JPH0332589B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a hydrophilic film-forming agent for imparting wettability to the surface of objects, particularly the surface of heat exchange equipment. In recent years, as heat exchangers have improved in performance and become smaller, there has been a trend to narrow the fin spacing and increase the fin density. For this reason, so-called bridges are likely to be formed due to moisture condensed between the fins, and this also increases ventilation resistance, causing noise generation and energy consumption. The cause of such bridge formation is the poor wettability of the fin material itself to water. In other words, the fins of heat exchangers are mainly made of metal materials such as aluminum;
Since aluminum is a metal material that is easily oxidized, its surface is covered with a dense oxide film caused by natural oxidation, so it has poor wettability, and moisture in the air that condenses on the surface of the fin material is The surface of the fin material was not uniformly wetted, but spherical water droplets condensed on the surface of the fin material, resulting in the formation of bridges of water droplets between the narrow spaces of the fin material.
In addition, the poor wettability of the fin material surface itself
It also caused a significant decrease in the cooling efficiency of the heat exchanger. In particular, when aluminum is used as heat exchange equipment, the surface is coated with an oxide film or chromate by a method such as anodizing or chemical treatment to prevent corrosion of the equipment due to moisture adhering to the surface. Although coating with a chemical film such as a film has been practiced, the surface of the equipment coated with this film has poorer wettability than bare aluminum material. . Conventionally, in order to impart hydrophilicity to surfaces with poor wettability, it has been known to add silica particles or surfactants as hydrophilicity imparting agents to resin paints, for example, but the former When the formed material is subjected to die molding or the like, there is a problem in that the die is abraded, and the latter has the disadvantage that the surfactant is eluted over time, resulting in deterioration of hydrophilicity. In view of the above circumstances, the present inventors conducted various experiments in order to obtain a coating agent for forming a hydrophilic film that is hydrophilic and has little deterioration due to long-term use, and also reduces die wear due to the film formed during molding. result,
It has been found that by applying a coating agent containing fine ion exchange resin powder evenly dispersed in a resin paint to the material to be treated and drying it, it is possible to form a film that is extremely suitable for the above purpose. I found it. The present invention has been made based on the above findings. That is, the present invention provides a method for forming a hydrophilic film for imparting wettability to the surface of a heat exchanger material, characterized in that ion-exchange resin powder is dispersed in a resin paint consisting of a film component and a film-forming auxiliary element. It is a drug. The present invention will be explained in more detail below. As the coating film component used in the film forming agent of the present invention, thermoplastic synthetic resins and thermosetting synthetic resins that have been conventionally used for resin coatings can be appropriately selected and used. Considering the usage conditions of the product to which the film is applied and the stability of the ion exchange resin, it is preferable to use a thermoplastic resin with a softening temperature of 80° C. or higher.
In the case of thermosetting resins, if the baking heating time of the coating film exceeds 10 minutes, the curing temperature of the resin should be 150°C.
It is preferable to select a resin with a curing temperature of 150° C. or higher, and when using a resin with a curing temperature of 150° C. or higher, it is preferable to use a heating means that allows the baking heating time to be 1 minute or less. Resins in coating film components that are compatible with these conditions include alkyd resins, acrylic resins, polyvinyl alcohol resins, vinyl acetate resins, epoxy resins, phenolic resins, polyester resins, urethane resins, etc., but are not necessarily limited to these. It's not something you can do. Furthermore, this film-forming agent contains water in the case of water-based paints, hydrocarbons,
As in the case of ordinary paints, alcohols, esters, ketones, ethers, etc. can be used as appropriate depending on the characteristics of the resin used. In addition, the amount of these media added can be adjusted within an appropriate range in order to develop fluidity depending on the application method, just like in ordinary paints, and can be adjusted according to the desired hydrophilicity level. It can be limited to an appropriate range. The ion exchange resin is made by copolymerizing styrene or methacrylic acid with divinylbenzene as a crosslinking agent, and contains a sulfonic acid group, a carboxylic acid group, a phosphonic acid group, a phosphinic acid group, or a quaternary ammonium group as a hydrophilic atomic group. Those to which secondary or tertiary amines have been added are often used as cation exchange resins and anion exchange resins. Exchange capacity is 2.0 [meq/
(g-Dry/R)] The above are preferably used for the present invention. If it is less than 2.0, the required wettability cannot be sufficiently secured. In addition, those based on phenolic resin also
Any ion exchange resin that is insoluble and has surfactant properties can be used. Among these ion exchange resins, cation exchange resins (including salt types substituted with alkali metals) are suitable for application because they are highly hydrophilic, and sulfonic acid type strongly acidic cation exchange resins are more suitable. Optimal. Depending on the desired hydrophilicity level, a mixture of a strongly acidic cation exchange resin and a weakly acidic cation exchange resin, a mixture of a highly basic ion exchange resin and a weakly basic ion exchange resin, or a mixture of a cation exchange resin and an anion. It is also possible to apply two or more types of resins mixed together with exchange resins. Commercially available ion exchange resins are usually in the form of particles of 10 to 50 mesh, and are used after being crushed depending on the desired film thickness. In other words, the typical film thickness is 0.5μm
Since the particle size is approximately 3 μm, the particles are pulverized to an average particle size of 1 μm or less by, for example, a vibrating ball mill, taking into consideration the smoothness of the film, the uniformity of the film, etc. before use. In this case, if a finely pulverized product is available for special purpose analysis or ultra-high purity use, it goes without saying that it can be used as is. Further, it is also possible to use a method of adjusting the final particle size to a desired size by secondary use of the kneading process with the resin paint. The amount of ion exchange resin added to the coating film components in the present film forming agent can be determined as appropriate depending on the exchange capacity of the ion exchange resin used and the desired level of hydrophilicity for the film to be formed. , the proportion of ion exchange resin in the total amount of coating film components and ion exchange resin powder must be 0.1 or more on a dry weight basis (hereinafter referred to as
The above ratio is called the "replacement resin ratio"). When the exchange resin ratio is 0.1 or less, it becomes difficult to stably obtain a desired hydrophilicity level. The exchange resin ratio is preferably in the range of 0.3 to 0.7. If it is 0.7 or more, the adhesion to the substrate will be poor. In addition, the solvent of the coating film forming auxiliary element may be added to the mixed stock solution of the coating film component and ion exchange resin at the time of use, or the solvent may be used in the form of adding and mixing the three components together from the beginning. Added to film forming agent. Furthermore, the present film-forming agent allows the addition of various additives that impart various properties as a coating material. That is, dispersants, antifungal agents, antiskinning agents, slip agents, antifoaming agents, etc. may each be contained in an amount of about 1 to 2%, if desired. In addition, as an initial hydrophilicity improver of the present film forming agent, for example, 2
A small amount of surfactant, ~3%, may be added. Next, the method of using the present film-forming agent will be described. Application methods for ordinary paints, ie, roll coating, spraying, dipping, brushing, spin coating, etc., are applicable. If the paint is a dry paint, it is air-dried as it is after application to fix the film, and if it is a baking type paint, it is baked under heating conditions within a range that does not impair the properties of the ion exchange resin. As a pretreatment for the film forming treatment, it is also an effective means to use a base film treatment (for example, anodization treatment, chromate treatment, etc.) for the purpose of improving the corrosion resistance of the base surface and the adhesion of the film. The hydrophilic film-forming agent according to the present invention has been described above. When the film-forming agent of the present invention is used, a hydrophilic film can be formed on the surface of the treated material over a long period of time with little deterioration over time. Furthermore, it has excellent properties such as less die wear during die molding of the material to be treated after the film has been formed. Therefore, it can be used very effectively as a hydrophilic film-forming agent for fin members for high-density finned heat exchangers. Next, examples of the present invention are listed. Example 1 Commercially available sulfonic acid type polystyrene cation exchange resin: 4.5 [meq/(g-Dry-R)] (ROHM&
Anbanlite IR-120 (manufactured by Haas) was ground in a ball mill for about 30 minutes and dried with an infrared lamp to obtain particles with an average particle size of 15 μm and a water content of 12%. Next, 200 g of this fine powder, 650 g of an epoxy ester water-soluble paint (manufactured by Dainippon Ink Co., Ltd., Water Sol S-352; solid content 46%), 100 g of butyl cellosolve, and 400 g of water were placed in a pot mill for about 6 hours. The mixture was mixed to ensure uniform dispersion. As a result, the secondary particle diameter of the ion exchange resin is 0.5~
It became 1μm. The obtained film-forming agent was applied to a previously cleaned aluminum panel using a bar coater (#12), and dried and fixed at 230° C. for 30 seconds. Comparative Examples: When the epoxy ester paint used in Example 1 was applied as is (Comparative Example 1), and when a commercially available thermosetting acrylic resin paint (solid content 18%) containing a wetting surfactant was applied. (Comparative example 2)
The coating and drying conditions were the same as in Example 1. Table 1 lists the results of various tests performed on these Examples and Comparative Examples.

[Table] The initial wettability in the table is the wet state after immersing the sample in deionized water and pulling it out for 30 seconds.
Shown as 100%. From the results in Table 1, when the resin paint of Comparative Example 2 was used, die molding processability after film formation was good, but the deterioration of hydrophilicity (expressed as water wettability in this case) was significant. It can be seen that this is significantly inferior to the case based on the invention. Example 2 To the composition of Example 1, 8 g of a 5% solution of cobalt naphthenate was added as a dryer, and after the same kneading operation, using a roll coater,
The coating was applied to a fin plate for an aluminum heat exchanger that had been previously degreased, and after forced drying, it was left indoors for 3 days to fix the coating. Next, when the same test as in Example 1 was conducted, almost the same effects were obtained, and in particular, the durability against xylene was significantly improved, and the corrosion resistance was also improved. This seems to be because cobalt naphthenate acts as a catalyst. Example 3 Weakly acidic cation exchange resin 10 [meq/(g-Dry
-R)] (Manufactured by Rohm & Haas, Amberlight
IRC-50) dry fine powder (average particle size 1.0μm, water content 5%) 250g, modified alkyd resin paint (Dainippon Ink Co., Ltd., P-786-50) 700g, xylene
300c.c., dispersant (BM1000, manufactured by West German BM) 30g,
7 g of leveling agent (BM, West Germany, BM1800A) was added and mixed in a high speed stirrer for 30 minutes. The solid content of the alkyd resin paint was 50%, and the exchange resin ratio of the resulting film forming agent was 0.38. This film-forming agent was applied to a galvanized steel plate by brushing and heated to 200°C to form a film. When the water wettability of the film was measured under the same conditions as in Example 1, a wet test result of 97% was obtained after 48 hours, indicating that there was very little deterioration in hydrophilicity.

Claims (1)

[Scope of Claims] 1. A hydrophilic coating for imparting wettability to the surface of a heat exchanger material, characterized in that it is formed by dispersing ion-exchange resin powder in a resin coating consisting of coating film components and film-forming auxiliary elements. Forming agent. 2 The proportion of ion exchange resin in the total amount of coating film components and ion exchange resin powder is on a dry weight basis.
A hydrophilic film-forming agent for imparting wettability to the surface of a heat exchange device according to claim 1, wherein the hydrophilic film-forming agent has a wettability of 0.1 or more.