JPH0149551B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a surface treatment method for fluororesin coating. It has been well known for a long time to coat a metallic base material with a fluororesin. However, due to the property of fluororesin that it does not exhibit melt flowability even when heated above its melting point, the resulting coating film is essentially porous even if it is fired during the coating process. do not have. For this reason, when a metal substrate coated with fluororesin comes into contact with a corrosive liquid, the liquid permeates through the fluororesin coating, corrodes the metal substrate, and as a result, blisters occur in the coating. or peeling may occur. Various methods have been developed to overcome this drawback, one of which is a method in which an enamel or glass film is formed on the surface of a metal substrate and then a fluororesin is coated thereon. However, this method has the problem of poor adhesion between enamel or glass and fluororesin, which is difficult to solve. On the other hand, it is also well known to coat glass or ceramics themselves with fluororesin. However, in this case as well, there still exists a difficult problem of poor adhesion between glass or ceramics and fluororesin. As a means for solving the above problem, a method is known in which a primer is applied in advance to the surface of glass, ceramics, enamel, etc. This primer is mainly composed of a component that adheres to the above-mentioned glass, ceramics, enamel, etc. (herein referred to as an adhesion aid) and a fluororesin, and is made into a liquid by using an appropriate liquid medium. It is coated with However, even if the fluororesin is applied to the surface of the substrate using this method, the coating will easily peel off from the substrate when immersed in hot water or exposed to steam, making it extremely impractical. . Another method is to adhere high melting point refractory materials such as alumina or titania in a semi-molten state to the surface of the base material to form a highly uneven surface, increasing the anchoring effect and adhesion of the fluororesin coating. Although attempts have been made to improve the heat resistance, they are still insufficient and have not yet resulted in a product with satisfactory hot water and steam resistance. The present invention has been made in order to solve the above-mentioned difficulties. Specifically, the present invention provides the following advantages when coating the surface of a silicic acid base material with a fluororesin primer and then applying a fluororesin coating. The same ingredients as the adhesion aid contained in the fluororesin primer, (b) The same ingredients as those generated in the primer film after baking from the adhesion aid, (c) The same ingredients as the above (b) after baking. The present invention relates to a surface treatment method for fluororesin coating, characterized in that glass powder, enamel glaze, or ceramic glaze containing at least one of the components to be produced is applied to a substrate in advance and fired. In the present invention, prior to applying a conventional primer to the surface of the substrate, glass powder, enamel glaze, or ceramic glaze containing at least one of the components (a) to (c) above is applied to the substrate in advance. It is characterized by being baked. As a result, extremely excellent hot water resistance and water vapor resistance can be imparted to the adhesion between the base material and the fluororesin primer film. In the present invention, the above-mentioned adhesion auxiliary agent forms a coating film that adheres to the base material such as metal, ceramics, glass, etc., and the coating film has heat resistance equal to or higher than that of the fluororesin used, and has a temperature of 200°C. Pencil hardness is HB or higher. Specifically, heat-resistant synthetic resins such as polyamide-imide resin, polyimide resin, polyethersulfone resin, polysulfone resin, polyoxybenzoyl polyester resin, epoxy resin, and silicone resin, and silicic acid such as colloidal silica, amine silicate, and lithium polysilicate. Examples include salts, organic titanium or zirconium compounds such as tetrabutyl titanate, tetrapropyl titanate, and tetrabutyl zirconate, and phosphates such as the reaction product of aluminum hydroxide and orthophosphoric acid. These adhesion aids can be used in combination with a liquid medium if necessary, such as N-methylpyrrolidone or dimethylformamide in the case of heat-resistant synthetic resins, water in the case of silicates, etc.
Specific examples include alcohols in the case of organic titanium or zirconium compounds, and water in the case of phosphates. Therefore, in the present invention, the above component (b) is as follows:
It suffices if the component is the same as that produced in the primer film from the adhesion aid after firing, and is selected and used depending on the type of adhesion aid used. For example, heat-resistant resins and silicates remain almost unchanged after firing, and organic titanium or zirconium compounds are used, such as titanium oxide or zirconia. These components (A) to (C) are used singly or in combination to form glass powder, enamel glaze, or ceramic glaze, usually at a volume ratio of 2/100 to 100% of the powder or glaze.
It is contained in an amount of about 100%. The glass powder, enamel glaze, or ceramic glaze in this case is not particularly limited, and a wide variety of conventionally used glazes can be used. When carrying out the method of the present invention, first, a glass powder enamel glaze or a ceramic glaze containing at least one of the components (a) to (c) above is applied to a siliceous base material according to a conventional method to form a coating. Form. Examples of the siliceous base material include enamel, glass, and various ceramic base materials. After that, a fluororesin primer is usually applied to a film thickness of about 8 to 12 μm after firing, preferably at 350°C or higher, usually at 380°C after removing volatile components.
Fire at around ℃. As the fluororesin primer in this case, those conventionally used are used. The fluororesin primer is used to form an intermediate layer between the fluororesin and the base material to increase adhesive strength when applying the fluororesin to the base material. It contains adhesive components, that is, an adhesion aid and a fluororesin. As the fluororesin, a single or copolymer of tetrafluoroethylene is usually used, and examples of the copolymerization component include hexafluoropropylene, ethylene, propylene, vinylidene fluoride, fluoroalkyl vinyl ether, and chlorotrifluoroethylene. The base material thus coated with the fluororesin primer is then coated with a fluororesin paint and fired in accordance with a conventional method. In this case, fluororesin paints that have been used conventionally are used. The fluororesin used in this case is the same as the fluororesin in the fluororesin primer. According to the method of the present invention, by providing a glass powder, enamel glaze or ceramic glaze layer containing at least one of the components (a) to (c) above before applying the fluororesin primer to the base material. The adhesion of the film is significantly improved when immersed in hot water or exposed to water vapor, making it extremely desirable for practical use. The present invention will be explained below with reference to Examples. Example 1 An enameled steel plate is prepared according to a conventional method using enamel glazes having two compositions shown in Table 1 below.

【table】

[Table] Next, a predetermined amount of the predetermined components shown in Table 2 are mixed with the above-mentioned top coating glaze and baked on the above-mentioned enameled steel plate under predetermined baking conditions. After that, a specified fluororesin primer shown in Table 2 was applied on top of this so that the film thickness after firing would be 8 to 12μ, and after sufficiently volatilizing the volatile components in an infrared dryer, it was heated to 380℃. Bake for 10 minutes in an electric furnace and allow to cool at room temperature. Next, a fluororesin topcoat paint manufactured by Daikin Industries, Ltd. (Polyflon Enamel "ES-5109BK") was applied on top of this primer coating so that the film thickness after firing was 20 to 25 μm, and the coating was applied in the same manner as the primer. After removing volatile components, it was fired for 15 minutes in an electric furnace maintained at 380°C, and then allowed to cool at room temperature. The coating films thus obtained were each subjected to a 3-hour immersion test in hot water at 90 to 95°C, and the physical properties of the coating films were measured. The physical properties of the coating film were determined by a pencil hardness test (JIS K5400) before (initial value) and after immersion in hot water for each coating film obtained by the above method under the conditions shown in Tables 1 and 2. Measured by drawing test (JIS K6894). This result is the second
Shown in the table. For comparison, Table 2 also shows the physical properties of an enamel glaze for top coating that did not contain any of the specified ingredients, but was otherwise treated in exactly the same manner.

【table】

[Table] Example 2 A fluororesin-coated enamel plate was prepared in exactly the same manner as in Example No. 1 of Example 1, except that the blending ratio of additive powder/enamel glaze was varied. The resulting fluororesin-coated enamel plate was immersed in hot water in the same manner as in Example 1, and changes in the adhesion of the coating film were examined. The results are shown in Table 3.

[Table] Comparative Example 1 In number 1 of Example 1 (Table 2), in addition to titanium powder, a blowing agent was added to the enamel glaze for top coating.
Al ₂ (SO ₄ ) ₃ as foaming agent / Enamel glaze for top coating = 20 /
A mixture mixed at a ratio of 100 (weight ratio) was baked under the same conditions as in Example 1. The enamel interface after baking is
Due to the decomposition of the blowing agent, the material was porous with many irregularities. Next, after carrying out the same treatment as in Example 1, the physical properties of the coating film were measured and were as follows. Pencil hardness test Initial value F After immersion in hot water B Drawing test Initial value 4 After immersion in hot water 2

Claims (1)

[Scope of Claims] 1. When coating the surface of a silicic acid base material with a fluororesin primer and then applying a fluororesin coating, (a) the same component as the adhesion aid contained in the fluororesin primer; (b) A glass powder or enamel glaze containing at least one of the following components: (b) The same component as that produced in the primer film after firing from the adhesive aid; (c) At least one component that produces the same component as in (b) above upon firing. Or, a method for preparing a base for coating with a fluororesin, which comprises applying a ceramic glaze to a base material in advance and firing it. 2. The base treatment method according to claim 1, wherein the adhesion aid is at least one of a heat-resistant synthetic resin, an organic titanium compound, an organic zirconium compound, a silicate, and a phosphate. 3. Claim No. 3, wherein the heat-resistant synthetic resin is a heat-resistant synthetic resin made of at least one of polyamide-imide resin, polyimide resin, polyethersulfone resin, polysulfone resin, polyoxybenzoyl polyester resin, epoxy resin, and silicone resin. The surface treatment method described in Section 2. 4. The surface treatment method according to claim 2, wherein the organic titanium and organic zirconium compound are organic titanium or organic zirconium compounds comprising at least one of tetrabutyl zirconate, tetrapropyl titanate, and tetrabutyl titanate. 5. The surface treatment method according to claim 2, wherein the silicate is at least one of colloidal silica, amine silicate, and lithium polysilicate. 6. The surface treatment method according to claim 2, wherein the phosphate is a phosphate consisting of a reaction product of aluminum hydroxide and orthophosphoric acid.