JP2012170885A - Air-knife coating apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an air-knife coating apparatus capable of obtaining a uniform coated surface by preventing a coating liquid mist from sticking to the tip of an air-knife head and to a plate-like member provided upstream thereof even under long-time coating.SOLUTION: The air-knife coating apparatus is designed in such a relationship that a distance (a) between a baffle plate and a plate-like member, a distance (b) between the plate-like member and the air-knife head, a distance (c) between the baffle plate and a backup roll, and a distance (d) between a mist removing box and a web before abutting on the backup roll, simultaneously satisfy expression (1): (a+b)>c≥d (wherein a>b), and expression (2): (a+b)/(a+b+d)<0.7.

Description

  The present invention relates to a coating apparatus that coats a coating liquid on a support (hereinafter referred to as “web”), and more particularly to a coating apparatus that performs coating with an air knife after coating the coating liquid on a continuously running web. is there.

  There are various types of coating apparatuses that perform coating on a continuously running web, and an air knife coating apparatus is suitable for coating a coating liquid having a relatively low viscosity with a small coating amount.

  The air knife coating device supplies a coating liquid to the surface of a continuously running web, blows out a gas such as air from the tip of the air knife head, removes excess coating liquid on the web by a gas flow like a blade, Therefore, it is set to a predetermined coating amount, and since the shearing force by the air knife is small compared to the contact type coating method, it is suitable for those having a relatively uniform coating layer along the unevenness of the web surface. Has been.

  The coating liquid scraped off by the gas blown out from the air knife head becomes liquid or mist, and the liquid coating liquid is recovered after falling by natural fall due to its own weight, and the mist-shaped coating liquid floats around the air knife head. In some cases, however, it adheres to the tip of the air knife head, resulting in coating irregularities or coating defects such as streaks.

  In order to prevent such defects, it is known to provide a mist removal box as a preventive measure. For example, Japanese Patent Laid-Open No. 7-35478 (Patent Document 1) discloses an apparatus in which intake ducts are provided in parallel with an air knife on the upstream side and the downstream side of a traveling web.

  However, as the mist processing amount increases due to the increase in the coating speed, mist tends to adhere to the tip of the air knife head, and it is necessary to increase the mist removal capability. However, if the blower is too large, the recovered liquid is sucked and recovered. There was a risk of lowering the yield of liquid and failure of the blower device. As a preventive measure, it is known to provide a flat member. For example, in Japanese Patent Application Laid-Open No. 2002-248407 (Patent Document 2), a plate-like member is brought close to and opposed to almost the entire coating width on the upstream side of an air knife head to prevent floating mist from adhering to the tip of the air knife head. An apparatus is disclosed.

  FIG. 4 is a schematic side view of the periphery of an air knife head of a conventional air knife coating apparatus. The mist removal box 4 is provided with a cover 12 and a mist removal box top plate 8 that cover from the entry side of the backup roll 2 to the lower part of the air knife head 1 and a mist removal port 4a that is sucked to the blower side on the side of the cover An excess liquid recovery port 4b is provided on the floor surface. Since the mist removal box 4 is sucked from the mist removal port 4a, it has a negative atmospheric pressure from the outside. A flat plate member 3 is attached to the top of the mist removal box top plate 8 of the mist removal box 4.

  FIG. 5 is a schematic diagram showing mist adhesion and air flow after long-time application in a conventional air knife coating apparatus. The flat plate member 3 is attached to prevent the floating mist from adhering to the tip of the air knife head 1 as described above. As shown in FIG. The air flowing in between the members 3 (flowing in the direction of the arrow in the figure) causes the air to wrap around at the tip of the flat plate member 3, and the mist adheres to the flat plate member 3 to form a mist adhesion pool 13. Due to this, coating defects such as coating unevenness and streaks may occur, and improvement has been demanded.

Japanese Patent Laid-Open No. 7-35478 JP 2002-248407 A

  The present invention solves the above-mentioned problems, and even if the capacity of the air blower is not increased more than necessary, the coating liquid mist is applied to the tip of the air knife head and the tip of the flat plate member provided on the upstream side even if it is applied for a long time. An air knife coating apparatus capable of preventing adhesion and obtaining a uniform coated surface is provided.

The above-described problems of the present invention have been solved by the following invention.
Air knife coating that determines the coating amount by supplying the coating liquid to a continuously running web with a coating liquid supply device, coating it with a predetermined coating width, and then scraping off the excess coating liquid with a gas flow blown from the air knife head. In the apparatus, the coating apparatus has an air knife head and a backup roll facing the air knife head, and further, on the upstream side of the air knife head, a flat plate member facing the air knife head and facing the entire coating width, A baffle plate facing the flat plate member and facing the entire coating width, and a mist removing box for collecting mist generated when the coating liquid is scraped off by an air knife head is provided at least in this order. , Distance a between baffle plate and flat plate member, distance b between flat plate member and air knife head, baffle plate and back The distance c between Ppuroru, and the distance d between the web before the mist removal box in contact with the backup roll, but air knife coating apparatus in a relationship satisfying the following formula 1, 2 at the same time.
Formula 1) (a + b)> c ≧ d However, Formula 2 where a> b: (a + b) / (a + b + d) <0.7

  According to the present invention, it is possible to prevent the coating liquid mist from adhering to the tip of the air knife head and the tip of the flat member provided on the upstream side even if it is applied for a long time without increasing the capacity of the air blower more than necessary, An air knife coating apparatus capable of obtaining a uniform coated surface can be provided.

It is a schematic side view which shows one embodiment of the air knife coating device of this invention. It is the schematic which shows the adhesion of the mist and the flow of air after long-time application | coating in the air knife coating device of this invention. It is the schematic which shows the adhesion of the mist and the flow of air after long-time application | coating in the air knife coating device of this invention. It is a schematic side view around the air knife head of the conventional air knife coating device. It is the schematic which shows the adhesion of the mist after long-time application | coating in the conventional air knife coating device, and the flow of air.

  Embodiments of an air knife applicator according to the present invention will be described below with reference to the drawings. FIG. 1 is a schematic side view showing an embodiment of an air knife coating device of the present invention. For the web 6 that continuously contacts the backup roll 2 in the direction of the arrow in the figure, the gas accompanying the web 6 is shut off by the gas shut-off device 7, and then the coating solution (not shown) is applied from the coating solution supply device 5 to the web 6. Is applied, and the coating liquid is measured by the air knife head 1 to form a coating layer. In the air knife coating device of the present invention, a plate-like member that faces the air knife head 1 in the vicinity of the air knife head 1 and faces the entire coating width in order to suppress adhesion of mist to the tip of the air knife head 1 on the upstream side in the web traveling direction of the air knife head 1. 3 is installed on the upstream side of the flat plate-like member 3 in order to rectify the air flowing in from the outside. A mist removal box 4 for collecting mist generated when the coating liquid is scraped off by the air knife head 1 is disposed on the side. Since the mist removal box 4 sucks air and mist from the mist removal port 4a, the inside of the mist removal box 4 becomes minus atmospheric pressure from the outside. The suction amount from the mist removal port 4a is appropriately determined according to the coating speed, coating amount, coating width, and the like.

  The air knife coating device of the present invention adjusts the coating amount by scraping off the coating solution applied by the coating solution supply device 5 provided on the upstream side of the air knife head 1 with the air blown from the air knife head 1. The air volume of the air knife head 1 is determined by various conditions such as the scraping amount, the coating speed, the distance from the web 6 to the tip of the air knife head, and the like. Of the coating liquid scraped off, the liquid falls onto the floor surface of the mist removal box 4 and is recovered from the excess liquid recovery port 4b. On the other hand, the mist-like gas floats around the air knife head 1 and is sucked and removed from the mist removal port 4a.

  In the air knife coating apparatus of the present invention, the floating member mist is prevented from adhering to the tip of the air knife head 1 by the flat plate member 3 provided on the upstream side of the air knife head 1, but the floating mist increases as the coating is continuously performed. Then, it adheres to the vicinity of the front end portion of the flat plate member 3, and application defects such as application stripes occur. Therefore, it is necessary to rectify the air in the vicinity of the tip portion of the flat plate member 3, and the baffle plate 9 that is close to the flat plate member 3 and faces the entire coating width is provided on the upstream side of the flat plate member 3.

FIG. 2 is a schematic view showing mist adhesion and air flow after long-time application in the air knife coating apparatus of the present invention. The distance a between the baffle plate 9 and the flat plate member 3 shown in FIG. 2, the distance b between the flat plate member 3 and the air knife head 1, the distance c between the baffle plate 9 and the backup roll 2, and the web before contacting the backup roll 2 The distance d between 6 and the mist removal box 4 is determined by the amount of mist, the amount of air knife 1 blown out, and the amount of suction of the mist removal box 4. In the air knife applicator of the present invention, the a, b, c and d are attached so as to satisfy the following expressions 1 and 2 at the same time.
Formula 1) (a + b)> c ≧ d where a> b Formula 2) (a + b) / (a + b + d) <0.7
The distances a, b, c, and d represent the distances at the closest part between the respective members.

  The baffle plate 9 is disposed at a position facing the upstream side of the flat plate member 3 so that a gap having a distance a is formed between the baffle plate 9 and the flat plate member 3. As shown in FIG. 3, air is introduced from the outside into the gaps having the distances a, b, and d by sucking the mist removal box 4 from the mist removal port 4 a to make it negative pressure, and the air knife head It is thought that mist is prevented from adhering to the tip of 1. At this time, the distance c between the baffle plate 9 and the backup roll 2 is made smaller than the sum of the distance a between the baffle plate 9 and the flat plate member 3 and the distance b between the flat plate member 3 and the air knife head 1. By increasing the wind speed of air and forming rectification sufficiently inside the mist removal box 4, the retention of air near the flat plate member 3 is reduced, and the floating mist adheres to the tips of the air knife head 1 and the flat plate member 3. Can be improved. The total of the distance a between the baffle plate 9 and the flat plate member 3 on the downstream side and the distance b between the flat plate member 3 and the air knife head 1 with respect to the distances (a + b + d) of all the gaps through which air flows from the outside. When the ratio of (a + b) is large, the wind speed of the air flowing into the mist removal box 4 is so weak that rectification cannot be formed sufficiently inside. By making the said ratio smaller than 0.7, it can improve that floating mist adheres to the front-end | tip of the air knife head 1 and the flat member 3. Further, the distance e between the tip of the mist removal box top plate 8 and the web 6 (the distance from the tip of the mist removal box top plate 8 to the web 6 on the extended line from the tip) is the distance between the baffle plate 9 and the backup roll 2. It is preferable to make it wider than c, and thereby, it is possible to prevent liquid pooling and splashing on the mist removal box top plate 8 caused by the natural fall of the liquid coating liquid due to its own weight.

  The distance a between the baffle plate 9 and the flat plate member 3 is preferably 10 to 40 mm, more preferably 15 to 25 mm. The distance b between the flat plate member 3 and the air knife head 1 is preferably 10 mm or less, and more preferably 3 to 8 mm. The distance c between the baffle plate 9 and the backup roll 2 is preferably 10 to 25 mm, more preferably 10 to 20 mm. Furthermore, the distance d between the web 6 and the mist removal box 4 before contacting the backup roll 2 is preferably 50 mm or less, more preferably 10 to 20 mm.

  Examples are given below to clarify the effects of the present invention. However, the present invention is not limited to the examples described below.

  The air knife applicator used in this experiment is the air knife applicator shown in FIG. 1, and a flat plate member 3 made of stainless steel having a thickness of 5 mm was attached so that the distance b from the air knife head 1 was 5 mm. The baffle plate 9 is installed at a distance a between the baffle plate 9 and the plate-like member 3 of 20 mm, a distance c between the baffle plate 9 and the backup roll 2 of 15 mm, the web 6 before contacting the backup roll 2 and the mist removal box 4. The distance d between them was 15 mm, the distance e between the mist removal box top plate and the web was 20 mm, the baffle plate 9 was 5 mm thick, and the material was made of Teflon (registered trademark). As a comparative air knife coating device, the same b · c · d as in the above example and a = 40 mm (Comparative 1), and the same as a · b · c in the above example and d = 30 mm (Comparison) 2) The same a, b, and d as in the above example and c of 25 mm (Comparative 3), and the flat member 3 attached and the baffle plate not attached (Comparative 4) were used.

The web is a PET film with a thickness of 100 μm, and a coating liquid (colored by adding a blue dye) made of 1% by weight of polyvinyl alcohol is applied, and the coating amount is 20 ml / m ² after being blown off with an air knife. The air pressure of the air flow blown out from the air knife head 3 was adjusted. The coating speed was changed to 100 and 150 m / min.

  For confirmation of the effect, the state of generation of the streaks after 2 hours and 12 hours from the start of application was examined visually.

  From the above results, in the air knife coating apparatus according to the present invention, no streak occurred at the coating speeds of 100 and 150 m / min even after long-time coating. However, in the conventional air knife applicator without the baffle plate (Comparative 4), even after the application speed of 100 m / min, the streaks are generated after the application for a long time, and the air knife applicator that does not satisfy the relationship of the distances a to d of the present invention ( In comparisons 1-3), streaks were generated during long-time application at an application speed of 150 m / min where the amount of floating mist increased. In comparison 1, the amount of air flowing in is large, but the wind speed is weak because the opening is large. In comparison 2, the amount of air entrained from the upstream side is large, and air rectification cannot be formed to the inside of the mist removal box 4, and in comparison 3, It is presumed that the wind speed inside the device was insufficient, leading to an increase in floating mist.

  Moreover, the thickness, material, shape, and the like of the illustrated flat plate member 3 and the baffle plate 9 are merely examples, and are not limited to these conditions, and can be appropriately changed in design. The web in the present invention includes paper, plastic film, resin-coated paper, synthetic paper and the like.

1 Air knife head 2 Backup roll
DESCRIPTION OF SYMBOLS 3 Flat member 4 Mist removal box 4a Mist removal port 4b Excess liquid collection port 5 Coating liquid supply apparatus 6 Web 7 Air blocker 8 Mist removal box top plate 9 Baffle plate 10 Coating roll 11 Guide roll 12 Cover 13 Mist adhesion accumulation a Distance b between baffle plate and flat plate member b Distance between flat plate member and air knife head c Distance between baffle plate and backup roll d Distance between web before contacting backup roll and mist removal box e Mist removal box top plate Web distance

Claims (1)

Air knife coating that determines the coating amount by supplying the coating liquid to a continuously running web with a coating liquid supply device, coating it with a predetermined coating width, and then scraping off the excess coating liquid with a gas flow blown from the air knife head. In the apparatus, the coating apparatus has an air knife head and a backup roll facing the air knife head, and further, on the upstream side of the air knife head, a flat plate member facing the air knife head and facing the entire coating width, A baffle plate facing the flat plate member and facing the entire coating width, and a mist removing box for collecting mist generated when the coating liquid is scraped off by an air knife head is provided at least in this order. , Distance a between baffle plate and flat plate member, distance b between flat plate member and air knife head, baffle plate and back The distance c between Ppuroru, and the distance d between the web before the mist removal box in contact with the backup roll, but air knife coating apparatus in a relationship satisfying the following formula 1, 2 at the same time.
Formula 1) (a + b)> c ≧ d However, Formula 2 where a> b: (a + b) / (a + b + d) <0.7