JP5589937B2 - Heat exchanger coating method - Google Patents

Description

  The present invention relates to a coating method of a heat exchanger in an air conditioner, and relates to a coating method that takes into consideration the characteristics of an existing coating material and restores the adhesion prevention property of dirt and maintains the anticorrosion effect.

  In general, an air conditioner is used indoors and adjusts temperature by exchanging heat while circulating the air. Therefore, dust, dust, oil stains, etc. in the room adhere to and accumulate on the heat exchanger of the air conditioner. In particular, the aluminum fins provided in the heat exchanger have a complicated uneven structure, so that the interval between the fins is narrow and clogging due to dirt is likely to occur. When clogging occurs, the heat exchange efficiency decreases and the amount of power increases. Further, in a hot and humid atmosphere, there is a problem that mold and bacteria propagate in the heat exchanger and are unsanitary and unpleasant odors are generated when these are released indoors. For this reason, it is usually necessary to periodically maintain the air conditioner and clean the heat exchanger.

  As a conventional maintenance method of a heat exchanger of an air conditioner, there is a method of forming a coating film using a coating agent that forms a ceramic film that is cured at room temperature after the heat exchanger is cleaned with a cleaning fluid. (For example, refer to Patent Document 1).

JP 2006-138501 A

  Aluminum fins are generally used in heat exchangers, but a hydrophilic film is added to the surface of the aluminum fins to increase the fluidity of the condensed water on the surface of the aluminum fins during cooling operation and to prevent corrosion. ing. Therefore, it is necessary to perform maintenance such as cleaning periodically.

  However, when the maintenance period is long, the hydrophilic film of the aluminum fin peels, thins, and deteriorates, the surface becomes uneven, dirt is easily attached, the anticorrosion effect is reduced, and the film becomes brittle. It happens.

Therefore, Patent Document 1 proposes a method of applying a ceramic coating or the like that cures at room temperature on a hydrophilic film applied to an aluminum fin after washing the heat exchanger.
However, since such a ceramic coating is usually a thin film and has a structure with more pores, it is not necessary to repair the peeling portion of the hydrophilic film originally applied to the aluminum fin, or the thinned or deteriorated portion. However, it is impossible to solve problems such as unevenness on the surface, easy adhesion of dirt, reduced anticorrosion effect, and embrittlement of the film.

  The present invention has been made to solve the above-described problems, and obtains a coating method for a heat exchanger that repairs unevenness on the surface, restores the adhesion property of dirt, and maintains the anticorrosion effect. With the goal.

  The coating method for the heat exchanger of the air conditioner according to the present invention is the first hydrophilic film on the first hydrophilic film applied to the aluminum fin constituting the heat exchanger of the air conditioner. Applying a second hydrophilic film having different properties, forming a coating film having both hydrophilic and hydrophobic characteristics including silica fine particles and fluororesin particles on the second hydrophilic film; It is characterized by including.

  According to this invention, since the unevenness | corrugation of the surface of the deteriorated 1st hydrophilic film can be repaired, adhesion of stain | pollution | contamination can be suppressed and the anticorrosion effect can be maintained. Further, since the second hydrophilic film and the coating film are firmly adhered, the hydrophilic film can be further prevented from peeling off.

It is process drawing which shows the coating method of the heat exchanger which concerns on Embodiment 1 of this invention. It is a figure which shows the coating process of the heat exchanger which concerns on Embodiment 1 of this invention. Graph showing the relationship between the number of coatings and adsorbed water Model showing adhesion between coating film and second hydrophilic film

Embodiment 1 FIG.
Next, Embodiment 1 of the present invention will be described with reference to the drawings. In the following description of the drawings, the same or similar reference numerals are used for the same or similar parts. However, the drawings are schematic and ratios of dimensions and the like are different from actual ones. Accordingly, specific dimensions and the like should be determined in consideration of the following description, and the relationship and ratio of each other's dimensions may be different from the actual case even between the drawings.

FIG. 1 is a process diagram showing a heat exchanger coating method according to Embodiment 1 of the present invention.
FIG. 2 is a diagram showing the state of each step in FIG. This will be described below with reference to the drawings.

  In the figure, (a) shows an initial state of aluminum fins constituting the heat exchanger of the air conditioner before performing the coating method of the heat exchanger according to Embodiment 1 of the present invention. The surface of the first hydrophilic film 2 that has been applied to the surface of the aluminum fin 1 that has been used for a long period of time may be peeled off in some places because of being exposed to air or water, and may have thinned and deteriorated portions. . Further, dirt 3 such as dust or oil in the air is attached. Usually, the longer the period of use, the greater the degree of damage, and the greater the proportion of peeling, thinning, and deteriorated parts. Since unevenness occurs in the peeled or thinned portion, dirt easily accumulates in that portion, and a sufficient anticorrosive effect cannot be obtained. Furthermore, a part of the first hydrophilic film 2 may be embrittled.

  (B) in the drawing shows a state after the cleaning process is performed on the initial state (a). The cleaning process is preferably a method in which a cleaning liquid is injected at a high pressure using a nozzle or the like. With this method, not only can dirt be removed cleanly, but also the deteriorated portion of the first hydrophilic film 2 can be removed. Since the first hydrophilic film 2 has deteriorated and become brittle due to long-term use in the market, the first hydrophilic film 2 and the second hydrophilic film 4 are adhered by removing the deteriorated part. The sex can be increased.

  The cleaning liquid is not particularly limited, but acid or alkali is preferable. By using acid or alkali, when the surface of the first hydrophilic film 2 is deteriorated and has a low molecular weight, the deteriorated portion can be more effectively removed. Since the deteriorated portion is fragile, the adhesion with the second hydrophilic film 4 can be further improved by removing the deteriorated portion. As a result of the cleaning treatment, the dirt 3 and the deteriorated portion are removed from the aluminum fin 1, and the remaining first hydrophilic film 2 has a peeled or thinned portion.

  In the figure, (c) shows a state after the second hydrophilic film 4 is applied in the state (b). The second hydrophilic film 4 repairs the peeling or thinned portion of the first hydrophilic film 2 to form a flat surface. Next, the second hydrophilic film 4 will be described.

  The second hydrophilic film 4 desirably has a thickness of 0.5 μm or more and 50 μm or less. By having a film thickness in this range, peeling or thinning of the first hydrophilic film 2 can be sufficiently repaired. In addition, since the first hydrophilic film 2 generally has a thickness of about several μm, when the thickness of the second hydrophilic film is less than 0.5 μm, the peeled portion of the first hydrophilic film 2 cannot be repaired, The uneven shape is taken over. On the other hand, when the thickness is larger than 50 μm, the distance between adjacent aluminum fins 1 is narrowed, leading to a decrease in air volume and the like, and the performance may be deteriorated compared to the conventional heat exchange performance.

  Moreover, it is desirable that the second hydrophilic film 4 contains many polar groups such as OH groups, C═O groups, or NH groups. Since the coating film 5 uses an aqueous coating agent, it has been experimentally obtained that the silica particles constituting the film contain a large amount of adsorbed water even after being applied and dried.

FIG. 3 is a graph showing the relationship between the number of times of coating and adsorbed water. In the sample dried after applying the coating film 5, the temperature of the sample is increased in vacuum using a temperature-programmed desorption gas analyzer. The desorbed gas was detected with a mass spectrometer, and the water content was measured. The temperature-programmed desorption gas analyzer used here is ESCO-WA1000A, and the temperature of the sample stage is changed from room temperature to 1000 ° C. under conditions of a vacuum degree of 3 × 10 ⁻⁹ Torr and 1 ° C./sec. The moisture content of the separated gas was measured with a mass spectrometer. The measured mass number is M / z = 18.

  In the figure, according to the number of times of coating, the respective moisture amounts of no coating, one coating, and three coatings are indicated by solid lines. These solid lines indicate the physical adsorption water which is the water adsorbed almost by van der Waals force, the chemically adsorbed water which is the water adsorbed by hydrogen bond, and the OH group which is chemically bonded like Si-OH. It is thought that it consists of the integrated amount of chemically bound water. As can be seen from the figure, the amount of water increases as the number of coatings increases, and the silica particles constituting the coating film 5 contain a large amount of water such as adsorbed water and bound water.

  (D) in the figure shows a state after the coating film 5 is applied to the state (c). As the coating agent for the coating film 5, an aqueous coating agent having both hydrophilic and hydrophobic characteristics including silica fine particles and fluororesin particles is used. The second hydrophilic film 4 and the coating film 5 can obtain strong adhesion by forming a hydrogen bond between the polar group of the second hydrophilic film 4 and the adsorbed water of the coating film 5. FIG. 4 is a model diagram showing the adhesion.

  The coating film 5 is considered to obtain a certain degree of adhesion with the first hydrophilic film 2, but when the first hydrophilic film 2 is peeled off from the aluminum fin 1 due to deterioration over many years, the aluminum surface is exposed. In addition, since the aluminum surface is hydrophobic, sufficient adhesion cannot be obtained with the coating film 5 using an aqueous coating agent. Furthermore, even application may not be possible.

  Further, even when the first hydrophilic film 2 is brittle, it is considered that sufficient adhesion with the coating film 5 cannot be obtained. By applying the second hydrophilic film 4 having a large number of polar groups, the polar groups are exposed on the surface, and the coating film 5 can be applied more firmly. The material of the second hydrophilic film 4 is a general hydrophilic resin, for example, a material using water or a solvent including polyvinyl alcohol, polyamide resin, amino resin and the like. However, the properties such as viscosity are different from those of the first hydrophilic film 2. The first hydrophilic film 2 is generally applied by immersing the aluminum fin portion constituting the heat exchanger in a tank containing the first hydrophilic film 2, whereas the second hydrophilic film 4 is described later. As mentioned above, it originates in applying by the method of spraying or spraying.

  Further, in the above description, the cleaning agent is preferably an acid or an alkali. However, it is usually necessary to perform water cleaning after the cleaning to remove the cleaning agent. This is because the cleaning agent remains on the aluminum fins 1 if the water is not washed, and the aluminum is corroded. Aluminum is usually corroded at a pH of 3.5 or less or PH 8.5 or more. Therefore, the residual cleaning agent after cleaning can be neutralized by imparting alkaline properties to the second hydrophilic film 4 when the cleaning agent is acidic, and acidic properties when the cleaning agent is alkaline. If 1 is controlled within the range of PH3.5 to PH8.5, it is not necessary to perform a water washing step.

  As a method for imparting alkaline or acidic properties to the second hydrophilic film 4, for example, by adding a weakly acidic solution such as carbonic acid or a weakly alkaline solution such as sodium hydrogencarbonate, the second hydrophilic film 4 is made alkaline. Or the method of making it acidic etc. can be considered.

  The second hydrophilic film 4 is preferably applied by a method of spraying the material of the second hydrophilic film 4. It is because it can apply | coat easily in the state in which the air conditioner was installed, or the assembled state. Further, it may be atomized and sprayed.

  As a method for applying the second hydrophilic film 4, a thin rod-like material with a cloth soaked with the material of the second hydrophilic film 4 may be used. In this case, it is desirable to use what was made into the optimal shape for the heat exchanger made into object. When this method is used, only a necessary amount of the hydrophilic film material is used.

  Next, the coating agent for the coating film according to Embodiment 1 of the present invention will be described. The average particle size of the silica fine particles used in the coating agent described above is preferably 15 nm or less, particularly 4 to 15 nm, when measured by a light scattering method. Further, by using silica fine particles having a particle diameter in this range, when dried, the silica fine particles aggregate to form a denser film, and the silica dissolved in equilibrium in the aqueous coating composition Since the components increase, it can serve as a binder, and a relatively high strength coating film 5 can be obtained.

  Furthermore, since the light scattering of the silica fine particles is reduced, the transparency of the resulting coating film 5 is improved, and changes in the color tone and hue of the component surface can be suppressed. When the average particle size of the silica fine particles is less than 4 nm, the stability of the coating composition is lowered, and the obtained strength and antifouling performance may be lowered. Further, when the average particle size of the silica fine particles exceeds 15 nm, sufficient strength of the coating film 5 cannot be obtained.

  Moreover, content of the silica fine particle contained in a coating agent is 0.1-5 mass%, Preferably it is 0.3-2.5 mass%. If it is content of this range, the uniform thin coating film 5 can be formed on the aluminum fin 1 also by the spraying method mentioned later. When the silica content is less than 0.1% by mass, it is difficult to form a coating film at room temperature. On the other hand, when the content of the silica fine particles exceeds 5% by mass, the resulting coating film becomes non-uniform and cloudy, and cracks and peeling easily occur.

  The average particle diameter of the fluororesin particles contained in the coating agent is not particularly limited, but is preferably 50 nm to 500 nm, more preferably 100 nm to 250 nm. When the average particle diameter exceeds 500 nm, the hydrophobic portion of the resulting coating film becomes too large, or the unevenness of the coating film 5 becomes too large, and the antifouling performance may not be obtained. On the other hand, when the average particle size is less than 50 nm, the stability of the coating film 5 may not be obtained, or the hydrophobic portion may not be exposed on the surface of the coating film 5 and a desired antifouling performance may not be obtained. It is.

  The mass ratio of the silica fine particles and the fluororesin particles contained in the coating agent is 40:60 to 95: 5, preferably 50:50 to 90:10. If the mass ratio is within this range, the hydrophilic part composed of silica fine particles and the hydrophobic part composed of fluororesin particles have a good balance, and a coating film that can be cured at room temperature can be obtained. It can have antifouling performance. When the mass ratio of the fluororesin particles exceeds 60, the coating film is difficult to solidify only by drying at room temperature. Even if it can be solidified, it may become cloudy and the texture may be lost, or a coating film having a desired strength may not be obtained. On the other hand, if the mass ratio of the fluororesin particles is 5 or less, the hydrophobic part may be too small to obtain the desired antifouling performance.

  The moisture contained in the coating agent is not particularly limited. Further, the water content is not particularly limited, but should be appropriately adjusted according to the coating method. Generally it is 30-99.5 mass%. Further, an organic solvent or the like may be mixed in order to adjust the stability, coating property and drying property as the coating composition.

  In addition to the above components, the coating agent can further contain silica fine particles having an average particle diameter of 20 to 200 nm. By including silica fine particles having this range, fine irregularities can be formed on the surface of the resulting coating film, and the hydrophilicity of the coating film can be improved. If the average particle size of the silica fine particles is less than 20 nm, the coating film surface is not formed with irregularities of a desired size, and the effect may not be obtained. On the other hand, when the average particle size of the silica fine particles exceeds 200 nm, the surface unevenness of the resulting coating film becomes too large, and fine dirt is easily trapped by the surface unevenness, and the antifouling performance may be lowered.

  The coating agent may contain a surfactant, an organic solvent, or the like for the purpose of improving the wettability of the coating composition or the adhesion of the coating film. Moreover, you may contain a coupling agent and a silane compound, and when these are contained, the effect of a coating film strength improvement and hydrophilicity adjustment will be acquired.

  In the present embodiment, the coating method of the heat exchanger composed of aluminum fins has been described, but the present invention is not limited to aluminum fins. For example, the same effect can be obtained by coating the heat exchanger composed of copper fins by the same method.

  The coating method of the coating film 5 used in this embodiment may be applied by a spraying method so that it can be easily applied in a state where an air conditioner is installed or in an assembled state. The solution to be sprayed may be atomized and sprayed.

  With respect to the method for applying the second hydrophilic film 4 and the method for applying the coating film 5 used in the present embodiment, a dipping method can be used as long as the heat exchanger can be separated from the main body. If the dipping method is used, there is no remaining coating, and sufficient antifouling performance and anticorrosive effect can be obtained.

  1 Aluminum fin, 2nd hydrophilic film, 3 dirt, 4th hydrophilic film, 5 coating film

Claims (4)

  Applying a second hydrophilic film having a property different from that of the first hydrophilic film on the first hydrophilic film applied to the fins constituting the heat exchanger of the air conditioner; A method of coating a heat exchanger, comprising: forming a coating film having both hydrophilic and hydrophobic characteristics including silica fine particles and fluororesin particles on a second hydrophilic film.   The coating method for a heat exchanger according to claim 1, wherein the coating film contains silica fine particles having an average particle diameter of 2 to 15 nm and fluororesin particles having an average particle diameter of 50 to 500 nm.   3. The heat exchanger coating method according to claim 1, wherein the second hydrophilic film is formed with a film thickness of 0.5 μm or more and 50 μm or less.   4. The heat exchanger coating method according to claim 1, wherein the second hydrophilic film has a predetermined alkaline or acidic pH value. 5.

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