JPH0359747B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to a method for applying electrostatic coating to a shape made by extruding aluminum or an aluminum alloy, or a shape made by bending a plate. BACKGROUND OF THE INVENTION In recent years, shapes made of aluminum and the like have been increasingly used in all fields such as building materials, ships, and vehicle materials due to their many properties. Generally, such shapes are coated with a base layer such as an anodized film or a chemical conversion film for the purpose of surface protection, and then electrostatically painted for decoration.
Recently, there has been an increasing demand for metallic coatings in terms of design. This metallic coating has the drawback that color unevenness tends to occur and it is difficult to repaint on-site after the coating film has deteriorated. However, building exterior walls are expected to be maintenance-free for at least 20 years, weather resistant, and stain resistant. For this reason,
There is a trend toward the adoption of unconventional high-grade, naturally expensive paints such as fluorocarbon resin paints, and as a result, it has become much more important than ever to apply a uniform coating film to prevent uneven coloring and to save on paint costs. It's coming. In addition, in these electrostatic painting processes, these shapes are hung one by one on hangers and suspended vertically.
Electrostatically coated in a coating device. Problems to be Solved by the Invention Some shapes require painting only on one surface of the shape, such as spandrel materials for curtain walls and decking materials for vehicle cargo beds. However, in conventional electrostatic painting, the paint inevitably adheres to the front and back surfaces of the shape, so even such shapes were coated on both the front and back. This method has disadvantages in that the paint is wasted and the coating time becomes longer than necessary, reducing productivity. In addition, in the conventional electrostatic painting method,
For the purpose of shortening the above-mentioned painting time, etc., each electrostatic coating booth applies a thick coating film, but if the coating film is applied thickly at once, the paint may flow, sag, or reach the edges. There is a problem in that pooling occurs, especially in the case of metallic paints, powder swimming occurs, and the waste of paint due to the backside coating further increases. Furthermore, in the conventional method of transporting the shapes one by one by hooking them onto a hanger, there are problems in that productivity is low and that electrical failure is likely to occur when paint adheres to the hanger. Therefore, it is an object of the present invention to solve the above-mentioned problems, and to eliminate waste of paint and improve productivity, especially in the electrostatic coating of shapes that only need to be coated on one surface. The object of the present invention is to provide an electrostatic coating method that can be used to coat objects. A further object of the present invention is to provide an electrostatic coating method that can uniformly coat the surface of a shaped material with no unevenness and a good finish. Means and Effects for Solving the Problems According to the present invention, in order to achieve the above object,
Two vertically suspended sections in contact with each other back-to-back are moved around the outer periphery of each even number of coating devices, with one outer surface thickened and the other outer surface thickened. Provided is a method for electrostatically coating a section, which is characterized by repeating the step of applying a thin layer simultaneously multiple times alternately. In this way, since the two sections are hung vertically and are in contact with each other back-to-back, only the outside surface of each section is painted, saving the amount of paint that would be required to paint the back side using traditional methods. At the same time, since two sections are coated at the same time, the coating time required for each section is shortened, and productivity is greatly improved. In order to perfect this effect, it is preferable to transport two profiles of the same type in a vertically suspended state, with their outer surfaces in contact with each other back-to-back so that they have the same shape. desirable. When the two sections in this state are transported around each even number of coating devices, one of the sections is coated at the same time, with one outer surface being thicker and the other outer surface being thinner. be done. By alternately reversing the direction of circumference around each coating device of the above-mentioned section, the above-mentioned coating process is carried out alternately, and such thin-film coating and thick-film coating are repeated several times alternately on the outer surface of the section. As a result, a predetermined coating thickness can be obtained, resulting in a uniform and fine finish with no uneven coating. Embodiments Hereinafter, the present invention will be described in further detail while describing embodiments shown in the accompanying drawings. Before applying the electrostatic coating process of the present invention, shapes made of aluminum or the like are first degreased, washed with water, and
After treatments such as drying and pre-treatments such as etching and smut removal as necessary, various surface treatments such as ordinary chemical conversion coating treatment and anodizing treatment are performed, but in the present invention, the treatment is limited to specific treatments. It can be applied to electrostatic coating of all shapes. An example of an electrostatic coating process includes the following steps. Hanging → Degreasing → Washing → Chromate conversion film treatment → Washing → Draining and drying → Painting (1st and 2nd booths) → Setting → Painting (3rd and 4th booths)
→ Setting → Baking The schematic structure of the electrostatic coating process in the above example is shown in FIG. 1, and the coating mode in each booth is shown in FIGS. 2 and 3. As shown in Fig. 2, two sections 1a, 1b
are suspended by hooking the hanger 3 through the holes 2a and 2b with both ends thereof butted and in contact with each other, and are transported by the conveyor 4 in a vertically suspended state. FIG. 1 shows a typical arrangement of an electrostatic coating apparatus, in which four booths for electrostatic coating are arranged in a staggered manner. Although such a staggered arrangement is preferable because the transfer route is the shortest, it is not necessarily limited to this arrangement. The vertically suspended sections 1a and 1b as described above are
First, as the disk 5 is being transported around the first booth 6, as shown in FIGS. 2 and 3, the disk 5 is rotating and reciprocating up and down while spouting paint from the outer periphery. Although the paint is applied under electrostatic force (high voltage generator etc. are not shown), most of the paint adheres to the outer surface of the profile 1a facing the disk 5 side, and does not adhere to the outer surface of the profile 1b on the opposite side. Adheres thinly. When being transferred from the first booth 6 to the second booth 7, the sections 1a and 1b are inverted, so that when going around the disk 5 in the second booth, the other section 1b faces the disk. Transported around,
At this time, most of the paint is applied to the outer surface of the profile 1b, and a thin amount of paint is attached to the outer surface of the opposite profile 1a. In this way, the first booth in the first booth 6 and the second booth 7
After passing through the painting process A, the sections 1a and 1b are set while being transferred through the setting route B.
Further, similarly to the above, after being subjected to the second painting step C in the third booth 8 and the fourth booth 9, setting after the completion of painting is performed when being transferred through the setting path D. Conventionally, in the case of the electrostatic coating process shown in Figure 1, a single profile was transferred, so coating was performed only in the first and third booths whose surfaces faced the disk. , painting in the second and fourth booths will be suspended. In the electrostatic coating method of the present invention described above, in each booth, the ratio of the amount of paint deposited on the surface of the shape facing the disk to the amount of paint deposited thinly on the surface of the shape on the opposite side is set to 7:3, and the ratio is set in 4 stages. If a coating film thickness of 40μ is achieved using this method, the coating thickness at each step will be as shown in the table below.

[Table] Although four electrostatic coating devices are used in the embodiments described above, it is of course possible to use a larger number of devices. In addition, as shown in Fig. 2, two sections 1a, 1
It is preferable to butt both ends of b against each other to make a flat surface, as this will allow sufficient paint to adhere to the edges of each shape, but if it is not necessary to paint the edges, it is preferable to use two shapes. They may be brought into contact so as to interlock with each other. Generally, in the case of a single hanger, when paint is applied to the hanger, electrical failure occurs in the contact area between the hole in the shape and the hanger, but in the case of the present invention, the shapes are suspended on the hanger with the shapes in contact with each other. Therefore, painting can be performed if even one of the two hangers is energized. FIG. 4 shows a state in which spandrel materials 10a and 10b used as profile members for the outer wall of a curtain wall are hung vertically on a hanger 3 with their backs in contact with each other. Particularly in the case of such spandrel materials, if you apply a thick layer of paint all at once to the final thickness, as with conventional single-hanging methods, the paint will flow, sag, and accumulate on the edges, especially with metallic paints. Powder may swim, but as in the present invention, the amount of paint applied at one time is smaller and thinner than before, and relatively thick and thin paints are applied alternately, resulting in a uniform and clean finish. Furthermore, since the amount of paint discharged into the booth can be reduced, paint can be saved. FIG. 5 shows a state in which two plates 11a and 11b are stacked and suspended from the hanger 3. Effects of the Invention As described above, according to the electrostatic coating method of the present invention, the paint sprayed from the coating device is applied only to the outer surface of each of the two vertically suspended shapes that are in contact with each other back to back. Because it adheres, the paint required for painting the back side, which is done with the conventional single-hanging method, can be saved, and since two shapes are painted at the same time, productivity is doubled. Also, after painting two sections at the same time so that one outer surface is thicker and the other outer surface is thinner, the next thicker painted surface is painted thinner, the thinner painted surface is painted thicker, and so on. This process is repeated multiple times alternately, resulting in a uniform, fine-grained finish with no uneven coating. Furthermore, since the two shapes are suspended from each hanger and hung vertically with their backs in contact with each other, even if a contact failure occurs between one hanger and the shape due to paint not adhering to the hanger,
Since electricity is supplied from the other hanger, there is also the advantage that painting defects will not occur.

[Brief explanation of drawings]

Fig. 1 is a schematic configuration diagram of an embodiment of the electrostatic coating method of the present invention, Fig. 2 is an explanatory diagram showing the state of electrostatic coating, and Fig. 3 is a diagram showing the state of transport of shapes in the electrostatic coating booth. FIG. 4 is a partial perspective view showing a state in which two spandrel materials are suspended from a hanger, and FIG. 5 is a perspective view showing a state in which two plates are suspended from a hanger. 1a and 1b are sections, 3 is a hanger, 4 is a conveyor, 5 is a disk, 6 is a first booth, 7 is a second booth, 8 is a third booth, and 9 is a fourth booth.

Claims (1)

[Claims] 1. While transporting two vertically suspended shapes that are in contact with each other back-to-back along the outer periphery of each even-numbered coating device, one of the outer surfaces of the above-mentioned shapes is made thicker, and the outer surface of the other is thickened. An electrostatic coating method for shapes, which is characterized by repeating the process of coating thinly and simultaneously multiple times alternately.