U.S. patent application number 15/110336 was filed with the patent office on 2016-11-10 for pan-based carbon fiber and production method therefor.
The applicant listed for this patent is THE UNIVERSITY OF TOKYO. Invention is credited to Tetsunori Higuchi, Mami Sakaguchi.
Application Number | 20160326672 15/110336 |
Document ID | / |
Family ID | 53523853 |
Filed Date | 2016-11-10 |
United States Patent
Application |
20160326672 |
Kind Code |
A1 |
Higuchi; Tetsunori ; et
al. |
November 10, 2016 |
PAN-BASED CARBON FIBER AND PRODUCTION METHOD THEREFOR
Abstract
A polyacrylonitrile (PAN)-based carbon fiber includes three or
more phases different in crystal size.
Inventors: |
Higuchi; Tetsunori; (Tokyo,
JP) ; Sakaguchi; Mami; (Tokyo, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
THE UNIVERSITY OF TOKYO |
Tokyo |
|
JP |
|
|
Family ID: |
53523853 |
Appl. No.: |
15/110336 |
Filed: |
December 26, 2014 |
PCT Filed: |
December 26, 2014 |
PCT NO: |
PCT/JP2014/084468 |
371 Date: |
July 7, 2016 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
D01F 8/08 20130101; D01F
9/225 20130101; D01D 5/34 20130101; D01D 5/06 20130101; D01F 9/22
20130101 |
International
Class: |
D01F 9/22 20060101
D01F009/22; D01D 5/06 20060101 D01D005/06 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 8, 2014 |
JP |
2014-001505 |
Claims
1.-12. (canceled)
13. A polyacrylonitrile (PAN)-based carbon fiber comprising three
or more phases different in crystal size.
14. The PAN-based carbon fiber according to claim 13, wherein
respective phases are layered.
15. The PAN-based carbon fiber according to claim 14, wherein said
carbon fiber has a sheath-core structure having three or more
layers, and satisfies conditions A to D: A: in a sectional area in
a direction perpendicular to a fiber axis, an area occupied by a
core occupies 10 to 70% of the whole of said sectional area, B: a
thickness of a sheath is 100 nm to 10,000 nm, C: a thickness of an
intermediate layer is more than 0 and 5,000 nm or less, and D: a
diameter in said direction perpendicular to said fiber axis is 2
.mu.m or more.
16. The PAN-based carbon fiber according to claim 14, wherein said
carbon fiber has a sheath-core structure having three or more
layers, and satisfies conditions E to H: wherein a crystal size of
a core is Lc1, a crystal size of a sheath is Lc2, and a crystal
size of an intermediate layer is Lc3. E: Lc1/Lc3.gtoreq.1.05, F:
Lc1/Lc2.gtoreq.1.05, G: 1.0.ltoreq.Lc1.ltoreq.7.0 nm, and H:
Lc2.noteq.Lc3.
17. The PAN-based carbon fiber according to claim 15, wherein an
orientation degree f of a crystal of a core is 0.7 or less.
18. The PAN-based carbon fiber according to claim 15, wherein said
carbon fiber has a sheath-core structure having three or more
layers, and satisfies conditions E to H: wherein a crystal size of
a core is Lc1, a crystal size of a sheath is Lc2, and a crystal
size of an intermediate layer is Lc3. E: Lc1/Lc3.gtoreq.1.05, F:
Lc1/Lc2.gtoreq.1.05, G: 1.0.ltoreq.Lc1.ltoreq.7.0 nm, and H:
Lc2.noteq.Lc3.
19. The PAN-based carbon fiber according to claim 16, wherein an
orientation degree f of a crystal of a core is 0.7 or less.
20. A method of producing a PAN-based carbon fiber according to
claim 13 comprising: spinning a solution of a polymer prepared by
modifying PAN with an amine-base compound and oxidizing it with a
nitro compound to prepare a spun fiber; performing stabilization of
said spun fiber in air at 280.degree. C. or higher and 400.degree.
C. or lower for 10 seconds or more and 15 minutes or less; and
thereafter, performing carbonization.
Description
TECHNICAL FIELD
[0001] This disclosure relates to a polyacrylonitrile (hereinafter,
referred to as PAN)-based carbon fiber comprising three or more
phases different in crystal size, and a production method
therefor.
BACKGROUND
[0002] Carbon fiber is broadly used in various uses, for example,
for aerospace materials for airplanes, rockets and the like, and
for sport articles such as tennis rackets and golf shafts and,
further, is also used for transportation and mechanical fields such
as ships and vehicles, from its properties such as mechanical and
chemical properties and lightness in weight. Further, in recent
years, from high conductivity or high radiation property of carbon
fiber, application to uses for parts for electronic equipment such
as housings of portable telephones or personal computers, or for
electrodes of fuel cells, is strongly required. In particular,
PAN-based carbon fiber, because of its high specific strength, is
used in particular for aerospace materials for airplanes, space
satellites and the like, for members for vehicles and the like and,
recently, application to vehicle members is being remarkably
increased. Therefore, it is desired to improve the productivity of
carbon fiber.
[0003] The PAN-based carbon fiber can be obtained by inducing a
polymer solution dissolved with mainly PAN into a solvent to a
PAN-based fiber by spinning, and burning it at a high temperature
under a condition of an inert atmosphere. When the PAN-based fiber
is made into a carbon fiber, the PAN-based fiber is passed through
a process of air stabilization (cyclization reaction and oxidation
reaction of PAN) which heats the PAN-based fiber in air at a high
temperature such as 200 to 300.degree. C. It is general to obtain a
carbon fiber by further treating it in a carbonization furnace at
2,000.degree. C. to 3,000.degree. C. for several minutes. However,
because an exothermic reaction progresses in the stabilization
process, heat removal is required when a large amount of PAN-based
fibers are stabilized. Therefore, for temperature control, a
long-time treatment is required, and it is necessary to restrict
the fineness of the PAN-based precursor fiber to a small fineness
of a specified value or less to finish air stabilization in a
desired period of time. Thus, in the known process of producing a
carbon fiber, the known stabilization process is a rate-limiting
factor, and it cannot be said to be a sufficiently efficient
process.
[0004] Further, although a carbon fiber is excellent in specific
strength and specific elastic modulus, it has a defect of a very
low degree of elongation. An increase of degree of elongation of
carbon fiber is strongly desired accompanying with an increase of
demand for carbon fiber. So far, to increase the degree of
elongation of carbon fiber, although a fiber spun with a raw
material composition, the main component of which is a polymer
compound compounded with an aromatic sulfonic group or a salt
thereof via a methylene-type bond, is disclosed (JP 6-173122 A),
there is a defect in that the cost of the main raw material is too
high. Further, although technologies intended to improve properties
of carbon fiber by making a hollow carbon fiber or a
dual-structured carbon fiber are also known (JP 2008-169511 A, JP
2007-291557 A and JP 2001-73230 A), the degree of elongation
thereof is still insufficient. Therefore, a long fiber of carbon
fiber having a sufficient degree of elongation relative to its
strength has not been obtained.
[0005] Namely, it is required to greatly shorten the time for
stabilization of a fiber and obtain a carbon fiber having a high
degree of elongation.
[0006] Accordingly, to satisfy the above-described requirements, it
could be helpful to provide a PAN-based carbon fiber capable of
greatly shortening the time for stabilization of a fiber and
exhibiting a high degree of elongation while maintaining a
sufficiently high strength, and a production method therefor.
SUMMARY
[0007] We thus provide a PAN-based carbon fiber comprising three or
more phases different in crystal size.
[0008] In the above-described PAN-based carbon fiber, it is
preferred that the respective phases are layered.
[0009] Further, it is preferred that this PAN-based carbon fiber
has a sheath-core structure having three or more layers, and
satisfies conditions A to D:
A: in a sectional area in a direction perpendicular to a fiber
axis, an area occupied by a core occupies 10 to 70% of the whole of
the sectional area, B: a thickness of a sheath is in a range of 100
nm to 10,000 nm, C: a thickness of an intermediate layer is more
than 0 nm and 5,000 nm or less, and D: a diameter in the direction
perpendicular to the fiber axis is 2 .mu.m or more.
[0010] Further, it is preferred that the above-described PAN-based
carbon fiber has a sheath-core structure having three or more
layers, and satisfies conditions E to H:
wherein a crystal size of a core is referred to as Lc1, a crystal
size of a sheath is referred to as Lc2, and a crystal size of an
intermediate layer is referred to as Lc3.
E: Lc1/Lc3.gtoreq.1.05,
F: Lc1/Lc2.gtoreq.1.05
G: 1.0.ltoreq.Lc1.ltoreq.7.0 nm, and
H: Lc2.noteq.Lc3
[0011] Further, in the above-described PAN-based carbon fiber
having a sheath-core structure with three or more layers, it is
preferred that an orientation degree f of a crystal of a core is
0.7 or less.
[0012] Further, it is preferred that the PAN-based carbon fiber is
obtained by carbonizing a fiber spun from a single kind of polymer
solution for spinning.
[0013] Further, it is preferred that the PAN-based carbon fiber is
obtained by spinning a fiber from a polymer solution for spinning
satisfying points A and B and carbonizing the spun fiber:
A: a polymer in the polymer solution for spinning is a polymer
prepared by modifying PAN with an amine-based compound and
oxidizing it with a nitro compound, and B: the nitro compound is
not contained in the polymer solution for spinning.
[0014] Further, in such a PAN-based carbon fiber, in the
above-described A relating to a polymer in the polymer solution for
spinning, it is preferred that it is obtained using a polymer
solution for spinning containing PAN oxidized using a nitro
compound, in particular, nitrobenzene, at an amount of 10 wt % or
more relative to PAN.
[0015] Furthermore, it is preferred that the PAN-based carbon fiber
is obtained using a polymer solution for spinning having a
divergent structure in which a gradient a is 0.1 or more and 0.3 or
less as the result determined by GPC (Gel Permeation
Chromatography).
wherein the gradient a means a gradient a represented by Mark
Houwink-Sakurada equation (1):
[.eta.]=KMw.sup.a (1)
wherein [.eta.] is an intrinsic viscosity, K is a constant inherent
for a material, and Mw is a weight average molecular weight.
[0016] A method of producing a PAN-based carbon fiber comprises the
steps of: spinning the above-described polymer solution for
spinning; performing stabilization in air at 280.degree. C. or
higher and 400.degree. C. or lower for 10 seconds or more and 15
minutes or less; and thereafter, performing carbonization. In this
method, it is preferred that the stabilization is performed using
an infrared heater (for example, a ceramic heater) and a hot air
drier (for example, a hot air circulation drier) together.
[0017] In the PAN-based carbon fiber and the production method
therefor, by configuring the carbon fiber from three or more phases
different in crystal size, or by the production method wherein a
specified polymer for spinning is spun, stabilization is performed
under specified conditions and thereafter carbonization is
performed, the time for stabilization can be greatly shortened and
productivity can be improved, and a PAN-based carbon fiber capable
of exhibiting a high degree of elongation while maintaining a
sufficiently high strength can be obtained.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] FIG. 1 shows a schematic sectional view in a direction
perpendicular to a fiber axis showing an example of a sheath-core
structure having three layers, and a partially enlarged view
thereof.
[0019] FIG. 2 shows diagrams exemplifying electron diffractions of
TEM (Transmission Electron Microscope) in a core, an intermediate
layer and a sheath of a sheath-core structure.
[0020] FIG. 3 is a characteristic diagram showing distribution
curves converted from the light and shade of the electron
diffraction diagrams depicted in FIG. 2.
[0021] FIG. 4 is a schematic vertical sectional view showing an
example of a hot air circulation furnace equipped with an infrared
heater which is used for stabilization.
EXPLANATION OF SYMBOLS
[0022] 1: sheath-core structure having three or more layers [0023]
2: core [0024] 3: intermediate layer [0025] 4: sheath [0026] 11:
hot air circulation drier [0027] 12: non-treated fiber (fiber
before treatment) [0028] 13: stabilized fiber (fiber after
treatment) [0029] 14a, 14b: roller [0030] 15a, 15b: opening [0031]
16: ceramic heater [0032] 17: punching metal for attaching ceramic
heater [0033] 18: flow of hot air
DETAILED DESCRIPTION
[0034] Hereinafter, examples will be explained in detail.
[0035] A carbon fiber means a fiber composed of 90% or more with C
(carbon) component. It is possible to determine the content of C
component by elemental analysis.
[0036] It is necessary that the PAN-based carbon fiber comprises
three or more phases different in crystal size. By forming three or
more phases, high functions can be provided to the carbon fiber.
Further, the carbon fiber is preferably a carbon fiber in which the
above-described respective phases are layered. By the layered
structure, it tends that the strength of the carbon fiber is
maintained and the carbon fiber has a high degree of
elongation.
[0037] Further, the carbon fiber preferably forms a sheath-core
structure having three or more layers to exhibit the desired
properties. For example, as shown in FIG. 1, the sheath-core
structure 1 having three or more layers is a structure having an
intermediate layer 3 (for example, a plurality of intermediate
layers) between a core 2 and a sheath 4, which is a structure
formed in three or more layers as a whole, and in particular, it is
preferred to be a structure of three layers. In the sheath-core
structure having three or more layers, it is more preferred that a
crystal size of the core Lc1, a crystal size of the sheath Lc2, and
a crystal size of the intermediate layer Lc3 have relationships of
Lc1/Lc3.gtoreq.1.05, Lc1/Lc2.gtoreq.1.05, and
1.5.gtoreq.Lc1.ltoreq.7.0 nm. More preferably, the relationships
are Lc1/Lc3.gtoreq.1.10 and Lc1/Lc2.gtoreq.1.08. Further
preferably, the relationships are Lc1/Lc3.gtoreq.1.15 and
Lc1/Lc2.gtoreq.1.1. Lc referred here indicates an overlap thickness
of graphite moment in a direction of fiber axis. The crystal size
Lc of each layer can be determined by converting from the light and
shade of the electron diffraction diagrams of TEM (Transmission
Electron Microscope) exemplified in FIG. 2 to the distribution
curves as shown in FIG. 3, and calculating Lc using a half-value
width of each peak. For example, a crystal size can be calculated
as a relative value of the known Lc of T300 (carbon fiber supplied
by Toray Industries, Inc.). In FIG. 2, a portion appearing in a
rod-like form is a shade of a measuring device.
[0038] Furthermore, so that a core becomes in a softer condition,
an orientation degree f of the core is preferably 0.7 or less, and
more preferably 0.6 or less.
[0039] By forming such a structure, a high degree of elongation of
a carbon fiber can be achieved. The reason of a high degree of
elongation is supposed in that, by forming an intermediate layer as
a hard layer, relatively soft sheath and core take charge of impact
caused when the intermediate layer is broken, and the carbon fiber
elongates without reaching breakage.
[0040] A high degree of elongation of a carbon fiber means one in a
range of 1.1% or more and 2.5% or less, more preferably in a range
of 1.2 to 2.5%, and particularly preferably in a range of 1.3 to
2.5%. To the contrary, a low degree of elongation means one of 1.0%
or less. The higher the degree of elongation, the better molding
processing property becomes, thereby suppressing occurrences of
fluff in the process of obtaining a final product.
[0041] Next, the thicknesses of the respective layers in the carbon
fiber will be explained. It is preferred that the core occupies 10
to 70% relative to the cross-sectional area of the fiber, the
thickness of the sheath is 100 nm to 10,000 nm in a direction
perpendicular to the fiber axis so as to cover the core, and the
thickness of the intermediate layer is more than 0 nm and 5,000 nm
or less. More preferably, the thickness of the intermediate layer
is 100 nm to 5,000 nm. Further, it is preferred that the core
occupies 30 to 50% relative to the cross-sectional area of the
fiber.
[0042] A flame resistant fiber is liable to be flattened in section
at an initial stage of carbonization, and tends to become a fiber
bundle intermingled with flat yarns. By flattening, because the
surface area of the fiber increases, the fiber bundle easily
radiates heat, and the time for stabilization tends to be able to
be shortened. The cross-sectional shape of a fiber can be observed
by a laser microscope. The rate of interminglement of flat yarns
was determined by counting the numbers of non-circular ones and
circular ones, respectively, in a photograph taken at 1,000 times
in magnification of a section of a fiber bundle using a laser
microscope. Counting was performed by referring a single yarn with
a ratio of a minor axis to a major axis of 1 to 0.8 as a circular
one, and a single yarn with a ratio of a minor axis to a major axis
of 0.1 or more and less than 0.8 as a flat yarn.
[0043] Next, several characteristics of the production method to
obtain a carbon fiber will be raised.
[0044] In the carbon fiber, because it is possible to obtain a
carbonized yarn having a sheath-core structure with three or more
layers by wet spinning a single kind of polymer and burning it,
there is merit in that it is not necessary to perform compounding,
coating or the like, after spinning. Further, because the
respective layers are strongly combined by performing spinning and
burning and forming three or more layers from a single kind of
polymer, achieved is a structure in which it is possible to
supplement poor points of the layers each other, as
aforementioned.
[0045] Next, a polymer solution for spinning will be described. The
polymer solution for spinning is preferred to be a polymer prepared
by modifying PAN with an amine-based compound and oxidizing it with
a nitro compound.
[0046] By using a polymer solution for spinning not containing a
nitro compound, it tends to become possible that an exothermic
reaction in stabilization of a spun fiber is suppressed, thereby
realizing stabilization of the fiber within a shorter period of
time. Furthermore, by using a polymer solution for spinning not
containing a nitro compound, because nitrobenzene does not exist in
the spun coagulated yarn and/or dried fiber, it is possible to form
a carbon fiber having a three-layer structure through stabilization
and carbonization. When a nitro compound is left in the polymer
solution for spinning, it is supposed that the nitro compound in
the fiber operates as an oxidant even in the process of
stabilization, and it is believed that this oxidation during
formation of a structure of a fiber is a cause of becoming a carbon
fiber with a two-layer structure. As a method of controlling an
amount of the nitro compound left in a polymer solution for
spinning to 0%, there are two kinds of methods of a method of
removing it by washing with ethanol after PAN is modified with an
amine-based compound and a nitro compound, and a method of making a
nitro compound easily react by increasing the amount of amine-based
compound. Since washing takes time and incurs cost and there is a
possibility of being left in the polymer, more preferred is the
latter method of controlling the amount of the residual nitro
compound to 0% in the reaction system. Concrete explanation of such
a method will be described later.
[0047] In PAN composed of only acrylonitrile, a long period of time
is required for stabilization of a fiber after spinning, further,
burning and fusion and the like are caused during stabilization of
the fiber, and the properties of a carbon fiber finally made tend
to be lowered.
[0048] As a state "modified with an amine-based compound" referred
here, exemplified is a state where an amine-based compound is
chemically reacted with PAN as a raw material, or a state where an
amine-based compound is incorporated into a polymer by hydrogen
bonding or an interaction such as van der Waals force.
[0049] It is determined by the following methods whether a polymer
for spinning is modified with an amine-based compound or not.
A. Method of analyzing a difference in structure with a polymer
which is not modified, by spectroscopic manner, for example, using
NMR spectrum, infrared absorption (IR) spectrum or the like
aforementioned. B. Method of determining masses of a polymer before
and after making a polymer for spinning by a method described later
and confirming whether the mass of the polymer for spinning is
increased relative to the mass of PAN as a raw material or not.
[0050] In the former method, a section originating from an
amine-based compound used as a modifier is added as a new spectrum
in a spectrum of a polymer for spinning modified with the
amine-based compound, relative to a spectrum of PAN as a raw
material.
[0051] The mass of a polymer for spinning modified with an
amine-based compound increases by 1.1 times or more, preferably 1.2
times or more, particularly preferably 1.3 times or more, relative
to PAN as a raw material. Further, in an increase, the upper limit
is preferably 3 times or less, more preferably 2.6 times or less,
and further preferably 2.2 times or less. If the change in mass is
smaller or greater than such a range, there is a possibility that
the spinning property is damaged and the strength or the degree of
elongation of a carbon fiber is reduced.
[0052] As an amine-based compound capable of being used to modify a
polymer for spinning, although any of compounds having primary to
quaterary amino group may be employed, concretely, polyethylene
polyamines such as ethylene diamine, diethylene triamine,
triethylene tetramine, tetraethylene pentamine, pentaethylene
hexamine and N-aminoethyl piperazine, and ortho, meta and para
phenylene diamines can be exemplified.
[0053] In particular, it is also preferred to have a functional
group having an element of oxygen, nitrogen, sulfur or the like
such as a hydroxyl group except an amino group, and it is
preferably a compound having two or more functional groups
including an amino group and such a functional group except the
amino group, from the viewpoint of reactivity and the like.
Concretely, ethanol amine group such as monoethanol amine,
diethanol amine, triethanol amine and N-aminoethyl ethanol amine
can be exemplified. Among these, in particular, monoethanol amine
is more preferred. These can be used solely or at a combination of
two or more kinds. In a compound having a functional group except
an amino group, for example, having a hydroxyl group, there is a
possibility that the hydroxyl group modifies a polymer for
spinning.
[0054] The nitro compound is an oxidant and oxidizes PAN.
Therefore, the fiber spun using PAN modified with an amine and
oxidized by a nitro compound tends to be able to be finished with
stabilization in a very short period of time of 10 seconds or more
and 15 minutes or less. As the nitro compound, concretely, an
oxidant of nitro-based, nitroxide-based or the like can be
exemplified. Among these, as particularly preferable ones, aromatic
nitro compounds such as nitrobenzene, o, m, p-nitrotoluene,
nitroxylene, o, m, p-nitrophenol and o, m, p-nitrobenzoic acid can
be exemplified. In particular, nitrobenzene having a simple
structure is most preferably used, since it is little in risk, and
a quick oxidation is possible because of less steric hindrance.
[0055] Although the amount to be added of these oxidants is not
particularly restricted so that PAN is sufficiently oxidized, it is
preferred to use a nitro compound at 10 wt % or more relative to
PAN, more preferably 15 wt % or more. Further, as the amount to be
added of a nitro compound, to control the remaining rate of the
nitro compound in the aforementioned polymer solution for spinning
at 0%, it is preferred to use 1 to 50 parts by mass relative to 100
parts by mass of an amine-based compound to be employed. It is more
preferred to use 20 to 45 parts by mass. At that time, the reaction
temperature is preferably 130 to 300.degree. C., and more
preferably 130 to 250.degree. C. The reaction time is preferably 4
hours or more and 10 hours or less, and more preferably 5 hours or
more and 8 hours or less. If heated for a time more than 10 hours,
a polymer is too damaged, and finally the strength of a carbon
fiber is reduced. In a time less than 4 hours, the nitro compound
is liable to be left in the system, the structure of a carbon fiber
finally obtained does not become three layers, and the degree of
elongation tends to be reduced.
[0056] When PAN is modified under a condition present with an
amine-based compound after being dissolved in a polar organic
solvent, the amine-based compound and the polar organic solvent and
an oxidant may be mixed before addition of PAN and may be
simultaneously with addition of PAN. It is preferred that first
PAN, an amine-based compound and a polar organic solvent are mixed,
and after dissolution by heating, a polymer for spinning is
prepared by adding an oxidant, from the viewpoint of less insoluble
substances. Of course, it is not obstructed to mix a component
other than PAN, an oxidant, an amine-based compound and a polar
organic solvent with such a solution.
[0057] In the polymer for spinning, inorganic particles such as
alumina or zeolite, a pigment such as carbon black, an antifoaming
agent such as silicone, stabilizer.cndot.flame retardant such as a
phosphorus compound, various kinds of surfactants, and other
additives may be contained. Further, for the purpose of improving
the solubility of a polymer for spinning, an inorganic compound
such as lithium chloride or calcium chloride can be contained.
These may be added before expediting the reaction, and may be added
after expediting the reaction.
[0058] Further, the molecular weight and the shape of a polymer for
spinning are determined by GPC, and it is preferred that the value
of the gradient a (hereinafter, referred to as "a") is 0.1 to 0.3.
The "a" determined by GPC means "a" represented by Mark
Houwink-Sakurada equation (1).
[.eta.]=KMw.sup.a (1)
wherein [.eta.] is an intrinsic viscosity, K is a constant inherent
for a material, and Mw is a weight average molecular weight.
[0059] It is known that a polymer exists in a polymer solution as a
rod-like polymer as the value of this gradient "a" is closer to 2,
as a random coil-like polymer as closer to 0.7, and as a spherical
polymer as closer to 0.
[0060] It is preferred that the "a" of a polymer for spinning is
0.1 to 0.3, and it is understood that the polymer for spinning
becomes a divergent structure much closer in shape to a spherical
shape than to a rod-like shape. By employing a divergent structure,
molecules are more intertwined with each other as compared to
employing a straight-chain structure. Accordingly, when
stabilization of a spun fiber is performed, molecules of the
polymer are easily combined with each other, and the time for the
stabilization of the fiber tends to be able to be shortened.
Therefore, when the "a" exceeds 0.3, the stabilization becomes
insufficient, there is a tendency to be decomposed in a
carbonization process and a tendency that the differences between
the "Lc"s and between the orientation degree "f"s of three layers
of a carbon fiber are smallened and the degree of elongation is
reduced. Further, when the "a" becomes less than 0.1, because the
molecular weight itself is being greatly decreased, spinning
becomes difficult. Further, even if spinning can be carried out,
the strength of the fiber tends to be fairly reduced.
[0061] Next, PAN as a raw material will be explained.
[0062] PAN may be a homo PAN and may be a copolymerized PAN. With
the copolymerized PAN, from the viewpoint of the solubility of a
polymer and the flame resistant property of a fiber, the structural
unit originating from acrylonitrile (hereinafter, referred to as
AN) is preferably 85 mol % or more, more preferably 90 mol % or
more, and further preferably 92 mol % or more.
[0063] As concrete copolymerization components, allyl sulfonic acid
metal salt, methallyl sulfonic acid metal salt, acrylic ester,
methacrylic ester, acrylic amide and the like can be also
copolymerized. Further, except the above-described copolymerization
components, as components for accelerating stabilization,
components containing a vinyl group, concretely, acrylic acid,
methacrylic acid, itaconic acid and the like, can also be
copolymerized, and a part or the whole amount thereof may be
neutralized with an alkali component such as ammonia.
[0064] Further, in PAN as a raw material, it is preferred that the
"a" determined by GPC is 0.4 or more and 0.7 or less.
[0065] When PAN is dissolved in a polar organic solvent, the shape
and form of the PAN may be any of powder, flake and fiber, and
polymer waste, yarn waste and the like generated during
polymerization or at the time of spinning can also be used as
recycled raw material. Desirably, it is preferred to be in a form
of powder, in particular, microparticles of 100 .mu.m or less, from
the viewpoint of solubility into solvent.
[0066] The polymer solution for spinning can be made by dissolving
a polymer for spinning in an organic solvent. With respect to the
concentration of the polymer solution for spinning, when the
concentration is low, productivity at the time of spinning tends to
be low although the effect due to our method itself is not damaged,
and when the concentration is high, flowability is poor and it
tends to be hard to be spun. In consideration of being served to
spinning, it is preferably 8 to 30 mass %. The concentration of the
polymer for spinning can be determined by the following method.
[0067] The polymer solution for spinning is weighed, the solution
of about 4 g is put into distilled water of 500 ml and boiled. A
solid material is once taken out, it is again put into distilled
water of 500 ml and boiled. A residual solid component is placed on
an aluminum pan, dried for one day by an oven heated at a
temperature of 120.degree. C., and a polymer for spinning is
isolated. The isolated solid component is weighed, and the
concentration is determined by calculating a ratio with the mass of
the original polymer solution for spinning.
[0068] Further, the polymer for spinning tends to be easily made
into a solution when employing, in particular, a polar organic
solvent as the solvent among organic solvents. This is because the
polymer for spinning modified with an amine-based compound is high
in polarity and the polymer is well dissolved by a polar organic
solvent.
[0069] The polar organic solvent means a solvent having an amino
group, an amide group, a sulfonyl group, a sulfone group and the
like and further having a good compatibility with water, and as
concrete examples, ethylene glycol, diethylene glycol, triethylene
glycol, a polyethylene glycol having a molecular weight of about
200 to 1,000, dimethyl sulfoxide (hereinafter, also abbreviated as
DMSO), dimethyl formamide, dimethyl acetamide, N-methyl pyrrolidone
and the like can be used. These may be used solely, and may be used
as a mixture of two or more kinds. In particular, DMSO is
preferably used because of its high dissolvability relative to
PAN.
[0070] The viscosity of the polymer solution for spinning can be
set in respective preferable ranges depending upon a forming method
or a molding method using the polymer, a molding temperature, a
kind of a die or a mold and the like. Generally, it can be 1 to
1,000 Pas in the measurement at 50.degree. C. More preferably, it
is 10 to 100 Pas, and further preferably, it is 20 to 600 Pas. Such
a viscosity can be measured by various viscosity measuring devices,
for example, a rotary-type viscometer, a rheometer, a B-type
viscometer or the like. The viscosity determined by any one method
may be controlled in the above-described range. Further, even if
out of such a range, by heating or cooling at the time of spinning,
it can be used as an appropriate viscosity.
[0071] As the method of obtaining a polymer solution for spinning,
the following methods are exemplified.
A. A method of modifying PAN with an amine and oxidizing with a
nitro compound in a solution as described above. B. A method of
isolating PAN modified with an amine and oxidized with a nitro
compound, and directly dissolving it in a solvent.
[0072] In directly dissolving PAN spun after modification and
oxidation in an organic solvent, the dissolution may be performed
under an atmospheric pressure, and as the case may be, it may be
performed under a pressurized or pressure-reduced condition. As an
apparatus used for the dissolution, except a usual reaction vessel
with an agitator, a mixer such as an extruder or a kneader can be
used solely or at a form of combination thereof.
[0073] In this case, the dissolution is preferably performed using
an amine-based compound and a polar organic solvent at the sum
thereof of 100 to 1,900 parts by mass, preferably 150 to 1,500
parts by mass, relative to 100 parts by mass of an acrylic-based
polymer.
[0074] Although it is preferred that non-reacted substances,
insoluble substances, gel and the like are not contained in the
polymer solution for spinning obtained by the above-described
method, there is a possibility that they are left at a fine amount.
It is preferred to filtrate or disperse non-reacted substances or
insoluble substances using a sintered filter or the like before
formation into fibers.
[0075] Next, the method of producing a flame resistant fiber
suitable to obtain a carbon fiber will be explained.
[0076] As the method of spinning the polymer solution for spinning
into a fiber, a wet spinning or a dry/wet spinning is employed to
improve productivity of the process. Preferably, a wet spinning is
used.
[0077] Concretely, the spinning can be performed by preparing the
aforementioned polymer solution for spinning as a polymer solution
for spinning, elevating the pressure through a pipe by a booster
pump or the like, extruding with metering by a gear pump or the
like, and discharging from a die. As the material of the die, SUS
(stainless), gold, platinum and the like can be appropriately
used.
[0078] Further, it is preferred that, before the polymer solution
for spinning flows into holes of the die, the polymer solution for
spinning is filtrated or dispersed using a sintered filter of
inorganic fibers or using a woven fabric, a knitted fabric, a
nonwoven fabric or the like comprising synthetic fibers such as
polyester or polyamide as a filter, from the viewpoint that the
fluctuation of the cross-sectional areas of single fibers in a
fiber aggregate to be obtained can be reduced.
[0079] As the hole diameter of the die, an arbitrary range of 0.01
to 0.5 mm.phi. can be employed, and as the hole length, an
arbitrary range of 0.01 to 1 mm can be employed. Further, as the
number of the holes of the die, an arbitrary range of 10 to
1,000,000 can be employed. As the hole arrangement, an arbitrary
one such as a staggered arrangement can be employed, and the holes
may be divided in advance so as to realize easy yarn dividing.
[0080] Coagulated yarns are obtained by discharging the polymer
solution for spinning from the die directly or indirectly into a
coagulation bath. It is preferred that the liquid for the
coagulation bath is formed from a solvent used for the polymer
solution for spinning and a coagulation acceleration component,
from the viewpoint of convenience, and it is more preferred to use
water as the coagulation acceleration component. Although the rate
of the solvent for spinning to the coagulation acceleration
component in the coagulation bath and the temperature of the liquid
for the coagulation bath are appropriately selected and set in
consideration of denseness, surface smoothness, spinnability and
the like of the coagulated yarns to be obtained, in particular, as
the concentration of the coagulation bath, an arbitrary
concentration can be employed within a range of solvent/water=0/100
to 95/5, and 30/70 to 70/30 is preferable, and 40/60 to 60/40 is
particularly preferable. Further, as the temperature of the
coagulation bath, an arbitrary temperature of 0 to 100.degree. C.
can be employed. Further, as the coagulation bath, if an alcohol
such as propanol or butanol reducing an affinity with water is
employed, it can also be used as 100% bath.
[0081] In the method of producing a carbon fiber, the degree of
swelling of the coagulated yarn obtained is preferably controlled
to 50 to 1,000 mass %, more preferably 200 to 900 mass %, and
further preferably 300 to 800 mass %. The degree of swelling of the
coagulated yarn controlled in such a range greatly relates to the
toughness and easiness in deformation of the coagulated yarn and
affects the spinnability. The degree of swelling is decided from
the viewpoint of spinnability, and affects a stretching property in
bath at a later process, and if in such a range, the coefficient of
variation of the cross-sectional areas of single fibers can be made
small in the carbon fibers to be obtained. The degree of swelling
of the coagulated yarn can be controlled by the affinity between
the polymer for spinning forming the coagulated yarn and the
coagulation bath and the temperature or the concentration of the
coagulation bath, and a degree of swelling in the above-described
range can be achieved by controlling the temperature of the
coagulation bath or the concentration of the coagulation bath in
the aforementioned range relative to a specified polymer for
spinning.
[0082] Next, it is preferred that the coagulated yarn is stretched
in a stretching bath or washed in a water washing bath. Of course,
it may be stretched in a stretching bath as well as washed in a
water washing bath. The draw ratio for the stretching is preferably
1.05 to 5 times, more preferably 1.1 to 3 times, and further
preferably 1.15 to 2.5 times. For the stretching bath, hot water or
solvent/water is used, and the concentration of solvent/water for
the stretching bath can be set at an arbitrary concentration of
0/100 to 80/20. Further, for the water washing bath, usually hot
water is used, and the temperature of both the stretching bath and
the water washing bath is preferably 30 to 100.degree. C., more
preferably 50 to 95.degree. C., and particularly preferably 65 to
95.degree. C.
[0083] The fiber completed with coagulation is dried, and as
needed, stretched to become a carbon fiber through stabilization
and carbonization.
[0084] As the drying method, a drying method of bringing the fiber
into direct contact with a plurality of dried and heated rollers, a
drying method of sending hot air or water vapor, a drying method of
irradiating infrared rays or electromagnetic rays with a high
frequency, a drying method of making a pressure reduced condition
or the like can be appropriately selected and combined. Usually, in
a drying method due to hot air, hot air is sent in a direction
parallel or perpendicular to the running direction of the fiber.
For the infrared rays of radiation-heating type, far infrared rays,
mid infrared rays or near infrared rays can be employed, and
radiation of microwaves can also be employed. Although the
temperature for the drying can be employed arbitrarily at
approximately 50 to 250.degree. C., generally, the drying takes a
long time at a low temperature and a short time at a high
temperature.
[0085] When stretching is carried out after drying, the specific
gravity of the fiber after drying is usually 1.15 to 1.5,
preferably 1.2 to 1.4, and more preferably 1.2 to 1.35. The
coefficient of variation of the cross-sectional areas of single
fibers in the fiber aggregate after drying is preferably 5 to 30%,
more preferably 7 to 28%, and further preferably 10 to 25%.
Further, elongation of the single fiber in the fiber aggregate
after drying is preferably 0.5 to 20%. Furthermore, in the fiber
aggregate after drying, oxidation calorific value (J/g) determined
by differential scanning calorimetry (DSC) is preferably 50 to
4,000 J/g. As the case may be, not a continuous drying but a batch
drying can be carried out.
[0086] For such a stretching process, because a fiber is
plasticized with moisture, it is preferred to use a method of
heating the fiber at a condition of containing water in the fiber
such as a bath stretching using warm water or hot water, a
stretching using steam (water vapor), or a heat stretching by a
dryer or rolls after providing water to the fiber in advance, and
heating/stretching by steam stretching is particularly
preferred.
[0087] In bath stretching, it is preferred that the stretching is
carried out at a temperature of, preferably 70.degree. C. or
higher, more preferably 80.degree. C. or higher, and further
preferably 90.degree. C. or higher. At this stage, the fiber
structure is already densified even if the temperature is elevated,
there is no fear of generating micro voids, and a stretching at a
temperature as high as possible is preferred because a high effect
due to molecular orientation can be obtained. Although it is
preferred to use water for the bath, the stretching property may be
further enhanced by adding a solvent or other additives.
[0088] Although a higher stretching temperature is preferred, in a
bath stretching, basically 100.degree. C. becomes the upper limit.
Accordingly, a stretching using steam is employed more preferably.
Although the temperature of the stretching is preferred to be
higher, when a saturated vapor is used, because the internal
pressure of the apparatus is high, there is a possibility that the
fiber is damaged by blowing vapor. For the purpose of obtaining a
carbon fiber with a degree of orientation of the sheath of 65% or
more, a saturated vapor with a temperature of 100.degree. C. or
higher and 150.degree. C. or lower may be used. If the temperature
exceeds 150.degree. C., the effect due to the plasticization
gradually gets to the top, and damage of the fiber due to blowing
vapor becomes greater than the effect due to the plasticization. As
the stretching treatment apparatus using a saturated vapor, an
apparatus devising to pressurize the inside of the treatment
apparatus by providing a plurality of apertures at the fiber inlet
and outlet is preferably used.
[0089] It is also possible to use a super-heated atmospheric
high-temperature steam to prevent the damage of the fiber due to
blowing vapor. This becomes possible by heating an atmospheric
steam using electric heating, water vapor heating, induction
heating or the like and, thereafter, introducing it into the
stretching treatment apparatus. Although it is possible to employ a
range of 100.degree. C. or higher and 170.degree. C. or lower for
the temperature, it is preferred to be 110.degree. C. or higher and
150.degree. C. or lower. If the temperature is too high, the
moisture contained in the steam is reduced, and the effect of
plasticizing the fiber becomes hard to be obtained.
[0090] The draw ratio for the bath stretching and the draw ratio
for the stretching by steam are preferably 1.5 times or more, and
more preferably 2.0 times or more. To promote the molecular
orientation, the draw ratio for the stretching is preferred to be
higher, and an upper limit thereof is not particularly present.
However, from restriction on stability of spinning, it is
frequently difficult to exceed about 6 times.
[0091] Further, in the method of stretching the fiber, the means
thereof is not restricted to the bath stretching or the steam
stretching. For example, heat stretching by a drying furnace or a
hot roller or the like after providing moisture may be
possible.
[0092] A non-contact type stretching machine using a drying
furnace, further, a contact type stretching machine using a contact
plate, a hot roller or the like, can also be used. However, in a
contact type stretching machine, evaporation of moisture is fast
and, further, there is a high possibility that a fiber is
mechanically scratched at a point occurred with stretching.
Further, in a non-contact type stretching machine, a required
temperature becomes 250.degree. C. or higher, and as the case may
be, thermal decomposition of the polymer starts. Furthermore, when
a non-contact type stretching machine or a contact type stretching
machine is used, the effect due to stretching is low, and it is
more difficult to obtain a carbon fiber with a high orientation
than the stretching method using moisture. From these reasons, it
is more preferred to use a bath stretching or a steam
stretching.
[0093] The stretched yarn thus stretched is preferably dried again,
as needed. The moisture percentage of the fiber is preferably 10%
or less, and more preferably 5% or less. As this drying method,
bringing the fiber into contact directly with a plurality of dried
and heated rollers or hot plates, sending hot air or water vapor,
irradiating infrared rays or electromagnetic rays with a high
frequency, making a pressure reduced condition and the like can be
appropriately selected and combined. It is preferred to employ
drying due to rollers to perform an efficient drying. The number of
the rollers is not restricted. The temperature of the rollers is
preferably 100.degree. C. or higher and 250.degree. C. or lower,
and more preferably 150.degree. C. or higher and 200.degree. C. or
lower. If the drying at this process is insufficient, there is a
possibility to cause a fiber breakage when a tension is applied to
the fiber at a heat treatment process carried out later.
[0094] To the coagulate yarn, or the fiber at a water swelling
state after being water washed and stretched, an oil component can
be appropriately provided depending upon the necessity of a
higher-order processing. When an oil component is provided, usually
the concentration of the oil is set at 0.01 to 20 mass %. As the
method of providing, it may be appropriately selected and employed
in consideration of being provided uniformly up to the interior of
the yarn. Concretely, a method such as dipping of the yarn into an
oil bath or spray or dropping onto the running yarn is employed.
The oil comprises, for example, a main oil component such as
silicone and a diluent component for diluting it. The concentration
of oil means a content of the main oil component relative to the
whole of the oil. The kind of the oil component is not particularly
restricted, polyether-based one, polyester surfactant, silicone,
amino-modified silicone, epoxy-modified silicone or
polyether-modified silicone can be provided solely or at a mixture
thereof, and other oil components may be provided.
[0095] The adhesion amount of such an oil component is determined
as a rate relative to the dried mass of the fiber included with the
oil component, and it is preferably 0.05 to 5 mass %, more
preferably 0.1 to 3 mass %, and further preferably 0.1 to 2 mass %.
If the adhesion amount of an oil component is too little, there is
a possibility that fusion of single fibers to each other occurs and
the tensile strength of an obtained carbon fiber is reduced and, if
too much, there is a possibility that it becomes difficult to
obtain the desired effect.
[0096] The fiber obtained by the above-described process is
transferred to a process for stabilization. The fiber before being
transferred to the stabilization process is preferably in a dried
condition. As the method of stabilization, in particular, it is
preferred to use a dry-heating apparatus to control chemical
reaction and suppress unevenness in fiber structure, and concrete
equipment thereof will be described later. The temperature and the
treatment length are appropriately selected depending upon the
oxidation degree of the used polymer for spinning, the fiber
orientation degree and the required properties for a final product.
Concretely, the treatment temperature for the stabilization is
preferably 280.degree. C. or higher and 400.degree. C. or lower.
More preferably, it is 300.degree. C. or higher and 360.degree. C.
or lower, and particularly preferably, it is 300.degree. C. to
330.degree. C. If the temperature is lower than 280.degree. C., a
problem tends to occur in a carbonization process. If the
temperature exceeds 400.degree. C., the fiber tends to be
decomposed in a stabilization furnace. The treatment time of the
stabilization is preferably 10 seconds or longer to prevent
decomposition in a carbonization process. Further, when the
treatment time of the stabilization exceeds 15 minutes, because the
merit of shortening the time for stabilization becomes small and
besides the fiber is fuzzed to cause reduction of strength and
degree of elongation, it is preferred that the treatment time of
the stabilization is 15 minutes or shorter. From the viewpoint of
suppressing occurrences of fluff, more preferably it is 5 minutes
or shorter.
[0097] Further, it is preferred to perform a stretching when the
heat treatment is carried out. By carrying out the stretching
treatment, the molecular orientation can be further enhanced. The
draw ratio for this stretching is preferably 1.05 to 4 times. The
draw ratio is set from required strength and fineness of the flame
resistant fiber, process passing-through property and the
temperature of the heat treatment. Concretely, the draw ratio for
the stretching is 1.1 to 4 times, preferably 1.2 to 3 times, and
more preferably 1.3 to 2.5 times. Further, it is also important to
perform heat treatment at the time of stretching, and as the time
for the heat treatment, an arbitrary value of 1 to 15 minutes can
be employed depending upon the temperature. Stretching and
treatment for stabilization may be performed either simultaneously
or separately.
[0098] Among dry-heating apparatuses, in particular, it is
preferred to use an infrared heater and a hot air drier together.
By employing heating due to an infrared heater and a hot air drier
together, the treatment time for stabilization tends to be
shortened.
[0099] To use an infrared heater and a hot air drier together
includes to treat separately from each other, and it is
particularly preferred to provide an infrared heater in a hot air
circulation drier and perform simultaneous treatment of emission
(radiation) and heat transfer by the integrated hot air circulation
drier equipped with the infrared heater. By using the integrated
apparatus, high temperature-elevation.cndot.short-time treatment
due to the infrared heater and uniform treatment of single fibers
due to hot air can be achieved simultaneously. Although a metal, a
ceramic or the like can be used as the material of the infrared
heater, it is preferred to be made from a ceramic from its high
heat radiation rate and high thermal stability.
[0100] A schematic structure of a hot air circulation drier
equipped with an infrared heater is exemplified in FIG. 4, and as
shown in the figure, it can be manufactured, for example, by
providing two or more openings 15a, 15b to a forced-type hot air
circulation drier 11 sold on the market so as to be able to treat a
fiber continuously and, further, attaching an electric ceramic
heater 16 sold on the market (for example, a ceramic plate heater
"PLC-323", supplied by NORITAKE CO., LTD.) inside the drier. It is
preferred that two or more ceramic heaters are installed and,
further, it is particularly preferred that they are installed to be
able to irradiate the infrared rays to the fiber from both
directions of upper and lower sides or left and right sides to
irradiate the infrared rays to the fiber uniformly. With respect to
the treatment by the hot air circulation drier 11, for example, a
non-treated fiber 12 (fiber before treatment) is introduced into
hot air circulation drier 11 from opening 15a while being guided by
a roller 14a, it is irradiated with the infrared rays from both
directions of upper and lower sides by ceramic heaters 16 attached
to, for example, punching metals 17 for attaching ceramic heaters,
and at the same time, heat transfer treatment due to hot air (the
flow of the hot air is shown by arrows 18) is performed, and a
stabilized fiber 13 (fiber after treatment) is sent out from
opening 15b while being guided by a roller 14b.
[0101] As the circulation system of the hot air circulation drier,
both a down flow system and an up flow system can be applied. As a
fan to control the circulation amount of hot air, although a
propeller fan and a sirocco fan can be used, it is preferred to use
a sirocco fan from the viewpoint of its good wind resistance. It is
preferred to rotate this fan by a motor after conversion to a
direct current by an inverter. As a concrete inverter,
"FR-E720-0.2K" supplied by Mitsubishi Electric Corporation can be
exemplified, and as an induction motor, "5IK60A-SF" supplied by
ORIENTAL MOTOR Co., Ltd. can be exemplified. Further, as the
rotational speed of the fan, it is preferably 500 to 1,500 rpm, and
to shorten the treatment time within a range which does not cause
to fuzz, particularly preferably it is 800 to 1,200 rpm.
[0102] Furthermore, by suppressing exothermic reaction at the time
of stabilization, it is possible to shorten the treatment time for
stabilization and perform stabilization, which has been performed
by two furnaces, by a single furnace.
[0103] The fibers having been spun are in a bundle form comprising
a plurality of single fibers, the number of single fibers included
in a single bundle can be appropriately selected depending upon the
purpose of use and, to control the aforementioned preferred number,
it can be adjusted by the number of holes of a die, and a plurality
of spun fibers may be doubled.
[0104] Further, to control the fineness of the single fiber in the
aforementioned preferable range, it can be controlled by selecting
the hole diameter of a die or appropriately deciding the discharge
amount from a die.
[0105] Further, when the fineness of a single fiber is made
greater, making the time for drying longer, or elevating the
temperature for drying higher, is preferred from the viewpoint of
reduction of the amount of residual solvent.
[0106] Further, the cross-sectional shape of a single fiber can be
controlled by the shape of a discharge hole of a die such as a
circular hole, an oval hole or a slit and the condition at the time
of removing a solvent.
[0107] Next, a production method suitable to obtain a carbon fiber
using the obtained flame resistant fiber will be explained.
[0108] A carbon fiber is obtained by heat treating the flame
resistant fiber at a high temperature in an inert atmosphere,
so-called carbonizing. As a concrete method of obtaining a carbon
fiber, a carbon fiber can be obtained by treating the
aforementioned flame resistant fiber at a highest temperature in an
inert atmosphere of 1,000.degree. C. or higher and lower than
2,000.degree. C. More preferably, as the lower side of the highest
temperature, 1,000.degree. C. or higher, 1,200.degree. C. or higher
and 1,300.degree. C. or higher are preferred in order, and as the
upper side of the highest temperature, 1,800.degree. C. or lower
can also be employed. Further, by further heating such a carbon
fiber in an inert atmosphere at a temperature of 2,000 to
3,000.degree. C., a carbon fiber developing in graphite structure
can also be obtained.
[0109] In the carbon fiber, the density is preferably 1.6 to 1.9
g/cm.sup.3, and more preferably 1.7 to 1.9 g/cm.sup.3. If such a
density is too small, there is a possibility that many pores are
present in a single fiber and the fiber strength is reduced, and on
the contrary, if too great, there is a possibility that the
denseness becomes too high and the degree of elongation is reduced.
Such a density can be determined utilizing immersion method or
sink-float method based on JIS R 7603(1999).
[0110] Usually, the single fibers of the carbon fibers are gathered
to form an aggregate such as a fiber bundle. In forming the fibers
as a bundle, although the number of single fibers per one bundle is
appropriately decided depending on the purpose of use, from the
viewpoint of higher-order processing property, it is preferably 50
to 100,000/bundle, more preferably 100 to 80,000/bundle, and
further preferably 200 to 60,000/bundle.
[0111] The tensile strength of a single fiber is preferably 1.0 to
10.0 GPa, more preferably 1.5 to 7.0 GPa, and further preferably
2.0 to 7.0 GPa. Such a tensile strength can be determined based on
JIS R7606(2000) using a universal tensile testing machine (for
example, small-sized desk-top tester EZ-S, supplied by Shimadzu
Corporation).
[0112] It is desired that the diameter of the single fiber is 2
.mu.m or more, in particular, 2 .mu.m to 70 .mu.m, preferably 2 to
50 .mu.m, and more preferably 3 to 20 .mu.m. If such a diameter of
the single fiber is less than 2 .mu.m, there is a possibility that
the fiber is liable to be broken, and if more than 70 .mu.m, a
defect rather tends to be caused. The single fiber of the carbon
fiber may be one having a hollow portion. In this case, the hollow
portion may be either continuous or discontinuous.
[0113] From the viewpoint of reducing cost, it is preferred to
produce a carbon fiber continuously by one process from a polymer
for spinning to the carbon fiber.
[0114] The carbon fiber tends to have a peak nearly at 26.degree.
in X-ray diffraction (XRD) similarly in a general PAN-based carbon
fiber.
EXAMPLES
[0115] Next, our fibers and methods will be explained more
concretely by Examples. In the Examples, the respective properties
and characteristics were determined by the following methods.
Preparation of Polymer Solutions for Spinning (a, c to e)
[0116] A thermometer, a cooler, an agitator and a nitrogen
introducing tube were attached to a three neck flask having a
sufficient capacity. In this flask, PAN was dissolved in DMSO at
the rate described in Table 1, an amine-based compound and a nitro
compound were added, and while stirring by a stirring blade at 300
rpm, heating was carried out in an oil bath at 150.degree. C. for
the time described in Table 1 to perform a reaction.
Preparation of Polymer Solution for Spinning (b)
[0117] PAN and DMSO were put into a polyethylene bottle of 2 L, and
they were stirred at 80.degree. C. for the time described in Table
1 to dissolve PAN.
Isolation of Polymer for Spinning
[0118] The obtained polymer solution for spinning was washed with
ethanol or hot water, and the precipitate was dried to obtain a
polymer for spinning.
Spinning
[0119] By the above-described method, the obtained polymer solution
for spinning was served to a wet spinning apparatus as it was,
thereby forming fibers. The dried fiber was 1 denier.
Determination of Molecular Weight by GPC
[0120] It was dissolved in N-methyl pyrrolidone (added with
0.01N-lithium bromide) so that the concentration of a polymer for
spinning to be determined became 2 mg/mL to prepare a specimen
solution. With respect to the prepared specimen solution, a
distribution curve of the absolute molecular weight was determined
from the GPC curve measured at the following conditions using a GPC
apparatus, and a weight average molecular weight Mw was calculated.
The measurement was carried out at n=1. [0121] GPC apparatus:
PROMINAICE (supplied by Shimadzu Corporation) [0122] Column: polar
organic solvent-system GPC column TSK-GEL-.alpha.-M (.times.2)
(supplied by Tosoh Corporation) [0123] Detector: (viscosity
detection and R1 detection system) Viscotek Model 305TDA Detectors
(supplied by Malvern Corporation) [0124] Flow rate: 0.6 mL/min.
[0125] Temperature: 40.degree. C. [0126] Filtration of sample:
membrane filter (0.45 .mu.m cut) [0127] Amount of injection: 100
.mu.L
Determination of Residual Amount of Nitro Compound by GC-MS
[0128] A calibration curve of an added nitro compound was made. The
method of determining a sample is as follows.
[0129] A polymer extract extracted with ethanol was determined by
GC-MS (Gas Chromatography-Mass Spectroscopy), and compounds present
in the extract were identified by automatic analysis. The
measurement was carried out at n=1.
[0130] The conditions of the determination of GC-MS are as follows.
[0131] System: GCMS-QP2010 Ultra (supplied by Shimadzu Corporation)
[0132] Column oven temperature: 500.degree. C. [0133] Column flow
rate: 1 mL/min. [0134] Column: PtxR Amine, film thickness: 1 .mu.m,
length: 30 cm, inner diameter: 0.25 mm GC determination program:
[0135] Temperature elevation speed: 10.degree. C./min. [0136] Range
of determination: 50.degree. C. (maintained for 1
min.).fwdarw.280.degree. C. (maintained for 1 min.) M/Z (M: mass of
molecule, Z: number of electric charge) determination program:
[0137] Scanning speed: 1250 [0138] Starting time: 8 min. [0139]
Finishing time: 25 min. [0140] Scanning speed: 1250 [0141] Starting
m/z: 50 [0142] Finishing m/z: 400
Stabilization
[0143] The treatment was carried out under a condition of air at
predetermined temperature and temperature elevation speed, using
one furnace of a hot air circulation drier incorporated with an
infrared heater as shown in FIG. 4. The hot air circulation drier
was a down flow-system one, a sirocco fan having a diameter of 200
mm was controlled by an inverter (FR-E720-0.2K) supplied by
Mitsubishi Electric Corporation and, further, it was rotated by an
induction motor (5IK60A-SF) supplied by ORIENTAL MOTOR Co., Ltd.
The wind direction of the hot air was a cross flow, and the
rotational speed of the fan was 1,200 rpm. Furthermore, as the
infrared heater in the hot air circulation drier, and six electric
ceramic plate heaters (PLC-323) supplied by NORITAKE CO., LTD. were
installed at each of the upper side and the lower side relative to
a yarn path, respectively. The temperature of the hot air in the
furnace and the temperature of the infrared heater were set at an
identical temperature.
Carbonization
[0144] The treatment was carried out under a nitrogen atmosphere at
a predetermined temperature and at a tensile condition. The
carbonization was carried out by two furnaces. In the first
furnace, the treatment was carried out at a temperature of 700 to
800.degree. C., and in the second furnace, the treatment was
carried out at a temperature of 1,300.degree. C. The temperature
elevation speed was 50 to 200.degree. C.
Determination of Density of Fiber
[0145] It was determined based on the sink-float method of JIS R
7603(1999).
Determination of Areal Weight of Fiber Bundle
[0146] The mass of a sample cut out by 1 m from 12,000 carbon
fibers was measured, and it was determined as the areal weight. The
unit of the areal weight is g/m.
Calculation of Diameter of Single Fiber
[0147] An average value calculated from the above-described density
of fiber and areal weight of fiber bundle by the following equation
Equation (1) was calculated as a diameter of a cross section of a
single fiber.
l = Mf 120000 .times. .rho. .times. 100 .times. .pi. .times. 20000
= Mf .rho. .times. 10.3 ( 1 ) ##EQU00001##
[0148] In the above-described Equation (1), represented are 1:
diameter of single fiber (.mu.m), Mf: areal weight of 12,000 carbon
fibers (g/m), and .rho.: density (g/cm.sup.3).
Determination of Strength and Degree of Elongation of Single Fiber
by Tensing Single Fiber
[0149] The strength and degree of elongation of a single fiber were
determined under the following conditions based on JIS R7606
(2000). Further, the strength was calculated by dividing a maximum
load in an S-S curve with the cross section calculated from the
density and the areal weight. Further, the degree of elongation was
calculated from a displacement. The number of n was set at 5 or
more.
[0150] The conditions for the determination are as follows. [0151]
System: small-sized desk-top tester EZ-S (supplied by Shimadzu
Corporation) [0152] Load cell: 20N (PEG50NA) [0153] Operation for
control: loading [0154] Testing control: stroke [0155] Testing
speed: 1 mm/min. [0156] Sampling: 50 msec. [0157] Free length pace
between grippers: 25 mm
TEM Observation
[0158] After a specimen was embedded with a resin on a Si base
plate, two protective layers of Pt-based (conductive treatment) and
C-based layers were deposited. This specimen was chipped in a fiber
axis direction by the following method to prepare a thin-film test
piece having a thickness of several-hundred .mu.m. Further, it was
chipped in parallel to the fiber axis direction to be able to pick
up a center of a fiber, thereby preparing a thin-film test piece
having a thickness of several-hundred .mu.m. If hitting a void
present in a fiber when a thin film for TEM is prepared, a sample
is prepared at another position with no voids. [0159] Method: FIB
(Focused Ion Beam) [0160] System: SMI3200SE supplied by SINT
Corporation, FB-2000A supplied by Hitachi, Ltd., STRATA400S
supplied by FEI Corporation [0161] System: transmission electron
microscope; H-9000UHR No. 2 machine supplied by Hitachi, Ltd.
[0162] Acceleration voltage: 300 kV [0163] Diaphragm of restricted
visual field: about 300 nm.phi. Making of Intensity Distribution
Graph and Calculation of Crystal Size and Orientation Degree from
TEM Image
[0164] Intensity distribution graph was made from shades of colors
by image analysis of TEM image. Further, from the intensity
distribution graph, a crystal size Lc was calculated from a
half-value width of a peak corresponding to (002) plane by the
following equation Equation (2), and an orientation degree of a
crystal was calculated from a total width of a half-value of the
intensity distribution in each orientation direction by the
following equation Equation (3).
L c = ln 2 .pi. .lamda. sin .theta. h - sin .theta. l ( 2 )
##EQU00002##
[0165] In the above-described equation Equation (2), .theta.h: high
angle side of (002) plane, and .theta.l: low angle side of (002)
plane.
f = 180 - FWHM 180 ( 3 ) ##EQU00003##
[0166] In the above-described equation Equation (3), FWHM is a
total width of a half-value of intensity distribution in each
orientation direction.
Elemental Analysis
[0167] Measurement was carried out with n number of 2, and an
average value of these two values was determined as the measured
value. However, when a difference between the two values (the
respective elemental rates of C, H and N) was more than .+-.0.4%,
the measurement was repeated until it became .+-.0.4% or less.
[0168] The conditions for the measurement are as follows. [0169]
System: small-sized elemental analysis device, EuroEA3000 supplied
by Evisa Corporation [0170] Cup: Tin capsules Pressed 5.times.9 mm
Code E12007 [0171] Reaction tube: Packed reactor single for CHNS/S
18/6 mm Code E13040 [0172] Carrier: 60 kPa [0173] Purge: 80 mL/min.
[0174] Oxygen: 15 mL [0175] AP O.sub.2: 35 kPa [0176] Oxygen Time:
6.6 sec. [0177] Sample Delay: 5 sec. [0178] Run Time: 320 sec.
[0179] Front Furnace: 980.degree. C. [0180] Oven: 100.degree.
C.
Observation of Fiber Bundle by SEM
[0181] SEM determination was carried out at the following
conditions. [0182] System: VK-9800 (supplied by KEYENCE
Corporation) [0183] Acceleration voltage: 10 kV [0184] Spot
diameter: 4
Laser Microscope
[0185] The observation of a fiber in a laser microscope was carried
out at the following conditions. [0186] System: VK-X210 (supplied
by KEYENCE Corporation) [0187] Lens: 50.times. (integrated lens:
20.times.), observed at a total magnification of 1,000 times.
Example 1
[0188] Polymer solution for spinning (a) was wet spun at a number
of filaments of 12,000 to obtain fibers through a drying process.
The obtained fibers were served to stabilization at conditions of
300.degree. C. and 5 minutes, and carbonization was carried out at
a carbonization temperature of 1,300.degree. C.
[0189] As the result of TEM observation, the obtained carbon fiber
had a 3-layer sheath-core structure. With respect to Lc, it was 1.6
nm at the sheath, 1.8 nm at the intermediate layer and 2.1 nm at
the core. With respect to orientation degree f, the sheath was
oriented at 0.86, the intermediate layer was oriented at 0.89 and
the core was oriented at 0.6 or less. As the result of tensing a
single fiber, the tensile strength was 2.1 GPa, the degree of
elongation was 1.7%, and they were good results.
Example 2
[0190] Polymer solution for spinning (a) was treated in a manner
similar to that in Example 1 to obtain fibers. The obtained fibers
were served to stabilization. For the obtained fibers, the
stabilization was carried out at conditions of 320.degree. C. and 5
minutes, and carbonization was carried out at a carbonization
temperature of 1,300.degree. C.
[0191] As the result of TEM observation, the obtained carbon fiber
had a 3-layer sheath-core structure. With respect to Lc, it was 1.6
nm at the sheath, 1.8 nm at the intermediate layer and 2.1 nm at
the core. With respect to orientation degree f, the sheath was
oriented at 0.86, the intermediate layer was oriented at 0.89 and
the core was oriented at 0.6 or less. As the result of tensing a
single fiber, the tensile strength was 2.1 GPa, the degree of
elongation was 1.6%, and they were good results.
Example 3
[0192] Polymer solution for spinning (a) was treated in a manner
similar to that in Example 1 to obtain fibers. The obtained fibers
were served to stabilization. For the obtained fibers, the
stabilization was carried out at conditions of 340.degree. C. and 5
minutes, and carbonization was carried out at a carbonization
temperature of 1,300.degree. C.
[0193] As the result of TEM observation, the obtained carbon fiber
had a 3-layer sheath-core structure. With respect to Lc, it was 1.6
nm at the sheath, 1.8 nm at the intermediate layer and 2.1 nm at
the core. With respect to orientation degree f, the sheath was
oriented at 0.86, the intermediate layer was oriented at 0.89 and
the core was oriented at 0.6 or less. As the result of tensing a
single fiber, the tensile strength was 2.2 GPa, the degree of
elongation was 1.5%, and they were good results.
Example 4
[0194] Polymer solution for spinning (a) was treated in a manner
similar to that in Example 1 to obtain fibers. The obtained fibers
were served to stabilization. For the obtained fibers, the
stabilization was carried out at conditions of 360.degree. C. and 5
minutes, and carbonization was carried out at a carbonization
temperature of 1,300.degree. C.
[0195] As the result of TEM observation, the obtained carbon fiber
had a 3-layer sheath-core structure. With respect to Lc, it was 1.6
nm at the sheath, 1.8 nm at the intermediate layer and 2.1 nm at
the core. With respect to orientation degree f, the sheath was
oriented at 0.86, the intermediate layer was oriented at 0.89 and
the core was oriented at 0.6 or less. As the result of tensing a
single fiber, the tensile strength was 2.2 GPa, the degree of
elongation was 1.5%, and they were good results.
Example 5
[0196] Polymer solution for spinning (a) was treated in a manner
similar to that in Example 1 to obtain fibers. The obtained fibers
were served to stabilization. For the obtained fibers, the
stabilization was carried out at conditions of 300.degree. C. and
10 minutes, and carbonization was carried out at a carbonization
temperature of 1,300.degree. C.
[0197] As the result of TEM observation, the obtained carbon fiber
had a 3-layer sheath-core structure. With respect to Lc, it was 1.6
nm at the sheath, 1.8 nm at the intermediate layer and 2.1 nm at
the core. With respect to orientation degree f, the sheath was
oriented at 0.86, the intermediate layer was oriented at 0.89 and
the core was oriented at 0.6 or less. As the result of tensing a
single fiber, the tensile strength was 2.2 GPa, the degree of
elongation was 1.6%, and they were good results.
Example 6
[0198] Polymer solution for spinning (a) was treated in a manner
similar to that in Example 1 to obtain fibers. The obtained fibers
were served to stabilization. For the obtained fibers, the
stabilization was carried out at conditions of 360.degree. C. and
10 minutes, and carbonization was carried out at a carbonization
temperature of 1,300.degree. C.
[0199] As the result of TEM observation, the obtained carbon fiber
had a 3-layer sheath-core structure. With respect to Lc, it was 1.6
nm at the sheath, 1.8 nm at the intermediate layer and 2.1 nm at
the core. With respect to orientation degree f, the sheath was
oriented at 0.86, the intermediate layer was oriented at 0.89 and
the core was oriented at 0.6 or less. As the result of tensing a
single fiber, the tensile strength was 2.4 GPa, the degree of
elongation was 1.6%, and they were good results.
Example 7
[0200] Polymer solution for spinning (a) was treated in a manner
similar to that in Example 1 to obtain fibers. The obtained fibers
were served to stabilization. For the obtained fibers, the
stabilization was carried out at conditions of 300.degree. C. and
15 minutes, and carbonization was carried out at a carbonization
temperature of 1,300.degree. C.
[0201] As the result of TEM observation, the obtained carbon fiber
had a 3-layer sheath-core structure. With respect to Lc, it was 1.6
nm at the sheath, 1.8 nm at the intermediate layer and 2.0 nm at
the core. With respect to orientation degree f, the sheath was
oriented at 0.86, the intermediate layer was oriented at 0.89 and
the core was oriented at 0.6 or less. As the result of tensing a
single fiber, the tensile strength was 2.3 GPa, the degree of
elongation was 1.6%, and they were good results.
Example 8
[0202] Polymer solution for spinning (a) was treated in a manner
similar to that in Example 1 to obtain fibers. The obtained fibers
were served to stabilization. For the obtained fibers, the
stabilization was carried out at conditions of 360.degree. C. and
15 minutes, and carbonization was carried out at a carbonization
temperature of 1,300.degree. C.
[0203] As the result of TEM observation, the obtained carbon fiber
had a 3-layer sheath-core structure. With respect to Lc, it was 1.6
nm at the sheath, 1.8 nm at the intermediate layer and 2.1 nm at
the core. With respect to orientation degree f, the sheath was
oriented at 0.85, the intermediate layer was oriented at 0.88 and
the core was oriented at 0.6 or less. As the result of tensing a
single fiber, the tensile strength was 2.4 GPa, the degree of
elongation was 1.6%, and they were good results.
Example 9
[0204] Polymer solution for spinning (d) was treated in a manner
similar to that in Example 1 to obtain fibers. The obtained fibers
were served to stabilization. For the obtained fibers, the
stabilization was carried out at conditions of 360.degree. C. and
15 minutes, and carbonization was carried out at a carbonization
temperature of 1,300.degree. C.
[0205] As the result of TEM observation, the obtained carbon fiber
had a 3-layer sheath-core structure. With respect to Lc, it was 1.4
nm at the sheath, 1.6 nm at the intermediate layer and 1.8 nm at
the core. With respect to orientation degree f, the sheath was
oriented at 0.82, the intermediate layer was oriented at 0.84 and
the core was oriented at 0.6 or less. As the result of tensing a
single fiber, the tensile strength was 2.0 GPa, the degree of
elongation was 1.3%, and they were good results.
Example 10
[0206] Polymer solution for spinning (e) was treated in a manner
similar to that in Example 1 to obtain fibers. The obtained fibers
were served to stabilization. For the obtained fibers, the
stabilization was carried out at conditions of 360.degree. C. and
15 minutes, and carbonization was carried out at a carbonization
temperature of 1,300.degree. C.
[0207] As the result of TEM observation, the obtained carbon fiber
had a 3-layer sheath-core structure. With respect to Lc, it was 1.4
nm at the sheath, 1.6 nm at the intermediate layer and 1.8 nm at
the core. With respect to orientation degree f, the sheath was
oriented at 0.82, the intermediate layer was oriented at 0.84 and
the core was oriented at 0.6 or less. As the result of tensing a
single fiber, the tensile strength was 1.6 GPa, the degree of
elongation was 1.6%, and they were good results.
Example 11
[0208] Polymer solution for spinning (a) was treated in a manner
similar to that in Example 1 to obtain fibers. The obtained fibers
were served to stabilization. For the obtained fibers, the
stabilization was carried out at conditions of 360.degree. C. and
30 minutes, and carbonization was carried out at a carbonization
temperature of 1,300.degree. C.
[0209] As the result of TEM observation, the obtained carbon fiber
had a 3-layer sheath-core structure. With respect to Lc, it was 1.6
nm at the sheath, 1.8 nm at the intermediate layer and 2.0 nm at
the core. With respect to orientation degree f, the sheath was
oriented at 0.79, the intermediate layer was oriented at 0.81 and
the core was oriented at 0.6 or less. As the result of tensing a
single fiber, because the time for stabilization was too long, the
fiber was fuzzed and the thickness thereof became small and,
therefore, the tensile strength was reduced to 1.7 GPa, the degree
of elongation was reduced to 1.5%, but they were good results.
Comparative Example 1
[0210] Polymer solution for spinning (a) was wet spun in a manner
similar to that in Example 1 to obtain fibers through a drying
process. The obtained fibers were served to stabilization at
conditions of 240.degree. C. and 15 minutes. Although the
stabilized fiber was tried to be carried out with carbonization at
a carbonization temperature of 1,300.degree. C., the fiber was
burned and broken immediately after being introduced into a
furnace, and could not be carbonized as a carbon fiber.
Comparative Example 2
[0211] Polymer solution for spinning (a) was wet spun in a manner
similar to that in Example 1 to obtain fibers through a drying
process. The obtained fibers were served to stabilization at
conditions of 260.degree. C. and 15 minutes. Although the
stabilized fiber was tried to be carried out with carbonization at
a carbonization temperature of 1,300.degree. C., the fiber was
burned and broken immediately after being introduced into a
furnace, and could not be carbonized as a carbon fiber.
Comparative Example 3
[0212] Polymer solution for spinning (b) was wet spun in a manner
similar to that in Example 1 to obtain fibers through a drying
process. The obtained fibers were served to stabilization at
conditions of 240.degree. C. and 15 minutes. Although the
stabilized fiber was tried to be carried out with carbonization at
a carbonization temperature of 1,300.degree. C., the fiber was
burned and broken immediately after being introduced into a
furnace, and could not be carbonized as a carbon fiber.
Comparative Example 4
[0213] Polymer solution for spinning (b) was wet spun in a manner
similar to that in Example 1 to obtain fibers through a drying
process. The obtained fibers were served to stabilization. The
fiber was stabilized at conditions of 280.degree. C. and 15
minutes. Although a fusion happened at the stage of the
stabilization, the fiber was carbonized as it was. Although the
stabilized fibers were tried to be carried out with carbonization
at a carbonization temperature of 1,300.degree. C., most of the
fibers were burned and broken in a furnace. As the result of
tensing a single fiber with respect to parts barely taken as carbon
fibers, the tensile strength was reduced to 1.3 GPa, the degree of
elongation was 1.0%, and they were very low tensile strength and
degree of elongation to cause poor results.
Comparative Example 5
[0214] Polymer solution for spinning (b) was wet spun in a manner
similar to that in Example 1 to obtain fibers through a drying
process. Although the obtained fibers were tried to be carried out
with stabilization at conditions of 300.degree. C. and 15 minutes,
they were burned and broken in a furnace for stabilization.
Comparative Example 6
[0215] Polymer solution for spinning (b) was wet spun in a manner
similar to that in Example 1 to obtain fibers through a drying
process. Although the obtained fibers were tried to be carried out
with stabilization at conditions of 360.degree. C. and 15 minutes,
they were burned and broken in a furnace for stabilization.
Comparative Example 7
[0216] Polymer solution for spinning (c) was treated in a manner
similar to that in Example 1 to obtain fibers. The obtained fibers
were served to burning at conditions similar to those in Example 7
to obtain carbon fibers. Because a nitro compound was left in the
polymer solution for spinning, as the result of TEM observation,
the obtained carbon fiber had a 2-layer sheath-core structure. With
respect to Lc, it was 1.7 nm at the sheath and 1.5 nm at the core.
With respect to orientation degree f, the sheath was oriented at
0.86, and the core was oriented at 0.83 or less. As the result of
tensing a single fiber, the tensile strength was 1.9 GPa, and the
degree of elongation was 0.8%. In particular, the degree of
elongation was greatly reduced as compared with Example 8, and it
was a poor result.
Comparative Example 8
[0217] Polymer solution for spinning (a) was wet spun at a number
of filaments of 12,000 to obtain fibers through a drying process,
in a manner similar to that in Example 1. The obtained fibers were
served to stabilization at conditions of 300.degree. C. and 5
minutes similar to those in Example 1, using a hot air circulation
drier equipped with no infrared heater, and carbonization was
carried out at a carbonization temperature of 1,300.degree. C.
[0218] As the result of TEM observation, the obtained carbon fiber
had substantially a 2-layer sheath-core structure. With respect to
Lc, it was 1.6 nm at the sheath and 2.2 nm at the core. With
respect to orientation degree f, the sheath was oriented at 0.80,
and the core was oriented at 0.6 or less. As the result of tensing
a single fiber, the tensile strength was 1.8 GPa, and the degree of
elongation was 1.0% and much lower than that in Example 1, and
occurrences of fluff was also high.
Comparative Example 9
[0219] Polymer solution for spinning (a) was wet spun at a number
of filaments of 12,000 to obtain fibers through a drying process,
in a manner similar to that in Example 1. The obtained fibers were
served to stabilization at conditions of 300.degree. C. and 5
minutes similar to those in Example 1, using only an infrared
heater (without hot air circulation), and carbonization was carried
out at a carbonization temperature of 1,300.degree. C., but yarn
breakage happened because of unevenness of treatment.
[0220] The polymer solutions for spinning (a) to (e) used in the
above-described respective Examples and Comparative Examples are
shown in Table 1, the conditions and results of Examples 1 to 11
are shown in Table 2, and the conditions and results of Comparative
Examples 1 to 9 are shown in Table 3, respectively.
TABLE-US-00001 TABLE 1 Polymer solution for spinning a b c d e Raw
material acrylonitrile homopolymer part by 11 15 11 10 11
nitrobenzene weight 2 2 1.5 1.5 monoethanol amine 5 2 3 7 Polar
solvent dimethyl sulfoxide 82 85 85 85.5 80.5 Conditions
dissolution or reaction .degree. C. 150 80 150 151 152 for reaction
temperature dissolution or reaction time h 6 6 6 10 7 Properties of
residual rate of nitro compound % 0 0 24 0 0 polymer Mark-Houwink a
0.21 0.5 0.22 0.4 0.07 solution
TABLE-US-00002 TABLE 2 Exam Exam- Exam- Exam- Exam- Exam- Exam-
Exam- Exam- Example Example Unit ple 1 ple 2 ple 3 ple 4 ple 5 ple
6 ple 7 ple 8 ple 9 10 11 Kind of polymer PAN(a) PAN(a) PAN(a)
PAN(a) PAN(a) PAN(a) PAN(a) PAN(a) PAN(d) PAN(e) PAN(a) solution
for spinning Conditions Temperature for .degree. C. 300 320 340 360
300 360 300 360 360 360 360 for burning stabilization Time for min
5 5 5 5 10 10 15 15 15 15 30 stabilization Time for .degree. C.
1300 1300 1300 1300 1300 1300 1300 1300 1300 1300 1300
carbonization TEM Structure 3-layer 3-layer 3-layer 3-layer 3-layer
3-layer 3-layer 3-layer 3-layer 3-layer 3-layer analysis sheath/
sheath/ sheath/ sheath/ sheath/ sheath/ sheath/ sheath/ sheath/
sheath/ sheath/ core core core core core core core core core core
core Crystal Sheath nm 1.6 1.6 1.6 1.6 1.6 1.6 1.6 1.6 1.4 1.5 1.5
size Lc Intermediate layer 1.8 1.8 1.8 1.8 1.8 1.8 1.8 1.8 1.6 1.8
1.8 Core 2.1 2.1 2.1 2.2 2.1 2.1 2.0 2.1 1.8 2.1 2.1 Orientation
Sheath 0.86 0.86 0.86 0.86 0.86 0.86 0.86 0.85 0.82 0.80 0.80
degree f Intermediate layer 0.89 0.89 0.89 0.89 0.89 0.89 0.89 0.88
0.84 0.82 0.82 Core 0.56 0.55 0.55 0.55 0.55 0.55 0.56 0.54 0.54
0.54 0.54 Rate of flat yarn 70% 80% 70% 80% 80% 80% 70% 70% 60% 90%
70% Tensile Strength GPa 2.1 2.1 2.2 2.2 2.2 2.4 2.3 2.4 2.0 1.6
1.7 strength of Degree of % 1.7 1.6 1.5 1.5 1.6 1.6 1.6 1.6 1.3 1.6
1.5 single fiber elongation
TABLE-US-00003 TABLE 3 Com- Com- Com- Com- Com- Com- Com- Com- Com-
parative parative parative parative parative parative parative
parative parative Unit Example 1 Example 2 Example 3 Example 4
Example 5 Example 6 Example 7 Example 8 Example 9 Raw Kind of
PAN(a) PAN(a) PAN(b) PAN(b) PAN(b) PAN(b) PAN(c) PAN(a) PAN(a)
material polymer solution for spinning Conditions Apparatus A A A A
A A A B C for burning Temperature .degree. C. 240 260 240 280 300
360 300 300 300 for stabilization Time for min 15 15 15 15 15 15 15
5 5 stabilization Time for .degree. C. 1300 1300 1300 1300 1300
1300 1300 1300 1300 carbonization TEM Structure F2 F2 F2 hollow F1
F1 2-layer 2-layer F2 analysis sheath/core sheath/core Crystal
Sheath nm -- -- -- 1.8 -- -- 1.7 1.6 -- size Lc Intermediate -- --
-- none -- -- none none -- layer Core -- -- -- none -- -- 1.5 2.2
-- Orientation Sheath -- -- -- 0.86 -- -- 0.86 0.86 -- degree f
Intermediate -- -- -- 0.89 -- -- none none -- layer Core -- -- --
-- -- -- 0.83 0.56 -- Rate of flat yarn -- -- -- 0% -- -- 40% 30%
-- Tensile Strength GPa -- -- -- 1.3 -- -- 1.9 1.8 -- strength of
Degree of % -- -- -- 1.0 -- -- 0.8 1 -- single fiber elongation
Apparatus for burning conditions: A; hot air circulation drier
equipped with infrared heater, B; hot air circulation drier, C;
infrared heater F1: fused or cut by being molten, impossible in
stabilization as fiber bundle, F2: burnt in furnace, impossible in
carbonization
[0221] The PAN-based carbon fiber and the production method
therefor can be applied to production of any PAN-based carbon fiber
required with shortening of time for stabilization and a high
degree of elongation.
* * * * *