Note: Descriptions are shown in the official language in which they were submitted.
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A PROCESS FOR MAKING A NON-WOVEN WEB
Related Application
[0001] This application claims priority from U.S. Provisional Patent
Application
No. 61/387,109, filed September 28, 2010.
Background of the Invention
[0002] Non-woven spun-bond webs formed from filaments or fibers are
typically made
from a thermoplastic resin on an apparatus such as that disclosed in U.S. Pat.
No. 5,814,349
Such apparatus typically
includes a spinneret for producing a curtain of strands and a process-air
blower for blowing
process air onto the curtain of strands for cooling same to form thermoplastic
filaments. The
thermoplastic filaments are then typically, aerodynamically entrained by the
process air for
aerodynamic stretching of the thermoplastic filaments which are then, after
passing through a
diffuser, deposited upon a continuously circulating sieve belt or fabric for
collecting the
interentangled filaments and forming a web thereon. The web, so formed, is
then subject to
further processing. An exemplary apparatus of this type, particularly for high-
speed spun-
bond web production, is currently available from Reifenhauser GmbH Co.
Maschinenfabrik,
Troisdorf, Germany and sold under the name Reicofil . Other exemplary forming
machines
are available from Oerlikon Neumag, Neumunster, Germany.
[0003] Such equipment endeavors to operate at higher and higher speeds,
Most of the
high-speed technology involves less than 2 denier filament base webs, with the
highest speed
spinning relative to less than 1 denier, termed micro denier webs. The high-
speed spinning
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involves high velocity, small diameter fibers that will naturally exhibit
bounce at impact, due
to the high-speed, and bleed through the sieve belt or fabric, due to their
small size relative to
fabric open area. Also, in some machines fabrics need to allow for the removal
of excessive
quantities of air in "sealed" type arrangements as disclosed in the aforesaid
patent. In other
machines, there is no sealed chamber, but the material drains onto a web, In
such a situation,
accordingly it is desirable to have a fabric with high permeability, low
bleed, and sufficient
topography to avoid uncontrollable fiber "splashing" during deposition. Also,
new high-speed
systems place the diffuser close to the fabric which increases both the
magnitude and quantity
of high velocity vertical impingement of fiber onto the fabric.
[0004] Current fabrics or belts used in high-speed spun-bond manufacturing
lines are a
compromise between good hold down and excessive bleed through, For example,
while a
fabric may provide for good hold down of the web, it may do so at the expense
of fiber
penetration and bleed through into the fabric or belt, Alternatively, while a
fabric may limit
bleed through of deposited filaments, it does so at the expense of web hold
down. One
exemplary fabric is discussed in U.S, Patent No. 7,578,317.
Another exemplary fabric is discussed in International Patent Publication WO
09/030033.
It may be desirable to provide other fabrics for spun-bond manufacturing
lines,
particularly those that operate at high speeds.
Summary of the Invention
[0005] As a first aspect, embodiments of the present invention are directed
to a method of
manufacturing a non-woven web. The method comprises the step of collecting
stretched
filaments that form the non-woven web on a fabric in an apparatus for the
formation of non-
woven webs, The fabric comprises machine direction (MD) yarns and cross-
machine
direction (CMD) yarns, wherein the MD arid CAD yarns are interwoven in a
repeating
pattern in which at least some of the CMD yarns are interwoven with the MD
yarns in pairs
that follow the same weaving sequence. Such a fabric can provide potential
advantages such
as reduced air leakage, reduced air disturbances, and improved web hold-down
effect.
[0006] As a second aspect, embodiments of the present invention are
directed to a method
of manufacturing a non-woven web comprising the step of collecting stretched
filaments that
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form the non-woven web on a fabric in an apparatus for the formation of non-
woven webs,
wherein the fabric comprises MD yarns, single bottom CMD yarns, and top CMD
yarns,
wherein the MD and CMD yarns are interwoven in a repeating pattern in which at
least some
of the top CMD yarns are interwoven with the MD yarns in pairs that follow the
same
weaving sequence.
[0007] As a third aspect, embodiments of the present invention are directed
to a method
of manufacturing a non-woven web comprising the step of collecting stretched
filaments that
form the non-woven web on a fabric in an apparatus for the formation of non-
woven spun-
bond webs, wherein the fabric comprises MD yarns and CMD yarns, wherein the MD
and
CMD yarns are interwoven in a repeating pattern in which all of the CMD yarns
are
interwoven with the MD yarns in pairs that follow the same weaving sequence,
and wherein
the CMD yarns are round in cross-section.
Brief Description of the Figures
[0008] Figures 1 and 2 are schematic diagrams of a spun-bond manufacturing
apparatus.
[0009] Figure 3 is an enlarged view of an exemplary weave pattern for a
fabric employed
in the apparatus of Figures 1 and 2.
[0010] Figure 4 is an enlarged cross-section of an exemplary weave pattern
for an
alternative fabric employed in the apparatus of Figures 1 and 2.
[0011] Figure 5 is an enlarged cross-section of an exemplary weave pattern
for another
alternative fabric employed in the apparatus of Figures 1 and 2.
[0012] Figure 6 is an enlarged cross-section of an exemplary weave pattern
for still
another alternative fabric employed in the apparatus of Figures 1 and 2.
Detailed Description of Embodiments of the Invention
[0013] The present invention will now be described more fully hereinafter,
in which
preferred embodiments of the invention are shown. This invention may, however,
be
embodied in different forms and should not be construed as limited to the
embodiments set
forth herein. Rather, these embodiments are provided so that this disclosure
will be thorough
and complete, and will fully convey the scope of the invention to those
skilled in the art. In
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the drawings, like numbers refer to like elements throughout. Thicknesses and
dimensions of
some components may be exaggerated for clarity.
[0014] Unless otherwise defined, all terms (including technical and
scientific terms) used
herein have the same meaning as commonly understood by one of ordinary skill
in the art to
which this invention belongs. It will be further understood that terms, such
as those defined
in commonly used dictionaries, should be interpreted as having a meaning that
is consistent
with their meaning in the context of the relevant art and will not be
interpreted in an idealized
or overly formal sense unless expressly so defined herein.
[0015] The terminology used herein is for the purpose of describing
particular
embodiments only and is not intended to be limiting of the invention. As used
herein, the
singular forms "a", "an" and "the" are intended to include the plural forms as
well, unless the
context clearly indicates otherwise. It will be further understood that the
terms "comprises"
and/or "comprising," when used in this specification, specify the presence of
stated features,
integers, steps, operations, elements, and/or components, but do not preclude
the presence or
addition of one or more other features, integers, steps, operations, elements,
components,
and/or groups thereof. As used herein the expression "and/or" includes any and
all
combinations of one or more of the associated listed items.
[0016] In addition, spatially relative terms, such as "under", "below",
"lower", "over",
"upper" and the like, may be used herein for ease of description to describe
one element or
feature's relationship to another element(s) or feature(s) as illustrated in
the figures. It will be
understood that the spatially relative terms are intended to encompass
different orientations of
the device in use or operation in addition to the orientation depicted in the
figures. For
example, if the device in the figures is turned over, elements described as
"under" or
"beneath" other elements or features would then be oriented "over" the other
elements or
features. Thus, the exemplary term "under" can encompass both an orientation
of over and
under. The device may be otherwise oriented (rotated 90 degrees or at other
orientations) and
the spatially relative descriptors used herein interpreted accordingly.
[0017] Well-known functions or constructions may not be described in detail
for brevity
and/or clarity.
[0018] Turning now more particularly to the drawings, Figures 1 and 2 are
generally
diagrammatic drawings of an apparatus 10 for high-speed spun-bond production
for a non-
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woven web of material. For purposes of this discussion, the term "web" is
being used to
designate the non-woven fabric which is being produced by the high-speed spun-
bond
apparatus. This is to be distinguished from the sieve belt or fabric or
continuous endless belt
or seamed belt on which the web is formed as referenced in the aforesaid U.S.
Patent No.
5,814,349. The fabric as disclosed herein equates to the aforesaid belt. In
this regard, Figures
1 and 2 are shown as merely representative of a spun-bond apparatus and should
not be
considered exclusive to the present invention.
[0019] Turning now to Figure 3, a fabric 20 that can be employed in the
apparatus of
Figures 1 and 2 is illustrated therein. The fabric 20 includes MD yarns 22,
24, 26, 28, 30 and
CMD yarns 40a, 40b, 42a, 42b and 44a, 44b that are interwoven with the MD
yarns. The
MD yarns and CMD yarns are woven in a plain weave pattern (i.e., an "over
1/under 1"
repeating pattern), with the exception that the CMD yarns are woven with the
MD yarns in
pairs, such that CMD yarns of the same pair follow the same weaving sequence.
For
example, CMD yarns 40a, 40b both pass under MD yarn 22, over MD yarn 24, under
MD
yarn 26, over MD yarn 28, and under MD yarn 30. The same pairing occurs for
the other
CMD yarns as they interweave with the MD yarns.
[0020] The yarns comprising the fabric 20 typically comprise monofilaments,
usually
round monofilaments. Some of the yarns in either the MD and/or CMD may be
static
dissipative yarns, typically with a copper sulfide or carbon coating. In some
embodiments
the yarns of a yarn pair may be different yarns; for example, one yarn of a
pair may have a
different diameter than the other yarn of the pair or may be formed of a
different material.
[0021] Adjacent round CMD yarns can create a distinct shape which guides
air drawn
through the fabric 20 in an advantageous manner for the web forming process.
Potential
advantages may include reduced air leakage, reduced air disturbances, and
improved web
hold-down effect. Also, adjacent round CMD yarns can create convex contact
areas with the
web whereby the contact surface is interrupted (as, for example, area 50 in
Figure 3). This
may facilitate removal of dirt and molten drops of polymer left over from the
web forming
process.
[0022] The illustrated weave pattern of the fabric 20 may vary. An
alternative exemplary
weave pattern is shown in Figure 4, which illustrates a fabric 120. The fabric
120 includes
MD yarns 122, 124, 126, 128, single bottom CMD yarns 130, 134, 138, 142, and
paired top
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CMD yarns 132a, 132b, 136a, 136b, 140a, 140b, 144a, 144b, As can be seen in
Figure 4,
the MD yarns are interwoven with the CMD yarns such that each MD yarn passes
over two
adjacent single bottom CMD yarns and one pair of paired top CMD yarns, then
under two
adjacent single bottom CMD yarns and three pairs of paired top CMD yams. For
example,
MD yarn 122 passes over adjacent single bottom CMD yarns 130 and 134 as well
as paired
top CMD yarns 132a, 132b, then passes under adjacent single bottom CMD yarns
138, 142
and paired top CMD yarns 136a, 136b, 140a, 140b, 144a, 144b. The result is a
fabric in
which single bottom CMD yarns alternate with paired top CMD yams within the
weave. As
illustrated in Figure 4, in some embodiments the single CMD yarns may be of a
different
size and/or material type than the paired CMD yarns,
[0023] Modifications of the fabric 120 are shown in Figures 5 and 6, Figure
5 illustrates
a fabric 120' which is identical to the fabric 120 with the exception that the
top CMD yarns
132a', 132b'-144a'-144b' within a pair are of different sizes. As mentioned
above, the yarns
of the pair may also be formed of different materials. Figure 6 illustrates a
fabric 120" that
is identical to the fabric 120 with the exception that the paired top CMD
yarns are replaced
with a trio of top CMD yarns (e.g,, CMD yarns 132a", 132b"). Thus, it can be
seen that in
some embodiments, the paired yarns may be replaced with three or more yams
that weave in
the same sequence,
[0024] Those of skill in this art will appreciate that although a spun-bond
apparatus is
shown herein, the fabrics 20, 120, 120', 120" may be equally suited for the
formation of a
non-woven web via another manufacturing technique, such as an air-laid
technique,
[0025] The foregoing is illustrative of the present invention and is not to
be construed as
limiting thereof. Although exemplary embodiments of this invention have been
described,
those skilled in the art will readily appreciate that many modifications are
possible in the
exemplary embodiments without materially departing from the novel teachings
and
advantages of this invention. Accordingly,' all such modifications are
intended to be included
within the scope of this invention as recited in the claims. The invention is
defined by the
following claims.
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