JPH05222339A - Water-repellent coating composition and heat exchanger coated with water-repellent coating composition - Google Patents

Abstract

PURPOSE:To prepare the title compsn. capable of forming a water-repellent film which is excellent in adhesion to a substrate surface, retards the clogging due to frosting between fins of a heat exchanger, and reduces the decrease in heating capacity. CONSTITUTION:The title compsn. is prepd. by compounding a silicone resin soln., a resin modifier having at least two kinds of reactive group in the molecule, and fine inorg. particles having a particle size of 4mum or lower in an amt. of 5-60wt.% based on the solid content of the soln.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a composition for coating a substrate surface for the purpose of imparting water repellency and a heat exchanger used in a cooling system such as an air conditioner or a refrigerating machine. is there.

[0002]

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

In the air conditioners, the ratio of air heat source heat pump type air conditioners (hereinafter simply referred to as heat pumps) is increasing rapidly, and more than half of household room air conditioners and commercial room air conditioners account for more than half. ing. Most of the heat exchangers used in these heat pumps are fin-tube type heat exchangers which are composed of aluminum fins and a refrigerant pipe that is orthogonal to the aluminum fins. In a heat pump, water is condensed on the fin surface of the indoor heat exchanger during cooling, and the bridge phenomenon of condensed water between the fins causes a reduction 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 forms on the heat exchanger, ventilation resistance increases, causing a decrease in heating capacity.Further progressing causes clogging of fins due to frost formation, in which case heating operation is temporarily stopped and defrosting is performed. Since it is necessary to do so, it also causes 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 formation on the outdoor heat exchanger during heating, reduce the number of defrosting, and 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 of making the fin surface water-repellent and rolling off the condensed water, which is disclosed in Japanese Utility Model Publication No. 48-11414 and Japanese Utility Model Publication 51.
Coatings of tetrafluoroethylene resin, chlorotrifluoroethylene resin, and the like as proposed in Japanese Patent No. 15261 are known.

[0004]

On the surface of the fin material coated with the resin having excellent water repellency, it is possible to roll off a relatively large amount of condensed water having a diameter of 2 mm or more from the surface of the fin. As a material, 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 the fins in order to increase the capacity. The fin spacing of the current heat exchanger is generally about 2 to 3 mm, and it is considered that the fin spacing will be further reduced from now on. Therefore, it is not possible to drop fine water droplets having a diameter of about 1 mm from the fin surface by the method of applying the resin having excellent water repellency. Therefore, since the water droplets remaining on the fin surface accumulate between the fins, the water repellent effect is insufficient, such as resistance to ventilation, or freezing and frosting.

Therefore, the present invention provides a fin material for a high-performance heat exchanger, which is provided with a coating material capable of imparting higher water repellency and capable of constantly removing condensed water on the fin surface so as not to lower the cooling and heating capacity of the heat pump. Is provided.

[0007]

In order to achieve this object, the water-repellent coating composition of the present invention contains at least 2 in a solution and a molecule of a silicone resin compound which is generally known to have high water repellency. It is composed of a resin modifier having different kinds of functional groups and inorganic fine particles having a particle size of 4 μm or less and having a composition ratio of 5 to 60% by weight with respect to the solid content in the solution.

[0008]

In addition to the water-repellent effect of the silicone resin, the surface of the base material coated with the water-repellent coating composition having the above-mentioned structure has a fine contact between the surface and water droplets due to the fine irregularities on the surface formed by the inorganic fine particles. It becomes smaller and the water repellency becomes significantly higher. Further, due to the effect of the resin modifier having at least two kinds of functional groups in the molecule, the bond between the silicone-based resin and the inorganic fine particles and between the silicone-based resin and the substrate surface becomes stronger.

[0009]

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

In Examples 1 to 6, inorganic fine particles having a predetermined particle diameter were added to the solid content in the silicone resin coating agent.
30%, 10% of various resin modifiers as active ingredients are added, stirred and dispersed at room temperature to prepare a coating composition,
Dip coating on a 0.5 mm thick aluminum plate,
It was dried and cured for 60 minutes in a hot air drying oven at ℃.
Further, in Comparative Examples 2 to 9, a predetermined amount of inorganic fine particles having a predetermined particle diameter was added to the silicone resin coating agent with respect to the solid content in the silicone resin coating agent, and the mixture was stirred and dispersed at room temperature to obtain a coating composition. Example 3
As in Nos. 5 to 5, the aluminum plate having a thickness of 0.5 mm was dip-coated and dried and hardened in a hot air drying oven at 100 ° C. for 60 minutes. In Comparative Example 1, only the silicone resin coating agent was similarly applied by dip coating to an aluminum plate having a thickness of 0.5 mm and dried and hardened in a hot air drying oven at 100 ° C. for 30 minutes.

The coating film was evaluated by the adhesion of the coating film and the water repellency effect. Regarding adhesion, JIS: K-54
The pencil scratching test with 00 and water repellency were evaluated by measuring the contact angle with water. The contact angle with respect to water is represented by the angle θ formed by the water droplet 3 formed on the surface of the sample 2 of the base material 1 and the surface of the sample 2 as shown in FIG. It can be said that it is highly water-based. The contact angle to water was measured with a contact angle meter DA-T type manufactured by Kyowa Interface Science.

The results are shown in Table 1.

[0013]

[Table 1]

As can be seen from Table 1, in Examples 1 to 6 and Comparative Examples 3, 4, 5, 6, 8, and 9, the contact angles with water were only those of Comparative Examples 1 and 2 or the silicone type resins. The contact angle is remarkably larger than that of the silicon dioxide powder added in an amount of 2% by weight and the silicon dioxide powder of Comparative Example 7 having a particle diameter of 8 μm added. That is, by adding 5 wt% or more of silicon dioxide powder having a particle size of 4 μm or less,
It shows that the water repellency is significantly improved. This is because when fine particles are added to the water-repellent resin, the surface is made water-repellent by the water-repellent resin, and fine unevenness is formed on the surface by adding the fine particles. 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 is increased (morphological effect).

However, when the silicon dioxide powder is added in an amount of 70% by weight or more, the water repellency is improved, but the coating film itself becomes brittle, and a good coating film cannot be obtained due to cracking.
If the particle size exceeds 4 μm and the addition amount is less than 5% by weight, it is considered that effective fine unevenness does not occur and the effect of improving water repellency is reduced.

As the fine particles to be added, inorganic silica was used in the present embodiment, but it is considered that any fine particles capable of imparting fine irregularities on the surface have the same effect. On the other hand, regarding the adhesion of the coating film, Comparative Examples 1 to 6
Therefore, as the amount of silicon dioxide powder added increases, the tendency tends to deteriorate. This is because some of the reactive groups such as silanol groups contained in the silicone resin that contribute to the adhesion to the substrate surface are
It is considered that it is consumed for bonding with the added inorganic fine particles, so that the chance of bonding between the substrate and the water repellent coating composition is reduced. On the other hand, as in Examples 1 to 6, at least two kinds of reactive groups in the molecule, that is, methoxy group, ethoxy group, silanol group, a reactive group that chemically bonds to an inorganic material, a vinyl group, and an amino group are added to the silicone resin. By adding a resin modifier having a reactive group that chemically bonds with an organic material such as a group, the adhesion is improved to the same level as that without silicon dioxide. In particular, the effect of the resin modifier having an amine functional group in the molecule of Examples 1 to 4 is greater.

In Examples 1 to 6, resin modifiers having a methoxy group or the like which is a functional group chemically bonded to an inorganic material and an amino group or the like which is a functional group chemically bonded to an organic material are used in the molecule. It is considered that this is because the addition of the silicone resin strengthens the bond between the silicone resin and the inorganic fine particles, increases the strength of the coating film itself, and increases the bonding opportunities between the substrate and the water-repellent coating composition.

From the above results, it is possible to provide a water repellent coating composition having excellent water repellency and capable of firmly bonding to a substrate by adding inorganic fine particles and a resin modifier to a silicone resin.

[0019]

As described above, in the present invention, a solution comprising a silicone resin compound generally known to have high water repellency and a resin modifier having at least two kinds of functional groups in the molecule and a particle size of 4 μm. The composition is composed of inorganic fine particles having a composition ratio of 5 to 60% by weight based on the solid content of the solution, and the substrate coated with the water repellent coating composition has a very high water repellency. And shows a strong bond with the substrate. 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 interval 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 as a 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 diagram illustrating a contact angle.

[Explanation of symbols]

 1 substrate 2 sample 3 water droplet θ contact angle

Claims (2)

[Claims] 1. A solution comprising a silicone resin compound and a resin modifier having at least two kinds of functional groups in a molecule, a particle size of 4 μm or less, and a composition ratio of 5 to 60 with respect to a solid content in the solution. A water-repellent coating composition comprising inorganic fine particles in a weight percentage. 2. A plate-like fin in which a large number of plate-like 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 into the plate-like fin, and a solution containing a silicone resin compound and A resin modifier having at least two kinds of functional groups in the molecule and a particle size of 4 μm or less,
The composition ratio to the solid content in the solution is 5 to 60% by weight.
A heat exchanger coated with a composition for water-repellent coating, which comprises