Nonwoven fabric manufacturing method

Abstract

To provide a production method and a production apparatus of nonwoven fabric, in each of which temperature drop of a spinning space is suppressed.SOLUTION: A production method of nonwoven fabric is provided, comprising a spinning step of delivering molten thermoplastic resin from a spinning nozzle to form fiber, and a step of sucking the fiber in a plurality of suction regions in arranged in a row from the upstream side in the machine flow direction, collecting the sucked fiber on a collecting surface and depositing the collected fiber along with migration of the collecting surface to the downstream side. The suction regions include upstream suction regions controlled in such a manner that the suction force for the fiber at the upstream suction region is smaller than that at the downstream side. A production apparatus for use in the production method is also provided.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for producing a nonwoven fabric. [Background technology]

[0002] Nonwoven fabrics are used in a variety of fields, and various techniques relating to their manufacturing methods have been proposed. For example, Patent Documents 1 to 3 describe manufacturing methods in which fibers spun using a spinning nozzle are sucked and collected to form a nonwoven fabric, which is then transported by a conveyor. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-154009 [Patent Document 2] Japanese Patent Application Laid-Open No. 2013-249566 [Patent Document 3] Japanese Patent Application Laid-Open No. 2013-204208 Summary of the Invention [Problem to be solved by the invention]

[0004] In the above-described method for producing a nonwoven fabric by spinning, fibers are generally collected by suctioning the collecting surface from the side opposite to the spinning side. However, as the fibers move downstream in the conveying direction, they are gradually collected and accumulated, and therefore the amount of outside air taken in by suction is greater on the upstream side than on the downstream side. Due to the difference in the amount of outside air taken in, the temperature on the upstream side becomes lower than on the downstream side, and the ability to draw the spun fibers due to suction on the upstream side decreases, which tends to result in an increase in fiber diameter.

[0005] In view of the above circumstances, the present invention relates to a method for producing a nonwoven fabric that suppresses a decrease in the temperature of a spinning space. [Means for solving the problem]

[0006] The present invention provides a method for producing a nonwoven fabric, comprising: a spinning step in which molten thermoplastic resin is discharged from a spinning nozzle to form fibers; and a step in which the fibers are sucked in a plurality of suction zones arranged from the upstream side in the machine flow direction and collected on a collection surface, and the fibers are deposited as they move downstream on the collection surface, wherein the plurality of suction zones include an upstream suction zone that controls the suction force on the fibers to be smaller than that on the downstream side.

[0007] The present invention also provides a nonwoven fabric manufacturing apparatus comprising: a spinning apparatus having a plurality of spinning nozzles that discharge molten thermoplastic resin; and a collecting device that sucks in fibers discharged from the plurality of spinning nozzles and collects them on a collecting surface, and deposits the fibers as the collecting surface moves downstream, wherein the plurality of spinning nozzles include a first spinning nozzle provided upstream and a second spinning nozzle provided downstream of the first spinning nozzle, and the collecting device has a plurality of suction regions including a first suction region corresponding to the first spinning nozzle and a second suction region corresponding to the second spinning nozzle, and has a suction force control mechanism that makes the suction force of the first suction region different from the suction force of the second suction region. [Effects of the Invention]

[0008] According to the method for producing a nonwoven fabric of the present invention, it is possible to suppress a decrease in the temperature of the spinning space. Furthermore, the method for producing a nonwoven fabric of the present invention can be suitably carried out by the apparatus for producing a nonwoven fabric of the present invention. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a schematic diagram showing a preferred example of the configuration of a manufacturing apparatus used in the method for manufacturing a nonwoven fabric of the present invention. [Figure 2] FIG. 2 is a plan view of the belt conveyor of one configuration example as viewed in the ID direction. [Figure 3] FIG. 10 is a perspective view schematically illustrating a communication portion provided in a partition plate. [Figure 4] FIG. 10 is a plan view of a belt conveyor of another configuration example, viewed in the ID direction. DETAILED DESCRIPTION OF THE INVENTION

[0010] A preferred embodiment of the method for producing a nonwoven fabric according to the present invention will be described below with reference to the accompanying drawings, although the scope of the present invention is not limited to the embodiment exemplified below. In this specification, the machine direction (conveying direction) of the manufacturing equipment during the production of nonwoven fabric is referred to as the MD direction (machine direction), and the width direction (orthogonal direction) perpendicular to the machine direction is referred to as the CD direction (cross direction).Furthermore, the direction perpendicular to the MD and CD directions, i.e., the discharge direction of the spinning nozzle described below, is referred to as the ID direction (injection direction).

[0011] The method for producing the nonwoven fabric of this embodiment includes a spinning step and a fiber collecting step. The spinning step is a step of forming fibers by discharging a molten thermoplastic resin from a spinning nozzle. The collection step is a step of suctioning the fibers in a plurality of suction zones arranged from the upstream side in the machine flow direction (flow direction of the manufacturing apparatus) and collecting them on a collection surface, and depositing the fibers as they move downstream on the collection surface. In a preferred configuration example of the manufacturing apparatus 100 shown in Figure 1, the spinning step and collection step are performed in the spinning apparatus 10 and collection apparatus 20, respectively. First, the manufacturing apparatus shown in Fig. 1 will be described below, followed by a description of the suction area in the manufacturing method for the nonwoven fabric of this embodiment.

[0012] 1, the manufacturing apparatus 100 according to this embodiment includes a spinning apparatus 10 and a collecting apparatus 20. The spinning apparatus 10 includes an extruder 11, a gear pump 12, a manifold 13, and a spinning device 14.

[0013] The extruder 11 is a device that melts a thermoplastic resin (polymer) and extrudes the molten thermoplastic resin (hereinafter referred to as "molten polymer") toward the gear pump 12. The thermoplastic resin melted by the extruder 11 can be any thermoplastic resin commonly used as a material for nonwoven fabrics, without any particular restrictions. The extruder 11 has, for example, a barrel (not shown) with a built-in screw and a raw material input section. The thermoplastic resin is supplied into the extruder 11 from the raw material input section as, for example, pellets, and is heated by the extruder 11 to become a molten polymer. The molten polymer is then supplied from the extruder 11 to the spinning device 14 via the gear pump 12. The thermoplastic resin supplied into the extruder 11 may be prepared by directly feeding the thermoplastic resin and optional components into the extruder 11 instead of pellets.

[0014] The gear pump 12 is a pump that continuously sends a fixed amount of molten polymer to the spinning device 14. As illustrated in Fig. 1 , the gear pump 12 has a first gear pump 121 and a second gear pump 122. The first gear pump 121 sends the molten polymer supplied from the extruder 11 to a first spinning device 141 and a second spinning device 142, which will be described later. Similarly, the second gear pump 122 sends the molten polymer supplied from the extruder 11 to a third spinning device 143 and a fourth spinning device 144, which will be described later.

[0015] The manifold 13 is a support member that supports the spinning device 14. As illustrated in Fig. 1, the manifold 13 has a first manifold 131 and a second manifold 132. The first manifold 131 is provided on the upstream side in the MD direction, and the second manifold 132 is provided on the downstream side in the MD direction. The first manifold 131 supports a first spinning device 141 and a second spinning device 142, and the second manifold 132 supports a third spinning device 143 and a fourth spinning device 144, which will be described later.

[0016] The spinning device 14 is connected to the extruder 11 via a gear pump 12. A molten polymer is supplied to the spinning device 14 from the extruder 11 via the gear pump 12. The spinning device 14 has a spinning nozzle L at its tip that discharges the molten polymer. A plurality of spinning nozzles L may be arranged at equal intervals in the CD direction to form a nozzle row. As described above, the spinning device 10 has a plurality of spinning nozzles for ejecting the molten thermoplastic resin.

[0017] The spinning nozzle L extrudes the molten polymer in the ID direction, which is perpendicular to the MD and CD directions. Fibers are formed from the molten polymer extruded from the spinning nozzle L. Various methods can be used to form the fibers, such as hot air stretching and electric field stretching. These fibers are collected and deposited on a collecting surface by suction, as described below, and the fibers are entangled with each other to form a nonwoven fabric.

[0018] As illustrated in FIG. 1, the spinning device 14 includes, from the upstream side in the MD direction, a first spinning device 141, a second spinning device 142, a third spinning device 143, and a fourth spinning device 144. The first spinning device 141 and the second spinning device 142 are provided in a first manifold 131 on the upstream side in the MD direction, and the third spinning device 143 and the fourth spinning device 144 are provided in a second manifold 132 on the downstream side in the MD direction. The first spinning device 141 to the fourth spinning device 144 are provided with spinning nozzles L1 to L4, respectively. The MD direction, CD direction, and ID direction shown in FIG. 1 are three axial directions that are perpendicular to each other, and are common to all the drawings exemplified below. The number of spinning nozzles arranged in the MD direction is not limited to that shown in FIG. 1 and can be set appropriately.

[0019] The collecting device 20 has a belt conveyor 21 that serves as a fiber collecting surface, and a suction power unit 22. As a result, the collecting device 20 sucks the fibers discharged from the plurality of spinning nozzles and collects them on the collecting surface, and deposits the fibers as the collecting surface moves downstream.

[0020] The belt conveyor 21 has a conveyor roll 211 and a belt 212. The belt 212 is supported by the conveyor roll 211 and formed into a ring. As the conveyor roll 211 rotates, the belt 212 moves from the upstream side to the downstream side in the MD direction on its upper surface facing the spinning device. Therefore, the collection surface 212S, which is the surface on the upper surface of the belt 212, moves from the upstream side to the downstream side in the MD direction. Note that, after reaching the downstream conveyor roll 211, the belt 212 reverses direction on its lower surface and returns to the upstream conveyor roll 211. The deposited fibers 8 are peeled off from the belt on the downstream side and move to a roll further downstream. The belt 212 is typically a mesh belt, but the type is not particularly limited as long as it can collect the molten polymer discharged from the spinning device 14.

[0021] The belt conveyor 21 of this embodiment has a plurality of suction compartments 213 in the internal space between the upper and lower surfaces of the looped belt 212. As shown in FIG. 2, the plurality of suction compartments 213 are arranged in a lattice pattern along the MD and CD directions. The suction compartments 213 are spaces defined by a plurality of partition plates B arranged in a lattice pattern. The suction compartments 213 are an example of a "suction space." For ease of explanation, the belt 212 is not shown in FIG. 2.

[0022] In this embodiment, suction regions E11 to E15 are formed aligned in the MD direction, as illustrated in Fig. 2. Each of these suction regions E11 to E15 includes a plurality of suction sections 213, extends along the CD direction, and, as will be described later, is a plurality of suction regions aligned from the upstream side in the machine flow direction. Hereinafter, when there is no need to particularly distinguish between suction regions E11 to E15, they will be simply referred to as suction regions E.

[0023] The suction region E15 is composed of a plurality of suction sections 213 located furthest downstream in the MD direction among the plurality of suction sections 213. The suction region E15 corresponds to the spinning nozzle 4 of the fourth spinning device 144. The suction region E14 is composed of a plurality of suction sections 213 located adjacent to the downstream side of the suction region E15. The suction region E14 corresponds to the spinning nozzle 3 of the third spinning device 143. The suction region E13 is composed of a plurality of suction sections 213 located adjacent to the downstream side of the suction region E14. The suction region E13 is located between the third spinning device 143 and the second spinning device 142 and does not correspond to any of the spinning nozzles. The suction region E12 is composed of a plurality of suction sections 213 located adjacent to the downstream side of the suction region E13. The suction region E12 corresponds to the spinning nozzle L2 of the second spinning device 142. The suction region E11 is composed of a plurality of suction sections 213 located most upstream in the MD direction among the plurality of suction sections 213. The suction region E11 corresponds to the spinning nozzle L1 of the first spinning device 141. The number of suction regions E arranged in the MD direction and the number of suction compartments 213 are not limited to those shown in FIG. 2, and can be set appropriately.

[0024] Here, each of the partition plates B1 extending in the MD direction among the partition plates B is provided with a communication hole 215 as shown in Fig. 3. The communication hole 215 is provided in a portion of the partition plate B1 that separates adjacent suction compartments (suction spaces) 213 in the CD direction. This allows each of the multiple suction compartments (suction spaces) 213 that constitute each of the suction regions E11 to E15 to communicate with each other in the CD direction.

[0025] The suction power unit 22 includes a plurality of suction blowers 221. The suction blowers 221 are devices connected to each of the suction areas E11 to E15 and suck them. In Fig. 2, the suction blowers 221 are connected in the CD direction to the suction compartments 213 that are located outermost in the CD direction of each of the suction areas E11 to E15. In the collection device 20, the suction force of the suction blower 221 is controlled to be different for each of the suction regions E11 to E15. The suction force is controlled by a suction force control mechanism. Note that the "suction force" refers to, for example, the amount of air (suction air volume) with which the suction blower 221 suctions the suction region E, and this also applies to the following description.

[0026] The above-mentioned suction force control mechanism is, for example, the following mechanism. The suction control mechanism of the first embodiment is a mechanism provided in the suction power unit 22 itself. That is, an individual suction blower 221 is connected to each of the suction regions E11 to E15, and the suction force is controlled independently for each suction region (not shown). By varying the suction force of each suction blower 221, the suction forces in the suction regions E11 to E15 are made different. The second embodiment of the suction control mechanism is a mechanism for varying the opening area of ​​the communication holes 215, which is provided for each of the partition plates B1. Various mechanisms can be employed to adjust the size (opening area) of the opening region 215a of the communication holes 215. For example, a set of shielding plates with various shielding areas can be used. A shielding plate with a larger shielding area is installed in the communication holes 215 for a suction region where a smaller suction force is desired to be applied, thereby narrowing the opening area. Alternatively, a shielding plate with a smaller shielding area or no shielding plate is installed for a suction region where a larger suction force is desired to be applied, thereby relatively widening the opening area. Alternatively, the shielding plate may have a shutter function, and the aperture of the shutter may be appropriately controlled from outside the collection device 20. A suction control mechanism using such a shielding plate can control the suction force to vary among the suction regions E11 to E15. In the suction control mechanism of this second embodiment, the number of suction blowers 221 can be made smaller than in the suction control mechanism of the first embodiment. In this case, for example, as shown in Fig. 2, two suction blowers 221 are connected to each of the suction regions E11 to E15 from both ends in the CD direction of the suction region E, and while sucking the entire suction region, the suction force for each of the suction regions E11 to E15 can be made different by the mechanism for varying the open area.

[0027] In the collection device 20, the connection direction of the suction blower 221 to the suction regions E11 to E15 is not limited to the CD direction as shown in Fig. 2, but may also be the ID direction. In the case of the ID direction, it is preferable that the suction blower 221 be connected from the lower surface side of the suction region E (the side opposite to the spinning nozzle L). In this case, from the viewpoint of improving the collection of spun fibers, it is preferable that the suction blower 221 be connected from the lower surface side in the ID direction to the suction compartments 213 that are located outermost in the CD direction of each of the suction regions E11 to E15.

[0028] In this embodiment, the patterns for varying the suction force include various combinations of suction regions that are relatively upstream and downstream. In this embodiment, the following combinations are available. This combination of suction regions that are relatively upstream and downstream is referred to as the first suction region (upstream side) and the second suction region (downstream side). (A1) Upstream side: Suction area E11, Downstream side: Suction area E12 (A2) Upstream side: Suction area E11, Downstream side: Suction area E13 (A3) Upstream side: Suction area E11, Downstream side: Suction area E14 (A4) Upstream side: Suction area E11, Downstream side: Suction area E15 (A5) Upstream side: Suction area E12, Downstream side: Suction area E13 (A6) Upstream side: Suction area E12, Downstream side: Suction area E14 (A7) Upstream side: Suction area E12, Downstream side: Suction area E15 (A8) Upstream side: Suction area E13, Downstream side: Suction area E14 (A9) Upstream side: Suction area E13, Downstream side: Suction area E15 (A10) Upstream side: Suction area E14, Downstream side: Suction area E15

[0029] In this embodiment, it is preferable to control the suction force for the relatively upstream and downstream suction regions (first suction region, second suction region) corresponding to the combination of relatively upstream and downstream spinning nozzles, depending on the deposition status of fibers on the collection surface 212S. This combination of relatively upstream and downstream spinning nozzles L is referred to as the first spinning nozzle (upstream side) and the second spinning nozzle (downstream side). That is, the suction force of the first suction region corresponding to the first spinning nozzle relatively upstream in the MD direction is made different from the suction force of the second suction region corresponding to the second spinning nozzle downstream. This allows the amount of outside air taken in during suction to be controlled within a desired range, favorably maintaining the temperature of the spinning space and forming fibers with a desired fiber diameter from the spinning nozzle L. In addition, the suction amount downstream is increased depending on the deposition of fibers, suppressing fiber scattering and favorably producing a nonwoven fabric with a desired basis weight. Such combinations (first spinning nozzle and first suction region and second spinning nozzle and second suction region) are suction regions E11, E12, E14 and E15 corresponding to spinning nozzles L1 to L4, and include the following combinations. (B1) Upstream side: spinning nozzle L1 and suction zone E11, downstream side: spinning nozzle L2 and suction zone E12 (B2) Upstream side: spinning nozzle L1 and suction zone E11, downstream side: spinning nozzle L3 and suction zone E14 (B3) Upstream side: spinning nozzle L1 and suction zone E11, downstream side: spinning nozzle L4 and suction zone E15 (B4) Upstream side: spinning nozzle L2 and suction zone E12, downstream side: spinning nozzle L3 and suction zone E14 (B5) Upstream side: spinning nozzle L2 and suction zone E12, downstream side: spinning nozzle L4 and suction zone E15 (B6) Upstream side: spinning nozzle L3 and suction zone E14, downstream side: spinning nozzle L4 and suction zone E15

[0030] Next, the spinning step and collection step performed using the above-described manufacturing apparatus 100 in the method for manufacturing the nonwoven fabric of this embodiment will be described.

[0031] The spinning nozzle L, to which molten polymer is supplied from the extruder 11 via the gear pump 12, discharges the molten polymer toward the corresponding suction zone E, where it is stretched to form fibers. The spinning process for forming these fibers is performed in parallel in each of the suction zones E11 to E15, as illustrated in FIG. 1. The formed fibers are sucked by the suction forces of the suction zones E11 to E15, which are aligned from the upstream side in the MD direction, and collected on the collection surface 212S. As the collection surface 212S moves downstream, fibers discharged from the downstream spinning nozzle are further deposited on the collection surface 212S in the downstream suction zone E, in addition to the fibers collected on the collection surface 212S in the upstream suction zone E. Due to this difference in the amount of deposited fiber, the spinning space between the spinning nozzle L and the collection surface 212S is prone to differences in the suction forces exerted by the suction zones E on the upstream and downstream sides.

[0032] In the nonwoven fabric manufacturing method of this embodiment, the suction force of the suction zone E is controlled in response to changes in the amount of accumulated fibers. That is, the multiple suction zones include an upstream suction zone that controls the suction force of the fibers to be smaller than that of the downstream suction zone. For example, among suction zones E11 to E15, in the combinations of the first suction zone and the second suction zone (A1) to (A10) described above, the suction force of the first suction zone is controlled to be smaller than that of the second suction zone. Among these, in the combinations (B1) to (B6) described above, it is preferable that the fibers discharged from the first spinning nozzle are collected in the first suction zone with a suction force smaller than that of the second suction zone, and the fibers discharged from the second spinning nozzle are collected in the second suction zone with a suction force larger than that of the first suction zone. This control is performed by the suction force control mechanism provided in the collection device 20. This allows the amount of outside air taken in by suction at the upstream suction region in the spinning space between the spinning nozzle L and the collection surface 212S to be reduced compared to the amount at the downstream suction region. By reducing the amount of outside air taken in, the temperature of the upstream spinning space can be prevented from decreasing. This maintains the temperature of the upstream spinning space within a desired range, maintaining the drawing ability when the molten polymer is discharged from the spinning nozzle and turned into fibers, and preventing the fiber diameter from becoming thicker. As a result, fibers of the desired fiber diameter can be collected on the collection surface 212S. Furthermore, as described above, in the downstream suction zone, the amount of accumulated fibers on collecting surface 212S is relatively greater than that on the upstream side. In contrast, in this embodiment, in the downstream suction zone where the amount of accumulated fibers is relatively greater, suction is performed with a relatively greater suction force than in the upstream suction zone. This prevents a reduction in the suction force of suction zone E via collecting surface 212S, allowing for effective suction to be applied to the spun fibers, preventing the fibers from scattering. As a result, a nonwoven fabric of the desired basis weight can be produced on collecting surface 212S with a good yield.

[0033] In the combinations of suction zones (A1) to (A10) and (B1) to (B6) above, the ratio of the suction force (suction air volume) of the upstream suction zone (first suction zone) to the suction force (suction air volume) of the downstream suction zone (second suction zone) is preferably 0.9 or less, more preferably 0.83 or less, and even more preferably 0.75 or less, from the viewpoint of further enhancing the above-mentioned effects. Moreover, the ratio of the suction forces (suction air volumes) is preferably 0.1 or more, more preferably 0.5 or more, and even more preferably 0.6 or more, from the viewpoint of facilitating the suppression of flying fibers.

[0034] Regarding such control of the suction force, in the suction region corresponding to the spinning nozzle, it is preferable that there is at least one combination of a first suction region on the upstream side with a relatively small suction force and a second suction region on the downstream side with a relatively large suction force. That is, it is preferable that there is at least one combination of the aforementioned (B1) to (B6). Among them, it is more preferable to control the suction force of the suction region E11 located on the most upstream side to be the smallest. In that case, the suction forces of the respective suction regions E12, E14, and E15 may be in any order from the upstream side to the downstream side. However, from the viewpoint of making the action by the above control of the suction force more effective, it is further preferable to control the suction force to gradually decrease from the downstream side to the upstream side (E11 < E12 < E14 < E15). That is, among the respective suction regions E11, E12, E14, and E15 that suck the fibers discharged from the spinning nozzle L, the suction force of the suction region E15 that sucks and collects the fibers discharged from the spinning nozzle L4 is the largest, the suction force of the suction region E14 that sucks and collects the fibers discharged from the spinning nozzle L3 is the second largest, the suction force of the suction region E12 that sucks and collects the fibers discharged from the spinning nozzle L2 is the third largest, and it is preferable to control the suction force of the suction region E11 that sucks and collects the fibers discharged from the spinning nozzle L1 to be the smallest. At this time, in the non-corresponding suction region E13 of the spinning nozzle, it is preferable that the suction force satisfies E12 ≤ E13 ≤ E14. Thereby, it is expected that the temperature of the spinning space can be uniformly controlled and the fiber diameter of the spun fiber and the basis weight of the non-woven fabric can be made uniform.

[0035] Furthermore, in the method for manufacturing a non-woven fabric according to the present embodiment, it is preferable to include a region where the suction force of the fibers is increased toward the inside rather than the outside in the CD direction orthogonal to the MD direction. Specifically, in the plurality of suction compartments 213 shown in FIG. 3, as illustrated in FIG. 4, suction regions E21 to E26 are formed. Here, a plurality of communication portions 215 are provided in each of the plurality of partition plates B2 extending in the CD direction among the plurality of partition plates B of the suction compartment 213. Thereby, each of the plurality of suction compartments 213 constituting each of the suction regions E21 to E26 communicates with each other in the MD direction. The suction regions E21 to E26 extend along the MD direction and are arranged adjacent to one another in the CD direction. The suction regions E21 and E26 are provided outside the suction regions E22 and E23, and the suction regions E22 to E25 are provided inside the suction regions E21 and E26.

[0036] In the embodiment illustrated in Fig. 4, suction zones E21 and E26 mainly include the margins of the nonwoven fabric to be produced, corresponding to the portions that do not reach the desired basis weight. That is, the amount of fiber accumulation on the collection surface 212S of suction zones E21 and E26 is smaller than that of the suction zones E22 to E25 located inside them. Therefore, the suction force of the suction zones E22 to E25 located inside them in the CD direction is made stronger than that of the suction zones E21 and E26 located outside them. In this case, the suction blowers 221 are preferably connected to the suction sections 213 at both ends in the MD direction of each of the suction zones E21 to E26. This suction force can be controlled by the suction force control mechanism described above. In the case of the suction control mechanism of the second aspect described above, control is performed as follows. That is, the size (opening area) of the opening area 215a of the communication holes 215 provided in the partition plate B2 separating the suction compartments 213 constituting each of the suction areas E21 to E26 is made larger in the suction areas E22 to E25 than in the suction area E21 and the suction area E26. As a result, the suction force with which the suction blower 221 suctions the suction areas E21 and E26 is smaller than the suction force with which the suction blower 221 suctions the suction areas E22 to E25. This control of the suction force in the CD direction can suppress the amount of outside air intake at the positions of the suction zones E21 and E26 more than at the positions of the suction zones E22 to E25. This maintains the temperature of the spinning space corresponding to the outer suction zones E21 and E26 in the CD direction within a desired range. This, combined with the control of the suction forces E11 to E15 aligned in the MD direction, suppresses fiber diameter increase in a wider spinning space. Furthermore, fiber scattering is suppressed not only downstream in the MD direction but also inside in the CD direction. As a result, a nonwoven fabric of a desired basis weight can be produced on the collecting surface 212S with a more favorable yield. The control of the suction force in the CD direction may be performed on some or all of the suction zones 213 in the MD direction in the suction zones E21 to E25. Furthermore, the control of the suction amount in the CD direction may be varied in the MD depending on the amount of fiber deposition. For example, the suction force in the CD direction may be controlled in some of the suction regions E11 to E15 aligned in the MD direction as shown in Figure 2, or the degree of control of the suction force in the CD direction may be varied for each of the suction regions E11 to E15 aligned in the MD direction. When the suction forces of the suction regions E11 to E15 and the suction regions E21 to E26 are controlled simultaneously, suction sections are set for each of the MD direction and the CD direction. In the configuration illustrated in Figure 2, the suction compartments (opening areas 215a shown in Figure 3) at both ends (outside) of each suction area E11 to E15 are set so that the suction force is smaller on the upstream side, while the size (opening area) of the opening area 215a of the communication hole 215 provided in the partition plate B2 that separates the suction compartments 213 that make up each suction area E21 to E26 is set to be larger in the suction areas E22 to E25 than in the suction area E21 and suction area E26.

[0037] The nonwoven fabric manufacturing method and manufacturing apparatus of this embodiment can be applied to various direct spinning nonwoven fabric manufacturing methods. Examples include electrospinning, spunbonding, spunmelt, and meltblown methods. Depending on the type, other processes may be included in addition to the spinning and collection processes described above. For example, the fiber aggregate deposited on the collection surface 212S may be embossed.

[0038] Among these, the nonwoven fabric manufacturing method and manufacturing apparatus of the present embodiment are preferably applied to electrospinning. In the electrospinning method, a solution or melt of a resin capable of fiber formation is charged and discharged into an electric field. This electric field stretches the discharged liquid to form fibers, and these fibers are then deposited on the collection surface 212S to form a fine fiber layer. Specifically, a positive high voltage is applied to the spinning nozzle L. The power supply 30 shown in FIG. 1 is, for example, a DC high-voltage power supply with a positive output of approximately 10 to 30 kV. Meanwhile, the collection surface 212S is negatively charged. This applies an electric field to the molten polymer in the spinning nozzle L, causing it to be discharged. The discharged molten polymer is stretched toward the negatively charged collection surface 212S by the action of the electric field, becoming ultrafine fibers. These ultrafine fibers are collected and deposited on the collection surface 212S by the suction force in the suction area E. This results in a nonwoven fabric with the ultrafine fibers still deposited.

[0039] In the electrospinning method, the resin solution or melt discharged as described above is stretched by Coulomb force in an electric field, thereby producing ultrafine fibers on the order of nanometers that cannot be achieved by conventional stretching using air, etc. The electrospinning method makes it possible to produce nonwoven fabrics with ultrafine fibers on the order of nanometers, which are orders of magnitude smaller than those obtainable by conventional manufacturing methods (e.g., meltblown methods). Furthermore, in the electrospinning method, the fibers are stretched by electrical force, so long fibers are formed without breaking, compared to, for example, the meltblown method, which uses high-temperature gas for stretching. Furthermore, the solution discharged by the Coulomb force in the electric field is stretched, and the solvent instantly evaporates, solidifying the raw material to form nanofibers. Therefore, in nonwoven fabrics obtained by the electrospinning method, the long fibers are often not fused together, and are formed by entanglement of the fibers, so the density is moderately suppressed, and high flexibility is achieved without inhibiting the movement of the fibers. Thus, nonwoven fabrics obtained by the electrospinning method tend to be relatively bulky, unlike, for example, meltblown nonwoven fabrics, and are more flexible.

[0040] When electrospinning is applied to the nonwoven fabric manufacturing method and manufacturing apparatus of this embodiment, the average fiber diameter of the obtained nonwoven fabric can be set to 0.2 μm or more and 5 μm or less.

[0041] Because the fibers formed by electrospinning through the spinning nozzle L are extremely fine, on the order of nanometers, conventionally, scattering would be likely to occur during the deposition process on the collection surface 212S. In contrast, the nonwoven fabric manufacturing method and manufacturing apparatus of this embodiment increase the suction force downstream in the MD direction, and in addition, increase the suction force on the inner side in the CD direction, thereby effectively suppressing fiber scattering during the deposition process. As a result, a fine-grained, highly flexible nonwoven fabric obtained by spinning ultrafine fibers can be produced at a desired basis weight with good yield. [Explanation of symbols]

[0042] 10 Spinning equipment 14 Spinning Device 20 Collection device 21 Conveyor Belt 22 Suction power section 100 Manufacturing equipment 141 First spinning device 142 Second Spinning Device 143 Third Spinning Device 144 Fourth Spinning Device 211 Conveyor Roll 212 Belt 212S Collection surface 213 Suction compartment 215 Communication hole, 215a Open hole area 221 Suction blower B, B1, B2 dividers E, E11~E15, E21~E26 Suction area L, L1~L4 nozzles

Claims

1. The method includes a spinning process in which a molten thermoplastic resin is discharged from a spinning nozzle using an electrospinning method to form fibers; and a process in which the fibers are sucked into a plurality of suction zones that are arranged from the upstream side in the machine flow direction and are partitioned by partition plates on the opposite side of the collecting surface from the spinning nozzle side, and the fibers are collected on the collecting surface, and the fibers are deposited as the collecting surface moves downstream, the partition plate has a communication hole that connects the suction spaces of the plurality of suction regions and a variable mechanism for changing the opening area of ​​the communication hole, A method for manufacturing a nonwoven fabric, wherein the plurality of suction zones include an upstream suction zone that controls the suction force on the fibers to be smaller than that on the downstream side.

2. The spinning nozzle has a first spinning nozzle on the upstream side and a second spinning nozzle on the downstream side of the first spinning nozzle, The plurality of suction regions include a first suction region corresponding to the first spinning nozzle and a second suction region corresponding to the second spinning nozzle, 2. A method for producing a nonwoven fabric as described in claim 1, wherein in the collecting step, the fibers discharged from the first spinning nozzle are collected in the first suction region with a suction force smaller than that in the second suction region, and the fibers discharged from the second spinning nozzle are collected in the second suction region with a suction force larger than that in the first suction region.

3. The method for producing a nonwoven fabric according to claim 1 or 2, wherein the suction region includes a region in which the suction force of the fibers is greater on the inside than on the outside in a direction perpendicular to the machine direction.

4. The method for producing a nonwoven fabric according to any one of claims 1 to 3, wherein the average fiber diameter of the obtained nonwoven fabric is 0.2 µm or more and 5 µm or less.

5. a spinning device having a plurality of spinning nozzles for discharging a molten thermoplastic resin and forming fibers by an electrospinning method; a collecting device that sucks the fibers discharged from the plurality of spinning nozzles and collects them on a collecting surface, and deposits the fibers as the collecting surface moves downstream, The plurality of spinning nozzles include a first spinning nozzle provided upstream and a second spinning nozzle provided downstream of the first spinning nozzle, The collection device is a suction force control mechanism having a plurality of suction regions, including a first suction region corresponding to the first spinning nozzle and a second suction region corresponding to the second spinning nozzle, and which reduces the suction force of the first suction region to be lower than the suction force of the second suction region; a partition plate having a communication hole that connects the suction spaces of the plurality of suction regions and a variable mechanism for changing the opening area of ​​the communication hole, the partition plate dividing the plurality of suction regions on the opposite side of the spinning nozzle on the collection surface; A nonwoven fabric manufacturing apparatus comprising:

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