JP2003039012A - Substrate treatment method in powder coating - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a substrate treatment method enabling easy treatment and excellent in the adhesiveness of a powder coating in powder coating. SOLUTION: In forming a coating film layer on the surface of an aluminum plate 10 becoming a substrate by powder coating, a projection material 21, which is obtained by processing a melamine resin (thermosetting resin) having iron oxide added thereto into particles having a sharp polygonal shape, is preliminarily sprayed on the surface of the aluminum plate 10 to apply blast treatment thereto. By this method, the optimum surface roughness is applied to the surface of the aluminum plate 10.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface treatment method for coating the surfaces of building materials, home appliances and the like by the powder coating method.

[0002]

2. Description of the Related Art In recent years, when coating building materials such as aluminum sashes and fences, home appliances such as refrigerators, steel furniture and office supplies, etc., powders that are applied without using organic solvents or solvents such as water The painting is being reviewed. Since this powder coating does not use an organic solvent, it is not only attracting attention from the environmental point of view, but it can also be coated with a powder coating compounded only in the coating film forming part, so at room temperature It has the advantage of being able to use paints that do not dissolve and polymer resins that are difficult to dissolve. Conventionally, there were problems with the smoothness and thinning of the coating layer, but now it is a liquid coating. It is becoming possible to obtain a coating film having a surface property comparable to the above. This powder coating is roughly classified into an electrostatic powder coating method and a fluidized-bed coating method, but a relatively thin coating layer is formed on a metal base material such as the above-mentioned building materials, home appliances and office supplies. In some cases, an electrostatic powder coating method suitable for thinning is used. In this electrostatic powder coating method, as shown in FIG. 3, the surface of a base material 30 such as aluminum or iron is charged with a powder coating material 31 containing a polyester-based, acrylic-based or epoxy = polyester-based resin. After the attachment, the powder coating material 31 is baked on the surface of the base material 30 by heating in a drying oven such as a baking drying oven to be cured, and then cooled to form the coating layer 32. As a method for adhering the powder coating material 31 to the surface of the base material 30, for example, as shown in FIG.
Powder coating 3 charged by electrostatic gun 40 on the surface of 0
There is an externally charged electrostatic coating method in which 1 is attached by the electrostatic effect. Specifically, the corona pin 41 provided at the tip of the electrostatic gun 40 is attached to the corona pin 41 by the high voltage generating device 42 by 30 to 1
A high voltage of 00 kV is applied to generate corona discharge between the corona pin 41 and the base material 30, thereby ionizing the air between the corona pin 41 and the base material 30. The powder coating material 31 discharged from the tip of the electrostatic gun 40 collides with the above-mentioned ions and is charged, and moves along the electric force line 43 as shown by the broken line in the figure, and by the electrostatic effect, It adheres to the surface of the base material 30.

In powder coating of iron-based materials such as cold-sweat rolled steel sheets and hot-dip galvanized steel sheets, the surface of the substrate 30 is alkali-degreased in advance, and a zinc phosphate coating or chromate coating is formed on the surface. It is formed and subjected to degreasing and rustproofing treatment to improve the surface condition of the base material and to improve the adhesion of the powder coating material 31 due to the anchor effect of the coating film. When the base material is an aluminum plate or alumite, in addition to the zinc phosphate treatment and chromate treatment described above, a corrosion-resistant oxide film is formed by alumite treatment (complete sealing treatment or semi-sealing treatment) by anodic oxidation. Then, a method of improving the adhesion of the powder coating material 31 is also performed. Further, on the surface of the base material 30, abrasive sand, alumina, silicon carbide, iron powder (iron shot), or a projection material such as glass beads is mixed in the compressed air flow and pressure-fed to the injection nozzle, and the nozzle of the injection nozzle is used. A method of spraying the shot material onto the surface of the base material 30 from the mouth and performing a blasting treatment for polishing the surface to roughen the surface of the base material 30 and improve the adhesion of the powder coating material 31 is also performed.

[0004]

However, the above chemical treatment such as film treatment and alumite treatment requires not only expensive equipment, but also management of chemicals and maintenance of working environment from the viewpoint of environmental protection, and further, A large-scale treatment facility was necessary because it was necessary to sufficiently treat the waste liquid. on the other hand,
When the surface of the base material 30 is blasted by using a shot material such as abrasive sand or iron shot, the surface of the base material 30 is ground more than necessary, and the surface of the base material 30 is damaged or surface roughness becomes large. Will end up. For this reason, there is a problem that unevenness remains on the surface after coating, resulting in poor appearance.

The present invention has been made in view of the conventional problems, and an object of the present invention is to provide an undercoating method which is easy to treat in powder coating and has excellent adhesion of powder coating. To do.

[0006]

The ground treatment method in powder coating according to claim 1 of the present invention is characterized in that a blast treatment for spraying a projection material composed of resin particles is applied to the surface of the base material. Thus, the surface of the base material to which the powder coating material is attached can be surface-treated to have an optimum surface roughness without damaging the surface of the base material, so that the adhesion of the powder coating material can be improved. Thus, it becomes possible to form a coating layer having excellent surface properties on the surface of the base material.

The ground treatment method in powder coating according to a second aspect is characterized in that the shape of the resin blast material is a sharp polygonal shape in order to efficiently perform the blast treatment. The surface treatment method in powder coating according to claim 3 is characterized in that the resin is a thermosetting resin.
According to a fourth aspect of the present invention, there is provided an undercoating method in powder coating, wherein the thermosetting resin is a melamine-based resin, a urea-based resin or a phenol-based resin. According to a fifth aspect of the present invention, there is provided an undercoating method in powder coating, wherein one or both of iron oxide and carbon are added to the thermosetting resin. According to a sixth aspect of the present invention, there is provided a ground treatment method in powder coating, wherein conductive particles are added to the thermosetting resin. The surface treatment method in powder coating according to claim 7 is characterized in that a surface active agent is not applied to the resin shot material.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic view showing an air blasting process, which is one method for performing the surface treatment of the aluminum plate 10. Reference numeral 20 denotes a pressure tank 22 for accommodating a blast material 21. A projectile material supply means for pumping the projectile material 21 together with the compressed air, and 23 are jet nozzles for jetting the projectile material 21 under pressure onto the aluminum plate 10. In the present embodiment, the projection material 2
As 1, a melamine-based resin (thermosetting resin) to which iron oxide is added is used, which is processed into granular particles having a sharp polygonal shape with a size of about 500 to 850 μm.
Using a 10 mm injection nozzle 23, the resin shot material 21 pressure-fed with the compressed air flow from the shot material pressure tank 22 is applied to the surface of the resin molded product 11 on the aluminum plate 10, and the internal pressure is 0.1 to 0.7 MPa. Blasting is performed by spraying at a projection distance of 30 to 700 mm. Since the melamine-based resin processed into the above-mentioned sharp polygonal granularity has a lower hardness than the conventional shot material, the aluminum plate 1 on which the powder coating material 31 is adhered.
The surface can be surface-treated to have a predetermined surface roughness without damaging the surface. As a result, the aluminum plate 1
The aluminum oxide layer formed on the surface layer of No. 0 is removed to allow aluminum to appear on the surface, and the aluminum plate 10 as a base material
It is possible to improve the surface potential of and improve the electrostatic effect. That is, since the positive charge of aluminum that appears on the surface attracts the powder paint 31 that is negatively charged, it can be brought into close contact with the surface of the aluminum plate 10. Further, by making the surface of the aluminum plate 10 have a predetermined surface roughness, the powder paint 31 can be brought into close contact with the surface of the aluminum plate 10 by the anchor effect, so that the adhesion of the powder paint 31 is improved. You can The powder coating process is preferably performed within a few hours after the blasting process in consideration of the oxidation of the surface of the aluminum plate 10.

In the above-mentioned embodiment, the aluminum plate 10 was ground to have a predetermined surface roughness by the air blasting process. However, as shown in FIG. The same effect can be obtained by adopting the centrifugal blasting process in which the projection material 21 is projected onto the surface of the aluminum plate 10 by using the impeller-equipped rotor 24 having the plurality of blade portions 24W protruding in the direction. Also in this case, the diameter and the number of revolutions of the rotor 24 are appropriately selected according to the target surface roughness, but the rotation speed of the rotor 24 is about 30 m / s to 150 m / s. It is practical and desirable to do so.

In the blasting process, generally, the smaller the particle size of the shot material and the lower the impact force, the finer the surface roughness after the process, but the particle size of the thermosetting resin used as the shot material 21. Or the nozzle diameter of the injection nozzle 23,
The injection pressure, the distance between the aluminum plate 10 and the injection nozzle 23, etc.
It is appropriately selected depending on the target surface roughness. In resin blast, static electricity may be generated on the surface of the blast material due to collision between the resin blast materials during blasting, and the blast effect may be reduced. It often prevents the occurrence of. When the shot material having this antistatic coating (surfactant) is used as the shot material for the surface treatment of electrostatic powder coating, the non-conductive surfactant is used as the surface of the aluminum plate 10. Therefore, there are problems that the adhesive force of the powder coating material 31 is reduced and that pinholes are easily formed. On the other hand, in the resin shot material of the present invention, the application of the surfactant is omitted and
%, A coloring agent such as iron oxide or carbon black is added to suppress the generation of static electricity in the resin blast material. Will not adhere. Therefore, the powder coating material 31 can be surely adhered to the aluminum plate 10,
The aluminum plate 10 having the coating layer 32 having excellent surface properties can be obtained. Further, conductive particles such as nickel particles may be added instead of the colorant such as iron oxide or carbon black.

In the above embodiment, the melamine-based thermosetting resin is used as the resin used in the shot material. However, the resin is not limited to this and may be, for example, a urea-based, phenol-based, or polycarbonate-based thermosetting resin. The same effect can be obtained even when a volatile resin is used. Even at this time, as described above, by admixing the coloring agent such as iron oxide or carbon black into the resin, the adhesive force of the powder coating material 31 can be improved without lowering the blasting efficiency. .

<Example> The present invention will be specifically described below with reference to Examples and Comparative Examples, but the present invention is not limited to the following. [Example 1] An aluminum plate (A505
2), using an injection nozzle with a nozzle diameter of φ6 mm, the injection pressure is 0.25 MPa, and the distance between the aluminum plate and the nozzle is 20.
Set to 0 mm and the particle size is 500 ~ on the surface of the aluminum plate.
The aluminum plate was blast-treated by projecting melamine resin crushed into an acute polygonal shape of 840 μm. The above melamine resin has a Mohs hardness of 3 to 4 and a specific gravity of 1.47, and the surface roughness of the aluminum plate after the blast treatment is Rmax =
It was 29 μm. Next, polyester powder (manufactured by Kubo Paint Co., Ltd.) was adhered to the aluminum plate using an electrostatic powder coating device (manufactured by Japan Parker Rising Co., Ltd .; GX5000 manual gun model), and then 185 ° C. in an oven. Two
After heating for 0 minutes, the film was naturally cooled to form a coating film having a thickness of about 50 μm, and the appearance was inspected. In addition, a corrosion test with salt spray (100 hr) was performed on this painted aluminum plate,
Table 1 below shows the results of observing the corrosion state and performing a forced peeling test (tape peeling from the crosscut) after the corrosion test. Further, Table 2 shows the results of a combined cycle test (50 cycles) in which salt spray-drying-wetting was repeated instead of the salt spray. In addition, as comparative examples, those not subjected to the base treatment (Comparative Example 1), those subjected only to degreasing treatment (Comparative Example 2), those subjected to alumite treatment (Comparative Example 3), those treated with zinc phosphate (Comparative Example 4) ), The results of similar tests are also shown. In addition, as a base treatment shown in Comparative Example 5, iron shot,
The blasting treatment using a conventional blasting material such as sand, alumina, glass beads, etc. caused a large surface roughness and pinholes were generated, so the appearance inspection was defective. Therefore, no durability test was performed on Comparative Example 5.

[Table 1]

[Table 2] As is clear from Table 1 and Table 2, the coating layer treated by the base treatment method using the resin blast of the present invention has a good appearance (surface state) and is equivalent to the conventional alumite treatment and zinc phosphate treatment. It was confirmed that it has not only corrosion resistance but also excellent adhesion to an aluminum plate.

[Embodiment 2] A base material to be pretreated is a hot-dip galvanized steel sheet, and iron, cold-rolled steel sheet (SPC).
In the same manner as in Example 1 described above, a coating film made of polyester was formed on the sample C), and both salt spray test (100 hr) and combined cycle test (50 cycles) were performed. Are shown in Table 3 below. As a comparative example, one not subjected to the base treatment (Comparative Example 6,
The results of the same tests are also shown for 8), those subjected to chrome plating (Comparative Examples 7 and 9) and those treated with zinc phosphate (Comparative Example 10).

[Table 3] As is clear from Table 3, even in the case of iron-based materials, the coating layer formed by the base treatment method using the resin blast of the present invention has the same corrosion resistance as the conventional chromium plating treatment and zinc phosphate treatment. At the same time, it was confirmed that the adhesiveness to the base material was also excellent.

[0014]

As described above, according to the present invention,
When the coating layer is formed on the surface of the base material, the blasting process of spraying the projection material composed of the resin particles onto the surface of the base material in advance is performed, so that the base material surface can be optimized without being damaged. The surface can be treated to have a surface roughness, and the adhesion of the powder coating material can be improved.

[Brief description of drawings]

FIG. 1 is a schematic view showing an air blast treatment according to the present invention.

FIG. 2 is a schematic view showing a centrifugal blast treatment according to the present invention.

FIG. 3 is a diagram for explaining the outline of powder coating.

FIG. 4 is a diagram showing an outline of an externally charged powder coating method.

[Explanation of symbols]

10 Aluminum plate, 20 Projectile material supplying means, 21 Projectile material, 22 Pressurized tank, 23 Injection nozzle, 23S injection port, 24 Impeller rotor, 30 Base material, 31 Powder coating material, 32 Coating layer, 40 Electrostatic Gun, 41 Corona pin, 42 High voltage generator, 43 Electric lines of force.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Tetsuya Kaji             387-58 Sekiya, Kamakura City, Kanagawa Prefecture (72) Inventor, real name Tadashi             4-39-23 Nagaoka, Mizuho-cho, Nishitama-gun, Tokyo F-term (reference) 4D075 BB04Y BB91Y CA13 CA33                       DA06 DB02 DB05 DB07 DC11                       DC18 DC38 EA02 EB22 EB33                       EB35

Claims (7)

[Claims] 1. A powder characterized in that, when a coating layer is formed on the surface of a base material by a powder coating method, a blasting process of spraying a shot material composed of resin particles is previously applied to the surface of the base material. The method of surface treatment for body painting. 2. The ground treatment method in powder coating according to claim 1, wherein the resin shot material has a sharp polygonal shape. 3. The ground treatment method in powder coating according to claim 1, wherein the resin is a thermosetting resin. 4. The ground treatment method in powder coating according to claim 3, wherein the thermosetting resin is a melamine-based resin, a urea-based resin or a phenol-based resin. 5. The ground treatment method in powder coating according to claim 3, wherein one or both of iron oxide and carbon are added to the thermosetting resin. 6. The ground treatment method for powder coating according to claim 3, wherein conductive particles are added to the thermosetting resin. 7. The ground treatment method in powder coating according to claim 1, wherein the resin shot material is not coated with a surface active agent.