U.S. patent application number 11/282108 was filed with the patent office on 2007-05-17 for filament networks and methods of making same for use in the manufacture of products with enhanced characteristics.
This patent application is currently assigned to Ladama, LLC a Nevada LLC. Invention is credited to Tung-Yuan Ke.
Application Number | 20070111000 11/282108 |
Document ID | / |
Family ID | 38041196 |
Filed Date | 2007-05-17 |
United States Patent
Application |
20070111000 |
Kind Code |
A1 |
Ke; Tung-Yuan |
May 17, 2007 |
Filament networks and methods of making same for use in the
manufacture of products with enhanced characteristics
Abstract
The present invention relates to the production of filament
networks that can serve as intermediates for the production of
goods to impart enhanced performance characteristics such as
strength and flame resistance. This filament network intermediate
includes a plurality of filaments of one or more types of
materials, wherein the filaments are randomly associated in the
network in a wool-like configuration. The present invention also
relates to a two-step process for making filament networks that may
be performed by a single apparatus. The present invention further
relates to an apparatus for feeding and drafting fibers to produce
filament networks.
Inventors: |
Ke; Tung-Yuan; (Shen Kang
Hsiang, TW) |
Correspondence
Address: |
DUANE MORRIS LLP
101 WEST BROADWAY
SUITE 900
SAN DIEGO
CA
92101-8285
US
|
Assignee: |
Ladama, LLC a Nevada LLC
Carlsbad
CA
|
Family ID: |
38041196 |
Appl. No.: |
11/282108 |
Filed: |
November 16, 2005 |
Current U.S.
Class: |
428/373 |
Current CPC
Class: |
D10B 2101/20 20130101;
D02G 3/443 20130101; D10B 2331/021 20130101; D10B 2321/10 20130101;
Y10T 428/2929 20150115 |
Class at
Publication: |
428/373 |
International
Class: |
D02G 3/00 20060101
D02G003/00 |
Claims
1. A method for producing a filament network comprising the steps
of: a) providing at least one starting fiber comprising a plurality
of longitudinally aligned filaments; b) introducing the starting
fibers into a drafting component, wherein the drafting component
comprises a first pair of rollers and a second pair of rollers,
wherein the second pair of rollers is downstream of the first pair,
and wherein the first pair of rollers turns at a first speed and
the second pair of rollers turns at a second speed; c) drawing the
starting fibers through the drafting component between the first
pair of rollers and the second pair of rollers while applying
pressure onto the first pair of rollers and the second pair of
rollers, wherein the second speed is faster than the first speed,
to form a filament network comprising a wool-like random collection
of wavy filaments.
2. The method of claim 1, wherein the second speed is between 1.1
to 50 times faster than the first speed.
3. The method of claim 1, wherein step a) further comprises
providing two precursor fibers.
4. The method of claim 1, wherein at least one precursor fiber is a
stainless steel fiber.
5. The method of claim 1, wherein at least one precursor fiber is a
polymeric material.
6. The method of claim 5, wherein the polymeric material is an
aramid fiber.
7. The method of claim 5, wherein the polymeric material is
oxidized PAN.
8. The method of claim 7, wherein the precursor fiber has filaments
of no greater than 192K.
9. The method of claim 7, wherein the precursor fiber has filaments
of no greater than 96K.
10. The method of claim 7, wherein the precursor fiber has
filaments of no greater than 48K.
11. The method of claim 1 further comprising the step of forming
yarn from the filament network.
12. An apparatus for drafting at least one precursor fiber
comprising a plurality of longitudinally aligned filaments to form
a fibrous network, wherein said apparatus comprises: a) a first
pair of rollers having a first rolling speed; b) a second pair of
rollers downstream from the first set of rollers having a second
roller speed, wherein the second roller speed is at least 1.1 times
greater than the first speed; and c) a pressurizing element that
applies pressure onto both the first and second pairs of
rollers.
13. The apparatus of claim 12, wherein the pressurizing element is
a weighted element that applies pressure cooperatively onto both
the first and second pair of rollers.
14. The apparatus of claim 13, wherein the weighted element is a
pendulum carrier.
15. The apparatus of claim 12, wherein one roller in the first and
second pairs of rollers is a metal roller with teeth.
16. The apparatus of claim 12, wherein one roller in the first and
second pairs of rollers has a cot with a hardness of about 75 to
90.
17. The apparatus of claim 12 further comprising an intermediate
pair of rollers between the first and second pairs of rollers, and
driven at an intermediate speed faster than the first speed.
18. The apparatus of claim 17, wherein the intermediate speed is
between 1.1 to 50 times faster than the first speed.
19. A filament network made from a fibrous starting material,
wherein the fibrous starting material further comprises a plurality
of aligned individual filaments with limited twists, and wherein
said filament network comprises a plurality of filaments held
together by mechanical, physical and noncovalent chemical
forces.
20. The network of claim 19, wherein said fibrous starting material
is fibers of the same type.
21. The network of claim 20, wherein the fiber is a stainless steel
fiber having no greater than 192K filaments.
22. The network of claim 21, wherein each filament of the network
made from the stainless fiber has a length of no greater than 40
cm.
23. The network of claim 20, wherein the fiber is a polymeric fiber
having no greater than 192K filaments.
24. The network of claim 23, wherein each filament of the network
made from the polymeric fiber has a length of no greater than 40
cm.
25. The network of claim 23, wherein the polymeric fiber is an
aramid fiber.
26. The network of claim 23, wherein the polymeric fiber is
oxidized polyacrylonitrile (PAN).
27. The network of claim 26, wherein the oxidized PAN has a density
of between 1.30 to 1.50 g/cm.sup.3, a carbon content of between 55
to 68%, and a Limiting Oxygen Index (LOI) value of between 40 to
60%.
28. The network of claim 26, wherein the oxidized PAN fiber has no
greater than 96K filaments of no greater than 25 micrometers in
diameter in each filament.
29. The network of claim 26, wherein each filament of the network
made from the oxidized PAN fibers has a length of no greater than
40 cm, a diameter of no greater than 20 micrometers, and an average
weight of no greater than 0.4 g/10 cm.
Description
TECHNICAL FIELD
[0001] The present invention relates to the production of filament
networks that can serve as intermediates for the production of
goods to impart enhanced performance characteristics such as
strength and flame resistance. This filament network intermediate
includes a plurality of filaments of one or more types of
materials, wherein the filaments are randomly associated in the
network in a wool-like configuration. The present invention also
relates to a two-step process for making filament networks that may
be performed by a single apparatus. The present invention further
relates to an apparatus for feeding and drafting fibers to produce
filament networks.
BACKGROUND OF THE INVENTION
[0002] Carbon fibers are long bundles of linked graphite plates
that form a crystal structure laying parallel to the axis of the
fiber. Like all crystalline structures, they are anisotropic. Their
elastic modulus is higher in the direction of the axis than it is
against the axis. In other words, the individual filaments in the
fibers can withstand pulling from one end of the fiber to the other
to a greater degree than they can withstand bending at an angle
from the axis. Accordingly, most carbon fibers are assembled from
thousands of individual filaments.
[0003] Carbon fibers exhibit remarkable mechanical, physical and
chemical properties. In addition to being nonflammable, they are
light, stiff, and strong. Their strength can compete with the
strongest steels and their stiffness is generally greater than any
metal, ceramic or polymer-based material. Furthermore, carbon
fibers provide additional desired properties, including excellent
corrosion and fatigue resistance, and dimensional stability. Thus,
carbon fibers and their composites with other materials are ideally
suited to applications where chemical inertness, strength,
stiffness, lightness, and fatigue resistance are important
requirements. For example, in the aerospace and defense industries,
carbon fibers have been increasingly used both in the interior of
aircrafts as flame resistant materials as well as in the critical
structural components to increase fuel efficiency and to enhance
structural strength.
[0004] Carbon fibers are made from a large variety of precursor
materials. Among these precursors are polyacrylonitrile (PAN),
cellulosic fibers such as rayon and cotton, petroleum or coal tar
pitch, and certain phenolic fibers. However, different precursor
materials produce carbon fibers with different morphologies and
different specific characteristics. Pitch-based carbon fiber has
much greater stiffness, but it is brittle and costly to produce.
Even so, it is widely used in high-performance applications, such
as military aircraft, spacecraft, and missiles. In contrast,
PAN-based carbon fibers have much greater tensile strength and are
relatively low in cost. Accordingly, this precursor material is
particularly well suited for use in the construction of consumer
goods, such as sporting goods and high-performance apparel.
[0005] Various methods for the production of carbon fibers are
known, and include pyrolytic processes, or "pyrolysis" reactions.
It is well established that the mechanical properties of carbon
fibers are improved by increasing crystallinity and orientation.
The best way to achieve this is to start with a highly oriented
precursor and then maintain the initial high orientation during the
process of stabilization and carbonization through tension. Thus,
one common pyrolysis reaction is an "oxidative stabilization"
process in which a fiber is treated at about 200-300.degree. C.
under tension in an oxidizing environment. During the process,
oxygen, nitrogen and/or hydrogen is removed from the fiber,
resulting in an increase of carbon content in the fiber. In
addition to preventing fiber shrinkage, the tension applied during
this process maintains the molecular orientation of the fiber,
which in turn increases the tensile strength of the stabilized
fiber.
[0006] Polyacrylonitrile (PAN) is one of the most common precursors
for carbon fibers because of the combination of tensile and
compressive properties as well as the carbon yield. During
pyrolysis, the oxidation and stabilization induce intramolecular
cyclization of the oriented molecules with the release of most of
the hydrogen and part of the nitrogen from the fibers. The
resulting PAN polymers are called "oxidized PAN", which have a
carbon content of about 55-68% and a density of about 1.30 to 1.50
g/cm.sup.3. As flame resistant materials, oxidized PAN fibers have
several advantages. For example, these fibers have high Limiting
Oxygen Indexes ("LOI"), typically between 40-60% oxygen, making
them much more flame resistant than many other organic fibers. In
addition, they have excellent heat insulation properties, which are
derived from the heat stabilized PAN chemistry and resultant low
thermal conductivity. Also, unlike other flame resistant organic
fibers, oxidized PAN fibers retain their appearance, hand and
textile characteristics after open flame exposure. Furthermore, the
oxidized fibers are electrically non-conductive and function as
effective electrical insulator even after exposure to heat and open
flames. They also have excellent chemical resistance to organic
solvents and most acids and bases. Lastly, oxidized PAN fibers are
much softer and more pliable than carbon fibers. Accordingly,
oxidized PAN fibers are ideally suited for heat resistant, thermal
insulation and textiles for high-technology applications, and have
been used as fire blocking fabrics for seating in aerospace and
automobile industries, and as protective clothing for people
exposed to the danger of an open flame.
[0007] Currently, there are three types of oxidized PAN fibers
available commercially: staple fibers, large tow fibers and small
tow fibers. In order to use these fibers in the production of
industrial and consumer products, they are often spun into yam
using complex, multi-step processes. For staple fibers, the first
step in the production of yarn is "carding", in which the fibers
are opened and combed over cylinders that contain extremely fine
wires or teeth aligned, and then aligned in one direction to form a
large loosely assembled but not twisted continuous strands of
fibers known as "sliver". Second, several strands of sliver are
then drawn multiple times onto drawing frames to further align the
fibers to improve uniformity as well as to reduce the diameter of
the sliver. Third, the drawn sliver is fed into a roving frame to
produce "roving" by further reducing the diameter and imparting a
slight false twist. Finally, the roving is fed into the spinning
(i.e., winding and/or twisting) frame where it is spun into yarn.
For large tow, the first step is different, and consists of a
stretch-breaking process in which the large tow is broken into
multiple fragments and aligned into sliver. The sliver is then
further processed as described above. These processes are
laborious, inefficient and costly, and often require more than one
type of apparatus to perform.
[0008] Accordingly, there is a need to develop processes that are
efficient and economical that can ideally be performed by a single
apparatus using less complex operational manipulations. There is
also a need to produce intermediates for use in both woven and
nonwoven goods. Hence, the present invention relates to the
production of fine "filament networks" that can serve as
intermediates for the production of goods to impart enhanced
performance characteristics such as strength and flame resistance.
The present invention also relates to a process for making filament
networks in two simple steps that are performed by a single
apparatus. The present invention further relates an apparatus for
feeding and drafting fiber to produce filament networks.
SUMMARY OF THE INVENTION
[0009] In accordance with the present invention, a filament network
intermediate includes a plurality of wool-like filaments with a
length of no greater than 40 cm. The filament network is obtained
from a variety of fibers, including oxidized PAN fibers, stainless
steel fibers, aramid fibers, and polyester fibers. Unlike their
precursor fibers, which generally have long and well aligned
filaments, the filament networks produced are wool-like filament
networks which contain a plurality of short wavy filaments randomly
piled together and the filaments are held together by mechanical,
physical and noncovalent chemical forces. In one aspect, oxidized
PAN filament networks are produced from long and aligned oxidized
PAN fibers. The filaments of the networks have a length of no
greater than 22 cm and a width of no greater than about 12
micrometers. In another aspect, a stainless steel filament network
is produced from an aligned and long stainless steel fiber. The
filaments of the network product have a length of no greater than
about 10 cm and a width of no greater than about 8 micrometers. In
yet another aspect, the aramid filament network is produced from an
aligned and long aramid fiber. The filaments of the network product
have a length of no greater than about 22 cm and a width of no
greater than about 12 micrometers.
[0010] In another embodiment of the present invention, an apparatus
for producing a filament network includes a feeding component and a
drafting component. The feeding component delivers one or more
types of fibers to the drafting component. In one aspect, the
drafting component comprises two pairs of rollers and a
pressurizing element, such as a weight element. The weight element
can be adjusted to exert appropriate pressure on each pair of
rollers so that the fiber can only be moved by the rotation of the
rollers. The drafting of a fiber is accomplished by the force
created by the two pairs of rollers, wherein the first rollers
rotate slower than the last rollers. This causes the fiber to be
both stretched and broken between the two pairs of rollers. In
another aspect, the drafting component further comprises one or
more intermediate pairs of rollers. The intermediate pairs are so
arranged that the fiber to be drafted contacts first with the first
rollers, then with the intermediate rollers, and then with the last
rollers to exit the drafting component to form a wool-like filament
network. Preferably, the apparatus comprises one intermediate pair
of rollers. In yet another aspect, the apparatus of the present
invention may further comprise a twisting and winding component,
wherein the filament network formed during the feeding and drafting
components is spun into yarn.
[0011] In yet another embodiment of the present invention, a method
of forming a fluffy and randomized filament network intermediate
product from an aligned and long fiber includes feeding and
drafting steps. One or more types of fibers are first delivered
simultaneously from the feeding component to the drafting component
with minimum twisting. The fibers are then drafted to produce the
filament network intermediate. This intermediate can be further
processed into fine spun yarns on the same apparatus, or it can be
used in the manufacture of nonwoven products.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] FIG. 1 depicts the structures of PAN, oxidized PAN, and PAN
carbon fiber.
[0013] FIG. 2 depicts an exemplary apparatus.
[0014] FIG. 3 depicts an expanded view of the drafting component of
the apparatus of FIG. 2.
[0015] FIG. 4 depicts a graphic representation of the drafting, and
twisting and winding components of the apparatus of FIG. 2.
DETAILED DESCRIPTION OF THE INVENTION
[0016] The present invention relates to the production of filament
networks that can serve as intermediates for the production of
goods to impart enhanced performance characteristics such as
strength and flame resistance. This filament network intermediate
includes a plurality of filaments of one or more types of
materials, wherein the filaments are randomly associated in the
network in a wool-like configuration. The present invention also
relates to a two-step process for making filament networks that may
be performed by a single apparatus. The present invention further
relates to an apparatus for feeding and drafting fibers to produce
filament networks.
[0017] To facilitate understanding of the invention set forth in
the disclosure that follows, a number of terms are defined
below.
DEFINITIONS
[0018] The term "filament" refers to a single strand of fibrous
material, which may be part of an organized or random collection of
filaments. For example, a plurality of filaments may be brought
together by winding and/or twisting the filaments together to form
yarn.
[0019] The term "yarn" refers to an assemblage of twisted filaments
with a virtually continuous length that is suitable for use in
weaving, either alone or with other filaments or yarns, into
textile materials.
[0020] The term "filament network" refers to a random collection of
untwisted filaments that are held together by mechanical, physical
and noncovalent chemical forces.
[0021] The term "wool-like" refers to a filament network in which
the random collection of untwisted filaments includes individual
filaments that are partially or completely crinkled, curled,
crimped, wavy and/or otherwise curved.
[0022] The term "PAN" refers polyacrylonitrile, as depicted in FIG.
1.
[0023] The term "oxidized PAN" refers to polyacrylonitrile fiber
which has been oxidatively stabilized, as depicted in FIG. 1.
Oxidized PAN can also be further processed to form carbonized PAN
as also depicted in FIG. 1.
[0024] The term "carbon fiber" refers to a fiber containing at
least 90% carbon, which is usually obtained by the controlled
pyrolysis of appropriate fibers.
[0025] The term "tow" refers to a collection of untwisted fibers
that are arranged longitudinally, which is often referred to in
terms of the number of filaments in the collection, such as 3K, 6K,
etc.
[0026] The term "LOI" refers to the limiting oxygen index, which is
a measure of the percentage of oxygen that has to be present to
support combustion of a material. The higher the LOI, the lower the
flammability.
[0027] The term "draft ratio" refers to the ratio of the speed of
the first and last rollers of a drafting component.
[0028] The meaning of other terminology used herein should be
easily understood by someone of reasonable skill in the art.
Starting Materials
[0029] The present invention provides a simple, efficient and
cost-effective method to draft various fibers into wool-like
filament networks. A typical fibrous starting material has
straight, long filaments with very limited inter- and
intra-filament twisting. The filaments are also well organized and
aligned longitudinally (i.e., they are parallel to one another.) An
exemplary starting material includes, without limitation, PAN
fibers, oxidized PAN fibers, polyester fibers, aramid fibers, nylon
fibers, rayon fibers, and metal fibers such as stainless steel
fibers, nickel fibers, alloy fibers.
[0030] Typical starting or precursor materials are filament tows
consisting of parallel filaments of a uniform length equal to the
length of the tow. Preferably, these precursor tows have a twist
number less than 50 per meter and each filament has a length of no
less than 2 meters. More preferably, the precursors have a twist
number less than 25 per meter. Yet more preferably, the precursors
have a twist number less than 10 per meter. Most preferably, the
precursors have a twist number less than 5 per meter. For polymeric
fibers, it is preferred that each filament has a decitex (1
g/10,000 meters) of no greater than 67 and the total measure of the
tow is no greater than 32,000 decitex. For stainless fiber, it is
preferred that each filament has a decitex of no greater than 550
and the total measure of the tow is no more than 260,000
decitex.
[0031] In one embodiment, the starting material is oxidized PAN tow
with no greater than 192 K filaments and a filament diameter of no
greater than 50 micrometers. Preferably, the oxidized PAN has a tow
of no greater than 96K, and a filament diameter of no greater than
25 micrometers. More preferably, the oxidized PAN has a tow of no
greater than 48K. Yet more preferably, the oxidized PAN has a tow
of no greater than 24K. Yet more preferably, the oxidized PAN has a
tow of no greater than 12K. Oxidized PAN tow is commercially
available from a number of different companies, such as Asahi
Chemical Industry Co., Ltd. at Osaka, Japan (LASTAN.RTM.), Zoltek
at St. Louis, Mo. (PYRON.RTM.), SGL Carbon AG at Wiesbaden, Germany
(PANOX.RTM.), Dow Chemical Company at Midland, Mich. (CURLON.RTM.),
etc. However, the present invention is not limited by the source of
oxidized PAN tow. In addition, many publications are available with
sufficient information to allow one to manufacture oxidized PAN tow
with desired structures and properties.
[0032] The present invention is also not limited by the chemical
composition of oxidized PAN, which is a function of the composition
of the PAN precursor, and the oxidative stabilization process to
convert PAN into oxidized PAN. The PAN precursor can be, for
example, a homopolymer of acrylonitrile, acrylonitrile based
copolymers, and acrylonitrile based terpolymers. The copolymers
preferably contain at least about 85% (by mole) of acrylonitrile
monomers and up to 15% (by mole) of one or more mono-vinyl units.
Exemplary other vinyl monomers that are able to copolymerized with
acrylonitrile include methacrylic acid esters and acrylic acid
esters such as methyl methacrylate, ethyl methacrylate, propyl
methacrylate, butyl methacrylate, methyl acrylate and ethyl
acrylate; vinyl esters such as vinyl acetate and vinyl propionate;
acrylic acid, methacrylic acid, maleic acid, itaconic acid and
salts thereof; vinylsulfonic acid and the salt thereof.
[0033] The oxidized PAN that is useful in the practice of the
present invention can be produced from various PAN fibers using
well established oxidative pyrolytic processes. Normally, oxidative
stabilization is performed at atmospheric pressure in the presence
of oxygen at a temperature of about 200-300.degree. C. The chemical
composition of oxidized PAN is affected by the duration of time and
the temperature of the oxidation process. In one aspect, the
oxidized PAN used in the practice of the present invention has a
density of about 1.30 to 1.50 g/cm.sup.3, a carbon content of about
55 to 68%, and an "LOI" (Limiting Oxygen Index) value of about 40
to 60%.
[0034] In another embodiment, the starting material is polyester
fiber with a tow of no greater than 192K and a filament diameter of
no greater than 50 micrometers. Preferably, the polyester fiber has
a tow of no greater than 96K and the filament has a diameter of no
greater than 25 micrometers. More preferably, the polyester fiber
has a tow of no greater than 48K. Yet more preferably, the
polyester fiber has a tow of no greater than 24K. Yet more
preferably, the polyester fiber has a tow of no greater than
12K.
[0035] In yet another embodiment, the starting material is
stainless steel fiber with a tow of no greater than 192K and a
filament diameter of no greater than 50 micrometers. Preferably,
the precursor fiber has a tow of about no greater than 96K and the
filament has a diameter of no greater than 20 micrometers. More
preferably, the stainless steel fiber has a tow of no greater than
48K. Yet more preferably, the stainless steel fiber has a tow of no
greater than 24K. Yet more preferably, the stainless steel fiber
has a tow of no greater than 12K.
[0036] In yet another embodiment, the starting material is an
aramid fiber with a tow of no greater than 192K and a filament
diameter of no greater than 50 micrometers. Preferably, the
precursor fiber has a tow of no greater than 96K and its filament
has a diameter of no greater than 20 micrometers. More preferably,
the aramid fiber has a tow of no greater than 48K. Yet more
preferably, the aramid fiber has a tow of no greater than 24K. Yet
more preferably, the aramid fiber has a tow of no greater than 12K.
An aramid fiber is an aromatic polyamide and comes with many
different grades and properties for various applications. The
aramid fiber has excellent environmental and thermal stability,
static and dynamic fatigue resistance, and impact resistance. The
fiber has the highest specific tensile strength of any commercially
available continuous filament tow. Examples of aramid fibers
include, but are not limited to, KEVLAR.RTM. by DuPont (Greenville,
Del.), TWARON.RTM. and TECHNORA.RTM. by Teijin (Arnhem,
Netherlands).
[0037] The methods and apparatuses of the present invention can
also be used to draft two or more strands of fibers simultaneously.
When the fibers drafted are of different types, a blended filament
network is obtained. Other fibers that may be used include linear
fibers that may be selected from natural or synthetic fibers.
Exemplary fibers include carbon fibers, ceramic fibers, glass
fibers, metal fibers, carbonaceous fibers (e.g. cotton, wool,
polyester, polyolefin, nylon, rayon or novoloid phenolic),
inorganic fibers (e.g. silica, silica alumina, potassium titanate,
silicon carbide, silicon nitride, boron nitride, and boron),
acrylic fibers, tetrafluoroethylene fibers, polyamide fibers, vinyl
fibers, protein fibers, and oxide fibers derived from boron, thoria
or zirconia.
Processing/Apparatus
[0038] In one aspect of the present invention, the apparatus of the
present invention comprises feeding and drafting components, and an
optional spinning component. The feeding process involves feeding a
continuous precursor fiber into the drafting mechanism. The feeding
process is passive and maintains the fiber in a flat configuration,
with minimum twist (i.e. no more than double the twist of the
starting material.)
[0039] Typically, the feeding component is a "ring spinning frame".
However, other conventional feeding methods may also be
appropriate. Furthermore, the feeding component may comprise two or
more feeding elements so that two or more strands of fibers may be
drafted simultaneously. When the fibers fed are of different types,
a blended filament network is produced.
[0040] FIG. 2 depicts a representative apparatus having a feeding
component, a drafting component and a spinning component. As shown,
the apparatus is a dual-mode apparatus that is capable of forming
two yarns. The feeding component consists of four rollers, 1a, 1b,
2a and 2b, on which the starting material is placed. As discussed
above, the starting material on rollers 1a and 1b, and 2a and 2b,
may be the same or different.
[0041] The starting material enters the drafting component, and is
fed through a system of roller pairs, 3 (first pair), 4 (second
pair) and 5 (third pair), with the roller pairs being "pressurized"
by application of pressure via pendulum 6. A more detailed
depiction of the drafting component is shown in FIG. 3. It should
be well understood that an alternative embodiment of this drafting
component may consist of only two pairs of rollers. Alternatively,
it is possible to include more than one feeding component in an
apparatus, each with at least two pairs of rollers.
[0042] The drafting process produces a stretched fiber that exits
the drafting component as a wool-like filament network. For the
drafting process to be operated effectively, the rollers of each
pair are arranged such that the center of each roller, i.e., the
axis (shown as the "X" in FIG. 3), is parallel to each other. This
parallel alignment is also depicted in FIG. 4 by the dashed line
between rollers. Optionally, the axes of each pair may also be
parallel to each other as depicted by the dotted line between the
rollers of pair 4.
[0043] During the drafting process, each roller of a pair applies
an equal and opposite pressure onto opposing sides of the fiber to
a degree so that the fiber can only be moved by the rotation of the
rollers and can not slip away from the rollers. The pressure
applied onto each pair of rollers may be accomplished by any
conventional method either independently or cooperatively. For
example, a weight element can be used to exert appropriate pressure
onto the rollers. The pressure can be generated by applying the
weight element onto at least one of the rollers of each pair. To
simplify the design of the apparatus of the present invention, the
weight element is applied to only one of the two rollers of each
pair.
[0044] Preferably, the drafting component has a single weight
element 6 (a pendulum carrier) that cooperatively exerts
appropriate pressure onto each pair of rollers so that the fiber
can only be moved by the rotation of the mechanically driven
rollers. Preferably, as shown in FIG. 2, one roller from the first
3 and second 4 pairs of rollers is attached to the pendulum
carrier. The remaining two rollers 5 are preferably attached to the
frame of the apparatus. The pressure is adjusted by the weight of
pendulum and by varying the relative position of the pendulum
carrier and the rollers. The pendulum carrier is preferably
detachable from the drafting component or swings open on a hinge
for easy access to the rollers. Rotation of the rollers may be
accomplished by any conventional method manually or
automatically.
[0045] The roller can be made from a variety of materials,
including but without limitation, rubber, metals such as steel and
aluminum, wood, polymer resins, and composite materials such as
fiberglass. The two rollers attached to the apparatus will usually
have an uneven surface, or "teeth" (i.e. any uneven surface of any
configuration, which includes ridges, striations, individual
protrusions, etc.), and are driven mechanically. As such, one
exemplary roller material is metal. The teeth on the surface of the
roller can have several different arrangements, such as that the
alignment of the teeth is parallel to the axis of the roller or
forms an angle relative to the axis of roller. The teeth are
usually evenly distributed on the surface of the roller for the
consistency of the quality of the filament network produced. In
contrast, the two rollers on the pendulum carrier preferably have
"cots" (i.e., outside covering) and are slave rollers which are
driven by the other two rollers attached to the apparatus. The cots
can be made from various materials such as rubbers, plastics,
polymers, natural polymers, cotton, ceramics, metals, and alloys.
In one aspect, the cot is rubber with hardness of 50 to 90. In
another aspect, the rubber cot has a hardness of 75.
[0046] Essentially, the drafting component stretches, breaks, and
randomizes the long and organized precursor fibers to form a
wool-like filament network. Drafting is accomplished by a
stretching force created due to the difference in speed between
pairs of rollers, wherein at least one downstream pair of rollers
operates at a greater speed than the closest upstream pair of
rollers. The pressure on the rollers is adjusted according to the
type of feed fiber and the drafting ratio. The pressure on the
rollers can be same or different. In the present invention, this is
accomplished using different pendulum weights. By varying the speed
difference and the pressure exerted by the pendulum, the apparatus
is able to process different fibers with various tows, and produce
filament networks with various characteristics, such as different
average filament diameters.
[0047] In another embodiment, the drafting component has three or
more pairs of rollers. In one aspect, the drafting component has no
greater than 10 pairs of rollers. In another aspect, the drafting
component has three to six pairs of rollers. In yet another aspect,
the drafting component has three pairs of rollers. As depicted in
FIG. 4, the arrangement of rollers is such that the fiber being
drafted first contacts roller pair 3 (first rollers, then passes
through the second rollers, and comes out of the last rollers as a
stretched fiber for further drafting or as a fluffy filament
network intermediate. The three pairs of rollers can have a variety
of arrangements within the drafting component. One exemplary
arrangement for the three pairs of rollers is illustrated in FIG.
4. Similar to other two pairs, the second rollers are so arranged
that the center of each roller, the axis, is parallel to each
other. Optionally, the axes of the second rollers may also be
parallel to one of the other two pairs or both. Preferably, the
drafting component has a pendulum carrier as a single weight
element which cooperatively exerts appropriate pressure to all
three pairs of rollers. Similar to the drafting component described
above, one roller from each pair is attached to the pendulum
carrier and the other roller is attached to the apparatus. However,
the second rollers are removable from the apparatus so that the
drafting component can easily be transformed into a drafting
component with two pairs of rollers as described above and vice
verse. The pressure exerted onto each pair of rollers is adjusted
by the weight of pendulums and by varying the relative position of
pendulums on the pendulum carrier to rollers. The three rollers
attached to the apparatus are preferably metal rollers with teeth
and driven mechanically whereas the other three are slave rollers
and driven by its counterpart. The teeth on the surface of the
roller can have several different arrangements. For example, the
alignment of the teeth can be parallel to the axis of the roller or
form an angle relative to the axis of roller. Preferably, the teeth
are evenly distributed on the surface of the roller for the
consistency of the quality of the filament network produced. On the
other hand, the three rollers on the pendulum carrier preferably
have cots. In one aspect, the cot is rubber with hardness of 50 to
90. In another aspect, the rubber cot has a hardness of 75.
[0048] Typically, the speed of the second rollers is driven slight
faster than that of the first rollers so that a small force is
exerted on the fiber. Often, this force is used to straighten the
fiber for effective drafting. Sometimes, the incorporation of the
second rollers also enhances the stability of the drafting
component for sustainable and continuous operation. Drafting is
accomplished by a stretching force created due to the difference in
speed between the last and immediately upstream pairs of rollers.
The second rollers run slower than the last pair under appropriate
pressure to prevent slipping. However, the draft ratio is
calculated based on the ratio of the speed of the last rollers
verse the speed of the first rollers. The pressure on each pair of
rollers can be adjusted according to the type of feeding fiber and
the drafting ratio. In the present invention, this is accomplished
using different weight of pendulums and relative position of
pendulums to the rollers. By varying the speed difference and the
pressure exerted by the pendulum, the apparatus is able to process
different fibers with various tows as well as two or more fibers,
of the same kinds or different types, simultaneously.
[0049] In another aspect of the present invention, the apparatus
further comprises a spinning component as depicted in FIG. 2. By
incorporating this third component, the filament network is
directly processed into fine yarn with a yarn count of 1 to 60 Nm
on the same apparatus. In one aspect, the oxidized PAN filament
networks drafted from small tow PAN of various tow sizes can be
spun into yams with about 10 to 28 Nm. The unit, "Nm", is a measure
of the thickness of yarn in term of the length in meters for one
gram of yam. For instance, if one gram of yarn is 20 meters in
length, then the yarn count is 20 Nm. Therefore, the higher the Nm,
the thinner the yams. The process of the present invention can
produce very thin yarn in a simple, efficient and economical
process.
Intermediate
[0050] The apparatus of the present invention can process a variety
of different fibers as disclosed above and produce a wool-like
filament network intermediate with distinct physical
characteristics from the precursor fiber. Unlike the well organized
and aligned filaments of a precursor fiber, the filament network
produced using the present invention is a wool-like collection of
random filaments with very little parallel interactions between
individual filaments and no visible twist between the individual
filaments. The filament network may be composed of filaments from a
single fiber. The intermediate may also be composed of filaments
from several fibers to form blended filament networks. The blended
networks may be formed by drafting two or more different fibers on
the same apparatus simultaneously or by mixing the intermediate
networks obtained individually. These filament network
intermediates can be further processed into yams with very small
yarn count and with additional enhanced properties and
characteristics, such as increased tensile strength.
[0051] Generally, an individual filament of the network
intermediate has a diameter of no greater than that of the original
filament of the precursor fiber, and the intermediate contains
multiple short wavy filaments that are randomly piled together. In
one embodiment, the filament networks were obtained from an aligned
and continuous oxidized PAN fiber with filaments of no greater than
192K. Preferably, the precursor fiber has filaments of no greater
than 96K. More preferably, the precursor fiber has filaments of no
greater than 48K. Yet more preferably, the precursor fiber has
filaments of no greater than 24K. Yet more preferably, the
precursor fiber has filaments of no greater than 12K. Each filament
of the oxidized PAN network thus produce is no longer than 40 cm in
length.
[0052] In another embodiment, the fluffy filament network was
obtained from an aligned and continuous stainless steel fiber with
filaments of no greater than 192K. Preferably, the precursor fiber
has filaments of no greater than 96K. More preferably, the
precursor fiber has filaments of no greater than 48K. Yet more
preferably, the precursor fiber has filaments of no greater than
24K. Yet more preferably, the precursor fiber has filaments of no
greater than 12K. Each filament of stainless steel network has a
length of no greater than 40 cm.
[0053] In yet another embodiment, the fluffy filament network was
obtained from an aligned and continuous aramid fiber with a tow of
no greater than 192K. Preferably, the precursor fiber has filaments
of no greater than 96K. More preferably, the precursor fiber has
filaments of no greater than 48K. Yet more preferably, the
precursor fiber has filaments of no greater than 24K. Yet more
preferably, the precursor fiber has filaments of no greater than
12K. Each filament of aramid network has a length of no greater
than 40 cm.
Post-Processing
[0054] The filament networks produced using the present invention
can be further processed mechanically and/or chemically. The
filament networks may be used in substantially any desired
fabricated form, woven or non-woven. The networks can be readily
spun into yarn using conventional processes. The fibers can then be
woven, stitched, braided, knitted, or formed into non-woven sheets,
as well as other flat or three-dimensional shaped structures.
Exemplary products obtained through mechanical processing are
herringbone weave cloth, twill weave tape, tubular woven fabric,
paper, blankets, roving, yarn, cord, and rope. Filamentous
materials can also be formed directly into sheets and other
structures, either alone or in combination with other filaments,
fibers, or compositions, such as resin.
[0055] The filament networks may also be treated chemically to
impart new characteristics. For example, the filament networks may
be fluorinated as disclosed in U.S. Pat. No. 4,857,394 so as to
provide flexible fibers with different electrical conductivity.
Another example is to convert oxidized PAN filament networks into
carbon fibers by pyrolysis. This process involves two steps:
carbonization and graphitization. During the carbonization process,
the filament network is treated at about 1,000.degree. C. in an
inert atmosphere to further remove the non-carbon elements to yield
carbon fiber with a carbon content of over 90%. During
graphitization, the fiber is further treated at temperatures
between 1,500-3,000.degree. C. to improve the ordering and
orientation of the crystallites in the direction of the fiber
axis.
Applications
[0056] The filament networks produced by the process of the present
invention can be used as intermediates for the production of a
range of industrial and consumer products. For example, oxidized
PAN filaments are chemically resistant, thermally stable, and
physiologically harmless. The filament networks also have excellent
processing properties such as superior blending and handing
characteristics. They are ideally suited for heat resistant,
thermal and acoustic insulation and technical textiles. The
oxidized PAN filament networks can also be used as asbestos
replacing additives in friction linings of automotive disc and drum
brakes.
[0057] The oxidized PAN filaments and their downstream products
such as yams and fabrics can be further processed under high
temperatures into carbon fibers that have very high flame proof
characteristics and are electrically conductive. Such carbon-based
intermediate materials are useful in the production of a variety of
industrial and consumer products, such as apparel and other
textile-based products, belts and hoses, composites, fiber optics,
electromechanical materials, friction sensitive products such as
gaskets and brake pads, tires, ropes and cables. The filament
networks can also be processed into activated PAN fiber. This
product has very high surface area thus has high adsorption rate
and capacity. It can be used to develop air filter, mask, water
purification, odor adsorbing cloth, and protecting clothing.
EXAMPLES
[0058] The apparatus for the following examples had either two or
three pairs of rollers as indicated in each example. All of the
rollers attached to the apparatus had the same diameter of 31.84
mm, whereas all of the rollers attached to the pendulum had cots
with the same hardness, i.e., 75.
Example I
An Oxidized PAN Filament Network Produced from a Fiber with a Tow
of 6K
[0059] The precursor fiber is an oxidized PAN with a tow size of
6K, a tow denier of 7,200, and tow weight of 0.8 g/meter. Its
general physical properties are summarized in Table 1. The
precursor fiber contains parallel filaments of a uniform length
equal to the length of tow, which often exceeds 2 meters. The
filament is also well organized and aligned longitudinally.
Additionally, the precursor fiber has very limited twists,
typically less than 5 turns per meter. The oxidized PAN fiber was
drafted using the apparatus with two pairs of rollers, the first
rollers and last rollers. The distance between two rollers attached
to the apparatus was set to about 240 mm. To obtain a draft ratio
of 27.2, the speeds of the last and preceding rollers were set at
227 and 8.3 rpm, respectively. The same pressure was applied to
both pairs of rollers. The pressure was adjusted to about 28 Kg by
varying the weight on the pendulum carrier. The drafting process
broke and randomized the long and organized filaments of the
precursor fiber to form a fluffy web which has very little parallel
interactions between individual filaments and no visible twist
between the individual filaments. The filament of the network
appears wavy and has a length of no greater than about 22 cm and a
width of no greater than 12 micrometers. The network has an average
weight of about 0.077 g/10cm. TABLE-US-00001 TABLE 1 Physical
Properties Data Filament denier 1.2 denier Density 1.40 g/cm.sup.3
Single filament diameter 11 micrometer Tensile strength 2.0
g/denier Elastic modulus 450 Kg/mm.sup.2 Moisture regain 9%
Strength at break 14 CN/tex Elongation at break 10% LOI 55.sup.
[0060] The filament network was further processed by winding and
twisting to yield a yarn with a yarn count of 34 Nm, a tensile
strength of 250-300 g, a tensile elongation of 10%, and a twist
count of 525 (T/meter).
Example II
An Oxidized PAN Filament Network Produced from a Fiber with a Tow
of 12K
[0061] The precursor fiber is an oxidized PAN with a tow size of
12K, a tow denier of 14,400, and tow weight of 1.6 g/meter. Its
general physical properties are summarized in Table 1. The
precursor fiber contains parallel filaments of a uniform length
equal to the length of tow, which often exceeds 2 meters.
Additionally, the precursor fiber has very limited twists,
typically less than 5 turns per meter. The oxidized PAN fiber was
drafted using the apparatus having only first and last pairs of
rollers. The distance between the rollers attached to the apparatus
was set to about 240 mm. To obtain a draft ratio of 8, the speeds
of the first and last rollers were set at 125 and 15.6 rpm,
respectively. The pressures applied onto the first and last rollers
were 42 and 45 Kg, respectively. The pressure was adjusted by
varying the weight on the pendulum carrier and the position of the
pendulum on the pendulum carrier. The drafting process broke and
randomized the long and organized filaments of the precursor fiber
to form a wool-like filament network, which has very little
parallel interactions between individual filaments and has no
visible twists between individual filaments. The filaments of the
network appear wavy and have a length of no greater than about 22
cm and a width of no greater than about 12 micrometers. The network
has an average weight of about 0.159 g/10 cm.
[0062] The filament network was further processed by winding and
twisting to yield a yarn with a yarn count of 5 Nm, a tensile
strength of about 2000 g, a tensile elongation of 10%, and a twist
count of 100 (T/meter).
Example III
An Oxidized PAN Filament Network Produced from Two Feeding
Fibers
[0063] This example illustrates the drafting of two fibers of the
same type simultaneously. However, the drafting process is
equitably applicable to two or more fibers of different kinds. The
two fibers were fed using a feeding component as depicted in FIG.
1. The two precursor fibers are oxidized PAN fibers with a tow size
of 6K, a tow denier of 7,200, and tow weight of 0.8 g/meter. Their
general physical properties are summarized in Table 1. The
precursor fiber contains parallel filaments of a uniform length
equal to the length of tow, which often exceeds 2 meters. The
filament is also well organized and aligned longitudinally.
Additionally, the precursor fiber has very limited twists,
typically less than 5 turns per meter. The oxidized PAN fibers were
drafted using the apparatus with two pairs of rollers. The distance
between the two rollers attached to the apparatus was set to about
240 mm. To obtain a draft ratio of 27.2, the speeds of the rollers
were set at 227 and 8.3 rpm, respectively. The same pressure was
applied to both sets of rollers. The pressure was adjusted to about
28 Kg by varying the weight of a pendulum on the pendulum carrier.
The drafting process broke and randomized the long and organized
filaments of the precursor fibers to produce a wool-like filament
network which has very little parallel interactions between
individual filaments and has no visible twist between the
individual filaments. The filament of the network appears wavy and
has a length of about no greater than about 22 cm and a width of no
greater than about 12 micrometers. The network has average weight
of about 0.154 g/10 cm.
[0064] The filament network was further processed by winding and
twisting to yield a yarn with a yarn count of 17 Nm, a tensile
strength of about 500-600 g, a tensile elongation of about 10%, and
a twist count of about 375 (T/meter).
Example IV
A Stainless Steel Filament Network
[0065] The precursor fiber is a stainless steel fiber with a tow
size of 4K, and tow weight of 1.6 g/meter. In addition to its major
chemical element, iron (Fe), the steel fiber also contains several
other elements as listed in Table 2. The precursor fiber contains
parallel filaments of a uniform length equal to the length of tow,
which often exceeds 2 meters. The filament is also well organized
and aligned longitudinally. Additionally, the precursor fiber has
very limited twists, typically less than 5 turns per meter. The
filament has a tenacity strength of 7.5 CN and a diameter of 8
micrometer. The stainless steel fiber was drafted using the
apparatus with three pairs of rollers. The distance between the
first and second rollers attached to the apparatus was set to be
100 mm whereas the distance between the second and the third
rollers attached to the apparatus was set to be 140 mm. To obtain a
draft ratio of 17.6, the speeds of the first, second and third
rollers were set at 200, 11.4, and 10.8 rpm, respectively. The same
pressure was applied to the first and second rollers and was set at
42 Kg. The pressure applied onto the first rollers was set at 45
Kg. Similar to the previous examples, the pressure was adjusted by
varying the weight of the pendulum and the position of the pendulum
on the pendulum carrier. The drafting process broke and randomized
the long and organized filaments of the precursor fiber to form a
wool-like filament network which has very little parallel
interactions between individual filaments and has no visible twist
between the individual filaments. The filament of the network
appears wavy and has a length of no greater than about 10 cm and a
width of about 8 micrometers. The network has an average weight of
about 0.16 g/10cm. TABLE-US-00002 TABLE 2 Chemical Compositions
Percent (%) C 0.03 Si 1.0 Mn 2.0 Ni 10.0-14.0 Cr 16.0-18.0
[0066] The filament network was further processed by winding and
twisting to yield a yarn with a yarn count of 11 Nm and a twist
count of 500 (T/meter).
Example V
[0067] An Aramid Filament Network Produced from an Aramid Fiber
with a tow of 1K
[0068] The precursor fiber is an aramid fiber with a tow size of
1K, a tow denier of 1,530, and tow weight of 0.17 g/meter. Its
general physical properties are summarized in Table 3. The
precursor fiber contains parallel filaments of a uniform length
equal to the length of tow, which often exceeds 2 meters. The
filament is also well organized and aligned longitudinally and has
a diameter of 12 micrometer. Additionally, the precursor fiber has
very limited twists, typically less than 5 turns per meter. The
aramid fiber was drafted using the apparatus with two sets of
rollers, the first and last rollers. The distance between the first
and last rollers mounted on the apparatus was about 240 mm. To
obtain a draft ratio of 8.5, the speeds of the first and last
rollers were set at 170 and 10 rpm, respectively. The pressures
applied onto the first and last rollers were above about 42 and 45
Kg, respectively. The pressure was adjusted by varying the weight
of the pendulum and the position on the pendulum carrier. The
precursor aramid fiber was drafted twice. The first drafting
resulted in a stretched fiber. The second drafting broke and
randomized the long and organized filaments of the precursor fiber
to form a wool-like filament network which has very little parallel
interactions between individual filaments and has no visible twist
between the individual filaments. The filament of the network
appears wavy and has a length of no greater than about 22 cm and a
width of about 12 micrometers. The network has an average weight of
about 0.015 g/10 cm. TABLE-US-00003 TABLE 3 Physical Properties
Data Filament denier 1.53 denier Tenacity 23 g/denier Tensile
strength 3,000 N/mm.sup.2 Tensile modulus 67 kN/mm.sup.2 Elongation
at break .sup. 3% Filament diameter 12 micrometer Density 1.38
g/cm.sup.3 Decomposition point 500 LOI 29
[0069] The filament network was further processed by winding and
twisting to produce a yarn with a yarn count of 50 Nm and a twist
count of 800 T/meter.
[0070] The examples set forth above are provided to give those of
ordinary skill in the art with a complete disclosure and
description of how to make and use the preferred embodiments of the
compositions, and are not intended to limit the scope of what the
inventors regard as their invention. Modifications of the
above-described modes (for carrying out the invention that are
obvious to persons of skill in the art are intended to be within
the scope of the following claims. All publications, patents, and
patent applications cited in this specification are incorporated
herein by reference as if each such publication, patent or patent
application were specifically and individually indicated to he
incorporated herein by reference.
* * * * *