KR100702870B1 - Method for manufacturing continuous phase mat using electrospinning and mat prepared therefrom - Google Patents

Abstract

The present invention relates to a method for producing a continuous phase mat using electrospinning and a mat manufactured therefrom, wherein the polymer spinning solution in the polymer spinning solution main tank 4 is subjected to a high voltage, and one or more unit blocks are in a lateral or longitudinal direction. High voltage is applied through the nozzles 2a in the nozzle block 2, which are arranged in a C-shape in a state of being arranged in a state of being arranged, and the collector 3, which is a cylindrical conductor, is rotated with one side wrapped by the nozzle block 2. Electrospinning the nanofibers onto the collector 3, and then separating the integrated nanofibers from the collector 3 into a continuous mat 5 using a transfer roller 6. Next, it is wound up on the winder 7 to produce a continuous mat.

The present invention can freely adjust the orientation of the nanofibers in the mat axis direction in accordance with the rotational speed of the collector.

In addition, in the present invention, since the nozzle block 2 surrounds one side of the rotating cylindrical collector 3, a large amount of nozzles can be arranged in the transverse direction or the longitudinal direction of the nozzle block 2 in a very narrow space. Productivity is very high, the nozzle block (2) is composed of a plurality of unit blocks to facilitate the radiation rate control and improve the fiber forming ability.

 Electrospinning, mat, nonwoven fabric, composite material, nanofiber, rotary collector, nozzle block

Description

Method for manufacturing continuous phase mat using electrospinning and mat manufactured therefrom {Method of manufacturing continuous mats by electrospinning and mats manufactured thereby}

1 is a schematic view of the manufacturing process of the continuous phase mat according to the present invention.

2 is a perspective view of a C-shaped nozzle block 2 composed of five unit blocks.

Figure 3 is a schematic diagram of a manufacturing process of the present invention for producing a continuous mat using two nozzle blocks and two collectors.

Figure 4 is an electron microscope photograph of the surface of the continuous mat prepared in Example 1.

* Description of symbols on the main parts of the drawings

1: high voltage generator 2: C-shaped nozzle block

2a: nozzle 3: collector

4: polymer spinning solution main tank 5: mat consisting of nanofibers

6: mat feed roller 7: winding machine

A, B: Type of polymer.

The present invention relates to a method for producing a continuous phase mat, nonwoven fabric or sheet (hereinafter referred to as "mat") using electrospinning, and to a continuous phase mat produced therefrom. By using C-shaped nozzle blocks in which the above unit blocks are arranged in the lateral or longitudinal direction, a large number of nozzle arrangements are possible in the unit space, so that the yield per unit time is high even in a very small place, and The present invention relates to a method for producing a continuous mat, in which the orientation angles of nanofibers can be freely adjusted so that the mechanical properties of the mat can be easily adjusted.

In the present invention, the nanofiber means a fiber having a fiber diameter of 1,000 nm or less, more preferably 500 nm or less.

Mats composed of nanofibers can be widely used for general clothing, artificial leather, filters, diapers, sanitary napkins, sutures, anti-adhesion agents, wiping cloths, artificial blood vessels, bone fixing devices, and especially for artificial leather. Very useful for

Conventional techniques for producing ultrafine fibers or nanofibers suitable for the manufacture of artificial leather and the like are known as island-in-the-sea composite spinning, split composite spinning and blend spinning.

However, in the case of island-in-the-sea composite spinning or blend spinning, one of the two polymer components constituting the fibers must be eluted and removed for the finer fibers. In order to manufacture, there has been a problem of undergoing complex processes such as melt spinning, short fiber production, nonwoven fabric production, urethane impregnation, and one component elution. Nevertheless, the conventional method could not produce fibers with a diameter of 1,000 nm or less.

On the other hand, in the split type composite spinning method, two polymer components having different dyeing characteristics (for example, polyester and polyamide) coexist in the fiber, so that a dyeing band appears, and the artificial leather manufacturing process has a complicated problem. In addition, it was difficult to produce fibers with a diameter of 2,000 nm or less by the above method.

As another conventional technique for manufacturing nanofibers, US 4,323,525 and the like have proposed an electrospinning method.

The electrospinning method continuously supplies the polymer spinning liquid in the spinning liquid main tank into a plurality of nozzles to which a high voltage is applied through a metering pump, and continuously supplies the spinning liquid supplied to the nozzle with a high voltage of 5 kV or more through the nozzle. A fiber web is manufactured by spinning and focusing on a hanging belt type focusing device.

In the conventional electrospinning method, the radiation distance (distance between the nozzle and the collector) is very short in the electrospinning process, and thus the method of stretching by applying a separate physical force is very limited, so the mechanical properties are very low. In addition, the method can not control the orientation angle of the nanofibers in the mat axis direction, there is a problem that the production per unit time is low because it can not arrange a large number of nozzles in a narrow space.

On the other hand, when manufacturing a mat composed of nanofibers, by placing the conductor wires on both sides of a non-conductor such as quartz by arranging the nanofibers in the fiber axis direction, and then electrospinning them, these conductor wires The arrangement of fibers has already been published (Dan Li, Yuliang Wang, and Younan Xia, Advanced Materials Vol 16 (4), pp361-366, 2004). However, this method is less likely to industrialize and is not a way to introduce the stretching force.

The physical properties of the mat electrospun by the conventional method are very difficult to achieve 10 MPa.

As described above, the conventionally known techniques are not able to arbitrarily adjust the arrangement of nanofibers in the mat axis direction, and in particular, it is very difficult to manufacture a mat arranged more than 30 ° in the mat axis direction, and a large amount of nozzles in a narrow space There was a problem in that the output per unit time was low because they could not be arranged.

Therefore, the conventional method could not solve the problem of low production per unit time during electrospinning and low mechanical properties of the product.

In the present invention, when manufacturing a continuous mat made of nanofibers by electrospinning method, a large amount of nozzles can be arranged even in a narrow space, thereby increasing productivity per unit time and easily adjusting the orientation angle of the nanofibers in the mat axis direction. We want to provide a way to do it.

In addition, the present invention is to provide a continuous mat of nanofibers excellent in physical properties and composed of nanofibers suitable for various industrial materials, such as filters, diapers, sanitary napkins, artificial blood vessels, as well as artificial leather.

In the method for producing a continuous phase mat using the electrospinning of the present invention for achieving the above problems, a high voltage is applied to the polymer spinning solution in the polymer spinning solution main tank (4) one or more unit blocks in the transverse or longitudinal direction Collector 3, which is a cylindrical conductor that is subjected to high voltage through the nozzles 2a in the nozzle block 2, which is arranged in a C-shape and is rotated in a state in which one side is wrapped by the nozzle block 2, Electrospun onto the collector (3) to integrate the electrospun nanofibers, and then using the transfer roller (6) to separate the nanofibers from the collector (3) in the form of a continuous mat (5) , It is characterized in that wound on the winder (7).

In addition, the continuous mat of the present invention is made by the above method is composed of nanofibers, necking (Necking) stress on the stress-strain graph It is characterized by the appearance of stress-strain curves in the form or in part / stretched form.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

First, in the present invention, as shown in FIG. 1, the nozzle block 2 having the polymer spinning solution in the polymer spinning solution main tank 4 is C-shaped with one or more unit blocks arranged in the transverse or longitudinal direction. Electrospinning to the collector (3), which is a cylindrical conductor that is rotated in a state in which one side is wrapped by the nozzle block through the nozzle (2a) in the) to accumulate the nanofibers electrospun on the collector (3) .

1 is a process schematic diagram of the present invention.

As shown in FIG. 2, the nozzle block 2 has a high voltage applied thereto and is combined in a C shape with one or more unit blocks arranged in a lateral or longitudinal direction.

Fig. 2 is a perspective view of the C-shaped nozzle block 2 used in the present invention.

On the other hand, the collector (3) is a cylindrical conductor is rotated in a form wrapped on one side by the nozzle block (2) and is subjected to a high voltage.

As described above, the present invention is characterized by simultaneously using the C-shaped nozzle block 2 and the rotating cylindrical collector 3 described above during electrospinning.

In order to uniformly integrate the nanofibers on the collector 3 during the electrospinning, the nozzle block 2 is preferably reciprocated from side to side.

Next, the transfer roller 6 is used to separate the nanofibers accumulated from the collector 3 in the form of a continuous mat 5, which is then wound up in the winder 7.

The continuous mat 5 separated from the collector 3 may be embossed, dried or stretched before being wound onto the winder.

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Meanwhile, in the present invention, as shown in FIG. 3, two or more mats may be simultaneously manufactured using two or more C-shaped nozzle blocks 2 and collectors 3, respectively.

In this case, the same polymer spinning solution may be supplied to each of the two or more C-shaped nozzle blocks 2, or different polymer spinning solutions may be supplied to produce different types of mats.

The hybrid mat may be manufactured by lining before winding up other types of mats manufactured simultaneously as described above.

3 is a schematic view of the manufacturing process of the present invention for producing a continuous mat using two nozzle blocks and two collectors, and reference numerals are omitted.

In addition, it is also possible to manufacture a hybrid mat by laminating on both sides of the fibrous base before winding each of the two layers of mat produced simultaneously as described above.

The two or more C-shaped nozzle blocks 2 and the collector 3 may have the same diameter as each other, or may have different diameters from each other.

The nozzles 2a and the collectors 3 arranged on the C-shaped nozzle block are connected to the high voltage generator 1 to be subjected to a high voltage.

In addition, the upper surface of the collector (3) is attached to the non-conductor plate that serves to block the current flow at the same time to support the collector, the non-conductive plate is good to use a constant space to reduce the weight in the center You can get the result.

The material of the non-conductor plate is polypropylene, polyethylene, teflon, or a polymer of which they are composite materials. In order to facilitate the rotation through the motor, it is advantageous that the non-conductor plate has a free space.

The collector (3) is rotated by a rotating motor. In order to configure the collector in a multi-layer, to prevent the scattering of nanofibers during electrospinning and to eliminate the phenomenon that the electrospun fibers are attached to the collector of another layer, a non-conducting separator (divider) between each layer constituting the collector. It is more preferable to install it.

In addition, the height of the collector 3 is appropriately adjusted according to the width of the mat to be manufactured.

The present invention can arrange a large number of nozzles in a narrow space can solve the limitation of mass production, which is a disadvantage of general electrospinning. In general, in the case of electrospinning with one nozzle in the electrospinning, the discharge amount is generally very small, 0.6-2.0mg / min. Therefore, for mass production, it is very important to increase the production efficiency by arranging a large number of nozzles in a narrow space. In this respect, the present invention has a great advantage.

On the other hand, the mat produced by the conventional electrospinning method is very weak physical properties. The strength of physical properties of general conventional mats is very low, such as 10 MPa. For this reason, there are restrictions on the use of parts requiring strong physical properties. The present invention can solve this problem by adjusting the rotational speed of the collector (3). Specifically, the angle of orientation of the nanofibers with respect to the mat axis can be adjusted by adjusting the rotation speed of the collector 3, so that the physical properties required for various applications can be provided. For example, electrospinning a collector rotating at 5 m / sec controls the orientation angle of the nanofibers with respect to the mat axis (the moving direction of the mat (machine direction)) to 3 ° or less, thereby greatly improving the physical properties of the mat.

In addition, the present invention may prepare an isotropic composite mat by manufacturing two or more layers of mats having different orientation angles of the nanofibers with respect to the mat axis and then laminating them.

In the C-shaped nozzle block 2, the nozzles 2a are arranged diagonally in the transverse direction or the longitudinal direction, or arranged in a straight line in the transverse direction or the longitudinal direction.

The present invention can increase the production per unit time by arranging a large amount of nozzles in a narrow space. The C-shaped nozzle block 2 may be composed of one or two or more unit blocks, but when the two or more unit blocks are combined in a state arranged in the horizontal or longitudinal direction, the nozzle replacement operation is convenient and used. When the polymer to be changed is easy to clean, it is possible to stably form the Taylor cone at the end of the nozzle during electrospinning, thereby improving the nanofiber forming ability.

On the other hand, the nozzle (2a) is arranged in the C-shaped nozzle block 2, as shown in Figure 2 and its length or diameter can be variously adjusted according to the width or thickness of the desired mat. In addition, the length and diameter of the collector 3 can be freely selected according to the width and thickness of the desired mat. The C-shaped nozzle block 2 and the collector 3 may be formed in a multilayer as described above. When the C-shaped nozzle block 2 is divided into two or more layers up and down, and each of the polymer spinning solutions having different types or concentrations is supplied to each layer, mats having different polymer types or nanofiber thicknesses can be simultaneously produced. In addition, when these are laminated before winding, a hybrid mat can be easily produced.

In addition, a hybrid mat may be manufactured by supplying a polymer spinning solution having a different type or concentration to each unit block constituting the nozzle block 2.

The C-shaped nozzle block 2 is preferably placed on a fixed frame so that the distance between the nozzle 2a and the collector 3 can be arbitrarily adjusted.

In addition, by adjusting the diameter of the nozzle block 2 and the collector 3, the distance (radiation distance) between them may be adjusted.

 Polymer spinning solutions include polyester resins, nylon resins, polysulfone resins, polylactic acid, chitosan, collagen, cellulose, fibrinogen, copolymers thereof, sol-gels containing metal components, copolymers thereof And components selected from the group consisting of mixtures thereof and the like can be used.

SUMMARY OF THE INVENTION The gist of the present invention is a cylindrical collector which rotates in a state in which one or more unit blocks are wrapped in a C-shape with one or more unit blocks arranged in a lateral or longitudinal direction, and one side of which is wrapped by the nozzle block 2. The physical properties of the mat can be easily controlled by freely adjusting the angle of orientation of the nanofibers in the mat axial direction according to the rotational linear velocity of (3).

In general, mats produced by electrospinning, etc., it is very difficult to have a system that can apply a separate physical force and the like during the electrospinning process. The reason is that the distance between the nozzle and the collector is very narrow (30 cm or less), so it is very difficult to apply mechanical force in a narrow space.

In the present invention, the nanofibers are arranged in the mat axial direction by using the centrifugal force of the rotating collector 3.

The present invention partially or completely stretched by arranging nanofibers side by side on the collector 3 by electrospinning the polymer spinning solution on the collector 3 rotating through a plurality of nozzles arranged on the C-shaped nozzle block 2. Manufacture the mat.

It is a common phenomenon that the fiber produced by electrospinning proceeds a considerable part of crystallization according to the properties of the material. In addition, since the orientation of the nanofibers with respect to the mat axis is very low, the mechanical properties are very low, it is very difficult to increase the physical properties through a separate stretching process. The reason for this is that crystals have already been formed, the elongation is remarkably deteriorated, and the mechanical properties are inevitably low because the orientation of the mat axis is low. Therefore, it is possible to suppress the formation of crystals during the electrospinning process, as well as to arrange the electrospun fibers uniformly in the mat axis direction, thereby producing a mat having excellent mechanical properties. When the nanofibers produced by electrospinning are focused on the collector 3, which is a rotating cylindrical rotor, crystal formation can be suppressed and nanofibers can be arranged in a line about the mat axis. Manufacturing becomes possible. If the collector's rotational linear velocity is too low, it is difficult to suppress crystal formation and it is not possible to orient the electrospun nanofibers about the mat axis in a line. In the present invention, it is possible to obtain a mat in which the crystallinity is low or the partially / fully drawn nanofibers are well oriented with respect to the mat axis. Therefore, the mechanical properties can be obtained much better than the properties obtained by the melt blown or spunbond method, and if necessary, the drawing is made by using the linear speed difference of the rollers, if necessary, the nanofiber with excellent mechanical properties. The constructed mat can be manufactured.

In order to manufacture a hybrid type mat made of various widths or two or more kinds of polymers, the above-described multilayer C-shaped nozzle block and the corresponding multilayer cylindrical collector can be easily manufactured.

 According to the present invention, two or more kinds of mats having different mat widths may be manufactured by varying the length (height) of each layer constituting the multilayer C-shaped nozzle block and the multilayer cylindrical collectors, and various types of mats may be manufactured by embossing them. In addition, two or more types of polymers may be used to prepare hybrid mats composed of mats with different nanofiber diameters. Most typically, in the collector 3, polyurethane can be spun on one layer and nylon on the other, and combined with an embossing roller to produce a hybrid mat composed of two kinds of nanofibers of different polymers. .

In addition, in the present invention, a hybrid mat can be easily manufactured by supplying a different type of polymer spinning solution to each of the unit blocks constituting the C-shaped nozzle block 2.

Meanwhile, in the present invention, as shown in FIG. 3, two or more continuous mats are simultaneously manufactured using two or more C-shaped nozzle blocks 2 and two or more collectors 3, and the hybrid mats are stacked by stacking them. It can manufacture. 3 is a process schematic according to the above method.

At this time, by supplying a high molecular spinning solution having different polymer types or concentrations to the C-shaped nozzle blocks 2, a hybrid mat can be easily manufactured.

When the spinning solution of the same polymer having different concentrations is respectively supplied to two or more C-shaped nozzle blocks 2, it is possible to manufacture a mat composed of two or more kinds of nanofibers having different thicknesses.

In addition, supplying a different spinning solution with a different polymer type may change the diameter of the nanofibers due to different polymer types, thereby preparing a mat composed of two or more types of nanofibers having different diameters and polymer types.

 For example, in the case of nylon 6, the diameter of nanofibers generally produced is about 100-300 nm, and in the case of polyurethane, about 200-500 nm. Therefore, it is very easy to manufacture two types of hybrid mats having different diameters as well as nanofibers.

In the present invention, the hybrid mat of the side by side (SIDE BY SIDE) type in which different polymers are regularly repeated by supplying two or more types of polymer spinning solutions to each other nozzle alternately in the same nozzle block and then electrospinning them. It includes a method of producing.

The nozzle 2 may have a core-shell structure or a triple or more tubular structure.

The number of the nozzles 2 is one or more, more preferably 100 or more.

When electrospinning the polymer spinning solution on the rotating cylindrical collector 3 as described above, it is more preferable to supply the solution for separating the nanofibers to the collector 3.

The solution for separating nanofibers is one or a mixture of two or more selected from water, an organic solvent, a surfactant, and a silicone oil.

Next, as shown in FIG. 1, the nanofibers 2b integrated on the cylindrical chelator 3 are separated into a continuous mat form using the transfer roller 6, and then the winder 7 Wind on Before winding the separated mat, it may be dried using a dryer, multi-stretched using a stretching roller having a different rotation linear speed, or heat-treated. In addition, the manufactured mat may be impregnated with a thermoplastic resin or a thermosetting resin.

The continuous mat of the present invention manufactured by the manufacturing method of the present invention described above is composed of nanofibers, characterized in that the stress-strain curve in the form of necking (Necking) stress or partial / fully stretched on the stress-strain graph It is done.

Nanofibers constituting the mat of the present invention may be in the form of a hollow (hollow) or in the form of pores on the surface.

In particular, the continuous mat of the present invention has excellent physical properties because the nanofibers are arranged at an orientation angle of 10 ° or less in the mat axis direction.

Hereinafter, the present invention will be described in detail through Examples and Comparative Examples. However, the present invention is not limited to the protection range by the following examples.

Example 1

A polymer spinning solution was prepared by dissolving a nylon 66 resin having a relative viscosity of 3.0 in 96% sulfuric acid solution at a concentration of 15% by weight in formic acid / acetic acid (volume ratio: 70/30). The surface tension of the polymer spinning solution was 37 mN / m, the solution viscosity was 420 centipoise at room temperature, and the electrical conductivity was 340 mS / m.

A high voltage is applied to the spinning solution prepared as described above as shown in FIG. 1 and high voltage is applied through the nozzles 2a of the nozzle block 2, which are combined in a C shape with 128 unit blocks arranged in a transverse direction. And electrospun onto the collector 3 by electrospinning to a cylindrical conductor (stainless steel) collector 3 rotating at a rotational linear speed of 10 m / min with one side wrapped by the nozzle block 2. The fibers were integrated.

The collector was rotated in connection with the rotary motor by a connecting rod, the length was 200cm, the radius was 185cm. The nozzle block 2 had a radius of 200 cm and a length (mat width direction) of 180 cm. 72 nozzles were horizontally arranged in one unit block constituting the nozzle block 2, so that the total number of nozzles in the nozzle block 2 was 12,090. During the electrospinning, the nozzle block 2 was reciprocated at a speed of 2 m / min to make the nanofiber lamination density uniform. The diameter of the nozzle was 1 mm, the voltage was 35 kV, and the spinning distance was 13 cm.

In addition, during electrospinning, water (nanofiber separation solution) was supplied to the collector.

Next, the nanofibers integrated in the collector 7 were separated into mats by using the transfer roller 6, and then wound to prepare a mat having a weight of 0.81 g / m 2 and a width of 1.6 m.

The result of photographing the surface of the manufactured mat with an electron microscope photograph is shown in FIG.

The present invention can easily adjust the orientation angle of the nanofibers with respect to the mat axis direction, and a large amount of nozzles can be arranged in a narrow space, high productivity per unit time.

Therefore, the present invention can mass-produce nanofiber mats having various physical properties in a continuous process.

In addition, the present invention can easily produce a hybrid mat made of nanofibers having different polymer types or diameters.

Nanofiber mat produced by the present invention is artificial leather, air cleaning filter, wiping cloth, golf gloves, wigs, daily necessities such as artificial dialysis filter, artificial blood vessels, anti-adhesion agent, artificial bone, flooring material, composite material It is useful for various industrial materials such as application fields.

Claims (26)

The polymer spinning solution in the polymer spinning solution main tank (4) has a high voltage applied to the nozzle block located at the bottom of the collector (3), which is combined in a C shape with one or more unit blocks arranged in the transverse or longitudinal direction. A high voltage is applied through the nozzles 2a in (2) and is electrospun into the collector 3, which is a cylindrical conductor that is rotated in a state in which one side is wrapped by the nozzle block 2, and at the same time, the collector 3 After supplying a solution for nanoseparation to accumulate the nanofibers electrospun into the collector (3), and using the transfer roller (6) the nanofibers from the collector (3) in the form of a continuous mat (5) After separation, the method of manufacturing a continuous mat using an electrospinning, characterized in that it is wound on a winder (7). A method of producing a continuous mat using electrospinning according to claim 1, characterized in that it is embossed, dried or stretched before winding the continuous mat (5) separated from the collector (3). A method of manufacturing a continuous mat using electrospinning according to claim 1, characterized in that the nozzles (2a) are arranged diagonally or in a row in the transverse direction or in the longitudinal direction in the nozzle block (2). The method of claim 1, wherein the nozzle block (2) is composed of one or two or more unit blocks. The method of claim 4, wherein the two or more unit blocks are assembled in a C-shaped frame. The method of manufacturing a continuous mat using electrospinning according to claim 1, wherein the nozzle block (2) reciprocates from side to side. delete The method for producing a continuous mat using electrospinning according to claim 1, wherein the nozzle has a double-shell structure or a triple-pipe structure. The method of claim 1, wherein the polymer spinning solution is a polyester resin, nylon resin, polysulfone resin, polylactic acid, chitosan, collagen, cellulose, fibrinogen, sol-gel containing a metal component, copolymers thereof and these Method for producing a continuous mat using the electrospinning, characterized in that consisting of a component selected from the group consisting of a mixture of. delete The method of claim 1, wherein the solution for separating nanofibers is one, or a mixture of two or more selected from water, an organic solvent, a surfactant, and a silicone oil. The method for producing a continuous mat using electrospinning according to claim 1, wherein the number of nozzles (2) is one or more. The method for producing a continuous mat using electrospinning according to claim 1, wherein the number of nozzles (2) is 100 or more. delete delete delete The method of manufacturing a continuous mat using electrospinning according to claim 1, wherein two or more mats are simultaneously manufactured using two or more nozzle blocks (2) and collectors (3). 18. The method of manufacturing a continuous mat using electrospinning according to claim 17, characterized in that two or more different types of polymer spinning solutions are supplied to each of the two or more nozzle blocks (2). 18. The method for producing a continuous mat of claim 17, wherein the two or more mats are laminated before winding. Method according to claim 17, characterized in that the diameter of each of the two or more nozzle blocks (2) is different from each other. Method according to claim 17, characterized in that the diameter of each of the two or more collectors (3) is different from each other. 18. The method for producing a continuous mat using electrospinning according to claim 17, wherein at least two mats are laminated on both sides of the fiber base before winding. A continuous mat made of nanofibers prepared by the method of claims 1 to 22, characterized in that a stress-strain curve in the form of necking stress or partial / complete stretch is shown on a stress-strain graph. 24. The continuous mat according to claim 23, wherein the nanofibers are hollow or have pores formed on the surface thereof. 24. The continuous mat according to claim 23, wherein the nanofibers are arranged at an angle of 10 degrees or less in the axial direction of the continuous mat. 24. A continuous mat as claimed in claim 23, wherein a thermoplastic or thermosetting resin is contained between the nanofibers.

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