JP3204460B2 - Control method of coating film thickness by roll coater - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling a coating film thickness by a roll coater, and more particularly to a roll coater capable of controlling the coating film thickness with high precision when continuously coating a strip such as a steel plate. The present invention relates to a method for controlling a coating film thickness by using a method.

[0002]

2. Description of the Related Art In steel sheets, in order to improve the performance such as corrosion resistance, it is common practice to coat chromium, resin or the like on, for example, a galvanized steel sheet.

[0003] The steel sheet is coated by passing the steel sheet paid out from a pay-off reel in the entrance facility through successive steps of degreasing, coating with a roll coater, and drying in an oven while continuously transporting the steel sheet. Will be The coated steel sheet is taken up by a take-up device in a delivery facility.

[0004] Generally, a roll coater used for continuous coating of a steel sheet is a steel pick-up roll for pulling up the paint in a paint pan and receiving the paint from the pick-up roll and transferring the paint to the surface of the steel sheet for coating. Rubber-lined applicator roll.

[0005] In the case of coating with this roll coater, the coating film thickness is controlled by the peripheral speed of the roll, the pressing force (nip pressure) between the pick-up roll and the applicator roll, and the gap between the steel plate and the applicator roll. The pressing force is controlled appropriately.

However, in recent years, coated steel sheets have been used for a wide range of applications such as home appliances, automobiles, building materials, etc., and the quality required in order to improve rust prevention ability has been increased, and the accuracy of the coating film thickness has been improved. Has also become very demanding.

Conventionally, as a method of controlling the coating film thickness when coating with a roll coater, for example, Japanese Patent Publication No.
-45863, Tokiko 1-26751, Tokiko 3-23
No. 225 discloses a technique for determining an operation amount, for example, a nip pressure, according to a deviation between a set adhesion amount of paint and a detected adhesion amount based on past operation results.

[0008]

However, the above publications do not disclose any specific method for determining the operation amount.

In general, there is a relationship between the nip pressure and the paint adhesion amount as shown in the diagram of FIG. 5, and when the nip pressure is small, the adhesion amount greatly changes with the change in the nip pressure. Conversely, when the nip pressure is large, the change in the amount of adhesion with respect to the change in the nip pressure is very small.

The curve showing the relationship between the two shown in FIG. 5 will change if the coating conditions such as the type of coating material, dilution ratio, roll peripheral speed, line speed, etc., change.

Therefore, when a change occurs between the target value and the measured value of the paint adhesion amount during coating, it is necessary to set the nip pressure to an appropriate value so as to make the deviation zero. It is almost impossible to determine the nip pressure operation amount for setting the deviation of the adhesion amount to zero from the relationship shown in FIG. 5 based on the past operation results for many coating conditions actually employed. There is a problem that is impossible.

As another method for setting the target paint adhesion amount, a nip pressure N with respect to a deviation ΔM of the paint adhesion amount M is used.
There is also a method in which the manipulated variable .DELTA.Np (.DELTA.Np / .DELTA.M) of p is fixed and the manipulated variable is adjusted step by step until the deviation becomes zero, but as described above, this method includes the nip pressure Np and the nip pressure Np. Since the relation of the adhesion amount M is not constant, it takes too much time to correct the deviation or the nip pressure Np
Is operated too much, and the amount of adhesion exceeds the target value.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned conventional problems. When a belt-shaped body is continuously coated by a roll coater, when an actual measured value of the paint adhesion amount deviates from a target value, It is an object of the present invention to provide a method for controlling a coating film thickness by a roll coater which can quickly set the measured value to a target value.

[0014]

SUMMARY OF THE INVENTION According to the present invention, there is provided a roll coater having an applicator roll for transferring a coating material to a strip and a preceding roll connected to the preceding stage of the applicator roll. in the coating film thickness control method according to a roll coater at the time of painting strip to, application
At least the surface of the tarol is formed of an elastic material,
When controlling the nip pressure between the applicator roll and the preceding roll based on the deviation between the target value and the measured value of the paint adhesion amount and the rate of change of the nip pressure with respect to the paint adhesion amount at the measured value , the paint The formula that gives the adhesion amount is
Supply of paint sent to the belt side by rotation of the data roll
Remaining in the applicator roll and the quantity q _A, without being transferred to the strip
Co Setting basic equation for evaluating the difference between the leakage flow rate q _L that
At the gap between the applicator roll and the preceding roll.
Determined by applying the body lubrication theory,
_A formula giving the quantity qA is derived, and the applicator roll and belt
The gap with the body is also determined by applying the elastohydrodynamic lubrication theory.
Because, guiding the formula giving the leak flow rate q _L with the gap
Come equation giving an expression and leakage flow rate providing a supply flow rate q _A q _L
Is achieved by applying the above formula to the basic formula, thereby achieving the above object.

[0015]

[0016]

In the present invention, the nip pressure Np between the applicator roll and the preceding roll is defined as the deviation between the target value and the measured value of the paint adhesion amount, and the rate of change of the nip pressure with respect to the paint adhesion amount at the measured value. , It is possible to easily determine the operation amount of the nip pressure necessary for correcting the deviation of the adhesion amount.

Accordingly, it is possible to quickly reset the paint adhesion amount to the target value. Therefore, even when conditions such as the type of paint (viscosity, density, specific gravity), roll peripheral speed, line speed, etc. change. It is possible to stably paint with a desired film thickness.

[0018] Also, in this case, as an expression giving the coating weight, the supply flow rate q _A of the paint fed from the applicator roll to the strip, as well as evaluating the difference between the leakage flow rate q _L remaining on the applicator roll and a supply flow rate q _a and the leak flow rate q _L, respectively were obtained by applying the elastohydrodynamic lubrication theory, it was determined by evaluating the gap between the gap and the applicator roll and strip the applicator roll and front roll Use an expression
As a result, the amount of paint applied can be quickly controlled to a target value even in thin film coating.

[0019]

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

First, a method for deriving an equation for giving the paint adhesion amount used in this embodiment will be described in detail.

FIG. 1 is a schematic configuration diagram showing a roll coater applied to one embodiment of the present invention together with its operation.

In the present embodiment, when the steel sheet S is coated by the roll coater 10, the thickness of the steel sheet S can be controlled with high precision.

The roll coater 10 picks up the paint P in the paint pan (paint reservoir) 12, pulls up the paint together with the pickup roll 14, transfers a part of the paint in the direction of the steel sheet S, and An applicator roll 16 transfers the paint to the steel sheet S, and a backup roll 18 presses the steel sheet S against the applicator roll 16 when the paint is transferred by the applicator roll 16.

The pickup roll 14 has a radius R _P
Of a steel roll, which rotates at a circumferential speed V _P, the applicator roll 16 is a roll radius R _A which rubber lined on the surface, the pick up roll 14
, At the peripheral speed _VA in the forward direction. On the other hand, the backup roll 18 is a steel roll having a radius R _S , and rotates with the steel plate S at a peripheral speed LS in a direction opposite to the applicator roll 16.

[0025] In the above-mentioned roll coater 10, and the gap between the pick-up roll 14 and the applicator roll 16 and h _PA, the total flow rate q _AB of paint passing between the gap h _PA
Is the pickup roll 14 side and the applicator roll 1
It is separated into 6 sides. Return flow q _P coating deposited on the pickup roll 14 is returned to the paint pan 12, paint deposited on the applicator roll 16 is a supply flow rate q _A is sent to the steel sheet S side.

The supply flow rate q _A, the gap between the rest and at the same time when sent to the steel sheet S part (referred strip flow) q _S is transferred onto the steel sheet S is applicator roll 16 and the backup roll 18 h Leak flow through _AS q
_L.

[0027] Thus, (a solid deposition amount per unit area, the coating layer corresponds to the thickness) coating weight after drying when a is M, the paint adhesion of the steel sheet S that has been coated under the strip flow q _S The quantity M is given by the following equation (1). The unit of the paint adhesion amount M is [g / m ² ], γ is the specific gravity of the paint, C
Is the solids concentration of the paint.

[0028] _{M = q S · γ · C} / LS ... (1)

[0029] The strip flow q _S is is equal to the difference between the supply flow rate q _A and the leak flow rate q _L, the equation (1) may be the following equation (2).

[0030] _{M = (q A - q L} ) · γ · C / LS ... (2)

In this embodiment, the film thickness is controlled by the roll coater 10 using the above expression (2) as a basic expression for controlling the film thickness. The actual film thickness control equation is the above equation (2).
q _A, created by substituting the controllable specific expression as q _L. The supply flow rate q _A, the leakage flow rate q _L can be determined as follows.

In the roll coater 10, the following equations (3) to (5) are established. That is, equation (3) gives the total flow q _PA is given by the product of the gap between the pick-up roll 14 and the applicator roll 16 and the average speed of the two rolls 14, 16, and equation (4) gives the return flow q _P And supply flow q _A
The sum of the total flow rate q _PA, given from equation (5) ratio of the peripheral speed of the rolls (the ratio of q _A and q _P) distribution ratio of the total flow rate q _PA (alpha, beta is a constant) This is shown respectively.

[0033] _{q PA = h PA (V P} + V A) / 2 ... (3) q PA = q P + q A ... (4) q A / q P = α (V A / V P) β ... (5 )

[0034] From the relationship of the above (3) to (5), the supply flow rate q _A is given by the following equation (6).

[0035] _{q A = [α (V A} / V P) β / {1 + α (V A / V P) β}] × h PA (V A + V P) / 2 ... (6)

On the other hand, the leak flow rate q _L is given by the following equation (7). Here, λ is a constant.

Q _L = λ h _AS ( _VA− LS) (7)

[0038] substituted (6) and the supply flow rate q _A of the formula (7) of the leak flow rate q _L to each of the (2) basic formula,
The following formula (8) for a specific film thickness control formula is obtained.

[0039] M = (γC / LS) [ α (V A / V P) β / {1 + α (V A / V P) β} h PA (V A + V P) / 2 -λ h AS (V A - LS)] ... (8)

The film thickness control equation (8) expresses the gaps h _PA and h _AS between the pickup roll 14 and the applicator roll 16 and between the applicator roll 16 and the steel sheet S as predetermined values. In other words, the distance between the axes of the pickup roll 14 and the applicator roll 16 is larger than the sum of the respective roll radii, and there is a positive gap between the two rolls. This is effective when there is a positive gap between

Accordingly, the film thickness control equation (8) is applied to the film thickness control when the coating film thickness is relatively large.

Next, when the distance between the axes of the pickup roll and the applicator roll 16 is smaller than the sum of the respective roll radii of the pickup roll and the applicator roll 16, that is, the gap between the pickup roll 14 and the applicator roll 16 is apparently A description will be given of a model formula applicable in the case of negative values.
As described above, the phenomenon that the apparent gap between the rolls is a negative gap is caused by the fact that the rubber lined to the applicator roll 16 is rolled when the pressing force between the rolls is increased to obtain a thin coating film thickness. It is caused by deformation that shrinks in the radial direction. This phenomenon similarly occurs between the applicator roll 16 and the backup roll 18, that is, between the steel plate S.

When the rolls are strongly pressed to obtain a thin coating film as described above, a negative gap exists between the rolls or between the rolls and the steel sheet S. Will not do. Then, the roll gaps h _PA and h _AS included in the film thickness control formula (8) are evaluated based on the theory of elastohydrodynamic lubrication, and the values are evaluated by the formula (8)
Substituting into the formula, a new film thickness control formula that can be applied even when the gap between the pickup roll 14 and the applicator roll 16 or between the applicator roll 16 and the steel plate S is an apparently negative gap is created.

According to one embodiment to which the elastohydrodynamic lubrication theory is applied, the gap h _PA is given by the following equation (9).

[0045]

(Equation 1)

[0046] In this _{case, 2 / E PA = (1} -ν P 2) / E P + (1-ν A 2) / E A ... (10) R PA = (R P · R A) / (R P + R _a) where, N _P: nip pressure between the rolls (total) l: roll surface length E _P: pickup roll Young's modulus [nu _P: pickup roll Poisson's ratio E _a: applicator roll Young's modulus [nu _a: applicator roll Poisson ratio

The gap h _AS is given by the following equation (11) according to one embodiment to which the theory of elastohydrodynamic lubrication is similarly applied.

[0048]

(Equation 2)

[0049] In this _{case, 2 / E AS = (1} -ν A 2) / E A + (1-ν S 2) / E S ... (12) R AS = R A · R S / (R A + R S ) However, N _A: the pressing force (total) B: plate width E _S: strip Young's modulus [nu _S: strip Poisson's ratio E _A: applicator roll Young's modulus [nu _A: applicator roll Poisson's ratio

By substituting the above equations (9) and (11) into the above equation (8) and rearranging, the following equation (13) for controlling the film thickness is obtained.

[0051]

(Equation 3)

The gap between the pickup roll 14 and the applicator roll 16 and the gap between the applicator roll 16 and the steel sheet S are apparently controlled by controlling the coating by the roll coater 10 using the above-mentioned film thickness control formula. Even in the case of a negative value, it is possible to accurately control the coating film thickness.

In this embodiment, the above equation (13) is further transformed into the following equation (13A).

[0054]

(Equation 4)

In the above equation (13A), K is the concentration of the paint,
This is a correction coefficient obtained from the adhesion amount detection value when the viscosity, the rubber elasticity, and the like have changed from the set values.

FIG. 2 is a diagram schematically showing the relationship between the paint adhesion amount M and the nip pressure Np.
When M ₁ / M ₀ , it is a solid line, and when K = 1, that is, (1
Equation (3) is indicated by broken lines.

When the above equation (13A) is further modified with respect to the nip pressure Np, the following equation (14) is obtained.

[0058]

(Equation 5)

When the above equation (14) is differentiated with respect to the adhesion amount M, the following equation (15) is obtained.

[0060]

(Equation 6)

Now, the set value (target value) of the paint adhesion amount is M _0.
In the case where the actual adhesion amount detection value (actual measurement value) is M ₁ , first, K = M ₁ / M ₀ is calculated to correct the equation (13A), and the K value is used. From the above equation (15), the differential value d Np / d M at the actually measured value M ₁ is obtained.
(M = M ₁ ) is calculated. Then, using this differential value,
The nip pressure operation amount ΔNp for correcting the paint adhesion amount deviation M ₁ −M ₀ is determined by the following equation, and the nip pressure Np is corrected.

[0062]

(Equation 7)

If the adhesion amount deviation does not become 0 by one correction, the second nip pressure operation amount is further determined by the same calculation, and the nip pressure is corrected. The above operation is repeated until the adhesion amount detection value reaches the set value.

FIG. 2 conceptually shows a method of calculating the nip pressure operation amount ΔNp when the adhesion amount detection value is M ₁ .

As described above, by controlling the nip pressure in accordance with the above equation (16), the deviation of the adhesion amount can be obtained regardless of the kind of the paint, the dilution ratio, the roll peripheral speed, the line speed, and the like. The nip pressure can be efficiently corrected irrespective of how much the amount is relative to the target amount and in which direction the amount is increased or decreased.

The method for controlling the film thickness according to the present embodiment uses the
%, A water-based paint having a viscosity of 1.3 cP and a specific gravity of 1.1 and a thickness of 0.3.
Line speed LS = 60 mpm on a steel plate of 7 mm and width of 1450 mm
In was actually applied to a coating line which is painted, as shown in FIG. 3, the state adhesion amount detection value is M ₁ 2
The coating amount was able to be set to the target value by the number of correction operations.

On the other hand, when the operation amount of the nip pressure with respect to the adhesion amount deviation was fixed at 10 [Kg] / 10 [mg / m ² ] and the conventional method of correcting the nip pressure stepwise was applied to the same line. , As shown in FIG.
Four operations were required until ₁ became zero.

Although the present invention has been described in detail, the present invention is not limited to the above-described embodiment.
Various changes can be made without departing from the gist of the invention.

[0069]

[0070]

As described above, according to the present invention, when a belt-like body is continuously coated with a roll coater, if the actual measured value of the paint adhesion amount deviates from a target value, the measured value can be quickly reduced. Can be set to the target value.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing a roll coater applied to one embodiment according to the present invention.

FIG. 2 is a diagram for explaining the operation of the embodiment.

FIG. 3 is a diagram showing an example of a control result of a paint adhesion amount according to the present invention.

FIG. 4 is a diagram showing a result of controlling a paint adhesion amount by a conventional method.

FIG. 5 is a diagram showing a correlation between a paint adhesion amount and a nip pressure.

[Explanation of symbols]

10 ... roll coater, 12 ... coating pan, 14 ... pick-up roll, 16 ... applicator roll, 18 ... backup roll, S ... steel, q _A ... supply flow rate, q _L ... leak flow rate, q _PA ... total flow rate, q _P … Return flow rate.

Continuation of the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) B05D 1/28 B05C 1/08 B05D 3/00 B05D 7/14

Claims (1)

(57) [Claims] 1. A method for coating a continuously moving strip by means of a roll coater having an applicator roll for transferring a coating material to the strip and a preceding roll connected to the front of the applicator roll. In the method for controlling the coating thickness by a roll coater , at least the surface of the applicator roll is formed of an elastic material.
Is to have, the nip pressure between the applicator roll and front roll, the deviation between the actual measurement value and the target value of the coating weight, and the control based on the rate of change of the nip pressure against the coating weight of the measured values When applying the formula, the formula that gives the paint adhesion amount is applied to the rotation of the applicator roll.
A supply amount q _A paint sent to more strip side, rolling the strip
The leak flow rate q _L remaining on the applicator roll not photographed
Set the basic formula to evaluate the difference, and fill the gap between the applicator roll and the preceding roll with elastic fluid.
The supply flow rate q _A is obtained by applying the slip theory and using the gap.
The giving leads to expression, and, likewise elastohydrodynamic the gap between the applicator roll and the strip
The leak flow is obtained by applying the lubrication theory and using the gap.
Leads to the formula giving the amount q _L, expressions and leakage flow rate providing a supply flow rate q _A and the formula giving the q _L
Is applied to the above-mentioned basic formula to produce a coating film thickness control method using a roll coater.