Production method of nonwoven fabric and production apparatus of nonwoven fabric

Abstract

To provide a technique capable of suppressing fluffing on a single side of nonwoven fabric.SOLUTION: A production method of nonwoven fabric includes a transportation step of transporting a sheet in a fixed direction, and an embossing step of embossing one side of the sheet during transportation, using an embossing roller with protrusion apexes disposed on the outer peripheral surface, which are at least heated, and an anvil roller disposed opposite to the embossing roller, of which surface temperature is lower than the temperature of the apexes.SELECTED DRAWING: Figure 5

Description

[Technical field]

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

[0002] Conventionally, methods for producing nonwoven fabrics including multiple fiber layers are known. For example, Patent Document 1 discloses a nonwoven fabric production apparatus and a nonwoven fabric production method capable of producing a multi-layered nonwoven fabric. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2021-070875 Summary of the Invention [Problem to be solved by the invention]

[0004] Nonwoven fabrics may become fuzzed due to wear. A fuzzed nonwoven fabric feels bad on the skin and is not suitable for use as a skin-contacting surface of a sanitary product that comes into contact with the skin (e.g., a mask or an absorbent article). However, since a nonwoven fabric can be engaged with another sheet by entanglement of fibers, it is preferable that the surface to be laminated to another sheet has fuzz.

[0005] An object of the present invention is to provide a technique capable of suppressing the occurrence of fluff on one side of a nonwoven fabric. [Means for solving the problem]

[0006] A method for producing a nonwoven fabric according to one aspect of the present invention includes the steps of: a conveying step of conveying the sheet in a fixed direction; an embossing step of embossing one side of the sheet being conveyed by an embossing roller in which at least the top portion of a convex portion provided on an outer peripheral surface is heated, and an anvil roller disposed opposite the embossing roller and having a surface temperature lower than that of the top portion; Includes. Effect of the Invention

[0007] According to the present invention, the occurrence of fluffing on one side of a nonwoven fabric can be suppressed. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a plan view of a nonwoven fabric according to an embodiment. [Diagram 2] FIG. 2 is a cross-sectional view in the CD direction of the nonwoven fabric according to the embodiment. [Diagram 3] FIG. 3 is a table showing the results of an experiment on the relationship between the surface temperature of a heated roll when polylactic acid fibers are passed through the heated roll and the degree of adhesion to the heated roll. [Figure 4] FIG. 4 is a flowchart of a method for producing a nonwoven fabric according to an embodiment of the present invention. [Diagram 5] FIG. 5 is a table showing an example of the manufacturing conditions of the nonwoven fabric. [Figure 6] FIG. 6 is a diagram showing a nonwoven fabric manufacturing apparatus for manufacturing the nonwoven fabric according to the embodiment. [Figure 7] FIG. 7 is an enlarged view showing an embossing device extracted from a nonwoven fabric manufacturing apparatus for manufacturing a nonwoven fabric according to an embodiment of the present invention. [Figure 8] FIG. 8 is a diagram showing an arrangement pattern of embossments to be added to the nonwoven fabric according to the embodiment. [Figure 9] FIG. 9 is a photograph of the surface of the nonwoven fabric according to the embodiment, taken with an optical microscope. [Figure 10] FIG. 10 is a table showing the conditions of the nonwoven fabric used in the experiment and the verification results regarding the surface roughness of the nonwoven fabric according to the embodiment. [Figure 11] FIG. 11 is a photograph showing the results of an investigation into fluffing of the nonwoven fabric according to the embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, an embodiment of the present invention will be described. The embodiment described below is one aspect of the present invention, and is not intended to limit the technical scope of the present invention.

[0010] <Embodiment> Fig. 1 is a plan view of nonwoven fabric C according to this embodiment (an example of a "sheet" in the present application) as viewed from above. Fig. 2 is a cross-sectional view in the CD direction of nonwoven fabric C cut along line AA shown in Fig. 1. Nonwoven fabric C is a sheet with the longitudinal direction in the MD direction, and is composed of multiple layers.

[0011] As shown in FIG. 2, the nonwoven fabric C has a layered structure in which three fiber layers C1 are laminated. In the nonwoven fabric C, each fiber layer C1 is compressed and bonded to each other by embossing. The embossing is performed by passing the nonwoven fabric through an embossing roller heated to a predetermined temperature, thereby fusing the fibers together. The nonwoven fabric C according to this embodiment is a spunbonded nonwoven fabric in which embossing is added to one side of the nonwoven fabric formed by fusing the fibers together using an embossing roller. Such a nonwoven fabric C is suitable for absorbent articles such as diapers and materials for masks.

[0012] Each fiber layer C1 is formed of fibers made of polylactic acid resin. Polylactic acid (PLA) is a biodegradable resin that is hydrolyzed by moisture in the natural world to lower molecular weight, and then is eventually decomposed by microorganisms into carbon dioxide and water. The nonwoven fabric C according to this embodiment is a biodegradable nonwoven fabric made of polylactic acid.

[0013] A nonwoven fabric including multiple fiber layers becomes fuzzed due to wear. A fuzzed nonwoven fabric feels bad on the skin and is not suitable for use as a skin-contacting surface of a sanitary product that comes into contact with the skin (e.g., a mask or an absorbent article). However, since a nonwoven fabric can be engaged with another sheet by entanglement of fibers, it is preferable that the surface to be laminated to another sheet has fuzz.

[0014] Therefore, the inventor of the present application has found a method and an apparatus for manufacturing a nonwoven fabric in which fluffing is suppressed on one side and fluffing is easily generated on the other side. The inventor of the present application has also found that by adding embossing to only one side of the nonwoven fabric, it is possible to manufacture a nonwoven fabric in which fluffing is suppressed on one side and fluffing is easily generated on the other side. By adding embossing to one side of the nonwoven fabric, for example, the rigidity of the nonwoven fabric is increased, and a mask using a nonwoven fabric with embossing added to one side can maintain a shape away from the mouth, improving the fit of the mask when worn.

[0015] The crystallization rate of polylactic acid is slower than that of thermoplastic resins such as polypropylene (PP). When nonwoven fabric made from polylactic acid is manufactured by the spunbond method, the polylactic acid fibers discharged from the nozzle (discharge port, spinneret 23 shown in FIG. 6) in the spinning process do not crystallize on the conveyor under the manufacturing conditions for nonwoven fabric made from polypropylene. In addition, polylactic acid has low heat resistance when the crystallinity is low, so when fiber layers of polylactic acid with low crystallinity are fused together using a heated roll, the fibers with low heat resistance stick to the heated roll. In addition, polylactic acid with insufficient crystallinity undergoes thermal shrinkage when heated, so when fibers of polylactic acid with low crystallinity are passed through a heated roll, there is a problem that the surface becomes uneven due to thermal shrinkage. In addition, the glass transition temperature of polylactic acid is about 60°C. In general, thermoplastic resins crystallize, If the fiber is not yet crystallized or has a low degree of crystallinity, and is heated above the glass transition temperature of the fiber by a heated roll, the fiber will stick to the heated roll. To solve these problems, a method of increasing the crystallinity of the resin by adding a crystal nucleating agent (nucleating agent) to the raw material polylactic acid can be adopted, but this creates another problem in that the crystal nucleating agent remains after the biodegradable nonwoven fabric is decomposed. In addition, if a crystal nucleating agent is added to the raw material resin of the nonwoven fabric, it becomes difficult to pull the fibers tightly in the spinning process, and the fiber diameter becomes large. As the fiber diameter increases, the nonwoven fabric becomes hard and feels bad on the skin. Nonwoven fabrics that feel bad on the skin are not suitable as materials for absorbent articles or masks.

[0016] The inventors of the present application discovered that, in the case of thermoplastic resins such as polypropylene, if the surface temperature of the heated roll is set to the glass transition temperature of the fibers or higher, the fibers stick to the heated roll, but in the case of polylactic acid resins, if the surface temperature of the heated roll is set to 110°C or higher, which is higher than the glass transition temperature of polylactic acid, 60°C, the fibers of polylactic acid do not stick to the heated roll. This is thought to be because, even if the surface temperature of the heated roll exceeds the glass transition temperature, if it is in the temperature range of 90 to 110°C, the fibers stick to the heated roll without fusing together, but when the surface temperature of the heated roll is 110°C or higher, the amount of fibers fusing together increases, so even if some fibers stick to the heated roll, the fibers in the nonwoven fabric will fuse together after passing through the heated roll.

[0017] Figure 3 is a table showing the results of an experiment on the relationship between the surface temperature of a heated roll when polylactic acid fibers are passed through the heated roll and the degree of adhesion to the heated roll. In the "degree of adhesion" column in the table in Figure 3, "x" is indicated if the degree of adhesion is problematic in terms of manufacturing, "o" is indicated if a small amount of fiber adhered to the heated roll but the degree of adhesion is not problematic in terms of manufacturing, and "◎" is indicated if the fiber did not adhere to the heated roll at all.

[0018] In the nonwoven fabric manufacturing method according to the present embodiment, a nonwoven fabric using a polylactic acid resin as a raw material can be manufactured by setting the surface temperature of the heated roll to 110°C or higher. When the surface temperature of the heated roll is 110°C or higher but lower than 120°C, for example, a release agent can be applied to the heated roll to prevent the fibers from sticking to the heated roll. When the surface temperature of the heated roll is lower than 60°C, the polylactic acid fibers do not fuse together, and the required strength cannot be obtained in the completed nonwoven fabric.

[0019] Moreover, the surface temperature of the heated roll is preferably 120° C. or higher. By setting the surface temperature of the heated roll to 120° C. or higher, it is possible to prevent the fibers from sticking to the heated roll even without applying a release agent to the heated roll.

[0020] More preferably, the surface temperature of the heat roll is 145° C. or higher.

[0021] The melting point of the polylactic acid fiber is 150° C. or higher. More specifically, the melting point of the polylactic acid fiber is about 170° C.

[0022] In this embodiment, no nucleating agent is added to the raw material polylactic acid. As a result, the nonwoven fabric according to this embodiment does not contain a nucleating agent. As a result, the nonwoven fabric according to this embodiment does not leave behind any nucleating agent after being decomposed in nature. In addition, if the raw resin contains a nucleating agent, the resin cannot be pulled strongly in the spinning process, and the fibers become thicker. In addition, the manufacturing cost of the nonwoven fabric increases by the amount of the nucleating agent used. However, since the nonwoven fabric according to this embodiment does not contain a nucleating agent, these problems do not occur.

[0023] Next, a method for producing the nonwoven fabric C according to this embodiment will be described with reference to FIG. 1 is a flow chart of a method for producing a nonwoven fabric C according to the present embodiment. First, in the production method according to the present embodiment, molten polylactic acid resin is discharged vertically downward from a die, and the resin is pulled vertically downward by an air flow to form a fiber (step S101). In this spinning step, the fiber diameter is set to 15 μm or less. In step S102, the fibers are piled up on a conveyor and conveyed. The conveying speed of the fibers in the conveying step of S102 may be 40 m / min or more and 120 m / min or less. In step S103, the primary embossing step is performed. In the primary embossing step, the fibers laminated in three layers are passed through a pair of embossing rollers to emboss both sides, and the fibers are fused together. In step S104, the sheet formed in S103 is conveyed by a conveyor (an example of the "conveying step" in this application). The fiber conveying speed in the conveying step of S104 is 20 m / min or more and 60 m / min or less. In step S105, which is the next step after step S104, a secondary embossing process is performed on the sheet being conveyed in S104. In the secondary embossing process, the sheet is passed between an embossing roller and an anvil roller arranged opposite the embossing roller, and embossing is added to only one side of the sheet (an example of the "embossing process" as referred to in this application).

[0024] The crystallinity of the polylactic acid resin prior to the primary embossing process in step S103 is 35% or more. In this embodiment, by setting the crystallinity of the polylactic acid resin to 35% or more, it is possible to suppress the thermal shrinkage of the polylactic acid fibers in the fusion process.

[0025] FIG. 5 is a table showing an example of manufacturing conditions for a nonwoven fabric. In the "raw material" column, "+nucleating agent" indicates that a crystal nucleating agent is added to polylactic acid. In the "discharge rate (g / min·hole)" column, each value indicates the discharge rate of fiber per minute from the spinneret 23 shown in FIG. 6. In the "injector pressure (Mpa)" column, each value indicates the pressure of the injector 40 shown in FIG. 6. In the "diameter (μm)" column, each value indicates the fiber diameter after the spinning process. In the "crystallinity" column, each value indicates the crystallinity of the fiber after the spinning process. In the "heat roll temperature (℃)" column, the value (145℃) indicates the surface temperature of the heat roll in the fusion process. In the "sticking phenomenon" column, the phenomenon of the fiber sticking to the heat roll is shown. As shown in the table of FIG. 5, by making the fiber diameter of polylactic acid 15μm or less, the crystallinity of the polylactic acid resin can be made 35% or more. Even if the fiber diameter is greater than 15 μm, the degree of crystallinity can be increased to 35% or more by adding a crystal nucleating agent to the polylactic acid.

[0026] Next, a method and an apparatus for producing a nonwoven fabric according to this embodiment will be described with reference to Fig. 6 and Fig. 7. Fig. 6 is a diagram showing a nonwoven fabric production apparatus M for producing a nonwoven fabric C according to this embodiment. In Fig. 6, the nonwoven fabric production apparatus M is provided with three sets of ejection devices (fiber ejection devices) 10, and each of the ejection devices 10 (10A, 10B, 10C) is constructed with a spinning device 20, a cold air device 30, and an injector 40. The nonwoven fabric production apparatus M can produce a three-layered nonwoven fabric by being provided with the ejection devices 10A, 10B, and 10C.

[0027] In the nonwoven fabric manufacturing apparatus M, together with the ejection device 10, the collecting conveyor 50, the embossing device 60, the embossing device 90, and the winder 70 are arranged in series so that various processes can be performed. The ejection devices 10A, 10B, and 10C are arranged in series in the conveying direction relative to the conveying surface above the collecting conveyor 50. The nonwoven fabric manufacturing apparatus M is constructed so as to continuously manufacture nonwoven fabrics whose CD direction (width direction) is the direction toward the paper surface of FIG. 6, and manufactures nonwoven fabrics by the so-called spunbond method in which spun fibers (filaments) are collected in a sheet shape and embossed to appropriately bond the fibers together.

[0028] The spinning device 20 is configured to include an extruder 21 and a spinneret 23. The extruder 21 melts the raw resin R (R1, R2, R3) supplied to a hopper 22, and sends a predetermined flow rate of the melt to the spinneret 23 by the rotation of a spiral rotor 21r. 23 has a plurality of composite spinning nozzles (not shown) configured to discharge while forming a desired fibrous structure, and spins (discharges) the molten material from the extruder 21 in the direction of gravity as a bundle F of a plurality of filaments (fibers) f (hereinafter referred to as a "filament aggregate"). As the raw material resin R, a polylactic acid-based resin is used as described above.

[0029] The cold air device 30 includes a pair of open-type blowers 31 and 32 arranged at opposing positions. The cold air device 30 is arranged between the spinning device 20 and the injector 40 when viewed in the spinning direction (gravity direction). The cold air device 30 blows cooling air Ac from each of the blowers 31 and 32 onto the filament aggregate F discharged from the spinning device 20 and passing from above to below to cool it. Here, the cold air device 30 is installed such that one blower 31 is a large type that can be used as a main blower, and the other blower 32 facing it is a small type that can be used as a sub blower and auxiliary. In the open-type nonwoven fabric manufacturing apparatus M, air can flow in from outside the cold air device 30 when cooling with the cold air device 30.

[0030] The injector 40 has a structure that generates a low pressure region on the inlet side of the body 41 by blowing downward high pressure air as a driving fluid onto the filament aggregate F that descends to pass through the body 41 from above in the spinning direction toward below. The injector 40 draws the descending filament aggregate F so as to draw it into the low pressure region on the inlet side of the body 41, while also drawing it downward within the body 41 with high pressure air, thereby stretching the filament aggregate F that descends from above in the spinning direction toward below via the cooling air device 30. Note that the process from when the polylactic acid resin is discharged from the spinneret 23 of the spinning device 20 until the filament aggregate is deposited on the collecting conveyor is the process of step S101 (spinning process) shown in FIG. 4.

[0031] The collecting conveyor 50 is constructed with a main conveyor 51, sub-conveyors 52 and 53, and a suction box (suction means) 54. The main conveyor 51 is installed so that a mesh-like collecting belt 151, which is formed wider than the width of the filament aggregate F and is breathable on both sides, is wound around a group of rollers 151r and driven to rotate. The sub-conveyors 52 and 53 are also installed so that mesh-like collecting belts 152 and 153, which are formed wider than the width of the filament aggregate F and are breathable on both sides, are wound around a group of rollers 152r and a group of rollers 153r, respectively, and driven to rotate in opposite directions.

[0032] The collecting belt 151 is wound around a group of rollers 151r with a length such that the upper surface 151a is reliably positioned at the spraying points below the ejection devices 10A, 10B, and 10C, and is adapted to receive and transport the filament aggregate Fa drawn by the injector 40, which is pulled down by the injector 40, to collect it in a cloth (sheet) form. That is, the collecting belt 151 has a sufficient area to collect the sheet-like filament aggregate Fa by rotating from the upstream end (leading end) to the downstream end (rear end) in the rotating direction (transport direction) of the upper surface 151a, and functions as a collecting surface and a transport surface. The filament aggregate Fa becomes the lower fiber layer C1 in the nonwoven fabric C shown in FIG. 2.

[0033] The collecting belt 152 is wound around a group of rollers 152r with its upper surface 152a positioned at a spraying point below the ejection device 10B located at the middle of the rotational movement direction of the upper surface 151a of the collecting belt 151, and is adapted to collect the filament aggregate Fb in sheet form by receiving and transporting it as it is pulled down by the injector 40. The collecting belt 153 is wound around a group of rollers 153r with its upper surface 153a positioned at a spraying point below the ejection device 10C located at the downstream end (rearmost) of the rotational movement direction of the upper surface 151a of the collecting belt 151, and is adapted to collect the filament aggregate Fc in sheet form by receiving and transporting it as it is pulled down by the injector 40. The filament assembly Fb becomes the middle fiber layer C1 in the nonwoven fabric C shown in FIG.

[0034] These collecting belts 152, 153 are installed at a position downstream from below the ejection device 10A located at the upstream end (leading end) in the circulating direction of the upper surface 151a of the collecting belt 151, and are positioned between the upper surface 151a and the ejection devices 10B, 10C and driven to rotate in the reverse direction, so that the upper surfaces 152a, 153a function as a collecting surface and a conveying surface for collecting the sheet-like filament assemblies Fb, Fc. These collecting belts 152, 153 are driven to rotate so as to sandwich the sheet-like filament assemblies Fb, Fc between their lower parts facing the upper surface (upper part) 151a of the collecting belt 151 without peeling off and turning over, and function to assist in conveying them downstream.

[0035] The suction box 54 is housed in the collecting belt 151 of the main conveyor 51 and is partitioned into suction chambers 154a, 154a-2, 154b, 154b-2, 154c, and 154c-2, each of which functions as a decompression chamber. Suction ports (not shown) are arranged in the suction chambers 154a to 154c-2 so as to suck the upper side, and suction fans 155a to 155c-2, which can be driven individually, are connected to the suction chambers 154a to 154c-2 so as to be capable of sucking the upper side.

[0036] The suction chambers 154a, 154b, and 154c are installed so as to be located below the injectors 40 of the ejection devices 10A, 10B, and 10C, respectively, and the suction chambers 154a-2, 154b-2, and 154c-2 are installed so as to be located downstream of these suction chambers 154a, 154b, and 154c.

[0037] The suction chamber 154a is installed so as to be located directly below the collection belt 151 of the main conveyor 51 below the injector 40 of the ejection device 10A, and the suction fan 155a is driven to reduce pressure, thereby sucking in the area from directly below the collection belt 151 upward.

[0038] The suction chamber 154a-2 is installed adjacent to the downstream side of the suction chamber 154a so as to be located directly below the collection belt 151 of the main conveyor 51 between it and the suction chamber 154b located below the ejection device 10B, as described below. The suction fan 155a-2 is driven to reduce pressure and suck in the area above the collection belt 151.

[0039] As a result, the filament aggregate Fa spun by the ejection device 10A is sucked by the suction chamber 154a below the collecting belt 151 of the main conveyor 51 so as to be collected on the upper surface 151a. Therefore, the filament aggregate Fa is collected in a sheet-like shape on the upper surface 151a and held and transferred as the collecting belt 151 moves around in the length direction. Thereafter, the filament aggregate Fa is transferred from the suction chamber 154a to the adjacent suction chamber 154a-2 as the collecting belt 151 moves around in the length direction, and is sucked and held so as to maintain the sheet-like shape and transferred.

[0040] The suction chamber 154b is installed so as to be located directly below the collecting belt 151 of the main conveyor 51 below the injector 40 of the ejection device 10B, and when the suction fan 155b is driven to reduce pressure, it sucks in the area directly below the collecting belt 151 and above the collecting belt 152 of the sub-conveyor 52.

[0041] The suction chamber 154b-2 is installed adjacent to the downstream side of the suction chamber 154b so as to be located directly below the collection belt 151 of the main conveyor 51 between it and the suction chamber 154c located below the ejection device 10C, as described below. The suction fan 155b-2 is driven to reduce pressure and suck in the area above the collection belt 151.

[0042] As a result, the filament aggregate Fa spun by the ejection device 10A is sucked into the suction chamber. Following the suction chambers 154a and 154a-2, the sheet-like material is sucked and held on the upper surface 151a by the suction chambers 154b and 154b-2 below the collecting belt 151 of the main conveyor 51 and transported.

[0043] Further, the filament aggregate Fb spun by the ejection device 10B is sucked by the suction chamber 154b below the collecting belt 151 of the main conveyor 51 so as to be collected on the upper surface 152a of the collecting belt 152 of the sub-conveyor 52 on the upper surface 151a. Therefore, the filament aggregate Fb is collected and held in a sheet-like shape on the upper surface 152a as the collecting belt 152 moves around in the length direction, and is transported.

[0044] Incidentally, the collecting belt 152 of the sub-conveyor 52 rotates in the opposite direction to the collecting belt 151 of the main conveyor 51, so that the upper surface 152a of the collecting belt 152 moves in the opposite direction, and then is turned upside down and moves in the same direction facing the upper surface 151a of the collecting belt 151 of the main conveyor 51. Therefore, the filament aggregate Fb spun by the ejection device 10B is collected and held in a sheet-like shape on the upper surface 152a of the collecting belt 152 of the sub-conveyor 52 and transferred, and then overlaps the sheet-like filament aggregate Fa on the upper surface 151a of the collecting belt 151 of the main conveyor 51, and is sucked and held in the sheet-like shape by the suction chamber 154b below the collecting belt 151 of the main conveyor 51 and transferred.

[0045] As a result, the filament aggregate Fab (Fa, Fb) that is collected, held, and stacked in a sheet shape below the ejection device 10B is transferred from the suction chamber 154b to the adjacent suction chamber 154b-2 as the collection belt 151 moves around in the longitudinal direction, and is transported while being suctioned and held so as to maintain the sheet shape.

[0046] The suction chamber 154c is installed so as to be located directly below the collecting belt 151 of the main conveyor 51 below the injector 40 of the ejection device 10C, and when the suction fan 155c is driven to reduce pressure, it sucks in the area directly below the collecting belt 151 and above the collecting belt 153 of the sub-conveyor 53.

[0047] The suction chamber 154c-2 is installed adjacent to the downstream side of the suction chamber 154c and is located immediately below the end of the collection belt 151 of the main conveyor 51, as described below. The suction fan 155c-2 is driven to reduce pressure and suck in the area from directly below the collection belt 151 upward.

[0048] As a result, the filament aggregates Fab spun by the ejection devices 10A and 10B are transported, following the above-mentioned suction chambers 154a to 154b-2, by the suction chambers 154c and 154c-2 below the collecting belt 151 of the main conveyor 51, while remaining in a sheet-like form overlapping on the upper surface 151a.

[0049] The filament aggregate Fc spun by the ejection device 10C is sucked by the suction chamber 154c below the collecting belt 151 of the main conveyor 51 so as to be collected on the upper surface 153a of the collecting belt 153 of the sub-conveyor 53 on the upper surface 151a. Therefore, the filament aggregate Fc is collected in a sheet-like shape on the upper surface 153a and held and transported as the collecting belt 153 moves around in the length direction. The filament aggregate Fc becomes the upper fiber layer C1 in the nonwoven fabric C shown in FIG. 2.

[0050] Incidentally, the collecting belt 153 of the sub-conveyor 53 also rotates in the opposite direction to the collecting belt 151 of the main conveyor 51, so that the upper surface 153a of the collecting belt 153 moves in the opposite direction and is then turned upside down to be in contact with the upper surface 153b of the collecting belt 151 of the main conveyor 51. Therefore, the filament aggregate Fc spun by the ejection device 10C is collected and held in a sheet-like form on the upper surface 153a of the collecting belt 153 of the sub-conveyor 53 and transferred, and then overlaps the sheet-like filament aggregate Fab on the upper surface 151a of the collecting belt 151 of the main conveyor 51, and is sucked and held in the sheet-like form by the suction chamber 154c below the collecting belt 151 of the main conveyor 51 and transferred.

[0051] As a result, the filament aggregate Fabc (Fa, Fb, Fc) that is collected, held, and stacked in a sheet shape below the ejection device 10C is transferred from the suction chamber 154c to the adjacent suction chamber 154c-2 as the collection belt 151 moves around in the longitudinal direction, and is transported while being suctioned and held so as to maintain the sheet shape.

[0052] In short, the collecting conveyor 50 collects and holds the filament assemblies Fa, Fb, Fc spun by the ejecting devices 10A, 10B, 10C on the upper surfaces 151a-153a of the collecting belts 151-153 by suction in the suction boxes 54 in the form of a sheet of a predetermined thickness, and then stacks them to form a filament assembly Fabc (nonwoven fabric C) before embossing, which is transported downstream and handed over to the embossing device 60. The process in which the filament assembly is piled up on the collecting conveyor and transported is the process of step S102 shown in FIG.

[0053] As described above, the collecting conveyor 50 of this embodiment is arranged such that the suction chambers 154a to 154c-2 of the suction box 54 installed under the collecting belt 151 of the main conveyor 51 correspond to the injectors 40 of the ejection devices 10A to 10C, and the suction fans 155a to 155c-2 connected to each of them are set to suck at a wind speed (air volume) according to the partitioned range (area) of the suction chambers 154a to 154c-2 and the required suction pressure. Here, the partitioned range and suction pressure of the suction chambers 154a to 154c-2 may be set appropriately.

[0054] Specifically, the suction chamber 154a, without the use of a sub-conveyor, sucks in the filament aggregate Fa that is pulled down from the outlet of the injector 40 of the ejection device 10A directly above the collecting belt 151 of the main conveyor 51 from below the collecting belt 151, and collects and holds it in a sheet-like form.

[0055] This suction chamber 154a is partitioned so that a suction pressure Pa capable of stably holding the descending filament aggregate Fa is generated under the conveying surface of the collection belt 151 in a narrow range approximately equal to the spray area in the transport direction, and the interior of this partitioned range is sucked in by the suction fan 155a to create a negative pressure.

[0056] The suction chambers 154b, 154c respectively suck the filament assemblies Fb, Fc pulled down from the outlets of the injectors 40 of the ejection devices 10B, 10C directly above the collecting belts 152, 153 of the sub-conveyors 52, 53 from below the collecting belt 151, and collect and hold them in a sheet-like form. These sub-conveyors 52, 53 sandwich the sheet-like filament assemblies Fb, Fc collected and held on the collecting belts 152, 153 between the collecting belts 152, 153 below, and send them downstream as filament assemblies Fab, Fabc.

[0057] These suction chambers 154b, 154c are driven by suction fans 155b, 155c to generate suction pressures Pb, Pc capable of stably holding the descending filament assemblies Fb, Fc under the conveying surfaces of the collecting belts 152, 153, creating negative pressure. Note that, like the suction chamber 154a, these suction chambers 154b, 154c also generate the desired suction pressures Pb, Pc in a narrow partitioned range approximately equal to the spraying area in the conveying direction of the descending filament assemblies Fb, Fc. The suction chambers 154b, 154c are sucked by the suction fans 155b, 155c to create a negative pressure so that optimal suction pressures Pb, Pc are generated on the collecting belts 152, 153 of the sub-conveyors 52, 53. At the same time, the suction chambers 154b, 154c suck the collecting belts 152, 153 of the sub-conveyors 52, 53 through the filament assemblies Fab, Fabc on the collecting belt 151. For this reason, the suction chambers 154b, 154c may increase or decrease the suction volume by adjusting the suction range in the transport direction under the collecting belt 151 so that optimal suction pressures Pb, Pc are generated on the collecting belts 152, 153. Similarly, the suction range inside the collecting belts 152, 153 may be divided into adjustable sections, etc.

[0058] Thereby, the suction chambers 154b and 154c, like the suction chamber 154a, can continuously suck and hold the filament assemblies Fab and Fabc that are increased from the sheet-like filament assembly Fa via the collection belt 151 of the main conveyor 51.

[0059] The suction chambers 154a-2, 154b-2, and 154c-2 continuously suck and hold the sheet-like filament assemblies Fa, Fab, and Fabc on the collection belt 151 of the main conveyor 51 downstream of the suction chambers 154a, 154b, and 154c, respectively.

[0060] The suction chambers 154a-2, 154b-2, and 154c-2 are driven by the suction fan 155a-2 to generate suction pressures Pa-2, Pb-2, and Pc-2 that continuously suck and hold the sheet-like filament aggregates Fa, Fab, and Fabc on the collecting belt 151. The suction chambers 154a-2 and 154b-2 are disposed between the suction chambers 154a, 154b, and 154c, and are continuous to suck without gaps, so that they are installed to suck a wide partition range so as to connect the separate collection positions of each of the ejection devices 10. The suction chamber 154c-2 is installed to suck a shorter partition range because it only delivers the sheet-like filament aggregate Fabc received from the suction chamber 154c to the embossing device 60 adjacent to the downstream side.

[0061] As a result, the suction chambers 154a-2, 154b-2, and 154c-2 can suck and hold the sheet-like filament assemblies Fa, Fab, and Fabc located on the upper surface 151a via the collecting belt 151 of the main conveyor 51 in succession to the suction chambers 154a, 154b, and 154c, respectively. At this time, the sheet-like filament assemblies Fa and Fab on the collecting belt 151 of the main conveyor 51 are sucked and held by the suction chambers 154a-2 and 154b-2, respectively, and are sandwiched between the collecting belts 152 and 153 of the sub-conveyors 52 and 53 without floating up. In addition, the sheet-like filament assemblies Fa and Fab are superimposed on the sheet-like filament assemblies Fb and Fc that are collected and held by the collecting belts 152 and 153 and turned upside down, to become the sheet-like filament assemblies Fab and Fabc, which are then sucked and held and transported downstream.

[0062] As described above, the collecting conveyor 50 is set so that the individual suction fans 155a to 155c-2 suck at a required wind speed so that a suction pressure P sufficient for collecting and holding the sheet-like filament aggregate F is generated for each of the suction chambers 154a to 154c-2 of the suction box 54 on the collecting belt 151 of the main conveyor 51. Note that the relative relationship (strength) of the suction pressure P on the collecting surface (transport surface) of the filament aggregate F for each of the suction chambers 154a to 154c-2 described below will be explained by calculating and substituting a wind speed value according to the separation space from the connection points of the suction fans 155a to 155c-2 to the collecting surface.

[0063] For example, the suction box 54 is configured such that the suction pressures Pa, Pb, and Pc of the suction chambers 154a, 154b, and 154c located at the points on the collecting conveyor 50 where the filament aggregate F is sprayed by the spray devices 10A, 10B, and 10C are greater than the suction pressures Pa-2, Pb-2, and Pc-2 of the suction chambers 154a-2, 154b-2, and 154c-2 located downstream of the suction chambers. In addition, the suction pressure Ps (Pa, Pa-2) of the suction chambers 154a, 154a-2 at the front in the transport direction of the filament aggregate F, the suction pressure Pm (Pb, Pb-2) of the intermediate suction chambers 154b, 154b-2, and the suction pressure Pe (Pc, Pc-2) of the rearmost suction chambers 154c, 154c-2 are adjusted so that the suction pressure Pm at the intermediate position is smaller than the front suction pressure Ps and the rearmost suction pressure Pe (Ps>Pm and Pe>Pm) because both the upstream and downstream sides are suctioned and held in place. In addition, the suction pressures Pa, Pb, and Pc are adjusted according to the basis weight of the filament aggregate F on the transport surface so as not to excessively reduce the pressure in the suction chambers 154a, 154b, and 154c, thereby preventing the smooth relative movement of the collecting belt 151.

[0064] In detail, the suction chamber 154a is configured to set the suction pressure Pa of the collection belt 151 of the main conveyor 51, which collects and holds the filament aggregate Fa spun by the ejection device 10A in a sheet shape, so that the basis weight of the semi-finished product wound into a roll shape by the winder 70 is, for example, 10 to 30 g / m 2 When manufacturing the nonwoven fabric C, the wind speed Pa is set to 7.5. This suction pressure (wind speed) Pa is set to a relatively strong value so that the filament aggregate Fa is attracted to the upper surface 151a of the collecting belt 151 regardless of its basis weight, since this is the point where the filament aggregate Fa is sucked and begins to be collected and held in a sheet form.

[0065] The suction chamber 154a-2 is connected to the suction chamber 154a in the same manner, with a suction pressure of Pa-2 and a basis weight of 10 to 30 g / m 2 When manufacturing the nonwoven fabric C, the wind speed Pa-2 is set to 3.8. Here, as with the suction pressure Pa, the suction pressure (wind speed) Pa-2 is sufficient to maintain the shape of the filament aggregate Fa that is sucked and held in a sheet shape, regardless of the basis weight (weighing) of the filament aggregate Fa, and is held low at about half the suction pressure Pa because the filament aggregate Fa is sandwiched between the collecting belts 151 and 152 of the main conveyor 51 and the sub-conveyor 52 as it is.

[0066] The suction chamber 154b has a suction pressure Pb of, for example, 10 to 30 g / m 2 When manufacturing the nonwoven fabric C, the wind speed Pb is set to 6.0. Like the suction pressure Pa, the suction pressure (wind speed) Pb is set to a strong value regardless of the basis weight because the filament aggregate Fb is collected and formed into a sheet on the collecting belt 152 of the sub-conveyor 52, but because the filament aggregate Fab on the collecting belt 151 of the main conveyor 51 is sucked in between, the wind speed Pb is set to a low value so as not to restrict the movement of the collecting belt 151.

[0067] The suction chamber 154b-2 is connected to the suction chamber 154b and has a suction pressure Pb-2, for example, a basis weight of 10 to 30 g / m 2When manufacturing the nonwoven fabric C, the wind speed Pa is set to 3.2. Here, the suction pressure (wind speed) Pb-2 is set to a level that maintains the shape of the filament aggregates Fb and Fab in a sheet shape, regardless of the basis weight (weighing) of the filament aggregates Fb and Fab, as with the suction pressure Pb, and is set to a very low value because the filament aggregates F are sandwiched between the collecting belts 151 and 153 of the main conveyor 51 and the sub-conveyor 53 as is, and is set so that the filament aggregates F with a smaller basis weight are sucked more strongly so that they are reliably sucked and held and enter between the collecting belts 151 and 153. Note that, on the collecting belt 151 of the main conveyor 51 below the sub-conveyor 53, the sheet-like filament aggregate Fc collected and held by the collecting belt 153 is sandwiched in a state where it is overlapped with the sheet-like filament aggregate Fab, sucked and held, and transferred downstream.

[0068] The suction chamber 154c is configured to have a suction pressure Pc of, for example, 10 to 30 g / m 2 When manufacturing the nonwoven fabric C, Pa is set to 7.4. The suction pressure (wind speed) Pc is set to be equal to the suction pressure Pa and Pb, and is set to be equal to the suction pressure Pb when the filament aggregate Fc is captured by the sub-conveyor 53. Since the filament aggregate Fabc on the collecting belt 151 of the main conveyor 51 is sucked in while being interposed, the value is set to a high value so as not to restrict the movement of the collecting belt 151, since the filament aggregate Fabc is collected and formed on the belt 153.

[0069] The suction chamber 154c-2 is connected to the suction chamber 154c and has a suction pressure Pb-2, for example, a basis weight of 10 to 30 g / m 2 When manufacturing the nonwoven fabric C, the suction pressure (wind speed) Pc-2 is set to Pa=3.2 to 3.8. The suction pressure (wind speed) Pc-2 is set lower than the suction pressure Pa according to the basis weight so that the filament aggregate Fabc conveyed from under the sub-conveyor 53 is reliably sucked and held by the collecting belt 151 of the main conveyor 51 and delivered to the embossing device 60.

[0070] In the nonwoven fabric manufacturing apparatus M, the line speed of the collecting belts 151, 152, and 153 is 40 m / min or more and 120 m / min or less. The fiber discharge rate of the ejection devices 10A, 10B, and 10C is 0.5 / min / hole (0.5 / min·hole) or less. The filament aggregates Fa, Fb, and Fc (three layers of the fiber layer C1) are produced at a spinning speed of 10 to 150 m / s (preferably 20 m / s or more and 150 m / s or less). In the nonwoven fabric C produced under these conditions, the fiber diameter in the fiber layer C1 is 15 μm or less. The spinning speed can be adjusted by the ejection pressure of the ejection devices 10A, 10B, and 10C.

[0071] The embossing device 60 includes a pair of embossing rollers 61, 62, which rotate relative to each other with their cylindrical outer circumferential surfaces 61a, 62a pressed against each other. The embossing rollers 61, 62 are, for example, made of metal and are an example of the above-mentioned heated roll. In the embossing device 60, embossing protrusions (not shown) arranged regularly or irregularly on the cylindrical outer circumferential surface 62a of the upper embossing roller 62 are pressed against the smooth cylindrical outer circumferential surface 61a of the lower embossing roller 61 with a desired pressing force. In this embossing process, both sides of the filament aggregate Fabc (nonwoven fabric C) are embossed. The embossed area ratio may be 5% or more and 25% or less.

[0072] As a result, the embossing device 60 feeds the filament aggregate Fabc sandwiched between the embossing rollers 61 and 62 in the relative rotation direction, and performs embossing to squeeze and bond the filaments f together at a plurality of embossing points corresponding to the formation positions of the embossing protrusions, thereby processing the filaments f into a nonwoven fabric that maintains its sheet-like shape. The embossing protrusions formed on the cylindrical outer peripheral surface 62a of the embossing roller 62 may be formed on the cylindrical outer peripheral surface 61a side of the embossing roller 61, or may be formed on both of these cylindrical outer peripheral surfaces 61a, 62a, and may be formed in a concave shape, not limited to a convex shape, and may be pressed against the opposing cylindrical surface to squeeze and bond the filaments fbc, for example, by pressing a continuous rib shape. The embossing of the filament aggregate Fabc by the embossing device 60 is the process of step S103 (first embossing process) shown in FIG. 4. The surface temperature of the embossing rollers 61, 62 is 110° C. or higher, preferably 120° C. or higher, and more preferably 145° C. or higher. As shown in FIG. 3, by setting the surface temperature of the embossing rollers 61, 62 to 120° C. or higher, it is possible to prevent the fibers from sticking to the embossing rollers 61, 62 even if a release agent is not applied to the embossing rollers 61, 62.

[0073] The nonwoven fabric that has passed through the embossing rollers 61, 62 is transported by a transport device (transportation process), and an embossed portion 80 is formed on one side of the nonwoven fabric in the secondary embossing process. FIG. 7 is an enlarged view showing an embossing device 90 that performs the secondary embossing process, extracted from the nonwoven fabric manufacturing apparatus M. In the secondary embossing process, an embossed portion 80 is formed on one side of the nonwoven fabric C by an embossing roller 92 and an anvil roller 91 provided in the embossing device 90. The embossed portion formed on the nonwoven fabric C in the secondary embossing process 80 is an embossment with a shallower depression than the embossment produced by embossing device 60.

[0074] The embossing device 90 includes a cylindrical metallic embossing roller 92 and a cylindrical anvil roller 91 arranged opposite the embossing roller 92, and the embossing roller 92 and the anvil roller 91 rotate relative to each other. The embossing roller 92 is an example of the above-mentioned heat roll. This embossing device 90 presses convex embossing protrusions 92b (an example of the "protrusion" in this application) arranged regularly or irregularly on the cylindrical outer circumferential surface 92a of the upper embossing roller 92 against the smooth cylindrical outer circumferential surface 91a of the lower anvil roller 91 with a desired pressure. The area ratio of the embossed portion 80 is 9% or more and 30% or less. In addition, the surface of the nonwoven fabric that contacts the anvil roller 91 (the other surface) does not have the embossed portion 80 formed thereon, or the size of the embossed portion 80 is smaller or the amount of the embossed portion 80 is smaller than that of the surface to which the embossed portion 80 is added. Therefore, the surface to which the embossed portion 80 is added is not harder and is less susceptible to fluffing, facilitating the production of a laminated nonwoven fabric (for example, a mask material) by further laminating other nonwoven fabrics.

[0075] In this way, the embossing device 90 feeds the nonwoven fabric C sandwiched between the embossing roller 92 and the anvil roller 91 in the relative rotation direction, and adds embossing units 80 to the nonwoven fabric C, which squeeze at a plurality of embossing locations corresponding to the positions where the embossing protrusions 92b are formed. The embossing roller 92 may be disposed on the lower side and the anvil roller 91 on the upper side. The process in which the embossing device 90 adds the embossing units 80 to the nonwoven fabric is the process of step S105 (secondary embossing process) shown in FIG. 4.

[0076] Moreover, the linear pressure that the embossing protrusions 92b provided on the embossing roller 92 apply to the anvil roller 91 is 35 kg / cm or more and 100 kg / cm or less. By satisfying this condition, it is possible to add embossed portions 80 only to the surface of the nonwoven fabric that comes into contact with the embossing roller 92.

[0077] In the secondary embossing process, the tops of the embossing projections 92b provided on the outer peripheral surface of the embossing roller 92 are heated to a temperature at which the nonwoven fabric C can be embossed. If the temperature is too high (for example, above the melting point of the raw material), the nonwoven fabric C will shrink in width or break, and if the temperature is too low, the embossed portion 80 will not be formed. Specifically, the appropriate temperature varies depending on the raw material of the nonwoven fabric, but when the raw material is a polylactic acid resin, the temperature is preferably 135°C or higher and 155°C or lower, and more preferably 140°C or higher and 155°C or lower, as shown in FIG. 3. If the tops of the embossing projections 92b exceed 155°C, the occurrence of width shrinkage of the nonwoven fabric C can be suppressed by 90%. In addition, by setting the temperature at 135°C or higher, the rigidity obtained by the embossing process can improve the feel against the skin. Furthermore, when the apex of the embossed projections 92b is heated to 140°C or higher, sufficient fusion strength for suppressing fiber fuzzing is exerted, and fiber fuzzing can be suppressed. In this embodiment, the raw material of the nonwoven fabric C is polylactic acid, and the temperature when the embossed portion 80 is applied to the nonwoven fabric C made of polylactic acid is 135°C or higher and 155°C or lower. In the case of the nonwoven fabric C made of polylactic acid, if the surface temperature of the roller used for the embossed portion 80 is in the temperature range of 90°C or higher and lower than 110°C, the fibers may not fuse together and the nonwoven fabric may stick to the embossing roller 92.

[0078] The surface temperature of the anvil roller 91 is lower than the temperature at which embossing can be formed on the sheet-like nonwoven fabric C, and is preferably 70° C. or lower. As explained in FIG. 3, the nonwoven fabric C made of polylactic acid resin has high adhesion to the roller used in the secondary embossing process when the surface temperature of the roller is 90° C. or higher but lower than 110° C., and when the surface temperature is 110° C. or higher, the fibers in the nonwoven fabric are fused together. Therefore, by keeping the temperature of the anvil roller 91 at 70° C. or lower, it is possible to prevent the nonwoven fabric from sticking to or wrapping around the anvil roller 91, and It is possible to suppress the formation of embossed portions 80 due to fusion of fibers on the anvil roller 91. In this embodiment, the surface temperature of the anvil roller 91 made of polylactic acid is preferably 60° C. or higher and 70° C. or lower to prevent width shrinkage.

[0079] The outer peripheral surface 91a of the anvil roller 91 is made of rubber. If the outer peripheral surface 91a of the anvil roller 91 is made of rubber, which has a higher elasticity than metal, the time that the nonwoven fabric passes between the embossing roller 92 and the anvil roller 91 will be longer, and the time that the embossing protrusions 92b provided on the embossing roller 92 contact the nonwoven fabric will be longer. In addition, the contact area of ​​the embossing protrusions 92b with the nonwoven fabric will also be wider, so that it is possible to add the embossed portion 80 to the nonwoven fabric even if the heat applied to the nonwoven fabric is low, compared to the case where heat is applied from both sides of the nonwoven fabric in the thickness direction. In addition, it is possible to add the embossed portion 80 only to the sheet that the embossing roller 92 is in contact with.

[0080] The surface of the nonwoven fabric C to which the embossed portions 80 are added is the surface that comes into contact with the embossing roller 92. By adding the embossed portions 80 only to the surface that comes into contact with the embossing roller 92, it is possible to suppress fuzzing on the surface to which the embossed portions 80 are added and to increase the rigidity of the nonwoven fabric C.

[0081] FIG. 8 is a diagram showing an example of the arrangement of embossed portions 80 added to the nonwoven fabric C according to the embodiment. The arrangement pattern of the embossed portions 80 is the same as the arrangement pattern of the embossed protrusions 92b of the embossing roller 92. The shape of the embossed protrusions 92b provided on the embossing roller 92 is elliptical. Since the elliptical shape does not have corners, it is not caught and can improve the feeling of contact with the skin. The left-right direction on the paper surface of FIG. 8 is the CD direction, and the up-down direction is the MD direction. In addition, the elliptical embossed portions 80 may be arranged in a staggered pattern as shown in FIG. 8(a), and fluffing may be prevented by the multiple embossed portions 80 adjacent in the MD and CD directions of the nonwoven fabric C. In addition, as shown in FIG. 8(b), the major axes of the elliptical embossed portions 80 may be arranged in a matrix pattern in which they are parallel. By arranging the major axes of the multiple embossed portions 80 parallel to each other, it is possible to increase the rigidity in one direction, and for example, when used in a mask, it is easy to maintain the three-dimensional shape of the mask away from the mouth. Also, as shown in FIG. 8(c), a plurality of embossed sections 80 may be arranged in a line in the CD direction of the nonwoven fabric, and the plurality of adjacent embossed sections 80 in the CD direction of the nonwoven fabric C may prevent fuzzing of the nonwoven fabric C. Also, as shown in FIG. 8(d), a plurality of embossed sections 80 may be arranged in a line in the MD direction of the nonwoven fabric C, and the plurality of adjacent embossed sections 80 in the MD direction of the nonwoven fabric C may prevent fuzzing of the nonwoven fabric C. Also, as shown in FIG. 8(e), the major axes of the embossed sections 80 may be arranged in different directions for each row, and the plurality of adjacent embossed sections 80 in the MD and CD directions of the nonwoven fabric C may prevent fuzzing of the nonwoven fabric C. The shape of the embossed sections 80 is not limited to an ellipse.

[0082] The embossing device 90 is provided with an anvil roller 91 at a position facing the embossing roller 92. The surface temperature of the anvil roller 91 is lower than the top of the embossing protrusions 92b provided on the embossing roller 92, and is a temperature at which the anvil roller 91 does not form the embossed portion 80 in the nonwoven fabric. Specifically, it is 70°C or lower.

[0083] The winder 70 receives the nonwoven fabric C, in which the filaments f of the filament aggregate Fabc are intertwined and bonded by the embossing device 60 and an embossed portion 80 is added to one side by the embossing device 90, while adjusting the tension so as not to slacken, and continuously winds the nonwoven fabric C into a roll without wrinkles and with the desired winding hardness.

[0084] As a result, the filament aggregate Fabc is formed into a sheet and rolled by the winder 70. The nonwoven fabric C of a desired length wound in a shape can be prepared so as to be capable of being supplied to the next processing step or the like.

[0085] By the manufacturing method described above, it is possible to manufacture the nonwoven fabric C having the embossed portion 80 added only to one surface thereof.

[0086] FIG. 9 is a photograph taken with an optical microscope of the surface of nonwoven fabric C to which an embossed portion 80 has been added by the above-mentioned manufacturing method. The optical microscope used is a Keyence VHX, and the photograph is magnified 30 times. The photographs are magnified 50 times and 100 times. The black circular patterns in the photographs are the embossing formed by the embossing device 60 in the first embossing process, and the white circular patterns are the embossed portion 80 added by the embossing device 90 in the second embossing process. The black circular embossing and the white circular embossed portion 80 are visible on the surface to which the embossed portion 80 has been added, but the white circular embossed portion 80 is not visible on the back surface to which the embossed portion 80 has not been added, and only the black circular embossing is visible. Therefore, it was found that the embossed portion 80 added by the embossing device 90 in the second embossing process is thinner than the embossing formed by the embossing device 60 in the first embossing process, and the embossed portion 80 added by the embossing device 90 is not visible on the surface to which the embossed portion 80 has not been added. Therefore, it is considered that the nonwoven fabric C produced by the above-mentioned production method has the embossed portion 80 added only to one side, and the added embossed portion 80 does not reach the back side.

[0087] <Experiment> Next, an experiment was conducted to verify the surface roughness relative to the area ratio of the embossing. While it is preferable to add the embossed portion 80 to one side of the nonwoven fabric C, if there are too many places where the embossed portion 80 is applied, the surface of the nonwoven fabric to which the embossed portion 80 is added becomes hard, and there is a possibility that the surface roughness may become poor. Therefore, an experiment was conducted to verify the relationship between the area ratio of the embossed portion added to the nonwoven fabric to which the embossed portion is added and the surface roughness, and to verify the area ratio of the embossed protrusions 92b necessary to manufacture the nonwoven fabric C that is comfortable against the skin while suppressing pilling. The nonwoven fabrics used in the experiment were the comparative example and prototypes 1 to 18 shown in FIG. 10.

[0088] FIG. 10 is a table showing the conditions of the comparative examples and the prototypes used in the experiment. The nonwoven fabric used in the experiment has a laminated structure in which fiber layers are laminated, and is manufactured by compressing and bonding the laminated fiber layers. In the first embossing process, the area ratio of the emboss formed when the laminated fiber layers are compressed and bonded is 8.3%, and the nonwoven fabric used is a nonwoven fabric made of polylactic acid. In the second embossing process, the nonwoven fabrics of prototypes 1 to 18 are nonwoven fabrics in which an embossed part is added to one side by a prototype device manufactured by Yuri Roll Co., Ltd. The conveying speed of the nonwoven fabric in the second embossing process is 40 m / min, and the embossing roller 92 is 140° C. The anvil roller 91 is made of rubber, and its temperature is 65° C. The surface to which the embossed part is added is the processed surface or the front surface, and the surface to which the embossed part is not added is the back surface. The "Additional embossing" column in the table of FIG. 10 indicates whether or not an embossed portion is added by the secondary embossing process of the nonwoven fabric of the comparative example and each prototype. The "Shape of embossed protrusion" column in the table of FIG. 10 indicates the shape of the embossed protrusion of the embossing roller 92 in the secondary embossing process of the nonwoven fabric of the comparative example and each prototype. The comparative example does not have an embossed portion by the secondary embossing process, and each prototype has an embossed portion of the same shape as the embossed protrusion. The "Area ratio (%) of embossed protrusions provided on the outer peripheral surface of the embossing roller" column in the table of FIG. 10 indicates the ratio of the outer peripheral surface of the embossing roller that is occupied by the embossed protrusions provided on the outer peripheral surface of the embossing roller used in the secondary embossing process. The ratio of the outer peripheral surface of the embossing roller that is occupied by the embossed protrusions corresponds to the embossed area ratio of the embossed portion formed on the nonwoven fabric. The "Area ratio (%) of the embossed protrusions provided on the outer peripheral surface of the embossing roller" column in the table of FIG. 10 indicates the ratio of the outer peripheral surface of the embossing roller that is occupied by the embossed protrusions. The ratio of the outer peripheral surface of the embossing roller that is occupied by the embossed protrusions corresponds to the embossed area ratio of the embossed portion formed on the nonwoven fabric. The "Width (mm)" column lists the width of the nonwoven fabric of the comparative example and each prototype.

[0089] Figure 10 shows the results of an experiment to verify the surface roughness relative to the embossed area ratio. The "Surface roughness (μm)" column in Figure 10 shows the surface roughness of the nonwoven fabric measured using KESFB4-A-SE. The roughness of the surface is described. The rougher the surface roughness, the smaller the area of ​​the embossed part and the better the skin feel. In addition, the skin feel relative to the surface roughness was confirmed by a sensory test. 20 people actually touched the nonwoven fabrics of the comparative example and prototypes 1 to 18 to confirm the softness and fuzzing state of the nonwoven fabric. In the column showing "softness" in FIG. 10, "◎" was written when 0 people answered that the softness was poor, "〇" was written when 1 to 3 people answered that the softness was poor, "△" was written when 4 to 6 people answered that the softness was poor, and "×" was written when 7 or more people answered that the softness was poor. In the column showing "fuzzing state" in FIG. 10, "◎" was written when 0 people felt fuzzing, "〇" was written when 1 to 3 people felt fuzzing, "△" was written when 4 to 6 people felt fuzzing, and "×" was written when 7 or more people felt fuzzing.

[0090] 10, it was found that the softness and fuzziness were both rated as "◎" or "◯" and the texture was good when the embossed area ratio was in the range of 9% to 30%. It was also found that the surface roughness of nonwoven fabrics with this embossed area ratio in the range of 9% to 30% was 1.6 μm or less. Therefore, it is considered that if the area ratio of the embossed projections 92b on the outer peripheral surface 92a of the embossing roller 92 is 9% to 30%, it will be possible to manufacture a nonwoven fabric C that is comfortable against the skin.

[0091] In addition, an experiment was conducted to verify whether the addition of the embossed portion 80 could suppress the fuzzing of the nonwoven fabric. In the experiment, an abrasion test was conducted on the surface with the embossed portion added and the surface without the embossed portion (rear surface) of the nonwoven fabric of the comparative example using a nonwoven fabric to which no embossed portion was added during production, and the prototypes 1 to 18 to which the embossed portion was added during production. In the abrasion test, a James Heals abrasion and pilling tester "Maxi-Martindale" was used to draw Lissajous curves on the nonwoven fabric 80 times at a pressure of 12 kPa, and the condition of the nonwoven fabric was then confirmed. If no fuzzing was observed on the nonwoven fabric after the abrasion test, it indicates that fuzzing was suppressed.

[0092] FIG. 11 is a photograph showing the results of an experiment verifying that a nonwoven fabric with an embossed portion added suppresses fuzzing. FIG. 11 shows photographs of the comparative example and prototypes 7, 8, 9, and 17. Comparing the comparative example with prototypes 7, 8, 9, and 17, fuzzing was observed on both the front and back sides of the comparative example. Prototypes 7, 8, 9, and 17 did not show fuzzing on the processed side, but did show fuzzing on the back side. This shows that adding an embossed portion to the nonwoven fabric can suppress fuzzing. This shows that adding an embossed portion 80 to the nonwoven fabric can suppress fuzzing.

[0093] The nonwoven fabrics of the comparative example and prototypes 1 to 18 used to verify the feel on the skin, such as the state of fuzzing in FIG. 10, are nonwoven fabrics before the abrasion test, and are different from the nonwoven fabrics in a fuzzed state due to the abrasion test, as shown in the photograph in FIG. 11.

[0094] Judging the above experimental results comprehensively, it is preferable that the area ratio of the embossed protrusions 92b provided on the outer peripheral surface 92a of the embossing roller 92, which produces nonwoven fabric C that is soft to the touch while suppressing pilling, is 9% or more and 30% or less, and the surface roughness is 1.6 μm or less.

[0095] <Other embodiments> Although the embodiments of the present invention have been described above, the above-mentioned various embodiments are combined as much as possible. In the above embodiment, the spunbond nonwoven fabric is taken as an example, but the present invention is not limited to this. For example, the present invention is also applicable to spunbond nonwoven fabric, thermal bond nonwoven fabric, chemical bond nonwoven fabric, needle punch nonwoven fabric, and stitch bond nonwoven fabric.

[0096] In the embodiment of the present invention, the raw material of the fiber layer is polylactic acid, but is not limited to polylactic acid, and polypropylene, polyethylene terephthalate, polyethylene, polyhydroxyalkanoate, etc. may be used. When the raw material of the nonwoven fabric C is polypropylene, the temperature of the top of the embossing protrusions 92b provided on the embossing roller 92 in the secondary embossing process is preferably 130°C or higher and 155°C or higher.

[0097] In the embodiment of the present invention, the outer peripheral surface 91a of the anvil roller 91 is made of rubber, but is not limited to rubber. For example, a metal may be used that is controlled to be at a lower temperature than the top of the embossed protrusion 92b by providing a cooling mechanism, and it is also possible to use a material with low thermal conductivity as the raw material. [Explanation of symbols]

[0098] C··Non-woven fabric C1 Fiber layer M·Nonwoven fabric manufacturing equipment 10, 10A, 10B, 10C...Ejection device 20. Spinning equipment 30·Cold air device 40··Injector 50··Collection conveyor 51 Main conveyor 52, 53 Sub conveyor 54 Suction box 60··Embossing device 70 Winder 80··Embossed section 90··Embossing device 141, 142: Signboard 151, 152, 153 Collection belt 154a, 154b, 154c Suction chamber 162 Adjustment roller f filament fr Rotation diameter F, Fa, Fab, Fabc, Fb, Fc filament assembly Lc Intersection distance Ld...Open interval Lr Evacuation interval P, Pa, Pb, Pc, Pe, Pm, Ps Suction pressure (wind speed)

Claims

1. a conveying step of conveying the sheet in a fixed direction; an embossing step of embossing one side of the sheet being conveyed by an embossing roller in which at least the top portion of a convex portion provided on an outer peripheral surface is heated, and an anvil roller disposed opposite the embossing roller and having a surface temperature lower than that of the top portion; A method for producing a nonwoven fabric comprising the steps of:

2. the temperature of the zenith portion is a temperature at which the embossing process can be performed on the sheet, the surface temperature of the anvil roller is lower than the temperature at which the embossing process can be performed on the sheet; The method for producing a nonwoven fabric according to claim 1.

3. The outer surface of the anvil roller is formed of rubber. The method for producing a nonwoven fabric according to claim 1 or 2.

4. an outer peripheral surface of the embossing roller is provided with embossing protrusions for forming an embossment on one surface of the sheet, and an area ratio of the embossing protrusions to the outer peripheral surface of the embossing roller is 9% or more and 30% or less; The method for producing a nonwoven fabric according to claim 1 or 2.

5. The raw material of the sheet is a polylactic acid resin, The surface temperature of the anvil roller is 70° C. or less. The method for producing a nonwoven fabric according to claim 1 or 2.

6. The temperature of the convex portion is 155° C. or less. The method for producing a nonwoven fabric according to claim 1 or 2.

7. The temperature of the protrusion is 135° C. or higher. The method for producing a nonwoven fabric according to claim 6.

8. The temperature of the protrusion is 140° C. or higher. The method for producing a nonwoven fabric according to claim 6.

9. In the conveying step, a conveying speed of the sheet is 20 m / min or more and 60 m / min or less. The method for producing a nonwoven fabric according to claim 1 or 2.

10. The linear pressure applied by the protrusion to the anvil roller is 35 kg / cm or more and 100 kg / cm or less. The method for producing a nonwoven fabric according to claim 1 or 2.

11. The zenith portion is elliptical in shape. The method for producing a nonwoven fabric according to claim 1 or 2.

12. A conveying device that conveys a sheet in a fixed direction; an embossing device for embossing one side of the sheet being conveyed by an embossing roller in which at least the top portion of a convex portion provided on an outer peripheral surface is heated, and an anvil roller disposed opposite the embossing roller and having a surface temperature lower than that of the top portion; A nonwoven fabric manufacturing apparatus comprising:

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