JPH10277440A - Electrostatic coating method of water paint and electrostatic coating device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a contact electrified electrostatic coating method incorpolating an electrical insulating device for a water paint with an electric conductivity. SOLUTION: A paint-supply discharge electrode 4 and a coating discharge electrode 5 are provided at the tip of a main-body vessel 1 formed with an insulating material to apply a DC high voltage. A paint feed nozzle 8 is provided opposite to the paint-supply discharge electrode 4 in the main-body vessel and a grounded water paint is supplied. Consequently, the water paint is electrostatically charged, is atomized, is adsorbed to the paint-supply discharge electrode 4 and loses an electric charge. The water paint losing the electric charge is pneumatically transferred to the coating discharge electrode 5, is recharged, is atomized and flys to a material to be coated to coat the material.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrostatic coating using a water-based paint having conductivity.

[0002]

2. Description of the Related Art Electrostatic coating is used for coating metal products using a non-conductive organic solvent-containing coating. The principle is that the discharge electrode provided in the electrostatic coating machine has 60
By applying a DC high voltage of up to 120 kv, the paint sent from a paint storage tank or the like is charged and applied by Coulomb force generated between the paint and a grounded object. It has been practiced for a long time because of its efficiency.

[0003] Recently, the use of water-based paints has been expected as a measure against pollution and for the prevention of fires in paint factories. However, when a high voltage is applied to the discharge electrode of the electrostatic coating machine to bring it into contact with the water-based paint, the water-based paint has conductivity. Electric leakage from the tank not only prevented the electrostatic painting from being performed efficiently, but was extremely dangerous. Therefore, water-based paints have not been widely used.

In order to solve this problem, various types of so-called bolt blocks for electrically blocking the paint supply path have been tried. However, since a high voltage is applied to the path from the bolt block to the electrostatic coating machine. In addition, metal products cannot be used, it is difficult to transfer a large amount of paint to an electrostatic coating machine, and it is difficult to prevent electric leakage due to leakage of paint from a connection portion such as a tube.

In Japanese Patent Publication No. Hei 5-10983, there is disclosed an apparatus for electrostatically coating while arranging discharge electrodes at a position two to four times the diameter of the spraying end from the spraying end of the sprayer head while ensuring insulation. I have. According to this device, the spraying end supplying the paint and the discharge electrode are separated from each other, so that the insulation can be reliably achieved. However, because the discharge electrode is far from the paint outlet,
The coating did not come into contact with the coating material with certainty, and therefore the charging rate was low, and high coating efficiency could not be obtained. Therefore, an object of the present invention is to supply a grounded water-based paint to a discharge electrode to which a high voltage is applied while reliably insulating it practically. It is to provide a painting machine.

[0006]

Means provided by the present invention is to provide a coating supply discharge electrode and a coating discharge electrode at one end of a cylindrical container body formed of an insulating material, and to face the supply discharge electrode. Then, the paint supply nozzle is disposed in the container. A grounded water-based paint is supplied to the nozzle, the water-based paint is atomized by electrostatic force from the supply discharge electrode, and is made to fly inside the container body, and collected at one end of the supply discharge electrode. Then, the paint is transferred to the coating discharge electrode by pneumatic force, recharged, and flown toward the grounded object to be coated.

[0007]

According to the present invention, a paint supply discharge electrode is provided at one end in a cylindrical container formed of an insulating material, and a paint nozzle is provided in the container so as to face the discharge electrode. An aqueous paint maintained at ground potential is provided. Therefore, it is charged (positive) by the electrostatic force from the supply discharge electrode (negative polarity) disposed at one end of the cylindrical container, atomized, and directed toward the supply discharge electrode in the cylindrical container. Start flying, lose charge and stick. Therefore, no current other than the discharge current flows to the aqueous paint side. Further, the paint collected in the supply discharge electrode is transferred to the coating discharge electrode by compressed air, so that it is charged again (but negatively charged) and applied to the object to be coated. Hereinafter, the details of the structure, embodiment, and operation of the electrostatic coating method and the electrostatic coating machine provided by the present invention will be described with reference to examples.

[0008]

FIG. 1 is a sectional view showing an electrostatic coating machine according to an embodiment of the present invention, and FIG. 2 is a view of the electrostatic coating machine as viewed from the side of an object to be coated. In FIG. 1, reference numeral 1 denotes a cylindrical container main body formed of an insulator. Reference numeral 4 denotes a supply discharge electrode, and reference numeral 5 denotes a coating discharge electrode. Reference numeral 8 denotes a paint supply nozzle. Reference numeral 12 denotes a compressed air connection port for transferring paint. As shown in FIG. 1, discharge electrodes 4 and 5 are provided at one end of the cylindrical container body 1, and a paint nozzle 8 is provided inside the container body 1. Discharge electrodes 4 and 5
Power supply 30 in parallel or series
As a result, a DC high voltage having the same polarity and voltage is applied. Reference numeral 20 denotes a handle or a support, and the coating is performed with the center axis of the container 1 being vertical or horizontal. The paint supply amount is adjusted by the paint supply pressure so as not to exceed the electrostatic attraction of the discharge electrode 4.

The container body 1 is a cylindrical container having a diameter of 30 to 100 mm, and is formed of a resin product such as acrylic or PVC. It is preferable to use a transparent material because the state of contamination inside the main body can be clearly understood. If the diameter of the main body 1 is too small, it will be contaminated with flying paint, so it is preferable that the diameter is 30 mm or more. When applying 60 kv, the distance between the discharge electrode 4 and the paint nozzle 8 needs to be 30 mm or more, and more preferably 40 mm or more. However, when the thickness is 150 mm or more, the suction force due to the electrostatic force is weakened, which is not preferable. Therefore 40m
m or more and 150 mm or less. Similarly, when 120 kv is applied, 60 mm or more is required, 80 mm or more is more preferable, and 300 mm or more is not required.

The discharge electrodes 4 and 5 are made of metal such as stainless steel, copper, aluminum and brass. The coating discharge electrode 5
As shown in FIG. 1, a sharp divergent cup with a tip having a diameter of 15 to 40 mm is formed. It is preferable to form the body of the cup with an insulating material and to dispose a ring-shaped electrode at the tip because the amount of unnecessary discharge from the outer periphery of the discharge electrode is reduced. The supply discharge electrode 4 is made of a metal tube and has a smooth inner surface without any step. As shown in FIG. 2, the supply discharge electrode 4 is connected in the tangential direction of the sectional circle of the coating discharge electrode 5. It is preferable that the outer diameter and the inner diameter be at least larger than the inner diameter of the paint nozzle 8 and less than half of the bottom diameter of the cup-shaped discharge electrode 5.

The paint nozzle 8 is formed of an insulator tube having a length of 3 to 10 mm, and is connected to a tip of a metal tube 9. The metal tube 9 is grounded inside or outside the container 1 and is further connected to an external paint supply path (not shown).

As shown in FIG. 1, the air connection port 12 is provided below the paint nozzle 8, and is supplied with compressed air of ^{2 to} 7 kg / cm ² . The supplied air is a resin perforated plate 1
0, is supplied to the inside of the main body 1, the speed is increased at the tip of the container 1, and is sprayed together with the paint adhered to the discharge electrode 4 in the tangential direction of the cross-sectional circle of the discharge electrode 5. Therefore, the paint is given a centrifugal force, is transported to the object-side tip while rotating inside the cup electrode 5, and reliably contacts and recharges corona discharge ions formed at the tip of the discharge electrode 5. Therefore, the paint is atomized by the centrifugal force of the air and the electric charge obtained by the paint itself, and flies toward the object to be coated.

FIG. 3 shows a pin type discharge electrode for painting, and FIG.
FIG. 9 is a view showing another embodiment in which the coating discharge electrode and the supply discharge electrode are integrated, and the degree of atomization and the charging rate are different, so that they can be used properly according to the application. (In FIG. 3, 6 is a metal perforated plate.)

[0014]

According to the present invention, since the water-based paint is charged in direct contact with the discharge electrode, a high charging rate and therefore a high coating efficiency can be obtained. In addition, since the insulating mechanism is built in, no current other than the discharge current flows to the grounded water-based paint side.
Therefore, the same metal equipment as before can be used for the paint transport route. In addition, stable electrostatic coating can be performed without damaging the human body or equipment.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an embodiment.

FIG. 2 is a view from the side of an object to be coated.

FIG. 3 is a diagram showing another embodiment.

FIG. 4 is a diagram showing another embodiment.

[Explanation of symbols]

 1, cylindrical container main body 4, water-based paint supply discharge electrode 5, coating paint discharge electrode 8, water-based paint supply nozzle 12, compressed air connection port

Claims (2)

[Claims] 1. A paint supply discharge electrode and a paint discharge electrode are disposed at one end of a cylindrical container body formed of an insulating material, and a paint supply nozzle is provided in the container so as to face the supply discharge electrode. Is provided, the grounded water-based paint is supplied to the nozzle, and the water-based paint is atomized by electrostatic force from the supply discharge electrode,
Flying the inside of the container, collecting at one end of the supply discharge electrode, transferring this to the coating discharge electrode by air force, recharging, and flying toward the grounded coating object Electrostatic coating method for water-based paint 2. A cylindrical container body formed of an insulating material.
(2) a nozzle for supplying a grounded water-based paint, (3)
A paint supply electrode facing the nozzle, (4) a paint electrode facing the grounded object, and (5) a water-based paint collected at one end of the supply electrode. An electrostatic coating machine for water-based paint, comprising a nozzle for supplying compressed air to be transferred to an electrode, wherein the two discharge electrodes are provided at one end of the cylindrical container body, and the paint supply nozzle is provided in the container body.