JPS59229198A - Surface treatment procedure for heat exchanger - Google Patents

Abstract

PURPOSE:To improve the hydrophilic property of metal surface, by forming a known thermoplastic high-polymeric resin film over the metallic surface of heat exchanger, and then heat-drying hydrophilic solid micro-grains over the film for securing. CONSTITUTION:After a thermoplastic high-polymeric resin film is formed over the metallic film of heat exchanger for improving its anti-corrosive property, hydrophilic solid micro-grains such as, for example, a silica micro-grain, an alumina micro-grain and a potassium calcium carbonate micro-grain are coated over the film. Then, the thermoplastic high-polymeric resin film is heated and dried at a temperature above its softening point. A solid micro-grain is thus implanted for securing in the thermoplastic high-polymeric resin film, and thereby improving its hydrophilic property.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for surface treatment of metal parts constituting a heat radiating section and a cooling section of a heat exchanger.

Conventionally, most heat exchangers are designed to have as large an area as possible for the heat dissipation section and cooling section in order to improve the heat dissipation or cooling effect, so the spacing between the fins is narrow. . Therefore, when used for cooling, moisture in the atmosphere condenses on the surface of the heat exchanger, especially in the gaps between the fins. The aggregated water tends to form spherical water droplets with hydrophobic fin surfaces (and may clog the fin gaps, increasing ventilation resistance and reducing the heat exchange rate. The water droplets are scattered by the heat exchanger's blower and tend to overflow from the water droplet tray installed at the bottom of the heat exchanger, which has the disadvantage of staining the area around the heat exchanger with water.On the other hand, when used for heating Even in winter, frost builds up on the outdoor unit and reduces thermal efficiency, so the heat exchanger is sometimes run in reverse to warm the outdoor unit and defrost it.This defrosting operation is quick and efficient. It is essential for the function of heating and cooling air conditioners. Therefore, in order to quickly remove the water droplets that melt during defrosting, it is effective to make the fin surface hydrophilic. In order to prevent clogging due to water droplets remaining in the fin gaps of the heat dissipation section or cooling section of the heat exchanger, treatment is carried out to make the surface of the heat exchanger hydrophilic and improve water wettability. Treatments that improve water temperature resistance are not sufficient in terms of corrosion resistance, and especially in the case of aluminum heat exchangers, rust prevention treatment is often required.

The method of giving a hydrophilic surface to these heat exchangers is (1
) 7 'A method of completely forming a polymer resin film containing J-force particles, calcium carbonate or a surfactant, (2) A method of forming a polymer resin film completely containing J-force particles, calcium carbonate or surfactant, (2) Water glass, lithium phosphoric acid, etc. on an anodic oxide film, boehmite film, resin film or chromate conversion film Method of applying colloidal silica, (3) directly to metal surfaces, water glass, lithium/licade.

A method of completely applying colloidal silica or the like is known.

However, in the mixed coating system of (1) side fat coating and hydrophilic solid particles such as phosphor particles and calcium carbonate particles, mt
The resin coats the surface of the aqueous solid particles to give them a sufficient hydrophilic surface.Also, in a resin film containing a surfactant, the surfactant is easily washed away by water, resulting in a long lasting hydrophilicity. There are some difficulties.

(2), (3) water glass, lithium 7 silicate,
The method of applying silica fine particles provides a hydrophilic surface, but has the disadvantage that it has poor adhesion and is easily peeled off, particularly in areas with excessive adhesion, and the peeled off solids become powder and scatter. In addition, water glass, lithium/licade, etc. are partially dissolved by water that condenses in the heat exchanger section, accumulates at the bottom of the fins, dries out roughly when the heating/cooling is stopped, and scatters as powder when the heating/cooling is restarted. have Substances that are effective in imparting hydrophilic properties include these crystal fine particles, calcium carbonate, water glass, lithium silicate, etc., but they have difficulty in adhesion and are easily scattered as powder, especially white powder, which imparts hydrophilic properties. The surface treatment work is difficult, there is a problem of excess film due to pooling of the treatment liquid, and the film has to be treated in as small a quantity as possible, so it has disadvantages such as not being able to impart sufficient hydrophilic properties.

The object of the present invention is to provide a metal surface of a heat exchanger with a good hydrophilic surface that eliminates these drawbacks.

The present inventors have conducted various studies as a method for suppressing the coating from falling off from heat exchangers that have been given hydrophilicity 11] and becoming white powder and scattering. After forming a known thermoplastic polymer resin film that generally improves corrosion resistance, hydrophilic solid fine particles are applied thereon and heated and dried at a temperature higher than the softening point of the thermoplastic polymer resin film. The present invention was completed based on the discovery that a hydrophilic surface with excellent adhesion can be provided on a polymer resin film.

To explain the non-invention in more detail, polymer resin films generally exhibit excellent adhesion to metal surfaces, but heating a thermoplastic polymer resin film, which is one type of film, increases the adhesion of the film. By taking advantage of this property and softening, the hydrophilic solid fine particles are made to have an affinity with the thermoplastic polymer resin film with increased stickiness, and by embedding them in the softened resin layer, the solid fine particles become difficult to fall off. I understand.

Naturally, in this treatment method, the object to be treated on which a thermoplastic polymer resin film has been formed is heated in advance to a temperature higher than the softening point of the resin film, and hydrophilic solid fine particles are sprayed onto it or treated by a fluidized dip coating method. Is possible.

The thermoplastic polymer resin coating used in the present invention includes vinyl-based materials such as vinyl chloride, vinyl butyral, hnylidene chloride, vinyl acetate, and vinyl formal, olefin-based materials such as styrene, ethylene, and propylene, acetal-based materials, methacrylates, and acrylic materials. , acrylic type such as hydroxyacrylate and acrylic acid, nylon thread, and urethane type.

Butadiene type and copolymers thereof.

The softening point of thermoplastic resin varies depending on the type of resin, 2M degree, etc., and cannot be determined in part, but it can be determined by the Pikar penetration test,
It is measured by the ring and ball softening point test method.

Silica particles are used as hydrophilic solid particles.

Examples include alumina fine particles and calcium carbonate fine particles. These may also be provided in the form of a sol dispersed in a solution. These fine particles suitably have a particle size of 10 microns or less, preferably 2 microns or less. The thickness of the thermoplastic polymer resin film formed in the present invention is preferably in the range of 0.05 to 20 microns, preferably 0.3 microns, since corrosion resistance will be poor if it is too thin, and thermal efficiency will be poor if it is too thick. ~2 microns range.

Further, the activation amount of the hydrophilic solid fine particles on the thermoplastic polymer resin film is preferably 50 to 2000 η/d.

The invention will be explained below by giving examples.

Example 1 Degreased and cleaned aluminum coil material for heat exchanger (AIl
oo) Apply thermoplastic acrylic resin emulsion (registered trademark, Primal AC-33, manufactured by Om & Haas Japan) to the surface and dry in a hot air circulation oven at 13°C for 3 minutes to form a 2 micron film. A film was formed.

Further, a colloidal aqueous dispersion of silicic anhydride fine particles (registered trademark, Snowtex N2, Nissan Chemical) was applied, and after heating and drying for 5 minutes in a 130°C hot air circulation type open oven, an aluminum coil material was wound up. The amount of silicic anhydride fine particles coated on the thermoplastic resin film was 0.5y-/-, and the temperature of the object to be treated was 120-1300C.

Even when the treated aluminum coil material was wiped with gauze, no peeling of the white powder was observed. Further, the water contact angle was 10 degrees or less, and the water wettability was good.

Comparative Example 1 After forming a thermoplastic acrylic resin film with a film thickness of 2 microns on the surface of an aluminum coil material for a heat exchanger in the same manner as in Example 1, a colloidal aqueous dispersion of silicic anhydride fine particles (registered trademark, After applying Snowtex N2 (Nissan Chemical), it was left to dry at room temperature (20° C.) for 30 minutes.

As a result of wiping the treated aluminum coil material with gauze, peeling of the white flaky powder was observed, and the peeling off was particularly severe in the lower part where the excess adhered. Further, the water contact angle was 60 degrees, and the water wettability was poor.

Comparative Example 2 The same method as in Example 1 was carried out except that a thermosetting urethane resin film was formed on the surface of the aluminum coil material for a heat exchanger instead of the thermoplastic acrylic resin emulsion.

When the treated aluminum coil material was wiped with gauze, peeling of white powder was observed.

As described above, by carrying out the present invention, the hydrophilic solid fine particles attached to the thermoplastic/polymer resin film on the metal surface of the heat exchanger will not fall off, and will remain on the metal surface of the heat exchanger for a long period of time. Corrosion resistance and a hydrophilic surface can be imparted.

Agent: Tadashi Oka

Claims (1)

[Claims] Forming a thermoplastic polymer resin film on the narrow metal surface of the heat exchanger, then applying hydrophilic solid fine particles thereon, and then heating and drying the thermoplastic polymer resin film at a temperature equal to or higher than the softening point. A heat exchanger surface treatment method featuring