JPS5839238B2 - Drying method for electrodeposited paint on objects to be coated - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for drying a paint that has been electrodeposited on a workpiece, and more specifically, the present invention relates to a method for drying a paint that has been electrodeposited on a workpiece. After that, the electrodeposition zone
Washing zone - Setting zone (normal temperature drying zone) -
In an electrodeposition coating line consisting of a baking drying oven, the purpose of electrodeposition coating is to improve the efficiency of normal temperature drying in the setting zone by sending hot air near the entrance of the baking drying oven into the setting zone. The present invention relates to a method for drying painted paint.

Electrodeposition paints generally use a water-based solvent, so compared to volatile solvents such as thinner, it is not possible to adjust the natural evaporation temperature of the solvent by changing the boiling point of the solvent.

For this reason, the solvent contained in the paint applied to the object by electrodeposition (if it dries rapidly, it will suddenly evaporate at a temperature equivalent to the boiling point of water, causing surface problems such as popping (flanks) on the paint film. There was a problem with defects appearing.

For this purpose, conventionally, in an electrodeposition coating line consisting of an electrodeposition coating zone ■ - a water washing zone ■ - a setting zone ■ - a baking drying oven ■ as shown in Figure 1, the coated material is attached to a coating conveyor ■. The object ■ moves inside the booth ■,
The object to be coated is immersed in the electrodeposition bath ■ to electrodeposit the electrodeposition paint, and then in the washing zone ■, the unelectrodeposited paint liquid adhering to the object to be coated is washed away with a shower, and the object to be coated is transferred to the setting zone ■. The film was transferred to a drying oven to dry the water droplets adhering to it in the shower at room temperature, and then transferred to a baking drying oven to evaporate the water as a solvent.

The disadvantage of this case is that the drying time at room temperature in the setting zone is very long, from 10 to 30 minutes, which increases the length of the electrodeposition coating line and increases equipment costs and equipment space.

To this end, as shown in Figure 2, one or more air blow devices (■) are installed within the setting zone (■).
You can physically remove moisture adhering to the surface of the workpiece by air blowing, or install a hot air inlet ■ and hot air outlet ■ in the setting zone ■ as shown in Figure 3.
The idea was to install a heater and blow warm air at about 80°C onto the object to forcibly heat it.

However, the methods shown in FIGS. 2 and 3 were not satisfactory in terms of the quality of the coating, as they caused flaking and sagging phenomena.

The present invention provides an easy and low-cost method for drying electrodeposition paints commonly referred to as anionic and cationic electrodeposition paints.

More specifically, by installing an air blower that blows air in the opposite direction to the flow of the conveyor between the setting chamber (1) and the drying oven (2), the hot air in the drying oven is drawn into the setting chamber and applied to the object to be coated. By evaporating the moisture in the electrocoated paint and the moisture attached during washing with water in the setting chamber using hot air that is gradually raised from room temperature to the temperature in the drying oven, the drying time in the setting chamber is reduced. This is a method for drying paint that has been electrodeposited on an object to be coated, with the aim of shortening the drying time and improving the quality of the electrodeposited surface.

A preferred embodiment of the present invention will be explained based on FIGS. 4 and 5.

The present invention is applied to a painted object attached to a painting conveyor.
moves through the booth ■, is immersed in the electrodeposition tank ■ to electrodeposit the electrodeposition paint, and then in the washing zone ■, the unelectrodeposited paint liquid adhering to the object to be coated is washed away with a shower. It is characterized in that it is transferred to a setting zone (3) and dried with hot air that is successively raised from room temperature to the temperature inside the drying oven as it passes through this setting zone.

In order to increase the drying temperature in the setting zone ■ sequentially, the direction of the air outlet ■ on the inlet side wall of the baking drying oven ■ should be from the baking drying oven ■ toward the setting zone ■ and toward the object to be coated. By installing a plurality of air blow devices ■ in the vertical direction and blowing out an appropriate amount of air from these air blow devices, the heat inside the baking drying oven is attracted to the setting zone ■, and the final end (exit High-temperature warm air is sent to the area (near the entrance), while the beginning of the setting zone (near the entrance) is cooled by indoor air and is blown to almost room temperature.

The amount of induced heat can be controlled by changing the direction angle of the air outlet (2), and the forced heating temperature can be set arbitrarily.

In the present invention, the object to be coated moves and is blown with air by the air blowing device (1), and water droplets remaining on the lower end or recesses of the object to be coated are forcibly blown away.

Next, it moves to a baking drying oven [phase], where the moisture is finally evaporated and the coating film is fixed.

The air blowing device according to the present invention is equipped with one or more air outlets, the direction of which can be freely adjusted, and is installed on both side walls of the inlet of the drying oven. The amount of air blown can also be set arbitrarily.

The method according to the present invention is effective for drying electrodeposition paints using water as a solvent, and provides the following effects.

(1) Drying in the setting room ranges from room temperature to approximately 80°C.
Since the heating is performed by gradually increasing the temperature to ℃, the solvent evaporates slowly and does not cause any popping (
Armpit) does not occur.

(2) The heat source used for forced heating can use the exhaust heat of the baking drying oven, and compared to the conventional method using only an air blow device and the forced heating method using hot air, each of the following can be used. It is possible to obtain the same or better coating quality with less energy.

Next, the present invention will be explained in detail.

EXAMPLE A comparison was made between coated objects which were electrodeposited at room temperature and washed with water after electrodeposition, and dried by the conventional method and the drying method of the present invention.

The coating conditions and drying method are as follows.

(1) Coating conditions (2) Drying method (a) Conventional method a (room temperature drying method in the setting room: 1st
Figure) Setting: 30℃ x 15 minutes) Baking drying: 180℃ x 30 minutes (exhaust gas damper opening 3/4) (B) Conventional method b (normal temperature drying method using two-stage air blow in the setting chamber: Figure 2) ) Setting 30°C x 7 minutes ■ Air blow 200 N rrl/n (Number of nozzles: 26) (Blowing direction: perpendicular to the direction of movement of the object to be coated) ■ Setting 30°C x 8 minutes ○ Air blow 200 N rn' /n (Second attachment direction: perpendicular to the direction of movement of the object to be coated Number of gaps: 26 ■ Baking drying 180℃ x 30 minutes (exhaust gas damper opening 3/4) (c) Conventional method C (hot air blowing from setting chamber) Heat drying method by attaching: Fig. 3) Setting: 60°C x 15 minutes■ Baking drying: 180'C x 30 minutes (exhaust gas damper opening h) Invention method Setting: 30°→100°C x 15 minutes■ Air blowing 200 Nr7+3 (Number of nozzles = 26 spraying direction: 13 perpendicular to the direction of movement of the object to be coated, 13 at 135 degrees to the direction of movement of the object to be coated) Baking drying 180℃ x 30 minutes (exhaust gas damper opening 1/2 ) The results obtained using the above coating conditions and drying method are shown in Table 1 below.

As is clear from the above results, the conventional method a
It's almost impossible.

Furthermore, as seen in the conventional method blc using air blowing, even if the amount of air blowing is doubled, coating defects can hardly be eliminated.

Furthermore, as seen in Conventional Method C using forced heating, coating defects remain at the lower end and recessed portions of the object to be coated where water droplets remain.

As described above, drying the electrodeposition paint by the method of the present invention does not cause paint defects such as wrinkles and sagging, and the amount of air blowing is small, and the heat required for forced heating is reduced by the baking drying oven. By closing the exhaust gas damper opening, exhaust heat can be fully utilized, allowing effective drying work with low energy costs.

Furthermore, by adjusting the direction and air volume of the air blow nozzle, the amount of exhaust heat utilized can be adjusted, and the conditions for forced heating in the setting process can be arbitrarily selected.

[Brief explanation of the drawing]

Fig. 1 is a vertical cross-sectional side view showing an outline of the drying process according to the conventional method, Fig. 2 is a cross-sectional view of the air blowing process of the conventional method, which is used to eliminate the above-mentioned coating defects, and Fig. 3 is a cross-sectional view of the drying process according to the conventional method. FIG. 4 is a vertical side view schematically showing an embodiment of the method according to the present invention, and FIG. A simplified view of the l-A line. ■・・・Electrodeposition coating zone, ■・・・Water washing zone, ■・・・Setting sheath, ■・・・・・・
・・Baking drying oven, ■・・・Painting conveyor, ■・
...Object to be coated, ■...Tooth, ■...
・Electrodeposition tank, ■... Air blow device, ■...
...Warm air inlet, ■...Warm air outlet, ■...Air outlet.

Claims (1)

[Claims] 1 In an electrodeposition coating line consisting of an electrodeposition coating process - a water washing process - a setting process - a baking drying process, an air blow device installed at the entrance of the baking drying oven is used to dry the paint that has been electrodeposited on the object to be coated. This allows compressed air to be blown into the setting chamber in a direction almost opposite to the flow of the coating conveyor and toward the object to be coated, thereby drawing the exhaust heat from the drying oven into the setting chamber, and discharging the coating material after washing with water. A method for drying paint that has been electrodeposited on an object to be coated, which is characterized by heating and drying the object with gradually raised hot air from room temperature in the setting process to a temperature close to the temperature inside the drying oven. .