U.S. patent application number 10/151781 was filed with the patent office on 2003-01-02 for method for forming spread nonwoven webs.
This patent application is currently assigned to 3M Innovative Properties Company. Invention is credited to Berrigan, Michael R., Fay, William T..
Application Number | 20030003834 10/151781 |
Document ID | / |
Family ID | 29582059 |
Filed Date | 2003-01-02 |
United States Patent
Application |
20030003834 |
Kind Code |
A1 |
Berrigan, Michael R. ; et
al. |
January 2, 2003 |
Method for forming spread nonwoven webs
Abstract
A new fiber-forming method, and related apparatus, and webs
prepared by the new method and apparatus are taught. In the new
method a) a stream of filaments is extruded from a die of known
width and thickness; b) the stream of extruded filaments is
directed through a processing chamber that is defined by two
narrowly separated walls that are parallel to one another, parallel
to said width of the die, and parallel to the longitudinal axis of
the stream of extruded filaments; c) the stream of filaments passed
through the processing chamber is intercepted on a collector where
the filaments are collected as a nonwoven fibrous web; and d) a
spacing between the walls of the processing chamber is selected
that causes the stream of extruded filaments to spread before it
reaches the collector and be collected as a web significantly wider
in width than the die. Generally the increase in width is
sufficient to be economically significant, e.g., to reduce costs of
web manufacture. Such economic benefit can occur in widths that are
50, 100 or 200 or more millimeters greater in width than the width
of the die. Preferably, the collected web has a width at least 50
percent greater than said width of the die. The processing chamber
is preferably open to the ambient environment at its longitudinal
sides to allow pressure within the processing chamber to push the
stream of filaments outwardly toward the longitudinal sides of the
chamber.
Inventors: |
Berrigan, Michael R.;
(Oakdale, MN) ; Fay, William T.; (Woodbury,
MN) |
Correspondence
Address: |
Attention: Roger R. Tamte
Office of Intellectual Property Counsel
3M Innovative Properties Company
P.O. Box 33427
St. Paul
MN
55133-3427
US
|
Assignee: |
3M Innovative Properties
Company
|
Family ID: |
29582059 |
Appl. No.: |
10/151781 |
Filed: |
May 20, 2002 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10151781 |
May 20, 2002 |
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09835904 |
Apr 16, 2001 |
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09835904 |
Apr 16, 2001 |
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09716786 |
Nov 20, 2000 |
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Current U.S.
Class: |
442/409 ;
156/166; 156/167; 156/180; 442/401 |
Current CPC
Class: |
Y10T 442/69 20150401;
Y10T 442/681 20150401; D01D 5/0985 20130101; D04H 3/02 20130101;
D04H 3/03 20130101; D04H 3/16 20130101 |
Class at
Publication: |
442/409 ;
442/401; 156/166; 156/167; 156/180 |
International
Class: |
D04H 003/08; B32B
001/00; D04H 001/54; D04H 005/06; D04H 003/14; D04H 003/16 |
Claims
What is claimed is:
1. A method for preparing a nonwoven fibrous web comprising a)
extruding a stream of filaments from a die having a known width and
thickness; b) directing the stream of extruded filaments through a
processing chamber that is defined by two narrowly separated walls
that are parallel to one another, parallel to said width of the
die, and parallel to the longitudinal axis of the stream of
extruded filaments; c) intercepting the stream of filaments passed
through the processing chamber on a collector where the filaments
are collected as a nonwoven fibrous web; and d) selecting a spacing
between the walls of the processing chamber that causes the stream
of extruded filaments to spread and be collected as a functional
web at least 50 millimeters wider than said width of the die.
2. A method of claim 1 in which the processing chamber defined by
the two parallel walls is open to the ambient environment at its
longitudinal sides.
3. A method of claim 1 in which the width of the walls in a
direction transverse to the direction of filament travel is greater
at points downstream of the filament travel than upstream
points.
4. A method of claim 3 in which the processing chamber is closed to
the ambient environment over at least part of the length of its
longitudinal sides.
5. A method of claim 1 in which the parallel walls converge toward
one another in the direction of filament travel.
6. A method of claim 1 in which the functional web collected is at
least 100 millimeters wider than said width of the die.
7. A method of claim 1 in which the collected functional web is at
least 200 millimeters wider than said width of the die.
8. A method of claim 1 in which the filaments spread to a width at
least 50% greater than said width of the die before they reach the
collector.
9. A method of claim 1 in which the filaments spread to a width at
least two times said width of the die before they reach the
collector.
10. A method of claim 1 in which the stream of filaments forms a
lofty nonwoven web having a thickness of at least 5 mm and a loft
of at least 10 cc/gram.
11. A method of claim 1 in which the solidity of the extruded
filaments entering the processing chamber is controlled so that the
filaments are autogenously bondable when collected on the
collector.
12. A method of claim 1 in which at least one of the walls defining
the processing chamber is instantaneously movable toward and away
from the other wall and is subject to movement means for providing
instantaneous movement during passage of the filaments.
13. A method for preparing a nonwoven fibrous web comprising a)
extruding a stream of filaments from a die having a known width and
thickness; b) directing the stream of extruded filaments through a
processing chamber that is defined by two narrowly separated walls
that are parallel to one another, parallel to said width of the
die, and parallel to the longitudinal axis of the stream of
extruded filaments; the processing chamber including air knives
that exert a pulling force on the filaments in the direction of
travel through the processing chamber; the parallel walls
converging toward one another in the direction of filament travel
at a point downstream from the air knives, and the processing
chamber being open to the ambient environment at its longitudinal
sides; c) intercepting the stream of filaments passed through the
processing chamber on a collector where the processed filaments are
collected as a nonwoven fibrous web; and d) selecting a spacing
between the walls of the processing chamber that causes the stream
of extruded filaments to spread and be collected as a functional
web at least 100 millimeters wider than said width of the die.
14. A method of claim 13 in which the collected functional web has
a width at least 200 millimeters greater than said width of the
die.
15. A method of claim 13 in which the collected functional web has
a width at least 50 percent greater than the width of said die.
16. A method of claim 13 in which at least one of the walls
defining the processing chamber is instantaneously movable toward
and away from the other wall and is subject to movement means for
providing instantaneous movement during passage of the
filaments.
17. A method for preparing a nonwoven fibrous web comprising a)
extruding a stream of filaments from a die having a known width; b)
directing the stream of extruded filaments through a processing
chamber that is defined by two narrowly separated walls that are
parallel to one another, parallel to said width of the die, and
parallel to the longitudinal axis of the stream of extruded
filaments; the processing chamber including air knives exerting a
pulling force on the filaments in the direction of filament travel;
c) intercepting the stream of filaments on a collector where the
processed filaments are collected as nonwoven fibrous web; and d)
selecting a spacing between the walls of the processing chamber,
and arranging those walls to diverge away from one another in the
direction of filament travel over a main length of the processing
chamber downstream from the air knives, whereby to cause the stream
of extruded filaments to have a selected width narrower than said
width of the die before the stream reaches the collector.
18. A fibrous nonwoven web comprising a collected mass of fibers
prepared by the method of claim 1.
19. A web of claim 18 in which the collected mass of fibers is at
least 5 mm thick and has a loft of at least 10 cc/g.
20. A web of claim 18 in which fibers of the collected mass are
autogenously bonded together.
21. A web of claim 18 in which the collected mass of fibers in the
fibrous nonwoven web comprises only fibers that traveled within the
processing chamber over the length of the chamber.
22. A fibrous nonwoven web comprising a collected mass of fibers
prepared by a method of claim 13.
23. A web of claim 22 in which the collected mass of fibers is at
least 5 mm thick and has a loft of at least 10 cc/g.
24. A web of claim 22 in which fibers of the collected mass are
autogenously bonded together.
Description
REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation-in-part of application
Ser. No. 09/835,904, filed Apr. 16, 2001, which itself was a
continuation-in-part of application Ser. No. 09/716,786, filed Nov.
20, 2000.
FIELD OF THE INVENTION
[0002] This invention relates to methods for preparing nonwoven
webs from fibers extruded from an extrusion die.
BACKGROUND OF THE INVENTION
[0003] Fibrous nonwoven webs are conventionally prepared by
extruding a liquid fiber-forming material through a die to form a
stream of filaments, processing the filaments during their travel
from the extrusion die (e.g., quenching and drawing them), and then
intercepting the stream of filaments on a porous collector. The
filaments deposit on the collector as a mass of fibers that either
takes the form of a handleable web or may be processed to form such
a web.
[0004] Typically, the collected mass or web is approximately the
same width as the width of the die from which filaments were
extruded: if a meter-wide web is to be prepared, the die is also
generally on the order of a meter wide. Because wide webs are
usually desired for the most economic manufacture, wide dies are
also generally used.
[0005] But wide dies have some disadvantages. For example, dies are
generally heated to help process the fiber-forming material through
the die; and the wider the die, the more heat that is required.
Also, wide dies are more costly to prepare than smaller ones, and
can be more difficult to maintain. Also, the width of web to be
collected may change depending on the intended use of the web; but
accomplishing such changes by changing the width of the die or
proportion of the die being utilized can be inconvenient.
SUMMARY OF THE INVENTION
[0006] The present invention provides a method for preparing
fibrous nonwoven webs that have a controlled or selected width that
is tailored to the intended use of the web and is significantly
different from the width of the die from which filaments forming
the web were extruded. In brief summary, a method of the invention
comprises a) extruding a stream of filaments from a die having a
known width and thickness; b) directing the stream of extruded
filaments through a processing chamber that is defined by two
narrowly separated walls that are parallel to one another, parallel
to the width of the die, and parallel to the longitudinal axis of
the stream of extruded filaments; c) collecting the processed
filaments as a nonwoven fibrous web; and d) tailoring the width of
the stream of filaments to a width different from the width of the
die by adjusting the spacing between the walls to a selected amount
that produces the tailored width. Most often, the desired tailored
width of the stream of filaments is substantially greater than the
width of the die, and the stream of filaments spreads as it travels
from the die to the collector, where it is collected as a
functional web. Generally, the width of the web upon collection is
at least 50 or 100 millimeters or more greater than the width of
the die; and preferably the width of the web is at least 200
millimeters or more greater than the width of the die. Narrower
widths can also be obtained, thus adding further flexibility.
[0007] Preferably, the processing chamber is open to the ambient
environment at its longitudinal sides over at least part of the
length of the walls. Also, the walls preferably converge toward one
another in the direction of filament travel to assist widening of
the stream of extruded filaments.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] FIG. 1 is a schematic overall diagram of an apparatus useful
in a method of the invention for forming a nonwoven fibrous
web.
[0009] FIG. 2 is a schematic view of the apparatus of FIG. 1,
viewed along the lines 2-2 in FIG. 1.
[0010] FIG. 3 is an enlarged side view of a processing chamber
useful in the invention, with mounting means for the chamber not
shown.
[0011] FIG. 4 is a top view, partially schematic, of the processing
chamber shown in FIG. 3 together with mounting and other associated
apparatus.
[0012] FIG. 5 is a top view of an alternative apparatus for
practicing the invention.
[0013] FIG. 6 is a sectional view taken along the lines 6-6 in FIG.
5.
[0014] FIG. 7 is a schematic side view of part of an alternative
apparatus useful in carrying out the invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT
[0015] FIG. 1 shows an illustrative apparatus for carrying out the
invention. Fiber-forming material is brought to an extrusion head
or die 10--in this illustrative apparatus, by introducing a
fiber-forming material into hoppers 11, melting the material in an
extruder 12, and pumping the molten material into the extrusion
head 10 through a pump 13. Although solid polymeric material in
pellet or other particulate form is most commonly used and melted
to a liquid, pumpable state, other fiber-forming liquids such as
polymer solutions could also be used.
[0016] The extrusion head 10 may be a conventional spinnerette or
spin pack, generally including multiple orifices arranged in a
regular pattern, e.g., straightline rows. Filaments 15 of
fiber-forming liquid are extruded from the extrusion head and
conveyed to a processing chamber or attenuator 16. The distance 17
the extruded filaments 15 travel before reaching the attenuator 16
can vary, as can the conditions to which they are exposed.
Typically, quenching streams of air or other gas 18 are presented
to the extruded filaments by conventional methods and apparatus to
reduce the temperature of the extruded filaments 15. Alternatively,
the streams of air or other gas may be heated to facilitate drawing
of the fibers. There may be one or more streams of air (or other
fluid)--e.g., a first air stream 18a blown transversely to the
filament stream, which may remove undesired gaseous materials or
fumes released during extrusion; and a second quenching air stream
18b that achieves a major desired temperature reduction. Depending
on the process being used or the form of finished product desired,
the quenching air may be sufficient to solidify the extruded
filaments 15 before they reach the attenuator 16. In other cases
the extruded filaments are still in a softened or molten condition
when they enter the attenuator. Alternatively, no quenching streams
are used; in such a case ambient air or other fluid between the
extrusion head 10 and the attenuator 16 may be a medium for any
change in the extruded filaments before they enter the
attenuator.
[0017] The stream of filaments 15 passes through the attenuator 16,
as discussed in more detail below, and then exits. As illustrated
in FIGS. 1 and 2, the stream exits onto a collector 19 where the
filaments, or finished fibers, are collected as a mass of fibers 20
that may or may not be coherent and take the form of a handleable
web. As discussed in more detail below and as illustrated in FIG.
2, the fiber or filament stream 15 preferably has spread when it
exits from the attenuator and travels over the distance 21 to the
collector 19. The collector 19 is generally porous and a
gas-withdrawal device 14 can be positioned below the collector to
assist deposition of fibers onto the collector. The collected mass
20 may be conveyed to other apparatus such as calenders, embossing
stations, laminators, cutters and the like; or it may be passed
through drive rolls 22 (FIG. 1) and wound into a storage roll 23.
After passing through the processing chamber, but prior to
collection, extruded filaments or fibers may be subjected to a
number of additional processing steps not illustrated in FIG. 1,
e.g., further drawing, spraying, etc.
[0018] FIG. 3 is an enlarged side view of a representative,
preferred processing device or attenuator 16 useful in practicing
the invention. This representative and preferred device comprises
two movable halves or sides 16a and 16b separated so as to define
between them the processing chamber 24: the facing surfaces 60 and
61 of the sides 16a and 16b form the walls of the chamber. The
illustrative device 16 allows a convenient adjustment of the
distance between the parallel walls of the processing chamber to
achieve a desired control over the width of the stream of extruded
filaments according to the invention. The extent of spreading of
the stream of extruded filaments or fibers can be controlled in
this device by adjusting the distance between the walls 60 and 61
of the attenuator or processing device 16. This device is also
preferred because it offers a desired continuity of operation even
when running at high speeds with narrow-gap processing chambers and
fiber-forming material in a softened condition when it enters the
processing chamber. Such conditions tend to cause plugging and
interruption of prior-art processing devices. Spreading of the
stream of filaments according to the invention is aided by the
ability to decrease the spacing between the walls of a processing
chamber to narrow spacings, in at least some cases narrower than
conventionally used with processing chambers in direct-web
formation processes. The spacings used can create pressure within
the chamber, causing the air flow to spread to a width as allowed
by the configuration of the processing chamber and to carry
extruded filaments throughout that width.
[0019] A means for adjusting the distance between the walls 60 and
61 for the preferred attenuator 16 is illustrated in FIG. 4, which
is a top and somewhat schematic view at a different scale showing
the attenuator and some of its mounting and support structure. As
seen from the top view in FIG. 4, the processing or attenuation
chamber 24 of the attenuator 16 is typically an elongated or
rectangular slot, having a transverse length 25 (transverse to the
longitudinal axis or path of travel of filaments through the
attenuator and parallel to the width of the extrusion head or die
10).
[0020] Although existing as two halves or sides, the attenuator 16
functions as one unitary device and will be first discussed in its
combined form. (The structure shown in FIGS. 3 and 4 is
representative only, and a variety of different constructions may
be used.). Slanted entry walls 62 and 63 define an entrance space
or throat 24a into the attenuation chamber 24. The entry
wall-sections 62 and 63 preferably are curved at the entry edge or
surface 62a and 63a to smooth the entry of air streams carrying the
extruded filaments 15. The wall-sections 62 and 63 are attached to
a main body portion 28, and may be provided with a recessed area 29
to establish a gap 30 between the body portion 28 and wall-sections
62 and 63. Air or other gas may be introduced into the gaps 30
through conduits 31, creating air knives (i.e., pressurized gaseous
streams represented by the arrows 32) that exert a pulling force on
the filaments in the direction of filament travel and increase the
velocity of the filaments, and that also have a further quenching
effect on the filaments. The attenuator body 28 is preferably
curved at 28a to smooth the passage of air from the air knife 32
into the passage 24. The angle (.alpha.) of the surface 28b of the
attenuator body can be selected to determine the desired angle at
which the air knife impacts a stream of filaments passing through
the attenuator. Instead of being near the entry to the chamber, the
air knives may be disposed further within the chamber.
[0021] The attenuation chamber 24 may have a uniform gap width (the
horizontal distance 33 on the page of FIG. 2 between the two
attenuator sides or walls 60 and 61 is herein called the gap
thickness) over its longitudinal length through the attenuator (the
dimension along a longitudinal axis 26 through the attenuation
chamber is called the axial length). Alternatively, as illustrated
in FIG. 3, the gap thickness may vary along the length of the
attenuator chamber. Preferably, the attenuation chamber narrows in
thickness along its length toward the exit opening 34, e.g., at an
angle .beta.. Such a narrowing, or converging of the walls 60 and
61 at a point downstream from the air knives has been found to
assist in at least some embodiments of the invention in causing the
stream of extruded filaments to spread as it moves toward and
through the exit of the attenuator and travels to the collector 19.
In some embodiments of the invention the walls may slightly diverge
over the axial length of the attenuation chamber at a point
downstream from the air knives (in which case the stream of
extruded filaments deposited on the collector may be narrower than
the width of the extrusion head or die 10, which can be desirable
for some products of the invention). Also, in some embodiments, the
attenuation chamber is defined by straight or flat walls so that
the spacing or gap width between the walls is constant over part or
all the length of the walls. In all these cases, the walls 60 and
61 defining the attenuation or processing chamber are regarded
herein as parallel to one another, because over at least a portion
of their length the deviation from exact parallelism is relatively
slight, and there is preferably substantially no deviation from
parallelism in a direction transverse to the longitudinal length of
the chamber (i.e., perpendicular to the page of FIG. 3). As
illustrated in FIG. 3, the wall-sections 64 and 65 (of the walls 60
and 61, respectively) that define the main portion of the
longitudinal length of the passage 24 may take the form of plates
36 that are separate from, and attached to, the main body portion
28.
[0022] Even if the walls defining the processing chamber converge
over at least part of their length, they may also spread over a
subsequent portion of their length, e.g., to create a suction or
venturi effect. The length of the attenuation chamber 24 can be
varied to achieve different effects; variation is especially useful
with the portion between the air knives 32 and the exit opening 34,
sometimes called herein the chute length 35. Longer chute lengths,
chosen together with the spacing between the walls and any
convergence or divergence of the walls, can increase spreading of
the stream of filaments. Structure such as deflector surfaces,
Coanda curved surfaces, and uneven wall lengths may be used at the
exit to achieve a desired additional spreading or other
distribution of fibers. In general, the gap width, chute length,
attenuation chamber shape, etc. are chosen in conjunction with the
material being processed and the mode of treatment desired to
achieve other desired effects. For example, longer chute lengths
may be useful to increase the crystallinity of prepared fibers.
Conditions are chosen and can be widely varied to process the
extruded filaments into a desired fiber form.
[0023] As illustrated in FIG. 4, the two sides 16a and 16b of the
representative attenuator 16 are each supported through mounting
blocks 37 attached to linear bearings 38 that slide on rods 39. The
bearing 38 has a low-friction travel on the rod through means such
as axially extending rows of ball-bearings disposed radially around
the rod, whereby the sides 16a and 16b can readily move toward and
away from one another. The mounting blocks 37 are attached to the
attenuator body 28 and a housing 40 through which air from a supply
pipe 41 is distributed to the conduits 31 and air knives 32.
[0024] In this illustrative embodiment, air cylinders 43a and 43b
are connected, respectively, to the attenuator sides 16a and 16b
through connecting rods 44 and apply a clamping force pressing the
attenuator sides 16a and 16b toward one another. The clamping force
is chosen in conjunction with the other operating parameters so as
to balance the pressure existing within the attenuation chamber 24,
and also, as discussed below, to set a desired spacing between the
walls of the processing chamber. In other words, the clamping force
and the force acting internally within the attenuation chamber to
press the attenuator sides apart as a result of the gaseous
pressure within the attenuator are in balance or equilibrium under
preferred operating conditions. Filamentary material can be
extruded, passed through the attenuator and collected as finished
fibers while the attenuator parts remain in their established
equilibrium or steady-state position and the attenuation chamber or
passage 24 remains at its established equilibrium or steady-state
gap width.
[0025] After startup and established operation of the
representative apparatus illustrated in FIGS. 1-4 (i.e., to obtain
a selected width of stream of filaments), movement of the
attenuator sides or chamber walls generally occurs only if and when
there is a perturbation of the system (sometimes the walls are
intentionally moved during operation of the process to obtain a
different width of stream). Such a perturbation may occur when a
filament being processed breaks or tangles with another filament or
fiber. Such breaks or tangles are often accompanied by an increase
in pressure within the attenuation chamber 24, e.g., because the
forward end of the filament coming from the extrusion head or the
tangle is enlarged and creates a localized blockage of the chamber
24. The increased pressure can be sufficient to force the
attenuator sides or chamber walls 16a and 16b to move away from one
another. Upon this movement of the chamber walls the end of the
incoming filament or the tangle can pass through the attenuator,
whereupon the pressure in the attenuation chamber 24 returns to its
steady-state value before the perturbation, and the clamping
pressure exerted by the air cylinders 43 returns the attenuator
sides to their steady-state position. Other perturbations causing
an increase in pressure in the attenuation chamber include "drips,"
i.e., globular liquid pieces of fiber-forming material falling from
the exit of the extrusion head upon interruption of an extruded
filament, or accumulations of extruded filamentary material that
may engage and stick to the walls of the attenuation chamber or to
previously deposited fiber-forming material.
[0026] In effect, one or both of the sides 16a and 16b of the
illustrative attenuator 16 "float," i.e., are not held in place by
any structure but instead are mounted for a free and easy movement
laterally in the direction of the arrows 50 in FIG. 1. In a
preferred arrangement, the only forces acting on the attenuator
sides other than friction and gravity are the biasing force applied
by the air cylinders and the internal pressure developed within the
attenuation chamber 24. Other clamping means than the air cylinder
may be used, such as a spring(s), deformation of an elastic
material, or cams; but the air cylinder offers a desired control
and variability.
[0027] Many alternatives are available to cause or allow a desired
movement of the processing chamber wall(s). For example, instead of
relying on fluid pressure to force the wall(s) of the processing
chamber apart, a sensor within the chamber (e.g., a laser or
thermal sensor detecting buildup on the walls or plugging of the
chamber) may be used to activate a servomechanical mechanism that
separates the wall(s) and then returns them to their steady-state
position. In another useful apparatus of the invention, one or both
of the attenuator sides or chamber walls is driven in an
oscillating pattern, e.g., by a servomechanical, vibratory or
ultrasonic driving device. The rate of oscillation can vary within
wide ranges, including, for example, at least rates of 5,000 cycles
per minute to 60,000 cycles per second.
[0028] In still another variation, the movement means for both
separating the walls and returning them to their steady-state
position takes the form simply of a difference between the fluid
pressure within the processing chamber and the ambient pressure
acting on the exterior of the chamber walls. More specifically,
during steady-state operation, the pressure within the processing
chamber (a sunmmation of the various forces acting within the
processing chamber established, for example, by the internal shape
of the processing chamber, the presence, location and design of air
knives, the velocity of a fluid stream entering the chamber, etc.)
is in balance with the ambient pressure acting on the outside of
the chamber walls. If the pressure within the chamber increases
because of a perturbation of the fiber-forming process, one or both
of the chamber walls moves away from the other wall until the
perturbation ends, whereupon pressure within the processing chamber
is reduced to a level less than the steady-state pressure (because
the gap thickness or spacing between the chamber walls is greater
than at the steady-state operation). Thereupon, the ambient
pressure acting on the outside of the chamber walls forces the
chamber wall(s) back until the pressure within the chamber is in
balance with the ambient pressure, and steady-state operation
occurs. Lack of control over the apparatus and processing
parameters can make sole reliance on pressure differences a less
desired option.
[0029] In sum, besides being instantaneously movable and in some
cases "floating," the wall(s) of the illustrative processing
chamber are also generally subject to means for causing them to
move in a desired way. The walls in this illustrative variety can
be thought of as generally connected, e.g., physically or
operationally, to means for causing a desired instantaneous
movement of the walls. This movement means may be any feature of
the processing chamber or associated apparatus, or an operating
condition, or a combination thereof that causes the intended
movement of the movable chamber walls--movement apart, e.g., to
prevent or alleviate a perturbation in the fiber-forming process,
and movement together, e.g., to establish or return the chamber to
steady-state operation.
[0030] In the embodiment illustrated in FIGS. 1-3, the gap
thickness 33 of the attenuation chamber 24 is interrelated with the
pressure existing within the chamber, or with the fluid flow rate
through the chamber and the fluid temperature. The clamping force
matches the pressure within the attenuation chamber and varies
depending on the gap thickness of the attenuation chamber: for a
given fluid flow rate, the narrower the gap width, the higher the
pressure within the attenuation chamber, and the higher must be the
clamping force. Lower clamping forces allow a wider gap width.
Mechanical stops, e.g., abutting structure on one or both of the
attenuator sides 16a and 16b may be used to assure that minimum or
maximum gap thicknesses are maintained.
[0031] In one useful arrangement, the air cylinder 43a applies a
larger clamping force than the cylinder 43b, e.g., by use in
cylinder 43a of a piston of larger diameter than used in cylinder
43b. This difference in force establishes the attenuator side 16b
as the side that tends to move most readily when a perturbation
occurs during operation. The difference in force is about equal to
and compensates for the frictional forces resisting movement of the
bearings 38 on the rods 39. Limiting means can be attached to the
larger air cylinder 43a to limit movement of the attenuator side
16a toward the attenuator side 16b. One illustrative limiting
means, as shown in FIG. 4, uses as the air cylinder 43a a
double-rod air cylinder, in which the second rod 46 is threaded,
extends through a mounting plate 47, and carries a nut 48 which may
be adjusted to adjust the position of the air cylinder. Adjustment
of the limiting means, e.g., by turning the nut 48, positions the
attenuation chamber 24 into alignment with the extrusion head
10.
[0032] Because of the described instantaneous separation and
reclosing of the attenuator sides 16a and 16b, the operating
parameters for a fiber-forming operation are expanded. Some
conditions that would previously make the process inoperable--e.g.,
because they would lead to filament breakage requiring shutdown for
rethreading--become acceptable with a method and apparatus of this
preferred embodiment; upon filament breakage, rethreading of the
incoming filament end generally occurs automatically. For example,
higher velocities that lead to frequent filament breakage may be
used. Similarly, narrow gap thicknesses, which cause the air knives
to be more focused and to impart more force and greater velocity on
filaments passing through the attenuator, may be used. Or filaments
may be introduced into the attenuation chamber in a more molten
condition, thereby allowing greater control over fiber properties,
because the danger of plugging the attenuation chamber is reduced.
The attenuator may be moved closer to or further from the extrusion
head to control among other things the temperature of the filaments
when they enter the attenuation chamber.
[0033] Although the chamber walls of the attenuator 16 are shown as
generally monolithic structures, they can also take the form of an
assemblage of individual parts each mounted for the described
instantaneous or floating movement. The individual parts comprising
one wall engage one another through sealing means so as to maintain
the internal pressure within the processing chamber 24. In a
different arrangement, flexible sheets of a material such as rubber
or plastic form the walls of the processing chamber 24, whereby the
chamber can deform locally upon a localized increase in pressure
(e.g., because of a plugging caused by breaking of a single
filament or group of filaments). A series or grid of biasing means
may engage the segmented or flexible wall; sufficient biasing means
are used to respond to localized deformations and to bias a
deformed portion of the wall back to its undeformed position.
Alternatively, a series or grid of oscillating means may engage the
flexible wall and oscillate local areas of the wall. Or, in the
manner discussed above, a difference between the fluid pressure
within the processing chamber and the ambient pressure acting on
the wall or localized portion of the wall may be used to cause
opening of a portion of the wall(s), e.g., during a process
perturbation, and to return the wall(s) to the undeformed or
steady-state position, e.g., when the perturbation ends. Fluid
pressure may also be controlled to cause a continuing state of
oscillation of a flexible or segmented wall.
[0034] The above description of the representative attenuator 16
shows that the walls 60 and 61 are movable to adjust the distance
or select a spacing between them. Also, the walls are movable
during operation of the illustrative apparatus to change the width
of the collected web without stopping the operation. For example,
increased pressure applied to the attenuator halves through the air
cylinders 43a and/or 43b will cause the walls 60 and 61 to move
closer together. Also, mechanical stops may be applied against the
attenuator halves to cause the walls 60 and 61 to converge or
diverge over the length of filament travel near the exit 34 of the
processing chamber. In other, less convenient embodiments of the
invention, the walls of the chamber are not moveable but instead
may be fixed in the position that achieves a desired width of
filament stream (e.g., the walls may be supported by apparatus that
is not readily moved once a desired spacing has been selected, so
that the spacing is not changed either intentionally or
instantaneously during operation of the device).
[0035] FIGS. 5 and 6 show an illustrative processing device that
facilitates movement of the walls defining the processing chamber,
particularly a pivoting of the walls to change the angle .beta. at
which the walls converge or diverge as they near the exit of the
device. The device 70 shown in FIGS. 5 and 6 includes mounting
brackets 71a and 71b, which each pivotably support a device or
attenuator half 72a and 72b on pins 73. The pins 73 rotatably
extend into support blocks 74a and 74b, which are each affixed to a
main body portion 75a and 75b, respectively, of a device half 72a
and 72b. The mounting brackets 71a and 71b are each connected to an
air cylinder 76a and 76b, respectively, through a rod 85 sliding in
a support bracket 86. The air cylinders apply clamping pressure
through the mounting brackets 71a and 71b onto the device halves
72a and 72b and thereby onto the processing chamber 77 defined
between the attenuator halves. The mounting brackets 71a and 71b
are attached to mounting blocks 78 which slide at low friction on
rods 79.
[0036] Pivoting of a device or attenuator half is accomplished with
adjustment mechanism pictured best in FIG. 6, taken on the lines
6-6 of FIG. 5 (with wall-sections 62' and 63' added). Each
adjustment mechanism in the illustrated apparatus includes an
actuator 80a or 80b, connected respectively between the bracket 71a
or 71b and plates 81a or 81b, which correspond to the plates 36 in
FIG. 2. One useful actuator comprises a threaded drive shaft 82a or
82b within the actuator that is driven by an electric motor to
advance or retract the shaft. Movement of the shaft is conveyed
through the plates 81a and 81b to pivot the device half about the
pins 73.
[0037] As will be seen, in the preferred embodiments of processing
chamber 24 and 77 illustrated in FIGS. 3-6, there are no side walls
at the ends of the transverse length of the chamber. This means
that the processing chamber is open to the ambient environment
around the device. The result is that currents of air or gas in
which the stream of filaments is entrained can spread out the sides
of the chamber under the pressure existing within the chamber.
Also, air or other gas can be drawn into the chamber. Similarly,
fibers passing through the chamber can spread outwardly outside the
chamber as they approach the exit of the chamber. Such a spreading
can be desirable, as discussed above, to widen the mass of fibers
collected on the collector.
[0038] In preferred embodiments substantially the whole stream of
filaments travels within the processing chamber over the full
length of the chamber (as represented by the lines 15a in FIG. 2),
because that achieves a greater uniformity of properties between
fibers in a collected web. For example, the fibers have a similar
extent of attenuation and similar fiber size. The width of the
processing device or attenuator (illustrated by 16 in FIG. 2 and
pictured in solid lines) may be wider than the active width of the
extrusion head or die 10 to accommodate travel of the filaments
within the processing chamber. In other embodiments the fiber
stream may spread outside a lesser-width processing chamber (as
illustrated by the stream 15' shown in broken lines traveling
through processing device 16' in FIG. 2). If the spreading is
sufficient to cause an undesired variation in fiber properties, the
collected mass of fibers may be trimmed so that only fibers that
were substantially retained within the processing chamber during
their travel to the collector are included within the finished
fibrous nonwoven web. However, because travel through the
processing chamber is generally only a minor portion of the travel
of extruded filaments from the extrusion head to the collector
(principal drawing of filaments and reduction in filament diameter
often occurs before the filaments enter the processing chamber and
after they leave the processing chamber), travel outside the sides
of the processing chamber may not greatly affect the properties of
the fibers.
[0039] The width of the collected web can be tailored to a desired
width by control of the various parameters of the fiber-processing
operation, including the spacing between the walls of the
processing chamber. The finished web is a functional web (though
various other steps such as bonding, spraying, etc. as discussed
above may be needed for an intended use); that is, the collection
of fibers is sufficient, generally with a degree of uniformity in
properties across its width, for the web to function adequately for
its intended use. Usually the basis weight of the web varies by not
more than 30 percent across the width of the finished web, and
preferably by not more than 10 percent. However, the web can be
tailored to have special properties, including broader variation in
properties, and including an intention to cut a collected web into
segments of different properties.
[0040] For reasons of economics, the finished web is generally
tailored to have a significantly wider width than the die from
which filaments were extruded. The increase in width can be
affected by parameters noted above, such as the spacing between the
walls of the processing chamber, as well as other parameters such
as the width of web being collected, the length of the attenuator,
and the distance between the exit of the attenuator and the
collector. Increases of 50 millimeters can be significant for some
widths of web, but most often an increase of at least 100
millimeters is sought, and preferably an increase of 200
millimeters or more is obtained. The latter increase can offer
significant commercial benefits to the widening process.
[0041] The included angle encompassed or occupied by the spread web
15 (the angle .gamma. in FIG. 2) depends on the targeted width of
the web to be collected as well as parameters such as the distance
from attenuator to collector. With common distances between
attenuator and collector, the included angle .gamma. of the stream
15 is at least 10.degree., and more commonly is at least 15 or
20.degree.. In many embodiments of the invention, the finished web
(i.e., the collected web or trimmed portion of the collected web)
is at least 50 percent wider than the width of the extrusion head
or die (meaning the active width of the die, namely that portion
through which fiber-forming liquid is extruded).
[0042] FIG. 7 shows, from the same point of view as FIG. 2, an
alternative apparatus 89 useful in the invention, which has a
fan-shaped attenuator 90 that is advantageous in processing a
spreading stream of filaments. The processing chamber, and the
walls defining the processing chamber, spread or widen over the
length of the processing chamber. Within the processing chamber the
forces acting on the filaments is rather uniform over the whole
width of the stream. The spacing of the walls is selected to cause
the stream of filaments to spread in a desired amount.
[0043] Preferably the processing chamber 89, as in the case of the
previously described chamber 16, has no sidewalls over most or all
of the length of the parallel walls defining the processing chamber
(as so as to allow the gaseous stream carrying the filaments to
spread and to thus spread the stream of filaments). However, the
processing chamber of the apparatus 89 in FIG. 7, as well as the
processing chamber in other embodiments, can include side walls;
and spreading or narrowing of the stream of extruded filaments or
fibers is still obtained by controlling the spacing between the
walls that define the processing chamber. Sidewalls can have the
advantage that they limit the intake of air from the sides that
might affect the flow of filaments. In these embodiments a single
sidewall at one transverse end of the chamber is generally not
attached to both chamber halves or sides, because attachment to
both chamber sides would prevent movement together or apart of
devices halves, including the instantaneous separation of the sides
as discussed above. Instead, a sidewall(s) may be attached to one
chamber side and move with that side when and if it moves during
adjustment of the adjustment mechanism or in response to
instantaneous movement means as discussed above. In other
embodiments, the side walls are divided, with one portion attached
to one chamber side, and the other portion attached to the other
chamber side, with the sidewall portions preferably overlapping if
it is desired to confine the stream of processed fibers within the
processing chamber.
[0044] While spreading of the collected stream of filaments is
generally preferred, formation of webs narrower than the die (e.g.,
75% or 50% of the width of the die or narrower) may be useful. Such
narrowing can be obtained by controlling the spacing between the
walls of the processing chamber; also, diverging of the walls in
the direction of filament travel has been found to be potentially
helpful in achieving such a narrowing.
[0045] A wide variety of fiber-forming materials may be used to
make fibers with a method and apparatus of the invention. Either
organic polymeric materials, or inorganic materials, such as glass
or ceramic materials, may be used. While the invention is
particularly useful with fiber-forming materials in molten form,
other fiber-forming liquids such as solutions or suspensions may
also be used. Any fiber-forming organic polymeric materials may be
used, including the polymers commonly used in fiber formation such
as polyethylene, polypropylene, polyethylene terephthalate, nylon,
and urethanes. Some polymers or materials that are more difficult
to form into fibers by spunbond or meltblown techniques can be
used, including amorphous polymers such as cyclic olefins (which
have a high melt viscosity that limits their utility in
conventional direct-extrusion techniques), block copolymers,
styrene-based polymers, and adhesives (including pressure-sensitive
varieties and hot-melt varieties). The specific polymers listed
here are examples only, and a wide variety of other polymeric or
fiber-forming materials are useful. Interestingly, fiber-forming
processes of the invention using molten polymers can often be
performed at lower temperatures than traditional direct extrusion
techniques, which offers a number of advantages.
[0046] Fibers also may be formed from blends of materials,
including materials into which certain additives have been blended,
such as pigments or dyes. Bicomponent fibers, such as core-sheath
or side-by-side bicomponent fibers, may be prepared ("bicomponent"
herein includes fibers with two or more than two components). In
addition, different fiber-forming materials may be extruded through
different orifices of the extrusion head so as to prepare webs that
comprise a mixture of fibers. In other embodiments of the invention
other materials are introduced into a stream of fibers prepared
according to the invention before or as the fibers are collected so
as to prepare a blended web. For example, other staple fibers may
be blended in the manner taught in U.S. Pat. No. 4,118,531; or
particulate material may be introduced and captured within the web
in the manner taught in U.S. Pat. No. 3,971,373; or microwebs as
taught in U.S. Pat. No. 4,813,948 may be blended into the webs.
Alternatively, fibers prepared by the present invention may be
introduced into a stream of other fibers to prepare a blend of
fibers.
[0047] A fiber-forming process of the invention can be controlled
to achieve different effects and different forms of web. The
invention is particularly useful as a direct-web-formation process
in which a fiber-forming polymeric material is converted into a web
in one essentially direct operation, such as is done in spunbond or
meltblown processes. Often the invention is used to obtain a mat of
fibers of at least a minimum thickness (e.g., 5 mm or more) and
loft (e.g., 10 cc/gram or more); thinner webs can be prepared, but
webs of some thickness offer some advantages for uses such as
insulation, filtration, cushioning, or sorbency. Webs in which the
collected fibers are autogenously bondable (bondable without aid of
added binder material or embossing pressure) are especially
useful.
[0048] As further examples of process control, a process of the
invention can be controlled to control the temperature and solidity
(i.e., moltenness) of filaments entering the processing chamber
(e.g., by moving the processing chamber closer to or further from
the extrusion head, or increasing or decreasing the volume or the
temperature of quenching fluids). In some cases at least a majority
of the extruded filaments of fiber-forming material solidify before
entering the processing chamber. Such solidification changes the
nature of the action of the air impacting the filaments in the
processing chamber and the effects within the filaments, and
changes the nature of the collected web. In other processes of the
invention the process is controlled so that at least a majority of
the filaments solidify after they enter the processing chamber,
whereupon they may solidify within the chamber or after they exit
the chamber. Sometimes the process is controlled so that at least a
majority of the filaments or fibers solidify after they are
collected, so the fibers are sufficiently molten that when
collected they may become adhered at points of fiber
intersection.
[0049] A wide variety of web properties may be obtained by varying
the process. For example, when the fiber-forming material has
essentially solidified before it reaches the attenuator, the web
will be more lofty and exhibit less or no interfiber bonding. By
contrast, when the fiber-forming material is still molten at the
time it enters the attenuator, the fibers may still be soft when
collected so as to achieve interfiber bonding.
[0050] Use of a processing device as illustrated in FIGS. 1-7 can
have the advantage that filaments may be processed at very fast
velocities. Velocities can be achieved that are not known to be
previously available in direct-web-formation processes that use a
processing chamber in the same role as the typical role of a
processing chamber of the present invention, i.e., to provide
primary attenuation of extruded filamentary material. For example,
polypropylene is not known to have been processed at apparent
filament speeds of 8000 meters per minute in processes that use
such a processing chamber, but such apparent filament speeds are
possible with the present invention (the term apparent filament
speed is used, because the speeds are calculated, e.g., from
polymer flow rate, polymer density, and average fiber diameter).
Even faster apparent filament speeds have been achieved, e.g.,
10,000 meters per minute, or even 14,000 or 18,000 meters per
minute, and these speeds can be obtained with a wide range of
polymers. In addition, large volumes of polymer can be processed
per orifice in the extrusion head, and these large volumes can be
processed while at the same time moving extruded filaments at high
velocity. This combination gives rise to a high productivity
index--the rate of polymer throughput (e.g., in grams per orifice
per minute) multiplied by the apparent velocity of extruded
filaments (e.g., in meters per minute). The process of the
invention can be readily practiced with a productivity index of
9000 or higher, even while producing filaments that average 20
micrometers or less in diameter.
[0051] Various processes conventionally used as adjuncts to
fiber-forming processes may be used in connection with filaments as
they enter or exit from the attenuator, such as spraying of
finishes or other materials onto the filaments, application of an
electrostatic charge to the filaments, application of water mists,
etc. In addition, various materials may be added to a collected
web, including bonding agents, adhesives, finishes, and other webs
or films.
[0052] Although there typically is no reason to do so, filaments
may be blown from the extrusion head by a primary gaseous stream in
the manner of that used in conventional meltblowing operations.
Such primary gaseous streams cause an initial attenuation and
drawing of the filaments.
[0053] The fibers prepared by a method of the invention may range
widely in diameter. Microfiber sizes (about 10 micrometers or less
in diameter) may be obtained and offer several benefits; but fibers
of larger diameter can also be prepared and are useful for certain
applications; often the fibers are 20 micrometers or less in
diameter. Fibers of circular cross-section are most often prepared,
but other cross-sectional shapes may also be used. Depending on the
operating parameters chosen, e.g., degree of solidification from
the molten state before entering the attenuator, the collected
fibers may be rather continuous or essentially discontinuous. The
orientation of the polymer chains in the fibers can be influenced
by selection of operating parameters, such as degree of
solidification of filament entering the attenuator, velocity and
temperature of air stream introduced into the attenuator by the air
knives, and axial length, gap width and shape (because, for
example, shape can influence a venturi effect) of the attenuator
passage.
[0054] Unique fibers and fiber properties, and unique fibrous webs,
have been achieved on processing devices as pictured in FIGS. 1-7.
For example, in some collected webs, fibers are found that are
interrupted, i.e., are broken, or entangled with themselves or
other fibers, or otherwise deformed as by engaging a wall of the
processing chamber. The fiber segments at the location of the
interruption--i.e., the fiber segments at the point of a fiber
break, and the fiber segments in which an entanglement or
deformation occurs--are all termed an interrupting fiber segment
herein, or more commonly for shorthand purposes, are often simply
termed "fiber ends": these interrupting fiber segments form the
terminus or end of an unaffected length of fiber, even though in
the case of entanglements or deformations there often is no actual
break or severing of the fiber. The fiber ends have a fiber form
(as opposed to a globular shape as sometimes obtained in
meltblowing or other previous methods) but are usually enlarged in
diameter over the intermediate portions of the fiber; usually they
are less than 300 micrometers in diameter. Often, the fiber ends,
especially broken ends, have a curly or spiral shape, which causes
the ends to entangle with themselves or other fibers. And the fiber
ends may be bonded side-by-side with other fibers, e.g., by
autogenous coalescing of material of the fiber end with material of
an adjacent fiber.
[0055] Fiber ends as described arise because of the unique
character of the fiber-forming process of FIGS. 1-7, which can
continue in spite of breaks and interruptions in individual fiber
formation. Such fiber ends may not occur in all collected webs of
the invention (for example, they may not occur if the extruded
filaments of fiber-forming material have reached a high degree of
solidification before they enter the processing chamber).
Individual fibers may be subject to an interruption, e.g., may
break while being drawn in the processing chamber, or may entangle
with themselves or another fiber as a result of being deflected
from the wall of the processing chamber or as a result of
turbulence within the processing chamber, perhaps while still
molten; but notwithstanding such interruption, the fiber-forming
process continues. The result is that the collected web includes a
significant and detectable number of the fiber ends, or
interrupting fiber segments where there is a discontinuity in the
fiber. Since the interruption typically occurs in or after the
processing chamber, where the fibers are typically subjected to
drawing forces, the fibers are under tension when they break,
entangle or deform. The break, or entanglement generally results in
an interruption or release of tension allowing the fiber ends to
retract and gain in diameter. Also, broken ends are free to move
within the fluid currents in the processing chamber, which at least
in some cases leads to winding of the ends into a spiral shape and
entangling with other fibers.
[0056] Analytical study and comparisons of the fiber ends and
middle portions typically reveals a different morphology between
the ends and middles. The polymer chains in the fiber ends usually
are oriented, but not to the degree they are oriented in the middle
portions of the fibers. This difference in orientation can result
in a difference in the proportion of crystallinity and in the kind
of crystalline or other morphological structure. And these
differences are reflected in different properties.
[0057] In general, when fiber middles and ends prepared by this
invention are evaluated using a properly calibrated differential
scanning calorimeter (DSC), the fiber middles and ends will differ
from each other as to one or more of the common thermal transitions
by at least the resolution of the testing instrument (0.1.degree.
C.), due to the differences in the mechanisms operating internally
within the fiber middles and fiber ends. For example, when
experimentally observable, the thermal transitions can differ as
follows: 1) the glass transition temperature, T.sub.g, for middles
can be slightly higher in temperature than for ends, and the
feature can diminish in height as crystalline content or
orientation in the fiber middle increases; 2) when observed, the
onset temperature of cold crystallization, T.sub.c, and the peak
area measured during cold crystallization will be lower for the
fiber middle portion relative to the fiber ends, and finally, 3)
the melting peak temperature, T.sub.m, for the fiber middles will
either be elevated over the T.sub.m observed for the ends, or
become complex in nature showing multiple endothermic minima (i.e.,
multiple melting peaks representing different melting points for
different molecular portions that, for example, differ in the order
of their crystalline structure), with one molecular portion of the
middle portion of the fiber melting at a higher temperature than
molecular portions of the fiber ends. Most often, fiber ends and
fiber middles differ in one or more of the parameters glass
transition temperature, cold crystallization temperature, and
melting point by at least 0.5 or 1 degree C.
[0058] Webs including fibers with enlarged fibrous ends have the
advantage that the fiber ends may comprise a more easily softened
material adapted to increase bonding of a web; and the spiral shape
can increase coherency of the web.
EXAMPLES
[0059] Apparatus as shown in FIG. 1 was used to prepare fibrous
webs from a number of different polymers as summarized in Table 1.
Specific parts of the apparatus and operating conditions were
varied as described below and as also summarized in Table 1. The
extrusion die used in all the examples had an active width of four
inches (about 10 centimeters). Table 1 also includes a description
of characteristics of the fibers prepared, including the width of
the nonwoven web collected.
[0060] Examples 1-22 and 42-43 were prepared from polypropylene;
Examples 1-13 were prepared from a polypropylene having a melt flow
index (MFI) of 400 (Exxon 3505G), Example 14 was prepared from
polypropylene having a MFI of 30 (Fina 3868), Examples 15-22 were
prepared from a polypropylene having a MFI of 70 (Fina 3860), and
Examples 42-43 were prepared from a polypropylene having a MFI of
400 (Fina 3960). Polypropylene has a density of 0.91 g/cc.
[0061] Examples 23-32 and 44-46 were prepared from polyethylene
terephthalate; Examples 23-26, 29-32 and 44 were prepared from PET
having an intrinsic viscosity (IV) of 0.61 (3M 651000), Example 27
was prepared from PET having an IV of 0.36, Example 28 was prepared
from PET having an IV of 0.9 (a high-molecular-weight PET useful as
a high-tenacity spinning fiber supplied as Crystar 0400 supplied by
Dupont Polymers), and Examples 45 and 46 were prepared from PETG
(AA45-004 made by Paxon Polymer Company, Baton Rouge, La.). PET has
a density of 1.35 and PETG has a density of about 1.30.
[0062] Examples 33 and 41 were prepared from a nylon 6 polymer
(Ultramid PA6 B-3 from BASF) having an MFI of 130 and a density of
1.15. Example 34 was prepared from polystyrene (Crystal PS 3510
supplied by Nova Chemicals) and having an MFI of 15.5 and density
of 1.04. Example 35 was prepared from polyurethane (Morton
PS-440-200) having a MFI of 37 and density of 1.2. Example 36 was
prepared from polyethylene (Dow 6806) having a MFI of 30 and
density of 0.95. Example 37 was prepared from a block copolymer
comprising 13 percent styrene and 87 percent ethylene butylene
copolymer (Shell Kraton G1657) having a MFI of 8 and density of
0.9.
[0063] Example 38 was a bicomponent core-sheath fiber having a core
(89 weight percent) of the polystyrene used in Example 34 and a
sheath (11 weight percent) of the copolymer used in Example 37.
Example 39 was a bicomponent side-by-side fiber prepared from
polyethylene (Exxact 4023 supplied by Exxon Chemicals having a MFI
of 30); 36 weight percent) and a pressure-sensitive adhesive 64
weight percent). The adhesive comprised a terpolymer of 92 weight
percent isooctylacrylate, 4 weight percent styrene, and 4 weight
percent acrylic acid, had an intrinsic viscosity of 0.63, and was
supplied through a Bonnot adhesive extruder.
[0064] In Example 40 each fiber was single-component, but fibers of
two different polymer compositions were used--the polyethylene used
in Example 36 and the polypropylene used in Examples 1-13. The
extrusion head had four rows of orifices, with 42 orifices in each
row; and the supply to the extrusion head was arranged to supply a
different one of the two polymers to adjacent orifices in a row to
achieve an A-B-A . . . pattern.
[0065] In Example 47 a fibrous web was prepared solely from the
pressure-sensitive adhesive that was used as one component of
bicomponent fibers in Example 39; a Bonnot adhesive extruder was
used.
[0066] In Examples 42 and 43 the air cylinders used to bias the
movable sides or walls of the attenuator were replaced with coil
springs. In Example 42, the springs deflected 9.4 millimeters on
each side during operation in the example. The spring constant for
the spring was 4.38 Newtons/millimeter so the clamping force
applied by each spring was 41.1 Newtons. In Example 43, the spring
deflected 2.95 millimeters on each side, the spring constant was
4.9 Newtons/millimeter, and the clamping force was 14.4
Newtons.
[0067] In Example 44 the extrusion head was a meltblowing die,
which had 0.38-millimeter-diameter orifices spaced 1.02 millimeters
center to center. The row of orifices was 101.6 millimeters long.
Primary meltblowing air at a temperature of 370 degrees C. was
introduced through a 203-millimeter-wide air knife on each side of
the row of orifices at a rate of 0.45 cubic meters per minute (CMM)
for the two air knives in combination.
[0068] In Example 47 pneumatic rotary ball vibrators oscillating at
about 200 cycles per second were connected to each of the movable
attenuator sides or walls; the air cylinders remained in place and
aligned the attenuator chamber under the extrusion head and were
available to return the attenuator sides to their original position
in the event a pressure buildup forced the sides apart. During
operation of the example, a lesser quantity of pressure-sensitive
adhesive stuck onto the attenuator walls when the vibrators were
operating than when they were not operating. In Examples 7 and 37
the clamping force was zero, but the balance between air pressure
within the processing chamber and ambient pressure established the
gap between chamber walls and returned the moveable side walls to
their original position after any perturbations.
[0069] In each of the examples the polymer formed into fibers was
heated to a temperature listed in Table 1 (temperature measured in
the extruder 12 near the exit to the pump 13), at which the polymer
was molten, and the molten polymer was supplied to the extrusion
orifices at a rate as listed in the table. The extrusion head
generally had four rows of orifices, but the number of orifices in
a row, the diameter of the orifices, and the length-to-diameter
ratio of the orifices were varied as listed in the table. In
Examples 1-2, 5-7, 14-24, 27, 29-32, 34, and 36-40 each row had 42
orifices, making a total of 168 orifices. In the other examples
with the exception of Example 44, each row had 21 orifices, making
a total of 84 orifices.
[0070] The attenuator parameters were also varied as described in
the table, including the air knife gap (the dimension 30 in FIG.
3); the attenuator body angle (.alpha. in FIG. 3); the temperature
of the air passed through the attenuator; quench air rate; the
clamping pressure and force applied to the attenuator by the air
cylinders; the total volume of air passed through the attenuator
(given in actual cubic meters per minute, or ACMM; about half of
the listed volume was passed through each air knife 32); the gaps
at the top and bottom of the attenuator (the dimensions 33 and 34,
respectively, in FIG. 3); the length of the attenuator chute
(dimension 35 in FIG. 3); the distance from the exit edge of the
die to the attenuator (dimension 17 in FIG. 1); and the distance
from the attenuator exit to the collector (dimension 21 in FIG. 1).
The air knife had a transverse length (the direction of the length
25 of the slot in FIG. 4) of about 120 millimeters; and the
attenuator body 28 in which the recess for the air knife was formed
had a transverse length of about 152 millimeters. The transverse
length of the wall 36 attached to the attenuator body was varied:
in Examples 1-5, 8-25, 27-28, 33-35, and 37-47, the transverse
length of the wall was 254 millimeters; in Example 6, 26, 29-32 and
36 it was about 406 millimeters; and in Example 7 it was about 127
millimeters.
[0071] Properties of the collected fibers are reported including
the average fiber diameter, measured from digital images acquired
from a scanning electron microscope and using an image analysis
program UTHSCSA IMAGE Tool for Windows, version 1.28, from the
University of Texas Health Science Center in San Antonio (copyright
1995-97). The images were used at magnifications of 500 to 1000
times, depending on the size of the fibers.
[0072] The apparent filament speed of the collected fibers was
calculated from the equation,
V.sub.apparent=4M/.rho..pi.d.sub.f.sup.2, where
[0073] M is the polymer flow rate per orifice in grams/cubic
meter,
[0074] .rho. is the polymer density, and
[0075] d.sub.f is the measured average fiber diameter in
meters.
[0076] The tenacity and elongation to break of the fibers were
measured by separating out a single fiber under magnification and
mounting the fiber in a paper frame. The fiber was tested for
breaking strength by the method outlined in ASTM D3822-90. Eight
different fibers were used to determine an average breaking
strength and an average elongation to break. Tenacity was
calculated from the average breaking strength and the average
denier of the fiber calculated from the fiber diameter and polymer
density.
[0077] Samples were cut from the prepared webs, including portions
comprising a fiber end, i.e., a fiber segment in which an
interruption taking the form of either a break or an entanglement
had occurred, and portions comprising the fiber middle, i.e., the
main unaffected portion of the fibers, and the samples were
submitted for analysis by differential scanning calorimetry,
specifically Modulated DSC.TM. using a Model 2920 device supplied
by TA Instruments Inc, New Castle, Del., and using a heating rate
of 4 degrees C./minute, a perturbation amplitude of plus-or-minus
0.636 degrees C., and a period of 60 seconds. Melting points for
both the fiber ends and the middles were determined; the maximum
melting point peak on the DSC plots for the fiber middles and ends
are reported in Table 1.
[0078] Although in some cases no difference between middles and
ends was detected as to melting point, other differences were often
seen even in those examples, such as differences in glass
transition temperature.
[0079] The samples of fiber middles and ends were also submitted
for X-ray diffraction analysis. Data were collected by use of a
Bruker microdiffractometer (supplied by Bruker AXS, Inc. Madison,
Wis.), copper K.sub..alpha. radiation, and HI-STAR 2D position
sensitive detector registry of the scattered radiation. The
diffractometer was fitted with a 300-micrometer collimator and
graphite-incident-beam monochromator. The X-ray generator consisted
of a rotating anode surface operated at settings of 50 kV and 100
mA and using a copper target. Data were collected using a
transmission geometry for 60 minutes with the detector centered at
0 degrees (2.theta.). Samples were corrected for detector
sensitivity and spatial irregularities using the Bruker GADDS data
analysis software. The corrected data were averaged azimuthally,
reduced to x-y pairs of scattering angle (2.theta.) and intensity
values, and subjected to profile fitting by using the data analysis
software ORIGIN.TM. (supplied by Microcal Software, Inc.
Northhampton, Mass.) for evaluation of crystallinity.
[0080] A gaussian peak shape model was employed to describe the
individual crystalline peak and amorphous peak contributions. For
some data sets, a single amorphous peak did not adequately account
for the total amorphous scattered intensity. In these cases
additional broad maxima were employed to fully account for the
observed amorphous scattered intensity. Crystallinity indices were
calculated as the ratio of crystalline peak area to total scattered
peak area (crystalline plus amorphous) within the 6-to-36 degree
(2.theta.) scattering angle range. A value of unity represents 100
percent crystallinity and a value of zero corresponds to a
completely amorphous material. Values obtained are reported in
Table 1.
[0081] As to five examples of webs made from polypropylene,
Examples 1, 3, 13, 20 and 22, X-ray analysis revealed a difference
between middles and ends in that the ends included a beta
crystalline form, measured at 5.5 angstroms.
[0082] Draw area ratios were determined by dividing the
cross-sectional area of the die orifice by the cross-sectional area
of the completed fibers, calculated from the average fiber
diameter. Productivity index was also calculated.
1 TABLE 1 Example Number 1 2 3 4 5 6 7 8 9 10 Polymer PP PP PP PP
PP PP PP PP PP PP MFI/IV 400 400 400 400 400 400 400 400 400 400
Melt Temperature (C) 187 188 187 183 188 188 188 188 180 188 Number
of Orifices 168 168 84 84 168 168 168 84 84 84 Polymer Flow Rate
(g/orifice/min) 1.00 1.00 1.00 1.04 1.00 1.00 1.00 0.49 4.03 1.00
Orifice Diameter (mm) 0.343 0.508 0.889 1.588 0.508 0.508 0.508
0.889 0.889 0.889 Orifice L/D 9.26 6.25 3.57 1.5 6.25 6.25 6.25
3.57 3.57 3.57 Air Knife Gap (mm) 0.762 0.762 0.762 0.762 0.762
0.762 0.762 0.381 1.778 0.381 Attenuator Body Angle (degrees) 30 30
30 30 30 30 30 20 40 20 Attenuator Air Temperature (C) 25 25 25 25
25 25 25 25 25 25 Quench Air Rate (ACMM) 0.44 0.35 0.38 0.38 0.38
0.37 0 0.09 0.59 0.26 Clamping Force (Newtons) 221 221 59.2 63.1
148 237 0 23.7 63.1 43.4 Attenuator Air Volume (ACMM) 2.94 2.07
1.78 1.21 2.59 2.15 2.57 1.06 >3 1.59 Attenuator Gap (Top) (mm)
4.19 3.28 3.81 4.24 3.61 2.03 3.51 2.03 5.33 1.98 Attenuator Gap
(Bottom) (mm) 2.79 1.78 2.90 3.07 3.18 1.35 3.51 2.03 4.60 1.88
Chute Length (mm) 152.4 152.4 152.4 152.4 76.2 228.6 25.4 152.4
152.4 152.4 Die to Attenuator Distance (mm) 317.5 317.5 317.5 317.5
317.5 304.8 304.8 304.8 304.8 914.4 Attenuator to Collector Dist
(mm) 609.6 609.6 609.6 609.6 609.6 609.6 609.6 609.6 609.6 304.8
Average Fiber Diameter (.mu.) 10.56 9.54 15.57 14.9 13.09 10.19
11.19 9.9 22.26 14.31 Apparent Filament Speed (m/min) 12600 15400
5770 6530 8200 13500 11200 6940 11400 6830 Tenacity (g/denier) 2.48
4.8 1.41 1.92 2.25 2.58 2.43 2.31 0.967 1.83 Percent elongation to
break (%) 180 180 310 230 220 200 140 330 230 220 Draw Area Ratio
1050 2800 3260 11400 1510 2490 2060 8060 1600 3860 Melting Point -
Middles (.degree. C.) 165.4 165.0 164.1 164.1 165.2 164.0 164.3
165.2 164.3 165.4 Second Peak (.degree. C.) Melting Point - Ends
(.degree. C.) 163.9 164.0 163.4 163.4 163.2 162.5 164.0 163.3 164.3
163.2 Second Peak (.degree. C.) Crystallinity Index - Middles 0.44
0.46 0.42 0.48 0.48 0.52 0.39 0.39 0.50 0.40 Productivity Index g
.multidot. m/hole .multidot. min.sup.2 12700 15500 5770 6760 8240
13600 11300 3380 45800 6830 Web Width (mm) N/M 508 584 292 330 533
102 267 203 241 Fiber stream included angle (.gamma.) (degrees) N/M
37 43 18 21 39 -- 15 10 26 Example Number 11 12 13 14 15 16 17 18
19 Polymer PP PP PP PP PP PP PP PP PP MFI/IV 400 400 400 30 70 70
70 70 70 Melt Temperature (.degree. C.) 190 196 183 216 201 201 208
207 206 Number of Orifices 84 84 84 168 168 168 168 168 168 Polymer
Flow Rate (g/orifice/min) 1.00 1.00 1.00 0.50 1.00 0.50 0.50 0.50
0.50 Orifice Diameter (mm) 0.889 0.889 1.588 0.508 0.343 0.343
0.343 0.343 0.343 Orifice L/D 3.57 3.57 1.5 3.5 9.26 3.5 3.5 3.5
3.5 Air Knife Gap (mm) 0.381 1.778 0.762 1.270 0.762 0.762 0.762
0.762 0.762 Attenuator Body Angle (degrees) 20 40 30 30 30 30 30 30
30 Attenuator Air Temperature (.degree. C.) 25 25 121 25 25 25 25
25 25 Quench Air Rate (ACMM) 0 0.59 0.34 0.19 0.17 0 0.35 0.26 0.09
Clamping Force (Newtons) 27.6 15.8 55.2 25.6 221 27.6 27.6 27.6
27.6 Attenuator Air Volume (ACMM) 0.86 1.19 1.25 1.24 2.84 0.95
0.95 1.19 1.54 Attenuator Gap (Top) (mm) 2.67 6.30 3.99 5.26 4.06
7.67 5.23 3.78 3.78 Attenuator Gap (Bottom) (mm) 2.67 6.30 2.84
4.27 2.67 7.67 5.23 3.33 3.33 Chute Length (mm) 152.4 76.2 152.4
152.4 152.4 152.4 152.4 152.4 152.4 Die to Attenuator Distance (mm)
101.6 127 317.5 1181.1 317.5 108 304.8 292.1 292.1 Attenuator to
Collector Dist. (mm) 914.4 304.8 609.6 330.2 609.6 990.6 787.4
800.1 800.1 Average Fiber Diameter (.mu.) 18.7 21.98 14.66 16.50
16.18 19.20 17.97 14.95 20.04 Apparent Filament Speed (m/min) 4000
2900 6510 2570 5370 1900 2170 3350 1740 Tenacity (g/denier) 0.52
0.54 1.68 2.99 2.12 2.13 2.08 2.56 0.87 Percent elongation to break
(%) 150 100 110 240 200 500 450 500 370 Draw Area Ratio 2300 1600
12000 950 450 320 360 560 290 Melting Point - Middles (.degree. C.)
162.3 163.9 164.5 162.7 164.8 164.4 166.2 163.9 164.1 Second Peak
(.degree. C.) 167.3 164.4 Melting Point - Ends (.degree. C.) 163.1
163.4 164.3 163.5 163.8 163.7 164.0 163.9 163.9 Second Peak
(.degree. C.) 166.2 Crystallinity Index - Middles 0.12 0.13 0.46
0.53 0.44 0.33 0.43 0.37 0.49 Productivity Index g .multidot.
m/hole .multidot. min.sup.2 4000 2900 6500 1280 5390 950 1080 1680
870 Web Width (mm) 292 114 381 254 432 127 165 279 406 Fiber stream
included angle (.gamma.) (degrees) 12 2.4 26 26 30 1.4 4.6 13 22
Example Number 20 21 22 23 24 25 26 27 Polymer PP PP PP PET PET PET
PET PET MFI/IV 70 70 70 0.61 0.61 0.61 0.61 0.36 Melt Temperature
(.degree. C.) 221 221 221 278 290 281 290 290 Number of Orificies
168 168 168 168 168 84 84 168 Polymer Flow Rate (g/orifice/min)
0.50 0.50 0.50 1.01 1.00 0.99 0.99 1.01 Orifice Diameter (mm) 0.343
0.343 0.343 0.343 0.508 0.889 1.588 0.508 Orifice L/D 3.5 3.5 3.5
3.5 3.5 3.57 3.5 3.5 Air Knife Gap (mm) 0.762 0.762 0.762 1.778
1.270 0.762 0.381 1.270 Attenuator Body Angle (degrees) 30 30 30 20
30 30 40 30 Attenuator Air Temperature (.degree. C.) 25 25 25 25 25
25 25 25 Quench Air Rate (ACMM) 0.09 0.30 0.42 0.48 0.35 0.35 0.17
0.22 Clamping Force (Newtons) 27.6 150 17.0 3.9 82.8 63.1 3.9 86.8
Attenuator Air Volume (ACMM) 1.61 >3 1.61 2.11 2.02 2.59 0.64
2.40 Attenuator Gap (Top) (mm) 3.78 3.78 3.78 4.83 5.08 5.16 2.21
5.03 Attenuator Gap (Bottom) (mm) 3.33 3.35 3.35 4.83 3.66 4.01
3.00 3.86 Chute Length (mm) 152.4 152.4 152.4 76.2 152.4 152.4
228.6 152.4 Die to Attenuator Distance (mm) 508 508 685.8 317.5
533.4 317.5 317.5 127 Attenuator to Collector Dist. (mm) 584.2
584.2 431.8 609.6 762 609.6 609.6 742.95 Average Fiber Diameter
(.mu.) 16.58 15.73 21.77 11.86 10.59 11.92 13.26 10.05 Apparent
Filament Speed (m/min) 2550 2830 1490 6770 8410 6580 5320 9420
Tenacity (g/denier) 1.9 1.4 1.2 3.5 5.9 3.6 3.0 3.5 Percent
elongation to break (%) 210 220 250 40 30 40 50 20 Draw Area Ratio
430 480 250 840 2300 5600 1400 2600 Melting Point - Middles
(.degree. C.) 165.9 163.9 165.7 260.9 259.9 265.1 261.0 256.5
Second Peak (.degree. C.) 167.2 258.5 267.2 -- 258.1 268.3 Melting
Point - Ends (.degree. C.) 164.1 164.0 163.7 257.1 257.2 255.7
257.4 257.5 Second Peak (.degree. C.) 253.9 254.3 268.7 253.9 --
Crystallinity Index - Middles 0.5 0.39 0.40 0.10 0.20 0.27 0.25
0.12 Productivity Index g .multidot. m/hole .multidot. min.sup.2
1270 1410 738 6820 8400 6520 5270 9500 Web Width (mm) 203 406 279
N/M 254 N/M 216 457 Fiber stream included angle (.gamma.) (degrees)
10 29 23 N/M 11 N/M 11 27 Example Number 28 29 30 31 32 33 34 35
Polymer PET PET PET PET PET Nylon PS Urethane MFI/IV 0.85 0.61 0.61
0.61 0.61 130 15.5 37 Melt Temperature (.degree. C.) 290 282 281
281 281 272 268 217 Number of Orifices 84 168 168 168 168 84 168 84
Polymer Flow Rate (g/orifice/min) 0.98 1.01 1.01 1.01 1.01 1.00
1.00 1.98 Orifice Diameter (mm) 1.588 0.508 0.508 0.508 0.508 0.889
0.343 0.889 Orifice L/D 3.57 6.25 6.25 6.25 6.25 6.25 9.26 6.25 Air
Knife Gap (mm) 0.762 0.762 0.762 0.762 0.762 0.762 0.762 0.762
Attenuator Body Angle (degrees) 30 30 30 30 30 30 30 30 Attenuator
Air Temperature (.degree. C.) 25 25 25 25 25 25 25 25 Quench Air
Rate (ACMM) 0.19 0 0.48 0.48 0.35 0.08 0.21 0 Clamping Force
(Newtons) 39.4 82.8 86.8 82.8 82.8 39.4 71.0 86.8 Attenuator Air
Volume (ACMM) 1.16 2.16 2.16 2.15 2.15 2.12 2.19 >3 Attenuator
Gap (Top) (mm) 3.86 3.68 3.68 3.58 3.25 4.29 4.39 4.98 Attenuator
Gap (Bottom) (mm) 3.10 3.10 3.10 3.10 2.64 3.84 3.10 4.55 Chute
Length (mm) 76.2 228.6 228.6 228.6 228.6 76.2 152.4 76.2 Die to
Attenuator Distance (mm) 317.5 88.9 317.5 457.2 685.8 317.5 317.5
317.5 Attenuator to Collector Distance (mm) 609.6 609.6 609.6 482.6
279.4 831.85 609.6 609.6 Average Fiber Diameter (.mu.) 12.64 10.15
10.59 11.93 10.7 12.94 14.35 14.77 Apparent Filament Speed (m/min)
5800 9230 8480 6690 8310 6610 5940 9640 Tenacity (g/denier) 3.6 3.1
4.7 4.1 5.6 3.8 1.4 3.3 Percent elongation to break (%) 30 20 30 40
40 140 40 140 Draw Area Ratio 16000 2500 2300 1800 2300 4700 570
3600 Melting Point - Middles (.degree. C.) 268.3 265.6 265.3 262.4
261.4 221.2 23.7? Second Peak (.degree. C.) 257.3 257.9 269.5 *
218.2 ? Melting Point - Ends (.degree. C.) 254.1 257.2 257.2 257.4
257.4 219.8 ? Second Peak (.degree. C.) 268.9 268.4 * * * -- -- --
Crystallinity Index - Middles 0.22 0.09 0.32 0.35 0.35 0.07 0 0
Productivity Index g .multidot. m/hole .multidot. min.sup.2 5690
9320 8560 6740 8380 6610 5940 19100 Web Width (mm) 305 559 559 711
457 279 318 279 Fiber stream included angle (.gamma.) (degrees) 19
41 41 65 65 12 20 17 Example Number 36 37 38 39 40 41 42 Polymer PE
B1. Copol. PS/copol. PE/PSA PE/PP Nylon PP MFI/IV 30 8 15.5/8
30/.63 30/400 130 400 Melt Temperature (.degree. C.) 200 275 269
205 205 271 206 Number of Orifices 168 168 168 168 168 84 84
Polymer Flow Rate (g/orifice/min) 0.99 0.64 1.14 0.83 0.64 0.99
2.00 Orifice Diameter (mm) 0.508 0.508 0.508 0.508 0.508 0.889
0.889 Orifice L/D 6.25 6.25 6.25 6.25 6.25 6.25 6.25 Air Knife Gap
(mm) 0.762 0.762 0.762 0.762 0.762 0.762 0.762 Attenuator Body
Angle (degrees) 30 30 30 30 30 30 30 Attenuator Air Temperature
(.degree. C.) 25 25 25 25 25 25 25 Quench Air Rate (ACMM) 0.16 0.34
0.25 0.34 0.34 0.08 0.33 Clamping Force (Newtons) 205 0.0 27.6 23.7
213 150 41.1 Attenuator Air Volume (ACMM) 2.62 0.41 0.92 0.54 2.39
>3 >3 Attenuator Gap (Top) (mm) 3.20 7.62 3.94 4.78 3.58 4.19
3.25 Attenuator Gap (Bottom) (mm) 2.49 7.19 3.56 4.78 3.05 3.76
2.95 Chute Length (mm) 228.6 76.2 76.2 76.2 76.2 76.2 76.2 Die to
Attenuator Distance (mm) 317.5 666.75 317.5 330.2 292.1 539.75
317.5 Attenuator to Collector Dist (mm) 609.6 330.2 800.1 533.4
546.1 590.55 609.6 Average Fiber Diameter (.mu.) 8.17 34.37 19.35
32.34 8.97 12.8 16.57 Apparent Filament Speed (m/min) 19800 771
4700 1170 11000 6700 10200 Tenacity (lb/dtex) 1.2 1.2 1.1 3.5 0.8
Percent elongation to break (%) 60 30 100 50 170 Draw Area Ratio
3900 220 690 250 3200 4800 2900 Melting Point - Middles (.degree.
C.) 118.7 165.1 Second Peak (.degree. C.) 123.6 Melting Point -
Ends (.degree. C.) 122.1 164.5 Second Peak (.degree. C.)
Crystallinity Index - Middles 0.72 0 0 0.36 0.08 0.43 Productivity
Index g .multidot. m/hole .multidot. min.sup.2 19535 497 5340 972
7040 6640 20400 Web Width (mm) N/M 89 406 N/M N/M 279 305 Fiber
stream included angle (.gamma.) (degrees) N/M 22 11 11 17 19
Example Number 43 44 45 46 47 Polymer PP PET PETG PETG PSA MFI/IV
400 0.61 >70 >70 0.63 Melt Temperature (.degree. C.) 205 290
262 265 200 Number of Orifices 84 ** 84 84 84 Polymer Flow Rate
(g/orifice/min) 2.00 0.82 1.48 1.48 0.60 Orifice Diameter (mm)
0.889 0.38 1.588 1.588 0.508 Orifice L/D 6.25 6.8 3.5 3.5 3.5 Air
Knife Gap (mm) 0.762 0.762 0.762 0.762 0.762 Attenuator Body Angle
(degrees) 30 30 30 30 30 Attenuator Air Temperature (.degree. C.)
25 25 25 25 25 Quench Air Rate (ACMM) 0.33 0 0.21 0.21 0 Clamping
Force (Newtons) 14.4 98.6 39.4 27.6 *** Attenuator Air Volume
(ACMM) 2.20 1.5 0.84 0.99 0.56 Attenuator Gap (Top) (mm) 4.14 4.75
3.66 3.56 6.30 Attenuator Gap (Bottom) (mm) 3.61 4.45 3.38 3.40
5.31 Chute Length (mm) 76.2 76.2 76.2 76.2 76.2 Die to Attenuator
Distance (mm) 317.5 102 317 635 330 Attenuator to Collector
Distance (mm) 609.6 838 610 495 572 Average Fiber Diameter (.mu.)
13.42 8.72 19.37 21.98 38.51 Apparent Filament Speed (m/min) 15500
10200 3860 3000 545 Tenacity (g/denier) 3.6 2.1 1.64 3.19 --
Percent elongation to break (%) 130 40 60 80 -- Draw Area Ratio
4388 1909 6716 5216 1699 Melting Point - Middles (.degree. C.)
164.8 257.4 Second Peak (.degree. C.) 254.4 Melting Point - Ends
(.degree. C.) 164.0 257.4 Second Peak (.degree. C.) 254.3
Crystallinity Index - Middles 0.46 <0.05 0 0 Productivity Index
g .multidot. m/hole .multidot. min.sup.2 31100 8440 5700 4420 330
Web Width (mm) 191 381 203 254 N/M Fiber stream included angle
(.gamma.) (degrees) 8 19 10 17 N/M * multiple values ** meltblowing
die, *** walls oscillated at 200 cycles/sec.
* * * * *