JPS604756B2 - Fluororesin coating method - Google Patents

Description

Detailed Description of the Invention The present invention forms a mixed film of ceramic and resin on the surface of an aluminum base material using a melt atomization method, and removes the resin contained in this film by thermal decomposition. The present invention relates to a method for forming a base treatment suitable for coating.

Fluororesin coatings have superior heat resistance, corrosion resistance, non-adhesiveness, low friction, and electrical insulation properties compared to other polymeric material coatings, and are used in a wide range of fields to take advantage of these properties. There is.

For example, household appliances such as hot plates and irons take advantage of their heat resistance, non-adhesiveness, and low friction properties, and bearing surfaces make good use of their low friction properties. Among fluororesins, polytetrafluoroethylene has superior properties as compared to other polytrifluorochloroethylenes, tetrafluoroethylene-6-propylene copolymers, etc., and is very commonly used. However, although these resins such as polytetrafluoroethylene have low friction properties, they have the disadvantage of weak adhesive strength. In addition, fluororesin itself has low hardness, and when used as a device for a long period of time, the coating will wear out, or if it is rubbed against metal chips, the coating will tear and the metal base will be exposed, causing corrosion of the base material.
Causes film peeling. In order to improve the adhesion between the fluororesin and the base material and to reduce the wear of the fluororesin film, the following treatments are usually carried out.

Means for improving adhesion to the base material include chemical etching methods such as hydrochloric acid treatment and mechanical methods such as sandblasting.

However, in the case of chemical treatment methods, such as hydrochloric acid treatment, the acid corrodes the base material, so sufficient cleaning is required after treatment, and especially in the case of die-cast base materials, the corrosive liquid may penetrate into the cavities, etc. However, corrosion is likely to continue even after cleaning.

In addition, in the case of die-cast base materials in which metals that are easily corroded are cast, the process becomes complicated because the exposed parts of the cast metal must be sealed so that they do not come into contact with the treatment liquid during acid treatment. There is. Further, when mechanical treatment is applied, it is difficult to make the substrate surface extremely uneven, and there is a limit to the technical drawing effect on the fluororesin film.

Therefore, a pretreatment coating of a primer layer containing a binder such as chromate or iron oxide is usually used to improve the adhesion of the coating to the substrate. On the other hand, as a means to improve the mechanical abrasion resistance of the coating, a ceramic or hard metal thermal spray coating layer is provided as a base treatment for the dual-component resin coating, or an alumite layer is provided on the surface of the aluminum base material, and the cracks in this alumite layer are Fluorine resin is embedded inside. However, in the method of providing a thermal sprayed coating layer, the fluororesin layer digs into the irregularities on the surface of the thermal sprayed layer.
A mere immersion effect has weak adhesion and requires a primer layer between the sprayed layer and the fluororesin layer.

In addition, the method of anodizing the aluminum surface to form hard alumite is a method of adhering the emitting resin by applying thermal shock to the hard alumite layer to create cracks, and then injecting the base resin dispersion into the inside of these cracks. This impregnation process requires time and effort.

There is also a limit to how thick the film can be made. When coating with a fluororesin as described above, the current situation is that the base preparation process and coating process for coating are complicated, especially under usage conditions that require abrasion resistance.

In contrast, the present invention has good adhesion between the fluororesin and the base material,
Moreover, it provides a coating method that is simple in terms of manufacturing process. The coating method and structure will be explained below.

As shown in FIG. 1, the surface of the base material 1 is subjected to a blast treatment, and then a thermal spray layer 2 made of a ceramic material is formed. The particle size of the blasting material is #8, which is suitable for the roughness of the surface, and various materials are possible as the thermal spraying material, but especially A.
The I203-Ti02 component is suitable in terms of adhesion to the base material and cost. As an example AI203-Ti02
The conditions for plasma spraying are: arc voltage 40V, arc current 1000A, arc gas (A
r10daye), the powder supply rate was 3 m/sec, and the film thickness was 2
Preferably around 0. A sprayed layer 3 containing a mixture of ceramic and organic resin is formed on this AI203-Ti02 layer. The ceramic material at this time is the same as that of the ceramic layer described above in order to match the coefficient of thermal expansion. Epoxy, polyethylene, nylon, polyamide, etc. are used as the organic material. Since ceramic and organic materials have different melting points, they cannot be mixed and sprayed at the same time, but must be melted individually and then atomized. When plasma spraying is used, two spray guns are installed, and the ceramic and organic resin are simultaneously sprayed from each spray gun. The appropriate ratio of organic resin in the mixed film of ceramic and organic resin is about 5 to 20%, and as the amount of organic resin increases, the adhesion of the film deteriorates. Film thickness is N203-Ti02
As with the layer, if the thickness is about 20 mm, peeling will occur. After forming this mixed radiation layer of ceramic and organic resin, the entire substrate is heat-treated to thermally decompose and vaporize the organic resin. The higher the heating temperature, the more accelerated the decomposition of the resin, but it is limited by the melting point of the base material and the thermal expansion of the sprayed layer and the base material. When Motomura is made of AI and the ceramic material is made of AI203-Ti02, the optimum temperature is 400 to 500 qo. By this heat treatment, the resin component 4 in the sprayed layer is decomposed and the layer becomes porous 5. This porous material 5 is also formed on the surface of the mixed traverse layer 3, making the surface uneven with an excellent tree-killing effect. After thermal decomposition, some resin residue remains on the surface, but remove it with air. Thereafter, a fluororesin dispersion is applied and fired to form a fluororesin film 6.
In FIG. 1, after the base material 1 is blasted, a ceramic sprayed layer 2 is formed thereon, and a mixed layer 3 of ceramic and organic material is further provided thereon.

4 indicates the organic material in the mixed layer.

The ceramic layer is provided as a buffer layer between the base material and the mixed layer to improve adhesion. In FIG. 2, the entire substrate shown in FIG. 1 is heat-treated to remove the resin in the mixed layer 3 and create pores 5, and then a fluororesin film 6 is formed. This heat treatment creates numerous irregularities on the surface of the mixed layer, which are traces of resin removal, and strengthens the adhesive strength of the fluororesin. By using this coating method, it is possible to obtain a wear-resistant coating with good adhesion without causing any corrosion-promoting effect on the base material as seen in chemical etching and anodizing, and without requiring a primer layer.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a base material before heat treatment according to the method of the present invention, and FIG. 2 is a sectional view of a base material coated with the same fluororesin and after heat treatment. 1... Base material, 2, 3... Thermal spray layer, 4... Resin component, 5...
...Porous, 6...Fluororesin film.

Claims (1)

[Claims] 1. After forming a film layer by melt-spraying hard ceramic on a roughened metal surface, and forming a film layer containing a mixture of organic material and ceramic on this film by melt-spraying, the organic material in this film is A fluororesin coating method characterized by heating at a temperature above pyrolysis to remove pyrolyzed products on the surface, then applying and firing a fluororesin dispersion onto the porous ceramic surface.