JPH0611916B2 - Organic lining method for metal articles - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Industrial Field of the Invention The present invention relates to a method for organic lining a metal article, and more specifically, when a metal article is coated with a high melting point thermoplastic resin by a powder baking method, The present invention relates to a method for obtaining a coating layer having good adhesion.

(Prior Art) As a method for coating the surface of a metal article with resin, a resin powder is sprayed onto a heated metal article or immersed in a resin powder flow tank to form a uniformly melted resin layer on the surface of the metal article. A method for forming a strong coating layer by allowing the coating to cool and then cooling is widely used.

(Problems to be solved by the invention) In this method, the heating temperature of the metal article is usually set in consideration of cooling during the transition to the baking process of the resin powder, securing a heat capacity for melting the resin, and the like. 10 from melting point
It is necessary to increase the temperature to about 0 ° C. Therefore, when it is attempted to coat a high melting point thermoplastic resin such as nylon or saturated polyester, it is necessary to heat the article to a high temperature of about 400 ° C., and for an article having a large heat capacity, a heating furnace is used.
Hold for about 0 to 15 minutes is required, oxidation of the surface of the metal article progresses in this process, and it is difficult for the coating layer and the metal article to adhere to each other,
It easily peels off. In particular, in a zinc-plated metal article, the oxide layer is easily peeled off, so that the adhesion is further reduced.

Furthermore, the method of performing the same treatment before the heating step, which is adopted as a method of improving the adhesion, is not exposed to the expected effect because it is exposed to a high temperature in the heating step and surface oxidation occurs as described above. . Further, in the case of zinc plating, which is usually difficult to adhere to, a method of chemical conversion treatment of the surface to improve adhesion is also used.
When heated above about 00 ° C., the effect cannot be obtained, and it cannot be applied to baking coating of high melting point resin.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a method for coating a metal article with a high melting point thermoplastic resin with good adhesion.

(Means for Solving the Problems) In order to achieve the above object, the metal organic lining method according to the present invention includes the following steps in a method of coating a metal article with a high melting point thermoplastic resin by powder baking. It is characterized by that.

Heating the metal article to be coated to a temperature higher than the baking temperature of the thermoplastic resin to be coated by a predetermined temperature, and after heating, until the metal article is cooled to the baking temperature of the thermoplastic resin. A step of grinding the surface between the steps, a step of cooling the metal article to the baking temperature of the thermoplastic resin, a step of forming a coating layer of powder of the thermoplastic resin on the metal article, and then a strong coating of the thermoplastic resin. Cooling until a layer is formed.

The present invention is to polish a metal article to be subjected to a baking coating by a wire brush, sandpaper, etc. for a short time after the heating step and during the cooling to the baking temperature. It is characterized in that the oxide layer is removed and the surface is provided with irregularities for obtaining an anchoring effect to improve the adhesion. The biggest difference from the prior art is that a surface roughening step is provided after the heating step.

The present invention will be described in more detail.

In the present invention, first, the metal article to be coated is heated to a temperature higher by a predetermined temperature than the baking temperature of the thermoplastic resin to be coated.

The metal article to be coated is not basically limited in the present invention, and the metal article conventionally used in this type of organic lining method can be effectively used.
The method according to the present invention is very useful particularly for a zinc plated metal article.

The thermoplastic resin with which such a metal article is coated is not basically limited in the present invention. Although various thermoplastic resins can be used, the effect of the present invention can be remarkably obtained when applied to high melting point thermoplastic resins such as nylon and saturated polyester.

In the present invention, the metal article as described above is heated to a temperature higher by a predetermined temperature than the baking temperature. The reason why the temperature is higher than the baking temperature is to prevent the temperature from lowering below the baking temperature due to cooling during baking.
Therefore, the predetermined temperature is functionally determined in consideration of the time between baking the powder and the heat capacity of the metal article.

After heating in this way, the surface of the metal article is ground until it is cooled to the baking temperature of the thermoplastic resin.

The method of grinding a metal article is not limited to a basic method in the present invention, and can be ground using, for example, sandpaper, a wire brush or the like. By grinding in this manner, the oxide layer on the surface of the metal article can be removed, and concavities and convexities exhibiting an anchoring effect can be formed.

Next, after cooling the metal article to the baking temperature of the thermoplastic resin by a method such as air cooling, a coating layer of powder is formed on the metal article.

The method for forming the coating layer of powder is not basically limited in the present invention. For example, the powder is sprayed with an air gun or soaked in a fluidized bed of powder to form the coating layer. You can

After forming the coating in this way, it is cooled to form a strong coating layer.

The cooling method as described above is not basically limited in the present invention, and for example, water cooling, air cooling or the like can be used.

Next, examples of the present invention will be described.

(Embodiment 1) FIG. 1 is a view for explaining a processing step of baking and coating a saturated polyester resin on a steel article subjected to hot dip galvanizing in a batch system as a first embodiment of the present invention. A heating furnace, 2 is a surface roughening device using an electric wire brush, 3 is a fluidized immersion tank for saturated polyester resin powder, and 4 is a water tank for cooling.

The molten zinc plated article to be coated is held in the heating furnace 1, heated to about 380 ° C., and then taken out from the heating furnace 1,
Wire brushing is performed in the surface roughening device 2 for about 1 minute to remove oxides and roughen the surface. When this step is completed, the temperature of the article is air-cooled to 320-350 ° C., which is the optimum treatment temperature for the saturated polyester resin, so that the article is immediately moved to the fluidized dipping tank 3 and the article is dipped for about 5 seconds while shaking. Then, after air cooling for about 5 minutes, it is immersed in the water tank 4 and cooled to room temperature. In this way, a saturated polyester coating having a film thickness of about 300 μm is completed.

Since the resin is baked immediately after brushing the wire, there is little surface oxidation and unevenness is formed on the surface, so that a very tight coating is formed.

FIG. 2 is a diagram comparing the adhesion of the coating according to the method of this embodiment with that according to the conventional method.

The test piece used was a steel plate of 50 × 100 × 2 ^t mm, which was plated with molten zinc of about 70 μm, left in the room for about one month, and then coated with a saturated polyester resin of 300 μm in thickness by various methods. Adhesion is made by adhering one end of a steel cylinder with a diameter of 20 mm to the test piece, making a cut along the circumference to reach the zinc plating layer, fixing the test piece to a tensile tester, and making the cylinder the adhesive surface. This was done by pulling in the vertical direction and measuring the load at which the coating delaminated.

In FIG. 2, sample number A is obtained by the method of this embodiment, B is obtained by performing the wire brushing of the method of this embodiment before the heating step as in the prior art, and C is the prior art before the heating step. Was subjected to the chemical conversion treatment, and was not subjected to wire brushing after heating, was air-cooled to the treatment temperature, and was subjected to the treatments after the baking treatment step of this embodiment. Other processing conditions such as the heating temperature, the processing temperature, the immersion time in the fluidized immersion tank, and the air cooling / cooling process for both B and C are the same as those of the method of this embodiment. Sample A according to the method of this embodiment is B according to the related art,
Adhesion is significantly greater than C.

As is clear from this result, the method of the present invention significantly improves the adhesion of the coating as compared to the prior art.

(Embodiment 2) FIG. 3 is a view for explaining a treatment step of continuously baking and coating a saturated polyester resin on a steel pipe plated with molten zinc as a second embodiment of the present invention, and 5 is induction heating. A furnace, 6 is a surface roughening device using an electric wire brush, 7 is a tank for spraying a saturated polyester resin powder with a spray gun, 8 is a cooling tank with water spray, and 9 is a roller for moving a steel pipe.

A series of coating treatments can be completed while moving the steel pipe at a speed of approximately 5 m / min. The capacity of the heating furnace, the length of each device / tank, and the mutual distance are appropriately selected according to the desired coating thickness.

By simply adding the surface roughening device 6 to the prior art continuous baking coating device for steel pipes, it is possible to realize a coating exhibiting excellent adhesion, which is almost the same as the value shown in FIG.

(Effects of the Invention) As described above, according to the present invention, it becomes possible to coat a metal article with a thermoplastic resin having a high melting point with good adhesion, and the range of selection of coating resin is significantly expanded.

In particular, it is excellent in weather resistance and has great coating strength and is very promising as a coating resin, but since the heating temperature for baking treatment is as high as about 380 ° C., it is very difficult to treat it on zinc plating. The existing saturated polyester can be easily coated, and a very large industrial effect is expected.

[Brief description of drawings]

FIG. 1 is a diagram for explaining a treatment step of baking and coating a saturated polyester resin on a steel article plated with molten zinc according to the first embodiment of the present invention in a batch method, and FIG. 2 is a first embodiment. FIG. 3 is a diagram comparing the adhesion of the coating by the method of 1) with that of the prior art, and FIG. 3 shows a treatment process of continuously baking and coating a saturated polyester resin on a steel pipe coated with molten zinc as a second embodiment of the present invention. It is a figure explaining. 1 …… Heating furnace, 2 …… Surface roughening device with electric wire brush, 3 …… Saturated polyester resin powder fluidized immersion tank, 4…
… Cooling water tank, 5 …… Induction heating furnace, 6 …… Surface roughening device with electric wire brush, 7 …… Saturation polyester resin powder spray tank with spray gun, 8 …… Water spray cooling tank, 9 …… Roller that moves the steel pipe.

Claims (1)

[Claims] 1. A method of coating a metal article with a high melting point thermoplastic resin by powder baking, comprising the following steps: an organic lining method for a metal article. Heating the metal article to be coated to a temperature higher than the baking temperature of the thermoplastic resin to be coated by a predetermined temperature, and after heating, until the metal article is cooled to the baking temperature of the thermoplastic resin. A step of grinding the surface between the steps, a step of cooling the metal article to the baking temperature of the thermoplastic resin, a step of forming a coating layer of powder of the thermoplastic resin on the metal article, and then a strong coating of the thermoplastic resin. Cooling until a layer is formed.