U.S. patent application number 10/571270 was filed with the patent office on 2007-02-08 for wholly aromatic polyamide fiber and process for producing the same.
Invention is credited to Hiroshi Fujita, Sadahito Hashidate, Susumu Honda, Shunichi Matsumura, Hideaki Nitta, Yasushige Yagura.
Application Number | 20070031663 10/571270 |
Document ID | / |
Family ID | 34308680 |
Filed Date | 2007-02-08 |
United States Patent
Application |
20070031663 |
Kind Code |
A1 |
Honda; Susumu ; et
al. |
February 8, 2007 |
Wholly aromatic polyamide fiber and process for producing the
same
Abstract
A wholly aromatic polyamide fiber which has excellent mechanical
properties (toughness factor) and can be produced while attaining a
satisfactory operation stability in the fiber formation step. The
fiber comprises 100 parts by mass of a wholly aromatic polyamide
and 0.05 to 20 parts by mass of particles of a lamellar clay
mineral, e.g., hectorite, saponite, stevensite, beidellite,
montmorillonite, or swelling mica.
Inventors: |
Honda; Susumu; (Yamaguchi,
JP) ; Nitta; Hideaki; (Yamaguchi, JP) ;
Matsumura; Shunichi; (Yamaguchi, JP) ; Yagura;
Yasushige; (Yamaguchi, JP) ; Fujita; Hiroshi;
(Yamaguchi, JP) ; Hashidate; Sadahito; (Yamaguchi,
JP) |
Correspondence
Address: |
SUGHRUE MION, PLLC
2100 PENNSYLVANIA AVENUE, N.W.
SUITE 800
WASHINGTON
DC
20037
US
|
Family ID: |
34308680 |
Appl. No.: |
10/571270 |
Filed: |
September 13, 2004 |
PCT Filed: |
September 13, 2004 |
PCT NO: |
PCT/JP04/13693 |
371 Date: |
March 9, 2006 |
Current U.S.
Class: |
428/364 ;
264/178F; 264/203; 428/372; 428/397 |
Current CPC
Class: |
Y10T 428/2927 20150115;
D01F 1/10 20130101; Y10T 428/2913 20150115; Y10T 428/2973 20150115;
D01F 6/905 20130101 |
Class at
Publication: |
428/364 ;
428/372; 428/397; 264/178.00F; 264/203 |
International
Class: |
D02G 3/00 20060101
D02G003/00 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 16, 2003 |
JP |
2003-322785 |
Claims
1. Drawn and oriented wholly aromatic polyamide fibers comprising a
resin composition comprising a matrix composed of a wholly aromatic
polyamide resin and layer-structured clay mineral particles
dispersed and distributed in an amount of 0.05 to 20 parts by mass,
based on 100 parts by mass of the matrix, in the matrix.
2. The wholly aromatic polyamide fibers as claimed in claim 1,
wherein a plurality of regions, in which the layer-structured clay
mineral particles are distributed in a relatively high distribution
density, are scatteringly distributed in the wholly aromatic
polyamide matrix.
3. The wholly aromatic polyamide fibers as claimed in claim 1,
wherein when the wholly aromatic polyamide fibers are cross-cut
along the fiber axes, the resultant cross-sectional profiles are
observed with an electronic microscope at a magnification of
100,000, and in each cross-sectional profile, a total area S1 of a
plurality of regions in which regions a change in conditions of the
fiber cross-sectional profile due to an influence of the
layer-structured clay mineral particles distributed in the
observation area S2 of 25 .mu.m.sup.2 is found, is measured, the
degree of dispersion Y of the layer-structured clay mineral
particles in each fiber, defined by the equation (1):
Y(%)=(S1/S2).times.100 (1) is in the range of from 0.1 to 40.
4. The wholly aromatic polyamide fibers as claimed in claim 1,
wherein the layer-structured clay mineral comprises at least one
selected from hectorite, saponite, stevensite, beidellite,
montmorillonite and swelling mica.
5. The wholly aromatic polyamide fibers as claimed in claim 1,
wherein the layer-structured clay mineral particles are ones
treated with an intercalating agent.
6. The wholly aromatic polyamide fibers as claimed in claim 1,
wherein the layer-structured clay mineral particles have an average
layer thickness of 10 to 500 nm.
7. The wholly aromatic polyamide fibers as claimed in claim 1,
wherein the layer-structured clay mineral particles have a degree
of orientation A of 50% or more, determined in accordance with the
equation (2): A(%)=[(180-w)/180].times.100 (2) In equation (2), w
represents a half value width of an intensity distribution
determined, in an X-ray analysis of the layer-structured clay
mineral particles, along a Debye ring of a reflection peak in a
(001) plane of the layer-structured clay mineral particles.
8. The wholly aromatic polyamide fibers as claimed in claim 1,
wherein a ratio (T/To) of a tensile strength (T) of the wholly
aromatic polyamide fibers to a tensile strength (To) of comparative
wholly aromatic polyamide fibers identical to the wholly aromatic
polyamide fibers except that the layer-structured clay mineral
particles are not contained therein, is 1.1 or more.
9. The wholly aromatic polyamide fibers as claimed in claim 1,
wherein a ratio (E/Eo) of an ultimate elongation (E) of the wholly
aromatic polyamide fibers to an ultimate elongation (Eo) of
comparative wholly aromatic polyamide fibers identical to the
wholly aromatic polyamide fibers except that the layer-structured
clay mineral particles are not contained therein, is 1.1 or
more.
10. The wholly aromatic polyamide fibers as claimed in claim 1,
wherein the toughness factor (TF) of the wholly aromatic polyamide
fibers defined by the equation (3): TF=T'.times.E'.sup.1/2 (3) In
which equation (3), T' represents a numeral value of the tensile
strength in unit of g/1.1 dtex of the wholly aromatic polyamide
fibers and E' represents a numeral value of the ultimate elongation
in unit of % of the wholly aromatic polyamide fibers, is 30 or
more.
11. The wholly aromatic polyamide fibers as claimed in claim 10,
wherein the ratio (TF/TFo) of the tenacity factor (TF) of the
wholly aromatic polyamide fibers to the tenacity factor (TFo) of
comparative wholly aromatic polyamide fibers identical to the
wholly aromatic polyamide fibers except that the layer-structured
clay mineral particles are not contained therein, is 1.1 or
more.
12. The wholly aromatic polyamide fibers as claimed in claim 1,
wherein the layer-structured clay mineral particles contain organic
onium ions located between layers thereof.
13. The wholly aromatic polyamide fibers as claimed in claim 1,
wherein the wholly aromatic polyamide resin is selected from
meta-wholly aromatic polyamide resins.
14. A process for producing drawn and oriented wholly aromatic
polyamide fibers comprising extracting a spinning liquid comprising
a solvent and a wholly aromatic polyamide resin and
layer-structured clay mineral particles in an amount of 0.05 to 20
parts by mass per 100 parts by mass of the wholly aromatic
polyamide resin through a spinneret to form filamentary streams of
the spinning liquid; Introducing the filamentary streams of the
spinning liquid into an aqueous coagulation bath to coagulate the
filamentary streams of the spinning liquid; drawing the resultant
undrawn filaments in a wetted atmosphere; and dry-heat treating the
resultant drawn filaments.
15. The process for producing wholly aromatic polyamide fibers as
claimed in claim 14, wherein the spinning liquid is prepared by
mixing a solution A comprising a portion of the solvent, a portion
of the wholly aromatic polyamide resin and layer-structured clay
mineral particles in an amount of 30 to 300 parts by mass per 100
parts by mass of the wholly aromatic polyamide resin with a
solution B comprising the remaining portion of the solvent, the
remaining portion of the wholly aromatic polyamide resin, and
satisfies the requirements (1) and (2): (1) the viscosity of the
solution (A) at a shear rate of 0.1 second.sup.-1 is 15 to 80 times
the viscosity thereof at a shear rate of 10 second.sup.-1, and (2)
the viscosity of the solution (A) at a shear rate of 0.1
second.sup.-1 is 40 to 20 times the viscosity of the solution (B)
at a shear rate of 0.1 second.sup.-1.
16. The process for producing wholly aromatic polyamide fibers as
claimed in claim 14, wherein the concentration of the wholly
aromatic polyamide resin in the spinning solution is 0.1 to 30% by
mass.
17. The process for producing wholly aromatic polyamide fibers as
claimed in claim 14, wherein the draw ratio of the undrawn
filaments in the wetted atmosphere is in the range of 0.3 to 0.6
times the maximum draw ratio of the undrawn filaments.
18. The process for producing wholly aromatic polyamide fibers as
claimed in claim 14, wherein the solvent is selected from polar
amide solvents.
19. The process for producing wholly aromatic polyamide fibers as
claimed in claim 14, wherein the wholly aromatic polyamide resin is
selected from meta-wholly aromatic polyamide resins.
20. The wholly aromatic polyamide fibers as claimed in claim 2,
wherein when the wholly aromatic polyamide fibers are cross-cut
along the fiber axes, the resultant cross-sectional profiles are
observed with an electronic microscope at a magnification of
100,000, and in each cross-sectional profile, a total area S1 of a
plurality of regions in which regions a change in conditions of the
fiber cross-sectional profile due to an influence of the
layer-structured clay mineral particles distributed in the
observation area S2 of 25 .mu.m.sup.2 is found, is measured, the
degree of dispersion Y of the layer-structured clay mineral
particles in each fiber, defined by the equation (1):
Y(%)=(S1/S2).times.100 (1) is in the range of from 0.1 to 40.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to wholly aromatic polyamide
fibers containing a layer-structured clay mineral, and a production
process thereof. More particularly, the present invention relates
to wholly aromatic polyamide fibers containing a layer-structured
clay mineral and having improved mechanical characteristics,
particularly toughness, and a production process thereof.
[0003] 2. Description of the Related Art
[0004] Considerable interest has been focused on the imparting of
high added value to polymers and enhancement of their performance
in recent years. Compound materials obtained by containing a filler
in a polymer have been actively developed in order to impart high
added value and high performance to polymers. In the past, fibrous
or acicular fillers have been used as reinforcing fillers for the
purpose of improving the mechanical characteristics and heat
resistance of polymers and, as a result, known polymer materials
are improved in terms of tensile strength, modulus of elasticity,
bending strength, thermal dimensional stability and creep
characteristics as well as in terms of various other properties
such as improved warping, wear resistance, surface hardness, heat
resistance and impact resistance.
[0005] However, the strength of a compound material is known to be
greatly affected not only by the strength of the polymer serving as
the matrix of the compound material as well as the strength of the
filler itself, but also by the interface adhesion between the
filler and polymer, and the quality of the wettability of the
polymer to the filler has an effect not only on the ease of
production, but also on the strength of the finished product. For
reasons such as these, it is not always possible to obtain a
compound material having superior strength even if a filler or
polymer having high strength and elasticity is used for the
material.
[0006] Moreover, compound materials containing a filler are
generally known to have the disadvantage of low ultimate
elongation.
[0007] On the other hand, in the production process of wholly
aromatic polyamide fibers (to be referred to as aramid fibers),
there is a desire to further improve process stability and quality
(prevention of filament breakage). In general, a toughness factor
(TF) is typically known to be used as a parameter for evaluating
industrial aramid fibers. Toughness factor (TF) is represented by
the product of tensile strength (T') as measured in units of
grams/deneer and the square root of ultimate elongation (%)
(TF=T'.times.E.sup.1/2). In the case of fibers having a high
toughness factor, the amount of the fibers retained on the drawing
roll in the drawing process is known to decrease, and as a result,
filament breakage in the resulting fibers is reduced resulting in
improvement of stability of the drawing process and improved
quality of the resulting fiber threads.
[0008] Although a known example of a process for improving fiber
mechanical strength involves improving the degree of orientation of
fibers by drawing, in the case of using such a process, as ultimate
elongation is known to decrease with the improvement tensile
strength, it becomes difficult to produce filaments having a high
toughness factor.
[0009] In the past, containing a filler in the form of a
layer-structured clay mineral was proposed to improve the
mechanical properties and dimensional stability of polyamide fibers
(see Japanese Unexamined Patent Publication Nos. H3-31364,
H4-209882 and H8-3818). However, these are all targeted at
thermoplastic polyamide, and the use of a layer-structured clay
mineral for non-thermoplastic polyamide, in the form of wholly
aromatic polyamide fibers, is not disclosed in these patent
documents.
[0010] In addition, processes using layer-structured clay minerals
as fillers have been examined for the purpose of improving the
mechanical characteristics and heat resistance of wholly aromatic
polyamide. For example, Japanese Unexamined Patent Publication No.
H11-236501 discloses a process for obtaining a wholly aromatic
polyamide compound material that is useful as a highly
heat-resistant material by mixing an aqueous solution containing a
diamine monomer and an organic solvent solution of an acylated
dicarboxylic acid monomer that is soluble in water, and adding a
clay mineral to the aqueous solution or organic solvent solution
during polycondensation of the monomers, Japanese Unexamined Patent
Publication No. H11-255839 discloses a process for efficiently
obtaining a compound by solution polymerizing a wholly aromatic
polyamide in a solvent solution of a layer-structured clay mineral
capable of completely dissolving said layer-structured clay
mineral, while Japanese Unexamined Patent Publication No.
H11-256034 proposes a process for obtaining a wholly aromatic
polyamide compound having improved mechanical properties in which a
layer-structured clay mineral is highly and finely dispersed in a
wholly aromatic polyamide by removing an organic solvent from a
solution composed of the wholly aromatic polyamide, the
layer-structured clay mineral and the organic solvent.
[0011] However, the improvement of the mechanical properties of
wholly aromatic polyamide fibers by containing a layer-structured
clay mineral as filler, and wholly aromatic polyamide fibers
containing a layer-structured clay mineral as filler and having a
high toughness factor as a result of thereof, are not known from
documents of the prior art.
SUMMARY OF THE INVENTION
[0012] An object of the present invention is to provide wholly
aromatic polyamide fibers having high mechanical properties, and a
high toughness factor in particular, that can be spun with
satisfactory process stability in a spinning process, and a process
for industrially producing the same.
[0013] According to research conducted by the inventors of the
present invention, drawn and oriented wholly aromatic polyamide
fibers obtained by wet spinning and drawing a spinning liquid
containing a wholly aromatic polyamide and a layer-structured clay
mineral were found to have superior mechanical characteristics, and
particularly superior toughness factor. More surprisingly, it was
also found by the inventors of the present invention that, instead
of completely uniformly dispersing each layer of the
layer-structured clay mineral in the fibers, by scatteringly
distributing a plurality of regions having a relatively high
layer-structured clay mineral distribution density in the aromatic
polyamide polymer matrix that composes the particles, the effect of
improving the mechanical characteristics of the fibers, and
particularly the toughness factor, can be further enhanced by the
layer-structured clay mineral particles.
[0014] Drawn and oriented wholly aromatic polyamide fibers of the
present invention comprise a resin composition comprising a matrix
composed of a wholly aromatic polyamide resin and layer-structured
clay mineral particles dispersed and distributed in an amount of
0.05 to 20 parts by mass, based on 100 parts by mass of the matrix,
in the matrix.
[0015] In the wholly aromatic polyamide fibers of the present
invention, a plurality of regions, in which the layer-structured
clay mineral particles are distributed in a relatively high
distribution density, are preferably scatteringly distributed in
the wholly aromatic polyamide matrix.
[0016] In the wholly aromatic polyamide fibers of the present
invention, when the wholly aromatic polyamide fibers are cross-cut
along the fiber axes, the resultant cross-sectional profiles are
observed with an electronic microscope at a magnification of
100,000, and in each cross-sectional profile, a total area S1 of a
plurality of regions in which regions a change in conditions of the
fiber cross-sectional profile due to an influence of the
layer-structured clay mineral particles distributed in the
observation area S2 of 25 .mu.m.sup.2 is found, is measured, the
degree of dispersion Y of the layer-structured clay mineral
particles in each fiber, defined by the equation (1):
Y(%)=(S1/S2).times.100 (1) is preferably in the range of from 0.1
to 40.
[0017] In the wholly aromatic polyamide fibers of the present
invention, the layer-structured clay mineral preferably comprises
at least one selected from hectorite, saponite, stevensite,
beidellite, montmorillonite and swelling mica.
[0018] In the wholly aromatic polyamide fibers of the present
invention, the layer-structured clay mineral particles are
preferably ones treated with an intercalating agent.
[0019] In the wholly aromatic polyamide fibers of the present
invention, the layer-structured clay mineral particles preferably
have an average layer thickness of 10 to 500 nm.
[0020] In the wholly aromatic polyamide fibers of the present
invention, the layer-structured clay mineral particles preferably
have a degree of orientation A of 50% or more, determined in
accordance with the equation (2): A(%)=[(180-w)/180].times.100 (2)
in equation (2), w represents a half value width of an intensity
distribution determined, in an X-ray analysis of the
layer-structured clay mineral particles, along a Debye ring of a
reflection peak in a (001) plane of the layer-structured clay
mineral particles.
[0021] In the wholly aromatic polyamide fibers of the present
invention, a ratio (T/To) of a tensile strength (T) of the wholly
aromatic polyamide fibers to a tensile strength (To) of comparative
wholly aromatic polyamide fibers identical to the wholly aromatic
polyamide fibers except that the layer-structured clay mineral
particles are not contained therein, is preferably 1.1 or more.
[0022] In the wholly aromatic polyamide fibers of the present
invention, a ratio (E/Eo) of an ultimate elongation (E) of the
wholly aromatic polyamide fibers to an ultimate elongation (Eo) of
comparative wholly aromatic polyamide fibers identical to the
wholly aromatic polyamide fibers except that the layer-structured
clay mineral particles are not contained therein, is preferably 1.1
or more.
[0023] In the wholly aromatic polyamide fibers of the present
invention, the toughness factor (TF) of the wholly aromatic
polyamide fibers defined by the equation (3):
TF=T'.times.E'.sup.1/2 (3)
[0024] In which equation (3), T' represents a numeral value of the
tensile strength in unit of g/1.1 dtex of the wholly aromatic
polyamide fibers and E' represents a numeral value of the ultimate
elongation in unit of % of the wholly aromatic polyamide fibers, is
preferably 30 or more.
[0025] In the wholly aromatic polyamide fibers of the present
invention, the ratio (TF/TFo) of the toughness factor (TF) of the
wholly aromatic polyamide fibers to the tenacity factor (TFo) of
comparative wholly aromatic polyamide fibers identical to the
wholly aromatic polyamide fibers except that the layer-structured
clay mineral particles are not contained therein, is preferably 1.1
or more.
[0026] In the wholly aromatic polyamide fibers of the present
invention, the layer-structured clay mineral particles preferably
contain organic onium ions located between layers thereof.
[0027] In the wholly aromatic polyamide fibers of the present
invention, the wholly aromatic polyamide resin is preferably
selected from meta-wholly aromatic polyamide resins.
[0028] A process of the present invention for producing drawn and
oriented wholly aromatic polyamide fibers comprises extracting a
spinning liquid comprising a solvent and a wholly aromatic
polyamide resin and layer-structured clay mineral particles in an
amount of 0.05 to 20 parts by mass per 100 parts by mass of the
wholly aromatic polyamide resin through a spinneret to form
filamentary streams of the spinning liquid;
[0029] Introducing the filamentary streams of the spinning liquid
into an aqueous coagulation bath to coagulate the filamentary
streams of the spinning liquid;
[0030] drawing the resultant undrawn filaments in a wetted
atmosphere; and
[0031] dry-heat treating the resultant drawn filaments.
[0032] In the process of the present invention for producing wholly
aromatic polyamide fibers, preferably the spinning liquid is
prepared by mixing a solution A comprising a portion of the
solvent, a portion of the wholly aromatic polyamide resin and
layer-structured clay mineral particles in an amount of 30 to 300
parts by mass per 100 parts by mass of the wholly aromatic
polyamide resin with a solution B comprising the remaining portion
of the solvent, the remaining portion of the wholly aromatic
polyamide resin, and satisfies the requirements (1) and (2):
[0033] (1) the viscosity of the solution (A) at a shear rate of 0.1
second.sup.-1 is 15 to 80 times the viscosity thereof at a shear
rate of 10 second.sup.-1, and
[0034] (2) the viscosity of the solution (A) at a shear rate of 0.1
seconds.sup.-1 is 4 to 20 times the viscosity of the solution (B)
at a shear rate of 0.1 second.sup.-1.
[0035] In the process of the present invention for producing wholly
aromatic polyamide fibers, the concentration of the wholly aromatic
polyamide resin in the spinning solution is preferably 0.1 to 30%
by mass.
[0036] In the process of the present invention for producing wholly
aromatic polyamide fibers, the draw ratio of the undrawn filaments
in the wetted atmosphere is preferably in the range of 0.3 to 0.6
times the maximum draw ratio of the undrawn filaments.
[0037] In the process of the present invention for producing wholly
aromatic polyamide fibers, the solvent is preferably selected from
polar amide solvents.
[0038] In the process of the present invention for producing wholly
aromatic polyamide fibers, the wholly aromatic polyamide resin is
preferably selected from meta wholly aromatic polyamide resins.
BRIEF DESCRIPTION OF THE DRAWINGS
[0039] FIG. 1 is an electron micrograph of a cross-section of one
example of wholly aromatic polyamide fibers of the present
invention.
BEST MODE FOR CARRYING OUT THE INVENTION
[0040] In the wholly aromatic polyamide used in the present
invention, the aromatic rings, from which the primary backbone of
repeating units of the wholly aromatic polyamide is constituted,
are mutually bonded through amide bonds, and the wholly aromatic
polyamide is preferably selected from meta-wholly aromatic
polyamides. This type of wholly aromatic polyamide is normally
produced by low-temperature solution polymerization or interfacial
polymerization of an aromatic dicarboxylic acid dihalide and an
aromatic diamine in a solution thereof.
[0041] Although the diamine component used in the present invention
preferably contains one or more types of, for example,
paraphenylene diamine, 2-chloroparaphenylene diamine,
2,5-dichloroparaphenylene diamine, 2,6-dichloroparaphenylene
diamine, m-phenylene diamine, 3,4'-diaminodiphenyl ether,
4,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl methane,
4,4'-diaminodiphenyl sulfone or 3,3'-diaminodiphenyl sulfone, it is
not limited thereto. Among these diamine compounds, p-phenylene
diamine, m-phenylene diamine and 3,4'-diaminodiphenyl ether are
used preferably.
[0042] In addition, although the aromatic dicarboxylic acid
dihalide component used in the present invention preferably
contains one or more types of, for example, diisophthalic acid
dichloride, terephthalic acid dichloride, 2-chloro-terephthalic
acid dichloride, 2,5-dichloroterephthalic acid dichloride,
2,6-dichloroterephthalic acid dichloride or 2,6-napthalene
dicarboxylic acid dichloride, it is not limited thereto. Among
these aromatic dicarboxylic acid dihalides, terephthalic acid
dichloride and/or isophthalic acid dichloride are used
preferably.
[0043] Among the aforementioned wholly aromatic polyamides,
polymetaphenylene isophthalamide and
copolyparaphenylene-3,4'-dioxydiphenylene terephthalamide are used
preferably, while polymetaphenylene isophthalamide is used
particularly preferably.
[0044] At least one type of solvent when preparing a spinning
liquid by polymerizing a wholly aromatic polyamide, examples of
which include, but are not limited to, organic polar amide-based
solvents such as N,N-dimethylformamide, N,N-dimethylacetoamide,
N-methyl-2-pyrrolidone and N-methylcaprolactam, water-soluble ether
compounds such as tetrahydrofuran and dioxane, water-soluble
alcohol compounds such as methanol, ethanol and ethylene glycol,
water-soluble ketone compounds such as acetone and methyl ethyl
ketone, and water-soluble nitrile compounds such as acetonitrile
and propionitrile. The aforementioned solvent may also be a mixture
of two or more types of the aforementioned compounds. The solvent
used in the process of the present invention is preferably
dehydrated.
[0045] In this case, a suitable amount of a conventionally known
inorganic salt may be added to the polymerization mixture before
polymerization, during polymerization or at completion of
polymerization in order to increase solubility. Examples of such
inorganic salts include lithium chloride and calcium chloride.
[0046] In addition, when producing a wholly aromatic polyamide from
the aforementioned diamine component and the aforementioned acid
halide component, the molar ratio of the diamine component to the
acid halide component is preferably controlled to 0.90 to 1.10, and
more preferably to 0.95 to 1.05.
[0047] A molecular terminal of a wholly aromatic polyamide used in
the present invention may be blocked. In the case of using a
terminal blocking agent for this purpose, examples of the blocking
agent used include phthalic acid chloride and substituted forms
thereof, while examples of the amine component include aniline and
substituted forms thereof.
[0048] In general, an aliphatic amine, aromatic amine and
quaternary ammonium salt can be used in combination to capture an
acid such as a hydrogen halide formed in reactions between acid
halides and diamines.
[0049] Following completion of the aforementioned polymerization
reaction, a basic inorganic compound such as sodium hydroxide,
potassium hydroxide, calcium hydroxide or calcium oxide may be
added to the reaction mixture as necessary to neutralize the
reaction.
[0050] There are no special limitations on the reaction conditions
for producing a wholly aromatic polyamide of the present invention.
The reaction between the acid halide and diamine typically proceeds
rapidly, and the reaction temperature is normally -25 to
100.degree. C., and preferably -10 to 80.degree. C.
[0051] A wholly aromatic polyamide polymer obtained in this manner
can be extracted in the form of pulp-like flakes by charging and
submerging it in a non-solvent such as water or alcohol. Although
the polymer flakes can be redissolved in solvent and the resulting
solution can be used for wet spinning, a solution obtained by a
polymerization reaction can also be used as is as a spinning
liquid. Although there are no particular limitations on the solvent
used when redissolving the polymer flakes provided it dissolves
said wholly aromatic polyamide, a solvent used in polymerization of
the aforementioned wholly aromatic polyamide is used
preferably.
[0052] Next, the layer-structured clay mineral used in the present
invention has cation exchange ability and demonstrates the property
of swelling as a result of incorporating water between layers
thereof, and a smectite clay mineral and swelling mica are used
preferably. Specific examples of layer-structured clay minerals
include smectite clay minerals such as hectorite, saponite,
stevensite, beidelite and montmorillonite (including their natural
and chemically synthesized forms), as well as substituted forms,
derivatives or mixtures thereof. In addition, examples of swelling
mica include synthetic swelling mica that is chemically synthesized
and has Li and Na ions between the layers thereof, as well as
substituted forms, derivatives or mixtures thereof.
[0053] In the present invention, layer-structured clay mineral
particles that have been treated with a surface treatment agent
containing organic onium ions (intercalating agent) are preferably
used for the aforementioned layer-structured clay mineral
particles. Treatment with said organic onium ions improves the
dispersivity of the wholly aromatic polyamide of the resulting
layer-structured clay mineral particles in the matrix, and is able
to improve filament formability and the toughness factor of the
resulting fibers.
[0054] The organic onium ion used in the aforementioned surface
treatment is preferably selected from quaternary ammonium ions
having a chemical structure represented by the following formula
(1): ##STR1## (wherein, R.sub.1, R.sub.2, R.sub.3 and R.sub.4
respectively and independently represent an alkyl group having 1 to
30 carbon atoms or a hydroxypolyoxyethylene group represented by
--(CH.sub.2CH.sub.2O).sub.nH). Here, alkyl groups having 1 to 18
carbon atoms are preferable among the alkyl groups having 1 to 30
carbon atoms represented by R.sub.1, R.sub.2, R.sub.3 and
R.sub.4.
[0055] Preferable examples of quaternary ammonium compounds used
include, but are not limited to, dodecyl trimethyl ammonium
chloride, tetradecyl trimethyl ammonium chloride, hexadecyl
trimethyl ammonium chloride, octadecyl trimethyl ammonium chloride,
oleyl trimethyl ammonium chloride, didodecyl dimethyl ammonium
chloride, ditetradecyl dimethyl ammonium chloride, dihexadecyl
dimethyl ammonium chloride, dioctadecyl dimethyl ammonium chloride,
dioleyl dimethyl ammonium chloride, dodecyl diethylbenzyl ammonium
chloride, tetradecyl dimethylbenzyl ammonium chloride, hexadecyl
dimethylbenzyl ammonium chloride, octadecyl dimethylbenzyl ammonium
chloride, oleyl dimethylbenzyl ammonium chloride, trioctyl methyl
ammonium chloride, hydroxypolyoxypropylene methyl diethyl ammonium
chloride, hydroxypolyoxyethylene dodecyl dimethyl ammonium
chloride, hydroxypolyoxyethylene tetradecyl dimethyl ammonium
chloride, hydroxypolyoxyethylene hexadecyl dimethyl ammonium
chloride, hydroxypolyoxyethylene octadecyl dimethyl ammonium
chloride, hydroxypolyoxyethylene oleyl dimethyl ammonium chloride,
dihydroxypolyoxyethylene dodecyl methyl ammonium chloride,
bis(hydroxypolyoxyethylene) tetradecyl methyl ammonium chloride,
bis(hydroxypolyoxyethylene) hexadecyl methyl ammonium chloride,
bis(hydroxypolyoxyethylene) octadecyl methyl ammonium chloride and
bis(hydroxy-polyoxyethylene) oleyl methyl ammonium chloride.
[0056] An example of a method for treating layer-structured clay
mineral particles with organic onium ion normally consists of
mixing 1 part by weight of layer-structured clay mineral particles
and 1 to 10 parts by weight of organic onium ion in water followed
by drying this mixture. The amount of water used is preferably 1 to
100 times the amount of layer-structured clay mineral. In addition,
the temperature during mixing is preferably 30 to 70.degree. C.,
and the mixing time is preferably 0.5 to 2 hours. Preferable drying
conditions consist of drying at normal pressure for 3 days at 70 to
100.degree. C. and then vacuum drying for 2 days.
[0057] The average layer thickness of the layer-structured clay
mineral particles in the wholly aromatic polyamide fibers of the
present invention is preferably 500 nm or less and more preferably
200 nm or less. Furthermore, the average layer thickness of the
layer-structured clay mineral referred to here indicates the
average value of layer thickness as measured for all
layer-structured clay mineral particles observed in a
cross-sectional area of 25 .mu.m.sup.2 during measurement with an
electron microscope (magnification: 100,000.times.) of longitudinal
cross-sections of the fibers. If the average layer thickness of the
layer-structured clay mineral is greater than 500 nm, it may be
difficult to ensure forming stability during spinning of the
resulting resin composition. On the other hand, if it is attempted
to disperse the layer-structured clay mineral particles are down to
the molecular level, it is necessary to lower the concentration of
the spinning liquid in order to ensure thickening effects and
dispersivity of the layer-structured clay mineral particles which,
in addition to lowering the production efficiency of the spinning
process, also tends to reduce the effect of improving the toughness
of the resulting fibers. Consequently, the average layer thickness
of the layer-structured clay mineral particles is preferably 10 nm
or more and more preferably 12 nm or more. In addition, the
vertical and horizontal dimensions of the layer-structured clay
mineral particles used in the present invention are preferably (50
to 1000 nm).times.(50 to 1000 nm), and more preferably (100 to 500
nm).times.(100 to 500 nm).
[0058] Moreover, when the total surface area S1 is measured at a
plurality of regions, in which changes in the state of the fiber
cross-sections are observed due to the effects of the
layer-structured clay mineral particles, per an observed
cross-sectional area S2 of 25 .mu.m.sup.2, by cutting the wholly
aromatic polyamide fibers along the fiber axes thereof and
observing the longitudinal cross-sections with an electron
microscope at a magnification of 100,000.times., the degree of
dispersion Y within each fiber of the layer-structured clay mineral
particles as defined by the following formula (1):
Y(%)=(S1/S2).times.100 (1) is preferably within the range of 0.1 to
40 and more preferably within the range of 0.5 to 30. If the degree
of dispersion Y is less than 0.1, there is little improvement in
the toughness factor, while if the degree of dispersion Y exceeds
40, the transparency of the spinning liquid prepared from the
wholly aromatic polyamide, layer-structured clay mineral particles
and solvent becomes low and moldability decreases.
[0059] In the aforementioned microscopic observations, changes in
the state of the fibers observed in the fiber cross-sections are
caused by layer-structured clay mineral particles distributed in
said cross-sectional regions being distributed at a higher
distribution density as compared with other regions. It was first
found in the present invention that the toughness factor of the
resulting fibers can be increased by scatteringly distributing
regions having a relatively high distribution density of
layer-structured clay mineral particles in the wholly aromatic
polyamide polymer matrix of the fibers in this manner. The suitably
scattered distribution of regions having a relatively high
distribution density of layer-structured clay mineral particles can
be achieved by controlling the degree of dispersion Y of the
layer-structured clay mineral particles to within the range of 0.1
to 40.
[0060] FIG. 1 shows a cross-section of an example of a wholly
aromatic polyamide drawn fiber of the present invention. In FIG. 1,
a plurality of regions having a high distribution density of
layer-structured clay mineral are observed to be scatteringly
distributed in the form of staple fibers in the fiber
cross-section. The staple fiber-like regions are elongated along
the direction of the fiber axis.
[0061] Although the reason for the improvement in toughness factor
of the resulting fibers as a result of scatteringly distributing
regions having a relatively high distribution density of
layer-structured clay mineral particles in the fibers as previously
described is still not sufficiently clear, when these regions
containing layer-structured clay mineral particles at a high
distribution density are drawn, it is presumed that a network
structure is formed by the layer-structured clay mineral particles
and the wholly aromatic polyamide polymer molecules, and this
network structure is oriented along the direction of the fiber axes
due to drawing. The formation of this network structure oriented
between the layer-structured clay mineral particles and polymer is
thought to greatly contribute to improvement of toughness factor
even if the content of the layer-structured clay mineral particles
is relatively small.
[0062] In the present invention, fillers other than the
layer-structured clay mineral can be used in combination in the
wholly aromatic polyamide polymer provided they are within a range
that does not impair physical properties or process stability
during spinning. Although fibrous fillers or non-fibrous fillers
such as plate-like, scale-like, granular, irregular shaped or
crushed fillers can be used for the filler, non-fibrous fillers are
particularly preferable. Specific examples include potassium
titanate whiskers, palladium titanate whiskers, aluminum borate
whiskers, silicon nitride whiskers, mica, talc, kaolin, silica,
calcium carbonate, glass beads, glass flakes, glass microballoons,
clay, molybdenum disulfide, wollastonite, titanium dioxide, zinc
oxide, calcium polyphosphate, graphite, metal powder, metal flakes,
metal ribbon, metal oxides, carbon powder, black lead, carbon
flakes and scaly carbon. Moreover, in the case the monofilament
fineness of the wholly aromatic polyamide fibers is large, glass
fibers, carbon fibers such as PAN and pitch fibers, metal fibers
such as stainless steel fibers, aluminum fibers or brass fibers,
organic fibers such as wholly aromatic polyamide fibers, gypsum
fibers, ceramic fibers, asbestos fibers, zirconia fibers, alumina
fibers, silica fibers, titanium dioxide fibers, silicon carbide
fibers, rock wool or metal ribbon can be used. Two or more types of
these fillers may also be used in combination.
[0063] Furthermore, the aforementioned fillers can also be used
after treating the surface thereof with a known coupling agent
(such as a silane-based coupling agent or titanate-based coupling
agent) or other surface treatment agent.
[0064] In the wholly aromatic polyamide fibers of the present
invention, it is necessary that the layer-structured clay mineral
be contained within the range of 0.05 to 20 parts by weight,
preferably 0.1 to 10 parts by weight, and more preferably 0.5 to 5
parts by weight, relative to 100 parts by weight of the wholly
aromatic polyamide. If the content of layer-structured clay mineral
is less than 0.05 parts by weight relative to 100 parts by weight
of said wholly aromatic polyamide, improvement of toughness factor
is not observed, while if the content exceeds 20 parts by weight,
the transparency of the spinning liquid composed of the
layer-structured clay mineral, wholly aromatic polyamide and
solvent becomes low and moldability decreases thereby making this
undesirable.
[0065] In addition, if the degree of orientation A of the
layer-structured clay mineral in the fibers is 50% or more,
preferably 70% or more and more preferably 80% or more, mechanical
properties (toughness factor) and various physical properties such
as thermal dimensional stability are improved, thereby making this
preferable. Furthermore, the degree of orientation A of the
layer-structured clay mineral particles is determined according to
the following formula from the intensity distribution measured
along a Debye ring of a reflection peak in a (001) plane of the
layer-structured clay mineral particles measured by X-ray analysis.
A=(180-w)/180.times.100 In this formula, w represents the half
value width (degrees) of an intensity distribution measured along a
Debye ring of a reflection peak.
[0066] The wholly aromatic polyamide fibers of the present
invention preferably have a tensile strength that is 10% or more
better, and an ultimate elongation (E) that is 10% or more better,
than comparative wholly aromatic polyamide fibers that are
completely identical to the aforementioned wholly aromatic
polyamide fibers with the exception of not containing a
layer-structured clay mineral. Moreover, the wholly aromatic
polyamide fibers of the present invention have a toughness factor
(TF) that is 10% or more better, particularly 20% or more better,
and preferably 30% or more better than the comparative wholly
aromatic polyamide fibers. Furthermore, the toughness factor (TF)
referred to here is defined as the product of tensile strength (T')
as measured in units of grams/deneer and ultimate elongation (E) as
measured in units of percent, namely T'.times.(E).sup.1/2.
[0067] If toughness factor is improved by 30% or more in this
manner, as the strength of the fibers is improved, there is less
filament breakage in the fibers even if the draw ratio is increased
(improved quality), and retention of monofilaments on a drawing
roller and so forth during drawing decreases (improved process
stability). In particular, an improvement of the toughness factor
of 10% or more is preferable since stabilization effects in the
drawing process become large.
[0068] Moreover, the wholly aromatic polyamide fibers of the
present invention may also contain other additives such as
antioxidants, heat stabilizers, weather resistance agents, dyes,
antistatic agents, flame retardants or electrical conductivity
agents within a range that does not impair the effects of the
present invention.
[0069] The wholly aromatic polyamide fibers of the present
invention can be produced by, for example, a process like that
described below. Namely, the wholly aromatic polyamide fibers of
the present invention can be produced by a process comprising the
steps of: (1) preparing a spinning liquid (dope) composed of wholly
aromatic polyamide, layer-structured clay mineral and solvent, (2)
coagulating the spinning liquid by introducing streams of the
spinning liquid into an aqueous coagulation bath, (3) drawing the
coagulated filaments in a wetted atmosphere, and (4) dry-heat
treating the drawn filaments.
[0070] The blending ratio of the layer-structured clay mineral to
the wholly aromatic polyamide in the spinning liquid is controlled
to within the range of 0.05 to 20 parts by weight, preferably 0.1
to 10 parts by weight, and particularly preferably 0.5 to 5 parts
by weight with respect to 100 parts by weight of the wholly
aromatic polyamide. In addition, the polymer concentration in the
spinning liquid is preferably 0.1 to 30% by weight, more preferably
1 to 25% by weight, and even more preferably 15 to 25% by weight.
Moreover, the haze of the spinning liquid is preferably adjusted to
10 or less and more preferably to 5 or less.
[0071] Furthermore, there are no limitations on the process used to
prepare the spinning liquid. Examples of processes that can be used
include: (A) a process in which the layer-structured clay mineral
is added to a solution of the wholly aromatic polyamide, (B) a
process in which a solution of the wholly aromatic polyamide and a
dispersion of the layer-structured clay mineral are mixed with each
other, and (C) a process in which the wholly aromatic polyamide is
added to a solution of the layer-structured clay mineral.
[0072] When preparing the spinning liquid from the wholly aromatic
polyamide polymer, layer-structured clay mineral particles and a
solvent, the spinning liquid used in the present invention is
preferably prepared by preparing a solution A, comprising a portion
of the solvent, a portion of the wholly aromatic polyamide polymer,
and 30 to 300 parts by weight of the layer-structured clay mineral
particles relative to 100 parts by weight of this wholly aromatic
polyamide polymer, separately preparing a solution B, comprising
the remainder of the solvent and the remainder of the wholly
aromatic polyamide polymer, and mixing solution A and solution B,
such that the solvent A and the solvent B satisfy the following
conditions at that time: [0073] (1) the viscosity of the solution A
at a shear rate of 0.1 second.sup.-1 is 15 to 80 times the
viscosity thereof at a shear rate of 10 second.sup.-1; and, [0074]
(2) the viscosity of the solution A at a shear rate of 0.1
second.sup.-1 is 4 to 20 times the viscosity of solution at a shear
rate of 0.1 second.sup.-1.
[0075] As a result thereof, regions having a relatively high
density of layer-structured clay mineral particles can be uniformly
dispersed and distributed in the spinning liquid which, together
with stabilizing the spinning process, makes it possible to control
the degree of dispersion Y of the layer-structured clay mineral
particles in the resulting fibers to a desired value, thereby
enhancing the effect of improving the toughness factor of the
resulting fibers.
[0076] Here, if the ratio of the layer-structured clay mineral to
the wholly aromatic polyamide in solution A is less than 30 parts
by weight, the difference in viscosity with solution B decreases,
the layer-structured clay mineral is more easily uniformly
distributed in the resulting spinning liquid, and the effect of
improving the toughness factor is reduced. On the other hand, if it
exceeds 300 parts by weight, the distribution density of the
layer-structured clay mineral becomes remarkably less uniform and,
as a result, the stability of the spinning process may
decrease.
[0077] In addition, if the viscosity of solution A at a shear rate
of 0.1 second.sup.-1 is less than 4 times the viscosity of solution
B at a shear rate of 0.1 second.sup.-1, the layer-structured clay
mineral is easily uniformly distributed, and as a result, the
formation of regions having a comparatively large distribution
density of layer-structured clay mineral particles decreases, and
the effect of improving the toughness factor is reduced. On the
other hand, if it exceeds 20 times, the formation of regions having
a relatively high distribution density of layer-structured clay
mineral particles in the spinning liquid during the spinning
process becomes excessive, and as a result, increases in packing
pressure and so forth occur, and process stability may decrease.
Moreover, if the viscosity of solution A at a shear rate of 0.1
second.sup.31 1 is less than 15 times the viscosity thereof at a
shear rate of 10 second.sup.-1, the layer-structured clay mineral
is easily uniformly distributed in the fibers and, as a result, the
formation of regions having a comparatively large distribution
density of layer-structured clay mineral particles decreases, and
the effect of improving the toughness factor is reduced. On the
other hand if it exceeds 20 times, the formation of regions having
a relatively high distribution density of layer-structured clay
mineral particles in the spinning liquid during the spinning
process becomes excessive and, as a result, the process stability
may decrease.
[0078] Although the solvent used to prepare the spinning liquid is
arbitrary, provided it dissolves the wholly aromatic polyamide,
those consisting primarily of an amide-based polar solvent are
preferable, specific examples of which include aprotic amide-based
organic solvents such as N-methyl-2-pyrrolidone (NMP),
N-ethyl-2-pyrrolidone, N,N-dimethylacetoamide, dimethylformamide,
tetramethyl urea, hexamethylphosphoramide and N-methylbutyrolactam.
Although the temperature of the spinning liquid should be suitably
set according to the solubility of the wholly aromatic polyamide,
it is preferable to set within the range of 50 to 90.degree. C.
from the standpoint of spinability in the case of polymetaphenylene
isophthalamide.
[0079] In the process of the present invention, filamentary streams
of the spinning liquid are introduced, for example, directly into
an aqueous coagulation bath from a spinneret normally having 10 to
30,000 discharge holes to coagulate the filamentary stream and form
undrawn fibers. There are no particular limitations on the
composition of the aqueous coagulation bath used here and, although
the composition should be suitably selected according to the types
of the wholly aromatic polyamide and solvent used, a conventionally
known aqueous coagulation bath containing an inorganic salt and/or
solvent can be used. More specifically, if the wholly aromatic
polyamide is polymetaphenylene isophthalamide and the solvent is
N-methyl-2-pyrrolidone (NMP), a preferable example of the aqueous
solution has a calcium chloride concentration of 34 to 42% by
weight and an NMP concentration of 3 to 10% by weight. In this
case, the temperature of the aqueous coagulation bath is suitably
within a range of 80 to 95.degree. C., the immersion time of the
fibers in the coagulation bath is suitably within the range of 1 to
11 seconds.
[0080] Since a considerable amount of solvent remains on the
undrawn fibers removed from the coagulation bath, the undrawn
fibers are preferably washed to extract and remove the residual
solvent. Examples of methods that are employed include passing the
undrawn fibers through a water bath after having removed them from
the coagulation bath, and spraying water onto the undrawn fibers.
The solvent content in the fibers after washing is preferably
controlled to 30% by weight or less, and if this content is
exceeded, water may penetrate into the fibers in the next drawing
process or voids may be easily formed resulting in decreased fiber
strength.
[0081] The washed undrawn fibers are drawn in a wetted atmosphere,
and preferably in a warm water bath while, simultaneously, residual
solvent and inorganic salts such as calcium chloride used in
combination as necessary, are removed by washing. The drawing
temperature during the aforementioned drawing is suitably set
according to the amount of solvent remaining in the undrawn fibers.
For example, in the case the amount of residual solvent is 50% or
more relative to the polymer weight, the drawing temperature is
preferably controlled to 0 to 50.degree. C., while in the case the
amount of residual solvent is less than 50% relative to the polymer
weight, the drawing temperature is preferably controlled to 50 to
100.degree. C. In addition, the draw ratio is preferably controlled
to 1.05 times or more, more preferably 1.10 times or more and even
more preferably 0.3 to 0.6 times the maximum draw ratio of the
undrawn fibers (draw ratio at which filament breakage begins to
occur when drawn under identical conditions).
[0082] The resulting drawn fibers are normally dried at a
temperature of 100.degree. C. or higher followed by hot drawing as
necessary and subsequent heat treatment using a heating roller or
heating plate.
[0083] Wholly aromatic polyamide fibers obtained in this manner are
then housed in a drum as necessary, coiled or sent directly to
post-processing, or after crimping as necessary, are cut and
supplied to any subsequent desired process as short fibers.
EXAMPLES
[0084] The following provides a more detailed explanation of the
present invention through examples thereof.
[0085] In the examples, the specific properties were measured by
the following tests.
[0086] (Intrinsic Viscosity IV)
[0087] A test polymer was dissolved in NMP at a concentration of
0.5 g/100 ml, and the viscosity of this solution was measured at
30.degree. C. using an Ostwald viscometer, after which intrinsic
viscosity was calculated from this measured value.
[0088] (Viscosity)
[0089] The viscosity of the spinning liquid was measured at
70.degree. C. using a viscometer manufactured by Rheometric
Scientific (trade name: Rheomat 115).
[0090] (Fineness)
[0091] Fineness was measured in compliance with JIS-L-1015.
[0092] (Tensile Strength, Ultimate Elongation)
[0093] Tensile strength and ultimate elongation were measured in
compliance with JIS-L-1015 using a sample length of 20 mm, initial
load of 0.05 g/dtex and drawing speed of 20 mm/min.
[0094] (Layer-Structured Clay Mineral Degree of Orientation A)
[0095] The degree of orientation was measured using an X-ray
generator (Rigaku Denki, RU-200B) under conditions of CuK .alpha.
rays for the target, voltage of 45 kV and current of 70 mA. The
incident X-rays were converged and converted to monochromatic rays
with a multilayer-structured mirror manufactured by Osmic followed
by measurement of the fiber sample using the vertical transmission
method. Detection of refracted X-rays was measured using an imaging
plate (Fuji Photo Film) measuring 200 mm.times.250 mm under
conditions of a camera length of 250 mm. The degree of orientation
of the clay layer surface was determined with the following formula
from the intensity distribution measured along a Debye ring of a
reflection peak in a (001) plane. A=(180-w)/180.times.100 In this
formula, w represents the half width value of the intensity
distribution measured along a Debye ring of the reflection
peak.
[0096] (Spinning Liquid Haze)
[0097] The haze of the spinning liquid filled into a cell having an
optical path length of 1 cm was measured using the NDH2000
Turbidity Meter manufactured by Nippon Denshoku.
[0098] (Average Layer Thickness of Layer-Structured Clay Mineral
Particles)
[0099] The layer thicknesses of all layer-structured clay mineral
particles observed in a cross-sectional area measuring 25
.mu.m.sup.2 in a transmitting electron micrograph (TEM,
magnification: 100,000.times.) of a fiber longitudinal
cross-section measured using the H-800 Electron Microscope
manufactured by Hitachi, Ltd., followed by calculation of their
average value.
[0100] (Degree of Dispersion (Y) of Layer-Structured Clay
Mineral)
[0101] The aforementioned wholly aromatic polyamide fibers were cut
along the fiber axis, and the resulting longitudinal cross-sections
were observed at a magnification of 100,000.times. with a
transmitting electron microscope (Model H-800) manufactured by
Hitachi, Ltd. When the total surface area S1 of a plurality of
regions in which changes in the state of the fiber cross-sections
were observed due to the effects of the aforementioned
layer-structured clay mineral particles per 25 .mu.m.sup.2 of the
observed cross-sectional area S2 was measured, the degree of
dispersion Y of the layer-structured clay mineral particles in the
fibers as defined by the aforementioned formula (1) was calculated
according to the following formula. Y(%)=(S1/S2).times.100
[0102] The average value of Y was determined from three
measurements.
[0103] (Solution Shear Viscosity)
[0104] The shear viscosity of the solution when preparing the
spinning liquid was measured at a temperature of 70.degree. C.
using the Rheomat 115 manufactured by Rheometric Scientific.
[0105] (Fiber Solvent Content N)
[0106] The fibers were centrifuged for 10 minutes (rotating speed:
5000 rpm) prior to drawing and then boiled for 4 hours in methanol
to extract the solvent and water in the fibers. The weight of the
methanol solution M2 after extraction and the dry weight of the
fibers M1 were measured and the solvent weight concentration C (%)
in the extract was determined with a gas chromatograph followed by
calculation of the solvent content N according to the following
formula. N=(C/100.times.M2)/M1.times.100
[0107] (Filament Breakage)
[0108] A plurality of the resulting drawn fibers were uniformly
formed into a fiber bundle, one end of the fiber bundle was
immobilized and then the bundle was cut so that the length to the
other end, from the immobilized end, was 20 cm. The total number of
filaments of the fiber bundle at this time was designated as H.
Next, the fiber bundle was moved back and forth 10 times in the
longitudinal direction in a bath filled with water (longitudinal
width: 0.5 m), after which the fiber bundle was taken out followed
by counting the number of filaments that remained in the bath. This
procedure was repeated five times and the total number of filaments
that remained in the bath was designated as M. The number of broken
filaments in 15000 m (X) was then calculated using the formula
below and this was repeated three times to determine the average
value. X=M.times.15000/(H.times.T.times.0.2)
EXAMPLE 1
[0109] 215 g of polymetaphenylene isophthalamide having an
intrinsic viscosity of 1.35 dl/g were dissolved in 785 g of NMP and
stirred to a uniformly transparent dope. Separate from this
procedure, a layer-structured clay mineral in the form of a
smectite clay mineral treated with polyoxypropylene methyl diethyl
ammonium chloride (trade name: Lucentite SPN, Co-op Chemical) was
mixed and dispersed in NMP to a concentration of 1% by weight. The
resulting layer-structured clay mineral dispersion was added to the
wholly aromatic polyamide solution so as to have the composition
shown in Table 1 followed by stirring to prepare a spinning liquid
(dope). The haze of the resulting dope was 2.41. After degassing
the resulting dope, it was extruded into the shape of filamentary
streams from a spinneret having a cap diameter of 0.07 mm and 100
holes, the filamentary streams were introduced into a coagulation
bath composed of a 43% aqueous calcium chloride solution
(containing 1% by weight NMP) at 85.degree. C., and then coagulated
at a spinning speed of 7 m/min. After washing, the resulting
undrawn fibers were drawn to 2.4 times in boiling water followed by
drying at 120.degree. C. and then subjecting to drawing heat
setting by 1.75 times at 350.degree. C. to obtain wholly aromatic
polyamide fibers containing a layer-structured clay mineral.
Measurement of the longitudinal cross-section of the filaments by
TEM demonstrated that the average layer thickness of the
layer-structured clay mineral particles was 90 nm. In addition, the
degree of orientation A of the layer-structured clay mineral
particles as obtained from the results of X-ray diffraction was
91%. The tensile strength, ultimate elongation and toughness factor
(TF) of the resulting fibers are shown in Table 1.
EXAMPLE 2
[0110] Wholly aromatic polyamide fibers having the composition
shown in Table 1 were produced in the same manner as Example 1 with
the exception that smectite layer-structured clay mineral (trade
name: Lucentite STN, Co-op Chemical) treated with trioctyl methyl
ammonium chloride was used for the layer-structured clay mineral.
The haze of the spinning liquid at this time was 1.92. In addition,
the average layer thickness of the layer-structured clay mineral
particles was 86 nm, and the degree of orientation A was 91%. The
tensile strength, ultimate elongation and toughness factor (TF) of
the resulting fibers are shown in Table 1.
Comparative Example 1
[0111] Wholly aromatic polyamide fibers were produced in the same
manner as Example 1 with the exception of not containing
layer-structured clay mineral. The tensile strength, ultimate
elongation and toughness factor (TF) of the resulting fibers are
shown in Table 1. TABLE-US-00001 TABLE 1 Amt. of Degree of layer-
orientation struc- A of layer- tured structured clay Fila- clay
Tensile mineral ment mineral strength Ultimate Tough- added
fineness particles (cN/ elongation ness (wt %) (dtex) (%) dtex) (%)
factor Ex. 1 2.0 1.74 91 4.42 40.7 32 Ex. 2 1.0 1.21 91 5.56 28.9
34 Comp. 0 2.26 -- 3.89 29.5 24 Ex. 1
EXAMPLE 3
[0112] 0.16 parts by weight of polymetaphenylene isophthalamide
having an intrinsic viscosity of 1.9 dl/g were dissolved in 1.46
parts by weight of NMP and stirred to a uniformly transparent dope.
0.18 parts by weight of layer-structured clay mineral in the form
of smectite clay mineral treated with polyoxypropylene methyl
diethyl ammonium chloride (trade name: Lucentite SPN, Co-op
Chemical) were added to this dope followed by stirring to prepare
Polymer Solution A. Separate from this procedure, 17.44 parts by
weight of polymetaphenylene isophthalamide were dissolved in 63.68
parts by weight of NMP to prepare transparent Polymer Solution
B.
[0113] After mixing and stirring the Polymer Solutions A and B,
17.08 parts by weight of NMP were further added to this mixture to
prepare a spinning liquid composed of 17.60 parts by weight of
polymetaphenylene isophthalamide, 0.18 parts by weight of Lucentite
SPN (trade name) and 82.22 parts by weight of NMP.
[0114] This spinning liquid was heated to 85.degree. C. and
extruded in the form of a filament stream from a spinneret having a
hole diameter of 0.07 mm and 1500 holes and then introduced into a
coagulation bath at 85.degree. C. to prepare undrawn fibers. The
composition of the coagulation bath consisted of 40% by weight of
calcium chloride, 5% by weight of NMP and 55% by weight of water,
and the immersion length (effective coagulation bath length) was
100 cm. After passing the undrawn fibers through the coagulation
bath at a speed of 7.0 m/min, the fibers were temporarily pulled
out of the bath into air. The coagulated undrawn filaments were
sequentially washed in first through third aqueous washing baths.
The total immersion time of this washing was 50 seconds.
Furthermore, water at a temperature of 30.degree. C. was used for
the first through third washing baths. Next, the washed and undrawn
filaments were drawn 2.4 times in hot water at 95.degree. C., and
after washing by continuing to immerse for 48 seconds in hot water
at 95.degree. C., the filaments were dry-heat treated by winding
onto a roller having a surface temperature of 130.degree. C.
Subsequently, the filaments were drawn 1.75 times while contacting
with a heating plate having a surface temperature of 330.degree. C.
to produce polymetaphenylene isophthalamide fibers. The fineness of
these fibers was 2.26 dtex, the tensile strength was 5.16 cN/dtex,
and the ultimate elongation was 43.2%.
[0115] The maximum draw ratio in the above-mentioned was 4.7 (draw
ratio/maximum draw ratio=0.51),k and the solvent content before
drawing was 5.0 parts by weight relative to 100 parts by weight of
the wholly aromatic polyamide.
[0116] In addition, the number of broken filaments in the
above-mentioned spinning and drawing processes were 6 per length of
15000 m, and the degree of dispersion Y of the layer-structured
clay mineral was 3%. The test results are shown in Table 2.
EXAMPLE 4
[0117] 0.32 parts by weight of the same polymetaphenylene
isophthalamide powder used in Example 3 were dissolved in 6.46
parts by weight of NMP cooled to -10.degree. C. to prepare a
transparent polymer solution. 0.72 parts by weight of
layer-structured clay mineral in the form of smectite clay mineral
(trade name: Lucentite SPN, Co-op Chemical) were added thereto
followed by stirring to prepare Polymer Solution A. Separate from
this procedure, 13.28 parts by weight of polymetaphenylene
isophthalamide were dissolved in 48.49 parts by weight of NMP
cooled to -10.degree. C. to prepare transparent Polymer Solution
B.
[0118] After mixing and stirring the Polymer Solutions A and B,
30.73 parts by weight of NMP were further added to this mixture to
obtain a spinning liquid composed of 17.60 parts by weight of
polymetaphenylene isophthalamide, 6.80 parts by weight of Lucentite
SPN (trade name) and 76.6 parts by weight of NMP.
[0119] This spinning liquid was spun and drawn according to the
same conditions and procedure as Example 3 to produce
polymetaphenylene isophthalamide fibers having fineness of 2.18
dtex, tensile strength of 6.03 cN/dtex, and ultimate elongation of
45.3%.
[0120] The number of broken filaments in the above-mentioned
spinning and drawing processes were 10 per length of 15000 m, and
the degree of dispersion Y of the layer-structured clay mineral was
25%. The test results are shown in Table 2. TABLE-US-00002 TABLE 2
Example 3 Example 4 Layer-structured clay mineral wt %* 1.0 4.0
Solution A viscosity: Shear viscosity: 0.1 sec.sup.-1 (poise) 2730
3420 Shear viscosity: 10 sec.sup.-1 (poise) 90 95 Solution B
viscosity: Shear viscosity: 0.1 sec.sup.-1 (poise) 420 410 Fineness
(dtex) 2.26 2.18 Tensile strength (cN/dtex) 5.17 5.32 Ultimate
elongation (%) 43.2 45.3 Toughness factor (TF) 38.5 40.6 Filament
breakage (no./15000 m) 6 10 Degree of dispersion Y (%) 3 25 *Based
on weight of wholly aromatic polyamide.
EXAMPLE 5
[0121] Spinning and drawing were carried out according to the same
conditions and procedure as Example 3. However, although the same
spinning solution as Example 3 was used, the hot water draw ratio
was 2.8 times, and the hot plate draw ratio at 330.degree. C. was
1.50 times. Polymetaphenylene isophthalamide fibers were obtained
that had a filament fineness of 2.22 dtex, tensile strength of 5.49
cN/dtex and ultimate elongation of 40.7%.
[0122] The maximum draw ratio in the hot water drawing process was
4.7 (draw ratio/maximum draw ratio=0.60), and the solvent content
of the fibers prior to drawing was 5.0 parts by weight relative to
100 parts by weight of the wholly aromatic polyamide.
[0123] In addition, the number of broken filaments in the fibers
was 8 per 15000 m. The test results are shown in Table 3.
EXAMPLE 6
[0124] Spinning and drawing were carried out according to the same
conditions and procedure as Example 3. However, although the same
spinning solution as Example 3 was used, the washing time prior to
hot water drawing was 34 seconds. Fibers were obtained that had a
filament fineness of 2.21 dtex, tensile strength of 6.12 cN/dtex
and ultimate elongation of 48.3%.
[0125] The maximum draw ratio in the hot water drawing process was
4.9 (draw ratio/maximum draw ratio=0.49), and the solvent content
of the fibers prior to drawing was 14.0 parts by weight relative to
100 parts by weight of the wholly aromatic polyamide.
[0126] In addition, the number of broken filaments in the fibers
was 2 per 15000 m. The test results are shown in Table 3.
TABLE-US-00003 TABLE 3 Example 3 Example 5 Example 6
Layer-structured clay mineral wt %* 1.0 1.0 1.0 NMP content in
undrawn fibers ppw* 5.0 5.0 14.0 Maximum draw ratio 4.7 4.7 4.9
Draw ratio 2.4 2.8 2.4 Draw ratio/max. draw ratio Ratio 0.51 0.60
0.49 Filament fineness (dtex) 2.26 2.22 2.21 Tensile strength
(cN/dtex) 5.16 5.49 6.12 Elongation (%) 43.2 40.7 48.3 Filament
breakage (No./15000 m) 6 8 2 *Based on weight of wholly aromatic
polyamide **Content per 100 parts by weight of wholly aromatic
polyamide
INDUSTRIAL APPLICABILITY
[0127] As wholly aromatic polyamide fibers of the present invention
have improved mechanical strength, degree of elongation and
toughness factor as compared with fibers of the prior art not
containing a layer-structured clay mineral, they can be used in
various applications that take advantage of these characteristics.
In addition, according to the production process of the present
invention, the occurrence of filament breakage during spinning and
drawing can be reduced, and fibers of stable quality can be stably
produced industrially.
* * * * *