JPH01176478A - Applied film thickness control of strips - Google Patents

Abstract

PURPOSE:To apply a low viscosity liquid to form a uniform coat by measuring the thickness of the coat, after drying, obtained with a gravure roll as a pickup roll and controlling the peripheral speed of the gravure roll through arithmetic and logic operation of a difference between the measurement value and a target value. CONSTITUTION:An application liquid with a viscosity range of 1.1-1.5cp is applied on the surface of a strip 12 running with the help of an applicator roll 8, a backup roll 10 and a pickup roll, after drying, in such a way that the thickness of the coat is 0.2-1.5mum. At that time, the thickness of an applied coat after drying is measured using a gravure roll 6A obtained by providing a recess of appropriate mesh on the afore-mentioned pickup roll. After this, the peripheral speed of the roll 6A is controlled by arithmetic and logic operation of the difference between the measurement value and a target value. As a result, a low viscosity liquid with viscosity of 1.1-1.5cp can be applied in uniform thickness.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a method for controlling the thickness of a coating film on a strip, and particularly to a method for controlling the thickness of a coating film that can uniformly apply a low-viscosity coating liquid to an electrical steel sheet or a color steel sheet. Used in fields such as industrial strips.

[Conventional technology]

Processes such as applying coating liquids such as paints and insulating agents to metal strips, and drying and baking are usually carried out in a continuous line. To apply the coating liquid, use the coating liquid volume vij as shown in Figure 3.
2, the coating liquid 4 is scooped up on the surface of the pickup roll 6, then the coating liquid 4 is transferred from the pickup roll 6 to the surface of the applicator roll 8, and finally the applicator roll 8 and the backup roll 10 are used to transfer the coating liquid 4 to the strip 1.
A method has been adopted in which the strip 12 is sandwiched between strips 2 and 2 and coated on the surface of the strip 12.

These coating film thicknesses must be kept constant for quality control reasons, and conventionally the film thicknesses have generally been controlled by adjusting the nip pressure and circumferential speed of the applicator roll 8. However, when the viscosity of the coating liquid is low in the 1.1 to 1.5 c'p range, the conventional method described above tends to result in a coating film thinner than the target, making it difficult to apply uniformly. Ta.

[Problem that the invention seeks to solve]

An object of the present invention is to solve the problems of the prior art described above and to provide a method for controlling the coating film thickness of a strip, which enables uniform coating even when the viscosity of the coating liquid is as low as 1.1 to 1. be.

[Means and operations for solving the problems] The gist of the present invention is as follows.

That is, the strip is coated with a coating solution having a viscosity of 1.1 to 1 Sep on the surface of a running strip using an applicator roll, a backup roll and a pickup roll so that the film thickness after drying is 02 to 15 μm. In the coating film thickness control method, a gravure roll is used as the pickup roll to measure the coating film thickness after drying, and the circumferential speed of the pickup roll is controlled from a difference calculation between the measured value and the target value, thereby achieving the target value. This is a method for controlling the coating film thickness of a strip, which is characterized by obtaining the film thickness.

The present inventors investigated a method for uniformly applying a coating liquid with a very low viscosity, and found that a gravure roll with appropriate mesh recesses was used on the pick-up roll, and the circumferential speed of the roll was controlled. We found that the film thickness could be controlled with high precision by

Gravure roll is a linear or circular or
The gravure roll 6A used as the pick-up roll 6 in the present invention is a roll provided with angular recesses, as shown in FIG. A range of 17 to 45 is desirable.The reason is that if it is less than 17 meshes or more than 45 meshes, the pick-up roll 6 will not be able to scoop up the coating solution sufficiently, resulting in a decrease in the accuracy of film thickness control.

The details of the invention will be explained with reference to the embodiment shown in FIG.

In the present invention as well, the coating liquid 4 scooped up by the pickup roll 6 is applied to the strip 12 by the applicator roll 8 and baked in the baking oven 16. As the pick-up roll 6, as shown in FIG. 2, a gravure roll 6A having a recess 14, which is a feature of the present invention, is used.

The strip 12 leaving the baking oven 16 is detected by three film thickness detectors 1.
8, the film thickness at three points in the width direction is measured, and an average value calculation circuit 20 calculates an average measurement value of these measurement values.

On the other hand, the target film thickness value has been input into the storage device 22 in advance.
The target film thickness value and the average measured value are input to the difference calculation circuit 24, and the difference is calculated. This difference is input to the roll circumferential speed calculating circuit 26, and the circumferential speed of the pickup roll 6A is calculated so that the coating film thickness becomes the target film thickness. This calculated peripheral speed is input to the roll peripheral speed command port FIs28, a command to set the pickup roll 6A to the required peripheral speed is transmitted to the motor 30 with a reduction gear for changing the peripheral speed, and the peripheral speed of the pickup roll 6A is determined based on the film thickness measurement value. is controlled and the target film thickness can be obtained.

As described above, the present invention uses the gravure roll 6A as the pickup roll 6, measures the film thickness of the strip 12 after coating and baking, calculates the difference between the measured film thickness value and the target value, and calculates the circumferential speed of the pickup roll 6A. By controlling this, we were able to uniformly apply a low viscosity coating liquid.

Next, the reason for the numerical limitation in the present invention will be explained.

If the viscosity of the coating liquid is in the range of 11 to 1, Sep,
It is impossible to uniformly control the film thickness with the conventional method, but it is possible with the conventional method in the case of a coating liquid with a high viscosity exceeding 1 Sep. Therefore, in the present invention, the viscosity of the coating liquid can be controlled was limited to low viscosities in the range of 11 to 1.5 cp.

Further, in the case of a steel plate coated with a low-viscosity coating liquid, which is the object of the present invention, the film thickness after drying is also in the range of 0.2 to 1.5 μm. In this type of steel plate, the film thickness is 02μ
If the thickness is less than the shoulder, the effect will be poor, and if the film is thicker than 1.5 μm, defects such as peeling will occur. Therefore, in the present invention, the film thickness after drying is limited to a range of 02 to 15 μm.

〔Example〕

A low viscosity coating liquid was applied to a strip using the method of the present invention and the conventional method under the conditions shown in Table 1, and the results were compared.

The target film thickness after drying is 1 μm in each case. The film thickness after drying was measured and the results are also shown in Table 1.

As is clear from Table 1 (Table 1), the embodiments of the present invention can coat a film with a uniform thickness even with a coating liquid of low viscosity compared to the conventional example.

〔Effect of the invention〕

As is clear from the above embodiments, the present invention uses a gravure roll in which a pick-up roll is provided with a recess, measures the film thickness after drying, calculates the difference between the measured value and the target value, and calculates the difference between the measured value and the target value. By controlling the circumferential speed of
．． It was possible to uniformly apply a film thickness of a low viscosity coating liquid of 1 to 1, Sep.

[Brief explanation of the drawing]

FIG. 1 is a schematic perspective view showing the configuration of an apparatus according to an embodiment of the present invention;
FIG. 2 is a perspective view showing a gravure roll used as a pickup roll according to an embodiment of the present invention, and FIG. 3 is a sectional view showing the arrangement of the roll in a coating line.

Claims (1)

[Claims] (1) A strip in which a coating liquid with a viscosity in the range of 1.1 to 1.5 cp is applied to the surface of the running strip using an applicator roll, a backup roll, and a pickup roll so that the film thickness after drying is 02 to 1.5 μm. In the coating film thickness control method, a gravure roll is used as the pickup roll to measure the coating film thickness after drying,
A method for controlling the coating film thickness of a strip, characterized in that a target film thickness is obtained by controlling the circumferential speed of the pickup roll based on a difference calculation between the measured value and the target value.