Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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NONWOVEN FAB~JP.S_.,.ARTICLES INCLUDING NONWOVEN FABRICS, ANU
METHODS OF MAKING NONWOVEN FABRICS
CROSS-REFERENCE TO RELATED APPLICATION
This application claims priority to U.S. provisional application entitled,
"Bulky/Extensible Fabric," having serial number 60/723,197, filed on October
3rd,
2005, which is entirely incorporated herein by reference.
FIELD OF THE INVENTION(S)
The present disclosure relates to nonwoven fabrics in general and nonwoven
fabrics that exhibit higher bulk properties.
BACKGROUND
The requirements of nonwoven fabrics used in applications concerned with
hygiene, medical fabrics, wipes, and the like continue to grow. Moreover,
utility,
economy, and aesthetic qualities often must be met simultaneously. The market
continues to expand for polyolefin fibers and items made therefrom having
enhanced
properties and improved softness or bulk.
The production of polymeric fibers for nonwoven materials usually involves
the use of a mix of at least one _polymer with nominal amounts of additives,
such as
stabilizers, pigments, antacids and the like. The mix is melt extruded and
processed
into fibers and fibrous products using conventional commercial processes.
Nonwoven fabrics can be produced by making a web, and then thermally bonding
the fibers together. For example, staple fibers are converted into nonwoven
fabrics
using, for example, a carding machine, and the carded fabric is thermally
bonded.
The thermal bonding can be achieved using various heating techniques,
including
heating with heated rollers, hot air, and heating through the use of
ultrasonic
welding.
Fibers can also be produced and consolidated into nonwovens in various
other manners. For example, the fibers and nonwovens can be made by the
spunbonding or meltblowing processes or a combination thereof. Also,
consolidation
processes can include needlepunching, through-air thermal bonding, ultrasonic
welding and hydroentangling.
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ManX nonwoven fabrics, such as conventional thermally bonded nonwoven
.
fabrics, do not exhibit sufficient bulk or extensibility for certain end uses.
Therefore,
a need exists for nonwoven fabrics that exhibit sufficient bulk and
extensibility.
SUMMARY
Briefly described, embodiments of this disclosure include nonwoven fabrics,
methods of making nonwoven fabrics, articles including nonwoven fabric, and
the
like.
An embodiment of a fabric, among others, includes a nonwoven fabric having
at least a first fiber and a second fiber. The first fiber has a first fiber
shrinkage
percent and the second fiber has a second fiber shrinkage percent. The
difference
in the first fiber shrinkage percent and the second fiber shrinkage percent is
at least
8%.
An embodiment of a fabric, among others, includes a nonwoven fabric having
at least a first domain of shrinkage and a second domain of shrinkage. The
first
domain and the second domain define differentiated domains of shrinkage. The
nonwoven fabric includes at least a first fiber and a first shrinking fiber.
An embodiment of an article, among others, includes a nonwoven fabric as
described herein, where the article is selected from a cleaning wipe, a
diaper, a
textile stretch component, an incontinence care product, a feminine care
product,
and a filter.
An embodiment of a method of forming a nonwoven fabric, among others,
includes: providing a nonwoven fabric including a first fiber and a second
fiber,
wherein the first fiber has a first fiber shrinkage percent and the second
fiber has a
second fiber shrinkage percent, wherein the difference in the first fiber
shrinkage
percent and the second fiber shrinkage percent is at least 8%; forming at
least a first
domain of shrinkage and a second domain of shrinkage, wherein the first domain
and the second domain define differentiated domains of shrinkage, wherein a
portion
of the first fiber and a portion of the second fiber in the first domain are
bonded; and
heating the nonwoven fabric to an activation temperature of the second fiber,
wherein the second fiber shrinks and causes the first fiber to gather to
increase the
thickness of the nonwoven fabric in the second domain.
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,Anem4odime,n#,õQf a,RX,pethod of forming a nonwoven fabric, among others,
includes: providing a nonwoven fabric including a first fiber and a second
fiber,
wherein the first fiber has a first fiber shrinkage percent and the second
fiber has a
second fiber shrinkage percent, wherein the difference in the first fiber
shrinkage
percent and the second fiber shrinkage percent is at least 8%; and heating the
nonwoven fabric to an activation temperature of the second fiber, wherein the
second fiber shrinks and causes the first fiber to gather to increase the
thickness of
the nonwoven fabric.
BRIEF DESCRIPTION OF THE DRAWINGS
Many aspects of the disclosure can be better understood with reference to the
following drawings. The components in the drawings are not necessarily to
scale,
emphasis instead being,placed upon clearly illustrating the principles of the
present
disclosure. Moreover, in the drawings, like reference numerals designate
corresponding parts throughout the several views.
FIGS. 1A and 1 B illustrate graphs of a shrinking fiber (FIG. 1A) and a non-
shrinking fiber (FIG. I B).
FIGS. 2A and 2B illustrate photomicrographs of cross sectional views of
nonwoven webs of the present disclosure. FIG. 2A illustrates an embodiment of
a
nonwoven web used for producing the bulky nonwoven fabric that has not been
activated by a thermal bulking step. FIG. 2B illustrates the nonwoven web that
has
been activated to produce the bulky nonwoven web.
FIG. 3 illustrates Table 1, which describes a number of embodiments of
nonwoven fabrics of the present disclosure.
DETAILED DESCRIPTION
Embodiments of the present disclosure will employ, unless otherwise
indicated, techniques of textiles, chemistry, and the like, which are within
the skill of
the art. Such techniques are explained fully in the literature.
The following examples are put forth so as to provide those of ordinary skill
in
the art with a complete disclosure and description of how to perform the
methods
and use the compositions and compounds disclosed and claimed herein. Efforts
have been made to ensure accuracy with respect to numbers (e.g., amounts,
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tem,neratu,re,,..~õerrors and deviations should be accountea tor. uniess
indicated otherwise, parts are parts by weight, temperature is in C, and
pressure is
at or near atmospheric. Standard temperature and pressure are defined as 25 C
and I atmosphere.
Before the embodiments of the present disclosure are described in detail, it
is
to be understood that, unless otherwise indicated, the present disclosure is
not
limited to particular materials, reagents, reaction materials, manufacturing
processes, or the like, as such can vary. It is also to be understood that the
terminology used herein is for purposes of describing particular embodiments
only,
and is not intended to be limiting. It is also possible in the present
disclosure that
steps can be executed in different sequence where this is logically possible.
It must be noted that, as used in the specification and the appended claims,
the singular forms "a," "an," and "the" include plural referents unless the
context
clearly dictates otherwise. Thus, for example, reference to "a support"
includes a
plurality of supports. In this specification and in the claims that follow,
reference will
be made to a number of terms that shall be defined to have the following
meanings
unless a contrary intention is apparent.
It should be noted that ratios, concentrations, amounts, and other numerical
data may be expressed herein in a range format. It is to be understood that
such a
range format is used for convenience and brevity, and thus, should be
interpreted in
a flexible manner to include not only the numerical values explicitly recited
as the
limits of the range, but also to include all the individual numerical values
or sub-
ranges encompassed within that range as if each numerical value and sub-range
is
explicitly recited. To illustrate, a concentration range of "about 0.1% to 5%"
should
be interpreted to include not only the explicitly recited concentration of
about 0.1 wt%
to about 5 wt%, but also include individual concentrations (e.g., 1%, 2%, 3%,
and
4%) and the sub-ranges (e.g., 0.5%, 1.1%, 2.2%, 3.3%, and 4.4%) within the
indicated range.
Definitions
In describing and claiming the disclosed subject matter, the following
terminology will be used in accordance with the definitions set forth below.
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The term "n,cnuvQU,e,n,','.,.fabric, sheet, or web as used herein means a
textiie
structure of individual fibers, filaments, or threads that are directionally
or randomly
oriented and interact with one another by friction, and/or cohesion, and/or
adhesion,
as opposed to a regular pattern of mechanically inter-engaged fibers (e.g., it
is not a
woven or knitted fabric). Examples of nonwoven fabrics and webs include, but
are
not limited to, carded webs, spunbond continuous filament webs, meltblown
webs,
air-laid webs, and wet-laid webs. Suitable bonding methods include thermal
bonding, chemical or solvent bonding, resin bonding, mechanical needling,
hydraulic
needling, stitch-bonding, combinations thereof, and the like. An illustrative,
nonlimiting embodiment of the present disclosure includes carded thermal bond
nonwoven fabrics.
The terms "bonded" or "bonding" are used herein to describe areas of a
nonwoven fabric having inter-fiber bonding or entanglement beyond which occurs
in
nonwoven fabrics.
The term "bulk" or "loft" is used as an indication of the bulk specific volume
of
the nonwoven for a given areal density. The terms "bulk" and "loft" are
generally
used interchangeably. As such, the term "bulk" is used to describe both "bulk"
and
"loft". Bulk specific volume can be obtained by dividing the bulk volume of a
nonwoven sample by its mass. A bulky nonwoven is relatively less dense rather
than compressed. Areal density is mass per unit area and is generally reported
as
grams per square meter (gsm). Areal density is often referred to as "basis
weight"
and the terms are equivalent.
The terms "shrink", "shrinkage", "shrinking" as used in reference to fibers
refers to the reduction in the length of the fiber as measured by
thermomechanical
analysis (TMA). A typical instrument for measuring shrinkage is the Model
Q400,
made by TA Instruments. A discussion of shrinkage can be found in "Thermal
Characterization of Polymeric Materials", Academic Press (1981) pp. 736-743,
which
is incorporated herein by reference. FIGS. 1A and 1 B illustrate graphs of a
shrinking
fiber and a non-shrinking fiber.
The term "extensibility" as used in reference to nonwoven fabrics refers to
the
ability of the fabric to exhibit large elongation upon application of stress.
The term "elasticity" refers to the ability of an extensible nonwoven to
return
essentially to its pre-stressed state upon release of the stress.
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The,terKp ",aQtiuq,4o,rl'õ,refers to a process used to increase bulk
subsequent to
the formation of the nonwoven fabric.
General Discussion
Briefly described, embodiments of this disclosure include nonwoven fabrics,
methods of making nonwoven fabrics, articles including nonwoven fabric, and
the
like. The nonwoven fabric of the present disclosure have improved effects
(e.g.,
increased bulk, adjustable textural feel, improved foreign particle
entrapment,
increased areal density, and the like) as compared to other nonwoven fabrics.
In addition, the nonwoven fabrics are highly extensible relative to other
nonwoven fabrics. The degree of extensibility is dependent on the activation
temperature, fabric construction, bonding pattern, and the like. Under some
conditions, a degree of elasticity may also be present which in turn, is
dependent on
the activation temperature, fabric construction, bonding pattern, and the
like.
The nonwoven fabrics can be included in articles such as, but not limited to,
cleaning wipes, diapers, textile stretch components, incontinence care
products,
feminine care products, filters, felts, and the like. The nonwoven fabrics can
be used
in articles in the landing zones, in the acquisition/distribution layers,
stretch ears,
topsheet, backsheet, and the like.
The nonwoven fabrics can be tailored to have a pre-determined bulk, a certain
softness/harshness, areal density, and the like, by selecting components of
the
nonwoven fabric (e.g., fibers), parameters for treating the nonwoven fabric,
bonding
patterns, and the like. In other words, the nonwoven fabric can be designed
for
many applications such as, but not limited to, cleaning surfaces (e.g., soft
surface or
rough surface); acquiring, distributing or delivering liquids; adding comfort,
filtering
liquids, gases or powders; acoustic attenuation; and/or combinations thereof.
In general, the nonwoven fabric includes one or more nonwoven layer(s),
where the nonwoven layer(s) includes at least a first fiber and a second
fiber. The
first fiber and the second fiber have different levels or rates of shrinkage
under
certain conditions (e.g., activation temperature and time to shrink the
fibers, and
degree of constraints against dimensional change). Upon activation, the second
fiber shrinks, and as the second fiber shrinks in size it pulls some first
fibers with it to
produce one or more areas of increased bulk.
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Thp,lp,gpwgu~~,,f~~;~r~c~~an increase in bulk by about 20 to 500 %, about 3U
to
450 %, and about 50 to 350 % relative to the bulk of the unactivated nonwoven
fabric. The nonwoven fabric can increase in thickness by about 30 to 650 %,
about
45 to 550 %, and about 60 to 500 % relative to the thickness of the
unactivated
nonwoven fabric.
The activation conditions (e.g., temperature and time or degree of constraints
against dimensional change) applied to the nonwoven fabric depend, at least in
part,
upon the fiber composition, the amount of shrinkage desired, the textural feel
(e.g.,
from soft to rough) of the nonwoven fabric desired, the amount of bulkiness
desired,
the level of extensibility and elasticity desired, and the like. The
activation of the
fibers in nonwoven fabric is typically performed while the fibers are in a
relaxed state
(e.g., little or no tension in the machine direction or the cross direction
relative to the
force generated by the shrinking fibers). In another embodiment, the shrinkage
can
be controlled in the machine direction and/or the cross direction using
controlled
dimensional change processes such as, but not limited to, tenter frame
processes,
sanforizing processes, creping processes, allied processes, and combinations
thereof. The activation conditions, the fiber types, the number of nonwoven
layers in
the nonwoven fabric, and the like, are selected to produce desired effects
(e.g., bulk,
textural feel, and combinations thereof). The shrinkage can also be controlled
in the
machine direction and/or the cross direction by controlling the_ ratio of the
number of
fibers oriented in the machine direction to the number of fibers oriented in
the cross
direction.
In general, the activation temperature (e.g., of the oven or other heat
source)
of the second fiber is below the melting point of the polymer. Therefore, the
activation conditions are dependent, at least in part, upon the type of
polymeric fibers
used as the second fiber. For example, the activation temperature when the
second
fiber is polypropylene is about 125 C to 150 C for a time of about 10 seconds
to 1
minute. The activation temperature can be achieved by processes such as, but
not
limited to, heated gas, infrared heating sources, ovens, and the like. One
skilled in
the art can modify one or both of the temperature and time conditions to
achieve the
desired results.
In another embodiment, the nonwoven fabric includes a pattern of
differentiated domains of shrinkage. The differentiated domains of shrinkage
are
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~e~~I~neWO 2007/041620 at#ern (described below) of first domains and
PCT/US2006/038747
G~ domains. The first domain of shrinkage is defined as the area of the
nonwoven
fabric that is bonded (e.g., a portion of the first fibers and the second
fibers are
bonded to one another), while the second domain of shrinkage is defined as the
area
of the nonwoven fabric that is not bonded. The shrinkage of the first domain
under
activation conditions is very small relative to the shrinkage of the second
domain
under activation conditions.
The first fibers and the second fibers are included in both the first domains
and the second domains and portions of fibers may be in both domains. As
mentioned above, the first fiber and the second fiber have different rates of
shrinkage under certain conditions (e.g., activation temperature and time to
shrink
the fibers). Exposing the nonwoven fabric to activation conditions causes the
second fibers to shrink in length. As the second fibers shrink, the second
fibers pull
the first fibers along with them. The shrinkage of the second fibers causes
the first
fibers to gather in regions of the second domain, which can increase bulk of
the
nonwoven fabric. The increase in bulk is enhanced when the nonwoven fabric is
pattern bonded so that the bonded regions prevent disentanglement of the first
fibers
and the second fibers.
In an exemplary embodiment, a nonwoven fabric includes a single nonwoven
layer including a mixture of first and second fibers. The nonwoven fabric has
a
pattern of differentiated domains of shrinkage cause by bonding first domains
of the
nonwoven fabric (first bonding domain), and leaving other portions unbonded
(second bonding domain). In an embodiment, the first fiber is a non-shrinking
fiber
(defined below) and the second fiber is a shrinking fiber. The non-shrinking
fiber and
the shrinking fiber have different rates of shrinkage under certain activation
conditions. The nonwoven fabric is exposed to activation conditions that cause
the
shrinking fiber to shrink, while the non-shrinking fiber does not
substantially shrink
(as described below). The shrinking fiber causes the non-shrinking fibers to
gather
in the second domains and increase bulk of the nonwoven fabric.
In another exemplary embodiment, a nonwoven fabric includes a first
nonwoven layer including a first fiber, a second nonwoven layer including a
second
fiber, and a third nonwoven layer including the first fiber. The nonwoven
fabric has a
pattern of differentiated domains of shrinkage caused by bonding first domains
of the
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,,noawouo,n,fabr.ic.,:(ehq~,Qn dog the first, the second, and the third
nonwoven layers),
and leaving other portions unbonded (second bonding domain). In an embodiment,
the first fiber is a non-shrinking fiber (defined below) and the second fiber
is a
shrinking fiber. The non-shrinking fiber and the shrinking fiber have
different
degrees of shrinkage under certain activation conditions. The nonwoven fabric
is
exposed to activation conditions that cause the shrinking fiber to shrink,
while the
non-shrinking fiber does not substantially shrink (as described below). The
shrinking
fiber in the second nonwoven layer causes the non-shrinking fibers in the
first and
third nonwoven layers to gather in the second domains and increase bulk of the
nonwoven fabric.
Nonwoven Fabric
As mentioned above, the nonwoven fabric includes, but is not limited to, at
least a first fiber and a second fiber. In an embodiment, the nonwoven fabric
includes a first fiber, a second fiber, and a third fiber. Other embodiments
may
include four or more fibers (e.g., a first fiber, a second fiber, ... and
a"nt"" fiber).
Details about the fibers are described herein.
The nonwoven fabric can include one or more nonwoven layers (e.g., a first
nonwoven layer, a second nonwoven layer, ... and a"nt"" nonwoven layer).
Embodiments of the present disclosure can include nonwoven fabrics having 1,
2, 3,
4, 5, 6, 7, 8, 9, 10, or more, nonwoven layers. Each nonwoven layer can
include, but
is not limited to, a first.fiber and/or a second fiber as well as additional
fibers. In an
embodiment, the nonwoven layers alternate between a nonwoven layer including a
first fiber and a nonwoven layer including a second fiber. In an embodiment,
the
nonwoven layers alternate between a nonwoven layer including a non-shrinkable
fiber and a nonwoven layer including a shrinkable fiber. Representative
embodiments of nonwoven fabrics are described herein, while other embodiments
having at least the first fiber and the second fiber that have different
levels or rates of
shrinkage are also included within the scope of the present disclosure.
In one embodiment, the nonwoven fabric includes one nonwoven layer. The
nonwoven layer includes at least the first fiber and the second fiber. In
another
embodiment, the nonwoven layer includes the first fiber, the second fiber, and
one or
more additional fibers.
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in an emaodiment, the nonwoven fabric includes a first nonwoven layer and a
... .,,~.. .,.,,., ...,;. .. .m... ...,.,. r.
second nonwoven layer. The first nonwoven layer is disposed on the second
nonwoven layer. In one embodiment, the first nonwoven layer is made of the
first
fiber and the second nonwoven layer is made of the second fiber. In another
embodiment, the first nonwoven layer is made of the first fiber and the second
fiber
and the second nonwoven layer is made of the first fiber, the second fiber, a
third
fiber, or any combination thereof.
In an embodiment, the nonwoven fabric includes a first nonwoven layer, a
second nonwoven layer, and a third nonwoven layer. In one embodiment, the
first
nonwoven layer and the third nonwoven layer are made of the first fiber, while
the
second nonwoven layer is made of the second fiber. In another embodiment, the
first nonwoven layer is made of a first fiber, the second nonwoven layer is
made of a
second fiber, and the third nonwoven layer is made of a third fiber. In
another
embodiment, any of the nonwoven layers described in the previous embodiments
can include combinations of the first fiber, the second fiber, the third
fiber, and/or one
or more other fibers.
In each of the embodiments of the nonwoven fabrics, the types of fibers and
the combination of fibers (e.g., in the same or different layers) can be
selected
according to the particular characteristics (e.g., bulk of the nonwoven
fabric, texture
of one or more surfaces of the nonwoven fabric, and the like) desired for a
particular
nonwoven fabric. It should be noted that conditions under which the nonwoven
fabric is bonded and activated as well as the pattern of differentiated
domains of
shrinkage could be used to tailor the characteristics of the nonwoven fabric.
The nonwoven fabrics can be formed using one or more processes. The
nonwoven fabrics can be formed using processes such as, but not limited to,
carded
thermal bond, carded spun lace, carded through-air bond, wet laying, carded
needlepunch, spun bond, air laying, melt blowing, and combinations thereof,
each of
which have the meaning typically attributed to them in the art. In an
embodiment,
the nonwoven fabrics are formed using carded thermal bond processes.
Additional
details regarding embodiments of the nonwoven fabric are described in the
examples.
As mentioned above, the nonwoven fabrics have a pattern of differentiated
domains of shrinkage. The patterns of differentiated domains of shrinkage can
be
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õmade, wsinn,.,mow~,,,~~~~~r~~,,(e.g., which can be provided by any nonwoven
roll
maunfacturer, such as Andritz Kusters GmbH & Co. KG (Germany), and the like)
or
by using other patterns as well. The patterns can be made using processes such
as,
calendar bonding with patterned rolls, patterning jets in hydroentangling,
patterned
needlepunching, and the like, and combinations thereof.
After the fibers of the nonwoven fabric have been subject to activation
conditions to form the bulk, the nonwoven fabric can be post treated. The post
treatments include, but are not limited to, corona, plasma, soil release,
flame
retardant, anti-microbial, softener, and the like, and combinations thereof.
Fibers
The first fiber can include, but is not limited to, natural fibers or
naturally
derived fibers (hereinafter referred to as "natural fiber"), thermoplastic
polymer fibers,
and thermoset and high performance polymer fibers. The second fiber can
include,
but is not limited to, polymeric fibers (e.g., thermoplastic polymer fibers).
Additional
fibers (e.g., the third fiber and so on) can include, but are not limited to,
natural
fibers, polymeric fibers, and thermoset and high performance fibers. The first
fiber
and the second fiber can include, but are not limited to, polymer blend
fibers, bi-
component fibers (e.g., a fiber comprising of two different polymers of
differing
chemical constitution/properties), and bi-constituent fibers (e.g., fiber
composed of
two or more dissimilar fibers combined before the extrusion process). The
first fiber
and the second fiber can be made by the same process or by a different
process.
The natural fibers can include, but are not limited to, plant fibers,
vegetable
fibers, and animal/insect fibers. The natural fibers are derived from fibers
of animal
coats and silkworm cocoons, and fiber of plants seeds, leaves, stems, and the
like.
Exemplar natural fibers include, but are not limited to, wool, cotton, silk,
linen, ramie,
hemp, and jute. In an embodiment, the natural fiber includes, but is not
limited to,
rayon, Lyoceli, polylactic acid, soybean protein,and combinations thereof.
The thermoset and high performance polymers can include, but are not
limited to, carbon fibers, glass fibers, polyacrylonitrile fibers, polyvinyl
alcohol fibers,
polyaramid fibers, combinations thereof, and the like.
The polymeric fibers and thermoplastic polymer fibers can be made of
copolymers, terpolymers, and higher polymers. It should be noted that the term
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õcq,po,l~rmpr,'p in,cludes two o more monomers in the same polymer chain. I ne
polymeric fibers and thermoplastic polymer fibers can be mono-component or
multi-
component. The polymer fibers and thermoplastic polymer fibers can be polymer
blends.
The polymeric fibers and thermoplastic polymer fibers can include
thermoplastic polymers such as, but not limited to, polymer blends or
copolymers of
each of the following: polyolefins, polyesters, polypropylene, polyethylene,
polybutene, polymethylpentene, ethylene-propylene, polyamides, polyurethanes,
polyvinyl acetates, ethylene vinyl acetates, polyetheresters,
polyetherurethane,
polyvinyl acetates, and combinations thereof.
In an embodiment, the polymeric fibers and thermoplastic polymer fibers can
be made of materials such as, but not limited to, polymer blends or copolymers
of
each of the following: polyolefins, polyesters, polyamides, polyvinyl
acetates,
polyacrylonitriles, polyvinyl alcohol and ethylene acrylic acid, combinations
thereof.
In an embodiment, the polymeric fibers and thermoplastic polymer fibers can
include spinnable polymeric materials such as polyolefins and blends
comprising
'polyolefins (e.g., See U.S. Pat. Nos. 5,733,646, 5,888,438, 5,431,994,
5,318,735,
5,281,378, 5,882,562 and 5,985,193, the disclosures of which are incorporated
by
reference herein in their entireties).
In an embodiment, the polymer is a polypropylene or a blend including a
polypropylene. The polypropylene can include polypropylenes that are
spinnable.
The polypropylene can be atactic, heterotactic, syndiotactic, isotactic and
stereoblock polypropylene--including partially and fully isotactic, or at
least
substantially fully isotactic--polypropylenes.
The terms polymers (e.g., polyolefins, polypropylene, polyethylene, and the
like) include homopolymers and heteropolymers (e.g., copolymers and
terpolymers),
and mixtures thereof (including blends and alloys produced by mixing separate
batches or forming a blend in situ). For example, the polymer can include
copolymers of olefins, such as propylene, and these copolymers can contain
various
components.
As used herein, polypropylene is utilized in its ordinary commercial meaning
wherein the polypropylene is a substantially linear molecule. Further, as used
herein, a polypropylene composition includes a material that contains a broad
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ht;d,i~~r.jho~l~)qt~;,,of linear polypropylene to enable the obtaining ot
tiaers
and filaments that have superior spinning and thermal bonding characteristics.
Conventional polymeric fibers include polypropylene staple fibers. These
fibers may also include bicomponent fibers containing various combinations of
polypropylene or a combination of other polymeric materials such as
polyethylene. A
polymeric fiber of particular interest conventionally used in producing
nonwoven
webs or fabrics is a high thermal bond strength spun melt fiber described in
US
Patent No. 5,281,378, incorporated herein by reference in its entirety.
In an embodiment, the polypropylene can have an average molecular weight
from about 3x105 to about 5x105, a spun melt flow rate, MFR (determined
according
to ASTM D-1238-86 (condition L; 230/2.16), which is incorporated by reference
herein in its entirety) of about 7 to about 50 dg/min, and/or a spin
temperature within
the range of about 220 to 315 C, about 240 to 300 C, and about 255-285 C.
In an embodiment, the polypropylene can be linear or branched, such as
disclosed by U.S. Pat. No. 4,626,467, which is incorporated by reference
herein in its
entirety, and is preferably linear. In addition, the polypropylene to be made
into
fibers can include polypropylene compositions as taught in U.S. Pat. Nos.
5,629,080,
5,733,646 and 5,888,438 and European Patent Application No. 0 552 013, which
are
incorporated by reference herein in their entireties. Furthermore, polymer
blends
such as disclosed in U.S. Pat. No. 5,882,562, and European Patent Application
No.
0 719 879, which are incorporated by reference herein in their entireties, can
also be
utilized.
The first and the second fiber can have the same or a different size and/or
cross-section. The first fiber and the second fiber can have a denier of about
0.1 to
50 denier per filament. The first fiber and the second fiber can be continuous
or
staple, with a length of about 1 mm to 250 mm.
The melt flow rate, MFR, is dependent upon the type of polymer the fiber is
made of, and, thus, the MFR can vary depending on which fibers are selected
for
each particular application. In an embodiment, the first polyolefin fiber and
the
second polyolefin fiber can have a melt flow rate (determined according to
ASTM D-
1238-86 (condition L; 230/2.16), which is incorporated by reference herein in
its
entirety) of about 10 to 400 dg/min, but the MFR depends on the chemical
composition of the fibers.
13
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WO 2007/041620 PCT/US2006/038747
an embodimept,thg first fiber has a first fiber shrinkage percentage
(measured using TMA) and the second fiber has a second fiber shrinkage
percentage, where the difference in the first fiber shrinkage percentage and
the
second fiber shrinkage percentage is at least about 8%, is at least about 9%,
is at
least about 10%, is at least about 12%, or is at least about 15%. It should be
noted
that in an embodiment the first fiber might not shrink and increase in length.
In an embodiment, the first fiber has a first fiber shrinkage of less than
about
10%, less than about 8%, less than about 6%, less than about 3%, or less than
about 1%, where each is measured at the same conditions (e.g., a temperature
near
the activation temperature of the fiber of interest), and may be referred to
as the
"non-shrinking fiber".
The non-shrinking fiber can include, but is not limited to, polypropylene,
polyester, and combinations thereof. In an embodiment where the non-shrinking
fiber is made of polypropylene, the fiber shrinkage is less than about 10 % at
about
140 C. It should be noted that in an embodiment the non-shrinking fiber might
not
shrink and increase in length.
The second fiber has a fiber shrinkage of greater than about 9%, greater than
about 10%, greater than about 11 %, greater than about 12%, greater than about
13%, and may be referred to as the "shrinking fiber".
The shrinking fiber can include, but is not limited to, polypropylene,
polyester,
polyethylene, and bicomponent fibers made therefrom. In an embodiment where
the
shrinking fiber is made of polypropylene, the fiber shrinkage is about 9 to 40
% at
140 C.
The production of polymeric fibers for nonwoven materials can include the use
of a mix of at least one polymer with nominal amounts of additives, such as,
but not
limited to, antioxidants, stabilizers, pigments, antacids, process aids and
the like.
Thus, the polymer or polymer blend can include various additives, such as, but
not
limited to, melt stabilizers, antioxidants, pigments, antacids, antistatic
aids,
emulsifiers, preservatives, and process aids. The types, identities, and
amounts of
additives can be determined by those of ordinary skill in the art upon
consideration of
requirements of the product.
Various finishes can be applied to the fibers to maintain or render them
hydrophilic or hydrophobic. Finish compositions including hydrophilic finishes
or
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WO 2007/041620 PCT/US2006/038747
hy,d.r,op~q.hi.c,,fj,nish,esõMgayelected by those of ordinary skill in the art
according to
the characteristics of the apparatus and the needs of the product being
manufactured.
Also, one or more components can be included in the polymer blend for
modifying the surface properties of the fiber, such as to provide the fiber
with repeat
wettability, or to prevent or reduce build-up of static electricity.
Hydrophobic finish
compositions preferably include antistatic agents. Hydrophilic finishes may
also
include such agents.
Additional details regarding embodiments of the nonwoven fabric are
described in the examples.
Examples
Now having described the embodiments of the present disclosure, in general,
the Examples describe some additional embodiments of the present disclosure.
While embodiments of present disclosure are described in connection with the
Examples and the corresponding text and figures, there is no intent to iimit
embodiments of the present disclosure to these descriptions. On the contrary,
the
intent is to cover all alternatives, modifications, and equivalents included
within the
spirit and scope of embodiments of the present disclosure.
Table 1, as shown in FIG. 3, illustrates some exemplar embodiments of
nonwoven fabrics A-G with combinations of fibers NS1, NS2, NS3, NS4, NS5, S1,
and
S2. The examples provide a number of embodiments ranging in fabric weight,
construction, fiber composition, fiber type, the number of nonwoven layers,
method of
fabric formation, and the like.
FIGS. 2A and 2B illustrate photomicrographs of cross sectional views of
nonwoven fabric of A in Table 1. FIG. 2A illustrates an embodiment of a
nonwoven
fabric used for producing the bulky nonwoven fabric that has not been
activated by a
thermal bulking step. FIG. 2B illustrates the nonwoven web that has been
activated
to produce the bulky nonwoven web
It should be emphasized that the above-described embodiments of the
present disclosure are merely possible examples of implementations, and are
set
forth only for a clear understanding of the principles of the disclosure. Many
variations and modifications may be made to the above-described embodiments of
CA 02624808 2008-04-03
WO 2007/041620 PCT/US2006/038747
th,e,rc~isc~g~,~re vyithqut depart,ing substantially from the spirit and
principies oT tne
disclosure. All such modifications and variations are intended to be included
herein
within the scope of this disclosure and protected by the following claims.
16
