JPH07111317B2 - Aluminum fin material for heat exchanger - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to aluminum or aluminum alloys (hereinafter referred to as aluminum or aluminum alloys) used for heat exchangers for condensers, evaporators, etc. of commercial and household air conditioners, or heat exchangers for automobile radiators, etc. The present invention relates to a fin material for a heat exchanger made of aluminum, and particularly to a precoat fin material for a heat exchanger which has a coating layer having excellent hydrophilicity formed on the surface thereof and which can be easily tested for air tightness.

[0002]

2. Description of the Related Art As a fin material for a heat exchanger, aluminum, which is lightweight, has excellent workability and thermal conductivity, has been widely used.

In recent years, in order to make room air conditioners more compact and to save energy, various measures have been taken to further improve the heat transfer efficiency, such as raising the louvers and shortening the distance between the fins.

Therefore, when water is condensed on the fins, the water droplets form a bridge between the fins, which increases ventilation resistance, and the water droplets resonate with the ventilation to generate noise. At the same time, problems such as corrosion of fin material due to water began to occur.

Therefore, in order to improve this, the fin material has been subjected to a corrosion resistance treatment and a hydrophilization treatment (to reduce the contact angle at the time of water condensation so as not to form water droplets).

For example, there is known a technique for forming a coating layer in which an inorganic material such as silica or alumina is mixed with an organic resin as a material having excellent hydrophilicity (JP-A-54-14265).
No. 0, see JP-A-55-99978). However, the tool subjected to these treatments had a large tool wear during processing and had insufficient corrosion resistance.

Further, the nonionic surfactant of HLB 8 to 15 and the nonionic surfactant of HLB 16 to 20 are each in the range of 1 to 29 parts by weight with respect to the solid content of the water-soluble resin, and the total amount is 2 to 30. There is a proposal of a resin composition for surface treatment which is added so as to be added by weight (Japanese Patent Laid-Open No. 63-304067).
issue).

Alternatively, an aluminum fin material baked with a water-soluble resin containing a surfactant having a molecular weight of a hydrophobic group (lipophilic group) of 400 or less (JP-A-64-61239)
No.) has been proposed.

The fin materials obtained by the latter two proposals have good hydrophilicity and appropriate corrosion resistance.
It is considered that the purpose was achieved for the time being.

However, in the heat exchanger, the fin material is press-molded, assembled, brazed to a copper pipe, and then the resulting heat exchanger is immersed in a water tank and air or the like is fed into the copper pipe to determine whether bubbles are generated. Airtightness tests of copper pipes and brazed parts are being conducted. At this time, the water (hereinafter referred to as airtight water) in the water tank becomes cloudy due to the eluate and effluent (press oil, surfactant, etc.) from the fins, copper pipes, etc. If not, it will be impossible. In such cases, measures such as increasing the frequency of replacing the airtight water have been taken, but there has been a need to increase the cost and the accuracy of the airtight test.

From this point of view, the problem of airtight water turbidity could not be solved by adopting the proposed means of coating and baking the surfactant-containing water-soluble resin.

[0012]

DISCLOSURE OF THE INVENTION The present invention is a coating film in which coarse water droplets do not stop on the surface of the fin even when water is condensed on the aluminum fin, and a thin water layer flows down. This coating has excellent corrosion resistance, moisture,
In addition to preventing corrosion due to humidity, it does not become cloudy even if there is eluate or spillage in press oil or other airtight water, and it is easy to confirm bubbles from leaked parts such as pinholes, etc. The purpose is to develop an aluminum fin material that has been painted so that it does not hinder the work.

[0013]

According to the present invention, a surfactant having an HLB of 14 or more and a lipophilic group having an average molecular weight of 400 or less and a surfactant having an HLB of 7 or less are added to aluminum or an aluminum alloy material. Apply hydrophilic resin paint,
The above object was achieved by developing an aluminum fin material for a heat exchanger, which is characterized by being baked.

Further, an aluminum fin material for a heat exchanger according to claim 1 has been developed, in which an hydrophilic film is applied to an aluminum or aluminum alloy material which has been subjected to oxide film formation by alternating current electrolysis, resin coating, and chromate phosphoric acid or chromate chromate treatment and is baked. By doing so, a paint for the aluminum fin material for the heat exchanger is also provided.

Aluminum thin plates used in the fin material for heat exchangers of the present invention include JIS 1100 and JI.
Pure aluminum plate such as S 1050, JIS 201
7, Al-Cu alloy plate such as JIS 2024, JIS
Al-Mn alloy plate such as 3003 and JIS 3004, Al-M such as JIS 5052 and JIS 5083
g-based alloy plate and further Al-Mg such as JIS 6061
Any of -Si alloy plates may be used, and the shape thereof may be either a sheet or a coil.

In producing the fin material for a heat exchanger of the present invention, the aluminum thin plate as described above is degreased, washed with water and dried, and then the surface active agent having an average molecular weight of 400 or less in the lipophilic base portion. A water-soluble hydrophilic resin containing an agent and a surfactant having an HLB of 7 or less is applied, and baking is performed.

In this case, prior to the coating of the hydrophilic resin, a base treatment for improving corrosion resistance and coating film adhesion may be performed.

For example, an aluminum material having a pH of 9 to 1
3. In an alkaline aqueous solution having a bath temperature of 35 to 85 ° C., at a current density of 4 to 50 A / dm ² , an AC electrolysis treatment was performed for a time at which the amount of electricity exceeded 80 C / dm ² , and a film was formed on the surface of the aluminum plate. A method of forming an oxide film having a thickness of 500 to 5000Å (Japanese Patent Application No. 2-109341), or polyacrylic acid, polymethacrylic acid polyacrylic acid derivative, polymethacrylic acid derivative, urethane resin, urethane resin derivative, epoxy on an aluminum plate. Resin, epoxy resin derivative, polyamide, polyamide derivative, etc., or a copolymer or mixture of two or more of them, or trivalent chromium, hexavalent chromium, SiO ₂ ,
0.4 ~ 5μ paint containing silicate, zirconium salt, etc.
A method of applying a coating having a thickness of m and baking to form a corrosion resistant film (JP-A 61-107198, JP-A 1-2257).
No. 95) or aluminum plate material is subjected to chromate phosphate or chromate chromate treatment by a method such as spraying or dipping to form a film having a chromium deposition amount of 5 to 100 mg / m ² (JP-A-62-105629), etc. However, the method is not limited to these methods.

The hydrophilic resin used in the hydrophilic resin coating material used in the present invention (the base resin has a water contact angle of 40 when the resin alone is used).
It is preferably not more than °. ), Specifically, cellulose derivatives, acrylic acid (polyacrylic acid) or its derivatives, methacrylic acid or its derivatives, polyamide or its derivatives, polyvinyl alcohol or its derivatives, polyamide or its derivatives, polyvinyl alcohol or its derivatives, etc. Or a water-soluble resin such as a copolymer or a mixture thereof, or a hydrophilic resin emulsion thereof.

The surfactant, which is a constituent of the hydrophilic resin coating composition, includes a surfactant having a lipophilic group having an average molecular weight of 400 or less (hereinafter referred to as surfactant A) and a surfactant having an HLB of 7 or less ( Hereinafter referred to as surfactant B).

Surfactant A is added in order to improve the hydrophilicity of the coating film, that is, to prevent the formation of water droplets of condensed water to form a water film and improve the flow of the coating film. Polyoxyethylene derivative, sorbitan derivative, nonionic surfactants and / or phosphoric acid ester derivatives such as sucrose fatty acid ester derivative, an average molecular weight of the lipophilic groups is 400 or less interfacial active agent sulfonic acid ester derivatives or mixtures thereof can be used.

Surfactant B is added to prevent clouding of airtight water, and is a nonionic surfactant such as polyoxyethylene derivative, sorbitan derivative, sucrose fatty acid ester derivative and / or phosphoric acid. Anionic surfactants such as ester derivatives and sulfonic acid ester derivatives having an HLB of 7 or less.

Specifically, sorbitan triolefin acid ester, sorbitan tristearic acid ester, sorbitan sesquioleic acid ester, sorbitan monooleic acid ester, sorbitan monostearic acid ester,
There are sorbitan monopalmitate, propylene glycol monostearate, propylene glycol monolaurate, diethylene glycol monostearate, diethylene glycol monolaurate and the like, or mixtures thereof.

The mixing ratio of the surfactant A and the surfactant B is such that 1 part by weight of the surfactant A is 0.2 parts by weight of the surfactant B.
A ratio of 5 to 2.00 parts by weight is suitable.

Surfactant A cannot be expected to have the effect of preventing airtight water turbidity. Therefore, when the content of surfactant B is less than 0.20, it has almost no airtight water turbidity prevention effect, and the content is 2.00 times. If it exceeds, the property of the surfactant B, which is inferior in hydrophilicity, becomes stronger, the hydrophilicity of the coating film is lowered, and the formation of water droplets can be seen.

The ratio of the surfactant composition (not to be added separately) to the base resin is 0.1 to 30% by weight, preferably 1 to 20% by weight of the resin coating solid content. The range of weight% is good. A blending amount of 0.1% by weight or less has no effect on the hydrophilicity of the coating film and prevention of clouding of airtight water, and a blending amount of more than 30% by weight unfavorably reduces the strength of the hydrophilic coating film.

Such a hydrophilic resin paint is applied to an aluminum thin plate. The coating method may be any of commonly used methods such as roll coating and spray coating.

The coating thickness is about 0.1 to 10 μm, preferably about 0.2 to 1 μm. If the thickness is 0.1 μm or less, coating defects (pinholes, etc.) are likely to occur and the hydrophilicity is lowered.
On the other hand, if it exceeds 10 μm, cohesive failure of the coating film easily occurs,
Hydrophilicity is not particularly changed either, so it is unsuitable.

The conditions such as baking temperature and baking time may be appropriately selected according to the hydrophilic resin used. Generally, it is a thermoplastic resin of several tens of degrees C. to several hundreds of degrees C.
It may be baked with a thermosetting resin for several dozens of minutes to 100 ° C. to 300 ° C. for several seconds to several minutes.

[0030]

Action The action of the surfactant B in the present invention has not been confirmed, but it is estimated as follows.

That is, the fin material that has been molded while the press oil or the like remains attached is assembled in the heat exchanger as it is and immersed in airtight water. Therefore, the mixture of the press oil brought into the airtight water and the surfactant added to the coating film is suspended and the water becomes cloudy.

In this case, the surfactant and HLB value eluted in the airtight water and the required H suitable for solubilizing the press oil.
When the LB values are almost equal, the press oil has the highest solubilization amount and the airtight water becomes transparent.

Generally, the hydrophilicity-improving surfactant (surfactant A) has an HLB of about 14 or more, most of which is about 16 to 20, whereas the required HLB value of the press oil is about 10 to 1.
At 4, both do not match. As a result, the press oil is suspended without being solubilized, and it is presumed that the liquid becomes cloudy.

When a surfactant having an HLB of 7 or less is added in an amount in the range of 1/4 to 2 times that of the surfactant for improving hydrophilicity, the HLB of the whole surfactant is lowered. For example, for 10 surfactants with an HLB of 18 to 2 surfactants with an HLB of 4
When added at a rate of 20, the total HLB is reduced to about 9-15, which is close to the HLB suitable for solubilizing the press oil. As a result, it is considered that the affinity between the press oil and water is increased and the oil is solubilized to prevent clouding.

The details of the mechanism for solubilizing the press oil are unknown, but when a surfactant having an HLB of 7 or less is added (because the lipophilic group of such a surfactant is long), hydrocarbons in the press oil are Dissolves in the hydrocarbon part inside the micelle (or emulsion) (sandwich type dissolution), and the components such as fatty acid and fatty acid ester in the press oil form a polar group part between the polar groups of the surfactant and a non-polar group part. It is presumed that the amount of solubilization of the press oil is increased due to dissolution by intercalation between the hydrocarbon groups of the activator molecule (palisade type dissolution). Since the amount of palisade type dissolved is usually larger than the amount of sandwich type dissolved, it is considered that the amount of surfactant added with HLB of 7 or less is relatively at least good.

In the baked paint, most of the surfactant added to the hydrophilic resin has the hydrophilic group on the outside,
The lipophilic group is adsorbed on the surface in the form of facing the coating film, and part of the hydrophilic group of the surfactant and the hydrophilic group of the coating film are bonded to each other, with the lipophilic group facing the outside of the coating film. It is presumed that it is adsorbed.

The hydrophilicity is better as the average molecular weight of the lipophilic group of the surfactant to be added is smaller, and has no correlation with the HLB value.
This is considered as follows.

HLB merely represents the ratio of the size (molecular weight) of the hydrophilic group to the lipophilic group. If the molecular weight of the hydrophilic group is large, the HLB is high even if the molecular weight of the lipophilic group is large. The hydrophilicity of the coating film is preferably such that the ratio of the area occupied by the hydrophilic groups on the surface to the lipophilic groups is high (the area of the hydrophilic groups is large and the area of the lipophilic groups is small), and it is a surfactant with a high HLB. However, when the molecular weight of the lipophilic group is large, the area occupied by the lipophilic group becomes large when adsorbing so that the hydrophilic group is directed to the surface of the coating film, and the hydrophilicity decreases. If the average molecular weight of the lipophilic group is small, such a problem does not occur and the hydrophilicity is improved. A surfactant having an average molecular weight of the lipophilic group of 400 or less is suitable for this purpose.

Surfactant B added to prevent airtight turbidity
(HLB is 7 or less) is a surfactant having a large average molecular weight of the lipophilic group, which is disadvantageous for hydrophilicity, and therefore the addition amount needs to be reduced as much as possible. However, if the addition amount is too small, the effect of preventing the airtight water turbidity is lowered, and therefore it is 0.25 to 2.00 relative to the surfactant A from the balance of both.
I think it has doubled.

[0040]

Examples (1) Sample preparation JIS A-1200-H24, 0.115 mm thick aluminum thin plate (fin material for drawless molding) is a degreasing material [Surf Cleaner 322N; Nippon Paint Co., Ltd.].
Using an 8.2% aqueous solution, spray cleaning was performed at 70 ° C. for 3 seconds. Then, after washing with water and drying, and pretreatment (coating-baking or formation of chemical conversion film-drying), a hydrophilic resin coating was applied and baked to obtain a sample.

(2) Test method Airtight water turbidity test A sample was immersed in a volatile press oil [Daphni AF-2A; Idemitsu Petroleum Co., Ltd.] for 1 minute at room temperature, and after pulling up, it was dried at room temperature for 1 minute to obtain a sample. 1000c for 1m ²
Immerse in pure water of c at room temperature for 30 seconds and pull up the sample. After pulling up the sample, the absorbance of the pure water was measured at a wavelength of 660 nm and a cell thickness of 50 mm.

Hydrophilicity test Samples were immersed in volatile press oil [Daphni AF-2A; Idemitsu Petroleum Co., Ltd.] for 1 minute at room temperature, pulled up and dried for 1 minute at room temperature. The contact angle with was measured.

(Example 1, Comparative Example 1) As a base treatment, a weak alkaline electrolytic bath [pyrophosphate-based bath (pH 10.5)]
AC electrolysis treatment was carried out at 70 ° C., 8 A / dm ² for 30 seconds, and a hydrophilic resin paint having the composition shown in Table 1 was applied thereto at a coating film thickness of 1.0 g / m ² and a baking temperature of 250 ° C. (MPT). 1
Baked for a minute. The base resin in this case is special modified cellulose [Mitsui Toatsu Co., Ltd., trade name WH-10]. The test results are shown in Table 1.

[0044]

[Table 1]

(Example 2, Comparative Example 2) Acrylic paint [Esvia AL-50B; Shinto Paint Co., Ltd.] was applied as a base treatment, the film thickness was 1.0 g / m ² , and the baking temperature was 29.
Aluminum plate material baked at 0 ° C. (MPT) for 30 seconds was coated with a hydrophilic resin coating as shown in Table 2 at a coating thickness of 1.0 g /
m ² , baking temperature 200 ° C. (MPT), 1 minute baking sample. The base resin is an acrylic hydrophilic resin [Mitsui Toatsu Co., Ltd., trade name XCE-1845]. The test results are shown in Table 2.

[0046]

[Table 2]

(Example 3, Comparative Example 3) As a base treatment, a chromate phosphate [Alsurf 401/45 solution; Nippon Paint Co., Ltd.] solution was sprayed to deposit 30 m of chromium.
An aluminum plate material of g / m ² was obtained. On top of this, a hydrophilic resin paint having the composition shown in Table 3 was applied to give a coating film thickness of 1.0 g / m ² ,
A baking temperature of 240 ° C. (MPT) was applied for 1 minute and baking was performed to obtain a sample. Acrylic hydrophilic resin (Surf Alcoat 160; Nippon Paint Co., Ltd.) is used as the base resin, and the test results are shown in Table 3.

[0048]

[Table 3]

[0049]

INDUSTRIAL APPLICABILITY According to the present invention, the surface of an aluminum fin material is provided with a surfactant having a lipophilic group having an average molecular weight of 400 or less (surfactant A) and a surfactant having an HLB of 7 or less (surfactant B). It is the one obtained by baking a hydrophilic resin paint containing

As a result, the corrosion resistance of the aluminum fin material is improved, and even if moisture condenses on the fin material, not only does it have the ability to flow as a thin water film without forming a bridge, but it has been a problem in the past. In addition, it was possible to provide a painted aluminum fin material that can prevent clouding of the airtight water during the airtightness test of the heat exchanger and can easily confirm bubbles.

Front page continuation (72) Inventor Nobuyoshi Sasaki 4-3-18 Nihombashi Muromachi, Chuo-ku, Tokyo Inside Sky Aluminum Co., Ltd. (56) References Japanese Patent Publication No. Hei 6-4809 (JP, B2)

Claims (4)

[Claims] 1. A hydrophilic resin coating comprising a surfactant having an HLB of 14 or more and a lipophilic group having an average molecular weight of 400 or less and a surfactant having an HLB of 7 or less, applied to aluminum or an aluminum alloy material, and baked. Aluminum fin material for heat exchangers characterized by 2. A hydrophilic resin coating composition, wherein HLB is 14 or more and 1 part by weight of a surfactant having an average molecular weight of 400 or less of a lipophilic group and 0.25 of a surfactant having HLB of 7 or less. ~ 2.0
The aluminum fin material for a heat exchanger according to claim 1, which is contained in an amount of 0 part by weight and 0.2 to 30% by weight in the hydrophilic resin. 3. The aluminum fin material for a heat exchanger according to claim 1, wherein a hydrophilic resin coating material is applied to and baked on an aluminum or aluminum alloy material which has been subjected to formation of an oxide film by AC electrolysis, resin coating, and chromate phosphate or chromate chromate treatment. 4. A mixture of 0.1 part by weight to 2.0 parts by weight of a surfactant having an HLB of 7 or less with 1 part by weight of a surfactant having an HLB of 14 or more and an average molecular weight of a lipophilic group of 400 or less. A hydrophilic resin coating material for an aluminum fin material, characterized in that a surfactant is mixed with a hydrophilic resin in a proportion of 0.2 to 30% by weight.