JP2023061359A - Fabric production method of nonwoven fabric, nonwoven fabric, and production apparatus of nonwoven fabric - Google Patents

Abstract

To provide a nonwoven fabric made from polylactic acid.SOLUTION: A production method of nonwoven fabric made from polylactic acid-based raw material includes a spinning step of discharging a molten polylactic acid-based resin from a nozzle and drawing the polylactic acid-based resin into a fibrous form with air stream, and a fusing step of fusing the polylactic acid-based fibers passing through a heated roll. In the spinning step, the fiber diameter of the polylactic acid-based resin is 15 μm or less.SELECTED DRAWING: Figure 5

Description

TECHNICAL FIELD The present invention relates to a nonwoven fabric manufacturing method, a nonwoven fabric, and a nonwoven fabric manufacturing apparatus.

Conventionally, a method for producing a nonwoven fabric containing a plurality of fiber layers is known (for example, Patent Document 1). Raw materials for non-woven fabrics are generally thermoplastic resins such as polypropylene (PP).

JP 2021-70875 A

By the way, in recent years, attention has been paid to biodegradable nonwoven fabrics that are decomposed in the natural world. Polylactic acid (PLA) is used as a raw material for biodegradable nonwoven fabrics. Since polylactic acid has a slower crystallization speed than thermoplastic resins such as polypropylene, there is a problem that polylactic acid does not crystallize under conventional manufacturing conditions for nonwoven fabrics using thermoplastic resins as raw materials. If uncrystallized polylactic acid fibers are passed through a hot roll to fuse the fibers together, the fibers stick to the hot rolls, making it impossible to manufacture nonwoven fabrics using polylactic acid as a raw material. Gone.

An object of the present invention is to provide a nonwoven fabric using polylactic acid as a raw material.

A method for manufacturing a nonwoven fabric according to one aspect of the present invention is a method for manufacturing a nonwoven fabric using a polylactic acid as a raw material, in which a melted polylactic acid resin is discharged from a die and the polylactic acid resin is stretched by an air flow. It includes a spinning step to make it fibrous, and a fusion step of passing the polylactic acid-based resin fibers through a hot roll to fuse the fibers, and in the spinning step, the fiber diameter of the polylactic acid-based resin is 15 μm. It is assumed that:

In the spinning step, the drawing speed for drawing the polylactic acid resin may be 180000/min or more.

A crystal nucleating agent may not be added to the polylactic acid-based resin.

In the spinning step, a discharge amount of the polylactic acid-based resin from the spinneret may be 0.5 g/min/hole or less.

In the spinning step, the polylactic acid-based resin may be cooled by cooling air between the spinneret and a drawing device for drawing the polylactic acid-based resin.

In the spinning process, air may be allowed to flow in from the outside.

Moreover, the present invention can be grasped from the side of the nonwoven fabric. For example, the present invention provides a nonwoven fabric formed by passing fibers through a hot roll and fusing the fibers, and using polylactic acid as a raw material, wherein the fiber diameter of the polylactic acid resin is 15 μm or less. may

According to the present invention, a nonwoven fabric using polylactic acid as a raw material can be realized.

FIG. 1 is a plan view of a nonwoven fabric according to an embodiment. FIG. 2 is a cross-sectional view of the nonwoven fabric according to the embodiment. FIG. 3 is a table relating to manufacturing conditions for nonwoven fabrics. FIG. 4 is a graph representing fiber speed during the spinning process. FIG. 5 is a flow chart regarding a method for manufacturing a nonwoven fabric according to an embodiment. FIG. 6 is a diagram showing a nonwoven fabric manufacturing apparatus for manufacturing a nonwoven fabric according to the embodiment. FIG. 7 is a table showing experimental results regarding the relationship between the surface temperature of the hot roll and the degree of sticking to the hot roll when polylactic acid fibers are passed through the hot roll. FIG. 8 is a table showing an example of manufacturing conditions for a nonwoven fabric.

Embodiments of the present invention will be described below with reference to the drawings. 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 a nonwoven fabric C according to this embodiment as viewed from above. FIG. 2 is a cross-sectional view in the CD direction when the nonwoven fabric C is cut along line AA shown in FIG. The nonwoven fabric C is a sheet whose longitudinal direction is the MD direction, and is composed of a plurality of layers.

As shown in FIG. 2, the nonwoven fabric C has a layer structure in which three fiber layers C1 are laminated. In the nonwoven fabric C, the fiber layers C1 are compression-bonded to each other by embossing. Embossing is performed by passing the nonwoven fabric C through a heated roll heated to a predetermined temperature, thereby fusing the fibers. The nonwoven fabric according to this embodiment is a thermal bonded nonwoven fabric formed by fusing fibers together with a hot roll. The embossed area ratio is 5% or more and 25% or less, more preferably 6% or more and 20% or less. Moreover, the basis weight of each fiber layer is 10 g/m ² (gsm) or more and 30 g/m ² or less. Such a nonwoven fabric C is suitable as a material for absorbent articles such as diapers and masks.

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

Polylactic acid has a slower crystallization speed than thermoplastic resins such as polypropylene (PP). When a nonwoven fabric made of polylactic acid is produced by the spunbond method, the manufacturing conditions for the nonwoven fabric made of polypropylene are that the polylactic acid discharged from the spinneret (discharge port, spinneret 23 shown in FIG. 6) in the spinning process is The fibers do not crystallize on the conveyor. Polylactic acid with a low degree of crystallinity has low heat resistance, so if you try to fuse fiber layers of polylactic acid with a low degree of crystallinity with a hot roll, the fibers with low heat resistance stick to the hot roll. It sticks. In addition, since polylactic acid with insufficient crystallinity causes heat shrinkage when heated, when polylactic acid fiber with low crystallinity is passed through a hot roll, heat shrinkage occurs and the surface becomes uneven. There is a problem. Moreover, the glass transition temperature of polylactic acid is about 60°C. In general, when a thermoplastic resin is not crystallized or has a low degree of crystallinity and is heated to a temperature higher than the glass transition temperature of the fiber by a hot roll, the fiber sticks to the hot roll. In order to solve these problems, it is possible to adopt a method of increasing the crystallinity of the resin by adding a crystal nucleating agent (nucleating agent) to the raw material polylactic acid. Another problem arises that the crystal nucleating agent remains. In addition, if the raw material resin of the nonwoven fabric contains a crystal nucleating agent, it is difficult to strongly pull the fibers in the spinning process, resulting in an increase in fiber diameter. As the fiber diameter of the non-woven fabric increases, the non-woven fabric becomes harder and less comfortable on the skin. A non-woven fabric that feels bad on the skin is not suitable as a material for absorbent articles or masks.

Therefore, the inventors of the present application found conditions for increasing the crystallinity of polylactic acid and preventing the fibers of polylactic acid from sticking to the heating roll, because the heat resistance of polylactic acid increases when the degree of crystallinity is high. rice field. The inventors of the present application have found that when the fiber diameter of polylactic acid is 15 μm or less, the degree of crystallinity increases and the fibers do not stick to the heating roll (Experimental Example 1). That is, the inventors of the present application have found that the crystallinity of thermoplastic resin fibers increases as the fiber diameter decreases. Polylactic acid, which has a slower crystallization rate than polypropylene, is considered to be placed on the conveyor in an amorphous state after the spinning process under the manufacturing conditions for nonwoven fabrics using polypropylene as a raw material. It is believed that the fiber sticks to the heat roll when the lactic acid fiber is heated to about the glass transition temperature (60° C.) of polylactic acid by the heat roll.

In addition, the inventors of the present application have found that the fiber diameter of polypropylene increases when the amount of fiber discharged from the spinneret in the spinning process is increased, but the fiber diameter of polylactic acid increases even if the fiber discharge rate of the fiber from the spinneret is increased in the spinning process. was almost unchanged (Experimental Example 2). In other words, even if the amount of fiber ejected from the spinneret changes during the spinning process, the fiber diameter of the polylactic acid is almost the same after being fined to the spinning limit.

In addition, the inventors of the present application have found that polylactic acid tends to make the fibers thinner as the fibers are pulled (Experimental Example 3). Note that Experimental Example 3 is performed by changing the ejector pressure.

In addition, the inventors of the present application have found that even if the fiber diameter of polypropylene and polylactic acid after completion is the same, the amount of stretching increases and the degree of crystallinity tends to increase when the discharge rate of the fiber is large. (Experimental Example 4). This means that the higher the fiber discharge rate, the higher the crystallinity.

FIG. 3 is a table relating to manufacturing conditions for nonwoven fabrics. In the table of FIG. 3, each of the 12 manufacturing conditions is numbered 1-12. Each number in the "No." column indicates the number assigned to each manufacturing condition. "+Nucleating agent" in the "raw material" column indicates that a crystal nucleating agent is added to polylactic acid. Each numerical value in the column of "discharge amount (g/min/hole)" indicates the amount of fiber discharged per minute from the spinneret 23 shown in FIG. Each numerical value in the "injector pressure (Mpa)" column indicates the pressure of the injector 40 shown in FIG. Each numerical value in the "diameter (μm)" column indicates the fiber diameter (fiber diameter) after the spinning process. In manufacturing condition No. 7, the fiber diameter was not measured because a phenomenon in which the fiber was cut (thread breakage) occurred after the spinning process. Each numerical value in the "Crystallinity" column indicates the crystallinity of the fiber after the spinning process. In manufacturing condition No. 7, the degree of crystallinity was not measured because a phenomenon in which fibers were cut (thread breakage) occurred after the spinning process. The numerical value (145° C.) in the “heat roll temperature (° C.)” column indicates the surface temperature of the heat roll in the fusion bonding step. The "Sticking Phenomenon" column indicates whether or not the fiber sticks to the heat roll.

The manufacturing conditions, which are an example of Experimental Example 1 above, are the numerical values shown in the columns of "Diameter" and "Sticking Phenomenon". As shown in the columns of "diameter" and "sticking phenomenon" for each production condition, when the fiber diameter of polylactic acid was 15 μm or less, the degree of crystallinity was 35% or more, and the sticking phenomenon did not occur. On the other hand, when the fiber diameter of polylactic acid was larger than 15 μm, the degree of crystallinity was less than 35, resulting in a sticking phenomenon. For example, as shown in the columns of Nos. 1, 10, and 11 "diameter" and "sticking phenomenon".

The manufacturing conditions, which are an example of Experimental Example 2 above, are the numerical values shown in the columns of "discharge rate" and "diameter". As shown in the columns of "Discharge amount" and "Diameter" for each production condition, the fiber diameter of polylactic acid did not change due to the fact that the amount of fiber discharged from the spinneret was increased in the spinning process. For example, as shown in the columns of Nos. 9, 10, and 11 "discharge rate" and "diameter".

The manufacturing conditions, which are an example of Experimental Example 3 above, are the numerical values shown in the columns of "injector pressure" and "diameter". As shown in the "injector pressure" and "diameter" columns for each manufacturing condition, the more the polylactic acid fiber is pulled, the thinner the fiber becomes. For example, as shown in the columns of Nos. 9, 10 and 11 "injector pressure" and "diameter".

The production conditions, which are an example of Experimental Example 4 above, are the numerical values shown in the columns of "injector pressure" and "crystallinity". As shown in the columns of "injector pressure" and "crystallinity" for each production condition, the greater the pulling amount, the higher the crystallinity. For example, as shown in the columns of Nos. 2 and 3, "injector pressure" and "crystallinity".

As shown in the table of FIG. 3, by setting the fiber diameter of polylactic acid to 15 μm or less, the degree of crystallinity of the polylactic acid resin can be increased to 35% or more. Even when the fiber diameter is larger than 15 μm, the degree of crystallinity can be increased to 35% or more by adding a crystal nucleating agent to the polylactic acid. By setting the crystallinity of the polylactic acid resin to 35% or more, it is possible to suppress thermal shrinkage of the polylactic acid fibers in the fusion bonding step.

In addition, the inventors of the present application have found that the fiber diameter can be reduced when the amount of polylactic acid fiber discharged increases, so that the degree of crystallinity of the polylactic acid resin increases. It is presumed that when the ejection amount is increased, the crystallinity of the polylactic acid resin is increased because the molecules are highly oriented. Accordingly, the inventors of the present application have found that the degree of crystallinity of polylactic acid can be increased by adjusting the fiber drawing speed. If the discharge rate is increased, the fiber speed (yarn speed) is increased even if the fiber diameter is the same, and the fiber drawing time is shortened. In the spinning process, the faster fiber speed reduces the time it takes the yarn to pass from the spinneret to the ejector. In addition, the drawing speed is increased even if the fiber pulling speed is the same at the same drawdown rate (drawing ratio, yarn speed at the ejector/yarn speed at the spinneret). However, since it is actually difficult to measure how the fiber speed changes in the spinning process, the average speed is calculated for convenience from the average speed of the first and last yarns that can be calculated.

Here, a method for calculating a convenient average speed of fibers in the spinning process will be described with reference to FIG. FIG. 4 is a graph representing fiber speed during the spinning process. The horizontal axis of FIG. 4 represents the position of the fiber. In the graph of FIG. 4, the origin is the base position, and the horizontal axis represents the position of the fiber up to the injector (injector 40 shown in FIG. 6). The vertical axis in FIG. 4 represents the fiber speed. The fiber speed at the spinneret is V1, and the fiber speed at the injector is V2. Further, the line L1 in FIG. 4 represents the transition of the fiber speed when the fiber discharge amount is relatively small, and the line L2 in FIG. 4 represents the transition of the fiber speed when the fiber discharge amount is relatively large. there is Actually, the fiber speed changes in curves like lines L1 and L2, but it is difficult to measure the fiber speed at each position. The average speed for convenience is calculated by the following equation (1). In the graph of FIG. 4, V1 and V2 represent fiber velocities when the fiber discharge amount is relatively large, represented by line L2.
(Number 1)
Average speed=(V1+V2)/2 (1)
Also, the transit time of the fiber is calculated by the following formula (2).
(Number 2)
Passage time=2L/(V1+V2) (2)
Then, the drawdown rate (ratio of drawing the yarn, draw ratio) is calculated by the following formula (3).
(Number 3)
Drawdown rate = V2/V1 (3)
Then, the drawing speed is calculated by the following formula (4).
(Number 4)
Stretching speed=drawdown rate/passing time=V2/V1×(V1+V2)/2L (4)
This stretching speed (1/min) is used as a parameter. In the present embodiment, in the spinning process, the drawing speed for drawing the polylactic acid resin is set to 180000/min or more.

Also, if the fiber diameter is the same, the drawdown rate does not depend on the amount of fiber discharged. Note that the drawdown rate is an index of how much the fiber is stretched by the ejector. In addition, the larger the amount of polylactic acid fiber discharged, the smaller the fiber diameter and the higher the degree of crystallinity of the polylactic acid, which increases the thermal stability and strength of the fiber. Incidentally, as described above, the polylactic acid resin is stretched in a short time, the molecular orientation progresses in the stretching step, and the degree of crystallinity increases.

In the present embodiment, by manufacturing a fiber layer using polylactic acid as a raw material under the conditions described above, the degree of crystallinity of the resin is increased, and even if this fiber layer is heated with a hot roll, the fiber sticks to the hot roll. can be prevented. Therefore, according to this embodiment, a nonwoven fabric using polylactic acid as a raw material can be realized.

In the present embodiment, no crystal nucleating agent is added to the raw material polylactic acid. As a result, the nonwoven fabric according to this embodiment does not contain a crystal nucleating agent. Thereby, the nonwoven fabric according to the present embodiment does not leave the crystal nucleating agent after being decomposed in the natural world. In addition, if the raw material resin contains a crystal nucleating agent, the resin cannot be strongly pulled in the spinning process, resulting in thick fibers. In addition, the use of the crystal nucleating agent increases the manufacturing cost of the nonwoven fabric. However, since the nonwoven fabric according to the present embodiment does not contain a crystal nucleating agent, these problems do not occur. The nonwoven fabric according to this embodiment does not contain a crystallization accelerator. In the method for producing a nonwoven fabric according to this embodiment, it is not necessary to add a crystallization accelerator to the polylactic acid.

Next, based on FIG. 5, the manufacturing method of the nonwoven fabric which concerns on this embodiment is demonstrated. FIG. 5 is a flow chart relating to the method for manufacturing a nonwoven fabric according to this embodiment. First, in the manufacturing method according to the present embodiment, a molten polylactic acid resin is discharged vertically downward from a spinneret, and the resin is pulled vertically downward by an air current to form fibers (step S101, the “spinning step” referred to in the present application). example). In this spinning process, the fiber diameter is set to 15 μm or less. In step S102 following step S101, the fibers are deposited on a conveyor and conveyed (an example of the "conveyance step" referred to in the present application). The fiber conveying speed in the conveying step may be 40 m/min or more and 120 m/min or less. In step S103, which follows step S102, the fibers laminated in three layers are passed through hot rolls to fuse the fibers (an example of the "fusion step" referred to in the present application).

Next, based on FIG. 6, the nonwoven fabric manufacturing method and manufacturing apparatus according to the present embodiment will be described. FIG. 6 is a diagram showing a nonwoven fabric manufacturing apparatus M for manufacturing a nonwoven fabric according to this embodiment. In FIG. 6, the nonwoven fabric manufacturing apparatus M is equipped with three sets of jetting devices (fiber jetting devices) 10, and each of the jetting devices 10 (10A, 10B, 10C) is a spinning device 20 (referred to as a "jetting device" in the present application). part"), a cold air device 30 (an example of the "cooling part" in the present application), and an injector 40 (an example of the "extending part" in the present application). The nonwoven fabric manufacturing apparatus M can manufacture three layers of the nonwoven fabric C by providing the ejection devices 10A, 10B, and 10C.

In the nonwoven fabric manufacturing apparatus M, together with the ejection device 10, a collection conveyor (an example of a "sheet conveying section" in the present application) 50, an embossing device 60 (an example of the "fusion section" in the present application), and a winder 70 are various. The processes are arranged serially so that they can be executed. The ejection devices 10A, 10B, and 10C are arranged in series in the conveying direction with respect to the conveying surface above the collection conveyor 50. As shown in FIG. The nonwoven fabric manufacturing apparatus M is constructed so as to continuously manufacture the nonwoven fabric C in which the direction toward the paper surface of FIG. The nonwoven fabric C is manufactured by a so-called spunbond manufacturing method, in which the fibers are appropriately bonded by embossing the fibers while the fibers are being embossed.

The spinning device 20 comprises an extruder 21 and a spinneret 23 . The extruder 21 melts the raw material resins R (R1, R2, R3) supplied to the hopper 22, and sends out a predetermined flow rate of melted material to the spinneret 23 by rotating the spiral rotor 21r. The spinneret 23 has a plurality of composite spinning nozzles (not shown) configured to discharge while forming the desired fibrous structure, and the melt from the extruder 21 into a plurality of filaments (fibers) f. A bundle (hereinafter referred to as "filament assembly") F is spun (discharged) in the direction of gravity. As the raw material resin R, a polylactic acid-based resin is employed as described above.

The cooling air device 30 includes a pair of open-type air 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 (gravitational direction). The cooling air device 30 cools the filament assembly F discharged from the spinning device 20 and passing downward from above by blowing cooling air Ac from each of the blowers 31 and 32 . Here, the cooling air device 30 is installed by installing a large type so that one blower 31 can be used as a main, and a small type is selected and installed so that the other blower 32 facing each other can be used as a sub. . In the open-type nonwoven fabric manufacturing apparatus M, air from the outside of the cold air device 30 can flow in during cooling by the cold air device 30 .

The injector 40 (an example of a "drawing device" referred to in the present application) applies downward high-pressure air as a driving fluid to the filament assembly F that descends so as to pass through the body 41 from above in the spinning direction. It has a structure that generates a low pressure region on the inlet side of the body 41 by blowing. The injector 40 pulls the descending filament assembly F into the low-pressure area on the entrance side of the body 41, and also pulls it downward with high-pressure air in the body 41, so that The filament assembly F descending from above in the spinning direction is drawn. The process (spinning process) of step S101 shown in FIG. 5 is the process from the time before the polylactic acid resin is discharged from the spinneret 23 of the spinning device 20 until the filament assembly is deposited on the collecting conveyor.

The collection conveyor 50 is constructed by including 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 net-like collection belt 151 wider than the width of the filament assembly F and permeable to the front and back is wound around a group of rollers 151r and driven to rotate. In the sub-conveyors 52 and 53, mesh collection belts 152 and 153, which are wider than the width of the filament assembly F and can be ventilated on the front and back sides, are wound around rollers 152r and 153r, respectively, and are oriented in opposite directions. It is installed so that it can be driven around.

The collection belt 151 has a length such that the upper surface 151a is reliably positioned at the ejection point below the ejection devices 10A, 10B, and 10C, and is wound around a group of rollers 151r. The filament assembly Fa stretched by the injector 40 is received and transported to collect it in a cloth-like (sheet-like) shape. That is, the collection belt 151 is driven to rotate from the upstream end (head) toward the downstream end (tail) in the direction of circulating movement (transportation direction) of the upper surface 151a, so that the sheet-like filament assembly is collected. It has a sufficient area to collect Fa and functions as a collection surface and a transport surface. In addition, the filament aggregate Fa becomes the fiber layer C1 on the lower layer side shown in FIG.

The collecting belt 152 is wound around a group of rollers 152r with its upper surface 152a positioned at a jetting position below the jetting device 10B, which is positioned in the middle of the circulating movement direction of the upper surface 151a of the collecting belt 151. The filament assembly Fb that is pulled down by is received and transported to collect it in the form of a sheet. Further, the collection belt 153 has the upper surface 153a positioned at the jetting position below the jetting device 10C positioned at the downstream end (the rearmost end) of the upper surface 151a of the collection belt 151 in the direction of revolving movement, and the rollers 153r group. , and collects the filament assembly Fc drawn down by the injector 40 in a sheet form by receiving and transporting the filament assembly Fc. In addition, the filament assembly Fb becomes the intermediate fiber layer C1 shown in FIG.

These collection belts 152 and 153 are installed at a position deviated downstream from below the ejection device 10A located at the upstream end (head) of the upper surface 151a of the collection belt 151 in the direction of revolving movement. Positioned between the upper surface 151a and the ejection devices 10B and 10C and driven to rotate in the reverse direction, the respective upper surfaces 152a and 153a serve as collecting surfaces and conveying surfaces for collecting the sheet-like filament aggregates Fb and Fc. function as These collection belts 152 and 153 are rotated so as to sandwich the sheet-like filament aggregates Fb and Fc between the collection belt 151 and the lower portion facing the upper surface (upper portion) 151a without peeling off and turning over. It functions to drive and assist transport to the downstream side.

The suction box 54 is accommodated in the collection belt 151 of the main conveyor 51 and divided into suction chambers 154a, 154a-2, 154b, 154b-2, 154c, and 154c-2 functioning as vacuum chambers. These suction chambers 154a to 154c-2 are provided with suction ports (not shown) so as to suck the upper portion, and are connected to individually drivable suction fans 155a to 155c-2 so as to be capable of suction.

The suction chambers 154a, 154b, 154c are installed below the injectors 40 of the ejection devices 10A, 10B, 10C, respectively. , 154b and 154c.

The suction chamber 154a is installed so as to be positioned directly below the collection belt 151 of the main conveyor 51 below the injector 40 of the ejection device 10A. Suction upwards from directly below.

The suction chamber 154a-2 is adjacent to the downstream side of the suction chamber 154a and, as will be described later, is positioned directly below the collection belt 151 of the main conveyor 51 between the suction chamber 154b positioned below the ejection device 10B. When the suction fan 155a-2 is driven to reduce the pressure, the collection belt 151 is sucked from directly below it.

As a result, the filament assembly Fa spun by the ejection device 10A is sucked 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. For this reason, the filament assembly Fa is collected and held in a sheet form on the upper surface 151a as the collection belt 151 revolves in the longitudinal direction, and is transported. After that, the filament assembly Fa is transferred from the suction chamber 154a to the adjacent suction chamber 154a-2 as the collection belt 151 rotates in the longitudinal direction, and is sucked so as to maintain the sheet shape. held and transported.

The suction chamber 154b is installed so as to be positioned directly below the collection belt 151 of the main conveyor 51 below the injector 40 of the ejection device 10B. , the upper part of the collection belt 152 of the sub-conveyor 52 is sucked from directly below.

The suction chamber 154b-2 is adjacent to the downstream side of the suction chamber 154b and, as will be described later, is positioned directly below the collection belt 151 of the main conveyor 51 between the suction chamber 154c positioned below the ejection device 10C. When the suction fan 155b-2 is driven to reduce the pressure, the collection belt 151 is sucked from directly below it.

As a result, the filament assembly Fa spun by the jetting device 10A is transferred to 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. It is sucked and held in the form of a sheet and transferred.

Also, the filament assembly Fb spun by the ejection device 10B is collected on the upper surface 152a of the collection belt 152 of the sub-conveyor 52 on the upper surface 151a by the suction chamber 154b below the collection belt 151 of the main conveyor 51. is attracted to Therefore, the filament assembly Fb is collected and held in a sheet form on the upper surface 152a as the collection belt 152 revolves in the longitudinal direction, and is transported.

By the way, since the collection belt 152 of the sub-conveyor 52 rotates in the opposite direction to the collection belt 151 of the main conveyor 51, the upper surface 152a of the collection belt 152 moves in the opposite direction and then is turned upside down. Then, they face the upper surface 151a of the collection belt 151 of the main conveyor 51 and move in the same direction. For this reason, the filament assembly Fb spun by the ejection device 10B is collected and held in a sheet form on the upper surface 152a of the collection belt 152 of the sub-conveyor 52, and after being transported, is transferred to the collection belt 151 of the main conveyor 51. The sheet-like filament assembly Fa on the upper surface 151a is overlapped with the sheet-like filament assembly Fa, and the sheet-like filament assembly Fa is sucked and held by the suction chamber 154b below the collection belt 151 of the main conveyor 51 and transferred.

As a result, the filament assembly Fab (Fa, Fb) collected and held in a sheet form and stacked under the jetting device 10B moves around the suction chamber 154b as the collecting belt 151 moves in the longitudinal direction. 154b-2, and transferred while being sucked and held so as to maintain the sheet shape.

The suction chamber 154c is installed so as to be positioned directly below the collection belt 151 of the main conveyor 51 below the injector 40 of the ejection device 10C. The upper part of the collecting belt 153 of the sub-conveyor 53 is sucked from directly below.

The suction chamber 154c-2 is adjacent to the downstream side of the suction chamber 154c and is installed so as to be positioned immediately below the end of the collection belt 151 of the main conveyor 51, as will be described later. 155c-2 is driven and decompressed, thereby sucking the collection belt 151 directly below and above.

As a result, the filament assembly Fab spun by the jetting devices 10A and 10B continues to the suction chambers 154a to 154b-2 described above, and then the collecting belt 151 of the main conveyor 51.
The lower suction chambers 154c and 154c-2 suck and hold the sheet-like sheet overlaid on the upper surface 151a and transfer it.

Also, the filament assembly Fc spun by the ejection device 10C is collected on the upper surface 153a of the collection belt 153 of the sub-conveyor 53 on the upper surface 151a by the suction chamber 154c below the collection belt 151 of the main conveyor 51. is attracted to Therefore, the filament assembly Fc is collected and held in a sheet form on the upper surface 153a as the collection belt 153 revolves in the longitudinal direction, and is transported. In addition, the filament assembly Fc becomes the fiber layer C1 on the upper layer side shown in FIG.

By the way, since 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, the upper surface 153a of the collecting belt 153 moves in the opposite direction and then turns upside down. Then, they face the upper surface 151a of the collection belt 151 of the main conveyor 51 and move in the same direction. Therefore, the filament assembly Fc spun by the ejection device 10C is collected and held in a sheet form on the upper surface 153a of the collecting belt 153 of the sub-conveyor 53, and then transferred to the collecting belt 151 of the main conveyor 51. The sheet-like filament assembly Fab on the upper surface 151a is overlapped with the sheet-like filament assembly Fab, and the suction chamber 154c under the collection belt 151 of the main conveyor 51 sucks and holds the sheet-like filament assembly Fab and transfers it.

Therefore, the filament assembly Fabc (Fa, Fb, Fc) collected and held in a sheet form and stacked under the jetting device 10C is sucked as the collecting belt 151 rotates in the longitudinal direction. The sheet is passed from the chamber 154c to the adjacent suction chamber 154c-2 and transferred while being sucked and held so as to maintain the sheet shape.

In short, the collection conveyor 50 is configured to form a sheet of a predetermined thickness by the suction box 54 on the upper surfaces 151a to 153a of the collection belts 151 to 153, and the filament aggregates Fa, Fb, and Fc spun by the ejection devices 10A, 10B, and 10C. The filament assembly Fabc (nonwoven fabric C) before embossing is made into a filament assembly Fabc (nonwoven fabric C) before embossing by collecting the filaments while holding them under vacuum, and then transferring them downstream to the sushi embossing device 60 . Note that the step of stacking and conveying the filament assembly on the collection conveyor is the step of step S102 shown in FIG.

The embossing device 60 includes a pair of embossing rolls (heat rolls) 61 and 62, and their cylindrical outer peripheral surfaces 61a and 62a are pressed against each other and relatively rotated. This embossing device 60 has a smooth cylindrical outer peripheral surface 61a of a lower embossing roll 61 and an embossing protrusion (not shown) arranged regularly or irregularly on a cylindrical outer peripheral surface 62a of an upper embossing roll 62 as desired. Press with a pressure contact force. The embossing area ratio may be 5% or more and 25% or less.

As a result, the embossing device 60 feeds out the filament assembly Fabc sandwiched between the embossing rolls 61 and 62 (an example of the “heat roll” referred to in the present application) in the relative rotation direction, and a plurality of filament aggregates Fabc corresponding to the formation positions of the embossing projections. The filaments f are embossed at the embossed portions to be pressed and joined while being entangled with each other, and processed into a nonwoven fabric C that maintains its sheet-like shape. The embossing projections formed on the cylindrical outer peripheral surface 62a of the embossing roll 62 may be formed on the cylindrical outer peripheral surface 61a side of the embossing roll 61, or may be formed on both of these cylindrical outer peripheral surfaces 61a and 62a. Furthermore, it is not limited to a convex shape, and may be formed in a concave shape and, for example, a continuous rib shape may be pressed against the mating cylindrical surface to be pressure-bonded. The embossing of the filament assembly Fabc filament assembly by the embossing device 60 is the process (fusion process) of step S103 shown in FIG. The surface temperature of the embossing rolls 61 and 62 is 110° C. or higher, preferably 120° C. or higher, and more preferably 145° C. or higher. By setting the surface temperature of the embossing rolls 61 and 62 to 120° C. or more, sticking of fibers to the embossing rolls 61 and 62 can be prevented without coating the embossing rolls 61 and 62 with a release agent.

The winder 70 receives the nonwoven fabric C in which the filaments f of the filament assembly Fabc are entangled and joined by the embossing device 60 while adjusting the tension so as not to loosen the nonwoven fabric C, and continuously winds the nonwoven fabric C into a desired winding without wrinkles. Wind up into a roll with firmness.

As a result, the winder 70 can prepare a desired length of the nonwoven fabric C in which the filament assembly Fabc is formed into a sheet and wound into a roll so that it can be supplied to the next processing step or the like.

In the collection conveyor 50 of the present embodiment, as described above, the suction chambers 154a to 154c-2 of the suction box 54 installed under the collection belt 151 of the main conveyor 51 are the injectors of the ejection devices 10A to 10C. The suction fans 155a to 155c-2 connected to each of the suction chambers 154a to 154c-2 are divided and installed so as to correspond to every 40 units, and the suction fans 155a to 155c-2 connected to the suction chambers 154a to 154c-2 are divided and installed according to the required suction pressure. It is set to suck at the corresponding wind speed (air volume). Here, the partition range and suction pressure of the suction chambers 154a to 154c-2 may be appropriately set.

Specifically, the suction chamber 154a captures the filament assembly Fa 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 intervention of a sub-conveyor. It is sucked from below the collecting belt 151 to collect and hold it in the form of a sheet.

The suction chamber 154a is partitioned so that a suction pressure Pa capable of stably holding the descending filament assembly Fa is generated under the conveying surface of the collecting belt 151 in a narrow range about the spraying region in the transport direction. The inside of the partitioned area is sucked by the suction fan 155a and the pressure is reduced to a negative pressure.

The suction chambers 154b and 154c suck the filament aggregates Fb and Fc pulled down from the exits 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, respectively. The particles are sucked from below the collecting belt 151 via 52 and 53 to be collected and held in the form of a sheet. These sub-conveyors 52 and 53 sandwich the sheet-like filament aggregates Fb and Fc collected and held on the collection belts 152 and 153, respectively, between them and the collection belt 151 at the bottom to transport the filament assembly Fab. , Fabc downstream.

These suction chambers 154b and 154c are equipped with suction fans 155b and 155c so that suction pressures Pb and Pc capable of stably holding the descending filament aggregates Fb and Fc are generated below the conveying surfaces of the collecting belts 152 and 153. It is driven to a negative pressure. Similar to the suction chamber 154a, these suction chambers 154b and 154c are designed so that the desired suction pressures Pb and Pc are generated in a narrow division range equivalent to the jetting region of the descending filament aggregates Fb and Fc in the transfer direction. , and suction fans 155b and 155c to create a negative pressure. At the same time, these suction chambers 154b and 154c suck the collection belts 152 and 153 of the sub-conveyors 52 and 53 through the filament aggregates Fab and Fabc on the collection belt 151, respectively. For this reason, these suction chambers 154b and 154c adjust the suction range in the transfer direction under the collection belt 151 so that the optimum suction pressures Pb and Pc are generated on the collection belts 152 and 153, thereby increasing the suction volume. It may be increased or decreased, and the collection belts 152 and 153 may also be partitioned so that the suction range can be adjusted.

As a result, the suction chambers 154b and 154c continue to suck and hold the filament aggregates Fab and Fabc increased from the sheet-like filament aggregate Fa via the collection belt 151 of the main conveyor 51, similarly to the suction chamber 154a. can do.

The suction chambers 154a-2, 154b-2 and 154c-2 respectively continuously feed the sheet-like filament aggregates Fa, Fab and Fabc on the collecting belt 151 of the main conveyor 51 downstream of the suction chambers 154a, 154b and 154c. Aspirate and hold.

These suction chambers 154a-2, 154b-2 and 154c-2 have suction pressures Pa-2 and Pb-2 for continuously sucking and holding the sheet-like filament aggregates Fa, Fab and Fabc on the collection belt 151, respectively. , Pc-2 is driven to create a negative pressure. The suction chambers 154a-2 and 154b-2 are interposed between the suction chambers 154a, 154b and 154c and are continuous so as to suck without gaps. It is installed to suck a wider division range so as to connect the In addition, the suction chamber 154c-2 is installed so as to suction a relatively short sectioned range because it only transfers the sheet-like filament assembly Fabc received from the suction chamber 154c to the embossing device 60 adjacent on the downstream side. ing.

As a result, the suction chambers 154a-2, 154b-2, and 154c-2 respectively suck the sheet-like filament aggregates Fa, Fab, and Fabc located on the upper surface 151a via the collecting belt 151 of the main conveyor 51. Suction and hold can be continuously applied to chambers 154a, 154b, 154c. At this time, since the sheet-like filament aggregates 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, the sub-conveyors 52 and Fab do not float up. It is sandwiched between collection belts 152 and 153 of 53. The sheet-like filament aggregates Fa and Fab are collected and held by the collecting belts 152 and 153, and the sheet-like filament aggregates Fb and Fc which are turned upside down are superimposed to obtain the sheet-like filament aggregates Fab, It is made Fabc and transferred downstream while being sucked and held.

The collecting conveyor 50 applies a sufficient suction pressure P to collect and hold the sheet-like filament assembly F on the collecting belt 151 of the main conveyor 51, as described above. The individual suction fans 155a to 155c-2 are set to draw at the required wind speeds so as to occur every 154c-2. The relative relationship (strength) of the suction pressure P on the collection surface (conveyance surface) of the filament assembly F in each of the suction chambers 154a to 154c-2, which will be described below, depends on the connection points of the suction fans 155a to 155c-2. A description will be given by calculating a wind speed value corresponding to the space to the collection surface and using it as a substitute.

For example, the suction box 54 is arranged such that the suction pressures Pa, Pb, and Pc of the suction chambers 154a, 154b, and 154c located at the locations where the filament aggregates F are jetted by the jetting devices 10A, 10B, and 10C on the collection conveyor 50 are respectively downstream. are adjusted to be greater than the suction pressures Pa-2, Pb-2 and Pc-2 of the suction chambers 154a-2, 154b-2 and 154c-2 located on the side. In addition, the suction pressure Ps (Pa, Pa-2) of the suction chambers 154a, 154a-2 on the leading side in the transfer direction of the filament aggregate F, and the suction pressure Pm ( Pb, Pb-2) and the suction pressure Pe (Pc, Pc-2) of the suction chambers 154c, 154c-2 on the rearmost side. The positional suction pressure Pm can be adjusted to be lower than the leading side suction pressure Ps and the rearmost side suction pressure Pe (Ps>Pm and Pe>Pm). Moreover, each suction pressure Pa, Pb, Pc
In other words, it is adjusted according to the basis weight of the filament assembly F on the conveying surface so that the suction chambers 154a, 154b, and 154c are not excessively decompressed and the smooth relative movement of the collection belt 151 is not hindered. .

Specifically, the suction chamber 154a is wound into a roll by the winder 70, for example, as the suction pressure Pa in the collection belt 151 of the main conveyor 51 that collects and holds the filament assembly Fa spun by the ejection device 10A in a sheet form. The wind speed Pa is set to 7.5 when manufacturing the nonwoven fabric C having a basis weight of 10 to 30 g/m ² of the semi-finished product. The suction pressure (wind speed) Pa is the point where the filament assembly Fa is sucked to start collecting and holding it in a sheet form. It is set to a strong value so that

The suction chamber 154a-2 follows the suction chamber 154a, and similarly, the suction pressure Pa-2 is set to, for example, a wind speed Pa-2 of 3.8 when manufacturing a nonwoven fabric C with a basis weight of 10 to 30 g/m ² . is set to Here, the suction pressure (wind speed) Pa-2 may be such that the sheet-like shape is maintained by suction regardless of the basis weight (weighing weight) of the filament assembly Fa, similarly to the suction pressure Pa. , is sandwiched between the collecting belts 151 and 152 of the main conveyor 51 and the sub-conveyor 52 as it is, so the suction pressure Pa is suppressed to about half of the suction pressure Pa.

The suction pressure Pb in the suction chamber 154b is set at, for example, a wind speed Pb of 6.0 when fabricating a nonwoven fabric C with a basis weight of 10 to 30 g/m ² . Similar to the suction pressure Pa, the suction pressure (wind speed) Pb is set to be high regardless of the basis weight because the filament assembly Fb is collected and formed into a sheet on the collection belt 152 of the sub-conveyor 52. However, since the filament assembly Fab on the collection belt 151 of the main conveyor 51 is sucked while intervening, it is kept low so as not to limit the movement of the collection belt 151 .

In the suction chamber 154b-2, following the suction chamber 154b, the suction pressure Pb-2 is set to, for example, a wind speed Pa of 3.2 when manufacturing a nonwoven fabric C with a basis weight of 10 to 30 g/m ² . Here, the suction pressure (wind speed) Pb-2 maintains a sheet-like suction-held shape regardless of the basis weight (weighing weight) of the filament aggregates Fb and Fab, similarly to the suction pressure Pb. Since it is sandwiched between the collection belts 151 and 153 of the main conveyor 51 and the sub-conveyor 53 as it is, it is suppressed to a very low value and is reliably sucked and held between the collection belts 151 and 153. The filament assembly F with a smaller basis weight is set to be strongly attracted so as to enter into the . On the collection belt 151 of the main conveyor 51 under the sub-conveyor 53, the sheet-like filament assembly Fc collected and held by the collection belt 153 is sandwiched in a state of being superimposed on the sheet-like filament assembly Fab. It is sucked and held and transferred downstream.

The suction pressure Pc of the suction chamber 154c is set to Pa=7.4, for example, when fabricating a nonwoven fabric C with a basis weight of 10 to 30 g/m ² . Similar to the suction pressures Pa and Pb, the suction pressure (wind speed) Pc is set to a strong value regardless of the basis weight because the filament assembly Fc is collected and formed on the collection belt 153 of the sub-conveyor 53. However, since the filament assembly Fabc on the collection belt 151 of the main conveyor 51 is sucked while intervening, it is kept low so as not to limit the movement of the collection belt 151 .

The suction chamber 154c-2 follows the suction chamber 154c and has a suction pressure Pb-2 of, for example, Pa=3.2 to 3 when manufacturing a nonwoven fabric C having a basis weight of 10 to 30 g/m ² .
. set to 8. The suction pressure (wind speed) Pc-2 is set so that the collection belt 151 of the main conveyor 51 reliably sucks and holds the filament assembly Fabc carried out from under the sub-conveyor 53 and delivers it to the embossing device 60. It is set to be lower than the suction pressure Pa according to the basis weight.

In addition, in the nonwoven fabric manufacturing apparatus M, the collection belts 151, 152, 153 have a line speed of 40 m/min or more and 120 m/min or less. In addition, 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 to 150 m/s). Further, 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 jet pressure of the jetting devices 10A, 10B and 10C.

By the manufacturing method described above, it is possible to manufacture a non-woven fabric using a polylactic acid-based resin as a raw material. Although the raw material is polylactic acid, the nonwoven fabric may contain monomers other than polylactic acid as long as the effects of the present invention are not impaired. Lactic acid includes L-lactic acid and D-lactic acid, which are optical isomers. Polylactic acid, which is a polymer of L-lactic acid, is used as the raw material in the present embodiment. The proportion of D-lactic acid in polylactic acid used as a raw material is desirably 1% or less.

<Modification 1>
Next, modification 1 will be described. The inventors of the present application have found that with thermoplastic resins such as polypropylene, the fibers stick to the heat roll when the surface temperature of the heat roll is higher than the glass transition temperature of the fiber, but with polylactic resin, the surface temperature of the heat roll is It was found that the polylactic acid fibers do not stick to the heating roll when the glass transition temperature of polylactic acid is 110°C or higher, which is higher than 60°C. This is because, although the surface temperature of the heat roll exceeds the glass transition temperature, if the temperature is less than 90 to 110° C., the fibers are not fused to each other and stick to the heat roll. When the surface temperature reaches 110°C or higher, the amount of fibers fused together increases, so even if some fibers stick to the hot rolls, the fibers in the nonwoven fabric are fused together after passing through the hot rolls. it is conceivable that.

FIG. 7 is a table showing experimental results regarding the relationship between the surface temperature of the hot roll and the degree of sticking to the hot roll when polylactic acid fibers are passed through the hot roll. In the column of "Degree of sticking" in the table of FIG. 7, if the degree of sticking causes a problem in manufacturing, "X" is indicated, and a small amount of fiber sticks to the heat roll, but there is no problem in manufacturing. When the degree of sticking was not observed, "◯" was indicated, and when the fiber did not stick to the heat roll at all, "⊚" was indicated.

In the nonwoven fabric manufacturing method according to the present embodiment, by setting the surface temperature of the hot roll to 110° C. or higher, the nonwoven fabric can be manufactured using the polylactic acid resin as the raw material. When the surface temperature of the heat roll is 110° C. or more and less than 120° C., for example, the fibers can be prevented from sticking to the heat roll by applying a releasing agent to the heat roll. If the surface temperature of the heat roll is less than 60° C., the polylactic acid fibers will not be fused to each other, so that the finished nonwoven fabric will not have the required strength.

Also, preferably, the surface temperature of the heat roll is 120° C. or higher. By setting the surface temperature of the hot roll to 120° C. or higher, sticking of the fibers to the hot roll can be prevented without coating the hot roll with a releasing agent.

Also, more preferably, the surface temperature of the heat roll is 145° C. or higher.

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

In this modification, the surface temperature of the hot roll in the fusion bonding step (step S103) shown in FIG. °C or less, it is possible to prevent the fibers from sticking to the heat roll.

<Modification 2>
Next, modification 2 will be described. In this modified example, the degree of crystallinity of the polylactic acid-based resin is 35% or more in the stage before the fusion bonding step of step S103 shown in FIG. In this modified example, by setting the crystallinity of the polylactic acid resin to 35% or more, it is possible to suppress thermal shrinkage of the polylactic acid fibers in the fusion bonding step.

FIG. 8 is a table showing an example of manufacturing conditions for a nonwoven fabric. "+Nucleating agent" in the "raw material" column indicates that a crystal nucleating agent is added to polylactic acid. Each numerical value in the column of "discharge amount (g/min/hole)" indicates the amount of fiber discharged per minute from the spinneret 23 shown in FIG. Each numerical value in the "injector pressure (Mpa)" column indicates the pressure of the injector 40 shown in FIG. Each numerical value in the "diameter (μm)" column indicates the fiber diameter after the spinning process. Each numerical value in the "Crystallinity" column indicates the crystallinity of the fiber after the spinning process. The numerical value (145° C.) in the “heat roll temperature (° C.)” column indicates the surface temperature of the heat roll in the fusion bonding step. The "Sticking Phenomenon" column indicates whether or not the fiber sticks to the heat roll. As shown in the table of FIG. 8, by setting the fiber diameter of polylactic acid to 15 μm or less, the degree of crystallinity of the polylactic acid resin can be increased to 35% or more. Even when the fiber diameter is larger than 15 μm, the degree of crystallinity can be increased to 35% or more by adding a crystal nucleating agent to the polylactic acid.

Moreover, the fabric weight of the nonwoven fabric obtained by the nonwoven fabric manufacturing method according to the present embodiment may be 5 gsm (g/m ² ) or more. Such a nonwoven fabric can have a good tactile feel. In addition, it is possible to obtain strength that can be processed with a mask or diaper processing apparatus. In addition, since no additive such as a crystal nucleating agent is added to the raw material polylactic acid, the nonwoven fabric can be completely decomposed during naturalization.

<Other embodiments>
Although the embodiments of the present invention have been described above, the various embodiments described above can be combined as much as possible. In addition, although the spunbond nonwoven fabric was mentioned as an example in the above embodiment, the present invention is not limited to this. For example, the present invention is applicable to spunbonded nonwoven fabrics, thermal bonded nonwoven fabrics, chemical bonded nonwoven fabrics, needle punched nonwoven fabrics, and stitch bonded nonwoven fabrics.

C Non-woven fabric C1 Fiber layer M Non-woven fabric production devices 10, 10A, 10B, 10C Ejection device 20 Spinning device 30 Cold air device 40 Injector 50 Collecting conveyor 51 Main Conveyors 52, 53 Sub-conveyor 54 Suction box 60 Embossing device 70 Winders 141, 142 Guide plates 151, 152, 153 Collection belts 154a, 154b, 154c Suction chamber 162 Adjustment roller f Filament fr Rotational diameter F, Fa, Fab, Fabc, Fb, Fc Filament assembly Lc Intersection interval Ld Release interval Lr Withdrawal interval P, Pa, Pb, Pc, Pe, Pm, Ps Suction pressure (wind speed)

Claims (28)

A nonwoven fabric manufacturing method using polylactic acid as a raw material,
A spinning step of discharging a molten polylactic acid-based resin from a spinneret and drawing the polylactic acid-based resin with an air flow to make it fibrous;
A fusing step of passing the fibers of the polylactic acid resin through a hot roll to fuse the fibers;
including
In the spinning step, the fiber diameter of the polylactic acid resin is 15 μm or less,
Nonwoven fabric manufacturing method. In the spinning step, the drawing speed for drawing the polylactic acid resin is 180000/min or more.
The method for producing a nonwoven fabric according to claim 1. No crystal nucleating agent is added to the polylactic acid-based resin,
The nonwoven fabric manufacturing method according to claim 1 or 2. In the spinning step, the amount of the polylactic acid-based resin discharged from the spinneret is 0.5 g/min/hole or less.
The nonwoven fabric manufacturing method according to claim 1 or 2. In the spinning step, the polylactic acid-based resin is cooled by cooling air between the spinneret and a drawing device for drawing the polylactic acid-based resin.
The nonwoven fabric manufacturing method according to claim 1 or 2. In the spinning process, air from the outside can flow in,
The nonwoven fabric manufacturing method according to claim 1 or 2. A nonwoven fabric made of polylactic acid as a raw material, formed by passing fibers through a hot roll and fusing the fibers together,
The fiber diameter of the polylactic acid-based resin is 15 μm or less,
non-woven fabric. A nonwoven fabric manufacturing method using polylactic acid as a raw material,
A spinning step of discharging a molten polylactic acid-based resin from a spinneret and drawing the polylactic acid-based resin with an air flow to make it fibrous;
A fusing step of passing the fibers of the polylactic acid resin through a hot roll to fuse the fibers;
including
In the spinning step, the drawing speed for drawing the polylactic acid resin is 180000/min or more.
Nonwoven fabric manufacturing method. A crystal nucleating agent and a crystallization accelerator are not added to the polylactic acid resin.
The method for producing a nonwoven fabric according to claim 8. In the spinning step, the discharge amount of the polylactic acid resin from the spinneret is 0.5 g/m
is less than or equal to in/hole
The method for producing a nonwoven fabric according to claim 8 or 9. In the spinning step, the polylactic acid-based resin is cooled by cooling air between the spinneret and a drawing device for drawing the polylactic acid-based resin.
The method for producing a nonwoven fabric according to claim 8 or 9. In the spinning process, air from the outside can flow in,
The method for producing a nonwoven fabric according to claim 8 or 9. A nonwoven fabric manufacturing apparatus for manufacturing a nonwoven fabric using polylactic acid resin as a raw material,
a discharge part for melting and discharging the polylactic acid-based resin;
a stretching section for stretching the polylactic acid-based resin by an air flow;
a cooling section disposed between the discharge section and the stretching section for blowing cooling air against the polylactic acid-based resin;
a sheet conveying unit that collects the fibers of the polylactic acid resin stretched by the stretching unit on a conveying surface and conveys them in a conveying direction while making them into a sheet-shaped nonwoven fabric;
a fusing part that fuses the fibers of the polylactic acid resin by heating them;
with
The stretching speed at which the stretching portion stretches the polylactic acid resin is 180000/min or more.
Non-woven fabric manufacturing equipment. The ejection part has a mouthpiece for ejecting the polylactic acid resin,
The discharge amount of the polylactic acid-based resin from the die is 0.5 g/min/hole or less.
The nonwoven fabric manufacturing apparatus according to claim 13. The fusing unit has a heat roll for heating the fibers of the polylactic acid-based resin,
The surface temperature of the heat roll is 110° C. or higher.
The nonwoven fabric manufacturing apparatus according to claim 13 or 14. The surface temperature of the heat roll is 145° C. or higher.
The nonwoven fabric manufacturing apparatus according to claim 15. The fused portion is formed by embossing the fiber,
The area ratio of the embossing is 5% or more and 25% or less.
The nonwoven fabric manufacturing apparatus according to claim 13 or 14. The conveying speed at which the sheet conveying unit conveys the fibers of the polylactic acid resin is 40 m/min or more and 120 m/min or less.
The nonwoven fabric manufacturing apparatus according to claim 13 or 14. Air from the outside can flow into the cooling unit,
The nonwoven fabric manufacturing apparatus according to claim 13 or 14. The discharge part spins out a filament assembly of the polylactic acid-based resin,
The nonwoven fabric manufacturing apparatus according to claim 13 or 14. A method for producing a nonwoven fabric using a polylactic acid-based resin as a raw material,
a spinning step of discharging the molten polylactic acid-based resin from a spinneret and drawing the polylactic acid-based resin with an air current to form fibers;
A fusing step of passing the fibers of the polylactic acid resin through a hot roll to fuse the fibers;
including
In the fusion bonding step, the surface temperature of the heat roll is 110° C. or higher.
Nonwoven fabric manufacturing method. In the fusion bonding step, the surface temperature of the heat roll is 145° C. or higher.
22. The method of manufacturing a nonwoven fabric according to claim 21. The melting point of the fiber is 150° C. or higher.
23. The method for producing a nonwoven fabric according to claim 21 or 22. The degree of crystallinity of the polylactic acid-based resin in the pre-stage of the fusion bonding step is 35% or more.
23. The method for producing a nonwoven fabric according to claim 21 or 22. The nonwoven fabric has a basis weight of 5 gsm or more.
23. The method for producing a nonwoven fabric according to claim 21 or 22. In the fusing step, the fibers are embossed,
The area ratio of the embossing is 6% or more and 20% or less.
23. The method for producing a nonwoven fabric according to claim 21 or 22. including a conveying step of conveying the fibrous polylactic acid-based resin,
The conveying speed in the conveying step is 40 m/min or more and 120 m/min or less.
23. The method for producing a nonwoven fabric according to claim 21 or 22. No crystal nucleating agent is added to the polylactic acid-based resin,
23. The method for producing a nonwoven fabric according to claim 21 or 22.

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