Note: Descriptions are shown in the official language in which they were submitted.
CA 02511030 2003-08-28
LYOCELL MULTI-FILAMENT FOR TIRE CORD AND METHOD OF
PRODUCING THE SAME
FIELD OF THE INVENTION
This application is a division of Canadian Application
Serial No. 2,438,445, filed August 28, 2003. The claims of
the present application are directed to a lyocell multi-
filament, a tire cord, a dip cord, and an automobile tire.
However, for the purpose of a comprehensive understanding
of the invention, including all objects and features which
are inextricably bound-up in one and the same inventive
concept, the teachings of those features claimed in the
parent Canadian Application Serial No. 2,438,445 are
retained herein.
Accordingly, the retention of any such objects or
features which may be more particularly related to the
parent application or a separate divisional thereof should
not be regarded as rendering the teachings and claiming
ambiguous or inconsistent with the subject matter defined
in the claims of the divisional application presented
herein when seeking to interpret the scope thereof and the
basis in this disclosure for the claims recited herein.
The present invention pertains to a lyocell multi-
filament for a tire cord, a method of producing the same,
the tire cord and a tire for an automobile using the same.
More particularly, the present invention relates to a
lyocell multi-filament for a tire cord, which has excellent
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physical properties for the tire cord, thereby providing a
tire with improved driving stability, dimensional
stability, and uniformity for an automobile, a method of
producing the same, the tire cord and a tire for an
automobile using the same.
BACKGROUND OF THE INVENTION
As is well known to those skilled in the art, a
material of a tire cord used as a framework constituting
a tire is selected from the group consisting of polyester,
nylon, aramid, rayon, and steel. In this regard, it is
required that the material of the tire cord has the
following excellent physical properties: 1) high strength
and initial modulus, 2) excellent heat resistance, and no
degradation under dry and wet heat, 3) excellent fatigue
resistance, 4) excellent dimensional stability, and 5)
excellent adhesiveness to rubbers (refer to Fukuhara, Fiber
& Industry, 1980, Vol. 36, pp 290). However, the above
materials cannot have all the above excellent physical
properties as described above, so the material of the tire
cord depends on the intended use of the tire cord.
For example, a radial tire, requiring excellent
initial modulus (elasticity), heat resistance, and
dimensional stability, for high-speed driving of an
automobile comprises a tire cord mostly consisting of a
rayon fiber with low shrinkage and excellent dimensional
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stability. At this time, the initial modulus is usually
expressed as load per unit stretch for a certain fiber
denier, in other words, as a slope of an elongation-load
curve in a strength and elongation test. The higher the
initial modulus of the tire cord is, the less the tire will
be deformed, so the high initial modulus contributes to
improving fatigue resistance, heat resistance, and
durability of the tire. Particularly, the high initial
modulus improves transverse-strength of the radial tire,
thus excellent driving stability of the radial tire is
secured. Additionally, the rayon tire cord has excellent
driving stability in comparison with various tire cords
consisting of other materials because its physical
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properties are rarely degraded at a temperature of 80 to
100°C during driving of the automobile.
However, the rayon tire cord has relatively low
tenacity and its modulus is greatly degraded by moisture, so
it is difficult to control moisture and quality of the tire
during the production of the tire including the rayon tire
cord. Additionally, even if the tire including the rayon
tire cord is manufactured, when a surface of the tire is
damaged and moisture penetrates into the damaged tire,
strength and modulus of the tire are reduced, thus being
poor in terms of its performance. Accordingly, there is a
need to develop a tire cord having excellent strength and
modulus against moisture, in addition to having excellent
tenacity.
Meanwhile, an artificial lyocell fiber consisting of
cellulose is advantageous in that elongation is low and
tenacity is high, so its dimensional stability is excellent,
and its strength preservation proportion is 80 % or higher
when the lyocell fiber absorbs water because of its low
moisture regain. Accordingly, in comparison with rayon
(60 %), the lyocell fiber is competitive in terms of low
reduction of modulus and low deformation. However, the
lyocell fiber has not been used as the tire cord because of
the spinning related problems.
A commercial value of fibers used in the tire cord or
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other industrial materials depends on their physical
properties such as tenacity and modulus while the commercial
value of fibers for clothes depends on dyeability for vivid
or bright colors and ease of care.
Accordingly, each textile maker continuously improves
each textile's qualities using various fiber production
technologies according to use of the fibers. Various
technologies have been developed to improve physical
properties of the fibers. For example, when molecular
chains constituting a polymer are desirably oriented along a
fiber axis, the fibers have excellent physical properties
useful to be applied to clothes and various industrial
fields. In this regard, orientation is conducted during the
drafting process, so the drafting process is one of the most
important processes capable of improving physical properties
of the fibers.
Furthermore, the drafting process is conducted under a
thermoplastic state in which fluidity of molecules is good
according to a melt-spinning process. Additionally,
according to a solution-spinning process, after a solution
including three components, that is, a solvent, a non-
solvent, and a polymer is prepared, the solution is spun
using a wet spinning or dry spinning method. The drafting
process is conducted while vaporizing the solvent in the
case of the dry spinning method, but in the case of the wet
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spinning methods, drafting of the fibers is conducted
during the coagulation process, depending on the
concentration and temperature of a coagulation liquid.
Further, in the case of producing the lyocell fiber,
when a solution including NMMO (n-methyl morpholine N
oxide), water, and cellulose at a relatively high
temperature ranging from 80 to 130°C is spun in such a way
that a spinning nozzle is dipped in a coagulation bath
according to the traditional wet spinning method, the
solution is too quickly coagulated to secure desirable
physical properties. Additionally, it is difficult to
sufficiently vaporize the solvent from a high viscous
cellulose solution of about 10,000 poises using only the
dry spinning method.
Meanwhile, a dry-wet method may be used to improve
physical properties of the fibers and spinning efficiency
by properly utilizing air gaps positioned between the
spinning nozzle and the coagulation bath.
For example, EP. Pat. A-259, 672 discloses a process of
producing an aramid fiber, in which the drafting and
coagulation processes are conducted using air gaps to
improve physical properties of the aramid fiber, and U.S.
Pat. No. 4, 501, 886 suggests a process of spinning cellulose
triacetate using air gaps. Additionally, Japanese Pat. No.
81,723 by Mitsubishi Rayon Co. describes a high-speed
spinning process of a PAN (polyacrylonitrile fiber) using
air gaps, East German Pat. No. 218,124 discloses a process
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of spinning a cellulose solution using a tertiary
aminoxide-based aqueous solution, in which air gaps are
used to prevent a plurality of filaments from adhering to
each other, and U.S. Pat. No. 4,261,943 discloses a process
of spraying water acting as a non-solvent to air gaps each
having a space of 50 to 300 mm to prevent a plurality of
filaments from adhering to each other.
The processes as described above contribute to
improving orientation of the fibers using the air gaps.
However, they are not useful to be directly applied to the
production of a lyocell multi-filament, because filaments
are apt to adhere to each other because of a great number
of filaments, so desired spinning efficiency is not
obtained. As well, the lyocell fiber produced by the above
processes has inadequate tenacity and elongation for use as
a tire cord.
Further, H. Chanzy et al. (Polymer, 1990 Vol. 31, pp
400-.405) propose a process of producing a fiber using air
gaps, in which salts such as ammonium chloride or calcium
chloride are added to a solution of cellulose with a degree
of polymerization (DPw) of 5000 in NMMO and the resulting
mixture is then spun to produce a fiber with tenacity of
56.7 cN/tex and elongation at break of 4%. However, it is
difficult to commercialize this process because of various
disadvantages, for example the recovery of the coagulation
solution containing salts.
Further, U.S. Pat. No. 5,942,327 describes a process
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of producing a fiber with tenacity of 50 to 80 cN/tex,
elongation of 6 to 25%, and monofilament fineness of 1.5
dtex using air gaps, in which a solution of cellulose with
the degree of polymerization (DPw) of 1360 in NMMO hydrate
is spun. At this time, the number of filaments of the
resulting fiber is just 50 filaments. In general, the
filament for a tire cord must have fineness of about 1000
deniers, so hundreds of plies of filaments are needed to
secure fineness of about 1000 deniers. Accordingly, the
product disclosed in this patent is disadvantageous in that
it is difficult to secure the tire cord with desired
physical properties after twisting or dipping.
Practically, it is difficult to control spinning conditions
of quenching in the air-gap, washing, and drying of the
fiber during spinning of the fiber with large denier in
comparison with the spinning process of the fiber with
small denier, so rarely securing desired physical
properties of the fiber and scarcely maintaining uniformity
of the filaments. Accordingly, it is nearly impossible to
produce the industrial fiber referring to physical
properties of the fiber with 50 filaments. Furthermore, a
process of spinning the solution to the air gaps requires
a new design accompanying with additional considerations,
such as an outer diameter of the spinning nozzle, a
diameter of an orifice, intervals between orifices, a
length of each of the air gaps, feeding conditions of
cooling air, and a drying condition of the filaments
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depending on a feeding direction of the coagulation liquid
and a spinning speed, because adherence of the filaments to
each other and quenching ef f iciency are varied according to
an increase of the number of the filaments. In this
regard, physical properties of the fiber depend on the
design.
Moreover, U.S. Pat. No. 5,252,284 discloses a process
of spinning a fiber under conditions of air gaps each
having a length within about 10 mm and a winding speed of
45 m/min to produce the fiber consisting of 800 to 1900
filaments. However, the product disclosed in this patent
is disadvantageous in that elongation is a relatively high
15.4% and tenacity is at most 47.8 cN/tex, thus securing
insufficient competitiveness of the fiber for use as a tire
cord in terms of tenacity and productivity.
Additionally, some methods of producing a mixture
solution of cellulose and polymer using NMMO are known in
the art.
For example, U.S. Pat. No. 3,447,939 discloses a
process of producing a solution containing cellulose and
polyvinyl alcohol dissolved in NMMO, and U.S. Pat. No.
3,508,941 proposes a method of dissolving a mixture of
cellulose and polyvinyl alcohol in NMMO to extract the
mixture. Further, according to U.S. Pat. No. 4,255,300,
when a mixing ratio of cellulose and polyvinyl alcohol is
4:1 to 2:1 and a percent composition ratio of a polymer to
a solvent is 20°s or lower, a fiber has excellent
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elongation. However, U.S. Pat. No. 4,255,300 does not
disclose the fact that the tenacity of the fiber is
improved because polyvinyl alcohol is added to cellulose.
Meanwhile, U.S. Pat. No. 6,245,837 discloses aprocess
of producing a fiber with a tenacity of 27 cN/tex, in which
a mixture including cellulose, polyethylene, polyethylene
glycol,polymethylmethacrylate, and polyacrylamide is
dissolved in a NMMO solution. However, this patent is
disadvantageous in that the fiber has very poor tenacity to
be used as an industrial filament or a tire cord.
Therefore, there remains a need to develop a cellulose
solution for a high strength cellulose filament.
The present inventors have made an effort to develop
the cellulose solution for a high strength cellulose
filament, and found that a cellulose/polyvinyl alcohol/NMMO
solution suppresses the generation of fibril while a
cellulose fiber is formed and the cellulose fiber having
excellent flexibility and tenacity can be produced using
the cellulose/polyvinyl alcohol/NMMO solution, thus the
cellulose/polyvinyl alcohol/NMMO solution is usefully
applied to an industrial filament or tire cord.
Furthermore, the present inventors have conducted
extensive studies into the method of producing a lyocell
filament useful as a tire cord, resulting in the finding
that lyocell multi-filaments for tire cords with excellent
physical properties can be obtained by providing a method
of producing the lyocell multi-filament, comprising the
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steps of dissolving mixed powder of cellulose and polyvinyl
alcohol in a mixed solvent of N-methyl morpholine N-oxide
and water to prepare a dope, extruding the dope using a
spinning nozzle orifices through air gaps into a conical
upper solidifying bath to solidify the dope to produce a
multi-filament, feeding the multi-filament through a
lower coagulation bath to a washing bath, washing the
mufti-filament, drying and oiling the mufti-filament, and
winding the resulting mufti-filament, thereby accomplishing
the present invention.
SUMMARY OF THE INVENTION
Therefore, the present invention has been made keeping
in mind the above disadvantages occurring in the prior art ,
and an object of the present invention is to provide a
method of producing a lyocell filament for a tire cord in
high yield, wherein the filament has excellent tenacity and
modulus, thereby facilitating a production of a tire with
improved driving stability, dimensional stability, and
uniformity for an automobile.
According to one aspect of the present invention,
there is provided a method of producing a lyocell multi-
filament for a tire cord, comprising i) dissolving mixed
powder of cellulose and polyvinyl alcohol in a mixed
solvent of N-methyl morpholine N-oxide and water to prepare
a dope; ii) extruding the dope using a spinning nozzle
including orifices through air gaps into a conical upper
CA 02511030 2003-08-28
coagulation bath to coagulate the dope at an effective spinning
speed to produce a multi-filament, said orifices each having a
diameter (D) of 100 to 300 um, a length (L) of 200 to 2400 um,
and a ratio of the length to the diameter (L/D) of 2 to 8, and
being spaced apart from each other at intervals of 2.0 to 5.0
mm; iii) feeding the multi-filament through a lower coagulation
bath to a washing bath, and washing the multi-filament; and iv)
drying and oiling the multi-filament and winding the resulting
multi-filament.
According to another aspect of the present invention,
there is provided a lyocell multi-filament having tenacity of
5 to 10 g/d, elongation of 3 to 13%, modulus of 200 to 400 g/d,
birefringence of 0.038 to 0.050, crystallinity of 40 to 52%,
shrinkage of -0.5 to 3%, strength maintenance after a high
temperature and saturated vapor treatment of 90% or higher, and
fineness of 1000 to 2500 deniers.
The lyocell multi-filament of the present invention
preferably has an elongation of 0.5 to 4.0% at a load of 4.5
kg.
According to yet another aspect of the present invention,
there is provided a tire cord comprising the lyocell multi-
filament of the present invention.
Furthermore, the present invention also provides.a dip
cord for tire cords, produced using the tire cord described
above.
The dip cord of the present invention preferably has
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a fineness of 3000 to 6000 deniers, twist constant of 0.67
to 0.85, and a load at break of 14.0 to 28.0 kg.
As another aspect of the present invention, there is
provided a tire for automobiles, comprising the lyocell
multi-filament described above, as well as a tire
comprising the dip cord described herein.
BRIEF DESCRIPTION OF THE DRAWINGS
The above and other objects, features and other
advantages of the present invention will be more clearly
understood from the following detailed description taken in
conjunction with the accompanying drawings, in which:
FIG. 1 schematically illustrates the spinning process
according to the present invention.
DETAILED DESCRIPTION OF THE INVENTION
Based on the present invention, the above object can
be accomplished by providing a method of producing a
lyocell multi-filament for a tire cord, comprising i)
dissolving mixed powder of cellulose and polyvinyl alcohol
in a mixed solvent of N-methyl morpholine N-oxide (NMMO)
and water to prepare a dope, ii) extruding the
dope using a spinning nozzle including orifices through
air gaps into a conical upper coagulation bath to coagulate
the dope to produce a multi-filament, iii) feeding the
multi-filament into a lower coagulation bath, changing
moving course of the multi-filament to a washing bath, and
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washing the multi-filament, and iv) drying and oiling the
multi-filament and winding the resulting multi-filament.
At this time, the orifices each have a diameter (D) of 100
to 300 um, a length (L) of 200 to 2400 um, and a ratio of
the length to the diameter (L/D) of 2 to 8, and are spaced
apart from each other at intervals of 2.0 to 5.0 mm.
Additionally, the present invention provides a lyocell
multi-filament having fineness of 1000 to 2500 deniers and
load at break of 5.0 to 25.0 kg. The lyocell multi
filament consists of 500 to 1500 filaments
each having fineness of 0.5 to 4.0 deniers.
Furthermore, the present invention provides a tire
cord for an automobile and a tire for an automobile using
the lyocell multi-filament.
In the i) step of the method of producing the lyocell
multi-filament according to the present invention, mixed
powder of cellulose and PVA (polyvinyl alcohol) is
dissolved in a mixed solvent of NMMO (N-methyl morpholine
N-oxide) and water to prepare a dope.
Further, a pulp with a highly pure cellulose is used
so as to produce a lyocell multi-filament for a tire cord
according to the present invention. Because lignin has an
amorphous structure and hemicellulose has a poor
crystalline structure, it is preferable to use the pulp
containing a high a-cellulose content and a minimum amount
of lignin and
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hemicellulose so as to produce a high quality cellulose-
based fiber. Additionally, the cellulose-based fiber is
highly oriented and crystallized using cellulose molecules
with the high degree of polymerization, thereby securing
excellent physical properties. In this regard, it is
preferable to use a soft wood pulp with a degree of
polymerization (DPW) of 800 to 1200 containing 93 ~ or
higher a-cellulose content.
PVA is added to cellulose during the preparation of
the dope so as to produce the desirable lyocell multi
filament for the tire cord according to the present
invention, thereby improving fibril resistance, flexibility,
and tenacity of the lyocell multi-filament. At this time,
PVA functions to reduce viscosity of a cellulose solution to
increase fluidity of the cellulose solution to improve
homogeneity of the solution. Additionally, the homogeneous
cellulose solution contributes to improving spinning
efficiency thereof and producing the lyocell multi-filament
with excellent physical properties.
Furthermore, useful as a solvent needed during
preparing the dope is the mixed solvent of NMMO and water in
the present invention, and NMMO1H20 containing 10 to 20 wt~
water, and preferably 13 wt~ water is used as NMMO.
Meanwhile, it is necessary to prepare the highly
homogeneous and highly concentrated dope while increasing
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the penetration of the solvent into the mixed powder of
cellulose and PVA so as to produce the fiber with excellent
physical properties. For this reason, it is needed to
secure a device capable of providing high shear stress to
the solution and to maintain a temperature of the solution
at 80 to 130°C. For example, when the temperature is higher
than 130 ~, a molecular weight of cellulose is reduced due
to the thermal decomposition of cellulose, thus undesirably
increasing end groups of molecular chains of cellulose to
reduce its physical properties and cause the decomposition
of NI~tO. On the other hand, when the temperature is lower
than 80°C, time and energy consumed to sufficiently dissolve
cellulose in the solvent are increased and there is a
disadvantage such that a low concentration of cellulose
solution must be prepared.
Moreover, it is necessary to uniformly mix cellulose
and PVA with liquid NMMO before cellulose is dissolved in
the mixed solution of NMMO and water to sufficiently
penetrate liquid NI~tO into cellulose powder to swell the
mixture of cellulose and PVA so as to produce the
homogeneous dope without undissolved cellulose particles.
Accordingly, in order to prepare the highly
homogeneous cellulose solution, cellulose powder mixed with
PVA and the concentrated NMMO liquid are put into a kneader
at the same time and all of them are mixed with each other
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in the kneader. The resulting mixture is repeatedly
dispersed, sheared, compressed, drawn, and folded in the
kneader to produce a paste of the swollen mixture of
cellulose and PVA. The paste thus produced is continuously
stuffed into an extruder connected to the kneader and then
dissolved in the extruder, thereby accomplishing the highly
homogeneous cellulose/PVA dope.
In detail, cellulose powder with an average particle
size of 500 ~ or smaller is produced by a crusher, and the
cellulose powder is mixed with PVA powder having the degree
of polymerization of 1000 to 4000 in a powder mixer. The
mixed powder of cellulose and PVA contains 0.5 to 30 wt% PVA,
and preferably 1 to 10 wt% PVA. when a PVA content in the
mixed powder is less than 0.5 wt%, physical properties such
as fibril resistance of the fiber become poor. On the other
hand, when the PVA content is more than 30 wt%, the PVA is
extracted in a coagulation bath after the dope is spun, so
undesirably increasing recovery cost of NMMO.
Hereinafter, there will be given a detailed
description of the production of the dope. First of all, 50
wt% NMMO aqueous solution is concentrated to prepare the
NN~IO aqueous solution containing 10 to 20 wt% water, and
poured in conjunction with the mixed powder of cellulose and
PVA into the kneader. At this time, NNll~iO functions to swell
the mixed powder, and is maintained to 70 to 100 C, and
CA 02511030 2003-08-28
preferably 80 to 90°C in terms of temperature during
feeding NMMO into the kneader. The mixed powder and
concentrated NMMO are injected into the kneader at 65 to
90°C, and preferably 75 to 80°C to produce the resulting
mixture, and the resulting mixture contains 5 to 20 wt%
mixed powder of cellulose and PVA, and preferably 9 to 14
wt% mixed powder according to the degree of polymerization
of cellulose. The mixed powder of cellulose and PVA and
liquid NMMO are repeatedly compressed, drawn, folded, and
sheared in the kneader to produce the homogeneous
cellulose/PVA paste, and the paste thus produced is fed
into the extruder while being maintained at 75 to 80°C.
The paste is melted in the extruder at 85 to 105°C to
accomplish the dope.
Furthermore, in the ii) step of the method of
producing the lyocell multi-filament according to the
present invention, the dope is extruded through a spinning
nozzle including a plurality of orifices, reaches a conical
upper coagulation bath through air gaps between the
filaments, and is solidified to obtain the multi-filament.
At this time, each of the orifices has a diameter (D) of
100 to 300 um, a length (L) of 200 to 2400 ~Zm, and a ratio
of the length to the diameter (L/D) of 2 to 8, and an
interval between adjacent orifices is 2.0 to 5.0 mm.
Figure 1 schematically illustrates the spinning
process according to the present invention. With reference
to Figure
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CA 02511030 2003-08-28
1, the cellulose solution is quantitatively fed from a gear
pump 1 through the spinning nozzle 2 and air gaps 3 to a
surface of a coagulation liquid. The spinning nozzle 2 has
a circular cross-section, and a diameter of 50 to 160 mm,
preferably 80 to 130 mm. When the diameter of the spinning
nozzle 2 is smaller than 50 mm, cooling efficiency of the
cellulose solution is reduced and the partially solidified
cellulose filaments are attached to each other because
intervals between the orifices are very short. On the other
hand, when the diameter is larger than 160 mm, auxiliary
devices such as a spinning pack and the spinning nozzle
become undesirably large. Moreover, when the diameter of
each of the orifices is smaller than 100 ~, yarn breaking
occurs during spinning the cellulose solution to reduce
spinning efficiency, but when the diameter of each orifice
is larger than 300 pmt, a solidifying speed of the cellulose
solution in the coagulation bath is slow and it is difficult
to wash the multi-filament to remove NMD~IO. Additionally,
when the length of each orifice is shorter than 200 fan,
orientation of the cellulose solution becomes poor to
degrade physical properties of the multi-filament. On the
other hand, when the length is longer than 2400 um, great
expense and effort are undesirably required to produce the
orifices.
Meanwhile, the number of orifices is 500 to 1500, and
1?
CA 02511030 2003-08-28
preferably 800 to 1200 because the multi-filament is
industrially used as a tire cord and the cellulose solution
must be uniformly cooled. Efforts have been made to develop
industrial lyocell fibers, but the lyocell multi-filament
with high tenacity for tire cords have not yet been
developed because it is difficult to secure excellent
spinning efficiency and sophisticated technologies are
needed due to the great number of filaments. To avoid the
above disadvantages, the spinning nozzle 2 including the
above desirable number of orifices is used in the present
invention. When the number of orifices is less than 500,
fineness of each filament becomes large, so NN~IO is not
sufficiently removed from the filaments for a short time to
cause incomplete solidification and washing of the filaments.
On the other hand, when the number of orifices is more than
1500, the adjacent filaments are attached to each other in
the air gaps and stability of each of the filaments is
reduced, thus physical properties of the multi-filament are
degraded, and some problems may occur in the twisting and
heat-treatment process which are processes required to apply
the multi-filament to tire cords.
Additionally, when the dope passing through the
spinning nozzle 2 is solidified in the upper coagulation
liquid, it is difficult to obtain the multi-filament with a
dense and homogeneous structure because a surface and an
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interior of a thick strand of the solidified dope have
different solidifying rates. Accordingly, the cellulose
solution, that is, the dope, is spun through the air gaps 3
with desirable space to produce fine fibers in the
coagulation liquid. When the thickness of each of the air
gaps is thin, the surface solidification of the spun dope is
quickly conducted and occurrence of micropores in the multi-
filament is increased in the solvent-removing process to
prevent a draw ratio from being increased and reduce a
spinning speed. On the other hand, when the thickness of
each of the air gaps is thick, the filaments are attached to
each other and affected by a temperature and humidity of
each air gap, thus the production of the multi-filament is
unstable. Hence, the width of the air gap is preferably 20
to 300 mm, and more preferably 30 to 200 mm.
When the dope passes through the air gaps 3, quenching
air is supplied to the filaments so as to properly cool the
filaments to prevent them from being melted and attached to
each other and to increase dipping resistance of the
filaments to the coagulation liquid. Additionally, a sensor
5 is installed between a quenching air supplier 6 and the
filaments to monitor the temperature and humidity of the air
gaps and control them. The cooling air is preferably
maintained at 5 to 20°C. For example, when a temperature of
the cooling air is lower than 5°C, the solidification of the
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filaments is quickly promoted, so the high-speed spinning
process is not feasible. But, when the temperature is
higher than 20°C, yarn breaking may occur because dipping
resistance of the filaments to the coagulation liquid is
reduced.
Moreover, a moisture content in the cooling air
affects the solidification of the filaments, and relative
humidity (RH) in the air gaps 3 is preferably 10 to 50
In detail, dry air with relative humidity (RH) of 10 to 30
is supplied near the spinning nozzle and wet air with
relative humidity (RH) of 30 to 50 ~ is supplied near the
coagulation liquid so as to improve a solidification speed
of the filaments and prevent the filaments from attaching to
a surface of the spinning nozzle. The cooling air is
supplied to the filaments in such a way that it flows in
parallel with surfaces of the vertically moving filaments.
At this time, a flowing speed of the cooling air is
preferably 1 to 10 m/sec, and more preferably 2 to 7 m/sec.
When the flowing speed is less than 1 m/sec, the cooling air
does not sufficiently affect the filaments, a portion of
each of the filaments which the cooling air reaches late is
different from another portion of each of the filaments
which the cooling air reaches early in terms of the
solidifying speed, and yarn breaking occurs, thereby the
homogeneous filaments being rarely produced. On the other
CA 02511030 2003-08-28
hand, when the flowing speed is more than 10 m/sec, the
filaments vibrate, so the filaments may be attached to each
other and spinning stability of the filaments is not secured
because the dope is not uniformly spun.
As for a composition in the upper solidifying bath
according to the present invention, it is preferable that a
concentration of NMMO in water in the upper coagulation bath
is 5 to 20
When the filaments pass through the upper coagulation
bath 4, if the spinning speed is increased by 50 m/min or
more, the coagulation liquid seethes due to friction between
the filaments and the coagulation liquid. This phenomenon
functions to reduce stability of the production of the
multi-filament when physical properties of the multi
filament and the spinning speed are improved by drawing the
multi-filament to improve productivity of the multi-filament.
Accordingly, a doughnut-shaped mesh net 7 is installed on
the upper coagulation bath 4 to cause the solidifying liquid
to flow in the same direction as movement of the filaments
to spontaneously draw and orient the multi-filament.
Furthermore, in the iii) step of the method of
producing the lyocell multi-filament according to the
present invention, the multi-filament is fed through a lower
coagulation bath 8 to a washing bath. In detail, the lower
coagulation bath 8 functions to recover the coagulation
21
CA 02511030 2003-08-28
liquid 10 flowing down along the filaments discharged from
the upper coagulation bath 4, and a roller 9 installed in
the lower coagulation bath 8 functions to change the moving
direction of the filaments. Additionally, the roller 9
rotates so as to reduce frictional resistance of the roller
9 to the filaments. Furthermore, a control bath is
separately installed so as to control a concentration of the
coagulation liquid in the upper coagulation bath 4 in such a
way that it is the same as a concentration of the
coagulation liquid in the lower coagulation bath 8 or a
difference between concentrations of the upper and lower
coagulation bath 4 and 8 is within 0.5 %. In this regard, a
temperature and concentration of the coagulation liquid must
be constant because the solvent removing and drawing
processes which seriously affect physical properties of the
filaments are simultaneously conducted when the filaments
pass through the upper and lower coagulation bath 4 and 8.
The filaments passing through the lower coagulation bath are
rinsed in the rinsing bath. At this time, the filaments are
rinsed according to a traditional rinsing process.
Moreover, in the iv) step of the method of producing
the lyocell multi-filament according to the present
invention, the washed multi-filament is dried, oiled, and
wound according to a traditional process, thereby
accomplishing an industrial filament for tire cords.
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CA 02511030 2003-08-28
The lyocell multi-filament according to the present
invention has fineness of 1000 to 2500 deniers and load
at break of 5.0 to 25.0 kg. Further, the mufti-filament
consists of 500 to 1500 filaments each having fineness of
0.5 to 4.0 deniers. Additionally, the mufti-filament has
tenacity of 5 to 10 g/d, elongation of 3 to 13%, modulus
of 200 to 400 g/d, birefringence of 0.038 to 0.050,
crystallinity of 40 to 52%, shrinkage of -0.5 to 3%; and
strength maintenance of 90% or more after the heat and
saturated vapor treatment at a high temperature, thereby
being usefully applied to the tire cord for an
automobile.
According to the present invention, disadvantages
occurring in the method of producing the lyocell multi-
filament using a wet spinning process are desirably
overcome, and the maximum spinning speed is 250 m/min.
That is to say, even though the number of orifices of the
spinning nozzle is large, the homogeneous cellulose
solution and the cooling air with desirable temperature
and humidity are used, so spinning efficiency is
excellent and friction between the filaments and the
solidifying liquid in the solidifying bath is reduced,
thereby accomplishing the high-speed spinning process.
A better understanding of the present invention may
be obtained by reading the following examples which are
set forth to illustrate, but are not to be construed to
limit
23
CA 02511030 2003-08-28
the present invention.
Dopes and lyocell multi-filaments produced according
to examples and comparative examples as will be described
below are evaluated as follows:
(a) Degree of polymerization (DPw)
An intrinsic viscosity (IV) of cellulose dissolved in
a solvent was obtained at 25 ~ 0.01'C within a concentration
range of 0.1 to 0.6 g/dl by a Ubbelohde viscometer using a
0.5M cupriethylenediamine hydroxide solution prepared
according to ASTM D539-51T. At this time, the intrinsic
viscosity was obtained by extrapolating a specific viscosity
against the concentration, and the intrinsic viscosity thus
obtained was substituted for the Mark-Houwink's equation, as
will be described below, to obtain a degree of
polymerization.
[IV] - 0.98 X 10-ZDPW°~s
(b) Attachment of the filaments
Filament was repeatedly cut to lengths of 1 m, and the
cut yarn with a length of 1 m was cut again to produce a
sample with a length of 0.1 m. The above procedure was
repeated so as to produce five samples. The samples thus
produced were dried at 107 C for 2 hours without load, and
then observed by naked eye using an Image Analyzer to
24
CA 02511030 2003-08-28
10
determine whether the filaments were attached to each other
or not. If any attachment between the filaments was found,
the filament was evaluated as "fail (F)", but if no
attachment is found, it was evaluated as "pass (P)".
(c) Strength (kgf) and elongation at specific load (%)
After the samples were dried at 107°C for 2 hours,
strength and elongation of each sample with a length of 250
mm were measured using a low-speed elongation type of
tensile strength tester manufactured by Instron'~ Co. at a
tension speed of 300 m/min and at 80 TPM (twist/m). At this'
time, elongation at specific load is measured as elongation
at load of 4.5 kg.
(d) Shrinkage (%)
After each sample was left at a temperature of 25 C and
a relative humidity of 65 % for 24 hours, a first length
(Lo) of each of the samples measured at a load of 20 g and a
second length (L1) of each of the samples measured after
being treated at the load of 20 g at 150 C for 30 minutes
were used to calculate shrinkage of each sample by the
following equation.
S (%) - (La-L1) / Lo X 100
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CA 02511030 2003-08-28
(e) Birefringence
Birefringence of each sample was measured using a
polarization microscope adopting a Na-D light source and a
Berek compensator.
(f) Crystallinity
Crystallinity of each sample was assessed using a wide
rM
angle X-ray diffractometer (manufactured by Ricaku Co., X-
ray source: CuKa (Ni filter), output: 50 KV and 200 mA, and
angle range: 28 = 5 to 45°)
(g) Strength maintenance after the saturated vapor
treatment
After exposed to high temperature and moisture, each
sample was left in an autoclave (manufactured by the present
inventors) at 170 C for 10 min under a saturated vapor
atmosphere so as to evaluate its shape and physical property
stability. The resulting sample was then dried to measure
its strength, and a ratio of the measurements of the
strength before and after the saturated vapor treatment was
calculated to evaluate the strength maintenance of each
sample.
EXAMPLE 1
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CA 02511030 2003-08-28
Mixed powder in which pulp with the degree of
polymerization (DPW) of 1200 containing a a-cellulose
content of 97 % is mixed with PVA in a weight ratio of 20 .
1, NN~IO~IHzO, and 0.01 wt% propyl gallate were mixed to
produce an 11.5 % cellulose solution. Spinning nozzles with
a diameter of 120 mm including 800, 1000, and 1200 orifices
were used to extrude the cellulose solution. At this time,
a diameter of each of the orifices was 150 Vin, and a ratio
of a length to the diameter (L/D) of each orifice was 4 for
all the spinning nozzles. When the cellulose solution (head
temperature: 110 C) passed through the spinning nozzle flew
through air gaps at a point spaced apart from the spinning
nozzle by 50 mm, cooling air with a temperature of 20'C and
relative humidity of 40 % blew at a speed of 4 m/sec to the
solution, and an extruding amount and spinning speed of the
solution were controlled in such a way that fineness of the
resulting multi-filament was 1500 to 2000 deniers. A
temperature of a coagulation liquid was 20~ and the
coagulation liquid contained 20 % NNll~IO and 80 % water, and
the coagulation liquid circulated between an upper and a
lower coagulation bath. At this time, a temperature of the
cooling air and a concentration of the coagulation liquid
were continuously monitored using a sensor and a
refractometer. NMN10 remaining on the multi-filament
discharged from the upper and lower coagulation bath was
27
CA 02511030 2003-08-28
rinsed, and the washed multi-filament was dried and wound.
Physical properties of the multi-filament are described in
Table 1.
TABLE 1
Example
1
Spinning conditions 1-1 1-2 1-3 1-4 1-5
Nozzle diameter(mm) 120 120 120 120 120
Number of orifices 800 1000 1200 1000 1000
Orifice diameter(um) 150 150 150 150 150
Fineness of multi-filament 1510 1508 1502 1720 2000
(d)
lPhysical properties
Attachment Pass Pass Pass Pass Pass
Tenacity(g/d) 6.5 7.7 9.4 7.5 5.7
Elongation at specific load2.1 1.9 1.1 1.9 2.7
(%)
Elongation at break (%) 8.4 6.7 3.9 9.7 12.5
Modulus (g/d) 230 270 350 280 205
Crystallinity (%) 44 48 51 50 42
Birefringence (0n X 10') 0.043 0.0460.048 0.0490.042
zStrength maintenance (%) 93 94 92 95 95
lPhysical properties: physical properties of the multi-filament
ZStrength maintenance: Strength maintenance after the saturated
vapor treatment
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From the Table 1, it can be seen that the number of
the orifices rarely affects spinning efficiency of the
cellulose solution, and when the number of the orifices is
slightly increased, tenacity is increased and elongations at
specific load and at break are decreased. As for modulus,
it is the highest when the number of the orifices is 1200.
When the extruding amount and spinning speed are controlled
in such a way that fineness of the multi-filament is 1500 to
2000, attachment of the filaments to each other is scarcely
affected. Additionally, tenacity is reduced but elongation
is apt to be increased with an increase of fineness of the
multi-filament.
EXAMPLE 2
First mixed powder in which pulp with the degree of
polymerization (DPW) of 800 containing a a-cellulose content
of 97 % is mixed with PVA in a weight ratio of 20 . 1,
second mixed powder in which pulp with the degree of
polymerization (DPW) of 1200 containing a a-cellulose
content of 97 % is mixed with PVA in a weight ratio of 20
1, NMMO~1H20, and 0.01 wt% propyl gallate were mixed to
produce two different cellulose solution samples. In this
regard, a concentration of the cellulose solution including
the pulp with the degree of polymerization of 800 was 13.5 %,
29
CA 02511030 2003-08-28
and that of the cellulose solution including the pulp with
the degree of polymerization of 1200 was 11.5 %. Spinning
nozzles with a diameter of 120 mm including 1000 orifices
with three types of diameters of 120, 150, and 200 um were
used to extrude the cellulose solution. At this time, a
ratio of a length to the diameter (L/D) of each orifice was
5 for all the spinning nozzles. Cooling air was fed to air
gaps according to the same procedure as the example 1, and
an extruding amount and spinning speed of the solution were
controlled in such a way that fineness of the resulting
multi-filament was 1500 deniers. Subsequently, the
cellulose solution passed through a coagulation liquid, was
washed, dried, and wound to accomplish the multi-filament.
Physical properties of the multi-filament are described in
Table 2.
As described above, the spinning nozzle including 1000
orifices was used, and the pulps each having the degree of
polymerization (DPW) of 800 and 1200 were used to produce
the multi-filament and dip cord in example 2. From the
Table 2, it can be seen that tenacity is apt to be increased
with an increase of the diameter of the orifice, and much
more increased in the case of using the pulp with DPw of 800
than in the case of using the pulp with DPw of 1200.
Additionally, elongation is reduced but modulus is increased
in accordance with an increase of the diameter of the
CA 02511030 2003-08-28
orifice. Further, tenacity and modulus are highest when the
degree of polymerization of the pulp is 1200 and the
diameter of the orifice is 200.
COMPARATIVE EXAMPLE 1
An 11.5 % cellulose solution was produced using a
mixture of pulp with the degree of polymerization (DPw) of
1200 containing a a-cellulose content of 97 ~, NMMO~1H20, and
0.01 wt~ propyl gallate without PVA. Spinning nozzles with
a diameter of 120 mm including 1000 orifices with two types
of diameters of 120 and 150 um were used to extrude the
cellulose solution. At this time, a ratio of a length to
the diameter (L/D) of each orifice was 5 for all the
spinning nozzles. Cooling air was fed to air gaps according
to the same procedure as the example 1, and an extruding
amount and spinning speed of the solution were controlled in
such a way that fineness of the resulting multi-filament was
1500 deniers. Subsequently, the cellulose solution passed
through a coagulating liquid, was washed, dried, and wound
to accomplish the multi-filament. Physical properties of
the multi-filament are described in Table 2.
TABLE 2
Example 2 ~ Comp. Ex. 1
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CA 02511030 2003-08-28
Spinning conditions 2-1 2-2 2-3 2-4 2-5 2-6 1-1 1-2
DPW of cellulose 800 800 800 1200 1200 1200 1200 1200
lCon. of cellulose 13.5 13.5 13.5 11.5 11.5 11.5 11.5 11.5
(%)
Orifice diameter 120 150 200 120 150 200 120 150
(~)
ZFineness (d) 1510 1505 1511 1500 1508 1507 1502 1505
Physical properties
Attachment Pass Pass Pass Pass Pass Pass Pass Pass
Tenacity(g/d) 5.7 6.3 7.5 7.9 9.4 9.7 4.5 4.8
'Elongation (%) 2.9 1.6 1.0 1.2 1.1 1.0 2.5 2.7
Elongation at break 7.2 5.8 4.9 7.5 3.9 3.8 8.7 6.9
(%)
Modulus (g/d) 210 247 266 280 330 368 173 188
Crystallinity (%) 48 48 49 50 50 51 38 39
Birefringence (fin 0.0450.0450.0420.0480.0490.0490.0370.037
X 103)
SStrength maintenance93 94 92 92 95 98 84 88
(%)
lCon. of cellulose (%): Concentration of cellulose
Fineness (d): Fineness of multi-filament
'Physical properties: physical properties of the multi-filament
'Elongation (%): Elongation at specific load (%)
SStrength maintenance: Strength maintenance after the saturated
vapor treatment
COMPARATIVE EXAMPLE 2
The cellulose solution was produced according to the
32
CA 02511030 2003-08-28
same procedure as comparative example 1, and the physical
properties of the multi-filament were estimated while
varying the number of orifices each having a diameter of 150
,cmi. When the number of orifices is 400, the spinning
efficiency is not poor but draft (ratio of winding speed of
the multi-filament/extruding speed of the cellulose
solution) is reduced because an extruding speed of the
solution was much faster than a winding speed of the multi-
filament, thereby reducing tenacity.
When the number of the orifices is 1000 and fineness
of the multi-filament is 800 and 2300 denier, physical
properties of the multi-filament and dip cord are described
in Table 3. If fineness of the multi-filament is 800 denier,
strength is too poor to apply the multi-filament to a tire
cord. The multi-filament with fineness of 2300 denier is
not useful to be applied to the tire cord because of
excessively high fineness. Furthermore, the spinning
nozzles including orifices having diameters of 90 and 350 ~
are insufficiently competitive in terms of spinning
efficiency, causing yarn breaking. Particularly, when the
diameter of the orifice is 350~.~t, most of filaments are
attached to each other, thereby greatly reducing the
physical properties of the multi-filament.
TABLE 3
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CA 02511030 2003-08-28
Comparative
Example
2
Spinning conditions 2-1 2-2 2-3 2-4 2-5 2-6
DPw of cellulose 1200 1200 1200 1200 1200 1200
Orifice diameter (~) 150 150 150 90 350 150
Number of orifices 400 1000 1000 1000 1000 1000
Fineness of multi-filament1503 800 2300 1511 1510 1508
lPhysical properties
Attachment F F F F F Pass
Tenacity(g/d) 4.9 4.1 4.8 2.9 4.2 4.7
Elongation at specific 2.1 1.6 1.3 1.5 1.9 1.1
load (%)
Elongation at break (%) 6.5 3.4 9.1 6.0 6.3 5.3
Modulus (g/d) 173 169 174 119 170 177
Crystallinity (%) 39 36 39 34 36 36
Birefringence (fin X 103)0.0440.0440.0420.0450.0390.044
Strength maintenance (%) 88 89 87 80 85 88
lPhysical properties: physical properties of the multi-filament
ZStrength maintenance: Strength maintenance after the saturated
vapor treatment
Therefore, the present invention provides a lyocell
multi-filament having excellent physical properties useful
as a tire cord, thereby producing a tire for an automobile
having improved driving stability, dimensional stability,
and uniformity using the tire cord.
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CA 02511030 2003-08-28
The present invention has been described in an
illustrative method, and it is to be understood that the
terminology used is intended to be in the nature of
description rather than of limitation. Many modifications
and variations of the present invention are possible in
light of the above teachings. Therefore, it is to be
understood that within the scope of the appended claims, the
invention may be practiced otherwise than as specifically
described.
35
