U.S. patent application number 17/587362 was filed with the patent office on 2022-05-12 for liquid barrier nonwoven fabrics with ribbon-shaped fibers.
The applicant listed for this patent is AVINTIV Specialty Materials Inc.. Invention is credited to Carlton F. Dwiggins, Pierre D. Grondin, Ralph A. Moody, III, John F. Steffen.
Application Number | 20220145503 17/587362 |
Document ID | / |
Family ID | 1000006107924 |
Filed Date | 2022-05-12 |
United States Patent
Application |
20220145503 |
Kind Code |
A1 |
Dwiggins; Carlton F. ; et
al. |
May 12, 2022 |
Liquid Barrier Nonwoven Fabrics with Ribbon-Shaped Fibers
Abstract
A nonwoven fabric useful as a component in a personal hygiene
product and a nonwoven personal hygiene component, which is
substantially free or free of non-ribbon shaped (e.g.,
round-shaped) spunbond fibers and includes a meltblown layer
between and in direct contact with ribbon-shaped spunbond layers.
The meltblown layer has a basis weight of at least about 0.008 gsm
and not greater than about 5 gsm, and the nonwoven fabric or
component has a basis weight of at least about 8 gsm and not
greater than about 40 gsm, a pore size of less than or equal to
about 27 microns when measured at 10% of cumulative filter flow.
The nonwoven fabric also can have a low surface tension liquid
strike through flow of less than 0.9 ml per second, a ratio of low
surface tension liquid strike through flow to air permeability of
greater than or equal to about 0.016, or both. Personal hygiene
articles can incorporate the nonwoven fabric or component.
Inventors: |
Dwiggins; Carlton F.;
(Mooresville, NC) ; Grondin; Pierre D.;
(Mooresville, NC) ; Moody, III; Ralph A.;
(Mooresville, NC) ; Steffen; John F.; (Denver,
NC) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
AVINTIV Specialty Materials Inc. |
Charlotte |
NC |
US |
|
|
Family ID: |
1000006107924 |
Appl. No.: |
17/587362 |
Filed: |
January 28, 2022 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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13205268 |
Aug 8, 2011 |
11274384 |
|
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17587362 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
D04H 1/43912 20200501;
B32B 2555/02 20130101; D04H 1/43918 20200501; D04H 3/018 20130101;
B32B 5/26 20130101; B32B 2555/00 20130101; D04H 13/00 20130101;
B32B 2262/0253 20130101; B32B 5/022 20130101; B32B 2307/724
20130101 |
International
Class: |
D04H 13/00 20060101
D04H013/00; B32B 5/26 20060101 B32B005/26; D04H 3/018 20060101
D04H003/018; B32B 5/02 20060101 B32B005/02; D04H 1/4391 20060101
D04H001/4391 |
Claims
1-20. (canceled)
21. A method of forming a nonwoven fabric, comprising: (i)
providing or forming a first spunbond layer comprising a first
plurality of ribbon-shaped continuous filaments; (ii) directly
depositing a meltblown layer onto the first spunbond layer from a
die having a die-to-collector distance from about 110 mm to about
150 mm; (iii) depositing a second spunbond layer comprising a
second plurality of ribbon-shaped continuous filaments directly
onto the meltblown layer; and (iv) consolidating the first spunbond
layer, the meltblown layer, and the second spunbond layer together
to form the nonwoven fabric.
22. The method of claim 21, wherein the meltblown layer comprises
meltblown fibers in an amount of at least 0.1% by weight of the
nonwoven fabric and not greater than about 40% by weight of the
nonwoven fabric.
23. The method of claim 21, wherein the meltblown layer has a basis
weight no greater than 5 gsm.
24. The method of claim 21, wherein at least one of the first
spunbond layer, the second spunbond layer, and the meltblown layer
comprise polypropylene.
25. The method of claim 24, wherein each of the first spunbond
layer, the second spunbond layer, and the meltblown layer comprises
polypropylene.
26. The method of claim 21, wherein the nonwoven fabric contains
less than about 10% by weight non-ribbon shaped spunbond fibers,
and wherein the nonwoven fabric has a basis weight of at least
about 8 gsm and not greater than about 40 gsm.
27. The method of claim 21, wherein the meltblown layer consists of
(i) from 1% to 10% by weight of non-ribbon shaped meltblown fibers,
and (ii) ribbon-shaped meltblown fibers.
28. The method of claim 21, wherein the nonwoven fabric has a pore
size of about 14.5 microns to less than or equal to about 21
microns when measured at 10% of cumulative filter flow.
29. The method of claim 21, wherein the nonwoven fabric has a low
surface tension liquid strike through flow of less than 0.9 ml per
second, an air permeability of at least 10 m.sup.3/m.sup.2/min. and
a ratio of low surface tension liquid strike through flow to air
permeability of greater than or equal to 0.016 and less than or
equal to 0.021.
30. The method of claim 21, wherein at least one of the first
plurality of ribbon-shaped continuous filaments and the second
plurality of ribbon-shaped continuous filaments comprises fibers
having a cross-section with an aspect ratio of at least 2.5:1 and
no great than about 7:1.
31. The method of claim 21, wherein the depositing a meltblown
layer comprises depositing a first meltblown layer directly onto
the first spunbond layer from a first die having a first
die-to-collector distance from about 110 mm to about 150 mm and
depositing at least a second meltblown layer directly onto the
first meltblown layer from a second die having a second
die-to-collector distance from about 110 mm to about 150 mm.
32. The method of claim 21, wherein consolidating the first
spunbond layer, the meltblown layer, and the second spunbond layer
together to form the nonwoven fabric comprises a thermal bonding
operation.
33. The method of claim 32, wherein the thermal bonding operation
forms a plurality of discrete bond areas
34. A nonwoven fabric, comprising: a first spunbond layer
comprising a first plurality of ribbon-shaped continuous filaments;
a second spunbond layer comprising a second plurality of
ribbon-shaped continuous filaments; and a meltblown layer disposed
between the first spunbond layer and the second spunbond layer,
wherein said meltblown layer has a basis weight of not greater than
about 5 gsm; wherein the nonwoven fabric has a basis weight of at
least 8 gsm and not greater than about 40 gsm, a low surface
tension liquid strike through flow of less than 0.9 ml per second,
an air permeability of at least 10 m.sup.3/m.sup.2/min. and a ratio
of low surface tension liquid strike through flow to air
permeability of greater than or equal to 0.016 and less than or
equal to 0.021; wherein the meltblown layer has been deposited
directly onto the second ribbon-shaped spunbond layer from at least
one die having a die-to-collector distance from about 110 mm to
about 150 mm.
35. The nonwoven fabric of claim 34, wherein the nonwoven fabric
has a pore size of about 14.5 microns to less than or equal to
about 21 microns when measured at 10% of cumulative filter
flow.
36. The nonwoven fabric of claim 34, wherein at least one of the
first spunbond layer and second spunbond layer comprises fibers
having a cross-section with an aspect ratio of at least 2.5:1 and
no great than about 7:1.
37. The nonwoven fabric of claim 34, wherein the meltblown layer
consists of (i) from 1% to 10% by weight of non-ribbon shaped
meltblown fibers, and (ii) ribbon-shaped meltblown fibers
38. The nonwoven fabric of claim 34, wherein the meltblown layer
comprises multiple directly adjoining meltblown sub-layers.
39. The nonwoven fabric of claim 34, wherein the nonwoven fabric
contains less than about 10% by weight non-ribbon shaped spunbond
fibers.
40. The nonwoven fabric of claim 34, wherein the first spunbond
layer, the second spunbond layer, and the meltblown layer are
bonded together by a plurality of discrete bond areas.
Description
FIELD OF INVENTION
[0001] The present invention relates to fibrous nonwoven fabrics
that are useful as liquid barrier fabrics in personal hygiene
products, and, particularly, nonwoven fabrics that include
ribbon-shaped spunbond layers that are in direct contact with at
least one intervening meltblown layer. Nonwoven fabrics of this
invention exhibit enhanced low surface tension liquid resistance
and air permeability.
BACKGROUND
[0002] Nonwoven absorbent articles, such as disposable diapers,
training pants, incontinent wear, and feminine hygiene products,
have used nonwoven fabrics for many purposes, such as liners,
transfer layers, absorbent media, backings, and the like. For many
such applications, the barrier properties of the nonwoven can serve
a significant function. For example, U.S. Pat. No. 5,085,654 to
Buell discloses disposable diapers provided with breathable leg
cuffs that are formed from material, such as thermoplastic films,
which allows passage of vapor while tending to retard the passage
of liquid. Buell discloses a cuff having a breathable portion that
is different in character from an impermeable portion of the
cuff.
[0003] Nonwoven fabrics that include fibers or filaments having
different cross-sectional shapes have also been disclosed. For
example, United States Patent Publ. No. 2005/0215155 A1 to Young et
al. discloses in part a laminate comprising a first nonwoven layer
comprising first continuous filaments, a second nonwoven layer
comprising second continuous filaments, and a third nonwoven layer
comprising fine fibers, wherein the first and second continuous
filaments have cross-sectional shapes that are distinct from one
another.
[0004] U.S. Pat. No. 6,471,910 to Haggard et al. discloses a
nonwoven fabric formed from a spunbond process by extruding
generally ribbon-shaped fibers as defined therein through
slot-shaped orifices of a spinneret. Haggard et al. discloses
nonwoven webs or fabrics composed solely of the ribbon-shaped
fibers as defined therein and discloses the fibers can be used in
combination with fibers of other transverse cross-sections and in
combination with other technologies to form composite materials,
such as meltblown or film composites without illustration or
reference to a laminate having a structure of two spunbond layers
surrounding a meltblown layer or specific improved low surface
tension liquid resistance or air permeability.
[0005] United States Patent Publ. No. 2005/0227563 A1 to Bond
discloses a fibrous fabric including at least one layer comprising
a mixture of shaped fibers having two or more different
cross-sections. Bond discloses a laminate with at least one first
layer comprising a mixture of shaped fibers having cross-sectional
shapes that are distinct from one another and at least one second
layer comprising different fibers that are not identical in
cross-sectional shape and ratio to the fibers in the first
layer.
[0006] U.S. Pat. No. 7,309,522 to Webb et al. discloses fibers,
elastic yarns, wovens, nonwovens, knitted fabrics, fine nets, and
articles produced from fibers comprising a styrenic block
copolymer. Webb et al. discloses the shape of the fiber can vary
widely, wherein a typical fiber has a circular cross-sectional
shape, but sometimes fibers have different shapes, such as
tri-lobal shape, or what is said to be a flat `ribbon` like shape,
which may be included in a three layer spunbond-meltblown-spunbond
"sandwich". Webb et al. does not disclose the improvement of low
surface tension liquid resistance or air permeability.
[0007] U.S. Pat. No. 5,498,468 to Blaney discloses a method of
making a flexible fabric composed of a fibrous matrix of
ribbon-like, conjugate, spun filaments. Blaney discloses applying a
flattening force to the fibrous matrix to durably distort the core
of individual filaments into a ribbon-like configuration as
characterized in the reference. Blaney also discloses a method that
includes drawing the extruded conjugate filaments as they are being
quenched and applying a flattening force to durably distort the
core of individual filaments into a ribbon-like configuration of
the reference.
[0008] United States Patent Publ. No. 2006/0012072 A1 to Hagewood
et al. discloses a fibrous product including a mixture of different
shaped fibers that are formed using a spin pack assembly including
a spinneret with at least two spinneret orifices having different
cross-sections. Hagewood et al. shows a fibrous web containing a
mixture of multicomponent solid round, monocomponent trilobal
fibers, and meltblown fibers in examples.
[0009] U.S. Pat. No. 6,613,704 B1 to Arnold et al. discloses
nonwoven webs of continuous filaments having a mixture or blend of
first and second continuous filaments, wherein the second
continuous filaments are different from the first continuous
filaments in one or more respects such as size, cross-sectional
shape, polymer composition, crimp level, wettability, liquid
repellency, and charge retention. Arnold et al. discloses that the
second continuous filaments can be substantially surrounded by the
first continuous filaments wherein the ratio of first continuous
filaments to second continuous filaments exceeds about 2:1.
[0010] Resistance to low surface tension liquid strike through and
breathability are performance characteristics of liquid barrier
fabrics. Liquid strike through generally refers to the permeability
of liquid through the fabric and breathability generally refers to
the permeability to air and vapor through the fabric.
[0011] The present inventors have recognized that there is a need
for a fabric that can be used in personal hygiene products that
achieves a synergistic balance of low surface tension liquid strike
through and breathability with unique combinations of fibers and
nonwoven fibrous layers having different structures.
SUMMARY
[0012] A nonwoven fabric usable as a component in a personal
hygiene product is provided which includes a first ribbon-shaped
spunbond layer, a second ribbon-shaped spunbond layer and a
meltblown layer disposed between the first and second ribbon-shaped
spunbond layers. The meltblown layer is in direct contact with the
first and second ribbon-shaped spunbond layers. As an option, the
meltblown layer can include multiple directly adjoining meltblown
sub-layers, which can be present as a stack, wherein the two outer
sides of the stack are in direct contact with the first and second
ribbon-shaped spunbond layers, respectively. As an option, one or
more of the first ribbon-shaped spunbond layer, the second
ribbon-shaped spunbond layer and the meltblown layer comprises
polypropylene, as defined herein. The meltblown layer comprises
meltblown fibers in an amount of at least 0.1% by weight of the
nonwoven fabric and not greater than about 40% by weight of the
nonwoven fabric, and the meltblown layer has a basis weight no
greater than 5 gsm. The nonwoven fabric is substantially free or
free of non-ribbon shaped spunbond fibers (e.g., round-shaped
spunbond fibers). The nonwoven fabric has a basis weight of at
least about 8 grams/m.sup.2 (gsm) and not greater than about 40 gsm
and a pore size measured at 10% of cumulative filter flow of no
more than about 27 microns.
[0013] As an option, the nonwoven fabric can contain round-shaped
spunbond filaments in an amount of less about 10% by weight, or
less than about 5% by weight, or less than about 1% by weight, or
0% by weight to about 10% by weight, or lesser range amounts, such
as disclosed herein, with respect to the entire nonwoven fabric. As
another option, the first and second ribbon-shaped spunbond layers
comprise fibers having a cross-section with an aspect ratio greater
than about 1.5:1, or from about 1.55:1 to about 7:1, or from about
1.6:1 to about 7:1, or from about 1.75:1 to about 7:1, or from
about 2.5:1 to about 7:1, or other values such as disclosed herein.
As another option, the nonwoven fabric has a pore size measured at
25% of cumulative filter flow of less than about 23 microns.
[0014] As another option, the nonwoven fabric has an air
permeability of at least about 10 m.sup.3/m.sup.2/min or other
values such as disclosed herein. As another option, the nonwoven
fabric can have a low surface tension liquid strike through flow of
less than 0.9 ml per second, or less than 0.8 ml per second, or
other values such as disclosed herein. As another option, the
meltblown layer of the nonwoven fabric has a basis weight of at
least about 0.3 gsm and no greater than about 5 gsm, or at least
about 0.4 gsm and no greater than about 4 gsm, or at least about
0.7 gsm and no greater than about 2 gsm, or other values such as
disclosed herein. As another option, the nonwoven fabric has a
basis weight of at least about 8.5 gsm and not greater than about
30 gsm, or at least about 11 gsm and not greater than about 25 gsm,
or other values such as disclosed herein. As another option, the
first and second spunbond layers and the meltblown layer are bonded
together by a plurality of discrete bond areas. As another option,
the discrete bond areas can be thermal bonds formed as a plurality
of bond points wherein the plurality of bond points comprise up to
about 25% of the surface area of nonwoven fabric, such as from
about 10% to about 25% of the surface area of the nonwoven fabric,
or other percentages such as disclosed herein.
[0015] It is to be understood that both the foregoing general
description and the following detailed description are exemplary
and explanatory only and are intended to provide a further
explanation of the present invention, as claimed.
[0016] The accompanying drawings, which are incorporated in and
constitute a part of this application, illustrate some of the
embodiments of the present invention and together with the
description, serve to explain the principles of the present
invention. Features having the same referencing numeral in the
various figures represent similar elements unless indicated
otherwise. The figures and features depicted therein are not
necessarily drawn to scale.
BRIEF DESCRIPTION OF DRAWINGS
[0017] FIG. 1 is a perspective view of a nonwoven fabric useable in
a personal hygiene product in accordance with an embodiment of the
invention.
[0018] FIG. 2 is a schematic diagram of a forming system used to
make a nonwoven fabric in accordance with an embodiment of the
present invention.
[0019] FIGS. 3A-F illustrate cross-sectional enlarged views of
several different shapes of fibers, wherein FIGS. 3A-E showing
various ribbon-shaped fibers in accordance with embodiments of the
present invention.
[0020] FIG. 4 is a fragmentary perspective view, with sections
broken away, of a nonwoven fabric in accordance with an embodiment
of the present invention.
[0021] FIG. 5 is a sectional view along line 4-4 of FIG. 4.
[0022] FIG. 6 illustrates the correlation between the difference in
Flow Ratio and the difference in pore size at 10% cumulative filter
flow for spunbond/meltblown/meltblown/spunbond (S/M/M/S) nonwoven
fabrics made with ribbon-shaped spunbond fibers and round-shaped
spunbond fibers, in accordance with descriptions in the Examples
section herein.
[0023] FIG. 7 illustrates the correlation between the difference in
Flow Ratio and the difference in pore size at 25% cumulative filter
flow for spunbond/meltblown/meltblown/spunbond (S/M/M/S) nonwoven
fabrics made with ribbon-shaped spunbond fibers and round-shaped
spunbond fibers in accordance with descriptions in the Examples
section herein.
DEFINITIONS
[0024] As used herein, the term "fiber(s)" generally can refer to
continuous filaments, substantially continuous filaments, staple
fibers, and other fibrous structures having a fiber length that is
substantially greater than its cross-sectional dimension(s).
[0025] As used herein, the term "continuous filament(s)" refers to
a polymer strand or polymer fiber that is not broken during the
regular course of formation.
[0026] As used herein, the term "fine fiber(s)" refers to discrete
polymer fibers or strands with an average dimension dl, as defined
herein, not to exceed about 10 .mu.m.
[0027] As used herein, the term "ribbon-shaped" refers to a
cross-sectional geometry and aspect ratio. With respect to the
cross-sectional geometry, "ribbon-shaped" refers to a cross-section
that includes at least one pair (set) of symmetrical surfaces. For
example, the cross section can be a polygon which includes two
different pairs of opposite symmetrical surfaces or only one set
thereof. For example, with reference to FIG. 3A for sake of
illustration and not limitation, the overall shape 35 has an
imaginary major bisector 300, and a minor bisector (not shown),
which is perpendicular to the major bisector, wherein opposite
surfaces 351 and 352 are symmetrical surfaces with respect to each
other with reference to the imaginary bisector 300. Other
ribbon-shape geometries having at least one set of symmetrical
surfaces are illustrated, for example, in FIGS. 3B-3E. The major
bisector 300 can be straight (e.g., FIGS. 3A-3D), curvilinear
(e.g., FIG. 3E), or other shapes, depending on the cross-sectional
shape of the fiber. "Ribbon-shaped" can include, for example, a
shape having two sets of parallel surfaces forming a rectangular
shape (e.g. FIG. 3A). "Ribbon-shaped" can also include, for
example, a cross-section having one set of parallel surfaces, which
can be joined to one another by shorter rounded end joints having a
radius of curvature (e.g., FIG. 3B). "Ribbon-shaped" additionally
can include, for example, "dog-bone" shaped cross-sections, such as
illustrated in FIG. 3C, and oval or elliptical shaped
cross-sections, such as illustrated in FIG. 3D. In these
cross-sections illustrated in FIGS. 3C and 3D, the term
"ribbon-shaped" refers to a cross-section that includes sets of
symmetrical surfaces which comprise rounded (e.g. curvilinear or
lobed) surfaces, that are oppositely disposed. As illustrated in
FIG. 3D, the oval shaped cross-sections can have rounded or
curvilinear type top and bottom symmetrical surfaces, which are
joined to one another by shorter rounded end joints at the sides
having a relatively smaller radius of curvature than the top and
bottom symmetrical surfaces. The term "ribbon-shaped" also includes
cross-sectional geometry that includes no more than two square
ends, or round ends, or "lobes" along the perimeter of the
cross-section. FIG. 3C, for example, shows a bi-lobal
cross-section. The lobes differ from the indicated rounded end
joints included in the cross-sections such as shown in FIGS. 3B and
3D referred to above. Surface irregularities like bumps or
striations or embossed patterns that are relatively small when
compared to the perimeter of the cross-section, or are not
continuous along the length of the fibers are not included in the
definition of "lobes," or the rounded end joints. It can also be
understood that the above definition of "ribbon-shaped" covers
cross-sectional geometries in which one or more of the sets of
surfaces (e.g., the opposite lengthwise surfaces) are not straight
(e.g. FIG. 3E), provided such cross-sectional geometries meet the
aspect ratio requirements as defined below.
[0028] With respect to aspect ratio, a "ribbon-shaped"
cross-section has an aspect ratio (AR) of greater than 1.5:1. The
aspect ratio is defined as the ratio of dimension d1 and dimension
d2. Dimension d1 is the maximum dimension of a cross-section,
whether ribbon-shaped or otherwise, measured along a first axis.
Dimension d1 is also referred to as the major dimension of the
ribbon-shaped cross-section. Dimension d2 is the maximum dimension
of the same cross-section measured along a second axis that is
perpendicular to the first axis that is used to measure dimension
d1, where dimension d1 is greater than dimension d2. Dimension d2
is also referred to as the minor dimension. As an option, the major
bisector 300 can lie along the first axis and the minor bisector
(not shown) can lie along the second axis. Examples of how
dimensions d1 and d2 are measured are illustrated in FIGS. 3A, 3B,
3C, 3D, and 3E, which illustrate ribbon-shaped cross-sections and
in FIG. 3F which illustrates a non-ribbon-shaped cross-section as
described below. Aspect ratio is calculated from the normalized
ratio of dimensions d1 and d2, according to formula (1):
AR=(d1/d2):1 (1) [0029] The units used to measure d1 and d2 are the
same.
[0030] The term "ribbon-shaped" excludes for example,
cross-sectional shapes that are round, circular or round shaped as
defined herein. As referred to herein, the terms "round",
"circular" or "round-shaped" refer to fiber cross-sections that
have an aspect ratio or roundness of 1:1 to 1.5:1. An exactly
circular or round fiber cross-section has an aspect ratio 1:1 which
is less than 1.5:1. Any fiber that does not meet the indicated
criteria for "ribbon-shaped" fiber as defined herein is "non-ribbon
shaped". Other non-ribbon shaped fibers include, for example,
square, tri-lobal, quadri-lobal, and penta-lobal cross-sectional
shaped fibers. For example, a square shaped cross-section has an
aspect ratio of 1:1 which is less than 1.5:1. A tri-lobal
cross-section fiber, for example, has three round ends or "lobes",
and thus does not meet the definition for "ribbon-shaped"
cross-section. Illustrations of some of these shapes and the
manners of evaluating the aspect ratios thereof in accordance with
embodiments are included herein.
[0031] As used herein, a "nonwoven(s)" refers to a fiber-containing
material which is formed without the aid of a textile weaving or
knitting process.
[0032] As used herein, the terms "nonwoven fabric" or "nonwoven
component" may be used interchangeably and refer to a nonwoven
collection of polymer fibers or filaments in a close association to
form one or more layers, as defined herein. The one or more layers
of the nonwoven fabric or nonwoven component can include staple
length fibers, substantially continuous or discontinuous filaments
or fibers, and combinations or mixtures thereof, unless specified
otherwise. The one or more layers of the nonwoven fabric or
nonwoven component can be stabilized or unstabilized.
[0033] As used herein, the term, "spunmelt" refers to methods of
producing nonwovens by extruding polymer into fibers or filaments
and bonding the fibers or filaments thermally, chemically, or
mechanically.
[0034] As used herein, the term "absorbent article(s)" refers to
devices that absorb and contain liquid, and more specifically,
refers to devices that are placed against or in proximity to the
body of the wearer to absorb and contain the various exudates
discharged from the body.
[0035] As used herein, the term, "personal hygiene product" refers
to any item that can be used to perform a personal hygiene function
or contribute to a hygienic environment of an individual. Personal
hygiene products of the invention include, but are not limited to,
diapers, training pants, absorbent underpants, incontinence
articles, feminine hygiene products (e.g., sanitary napkins),
medical protective barrier articles, such as garments and drapes,
sterilization wraps and foot covers.
[0036] The term "personal hygiene component" refers to a nonwoven
component of a personal hygiene product, for example, a leg cuff
used in a diaper, training pants, absorbent underpants or
incontinence article, or other segment of a feminine hygiene
product, or medical protective barrier article are personal hygiene
components.
[0037] The term "dimension" is a measurement of the cross-section
of the fibers described herein. In instances where the fiber has a
round or circular cross-section, the dimension of the fiber will be
the same as the diameter of the fiber.
[0038] The term "spunbond" or "S" may be used interchangeably with
"continuous filament(s) or fiber(s)" and refers to fibers or
filaments which are formed by extruding a molten material as
filaments from a plurality of fine capillaries in a spinneret, and
the dimension of the extruded filaments then may be reduced by
drawing or other known methods. The term "spunbond" also includes
fibers that are formed as defined above, and which are then
deposited or formed in a layer in a single step.
[0039] The term "meltblown" or "M" may be used interchangeably with
"fine fibers" or "discontinuous fibers" and refers to fibers formed
by extruding a molten material and drawing the extruded molten
material with high-velocity fluid into fibers having dimension dl,
as defined herein, of less than 10 microns, or more specifically
less than 5 microns or even more specifically, less than 2 microns.
The term "meltblown" also includes fibers that have a round
cross-sectional geometry and an aspect ratio of less than 1.5:1.
The term "meltblown" also includes fibers that are described as not
continuous, in contrast to spunbond fibers. The term "meltblown"
also includes fibers formed by a process in which molten material
is extruded through a plurality of fine die capillaries into a
high-velocity gas stream which attenuates the fibers of molten
material to reduce their dimensions to a dimension d1 of less than
about 10 microns or, more specifically, a dimension d1 of less than
about 3 microns.
[0040] As used herein, a "sub-layer" is defined as similar material
or similar combination of materials formed from a single production
beam, wherein the material exists in at least one major plane
(e.g., an X-Y plane) with a relatively smaller thickness extending
in the orthogonal direction thereto (e.g., in a Z direction
thereto). The fibers of a sub-layer, for example, may include only
spunbond fibers, only meltblown fibers or only a single type of
fibers. As used herein, a "layer" is defined as one or more
sub-layers comprising fibers made from the same resin and fibers
that are defined as the same type of fiber (e.g., only spunbond,
only meltblown or only another type of fiber).
[0041] The term "component" is used herein to refer to a segment or
portion of an article or product.
[0042] As used herein, a "laminate" generally refers to at least
two joined together nonwoven layers contacting along at least a
portion of adjoining faces thereof with or without interfacial
mixing.
[0043] As used herein, "substantially free," as used with respect
to the content of round-shaped fibers in a nonwoven fabric, refers
to less than 10% by weight based on the total weight of the
nonwoven fabric.
[0044] As used herein, "comprising" or "comprises" is synonymous
with "including," "containing," "having", or "characterized by,"
and is open-ended and does not exclude additional, unrecited
elements or method steps, and thus should be interpreted to mean
"including, but not limited to . . . ".
[0045] As used herein, "consisting of" excludes any element, step,
or ingredient not specified.
[0046] As used herein, "consisting essentially of", refers to the
specified materials or steps and those that do not materially
affect the basic and novel characteristic(s) of the nonwoven
fabrics of the invention as described herein.
DETAILED DESCRIPTION
[0047] The present invention is directed to a nonwoven fabric
usable as a component in a personal hygiene product. The nonwoven
fabric has at least one meltblown layer disposed between and in
direct contact with ribbon-shaped spunbond layers. The nonwoven
fabric is at least substantially free of non-ribbon shaped spunbond
fibers (e.g., round-shaped spunbond fibers), such as less than 10%
by weight of the fabric is non-ribbon shaped spunbond fiber.
Improved Performance Characteristics of Nonwoven Fabric
[0048] A benefit of this invention, and such as shown in the
examples, is the provision of better resistance to low surface
tension liquid when compared to a nonwoven fabric of similar
general construction but made from round-shaped spunbond fibers in
the spunbond layers. Further, nonwoven fabrics have been developed
in the present invention which can be used, for example, as a
barrier layer in a diaper or other personal hygiene products that
have synergistic barrier properties when encountering low surface
tension liquids of types which are commonly encountered in such
uses, while being air and moisture vapor breathable and
manufacturable at low cost. Breathability is an important
consideration as air and vapor movement through the fabric is
associated with wearer comfort. The nonwoven fabrics of the present
invention can provide enhanced breathability without compromising
liquid barrier properties.
[0049] It has been found that examples of similar nonwoven fabric
construction comprising meltblown fibers and spunbond fibers that
are round-shaped perform differently than those that are
ribbon-shaped in regard to air permeability and resistance to
penetration by low surface tension liquid (referred to herein as
"LSTST-Flow"). It has been observed, for example, that the ratio of
LSTST-Flow to air permeability (referred herein as "Flow Ratio")
can be affected by the selected materials and design of the
nonwoven fabric and fibers in previously unrecognized manners. It
has been demonstrated, for example, that there is a superior range
of construction involving a synergistic combination of meltblown
fibers and ribbon-shaped spunbond fibers in adjoining layers,
wherein the resistance to liquid flow can be increased with less
reduction in air permeability. It has been found, for example, that
the use of ribbon-shaped spunbond fibers in spunbond layers that
sandwich meltblown layer(s) having a restricted total content of
meltblown fibers, wherein the meltblown fiber web formation is
designed to have provide a nonwoven fabric with a pore size
measured at 10% of cumulative filter flow of no more than about 27
microns and/or a pore size measured at 25% cumulative filter flow
of less than 23 microns, can yield unique beneficial effects on the
breathability and liquid barrier properties of the nonwoven
fabric.
[0050] As an option, a nonwoven fabric that has a reduced Flow
Ratio can be provided, which includes a meltblown layer or
meltblown layers having a total basis weight of at least about
0.008 gsm and no greater than about 5 gsm, as sandwiched between
spunbond layers comprising ribbon-shaped spunbond fibers in a
nonwoven fabric that has a total basis weight of at least about 8
gsm and not greater than about 40 gsm.
[0051] As an option, a nonwoven fabric is provided that has an air
permeability of at least about 9 m.sup.3/m.sup.2/min, or at least
about 10 m.sup.3/m.sup.2/min, or at least about 15
m.sup.3/m.sup.2/min, or at least about 20 m.sup.3/m.sup.2/min, or
at least about 25 m.sup.3/m.sup.2/min, or at least about 30
m.sup.3/m.sup.2/min, or at least about 35 m.sup.3/m.sup.2/min, or
at least about 40 m.sup.3/m.sup.2/min, or at least about 45
m.sup.3/m.sup.2/min, or at least about 50 m.sup.3/m.sup.2/min, or
greater values. As an option, a nonwoven fabric is provided that
has an air permeability of at least about 9 m.sup.3/m.sup.2/min to
no greater than 140 m.sup.3/m.sup.2/min, or at least about 12
m.sup.3/m.sup.2/min to no greater than about 130
m.sup.3/m.sup.2/min, or at least about 15 m.sup.3/m.sup.2/min to no
greater than about 120 m.sup.3/m.sup.2/min, or at least about 20
m.sup.3/m.sup.2/min to no greater than about 110
m.sup.3/m.sup.2/min, or at least about 25 m.sup.3/m.sup.2/min to no
greater than about 100 m.sup.3/m.sup.2/min, or at least about 30
m.sup.3/m.sup.2/min to no greater than about 95
m.sup.3/m.sup.2/min, or at least about 40 m.sup.3/m.sup.2/min to no
greater than about 90 m.sup.3/m.sup.2/min, or at least about 45
m.sup.3/m.sup.2/min or no greater than about 85
m.sup.3/m.sup.2/min, or at least about 50 m.sup.3/m.sup.2/min to no
greater than about 80 m.sup.3/m.sup.2/min, or other ranges within
these values.
[0052] As another benefit of these constructions, the nonwoven
fabric can have a LSTST-Flow of less than 0.9 ml per second, or
less than 0.8 ml per second, or less than 0.7 ml per second, or
less than 0.6 ml per second, or less than 0.5 ml per second, or
less than 0.4 ml per second, or less than 0.3 ml per second, or
lower range values.
[0053] As a further option, a nonwoven fabric is provided that has
a Flow Ratio of less than or equal to about 0.06, or less than or
equal to about 0.058, or less than or equal to about 0.056, or less
than or equal to about 0.054, or less than or equal to about 0.052,
or less than or equal to about 0.05, or less than or equal to about
0.048, or less than or equal to about 0.046, or less than or equal
to about 0.044, or less than or equal to about 0.042, or less than
or equal to about 0.04, or less than or equal to about 0.038, or
less than or equal to about 0.036, or less than or equal to about
0.034, or less than or equal to about 0.032, or less than or equal
to about 0.030, or less than or equal to about 0.028, or less than
or equal to about 0.026, or less than or equal to about 0.024, or
less than or equal to 0.023, or less than or equal to 0.022, or
lesser range values, or from at least about 0.015 to no greater
than about 0.06, or from at least about 0.015 to no greater than
about 0.058, or from at least about 0.015 to no greater than about
0.056, or from at least about 0.015 to no greater than about 0.054,
or from at least about 0.015 to no greater than about 0.052, or
from at least about 0.015 to no greater than about 0.050, or from
at least about 0.018 to no greater than about 0.04, or from at
least about 0.018 to no greater than about 0.035, or from at least
about 0.018 to no greater than about 0.030, from at least about
0.018 to no greater than about 0.025, or from at least about 0.019
to no greater than about 0.025, or from at least about 0.019 to no
greater than about 0.024, from at least about 0.019 to no greater
than about 0.023, or at least about 0.019 to no greater than about
0.022 or other ranges within these values. As another benefit of
these constructions, any of these reduced LSTST-Flow to air
permeability ratios can be provided in a nonwoven fabric of the
present invention which has a pore size measured at 10% of
cumulative filter flow of no more than about 27 microns or at 25%
cumulative filter flow of no more than 23 microns. As another
option, any of these reduced Flow Ratios can be provided in a
nonwoven fabric of the present invention which has a pore size
measured at 10% of cumulative filter flow of no more than about 25
microns, or no more than 23 microns or no more than 21 microns.
Nonwoven Fabric Structure
[0054] FIG. 1 illustrates a nonwoven fabric of an option of the
present invention in a perspective view with cut-aways to show
detail. The three or four layer nonwoven fabric 10 shown in FIG. 1
can be created from the forming machine described with respect to
FIG. 2 herein. In FIG. 1, the nonwoven fabric 10 has a first
ribbon-shaped spunbond layer 12 of first ribbon-shaped spunbond
fibers 13 (e.g., continuous spunbond filaments), a meltblown layer
14 of meltblown fibers 15, and a second ribbon-shaped spunbond
layer 16 of second ribbon-shaped spunbond fibers 17 (e.g.,
continuous spunbond filaments). As illustrated in FIG. 1, the first
ribbon-shaped spunbond layer 12, meltblown layer 14, and second
ribbon-shaped spunbond layer 16 are in direct contact with the
respective adjoining layer or layers to each of them. As used
herein, the wording "direct contact" between a ribbon-shaped
spunbond layer (12 or 16) and a meltblown layer 14, or between
meltblown sub-layers 14A and 14B if used, can mean that at least
about 50%, or at least about 60%, or at least about 70%, or at
least about 80%, or at least about 90%, or at least about 95%, or
at least about 99%, or 100%, of the surfaces areas of the adjacent
faces of the two respective layers are in physical contact with
each other (e.g., contact areas are free of interposed different
materials or air pockets that space the surfaces of the adjoining
layers apart).
[0055] The first ribbon-shaped spunbond layer 12 comprised of first
ribbon-shaped spunbond fibers 13 can have a basis weight, for
example, of at least about 3.9 gsm and not greater than about 19.5
gsm, or at least 4.1 gsm and not greater than about 13 gsm, or at
least about 5.1 gsm and not greater than about 11.5 gsm, or at
least about 5 gsm and not greater than about 6.5 gsm, or at least
about 5.5 gsm and no greater than about 6.25 gsm or other ranges
amounts within these ranges. As another option, the first
ribbon-shaped spunbond layer 12 comprised of first ribbon-shaped
spunbond fibers 13 can have a basis weight, for example, 6 gsm. As
an option, the first ribbon-shaped spunbond layer 12 can comprise
first ribbon-shaped spunbond fibers 13 with denier (g/9,000 m) in
the range, for example, of from about 1.0 to about 4.0, or from
about 1.0 to about 3.5, or from about 1.0 to about 3.2, or from
about 1.0 to about 2.8, or from about 1.0 to about 2.4, or from
about 1.0 to about 2.0, or other denier values. As another option,
the first ribbon-shaped spunbond layer 12 can comprise first
ribbon-shaped spunbond fibers 13 having an average dimension d1 of
greater than about 12.5 .mu.m, or from about 12.5 .mu.m to about 50
.mu.m, or from about 12.5 .mu.m to about 40 .mu.m, or from about
12.5 .mu.m to about 30 .mu.m, or from about 12.5 .mu.m to about 28
.mu.m, or other values. The dimension d1 can be determined, for
example, as part of the aspect ratio measurements which are
described in the examples section herein.
[0056] As indicated, the first ribbon-shaped spunbond fibers 13 can
have cross-sectional shapes including, but not limited to, shapes
selected from the group consisting of flat, oval, bi-lobal,
rectangular, and any combinations thereof. As an option, the first
ribbon-shaped spunbond fibers 13 can all have the same
cross-sectional geometry (e.g., all rectangular, or all bi-lobal,
or all flat, or all oval) with respect to each other within the
indicated required range for ribbon-shaped fibers. As another
option, the first ribbon-shaped spunbond fibers 13 can have the
same or different aspect ratios with respect to each other within
the indicated required range for ribbon-shaped fibers. As another
option, the first ribbon-shaped spunbond fibers can have the same
cross-sectional geometry and the same aspect ratio with respect to
each other, with both the cross-sectional geometry and aspect ratio
being within the indicated required range for ribbon-shaped fibers.
For example, the first ribbon-shaped spunbond fibers 13 can all
comprise rectangular cross-sectional geometry, wherein the aspect
ratio is 2:1 for all of the fibers. As another option, the first
ribbon-shaped spunbond fibers can have the same cross-sectional
geometry but different aspect ratio with respect to each other. For
example, the first ribbon-shaped spunbond fibers 13 can have the
same rectangular cross-section while the aspect ratio first
ribbon-shaped spunbond fibers 13 can vary, e.g., in a range from
about 1.75:1 to about 2.25:1, or other aspect ratio values within
the indicated required criterion (i.e., AR>1.5:1). Where the
aspect ratios may vary, the denier of the first ribbon-shaped
spunbond fibers also can vary.
[0057] The nonwoven fabric 10 further comprises a second
ribbon-shaped spunbond layer 16 which is comprised of second
ribbon-shaped spunbond fibers 17. The second ribbon-shaped spunbond
layer 16 can have a basis weight in the ranges indicated for the
first ribbon-shaped spunbond layer 12. As options, the second
ribbon-shaped spunbond fibers 17 in the second ribbon-shaped
spunbond layer 16 can have cross-sectional geometries, aspect
ratios, denier, dimension d1 values, average dimension d1 values
and combinations thereof that are similar to that indicated for the
first ribbon-shaped spunbond fibers 13 of the first ribbon-shaped
spunbond layer 12. As an option, the second ribbon-shaped spunbond
fibers 17 may have the same cross-sectional geometry and the same
aspect ratio with respect to each other. As another option, the
second ribbon-shaped spunbond fibers can have the same
cross-sectional geometry but different aspect ratio with respect to
each other.
[0058] As an option, the cross-sectional geometry and/or aspect
ratios selected and used for the first and second ribbon-shaped
spunbond fibers 13 and 17 in one of the first and second
ribbon-shaped spunbond layers 12 and 16, respectively, can be the
same with respect to the other ribbon-shaped spunbond layer (12 or
16). For example, as an option, both the first and second
ribbon-shaped spunbond layers 12 and 16 can contain ribbon-shaped
spunbond fibers 13 and 17, respectively, having rectangular
cross-sectional geometries and/or similar aspect ratios with
respect to each other. Alternatively, one of the first and second
ribbon-shaped spunbond layers 12 and 16 can include ribbon-shaped
spunbond fibers 13 and 17, respectively, with different aspect
ratios from the ribbon-shaped spunbond fibers (13 or 17) of the
other of the first and second ribbon-shaped spunbond layers (12 or
16). As yet another option, the first spunbond layer 12 has first
ribbon-shaped spunbond fibers 13 with a mixture of aspect ratios
of, while the second spunbond layer 16 has second ribbon-shaped
fibers 17 having a single aspect ratio or a different mixture of
aspect ratios than the first ribbon-shaped spunbond fibers 13.
[0059] As an option, the number of different aspect ratios of the
ribbon-shaped spunbond fibers allowed in a single ribbon-shaped
spunbond layer is controlled. As an option, each of the first
ribbon-shaped spunbond layer 12 and second ribbon-shaped spunbond
layer 16 can comprise similar ribbon-shaped spunbond fibers with
respect to aspect ratios in an amount of at least about 90% by
weight, or at least about 91% by weight, or at least about 92% by
weight., or at least about 93% by weight, or at least about 94% by
weight, or at least about 95% by weight, or at least about 96% by
weight, or at least about 97% by weight., or at least about 98% by
weight, or at least about 99% by weight, or 100% by weight, of the
total fiber content of each respective ribbon-shaped spunbond
layer.
[0060] The nonwoven fabric 10 can include more than two
ribbon-shaped spunbond layers. As an option, the additional
ribbon-shaped spunbond layers can include ribbon-shaped spunbond
fibers having the same or different cross-sectional geometries
and/or aspect ratios as the first and/or second ribbon-shaped
fibers 13 or 17 as described herein. The additional ribbon-shaped
spunbond layers can be disposed to be in direct contact with either
the first or second ribbon-shaped spunbond layers 12 or 16,
respectively. It will be understood that the total amount of the
ribbon-shaped spunbond fibers in the additional ribbon-shaped
spunbond layers will be consistent with basis weights and basis
weight percentages disclosed herein. As an option, the nonwoven
fabric 10 excludes non-ribbon shaped spunbond fibers.
[0061] As also indicated in FIG. 1, the nonwoven fabric 10
comprises a meltblown layer 14 which itself is comprised of
meltblown fibers 15. The meltblown layer 14 can have a basis
weight, for example, of from at least about 0.008 gsm to no greater
than about 5 gsm, or from at least about 0.4 gsm to no greater than
about 4 gsm, or from at least about 0.7 gsm to no greater than
about 2 gsm, or from at least about 1.0 gsm to no greater than
about 2 gsm, or from at least about 1.1 gsm to no greater than
about 1.7 gsm, or from at least about 1.2 gsm to no greater than
about 1.4 gsm or from at least about 0.5 gsm to no greater than
about 4 gsm, or from at least about 0.6 gsm to no greater than
about 3 gsm, or other values within these ranges. As an option, the
meltblown layer 14 can comprise meltblown fibers 15 having an
average dimension d1 that does not exceed about 10 .mu.m, or does
not exceed about 7.5 .mu.m, or does not exceed about 5 .mu.m, or
does not exceed 3 .mu.m or does not exceed 1.8 .mu.m, or is from
about 0.3 to about 10 .mu.m, or is from about 1 to about 10 .mu.m,
or is from about 1 to about 7.5 .mu.m, or is from about 0.5 to
about 5 .mu.m, or other ranges within these values. As an option,
two or more meltblown sub-layers 14A and 14B of meltblown fibers
15A and 15B can be used to form the meltblown layer 14 and can be
disposed between first and second ribbon-shaped spunbond layers 12
and 16, respectively. The meltblown sub-layers 14A and 14B, if
used, can have an interface 140, which is indicated by the dashed
line in FIG. 1. One meltblown sub-layer 14B can be provided in
direct contact with the second meltblown sub-layer 14A. Although
one or two meltblown layers are illustrated in FIG. 1 as used in
nonwoven fabric 10, additional meltblown sub-layers (e.g., three,
four, etc.) can be disposed between the ribbon-shaped spunbond
layers 12 and 16, respectively.
[0062] Where multiple directly adjoining meltblown sub-layers are
present as a stack 141, such as illustrated by sub-layers 14A and
14B, the two outer sides 142 and 143 of the stack 141 are in direct
contact with the first and second ribbon-shaped spunbond layers 12
and 16, respectively. As an option, if three or more meltblown
sub-layers are used (not shown), the two outermost meltblown
sub-layers of the stack can have an outer side that directly
contacts an adjoining ribbon-shaped spunbond layer (12 or 16) and
an inner side in contact with the middle or intermediate meltblown
sub-layer or layers of the same stack, which are spaced from the
ribbon-shaped spunbond layers (12 and 16). If two or more meltblown
sub-layers are used, then the previously described meltblown basis
weights apply to combined total basis weights of the two or more
meltblown sub-layers or to the whole meltblown layer 14 made from
the various meltblown sub-layers. For example, if three meltblown
sub-layers are used, the total combined basis weight of the three
meltblown sub-layers can be, for example, from at least about 0.008
gsm to no greater than about 5 gsm, or the other indicated ranges.
The meltblown sub-layers 14A and 14B, if used, can have similar
fiber and web features and materials as described for the meltblown
layer 14, however, the indicated calculation of meltblown sub-layer
basis weights will be based on their combined values. As
illustrated in FIG. 1, the first ribbon-shaped spunbond layer 12,
the meltblown sub-layers 14A and 14B or meltblown layer 14, and the
second ribbon-shaped spunbond layer 16 are in direct contact with
their adjoining layer or layers. In an option, the meltblown layer
14, or meltblown sub-layers 14A and 14B if used, comprise fine
fibers in amount of at least about 80% by weight, or at least 85%
by weight, or at least 90% by weight, or at least 91% by weight, or
at least 92% by weight, or at least 93% by weight, or at least 94%
by weight, or at least 95% by weight, or at least 96% by weight, or
at least 97% by weight, or at least 98% by weight, or at least 99%
by weight, or 100% by weight, based on the total basis weight of
the meltblown layer 14 or each respective meltblown sub-layer 14A
and 14B, as applicable.
[0063] The resultant nonwoven fabric 10 has the meltblown layer 14
(or meltblown sub-layers 14A and 14B) interposed between the first
and second ribbon-shaped spunbond layers 12 and 16. The nonwoven
fabric 10 can be consolidated by mechanic embossing methods or
other nonwoven fabric consolidation methods, which are illustrated
in greater detail with respect to FIG. 2 herein. As an option, the
nonwoven fabric 10 having a first ribbon-shaped spunbond layer 12,
meltblown layer 14 (or meltblown sub-layers 14A and 14B), and
second ribbon-shaped spunbond layer 16, contains less than about
10% by weight, or less than about 9% by weight, or less than about
8% by weight, or less than about 7% by weight, or less than about
6% by weight, or less than about 5% by weight, or less than about
4% by weight, or less than about 3% by weight, or less than about
2% by weight, or less than about 1% by weight, or 0% by weight, or
from 0% to about 10% by weight, from 0% to about 7% by weight, from
0% to about 5% by weight, or from 0% to about 3% by weight, from 0%
to about 2% by weight, from 0% to about 1% by weight, of total
non-ribbon shaped spunbond fibers based on the total basis weight
of the nonwoven fabric. As another option, these ranges also can
apply specifically to round-shaped spunbond fibers. As another
option, these restrictive amounts of the non-ribbon shaped or
round-shaped spunbond fibers in particular also can apply to each
the respective basis weights of the first or second ribbon-shaped
spunbond layers 12, 16 and meltblown layer 14 or to combinations of
the respective basis weights of the first or second ribbon-shaped
spunbond layers 12, 16 and meltblown layer 14.
[0064] As another option, the nonwoven fabric 10 can exclude the
presence of any intervening component between the meltblown layer
14 or the stack 141 of meltblown sub-layers 14A, 14B and the first
or second ribbon-shaped spunbond layers 12 or 16. The intervening
component may include layer of non-ribbon shaped spunbond fibers,
such as round spunbond fibers or other fibers that cannot be
characterized as a ribbon-shaped spunbond fiber or meltblown fiber.
In addition, as another option, the nonwoven fabric 10 can exclude
an intervening component, as defined above, between the meltblown
sub-layers 14A and 14B, if used. The exclusion of an intervening
component is subject to the disclosure herein of the direct contact
between the ribbon-shaped spunbond layers 12 and 16 and meltblown
layer 14 or meltblown sub-layers 14A and 14B, if used.
[0065] As another option, the meltblown layer 14, or meltblown
sub-layers 14A and 14B if used, contains meltblown fibers in a
total amount of at least 0.1% by weight to no greater than 40% by
weight of the nonwoven fabric (e.g., with reference to nonwoven
fabric 10), or at least 0.5% by weight to no greater than 40% by
weight of the nonwoven fabric, at least 1% by weight to no greater
than 40% by weight of the nonwoven fabric, or at least 2% by weight
to no greater than 30% by weight of the nonwoven fabric, or at
least 3% by weight to no greater than 25% by weight of the nonwoven
fabric, or at least 4% by weight to no greater than 20% by weight
of the nonwoven fabric, or at least 5% by weight to no greater than
15% by weight of the nonwoven fabric, or other range values within
these ranges. As an option, the meltblown layer 14, or meltblown
sub-layers 14A and 14B if used, contains meltblown fibers in a
total amount of about 10% by weight of the nonwoven fabric. The
total basis weight of the nonwoven fabric 10 can be, for example,
at least about 8 gsm and not greater than about 40 gsm, or at least
8.5 gsm and not greater than about 35 gsm, or at least about 9 gsm
and not greater than about 30 gsm, or at least about 10 gsm and not
greater than about 25 gsm, or at least about 11 gsm and not greater
than about 15 gsm, or at least about 12 gsm and not greater than
about 14 gsm, or other ranges amounts within these ranges,
regardless of whether the nonwoven fabric 10 includes three, four
or more layers.
Manufacture of Nonwoven Fabric
[0066] With reference to FIG. 2, a schematic diagram of a forming
machine 20 which can be used to make an embodiment of the nonwoven
fabric 10 is shown. The forming machine 20 is shown as having a
beam 21 for the formation or extrusion of the first ribbon-shaped
spunbond fibers 13, a beam 23 for the formation or extrusion of the
meltblown fibers 15, and a beam 25 for the formation or extrusion
of the second ribbon-shaped spunbond fibers 17. The forming machine
20 has an endless forming belt 27 including a collection surface 22
wrapped around rollers 28 and 29 so the endless forming belt 27 is
driven in the direction as shown by the arrows.
[0067] Beam 21 can produce the first ribbon-shaped spunbond fibers
13, for example, by use of a conventional spunbond extruder with
one or more spinnerets which form ribbon-shaped spunbond fibers of
polymer. The formation of the first ribbon-shaped spunbond fibers
13 and operation of such a spunbond forming beam is within the
ability of those of ordinary skill in the art in view of the
descriptions herein. Suitable polymers include any natural or
synthetic polymer that are suitable for forming spunbond fibers
such as polyolefin, polyester, polyamide, polyimide, polylactic
acid, polyhydroxyalkanoate, polyvinyl alcohol, polyacrylates,
viscose rayon, lyocell, regenerated cellulose, or any copolymers or
combinations thereof. As an option, the polymer is a thermoplastic
resin material. As used herein, the term "polyolefin" includes
polypropylene, polyethylene and combinations thereof. As used
herein, the term "polypropylene" includes all thermoplastic
polymers where at least 50% by weight of the building blocks used
are propylene monomers. Polypropylene polymers also include
homopolymer polypropylenes in their isotactic, syndiotactic or
atactic forms, polypropylene copolymers, polypropylene terpolymers,
and other polymers comprising a combination of propylene monomers
and other monomers. As an option, polypropylenes, such as isotactic
homopolymer polypropylenes made with Ziegler-Natta, single site or
metallocene catalyst system, may be used as the polymer.
Polypropylene, for example, may be used which has a melt flow rate
(MFR) of from about 8.5 g/10min. to about 100 g/10min. or
preferably from 20 to 45 g/10 min., or other values. With respect
to polypropylene, MFR refers to the results achieved by testing the
polymer composition by the standard test method ASTM D1238
performed at a temperature of 230.degree. C. and with a weight of
2.16 kg. As another option, the first ribbon-shaped spunbond fibers
13 as defined herein contain polypropylene in amounts of at least
about 50% by weight, or at least about 55% by weight, or at least
about 60% by weight, or at least about 65% by weight, or at least
about 70% by weight or at least about 75% by weight, or at least
about 80% by weight, or at least about 85% by weight or at least
about 90% by weight, or at least about 95% by weight, or at least
about 96% by weight, or at least about 97% by weight, or at least
about 98% by weight, or at least about 99% by weight, or about 100%
by weight, or at least about 50% to about 100% by weight, or at
least about 60% to about 100% by weight, or at least about 70% to
about 100% by weight, or at least about 80% to about 100% by
weight, or at least about 90% to about 100% by weight of the first
ribbon-shaped spunbond fibers 13. As another option, the first
ribbon-shaped spunbond fibers 13 as defined herein may be formed as
homogenous solid fibers, which are distinguished from
multicomponent solid fibers (e.g., sheath-core fibers, bicomponent
fibers, conjugate fibers), hollow fibers, or any combinations
thereof.
[0068] In using beam 21 to produce the first ribbon-shaped spunbond
fibers 13, the polymer is heated to become molten, and is extruded
through the orifices in the spinneret. The extruded polymer fibers
are rapidly cooled, and can be drawn by mechanical drafting
rollers, fluid entrainment or other suitable means, to form the
desired denier fibers. The fibers resulting from beam 21 are laid
down onto the endless forming belt 27 to create the first
ribbon-shaped spunbond layer 12. Beam 21 can include one or more
spinnerets depending upon the speed of the process or the
particular polymer being used. The dimensions d1 and d2 of the
first ribbon-shaped spunbond fibers 13 can be controlled by factors
including, but not limited to, spinning speed, mass throughput,
temperature, spinneret geometry, blend composition, and/or
drawing.
[0069] The spinnerets of beam 21 have orifices with a distinct
cross-section that imparts a ribbon-shaped cross-sectional geometry
to the spunbond fibers. As an option, the distinct cross-section of
the spinneret orifices can generally correspond in cross-sectional
geometry to that desired in the first ribbon-shaped spunbond fibers
13 formed using the spinnerets. For example, spinnerets with
rectangular-shaped orifices can be used to form ribbon-shaped
spunbond fibers having a rectangular cross-sectional geometry, a
generally rectangular cross-sectional geometry with round edges or
oval cross-sectional geometry, depending on processing
conditions.
[0070] FIGS. 3A-3E depict several illustrative ribbon-shaped
cross-sections that can be used. FIG. 3A shows a rectangular
cross-sectional geometry 35, which has two longitudinal flat
surfaces 351 and 352, and two squared ends 353 and 354 which are
longitudinally parallel to each other; FIG. 3B shows a flat
cross-sectional geometry 36; FIG. 3C shows a bi-lobal
cross-sectional geometry 37; FIG. 3D shows an oval cross-sectional
geometry 38; and FIG. 3E shows a ribbon-shaped cross-section 39
with at least two curvilinear surfaces. These examples of
ribbon-shaped cross-sectional geometries as defined herein are for
illustration and are not exhaustive. In FIGS. 3A-3E, dimension dl,
as defined herein, is taken along a first axis and dimension d2, as
defined herein, is taken along a second axis perpendicular to the
first axis of the cross-section, wherein dimension d1 is greater
than dimension d2. The aspect ratio of these cross-sectional
geometries can be calculated as the ratio: (d1/d2). The result can
be reported the ratio of dimension d1 to dimension d2 or, as a
normalized value of (d1/d2):1. Further, the flat cross-sectional
geometry such as illustrated in FIG. 3B, can refer to geometries,
for example, that have at least two opposite flat sides and rounded
sides. FIG. 3F shows a round or circular cross-sectional geometry
40. The dimensions d1 and d2 are equivalent in this illustration so
the aspect ratio is 1:1. As indicated, round cross-sections have an
aspect ratio less than 1.5:1 and are not ribbon-shaped as defined
herein. As an option, the term "ribbon-shaped" includes
cross-sections having an aspect ratio of greater than 1.5:1, or
about 1.51:1 or greater, or about 1.55:1 or greater, or about 1.6:1
or greater, or about 1.75:1 or greater, or about 2.0:1 or greater,
or about 2.25:1 or greater, or about 2.5:1 or greater, or about
2.75:1 or greater, or about 3:1 or greater, or about 3.25:1 or
greater, or about 3.5:1 or greater, or about 3.75:1 or greater, or
about 4:1 or greater, or about 4.5:1 or greater, or about 5:1 or
greater, or about 5.5:1 or greater, or about 6:1 or greater, or
about 6.5:1 or greater, or greater than or equal to at least about
1.55:1 and less than or equal to about 7:1 (i.e., from about 1.55
to about 7:1), or from about 1.6:1 to about 7:1, or from about
2.5:1 to about 5.5:1, or from about 2.75:1 to 5:1, or from about
3:1 to about 4.5:1, or from about 3.25:1 to about 4:1, or from
about 3.5:1 to about 3.75:1, or from about 2.5:1 to about 5:1, or
from about 2.5:1 to about 4.5:1, or from about 2.5 to about 4:1, or
from about 2.5 to about 3.75, or from about 2.5:1 to about 6:1, or
other values. Methods for preparing continuous filaments having
different cross-sectional shapes or geometries which may be adapted
for use in making ribbon-shaped filaments of the present invention
are disclosed, for example, in U.S. Patent Application Publ. No.
2005/0227563 A1 (e.g., paragraphs [0054]-[0073]), which is
incorporated herein by reference.
[0071] Beam 23 produces meltblown fibers 15A. As known to those
skilled in the art, a typical method of producing meltblown fibers
is by the meltblown process that includes extruding a molten
material, such as a thermoplastic polymer, through a die 30
containing a plurality of orifices. The die 30 can contain from
about 20 to about 100 orifices per inch of die width, or other
values suitable for the meltblown layer formation. As the
thermoplastic polymer, for example, exits the die 30, high pressure
fluid, usually air, attenuates and spreads the polymer stream to
form the meltblown fibers 15A. The meltblown process allows the use
of various different polymers. Non-limiting examples include
polypropylene (e.g., MFR of at least about 400 g/10min. to no
greater than about 2000 g/10min.), blends including polypropylene
(e.g. MFR of at least about 7.5 g/10min. to no greater than about
2000 g/10min.), polyethylene (e.g., melt flow index (MFI) of at
least about 20 g/10min. to no greater than about 250 g/10 min.),
polyester (e.g., intrinsic viscosity of at least about 0.53 dL/g to
no greater than about 0.64 dL/g), polyamide, polyurethane,
polyphenylene sulphide, or other fiber materials, such as those
indicated for use in forming the first ribbon-shaped spunbond
fibers 13. With respect to polypropylene, MFR is a measure of
polymer viscosity performed as per standard test method ASTM D1238
using a temperature of 230.degree. C. and a weight of 2.16 kg. With
respect to polyethylene, MFI is a measure of polymer viscosity
performed as per standard test method ASTM D1238 using a
temperature of 190.degree. C. and a weight of 2.16 kg. Any of the
foregoing polypropylene polymers may include vis-breaking additives
(e.g. peroxide additives or non-peroxide containing additives,
which are available, for example, under the tradename Irgatec.RTM.
CR 76, from BASF Corporation of Ludwigshafen, Germany. The polymers
and blends used during meltblown production ordinarily have a low
viscosity or are designed and processed in a way to have their
viscosity reduced during their extrusion one of the variables used
to decrease their in situ viscosity is the use of a relatively high
melt temperature (compared to other production processes). The melt
temperature can be adjusted during production by means of
electrical heating systems in the extrusion section or other means
known in the industry. The meltblown fibers 15 resulting from beam
23 are laid down onto first ribbon-shaped spunbond layer 12,
carried by the endless forming belt 27, to create the meltblown
layer 14. The construction and operation of beam 23 for forming the
meltblown fibers 15 and the meltblown layer 14 can be adapted based
on conventional equipment in view of the present disclosures. For
example, U.S. Pat. No. 3,849,241 (e.g., column 7, line 14 to col.
12, line 29), which is incorporated herein by reference, shows such
conventional arrangements which may be adapted. Other methods for
forming the meltblown layer 14 are contemplated for use with the
present invention.
[0072] Beam 25 produces the second ribbon-shaped spunbond fibers
17, such as by use of a conventional spunbond extruder, and can
have a substantially similar design as beam 21. Beam 25 can involve
different processing parameters than those of beam 21 as long as
ribbon-shaped spunbond fibers are formed. For example, the polymer
used in beam 25 can be similar or different from the polymers used
in beam 21. The temperature and attenuation for beam 25 can also
differ from beam 21. The spinnerets of beam 25 have orifices with a
distinct cross-section that impart a ribbon-shaped cross-sectional
geometry to the resulting ribbon-shaped spunbond fibers 17. The
spinnerets of beam 25 yield ribbon-shaped spunbond fibers 17 with a
cross-sectional geometry and/or aspect ratio which is the same or
different from the ribbon-shaped cross-sectional geometry and
aspect ratio of first ribbon-shaped spunbond fibers 13. The second
ribbon-shaped spunbond fibers 17 of the second ribbon-shaped
spunbond layer 16 can comprise, for example, ribbon-shaped fibers
having a cross-sectional geometry such as illustrated in FIGS.
3A-3E. The second ribbon-shaped spunbond fibers 17 resulting from
beam 25 are laid down onto the meltblown layer 14, which is on the
first ribbon-shaped spunbond layer 12 that is carried on the
endless forming belt 27, to create the second ribbon-shaped
spunbond layer 16.
[0073] In another option, the forming machine 20 can include a beam
31 located along endless forming belt 27 between beam 23 and beam
25. Beam 31 can be configured to produce a second meltblown layer
on meltblown layer 14 or a second meltblown sub-layer 14B, before
the formation of the second ribbon-shaped spunbond layer 16 thereon
at beam 25. This arrangement, if used, can form two consecutive
meltblown layers, such as meltblown sub-layers 14A and 14B as
illustrated in FIG. 1. Beam 31, if included, can have similar or
dissimilar settings, and operabilities as beam 23 and may use the
same or different polymers as used in beam 23. Additional beams can
be added to form additional meltblown layers or sub-layers or
additional ribbon-shaped spunbond layers, consistent with the
nonwoven fabric 10 described herein.
[0074] The resulting nonwoven fabric 10 can be fed through bonding
rolls 32 and 33 to consolidate the nonwoven fabric 10. As an
option, the nonwoven fabric 10 can be embossed with a pattern from
at least one side. FIG. 5 illustrates the nonwoven fabric 10 after
being embossed with a pattern on both sides. The surfaces of one or
both of the bonding rolls 32 and 33 can be provided, for example,
with a raised pattern such as spots or grids. As an option, one
bonding roll 32 or 33 can include a raised pattern while the other
bonding roll (32 or 33) can be smooth. The bonding rolls 32 and 33
can be heated to the softening temperature of the polymer used to
form the layers of the nonwoven fabric 10. As the nonwoven fabric
10 passes between the heated bonding rolls 32 and 33, the material
is embossed by the bonding rolls in accordance with the pattern on
the rolls to create a pattern of discrete bonded areas. The bonded
areas are bonded from layer to layer with respect to the particular
filaments and/or fibers within each layer. FIG. 4 shows an
illustration of a nonwoven fabric 10 with a pattern 18 of such
discrete thermally bonded areas 19. The total area of the bond
pattern 18 relative to the overall surface area of the fabric can
be, for example, from about 10% to about 25%, or from about 13% to
about 25%, or from about 15% to about 25%, or from about 18% to
about 25%, or from about 15% to about 23%, or from about 16% to
about 23%, or other values. The embossed pattern shape of the
discrete thermally bonded areas 19 can be, for example, diamond,
oval, or other discrete shapes. FIG. 5 shows a view of one of the
indicated discrete thermally bonded areas 19 through the
cross-section of the nonwoven fabric 10. The bonding rolls 32 and
33 can have embossing protuberances that are synchronized to
compress the nonwoven fabric 10 from opposite sides at
corresponding locations (as shown) or different locations on each
side of the nonwoven fabric 10. The depth of compression produced
from the opposite sides of the nonwoven fabric 10 by the embossing
protuberances of the respective bonding rolls 32 and 33 can have
different (as shown) or the same. Such bonding, which is sometimes
referred to as discrete area or spot bonding, is well-known in the
art and can be carried out as described by means of heated rolls or
by means of ultrasonic heating of the nonwoven fabric 10 to produce
fibers and layers having discrete thermally bonded fibers. Thermal
pattern bonding such as described, for example, in Brock et al.,
U.S. Pat. No. 4,041,203 (e.g., col. 6, lines 10-28), which is
incorporated herein by reference, can be adapted to provide the
indicated discrete or spot bonding. In FIG. 5, the fibers of the
meltblown layer 14 in the fabric laminate 10 can fuse within the
bond areas while the ribbon-shaped fibers 13 and 17 of the first
and second ribbon-shaped spunbond layers 12 and 16, respectively,
retain some of their integrity, in order to achieve good strength
characteristics. For heavier basis weight nonwoven fabrics, for
example, sonic bonding methods and devices which are generally
known can be adapted for use. Other nonwoven fabric bonding methods
known in the art also can be adapted and used. Furthermore, it is
envisioned that the nonwoven fabric may be created from discrete
spunbond or meltblown layers that are formed, rolled, and later
joined or laminated by methods well known in the art (including
stacking the discrete layers without bonding) rather than the
discrete spunbond and/or meltblown layers being laid by a single
forming machine as presented above.
[0075] As an option, the forming machine 20 can be provided as a
modular structure of the spunbond and meltblown components. A
common operating console for all the spinning stations can be
provided with the common high speed belt for all spinning stations.
A high speed winding system (not shown) can be provided as an
option with a downstream slitter and rewinder downstream of the
embossing station.
[0076] In further reference to FIG. 2, distance 34 is the distance
from the die of beam 23 to the collection surface 22 of the endless
forming belt 27. As indicated, nonwoven fabrics made from the first
and second ribbon-shaped spunbond layers 12 and 16 as outer layers
with an interposed meltblown layer 14 as described can have a
significantly lower Flow Ratio than equivalent examples made from
round-shaped spunbond fibers or round-shaped spunbond layers. It
also has been observed that the difference in the Flow Ratio can be
more pronounced for examples where the meltblown fibers 15A were
applied to the ribbon-shaped spunbond layer 12 and meltblown fibers
15B were applied to the underlying meltblown fibers 15A and
ribbon-shaped spunbond layer 12 from a smaller distance from die to
collector (or "DCD") from beam 23, beam 31 or other beams. For
example, in examples with an S/M/S or S/M/M/S layered construction,
having a total basis weight of at least about 13 to no greater than
about 14 gsm, which includes about meltblown fibers in an amount of
at least about 1.3 gsm to no greater than about 1.5 gsm, the DCD
can have a significant impact on the above mentioned Flow Ratio.
That relationship between the change in ratio and the DCD indicates
that the synergy between the meltblown fibers 15A and 15B and
ribbon-shaped spunbond fibers 13, 17 can be even more pronounced
when the meltblown fibers 15A and 15B are projected with more force
due to having to travel a shorter distance toward the underlying
ribbon-shaped spunbond layer 12. The meltblown fibers 15A and 15B
may have the ability to form a more two-dimensional and rigid web
when applied to an underlying ribbon-shaped spunbond layer 12
rather than an underlying round-shaped spunbond layer. This is
supported by gathered pore size data, such as disclosed in the
examples section herein. The data indicates that the synergy exists
specifically for examples where there are fewer large pores or, in
other words, there is a lower fraction of large pores in the pore
distribution.
Uses of Nonwoven Fabrics
[0077] The nonwoven fabrics of the present invention can be used as
a barrier fabric or other component within a multitude of personal
hygiene products. These personal hygiene products can include, for
example, diapers. Diapers can include various diaper components,
such as described in U.S. Patent Application Publ. No. 2005/0215155
A1 (e.g., paragraphs [0047]-[0069]), which is incorporated herein
by reference. The nonwoven fabrics of the present invention can be
used in place of the nonwoven fabrics described in the diapers or
diaper components of the above incorporated published patent
application, such as, for example, the nonwoven fabrics that form
the topsheet, backsheet or leg cuffs. The nonwoven fabrics of the
present invention can also be used as a core wrap in diapers or
diaper components. Furthermore, the nonwoven fabric of the present
invention can be used in place of other substrates wherein the
breathability and/or barrier protection characteristics of the
nonwoven fabric of the present invention are desired. As an option,
the nonwoven fabric of the present invention can be used as a
diaper or adult incontinence product leg cuff. As another option,
the nonwoven fabrics of the present invention can be used as a
barrier layer within absorbent personal hygiene products. The
nonwoven fabric can be used as a barrier layer, such as a
backsheet, topsheet, anal cuff, outer cover, and barrier cover.
Furthermore, the nonwoven fabric of the present invention can be
used in disposable personal hygiene products including, but not
limited to, drapes (e.g., surgical and other medical drapes), gowns
(e.g., surgical and other medical gowns), sterilization wraps, and
foot covers.
[0078] The present invention will be further clarified by the
following examples, which are intended to be only exemplary of the
present invention.
EXAMPLES
Test Methods
[0079] Basis Weight
[0080] Basis weight of the following examples was measured in a way
that is consistent with ASTM D756 and EDANA ERT-40,3-90 test
method. The results were provided in units of mass per unit area in
g/m.sup.2 (gsm) and were obtained by weighing a minimum of ten 10
cm by 10 cm samples of each of the Comparative Examples and
Examples below.
[0081] Air Permeability
[0082] Air permeability data were produced using a TexTest FX3300
Air Permeability Tester manufactured by TexTest AG of Zurich,
Switzerland. The TexTest FX3300 Air Permeability Tester was used
accordingly with the manufacturer's instructions using a 38 mm
orifice and a pressure drop of 125 Pa as per test method ASTM D-737
test method. Readings were made on single ply or layer samples and
double ply or layer samples of the Comparative Examples and
Examples below and, the results were recorded in the units of
m.sup.3/m.sup.2/min.
[0083] Low Surface Tension Strike Through (LSTST)
[0084] The Low Surface Tension Strike Through method utilized was
based on EDANA test method WSP70.3(05) with a few modifications. A
first modification to EDANA test method WSP70.3(05) was that a low
surface tension fluid, described below in more detail, was utilized
instead of simulated urine solution of a 9 g/1 solution of sodium
chloride in distilled water having a surface tension of 70.+-.2
mN/m. A second modification to EDANA test method WSP70.3(05) was
that for the samples of the Comparative Examples and Examples where
the strike through time was less than 8 seconds when performed on a
single ply, the measurement was performed on two plies or layers of
the sample. The second modification was needed to increase the time
needed to absorb the 5 ml of fluid and subsequently reduce the
variability of the Low Surface Tension Strike Through method. A
third modification to EDANA test method WSP70.3(05) was that the
Ahlstrom Filtration filter paper code #989 (available from
Empirical Manufacturing, Inc., 7616 Reinhold Drive, Cincinnati,
Ohio 45237, USA) having dimensions of 4 inches by 4 inches was used
as a blotter or absorbent paper positioned under the sample,
instead of the suggested blotter paper ERT FF2, which is available
from Hollingsworth & Vose Co. or East Walpole, Mass. The five
blotter papers used per test were stacked with the rougher surface
facing the incoming fluid.
[0085] The low surface tension liquid utilized in the EDANA test
method WSP70.3(05) was prepared as follows: in a clear clean flask,
500 ml distilled water was provided and 2.100 grams of an nonionic
surfactant, which is available under the trademark Triton.RTM.
X-100 from Sigma-Aldrich of St. Louis, Mo., was added to the flask
containing the 500 ml distilled water. Thereafter, distilled water
in an amount of 5,000 ml was added to the same flask. The distilled
water and nonionic surfactant solution was mixed for a minimum of
30 minutes. The surface tension of the solution was measured, to
ensure it was between 31 mN/m and 32.5 mN/m, and preferably about
32mN/m, to qualify as a low surface tension liquid. The surface
tension of the solution was determined by method D1331-56
("Standard test method for surface and interfacial tension solution
of surface active agents") using a Kruss K11 MK1 tensiometer.
[0086] For the purposes herein, the LSTST-Time is defmed as the
strike through time in seconds measured by this method. The
LSTST-Flow is defmed as follow:
LSTST .times. - .times. Flow = 5 .times. ( ml ) / LSTST .times. -
.times. Time .function. ( seconds ) . ##EQU00001##
[0087] The units for LSTST-Flow are ml/sec. It is an expression of
the average flow rate of the low surface tension fluid through the
sample during the duration of the test.
[0088] Flow Ratio
[0089] Flow Ratio is defmed as the ratio of LSTST-Flow to air
permeability. This comparison was performed by measuring the
LSTST-Flow and air permeability of each of the Comparative Examples
and Examples below. The measurements were taken of each example
while ensuring the samples used for the measurements had the same
number of plies for both the LSTST-Flow and air permeability
measurements.
Flow .times. .times. Ratio = FR = LSTST .times. - .times. Flow
.times. / .times. Air .times. .times. permeability .
##EQU00002##
[0090] For the Flow Ratio, the units for LSTST-Flow are ml/sec, and
the units for air permeability are m.sup.3/m.sup.2/min.
[0091] Fiber Dimension and Aspect Ratio
[0092] Fiber Dimension Test Method 1 is utilized to measure the
dimensions d1 and d2 of round fibers in the samples of the
Comparative Examples and Examples below. Fiber Dimension Test
Method 1 assumes that round fiber have dimensions d1 and d2 that
are equal. As will be discussed below, Fiber Dimension Test Method
1 was also used to measure the dimension d1 or the fiber width of
the ribbon-shaped spunbond fibers of Examples 7-12 and 15-16 for
comparison purposes. Fiber Dimension Test Method 1 was measured
using a microscope positioned to view the fabric at 90.degree. from
the fabric surface. For spunbond fibers specifically, an optical
microscope was used to magnify the side-view of the selected fibers
in order to measure dimension d1 of the fibers. The optical
microscope was first calibrated using an acceptable standard (e.g.
Optical grid calibration slide 03A00429 S16 Stage Mic 1MM/0.01 DIV
available from Pyser-SGI Limited of Kent, UK or SEM Target grid SEM
NIST SRM 4846 #59-27F). For each layer, Fiber Dimension Test Method
1 utilized the common practice of selecting fibers at random to
measure the dimension d1 of fibers. In each layer of the sample
taken from the Comparative Examples and Examples, fibers were
selected by drawing a line between two points of the sample being
examined and selecting a minimum of 10 fibers for measurement. Such
an approach minimizes multiple measurements of the same fiber.
After magnification, the dimensions d1 were measured of the
selected fibers along the same axis as the line drawn between two
points of the sample. The average of the measured dimensions d1 of
the fibers was calculated based on the count of the fibers. As
stated above, because the dimensions d1 and d2 are assumed equal
for round-shaped fibers, the aspect ratio for such fibers was about
1:1.
[0093] Accordingly, the dimension d1 of the meltblown fibers were
also measured as per Fiber Dimension Test Method 1 with the
exception that a scanning electron microscope was used to achieve a
greater degree of magnification. It is generally accepted that
meltblown fibers have a round cross-sectional geometry, therefore
it was assumed that meltblown fiber cross-sections will have
dimensions d1 and d2 that are equal, producing an aspect ratio of
1:1.
[0094] For ribbon-shaped spunbond fibers, Fiber Dimension Test
Method 1 is not a suitable method to measure the dimensions d1 and
d2 needed for the computation of the aspect ratio. This is because
Fiber Dimension Test Method 1 does not provide information about
dimension d2 and, also because the average fiber dimension of the
ribbon-shaped spunbond fibers that was observed and measured by
Fiber Dimension Test Method 1 is typically less than the actual
average of dimension dl, as defined herein. The discrepancy between
the average fiber dimension observed and measured by Fiber
Dimension Test Method 1 and actual average of dimension d1 is
because not all of the ribbon-shaped spunbond fibers observed are
lying flat in the X-Y plane of the ribbon-shaped spunbond layer,
with their respective longest cross-sectional dimension all
positioned along the X-Y plane or all positioned along the Z plane
that is perpendicular to the X-Y plane. Therefore, Fiber Dimension
Test Method 2 was used to measure the dimensions d1 and d2 and
determine the aspect ratios of ribbon-shaped spunbond fibers,
consistent with the definition of aspect ratio. For Fiber Dimension
Test Method 2, a sample was taken from the Examples below and the
ribbon-shaped spunbond fibers in the sample were cut perpendicular
to their length. After cutting the ribbon-shaped spunbond fibers,
their cross-sections were observed using an optical microscope that
had been calibrated in a similar manner as in Fiber Dimension Test
Method 1. The dimensions d1 and d2 were measured for a minimum of 8
representative ribbon-shaped spunbond fibers selected from the
sample and average of the measurements of dimensions d1 and d2,
respectively, was calculated based on number of fibers. The Fiber
Dimension Test Method 2 is also a suitable method to measure
dimension d1 and d2 and compute the aspect ratio for round-shaped
fibers.
[0095] Pore Size Distribution
[0096] The pore size distributions of the Comparative Examples and
Examples were measured using a capillary flow porometer. The
instrument used was a PMI Capillary Flow Porometer model
CFP-1200-ACL-E-X-DR-2S, available from Porous Materials, Inc. of
Ithaca, N.Y. The instrument utilized a wetting fluid having a
surface tension of 15.9 mN/m, available under the trademark
Galwick.RTM. from Porous Materials, Inc.
[0097] The method used to measure the cumulative flow and pore size
distribution was provided by the equipment manufacturer and is
identified as "Capillary Flow Porometry Test" using the "Wet up/Dry
up" mode. A wrinkle free, clean circular sample is obtained from
the Comparative Examples and Examples having a diameter of about
1.0 cm. The sample was saturated with the wetting fluid and then
mounted into the cell of the PMI Capillary Flow Porometer, as per
the manufacturer's instruction. When the mounting was complete, the
apparatus was run by the apparatus software in the "Wet up/Dry up"
mode to first record a flow vs. pressure curve for the sample
saturated with the wetting fluid. When the flow v. pressure curve
is recorded for the saturated sample, and the fluid has been
expulsed from the pores, a flow vs. pressure curve was measured a
second time on the same sample mounted in the instrument. The data
generated includes the mean flow pore or "MFP," where the pore size
was calculated from the pressure where the half-dry curve
intersects with the wet curve. The mean flow pore diameter was such
that 50% of the flow is through pores larger than the mean flow
pore. The measurement of pore size at 10% cumulative filter flow
and the pore size at 25% cumulative filter flow were used as a way
to characterize the presence of large pores.
EXAMPLES AND RESULTS
[0098] Comparative Examples and Examples 1 to 16 included nonwoven
fabrics that were prepared on a line fitted with four production
beams (e.g., first, second, third and fourth production beams,
respectively) designed by Reifenhauser Reicofil GmbH & Co. KG
of Troisdorf, Germany. The first production beam formed spunbond
fibers that were deposited on a moving belt to form a first
spunbond layer. The second production beam formed meltblown fibers
that were laid on top of the first spunbond layer to form a first
meltblown sub-layer. The third production beam formed meltblown
fibers that were laid on top of the first meltblown sub-layer to
form a second meltblown sub-layer. The distance from die to
collector (DCD) for the second and third meltblown production beams
were adjusted between the various samples as indicated herein. The
fourth production beam formed spunbond fibers that were laid on top
of the second meltblown sub-layer to form a second spunbond layer.
The resulting stack of layers was bonded together using a calender
fitted with a smooth roll and an embossed roll. The embossed roll
was provided with two different patterns that were positioned side
by side to provide Comparative Examples and Examples with specific
bonding patterns as indicated below. One of the patterns is
identified in the data below as pattern A and includes an angled
oval pattern embossed with pattern available under the commercial
code U2888 from A+E Ungricht GMBH & Co. KG of Monchengladbach,
Germany. Pattern A is described as being formed from a plurality of
raised pins with a surface contact area or "land" area covering at
least about 16% and no greater than about 20% of the total area of
the embossed portion of the roll containing pattern A and having a
pin density of about 50 pins/cm.sup.2. The second pattern on the
embossed roll is identified in the data below as pattern B, which
is available under the commercial code U5444 through equipment
manufacturer Reifenhauser Reicofil GmbH & Co. KG of Troisdorf,
Germany and is produced by A+E Ungricht GMBH & Co. Kg of
Monchengladbach, Germany. Pattern B included an angled oval pattern
having a plurality of raised pins with a surface contact area or
"land" area covering more than 18% and no greater than 25% of the
total area of the embossed portion of the roll containing pattern B
and having a pin density of about 62.4 pins/cm.sup.2. The resulting
fabrics obtained from pattern A and pattern B included an S/M/M/S
layered construction.
[0099] For the production of the Comparative Examples and Examples
1 to 16, the first and fourth beams were fitted with the spinnerets
including either capillaries with a round cross-sectional geometry
to produce round-shaped spunbond fibers or capillaries with
ribbon-shaped cross-sectional geometry that produced the
ribbon-shaped spunbond fibers. The capillaries with the round
cross-sectional geometry had dimension d1 and d2 of 0.6 mm and an
aspect ratio of about 1.0:1.0. The capillaries with the
ribbon-shaped cross-sectional geometry had a rectangular shape with
rounded corners, a dimension d1 of about 1.5 mm and dimension d2 of
about 0.24 mm producing an aspect ratio of about 6.25:1. The
throughput was maintained on average at about 0.4 gram per
capillary or hole and per minutes (ghm)
[0100] In each of Comparative Examples and Examples 1 to 16, the
spunbond fibers formed by the first production beam and the fourth
production beam were extruded from a polypropylene resin having a
melt flow rate ("MFR") of 36 g/10 min., available under the
tradename PP3155 from ExxonMobil Chemicals, Inc. of Houston, Tex.
For Comparative Examples and Examples 1 to 16, the molten polymer
temperature was recorded at about 242.degree. C. for first
production beam and about 245.degree. C. for fourth production
beam. In each of Comparative Examples and Examples 1 to 16, the
meltblown fibers formed by the second and third production beams
were extruded from a polypropylene resin having a MFR of 1500 g/10
min. In each of Comparative Examples and Examples 1 to 16, the
meltblown layer, which included meltblown fibers formed by the
second and third production beams, had basis weight of about 10% of
the total basis weight.
[0101] Examples 7-12 and 15-16 included two spunbond layers formed
from ribbon-shaped spunbond fibers. Accordingly, select
representative samples were taken from Examples 7-12 and the
dimensions d1 and d2 for the ribbon-shaped spunbond fibers in each
representative sample were measured according to Fiber Dimension
Test Method 2. Based on this method, it was found that Examples
7-12 had an average dimension d1 of about 27.0 microns and an
average cross-sectional dimension d2 of about 8.3 microns. From
these average dimensions d1 and d2 an aspect ratio of about 3.25:1
was calculated for the ribbon-shaped spunbond fibers of Examples
7-12. For each of Examples 15 and 16, the ribbon-shaped spunbond
fibers were formed using the same process conditions. Accordingly,
select representative samples were taken from Examples 15 and 16
and the dimensions d1 and d2 for the ribbon-shaped spunbond fibers
in each sample were measured according to Fiber Dimension Test
Method 2. The average dimension d1 was 26.1 microns and the average
dimension d2 was 8.4 microns. From the average d1 and d2 an aspect
ratio of about 3.15:1 was calculated for the ribbon-shaped spunbond
fibers of Examples 15 and 16 Comparative Examples 1-6 and 13-14
included two spunbond layers formed from round-shaped spunbond
fibers. For those round-shaped spunbond fibers, the averages of
dimensions d1 were measured according to Fiber Dimension Test
Method 1.
Comparative Example 1
[0102] Comparative Example 1 was produced on the above described
production beams wherein the first and fourth production beans had
spinnerets with capillaries having a round cross-sectional
geometry, as indicated above. The resulting S/M/M/S layers were
then bonded using the embossed roller with pattern A. The resulting
fabric included a first round-shaped spunbond layer, two meltblown
layers and a second round-shaped spunbond layer, wherein the
spunbond layers have fibers with a round cross-sectional geometry
and an aspect ratio of less than 1.5. The meltblown layers of
Comparative Example 1 were formed from the second and third
production beams, which were positioned such that the DCD was 110
mm. The process conditions for forming Comparative Example 1 were
selected to approximate the commercial production of S/M/M/S
suitable for use as barrier leg cuff fabric. The average basis
weight for each layer was calculated based on the measured total
basis weight for the fabric and the throughput recorded for each
production beam The total basis weight measurement, the basis
weight calculations for each layer and average fiber dimension
measurements, according to Fiber Dimension Test Method 1, for
Comparative Example 1 are reproduced below in Table 1:
TABLE-US-00001 TABLE 1 Basis Weight Measurement and Calculations
Per Layer and Average Fiber Dimension Measurements for Comparative
Examples 1 & 2. Basis Weight Round-shaped spunbond fibers from
1.sup.st 5.94 gsm production beam Meltblown fibers from 2.sup.nd
production beam 0.66 gsm Meltblown fibers from 3.sup.rd production
beam 0.66 gsm Round-shaped spunbond fibers from 4.sup.th 5.94 gsm
production beam Total basis weight measured 13.2 gsm Average Fiber
Dimension Measurements According To Fiber Dimension Test Method 1
Round-shaped spunbond fibers from 1.sup.st 14.0 .mu.m production
beam Meltblown fibers from 2.sup.nd production beam 1.1 .mu.m
Meltblown fibers from 3.sup.rd production beam 1.2 .mu.m
Round-shaped spunbond fibers from 4.sup.th 14.5 .mu.m production
beam
Comparative Example 2
[0103] Comparative Example 2 was produced in the same manner as
Comparative Example 1 with the exception that the bonding pattern B
was used. Comparative Example 2 had the same total basis weight
measurement, basis weight calculations per layer and average fiber
dimension measurements as Comparative Example 1, which are provided
above in Table 1.
Comparative Example 3
[0104] Comparative Example 3 was produced in the same manner as
Comparative Example 1 with the exception that the DCD was 150 mm.
The total basis weight measurement, basis weight calculations per
layer and average fiber dimension measurements, according to Fiber
Dimension Test Method 1, for Comparative Example 3 are reproduced
below in Table 2:
TABLE-US-00002 TABLE 2 Basis Weight Measurement and Calculations
Per Layer and Average Fiber Dimension Measurements for Comparative
Examples 3 & 4 Basis Weight Round-shaped spunbond fibers from
1.sup.st 5.9 gsm production beam Meltblown fibers from 2.sup.nd
production beam 0.66 gsm Meltblown fibers from 3.sup.rd production
beam 0.66 gsm Round-shaped spunbond fibers from 4.sup.th 5.9 gsm
production beam Total basis weight measured 13.1 gsm Average Fiber
Dimension Measurements According To Fiber Dimension Test Method 1
Round-shaped spunbond fibers from 1.sup.st 14.5 .mu.m production
beam Meltblown fibers from 2.sup.nd production beam 1.1 .mu.m
Meltblown fibers from 3.sup.rd production beam 1.2 .mu.m
Round-shaped spunbond fibers from 4.sup.th 14.0 .mu.m production
beam
Comparative Example 4
[0105] Comparative Example 4 was produced in the same manner as
Comparative Example 2 with the exception that the DCD was 150 mm.
Comparative Example 4 had the same total basis weight measurement,
basis weight calculations per layer and average fiber dimension
measurements as Comparative Example 3, which are provided above in
Table 2.
Comparative Example 5
[0106] Comparative Example 5 was produced in the same manner as
Comparative Example 1 with the exception that the DCD was 190 mm.
The total basis weight measurement, basis weight calculations per
layer and average fiber dimension measurements, according to Fiber
Dimension Test Method 1, for Comparative Example 5 are reproduced
below in Table 3:
TABLE-US-00003 TABLE 3 Basis Weight Measurement and Calculations
Per Layer and Average Fiber Dimension Measurements for Comparative
Examples 5 & 6 Basis Weight Round-shaped spunbond fibers from
1.sup.st 5.85 gsm production beam Meltblown fibers from 2.sup.nd
production beam 0.65 gsm Meltblown fibers from 3.sup.rd production
beam 0.65 gsm Round-shaped spunbond fibers from 4.sup.th 5.85 gsm
production beam Total basis weight measured 13.0 gsm Average Fiber
Dimension Measurements According To Fiber Dimension Test Method 1
Round-shaped spunbond fibers from 1.sup.st 13.5 .mu.m production
beam Meltblown fibers from 2.sup.nd production beam 1.2 .mu.m
Meltblown fibers from 3.sup.rd production beam 1.2 .mu.m
Round-shaped spunbond fibers from 4.sup.th 14.5 .mu.m production
beam
Comparative Example 6
[0107] Comparative Example 6 was produced in the same manner as
Comparative Example 2 with the exception that the DCD was 190 mm.
Comparative Example 6 had the same total basis weight measurement,
basis weight calculations per layer and average fiber dimension
measurements as Comparative Example 5, which are provided above in
Table 3.
Example 7
[0108] Example 7 was produced using the same production beams as
Comparative Example 1, except the first and fourth production beams
included spinnerets included capillaries having a ribbon-shaped
geometry, as indicated above. As a result, Example 7 included two
spunbond layers of ribbon-shaped spunbond fibers instead of
round-shaped spunbond fibers. While the polymer throughputs for the
first and fourth production beams were kept about the same as those
used for Comparative Example 1, some of the other fiber spinning
conditions (e.g. volume of cooling air) had to be adjusted to
achieve process stability. The total basis weight measurement,
basis weight calculations per layer and average fiber dimension
measurements, according to Fiber Dimension Test Method 1, for
Example 7 are reproduced below in Table 4:
TABLE-US-00004 TABLE 4 Basis Weight Measurement and Calculations
Per Layer and Average Fiber Dimension Measurements for Examples 7
& 8 Basis Weight Round-shaped spunbond fibers from 1.sup.st
6.075 gsm production beam Meltblown fibers from 2.sup.nd production
beam 0.675 gsm Meltblown fibers from 3.sup.rd production beam 0.675
gsm Round-shaped spunbond fibers from 4.sup.th 6.075 gsm production
beam Total basis weight measured 13.5 gsm Average Fiber Dimension
Measurements According To Fiber Dimension Test Method 1
Ribbon-shaped spunbond fibers from 1.sup.st 19.5 .mu.m production
beam Meltblown fibers from 2.sup.nd production beam 1.1 .mu.m
Meltblown fibers from 3.sup.rd production beam 1.2 .mu.m
Ribbon-shaped spunbond fibers from 4.sup.th 21.0 .mu.m production
beam
Example 8
[0109] Example 8 was produced in the same manner as Example 7 with
the exception that the bonding pattern B was used. The total basis
weight calculation for Example 8 was the same total basis weight as
Example 7. In addition, the individual S/M/M/S layers of Example 8
had the same basis weight calculations as Example 7, shown in Table
4. The average fiber dimension of the fibers made from beams 1, 2,
3, and 4 in Example 8 were measured using Fiber Dimension Test
Method 1 and were the same as Example 7, shown above in Table
4.
Example 9
[0110] Example 9 was produced in the same manner as Example 7 with
the exception that the DCD was set at 150 mm. The total basis
weight measurement, basis weight calculations per layer and average
fiber dimension measurements, according to Fiber Dimension Test
Method 1, for Example 9 are reproduced below in Table 5:
TABLE-US-00005 TABLE 5 Basis Weight Measurement and Calculations
per Layer and Average Fiber Dimension Measurements for Examples 9
& 10 Basis Weight Round-shaped spunbond fibers from 1.sup.st
6.21 gsm production beam Meltblown fibers from 2.sup.nd production
beam 0.69 gsm Meltblown fibers from 3.sup.rd production beam 0.69
gsm Round-shaped spunbond fibers from 4.sup.th 6.21 gsm production
beam Total basis weight measured 13.8 gsm Average Fiber Dimension
Measurements According to Fiber Dimension Test Method 1
Ribbon-shaped spunbond fibers from 1.sup.st 20.5 .mu.m production
beam Meltblown fibers from 2.sup.nd production beam 1.1 .mu.m
Meltblown fibers from 3.sup.rd production beam 1.2 .mu.m
Ribbon-shaped spunbond fibers from 4.sup.th 22.5 .mu.m production
beam
Example 10
[0111] Example 10 was produced in the same manner as Example 8 with
the exception that the DCD was set at 150 mm. The total basis
weight calculation for Example 10 were the same total basis weight
as Example 9. In addition, the individual S/M/M/S layers of Example
10 had the same basis weight calculations as Example 9, shown in
Table 5. The average fiber dimension of the fibers made from beams
1, 2, 3, and 4 in Example 10 were measured using Fiber Dimension
Test Method 1 and were the same as Example 9, shown above in Table
5.
Example 11
[0112] Example 11 was produced in the same manner as Example 7 with
the exception that the DCD was set at 190 mm. The total basis
weight measurement, basis weight calculations per layer and average
fiber dimension measurements, according to Fiber Dimension Test
Method 1, for Example 11 are reproduced below in Table 6:
TABLE-US-00006 TABLE 6 Basis Weight Measurement and Calculations
per Layer and Average Fiber Dimension Measurements for Examples 11
& 12 Basis Weight Round-shaped spunbond fibers from 1.sup.st
5.805 gsm production beam Meltblown fibers from 2.sup.nd production
beam 0.645 gsm Meltblown fibers from 3.sup.rd production beam 0.645
gsm Round-shaped spunbond fibers from 4.sup.th 5.805 gsm production
beam Total basis weight measured 12.9 gsm Average Fiber Dimension
Measurements According To Fiber Dimension Test Method 1
Ribbon-shaped spunbond fibers from 1.sup.st 19.5 .mu.m production
beam Meltblown fibers from 2.sup.nd production beam 1.1 .mu.m
Meltblown fibers from 3.sup.rd production beam 1.2 .mu.m
Ribbon-shaped spunbond fibers from 4.sup.th 21.0 .mu.m production
beam
Example 12
[0113] Example 12 was produced in the same manner as Example 8 with
the exception that the DCD was set at 190 mm. The total basis
weight calculation for Example 12 was the same total basis weight
as Example 11. In addition, the individual S/M/M/S layers of
Example 12 had the same basis weight calculations as Example 11,
shown in Table 6. The average fiber dimension of the fibers made
from beams 1, 2, 3, and 4 in Example 12 were measured using Fiber
Dimension Test Method 1 and were the same as Example 11, shown
above in Table 6.
Comparative Example 13
[0114] Comparative Example 13 was made using the production beams
described above with reference to Comparative Examples 1-6. The
resulting fabric included a first round-shaped spunbond layer, two
meltblown layers and a second round-shaped spunbond layer having
fibers with a round cross-sectional geometry and an aspect ratio of
less than 1.5:1. However process conditions including polymer
throughputs were modified to produce an S/M/M/S fabric that is more
typical of those used for medical protective barrier applications,
such as gown and drapes. The basis weight measurement, basis weight
calculations per layer and average fiber dimension measurements,
according to Fiber Dimension Test Method 1, for Comparative Example
13 are reproduced below in Table 7:
TABLE-US-00007 TABLE 7 Basis Weight Measurement and Calculations
per Layer and Average Fiber Dimension Measurements for Comparative
Examples 13 & 14 Basis Weight Round-shaped spunbond fibers from
1.sup.st 18.1 gsm production beam Meltblown fibers from 2.sup.nd
production beam 4.4 gsm Meltblown fibers from 3.sup.rd production
beam 4.4 gsm Round-shaped spunbond fibers from 4.sup.th 18.1 gsm
production beam Total basis weight measured 45.5 gsm Average Fiber
Dimension Measurements According To Fiber Dimension Test Method 1
Round-shaped spunbond fibers from 1.sup.st 14.0 .mu.m production
beam Meltblown fibers from 2.sup.nd production beam 1.5 .mu.m
Meltblown fibers from 3.sup.rd production beam 1.4 .mu.m
Round-shaped spunbond fibers from 4.sup.th 14.5 .mu.m production
beam
Comparative Example 14
[0115] Comparative Example 14 was produced in the same manner as
Comparative Example 13, except that bonding pattern B was utilized.
Comparative Example 14 had the same total basis weight, basis
weight calculations per layer and average fiber dimension
measurements as Comparative Example 13, which are provided above in
Table 7.
Example 15
[0116] Example 15 was made in the same manner and using the same
production beams as Comparative Example 13, except that the first
and fourth production beams included spinnerets having capillaries
with a ribbon-shaped geometry, as indicated. Example 15 included
two ribbon-shaped spunbond layers formed from ribbons-shaped
spunbond fibers. The total basis weight for Example 15 was the same
total basis weight calculation as Comparative Example 13. In
addition, the individual S/M/M/S layers of Example 15 had the same
basis weight calculations as Comparative Example 13, shown in Table
7. The average fiber dimension measurements, according to Fiber
Dimension Test Method 1 for Example 15 are reproduced below in
Table 8:
TABLE-US-00008 TABLE 8 Basis Weight Measurement and Calculations
per Layer Average Fiber Dimension Measurements for Examples 15
& 16 Basis Weight Ribbon-shaped spunbond fibers from 1.sup.st
18.25 gsm production beam Meltblown fibers from 2.sup.nd production
beam 4.5 gsm Meltblown fibers from 3.sup.rd production beam 4.5 gsm
Ribbon-shaped spunbond fibers from 4.sup.th 18.25 gsm production
beam Total basis weight measured 45.5 gsm Average Fiber Dimension
Measurements According To Fiber Dimension Test Method 1
Ribbon-shaped spunbond fibers from 1.sup.st 22.5 .mu.m production
beam Meltblown fibers from 2.sup.nd production 1.5 .mu.m beam
Meltblown fibers from 3.sup.rd production 1.3 .mu.m beam
Ribbon-shaped spunbond fibers from 4.sup.th 20.5 .mu.m production
beam
Example 16
[0117] Example 16 was made in the same manner as Example 15 with
the exception that the bonding pattern B was used. The total basis
weight measurement for Example 16 was the same total basis weight
as Comparative Example 14. In addition, the individual S/M/M/S
layers of Example 16 had the same basis weight calculations as
Comparative Example 14, shown in Table 7. The average fiber
dimension of the fibers made from beams 1, 2, 3, and 4 in Example
16 were measured using Fiber Dimension Test Method 1 and were the
same as Example 15, shown above in Table 8.
Comparative Example 17
[0118] Comparative Example 17 was produced on a line having a
single production beam fitted with a spinneret having capillaries
with a round-cross-sectional geometry having a dimension d1 of 0.6
mm and an aspect ratio of 1.0:1.0. Comparative Example 17, thus,
included a single spunbond layer including round-shaped spunbond
fibers extruded from a isotactic homopolymer polypropylene resin
having a MFR of about 35g/10 min. The round-shaped spunbond fibers
of Comparative Example 17 were produced at a throughout of about
128 kg per hours per meter width of the die productive area
(kg/h/m). The round-shaped spunbond layer was bonded using an
embossed roll having a bonding pattern known as Design #6396
provided by Overbeck & Co. GmbH of Krefeld, Germany. This
pattern consisted of square diamond shaped pins having sides each
having a length of 0.75 mm. The pins are present at a density of
about 33.9 pin/cm.sup.2, providing a pin contact surface area that
covers about 19% of the total bonding surface of the embossed
portion of the roll. Comparative Example 17 had a basis weight of
about 17.5 gsm and included round-shaped spunbond fibers having a
denier of about 1.9 based on dimension d1 of about 17.3
microns.
Example 18
[0119] Example 18 was also produced from the same polymer resin as
Comparative Example 17 on the same production line, the same beam
and same throughput, with the exception that production beam
included a spinneret with capillaries having a ribbon-shaped
cross-sectional geometry that is similar to the capillaries used
for Sample 7-12 and 15-16. The resulting fabric included a
ribbon-shaped spunbond layer of Example 18 was bonded with same
embossing diamond pattern as Comparative Example 17 and had a basis
weight calculation measured at about 17 gsm. The ribbon-shaped
spunbond layer of Example 18 included ribbon-shaped spunbond fibers
having a dimension d1 of 39 microns and a dimension d2 of 11
microns, measured according to Fiber Dimension Test Method 2
providing an aspect ratio of 3.55:1.
[0120] The processing conditions for Comparative Examples and
Examples 1-16 are shown in Table 9. The test results for
Comparative Examples and Examples 1, 3, 5, 7,9, 11, 13 and 15 made
using bonding pattern A are shown in Table 10. The test results for
Comparative Examples and Examples 2, 4, 6, 8, 10, 12, 14 and 16
made using bonding pattern B are shown in Table 11. The test
results for Comparative Example 17 and Example 18 are shown in
Table 12.
[0121] Discussion of Results
[0122] When a nonwoven fabric is intended to be used in a personal
hygiene product or as a component of a personal hygiene product, an
important characteristic is its resistance to penetration by body
exudates. Those body exudates are often of low surface tension due
to their organic content; examples are runny bowel movement, blend
of runny bowel movement and urine (e.g., such a blend is projected
to have a 32 mN/m surface tension, as taught in U.S. Pat. No.
7,626,073 column 9, lines 9-12), or urine contaminated with lotion
or other body exudates like blood or menstrual fluids. Therefore, a
way to assess the liquid barrier capability of nonwoven fabric is
to test them using the LSTST test described above. For such a
nonwoven fabric, it is therefore desirable to achieve the highest
LSTST-Time or the lowest LSTST-Flow possible. It is also desirable
that such personal hygiene product is comfortable and breathable
and thus, that the nonwoven fabric used in the personal hygiene
product allows hot air and vapor moisture to pass through the
nonwoven fabric. It is generally accepted that more movement of hot
air and vapor moisture can occur through nonwoven fabrics having
higher air permeability. However, for a typical nonwoven fabric
having a layered S/M/M/S construction, an increase in air
permeability is usually achieved at the expense of the liquid
barrier performance or LSTST-Flow.
[0123] Comparative Examples 1-6 and Examples 7-12 had a total
fabric basis weight measurement of about 13 gsm and included a
meltblown fiber content of about 10% by weight of the total fabric
basis weight. The S/M/M/S layered construction of Comparative
Examples 1-6 and Examples 7-12 was typical of what is used as
barrier leg cuff in baby diaper or adult incontinence products (as
shown, e.g., in U.S. Pat. Appin. Publ. No. 2005/0215155 A1). The
performance of Comparative Examples 1-6 and Examples 7-12 indicate
the influence of the cross-section geometry and aspect ratio of the
spunbond fibers and DCD on liquid barrier performance and air
permeability. Comparative Examples 1-6 and Examples 7-12 were
tested and measurements for air permeability and LSTST-Flow were
obtained. The resulting measurements were used to calculate the
Flow Ratio. The results are shown in Tables 10 and 11.
[0124] It was observed that by comparing Comparative Example 1 with
Example 7 and comparing Comparative Examples 2 with Example 8, that
Examples 7 and 8, which included two ribbon-shaped spunbond layers
had a substantially lower Flow Ratio than equivalent Comparative
Examples 1 and 2, which included two round-shaped spunbond layers.
In addition, the comparison of Comparative Example 1 with Example 7
and the comparison of Comparative Example 2 with Example 8 also
indicate that a lower Flow Ratio represents a more favorable
balance between liquid barrier property and air permeability.
Specifically, where air permeability is equal between nonwoven
fabrics, a nonwoven fabric with a lower Flow Ratio will exhibit a
better resistance to flow of low surface tension liquid. The same
observation was made while comparing Comparative Example 3 with
Example 9 and while comparing Comparative Examples 4 and Example
10.
[0125] It is noted that the observation that a lower Flow Ratio
represents a more favorable balance between liquid barrier property
and air permeability described above in nonwoven fabrics that
included two ribbon-shaped spunbond layers did not appear to
materialize when comparing Comparative Example 5 with Example 11
and when comparing Comparative Examples 6 with Example 12. It is
thought that the lower Flow Ratio results observed for Examples
7-10, which included meltblown layers formed using production beams
having a DCD of 110 mm and 150 mm, was due to ability of meltblown
fibers formed at the lower DCD to form a more compact and better
supported web when deposited on a first ribbon-shaped spunbond
layer and covered by a second ribbon-shaped spunbond layer. In
particular, it is thought that the meltblown fibers form a more
compact web when disposed between the two ribbon-shaped spunbond
layers than when the meltblown fibers are disposed between two
round-shaped spunbond layers. The more compact web that is formed
should result in a slight downward shift in pore size distribution
for the high side of the pore size distribution curve at 10% and
25% cumulative filter flows, indicating a lower number of larger
pores or a lower fraction of larger pores in the pore distribution
curve. The more compact web is also thought to lower the ability
for the liquid to travel within the X-Y plane of the meltblown
layer after the liquid enters the fabric along the Z-axis, which is
oriented perpendicular to a major surface of the fabric. In
general, a correlation was observed between the improvement or
degradation of the Flow Ratio and the difference in pore size
measured at 10% and 25% cumulative filter flow (see, e.g., FIGS. 6
and 7). It is thought that the presence of larger pores have the
greatest impact on the flow of low surface tension liquid through
the fabric. Accordingly, as the number of larger pores increases,
the LSTST-Flow measurement also increases.
[0126] It also was observed that the difference in Flow Ratio, as
well as the reduction in pore size at 10% and 25% cumulative filter
flow, becomes more favorable as the DCD is reduced. These results
are shown in Tables 10 and 11. Based on these observations, it is
thought that the level of energy at which the meltblown fibers are
projected toward the underlying layer influence the liquid barrier
performance of a fabric. At a lower DCD, a more compact web is
formed by meltblown fiber than at high DCD, which is attributed to
the difference in kinetic energy remaining when the fibers reach
the forming surface. It was thought that at the process conditions
used for Examples 11-12, including meltblown fibers formed at a DCD
of 190 mm, the kinetic energy of the meltblown fibers reaching
underlying ribbon-shaped spunbond layer was so low or attenuated
that it formed a bulkier and less uniform web that did not benefit
from the flatter surface offered by the first ribbon-shaped
spunbond layers of Examples 7-10.
[0127] Comparative Examples 13-14 and Examples 15-16 were compared
to investigate the impact of the cross-sectional geometry and
aspect ratio of the spunbond fibers and bonding pattern on heavier
nonwoven fabrics that contain a higher percentage of meltblown
fibers. By comparing Comparative Example 13 with Example 15 and
Comparative Examples 14 with Example 16, no significant benefit was
observed in regard to Flow Ratio. It is thought that as the amount
of meltblown fiber was increased, the impact of the cross-sectional
geometry and aspect ratio of the spunbond fibers is diminished.
[0128] It was observed from the data collected in Tables 10 and 11
for Comparative Examples 1 to 6, Example 7 to 12, Comparative
Examples 13-14 and Example 15-16, that the relative benefit in Flow
Ratio attributed to the use of ribbon-shaped spunbond fibers rather
than round-shaped spunbond fibers for was not largely influence by
the bonding pattern used.
[0129] In another experiment, Comparative Example 17 and Example 18
were produced to compare spunbond layers made from round-shaped
spunbond fibers with spunbond layers made from ribbon-shaped
spunbond fibers. The air permeability, LSTST, and flow ratio
results for Comparative Example 17 and Example 18 are shown in
Table 12. Example 18 did not exhibit an advantage in regard to Flow
Ratio when compared to Comparative Example 17. Based on this
observation, it is believed that the lower Flow Ratio representing
a more favorable balance between liquid barrier property and air
permeability discussed above is not due to the ribbon-shaped
spunbond fibers or layers alone, but is rather due to the
combination of ribbon-shaped spunbond layer and a layer of
meltblown fibers.
[0130] The results have shown the unexpected findings that nonwoven
fabrics can benefit in regard to Flow Ratio by incorporating
ribbon-shaped spunbond fibers rather than round-shaped spunbond
fibers in a layered construction with meltblown layers. In
addition, the results have shown the unexpected findings that
nonwoven fabrics can benefit in regard to Flow Ratio when the
meltblown layer is designed to provide a nonwoven fabric that has a
pore size measured at 10% of cumulative filter flow of no more than
about 27 microns. Moreover, it is believed that providing a
nonwoven fabric with a total content of meltblown fibers that is
tailored to avoid forming an excessively tight structure can
enhance the benefits of ribbon-shaped spunbond layers made of
ribbon-shaped spunbond fibers.
TABLE-US-00009 TABLE 9 Comparative Examples and Examples 1 & 2
7 & 8 3 & 4 9 & 10 5 & 6 11 & 12 13 & 14 15
& 16 Shape of spunbond Round Ribbon Round Ribbon Round Ribbon
Round Ribbon fibers Throughput for 1.sup.st and Kg/h (1) 169/171
167/171 169/171 167/171 169/171 167/171 174/176 172/176 4.sup.th
beams producing the spunbond fiber layers Throughput for 2.sup.nd
and Kg/h (1) 18/19 19/19 18/19 19/19 18/19 19/19 43/43 43/43
3.sup.rd beams producing the meltblown fibers Line speed meters/min
449 449 449 449 449 449 150 150 Distance from die to mm 110/110
110/110 150/150 150/150 190/190 190/190 180/200 180/200 collector
(DCD for meltblown 2.sup.nd and 3.sup.rd beams) (1) The productive
length of the spinneret was about 1.1 meter
TABLE-US-00010 TABLE 10 TEST RESULTS FOR COMAPRATIVE EXAMPLES AND
EXAMPLES MADE USING THE BONDING PATTERN A Comparative Examples and
Examples 1 7 3 9 5 11 13 15 Shape of spunbond fibers Round Ribbon
Round Ribbon Round Ribbon Round Ribbon DCD for the meltblown
2.sup.nd and 110/110 110/110 150/150 150/150 190/190 190/190
180/200 180/200 3.sup.rd beams (mm) Basis weight (gsm) 13.2 13.5
13.1 13.8 13 12.9 45.5 45.5 Air Permeability for a single ply 40
37.5 50 50 56 58 7.25 6.35 (m.sup.3/m.sup.2/min) LSTST-Time
measured on -- -- -- -- -- -- 38 42 single ply sample (second)
LSTST-Flow for single-ply -- -- -- -- -- -- 0.132 0.119 measurement
(ml/sec) Flow Ratio for single-Ply -- -- -- -- -- -- 0.018 0.019
measurement Difference in Flow Ratio for 3% ribbon vs. round
filament samples tested as single ply Air Permeability for two
plies 21.5 17 24 20.5 27.5 22.5 -- -- (m.sup.3/m.sup.2/min)
LSTST-Time measured on two 9.4 14.2 9.4 12.8 9.1 10.1 -- -- plies
of sample(second) LSTST-Flow for two-plies 0.53 0.35 0.53 0.39 0.55
0.50 -- -- measurement (ml/sec) Flow Ratio for two-plies 0.0247
0.0207 0.0222 0.0191 0.0200 0.0220 -- -- measurement Difference in
Flow Ratio for -16% -14% 10% ribbon vs. round filament samples
tested as two plies Pore size at 10% cumulative 16 14.5 22 19 26 30
8.5 9 filter flow (micron) Pore size at 25% cumulative 14.5 13.5 19
16 20 23 7.5 8 filter flow (micron)
TABLE-US-00011 TABLE 11 TEST RESULTS FOR COMPARATIVE EXAMPLES AND
EXAMPLES MADE USING THE BONDING PATTERN B Comparative Examples and
Examples 2 8 4 10 6 12 14 16 Shape of spunbond fibers Round Ribbon
Round Ribbon Round Ribbon Round Ribbon DCD for the meltblown
2.sup.nd and 110/110 110/110 150/150 150/150 190/190 190/190
180/200 180/200 3.sup.rd beams (mm) Basis weight (gsm) 13.2 13.5
13.1 13.8 13 12.9 45.5 45.5 Air Permeability for a single ply 38 33
46 39 53 48.5 6.6 6.2 (m.sup.3/m.sup.2/min) LSTST-Time measured on
-- -- -- -- -- -- 32 34 single ply sample (second) LSTST-Flow for
single-ply -- -- -- -- -- -- 0.156 0.147 measurement (ml/sec) Flow
Ratio for single-Ply -- -- -- -- -- -- 0.024 0.024 measurement
Difference in Flow Ratio for 0% ribbon vs. round filament samples
tested as single ply Air Permeability for two plies 19.5 15.5 22 18
25.5 19 3.1 2.45 (m.sup.3/m.sup.2/min) LSTST-Time measured on two
10.2 15.1 9.9 13.8 9.2 11 plies of sample(second) LSTST-Flow for
two-plies 0.49 0.33 0.51 0.36 0.54 0.45 measurement (ml/sec) Flow
Ratio for two-plies 0.0251 0.0214 0.0230 0.0201 0.0213 0.0239
measurement Difference in Flow Ratio for -15% -12% 12% ribbon vs.
round filament samples tested as two plies Pore size at 10%
cumulative 14.5 14.5 25 21 22 35 8 9.2 filter flow (micron) Pore
size at 25% cumulative 13.5 13 19 16.5 19 27 7.1 8.1 filter flow
(micron)
TABLE-US-00012 TABLE 12 Comparative Example and Example 17 18 Shape
of spunbond fibers Round Ribbon Basis weight (gsm) Air Permeability
for a single ply 235 165 (m.sup.3/m.sup.2/min) Air Permeability for
two plies (m.sup.3/m.sup.2/min) 125 90 LSTST-Time measured on two
plies of 4 5.2 sample(second) LSTST-Flow for two-plies measurement
1.25 0.96 (ml/sec) Flow Ratio for two-plies measurement 0.0100
0.0107 Difference in ratio for ribbon vs. round 7% filament samples
tested as two plies
[0131] Unless indicated otherwise, all amounts, percentages, ratios
and the like used herein are by weight. When an amount,
concentration, or other value or parameter is given as either a
range, preferred range, or a list of upper preferable values and
lower preferable values, this is to be understood as specifically
disclosing all ranges formed from any pair of any upper range limit
or preferred value and any lower range limit or preferred value,
regardless of whether ranges are separately disclosed. Where a
range of numerical values is recited herein, unless otherwise
stated, the range is intended to include the endpoints thereof, and
all integers and fractions within the range. It is not intended
that the scope of the invention be limited to the specific values
recited when defining a range.
[0132] Although the invention herein has been described with
reference to particular embodiments, it is to be understood that
these embodiments are merely illustrative of the principles and
applications of the present invention. It will be apparent to those
skilled in the art that various modifications and variations can be
made to the method and apparatus of the present invention without
departing from the spirit and scope of the invention. Thus, it is
intended that the present invention include modifications and
variations that are within the scope of the appended claims and
their equivalents.
* * * * *