U.S. patent application number 11/570663 was filed with the patent office on 2008-10-02 for filament bundle type nano fiber and manufacturing method thereof.
This patent application is currently assigned to KOREA RESEARCH INSTITUTE OF CHEMICAL TECHNOLOGY. Invention is credited to Young-Taik Hong, Seung-Yong Jee, Hyo-Jung Kim, Seok Kim, Jae-Rock Lee, Soo-Jin Park.
Application Number | 20080241538 11/570663 |
Document ID | / |
Family ID | 35509695 |
Filed Date | 2008-10-02 |
United States Patent
Application |
20080241538 |
Kind Code |
A1 |
Lee; Jae-Rock ; et
al. |
October 2, 2008 |
Filament Bundle Type Nano Fiber and Manufacturing Method
Thereof
Abstract
A filament type nano-sized long fiber and a method of producing
the same are disclosed. In the method, a spinning solution or a
spinning melt is electro-spun in drops using a spinneret to which a
critical voltage is applied, and the spun drops are continuously
collected on a multi-collector. The spinning solution is produced
by dissolving a blend or copolymer consisting of two or more kinds
of polymers in a solvent. The spinning melt is produced by melting
the polymers. The multi-collector is selected from the group
consisting of a plate type collector, a roll type collector, and a
combination thereof. The filament type nano-sized long fiber is
processed into a yarn through one step during the electrospinning
process, and thus, mechanical properties are better than those of a
conventional nanofiber non-woven fabric. Consequently, the filament
type nano-sized long fiber can be utilized for the extended
application.
Inventors: |
Lee; Jae-Rock; (Daejun,
KR) ; Jee; Seung-Yong; (Daejun, KR) ; Kim;
Hyo-Jung; (Daejun, KR) ; Hong; Young-Taik;
(Daejun, KR) ; Kim; Seok; (Daejun, KR) ;
Park; Soo-Jin; (Daejun, KR) |
Correspondence
Address: |
BELL, BOYD & LLOYD, LLP
P.O. Box 1135
CHICAGO
IL
60690
US
|
Assignee: |
KOREA RESEARCH INSTITUTE OF
CHEMICAL TECHNOLOGY
Daejun
KR
|
Family ID: |
35509695 |
Appl. No.: |
11/570663 |
Filed: |
September 17, 2004 |
PCT Filed: |
September 17, 2004 |
PCT NO: |
PCT/KR04/02385 |
371 Date: |
March 27, 2007 |
Current U.S.
Class: |
428/401 ;
264/465; 428/364; 977/788 |
Current CPC
Class: |
Y10T 428/29 20150115;
D01F 6/90 20130101; D01F 6/80 20130101; Y10T 428/298 20150115; D01D
5/0076 20130101; Y10T 428/2913 20150115; Y10T 428/2929
20150115 |
Class at
Publication: |
428/401 ;
264/465; 428/364; 977/788 |
International
Class: |
D01D 5/00 20060101
D01D005/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 17, 2004 |
KR |
10-2004-0044902 |
Claims
1. A filament bundle type nano-sized fiber produced through a
process comprising electrospinning a spinning solution or a
spinning melt in drops using a spinneret to which a critical
voltage is applied, and continuously collecting the spun drops on a
multi-collector, the spinning solution having been produced by
dissolving a blend or copolymer consisting of two or more kinds of
polymers in a solvent, the spinning melt being produced by melting
the polymers, and the multi-collector is selected from the group
consisting of a plate type collector, a roll type collector, and a
combination thereof.
2. The filament bundle type nano-sized fiber as set forth in claim
1, wherein each of the polymers is a mixture of two or more
selected from the group consisting of polyimide, polyamide,
polyethylene, polypropylene, polyester, polyvinylidene fluoride,
polyacrylonitrile, polysulfone, and polyethylene oxide.
3. The filament bundle type nano-sized fiber as set forth in claim
1, wherein each of the polymers contains one or more amine groups
selected from the group consisting of monoamine, diamine, triamine,
and tetramine.
4. The filament bundle type nano-sized fiber as set forth in claim
1, wherein each of the polymers is a polyamide-polyimide copolymer
including a compound expressed by Formula 1, in which m is 1-99 mol
%, and the other compound expressed by Formula 2, in which n is
1-99 mol %. Formula 1 ##STR00002##
5. The filament bundle type nano-sized fiber as set forth in claim
4, wherein the polyamide-polyimide copolymer has a number average
molecular weight of 200-1,000,000.
6. The filament bundle type nano-sized fiber as set forth in claim
1, wherein the solvent is any one selected from the group
consisting of N-methyl-2-pyrrolidone, .gamma.-butyrolactone,
2-butoxyethanol, dimethylacetamide, and dimethylformamide.
7. The filament bundle type nano-sized fiber as set forth in claim
1, wherein a filament type nanofiber is a nano-sized long fiber
having a diameter of 1-1,000 nm.
8. A method of producing a filament bundle type nano-sized fiber,
comprising: 1) preparing a spinning solution, wherein 10-50 wt % of
blend or copolymer consisting of two or more kinds of polymers is
dissolved in a solvent, or a spinning melt, which is produced by
heating the polymers to at least a melting point of the polymers to
melt the polymers; 2) electrospinning the spinning solution or the
spinning melt in drops using a spinneret to which a critical
voltage is applied; and 3) discharging the spun drops onto a first
collector to produce nanofibers, and recollecting the nanofibers,
which are collected on the first collector, on a second collector
to continuously collect the nanofibers, wherein at least one of the
first and second collectors rotates.
9. The method as set forth in claim 8, wherein one or more
collectors are further used in addition to the first and second
collectors.
10. The method as set forth in claim 8, wherein the first collector
consists of a metal plate or mesh made of an electrically
conductive material, and is fixed.
11. The method as set forth in claim 8, wherein the second
collector is selected from the group consisting of a glass tube,
plastic tube, rod made of a material capable of generating static
electricity, and a tube or rod coated with the material capable of
generating static electricity.
12. The method as set forth in claim 8, wherein the second
collector is a roll type and rotates at 1-100 rpm.
13. The method as set forth in claim 8, wherein a distance between
the spinneret and the first collector is 1-100 cm.
14. The method as set forth in claim 8, wherein a distance between
the first and second collectors is 1-100 cm.
15. The method as set forth in claim 8, wherein the first collector
consists of a metal plate or mesh made of an electrically
conductive material, and rotates at 1-1,000 rpm.
Description
TECHNICAL FIELD
[0001] The present invention relates to a filament type nano-sized
long fiber and a method of producing the same. More particularly,
the present invention pertains to a filament type nano-sized long
fiber and a method of producing the same using an improved
electrospinning process. In the method, a spinning solution or a
spinning melt is electro-spun in drops using a spinneret to which a
critical voltage is applied, and the spun drops are continuously
collected on a multi-collector. In this regard, the spinning
solution is produced by dissolving a blend or copolymer consisting
of two or more kinds of polymers in a solvent. The spinning melt is
produced by melting the polymers. Furthermore, the multi-collector
is selected from the group consisting of a plate type collector, a
roll type collector, and a combination thereof.
BACKGROUND ART
[0002] A nanofiber is an ultra-fine fiber having a diameter of
1-800 nm, and has various physical properties that cannot be gained
from a conventional fiber. Accordingly, a web, composed of the
nanofiber, as a membrane type porous material may be usefully
applied to various fields, such as filters, wound dressings,
artificial supporters, defensive clothes against biochemical
weapons, separation membranes for secondary batteries, and
nanocomposites.
[0003] A representative example of a conventional process of
producing the nanofiber includes an electrospinning process where a
raw material solution of a fiber is spun while being charged to
produce a fiber having a very small diameter. Examples of the
production of the nanofiber using the electrospinning process are
disclosed in Korean Pat. Laid-Open Publication Nos. 2000-11018,
2003-3925, and 2003-77384, and U.S. Pat. No. 6,183,670. However,
the nanofiber produced according to the conventional
electrospinning process is limited to a non-woven fabric type. With
respect to this, Doshi et al. assert that nanofibers are produced
in a form of nanoweb, that is, non-woven fabric, because, when
drops, which consist of a polymer solution and are formed at a tip
of a spinneret, burst by an applied high voltage and are then
collected on a collector to produce the nanofibers through the
conventional electrospinning process, the nanofibers are
anisotropically oriented in the collector [Doshi and Reneker,
"Electrospinning Process and Application", Journal of
Electrostatics, 1995, 35, 151-160].
[0004] Furthermore, they point out a problem that since the
non-woven fabric type nanofiber consists of a single fiber, while
the drops, which are formed at the tip of the spinneret during the
electrospinning process, are spun toward the collector at a
critical voltage (V.sub.c), the single fibers collide with each
other before the drops reach the collector. Consequently, the
single fibers are interfered or combined with each other, causing
conglomeration. With respect to this, Korean Pat. Laid-Open
Publication No. 2002-50381 discloses the production of a nanofiber
employing a copolymer of polyethylene terephthalate and polyester,
instead of a single component, as a spinning solution through a
conventional electrospinning process. However, that nanofiber does
not break from a non-woven fabric type, either. The non-woven
fabric type nanofiber has very poor mechanical strength.
Particularly, if the nanofibers are intertwined into a thread,
undesirably, an additional connection fiber is required to connect
the single fibers to each other, and the final thread is readily
broken. Accordingly, there remains a need to improve the non-woven
fabric type nanofiber so as to be applied to various fields.
[0005] Therefore, the present inventors have conducted studies into
the production of a nanofiber capable of being applied to various
fields, resulting in the finding of the following fact. In a
procedure of producing the nanofiber where drops, which consist of
a polymer solution and are formed at a tip of a spinneret, burst by
an applied high voltage to be collected on a collector according to
a conventional electrospinning process, after the polymer solution
is spun to one or more first collectors to produce the nanofiber,
the nanofiber, which is collected on the first collector, is
recollected onto a second collector to be continuously collected
thereon, thereby continuously producing a filament type nanofiber
having mechanical properties that are better than a conventional
nanofiber. Based on the above finding, the present inventors
accomplished the present invention.
DISCLOSURE OF THE INVENTION
Technical Objects
[0006] An object of the present invention is to provide a filament
type nano-sized long fiber.
[0007] Another object of the present invention is to provide a
method of producing a filament type nano-sized long fiber. In the
method, a spinning solution or a spinning melt is electro-spun in
drops using a spinneret to which a critical voltage is applied, the
spun drops are collected on one or more first collectors to form a
nanofiber, and the nanofiber, which is collected on the first
collectors, is recollected onto a second collector to be
continuously collected thereon. In this regard, at least one
collector revolves.
[0008] A further object of the present invention is to provide a
method of producing a filament type nano-sized long fiber, which is
realized by a design of a molecular structure suitable in
electrospinning, or an optimum combination condition of compounds
having such molecular structure.
Technical Solution
[0009] In order to accomplish the above objects, the present
invention provides a filament type nano-sized long fiber produced
through a process which comprises electrospinning a spinning
solution or a spinning melt in drops using a spinneret to which a
critical voltage is applied, and continuously collecting the spun
drops in a multi-collector. The spinning solution is produced by
dissolving a blend or copolymer consisting of two or more kinds of
polymers in a solvent. The spinning melt is produced by melting the
polymers. The multi-collector is selected from the group consisting
of a plate type collector, a roll type collector, and a combination
thereof.
[0010] In this regard, each of the polymers is a mixture of two or
more selected from the group consisting of polyimide, polyamide,
polyethylene, polypropylene, polyester, polyvinylidene fluoride,
polyacrylonitrile, polysulfone, and polyethylene oxide. More
preferably, each of the polymers contains one or more amine groups
selected from the group consisting of monoamine, diamine, triamine,
and tetramine. It is most preferable to use a polyamide-polyimide
copolymer as that polymer. The solvent is any one selected from the
group consisting of N-methyl-2-pyrrolidone, .gamma.-butyrolactone,
2-butoxyethanol, dimethylacetamide, and dimethylformamide.
Additionally, the present invention provides a filament yarn
consisting of a nano-sized long fiber having a diameter of 10-500
nm.
[0011] The present invention provides a method of producing the
nano-sized long fiber having the diameter of 10-500 nm. More
specifically, the method comprises 1) preparing a spinning
solution, in which 10-50 wt % of blend or copolymer consisting of
two or more kinds of polymers is dissolved in a solvent, or a
spinning melt, which is produced by heating the polymers at a
melting point or higher to melt the polymers, 2) electrospinning
the spinning solution or the spinning melt in drops using a
spinneret to which a critical voltage is applied, and 3)
discharging the spun drops onto a first collector to produce
nanofibers, and recollecting the nanofibers, which are collected on
the first collector, on a second collector to continuously collect
the nanofibers. At least one of the first and second collectors
rotates. Furthermore, one or more collectors may be further
employed in addition to the first and second collectors.
[0012] The first collector consists of a metal plate or mesh made
of an electrically conductive material, and is fixed or rotates at
10-1000 rpm. It is preferable to use the plate-type first
collector. The second collector consists of a glass or plastic tube
or rod made of a material capable of generating static electricity,
or a tube or rod coated with the material. As well, it is
preferable that the second collector be a roll type and rotate at
20-80 rpm.
[0013] In the method of the present invention, during the
electrospinning process, it is preferable that a distance between
the spinneret and the first collector be 5-20 cm, and that a
distance between the first and second collectors be 3-25 cm.
ADVANTAGEOUS EFFECTS
[0014] As described above, a filament type nano-sized long fiber,
which is produced using an improved electrospinning process
according to the present invention, has mechanical properties that
are better than a conventional nanofiber non-woven fabric, thereby
being applied as a substitute to all fields employing a
conventional fiber having a micron-sized diameter. For example,
first, the fiber of the present invention is useful as medical
filters for kidney dialysis and purification of the blood, and
various membrane reinforcing materials for genetic separation.
Second, the fiber of the present invention is useful to produce
ultra-thin reinforcing films and ultra-slim PCBs in
electric/electronic fields. Third, the fiber of the present
invention may be useful for ultra-small and ultra-light flying
bodies or unmanned flying robots. Fourth, the fiber of the present
invention is useful as a reinforcing material for an optical cable
in an optical communication field.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] FIG. 1 illustrates an electrospinning process using a
multi-collector according to the first embodiment of the present
invention;
[0016] FIG. 2 is a SEM (scanning electron microscope) image of a
surface of a nanofiber produced according to the first embodiment
of the present invention, which is magnified 300 times;
[0017] FIG. 3 is a SEM image of the surface of the nanofiber
produced according to the first embodiment of the present
invention, which is magnified 20,000 times;
[0018] FIG. 4 illustrates an electrospinning process using a
multi-collector according to the second embodiment of the present
invention;
[0019] FIG. 5 is a SEM image of a surface of a nanofiber produced
according to the second embodiment of the present invention, which
is magnified 3,000 times;
[0020] FIG. 6 illustrates an electrospinning process using a
multi-collector according to the third embodiment of the present
invention;
[0021] FIG. 7 is a SEM image of a surface of a nanofiber produced
according to the third embodiment of the present invention, which
is magnified 300 times;
[0022] FIG. 8 illustrates an electrospinning process using a
multi-collector according to the fourth embodiment of the present
invention;
[0023] FIG. 9 is a SEM image of a surface of a nanofiber produced
according to the fourth embodiment of the present invention, which
is magnified 50 times;
[0024] FIG. 10 illustrates an electrospinning process using a
multi-collector according to the fifth embodiment of the present
invention;
[0025] FIG. 11 is a SEM image of a surface of a nanofiber produced
according to the fifth embodiment of the present invention, which
is magnified 300 times;
[0026] FIG. 12 illustrates an electrospinning process using a
multi-collector according to the sixth embodiment of the present
invention;
[0027] FIG. 13 is a SEM image of a surface of a nanofiber produced
according to the sixth embodiment of the present invention, which
is magnified 300 times;
[0028] FIG. 14 illustrates a conventional electrospinning process
employing a single collector;
[0029] FIG. 15 is a SEM image of a surface of a nanofiber produced
according to the conventional electrospinning process employing the
single collector, which is magnified 300 times; and
[0030] FIG. 16 is a SEM image of the surface of the nanofiber
produced according to the conventional electrospinning process
employing the single collector, which is magnified 20,000
times.
BEST MODE FOR CARRYING OUT THE INVENTION
[0031] Hereinafter, a detailed description will be given of the
present invention. The present invention provides a filament type
nano-sized long fiber produced through a process which comprises
electrospinning a spinning solution or a spinning melt in drops
using a spinneret to which a critical voltage is applied, and
continuously collecting the spun drops in a multi-collector. The
spinning solution is produced by dissolving a blend or copolymer
consisting of two or more polymers in a solvent, and the spinning
melt is produced by melting the polymers. The multi-collector is
selected from the group consisting of a plate type collector, a
roll type collector, and a combination thereof.
[0032] More specifically, in the electrospinning, after the drops
are spun onto a first collector to form a nanofiber, the nanofiber,
which is collected on the first collector, is recollected onto a
second collector to be continuously collected thereon. At this
time, at least one of the collectors rotates. Thereby, a nano-sized
filament yarn is provided in the type of a bunch of continuous
yarns. The filament yarn has a diameter of 10-500 nm and has a
twisting property (FIGS. 2, 5, 7, 9, 11, and 13).
[0033] On the other hand, when using a conventional electrospinning
process, a nanofiber is produced in the type of net-shaped
non-woven fabric (FIGS. 15 and 16).
[0034] If staples are processed into a continuous yarn,
undesirably, breaking may easily occur because the staples must be
connected to each other. However, in the present invention, the
continuous yarn is produced through a continuous process, and thus,
the nanofiber can be produced through one process without breakage
of the nanofiber.
1. Production of a Spinning Solution or a Spinning Melt
[0035] A nanofiber of the present invention is realized by
providing a design of a molecular structure suitable to an
electrospinning process, or an optimum combination condition of
compounds having such molecular structure.
[0036] In detail, any polymer may be used to produce the spinning
solution of the present invention as long as it has excellent
miscibility to a solvent and excellent mechanical strength.
Illustrative, but non-limiting, examples of the polymer include a
mixture of two or more selected from the group consisting of
polyimide, polyamide, polyethylene, polypropylene, polyester,
polyvinylidene fluoride, polyacrylonitrile, polysulfone, and
polyethylene oxide. More preferably, the polymer of the present
invention includes one or more amine groups selected from the group
consisting of monoamine, diamine, triamine, and tetramine. Diamine
is selected from the group consisting of phenylenediamine,
oxyphenylenediamine, and alkyl phenylenediamine.
[0037] Most preferably, the polymer is a polyamide-polyimide
copolymer consisting of a compound, expressed by Formula 1, and
another compound, expressed by Formula 2.
In Formula 1, it is preferable that m be 20-35 mol %. In this
regard, when m is less than 20 mol %, undesirably, the polymer is
excessively flexible because of low crystallinity. When m is more
than 40 mol %, undesirably, the polymer is brittle because of poor
impact resistance due to high crystallinity. Furthermore, it is
preferable that n be 65-80 mol %. When n is less than 65 mol %,
impact resistance is poor because of high crystallinity, and when n
is more than 80 mol %, undesirably, it is excessively flexible
because of low crystallinity. The polyamide-polyimide copolymer
(m+n) has a number average molecular weight of about 500-10,000.
When the number average molecular weight is less than 500,
viscosity and mechanical strength are low due to the low molecular
weight. When the number average molecular weight is more than
10,000, undesirably, viscosity is excessively increased and it is
hard to process the polymer according to an increase in the
molecular weight.
Formula 1
##STR00001##
[0039] A polymer used in a conventional electrospinning process
consists of one component phase, whereas the polymer used in the
present invention is a blend or a copolymer consisting of two
component phases. Accordingly, in the conventional electrospinning
process, when a cone formed at a tip of a spinneret is spun at a
critical voltage (V.sub.c) toward a collector, single fibers
collide with each other before they reach the collector, and thus,
they are interfered or combined with each other, causing
conglomeration, thereby creating a non-woven fabric type fine
fiber. On the other hand, the use of the polymer blend or copolymer
consisting of the two component phases according to the present
invention prevents the interference or combination between single
fibers, thereby producing a continuous yarn.
[0040] Any solvent capable of desirably dissolving the polymer may
be used as the solvent of the present invention. Illustrative, but
non-limiting, examples of the solvent are selected from the group
consisting of N-methyl-2-pyrrolidone, .gamma.-butyrolactone,
2-butoxyethanol, dimethylacetamide, and dimethylformamide. It is
more preferable to use N-methyl-2-pyrrolidone.
[0041] Even though the same polymer is employed, an intrinsic
critical voltage (V.sub.c) may be changed depending on viscosity of
the polymer solution. Furthermore, frictional force applied to the
polymer solution depends on a diameter and a material of a
spinneret, and thus, a speed of the polymer solution flowing toward
the lowest stage of the spinneret, and a form of a cone-shaped drop
may be changed depending on the diameter and the material. In this
regard, the diameter and the material of the spinneret indirectly
affects the formation of the cone-shaped drop during the
electrospinning process, whereas a concentration of the polymer
solution acts as a most important factor affecting that formation.
Accordingly, a discharging speed of the polymer solution (ml/min)
and the formation of the drop at the tip of the spinneret depend on
the concentration of the polymer solution during the
electrospinning process. With respect to this, it is preferable
that the polymer solution of the present invention contain 10-50 wt
% of polymer based on the solvent. When the concentration is less
than 10 wt %, the breaking of the spun fiber occurs. When the
concentration is more than 50 wt %, viscosity significantly
increases, making a shape of the cone formed at the spinneret
unstable.
[0042] Hence, in the present invention, if the electrospinning
process is conducted employing the spinneret, which is provided
with a tube that has a diameter of 0.42 mm and is made of stainless
steel, it is preferable to use the spinning solution in which 25 wt
% of polyamide-polyimide copolymer is dissolved in a
N-methyl-2-pyrrolidone solvent. In this case, the discharging speed
is 0.3 ml/min.
[0043] The spinning melt, which is produced by melting the polymer
at a melting temperature or higher, may be applied to the
electrospinning process instead of the spinning solution in which
the blend or copolymer consisting of two or more components is
dissolved in the solvent. In the present invention, a
multi-collector is employed in the course of electrospinning the
nanofiber to improve the conventional electrospinning process. Any
material used in the conventional process may be applied to the
nanofiber of the present invention. For example, a ceramic melt, a
metal melt, an organic-inorganic hybrid melt, a metal-organic
composite melt, a carbon melt, or a sol-gel solution may be
employed, and the melt can be produced by heating the material at a
phase transition temperature or higher.
2. Electrospinning Employing a Multi-Collector
[0044] In a method of producing a nanofiber according to the
present invention, the multi-collector is employed during an
electrospinning process to improve a conventional electrospinning
process. In detail, a method of producing the nanofiber according
to the present invention comprise 1) preparing a spinning solution,
in which 10-50 wt % of blend or copolymer consisting of two or more
kinds of polymers is dissolved in a solvent, or a spinning melt,
which is produced by heating the polymers at a melting point or
higher to melt the polymers, 2) electrospinning the spinning
solution or the spinning melt in drops using a spinneret to which a
critical voltage is applied, and 3) discharging the spun drops onto
a first collector to produce nanofibers, and recollecting the
nanofibers, which are collected on the first collector, onto a
second collector to continuously collect the nanofibers. During the
collection, at least one of the first and second collectors
rotates.
[0045] In the method, one or more collectors may further employed
in addition to the first and second collectors.
[0046] The first collector is made of an electric conductive metal
plate or a metal mesh. A shape of the first collector is not
limited, but it is preferable to use a plate-type collector, which
is of a disk or rectangular shape. A size of the plate-type
collector depends on viscosity of a polymer solution and a critical
voltage (V.sub.c) corresponding to the viscosity, and it is
preferable that the size be the same as or larger than a collected
area of the nanofiber produced by the spinning using the spinneret.
Furthermore, it is preferable that a distance between the spinneret
and the first collector be 5 to 20 cm. When the distance is less
than 5 cm, the formation of a fiber is unstable because of
formation of particles, and when the distance is more than 20 cm,
the nanofiber deviates from a collector region, failing in economic
efficiency. The first collector may be positioned perpendicular or
parallel to the spinneret, and one or more first collectors may be
employed. Additionally, the first collector may be fixed to a base
or rotate at a predetermined speed. When the first collector
rotates, the desirable speed depends on a twist of the desired
nanofiber, and may be 10-1000 rpm. At this stage, when the speed is
10 rpm or less, the nanofiber is collected on only a specific
portion because of the low speed. When the speed is 1000 rpm or
more, the nanofiber is insufficiently formed from the spinneret and
thus breaking of the nanofiber occurs, resulting in a reduced yield
of the nanofiber.
[0047] The second collector is made of a material capable of
generating static electricity, and may consist of a glass or
plastic tube or rod, or a tube or rod coated with the material. The
second collector is a roll-type collector rotating at 20-80 rpm. In
this respect, a distance between the first and second collectors
and the rotating speed depends on a diameter of the desired
nanofiber, and may be determined so that the nanofiber is not
broken. Preferably, the distance is 3-25 cm. If the distance is
less than 3 cm, fibers are entangled, and if the distance is more
than 25 cm, the fibers may be broken.
In a procedure of recollecting the nanofiber, which was collected
on the first collector, onto the second collector, a process where
the nanofiber, collected on the first collector, is transferred
onto the second collector using an additional charged rod, or
another process where the second collector, which is made of a
material generating static electricity, moves toward the first
collector, a portion of the collected nanofiber is transferred onto
the second collector, and the second collector moves, may be
employed.
[0048] FIG. 1 illustrates the first embodiment of the present
invention, in which a spinning solution is fed through a spinning
solution feeding part 102 into a spinneret 103 to form drops at a
tip of the spinneret 103. At this stage, a voltage from a high
voltage generator 101, which is set to a predetermined voltage, is
applied to the spinning solution feeding part 102 to burst the
drops, and thus, the nanofiber is collected on a disk-type first
collector 104, which is located perpendicular to the spinneret 103
while rotating. The spun nanofiber 105 collected on the disk-type
first collector 104 is transferred so as to be continuously
collected on a rotating roll-type second collector using a charged
rod, thereby creating a nano-sized long fiber 107 (FIGS. 2 and
3).
[0049] FIG. 4 illustrates an electrospinning process using a
multi-collector according to the second embodiment of the present
invention, in which a nanofiber is collected on a rotating
disk-type first collector 104 provided parallel to a spinneret 103.
Subsequently, a roll-type second collector 106 moves toward the
disk-type first collector 105 to transfer 108 a portion of the spun
nanofiber 105, collected on the disk-type first collector 104, onto
the roll-type second collector 106 so as to collect the nanofiber
in the second collector. Next, while the roll-type second collector
106 becomes distant from the disk-type first collector 104 by a
predetermined distant to the extent that the nanofiber 105 is not
broken, and the roll-type second collector 106 rotates at 20-80 rpm
while axially moving, thereby creating a nanofiber 107 (FIG.
5).
[0050] FIG. 6 illustrates an electrospinning process using a
multi-collector according to the third embodiment of the present
invention. A plate-type first collector 104a is provided
perpendicular to a spinneret 103 and a plate-type second collector
104b is positioned at an angle of 90 degrees to the plate-type
first collector 104a. In this regard, the plate-type first
collector 104a is charged, but the plate-type second collector 104b
is not charged. Drops are continuously collected on the collectors
to produce a nano-sized long fiber 107 (FIG. 7).
[0051] FIG. 8 illustrates an electrospinning process using a
multi-collector according to the fourth embodiment of the present
invention. A roll-type first collector 106a is provided
perpendicular to a spinneret 103 and positioned at a base part, and
a roll-type second collector 106b is located over the roll-type
first collector 106a by a height of 5-10 cm. The roll-type first
collector 106a and the roll-type second collector 106b rotate at
the same speed. The nanofiber spun from the spinneret 103 to the
first collector 106a is recollected on the second collector 106b to
produce a nanofiber 107 (FIG. 9).
[0052] FIG. 10 illustrates an electrospinning process using a
multi-collector according to the fifth embodiment of the present
invention. A spinneret 103 is provided at an upper position and a
plate-type first collector 104a made of a metal is provided at a
lower position so as to be immovable. A plate-type second collector
104b is positioned at an angle of 90 degrees to the plate-type
collector 104a. The plate-type first collector 104a and the
plate-type second collector 104b form an L-shaped dual collector,
which is provided with the two plate-type collectors. The
plate-type first collector 104a is connected to the plate-type
second collector 104b through a medium part 109, which is located
under the plate-type second collector 104b. The medium part 109 is
made of a nonconductive material so as to independently charge the
first and second collectors. Drops are continuously collected on
the dual collector to produce a nanofiber 107 (FIG. 11).
[0053] FIG. 12 illustrates an electrospinning process using a
multi-collector according to the sixth embodiment of the present
invention. A spinneret 103 is provided at an upper position, and a
disk-type first collector 104 is provided parallel to the spinneret
103 while rotating. Additionally, a roll-type second collector 106c
consisting of a caterpillar conveyer belt is provided perpendicular
to the disk-type first collector 104. A nanofiber 107 is
continuously produced using the multi-collector (FIG. 13).
MODE FOR CARRYING OUT THE INVENTION
[0054] A better understanding of the present invention may be
obtained through the following preparation examples, examples, and
a comparative example which are set forth to illustrate, but are
not to be construed as the limit of the present invention.
PREPARATION EXAMPLE 1
First Preparation of Spinning Solution
[0055] A polymer copolymer, which consists of 30 mol % of
polyamide-based polymer with an average molecular weight and 70 mol
% of polyimide-based polymer with an average molecular weight, was
added to a N-methyl-2-pyrrolidine solvent, and sufficiently
dissolved at room temperature for 20-30 min using a ultrasonic
device. In this regard, a spinning solution contains 25 wt % of
polyamide-polyimide copolymer with a number average molecular
weight of 1000 based on the solvent.
PREPARATION EXAMPLE 2
Second Preparation of Spinning Solution
[0056] Polyethylene terephthalate having an intrinsic viscosity of
0.64 was mixed with a polyester copolymer, which contains 30 mol %
of isophthalic acid and 15 mol % of diethylene glycol and which has
an intrinsic viscosity of 0.60, in a weight ratio of 75:25, and
then dissolved in a mixed solvent (50:50) of trifluoroacetic acid
and methylene glycol to produce a spinning solution containing 15
wt % of solids.
PREPARATION EXAMPLE 3
Preparation of Spinning Melt
[0057] A mixed composition, which consists of 30 mol % of
polyamide-based polymer with an average molecular weight and 70 mol
% of polyimide-based polymer with an average molecular weight, was
melted in an electric furnace at 350.degree. C. to produce a
spinning melt.
EXAMPLE 1
First Production of Nano-Sized Long Fiber
[0058] As shown in FIG. 1, a spinning solution, which contains 25
wt % of polyamide-polyimide copolymer produced through preparation
example 1, was fed through a spinning solution feeding part 102 to
a spinneret 103 at a speed of 0.3 ml/min, thereby forming a drop at
a tip of the spinneret having a diameter of 0.42 mm. At this stage,
a voltage was applied to the spinning solution feeding part 102
using a high voltage generator 101 in which a critical voltage was
set to 1.5 kv/cm to burst the drop, and consequently, a nanofiber
is collected on a disk-type first collector 104 which was provided
perpendicular to the spinneret 103 and rotated at 40 rpm.
Subsequently, the spun nanofiber 105 was transferred from the
disk-type first collector 104 to a roll-type second collector,
rotating at 20 rpm, using an additional charged rod so as to be
continuously collected therein. At this stage, a distance between
the spinneret 103 and the disk-type first collector 104 was set to
10 cm, and a distance between the disk-type first collector 104 and
the roll-type second collector 106 was set to 10 cm. The resulting
nanofiber was observed while being magnified 300 and 20,000 times
using a scanning electron microscope, thereby confirming that a
long fiber having an average diameter of 0.4 .mu.m was produced
(FIGS. 2 and 3).
EXAMPLE 2
Second Production of Nano-Sized Long Fiber
[0059] A spinning solution, which contains 25 wt % of
polyamide-polyimide copolymer produced through preparation example
1, was fed through a spinning solution feeding part 102 to a
spinneret 103 at a speed of 0.3 ml/min, thereby forming a drop at a
tip of the spinneret having a diameter of 0.42 mm. At this stage, a
voltage was applied using a high voltage generator 101 in which a
critical voltage was set to 1.3 kv/cm to burst the drop, and
consequently, a nanofiber is collected on a disk-type first
collector 104 which was provided parallel to the spinneret 103 and
rotated at 40 rpm. Subsequently, a roll-type second collector 106
moved toward the disk-type first collector 104, so that they were
spaced from each other by a distance of 4 cm. Consequently, a
portion of the spun nanofiber 105, which was collected on the
disk-type first collector 104, was collected onto the roll-type
second collector 106. Next, the roll-type second collector 106
became distant from the disk-type first collector 104 by a
predetermined distance to the extent that the spun nanofiber 105
was not broken, and the roll-type second collector 106 rotated at
20-60 rpm while axially moving, thereby creating the resulting
nanofiber. At this stage, a distance between the spinneret 103 and
the disk-type first collector 104 was 4 cm, and a distance between
the disk-type first collector 104 and the roll-type second
collector 106 was 10 cm (FIG. 4). The resulting nanofiber was
observed while being magnified 3,000 times using a scanning
electron microscope, thereby confirming that a twisted long fiber
having an average diameter of 0.8 .mu.m was produced (FIG. 5).
EXAMPLE 3
Third Production of Nano-Sized Long Fiber
[0060] A spinning solution, which contains 25 wt % of
polyamide-polyimide copolymer produced through preparation example
1, was fed through a spinning solution feeding part 102 to a
spinneret 103 at a speed of 0.3 ml/min, thereby forming a drop at a
tip of the spinneret having a diameter of 0.42 mm. An
electrospinning process was conducted under the same conditions as
example 1 except that a procedure of FIG. 6 was carried out. A
plate-type first collector 104a is made of a metal plate
perpendicular to the spinneret, and a plate-type second collector
104b was at an angle of 90 degrees to the plate-type first
collector 104a and spaced from the first collector by a distance of
3-5 cm. At this stage, the spinneret was charged into "+", the
plate-type first collector 104a was charged into "-", and the
plate-type second collector 104b was not charged. Thereby, a spun
nanofiber 105 was collected.
[0061] As shown in FIG. 7, a surface of the nanofiber produced
through example 3 was observed using a scanning electron microscope
while being magnified 300 times, thereby confirming that the
resulting nanofiber was a nano-sized long and twisted fiber having
an average diameter of 1.4 .mu.m.
EXAMPLE 4
Fourth Production of Nano-Sized Long Fiber
[0062] A spinning solution, which contains 25 wt % of
polyamide-polyimide copolymer produced through preparation example
1, was fed through a spinning solution feeding part 102 to a
spinneret 103 at a speed of 0.3 ml/min, thereby forming a drop at a
tip of the spinneret having a diameter of 0.42 mm. An
electrospinning process was conducted under the same conditions as
example 1 except that a procedure of FIG. 8 was carried out. The
spinneret 103 having a diameter of 0.42 mm was provided at an upper
position, and two roll-type collectors 106a, 106b were provided at
a lower position. The first collector 106a, in which a spun
nanofiber was first collected, was a roll type, made of a metal,
and rotated at 40 rpm. The roll-type second collector 106b was
located over the roll-type first collector 106a by a height of 5-10
cm and rotated at the same rotating speed as the first collector.
The roll-type second collector 106b was made of a glass capable of
generating static electricity. At this stage, the spinneret 103 was
charged into "+", and the roll-type first collector 106a at a
bottom position was charged into "-".
[0063] As shown in FIG. 9, a surface of the nanofiber produced
through example 4 was observed using a scanning electron microscope
while being magnified 50 times, thereby confirming that the
resulting nanofiber was a nano-sized long and twisted fiber having
an average diameter of 5.1 .mu.m.
EXAMPLE 5
Fifth Production of Nano-Sized Long Fiber
[0064] A spinning solution, which contains 25 wt % of
polyamide-polyimide copolymer produced through preparation example
1, was fed through a spinning solution feeding part 102 to a
spinneret 103 at a speed of 0.3 ml/min, thereby forming a drop at a
tip of the spinneret having a diameter of 0.42 mm. An
electrospinning process was conducted under the same conditions as
example 1 except that a procedure of FIG. 10 was carried out. The
spinneret 103 having the diameter of 0.42 mm was provided at an
upper position, and a plate-type first collector 104a made of a
metal was provided at a lower position so as to be immovable. A
plate-type second collector 104b was at an angle of 90 degrees to
the plate-type first collector 104a. The plate-type first collector
104a and the plate-type second collector 104b were made of the same
material and constituted an L-shaped dual collector. The plate-type
first collector 104a and the plate-type second collector 104b
formed the L-shaped dual collector, which was provided with the two
plate-type collectors. The plate-type first collector 104a was
connected through a medium part 109, which was located under the
plate-type second collector 104b, to the plate-type second
collector 104b. The medium part 109 was made of a nonconductive
material so as to independently charge the first and second
collectors. At this stage, the spinneret 103 was charged into "+",
and the L-shaped dual collector 104a, 104b was charged into
"-".
[0065] As shown in FIG. 11, a surface of the nanofiber produced
through example 5 was observed using a scanning electron microscope
while being magnified 300 times, thereby confirming that the
resulting nanofiber was a nano-sized long and twisted fiber having
an average diameter of 2.5 .mu.m.
EXAMPLE 6
Sixth Production of Nano-Sized Long Fiber
[0066] A spinning solution, which contains 25 wt % of
polyamide-polyimide copolymer produced through preparation example
1, was fed through a spinning solution feeding part 102 to a
spinneret 103 at a speed of 0.3 ml/min, thereby forming a drop at a
tip of the spinneret having a diameter of 0.42 mm. An
electrospinning process was conducted in the same manner as a
procedure of FIG. 12. A spinneret 103 having a diameter of 0.42 mm
was provided at an upper position, and a disk-type first collector
104 was provided parallel to the spinneret 103 while rotated at 50
rpm. Additionally, a roll-type second collector 106c consisting of
a caterpillar conveyer belt was provided perpendicular to the
disk-type first collector 104. At this stage, the electrospinning
process was conducted under conditions that a distance between the
spinneret 103 and the disk-type first collector 104 was 4 cm, a
critical voltage was set to 1.3 kv/cm, the spinneret was charged
into "+", and the disk-type first collector 104 was charged into
"-", thereby continuously producing a fiber.
[0067] As shown in FIG. 13, a surface of a nanofiber produced
through example 6 was observed using a scanning electron microscope
while being magnified 300 times, thereby confirming that the
resulting nanofiber was a nano-sized long and twisted fiber having
an average diameter of 4.5 .mu.m.
COMPARATIVE EXAMPLE 1
Production of Nanofiber
[0068] A spinning solution, which contains 25 wt % of
polyamide-polyimide copolymer produced through preparation example
1, was fed into a spinning solution feeding part 202. When a
voltage was applied using a high voltage generator 201 in which a
critical voltage was set to 1 kv/cm, the spinning solution was spun
from a tip of a spinneret 203 in drops. Subsequently, after the
spinning, the spinning solution was collected on a plate-type
collector 204 which was perpendicular to the spinneret and
consisted of a metal mesh (FIG. 14). A nanofiber web 207 collected
on the collector 204 was observed while being magnified 300 times
using a scanning electron microscope, thereby confirming that the
resulting web was produced in the type of non-woven fabric as shown
in FIG. 15. Additionally, the nanofiber web was observed while
being magnified 20,000 times, thereby confirming that the
nanofibers constituting the web had an average diameter of 0.5
.mu.m (FIG. 15). In this regard, a diameter of the spinneret, a
distance between the spinneret and the metal collector, and the
critical voltage were the same as those of example 1.
Average diameters and diameter ranges of the nanofibers produced
through examples 1 to 6 and comparative example 1 are described in
Table 1.
TABLE-US-00001 TABLE 1 Diameters of the nanofibers Example Average
diameter (nm) Diameter range (nm) Example 1 400 90-800 Example 2
700 200-2200 Example 3 1200 400-4500 Example 4 5100 2000-11000
Example 5 2500 900-5100 Example 6 4400 3200-10000 Comparative
example 1 500 200-1500
[0069] From Table 1, it can be seen that the fibers produced
through examples 1 to 6 and comparative example 1 are nanofibers
each having a nano-sized diameter range. Particularly, the
diameters of the nanofibers produced through examples 1 to 6 can be
controlled depending on the critical voltage and a moving speed of
the spinning solution or the spinning melt fed into the spinneret.
Furthermore, the nanofiber produced through comparative example 1
has the type of non-woven fabric (FIGS. 15 and 16). On the other
hand, it can be seen that the nanofibers produced through examples
1 to 6 are filament type (twisted) long fibers, from the SEM image
results of FIGS. 2, 5, 7, 9, 11, and 13.
INDUSTRIAL APPLICABILITY
[0070] As described above, a filament type nano-sized long fiber,
which is produced using an improved electrospinning process
according to the present invention, has mechanical properties that
are better than a conventional nanofiber non-woven fabric, thereby
being applied as a substitute to all fields employing a
conventional fiber having a micron-sized diameter. For example,
first, the fiber of the present invention is useful as medical
filters for kidney dialysis and purification of the blood, and
various membrane reinforcing materials for genetic separation.
[0071] Second, the fiber of the present invention is useful to
produce ultra-thin reinforcing films and ultra-slim PCBs in
electric/electronic fields.
Third, the fiber of the present invention may be useful for
ultra-small and ultra-light flying bodies or unmanned flying
robots.
[0072] Fourth, the fiber of the present invention is useful as a
reinforcing material for an optical cable in an optical
communication field.
* * * * *