JP2584109B2 - Paint for water-repellent coating and heat exchanger coated with the paint - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a paint for coating the surface of a substrate for imparting water repellency, and a heat exchanger to which the paint is applied.

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

The proportion of air conditioner heat pump type air conditioners (hereinafter simply referred to as heat pumps) in air conditioners has been increasing rapidly, and more than half of household air conditioners and commercial room air conditioners are occupied. Most of the heat exchangers used in these heat pumps are fin tube type heat exchangers composed of aluminum fins and refrigerant pipes which are perpendicular to the 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, at the time of heating, in the outdoor heat exchanger, at the time of cooling described above,
The same phenomenon as the indoor heat exchanger occurs. If frost is formed on the heat exchanger, ventilation resistance increases, causing a decrease in the heating capacity.If the fin is further advanced, clogging of the fins due to frost occurs, in which case the heating operation is temporarily stopped and defrosting is performed. It is necessary to perform heating, which may cause a decrease in heating comfort. Therefore, in order to reduce the decrease in the cooling capacity and the heating capacity and to reduce the frost of the outdoor heat exchanger during heating, to reduce the number of times of defrosting, and to improve the comfort, the indoor unit and the It is good to always remove the condensed water on the fin surface of the heat exchanger of the outdoor unit. As a method therefor, there is a method in which condensed water is rolled off by making the fin surface water-repellent, and a tetrafluoroethylene resin such as the one proposed in Japanese Utility Model Laid-Open Nos. Coatings such as trifluoroethylene 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 narrow in order to increase the capacity and increase the total fin surface area. The fin spacing of current heat exchangers is generally about 2-3 mm and is expected to become increasingly narrower in the future. 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. Therefore, a high-performance fin material for a heat exchanger capable of constantly removing condensed water on the fin surface without lowering the cooling / heating capacity of the heat pump is desired, and a coating material capable of imparting higher water repellency is required.

Means for Solving the Problems In order to achieve this object, the present invention has a three-dimensional crosslinked body comprising two kinds of the following general formula (I) as constituent units, R: methyl group or phenyl group (I) a solution containing a silicone resin compound in which the R / Si ratio in the formula is greater than 1.0 and less than 1.7, and an inorganic material dispersed in the solution and having a surface subjected to hydrophobic treatment. The water-repellent coating paint is formed from the fine particles, and this paint is applied to the surface of the plate-like fin of the heat exchanger.

Action In addition to the water-repellent effect of the three-dimensionally crosslinked silicone-based resin compound, the surface of the substrate coated with the water-repellent coating paint having the above-described structure has surface and water droplets due to fine irregularities on the surface formed by inorganic fine particles. And the water repellency is extremely high.

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

In Examples 1 to 3 and Comparative Examples 4, 6, and 7, the surface was water-repellent to a coating agent containing various silicone resins in which the three-dimensionally crosslinked body was a constituent unit and R / Si in the base constituent unit was changed. 10 wt% or 7.5 wt% based on the solid content in the silicone resin coating agent of the inorganic powder subjected to the hydrophobizing treatment or the inorganic powder not subjected to the hydrophobizing treatment, and stirred and dispersed at room temperature. Create coating paint, thickness 0.5mm
Is applied by dip coating on an aluminum plate of No. 1 and dried and cured in a hot air drying oven at 150 ° C. for 30 minutes. Comparative Example 5
Similarly, a coating agent containing a silicone-based resin having an R / Si ratio of 1.6 using a three-dimensional crosslinked product as a structural unit is similarly applied to a 0.5 mm-thick aluminum plate by dip coating, and then dried in a hot-air drying oven at 150 ° C for 30 minutes.
It was dried and cured for minutes. Further, Comparative Example 8 shows that, for a coating agent containing a monomeric silicone resin having no three-dimensional crosslinked body, an inorganic powder whose surface was subjected to a hydrophobic treatment was applied to a solid content in the silicone resin coating agent. Ten
wt% or 7.5wt%, and dip-coated on a 0.5mm thick aluminum plate in the same
It was dried and cured for minutes. Evaluation of film strength is JIS: K
A -5400 pencil scratch test was performed. The water repellency effect was evaluated by measuring the contact angle with water. The pencil scratch test is a test for examining the scratch resistance of a coating film by cracking the coating film when the hardness of the pencil core is changed, and is represented by a pencil hardness symbol. Further, as shown in the figure, the contact angle with water is represented by the angle θ formed between the water droplet 3 formed on the surface of the sample 2 and the surface of the sample 2, and it can be said that the larger the contact angle θ, the higher the water repellency. The contact angle to 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, Examples 1 to 3 were Comparative Examples 5 in which no silica fine particles were added.
Compared with, the contact angle is greatly improved. Further, the water repellency is higher and the film formability is better than when silica fine particles whose surface is not subjected to hydrophobic treatment in Comparative Example 4 are added. Furthermore, R /
When the inorganic particles are added to the silicone resin having a Si ratio of 1.7 or more, the water repellency is significantly improved as in Examples 1 to 3 as can be seen from Comparative Examples 6 and 7, but the coating film strength is very weak. However, there is a problem in practical use. Also in the case of applying a coating agent containing a monomeric silicone resin compound having no three-dimensional crosslinked product of Comparative Example 8, the same effect as in Examples 1 to 3 was observed by adding silica fine particles. Also However, the film strength is extremely weak, and practical application is difficult. That is, in the present example, the water repellency was able to be greatly improved, and the film strength and film formability were able to be improved.

This is because when a fine powder is added to a water-repellent resin, the surface of the water-repellent resin becomes water-repellent, and in addition, the contact area of the droplet becomes smaller due to the fine irregularities of the fine powder. Greatly reduces the adhesion between the droplets and the fin surface,
It is considered that the water repellency becomes higher (morphological effect). It is also considered that the addition of inorganic fine particles whose surface has been hydrophobized results in significantly improved dispersibility and improved film formability as compared with the case where fine particles not subjected to surface treatment are added.
Further, when a silicone-based resin compound that is a three-dimensionally crosslinked body is used, crosslinking between the resinous compounds proceeds, resulting in a three-dimensional network structure, and a coating film having excellent strength. On the other hand, a monomeric silicone resin having no three-dimensional crosslinked product has a weak bond between constituent units and does not form a strong coating film.

Effects of the Invention As described above, in the present invention, a coating material for a water-repellent coating has a three-dimensionally crosslinked body as a constituent unit, and a solution containing a silicone-based resin compound having an R / Si ratio of greater than 1.0 and less than 1.7, It is composed of inorganic fine particles dispersed in a solution and the surface of which has been hydrophobized, and is excellent in film formability and extremely high in film by applying, drying and curing this paint for water repellent coating. A film exhibiting strength and water repellency is obtained. When this water-repellent coating paint is applied to the fin material for heat exchangers and the heat exchanger is configured, even if the fin spacing is as narrow as about 2 mm, effective performance to roll off water droplets condensed on the fin surface Have. Therefore, by delaying the clogging between the fins due to the frost formation of the heat exchanger of the heat pump air conditioner, the heat pump reduces the cooling capacity and the heating capacity and reduces the defrosting interval of the heating outdoor heat exchanger. It can be extended and comfort can be improved.

[Brief description of the drawings]

 The figure illustrates the contact angle. 1 ... substrate, 2 ... sample, 3 ... water droplet, 4 ... contact angle.

Claims (3)

(57) [Claims] 1. A silicone resin having a three-dimensional crosslinked body comprising two kinds of the following general formula (I) as constituent units, wherein the R / Si ratio in the formula (I) is larger than 1.0 and smaller than 1.7. A water-repellent coating composition comprising a solution containing a compound and inorganic fine particles. R: methyl group or phenyl group 2. The water-repellent coating composition according to claim 1, wherein the surface of the inorganic fine particles to be added is subjected to a hydrophobic treatment. 3. A plurality of plate-like fins, which are arranged in parallel at regular intervals and through which an air current flows, and a heat transfer tube inserted at right angles to the plate-like fins, wherein the plate-like fins have the following general formula ( A solution containing a silicone-based resin compound having a three-dimensional crosslinked body having two types of constituent units (I) and wherein the R / Si ratio in the formula (I) is greater than 1.0 and less than 1.7; Heat exchanger coated with paint. R: methyl group or phenyl group