WO2006123858A1

WO2006123858A1 - Method of manufacturing mats consisting of nanofibers by electrospinning and mats manufactured thereby

Info

Publication number: WO2006123858A1
Application number: PCT/KR2006/000959
Authority: WO
Inventors: Hak-Yong Kim
Original assignee: Industrial Cooperation Foundation Chonbuk National University
Priority date: 2005-05-18
Filing date: 2006-03-16
Publication date: 2006-11-23

Abstract

Disclosed are a method of manufacturing a continuous mat by electrospinning, and a mat manufactured thereby. Electronspun nano fibers 2 b are collected on a collector 3 by electrically spinning a polymer spinning dope in a spinning dope main tank 4 onto the collector 3, which is a cylindrical conductive material with a high voltage applied thereto and which rotates being located within a hollow portion of a cylindrical nozzle block 2, through nozzles 2a in the cylindrical nozzle block 2 having a high voltage applied thereto and being formed in a core shell shape having the hollow portion, with part of a side wall being cut and opened, and then the collected nano fibers 2b are separated from the collector 3 in the form of a continuous mat 5 by a feed roller 6 and wound on a winding machine 7. It is possible to prepare a continuous mat having various physical properties because the orientation of the nano fibers can be freely and variously adjusted in a mat axis direction according to a rotation velocity of the collector. Additionally, a large amount of nozzles can be arranged in a circumferential direction of the cylindrical nozzle block 2 within a very narrow space because the rotating cylindrical collector 3 is located within the hollow portion of the cylindrical nozzle block 2, which leads to a very high productivity.

Description

METHOD OF MANUFACTURING MATS CONSISTING OF NANOFIBERS

BY ELECTROSPINNING AND MATS MANUFACTURED THEREBY

TECHNICAL FIELD

The present invention relates to a method of manufacturing a

continuous mat consisting of nanofibers, nonwoven fabric, or sheet

(hereinafter, commonly referred to as a "mat") by electrospinning and a

continuous mat manufactured thereby, and more particularly, to a

method of manufacturing a continuous mat consisting of nanofibers,

which achieves a high yield per unit time even in a very narrow place

since a large quantity of nozzles can be arranged within a unit space, and

which makes it easy to adjust mechanical properties of the mat because

the orientation angle (θ) of nano fibers relative to a mat axis can be freely

adjusted, by using a cylindrical nozzle block.

In the present invention, the nano fiber refers to a fiber having a

fiber diameter 1,000 nm or less, and more preferably, 500 nm or less.

A mat composed of a nano fiber can be utilized for artificial leather,

filters, diapers, sanitary pads, sutures, antisetting agents, wiping cloths, artificial vessels, bone fixing devices and the like, and in particular, it is very useful for the production of the artificial leather.

BACKGROUND ART

As conventional techniques for preparing an ultra fine fiber or nano fiber suitable for the production of artificial leather, there are known a sea-island type conjugated spinning method, a division type conjugated spinning method, a blend spinning method and so on.

However, in case of the sea-island type conjugated spinning method or the blend spinning method, one of two polymer components comprising a fiber must be dissolved and removed for making the ultra fine fiber. In order to produce artificial leather from the fiber prepared by these methods, a complex process must be carried out, including melt spinning, nano fiber production, non-woven fabric production, urethane impregnation and single component dissolution. Nevertheless, it has been impossible to produce a fiber with a diameter 1 ,000 nm or less by the above two methods.

In case of the spit type conjugate spinning method, it has been problematic in that since two polymer components (for example, polyester and polyamide) with different dyeing properties co-exist in a fiber, uneven dyeing occurs and an artificial leather production process is complicated. In addition, it has been difficult to produce a fiber with a diameter 2,000 nm or less by the above method.

As another conventional technique for preparing a nano fiber, an electrospinning method is suggested in U.S. Patent No. 4,323,525.

In the electrospinning method, a polymer spinning dope in a spinning dope main tank is continuously and constantly fed into a plurality of nozzles, which has a high voltage applied, through a metering pump. Subsequently, the spinning dope fed to the nozzles is spun and collected through the nozzles on a collector of an endless belt type having a high voltage, more than 5 kV, thereby producing a fiber web.

In the conventional electrospinning method, a spinning distance (distance between the nozzle and the collector) is so short in an electrospinning process that a method capable of drawing by applying a physical force is restrictive, and thus the mechanical properties are very low. Further, the aforementioned method has beenproblematic in that the orientation angle of nano fibers relative to a mat axis direction cannot be adjusted, and the yield per unit time is low because it is not possible to arrange a large quantity of nozzles within a narrow space.

Meanwhile, as a method for arranging nano fibers in a fiber axis direction when preparing a mat composed of nano fibers, it has been already explained that fibers are arranged between conductive lines by placing the conductive lines on both sides of a nonconductive material such as quartz and then performing electrospinning thereon [Dan Li, Yuliang Wang, and Younan Xia, Advanced Materials VoI 16(4), pp361-366, 2004]. However, this method has a low possibility of industrialization, and any drawing force cannot be applied to this method.

In the conventional method, it is very difficult to achieve physical properties of 10 MPa from the electrically spun mat.

As seen from above, it is impossible to arbitrarily adjust the arrangement of nano fibers in a mat axis direction by the prior art techniques known up to now, especially, it is very difficult to produce a mat in which nano fibers are arranged at over 30° in a mat axis direction, and the yield per unit time is low since a large quantity of nozzles cannoi be arranged within a narrow space.

DETAILED DESCRIPTION OF THE INVENTION TECHNICAL PROBLEMS

The present invention provides a process of preparing a continuous mat composed of nano fibers or coated with nano fibers by electropsinning, which offers a high yield per unit time and allows easy adjustment of the orientation angle (θ) of nano fibers relative to a mat axis direction because a large quantity of nozzles can be arranged even in a narrow space. Additionally, the present invention is intended to provide a continuous mat of a nano fiber which is superior in physical properties composed of one or two types of nano fibers and is suitable for various industrial materials, such as a filter, diaper, sanitary pad, artificial vessel and so on, as well as artificial leather.

TECHNICAL SOLUTIONS

To solve the above-described problems, there is provided a method of manufacturing a continuous mat consisting nanofibers by electrospinning, wherein electrospun nano fibers 2b are collected on a collector 3 by electrically spinning a polymer spinning dope in a spinning dope main tank 4 onto the collector 3, which is a cylindrical conductive material with a high voltage applied thereto and which rotates being located within a hollow portion of a cylindrical nozzle block 2, through nozzles 2a in the cylindrical nozzle block 2 having a high voltage applied thereto and being formed in a core shell shape having the hollow portion, with part of a side wall being cut and opened, and then the collected nano fibers 2b are separated from the collector 3 in the form of a continuous mat 5 by a feed roller 6 and wound on a winding machine 7.

Furthermore, the continuous mat of the present invention is prepared in the above method and composed of nano fibers, and shows a necking stress or a partial /complete stretched stress-strain curve on a stress-strain graph. The continuous mat of the present invention comprises a mat having nano fibers coated on a fiber base 9.

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

First, in the present invention, as shown in FIG. l, electrospun nano fibers 2b are collected on a collector 3 by electrically spinning a polymer spinning dope in a spinning dope main tank 4 onto the collector 3, which is a rotating conductive material, through nozzles 2a in Ihe cylindrical nozzle block 2. FIG. l is a schematic process view of the present invention.

As shown in FIG. 3, the cylindrical nozzle block 2 has a high

voltage applied thereto and is formed in a core shell shape having a hollow portion at the inner center, with part of a side wall being cut and

opened.

FIG. 3 is a schematic perspective view of the cylindrical nozzle block 2 used in the present invention.

Meanwhile, the collector 3 is a cylindrical conductive material,

which rotates being located within the hollow portion and has a high

voltage applied thereto.

As above, in the present invention, at the time of electrospinning,

the above-explained cylindrical nozzle block 2 and the rotating cylindrical

collector 3 are used at the same time.

At the time of electrospinning, it is preferable that the nozzle block 2 reciprocates up and down in order to uniformly collect nano fibers onto

the collector 3.

Next, the collected nano fibers 2b are separated from the collector 3 in the form of a continuous mat 5 by using a feed roller 6, and then the

nano fibers are wound around a winding machine 7. The continuous mat 5 separated from the collector 3 may be embossed, dried or drawn before being wound around the winding

machine.

Each of the cylindrical nozzle block 2 and the collector 3, which are a cylindrical conductive material, may be in a multilayer form which is

divided into two or more layers by a dividing plate which is a

non-conductive material.

In a case where the cylindrical nozzle block 2 and the collector 3

are in a multilayer form, they are a dividing type or an integral type, and

the length (height) of each of the layers of them may be different from

each other.

Meanwhile, in the present invention, as shown in FIG.5, it is also

possible to prepare two or more mats simultaneously by using two or

more cylindrical nozzle blocks 2 and two or more collectors 3,

respectively.

In this case, the same polymer spinning dope may be fed into each

of the two or more cylindrical nozzle blocks 2, and it is also possible to

prepare mats of different kinds by feeding different polymer spinning

dopes.

It is possible to prepare a hybrid mat by laminating the mats of

different kinds manufactured simultaneously before winding them.

Moreover, as shown in FIG.9, it is also possible to prepare a hybrid mat by laminating the two layers of mats, prepared simultaneously, on both sides of a fiber base 9 before winding them.

The two or more cylindrical nozzle blocks 2 and the two or more collectors 3 may be the same or different from each other in diameter.

The nozzles 2a arranged in the cylindrical nozzle blocks and the collectors 3 are connected to a high voltage generator 1 and have a high

voltage applied thereto.

Moreover, a non-conductive plate serving to support the collectors

and preventing a current flow are attached onto the upper surface of the

collectors 3. If a certain space is formed at a center portion of the

non-conductive plate for use in order to reduce the weight, a good result

can be obtained.

The non-conductive plate is made of polypropylene, polyethylene, Teflon, or a polymer which is a mixture thereof. It is advantageous that

the non-conductive plate has an empty space so as to make rotation

smooth through a motor.

The collector 3 rotates by a rotary motor. If it is desired to

construct the collector in multilayers, it is more preferable to install a

dividing plate (partition), which is a non-conductive material, between each layer of the collector in order to prevent dispersion of nano fibers during electrospinning and eliminate the phenomenon of adhesion of

electrospun fibers onto the other layers of the collector.

The height of the collector 3 is properly adjusted according to the

width of the mat to be prepared. FIG.2 is a plane view of the cylindrical nozzle block 2 and of the collector 3. The present invention is characterized in that, as shown in FIG.2, the rotating cylindrical collector 3 exists within the hollow portion of the cylindrical nozzle block 2. The present invention can solve the limit of mass production,

which is a demerit of general electrospinning, because a large quantity of

nozzles can be arranged within a narrow space. Generally, in case of

electrospinning using one nozzle, the discharge amount is 0.6 to 2.0

mg/min, which is very small. Therefore, for mass production, it is very

important to increase production efficiency by arranging a large quantity

of nozzles within a narrow space. In this respect, the present invention

has a great advantage.

Meanwhile, the mat prepared in the prior art electrospinning

method is very weak in terms of physical properties. The strength of the

properties of the prior art mat is about 10MPa, which is very low. Due to

this, there are restrictions on the use of parts requiring strong properties.

The present invention can solve such a problem by adjusting the

rotational velocity of the collector 3. Specifically, since the orientation

angle (θ) of nano fibers relative to a mat axis can be adjusted by adjusting

the rotational velocity of the collector 3, properties required for various

uses can be obtained. For instance, if electrospinning is performed on the collector rotating at 5 m/sec, the orientation angle of nano fibers

relative to a mat axis [traveling direction (machine direction) of the mat] is controlled to 3° or less, thereby greatly improving the physical properties

of the mat.

Moreover, in the present invention, it is possible to prepare an

isotropic composite mat by manufacturing two or more layers of mats having a different orientation angle (θ) of nano fibers relative to a mat axis,

respectively, and then laminating them.

As shown in FIG.2, within the cylindrical nozzle block 2, the

nozzles 2a are arranged diagonally in a circumferential direction, or

arranged linearly in a circumferential direction.

In the present invention, a yield per unit time can be increased by

arranging a large quantity of nozzles within a narrow space. The

cylindrical nozzle block 2 may consist of one or two or more unit blocks,

however, in a case where it consists of two or more unit blocks, it is

convenient to replace the nozzles, and it is easy to do cleaning if it is

desired to change the polymer to be used.

Meanwhile, the nozzles 2a are arranged on the cylindrical nozzle

block 2 as shown in FIG.3, and the length or diameter thereof are

variously adjustable according to a desired width, thickness, etc. of the

mat. Further, the length or diameter of the collector 3 can be freely

selected according to a desired width or thickness of the mat. The

cylindrical nozzle block 2 and the collector 3 can be constructed in

multilayers as explained above. By dividing the cylindrical nozzle block

2 into more than two layers and feeding polymer spinning dopes having a different concentration to each layer, mats having a different type of

polymer or different thickness of nano fibers can be prepared simultaneously. Further, by laminating them before winding, a hybrid

mat can be prepared easily. It is better to place the cylindrical nozzle block 2 on a given frame

so as to arbitrarily adjust the distance between the nozzles 2a and the

collector 3.

FIG.4 is a schematic view showing an angle (θ) between the center

line of the nozzles and the horizontal axis of the collector. The angle (θ)

between the center line of the nozzles and the horizontal axis of the

collector is -30 to 50°, and more preferably, -5 to 30^°. If it is above +50 \

it is not easy to adjust the distance between the collector and the nozzles,

thereby degrading the efficiency of electrospinning. If it is less than -30 ,

the efficiency of electrospinning is degraded and the dropping of the

spinning dope occurs a lot, thereby lowering the nano fiber forming

properties and deteriorating the quality of a finished product.

The polymer spinning dope includes components selected from the

group consisting of polyester resin, nylon resin, polysulfoiie resin,

polylactic acid, chitosan, collagen, cellulose, fibrinogen, a copolymer

thereof, sol-gel containing a metal component, a copolymer thereof and a

mixture thereof.

The gist of the present invention is to easily control physical

properties of the mat by freely adjusting the orientation angle (θ) of nano fibers relative to a mat axis direction according to the rotational linear

velocity of collector 3 since the cylindrical nozzle block 2 is located in the outside and the rotating cylindrical collector 3 is located within the

hollow portion of the nozzle block 2. Generally, it is difficult for the mat prepared by electrospinning to have a system capable of applying a physical force during an electrospinning process. Because the distance between the nozzles and the collector is 30cm or less, which is very slight, it is very difficult Io apply a mechanical force to a narrow space.

In the present invention, nano fibers are arranged in a mat axis direction using a centrifugal force of the collector 3 which is rotating.

In the present invention, a partially or completely drawn mat is prepared by electrically spinning a polymer spinning dope onto a rotating collector 3 through a plurality of nozzles arranged in a cylindrical nozzle block 2 and arranging nano fibers side by side on the collector 3.

As for a fiber prepared by electrospinning, it. is a general phenomenon that crystallization is performed to a considerable extent according to the characteristics of the material. Additionally, the orientation degree of nano fibers relative to a mat axis is very low, thus the mechanical properties are very low and it is very difficult to increase the physical properties through a separate drawing process. The reason of which is because the drawing properties are substantially deteriorated due to formed crystalline and the mechanical properties are very low due to a low orientation degree relative to the mat axis direction. Therefore, it is possible to prepare a mat which suppresses the crystalline formation during an electrospinning process, and which is very superior in physical properties by arranging fibers electrospun at regular intervals in the mat axis direction. If the nano fibers formed in the electrospinning process

are collected on the collector 3, which is a cylindrical rotating body,

crystalline formation can be suppressed and the nano fibers can be

arranged in a row relative to the mat axis, thereby enabling it to prepare a mat which has superior physical properties. If the rotational linear velocity of the collector is too low, it is difficult to suppress crystalline

formation, and it is impossible to orient electrospun nano fibers in a row

relative to the mat axis. In the present invention, depending on material, it is possible to obtain a mat having a low crystallinity or having partially/ completely drawn nano fibers oriented well relative to the mat

axis. Therefore, mechanical properties superior than properties

obtained by a melt-blown or spun bonding method can be obtained, and if drawing is required, if necessary, a mat composed of nano fibers having superior mechanical properties can be prepared by performing drawing

using a difference in the linear velocity of a roller.

If it is desired to prepare a mat of a hybrid type being composed of polymers of various width or two or more types, it can be prepared easily by using the above-explained multilayered cylindrical nozzle blocks and multilayered cylindrical collectors. In the present invention, two or more types of mats having εi different mat width can be prepared by differentiating the length (height) of each of the layers of the multilayered cylindrical nozzle block and of the multilayered cylindrical collectors, and various types of mats can be prepared by embossing these mats. Additionally, a hybrid mat composed of mats having a different nano fiber diameter can be prepared

by using two or more types of polymers. As the most representative one,

it is possible to prepare a hybrid mat composed of two types of different

polymers and nano fibers by simultaneously spinning po Iy ure thane onto

one layer and nylon onto another layer in the collector 3 and combining them by use of an embossing roller or the like.

Meanwhile, in the present invention, as shown in FIG.5, a hybrid

mat can be prepared by simultaneously preparing two or more continuous mats using two or more cylindrical nozzle blocks 2 and two or

more collectors 3 and then laminating them. FIG.5 is a schematic

process view according to the above method.

At this time, if a polymer spinning dope of a different polymer type or concentration is fed to the cylindrical nozzle blocks 2, respectively, it

makes it easier to prepare a hybrid mat.

If a spinning dope of the same polymer having a different concentration is fed to two or more cylindrical nozzle blocks 2,

respectively, a mat composed of nano fibers of two or more types having a different thickness can be prepared. Additionally, if a spinning dope of a different polymer type is led to them, respectively, the diameter of nano fibers is varied due to a difference in the type of polymers, thereby enabling preparation of a mat composed of nano fibers of two or more types having a different diameter and a different polymer type.

For example, in case of nylon 6, the diameter of generally prepared

nano fibers is 100 to 300 nm, and in case of polyurethane, the diameter

thereof is 200 to 500 nm. Hence, this makes it very easy to prepare two

types of hybrid mats having a different diameter and type of nano fibers.

Furthermore, in the present invention, there is included a process

of preparing a hybrid mat of a side-by-side type in which different

polymers are arranged in a regular, repeating manner by electrically

spinning two or more types of polymer spinning dopes through respective

nozzles arranged longitudinally in one or more rows.

The nozzles 2 may be of a dual core-shell structure or a triple or

more core- shell structure.

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

100 or more.

When electrically spinning a polymer spinning dope onto the

cylindrical collector 3 which is rotating, it is more preferable to feed a

nano fiber separating solution to the collector 3.

The nano fiber separating solution is one or two or more types of

mixtures selected from water, an organic solvent, surfactant, and silicon

oil.

Next, as shown in FIG. l , the nano fibers 2b collected on the cylindrical collector 3 are separated in the form of a continuous mat 5 by

using a feed roller 6, and then wound around a winding machine 7. Before winding the separated mat, it may be dried by a drier, drawn in

multiple stages by another drawing roller having a different rotational

linear velocity, or heated. A thermoplastic resin or thermosetting resin may be impregnated in the prepared mat.

Meanwhile, in the present invention, as shown in FIG.10, the polymer spinning dope in the polymer spinning dope main tank 4 is electrically spun on a fiber base 9 passing over the collector 3, which is a

rotating cylindrical conductive material, through the nozzles 2a in the cylindrical nozzle block 2, and the electrospun nano fibers 2b are coated

on the fiber base 9.

FIG.10 is a schematic process view of the present invention.

The fiber base 9 is a two-dimensional fiber base, such as a nonwoven fabric, woven fabric, knitted fabric, membrane, braid, etc., which is continuously fed onto the collector 3 from a supply roller.

At the time of electrospinning, it is preferable that the cylindrical

nozzle block 2 reciprocates up and down in order to uniformly coat nano

fibers on the fiber base 9 passing over the collector 3.

Next, the mat 10 coated with nano fibers is wound on the winding machine 7 by using the feed roller 6. The mat 10 coated with nano fibers may be embossed or dried before being wound around the winding machine 7.

The continuous mat of the present invention prepared by the above-described method according to the present invention is composed of nano fibers, and shows a necking stress or a partial/ complete stretched stress-strain curve on a stress-strain graph.

Meanwhile, the mat coated with nano fibers of the present invention prepared in the preparing process as shown in FIG.10 is composed of a fiber base 9 and nano fibers 2a coated on the fiber base 9.

The nano fibers coated on the mat 6 have a hollow shape or a shape in which pores are formed on the surfaces, and they are arranged at an orientation angle of les than 10° in the axis direction of the mat 6,

so the physical properties of the coating mat 7 are very superior. The nano fibers of the mat of the present invention may have a hollow shape or have pores formed on the surfaces.

Particularly, the continuous mat of the present invention is very superior in physical properties because the nano fibers are arranged at an orientation angle of 10° or less in the mat axis direction.

ADVANTAGEOUS EFECTS

The present invention allows easily adjustment of the orientation angle (θ) of nano fibers relative to a mat axis direction, and offers a high yield per unit time because a large quantity of nozzles can be arranged even in a narrow space.

Accordingly, the present invention can mass produce a nano fiber mat having various physical properties in a continuous process.

Additionally, the present invention can easily produce a hybrid mat composed of nano fibers having a different type of polymer or a

different diameter.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of a process of preparing a continuous

mat according to the present invention;

FIG.2 is a plane view of a cylindrical nozzle block and of a collector

of FIG.1 ;

FIG. 3 is a schematic perspective view of a cylindrical nozzle block

2 according to the present invention;

FIG.4 is a schematic view showing an angle (θ) between the nozzles

and the horizontal axis of the collector;

FIG.5 is a schematic view of a process of preparing a continuous

mat using two cylindrical nozzle blocks and two collectors according to

the present invention;

FIG.6 is an electron micrograph of the surface of the continuous

mat prepared by Example 1 ;

FIG.7 is an electron micrograph of the surface of the continuous

mat prepared by Example 2; FIG.8 is an electron micrograph of the surface of the continuous

mat prepared by Example 3;

FIG.9 is a schematic view of a process in which two continuous

mats are prepared by using two cylindrical nozzle blocks and two collectors, and then they are continuously laminated on both sides of a fiber base 9; and

FIG.10 is a schematic view of a process of preparing the a continuous mat by electrically spinning a polymer spinning dope onto the fiber base 9 passing over the collector according to the present invention .

BEST MODE FOR CARRYING OUT THE INVENTION

The present invention is now understood more concretely by comparison between examples of the present invention and comparative examples. However, the present invention is not limited to such

examples.

Example 1

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

Then, as shown in FIG. l, the prepared spinning dope was electrically spun onto a cylindrical (stainless steel) collector 3, which is a cylindrical conductive material with a high voltage applied thereto arid which rotates at a rotation linear velocity of 10 m/min, being located within a hollow portion of the cylindrical nozzle block 2, through nozzles 2a in the cylindrical nozzle block 2 having a high voltage applied thereto

and being formed in a core shell shape having the hollow portion, with

part of a side wall being cut and opened, such that the electrospun nano

fibers were collected on the collector 3. The length (height) of the

collector was 1.8m, and polypropylene was used as a support layer in the

inside thereof.

The collector rotates by being connected to a rotary motor by a

connecting rod, and the radius thereof was 1.85 m. The cylindrical

nozzle block 2 had a radius of 2.0 m and a length (height) of 1.8 m, was

divided into two unit blocks, has nozzles arranged in a diagonal direction,

and has one side of a side wall being cut to 56 cm and opened in order to

discharge the mat. 9,600 nozzles were arranged in columns and rows in

one unit block of the nozzle block 2, thus the total number of nozzles in

the cylindrical nozzle block 2 was 19,200. The angle (θ) between the

nozzles and the central axis of the collector was set to +8^°. At the time of

electrospinning, the nozzle block 2 was reciprocated up and down at a

velocity of lm/min, thereby making the lamination density of the nano

fibers uniform. The diameter of the nozzles was lmm, the voltage

thereof was 35 kV, and the spinning distance thereof was 15 cm. Additionally, at the time of electrospinning, water (nano fiber

separating solution) was fed to the collector.

Next, the nano fibers collected on the collector were separated in a mat form by using a feed roller 6 and wound on a winding machine 7, thereby preparing a mat having a weight of 1.40 g/m² and a width of 1 .5 m.

A result obtained by taking an electron micrograph of the surface

of the prepared mat is as in FIG.6.

Example 2

A polymer spinning dope was prepared by dissolving nylon 66 resin, which has a relative viscosity of 3.2 in a 96% sulfuric acid solution, in formic acid at a concentration of 15% by weight. The polymer spinning dope had a surface tension of 50 mN/m, a solution viscosity of 540 centipoise at an ambient temperature and an electrical conductivity of 430 mS/m.

Then, as shown in FIG. l, the prepared spinning dope was electrically spun onto a cylindrical (stainless steel) collector 3, which is a cylindrical conductive material with a high voltage applied thereto and which rotates at a rotation linear velocity of 5 m/min, being located within a hollow portion of the cylindrical nozzle block 2, through nozzles

2a in the cylindrical nozzle block 2 having a high voltage applied thereto and being formed in a core shell shape having the hollow portion, with part of a side wall being cut and opened, such that the electrospun nano fibers were collected on the collector 3. The length (height) of 1 lie collector was 1.8m, and polypropylene was used as a support layer in the inside thereof. The collector rotates by being connected to a rotary motor b}_^ a connecting rod, and the radius thereof was 1.85 m. The cylindrical nozzle block 2 had a radius of 2.0 m and a length (height) of 1.8 m, was divided into two unit blocks, has nozzles arranged in a diagonal direction, and has one side of a side wall being cut to 56 cm and opened in order to discharge the mat. 9,600 nozzles were arranged in columns and rows in one unit block of the nozzle block 2, thus the total number of nozzles in the cylindrical nozzle block 2 was 19,200. The angle (θ) between the nozzles and the central axis of the collector was set to +8°. At the time of

electrospinning, the nozzle block 2 was reciprocated up and down at a velocity of lm/min, thereby making the lamination density of the nano fibers uniform. The diameter of the nozzles was lmm, the voltage thereof was 35 kV, and the spinning distance thereof was 15 cm.

Additionally, at the time of electrospinning, water (nano fiber separating solution) was fed to the collector.

Next, the nano fibers collected on the collector were separated in a mat form by using a feed roller 6 and wound on a winding machine 7, thereby preparing a mat having a weight of 2.80 g/m² and a width of 1.5 m. A result obtained by taking an electron micrograph of the surface of the prepared mat is as in FIG.7.

Example 3

A polymer spinning dope was prepared by dissolving nylon 66 resin, which has a relative viscosity of 3.0 in a 96% sulfuric acid solution, in formic acid/ acetic acid (volume ratio: 70:30) at a concentration of 15% by weight. The polymer spinning dope had a surface tension of 37 mN/rn, a solution viscosity of 420 centipoise at an ambient temperature and an

electrical conductivity of 340 mS/m.

Then, as shown in FIG. l, the prepared spinning dope was electrically spun onto a cylindrical (stainless steel) collector 3, which is a cylindrical conductive material with a high voltage applied thereto and which rotates at a rotation linear velocity of 150 m/min, being located within a hollow portion of the cylindrical nozzle block 2, through nozzles 2a in the cylindrical nozzle block 2 having a high voltage applied thereto and being formed in a core shell shape having the hollow portion, with part of a side wall being cut and opened, such that the electro spun nano fibers were collected on the collector 3. The length (height) of the collector was 1.0m, and polypropylene was used as a support layer in the inside thereof.

The collector rotates by being connected to a rotary motor by a connecting rod, and the radius thereof was 1.0 m. The cylindrical nozzle block 2 had a radius of 3.0 m and a length (height) of 1.0 m, was divided into two unit blocks, has nozzles arranged in a diagonal direction, and has one side of a side wall being cut to 60 cm and opened in order to discharge the mat. 8, 160 nozzles were arranged in columns and rows in one unit block of the nozzle block 2, thus the total number of nozzles in the cylindrical nozzle block 2 was 16,320. The angle (θ) between the nozzles and the central axis of the collector was set to +5^°. At the time of electrospinning, the nozzle block 2 was reciprocated up and down at a velocity of lm/min, thereby making the lamination density of the nano fibers uniform. The diameter of the nozzles was lmm, the voltage thereof was 35 kV, and the spinning distance thereof was 15 cm.

Next, the nano fibers collected on the collector were separated in a mat form by using a feed roller 6 and wound on a winding machine 7, thereby preparing a mat having a weight of 0.25 g/m² and a width of 0.5 m.

A result obtained by taking an electron micrograph of the surface of the prepared mat is as in FIG.8. The orientation angle (θ) of the nano fibers relative to the mat axis was 1.9°.

Example 4

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

Then, as shown in FIG. l, the prepared spinning dope was

electrically spun onto a nonwoven fabric (weight: 15g/m²) passing at a

velocity of 30 m/min over a cylindrical (stainless steel) collector 3, which

is a cylindrical conductive material with a high voltage applied thereto

and which rotates at a rotation linear velocity of 30 m/min, being located

within a hollow portion of the cylindrical nozzle block 2, through nozzles

2a in the cylindrical nozzle block 2 having a high voltage applied thereto

and being formed in a core shell shape having the hollow portion, with

part of a side wall being cut and opened, such that the electrospun nano

fibers 2b were coated on the nonwoven fabric. The length (height) of the

collector was 1.8m, and polypropylene was used as a support layer in the

inside thereof.

The collector rotates by being connected to a rotary motor by a

connecting rod, and the radius thereof was 1.85 m. The cylindrical

nozzle block 2 had a radius of 2.0 m and a length (height) of 1.8 m, was

divided into two unit blocks, has nozzles arranged in a diagonal direction,

and has one side of a side wall being cut to 80 cm and opened in order to

discharge the mat. 9,600 nozzles were arranged in columns and rows in one unit block of the nozzle block 2, thus the total number of nozzles in

the cylindrical nozzle block 2 was 19,200. The angle (θ) between the nozzles and the central axis of the collector was set to +5^°. At the 1 imc of

electrospinning, the nozzle block 2 was reciprocated up and down at a velocity of 10 m/min, thereby making the lamination density of the nano fibers uniform. The diameter of the nozzles was lmm, the voltage thereof was 35 kV, and the spinning distance thereof was 15 cm.

Next, the nonwoven fabric 10 coated with the nano fibers were wound on a winding machine 7 by using a feed roller 6, thereby preparing a mat having a width of 1.5 m with a coating amount of 0.48 g/ m² of nano fibers having an average diameter of 180 nm.

A result of evaluation of various physical properties of the prepared mat was as shown in Table 1.

Example 5

A polymer spinning dope was prepared by dissolving a polystyrene resin (purchased from Aldrich Chemical Company) having a number average molecular weight of 140,000 in tetrahydrofuran at a concentration of 45% by weight.

Then, as shown in FIG. l, the prepared spinning dope was electrically spun onto a nonwoven fabric (weight: 15g/m²) passing at a velocity of 60 m/min over a cylindrical (stainless steel) collector 3, which is a cylindrical conductive material with a high voltage applied thereto and which rotates at a rotation linear velocity of 60 m/min, being located within a hollow portion of the cylindrical nozzle block 2, through nozzles 2a in the cylindrical nozzle block 2 having a high voltage applied thereto and being formed in a core shell shape having the hollow portion, with part of a side wall being cut and opened, such that the electrospuri nano

fibers 2b were coated on the nonwoven fabric. The length (height) of the

collector was 1.8m, and polypropylene was used as a support layer in the

inside thereof.

The collector rotates by being connected to a rotary motor by a

connecting rod, and the radius thereof was 1.85 m. The cylindrical

nozzle block 2 had a radius of 2.0 m and a length (height) of 1.8 m, was

divided into two unit blocks, has nozzles arranged in a diagonal direction,

and has one side of a side wall being cut to 80 cm and opened in order to

discharge the mat. 9,600 nozzles were arranged in columns and rows in

one unit block of the nozzle block 2, thus the total number of nozzles in

the cylindrical nozzle block 2 was 19,200. The angle (0) between the

nozzles and the central axis of the collector was set to +5^°. At the time of

electrospinning, the nozzle block 2 was reciprocated up and down at a

velocity of 10 m/min, thereby making the lamination density of the nano

fibers uniform. The diameter of the nozzles was lmm, the voltage

thereof was 35 kV, and the spinning distance thereof was 20 cm.

Next, the nonwoven fabric 10 coated with the nano fibers were

wound on a winding machine 7 by using a feed roller 6, thereby preparing

a mat having a width of 1.5 m with a coating amount of 2.4 g/m² of nano fibers having an average diameter of 480 nm. A result of evaluation of

various physical properties of the prepared mat was as shown in Table 1 . Table 1

Result of Evaluation of Physical Properties

Example 4 Example 5

Air Permeability 11.7 12.5 (cc/cm²/sec)

Pressure Drop 6.4 6.0 (mmH₂O)

Filtration Efficiency 99.999 99.999

(%)

In the present invention, various physical properties of the mat (coating mat) coated with nano fibers were evaluated by the following method.

* Air Permeability (cc/cm²/sec)

It was measured according to the KSK 0570 method. As the measuring instrument, a Fx 330 tester from Textest was used. The pressure was 125 Pa, and the area measured was 38 cm².

^• Pressure Drop (mmFføO)

It was measured by a TSI 8110 measuring device from TST. When passing a flow amount of 32# per minute through the surface area of 100cm² of samples, the difference between the pressure before passing through the samples and after passing through the samples was expressed as a pressure drop.

INDUSTRIAL APPLICABILITY

The nano fiber mat prepared according to the present invention is useful as materials for various industrial fields, such as an artificial dialyzing filter, artificial vessel, anti-adhesion agent, artificial bone, bottom decoration material, compound material and so on, as well as daily necessities, such as artificial leather, air cleaning filters, wiping cloths, golf gloves, wigs and so on.

Claims

WHAT IS CLAIMED IS:

1. A method of manufacturing a continuous mat consisting

nanofibers by electrospinning, wherein electronspun nano fibers 2b are

collected on a collector 3 by electrically spinning a polymer spinning dope

in a spinning dope main tank 4 onto the collector 3, which is a cylindrical

conductive material with a high voltage applied thereto and which rotates

being located within a hollow portion of a cylindrical nozzle block 2,

through nozzles 2a in the cylindrical nozzle block 2 having a high voltage

applied thereto and being formed in a core shell shape having the hollow

portion, with part of a side wall being cut and opened, and then the

collected nano fibers 2b are separated from the collector 3 in the form of εi

continuous mat 5 by a feed roller 6 and wound on a winding machine 7.

2. The method of claim 1, wherein the continuous mat 5

separated from the collector 3 is embossed, dried or drawn before being

wound.

3. The method of claim 1, wherein the nozzles 2a are arranged diagonally in a circumferential direction, or linearly in a circumferential

direction within the cylindrical nozzle block 2.

4. The method of claim 1 , wherein the cylindrical nozzle block 2 consists of one or two or more unit blocks.

5. The method of claim 1 , wherein the nozzle block 2

reciprocates up and down.

6. The method of claim 1, wherein the angle (θ) between the

horizontal axis of the collector 7, which is a cylindrical conductive

material, and the nozzles 2a is -30 to 50^°.

7. The method of claim 1, wherein the angle (θ) between the

horizontal axis of the collector 7, which is a cylindrical conductive

material, and the nozzles 2a is -5 to 30^°.

8. The method of claim 1, wherein the nozzles are of a dual

core-shell structure or a triple or more core-shell structure.

9. The method of claim 1 , wherein the nozzles 2a are

longitudinally arranged in two or more rows such that the angle (0) between the horizontal axis of the collector 3, which is a cylindrical conductive material, and the nozzles 2a is different from each other.

10. The method of claim 1 , wherein the polymer spinning dope

includes components selected from the group consisting of polyester resin, nylon resin, polysulfone resin, polylactic acid, chitosan, collagen,

cellulose, fibrinogen, a copolymer thereof, sol-gel containing a metal

component, a copolymer thereof and a mixture thereof.

1 1. The method of claim 1 , wherein a nano fiber separating

solution is fed onto the collector 3 which is a cylindrical conductive

material.

12. The method of claim 1 1 , wherein the nano fiber separating

solution is one or two or more types of mixtures selected from water, an

organic solvent, surfactant, and silicon oil.

13. The method of claim 1, wherein the number of the nozzles

2a is one or more.

14. The method of claim 1 , wherein the number of the nozzles

2a is 100 or more.

15. The method of claim 1 , wherein each of the cylindrical nozzle block 2 and the collector 3, which is a cylindrical conductive

material, are in a multilayered form which is divided into two or more layers by a dividing plate which is a non-conductive material.

16. The method of claim 15, wherein each of the cylindrical nozzle block 2 and the collector 3 having a multilayered form are an integral type or a dividing type.

17. The method of claim 15, wherein the height of each of the

layers of the cylindrical nozzle block 2 and the collector 3, respectively, is different from each other.

18. The method of claim 1, wherein two or more mats are simultaneously prepared by using two or more cylindrical nozzle blocks 2 and two or more collectors 3, which are a cylindrical conductive material, respectively.

19. The method of claim 18, wherein two or more different types of polymer spinning dopes are fed to the two or more cylindrical nozzle blocks 2, respectively.

20. The method of claim 18, wherein the two or more prepared mats are laminated before winding the mats.

21. The method of claim 18, wherein the two or more cylindrical nozzle blocks 2 are different in diameter from each other.

22. The method of claim 18, wherein the two or more collectors 3, which are a cylindrical conductive material, are different in diameter from each other.

23. The method of claim 1, wherein the polymer spinning dope is electrically spun on a fiber base 9, passing over the collector 3, through the nozzles 2a.

24. The method of claim 23, wherein the fiber base 9 is one selected from the group consisting of a nonwoven fabric, woven fabric, knitted fabric, membrane, and braid.

25. The method of claim 23, wherein the fiber base 9 is continuously fed onto the collector 3 from a supply roller.

26. A continuous mat manufactured in the method of any one of claims 1 to 25, which is composed of nano fibers, and shows a necking stress or a partial/ complete stretched stress-strain curve on a stress-strain graph.

27. The continuous mat of claim 26, wherein the nano fibers have a hollow shape or have pores formed on the surfaces.

28. The continuous mat of claim 26, wherein the nano fibers are arranged at an angle of 10° or less in the axis direction of the

continuous mat.

29. The continuous mat of claim 26, wherein a thermoplastic resin or thermosetting resin is contained between the nano fibers.