JPH10272412A - Setting method of coating condition of roll coater - Google Patents

Abstract

PROBLEM TO BE SOLVED: To minimize influence of a setting error of an initial roller reference point by making a ratio of a variation of thickness of a coating film against a variation of a pressing quantity between an applicator roller and a pick-up roller smaller than a specific value. SOLUTION: In a roll coater, the thickness of a coating film formed on a belt-like body 5 by coating is decided by viscosity of the coating film, a carrier speed of the belt-like body 5, a circumferential speed ratio between an applicator roller 3 and a pick-up roller 2 against the carrier speed, thickness of an elastic material and the elastic modulus on the applicator roller 3 and a pressing quantity between the rollers 2, 3 etc. A sensitivity Δt/Δδof a variation Δt (μm) of the thickness of the coating film against a variation Δδ (mm) of the pressing quantity between the rollers 2, 3 is made smaller than 20 μm/mm. By coating within this region, deviation of the thickness of the coating film due to the initial setting error indispensably contained in the pressing quantity between the roller 2, 3 and the setting error of the pressing quantity, can be restrained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for setting coating conditions which enables a coating film thickness to be controlled with high precision when continuously coating a strip-shaped material such as a steel plate in a roll coater type coating apparatus.

[0002]

2. Description of the Related Art In recent years, coated steel sheets have been widely used for home electric appliances and the like, and the required accuracy of coating film thickness has become extremely high due to the quality requirements for rust prevention, workability, and weldability.

FIG. 1 shows an outline of a roll coater type coating apparatus. Conventionally, this roll coater device has been widely used as a device for continuously applying a coating material to a strip material such as a steel strip or paper. The roll coater type coating apparatus includes a metal pickup roll 2 that pulls up the paint 6 in the paint pan 1,
It is composed of a rubber-lined applicator roll 3 that receives paint from the pickup roll 2, transfers the paint to the surface of the strip 5, and applies the paint, and a backup roll 4 that supports the strip 5.

When coating with a roll coater type coating apparatus,
The thickness of the coating film is controlled by appropriately controlling the ratio of the peripheral speed of the pick-up roll 2 and the applicator roll 3 to the transport speed of the belt-like body 5 and the state of the pressing between the pick-up roll 2 and the applicator roll 3. Hereinafter, unless otherwise noted, the pickup roll 2 and the applicator roll 3
The gap is simply referred to as "between rolls." Regarding the peripheral speed of each roll, when the peripheral speed of the applicator roll 3 is Ua and the peripheral speed of the pickup roll 2 is Up, Ua / Up is referred to as a peripheral speed ratio. Normally, U for peripheral speed Ub of backup roll
b: Ua: Up = 1: 1.1 to 1.5: 0.2 to 0.5

[0005] The gap between the strip 5 and the applicator roll does not directly become the coating thickness, but the paint supplied from the applicator roll 3 is transferred to the strip 5 and becomes the coating thickness before drying. Therefore, the setting of the gap between the pickup roll 2 and the applicator roll 3 governs the amount of paint supplied to the applicator roll 3. Due to the mutual rotation of the pick-up roll 2 and the applicator roll 3 and the viscosity of the paint, a fluid pressure acts to push the gap between the two rolls, and the rubber lining on the surface of the applicator roll 3 is deflected by this fluid pressure. The thickness of the paint becomes thicker. Factors such as the number of rotations of the roll and the elasticity of the lining on the surface of the applicator roll 3 are complicatedly related to determine the thickness of the coating film. The conditions governing the coating thickness, such as the peripheral speed of each roll, the viscosity of the paint, the gap between the rolls, and the elasticity of the rubber lining of the applicator roll, are collectively referred to as coating conditions. In the following description, unless otherwise specified, the coating thickness refers to the thickness of the coating in an undried state in a roll coater.

The pick-up roll 2 and the applicator roll 3 are moved from the line contact state between the two rolls (this is referred to as a reference point between the rolls) in a direction in which the rolls are further tightened, and the applicator roll 3 is compressed and deformed. We are painting. At this time, the amount of movement when moving between the rolls in the direction of tightening the rolls from the reference point is called the roll pushing amount. The operation of setting the reference point between the rolls is necessary when the mechanical elements between the rolls change, such as the start-up after the repair of the rolls.

When setting the reference point between the rolls, it is difficult to automatically detect the moment of contact between the rolls because the surface of the applicator roll 3 is rubber-lined.
Therefore, an operator inserts a spacer such as a gap gauge between the rolls, adjusts the roll gap so that the pickup roll 2, the applicator roll 3, and the spacer come into contact with each other in a uniform contact state in the roll width direction. Usually, an operation of giving a pushing amount corresponding to the thickness of a roll and setting a reference point between rolls is performed.

[0008] The thickness of the coating film of the paint adhered to the strip 5 cannot be measured as it is, but can be measured in a state where the solvent is dried. The thickness of the coating film can be measured on-line by a measuring device such as infrared rays or radiation. However, the measuring device must be placed after passing through the drying furnace, and is located at a position far from the roll coater. Therefore, the method of continuously measuring the thickness of the coating film after drying to obtain a deviation from a target value and feeding back the amount of pressing between rolls and the peripheral speed of the rolls has a large control delay, and there is a limit to automatic control. Therefore, it is necessary to set the coating conditions before starting the operation. These operations are performed step by step as follows.

First, before the operation, the viscosity of the paint, the film thickness,
Production specifications such as line speed are given, and as work on site, setting work such as selecting the applicator roll 2 to determine the elasticity of the lining, setting a reference point between the rolls, and setting the amount of pushing between the rolls Perform

Next, if the operating conditions such as the type of paint, the type of strip, and the line speed change during the operation (this is called setup change), the peripheral speed ratio and the pushing amount must be reset. .

Further, during operation in one setup,
For example, when the actual measured value of the coating film thickness is found and there is an error from the target value, or when the line speed is changed, it is necessary to correct the pushing amount. Even if the peripheral speed ratio between rolls is adjusted, the coating thickness can be corrected, but the surface texture and color tone also change,
Normally, the peripheral speed ratio does not change much.

At each stage of setting the coating conditions as described above,
Although the inter-roll press amount is set or corrected, the inter-roll press amount has two problems. One of them is that the setting error of the reference point between the rolls is considerably large because the setting operation of the reference point between the rolls is performed in an unnatural work posture on the site or the operation itself requires skill. .

Second, since there is a complicated relationship between the conditions, setting when changing the roll pushing amount and making corrections during operation are difficult to standardize and require skill. is there. Given the type of paint and line speed,
A work standard is determined for the method of selecting the lining of the applicator roll 2 and the setting of the peripheral speed ratio between the rolls. However, since the rubber lining of the applicator roll 3 swells or wears out due to the solvent in the paint during operation, it is more difficult to control the coating thickness by the amount of pressing between the rolls. .

In order to solve this problem, Japanese Patent Application Laid-Open No. HEI 5-220441 discloses a method for controlling the thickness of a coating film by comparing the difference between the amount of paint supplied and the amount of leakage remaining on the applicator roll 3 without adhering to the strip. Is determined by a model formula as the amount of a coating film, and the thickness of the coating film is controlled.

Further, Japanese Patent Application Laid-Open No. 4-145975 discloses a method in which a set value and a roll pressing amount in various past coating conditions are stored and reproduced to reproduce the values.

[0016]

Problems to be Solved by the Invention
The method of controlling the roll pushing amount based on the past operation results as disclosed in Japanese Patent Publication No. 5 (2005) No. 5 discloses a method for controlling the roll while including the variation and error in the reference point setting work between the rolls. The accuracy of the thickness setting was not sufficient.

In the control of the coating thickness by the pressing force between rolls as disclosed in JP-A-5-220441, the condition of the roll gap changes with time due to the deterioration and swelling of the lining material on the roll surface. However, it also becomes an error factor in controlling the coating thickness.

It is an object of the present invention to minimize the influence of these errors in the initial roll reference point setting, and to reduce the coating thickness error due to the indentation error during setup change and indentation correction during operation. Is to make the control of the indentation amount easy by reducing the variation in the thickness, and to enhance the accuracy of controlling the coating film thickness.

[0019]

Means for Solving the Problems The present inventors have elucidated the relationship between the coating thickness and the coating conditions in controlling the coating thickness.
Among these coating conditions, for example, conditions other than those determined by manufacturing specifications, such as a paint type and a line speed, can be selected and determined at an operation site. Among them, the inventor (1) thickness of the lining material of the applicator roll 3,
Paying attention to the fact that the thickness of the coating film can be controlled by selecting the appropriate conditions of (2) the peripheral speed ratio between the pickup roll 2 and the applicator roll 3 and (3) the pushing amount between the rolls. did.

The gist of the present invention lies in the following two points. (1) When painting with a roll coater composed of an applicator roll lined with an elastic material on its surface, a pickup roll, and a backup roll supporting the strip, the amount of pushing between the applicator roll and the pickup roll Setting the coating conditions such that the ratio Δt / Δδ of the variation Δt (μm) of the coating film thickness to the variation Δδ (mm) of the coating film becomes smaller than 20 μm / mm. Method.

(2) Δt / Δδ is the allowable error Terr of the coating film thickness with respect to the maximum error Gerr (μm) when setting the initial position between the applicator roll and the pickup roll.
(1) The method for setting the coating conditions of the roll coater according to the above (1), wherein the coating conditions are set so as to be equal to or less than the ratio (μm) Terr / Gerr.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS As described above, in a roll coater, the viscosity of a coating material, the conveying speed (line speed) of a strip, and the peripheral speed ratio between the rolls, the thickness and elasticity of an elastic material on an applicator roll are measured. The thickness of the coating film formed on the strip is determined by the coating conditions such as the coefficient and the amount of pressing between the rolls. Among these coating conditions, the paint viscosity is determined by the type and dilution ratio of the paint, the elastic modulus changes with temperature and the deterioration of the elastic material, and the line speed is determined by the production speed. It cannot be used for control. However, (1) the hardness and thickness of the elastic material of the lining material of the pick-up roll can be selected from several types of rolls, (2) the peripheral speed ratio between the rolls can be given as a setup condition, 3) These three conditions were chosen because the indentation between rolls can be controlled directly. In the present invention, by selecting an appropriate range of these three coating conditions, the setting error of the reference point between the rolls and the variation of the coating film thickness caused by the setting error of the roll pushing amount are controlled and suppressed. .

FIG. 2 shows the effect of these three coating conditions on the film thickness. Here, when the peripheral speed ratio and the thickness of the elastic material are determined, the coating thickness is determined from the pressing amount between the rolls, and the ratio Δt / of the coating thickness change Δt to the pressing amount change amount Δδ.
Δδ (the gradient of each curve in FIG. 2; hereinafter, this is referred to as sensitivity) greatly changes depending on the absolute value of the pushing amount.

Using this relationship, the thickness (or hardness) of the lining material and the roll peripheral speed ratio are determined so that the sensitivity is reduced, and a target range of the indentation amount δ is selected. It is an object of the present invention to suppress the occurrence of a variation in coating film thickness due to an error in setting a reference point between rolls and an error in setting a roll pushing amount by manipulating the amount.

For example, in FIG. 2, where the amount of pressing is large in the area on the right half of FIG.
Even if there is δ, the error Δt exerted on the coating film thickness can be reduced. Further, when a film thickness of Ta is required, assuming that the thickness of the elastic material is constant, the curve moves upward as the peripheral speed ratio increases, and the control point moves rightward for the same Ta. (Δt / Δδ) becomes smaller. Or,
Assuming that the peripheral speed ratio is constant, the curve moves upward as the elastic material of the applicator roll 3 becomes thicker, and the sensitivity in the vicinity of the coating thickness of Ta decreases. By applying the coating in such a region having a small sensitivity, it is possible to suppress the initial setting error necessarily included in the pressing amount between the rolls and the variation in the coating film thickness caused by the setting error of the pressing amount.

In order to set such a small sensitivity region, data on various roll peripheral speed ratios, lining thickness, and roll pushing amount are collected, and a graph as shown in FIG. May be derived. However, this method is complicated and error-prone. Therefore, the inventor converted these coating conditions into mathematical expressions as described below, and made a model suitable for computer control.

The inventor conducted various experiments with the above-mentioned roll coater coating apparatus for steel strip. For the test, a roll coater type coating apparatus as shown in FIG. 1 was used. The apparatus includes a pickup roll 2 for pulling up a paint 6 in a paint pan 1, an applicator roll 3 for receiving the paint from the pickup roll 2 and transferring a part of the paint to a belt 5, and applying the paint to the applicator roll 3. When transferring, the band 5
Is pressed against the applicator roll 3. The pickup roll 2 is a steel roll having a diameter of 250 mm and rotates at a peripheral speed Up.
The applicator roll 3 is made of a steel roll having a diameter of 200 mm, and is lined with rubber having a thickness L and an elasticity coefficient E on the surface thereof.
It rotates at a peripheral speed Ua with respect to the pickup roll 2 in the forward direction. On the other hand, the backup roll 4 is a steel roll having a diameter of 750 mm,
, And rotates at the peripheral speed Ub together with the belt-like body 5. As a result of various experiments, the inventor has found that the thickness t of the coating film formed on the strip (steel strip) is given by the following equation (1).

[0028]

(Equation 1)

Where Um = (Ua + Up) / 2 A: constant B (δ) = 0.541δ + 3.454 C (δ) = 3.224δ + 23.117 δ: indentation between rolls μ: viscosity of paint E: elasticity of rubber lining Coefficient L: thickness of rubber lining From this, the film thickness sensitivity is obtained by differentiating (1) with δ,

[0030]

(Equation 2)

## EQU1 ## Further, the inventors conducted a test to confirm the limit value of the coating film thickness sensitivity. Test material is 1200 width
A steel strip having a thickness of 0.8 mm and a thickness of 0.8 mm was used. Line speed is 40m / min
The paint should have a viscosity of 0.4 Pa
It was applied as μm. The initial modulus of elasticity of the lining rubber on the applicator roll was 68.5 kgf / cm ² . At this time, the setting of the reference position between the rolls (setting of the zero position of the roll gap) was carried out by the same method as in the related art (visual observation of the operator, manual work). The setting accuracy by this method was ± 100 μm.

From the test results, the relationship between the amount of indentation between the rolls and the coating thickness under the operating conditions was derived from the equation (1) based on the parameters of the equation (1), and is graphed in FIG. Note that the sensitivity (Δt / Δδ) can be easily obtained from Expression (2).

In each curve of the graph of FIG. 3, when the indentation amount between the rolls is around δ = 0.5 mm, the slope of the curve sharply rises to the left, and it is extremely difficult to change the setup from thin to thick. Is represented. In normal operation, when changing the coating film thickness only by changing the indentation amount without changing the lining thickness and the peripheral speed ratio, the coating film thickness is often changed up to about ± 10 μm. For example, under the condition of the point B in FIG. 3, the sensitivity at the point B ′ is 60 μm / mm for a setup change from thin to thick 10 μm (from point B to point B ′).
With such a sensitivity, it is possible to control the accuracy of the coating film thickness. However, in the case of point A, if the coating thickness is changed from thin to thick by 10 μm (from point A to point A ′), the sensitivity becomes 250 μm / mm, and stable control of the coating thickness is difficult. is there. Therefore, in the normal operation range, when the normal setup change is considered, the sensitivity (Δt / Δδ) is 20 μm /
Coating conditions (applicator roll lining thickness and hardness, inter-roll peripheral speed ratio, and indentation amount)
It is necessary to choose.

[0034]

【Example】

(Example 1) In order to confirm the effect of the present invention, the conditions of the combination of four different lining rubber thicknesses and the peripheral speed ratios (FIG. 3)
A to D) were applied. On this occasion,
The setting of the roll gap was performed every time, and the influence of the change with time was removed, and the influence of the unavoidable variation at the time of setting was added.

FIGS. 4 (a) to 4 (d) show variations in the coating thickness as a result of the coating test. According to this, the maximum error of the coating film thickness was ± 5 μm under the condition A (Δt / Δδ = 42 μm / mm) with high sensitivity, but the maximum error of the coating film thickness decreased as the sensitivity decreased, and the sensitivity was the smallest. Condition D (8 μm / mm)
In this case, the maximum error was ± 1 μm or less, and the occurrence of the error could be suppressed by coating under the condition that the change in the coating film thickness was small with respect to the low indentation change.

(Example 2) FIG. 5 shows the target film thicknesses of 30, 40 and 50 μm for the line speed, steel strip and paint under the same conditions as in Example 1, respectively, and the tolerance of the film thickness is ±. This is a graph in which the operating conditions in the case of 5% are based on the above equation (1). The sensitivity (Δt / Δδ) was obtained from the equation (2). The initial setting between the rolls is the same as in the first embodiment. In this coating test, for each target coating thickness, the coating conditions (lining, peripheral speed between rolls, and indentation amount) with different sensitivities (Δt / Δδ) were used, respectively.
Coating was performed several times for each target coating thickness.

FIG. 6 shows the variation of the coating thickness as a result of the coating test. According to this, the sensitivity (Δt
/ Δδ) has a small coating thickness error under coating conditions.
Even when there is a setting error of ± Gerr when setting the roll gap reference, the variation control range of coating film thickness is ± Terr μm
In order to keep the sensitivity (Δt / Δδ) below the ratio of the allowable coating thickness error Terr and the maximum error Gerr generated in setting the relative position between the rolls, the coating conditions (lining and peripheral speed between rolls) that are less than Terr / Gerr , And the amount of indentation).

[0038]

By using the method according to the present invention in setting conditions for applying to a belt-like body by a roll coater type coating apparatus, an error in a position point between rolls and a change in a pushing amount due to a setup change. Since the variation in the coating thickness due to the error can be suppressed, the coating thickness can be easily and accurately obtained.

[Brief description of the drawings]

FIG. 1 is an explanatory view schematically showing a roll coater type coating apparatus for carrying out a method for setting a coating film thickness of the present invention.

FIG. 2 is an explanatory diagram showing a basic concept of a method for setting a coating film thickness of the present invention.

FIG. 3 is an explanatory diagram showing coating conditions in Example 1.

FIG. 4 is an explanatory diagram showing coating film thickness accuracy according to Example 1.

FIG. 5 is an explanatory view showing coating conditions of Example 2.

FIG. 6 is an explanatory diagram showing a coating film thickness accuracy according to Example 2.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Paint pan 2 Pickup roll 3 Applicator roll 4 Backup roll 5 Strip 6 Paint

Claims (2)

[Claims] When coating is performed using a roll coater composed of an applicator roll lined with an elastic material on its surface, a pickup roll, and a backup roll for supporting a strip-shaped material, the coating between the applicator roll and the pickup roll is performed. A coating condition for a roll coater, wherein a coating condition is set such that a ratio Δt / Δδ of a variation Δt (μm) of a coating film thickness to a variation Δδ (mm) of an indentation amount is smaller than 20 μm / mm. How to set. 2. Δt / Δδ is a permissible error Terr of the coating film thickness with respect to a maximum error Gerr (μm) when setting an initial position between the applicator roll and the pickup roll.
The method of setting coating conditions for a roll coater according to claim 1, wherein the coating conditions are set so as to be equal to or less than the ratio (μm) Terr / Gerr.