JPH10235262A - Coating method and device therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a die-coating method by which the coating soln. before a film is formed and on the surface of the tip of a lip is not dried, and the striped mottles are not generated. SOLUTION: At least one surface of a traveling film is continuously coated with a coating soln. extruded from the slit of a die. In this method, the humidity of the atmosphere around the die lip is controlled to 60-95% RH. The coating soln. is ectruded from the die slit and applied on the traveling film to form a coating film on the surface by this coating device, and a means for controlling the humidity of the atmosphere around the die lip is provided to keep the humidity of the atmosphere at 60-95% RH.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coating method and a coating apparatus for continuously forming a coating film on a film running by a die, and more particularly to a high speed off-line coating of a running film by a die or a high speed in a film manufacturing process. The present invention relates to a coating method and a coating apparatus which can be applied to in-line coating and form a coating film (also referred to as a coating layer) having a uniform and good appearance.

[0002]

2. Description of the Related Art A film such as a plastic film (collectively referred to as a film including a sheet-like substrate) has functions such as easy adhesion, easy slip, gas barrier property, moisture proof property, antistatic property, ink receiving property, and the like. In general, coating is performed for the purpose of imparting the following. As a coater used for this, for example, a gravure coater, a kiss roll coater, a curtain coater, a knife coater, an extrusion die coater and the like are known. For example, in a roll coater, a configuration is often used in which a coating liquid is measured based on the interval between rolls and the size of a gravure roll mesh, and the measured coating liquid film is transferred by a roll. However, such a usual roll coater has a drawback that the property of the coating liquid is liable to change due to drying because the area of the coating liquid exposed to the air is large.

[0003] A die coater is known as a method for compensating for such a drawback of the roll coater. The die coater controls the amount of coating at a small distance between the edge of the fixed die lip and the running film. If this die coater is used, the area where the coating liquid comes into contact with the air is limited to the coating liquid formed between the edge of the die lip and the running film. Can be reduced. However, in the die coater, foreign matter easily adheres to the tip of the die lip, and a vertical streak is likely to be formed on the coating surface. There was a problem that occurred. Also, the coating liquid portion fluctuates greatly at the moment when the die lands on the running film, and also fluctuates due to vibration of the running film even in the coating state, and the tip of the lip is stained with the coating liquid. There was also a problem that the scum formation of the scum caused muscle spots.

[0004]

SUMMARY OF THE INVENTION To solve these problems,
A method of humidifying the periphery of the lip of the die to prevent the coating liquid of the portion and the lip tip from drying is considered. However, when humidification is performed for a long time using only a commercially available ultrasonic humidifier, water droplets that have condensed on the surface of the die and its peripheral devices fall on the running film, causing fatal coating defects and rusting the devices. Occurs. Further, when an enclosure is provided in the entire coating apparatus and temperature and humidity are controlled at a temperature lower than the dew point, the temperature and humidity adjustment equipment generally becomes expensive, and the enclosure causes a problem of significantly impeding coating workability.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems, and a coating method and a coating method by a die coating method which prevent drying of a coating liquid before forming a film and a coating liquid on the surface of a lip tip, and which does not cause stripes. It is to provide a device.

[0006]

The above object is achieved by the present invention described below. That is, the present invention is characterized in that, in a coating method for continuously applying a coating liquid extruded from a slit of a die to at least one surface of a running film, the humidity of the atmosphere around the die lip is set to 60 to 95 RH%. A coating method, and a coating apparatus for continuously forming a coating film on the surface by extruding a coating liquid from a slit of a die into a running film performing the method,
A coating apparatus characterized by providing humidity adjusting means for adjusting the humidity of an atmosphere around a die lip, and maintaining the humidity of the atmosphere at 60 to 95 RH%.

As a result of various studies, if the humidity of the atmosphere is in the range of 60 to 95 RH%, the occurrence of muscle spots can be prevented to the extent that there is no practical problem, and there is no problem such as dew condensation for a long period of time. He found that he could drive and was done. This atmosphere humidity from both sides of prevention of streak, dew condensation,
The range of 65 to 90 RH% is more preferable.

[0008] In the present invention, from the above-mentioned point, the humid air supplied to the periphery of the die lip is preferably humid air containing no water droplets having a diameter of 10 µm or more, and more preferably containing no water droplets having a diameter of 5 µm or more.

The humidity adjusting means comprises an airtight tank provided with a spray nozzle, a filtering means for removing water droplets from the humid air from the airtight tank, and a humidifying nozzle for supplying the filtered humid air around the die lip. This is preferable because the structure is simple and the desired humid air can be stably supplied.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention will be described below with reference to the drawings. FIG. 1 is an explanatory diagram of the overall configuration of an example of a coating device according to the present invention, and FIG. 2 is an explanatory diagram of a humidifying nozzle. In the figure, 1 is a film, 2 is a die, 2a is a die manifold, 2b is a die lip, 3 is a coating solution, 4 is a coating film, 5 is a compressed air source, 6 is an airtight tank, 7 is a spray nozzle, 8
Is the water surface, 9 is the drain hole, 10 is the valve, 11 is the filtration means, 12, 12a,
12b is a humidifying nozzle, 13 is a slit for ejecting air from the humidifying nozzle, a is a running direction of a film, b is a flowing direction of compressed air, c is a flowing direction of water, d is a flowing direction of humid air,
e is the blowing direction of the humidified air.

It is clear from the gist of the present invention that the film 1 is not particularly limited by the thickness and the material. Specific examples include a plastic film.
Examples of the plastic film include a polyolefin film (eg, a polyethylene film, a polypropylene film, etc.), a polyester film (eg, a polyethylene terephthalate film, a polyethylene-2,6-naphthalate film, etc.), a polyamide film (eg, a polyether ketone film, etc.), Examples thereof include a polycarbonate film. Among them, a polyester film, particularly a polyethylene terephthalate film and a polyethylene-2,6-naphthalate film are preferred. Thickness wound on a roll is preferable from the viewpoint of production.

The die 2 spreads a coating liquid sent from a coating liquid supply system (not shown) uniformly in the film width direction in the manifold 2a, and extrudes the coating liquid through the slit of the die lip 2b with a constant width onto the opposite film 1. A coating film 4 having a constant thickness determined by the distance between the tip of the die lip 2b and the film facing surface is formed on the film 1. The discharge direction from the die 2 may be applied to the upper surface of the film 1 with the exit of the die lip 2b facing downward as shown in the drawing, or may be applied to the lower surface of the film 1 with the exit of the die lip 2b facing upward as shown in the drawing. Good.

In the present invention, the coating liquid 3 is selected according to the functional characteristics imparted to the film 1 by the coating film 4. That is, functional properties to be imparted, for example, adhesion (including easy adhesion,
Heat sealability), slipperiness (runnability), antistatic properties, conductivity, abrasion resistance, abrasion resistance, weather resistance, mold release properties, chemical resistance (including, water resistance, solvent resistance), Any coating liquid may be used as long as it is a surface treatment coating liquid that imparts easy printability, flowability, antifouling properties, writing properties, light shielding properties, waterproofness, gas barrier properties, and the like. As these coating liquids, those conventionally known or used can be used. The viscosity of the coating liquid is preferably 1 to 200 centipoise (cp), more preferably 1.1 to 20 cp.

As shown, the humidity adjusting means of this embodiment comprises a compressed air source 5 for supplying compressed air to a spray nozzle 7, a spray nozzle
7 is provided with a water tank 10 for supplying moisture, a spray nozzle 7 for creating supersaturated moist air, an airtight tank 6 for storing moist air and removing water droplets, and a filtering means 11 for removing mist from moist air from the airtight tank 6. Humidifying nozzles 12a and 12b for supplying the humid air from the filtering means 11 to around the outlet of the die lip 2a.
Consists of

As the spray nozzle 7, for example, a mist from a commercially available ultrasonic humidifier may be used, but a type using compressed air is preferable because the mist transport capacity is insufficient. The average particle size of the mist is spray nozzle even when used for a long time.
It is sufficient that 7 has a size that does not cause clogging, and it is preferably 5 to 500 μm.

Since the internal pressure of the airtight tank 6 is slightly increased by the injection of the spray nozzle 7, a pressure-resistant tank is preferably used.
Further, it is preferable to dispose a discharge hole 9 provided with an on-off valve as a means for discharging the water 8 collected at the bottom to the outside.

The filtering means 11 is provided immediately after the airtight tank 6 in order to remove droplets having a diameter of 10 μm or more contained in the supersaturated humid air from the airtight tank 6.
It is preferably from 0.1 to 5 μm, more preferably from 0.3 to 2 μm. The material of the filtration element is not particularly limited, for example, PP or PET
A volume filtration element using a nonwoven fabric of the above, or a SUS or bronze sintered type filtration element can be used.

As shown in FIG. 2, the humidifying nozzle 12 is formed of a cylindrical body having a predetermined diameter longer than the width of the die lip 2b, ie, the width of the coating film 4, and has a slit for blowing air longer than the width of the coating film 4 on its side wall. 13 is formed, and FIG.
As shown in the figure, two humidifying nozzles 12a and 12b are arranged before and after the die lip 2b so as to inject humid air in the direction of arrow e toward an open atmosphere where the tip of the die lip 2b is not enclosed. Humidifying nozzle 1 depending on the shape and size of die 2
The hole diameter of the cylinder of 2 is about 5 to 50 mm, more preferably 10 to
20mm is good. The material may be any material that does not easily rust and is rigid. A humidifying nozzle 1
Preferably, 2 is attached to the die 2 via a support.
The slit 13 is required to jet the moist air uniformly in the die width direction. Although it depends on the capacity of the compressed air source 5, the opening width of the slit 13 is preferably 0.1 to 2 mm. Hereinafter, an example in which coating is performed by the coating apparatus having the above configuration will be described.

[0019]

【Example】

Example 1 10 cp aqueous emulsion coating liquid (including polyester binder) using the coating apparatus shown in FIGS. 1 and 2
Was applied to a film 1 having a width of 400 mm in the direction of arrow a. Here, the injection nozzle 7 uses a two-fluid nozzle that sprays water with compressed air, the compressed air pressure is 3.0 kg / cm ² , the airtight tank 6 is made of stainless steel, has a capacity of 20 liters, and the filtration means 11 for filtering mist is PP. 0.3μ absolute filtration accuracy with non-woven fabric
m, humidification nozzle 12 is made of stainless steel, hole diameter 12mm, length 420mm
Further, a slit having a width of 0.5 mm and a length of 400 mm was used.

First, before the start of coating, the room temperature and the humidity were measured without operating the humidity adjusting means. As a result, the room temperature was 35 ° C. and the humidity was 40%. Therefore, when the humidity adjusting means was activated, the humidity around the tip of the die lip 2b was 80%.
, The application was started and continuous application was performed for 16 hours. During this continuous application, the humidity around the start of application of the coating liquid at the tip of the die lip 2b to the film 1 can be maintained at approximately 80%, and good application without streaking due to scum generation can be achieved. I did it. There was no condensation on the die 2 and its peripheral devices. Furthermore, after the application was completed, the tip of the die lip 2b was stained with the coating liquid, and was wiped with a cloth. As a result, no scum was attached.

Comparative Example 1 Coating was performed under the same conditions as in Example 1 except that the humidity adjusting means was removed. About 6 hours after the start of the application, the scum adhered to the edge of the tip of the die 2, and streaks occurred. Thereafter, application was continued for another 1 hour, but the streak did not disappear.Therefore, application was suspended, the die 2 was retired, and the tip surface was wiped.The scummed coating liquid was attached to the surface of the tip of the die 2. Could not be wiped off.

Comparative Example 2 The periphery of the die 2 was directly humidified by using a commercially available ultrasonic humidifier instead of the humidity adjusting means shown in FIG. 1, and the other coating conditions were the same as in Example 1. Was carried out. Approximately 10 minutes after the start of the application, water droplets condensed on the surface of the die 2 adhered. Soon, the water droplets dripped onto the film 1, and were stretched at the tip of the die lip 2b, and elliptical uncoated spots were confirmed.

[0023]

According to the present invention, a long time stable coating of a die coat method can be achieved, in which only the humidity of the atmosphere around the tip of the die lip is maintained within a predetermined range and no streak due to scumming of the coating liquid occurs. This makes it possible to improve the productivity of highly functional films. Also, since it can be implemented with a simple configuration,
It is also advantageous in terms of cost. As described above, the present invention greatly contributes to enhancing the functionality of the film.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of an overall configuration of an example of a coating apparatus according to the present invention.

FIG. 2 is a perspective view of the humidifying nozzle of FIG. 1;

[Explanation of symbols]

 Reference Signs List 1 running film 2 die 2a manifold 2b die lip 3 coating liquid 4 coating film 5 compressed air source 6 hermetic tank 7 spray nozzle 8 water surface 9 discharge hole 10 water tank 11 filtration means 12a upstream humidification nozzle 12b downstream humidification nozzle 13 slit a Film running direction b Compressed air flow direction c Water flow direction d Wet air flow direction e Wet air blowing direction

Claims (6)

[Claims] 1. A coating method for continuously applying a coating liquid extruded from a slit of a die to at least one surface of a running film, wherein a humidity of an atmosphere around a die lip is set to 60 to 95 RH%. Coating method. 2. A humid air having a diameter of 10 μm or more and containing no water droplets is supplied to the atmosphere, and the humidity is adjusted to 60 to 95 RH.
%. 3. The coating method according to claim 1, wherein the atmosphere is an open atmosphere. 4. A coating apparatus for extruding a coating liquid through a slit of a die on a running film to continuously form a coating film on the surface thereof, wherein humidity adjusting means for adjusting the humidity of the atmosphere around the die lip is provided. Humidity of 60-95
A coating apparatus characterized by maintaining the RH%. 5. The humidity adjusting means comprises an airtight tank provided with a spray nozzle, a filtering means for removing water droplets from humid air from the airtight tank, and a humidifying nozzle for supplying the filtered humid air around the die lip. The coating device according to claim 4. 6. The coating apparatus according to claim 5, wherein the absolute filtration accuracy of the filtration means is 0.1 to 5 μm.