Note: Descriptions are shown in the official language in which they were submitted.
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TITLE
PROCESS FOR IMPARTING PERMANENCE TO A SHAPED NON
THERMOPLASTIC FIBROUS MATERIAL
BACKGROUND OF THE INVENTION
Field of the Invention
The present invention relates to a process to impart permanence to
a shaped non thermoplastic fibrous material comprising amino groups. It
also relates to permanently shaped fibrous material obtainable from that
process.
Description of the Related Art
Many textile processes involve the twisting of multi-filament fiber
prior to subsequent manufacturing into woven, knitted or braided
structures. Twisting is the process of combining filaments into yarn by
arranging them according to a helix pattern or combining two or more
parallel single yarns into plied yarns or cords. Twist is generally expressed
as the number of turns around the longitudinal axis of the fiber per unit
length of the fiber; i.e. turns per meter abbreviated as tpm. Multi-filament
yarn twisting is generally considered as a processing aid providing high
cohesion to the yarn. It is also considered as a suitable filament
arrangement for an optimum load sharing. Twisting is also used to impart
to the yarn surface a uniform morphology allowing for a better anchoring
of the matrix, such as a rubber, which in turn contributes to a more
efficient stress transfer and a better mechanical adhesion between the
matrix and the reinforcing fiber. Therefore twisting is generally employed
to increase strength, smoothness and uniformity or to obtain specific
effects in the yarn.
For these reasons, it may be interesting to provide fibers stabilized
in a particular shape, for instance under a twisted form. US 5, 794, 428
discloses a process to permanently set the twist of a thermoplastic fiber.
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However, high-modulus, high-strength non thermoplastic fibrous
material, and more generally crystalline fibers, such as aramid fibers, are
difficult to stabilize at moderate and high twist levels because they have a
natural tendency to untwist readily.
For low and medium twist levels, it is known to use the so-called S
and Z twist arrangement, which is a two step process combining a S
twisted yarn with a Z twisted yarn leading to a stabilized combined
assembly. Nonetheless, in the case of non thermoplastic fibers comprising
amino groups, for high tpm exceeding for example a hundred turns per
meter for a 1670 dtex yarn, it is not practical, productivity and uniformity
wise, to use that process.
Now, it has been found that by submitting a shaped fibrous material
to a constant and uniformly distributed electromagnetic field generated by
a specific microwave, it was possible to impart permanence to said
shaped fibrous material, even though this material is a high modulus or a
high strength non thermoplastic material comprising amino groups.
Microwave heating is a well known technology with industrial as
well as domestic applications. US 5, 175, 239 and US 5, 146, 058 disclose
the use of a microwave to heat treat para-aramid fibers in order to obtain
fibers showing internal cracks through the ,filament cross-section.
SUMMARY OF THE INVENTION
One aspect of the invention is a process to impart permanence to a
shaped non thermoplastic fibrous material comprising submitting, under
low tension, the shaped non thermoplastic fibrous material to a constant
and uniformly distributed electromagnetic field generated by a single
mode Transverse Magnetic 010 mode cylindrical resonant cavity
microwave reactor,
- the uniformly distributed electromagnetic field being operated at
frequencies of from 5 MHz to 500 GHz,
- the shaped non thermoplastic fibrous material being processed
through the uniformly distributed electromagnetic field at a rate
of from 0.01 to 1200 m/min,
- the rate of the increase in temperature of the shaped non
thermoplastic fibrous material being less than 300°C/s,
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- the shaped non thermoplastic fibrous material comprising i) at
least one polymeric structure comprising amino groups and ii) at
least 0.05 weight % of an aqueous composition.
Another aspect of the invention is a permanently shaped non
thermoplastic fibrous material obtainable or obtained through the process
described above.
Another aspect of the invention is a structure comprising the
permanently shaped non thermoplastic fibrous material of the invention.
This structure may be a woven, knitten, braided, spiralled, felted,
unidirectionally laid down or non woven structure. Non woven structure
may include fleeces, wadding, felt.
Another aspect of the invention is a method of imparting
permanence to a shaped fibrous non thermoplastic material comprising
submitting said shaped non thermoplastic fibrous material to a constant
and uniformly distributed electromagnetic field generated by a single
mode Transverse Magnetic 010 mode cylindrical resonant cavity
microwave reactor.
Another aspect of the invention is a process to impart permanence
to a twisted pare-aramid fiber comprising submitting said fiber. under a
tension of less than 0.2 gpd, to a constant and uniformly distributed
electromagnetic field produced by a single mode Transverse Magnetic
010 mode cylindrical resonant cavity microwave reactor,
- the uniformly distributed electromagnetic field being operated at
frequencies of from 5 MHz to 500 GHz,
- the fiber being processed through the microwave reactor at a
rate of from 0.01 to 1200 m/min,
- the rate of the increase in temperature of the fiber being less
than 300°C/s,
- the fiber comprising at least 0.05 weight % of an aqueous
composition.
A permanent shape for a non thermoplastic fibrous material may be
required for special applications such as imparting to a fiber a stretch
factor independent from the elastomeric nature of the fiber. For instance,
such a permanently shaped fiber may be used in a rubber composite in
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order to decrease the elongation gradient between the fiber and the
rubber.
With the process of the invention, it is possible to impart to a non
thermoplastic fiber a permanent twist of up to the maximum operational
twist level. The maximum operational twist level is generally considered as
a twist level which will not provoque fracture or rupture of the filaments
composing the twist assembly. For instance, this permanent twist level
can reach 1000 tpm for a 1670 dtex yarn made of para-aramid fiber. The
fiber shows no internal crack such as the one which could appear through
the filament cross-section like described in US 5, 175, 239. It has a high
cohesion and a high stability. In particular, with the process of the
invention, it is possible to stabilize in a highly uniform manner a twisted
non thermoplastic fiber. This high stabilization may be operated for any
twist level necessary for any subsequent processing such as spiraling,
knitting, weaving, braiding, felting or embedding in an elastomer matrix or
a composite matrix.
Such a permanently twisted non thermoplastic fiber may be used
as a sewing thread, a fiber to reinforce various matrixes or a woven or
knitted fabric, making it possible to achieve high cohesion and stability in a
woven or knitted structure. The woven or knitted structure made of a
permanently twisted non thermoplastic fiber of the invention is highly
stable dimensionally and will not present residual torque effect. Such a
structure is also stretchable.
The process of the invention also has the advantage of eliminating
intermediate steps which would be necessary to processes of the prior art
to maintain the shape of a fibrous material.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is a schematic diagram of a process according to the
present invention where the fibrous material is a fiber
Fig. 2 is a drawing showing a perspective view of the microwave
reactor with a linear trajectory for the fiber path.
Fig. 2a is a drawing showing the constant and uniformly distributed
electromagnetic field generated by a microwave reactor according to Fig.2
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Fig. 3 is a drawing showing a perspective view of the microwave
reactor with a sinusoidal trajectory for the fiber path.
Fig. 4 is a scanning electron microscopy picture of a cross section
of a bundle of filaments of Example 1 of the present application.
Fig. 4a is the related close-up of a single filament of Fig. 4.
Fig. 5 is a scanning electron microscopy picture of a cross section
of a bundle of filaments of Example 2 of the present application.
Fig. 5a is the related close-up of a single filament of Fig. 5.
Fig. 6 is a scanning electron microscopy picture of a cross section
of a bundle of filaments of Example 3 of the present application.
Fig. 6a is the related close-up of a single filament of Fig. 6.
Fig. 7 is a scanning electron microscopy picture of a cross section
of a bundle of filaments of Example 4 of the present application.
Fig. 7a is the related close-up of a single filament of Fig. 7.
Fig. 8 is a scanning electron microscopy picture of a cross section
of a bundle of filaments of Example 5 of the present application.
Fig. 8a is the related close-up of a single filament of Fig. 8.
DETAILED DESCRIPTION OF THE DRAWINGS
Referring to FIG.1, fiber 11 from supply tension regulated roll 12 is
fed over rolling guide 13 to assure the desired alignment of the fiber. The
fiber is fed to the pretreatment unit 14 where it can be watered so that the
amount of water content in the fiber is at least 0.05 weight %. The water
pretreatment can be optional in the case of a never-dried fiber having
already more than 0.05 weight % water. The pretreatment unit 14 can
alternatively be a dewatering unit to tailor the amount of water contained
in the supply fiber 11. It can also be a temperature adjusting pretreatment
and/or a coating or plasma or any suitable treatment. Optionally, the
pretreatment unit can be a twisting unit or any texturizing unit imparting a
filament deformation. From the pretreatment unit 14, the fiber is fed to
tension-control roll 15 and then passes into the microwave resonant cavity
reactor 16. The process can be tailored to include several resonant cavity
reactors in any suitable arrangement in series or irYparallel. The
microwave electromagnetic field is controlled through the microwave
control 17. The fiber is maintained in the cavity at a relatively low tension,
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preferably suitable to maintain the shape of the fibrous material,
preferably less than 0.2 g/denier. At the exit of the microwave, the fiber is
fed to a tension-control roll 18 and then to a guide 19. The fiber is then fed
to rolling guide 20 to assure the desired alignment of the fiber. The fiber is
fed to the post-treatment unit 21 where it can be further heated, dried or
surface treated by coating or plasma treatment for instance or by any
other suitable post treatment. The use of the post-treatment unit is
optional. The fiber then passes through a rolling-tension guide 22. Finally,
the fiber is wound using a tension controlled precision winder 23.
The process of Fig. 1 can be further modified to allow the treatment
of several fibers run in parallel.
Referring now to FIG. 2, a cylindrical microwave resonant cavity
reactor indicated generally as 30 suitable for use in the present invention
is depicted. The reactor comprises a cavity defined by a cylinder 31
designed to support a TM010 (Transverse Magnetic 010) mode and the
desired resonant condition at the center frequency which is generally set
for industrial applications at 915 MHz or 2450 MHz. Suitable dimension for
a 915 MHz resonant condition are provided on Fig. 2. Typical units are
915 MHz, 400 W amplifier coupled to a 28 VDC, 53 A switching power
supply or 915 MHz, 800 W amplifier coupled to a 28 VDC, 107 A power
supply.
The circular cross section reactor combines the radially symmetric
electromagnetic field distributions and the well defined axial
electromagnetic field profile. By "circular cross section" is meant herein a
circular or an oval cross section.
A microwave source 32 initiates the microwave. The fiber 11 is fed
through inlet port 33 and exits through outlet port 34. The fiber path is
linear.
Referring to FIG. 3, a cylindrical microwave resonant cavity reactor
40 is depicted, similar to the one shown in FIG. 2 but comprising in
addition ceramic guides 41 allowing the fiber path to be sinusoidal.
DETAILED DESCRIPTION
"Fibrous material", as used herein, includes endless fibers such as
filaments, short fibrous structures, short cut fibers, microfibers, multi-
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filaments, cords, yarns, fibers, felt, fabric, woven, knitted, braided,
spiraled, felted structures or nonwoven forms. The fibers may be made
into yarns of short fibrous structures which are spun into staple fibers, into
yarns of endless fibers or into stretchbroken yarns which can be described
as intermediate yarns between staple and continuous yarns. The yarn,
fiber, fabric, woven, knitted, braided, spiraled, felted structure or
nonwoven form may be made of continuous filaments, short fibers or pulp.
"Shaped fibrous material" as used herein, includes any fiber, fabric,
textile, garment, fibrous structure or finished product made of the fibrous
material as defined above, having been submitted to any shaping process
such as twisting, weaving, braiding, crimping, plying, knitting, spiraling,
felting, unidirectionally laying down or any other deformation.
"Aqueous composition", as used herein, includes water, solvents,
and/or mixture thereof under the form of a solution, an emulsion or a
dispersion. It can contain salts, polymers, or other emulsified, dispersed or
dissolved chemical compounds. Preferably, the aqueous composition is
water. This aqueous composition may be present within the fibrous
material under the free form and/or under the bound form. In a preferred
embodiment of the invention, the aqueous composition is present under
both forms, free and bound.
"Thermoplastic material", as used herein, means a material that
softens when exposed to heat and returns to its original condition when
cooled to room temperature. A non thermoplastic material does not soften
when exposed to heat.
The non thermoplastic fibrous material suitable in the present
invention includes any natural or man made non thermoplastic fibrous
material comprising at least one polymeric structure comprising amino
groups. "Amino groups", as used herein, includes amine groups, amide
groups and/or amino-acid groups. Man made and natural fibrous material
include polyamides, polyamines, polyimides such as polybenzimidazole
(PBI), polyphenylenebenzobisoxazole (PBO), natural silk, spider silk, hair
and all natural fibers presenting amino-acid sequences. These groups can
be part of a linear or branched, cyclic or heterocyclic, saturated or
unsaturated, aliphatic or aromatic chemical structure. Preferred polymeric
structures comprising amino groups include polyamides, polyamines,
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polyimides, aramids, blends and mixtures thereof. Preferably, the
polymeric structure comprising amino groups is an aramid.
Aramids are polymers that are partially, preponderantly or
exclusively composed of aromatic rings, which are connected through
carbamide bridges or optionally, in addition also through other bridging
structures. The structure of such aramids may be elucidated by the
following general formula of repeating units:
(-N H-A1-N H-CO-A2-CO)n
wherein A1 and A2 are the same or different and signify aromatic and/or
polyaromatic and/or heteroaromatic rings, that may also be substituted.
Typically A1 and A2 may independently from each other be selected from
1,4-phenylene, 1,3-phenylene, 1,2-phenylene, 4,4'-biphenylene, 2,6-
naphthylene, 1,5-naphthylene, 1,4-naphthylene, phenoxyphenyl-4,4'-
diyelen, phenoxyphenyl-3,4'-diylen, 2,5-pyridylene and 2,6-quinolylene
which may or may not be substituted by one or more substituents which
may comprise halogen, C1-C4-alkyl, phenyl, carboalkoxyl, C1-C4-alkoxyl,
acyloxy, vitro, dialkylamino; thioalkyl, carboxyl and sulfonyl. The -CONH-.
group may also be replaced by a carbonyl-hydrazide (-CONHNH-) group,
azo-or azoxygroup.
These aramids are generally prepared by polymerization of diacid
chloride, or the corresponding diacid, and diamine.
Examples of aramids are poly-m-phenylene-isophthalamide and
poly-p-phenylene-terephthalamide.
Additional suitable aromatic polyamides are of the following
structure:
(-NH-Ar1-X-Ar2-NH-CO-Ar1-X-Ar2-CO-)n
in which X represents O, S, S02, NR, N2, CR2, CO.
R represents H, C1-C4-alkyl and Ar1 and Ar2 which may be same
or different are selected from 1,2-phenylene, 1,3-phenylene and 1,4-
phenylene and in which at least one hydrogen atom may be substituted
with halogen and/or C1-C4-alkyl.
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Further useful polyamides are disclosed in U.S. Pat. No. 4,670,343
wherein the aramid is a copolyamide in which preferably at least 80% by
mole of the total A1 and A2 are 1,4-phenylene and phenoxyphenyl-3,4'-
diylene which may or may not be subsituted and the content of
phenoxyphenyl-3,4'-diylene is 10% to 40% by mole.
Additives may be used with the aramid and, in fact, it has been
found that up to as much as 10% by weight, of other polymeric materials
may be blended with the aramid or that copolymers may be used having
as much as 10% of other diamine substituted for the diamine of the
aramid or as much as 10% of other diacid chloride substituted for the
diacid chloride of the aramid.
In addition to the at least one polymeric structure comprising amino
groups, the non thermoplastic fibrous material of the invention may also
comprise at least one thermoplastic polymer. Such thermoplastic polymer
includes polyvinylchloride, nylon, polyfluorocarbon, polyethylene,
polypropylene and mixtures thereof.
"Constant and uniformly distributed electromagnetic field ", as used
herein, means an electromagnetic field which is radially symmetric and
axially invariant. Such an electromagnetic field may be produced by a
microwave reactor. "Microwave", as used herein, means electromagnetic
radiation in the range of frequency from 5 MHz to 500 GHz. Because of
Government regulation and the present availability of magnetron power
sources, the frequency normally is 915 or 2450 MHz for industrial
applications.
The microwave reactor suitable for the present invention is a single
mode microwave reactor with a cylindrical geometry. In such a geometry,
when the fibrous material is a fiber, the electromagnetic field is
predictable, uniformly distributed around the fiber.
This circular cross section reactor, depicted in figures 2 and 3
combines the radially symmetric electromagnetic field distributions and the
well defined axial electromagnetic field profile.
An example of a particularly suitable reactor for the invention is the
single mode TM010 (Transverse Magnetic 010 mode) cylindrical resonant
cavity, described in A.C. Metaxas and R.J. Meredith, Industrial Microwave
Heating, Peter Peregrinus Ltd., London, England, 1983, pp. 183-193,
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equipped with an American Microwave Technology (AMT) solid-state
amplifier as microwave power source, 32.7 cm wavelength, powered from
a 28 VDC power supply and with a maximum power level of 400W, with
dimensions of an inner length (L) of 30 cm and an inner radius ( R) of
12.5 cm and generating a resonant frequency of 915 MHz.
Associations in series or in parallel or any suitable arrangements of
the previously described cavities are considered to be part of the scope of
the invention.
"Under low tension", as used herein, means substantially very low
tension. When the fibrous material is any fibrous structure but a fiber, it is
preferably submitted to no tension at all. When the fibrous material is a
fiber, the tension is preferably less than 0.2 gpd (grams per denier).
"Permanence", as used herein, is measured according to the
following test: the permanently shaped non thermoplastic fibrous material
obtained through the process of the invention is "unshaped" : in other
words, the basic fibrous material composing the permanently shaped
fibrous material is taken back to the original linear position it had before
it
was ever imparted a shape. For instance, if the permanently shaped
fibrous material is a twisted fiber, it is untwisted; if it is a crimped
fiber, it is
uncrimped; if it is a knitted fabric, it is unknitted so that the fibrous
material
is extented in its original linear position. This "unshaping process" must be
done under a certain tension because of the natural elasticity acquired by
the fibrous material through the process of the invention. Once the fibrous
material is completely unshaped, ie once it is back to its linear original
position, it is relieved of any tension and freed to come back to the shape
it had before the "unshaping" process. By comparing the respective level
of the shape of the fibrous material before and after the "unshaping"
process, one can then measure the percentage of shape retention of the
fibrous material. This percentage is the permanence of the shape. With
the process of the invention, the permanence is at least 30%, preferably
at least 50%, and more preferably at least 70%. That means that a
shaped fibrous material submitted to the process of the invention retains
at least 30% of its shape after "unshaping". When the shaped fibrous
material is a twisted fiber, the fiber retains at least 70%, preferably at
least
80%, more preferably at least 90%, and even more preferably at least
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96%, of the twist imparted, this twist being measured as described in the
examples below.
The process of the invention allows to impart to para-aramid fibers
permanent high twist level never reached before. For instance, for
industrial fibers, the optimum twist level Tpm (turns per meter) is
calculated for a generally accepted twist multiplier TM of 1.1 using the
following relationship given in ASTM D 885-98 as formula (10).
Tpm = 960 (1.1 )/ (tex)-'~2
As an example for a 1670 dtex para-aramid fiber and a TM of 1.1,
the optimum calculated twist level is about 80 tpm. This value is given by:
Tpm = (1.1 ) 960 (tex)-'~2 = (1.1 ) 960 (167)-'~2
In the case of a para-aramid fiber of a dtex of 1670 first twisted at
500 tpm and then submitted to the process of the invention, a permanent
twist level of 400 tpm is observable.
In one embodiment of the invention, the fibrous material is a fiber.
"Fiber", as used herein, means a fibrous material having a length at least
1000 times its diameter or width. The fibers are preferably polyamide
fibers and more preferably aramid fibers. Fibers which are exclusively
composed of aromatic polyamides are preferred. Para-aramid fibers which
are formed of polyp-phenylene terephthalamide) are more preferred.
Preferably, the fiber has a modulus of about 10 to about 2500
g/den, preferably of about 1000 to about 2500 g/den, and a tenacity of
about 3 to about 50 g/den, preferably of about 3 to about 38 g/den. The
modulus and the tenacity are measured according to the ASTM D 885-98
method.
The fibers are generally spun from an anisotropic spin dope using
an air gap spinning process such as is well known and is described in
United States Patent No. 3,767,756 or 4,340,559. Fibers are spun from
an anisotropic spin dope at about 80°C, through an air gap, into an
aqueous coagulating bath of about 5°C, and through an aqueous rinse
and wash. The resulting fibers are so-called "never-dried" and include at
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least 0.05% by weight, preferably from 0.05 to 400%, by weight, water,
this water content being measured according to ASTM D885-98 for the
moisture regain level. This water is uniformly distributed along the length
of the fiber.
It is possible to use never-dried or partially or totally dried fibers as
the fibrous material for the process of the invention : in the case of totally
dried fibers, it is important that the fiber be immersed in an aqueous
composition for several hours prior to the microwave processing, so that
they include at least 0.05 weight % of an aqueous composition.
It is also possible to use fibers comprising mixtures of the above
materials including hybrid fibers, blends of different fibers such as natural
and man made fibers. Furthermore, two-component fibers may also be
used in accordance with the invention, for instance fibers in which the core
consists of a different material from the skin or in which the various
filaments are from different nature.
The fibers suitable for the present invention may be round, flat or
may have another cross-sectional shape or they may be hollow fibers.
In a preferred embodiment of the invention, the shaped fibrous
material is a twisted fiber.
The shaped fibrous material, preferably the twisted fiber, is
processed through the constant and uniformly distributed electromagnetic
field at a speed which may be adjusted between 0.01 and 2000 m/min.
Typical speeds are 60 m/min for the fibrous material treatment other than
during the spinning process, and 800 m/min for the speed during the
manufacturing of the fibrous material.
During the process of the invention, the fibrous material is
maintained at a very low tension. It preferably undergoes no tension at all.
When the fibrous material is a fiber, the tension is preferably less than 0.2
g/d.
It is very important that the fibrous material be not degraded during
the process of the invention. In this view, the rate of the increase of
temperature of the fibrous material is less than 300°C/s during the
time it
is submitted to the electromagnetic field. In a preferred embodiment of the
invention, the dwell time of the fibrous material in the microwave reactor is
more than 0.1 s, and more preferably it is the necessary time so that the
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difference between the temperature of the outcoming fibrous material and
the temperature of the incoming fibrous material is less than 300°C.
The temperature of the incoming fibrous material may be selected
and is only limited by the temperature resistance of the components, this
being valid for very low as well as very high temperatures. Nonetheless a
range of 10 °C to 100 °C is preferred, with a range of from 15
°C to 45 °C
being more preferred.
When the fibrous material is a fiber, the fiber path may be a linear
trajectory perfectly coinciding with the reactor main central axis, as shown
on fig 2. The fiber path may alternatively be sinusoidal as shown in figure
3: in such a case, one obtains a periodically varying electromagnetic
profile along the fiber which can result in special fiber mechanical and
chemical properties uniformly distributed along the fiber length.
Furthermore the sinusoidal fiber path can be offset from the geometric
center of the reactor producing similar effects. Alternatively inserts placed
appropriately in the reactor can be engineered to produce a similar
periodic fiber treatment. Additionally, such inserts, with for example
variable thickness, can be used to produce a gradient distribution of the
axial electromagnetic field matching the variation of absorbency of the
fiber from its entry in the reactor to .its outlet. This later case can be
used
for the linear fiber path still producing a gradient from the inlet to the
outlet
of the reactor. Other variations, such as a sinusoidal fiber path with
variable amplitude, or a non-circular but oval cavity cross section, are
possible within the scope of the invention which should not be restricted to
the above alternate constructions and fiber path configurations.
In a preferred embodiment, nitrogen or air can be circulated
through the reactor to evacuate water vapor.
At the exit of the microwave reactor, the temperature of the
outcoming fibrous material is preferably less than 100°C, and more
preferably less than 45°C.
At the exit of the microwave reactor, the fibrous material may
undergo an additional treatment. For instance, it may be further heated or
surface treated or coated with various polymeric solutions, like epoxy-latex
formulations for a pneumatic production line. It can also be subject to a
plasma, an electrostatic discharge, or a corona treatment.
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With the specific design of the reactor of the process of the
invention, the fiber, which initially has a fixed microwave loss factor along
its length, is exposed to the same electromagnetic field strength over its
entire length, except for the inlet and outlet which are special boundaries.
The fiber therefore undergoes an isotropic treatment all along its length
and therefore shows constant properties as regards tenacity, modulus,
residual water content, twist uniformity and permanent shaping.
The permanently shaped fibers obtained through the process of the
present invention show no internal cracks. Their morphology and density
remain almost unchanged. They exhibit no shrinkage during the process
They usually have a specific breaking strength of about 2.65 to about 33.5
cN/dtex (about 3 to about 38 g/den, preferably about 15 to about 38
g/den) and a specific modulus of about 8.83 to about 2297 cN/dtex (about
10 to about 2500 g/den, preferably about 1000 to about 2500 g/den).
The invention will be explained in more detail with reference to the
following examples.
EXAMPLES
2U Example 1
A regular bobbin of Kevlar~ 29 para-aramid yarn made of 1000
filaments of 1.5 denier per filament, equivalent to a total of 1670 dtex
linear density, has been used as a feed material for all the examples cited
below. This material is thereafter referred to as K29. The moisture
content measured on K29 using ASTM D885-98 is 5.9 weight percent.
A sufficient amount of K29 yarn has been twisted, using a
SAURER ALLMA~ elasto-twister AZB 200/240 Kevlar~ set at 500 tpm,
and directly wound on plastic cylindrical tubes, which tubes are known to
resist to water exposure without appreciable swelling or shrinkage. The
twisted 500 tpm K29 yarn is thereafter referred to as M3D. Using a twist
counter, Zeigle D311, the real tpm was confirmed to be 609 tpm which is
quite a usual divergence vs. the set point of 500 tpm since it is a high twist
level using a manual control of the twisting machine.
A 50 cm sample of M3D is freed to relax and let untwist to its
natural equilibrium level. Using a twist counter, the relaxed sample of
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M3D is untwisted completely to measure the residual twist. The zero twist
level is confirmed by driving a pin through the middle and along the axis of
the filament bundle. One should be able to freely move the pin in the axial
direction from one boundary of the sample to the other without being
stopped by a blockage of the pin . The residual twist level was measured
to be 309 tpm , i.e. 51 % of the initial twist. The permanence is therefore
51 %. The water content of the relaxed sample remains unchanged at
about 5.9 weight percent.
The SEM (Scanning Electron Micrograph) analysis of the
morphology of a sample of M3D shows that the filaments are unchanged
and in particular no crack parallel with the longitudinal axis of the
filaments
have been observed. Fig. 4 shows the cross section of a bundle of
filaments of M3D and Fig. 4a of the unaltered cross section of a single
filament of M3D. By unaltered cross section is meant that the cross
section is undamaged, in other words that there are no cracks across the
section.
Example 2
A sufficient amount of K29 yarn has been twisted, using a
SAURER ALLMA~ elasto-twister AZB 200/240 Kevlar~ set at 500 tpm,
and directly wound on plastic cylindrical tubes, which tubes are known to
resist to water exposure without appreciable swelling or shrinkage. The
twisted 500 tpm K29 yarn is thereafter referred to as M3D. Using a twist
counter, Zeigle D311, the real tpm was confirmed to be 617 tpm which is
quite a usual divergence vs. the set point of 500 tpm since it is a high twist
level using a manual control of the twisting machine.
A sufficient number of bobbins of M3D were immersed for 48
hours in a recipient containing de-ionised water; the resulting fiber is
hereinafter referred to as M1500. The moisture content measured on M1-
500 using ASTM D885-98 is 22.1 weight percent.
A 50 cm sample of M1-500 is freed to relax and let untwist to its
natural equilibrium level. Using a twist counter the relaxed sample of M1-
500 is untwisted completely to measure the residual twist. The zero twist
level is confirmed by driving a pin through the middle and along the axis of
the filament bundle. One should be able to freely move the pin in the axial
CA 02468336 2004-06-03
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direction from one boundary of the sample to the other without being
stopped by a blockage of the pin . The residual twist level was measured
to be 409 tpm , i.e. 66 % of the initial twist. The permanence is therefore
66%.
The SEM (Scanning Electron Micrograph) analysis of the
morphology of a sample of M1-500 shows that the filaments are
unchanged and in particular no crack parallel with the longitudinal axis of
the filaments have been observed. Fig. 5 shows the cross section of a
bundle of filaments of M1-500 and Fig. 5a of the unaltered cross section
of a single filament of M1-500.
Example 3
A sufficient amount of K29 yarn has been twisted, using a
SAURER ALLMA~ elasto-twister AZB 200/240 Kevlar~ set at 500 tpm,
and directly wound on plastic cylindrical tubes, which tubes are known to
resist to water exposure without appreciable swelling or shrinkage. The
twisted 500 tpm K29 yarn is thereafter referred to as M3D. Using a twist
counter, Zeigle D311, the real tpm was confirmed to be 611 tpm which is
quite a usual divergence~vs..the set point of 500 tpm since it is a high twist
level using a manual control of the twisting machine.
A sufficient number of bobbins of M3D were immersed for 48
hours in a recipient containing de-ionised water. A bobbin was taken off
the recipient and was fed at 6 meters per minute to the off-line treatment
unit of figure 1. The corresponding resident time in the cylindrical TM010
resonant cavity was 3 seconds. The resonant cylindrical cavity is depicted
on Fig. 2 which also provides its dimensions. The fiber temperature
entering the cavity was about 20 degree centigrade compared to less than
40 degree centigrade for the "treated" fiber exiting the cavity. The water
content, using ASTM D885-98 method, of the fiber entering the cavity was
22.1 weight percent compared to 18.8 weight percent for the "treated"
fiber exiting the cavity. The exiting fiber, referred thereinafter as to M3A,
was wound onto cylindrical plastic tubes.
A 50 cm sample of M3A is freed to relax and let untwist to its
natural equilibrium level. Using a twist counter the relaxed sample of M3A
is untwisted completely to measure the residual twist. The zero twist level
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is confirmed by driving a pin through the middle and along the axis of the
filament bundle. One should be able to freely move the pin in the axial
direction from one boundary of the sample to the other without being
stopped by a blockage of the pin . The residual twist level was measured
to be 589 tpm , i.e. 96 % of the initial twist. The permanence is therefore
96%.
The SEM (Scanning Electron Micrograph) analysis of the
morphology of a sample of M3A shows that the filaments are unchanged
and in particular no crack parallel with the longitudinal axis of the
filaments
have been observed. Fig. 6 shows the cross section of a bundle of
filaments of M3A and Fig. 6a of the unaltered cross section of a single
filament of M3A.
Example 4
A sufficient amount of K29 yarn has been twisted, using a
SAURER ALLMA~ elasto-twister AZB 200/240 Kevlar~ set at 500 tpm,
and directly wound on plastic cylindrical tubes, which tubes are known to
resist to water exposure without appreciable swelling or shrinkage. The
twisted 500 tpm K29 yarn is 'thereafter referred to as M3D. Using a twist
counter, Zeigle D311, the real tpm was confirmed to be 604 tpm which is
quite a usual divergence vs. the set point of 500 tpm since it is a high twist
level using a manual control of the twisting machine.
A bobbin of M3D was fed at 6 meters per minute to the off-line
treatment unit of figure 1. The corresponding resident time in the
cylindrical TM010 resonant cavity was 3 seconds. The resonant cylindrical
cavity is depicted on Fig. 2 which also provides its dimensions. The fiber
temperature entering the cavity was about 20 degree centigrade
compared to less than 40 degree centigrade for the "treated" fiber exiting
the cavity. The water content, using ASTM D885-98 method, of the fiber
entering the cavity was 5.9 weight percent compared to 1.5 weight percent
for the "treated" fiber exiting the cavity. The exiting fiber, referred
thereinafter as to M3C, was wound onto cylindrical plastic tubes.
A 50 cm sample of M3C is freed to relax and let untwist to its
natural equilibrium level. Using a twist counter the relaxed sample of M3C
is untwisted completely to measure the residual twist. The zero twist level
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is confirmed by driving a pin through the middle and along the axis of the
filament bundle. One should be able to freely move the pin in the axial
direction from one boundary of the sample to the other without being
stopped by a blockage of the pin . The residual twist level was measured
to be 483 tpm, i.e. 80 % of the initial twist. The permanence is therefore
80%.
The SEM (Scanning Electron Micrograph) analysis of the
morphology of a sample of M3C shows that the filaments are unchanged
and in particular no crack parallel with the longitudinal axis of the
filaments
have been observed. Fig. 7 shows the cross section of a bundle of
filaments of M3C and picture Fig. 7a of the unaltered cross section of a
single filament of M3C.
Example 5
A sufficient amount of K29 yarn has been twisted, using a
SAURER ALLMA~ elasto-twister AZB 200/240 Kevlar~ set at 500 tpm,
and directly wound on plastic cylindrical tubes, which tubes are known to
resist to wafier exposure without appreciable swelling or shrinkage. The
twisted 500 tpm K29 yarn is thereafter referred to as M3D. Using a fiwist
. counter, Zeigle D311, the real tpm was confirmed to be 583 tpm which is
quite a usual divergence vs. the set point of 500 tpm since it is a high twist
level using a manual control of the twisting machine.
A sufficient number of bobbins of M3D were immersed for 48
hours in a recipient containing de-ionised water. A bobbin was taken off
the recipient and was fed at 50 meters per minute to the off-line treatment
unit of figure 1. The corresponding resident time in the cylindrical TM010
resonant cavity was 0.4 seconds. The resonant cylindrical cavity is
depicted on Fig. 2 which also provides its dimensions. The fiber
temperature entering the cavity was about 20 degree centigrade
compared to less than 40 degree centigrade for the "treated" fiber exiting
the cavity. The water content, using ASTM D885-98 method, of the fiber
entering the cavity was 22.1 weight percent. An almost unchanged weight
percent for the "treated" fiber exiting the cavity was found. The exiting
fiber, referred thereinafter as to M4A, was wound onto cylindrical plastic
tubes.
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A 50 cm sample of M4A is freed to relax and let untwist to its
natural equilibrium level. Using a twist counter the relaxed sample of M4A
is untwisted completely to measure the residual twist. The zero twist level
is confirmed by driving a pin through the middle and along the axis of the
filament bundle. One should be able to freely move the pin in the axial
direction from one boundary of the sample to the other without being
stopped by a blockage of the pin . The residual twist level was measured
to be 357 tpm , i.e. 61 % of the initial twist. The permanence is therefore
61 %.
The SEM (Scanning Electron Micrograph) analysis of the
morphology of a sample of M4A shows that the filaments are unchanged
and in particular no crack parallel with the longitudinal axis of the
filaments
have been observed. Fig. 8 shows the cross section of a bundle of
filaments of M4A and Fig. 8a of the unaltered cross section of a single
filament of M4A.
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Permanence
SAMPLE INITIAL RELAXED
REFERENCE TWIST RESIDUAL RESIDUAL
TWIST TWIST
M3D control 609 309 51
Example 1
M 1-500 617 409 66
Example 2
M3A 611 589 96
Example 3
M3C 604 483 80
Example 4
I
IVlA4 583 ~ 357 61
Example 5
These results show that a fibrous material submitted to the process of the
invention can retain up to 96% of its shape.
