JPH06262128A - Continuous coating method for beltlike material - Google Patents

Abstract

PURPOSE:To attain uniform and smooth beautiful coating independently of the kind of a coating liquid and a material to be coated and to build up a coating means facilitating a film thickness control easily. CONSTITUTION:In curtain flow coating where a curtain of the coating fluid formed by allowing it to flow down on a running belt like material from a slit formed nozzle is continuously coated, the coating is performed while an auxiliary curtain 25 of liquid insoluble to the coating liquid being laid over the side to be an upper surface of a coating film of the curtain 24 of the prescribed coating liquid is formed, or further the coating is performed while the auxiliary curtain 25 is heated by a heating means.

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.

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,
A measure is taken to prevent contraction by hanging edge guides made of wire, rods, chains, etc. from both ends of the slit-shaped nozzle 1 and arranging both ends of the coating liquid carten 2 along them. 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, for example, by forming another slit beside the coating liquid flow-down slit of the above-mentioned nozzle to form an auxiliary curtain of "a liquid insoluble in the coating liquid" which overlaps with the coating liquid carten, coating is performed. It has been found that, by carrying out the above, the Karten flow is stabilized, film breakage and vibration are suppressed, and a smooth and uniform coating film can be formed without damaging the material to be coated.

In addition, when the auxiliary curtain is heated by an appropriate heating means, the viscosity of the coating solution is lowered and the smoothing of the coating film surface is further promoted. It was also found that it is possible to form a different coating film.

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 process for coating as described above, coating is performed while forming an auxiliary coating of "a liquid insoluble in the coating liquid" on the side of the coating liquid which becomes the coating film upper surface. Alternatively, or further, by applying while heating the auxiliary curtain by a heating means, it is possible to stably produce a smooth, uniform and beautiful coating material with high productivity ". .

The above-mentioned "liquid insoluble in the coating liquid" is not particularly specified as long as it is insoluble in the coating liquid to be applied, but preferably has a large surface tension (preferably about 100 dyn / It can be said that a liquid having a stable falling film is more preferable, and a liquid metal such as mercury is more preferable in terms of versatility. Depending on the type of coating liquid, other suitable liquids include, for example, oils and fats insoluble in coating materials such as silicone oil, higher fatty acids, and aqueous liquids having high polarity. As a heating means for the auxiliary curtain, it is preferable to use a radiant heating device (electric heater or the like) or an induction heating device capable of heating without contact.

[0017]

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. Insoluble liquid "is supplied. In addition, the "coating liquid" is to the chamber in front of the header-21 (the entrance side of the strip-shaped material), and the "liquid not soluble in the coating liquid" is to the rear (the direction of the strip-shaped material advancing) so as to overlap the upper surface of the coating film. Supplied to the chamber.

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
24 is formed, but in this example of the present invention, since the rear chamber to which the "liquid insoluble in the coating liquid" is supplied also has a slit opened in the header-outlet portion so as to overlap in parallel with the coating liquid outflow slit. , Header-21 exit (slit part)
Then, the coating liquid curten 24 and the curtain (auxiliary curten 25) of "a liquid insoluble in the coating liquid" overlap as a parallel flow, and
It becomes the liquid flow chart of the layer and flows down. In this case, since the auxiliary curtain 25 is on the rear side of the coating liquid carten 24 (the traveling direction side of the strip-shaped material), the coating liquid carten 24 is attached to the upper surface of the strip-shaped material 22. A liquid film is formed so that an auxiliary curtain (a liquid curten that is insoluble in the coating liquid) 25 covers 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.

In particular, when a liquid metal (such as mercury) is used as the auxiliary curtain 25, the average specific gravity and film thickness of the coating film at the nozzle outlet are further increased to increase the stability, and the interface between the liquid films is also increased. Due to the high tension, the leveling is remarkably promoted at the interface between the coating film applied to the belt-shaped material 22 and the auxiliary curtain 25, which is very preferable for obtaining a smooth and uniform coating film.

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 equation, 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,
It is effective to increase the surface tension and decrease the viscosity. However, the surface tension in air of ordinary solvent-based paints is only about 30 dyn / cm, whereas the surface tension of liquid metal is 400 dyn / cm or more. Therefore, contacting with liquid metal improves the leveling property. It can be greatly improved.

The coating strip thus leveled is sent to a drying oven to dry and cure the coating film, but the film of the auxiliary curtain (a film of a liquid insoluble in the coating liquid).
Is separated and collected before entering the drying furnace. Since this auxiliary curtain is composed of "a liquid insoluble in the coating liquid", the auxiliary curtain covering the coating film can be easily separated by a method such as inclining the belt-shaped material. You can
However, in the case of an auxiliary carten film made of an electromagnetic fluid such as liquid metal or a magnetic fluid, it can be recovered by utilizing an electromagnetic field.

By the way, since the leveling property of the coating film applied to the strip-shaped material is also improved by heating the coating film at a low temperature, heating the coating film at a low temperature by an appropriate means results in a smooth and beautiful coating. Very desirable to do. Figure 2
FIG. 3 is an explanatory diagram of an example of the present invention in which the auxiliary caten is heated by a heating means to raise the temperature of the coating film, thereby further improving the leveling property.

That is, in this example, the "coating liquid" and the "liquid insoluble in the coating liquid" supplied to the header-21 are supplied to the "coating liquid curtain 24 and the auxiliary curtain" through the slits in the header-outlet portion.
It 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 25 overlapping, but a coil 26 for creating an alternating magnetic field at the header-exit (nozzle exit) is provided. The difference is that the induction heating device 27 is provided and is disposed downstream of the header 21 so as to face the coating material surface.

In this way, when the coil 26 is attached to the outlet of the header to create a controlled alternating magnetic field, the auxiliary car
When the "liquid insoluble in the coating liquid" for the ten is a liquid metal, the auxiliary magnet 25 causes the coating liquid cover by the alternating magnetic field.
Since it is pressed into the ten 24 side with an appropriate magnetic pressure, it is possible to appropriately control the coating thickness without mechanical contact.

If the auxiliary curtain (a liquid layer insoluble in the coating liquid) 25 is heated by the induction heating device 27, the coating film is heated at a low temperature by using the auxiliary curten 25 as a medium. The viscosity of the coating film decreases and the leveling property of the coating film improves. 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 and It is good to know the lowest temperature. That is, the viscosity of paint or the like generally changes with temperature. For example, FIG. 3 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 material whose leveling of the coating film has progressed by low temperature heating is sent to the drying furnace 28, where the gas jet nozzle
Although it is dried and hardened by the hot air from 29, the film of the auxiliary curtain (liquid insoluble in the coating liquid) 25 applied on the coating film is deflected by the deflector roll immediately before entering the drying oven 28.
It is peeled off at the bent portion of the tank and collected in the tank 30. Then, the recovered fluid for auxiliary curtain (a liquid insoluble in the coating liquid) is filtered by a filter and sent again to the header 21 by the pump 31 for reuse. Of course, when the auxiliary curtain fluid (a liquid insoluble in the coating liquid) is a magnetic fluid, it may be recovered by using a magnet or the like.

The distance between the coating nozzle and the surface of the strip-shaped material and the slit spacing are, of course, adjusted according to the type of the strip-shaped material, the coating thickness or the feeding speed.

[0032]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The chart shown in FIG. 2 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, mercury was used as a fluid for the auxiliary curtain (a liquid insoluble in the coating liquid).

The results of this coating test (surface properties of the finished coating film) are 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.

[0034]

[Table 1]

The results shown in Table 1 also show that the method of the present invention makes it possible to stably perform beautiful coating of strip steel sheets 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.

[0036]

[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 a schematic explanatory diagram regarding another example of the coating method of the present invention.

FIG. 3 is a graph showing a change state of paint viscosity depending on paint temperature.

FIG. 4 is an explanatory diagram of the curtain floating coating.

FIG. 5 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 Coil for creating alternating magnetic field 27 Induction heating device 28 Drying furnace 29 Gas jet nozzle 30 Tank 31 Pump

Claims (2)

[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. A continuous coating method for a strip-shaped material, characterized in that the coating is performed while forming an auxiliary curtain of "a liquid insoluble in the coating liquid" on the side of the coating film which is the top surface of the coating film. 2. The continuous coating method for a strip-shaped material according to claim 1, wherein the coating is carried out while heating the auxiliary curtain by the heating means.