Note: Descriptions are shown in the official language in which they were submitted.
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QP-37 40-B
TITLE
Spinnable Dopes and Articles Therefrom
Background
Poly-p-phenylenebenzobisthiazole, poly-p-
phenylenebenzobisoxazole and poly-2,5-benzoxazole are
intractable polymers by which i~ meant they are non-
melting but soluble. Mixtures of these polymers have
been m~de with thermoplastic polymers to provide
melt-processability. Mixtures of these polymers with
other intractable polymers have been made for various
purposes. Procedures for making these mixtures have
been deficient since the available techniques for
preparing solutions of the polymer combinations for
processing have required isolation of the intractable
polymer from its polymerization solvent, polyphos-
; phoric acid, prior to preparation of the mixed polymer
solution. The present invention overcomes these
deficiencies.
Summary of the Invention
This invention provides a spinnable
quaternary dope comprising the polymer combination of
a first polymer selected from poly-p-phenylenebenzo-
bisthiazole, poly-p-phenylenebenzobisoxazole or
poly-2,5-benzoxazole and a second polymer selected
from a thermoplastic polymer or another intractable
polymer in the proportions of 5% to 70% by weight of
the first polymer and 30% to 95% by weight of the
second polymer in a solvent combination of polyphos-
phoric acid and methanesulfonic acid or chlorosulfonic
acid, the concentration of said polymer combination in
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said solvent combination being at least 1 percent by
weight. A method for preparing this spinnable
quaternary dope and fibers therefrom are also
comprehended.
Detailed Description cf the Invention
Poly-p-phenylenebenzobisthiazole (PBT), poly-
p-phenylenebenzobisoxazole (Pso), and poly-2,5-
benzoxazole (As-PBO) are prepared in polyphosphoric
acid (PPA) (see U.S. Patent No. 4,533,693). Since
they are highly intractable polymers, hence not
amenable to melt-processing, efforts have been made to
combine th~em with thermoplastic polyamides. The
procedure normally followed, involves isolating the "
PBT, PBO or As-PaO from the polymerization solvent and
redissolving it in methanesulfoni~ acid at low
concentrations. The thermoplastic polyamide is then
added to the solution such that the total polymer
concentration is under 5 percent by weight. The
~ solution is then processed into fibers or films.
; 20 The present invention provides a novel
spinnable quaternary dope and a technique for pre-
paring it which is unobvious from and superior to the
prior art procedures. It involves first preparing a
solution of a thermoplastic polymer in methanesulfonic
acid (MSA) or chlorosulfonic acid or an equivale,nt
strong acid. Any of a variety of thermoplastic
polymers may be used as the component which provides
melt-processability. Thermoplastic polyamides are
preferred. The concentration of the thermoplastic
polymer in solution may range from about 0.5-20% on a
weight basis, preferably 1-15%. In place of the
thermoplastic polymer one may use an intractable
polymer, such as poly~2,5(6)-benzimidazole (ABPBI).
To the solution of the thermoplastic or
intractable polymer, one adc1s a solution cf PBT, PBO
or AB-PBO in the polyphosphoric acid polymerization
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solvent and then shear mixes the combined solutions.
Preferably the PBT, PBO or AB-PBO should have an
intrinsic viscosity of at least lS dL/g as measured in
MSA. The concentration of the PBT, PBO or AB-PBO in
the polyphosphoric acid should be at least 0.5 and
preferably between 1 and 20 weight percent. The
combined polymer concentration of the resulting
quaternary solution should be at least 1% by weight
and the MSA/PPA solvents ratio should range from 95/5
to 5/95 on a weight basis. The presence of PPA
increases spin solution viscosity for improved
spinnability. In practice, chunks of the PBT, PBO or
AB-PBO in polyphosphoric acid are added to the
thermoplastic polymer solution with shear mixing,
preferably without applying external heating to avoid
degradation of less stable thermoplastic polymer. An
Atlantic Mixer is quite useful for this purpose,
shearing being effected by the wall wiping mechanism.
The proportions of the solutions are selected to yield
the ratio of PBT, PBO or AB-PBO to thermoplastic or
intractable polymer desired in the dope. It is
preferred that the concentrations of both solutions be
about equal so that the final concentration of total
polymer in the quaternary dope remains constant while
~5 the ratio of the two solutions are varied to obtain
different polymer ratios. The ratio of PPA to MSA or
chlorosulfonic acid is preferably in the range of
60:40 to 30:70 on a weiqht percent basis. To obtain
maximum benefits, the PBT, PBO or AB-PBO should
constitute from 5 to 70% by weight of the polymer
mixture. The second polymer should range from 30 to
95% by weight. Preferably, the polymers should be in
the ratio of 60:40 to ~0:60 by weight.
The present invention provides advantages of
operation since the PBT, PBO or AB-PBO need not be
separated from the polymerization solvent. Further, by
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combining the polymers as solutions an obstacle
previously ~acing the art was removed. Thermoplastic
polyamide, for example, is relatively insoluble in
polyphosphoric acid at room temperature. When heating
to promote dissolution in the polyphosphoric acid, it
is found that there is severe degradation of the
thermoplastic polyamide. Surprisingly, the solutions
can be combined with shear mixing without use of the
high temperatures that would degrade the thermoplastic
polyamide. A further advantage is that the rheology
of the resulting quaternary solution from the combined
solutions is such as to permit air-gap spinning.
Fibers spun from such quaternary solutions have been
found to possess tensile properties that are
substantially greater than those spun from ternary
solutions of the same polymer combination. Novel
microstructures have been observed in scanning
electron micrographs of cross-sections transverse to
the fiber length. Films, bars and other composite
articles may be prepared by windin~ those composite
fibers of the invention containing a thermoplastic
polymer as the second polymer into a form and
compression molding it with heat.
The following examples illustrate the
invention and are not intended as limiting. Intrinsic
viscosities were measured in MSA:
Example 1
15 parts by weight of thermoplastic polyamide
were added to 85 parts by weight of MSA in a glass jar
and stirred at room temperature using a simple
polytetrafluoroethylene coated magnetic stirrer. The
thermoplasti~ polyamide employed is an amorphous
copolymer of (48tt) bis~p-aminocyclohexyl)methane,
isophthalic and dodecanedioic acids in a 100/60/~0 mol
percent basis. The solution was a brown viscous
liquid. 60.5g of the solution was poured irlto an
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Atlantic Mixer (Model No. 2CV, Capacity: 150 cc).
Then 61.8 grams of a 14.5 wt. % dope of PsT ~19.6 dL/g
intrinsic viscosity) in PPA were added to the mixture
with the mixer operating at low speed and without
applying external heating. The PBT/PPA dope broke up
and "dissolved" into the polyamide-MSA solution.
Mixing was continued into the next day, when the
mixture became homogeneous. The resulting t~uaternary
solution or dope exhibited shear opalescence. It was
stirred and deaerated under vacuum overnight. The
dope was transferred to a spin cell and spun at 54C
through a 0.25 inch air gap into an ice water bath to
extract solvent. The dope was spun from a 10-hole
spinneret (0.004 in holes) at 7.5 m/min. The through-
put rate was 0.02 ml/min/hole. To ensure completeremoval of the acid solvents, bobbins of yarn were
immersed in water overnight and then air dried. The
as-spun composite yarn (psT/polyamide~ 50/50 by weight
or 42/58 by volume) had the following ~ilament tensile
properties ~denier, tenacity, elongation, modulus)
(D/T/E/M): 66 denier, 4.3 gpd, 1.4%, 344 gpd. and an
orientation angle of 15. Thermal stability was
evaluated by threading the yarn through a horizontal
hot tube with one end tied and a 10-gram load on the
other end. The temperature was raised to 716C over a
period of 3 hours 30 minutes at which point the yarn
broke.
Example 2
15 grams of an amorphous thermoplastic poly-
amide, a copolymer of hexamethylene diamine, ~20tt)
bis~p-aminocyclohexyl)methane, isophthalic and
terephthalic acids in a 96/4/70/30 mol percent basis,
was dissolved in 85 grams of MSA at room temperature.
72.3 grams o~ the solution was mixed with 73.2 grams
of the same PBT/PPA dope used in Example 1 to give
PBT/polyamide weight ratio of 50/50 and MSA/PPA
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solvents ratio of 50/50. The mixing was done without
external heat. After several hours, a homogeneous
quaternary spin dope was obtained. It was shear
opalescent and light metallic green. Mixing was
continued to the next day when vacuum was applied to
deaerate the dope. After remaining quiescent over a
weekend, some phase separation took place. The dope
was mixed for 2.5 hours before transferring to the
spin cell. It was spun at 60C from a 10-hole
spinneret of 0.005 in hole diameter through a 0.75 in
air gap at 7.5m/min with spin-stretch factor of 4.7
into ice water. The yarn was immersed in water for
several days, then in acetone to remove any residual
MSA and then air dried. The 50/50 PBT/polyamide
composite fiber tensile properties (T/E/N) are: 3.7
gpd, 0.6%, 390 gpd. The same thermal stability test
was made as in Example 1 and the yarn survived till
723C. In a separate experiment, a higher PBT to
polyamide ratio of 62/38 was used. The spun composite
fiber had T/E/M properties of 5.7 gpd~0.82/691 gpd.
Example 3
A solution was made using 30 grams of the
polyamide of Example 1 and 170 grams of MSA. 94.~
grams of this solution were mixed with 141.3 grams of
the same P~T/PPA dope used in the above examples to
make a spin dope where the psT/polyamide ratio was
60/40 by weight or 53/47 by volume and MSA/PPA ratio
of 40/60. The homogeneou~ quaternary spin dope was
heated to 60C to reduce viscosity for trans~er to the
spin cell. Yarn was spun at 75C through a 0.375 in
air gap, at 7.5 m/min using 10-hole spinneret with
0.005 in holes. Spinning was exeellent. After over-
night immersion in water, the bobbin of yarn was
imrnersed in acetone the next night to extract any
residual MSA. The dried composite ~iber T/~,~M
properties are 5.3 gpd/l.O~f342 gpd.
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Example 4
A spin dope of PBT and the polyamide of
Example 1 at a polymer ratio of 59.2/40.8 by weight
~51/49 by volume) was made using 54.3 grams of the
polyamide/MSA solution of Example 3 and ~1.4 grams of
the same P8T/PPA dope used in the above examples. The
resulting quaternary spin dope with a MSA/PPA ratio of
40/60 was mixed without external heating. On the
following day, the temperature was raised to and kept
at 75C for 1.5 hours to reduce viscosity before
transfer to the spinning cell. Yarn was spun at 75C,
through a 0.5 in air gap, at 7.5 m/min using a 10-hole
spinneret having 0.005 in holes. The as-spun
composite fiber had T/E/M properties of 7.3 gpd/1.5~/
586 gpd.
Example 5
A quaternary spin dope containing cis-P~O and
the polyamide of Example 1 in a 66/34 weight ratio
(59/41 by volume) was made using 65.2 grams of 15% of
the polyamide in MSA and 136.2 grams of 14.1% cis-PBO
(intrinsic viscosity of 16.6 dL/g) in PPA. The
mixture with a MSA/PPA ratio of 32/68 was mixed
overnight under house vacuum (24 in vacuum) without
applying external heat. The resulting quaternary dope
was heated to 60C the next day to improve flowability
for filling the spin cell. The dope was shear aniso-
tropic. Yarn was spun at 60C through a 0.75 in air
gap at 7.5 m/min using 3 10-hole (0.005 in holes)
spinneret. The composite fiber has the following
T/E/M tensile properties: ~.4 gpd/2.2%/324 gpd. The
fiber orientation angle is 17.
Example 6
A quaternary spin dope containing AB-PBO from
3-amino-4-hydroxybenzoic acid and the polyamide of
Example 1 in 66,'34 weight (~0/40 volume) ratio was
made using 69.5 grams of the polyamide in I~SA and
139.8 grams of AB-PB0 (intrinsic viscosity of 8.8
dL/g) in PPA. The AB-PBO/PPA dope viscosity was high
and it could not be mixed with the polyamide/MSA
solution until it was heated up to 70C at which time
a homogeneous dope was prepared. The dope was removed
from the mixer and charged into the spin cell. Yarn
was spun at 70C through a 0.7 in air gap, and at a
throughput rate of 0.02 ml/min/hole but at a windup
speed of 2.0 m/min. The dried composite fiber has
T/E/M tensile properties of 2.3 gpd/12.5%/36 gpd. The
fiber orientation angle is 45.
Example 7
A quaternary spin dope consisting of 3.0 weighk
percent solids (60 weight percent PBT/40 weight
percent) of the polyamide of Example 1, in 97 weight
percent mixed solvents (50 weight percent MSA/50
weight percent PPA) was prepared from a solution of
the polyamide of Example 1 at 1.35 weight percent
concentration in MSA/PPA (55.9 weight percent MSA/44.1
weight percent PPA) and a dope of PBT (17.0 dL/g
intrinsic viscosity) at 14.9 weight percent
concentration of PPA. Preparation was as follows:
110.2 grams of MSA and 87.0 grams of PPA were mixed
together in a glass jar at room temperature using a
magnetic stirrer coated with Teflon~ fluoropolymer.
2.7 grams of the polyamide was added to the MSA/PPA
mixed solvents and stirred at room temperature. The
solution was poured into an Atlantic Mixer. Then 27.3
grams of the P~T/PPA dope were added to the Mixer
while operating at slow speed under vacuum (for
deaeration) without applying external heat. The
PBT/PPA dope was found to gradually break up and
"dissolve" into the polyamide MSA/PPA solution. The
next day there were still a few chunks of PBT/PPA dope
stuck at the top of the Mixer blades. The chunkæ of
PBT/PPA dope were scraped into the rest of the spin
dope, and mixing was continued into the next day when
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the mixture became a homogeneous phase, gel-like in
consistency. The quaternary spin dope was transferred
to a spin cell and air-gap spun (0.25 in air-gap) at
room temperature at 12.6 meter/minute using a 10-hole
spinneret with hole diameter of 0.005 in and a spin-
stretch factor of 4.0 [a 10-holP spinneret with a hole
diameter of 0.010 in was also usad to air-gap spin
(0.25 in air-gap) yarn a~ room temperature and 2.0,
4.0 and 6.0 meter/minute with a spin-stretch factor of
2.5, 5.0, and 7.6, respectively.~ The throughput rate
was 0.04 ml/min/hole. To ensure complete removal of
the acid solvents, the bobbins of yarn were immerse~
in water (the extraction solvent) overnight and then
air dried. The as-spun yarn (PBT/polyamide, 60/40 by
weight or 52/48 by ~olume) tensile properties (denier,
tenacity, elongation, modulus) are: 39 denier, 2~2
gpd, 6.3%, 113 gpd. The orientation angle measured by
wide angle X-ray diffraction is 40. The relatively
low tensile properties are attributed to inade~uate
deaeration.
Exam~le 8
A quaternary spin dope consisting of 5.8 weight
percent solids (60 weight percent PBT/40 weight
percent ABPBI) in 94.2 weight percent solvent (79
weight percent MSA/21 weight percent PPA) was prepared
from a solution of ABPBI at 3.0 weight percent
concentration in MSA and the same PBT/PPA dope of
Example 1. Preparation was as follows: 4.8 grams of
ABPBI, poly-2,5(6)-benzimidazole (5.17 inherent
viscosity) polymer, measured at 0~5 g/100 ml sulfuric
acid, was added to 155.2 grams MSA in a glass jar and
stirred at 60C using the magnetic stirrer coated with
Teflon~ fluoropolymer. The solution was extremely
viscous. The solution was poured into an Atlantic
Mixer. Then 48.0 grams of cut up pieces of the
PBT/PPA dope were added to the Mixer while operating
at slow speed under
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/ vacuum (for deaeration) and 50C. The PBT/PPA dope
/ was found to gradually break up and "dissolve" into
the ABPBI/MSA solution. Mixing was continued into the
next day. The spin dope ~as transferred to a spin
cell and air-gap spun (0.25 in air-gap) at room
temperature at 12.6 meter/minute using a 10-hole
spinneret with hole diameter of 0.005 in and a
spin-stretch factor of 4.0 indicating that the as-spun
yarn could sustain a spin-stretch. The throughput
rate was 0.04 ml/min/hole. Due to the presence of
many air pockets, the throughput rate was increased to
0.08 ml/min/hole, and yarn was spun at 7.S
meter/minute with a spin-stretch factor of 1.2. To
ensure complete removal of the acid solvents, the
bobbins of yarn were immersed in water (the extraction
~olvent) overnight and then air d~ied. The as-spun
filament (PBT/ABPBI, 60/40 by weight or volume)
tensile properties (denier, tenacity, elon~ation,
modulus) are: 9.8 denier/filament, 6.2 gpd, 10.7~,
272 ~pd. ~he orientation angle for the as-spun fiber
is 31.
Example 9
Unidirectional test bars were prepared by
winding the P~T/polyamide yarn of Example 1 around a 7
in x 7 in x 0.25 in plate such that the yarn was laid
parallel and 3.5 layers thick. A layer of polyimide
film (Kapton * - E. I. du Pont de Nemours and Co.,
Inc.~ coated with a mold release agent (Frekote *33 )
was placed on the plate before and after the yarns
were wound. Finally, a thin metal sheet was placed on
each side of the structure. ~his whole assembly was
then heated and pressed at 315C and 6,000 pounds (122
psi) for lS minutes. Two (2) coherent films were
obtained. 0.25 in x 6.0 in strips were cut parallel
to the fiber direction and 4~8 g of the strips were
stacked inside an open-ended H-shaped female mold.
* denotes trademark
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With the male part of the mold and 0.118 in thick
shims in place, pressure was applied initially at 300
lbs (200 psi), raised to a maximum of 5,400 lbs (3,600
psi) at 315C and released during the cool down
period. The resulting bar, 0.25 in x 6 in x 0.113 in,
has a flex strength/modulus of 42 kpsi/9.6 mpsi and
short-beam-shear strength of 2.4 kpsi. A thin strip,
about 0.78 mm thick, was removed from the bar. It0 exhibited an orientation angle of 13.
ExamPle 10
A direct winding technique was also used for
making unidirectional test bars. The same H-shaped
mold was mounted on a rotating shaft and the
PBT/polyamide yarn of Example 2 was wound into the
open ended female section 0.25 in x 6.0 in area on
both sides of the mold. After 4.7 grams of yarn was
wound, the male section was placed on both sides of
the mold and cold pressed at 5,000 pounds to compact
the fiber into two bars. The exposed fiber ends at
both ends of the mold were cut with a razor blade.
Then the mold was opened and the two bars were stacked
together and hot pressed in the mold using 0.1195 in
shim thickness at 315C and 5,000 pounds (3,333 psi)
25 for 20 minutes. An initial cold pressure of only 500
pounds was used, but the pressure was maintained at
6,000 pounds during cool down. Final bar dimensions
were 0.1035 in x 0.25 in x 6 in. Measured flex
strength/modulus properties are 54 kpsi/8.8 mpsi with
short-beam-shear strength tSBSS) of 4.4 kpsi. A thin
strip, abouk 0~68 mm thick, was removed from the bar.
It exhibited an orientation angle o~ 11.
By building successive layers of coating on a
mold, ollowed by extraction and drying, an in situ
composite o~ complex shape is easily prepared from the
quaternary dopes. A small cylinder was prepared by
coating a stainless steel rod with a dope o~ the
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invention containing 15% solids. Each coating was
extracted by washing in water and drying with a hot
air gun. After application of four coats, the
cylinder was consolidated using a hot air gun at
315C.
Fibrids were made by mechanical shear
precipitation of dopes of the invention (5 grams dope
into 300 mls of water in a Waring*blender) and small
paper samples were prepared. A slurry was made by
blending in a blender 0.5 gram of fibrids in 500 ml
water. The slurry was filtered using a #40 filter
paper in a 9-cm diameter Buchner funnel. ~he wet
paper, about 3 in diameter, was then cold pressed at
8,000 pounds pressure. Films were produced from these
papers by consolidating at 315C and 100 psi.
* denotes trade mark
