JPH10128205A - Coating material circulator of roll coater - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stabilize the characteristics of a coating material and to execute film thickness coating with high accuracy by providing a coating material circulator of a roll coater with a nonvolatile residue controller for keeping the nonvolatile residue of the coating material constant and a coating material temp. controller for keeping the temp. of the coating material constant. SOLUTION: The nonvolatile residue controller 60 computes the nonvolatile residue of the coating material at the time when the temp. and viscosity of the coating material are detected from the detected temp. and viscosity and determines the difference in the nonvolatile residues between the resulted and measured nonvolatile residue and the separately already inputted target nonvolatile residue. The amt. of the coating material of a circulation tank is determined from the coating material level and the amts. of the coating materials in a supply pipe, coater pan and return pipe are added thereto to determine the total circulation amt. of the coating material. The amt. of the solvent to be added is computed from this total circulation amt. of the coating material and the difference in the nonvolatile residue and a solvent adding device 50 is operated. The coating material temp. controller 30 determines the deviation between the information on the coating material temp. from a coating material detecting means 25 and the set temp. set by a temp. setter 37 and controls a heat exchanger 22 in such a manner that this deviation is eliminated. As a result, the characteristics of the coating material are stabilized.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coating technique using a roll coater used in the field of producing coated steel sheets, and more particularly to a paint circulation device for a roll coater used for coating a steel strip.

[0002]

2. Description of the Related Art A coated steel sheet is obtained by applying a coating to a steel strip, and a roll coater capable of high-speed processing and simultaneous coating on both sides is adopted as a coating apparatus for that purpose. FIG. 7 is a diagram showing the principle of a conventional roll coater.
Picks up the paint 102 stored in the coater pan 101 with a pickup roll 103, flattens the paint with a metering roll 104,
05 is applied to the steel strip 106. 107
Reference numeral denotes a backup roll, which is a guide roll for causing the steel strip 106 to face the applicator roll 105.

The paint 102 stored in the coater pan 101
Management is extremely important. Therefore, the mixing tank 111
In, the purchased paint and the solvent are stirred by the stirrer 112,
Circulation tank 1 via supply pipe 114 with supply pump 113
Send paint to 15. The paint stored in the circulation tank 115 is
After the preparation of the coater pan 101 and the like is completed, the remaining paint that has been continuously sent to the coater pan 101 by the circulation pump 116 through the supply pipe 117 and picked up by the pip-up roll 103 overflows and returns to the return pipe 118. To return to the circulation tank 115.

A temperature controller 1 is connected to the supply pipes 114 and 117.
21 and 122 are provided, and the temperature measuring element 123 provided at the circulation tank 115 and the temperature measuring element 12 provided at the outlet of the supply pipe 117 are provided.
4. The control device 126 adjusts the temperature of the paint in the circulation tank 115 and the coater pan 101 to a predetermined value based on the temperature information of the temperature measuring element 125 provided in the coater pan 101. The apparatus 100 is said to exhibit the effect that stable coating can be performed with a roll coater of a three-roll system, and that there is no defective coating thickness at the initial coating after changing the coating.

[0005]

Since the viscosity of the paint depends on the temperature, it is possible to stabilize the paint by keeping the temperature of the paint constant. However, in recent years, organic multi-layer steel sheets for automobiles aimed at improving corrosion resistance are required to have strict coating film thickness accuracy from the viewpoint of corrosion resistance and weldability, and sufficient results cannot be obtained only by the above temperature control. I understood.

[0006]

Therefore, the present inventors have studied in detail, and in the actual apparatus, the solvent is waiting from the paint between the time when the paint and the solvent are mixed and applied to the steel strip. It was found that the ratio of the non-volatile residue of the paint changed and the properties of the paint changed as a result. I felt the need to control the non-volatile residue of the paint, and as a result of various attempts, came to find out that the characteristics of the paint could be kept constant by combining the control of the non-volatile residue and the control of the temperature.

More specifically, the first aspect of the present invention is to apply the paint stored in the coater pan to a steel strip via a roll, overflow the excess paint in the coater pan, and then return the excess paint to the circulation tank with a return pipe. In a paint circulating device of a roll coater that circulates paint by feeding paint to the coater pan through a supply pipe, a heat exchanger is provided in the middle of the paint supply pipe, and a primary supply pipe of the heat exchanger is provided. Or provide a solvent addition device to put the solvent in the circulation tank, provided a paint level detection means to detect the level of paint in the circulation tank,
A paint temperature detecting means for detecting the temperature of the paint and a paint viscosity detecting means for detecting the viscosity of the paint are provided on the secondary supply pipe or the coater pan of the heat exchanger, and the paint temperature and the viscosity of the paint are detected based on the detected paint temperature and viscosity. The non-volatile residue is calculated, and the non-volatile residue difference between the obtained measured non-volatile residue and the separately input target non-volatile residue is calculated. On the other hand, the paint amount in the circulation tank is obtained from the paint level, and the supply pipe is determined. Calculate the paint circulation amount from the paint circulation total amount and the nonvolatile residue difference by adding the paint amount in the coater pan and the return pipe, calculate the paint addition amount from the paint circulation total amount and the nonvolatile residue difference, and operate the solvent addition device. A paint temperature control device attached to the solvent adding device and controlling the heat exchanger based on the temperature information of the temperature detecting means to adjust the solvent-added paint to a predetermined temperature is attached to the heat exchanger. To And butterflies.

[0008] Since the nonvolatile residue control device can make the nonvolatile residue of the paint constant, and the paint temperature control device can make the paint with the fixed nonvolatile residue a predetermined temperature,
The characteristics of the paint are stable, and highly accurate film thickness coating can be performed.

According to a second aspect of the present invention, the paint circulation device of the roll coater according to the first aspect further includes an addition timing control unit for permitting the next addition after a predetermined time has elapsed from the previous addition of the solvent. . The above-mentioned fixed time is a time required for the solvent added by the solvent addition device to reach the coater pan from the addition point or longer. By giving such a fixed time, the non-volatile residue can be further stabilized, and a good coating can be performed.

[0010]

Embodiments of the present invention will be described below with reference to the accompanying drawings. The drawings should be viewed in the direction of reference numerals. FIG. 1 is a diagram showing the principle of a roll coater according to the present invention. A paint circulation device 1 for a roll coater supplies a paint mixing tank 2, a stirrer 3, and a mixed paint from the mixing tank 2 to the next circulation tank 4. Supply pipe 5 and supply pump 6, and paint and solvent stirrer 7 provided in circulation tank 4
A supply pipe 11 and a pump 12 for feeding paint to the coater pan 10; a return pipe 13 for returning paint overflowed in the coater pan 10 to the circulation tank 4;
A pick-up roll 15 and an applicator roll 16 for picking up the paint and applying it to the steel strip 14, a paint temperature control device 30, a solvent addition device 50, and a nonvolatile residue control device 60, which will be described in detail later.

The circulation tank 4 is provided with a paint level detecting means 2.
The paint level detecting means 21 is preferably a float type liquid level meter or an ultrasonic type liquid level meter, and detects the liquid level of the paint in the circulation tank 4. The supply pipe 1
1 is provided with a heat exchanger 22 in the middle thereof, so that the primary side supply pipe 23 for sending the paint to the heat exchanger 22 with the heat exchanger 22 as a boundary, and the secondary side for drawing the paint from the heat exchanger 22 It is distinguished from the supply pipe 24. The heat exchanger 22 may be any of a plate heat exchanger, a double tube heat exchanger, and a multi-tube heat exchanger.

A paint temperature detecting means 25 is provided near the outlet of the secondary supply pipe 24. This paint temperature detecting means 25
Is a so-called thermometer, which is preferably a thermocouple or a resistance thermometer, and is a means for measuring the temperature of the paint. Further, the coater pan 10 is provided with a paint viscosity detecting means 26. The paint temperature detecting means 25 and the paint viscosity detecting means 26
Since the temperature and the viscosity of the paint immediately before being applied to the paint are measured, the installation position may be any position near the outlet of the coater pan 10 or the secondary supply pipe 24.

The paint temperature control device 30 is provided with the heat exchanger 2
A hot / cold water supply pipe 31 for supplying hot or cold water to the heat exchanger 2 and a hot water tank 33 from an outlet pipe 32 from the heat exchanger 22.
Hot water return pipe 34, a drain pipe 35 for discharging cold water from the outlet pipe 32, a hot water pump 36 for circulating hot water, and paint temperature information and a temperature setting unit 37 from the paint temperature detecting means 25. And a temperature controller 38 which adjusts the heat exchanger 22 so as to eliminate the deviation.

Specifically, when the temperature of the paint is higher than the set temperature, the temperature controller 38 opens the first cold water valve 41, closes the first hot water valve 42, opens the second cold water valve 43, and opens the first hot water valve. By closing the valve 44, the cold water is sent to the heat exchanger 22 and drained through the drain pipe 35. Since the paint is cooled by the heat exchanger 22, the temperature of the paint falls. The degree of opening of the first chilled water valve 41 or the second chilled water valve 43 is gradually changed by PI (proportional / integral) control or PID (proportional / integral / derivative) control according to the temperature difference between the paint temperature and the set temperature. Thereby, the paint temperature can be brought close to the set temperature. Of course, the object can also be achieved by controlling the first cold water valve 41 or the second cold water valve 43 to be on / off.

When the temperature of the paint is lower than the set temperature, the first cold water valve 41 is closed and the first hot water valve 42 is closed.
, The second cold water valve 43 is closed, and the first hot water valve 4
By opening 4, hot water is sent to the heat exchanger 22 and returned to the hot water tank 33 through the hot water return pipe 34. Heat exchanger 22
, The temperature of the paint rises. The temperature controller 38 monitors the temperature of the hot water in the hot water tank with the temperature sensor 45, and when the temperature drops, opens the valve 46 and supplies high-temperature hot water via the supply pipe 47. The valve 46 and the supply pipe 47 may be replaced with an electric heater for directly warming hot water.

The solvent adding device 50 includes a solvent container 51, a solvent supply pipe 52, a solvent valve 53, and a solvent flow meter 54. The solvent flow meter 54 includes an area flow meter and a positive displacement flow meter.

The non-volatile residue controller 60 calculates the non-volatile residue of the paint from the detected temperature and viscosity of the paint, and calculates the non-volatile residue of the obtained measured non-volatile residue and the separately input target non-volatile residue. On the other hand, the amount of paint in the circulation tank is obtained from the above-mentioned paint level, and the amount of paint in the supply pipe, coater pan and return pipe is added thereto to obtain the total amount of paint circulation. , A non-volatile residue controller 61 for operating the solvent addition device 50, a target non-volatile residue setter 62 for driving in the non-volatile residue, and a certain time after the previous solvent addition. And the addition timing control unit 63 that permits the next addition.

The operation of the above-described nonvolatile residue control device will now be described. FIG. 2 is a flow chart of the addition of a solvent to the roll coater according to the present invention, where STxx indicates step numbers. ST01: When the viscosity of the paint is μ, the temperature of the paint is t, and the non-volatile residue is NV, the following equation is established. NV = a · lnμ−b / (273 + t) + c Here, a, b, and c are constants for each paint, and viscosity-temperature data for each NV of the target paint is collected, regression-calculated, and stored in a table in advance. Make it. In ST01, constants a, b, and c corresponding to the paint are determined based on these tables. ST02: Read target NV (target non-volatile residue) according to the paint. This target NV is the target non-volatile residue setter 6 in FIG.
This is a value previously input at 2.

ST03: Addition timing control section 6 in FIG.
At 3, it is checked whether the elapsed time Tadd from the previous solvent addition is equal to or longer than the minimum elapsed time Ttime. The reason for providing this step will be described later. ST04: The paint viscosity viscosity μ and the paint temperature t are read by the paint viscosity detecting means 26 and the paint temperature detecting means 25 in FIG.

ST05: Measured from viscosity μ and paint temperature t N
Find V. That is, measurement NV = a · lnμ−b /
(273 + t) + c. ST06: Find the difference between the measured NV and the target NV. However, the measured NV is not smaller than the target NV. The process proceeds to the next step when the difference between the two is equal to or larger than the allowable difference α. ST07: The paint level in the circulation tank 4 is known by the paint level detecting means 21 in FIG. Assuming that the circulation tank 4 is a simple cylindrical tank and the bottom area is A and the height from the bottom of the paint is H, the amount q1 of paint in the circulation tank can be obtained by A · H.

ST08: Since the coater pan 10 overflows and the height from the bottom of the paint is constant, the coater pan 1
The amount q2 of the paint in 0 is a fixed value and is known. Supply pipe 11 from circulation tank 4 to coater pan 10 (heat exchanger 2
2 channels. The inner volume of () is constant unless the pipe is redesigned or modified, and the amount q3 of the paint in the supply pipe 11 is also known. Therefore, the circulating paint total amount Q is q1 + q2 + q3
Can be obtained by

ST09: The solvent addition amount P is calculated as (measurement NV-
Target NV) / Target NV × Q can be easily obtained. ST10: Open the solvent valve 53 of FIG.
The amount is measured at 4 and when the amount reaches P, the solvent valve 53
Close. ST11: Reset the timer for measuring Tadd and start counting. ST12: If there is no command to end the control, the process returns to ST01, and if there is, the control is ended.

The reason for providing ST03, that is, FIG.
The reason why the addition timing control unit 63 is provided in the above is as follows. When a solvent is added to the circulation tank 4 and stirred by the stirrer 7 as in the embodiment, the solvent and the coating material become new non-volatile residue conditions in a short time. On the other hand, the coater pan 10 has a certain amount of time before it is replaced with the new non-volatile residue condition because the paint under the previous non-volatile residue condition is accumulated, and this time is referred to as residence time.

This residence time depends on the heat exchanger 2 as in the present invention.
In a device of the type in which a solvent is added on the primary side of the coating material 2 and the temperature of the coating material after the addition of the solvent is adjusted by the heat exchanger 22 and is supplied to the coater pan 10, this always occurs. If the next solvent is added within the residence time, the non-volatile residue of the paint of the coater pan 10 becomes smaller than the target non-volatile residue because the solvent is added based on the old information, and the target non-volatile residue is not easily approached. Occurs. Therefore, it is desirable to perform the next solvent addition after a certain time (residence time) has elapsed.

If the circulating paint total amount Q is 100 kg and the capacity of the circulating pump 12 is 10 kg / min, 1
The paint makes one cycle in 0 min (minute). Therefore, the fixed time (residence time) is set to about 10 minutes.

[0026]

Embodiments of the present invention will be described below, but the present invention is not limited to the embodiments. Using the two-roll type roll coater and the coating circulation device shown in FIG.
~ 2.3mm, 600 ~ 1600mm wide steel strip 60 ~
The coating with a dry film thickness of 1.0 μm was performed while feeding at a rate of 130 m / min.

FIG. 3 is a graph showing the change over time in the paint temperature. The horizontal axis represents time, and the vertical axis represents paint temperature. The paint temperature for 12 hours immediately after the start of painting is recorded by the paint temperature detecting means 25 in FIG. In the graph, the disordered portion is due to the influence of the addition of the solvent. The paint temperature was in the range of 37.5 ± 1.0 ° C., despite the addition of the solvent, the change in the dimensions of the steel strip, and the change in the ambient temperature.

FIG. 4 is a graph showing the time-dependent change in the viscosity of the coating composition. The horizontal axis represents time, and the vertical axis represents the coating viscosity. The unit of viscosity is cps (centipoise). As the time elapses, the viscosity of the paint increases, and the solvent is added at a point where the paint deviates from the target NV by a certain amount or more. This drop becomes more pronounced as the solvent injection speed increases,
If the solvent is introduced slowly, it becomes inconspicuous. Note that the target NV slightly changes from a low-viscosity side to a high-viscosity side in accordance with the coating schedule determined from the contents of the order, and thus has a gentle upper right curve. The range of viscosities at 12 hours was 33-38 cps.

FIG. 5 is a graph showing the relationship between the paint temperature, the paint viscosity, and the non-volatile residue. The non-volatile residue (N
V) is shown in%. A paint temperature of 37.5 ° C. is derived from FIG. 3 and 33 cps and 38 cps are derived from FIG. 4 and plotted in FIG. 5, where the intersection between 37.5 ° C. and 33 cps is almost NV =
The intersection of 37.5 ° C. and 38 cps corresponds to approximately NV = 16. Calculating (16-15) / 15 results in 0.067. 5. With respect to the target non-volatile residue
It is considered that the influence is about 7%. However, if the dry coating film thickness is 1.0 μm, only a fluctuation of the film thickness of 0.067 μm is obtained, so that a coating film having a very uniform thickness can be obtained.

FIG. 6 is a graph showing the change in the average paint temperature over the whole year. The horizontal axis represents the month, and the vertical axis represents the average paint temperature. The temperature change is ± 1 ° C when inspected throughout the year.
, And the standard deviation of the variation is 0.3 to 0.1.
It was 4. Therefore, according to the apparatus according to the present invention, it is possible to carry out good coating throughout the four seasons.

The addition timing control unit 6 shown in FIG.
3 may be incorporated in the nonvolatile residue controller 61.
The same applies to the target non-volatile residue setter 62.

[0032]

According to the present invention, the following effects are exhibited by the above configuration. Claim 1 includes a non-volatile residue control device that makes the non-volatile residue of the paint constant in the paint circulation device of the roll coater, and a paint temperature control device that makes the temperature of the paint constant,
The non-volatile residue control device can keep the non-volatile residue of the paint constant, and the paint temperature control device can keep the non-volatile residue constant paint at a predetermined temperature. High film thickness coating can be performed.

According to a second aspect of the present invention, the paint circulating device of the roll coater according to the first aspect further includes an addition timing control unit for permitting the next addition after a predetermined time has elapsed from the previous addition of the solvent. . The above-mentioned fixed time is a time required for the solvent added by the solvent addition device to reach the coater pan from the addition point or longer, and by giving such a fixed time, the non-volatile residue is further stabilized. And still achieve good coating.

[Brief description of the drawings]

FIG. 1 is a principle diagram of a roll coater according to the present invention.

FIG. 2 is a flow chart of the solvent addition of the roll coater according to the present invention.

FIG. 3 is a graph showing a change over time in paint temperature.

FIG. 4 is a graph showing the change over time in paint viscosity.

FIG. 5 is a graph showing the relationship between paint temperature, paint viscosity, and non-volatile residue.

FIG. 6 is a graph showing changes in average paint temperature throughout the year.

FIG. 7 is a principle diagram of a conventional roll coater.

[Explanation of symbols]

1 ... Paint circulation device for roll coater, 4 ... Circulation tank, 1
0: coater pan, 11: supply pipe, 13: return pipe, 14 ...
Steel strip, 15 roll (pickup roll), 16 roll (applicator roll), 21 paint level detecting means, 22 heat exchanger, 23 primary supply pipe, 24 secondary supply pipe, 25 ... paint temperature detecting means, 26 ... paint viscosity detecting means, 30 ... paint temperature control device, 50 ... solvent addition device, 60 ... nonvolatile residue control device, 62 ... target nonvolatile residue setting device, 63 ... addition timing control unit.

Claims (2)

[Claims] 1. A paint stored in a coater pan is applied to a steel strip via a roll, and after excess paint in the coater pan overflows, the paint is returned to a circulation tank by a return pipe, and the paint in the circulation tank is supplied through a supply pipe. In a paint circulation device of a roll coater that circulates paint by sending it to the coater pan, a heat exchanger is provided in the middle of the paint supply pipe, and a primary supply pipe or a circulation tank that sends paint to the heat exchanger is provided. A solvent adding device for introducing a solvent is provided, a paint level detecting means for detecting a paint level in a circulation tank is provided, and a paint temperature for detecting a paint temperature in a secondary supply pipe or a coater pan for leading paint from the heat exchanger. A detection means and a paint viscosity detection means for detecting the viscosity of the paint are provided. The nonvolatile residue of the paint at that time is calculated from the detected temperature and viscosity of the paint, and the obtained measurement non-volatility is obtained. The non-volatile residue difference between the residue and the separately input target non-volatile residue is determined, while the paint amount in the circulation tank is determined from the paint level, and the paint amount in the supply pipe, the coater pan and the return pipe is added thereto, and the paint quantity is calculated. Determine the total circulation amount, calculate the paint addition amount from the total paint circulation amount and the non-volatile residue difference, and attach a non-volatile residue control device for operating the solvent addition device to the solvent addition device; A paint circulating device for a roll coater, wherein a paint temperature control device for controlling the heat exchanger based on temperature information to adjust the paint to which the solvent is added to a predetermined temperature is attached to the heat exchanger. 2. A roll coater according to claim 1, further comprising an addition timing control unit for permitting the next addition after a predetermined time has elapsed from the previous addition of the solvent. Paint circulation device.