JPH11104540A - Partition plate used for coater pan and roll coater coating device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently remove the air bubbles intruded into a coating material by forming network-like aperture of a specific range in the opening size of the meshes used for a coater pan contg. the coating material for applying coating on a metallic sheet by a coater roll. SOLUTION: The coating material from which the air bubbles are removed is supplied from a coating material discharge port 13a disposed near the bottom of a coating material prepn. tank 1 through coating material piping 13 to the coater pan 2 which is provided with a partition plate 80 so as to hold a pickup roll 15 partly immersed into the coating material in the coater pan 2. The partition plate 80 is formed of a high-molecular resin partition plate having a network-like apertures of 150 to 2000 μm in the opening size of the meshes. The upper part thereof and both side parts thereof are reinforced with SUS plates 81. As a result, the air bubbles in the coating material are trapped and ruptured by the network part when the coating material passes the network-like aperture of the partition plate 80. The air bubbles intruded into the coating material are thus efficiently defoamed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for efficiently removing air bubbles entrained in a paint, or dispersing pigments, aggregates, and metal powders such as aluminum in the paint efficiently to reduce paint defects. The present invention relates to a roll coater coating apparatus for continuously producing a coated metal plate with less occurrence.

[0002]

2. Description of the Related Art Many coated metal sheets are manufactured by roll coater coating. In roll coater coating, usually, a roll partially immersed in the paint in a coater pan is rotated to pump up the paint, and the pumped paint is directly transferred to a metal plate or a further roll. Then, the paint adhered to the transferred roll is applied to a metal plate as a material to be coated to form a coating film.

[0003] Referring to Fig. 7, a case where a steel plate is coated by a roll coater coating apparatus using three coater rolls will be described as an example. In FIG. 7, three coater rolls are a pick-up roll 15, an applicator roll 16, and a doctor roll 18, 5 is a paint tank, 2 is a coater pan, and 21 is a paint circulation for sending paint from the paint tank 5 to the coater pan 2. The pump and the paint tank 5 are provided below the coater pan 2.

A part of the pickup roll 15 is immersed in the coater pan 2 containing the paint, and the pickup roll 15 is rotated to adjust the thickness of the paint 20 pumped from the coater pan 2 by the doctor roll 18. Then, it is applied to a steel plate 17 which is wound around a backing roll 19 via an applicator roll 16 and travels. The steel plate 17 to which the paint is applied is baked by a baking facility (not shown) to become a coated steel plate.

On the other hand, the paint 20 is sent from the paint tank 5 by the paint circulation pump 21 to the coater pan 2 via the paint supply pipe 22, and a part of the paint 20 adheres to the steel plate 17. It returns to the paint tank 5 again via the pipe 23.

In the paint tank 5, the paint is stirred by a stirring device 24 having stirring blades in order to make the paint concentration uniform. Further, the paint 20 which has adhered to the steel plate 17 and has been reduced
In order to replenish the paint tank 5, the paint tank 5
The paint 20 is supplied.

When the steel plate 17 is coated by circulating the coating material 20 using the coating apparatus as described above, bubbles generated during the circulation of the coating material are caught in the coating material 20 and carried into the coater pan 2. The paint 20 adheres to the steel plate 17 via the pickup roll 15 and the applicator roll 16 while entraining the air bubbles, and causes a coating film defect such as blistering and foaming on the coating surface of the steel plate 17.

[0008] In recent years, with the expanded use of painted steel sheets in the fields of building materials and home electric appliances, the diversification of products of painted steel sheets,
Further quality improvements are being made. Correspondingly, the composition of the resin components, auxiliaries, solvents, etc. of the paint becomes more complicated, and in addition to this, various additives are used in combination, and the paint becomes more likely to generate bubbles. I have. Further, more various particles such as pigments, skeletons, and aluminum powder have been added to improve the design. Since these compound particles are sedimentable particles, in order to improve the dispersion state in the paint, stirring is strengthened by a stirring blade in a paint tank. It is easier to get caught inside.

Addition of an antifoaming agent has been studied to suppress the generation of bubbles. However, the addition of an antifoaming agent may easily cause other coating defects such as repelling and poor leveling, and it is currently difficult to completely prevent the generation of air bubbles with this type of additive.

Therefore, measures for defoaming by improving the coating apparatus are being studied. (1) JP-A-6-321152 describes a technique for removing air bubbles from a paint supplied to a coater pan. Specifically, for example, in Example 2, as shown in FIG. 8, a part of the pickup roll 15 is dipped in the coater pan 2 to apply paint to the roll surface, and is continuously applied to the strip. In the roll coater, the inside of the coater pan 2 is horizontally divided into two sections 31a and 31c by a single weir plate 30, and a paint supply port 32 and a discharge port 33 are provided in a first section 31a and a second section 31a. The pickup rolls 15 are respectively arranged on the base 31c and the bottom of the weir plate 30 is slightly higher than the bottom of the coater pan 2 so that the first section 31a and the second section 31 are arranged.
c is communicated at the bottom of the coater pan 2 and the height of the paint outlet 33 in the first section 31 a is higher than the bottom of the coater pan 2. With such a configuration, bubbles contained in the paint due to the circulation of the paint rise in the section 31a of the coater pan partitioned by the weir plate 30 and disappear on the liquid surface, so that the bubbles are picked up. Division 3 on the roll 15 side
1c and is prevented from adhering to this roll.

(2) Japanese Patent Application Laid-Open No. 56-81112 discloses that a resonance frequency of 10 to 50
A technique is described in which air bubbles in a paint are removed by a defoaming apparatus having a KHz ultrasonic vibrator before the paint reaches a painted portion. Specifically, in Example 1, in the curtain coater coating using the apparatus shown in FIG.
The paint falling in the form of a film from the head tank 40 provided at the upper part of the object to be coated is collected in the paint tank 41 provided at the lower part, sent to the defoaming chamber 43 from this tank, and defoamed in the defoaming chamber 43. Thereafter, a circulation system is used in which the head tank 40 is returned to the head tank 40 provided at the upper portion. The coating is performed when the object to be coated passes on the conveyor device 44.

The paint in the paint tank 41 is supplied to a gear pump 42.
Is sent to a defoaming chamber 43 equipped with an ultrasonic defoaming device. In the paint fed into the defoaming chamber 43, bubbles in the paint float on the surface by the action of the ultrasonic oscillator 45 and the vibrator 46. Compressed air is fed into the defoaming chamber 43 via a compressor 47 and a regulator 48,
The air bubbles are removed by increasing the pressure in the void portion of the defoaming chamber 43 and at the same time applying a certain wind speed to the liquid surface. The defoamed paint flows out of the paint discharge port 49 and is poured into the head tank 40 along the guide plate 50.

(3) Japanese Patent Application Laid-Open No. 62-97668 discloses that in dip coating, one
By applying ultrasonic waves of 0 KHz or more and 50 KHz or less, after coating, the dents of the object to be coated and the bubbles formed in the voids are destroyed, and the coating of the object to be coated is applied evenly and with a strong adhesive force. Is described. Also, JP-A 2-3-3
No. 1852 discloses that an ultrasonic oscillator is installed inside a paint tank in which an object to be coated is immersed, thereby making it possible to remove bubbles in the paint generated at the time of supplying the paint and to stir the paint every time the paint is applied. It is described that simple application becomes possible.

[0014]

However, the technique described in the above publication has the following problems. (1) In the case of the technique described in Japanese Patent Application Laid-Open No. 6-321152, the area of the first section 31a for raising bubbles in the coater pan 2 is narrow.
The paint supplied into the first section 31 has bubbles therein.
a, the pickup roll 15
Flows into the second section 31c on the side. Further, if the area of the first section 31a is made to have a volume sufficient for the rise of air bubbles, the sedimentation of metal powder and the like mixed in the paint in this section becomes large, and the uniformity of the paint in the pickup roll portion decreases,
A non-uniform coating film is formed, and it is not possible to achieve both removal of air bubbles and good dispersion of metal powder and the like mixed in the paint.

(2) In the case of the technique described in Japanese Patent Application Laid-Open No. 56-81112, bubbles floating in the defoaming chamber are forcibly broken by compressed air, so that solvent evaporation from the paint surface is large. The change in paint viscosity is large,
In addition, skinning occurs on the surface of the paint, and this
May be brought inside. In addition, the defoaming processing chamber 43
Air bubbles that have floated on the top of the paint are collected, but large air bubbles that remain without being broken are brought into the head tank 40 as they are, or small air bubbles that are not broken are collected after being sent to the head tank 40. Can result in large bubbles.

When this technique is applied to the coating of a roll coater to which the present invention is applied, the above-mentioned air bubbles may be brought into a coater pan, and the above-mentioned Japanese Patent Application Laid-Open No. Hei 6 (1996) -1994.
It is necessary to take measures against defoaming in a coater pan as disclosed in Japanese Patent No. 3152152, and it is difficult to solve the problem of the present invention by this technique.

(3) The techniques described in JP-A-62-97668 and JP-A-2-31852 are intended for dip coating, and are used for continuous coating of steel sheets by roll coater coating while circulating the coating. The present invention relates to a technology different from the technology targeted by the invention. All of the techniques described in these publications use defoaming in the coating part using ultrasonic waves, but when this technique is applied to roll coater coating targeted by the present invention, in the process of defoaming. Since the bubbles floating on the surface adhere to the steel plate, it is difficult to solve the problem of the present invention by this technique.

The technique described in the above-mentioned publication is insufficient as a measure against bubbles contained in the coating material, or neither describes nor suggests measures against bubbles in roll coater coating.

The present invention has been made in view of the above circumstances, and efficiently removes bubbles entrained in a paint when a roll coater is applied to a metal plate while circulating the paint contained in a coater pan. And a coating apparatus capable of continuously producing a coated metal plate with less coating defects by improving the dispersion of pigments, aggregates, particles of metal powder such as aluminum, etc. in the coating. With the goal.

[0020]

Means for Solving the Problems The present inventors have conducted various studies on the state of air bubbles that cause coating defects and the state of air bubbles in each part of the coater pan and the paint circulation apparatus.

As a result, large air bubbles having a size of several hundred μm or more easily break during the coating stage and rarely cause coating defects, but fine air bubbles having a size of about several tens μm or less are pumped up by a pickup roll. When it was applied, it remained after application, and it was found that it was easy to become a coating defect.

It was also found that the generation of fine bubbles having a size of about several tens μm or less was due to the following reasons.

(Case 1) When the paint tank is lower than the position of the coater pan At the time of painting, air bubbles are caught in the paint as the pickup roll rotates, or the paint is drawn between the pickup roll and the applicator roll and between the applicator roll and the steel plate. Air bubbles are generated due to the fall of paint that has fallen into the coater pan or the like. These bubbles are caught in the paint overflowing from the coater pan and are sent to the paint tank without disappearing.

When the paint overflowing from the coater pan falls into the paint tank, new air bubbles are generated.

When the paint is replenished in the paint tank, or in order to make the paint concentration uniform, the mixture is stirred by a stirring device provided with stirring blades. At this time, bubbles are trapped in the paint.

The above-mentioned bubbles are a mixture of bubbles of various sizes. When the paint is supplied from the paint tank to the coater pan by pressurizing with the paint circulation pump while these bubbles are entrained in the paint, the bubbles in the paint are reduced to about several tens μm by releasing the discharge pressure. It becomes fine bubbles. Also, new air bubbles are generated in the paint circulation pump itself. The paint is fed into the coater pan while entraining these fine air bubbles.

(Case 2) When the position of the paint tank is higher than the position of the coater pan When the paint enters the paint tank, large bubbles may be generated, and the paint including the bubbles is directly sent to the coater pan. In some cases, it is worse than in the case 1.

Therefore, in order to prevent the above-mentioned paint defects, the paint is stirred in a paint tank to make the paint concentration uniform and
After uniformly dispersing the particles of metal powder and the like mixed in the paint, air bubbles in the paint are reduced in a separate tank, and these tanks are provided above the coater pan. We thought that it would be effective to supply the paint from the paint adjustment tank to the coater pan without using a paint circulation pump, which has a great effect on miniaturization of the paint.

Regarding the treatment for reducing bubbles in the paint, the ultrasonic degassing process was investigated by considering that it is possible to efficiently defoam even a small-capacity processing tank by using ultrasonic waves. did.

(Experimental Example 1) A sample in which about 100 ml (about 7 cm in height) of an aminoalkyd clear paint having a viscosity of 300 cp was put into a 1250 ml glass beaker, and bubbles were forcibly entrained using a small high-speed disperser was obtained. Created. After a lapse of one minute, the sample was sampled with a dropper from a portion 2 cm below the bottom of the glass beaker containing the sample and a portion 2 cm below the liquid level.
The sampled sample was dropped on a slide glass via a spacer, and a cover glass was placed on the slide glass. Then, the number of bubbles recognized as light spots by microscopic observation at a magnification of 3 was counted. In addition, the number of bubbles was similarly examined for a sample sampled after 5 minutes.

As shown in FIG. 1, a glass beaker 61 containing a sample 60 prepared in the same manner as above was placed in tap water 6.
38KHz ultrasonic cleaner Ultrasonic C containing 2
After placing on a -20 (manufactured by Ultrasonic Industrial Co., Ltd.) 63 and performing ultrasonic treatment for 1 minute and 5 minutes, sampling was performed from a portion 2 cm below the bottom (point a) and a portion 2 cm below the liquid level (point b). The sample was examined for the number of bubbles in the same manner as described above.

The results of the investigation are shown in Table 1.

[0033]

[Table 1]

From Table 1, it can be seen that the number of bubbles is greatly reduced in a short time by the ultrasonic treatment, and particularly remarkable in the portion near the bottom of the glass beaker. It was found that defoaming was promoted and efficient defoaming treatment was possible.

(Experimental Example 2) In Experimental Example 1, although the number of air bubbles is greatly reduced in a short time, a small amount of air bubbles is present in the glass beaker, especially in the upper part. In order to remove the existing air bubbles, the removal of the air bubbles by a partition plate for controlling the flow of the paint was examined using a simple experimental apparatus for circulating the paint shown in FIG.

In FIG. 2, reference numeral 72 denotes a partition plate for controlling the flow of the paint. The partition plate 72a has a gap at the bottom where the paint can easily flow, and the partition plate 72b at the top has a portion through which the paint passes. Become.

After about 1000 ml of an amino alkyd clear paint having a viscosity of 300 cp was added, a sample was prepared by forcibly entraining bubbles using a small high-speed despacer. Then, in the experimental apparatus of FIG. 2, partition plates 72a and 72b having mesh-shaped openings having different materials and mesh opening sizes were used, and a sample 70
Is circulated for 5 minutes using the pump 71,
A sample 70 was sampled with a dropper from a portion (point c) 2 cm below the liquid level (depth 10 cm). The sampled sample 70 was dropped on a slide glass via a spacer, and a cover glass was placed on the slide glass. After that, the number of bubbles recognized as light spots by microscopic observation at a magnification of 3 was counted.

Table 2 shows the results of the investigation.

[0039]

[Table 2]

From Table 2, the material of the partition plate is a polymer resin,
It was found that the effect of reducing the number of bubbles was large when the mesh had a mesh-like opening having a mesh size of 150 to 2000 μm.

A partition plate for controlling the flow of the paint is provided in the coater pan, as in the weir plate 30 described in the above-mentioned Japanese Patent Application Laid-Open No. 6-321152. Reductions have been made. When a partition plate of a material shape having a large bubble reduction effect, which is evident from Table 2, is used as a partition plate in the coater pan, the bubbles in the paint of the pickup roll can be reduced by the bubble reduction effect of the partition plate. . Further, when the paint supplied to the coater pan is subjected to a defoaming treatment in advance to reduce bubbles, the above effect can be further improved.

The present invention is based on such findings and ideas, and the means of the present invention for solving the above problems are as follows.

(1) A polymer resin partition plate having a mesh-like opening having a mesh opening size of 150 to 2000 μm, which is used for a coater pan in which a paint for applying a coating to a metal plate by a coater roll is used. (First invention).

(2) A coater pan in which paint for coating a metal plate is applied by a coater roll, a paint collection tank for receiving paint overflowing from the coater pan below the coater pan, and a paint tank above the coater pan. A paint tank for performing agitation and an ultrasonic oscillator for performing defoaming of the paint sent from the paint tank are provided at a bottom portion, and a paint adjustment tank for supplying a paint to a coater pan is provided. In a roll coater coating device, the collection tank and the paint tank are connected via a paint supply pipe having a paint circulation pump for transferring paint discharged from the paint collection tank to the paint tank in the middle of the paint tank. A roll coater coating apparatus comprising the above-mentioned partition plate (1) in a coater pan.

(3) A roll coater coating apparatus according to the above (2), wherein the paint adjusting tank comprises means for adjusting the temperature of the paint (third invention).

By providing the partition plate defined in the first invention in the coater pan and controlling the flow of the paint in the coater pan, when the paint passes through the mesh opening of the partition plate, Bubbles are trapped in the mesh portion and are more efficiently defoamed, so that bubbles in the paint can be reduced.

In the first invention, the mesh size is limited to 150 to 2000 μm because, when the mesh size is smaller than 150 μm, it becomes difficult for the paint to pass through the mesh-shaped opening, and Since the flow is similar to that of the plate, the effect of trapping air bubbles is insufficient, and when the mesh size is larger than 2000 μm, the effect of trapping air bubbles when the paint passes through the mesh-shaped opening. Is almost eliminated.

In the second invention, as described below, since the air bubbles in the paint sent to the coater pan are reduced, by providing the partition plate defined in the first invention in the coater pan, Further, defoaming can be performed more efficiently, and bubbles in the paint can be further reduced. Further, the dispersion of the particles in the paint can be improved.

Since the paint tank for agitating the paint and the paint adjusting tank for the defoaming treatment are separated, the paint tank is used to make the paint concentration uniform and the particles such as metal powder mixed in the paint uniform. Sufficient stirring required for dispersion can be achieved.

A part of the fine bubbles contained in the paint sent by the paint circulation pump is lifted and removed in this tank, and the paint circulation pump which has a great influence on the miniaturization of the bubbles contained in the paint is provided. Since the paint can be sent from the paint tank to the paint adjustment tank without using it, the load of the defoaming process in the paint adjustment tank can be reduced.

The defoaming in the paint adjusting tank is efficiently performed by the ultrasonic oscillator provided at the bottom of the paint adjusting tank.

Further, since the paint can be sent from the paint adjusting tank to the coater pan without using a paint circulation pump which has a great influence on miniaturization of the bubbles contained in the paint, the paint containing few bubbles is applied to the coater pan. Can be supplied.

By providing an ultrasonic oscillator in the paint adjusting tank, the temperature of the paint rises, and therefore the viscosity of the paint changes, which may affect the coating work such as a change in the coating thickness and the coating quality. A similar problem may occur due to a change in the paint temperature due to a seasonal variation in the temperature. According to the third aspect of the present invention, by providing the paint adjusting tank with the temperature adjusting means, a change in the temperature of the paint adjusting tank can be prevented, and the above problem can be prevented.

[0054]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 3 shows a first embodiment of the present invention. In FIG. 3, 1 is a paint adjustment tank, 2 is a coater pan,
3 is a paint recovery tank, 4 is a paint circulation pump, 5 is a paint tank, 6 is an ultrasonic oscillator, 9 is an overflow pipe, 10 is a paint supply pipe, and 11 is a paint adjusting tank 1 from the paint tank 5.
Is a paint pipe for sending paint from the paint adjusting tank 1 to the coater pan 2, 12 and 14 are flow rate control devices, 15 is a pickup roll, 16 is an applicator roll, and 80 is a partition plate. Paint adjustment tank 1
The paint tank 5 is provided above the coater pan.

The paint overflowing from the coater pan 2 is collected in the paint collection tank 3 via the overflow pipe 9. The lower part of the overflow pipe 9 is immersed in the paint recovered in the paint recovery tank 3. The paint collection tank 3 contains bubbles introduced from the coater pan 2 or the coater pan 2.
Air bubbles generated when falling from the surface are floated and defoamed, and air bubbles in the paint flowing out from the air bubbles can be reduced. Therefore,
This leads to a reduction in the load when the defoaming process is performed in the paint adjusting tank 1, thereby contributing to a reduction in the capacity of the paint adjusting tank, a reduction in the output of the ultrasonic oscillator 6, and the like. In particular, when the paint recovery tank 3 is a hopper, the linear velocity of the paint can be changed to improve the floating and defoaming effect of air bubbles, thereby contributing to a reduction in the capacity of the tank.

The paint recovered in the paint recovery tank 3 is passed through the paint supply pipe 10 by the paint circulation pump 4 and is supplied to the paint tank 5.
Sent to In the paint tank 5, as needed, a paint supply tank (not shown) supplies a reduced amount of paint adhered to the metal plate and a solvent for viscosity adjustment is supplied. In the paint tank 5, a stirrer 2 having stirring blades is used in order to equalize the concentration of these paints or to uniformly disperse particles such as pigments, aggregates and metal powders such as aluminum in the paints.
4 with stirring. In addition, some of the fine bubbles contained in the paint sent by the paint circulation pump 4 are floated and removed in this tank.

Next, the paint is sent from the paint tank 5 to the paint adjusting tank 1 via the paint pipe 11. Between the paint tank 5 and the paint adjustment tank 1, a flow control device 12 for controlling the flow rate of the paint supplied from the paint tank 5 to the paint adjustment tank 1 is installed, and linked with the pump, the fluid in the paint tank is controlled. The surface position can be controlled. Since the paint tank 5 is provided above the coater pan 2, when the paint is sent to the paint adjusting tank 1, it is possible to prevent finer bubbles contained in the paint and to generate new bubbles.

An ultrasonic oscillator 6 is provided at the bottom of the paint adjusting tank 1.
Is provided. Due to the cavitation of the ultrasonic oscillator 6, the bubbles in the paint collide with each other to form large bubbles, which float and break, so that the bubbles in the paint in the paint adjusting tank 1 can be efficiently removed. In addition, since the paint is agitated at that time, the paint concentration and the dispersion of particles such as metal powder mixed in the paint can be made uniform.

The frequency of the ultrasonic oscillator is 20 to 50 KH
z, more preferably 25 to 40 KHz, the defoaming efficiency is good. If this frequency is less than 20 KHz, cavitation hardly occurs, and the defoaming efficiency is reduced.
On the other hand, if the frequency exceeds 50 KHz, a problem in the working environment occurs, which is not preferable. As the ultrasonic oscillator, it is possible to use an ultrasonic oscillator whose output can be varied so as to cope with different defoaming efficiency and dispersion efficiency depending on the type of paint.

As the vibrator of the ultrasonic generating source, a magnetostrictive vibrator, a piezoelectric vibrator, an electrostrictive vibrator or the like can be used. Examples of the magnetostrictive vibrator include nickel, ferrite, and alfel alloy. Examples of the piezoelectric vibrator include quartz and Rochelle salt. Examples of the electrostrictive vibrator include barium titanate and lead zirconate titanate.

It is advantageous from the point of defoaming that the ultrasonic oscillator 6 is installed at the bottom of the paint adjusting tank 1. The method of installation may be a method of putting it into the inside of the paint adjustment tank, or a method of installing it inside the inside of the paint adjustment tank or the bottom surface, but is not limited to these installation methods.

When the ultrasonic oscillator 6 is provided on the entire bottom surface of the paint adjusting tank 1, bubbles generated by cavitation generated near the paint outlet 13a from the paint adjusting tank 1 to the coater pan 2 flow into the coater pan. there is a possibility. Therefore, when paint defects due to air bubbles are likely to occur, it is desirable not to provide the ultrasonic oscillator 6 near the paint outlet 13a from the paint adjustment tank 1 to the coater pan 2.

The paint from which bubbles have been removed is supplied to the paint adjusting tank 1.
The paint is sent to the coater pan 2 via the paint pipe 13 from a paint outlet 13 a provided near the bottom of the coater pan 2. Between the paint control tank 1 and the coater pan 2, a flow control device 14 for controlling the flow rate of the paint supplied from the paint control tank 1 to the coater pan 2 is installed. The liquid level position can be controlled.

By providing the paint adjusting tank 1 above the coater pan 2, the paint can be supplied to the coater pan 2 without using a paint circulating pump. The problem of bubbles generated by itself is eliminated.

The paint outlet 13a from the paint adjusting tank 1 to the coater pan 2 is preferably provided at a position near the bottom of the paint adjusting tank 1. Since bubbles in the paint float by the action of ultrasonic waves, there are fewer bubbles at the bottom. Therefore, by discharging the paint from the position near the bottom to the coater pan 2, paint with less air bubbles can be supplied to the coater pan. Further, even if settling foreign substances such as sludge are present at the bottom, they are not discharged to the coater pan 2.

The paint supply port 1 to the paint adjustment tank 1
1b and a paint discharge port 13a from the paint adjustment tank 1 to the coater pan 2 are preferably provided on the opposite sides of the paint adjustment tank 1, respectively. With such an arrangement,
Bubble removal can be better.

FIG. 4 shows the partition plate 80 in the coater pan 2. The partition plate 80 is a polymer resin partition plate having a mesh-like opening having a mesh opening size (d) of 150 to 2000 mμ as defined in the first invention, and the upper and both sides are SUS plates 81. Pickup roll 1 reinforced with a part and partially immersed in paint in coater pan 2
5 are provided.

A generally used plate-like partition plate has an action of controlling the flow of paint and floating air bubbles to some extent. However, when the flow rate of the paint is large or the size of the foam is several tens μm or less, the paint flows along the partition plate while the bubbles are entrapped in the paint, so that the bubbles may flow into the pickup roll 15 side. is there.

By providing a polymer resin partition plate 80 having a mesh-shaped opening defined in the first invention in the coater pan 2, when the paint passes through the mesh-shaped opening,
Air bubbles in the paint are trapped in the mesh portion and broken, and the bubbles in the paint after passing through the mesh opening are reduced.

When the partition plate is made of a polymer resin, the effect of trapping bubbles at the mesh portion is more excellent than when the partition plate is made of a metal. From the viewpoint of paint resistance, the partition plate is more preferably made of a fluororesin.

The reason that the polymer resin partition plate has a greater effect of trapping air bubbles at the mesh portion than the metal partition plate is that the polymer resin partition plate has a greater effect on paint and metal than the metal partition plate. This is considered to be due to the excellent wettability of the particles, and an excellent effect of trapping air bubbles in the mesh portion. The mesh opening is preferably provided on the entire surface of the partition plate from the surface for removing bubbles, but may be provided on a part of the surface of the partition plate, if necessary.
In order to ensure strength, a reinforcing member such as a SUS plate may be attached around the partition plate.

The partition plate has no paint flowing portion at the bottom portion, and the more the paint passes through the partition plate, the better the air bubble removing effect. However, if necessary, a part of the paint may pass through a partition plate having a paint circulating portion at the bottom.

It is desirable that the type of the partition plate is appropriately selected depending on the viscosity of the paint, the kind of the pigment contained in the paint, and the like.

The paint that has passed through the partition plate 80 is pumped up by the pickup roll 15 and
6. Backing roll 1 via doctor roll 18
9 and is applied to a steel plate 17 which travels around. Since the paint that is picked up by the pickup roll 15 has few bubbles, it is possible to reduce the occurrence of coating defects due to the inclusion of bubbles.

FIG. 5 shows a second embodiment of the present invention.
In the apparatus of FIG. 5, the paint adjusting tank 1 of the apparatus of FIG.
A partition plate 7a having a paint distribution section at the bottom and a partition plate 7b having a paint overflow section at the top are further provided. By providing the partition plates 7a and 7b also in the paint adjusting tank 1, the flow of the paint in the paint adjusting tank 1 can be controlled, so that the air bubble removing effect in the paint adjusting tank can be improved. As the partition plates 7a and 7b, similar to the partition plate 80 installed in the coater pan 2, a high-polymer resin partition plate having a mesh opening having a mesh spread size of 150 to 2000 μm is used. The paint flows through the paint flowing portion and the mesh-like opening at the bottom of the partition plate, and the paint flows through the paint flowing portion and the mesh-like opening at the upper portion of the partition plate 7b. improves.

In the partition plate 7a having a paint circulating section at the bottom, when the paint flows through the partition plate 7a, the floating bubbles are trapped, and the bubbles in the paint passing through the mesh opening are meshed. A trap is trapped in the section to prevent bubbles from being blown into the coater pan 2.

In the partition plate 7b having a paint flowing portion at the top, air bubbles in the paint passing through the mesh opening are trapped in the mesh portion to prevent the bubbles from breaking and being sent to the coater pan 2. . Further, sedimentary foreign substances such as sludge are trapped, and these foreign substances are prevented from being sent into the coater pan 2.

It is preferable that the partition plate 7 has a mesh-like opening as described above, and is provided with a partition plate 7a having a paint distribution portion at the bottom and a partition plate 7b having a paint distribution portion at the top. A plurality of these partition plates may be provided alternately.

The mesh openings are preferably provided on the entire surfaces of the partition plates 7a and 7b, but may be provided on a part of the surfaces of the partition plates as necessary. If necessary, a reinforcing member such as a SUS plate may be attached to the periphery of the partition plate or the like to secure the strength.

The partition plate 7a having a paint distribution section at the bottom is
A part of the lower part of the partition plate may have a concave shape. The partition plate 7b having a paint distribution section at the top may have a shape in which a part of the upper portion of the partition plate is concave.

If there is no obstacle to the flow of the paint in the paint adjusting tank, a partition plate having no paint distribution section at the bottom or top may be used.

Further, if necessary, a partition plate 7 having a mesh opening defined in the present invention and having a paint distribution section at the bottom.
Only a can be used.

When the number of partition plates is increased, the ability to separate and remove air bubbles in the paint is increased, but the ability to disperse particles such as pigments, aggregates, and aluminum powder is reduced.
It is desirable to appropriately select the number of partition plates according to the required quality.

According to the second embodiment, the bubbles in the paint sent to the coater pan 2 can be reduced as compared with the first embodiment, so that the bubble reduction effect in the coater pan 2 is further improved, Since the number of bubbles in the paint that the pick-up roll 15 draws is further reduced, the effect of the first embodiment for reducing coating defects can be further improved.

FIG. 6 shows a third embodiment of the present invention. In the apparatus shown in FIG. 6, a jacket 8 is provided on the outer side of the paint adjusting tank 1 in addition to the apparatus shown in FIG. The temperature of the paint in the paint adjusting tank 1 is detected by a temperature detector (not shown), and the temperature of the water in the water jacket 8 is adjusted to maintain the paint temperature at a constant temperature. In the case of the present embodiment, since the temperature in the paint adjusting tank 1 can be kept constant, the variation in the thickness of the applied coating film can be further reduced in addition to the operation and effect of the second embodiment.

In the above description of each embodiment of the present invention, a case where three coater rolls are used is shown, but the apparatus of the present invention employs a roll coater without depending on the number of rolls used. The effects of the present invention can be exhibited in a coating apparatus for performing coating.

In the apparatus of the present invention, the paint used for coating is not only a low-viscosity water-based paint but also a known resin, pigment, modifier, additive, and solvent, which are selected and combined as necessary. A high-viscosity paint having a viscosity of 50 cp or more (measured at 20 ° C.) can also be used.

As the resin, amino resin, alkyd resin, polyester resin, epoxy resin, acrylic resin,
Examples thereof include a urethane resin and a phenol resin.

Examples of the pigment include inorganic pigments and organic pigments such as titanium oxide, carbon black, iron oxide, graphite, ferrocyanine blue and phthalocyanine green; extender pigments such as barium sulfate, talc and mica; aluminum powder; Those used for paints, inks and the like can be applied.

As additives, pigment dispersants, leveling agents, anti-settling agents, ultraviolet absorbers and the like can be used. As the solvent, toluene, xylene, sorbet 100, sorbet 150, butyl acetate, ethyl acetate, butanol,
Those generally used as paint diluents such as cellosolve, butyl cellosolve, methyl isobutyl ketone, cyclohexane and cellosolve acetate can be used.

[0092]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In the coating apparatus shown in FIGS.
After coating for 000 m, the number of coating defects caused by air bubbles and the variation in coating film thickness with respect to the reference film thickness were investigated. The number of coating defects was determined by visual observation of the appearance of the coated steel sheet, and the variation in coating film thickness was determined by a fluorescent X-ray film thickness meter. In the coating apparatus shown in FIG. 6, the paint temperature in the paint adjusting tank was controlled to be constant. For comparison, the same investigation as above was conducted using the coating apparatus shown in FIG.

Table 3 shows the test conditions and the inspection results.

[0094]

[Table 3]

Inventive Examples 1 to 7 have less occurrence of coating defects than Comparative Examples 1 and 6 in which no partition plate is present in the coater pan and Comparative Examples 2 to 6 which are out of the range of the present invention even when the partition plate is out of the range of the present invention.

Inventive Examples 3 to 7 in which a partition plate was further provided in the paint adjusting tank in addition to the partition plate in the coater pan,
The occurrence of coating defects is smaller than in Invention Examples 1 and 2 in which there is no partition plate in the paint adjustment tank.

In Invention Examples 6 and 7 in which the paint temperature in the paint adjustment tank was controlled to be constant, the paint temperature in the paint adjustment tank was not controlled to be constant, so that the paint temperature was changed with time. The variation in the coating film thickness is smaller than those of Invention Examples 1 to 5 which have been increased by the same amount.

[0098]

According to the present invention, when a steel sheet is coated using the apparatus of the present invention, the occurrence of coating defects can be reduced, or the variation in coating film thickness can be further reduced.

[Brief description of the drawings]

FIG. 1 is a view showing an experimental facility used for examining the defoaming property of a paint by ultrasonic waves.

FIG. 2 is a view showing experimental equipment used for examining the defoaming property of a paint by a partition plate in a coater pan.

FIG. 3 is a diagram showing a first embodiment of the roll coater coating apparatus of the present invention.

FIG. 4 is a view showing a partition plate used in the roll coater coating apparatus shown in FIG. 3;

FIG. 5 is a view showing a second embodiment of the roll coater coating apparatus of the present invention.

FIG. 6 is a diagram showing a third embodiment of the roll coater coating apparatus of the present invention.

FIG. 7 is a view for explaining a conventional coating apparatus.

FIG. 8 is a diagram illustrating measures against bubbles in a coater pan according to the related art.

FIG. 9 is a view for explaining a paint defoaming facility using ultrasonic waves in a conventional technique.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 paint adjustment tank 2 coater pan 3 paint collection tank 4 paint circulation pump 5 paint tank 6 ultrasonic oscillator 7, 7 a, 7 b partition plate 8 cooling device (water jacket) 10 paint supply pipe 15 pickup roll 16 applicator roll 17 steel plate 80 partition Board

Claims (3)

[Claims] 1. A polymer resin partition plate having a mesh opening having a mesh opening size of 150 to 2000 μm, which is used for a coater pan into which a paint for applying a coating to a metal plate by a coater roll is applied. 2. A coater pan in which paint for coating a metal plate is applied by a coater roll, a paint collection tank for receiving paint overflowing from the coater pan below the coater pan, and a stirring of the paint above the coater pan. A paint tank for performing the defoaming and an ultrasonic oscillator for defoaming the paint sent from the paint tank at the bottom, a paint adjusting tank for supplying the paint to the coater pan, and the paint recovery. A roll coater coating apparatus in which a tank and the paint tank are connected via a paint supply pipe having a paint circulation pump for transferring paint discharged from the paint collection tank to the paint tank in the middle thereof; A roll coater coating apparatus comprising the partition plate according to claim 1 in a pan. 3. The roll coater coating apparatus according to claim 2, wherein the paint adjusting tank includes a paint temperature adjusting means.