JPS59183866A - Powder coating method - Google Patents

Abstract

PURPOSE:To perform powder coating in good efficiency even in performing coating in large quantities, by subjecting the support jig part of an object to be coated to mold release treatment while interposing a low m.p. resin insert to said support jig. CONSTITUTION:In performing powder coating while supporting an object to be coated which is preheated to a temp. equal to or higher than the m.p. of a powdery paint by a support jig 3, mold release treatment is applied to the support jig part 4 contacted with the object to be coated while a resin insert 5 having a m.p. lower than the temp. at which the object to be coated is preheated is interposed to the support jig part 4. By this method, the dimension of the resin insert is selected to form a continuous coating having the same thickness and moreover, repairing of the contact part of the object to be coated and the support jig becomes unnecessary.

Description

[Detailed description of the invention] The present invention relates to a powder coating method.

Powder coating is widely used in various fields because it can provide a uniform and thick coating film and has excellent workability. However, in conventional powder coating, as shown in FIG. 1, a support 3 is inserted into a through hole 2 of an object 1 to be coated, for example, a steel plate, which has been preheated to a temperature higher than the melting point of the powder coating. The object to be coated is suspended and supported, or, as shown in FIG. For example, a powder coating is applied to the surface of an object by melting it and attaching it to the surface using a fluidized dipping method. Therefore, in the case shown in FIG. 1, the paint does not adhere to the part of the wall surface of the through hole that is in contact with the support, and
In the case shown in FIG. 2, the paint does not adhere to the part of the object to be coated that is in contact with the support.

For this purpose, in the past, after powder coating, paint was applied anew to the contact area between the object to be coated and the support as described above to perform repairs. However, since this repair is generally done in the cold using liquid resin paint with different paint properties, it is not easy to form a continuous paint film with the powder paint film, and therefore, the repair process is difficult. Paint film defects are likely to occur in some areas. In particular, when the coating film is thick, repair using a liquid resin paint is not easy because the viscosity of the liquid resin paint is low.

The present invention has been made in order to solve the above-mentioned problems in powder coating, and in particular, in powder coating of objects to be coated with a thick film, it is possible to repair the contact portion of the support as described above. The purpose is to provide powder coating that eliminates the need for powder coating.

The powder coating method according to the present invention is a method in which an object to be coated that has been preheated to a temperature higher than the melting point of the powder coating is powder coated while being supported by a support, in which the part of the support that comes into contact with the object to be coated is It is characterized in that, in addition to the mold release treatment, an inclusion made of a resin having a melting point lower than the temperature at which the object to be coated is preheated is interposed in the portion of the support that comes into contact with the object to be coated.

3 and 4 show the method of the invention corresponding to FIG. Object 1 to be coated preheated to a temperature higher than the melting point of the powder coating
has a through hole 2 called a hook hole at an appropriate position, and a support 3, ie, a hook wire, is inserted through this through hole to support the object to be coated.

In the method of the present invention, at least the support part 4 that contacts the object to be coated is subjected to mold release treatment in advance by baking with silicone resin, coating with fluororesin, wrapping with fluororesin tape, etc. An inclusion 5 made of a resin having a melting point lower than the temperature at which the object to be coated is preheated is interposed between the tool part and the object to be coated that is in contact with the tool part.

This inclusion is formed into a sheet shape or a pellet shape, for example, depending on the shape of the support part that comes into contact with the object to be coated.

Therefore, when the object to be coated is powder coated in this way, the fifth
- As shown in the figure, a powder coating film 6 is formed with a predetermined thickness on the surface of the object that is not in contact with the support 3, and is interposed between the object and the support, Inclusions having a melting point lower than the preheating temperature of the object to be coated melt during powder coating, and as the object to be coated is cooled after powder coating, they solidify or harden to form the coating film 7. At the same time, the supporting tool that has been subjected to the mold release treatment can be easily removed from the coating film 7.

FIG. 6 shows the method of the present invention corresponding to the second method, in which the object to be coated 1
In the same way as described above, an inclusion 5 made of resin is interposed in the support part 4 that contacts the support part 4, and is subjected to powder coating.

The above-mentioned resin inclusions may be made of the same type of resin as the powder coating used for powder coating, or may be made of a different type of resin, but if the powder coating is a thermoplastic resin coating, resin inclusions may be made of a resin of a different type. It is desirable that the inclusions are also made of a thermoplastic resin, and if the powder coating is a thermosetting resin coating, it is desirable that the resin inclusions be made of a thermosetting resin. When such resin inclusions are made of thermoplastic resin, extrusion method,
Formed into a sheet by calendering, powder sintering, etc.
It is cut into predetermined dimensions and ready for use. In addition, when it is made of a thermosetting resin, it is used in the form of sheets or pellets by means of prepreg impregnated into a fiber base material, powder sintering method, cold molding of powder, or the like.

When performing powder coating using a powder coating made of thermosetting resin, heating is usually applied after the powder coating is cured, but post-coating heating may damage the coated object. If the temperature is higher than the preheating temperature, there is no problem even if the temperature of the resin inclusions is lower than the postheating temperature. Further, the resin inclusion may be interposed between the support and the object before or after preheating the object to be coated. The size of the resin inclusion is usually preferably the same area as the part of the support that contacts the object to be coated, and the thickness thereof is preferably greater than or equal to the thickness of the powder coating film. The film thickness of powder coating is usually 0.3
Since the thickness of the resin inclusions is about 2 cranes, the thickness of the resin inclusions is also, for example,
The length is preferably about 0.3 to 311 m.

By selecting the dimensions of the resin inclusions in this way, the coating film formed by the resin inclusions forms a continuous coating film with approximately the same thickness as the powder paint coating film, so that after painting, it is possible to There is no need to repair the part where the support comes into contact with the support. Therefore, according to the method of the present invention, powder coating can be efficiently performed even in the case of mass coating.

The present invention will be explained below with reference to Examples.

Example 1 As shown in FIGS. 3 and 4, a 3.2 fl thick steel plate with a hook hole of 5 mm in diameter was sandblasted, and then a wire hook coated with fluororesin and having a double hook angle was inserted into the hook hole. The steel plate was suspended so that the fluororesin coating part was in contact with the wall of the hook hole, and preheated in an oven at 220"C. Meanwhile, the epoxy resin was M65O bisphenol A epoxy resin 10
0 parts by weight, 4 parts by weight of dicyandiamide, 1 part by weight of 2-methylimidazole, and 40 parts by weight of titanium oxide. At the same time, a powder having the same composition was cold-formed to a thickness of 1 mm, It was molded into pellets of 3111 and 2 pieces each in length and width.

The preheated steel plate is taken out of the oven, the pellets are interposed between the wall of the hook hole and the wire hook that has been released, and the steel plate is powdered with the powder coating using the fluidized dipping method. After the body was painted, it was returned to an oven at 180°C to cure the paint film. After cooling the object to be coated, when the wire hook is removed, the resin forms a continuous coating film with the powder paint coating underneath, and a coating film with a thickness of 500 to 600μ that passes a 500V pressure test is created. was able to obtain. Further, the painted steel plate was immersed in hot water at 100°C for 20 days, but no change in appearance was observed.

Comparative Example A steel plate was coated by the fluidized dipping method in the same manner as in Example 1 except that the resin pellets were not used, and then the portion where the hook hole was in contact with the wire hook was coated with bisphenol having an epoxy resin equivalent of 190. A liquid resin consisting of 100 parts by weight of A-type epoxy resin, 11 parts by weight of diethylenetriamine, and 40 parts by weight of titanium oxide was applied, and 24 parts by weight of
It was left to stand at room temperature for an hour to harden. Thereafter, the painted steel plate was immersed in hot water at 100° C. for 20 days in the same manner as in Example 1, and blisters were observed in the portions that had been in contact with the wire hooks.

Example 2 5 mm square wire hooks coated with fluororesin were placed facing each other with an interval of 60 (inches), and the wire hooks were placed at appropriate positions with the same resin composition as used in Example 1, with a thickness of 1 mm, vertically and horizontally. A pellet with 5 fins and 2 stripes was placed on each pellet, and a steel round bar with a diameter of 16 mm and a length of 1000 mm was placed on top of the pellet to support it. The iron rod was powder coated using an electrospray coating method to form a coating film of about 200 μm, and then heated at 200° C. for 5 minutes to cure the coating film.

In the coating film obtained in this way, the coating film in the area where the resin pellets were interposed was slightly thicker than the surrounding area, but
It also passed the V pinhole test and did not require any repairs.

[Brief explanation of the drawing]

Fig. 1 is a sectional view of the main parts showing a conventional method of supporting the coated object in powder coating, Fig. 2 is a front view of the same main parts, and Figs. 3 and 4 show examples of the method of the present invention. FIG. 5 is a cross-sectional view of the main part, and FIG. 6 is a cross-sectional view of the main part showing coating film formation by the method of the present invention.
The figure is a front view of main parts showing another embodiment of the method of the present invention. DESCRIPTION OF SYMBOLS 1...Object to be coated, 2...Through hole, 3...Support, 5
...Resin inclusions, 6.. Powder paint coating film, 7.. Coating film consisting of resin inclusions υ. Figure 1 Figure 2 Figure 4 Figure 3 'IV Figure 5 Figure 6

Claims (1)

[Claims] (1) In a method of powder coating an object to be coated that has been preheated to a temperature higher than the melting point of the powder coating while supporting it with a support, the part of the support that comes into contact with the object to be coated is subjected to mold release treatment, and
A powder coating method characterized in that an inclusion made of a resin having a melting point lower than the temperature at which the object to be coated is preheated is interposed between the object to be coated and a support portion that comes into contact with the object.