U.S. patent application number 11/427094 was filed with the patent office on 2008-01-03 for particulate-loaded polymer fibers and extrusion methods.
This patent application is currently assigned to 3M Innovative Properties Company. Invention is credited to James C. Breister, Stanley C. Erickson, William J. Kopecky, Roger J. Stumo, Bruce B. Wilson.
Application Number | 20080003430 11/427094 |
Document ID | / |
Family ID | 38845955 |
Filed Date | 2008-01-03 |
United States Patent
Application |
20080003430 |
Kind Code |
A1 |
Wilson; Bruce B. ; et
al. |
January 3, 2008 |
PARTICULATE-LOADED POLYMER FIBERS AND EXTRUSION METHODS
Abstract
Particulate-loaded polymer fibers along with methods and systems
for extruding polymeric fibers are disclosed. The
particulate-loaded polymer fibers have a fiber body that includes a
polymeric binder with a plurality of particles distributed within
the polymeric binder. Some of the particles are completely
encapsulated within the polymeric binder and others may be embedded
such that they are partially exposed on the outer surface of the
fiber body. The polymers used in the fibers may be of high
molecular weight and the encapsulated particles may be
preferentially distributed towards the outer surfaces of the
fibers.
Inventors: |
Wilson; Bruce B.; (Woodbury,
MN) ; Stumo; Roger J.; (Shoreview, MN) ;
Erickson; Stanley C.; (Scandia, MN) ; Kopecky;
William J.; (Hudson, WI) ; Breister; James C.;
(Oakdale, MN) |
Correspondence
Address: |
3M INNOVATIVE PROPERTIES COMPANY
PO BOX 33427
ST. PAUL
MN
55133-3427
US
|
Assignee: |
3M Innovative Properties
Company
|
Family ID: |
38845955 |
Appl. No.: |
11/427094 |
Filed: |
June 28, 2006 |
Current U.S.
Class: |
428/375 |
Current CPC
Class: |
D01F 6/60 20130101; D01F
1/10 20130101; Y10T 428/2933 20150115; D01D 4/02 20130101 |
Class at
Publication: |
428/375 |
International
Class: |
D02G 3/00 20060101
D02G003/00 |
Claims
1. A particulate-loaded polymeric fiber comprising a fiber body
that comprises a polymeric binder and a plurality of particles
encapsulated within the polymeric binder, wherein the polymeric
binder consists essentially of one or more polymers, and wherein
the encapsulated particles comprise an encapsulated particle
density, and wherein the encapsulated particle density is higher
proximate an outer surface of the fiber.
2. A fiber according to claim 1, wherein the encapsulated particle
density within the outermost 20% of the volume of the fiber is two
times or more the encapsulated particle density within the
innermost 20% of the volume of the fiber.
3. A fiber according to claim 1, wherein the plurality of particles
consist essentially of non-polymeric particles.
4. A fiber according to claim 1, wherein the plurality of particles
have a maximum size of 100 micrometers or less.
5. A fiber according to claim 1, wherein all of the one or more
polymers comprise a melt flow index of 30 or less measured at the
conditions specified for the one or more polymers.
6. A fiber according to claim 1, wherein all of the one or more
polymers comprise a melt flow index of 10 or less measured at the
conditions specified for the one or more polymers.
7. A fiber according to claim 1, wherein all of the one or more
polymers comprise a melt flow index of 1 or less measured at the
conditions specified for the one or more polymers.
8. A fiber according to claim 1, wherein all of the one or more
polymers comprise a melt flow index of 0.1 or less measured at the
conditions specified for the polymers.
9. A fiber according to claim 1, wherein the one or more polymers
are semi-crystalline polymers.
10. A fiber according to claim 9, wherein the semi-crystalline
polymers are nylon.
11. A particulate-loaded polymeric fiber comprising: a fiber body
comprising one or more polymers, and wherein all of the one or more
polymers comprise a melt flow index of 10 or less measured at the
conditions specified for the one or more polymers; and a first
plurality of particles encapsulated within the fiber body and a
second plurality of particles embedded in an outer surface of the
fiber body, wherein the encapsulated first plurality of particles
comprise an encapsulated particle density, and wherein the
encapsulated particle density of the first plurality of particles
is highest proximate an outer surface of the fiber.
12. A fiber according to claim 11, wherein the encapsulated
particle density of the first plurality of particles within the
outermost 20% of the volume of the fiber is two times or more the
encapsulated particle density of the first plurality of particles
within the innermost 20% of the volume of the fiber.
13. A fiber according to claim 11, wherein the first plurality of
particles and the second plurality of particles consist essentially
of non-polymeric particles.
14. A fiber according to claim 11, wherein the first plurality of
particles and the second plurality of particles have a maximum size
of 100 micrometers or less.
15. A fiber according to claim 11, wherein all of the one or more
polymers comprise a melt flow index of 30 or less measured at the
conditions specified for the one or more polymers.
16. A fiber according to claim 11, wherein all of the one or more
polymers comprise a melt flow index of 10 or less measured at the
conditions specified for the one or more polymers.
17. A fiber according to claim 11, wherein all of the one or more
polymers comprise a melt flow index of 1 or less measured at the
conditions specified for the one or more polymers.
18. A fiber according to claim 11, wherein all of the one or more
polymers comprise a melt flow index of 0.1 or less measured at the
conditions specified for the polymers.
19. A fiber according to claim 11, wherein the one or more polymers
are semi-crystalline polymers.
20. A fiber according to claim 19, wherein the semi-crystalline
polymers are nylon.
21. A method of making a particulate-loaded polymeric fiber, the
method comprising: entraining a plurality of particles within a
polymer melt stream; passing the polymer melt stream with the
plurality of particles entrained therein through an orifice located
within a die, wherein the orifice comprises an entrance, an exit
and an interior surface extending from the entrance to the exit,
wherein the orifice comprises a semi-hyperbolic converging orifice,
and wherein the polymer melt stream enters the orifice at the
entrance and leaves the orifice at the exit; delivering lubricant
to the orifice separately from the polymer melt stream, wherein the
lubricant is introduced at the entrance of the orifice; and
collecting the particulate-loaded polymeric fiber comprising the
polymer melt stream and a plurality of particles encapsulated
within the polymer melt stream, wherein the encapsulated particles
comprise an encapsulated particle density within the fiber, and
wherein the encapsulated particle density is higher proximate an
outer surface of the fiber.
22. A method according to claim 21, wherein the encapsulated
particle density within the outermost 20% of the volume of the
fiber is two times or more the encapsulated particle density within
the innermost 20% of the volume of the fiber.
23. A method according to claim 21, wherein the plurality of
particles consist essentially of non-polymeric particles.
24. A method according to claim 21, wherein the polymer melt stream
comprises one or more polymers, and wherein all of the one or more
polymers comprise a melt flow index of 30 or less measured at the
conditions specified for the one or more polymers.
25. A method according to claim 21, wherein the polymer melt stream
comprises one or more polymers, and wherein all of the one or more
polymers comprise a melt flow index of 10 or less measured at the
conditions specified for the one or more polymers.
26. A method according to claim 21, the polymer melt stream
comprises one or more polymers, and wherein all of the one or more
polymers comprise a melt flow index of 1 or less measured at the
conditions specified for the one or more polymers.
27. A method according to claim 21, wherein all of the one or more
polymers comprise a melt flow index of 0.1 or less measured at the
conditions specified for the polymers.
28. A method according to claim 21, wherein the polymer melt stream
consists essentially of one polymer with a melt flow index of 30 or
less measured at the conditions specified for the one or more
polymers.
29. A method according to claim 21, wherein the polymer melt stream
consists essentially of one polymer with a melt flow index of 10 or
less measured at the conditions specified for the one or more
polymers.
30. A method according to claim 21, wherein the polymer melt stream
consists essentially of one polymer with a melt flow index of 1 or
less measured at the conditions specified for the polymer.
31. A method according to claim 21, wherein the polymer melt stream
consists essentially of one polymer with a melt flow index of 0.1
or less measured at the conditions specified for the polymer.
32. A method according to claim 21, wherein the polymer melt stream
consists essentially of one or more semi-crystalline polymers.
33. A method according to claim 33, wherein the semi-crystalline
polymers are nylon.
34. A method according to claim 21, wherein the polymer melt stream
with the plurality of particles entrained therein is delivered to
the entrance of the orifice through an opening that comprises a
smaller cross-sectional area than the cross-sectional area of the
entrance of the orifice.
35. A method according to claim 21, wherein delivering the
lubricant comprises delivering the lubricant through a continuous
slot formed about the entrance of the orifice.
36. A method according to claim 21, wherein delivering the
lubricant comprises delivering the lubricant through a plurality of
openings located about the entrance of the orifice.
37. A method according to claim 21, wherein at least a portion of
the lubricant evaporates from the polymer melt stream after the
polymer melt stream leaves the exit of the orifice.
38. A method according to claim 21, wherein the die comprises a
plurality of orifices, and wherein the method further comprises
independently delivering the lubricant to each orifice of the
plurality of orifices.
39. A method according to claim 21, wherein collecting the fiber
comprises pulling the fiber, wherein the fiber is elongated during
the pulling.
40. A method according to claim 21, wherein the average temperature
of the polymer melt stream passing into the entrance of the orifice
is within 10 degrees Celsius or less above a melt processing
temperature of the polymer melt stream.
41. A method according to claim 21, wherein the average temperature
of the polymer melt stream is at or below a melt processing
temperature of the polymer melt stream before the polymer melt
stream leaves the exit of the orifice.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to the field of
particulate-loaded polymer fibers along with extrusion processing
and apparatus for manufacturing the same.
BACKGROUND OF THE INVENTION
[0002] Conventional fiber forming methods and apparatus typically
involves the extrusion of polymeric material through orifices. The
rates, pressures and temperatures of the typical fiber extrusion
process represent a compromise between economic requirements and
the physical characteristics of the polymeric material. For
example, the molecular weight of the polymeric material is directly
tied to both melt viscosity and polymeric material performance.
Unfortunately, improvements in polymeric material performance are
conventionally tied to increased molecular weight and corresponding
relatively high melt viscosities. The higher melt viscosities
typically result in slower, less economically viable processes for
forming fibers.
[0003] To address the high melt viscosities of higher molecular
weight polymers, conventional processes may rely on relatively high
temperature processing in an effort to lower the melt viscosity of
the polymeric material. The process temperature may typically,
however, be limited by degradation of the polymeric material at
higher temperatures. In conjunction with increased process
temperatures, the process pressures, i.e., the pressure at which
the polymer is extruded, may also be increased to improve process
speed. Process pressure may, however, be limited by the equipment
employed to extrude the fibers. As a result, the processing speed
in conventional processes is typically constrained by the factors
discussed above.
[0004] In view of the issues discussed above, the conventional
strategy in extruding molten polymer for fiber making is to reduce
the molecular weight of the polymeric material to attain
economically viable processing rates. The reduced molecular weight
results in a corresponding compromise in material properties of the
extruded polymeric fibers.
[0005] To at least partially address the compromises in material
properties of conventional extruded fibers, the fiber strength may
be improved by orienting the polymeric material in the fiber.
Orientation is imparted by pulling or stretching the fiber after it
exits the extrusion die. As a result, the polymeric material used
for the fibers typically must have a substantial tensile stress
carrying capability in the semi-molten state in which the polymeric
material exits the die (or the fibers will merely break when
pulled). Such properties are conventionally available in
semi-crystalline polymers such as, e.g., polyethylene,
polypropylene, polyesters, and polyamides. Thus, conventional fiber
extrusion processes can be performed with only a limited number of
polymeric materials.
SUMMARY OF THE INVENTION
[0006] The present invention provides particulate-loaded polymer
fibers along with methods and systems for extruding polymeric
fibers.
[0007] The particulate-loaded polymer fibers have a fiber body that
includes a polymeric binder with a plurality of particles
distributed within the polymeric binder. Some of the particles are
completely encapsulated within the polymeric binder and others may
be partially exposed on the outer surface of the fiber body.
[0008] Among the potential advantages of particulate-loaded fibers
of the present invention is that the polymeric fiber body can be
formed of polymers with relatively low melt flow index or
relatively high melt viscosity (and corresponding high molecular
weight as discussed herein). As a result, the potential benefits
associated with fibers manufactured using such polymers in methods
of the present invention may also be available for
particulate-loaded fibers.
[0009] Another potential advantage of the present invention is that
the particles within the fiber body may preferably be distributed
such that the particle density (i.e., the number of particles per
unit volume of the fiber body) is higher proximate the outer
surface of the fiber. That distribution of particles within the
fiber may be advantageous for enhancing fiber strength (by, e.g.,
providing a central core that includes fewer particles).
[0010] The particle distribution profile may also be advantageous
in situations where it is desired that the particles be
encapsulated near the outer surface of the fiber or partially
exposed on the outer surface of the fiber. This may be particularly
true in situations in which it is beneficial if additional
particles are exposed as portions of the polymeric binder are
removed during use (as may happen in, e.g., fibers used in abrasive
articles, etc.).
[0011] Another potential advantage of the particle distribution
seen in melt-extruded fibers of the present invention is that the
amount of particles needed to provide a selected particle density
proximate the outer surface of the fiber may be reduced because the
particles are preferentially distributed proximate the outer
surface of the fiber.
[0012] The extrusion process used to manufacture the fibers may
preferably involve the delivery of a lubricant separately from a
polymer melt stream to each orifice of an extrusion die such that
the lubricant preferably encases the polymer melt stream as it
passes through the die orifice. The use of a lubricant delivered
separately from the polymer melt stream in a polymeric fiber
extrusion process can provide a number of potential advantages.
[0013] For example, the use of separately-delivered lubricant can
provide for oriented polymeric fibers in the absence of pulling,
i.e., in some embodiments it may not be necessary to pull or
stretch the fiber after it exits the die to obtain an oriented
polymeric fiber. If the polymeric fibers are not pulled after
extrusion, they need not exhibit substantial tensile
stress-carrying capability in the semi-molten state that they are
in after exiting the die. Instead, the lubricated extrusion methods
of the present invention can, in some instances, impart orientation
to the polymeric material as it moves through the die such that the
polymeric material may preferably be oriented before it exits the
die.
[0014] One potential advantage of reducing or eliminating the need
for pulling or stretching to impart orientation is that the
candidate polymeric materials for extruding polymeric fibers can be
significantly broadened to include polymeric materials that might
not otherwise be used for extruded fibers. Heterophase polymers may
also be extruded into an oriented fiber via the proposed method.
Composite fiber constructions such as `sheath/core` or
`islands-in-the-sea` or `pie` or `hollow pie` are also compatible
with this method.
[0015] Potential advantages of the methods of the present invention
may include, e.g., the ability to extrude multiple polymeric fibers
simultaneously at relatively low pressures. The relatively low
pressures may result in cost savings in terms of equipment and
process costs.
[0016] For the purposes of the present invention, the term "fiber"
(and variations thereof) means a slender, threadlike structure or
filament that has a substantially continuous length relative to its
width, e.g., a length that is at least 1000 times its width. The
width of the fibers of the present invention may preferably be
limited to a maximum dimension of 5 millimeters or less, preferably
2 millimeters or less, and even more preferably 1 millimeter or
less.
[0017] The fibers of the present invention may be monocomponent
fibers; bicomponent or conjugate fibers (for convenience, the term
"bicomponent" will often be used to mean fibers that consist of two
components as well as fibers that consist of more than two
components); and fiber sections of bicomponent fibers, i.e.,
sections occupying part of the cross-section of and extending over
the length of the bicomponent fibers.
[0018] Another potential advantage of some embodiments of the
present invention may be found in the ability to extrude polymers
with a low Melt Flow Index (MFI). In conventional polymeric fiber
extrusion processes, the MFI of the extruded polymers is about 35
or higher. Using the methods of the present invention, the
extrusion of polymeric fibers can be achieved using polymers with a
MFI of 30 or less, in some instances 10 or less, in other instances
1 or less, and in still other instances 0.1 or less. Before the
present invention, extrusion processing of such high molecular
weight (low MFI) polymers to form fibers was typically performed
with the use of solvents to dissolve the polymers thereby reducing
their viscosity. Such methods carried with them the difficulty of
dissolving the high molecular polymers and then removing the
solvent (including disposal or recycling). Examples of low melt
flow index polymers that may potentially be used in connection with
the present invention may include LURAN S 757 (ASA, 8.0 MFI)
available from BASF Corporation of Wyandotte, Mich.; P4G2Z-026 (PP,
1.0 MFI) available from Huntsman Polymers of Houston, Tex.; FR PE
152 (HDPE, 0.1 MFI) available from PolyOne Corporation of Avon
Lake, Ohio; 7960.13 (HDPE, 0.06 MFI) available from ExxonMobil
Chemical of Houston Tex.; and ENGAGE 8100 (ULDPE, 1.0 MFI)
available from ExxonMobil Chemical of Houston Tex.
[0019] Another potential advantage of some methods of the present
invention may include the relatively high mass flow rates that may
be achieved. For example, using the methods of the present
invention, it may be possible to extrude polymeric material into
fibers at rates of 10 grams per minute or higher, in some instances
100 grams per minute or higher, and in other instances at rates of
400 grams per minute or higher. These mass flow rates may be
achieved through an orifice having an area of 0.2 square
millimeters (mm.sup.2) or less.
[0020] Still another potential advantage of some methods of the
present invention may include the ability to extrude polymeric
fibers that include orientation at the molecular level that may,
e.g., enhance the strength or provide other advantageous
mechanical, optical, etc. properties. If the polymeric fibers are
constructed of amorphous polymers, the amorphous polymeric fibers
may optionally be characterized as including portions of rigid or
ordered amorphous polymer phases or oriented amorphous polymer
phases (i.e., portions in which molecular chains within the fiber
are aligned, to varying degrees, generally along the fiber
axis).
[0021] Although oriented polymeric fibers are known, the
orientation is conventionally achieved by pulling or drawing the
fibers as they exit a die orifice. Many polymers cannot, however,
be pulled after extrusion because they do not possess sufficient
mechanical strength immediately after extrusion in the molten or
semi-molten state to be pulled without breaking. The methods of the
present invention can, however, eliminate the need to draw
polymeric fibers to achieve orientation because the polymeric
material may be oriented within the die before it exits the
orifice. As a result, oriented fibers may be extruded using
polymers that could not conventionally be extruded and drawn in a
commercially viable process.
[0022] In some methods of the present invention, it may be
preferably to control the temperature of the lubricant, the die, or
both the lubricant and the die to quench the polymeric material
such that the orientation is not lost or is not significantly
reduced due to relaxation outside of the die. In some instances,
the lubricant may be selected based, at least in part, on its
ability to quench the polymeric material by, e.g., evaporation.
[0023] In one aspect, the present invention provides a
particulate-loaded polymeric fiber having a fiber body that
includes a polymeric binder and a plurality of particles
encapsulated within the polymeric binder, wherein the polymeric
binder consists essentially of one or more polymers, and wherein
the encapsulated particles have an encapsulated particle density,
and wherein the encapsulated particle density is higher proximate
an outer surface of the fiber.
[0024] In another aspect, the present invention provides a
particulate-loaded polymeric fiber having a fiber body that
includes one or more polymers, and wherein all of the one or more
polymers have a melt flow index of 10 or less measured at the
conditions specified for the one or more polymers; and a first
plurality of particles encapsulated within the fiber body and a
second plurality of particles embedded in an outer surface of the
fiber body, wherein the encapsulated first plurality of particles
have an encapsulated particle density, and wherein the encapsulated
particle density of the first plurality of particles is highest
proximate an outer surface of the fiber.
[0025] In another aspect, the present invention provides a method
of making a particulate-loaded polymeric fiber by entraining a
plurality of particles within a polymer melt stream; passing the
polymer melt stream with the plurality of particles entrained
therein through an orifice located within a die, wherein the
orifice has an entrance, an exit and an interior surface extending
from the entrance to the exit, wherein the orifice is a
semi-hyperbolic converging orifice, and wherein the polymer melt
stream enters the orifice at the entrance and leaves the orifice at
the exit; delivering lubricant to the orifice separately from the
polymer melt stream, wherein the lubricant is introduced at the
entrance of the orifice; and collecting the particulate-loaded
polymeric fiber including the polymer melt stream and a plurality
of particles encapsulated within the polymer melt stream, wherein
the encapsulated particles comprise an encapsulated particle
density within the fiber, and wherein the encapsulated particle
density is higher proximate an outer surface of the fiber.
[0026] In another aspect, the present invention may provide a
method of making a polymeric fiber by passing a polymer melt stream
through an orifice located within a die, wherein the orifice has an
entrance, an exit and an interior surface extending from the
entrance to the exit, wherein the orifice is a semi-hyperbolic
converging orifice, and wherein the polymer melt stream enters the
orifice at the entrance and leaves the orifice at the exit;
delivering lubricant to the orifice separately from the polymer
melt stream, wherein the lubricant is introduced at the entrance of
the orifice; and collecting a fiber including the polymer melt
stream after the polymer melt stream leaves the exit of the
orifice.
[0027] In another aspect, the present invention may provide a
method of making a polymeric fiber by passing a polymer melt stream
through an orifice of a die, wherein the orifice has an entrance,
an exit and an interior surface extending from the entrance to the
exit, wherein the orifice is a semi-hyperbolic converging orifice,
wherein the polymer melt stream enters the orifice at the entrance
and leaves the orifice at the exit, wherein the polymer melt stream
includes a bulk polymer, wherein the bulk polymer is a majority of
the polymer melt stream, and wherein the bulk polymer consists
essentially of a polymer with a melt flow index of 1 or less
measured at the conditions specified for the polymer in ASTM D1238;
delivering lubricant to the orifice separately from the polymer
melt stream; and collecting a fiber including the bulk polymer
after the polymer melt stream leaves the exit of the orifice.
[0028] These and other features and advantages of various
embodiments of the methods, systems, and articles of the present
invention may be described below in connection with various
illustrative embodiments of the present invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0029] FIG. 1 is an idealized enlarged cross-sectional view of one
particulate-loaded fiber according to the present invention.
[0030] FIG. 2 is a schematic diagram illustrating a process window
for methods according to the present invention.
[0031] FIG. 3 is an enlarged cross-sectional view of a portion of
one exemplary die that may be used in connection with the present
invention.
[0032] FIG. 4 is an enlarged view of the orifice in the die of FIG.
3.
[0033] FIG. 5 is a plan view of a portion of one exemplary
extrusion die plate that may be used in connection with the present
invention.
[0034] FIG. 6 is a schematic diagram of one system including a die
according to the present invention.
[0035] FIG. 7 is an enlarged cross-sectional view of another
extrusion apparatus that may be used in connection with the present
invention.
[0036] FIG. 8 is an enlarged plan view of another exemplary die
orifice and lubrication channels that may be used in connection
with the present invention.
[0037] FIG. 9 is an enlarged cross-sectional view of one exemplary
polymeric fiber exiting a die orifice in accordance with the
methods of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0038] In the following detailed description of illustrative
embodiments of the invention, reference is made to the accompanying
figures of the drawing which form a part hereof, and in which are
shown, by way of illustration, specific embodiments in which the
invention may be practiced. It is to be understood that other
embodiments may be utilized and structural changes may be made
without departing from the scope of the present invention.
[0039] As discussed above, the present invention provides methods
and systems for manufacturing polymeric fibers through a lubricated
flow extrusion process. The present invention also provides
particulate-loaded polymeric fibers that may preferably be
manufactured using such systems and methods.
[0040] FIG. 1 is an idealized cross-sectional view of one exemplary
particulate-loaded fiber 2 in accordance with the present
invention. The fiber 2 is formed with a longitudinal axis 3
extending along its length. The fiber 2 includes a body 4 formed of
one or more polymers (sometimes referred to herein as a polymeric
binder). The body 4 extends along the length of the longitudinal
axis 3 and includes an outer surface 5. Although the fiber body 4
depicted in FIG. 1 has a generally circular cross-section shape
(taken transverse to the longitudinal axis 3), the fibers of the
present invention may take any suitable cross-sectional shape,
e.g., oval, triangular, rectangular, hexagonal, irregular, etc.
[0041] The one or more polymers used to form the fiber body 4 may
have any composition as described herein. For example, it may be
preferred that the one or more polymers of fiber body 4 have a melt
flow index (MFI) 30 or less, 10 or less, 1 or less, 0.1 or less,
etc.; it may be preferred that the one or more polymers be
semi-crystalline polymers (e.g., nylon); etc.
[0042] Also depicted in connection with FIG. 1 are particles 6
which are encapsulated (where "encapsulated" means that that
particles are completely contained within the polymer forming the
fiber body 4. In addition to particles 6 that are encapsulated
within the polymeric body 4, the fiber 2 may also includes
particles 7 that are only embedded (or partially encapsulated) in
the polymer forming the fiber body 4 such that a portion of the
particle is exposed on the outer surface 5 of the fiber body 4.
[0043] Among the particles 6 encapsulated within the body 4, it may
be preferred that the encapsulated particles 6 are distributed
within the fiber such that the encapsulated particle density is
higher proximate the outer surface 5 of the fiber 2. As used
herein, "encapsulate particle density" refers to the number of
encapsulated particles per unit volume of the fiber. In some
embodiments, it may be preferred that the encapsulated particle
density within the outermost 20% of the volume of the fiber be two
times or more the particle density within the innermost 20% of the
volume of the fiber. Alternatively, it may be preferred that 50% or
more of the encapsulated particles be located within the outermost
20% of the fiber. In another alternative, it may be preferred that
90% of the encapsulated particles be located within the outermost
10% of the volume of the fiber.
[0044] The particles 6 (and particles 7 exposed on the outer
surface 5) may preferably be formed of materials that do not
readily intermix with or melt into the polymeric body 4. It may be
preferred that the particles 6 & 7 be formed of non-polymeric
materials (although it should be understood that some particles may
be used in connection with the present invention if their melt
processing temperatures (as defined herein) are high enough such
that the particles 6 & 7 retain their separate and distinct
form from the surrounding fiber body 4). Examples of some
potentially suitable non-polymeric particles that may be used in
particulate-loaded fibers of the present invention may include,
e.g., metals, metal oxides (e.g., aluminum oxide), ceramics,
glasses, minerals, etc.
[0045] In some instances, the particles added to fibers of the
present invention may include optical functionality as, e.g.,
retroreflectors, etc. Examples of some potentially suitable optical
elements that may be used as particles in connection with the
present invention may be described in, e.g., U.S. Pat. Nos.
4,367,919 (Tung et al.); 5,774,265 (Mathers et al.); 5,835,271
(Stump et al.); 5,853,851 (Morris), etc.
[0046] The particles used in connection with the particulate-loaded
fibers of the present invention may potentially be characterized on
the basis of their size. It may be preferred, for example, that the
particles be small enough such that they do not inhibit fiber
formation or extrusion (if that is the process by which the fibers
are formed). In some instances, it may be preferred that the
particles have a maximum dimension of 1 millimeter or less, 500
micrometers or less, 250 micrometers or less, 100 micrometers or
less, 50 micrometers or less, or 10 micrometers or less. As used
herein, "maximum size" of particles is determined by screening or
sieving such that the particles pass through a screen or sieve with
openings of the particle size or larger. For example, particles
with a maximum size of 100 micrometers or less would pass through a
screen or sieve with openings that are 100 micrometers across. In
another manner of characterizing particle size in connection with
the particle-loaded polymeric fibers of the present invention, the
maximum size may be described as a function of the fiber diameter.
For example, it may be preferred that the maximum size of the
particles in a particulate-loaded fiber of the present invention be
10% or less of the fiber diameter, 30% or less of the fiber
diameter, or 50% or less of the fiber diameter.
[0047] The particulate-loaded fibers of the present invention may
preferably be manufactured by methods that involve the extrusion of
a polymer melt stream from a die having one or more orifices. The
particles to be encapsulated within the body of the fiber are
preferably entrained within the polymer melt stream as it is
delivered to the die.
[0048] A lubricant is delivered to the die separately from the
polymer melt stream, preferably in a manner that results in the
lubricant being preferentially located about the outer surface of
the polymer melt stream as it passes through the die. The lubricant
may be another polymer or another material such as, e.g., mineral
oil, etc. It may be preferred that the viscosity of the lubricant
be substantially less than the viscosity of the lubricated polymer
(under the conditions at which the lubricated polymer is extruded).
Some exemplary dies and fibers that may be extruded from them are
described below.
[0049] One potential advantage of using a lubricant in the methods
and systems of the present invention is that the process window at
which fibers may be manufactured may be widened relative to
conventional polymer fiber extrusion processes. FIG. 2 depicts a
dimensionless graph to illustrate this potential advantage. The
flow rate of the polymer melt stream increases moving to the right
along the x-axis and the flow rate of the lubricant increases
moving upward along the y-axis. The area between the broken line
(depicted nearest the x-axis) and the solid line (located above the
broken line) is indicative of area in which the flow rates of the
polymer melt stream and the lubricant can be maintained at a steady
state with respect to each other. Characteristics of steady state
flow are preferably steady pressures for both the polymer melt
stream and the lubricant. In addition, steady state flow may also
preferably occur at relatively low pressures for the lubricant
and/or the polymer melt stream.
[0050] The area above the solid line (on the opposite side of the
solid line from the broken line) is indicative of the region in
which an excess of lubricant may cause flow of the polymer melt
stream through the die to pulse. In some instances, the pulsation
can be strong enough to interrupt the polymer melt stream flow and
break or terminate any fibers exiting the die.
[0051] The area below the broken line (i.e., between the broken
line and the x-axis) is indicative of the conditions at which the
lubricant flow stalls or moves to zero. In such a situation, the
flow of the polymer melt stream is no longer lubricated and the
pressure of the polymer melt stream and the lubricant typically
rise rapidly. For example, the pressure of the polymer melt stream
can rise from 200 psi (1.3.times.10.sup.6 Pa) to 2400 psi
(1.4.times.10.sup.7 Pa) in a matter of seconds under such
conditions. This area would be considered the conventional
operating window for traditional non-lubricated fiber forming dies,
with the mass flow rate of the polymers being limited principally
by the high operating pressures.
[0052] The widened process window illustrated in FIG. 2 may
preferably be provided using a die in which the orifices converge
in a manner that results in essentially pure elongational flow of
the polymer. To do so, it may be preferred that the die orifice
have a semi-hyperbolic converging profile along its length (i.e.,
the direction in which the first polymer flows) as discussed
herein.
[0053] Among the potential advantages of at least some embodiments
of the present invention is the ability to manufacture polymeric
fibers of polymeric materials that are not typically extruded into
polymeric fibers. Melt flow index is a common industry term related
to the melt viscosity of a polymer. American Society for Testing
and Materials (ASTM) includes a test method (ASTM D1238). This test
method specifies loads and temperatures that are to be used to
measure specific polymer types. As used herein, melt flow index
values are to be obtained at the conditions specified by ASTM D1238
for the given polymer type. The general principle of melt index
testing involves heating the polymer to be tested in a cylinder
with a plunger on top and a small capillary or orifice located at
the bottom of the cylinder. When thermally equilibrated, a
predetermined weight is placed on the plunger and extrudate is
collected and weighed for a predetermined amount of time. A higher
melt index value is typically associated with a higher flow rate
and lower viscosity, both of which may be indicative of a lower
molecular weight. Conversely, low melt index values are typically
associated with lower flow rates and higher viscosities, both of
which may be indicative of a higher molecular weight polymer.
[0054] In conventional polymeric fiber extrusion processes, the MFI
of the extruded polymers is about 35 or higher. Using the methods
of the present invention, the polymer melt stream used to form the
extruded polymeric fibers may include one or more polymers, with
all of the one or more polymers exhibiting a MFI of 30 or less, in
some instances 10 or less, in other instances 1 or less, and in
still other instances 0.1 or less. In some embodiments, the polymer
melt stream may consist essentially of one polymer that preferably
exhibits a MFI of 30 or less, in some instances 10 or less, in
other instances 1 or less, and in still other instances 0.1 or
less.
[0055] In some embodiments, the polymer melt stream may be
characterized as including a bulk polymer that forms at least a
majority of the volume of the polymer melt stream. In some
instances, it may be preferred that the bulk polymer form 60% or
more of the volume of the polymer melt stream, or in other
instances, it may be preferred that the bulk polymer form 75% or
more of the volume of the polymer melt stream. In these instances,
the volumes are determined as the polymer melt stream is delivered
to the orifice of a die.
[0056] The bulk polymer may preferably exhibit a MFI of 30 or less,
in some instances 10 or less, in other instances 1 or less, and in
still other instances 0.1 or less. In embodiments that can be
characterized as including a bulk polymer, the polymer melt stream
may include one or more secondary polymers in addition to the bulk
polymer. In various embodiments, the secondary polymers may
preferably exhibit a MFI of 30 or less, in some instances 10 or
less, in other instances 1 or less, and in still other instances
0.1 or less.
[0057] Some examples of polymers that may be low MFI polymers and
that may be extruded into fibers in connection with the present
invention may include, e.g., Ultra High Molecular Weight
polyethylene (UHMWPE), Ethylene-Propylene-Diene-Monomer (EPDM)
rubber, high molecular weight polypropylene, polycarbonate, ABS,
AES, polyimids, norbornenes, Z/N and Metallocene copolymers (EAA,
EMAA, EMMA, etc), polyphenylene sulfide, ionomers, polyesters,
polyamides, and derivatives (e.g., PPS, PPO PPE).
[0058] Other examples of low MFI polymers that may be compatible
with the present invention are the traditional "glassy" polymers.
The term "glassy" used here is the same traditional use of a dense
random morphology that displays a glass transition temperature
(T.sub.g), characteristic of density, rheology, optical, and
dielectric changes in the material. Examples of glassy polymers may
include, but are not limited to: polymethylmethacrylates,
polystyrenes, polycarbonates, polyvinylchlorides, etc.
[0059] Still other examples of low MFI polymers that may be
compatible with the present invention are the traditional "rubbery"
polymers. The term "rubbery" is the same as used in traditional
nomenclature: a random macromolecular material with sufficient
molecular weight to form significant entanglement so as to result
in a material with a long relaxation time. Examples of "rubbery"
polymers may include, but are not limited to; polyurethanes, ultra
low density polyethylenes, styrenic block copolymers such as
styrene-isoprene-styrene (SIS), styrene-butadiene-styrene (SBS)
styrene-ethylene/butylene-styrene (SEBS), polyisoprenes,
polybutadienes, EPDM rubber, and their analogues.
[0060] For those polymers that are not typically characterized by
MFI, an alternative may be found in melt viscosity. While MFI is
inversely related to molecular weight, melt viscosity typically
increases with increasing molecular weight of the selected polymer.
Examples of polymers that may more typically be characterized by
melt viscosity include, e.g., polyesters, polyamides (e.g.,
nylons), etc. As used herein, melt viscosity for a given polymer is
measured at the temperature at which the polymer is delivered to
the entrance of the die orifice. It may be preferred that, for
polymers characterized by melt viscosity, the melt viscosity of the
polymers used in connection with the present invention be about 100
Pascal-seconds (Pas) or higher. The present invention may also be
used to melt extrude fibers using polymers with melt viscosity of
200 Pascal-seconds or higher, 300 Pascal-seconds or higher, or 400
Pascal-seconds or higher.
[0061] The present invention may also be used to extrude amorphous
polymers into fibers. As used herein, an "amorphous polymer" is a
polymer having little to no crystallinity usually indicated by the
lack of a distinctive melting point or first order transition when
heated in a differential scanning calorimeter according to ASTM
D3418.
[0062] In still other embodiments, a potential advantage of the
present invention may be found in the ability to extrude polymeric
fibers using a multiphase polymer as the polymer melt stream and a
lubricant. By multiphase polymer, we may mean, e.g., organic
macromolecules that are composed of different species that coalesce
into their own separate regions. Each of the regions has its own
distinct properties such as glass transition temperature (Tg),
gravimetric density, optical density, etc. One such property of a
multiphase polymer is one in which the separate polymeric phases
exhibit different theological responses to temperature. More
specifically, their melt viscosities at extrusion process
temperatures can be distinctly different. Examples of some
multiphase polymers may be disclosed in, e.g., U.S. Pat. Nos.
4,444,841 (Wheeler), 4,202,948 (Peascoe), and 5,306,548 (Zabrocki
et al.).
[0063] As used herein, "multiphase" refers to an arrangement of
macromolecules including copolymers of immiscible monomers. Due to
the incompatibility of the copolymers present, distinctly different
phases or "domains" may be present in the same mass of material.
Examples of thermoplastic polymers that may be suitable for use in
extruding multiphase polymer fibers according to the present
invention include, but are not limited to materials from the
following classes: multiphase polymers of polyethers, polyesters,
or polyamides; oriented syndiotactic polystyrene, polymers of
ethylene-propylene-diene monomers ("EPDM"), including
ethylene-propylene-nonconjugated diene ternary copolymers grafted
with a mixture of styrene and acrylonitrile (also known as
acrylonitrile EPDM styrene or "AES"); styrene-acrylonitrile ("SAN")
copolymers including graft rubber compositions such as those
comprising a crosslinked acrylate rubber substrate (e.g., butyl
acrylate) grafted with styrene and acrylonitrile or derivatives
thereof (e.g., alpha-methyl styrene and methacrylonitrile) known as
"ASA" or acrylate-styrene-acrylonitrile copolymers, and those
comprising a substrate of butadiene or copolymers of butadiene and
styrene or acrylonitrile grafted with styrene or acrylonitrile or
derivatives thereof (e.g., alpha-methyl styrene and
methacrylonitrile) known as "ABS" or
acrylonitrile-butadiene-styrene copolymers, as well as extractable
styrene-acrylonitrile copolymers (i.e., nongraft copolymers) also
typically referred to as "ABS" polymers; and combinations or blends
thereof. As used herein, the term "copolymer" should be understood
as including terpolymers, tetrapolymers, etc.
[0064] Some examples of polymers that may be used in extruding
multiphase polymer fibers may be found within the styrenic family
of multiphase copolymer resins (i.e., a multiphase styrenic
thermoplastic copolymer) referred to above as AES, ASA, and ABS,
and combinations or blends thereof. Such polymers are disclosed in
U.S. Pat. Nos. 4,444,841 (Wheeler), 4,202,948 (Peascoe), and
5,306,548 (Zabrocki et al.). The blends may be in the form of
multilayered fibers where each layer is a different resin, or
physical blends of the polymers which are then extruded into a
single fiber. For example, ASA and/or AES resins can be coextruded
over ABS.
[0065] Multiphase polymer systems can present major challenges in
fiber processing because the different phases can have very
different rheological responses to processing. For example, the
result may be poor tensile response of multiphase polymers. The
different rheological response of the different phases may cause
wide variations in the drawing responses during conventional fiber
forming processes that involve drawing or pulling of the extruded
fibers. In many instances, the presence of multiple polymer phases
exhibits insufficient cohesion to resist the tensile stresses of
the drawing process, causing the fibers to break or rupture.
[0066] In the present invention, the unique challenges that may be
associated with extruding multiphase polymers may be addressed
based on how the material is oriented during fiber formation. It
may be preferred that, in connection with the present invention,
the multiphase polymer material is squeezed or `pushed` through the
die orifice to orient the polymer materials (as opposed to pulling
or drawing). As a result, the present invention may substantially
reduce the potential for fracture.
[0067] Some multiphase polymers that may be used in the methods
according to the present invention are the multiphase AES and ASA
resins, and combinations or blends thereof. Commercially available
AES and ASA resins, or combinations thereof, include, for example,
those available under the trade designations ROVEL from Dow
Chemical Company, Midland, Mich., and LORAN S 757 and 797 from BASF
Aktiengesellschaft, Ludwigshafen, Fed. Rep. of Germany), CENTREX
833 and 401 from Bayer Plastics, Springfield, Conn., GELOY from
General Electric Company, Selkirk, N.Y., VITAX from Hitachi
Chemical Company, Tokyo, Japan. It is believed that some
commercially available AES and/or ASA materials also have ABS
blended therein. Commercially available SAN resins include those
available under the trade designation TYRIL from Dow Chemical,
Midland, Mich. Commercially available ABS resins include those
available under the trade designation CYOLAC such as CYOLAC GPX
3800 from General Electric, Pittsfield, Mass.
[0068] The multiphase polymer fibers can also be prepared from a
blend of one or more of the above-listed materials and one or more
other thermoplastic polymers. Examples of such thermoplastic
polymers that can be blended with the above-listed yielding
materials include, but are not limited to, materials from the
following classes: biaxially oriented polyethers; biaxially
oriented polyesters; biaxially oriented polyamides; acrylic
polymers such as poly(methyl methacrylate); polycarbonates;
polyimides; cellulosics such as cellulose acetate, cellulose
(acetate-co-butyrate), cellulose nitrate; polyesters such as
poly(butylene terephthalate), poly(ethylene terephthalate);
fluoropolymers such as poly(chlorofluoroethylene), poly(vinylidene
fluoride); polyamides such as poly(caprolactam), poly(amino caproic
acid), poly(hexamethylene diamine-co-adipic acid),
poly(amide-co-imide), and poly(ester-co-imide); polyetherketones;
poly(etherimide); polyolefins such as poly(methylpentene);
aliphatic and aromatic polyurethanes; poly(phenylene ether);
poly(phenylene sulfide); atactic poly(styrene); cast syndiotactic
polystyrene; polysulfone; silicone modified polymers (i.e.,
polymers that contain a small weight percent (less than 10 weight
percent) of silicone) such as silicone polyamide and silicone
polycarbonate; ionomeric ethylene copolymers such as
poly(ethylene-co-methacrylic acid) with sodium or zinc ions, which
are available under the trade designations SURLYN-8920 and
SURLYN-9910 from E.I. duPont de Nemours, Wilmington, Del.; acid
functional polyethylene copolymers such as poly(ethylene-co-acrylic
acid) and poly(ethylene-co-methacrylic acid),
poly(ethylene-co-maleic acid), and poly(ethylene-co-fumaric acid);
fluorine modified polymers such as
perfluoropoly(ethyleneterephthalate); and mixtures of the above
polymers such as a polyimide and acrylic polymer blend, and a
poly(methylmethacrylate) and fluoropolymer blend.
[0069] The polymer compositions used in connection with the present
invention may include other ingredients, e.g., UV stabilizers and
antioxidants such as those available from Ciba-Geigy Corp.,
Ardsley, N.Y., under the trade designation IRGANOX, pigments, fire
retardants, antistatic agents, mold release agents such as fatty
acid esters available under the trade designations LOXIL G-715 or
LOXIL G-40 from Henkel Corp., Hoboken, N.J., or WAX E from Hoechst
Celanese Corp., Charlotte, N.C. Colorants, such as pigments and
dyes, can also be incorporated into the polymer compositions.
Examples of colorants may include rutile TiO.sub.2 pigment
available under the trade designation R960 from DuPont de Nemours,
Wilmington, Del., iron oxide pigments, carbon black, cadmium
sulfide, and copper phthalocyanine. Often, the above-identified
polymers are commercially available with one or more of these
additives, particularly pigments and stabilizers. Typically, such
additives are used in amounts to impart desired characteristics.
Preferably, they are used in amounts of about 0.02-20 wt-%, and
more preferably about 0.2-10 wt-%, based on the total weight of the
polymer composition.
[0070] Another potential advantage of at least some embodiments of
the present invention is the ability to extrude the polymer melt
stream at a relatively low temperature. For example, in the case of
semi-crystalline polymers, it may be possible to extrude the
polymer melt stream when the average temperature of the polymer
melt stream as pushed through the entrance of each orifice in the
die is within 10 degrees Celsius or less above a melt processing
temperature of the polymer melt stream. In some embodiments, the
average temperature of the polymer melt stream may preferably be at
or below a melt processing temperature of the polymer melt stream
before the polymer melt stream leaves the exit of the orifice. To
do so, it may be preferred that the die temperature be controlled
to a temperature that is at or below the melt processing
temperature of the polymer melt stream.
[0071] Although not wishing to be bound by theory, it is theorized
that the present invention may rely on the dominance of the
lubricant properties to process the polymer during extrusion, with
the polymer viscosity playing a relatively minor factor in stress
(pressure and temperature) response. Further, the presence of the
lubricant may allow "quenching" (e.g., crystal or glass
"vitrification" formation) of the polymer within the die. A
potential advantage of in-die quenching may include, e.g.,
retaining orientation and dimensional precision of the
extrudate.
[0072] As used herein, the "melt processing temperature" of the
polymer melt stream is the lowest temperature at which the polymer
melt stream is capable of passing through the orifices of the die
within a period of 1 second or less. In some instances, the melt
processing temperature may be at or slightly above the glass
transition temperature if the polymer melt stream is amorphous or
at or slightly above the melting temperature if the polymer melt
stream is crystalline or semicrystalline. If the polymer melt
stream includes one or more amorphous polymers blended with either
or both of one or more crystalline and one or more semicrystalline
polymers, then the melt processing temperature is the lower of the
lowest glass transition temperature of the amorphous polymers or
the lowest melting temperature of the crystalline and
semicrystalline polymers.
[0073] One exemplary die orifice that may be used in dies according
to the present invention is depicted in the cross-sectional view of
FIG. 3 in which a die plate 10 and a complementary die plate cover
12 are depicted in a cross-sectional view. The die plate 10 and die
plate cover 12 define a polymer delivery passage 20 that is in
fluid communication with an orifice 22 in the die plate 10. The
portion of the polymer delivery passage 20 formed in the die plate
cover 12 terminates at opening 16, where the polymer melt stream
enters the portion of polymer delivery passage 20 formed within the
die plate 10 through opening 14. In the depicted embodiment, the
opening 16 in the die plate cover 12 is generally the same size as
the opening 14 in the die plate 10.
[0074] FIG. 4 depicts an enlarged view of the orifice 22 with the
addition of reference letter "r" indicative of the radius of the
orifice 22 and "z" indicative of the length of the orifice 22 along
the axis 11. The orifice 22 formed in the die plate 10 may
preferably converge such that the cross-sectional area (measured
transverse to the axis 11) is smaller than the cross-sectional area
of the entrance 24. It may be preferred that, as discussed herein,
the shape of the die orifice 22 be designed such that the
elongational strain rate of the polymer melt stream be constant
along the length of the orifice 22 (i.e., along axis 11).
[0075] As discussed herein, it may be preferred that the die
orifice have a converging semi-hyperbolic profile. The definition
of a "semi-hyperbolic" shape begins with the fundamental
relationship between volume flow, area of channel and fluid
velocity. Although cylindrical coordinates are used in connection
with the description of orifice 22, it should be understood that
die orifices used in connection with the present invention may not
have a circular cylindrical profile.
[0076] Flow through the orifice 22 along axis 11 can be described
at each position along the axis 11 by the following equation:
Q=V*A (1)
where Q is the measure of volumetric flow through the orifice, V is
the flow velocity through the orifice, and A is the cross-sectional
area of the orifice 22 at the selected location along the axis
11.
[0077] Equation (1) can be rearranged and solved for velocity to
yield the following equation:
V=Q/A (2)
[0078] Because the cross-sectional area of a converging orifice
changes along the length of the channel of the orifice, the
following equation can be used to describe the various
relationships between variables in Equation (2):
dV.sub.z/dz=(-Q/A.sup.2)(dA/dz) (3)
[0079] In Equation (3), the expression for the change in velocity
with the change in position down the length of the orifice also
defines extensional flow (O) of the fluid. Steady or constant
extensional flow may be a preferred result of flow through a
converging orifice. As a result, it may be preferred that the
cross-sectional area of the orifice change in such a way as to
result in constant extensional flow through the orifice. An
equation that defines steady or constant extensional flow may be
expressed as:
dV.sub.z/dz=.epsilon.=constant (4)
[0080] An expression that can be substituted for the change in area
with the change in position down the length of the orifice and that
will yield a constant or steady extensional flow may be expressed
as
f(r,z)=Constant=r.sup.2z (5)
[0081] A generic form of the expression of Equation (5) may be the
following:
f(r,z)=C.sub.1+C.sub.2r.sup.2z (6)
[0082] Equation (6) may be used to determine the shape of an
orifice 22 as used in connection with the present invention. To
design the shape of an orifice, it may be preferred that the
geometric constraint of the diameter of the exit 26 of the orifice
22 be determined (with the understanding that exit diameter is
indicative of the fiber size extruded from the orifice 22).
Alternatively, the diameter of the entrance 24 of the orifice 22
may be used.
[0083] When the radius (and, thus, the corresponding area) of one
of entrance 24 or the exit 26 of the orifice 22 is chosen, then the
other may be determined by selecting the desired extensional strain
selected, then the other radius (i.e., the radius of the entrance
24 or the exit 26) may preferably be determined by selecting the
desired extensional strain to experienced by the fluid (i.e.,
polymer melt stream) passing through the orifice 22.
[0084] This value, i.e., the extensional strain, may sometimes be
referred to as the "Hencky Strain." Hencky Strain is based on
extensional or engineering strain of a material being stretched.
The equation presented below describes Hencky Strain for a fluid in
passing through a channel, e.g., an orifice in the present
invention:
Hencky Strain on
Fluid=ln(r.sub.o.sup.2/r.sub.z.sup.2)=ln(A.sub.o/A.sub.z). (7)
Selection of the desired Hencky Strain to be experienced by the
fluid passing through the orifice fixes or sets the radius (and,
thus, the area) the other end of the orifice as discussed above.
The last remaining design feature is to establish the length of the
orifice to be lubricated. Once the length of the orifice 22 ("z" in
FIG. 4) is selected and the radii/areas of the entrance 24 and exit
are known, Equation 6 can be regressed for radius (area) change
with the change in position down the length of the orifice 22
(along the "z" direction) to obtain the constants C.sub.1 and
C.sub.2. The following equation provides the radius of the orifice
at each location along the "z" dimension (r.sub.z):
r.sub.z=[((z)(e.sup.s-1)+Length)/(r.sub.entrance.sup.2*Length)].sup.-1/2
(8)
where z is the location along the longitudinal axis in the z
direction as measured from the entrance of the orifice;
e=(r.sub.entrance).sup.2/(r.sub.exit).sup.2; s=Hencky Strain;
r.sub.entrance is the radius at the entrance to the orifice;
r.sub.exit is the radius at the exit of the orifice; and Length is
the overall length of the orifice in the z direction from the
entrance to the exit of the orifice. For a discussion of Hencky
Strain and associated principles, reference may be had to C. W.
Macosko "Rheology--Principles, Measurements and Applications," pp.
285-336 (Wiley-VCH Inc., New York, 1.sup.st Ed. 1994).
[0085] Returning to FIG. 3, the die plate 10 also includes a
lubricant passage 30 in fluid communication with a lubricant plenum
32 formed between the die plate 10 and the die plate cover 12. The
die plate 10 and the die plate cover 12 preferably define a gap 34
such that a lubricant passed into the lubricant plenum 32 through
the lubricant passage 30 will pass into the polymer delivery
passage 20 from slot 36 and through opening 14. As such, the
lubricant can be delivered to the orifice 22 separately from the
polymer melt stream.
[0086] The slot 36 may preferably extend about the perimeter of the
polymer delivery passage 20. The slot 36 may preferably be
continuous or discontinuous about the perimeter of the polymer
delivery passage 20. The spacing between the die plate 10 and the
die plate cover 12 that forms gap 34 and slot 36 may be adjusted
based on a variety of factors such as the pressure at which a
polymer melt stream is passed through the polymer delivery passage
20, the relative viscosities of the polymer melt stream and the
lubricant, etc. In some instances, the slot 36 may be in the form
of an opening or openings formed by the interface of two roughened
(e.g., sandblasted, abraded, etc.) surfaces forming gap 34 (or one
roughened surface and an opposing smooth surface).
[0087] FIG. 5 is a plan view of the die plate 10 with the die plate
cover 12 removed. Multiple openings 14, polymer delivery passages
20, die orifices 22, and lubricant plenums 32 are depicted therein.
The depicted polymer delivery passages 20 have a constant
cross-sectional area (measured transverse to the axis 11 in FIG. 3)
and are, in the depicted embodiment, circular cylinders. It should
be understood, however, that the polymer delivery passages 20 and
associated die orifices 22 may have any suitable cross-sectional
shape, e.g., rectangular, oval, elliptical, triangular, square,
etc.
[0088] It may be preferred that the lubricant plenums 32 extend
about the perimeters of the polymer delivery passages 20 as seen in
FIG. 5 such that the lubricant can be delivered about the perimeter
of the polymer delivery passages 20. By doing so, the lubricant
preferably forms a layer about the perimeter of a polymer melt
stream as it passes through the polymer delivery passages 20 and
into the die orifices 22. In the depicted embodiment, the plenums
32 are supplied by lubricant passages 30 that extend to the outer
edges of the die plate 10 as seen in FIG. 5.
[0089] It may be preferred that each of the plenums 32 be supplied
by an independent lubricant passage 30 as seen in FIG. 5. By
supplying each of the plenums 32 (and their associated die orifices
22) independently, control over a variety of process variable can
be obtained. Those variables may include, for example, the
lubricant pressure, the lubricant flow rate, the lubricant
temperature, the lubricant composition (i.e., different lubricants
may be supplied to different orifices 22), etc.
[0090] As an alternative, however, it may be preferred in some
systems that a master plenum be used to supply lubricant to each of
the lubricant passages 30 which, in turn, supply lubricant to each
of the plenums 32 associated with the orifices 22. In such a
system, the delivery of lubricant to each orifice may preferably be
balanced between all of the orifices.
[0091] FIG. 6 is a schematic diagram of one system 90 that may be
used in connection with the present invention. The system 90 may
preferably include polymer sources 92 and 94 that deliver polymer
to an extruder 96. Although two polymer sources are depicted, it
should be understood that only one polymer source may be provided
in some systems. In addition, other systems may include three or
more polymer sources. Furthermore, although only a single extruder
96 is depicted, it should be understood that system 90 may include
any extrusion system or apparatus capable of delivering the desired
polymer or polymers to the die 98 in accordance with the present
invention.
[0092] In addition to one or more polymer sources 92 and 94, the
system 90 also includes a particle source 91 that, in the depicted
embodiment, provides particles to be entrained within the polymer
from polymer source 92. Alternatively, the particle source 91 could
input its particles into the extruder 96 (or extruders if multiple
extruders are used). Regardless of the specific arrangement, it is
preferred that the particles from the particle source 91 be
entrained within the polymer melt stream as it is delivered to die
98.
[0093] The system 90 further includes a lubricant apparatus 97
operably attached to the die 98 to deliver lubricant to the die in
accordance with the principles of the present invention. In some
instances, the lubricant apparatus 97 may be in the form of a
lubricant polymer source and extrusion apparatus.
[0094] Also depicted in connection with the system 90 are two
fibers 40 being extruded from the die 98. Although two fibers 40
are depicted, it should be understood that only one fiber may be
produced in some systems, while other systems may produce three or
more polymer fibers at the same time.
[0095] FIG. 7 depicts another exemplary embodiment of a die orifice
that may be used in connection with the present invention. Only a
portion of the apparatus is depicted in FIG. 7 to illustrate a
potential relationship between the entrance 114 of the die orifice
122 and delivery of the lubricant through gap 134 between the die
plate 110 and the die plate cover 112. In the depicted apparatus,
the lubricant delivered separately from the polymer melt stream is
introduced at the entrance 116 of the orifice 122 through gap 134.
The polymer melt stream itself is delivered to the entrance 116 of
the die orifice 122 through polymer delivery passage 120 in die
plate cover 112.
[0096] Another optional relationship depicted in the exemplary
apparatus of FIG. 7 is the relative size of the entrance 114 of the
die orifice 122 as compared to the size of the opening 116 leading
from the polymer delivery passage 120 into the entrance 114. It may
be preferred that the cross-sectional area of the opening 116 be
less than the cross-sectional area of the entrance 114 to the die
orifice 122. As used herein, "cross-sectional area" of the openings
is determined in a plane generally transverse to the longitudinal
axis 111 (which is, preferably, the direction along which the
polymer melt stream moves through the polymer delivery passage and
the die orifice 122).
[0097] FIG. 8 depicts yet another potential apparatus that may be
used in connection with the present invention. FIG. 8 is an
enlarged plan view of one die orifice 222 taken from above the die
plate 210 (in a view similar to that seen in FIG. 5). The entrance
216 to the die orifice 222 is depicted along with the exit 226 of
the die orifice 222. One difference between the design depicted in
FIG. 8 and that depicted in the previous figures is that the
lubricant is delivered to the die orifice 222 through multiple
openings formed at the end of channels 234a, 234b, and 234c. This
is in contrast to the continuous slot formed by the gap between the
die plate and the die plate cover in the embodiments described
above. Although three openings for delivering lubricant are
depicted, it should be understood that as few as two and more than
three such openings may be provided.
[0098] FIG. 9 depicts a flow of the polymer melt stream 40 and a
lubricant 42 from the exit 26 of a die in accordance with the
present invention. The polymer melt stream 40 and lubricant 42 are
shown in cross-section, depicting the lubricant 42 on the outer
surface 41 of the polymer melt stream 40. It may be preferred that
the lubricant be provided on the entire outer surface 41 such that
the lubricant 42 is located between the polymer melt stream 40 and
the interior surface 23 of the die orifice.
[0099] Although the lubricant 42 is depicted on the outer surface
41 of the polymer melt stream 40 after the polymer melt stream 40
has left the orifice exit 26, it should be understood that, in some
instances, the lubricant 42 may be removed from the outer surface
41 of the polymer melt stream 40 as or shortly after the polymer
melt stream 40 and lubricant 42 leave the die exit 26.
[0100] Removal of the lubricant 42 may be either active or passive.
Passive removal of the lubricant 42 may involve, e.g., evaporation,
gravity or adsorbents. For example, in some instances, the
temperature of the lubricant 42 and/or the polymer melt stream 40
may be high enough to cause the lubricant 42 to evaporate without
any further actions after leaving the die exit 26. In other
instances, the lubricant may be actively removed from the polymer
melt stream 40 using, e.g., a water or another solvent, air jets,
etc.
[0101] Depending on the composition of the lubricant 42, a portion
of the lubricant 42 may remain on the outer surface 41 of the
polymer melt stream 40. For example, in some instance the lubricant
42 may be a composition of two or more components, such as one or
more carriers and one or more other components. The carriers may
be, e.g., a solvent (water, mineral oil, etc.) that are removed
actively or passively, leaving the one or more other components in
place on the outer surface 41 of the polymer melt stream 40.
[0102] In other situations, the lubricant 42 may be retained on the
outer surface 41 of the polymer melt stream 40. For example, the
lubricant 42 may be a polymer with a viscosity that is low enough
relative to the viscosity of the polymer melt stream 40 such that
it can function as a lubricant during extrusion. Examples of
potentially suitable polymers that may also function as lubricants
may include, e.g., polyvinyl alcohols, high melt flow index
polypropylenes, polyethylenes, etc.
[0103] Regardless of whether the lubricant 42 is removed from the
surface 41 of the polymer melt stream 40 or not, the lubricant 42
may act as a quenching agent to increase the rate at which the
polymer melt stream 40 cools. Such a quenching effect may help to
retain particular desired structures in the polymer melt stream 40
such as orientation within the polymer melt stream 40. To assist in
quenching, it may be desirable, for example, to provide the
lubricant 42 to the die orifice at a temperature that is low enough
to expedite the quenching process. In other instances, the
evaporative cooling that may be provided using some lubricants may
be relied on to enhance the quenching of the polymer melt stream
40. For example, mineral oil used as a lubricant 42 may serve to
quench a polypropylene fiber as it evaporates from the surface of
the polypropylene (the polymer melt stream) after exiting the
die.
[0104] The present invention may preferably rely on a viscosity
difference between the lubricant materials and the extruded
polymer. Viscosity ratios of polymer to lubricant of, e.g., 40:1 or
higher, or 50:1 or higher may preferably be a significant factor in
selecting the lubricant to be used in connection with the methods
of the present invention. The lubricant chemistry may be secondary
to its theological behavior. In this description, materials such as
SAE 20 weight oil, white paraffin oil, and polydimethyl siloxane
(PDMS) fluid are all examples of potentially suitable lubricant
materials. The following list is not intended to be a limit on the
lubricant candidates, i.e., other materials may be used as
lubricants in connection with the present invention.
[0105] Non-limiting examples of inorganic or synthetic oils may
include mineral oil, petrolatum, straight and branched chain
hydrocarbons (and derivatives thereof), liquid paraffins and low
melting solid paraffin waxes, fatty acid esters of glycerol,
polyethylene waxes, hydrocarbon waxes, montan waxes, amide wax,
glycerol monostearate. etc.
[0106] Many kinds of oils and fatty acid derivatives thereof may
also be suitable lubricants in connection with the present
invention. Fatty acid derivatives of oils can be used, such as, but
not limited to, oleic acid, linoleic acid, and lauric acid.
Substituted fatty acid derivatives of oils may also be used, such
as, but not limited to, oleamide, propyl oleate and oleyl alcohol
(it may be preferred that the volatility of such materials is not
so high so as to evaporate before extrusion). Examples of some
potentially suitable vegetable oils may include, but not limited
to, apricot kernel oil, avocado oil, baobab oil, black currant oil,
calendula officinalis oil, cannabis sativa oil, canola oil,
chaulmoogra oil, coconut oil, corn oil, cottonseed oil, grape seed
oil, hazelnut oil, hybrid sunflower oil, hydrogenated coconut oil,
hydrogenated cottonseed oil, hydrogenated palm kernel oil, jojoba
oil, kiwi seed oil, kukui nut oil, macadamia nut oil, mango seed
oil, meadowfoam seed oil, mexican poppy oil, olive oil, palm kernel
oil, partially hydrogenated soybean oil, peach kernel oil, peanut
oil, pecan oil, pistachio nut oil, pumpkin seed oil, quinoa oil,
rapeseed oil, rice bran oil, safflower oil, sasanqua oil, sea
buckthorn oil, sesame oil, shea butter fruit oil, sisymbrium irio
oil, soybean oil, sunflower seed oil, walnut oil, and wheat germ
oil.
[0107] Other potentially suitable lubricant materials may include,
e.g., saturated aliphatic acids including hexanoic acid, caprylic
acid, decanoic acid, undecanoic acid, lauric acid, myristic acid,
palmitic acid and stearic acid, unsaturated aliphatic acids
including oleic acid and erucic acid, aromatic acids including
benzoic acid, phenyl stearic acid, polystearic acid and xylyl
behenic acid and other acids including branched carboxylic acids of
average chain lengths of 6, 9, and 11 carbons, tall oil acids and
rosin acid, primary saturated alcohols including 1-octanol, nonyl
alcohol, decyl alcohol, 1-decanol, 1-dodecanol, tridecyl alcohol,
cetyl alcohol and 1-heptadecanol, primary unsaturated alcohols
including undecylenyl alcohol and oleyl alcohol, secondary alcohols
including 2-octanol, 2-undecanol, dinonyl carbinol and diundecyl
carbinol and aromatic alcohols including 1-phenyl ethanol,
1-phenyl-1-pentanol, nonyl phenyl, phenylstearyl alcohol and
1-naphthol. Other potentially useful hydroxyl-containing compounds
may include polyoxyethylene ethers of oleyl alcohol and a
polypropylene glycol having a number average molecular weight of
about 400. Still further potentially useful liquids may include
cyclic alcohols such as 4, t-butyl cyclohexanol and methanol,
aldehydes including salicyl aldehyde, primary amines such as
octylamine, tetradecylamine and hexadecylamine, secondary amines
such as bis-(1-ethyl-3-methyl pentyl) amine and ethoxylated amines
including N-lauryl diethanolamine, N-tallow diethanol-amine,
N-stearyl diethanolamine and N-coco diethanolamine.
[0108] Additional potentially useful lubricant materials may
include aromatic amines such as N-sec-butylaniline, dodecylaniline,
N,N-dimethylaniline, N,N-diethylaniline, p-toluidine,
N-ethyl-o-toluidine, diphenylamine and aminodiphenylmethane,
diamines including N-erucyl-1,3-propane diamine and
1,8-diamino-p-methane, other amines including branched tetramines
and cyclodecylamine, amides including cocoamide, hydrogenated
tallow amide, octadecylamide, eruciamide, N,N-diethyl toluamide and
N-trimethylopropane stearamide, saturated aliphatic esters
including methyl caprylate, ethyl laurate, isopropyl myristate,
ethyl palmitate, isopropropyl palmitate, methyl stearate, isobutyl
stearate and tridecyl stearate, unsaturated esters including
stearyl acrylate, butyl undecylenate and butyl oleate, alkoxy
esters including butoxyethyl stearate and butoxyethyl oleate,
aromatic esters including vinyl phenyl stearate, isobutyl phenyl
stearate, tridecyl phenyl stearate, methyl benzoate, ethyl
benzoate, butyl benzoate, benzyl benzoate, phenyl laurate, phenyl
salicylate, methyl salicylate and benzyl acetate and diesters
including dimethyl phenylene distearate, diethyl phthalate, dibutyl
phthalate, di-iso-octyl phthalate, dicapryl adipate, dibutyl
sebacate, dihexyl sebacate, di-iso-octyl sebacate, dicapryl
sebacate and dioctyl maleate. Yet other potentially useful
lubricant materials may include polyethylene glycol esters
including polyethylene glycol (which may preferably have a number
of average molecular weight of about 400), diphenylstearate,
polyhydroxylic esters including castor oil (triglyceride), glycerol
monostearate, glycerol monooleate, glycol distearate glycerol
dioleate and trimethylol propane monophenylstearate, ethers
including diphenyl ether and benzyl ether, halogenated compounds
including hexachlorocyclopentadiene, octabromobiphenyl,
decabromodiphenyl oxide and 4-bromodiphenyl ether, hydrocarbons
including 1-nonene, 2-nonene, 2-undecene, 2-heptadecene,
2-nonadecene, 3-eicosene, 9-nonadecene, diphenylmethane,
triphenylmethane and trans-stilbene, aliphatic ketones including
2-heptanone, methyl nonyl ketone, 6-undecanone, methylundecyl
ketone, 6-tridecanone, 8-pentadecanone, 11-pentadecanone,
2-heptadecanone, 8-heptadecanone, methyl heptadecyl ketone, dinonyl
ketone and distearyl ketone, aromatic ketones including
acetophenone and benzophenone and other ketones including xanthone.
Still further potentially useful lubricants may include phosphorous
compounds including trixylenyl phosphate, polysiloxanes, Muget
hyacinth (An Merigenaebler, Inc), Terpineol Prime No. 1
(Givaudan-Delawanna, Inc), Bath Oil Fragrance #5864 K
(International Flavor & Fragrance, Inc), Phosclere P315C
(organophosphite), Phosclere P576 (organophosphite), styrenated
nonyl phenol, quinoline and quinalidine.
[0109] Oils with emulsifier qualities may also potentially be used
as lubricant materials, such as, but not limited to, neatsfoot oil,
neem seed oil, PEG-5 hydrogenated castor oil, PEG-40 hydrogenated
castor oil, PEG-20 hydrogenated castor oil isostearate, PEG-40
hydrogenated castor oil isostearate, PEG-40 hydrogenated castor oil
laurate, PEG-50 hydrogenated castor oil laurate, PEG-5 hydrogenated
castor oil triisostearate, PEG-20 hydrogenated castor oil
triisostearate, PEG-40 hydrogenated castor oil triisostearate,
PEG-50 hydrogenated castor oil triisostearate, PEG-40 jojoba oil,
PEG-7 olive oil, PPG-3 hydrogenated castor oil, PPG-12-PEG-65
lanolin oil, hydrogenated mink oil, hydrogenated olive oil, lanolin
oil, maleated soybean oil, musk rose oil, cashew nut oil, castor
oil, dog rose hips oil, emu oil, evening primrose oil, and gold of
pleasure oil.
Test Methods
Modulus:
[0110] The moduli of the fibers of the invention were measured
using the procedures described in ASTM-D2653-01. 16 mm diameter
roller grips (MTS 100-034-764) were used with a 14 cm grip
separation and a crosshead speed of 25.4 cm/min. A 500 N load cell
was used. The diameters of the fibers were measured using an Ono
Sokki thickness gauge. 5 replicates were run and averaged.
Mass Flow Rate:
[0111] The mass flow rate was measured by a basic gravimetric
method. The exiting extrudate was captured in a pre-weighed
aluminum tray for a period of 80 seconds. The difference between
the total weight and the weight of the tray was measured in grams
or kilograms.
Melt Flow Index (MFI):
[0112] The melt flow indices of the polymers were measured
according to ASTM D1238 at the conditions specified for the given
polymer type.
EXAMPLES
[0113] The following non-limiting examples are provided to
illustrate the principles of the present invention.
Example 1
[0114] A polymeric fiber was produced using apparatus similar to
that shown in FIG. 6. A single orifice die as shown in FIG. 7 was
used. The die orifice was circular and had an entrance diameter of
1.68 mm, an exit diameter of 0.76 mm, a length of 12.7 mm and a
semi-hyperbolic shape defined by the equation:
r.sub.z=[0.00140625/((0.625*z)+0.0625)] 0.5 (9)
where z is the location along the axis of the orifice as measured
from the entrance and r.sub.z is the radius at location z.
[0115] Polypropylene homopolymer (FINAPRO 5660, 9.0 MFI, Atofina
Petrochemical Co., Houston, Tex.) was extruded with a 3.175 cm
single screw extruder (30:1 L/D) using a barrel temperature profile
of 177.degree. C.-232.degree. C.-246.degree. C. and an in-line
ZENITH gear pump (1.6 cubic centimeters/revolution (cc/rev)) set at
19.1 RPM. The die temperature and melt temperature were
approximately 220.degree. C. Chevron SUPERLA white mineral oil #31
as a lubricant was supplied to the entrance of the die using a
second ZENITH gear pump (0.16 cc/rev) set at 30 RPM.
[0116] The molten polymer pressure and corresponding mass flow rate
of the extrudate are shown in Table 1 below. The pressure
transducer for the polymer was located in the feed block just above
the die at the point where the polymer was introduced to the die.
The lubricant pressure transducer was located in the lubricant
delivery feed line prior to introduction to the die. A control
sample was also run without the use of lubricant.
Example 2
[0117] A polymeric fiber was produced as in Example 1 except that a
die similar to that depicted in FIG. 3 was used. The die orifice
had a circular profile with an entrance diameter of 6.35 mm, an
exit diameter of 0.76 mm, a length of 10.16 mm and a
semi-hyperbolic shape defined by Equation (8) as described
herein.
[0118] Molten polymer pressure and mass flow rate of the extrudate
are shown in Table 1 below with and without lubricant.
Example 3
[0119] A polymeric fiber was produced as in Example 1 except that a
die as shown in FIG. 2 was used. The die orifice had a circular
profile with an entrance diameter of 6.35 mm, an exit diameter of
0.51 mm, a length of 12.7 mm and a semi-hyperbolic shape defined by
Equation (8).
[0120] Polyurethane (PS440-200 Huntsman Chemical, Salt Lake City,
Utah) was used to form the fiber. The polymer was delivered with a
3.81 cm single screw extruder (30:1 L/D) using a barrel temperature
profile of 177.degree. C.-232.degree. C.-246.degree. C. and an
in-line ZENITH gear pump (1.6 cc/rev) set at 19.1 RPM. The die
temperature and melt temperature was approximately 215.degree. C.
Chevron SUPERLA white mineral oil #31 as a lubricant was supplied
to the entrance of the die via two gear pumps in series driven at
99 RPM and 77 RPM respectively. Molten polymer pressure and mass
flow rate of the extrudate is shown in Table 1 below. A control
sample was also run without the use of lubricant.
Mass Flow Rates for Examples 1-3:
TABLE-US-00001 [0121] TABLE 1 Melt Mass Flow Pressure Rate Example
(kg/cm.sup.2) (grams/min) 1 8.8 17.6 33.9 Control w/o lub. 8.8 17.6
4.1 2 6.3 8.4 106 Control w/o lub. 52.8 94 3 5.3 45 Control w/o
lub. 114 22.7
Table 1 shows that at similar melt pressures, substantially higher
mass flow rates may be obtained using the invention process
(Example 1), and at similar mass flow rates, polymer may be
extruded at significantly lower pressures (Example 2). As seen in
Example 3, melt pressure may be significantly reduced and mass flow
rate substantially increased simultaneously when using the
invention process.
Example 4
[0122] A polymeric fiber was produced using the die of Example 1.
High molecular weight polyethylene (Type 9640, 0.2 MI, Chevron
Phillips Chemical Co., Houston, Tex.) was extruded with a 38 mm
single screw extruder (30:1 L/D, 9 RPM) using a barrel temperature
profile of 177.degree. C.-200.degree. C.-218.degree. C. and an
in-line ZENITH gear pump (1.6 cubic centimeters/revolution
(cc/rev)) set at 3.7 RPM. The die temperature and melt temperature
were approximately 218.degree. C. Chevron SUPERLA white mineral oil
#31 (Chevron USA Inc., Houston, Tex.) as a lubricant was supplied
to the entrance of the die using a ZENITH dual gear single feed
gear pump (0.16 cc/rev) set at 80 RPM. The extruded fiber was
collected at the die exit manually and coiled by hand.
[0123] The molten polymer pressure varied between 241 N/cm.sup.2
(350 lbs/in.sup.2) and 550 N/cm.sup.2 (798 lbs/in.sup.2) at a mass
flow rate of 2.0-2.5 kg/hr (4.5-5.5 lbs/hr). The pressure
transducer for the polymer was located in the feed block just above
the die at the point where the polymer was introduced to the die.
The lubricant pressure transducer was located in the lubricant
delivery feed line prior to introduction to the die.
Example 5
[0124] A polymeric fiber was produced as in Example 1. The die
orifice had a circular profile with an entrance diameter of 6.35
mm, an exit diameter of 0.76 mm, a length of 127 mm and a
semi-hyperbolic shape defined by Equation (8) as described herein.
A high molecular weight fractional melt index polyethylene
(HD7960.13, 0.06 MI, ExxonMobil Chemical Inc., Houston, Tex.) was
extruded using a 19 mm single screw (30:1 L/D, 12 RPM) extruder
using a barrel temperature profile of 270.degree. C.-255.degree.
C.-240.degree. C. fitted with a 0.16 cubic centimeters per
revolution (0.16 cc/rev) gear pump operating at 6 RPM. The die
temperature and melt temperature were approximately 218.degree. C.
Chevron SUPERLA white mineral oil #31 (Chevron USA Inc., Houston,
Tex.) as a lubricant was supplied to the entrance of the die using
a Lorimer "air over oil" pneumatic high pressure pump (H. Lorimer
Corp., Longview, Tex.).
[0125] The extruded fiber was then quenched in a water bath
(approximately 20.degree. C.) positioned approximately 5 cm beneath
the die exit at a rate of 15 meter/min. The fiber was then length
oriented in-line between two pull rolls by immersing the fiber in a
hot water bath (79.degree. C.) with a draw ratio between the two
pull rolls of approximately 9:1. The oriented fiber was then run
over a heated platen set at 177.degree. C. to relax (heat set) the
fiber and then wound onto a core.
[0126] The average fiber diameter was 0.305 mm. The modulus of the
fiber was measured to be 205 kN/cm.sup.2 with a break tensile force
of 46 kN.
Example 6
[0127] A polymeric fiber was produced as in Example 1 except a high
molecular weight elastomeric polyethylene (ENGAGE 8100, 1.0 MI, Dow
Chemical Co., Midland, Mich.) was used to form the fiber. The
polymer was delivered with a 38 mm single screw extruder (32:1 L/D,
14 RPM) using a barrel temperature profile of 177.degree.
C.-200.degree. C.-2180C and an in-line ZENITH gear pump (1.6
cc/rev) set at 8 RPM resulting in a polymer flow rate of
approximately 2.4 kg/hr. The die temperature and melt temperature
was approximately 218.degree. C. Chevron SUPERLA white mineral oil
#31 as a lubricant was supplied to the entrance of the die using a
ZENITH dual gear single feed gear pump (0.16 cc/rev) set at 75 RPM.
The extruded fiber was collected at the die exit manually and
coiled by hand.
Example 7
[0128] A polymeric fiber was produced as in Example 1 except an
amorphous glassy polycarbonate (MACROLON 2407, Bayer Chemical Co.,
Leverkusen, Germany) was used to form the fiber. The polymer was
delivered with a 38 mm single screw extruder (32:1 L/D, 14 RPM)
using a barrel temperature profile of 177.degree. C.-200.degree.
C.-2290C and an in-line ZENITH gear pump (1.6 cc/rev) set at 8 RPM
resulting in a polymer flow rate of approximately 2.4 kg/hr. The
die temperature and melt temperature was approximately 229.degree.
C. Chevron SUPERLA white mineral oil #31 as a lubricant was
supplied to the entrance of the die using a ZENITH dual gear single
feed gear pump (0.16 cc/rev) set at 75 RPM. The extruded fiber was
collected at the die exit manually and coiled by hand.
Example 8
[0129] A polymeric fiber was produced as in Example 5 except that a
nylon-6 polyamide (ULTRAMID B4, BASF Corp., Wyandotte, Mich.) was
extruded using a 19 mm single screw (30:1 L/D, 18 RPM) extruder
using a barrel temperature profile of 250.degree. C.-300.degree.
C.-300.degree. C. fitted with a 0.16 cubic centimeters per
revolution (0.16 cc/rev) gear pump operating at 8 RPM. The die
temperature and melt temperature were approximately 260.degree. C.
Chevron SUPERLA white mineral oil #31 (Chevron USA Inc., Houston,
Tex.) as a lubricant was supplied to the entrance of the die using
a Lorimer "air over oil" pneumatic high pressure pump (H. Lorimer
Corp., Longview, Tex.). A 3 mm diameter (ID) copper tubing was used
to supply the lubricant from the pump to the die. The tubing was
wrapped 2.5 times around the 7.6 cm diameter die prior to the entry
port into the die. This was done to heat the temperature of the
lubricant up to that of the die.
[0130] The extruded fiber with a diameter of approximately 1
millimeter was then quenched in a water bath (approximately
20.degree. C.) positioned approximately 2.5 cm beneath the die exit
at a rate of 2.4 meter/minute. The fiber was then length oriented
in-line between two pull rolls by immersing the fiber in a hot
water bath (79.degree. C.) with a draw ratio between the two pull
rolls of approximately 4:1. The oriented fiber was then run over a
heated platen set at 177.degree. C. to relax (heat set) the fiber
and then over a second heated platen set at 121.degree. C. to
anneal the fiber and then wound onto a core. The modulus of the
fiber was measured to be 226 kN/cm.sup.2.
Example 9
[0131] A polymeric fiber was produced as in Example 8 except that
significantly lower process temperatures were used to obtain a melt
temperature slightly above the polymer melting point (230.degree.
C.) resulting in significantly higher modulus fibers. The nylon was
extruded using a barrel temperature profile of 240.degree.
C.-250.degree. C.-240.degree. C. The melt pump was set at
235.degree. C., the die feed block at 230.degree. C. and the die at
225.degree. C. The modulus of the fiber was measured to be 765
kN/cm.sup.2.
Example 10
[0132] A polymeric fiber was produced as in Example 1 except two
extruders were used to feed two materials to a sheath/core
feedblock resulting in a bicomponent coextruded fiber.
Polypropylene homopolymer (FINAPRO 5660, 9.0 MFI, Atofina
Petrochemical Co., Houston, Tex.) was used to form the core of the
fiber. The polymer was delivered with a 25 mm single screw extruder
(24:1 L/D) using a barrel temperature profile of 177.degree.
C.-200.degree. C.-232.degree. C. and an in-line ZENITH gear pump
(1.6 cc/rev) set at 24 RPM. FINAPRO 5660 pigmented with 2% orange
color concentrate (Type 66Y163, Penn Color Co., Doylestown, Pa.)
was used to form the sheath of the fiber. The polymer was delivered
with a 19 mm single screw extruder using a barrel temperature
profile of 177.degree. C.-195.degree. C.-215.degree. C.-232.degree.
C. and an in-line ZENITH gear pump (1.6 cc/rev) set at 24 RPM. The
melt pump was set at 232.degree. C., the die feed block at
232.degree. C. and the die at 232.degree. C. The die feed block
consisted of a series of 0.5 mm thick machined plates stacked to
provide a dual feed plate die as is well known in the art of
coextruded fibers.
[0133] The lubricant introduction manifold was attached at the
bottom of the plate stack. Universal Trans Hydraulic oil (Mills
Fleet Farm Inc., Brainerd, Minn.) was used as the lubricant and was
supplied to the entrance of the die using a ZENITH dual gear single
feed gear pump (0.16 cc/rev) set at 80 RPM. The extruded fiber was
collected at the die exit manually and coiled by hand.
Example 11
[0134] A polymeric fiber was produced as in Example 1 except a
multiphase acrylonitrile-styrene-butylacrylate polymer (CENTREX
833, Marine White, 3 MFI, Bayer Corp., Leverkusen, Germany) was
used to form the fiber. The polymer was delivered with a 38 mm
single screw extruder (32:1 L/D, 14 RPM) using a barrel temperature
profile of 177.degree. C.-200.degree. C.-2180C and an in-line
ZENITH gear pump (1.6 cc/rev) set at 8 RPM resulting in a polymer
flow rate of approximately 2.4 kg/hr. The die temperature and melt
temperature was approximately 218.degree. C. Chevron SUPERLA white
mineral oil #31 as a lubricant was supplied to the entrance of the
die using a ZENITH dual gear single feed gear pump (0.16 cc/rev)
set at 75 RPM. The extruded fiber was collected at the die exit
manually and coiled by hand.
Example 12
[0135] A polymeric fiber was produced as in Example 10 except a
nylon 12 (GRILAMID G-12, EMS Chemie AG, Switzerland) filled with
10% by weight aluminum oxide abrasive (P-2000, 400 grit, Fujimi
Corp., Ltd., Chicago, Ill.) was used to form the fiber. The filled
polymer was delivered with a 25 mm single screw extruder (24:1 L/D)
using a barrel temperature profile of 260.degree. C.-260.degree.
C.-260.degree. C. The feedblock and die were set at 260.degree. C.
Chevron SUPERLA white mineral oil #31 as a lubricant was supplied
to the entrance of the die using a ZENITH dual gear single feed
gear pump (0.16 cc/rev) set at 80 RPM. The extruded fiber was
collected at the die exit manually and coiled by hand. The outer
surface of the fiber was very rough with a large amount of abrasive
at or near the outer surface of the fiber.
[0136] As used herein and in the appended claims, the singular
forms "a," "and," and "the" include plural referents unless the
context clearly dictates otherwise. Thus, for example, reference to
"a fiber" may include a plurality of fibers and reference to "the
orifice" may encompass one or more orifices and equivalents thereof
known to those skilled in the art.
[0137] All references and publications cited herein are expressly
incorporated herein by reference in their entirety into this
disclosure. Illustrative embodiments of this invention are
discussed and reference has been made to possible variations within
the scope of this invention. These and other variations and
modifications in the invention will be apparent to those skilled in
the art without departing from the scope of the invention, and it
should be understood that this invention is not limited to the
illustrative embodiments set forth herein. Accordingly, the
invention is to be limited only by the claims provided below and
equivalents thereof.
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