JP2001121067A - Defoaming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a defoaming apparatus with a simple structure and capable of easily improving the defoaming effect. SOLUTION: The defoaming apparatus 6 is to be installed in an intermediate part of a coating material circulation system of a coating apparatus for circulating a coating material 1 between a coating part a coating material tank 2 to coat an object material A with a coating material 1 in a coating part. The deforming apparatus 6 is provided with a defoaming treatment chamber 7 for accelerating flotation separation of foams in the coating material 1 and an evacuation means 8 for accelerating defoaming floating foams in the deforming treatment chamber 7. The defoaming treatment chamber 7 is divided into two sections 13a, 13b in the horizontal direction by one partitioning plate 12 and these two sections 13a, 13b mutually communicate with each other in the space above the partitioning plate 12 and in the coating material in the lower side and a reception part of a coating material 2 containing foams is formed in one section 13a and a discharge part of the defoamed coating material 2 is formed in the other section 13b and a suction part 15 of the evacuation means 8 is formed above the liquid surface of the latter section 13b.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a defoaming apparatus used in a coating apparatus for circulating a coating material between a coating part and a coating tank and applying a coating material to a material such as a metal plate in the coating part.

[0002]

2. Description of the Related Art Many coated metal sheets are manufactured by a roll coating apparatus. A case where a steel plate is coated by a roll coating apparatus having two coating rolls will be described with reference to FIG.

In the apparatus shown in FIG. 2, 1 is a paint, 2 is a paint tank, 3 is a paint circulation pump, 4a and 4d are paint pipes,
5 is a paint pan, 9 is a pickup roll, 10 is an applicator roll, 11 is a backup roll, and S is a steel plate.

The paint 1 is sent from a paint tank 2 to a paint pan 5 by a paint circulation pump 3 via a paint pipe 4a. In the paint pan 5, the pickup roll 9 whose lower part is immersed in the paint 1 is rotated to pump up the paint 1, and the pumped paint 1 is transferred to the rotating applicator roll 10,
Further, it is transferred and coated on a steel sheet S which is wound around a backup roll 11 and travels. Steel plate S coated with paint 1
Is baked by a baking facility (not shown) into a coated steel plate. A part of the paint 1 sent from the paint tank 2 to the paint pan 5 adheres to the steel plate S, but excess paint 1 returns to the paint tank 2 via the paint pipe 4d.

In the apparatus shown in FIG. 2, the excess paint 1 pumped up by the pickup roll 9 is scraped off by the applicator roll 10, and bubbles are generated when returning to the paint pan 5. The paint 1 is circulating between the paint tank 2 and the paint pan 5, and the circulation of the paint 1 also generates air bubbles. When the paint 1 containing air bubbles is pumped up by the pickup roll 9, transferred to the applicator roll 10, and further transferred to the steel sheet S,
A coating defect occurs on the steel sheet S.

Normally, in the paint pan 2, air bubbles introduced into the paint pan 2 are placed in front of the pickup roll 9 in the paint pan 2 so that bubbles brought into the paint pan 2 are not caught in the paint 1 pumped by the pickup roll 9. Spaces and partitions are provided to promote floating and foam breaking. In order to prevent air bubbles from accumulating in the paint pan 5, the paint 1 overflows from the paint pan 5 and the paint tank 2
And discharge air bubbles to the paint tank 2 together with the paint 1,
The discharged bubbles float in the paint tank 2 and break.

When the paint 1 has a low viscosity, bubbles are strong in the action of floating and breaking bubbles, so that there are few bubbles in the paint, and thus the bubbles of the paint 1 pumped up by the pickup roll 9 are small.

[0008] In recent years, the required quality has been diversified with the expanded use of the coated steel sheet, and therefore, there is a case where the paint 1 having higher viscosity than before is used. With the high-viscosity paint 1, the action of floating bubbles and breaking bubbles becomes insufficient. Therefore, bubbles generated when the paint 1 scraped off by the applicator roll 10 returns to the paint pan 5 and bubbles generated during the circulation of the paint are accumulated in the paint 1 without breaking and increase, and the pickup roll is increased. 9 pumps the paint 1 containing air bubbles, and cannot prevent the occurrence of paint defects.

Japanese Patent Application Laid-Open No. 7-100423 describes that a defoaming device provided with a vacuum device is provided in the middle of a paint supply system to continuously remove bubbles from the paint.

FIG. 3 shows a defoaming device described in the above-mentioned publication. A paint 32 containing bubbles in a paint pan 31 is pumped up by a pickup roll 33 and transferred to a transfer roll 34.
After being stretched into a thin film at the transition portion between the transfer roll 34 and the pickup roll 33, it is transferred onto the surface of the transfer roll 34. The paint 32 transferred onto the transfer roll 34 is applied to the vacuum seal roll group 3
After passing through a nip portion between the transfer roll 5 and the transfer roll 34, it enters a vacuum chamber 37 maintained at a predetermined vacuum state by a vacuum pump 36.

The bubbles contained in the paint 32 film on the transfer roll 34 that has entered the vacuum chamber 37 expand in volume and break because the paint film thickness is thin. The bubbles in the paint 32 that have not been broken on the transfer roll 34 break due to the shearing deformation that occurs when the paint 32 transfers from the transfer roll 34 to the surface of the discharge roll 38. The defoamed paint 32a from which the air bubbles have been removed is discharged to the atmosphere through the vacuum roll group 35 by the rotation of the discharge roll 38.

The defoamed paint 32a discharged into the atmosphere from the vacuum chamber 37 by the discharge roll 38 is scraped by the scraper 40 of the collection means 40 disposed in contact with the surface of the collection roll 39.
a, and supplied to the coating unit 43 via the defoamed paint tank 41 and the pump 42.

[0013]

The defoaming device shown in FIG. 3 has a problem that the structure of the device is complicated and the equipment cost and the maintenance cost are high.

In consideration of the above circumstances, the present invention can be used in a coating apparatus for circulating a paint between a paint part and a paint tank and applying paint to a material to be painted in the paint part. It is an object of the present invention to provide a defoaming device capable of increasing the temperature.

[0015]

Means of the present invention for solving the above problems are as follows. (1) A defoaming device provided in the middle of a paint circulating system of a coating device for circulating paint between a coating portion and a paint tank, and coating a material to be coated in a coating portion, wherein the defoaming device is provided. Is provided with a defoaming treatment chamber that promotes the floating separation of bubbles in the paint and an exhaust unit that promotes the defoaming of the bubbles that floated in the defoaming treatment chamber,
The defoaming treatment chamber is internally partitioned by a single partition plate into two sections in a horizontal direction, and the two sections communicate with each other in a space above the partition plate and a paint below the partition plate;
One of the sections is provided with a receiving section for paint containing air bubbles, the other section is provided with a discharge section for defoamed paint, and the suction section of the exhaust means is disposed above the liquid level in the other section. And defoaming device.

(2) The defoaming device according to (1), wherein a net for breaking the sucked air bubbles is provided in the suction portion of the exhaust device.

(3) The defoaming apparatus according to (1) or (2), wherein the coating section is a roll coating apparatus having a paint pan.

[0018]

FIG. 1 is a diagram showing a main part of a roll coating apparatus provided with a defoaming apparatus according to an embodiment of the present invention. Hereinafter, an embodiment of the present invention will be described with reference to FIG.

In FIG. 1, 1 is a paint, 2 is a paint tank, 3 is a paint circulation pump, 4a to 4c are paint pipes, 5 is a paint pan, 6 is a defoaming device, and a defoaming treatment chamber 7 and an exhaust pump 8 are provided. Prepare. 9 is a pickup roll, 10 is an applicator roll, 11 is a backup roll, and S is a steel plate.

The interior of the defoaming chamber 7 is horizontally partitioned by a single partition plate 12 into two sections 13a and 13b. The sections 13a and 13b are divided into a space above the partition plate 12 and a paint In one area 13
a, the paint 1 discharged from the paint pan 5 via the paint pipe 4b is received, and the paint 1 is discharged from the bottom of the other area 13b to the paint tank 2 via the paint pipe 4c. . The suction port 15 of the suction pipe 14 of the exhaust pump 8 is provided on the side wall of the defoaming chamber 7 above the liquid level in the other area 13b, and the net 16 is provided at the suction port 15.

The paint 1 is sent from a paint tank 2 to a paint pan 5 by a paint circulation pump 3 via a paint pipe 4a. In the paint pan 5, the pickup roll 9 whose lower part is immersed in the paint 1 is rotated to pump up the paint 1, and the pumped paint 1 is transferred to the rotating applicator roll 10,
Further, it is transferred and coated on a steel sheet S which is wound around a backup roll 11 and travels. Steel plate S coated with paint 1
Is baked by a baking facility (not shown) into a coated steel plate.

Paint 1 pumped by pickup roll 9
A part of the paint adheres to the steel plate S, but the excess paint 1 is scraped off by the applicator roll 10, falls and returns to the paint pan 5. At that time, bubbles are generated. The generated bubbles are discharged to the area 13a of the bubble processing chamber 7 via the paint pipe 4b together with the excess paint 1. In the area 13a, the flow is calmed down, and the air bubbles in the paint 1 are trapped by the partition plate 12 and float on the bath surface.

The paint 1 in the area 13a from which air bubbles have been removed by floating
Flows from the communication part below the partition plate 12 to the area 13b.
In the area 13b, the paint 1 not removed in the area 13a
Bubbles inside float up and defoaming is further performed.

When the height of the air bubbles floating on the bath surface in the area 13a and exceeding the upper end of the partition plate 12, the air bubbles move to the area 1
It moves from 3a to zone 13b and accumulates together with air bubbles floating from zone 13b on the bath surface of zone 13b.
During this time, the bubbles come into contact with each other, so that the bubbles become large and break.

The atmosphere (air) in the defoaming chamber 7 is sucked by the exhaust pump 8 from the suction port 15 and exhausted out of the defoaming chamber 8. In response, the atmosphere of the defoaming chamber 7 flows from the areas 13 a to 13 b and further to the suction port 15. This further promotes the movement of the bubbles in the area 13a to the area 13b, the increase in the size of the bubbles, and the breakage of the bubbles.

The air bubbles accumulated without being broken are the suction ports 1
When it reaches the height of 5, it is sucked by the exhaust pump 8 and passes through the net 16 provided at the suction port 15. Since the bubbles are large and easily broken, the bubbles easily break when passing through the net 16, and the broken paint 1 returns into the bubble treatment chamber 7. Therefore, the paint 1 is prevented from entering the vacuum pump 8.

Defoamed paint 1 defoamed in area 13b
Returns from the outlet at the bottom of the area 13b to the paint tank 2 via the paint pipe 4c. The defoamed paint 1 returned to the paint tank 2 is sent again to the paint pan 5 by the paint circulation pump 3.

In the present apparatus, since the defoaming device 6 is arranged to defoam the paint 1 discharged from the paint pan 5, not only the bubbles generated during the circulation of the paint but also the pickup roll 9 It is possible to efficiently remove bubbles generated when the excess paint 1 that has been pumped back to the paint pan 5 and, even if the paint 1 has a high viscosity, it is ensured that bubbles are accumulated in the paint 1 and increased due to paint circulation. Can be prevented. Therefore, entrapment of air bubbles in the paint 1 pumped up by the pickup roll 9 can be prevented, and occurrence of a coating defect caused by entrainment of air bubbles can be prevented. In addition, the defoaming device 6 has a simple structure, and equipment and maintenance costs are low.

The defoaming device of the present invention can be widely used as a defoaming device of a coating device for coating while circulating the coating material. The coating device is not limited to a roll coating device, and the defoaming device may be provided either in the paint supply system to the coating unit or in the paint return system from the coating unit. In the case of roll coating equipment, if a defoaming device is installed behind the paint pan where many air bubbles are generated, that is, in the middle of the paint return system from the coating part to the paint tank, the defoaming effect can be improved with a small device. Is more effective.

[0030]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A paint 1 is circulated between a paint tank 2 and a paint pan 5 by using a roll coating device having a defoaming device 6 shown in FIG. 1, and each coating roll 9, 10 is indicated by an arrow in FIG. Rotated as shown, a steel plate S having a thickness of 1.0 mm and a width of 914 mm
The paint 1 was coated so that the dry film thickness became 1 μm, and the amount of coating defects caused by bubbles in the coated steel sheet was examined. At that time, the defoaming effect was examined for the presence or absence of the partition plate 12 and the exhaust device 8 in the defoaming device 6 and the presence or absence of the net 16 in the exhaust device 8. The amount of paint defects was evaluated by the number of paint defects caused by bubbles per 1000 m of steel plate length. Table 1 shows the survey results.

Table 1 also shows the incidence of coating defects on steel sheets when the same coating was performed with a coating apparatus (conventional apparatus) having no defoaming apparatus (conventional apparatus).

[0032]

[Table 1]

As is evident from Table 1, the steel sheet of the present invention has a significantly reduced incidence of coating defects as compared with the steel sheets of the comparative example and the conventional steel sheet. When the partition plate 12 and the net 16 are provided side by side, the above effect is further improved.

[0034]

The paint is circulated between the paint section and the paint tank,
When the defoaming device of the present invention is provided in a coating device for coating a material to be coated in a coating section, bubbles in the paint can be efficiently defoamed even with a high-viscosity paint. The defoaming device of the present invention,
The structure is simple, and equipment and maintenance costs are low.

[Brief description of the drawings]

FIG. 1 is a diagram showing a roll coating apparatus including a defoaming apparatus according to an embodiment of the present invention.

FIG. 2 is a diagram showing a conventional roll coating apparatus.

FIG. 3 is a diagram showing a defoaming device provided with a vacuum device provided in the middle of a conventional paint supply system.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Paint 2 Paint tank 3 Paint circulation pump 4a-4e Paint pipe 5 Paint pan 6 Defoaming device 7 Defoaming processing chamber 8 Exhaust pump 9 Pickup roll 10 Applicator roll 11 Backup roll 12 Partition plate 14 Suction pipe 15 Suction port 16 Net 31 paint pan 36 vacuum pump 37 vacuum chamber 43 coating part S steel plate

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Chitoshi Nojima 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Nihon Kokan Co., Ltd. F-term (reference) 4D011 AA01 AC04 AD03 BA12 BA13 BA20 4D075 AC21 AC84 AC95 BB56Z BB93Z CA47 DA03 DB02 EA05 4F040 AA22 AB04 AC01 BA23 CB22 DB06 DB25 4F042 AA21 CA01 CA07

Claims (3)

[Claims] 1. A paint circulating between a paint section and a paint tank,
What is claimed is: 1. A defoaming device which is disposed in a paint circulation system of a coating device for applying a paint to a material to be coated in a coating unit, wherein said defoaming device is a defoaming process for promoting floating separation of bubbles in the paint. A chamber and exhaust means for promoting defoaming of air bubbles floated in the defoaming chamber, wherein the interior of the defoaming chamber is horizontally partitioned by a single partition plate into two sections; The two areas communicate with each other in the space above the partition plate and in the paint below, and have a receiving part for paint containing air bubbles in one part, a discharge part for defoamed paint in the other part, and the other part. A suction section of the exhaust means is disposed above the liquid level in the area of (1). 2. The defoaming device according to claim 1, wherein a net for breaking the sucked air bubbles is provided in a suction portion of the exhaust device. 3. The defoaming device according to claim 1, wherein the coating unit is a roll coating device provided with a paint pan.