Note: Descriptions are shown in the official language in which they were submitted.
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ELASTIC COMPOSITE MEMBER AND
DISPOSABLE GARMENT USING THE SAME
FIELD
The present invention relates to elastic composite members. More specifically,
the
present invention relates to elastic composite members which include
entanglement fibers
hydroentangled with an elastomeric material. The present invention also
relates to
disposable articles using such elastic composite members. Examples of such
disposable
articles include sweat bands, bandages, body wraps, disposable underwears,
disposable
garments W cluding pull-on diapers and training pants, and disposable panties
for menstrual
use.
BACKGROUND
Elastic members such as elastic laminates and elastic composite members have
previously been used in a variety of disposable articles, including sweat
bands, bandages,
body wraps, and disposable garments including disposable diapers and
incontinence
devices. Such elastic members typically include at least one elastomeric
material and a
fibrous material joined to or combined with the elastomeric material. It is
generally
expected that these products provide good fit to the body and/or skin of the
user by using
suitable elastic members during the entire use period of products.
Elastic composite members which include entanglement fibers hydroentangled
with
an elastomeric material are known in the art. Examples of such elastic
composite members
are disclosed in, for example, U.S. Patent No. 5,334,446 entitled "Composite
Elastic
Nonwoven Fabric" issued to Quantrille et al. on August 2, 1994. Those elastic
composite
members often employ an elastomeric net (or scrim). Such an elastomeric net
tends to have
uneven (or rugged) surfaces since component strands intersect or cross one
another in a
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overlaid manner to form the elastomeric net. As a result, the elastic
composite members
including such an uneven elastomeric material also tend to have uneven (or
rugged) surfaces
even after entanglement fibers are hydroentangled with the elastomeric net.
Such an uneven elastic composite member tends to cause a red marking on a
wearer's skin when the wearer puts on a disposable article using the uneven
elastic
composite member. This is because if an elastic composite member has a rough
surface
(i.e., convex potions and concave portions in one surface), forces which are
generated by the
elastic composite member and are directed to the skin of the wearer are
concentrated at the
convex portions. It is believed that such concentration of the forces cause
the red marking
problem.
To improve the roughness of surfaces of elastic composite member, entanglement
f bers may be increased. However, such increase of entanglement fibers tends
to hurt the
ability of elongation of the elastic composite member, and, as a result, tends
to hurt
expected performance of disposable articles.
One typical example of disposable articles is a disposable garment. Infants
and
other incontinent individuals wear disposable garments such as diapers to
receive and
contain urine and other body exudates. Such disposable garments often use
elastic
members. For example, ear panels and waistbands of disposable garments
preferably
include an elastic member. The performance of the elastic member is important
since the
ear panels and/or waistbands contribute to provide a better fit to the
wearer's waist area.
In disposable pull-on garments, in particular, the performance of the elastic
member
also tends to impact on an ease of applicability. For example, if the
stretchability of the ear
panels and/or waistbands are very limited, the user who wants to apply a pull-
on garment to
a wearer has (or at least feels) a problem in its applicability. Examples of
pull-on garments
are disclosed, for example, in U.S. Patent No. 5,171,239 to Igaue et al., U.S.
Patent No.
4,610,681 to Strohbeen et al., WO 93/17648 published on September 16, 1993,
U.S. Patent
No. 4,940,464 to Van Gompel et al., U.S. Patent No. 5,246,433 to Hasse et al.,
and U.S.
Patent No. 5,569,234 to Buell et al.
Based on the foregoing, there is a need for elastic composite members using
entanglement fibers which have an improved surface roughness with a minimum
influence
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3
on the elongation ability. There is also a need for disposable articles which
use such elastic
composite members.
SUMMARY
The present invention is directed to an elastic composite member which is
elastically
extensible in at least one direction. The elastic composite member comprises a
plane
elastomeric material having a plurality of apertures formed therein; and a
fibrous material
including entanglement fibers. The entanglement fibers are hydroentangled with
the plane
elastomeric material through the apertures. The elastic composite member has a
Surface
Roughness (SRO) of less than about 5 pm.
The present invention is also directed to a disposable article including the
elastic
composite member.
The foregoing answers the need for elastic composite members using
entanglement
fibers which have an improved surface roughness with a minimum influence on
the
elongation ability. The foregoing also answers the need for disposable
garments which use
such elastic composite members.
These and other features, aspects, and advantages of the present invention
will
become evident to those skilled in the art from reading of the present
disclosure.
BRIEF DESCRIPTION OF THE DRAWINGS
While the specification concludes with claims particularly pointing out and
distinctly claiming the invention, it is believed that the invention will be
better understood
from the following description of preferred embodiments which is taken in
conjunction with
the accompanying drawings and which like designations are used to designate
substantially
identical elements, and in which:
Fig. 1 is a perspective view of a plane elastomeric material employed in
preferred
embodiments of the present invention;
Fig. 2 is a graph showing an example of the two-cycles of hysteresis curves of
a
plane elastomeric material, in a preferred embodiment;
Fig. 3 is a perspective view of an elastic composite member which is one
preferred
embodiment of the present invention;
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Fig. 4 is a perspective view of an elastic composite member which is another
preferred embodiment of the present invention;
Fig. 5 is a schematic representation of a pressure application device for
forming a
flattened elastic composite member;
Fig. 6 is a perspective view of one embodiment of the disposable garment of
the
present invention in a typical in use configuration;
Fig. 7 is a perspective view of another preferred embodiment of the disposable
garment of the present invention in a typical in use configuration;
Fig. 8 is a simplified plan view of the embodiment shown in Fig. 7 in its flat
uncontracted condition showing the various panels or zones of the garment;
Fig. 9 is a cross-sectional view of a preferred embodiment taken along the
section
line 9-9 of Fig. 8;
Fig. 10 is a cross-sectional view of a waistband 50 of a preferred embodiment
taken
along the section line 10-10 of Fig. 8;
Fig. 11 is a cross-sectional view of a waistband SO of another preferred
embodiment;
Figs. 12 and 13 are schematic diagrams explaining the test method for
measuring
Surface Roughness values of elastic composite members;
Fig. 14 is a cross-sectional view of a steel plate used for measuring Surface
Roughness values of elastic composite members; and
Fig. 15 is a graph showing a deviation of the surface of elastic composite
members
obtained by a measurement.
DETAILED DESCRIPTION
All cited references are incorporated herein by reference in their entireties.
Citation
of any reference is not an admission regarding any determination as to its
availability as
prior art to the claimed invention.
Herein, "comprise" means that other elements) and steps) which do not affect
the
end result can be added. These terms encompass the terms "consisting of and
"consisting
essentially of'.
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Herein, "plane elastomeric material" refers to elastomeric materials which
continuously extend in two dimensional directions. The plane elastomeric
material has a
first surface and a second surface opposing the first surface.
Herein, "extensible" and "elongatable" refer to materials that are capable of
5 extending in at least one direction to a certain degree without undue
rupture.
Herein, "elasticity", "elastically extensible" and "elastically elongatable"
refer to
extensible or elongatable materials that have the ability to return to
approximately their
original dimensions after the force that extended the material is removed.
Herein, "disposable" describes garments which are not intended to be laundered
or
otherwise restored or reused as a garment (i.e., they are intended to be
discarded after a
single use and, preferably, to be recycled, composted or otherwise disposed of
in an
environmentally compatible manner).
Herein, "pull-on garment" refers to articles of wear which have a defined
waist
opening and a pair of leg openings and which are pulled onto the body of the
wearer by
inserting the legs into the leg openings and pulling the article up over the
waist.
Herein, "pull-on diaper" refers to pull-on garments generally worn by infants
and
other incontinent individuals to absorb and contain urine and feces. It should
be understood,
however, that the present invention is also applicable to other pull-on
ganments such as
training pants, incontinent briefs, feminine hygiene garments or panties, and
the like.
Herein, "panel" denotes an area or element of the pull-on garment. (While a
panel is
typically a distinct area or element, a panel may coincide (functionally
correspond)
somewhat with an adjacent panel.)
Herein, "joined" or "joining" encompasses configurations whereby an element is
directly secured to another by affixing the element directly to the other
element, and
co~gurations whereby the element is indirectly secured to the other element by
affixing the
element to intermediate members) which in turn are affixed to the other
element.
Herein, "uncontracted state" is used to describe states of pull-on garments in
its
unseamed (i.e., seams are removed), flat and relaxed condition wherein ail
elastic materials
used are removed therefrom.
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Fig. 1 is a perspective view of a plane elastomeric material 520 used in one
preferred
embodiment of the present invention. The plane elastomeric material 520 has a
first surface
401 and a second surface 402 opposing the first surface 401. The plane
elastomeric material
520 of the present invention has a plurality of apertures 530 formed therein.
The apertures
530 formed in the plane elastomeric material 520 can be any shape and size as
long as the
entanglement fibers can be hydroentangled with the plane elastomeric material
520 through
the apertures 530. Preferred shapes of the apertures 530 include a circle, an
ellipse, a
triangle, a quadrilateral including a rectangle, a square and a trapezoid, and
the other
polygons.
In a preferred embodiment, the average aperture area of one aperture 530 is
from
about 1 mm2 to about 25 mm2, more preferably from about 3 mm2 to about 10 mm2.
Preferably, the ratio of the total area of the apertures 530 on the first
surface 401 (for
example) to the surface area of the first surface 401 is from about 10% to
about 90%, more
preferably from about 40% to about 60%.
The plane elastomeric material 520 may take any shape which can be suitably
provided in products. Preferred shapes of a plane elastomeric material 520
include a
quadrilateral including a rectangle and a square, a trapezoid, and the other
polygons.
The plane elastomeric material 520 of the present invention is elastically
extensible
in at least one direction (first direction). For example, the plane
elastomeric material 520
shown in Fig. 1 is elastically extensible in the structural direction D.
Herein, "structural
direction" (e.g., D and B) is intended to mean a direction which extends
substantially along
and parallel to the plane of the plane elastomeric material 520. In a
preferred embodiment,
the plane elastomeric material 520 is also elastically extensible in the
second direction
which is perpendicular to the first direction. The direction which has the
highest elongation
ability in the plane of the plane elastomeric material 520 is called
hereinafter as "primary
extensible direction". In a preferred embodiment, the plane elastomeric
material 520 shown
in Fig. 1 has the primary extensible direction in the structural direction D.
The elastomeric material used in the plane elastomeric material may include
all
suitable elastic materials known in the art. Elastomeric materials suitable
for use herein
include synthetic or natural rubber materials known in the art. Preferred
elastomeric
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materials include the diblock and triblock copolymers based on polystyrene and
unsaturated
or fully hydrogenerated rubber bolcks, and their blends with other polymers
such as
polystyrene polymers.
In a preferred embodiment, the elastomeric material contains from about 30 wt%
to
about 95 wt% of polystyrene, more preferably from about 50 wt% to about 85 wt%
of
polystyrene. Preferably, the elastomeric material is made from a polystyrene
thermoplastic
elastomer including styrene block copolymer based materials. Preferred styrene
block
copolymer based materials contain from about 1 wt% to about 70 wt% of
polystyrene, more
preferably from about 10 wt% to about 50 wt% of polystyrene. A preferred
polystyrene
thermoplastic elastomer is selected from the group consisting of a styrene-
butadiene-styrene
thermoplastic elastomer, a styrene-isopren-styrene thermoplastic elastomer, a
styrene
ethylene/butylene-styrene thermoplastic elastomer, a styrene-
ethylene/propylene-styrene
thermoplastic elastomer, an unsaturated styrene butadiene rubber or a fully
hydrogenated
styrene butadiene rubber, a mixture thereof, and their blends with other
polymers such as
polyethylene polymers.
In a preferred embodiment, the plane elastomeric material 520 has a basis
weight
from about 30 g/m2 to about 250 g/m2, preferably from about 60 g/m2 to about
200 g/m2,
and more preferably from about 100 g/m2 to about 160 g/m2.
In one embodiment, the plane elastomeric material 520 is a perforated film
(not
shown in Figs.) formed by an elastomeric material. The perforated film has a
multiplicity of
apertures 530 formed therein. In a preferred embodiment, the plane elastomeric
material
520 is in the form of a scrim as shown in Fig. 1.
Fig. 1 shows an elastomeric scrim 560 which are employed in preferred
embodiments of the present invention. The elastomeric scrim 560 includes a
plurality of
first strands 125 which intersect or cross (with or without bonding to) a
plurality of second
strands 127 at nodes 128 at a predetermined angle a, thereby forming a net-
like open
structure having a plurality of apertures 530. Each aperture 530 is defined by
at least two
adjacent first strands 125 and at least two adjacent second strands I27 such
that apertures
530 are substantially rectangular in shape. Other aperture configurations,
such as
parallelograms or circular arc segments, can also be provided. Such
configurations could be
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useful for providing non-linear elastic structural directions. Preferably, the
first strands 125
are substantially straight and substantially parallel to one another; and,
more preferably, the
second strands 127 are also substantially straight and substantially parallel
to one another.
More preferably, first strands 125 intersect second strands 127 at nodes 128
at a
predetermined angle a of about 90 degrees. Each node 128 is an overlaid node,
wherein
first strands 125 and second strands 127 are preferably joined or bonded
(although it is
contemplated that joining or bonding may not be required) at the point of
intersection with
the strands still individually distinguishable at the nodes 128. However, it
is believed that
other node configurations such as merged or a combination of merged and
overlaid would
be equally suitable.
Although it is preferred that first and second strands 125 and 127 be
substantially
straight, parallel, and intersect at an angle a of about 90 degrees, it is
noted that first and
second strands 125 and 127 can intersect at other angles a, and that first
strands 125 and/or
second strands 127 can be aligned in circular, elliptical or otherwise
nonlinear patterns
relative to one another. Although for ease of manufacture it is contemplated
that first
strands 125 and second strands 127 have a substantially circular cross-
sectional shape (prior
to application of a pressure for forming a flattened elastic composite member
as shown in
Fig. 5), the first and second strands 125 and 127 can also have other cross-
sectional shapes
such as elliptical, square, triangular or combinations thereof.
Preferably, the material for the first strands I25 is chosen so that the first
strands 125
can maintain the second strands 127 in relative alignment prior to forming an
elastic
composite member. It is also desirable that the materials for the first and
second strands
125 and 127 are capable of being deformed (or initially formed) into
predetermined shapes
upon application of a predetermined pressure or a pressure in combination with
a heat flux
prior to forming an elastic composite member. These deformed shapes (e.g.,
elliptical
second strands, substantially flat first strands and the like) can provide an
elastic composite
member which can be comfortably worn about the body without irritation or
other
discomfort.
In a preferred embodiment, the first strands 125 of the elastomeric scrim 560
have an
average cross sectional area of from about 0.0001 mm2 to about 0.5 mm2, and
the second
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strands I27 have an average cross sectional area of from about 0.01 mm2 to
about 2.5 mm2.
More preferably, the first strands 125 have an average cross sectional area of
from about
0.0025 mm2 to about 0.1 mm2, and the second strands 127 have an average cross
sectional
area of from about 0.1 mm2 to about 1 mm2.
In a preferred embodiment, the elastomeric scrim 560 has from about 5 to about
20
elastic strands per inch (about 2-8 strands/cm) in the structural direction B
(i.e., the first
strands I25) and from about 3 to about 15 elastic strands per inch (about 1-6
strands/cm) in
the structural direction D (i.e., the second strands 127). More preferably,
the elastomeric
scrim 560 has from about 10 to about 15 elastic strands per inch (about 4-6
strands/cm) in
the structural direction B and from about 5 to about 10 elastic strands per
inch (about 2-4
strands/cm) in the structural direction D.
In a preferred embodiment, the first and second strands I25 and 127 are forned
from
an identical elastomeric material. For example, the first and second strands
125 and 127 are
formed from an identical polystyrene thermoplastic elastomer which is selected
from the
group consisting of a styrene-butadiene-styrene thermoplastic elastomer, a
styrene-isopren-
styrene thermoplastic elastomer, a styrene-ethylene/butylene-styrene
thermoplastic
elastomer, a styrene-ethylene/propylene-styrene thermoplastic elastomer, a
fully
hydrogenated styrene butadiene rubber or an unsaturated styrene butadiene
rubber, and their
blends with other polymers such as polystyrene polymers. A preferred
elastomeric scrim
124 which container a styrene-butadiene-styrene thermoplastic elastomer is
manufactured
by the Conwed Plastics Company (Minneapolis, Minn., U.S.A.) under the
designation
X02514. This material also has about 12 elastic strands per inch (about 5
strands/cm) in the
structural direction B (i.e., the first strands 125) and about 7 elastic
strands per inch (about 3
strands/cm) in the structural direction D (i.e., the second strands 127).
Alternatively, the first and second strands 125 and 127 are formed from two
different material. For example, one of the first and second strands 125 and
127 is formed
from one of the above described polystyrene thermoplastic elastomer, while the
other of the
first and second strands 125 and 127 is formed from materials) other than the
above
described polystyrene thermoplastic elastomer. Such other materials) may be
either elastic
or non-elastic, and selected from suitable materials known in the art.
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Fig. 2 shows one preferred example of the extension and recovery force curves
for
the two cycle hysteresis of the plane elastomeric material 520 (e.g., an
elastomeric scrim
560). The curve E 1 shows the extension force in the f rst cycle, while the
curve R 1 shows
the recovery force in the first cycle. The curve E2 (shown in dashed lines)
shows the
5 extension force in the second cycle, while the curve R2 shows the recovery
force in the
second cycle. (These extension and recovery properties are measured as
follows: In the first
cycle, the plane elastomeric material 520 is subjected to an initial extension
force at a
crosshead rate of about 51 cm/min (about 20 in/min) at about 23oC and held for
about 30
seconds at 200% extension. The plane elastomeric material 520 is then allowed
to relax at
10 the same rate to the original state (i.e., 0% extension). The plane
elastomeric material 520 is
allowed to remain unconstrained for one minute before being subjected to a
second
extension force (for the second cycle) at the same rate and conditions.
Fig. 3 is a perspective view showing an elastic composite member of one
preferred
embodiment of the present invention. Referring to Fig. 3, the elastic
composite member
500 includes the plane elastomeric material 520 having the apertures 530 (not
shown in Fig.
3 but Fig. 1 ), and a fibrous material 540 including entanglement fibers 550.
The
entanglement f bers S50 are hydroentangled one another and with the plane
elastomeric
material 520 through the apertures 530. The entanglement fibers 550 are
depicted only in a
part of the elastic composite member S00 in Fig. 3 (and also in Fig. 4). The
elastic
composite member 500 has a first surface 501 and a second surface 502 opposing
the first
surface 501.
In a preferred embodiment, the plane elastomeric material 520 is an
elastomeric
scrim 560 such as shown in Fig. 1. In the embodiment shown in Fig. 3, the
first surface 501
of the elastic composite member S00 has upheaval portions 511 which are
upheaved by the
first strands 125, and upheaval portions S I 2 which are upheaved by the
second strands 127.
Similarly, the second surface 502 of the elastic composite member 500 has also
upheaval
portions (not shown in Fig. 3) which are upheaved by the first and second
strands 125 and
127.
The elastic composite member 500 of the present invention is elastically
extensible
in at least one direction (first direction). For example, the elastic
composite member S00
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shown in Fig. 3 is elastically extensible in the structural direction D. In a
preferred
embodiment, the elastic composite member S00 is also elastically extensible in
the second
direction which is perpendicular to the first direction. For example, the
elastic composite
member 500 shown in Fig. 3 is also elastically extensible in the structural
direction B. In a
preferred embodiment, the elastic composite member 500 shown in Fig. 3 has the
primary
extensible direction in the structural direction D.
The entanglement fibers 550 are hydroentangled one another. The entanglement
fibers SSO are also hydroentangled with the plane eiastomeric material 520
through the
apertures 530. Such an entanglement fiber structure can be formed by any fiber
hydroentanglement process known in the art. Preferred hydroentanglement
processes are
described in, for example, U.S. Patent No. 4,775,579 entitled "Hydroentangled
Elastic and
Nonelastic Filaments" issued to Hagy et al. on October 4, 1988; and U.S.
Patent No.
5,334,44b entitled "Composite Elastic Nonwoven Fabric" issued to Quantrille et
al. on
August 2, 1994.
In a preferred embodiment, the entanglement fibers 550 are hydroentangled one
another uniformly in adjacent apertures 530 of the plane elastomeric material
520. Herein,
"uniformly" is used to describe hydroentangled fibers disposed in adjacent
apertures have
substantially same in terms of the average void volume of the fibrous material
formed by
the entanglement fibers. Herein, "substantially same" means the deviation of
physical
amount (e.g., the void volume) of a material is within about 40%, more
preferably about
20% of the total amount.
In a preferred embodiment, the fibrous material 540 has a basis weight from
about 5
g/m2 to about 100 g/m2, more preferably from about 20 g/m2 to about 80 g/m2,
and yet
more preferably from about 30 g/m2 to about 60 g/m2.
Any type of fibers can be used for the entanglement fibers 550 of the present
invention. For example, natural fibers (e.g., wool and cotton fibers),
synthetic fibers (e.g.,
polyolefin, polyester, nylon, and rayon fibers), or a mixture of natural
fibers and/or synthetic
fibers can be used as the entanglement fibers. For ease of manufacture and
cost efficiency,
synthetic staple fibers are preferably used. More preferably, such synthetic
staple fibers are
formed from a polyolefin (e.g., polyethylene and polypropylene) or a
polyester. Preferred
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polyester material includes a polyethylene terephthalate, a polypropylene
terephthalate and a
polybutylene terephthalate, or mixtures thereof.
In one embodiment, the individual entanglement fibers 550 are formed from a
single
material which is selected from the above materials (i.e., the individual
fiber is not made
from two or more materials). Alternatively, the entanglement fibers 550 may be
formed
from a mixture of two (or more) materials which are selected from the above
materials.
In a preferred embodiment, the entanglement fibers 550 are bi-component
fibers.
Preferably, the entanglement fibers 550 have a bi-component fiber structure
formed by two
distinct materials, for example, a side-by-side cross section or an eccentric
cross section. In
a preferred embodiment, the bi-component fibers have a side-by-side cross
section of a
lower molecular weight polyethylene terephthalate and a higher molecular
weight
polyethylene terephthalate. In an alternative preferred embodiment, the bi-
component fibers
have an eccentric cross section of a polypropylene and a random
polypropylene/poiyethylene copolymer which preferably contains less than 15%
of
polyethylene.
Preferably, the entanglement fibers 550 have an average f ber thickness of
less than
about 4 denier per filament. More preferably, the entanglement fibers 550 have
an average
fiber thickness of more than about 0.5 denier per filament. Yet more
preferably, the
entanglement fibers 550 have an average fiber thickness of from about I to
about 2.5 denier
per filament.
In a preferred embodiment, the entanglement fibers 550 have an average fiber
length
of from about 1 cm to about 10 em. More preferably, the entanglement fibers
550 have an
average fiber length of from about 3 cm to about 7 cm. Yet more preferably,
the
entanglement fibers 550 have an average fiber length of from about 4 cm to
about 6 cm.
The elastic composite member 600 of the present invention has a Surface
Roughness
(SRO) of less than about 5 pm. SRO is a physical property of an elastic
composite member.
The SRO shows a degree of deviation of the surfaces of the elastic composite
member. For
example, an elastic composite member 600 which has a relatively higher value
of SRO
increases the possibility of causing a red marking on the wearer's skin when
the wearer puts
on a disposable article using such an elastic composite member. This is
because if an elastic
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composite member has a rough surface (i.e., convex potions and concave
portions in the
first surface 501 (or the second surface 502), forces which are generated by
the elastic
composite member 600 and are directed to the skin of the wearer are
concentrated at the
convex portions. It is believed that such concentration of the forces cause
the red marking
problem. A method for defining the SRO of elastic composite members is
described in the
"Test Methods" section.
In a preferred embodiment, the elastic composite member 600 has an SRO of less
than about 4 pm, more preferably less than about 3 Vim.
In a preferred embodiment, the elastic composite member 500 has a stress at
100%
elongation of from about SO gf/inch (about 20 gf/cm) to about 500 gf/inch
(about 200
gf/cm), preferably from about 150 gf/inch (about 60 gf/cm) to about 350
gf/inch (about 140
gf/cm), and more preferably from about 200 gf/inch (about 80 gf/cm) to about
300 gf/inch
(about 120 gf/cm).
In a preferred embodiment, the fibrous material 540 has a Strain Resistance
(SRE) of
less than about 100% at 100% elongation in the extensible direction. In the
embodiment
shown in Fig. 3, the extensible direction can be either the structural
direction D or B
(preferably, D). SRE is a physical property of entanglement fibers (i.e., a
fibrous material)
which are hydroentangled one another and with a plane elastomeric material in
an elastic
composite member. SRE of a fibrous material at a designated elongation in an
extensible
direction is obtained from the following expression:
SRE = ( TSC - TSE ) / TSE x 100 (%)
wherein,
TSC : average tensile strength of elastic composite member at the designated
elongation; and
TSE : average tensile strength of plane elastomeric material at the designated
elongation.
The SRE value shows a degree of resistance of the fibrous material when the
elastic
composite member is elongated to a designated elongation (e.g., 100% of the
original
length) especially in the first several times before the use of disposable
articles. For
example, a fibrous material 540 which has a relatively higher value of SRE
requires a
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14
relatively higher force to elongate the elastic composite member 500. Such a
fibrous
material 540 tends to hurt an expected performance of disposable articles
using the elastic
composite member. A method for measuring the tensile strength of elastic
composite
members and plane elastomeric materials is described in the "Test Methods"
section.
In a preferred embodiment, the fibrous material 540 has an SRE of less than
about
60%, and more preferably less than about 30% at 100% elongation in the
extensible
direction. In an alternative preferred embodiment, the fibrous material 540
has an SRE of
less than about 30%, and more preferably less than about 20% at 50% elongation
in the
extensible direction.
Preferred elastic composite members 500 are obtainable from Daiwabo Co., Ltd.,
Osaka, Japan, under Code Nos. PC I 70B and PC 170C. The fibrous materials 540
of these
elastic composite members 500 have the following SRE values at 50% and 100%
elongation
in the cross-machine direction (CD).
Table I
Sample Sample Code Stain Resistance
No. (%)
50% Elongation 100% Elongation
1 PC 160A 19 43
2 PC 160B 26 57
3 PC 170B 23 48
4 PC 170C 14 20
Fig. 4 is a perspective view of an elastic composite member 600 which is
another
preferred embodiment of the present invention. Referring to Fig. 4, the
elastic composite
member 600 includes the plane elastomeric material 520 having the apertures
530 (not
shown in Fig. 4), and a fibrous material 540 including entanglement fibers
550. The
entanglement fibers 550 are hydroentangled one another and with the plane
elastomeric
material 520 through the apertures 530. The entanglement fibers S50 are
depicted only in a
part of the elastic composite member 600. The elastic composite member 600 has
a first
surface 501 anc second surface 502 opposing the first surface SO1.
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In a preferred embodiment, the plane elastomeric material 520 is an
elastomeric
scrim 560 such as shown in Fig. 1. Compared with the embodiment shown in Fig.
3, the
elastic composite member 600 has lower upheaval portions 511' and 512' which
are
upheaved by the first and second strands 125 and 127 on the first and second
surfaces 501
5 and 502.
The elastic composite member 600 is elastically extensible in at least one
direction
(first direction). For example, the elastic composite member 600 shown in Fig.
4 is
elastically extensible in the structural direction D. In a preferred
embodiment, the elastic
composite member 600 is also elastically extensible in the second direction
which is
10 perpendicular to the first direction. For example, the elastic composite
member 600 shown
in Fig. 4 is also elastically extensible in the structural direction B. In a
preferred
embodiment, the elastic composite member 600 shown in Fig. 4 has the primary
extensible
direction in the structural direction D.
A preferred elastic composite member 600 which has a relatively lower SRO is
15 formed by applying a predetermined pressure at a predetermined temperature
to a precursor
elastic composite member for a predetermined time period. Herein, "precursor
elastic
composite member" can be any of the above described elastic composite members
500. The
resulting elastic composite member 600 is referred to as "flattened elastic
composite
member" hereinafter.
In a preferred embodiment, the predetermined temperature is lower than the
melting
point of the fibrous material. In a more preferred embodiment wherein the
plane
elastomeric material 520 includes soft segments and hard segments, the
predetermined
temperature is higher than the glass transition temperature of the hard
segments.
Fig. S shows one preferred example of a pressure application device 800 for
forming
a flattened elastic composite member. Any of the above described elastic
composite
members 500 can be used as a precursor elastic composite member 810 for
forming a
flattened elastic composite member 820. Refen-ing to Fig. 5, the pressure
application device
800 includes a first pressure plate 801 having a first surface 803, and a
second plate 802
having a second surface 804. The second pressure plate 802 is fixed, while the
first pressure
plate 801 is movable to apply a pressure P to the precursor elastic composite
member 810 in
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16
cooperation with the second pressure plate 802. Preferably, the first and
second surfaces
803 and 804 are substantially plane and are substantially parallel each other.
The elastic
composite member 810 is manually supplied to the pressure application device
800. A
preferred pressure application device 800 is available from Toyo Tester
Industry Co., Ltd.,
Osaka, Japan, under a trade name "Heat Sealer".
In the pressure application process, the first surface 803 of the elastic
composite
member 810 is heated to a temperature T1, while the second surface 804 is
heated to a
temperature T2. Preferably, the temperatures T1 and T2 are selected within a
predetermined
range so that any of the entanglement fibers 550 can not be melted at the
pressure P. This is
preferred because a melting of the entanglement fibers 550 tends to increase
the SRE value
of the resulting flattened elastic composite member 820. Additionally, by
avoiding such a
melting of any of the entanglement fibers 550, it is possible to maintain the
ability of the
elongation of the resulting flattened elastic composite member 820 within a
preferred range.
In preferred embodiments wherein the above described elastic composite members
500 (Code Nos. PC 160A; PC 1608; PC 1708 and PC I 70C) are used as precursor
elastic
composite members 810, the temperature T1 is from about 80°C to about
160°C, more
preferably from about 90°C to about 110°C. The temperature T2 is
preferably from about
40°C to about 65°C, more preferably from about 50°C to
about 60°C. The pressure P is
preferably from about 6 kg/cm2 to about 15 kg/cm2, more preferably from about
9 kg/cm2
to about 11 kg/cm2. The time period of the application of the pressure P is
preferably from
about 1 second to about 20 seconds, more preferably from about 5 seconds to
about 15
seconds. Preferably, the application of pressure P can be performed twice (or
more times)
to decrease the SRO value of the resulting elastic composite member 820. By
the
application of the temperatures T1 and T2 at the pressure P, the precursor
elastic composite
member 810 (i.e., the plane elastomeric material 520 as well as the fibrous
material 540) is
flattened to decrease the SRO value compared with that of the precursor
elastic composite
member 810 (e.g., the elastic composite member 500 shown in Fig. 3).
The resulting flattened elastic composite members 820 have the following SRO
values in the machine direction (MD) which are relatively higher than those in
the cross-
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17
machine direction (CD). (The below table also shows the SRO values of the
precursor
elastic composite members before the flattening formation for reference
purpose.)
Table II
Sample Sample CodeSurface Roughness Surface Roughness
No. (pm) (pm)
(before flattening) (after flattening)
1 PC 160A 7.9 4.3
2 PC 160B 7.1 4.0
3 PC 170B 4.4 3.9
4 PC 170C 4.1 2.7
The elastic composite member of the present invention can be incorporated into
a
variety of products wherein it is desired to provide an elastic elongation
ability in at least
one structural direction either partially or entirely. Examples of such
products include
disposable articles, including sweat bands, bandages, body wraps, and
disposable garments
including disposable diapers and incontinence products. In the following,
applications to
disposable pull-on garments are described as preferred embodiments of the
present
invention. One or more of the above described elastic composite members will
be
preferably used as, for example, the elastic members 70 and 700 shown in Figs.
9, 10 and
11.
Fig. 6 shows one preferred embodiment of a disposable pull-on garment of the
present invention (i.e., a unitary disposable pull-on diaper 120). Referring
to Fig. 6, the
disposable pull-on garment 120 has a front region 26; a back region 28 and a
crotch region
30 between the front region 26 and the back region 28. A chassis 41 is
provided in the
front, back and crotch regions 26, 28 and 30. The chassis 41 includes a liquid
pervious
topsheet 24, a liquid impervious backsheet 22 associated with the topsheet 24,
and an
absorbent core 25 (not shown in Fig. 6) disposed between the topsheet 24 and
the backsheet
22. The chassis 41 has side edges 220 which form edge lines 222 in the front
region 26.
The pull-on garment 120 further includes at least one pair of extensible ear
panels 45
each extending laterally outward from the corresponding sides of the chassis
41. Each of
the ear panels 45 has an outermost edge 240 which forms an outermost edge line
242. At
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least one of the outermost edge lines 242 has a nonuniform lateral distance
from the
longitudinal center line 100 (not shown in Fig. 6) in the uncontracted state
of the garment
120.
In a preferred embodiment, the ear panels 45 continuously extend from the
corresponding sides of the chassis 41 in the back region 28 to the
corresponding side edges
220 of the chassis 41 in the front region 26 as shown in Fig. 6.
Alternatively, the ear panels
45 may continuously extend from the corresponding sides of the chassis 41 in
the front
region 26 to the corresponding side edges of the chassis 41 in the back region
28 (not shown
in Fig. 6).
The pull-on garment 120 has the ear panels 45 joined to the chassis 41 to form
two
leg openings 34 and a waist opening 36. Preferably, the pull-on garment 120
further
includes seams 232 each joining the chassis 41 and the ear panels 45 along the
corresponding edge lines 222 and 242 to form the two leg openings 34 and the
waist
opening 36.
Fig. 7 shows another preferred embodiment of a disposable pull-on garment of
the
present invention (i.e., a unitary disposable pull-on diaper 20). Referring to
Fig. 7, the
disposable pull-on garment 20 includes a pair of extensible front ear panels
46 each
extending laterally outward from the corresponding sides of the chassis 41 in
the front
region 26, and a pair of extensible back ear panels 48 each extending
laterally outward from
the corresponding sides of the chassis 41 in the back region 28. Each of the
ear panels 46
and 48 has an outermost edge 240 which forms an outermost edge line 242. At
least one of
the outermost edge lines 242 has a nonuniform lateral distance LD from the
longitudinal
center line 100 (not shown in Fig. 7 but in Fig. 8) in the uncontracted state
of the garment
20. The pull-on garment 20 further includes seams 32 each joining the front
and back ear
panels 46 and 48 along the corresponding edge lines 242 to form the two leg
openings 34
and the waist opening 36.
In a preferred embodiment, at least one of, more preferably both of, the pairs
of the
ear panels 45, 46 and 48 are elastically extensible in at least the lateral
direction. In one
embodiment, the ear panels 45, 46 and 48 are also elastically extensible in
the longitudinal
direction. The elastically extensible ear panels 45, 46 and 48 provide a more
comfortable
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19
and contouring fit by initially conformably fitting the pull-on garment to the
wearer and
sustaining this fit throughout the time of wear well past when the pull-on
garment has been
loaded with exudates since the ear panels 45, 46 and/or 48 allow the sides of
the pull-on
garment to expand and contract.
The ear panels 45, 46 and 48 may be formed by unitary elements of the pull-on
garment 20 or 120 (i.e., they are not separately manipulative elements secured
to the pull-on
garment 20 or 120, but rather are formed from and are extensions of one or
more of the
various layers of the pull-on garment). In a preferred embodiment, each of the
ear panels
45, 46 and 48 is a projected member of the chassis 41 (more clearly shown in
Fig. 8).
Preferably, the ear panels 45, 46 and 48 include at least one unitary element
or a continuous
sheet material (e.g. the nonwoven outer cover 74 in Fig. 9) that forms a part
of the chassis
41 and continuously extends into the ear panels 45, 46 and 48. Alternatively,
the ear panels
45, 46 and 48 may be discrete members (not shown in Figs.) which do not have
any unitary
element that forms a part of the chassis 41, and may be formed by joining the
discrete
members to the corresponding sides of the chassis 41.
In a preferred embodiment, the pull-on garment 20 or 120 further includes seam
panels 66 each extending laterally outward from each of the ear panels 45, 46
and 48; and
tear open tabs 31 each extending laterally outward from the seam panel 66. In
a preferred
embodiment, each of the seam panels 66 is an extension of the corresponding
ear panels 45,
46 and 48, or at least one of the component elements used therein, or any
other combination
of the elements. More preferably, each of the tear open tabs 31 is also an
extension of the
corresponding seam panel 66 or at least one of its component elements used
therein, or any
other combination of its elements.
In a preferred embodiment, the corresponding edge portions of the chassis 41
and/or
the ear panels 45, 46 and 48 are seamed directly or indirectly (e.g., through
the seam panels
66), in an overlaping manner to make an overlapped seam structure.
Alternatively, the front
and ear panels 46 and 48 can be seamed in a butt seam manner (not shown in
Figs.). The
bonding of the seams 32 can be performed by any suitable means known in the
art
appropriate for the specific materials employed in the chassis 41 and/or the
ear panels 45, 46
and 48. Thus, sonic sealing, heat sealing, pressure bonding, adhesive or
cohesive bonding,
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sewing, autogeneous bonding, and the like may be appropriate techniques.
Preferably, the
seam panels 66 are joined by a predetermined pattern of heat/pressure or
ultrasonic welds
which withstands the forces and stresses generated on the garment 20 or 120
during wear.
A continuous belt 38 is formed by the ear panels 45, 46 and 48, and a part of
the
5 chassis 41 about the waist opening 36 as shown in Figs. 6 and 7. Preferably,
elasticized
waist bands 50 are provided in both the front region 26 and the back region
28. The
continuous belt 38 acts to dynamically create fitment forces in the pull-on
garment 20 or
120 when positioned on the wearer, to maintain the pull-on garment 20 or i20
on the wearer
even when loaded with body exudates thus keeping the absorbent core 25 (not
shown in Fig.
10 7) in close proximity to the wearer, and to distribute the forces
dynamically generated
during wear about the waist thereby providing supplemental support for the
absorbent core
without binding or bunching the absorbent core 25.
Fig. 8 is a partially cut-away plan view of the pull-on garment 20 of Fig. 7
in its
uncontracted state (except in the ear panels 46 and 48 which are left in their
relaxed
15 condition) with the topsheet 24 facing the viewer, prior to the ear panels
46 and 48 being
joined together by the seams 32. The pull-on garment 20 has the front region
26, the back
region 28 opposed to the front region 26, the crotch region 30 positioned
between the front
region 26 and the back region 28, and a periphery which is defined by the
outer perimeter or
edges of the pull-on garment 20 in which the side edges are designated 150 and
240, and the
20 end edges or waist edges are designated 152. The topsheet 24 has the body-
facing surface
of the pull-on garment 20 which is positioned adjacent to the wearer's body
during use. The
backsheet 22 has the outer-facing surface of the pull-on garment 20 which is
positioned
away from the wearer's body. The pull-on garment 20 includes the chassis 41
including the
liquid pervious topsheet 24, the liquid impervious backsheet 22 associated
with the topsheet
25 24, and the absorbent core 25 positioned between the topsheet 24 and the
backsheet 22. The
garment 20 further includes the front and back ear panels 46 and 48 extending
laterally
outward from the chassis 41, the elasticized leg cuffs 52, and the elasticized
waistbands 50.
The topsheet 24 and the backsheet 22 have length and width dimensions
generally larger
than those of the absorbent core 25. The topsheet 24 and the backsheet 22
extend beyond
the edges of the absorbent core 25 to thereby form the side edges 150 and the
waist edges
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21
152 of the garment 20. The liquid impervious backsheet 22 preferably includes
a liquid
impervious plastic film 68.
The pull-on garment 20 also has two centerlines, a longitudinal centerline 100
and a
transverse centerline 110. Herein, "longitudinal" refers to a line, axis, or
direction in the
plane of the pull-on garment 20 that is generally aligned with (e.g.
approximately parallel
with) a vertical plane which bisects a standing wearer into left and right
halves when the
pull-on garment 20 is worn. Herein, "transverse" and "lateral" are
interchangeable and refer
to a line, axis or direction which lies within the plane of the pull-on
garment that is
generally perpendicular to the longitudinal direction (which divides the
wearer into front
and back body halves). The pull-on garment 20 and component materials thereof
also have
a body-facing surface which faces the skin of wearer in use and an outer-
facing surface
which is the opposite surface to the body-facing surface.
Each of the ear panels 45, 46 and 48 has the outermost edge Iine 242. Herein,
"edge
line" refers to lines which define the outlines of the ear panels 45, 46 and
48 or the chassis
41. Herein, "outermost" refers to portions which are farthest from the
longitudinal
centerline 100. At least one of the edge lines 242 has a nonuniform lateral
distance LD
from the longitudinal center line 100 in the uncontracted state of the garment
20.
While the topsheet 24, the backsheet 22, and the absorbent core 25 may be
assembled in a variety of well known configurations, exemplary chassis
configurations are
described generally in U.S. Patent 3,860,003 entitled "Contractible Side
Portions for
Disposable Diaper" which issued to Kenneth B. Buell on January 14, 1975; and
U.S. Patent
5,151,092 entitled "Absorbent Article With Dynamic Elastic Waist Feature
Having A
Predisposed Resilient Flexural Hinge" which issued to Kenneth B. Buell et al.,
on
September 29, 1992.
Fig. 9 is a cross-sectional view of a preferred embodiment taken along the
section
line 4-4 of Fig. 8. The pull-on garment 20 includes the chassis 41 including
the liquid
pervious topsheet 24, the liquid impervious backsheet 22 associated with the
topsheet 24,
and the absorbent core 25 positioned between the topsheet 24 and the backsheet
22. The
pull-on garment 20 fiurther includes the front ear panel 46 extending
laterally outward from
the chassis 4I, and an inner barrier cuff 54. Although Fig. 9 depicts only the
structure of the
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22
front ear panel 46 and the chassis 41 in the front region 26, preferably a
similar structure is
also provided in the back region 28.
In a preferred embodiment, the front ear panel 46 is formed by a lamination of
an
extended part 72 of the barrier flap 56, an elastic member 70 and the nonwoven
outer cover
74. Any of the above described elastic composite members can be used as the
elastic
member 70.
The absorbent core 25 can be any absorbent member which is generally
compressible, confon;nable, non-irritating to the wearer's skin, and capable
of absorbing and
retaining liquids such as urine and other certain body exudates. The absorbent
core 25 may
be manufactured in a wide variety of sizes and shapes (e.g., rectangular,
hourglass,
"T"-shaped, asymmetric, etc.) and from a wide variety of liquid-absorbent
materials
commonly used in disposable pull-on garments and other absorbent articles such
as
comminuted wood pulp which is generally referred to as airfelt. Examples of
other suitable
absorbent materials include creped cellulose wadding; meltblown polymers
including
coform; chemically stiffened, modified or cross-linked cellulosic fibers;
tissue including
tissue wraps and tissue laminates; absorbent foams; absorbent sponges;
superabsorbent
polymers; absorbent gelling materials; or any equivalent material or
combinations of
materials.
The configuration and construction of the absorbent core 25 may vary (e.g.,
the
absorbent core 25 may have varying caliper zones, a hydrophilic gradient, a
superabsorbent
gradient, or lower average density and lower average basis weight acquisition
zones; or may
include one or more layers or structures). Further, the size and absorbent
capacity of the
absorbent core 25 may also be varied to accommodate wearers ranging from
infants through
adults. However, the total absorbent capacity of the absorbent core 25 should
be compatible
with the design loading and the intended use of the garment 20.
A preferred embodiment of the garment 20 has an asymmetric, modified hourglass-
shaped absorbent core 25 having ears in the front and back waist regions 26
and 28. Other
exemplary absorbent structures for use as the absorbent core 25 that have
achieved wide
acceptance and commercial success are described in U.S. Patent No. 4,610,678
entitled
"High-Density Absorbent Structures" issued to Weisman et al. on September 9,
1986; U.S.
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23
Patent No. 4,673,402 entitled "Absorbent Articles With Dual-Layered Cores"
issued to
Weisman et aI. on June 16, 1987; U.S. Patent No. 4,888,231 entitled "Absorbent
Core
Having A Dusting Layer" issued to Angstadt on December 19, 1989; and U.S.
Patent No.
4,834,735, entitled "High Density Absorbent Members Having Lower Density and
Lower
Basis Weight Acquisition Zones", issued to Aiemany et al. on May 30, 1989.
The chassis 41 may further include an acquisition/distribution core 84 of
chemically
stiffened fibers positioned over the absorbent core 25, thereby forming a dual
core system.
In a preferred embodiment, the fibers are hydrophilic chemically stiffened
cellulosic fibers.
Herein, "chemically stiffened fibers" means any fibers which have been
stiffened by
chemical means to increase stiffness of the fibers under both dry and aqueous
conditions.
Such means include the addition of chemical stiffening agents which, for
example, coat
and/or impregnate the fibers. Such means also include the stiffening of the
fibers by
altering the chemical structure of the fibers themselves, e.g., by cross-
linking polymer
chains.
The fibers utilized in the acquisition/distribution core 84 can also be
stiffened by
means of chemical reaction. For example, crosslinking agents can be applied to
the fibers
which, subsequent to application, are caused to chemically form intrafiber
crosslink bonds.
These crosslink bonds can increase stiffness of the fibers. Whereas the
utilization of
intrafiber crosslink bonds to chemically stiffen the fibers is preferred, it
is not meant to
exclude other types of reactions for chemical stiffening of the fibers.
In the more preferred stiffened fibers, chemical processing includes
intrafiber
crosslinking with crosslinking agents while such fibers are in a relatively
dehydrated,
defibrated (i.e. individualized), twisted, curled condition. Suitable chemical
stiffening
agents include monomeric crosslinking agents including, but not limited to, CZ-
Ca
dialdehydes and CZ-CB monoaldehydes having an acid functionality can be
employed to
form the cosslinking solution. These compounds are capable of reacting with at
least two
hydroxyl groups in a single cellulose chain or on proximately located
cellulose chains in a
single fiber. Such crosslinking agents contemplated for use in preparing the
stiffened
cellulose fibers include, but are not limited to, glutaraldehyde, glyoxal,
formaldehyde, and
glyoxylic acid. Other suitable stiffening agents are polycarboxylates, such as
citric acid.
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24
The polycarboxylic stiffening agents and a process for making stiffened fibers
from them
are described in U.S. Patent No. 5,190,563, entitled "Process for Preparing
Individualized,
Polycarboxylic Acid crosslinked Fibers" issued to Herron, on March 2, 1993.
The effect of
crosslinking under these conditions is to form fibers which are stiffened and
which tend to
retain their twisted, curled configuration during use in the absorbent
articles herein. Such
fibers, and processes for making them are cited in the above incorporated
patents.
Preferred dual core systems are disclosed in U.S. Patent No. 5,234,423,
entitled
"Absorbent Article With Elastic Waist Feature and Enhanced Absorbency" issued
to
Alemany et al., on August 10, 1993; and in U.S. Patent No. 5,147,345, entitled
"High
Efficiency Absorbent Articles For Incontinence Management" issued to Young,
LaVon and
Taylor on September 15, 1992. In a preferred embodiment, the
acquisition/distribution core
84 includes chemically treated stiffened cellulosic fiber material, available
from
Weyerhaeuser Co. (U.S.A.) under the trade designation of "CMC". Preferably,
the
acquisition/distribution core 84 has a basis weight of from about 40 g/m2 to
about 400
g/m2, more preferably from about 75 g/m2 to about 300 g/m2.
More preferably, the chassis 22 further includes an acquisition/distribution
layer 82
between the topsheet 24 and the acquisition/distribution core 84 as shown in
Fig. 9. The
acquisition/distribution layer 82 is provided to help reduce the tendency for
surface wetness
of the topsheet 24. The acquisition/distribution layer 82 preferably includes
carded, resin
bonded hiloft nonwoven materials such as, for example, available as Code No.
FT-6860
from Polymer Group, Inc., North America (Landisiville, New Jersey, U.S.A.),
which is
made of polyethylene telephthalate fibers of 6 dtex, and has a basis weight of
about 43
g/m2. A preferable example for the acquisition/distribution layer 82 and the
acquisition/distribution core 84 is disclosed in EP 0797968A1 (Kurt et al.)
published on
October 1, 1997.
The topsheet 24 is preferably compliant, soft feeling, and non-irritating to
the
wearer's skin. Further, the topsheet 24 is liquid pervious permitting Liquids
(e.g., urine) to
readily penetrate through its thickness. A suitable topsheet 24 may be
manufactured from a
wide range of materials such as woven and nonwoven materials; polymeric
materials such
as apertured formed thermoplastic films, apertured plastic films, and
hydroformed
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thermoplastic films; porous foams; reticulated foams; reticulated
thermoplastic films; and
thermoplastic scrims. Suitable woven and nonwoven materials can be included of
natural
fibers (e.g., wool or cotton fibers), synthetic fibers (e.g., polymeric fibers
such as polyester,
polypropylene, or polyethylene fibers) or from a combination of natural and
synthetic fibers.
5 The topsheet 24 is preferably made of a hydrophobic material to isolate the
wearer's skin
from liquids which have passed through the topsheet 24 and are contained in
the absorbent
core 25 (i.e., to prevent rewet). If the topsheet 24 is made of a hydrophobic
material, at least
the upper surface of the topsheet 24 is treated to be hydrophilic so that
liquids will transfer
through the topsheet more rapidly. This diminishes the likelihood that body
exudates will
10 flow off the topsheet 24 rather than being drawn through the topsheet 24
and being absorbed
by the absorbent core 25. The topsheet 24 can be rendered hydrophilic by
treating it with a
surfactant. Suitable methods for treating the topsheet 24 with a surfactant
include spraying
the topsheet 24 material with the surfactant and immersing the material into
the surfactant.
A more detailed discussion of such a treatment and hydrophilicity is contained
in U.S.
15 Patent No. 4,988,344 entitled "Absorbent Articles with Multiple Layer
Absorbent Layers"
issued to Reising, et ai. on January 29, 1991 and U.S. Patent No. 4,988,345
entitled
"Absorbent Articles with Rapid Acquiring Absorbent Cores" issued to Reising on
January
29, 1991.
In a preferred embodiment, the topsheet 24 is a nonwoven web that can provide
20 reduced tendency for surface wetness; and consequently facilitate
maintaining urine
absorbed by the core 25 away from the user's skin, after wetting. One of the
preferred
topsheet materials is a thermvbonded carded web which is available as Code No.
P-8 from
Fiberweb North America, Inc. (Simpsonville, South Carolina, U.S.A.). Another
preferred
topsheet material is available as Code No. S-2355 from Havix Co., Japan. This
material is a
25 bi-layer composite material, and made of two kinds of synthetic surfactant
treated
bicomponent fibers by using carding and air-through technologies. Yet another
preferred
topsheet material is a thermobonded carded web which is available as Code No.
Profleece
Style 040018007 from Amoco Fabrics, Inc. (Gronau, Germany).
Another preferred topsheet 24 includes an apertured formed film. Apertured
formed
films are preferred for the topsheet 24 because they are pervious to body
exudates and yet
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26
non-absorbent and have a reduced tendency to allow liquids to pass back
through and rewet
the wearer's skin. Thus, the surface of the formed film which is in contact
with the body
remains dry, thereby reducing body soiling and creating a more comfortable
feel for the
wearer. Suitable formed films are described in U.S. Patent No. 3,929,135,
entitled
"Absorptive Structures Having Tapered Capillaries", issued to Thompson on
December 30,
1975; U.S. Patent No. 4,324,246 entitled "Disposable Absorbent Article Having
A Stain
Resistant Topsheet", issued to Mullane, et a1. on April 13, 1982; U.S. Patent
No. 4,342,314
entitled "Resilient Plastic Web Exhibiting Fiber-Like Properties", issued to
Radel. et al. on
August 3, 1982; U.S. Patent No. 4,463,045 entitled "Macroscopically Expanded
Three-
Dimensional Plastic Web Exhibiting Non-Glossy Visible Surface and Cloth-Like
Tactile
Impression", issued to Ahr et al. on July 3I, 1984; and U.S. 5,006,394
"Multilayer
Polymeric Film" issued to Baird on Apri19, 1991.
In a preferred embodiment, the backsheet 22 includes the liquid impervious
film 68
as shown in, for example, Fig. 9. Preferably, the liquid impervious film 68
longitudinally
extends in the front, back and crotch regions 26, 28 and 30. More preferably,
the liquid
impervious film 68 does not laterally extend into the at least one of the ear
panels 46 or 48.
The liquid impervious film 68 has a body-facing surface 79 and an outer-facing
surface 77.
The liquid impervious film 68 is impervious to liquids (e.g., urine) and is
preferably
manufactured from a thin plastic film. However, more preferably the plastic
film permits
vapors to escape from the garment 20. In a preferred embodiment, a microporous
polyethylene film is used for the liquid impervious film 68. A suitable
microporous
polyethylene film is manufactured by Mitsui Toatsu Chemicals, Inc., Nagoya,
Japan and
marketed in the trade as PG-P. In a preferred embodiment, a disposable tape
(not shown in
Figs.) is additionally joined to the outer surface of the backsheet 22 to
provide a convenient
disposal after soiling.
A suitable material for the liquid impervious film 68 is a thermoplastic film
having a
thickness of from about 0.012 mm (0.5 mil) to about 0.051 mm (2.0 mils),
preferably
including polyethylene or polypropylene. Preferably, the liquid impervious f
Im has a basis
weight of from about 5 g/m2 to about 45 g/m2. However, it should be noted that
other
flexible liquid impervious materials may be used. Herein, "flexible" refers to
materials
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27
which are compliant and which will readily conform to the general shape and
contours of
the wearer's body.
The nonwoven outer cover 74 is joined with the outer-facing surface of the
liquid
impervious film 68 to form a laminate (i.e., the backsheet 22). The nonwoven
outer cover
74 is positioned at the outermost portion of the garment 20 and covers at
least a portion of
the outermost portion of the garment 20. In a preferred embodiment, the
nonwoven outer
cover 74 covers almost all of the area of the outermost portion of the garment
20. The
nonwoven outer cover 74 may be joined to the liquid impervious film 68 by any
suitable
attachment means known in the art. For example, the nonwoven outer cover 74
may be
secured to the Liquid impervious film 68 by a uniform continuous layer of
adhesive, a
patterned layer of adhesive, or an array of separate lines, spirals, or spots
of adhesive.
Suitable adhesives include a hotmelt adhesive obtainable from Nitta Findley
Co., Ltd.,
Osaka, Japan as H-2128, and a hotmelt adhesive obtainable from H.B. Fuller
Japan Co.,
Ltd., Osaka, Japan as JM-6064.
In a preferred embodiment, the nonwoven outer cover 74 is a carded nonwoven
web,
for example, obtainable from Havix Co., LTD., Gifu, Japan as E-2341. The
nonwoven
outer cover 74 is made of bi-component fibers of a polyethylene (PE) and a
polypropylene
(PP). The ratio of PE/PP is about 50/50. The PE/PP bi-component fiber has the
dimension
of 2d x 51 mm. Another preferred carded nonwoven web is obtainable from Chisso
Corp.,
Moriyama, Japan. The nonwoven outer cover 74 is also made of bi-component
fibers of a
polyethylene (PE) and a polypropylene (PP). The ratio of PE/PP is about 50/50.
In another preferred embodiment, the nonwoven web is a spunbonded nonwoven
web, for example, obtainable from Mitsui Petrochemical Industries, Ltd.,
Tokyo, Japan.
The nonwoven web is made of bi-component fibers of a polyethylene (PE) and a
polypropylene (PP). The ratio of PE/PP is about 80/20. The PE/PP bi-component
fiber has
the thickness is approximately 2.3d. Another spunbonded nonwoven web is
obtainable
from Fiberweb France S.A., under Code No. 13561 DAPP.
The backsheet 22 is preferably positioned adjacent the outer-facing surface of
the
absorbent core 25 and is preferably joined thereto by any suitable attachment
means known
in the art. For example, the backsheet 22 may be secured to the absorbent core
25 by a
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28
uniform continuous layer of adhesive, a patterned layer of adhesive, or an
array of separate
lines, spirals, or spots of adhesive. Adhesives which have been found to be
satisfactory are
manufactured by H. B. Fuller Company of St. Paul, Minnesota, U.S.A., and
marketed as
HL-1358J. An example of a suitable attachment means including an open pattern
network
of filaments of adhesive is disclosed in U.S. Patent No. 4,573,986 entitled
"Disposable
Waste-Containment Garment", which issued to Minetola et al. on March 4, 1986.
Another
suitable attachment means including several lines of adhesive filaments
swirled into a spiral
pattern is illustrated by the apparatus and methods shown in U.S. Patent No.
3,911,173
issued to Sprague, Jr. on October 7, 1975; U.S. Patent No. 4,785,996 issued to
Ziecker, et al.
on November 22, 1978; and U.S. Patent No. 4,842,666 issued to Werenicz on June
27,
1989. Alternatively, the attachment means may include heat bonds, pressure
bonds,
ultrasonic bonds, dynamic mechanical bonds, or any other suitable attachment
means or
combinations of these attachment means as are known in the art.
In an alternative embodiment, the absorbent core 25 is not joined to the
backsheet
22, and/or the topsheet 24 in order to provide greater extensibility in the
front region 26 and
the back region 28.
The pull-on garment 20 preferably further includes elasticized leg cuffs 52
for
providing improved containment of liquids and other body exudates. The
elasticized leg
cuffs 52 may include several different embodiments for reducing the leakage of
body
exudates in the leg regions. (The leg cuffs can be and are sometimes also
referred to as leg
bands, side flaps, barrier cuffs, elastic cuffs or gasketing cuffs.) U.S.
Patent 3,860,003
entitled "Contractable Side Portions for Disposable Diaper" issued to Buell on
January 14,
1975, describes a disposable diaper which provides a contractible leg opening
having a side
flap and one or more elastic members to provide an elasticized leg cuff. U.S.
Patent
4,909,803 entitled "Disposable Absorbent Article Having Elasticized Flaps"
issued to Aziz
et al. on March 20, 1990, describes a disposable diaper having "stand-up"
elasticized flaps
(barrier cuffs) to improve the containment of the leg regions. U.S. Patent
4,695,278 entitled
"Absorbent Article Having Dual Cuffs" issued to Lawson on September 22, 1987;
and U.S.
Patent 4,795,454 entitled "Absorbent Article Having Leakage-Resistant Dual
Cuffs" issued
to Dragoo on January 3, 1989, describe disposable diapers having dual cuffs
including a
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29
gasketing cuff and a barrier cuff. U.S. Patent 4,704,115 entitled "Disposable
Waist
Containment Garment" issued to Buell on November 3, 1987, discloses a
disposable diaper
or incontinence garment having side-edge-leakage-guard gutters configured to
contain free
liquids within the garment.
While each elasticized leg cuff 52 may be configured so as to be similar to
any of the
leg bands, side flaps, barrier cuffs, or elastic cuffs described above, it is
preferred that the
elasticized leg cuff 52 includes an elastic gasketing cuff 62 with one or more
elastic strands
64 as shown in Fig. 8, which is described in the above-referred U.S. Patent
Nos. 4,695,278
and 4,795,454. It is also preferred that each elasticized leg cuff 52 further
includes inner
barrier cuffs 54 each including a barrier flap 56 and a spacing means 58 which
are described
in the above-referenced U.S. Patent No. 4,795,454.
The pull-on garment 20 further includes an elasticized waistband 50 that
provides
improved fit and containment. The elasticized waistband 50 is that portion or
zone of the
pull-on garment 20 which is intended to elastically expand and contract to
dynamically fit
the wearer's waist. The waistband 50 includes an elastic member 700. Any of
the above
described elastic composite members can be used as the elastic member 700. The
waistband
50 is disposed along at least one, preferably both of the end edges 152 of the
disposable
garment 20. The elasticized waistband 50 preferably extends longitudinally
inwardly from
the end edge 152 of the pull-on garment 20 toward the waist edge 154 of the
absorbent core
25. Preferably, the pull-on garment 20 has two elasticized waistbands 50, one
positioned in
the back region 28 and one positioned in the front region 26, although other
pull-on diaper
embodiments can be constructed with a single elasticized waistband. The
elasticized
waistband 50 may be constructed in a number of different configurations
including those
described in U.S. Patent 4,SI5,595 entitled "Disposable Diapers with
Elastically
Contractible Waistbands" issued to Kievit et al. on May 7, 1985 and the above
referenced
U.S. Patent 5,1 S 1,092 issued to Buell.
Fig. IO is a cross-sectional view of one preferred embodiment taken along the
section line S-5 of Fig. 8. As shown in Fig. 10, both the backsheet 22 and the
topsheet 24
extend beyond the waist edge 154 of the absorbent core 25 to define a waist
flap 156.
Preferably, the juxtaposed areas of the backsheet 22 and the topsheet 24 are
joined together
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by an adhesive (not shown in Figs.). In a preferred embodiment, the waistband
SO is joined
to the waist flap 156. Preferably, the waistband 50 is disposed on and joined
to the topsheet
24 as shown in Fig. 10. Alternatively, the waistband 50 can be disposed and
joined between
the backsheet 22 and the topsheet 24 as shown in Fig. 11. The waistband 50 can
be joined
5 to the topsheet 24 (and the backsheet 22) by an adhesive means (not shown in
Figs.) such as
those well known in the art. For example, the waistband 50 may be secured to
the waist flap
156 by a uniform continuous layer of adhesive, a patterned layer of adhesive,
or an array of
separate lines or spots of adhesive. A preferred adhesive for use is available
from Ato
Findley Inc., WI, U.S.A., under the designation H2085.
10 In a preferred embodiment, the waistband 50 is secured to the waist flap
156 in an
elastically contractible condition so that in a normally unrestrained
configuration the
waistband 50 effectively contract or gather the waist flap 156. The waistband
50 can be
secured to the waist flap 156 in an elastically contractible condition in at
least two ways.
For example, the waistband 50 may be stretched and secured to the waist flap
156 while the
15 waist flap 156 is in an uncontracted condition. Alternatively, the waist
flap 156 may be
contracted, for example by pleating, and the waistband 50 is secured to the
contracted waist
flap 156 while the waistband 50 in its relaxed or unstretched condition.
Yet alternatively, the waistband 50 is joined, in its relaxed or unstretched
condition,
to the waist flap 156 which is in an uncontracted condition, thereby forming a
composite
20 laminate with the materials of the backsheet 22 and the topsheet 24. At
least a portion,
preferably the entire portion of the composite Laminate is then subjected to
mechanical
stretching sufficient to permanently elongate the non-elastic components which
are the
backsheet 22 and the topsheet 24. The composite laminate is then allowed to
return to its
substantially untensioned condition. Thus, the composite laminate is formed
into a "zero
25 strain" stretch laminate which works as elasticized waistband 50.
Herein, "zero strain" stretch laminate refers to a laminate included of at
least two
plies of material which are secured to one another along at least a portion of
their
coextensive surfaces while in a substantially untensioned ("zero strain")
condition; one of
the plies including a material which is stretchable and elastomeric (i.e.,
will return
30 substantially to its untensioned dimensions after an applied tensile force
has been released)
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31
and a second ply which is elongatable (but not necessarily elastomeric) so
that upon
stretching the second ply will be, at least to a degree, permanently elongated
so that upon
release of the applied tensile forces, it will not fully return to its
original undeformed
configuration. The resulting stretch laminate is thereby rendered elastically
extensible, at
least up to the point of initial stretching, in the direction of initial
stretching. Particularly
preferred methods and apparatus used for making stretch laminates utilize
meshing
corrugated rolls to mechanically stretch the components. Particularly
preferred apparatus
and methods are disclosed in U.S. Patent No. 5,167,897 issued to Weber et aI.
on December
1, 1992; U.S. Patent No. 5,156,793 issued to Buell et al. on October 20, 1990;
and U.S.
Patent No. 5,143,679 issued to Weber et aI. on September l, 1992.
In a preferred embodiment, the waistband 50 extends across essentially the
entire
lateral width of the absorbent core 25. Herein, "lateral width" refers to the
dimension
between the side edges of components of disposable garments. Herein, "across
essentially"
is used in this context to indicate that the waistband 50 does not need to
extend absolutely
across the entire width of the absorbent core 25 so long as it extends
sufficiently far across
the width thereof to provide the elasticized waistband. Preferably, the
waistband 50 extends
across only a portion of the lateral width of the absorbent core 25, more
preferably at least
between portions in the ear panels 46 and 48 (as shown in Fig. 8). In one
preferred
embodiment, the waistband 50 extends across the entire lateral width of the
garment 20 (not
shown Figs.).
The extent to which the waistband 50 extends inboard from the end edge 152 of
the
garment 20, and thus the longitudinal span of the resultant waistband, can
vary according to
the particular construction of the garment 20. The longitudinal span of the
waistband 50 is
at least about 5 mm, preferably from about 6 mm to about 60 mm, more
preferably from
about 15 mm to about 30 mm.
At least one of the ear panels 45, 46 and 48 includes the elastic member 70.
Any of
the above described elastic composite members can be used as the elastic
member 70. For
example, each of the front ear panels 46 shown in Fig. 9 includes the elastic
member 70
which preferably extends laterally outward from the chassis 41 to provide good
f tness by
generating the optimal retention (or sustained) force at the waist and side
areas of the
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32
wearer. Preferably, the elastic member 70 is extensible in at least one
direction, preferably
in the lateral direction to generate a retention (or sustained) force that is
optimal to prevent
the pull-on garment 20 from drooping, sagging, or sliding down from its
position on the
torso without causing the red marking on the skin of the wearer. In a
preferred embodiment,
each of the ear panels 45, 46 and 48 includes the elastic member 70.
The elastic member 70 is operatively joined to at least one of the nonwoven
webs 72
and 74 in the ear panels 45, 46 and 48 to allow the elastic member 70 to be
elastically
extensible in at least the lateral direction. In a preferred embodiment, the
elastic member 70
is operatively joined to the nonwoven webs 72 and 74 by securing them to at
least one,
preferably both of the nonwoven webs 72 and 74 while in a substantially
untensioned (zero
strain) condition.
The elastic member 70 can be operatively joined to the nonwoven webs 72 and
74,
by using either an intermittent bonding configuration or a substantially
continuous bonding
configuration. Herein, "intermittently" bonded laminate web means a laminate
web wherein
the plies are initially bonded to one another at discrete spaced apart points
or a laminate web
wherein the plies are substantially unbonded to one another at discrete spaced
apart areas.
Conversely, a "substantially continuously" bonded laminate web means a
laminate web
wherein the plies are initially bonded substantially continuously to one
another throughout
the areas of interface. It is preferred that the stretch laminate be bonded
over all or a
significant portion of the stretch laminate so that the inelastic webs (i.e.,
the nonwoven webs
72 and 74) elongate or draw without causing rupture, and the layers of the
stretch laminates
are preferably bonded in a configuration that maintains all of the layers of
the stretch
laminate in relatively close adherence to one another after the incremental
mechanical
stretching operation. Consequently, the elastic panel members and the other
plies of the
stretch laminate are preferably substantially continuously bonded together
using an
adhesive. In a particularly preferred embodiment, the adhesive selected is
applied with a
control coat spray pattern at a basis weight of about 7.0 grams/square m. The
adhesive
pattern width is about 6.0 cm. The adhesive is preferably an adhesive such as
is available
from Nitta Findley Co., Ltd., Osaka, Japan, under the designation H2085F.
Alternatively,
the elastic panel member and any other components of the stretch laminates may
be
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33
intermittently or continuously bonded to one another using heat bonding,
pressure bonding,
ultrasonic bonding, dynamic mechanical bonding, or any other method as is
known in the
art.
After the elastic member 70 is operatively joined to at least one of the
nonwoven
webs 72 and 74, at least a portion of the resultant composite stretch laminate
is then
subjected to mechanical stretching sufficient to permanently elongate the non-
elastic
components which are, for example, the nonwoven webs 72 and 74. The composite
stretch
laminate is then allowed to return to its substantially untensioned condition.
At least one
pair of, preferably both of the ear panels 45, 46 and 48 is thus formed into
"zero strain"
stretch laminates. (Alternatively, the elastic member 70 could be operatively
joined in a
tensioned condition and then subjected to mechanical stretching; although this
is not as
preferred as a "zero strain" stretch laminate.)
The elastic member 70 is preferably joined to, more preferably directly
secured to
the respective edges 78 of the liquid impervious film (i.e., the liquid
impervious film 68)
through an adhesive 76 as shown in Fig. 9. In a preferred embodiment, while
liquid
impervious film 68 longitudinally extends in the front, back and crotch
regions 26, 28 and
30, it does not laterally extend into at least one of, preferably each of the
extensible ear
panels 45, 46 and 48. In a more preferred embodiment, the elastic member 70 is
joined to
the respective edges 78 of the liquid impervious film 68 at the outer-facing
surface 77 as
shown in Fig. 9. In an alternative embodiment, the elastic member 70 may be
joined to the
respective edges 78 of the liquid impervious film 68 at the body-facing
surface 79 (not
shown in Figs.). Preferably, the adhesive 76 is applied in a spiral glue
pattern. In a
preferred embodiment, the adhesive 76 is a flexible adhesive with an amorphous
and
crystallizing component. Such a preferred adhesive is obtainable from Nitta
Findley Co.,
Ltd., Osaka, Japan, under the designation H2085F. Alternatively, the elastic
member 70
rnay be joined to the respective edges 78 of the liquid impervious film 68 by
any other
bonding means known in the art which include heat bonds, pressure bonds,
ultrasonic
bonds, dynamic mechanical bonds, or combinations of these attachment means.
Test Methods
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1. Tensile Strength
34
The following method is used to measure the tensile strength of elastic
composite
members and plane eIastomeric materials.
A tensile tester is prepared. The tensile tester has an upper jaw and a lower
jaw
which is located below the upper jaw. The upper jaw is movable and is
connected to an
extension force measuring means. The lower jaw is fixed in the tester. A test
specimen
(i.e., a plane elastomeric material or an elastic composite member to be
measured) which
has about 2.5 cm (about 1 inch) in width and about 10.2 cm (about 4 inches) in
length is
prepared and clamped with the upper jaw and the tower jaw so that the
effective specimen
length (L) (i.e., the initial distance between the upper and lower jaws before
application of
extension force) is about 5.1 cm (about 2 inch). Preferably, the test specimen
is aligned, by
clamping, with the direction which is most elastically extensible among all
two dimensional
directions within the test specimen. (This direction is referred as "primary
extensible
direction" below.) An extension force is continuously applied to the test
specimen through
the upper jaw at a cross-head speed of about 50 cm (about 20 inches) per
minute, to 300%
elongation of the test specimen. The applied extension force is recorded by a
recorder (e.g.,
a computer system). This measurement is conducted for a plane elastomeric
material and an
elastic composite member. Preferably, this measurement is repeatedly conducted
for at least
8 test specimens and the average value of the tensile strength at 100%
elongation are
obtained from the recorded data.
A tensile tester suitable for use is available from Instron Corporation ( 100
Royall
Street, Canton, MA02021, U.S.A.) as Code No. Instron 5564.
2. Surface Rou hness
To measure the surface roughness of the sample, a pianowire is prepared and
bent as
shown in Figs. 12 and 13. 5.0 gf (allowance, ~0.5 gf) of the contact force is
applied by a
spring of which spring constant is 25 tl gf/mm. The natural frequency of the
system
should be more than 30 Hz when the contactor is out of the contact.
In the roughness measurement, the specimen is moved between 2 cm interval by a
constant velocity of 0.1 cm/sec on a smooth steel plate placed horizontally
where the
tension of the specimen is kept S.0 gf/cm (force per unit length) and the
contactor is kept its
CA 02354538 2001-06-11
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position. The movement direction is an extensible direction of the specimen.
The
dimension of the plate is shown in Fig. 14. As a result, the change of the
thickness T (i.e.,
the deviation of the surface) are obtained and recorded as shown, for example,
in Fig. 15.
This measurement is conducted both for two surfaces opposing one another of
the sample.
5 Consequently, the value of Surface Roughness (SRO) is obtained from the
following
expression:
1 x
SRO = - j ~ T - T' ~ dx
X 0
10 wherein,
x : displacement of the contactor on the surface of sample;
X : 2 cm is taken in this measurement;
T : Thickness of the sample at position x; and
T' : Mean value of T
7 5 A suitable equipment for this test is available from Kato Tech Co., Ltd.,
Kyoto,
Japan, under Trade Name "Surface Tester (KES-FB4)".
It is understood that the examples and embodiments described herein are for
illustrative purpose only and that various modifications or changes will be
suggested to one
skilled in the art without departing from the scope of the present invention.
