JPH05287096A - Water-repellent surface treatment and water-repellent coating film - Google Patents

Abstract

PURPOSE:To improve the technology of surface treatment capable of giving a desired color tone in appearance and a water-repellent effect to the surface of a base material to make it also applicable to a base material having no electrical conductivity, simplify the process of treatment, and improve the durability of the water-repellent effect. CONSTITUTION:The surface of the base material 1 is coated with a coating (not shown in the figures) mixed with a fine powder of polytetrafluoroethylene to form a water-repellent coating film 4. As shown in the enlarged sectional view of Fig. (B), the water-repellent coating film has fine particles 4b of polytetrafluoroethylene dispersed and embedded in the coating 4a. In the water- repellent coating film 4, the coating 4a exhibits a desired color tone in appearance, while the fine particles 4b of polytetrafluoroethylene exhibit an excellent water-repellent effect.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface treatment method for imparting a desired color tone and water repellency to a substrate, and a water repellent coating film.

[0002]

2. Description of the Related Art FIG. 2 is a schematic sectional view showing a conventional technique for imparting a desired color tone and water repellency to a substrate 1.
In order to give the base material 1 a desired appearance, the surface of the base material 1 is coated with a colored paint to form a colored coating film 2. Although not shown, an undercoat may be applied between the base material 1 and the colored coating film 2. Further, the colored coating film 2 is covered with a water repellent coating 3 for imparting water repellency. Known materials for the water-repellent coating include fluorine-based materials and silicon-based materials. Generally, a water-repellent coating having a thickness of 5 to 70 μm is formed.

[0003]

According to the prior art described with reference to FIG. 2, a desired appearance color tone can be obtained by the colored coating film 2 and water repellency can be obtained by the water repellent coating 3. However, the surface treatment process is complicated because multiple layers must be applied to form a plurality of coating films. In addition, there are the following problems regarding the durability of the coating. That is, there are many types of paint,
Since they are called impact resistant paints, stain resistant paints, abrasion resistant paints, etc. depending on their characteristics, it is possible to select and use those having desired performance and color tone from these.
However, since the water-repellent coating 3 generally does not have good wear resistance and impact resistance, there is a risk that it will wear relatively early, and if the water-repellent coating is worn away and disappears, the water-repellent function is lost.

A technique for forming a hard coating having water repellency by electroplating is disclosed in a technical magazine "Kagaku", Vol. 46, No. 7 (1).
991), it is a technique belonging to electroplating and therefore requires that the base material be conductive, and cannot be applied to an electrically insulating material.

The present invention has been made in view of the above circumstances, and can impart a desired color tone and durable water repellency to the surface of a base material regardless of the presence or absence of conductivity.
Moreover, it is an object of the present invention to provide a surface treatment method having a simple treatment step and the water-repellent coating film.

[0006]

According to a test study conducted by the present inventor to achieve the above object, polytetrafluoroethylene has a remarkable hydrophobic property (contact angle 1).
Not only 10 °), but when the fine particles are dispersed in the coating film, the coating film itself exhibits excellent water repellency, and the original impact resistance, abrasion resistance, and resistance of the coating film (free of fine particles) Does not significantly impair the fouling property. The present invention is a practical application of the above-mentioned research results, and the water-repellent surface treatment method according to the present invention is a method in which a fine powder of polytetrafluoroethylene is mixed in a paint, and a synthetic resin is prepared using this paint. The base material is coated to form a water-repellent coating film in which fine particles of polytetrafluoroethylene are dispersed. The water-repellent coating film according to the present invention is characterized in that fine particles of polytetrafluoroethylene are dispersed and embedded in the coating film. However, in the present invention, the fine particles are
A particle having a diameter smaller than the average thickness dimension of the coating film. The term “dispersed embedding” means that most of the fine particles are dispersed and embedded, and it does not prevent a part of the particles from being exposed on the surface. Further, the paint in the present invention also includes a colorless and transparent clear paint.

[0007]

The water-repellent coating film of the present invention having the above structure is
Water repellency is exhibited by the action of dispersed fine particles of polytetrafluoroethylene. The above-mentioned polytetrafluoroethylene is originally a hydrophobic material and has water repellency, but when it is dispersed as fine particles in a coating film, the coating film becomes water repellant. Moreover, the coating film in which fine particles of polytetrafluoroethylene are dispersed does not significantly impair the original performance of the coating such as abrasion resistance and stain resistance. The water-repellent coating in the prior art has not so good abrasion resistance, and the thickness dimension is limited in order to express the color tone of the coating film in appearance, but as described above, the fine particles of polytetrafluoroethylene are used. The dispersed coating film is not limited by the film thickness dimension with respect to the appearance color tone, and maintains the water repellency as long as the coating film is not worn away and has good durability.

When a water-repellent coating film having the above structure is formed on the surface of a synthetic resin, the method of the present invention is applied to mix fine powder of polytetrafluoroethylene into the coating material, and the coating material is used for coating. When it is applied, it is not necessary that the synthetic resin as the base material has conductivity, and further, it is not necessary to apply a multi-layer coating for imparting water repellency (other purposes,
For example, it does not prevent the combined use of an undercoat to improve the adhesion of the coating film). Further, the coating material in which the polytetrafluoroethylene fine powder is mixed as described above can be easily applied using conventional coating equipment if the mixing ratio is appropriate (for example, 50% by weight or less).

Since the present invention does not use electroplating, the substrate does not need to be conductive, and synthetic resin, glass,
Water repellent surface treatment can be applied to various substrates such as ceramics and metals.

[0010]

EXAMPLE FIG. 1 (A) is a schematic cross-sectional view showing one example of the water-repellent coating film of the present invention constituted by carrying out the water-repellent surface treatment method of the present invention. A polytetrafluoroethylene powder having a particle size of 4 μm was mixed with an abrasion resistant coating in an amount of 30% (weight ratio), well stirred and dispersed and suspended to be applied on the surface of the substrate 1, and cured to have a thickness of 20 μm. The water-repellent coating film 4 was formed. When carrying out the present invention, the mixing ratio of the polytetrafluoroethylene powder is preferably 50% or less. This is because, if the amount is further mixed, the water repellency will not be further increased and the physical properties of the coating film will be deteriorated. When the present invention is carried out, the water-repellent coating film 4 has a thickness of 5 to 70 μm.
It is desirable to set m. Since it is difficult to apply a thickness less than 5 μm and the practical strength of the coating film is insufficient, it is difficult to apply a thickness of 70 μm and the practical quality cannot be improved due to excess quality. Is.

FIG. 1 is a partially enlarged view of the water-repellent coating film 4.
It shows in (B). Polytetrafluoroethylene fine particles 4b are dispersed and embedded in the cured coating material 4a. The color tone of the water-repellent coating film 4 of this example is almost the same as the original color tone of the coating material 4a forming the matrix thereof, and is the same as that of the comparative example (not shown) in which the polytetrafluoroethylene fine particles 4b are not mixed. In comparison, no significant difference was found in the test results regarding durability, wear resistance, weather resistance, chipping resistance, and stain resistance. The contact angle of the water-repellent coating film 4 of this example was 110 ° or more, and it was confirmed that the film had practically sufficient water repellency.

The above tetrafluoroethylene is a white waxy crystalline thermoplastic resin which is also called tetrafluoroethylene, polytetrafluoroethylene, tetrafluororesin, etc., and is one of the typical fluororesins. It is marketed under several product names, but notable ones are Teflon (DuPont, Mitsui Fluorochemical Co., Ltd.) and Polyflon (Daikin Industries, Ltd.). In this example, a paint Planet AX (trade name) manufactured by Origin Electric Co., Ltd. was mixed with polytetrafluoroethylene powder (average particle size 4 μm) manufactured by Wako Pure Chemical Industries, Ltd. in a weight ratio of 30% and used for contact. An angle of 110 ° or more was obtained.

[0013]

As described above, the water-repellent coating film of the present invention can be applied to the surface of a non-conductive substrate, has excellent water repellency, and has the durability of the above-mentioned water repellency. Is big. Moreover, the water-repellent coating film can be configured to have a desired appearance color tone. Further, according to the water-repellent surface treatment method of the present invention, the water-repellent coating film of the above-mentioned invention can be formed on a surface of a synthetic resin having no conductivity by a simple process by a usual coating facility without using a special device. A film can be formed.

[Brief description of drawings]

FIG. 1 shows one embodiment of a water-repellent coating film according to the present invention, which is configured by applying the water-repellent surface treatment method according to the present invention,
(A) is a schematic cross-sectional view, and (B) is an enlarged schematic cross-sectional view of a part of the water-repellent coating film of the above-mentioned embodiment.

FIG. 2 is a schematic cross-sectional view in the vicinity of a coating film shown for explaining a water-repellent surface treatment according to a conventional technique.

[Explanation of symbols]

1 ... Substrate, 2 ... Colored coating film, 3 ... Water-repellent coating,
4 ... Water-repellent coating film, 4a ... Paint, 4b ... Polytetrafluoroethylene fine particles.

Claims (2)

[Claims] 1. A method for imparting water repellency by coating a substrate, wherein fine powder of polytetrafluoroethylene is mixed in a paint, and a coating film is applied to the substrate by the above mixed paint to give polytetrafluoroethylene. A water-repellent surface treatment method comprising forming a water-repellent coating film in which fine particles of ethylene are dispersed. 2. A water-repellent coating film formed on the surface of a base material, wherein fine particles of polytetrafluoroethylene are dispersed and embedded in the coating film.