JPS6012156A - Electrostatic painting apparatus - Google Patents

Abstract

PURPOSE:To form a uniform paint film on a resin plate in good efficiency, in electrostatically painting the surface of a bad conductor such as a resin plate, by providing an inverse potential charging apparatus and a conductive plate to the rear surface of the resin plate to form an electric field between the resin plate and a painting machine. CONSTITUTION:In painting the surface 1A of an electrically bad conductor plate 1 such as a synthetic resin plate by an electrostatic painting machine 4, a corona discharge electrode 11 is arranged to the side of the rear surface 1B of the resin plate 1. Corona discharge is generated between a plurality of corona pins 11A vertically provided to the discharge electrode 11 and the conductor plate 14 arranged between said corona pins 11A and the resin plate 1 to form a positive ionized region A. An electric field E is formed between the painting machine 4 charged to negative potential and the conductor plater 14 and the rear surface 1B of the earthed resin plate 1 is charged to negative potential while the surface 1A thereof is charged to positive potential by dielectric action and negatively charged fine paint particles are uniformly and electrostatically applied to the surface 1A of the resin plate charged to positive potential by dielectric action.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electrostatic coating apparatus that can perform electrostatic coating satisfactorily even on objects having a high electrical resistance value.

In general, electrostatic coating equipment has a minus 30 to 90
By applying a high voltage of about kV and keeping the object to be coated at ground potential, an electrostatic field is formed between the coating machine and the object to be coated, and paint is supplied to the coating machine. By doing so, the paint particles are grouped and the tinned paint particles are charged, and the charged paint particles fly along the electrostatic field and are applied to the object to be coated.

By the way, 1. When the object to be coated is an electrically conductive material such as a metal body, this type of electrostatic coating device has no electrostatic effect over the entire circumference of the object because the object to be coated is always held at ground potential. It is possible to achieve a sufficiently high level of coating.

However, the surface of the object to be coated is an electrically poor conductor, such as various synthetic resins, glass, ceramics, wood, etc.
If the material has a high electrical resistance value such as insulating sintered metal (hereinafter referred to as "synthetic resin"), or if the surface of the metal plate is treated with such synthetic resin, the coating Even if the object is set to have a ground potential, if negatively charged paint particles are applied, the charge given by the paint particles will not escape to the ground, and the surface of the object will be saturated with static electricity. As a result, they become negatively charged, and even if charged paint particles are discharged from the paint sprayer, they do not coat the object to be coated, and no electrostatic effect can be obtained.

That is, the principle of electrostatic coating is that in a state where the electric 4 tension is large, there must be a potential difference between the surface of the object to be coated and the paint particles or the tip of the sprayer. This potential difference must be maintained until the painting is finished, and at the same time
It must be large enough to ensure effective transfer efficiency. The reason for this is, first, to create a sufficiently large electrical attraction between the charged paint particles and the surface of the object to be coated, and second, to transport the charged paint particles from the coating machine to the surface of the object to be coated. This is because lines of electric force acting on the paint particles are formed in a strong state. However, the fact that the electrical resistance of the surface of the object to be coated, such as that of synthetic resin materials, is high means that the above two factors that act on paint particles cannot be obtained sufficiently. This means that the dielectric constant of the object to be coated has a strong influence on the surface condition of the object, which hinders the adhesion of paint particles.

For this reason, in conventional technology, when applying electrostatic coating to synthetic resin materials, a 4-ton treatment liquid, which is a type of antistatic agent, is applied in advance to coat the surface of the synthetic resin with a conductive coating film. The coating process was then carried out in the following order: electrostatic coating was carried out by spraying charged paint particles, and then the coated object was placed in a baking oven and baked.

Here, the conductive treatment liquid is, for example, a conductive treatment agent 'io' made of a hydrophilic ionizable organic compound (trade name: "Alkalyt 726J" manufactured by General Mills, Inc., USA) whose main component is an aliphatic quaternary ammonium salt. , diluted with about 5% isozorobyl alcohol, is used, and the conductive treatment liquid is sprayed onto the surface of the synthetic resin using a sprayer, or a conductive film is formed on the surface of the synthetic resin by depping treatment.

This conductive film is usually applied to a thickness of 0.1 [μm] 8 degrees, and absorbs moisture in the air by the action of the hydrophilic ionizable organic compound contained in the conductive treatment liquid. It was designed to maintain the six-electrification property of the synthetic resin surface.

However, in the conventional technology described above, as mentioned above, the humidity in the air is adsorbed and thereby the conductivity of the synthetic resin surface is maintained, so when a conductive treatment liquid is used, the humidity of the coating atmosphere is In general, 40% or more is required at 20℃.Result of Part B 1 The method using the above conventional technology is limited by the humidity of the coating atmosphere, and even if the conditions are met, the coating of metals and materials is not possible in the extremely dry winter season with low humidity. The disadvantage was that the coating efficiency was inferior compared to that of . On the other hand, if the humidity is too high, a large amount of moisture will enter between the surface of the object to be coated and the paint film, impairing the adhesion of the paint film. Particularly in paint booths where temperature and humidity are not controlled, products produced during the rainy season often have the disadvantage of poor adhesion of the paint film.

In addition, since the conductive treatment liquid uses ionizable organic compounds, it can cause pollution if sprayed in large quantities, and workers must be careful when handling it. There is.

Furthermore, there is a drawback that the application of the conductive treatment liquid tends to cause rust on peripheral equipment. From these points,
The above-mentioned dilution equipment using a conductive treatment liquid has the problem that in order to use it effectively, it requires a large-scale painting process and an unmanned automatic pre-treatment coating machine. be.

In order to solve the runner-up points and problems such as i, the present application was previously filed as a prior application, which describes a coating machine that sprays paint onto the surface of a coated object with a high electrical resistance value, and a coating machine that - a high voltage generating device that applies a high voltage at one potential, a reverse potential charging device provided on the * surface side facing the coating machine while sandwiching the object to be coated; It consists of a high voltage generator for a reverse potential that applies a back pressure at a potential opposite to that of the high voltage generator, and the reverse potential charging device forms an ionization zone on the back side of the object to be coated. As a corona discharge,
In addition, the excitation reverse potential charging device is an electric field generating electrode that forms an i-field between the excitation reverse potential charging device and the object to be coated, and the excitation reverse potential charging device is used to blow ionized air toward the object to be coated. An ionized air generator is used to hold the object at a predetermined potential, and each of these means eliminates or attenuates the charge from the charged paint particles on the surface of the object to be coated, thereby increasing the connection between the surface of the object and the coating machine. We have devised a structure that can maintain a constant potential between the two.

However, even in the case of the above-mentioned prior application, since the object to be coated is made of a material with high electrical resistance such as synthetic resin, there is a problem in that the entire surface of the object to be coated cannot be uniformly maintained at a constant potential. There is. For this reason, the electrostatic effect deteriorates depending on the type of object to be coated, the thickness of the material, etc., and there has been a drawback that a uniform coating film cannot be obtained over the entire surface of the object to be coated.

The present invention was made in view of the drawbacks of the prior application described above, and an object of the present invention is to provide an electrostatic coating device that can obtain a uniform coating film over the entire surface of an object to be coated. It is something.

In order to achieve the above object, the characteristics of the configuration adopted by the present invention are as follows: between the reverse gravity charging device to which a high voltage from a high voltage generator for reverse potential is applied and the back side of the object to be coated; A conductor made of a good electrical conductor is disposed in close contact with the back surface or apart from the back surface, and the entire surface of the object is coated by an electrostatic field formed between the conductor and the object. The purpose is to enable uniform electrostatic induction.

Hereinafter, each embodiment of the present invention will be described based on the drawings.

First, FIG. 1 shows a first embodiment of the present invention. In the figure, 1 is a resin plate (hereinafter referred to as a resin plate) made of a synthetic resin material as an object to be coated, and the resin plate 1 is The handle 2 is suspended from a conveyor 3 which is at ground potential, and the resin board 1 is kept at ground potential before painting begins. Reference numeral 4 denotes a coating machine for electrostatically coating the front surface IA of the resin plate 1, and the coating machine 4 is attached via an insulating arm 5 to a reciprocator 6 so as to be movable up and down. Further, the coating machine 4 is connected to a paint pump 8 via a paint hose 7', and is also connected to a high voltage generator 10 via a high voltage cable 9. Here, the high voltage generator 10 boosts the commercial voltage to, for example, -90 (kV) DC high voltage, and
is configured to apply.

The corona discharge electrode 11 has a plurality of corona pins IIA@IIA formed in a skewer shape.

..., each corona pin IIA is arranged at a predetermined interval in the vertical direction through an insulating rod 11 Bf: to enable corona radiation across the entire back side of the conductive plate to be described later, and For example, the tip part is 10 (c
m] spaced apart from each other.

The electrode 11 is connected to a high voltage generator 13 for reverse potential via a high voltage cable 12. The high voltage cable 13 for reverse potential connects the commercial power supply to a DC high voltage having a reverse potential to that of the high voltage generator 10, for example, +
The voltage is increased to 30 (kV) and applied to each corona pin 11A, and a corona discharge is generated from the tip of the corona pin IIA toward a conductive plate to be described later, thereby creating an ionized sphere A of positive ions.
can now be formed.

Furthermore, 14 is a corona pin IIA of the corona discharge electrode 11.
A conductive plate made of a good electrical conductor such as a metal plate is disposed between the rear surface IB and the rear surface IB of the resin plate 1, and the conductive plate 14 is arranged between the rear surface IB and the rear surface IB. The conductive plate 14 is formed as a plate arranged with an interval of, for example, 2 [m] between them, and is suspended from a high place of the painting booth via an insulating support 15. The press is charged by the corona terminal current from the electrode 11, and an electrostatic field Ef is formed between the press and the coating machine 4, and the electrostatic field E is configured to induce positive static electricity on the front IA side of the object 1 to be coated. has been done.

In order to perform coating using the coating apparatus configured as described above, first, -90 (k) generated from the high voltage generator 10 is applied.
V) is applied to the coating machine 4, and then a predetermined amount of paint is supplied from the paint pump 8. As a result, the paint particles electrostatically atomized or air atomized by the atomizer 4 are negatively charged by the high voltage applied to the atomizer 4, and the resin plate 1
The resin flies along the lines of electric force formed between the resin plate 1 and coats the front surface IA of the resin plate 1.

However, due to the negatively charged paint particles, the front IA side of the resin plate 1, which has a large electrical resistance value, tends to become electrostatically saturated from the ground potential to negative one after another. However, the back surface IB and the corona discharge electrode 1 are located on the back surface IB side of the resin board 1 which is sandwiched between the resin board 1t and faces the coating machine 4.
A conductive plate 14 is disposed between the corona discharge electrode 1 and the corona discharge electrode 1.
Since the high voltage generators 1 and 3 for reverse potential are connected to 1, corona discharge is performed from the corona pin IIA toward the conductive plate 14, which is exposed to the ionization sphere A of the glass. .

As a result, since the conductive plate 14 is a good electrical conductor, its entire surface is uniformly positively charged, and an electric field E is formed between it and the coating machine 4 as shown. When the resin plate 1 transported by the conveyor 3 enters the electric field E, the air layer between the back surface IB of the resin plate 1 and the conductive plate 14 and the resin plate 1 itself serve as a dielectric layer, and the resin Front IA of board 1
Therefore, the negative charge charged by the charged paint particles on the front surface IA of the resin plate 1 can be eliminated or attenuated, and the surface potential of the resin plate 1 is It appears to be at ground potential. In this way, an effective potential difference is maintained between the entire surface of the resin plate 1 and the coating machine 4, and the paint particles sprayed from the coating machine 4 can be efficiently attached to the resin plate 1.

Of course, the pin electrode can also be used to maintain the entire surface of the conductive plate 14 at a uniform potential. Further, the conductive plate 14 is the resin plate 1
Although it has been described that the rear surface IB is separated from the rear surface IB, the rear surface I
In this case, for example, an aluminum foil or the like may be used as the conductor 14, and the aluminum foil or the like may be attached to the back surface IB. In this case as well, the resin plate 1 is used as a dielectric layer and the front surface I
This can induce the A side to be positive.

Next, FIGS. 2 and 3 show the second embodiment of the present invention. A third embodiment is shown, and the same components as those of the first embodiment described above are denoted by the same reference numerals, and the explanation thereof will be omitted.

First, FIG. 2 shows an embodiment of the cell 2 of the present invention, and 21 is a photo reverse potential charging device provided on the rear IB side facing the coating machine 4 while holding the resin plate 1 therebetween, and its ionized air generator. in,
The air generator 21 is connected via a high voltage cable 22 to a high voltage generator 23 for reverse potential charging. Here, the high voltage generator 23 for increasing the reverse potential band boosts the commercial power supply to, for example, +3' (kV), and by applying this high voltage to the ionized air generator 21, the air generator 21 is activated. It is configured to blow air sucked in from the outside as positively charged ionized air onto the back surface of the conductive plate 14. In addition, also in this example, the resin plate 1
There is no difference from the first embodiment in that a conductive plate 14 is provided at a slight distance on the rear surface IB side.

Although this embodiment is constructed as described above, the front surface IA of the resin plate 1 tends to be negatively saturated due to the negatively charged paint particles in this embodiment as well. However, a conductive plate f4 is disposed on the back IB side of the fingerboard 1 between the back IB and the ionized air generator 21, and the ionized air generator 21 has a high voltage generator for reverse potential. Since the device 23 is connected, the entire surface of the conductive plate 14 is uniformly positively charged by the positive ionized air blown by the ionized air generator 21, and the coating machine 4
An electric field E is formed between the two. □ As a result, when the resin plate 1 enters the electric field E in the same way as in the first embodiment, the air layer between the back surface IB of the resin plate 1 and the conductive plate 14 and the resin plate 1 itself become dielectric. As a layer, the front IA side of the resin plate 1 is induced to have a shirasu potential over the entire surface.

Therefore, the negative charge that has been charged on the front surface IA of the resin plate 1 by the charged paint particles can be eliminated or attenuated, and the surface potential of the resin plate 1 becomes apparently ground potential. Thus, an effective potential difference is maintained between the entire surface of the resin plate 1 and the coating machine 4, and the paint particles sprayed from the coating machine 4 can be efficiently attached to the resin plate 1.

In this embodiment as well, the four-electric board 14 may be brought into close contact with the back surface IB of the resin board 1.

Furthermore, FIG. 3 shows a third embodiment of the present invention, which is characterized in that an electric field generating electrode 31 is used in place of the corona discharge electrode 11 used in the first embodiment described above. . That is, the electric field generating electrode 31 is connected to the electrode bin 3.
It is constructed by coating the entire surface of 1A with a dielectric material 32 such as synthetic resin. This allows high voltage cable 1
When a positive high voltage is applied from the high voltage generator 13 for reverse potential through the conductive plate 14 and the electric field generating electrode 31, no corona discharge or the like is generated from the electric field generating electrode 31. An electrostatic field E is formed between the conductive plate 14 and the atomizer 4, and a positive electric field is induced to the front side 14A of the conductive plate 14, and a negative electric field is induced to the rear side 148. Electrostatic field E! is formed, the glass is guided to the front IA side of the resin plate 1, and the minus current is guided to the back IB side.

Although the present embodiment is configured as described above, an electric field El is formed between the back surface 14B of the conductive plate 14 and the field generating electrode 31, and the dielectric 32 interposed between the back surface 14B and the field generating electrode 31 and the air layer become a dielectric layer and are electrostatically induced, so that the front side 14A of the conductive plate 14 has a positive potential, and the back side 14B
side has a negative potential. On the other hand, the front 1 of the 4 electric board 14
An electric field E2 is also formed between the paint sprayer 4A and the paint sprayer 4, and the resin plate 1 and the air layer interposed between them act as a dielectric layer and are electrostatically induced, so that the front IA side of the resin plate 1 has a positive polarity. It is induced to have a potential. Therefore, a predetermined potential can be maintained between the front surface IA of the resin plate 1 and the coating machine 4,
In this state, electrostatic coating can be effectively performed by the coating machine 4.

Although this embodiment has been described as using the electrode bin 31A as the electric field generating electrode 31, a flat electrode disposed parallel to the conductive plate 14 may be used. In addition, from the viewpoint of AFi safety, cleanability, etc., the dielectric material 32 is
Although the above description assumes that the material is coated with a coating, it is not necessarily necessary to coat the material. Furthermore, in the case of one embodiment, there are six electric plates 14.
Back side 14B and electric field generation type lf! , 31 is desirably made as narrow as possible, and on the other hand, it is also possible to make the insulation plate 14 closely contact the back surface IB of the resin plate 1.

The embodiments of the present invention have been described in detail above, and although the resin plate 1 has been described as an example of the object to be coated, the object to be coated is not limited to a plate-shaped object, but may also be a rod-shaped object or a box-shaped object. , or may be of any shape, such as an automobile body or an electrical appliance. Therefore, the conductive plate 14 can also be formed into any shape to match the shape of the object to be coated; in this case, it is sufficient to attach it close to or in close contact with the back surface of the object to be coated. Furthermore, although it has been described that the handle 2 is of the □ type in which it is suspended from the conveyor 3, the conveyor 3 is a ground traveling type conveyor, and the handle is provided upwardly from the conveyor, and the handle is suspended from the conveyor 3. It may also be configured such that the object to be coated is placed on it and the coating work is performed.

The electrostatic coating device according to the present invention is as described in detail above, and includes a conductor between the reverse potential charging device and the back side of the object to be coated, either in close contact with the back surface or apart from the back surface. Since the structure is such that the surface side of the object to be coated can be electrostatically coated while maintaining the surface side at a predetermined potential, a uniform coating film can be formed over the entire surface.

[Brief explanation of the drawing]

Fig. 1 is a system diagram of an electrostatic coating device showing a first embodiment of the present invention, Fig. 2 is a system diagram showing a second embodiment of the invention, and Fig. 3 is a system diagram showing a third embodiment of the invention. FIG. 3 is a partial diagram showing an example. l...Object to be coated, 4...Coating machine, 10...High voltage generator, 11...Corona discharge electrode, 13.23...
High voltage generator for reverse potential, 14... conductor, 21...
・Ionized air generator, 31...Electric field generating electrode, A・
...Ionization sphere, Ea El p E2... Electrostatic field.

Claims (1)

[Claims] (1) A coating machine that sprays paint onto the surface of the object to be coated, which has a high electrical resistance value, and a high voltage generator that applies a high voltage to the potential of the coating. A reverse potential charging device is provided on the side of the row back facing the coating machine while sandwiching the object to be coated, and the reverse potential! , the equipment! 1tI In an electrostatic coating device comprising a high voltage generator for a reverse potential for applying a high voltage at a potential opposite to that of the high voltage generator, the four-level charging device and the back side of the object to be coated. Between the side and the back! 7. Alternatively, an electrostatic coating device characterized in that a conductor of good electrical conductivity G1-1p is disposed apart from the back surface.