JP2002248407A - Coating apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a coating apparatus capable of preventing the coating flaw such as a streak or the like caused by the coating liquid scraped off by an air knife head 3. SOLUTION: In the air knife coating apparatus for supplying the coating liquid to a continuously running web from a coating liquid feeder to coat the web over a predetermined coating width and blowing off the excess coating liquid by the air stream blown off from the air knife head to determine a coating amount, a flat plate-shaped member is opposed to the air knife head in close vicinity thereto over the almost entire region of the coating width on the upstream side of the air knife head with respect to the running direction of the web and a mist removing box held to atmospheric pressure lower than that of the outside is further arranged on the upstream side of the flat plate- shaped member in adjacent relationship.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coating apparatus for applying a coating liquid to a web, and more particularly to a coating apparatus for applying a coating liquid to a continuously running web and then performing measurement using an air knife. .

[0002]

2. Description of the Related Art There are various types of coating apparatuses for coating a continuously running web. Air is a suitable coating for applying a coating liquid having a relatively low viscosity in a small coating amount. There is a knife coating device.

An air knife coating apparatus supplies a coating solution to the surface of a continuously running web, blows out gas such as air from the tip of an air knife head, and generates excess coating on the web by a gas flow such as a blade. The liquid is removed and the coating amount is set to a predetermined amount.Since the shearing force by the air knife is smaller than that of the contact type coating method, the coating layer has a relatively uniform coating layer along the unevenness of the web surface. It is said to be suitable for things.

[0004] The coating liquid scraped off by the gas blown out from the air knife head becomes liquid and mist,
The liquid coating liquid is collected by dropping onto the floor of the mist removal box by gravity due to its own weight, and the mist-like coating liquid floats around and may adhere to the tip of the air knife head, possibly causing uneven coating or streaks. Coating defects occur. As a preventive measure, a mist removal box is provided.

FIG. 2 is a schematic side view showing the periphery of a conventional air knife head. The mist removal box 4 is provided with a cover that covers from the entry side of the backup roll 1 to the lower part of the air knife head 3. A mist removal port 4 a sucked toward the blower side is provided on the side of the cover, and an excess liquid recovery port 4 b is provided on the floor surface. Is provided. Since the mist removal box 4 is sucked through the mist removal port 4a, the pressure is negatively applied from the outside.

However, with an increase in the amount of mist due to an increase in the coating speed, mist tends to adhere to the tip of the air knife head 3. Therefore, it is necessary to increase the mist removal capability. However, if the blower is too large, the collected liquid is sucked, and the yield of the collected liquid may be reduced and the blower device may be damaged.

[0007]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems and prevents the application liquid mist from adhering to the tip of an air knife head without increasing the capacity of an air blower.
Provided is a coating device capable of obtaining a uniform coating surface.

[0008]

SUMMARY OF THE INVENTION It is an object of the present invention to supply a coating solution to a continuously running web by a coating solution supply device, apply the coating solution at a predetermined coating width, and then blow out the gas from an air knife head. In an air knife coating apparatus that determines the amount of coating by blowing down excess coating liquid with a flow, the flat plate-like member is applied to almost the entire coating width on the upstream side of the air knife head with respect to the running direction of the web. This is achieved by an air knife applicator characterized in that the knives are disposed close to and opposed to the knife head, and a mist removal box having a negative pressure from the outside is arranged adjacent to the upstream side of the flat member.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a coating apparatus according to the present invention will be described below with reference to the drawings. Figure 1
1 is a schematic side view of a coating apparatus showing an embodiment of the present invention. After the gas accompanying the web 5 running continuously in contact with the backup roll 6 is shut off by the gas shut-off device 8,
The coating liquid is supplied from the coating liquid supply device 9 to the web 5, and the coating liquid is measured by the air knife head 3 to form a coating layer. On the upstream side of the air knife head 3 in the web running direction, the plate-shaped member 2 is brought close to and opposed to the air knife head 3 over almost the entire coating width, and the air knife head 3 scrapes the upstream side of the plate-shaped member 2. A mist removal box 4 for removing the applied coating liquid is disposed adjacent to the mist removal box 4. The mist removal box 4 sucks air and mist from the mist removal port 4a, so that the inside of the mist removal box 4 has a negative pressure from the outside. The amount of suction from the mist removal port 4a is determined by the application speed, the application amount, the application width, and the like.

The coating solution applied on the upstream side is scraped off by air blown out from the air knife head 3 to adjust the amount of application. The air volume of the air knife head 3 is determined by various conditions such as the scraping amount, the coating speed, and the distance from the web 5 to the tip 3a of the air knife head. Among the scraped coating liquid, the liquid falls on the floor of the mist removal box 4 and is collected, but the mist-like gas floats around and is sucked and removed from the mist collection port.

As the coating speed increases, the amount of floating mist increases, and if the mist adheres to the vicinity of the tip 3a of the air knife head, coating defects such as streaks occur. Therefore, it is necessary to form a protective layer of air near the tip 3a of the air knife head, and at a position close to and opposed to the lower surface of the tip 3a of the air knife head on the upstream side in the running direction of the web 5 over almost the entire area of the coating width. (Preferably, flat member 2 having a width equal to or greater than the coating width) The flat member 2 was attached. The gap between the flat member 2 and the lower surface 3b of the air knife head 3 is determined by the amount of mist, the amount of air blown from the air knife 3, and the amount of suction of the mist removal box 4.

The plate-like member 2 is arranged at a position close to and opposed to the lower surface 3b of the air knife head 3 so that
A gap is formed between the flat plate member 2 and the lower surface 3b of the air knife head 3. By setting the inside of the mist removal box 4 to a negative pressure, air flows into the gap from the outside and the tip of the air knife head. It is considered that mist is prevented from adhering to the portion 3a. Although the distance from the flat member 2 to the backup roll 1 depends on the suction amount of the mist removal box 4, the distance from the backup roll 1 to the tip of the air knife head is equal to the distance between the flat member 2 and the tip of the air knife head. The height is preferably equal to or greater than the box side wall 4c of the mist removal box 4. Further, the dimension of the gap between the lower surface 3b of the air knife head 3 and the flat member 2 is preferably 10 mm or less, more preferably 3 mm.
It is preferably at least 8 mm.

[0013]

EXAMPLES Examples will be given below to clarify the effects of the present invention. However, the present invention is not limited by the embodiments described below.

Example 1 In this experiment, in the coating apparatus of the present invention, as shown in FIG. 1, the material of the plate-like member 2 was stainless steel, and a plate-like member having a thickness of 5 mm was attached to the air knife head 3 with a gap of 5 mm. Was. As a comparative coating apparatus, a coating apparatus without the flat member 2 was used.

A 100 μm-thick PET film is used for the web, and a coating solution (colored by adding a blue dye) of 1% by weight of polyvinyl alcohol is applied thereto, and the coating amount after blowing down with an air knife is 20 ml / m 2. the wind pressure of air flow blown out from the air knife head 3 such that ² was prepared. The coating speed was changed to 100,150 m / min.

To confirm the effect, the state of generation of streaks generated when mist adheres to the tip of the air knife head was investigated.

[0017]

[Table 1]

From the above results, in the coating apparatus according to the present invention, no streak was generated at coating speeds of 100 and 150 m / min. However, in the conventional coating apparatus having no flat member, streaks were generated even at a coating speed of 100 m / min.

As described above, according to the embodiment of the present invention, a flat member is provided over almost the entire coating width at a position close to and opposed to the lower surface of the air knife head as compared with the conventional coating apparatus. This makes it possible to prevent the occurrence of coating defects such as streaks.

The thickness, material, shape, and the like of the illustrated plate-like member 2 are merely examples, and are not limited to these conditions, and the design can be changed as appropriate. Also,
The web in the present invention includes paper, plastic film, resin-coated paper, synthetic paper, and the like.

[0021]

According to the present invention, a coating liquid is supplied to a continuously running web by a coating liquid supply device, and the web is coated with a predetermined coating width. In an air knife coating apparatus that determines a coating amount by blowing down a liquid, a flat plate-like member is opposed to the air knife head in almost the entire width of an application width on an upstream side of the air knife head with respect to a running direction of the web. Further, by disposing a mist removal box having a negative pressure from the outside on the upstream side of the flat member, an air layer is formed on the lower surface of the air knife head, and coating defects such as streaks can be prevented. An application device can be provided.

[Brief description of the drawings]

FIG. 1 is a side view showing one embodiment of a coating apparatus of the present invention.

FIG. 2 is a side view of the vicinity of an air knife head of a conventional coating apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Backup roll 2 Plate-shaped member 3 Air knife head 3a Tip of air knife head 3b Lower surface of air knife head 4 Mist removal box 4a Mist removal port 4b Excess liquid recovery port 4c Box side wall 5 Web 6 Backup roll 7 Guide roll 8 Air Cut-off device 9 Application liquid supply device

Claims (1)

[Claims] 1. A coating liquid is supplied to a continuously running web by a coating liquid supply device and coated with a predetermined coating width, and then the excess coating liquid is blown off by a gas flow blown out from an air knife head to be coated. In the air knife coating apparatus for determining the amount, a flat plate member is brought close to and opposed to the air knife head over almost the entire coating width on the upstream side of the air knife head with respect to the running direction of the web, and An air knife coating device, wherein a mist removal box having a negative pressure is externally arranged adjacent to the upstream side of the member.