JP2000107676A - Powder coating - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form a uniform coating film free from spots or the like by sticking powder particles blown up into a floating tank and given electric charge to the surface of a material to be coated and making arbitrary time elapse before lowering the given electric charge and further sticking the powder particles to the surface of the material to be coated. SOLUTION: Powder particles 4 put in a floating tank 2 are blown up by jetting of air passing through a perforated plate 3 from below to above. At this time, by feeding -60 kV as initial voltage for 30 sec from coating start-up to an electrode body 12 connected to a voltage device 9, air in the floating tank 2 is ionized to give electric charge to powder particles 4, and by air jetting from an air jetting hole of a coating air pipeline 13, the particles are caused to flow horizontally. In this way, the powder particle 4 are stuck to the surface of a material to be coated 11 movable by a moving device 10 to which a ground 6 is connected. When about 30 see elapsed after coating startup, applied voltage is dropped to about -15 kV to further stick the powder particles 4 to the surface of the material to be coated 11.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a powder coating method having excellent coating film smoothness.

[0002]

2. Description of the Related Art Painting of parts, not only automobile parts,
It is frequently used for the purpose of improving appearance and rust prevention. In the coating, powder coating is a technique that has attracted attention. Powder coating is easier to collect paint and has better recyclability than conventional solvent coating and water-soluble coating,
This technology has attracted attention because there is no need to worry about environmental pollution because no solvent is used.

[0003] However, powder coating is not as good in smoothness of finished appearance as solvent coating or the like, and in order to achieve a finished appearance equivalent to solvent coating, it is required to be 1.5 times or more, about 60 to 80 microns or more. Had to be formed.

In order to improve the smoothness of a powder coating thin film, there is one disclosed in Japanese Patent Application Laid-Open No. 9-208855. It has an average particle size of 5 to 15 microns, a 90% cumulative particle size of 15 to 25 microns, and a spherical particle shape used for powder coating.

[0005]

However, in the powder coating described above, for example, powder particles having an average particle diameter of 25 microns or less are required to have rust prevention properties like automobile parts and have a coating thickness of 2 μm.
When the particle diameter is required to be 5 microns or more, the charged powder particles having an excessive charge cause electrostatic repulsion due to the charge and are not sufficiently adhered to the surface of the object to be coated, so that a so-called spot is formed on a coated surface. The problem arises.

Therefore, an object of the present invention is to provide a powder coating method capable of obtaining a coating having excellent smoothness of a coating film by a simple method.

[0007]

Means for Solving the Problems To solve the above-mentioned problems, the invention of claim 1 blows up the powder particles into a floating tank to give an electric charge to the floating powder particles, and the object to be coated in the floating tank is provided. In the powder coating method of moving the powder particles to adhere to the surface of the object to be coated, after the charged powder particles blown up into the floating tank and adhered to the surface of the object to be coated, After the time, the application of electric charge to the suspended powder particles is stopped or a state in which a minute electric charge is applied, and the powder particles are further adhered to the surface of the object to be coated. The amount of charge increases due to the adhered powder particles, but after an arbitrarily set time, uncharged or finely charged powder particles are sprayed on the surface of the workpiece, Attaches to the surface of workpiece without electrostatic repulsion And it is possible to obtain a uniform coating film is not like plaques.

[0008]

Embodiments of the present invention will be described with reference to the drawings. 1 is a sectional view of a powder coating apparatus according to the present invention, FIG. 2 is an operation diagram of voltage and coating air pressure according to the present invention, and FIG. 3 is a front view and a sectional view of an electrode body according to the present invention.

As shown in FIG. 1, a powder coating apparatus 1
Is a floating tank 2 for coating an object 11 to be coated, a porous plate 3 disposed in a lower part of the floating tank 2, powder particles 4 supplied on the porous plate 3, And a blowing air passage 5 communicating with a blowing air supply device (not shown) that blows the powder particles 4 into the floating tank 2, and an electrode body that applies electric charges to the powder particles 4 floating in the floating tank 2. 12, a moving device 10 for moving the object 11 in the floating tank 2,
Painting air pipe 13 for flowing powder particles 4 in the horizontal direction
It is composed of

The powder particles 4 are supplied from the supply passage 8 to the porous plate 3.
It is supplied into the container 14 installed above, and is vibrated by the vibrating device 7 connected to the container 14, so that it is uniformly diffused on the porous plate 3 and is prevented from aggregating.

As shown in FIG. 3, the electrode body 12 has an electrode 12a projecting in a horizontal direction from a resistor 12c for ionizing air supplied through a passage 12b and an ionized air in the floating tank 2 horizontally. And an air injection hole 12d that flows in the direction.

First, the powder particles 4 are blown up into the floating tank 2 by air from an air passage 5 passing through the porous plate 3 from below to above.

The electrode assembly 12 connected to the voltage device 9 capable of generating a high voltage is supplied with -60 kV from the voltage device 9 for 30 seconds from the start of painting as an initial voltage as shown in FIG. At the same time, the air is ionized and caused to flow in the horizontal direction through the air injection holes, thereby imparting charges to the powder particles 4 and flowing in the horizontal direction in the floating tank 2. The coating air pipe 13 is sprayed with air for causing the powder particles 4 to flow in the horizontal direction in the floating tank 2. As shown in FIG. 2, the electrode body 12 ionizes the air and causes the air to flow. When the air pressure is weak, for example 0.1-0.2kg
f / cm ² .

The powder particles 4 given the flowing charge are:
It adheres to the surface of the object to be coated 11 which can move in the floating tank 2 by the moving device 10 to which the earth 6 is connected. Since the attached powder particles 4 are charged, the object 11 to be coated 11
The plurality of powder particles 4 repel each other on the surface of the substrate 11 and are uniformly dispersed on the surface of the object 11 to be coated.

After 30 seconds from the start of the coating, the voltage supplied from the voltage device 9 to the electrode body 12 is dropped as an intermediate voltage from -60 kV to -15 kV and supplied for 60 seconds. As a result, the powder particles 4 carry less electric charge.
When air is injected in a horizontal direction at a pressure of about f / cm ² , the air flows in the floating tank 2 in the horizontal direction, and
To form a uniform coating film.

However, the present invention is not limited to the above-mentioned initial voltage and its supply time, intermediate voltage and its supply time.

[0017]

[Table 1]

As shown in Table 1, the supply time may be appropriately set to 20 to 30 seconds at an initial voltage of -60 kV and to 60 to 90 seconds at an intermediate voltage of 0 to -15 kV.

[0019]

As described above, in the powder coating method according to the present invention, the initial voltage supplied for adding electric charge to the powder particles is stopped or reduced.
Although the amount of charge increases due to the attachment of the charged powder particles to the surface of the object to be coated, the uncharged or minutely charged powder particles after an arbitrarily set time. Is sprayed onto the surface of the object to be coated, and adheres to the surface of the object without electrostatic repulsion, thereby obtaining a uniform coating film without spots or the like.

In addition, since a high voltage is not always used, power consumption can be suppressed and coating can be performed at low cost.

[Brief description of the drawings]

FIG. 1 is a sectional view of a powder coating apparatus according to the present invention.

FIG. 2 is an operation diagram of a voltage and a coating air pressure according to the present invention.

FIG. 3 is a front view and a cross-sectional view of an electrode body according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Powder coating device 2 Floating tank 3 Porous plate 4 Powder particle 5 Blow-up air passage 9 Voltage device 11 Workpiece 12 Electrode body 13 Painting air piping

Claims (1)

[Claims] An electric charge is applied to the powder particles that are blown up and floated in a floating tank, and the object to be coated is moved in the floating tank to deposit the powder particles on the surface of the object to be coated. In the powder coating method of attaching, after the powder particles blown into the floating tank and given a charge adhere to the surface of the object to be coated, the charge is applied to the powder particles floating after an arbitrary time. A powder coating method, wherein the application is stopped or a small charge is applied, and the powder particles are further attached to the surface of the object to be coated.