JPH084777B2 - Coating method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a fluororesin coating method for a substrate made of aluminum or an aluminum alloy.

[Conventional technology]

Conventionally, a base treatment method for coating a fluororesin on a base material made of aluminum or an aluminum alloy is a method of roughening the surface by sandblasting, thermal spraying, etc. Chemical conversion treatments such as the chromic acid phosphate method and the chromic acid method are also performed.

[Problems to be solved by the invention]

However, when the surface of the base material is roughened by sandblasting or thermal spraying and coated with a fluororesin, an improvement in adhesiveness is observed, but the projections of the roughened base material are exposed, resulting in reduced corrosion resistance and non-adhesion. There is a problem such as a decrease in elasticity and a decrease in slipperiness. Further, even when the convex portion of the base material is not exposed, the film thickness is partially reduced, and the corrosion resistance is also lowered.

Furthermore, sand blasting and thermal spraying (1)
It cannot be applied to thin base materials such as foil or easily deformable base materials because stress is applied to the base materials. (2) It is not possible to process complicated base materials because there is no wraparound. (3) Rough surface Therefore, there are various problems that it cannot be applied to a base material that requires dimensional accuracy.

In conventional chemical conversion treatment, it is effective for fluororesin processing of low temperature baking of about 200 ° C or less, but since many fluororesins are often baked at high temperatures of 300 ° C to 400 ° C, heat resistance of chemical conversion treatment film There is a problem, 300 ℃ ~ 4
When baked at a high temperature of 00 ° C, there was a problem that the chemical conversion treatment film was cracked or peeled off, resulting in peeling of the fluororesin film.

The object of the present invention is to solve the above-mentioned problems of the prior art,
It does not roughen the surface of aluminum or its alloy substrate, and is effective for thin substrates such as foils and substrates with complicated shapes, and also impairs adhesion even at high temperature baking. An object of the present invention is to provide a coating method capable of obtaining a non-fluorine resin coating.

[Means and Actions for Solving Problems]

The above-mentioned object is to use a base material made of aluminum or an aluminum alloy with an inorganic salt of a water-soluble fluoride, for example, zinc fluoride, aluminum fluoride, ammonium fluoride, ammonium hydrogen fluoride, potassium fluoride, hydrogen fluoride. Potassium, calcium fluoride, iron fluoride, sodium fluoride, sodium hydrogen fluoride, barium fluoride,
Aqueous solution containing manganese fluoride as a main component, preferably one or two of ammonium fluoride, ammonium hydrogen fluoride, zinc fluoride, sodium fluoride, potassium fluoride.
This can be achieved by immersion treatment in an aqueous solution containing at least one species as a main component and forming a fluororesin-based film on the treated surface. This coating can be formed by applying a fluororesin-based paint and baking it.

 The present invention will be described in more detail below.

First, the base material surface is degreased. This degreasing method may be a general degreasing method such as degreasing with an organic solvent such as trichlene, alkaline degreasing with caustic soda, etc. and is not particularly limited.
Next, the base material whose surface has been cleaned by degreasing is immersed in an aqueous solution containing an inorganic salt of a water-soluble fluoride as a main component for treatment. At this time, the composition and concentration of the treatment liquid (aqueous solution), the treatment liquid temperature, and the treatment time are appropriately determined depending on the type of salt contained in the treatment liquid, the type of coating resin, and the like. As the composition of the treatment liquid, it is preferable to use, as a main component, one or more selected from ammonium fluoride, ammonium hydrogen fluoride, zinc fluoride, sodium fluoride, and potassium fluoride.
The most preferable treatment liquid is an aqueous solution containing potassium fluoride as a main component. For example, when an aqueous solution containing potassium fluoride as a main component is used as the treatment liquid, the concentration of potassium fluoride is 0.1 to 3% by weight, preferably 1 to 2% by weight. The treatment temperature is preferably higher, and the higher the treatment temperature, the shorter the treatment time. For example, if the processing temperature is 80 ℃, it will be 10-15 minutes, 95 ℃
In the above, the adhesive strength more than that of sandblasting can be obtained in 2 to 3 minutes, but it may be appropriately determined depending on the desired adhesive strength of the coating, workability and the like.

In the present invention, after degreasing, the substrate that has been subjected to the immersion treatment in the aqueous solution containing the inorganic salt of the water-soluble fluoride as the main component as described above can be washed with water or hot water, dried, and then coated with a fluororesin. However, steps such as washing with water, washing with hot water, and drying can be omitted. The fluororesins that can be used at this time include polyvinyl fluoride (PVF), polyvinylidene fluoride (PVdF), polychlorotrifluoroethylene (PCTFE), polytetrafluoroethylene (PTFE), and tetrafluoroethylene-hexafluoride. Propylene copolymer (FEP), ethylene-tetrafluoroethylene copolymer (ETFE), ethylene-chlorotrifluoroethylene copolymer (ECTFE), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA) ), Etc., and these may be used alone or in a composite composition in which they are mixed. In addition, these fluororesins alone or mixed,
Resins or elastomers other than fluororesin such as phenol resin, acrylic resin, silicone rubber, fluororubber, polyimide resin, polyamideimide resin, urethane resin, polyphenylene sulfide resin, polyparabanic acid amide resin, polyetherimide resin, parahydroxybenzoic acid resin It may be mixed with an appropriate amount. These components can be used in the form of powder, liquid paint dispersed in an aqueous or organic solvent dispersion medium, or in the form of a film or sheet.

Further, as the fluororesin coating method that can be used in the present invention, a coating method which is generally used in the past may be used, and spray coating, electrodeposition coating, electrostatic coating, fluidized dipping, roll coating,
It can be applied by curtain flow coating, spin coating, etc., and is selected as appropriate depending on the form of the paint. Further, coating methods such as film lamination and sheet lining can also be used.

A substrate treated with the fluororesin according to the above according to the present invention has improved adhesiveness without roughening the surface of the substrate and has excellent corrosion resistance, as shown in Examples below.

Hereinafter, the present invention will be described in more detail with reference to examples.

〔Example〕

Example 1 An aluminum plate (A-1100) was immersed in an aqueous solution having the composition shown in Table 1 under the conditions shown in Table 1 and washed with water.
After drying, Fluorine-based undercoating paint EK-1908GY (manufactured by Daikin Industries, Ltd.) and Fluorine-based overcoating paint EK-4300CR
The paint after mixing N (Daikin Industry Co., Ltd., trade name) in a weight ratio of 3: 7 has a film thickness of 15 to 20 μm after baking.
It was applied so that it would be m. Then, it was dried by an infrared dryer until the volatile components were sufficiently removed, and further baked at 380 ° C. for 15 minutes, and then left to cool at room temperature. PFA powder paint MP-10 (trade name of DuPont Mitsui Fluorochemicals Co., Ltd.) was baked by electrostatic coating for peel strength measurement.
Apply it to a film thickness of 100-120 μm, and after applying 350 ℃
After baking for 30 minutes, it was allowed to cool at room temperature.

The adhesion of the fluororesin coating obtained by the above method to the substrate
Table 1 shows the results measured by the 5 mm width 90 ° peel strength test. For comparison, the same base material was degreased with trichlene chilled liquid and steam, then sandblasted (Shinano random # 80, spraying pressure 3 kg / cm ² ) and similarly coated with fluororesin. Table 1 shows the results measured by the test.

As is clear from Table 1, the adhesive force of the coating film obtained by the coating method of the present invention is superior to that of trichlene degreasing and sandblasting.

A: NH ₄ F 2 wt% aqueous solution B: NH ₄ HF ₂ 1 wt% aqueous solution C: ZnF ₂ 0.5 wt% aqueous solution D: NaF 2 wt% aqueous solution E: KF 2 wt% aqueous solution Example 2 Aluminum plate (A-1100 ) Was degreased and the surface was adjusted.

(1) Immersion in 5 wt% caustic soda solution (60 ℃, 30
Second), (2) water washing, (3) 10 wt% nitric acid immersion (room temperature, 30
Seconds), (4) Washing with water, (5) Immersing 1.4 wt% potassium fluoride aqueous solution (boiling, 3 minutes), (6) Washing with water, (7) Drying.

The same coating film was formed on the treated aluminum plate under the same conditions as in Example 1.

Comparative Example 1 An aluminum plate (A-1100) was degreased with trichlene cold liquid and steam, and then sandblasted (Shinano random # 80, spraying pressure 3 kg / cm ² ), and the same as in Example 1 above. A fluororesin coating film was formed.

Comparative Example 2 After degreasing an aluminum plate (A-1100) with a trichlene cold liquid and steam, a fluororesin coating film was formed in the same manner as in Example 1.

The initial adhesion of the fluororesin coating films obtained in Example 2 and Comparative Examples 1 and 2 and the adhesion after immersion in hot water (95 ° C. or higher) for 96 hours were measured by a 5 mm width, 90 ° peak strength test. Table 2 shows the results of measuring the surface roughness of the base material before coating with the fluororesin.

It can be seen from Table 2 that the coating method of the present invention provides a high adhesive force with almost no roughness on the surface of the substrate, and the value is higher than the adhesive force of the sandblasting method obtained by roughening the substrate surface by 8 times or more. I understand. Further, even in hot water treatment, almost no decrease in adhesiveness was observed.

Example 3 An aluminum plate (A-1100) was degreased and surface-adjusted in the same manner as in Example 2, and a fluororesin-based modified 1-coat type paint TC-7109BKM (trade name, manufactured by Daikin Industries, Ltd.) Is spray-coated so that the film thickness after baking is 15 to 20 μm, dried by an infrared dryer until the volatile components are sufficiently removed, and further baked at 280 ° C. for 30 minutes,
It was left to cool at room temperature.

Comparative Example 3 An aluminum plate (A-1100) was degreased with a trichlene cold liquid and steam, and then sandblasted (Shinano Random # 80, spraying pressure 3 kg / cm ² ), and then Example 3
The fluororesin was applied in the same manner as shown in.

The aluminum plates coated with the fluororesin obtained in Example 3 and Comparative Example 3 were tested for corrosion resistance (change in appearance) and adhesion (cross-cut test) after hot water (95 ° C. or higher) immersion test and salt spray test. The measured results are shown in Tables 3 and 4.

As is clear from the results of Comparative Example 3 in Table 4, in the blasting treatment, the corrosion resistance is inferior due to the partial variation of the coating film based on the surface roughness of the base material, whereas the coating method of the present invention is applied to the base material surface. It can be seen that even a thin film has good corrosion resistance because excellent adhesion is obtained with almost no roughness.

Example 4 Initial adhesion when a fluororesin was similarly applied to the base material treated with various concentrations of the potassium fluoride aqueous solution in Example 2 and immersed in hot water (95 ° C. or higher) for 96 hours Fig. 1 shows the results of the measurement of the adhesiveness of the product by a 5 mm width 90 ° peel strength measurement test.

As shown in Fig. 1, good initial adhesion can be obtained when the potassium fluoride concentration is 0.1% by weight or more, but when the potassium fluoride concentration exceeds 3% by weight, a decrease in the adhesiveness is observed in hot water treatment. Recognize.

Example 5 The relationship between the treatment time and the adhesiveness when the temperature of the potassium fluoride aqueous solution was changed in Example 2 is shown in FIG. Second
From the figure, it can be seen that the adhesion is improved even if the treatment is carried out at a low temperature of about room temperature, but the higher the treatment temperature is, the better the adhesion can be obtained in a shorter time.

〔The invention's effect〕

As described above, the present invention provides excellent adhesion with almost no roughening of the surface of the base material in the method of coating the base material made of aluminum or aluminum alloy with the fluororesin. It is possible to solve the problems such as dimensional change of the base material, deterioration of corrosion resistance due to exposure of convex parts of the base material, deterioration of non-adhesiveness, deterioration of slipperiness and the like. Further, in the case of thin film processing, it was not possible to obtain a smooth coating surface by the surface treatment by blasting or thermal spraying, but according to the present invention, it is possible to obtain a smooth coating surface having high adhesion even with a thin film.

In addition, since the base treatment process is a dipping process, there is an effect that it is possible to easily perform base treatment on thin base materials such as foil and base materials with complicated shapes that could not be processed by blasting or thermal spraying, and no dust is generated. Further, there is an effect that a large amount of a large area base material can be processed at a time in a short time depending on the size of the processing tank.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between the peel strength result and the potassium fluoride concentration, which shows the adhesiveness after being immersed in hot water (95 ° C. or higher) for the initial adhesiveness when the fluororesin is applied, FIG. 2 is a graph showing the relationship between the treatment time when the temperature of the potassium fluoride aqueous solution is changed and the peel strength indicating the adhesiveness.

Claims (4)

[Claims] 1. A substrate made of aluminum or an aluminum alloy is immersed in an aqueous solution containing an inorganic salt of a water-soluble fluoride as a main component, and a fluororesin-based coating is formed on the treated surface. Coating method. 2. A patent characterized in that the inorganic salt of the water-soluble fluoride comprises one or more of ammonium fluoride, ammonium hydrogen fluoride, zinc fluoride, sodium fluoride and potassium fluoride. The coating method according to claim (1). 3. The aqueous solution containing an inorganic salt of a water-soluble fluoride as a main component is an aqueous solution containing 0.1 to 3% by weight of potassium fluoride and heated to 60 ° C. or higher. Covering method according to item (1). 4. The coating method according to claim 1, wherein the fluororesin coating is formed by applying a fluororesin coating and baking the coating.