JP2507119B2 - Water-repellent coating composition and heat exchanger coated with the water-repellent coating composition - Google Patents

Description

TECHNICAL FIELD The present invention relates to a composition for coating the surface of a substrate for the purpose of imparting water repellency, and cooling of air conditioners, freezers and refrigerating machines to which the composition is applied. It relates to a heat exchanger used in the system.

2. Description of the Related Art Silicone-based or fluorine-based resin compounds have been put to practical use in many fields as coating materials and surface treatment agents that have excellent water repellency and lubricity and take advantage of their properties. For example, it is also effective as a surface treatment for a heat exchanger of an air conditioner.

In air conditioners, the proportion of air-heat-source heat pump type air conditioners (hereinafter referred to as heat pumps) has been rapidly increasing, and home air conditioners, business room air conditioners, etc. account for more than half.
Further, most of the heat exchangers used in these heat pumps are fin-tube type heat exchangers composed of aluminum fins and refrigerant pipes that are orthogonal to the aluminum fins. In a heat pump, when cooling, moisture condenses on the fin surfaces of the indoor heat exchanger, and a bridge phenomenon of condensed water between the fins causes a decrease in the air volume passing through the heat exchanger, which in turn causes a decrease in cooling capacity. . On the other hand, during heating, in the outdoor heat exchanger, the same phenomenon as in the indoor heat exchanger occurs during cooling as described above. When frost is formed on the heat exchanger, ventilation resistance increases, which causes a decrease in heating capacity.Further progressing causes clogging of fins due to frost formation.
In that case, it is necessary to temporarily stop the heating operation and perform defrosting, which may cause deterioration of comfort of heating. Therefore, in order to reduce the decrease in the cooling capacity and the heating capacity, reduce the frost formation of the outdoor heat exchanger during heating, reduce the number of defrosting times, and improve the comfort, in order to improve the indoor unit and the outdoor unit, It is only necessary to always remove the condensed water on the fin surface of the heat exchanger. As a method therefor, there is a method of making the surface of the fin water-repellent and rolling off condensed water, such as a tetrafluoroethylene resin and a chloride as proposed in Japanese Utility Model Publication Nos. 48-11414 and 51-15261. Coatings such as trifluorinated ethylene resin are known.

Problems to be Solved by the Invention On the fin material surface coated with the resin having excellent water repellency, relatively large condensed water having a diameter of 2 mm or more can be rolled off from the fin surface, and as a fin material for a heat exchanger. Some effects can be expected. However, in recent heat exchangers, the fin spacing tends to be narrowed in order to increase the total surface area of fins for the purpose of high performance. The fin interval of the current heat exchanger is generally about 2 to 3 mm, and it is considered that the fin interval will be further narrowed. Therefore, in the method of applying a resin having excellent water repellency, fine water droplets having a diameter of about 1 mm cannot be dropped from the fin surface. Therefore, the water-repellent effect of the water droplets remaining on the fin surface was insufficient, such as a resistance to ventilation or frost as it was, because it remained between the fins.

The present invention solves the above problems and imparts higher water repellency in order to provide a high-performance heat exchanger fin capable of constantly removing condensed water on the fin surface so as not to reduce the heating and cooling capacity of the heat pump. A coating composition is provided.

Means for Solving the Problems To achieve this object, the water-repellent coating composition of the present invention has a water contact angle of the coating film surface after coating drying and curing.
It is composed of a solution of a resin compound having a degree of 90 ° or more, and inorganic or organic fine particles dispersed in the solution and capable of imparting fine irregularities to the surface after curing the coating film.

Further, a solution comprising a resin compound such that the water contact angle of the coating film surface after coating and drying and curing on the surface of the plate-like fin is 90 degrees or more, and dispersed in the solution, fine irregularities on the surface after coating film curing. It is a layer formed of inorganic or organic fine particles capable of imparting.

The surface of the base material coated with the water-repellent coating composition having the above-described structure has a water-repellent effect of the coating film itself and, due to fine irregularities on the surface formed of inorganic or organic fine particles, a contact area between the surface and water droplets. Becomes smaller and the water repellency becomes significantly higher. Therefore, by forming the water-repellent coating composition on the surface of the plate-shaped fin of the heat exchanger, water droplets can be rolled off from the surface of the plate-shaped fin.

Example One example of the present invention will be described below.

Examples 1 to 3 in the table show various inorganic fine particles for a silicone-based resin coating agent or a fluorine-based coating agent and a polypropylene-based coating agent, which have a contact angle to water after paint drying and curing of 90 degrees or more. Add a specified amount to the solid content of the coating agent, stir and disperse at room temperature to create a coating composition, and have a thickness of 0.5 mm.
It is applied by dipping onto an aluminum plate of No. 1 and dried and cured for 60 minutes in a hot air drying oven at 100 ° C. Further, in Comparative Example 1, similarly, a coating agent such as an acrylic resin having a contact angle with water of less than 90 degrees is similarly dip-coated on an aluminum plate having a thickness of 0.5 mm and dried in a hot air drying oven at 100 ° C. for 30 minutes. It is a cured product. The coating film was evaluated by the water repellency effect. The water repellency was evaluated by measuring the contact angle with water. The contact angle with respect to water is represented by an angle θ ′ formed by the water droplet 2 formed on the surface of the sample 1 and the surface of the sample 2 as shown in the figure. The larger the contact angle θ ′, the more the water repellency becomes. It can be said to be expensive. The contact angle with water was measured with a contact angle meter DA-T manufactured by Kyowa Interface Science.

 The results of these evaluations are shown in the table.

As can be seen from the table, in Examples 1 to 3, the contact angle with respect to water is significantly larger than that of the acrylic resin of Comparative Example 1 or the like. That is, it is shown that the water repellency is significantly improved in this example. This is a water repellent resin,
When the fine particles are added, the surface becomes water-repellent by the water-repellent resin, and in addition, when the fine particles are added, fine irregularities are formed on the surface. Therefore, it is considered that the contact area between the water droplet and the surface becomes small, the adhesive force of the water droplet on the surface is significantly reduced, and the water repellency becomes high (this is called a morphological effect).

And, Fig. 1 shows a schematic diagram of water droplets on the surface where the contact angle with water is 90 degrees or more and the surface has irregularities, and Fig. 2 shows the surface with a contact angle with water of less than 90 degrees. The schematic diagram of the water drop on the surface at the time of providing unevenness | corrugation is shown.
Here, 1 indicates the sample surface, and 2 indicates water droplets. The contact angle of the sample surface itself with water is represented by θ ′, which is called the true contact angle. Further, the contact angle of water on the horizontal plane is represented by θ ′, which is called an apparent contact angle. As can be seen from FIG. 1 and FIG. 2, the apparent contact angle θ ′ of the water droplet on the surface when the contact angle with water is 90 ° or more and the surface is uneven.
Is significantly larger than the true contact angle θ. That is, the contact area between the surface and the water droplets is greatly reduced, and the water repellency is improved. On the contrary, the apparent contact angle θ ′ of the water droplet on the surface when the unevenness is provided on the surface having a contact angle with water of less than 90 degrees is significantly smaller than the true contact angle θ. That is, the contact area between the surface and the water droplets is greatly increased, and the hydrophilicity is improved.

As described above, from the results of this time, a solution composed of a resin compound such that the water contact angle of the coating film after the coating is dried and cured is 90 degrees or more, and dispersed in the solution, fine irregularities are formed on the surface after curing the coating film. The surface coated with a water-repellent coating agent composed of impartable inorganic or organic fine particles exhibits extremely high water repellency as compared with conventional water-repellent coating agents. Incidentally, as the powder to be added, in this embodiment, inorganic silica was used, but the powder is not limited to this, and any inorganic or organic fine particles capable of imparting fine irregularities to the surface are the same. I think it has an effect.

Therefore, by applying the water-repellent coating treatment to the surface of the plate-shaped fins of the heat exchanger, it is possible to reliably remove water droplets and to manufacture a small heat exchanger.

Effects of the Invention As described above, in the present invention, a solution comprising a resin compound such that the water contact angle of the coating surface after coating drying and curing is 90 degrees or more, and dispersed in the solution, the surface after coating coating curing It is composed of inorganic or organic fine particles capable of imparting fine irregularities, and a substrate coated with this water-repellent coating composition exhibits extremely high water repellency. When this heat-repellent coating composition is applied to a fin material for a heat exchanger to form a heat exchanger, even if the fin spacing is as narrow as 2 mm, effective performance for rolling off water droplets condensed on the fin surface. Have. Therefore, by delaying the clogging between the fins due to frost formation on the heat exchanger of the heat pump air conditioner, it is possible to reduce the decrease in cooling capacity and heating capacity of the heat pump, and to reduce the defrosting interval of the outdoor heat exchanger during heating. It can be extended and can improve comfort.

[Brief description of drawings]

Fig. 1 is a schematic diagram explaining the contact angle, Fig. 2 is a schematic diagram of water droplets on the surface when the surface has a contact angle of 90 degrees or more, and Fig. 3 is the contact angle with water. But
The schematic diagram of the water drop on the surface at the time of providing unevenness on the surface which is less than 90 degrees is shown. 1 ... Substrate, 2 ... Sample, 3 ... Water drop, θ ... Contact angle.

Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI Technical display area F28F 1/32 F28F 1/32 G

Claims (2)

(57) [Claims] 1. The water contact angle of the coating film surface after the coating is dried and cured is 90.
A water-repellent coating composition composed of a solution of a resin compound having a degree of control of more than one degree, and inorganic or organic fine particles dispersed in the solution and capable of imparting fine irregularities to the surface after curing of a coating film. 2. A plate-shaped fin in which a large number of plate-shaped fins are arranged in parallel at a constant interval and through which an air flow flows, and a heat transfer tube inserted at a right angle to the plate-shaped fin, and the surface of the plate-shaped fin is coated and dried. A solution comprising a resin compound such that the water contact angle of the coating film after curing is 90 degrees or more, and an inorganic or organic fine particle layer dispersed in the solution and capable of imparting fine irregularities to the surface after curing the coating film. A heat exchanger coated with the composition for water-repellent coating formed by forming.