JPH08259851A - Water-repelling coating film, water-repelling coating material and fin for heat-exchanger - Google Patents

Abstract

PURPOSE: To provide a water-repelling coating film containing fluororesin powder having large particle diameter and fluororesin powder having small particle diameter in a state dispersed in the coating film and exposed on the surface of the film, having excellent water-repellency and free from the lowering of the water-repellency even after the use over a long period. CONSTITUTION: This coating film contains (A) fluororesin powder having an average particle diameter of 4.8-10μm and (B) fluororesin powder having an average particle diameter of 0.7-1.2μm in a state dispersed in the coating film and at least partly exposed on the surface of the film. The particle size distributions of the component A and the component B are preferably 3-15μm and 0.3-1.5μm, respectively. Preferably, the sum of the amounts of the component A and the component B is 15-80vol.% in terms of solid component and the amount of the component A is not smaller than that of the component B. The fluororesin constituting the components A and B is preferably a tetrafluoroethylene resin fluorinated to the terminals and having a molecular weight of 500-20,000. The binder resin to be used as a base is preferably different from the fluororesin powder.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a water repellent material.

[0002]

BACKGROUND OF THE INVENTION In various fields, it has been required to make a surface water-repellent. For example, in the heat exchanger fins constituting the heat exchanger, it has been sought to make the surface hydrophilic, but recently it has been proposed to make the surface water repellent. . That is, in order to prevent the increase of ventilation resistance due to the adhesion of condensed water generated during the operation of the heat exchanger and prevent the decrease of the heat exchange rate, it is possible to use aluminum excellent in lightness, workability and heat conductivity. Alternatively, the surface of the heat exchanger fin made of an aluminum alloy (hereinafter referred to as Al) is made hydrophilic (water wettable) so that even if condensed water adheres, it spreads immediately and the ventilation resistance does not increase. That is, if the surface is made hydrophilic, even if water droplets adhere, they spread laterally and the gaps between the heat exchanger fins are not blocked by water droplets. Therefore,
So far, research and development have been conducted on how to make the heat exchanger fin surface hydrophilic.

By the way, making the surface of the heat-exchanger fin hydrophilic makes it easier to wet with water, which means that mold and the like are also likely to propagate. Further, the hydrophilic film easily adsorbs the odorous components, and the adsorbed odorous components are released with the start of operation. As described above, making the surface of the heat-exchanger fin hydrophilic becomes a problem from the environmental point of view.

However, when the fin surface for the heat exchanger is made water repellent, condensed water can be prevented from adhering, the heat exchange rate can be improved, and the growth of mold and the like can be suppressed because water hardly adheres to the environment. From the aspect, it also produces a preferable result. In addition, when the heating operation is performed in the winter, frost formation on the outdoor unit heat exchanger is suppressed, and the defrosting time is shortened. From this point of view, it has been proposed to make the surface of the heat exchanger fin water-repellent.

Various proposals have hitherto been made as techniques for making the surface water repellent. For example, as disclosed in JP-A-6-122838 and JP-A-6-122839, a technique of dispersing graphite fluoride powder or tetrafluoroethylene resin powder in a coating film has been proposed. In the field of heat exchanger fins, as disclosed in JP-A-3-139571 and JP-A-5-117637,
A technique for dispersing inorganic or organic particles in a coating film made of a fluororesin or a silicone resin has been proposed.

However, these proposals have not been sufficient.

[0007]

DISCLOSURE OF THE INVENTION An object of the present invention is to provide a material exhibiting water repellency. The object of the present invention is to provide a fluororesin powder having an average particle diameter of 4.8 to 10 μm and an average particle diameter of 0.1.
It is achieved by a water-repellent coating film characterized in that a fluororesin powder of 7 to 1.2 μm is dispersed in the coating film, and at least a part of the fluororesin powder is exposed on the surface. It

Also, a coating film is provided on the surface of the heat exchanger fin made of aluminum or aluminum alloy, and in this coating film, a fluorine resin powder having an average particle size of 4.8 to 10 μm and an average particle size are provided. Of 0.7 to 1.2 μm is dispersed, and at least a part of the fluororesin powder is exposed on the surface. .

Further, it contains a fluorine-based resin powder having an average particle diameter of 4.8 to 10 μm, a fluorine-based resin powder having an average particle diameter of 0.7 to 1.2 μm, a binder resin, and a solvent. Achieved by the characteristic water-repellent paint.

In the above invention, the average particle size is 4.
Fluorine-based resin powder of 8 to 10 μm has a particle size distribution of 3.0.
˜15 μm, average particle size 0.7-1.2
The particle size distribution of the fluorine-based resin powder of μm is 0.3 to 1.5.
Those in the range of μm are preferable. That is, the water repellency is more effectively exhibited by adopting the fluororesin powder defined in this way.

Further, the sum of the content of the fluororesin powder having an average particle size of 4.8 to 10 μm and the content of the fluororesin powder having an average particle size of 0.7 to 1.2 μm is 15 solids. ~ 80
vol% and (average particle size of 4.8 to 10 μm
Content of fluorinated resin powder) ≧ (average particle size is 0.7 to
It is preferable that the content of the fluorine-based resin powder is 1.2 μm). That is, the water repellency is more effectively exhibited by defining the content of the fluororesin powder in this way.

Various kinds of binder resins can be used as the binder resin constituting the coating film of the present invention. For example, vinyl chloride resin, olefin resin, styrene resin, ester resin, amide resin, acrylic resin, epoxy resin, urethane resin, fluorine resin, silicon resin, etc. can be used. The base binder resin is preferably a resin different from the fluororesin powder mixed and dispersed.

Examples of the fluorine-based resin constituting the fluorine-based resin powder used in the present invention include tetrafluoroethylene resin, low-polymerization degree tetrafluoroethylene and graphite fluoride (preferably having an unbound fluorine content of A resin such as 3 wt% or less of graphite fluoride) (graphite fluoride is also a kind of fluorine resin in this specification) is used. Preferred is a tetrafluoroethylene resin having a molecular weight of 500 to 20000 (particularly 600 to 15000). Further, it is preferable that the terminal is fluorinated.
That is, it is preferable that the tetrafluoroethylene resin having a molecular weight of 500 to 20,000 be fluorinated up to the end.

The present invention is characterized in that two or more kinds of fluororesin powder are used instead of using one kind of fluororesin powder. For example, JP-A-6-122
As disclosed in Japanese Patent No. 838 and Japanese Patent Laid-Open No. 6-122839,
Not only one type of fluororesin powder is used. When only one type of fluororesin powder as in these publications is used, in order to obtain a higher water repellent surface, PTF
When the content of E was increased, water repellency was obtained in the initial stage, but after washing with water or the like, the water repellency was significantly reduced, which was not practical. As a result of earnestly studying this point and further research, a fluorine-based resin powder having an average particle diameter of 4.8 to 10 μm and a fluorine-based resin powder having an average particle diameter of 0.7 to 1.2 μm were obtained. It was found that at least resin powder should be used.

It is to be noted that the complete reason why the water repellency can be ensured for a long period of time by using the fluorine-based resin powder having the above characteristics has not been obtained at present. However, at the early stage of the achievement of the present invention, it was considered that the fluorine-based resin powder had fallen off from the coating film. For example, when a small fluorine-based resin powder having an average particle size of 0.7 to 1.2 μm is merely dispersed in the coating film, the fluorine-based resin powder is small and therefore strong in the coating film. It was thought that the water repellency was suddenly reduced because it was not retained on the surface and was easily removed. However, the average particle size is 4.8 to 10 μm
When a large fluorinated resin powder such as the one shown in Table 1 was dispersed in the coating film, the fluorinated resin powder should be firmly held in the coating film because it is large, and it was thought that it would not fall off. However, even in this case, the water repellency was drastically reduced. For this reason, it is unlikely that the falling of the fluororesin powder from the coating film is a decisive factor. Also, it was thought that it was due to the difference in the surface state, but since it shows a large water repellency in any case at the initial stage, it is difficult to think that this is a decisive factor. As described above, although the detailed reason has not been completely clarified, a fluorine-based resin powder having an average particle diameter of 4.8 to 10 μm and a fluorine-based resin powder having an average particle diameter of 0.7 to 1.2 μm are used. Is dispersed in the coating film, and when at least a part of the fluororesin powder is exposed on the surface,
Large water repellency was secured for a long time from the initial point. And no one has proposed the idea of dispersing two or more kinds of fluororesin powder in the coating film.

Next, regarding the particle size distribution of the fluororesin powder, in the production of the fluororesin powder, the fluororesin powder having an average particle size of 4.8 to 10 μm generally has a particle size distribution of 3. The fluororesin powder having an average particle size of 0.7 to 1.2 μm has a particle size distribution of 0.3 to 1.5 μm. Of course, it may be possible to manufacture a fluorine-based resin powder that deviates from this value, but in terms of cost, etc., it becomes the above.

Further, the fluorine-based resin powder having an average particle diameter of 4.8 to 10 μm is non-spherical (lumpy and has irregularities), as can be seen from FIG. 1 (SEM photograph). On the other hand, the fluorine-based resin powder having an average particle diameter of 0.7 to 1.2 μm is spherical, as can be seen from FIG. 2 (SEM photograph). This shape is from the viewpoint of manufacturing the fluororesin powder. The reason why the small fluorinated resin powder is preferably spherical is considered as follows. That is, in order to efficiently interpose the small fluorine-based resin powder between the large fluorine-based resin powders, it was considered that the spherical shape has a higher packing density and the higher the water repellency.

The higher the content of the fluorine-based resin powder, the more the water repellency. Therefore, the average particle size is 4.8.
It is preferable that the sum of the content of the fluororesin powder having a particle size of 10 μm and the content of the fluororesin powder having an average particle size of 0.7 to 1.2 μm is 15 vol% or more of the solid content. It is more preferably 25 vol% or more, still more preferably 45 vol% or more, and further preferably 60 vol% or more. A preferable upper limit value is 80 vol%. That is, when the amount is too large, the strength of the coating film decreases.

The relationship between the content of the fluororesin powder having an average particle diameter of 4.8 to 10 μm and the content of the fluororesin powder having an average particle diameter of 0.7 to 1.2 μm is as follows: 4.8
It is preferable that the content of the fluororesin powder A of 10 μm) ≧ (the content of the fluororesin powder B having an average particle size of 0.7 to 1.2 μm). That is, considering that the small fluorine-based resin powder B is present between the large fluorine-based resin powder A, the relatively large amount of the large fluorine-based resin powder A is preferable. Further, more preferably 1/100 ≦ B content / A content ≦ 1/5.

To form a coating film in which a fluororesin powder having an average particle diameter of 4.8 to 10 μm and a fluororesin powder having an average particle diameter of 0.7 to 1.2 μm are dispersed, the above-mentioned fluorine is used. System resin powder, binder resin, solvent, and if necessary, surfactant, lubricant, stabilizer, etc. are added, kneaded, coated by various coating means such as dipping or roll coating, and dried. Good. In the case of heat exchanger fins, the coating material may be applied to the surface of the Al material and then formed into a heat exchanger fin, or the surface may be formed after forming into a heat exchanger fin. You may apply the said coating material.

The present invention will be specifically described below with reference to examples.

[0022]

【Example】

Example 1 PTFE powder A fluorinated to the end having an average particle size of 5 μm (particle size distribution: 3 to 15 μm, particle shape is lump shown in FIG. 1, melting point 315 ° C., average molecular weight 8500,
True specific gravity 2.2, bulk specific gravity 4), and PTFE powder B (particle size distribution 0.3-
1.5 μm, particle shape is spherical as shown in FIG. 2, melting point 90-2
50 ° C., average molecular weight 700 to 1500, true specific gravity 2.3,
Bulk density 2), acrylic resin, solvent (isopropyl alcohol), PTFE powder A and PTFE powder B
Desired ratio (60% by volume of PTFE powder A, PTF
E powder B was blended so as to be 5 vol%), and sufficiently mixed and dispersed to prepare a water-repellent coating material.

This water-repellent coating is made of Al material (A1050)
It was applied to the surface so that the thickness after baking was 5 μm, and after baking, it was formed into a fin for a heat exchanger. A schematic cross-sectional view of this heat exchanger fin is shown in FIG. In FIG. 3, 1 is a fin base for heat exchanger made of Al material, 2 is a coating film, 3 is PTFE powder A having an average particle size of 5 μm, and 4 is an average particle size.
It is a PTFE powder B of μm.

[Second Embodiment] In the first embodiment, the PTFE
The same operation was performed except that the powder A was adjusted to 65 vol% and the PTFE powder B was adjusted to 7 vol%. [Example 3] In Example 1, the PTFE powder A was 55
Vol% and PTFE powder B were made to be 3 vol%, and the same operation was performed.

[Fourth Embodiment] In the second embodiment, the PTFE
The same procedure was performed except that a PTFE powder having an average particle size of 8 μm (particle size distribution: 3 to 15 μm, particle shape: lump shown in FIG. 1) was used as the powder A. Example 5 In Example 2, PTFE powder having an average particle size of 0.8 μm (particle size distribution 0.3 to 1.5 μm, particle shape is spherical as shown in FIG. 2) was used in place of PTFE powder B. Did the same.

[Comparative Example 1] An Al material (A1050) coated with a PTFE resin on the entire surface was molded into a fin for a heat exchanger. [Comparative Example 2] In Example 2, PTFE powder A was 70
The same procedure was performed except that the vol% and the PTFE powder B were adjusted to 0 vol%.

Comparative Example 3 In Example 2, PTFE was used.
The same operation was performed except that the powder A was 0 vol% and the PTFE powder B was 70 vol%. [Characteristics] With respect to the heat exchanger fins obtained in each of the above examples, contact angles of water droplets (initial and after washing) were examined. The results are shown in Table-1.

Table-1 Content of powder A Content of powder B Initial contact angle Contact angle after washing with water Example 1 60 vol% 5 vol% 168 ° 168 ° Example 2 65 vol% 7 vol% 174 ° 172 ° Example 3 55 vol% 3 vol% 160 ° 158 ° Example 4 65vol% 7vol% 170 ° 169 ° Example 5 65vol% 7vol% 174 ° 173 ° Comparative Example 1-108 ° 107 ° Comparative Example 2 70vol% 0vol% 170 ° 105 ° Comparative Example 30 vol % 70 vol% 171 ° 92 ° From this, it can be seen that the coating film according to the present invention has excellent water repellency, and the water repellency does not decrease even after long-term use.

On the other hand, the average particle size is 4.8 to 10 μm.
m fluorine-based resin powder, or an average particle size of 0.7-
When only 1.2 μm of the fluorine-based resin powder is contained, the water repellency is excellent at the initial stage, but the water repellency is significantly reduced after long-term use, which is practical. Lack. Further, since the coating film according to the present invention is excellent in water repellency for a long period of time, when it is used as a heat exchanger fin, not only the heat exchange efficiency is high, but also it is difficult to adsorb moisture, so that the mold etc. It is also preferable from the environmental point of view because it does not easily breed.

[0030]

[Effect] Excellent water repellency can be obtained over a long period of time.

[Brief description of drawings]

FIG. 1 is a SEM photograph of PTFE powder having an average particle size of 5 μm.

FIG. 2 SEM photograph of PTFE powder having an average particle size of 1 μm

FIG. 3 is a schematic cross-sectional view of a heat exchanger fin.

Claims (8)

[Claims] 1. A fluorine-based resin powder having an average particle diameter of 4.8 to 10 μm and a fluorine-based resin powder having an average particle diameter of 0.7 to 1.2 μm dispersed in a coating film. A water-repellent coating film, characterized in that at least a part of the base resin powder is exposed on the surface. 2. The fluororesin powder having an average particle size of 4.8 to 10 μm has a particle size distribution in the range of 3.0 to 15 μm and an average particle size of 0.7 to 1.2 μm. The water-repellent coating film according to claim 1, wherein the powder has a particle size distribution in the range of 0.3 to 1.5 µm. 3. The sum of the content of the fluororesin powder having an average particle diameter of 4.8 to 10 μm and the content of the fluororesin powder having an average particle diameter of 0.7 to 1.2 μm is 15 solids. ~ 80v
ol% and (content of fluorine-based resin powder having an average particle size of 4.8 to 10 μm) ≧ (average particle size of 0.7 to
The content of the fluorine-based resin powder of 1.2 μm), The water-repellent coating film according to claim 1 or 2. 4. The fluorine-based resin powder having an average particle size of 0.7 to 1.2 μm is spherical particles.
~ The water-repellent coating film according to claim 3. 5. The fluororesin powder has a molecular weight of 50.
It is the thing of 0-20000, Claim 1 characterized by the above-mentioned.
~ The water-repellent coating film according to claim 4. 6. The water-repellent coating film according to claim 1, wherein the fluorine-based resin powder is fluorinated up to the end. 7. A fluororesin powder having an average particle diameter of 4.8 to 10 μm, a fluororesin powder having an average particle diameter of 0.7 to 1.2 μm, a binder resin, and a solvent. Characteristic water repellent paint. 8. A fin for a heat exchanger, wherein the water-repellent coating film according to any one of claims 1 to 6 is provided on a surface of an Al material.