U.S. patent application number 09/972299 was filed with the patent office on 2002-10-03 for fine denier spunbond process and products thereof.
Invention is credited to Ferencz, Richard Leon.
Application Number | 20020142692 09/972299 |
Document ID | / |
Family ID | 22898164 |
Filed Date | 2002-10-03 |
United States Patent
Application |
20020142692 |
Kind Code |
A1 |
Ferencz, Richard Leon |
October 3, 2002 |
Fine denier spunbond process and products thereof
Abstract
A nonwoven fabric comprising one or more fine-denier spunbond
layers and one or more barrier layers. Each spunbond layer
comprises continuous filaments having a denier between 0.7 and 1.2,
which filaments are chosen from polyesters, polyolefins, and blends
thereof.
Inventors: |
Ferencz, Richard Leon; (Isle
of Palms, SC) |
Correspondence
Address: |
ROCKEY, MILNAMOW & KATZ, LTD.
TWO PRUDENTIAL PLAZA, STE. 4700
180 NORTH STETSON AVENUE
CHICAGO
IL
60601
US
|
Family ID: |
22898164 |
Appl. No.: |
09/972299 |
Filed: |
October 5, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60238497 |
Oct 6, 2000 |
|
|
|
Current U.S.
Class: |
442/401 ;
2/51 |
Current CPC
Class: |
Y10T 442/681 20150401;
B32B 5/022 20130101; D04H 1/559 20130101; D04H 1/56 20130101; D04H
3/016 20130101; B32B 27/12 20130101; B32B 5/26 20130101; B32B 27/02
20130101; B32B 2262/0253 20130101; B32B 2262/0276 20130101 |
Class at
Publication: |
442/401 ;
2/51 |
International
Class: |
A41D 013/12 |
Claims
What is claimed is:
1. A nonwoven barrier fabric, comprising a) a fine-denier spunbond
layer comprising a plurality of continuous thermoplastic filaments
having a denier of between 0.7 and 1.2 denier; b) a barrier layer
material deposited uniformly onto the fine denier spunbond layer
and the layers consolidated to form a composite fabric; and c) said
composite fabric having a hydrostatic head to barrier layer basis
weight ratio of about at least 4.9 cm/gsm.
2. A nonwoven barrier fabric as in claim 1, wherein: said
thermoplastic filaments are chosen from the group consisting of
polyolefins, polyesters and the blends thereof.
3. A nonwoven barrier fabric as in claim 2, wherein: said
polyolefins are chosen from the group consisting of polypropylene,
polyethylene, and blends thereof.
4. A nonwoven barrier fabric as in claim 1, wherein: the continuous
filaments may comprise bicomponent, multicomponent profiles and the
blends thereof.
5. A nonwoven barrier fabric as in claim 1, wherein the barrier
layer is selected from the group consisting of melt-blown,
cellulosic pulp, microporous film and monolithic film.
6. A nonwoven barrier fabric as in claim 5, wherein: said
melt-blown barrier layer having fiber diameters in the range of
about 1 to 10 microns and a basis weight of less than or equal to
about 10 grams/meter.sup.2.
7. A nonwoven barrier fabric as in claim 6, wherein: said
melt-blown barrier layer having a basis weight in the range of 1 to
8 grams/meter.sup.-2.
8. A nonwoven barrier fabric as in claim 1, wherein: said means of
consolidation are chosen from the group consisting of pressure
bonding, thermal calendering, and through-air bonding.
9. A nonwoven barrier fabric, comprising: a) a first fine-denier
spunbond layer comprising a plurality of continuous thermoplastic
filaments having a denier of between 0.7 and 1.2 denier; b) a
barrier layer material deposited onto the first fine denier
spunbond layer; c) a second spunbond layer deposited onto the
barrier layer; d) the first fine denier spunbond layer, the barrier
layer, and the second spunbond layer being consolidated into a
composite fabric structure; and e) said composite fabric having a
hydrostatic head to barrier layer basis weight ratio of about at
least 4.9 cm/gsm.
10. A nonwoven barrier fabric as in claim 9, wherein the second
spunbond layer is a fine-denier spunbond layer comprising a
plurality of continuous thermoplastic filaments having a denier of
between 0.7 and 1.2 denier.
11. A nonwoven barrier fabric as in claim 9, wherein: said
thermoplastic filaments are chosen from the group consisting of
polyolefins, polyesters and blends thereof.
12. A nonwoven barrier fabric as in claim 9, wherein: said
thermoplastic filaments of the first fine denier spunbond layer and
the second spunbond layer comprise different thermoplastic
polymers.
13. A nonwoven barrier fabric as in claim 10, wherein: said barrier
layer is a melt-blown barrier layer having fiber diameters in the
range of 1 to 10 microns and a basis weight less than or equal to
about 10 grams/meter.sup.2.
14. A nonwoven barrier fabric, comprising: a) a first fine-denier
spunbond layer comprising a plurality of continuous thermoplastic
filaments having a denier of between 0.7 and 1.2 denier; b) a first
barrier layer material deposited onto the first fine denier
spunbond layer; c) a second barrier layer deposited onto the first
barrier layer; d) a second spunbond layer deposited onto the second
barrier layer; e) said layers being consolidated into a composite
fabric structure; and f) said composite fabric having a hydrostatic
head to barrier layer basis weight ratio of about at least 4.9
cm/gsm.
15. A nonwoven fabric as in claim 14, wherein the second spunbond
layer is a fine-denier spunbond layer comprising a plurality of
continuous thermoplastic filaments having a denier of between 0.7
and 1.2 denier.
16. A nonwoven fabric, as in claim 14, wherein: said consolidation
method includes thermal calendering said laminate fabric structure
to exhibit a hydrostatic head rating of at least about 50 cm.
17. A disposable waste-containment garment, comprising; an
absorbent core, a liquid pervious topsheet, a liquid impervious
backsheet, said liquid impervious backsheet comprising a
fine-denier composite fabric, said fine-denier composite fabric
having a hydrostatic head to barrier layer basis weight ratio
greater than 4.9 cm/gsm.
18. A disposable waste-containment garment as in claim 17, wherein
the garment is a diaper.
19. A disposable waste-containment garment as in claim 17, wherein
the garment is a catamenial device.
20. A disposable garment comprising, a gown having a front panel, a
pair of back panels extending from opposed sides of the front
panel, and a pair of sleeve panels, wherein one or more of the
respective panels are comprised of a fine denier composite fabric
having a hydrostatic head to barrier basis weight ratio of about at
least 4.9 cm/gsm.
21. A disposable garment as in claim 20 wherein said gown is a
medical gown.
22. A disposable garment as in claim 20 wherein said gown is an
industrial protective garment.
23. A battery separator, comprising a) a first fine-denier spunbond
layer comprising a plurality of continuous polyolefin filaments
having a denier of between 0.7 and 1.2 denier; b) a barrier layer
material deposited onto the first fine denier spunbond layer; c)
the first fine denier spunbond layer, the barrier layer, and the
second spunbond layer being consolidated into a battery separator;
and e) said battery separator having a hydrostatic head to barrier
layer basis weight ratio of about at least 4.9 cm/gsm.
24. A battery separator as in claim 24, wherein the barrier layer
comprises one or more layers of melt-blown polyolefin microfibers.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims the priority of Provisional
Application Serial No. 60/238,497, which was filed on Oct. 6, 2000,
and the disclosure of which is herein incorporated by
reference.
TECHNICAL FIELD
[0002] The present invention relates generally to a method of
continuously extruding essentially endless, thermoplastic polymer,
fine denier filaments, and products produced thereby. Nonwoven
fabrics embodying the present invention exhibit unique performance
attributes, particularly when used in multiple layers, which offer
improved barrier characteristics. Incorporation of at least one
conventional filament layer onto a fine denier filament layer has
resulted in fabrics, which have exhibited enhanced barrier
performance in comparison to conventional continuous
filament/melt-blown barrier constructs.
BACKGROUND OF THE INVENTION
[0003] Nonwoven fabrics are used in a wide variety of applications
where the engineered qualities of the fabrics can be advantageously
employed. The use of selected thermoplastic polymers in the
construction of the fibrous fabric component, selected treatment of
the fibrous component (either while in fibrous form or in an
integrated structure), and selected use of various mechanisms by
which the fibrous component is integrated into a useful fabric, are
typical variables by which to adjust and alter the performance of
the resultant nonwoven fabric.
[0004] In and of themselves, continuous filament fabrics are
relatively highly porous, and ordinarily require an additional
component in order to achieve the required barrier performance.
Typically, barrier performance has been enhanced by the use of a
barrier melt-blown layer of very fine filaments, which are drawn
and fragmented by a high velocity air stream, and deposited into a
self-annealing mass. Typically, such a melt-blown layer exhibits
very low porosity, enhancing the barrier properties of composite
fabrics formed with spunbond and melt-blown layers.
[0005] Conventional spunbond/melt-blown/spunbond (SMS)-type fabrics
for protective apparel are manufactured in a basis weight range of
60-65 grams per square meter, typically relying upon a melt-blown
layer of more than 10 grams per square meter, to provide the
desired barrier function. Ordinarily, these types of fabrics have a
hydrostatic head rating of greater than 45 centimeters, before the
addition or topical treatment of the constructs with alcohol
resistant and anti-static chemistries.
[0006] Further prior art improvements on the SMS construct have
been made by incorporating multiple light-weight melt-blown barrier
layers, i.e. SMMS fabrics, in lieu of single heavy-weight
melt-blown layers. Fabrication in this manner has been found to
reduce hydrostatic head failures, which can otherwise result due to
defects that are common in melt-blown fabrics; the plural
melt-blown layers compensate for defects, which may exist in any
one layer. While multiple melt-blown layers act to facilitate
manufacturing efficiency, the complexity of such a process requires
additional equipment for each subsequent layer.
[0007] U.S. Pat. No. 5,464,688 teaches the use of modified
polypropylene resin with a higher melt flow rate to produce a
melt-blown web having average fiber diameters of from 1 to 3
microns and pore sizes distributed in the range from 7 to 12
microns compared to previously reported melt-blown webs, which have
pore sizes distributed predominantly in the range from 10 to 15
microns.
[0008] U.S. Pat. No. 5,482,765 teaches the addition of
fluorocarbons to either the melt-blown or spunbond layer and a
melt-blown layer with between 5 and 20% polybutylene. Such
modifications provide a laminate having improved barrier and
strength to weight ratios. The enhancement is measured by the ratio
of hydrostatic head to melt-blown layer basis weight of greater
than 115 cm/osy (3.38 cm/gsm).
[0009] The present invention contemplates that the provision of one
or more fine denier spunbond layers significantly improves the
overall barrier performance of the composite fabric. The fine
denier spunbond layer provides a more uniform interface between the
spunbond layer and a subsequent barrier layer applied during the
manufacture of the nonwoven fabric, resulting in improved barrier
performance in the fabricated article.
SUMMARY OF THE INVENTION
[0010] The present invention is directed to a nonwoven composite
fabric comprising one or more layers of fine denier spunbond
filaments and at least one layer of barrier material, wherein said
nonwoven composite fabric has a significantly improved barrier
performance as measured by the hydrostatic head to barrier layer
basis weight ratio being of about at least 4.9 cm/gsm. In a
preferred embodiment of the present invention, first and second
outer fabric layers are formed, each comprising continuous filament
spunbond layers of thermoplastic fibers, with the size of the
continuous filaments between about 0.7 and 1.2 denier, preferably
less than or equal to 1 denier. The barrier layer preferentially
comprises microfibers of finite length, wherein the average fiber
diameter is in the range of about 1 micron to about 10 microns, and
preferably between about 1 micron and 5 microns, said layers being
consolidated into a composite fabric.
[0011] The thermoplastic polymers of the continuous filament
spunbond layer or layers are chosen from the group consisting of
polyolefins and polyesters, wherein the polyolefins are chosen from
the group consisting of polypropylene, polyethylene, and
combinations thereof. It is within the purview of the present
invention that the continuous filament spunbond layer or layers may
comprise either the same or different thermoplastic polymers.
Further, the continuous filaments of the spunbond layer or layers
may comprise homogeneous, bicomponent, and/or multi-component
profiles and the blends thereof.
[0012] The barrier layer comprises a material selected from
suitable media, such media include: melt-blown, cellulosic pulp,
microporous film or monolithic film, with a microfiber media such
as melt-blown being preferred. The thermoplastic polymers of the
melt-blown microfibers are chosen from the group consisting of
polyolefins and polyesters, wherein the polyolefins are chosen from
the group consisting of polypropylene, polyethylene, and
combinations thereof. It is within the purview of the present
invention that the microfibers may comprise either the same or
different thermoplastic polymers. Further, the microfibers may
comprise homogeneous, bicomponent, and/or multi-component profiles
and the blends thereof. The melt-blown layer is in the basis weight
range of less than or equal to about 10 grams per square meter, the
basis weight of between 1 and 8 grams per square meter being most
preferred.
[0013] In a further aspect of the method of producing a nonwoven
fabric in accordance with the present invention, formation of a
composite fabric structure entails the formation of first and
second outer, spunbond web layers, and plural barrier melt-blown
layers, for example, two, melt-blown barrier layers. Preferably,
each of the outer, spunbond web layers are formed from a plurality
of endless filaments having a denier of between 0.7 and 1.2 denier,
with each outer layer preferably formed with the same basis weight,
and from the same denier filaments. Formation of plural barrier
melt-blown layers can be effected such that each of the melt-blown
layers is formed to have the same basis weight.
[0014] In a fabric formed in accordance with the present invention,
the incorporation of fine denier spunbond layers provide
substantial improvement in barrier function, allowing for reduction
in the amount of the spunbond and/or barrier layer required to meet
performance criteria. The fine denier spunbond layer provides a
more uniform support layer for the barrier layer during the
manufacturing process providing substantial improvement in barrier
function in the resulting end-use articles.
[0015] Formation of fabrics from fine denier spunbond materials,
particularly when combined with one or more barrier melt-blown
layers, has been found to provide enhanced barrier properties. The
present invention allows the production of a same weight fabric
with improved barrier properties or a lighter weight fabric that is
suitable for use as a barrier fabric, particularly for medical
gowns and industrial protective apparel. Use of the present fabric
as a battery separator component is also contemplated.
[0016] Other features and advantages of the present invention will
become readily apparent from the following detailed description,
the accompanying drawings, and the appended claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] FIG. 1 is a plan view of a diaper embodying this invention,
the diaper being shown in an uncontracted state.
[0018] FIG. 2 is an elevation of a surgical gown embodying this
invention.
DETAILED DESCRIPTION
[0019] While the present invention is susceptible of embodiment in
various forms, there will hereinafter be described, presently
preferred embodiments, with the understanding that the present
disclosure is to be considered as an exemplification of the
invention, and is not intended to limit the invention to the
specific embodiments disclosed herein.
[0020] The present invention is directed to a nonwoven composite
fabric, which entails formation of a layer of fine denier spunbond
filaments and at least one layer of barrier material. In order to
achieve desired barrier properties to weight ratios for the fabric
structure, the spunbond filaments preferably have a denier in the
range of about 0.7 to 1.2, and preferably have a denier less than
or equal to about 1.
[0021] A spunbond process involves supplying a molten polymer,
which is then extruded under pressure through a large number of
orifices in a plate known as a spinneret or die. The resulting
continuous filaments are quenched and drawn by any of a number of
methods, such as slot draw systems, attenuator guns, or Godet
rolls. The continuous filaments are collected as a loose web upon a
moving foraminous surface, such as a wire mesh conveyor belt. When
more than one spinneret is used in line for the purpose of forming
a multi-layered fabric, the subsequent webs is collected upon the
uppermost surface of the previously formed web. The web is then at
least temporarily consolidated, usually by means involving heat and
pressure, such as by thermal point bonding. Using this bonding
means, the web or layers of webs are passed between two hot metal
rolls, one of which has an embossed pattern to impart and achieve
the desired degree of point bonding, usually on the order of 10 to
40 percent of the overall surface area being so bonded.
[0022] The thermoplastic polymers of the continuous filament
spunbond layer or layers are chosen from the group consisting of
polyolefins and polyesters, wherein the polyolefins are chosen from
the group consisting of polypropylene, polyethylene, and
combinations thereof. It is within the purview of the present
invention that the continuous filament spunbond layer or layers may
comprise either the same or different thermoplastic polymers.
Further, the continuous filaments of the spunbond layer or layers
may comprise homogeneous, bicomponent, and/or multi-component
profiles and the blends thereof The barrier layer comprises a
material selected from suitable media, such media include:
melt-blown, cellulosic pulp, microporous film or monolithic film,
with microfiber media such as melt-blown being preferred.
Cellulosic pulp barrier layers are well-known for providing a
useful barrier performance in medical applications and include such
materials as wood pulp, in either a wetlaid tissue form or as an
airlaid fibrous layer. Suitable microporous film barrier layer can
include materials such as those reported in U.S. Pat. No.
5,910,225, the disclosure of which is herein incorporated by
reference, in which pore-nucleating agents are used to form the
micropores. Monolithic films as reported in U.S. Pat. No.
6,191,221, the disclosure of which is herein incorporated by
reference, can also be utilized as a suitable barrier means.
[0023] A preferred mechanism for forming a barrier layer is through
application of the melt-blown process. The melt-blown process is a
related means to the spunbond process for forming a layer of a
nonwoven fabric, wherein, a molten polymer is extruded under
pressure through orifices in a spinneret or die. High velocity air
impinges upon and entrains the filaments as they exit the die. The
energy of this step is such that the formed filaments are greatly
reduced in diameter and are fractured so that microfibers of finite
length are produced. This differs from the spunbond process whereby
the continuity of the filaments is preserved. The process to form
either a single layer or a multiple-layer fabric is continuous,
that is, the process steps are uninterrupted from extrusion of the
filaments to form the first and subsequent layers through
consolidation of the layers to form a composite fabric.
[0024] To form fine denier spunbond layers from conventional
spunbond equipment, several process parameters are modified. The
fine-fiber spunbond material is made by decreasing the extrusion
rate, while increasing the rate of the filaments. A thermoplastic
polymer can be selected to provide adequate melt strength so as to
minimize fiber breaks during the fiber draw-down process. The
actual extrusion and quench temperatures utilized and the other
specific changes to the process will depend upon the polymer resin
and the specific spunbond equipment. Specialized,
performance-enhanced spunbond layers such as those high-speed
spinning processes taught in U.S. Pat. No. 5,885,909, the
disclosure of which is herein incorporated by reference, can also
be practiced.
[0025] The melt-blown process, as well as the cross-sectional
profile of the spunbond filament or melt-blown microfiber are not a
critical limitation to the practice of the present invention.
[0026] By providing a fine denier spunbond layer upon which the
melt-blown layer is deposited, several enhancements of the fabric
are realized. For a given basis weight of the spunbond layer, a
finer denier fabric will give a greater number of filaments and a
smaller average pore size. The smaller average pore size will
result in a more uniform deposition of the melt-blown microfibers
onto the spunbond layer. A more uniform melt-blown layer will have
fewer weak points in the web at which a failure in barrier
performance can occur. The spunbond layer also serves to support
the melt-blown layer structurally in the composite material. A
finer denier spunbond layer provides a smaller average pore size
and a larger number of support points for the barrier layer; this
results in shorter spans of unsupported melt-blown microfibers.
This mechanism embodies the well-known concept that reduction in
the average span length results in enhanced structural
integrity.
EXAMPLES
[0027] Example 1 is a conventional SMS fabric comprising a spunbond
layer basis weight being 17 gsm and a melt-blown basis weight being
10 gsm. This construct was made in accordance with standard
practices as applied to equipment supplied by Reifenhauser GmbH for
the formation of fabric by thermal point bonding in a diamond
pattern at a coverage area of 17%. A thermoplastic resin was
provided in the form of polypropylene 3155 available from Exxon
Corporation.
[0028] Example 2 is a conventional SMMS fabric comprising a
spunbond layer basis weight being 15 gsm and a melt-blown basis
weight being 7.5 gsm. This construct was made in accordance with
standard practices as applied to equipment supplied by Reifenhauser
GmbH for the formation of fabric by thermal point bonding in a
diamond pattern at a coverage area of 17%. A thermoplastic resin
was provided in the form of polypropylene 3155 available from Exxon
Corporation.
[0029] Example 3 is an SMS fabric made in accordance with the
present invention, comprising a spunbond layer basis weight being
17 gsm and a melt-blown basis weight being 8 gsm. The polypropylene
resin used to form the spunbond layer was Achieve.RTM. 3854
available from Exxon Corporation. This construct was made in
accordance with standard practices as applied to equipment supplied
by Reifenhauser GmbH for the formation of fabric by thermal point
bonding in an oval pattern at a coverage area of 18%.
[0030] Example 4 is an SMMS fabric made in accordance with the
present invention, comprising a spunbond layer basis weight being
10 gsm and a melt-blown basis weight being 5 gsm. The polypropylene
resin used to form the spunbond layer was Achieve.RTM. 3854
available from Exxon Corporation. This construct was made in
accordance with standard practices as applied to equipment supplied
by Reifenhauser GmbH for the formation of fabric by thermal point
bonding in an oval pattern at a coverage area of 18%.
[0031] Example 5 is an SMMS fabric made in accordance with the
present invention, comprising a spunbond layer basis weight being
17 gsm and a melt-blown basis weight being 8 gsm. The polypropylene
resin used to form the spunbond layer was Achieve.RTM. 3854
available from Exxon Corporation. This construct was made in
accordance with standard practices as applied to equipment supplied
by Reifenhauser GmbH for the formation of fabric by thermal point
bonding in an oval pattern at a coverage area of 18%.
[0032] Example 6 is an SMMS fabric made in accordance with the
present invention, comprising a spunbond layer basis weight being 6
gsm and a melt-blown basis weight being 2.5 gsm. The polypropylene
resin used to form the spunbond layer was Achieve.RTM. 3854
available from Exxon Corporation. This construct was made in
accordance with standard practices as applied to equipment supplied
by Reifenhauser GmbH for the formation of fabric by thermal point
bonding in an oval pattern at a coverage area of 18%.
[0033] Example 7 is an SMS fabric made in accordance with the
present invention, comprising a spunbond layer basis weight being 7
gsm and a melt-blown basis weight being 3 gsm. The polypropylene
resin used to form the spunbond layer was Achieve.RTM. 3854
available from Exxon Corporation. This construct was made in
accordance with standard practices as applied to equipment supplied
by Reifenhauser GmbH for the formation of fabric by thermal point
bonding in an oval pattern at a coverage area of 18%.
[0034] For comparison purposes, examples of SMS fabrics from the
U.S. patent literature are also included in Table 1. Comparative
sample A is a polypropylene SMS fabric described in U.S. Pat. No.
5,464,688. Comparative sample B is a polypropylene SMS fabric
described in U.S. Pat. No. 5,482,765.
[0035] Table 1 sets forth composite fabrics formed in accordance
with the present invention compared to conventional SMS and SMMS
fabrics. Testing was done in accordance with the following standard
test methods.
1 Test Method Basis weight (grams/meter.sup.2) ASTM D3776 Tensiles
MD and CD Grab (g/cm) ASTM D5034 Tensiles MD and CD Elongation (%)
ASTM D5034 Tensiles MD and CD Strips ASTM D5035 Tensiles MD and CD
Elongation Strips ASTM D5035 Hydrostatic head (cm) INDA 80.4
[0036] In Table 1, the regular denier SMS material (Example 1) is
shown as having layers formed with various individual basis weights
of 17 gsm/10 gsm/17 gsm. The denier of the spunbond layer was
measured by common technique and was found to be 1.7 denier. The
melt-blown fiber diameters were measured to give an average of 2.0
microns. An SMMS material (Example 2) is also shown in Table 1, as
having layers formed with various individual basis weights of 15
gsm/7.5 gsm/7.5 gsm/15 gsm. The spunbond layers have filaments of
2.3 denier and the average melt-blown diameter is 2.8 microns. The
conventional SMS and SMMS fabrics exhibit hydrostatic head values
of 36.8 and 53 cm respectively. Normalization of the hydrostatic
head values for the two constructions to the melt-blown basis
weight gives values of 3.7 and 3.5 cm/gsm, respectively.
[0037] Example 3 represents a polypropylene SMS fabric made in
accordance with the invention, with individual layers of the
following basis weights, 17 gsm/8 gsm/17 gsm. The denier of the
spunbond layer was measured by common technique and was found to be
1.0 denier. The melt-blown fiber diameters were measured to give an
average of 2.1 microns. The hydrostatic head to basis weight ratio
for the fabric of Example 3 is 6.1. The improvement of barrier
property in the material made in accordance with this invention as
measured by hydrostatic head represents a 65% increase per gram per
square meter of the melt-blown barrier layer.
[0038] Comparative sample of SMS barrier fabrics reported in the
U.S. Patent literature are listed in Table 1. The total basis
weight for these two fabrics is 47 and 54 gsm respectively, with
each fabric having a melt-blown basis weight of 17 gsm. The
hydrostatic head to basis weight ratio for these products are 1.8
and 3.1 cm/gsm respectively. These values are significantly lower
than the values found for Example 3.
[0039] Example 4 represents a polypropylene SMMS fabric made in
accordance with the invention, with individual layers of the
following basis weights, 10 gsm/5 gsm/5 gsm/l 0 gsm. The denier of
the spunbond layer was measured by common technique and was found
to be 1.1 denier. The melt-blown fiber diameters were measured to
give an average value of 1.9 microns. The hydrostatic head to basis
weight ratio for the fabric of Example 4 is 4.9 cm/gsm. The
improvement of barrier property in the material made in accordance
with this invention as measured by hydrostatic head represents a
40% increase per gram per square meter of the melt-blown barrier
layer.
[0040] Example 5 represents a polypropylene SMMS fabric made in
accordance with the invention, with individual layers of the
following basis weights, 17 gsm/8 gsm/8 gsm/1 7 gsm. The
hydrostatic head value for this fabric is 90 cm, making this
material suitable for use in medical applications such as medical
gowns.
[0041] Other representative fabrics are presented in Table 2.
Examples 6-7 demonstrate the high ratio of hydrostatic head to
melt-blown basis weight, 7.4 and 7.8 cm/gsm respectively, in
lightweight constructs as embodied in the present invention. Such
lightweight constructs are particularly advantageous when used in
the fabrication of end-use articles requiring significant barrier
performance.
[0042] Disposable waste-containment garments are generally
described in U.S. Pat. No. 4,573,986, No. 5,843,056, and No.
6,198,018, the disclosures of which are incorporated herein by
reference.
[0043] An absorbent article incorporating an improved barrier
fabric of the present invention is represented by the unitary
disposable absorbent article, diaper 20, shown in FIG. 1. As used
herein, the term "diaper" refers to an absorbent article generally
worn by infants and incontinent persons that is worn about the
lower torso of the wearer. It should be understood, however, that
the present invention is also applicable to other absorbent
articles such as incontinence briefs, incontinence undergarments,
diaper holders and liners, feminine hygiene garments, training
pants, pull-on garments, and the like.
[0044] FIG. 1 is a plan view of a diaper 20 in an uncontracted
state (i.e., with elastic induced contraction pulled out) with
portions of the structure being cut-away to more clearly show the
construction of the diaper 20. As shown in FIG. 1, the diaper 20
preferably comprises a containment assembly 22 comprising a liquid
pervious topsheet 24; a liquid impervious backsheet 26 joined to
the topsheet; and an absorbent core 28 positioned between the
topsheet 24 and the backsheet 26. The absorbent core 28 has a pair
of opposing longitudinal edges, an inner surface and an outer
surface. The diaper can further comprise elastic leg features 32;
elastic waist features 34; and a fastening system 36, which
preferably comprises a pair of securement members 37 and a landing
member 38.
[0045] Practical application of an improved barrier fabric as
described in this invention for backsheet 26 results in a diaper
that is lighter in weight while maintaining performance. A lighter
weight backsheet material is expected to be more flexible and
therefore more conforming to deformation of the overall structure
as the diaper is worn.
[0046] Catamenial products, such as feminine hygiene pads, are of
the same general construction as the aforementioned diaper
structure. Again, a topsheet and a backsheet are affixed about a
central absorbent core. The overall design of the catamenial
product is altered to best conform to the human shape and for
absorbing human exudates. Representative prior art to such article
fabrication include U.S. Pat. No. 4,029,101, No. 4,184,498, No.
4,195,634, No. 4,408,357 and No. 4,886,513, the disclosures of
which are incorporated herein by reference.
[0047] Medical and industrial protective products, such as CSR,
medical gown, surgical drape and oversuits can benefit
significantly from the inclusion of an improved barrier fabric as
described in the present invention. Of particular utility in the
fabrication of such protective products is the use of lighter
weight fabrics with improved barrier to weight ratios, as it is
important for the finished product to be as lightweight as possible
yet still perform its desired function-. Patents generally
describing such protective products include U.S. Pat. No.
4,845,779, No. 4,876,746, No. 5,655,374, No. 6,029,274, and No.
6,103,647, the disclosures of which are incorporated herein by
reference.
[0048] Referring now to FIG. 2, there is shown a disposable garment
generally designated 110 comprising a surgical gown 112. The gown
112 comprises a body portion 114, which may be one-piece, having a
front panel 116 for covering the front of the wearer, and a pair of
back panels 118 and 120 extending from opposed sides of the front
panel 116 for covering the back of the wearer. The back panels 118
and 120 have a pair of side edges 122 and 124, respectively, which
define an opening on the back of the gown. The gown 112 has a pair
of sleeves 126 and 128 secured to the body portion 114 of the gown
for the arms of the wearer. In use, the back panels 118 and 120
overlap on the back of the wearer in order to close the back
opening of the gown, and suitable belt means (not shown) is
utilized to secure the back panels 118 and 120 in the overlapping
relationship.
[0049] SMS composite fabric is routinely used as a battery
separator between the positive and negative plates of a battery
cell in order to inhibit physical contact between the two opposing
plates. The battery separator must allow for the free flow of
electrons that are produced due to the chemical activity within the
cell, but must also provide a barrier such that any active
paste-like substances are prevented from penetrating the separator
material. With the highly improved barrier properties of the
nonwoven composite fabrics of the present invention, lighter weight
and less bulky fabrics may be employed, for example, as battery
separators. Less bulky fabrics allow for closer spacing of the
anode and cathode and an increase in the active material in the
battery for a given volume.
[0050] From the foregoing, numerous modifications and variations
can be effected without departing from the true spirit and scope of
the novel concept of the present invention. It is to be understood
that no limitation with respect to the specific embodiments
disclosed herein is intended or should be inferred. The disclosure
is intended to cover, by the appended claims, all such
modifications as fall within the scope of the claims.
2 TABLE 1 Examples Comparative Examples PROPERTY UNIT 1 2 3 4 5 A B
Layer basis gsm 17/10/17 15/7.5/7.5/15 17/8/17 10/5/5/10 17/8/8/17
15/17/15 18.7/17/18.7 weight Fabric basis gsm 44 45 42 30 50 47 54
weight Melt blown basis gsm 10 15 8 10 16 17 17 weight MD Grabs
g/cm 5960 4590 8102 4890 3776 -- -- CD Grabs g/cm 4120 3253 6472
3473 2631 -- -- MD Elongation % 62 55.5 50 50 39 -- -- CD
Elongation % 80 65.5 72 64 57 -- -- Hydrostatic head cm 36.8 53 49
49 90 29.9 53 (HSH) HSH/Melt-blown cm/gsm 3.7 3.5 6.1 4.9 5.6 1.8
3.1 Basis Weight
[0051]
3 TABLE 2 Examples PROPERTY UNIT 6 7 Layer basis weight gsm
6/2.5/2.5/6 7/2/2/7 Fabric basis weight gsm 17 18 Melt-blown basis
weight gsm 5 4 MD Strips g/cm 448 324 CD Strips g/cm 121 61 MD
Elongation % 19 20 CD Elongation % 121 30 Hydrostatic head (HSH) cm
37 31 HSH/Melt-blown basis cm/gsm 7.4 7.8 weight
* * * * *