JP7658066B2 - Nonwoven fabric manufacturing method and nonwoven fabric manufacturing device - Google Patents

Description

The present invention relates to a method and an apparatus for producing a nonwoven fabric .

Conventionally, composite fibers for forming nonwoven fabrics have been known (for example, Patent Document 1). The composite fibers described in Patent Document 1 have crimping properties to provide bulky nonwoven fabrics.

JP 2017-222972 A

Nonwoven fabrics with crimping properties have high elasticity because the fibers are looped. When highly elastic nonwoven fabrics are used as materials for absorbent articles, masks, etc., the nonwoven fabric stretches in the MD direction when pulled in the MD direction inside the processing machine during the manufacturing process, resulting in width shrinkage. Since the width of the nonwoven fabric is set according to the dimensions of the finished product, it is undesirable for the nonwoven fabric to shrink in width. In addition, in order to ensure stable operation, it is possible to match the width of the nonwoven fabric when it is fully stretched in the MD to the dimensions of the finished product, taking into account the occurrence of width shrinkage in the nonwoven fabric, but a fully stretched nonwoven fabric would lose bulk.

The present invention aims to provide a technology that can suppress the occurrence of width shrinkage in nonwoven fabrics.

In order to solve the above problem, the present invention provides a first fiber layer made of crimped fibers and a second fiber layer in which the fibers are oriented in the MD direction.

In detail, the present invention is a nonwoven fabric composed of multiple fiber layers, comprising a first fiber layer composed of crimpable fibers with a crimp number of 15 or more per 25 mm, and a second fiber layer having a fiber diameter of 2 to 100 denier and fibers oriented in the MD direction.

In the nonwoven fabric, the first fiber layer may have an MD breaking elongation of 50% or more.

In the nonwoven fabric, the first fiber layer, the second fiber layer, and the first fiber layer may be laminated in this order.

The present invention can also be seen as a method for producing a nonwoven fabric. For example, the present invention may be a method for producing a nonwoven fabric composed of multiple fiber layers, which may include a step of forming a first fiber layer composed of crimpable fibers with a crimp number of 15 or more per 25 mm, and a step of forming a second fiber layer having a fiber diameter of 2 to 100 denier and fibers oriented in the MD direction.

The present invention can also be seen from the aspect of a nonwoven fabric manufacturing apparatus. For example, the present invention may be a nonwoven fabric manufacturing apparatus for manufacturing a nonwoven fabric composed of a plurality of fiber layers, the nonwoven fabric manufacturing apparatus including a fiber spraying device for spraying fibers, and a sheet conveying device for collecting the bundle of fibers sprayed from the fiber spraying device on a conveying surface and conveying the bundle of fibers in a sheet-like nonwoven fabric in a conveying direction, the fiber spraying device including a first fiber spraying device for spraying filaments in a bundle to form a first fiber layer composed of crimpable fibers having a crimp number of 15 pieces/25 mm or more, and a second fiber spraying device for spraying filaments in a bundle to form a second fiber layer having a fiber diameter of 2 to 100 denier and fibers oriented in the MD direction.

The present invention makes it possible to suppress the occurrence of width shrinkage in nonwoven fabrics.

FIG. 1 is a plan view of a nonwoven fabric according to an embodiment. FIG. 2 is a cross-sectional view in the CD direction of the nonwoven fabric according to the embodiment. FIG. 3 is a diagram showing a nonwoven fabric manufacturing apparatus for manufacturing the nonwoven fabric according to the embodiment.

Below, embodiments of the present invention will be described with reference to the drawings. Note that the configurations of the following embodiments are examples, and the present invention is not limited to the configurations of these embodiments.

<Embodiment>
Fig. 1 is a plan view of the nonwoven fabric C according to this embodiment as viewed from above. Fig. 2 is a cross-sectional view in the CD direction of the nonwoven fabric C cut along line AA shown in Fig. 1. The nonwoven fabric C is a sheet whose longitudinal direction is the MD direction, and is composed of multiple layers.

As shown in FIG. 2, the nonwoven fabric C has a layered structure in which fiber layers are laminated in the following order from the bottom: crimped fiber layer C1 (an example of the "first fiber layer" in this application), spunbond fiber layer C2 (an example of the "second fiber layer" in this application), and crimped fiber layer C1. The crimped fiber layer C1 is a fiber layer made of crimpable fibers, and is formed to be bulky because the fibers are looped. The spunbond fiber layer C2 has fibers oriented in the MD direction (machine direction), and is formed thinner than the crimped fiber layer C1. The nonwoven fabric C according to this embodiment has bulky crimped fiber layers C1 on both the top and bottom, which improves the feel when used in absorbent articles, masks, etc.

The degree of crimping of the fibers in the crimped fiber layer C1 can be indicated, for example, by the number of crimps of the fibers measured in accordance with Japanese Industrial Standard JIS L1015. In this embodiment, the number of crimps in the crimped fiber layer C1 is 15/25 mm. In addition, the crimped fiber layer C1 has a breaking elongation in the MD direction of 50% or more.

In the spunbond fiber layer C2, the fiber diameter is 2 to 100 denier (2 denier or more and 100 denier or less). Note that this fiber diameter is the value when the line speed is 23 to 1125 m/min in the spunbond manufacturing method described below. In addition, in the spunbond fiber layer C2, the number density in the CD direction is 2 to 8 fibers/mm.

In the nonwoven fabric C, each fiber layer is compressed and bonded to each other by embossing. The embossed area ratio is 5 to 25%. The basis weight of each fiber layer is 10 to 30 g/ ^m2 . Such a nonwoven fabric C is suitable for use as a material for absorbent articles and masks.

The nonwoven fabric C according to the present embodiment is provided with a spunbond fiber layer C2, which suppresses elongation in the MD direction. As a result, even if the nonwoven fabric C is pulled in the MD direction inside a processing machine, elongation in the MD direction is suppressed. Therefore, the nonwoven fabric C according to the present embodiment can suppress the occurrence of width shrinkage. Such a nonwoven fabric C can achieve stable operation when used as a material while maintaining bulkiness.

Next, a manufacturing method and manufacturing device for the nonwoven fabric C according to this embodiment will be described with reference to FIG. 3. FIG. 3 is a diagram showing a nonwoven fabric manufacturing device M for manufacturing the nonwoven fabric C according to this embodiment. In FIG. 3, the nonwoven fabric manufacturing device M is equipped 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 ejection devices 10A and 10C are examples of a "first fiber ejection device" for forming the crimped fiber layer C1, and the ejection device 10B is an example of a "second fiber ejection device" for forming the spunbond fiber layer C2.

In the nonwoven fabric manufacturing apparatus M, the collecting conveyor (sheet transport device) 50, the embossing device 60, and the winder 70 are arranged in series together with the ejection device 10 so that various processes can be performed. The ejection devices 10A, 10B, and 10C are arranged in series in the transport direction relative to the transport surface above the collecting conveyor 50. The nonwoven fabric manufacturing apparatus M is constructed to continuously manufacture nonwoven fabric C, with the CD direction (width direction) being the direction toward the paper surface of FIG. 3, and manufactures nonwoven fabric C by the so-called spunbond method, in which the fibers (filaments) to be spun are collected in a sheet shape and embossed to appropriately bond the fibers together.

The spinning device 20 is configured with 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 rotating a spiral rotor 21r. The spinneret 23 has multiple composite spinning nozzles (not shown) configured to discharge the melt while forming a desired fibrous structure, and spins (discharges) the melt from the extruder 21 in the direction of gravity as a bundle F of multiple filaments (fibers) f (hereinafter referred to as a "filament aggregate").

Here, the raw resin R may be multi-layered by stacking sheet-like filaments of the same materials R1, R2, R3 without changing the type for each of the ejection devices 10A, 10B, 10C, or may be multi-layered by stacking sheet-like filaments of different materials R1, R2, R3 by changing the type for each of the ejection devices 10A, 10B, 10C. For example, the raw resin R may be a thermoplastic resin as the main component, and may be the same or different polyolefin resins such as polypropylene (PP) and polyethylene (PE), and may contain additives such as various stabilizers such as known heat stabilizers and weather stabilizers, antistatic agents, slip agents, antiblocking agents, antifogging agents, lubricants, dyes, pigments, natural oils, synthetic oils, waxes, etc.

The cold air device 30 is equipped with a pair of open-type blowers 31, 32 arranged in opposing positions. This cold air device 30 cools the filament aggregate F that is discharged from the spinning device 20 and passes from top to bottom by blowing cooling air Ac from each of the blowers 31, 32. Here, the cold air device 30 is installed with one blower 31 installed as a large type that can be used as the main blower, and the other facing blower 32 selected and installed as a small type that can be used as a secondary blower.

The injector 40 is structured to blow downward high-pressure air as a driving fluid onto the filament assembly F, which descends through the body 41 from above in the spinning direction, creating a low-pressure region on the inlet side of the body 41. The injector 40 draws the descending filament assembly F 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 assembly F, which descends from above in the spinning direction from above through the cold air device 30.

The collection 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 collection 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 collection 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.

The collection belt 151 is wound around a group of rollers 151r with a length that ensures that the upper surface 151a is positioned at the spraying point below the spraying devices 10A, 10B, and 10C, and is adapted to receive and transport the filament aggregate Fa pulled down by the injector 40, thereby collecting it in a cloth (sheet) form. That is, the collection belt 151 has a sufficient area to collect the sheet-like filament aggregate Fa by rotating from the upstream end (leading edge) to the downstream end (rear end) in the rotational movement direction (transport direction) of the upper surface 151a, and functions as a collection surface and a transport surface. The filament aggregate Fa becomes the lower crimped fiber layer C1 in the nonwoven fabric C.

The collection belt 152 is wound around a group of rollers 152r with its upper surface 152a positioned at the lower spraying point of the ejection device 10B located at the middle of the rotational movement direction of the upper surface 151a of the collection belt 151, and is adapted to collect the filament aggregate Fb in a sheet-like form by receiving and transporting it as it is pulled down by the injector 40. The collection belt 153 is wound around a group of rollers 153r with its upper surface 153a positioned at the lower spraying point of the ejection device 10C located at the downstream end (rear end) of the rotational movement direction of the upper surface 151a of the collection belt 151, and is adapted to collect the filament aggregate Fc in a sheet-like form by receiving and transporting it as it is pulled down by the injector 40. The filament aggregate Fb becomes the spunbond fiber layer C2 in the nonwoven fabric C.

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

The suction box 54 is housed within the collection belt 151 of the main conveyor 51 and is divided 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 these suction chambers 154a to 154c-2 so as to suck in the upper side, and suction fans 155a to 155c-2, which can be driven individually, are connected to enable suction.

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 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.

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, sucking in the air from directly below the collection belt 151 upward.

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, sucking in the area above the collection belt 151.

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

The suction chamber 154b 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 10B, and when the suction fan 155b is driven to reduce pressure, it sucks in the area directly below the collection belt 151 and above the collection belt 152 of the sub-conveyor 52.

The suction chamber 154b-2 is installed adjacent to the downstream side of the suction chamber 154b, and is 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, sucking in the area above the collection belt 151.

As a result, the filament aggregate Fa spun by the ejection device 10A is sucked and held in sheet form on the upper surface 151a by the suction chambers 154b and 154b-2 below the collection belt 151 of the main conveyor 51, following the suction chambers 154a and 154a-2 described above, and then transported.

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

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 form on the upper surface 152a of the collecting belt 152 of the sub-conveyor 52 and transported, 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 a sheet-like form by the suction chamber 154b below the collecting belt 151 of the main conveyor 51 and transported.

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 sucked, held, and transported so as to maintain the sheet shape.

The suction chamber 154c 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 10C, and when the suction fan 155c is driven to reduce pressure, it sucks in the area directly below the collection belt 151 and above the collection belt 153 of the sub-conveyor 53.

The suction chamber 154c-2 is installed adjacent to the downstream side of the suction chamber 154c, so as to be 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, thereby sucking in the air from directly below the collection belt 151 upward.

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 collection belt 151 of the main conveyor 51, while remaining in a sheet-like form overlapping on the upper surface 151a and held there by suction.

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

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 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 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 transported, and is then further overlapped with 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 a sheet-like form by the suction chamber 154c below the collecting belt 151 of the main conveyor 51 and transported.

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 sucked, held, and transported so as to maintain the sheet shape.

In short, the collection conveyor 50 collects and holds the filament aggregates Fa, Fb, Fc spun by the ejection devices 10A, 10B, 10C on the upper surfaces 151a-153a of the collection belts 151-153 in a sheet shape of a predetermined thickness using the suction box 54, and then stacks them to form the filament aggregates Fa, Fb, Fc before embossing, which are then transported downstream to the embossing device 60.

The embossing device 60 is equipped with a pair of embossing rolls 61, 62, which rotate relative to one another with their cylindrical outer circumferential surfaces 61a, 62a pressed against each other. This embossing device 60 presses embossing protrusions (not shown) arranged regularly or irregularly on the cylindrical outer circumferential surface 62a of the upper embossing roll 62 against the smooth cylindrical outer circumferential surface 61a of the lower embossing roll 61 with a desired pressure.

As a result, the embossing device 60 sends out the filament assembly Fabc sandwiched between the embossing rolls 61, 62 in the relative rotation direction, and performs embossing at a plurality of embossing locations corresponding to the formation positions of the embossing protrusions to entangle the filaments f with each other while squeezing and bonding them, thereby processing them into a nonwoven fabric C that maintains its sheet-like shape. The embossing protrusions formed on the cylindrical outer circumferential surface 62a of the embossing roll 62 may be formed on the cylindrical outer circumferential surface 61a side of the embossing roll 61, or may be formed on both of these cylindrical outer circumferential surfaces 61a, 62a, and further may be formed in a concave shape rather than a convex shape, and may be squeeze-bonded by pressing, for example, a continuous rib shape against the opposing cylindrical surface.

The winder 70 receives the nonwoven fabric C, in which the filaments f of the filament aggregate Fabc are intertwined and joined by the embossing device 60, while adjusting the tension so as not to cause slack, and continuously winds the nonwoven fabric C into a roll without wrinkles and with the desired winding tightness.

This allows the winder 70 to prepare the desired length of nonwoven fabric C, in which the filament aggregate Fabc is wound into a sheet shape and into a roll, so that it can be supplied to the next processing step, etc.

As described above, in the collection conveyor 50 of this embodiment, the suction chambers 154a to 154c-2 of the suction box 54 installed under the collection belt 151 of the main conveyor 51 are partitioned and installed to correspond to each injector 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.

Specifically, the suction chamber 154a collects and holds the filament aggregate Fa in a sheet form by sucking it from below the collection belt 151, which is pulled down from the outlet of the injector 40 of the ejection device 10A directly above the collection belt 151 of the main conveyor 51, without the need for a sub-conveyor.

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 conveying direction, and the inside of this partitioned range is sucked in by the suction fan 155a to create a negative pressure.

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

These suction chambers 154b, 154c are made negative by driving suction fans 155b, 155c so as 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. Note that, like the suction chamber 154a, these suction chambers 154b, 154c are also sucked and made negative by the suction fans 155b, 155c so as to generate the desired suction pressures Pb, Pc in a narrow partitioned range approximately equal to the spray area in the conveying direction of the descending filament assemblies Fb, Fc. At the same time, these suction chambers 154b, 154c suck the collecting belts 152, 153 of the sub-conveyors 52, 53 with the filament assemblies Fab, Fabc on the collecting belt 151 between them. 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 collection belt 151 so that optimal suction pressures Pb, Pc are generated on the collection belts 152, 153, and the suction range within the collection belts 152, 153 may also be similarly divided so that it is possible to adjust the suction range.

As a result, suction chambers 154b and 154c, like suction chamber 154a, can continuously suck and hold 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.

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 suction chambers 154a, 154b, and 154c, respectively.

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

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 collection belt 151 of the main conveyor 51, respectively, in succession to the suction chambers 154a, 154b, and 154c. At this time, the sheet-like filament assemblies Fa and Fab on the collection belt 151 of the main conveyor 51 are sucked and held by the suction chambers 154a-2 and 154b-2, respectively, so they do not float up and are sandwiched between the collection belts 152 and 153 of the sub-conveyors 52 and 53. 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 collection belts 152 and 153 and turned upside down, and are transported downstream while being sucked and held.

As described above, the collection conveyor 50 is set so that each suction fan 155a to 155c-2 of the suction box 54 generates a suction pressure P sufficient to collect and hold the sheet-like filament aggregate F on the collection belt 151 of the main conveyor 51 for each suction chamber 154a to 154c-2 of the suction box 54 at the required wind speed. Note that the relative relationship (strength) of the suction pressure P on the collection surface (transport surface) of the filament aggregate F for each suction chamber 154a to 154c-2 described below is explained by calculating and substituting a wind speed value according to the separation space from the connection point of the suction fans 155a to 155c-2 to the collection surface.

For example, the suction box 54 is adjusted so that the suction pressures Pa, Pb, Pc of the suction chambers 154a, 154b, 154c located at the points where the filament aggregate F is sprayed by the spray devices 10A, 10B, 10C on the collection conveyor 50 are greater than the suction pressures Pa-2, Pb-2, Pc-2 of the suction chambers 154a-2, 154b-2, 154c-2 located downstream of each of them. In addition, the suction pressure Ps (Pa, Pa-2) of the leading suction chambers 154a, 154a-2 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 can be adjusted to be smaller than the leading 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 and thus hinder the smooth relative movement of the collecting belt 151.

In detail, the suction chamber 154a sets the suction pressure Pa on the collecting belt 151 of the main conveyor 51 that collects and holds the filament aggregate Fa spun by the ejection device 10A in a sheet-like form to an air speed Pa of 7.5 when producing a nonwoven fabric C having a basis weight of 10 to 30 g/ ^m2 as a semi-finished product to be wound into a roll by the winder 70. This suction pressure (air speed) Pa is set to a strong value so that the filament aggregate Fa is adsorbed 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 starts to be collected and held in a sheet-like form.

The suction chamber 154a-2, following the suction chamber 154a, is set to a suction pressure Pa-2, for example, a wind speed Pa-2 of 3.8 when manufacturing a nonwoven fabric C having a basis weight of 10 to 30 g/m ^2. Here, like the suction pressure Pa, this 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 kept low at about half the suction pressure Pa because the filament aggregate Fa is sandwiched as it is between the collecting belts 151, 152 of the main conveyor 51 and the sub-conveyor 52.

In the suction chamber 154b, the suction pressure Pb is set to, for example, an air speed Pb = 6.0 when manufacturing a nonwoven fabric C with a basis weight of 10 to 30 g/m ^2. Like the suction pressure Pa, this suction pressure (air 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 since the filament aggregate Fab on the collecting belt 151 of the main conveyor 51 is sucked in between, it is kept low so as not to restrict the movement of the collecting belt 151.

The suction chamber 154b-2 is connected to the suction chamber 154b, and has a suction pressure Pb-2 set to an air speed Pa of 3.2 when manufacturing a nonwoven fabric C having a basis weight of 10 to 30 g/m ^2. Here, the suction pressure (air speed) Pb-2 is set to a level that maintains the shape of the filament aggregates Fb and Fab sucked and held in a sheet shape, similar to the suction pressure Pb, regardless of the basis weight (weighing) of the filament aggregates Fb and Fab. Since the filament aggregates Fb and Fab are sandwiched between the collecting belts 151 and 153 of the main conveyor 51 and the sub-conveyor 53 as they are, the suction pressure is set to a very low value, and the filament aggregates F with a smaller basis weight are set to be sucked more strongly so that they are reliably sucked and held and enter between the collecting belts 151 and 153. In addition, the sheet-like filament aggregate Fc collected and held by the collecting belt 153 is sandwiched and sucked and held in a superimposed state on the sheet-like filament aggregate Fab on the collecting belt 151 of the main conveyor 51 below this sub-conveyor 53, and is transported downstream.

The suction chamber 154c has a suction pressure Pc set to Pa=7.4 when manufacturing a nonwoven fabric C having a basis weight of 10 to 30 g/m ^2. This suction pressure (wind speed) Pc is set to a strong value, similar to the suction pressures Pa and Pb, regardless of the basis weight of the filament aggregate Fc, since the filament aggregate Fc is collected and formed on the collecting belt 153 of the sub-conveyor 53; however, since the filament aggregate Fabc on the collecting belt 151 of the main conveyor 51 is sucked in between, the suction pressure Pc is kept low so as not to restrict the movement of the collecting belt 151.

The suction chamber 154c-2 is connected to the suction chamber 154c and has a suction pressure Pb-2 set to Pa=3.2-3.8 when manufacturing a nonwoven fabric C having a basis weight of 10-30 g/m ^2. This suction pressure (wind speed) Pc-2 is set lower than the suction pressure Pa depending on 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.

In the nonwoven fabric manufacturing device M, the line speed of the collecting belts 151, 152, and 153 is 100 to 1200 m/min. The fiber discharge rate of the ejection devices 10A and 10C is 0.2 to 1.0 g/hole/min, and the fiber discharge rate of the ejection device 10B is 0.2 to 1.0 g/hole/min. The filament aggregates Fa and Fc (crimped fiber layer C1) are produced at a spinning speed of 1200 to 6500 m/s, and the filament aggregate Fb (spunbond fiber layer C2) is produced at a spinning speed of 100 to 1200 m/s. In the nonwoven fabric C produced under these conditions, the fiber diameter in the crimped fiber layer C1 is 8 to 30 μm, and the fiber diameter in the spunbond fiber layer C2 is 30 to 100 μm.

In the spunbond fiber layer C2, it is necessary to adjust the fibers so that they are oriented almost straight in the MD direction. This adjustment can be performed, for example, by installing an adjustment roller 162 that pulls the spunbond fibers at line speed on the upper surface 152a of the collection belt 152 of the nonwoven fabric manufacturing device M, so that the fibers can be oriented straight in the MD direction. The adjustment roller 162 may also be equipped with a cooling function to cool the fibers.

Even if the roller 162 is not installed, the fibers can be aligned straight in the MD direction by matching the spinning speed in the ejection device 10B with the line speed of the collection belt 152. The spinning speed in the ejection device 10B can be adjusted by the ejection pressure of the ejection device 10B.

The spinning speed in the ejection devices 10A and 10C is set faster than the line speed of the collection belts 151 and 153. This allows the fibers to be deposited in a loop (spiral) shape on the collection belts 151 and 153, creating a crimped fiber layer C1. The crimped fiber layer C1 has a width shrinkage (reduction rate of the original roll width after a width of 230 mm and a load of 2 kg are applied for 30 seconds) of less than 15%, and a bulkiness (the reciprocal of the density) of 20 or more.

The manufacturing method described above produces the nonwoven fabric C of this embodiment. The nonwoven fabric C of this embodiment maintains its bulk and can achieve stable operation when used as a material.

<Other embodiments>
Although the above-mentioned embodiments of the present invention have been described, the above-mentioned various embodiments can be combined as much as possible. In addition, the nonwoven fabric C according to the above-mentioned embodiment has a three-layer structure in which two crimped fiber layers C1 are arranged and a spunbond fiber layer C2 is arranged between them, but the present invention is not limited to this. For example, the nonwoven fabric C may have a two-layer structure in which a crimped fiber layer C1 and a spunbond fiber layer C2 are laminated. In addition, when the nonwoven fabric C has a three-layer structure, the spunbond fiber layer C2 does not have to be arranged between the two crimped fiber layers C1, and for example, the spunbond fiber layer C2, the crimped fiber layer C1, and the crimped fiber layer C1 may be laminated in this order. In addition, the nonwoven fabric C may be configured to have four or more layers as long as it has at least one spunbond fiber layer C2. In addition, the nonwoven fabric manufacturing apparatus M can be appropriately changed according to the nonwoven fabric C to be manufactured.

In addition, in the nonwoven fabric manufacturing apparatus M, if the fiber discharge speed of the ejection device 10B can be matched to the line speed of the repair belt 151, the sub-conveyor 52 does not need to be provided.

C. Nonwoven fabric C1. Crimped fiber layer C2. Spunbond fiber layer M. Nonwoven fabric manufacturing apparatus 10, 10A, 10B, 10C. Spraying device 20. Spinning device 30. Cooling air device 40. Injector 50. Collection conveyor 51. Main conveyor 52, 53. Sub-conveyor 54. Suction box 60. Embossing device 70. Winder 141, 14 2. Guide plates 151, 152, 153. Collection belts 154a, 154b, 154c. Suction chamber 162. Adjustment roller f. Filament fr. Rotation diameter F, Fa, Fab, Fabc, Fb, Fc. Filament assembly Lc. Intersection Ld. Opening interval Lr. Evacuation interval P, Pa, Pb, Pc, Pe, Pm, Ps. Suction pressure (wind speed)

Claims (2)

A method for producing a nonwoven fabric composed of a plurality of fiber layers, comprising the steps of:
forming a first fiber layer made of crimped fibers having a crimp number of 15 or more per 25 mm;
forming a second fiber layer having a fiber diameter of 2 to 100 denier and fibers oriented in the MD direction;
Including ,
In the step of forming the second fiber layer, the fibers are pulled by a roller at a speed at which the fibers are conveyed in order to orient the fibers in the MD direction.
Nonwoven fabric manufacturing method . A nonwoven fabric manufacturing apparatus for manufacturing a nonwoven fabric composed of a plurality of fiber layers, the nonwoven fabric manufacturing apparatus comprising: a fiber spraying device that sprays fibers; and a sheet conveying device that collects the bundle of fibers sprayed from the fiber spraying device on a conveying surface, forms the bundle of fibers into a sheet-like nonwoven fabric, and conveys the bundle in a conveying direction,
The fiber spraying device is
A first fiber spraying device that sprays filaments in a bundle to form a first fiber layer made of crimped fibers having a crimp number of 15 or more per 25 mm;
a second fiber spraying device for spraying filaments in a bundle to form a second fiber layer having a fiber diameter of 2 to 100 denier and fibers oriented in the MD direction;
having
the nonwoven fabric manufacturing apparatus includes a roller that pulls the fibers forming the second fiber layer at a speed at which the fibers forming the second fiber layer are conveyed in order to orient the fibers forming the second fiber layer in the MD direction;
Nonwoven fabric manufacturing equipment.

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