U.S. patent application number 16/275399 was filed with the patent office on 2019-06-13 for liquid crystal polyester fiber and producing method thereof.
This patent application is currently assigned to TORAY INDUSTRIES, INC.. The applicant listed for this patent is TORAY INDUSTRIES, INC.. Invention is credited to Yoshitsugu FUNATSU, Chieko KAWAMATA, Masato MASUDA.
Application Number | 20190177880 16/275399 |
Document ID | / |
Family ID | 53756836 |
Filed Date | 2019-06-13 |
United States Patent
Application |
20190177880 |
Kind Code |
A1 |
FUNATSU; Yoshitsugu ; et
al. |
June 13, 2019 |
LIQUID CRYSTAL POLYESTER FIBER AND PRODUCING METHOD THEREOF
Abstract
Provided is a liquid crystal polyester fiber having high
strength, high elastic modulus, high abrasion resistance, excellent
processability, and little thermal deformation at high temperature,
and also provided is a production method thereof. A liquid crystal
polyester fiber, characterized in that the peak half-value width of
the endothermic peak (Tm1) observed when measuring by differential
calorimetry under rising temperature conditions starting at
50.degree. C. and increasing 20.degree. C./min is 15.degree. C. or
higher, the polystyrene-converted weight-average molecular weight
is between 250,000 and 2,000,000 inclusive, the peak temperature of
the loss tangent (tan .delta.) is between 100.degree. C. and
200.degree. C. inclusive, and the peak value of the loss tangent
(tan .delta.) is between 0.060 and 0.090 inclusive. A mesh fabric
comprising the liquid crystal polyester fiber. A production method
for melt liquid crystal polyester fiber, characterized in that
liquid crystal polyester fiber obtained by melt-spinning is subject
to solid-phase polymerization, and subsequently heat treated at a
stretch ratio of at least 0.1% and under 3.0% at a temperature at
least 50.degree. C. higher than the endothermic peak temperature
(Tm1) as observed when measuring by differential calorimetry under
rising temperature conditions starting at 50.degree. C. and
increasing 20.degree. C./min.
Inventors: |
FUNATSU; Yoshitsugu;
(Mishima-shi, JP) ; MASUDA; Masato; (Mishima-shi,
JP) ; KAWAMATA; Chieko; (Mishima-shi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
TORAY INDUSTRIES, INC. |
Tokyo |
|
JP |
|
|
Assignee: |
TORAY INDUSTRIES, INC.
Tokyo
JP
|
Family ID: |
53756836 |
Appl. No.: |
16/275399 |
Filed: |
February 14, 2019 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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15113902 |
Jul 25, 2016 |
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PCT/JP2015/051451 |
Jan 21, 2015 |
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16275399 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
D01F 6/62 20130101; D01D
5/08 20130101; D01F 6/84 20130101; D10B 2331/04 20130101 |
International
Class: |
D01F 6/62 20060101
D01F006/62; D01F 6/84 20060101 D01F006/84 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 31, 2014 |
JP |
2014-016586 |
Claims
1. A method of producing a melt-spun liquid crystal polyester
fiber, said method comprising: melt spinning a liquid crystal
polyester fiber thereby polymerizing said fiber in a solid phase;
and heat stretching the polymer at a temperature of an endothermic
peak (Tm1)+50.degree. C. or more and at a stretch rate of 0.1% or
more and less than 3.0%, wherein the endothermic peak is observed
by a differential calorimetry under a temperature elevation
condition of 20.degree. C./min from 50.degree. C.; wherein
melt-spun liquid crystal polyester has: a peak half-value width of
15.degree. C. or more at an endothermic peak (Tm1) observed by a
differential calorimetry under a temperature elevation condition of
20.degree. C./min from 50.degree. C.; a weight-average molecular
weight in terms of polystyrene of 250,000 or more and 2,000,000 or
less; a peak temperature of a loss tangent (tan .delta.) of
100.degree. C. or more and 200.degree. C. or less; and a peak value
of the loss tangent (tan .delta.) of 0.060 or more and 0.078 or
less; and wherein the peak temperature and peak value of loss
tangent (tan .delta.) are determined by measuring a dynamic
viscoelasticity from 60.degree. C. to 210.degree. C. under the
conditions of a frequency of 110 Hz, an initial load of 0.13
cN/dtex, and a temperature elevation rate of 3.degree. C./m.
2. The method according to claim 1, wherein the heated fiber is
taken up under a yarn route regulation with yarn route guide in a
range of 1 cm or more and 50 cm or less from an exit portion of a
heating region.
3. The method according to claim 1, wherein the liquid crystal
polyester is a) a polymer of an aromatic oxycarboxylic acid
component; b) a polymer of an aromatic dicarboxylic acid component,
an aromatic diol component and/or an aliphatic diol component; or
c) a copolymer of a) and b).
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] The present application is a 37 C.F.R. .sctn. 1.53(b)
Divisional of copending U.S. application Ser. No. 15/113,902 filed
Jul. 25, 2016, which is the National Phase under 35 U.S.C. .sctn.
371 of International Application No. PCT/JP2015/051451 filed Jan.
21, 2015, which claims priority to Japanese Patent Application No.
2014-016586 filed Jan. 31, 2014, all of which are hereby expressly
incorporated by reference into the present application.
TECHNICAL FIELD OF THE INVENTION
[0002] Our invention relates to a liquid crystal polyester fiber
having high strength, high elastic modulus, high abrasion
resistance, excellent processability and less heat deformation at a
high temperature, and a manufacturing method thereof.
BACKGROUND ART OF THE INVENTION
[0003] A liquid crystal polyester is a polymer consisting of rigid
molecular chains, showing high strength and high elastic modulus
among fibers produced in a melt spinning process by applying a heat
treatment (solid-phase polymerization) to the molecular chains
highly-oriented in a fiber axial direction. As shown in pages
235-256 of Non-patent document 1, the liquid crystal polyester has
improved heat resistance and dimensional stability since the
solid-phase polymerization increases its molecular weight to raise
its melting point. Thus the liquid crystal polyester fiber has high
strength, high elastic modulus, excellent heat resistance and
excellent thermal dimensional stability by applying the solid-phase
polymerization.
[0004] On the other hand, the liquid crystal polyester fiber may
have disadvantages such as low interaction in a fiber axial
direction and poor abrasion resistance so that fibrillation is
caused by frictions in higher processing and weaving process,
because rigid molecular chains are highly oriented in the fiber
axial direction to form dense crystals. Recently, specifically for
filters and screen-printing gauzes made of monofilaments, higher
weaving density (higher mesh) and larger opening section areas are
demanded in order to improve the performance. Since improvements
such as higher single fiber fineness, higher strength and higher
elastic modulus are strongly demanded to achieve this, the liquid
crystal polyester fiber is being counted on because of its high
strength and high elastic modulus. Since the fault decrease in
fibril or the like is also strongly demanded for higher performance
at the same time, improvements of abrasion resistance of the liquid
crystal polyester fiber and processability are expected.
[0005] Further, thermal deformation should be less even at a high
temperature for mesh fabric products. For example, a great thermal
deformation at a high temperature with high load for reducing
wrinkles might cause non-uniform openings and degrade performances
of screen printing and filtration. From these viewpoints, it is
demanded for the liquid crystal polyester fiber to improve abrasion
resistance and suppress thermal deformation at a high temperature
at the same time.
[0006] In order to improve abrasion resistance of liquid crystal
polyester fiber, pages 18-19 of Patent document 1 suggest that
liquid crystal polyester fiber should be heat-treated at the
melting point+10.degree. C. or more, or the endothermic peak
temperature (Tm1)+10.degree. C. or more, wherein the Tm1 is
determined by differential calorimetry under temperature elevation
of 20.degree. C./min from 50.degree. C. Although that technology
can improve the abrasion resistance well, it cannot sufficiently
suppress the thermal deformation at a high temperature. The great
improvement of abrasion resistance is likely to increase the
thermal deformation at a high temperature although fiber after the
solid-phase polymerization is heat treated at a high temperature to
improve the abrasion resistance in Patent document 1. Therefore,
the technology disclosed in Patent document 1 by itself cannot
achieve both abrasion resistance improvement and thermal
deformation suppression at a high temperature.
[0007] Patent document 1 doesn't disclose any suggestion of
suppressing thermal deformation at a high temperature, as only
disclosing running stability in page 20 describing the change of
elongation ratio from 2%-relaxation rate to 10%-stretch rate about
high-temperature heat treatment of liquid crystal polyester fiber
after solid-phase polymerization. It doesn't even disclose any
suggestion of advantage of a guide provided after the heat
treatment with respect to the running stability for the heat
treatment.
[0008] Page 2 of Patent document 2 discloses a technology in which
liquid crystal polyester fiber after solid-phase polymerization is
subject to a thermal stretch by 10% or more as a high-temperature
heat treatment. However, Patent document 2 doesn't disclose any
suggestion to suppress a thermal deformation at a high temperature,
as only disclosing the purpose of the stretch, such as abrasion
resistance improvement and thinning by stretching fiber.
[0009] Page 15 of Patent document 3 discloses a technology to
thermally stretch the liquid crystal polyester fiber before
solid-phase polymerization by less than 1.005 ratio. With this
technology, the liquid crystal polyester fiber is stretched before
the solid-phase polymerization at a relatively low temperature of
the glass transition temperature+50.degree. C. or less, while it
discloses neither the improvement of abrasion resistance by the
heat treatment at a high temperature of the melting
point+50.degree. C. or more nor the suggestion about thermal
deformation at the high temperature. Although Patent document 3
discloses a dynamic viscoelastic measurement of tan .delta. to
obtain Tg (glass transition temperature) of the resin, it doesn't
disclose any relation between tan .delta. and thermal deformation
suppression at a high temperature.
[0010] Page 2 of Patent document 4 discloses a technology of
solid-phase polymerization (heat treatment) of liquid crystal
polyester fiber performed at a temperature of Tm-80.degree. C. or
less, and subsequently at another temperature between Tm-60.degree.
C. and Tm+20.degree. C. With this technology, the temperature for
solid-phase polymerization is raised stepwise to improve a
vibration damping characteristics, while it discloses neither the
improvement of abrasion resistance by the heat treatment at a high
temperature of the melting point+50.degree. C. or more nor the
suggestion about thermal deformation at the high temperature.
Although Patent document 4 discloses tan .delta. measured as an
index to represent vibration damping characteristics of solid-phase
polymerized liquid crystal polyester fiber, it doesn't disclose any
relation between tan .delta. of liquid crystal polyester fiber
prepared by a high-temperature heat treatment at the melting
point+50.degree. C. or more and thermal deformation suppression at
a high temperature.
PRIOR ART DOCUMENTS
Patent Documents
[0011] Patent document 1: JP2008-240230-A [0012] Patent document 2:
JP2010-189819-A [0013] Patent document 3: JP2006-89903-A [0014]
Patent document 4: JP-H4-289218-A
Non-Patent Documents
[0014] [0015] Non-patent document 1: "Reforming technology and the
latest applications of liquid crystal polymer", edited by Technical
information institute, Co., Ltd, pp. 235-256 (2006)
SUMMARY OF THE INVENTION
Problems to be Solved by the Invention
[0016] As an object of our invention, it could be helpful to
provide a liquid crystal polyester fiber having high strength, high
elastic modulus, high abrasion resistance, excellent processability
and less heat deformation at a high temperature, and a
manufacturing method thereof.
Means for Solving the Problems
[0017] The above-described object of our invention can be achieved
by the following means.
(1) A liquid crystal polyester fiber having: a peak half-value
width of 15.degree. C. or more at an endothermic peak (Tm1)
observed by a differential calorimetry under a temperature
elevation condition of 20.degree. C./min from 50.degree. C.; a
weight-average molecular weight in terms of polystyrene of 250,000
or more and 2,000,000 or less; a peak temperature of a loss tangent
(tan .delta.) of 100.degree. C. or more and 200.degree. C. or less;
and a peak value of the loss tangent (tan .delta.) of 0.060 or more
and 0.090 or less. (2) A mesh fabric comprising the liquid crystal
polyester fiber of (1). (3) A producing method of a melt-spun
liquid crystal polyester fiber characterized in that a liquid
crystal polyester fiber made by a melt spinning is polymerized in a
solid phase and then heated at a temperature of an endothermic peak
(Tm1)+50.degree. C. or more by a stretch rate of 0.1% or more and
less than 3.0%, wherein the endothermic peak is observed by a
differential calorimetry under a temperature elevation condition of
20.degree. C./min from 50.degree. C.
Effect According to the Invention
[0018] Our liquid crystal polyester fiber can be excellent in
abrasion resistance and processability, so that the weaving
performance in producing a product such as mesh fabric is enhanced
to reduce faults in the product. Further, it has a small thermal
deformation even at a high temperature, so that a fabric product
has only a small variation in performance and dimension through the
high-temperature treatment. Furthermore, the producing method of
our invention can produce the liquid crystal polyester fiber
efficiently.
EMBODIMENTS FOR CARRYING OUT THE INVENTION
[0019] Hereinafter, our liquid crystal polyester fiber will be
explained in details.
[0020] The liquid crystal polyester described in the specification
means a polyester capable of forming an anisotropic melting phase
(liquid crystallinity) when molten. This characteristic can be
recognized by observing light transmitted through the sample under
polarized radiation when a sample of liquid crystal polyester is
placed on a hot stage and heated in nitrogen atmosphere, for
example.
[0021] The liquid crystal polyester in the specification may
be:
[0022] a) a polymer of an aromatic oxycarboxylic acid
component;
[0023] b) a polymer of an aromatic dicarboxylic acid component, an
aromatic diol component and/or an aliphatic diol component; and
[0024] c) a copolymer of a) and b).
[0025] It is preferable that the liquid crystal polyester is a
wholly aromatic polyester prepared without the aliphatic diol
component for achieving high strength, high elastic modulus and
high heat resistance. The aromatic oxycarboxylic acid component may
be an aromatic oxycarboxylic acid such as hydroxy benzoic acid and
hydroxy naphthoic acid, and may be alkyl, alkoxy or halogen
substitution product of the aromatic oxycarboxylic acid. The
aromatic dicarboxylic acid component may be an aromatic
dicarboxylic acid such as terephthalic acid, isophthalic acid,
diphenyl dicarboxylic acid, naphthalene dicarboxylic acid,
diphenylether dicarboxylic acid, diphenoxyethane dicarboxylic acid
and diphenylethane dicarboxylic acid, and may be alkyl, alkoxy or
halogen substitution product of the aromatic dicarboxylic acid. The
aromatic diol component may be an aromatic diol component such as
hydroquinone, resorcinol, dioxydiphenyl and naphthalene diol, and
may be alkyl, alkoxy or halogen substitution product of the
aromatic diol. The aliphatic diol component may be an aliphatic
diol such as ethylene glycol, propylene glycol, butane diol and
neopentyl glycol.
[0026] It is preferable that the liquid crystal polyester is a
copolymer of p-hydroxy benzoic acid component, 4,4'-dihydroxy
biphenyl component, hydroquinone component, terephthalic acid
component and/or isophthalic acid component, a copolymer of
p-hydroxy benzoic acid component and 6-hydroxy 2-naphthoic acid
component, a copolymer of p-hydroxy benzoic acid component,
6-hydroxy 2-naphthoic acid component, hydroquinone component and
terephthalic acid component or the like, for achieving excellent
spinnability, high strength, high elastic modulus, and abrasion
resistance improved by high-temperature heat treatment after
solid-phase polymerization.
[0027] It is preferable that the liquid crystal polyester comprises
the following structural units (I), (II), (III), (IV) and (V).
Besides, "structural unit" means a unit capable of composing
repeated structures in a main chain of polymer in the
specification.
##STR00001##
[0028] This combination of structural units makes it possible for
the molecular chain to have a proper crystallinity and a
non-linearity, namely, a melting point capable of being melt spun.
Therefore a good yarn-making property can be exhibited at a
spinning temperature set between the melting point and the thermal
decomposition temperature of polymer, as providing fiber uniform
along the longitudinal direction, while the strength and elastic
modulus of fiber can be enhanced with appropriate
crystallinity.
[0029] Further, it is important to combine components of diol with
a high linearity and such a small bulk as structural units (II) and
(III), so that the molecular chain in the fiber can have an orderly
structure with less disorder while the crystallinity does not
increase excessively and the interaction in a direction
perpendicular to the fiber axis can be maintained. In addition to
obtaining high strength and elastic modulus as such, particularly
excellent abrasion resistance can be achieved by carrying out a
heat treatment at a high temperature after solid-phase
polymerization.
[0030] It is preferable the structural unit (I) is contained by 40
to 85 mol %, more preferably 65 to 80 mol %, further preferably 68
to 75 mol %, in total of structural units (I), (II) and (III). By
setting the content in such a range, the crystallinity can be
controlled properly, high strength and elastic modulus can be
achieved while the melting point can be controlled in a range
suitable for performing a melt spinning.
[0031] It is preferable that the structural unit (II) is contained
by 60 to 90 mol %, more preferably 60 to 80 mol %, further
preferably 65 to 75 mol % in total of structural units (II) and
(III). By setting the content in such a range, since the
crystallinity does not increase excessively and the interaction in
a direction perpendicular to the fiber axis can be maintained, the
abrasion resistance can be improved by carrying out a heat
treatment at a high temperature after solid-phase
polymerization.
[0032] It is preferable that the structural unit (IV) is contained
by 40 to 95 mol %, more preferably 50 to 90 mol %, further
preferably 60 to 85 mol % in total of structural units (IV) and
(V). By setting the content in such a range, the melting point of
the polymer can be controlled properly, a good spinnability can be
exhibited at a spinning temperature set between the melting point
and the thermal decomposition temperature of the polymer, so that
fiber uniform along the longitudinal direction is prepared.
Further, since the linearity of the molecular chain loosens
appropriately, the abrasion resistance can be improved while the
interaction in a direction perpendicular to the fiber axis can be
enhanced with a fluctuant fibril structure by carrying out a heat
treatment at a high temperature after solid-phase
polymerization.
[0033] Preferred ranges of the respective structural units of the
liquid crystal polyester are as follow. Desirable liquid crystal
polyester fiber can be obtained by controlling the composition in
these ranges so as to satisfy the above-described condition.
Structural unit (I): 45-65 mol % Structural unit (II): 12-18 mol %
Structural unit (III): 3-10 mol % Structural unit (IV): 5-20 mol %
Structural unit (V): 2-15 mol %
[0034] In addition to the above-described structural units, it is
possible to copolymerize an aromatic dicarboxylic acid such as
3,3'-diphenyl dicarboxylic acid and 2,2'-diphenyl dicarboxylic
acid, an aliphatic dicarboxylic acid such as adipic acid, azelaic
acid, sebacic acid and dodecanedionic acid, an alicyclic
dicarboxylic acid such as hexahydro terephthalic acid
(1,4-cyclohexane dicarboxylic acid), an aromatic diol such as
chloro hydroquinone, 4,4'-dihydroxy phenylsulfone, 4,4'-dihydroxy
diphenylsulfide and 4,4'-dihydroxy benzophenone, p-aminophenol or
the like, in the liquid crystal polyester by 5 mol % or less as far
as advantages of our invention are achieved.
[0035] It is possible to add a polyester, a vinyl-based polymer
such as polyolefin and polystyrene, or another polymer such as
polycarbonate, polyamide, polyimide, polyphenylene sulfide,
polyphenylene oxide, polysulfone, aromatic polyketone, aliphatic
polyketone, semi-aromatic polyester amide, polyetheretherketone and
fluororesin. It is preferable to add polyphenylene sulfide,
polyetheretherketone, nylon 6, nylon 66, nylon 46, nylon 6T, nylon
9T, polyethylene terephthalate, polypropylene terephthalate,
polybutylene terephthalate, polyethylene naphthalate,
polycyclohexane dimethanol terephthalate, polyester 99M or the
like. From a viewpoint of good yarn-making property, it is
preferable that such a polymer has a melting point within a range
of the melting point of the liquid crystal polyester.+-.30.degree.
C.
[0036] It is possible to add a small amount of an inorganic
substance such as various metal oxides, kaoline and silica or an
additive such as colorant, delustering agent, flame retardant,
anti-oxidant, ultraviolet ray absorbent, infrared ray absorbent,
crystal nucleus agent, fluorescent whitening agent, end-group
closing agent and compatibilizing agent as far as advantages of our
invention are achieved.
[0037] The liquid crystal polyester fiber should have a weight
average molecular weight (may be called merely "molecular weight")
of 250,000 to 2,000,000 in terms of polystyrene. The high molecular
weight of 250,000 or more contributes to high strength, elastic
modulus and elongation. Because the strength, elastic modulus and
elongation are likely to increase as the molecular weight becomes
higher, it is preferable that the molecular weight is 300,000 or
more, preferably 350,000 or more. The upper limit of molecular
weight may be around 2,000,000 and may be sufficient at 1,000,000.
The molecular weight is determined by the method to be explained in
the Example.
[0038] The liquid crystal polyester fiber should have 15.degree. C.
or higher of peak half-value width observed by differential
calorimetry under temperature elevation condition of 20.degree.
C./min from 50.degree. C. Tm1 in this determination method
represents a melting point of fiber. The wider the area of the peak
shape is, or the greater the heat of melting (.DELTA.Hm1) is, the
higher the crystallinity is. Also the smaller the half-value width
is, the higher the completeness of crystal is. By melt-spinning and
then polymerizing the liquid crystal polyester in a solid-phase,
Tm1 elevates, .DELTA.Hm1 increases and the half-value width
decreases, and the crystallinity and completeness of crystal
increases, so that the fiber increases in strength, elongation and
elastic modulus as improving in heat resistance. On the other hand,
the abrasion resistance deteriorates, probably because a difference
in structure between the crystal part and the amorphous part
becomes remarkable by increase of the completeness of crystal so
that destruction occurs in the interface therebetween. Accordingly,
while maintaining high Tm1 as well as high strength, elastic
modulus, elongation and heat resistance observed in fiber which has
been polymerized in a solid-phase, the crystallinity of our fiber
is decreased by increasing the peak half-value width above
15.degree. C. observed in liquid crystal polyester fiber without
solid-phase polymerization, so that the abrasion resistance can be
improved by decreasing the difference in structure between the
crystal/amorphous parts which becomes a trigger of the destruction
as well as fluctuating the fibril structure to soften a whole
fiber. It is preferable that the peak half-value width at Tm1 is
20.degree. C. or higher so that the greater width makes the higher
abrasion resistance. The upper limit of peak half-value width may
industrially be around 80.degree. C. and may be sufficient at
50.degree. C.
[0039] Although only one endothermic peak is ordinarily observed in
the liquid crystal polyester fiber, there may be a case of
observing two or more endothermic peaks, when the fiber structure
has been insufficiently solid-phase polymerized. In such a case,
the peak half-value width is determined as the sum of the
half-value widths of respective peaks.
[0040] It is preferable that the melting point (Tm1) of fiber is
290.degree. C. or more, preferably 300.degree. C. or more, and
further preferably 310.degree. C. or more. Such a high melting
point makes the heat resistance of fiber excellent. To achieve such
a high melting point of fiber, it is possible that a fiber is made
from liquid crystal polyester having a high melting point. It is
preferable that a melt-spun fiber is polymerized in a solid phase
so that the fiber has a high strength and elastic modulus as well
as excellent uniformity in a longitudinal direction. The upper
limit of melting point may be around 400.degree. C.
[0041] It is preferable that the heat of melting .DELTA.Hm1 is 6.0
J/g or less, although it varies depending upon the structural unit
composition of the liquid crystal polyester. The .DELTA.Hm1 of 6.0
J/g or less can decrease the crystallinity, fluctuates the fibril
structure and softens the fiber as a whole, and decreases the
difference in structure between the crystal/amorphous parts which
becomes a trigger of the destruction, so that the abrasion
resistance improves. It is preferable that the .DELTA.Hm1 is 5.0
J/g or less so that the abrasion resistance improves. It is
preferable that the .DELTA.Hm1 is 0.2 J/g or more, for achieving
high strength and elastic modulus.
[0042] It is surprising that the .DELTA.Hm1 is 6.0 J/g or less in
spite of high molecular weight of 250,000 or more. The liquid
crystal polyester having a molecular weight of 250,000 or more is
not fluidized with a remarkably high viscosity and is difficult to
be melt-spun even above the melting point. A liquid crystal
polyester fiber with such a high molecular weight can be obtained
by melt spinning liquid crystal polyester having a low molecular
weight to be subject to solid-phase polymerization. When the liquid
crystal polyester fiber is subject to solid-phase polymerization,
the molecular weight increases, the strength, elongation, elastic
modulus and heat resistance improve, and the crystallinity also
increases, so that the .DELTA.Hm1 increases. When the crystallinity
increases, the strength, elongation, elastic modulus and heat
resistance further increase, although the difference in structure
between the crystal part and the amorphous part becomes remarkable,
the interface therebetween is liable to be destroyed, and the
abrasion resistance decreases. However in our invention, the high
strength, elastic modulus and heat resistance can be maintained by
having such a high molecular weight as characterized in a
solid-phase polymerized fiber while the abrasion resistance can be
increased by having such a low crystallinity or such a low
.DELTA.Hm1 as observed in liquid crystal polyester without
solid-phase polymerization. Our invention has achieved a technical
advance improving the abrasion resistance by a structure change
such as decreased crystallinity.
[0043] It is preferable that the Tm2 of the fiber is 300.degree. C.
or more from a viewpoint of enhanced heat resistance. The upper
limit of Tm2 may be around 400.degree. C.
[0044] It is preferable that the .DELTA.Hm2 is 5.0 J/g or less,
preferably 2.0 J/g or less, because the excessive .DELTA.Hm2 might
increase the crystallinity as a polymer itself and make it
difficult to improve the abrasion resistance. Although only one
endothermic peak is ordinarily observed in the liquid crystal
polyester fiber when it is heated again after a cooling process in
the above-described measurement condition, there may be a case of
observing two or more endothermic peaks. In such a case, the
.DELTA.Hm2 is determined as the sum of .DELTA.Hm2 of respective
peaks.
[0045] The fiber has a peak temperature of loss tangent (tan
.delta.) of 100.degree. C. to 200.degree. C. preferably 120.degree.
C. to 180.degree. C. while it has a peak value of 0.060 to 0.090.
In the specification, the peak temperature of tan .delta. and peak
value are determined by the method to be described in Examples.
[0046] The tan .delta. is a ratio of loss elastic modulus to
storage elastic modulus. When the tan .delta. is high the ratio of
heat scatter per energy applied is high. It is thought that a peak
appears in temperature dependence of tan .delta. in a synthetic
fiber, and the peak temperature has significance like the glass
transition temperature as a temperature at which kineticism of
amorphous part begins to increase while the peak value has
significance like the amount of the amorphous part itself.
[0047] The liquid crystal polyester fiber has a low crystallinity
since it has been heat-treated at a high temperature after
solid-phase polymerization, so that it consists primarily of the
amorphous part and has a clear peak in the tan .delta.. The peak
value corresponds to the amount of amorphous part and therefore the
one having a high peak value has a great amount of amorphous part
and tends to deform thermally. Namely, to suppress the thermal
deformation, it is preferable that the peak temperature of tan
.delta. is high and the peak value is low. On the other hand, to
achieve a high abrasion resistance characterizing the fiber of our
invention, it is preferable that the peak value is high so that the
crystallinity of polymer is low. To achieve such conflicting
characteristics at the same time, it is necessary to set the tan
.delta. properly.
[0048] The tan .delta. peak value of the fiber should be 0.090 or
less. The peak value of 0.090 or less can suppress thermal
deformation at a high temperature. It is preferable that the peak
value is 0.085 or less so that the thermal deformation is
suppressed more. To prevent the abrasion resistance from
deteriorating by a high crystallinity derived from an excessively
low peak value, it is preferable that the peak value is 0.060 or
more, preferably 0.065 or more.
[0049] The peak temperature of tan .delta. is a temperature at
which the kineticism of amorphous part suddenly increases. The
temperature above the peak temperature might cause a thermal
deformation. Therefore, the peak temperature is preferably higher.
The peak temperature of the fiber should be 100.degree. C. or more,
preferably 130.degree. C. or more. The upper limit of peak
temperature may be around 200.degree. C.
[0050] As described later, such desirable peak temperature and peak
value of tan .delta. can effectively be achieved by properly
setting a stretch rate in a heat treatment after solid-phase
polymerization.
[0051] To enhance the strength of mesh fabric, it is preferable
that the liquid crystal polyester fiber has a strength of 12.0
cN/dtex or more, preferably 14.0 cN/dtex or more, further
preferably 15.0 cN/dtex or more. The upper limit of strength may be
around 30.0 cN/dtex.
[0052] It is preferable that the fiber has a strength fluctuation
rate of 10% or less, preferably 5% or less. The strength in the
specification means strength at a cutting process in measuring a
tensile strength described in JIS L1013:2010. The strength
fluctuation rate is measured by the method to be described in
Examples. The uniformity along a longitudinal direction is enhanced
and the fluctuation of fiber strength (product of strength and
fineness) is decreased by the strength fluctuation rate of 10% or
less, so that defects of fiber product reduce and yarn breakage
derived from a low strength portion in a higher processing can also
be suppressed.
[0053] To enhance the elastic modulus of fabric, it is preferable
that the elastic modulus of fiber is 500 cN/dtex or more,
preferably 600 cN/dtex or more, further preferably 700 cN/dtex or
more. The upper limit of elastic modulus may be around 1200
cN/dtex.
[0054] It is preferable that the fiber has an elongation of 1.0% or
more, preferably 2.0% or more. The elongation of 1.0% or more can
enhance the impact absorbency of fiber to improve the abrasion
resistance, and can make the processability in a higher processing
and handling ability excellent. The upper limit of elongation may
be around 10.0%. The fiber having a molecular weight of 250,000 or
more can have a high elongation.
[0055] In the specification, strength, elongation and elastic
modulus are determined by the method to be described in
Examples.
[0056] Because of its high strength and elastic modulus, the fiber
can be suitably used in applications, such as printing screen
gauzes and meshes for filter. Also, because a high strength can be
exhibited even with thin fiber fineness, it can be achieved to make
a fibrous material smaller in weight and thickness, and a yarn
breakage in a higher processing such as weaving process can also be
suppressed. The fiber having a molecular weight of 250,000 or more
can have a high strength and elastic modulus.
[0057] It is preferable that the fiber has a single fiber fineness
of 18.0 dtex or less. Such a thin single fiber fineness of 18.0
dtex or less, can make the molecular weight easily increase to
improve in strength, elongation and elastic modulus when
polymerized in a solid phase at fibrous state. Further, it makes
possible that the flexibility and the workability of fiber are
improved, that the surface area increases to enhance the adhesion
property with chemical agents such as an adhesive. Furthermore, it
makes possible that the thickness becomes thinner, that the weave
density is increased, and that the opening (area of opening part)
can be widened in case of being formed as a gauze comprising
monofilaments. The single-fiber fineness is more preferably 15.0
dtex or less, and further preferably 10.0 dtex or less. The lower
limit of single fiber fineness may be around 1.0 dtex.
[0058] It is preferable that the fiber has a birefringent rate
(.DELTA.n) of 0.250 or more and 0.450 or less. Such a range of the
.DELTA.n can make the fiber axial molecular orientation
sufficiently high to achieve high strength and elastic modulus.
[0059] It is preferable that the fiber has an abrasion resistance C
of 60 sec or more, preferably 90 sec or more, further preferably
180 sec or more. The abrasion resistance C is determined by the
method to be described in Examples. The abrasion resistance C of 60
sec or more can make it possible that fibrillation of liquid
crystal polyester fiber at a higher processing is suppressed, that
deterioration of the processability and weaving performance causes
by fibril accumulation is suppressed, that the clogging of opening
due to accumulated fibrils being woven therein is suppressed, and
that less deposition of fibrils onto guides extends the cycle for
cleaning or exchange.
[0060] It is preferable that the fiber has a thermal deformation
rate at a high temperature of 1.0% or less. The thermal deformation
rate of 1.0% or less can maintain a product performance even after
a high-temperature heat treatment. It is preferable that the
thermal deformation rate is 0.7% or less. The lower limit of
thermal deformation rate may be around 0.2%.
[0061] To make fiber products thinner and lighter, it is preferable
that the fiber has the number of filaments of 50 or less,
preferably 20 or less. In particular, such a fiber can be suitably
used in the technical field of monofilament having the number of
filaments of 1 requiring high fiber fineness, high strength, high
elastic modulus and high uniformity of single fiber fineness.
[0062] It is preferable that the fiber has a yarn length of 40,000
m or more. The length of 40,000 m can minimize faults caused by
connecting yarns in product-making process such as weaving process.
The upper limit of yarn length may be around 10,000,000 m although
the longer is the more preferable. Such a long yarn length of fiber
can effectively be prepared under conditions of a proper stretch
rate and a good running stability achieved by regulating a yarn
route with a guide after heat treatment.
[0063] A mesh fabric can be made from the liquid crystal polyester
fiber. Since the liquid crystal polyester fiber is excellent in
abrasion resistance and processability, the weaving performance in
making a product such as a mesh fabric is enhanced to make the
product with less faults. Further, the thermal deformation is small
even at a high temperature, so that the product doesn't change
greatly in dimension and performance even in a high-temperature
processing.
[0064] The liquid crystal polyester fiber has a high strength, high
elastic modulus and high abrasion resistance and a small thermal
deformation, and is excellent in processability, so that it can be
used in various fields such as general industrial material, civil
engineering and construction material, sport material, protective
clothing material, rubber-reinforcing material, electric material
(tension members in particular), acoustic material and general
clothing material. It can suitably be used for screen gauzes,
filters, ropes, nets, fishing nets, computer ribbons, base fabrics
for printed boards, canvases for paper machines, air bags, air
ships, base fabrics for domes or the like, rider suits, fishlines,
various lines (lines for yachts, paragliders, balloons, kite yarns
or the like), blind cords, support cords for wire screens, various
cords in automobiles or air planes, power transmission cords for
electric equipment or robots or the like. It can be particularly
suitable as woven fabrics for industrial materials comprising
monofilaments such as preferably used for printing screen gauzes
and filters, for such monofilaments which strongly require high
strength, high elastic modulus and thin fineness as well as good
abrasion resistance for improving weaving performance and fabric
quality.
[0065] Hereinafter a method for producing the liquid crystal
polyester fiber will be explained.
[0066] The composition and desirable composition ratio of the
liquid crystal polyester have been described in the part explaining
fibers.
[0067] To make a wider temperature range capable of melt spinning,
it is preferable that a melting point of the liquid crystal
polyester is 200 to 380.degree. C., and is preferably 250 to
360.degree. C. for enhancing spinnability. The melting point of the
liquid crystal polyester polymer means a value (Tm2) measured by
the method to be described in Examples.
[0068] It is preferable that the liquid crystal has a weight
average molecular weight (may be called "molecular weight") of
30,000 or more in terms of polystyrene. The molecular weight of
30,000 or more can enhance the yarn-making property with an
adequate viscosity at a spinning temperature. When the molecular
weight is too high, the viscosity becomes high and the flowability
deteriorates although the strength, elongation and elastic modulus
of the fiber are enhanced, and ultimately it becomes impossible to
flow. Therefore it is preferable that the molecular weight is
250,000 or less, preferably less than 200,000 or less. The weight
average molecular weight in terms of polystyrene is determined by
the method to be described in Examples.
[0069] It is preferable that the liquid crystal polyester is dried
before being melt spun, from a viewpoint of suppressing bubbling
caused by water mixture and of enhancing yarn-making property. It
is more preferable that vacuum drying is performed, because the
monomer which remains in the liquid crystal polyester can be
removed, so that yarn-making property is further enhanced. The
vacuum drying is usually performed at 100-200.degree. C. for 8-24
hours.
[0070] To prevent a systematic structure from being produced at the
time of polymerization in the melt spinning, it is preferable to
use an extruder-type extruding machine although any known method
can be employed for melt extrusion of liquid crystal polyester. The
extruded polymer is metered by a known metering device, such as a
gear pump through a pipe, and is introduced into a spinneret after
passing through a filter for removing foreign materials. It is
preferable that the temperature (spinning temperature) from the
polymer pipe to the spinneret is controlled above the melting point
of the liquid crystal polyester, preferably controlled to a
temperature of the melting point of the liquid crystal
polyester+10.degree. C. or more. It is preferable that the spinning
temperature is 500.degree. C. or less, preferably 400.degree. C. or
less, in case that the spinning temperature is so high that the
viscosity of the liquid crystal polyester increases to deteriorate
fluidity and yarn-making property. It is possible to individually
adjust the temperature at each portion from the polymer pipe to the
spinneret. In this case, the discharge can be stabilized by
controlling the temperature of a portion near the spinneret as
higher than the temperature of an upstream portion thereof.
[0071] To enhance the yarn-making property and uniformity of
fineness with the discharge, it is preferable that the spinneret
has a hole of small diameter and a long land length (length of a
straight pipe part having the same inner diameter as the hole of
the spinneret). It is preferable that the hole diameter is 0.05 mm
or more and 0.50 mm or less, preferably 0.10 mm or more and 0.30 mm
or less, in case that an excessively small hole diameter might
cause a clogging of holes. It is preferable that an L/D defined as
a quotient calculated by dividing land length L with hole diameter
D is 1.0 or more and 3.0 or less, preferably 2.0 or more and 2.5 or
less, in case that an excessively long land length might increase a
pressure loss.
[0072] To maintain the uniformity, it is preferable that the
spinneret has holes of 50 or less, preferably 20 or less. It is
preferable that an introduction hole positioned right above the
hole of the spinneret is straight shaped hole, from a viewpoint of
preventing the increased pressure loss. It is preferable that the
introduction hole and the spinneret hole are connected with a
tapered portion to suppress abnormal retention.
[0073] The polymer discharged from the spinneret holes passes
through heat retention region and cooling region and is solidified
and then is drawn up by a roller (godet roller) rotating at a
constant speed. It is preferable that the heat retention region
extends by a length of 200 mm or less from the spinneret surface,
preferably 100 mm or less, because the yarn-making property
deteriorates by an excessively long heat retention region. When the
atmosphere temperature in the heat retention region is raised with
a heating means, it is preferable that the atmosphere temperature
is 100.degree. C. or more and 500.degree. C. or less, preferably
200.degree. C. or more and 400.degree. C. or less. The polymer can
be cooled with inert gas, air, steam or the like. To reduce the
environmental load and energy, it is preferable that it is cooled
with air flow at room temperature (20-30.degree. C.) blown in
parallel or annularly.
[0074] From viewpoints of improved productivity and thinner
single-yarn fineness, it is preferable that the draw velocity
(spinning velocity) is 50 m/min or more, preferably 500 m/min or
more. Since the desirable liquid crystal polyester has a good
spinnability at a spinning temperature, the upper limit of draw
velocity may be around 2,000 m/min.
[0075] It is preferable that a spinning draft defined as a quotient
calculated by dividing a draw velocity with a discharge linear
velocity is 1 or more and 500 or less, and is more preferably 10 or
more and 100 or less to enhance a yarn-making property and
uniformity of fineness.
[0076] In a melt spinning process, it is preferable that oil
solution is applied between a cooling-solidification step of
polymer and a take-up step so that the handling property of fiber
is improved. The oil solution may be a known oil solution and is
preferably a general spinning oil solution or a mixed oil solution
of inorganic particle (A) and phosphate compound (B) to be
described later, in order to improve an unraveling-property to
unravel a fiber (hereinafter called raw yarn of spinning) prepared
by melt-spinning at a roll-back step before solid-phase
polymerization.
[0077] The take-up may be carried out by using a known winder to
form a package such as pirn, cheese and cone. To prevent a fiber
from fibrillating with friction, it is preferable to employ a pirn
winding in which a roller doesn't contact a package surface when
the fiber is taken up.
[0078] It is preferable that the melt-spun fiber has a single fiber
fineness of 18.0 dtex or less. The single fiber fineness is
determined by the method to be described in Examples. The single
fiber fineness of 18.0 dtex or less can increase the molecular
weight of polymer constituting the fiber at the time of solid-phase
polymerization in a fiber state, so that strength, elongation and
elastic modulus are improved. Further, the surface area can be
wider to increase the adhesion amount of fusion inhibitor of
inorganic particle (A) and phosphate compound (B). It is preferable
that the single fiber fineness is 10.0 dtex or less, preferably 7.0
dtex or less. The lower limit of single fiber fineness may be
around 1.0 dtex.
[0079] It is preferable that the melt-spun fiber has a strength of
3.0 cN/dtex or more, preferably 5.0 cN/dtex or more so that the
processability is enhanced by preventing yarn breakage in a
roll-back process before the solid-phase polymerization. The upper
limit of strength may be around 10 cN/dtex.
[0080] It is preferable that the melt-spun fiber has an elongation
of 0.5% or more, preferably 1.0% or more so that the processability
is enhanced by preventing yarn breakage in a roll-back process
before the solid-phase polymerization. The upper limit of
elongation may be around 5.0%.
[0081] It is preferable that the melt-spun fiber has an elastic
modulus of 300 cN/dtex or more, preferably 500 cN/dtex or more so
that the processability is enhanced by preventing yarn breakage in
a roll-back process before the solid-phase polymerization. The
upper limit of elastic modulus may be around 800 cN/dtex.
[0082] The strength, elongation and elastic modulus are determined
by the method to be described in Examples.
[0083] It is preferable that the melt-spun fiber has a molecular
weight of 30,000 or more. The molecular weight of 30,000 or more
can achieve a high strength, elongation and elastic modulus with
excellent processability. It is preferable that the molecular
weight is 250,000 or less, preferably 200,000 or less, because
excessively high molecular weight might slow the solid-phase
polymerization to fail to have a high molecular weight achieved.
The weight average molecular weight in terms of polystyrene is
determined by the method to be described in Examples. Besides, the
molecular weight doesn't tend to fluctuate greatly in a melt
spinning process.
[0084] Then the melt spun fiber is subject to solid-phase
polymerization after fusion inhibitor oil solution is applied to
the fiber. To enhance the adhesion efficiency, it is preferable
that the fusion inhibitor is applied to the fiber yarn while a melt
spun fiber yarn taken up is rolled back, or that the fusion
inhibitor is applied in a small amount to the melt spun fiber yarn
and then is applied additionally to the fiber while the taken-up
fiber yarn is rolled back, although the fusion inhibitor may be
applied to the fiber between the melt spinning and take-up
processes.
[0085] To make the fusion inhibitor uniformly adhere to a fiber
such as monofilament having a thin total fineness, it is preferable
that the fusion inhibitor is applied with a kiss roll (oiling roll)
made of metal or ceramic, although a guide-feed method may be
employed for the adhesion. A hank or a tow of fiber can be applied
by immersing it in a mixed oil solution.
[0086] It is preferable that the fusion inhibitor is a mixture of
inorganic particle (A) and phosphate compound (B). The mixture of
inorganic particle (A) and phosphate compound (B) applied can
suppress the fusion between fibers in solid-phase polymerization
and thermally denature the components in the solid-phase
polymerization process, to achieve excellent processability in the
following process and excellent post-workability to make a product.
In the specification, the fusion inhibitor made of inorganic
particle (A) and phosphate compound (B) is called "oil solution for
solid-phase polymerization", "mixed oil solution" or "oil solution"
for convenience although such an oil solution doesn't contain any
oil component.
[0087] The inorganic particle (A) in the specification is a known
inorganic particle and may be mineral, metal hydroxide such as
magnesium hydroxide, metal oxide such as silica and alumina,
carbonate compound such as calcium carbonate and barium carbonate,
sulfate compound such as calcium sulfate or barium sulfate, carbon
black, or the like. Such a heat-resistant inorganic particle is
applied onto the fiber to reduce contact areas between single
fibers in solid-phase polymerization, so that fusion is prevented
in the solid-phase polymerization process.
[0088] It is preferable that the inorganic particle (A) is easily
handled to perform the application process while it is easily
dispersed in water to reduce environmental load and is inert under
a solid-phase polymerization condition. From these viewpoints, it
is preferable to employ silica or mineral of silicate. It is
preferable that the mineral of silicate is a phyllo-silicate having
a layer structure. The phyllo-silicate may be kaolinite,
halloysite, serpentine, garnierile, smectites, pyrophyllite, talc,
mica or the like. From a viewpoint of availability, it is most
preferable to employ talc or mica.
[0089] The phosphate compound (B) may be a compound identified by
any one of following chemical formulae (1)-(3).
##STR00002##
[0090] Here, R1 and R2 indicate hydrocarbon, M1 indicates alkali
metal, M2 indicates any one of alkali metal, hydrogen, hydrocarbon
and oxygen-containing hydrocarbon. Besides n indicates an integer
of 1 or more. From a viewpoint of suppressing thermolysis, it is
preferable that the upper limit of n is 100 or less, preferably 10
or less.
[0091] From a viewpoint of reducing the environmental load of gas
generated with thermolysis in solid-phase polymerization, it is
preferable that the R1 has no phenyl group in the structure and
preferably consists of alkyl group. From a viewpoint of affinity to
the fiber surface, it is preferable that the R1 has a carbon number
of 2 or more. From a viewpoint of suppressing the weight reduction
rate caused by decomposition of organic components accompanied with
solid-phase polymerization to prevent carbide generated by the
decomposition in the solid-phase polymerization process from
remaining on the fiber surface, it is preferable that the carbon
number is 20 or less.
[0092] From a viewpoint of water solubility, it is preferable that
the R2 is a hydrocarbon having a carbon number of 5 or less,
preferably 2 or 3.
[0093] From a viewpoint of production cost, it is preferable that
the M1 is sodium or potassium.
[0094] Using both inorganic particle (A) and phosphate compound (B)
can enhance the dispersibility of inorganic particle (A) and enable
uniform application to fiber to exhibit excellent suppression of
fusion and adhesion of inorganic particle (B) onto the fiber
surface, so that decreased amount of inorganic particle (A) remains
on the fiber after a washing process and then fouling is suppressed
in the following processing.
[0095] Further, phosphate compound (B) can easily be removed with
water from fiber in the washing process after solid-phase
polymerization, through generating condensed phosphate salt with
dehydration and decomposition of organic components contained in
phosphate compound (B) under a solid-phase polymerization
condition. When phosphate compound (B) is solely applied to fiber,
the deliquescence of the condensed salt might make the phosphate
salt absorb moisture to deliquesce on the fiber surface even under
an ordinary fiber storage condition, so that washability
deteriorates because of increased viscosity. Namely, the excellent
washability is exhibited by using both inorganic particle (A) and
phosphate compound (B). We presume such an excellent washability is
exhibited by a mechanism in which inorganic particle (A) having a
good absorbency prevents the condensed salt of phosphate compound
(B) from naturally absorbing moisture to deliquesce and the
condensed salt of phosphate compound (B) absorbs water to expand as
running in water, so as to fall off the fiber surface by layer
fractions.
[0096] To uniformly apply inorganic particle (A) and phosphate
compound (B) to fiber by an adequate adhesion amount, it is
preferable to employ a mixed oil solution made by adding inorganic
particle (A) to diluted solution of phosphate compound (B) which is
preferably diluted with water for safety. From a viewpoint of
suppressing fusion, it is preferable that the concentration of
inorganic particle (A) is as high as 0.01 wt % or more, preferably
0.1 wt % or more and that the upper limit is 10 wt % or less,
preferably 5 wt % or less for uniform dispersion. From a viewpoint
of uniform dispersion, it is preferable that the concentration of
phosphate compound (B) is as high as 0.1 wt % or more, preferably
1.0 wt % or more. To prevent the mixed oil solution from excessive
adhesion caused by increased viscosity and adhesive spotting caused
by temperature dependency of viscosity, it is preferable that the
concentration of phosphate compound (B) is 50 wt % or less,
preferably 30 wt % or less.
[0097] It is preferable that "a" defined as adhesion rate of
inorganic particle (A) and "b" defined as adhesion rate of
phosphate compound (B) satisfy the following conditions.
Condition 1: 30.gtoreq.a+b.gtoreq.2.0 Condition 2: a.gtoreq.0.05
Condition 3: b/a.gtoreq.1
[0098] In Condition 1, it is preferable that the oil adhesion rate
(a+b) of oil solution for solid-phase polymerization is 2.0 wt % or
more for suppressing fusion, and is 30 wt % or lower in case that
excessive adhesion rate might make fiber sticky to deteriorate the
handling ability. It is more preferably 4.0 wt % or more and 20 wt
% or less. Here, the oil adhesion rate (a+b) of oil solution for
solid-phase polymerization is determined by the method to be
described in Examples for fiber after applying the oil solution for
solid-phase polymerization.
[0099] In Condition 2, the adhesion rate (a) of inorganic particle
of 0.05 wt % or more can suppress fusion by inorganic particles
remarkably. The upper limit of adhesion rate (a) may be around 5 wt
% or less, from a viewpoint of uniform adhesion.
[0100] In Condition 3, it is preferable that adhesion rate (b) of
phosphate compound (B) is equal to or more than adhesion rate (a)
of inorganic particle (A), so that the adhesion between inorganic
particle (A) and fiber is suppressed while excellent washability is
exhibited remarkably as derived from generating condensed salt in
solid-phase polymerization of phosphate compound (B).
[0101] Here, adhesion rate (a) of inorganic particle (A) and
adhesion rate (b) of phosphate compound (B) are calculated by the
following formula.
(Adhesion rate (a) of inorganic particle
(A))=(a+b).times.Ca/(Ca+Cb)
(Adhesion rate (b) of phosphate compound
(B))=(a+b).times.Cb/(Ca+Cb)
Here, Ca indicates a concentration of inorganic particle (A) in oil
solution for solid-phase polymerization, Cb indicates a
concentration of phosphate compound (B) in oil solution for
solid-phase polymerization.
[0102] Next, the melt spun liquid crystal polyester fiber is
subject to solid-phase polymerization. The solid-phase
polymerization can increase the molecular weight to increase
strength, elastic modulus and elongation. The solid-phase
polymerization may be performed to a hank or tow of fiber (placed
on a metal net or the like) or a continuous yarn between rollers.
To simplify the apparatus and improve the productivity, it is
preferable to be performed to a package made by taking up the fiber
on a core.
[0103] When the solid-phase polymerization is performed to the
package, the winding density of fiber package in solid-phase
polymerization should be important to prevent the fusion
prevention. To prevent a winding collapse, it is preferable that
the winding density is 0.01 g/cc or more. It is preferable that the
winding density is 1.0 g/cc or less, preferably 0.8 g/cc or less to
prevent the fusion-bonding. Here, the winding density is calculated
from fiber weight Wf [g] and occupied volume Vf [cc] of package
obtained from outer size of package and core bobbin size. In case
of package collapse by excessively small winding density, it is
preferable that the winding density is 0.1 g/cc or more. The
occupied volume Vf is determined by actually measuring the outer
size of package or by calculating from the outer size measured on
picture as assuming that the package is rotationally symmetric. The
Wf is determined by actually measuring the weight difference before
and after winding or by calculating from fineness and winding
length.
[0104] It is preferable to form such a package having a small
winding density when the package has been taken up in melt spinning
because the productivity for apparatus and the efficiency of
production can be improved. On the other hand, it is preferable to
make the winding density small when the package has been taken up
in melt spinning and then rolled back because the winding tension
can be small for the smaller winding density. Because the winding
density can be smaller by the smaller winding tension in the
roll-back, it is preferable that the winding tension is 0.50
cN/dtex or less, preferably 0.30 cN/dtex or less. The lower limit
of winding density may be around 0.01 cN/dtex.
[0105] To decrease the winding density, it is preferable that the
roll-back velocity is 500 m/m or less, preferably 400 m/m or less.
On the other hand, a higher roll-back velocity is advantageous for
productivity and it is preferable that the roll-back velocity is 50
m/m or more, preferably 100 m/m or more.
[0106] In order to form a stable package even with a low tension,
it is preferable that the winding formation is a taper-end winding
provided with tapered both ends. It is preferable that the taper
angle is 70.degree. or less, preferably 60.degree. or less. When
long fiber is required and the taper angle is too small to make a
large fiber package, it is preferable that the taper angle is
1.degree. or more, preferably 5.degree. or more. In the
specification, the taper angle is defined by the following
formula.
.theta. = tan - 1 ( 2 d l i - l o ) [ Formula 1 ] ##EQU00001##
[0107] .theta.: taper angle [.degree.], d: winding thickness [mm],
innermost stroke [mm], lo: outermost stroke [mm]
[0108] The winding number is also important for forming a package.
The winding number means the number of times of rotation of a
spindle during half reciprocation of a traverse. It is defined as a
product of a time for the half reciprocation of a traverse [min]
and the rotational speed of a spindle [rpm]. The greater winding
number indicates the smaller traverse angle. A smaller winding
number is advantageous for avoiding fusion-bonding because the
contact area between fibers becomes smaller while a greater winding
number makes a good shape of package by reducing the package
expansion and traverse failures at end faces. From these
viewpoints, it is preferable that the winding number is 2 or more
and 20 or less, preferably 5 or more and 15 or less.
[0109] The bobbin used for forming the fiber package may be any
type bobbin as long as it has a cylindrical shape, and it is
attached to a winder when taken up, and fiber is taken up to form a
package by rotating it. In solid-phase polymerization, although the
fiber package may be treated integrally with the bobbin, the
treatment may be carried out in a condition where only the bobbin
is taken out from the fiber package. When the treatment is carried
out in a condition where fiber is wound on the bobbin, the bobbin
should resist the temperature of solid-phase polymerization and is
preferably made of metal such as aluminum, brass, iron and
stainless steel. It is preferable that many holes are opened on the
bobbin so that by-product of polymerization is removed quickly to
perform solid-phase polymerization efficiently. When the treatment
is carried out in a condition where the bobbin is taken out from
the fiber package, it is preferable that an outer skin is attached
onto the outer layer of bobbin. To prevent fusion between fiber in
the innermost layer of package and bobbin outer layer in both
cases, it is preferable that cushion material is wound around the
outer layer of bobbin onto which liquid crystal polyester melt-spun
fiber is taken up. It is preferable that the cushion material is
made of felt comprising organic fiber or metal fiber, and has a
thickness of 0.1 mm or more and 20 mm or less. The above-described
outer skin may be replaced by the cushion material.
[0110] It is preferable that the fiber package has a yarn length
(winding amount) of 10,000 m or more and 10,000,000 m or less.
[0111] The solid-phase polymerization may be performed under
atmosphere of inert gas such as nitrogen or atmosphere of active
gas, such as air, containing oxygen, or under reduced pressure
condition. To simplify the apparatus and prevent fiber or core
material from oxidizing, it is preferable that it is performed
under nitrogen atmosphere. It is preferable that the solid-phase
polymerization is performed under atmosphere of low-humidity gas
having a dew point of -40.degree. C. or lower.
[0112] It is preferable that the maximum temperature of solid-phase
polymerization is Tm1-60.degree. C., where Tm1 [.degree. C.] is
defined as an endothermic peak temperature of the liquid crystal
polyester fiber to be subject to solid-phase polymerization. Such a
high temperature around the melting point makes it possible for the
solid-phase polymerization to progress immediately, so as to
improve the fiber strength. The Tm1 means a melting point of liquid
crystal polyester fiber and is determined by the measurement method
to be described in Examples. To prevent fusion-bonding, it is
preferable that the maximum temperature is less than Tm1 [.degree.
C.]. It is preferable that the solid-phase polymerization
temperature is increased stepwise or continuously to time, to
prevent fusion-bonding and improve time efficiency of solid-phase
polymerization. In this case, because the melting point of the
liquid crystal polyester fiber increases together with progress of
solid-phase polymerization, the solid-phase polymerization
temperature can be raised up to Tm1+100.degree. C. of the liquid
crystal polyester fiber before solid-phase polymerization process.
In this case, it is preferable that the maximum temperature during
solid-phase polymerization is Tm1-60 [.degree. C.] or more and less
than Tm1 [.degree. C.] of the fiber after solid-phase
polymerization, so that the solid-phase polymerization speed is
increased and fusion-bonding is prevented.
[0113] To sufficiently enhance the molecular weight or strength,
elastic modulus and elongation of fiber, it is preferable that the
solid-phase polymerization time is 5 hours or more, preferably 10
hours or more. On the other hand, it is preferable that the time is
100 hours or less, preferably 50 hours or less to improve
productivity because effects of enhanced strength, elastic modulus
and elongation are saturated over time.
[0114] From viewpoints of processability in the higher processing
and suppressed faults in appearance of product, it is preferable
that solid-phase polymerized fiber is washed. The fiber is washed
to remove oil solution for solid-phase polymerization to prevent
fusion-bonding, so that processability deterioration, which might
be caused by depositing the oil solution for solid-phase
polymerization on guides in a post process such as weaving process,
and fault generation, which might be caused by contaminating
depositions in products, are suppressed.
[0115] The washing method may be a method of wiping the fiber
surface with cloth or paper. In case that the solid-phase
polymerized yarn might fibrillate with kinetic load, it is
preferable to immerse the fiber in a liquid to which the oil
solution for solid-phase polymerization is soluble or dispersible.
It is more preferable that the washing is performed by blowing off
with fluid in addition to the immersing in liquid, so that the oil
solution for solid-phase polymerization expanded with liquid is
removed efficiently.
[0116] It is preferable that the washing liquid is water for
reducing environmental load. The liquid temperature should be
higher for enhancing removal efficiency and is preferably
30.degree. C. or more, preferably 40.degree. C. or more. Because
the liquid might evaporate remarkably when the liquid temperature
is too high, it is preferable that the liquid temperature is the
liquid boiling point-20.degree. C. or less, preferably the liquid
boiling point-30.degree. C. or less.
[0117] From a viewpoint of washing efficiency improvement, it is
preferable that a surfactant is added to the washing liquid. To
increase the removal rate and decrease the environmental load, it
is preferable that a surfactant is added by 0.01-1 wt %, preferably
0.1-0.5 wt %.
[0118] It is preferable that vibration or liquid flow is applied to
a liquid for washing to enhance washing efficiency. From viewpoints
of simplifying the apparatus and saving energy, it is preferable
that the liquid flow is applied to the liquid, although ultrasonic
vibration may be applied to the liquid. The liquid flow may be
applied with a nozzle or by stirring in a liquid bath. It is
preferable that it is applied with a nozzle so that the liquid is
easily circulated with the nozzle through the liquid bath.
[0119] To increase the washing load per hour, it is possible that a
hank, tow or package of fiber is immersed in the liquid. It is
preferable that the fiber running continuously is immersed in the
liquid. The method to immerse the fiber continuously may be
performed by leading the fiber with a guide or the like into the
liquid bath. To suppress fibrillation of solid-phase polymerization
caused by contact resistance to the guide, it is preferable that
both ends are provided with a slit through which fiber flows in the
bath without yarn route guide.
[0120] Fiber is unraveled from a package of solid-phase polymerized
yarn continuously fed. To suppress fibrillation in delamination of
slight fusion-bonding caused by solid-phase polymerization, it is
preferable that the yarn is unraveled in a direction
(fiber-rounding direction) perpendicular to rotation axis by
lateral-unraveling while the solid-phase polymerized package is
rotated.
[0121] Such an unraveling may be performed by a method such as
forcing the yarn to be driven at a constant rotation speed by a
motor or the like, controlling the rotation speed with a dancer
roller to regulate the unraveling speed, and drawing the yarn from
the solid-phase polymerized package placed on a free roll with a
speed-regulating roller to perform the unraveling. To remove oil
efficiently, it is preferable that a package of liquid crystal
polyester fiber is immersed in the liquid and then is unraveled as
is.
[0122] It is preferable that the fluid used to blow off is air or
water. It is particularly preferable that the fluid is air to dry
the surface of liquid polyester fiber to improve yield by
preventing contaminant deposition in a post-processing.
[0123] Next, the solid-phase polymerized fiber is heat-treated at a
temperature of the melting point+50.degree. C. or more. The melting
point is Tm1 determined by the method to be described in Examples.
Hereinafter, the melting point of fiber may be called Tm1. The
abrasion resistance greatly improves when liquid crystal polyester
fiber is heat treated at a temperature as high as Tm1+50.degree. C.
or more. The effect will become remarkable when the single fiber
fineness is small.
[0124] A rigid molecular chain like liquid crystal polyester has a
long relaxation time and inner layer also relaxes within the
relaxation time for surface layer as melting the fiber. By studying
technologies suitable for liquid crystal polyester fiber to improve
abrasion resistance, it was found that abrasion resistance of
liquid crystal polyester fiber can be improved by heating to reduce
crystallinity and crystal completeness as a whole fiber instead of
relaxation of molecular chain.
[0125] To reduce crystallinity, fiber has to be heated above the
melting point. However a thermoplastic synthetic fiber might reduce
strength and elastic modulus and cause thermal deformation and
fusion (meltdown) at such a high temperature particularly in case
of small single-fiber fineness. Such a behavior was seen with
liquid crystal polyester, however, we focused on the melting point
of liquid crystal polyester as a temperature transiting from
crystal to liquid crystal and found out that increase of molecular
weight of solid-phase polymerized liquid crystal polyester has made
relaxation time very long so that the molecular mobility of liquid
crystal is low. Therefore even with a short-time heat treatment at
a high temperature above the melting point, the crystallinity can
be reduced as keeping the orientation of molecular chains at a high
level while the strength and the elastic modulus are not greatly
deteriorated. From these facts, it was found that liquid crystal
polyester fiber having a small single-yarn fineness can be improved
in abrasion resistance by a short-time heat treatment at a high
temperature above Tm1+50.degree. C. without great loss of strength,
elastic modulus and heat resistance of liquid crystal polyester
fiber.
[0126] To lower the crystal completeness for the solid-phase
polymerized fiber, it is preferable that the heat treatment is
performed at a temperature of Tm1+60.degree. C. or more, preferably
Tm1+80.degree. C. or more, most preferably Tm1+130.degree. C. or
more. In case that excessively high treatment temperature might
increase the heat deformation of processed fiber at a high
temperature, it is preferable that the heat treatment is performed
at a temperature of Tm1+200.degree. C. or less, preferably
Tm1+180.degree. C. or less.
[0127] Although there is a case for carrying out a heat treatment
for liquid crystal polyester fiber even in a conventional
technology, it is generally carried out at a temperature of the
melting point or less because the liquid crystal polyester is
thermally deformed (fluidized) by stress even at a temperature of
the melting point or less. Even when the solid-phase polymerization
of liquid crystal polyester fiber is performed as a heat treatment,
the treatment temperature should be set below the melting point of
fiber or the fiber might be fused and melt down. In case of
solid-phase polymerization, the final temperature of solid-phase
polymerization may increase to a temperature higher than the
melting point of fiber to be treated because the melting point of
fiber may increase through the treatment. Even in this case, the
treatment temperature is lower than the melting point of fiber
being treated, that is, the melting point of fiber after the heat
treatment.
[0128] Such a high-temperature heat treatment, which doesn't mean
the solid-phase polymerization, increases abrasion resistance by
decreasing a structural difference between a dense crystal portion
formed by solid-phase polymerization and an amorphous portion,
namely by decreasing the crystallinity and crystal completeness.
Therefore even if Tm1 is varied by heat treatment, it is preferable
that the heat treatment is performed at a temperature of Tm1, which
is varied after the treatment, +50.degree. C. or more, preferably
the Tm1+60.degree. C. or more, further preferably the
Tm1+80.degree. C. or more, most preferably the Tm1+130.degree. C.
or more.
[0129] Although heat stretching of liquid crystal polyester fiber
may be included in the heat treatment, the heat stretching is a
process tensing the fiber at a high temperature, the orientation of
molecular chain in the fiber structure becomes high, the strength
and the elastic modulus increase, and the crystallinity and crystal
completion are maintained as they are, namely, high .DELTA.Hm1 is
maintained and the small peak half-value width of the melting point
is maintained. Therefore it becomes a fiber structure being
inferior in abrasion resistance and such a heat stretching should
be different from our heat treatment that aims to improve the
abrasion resistance by decreasing the crystallinity (decreasing
.DELTA.Hm1) and decreasing the crystal completion (increasing the
peak half-value width). In our high-temperature heat treatment, the
crystallinity decreases so that strength and elastic modulus do not
increase.
[0130] It is preferable that the high-temperature heat treatment is
performed as running fiber continuously, because the fusion-bonding
between fibers can be prevented and enhance the uniformity of the
treatment. To prevent fibrils from generating as achieving uniform
treatment, it is preferable that a non-contact heat treatment is
performed. The heat treatment may be performed by heating the
atmosphere or a radiation heating with a laser or an infrared ray
or the like. It is preferable that it is performed with a slit
heater having a block or a plate heater so that both advantages of
atmosphere heating and radiation heating enhance the stability for
the treatment.
[0131] The high-temperature heat treatment should be performed at a
stretch rate of 0.1% or more and less than 3.0%. In the
specification, the stretch rate is defined by the following formula
with yarn velocity (V0) before heat treatment and yarn velocity
(V1) after heat treatment. The yarn velocities before and after
heat treatment have the same meaning as the surface velocities of
roller regulating the yarn velocity before and after heat
treatment.
(Stretch rate [%])=(V1-V0).times.100/V0
[0132] The stretching and relaxing in a high-temperature heat
treatment have been described in prior art documents although that
only meant a high stretch could make fiber thinner in addition to
improvement of running stability or abrasion resistance. However,
it was found that stretching in a heat treatment contribute to
suppression of thermal deformation particularly at a high
temperature from a viewpoint of achieving both improved abrasion
resistance and suppressed thermal deformation. We assume the reason
is as follows.
[0133] The high-temperature heat treatment is carried out at a
temperature as high as the melting point+50.degree. C. or more as
described above. At this temperature, crystal portions of liquid
crystal polyester fiber melt to be amorphous (liquid crystal) with
orientation. Prior arts have aimed to disturb the orientation of
the amorphous material by heat relaxation at such a high
temperature.
[0134] It seems that the solid-phase polymerized liquid crystal
polyester fiber has a restriction point of which interaction is
strong. Such a restriction point makes it difficult to sufficiently
disturb the orientation of the amorphous material by heat
relaxation only. If the heat-treatment temperature is increased to
sufficiently disturb it, the heat relaxation is enhanced to disturb
the orientation of the amorphous material greatly, so that thermal
deformation becomes great at a high temperature. In other words, it
is difficult only by adjustment of the heat-treatment temperature
to achieve both the high abrasion resistance and suppression of
thermal deformation at a high temperature.
[0135] Therefore proper stretch is important. When the liquid
polyester in an amorphous (liquid crystal) state oriented under
high-temperature heat treatment is deformed slightly in a
longitudinal fiber axial direction, the restriction point is
destroyed while the orientation relaxation is suppressed by flow
deformation. That effect reduces interaction between liquid crystal
polyester to adjust the disturbance of orientation within a proper
range to achieve both the high abrasion resistance and suppression
of thermal deformation.
[0136] According to our assumption described above, higher
temperature and higher stretch rate could be effective. However,
the higher stretch could contribute to destroying the restriction
point greatly from 0% to 3% of stretch while the effect would be
saturated above the range. On the other hand, to make the stretch
rate higher, it is necessary to reduce resistance against
elongation deformation, namely elongation viscosity, while it is
necessary to increase heat-treatment temperature. In such a case,
thermal deformation cannot be suppressed since the effect of the
increased heat-treatment temperature surpasses the effect of
stretch.
[0137] Our invention is characterized by an advantage that the
improvement of abrasion resistance of liquid crystal polyester
fiber, which has conventionally been controlled only by
high-temperature heat-treatment temperature, can be controlled
separately with interaction increase and orientation disturbance by
a proper stretch. Such a characteristic achieve both the higher
abrasion resistance and suppression of thermal deformation.
[0138] The stretch rate should be 0.1% or more. The stretch rate of
0.1% or more can achieve the improvement of abrasion resistance. To
improve the abrasion resistance, it is preferable that the stretch
rate is as high as 0.5% or more, preferably 0.6% or more. On the
other hand, in case that excessively high stretch rate might have
too much disturbance of orientation of amorphous material to
increase thermal deformation at a high temperature, it is
preferable that the stretch rate is less than 3.0%, preferably less
than 2.5%.
[0139] It is preferable that the treatment velocity (yarn velocity)
is 100 m/min or more, preferably 200 m/min or more, further
preferably 300 m/min or more, so that the short-time processing can
be achieved at a high temperature while the abrasion resistance and
productivity are improved although depending on treatment length.
The upper limit of processing velocity may be around 1,000 m/min
from a viewpoint of running stability of fiber.
[0140] It is preferable that the treatment length (heater length)
is 100 mm or more, preferably 500 mm or more, from a viewpoint of
uniform processing in a case of non-contact heating although
depending on heating method. It is preferable that it is 3,000 mm
or less, preferably 2,000 mm or less, in case that too long
treatment length might cause non-uniform processing and fiber
meltdown by yarn sway inside a heater.
[0141] It is preferable that the fiber which has been heat treated
at a high temperature is taken up under a yarn route regulation
with yarn route guide in a range of 1 cm or more and 50 cm or less
from the fiber heating region.
[0142] We found in a long-run evaluation that when a proper stretch
is performed to slightly extend the fiber in heat treatment,
fluctuation of stretch point might cause a longitudinal unevenness
of fiber and yarn breakage. We assume that the stretch point
fluctuates because the tension is small enough to cause the yarn
sway in the heat treatment at a temperature as high as the melting
point+50.degree. C. or more. If the stretch rate were 0%, the fiber
wouldn't be extended at all and a possible yarn sway wouldn't cause
the yarn breakage. It seems that the stretch causes the effect of
yarn sway.
[0143] Therefore the regulation using the guide to reduce yarn sway
is effective. The liquid crystal polyester fiber before the
high-temperature heat treatment can be fibrillated by scratch while
the one after the heat treatment cannot be fibrillated by scratch
at a low tension since it already has an abrasion resistance
enhanced.
[0144] It is preferable that the yarn route guide is provided in a
position range of 1 cm or more and 50 cm or less from the heating
region. Since the fiber is cooled (air-cooled) after exiting the
heating region, it deforms slightly as being cooled even after
exiting the heating region. The effect of yarn sway is greatest in
this region, and it is preferable that the position range is 1 cm
or more and 50 cm or less as a cooling region, preferably 1 cm or
more and 20 cm or less.
[0145] It is preferable that one or more guides are provided. It is
preferable that three or less guides are provided because too many
guides might increase frequency of scratch to increase the
possibility of fibrillation. It is also preferable that a fiber is
fed among a plurality of guides arranged in a fiber running
direction. In this case the position of provision means a position
of guides closest to the heater.
[0146] The guide may be made of general material such as ceramic
and metal. To reduce damage to liquid crystal polyester fiber, it
is preferable that it has a metal surface plated with hard chrome.
To keep a proper coefficient of friction not to damage fiber, it is
preferable that the surface roughness is 2 to 8, preferably 2 to 4
in terms of Rzjis determined by the method of JIS B0601:2001.
[0147] When the fiber contacts the guide, the running tension ratio
before and after the guide should not be too high to reduce damage
to fiber. It is preferable that a ratio of T2/T1 is 1.0 or more and
2.0 or less, where the running tension (T2) is a tension in a
region closer to the winding side than the guide, and the running
tension (T1) is a tension in a region closer to the heating
region.
[0148] In the last, a fiber structural change in high-temperature
heat treatment will be explained from a viewpoint of difference in
fiber characteristics before and after processing.
[0149] Such a heat treatment means a short-time heat treatment at a
high temperature no less than the melting point (crystal-liquid
crystal transition temperature) of liquid polyester fiber, where
the crystallinity decreases but the orientation slightly relaxes.
Such a fact is shown in such a structural change that .DELTA.Hm1
decreases and half-value width at Tm1 increases while .DELTA.n
doesn't change almost at all by the heat treatment. The processing
time is too short to change the molecular weight. Reduced
crystallinity generally causes a great reduction of mechanical
characteristics. Although the strength and elastic modulus decrease
without increasing in our heat treatment, the strength and elastic
modulus are kept at a high level as maintaining high melting point
(Tm1) and heat resistance to maintain the high molecular weight and
orientation. The peak temperature of tan .delta. becomes high by
high-temperature heat treatment and the peak value rises. The
crystallinity is decreased by the heat treatment, so that the peak
value rises and abrasion resistance improves. The peak temperature
becomes high as a result that peaks of amorphous material are
increased by crystal melting. Namely, the abrasion resistance is
low, because the peak temperature is low and the crystallinity is
high in a condition of performing no heat treatment at a high
temperature.
EXAMPLES
[0150] Herein after, our invention will be explained with Examples.
Each characteristic value has been determined by the following
method.
[0151] A. Heat Characteristics (Tm1, Tm2, Tm1 Peak Half-Value
Width, .DELTA.Hm1, .DELTA.Hm2)
[0152] Differential calorimetry is carried out by DSC 2920 made by
TA Instruments Corporation to determine temperature of endothermic
peak temperature Tm1 [.degree. C.] under the condition of heating
from 50.degree. C. at temperature elevation rate of 20.degree.
C./min so that the heat of melting .DELTA.Hm1 [Jig] at Tm1 is
determined. Maintaining temperature of Tm1+20.degree. C. for five
minutes after determination of Tm1, cooling is carried out down to
50.degree. C. and then endothermic peak temperature Tm2 is
determined under the condition of heating again at temperature
elevation rate of 20.degree. C./min so that the heat of melting
(.DELTA.Hm2) [J/g] at Tm2 is determined. Fibers and resins are
subject to the same measurement. Thus determined Tm2 is regarded as
a melting point for the measurement of resins.
[0153] B. Weight Average Molecular Weight in Terms of Polystyrene
(Molecular Weight)
[0154] Using a mixed solvent of pentafluoro phenol/chloroform=35/65
(weight ratio) as solvent, a sample for GPC measurement is prepared
by dissolving to make the liquid crystal polyester have a
concentration of 0.04 to 0.08 weight/volume %. When insoluble
substance remains even after leaving at room temperature for 24
hours, the sample is left for additional 24 hours to collect the
supernatant as a measurement sample. The sample is subject to a
measurement using a GPC measurement apparatus made by Waters
Corporation to determine weight average molecular weight (Mw) in
terms of polystyrene.
Column: Shodex K-806M; two pieces, K-802; one piece Detector:
Differential refractive index detector RI
Temperature: 23.+-.2.degree. C.
[0155] Flow rate: 0.8 mL/min Injection amount: 200 .mu.L
[0156] C. Total Fineness, Single Fiber Fineness
[0157] A hank of fiber of 100 m is sampled with a sizing reel and
then the weight [g] is multiplied at 1,000 times so that 3 times of
measurements are carried out per 1 level to calculate an average
value as a fiber fineness [dtex]. The calculation result is divided
by the filament number to obtain a quotient as single fiber
fineness [dtex].
[0158] D. Strength, Elongation, Elastic Modulus, Strength
Fluctuation
[0159] Based on the method described in JIS L1013:2010 in condition
of sample length 100 mm and tensile velocity 50 mm/min, 10 times of
measurements per 1 level are carried out using Tensilon UCT-100
produced by Orientech Corporation to calculate an average value as
strength [cN], elongation [%] and elastic modulus [cN/dtex]. Here,
the elastic modulus means an initial tensile resistance degree. The
strength fluctuation is calculated by the following formula using
the greater absolute values of difference between the maximum or
minimum value and the average value of 10 times of strength
measurements.
Strength fluctuation [%]={(|maximum or minimum value-average
value|/average value).times.100}
[0160] E. Birefringence Index (.DELTA.n)
[0161] Using a polarization microscope (BH-2 made by Olympus
Corporation), 5 times of measurements are carried out per 1 level
of sample by the compensator method to calculate an average
value.
[0162] F. Loss Tangent (tan .delta.)
[0163] The peak temperature and peak value of loss tangent (tan
.delta.) are determined by measuring the dynamic viscoelasticity
from 60.degree. C. to 210.degree. C. with VIBRON DDV-II-EP made by
Orientec Corporation under condition of frequency 110 Hz, initial
load 0.13 cN/dtex, temperature elevation rate 3.degree. C./m. When
any peaks are not clearly observed, the maximum value of tan
.delta. is regarded as a peak value and its temperature is regarded
as a peak temperature in temperature elevation measurement. Namely,
60.degree. C. or 210.degree. C. is a peak temperature when no peak
is clearly observed. When a plurality of peaks are observed, the
maximum value is regarded as a peak value. When the peak top value
continues for a certain range of temperature, the average value of
the temperature is regarded as a peak temperature.
[0164] G. Oil Adhesion Rate to Fiber Weight
[0165] A sample of 100 mg or more of fibers is dried at 60.degree.
C. for 10 min and its dry weight (W0) is measured. The fiber is
immersed in 2.0 wt % sodium dodecyl benzene sulphonic acid solution
containing water of which weight is as 100 times or more as the
fiber weight, and then subject to ultrasonic cleaning at room
temperature for 20 min. The cleaned fiber is washed with water and
dried at 60.degree. C. for 10 min and its dry weight (W1) is
measured. The oil adhesion rate is calculated by the following
formula.
(Adhesion rate [wt %])=(W0-W1).times.100/W1
[0166] H. Abrasion Resistance C
[0167] Fiber applied with load of 1.23 cN/dtex is hung vertically.
A ceramic rod guide (made by Yuasa Itomichi Kogyo Corporation,
Material; YM-99C) having diameter of 4 mm is pushed onto the fiber
at a contact angle of 2.7.degree. in a direction perpendicular to
the fiber. The fiber is scratched by the guide in a fiber axial
direction at stroke length of 30 mm and stroke speed of 600
times/min and is observed with a stereo microscope every 30 sec.
The time period, until white powder or fibril is observed on the
rod guide or the fiber surface, is measured to determine the
abrasion resistance C by averaging the 5 times of measurement
results except for maximum and minimum values among 7 times of
measurements. When neither the white power nor the fibril is
observed after scratching for 360 sec, the time period is regarded
as 360 sec.
[0168] I. Thermal Deformation at High Temperature (Dry-Heat
Dimensional Change Rate)
[0169] The dry-heat hank dimensional change rate determined
according to the method described in JIS L1013:2010 is regarded as
a thermal deformation at high temperature. The measurement
condition is such that load of 3.0 cN/dtex is applied to measure a
hank length while the treatment is carried out at 150.degree. C.
for 5 min. The load is the same as the one to be subject to the
dry-heat treatment. The thermal deformation is calculated by the
following formula.
(Thermal deformation rate [%])=(L1-L0).times.100/L0
L0: hank length [cm] before dry-heat treatment L1: hank length [cm]
after dry-heat treatment
[0170] J. Yarn Breakage in Heat-Treatment Process
[0171] From the number of yarn-breakage times and the treated fiber
length in the heat-treatment process, the yarn-breakage times per
1,000,000 m is calculated by the following formula. The treated
fiber length is length corresponding to one solid-phase
polymerization package in Examples 1-8 and Comparative Examples 1-6
while the length is 5,000,000 m in Examples 9-11 and Reference
Example 3.
(Yarn breakage [times/1,000,000 m]=(the number of yarn-breakage
[times].times.100/(treated fiber length [10,000 m])
[0172] L. Yarn-Making Property
[0173] The number of yarn-breakage times is measured when 500,000 m
of fiber is wound in melt spinning process to determine the
yarn-making property according to the following standard. Since the
less the yarn breakage is the better the yarn-making property is,
it is industrially preferable that the number of yarn breakage
times is 2 or less.
.circle-solid. (Excellent): 0 times .smallcircle. (Good): 1-2 times
.DELTA. (Acceptable): 3-4 times x (Bad): 5 times or more
Reference Example 1
[0174] p-hydroxy benzoic acid of 870 parts by weight,
4,4'-dihydroxy biphenyl of 327 parts by weight, hydroquinone of 89
parts by weight, terephthalic acid of 292 parts by weight,
isophthalic acid of 157 parts by weight and acetic anhydride of
1,460 parts by weight (1.10 equivalent of the sum of phenolic
hydride group) were mixed in a reaction vessel of 5 L with an
agitating blade and a distillation tube, and after temperature was
elevated from room temperature to 145.degree. C. by 30 min while
agitated under nitrogen gas atmosphere, it was reacted at
145.degree. C. for 2 hours. Thereafter, the temperature was
elevated to 335.degree. C. by 4 hours. The polymerization
temperature was kept at 335.degree. C., the pressure was reduced
down to 133 Pa for 1.5 hours, and further the reaction was
continued for 40 min, and at the time when the torque reached 28
kgcm, the condensation polymerization was completed. Next, inside
of the reaction vessel was pressurized at 0.1 MPa, the polymer was
discharged as strand-like material through a spinneret having one
circular discharge port having diameter of 10 mm, and it was
pelletized by a cutter. Composition of thus obtained liquid crystal
polyester, melting point and molecular weight are shown in Table
1.
Reference Example 2
[0175] p-hydroxy benzoic acid of 907 parts by weight,
6-hydroxy-2-naphthoic acid of 457 parts by weight and acetic
anhydride of 946 parts by weight (1.03 mol equivalent of the sum of
phenolic hydride group) were mixed in a reaction vessel with an
agitating blade and a distillation tube, and after temperature was
elevated from room temperature to 145.degree. C. by 30 min while
agitated under nitrogen gas atmosphere, it was reacted at
145.degree. C. for 2 hours. Thereafter, the temperature was
elevated to 325.degree. C. by 4 hours. The polymerization
temperature was kept at 325.degree. C., the pressure was reduced
down to 133 Pa by 1.5 hours, and further the reaction was continued
for 20 min, and at the time when the torque reached a predetermined
level, the condensation polymerization was completed. Next, inside
of the reaction vessel was pressurized at 0.1 MPa, the polymer was
discharged as strand-like material through a spinneret having one
circular discharge port with diameter of 10 mm, and it was
pelletized by a cutter. Composition of thus obtained liquid crystal
polyester, melting point and molecular weight are shown in Table
1.
TABLE-US-00001 TABLE 1 Reference Reference Example 1 Example 2
p-hydroxybenzoate unit mol % 54 73 4,4'-dihydroxy biphenyl unit mol
% 16 0 Hydroquinone unit mol % 7 0 Terephthalic acid unit mol % 15
0 Isophthalic acid unit mol % 8 0 6-hydroxy-2-naphthoic acid unit
mol % 0 27 Liquid crystal Melting point .degree. C. 320 283
polyester Weight average .times.10,000 10.4 23.0 properties
molecular weight
Example 1
[0176] Using the liquid crystal polyester of Reference Example 1,
after vacuum drying was carried out at 160.degree. C. for 12 hours,
it was melt extruded by a single-screw extruder of .phi.15 mm made
by Osaka Seiki Kosaku Corporation, and the polymer was supplied to
a spinning pack while metered by a gear pump. In the spinning pack,
the polymer was filtered using a metal nonwoven fabric filter, and
the polymer was discharged in the condition shown in Table 2. The
introduction hole positioned right above the hole of the spinneret
is straight shaped hole while the introduction hole and the
spinneret hole are connected with a tapered portion. The discharged
polymer was cooled and solidified from the outer side of the yarn
by an annular cooling air wind after passing through the heat
retention region of 40 mm, and thereafter, a spinning oil solution
primarily constituting fatty acid ester compound was added, and all
filaments were wound to the first godet roll at a spinning velocity
shown in Table 2. After this was passed through the second godet
roll at the same velocity, all filaments except for one were sucked
by a suction gun, and the remaining one filament having the
filament number 1 was taken up into a pirn form via a dancer arm
using a pirn winder (EFT type take-up winder produced by Kamitsu
Seisakusho Corporation, no contact roller contacting with a take-up
package). During the take-up of 500,000 m, yarn breakage didn't
occur and the yarn-making property was good. Spun yarn properties
are shown in Table 2. Besides, no peak was clearly observed while
tan .delta. monotonically increased with temperature elevation in
the measurement with raw yarn of spinning. Therefore, the peak
temperature defined in the specification was 210.degree. C. and the
peak value was 0.067.
TABLE-US-00002 TABLE 2 Example 1 Example 4 Example 5 Example 7
Example 8 Liquid crystal polyester polymer Reference Reference
Reference Reference Reference Example 1 Example 1 Example 1 Example
1 Example 2 Melt Spinning temperature .degree. C. 345 345 345 345
325 spinning Discharge rate g/min 2.4 3.1 1.9 3.3 1.4 conditions
Spinneret opening mm 0.13 0.13 0.13 0.13 0.20 diameter Land length
mm 0.26 0.26 0.26 0.26 0.30 L/D -- 2.0 2.0 2.0 2.0 1.5 Opening
number units 4 4 4 5 4 Yarn velocity m/min 1000 600 1200 1500 600
Yarn draft -- 27 12 40 36 63 Spinnability --
.circle-solid.(Excellent) .circle-solid.(Excellent)
.largecircle.(Good) .largecircle.(Good) .largecircle.(Good) Spun
yarn Weight average .times.10,000 10.2 10.2 10.2 10.0 8.8
properties molecular weight Total fineness dtex 6.0 13.0 4.0 22.0
6.0 Filament number pieces 1 1 1 5 1 Single fiber fineness dtex 6.0
13.0 4.0 4.4 6.0 Tm1 .degree. C. 299 298 300 300 285 Strength
cN/dtex 6.4 6.1 6.2 6.6 8.7 Elongation % 1.5 1.5 1.4 1.4 2.1
Elastic modulus cN/dtex 531 514 545 588 547
[0177] The fiber was rolled back from this spun fiber package by
SSP-MV type rewinder (contact length of 200 mm, the number of
winding of 8.7, taper angle of 45.degree.) made by Kamitsu
Seisakusho Corporation. The spun fiber was unraveled in a vertical
direction (direction perpendicular to the fiber-rounding
direction). Without using a speed-regulating roller, oil solution
for solid-phase polymerization was supplied by an oiling roller
having a stainless-steel roll with satin-finished surface. The oil
solution for solid-phase polymerization employed was 6.0 wt %
phosphate compound (B) of phosphate compound (B1) shown in Chemical
formula (4) in which 1.0 wt % inorganic particle (A) of talc
SG-2000 (made by NIPPON TALC Co., Ltd.) was dispersed.
##STR00003##
[0178] Kevlar felt (areal weight: 280 g/m2, thickness: 1.5 mm)
rolled on a stainless-steel bobbin with holes was used as a core
member for the roll-back while the surface pressure was set to 100
gf. The oil adhesion rate to the rolled-back fiber of oil solution
for solid-phase polymerization as well as roll-back conditions are
shown in Table 3. Next, the stainless-steel bobbin with holes was
detached from the rolled-back package, solid-phase polymerization
was carried out in a condition of package where the fiber was taken
up on the Kevlar felt. The solid-phase polymerization was carried
out with a closed type oven to elevate temperature from room
temperature to 240.degree. C. by about 30 min and then keep the
temperature at 240.degree. C. for 3 hours. Again, the temperature
is elevated to the highest temperature shown in Table 3 by
4.degree. C./hour and kept the retention time shown in Table 3. In
the atmosphere of oven, dehumidified nitrogen was supplied at a
flow rate of 20 NL/min and discharged from an exhaust port to
prevent the inner pressure from becoming too high. Fiber properties
after solid-phase polymerization are shown in Table 3. The abrasion
resistance was poor since abrasion resistance C of fiber after
solid-phase polymerization was 30 sec only.
TABLE-US-00003 TABLE 3 Example 1 Example 4 Example 5 Example 7
Example 8 Roll-back Roll-back velocity m/min 400 400 400 400 400
condition Winding tension cN/dtex 0.16 0.10 0.30 0.10 0.16 Winding
density g/cc 0.5 0.3 0.6 0.3 0.5 Winding quantity .times.10,000 [m]
50.0 25.0 10.0 10.0 10.0 Oil adhesion rate (a + b) of oil wt % 15.0
12.2 18.6 20.0 15.2 solution for solid-phase polymerization
Solid-phase Highest temperature .degree. C. 290 290 290 290 290
polymerization Retention time to reach hr 20 20 20 20 20 highest
temperature Fiber properties Weight average molecular weight
.times.10,000 39.6 38.2 41.2 40.8 37.0 after solid-phase Total
fineness dtex 7 14 4 24 6 polymerization Filament number pieces 1 1
1 5 1 Single fiber fineness dtex 6.5 13.9 4.3 4.8 6.5 Strength
cN/dtex 22.6 20.1 21.7 21.3 21.1 Elongation % 2.8 2.6 2.6 2.6 3.1
Elastic modulus cN/dtex 988 952 1072 1014 820 Tm1 .degree. C. 332
332 334 333 318 .DELTA.Hm1 J/g 9.0 8.6 10.2 9.2 11.4 Peak
half-value width at Tm1 .degree. C. 10 12 8 10 7 Tm2 .degree. C.
333 332 334 331 316 .DELTA.Hm2 J/g 1.2 1.2 1.1 1.1 0.9 Oil adhesion
per fiber weight wt % 7.8 7.0 8.2 9.0 7.5
[0179] Finally, fiber was unraveled from the package after
solid-phase polymerization and successively subject to a
high-temperature non-contact heat treatment. The package after
solid-phase polymerization was attached to a free roll creel
(having a shaft and bearings to freely rotate outer layer, without
brakes and drive sources) and therefrom the yarn was drawn out in a
lateral direction (fiber-rounding direction). Successively the
fiber was dipped in a bath (with no guides to contact fiber inside)
of bath length of 150 cm (contact length of 150 cm) provided with
slits at both ends to remove oil solution by washing. The washing
liquid containing 0.2 wt % nonionic-anionic surfactant (Gran Up
US-30 made by Sanyo Chemical Industries Corporation) controlled at
50.degree. C. with an external tank was supplied into a tank by a
pump. The liquid was supplied into the tank through a pipe having
holes provided at intervals of 5 cm in the tank to generate a
liquid flow through the pipe in the tank. The washing liquid
overflowed from slits and holes for adjusting liquid level was
returned to the external tank in a certain mechanism.
[0180] Successively the fiber was dipped in a bath (with no guides
to contact fiber inside) of bath length of 23 cm (contact length of
23 cm) provided with slits at both ends to be rinsed with water at
50.degree. C. The washed fiber was passed through a bearing roller
guide and was contacted to air flow to blow off the water to be
removed, and then was passed through the first roller having a
separate roller at 200 m/min. The creel is a free roll, to which
tension is applied to unravel the solid-phase polymerized package
to feed the fiber.
[0181] The fiber which had passed through the roller was fed
between heated slit heaters and was subject to high-temperature
heat treatment under the conditions shown in Table 4. The slit
heaters were not provided with guides inside while the heater
didn't contact the fiber. The fiber which had passed through the
heater was passed through the second roller having a separate
roller. The yarn velocity before heat treatment represents a
surface velocity of the first roller while the yarn velocity after
heat treatment represents a surface velocity of the second roller.
A finishing oil solution primarily consisting of fatty acid
polyester compound is added to the fiber which had passed through
the second roller as using an oiling roller made of ceramic, and
was taken up into a pirn form with EFT type bobbin traverse winder
(made by Kamitsu Seisakusho Corporation). Fiber properties after
high-temperature heat treatment are shown in Table 4. An of the
liquid crystal polyester fiber was 0.35 representing a high
orientation.
[0182] Because the fiber obtained in Example 1 achieved both high
abrasion resistance and low thermal deformation rate, it is
expected that processability could be improved at a higher
processing, faults could be reduced and thermal deformation could
be suppressed in processing at a high temperature.
TABLE-US-00004 TABLE 4 Compar- Compar- Compar- Compar- ative ative
ative ative Example 1 Example 1 Example 2 Example 3 Example 2
Example 3 Example 4 Example 4 Fiber after solid-phase
polymerization Example 1 Example 1 Example 1 Example 1 Example 1
Example 1 Example 1 Example 4 High-temperature Heater temperature
.degree. C. 480 480 480 510 480 480 480 500 heat treatment Heater
length mm 1000 1000 1000 1000 1000 1000 1000 1000 Yarn velocity
before m/min 198 200 190 190 199 195 193 198 heat-treatment Yarn
velocity after m/min 200 200 200 200 200 200 200 200 heat-treatment
Stretch rate % 1.0 0.0 5.0 5.0 0.5 2.5 3.5 1.0 Treatment time sec
0.30 0.30 0.30 0.30 0.30 0.30 0.30 0.30 Running tension gf 0.5 0.3
1.8 0.3 0.4 0.9 1.2 0.5 Running stress cN/dtex 0.08 0.05 0.30 0.05
0.06 0.14 0.20 0.08 Yarn breakage times/ 0 12 50 16 0 10 20 0
million meters Fiber properties Weight average .times.10,000 39.3
39.2 Sampling 39.2 39.3 39.2 39.2 38.0 after high- molecular weight
impossible temperature Total fineness dtex 6.0 6.0 6.0 6.0 6.0 6.0
12.9 heat treatment Filament number pieces 1 1 1 1 1 1 1 Single
fiber fineness dtex 6.0 6.0 6.0 6.1 6.1 6.1 12.9 Strength cN/dtex
18.8 17.9 17.8 18.4 19.2 19.3 17.1 Elongation % 2.9 2.9 3.0 2.9 2.8
2.8 2.8 Elastic modulus cN/dtex 785 745 738 761 832 851 709 Tm1
.degree. C. 323 322 322 323 323 320 322 .DELTA.Hm1 J/g 0.8 0.6 0.6
0.7 1.5 5.1 0.6 Peak half-value .degree. C. 25 31 35 28 21 15 33
width at Tm1 Tm2 .degree. C. 333 333 334 333 333 333 333 .DELTA.Hm2
J/g 1.1 1.0 1.0 1.1 1.1 1.2 1.1 Abrasion resistance sec 360 360 360
360 180 48 240 tan .delta. peak value -- 0.077 0.091 0.092 0.085
0.065 0.059 0.072 tan .delta. peak temperature .degree. C. 143 145
145 144 142 139 143 Oil adhesion per fiber wt % 0.8 0.8 0.8 0.8 0.8
0.8 0.6 weight Thermal deformation % 0.4 1.1 1.2 0.7 0.3 0.2 0.5
rate at high temperature Compar- Compar- ative ative Example 5
Example 6 Example 7 Example 8 Example 5 Example 6 Fiber after
solid-phase polymerization Example 5 Example 1 Example 7 Example 8
Example 1 Example 8 High-temperature Heater temperature .degree. C.
460 500 520 480 No heat- No heat- heat treatment Heater length mm
1000 1000 1000 1000 treatment treatment Yarn velocity before m/min
198 396 199 198 carried out carried out heat-treatment Yarn
velocity after m/min 200 400 200 200 heat-treatment Stretch rate %
1.0 1.0 0.5 1.0 Treatment time sec 0.30 0.15 0.13 0.30 Running
tension gf 0.4 0.7 0.8 0.5 Running stress cN/dtex 0.03 0.11 0.08
0.08 Yarn breakage times/ 10 0 10 10 million meters Fiber
properties Weight average .times.10,000 40.8 39.2 40.1 37.1 39.6
36.9 after high- molecular weight temperature Total fineness dtex
4.0 6.0 21.8 6.8 6.0 6.0 heat treatment Filament number pieces 1 1
5 1 1 1 Single fiber fineness dtex 4.0 6.0 4.4 6.8 6.0 6.0 Strength
cN/dtex 18.0 18.6 16.3 18.5 21.1 20.1 Elongation % 2.8 2.9 2.6 3.0
2.7 3.0 Elastic modulus cN/dtex 765 764 704 749 905 767 Tm1
.degree. C. 322 322 323 306 332 318 .DELTA.Hm1 J/g 0.7 0.8 0.7 5.8
9.0 11.4 Peak half-value .degree. C. 26 26 27 16 10 7 width at Tm1
Tm2 .degree. C. 334 333 332 318 333 316 .DELTA.Hm2 J/g 0.9 1.2 1.1
0.9 1.2 0.9 Abrasion resistance sec 120 240 240 60 30 30 tan
.delta. peak value -- 0.077 0.075 0.080 0.085 0.041 0.064 tan
.delta. peak temperature .degree. C. 144 144 145 110 120 65 Oil
adhesion per fiber wt % 1.0 1.0 1.6 0.9 0.9 0.9 weight Thermal
deformation % 0.6 0.5 0.8 0.3 0.1 0.1 rate at high temperature
Comparative Examples 1-4, Examples 2 and 3
[0183] The effect of stretch rate in a high-temperature heat
treatment was evaluated. The solid-phase polymerized yarn obtained
in Example 1 was heat treated at a high temperature by the same
method as Example 1 except that the heat-treatment temperature and
stretch rate were changed according to Table 4. The stretch rate
was 5.0% in Comparative Example 2, in which the yarn breakage
occurred right after the heat treatment. The yarn breakage occurred
twice during the treatment of 40,000 m to cancel the test because a
sample of 30,000 m or more was not obtained. Properties of obtained
fiber are shown in Table 4. The table shows that obtained fiber can
achieve both excellent abrasion resistance and low thermal
deformation rate with less yarn breakage when the stretch rate is
0.1% or more and less than 3.0%. The stretch rate was low in
Comparative Example 1, in which relatively many times of yarn
breakage occurred in heat treatment while the tan .delta. peak
value and thermal deformation rate were high. The stretch rate was
5.0% in Comparative Example 3, in which the tan .delta. peak value
increased and thermal deformation rate was high because the
temperature was increased to suppress yarn breakage. The stretch
rate was high in Comparative Example 4, in which the abrasion
resistance was poor in spite of low tan .delta. peak value.
Examples 4 and 5
[0184] The effect of single fiber fineness was evaluated. The melt
spinning was carried out by the same method as Example 1 except
that the discharge rate and spinning velocity were changed
according to Table 2. The single fiber fineness was small in
Example 5, in which the yarn breakage occurred once although
spinnability was good. Properties of obtained fiber are shown in
Table 2. Next, the solid-phase polymerization was carried out by
the same roll-back method as Example 1, except that the winding
condition (quantity, tension and density) were changed according to
Table 3. Properties of obtained fiber after solid-phase
polymerization are shown in Table 3. The high-temperature heat
treatment was carried out by the same method as Example 1, except
that the heat-treatment temperature was changed according to Table
4. The single fiber fineness was small in Example 5, in which the
yarn breakage occurred once during the treatment of 100,000 m
although processability had almost no problem. Properties of
obtained fiber are shown in Table 4. The table shows that obtained
fiber can achieve both excellent abrasion resistance and low
thermal deformation rate even under various single fiber fineness
when the stretch rate is 0.1% or more and less than 3.0% under
controlled heat-treatment temperature.
Example 6
[0185] The effect of heat-treatment velocity was evaluated. The
solid-phase polymerized yarn obtained in Example 1 was heat treated
at a high temperature by the same method as Example 1, except that
the heat-treatment temperature and stretch rate were changed
according to Table 4. Properties of obtained fiber are shown in
Table 4. The table shows that obtained fiber can achieve both
excellent abrasion resistance and low thermal deformation rate with
less yarn breakage even under various velocities of treatment when
the stretch rate is 0.1% or more and less than 3.0% under
controlled heat-treatment temperature.
Example 7
[0186] The effect of the number of filaments was evaluated. The
melt spinning was carried out by the same method as Example 1,
except that the discharge rate, spinneret opening number and
spinning velocity were changed according to Table 2 while
discharged filaments were converged to make a multifilament. The
yarn breakage occurred once although spinnability had no problem.
Properties of obtained fiber are shown in Table 2. Next, the
solid-phase polymerization was carried out by the same roll-back
method as Example 1 except that the winding quantity was changed
according to Table 3. Properties of obtained fiber after
solid-phase polymerization are shown in Table 3. The
high-temperature heat treatment was carried out by the same method
as Example 1, except that the heat-treatment temperature and
stretch rate were changed according to Table 4. The yarn breakage
occurred once during the treatment of 100,000 m although
processability had almost no problem. Properties of obtained fiber
are shown in Table 4. The table shows that obtained fiber can
achieve both excellent abrasion resistance and low thermal
deformation rate even with multifilament when the stretch rate is
0.1% or more and less than 3.0% under controlled heat-treatment
temperature.
Example 8
[0187] The effect of polymer composition was evaluated. The polymer
obtained in Reference Example 2 was melt spun by the same method as
Example 1, except that the spinneret opening number, land length,
discharge rate and spinning velocity were changed according to
Table 2. The yarn breakage occurred once although spinnability had
no problem. Properties of obtained fiber are shown in Table 2.
Next, the solid-phase polymerization was carried out by the same
roll-back method as Example 1, except that the winding quantity was
changed according to Table 3. Properties of obtained fiber after
solid-phase polymerization are shown in Table 3. Next, the
high-temperature heat treatment was carried out by the same method
as Example 1. The yarn breakage occurred once during the treatment
of 100,000 m although processability had almost no problem.
Properties of obtained fiber are shown in Table 4. The table shows
that obtained fiber can achieve both good abrasion resistance and
low thermal deformation rate even under various composition when
the stretch rate is 0.1% or more and less than 3.0% under
controlled heat-treatment temperature.
Comparative Examples 5 and 6
[0188] The effect of high-temperature heat treatment was evaluated.
Using the solid-phase polymerized yarn obtained in Examples 1 and
8, the fiber was fed and taken up by the same heat-treatment method
as Examples 1 and 8, except that the rollers before and after the
heater were run at 200 m/min at room temperature while the heater
was not operated. Namely, the solid-phase polymerized fiber was
unraveled and washed to be rolled back without heat treatment.
Properties of obtained fiber are shown in Table 4. The table shows
that the high-temperature heat treatment was not carried out to
make the abrasion resistance low although thermal deformation rate
was low. The table also shows that both good abrasion resistance
and low thermal deformation rate cannot be achieved in a case such
as Comparative Example 5 in which the tan .delta. peak value was
low and Comparative Example 6 in which the peak temperature was
low.
Example 9, Reference Example 3
[0189] The effect of providing a guide at the exit of heating
region was determined through a long-run evaluation. Namely, the
solid-phase polymerized yarn of 5,000,000 m was subject to
high-temperature heat treatment to evaluate the yarn breakage in
particular. Using the solid-phase polymerized yarn obtained in
Example 1, the high-temperature heat treatment was carried out by
the same method as Example 1, except that two pieces of hard
chrome-plated satin-finished metal rod guides (made by Yuasa
Itomichi Kogyo Corporation, Rzjis=2-4) having diameter of 3.8 mm
were provided at the exit of heater for heat treatment according to
Table 5. The treatment length was 5,000,000 m corresponding to 10
pieces of solid-phase polymerized yarn (Example 9). The
high-temperature heat treatment of 5,000,000 m was carried out
under the same condition as Example 1 without providing a guide
(Reference Example 3). Reference example 3 and Example 1 have a
difference of treatment length only. Properties of obtained fiber
are shown in Table 5. The table shows that Example 9 is excellent
in running stability with less yarn breakage relative to Reference
Example 3. The properties show small strength fluctuation rates
representing less fluctuation. We presume the stable treatment
contributed to a smaller variation in the example because the
strength, elongation and elastic modulus were slightly higher than
Reference Example 3. Thus provided guide at the exit of heating
region can regulate the yarn route to suppress yarn breakage.
TABLE-US-00005 TABLE 5 Reference Example 9 Example 3 Example 10
Example 11 Fiber after solid-phase polymerization Example 1 Example
1 Example 1 Example 1 High-temperature Heater temperature .degree.
C. 480 480 480 480 heat treatment Heater length mm 1000 1000 1000
1000 Yarn velocity before m/min 198 198 195 195 heat treatment Yarn
velocity after m/min 200 200 200 200 heat treatment Stretch rate %
1.0 1.0 2.5 2.5 Treatment time sec 0.30 0.30 0.30 0.30 Guide
setting position cm 5 No guide 3 50 Running tension at gf 0.4 --
Unmeasurable 0.9 heating region side (T1) Running tension at gf 0.5
0.5 0.9 0.9 rewind side (T2) T2/T1 -- 1.25 -- -- 1.00 Yarn breakage
caused by times/ 0.2 0.8 2.2 8.0 heat treatment of million
5,000,000 m meters Fiber properties after Weight average
.times.10,000 39.3 39.3 39.2 39.2 high-temperature molecular weight
heat treatment Total fineness dtex 6.0 6.0 6.0 6.0 Filament number
pieces 1 1 1 1 Single fiber fineness dtex 6.0 6.0 6.1 6.1 Strength
cN/dtex 18.9 18.6 19.3 19.1 Strength variation rate % 4 8 5 5
Elongation % 2.9 2.8 2.9 2.8 Elastic modulus cN/dtex 788 776 851
816 Tm1 .degree. C. 322 323 324 323 .DELTA.Hm1 J/g 0.7 0.8 1.5 1.5
Peak half-value width .degree. C. 26 25 22 21 at Tm1 Tm2 .degree.
C. 332 333 333 333 .DELTA.Hm2 J/g 1.1 1.1 1.1 1.1 Abrasion
resistance sec 360 360 198 180 tan .delta. peak value -- 0.078
0.077 0.067 0.065 tan .delta. peak temperature .degree. C. 144 143
143 142 Oil adhesion per wt % 0.8 0.8 0.8 0.8 fiber weight Thermal
deformation % 0.4 0.4 0.3 0.3 rate at high temperature
Examples 10 and 11
[0190] The effect of position for setting a guide at the exit of
heating region was determined through a long-run evaluation. The
high-temperature heat treatment was carried out by the same method
as Example 9, except that the guide setting position was changed
according to Table 5. Examples 10 and 11 have the same stretch rate
as Example 3, and have different guide setting positions and
treatment lengths from Example 3. Properties of obtained fiber are
shown in Table 5. T1 wasn't able to be measured since the guide
setting position was close to the heating region (heater) in
Example 10. The yarn breakage was reduced in Example 10 better than
Example 3 in spite of long treatment length. The number of yarn
breakage times was reduced even in Example 11 better than Example
3. Thus the position distant from the heating region by 1 cm or
more and 50 cm or less can suppress yarn breakage.
* * * * *