JPS5850596B2 - Futsuso resin coating - Google Patents

Description

[Detailed description of the invention] Fluorine resins such as tetrafluoroethylene resin and tetrafluoroethylene-hexafluoropropylene copolymer have excellent heat resistance,
It is a resin with chemical resistance and also has properties such as non-adhesion.

Applications that take advantage of the characteristics of fluorocarbon resin include kitchen appliances such as rice cookers, thermos jars, and frying pans, in which metals such as aluminum are coated with fluorocarbon resin.

In particular, kitchen utensils made of aluminum coated with fluorocarbon resin have rapidly become popular in recent years, and in addition to the aforementioned jars and frying pans, hot plates, electric pots, and the like are also coated with fluorocarbon resin.

When coating metal with fluorocarbon resin, a coating method different from normal painting is used because the resin has difficulty adhering to metal.

In the case of aluminum, there are two main methods: chemical bonding and mechanical bonding.

The former is called a primer method, and is a method in which a single layer of primer having adhesive properties to both aluminum and fluorine resin is provided between the aluminum and fluorine resin, and the fluorine resin and aluminum are bonded through this layer.

The latter method is called the etching method, and is a method in which fine octopus-shaped irregularities are formed on the aluminum surface, and the fluorine-based resin penetrates into these irregularities, causing the aluminum and the fluorine-based resin to be mechanically bonded by an anchoring effect.

As means for providing such fine irregularities on the aluminum surface, there are a chemical etching method using hydrochloric acid or the like, and an electrochemical etching method in which an electrochemical treatment is performed using aluminum in an aqueous halide aqueous solution as an anode.

Comparing the chemical adhesion method and the mechanical adhesion method, the latter has a stronger adhesion between the resin and aluminum, and can also be subjected to forming processes such as drawing after coating the aluminum.

However, this fluorine-based resin-coated aluminum has low abrasion resistance against metals, etc., which poses a problem for applications that require abrasion resistance, such as hot plates, and several methods have been implemented to improve this problem. It is.

These methods include fluorocarbon resin, ceramic powder,
There is a method of mixing metal powder to coat the aluminum, a method of hardening the aluminum surface by spraying ceramic powder and metal powder onto the base aluminum, and then coating it with fluorocarbon resin. There is a method of hardening this surface by anodizing and coating this surface with a fluorocarbon resin.

The present invention relates to a coating in which an uneven surface of aluminum is roughened by etching (an anodized film is provided thereon, and a fluorine-based resin is further coated thereon).

As mentioned above, the adhesion between aluminum and fluorocarbon resin by the etching method is stronger than that by the primer method, and the anodic oxide film provided along the etched surface is much harder than aluminum, making it difficult to bond with metal. It also has great abrasion resistance.

The cross section of such a fluorocarbon resin coating is shown in the figure.
It will look like the figure.

In Figure 1, 1 is aluminum with fine irregularities on its surface, 2 is an anodic oxide film provided along the uneven surface, and 3
is a fluorine-based resin coated on it.

When a fluorine-based resin coating with such a cross-sectional structure is worn from the surface, the fluorine-based resin is relatively soft, so in the early stages the fluorine-based resin wears off, but the wear stops at the hard oxide film. , and since the pitch of the concaves and convexes is very small, 100 μm or less, the resin in the concave portions does not wear out any further, and the non-adhesiveness of the surface hardly decreases.

This state is illustrated in FIG. 2.

Furthermore, this anodic oxide film has good adhesion to aluminum, and not only improves wear resistance but also corrosion resistance, which is much better than that without an oxide film.

However, it has been found that the following two problems arise in the case where an anodic oxide film is provided on the finely uneven surface of aluminum provided by etching, and a fluorine resin coating is applied thereon.

For mass first, some types of aluminum (in this case, those with an anodized film on the etched surface and a fluorine resin coating on it are more likely to have a high resistance to aluminum and fluorine resin than those without anodizing treatment). This means that the adhesive strength with the resin will decrease and the resin will peel off easily.

Second, even when the etched surface is coated without anodizing, the adhesion strength varies considerably depending on the aluminum material used.

Furthermore, when used in other kitchen appliances etc., generally 1
They are used at high temperatures of 00°C or higher and are often heated and cooled repeatedly, so it is necessary to take into account the distortion of the covering plate due to heat.

Therefore, the inventors of the present invention conducted intensive studies to solve these problems, and as a result, they completed the present invention.

In other words, the feature of the present invention is that Mg in the aluminum to be coated is
The content of Mn is greater than or equal to 0.2 and less than 3φ, and the content of Mn is less than 0.2%.

The inventors of the present invention attempted to solve the above-mentioned problems by examining various aluminum materials.

Aluminum commonly used for kitchen utensils includes pure aluminum, Mn alloy aluminum, Mg alloy aluminum, and Mn-Mg alloy aluminum from the viewpoint of corrosion resistance and workability, and these aluminums were studied.

As a result, it was revealed that when the aluminum is Mn alloy aluminum, the adhesion between the etched surface and the fluorocarbon resin decreases due to anodic oxidation.

Almost no decrease in adhesion j was observed for pure aluminum and Mg alloy aluminum.

It has also been found that pure aluminum and Mn alloy aluminum have lower adhesion than Mg alloy aluminum and Mg--Mn alloy aluminum when coated on an etched surface without anodizing treatment.

Therefore, it is necessary that the aluminum used for the coated plate, which is the object of the present invention, is not an Mn alloy, that is, the Mn content is less than 0.2%. It is necessary that there be.

However, when the Mg content exceeds 3, problems arise in processability.

Therefore, the Mg content needs to be 0.2% to 3φ.

Further, as the fluorine-based resin to be coated, it is most desirable to use tetrafluoroethylene resin, which has the highest heat resistance, considering the use of hot plates and the like.

Examples of the present invention will be described below.

Examples Pure aluminum, Mn alloy aluminum, Mg alloy aluminum, and Mn-Mg alloy aluminum were used in the following manner.

First, these aluminum plates were chlorinated) Electrochemical etching was performed with an electric charge of 45Q/cnf in an aqueous IJ solution to form fine irregularities on the surface.

Furthermore, a part of this surface was anodized in 15 polysulfuric acid at 15 V for 5 minutes to provide a hard layer on the etched surface.

At this time, the liquid temperature was 20°C and 30°C.

In addition, the weight change before and after the anodizing treatment was measured to examine the formation of an anodized film.

Furthermore, an aqueous dispersion of tetrafluoroethylene resin was applied to the treated surfaces to a thickness of approximately 25μ, and after drying, it was heated at 380℃ for 2 hours.
Sintered for 0 minutes.

Peeling and adhesive strength were measured to examine the adhesive properties of these covered plates.

Furthermore, the tensile strength and elongation of the coated aluminum were measured.

The strain on the covering plate due to heating and cooling was also measured.

The test method is as follows.

First, make a covering plate with a thickness of 2 cm, a width of 30 cIrL, and a length of 40 Cr.
Form into a container shape of ft1 depth 2crrL and heat it at 200℃
100g of cold water was poured onto the center of the plate to cool it rapidly.

This test was repeated 5 times and the warpage at the center of the coated plate was measured.

This is illustrated in FIGS. 3 and 4.

FIG. 3 is a sectional view of the sample plate before the heating and cooling test, and FIG. 4 is a sectional view after the test.

After the test, the difference a between the heights of the ends and the center of the coated plate was measured, and this was taken as the warp of the plate.

The above results are shown in Table 1 as Examples and Comparative Examples.

These results can be summarized as follows.

■ Pure aluminum and Mn-based alloy aluminum (it has been revealed that those coated without anodizing the etched surface have inferior adhesion compared to Mg-based and Mg-Mn-based alloy aluminum). Ta.

The reason for this is presumed to be that the shape of the fine irregularities after etching is different.

2. Mn Alloy Aluminum and Mn-Mg Alloy Aluminum G Concerning the problem, the adhesion between aluminum and fluorocarbon resin is reduced by performing anodizing treatment.

The reason for this is assumed to be as follows.

The weight increase before and after anodizing is smaller for aluminum containing Mn than for aluminum not containing aluminum, and it is considered that aluminum containing Mn is more likely to dissolve during anodizing.

This is thought to be due to etching (this causes the shape of the fine irregularities to change, which reduces the anchoring effect on the resin and reduces adhesiveness).

Furthermore, although this decrease in adhesion is affected by conditions such as the liquid temperature during anodizing treatment, it can be seen that the influence of the aluminum material is greater than that.

From the above results, Mg-based aluminum alloys containing less than 0.24 Mn and 0.2 to 3 Mg are the most suitable for aluminum for kitchen appliances coated with fluorine-based resin after forming an anodized film after etching. It turned out to be desirable.

Furthermore, it has been revealed that such a coated plate made of aluminum has no practical problems with regard to thermal strain caused by heating and cooling cycle tests.

These are summarized in Table 2.

[Brief explanation of the drawing]

Figure 1 is a cross-sectional view of a product in which an anodized film is provided along the uneven surface by etching, and a fluorocarbon resin is further coated on top of the anodized film. It is a cross-sectional view of a state where it has started to itch. In FIGS. 1 and 2, numeral 1 is aluminum with fine irregularities on its surface, 2 is an anodized film provided along the irregular surface, and 3 is a fluorine-based resin coated thereon. Figures 3 and 4 are cross-sections of the coated plate before and after the heating and cooling cycle tests. a is the difference in height between the edge and center of the covering plate after the test.

Claims (1)

[Scope of Claims] 1. A kitchen utensil in which a fluorine-based resin is coated on an aluminum surface on which fine irregularities are formed by electrochemical or chemical etching, and an anodized film is further provided along the irregular surface. In the coating, M in aluminum
A fluorine-based resin coating characterized in that the content of g is 0.2% or more and less than 3%, and the content of Mn is less than 0.2%. 2. The fluorocarbon resin coating according to claim 1, wherein the fluorocarbon resin is tetrafluoroethylene resin.