JPS62176578A - Treatment of fin for heat exchanger - Google Patents

Abstract

PURPOSE:To enhance corrosion resistance and water resistance while keeping heat-exchange efficiency, in applying a specific treating agent containing a water-soluble resin, by applying preparatory treatment such as chromate treatment to a fin for a heat exchanger. CONSTITUTION:Prior to adapting a coating treatment agent to a fin for a heat exchanger, one preparatory treatment selected from chromate treatment, non-chromate treatment, a boehmite treatment, anodizing treatment, silane coupling treatment and water-soluble resin coating treatment is applied a first to the fin to form a first layer to the surface of the fin. Next, a coating treatment agent containing an addition reaction product of at least one component selected from a group consisting of urea, thiourea and guanidine and formaline or a condensate of said addition reaction product, if necessary, a water-soluble nylon resin and an alkali metal is applied to the fin to form a second layer.

Description

[Detailed description of the invention] Industrial applications The present invention relates to a method of coating fins for a heat exchanger.

Conventional technology As a technology to improve the corrosion resistance of heat exchanger fins without reducing the function of the heat exchanger, aluminum and its alloys, which are typical materials for heat exchanger fins, are used as alkali chromate, chromium chromate, and phosphoric acid chromate-1. A method of chemical conversion treatment using a chromate-based treatment agent such as -, or a treatment agent in which an aqueous resin is further added to the chromate-based treatment agent disclosed in JP-A-55-164264 is known. Further, as a treatment agent that further enhances the performance of these treatment agents, there is an alkali metal-based treatment agent containing urea resin and water-soluble nylon, as disclosed in Japanese Patent Application No. 60-273427. Although the coating treatment agent disclosed in Japanese Patent Application No. 60-273/127 containing a water-soluble resin usually maintains sufficient performance, it is desired to have even higher performance and a wider range of application.

OBJECTS OF THE INVENTION The present invention aims to maintain heat exchange efficiency and improve corrosion resistance and water resistance of fins for heat exchangers.

Structure of the Invention The present invention is a method for treating heat exchanger fins, which is characterized by pre-treating the heat exchanger fins before applying a treatment agent containing a water-soluble resin to the heat exchanger fins. The treatment agent contains an addition reaction product of at least one selected from the group of urea, thiourea and guanidine with formalin, or a condensation product of the addition reaction product, and optionally a water-soluble nylon resin and an alkali metal, and the treatment agent This treatment method is characterized in that the preliminary treatment of the agent is one of chromate treatment, non-chromate treatment, boehmite treatment, anodizing treatment, silane coupling treatment, and water-soluble resin coating treatment.

Patent application No. 60-273427 contains an addition reaction product of at least one selected from the group of urea, thiourea and guanidine with formalin, or a condensation product of the addition reaction, and optionally a water-soluble nylon resin and an alkali metal. It is a coating treatment agent that maintains heat exchange efficiency over a long period of time for heat exchanger fins made of aluminum and its alloys, and also exhibits good corrosion resistance and water resistance.

However, the present inventor attempted to use the coating treatment agent disclosed in Japanese Patent Application No. 60-273427 more effectively, and completed the present invention.

That is, when applying the coating treatment agent to heat exchanger fins, it can be further treated by one of chromate treatment, non-chromate treatment, boehmite treatment, anodizing treatment, silane coupling treatment, and water-soluble resin coating treatment. It was discovered that performance improved.

In other words, a coating treatment agent containing a water-soluble resin is an addition reaction product of formalin and at least one selected from the group of urea, thiourea, and guanidine, or a condensation product of the addition reaction product and, if necessary, a water-soluble resin. Those containing nylon resin and alkali metal are most suitable for carrying out the present invention.

The first pretreatment is chromate treatment, which is carried out using a phosphoric acid chromate-based chemical conversion treatment agent or a pretreatment agent containing a mixture of trivalent chromium and a resin.

Chromate chemical conversion treatment is roughly divided into three types, depending on the type of chemical solution used and the type of film produced: alkali chromate type, chromium chromate type, and phosphoric acid chromate type. Among these, the alkali chromate type and chromium chromate type contain hexavalent chromium in the film.

6111Ii chromium is not preferred because it reacts with the resin in the coating treatment agent, accelerates curing too much, and reduces hydrophilicity. The phosphoric acid chromate film mainly contains chromium phosphate (trivalent) and does not contain hexavalent chromium, so it does not significantly accelerate the hardening of the resin. Therefore, it improves corrosion resistance and water resistance without reducing the hydrophilicity of the coating agent.

Surface treatment agents containing chromium and resin also contribute to improving corrosion resistance and water resistance as a pretreatment for coating treatment agents.

In this case as well, trivalent chromium is preferred rather than hexavalent chromium for the above-mentioned reasons.

The resin used in this case is generally an acrylic resin.

In order to improve corrosion resistance and water resistance without reducing hydrophilicity as a base treatment for the coating agent, the appropriate cr adhesion m is 1 to 20 .mu./TIt.

Below IRg/rd, the effect of improving corrosion resistance is poor;
If it is higher than IIrg/g, the hydrophilicity will decrease. When resin is included, the total film thickness (2) is preferably 2 g/rd or less. If the total film thickness exceeds 2 g/rIL, it not only reduces the heat exchange efficiency as a heat exchanger but is also economically disadvantageous.

The second pretreatment, non-chromate treatment, is performed using a chemical conversion treatment containing zirconium and/or titanium as a main component or a pretreatment agent consisting of a mixture of zirconium and/or titanium and a resin.

The above treatment uses zirconium and/or
Alternatively, a film containing titanium as a main component is formed to improve the corrosion resistance of aluminum and the adhesion with the organic coating film.

The pretreatment is used as a base treatment for the coating agent, and in order to improve corrosion resistance and water resistance without reducing hydrophilicity, the appropriate coating amount is 1 to 30 m9/ffl.1 t.
rty/rd or less, the effect of improving corrosion resistance is poor;
If it exceeds rtry/rIt, hydrophilicity tends to decrease. If resin is included, the total coating amount is 2g/rr! The following are preferred. If the total film thickness exceeds 2 g/rtl, it not only reduces the heat exchange efficiency as a heat exchanger but is also economically disadvantageous.

The resin used in this case is generally an acrylic resin.

The third preliminary treatment is boehmite treatment, which is a chemical conversion treatment method in which a hydrated oxide film is formed on the aluminum surface in pure water or pure water added with ammonia or triethanolamine.

By pre-forming a boehmite film with excellent corrosion resistance and coating adhesion on aluminum fins, the corrosion resistance and water resistance of the coating treatment agent are improved.

The film P is preferably 0.01 to 083 μm.

A coating thickness of 0.01 μm or less is insufficient to improve corrosion resistance, and a coating thickness of more than 0.3 μm requires a long time to form, which is economically disadvantageous.

The fourth preliminary treatment is an anodizing treatment, in which aluminum is used as an anode in an acid solution and electrolytically treated to form a porous oxide film on the aluminum surface.

The resulting oxide film has corrosion resistance and adhesion to the organic film, and can be used as a base treatment for coating agents to improve corrosion resistance and water resistance without reducing hydrophilicity.

As the azodizing bath, one or more of sulfuric acid, oxalic acid, chromic acid, and phosphoric acid is used, but sulfuric acid and/or phosphoric acid is preferable, and the film thickness is 0.01-0. 5μ
m is preferred.

If it is less than 0.01 μm, the effect of improving corrosion resistance and water resistance is poor, and if it exceeds 0.5 μm, no further improvement in performance can be obtained, which is economically disadvantageous.

The fifth pretreatment is a silane coupling treatment, which is a treatment with water or a water/alcohol solution of a silane coupling agent.

A silane coupling agent has two or more different types of reactive groups in its molecule, and one of the reactive groups (alkoxy group or silanol group) forms a strong bond with the aluminum surface. Yet another organic reactive group (vinyl group,
methacrylic groups, epoxy groups, amine groups, etc.) form strong chemical bonds with the resin in the coating agent, improving corrosion resistance and water resistance without reducing the hydrophilicity of the coating agent.

Examples of such silane coupling agents include KBM
602, 603 (manufactured by Shin-Etsu Chemical Co., Ltd.), 3116
020°5I16026.5II6070. QZ-8
-5069 (manufactured by Toshi Silicone Co., Ltd.), etc. The adhesion m of the silane coupling agent is 1 to 20 # in terms of Si.
Ig/Td is preferred.

If it is less than 11 rtg/'rd, improvement in corrosion resistance and water resistance will be poor, and if it exceeds 20 rtg/'rd, it will be expensive and no further improvement in corrosion resistance or water resistance will be observed.

The sixth preliminary treatment is a water-soluble resin coating treatment, which is a treatment agent using a thermosetting resin, a thermoplastic resin, or a reaction-curing water-soluble resin.

The resin coat may be of any material as long as it has corrosion resistance and water resistance by itself, but generally an acrylic copolymer resin is used as the main component.

Although a curing agent is not necessary for self-crosslinking type acrylic resins, melamine is generally used.

The thickness of the water-soluble resin coat is preferably 0.2 to 29/rd. If it is less than 0.29/rd, the effect of improving corrosion resistance and water resistance is poor, and if it exceeds 29/7d, it not only reduces the heat exchange efficiency but also increases the cost.

An example of such a typical resin is Julimar-AT-
510,613 (manufactured by Nippon Tsumugi Pharmaceutical Co., Ltd.) to Cevian-47
86 (manufactured by Hoechst Synthesis) @.

These preliminary treatments involve forming a first layer on the fins made of aluminum and its alloys by methods such as dipping, spraying, electrolysis, and roll coating, and then applying a coating agent containing a water-soluble resin. When formed, it exhibits sufficient expected performance as a fin for a heat exchanger.

The present invention will be described in more detail below based on Examples.

The example test plate was J[5-A-11001124 with a thickness of 0.1M.
, width 100mm and length 200mm. A sheet of aluminum (200 nm) was used. This aluminum plate was previously degreased with a weak alkaline degreaser Ridrin 322N-8 manufactured by Nippon Paint Co., Ltd., washed with water, and then subjected to the following preconditioning and dried.

Thereafter, a film of the coating treatment agent was applied using a bar coater so that the amount of film formed was 17/min, and the film was then left in a drying oven kept at 240° C. for 30 seconds to dry by heating to form a film. Idemitsu Punch Oil (manufactured by Idemitsu Oil Co., Ltd.) was applied to the aluminum plate that had been made hydrophilic in this way, and after removing the sauce for about 24 hours, it was degreased with 1,1,1-trichloroethane, and then subjected to the following test. provided.

The composition of the hydrophilic coating agent was as follows.

Below margin cash register top UL3201 416gAQ nylon 8-90 2O NallCO324 total 1,000 'j cash register top UL
3201 Yuri A7 resin manufactured by Gunei Chemical Industry Co., Ltd. AO nylon A-90 Water-soluble nylon resin manufactured by Toshisha Co., Ltd. 1-
1. Phosphate phosphoromate type pretreatment After chemical conversion treatment using the phosphoromate type treatment agent Alodine 401/45 manufactured by Nippon Paint Co., Ltd. so that the effl with CR becomes 10Rg/rtL, it is washed with water and dried at 150℃ for 30 seconds. did.

C
After chemical conversion treatment so that the adhesion amount was 11yJ/TIt, it was washed with water and dried at 150°C for 30 seconds.

C
After chemical conversion treatment was carried out so that the adhesion amount was 20 cm/bottom, it was washed with water and dried at 150° C. for 30 seconds.

1-4 Resin-type chromate treatment 3 After chemical conversion treatment using Alodine NR6207, a resin-type chromate-based treatment agent manufactured by Nippon Paint Co., Ltd. whose main components are chromium and acrylic resin, so that Cr addition 1 is 5rItg/TIt, waterless washing was performed. , and dried at 150° C. for 30 seconds.

The total film suspension at this time was about 351 ftg/TIt.

1-5 Resin type chromate treatment Resin type chromate treatment agent Alodine NIt6207 manufactured by Nippon Paint Co., Ltd. whose main components are trivalent chromium and acrylic resin
After the sea urchin chemical conversion treatment was applied so that the amount of Cr deposited was 201 ftg/rd, it was washed without water and dried at 150°C for 30 seconds.

The total coating amount at this time was approximately 140 mg/Td.

2-1 Non-chromate type pre-treatment Non-chromate type treatment agent Alodine 41 manufactured by Nippon Paint Co., Ltd.
3 was subjected to chemical conversion treatment so that the amount of 7r applied was 10 In'J/rd, washed with water, and dried at 150°C for 30 seconds.

2-2 Non-chromate type pre-treatment Non-chromate type treatment agent Alodine 41 manufactured by Nippon Paint Co., Ltd.
3 was subjected to chemical conversion treatment so that the amount of Zr deposited was 30 my/rd, washed with water, and dried at 150°C for 30 seconds.

2-3 Resin-type non-chromate-treated resin-type non-chromate treatment agent Deoxylite 1 manufactured by Nippon Paint Co., Ltd. whose main components are zirconium and acrylic resin
47/148 was subjected to chemical conversion treatment so that the lr adhesion amount was 7 mg/rrt, and then washed without water and dried at 150°C for 30 seconds.

The total film weight at this time was about 20 mg/butt.

2-4 Resin-type non-chromate-treated resin-type non-chromate treatment agent Deoxylite 1 manufactured by Nippon Paint Co., Ltd. whose main components are zirconium and acrylic resin
47/148 Zr i'117ffi 30m9/r
After chemical conversion treatment as shown in d, the product was washed without water and dried at 150° C. for 30 seconds.

The total coating amount at this time was about 100 mg/Td.

3-1 Boehmite pretreatment Boehmite was boiled for 3 minutes in pure water to which 0.3 w/v% ammonia was added, then washed with water, and dried at 150°C for 30 seconds. The thickness of the boehmite film at this time was about 0.1μ.

4-1 Anodizing Pretreatment In a 5v/v% phosphoric acid aqueous solution at a temperature of 30°C, one valve is opened at a current density of 0.6 A/d using the aluminum plate as an anode and a 10x20x 1ax 5US316 stainless steel plate as a cathode. Anodized. Then washed with water and heated at 150℃ for 30 minutes.
Dry for seconds. The thickness of the boehmite film at this time is approximately 0.
．． It was 1μ.

5-1 Silane coupling pre-treatment bundle Silane coupling agent 5IIt3020 manufactured by Resilicone Co., Ltd. 0.5v
/v% aqueous solution at 20℃ for 5 seconds! After 10
It was dried at 0°C for 60 seconds. At this time, the adhesion period of the silane coupling agent was approximately 5 ay/rrl in terms of Si.

5-2 Silane coupling pretreatment 0.1 V/V% of silane coupling agent KBH602 manufactured by Shin-Etsu Chemical Co., Ltd.
After immersing in an aqueous solution at 20℃ for 5 seconds, it was heated to 100℃ for 6 seconds.
Dry for 0 seconds. At this time, the adhesion ω of the silane coupling agent was approximately 1 mg/end in terms of Si.

5-3 Silane coupling pre-treatment bundle Silane coupling agent QZ-8-5069 manufactured by Resilicone Co., Ltd. 2v/
After immersion in v% aqueous solution at 20°C for 10 seconds,
Dry at °C for 60 seconds. At this time, the amount of silane coupling agent during adhesion was approximately 20 mg/TIL at the Si exchange port.

6-1 Water-soluble resin coating pretreatment Acrylic resin Jurimer AT-613-1 manufactured by Nippon Tsumugi Co., Ltd.
After creating a 0w/v% aqueous solution and applying it with a bar coater so that the dry film adhesion amount was 1cJ/Td,
It was dried at 0°C for 30 seconds.

Performance evaluation: Table 1 Table 2 Table 3 Corrosion resistance JIS-2371,500 hours later, the area ratio of white rust on the flat surface was evaluated.

◎ White rust occurrence area rate 0% 0 Less than 10χΔ
50% (less than 50%)) 1 x 50% or more adhesion JIS-54006, 15 in sequence, first after heating and drying, secondly after immersing in tap water for 24 hours and peeling off with adhesive tape, remaining area Displayed in

Hydrophilicity Hydrophilic treated aluminum plate is immersed in running water for 7 days.
A 177-hour cycle test was performed five times for drying, and evaluation was made based on the water-wetted area immediately after drying and immersion in running water.

◎ Water wet area rate 100%0
Δ less than 90-100x
50 to less than 90% x less than 50% Water solubility Water dissolution rate after 24 hours of immersion in tap water Initial coating weight - Water dissolution weight of the coating after immersion - Initial coating thickness ◎ Water solubility weight less than 5% 〃 5 to 10 Less than Δ ,,
10 Less than 20 x 20 or more Water resistance 50°C tap water immersion) Judging the degree of blistering with the naked eye after 63 hours ◎ No abnormalities O Slightly fine blisters Δ Slightly blisters × Fine blisters on the entire surface Effect of the invention The method of the present invention does not have the conventional corrosion resistance and water resistance, but is an invention that has industrially excellent effects such as continuous maintenance of heat exchange efficiency.

Claims (1)

[Scope of Claims] 1) A method for treating fins for a heat exchanger, which comprises performing a preliminary treatment before applying a coating treatment agent containing a water-soluble resin to the fins for a heat exchanger. 2) The coating treatment agent containing a water-soluble resin is an addition reaction product of formalin and at least one selected from the group of urea, thiourea, and guanidine, or a condensation product of the addition reaction and, if necessary, a water-soluble nylon resin. 2. The method for treating heat exchanger fins according to claim 1, further comprising an alkali metal. 3) Pre-treatment is chromate treatment, non-chromate treatment,
The method for treating fins for a heat exchanger according to claim 1, wherein the treatment is selected from boehmite treatment, anodizing treatment, silane coupling treatment, and water-soluble resin coating treatment.