JPH05138110A - Method for controlling coating film thickness in roll coating - Google Patents

Abstract

PURPOSE:To improve the accuracy in the control of a coating film thickness by determining the friction force acting on the moving guide shoes of a roll stand from a difference in the pressing load at the time of loading and unloading of rolls and correcting the friction force from the actually measured load value, thereby determining the roll pressing force. CONSTITUTION:The pressing force is generated and this pressing force appears in load meters 8, 9 of screw shafts 6, 7 from the point of the time when the pickup roll 1 begins to come into contact with the applicator roll 2 if the pickup roll is pressed to the applicator roll. The pressing quantity between the rolls of this time is regarded zero and while the pressing force is further increased, the modulus of elasticity of the rubber constituting the applicator roll 2 is calculated by the pressing quantity between the rolls and the inclination of the force. The roll pressing force necessary for obtaining the target coating film thickness is determined from the modulus of elasticity, the viscosity of the coating film and the circumferential speeds and circumferential speed ratio of the rolls. On the other hand, the pressing force is increased until the pressing force attains a prescribed value and thereafter, the pressing force is removed and the friction force acting on the guide shoes 10, 11 of the roll stand by the force corresponding to a hysteresis BC is determined. The rolls are pressed again by the pressing force combining the friction force and the target pressing force.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for accurately measuring a roll pressing force when a coating liquid is applied to an object to be coated by a roll coater to accurately control a coating film thickness. It is a thing.

[0002]

2. Description of the Related Art Conventionally, a "roll coating method" using a roll coater has been generally adopted when a coating solution is applied to a continuously running strip.
It is one of the essential techniques for continuously applying coating liquids such as paints, inks, magnetic materials, adhesives or functional chemicals to strips of steel plates, various films, tapes or papers. .. FIG. 7 is an explanatory view of the above roll coating method, which includes a pickup roll 1 and an applicator roll 2.
(Generally, at least the surface layer is made of an elastic body such as rubber), and the coating liquid in the paint pan 3 is wound around the backup roll 4 and runs while traveling (steel plate or the like). 5 shows a typical two-roll roll coating method in which No. 5 is applied.

In this case, the film thickness of the coating liquid film is controlled by controlling the pressing amount between the applicator roll and the pickup roll or a metering roll additionally provided. This is because the coating film thickness depends on "the pressing force of the pickup roll or the metering roll against the applicator roll", and the pick-up roll or the metering roll is strongly resistant to the applicator roll. This is because the more the film is pressed, the thinner film can be realized.

Of course, the coating film thickness is, in addition to the pressing amount, the elastic modulus of the rubber constituting the applicator roll,
It also changes depending on the roll speed ratio and paint viscosity. However, since the "paint viscosity" is a factor that affects the gloss and color tone of the coating, it cannot be freely selected for controlling the coating film thickness. Further, the "elastic modulus of rubber" is not a factor that can be freely controlled for controlling the coating film thickness. Moreover,
The "roll peripheral speed" is better from the viewpoint of productivity, but if it is too fast, vertical stripes called "roll eyes" are formed on the coated surface, which is a limitation.

Therefore, in practice, the above-mentioned "roll peripheral speed ratio", "elasticity of rubber constituting the applicator roll" and "coating viscosity" are fixed and the coating film is fixed. The thickness must be controlled, and as a result, the actual coating film thickness is controlled by adjusting the pressing amount between the rolls.

Conventionally, in the roll coating work site, the amount of roll pressing is manually controlled based on experience as follows for each property of the coating liquid (paint or the like). Met. That is, first, the coating film thickness after trial coating and drying is measured by a gravimetric method. If this measured film thickness is thicker than the target coating film thickness, the roll pressing amount is increased and the coating film thickness is increased again. The roll pressing amount was controlled by a method of performing trial coating and confirming the film thickness adjustment result, but normally, this trial coating had to be performed 2-3 times. Therefore, in the field of roll coating, there has been an urgent need to study the automation of the film thickness control, which is a major obstacle in improving workability.

However, when trying to automate the film thickness control, not only the "pressing amount" between the rolls,
In particular, it is important to measure the "pressing force" to achieve the required pressing amount. Moreover, the application
If the elastic modulus of the rubber of the roll, the peripheral speed ratio of the roll and the viscosity of the paint are known, it has been found that the coating film thickness can be controlled extremely accurately by the pressing force as shown in FIG. There is.

However, there is a problem in practice that the pressing force cannot be accurately measured. In other words, in order to measure the pressing force between the rolls, it is originally desirable to modify the roll bearing portion and measure the bearing load, but this method is very complicated because the mechanism of the device is extremely complicated. Not. Therefore, as shown in FIG. 1, actually, the load shafts 8 and 9 are attached to the screw shafts 6 and 7 for pressing the rolls, and the pressing force is based on the measured values of the load scales. Although it is being grasped, in this case, the movement guide shoe of the roll mount that supports and slides the roll is supported.
It was extremely difficult to accurately measure the pressing force due to the influence of the frictional force acting on 10 and 11.

This is because no means for accurately measuring the frictional force acting on the moving guide shoe of the roll mount has been found, and the pressing force between the rolls is accurately measured. In order to control the film thickness appropriately, it is necessary to establish means for accurately measuring the above-mentioned "friction force acting on the moving guide shoe". Note that reference numerals 12 and 13 in FIG. 1 denote pressing amount measuring machines.

[0010]

From the above-mentioned viewpoints, the inventors of the present invention have measured the frictional force acting on the moving guide shoe of the roll mount during roll coating and accurately measured it. As a result of earnest studies to establish a means capable of grasping the pressing force between the rolls and appropriately controlling the film thickness based on this, the following has become clear.

That is, when performing a coating operation with a roll coater, if the roll starts contacting after the roll pressing operation starts, a "pressing force" appears on the load meter attached to the screw shaft. , This "pressing force" is the "pressing amount"
The behavior of the diagram shown in FIG. That is, the point A in FIG. 3 is the starting position of the roll contact, but the point B at which the pressing force reaches a predetermined value by continuing the loading as it is.
When the unloading is performed, the pressing amount remains unchanged and only the pressing force decreases to a specific value. Then, the pressing amount also starts to decrease following this, and when the point where the pressing amount starts to decrease is C, the pressing force between BC is exactly the frictional force (W) acting on the moving guide shoe of the roll base. Equivalent to double. Therefore, it is possible to easily and accurately measure the frictional force (W) acting on the moving guide shoe of the roll mount simply by loading and unloading the roll coater once.

Therefore, in order to make the actual pressing force between the rolls an accurate value as set, the above-mentioned measured value is grasped, and the load meter attached to the screw shaft is used as a "roll stand". It is sufficient to press the roll until the "measured required pressing force added with the frictional force (W) acting on the moving guide shoe", that is, "set pressing force + W".

The present invention has been made on the basis of the above-mentioned findings and the like. "The coating film thickness of the coating film is determined based on the measured value by a load meter attached to the roll pressing screw of the roll coater. When performing control, the frictional force acting on the moving guide shoe of the roll base is measured by measuring the difference between the pressing loads when the load is applied to the roll and when the load is unloaded, and the load is actually measured by the load cell. Correct the above frictional force from the value and
It is possible to appropriately control the coating film thickness by obtaining the roller pressing force and adjusting the roller pressing force based on this.

The method of controlling the coating film thickness according to the present invention will be described in detail below together with its operation.

Now, as described above with reference to FIG. 2,
If the elastic modulus of the rubber of the applicator roll, the peripheral speed ratio of the roll, and the viscosity of the paint are known, the coating film thickness by the roll coater can be controlled very accurately by the pressing force of the roll. I know I can.

Therefore, when the coating film thickness is automatically controlled, the pressing force for obtaining the target coating film thickness is calculated by a computer and is controlled. It was difficult to accurately measure the roll pressing force due to the influence of the frictional force acting on the guide shoe of the roll mounting base. However, according to the present invention, it is possible to accurately and automatically measure this frictional force to accurately grasp the roll pressing force, and based on this, it is possible to perform accurate coating film thickness control. ..

That is, as shown in FIG.
When the pickup roll is pressed against the applicator roll when the coating liquid is started to be applied by the taper, a pressing force is generated from the moment the roll comes into contact, and it is attached to the screw shaft. It appears on the load cell. At this time, the pressing amount between the rolls is set to 0, and the pressing amount between the rolls and the inclination of the pressing force are increased while further increasing the pressing force (see FIG.
A to B) is input to the computer, and the elastic modulus of the rubber that constitutes the applicator roll is calculated (the elastic modulus of the rubber changes as the rubber swells with the paint, Generally, it tends to decrease, so it is better to correct this by the method described later).

Then, as shown in FIG. 4, the elastic modulus, the paint viscosity, the roll peripheral velocity and the peripheral velocity ratio are input to the computer, and the roll necessary for obtaining the target coating film thickness is obtained. To obtain the pressing force.

On the other hand, after increasing the pressing force until the pressing force reaches a predetermined value, unloading is performed there, and the pressing force at the point where the pressing amount starts to decrease (point C in FIG. 3) is obtained. Here, since the force corresponding to BC in FIG. 3 is twice the frictional force acting on the guide shoe of the roll mount,
From this, the frictional force acting on the guide shoe of the gantry can be calculated.

When the calculation of the frictional force is completed by the above procedure, finally, the screw is pressed so that the measured value by the load meter attached to the screw becomes the target "pressing force + friction force". By accurately applying the pressing force in this way, the control accuracy of the coating film thickness is dramatically improved.

By the way, as previously mentioned, there is a phenomenon that the rubber of the applicator roll swells with the coating liquid during the coating of the coating liquid to lower the elastic modulus, and the volume of the rubber slightly increases. Get up. In such a case, the actual pressing force tends to decrease. Therefore, by using a “curve showing the application time and the decrease in elastic modulus of rubber” as shown in FIG. Correct the pressing force of.

Next, the effects of the present invention will be specifically described with reference to Examples in comparison with Comparative Examples.

EXAMPLES When coating a strip steel sheet with a roll coater of the type shown in FIG. 1, automatic coating film thickness control is carried out by applying the roll pressing force measuring method according to the present invention. went.
That is, first, the pickup roll is applied to the applicator roll 2.
When pressing the applicator roll 2, when the applicator roll 2 and the pick-up roll 1 are pressed and the pressing force is measured momentarily, the elastic modulus of the rubber forming the applicator roll 2 is measured. The target pressing force necessary to obtain the target coating film thickness was calculated by calculating the value, the viscosity of the paint, and the rotation speed of the roll (peripheral speed ratio of each roll) in the calculator.

At this time, the pressing of the roll is continued until the pressing force reaches the "target pressing force", and the hysteresis is grasped by automatically unloading when the "target pressing force" is reached. The frictional force acting on the guide shoe of the roll mount was measured from its hysteresis.

Next, the measured frictional force and the target pressing force were combined to the pressing force again to complete the pressing of the pickup roll 1 to the applicator roll 2.

The backup roll 4 and the application
As for the roll pressing between the tarrolls 2, a sufficient pressing force (about 20
0 kg or more) was given.

On the other hand, for comparison, FIG.
Using a roll coater of the type shown in (1), a trial coating was performed manually as in the prior art, and the roll pressing force was adjusted to perform a coating test on a strip steel sheet.

That is, first, a steel sheet for test coating is passed through a roll coater, trial coating is performed, and the film thickness is measured by a gravimetric method. If it is thicker than the target film thickness, the roll pressing force is applied. High,
The test coating is performed again and the film thickness is measured. This was repeated several times to find out the roll pressing force to give a predetermined film thickness, and then main coating was carried out based on this. Therefore, in the above-mentioned conventional method (comparative method), 30 minutes of trial coating was required to perform coating for 2 hours. In addition, in consideration of the decrease in rubber elasticity caused by the swelling of the rubber constituting the pickup roll due to the coating material, it is necessary to sample the coating film during coating and measure the coating film thickness by the gravimetric method to correct the pressing force. It was

FIG. 6 shows the results of coating carried out as described above, comparing the present invention example with the conventional example (comparative example). As is clear from the results shown in FIG. 6, although the conventional example (the example before the measurement of the pressing force) required a large number of steps, the accuracy of the coating thickness was not sufficient. In the example of the present invention, which was capable of performing the coating using the steel sheet as a product directly from the start of the coating work without requiring, in the work for a very short time, and a highly accurate coating film. It can be seen that a product coated steel sheet with excellent quality can be obtained under the thickness control.

The typical effects of the above-described embodiment according to the present invention with respect to the comparative example are listed below. a) The ability to accurately measure the roll pressing force enables automatic coating film thickness control by the roll coating method, resulting in no need for trial coating time, resulting in a significant increase in productivity. (In this example, the productivity was improved by 30% compared to the comparative example), b) The accuracy of the film thickness control was greatly improved ( As is clear from FIG. 6, the coating thickness error is 2 in the comparative example.
0% was improved to about 5% in the present invention), c) The amount of coating used was 15% due to the improvement of coating film thickness control accuracy.
, D) Corrosion resistance was improved due to significantly improved uniformity of coating film thickness, and coating variations and color differences were also reduced.

[0029]

[Summary of Effects] As described above, according to the present invention, the frictional force acting on the "moving guide shoe of the roll mount" has been an obstacle to the proper coating film thickness control by the roll coater. It becomes possible to grasp the exact pressing force between the rolls by properly measuring "", and it becomes possible to remarkably improve the control accuracy of the coating film thickness, which is extremely useful in industry.

[Brief description of drawings]

FIG. 1 is a schematic diagram illustrating the configuration of a roll coater.

FIG. 2 is a graph showing a relationship between a coating film thickness and a pressing force between rolls in roll coating.

FIG. 3 is a graph showing the relationship between the pressing force between rolls and the pressing amount in roll coating.

FIG. 4 is an explanatory diagram related to a coating film thickness control method in roll coating according to the present invention.

FIG. 5 is a graph showing a situation in which rubber constituting an applicator roll of a roll coater causes a decrease in elastic modulus due to swelling by a paint.

FIG. 6 is an example of the present invention (example in which pressing force is measured).
It is the graph which compared the "coating thickness error" by a comparative example (example before performing pressing force measurement).

FIG. 7 is a schematic diagram of a roll coating facility.

[Explanation of symbols]

 1 Pick-up roll 2 Applicator roll 3 Paint pan 4 Backup roll 5 Work piece 6 Screw shaft 7 Screw shaft 8 Load meter 9 Load meter 10 Guide shoe-11 Guide shoe-12 Pressing amount measurement Machine 13 Pressing amount measuring machine

Claims (1)

[Claims] 1. When controlling the coating film thickness based on the measured value of a load meter attached to a roll pressing screw of a roll coater, it acts on a moving guide shoe of a roll mount. The frictional force to be measured is measured by actually measuring the difference between the pressing loads when the load is applied to the roll and when the load is unloaded, and the roll pressing force is obtained by correcting the frictional force from the load measurement value obtained by the load cell. A method for controlling the coating film thickness, characterized in that the pressing force of the roll is adjusted based on this.