JPH06262130A - Continuous coating method - Google Patents

Abstract

PURPOSE:To continuously apply a homogeneous, smooth and beautiful coat on a strip. CONSTITUTION:A coating soln. is allowed to flow down from a slit nozzle to form the soln. curtain, which is continuously applied on a traveling strip by curtain flow coating. In this case, an auxiliary curtain 25 of a magnetic fluid insoluble in the coating soln. is formed and laid over the upper surface of the film of a coating soln. curtain 24. The magnetic fluid is recovered with a magnet roll 27 before entering a drying furnace 26, the auxiliary curtain 25 is pressed on a strip 22 by the magnetic force of a magnet 31 after coating to smooth the coating film surface, then the magnetic fluid is recovered by an appropriate means before entering the drying furnace 26, and further the coating film of the auxiliary curtain 25 is heated by a heating means 32 to promote the leveling of the coating film.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coating method for continuously applying a coating liquid such as a paint or a functional material onto a strip material such as a steel plate.

[0002]

2. Description of the Related Art Roll coating has heretofore been commonly used as a means for continuously applying a coating liquid such as a coating material by continuously running a belt-shaped material such as a metal plate, a synthetic resin film, or paper. Came.

However, according to roll coating, a regular streak pattern called "roll eye" tends to occur where the coating film thickness becomes uneven in the width direction of the coating material. There is a problem. This streak pattern remains after baking and drying and spoils the appearance of the surface of the coating material, but it occurs as the speed of movement (running) of the belt-shaped material to be coated increases and the peripheral speed of the roll increases. It became prominent and became an obstacle to improving productivity.

Further, in the case of roll coating, since only a coating solution having a relatively low viscosity can be applied, it is necessary to use a large amount of a diluent such as an organic solvent, which increases the cost of the coating solution. There was a concern that the efficiency of the drying furnace would decrease and that the diluent would volatilize, which could lead to global environmental problems.

Therefore, as a coating means for solving such a problem, a "coating flow coating method" or an "extrusion coating method" in which a coating liquid is flown out from a slit nozzle to perform coating. Etc. were devised.

Of these, the coating flow coating method is a coating means that has been put to practical use in a steel plate cutting line or the like, and as shown in FIG. A method of forming a coating film by causing the material to be coated 4 to travel under the ten 2 by the conveyor belt 3 and causing the coating liquid curl 2 to adhere to the upper surface of the material to be coated 4. The material 4 to be coated on which the coating film has been formed is subsequently conveyed to a drying oven where the coating film is dried and cured.

However, in this method, since a distance of about 50 to 450 mm is provided between the slit-shaped nozzle 1 and the material 4 to be coated, the coating liquid curt 2 flowing down tends to contract in the width direction due to surface tension. Show me. Therefore, in general,
An edge guide such as a wire, a rod or a chain is hung from both ends of the slit-shaped nozzle 1 and both ends of the coating liquid carten 2 are arranged along the edge guides to prevent the contraction. However, even if the speed of the material to be coated is increased to improve productivity, the coating liquid curt 2 flowing down due to the flow of ambient air due to running vibrates, which causes uneven coating.

On the other hand, in the extrusion coating method, as shown in FIG. 5, a die 12 having a slit 11 is brought close to a material 13 to be coated, and a coating solution is extruded from the die 12 to the material 12 to be coated. It is a means for applying directly and at the same time smoothing the application liquid at the tip of the die 12 to make it beautiful, and is generally applied for uniform application to a soft band-shaped body such as a resin film or paper. The reference numeral 14 indicates a backup roll.
It is Le.

However, when the extrusion coating method is applied to the coating of a hard material such as a steel sheet, scratches on the die tip due to contact between the steel sheet and the die 12 may occur, and Die 12 due to poor thickness accuracy
It was not possible to ignore the problem that the coating film thickness became uneven due to the variation in the distance between the steel plate and the steel sheet. When coating the steel sheet, set the distance between the steel sheet and the die tip to 3
It was necessary to make the thickness below 00 μm. Moreover, as in the case of the curtain flow coating method, there is a flow of atmospheric air that accompanies the material to be coated, so air is drawn in between the surface of the material to be coated and the coating liquid curtain to coat. It was also pointed out that defects are likely to occur.

However, as a solution to the above-mentioned problems pointed out in the curtain flow coating method and the extrusion coating method, a suction device is attached to a conveying device (conveyor belt) for the material to be coated. A method for preventing the vibration of the coating material (Japanese Patent Laid-Open No. 3-30860), or a method for blocking the air layer that accompanies the material to be coated by providing an associated air blocking roll, an associated air blocking air nozzle, etc. Kaihei 2-7537
No. 5, JP-A-3-65266) has been proposed. However, even if the above-mentioned measures for preventing the intrusion of the associated air are taken, or even if the vibration suppression measures for the material to be coated by the adsorption device are applied, it is possible to avoid the fluctuation of the coating film thickness due to the disturbance of the atmospheric air. There wasn't.

Regarding the curtain flow coating method, one end of an elastic guide plate for guiding the coating liquid carten from the slit-shaped nozzle to the surface of the material to be coated is referred to as "the coating of the slit-shaped nozzle is good. Side wall ”,
Means for forming a coating liquid carten without film breakage by causing the coating liquid to flow down along the upper surface of this guide plate has also been proposed (Actual Publication No. 2-104877).
issue). However, although this means was able to stably prevent film breakage of the coating liquid carten due to the flow of the surrounding air, it is difficult to stabilize the posture of the elastic guide plate, and the guide for stabilizing it is difficult. If the tip of the plate is mechanically pressed too much, it will not be possible to follow the vibration of the coating material that is running, and the film thickness fluctuation will increase,
It has been pointed out that the tip of the guide plate is scratched with the material to be coated, which causes defects in the surface of the coating film. Furthermore, when observing the coating film formed on the surface of the material to be coated, it was found that there are cases where it is not sufficiently satisfactory in terms of film thickness control and smoothing of the coating film surface.

In view of the above, the object of the present invention is to achieve a beautiful, uniform and smooth coating regardless of the type of coating liquid or material to be coated, and to easily control the film thickness. It was to establish the means of painting.

[0013]

Therefore, as a result of intensive studies to achieve the above object, the present inventor was able to obtain the following knowledge. That is, in the carten-flow coating method, which has the advantage that it is less restricted by the type of material to be coated compared to the extrusion coating method, as described above, it affects the surrounding air flow. As a result, the vibration of the "coating liquid curtain" flowing down may become large and the coating film may become non-uniform, and the elastic guide plate may be simply applied from the wall on the good side of the slit nozzle to the upper surface of the material to be coated.
It was difficult to form a uniform and smooth coating film with a well-controlled thickness even if a measure was taken to allow the coating solution to flow down along the coating solution. However, coating is performed while forming an auxiliary curtain of "magnetic fluid insoluble in the coating liquid" which overlaps with the coating liquid carten by, for example, providing another slit beside the coating liquid flowing slit of the nozzle. When the coating is carried out, the Karten flow is stabilized, film breakage and vibration are suppressed, and it becomes possible to form a smooth and uniform coating film without damaging the material to be coated. It has been found that the magnetic fluid auxiliary cartes can be easily separated and recovered by bending the material to be coated or using a magnet roll before entering the drying furnace.

In addition, after the coating liquid is applied, the auxiliary cartes, which are applied on the coating liquid film in an overlapping manner, are pressed against the surface of the material to be coated by the magnetic force of the magnetic field formed by the magnet, or by the appropriate heating means. It was also found that when the auxiliary curtain was heated, smoothing of the coating film surface was further promoted, and a smooth, homogeneous and beautiful coating film could be formed.

The present invention has been completed on the basis of the above-mentioned findings and the like, and "Continuously deposits a coating solution formed by flowing down from a slit nozzle on a running belt-shaped material. In the coating flow coating, the auxiliary coating of "magnetic fluid insoluble in the coating liquid" overlaps with the side of the coating liquid coat which is the upper surface of the coating film.
The coating is performed while forming a tenn, and then the magnetic fluid is recovered by using a magnet roll before entering the drying furnace, or the auxiliary curten is applied by a magnetic force of a magnet following the coating by a belt-shaped material. The surface of the coating film is smoothed by pressing and the magnetic fluid is recovered by an appropriate means before entering the drying oven, or the coating film of the auxiliary cartene is heated by a heating means. By promoting the leveling of, it is possible to stably produce a smooth, uniform and beautiful coating material with high productivity ”.

The above-mentioned "magnetic fluid insoluble in the coating liquid" is not particularly specified as long as it is insoluble in the coating liquid to be applied. That is, in general, "magnetic fluid"
Is a liquid that is a magnetic powder with a particle diameter of approximately 100Å (eg γ
-Fe ₂ O ₃ system, Ba ferrite system, CrO ₂ system, etc.) and a surfactant is added so as not to cause agglomeration due to contact between particles. The magnetic fluid used in the present invention is Although it depends on the type of the coating liquid, it is advisable to employ, as the above-mentioned "liquid", for example, "a liquid insoluble in the coating liquid" such as silicone oil insoluble in the paint or an aqueous liquid having a large polarity.

The magnetic field forming magnet for promoting the leveling of the coating film may, of course, be an electromagnet or a permanent magnet, and non-contact as a heating means for the auxiliary cartes. It is preferable to use a radiant heating device (electric heater, etc.) or an induction heating device capable of being heated by.

[0018]

The present invention will be described in more detail below with reference to the drawings. FIG. 1 illustrates an example of the curtain floating coating method according to the present invention. In this example,
As a coating nozzle device, the header-21 is divided into two chambers, front and rear, by a partition wall, and each chamber is opened like a slit at the header-exit portion, and these slits are overlapped in parallel and integrated into one chamber. A slit structure is used.

When coating the continuously running belt-shaped material (material to be coated) 22, the "coating liquid" and the "coating liquid" are applied to the two chambers of the header 21 through the flow rate adjusting valves 23, 23, respectively. Is supplied with an insoluble magnetic fluid. "Coating liquid"
Is supplied to the chamber in front of the header-21 (the entrance side of the strip), and the "magnetic fluid insoluble in the coating liquid" is supplied to the chamber in the rear (the direction of travel of the strip) so as to overlap the upper surface of the coating film. .

The "coating liquid" supplied to the header 21 flows down from the slit-shaped opening at the header-outlet portion as in the case of the conventional curtain flow coating, and the coating liquid coater is used.
In this example of the present invention, the rear chamber to which the "magnetic fluid insoluble in the coating liquid" is supplied also has a slit formed so as to overlap the coating liquid outflow slit in parallel with the header-outlet portion. Therefore, at the outlet (slit portion) of the header-21, the coating liquid kerten 24 and the "magnetic fluid insoluble in the coating liquid" tent (auxiliary kerten 25) overlap as a parallel flow to form two layers of liquid. It becomes a flow chart and flows down. In this case, since the auxiliary curtain 25 is on the rear side of the coating liquid carten 24 (on the traveling direction of the belt-shaped material), the coating liquid carten 24 is
Is deposited on the upper surface of the band-shaped material 22 and the auxiliary curtain (curtain of magnetic fluid insoluble in the coating liquid) 25 is coated on the upper surface of the coating film.

When the auxiliary curtain 25 is formed by overlapping with the coating liquid curten 24 as described above, the apparent liquid flow curten thickness at the nozzle outlet becomes very thick, which stabilizes the curten. As a result, the film breakage and vibration are prevented, and the surface of the coating film becomes very smooth. Therefore, even if the distance between the coating nozzle and the surface of the strip-shaped material is set to about 50 to 100 mm, beautiful coating can be performed.

When the band-shaped material 22 is coated with the coating liquid as described above, an auxiliary curtain is formed so as to cover the liquid film of the coating liquid.
Since 25 forms a layer, the interfacial tension between the liquid films promotes leveling at the interface between the liquid film of the coating liquid and the auxiliary curtain 25, which is very preferable for obtaining a smooth and uniform coating film. Be done.

That is, the leveling property of the coating film at the time of coating can be judged by "the time (T _1/2 ) at which the sinusoidal peak height of the Newtonian fluid becomes half" represented by the following equation. .

As is clear from the above formula, the half-life of the sinusoidal peak height (waviness) is inversely proportional to the surface tension of the coating film and proportional to the viscosity. Therefore, in order to promote leveling, the surface tension should be increased to increase the viscosity. It is effective to reduce
From this point, it can be said that the magnetic fluid for the auxiliary cartes preferably has a large surface tension.

The coating strip thus leveled is sent to a drying oven to dry and harden the coating film, but the film of the auxiliary caten (film of magnetic fluid insoluble in the coating liquid). Before entering the drying oven 26, it is separated using a magnet roll 27 and collected in a tank 28. However, since the auxiliary curtain is composed of "a fluid which is insoluble in the coating liquid", the auxiliary curten covering the coating film can be separated by a method such as inclining the belt-shaped material.

FIG. 2 is a schematic diagram illustrating an example of separating and recovering a magnetic fluid using the magnet roll 27.
A roll (magnet roll 27) incorporating an electromagnet inside is placed in contact with or in close proximity to the surface of the strip-shaped material after coating with the coating liquid, and coating is performed using the strong magnetic field generated by this magnet roll 27. The magnetic fluid covered on the surface is moved to the surface of the magnet roll 27, and the attracted magnetic fluid is transferred to the magnet roll 27.
It turns off the magnetic field when it comes to its lower position by the rotation of 27,
At the same time, the wiper 29 or the like scrapes the surface of the magnet roll 27 to collect it in the tank 28. here,
As the magnet roll 27, it is preferable to provide a minute (several microns) projection 30 on the roll surface as shown in FIG. 3 so that a portion having a larger magnetic field strength is formed. Collection efficiency can be improved.

By the way, the leveling of the coating liquid film applied to the strip-shaped material is carried out by applying a coating liquid and then applying an "auxiliary curl overlaid on the coating liquid film" by a magnetic force from a magnetic field formed by a magnet. It can be promoted by pressing it toward the material 22 to be coated, and the leveling property of the coating film can be improved by heating the coating liquid film at a low temperature, so that either or both of these means should be applied. Is more desirable for a smooth and beautiful coating.

FIG. 4 is an explanatory view of an example of the present invention in which the leveling property is further improved by the above means. That is, in this example, the "coating liquid" and the "magnetic fluid insoluble in the coating liquid" supplied to the header-21 are fed to the "coating liquid curtain 24" and the auxiliary curtain 25 through the slits of the header-outlet portion. 1 is the same as the example shown in FIG. 1 in that it is made to flow down as a two-layer liquid flow chart with overlapping magnets, but a magnet device 31 and an induction heating device 32 are provided downstream of the header-outlet portion (nozzle outlet portion). Are different in that they are arranged.

As described above, first, when the magnet device 31 is arranged on the downstream side of the header-outlet portion (in this example, the magnet device 31 is arranged on the lower surface side of the strip 22 to generate a magnetic field, the auxiliary curtain 25 made of magnetic fluid is The coating liquid film is pressed downward (in the direction of the material 22 to be coated) in a non-contact manner, and as a result, the coating liquid film is pressed against the surface of the strip-shaped material 22 by the auxiliary curtain 25, so that the leveling of the coating film surface is promoted. It

That is, when a magnetic field is applied to the magnetic fluid, a couple of forces are applied to each part of the magnetic fluid due to the action of aligning the magnetization direction of the particles with the direction of the magnetic field, and at the same time, the particles are placed in a strong magnetic field. A volume force is generated to move it. This volume force is represented by the strength H of the magnetic field and the magnetic moment M of the particle per unit volume, and is a correction term of Bernoulli's theorem as in the following equation.

[0031]

[Equation 1]

Therefore, when the magnet device 31 is arranged at the lower surface of the strip 22 and a strong magnetic field is generated, the auxiliary curtain 25 is pressed downward, whereby the coating liquid film surface is also pressed against the strip 22. That is, the leveling of the surface of the coating film progresses.

When the auxiliary curtain (a layer of magnetic fluid insoluble in the coating liquid) 25 is heated by the induction heating device 27, the auxiliary curten 25 is used as a medium to heat the coating liquid film at a low temperature. Therefore, the viscosity of the coating liquid film is lowered and the leveling property thereof is improved. Therefore, the leveling of the coating film is promptly promoted in combination with the increase in the interfacial tension due to the contact with the auxiliary curtain 25, and a more smooth coating film can be obtained. Here, as described above, the heating of the auxiliary curtain 25 may be performed by radiant heating using an electric heater or the like.

It is appropriate that the heating temperature of the coating film mediated by the auxiliary curtain is about 30 to 100 ° C., but the “relationship between the viscosity of the coating solution and the temperature” should be investigated in advance to find out the viscosity of the coating solution. It is good to know the lowest temperature. That is, the viscosity of paint or the like generally changes with temperature. For example, FIG. 5 is a graph showing the change in viscosity of the paint depending on the temperature. As is clear from this, the paint has a temperature of 30 to 1
When the temperature is increased to about 00 ° C, the viscosity is greatly reduced, the fluidity is improved, and the leveling time is shortened.

The coating strip having the coating film leveled by the action of the magnetic field generated by the magnet device 31 and the low temperature heating by the induction heating device 32 is sent to the drying furnace 26 and dried by hot air from the gas jet nozzle 33. It can be hardened,
The auxiliary curtain (magnetic fluid film insoluble in the coating liquid) 25 applied on the coating film is deflected immediately before entering the drying furnace.
It is peeled off at the bent part of the roll (magnet roll if necessary).
It is peeled off with a tank 27) and collected in a tank 28 or the like. Then, the recovered fluid for auxiliary curtain (magnetic fluid insoluble in the coating liquid) is filtered by a filter and sent again to the header 21 by the pump 34 for reuse. The distance between the coating nozzle and the surface of the band-shaped material and the slit spacing are, of course, adjusted according to the type of the band-shaped material, the coating film thickness or the feeding speed.

By the way, the magnetic fluid has the following unique phenomenon. That is, when the magnetic field becomes strong under a vertical magnetic field, the liquid surface of the magnetic fluid becomes unstable, and small protrusions are generated as shown in FIG. 6, where magnetic lines of force are gathered to try to lower the energy. Then, when magnetic lines of force are gathered on the protrusions in this way, magnetic fluid gathers on that portion, and the height of the protrusions becomes higher and higher, and a surface pattern in which surface tension, gravity, and magnetization energy are balanced occurs.

Therefore, by utilizing this characteristic, it becomes possible to manufacture a unique design coated plate having a coating film surface with an uneven pattern. That is, when coating is performed with a strong magnetic field in a curtain flow type coating device in which the magnet device 31 as shown in FIG. 4 is arranged, the auxiliary curtain ((magnetic fluid film insoluble in the coating liquid)
A projection pattern corresponding to the magnetic field distribution is formed on the surface of 25, and since it is pushed into the coating liquid film surface, a coating film surface having a pattern corresponding to various magnetic field distributions is obtained after separating the magnetic fluid, When this is dried and cured, a design coated plate that gives a unique atmosphere is obtained.

Next, the effects of the present invention will be described more specifically by way of examples.

EXAMPLE The chart shown in FIG. 4 as an example of the present invention.
Using a die coating device, a coating test was conducted in which a strip-shaped steel sheet was continuously coated with a general polyester paint. In this test, a magnetic fluid in which γ-Fe ₂ O ₃ fine particles were dispersed in "silicone oil insoluble in the paint" was used as the auxiliary curtain fluid.

The results of this coating test (surface properties of the finished coating film) were used to determine the conventional roll coating method and the curtain flow method.
The results are shown in Table 1 in comparison with the results obtained by the coating method and the extrusion coating method.

[0040]

[Table 1]

The results shown in Table 1 also show that the method of the present invention makes it possible to perform beautiful coating of strip steel sheets stably without being significantly affected by the viscosity and coating speed of the coating material. Can be confirmed. It was also confirmed that such stable coating can be sufficiently performed even in a wide range of the dry coating film thickness of 10 to 200 μm.

[0042]

[Summary of Effects] As described above, according to the present invention, smooth and beautiful continuous coating of various belt-shaped materials can be stably performed, and the productivity and quality of the belt-shaped coated products are remarkably improved. It can bring about useful effects in industry.

[Brief description of drawings]

FIG. 1 is a schematic explanatory diagram of an example of a coating method according to the present invention.

FIG. 2 is an explanatory view of a method of separating and recovering a magnetic fluid using a magnet roll.

FIG. 3 is an explanatory diagram according to another example of the magnet roll.

FIG. 4 is a schematic explanatory diagram regarding another example of the coating method of the present invention.

FIG. 5 is a graph showing a change state of paint viscosity depending on paint temperature.

FIG. 6 is an explanatory diagram regarding one characteristic example of a magnetic fluid.

FIG. 7 is an explanatory diagram of the curtain floating coating.

FIG. 8 is an explanatory diagram of extruded coating.

[Explanation of symbols]

 1 Slit Nozzle 2 Coating Liquid Carten 3 Conveyor Belt 4 Coating Material 11 Slit 12 Die 13 Coating Material 14 Backup Roll 21 Header 22 Strip-shaped Material (Coating Material) 23 Flow Control Valve 24 Coating Liquid Cover Ten 25 Auxiliary Curtain 26 Drying Furnace 27 Magnet Roll 28 Tank 29 Wiper 30 Protrusion 31 Magnet Device 32 Induction Heating Device 33 Gas Jet Nozzle 34 Pump

Claims (3)

[Claims] 1. A coating flow coating in which a coating material formed by flowing down from a slit nozzle to a running belt-shaped material is continuously applied to the coating material. The coating is performed while forming an auxiliary curtain of "magnetic fluid insoluble in the coating solution" on the side of the coating film which is the upper surface of the coating film of the coating film, and before using the magnet roll before entering the drying furnace. A continuous coating method characterized by recovering magnetic fluid. 2. A coating flow coating in which a coating material formed by flowing down a running belt-shaped material from a slit nozzle is continuously deposited on the coating material. Application is performed while forming an auxiliary magnetic coating of "magnetic fluid insoluble in the coating liquid" on the side of the coating film which is the top surface of the coating film, and the auxiliary magnetic recording sheet composed of the magnetic fluid is stripped by the magnetic force of the magnet. A continuous coating method characterized in that the surface of the coating film is smoothed by pressing it toward the material side, and then the magnetic fluid is recovered before entering the drying furnace. 3. The continuous coating method according to claim 1, wherein the leveling of the coating film is promoted by heating the coating film of the auxiliary curtain by a heating means.