JPH0659428B2 - Electrostatic flow dipping device for powder coating - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to an improved electrostatic flow dipping device in powder coating. More specifically, the present invention is
The present invention relates to an apparatus capable of performing coating with excellent charging efficiency and coating efficiency in powder coating by the electrostatic fluidization dipping method.

2. Description of the Related Art Conventionally, powder coating in which a synthetic resin powder such as an epoxy resin is attached to a metal surface and heat-fused to form a continuous coating film has a hard coating film and good abrasion resistance. It can be applied thickly (50 to 400μ), setting is not necessary, there is almost no loss of paint because uncoated powder is collected and reused, and since it is solvent-free, there is no risk of fire or poisoning due to solvent,
Since it has advantages such as, for example, outdoor durable structures that require thick coating, steel pipes, anticorrosion coating of chemical plants, etc., further utilizing excellent properties such as abrasion resistance and corrosion resistance, Widely used for painting steel furniture, appliances, industrial products such as enamel substitutes.

For such powder coating, various coating methods such as spraying method, fluidized dipping method, electrostatic spraying method and electrostatic fluidized dipping method are used. The dipping method combines the features of the fluidized dipping method and the electrostatic spraying method described above, and since it has high coating efficiency, it has recently been in the limelight in continuous automatic coating of a large amount of small quantities, such as a resistor. , It is used for the insulation coating of electric parts such as capacitors and other electric products, or for painting ironing boards and wire processing parts.

In this electrostatic fluidized dipping method, a device as shown in FIG. 1 of the accompanying drawings is usually used. FIG. 1 is a schematic cross-sectional view of an example of a conventionally used electrostatic fluidized dipping device, in which a chamber 1 made of an electrically insulating material such as hard vinyl chloride resin, glass fiber reinforced polyester, or reinforced polyester has a high density. An air rectifying plate (porous plate) 2 made of a porous plate such as polyethylene or ceramics is provided, and electrodes 3 are provided on the rectifying plate at regular intervals.

When a high DC voltage is applied to the electrode 3, the powder fluidized bed 5 introduced from the air inlet 4 and passing through the air straightening plate 2
The air therein is first charged, and then the charged air collides with the powder particles in the fluidized bed 5, whereby the charge of the air is transferred to the particles, which particles are essentially applied to the electrode 3 Since it has a charge of the same sign, it repels each other and moves upward, and as a result, a charged powder floating layer 6 is generated on the upper part of the powder fluidized bed 5. When the grounded object 7 to be coated passes on or in the powder floating layer, the charged powder particles are attracted to the object 7 by suction.

In such an electrostatic fluidized immersion method, air is efficiently charged to charge the powder, and a homogeneous charged powder floating layer is generated, so that the powder is efficiently and uniformly applied to the object to be coated. Therefore, various proposals have been made so far regarding the structure and shape of the electrodes, the structure of the flow tank, etc. (Japanese Patent Laid-Open Nos. 50-64333 and 55-55).
-51454 publication).

However, although these proposals have achieved the objectives to some extent with respect to the charging efficiency and the coating efficiency of the powder to the object to be coated, they are not always sufficient.

Problems to be Solved by the Invention Under the circumstances, an object of the present invention is to provide an apparatus capable of performing coating with excellent charging efficiency and coating efficiency in powder coating by the electrostatic fluidized dipping method. To provide.

Means for Solving Problems The present inventors have attempted to install a high-voltage applying electrode directly in a powder layer in a fluidized state in order to improve the charging efficiency at first, but at the beginning, it was extremely high. Even if it shows a good coating property, there is a problem that the electrode placed in the fluidized powder layer impedes the fluidity of the powder, so that the coating efficiency is gradually reduced.

The present inventors note that in order to solve such a problem, it is necessary to efficiently charge the flowing air and to form a good mixed state of the charged air and the powder particles. As a result of further research, in the electrostatic fluidized dipping device, the high voltage application electrode is formed of a specific conductive porous plate, and the air is allowed to pass through the electrode, thereby improving the efficiency of the moving air. It has been found that the air rectifying plate can be omitted in addition to the charging, and the present invention has been completed based on this finding.

That is, the present invention provides a conductive porous plate in which an electrode for high voltage application is made of a metal microsphere or a sintered body of metal short fibers in an electrostatic fluidized dipping device for performing powder coating with air rectified and applied with high voltage, or For powder coating, characterized in that a porous plate made of ceramics or an organic polymer material is formed of a conductive porous plate that has been subjected to a metal deposition treatment on the powder side surface, and has a structure that allows air to pass through it. An electrostatic fluidized dipping device is provided.

A feature of the present invention is that the air rectifying plate itself is made into an electrode, that is, a specific conductive porous plate having both the functions of the air rectifying plate and the electrode is provided at the same time. As compared with the conventional electrostatic fluidized dipping device in which the air rectifying plate and the electrode are separately installed, the loading efficiency, the powder coating efficiency and the throwing power are remarkably improved.

This is because, in the case of a conductive porous plate that has been subjected to a metal vapor deposition treatment on the powder side surface, it is a two-dimensional assembly of protruding electrodes with minute metal vapor deposition surfaces that can serve as electrodes, so the charging efficiency of the circulating air is extremely high. It is thought that well and charged air is uniformly blown to the powder. On the other hand, a conductive porous plate made of a sintered body of metal microspheres or metal short fibers can be regarded as one obtained by adding the thickness direction to the metal vapor deposition surface, that is, a three-dimensional projection electrode assembly, and similar effects can be obtained. Considered to have.

In the present invention, as the conductive porous plate having the functions of both the air rectifying plate and the high-voltage applying electrode at the same time, one made of a sintered body of metal microspheres or metal short fibers, or a ceramic or an organic polymer material. A porous plate having a powder side surface subjected to metal deposition treatment is used.

Examples of the metal used in the sintered body of the metal microspheres or the metal short fibers include any metal selected from conductive metals such as ammonium, copper, iron, zinc, titanium and other metals or alloys thereof. You can

A porous plate made of such metal microspheres or a sintered body of short fibers is relatively difficult to process and has a high unit price, but has high strength, all the air passages can serve as application electrodes, and the charging efficiency is high. It has high characteristics and does not impede fluidity. Further, a porous plate having an opening diameter of 1 to 200 μm and a porosity of 10 to 95% is preferably used.

On the other hand, as the metal used to perform the metal vapor deposition treatment on the powder side surface of the porous plate made of the ceramics or the organic polymer material, similar to the metal sintered body, any metal can be selected from the conductive metals. Metals can be used, and as the vapor deposition method, a usual method used for metal vapor deposition can be used. As the porous plate made of the organic polymer material, for example, a porous plate made of polyethylene or polymethylmethacrylate is preferably used. The opening diameter of the porous plate made of ceramics or organic polymer material is usually 5 to
The range of 200 μm and the porosity are preferably in the range of 10 to 95%.

The conductive porous plate obtained by subjecting the surface of the porous plate made of an organic polymer material to the metal deposition treatment has relatively low strength, but it can be processed into a free shape, is easy to maintain, and has a high charging efficiency. It is characterized by high price, no obstruction of fluidity, and relatively low price. On the other hand, conductive porous plate with metal deposition on the surface of ceramic porous plate has poor workability. It is characterized by its excellent strength.

As described above, since the conductive porous plate according to the present invention has respective characteristics, it may be appropriately selected as desired.

As the material of the chamber in the device of the present invention, those used in the chamber of a usual electrostatic fluidized dipping device, for example, hard vinyl chloride resin, glass fiber reinforced polyester, reinforced polyester, polyacrylic resin, etc. may be used. it can.

Further, as the powder used in the powder coating by the apparatus of the present invention, the powder used in the usual electrostatic fluidized dipping method,
Examples thereof include powders of organic polymer compounds such as epoxy resin, cellulose acetate butyrate, polyester, polypropylene, polyethylene, acrylic resin, and chlorinated polyester.

The electrostatic fluidized dipping device for powder coating of the present invention is provided with a conductive porous plate having both functions of an air rectifying plate and a high voltage applying electrode at the same time. Compared with the conventional electrostatic flow dipping device, by using, it is possible to perform coating with excellent charging efficiency and good powder coating efficiency and throwing power to the object to be coated. It is preferably used for insulating coating of electric parts such as capacitors, and other electric products, or for coating ironing boards, wire-processed parts and the like.

EXAMPLES Next, the present invention will be described in more detail with reference to Examples.

In the examples, an apparatus as shown in Fig. 2 was used.

That is, an end plate 12 made of an ABS resin plate having a thickness of 6 mm is integrally bonded to one opening of an acrylic resin cylindrical body 11 having an inner diameter of 120 mm, an outer diameter of 131 mm, and a length of 300 mm, and the vicinity of the end of the bonding of the end plate. Attach an air-introducing tube 13 with an inner diameter of 5 mm to the side of the cylindrical body of the
An apparatus having a structure in which a conductive porous plate 14 was set to 5 mm and a cable 15 from a high voltage power source was connected to the conductive porous plate 14 was used.

Example 1 Using the apparatus shown in FIG. 2, aluminum was used as a conductive porous plate on one surface of a polymethylmethacrylate porous plate having a thickness of 10 mm, an average opening diameter of 30 μm, and a porosity of 38 to 40%. A vapor-deposited material having a thickness of 3 μm was used, and the vapor deposition surface was placed on the upper side.

Mild steel with a length of 80 mm, a width of 18 mm, a thickness of 7 mm, and a weight of 95 g, with the lower end positioned approximately 40 mm above the vapor deposition surface of the conductive porous plate in the center of the tubular body of this device. The coated object 16 consisting of a rod was hung.

Next, 100 g of an epoxy resin powder [trade name F-219FBC manufactured by Somar Co., Ltd.] was charged as a coating powder, and then air was introduced from an air introduction tube and a voltage was applied to the conductive porous plate. .

The applied voltage was changed to 30 KV, 50 KV, and 70 KV, and the voltage was applied for 10 seconds to apply the powder to the mild steel rod. The results are shown in Table 1. The experiment was repeated 5 times to determine the average amount of coating.

Example 2 The applied voltage was 30 KV, and the voltage application time was 5 seconds, 10 seconds,
The same operation as in Example 1 was performed except that the time was changed to 15 seconds, and the coating amount was examined. The results are shown in Table 2.

Example 3 The applied voltage was 50 KV, the voltage application time was 5 seconds, 10 seconds,
The same operation as in Example 1 was performed except that the time was changed to 15 seconds, and the coating amount was examined. The results are shown in Table 3.

Comparative Example 1 The procedure of Example 1 was repeated, except that the conductive porous plate was placed so that the vapor deposition surface was on the lower side, and the coating amount was examined. The results are shown in Table 4.

Comparative Example 2 In Example 1, instead of the vapor-deposited polymethylmethacrylate porous plate, a wire mesh having a mesh as shown in Table 5 was formed on the upper surface of the same polymethylmethacrylate porous plate that was not vapor-deposited. The same operation as in Example 1 was carried out except that the closely contacted ones were used to examine the coating amount. The results are shown in Table 5.

Example 4 In Example 1, instead of the vapor-deposited porous plate made of polymethylmethacrylate, the thickness was 5 mm and the uniform opening diameter was 25 μm.
The coating amount was examined in the same manner as in Example 1, except that a porous ceramic plate having a porosity of 40 to 45% and having a thickness of 3 μm was deposited on one surface of the ceramic porous plate. The results are shown in Table 6.

Example 5 In Example 1, instead of the vapor-deposited porous plate made of polymethylmethacrylate, a thickness of 10 mm and a porosity of 4 were obtained by sintering copper fibers having an average fiber diameter of 60 μm and an average fiber length of 3 mm.
The same operation as in Example 1 was carried out except that 3% was used to examine the coating amount.

The results are shown in Table 7.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view of an example of an electrostatic flow dipping device for powder coating which is normally used. In the drawing, reference numeral 1 is a chamber, 2 is an air straightening plate, 3 is an electrode, and 4 is an air inlet. 5 is a powder fluidized bed, 6 is a powder floating layer, and 7 is an object to be coated. FIG. 2 is a schematic sectional view of an apparatus used in the embodiment of the present invention, in which reference numeral 11 is an acrylic resin tubular body and 12 is ABS.
A resin end plate, 13 is a tube body for introducing air, 14 is a conductive porous plate, 15 is a cable, and 16 is an object to be coated.

Claims (2)

[Claims] 1. An electrostatic fluidized dipping device for powder coating with rectified and high-voltage applied air, wherein a high-voltage application electrode is formed of a conductive porous plate made of a sintered body of metal microspheres or metal short fibers. The electrostatic fluidized dipping device for powder coating is characterized in that it has a structure that allows air to pass therethrough. 2. An electrostatic fluidized dipping device for performing powder coating with rectified and high-voltage applied air, wherein a high-voltage applying electrode is made of ceramics or an organic polymer material. An electrostatic fluidized dipping device for powder coating, characterized in that it is formed of a conductive porous plate that has been subjected to the above, and has a structure that allows air to pass through it.