U.S. patent application number 12/935539 was filed with the patent office on 2011-02-24 for para-aramid fiber and method of preparing the same.
This patent application is currently assigned to KOLON INDUSTRIES INC. Invention is credited to Jae Young Kim, Jae Young Lee, Tae Hak Park, Sang Young Yeo.
Application Number | 20110045297 12/935539 |
Document ID | / |
Family ID | 41377277 |
Filed Date | 2011-02-24 |
United States Patent
Application |
20110045297 |
Kind Code |
A1 |
Lee; Jae Young ; et
al. |
February 24, 2011 |
PARA-ARAMID FIBER AND METHOD OF PREPARING THE SAME
Abstract
An aramid fiber and a method of producing the same is disclosed,
which is capable of realizing high surface uniformity and improved
tensile strength and elongation property, wherein the method
comprises preparing an aromatic polyamide by polymerizing aromatic
diamine with aromatic diacid halide; preparing a spinning dope by
dissolving the aromatic polyamide in a solvent; and extruding the
spinning dope through a spinneret, and sequentially passing the
spinning dope through an air gap, a coagulation bath filled with a
coagulation solution, and a coagulation tube having a jet opening,
connected with the bottom of the coagulation bath, to obtain a
filament wherein a distance from the upper surface of the
coagulation solution contained in the coagulation bath to the jet
opening of the coagulation tube is within a range between 10 and 35
mm.
Inventors: |
Lee; Jae Young; (Daegu,
KR) ; Kim; Jae Young; (Gumi-si, KR) ; Park;
Tae Hak; (Chilgok-gun, KR) ; Yeo; Sang Young;
(Daegu, KR) |
Correspondence
Address: |
BIRCH STEWART KOLASCH & BIRCH
PO BOX 747
FALLS CHURCH
VA
22040-0747
US
|
Assignee: |
KOLON INDUSTRIES INC,
Kwacheon-si, Kyunggi-do
KR
|
Family ID: |
41377277 |
Appl. No.: |
12/935539 |
Filed: |
March 31, 2009 |
PCT Filed: |
March 31, 2009 |
PCT NO: |
PCT/KR09/01636 |
371 Date: |
October 28, 2010 |
Current U.S.
Class: |
428/400 ;
264/178R |
Current CPC
Class: |
B29C 48/05 20190201;
D10B 2331/021 20130101; D01F 6/605 20130101; B29C 48/919 20190201;
D03D 13/008 20130101; Y10T 428/2978 20150115; D01D 5/06 20130101;
D01D 7/00 20130101 |
Class at
Publication: |
428/400 ;
264/178.R |
International
Class: |
D01F 6/60 20060101
D01F006/60; B29C 47/88 20060101 B29C047/88 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 31, 2008 |
KR |
10-2008-0030077 |
Mar 24, 2009 |
KR |
10-2009-0024846 |
Claims
1. A method of preparing a para-aramid fiber comprising: preparing
an aromatic polyamide by polymerizing aromatic diamine with
aromatic diacid halide; preparing a spinning dope by dissolving the
aromatic polyamide in a solvent; and extruding the spinning dope
through a spinneret, and sequentially passing the spinning dope
through an air gap, a coagulation bath filled with a coagulation
solution, and a coagulation tube having a jet opening, connected
with the bottom of the coagulation bath, to obtain a filament,
wherein a distance from the upper surface of the coagulation
solution contained in the coagulation bath to the jet opening of
the coagulation tube is within a range between 10 and 35 mm.
2. The method of claim 1, wherein a distance from the bottom of the
coagulation bath to the jet opening is within a range between 5 and
20 mm.
3. The method of claim 1, wherein a distance from the upper surface
of the coagulation solution contained in the coagulation bath to
the bottom of the coagulation bath is within a range between 5 to
15 mm.
4. The method of claim 1, wherein the plurality of jet opening are
arranged at different heights so that a coagulation solution from
different positions is jetted to the inside of the coagulation tube
therethrough.
5. The method of claim 1, wherein a ratio of a jetting speed of the
coagulation solution jetted out from the jet opening to a
discharging speed of the filament discharged from the coagulation
tube is within a range of 0.8:1 to 1.2:1.
6. The method of claim 5, wherein the jetting speed of the
coagulation solution jetted out from the jet opening is within a
range between 150 to 800 mpm.
7. The method of claim 1, wherein the coagulation solution
contained in the coagulation bath is a sulfuric acid solution, and
a concentration of the sulfuric acid solution is within a range
between 5 to 15 weight %.
8. The method of claim 1, wherein the coagulation solution
contained in the coagulation bath is a sulfuric acid solution, and
the sulfuric acid solution is maintained at a temperature between 1
to 10.degree. C.
9. A para-aramid fiber formed in such a structure that an amide
group is connected with aromatic rings, and the aromatic rings are
linearly connected through the amide group, wherein a surface
roughness is RMS 0.2 .mu.m or less, and a tensile strength is
within a range between 22 g/d and 26 g/d.
10. The para-aramid fiber of claim 9, wherein the aramid fiber has
an elongation of 2.8 to 3.5%.
11. The para-aramid fiber of claim 9, wherein the aramid fiber has
a 5N or less of maximum resistance on drawing from a fabric,
wherein the fabric is a plain-woven fabric having a weaving density
of 260 g/m.sup.2, and the plain-woven fabric is made of the aramid
fiber having 1500 denier as weft and warp.
Description
TECHNICAL FIELD
[0001] The present invention relates to a para-aramid fiber, and
more particularly, to a para-aramid fiber with high
surface-uniformity and great strength, and a method of preparing
the same.
BACKGROUND ART
[0002] An aramid fiber may be classified into a para-aramid fiber
and a metha-aramid fiber, wherein the para-aramid fiber is made in
such a structure that benzene rings are linearly connected through
an amide group (CONH). At this time, a strength of para-aramid
fiber having a thickness of 5 mm is such as to lift up and maintain
a two-ton car. Thus, the para-aramid fiber is used in various
fields for advanced technology of aerospace industry as well as the
industry for developing a bullet-resistant material.
[0003] A process for making an aromatic polyamide fiber commonly
known as the aramid fiber includes steps of preparing an aromatic
polyamide by polymerizing aromatic diamine with aromatic diacid
chloride in a polymerization solvent containing
N-methyl-2-pyrrolidone(NMP); preparing a spinning dope by
dissolving the aromatic polyamide in a concentrated sulfuric acid
solution; and preparing a filament by spinning the spinning dope
using a spinneret and a coagulation bath.
[0004] This aramid fiber has a skin-core structure wherein the
modulus in a surface layer of the aramid fiber is higher than the
modulus in a core of the aramid fiber. That is, if a stress is
applied to the aramid fiber, the stress is concentrated on the
surface layer of the aramid fiber. Accordingly, a physical property
in the surface layer of the aramid fiber is the most important
component in determining the strength of the aramid fiber.
[0005] However, a related art method of preparing the aramid fiber
can not realize a high strength of the aramid fiber since it is
performed without consideration of the surface layer of the aramid
fiber.
DISCLOSURE OF INVENTION
Technical Problem
[0006] Therefore, the present invention has been made in view of
the above problems, and it is an object of the present invention to
provide an aramid fiber and a method of preparing the same, which
is capable of preventing one or more problems of the related
art.
[0007] The object of the present invention is to provide a
para-aramid fiber with a high strength by enhancing a surface
uniformity of aramid fiber, and a method of preparing the same.
Hereinafter, the aramid fiber indicates the para-aramid fiber.
[0008] Additional advantages, objects, and features of the
invention will be set forth in part in the description which
follows and in part will become apparent to those having ordinary
skill in the art upon examination of the following or may be
learned from practice of the invention. The objectives and other
advantages of the invention may be realized and attained by the
structure particularly pointed out in the written description and
claims hereof as well as the appended drawings.
Technical Solution
[0009] For studying methods of preparing aramid fiber with high
strength, it was found that surface uniformity of the aramid fiber
had an effect on strength of the aramid fiber. That is, the high
surface uniformity of the aramid fiber can improve the strength of
the aramid fiber.
[0010] Also, when studying methods of improving the surface
uniformity of the aramid fiber, it was found that the surface
uniformity of the aramid fiber could be improved by controlling a
spinning process.
[0011] To achieve these objects and other advantages and in
accordance with the purpose of the invention, as embodied and
broadly described herein, a method of preparing an aramid fiber
comprises preparing an aromatic polyamide by polymerizing aromatic
diamine with aromatic diacid halide; preparing an aromatic
polyamide by polymerizing aromatic diamine with aromatic diacid
halide; preparing a spinning dope by dissolving the aromatic
polyamide in a solvent; and extruding the spinning dope through a
spinneret, and sequentially passing the spinning dope through an
air gap, a coagulation bath filled with a coagulation solution, and
a coagulation tube having a jet opening, connected with the bottom
of the coagulation bath, to obtain a filament, wherein a distance
from the upper surface of the coagulation solution contained in the
coagulation bath to the jet opening of the coagulation tube is
within a range between 10 and 35 mm.
[0012] In another aspect of the present invention, there is a
para-aramid fiber formed in such a structure that an amide group is
connected with aromatic rings, and the aromatic rings are linearly
connected through the amide group, wherein a surface roughness is
RMS 0.2 .mu.m or less, and a tensile strength is within a range
between 22 g/d and 26 g/d.
ADVANTAGEOUS EFFECTS
[0013] The aramid fiber according to the present invention and the
method of preparing the same has the following advantages.
[0014] The surface uniformity of the aramid fiber can be improved
owing to the optimized spinning, thereby resulting in the improved
tensile strength and elongation property.
BRIEF DESCRIPTION OF DRAWINGS
[0015] FIG. 1 is a schematic view illustrating a spinning apparatus
according to one embodiment of the present invention.
BEST MODE FOR CARRYING OUT THE INVENTION
[0016] Reference will now be made in detail to the preferred
embodiments of the present invention, examples of which are
illustrated in the accompanying drawings. Wherever possible, the
same reference numbers will be used throughout the drawings to
refer to the same or like parts.
[0017] Hereinafter, aramid fiber according to the present invention
and a method of preparing the same will be described with reference
to the accompanying drawings.
1. PREPARING AROMATIC POLYAMIDE
[0018] First, a polymerization solvent is prepared.
[0019] The polymerization solvent is prepared by adding inorganic
salt to an organic solvent.
[0020] The organic solvent may be an amide-based organic solvent, a
urea-based organic solvent, or their mixture, for example,
N-methyl-2-pyrrolidone(NMP); N, N'-dimethylacetamide(DMAc);
hexamethylphosphoramide(HMPA); N,N, N', N'-tetramethyl urea(TMU);
N,N-dimethylformamide(DMF); or their mixtures.
[0021] The inorganic salt is added so as to enhance a degree of
polymerization of aromatic polyamide. In more detail, the inorganic
salt may be halogenated alkali metal salt or halogenated alkali
earth metal salt, for example, CaCl.sub.2, LiCl, NaCl, KCl, LiBr,
or KBr. This inorganic salt may be added solely, or may be added in
a mixing type of two or more. According as the inorganic salt is
added more, the degree of polymerization of aromatic polyamide is
increased. However, if too much inorganic salt is added,
undissolved inorganic salt may exist therein. Preferably, the
inorganic salt in the entire polymerization solvent is provided at
10 weight % or less.
[0022] Next, a mixture solution is prepared by dissolving aromatic
diamine in the polymerization solvent.
[0023] For example, the aromatic diamine may be
para-phenylenediamine; 4,4'-diaminobiphenyl;
2,6-naphthalenediamine; 1,5-naphthalenediamine; or
4,4'-diaminobenzanilide. However, it is not limited to these.
[0024] Next, a predetermined amount of aromatic diacid halide is
added to the mixture solution while stirring the mixture solution,
thereby resulting in preliminary polymerization.
[0025] The polymerization of the aromatic diamine with the aromatic
diacid halide is rapidly progressed while being accompanied by
heat. In this case, a high polymerization speed may cause a problem
related with a large polymerization difference among the polymers
finally obtained. In more detail, since a polymerization reaction
is not simultaneously progressed in the entire mixture solution,
the early polymerized polymer has long molecular chains by the
rapid polymerization reaction, while the late polymerized polymer
has shorter molecular chains as compared to those of the early
polymerized polymer. Furthermore, the more rapid polymerization
speed causes the larger difference in degree of polymerization
among the finally-obtained polymers. If there is the larger
difference in degree of polymerization among the finally-obtained
polymers, a property deviation becomes large, whereby it is
difficult to realize a desired property.
[0026] Accordingly, the polymerization process follows the
preliminary polymerization process related to preparation of the
polymer having the molecular chain of a predetermined length,
thereby minimizing the difference in degree of polymerization among
the finally-obtained polymers.
[0027] The example of the aromatic diacid halide may be
terephthaloyl dichloride; 4,4'-benzoyl dichloride;
2,6-naphthalenedicarboxyl acid dichloride; or
1,5-naphthalenedicarboxyl acid dichloride. However, it is not
limited to these.
[0028] After completing the preliminary polymerization process, the
remaining aromatic diacid halide is added to the mixture solution
while being stirred at a temperature between 0 and 30.degree. C.
for the polymerization process.
[0029] Since the aromatic diacid halide reacts with the aromatic
diamine at a mole ratio of 1:1, the aromatic diamine and the
aromatic diacid halide are added at the same mole ratio.
[0030] Preferably, the amounts of the aromatic diamine and aromatic
diacid halide are adjusted so that a concentration of the
finally-obtained polymer in the entire polymerized solution is
about 5 to 20 weight % when the polymerization process is
completed. If the concentration of the finally-obtained polymer is
less than 5 weight %, the polymerization speed is lowered and the
polymerization reaction has to be continued for a relatively long
period of time, whereby it lowers an economical efficiency. If the
concentration of the finally-obtained polymer is more than 20
weight %, it is difficult to obtain an intrinsic viscosity of
polymer above 5.5 due to the undesirable polymerization
reaction.
[0031] The detailed example of the aromatic polyamide finally
obtained by the polymerization process may be poly(paraphenylene
terephtalamide: PPD-T); poly(4,4'-benzanilide terephtalamide);
poly(paraphenylene-4,4'-biphenylene-dicarboxyl acid amide); or
poly(paraphenylene-2,6-naphthalenedicarboxyl acid amide).
[0032] Next, an alkali compound is added to the polymerized
solution containing the aromatic polyamide so as to neutralize the
acid produced during the polymerization reaction.
[0033] The acid produced during the polymerization reaction, for
example, hydrochloric acid, may cause a corrosion of a
polymerization apparatus. Thus, an inorganic or organic alkali
compound is added to the polymerized solution during or after the
polymerization reaction, whereby the acid produced by the
polymerization reaction is neutralized.
[0034] Since the aromatic polyamide obtained by the polymerization
reaction exists in shape of crumbs, the polymerized solution
containing aromatic polyamide has poor fluidity. In order to
improve the fluidity, the polymerized solution containing aromatic
polyamide is made as slurry by adding water to the polymerized
solution, and then the following process is performed with the
slurry-type polymerized solution, preferably. For this, water as
well as the alkali compound may be added to the polymerized
solution for the neutralization process.
[0035] The inorganic alkali compound may be selected from groups of
carbonate of alkali metal or alkali earth metal, hydride of alkali
earth metal, hydroxide of alkali earth metal, or oxide of alkali
earth metal, for example, NaOH, Li.sub.2CO.sub.3, CaCO.sub.3, LiH,
CaH.sub.2, LiOH, Ca(OH).sub.2, Li.sub.2O, or CaO.
[0036] Next, the aromatic polyamide, from which the acid is removed
by the neutralization process, is crushed.
[0037] If a grain size of the polymer is too large, it consumes a
long period of time for an extracting process to be described, and
an efficiency of extracting a polymerization solvent is lowered. In
this respect, a crushing process is performed so as to decrease the
grain size of the polymer before the extracting process.
[0038] Next, the polymerization solvent is extracted and removed
from the aromatic polyamide.
[0039] Since the polymerization solvent used for the polymerization
process is contained in the aromatic polyamide obtained by the
polymerization, the polymerization solvent has to be extracted from
the aromatic polyamide, and the extracted polymerization solvent
has be to re-used for the polymerization process.
[0040] The extracting process using water is the most economical
and efficient. The extracting process may be carried out by
sequential steps of installing a filter in a tub with an outlet,
pouring water while positioning the polymer above the filter, and
discharging the polymerization solvent contained in the polymer
together with water through the outlet.
[0041] After the extracting process, a dehydrating process is
performed so as to remove the remaining water. Then, the aromatic
polyamide is completed through a drying process. Thereafter, a
classification process may be performed so as to classify the
aromatic polyamide according to size for a spinning process.
2. PREPARING PARA-ARAMID FIBER
[0042] A spinning dope is prepared by dissolving the aromatic
polyamide prepared by the aforementioned method in a solvent.
[0043] The solvent may use concentrated sulfuric acid having a
concentration of 97 to 100%. Instead of the concentrated sulfuric
acid, chloro-sulfuric acid or fluoro-sulfuric acid may be used.
[0044] Preferably, the concentration of polymer in the spinning
dope is about 10 to 25 weight %, so as to realize a good fiber
property.
[0045] According as the concentration of polyamide polymer is
increased more, a viscosity of spinning dope is also increased.
However, if the concentration of polymer is more than a critical
concentration point, the viscosity of spinning dope is suddenly
decreased. At this time, the spinning dope is changed from an
optically-isotropic state to an optically-anisotropic state without
forming a solid phase. Structural and functional properties of the
optically-anisotropic spinning dope enable production of aramid
fiber having high strength without an additional drawing process.
Preferably, the concentration of the polyamide polymer in the
spinning dope is higher than the critical concentration point.
However, if the concentration of the polyamide polymer is too high,
it may cause a problem of low viscosity in the spinning dope.
[0046] As shown in FIG. 1, after the spinning dope extrudes through
a spinneret 10, the spinning dope sequentially passes through an
air gap 17, a coagulation bath 20, and a coagulation tube 30,
thereby preparing a filament 1.
[0047] The spinneret 10 is provided with a plurality of capillary
tubes 15, wherein each capillary tube 15 has a diameter of 0.1 mm
or less. If the diameter in each capillary tube 15 of the spinneret
10 is more than 0.1 mm, the strength of filament 1 becomes lowered
due to the poor molecular orientation of the prepared filament.
[0048] The air gap 17 may be used of an air layer or inert gas
layer. In order to enhance the property of the prepared filament,
it is preferable that the air gap have a length of 2 to 20 mm.
[0049] The coagulation bath 20 is positioned under the spinneret
10, wherein the coagulation bath 20 is filled with a coagulation
solution 22. Under the coagulation bath 20, there is the
coagulation tube 30. The coagulation tube 30 is connected with the
bottom of the coagulation bath 20.
[0050] Accordingly, as the spinning dope descends after extruding
through the capillary tube 15 of the spinneret 10, the spinning
dope is coagulated by sequentially passing through the air gap 17
and the coagulation solution 22, thereby preparing the filament 1.
This filament 1 is discharged through the coagulation tube 30.
Since the coagulation solution 22 as well as the filament 1 is
discharged through the coagulation tube 30, the coagulation bath 20
has to be continuously supplied with the coagulation solution by
the discharged amount.
[0051] Also, there is a jet opening 35 in the coagulation tube 30
so that the coagulation solution is jetted out from the jet opening
35 to the filament passing through the coagulation tube 30. The jet
opening 35 may include the plurality of jet openings, or be formed
in a ring shape along the periphery of the coagulation tube 30.
Preferably, the plurality of jet openings 35 are arranged in such a
way that the angle of the coagulation solution jetted out from the
jet openings is completely symmetric with respect to the filament.
Preferably, the jetting angle of coagulation solution jetted out
from the jet opening is about 0.degree. to 85.degree. with respect
to the longitudinal direction of the filament. Especially for the
commercial production process, the jetting angle is about
20.degree. to 40.degree..
[0052] Preferably, a distance (L) from the top surface of the
coagulation solution 22 contained in the coagulation bath 20 to the
jet opening 35 of the coagulation tube 30, and more particularly,
to the upper end of the jet opening 35 is within a range between 10
to 35 mm. If the distance (L) is less than 10 mm, the coagulation
solution is jetted to the filament being not sufficiently
coagulated, whereby crystal orientation of the filament may be
damaged. Meanwhile, if the distance (L) is more than 35 mm, the
coagulation solution is jetted to the filament being completely
coagulated, whereby the surface of filament may be damaged. Thus, a
process for jetting the coagulation solution from the jet opening
35 has to be performed under a state the filament is properly
coagulated. In this respect, the distance (L) is within the range
of 10 to 35 mm.
[0053] Preferably, a distance (L.sub.1) from the top surface of the
coagulation solution 22 contained in the coagulation bath 20 to the
bottom of the coagulation bath 20 is within a range between 5 to 15
mm. If the distance (L.sub.1) is less than 5 mm, it is difficult to
control the spinning process due to a vortex of air. Meanwhile, if
the distance (L.sub.1) is more than 15 mm, the filament is too
coagulated in the coagulation bath 20, thereby making it difficult
to set a position of the jet opening 35. That is, if the filament
is too coagulated in the coagulation bath 20, the jet opening 35
has to be positioned adjacent to the upper end of the coagulation
tube 30 so that the coagulation solution is jetted before the
complete coagulation of the filament. However, if the jet opening
35 is positioned too adjacent to the upper end of the coagulation
tube 30, it may cause a problem that the coagulation solution is
jetted under an insufficient convergence of the filament.
[0054] Preferably, a distance (L.sub.2) from the bottom of the
coagulation bath 20 to the jet opening 35, and more particularly,
to the upper end of the jet opening 35 is within a range between 5
to 20 mm. If the distance (L.sub.2) is less than 5 mm, the
coagulation solution is jetted under an insufficient convergence of
the filament, whereby it is difficult to obtain the uniform
coagulation in the filament. Meanwhile, if the distance (L.sub.2)
is more than 20 mm, it may cause a poor pumping for the coagulation
solution 22 contained in the coagulation bath 20. That is, when
jetting out the coagulation solution from the jet opening 35, a
pressure difference is generated between the coagulation bath 20
and the coagulation tube 30, whereby the coagulation solution 22
contained in the coagulation bath 20 is rapidly pumped to the
coagulation tube 30. In this case, if the jet opening 35 is
positioned at a distance far away from the bottom of the
coagulation bath 20, the pumping efficiency for the coagulation
solution 22 is lowered.
[0055] The plurality of jet openings 35 may be provided at
different heights so that the coagulation solution from different
positions is jetted to the inside of the coagulation tube 30
through the plurality of jet openings 35. Thus, a drag force
applied to the filament is distributed so that the surface of
filament becomes uniform and the orientation is improved, thereby
preventing the strength of filament from being lowered. Also, the
surface uniformity in the filament can be improved since it is
possible to prevent the sulfuric acid from being rapidly discharged
from the filament.
[0056] Preferably, a ratio of a jetting speed (V.sub.1) of the
coagulation solution jetted out from the jet opening 35 to a
discharging speed (V.sub.2) of the filament 1 discharged from the
coagulation tube 30 may be within a range of 0.8:1 to 1.2:1. If the
difference between the jetting speed (V.sub.1) of the coagulation
solution jetted out from the jet opening 35 and the discharging
speed (V.sub.2) of the filament 1 discharged from the coagulation
tube 30 becomes larger, the surface of filament 1 may be damaged.
Especially, if the ratio of V.sub.1:V.sub.2 is out of this range,
the surface of filament 1 may be damaged. In consideration of the
discharging speed of the filament 1, the jetting speed of the
coagulation solution jetted out from the jet opening 35 is between
150 to 800 mpm, preferably.
[0057] The coagulation solution 22 may be a sulfuric acid solution,
and more preferably, a solution prepared by adding a sulfuric acid
to water, ethylene glycol, glycerol, alcohol, or their mixtures.
For the process that the spinning dope passes through the
coagulation solution 22, the filament is prepared by removing the
sulfuric acid from the spinning dope. At this time, if the sulfuric
acid is rapidly removed from the surface of filament, the surface
of filament is coagulated before the sulfuric acid comes out of the
filament, whereby the uniformity of filament becomes lowered. In
order to overcome this problem, the coagulation solution 22
contains the sulfuric acid.
[0058] Preferably, a concentration of the sulfuric acid in the
coagulation solution 22 is about 5 to 15 weight %. If the
concentration of the sulfuric acid is less 5 weight %, the sulfuric
acid may be rapidly removed from the filament. Meanwhile, if the
concentration of the sulfuric acid is more than 15 weight %, it is
difficult that the sulfuric acid comes out from the filament.
[0059] Preferably, a temperature of the coagulation solution 22 is
within a range between 1 and 10.degree. C. If the temperature of
the coagulation solution 22 is below than 1.degree. C., it is
difficult that the sulfuric acid comes out from the filament.
Meanwhile, if the temperature of the coagulation solution 22 is
above than 10.degree. C., the sulfuric acid rapidly comes out from
the filament.
[0060] Then, the remaining sulfuric acid is removed from the
obtained filament.
[0061] The sulfuric acid remains in the filament prepared by the
spinning process. The sulfuric acid remaining in the filament may
be removed by a wet process using water or a mixture of water and
alkali solution.
[0062] The wet process may include steps, for example, a first step
for wetting the filament containing the sulfuric acid in an aqueous
caustic solution of 0.3 to 1.3%, and a second step for wetting the
filament in an aqueous caustic solution of 0.01 to 0.1%.
[0063] Then, a drying process is carried out so as to adjust the
amount of water contained in the filament.
[0064] The amount of water contained in the filament can be
adjustable by controlling a contacting time between the filament
and a drying roll, or a temperature in the drying roll.
[0065] For the aforementioned spinning, wetting, neutralizing and
drying processes, a tension is applied to the filament, wherein an
optimized value of the tension applied to the filament for the
drying process is determined based on the entire processing
conditions. However, it is preferable that the filament be dried
under the tension of about 0.1 to 3.0 gpd. If the tension for the
drying process is less than 0.1 gpd, the strength of filament is
lowered due to the decreased molecular orientation. Meanwhile, if
the tension for the drying process is more than 3.0 gpd, the
filament may be broken. At this time, a degree of the tension
applied to the filament can be controlled by adjusting a surface
speed of the roll which moves the filament.
[0066] The drying roll is heated by a predetermined means. At this
time, the drying roll is at least partially covered with a
heat-emission preventing means so as to prevent a heat loss,
preferably.
[0067] The para-aramid fiber prepared by the aforementioned process
according to the present invention is formed in such a structure
that an amide group is connected with aromatic rings, the aromatic
rings are linearly connected through the amide group, and the
surface roughness is the same as or less than RMS 0.2 .mu.m.
[0068] The small surface roughness indicates that the surface
uniformity is great. The aramid fiber according to the present
invention, which has the great surface uniformity, can obtain the
great tensile strength of 22 g/d to 26 g/d.
[0069] Also, the aramid fiber according to the present invention
has an elongation of 2.8 to 3.5%. If the surface of fiber is not
uniform, the fiber is apt to be broken by elongation. Since the
aramid fiber of the present invention has the great surface
uniformity, it is not easily broken by elongation, thereby
resulting in the high elongation range.
[0070] Also, the aramid fiber of the present invention has a 5N or
less of maximum resistance on drawing from a fabric, wherein the
fabric is a plain-woven fabric having a weaving density of 260
g/m.sup.2, and the plain-woven fabric is made of the aramid fiber
having 1500 denier as weft and warp.
[0071] Herein, the maximum resistance on drawing from a fabric
indicates a maximum resistance when drawing one strand of the fiber
from the fabric obtained by weaving the fiber. If the fiber has the
uniform surface, it is easy to draw the fiber from the fabric, so
that the resistance becomes small. That is, the small resistance on
drawing means that the fiber has the great surface uniformity.
3. EMBODIMENTS AND COMPARATIVE EXAMPLES
1) Embodiment 1
[0072] After preparing a polymerization solvent by adding
CaCl.sub.2 to N-methyl-2-pyrrolidone(NMP), para-phenylenediamine is
dissolved in the prepared polymerization solvent, to thereby
prepare a mixture solution.
[0073] While stirring the mixture solution, terephthaloyl
dichloride is added to the mixture solution, wherein a mole ratio
of the terephthaloyl dichloride is identical to that of the
para-phenylenediamine, thereby preparing poly(paraphenylene
terephtalamide). Here, a predetermined amount of the terephthaloyl
dichloride is first added to the mixture solution for the
preliminary polymerization, and then the remaining terephthaloyl
dichloride is added to the mixture solution. Then, water and NaOH
are added to a polymerized solution containing poly(paraphenylene
terephtalamide) so that acid is neutralized. After crushing
poly(paraphenylene terephtalamide), the polymerization solvent is
extracted from poly(paraphenylene terephtalamide) by using water,
and then dehydrating and drying processes are performed thereto,
thereby obtaining a final aromatic polyamide.
[0074] The final aromatic polyamide is dissolved in concentrated
sulfuric acid of 99%, thereby preparing a spinning dope. At this
time, a concentration of the aromatic polyamide in the spinning
dope is about 20 weight %. After that, the spinning dope is spun
through the use of a spinning apparatus shown in FIG. 1. That is,
after extruding the spinning dope through a spinneret 10, the
spinning dope is coagulated by passing through an air gap 17 having
a diameter of 7 mm, a coagulation bath 20 filled with a coagulation
solution 22 made of a sulfuric acid solution having a concentration
of 10 weight % at a temperature of 5.degree. C., and a coagulation
tube 30 positioned under the coagulation bath 20 sequentially,
thereby preparing a filament.
[0075] At this time, a distance (L) from the top surface of the
coagulation solution 22 contained in the coagulation bath 20 to a
jet opening 35 of the coagulation tube 30 is 20 mm; a distance
(L.sub.1) from the top surface of the coagulation solution 22 to
the bottom of the coagulation bath 20 is 10 mm; and a distance
(L.sub.2) from the bottom of the coagulation bath 20 to the jet
opening 35 is 10 mm.
[0076] Also, a jetting speed (V.sub.1) of the coagulation solution
jetted out from the jet opening 35 is set equal to a discharging
speed (V.sub.2) of the filament 1 discharged from the coagulation
tube 30. That is, each of the jetting speed (V.sub.1) and the
discharging speed (V.sub.2) is set as 600 mpm.
[0077] After that, the remaining sulfuric acid is removed from the
filament by a wet process. Then, aramid fiber having 1500 denier is
obtained by drying and winding the filament.
2) Embodiment 2
[0078] Aramid fiber is obtained by the same method as that of the
aforementioned embodiment 1 except that a distance from a distance
(L) from a top surface of a coagulation solution 22 contained in a
coagulation bath 20 to a jet opening 35 of a coagulation tube 30 is
10 mm; a distance (L.sub.1) from the top surface of the coagulation
solution 22 to the bottom of the coagulation bath 20 is 5 mm; and a
distance (L.sub.2) from the bottom of the coagulation bath 20 to
the jet opening 35 is 5 mm.
3) Embodiment 3
[0079] Aramid fiber is obtained by the same method as that of the
aforementioned embodiment 1 except that a distance from a distance
(L) from a top surface of a coagulation solution 22 contained in a
coagulation bath 20 to a jet opening 35 of a coagulation tube 30 is
35 mm; a distance (L.sub.1) from the top surface of the coagulation
solution 22 to the bottom of the coagulation bath 20 is 15 mm; and
a distance (L.sub.2) from the bottom of the coagulation bath 20 to
the jet opening 35 is 20 mm.
4) Embodiment 4
[0080] Aramid fiber is obtained by the same method as that of the
aforementioned embodiment 1 except that a jetting speed (V.sub.1)
of a coagulation solution jetted out from a jet opening 35 is 700
mpm, and a discharging speed (V.sub.2) of a filament 1 discharged
from a coagulation tube 30 is 600 mpm.
5) Embodiment 5
[0081] Aramid fiber is obtained by the same method as that of the
aforementioned embodiment 1 except that a jetting speed (V.sub.1)
of a coagulation solution jetted out from a jet opening 35 is 500
mpm, and a discharging speed (V.sub.2) of a filament 1 discharged
from a coagulation tube 30 is 600 mpm.
6) Comparative Example 1
[0082] Aramid fiber is obtained by the same method as that of the
aforementioned embodiment 1 except that a distance from a distance
(L) from a top surface of a coagulation solution 22 contained in a
coagulation bath 20 to a jet opening 35 of a coagulation tube 30 is
8 mm; a distance (L.sub.1) from the top surface of the coagulation
solution 22 to the bottom of the coagulation bath 20 is 5 mm; and a
distance (L.sub.2) from the bottom of the coagulation bath 20 to
the jet opening 35 is 3 mm.
7) Comparative Example 2
[0083] Aramid fiber is obtained by the same method as that of the
aforementioned embodiment 1 except that a distance (L) from a top
surface of a coagulation solution 22 contained in a coagulation
bath 20 to a jet opening 35 of a coagulation tube 30 is 40 mm; a
distance (L.sub.1) from the top surface of the coagulation solution
22 to the bottom of the coagulation bath 20 is 15 mm; and a
distance (L.sub.2) from the bottom of the coagulation bath 20 to
the jet opening 35 is 25 mm.
8) Comparative Example 3
[0084] Aramid fiber is obtained by the same method as that of the
aforementioned comparative example 2 except that a jetting speed
(V.sub.1) of a coagulation solution jetted out from a jet opening
35 is 400 mpm, and a discharging speed (V.sub.2) of a filament 1
discharged from a coagulation tube 30 is 600 mpm.
9) Comparative Example 4
[0085] Aramid fiber is obtained by the same method as that of the
aforementioned comparative example 2 except that a jetting speed
(V.sub.1) of a coagulation solution jetted out from a jet opening
35 is 750 mpm, and a discharging speed (V.sub.2) of a filament 1
discharged from a coagulation tube 30 is 600 mpm.
10) Comparative Example 5
[0086] Aramid fiber is obtained by the same method as that of the
aforementioned comparative example 1 except that a coagulation
solution 20 contained in a coagulation bath 20, wherein the
coagulation solution 20 is maintained at a temperature of 0.degree.
C.
11) Comparative Example 6
[0087] Aramid fiber is obtained by the same method as that of the
aforementioned comparative example 1 except that a coagulation
solution 20 contained in a coagulation bath 20, wherein the
coagulation solution 20 is maintained at a temperature of
15.degree. C.
12) Comparative Example 7
[0088] Aramid fiber is obtained by the same method as that of the
aforementioned comparative example 1 except that a coagulation
solution 20 contained in a coagulation bath 20, wherein the
coagulation solution 20 is made of a sulfuric acid solution having
a concentration of 3 weight %.
13) Comparative Example 8
[0089] Aramid fiber is obtained by the same method as that of the
aforementioned comparative example 1 except that a coagulation
solution 20 contained in a coagulation bath 20, wherein the
coagulation solution 20 is made of a sulfuric acid solution having
a concentration of 20 weight %.
[0090] The aforementioned embodiments and comparative examples can
be summarized as the following Table 1.
TABLE-US-00001 TABLE 1 Temperature of Concentration L L.sub.1
L.sub.2 V.sub.1 V.sub.2 coagulation of coagulation (mm) (mm) (mm)
(mpm) (mpm) V.sub.1:V.sub.2 solution (.degree. C.) solution (weight
%) Embodiment 1 20 10 10 600 600 1:1 5 10 Embodiment 2 10 5 5 600
600 1:1 5 10 Embodiment 3 35 15 20 600 600 1:1 5 10 Embodiment 4 20
10 10 700 600 1.17:1 5 10 Embodiment 5 20 10 10 500 600 0.83:1 5 10
Comparative 8 5 3 600 600 1:1 5 10 example 1 Comparative 40 15 25
600 600 1:1 5 10 example 2 Comparative 40 15 25 400 600 0.67:1 5 10
example 3 Comparative 40 15 25 750 600 1.25:1 5 10 example 4
Comparative 8 5 3 600 600 1:1 0 10 example 5 Comparative 8 5 3 600
600 1:1 15 10 example 6 Comparative 8 5 3 600 600 1:1 5 3 example 7
Comparative 8 5 3 600 600 1:1 5 20 example 8
[0091] In this Table 1, L indicates the distance from the upper
surface of the coagulation solution 22 contained in the coagulation
bath 20 to the jet opening 35; L.sub.1 indicates the distance from
the upper surface of the coagulation solution 22 contained in the
coagulation bath 20 to the bottom of the coagulation bath 20;
L.sub.2 indicates the distance from the bottom of the coagulation
bath 20 to the jet opening 35; V.sub.1 indicates the jetting speed
of the coagulation solution jetted out from the jet opening 35; and
V.sub.2 indicates the discharging speed of the filament 1
discharged from the coagulation tube 30.
4. EXPERIMENTAL EXAMPLES
1) Measuring Surface Roughness of Aramid Fiber
[0092] Samples are prepared by cutting aramid fibers of the
respective embodiments and comparative examples, wherein each
aramid fiber has a length of 25 cm. Then, a surface roughness for
each sample is measured by AFM (Atomic Force Microscopy)
corresponding to a surface-roughness measuring apparatus.
[0093] In more detail, after stably fixing each sample in a
V-shaped groove of a substrate, the surface roughness for each
sample is measured by Nanoscope III a Multimode made by Digital
Instruments in England. The results will be shown in the following
Table 2.
2) Measuring Tensile Strength of Aramid Fiber
[0094] Samples are prepared by cutting aramid fibers of the
respective embodiments and comparative examples, wherein each
aramid fiber has a length of 25 cm. Then, a tensile strength for
each sample is measured by an experimental method of ASTM
D-885.
[0095] In more detail, a force(g) is measured when each sample is
broken at a stretching speed 300 mm/minute by using Instron tester
(Instron Engineering Corp, Canton, Mass). Then, the measured force
is divided by a denier of the sample, thereby measuring a tensile
strength (g/d). The results will be shown in the following Table
2.
3) Measuring Elongation of Aramid Fiber
[0096] Samples are prepared by cutting aramid fibers of the
respective embodiments and comparative examples, wherein each
aramid fiber has a length of 25 cm. Then, an elongation for each
sample is measured.
[0097] In more detail, an elongated length is measured when each
sample is broken at a stretching speed 300 mm/minute by using
Instron tester (Instron Engineering Corp, Canton, Mass), and then
an elongation(%) is calculated. The results will be shown in the
following Table 2.
4) Measuring Maximum Resistance on Drawing Aramid Fiber from a
Fabric
[0098] Samples are prepared by plainly weaving a fabric with a size
of 80 mm.times.80 mm, wherein the fabric is made with the weft and
warp using aramid fibers according to the respective embodiments
and comparative examples. At this time, the fabric is made with a
weaving density of 260 g/m.sup.2. Then, a maximum resistance on
drawing aramid fiber for each sample is measured when drawing one
strand of aramid fiber from the fabric.
[0099] In more detail, a maximum force (N) is measured when drawing
one strand of aramid fiber from each sample at a stretching speed
300 mm/minute by using Instron tester (Instron Engineering Corp,
Canton, Mass). The results will be shown in the following Table
2.
TABLE-US-00002 TABLE 2 Surface Tensile Maximum resistance Roughness
Strength Elonga- on drawing from a (.mu.m) (g/d) tion (%) fabric
(N) Embodiment 1 0.10 25.5 3.45 3.9 Embodiment 2 0.18 22.9 3.15 4.9
Embodiment 3 0.11 25.2 3.43 4.1 Embodiment 4 0.13 24.1 3.27 4.3
Embodiment 5 0.15 23.5 3.24 4.6 Comparative 0.25 21.5 2.75 5.2
example 1 Comparative 0.21 21.7 2.79 5.1 example 2 Comparative 0.28
21.2 2.71 5.5 example 3 Comparative 0.27 21.3 2.73 5.3 example 4
Comparative 0.27 21.4 2.72 5.4 example 5 Comparative 0.32 21.0 2.70
5.7 example 6 Comparative 0.35 20.5 2.64 5.9 example 7 Comparative
0.40 20.0 2.60 6.2 example 8
[0100] It will be apparent to those skilled in the art that various
modifications and variations can be made in the present invention
without departing from the spirit or scope of the inventions. Thus,
it is intended that the present invention covers the modifications
and variations of this invention provided they come within the
scope of the appended claims and their equivalents.
* * * * *