JP2015222155A - Fin material for heat exchanger and method for manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fin material for a heat exchanger on which coating excellent in not only a hydrophilic property and an antifouling property but also a metal-mold abrasion property is formed.SOLUTION: On the surface of a base material made of aluminium or aluminium alloy, there are formed a hydrophilic coat having, as a main component, polyoxyethylene chain provided in the deposition amount of 0.4 g/m-1.2 g/m; and an antifouling property coat made by applying and drying aqueous paint containing alumina particles, silica particles, and a polyoxyethylene system lubricant and provided on the hydrophilic coat in the deposition amount of 0.1 g/m-0.5 g/m.

Description

  The present invention relates to a fin material for a heat exchanger having a coating film excellent in hydrophilicity, antifouling property, and mold wear and a method for producing the same.

The heat exchanger fin material is made of aluminum or aluminum alloy, which is superior in terms of lightness, workability, and thermal conductivity.
Also, when used on the evaporator side in a heat exchanger such as an air conditioner, if water vapor in the air is condensed and the condensed water adheres to the fins as water droplets, the airflow resistance increases, resulting in increased pressure loss and heat exchange. The capacity of the vessel is reduced. For this reason, in order to make the water condensed on the fins flow down easily, a hydrophilic coating film is formed on the surface.

Patent Document 1 discloses that a hydrophilic coating film containing silica particles and polyethylene glycol is formed on the surface of an aluminum alloy substrate on an organic resin such as polyacrylic acid that is metal-crosslinked with a Zr compound. ing.
Patent Document 2 discloses that a base coating layer containing a resin and zirconium is formed on an aluminum plate, and a hydrophilic coating layer containing a resin, colloidal silica, and a zirconium compound is formed thereon. Yes.

JP 2010-96416 A Japanese Patent No. 4667978

  By the way, it is press-molded in order to process the fin material into heat exchanger fins, but in the hydrophilic coating described in the patent document, silica particles with high Mohs hardness are present in the surface layer, so that mold wear occurs during press molding. It is likely to occur.

  This invention is made in view of such a situation, and it aims at providing the fin material for heat exchangers which formed the coating film which is excellent not only in hydrophilic property and antifouling property but in mold abrasion property. To do.

As a result of earnest research on the fin material for heat exchangers that is excellent in hydrophilicity, antifouling properties, and mold wear properties, the present inventors have obtained the following knowledge.
Polymer compounds containing polyoxyethylene chains such as polyethylene glycol and polyethylene oxide together with acrylic resins containing polyacrylic acid, polyvinyl alcohol, and the like can be used as hydrophilic coating materials. By adding this polymer compound containing a polyoxyethylene chain, it has the effect of promoting the curing reaction of the coating film to improve the adhesion, further imparting lubricity to the coating film after baking, There are effects such as prevention of seizing to the mold and suppression of mold wear.
On the other hand, when the polymer compound containing a polyoxyethylene chain is in the uppermost layer of the coating after baking, static electricity is likely to be generated, and hydrophilic and hydrophobic stains (dust etc.) are likely to adhere. In order to make this stain difficult to adhere, water-based paint containing alumina particles and silica particles is applied on the hydrophilic coating and dried to exert an antistatic effect to remove stains such as hydrophilic stains and hydrophobic stains. It becomes difficult to adhere.

Alumina particles and silica particles are hard to stick when applied alone, so a binder resin is added for adhesion, but when applied on a hydrophilic coating containing a polymer compound composed mainly of polyoxyethylene chains Alumina particles and silica particles enter the irregular surface of the hydrophilic coating film surface, adhere to the hydrophilic coating film even without the binder resin, and the alumina particles and silica particles remain even when washed with condensed water.
In this case, if silica particles having a high Mohs hardness are present in the uppermost layer of the coating, there is a risk that the mold wear resistance will deteriorate during press working. Therefore, by mixing alumina particles having a Mohs hardness lower than that of silica particles on the hydrophilic coating, and further mixing a polyoxyethylene-based lubricant (for example, polyoxyethylene alkyl ether) to improve lubricity, the lubricating component can be reduced. It exists in the uppermost layer of a coating film, and can reduce die wear during pressing.
Silica particles alone improve hydrophilicity but lack antifouling properties. Alumina particles alone improve antifouling properties, but hydrophilicity and stain resistance after press oil application deteriorate. Therefore, it is possible to achieve both hydrophilicity and antifouling properties by mixing alumina particles and silica particles.

If the top layer of the coating contains a polyoxyethylene-based lubricant, which is a lubricating component, the antistatic effect will be reduced, but the condensation component will be washed away due to the condensation water adhering to the fin surface during air conditioning operation. Thus, an antistatic effect can be exhibited.
Based on the above knowledge, the present invention is defined as the following solution.

That is, the heat exchanger fin material of the present invention, the surface of aluminum or an aluminum alloy substrate, a polyoxyethylene chain, which is provided in the deposition amount of 0.4g ^/ m ² ~1.2g / m 2 a hydrophilic film containing a polymer compound containing as a main component, alumina particles is provided in the deposition amount of 0.1g ^/ m ² ~0.5g / m 2 on the hydrophilic coating, silica particles and poly An antifouling film formed by applying and drying a water-based paint containing an oxyethylene-based lubricant is formed.

In the fin material for a heat exchanger according to the present invention, the alumina particles and the silica particles are contained such that Al ₂ O ₃ is 1 part by weight of SiO _{2 and} 0.25 part by weight to 1 part by weight of SiO ₂ . Good.
Since the Mohs hardness of the alumina particles is lower than that of the silica particles, mold wear can be effectively reduced by setting the mixing ratio of the alumina particles equal to or higher than that of the silica particles.

  In the heat exchanger fin material of the present invention, the surface dynamic friction coefficient is preferably 0.2 or less.

In the heat exchanger fin material of the present invention, the hydrophilic coating film preferably contains a fluororesin.
By containing a fluororesin in the hydrophilic coating, it is possible to further exert an antistatic effect and make it difficult to adhere dirt.

  In the fin after being assembled in the heat exchanger, the polyoxyethylene-based lubricant on the surface is washed away by dew condensation water, etc., but the alumina particles and silica particles are mixed and adhered, so that Dirty and hydrophilic can be exhibited.

Method of manufacturing a heat exchanger fin material of the present invention, the surface of a base material made of aluminum or an aluminum alloy, composed mainly of polyoxyethylene chain in the deposition amount of 0.4g ^/ m ² ~1.2g / m 2 forming a hydrophilic film containing that polymer compound, alumina particles in the deposition amount of 0.1g ^/ m ² ~0.5g / m 2 on the hydrophilic coating, silica particles and polyoxyethylene A water-based paint containing a lubricant is applied and dried to form an antifouling film.

In the manufacturing method of the fin material for heat exchangers of the present invention, the antifouling film may be formed after washing the hydrophilic film formed on the surface of the substrate.
By washing the hydrophilic coating, the uneven surface of the coating becomes large, and the adhesion between alumina particles and silica particles is improved.

  ADVANTAGE OF THE INVENTION According to this invention, the fin material for heat exchangers which formed the coating film which is excellent also not only in hydrophilic property and antifouling property but mold abrasion property can be obtained.

It is sectional drawing which shows typically the state before use in one Embodiment of the fin material for heat exchangers of this invention. It is sectional drawing which shows typically the state which assembled | attached and used the fin material for heat exchangers of FIG. 1 to the heat exchanger.

Embodiments of the present invention will be described below.
As shown in FIG. 1, the heat exchanger fin material is formed on a base material 1 made of aluminum or an aluminum alloy, a chemical conversion film 2 formed on the surface of the base material 1, and the chemical conversion film 2. A hydrophilic coating 3 and an antifouling coating 4 formed on the hydrophilic coating 3 are provided.
As the base material 1, for example, 1100, 1200, 1050, 3003, etc., are used as alloy numbers according to JIS standards. On the surface of the substrate 1, a thin chromate film that has been chromated is formed as the chemical conversion film 2.

The hydrophilic coating 3 contains a polymer compound mainly composed of a polyoxyethylene chain. The polymer compound having a polyoxyethylene chain as a main component can be selected from polyethylene glycol, polyethylene oxide, and the like.
Further, the fluororesin 5 may be added to the hydrophilic coating 3. As the fluororesin 5, PTFE dispersion, FEP dispersion, or the like can be used. As addition amount, 0.1 mass%-5 mass% are preferable.
The hydrophilic film 3 is provided in the deposition amount of 0.4 g ^/ m 2 to 1.2 g / ^{m 2} on the chemical conversion coating 2 of the substrate 1. When the deposition amount is less than 0.4 g / m ² , the hydrophilicity is insufficient and the stain resistance is not preferable. When the deposition amount exceeds 1.2 g / m ² , not only the cost increases, but also the adhesion to the substrate is impaired.

The antifouling coating 4 is formed by applying and drying a water-based paint containing fine particles composed of alumina particles 6a and silica particles 6b and a polyoxyethylene-based lubricant.
The alumina particles are fine particles having an average particle diameter of 10 nm to 100 nm, and are added to the coating material as an alumina sol which is an aqueous dispersion thereof. The silica particles are fine particles having an average particle diameter of 5 nm to 80 nm, and are added to the coating material as colloidal silica which is an aqueous dispersion thereof.
It is important that the fine particles of these alumina particles 6a and silica particles 6b are mixed, and the mixing ratio thereof is 1 part by weight of Al ₂ O _{3 and} 0.25 parts by weight of SiO _2. It is set to be 1 part by weight. In this case, the Mohs hardness is 6 for the silica particles 6b, whereas the alumina particle 6a is lower than that, and is 3.5-4. The fine particles of the alumina particles 6a and the silica particles 6b are preferably contained in an antifouling paint in an amount of 0.5% by mass to 5% by mass as a solid content.

  Select polyoxyethylene-based lubricant from polyoxyethylene lauryl ether, polyoxyethylene cetyl ether, polyoxyethylene stearyl ether, polyoxyethylene myristyl ether, polyoxyethylene octyl decyl, polyoxyethylene alkyl ether, etc. Can do.

The antifouling coating 4 made of such a composition is provided in the deposition amount of 0.1g ^{/ m 2} ~0.5g ^/ m 2 on the hydrophilic film 3 of the substrate 1. When the deposition amount is less than 0.1 g / m ² , the antifouling property is insufficient, and when it exceeds 0.5 g / m ² , not only the cost is increased, but also die wear during press molding is increased.
The coefficient of dynamic friction on the surface of the antifouling coating 4 is 0.2 or less.

The heat exchanger fin material configured as described above forms a hydrophilic coating 3 after forming a chemical conversion coating (chromate coating) 2 as a base film on the surface of the substrate 1 by performing a phosphoric acid chromate treatment, It is manufactured by forming an antifouling film 4 thereon.
In this case, after forming the hydrophilic film 3 and before forming the antifouling film 4, the surface of the hydrophilic film 3 is washed with water. Thereby, the unevenness | corrugation of the surface of the hydrophilic coating 3 becomes large, and the adhesiveness of the microparticles | fine-particles of the alumina particle 6a and the silica particle 6b improves so that it may mention later.

The heat exchanger fin material manufactured in this manner is subjected to processing such as bending and drilling by press molding, and is formed as a heat exchanger fin, and then incorporated into the heat exchanger. At the time of molding, a polyoxyethylene-based lubricant is added to the antifouling coating 4 on the surface of the fin material, and the coefficient of dynamic friction is as small as 0.2 or less, so that it is smoothly pressed, cracked in the fin, etc. Does not occur, and die wear can be reduced.
In this case, the fine particles composed of the alumina particles 6a and the silica particles 6b present in the antifouling coating 4 are hard particles and may wear the mold, but half of the alumina particles having a smaller Mohs hardness than the silica particles. Since they are mixed in the above amounts, the wear of the mold is suppressed as compared with the case of the silica particles alone, and the wear of the mold can be reduced due to the presence of the polyoxyethylene-based lubricant.

  When this fin material is incorporated and used as a heat exchanger, when condensation occurs on the fins during the initial heat exchanger operation, the polyoxyethylene-based lubricant is water-soluble. Washed away by water. Here, when the surface of the hydrophilic coating 3 existing under the antifouling coating 4 is exposed, static electricity is easily generated by the polymer compound mainly composed of polyoxyethylene chains, Hydrophobic dirt tends to adhere, but the fine particles of alumina particles 6a and silica particles 6b contained in the antifouling coating 4 have irregular surfaces on the surface of the hydrophilic coating 3 below. As shown in FIG. As described above, the surface of the hydrophilic coating 3 has unevenness due to washing with water at the time of manufacture, so that the fine particles of alumina particles 6a and silica particles 6b enter the unevenness and remain.

For this reason, the antifouling film 11 in which the fine particles of the alumina particles 6a and the silica particles 6b are in close contact with the surface of the hydrophilic film 3 is present, and the hydrophilicity and antifouling property can be continuously exhibited as fins. In this case, since the silica particles 6b and the alumina particles 6a are mixed, both functions of the hydrophilicity by the silica particles 6b and the antifouling property by the alumina particles 6a can be effectively exhibited.
Moreover, when the fluororesin 5 is added to the hydrophilic coating 3, the antistatic effect is further exerted and dirt is less likely to adhere.

  In addition, this invention is not limited to the said embodiment, A various change can be added in the range which does not deviate from the meaning of this invention.

Examples of the present invention will be described below.
A coating for a hydrophilic coating having the composition shown in Table 1 is applied to the surface of an aluminum alloy plate that has been subjected to phosphoric acid chromate treatment as a chemical conversion treatment, and baked in an oven at 220 ° C. (set temperature) × 30 seconds. did. Thereafter, the surface of the hydrophilic coating was washed by immersing it in warm water at 60 ° C. for 10 seconds, and the antifouling coating paint shown in Table 1 was applied on the washed hydrophilic coating with a bar coater. And baked in an oven at 120 ° C. (set temperature) × 30 seconds. In addition, an antifouling film was formed as it was without washing with water after forming the hydrophilic film.
In Table 1, the hydrophilic coating resin 1 and resin 2 were as follows.
Resin 1: What was obtained by mixing polyacrylic acid copolymer, polyvinyl alcohol and polyethylene oxide Resin 2: Mixing acrylic acid, 2-hydroxyethyl methacrylate, acrylonitrile, acrylamide copolymer, carboxymethylcellulose Na, polyethylene glycol In this case, the hydrophilic film with and without the fluororesin was prepared.
Further, the antifouling film was formed by a paint in which raw materials 1, 2, and 3 were mixed as shown in Table 1, raw material 1 was alumina sol, raw material 2 was colloidal silica, and raw material 3 was polyoxyethylene alkyl ether. The raw material 1 and the raw material 2 have shown the mixing ratio (weight part).
And the coating material which consists of 19 types of combinations shown in Table 1 was apply | coated with the application quantity of Table 2 and Table 3, and baked.

With respect to the obtained samples, various contact angles and dynamic friction coefficients were evaluated as the adhesion and hydrophilicity of the coating, and the powder adhesion rate and the mold wear resistance were evaluated as antifouling properties.
For adhesion, Kim Towel (registered trademark) affixed to a 1 pound hammer was placed on the coating surface of the sample, and the adhesion state of the coating after rubbing 10 times was observed. The case where peeling was not observed at all and the adhesion was judged to be good was marked as ◎, the case where some peeling was observed as ○, and the case where complete peeling was recognized as x.
For hydrophilicity, the contact angle after press oil drying, the contact angle after the wet and dry cycle, and the contact angle after the contamination test were evaluated.
The contact angle after drying the press oil was measured by applying the press oil (volatile oil) to the surface of the coating film of the sample and measuring the contact angle of the coating surface after drying at 150 ° C. for 5 minutes. Those having a contact angle of 20 ° or less were evaluated as ◯, and those having a contact angle exceeding 20 ° were evaluated as ×.
The contact angle after the wet / dry cycle was determined by measuring the contact angle on the surface of the sample after 14 hours of alternately immersing the sample in normal temperature flowing water at a flow rate of 3 L / min for 8 hours and drying at 80 ° C. for 16 hours. A contact angle of 40 ° or less was evaluated as ◯, and a contact angle exceeding 40 ° was evaluated as ×.
As the contact angle after the contamination test, 6 g of valmitic acid and a sample were placed in a beaker as contaminants, and the contact angle of the coating surface after heating exposure at 100 ° C. for 6 days was measured. Those having a contact angle of 60 ° or less were evaluated as ◯, and those having a contact angle exceeding 60 ° were evaluated as ×.
The coefficient of dynamic friction was measured using a Bowden friction tester, without applying press oil, pressing a steel ball size φ9 / 32 inch contact with a load of 200 g on the surface of the sample coating over a length of 10 mm on the surface of the sample. The frictional force at the time of one reciprocal sliding was measured to determine the dynamic friction coefficient. A sample having a coefficient of dynamic friction of 0.2 or less was marked with ◯, and a sample with a coefficient of dynamic friction exceeding 0.2 was marked with ×.
The powder adhesion rate was determined by immersing a 100 mm × 100 mm sample in normal temperature flowing water at a flow rate of 3 L / min for 1 hour, and then attaching each of 11 types and 12 types of test powders defined by JIS Z8901 to the surface of the sample coating. Then, the adhesion area ratio was measured by image analysis. A case where the adhesion area ratio was 0.1% or less was rated as ◎, a case where the adhesion area ratio was 0.2% or less was rated as ○, and a case where the adhesion area ratio exceeded 0.2% was rated as ×.
For mold wear, the sample was cut 1 million times by press working, and the wear state of the mold (slit blade) was observed. Slitting blades hardness should be designed HRC37～41, mold using a laser microscope as a quantitative evaluation to measure the wear area of the cutting edge of the (slit blade), the wear area of the two-dimensional cross-section 100 [mu] m ² or less of those of ◎ , those beyond the 100 [mu] m ² of 300 [mu] m ² or less ○, was × those exceed 300 [mu] m ^2.
These evaluation results are shown in Tables 4 and 5.

  As is clear from these results, it can be seen that the examples of the present invention are excellent in adhesion, hydrophilicity, and antifouling properties, and are less likely to cause mold wear during press working.

DESCRIPTION OF SYMBOLS 1 Base material 2 Chemical conversion film 3 Hydrophilic film 4 Antifouling film 5 Fluororesin 6a Alumina particle 6b Silica particle 11 Antifouling film

Claims (6)

The surface of aluminum or an aluminum alloy base material, a hydrophilic containing a polymer compound as a main component a polyoxyethylene chain, which is provided in the deposition amount of 0.4g ^/ m ² ~1.2g / m 2 and coating the alumina particles is provided in the deposition amount of 0.1g ^/ m ² ~0.5g / m 2 on the hydrophilic coating, the silica particles and an aqueous coating material containing a polyoxyethylene-based lubricant coating A fin material for a heat exchanger, wherein a dried antifouling film is formed. The alumina particles and silica particles, according to claim 1, Al ₂ O ₃ is SiO ₂ is characterized in that it is contained so as to be 0.25 part by weight to 1 parts by weight per 1 part by weight Fin material for heat exchanger.   The fin material for a heat exchanger according to claim 1 or 2, wherein the coefficient of dynamic friction of the surface is 0.2 or less.   The heat exchanger fin material according to any one of claims 1 to 3, wherein the hydrophilic film contains a fluororesin. The surface of aluminum or an aluminum alloy base material, forming a hydrophilic film containing a polymer compound as a main component a polyoxyethylene chain in the deposition amount of 0.4g ^/ m ² ~1.2g / m 2 and, parent alumina particles deposition quantity of 0.1g ^/ m ² ~0.5g / m 2 on the aqueous film, silica particles and polyoxyethylene lubricant by coating and drying an aqueous coating material containing an anti The manufacturing method of the fin material for heat exchangers characterized by forming a dirty film.   6. The method for producing a fin material for a heat exchanger according to claim 5, wherein the antifouling film is formed after washing the hydrophilic film formed on the surface of the substrate.

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