JPS5822261B2 - Electrostatic coating method for water-based paint - Google Patents

Description

[Detailed description of the invention] The present invention relates to an electrostatic coating method for water-based paint.

In recent years, diffusion of organic solvents in paints discharged from paint booths and drying ovens has become a problem, and water-based paints have been widely used as a means of dealing with this problem.

When using water-based paints, various problems occur compared to conventionally used organic solvent-based paints.

One of these is that since water-based paints are electrically conductive, it is difficult to apply electrostatic paints to water-based paints compared to general organic solvent-based paints.

In order to deal with these difficulties, a method of painting by spraying a water-based paint has been adopted, and various proposals have been made for charging methods.

According to one of them, as seen in the Landsburg REX gun, immediately after spraying, an electrode such as a pin placed between the spray gun and the object to be coated (hereinafter referred to as external charging method) , the paint mist is charged.

According to other suggestions, the Staif REA manufactured by Landsburg
As seen in the ERG-W gun manufactured by DeVilbiss Co., Ltd. or the EGD gun manufactured by Iwata Painting Machine Co., Ltd., an electrode is provided in the paint supply system insulated from earth, and the paint liquid immediately before spraying or the mist immediately after spraying is charged.

The coating method according to these proposals solves one of the problems associated with water-based paints.

However, when the inventors implemented all of the above-mentioned methods, they found that paint that did not adhere to the object to be coated (oversprayed paint ) was observed to adhere to the electrostatic coating gun.

As painting continues, and in extreme cases, in just a few minutes, the adhering conductive water-based paint can cause high voltage to leak to ground.
As a result, the electrostatic effect disappears.

In other words, a ground is created by electrically insulating and grounding the member that mechanically holds the electrode from the electrode, but when the electrode and the holding member are electrically connected by a conductive water-based paint. By doing so, the electrode is grounded.

As a result of intensive research, the present inventors have discovered that in order to solve the above-mentioned difficulties, the present inventors have found that, in an electrostatic coating method for charging atomized water-based paint, a sprayed paint is sprayed from behind the electrode used for charging. A method characterized in that air is supplied in substantially the same direction as the paint flow, and an electrostatic coating method in which a liquid water-based paint is charged inside a spray gun used for atomizing the water-based paint. A method is proposed, characterized in that an air stream flowing in substantially the same direction as the NRC paint stream is supplied from around the spray gun.

Next, a specific example in which the method according to the present invention is applied to an external charging method will be explained based on the drawings.

FIG. 1 is a diagram illustrating a situation in which a water-based paint is applied to an object 15 using a spray gun 2. As shown in FIG.

The spray gun 2 is supplied with water-based paint via a paint hose 11, and is supplied with atomizing air via a mater air hose 13.

In the case of airless atomization, the air hose 13 is omitted.

The air and water-based paint pass through a passageway (not shown) provided inside the spray gun 2 to the nozzle 12°, where the paint is atomized as it exits through an orifice provided therein.

The spray gun 2 is attached to the automatic coating machine 22 by a mounting jig 23.
is connected to.

A program in which a mounting jig 23 is predetermined to fit inside a slit 24 provided in an automatic coating machine 22.

Move by ram.

An external electrode rod 17 made of a metal tube is located above the spray gun 2 and whose position relative to the spray gun is fixed.

For example, a cable 16 for applying a high voltage of about -60 KV starts from two power sources (not shown) and connects to an external electrode rod 1.
7 in an electrically insulated state.

The high voltage cable 16 has a pin-shaped electrode 14 and a high resistance 18 (second
(Fig.) is conductive.

The external electrode rod 17 is made of a resin insulating material, and the pin-shaped electrode 11 is insulated from the automatic coating machine 22, the support 23, and the like.

Corona discharge occurs between the external electrode pin 14 to which a high voltage is applied and the grounded object 150 to be coated.

Therefore, when the water-based paint atomized by the spray gun passes through the corona discharge field, it is charged and directed toward the object to be coated.

In order to prevent a portion of the paint directed toward the object from overspraying as indicated by the dotted arrow 25 and then adhering to the outer electrode frame 17 or, in extreme cases, the mounting jig 13, an air blower 19 is installed. is provided.

Next, the air blower 19 will be explained in detail with reference to enlarged side views (FIG. 2) and (FIG. 3).

The air blower 19 is an annular body fixed to the outer peripheral surface of the external electrode rod 17, and has air blowing holes 426 arranged at equal intervals on the front end surface.

The air blowing hole may be one ring-shaped slit.

The air blower 19 must be placed behind the electrode pin 14.

This is not preferable because if the distance between the electrode pin 14 and the air blower 19 is too small and the latter comes out in front of the nozzle 12, there is a risk that paint ejected from the nozzle will collide with the air blower and close the hole.

The air blower 19 is connected by an air hose 20 to a compressed air supply source.

The airflow is therefore directed in the direction of the arrow 21.

The flow direction is the overspray flow direction 25 (first
Since it is oriented in the opposite direction to that shown in Figure), it can effectively prevent oversprayed paint from adhering.

Furthermore, since the spray direction and the air flow direction 25 are the same, the shape of the sprayed mist is not disturbed.

The air blown out from the air blower 19 is normally at room temperature.

According to the spray device as described above, the pin 1 used for charging
Since the air is sent from behind the electrode rod 4 in substantially the same direction as the spray flow, the pin 14 will not be grounded without the aqueous paint being deposited around the electrode rod 1γ.

In the illustrated spray device a pin-shaped electrode 14 is used.
However, this is an example of a known electrode.

Therefore, the method of the present invention is not limited to methods using such electrodes.

Further, although the air blower 19 is fixed to the electrode rod 17, it may be arranged so as to be slidable, or may be arranged apart from the electrode rod 17.

As an example, an air blower is arranged at the same height as the pin 14 between the electrode rod 17 and the spray gun.

An example of where a different electrode than that shown may be used is that an electrode (not shown) may be disposed within the nozzle 12.

In this case, it is preferable that the air blower (not shown) be constructed as an annular body surrounding the outer peripheral surface of the spray gun 2, and that air blowing holes are formed at equal intervals in the front end surface thereof.

As can be seen from the above description, according to the method of the present invention, the electrode is prevented from being grounded since air is blown toward the electrode from behind the electrode.

According to a preferred method according to the present invention, the water-based paint attached to the electrode rod or spray gun does not come into contact with the electrode pin because air is sent and spread from the entire circumference of the electrode rod 17 holding the electrode or the spray gun. grounding of the electrode pin is completely prevented.

It is effective to apply the method according to the present invention to water-based coating, especially continuous coating.

[Brief explanation of drawings]

Fig. 1 is a conceptual diagram of a temporary coating device for explaining one aspect of the method according to the present invention, Fig. 2 is an enlarged view of the apparatus in circle A in Fig. 1, and Fig. 3 is a front view of Fig. 2. It is. 2..., z, 7"v, -kang, 11... curved paint hose, 12... nozzle, 13... air hose, 14... Electrode pin, 15...
...Object to be coated, 17..Curved electrode, 19..Air blower.

Claims (1)

[Claims] 1. In an electrostatic coating method for charging atomized water-based paint, air is supplied from behind the electrode used for charging and in substantially the same direction as the sprayed paint flow. An electrostatic coating method for water-based paint, which is characterized by: 2. In an electrostatic coating method in which a liquid water-based paint is charged inside a spray gun used for atomizing the water-based paint, an air flow flowing in substantially the same direction as the sprayed paint stream is supplied from around the spray gun. An electrostatic coating method for water-based paint, which is characterized by: