminum has been used as a heat exchanger fin because of its excellent thermal conductivity and formability. In such a fin material, anticorrosion treatment is performed on the surface of the fin material for the purpose of preventing corrosion. Also, to prevent condensed water from remaining between the fins during the cooling operation, a surface treatment for improving the water droplet falling property, or conversely, a surface treatment for improving the hydrophilicity for the water droplet to be formed into a water film and falling. It is applied to the fin material.

There are the following methods for surface treatment for improving the hydrophilicity of the fin material. That is, a treatment method using a silicate (Japanese Patent No. 1769978), a treatment method of applying a film in which silica fine particles are dispersed in a thermosetting resin (JP-A-3-26972), a cellulose resin and an acrylic resin A method for forming a corrosion-resistant film (Japanese Patent Publication No. Hei 4-23632), a method for forming a hydrophilic film containing a hydrophilic organic compound and an organic curing agent such as a melamine resin, a urea resin or a benzoquanamine resin (Japanese Patent Publication No. Hei 5-236).
-15176).

[0004] When the hydrophilicity is good, the contact angle of water droplets attached to the fin material becomes small. The contact angle θ is
As shown in FIG. 1, the angle formed by the tangent line 22 and the plane 1 at a point rising from the plane 1 on the surface of the water droplet 2 means that the lower the contact angle θ, the thinner the water film and the better the hydrophilicity. When the hydrophilicity is good, the dropping property of water droplets becomes good, so that in the heat exchange part of the heat exchanger as shown in FIG. 2, the resistance at the time of blowing due to water droplets or water films attached to the fins is reduced. And excellent heat exchanger characteristics.

FIG. 3 is a schematic diagram showing the state of water droplets adhering to the fin surface. As shown in FIG. 3A, when the fin 5 has good hydrophilicity, the contact angle of the water droplet 6 is low, so that the water droplet 6 easily falls along the fin 5. For this reason, since the water drops do not block the airflow, the airflow resistance is reduced. On the other hand, in a heat exchanger composed of fins with poor hydrophilicity,
As shown in FIG. 3B, since the contact angle of the water droplet 8 is high, the water droplet 8 stays on the fin 7 or FIG.
As shown in (1), since the water droplet 11 contacts and stays in both the fin 9 and the fin 10 adjacent to the fin, the water droplet blocks the air flow, and the air flow resistance is significantly increased.

[0006]

The above-mentioned surface treatment method for improving the hydrophilicity of the fin material has the following problems. That is, although the treatment using silicate has good hydrophilicity, it contains hard silica, so the tool wear in forming the fins increases, and at the start of the cooling operation, the faint odor peculiar to water glass is generated. Will occur. Further, although the resin treatment containing silica fine particles generates little odor, tool wear is large, the contact angle of water droplets adhering to the surface increases, and the hydrophilicity decreases.

On the other hand, the processing method of forming a resin film disclosed in Japanese Patent Publication Nos. Hei 4-23632 and Hei 5-15176 has characteristics that tool wear is small and odor is hardly generated, but cooling is performed. If the operation and the blowing operation are repeated alternately, the contact angle of water droplets attached to the fin surface increases, and the hydrophilicity decreases. In addition, even if surface treatment is performed using polyacrylic acid as a polyvinyl-based resin, it is not possible to obtain persistent hydrophilicity.

[0008] The present invention has been made in view of the above problems, and by controlling the surface morphology of the fin material with a specific resin, tool wear and odor characteristics can be improved, and contact of water droplets can be improved. An object of the present invention is to provide a surface-treated fin material for a heat exchanger that can significantly improve hydrophilicity by reducing an angle.

[0009]

According to the present invention, there is provided a surface-treated fin material for a heat exchanger, comprising an aluminum or aluminum alloy plate having an epoxy crosslinking agent having a molecular weight of 500 or more and a polyvinyl resin having a polymerization degree of 50 or more. Is formed, and the epoxy-based crosslinking agent contains (—CH ₂ —CH ₂ —O— or —CH (CH ₃ ) —CH _{2 in} one molecule.
-O-) as a constitutional unit and two epoxy groups, and the coating is 0.2 to 4.0 parts by weight of the polyvinyl resin with respect to 1 part by weight of the epoxy crosslinking agent. , And one side of the surface has an average diameter of 0.1 in a 10 μm square measurement field of view.
The number of holes having a diameter of 5 to 5 μm is 5 or more as an average value of one or a plurality of measurement visual fields.

[0010] manufacturing process of the heat exchanger surface treatment fin material according to the present invention, in one molecule (-CH ₂ -CH ₂ -O- or _{-CH (CH 3) -CH 2 -O-} ) a structural unit Having a polymer to be used and two epoxy groups, the molecular weight of which is 1 part by weight of an epoxy crosslinking agent having a molecular weight of 500 or more, and the polymerization degree is from 0.2 to 4.0 parts by weight of a polyvinyl resin having a polymerization degree of 50 or more Is applied to an aluminum or aluminum alloy plate,
Then, the aluminum or aluminum alloy plate is
The baking is performed at a temperature of 0 to 250 ° C. for 5 to 60 seconds.

[0011]

The inventors of the present invention have found that a fin material treated with the above-mentioned water glass system suppresses tool wear and odor generation, and a fin material treated with a resin system has a hydrophilic sustainability (low contact angle). persistence) results of extensive research to achieve, in the molecule (-CH ₂ -CH ₂ -O- or -CH (C
By mixing a polyvinyl-based resin with an epoxy-based cross-linking agent having a polymer having H ₃ ) -CH ₂ -O-) and two epoxy groups, and applying the resulting mixture to an aluminum plate, the anti-durability is improved. It has been found that a fin material having good tool wear, odor characteristics and hydrophilicity can be obtained.

The polyvinyl resin having a molecular structure according to the present invention is a water-soluble resin itself and has good hydrophilicity. Inability to maintain the hydrophilicity of the material. Also, because this resin is highly hygroscopic, if you apply coil coating to an aluminum plate using this resin,
So-called blocking, in which the plates are stuck together after winding in a coil shape, occurs, and processing defects tend to occur during processing.

Therefore, by mixing the epoxy-based crosslinking agent having the molecular structure defined in the present invention with the polyvinyl-based resin to form a film, these blocking and processing defects do not occur and the hydrophilicity is excellent. Fin material can be obtained.

Hereinafter, the configuration of the surface-treated fin material according to the present invention and the method of manufacturing the same will be described in detail. First, the number, constituent units and molecular weight of the epoxy group of the epoxy-based crosslinking agent will be described. Number of epoxy groups in the epoxy-based cross-linking agent: 2 groups The epoxy-based cross-linking agent added to the treatment bath has two epoxy groups represented by the following chemical formula 1.

[0015]

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Further, in addition to these two epoxy groups, the epoxy crosslinking agent of the present invention contains (-CH ₂
It has a polymerized part having —CH ₂ —O— or —CH (CH ₃ ) —CH ₂ —O—) as a structural unit.

When the epoxy-based crosslinking agent has three or more epoxy groups or does not have the above-mentioned structural unit, the contact angle of water droplets is increased, and the hydrophilicity of the fin material is reduced. This decrease in hydrophilicity is presumed to be caused by an increase in crosslink density. On the other hand, when there is only one epoxy group, the polyvinyl resins are not crosslinked with each other, so that the polyvinyl resins easily flow away and the hydrophilicity is not maintained.

When the molecular weight of the epoxy-based cross-linking agent is 500 or more and the molecular weight of the epoxy-based cross-linking agent is small, similar to the above-mentioned epoxy-based cross-linking agent having three or more epoxy groups,
A decrease in hydrophilicity, which is thought to be caused by an increase in crosslink density, occurs. Therefore, the molecular weight of the epoxy crosslinking agent is set to 500 or more.

The upper limit of the molecular weight of the epoxy cross-linking agent is not particularly limited. The higher the molecular weight, the better the hydrophilicity of the fin material. However, the epoxy cross-linking agent having a molecular weight of 1500 or more has a high melting point and a room temperature (about 20 ° C.). ℃), it becomes solid and it is difficult to prepare a treatment bath. Therefore, the molecular weight of the epoxy-based crosslinking agent is preferably 1500 or less.

Incidentally, examples of such an epoxy-based crosslinking agent include ethylene polyethylene glycol diglycidyl ether and propylene polypropylene glycol diglycidyl ether. However, even in these epoxy cross-linking agents, the structural unit (—CH ₂ —CH ₂ —O— or —CH (CH ₃ )) has a molecular weight of 500 or more.
It is necessary to set the degree of polymerization of —CH ₂ —O—) to an appropriate value.
It is preferable that the setting is made to be 00 or less.

Next, the chemical structural formula and the degree of polymerization of the polyvinyl resin will be described.

First, the chemical structural formula of the polyvinyl resin is shown in the following chemical formula 2.

[0023]

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However, n is 50 or more, and the substituent Y is one or more of OH, NH ₂ or COOOZ, wherein Z in the COOOZ is a Na atom, a K atom, One or more of Li atoms and NH ₄ atomic groups.

The polyvinyl resin must be any of Na, K, NH ₄ or Li salt of polyacrylic acid, polyvinyl alcohol or polyamide resin.
These mixtures may be used.

Degree of polymerization of polyvinyl resin: When the degree of polymerization is 50 or more and less than 50, fine holes are not formed in the film, and the hydrophilicity of the fin material becomes insufficient. Therefore, the polymerization degree n of the polyvinyl resin shown in Chemical formula 2 is 50
Above. Although the upper limit of the degree of polymerization n is not particularly limited, if the degree of polymerization n exceeds 10,000, the viscosity of the treatment bath becomes large and the workability is reduced. For this reason, the polymerization degree of the polyvinyl resin is preferably 10,000 or less.

Next, the mixing ratio when a film is formed on a fin material by mixing the above-defined epoxy-based cross-linking agent with the above-described polyvinyl-based resin and forming a film on the fin material, and the resulting film. The holes will be described.

Mixing ratio: 0.2 to 4.0 parts by weight 1 part by weight of epoxy crosslinking agent and 0.1 part by weight of polyvinyl resin.
When mixed at a ratio other than 2 to 4.0 parts by weight, the appearance of the obtained film is transparent by visual observation, and fine holes are almost confirmed by surface morphology observation with an electron microscope. Did not. For this reason, after repeated drying and wetting of the fin material, the contact angle of water droplets attached to the fin material increases.

On the other hand, a film formed by mixing 0.2 to 4.0 parts by weight of a polyvinyl-based resin with 1 part by weight of an epoxy-based cross-linking agent has fine holes formed on its surface, and has a ground glass-like shape. The appearance is roughened. The fin material having such a film on the surface has good hydrophilicity between the fin material surface and water by absorbing moisture into fine holes in the fin material surface. Therefore, in order to obtain a fin material which has good water wettability, a low contact angle of water droplets, and which can maintain this low contact angle, a fin material film is coated with 1 part by weight of an epoxy-based crosslinking agent and a polyvinyl-based resin. 0.2-4.
It shall be formed by mixing 0 parts by weight.

Average diameter of holes: 0.1 to 5 μm When the above-mentioned holes are present on the surface of the fin material, the contact angle of water drops is reduced and the wettability is improved as compared with a smooth surface having no holes. When the average diameter of the holes is less than 0.1 μm, the contact angle of water droplets increases, and the hydrophilicity decreases. On the other hand, if the average diameter of the holes exceeds 5 μm, the contact angle similarly increases and the hydrophilicity decreases. Therefore, holes having an average diameter of 0.1 to 5 μm contribute to improvement in wettability and hydrophilicity.

The shape of the hole present in the film on the surface of the fin material is not limited to a circle, and may not have a constant diameter such as an ellipse. Therefore, the size of the hole is defined by the average diameter defined by the following equation 1.

[0032]

(1) Average diameter = (a + b) / 2 where a is the length of the major axis of the hole (the value of the largest diameter) b: the length of the minor axis of the hole (the value of the smallest diameter).

Hole formation density: square of 10 μm on each side
In the measurement visual field, when the average density of five or more holes has an average diameter in the above range that contributes to the improvement of the wettability and the hydrophilicity in the above range, the contact density of water droplets is increased and the hydrophilicity is reduced. It is considered that this decrease in hydrophilicity is caused by an increase in flat portions on the film surface. Therefore, the density of the above-mentioned holes is set to 5 or more per 10 μm square.

However, the formation density of the holes indicates that when one measurement field of 10 μm square is present, there are five or more holes having an average diameter within the above range in the measurement field of view, and the measurement field of view is In the case of a plurality of holes, the number of holes having an average diameter in the range is five or more as an average value for the plurality of measurement visual fields.

The thickness of the film is not particularly limited, but 1 to 2 μm is appropriate from the viewpoint of workability and economy. Further, since the film according to the present invention does not have corrosion resistance by itself, it is formed after performing an anticorrosion treatment such as chromate chromate treatment, phosphoric acid chromate treatment, coating type chromate treatment or anticorrosion resin primer coating on an aluminum plate as a base treatment. Is preferred.

In the method for producing a surface-treated fin material for a heat exchanger according to the present invention, a mixture of the above-mentioned epoxy-based crosslinking agent and polyvinyl-based resin is applied to the surface of an aluminum plate and baked. The baking temperature and time in this baking will be described.

Baking temperature: 150 to 250 ° C. If the baking temperature is lower than 150 ° C., the crosslinking temperature is too low, and the hydrophilicity of the fin material after baking decreases. Also, if the baking temperature exceeds 250 ° C,
The crosslinking density becomes too high, so that the hydrophilicity of the fin material is reduced, and the properties of the aluminum plate itself forming the fin material are reduced. Therefore, the baking temperature is 1
50 to 250 ° C.

Baking time: 5 to 60 seconds If the baking time is less than 5 seconds, the baking time is too short, the crosslinking density is insufficient, and the hydrophilicity of the fin material is reduced. If the baking time exceeds 60 seconds, the crosslink density becomes too high, and the hydrophilicity decreases. Therefore, the baking time is set to 5 to 60 seconds.

[0039]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in comparison with comparative examples and conventional examples outside the scope of the claims. Example No. 1 shown in Table 1 below. About the coating of 1-4, the aluminum plate (JIS A1100 H22, thickness 0.1) which gave the phosphoric acid chromate process (Alsurf 401/45 (4% / 0.4% each made by Nippon Paint))
1 mm, Cr amount 15 mg / m ² ), the thickness was adjusted to 1 μm by a bar coater, and the coating was heated at 200 ° C. for 30 seconds to bake the coating on an aluminum plate.

[0040]

[Table 1] Example No. Chemical structural formulas of the respective epoxy-based crosslinking agents in Nos. 1 to 4 are shown in the following Chemical Formulas 3 to 6, respectively.

[0041]

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[0042]

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[0043]

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[0044]

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On the other hand, in the conventional example No. In Examples 1 to 3, a fin material in which a film having the composition shown in Table 2 below was formed on the surface was used.

[0046]

[Table 2] Also, in Comparative Example No. Nos. 1 to 6 correspond to Example Nos. A fin material formed on the surface of a film having the composition shown in the following Table 3 and subjected to the same treatment as in Examples 1 to 4 was used.

[0047]

[Table 3]

Comparative Example No. The chemical structural formulas of the epoxy cross-linking agents in 1 and 2 are shown in the following chemical formulas 7 and 8, respectively. Also, in Comparative Example No. The chemical structural formula of Comparative Example No. 3 is Chemical Formula 3 described above. The chemical structural formula of 4 is the above-mentioned chemical formula 4. Then, in Comparative Example No. Each of the chemical structural formulas of 5 and 6 is the above chemical formula 5.

[0049]

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[0050]

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In order to evaluate the hydrophilicity, the fin material was immersed in tap water for 8 hours and then dried at a temperature of 80 ° C. for 16 hours as one cycle. 0.01 ml was attached, and the contact angle at that time was measured. The odor is 100
After immersing the fin material in tap water over a period of time, sensory evaluation (smelling by blowing breath) was performed and evaluated.
The one with no odor was set to 1 and the one with the strongest odor was set to 5 as the odor became stronger. Regarding the tool wear, the fin material was pressed using a drawless mold manufactured by Hidaka Seiki Co., Ltd. (100,000 punches, press oil AF2).
C, at a processing speed of 250 spm), the wear and seizure of the ironing punch (second ironing ironing rate: 50%) were investigated, and those with no abnormality were evaluated as good, those with slight seizure as Δ, and those with flaws. Was evaluated as x. In addition, an electron microscope (acceleration voltage 5 kV, magnification 200
(0x or 10000x), the fin material film surface is photographed, 5 places are selected from the obtained photographs, and the number of holes present in a measurement field of 10 μm square on each side is counted for each place, and the average value is calculated. The hole density was used. The results of these evaluations are shown in Table 4 below.

[0052]

[Table 4]

As shown in Table 4 above, Example No. 1-4
Since the hole density was 5 holes / 10 μm square or more, the contact angle after repeated wet and dry was as low as 14 to 17 °. These contact angles are almost equal to those of the glass type (conventional example No. 3), and these contact angles are lower than those in the case where the surface is treated with a resin-based resin having a smooth surface (conventional example No. 1). Example No. It can be said that the fin materials 1 to 4 have extremely good hydrophilicity. Further, regarding the odor and tool wear, the conventional resin-based processing material (conventional example No.
Good as in 1).

On the other hand, in the conventional example No. Examples 1 to 3 are the case of a resin-based treatment material, the case of applying a hydrophilic paint containing colloidal silica, and the case of performing a water glass-based treatment, respectively. Conventional example No. In No. 1, the contact angle of the water droplet after the wet and dry was 52 °, and the hydrophilicity was low. Also, in Conventional Example No. In No. 2, the tool abrasion was large, and the contact angle of the water droplet after the wet and dry was as large as 42 °, and the hydrophilicity was low. Further, in Conventional Example No. In No. 3, although the contact angle of the water droplet was as low as 14 °, the points of tool abrasion and odor were deteriorated as compared with the resin-treated one (conventional example No. 1).

Further, in Comparative Example No. Comparative Example No. 1 was an epoxy crosslinking agent having three epoxy groups. 2 has two epoxy groups, but has a structural unit (—CH ₂ —CH ₂
-O- or _{-CH (CH 3) -CH 2 -O-} ) no, if its molecular weight is small as 400 epoxy crosslinking agent, comparative example No. In Comparative Example No. 3, when the mixing ratio of the epoxy-based crosslinking agent to the polyvinyl-based resin was less than 0.2 with respect to the epoxy-based crosslinking agent 1, 4 is a case where the mixing ratio exceeds 4. The above Comparative Example No. In all of Nos. 1 to 4, the surface morphology was almost smooth and the hole density was less than 5/10 μm square, so that the contact angle of the water droplet after the wet and dry was as high as 42 to 48 °. Hydrophilicity deteriorated.

Comparative Example No. No. 5 is a case where the substituent Y of the polyvinyl resin shown in Chemical formula ₂ is other than OH, NH ₂ and COOZ group. No. 6 is a case where the degree of polymerization is less than 50. Comparative Example No. In Nos. 5 and 6, since the hole density was 0 or small, the contact angles were as high as 53 and 50 °, respectively, and the water droplets were repelled after the wet and dry.

[0057]

As described in detail above, according to the present invention,
By forming a predetermined film on the surface of the aluminum plate, it is possible to produce a surface-treated fin material for a heat exchanger having excellent low contact angle persistence and excellent odor and tool wear characteristics.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a contact angle of a water droplet on a plane 1;

FIG. 2 is a schematic view showing a heat exchange unit of the heat exchanger.

FIG. 3 is a schematic diagram showing a state of attachment of water droplets on a fin surface.

[Explanation of symbols]

 1; plane 2, 6, 8, 11; water drop 3, 5, 7, 9, 10; fin 4; steel pipe 22;

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-7-278464 (JP, A) JP-A-1-38228 (JP, A) JP-A-3-26381 (JP, A) JP-A-62-1987 234926 (JP, A) JP-A-59-12297 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) F28F 13/18 B32B 1/00-35/00

Claims (2)

(57) [Claims] 1. A film comprising a mixture of an epoxy-based crosslinking agent having a molecular weight of 500 or more and a polyvinyl-based resin having a polymerization degree of 50 or more is formed on the surface of an aluminum or aluminum alloy plate. (-
CH ₂ —CH ₂ —O— or —CH (CH ₃ ) —CH ₂ —O
-) Is composed of a polymer having a structural unit of-) and two epoxy groups, and the film is formed by a ratio of 0.2 to 4.0 parts by weight of the polyvinyl resin to 1 part by weight of the epoxy crosslinking agent. And one side of the surface is 1
A surface-treated fin material for a heat exchanger, wherein the number of holes having an average diameter of 0.1 to 5 μm in a square measurement field of 0 μm is 5 or more as an average value in one or a plurality of measurement fields. 2. A polymer having (--CH ₂ --CH ₂ --O-- or --CH (CH ₃ )-CH ₂ --O--) as a constitutional unit and two epoxy groups in one molecule. A mixture of 1 part by weight of an epoxy-based crosslinking agent having a molecular weight of 500 or more and 0.2 to 4.0 parts by weight of a polyvinyl-based resin having a degree of polymerization of 50 or more is applied to an aluminum or aluminum alloy plate;
Then, the aluminum or aluminum alloy plate is
A method for producing a surface-treated fin material for a heat exchanger, comprising baking at a temperature of 0 to 250 ° C. for 5 to 60 seconds.