U.S. patent application number 13/396009 was filed with the patent office on 2013-05-23 for method for preparing carbon fiber precursor.
This patent application is currently assigned to HYUNDAI MOTOR COMPANY. The applicant listed for this patent is Jeong Min Cho, Chi-Hoon Choi, Young-Ho Choi, Do Suck Han. Invention is credited to Jeong Min Cho, Chi-Hoon Choi, Young-Ho Choi, Do Suck Han.
Application Number | 20130130028 13/396009 |
Document ID | / |
Family ID | 48427242 |
Filed Date | 2013-05-23 |
United States Patent
Application |
20130130028 |
Kind Code |
A1 |
Choi; Young-Ho ; et
al. |
May 23, 2013 |
METHOD FOR PREPARING CARBON FIBER PRECURSOR
Abstract
Disclosed is a method for preparing a precursor fiber for a
carbon fiber. The precursor fiber of fine denier according to the
present invention is used to prepare a carbon fiber having
excellent tensile strength and compressive strength by a
conventional single component spinneret using a superdrawing
process to prepare a high strength and high elastic carbon fiber
with a reduction in stabilization time.
Inventors: |
Choi; Young-Ho; (Seongnam,
KR) ; Cho; Jeong Min; (Uiwang, KR) ; Han; Do
Suck; (Seongnam, KR) ; Choi; Chi-Hoon; (Suwon,
KR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Choi; Young-Ho
Cho; Jeong Min
Han; Do Suck
Choi; Chi-Hoon |
Seongnam
Uiwang
Seongnam
Suwon |
|
KR
KR
KR
KR |
|
|
Assignee: |
HYUNDAI MOTOR COMPANY
Seoul
KR
|
Family ID: |
48427242 |
Appl. No.: |
13/396009 |
Filed: |
February 14, 2012 |
Current U.S.
Class: |
428/364 ;
264/210.8 |
Current CPC
Class: |
Y10T 428/2913 20150115;
D01D 5/12 20130101; D01F 9/22 20130101; D01F 6/38 20130101; D01F
6/18 20130101; D01D 5/16 20130101 |
Class at
Publication: |
428/364 ;
264/210.8 |
International
Class: |
D02G 3/00 20060101
D02G003/00; D01D 5/12 20060101 D01D005/12 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 22, 2011 |
KR |
10-2011-0122476 |
Claims
1. A method for preparing a precursor fiber for a carbon fiber, the
method comprising: spinning an acrylonitrile fiber from a spinning
dope containing an acrylonitrile polymer; in response to spinning,
controlling the fiber diameter by superdrawing the fiber spun in
the first step; and in response, preparing a precursor fiber by
drawing the controlled.
2. The method of claim 1, wherein the acrylonitrile polymer is
prepared by copolymerization with at least one monomer selected
from the group consisting of acrylic acid (AA), methacrylic acid
(MA), itaconic acid (IA), methacrylate (MA), and acrylamide
(AM).
3. The method of claim 1, wherein the polyacrylonitrile comprises
90 to 99 wt % of acrylonitrile.
4. The method of claim 1, wherein the spinning dope comprises 5 to
25 wt % of acrylonitrile polymer is mixed with a solvent selected
from the group consisting of dimethylsulfoxide (DMSO),
N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), and
nitric acid.
5. The method of claim 1, wherein the superdrawing is performed at
a temperature above the glass transition temperature of the
acrylonitrile.
6. The method of claim 5, wherein the superdrawing is performed at
a temperature of 100 to 180.degree. C.
7. The method of claim 5, wherein the superdrawing is performed at
a strain rate of 0.4 to 400 l/sec
8. A precursor fiber for a carbon fiber prepared by the method of
claim 1.
9. The precursor fiber of claim 8, wherein the precursor fiber has
a diameter of 0.05 to 0.5 denier.
10. A carbon fiber prepared using the precursor fiber of claim 8.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims under 35 U.S.C. .sctn.119(a) the
benefit of Korean Patent Application No. 10-2011-0122476 filed Nov.
22, 2011, the entire contents of which are incorporated herein by
reference.
BACKGROUND
[0002] (a) Technical Field
[0003] The present invention relates to a method for preparing a
precursor fiber for a carbon fiber. More particularly, it relates
to a method for preparing a precursor fiber of fine denier used to
prepare a carbon fiber having excellent tensile strength and
compressive strength by a conventional single component spinneret
using a superdrawing process, thereby preparing a high strength and
high elastic carbon fiber with a reduction in stabilization
time.
[0004] (b) Background Art
[0005] Carbon fiber is a high strength (e.g., 3 to 7 GPa) and
highly elastic (150 to 950 GPa) fiber containing more than 92%
carbon and can be prepared by heat-treating a precursor material
with a high carbon yield at a fairly high temperature. As the
precursor material, an acrylonitrile polymer fiber having excellent
tensile strength and compressive strength and high tensile modulus
is most widely used. The degradation temperature of the
acrylonitrile polymer is lower than the melting temperature, and
thus it is difficult to perform melt-spinning. Some clothing fibers
are mass-produced by melt-spinning using a plasticizer such as
water. However, the acrylonitrile fiber for a carbon fiber is
typically prepared by solution spinning. The acrylonitrile fiber
prepared by solution spinning is drawn at a hydrothermal
temperature (.about.100.degree. C.) or subjected to multiple
drawings to prepare a high performance carbon fiber (see the
process diagram of FIG. 1). Typically, when an acrylonitrile
undrawn yarn is drawn, the orientation of molecules occurs, and
thus the degree of crystallization is increased.
[0006] Acrylonitrile drawn yarn as a precursor fiber is formed into
a carbon fiber through a stabilization process (e.g., at 250 to
350.degree. C.) in an oxidation atmosphere and a carbonization
process (e.g., at 800 to 1,500.degree. C.) in an inert atmosphere,
and a graphitization process (e.g., at to below a temperature of
2,500.degree. C.) is selectively performed. The stabilization
process involves the cyclization of a Polyacrylonitrile (PAN)
molecular structure and the combination of oxygen. For the
combination of oxygen, the diffusion of oxygen into stabilized PAN
fibers is required, and thus the stabilization time rapidly
increases depending on the thickness of the fiber. During the
carbonization process, ladder-like molecular structures formed in
the stabilization process are bonded to each other and modified
into graphite-like structures, and volatilization of elements other
than carbon occurs. During the stabilization and carbonization
processes, fiber contraction in the longitudinal direction occurs
due to physical or chemical causes, which may reduce the molecular
orientation of the finally obtained carbon fiber. Therefore, the
carbon fiber may have a well-developed crystalline structure in the
longitudinal direction by applying a tensile force to improve the
molecular orientation during the stabilization and carbonization
processes.
[0007] According to Griffith's flaw theory, if the same material is
used, when the fiber diameter is reduced, the surface area per unit
length is reduced, which reduces the probability of the occurrence
of defects, thereby increasing the tensile strength. Therefore,
when the diameter of the acrylonitrile precursor fiber is smaller,
the tensile force per unit area can be increased during the
stabilization and carbonization processes, thereby preparing a high
strength carbon fiber. A spinneret with a relatively smaller hole
is required to prepare a precursor fiber having a small diameter
and, in particular, an expensive multi-component spinning machine,
which can separate a desired fiber through a physical process
(e.g., side-by-side fiber) or a chemical process (e.g., a
islands-in-a-sea fiber) by simultaneously spinning at least two
polymers, is required to prepare a superfine fiber.
[0008] International Patent Publication No. WO2009/049174 discloses
a method for preparing an ultrafine carbon fiber having a high
tensile strength of about 4.5 GPa through composite spinning in the
form of core-shell (or sheath-core) or islands-in-a-sea. This
method, however, has problems in that a process of melting or
incinerating auxiliary components after the spinning as well as an
expensive composite spinning machine significantly increases the
manufacturing costs.
[0009] Moreover, U.S. Pat. No. 6,428,891 discloses a method for
preparing a carbon fiber by wet-spinning an acrylonitrile-based
precursor to form a coagulated fiber, subjecting the coagulated
fiber to primary drawing comprising in-bath drawing, and subjecting
the obtained fiber to secondary drawing involving pressurized steam
drawing. U.S. Pat. No. 6,641,915 discloses a method for preparing
an acrylonitrile fiber for a carbon fiber precursor by spinning an
acrylonitrile polymer in a solution to prepare a coagulated fiber,
drawing the coagulated fiber from a first coagulation bath, and
then stretching the coagulated fiber in a second coagulation bath.
Japanese Patent Application Publication No. 1989-052811 discloses a
method for preparing an acrylonitrile fiber for a carbon fiber
precursor by spinning an acrylonitrile polymer in a solution to
prepare a coagulated fiber and drawing the coagulated fiber from a
coagulation bath. However, in these techniques, it is difficult to
freely control the cross-sectional area of the fiber while
achieving mechanical properties as the carbon fiber precursor.
[0010] Meanwhile, Korean Patent Application Publication No.
10-1991-0002966 discloses an superdrawn polyethylene fiber
reinforced composite material comprising an superdrawn polyethylene
fiber and an epoxy resin modified with an elastomer, and Japanese
Patent Application Publication No. 2006-265788 discloses a method
for producing a composite fiber by melt-spinning a fiber to have a
diameter of 1 to 10 .mu.m and then superdrawing the fiber. However,
these techniques are to conduct superdrawing to modify the fiber,
and the prepared fiber has too low of a carbon yield to be used as
the carbon fiber precursor.
[0011] The above information disclosed in this Background section
is only for enhancement of understanding of the background of the
invention and therefore it may contain information that does not
form the prior art that is already known in this country to a
person of ordinary skill in the art.
SUMMARY OF THE DISCLOSURE
[0012] The present invention provides a method for preparing a
precursor fiber for a carbon fiber having excellent properties by
spinning a fiber and then preparing a fiber of fine denier using a
superdrawing process. Moreover, the present invention provides a
method for preparing a precursor fiber for a carbon fiber, which
can prepare a carbon fiber having excellent tensile strength and
tensile modulus by reducing the diameter of an as-spun to
acrylonitrile fiber extruded from an existing spinneret using a
superdrawing process.
[0013] Furthermore, the present invention provides a method for
preparing a precursor fiber for a carbon fiber, which can prepare a
precursor fiber having excellent molecular orientation and reduced
diameter and can prepare a carbon fiber having high strength and
high stiffness using a superdrawing process.
[0014] In one aspect, the present invention provides a method for
preparing a precursor fiber for a carbon fiber, the method
including: first spinning an acrylonitrile fiber from a spinning
dope containing an acrylonitrile polymer; then controlling the
fiber diameter by superdrawing the fiber spun; and in response,
preparing a precursor fiber by drawing the controlled fiber.
[0015] Other aspects and exemplary embodiments of the invention are
discussed infra.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] The above and other features of the present invention will
now be described in detail with reference to certain exemplary
embodiments thereof illustrated the accompanying drawings which are
given hereinbelow by way of illustration only, and thus are not
limitative of the present invention, and wherein:
[0017] FIG. 1 is a schematic process diagram showing a method for
preparing an ultrafine carbon fiber disclosed in International
Patent Publication No. WO2009/049174; and
[0018] FIG. 2 is a schematic process diagram showing a method for
preparing a precursor fiber for a carbon fiber in accordance with
an exemplary embodiment of the present invention.
[0019] It should be understood that the appended drawings are not
necessarily to scale, presenting a somewhat simplified
representation of various preferred features illustrative of the
basic principles of the invention. The specific design features of
the present invention as disclosed herein, including, for example,
specific dimensions, orientations, locations, and shapes will be
determined in part by the particular intended application and use
environment.
[0020] In the figures, reference numbers refer to the same or
equivalent parts of the present invention throughout the several
figures of the drawing.
DETAILED DESCRIPTION
[0021] Hereinafter reference will now be made in detail to various
embodiments of the present invention, examples of which are
illustrated in the accompanying drawings and described below. While
the invention will be described in conjunction with exemplary
embodiments, it will be understood that present description is not
intended to limit the invention to those exemplary embodiments. On
the contrary, the invention is intended to cover not only the
exemplary embodiments, but also various alternatives,
modifications, equivalents and other embodiments, which may be
included within the spirit and scope of the invention as defined by
the appended claims.
[0022] It is understood that the term "vehicle" or "vehicular" or
other similar term as used herein is inclusive of motor vehicles in
general such as passenger automobiles including sports utility
vehicles (SUV), buses, trucks, various commercial vehicles,
watercraft including a variety of boats and ships, aircraft, and
the like, and includes hybrid vehicles, electric vehicles, plug-in
hybrid electric vehicles, hydrogen-powered vehicles and other
alternative fuel vehicles (e.g., fuels derived from resources other
than petroleum). As referred to herein, a hybrid vehicle is a
vehicle that has two or more sources of power, for example both
gasoline-powered and electric-powered vehicles.
[0023] The present invention provides a method for preparing a
precursor fiber for a high strength carbon fiber by spinning,
superdrawing, and drawing an acrylonitrile fiber, which is shown in
the process diagram of FIG. 2.
[0024] Preferably, a precursor fiber for a carbon fiber prepared by
the present invention is obtained from an acrylonitrile polymer.
The acrylonitrile polymer used in an exemplary embodiment of the
present invention comprises an acrylonitrile monomer as a main
component and is prepared by copolymerization with another monomer.
The content of acrylonitrile may be 90 to 99 wt %, more preferably
95 to 99 wt %, with respect to the total weight of the polymer. If
the content of the acrylonitrile is less than 90 wt %, the
crystalline structures of the carbon fiber precursor and the carbon
fiber are not well developed, and thus the strength and stiffness
of the carbon fiber may be reduced. In some embodiments the
acrylonitrile polymer is prepared by copolymerization with another
monomer to reduce the stabilization time and improve the quality of
the final carbon fiber. The sum of the content of the acrylonitrile
polymer and the content of the acrylonitrile monomer is 100 wt %.
Here, the monomer may be one of either an acrylic acid (AA),
methacrylic acid (MA), itaconic acid (IA), methacrylate (MA), or
acrylamide (AM).
[0025] The method of the present invention may include preparing a
spinning dope by dissolving an acrylonitrile polymer in a solvent
or by solution polymerization to prepare the carbon fiber precursor
from the acrylonitrile polymer. Here, the process of dissolving the
acrylonitrile polymer in a solvent is more preferable. When a
polymer solution prepared by solution polymerization is directly
spun, low molecular weight components, initiator, catalyst, etc.
may degrade the mechanical properties of the carbon fiber precursor
and the carbon fiber. The solvent used in the spinning dope may be
either dimethylsulfoxide (DMSO), N,N-dimethylformamide (DMF),
N,N-dimethylacetamide (DMAc), and nitric acid. The acrylonitrile
polymer spinning dope (hereinafter referred to as the "spinning
dope") contains about 5 to 25 wt %, preferably, 10 to 20 wt % of
acrylonitrile polymer. If the content of the polymer is too small,
it is difficult to perform the spinning due to low viscosity,
whereas, if it is too high, the mechanical properties of the carbon
fiber precursor and the carbon fiber may be degraded due to
entanglement of acrylonitrile molecules. The spinning dope is kept
for more than 24 hours to remove air bubbles, and impurities are
removed by a filter having a pore size of less than 10 microns.
[0026] In a first step of spinning an acrylonitrile fiber from a
spinning dope, the spinning dope is spun in the form of fiber by a
typical solution spinning process. Here, a spinneret and a
coagulation bath are arranged according to a typical wet-spinning
or dry-jet wet spinning (similar to wet spinning except for
existing air gap between the spinneret and the coagulation bath)
method. Preferably, the air-jet spinning method improves the
orientation of acrylonitrile molecules in the precursor fiber,
which leads to the preparation of excellent carbon fiber.
[0027] When the spinning dope is spun, the distance between the
spinneret and the coagulation bath should be maintained at about 1
to 100 mm, more preferably 5 to 25 mm. A coagulation liquid used in
this process is a mixture of a solvent and a non-solvent and, when
the content of the non-solvent is higher and when the temperature
is higher, the solidification rate is increased. Water or alcohol
may be selectively used as the non-solvent.
[0028] According to the present invention, in a second step of
controlling the fiber diameter by superdrawing the fiber spun in
the first step, a superdrawing process is performed on the as-spun
fiber prepared by the above process. Here, the superdrawing process
is performed at a temperature above the glass transition
temperature, preferably at about 100 to 180.degree. C., more
preferably at 150 to 170.degree. C. The strain rate is set at about
0.4 to 400 l/sec, preferably at 150 to 250 l/sec. If the strain
rate is too high, the orientation of the molecules occurs rapidly,
whereas, if the strain rate is too low, the productivity is
reduced. Moreover, the superdrawn fiber may have a diameter of
about 0.05 to 0.5 denier.
[0029] In a third step of preparing a precursor fiber by drawing
the fiber controlled and prepared in the second step, a drawing
process is performed on the fiber prepared in the second step when
the fiber has a desired diameter through the superdrawing process.
The drawing process is performed at a temperature of about 150 to
180.degree. C. by a typical method.
[0030] As such, when a specific drawing rate is satisfied at a
temperature above the glass transition temperature of the polymer
by performing the superdrawing process without increasing the
oriented crystallization of the crystalline polymer, desirable
characteristics can be obtained. According to the present
invention, the superdrawing process is performed so that the
acrylonitrile precursor fiber produced from a single spinneret is
made thin by preventing the oriented crystallization as much as
desired, and the drawing process is performed to achieve the final
thickness and properties.
[0031] According to the prepared precursor fiber of the present
invention, the molecular orientation is improved and, in
particular, the cross-sectional area of the fiber is reduced by the
superdrawing process, which reduces the stabilization time, thereby
preparing a carbon fiber having improved strength.
[0032] The precursor fiber prepared according to the present
invention is used for the preparation of the carbon fiber. Here,
the carbon fiber may be prepared under typical stabilization and
carbonization conditions, and the stabilization time is set
inversely proportional to the cross-sectional area of the
fiber.
[0033] According to the prepared carbon fiber, the diameter of the
as-spun acrylonitrile fiber extruded from an existing spinneret can
be reduced to suit its use, thereby preparing a carbon fiber having
excellent tensile strength and tensile modulus. Moreover, the
carbon fiber prepared using the precursor fiber according to the
present invention has excellent properties and thus can be used for
the production of vehicle chassis and body parts, aircraft
structural materials, wind turbine blades, sporting goods,
construction structural materials, etc. When the carbon fiber of
the present invention is used as an aircraft structural material,
the fuel efficiency can be improved through weight reduction, and
the safety can be improved through increased stiffness.
[0034] Next, the present invention will be described in more detail
with reference to examples. The following examples are provided for
a better understanding of the present invention, and the present
invention is not limited by the following examples.
Example 1
Preparation of Precursor Fiber Using Superdrawing
[0035] 10 wt % of acrylonitrile polymer prepared by
copolymerization with 2 wt % of itaconic acid was dissolved in
dimethylsulfoxide and placed in a vacuum oven under reduced
pressure to remove air bubbles. Then, an as-spun fiber was prepared
by dry-jet wet spinning in which the distance between a spinneret
and a coagulation bath was set to 10 mm. In a first coagulation
liquid, dimethylsulfoxide and water were mixed in a ratio of 60:40
and, in a second coagulation liquid, a solvent and water were mixed
in a ratio of 40:60. A circular spinneret having a diameter of 120
.mu.m was used.
[0036] The as-spun fiber prepared under the above conditions was
subjected to superdrawing at a drawing rate of 200 l/sec using a
heating plate or godet roller at a temperature of 150.degree. C.
The drawing ratio was the ratio of the winding rate of the
superdrawn yarn to the feeding rate of the as-spun fiber and was
set to 90 times. The superdrawn yarn was drawn at a drawing rate of
450 l/sec at a temperature of 170.degree. C. The to drawing ratio
was the ratio of the winding rate of the drawn yarn to the feeding
rate of the superdrawn yarn and was set to 15 times.
Comparative Example 1
[0037] A precursor fiber was prepared in the same manner as Example
1, except that the superdrawing temperature was set at 70 io
Comparative Example 2
[0038] A precursor fiber was prepared in the same manner as Example
1, except that the superdrawing rate was set at 380 l/sec.
Comparative Example 3
[0039] A precursor fiber was prepared in the same manner as Example
1, except that the superdrawing process was not performed.
Comparative Example 4
[0040] An as-spun fiber having a diameter of 150 manner as Example
1, except that the superdrawing process was not performed.io of the
winding rate of the drawn yarn to the feeding rate of the
superdrawn yarn and. Then, the prepared as-spun fiber was drawn 15
times at a drawing rate of 450 l/sec at a temperature of 170 n f
and the islands were dissolved, thereby preparing a precursor
fiber.
Test Example
[0041] The tensile strength and tensile modulus of the precursor
fiber were measured according to ASTM D3822, in which the gauge
length was 25.4 mm and the crosshead speed was 0.254 mm/min The
degree of crystallization was obtained from the ratio of the sum of
a crystalline region and an amorphous region of a two-dimensional
X-ray diffraction graph to the area of crystalline areas
[(200,110), (201), (310,020), (003)] using X-ray diffraction. The
Herman's orientation factor of polyacrylonitrile (PAN) molecules
was calculated using Wilchinsky's method (Wilchinsky, Z. W.,
MEASUREMENT OF ORIENTATION IN POLYPROPYLENE FILM. Journal of
Applied Physics, 1960. 31(11): p. 1969-1972, the content of which
are hereby incorporated by reference in its entirety). The fiber
diameter was measured by measuring the density of the fiber using a
gravimeter, measuring the unit length and the fiber weight, and
converting the measured values into the diameter of a circular
cross-section yarn based on the following formula:
Diameter = 2 m .pi..rho. l ( cm ) ##EQU00001##
[0042] where m represents the weight (g) of the fiber, p represents
the density (g/cm.sup.3), and 1 represents the fiber length
(cm).
[0043] The test results are shown in the following table 1
TABLE-US-00001 TABLE 1 Com- Com- Com- Com- parative parative
parative parative Exam- Exam- Exam- Exam- Properties Example 1 ple
1 ple 2 ple 3 ple 4 Tensile strength 1.02 0.99 1 0.9 0.8 (GPa)
Tensile modulus 27 26 26 24 23 (GPa) Fiber diameter 1.1 13.5 3.9
10.4 1.6 (ibe Degree of 67 65 66 63 62 crystallization (%) Herman's
0.91 0.82 0.84 0.83 0.87 orientation factor (f.sub.PAN)
[0044] Referring to table 1, it can be seen that the fiber diameter
was significantly increased in Comparative Example 1 where the
superdrawing temperature was low, compared to Example 1. Moreover,
it can be seen that the reduction in fiber diameter in Comparative
Example 2 where the drawing rate was relatively high was smaller
than that of Example 1.
[0045] Furthermore, it can be seen that a precursor fiber having a
larger diameter and lower mechanical properties was prepared in
Comparative Example 3 where the superdrawing process was not
performed, compared to those of Example 1. In addition, it can be
seen that a precursor fiber having a smaller diameter and higher
mechanical properties could be prepared in Example 1, compared to
those of a precursor fiber prepared using an expensive composite
spinning machine in Comparative Example 4.
[0046] Therefore, when the precursor fiber is prepared by
superdrawing of the illustrative embodiment of the present
invention, it is possible to control the fiber diameter according
to the superdrawing conditions, thereby preparing a precursor fiber
having excellent mechanical properties. The thus prepared precursor
fiber can reduce the stabilization and carbonization time during
the preparation process of the carbon fiber, thereby reducing the
production cost. Moreover, it is possible to prepare a carbon fiber
with a well-developed crystalline structure, thereby improving the
mechanical properties of the carbon fiber.
[0047] As described above, according to the method for preparing
the precursor fiber for a carbon fiber of the illustrative
exemplary embodiment of the present invention, the cross-sectional
area of the fiber is reduced by the superdrawing process, which
reduces the stabilization time, and the carbon fiber with improved
strength can be prepared. The thus to prepared carbon fiber can be
used for the production of vehicle chassis and body parts, aircraft
structural materials, wind turbine blades, sporting goods,
construction structural materials, etc. When the carbon fiber of
the present invention is used as an aircraft structural material,
the fuel efficiency can be improved through weight reduction, and
the safety can be improved through increased stiffness.
[0048] The invention has been described in detail with reference to
exemplary embodiments thereof. However, it will be appreciated by
those skilled in the art that changes may be made in these
embodiments without departing from the principles and spirit of the
invention, the scope of which is defined in the appended claims and
their equivalents.
* * * * *