JPH053351B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a coating method using a curtain flow method, and particularly to a coating method using a roller curtain coater method. The present invention is applied to coating steel plates and other cut plates or coiled plates. (Prior Art) The slit method and the overflow method are already known as curtain flow coating techniques. For example, the slit method is
142870, and the paint head (container)
and discharged from the slit gap to form a curtain shape. In this method, the plate passing speed and slit gap are adjusted to obtain a predetermined coating film thickness. The overflow method changes the surface tension, viscosity, and other properties of the paint while diluting it with a solvent. The paint thus adjusted to an appropriate coating viscosity is allowed to overflow from the container and form a curtain. In this method, the plate passing speed is adjusted to obtain a predetermined coating film thickness. Furthermore, a curtain coater using a roller method has been developed in recent years. This invention is directed to a roller curtain corner, and the outline of the roller curtain corner is shown in FIG. As shown in the drawing, a paint P whose viscosity has been adjusted in advance is supplied to a roll gap between a painted rubber roll 2 and a metal doctor roll 3, discharged, and scraped off with a blade 4 brought into contact with the painted rubber roll 2. The scraped paint P flows down along the blade 4 to form a paint curtain C, and is applied to the object 1 to be painted (a cut steel plate in this example) passing below the blade 4. A predetermined coating film thickness is obtained by adjusting the roll gap, sheet passing speed, and peripheral speed of the coating rubber roll 2 and doctor roll 3. The doctor knife 5 limits the paint P adhering to the doctor roll 3. (Problems to be Solved by the Invention) In any of the conventional coating methods described above, it is necessary to appropriately manipulate coating film thickness adjustment conditions such as sheet threading speed, slit gap, roll gap, and roll circumferential speed. However, the current situation is that only a thin film with the thinnest thickness of about 25 μm (hereinafter referred to as dry film thickness) can be stably obtained. In particular, in the conventional coating method using a roller curtain coater, the coating film thickness is determined by (discharge amount from the roll gap)/(sheet passing speed).
Therefore, when coating a thin film of about 20 μm, for example, first adjust the roll gap and the peripheral speed of the coating rubber roll 2 and doctor roll 3.
To extremely reduce the amount of paint discharged from the roll gap. Even after this, if the predetermined coating film thickness is still not achieved, the plate passing speed is increased to reduce the coating film thickness. However, if the sheet threading speed is increased, the wind pressure caused by the traveling steel sheet may hit the paint curtain, causing the paint curtain to shake, or the paint curtain may be pulled by the traveling steel sheet and break.
For this reason, there was a problem in that the conventional roller curtain coater method could not form a stable thin film coating. (Means for Solving the Problems) The coating method using a roller curtain coater of the present invention supplies paint between a paint roll and a doctor roll adjacent to the paint roll, and discharges the paint from the gap between the two rolls. , a method in which a blade is brought into contact with the coating roll to scrape off paint from the coating roll and cause it to fall in a curtain shape, and to paint a plate running below the blade, which is close to the upstream side of the paint curtain with respect to the running direction of the plate. A windshield plate is provided, and the height of the paint curtain is set at a height that allows a predetermined paint film thickness to be obtained without causing paint curtain breakage. The windshield plate is disposed on the upstream side of the paint curtain so as to cover the entire upstream side of the paint curtain. In order to prevent wind pressure, it is better to have a narrower distance between the paint curtain and the windshield. When obtaining a thin film with a low discharge amount of about 20μm or less,
It is desirable that the paint curtain height is 100mm or more and 450mm or less. If the paint curtain height is less than 100 mm, and the paint film thickness is approximately 20 μm or less,
The paint curtain becomes very unstable. Moreover, if the paint curtain height exceeds 450 mm, the discharge amount will be too low, about 6 μm or less, and the continuous stability of the curtain will be poor, which is not preferable. Conventional paint curtain height is 50mm
~100 mm, and the paint curtain height in this invention is significantly higher than in the conventional one. (Function) In this invention, since the wind pressure generated by the traveling of the plate material is blocked from the paint curtain by the windshield plate, the paint curtain is not disturbed by the wind pressure. Furthermore, by increasing the height of the paint curtain, the angle of the paint curtain surface with respect to the vertical plane becomes smaller. Therefore, the component force along the paint curtain surface of the force by which the paint curtain is pulled by the plate in the running direction of the plate,
In other words, the tension applied to the paint curtain is reduced, and breakage of the paint curtain is prevented. As a result,
Even if the coating film thickness is 20 μm or less, coating can be performed stably without causing paint curtain breakage. (Example) FIG. 1 shows an outline of an apparatus for carrying out the present invention. A coating rubber roll 2 and a doctor roll 3 are arranged above the steel plate coil 1 with a required roll gap. A blade 4 for scraping off the paint P is arranged at the lowest end of the coating rubber roll 2, and is fixed in a vertical position. The blade 4 extends along the width direction of the roll and is in contact with the knife edge-shaped upper end galroll surface. In addition, steel plate coil 1
The height between the surface and the lower end of the blade 4 is the paint curtain height d. A windshield plate 6 is attached to the lower upstream side of the blade 4. Windshield plate 6
is close to the upstream side of the paint curtain C and spreads out so as to cover the entire surface of the curtain. Also, blade 4
Guides 7 are provided near the lower end of the paint curtain C along both sides of the paint curtain C. In the coating apparatus configured as described above, when paint P is supplied to the gap between the coating rubber roll 2 that is rotating (in the direction of the arrow) and the doctor roll 3 that is rotating in the opposite direction, the coating material P is supplied from the gap between the rolls. Discharged continuously. The discharged paint P is scraped off by the blade 4, and the paint P is scraped off by the blade 4 and the guide 7.
, and forms a paint curtain C. The paint that has fallen onto the steel plate coil 1 becomes a coating film F. In conventional thin film coating, the peripheral speed and roll gap between the coating rubber roll 2 and doctor roll 3 are adjusted to control the amount of curtain falling from the blade 4, that is, the discharge amount, and the thin film coating is further adjusted by the sheet passing speed. It was hot. In contrast, in the present invention, a windshield plate 6 having a height d of the paint curtain is further installed in front of the blade 4, and after taking an auxiliary measure to prevent the curtain from breaking, the height d of the paint curtain is adjusted. By increasing the paint curtain height d,
Even at low discharge rates, the curtains were stable and coating became possible. That is, as a result of various studies, the inventors of the present invention found that the paint curtain height d was determined as shown in straight line a and straight line b in Fig. 2 (both straight lines indicate different paints).
It was discovered that by adjusting the coating thickness, it is possible to adjust the coating film thickness, and furthermore, it is possible to coat a thin film of 20 μm or less without reducing the threading speed. FIG. 3 is a diagram illustrating the relationship between the paint curtain height d and the tensile force that affects the paint curtain strength. As is clear from Fig. 3, the angle of the paint curtain with respect to the vertical plane is the height d of the paint curtain.
Let θ ₁ be the angle when the angle is high, and θ ₂ be the angle when the angle is low, then θ ₂ >θ ₁ . Then, the force applied to the curtain thickness h ₁ at the curtain angle θ ₁ is smaller than the force applied to the curtain thickness h ₂ at the curtain angle θ ₂ . That is, when the paint curtain height d is high, the force with which the paint curtain is stretched becomes small, so that the paint curtain P is difficult to stretch thinly. After a while,
It is considered that by increasing the paint curtain height d, the paint curtain C becomes stable without causing curtain breakage. Therefore, the paint curtain height d is 100mm.
If it is above, the paint curtain C will be very stable even if the film thickness is about 20 μm or less. However, if the paint curtain height d exceeds 450 mm, the discharge amount will be too low, about 6 μm or less, and the continuous stability of the paint curtain C will be poor, which is not preferable. Here, the experimental results comparing the method of the present invention and the conventional method will be explained based on Table 1.

【table】

[Table] ○: Good ×: Occurrence of curtain breakage Adjustment of coating film thickness by the threading speed, coating rubber roll circumferential speed, doctor roll circumferential speed, and roll gap in Table 1, that is, adjustment of the discharge amount, is under the conditions generally used. be. The above-mentioned conditions for thin film coating of the present invention, that is, low discharge amount, were set as shown in Examples 1 to 8, the paint curtain height d was 100 to 450 mm, and a windshield plate was attached. As a result of coating under these conditions, the coating curtain had excellent continuous stability and a thin film coating of 7 to 22 μm was obtained. In addition, as shown in Comparative Example 1, simply controlling the various conditions of the discharge amount without providing a windshield plate will result in a decrease in the paint curtain height d.
Even if the coating temperature is increased, paint curtain breakage occurs and thin film coating cannot be obtained. Furthermore, if the discharge rate is too low, even if a windshield is provided, the paint curtain becomes unstable as shown in Comparative Examples 2 and 3, and the continuous stability of the paint curtain is poor. If the paint curtain height d is less than 100 mm as is generally done,
Even if the discharge rate is controlled to be low under various conditions and a windshield is provided, paint curtain breakage occurs and stable thin film coating cannot be achieved. Stable continuous coating was only possible up to a film thickness of 25 to 30 μm. (Effect of the invention) As described above, in addition to providing a windshield plate,
By making the curtain height significantly higher than in conventional methods, continuous coating can be performed stably without causing paint curtain breakage, even if the coating thickness is 20 μm or less.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram showing an example of a roller curtain coating apparatus that implements the method of the present invention, Fig. 2 is a diagram showing the relationship between film thickness and paint curtain height, and Fig. 3 is a diagram showing the relationship between paint curtain height and paint curtain. Drawings explaining the relationship of tensile force that affects strength, and the fourth
The figure is a schematic diagram showing an example of a conventional roller curtain coating device. 1... Steel plate coil or cut plate, 2... Painted rubber roll, 3... Metal doctor roll, 4... Blade, 5... Doctor knife, 6... Windshield plate,
7...Guide.

Claims (1)

[Scope of Claims] 1. Paint is supplied between a paint roll and a doctor roll adjacent to the paint roll, the paint is discharged from the gap between the two rolls, and a blade is brought into contact with the paint roll to remove the paint from the paint roll. In this method, a windshield plate is provided close to the upstream side of the paint curtain in the direction in which the paint curtain runs, so that the paint curtain does not break. A coating method using a roller curtain coater, characterized in that a paint curtain height is set at a height that provides a predetermined paint film thickness. 2. The coating method using a roller curtain coater according to claim 1, wherein the paint curtain height is 100 mm or more and 450 mm or less.