Note: Descriptions are shown in the official language in which they were submitted.
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ELASTIC MEMBER AND DISPOSABLE GARMENT
HAVING IMPROVED STRENGTH AGAINST STRESS APPLIED DURING USE
FIELD
The present invention relates to elastic members and disposable garments.
Examples of such disposable garments include disposable underwear, disposable
diapers including pull-on diapers and training pants, and disposable panties
for
~ 5 menstrual use. More specifically, the present invention relates to elastic
members
and disposable garments which have improved strength against stress applied
during use of products.
BACKGROUND
Elastic members have previously been used in a variety of disposable
products, including sweat bands, bandages, and disposable garments including
disposable diapers and incontinence devices. As used herein, the term "elastic
members" defers to an elastically stretchable single layer material, or two or
more
layered material which is often called "elastic laminate" and including at
least one
elastically stretchable single layer 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. Examples of such elastic
laminates that have been previously used include composites made from a
3o gatherable material joined to an elastic material, composites made from
mesh,
tissue and microfibers, as well as composites made from a central elastic
layer, a
breathable material, and an adhesive layer. Examples of such laminates are
described in U.S. Patent No. 4,522,863 to Keck et al. and U.S. Patent No.
4,977,011
to Smith.
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2
In the meantime, infants and other incontinent individuals wear disposable
garments such as diapers to receive and contain urine and other body exudates.
One type of the disposable garments, which is often called as "tape type", has
a
fastener system to hold the disposable garment at the wearer's waist area. As
the
fastener system, either an adhesive tape system or a mechanical fastener
system is
often used. Recently, elastically stretchable side panels are preferably used
in this
type of the disposable garments, because they can provide a better fit to the
wearer's waist area by jointly working with the fastener system. Another type
of
absorbent garments, which is often called as "pant type" or "pull-on", has
fixed sides
has become popular for use on children able to walk and often who are toilet
training. The pull-on garments have side panels which edges are seamed
together
to form two leg openings and a waist opening. These pull-on garments need to
fit
snugly about the waist and legs of the wearer without drooping, sagging or
sliding
down from its position on the torso to contain body exudates. Examples of
these
~5 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.
2o These disposable products often use an elastic member which comprises an
elastomeric material to provide good fitness to the skin or body of the user.
In some
of these products, a "zero strain" stretch laminate is preferably used for
elastic
members. In a manufacturing process for such "zero strain" stretch laminate,
the
elastomeric material is operatively joined to at least one component material
which -
25 forms a part of the side panel while in a substantially untensioned (zero
strain)
condition. At least a portion of the resultant composite stretch laminate is
then
subjected to mechanical stretching sufficient to permanently elongate the non-
elastic
components. The composite stretch laminate is then aNowed to return to its
substantially untensioned condition. Thus, the elastic member is formed into a
"zero
3o strain" stretch laminate. As used herein, the term "zero strain" stretch
laminate
refers to a laminate comprised 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
comprising a
material which is stretchable and elastomeric (i.e., will return substantially
to its
35 untensioned dimensions after an applied tensile force has been released)
and a
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3
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. Apparatus and methods for making stretch laminates are
disclosed, for example, in U.S. Patent No. 5,167,897 issued to Weber et al. on
December 1, 1992; U.S. Patent No. 5,156,793 issued to Bueil et al. on October
20,
1990; and U.S. Patent No. 5,143,679 issued to Weber et al. on September 1,
1992.
~o It should be noted that the Japanese equivalent applications to these U.S.
Patents
were published (laid open) in Japanese under the Nos. of H6-505681, H6-505408
and H6-505446, respectively.
In the manufacturing process for such "zero strain" stretch laminate, the
~5 elastomeric material tends to be mechanically damaged. If the elastomeric
material
does not have enough strength or toughness, the elastomeric material tends to
be
easily shred or torn by the stress which is applied to the elastomeric
material during
the mechanical stretching in the manufacturing process and during the use of
disposable products. Thus, it is desirable that the elastomeric material has
enough
2o strength or toughness so that it is not damaged by the mechanical
stretching
process and/or at least it is not easily shred or torn by the stress during
the
mechanical stretching in the manufacturing process and during the use of
disposable products. However, it has not been discussed what property (or
properties) needs to be considered in order to achieve this benefit for
elastic
25 members and disposable products. Thus, none of the existing art provides
all of the
advantages and benefits of the present invention.
SUMMARY
3o The present invention is directed to an elastic member, comprising an
elastomeric scrim material having a first surface and a second surface
opposing the
first surface, and a first coverstock layer which is joined to the first
surface of the
elastomeric material.
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In one aspect of the invention, the elastomeric scrim material has an
Elongation at Breaking (EB) of at least about 600%.
In another aspect of the invention, the elastomeric scrim material has a
Tearing Resistance (TR) of at least about 16 hours.
The present invention is also directed to a disposable garment, comprising a
chassis having a front region, a back region and a crotch region between the
front
region and the back region; at least one pair of side panels extending
laterally
outwardly from the chassis in the front or back region; and at least one of
the side
panels comprising an elastomeric material extending laterally outwardly from
the
chassis. The chassis comprises a liquid pervious topsheet, a liquid impervious
backsheet associated with the topsheet, and an absorbent core disposed between
the topsheet and the backsheet.
In yet another aspect of the invention, the elastomeric scrim material has an
Elongation at Breaking (EB) of at least about 600%.
In still another aspect of the invention, the elastomeric scrim material has a
2o Tearing Resistance (TR) of at least about 16 hours.
These and other features, aspects, and advantages of the present invention
will become evident to those skilled in the art from a 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
3o 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 cross-sectional view of an elastic member 70 of a preferred
embodiment of the present invention;
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Fig. 2 is a fragmentary enlarged side view of the elastic member 70 shown in
Fig.1;
5 Fig. 3 is a graph showing the two-cycles of hysteresis curves of an
elastomeric material,-in a preferred embodiment;
Fig. 4 is a graph showing the change of the retention force at 50% extension
according to a lapse of time, in a preferred embodiment;
Fig. 5 is a perspective view of a preferred embodiment of the disposable pull-
on garment of the present invention in a typical in use configuration;
Fig. 6 is a simplified plan view of the embodiment shown in Fig. 5 in its flat
uncontracted condition showing the various panels or zones of the garment; and
Fig. 7 is a cross-sectional view of a preferred embodiment taken along the
section line 7-7 of Fig. 6.
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.
As used herein, the term "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. The term "disposable" is used herein to describe
garments
3o 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). A "unitary" pull-on garment refers to pull-on garments which are
formed of
separate parts united together to form a coordinated entity, but the side
panels are
not separate elements joined to a separate chassis in that the side panels are
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6
formed by at least one layer which also forms the central panel or chassis of
the
garment (i.e., the garment does not require separately manipulative panels
such as
a separate chassis and separate side panels). The pull-on garment is also
preferably "absorbent" to absorb and contain the various exudates discharged
from
the body. A preferred embodiment of the pull-on garment of the present
invention is
the unitary disposable absorbent pull-on garment, pull-on diaper 20, shown in
Fig. 5.
As used herein, the term "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 garments such as training pants, incontinent briefs, feminine hygiene
garments or panties, and the like. As used herein, the term "panel" is used
herein to
denote 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.) As used herein, the term "joined" or "joining"
encompasses
~ 5 configurations whereby an element is directly secured to the other element
by
affixing the element directly to the other element, and configurations 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.
2o Referring to Fig. 1, there is shown an elastic member 70 of the present
invention which is elastically extensible in at least one direction. The
elastic member
70 comprises an elastomeric material 124 having a first surface 150 and a
second
surface 152 opposing the first surface 150, and a first coverstock layer 122
which is
joined to the first surface 150 of the elastomeric material 124. In a
preferred
25 embodiment, the first coverstock layer 122 is joined to the first surface
150 of the
elastomeric material 124 by an adhesive 160 as shown, for example, in Fig. 2.
More
preferably, the elastic member 70 further comprises a second coverstock layer
126
which is joined to the second surface 152 of the elastomeric material 124 by
an
adhesive 164.
The elastomeric material 124 of the present invention may be formed in a
wide variety of sizes, forms and shapes. In a preferred embodiment, the
elastomeric
material 124 is in the form of a continuous plane layer. Preferred forms of
continuous plane layer include a scrim, a perforated {or apertured form) film,
an
elastomeric woven or nonwoven, and the like. In an alternative embodiment, the
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7
elastomeric material 124 is in the form of strands (or strings) which are not
connected each other to form a continuous plane layer. The continuous plane
layer
may take any shape which can be suitably provided in the side panels.
Preferred
shapes of continuous plane layer include a quadrilateral including a rectangle
and a
square, a trapezoid, and the other polygons.
Eiastomeric materials which have been found to be especially suitable for the
elastomeric material 124 are styrenic block copolymer based scrim materials,
perforated (or apertured} elastic films, preferably with a thickness of from
about 0.05
1o mm to about 1.0 mm (0.002 inch - 0.039 inch). Other suitable elastomeric
materials
for the elastomeric material 124 include "live" synthetic or natural rubber,
other
synthetic or natural rubber foams, elastomeric films (including heat
shrinkable
elastomeric films), eiastomeric woven or nonwoven webs, elastomeric
composites,
or the like.
It has been found that the extension properties of the elastomeric material
124 such as the First Cycle Extension Force at 100% Extension (FCEF100%), the
First Cycle Extension Force at 200% Extension (FCEF200%), and the Second Cycle
Recovery Force at 50% Extension (SCRF50%) are important considerations in the
2o performance of disposable garments. The elastomeric material 124 of the
present
invention has extension properties within the defined ranges. The FCEF100% and
the FCEF200% are measures of the overall perceived "stretchness" during
applicationlremoving of disposable garments. These two properties also effect
the
ability of the applicator to achieve a suitable degree of application stretch.
An
elastomeric material 124 with a relatively high FCEF100% and FCEF200% can
causes difficulty in applying the disposable garment onto the wearer (i.e.,
ease of
application problem). On the other hand, an elastomeric material 124 with a
relatively low FCEF100% and FCEF200% may not achieve a suitable level of body
fitting/conformity. The SCRF50% also closely relates to the body
fitting/conformity of
3o disposable garments for the wearer. An elastomeric material 124 with a
relatively
high SCRF50% tends to cause red marking on the skin of the wearer and may be
uncomfortable for the wearer during usage. An elastomeric material 124 with a
relatively low SCRF50% may not provide enough elastic force to keep the diaper
in
place on the wearer or may not provide good body fit.
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8
The values of FCEF100%, FCEF200% and SCRF50% can be measured by
using a tensile tester. The tensile tester comprises 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 at a desk (or
floor). A
test specimen (i.e., the elastomeric material to be measured) which has about
2.54
cm (1.0 inch) in width and about 12.75 cm (5 inches) in length is prepared and
clamped between the upper jaw and the lower jaw so that the effective specimen
length (L) (i.e., gauge length) is about 5.08 cm (2.0 inches). The extension
force is
applied to the test specimen through the upper jaw. When no extension force is
applied to the test specimen, the test specimen is in its original length
(i.e., 0%
extension). A tensile tester suitable for use herein is available from Instron
Corporation (100 Royall Street, Canton, MA02021, U.S.A.) as Code No. Instron
5564.
~5 Fig. 3 shows one preferred example of the extension and recovery force
curves for the two cycle hysteresis of the elastomeric material 124. The curve
E1
shows the extension force in the first cycle, while the curve R1 shows the
recovery
force in the first cycle. The curve E2 (shown in dashed lines) shows the
extension
force in the second cycle, while the curve R2 shows the recovery force in the
second
2o cycle. The extension and recovery properties are measured as follows.
In the first cycle, the test specimen is subjected to an initial extension
force at
a crosshead rate of 50.8 cm/min (20 in/min) at about 23oC and held for 30
seconds
at 200% extension. The test specimen is then allowed to relax at the same rate
to
25 the original state (i.e., 0% extension). The test specimen 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.
In preferred embodiments, the FCEF100% of the elastomeric material 124 is
3o at least about 100 grams/inch. More preferably, the FCEF100% is between
about
120 to about 220 grams/inch, most preferably between about 150 grams/inch and
190 grams/inch to best fit the wearer. The FCEF200% is preferably between
about
160 grams/inch and about 320 grams/inch, more preferably befinreen about 180
grams/inch and about 260 grams/inch, and yet more preferably between about 200
s5 gramslinch and about 240 grams/inch.
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The SCRF50% of the elastomeric material 124 is preferably between about
40 grams/inch and about 130 grams/inch, more preferably between about 65
grams/inch and about 105 grams/inch, and yet more preferably between about 75
grams/inch and about 95 grams/inch.
It has been also found that the force relaxation of the elastomeric material
124 can greatly effect the force relaxation performance of disposable products
and/or garments. As used herein, the term "force relaxation" is used to mean
the
o gradual reduction of the extension/recovery forces caused when the material
is
pulled at a certain extension force and held for certain period of time. Under
normal
usage, a disposable diaper is worn for a couple of hours, and sometimes for
about 8
to 12 hours. It is important for the elastomeric material 124 used in
disposable
garments to maintain the majority of its extension/recovery forces during the
whole
~5 wearing time. The retention force which is defined as the second cycle
extension
force maintained after held for certain period of time (for example, 12 hours)
at 50%
extension is a measurement for the force relaxation of elastomeric materials.
The
Retention Force Held after 12 Hours at 50% Extension (RFH12H) is used herewith
for such a measurement. The RFH12H is defined as the extension force (g/inch)
of
2o the elastomeric material after the extension force for 50% extension is
applied to the
elastomeric material for 12 hours. An elastomeric material with a relatively
low
RFH12H (in other words, high force relaxation) can not provide sustained
fitting for
disposable products and/or garments during the use. Especially when the
disposable garment is loaded with body exudates and becomes heavy, the
25 elastomeric material used therein with a relatively low RFH12H tends to
cause the
garment sagging or slipping from its position on the torso of the wearer.
The RFH12H is measured by using the same tensile tester as the
FCEF100%, FCEF200% and SCRF50% measurements except that the
3o measurement is carried out in a constant temperature chamber. A constant
temperature chamber suitable for use herein is available from Instron
Corporation,
100 Royall Street, Canton, MA02021, U.S.A., under Type Code 3119-005. The
measurement is carried out at 37 °C with a 2.54cm (1.0 inch) wide
specimen. The
effective specimen length (gauge length) is 5.08 cm (2.0 inches). During the
35 measurement, the test specimen is subjected to an initial extension force
at a
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crosshead rate of 50.8 cm/min (20 in/min) and after reaching to 200% extension
it is
held for 30 seconds at 200% extension. The test specimen is then allowed to
relax
at the same rate to the original state (0% extension). The test specimen is
allowed
to remain unconstrained for one minute and then is subjected to a second
extension
5 force (for the second cycle) to 50% extension at the same crosshead rate and
is
held at 50% extension for 12 hours.
In a preferred embodiment, the elastomeric material 124 has a RFH12H of at
least about 40 g/inch, preferably at least about 50 g/inch, and more
preferably at
~o least about 60 g/inch.
One preferred example of the retention force change of an elastomeric
material is shown in Fig. 4. In Fig. 4, the vertical axis shows the retention
force, and
the horizontal axis shows the time length held at 50% extension (from 0 hour
to 12
~5 hours).
!n preferred embodiments where the eiastomeric material 124 is provided in
the "zero strain" stretch laminate such as, for example, the side panel 46
shown in
Fig. 7, it is preferred that the elastomeric material 124 has enough strength
or
2o toughness so as not to be damaged by the mechanical stretching process. If
the
elastomeric material 124 is damaged even partially, the elastomeric material
124
tends to be easily shred or torn by the stress which is consistently applied
to the side
panels, and thus the elastomeric material 124, during the use of disposable
garments. Elongation at Breaking (EB) and Tearing Resistance (TR) are two
25 mechanical properties for showing the strength or toughness of the
elastomeric
material 124 against the mechanical stretching process. An elastomeric
material
with a relatively low EB or a relatively low TR tends to be easily shred or
torn during
the mechanical stretching process or during the use of disposable garments.
3o In one aspect of of the present invention, the elastomeric material 124 has
an
EB of at least about 600%, preferably at least about 800%.
To measure the EB, a continuously increasing force is applied to a sample
elastomeric material (i.e., specimen) at a rate of 50.8 cm/min (20 in/min) at
about
35 23oC, and the applied force and the extension length (EL) is recorded. The
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specimen is about 2.54cm (1.Oinch) wide and the gauge length is about
5.08cm(2.Oinches). The EB (%) is defined by the following expression:
EB = ( EL / OL ) x 100 (%) ____ (1)
wherein EL is the extension length when the specimen is torn by an
application of excessive force, and OL is the original length (i.e., the gauge
length) of the specimen before the application of the force.
o A tensile tester suitable for measuring the EB herein is available from
Instron
Corporation (100 Royall Street, Canton, MA02021, U.S.A.), under the trade name
"Instron 5564".
In another aspect of the present invention, the eiastomeric material 124 has a
~5 TR of at least about 16 hours, more preferably at least about 24 hours. To
measure
the TR, a force which causes 100% extension is continuously applied to a
sample
elastomeric material (i.e., specimen). Thus, the specimen is pulled to 100%
extension and kept in a constant temperature water bath at 37oC. A constant
temperature water bath suitable for use herein is available from Yamato Co.,
Tokyo,
2o Japan, under the code name BK 43. The dimension of the specimen is about
3.60cm (1.43 inches) wide and about 3.81cm (1.50 inches) long. The TR (hours)
is
defined as the time period between the time when the force is first applied to
the
sample and the time when at least 30% of the sample width is torn.
25 It has been also found that the moisture vapor transmission rate (the
breathability) of the elastomeric material 124 is very important in reducing
the
incidence of heat rash and other skin problems associated with high heat and
humidity conditions during the usage of disposable products. The elastomeric
material 124 tends to have a direct impact on the moisture vapor transmission
rate
30 (i.e., breathability) of disposable products. It is preferred that the
elastomeric
material 124 has a relatively high open (or aperture) ratio to provide high
moisture
vapor transmission rate or high breathability for disposable products.
In a preferred embodiment, the elastomeric material 124 is in the form of a
35 perforated (or apertured form) film which has an open (or aperture) ratio
of at least
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12
about 8%, preferably at least about 15%. The open ratio OR(%) is defined by
the
following expression:
OR = ( OA / TA ) x 100 (%) ---- (2)
wherein OA is the total area of the open (or aperture) portions in the
perforated film, and TA is the total area of the perforated film.
In an alternative preferred embodiment, the elastomeric material 124 is in the
o form of a scrim which has an open ratio of at least about 30%, preferably at
least
about 40%, and more preferably at least about 50%.
In the preferred embodiment shown in Fig. 1, the elastomeric scrim 124 has a
plurality of first strands 125 and a plurality of second strands 127. The
plurality of
first strands 125 intersect the plurality of second strands 127 at nodes 130
at a
predetermined angle a, forming a net-like open structure having a plurality of
apertures 132. Each aperture 132 is defined by at least two adjacent first
strands
and at least two adjacent second strands, so that the apertures 132 are
substantially
rectangular in shape. Other confrgurations of the apertures 132, such as
2o parallelograms, squares, or circular arc segments, can also be provided.
Preferably,
the first and second strands 125 and 127 are substantially straight and
substantially
parallel to one another. Preferably, the first strands 125 intersect the
second
strands 127 at nodes 130 such that the angle a is about 90 degrees. The first
and
second strands 125 and 127 are preferably joined or bonded at nodes 90.
A preferred elastomeric scrim 124 is manufactured by the Conwed Plastics
Company under the designation X02514. This material has about 12 elastic
strands
per inch in the structural direction B (i.e., the first strands 125) and about
7 elastic
strands per inch in the structural direction D (i.e., the second strands 127).
This
3o elastomeric scrim 124 has an OR of from about 50% to about 60%. This
elastomeric scrim 124 also has a RFH12H of from about 50 grams/inch to about
65
grams/inch, a FCEF100% of about 175 grams/inch, a FCEF200% of about 240
grams/inch, a SCRF50% of about 85 grams/inch, an EB of at least about 800%,
and
a TR of at least 24 hours.
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13
In the embodiment shown in Fig. 1, the elastic member 70 comprises first and
second coverstock layers 122 and 126, and elastomeric material 124 disposed in
the first and second coverstock layers 122 and 126. The first coverstock layer
122
has an inner surface 142 and an outer surface 144. The inner surface 142 of
the
first coverstock layer 122 is the surface that is positioned facing the
elastomeric
material 124. The second coverstock layer 126 also has an inner surface 146
and
an outer surface 148. The inner surface 146 of the second coverstock layer 126
is
the surface that is positioned facing the elastomeric material 124. The
elastomeric
material 124 also has two planar surfaces, first surface 150 and second
surface 152,
o each of which is substantially parallel with the planes of the first and
second
coverstock layers 122 and 126. The first surface 150 is that planar surface of
the
elastomeric material 124 that is most closely adjacent with the inner surface
142 of
first coverstock layer 122. The second surface 152 is that planar surface of
elastomeric material 124 that is most closely adjacent to the inner surface
146 of the
~ 5 second coverstock layer 126.
Since the elastic member 70 will be subjected to mechanical stretching before
and during use, the first and second coverstock layers 122 and 126 preferably
has a
relatively high elongation at breaking, and are more preferably stretchable or
2o elongatable, yet more preferably drawable (but not necessarily
elastomeric), without
undue and preferably without any, tearing
or ripping. Further, the first and second coverstock layers 122 and 126 are
preferably compliant, soft feeling, and non-irritating to the wearer's skin
and give the
article the feel and comfort of a cloth garment. Suitable materials for the
first and
25 second coverstock layers 122 and 126 can be manufactured from a wide range
of
materials such as plastic films, apertured plastic films, woven or nonwoven
webs of
natural fibers (e.g., wood or cotton fibers), synthetic fibers (e.g.,
polyoiefins,
polyamides, polyester, polyethylene, or polypropylene fibers), or a
combination of
natural and/or synthetic fibers, or coated woven or nonwoven webs.
Preferably, each of the first and second coverstock layers 122 and 126 is an
identical consolidated nonwoven material. An exemplary preferred nonwoven
material is manufactured by the FiberWeb Company under the designation Sofspan
200. This material has a basis weight of 25 g/m2 before consolidation and a
basis
weight of about 63g/m2 after consolidation. As used herein, "basis weight" is
the
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14
weight of one square meter of planar web material. Alternatively, highly
strainable
nonwoven materials may be used. Alternatively, the first and second coverstock
layers 122 and 126 need not be of identical materials, as long as the desired
performance requirements, such as elastic performance, softness, flexibility,
breathability and durability, are met. As used herein, "consolidated nonwoven
material" means a nonwoven material that has been gathered or necked under
mechanical tension in the structural direction D so that the material can
elongate in
the structural direction D under low force.
Fig. 2 shows a fragmentary enlarged side view looking into the structural
direction B of the laminate 120 (i.e., the elastic member 70). It has been
found that
when the laminate 120 is bonded or otherwise anchored such that side anchor
zones A are created, such a laminate 120 is both highly elastic and
substantially free
from delamination and creep, while providing very good performance
characteristics
~5 in all performance categories with no trade-offs between any performance
characteristics required. The side anchoring is preferably performed by side
gluing
with adhesive beads to anchor the elastomeric material 124 between the
coverstock
layers 122 and 126 as a part of the lamination process. Alternatively, side
anchoring
may be performed by sewing, heat sealing, ultrasound bonding, needle punching,
2o alternative gluing processes, or by any other means known to those skilled
in the art.
Another alternative is to side anchor the layers of the laminate structure
after the
lamination of the elastomeric and coverstock components has been performed.
Preferably, the laminate 120 may particularly provide very good soft feel for
25 the wearer and for the consumer. This is important because consumers value
softness. In conventional laminates, the attempts to eliminate creep have
frequently
required an unacceptable decrease in softness, often accompanied by an
unacceptable decrease in the ability to activate. This is because such
previous
attempts (which have fallen short of eliminating creep) have focused on the
3o application of additional melt blown adhesive, often in an overall coating
pattern, in
the attempt to strengthen the bonds. This has generally resulted in an
undesirable
overall stiffening of the laminate. However, the laminates of the preferred
embodiments provide elimination of creep without the loss of consumer-desired
soft
feel and without compromise of activation ability.
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Referring to Fig. 2, a first adhesive 170 is applied to the inner surface 146
of
the second coverstock layer 126 in positions that correspond to each of the
outer
edges 180 of the laminate structure 120. The first adhesive 170 may
alternatively or
additionally be applied to the inner surface 142 of the first coverstock layer
122. For
5 ease of illustration, the description and Figures refer to application to
the second
coverstock layer 126 only.
This pattern creates side anchor zones A, which substantially eliminate the
delamination and creep associated with previously known laminates and which
allows the laminate 120 to experience higher strains without creeping or
delaminating. It has also been found that confining the first adhesive 170 to
the
edge areas 180 of the laminate structure 120 avoids impeding the extensibility
of the
laminate 120 and also avoids tears in the coverstock layers 122 and 126.
Preferably, the first adhesive 170 is applied as a plurality of beads 168, as
shown in
~5 Fig. 2. Preferably, the first adhesive 170 is a flexible adhesive with an
amorphous
and crystallizing component. Such a preferred adhesive is made by the Findley
Adhesive Company under the designation H9224.
More preferably, the laminate 120 includes a second adhesive 164. The
2o second adhesive 164 is preferably applied to the second surface 152 of the
elastomeric material 124, but could alternatively be applied to the first
surface 150 of
the eiastomeric material 24. The second adhesive 164 is preferably applied in
a
spiral spray pattern 166, thereby forming bond points 167b that are more
discrete
than would be formed by a linear spray application. Without being bound by
theory,
it is believed that most of the second adhesive 164 so sprayed aligns in the
structural direction D. Thus, it has been found that spiral spraying results
in very
good activation properties. As used herein, "activation" refers to the ability
to
stretch.
3o It has been found that spraying the layer of second adhesive 164 directly
onto
the second surface 152 of the elastomeric material 124 is more preferable than
applying the second adhesive 164 to the opposing (i.e., second) coverstock
layer
126. This is because the second adhesive 164 tends to penetrate through any
residual processing agents or oils that may remain on the surface of the
elastomeric
material 124. Such residual materials, if left to remain on the elastomeric
material
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16
124, may weaken the adhesive bonds and thus the laminate structure 120 over
time.
For example, if these residual materials are left intact, the bonds used to
form the
laminate 120 may weaken during the time interval prior to consumer purchase of
the
product.
Peel values for the laminate 120 in the spiral adhesive areas are typically
higher when the spirals 166 are applied directly to the elastomeric material
124 than
to the opposing (i.e., second) coverstock layer 126. As used herein, the term
"peel
value" refers to the amount of force required to separate the two layers of
coverstock
material, 122 and 126, from each other. Higher peel values typically equate to
less
chance of delamination in use.
A third adhesive 160 may also preferably be applied to the inner surface 142
of the first coverstock layer 122. Preferably, the third adhesive 160 is an
elastomeric
adhesive. In a manner similar to that described with reference to the second
spiral
adhesive application 166, the first adhesive 160 is preferably applied in a
spiral
spray pattern 162, thereby forming bond points 167a that are more discrete
than
would be formed by a linear spray application. Without being bound by theory,
it is
believed that most of the first adhesive 160 so sprayed aligns in the
structural
2o direction D.
Preferably, second and third adhesives 160 and 164 are the same
elastomeric adhesive. A preferred adhesive for use in the second and third
adhesive spiral sprays 162 and 166 is made by the Findley Adhesive Company
25 under the designation H2120. Preferably, the add-on level for each of the
second
and third spiral sprays 162 and 166 is about 4 to about 12 milligrams per
square
inch, more preferably about 8 milligrams per square inch.
The elastic material 124 of the present invention is applicable to a variety
of
so disposable products, including sweat bands, bandages, and disposable
garments
including disposable diapers and incontinence devices. Although preferred
embodiments of the present invention are described only for disposable
garments
including disposable pull-on diapers hereinafter, it will be apparent to those
of skill in
the art that the applications of the present invention are not limited to
those
ss embodiments.
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17
Referring to Fig. 5, a disposable garment 20 of the present invention
comprises a chassis 41 having a front region 26; a back region 28 and a crotch
region 30 between the front region 26 and the back region 28; and at least one
pair
of side panels 46 or 48 extending laterally outwardly from the chassis 41 in
the front
region 26 or the back region 28. The at least one of the side panels 46 or 48
comprises an elastomeric material 124 (not shown in Fig. 5) extending
laterally
outwardly from the chassis 41. The chassis 41 comprises a liquid pervious
topsheet
24, a liquid impervious backsheet 22 associated with the topsheet 24, and an
absorbent core 25 (not shown in Fig. 5) disposed between the topsheet 24 and
the
backsheet 22. In yet another aspect of the invention, the elastomeric material
124
has an EB of at least about 600%, and may additionally have other preferred
extension properties of the elastomeric material 124 which has been already
described. In still another aspect of the invention, the elastomeric material
124 has a
~ s TR of at least about 16 hours.
The at least one pair of side panels may be either a pair of front side panels
46 or a pair of back side panels 48. In a preferred embodiment wherein the
disposable garment 20 is a pull-on type disposable diaper, the at least one
pair of
2o side panels comprises a pair of front side panels 46 provided in the front
region 26
and a pair of back side panels 48 provided in the back region 28, and the
disposable
garment 20 further comprises seams 32 each joining the corresponding edges of
the
side panels 46 and 48, thereby forming two leg openings 34 and a waist opening
36.
In anothjer preferred embodiment wherein the disposable garment 20 is a tape
type -
25 disposable diaper, the at least one pair of side panels is the back side
panel 48.
Fig. 5 shows one preferred embodiment of a disposable garment of the
present invention (i.e., a pull-on diaper 20). The pull-on diaper 20 comprises
a
chassis 41 having the front region 26, the back region 28 and the crotch
region 30
3o between the front region 26 and the back region 28. The chassis 41
comprises the
liquid pervious topsheet 24, the liquid impervious backsheet 22 associated
with the
topsheet 24, and an absorbent core 25 (not shown in Fig. 5 but in Fig. 6)
disposed
between the topsheet 24 and the backsheet 22. The pull-on diaper 20 further
comprises the front side panels 46 each extending laterally outwardly from the
35 corresponding side of the chassis 41 in the front region 26, and back side
panels 48
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18
each extending laterally outwardly from the corresponding side of the chassis
41 in
the back region 28. Preferably, at least one pair of the front and back side
panels
46 and 48 are elastically extensible in at least the lateral direction. The
pull-on
diaper 20 further comprises seam panels 66 each extending laterally outwardly
from
each of the front and back side panels 46 and 48; and tear open tabs 31 each
extending laterally outwardly from the seam panels 66. Other preferred
examples of
the pull-on diaper 20 are disclosed in U.S. Patent No. 5,569,234 to Buell et
al. on
October 29, 1996.
Preferably at least one of, more preferably both of, the pairs of the front
and
back side panels 46 and 48 is elastically extensible. As used herein, the term
"extensible" refers to materials that are capable of extending in at least one
direction
to a certain degree without undue rupture. The terms "elasticity" and
"elastically
extensible" refer to extensible materials that have the ability to return to
~5 approximately their original dimensions after the force that extended the
material is
removed. As used herein, any material or element described as "extensible" may
also be elastically extensible unless othenrvise provided. The extensible side
panels
46 and/or 48 provide a more comfortable and contouring fit by initially
conformably
fitting the diaper to the wearer and sustaining this fit throughout the time
of wear well
2o past when the diaper has been loaded with exudates since the side panels 46
and/or 48 allow the sides of the diaper to expand and contract.
In a preferred embodiment, the front and back side panels 46 and 48 are
elastically extensible only in the lateral direction. In an alternative
embodiment, the
25 front and back side panels 46 and 48 are elastically extensible both in the
lateral and
longitudinal directions.
A continuous belt 38 is formed by the front and back side panels 46 and 48,
and a part of the chassis 41 about the waist opening 36. Preferably,
elasticized
3o waist bands 50 are provided in both the front region 26 and the back region
28. The
pull-on diaper 20 additionally comprises elastic leg features 52.
The continuous belt 38 acts to dynamically create fitment forces in the pull-
on
diaper 20 when positioned on the wearer, to maintain the pull-on diaper 20 on
the
35 wearer even when loaded with body exudates thus keeping the absorbent core
25 in
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19
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 25 without binding or bunching the absorbent core 25.
The front and back side panels 46 and 48 may be formed by unitary elements
of the pull-on diaper 20 (i.e., they are not separately manipulative elements
secured
to the pull-on diaper 20, but rather are formed from and are extensions of one
or
more of the various layers of the pull-on diaper). In a preferred embodiment,
each of
the front and back side panels 46 and 48 is a projected member of the chassis
41
~o (more clearly shown in Fig. 6). Preferably, the front side panels 46 and
back side
panels 48 comprises at least one unitary element or a continuous sheet
material
(e.g. the backsheet nonwoven 23 in Fig. 7) that forms a part of the chassis 41
and
continuously extends to the front side panels 46 and back side panels 48.
~5 In preferred embodiments, each of the seam panels 66 is an extension of the
corresponding front and back side panels 46 and 48, or at least one of the
component elements used therein, or any other combination of the elements.
Preferably, each of the tear open tabs 31 is also an extension of the
corresponding
seam panels 66 or at least one of their component elements used therein, or
any
20 other combination of the elements.
Alternatively, the front and side panels 46 and 48 may be discrete members
(not shown in the figures) which do not have any unitary element that forms a
part of
the chassis 41. The front and side panels are formed by joining the discrete
25 members to the side edges of the chassis 41.
The pull-on diaper 20 further comprises seams 32 each joining the
corresponding edges of the front and side panels 46 and 48, thereby forming
two leg
openings 34 and a waist opening 36. Preferably, the front and side panels 46
and
30 48 are seamed, more preferably through the seam panels 66, in an overlap
manner
to make an overlapped seam structure. Alternatively, the front and side panels
46
and 48 can be seamed in a butt seam manner (not shown in the figures). 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 front and back side
panels 46
35 and 48. Thus, sonic sealing, heat sealing, pressure bonding, adhesive or
cohesive
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WO 99/48681 PCT/US98/05896
bonding, 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 diaper 20 during wear.
5
Fig. 6 is a partially cut-away plan view of the pull-on diaper 20 of Fig. 5 in
its
flat-out, uncontracted state (i.e., with elastic induced contraction pulled
out except in
the side panels 46 and 48 which are left in their relaxed condition) with the
topsheet
24 facing the viewer, prior to the side panels 46 and 48 are joined together
by the
0 seams 32. The pull-on diaper 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 diaper 20 in which the side edges are
designated
150 and the end edges or waist edges are designated 152. The topsheet 24 has
~5 the body-facing surface of the pull-on diaper 20 which is positioned
adjacent to the
wearer's body during use. The backsheet 26 has the outer-facing surface or the
of
the pull-on diaper 20 which is positioned away from the wearer's body. The
pull-on
diaper 20 comprises the chassis 41 comprising the liquid pervious topsheet 24;
the
liquid impervious backsheet 26 associated with the topsheet 24; and the
absorbent
2o core 25 positioned between the topsheet 24 and the backsheet 26. The diaper
20
further comprises the front and back side panels 46 and 48 extending laterally
outwardly from the chassis 41; the elasticized leg cuffs 52; and the
elasticized
waistbands 50. The topsheet 24 and the backsheet 26 have length and width
dimensions generally larger than those of the absorbent core 25. The topsheet
24
2s and the backsheet 26 extend beyond the edges of the absorbent core 25 to
thereby
form the periphery of the diaper 20. The liquid impervious backsheet 26
preferably
comprises a liquid impervious plastic film 68 which is joined to the backsheet
nonwoven 23.
3o While the topsheet 24, the backsheet 26, 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
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21
Dynamic Elastic Waist Feature Having A Predisposed Resilient Flexural Hinge"
which issued to Kenneth B. Bueli et al., on September 29, 1992.
The pull-on diaper 20 also has two centerlines, a longitudinal centerline 100
and a transverse centerline 110. The term "longitudinal", as used herein,
refers to a
line, axis, or direction in the plane of the pull-on diaper 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 diaper 20 is worn. The
terms
"transverse" and "lateral", as used herein, are interchangeable and refer to a
line,
~o axis or direction which lies within the plane of the diaper that is
generally
perpendicular to the longitudinal direction (which divides the wearer into
front and
back body halves). The pull-on diaper 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.
Fig. 7 is a cross-sectional view of a preferred embodiment taken along the
section line 7-7 of Fig. 6. The pull-on diaper 20 comprises the chassis 41
comprising the liquid pervious topsheet 24; the liquid impervious backsheet 26
associated with the topsheet 24; and the absorbent core 25 positioned between
the
2o topsheet 24 and the backsheet 26. The diaper further comprises the front
side
panels 46 each extending laterally outwardly from the chassis 41; and the
elasticized leg cuffs 52. Although Fig. 7 depicts only the structure of the
front side
panel 46, preferably the back side panels 48 have the similar structures.
Preferably,
the chassis 41 further comprises an acquisitionldistribution layer 82 and/or
an
acquisition/distribution core 84 between the topsheet 24 and the absorbent
core 25.
Each of the front side panels 46 is formed by the lamination of an extended
part 72
of the barrier flap 56, an elastic member 70 and the backsheet nonwoven 74.
The absorbent core 25 may be any absorbent member which is generally
3o compressible, conformable, 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 diapers and other
absorbent articles such as comminuted wood pulp which is generally referred to
as
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22
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
o acquisition zones; or may comprise 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 diaper 20.
A preferred embodiment of the diaper 20 has an asymmetric, modified
hourgalss-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.
2o Patent No. 4,610,678 entitled "High-Density Absorbent Structures" issued to
Weisman et al. on September 9, 1986; U.S. Patent No. 4,673,402 entitled
"Absorbent Articles With Dual-Layered Cores" issued to Weisman et al. 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 Alemany et ai. on May 30, 1989.
The chassis 41 may further comprise an acquisition/distribution core 84 of
chemically stiffened fibers positioned over the absorbent core 25, thereby
forming a
3o dual core system. 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 comprise chemically
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23
treated stiffened cellulosic fiber material, available from Weyerhaeuser Co.
(U.S.A.)
under the trade designation of CMC.
More preferably, the chassis 22 further comprises an acquisition/distribution
layer 82 between the topsheet 24 and the acquisition/distribution core 84 as
shown
in Fig. 7. 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 comprises carded, resin bonded hiloft nonwoven materials such
as, for
example, available as Code No. FT-6860 from Polymer Group, Inc., North America
o (Landisivilie, 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.
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.,
s 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 thermoplastic films; porous foams;
reticulated foams; reticulated thermoplastic films; and thermoplastic scrims.
Suitable
2o woven and nonwoven materials can be comprised of natural fibers (e.g., wood
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. 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
2s 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 flow off the
topsheet
24 rather than being drawn through the topsheet 24 and being absorbed by the
3o 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. Patent Nos. 4,988,344 entitled "Absorbent Articles with
Multiple
35 Layer Absorbent Layers" issued to Reising, et al on January 29, 1991 and
U.S.
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24
Patent No. 4,988,345 entitled "Absorbent Articles with Rapid Acquiring
Absorbent
Cores" issued to Reising on January 29, 1991.
In preferred embodiments, the topsheet 24 is a nonwoven web that can
provide 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 thermobonded 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 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 comprises an apertured formed film.
Apertured formed films are preferred for the topsheet 24 because they are
pervious
to body exudates and yet 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
2o 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", which issued to Thompson on December 30, 1975; U.S.
Patent No. 4,324,246 entitled "Disposable Absorbent Article Having A Stain
Resistant Topsheet", which issued to Mullane, et al. on April 13, 1982; U.S.
Patent
No. 4,342,314 entitled "Resilient Plastic Web Exhibiting Fiber-Like
Properties", which
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", which issued to Ahr et al.
on July
31, 1984; and U.S. 5,006,394 "Multilayer Polymeric Film" issued to Baird on
April 9,
1991.
In preferred embodiments, the backsheet 22 comprises the liquid impervious
film 68 as shown in, for example, Fig. 7. The liquid impervious film 68 has a
body-
facing surface and an outer-facing surface. The liquid impervious film 68 is
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5
preferably 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 diaper 20. In a preferred embodiment, a microporous polyethylene film
is
used for the plastic film 68. A suitable microporous polyethylene film is
manufactured by Mitsui Toatsu Chemicals, Inc., Nagoya, Japan and marketed in
the
trade as Espoir No.
In a preferred embodiment, the liquid impervious film 68 (i.e., the plastic
film
68 in Fig. 6) extends in the front, back and crotch regions 26, 28 and 30.
Preferably,
~o the plastic film 68 has a nonuniform width so as to form a first portion 94
in at least a
portion of the crotch region 30, and a second portion 96 in at least a portion
of the
front or back region 26 and 28. The second portion 96 has a width dimension
less
than the width dimension of the first portion 94 such that the plastic film 68
does not
extend into the front side panels 46 or the back side panels 48. In a
preferred
~5 embodiment, the lateral width LW of the plastic film 68 gradually decreases
towards
the waist edges 152, as shown in Fig. 6.
A suitable material for the plastic 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
2c comprising polyethylene or polypropylene. Preferably, the plastic film has
a basis
weight of from about 5 glm2 to about 35 g/m2. However, it should be noted that
other flexible liquid impervious materials may be used. As used herein, the
term
"flexible" refers to materials which are compliant and which will readily
conform to
the general shape and contours of the wearer's body.
Preferably, the backsheet 22 further comprises a nonwoven web 23 which is
joined with the outer-facing surface of the plastic film 68 to form a laminate
(i.e., the
backsheet 22). The nonwoven web (or backsheet nonwoven) 23 is positioned at
the
outermost portion of the diaper 20 and covers at least a portion of the
outermost
3o portion of the diaper 20. In a preferred embodiment, the nonwoven web 23
covers
almost all of the area of the outermost portion of the diaper 20. The nonwoven
web
23 may be joined to the plastic film 68 by any suitable attachment means known
in
the art. For example, the nonwoven web 23 may be secured to the plastic 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
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26
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 web 23 is a carded nonwoven
web, for example, obtainable from Havix Co., LTD., Gifu, Japan as E-2341. The
nonwoven web 23 is made of bi-component fibers of a polyethylene (PE) and a
polyethylene terephthalate (PET). The ratio of PE/PET is about 40!60. The
PE/PET
bi-component fiber has the dimension of 2d x 51 mm. Another preferred carded
nonwoven web is obtainable from Chisso Corp., Osaka, Japan. The nonwoven
outer cover 23 is also made of bi-component fibers of a polyethylene (PE) and
a
polyethylene terephthalate (PET). The ratio of PE/PET is about 30/70.
In another preferred embodiment, the nonwoven web is a spunbonded
~5 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.
2o 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 uniform continuous layer of adhesive, a patterned layer
of
adhesive, or an array of separate lines, spirals, or spots of adhesive.
Adhesives
25 which have been found to be satisfactory are manufactured by H. B. Fuller
Company
of St. Paul, Minnesota and marketed as HL-1358J. An example of a suitable
attachment means comprising 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
3o attachment means comprising 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
35 comprise heat bonds, pressure bonds, ultrasonic bonds, dynamic mechanical
CA 02325534 2000-09-25
WO 99/48681 PCT/LS98/05896
27
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 diaper 20 preferably further comprises elasticized leg cuffs 52
for
providing improved containment of liquids and other body exudates. The
elasticized
o leg cuffs 52 may comprise several different embodiments for reducing the
leakage of
body exudates in the leg regions. (The leg cuff can be and is sometimes also
referred to as leg bands, side flaps, barrier cuffs, or elastic cuffs.) U.S.
Patent
3,860,003 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
~5 cuff (gasketing 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
20 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 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-
25 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 each elasticized leg cuff 52 comprises inner barrier cuffs 54
each
3o comprising a barrier flap 56 and a spacing means 58 (as shown in Figs. 5
and 6) as
described in the above-referenced U.S. Patent No. 4,909,803. In a preferred
embodiment, the elasticized leg cuff 52 additionally comprises an elastic
gasketing
cuff 62 with one or more elastic strands 64 (as shown in Fig. 6), positioned
outboard
of the barrier cuff 54 such as described in the above-referred U.S. Patent
Nos.
35 4,695,278 and 4,795,454.
CA 02325534 2000-09-25
WO 99/48681 PCT/US98/05896
28
The pull-on diaper 20 preferably further comprises an elasticized waistband
50 that provides improved fit and containment. The elasticized waistband 50 is
that
portion or zone of the pull-on diaper 20 which is intended to elastically
expand and
contract to dynamically fit the wearer's waist. The elasticized waistband 50
preferably extends longitudinally outwardly from at least one of the waist
edges of
the absorbent core 25 and generally forms at least a portion of the end edge
of the
pull-on diaper 20. Preferably, the pull-on diaper 20 has two elasticized
waistbands
50, one positioned in the back region 28 and one positioned in the front
region 26,
o although other pull-on diapers 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 4,515,595
entitled
"Disposable Diapers with Elastically Contractible Waistbands" issued to Kievit
et al.
on May 7, 1985 and the above referenced U.S. Patent 5,151,092 issued to Buell.
'15
The waistbands 50 may comprise materials that have been "prestrained", or
"mechanically prestrained" (i.e., subjected to some degree of localized
pattern
mechanical stretching to permanently elongate the material. The materials may
be
prestrained using deep embossing techniques as are known in the art.
Alternatively,
2o the materials may be prestrained by directing the material through an
incremental
mechanical stretching system as described in U.S. Patent No. 5,330,458
entitled
"Absorbent Article With Elastic Feature Having A Portion Mechanically
Prestrained"
issued to Buell et al., on July 19, 1994. The materials are then allowed to
return to
their substantially untensioned condition, thus forming a zero strain stretch
material
25 that is extensible. at least up to the point of initial stretching.
Examples of zero strain
materials are disclosed in U.S. Patent No. 2,075,189 issued to Galligan on
March
30, 1937; U.S. Patent No. 3,025,199 issued to Harwood on March 13, 1962; U.S.
Patent Nos. 4,107,364 and 4,209,563 issued to Sisson on August 15, 1978 and
June 24, 1980, respectively; U.S. Patent No. 4,834,741 issued to Sabee on May
30,
30 1989; and U.S. Patent No. 5,151,092 issued to Bueli et al., on September
29, 1992.
Referring to Fig. 7, at least one of the front and back side panels (i.e., the
front side panels 46 in this embodiment) comprises the elastic member 70 of
the
present invention. The elastic member 70 comprises the elastomeric material
124
35 which preferably extends laterally outwardly from the chassis 41 to provide
a good
CA 02325534 2000-09-25
WO 99/48681 PCT/US98/05896
29
fitness by generating an optimal retention (or sustained) force at the waist
area of
the wearer. Preferably, the elastomeric material 124 is extensible in at least
one
direction, preferably in a direction having a vector component in the lateral
direction
to generate a retention (or sustained) force that is optimal to prevent the
pull-on
diaper 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 preferred
embodiments, both of the front and back side panels 46 and 48 comprise the
elastomeric material 124.
o The elastic member 70 comprising the elastomeric material 124 (not shown in
Fig. 7) is operatively joined to at least one of the nonwoven webs 72 and 74
in the
front and back side panels 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
~5 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
2o continuous bonding configuration. As used herein, an "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
25 the plies are initially bonded substantially continuously to one another
throughout the
areas of interface. Because 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
3o the layers of the stretch laminate in relatively close adherence to one
another after
the incremental mechanical stretching operation, the elastic panel members and
the
other plies of the stretch laminate are substantially continuously bonded
together
using an adhesive. In a particularly preferred embodiment, the adhesive
selected is
applied in a spiral pattern (such as is shown in U.S. 3,911,173 (Sprague, Jr.)
and
35 U.S. 4,842,666 (Werenicz)) at a basis weight of about 0.00116 grams/square
cm
CA 02325534 2000-09-25
WO 99/48681 PCT/US98/05896
(0.0075 grams/square inch). The spirals have a width of about 1.9 cm (0.75 in)
and
either are positioned just next to each other or overlap slightly (less than 2
mm).
The adhesive is preferably an adhesive such as is available from Findley
Adhesives
under the designation H2120. Alternatively, the elastic panel member and any
other
components of the stretch laminates may be 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
o 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 front
~ 5 and back side panels 46 and 48 is thus formed into "zero strain" stretch
laminates.
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 al. on December 1, 1992; U.S. Patent No. 5,156,793 issued to Buell et al.
on
2o October 20, 1990; and U.S. Patent No. 5,143,679 issued to Weber et al. on
September 1, 1992. It should be noted that the Japanese equivalent
applications to
these U.S. Patents were published (laid open) in Japanese under the Nos. of H6-
505681, H6-505408 and H6-505446, respectively.
25 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
plastic film
68) though an adhesive 76 as shown in Fig. 7. Preferably, the adhesive 76 is
applied as an bead. In preferred embodiments, the adhesive 76 is a flexible
adhesive with an amorphous and crystallizing component. Such a preferred
3o adhesive is made by the Findley Adhesive Company under the designation
H9224.
Alternatively, the elastic member 70 may be joined to the respective edges 78
of the
plastic film 68 by any other bonding means known in the art which comprise
heat
bonds, pressure bonds, ultrasonic bonds, dynamic mechanical bonds, or
combinations of these attachment means.
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WO 99/48681 PCT/US98/05896
31
In a preferred embodiment, for example, in the embodiment shown in Fig. 6,
the elastic member 70 is joined to the second portion 96 which has a width
dimension less than the width dimension of the first portion 94. Preferably,
the
elastic member 70 is joined to the respective edges 78 of the plastic film 68
at the
outer-facing surface 77 as shown in Fig. 7. In an alternative embodiment, the
elastic
member 70 may be joined to the respective edges 78 of the plastic film 68 at
the
body-facing surface 79 (not shown in Figs.).
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 depending from the scope of the present
invention.
