JP2543288B2 - Roller marker coating film thickness control method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a roller curtain coater coating film thickness control method, and particularly to a coating film thickness control method capable of always obtaining a constant film thickness.

[0002]

2. Description of the Related Art A roll coater method is generally used as a coating method, and a method for controlling a coating film thickness on a normal coating line is as follows. When the central line speed / speed change command is i / p, the roll peripheral speed changes with the line speed according to the roll coater coating film thickness control formula, so that a constant film thickness can be obtained. Since the roll coater coating is a contact coating with a steel sheet, there is no particular problem with the above control method. [I / p = input]

[0003]

The peripheral speed of the coating roll of the roller curtain is changed in order to keep the coating thickness constant during line speed acceleration / deceleration, but the peripheral speed of the coating roll is changed by the non-contact coating method with the coil. It has been confirmed that it takes about 1 to 3 seconds until the coating film thickness changes on the steel sheet after the change. This film thickness response delay has a great influence on the thickness of the coating film on the steel sheet as described below. Generation of unbaked part due to generation of thick film → Adhesion to roll after coating, etc. Occurrence of crack in thick film part Occurrence of inconsistent film thickness

[0004]

The present invention advantageously solves the problems of the prior art. Since the roller curtain coater coating is a non-contact coating with the coil, the peripheral speed of the coating roll is changed when the film thickness is changed. After the change (the roller curtain coater changes the film thickness by accelerating and decelerating the coating roll), a certain delay time occurs until the film thickness on the steel plate changes. A constant film thickness (target film thickness) cannot be obtained on the steel plate by the response delay time, and it is considered that the thick film thickness has an adverse effect on the coater and thereafter, such as generation of an unbaked portion. Therefore, the present inventors have studied the optimum control method of the film thickness, and have completed the present invention as a control method that can always obtain a constant film thickness.

That is, according to the present invention, in a coating film thickness control method of a curtain coater for forming a coating film on an object to be coated by passing it through a flowing coating curtain, the roll peripheral speed condition of the coater is changed and then delayed for a certain period of time. A gist of a roller curtain coating film thickness control method is characterized in that a coating speed is controlled by changing a line speed.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings. FIG. 1 shows an embodiment of the present description. The coil (steel strip) 9 passes through the bridle roll 1, and the deflector roll 2 and the roll coater backup roll 3 through the baking furnace 8. The paint is applied by a roller curtain coater before the coil 9 passes through the baking oven 8. The paint applied here is a high molecular polyester top coat paint used for home appliances (refrigerator outer plates, washing machines, etc.) and has good processability, stain resistance, and
It has excellent adhesiveness.

The paint is supplied to the bubble ejector 7 to remove the minute bubbles that greatly contribute to the curtain stability condition. Bubble ejector 7
The paint that has passed through is supplied onto the doctor roll 5 of the two rolls of the roller curtain coater coater. The paint pool accumulated between the paint roll 4 and the doctor roll 5 passes through the gap between the rolls and is scraped off by the paint roll blade 6 installed at the lower part of the paint roll to form a curtain of paint. It is applied on the passing coil (steel strip) 9. The film thickness of the paint 10 applied on the coil (steel strip) 9 depends on the physical properties (specific gravity, viscosity) of each paint,
The gap between the coating roll 4 and the doctor roll 5, the rotational speed of the roll, and the line speed are appropriately adjusted.

FIGS. 2 and 3 show the results of the variation in the film thickness on the coil (steel strip) 9 with the decrease in the peripheral speed of the roller curtain coater coating roll 4 in the coating material used in this line. In the figure, the horizontal axis shows time, the left vertical axis shows the dry film thickness on the steel plate, and the right vertical axis shows the fluctuation of the peripheral speed of the coating roll 4.

In FIG. 2, the coating roll 4, which was kept constant at 40 mpm, started decelerating at the time of 9 s, and the
It slowed down to 27.5 mpm over a second. Although the dry film thickness on the steel plate was kept substantially constant at 25 μm, it was confirmed that the film thickness decreased 1.5 s after the peripheral speed of the coating roll 4 decreased.

In FIG. 3, the coating roll 4, which was kept constant at 48 mpm, started decelerating at the time of 10.5 s, and decelerated to 27.5 mpm in about 2.5 s. The dry film thickness on the steel sheet was kept constant at around 20 μm, but it was confirmed that the film thickness decreased after 2.2 s after the peripheral speed of the coating roll 4 decreased. FIG. 4 is a diagram showing the positional relationship among the coating roll, the coating roll blade, the blade holder, and the steel plate.

The film thickness response delay described with reference to FIGS. 2 and 3 occurs because the coating material passes through the portions shown in FIG. The paint supplied from the paint roll is scraped off by the paint roll blade. After passing the blade 8mm,
Paint roll blade holder inclined surface 27mm, vertical surface 45
Paint travels a distance of mm. After passing through the blade holder, the paint forms a curtain and is applied on a steel plate 150 mm below.

The response delay time of the film thickness can be calculated by the passage time at the above-mentioned location. Response delay time T = t ₁ + t ₂ + t ₃ + t ₄ ……………
………… (1) t ₁ : Time to pass blade blade (8 mm) t ₂ : Time to pass blade holder inclined surface (27 mm) t ₃ : Time to pass blade holder vertical surface (45 mm) t ₄ : Time to leave the blade and fall to the steel plate

The time in the equation (1) was calculated by the following model. The flow rate of the coating material applied on the vertical plane can be determined by the coating thickness, the coating material viscosity, and the coating material specific gravity. This time, the roller curtain coater paint curtain flow rate is used to predict the paint thickness on the blade surface, and the passing speed is calculated.
The calculation of ₁ , t ₂ , and t ₃ was performed. Also, the falling velocity of the curtain was calculated to be t _{4 because it} was assumed that the curtain would fall due to gravitational acceleration.

The formulas used for the calculation are shown below. Dripping speed of the paint in the part at x from the external table V = ρg (X ² −x ² ) / (2η) ………………
………… (2) Paint flow rate that passes through unit time and unit width Q = X ³ ρg / (3η) ………………
………… (3) Paint dripping speed in the outermost layer (x = 0) v ₀ = ρgX ² / (2η) …………
………… (4) Velocity of the outermost layer paint at the inclination angle α ° v ′ ＝ ρgX ² sin α / (2η) ………………
………… (5) Curtain fall time v _E = (2 × g × N + v ₀ ² ) ^1/2 ………………
………… (6) Falling time from blade to steel plate t ₄ = (v _E −v ₀ ) / g ………………
………… (7) However, the symbols are as described below. ρ: Density of fluid (g / cm ² ) g: Acceleration / deceleration of gravity (cm / s)
² ) η: Viscosity (poise) X: Coating thickness (cm) x: Distance from the outer surface (cm) Q: Flow rate (cm ³ / s ・ c)
m) N: Height of blade holder lowest point (cm)

The paint flow velocity in each part was calculated based on the equations (2) to (7), and the response delay time was obtained according to the following equation. T = t ₁ + t ₂ + t ₃ + t ₄ = blade vertical surface / v ₀ + blade inclined surface / v ′ + t ₄
…… (8)

Since there is a subtle difference between the measured value and the theoretical value, the correction coefficient α was multiplied. Corrected response delay time T ′ = αT α: Correction coefficient (changes depending on the paint)

(Example 1) Prerequisites g = 980 m / s ² N = 150 cm ρ = 1.2 g / cm ² measured value 1.5 s v ₀ = 7.1 cm / s v '= 4.7 cm / s t ₁ = 0.1s t ₂ = 0.6s t ₃ = 0.6s t ₄ = 0.5s T = 1.8s α = 0.83 T '= 1.5

(Example 2) Prerequisites g = 980 m / s ² N = 150 cm ρ = 0.99 g / cm ² Actual value 2.2 s v ₀ = 5.8 cm / s v ′ = 3.9 cm / s t ₁ = 0.2s t ₂ = 0.7s t ₃ = 0.8s t ₄ = 0.5s T = 2.2s α = 1.0 T '= 2.2

[0019]

According to the present invention described above, the film thickness response delay time is calculated according to a predetermined calculation formula, and it is possible to control the coating roll speed and the line speed with a time difference. It is possible to obtain a constant film thickness,
It has become possible to solve the disadvantages of the prior art.

[Brief description of drawings]

FIG. 1 is a schematic diagram of a roller curtain coater facility for carrying out the present invention.

FIG. 2 is a view showing a result of a change in coating film thickness with a decrease in coating roll peripheral speed.

FIG. 3 is a diagram showing a variation result of the coating film thickness with a decrease in the peripheral speed of the coating roll.

FIG. 4 is a view showing a positional relationship among a coating roll, a coating roll blade, a blade holder, and a steel plate.

[Explanation of symbols]

 1 Bridle Roll 2 Deflector Roll 3 Roll Coater Backup Roll 4 Coating Roll 5 Doctor Roll 6 Painting Roll Blade 7 Bubble Discharger 8 Baking Furnace 9 Coil (Steel Strip) 10 Paint

Claims (2)

(57) [Claims] 1. A method for controlling a coating film thickness of a curtain coater, wherein a coating film is formed on an object to be coated by passing it through a flowing coating curten, and a response delay shown below is obtained after changing a roll peripheral speed condition of the coater. A roller curtain coater coating thickness control method, characterized in that the coating thickness is controlled by delaying the time and changing the line speed. Response delay time T = t ₁ + t ₂ + t ₃ + t ₄ t ₁ : time for passing blade blade t ₂ : time for passing blade holder inclined surface t ₃ : time for passing blade holder vertical surface t ₄ : leaving blade Falling time to steel plate 2. The film thickness response delay calculation formula according to claim 1,
A roller curtain coater coating film control method, characterized in that the coating film thickness is controlled by delaying the time of a value obtained by multiplying a correction coefficient to correct the difference between the theoretical formula and the actually measured value to change the line speed. Correction response delay time T ′ = αT α: correction coefficient