Multilayer film manufacturing method and manufacturing device

Abstract

To provide a manufacturing method and manufacturing apparatus of a multilayer film which can impregnate a porous body with coating liquid while accurately forming a coating film on both surfaces of the porous body with any physical property.SOLUTION: A manufacturing method of a multilayer film comprises the steps of: forming a first coating film by applying the first coating liquid to one surface of a sheet-like support body that is continuously conveyed; laminating a sheet-like porous body on the first coating film in such a state that the first coating film is undried; forming a second coating film by applying the second coating liquid to a surface on a side that is not in contact with the first coating film of the porous body in such a state that the first coating film is undried, discharging the second coating liquid from a die having a discharge surface formed with a slit-like discharge port, applying the second coating liquid while curving or bending the support body 1 and a porous body 3 by pressing the discharge surface against the porous body via the second coating liquid and impregnating the porous body with at least one of the first coating film and the second coating film; and simultaneously drying the first and second coating films.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for producing a multilayer film in which coating films are formed on both sides of a porous body, and more particularly to a method and apparatus for producing a multilayer film that can efficiently impregnate a porous body with a coating liquid, regardless of the physical properties of the porous body. [Background technology]

[0002] Multilayer films formed by forming coating films on both sides of sheet-like porous materials such as nonwoven fabrics, cloth, fibers, mesh, paper, and sponges are used in a variety of fields, including fiber-reinforced plastics (prepregs), release papers, airbags, battery separators, electrodes, etc. In these applications, it is necessary to apply a coating liquid to both sides of the porous material with high precision and to impregnate the porous material with the coating liquid.

[0003] As a method for impregnating a porous body with a coating liquid while forming coating films on both sides of the porous body, for example, Patent Document 1 discloses a method in which a coating die is pressed against both sides of the porous body while the porous body is being conveyed. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-36761 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the method disclosed in Patent Document 1, the porous body is conveyed alone while being pressed against a coating die for coating, so high tension must be applied to the porous body. This poses a problem of stretching, wrinkling, and breakage occurring in porous bodies with low strength, such as thin porous bodies or porous bodies with high porosity.

[0006] Therefore, the present invention provides a method and apparatus for manufacturing a multilayer film that can accurately form coating films on both sides of a porous body, regardless of the physical properties of the porous body, while impregnating the porous body with a coating liquid. [Means for solving the problem]

[0007] The method for producing a multilayer film of the present invention that solves the above problems comprises: a step of applying a first coating liquid to one surface of a sheet-like support that is continuously conveyed to form a first coating film; Next, a step of laminating a sheet-like porous body on the first coating film while the first coating film is still wet; Next, a step of applying a second coating liquid to the surface of the porous body that is not in contact with the first coating film while the first coating film is still wet, thereby forming a second coating film, in which the second coating liquid is discharged from a die having a discharge surface with a slit-shaped discharge opening formed therein, and the discharge surface is pressed against the porous body via the second coating liquid, thereby curving or bending the support and the porous body while applying the second coating liquid, and impregnating the porous body with at least one of the first coating film and the second coating film; Then, the method includes a step of simultaneously drying the first and second coating films.

[0008] The multilayer film manufacturing apparatus of the present invention, which solves the above problems, a support conveying device that continuously conveys a sheet-like support; the above support a first coating device that coats one surface of the support, which is continuously transported by a transport device, with a first coating liquid to form a first coating film; a porous body supplying device that continuously supplies a sheet-like porous body so that the porous body is laminated on the first coating film downstream of the first coating device in the conveying direction; a second coating device that applies a second coating liquid to a surface of the porous body that is not in contact with the first coating film, downstream in the conveyance direction from a position where the porous body is stacked, to form a second coating film; a drying device located downstream of the second coating device in the conveyance direction and configured to simultaneously dry the first and second coating films; the second coating device is a die having a discharge surface on which a slit-shaped discharge port is formed, There is no support for the support from the opposite side of the ejection surface across the support, and the second coating liquid is applied while the ejection surface is pressed against the porous body. [Effects of the Invention]

[0009] According to the multilayer film manufacturing method and manufacturing apparatus of the present invention, by transporting the porous body while adhering the tensioned support and the porous body via the first coating film, the porous body can be transported without being subjected to high tension, preventing stretching, wrinkling, or breakage. Furthermore, by forming the second coating film while pressing the discharge surface of the die against the porous body, the effect of forcing the coating liquid into the porous body is obtained, allowing the porous body to be efficiently impregnated with the coating liquid. As a result, regardless of the physical properties of the porous body and coating liquid, the porous body can be impregnated with the coating liquid while accurately forming coating films on both sides, greatly improving the productivity of multilayer films. [Brief explanation of the drawings]

[0010] [Figure 1] 1A to 1C are schematic diagrams illustrating a method for manufacturing a multilayer film according to one embodiment of the present invention. [Figure 2] 2 is a detailed cross-sectional view showing an enlarged view of a tip A of the die 4 of the embodiment of FIG. 1. FIG. [Figure 3] 5A to 5C are schematic cross-sectional views showing a method for manufacturing a multilayer film according to another embodiment of the present invention. [Figure 4] 5A to 5C are schematic diagrams illustrating a method for manufacturing a multilayer film according to another embodiment of the present invention. [Figure 5] 5A to 5C are schematic cross-sectional views showing a method for manufacturing a multilayer film according to another embodiment of the present invention. [Figure 6] 7 is a diagram showing an example of the observation field of view of the camera 8 in the embodiment of FIG. 6. FIG. [Figure 7] FIG. 10 is a perspective view showing the inclination of a die 4 with the conveying direction of the support as the rotation axis. DETAILED DESCRIPTION OF THE INVENTION

[0011] Preferred embodiments of the present invention will be described below. Note that the following description is merely an example of an embodiment of the present invention, and the present invention should not be construed as being limited thereto. Various modifications are possible within the scope of the objects and effects of the present invention.

[0012] Figure 1 is a schematic diagram showing a method for producing a multilayer film according to one embodiment of the present invention. In this method, a first coating liquid is dispensed from a first coating device 2 onto one side of a support 1, which is transported by a support transport device consisting of a support unwinding device 11, a winding device 61, and multiple transport rollers, to form a first coating film (not shown). Next, while the first coating film is still wet (unsolidified), a sheet-like porous body 3, continuously supplied from a porous body supplying device 31, is laminated on top of the first coating film. Next, while the first coating film is still wet, a second coating liquid is dispensed from a second coating device, a die 4, onto the side of the porous body 3 that is not in contact with the first coating film (the upper surface in Figure 1), to form a second coating film. At this time, the second coating liquid is discharged from the die 4 having a slit-shaped discharge opening at its tip, without supporting the support 1 from the opposite side of the die 4, and the discharge surface of the die 4 is pressed against the porous body 3 via the second coating liquid, thereby forming a second coating film while curving or bending the support 1 and the porous body 3, thereby impregnating the porous body 3 with the first coating film or both the first and second coating films. Finally, the first and second coating films are simultaneously dried (or solidified) in the drying device 5 to form a multilayer film 6, which is then wound up by the winding section 61.

[0013] In the method for producing a multilayer film according to this embodiment, the porous body 3 is adhered via the first coating film to the support 1, which is conveyed by the support conveying device while tension is applied thereto, so that the porous body 3 can be conveyed without applying high tension. In this case, only the minimum tension required for conveying the porous body 3 from the porous body supplying device 31 to the laminating roller 32 needs to be applied. As a result, even porous bodies that are prone to wrinkling, stretching, or breaking, specifically porous bodies that are thin, have a high porosity, or have low material strength, can be conveyed stably without wrinkling, stretching, or breaking.

[0014] Next, the effect of the die 4 will be described. FIG. 2 is a detailed cross-sectional view, enlarged, of the tip portion A of the die 4 of the embodiment shown in FIG. 1. A first coating film 101 and a porous body 3 are laminated on the support 1, and a slit-shaped discharge port 41 is opened at the tip of the die 4. The second coating fluid discharged from the discharge port 41 is applied to the surface of the porous body 3, forming a coating fluid pool 7 between the tip of the die 4 and the porous body 3, to form a second coating film 102. At this time, the tip of the die 4 is pressed against the porous body 3, the first coating film 101, and the support 1 via the coating fluid pool 7, generating high pressure in the coating fluid pool 7. This pressure causes the second coating film 102 to impregnate the porous body 3, and causes the first coating film 101 to impregnate the porous body 3 pressed against the coating fluid pool 7, thereby efficiently impregnating the porous body 3 with the coating fluid. In particular, even when the porous body 3 is difficult to naturally impregnate into the first coating film 101 due to capillary force, gravity, or the like, specifically when the viscosity of the coating liquid is high, the affinity between the coating liquid and the porous body is low, or the impregnation time is short, the coating liquid can be efficiently impregnated into the porous body 3. As a result, a laminate of the support 1, the first coating film 101, the porous body 103 sufficiently impregnated with the coating liquid, and the second coating film 102 can be obtained.

[0015] Furthermore, since the support 1 is not supported from the opposite side of the die 4, the force applied by the die 4 causes the support 1 and the porous body 3 to bend, or if the pressure is even greater, they become bent to an extent that can be called bending.

[0016] Furthermore, even if a support roller or the like is provided at a position opposite the die 4 across the support 1 and the tip of the die 4 is brought close to the support 1 without curving or bending the support 1, high pressure is generated in the coating liquid reservoir 7, and the coating liquid can be impregnated into the porous body 3. However, if the support roller is eccentric, the eccentricity will cause fluctuations in the gap between the tip of the die 4 and the porous body 3, resulting in fluctuations in the pressure in the coating liquid reservoir 7 and not only making the impregnation of the porous body 3 unstable, but also, in some cases, causing the tip of the die 4 to come into contact with the porous body 3, resulting in wrinkles, stretching, or breakage of the porous body 3. Alternatively, if the support 1 has thickness unevenness, this thickness unevenness will directly lead to fluctuations in the gap between the tip of the die 4 and the porous body 3, causing similar problems. Therefore, it is preferable not to provide a support roller at a position opposite the die 4 across the support 1. When support rollers or the like are provided to stabilize the transport of the support 1, they are preferably provided upstream or downstream of the die 4, avoiding a position facing the die 4 across the support 1.

[0017] The material and shape of the support 1 are not particularly limited, and may be any material that can support and transport the porous body 3, such as a resin film such as a PET film, or a metal foil.

[0018] The material and shape of the porous body 3 are not particularly limited, and nonwoven fabric, cloth, fiber, mesh, paper, sponge, etc. can be used.

[0019] The type of coating liquid is not particularly limited, and may be a solution in which a polymer is dissolved in a solvent, a thermosetting or photocurable liquid polymer, a slurry, an emulsion, or the like. The first and second coating liquids may be the same or different. If the first and second coating liquids are different, and the second coating liquid more easily penetrates the porous body, and the force pressing the discharge surface of the die 4 against the porous body 3 is weak, resulting in little curvature or bending of the support 1 and the porous body 3, the first coating liquid may not penetrate the porous body, and only the second coating liquid may penetrate the porous body.

[0020] The coating method of the coating unit 2 is not particularly limited, and various coating methods can be selected, such as a die, spray, bar, blade, knife, comma, dip, etc. The material of the die 4 is also not particularly limited, and metals such as stainless steel, ceramics, resins, etc. can be used.

[0021] In this embodiment, the drying device 5 is used as an example of a method for solidifying the coating film, but the present invention is not limited to this and any method that can solidify the coating film may be used. For example, if the coating liquid is a photocurable liquid polymer, an exposure device may be used instead of the drying device 5.

[0022] 3 is a schematic cross-sectional view showing a method for producing a multilayer film according to another embodiment of the present invention, and is an enlarged view of a tip portion A of a die corresponding to the die 4 in FIG. 1. The support 1, the first coating film 101, and the porous body 3 are transported in the X direction in FIG. 3. Unless otherwise specified, the transport direction hereinafter refers to the transport direction X of the support 1. In the embodiment of FIG. 3, of the discharge surface of the die 4, a portion 42 upstream of the discharge port 41 in the transport direction is recessed in a direction away from the porous body 3 relative to a portion 43 downstream of the transport direction.

[0023] In this embodiment, the corner B of the portion 42 of the discharge surface of the die 4 on the upstream side in the conveying direction is unlikely to come into contact with the porous body 3 without going through the coating liquid reservoir 7, thereby preventing scratches, wrinkles, and breaks from occurring in the porous body 3 during the formation of the second coating film 102, and improving the quality of the multilayer film 6.

[0024] In this case, the size of the step H between the portion 42 on the upstream side in the conveying direction and the portion 43 on the downstream side in the conveying direction is not particularly limited, and may be determined depending on the state of the porous body 3 and the state of formation of the second coating film 102. The larger the step H between the portion 42 on the upstream side in the conveying direction and the portion 43 on the downstream side in the conveying direction, the less likely the portion 42 on the upstream side in the conveying direction is to come into contact with the porous body 3. However, if the step H is too large, the coating liquid reservoir 7 will overflow further upstream than the portion 42 on the upstream side in the conveying direction, making the thickness of the second coating film 102 unstable. Therefore, it is preferable not to make the step H too large.

[0025] FIG. 4 is a schematic diagram showing a method for producing a multilayer film according to another embodiment of the present invention, viewed from the Y direction, of a die corresponding to die 4 in FIG. 2 or 3. In the embodiment shown in FIG. 4, the support 1, first coating film 101, porous body 103, and second coating film 102 are transported toward the front of the page. A dashed line 44 within die 4 indicates the discharge flow path for the coating liquid, and the length of the discharge port (not shown) in the width direction of the support 1 is W, i.e., the coating width of the second coating film is W. Furthermore, of the discharge surface of die 4, a portion 43 downstream of the discharge port in the transport direction is recessed away from the porous body 103 at both side portions 43b outside the coating width W, relative to a portion 43a inside the coating width W.

[0026] In this embodiment, among the portion 43 downstream of the discharge surface of the die 4 in the conveying direction, the portion 43b where the second coating film 102 is not formed is less likely to come into contact with the porous body 103, thereby preventing scratches, wrinkles, and breaks from occurring in the porous body 3 during the formation of the second coating film 102, and improving the quality of the multilayer film 6.

[0027] In this case, the step between the portion 43a on the inside of the coating width W and the portion 43b on the outside of the coating width W in the portion 43 on the downstream side in the conveying direction is not particularly limited, and may be determined according to the state of the porous body 3. Similarly to the portion 43 on the downstream side in the conveying direction, it is also preferable that the portions on both sides outside the coating width W of the portion 42 on the upstream side in the conveying direction are recessed in a direction away from the porous body 3 more than the portion on the inside of the coating width W, from the viewpoint of preventing scratches, wrinkles, and breaks in the porous body.

[0028] Fig. 5 is a schematic cross-sectional view showing a method for manufacturing a multilayer film according to another embodiment of the present invention. In the embodiment shown in Fig. 5, the discharge surface is observed by a camera 8 from a position facing the discharge surface of the die 4 across the support 1. The depth to which the discharge surface of the die 4 is pressed against the porous body 3 in the Z direction in Fig. 5 is adjusted so that the second coating fluid pool 7 formed between the discharge surface and the porous body 3 completely covers the discharge orifice 41 within the field of observation. Specifically, if the second coating fluid pool 7 formed between the discharge surface and the porous body 3 does not completely cover the discharge orifice 41 within the field of observation, the discharge surface of the die 4 can be pressed deeper against the porous body 3.

[0029] FIG. 6 shows an example of the observation field of the camera 8 in this embodiment. FIG. 6(a) shows an example in which the second coating fluid puddle 7 formed between the discharge surface and the porous body 3 completely covers the discharge orifice 41 within the observation field. The dashed line 81 in FIG. 6 indicates the camera's observation field, the arrow range 41 on the discharge surface of the die 4 represents the discharge orifice, the arrow range 42 represents the upstream portion in the conveying direction, the arrow range 43 represents the downstream portion in the conveying direction, and the solid area represents the coating fluid puddle 7. For simplicity, the support, the first coating film 101, and the porous body 3 are omitted. The support is conveyed in the X direction in FIG. 6. In the example of FIG. 6(a), the coating fluid puddle 7 completely covers the discharge orifice 41 of the die 4, and the interface 71 on the upstream side of the coating fluid puddle 7 in the conveying direction is located upstream of the discharge orifice 41 in the conveying direction. Next, FIG. 6(b) shows an example in which the second coating fluid puddle 7 formed between the discharge surface and the porous body 3 does not completely cover the discharge orifice 41 within the observation field. A part of the interface 71 on the upstream side in the transport direction of the coating liquid reservoir 7 overlaps with the discharge port 41 .

[0030] When the observation field 81 is in the state shown in FIG. 6( b), air bubbles enter the discharge port 41 of the die 4 from the interface 71 on the upstream side of the coating fluid reservoir 7 in the transport direction, causing air bubbles and coating streaks in the second coating film 102. When the observation field 81 is in the state shown in FIG. 6( b), the discharge surface of the die 4 can be pressed deeply against the porous body 3 until the state shown in FIG. 6( a) is reached, thereby eliminating air bubbles and coating streaks in the second coating film 102 and improving the quality of the multilayer film. Furthermore, even when the observation field 81 is in the state shown in FIG. 6( a), when the interface 71 on the upstream side of the coating fluid reservoir 7 in the transport direction is close to the discharge port 41, pressing the discharge surface of the die 4 deeply against the porous body 3 can move the interface 71 on the upstream side of the coating fluid reservoir 7 in the transport direction away from the discharge port 41, thereby preventing air bubbles and coating streaks in the second coating film 102, which is more preferable.

[0031] Furthermore, it is more preferable to install multiple cameras 8 in the coating width direction of the die 4 or to scan the camera 8 in the coating width direction of the die 4 to observe the entire coating width direction of the discharge surface of the die 4. Specifically, by adjusting the depth to which the discharge surface of the die 4 is pressed against the porous body 3 and the inclination of the die 4 around the support conveyance direction as the rotation axis so that the coating liquid reservoir 7 completely covers the discharge port 41 across the entire coating width direction, it is possible to prevent the occurrence of bubbles and coating streaks across the entire coating width direction of the second coating film 102. Here, the inclination of the die 4 around the support conveyance direction as the rotation axis refers to the rotation state of the die 4 in the direction of arrow R when the conveyance direction of the support 1 is defined as X in Figure 7. [Industrial Applicability]

[0032] The multilayer film manufacturing method and manufacturing apparatus of the present invention can be widely applied to a variety of uses, such as fiber-reinforced plastics (prepregs), release papers, airbags, battery separators, and electrodes. [Explanation of symbols]

[0033] 1 Support 2. First coating device 3 Porous materials 4 Die (second coating device) 5 Drying equipment 6 Multilayer film 7 Second coating fluid reservoir 8. Camera 11 Support unwinding device 31 Porous material supply device 32 Laminating roller 41 Discharge port 42 The portion of the die discharge surface upstream of the discharge port in the conveying direction 43, 43a, 43b: Portions of the die discharge surface downstream of the discharge port in the conveying direction 44 Die discharge channel 61 Winding device 71 Interface on the upstream side of the second coating fluid reservoir 81 Camera field of view 101 First Coating 102 Second Coating 103 Porous body impregnated with coating liquid A Die tip B Corner of the upstream side of the conveying direction H step R Die tilt direction (rotation direction) W: width of second coating X: Transport direction of the support Z Die pressing direction

Claims

1. a step of applying a first coating liquid to one surface of a sheet-like support that is continuously conveyed to form a first coating film; Next, a step of laminating a sheet-like porous body on the first coating film while the first coating film is still wet; Next, a step of applying a second coating liquid to a surface of the porous body that is not in contact with the first coating film while the first coating film is still wet, thereby forming a second coating film, in which the second coating liquid is discharged from a die having a discharge surface with a slit-shaped discharge opening formed therein, and the discharge surface is pressed against the porous body via the second coating liquid, thereby curving or bending the support and the porous body while applying the second coating liquid, and impregnating the porous body with at least one of the first coating film and the second coating film; then simultaneously drying the first and second coating films; and The die may include: a portion of the discharge surface downstream of the discharge port in the conveying direction is recessed in a direction away from the porous body at both end portions on the outer side of the discharge port in the coating width direction, compared to portions other than the both end portions; The length of the discharge port in the coating width direction is shorter than the length of the porous body in the coating width direction. Method for manufacturing multilayer films.

2. 2. The method for producing a multilayer film according to claim 1, wherein in the step of impregnating the porous body with at least one of the first coating film and the second coating film, the porous body is impregnated with the first coating film or both the first coating film and the second coating film.

3. 3. The method for manufacturing a multilayer film according to claim 1, wherein the die has a discharge surface that is recessed in a direction away from the porous body at a portion upstream of the discharge port in the transport direction compared to a portion downstream of the discharge port in the transport direction.

4. The ejection surface of the die is observed from a position facing the ejection surface of the die across the support, adjusting the depth to which the ejection surface is pressed against the porous body so that a pool of the second coating liquid formed between the ejection surface and the porous body completely covers the ejection orifice within an observation field; The method for producing a multilayer film according to any one of claims 1 to 3.

5. The entire discharge surface in the coating width direction is observed from a position facing the discharge surface of the die across the support, adjusting the depth to which the discharge surface is pressed against the porous body and the inclination of the die with the conveying direction of the support as the rotation axis so that the pool of the second coating liquid completely covers the entire discharge outlet in the coating width direction; The method for producing the multilayer film according to claim 4.

6. a support conveying device that continuously conveys a sheet-like support; a first coating device that coats one surface of the support that is continuously transported by the support transport device with a first coating liquid to form a first coating film; a porous body supplying device that continuously supplies a sheet-like porous body so that the porous body is laminated on the first coating film downstream of the first coating device in the conveying direction; a second coating device that applies a second coating liquid to a surface of the porous body that is not in contact with the first coating film, downstream in the conveyance direction from a position where the porous body is stacked, to form a second coating film; a drying device that dries the first and second coating films simultaneously, the drying device being located downstream in the conveyance direction from the second coating device; the second coating device is a die having a discharge surface on which a slit-shaped discharge port is formed, and does not have anything to support the support from the opposite side of the discharge surface across the support, and applies the second coating liquid while pressing the discharge surface against the porous body; The die is a portion of the discharge surface downstream of the discharge port in the conveying direction is recessed in a direction away from the porous body at both end portions on the outer side of the discharge port in the coating width direction, compared to portions other than the both end portions; the length of the discharge port in the coating width direction is shorter than the length of the porous body in the coating width direction; Multilayer film manufacturing equipment.

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