JP6651920B2 - Method for producing coated web - Google Patents

Description

  The present invention relates to a method for producing a coated web in which a coating liquid is applied to both sides of a film, nonwoven fabric, paper, or the like.

  The method of applying a coating film on both sides of the web is roughly classified into a sequential coating method and a simultaneous coating method.However, the sequential coating method of applying a coating film to one side of the web has a long tact time and poor production efficiency. Is a simultaneous application method becoming mainstream.

  It is known that the simultaneous coating method performs coating by disposing a coating head such as a roll, a knife, or a slit die on both sides of the web, and which coating head is selected depends on the properties of the coating liquid to be coated. The thickness is selected in consideration of desired thickness accuracy of the coating film, cost, and the like.

  As such a coating head, Patent Literature 1 discloses a metering method in which a web is passed horizontally through a liquid storage portion that stores a coating liquid called a dope bath, and is horizontally opposed to a web surface in a direction perpendicular to the web surface with the web interposed therebetween. A coating head that forms a coating film by passing through a measuring section called a smoothing jig is disclosed. Patent Document 1 also discloses a coating head that forms a coating film by passing between two dies facing each other across a web with a predetermined clearance.

  Patent Document 2 discloses an application head in which a portion including a liquid storage unit and a measurement unit and a slit die in Patent Document 1 are combined in order to simultaneously apply two types of coating materials to both surfaces. I have. In the application by the application head, application to the lower layer in contact with the base material is performed by a portion where the liquid storage portion and the measuring portion are connected with a gentle inclination, and application to the upper layer (surface layer) is performed by a portion such as a slit die. .

JP 2011-12266 A European Patent No. 1270133

  In a coating head in which a coating film is simultaneously formed on both surfaces of a web by passing through a liquid storage portion and a measuring portion in Patent Documents 1 and 2, a coating liquid near the web in the liquid storage portion is drawn into the web, and thus the web is formed. The liquid level of the nearby coating liquid drops. When the lowered liquid level reaches the measuring section, a coating defect such as a thin coating film or no coating is caused. As the transport speed of the web at the time of application is increased or the amount measured by the measuring section is increased, that is, as the amount applied is increased, the amount of the coating liquid per unit time drawn into the web increases. Is lower. The lower the liquid level in the vicinity of the web, the more easily the coating defects described above and the web breakage due to the contact between the web and the measuring section due to the non-application.

  In order to suppress coating defects due to a decrease in the liquid level in the vicinity of the web, generally, a position where the liquid level of the coating liquid is managed in the liquid storage section is set higher. However, if the liquid level of the liquid storage section is set too high, the amount of the coating liquid in the coating head increases, and the amount of the coating liquid to be discarded when the coating is completed increases, resulting in a large loss of the coating liquid. Further, when the amount of the coating liquid in the liquid storage section increases, the residence time in the liquid storage section until the coating liquid is applied is also increased, so that depending on the coating liquid, the composition may change or the material may be deteriorated. . In addition, since the total amount of the coating head including the coating liquid also increases due to the increase in the coating liquid amount in the liquid storage section, it is necessary to change the coating head to a structure having high rigidity so as to withstand such a problem. It is necessary to make the mounting portion of the head robust enough to withstand an increase in weight, which leads to an increase in cost.

  As a countermeasure, it is conceivable to reduce the length in the width direction of the liquid storage section orthogonal to the web surface in order to suppress the amount of the coating liquid. However, if the width of the liquid storage section is made too narrow, the amount of coating liquid in the liquid storage section becomes small. When the consumption amount of the coating liquid increases, the liquid level of the coating liquid in the vicinity of the web is easily reduced by being drawn into the web. In such a case, the liquid level reaches the measuring section, and coating defects such as a reduced coating film thickness or no coating are likely to occur. In addition, when foreign matter is mixed in the measuring unit, or because the joint between the base materials passes through the measuring unit, the interval between the measuring units that are installed horizontally facing each other with the web temporarily Even when it is necessary to open, if the width of the liquid storage part of the coating head is narrow and the amount of coating liquid in the liquid storage part is small, the liquid level drops rapidly, leading to coating defects and web breakage.

  As described above, in the method for producing a coated web in which a coating film is simultaneously formed on both sides of the web by passing through the liquid storage section and the measuring section, the application amount per unit time is increased by increasing the transport speed of the web or the like. Even when the number is increased, a method for performing stable application has not been found.

  Therefore, an object of the present invention is to provide a method for producing a web in which a coating film is applied simultaneously and accurately on both surfaces of the web at high speed.

  In order to achieve the above object, a method for producing a coated web of the present invention includes a coating head having a measuring section provided at a predetermined interval and a liquid storage section for storing a coating liquid above the measuring section. Using a coating device provided, the web conveyed from the upper side in the vertical direction to the lower side is passed through the liquid storage section and the measuring section of the coating head, by a method of simultaneously applying a coating liquid to both sides of the web. When the coating liquid stored in the liquid storage section is drawn downward toward the measuring section by the web being conveyed, from the upper end of the liquid surface of the coating liquid to the lower end of the portion where the coating liquid is drawn in The length h1 and the length W in the direction orthogonal to the surface of the web to be transported of the liquid storage section are set to satisfy W> 2 × h1.

  In the method for producing a coated web according to the present invention, the h1 and the liquid level height h2 from the upper end of the liquid level of the coating liquid to the lower limit of the liquid storage section satisfy h2> h1. Is preferred.

  According to the present invention, in the production of a coated web in which a coating film is simultaneously formed on both sides of the web by passing through a coating head having a liquid storage section and a measuring section, a coating liquid near the web in the liquid storage section is used. Even if the liquid level of the coating liquid is lowered by being drawn into, the liquid level does not reach the measuring section, and also the web is not broken, and a coating film of a desired thickness is stably formed on both sides. It is possible to produce a precisely attached web.

FIG. 1 is a schematic view showing a coating apparatus for producing a coated web. Schematic sectional view of a coating head used in a coating apparatus for producing a coated web

  Preferred embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a schematic view showing a coating apparatus for producing a coated web, and FIG. 2 is a schematic sectional view of a coating head used in the coating apparatus. First, a coating apparatus used in the method for producing a coated web according to the present invention will be described using these.

  The coating apparatus 1 shown in FIG. 1 equipped with the coating head 10 shown in FIG. 2 is a coating apparatus that applies the coating liquid 40 to both surfaces of the web 2 to produce the coated web 20. The configuration of the coating apparatus 1 includes a coating head 10, a liquid level detecting unit 3 for detecting a liquid level of a coating liquid 40 in the coating head 10, a coating liquid tank 4 for storing a coating liquid to be supplied to the coating head 10, A pipe 5 connecting the coating liquid tank 4 and the coating head 10, a liquid feeding pump 6 provided in the middle of the pipe 5 to feed the coating liquid to the coating head 10, and a signal received from the liquid level detecting means 3 and sent. The control unit 7 instructs the operation and stop of the liquid pump 6.

  The coating head 10 shown in FIG. 2 has a measuring unit 11 provided at an interval t in a direction orthogonal to the surface of the web 2 and a liquid storage unit 12 provided above the measuring unit 11. The coating head 10 has members 15 and 15 ′ having a length equal to or greater than the width of the web 2 in the width direction of the web 2 and arranged to face each other across the web 2, and a web of the members 15 and 15 ′. Is formed of a horizontal plate (not shown) provided so as not to overflow the coating liquid 40 at an end portion in the width direction of. The interval t in the measuring section 11 can be freely changed by moving the members 15 and 15 'in a direction orthogonal to the surface of the web 2 by, for example, a stage mechanism including a drive source and a guide rail.

  Here, a method of supplying the coating liquid to the coating head 10 will be described. Note that the liquid level height from the upper end of the liquid level of the coating liquid 40 in the coating head 10 to the lower limit of the liquid storage unit 12 is h2.

  The supply of the coating liquid to the coating head 10 is performed by assuming that the liquid level height h2 has dropped to a predetermined lower limit (not shown, the same applies hereinafter) of the liquid storage unit 12 of the coating head 10. When the detecting means 3 detects, the control unit 7 operates the liquid supply pump 6 provided in the middle of the pipe 5 leading from the coating liquid tank 4 to the coating head 10. On the other hand, when the supply of the coating liquid 40 is stopped, the supply of the coating liquid to the coating head 10 causes the liquid level height h2 of the liquid storage unit 12 to reach a preset liquid level upper limit (not shown, the same applies hereinafter). When the liquid level detecting means 3 detects that the liquid has risen, the operation is performed by stopping the liquid sending pump 6 via the control unit 7.

  The supply of the coating liquid is not limited here, for example, using a pressurized coating liquid tank, a pipe connecting the coating liquid tank and the coating head, and a liquid feed valve provided in the middle of the pipe, The supply and stop of the coating liquid may be performed by opening and closing the liquid sending valve in response to the result of the liquid level detected by the liquid level detecting means.

  Next, the production of a coated web performed by applying the coating liquid 40 to the web 2 using the coating apparatus 1 shown in FIG. 1 having the coating head 10 shown in FIG. 2 will be described.

  First, before application, the web 2 is passed between the members 15 and 15 ′ of the application head 10 facing each other so that the web 2 passes from the liquid storage unit 12 to the measurement unit 11. Then, the members 15 and 15 ′ of the coating head 10 are moved in a direction perpendicular to the surface of the web 2 to set the interval t of the measuring unit 11 to a desired interval. The liquid is sent to and stored in the liquid storage unit 12 of the coating head 10. At this time, the liquid level height h2 from the upper end of the liquid level of the coating liquid 40 in the coating head 10 to the lower limit of the liquid storage unit 12 is a preset upper limit value of the liquid level. Then, by transporting the web 2 downward from vertically above the coating head 10, the web 2 is passed from the liquid reservoir 12 of the coating head 10 through the measuring unit 11, and the coating liquid 40 is applied to both surfaces of the web 2. The coated web 20 is produced by coating. At this time, the amount of the coating liquid applied to the coated web 20 is determined not only by the transport speed but only by the interval t of the measuring unit 11.

  Then, if the application is continued, the coating liquid 40 is continuously applied to the web 2 to produce the coated web 20. Therefore, the coating liquid 40 in the liquid storage section 12 gradually decreases and is set in advance. The liquid level height h2 decreases to the set liquid level lower limit. Then, the liquid level detecting means 3 detects this, and the liquid sending pump 6 provided in the middle of the pipe 5 leading from the coating liquid tank 4 to the coating head 10 is operated, and the coating liquid is stored in the liquid storage section 12. Supply. Then, when the liquid level detecting means 3 detects a preset liquid level upper limit of the liquid level height h2 of the liquid storage section 12, the liquid supply pump 6 is stopped to stop the supply of the coating liquid. Thereafter, as long as the application is continued, the supply of the coating liquid is detected when the liquid level lower limit is detected, and the supply of the coating liquid is stopped when the liquid level upper limit is detected.

  Here, the liquid level detecting means 3 may be any means, but does not hinder the transport of the web 2 or the flow of the coating liquid 40 in the coating head 10 and also suppresses the entry of foreign matter into the coating liquid 40. For this reason, a means for detecting the liquid level without contact is preferable.

  Next, with reference to FIG. 2, aspects of the measuring unit 11 and the liquid storage unit 12 of the coating head 10 when the coated web 20 is manufactured will be described in more detail.

  During the production of the coated web 20, the web 2 is first conveyed downward from vertically above the application head 10 and enters the liquid reservoir 12 of the application head 10. At this time, the liquid level of the coating liquid 40 in the liquid storage unit 12 is drawn into the web 2 conveyed vertically downward, and decreases as the distance from the web 2 to the web approaches the web. Draw an arc toward Web 2. The shape of the arc varies depending on the viscosity of the coating liquid 40, the transport speed of the web 2 to be transported, and the length of the liquid storage section 12 in a direction orthogonal to the web 2 surface.

  Here, the distance from the upper surface of the coating liquid 40 of the liquid storage unit 12 during coating to the lower end drawn into the web is h1, and the length of the liquid storage unit 12 in the direction orthogonal to the surface of the web 2 to be conveyed is h1. When W is set, W and h1 satisfy the relationship of W> 2 × h1.

  The shape of the liquid surface drawn by drawing the coating liquid 40 by the web 2 has an arc shape similar to a part of the circumference. Therefore, the liquid surface in a range within a distance h1 from the web 2 is inclined in a direction parallel to the direction perpendicular to the surface of the web 2 as approaching the web 2, and this indicates that the coating liquid 40 It means that you are drawn into. The distance between the web 2 and the member 15 or the distance between the web 2 and the member 15 ′, that is, half of the length W of the liquid storage portion 12 in the direction orthogonal to the web 2 surface is smaller than h1. The liquid surface of the coating liquid 40 is all inclined toward the web 2. This is because the coating liquid 40 is not sufficiently secured to be measured by the measuring unit 11, so that the drawing of the coating liquid 40 becomes strong. Indicates that it may be If the measuring unit 11 cannot perform proper measurement, the coating film thickness in the web 2 in the coating direction is not stable, and there is a possibility of causing coating defects such as a thin coating film or no coating film. In order to obtain a stable coating film, the relationship of W> 2 × h1 is satisfied.

  Next, assuming that the liquid level height from the liquid level upper end of the coating liquid 40 to the lower limit of the liquid storage unit 12 is h2, it is preferable that h2> h1 is satisfied.

  When the withdrawal height h1 exceeds h2, it means that the lower end of the liquid surface has reached the measuring unit 11, and the amount of the coating liquid 40 in the measuring unit 11 changes, so that the coating liquid to be applied is changed. It is preferable that h2> h1 is satisfied because the amount of the coating decreases and the applied coating liquid 40 breaks the film on the web 2.

  As described above, by using the method for manufacturing a coated web according to the present invention, a coated web having a uniform film thickness can be manufactured accurately.

  The present invention is applicable to, but not limited to, a method for producing a web such as paper, a metal thin film, a film, and a cloth having a coating film on both surfaces simultaneously.

REFERENCE SIGNS LIST 1 coating device 2 web 3 liquid level detecting means 4 coating liquid tank 5 pipe 6 liquid feed pump 7 control unit 10 coating head 11 measuring unit 12 liquid storage unit 15, 15 'member 20 coated web 40 coating liquid h1 coating liquid The length from the upper end of the liquid surface to the lower end of the portion where the coating liquid is drawn in. H2 The liquid surface height from the upper end of the liquid surface of the coating liquid to the lower limit of the liquid storage portion. Length t Interval of the weighing unit 11 in the direction perpendicular to the web surface

Claims (2)

Using a coating apparatus having a coating head having a measuring section provided at a predetermined interval and a liquid storage section for storing a coating liquid above the measuring section, the liquid is conveyed from the upper side in the vertical direction to the lower side. A method for producing a coated web in which a web is passed through the liquid storage section and the measuring section of the coating head to simultaneously apply a coating liquid to both sides of the web,
The length from the upper end of the liquid surface of the coating liquid to the lower end of the portion where the coating liquid is drawn when the coating liquid stored in the liquid storage section is drawn downward toward the measuring section by the web being conveyed. A method for producing a coated web, wherein h1 and a length W in a direction perpendicular to a web surface of the liquid storage section to be conveyed satisfy W> 2 × h1.   The method for producing a coated web according to claim 1, wherein h1 and a liquid level height h2 from a liquid level upper end of the coating liquid to a lower limit of the liquid storage section satisfy h2> h1.

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