Note: Descriptions are shown in the official language in which they were submitted.
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1
AHSORHENT ARTICLE WITH STRUCTURAL
ELASTIC-LIKE FILM WEB WAIST BELT
to
is
The present iron rdates to absorbent amides such as diapers, incontinent
briefs, training pants, and the like, and more particularly, to absorbent
articles having
an extensible waist feature providing dynamic fit about the wearer as well as
Zo improved containment characteristics of the absorbent amide.
Infants and other incontinent individuals wear absorbent articles such as
diapers to receive and contain urine and other body exudates. Absorbent
articles
Zs function both to contain the discharged materials and to isolate these
materials from
the body of the wearer and from the wesr~s garments and bed clothing.
Disposable
absorbent articles having many different basic designs: arc known to the art.
For
anmple, U. S. Patent Re. 26, I 52, entitled "Disposable Diaper" issued to
Duncan and
Baker an° Jarwary 31, 1967, describes a disposable diaper which has
achieved wide
3o acceptance and commercial success. U.S. Patent 3,860,003, entitled
"Contractible
Side Poitions For Disposable Diaper", issued to Huell on January 14, 1975,
describes
an elasticized leg cuff disposable diaper which has achieved wide acceptance
and
commercial success.
However, absorbent artida have s tendency to sag or gap away from and to
3s slide/stip down on the body of the wearer during wear. This sagging/gapping
and
sliding/stipping is caused by the relative mbtions of the wearer as the wearer
breathes,
moves and changes positions, by the downward forces generated when the
absorbent
article is loaded with body exudates, and by the deformation of the materials
of the
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WO 95/14433 PCTNS94/133117
absorbent article itself when subjected to such wearer's motions. This
sa88~8lBapping snd sliding/slipping of the absorbent article can lead to
premature
leakage and poor 5t of the absorbent article about the wearer in the waist
regions and
the leg regions of the absorbent article.
s In order to more snugly 5t absorbent articles about the wearer, certain
commercially available absorbent articles have been provided with elastic
features.
An example of a disposable diaper with elastic side panels is disclosed in
U.S. Patent
5,151,092 , entitled 'Absorbent Article With Dynamic Elastic Waist Feature
Having
Predisposed Flexural Hinge" issued to BueU, Clear, and Falcone on September
22,
Io 1992. However, elastics are costly and roquire a certain degree of
manipulation and
handling during assembly. Further, while elastics do provide a degree of
stretch for
the absorbent article, the components of the absorbent article to which the
elastics are
attached are typically not elastic such thu the elastics must be prestretched
prior to
being secured to the absorbent article or the inelastic componenu must be
subjected
is to mechanical stretching (e.g., ring rolling) to enable the added elastic
to be
effective. Otherwix, the added elastic is restrained by the inelastic
componenu.
Therefore, it is an object of an aspect of the present invention to provide a
relatively low
cost, easy to manufacture, absorbent artic~ having :<rstained dynamic fit
about the
wearer during ux.
. 20 It is a further object of an aspect of the present invention to provide
an absorbent article
having a unique waist feature, without the use of elastic, that provides
sustained
dynamic 8t and improved resistance to leakage during ux due to the
conformability
of the materials forming the waist feature by virtue of their rradily
extensible nature.
It is a still further object of an aspect of the present invention to provide
a waist feature on
is an absorbent article that exhibiu an 'elastic-like' behavior in the
direction of apptted
force or elongation without the use of additional elastic material.
These and other objects of aspects of the present invention will be more
readily apparent
when considered in reference to the following description and when taken in
conjunction with the accompanying drawings.
The present imrention provides absorbent articles such as disposable diapers,
incontinent briefs, diaper holders, training pants, feminine hygiene garmenu
and the
like, that have a unique waist feature that- improves the dynamic 5t as well
as the
CA 02263049 2003-O1-21
2a
containment characteristics of the absorbent article. Such absorbent articles
comprise
a chassis assembly preferably comprising a liquid pervious topsheet, a liquid
impervious backsheet, and an absorbent core positioned between the topsheet
and the
backsheet; an extensible waist belt; and a closure; system for maintaining the
absorbent article on the wearer. The absorbent core has side edges and waist
edges.
In accordance with one embodiment ofthe invention, a disposable absorbent
article comprises:
a chassis assembly having lateral edges, leg edges and an area, the chassis
assembly comprising a topsheet, a backsheet joined with the topsheet, and an
to absorbent core positioned between the topsheet and the backsheet, the
absorbent core
having side edges, waist edges and an area, the disposable absorbent article
having a
ratio of core area to chassis area o1' less than about 0.40:1.0; and an
extensible waist
belt joined with the chassis assembly adjacent one of the lateral edges, the
waist belt
comprising a structural elastic-like film web.
In accordance with another embodiment, a disposable absorbent article for
covering a wearer's crotch area, the disposable absorbent article comprises:
a chassis assembly having lateral edges, leg edges and an area, the chassis
assembly comprising a topsheet, a backsheet joined with the topsheet, and a
absorbent
core positioned between the topsheet and the hacksheet, the absorbent core
having
2o side edges, waist edges and an area, the disposable absorbent article
having a ratio of
the wearer's crotch area covered by the absorbent core to area of the
absorbent core of
at least 0.40 to 1.0; and an extensible waist belt joined with the chassis
assembly
adjacent one of the lateral edges, the waist belt comprising a structural
elastic-like
film web.
In accordance with another embodiment, a disposable absorbent article
comprises:
a chassis assembly having lateral edges, leg edges, a length, an area, a
maximum width in a first waist region and a maximum width in a second waist
region, the chassis assembly comprising a topsheet, a backsheet joined with
the
3o topsheet, and an absorbent core positioned between the topsheet and the
backsheet,
the absorbent core having side edges, and waist edges, the disposable
absorbent article
having a ratio of the width in the first waist region to the width in the
second waist
region of at least '1.3:1; and an extensible waist belt jcoined with the
chassis assembly
adjacent one of the lateral edges, the waist belt comprising a structural
elastic-like
CA 02263049 2002-03-27
film web.
2b
In accordance with another embodiment, a disposable absorbent article
comprises:
a chassis assembly having lateral edges, leg edges, a length measured in
centimeters, and an area measured in square centimeters, the chassis assembly
comprising a topsheet, a backsheet joined with the topsheet, and an absorbent
core
positioned between the topsheet and the backsheet, the absorbent core having
side
edges, waist edges and an area, the disposable absorbent article having a
ratio of the
chassis length to the area of the chassis of at least 0.45:1.0 centimeters to
square
1o centimeters; and an extensible waist belt joined with the chassis assembly
adjacent
one of the lateral edges, the waist belt comprising a structural elastic-like
film web.
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In an especially preferred embodiment of the present invention, the absorbent
article has a T-shape comprising a chassis assembly and an extensible waist
belt
disposed in the second waist region. The extensible waist belt provides an
extensible
feature that provides a more comfortable and contouring 5t by initially
conformably
to fitting the diaper to the wearer and by sustaining this fit. The extensible
waist belt
further develops and maintains wearing forces (tensions) that enhance the
tensions
developed and maintained by the closure rystem. The extensible waist belt
further
provides more effective application of the diaper. While each extensible waist
belt
may be constructed from a number of extensible materials, the extensible waist
belt
Is preferably comprises a structural elastic-Like film web.
The structural elastic-like film (SELF? web exhibits an elastic-Like behavior
in
the direction of elongation without the use of added elastic materials. The
SELF
web may exhibit an elongation and recovery with a definite and sudden increase
in
the force resisting elongation where this definite and sudden increase in
resistive
1o force restricts further elongation against relatively small elongation
forces. The
definite and sudden increase in the force resisting dongation is referred to
as a 'force
wall'. As used herein, the term 'force wall" refers to the bdlavior of the
resistive
force of a SELF web material during dongation wherein at some point in the
elongation, distinct from the untensioned or starting point, the force
resisting the
i5 applied elongation suddenly increases. After reaching the force waU,
additional
elongation of the SELF web material is only accomplished via an increase in
the
elongation force to overcome the higher resistive force of the SELF web.
The SELF web of the present invention induda a attainable network having
at least two distinct regions comprised of the same muerial composition. The
first
3o region is oriented substantially paralld to an axis of donguion such that
it will
undergo a molecular-level deformation in response to an applied axial
elongation in a
direction substantially parallel to the elongation axis before a substantial
portion of
the second region undergoes arty substantial molecular-level deformation. As
used
herein, the term "substantially parallel' refers to an orientation between two
axes
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_ WO 95/14453
4
whereby the subtended angle formed by the two axes or an extension of the two
axes is less than 45°. In the case of a curvilinear element it may be
more convenient
to use a linear axis which represents an average of the curvilinear element.
The
second regions initially undergo a substantially geometric deformation in
response to
s an applied elongation in a direction substantially parallel to the axis.
In a particularly preferred embodiment, the second region of the SELF web
is comprised of a plurality of raised rib-like elemenu. As used herein, the
term
"rib-like element" refers to an embossment, debossment or combination thereof
which has a major axis and a minor axis. Preferably, the major axis is at
least as long
to as the minor axis. The major axes of the rib-like elements are preferably
oriented
substantially perpendicular to the axis of applied elongation. The major axis
and the
minor axis of the rib-like elemenu may each be linear, curvilinear or a
combination
of linear and curvilinear. As used herein, the term "substantially
perpendicular"
refers to an orientation between two axes whereby the subtended angle formed
by
15 the two axes or an extension of the two axes is greater than 45°. In
the case of a
curvilinear element it may be more convenient to ux a linear axis which
represents
an average of the curvilinear element.
The rib-like elements allow the xcond region to undergo a substantially
"geometric deformation" which results in significantly less resistive forces
to an
Zo applied elongation than that exhibited by the "molecular-level deformation"
of the
first region. As used herein, the term "molecular-level deformation" refers to
deformation which occurs on a molecular level and is not discernible to the
normal
naked eye. That is, even though one may be able to discern the effect of a
molecular-level deformation, e.g., elongation of the SELF web, one is not able
to
is discern the deformation which allows or causes it to happen. This is in
contrast to
the term "geometric deformation". As used herein, the term "geometric
deformstioe" refers to deformations of the SELF web which are generally
discernible
to the normal naked eye when the SELF web or articles embodying the SELF web
are subjected to an applied elongation. Types of geometric deformation
include, but
3o are not limited to bending, unfolding, and rotating.
The SELF web preferably exhibiu at least two significantly different stages
of resistive force to an applied elongation along at least one axis when
subjected to
an applied elongation in a direction parallel to the axis. The SELF wcb
includes a
strainable network having at least two distinct regions. One of the regions is
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configured such that it will exhibit resistive forces in response to an
applied axial
elongation in a direction parallel to the axis before a substantial portion of
the other
region develops significant resistive forces to the applied elongation. At
least one of
the regions has a surface-pathlength which is greater than that of the other
region as
5 measured substantially parallel to the axis while the material is in an
untensioned
condition. The region exhibiting the longer surface-pathlength includes one or
more
rib-like elements which extend beyond the plane of the other region. The SELF
web
exhibits first resistive forces to the applied elongation until the elongation
of the web
is sufficient to cause a substantial portion of the region having the longer
surface-
io pathlength to enter the axis of applied elongation, (i.e., become
essentially coplanar
with the axis of applied elongation), whereupon the SELF web exhibits second
resistive forces to further elongation. The total resistive force to
elongation is higher
than the first resistive force to elongation provided by the first region.
Preferably, the firn region has a first surface-pathlength, L1, as measured
substantially parallel to the predetermined axis while the SELF web is in an
untensioned condition. The second region has a second surface-pathlength, L2,
as
measured substantially parallel to the predetermined axis while the SELF web
is in
an untensioned condition. The first surface-pathlength, L 1, is less than the
second
surface-pathlength, L2. The first region preferably has an elastic modulus E
1. The
2o first region has a cross-sectional area A1. The first region produces by
itself a
resistive force, P1, due to molecular-level deformation in response to an
applied
axial elongation, D. The second region produces a resistive force, P2, due to
geometric deformation in response to the applied axial elongation, D. The
second
region preferably has an elastic modulus E2, and a cross-sectional area A2.
The
resistive force, P1, is significantly greater than the resistive force, P2, so
long as
(L1+D) is less than L2.
Fr~eferably, while (Ll+D) is less than L2 the first region provides an initial
resistive force to the applied axial elongation, D, substantially satisfying
the equation
(A1 x E1 x D~L.1. When (L1+D) is greater than L2 the 5rst and second regions
3o provide a combined total resistive force, PT, to the applied axial
elongation, D,
satisfying the equation:
(A 1 x E 1 x Dl + ~~~42 x E2 x IL 1+D-L211
PT = L1 - L2
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6
In a preferred embodiment, the SELF web exhibits a Poisson lateral
contraction effect less than about 0.4 at 20% elongation as measured
perpendicular
to the axis of elongation. As used herein, the term "Poisson lateral
contraction
s effect" describes the lateral contraction behavior of a material which is
being
subjected to an applied elongation. Preferably, the SELF web exhibits a
Poisson
lateral contraction effect less than about 0.4 at 60% elongation as measured
perpendicular to the axis of elongation.
The surface-pathlength of the second region is at least about 15% greater
1o than that of the first region as measured parallel to the axis of
elongation while the
SELF web is in an untensioned condition. Preferably, the surface pathlength of
the
second region is at least about 30% greater than that of the first region as
measured
parallel to the axis of elongation while the SELF web is in an untensioned
condition.
Preferably, the absorbent article has an end edge in a 5rst waist region and
an
15 end edge in a second waist region. Preferably, one of the waist edges of
the
absorbent core is spaced from the adjacent end edge of the absorbent article
in the
first waist region by a distance A The other waist edge of the absorbent core
is
spaced from the adjacent end edge of the absorbent article in the second waist
region
by a distance of at least 2A
Zo
BRIEF DESCRIPTION OF THE DRAWINGS
While the specification concludes with claims particularly pointing out and
distinctly claiming the subject matter which is regarded as forming the
present
invention, it is believed that the invention will be betta understood from the
is following description which is taken in conjunction with the accompanying
drawings
' in which like designations are used to designate substantially identical
elements, and
in which:~ . .
Figure 1 is a plan view of a disposable diaper embodiment of the present
invention having portions cut-away to reveal underlying structure, the inner
surface
30 of the diaper facing the viewer,
Figure 2 is a sectional view of the disposable diaper shown in Figure 1 taken
along section line 2-2 of Figure 1;
Figure 3 is a plan view of an alternative diaper embodiment of the present
invention; -
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WO 95/14453 PCT/L'S94/1330~,
Figure 4 is a plan view of a further alternative diaper embodiment of the
present mvennon;
Figure 5 is a plan view illustration of a preferred embodiment of a SELF web
having a strainable network of the present invention with the deformations
facing
s toward the viewer;
Figure 5A is a segmented, perspective illustration of the SELF web of Figure
in an untensioned condition;
Figure SB is a segmented, perspective illustration of the SELF web of Figure
5 in a tensioned condition corresponding to stage I on the force-elongation
curve
to depicted in Figure 6;
Figure SC is a segmented perspective illustration of the SELF web of Figure
5 in a tensioned condition corresponding to stage II on the force-elongation
curve
depicted in Figure 6;
Figure 6 is a graph of the resistive force versus percent elongation comparing
~s the behavior of the SELF web of the present invention as shown in Figure 5,
with an
otherwise identical, planar, bax polymeric web material;
Figure 7 is a graph of the elastic hysteresis behavior of the SELF web of
Figure 6 when subjected to 60% elongation and examined for hysteresis
response;
Figure 8 is a simplified side elevational view of a preferred apparatus used
to
Zo form that portion of the SELF web of the present invention;
Figure 9 is a plan view of the oppoxd meshing plates of the apparatus of
Figure 8 laid side-by-side with their meshing surfaces exposed;
Figure 10 is a simplified side elevational view of a static press used to form
at
least a portion of the base film into a SELF web of the prexnt invention;
25 Figure 1 I is a simplified side elevational view of a continuous, dynamic
press
used to form predetermined portions of the bax 51m into a SELF web of the
present
Figure 12 is a simplified illustration of an apparatus uxd to form at least a
portion of s bax film into a SELF web of the prexnt invention;
3o Figure 13 is s simplified illustration of yet another apparatus used to
form at
least a portion of a base film into a SELF wsb of the present invention;
Figure 14 is a graph of the resistive force vs. percent elongation comparing
the
behavior of an alternative SELF web material which is a laminate comprised of
a
layer of a polymeric film, and a nonwoven layer secured by adhesive having a
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8
strainable network of the present invention to the otherwise identical
unformed,
planar, base web material;
Figure 15 is a graph of the elastic hysteresis behavior of the web material
having the strainable network of Figure 14 when subjected to 60°~o
percent elongation
s and examined for elastic hysteresis response; and
Figure 16 is a side view illustration of the torso of the body of a wearer.
DETAn ED DESCI'~~TION OF THE INVENTION
As used herein, the term "absorbent article" refers to devices which absorb
and
1o contain body exudates, and, more specifically, refers to devices which are
placed
against or in proximity to the body of the wearer to absorb and contain the
various
exudates discharged from the body. The term "disposable" is used herein to
describe
absorbent articles which are not intended to be laundered or otherwise
restored or
reused as an absorbent article (i.e., they arc intended to be discarded after
a single use
15 and, preferably, to be recycled, composted or otherwise disposed of in an
environmentally compatible manner). A "unitary" absorbent article refers to
absorbent articles which are formed of separate parts united together to form
a
coordinated entity so that they do not require separate manipulative parts
like a
separate holder and liner. A preferred embodiment of an absorbent article of
the
2o present invention is the unitary disposable absorbent article, diaper 20,
shown in
Figure 1. As used herein, the term "diaper" refers to an absorbent article
generally
worn by infanu and incontinent persons that is worn about the lower torso of
the
wearer. It should be understood, however, that the present invention is also
applicable to other absorbent articles such as incontinent briefs, training
pants,
2s feminine hygiene garments, and the Gke.
Figure 1 is s plan view of the diaper 20 of the present invention in its flat-
out,
uncontracted state (i.e., with elastic induced contraction pulled out) with
portions of
the structure being cut-away to more clearly show the construction of the
diaper 20
and with the portion of the diaper 20 which contacts the wearer, the inner
surface,
3o facing the viewer. As shown in Figure 1, the diaper 20 has a generally "T-
shape" and
comprises (a) a chassis assembly 22 preferably comprising: a liquid pervious
topsheet
Z4, a liquid impervious backsheet 26 joined with the topsheet 24, an absorbent
core
28 positioned between the topsheet 24 and the backsheet 26, and elasticized
leg cuffs
30; (b) an extensible waist belt 32; and (c) a closure system for fastening
the diaper
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9
on the wearer comprising a pair of tape tabs 34.
The diaper 20 is shown in Figure 1 to have an inner surface 36 (facing the
viewer in Figure I), an outer surface 38 opposed to the inner surface 36, a
first waist
region 40, a second waist region 42 opposed to the first waist region 40, and
a
s periphery which is defined by the outer edges of the diaper 20 in which the
longitudinal edges are designated 44 and the end edges are designated 46.
(While the
sitilled artisan wiU recognize that a diaper is usually described in terms of
having a
pair of waist regions and a crotch region between the waist regions; in this
application, for simplicity of terminology, the diaper 20 is described as
having only
1o waist regions, each of the waist regions including a portion of the diaper
which would
typically be designated as part of the crotch region). The inner surface 36 of
the
diaper 20 comprises that portion of the diaper 20 which is positioned adjacent
to the
wearers body during use (i.e., the inner surface 36 generally is formed by at
least a
portion of the topsheet 24 and other components joined to the topsheet 24).
The
15 outer surface 38 comprises that portion of the diaper 20 which is
positioned away
from the wearer's body (i.e., the outer surface 38 generally is formed by at
least a
portion of the backsheet 26 and other components joined to the backsheet 26).
The
first waist region 40 and the second waist region 42 txtend, respectively,
from the
end edges 46 of the periphery to the lateral centerline 48 of the diaper 20.
(The
20 lateral direction (x direction or width) is defined as the direction
parallel to the lateral
centerline 48 of the diaper 20; the longitudinal direction (y direction or
length) being
defined as the direction parallel to the longitudinal centerline 49; and the
axial
direction (Z direction or thickness) being defined as the direction extending
through
the thickness of the diaper 20.)
is Figure 1 shown a preferred embodiment of the chassis assembly 22 in which
the
topsheet 24 and the bscksheet 26 have length and width dimeruions generally
larger
than thost-of the absorbent core 28. The topsheet 24 and the backsheet 26
extend
beyond the edges of the absorbent core 28 to thereby form portions of the
periphery
of the diaper. The periphery defines the outer perimeter or, in other words,
the edges
30 of the diaper 20. The periphery comprises the longitudinal edges 44 and the
end
edges 46.
Figure 2 is a cross-sectional view of the diaper 20 taken along section lint 2-
2
of Figure 1 in the second waist region 42. Figure 2 shows the construction of
the
chassis assembly 22, the waist belt 32, anti the joining of the waist belt 32
with the
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10
chassis assembly 22. The chassis assembly 22 comprises the topsheet 24, the
backsheet 26, and the absorbent core 28 (generally shown in Figure 2). The
topsheet
24 and the backsheet 26 preferably extend longitudinally outwardly beyond the
waist
edge 59 of the absorbent core 28 to form an end flap 62; the lateral edge 60
of the
s chassis assembly 22 being formed at the distal edge 63 of the end flap 62 by
the edge
of the topsheet 24 and the backsheet 26. The waist bdt 32 is joined to the end
Bap
62 of the chassis assembly 22 adjacent the lateral edge 60. As shown in Figure
2, the
waist belt 32 is preferably directly joined to the backsheet 26 by a belt
attachment
element 50. The waist belt 32 is shown in Figure 2 to comprix a structural
elastic-
10 like film (SELF) web 52 (as described haeinaRer) preferably comprised of a
laminate
of two or more layers, in the embodiment shown in Figure 2 comprising three
layers:
an inner layer 53, an outer layer 55, and a support layer 54 betweat the inner
layer 53
and the outer layer 55. The inner lays 53 is the lays joined to the backsheec
26 by
the belt attachment element 50.
1s The chassis assembly 22 of the diaper 20 is shown in Figure 1 as comprising
the main body (chassis) of the diaper 20. The chassis assembly 22 comprises at
least
an absorbent core 28, preferably an outer covering lays comprising the
topsheet 24
and the backsheet 26, and more preferably elasticized leg cuffs 30. The
chassis
assembly 22 has a pair of leg edges 61 which typically form a portion of the
Zo longitudinal edges 44 of the diaper and a pair of lateral edges 60. In the
embodiment
shown in Figure 1, the extensible waist beh 32 is joirud to one of the lateral
edges
while the other lateral edge forms one of the end edges 46 of the diaper 20.
?has, the
chassis assanbly 22 comprises the main structure of the diaper with other
features
added to form the composite diaper structure. An exemplary example of s
chassis
~s a:sentbly of the prcsatt invention is described in U.S. Patent 3,860,003
issued to
Kenneth B. Budl on January 14, 1975.
The diaper 20 as shown in Figure 1, has a gateraliy "T-shape". The waist edge
59 of the absorbent core 28 in the fast waist region 40 is spaced from the
adjacent
3o end edge 46 of the diaper 20 in the fiat waist region by s distance A,
indicated as
110 in Figure 1. Preferably, the distance A is in the range of from about 1.5
centimeters to 8.0 centimeters, more preferably from about 1.5 centimeters to
5.0
centimeters, and most preferably is about 2.0 centimeters. The other waist
edge 59
of the absorbent core 28 in the second waist region 42 is spaced from the
adjacent
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end edge 46 of the diaper 20 in the second waist region by a distance
indicated as
112. Distance 112 is preferably at least 2A, more preferably at least 3 A, and
most
preferably is about 4A.
The distance 112, the distance between the waist edge 59 of the absorbent core
in the second waist region 42 and the adjacent end edge 46 of the diaper in
the
second waist region is not necessarily dependent upon or defined by the
dimension A,
(i.e,. the spacing of the waist edge of the absorbent core is the first waist
region from
the adjacent end edge of the diaper is the first waist region). The distance
112 is
preferably at least 6.0 centimeters, more preferably at least 7.0 centimeters,
and most
to preferably at least 8.0 centimeters. A particularly preferred embodiment of
a
disposable diaper 20 has a distance 112 of about 9.0 centimeters.
Referring now to Figure 1, the chassis 22 has a length 115 which extends
between the end edges 46 located in the first waist region 40 and the second
waist
region 42, respectively. The chassis 22 has a crotch width 117, which is
measured at
the narrowest portion of the chassis between the leg edges 61. The boundaries
of the
crotch width 117 and the crotch length 115 define the main panel of the
chassis. The
main panel of the chassis is that portion of the chassis which typically
contains a
substantial portion, and frequently, the entire absorbent core.
The absorbent core 28 may be any absorbent means which is capable of
2o absorbing and retaining liquids such as urine and other certain body
exudates. The
absorbent core 28 has a garment surface, a body surface, side edges 58, and
waist
edges 59. The absorbent core 28 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
z3 absorbent articles such as comminuted wood pulp which is generally referred
to as
airfdt. Examples of other suitable absorbent materials include creped
cellulose
wadding, ~meltbtown polymers including coform, cross-linked cellulose fibers,
tissue
including tissue wraps and tissue laminates, absorbent foams, absorbent
sponges,
superabsorbent polymers, absorbent gelling materials, or any equivalent
material or
3o combinations of materials. The cott>;guration and construction of the
absorbent core
may also be varied (e.g., the absorbent core may have varying caliper zones, a
hydrophilic gradient, a superabsortiertt gradient, or lower average density
and lower
average basis weight acquisition zones; or may comprise one or more layers or
structures). The total absorbent capacity of the absorbent core 28 should,
however,
CA 02263049 1999-02-23
WO 93/14433 PCTNS9i/13307
12
be compatible with the design loading and the intended ux of the diaper 20.
Further,
the sire and absorbent capacity of the absorbent core 28 may be varied to
accommodate wearers ranging from infants through adults. A preferred
embodiment
of the diaper has a rectangular-shape absorbent core.
s An absorbent swcture useful as the absorbent core 28 of the prexnt invention
that has achieved wide acceptance and commercial success is described in U.S.
Patent 4,610,678 entitled "High-Density Absorbent Strucnrra" issued to Weisman
and Goldman on September 9, 1986. U.S. Patent 4,673,402 entitled "Absorbent
Articles With Dual-Layered Cores" issued to Weisman, Houghton, and Geliert on
to June 16, 1987; U.S. Patent 4,888,231 ernitled "Absorbent Core Having A
Dusting
Layer" issued to Angstadt on Decanter 19, 1989; and U.S. Patent 4,834,735,
entitled "High Density Absorbent Mantas Having Lows Density and Lower Basis
Weight Acquisition Zones", issued to Alemany and Berg on May 30, 1989, also
describe absorbent structures that are useful in the praatt invention. The
absorbent
1s core 28 is preferably the dual-lays absorbent swcture described in U.S.
Patent
5,234,423 entitled "Absorbent Article With Elastic Waist Feature and Enhanced
Absorbency", issued to Alemany and Clear on August 10, 1993. -
The backsheet 26 is positioned adjacent the garment s<ufice of the absorbent
o core 28 and is preferably joined therrto by attschmern means (not shown)
such as
those will in the art. For example, the backsheet 26 may be xcured to the
absorbent core 28 by a uniform continuous lays 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. Fully Company of
St.
2s Paul, llZnnesota and marketed as HL-1258. The attachment means will
preferably
comprise an open pattern network of filaments of adhesive as is disclosed in
U.S.
Pateru 4;973,986 entitled "Disposable Waste-Containment Garment", which issued
to
Mmetola and Tucker on March 4, 1986.
An exemplary attachment means of an open pattern network of filaments
3o comprises severs! Gna of adhesive filama~ts swirled into a spiral pattern
such as is
illustrated by the apparatus and methods shown in U.S. Patent 3,911,173 issued
to
Sprague, Jr. on October 7, 1975; U.S. Patent 4,785,996 issued to Ziecka, et
al. on
November 22, 1978; and U.S. Patent 4,842,666 issued to Waenicz on June 27,
1989. Alternatively, the
CA 02263049 1999-03-09
' WO 95114453 PCT/US94/13307
13
attachment means may comprise 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.
The backsheet 26 is impervious to liquids (e.g., urine) and is preferably
s manufactured from a thin plastic film, although other flexible liquid
impervious
materials may also be used. As used herein, the term "flexible" refers to
materials
which are compliant and will readily conform to the general shape and contours
of
the human body. The backsheet 26 prevents the exudates absorbed and contained
in
the absorbent core 28 from wetting articles which contact the diaper 20 such
as
1o bedsheets and undergarments. The backsheet 26 may thus comprise a woven or
nonwoven material, polymeric films such as thermoplastic films of polyethylene
or
polypropylene, or composite materials such as a film-coated nonwoven material.
Preferably, the backsheet is a thermoplastic film having a thickness of from
about
0.012 mm (0.5 mil) to about 0.051 mm (2.0 mils).
15 The topsheet 24 is positioned adjacent the body surface of the absorbent
core
28 and is preferably joined thereto and to the backsheet 26 by attachment
means (not
shown) such as those well known in the art. Suitable attachment means are
described
with respect to joining the backsheet 26 to the absorbent core 28. As used
herein,
the term "joined" encompasses configurations whereby an element is directly
secured
Zo 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 an intermediate members) which in turn is axed to the
other
element. In a preferred embodiment of the present invention, the topsheet 24
and the
backsheet 26 are joined directly to each other in the diaper periphery and are
is indirectly joined together by directly joining them to the absorbent core
28 by the
attachment means (not shown).
The- topshett 24 is 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 may be
manufactured
3o from a wide range of materials, such as porous foams; reticulated foams;
apertured
plastic films; or woven or nonwoven webs of natural fibers (e.g., wood or
cotton
fibers), synthetic fibers (e.g., polyester or polypropylene fibers), or a
combination of
natural and synthetic fibers. Preferably, the topsheet 24 is made of a
hydrophobic
material to isolate the wearer's skin from liquids which have passed through
the
CA 02263049 1999-03-09
' WO 95/14x53
PCTNS9a~i33o ;
14
topsheet and are contained in the absorbent core 28 (i.e., to prevent rewet).
If the
topsheet is made of a hydrophobic material, at least the upper surface thereof
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
s rather than being drawn through the topsheet and being absorbed by the
absorbent
core. The topsheet can be rendered hydrophilic by treating it with a
surfactant.
Suitable methods for treating the topsheet with a surfactant include spraying
the
material with the surfactant and immersing the material in the surfactant. A
more
detailed discussion of such a treatment and hydrophilicity is contained in
U.S. Patent
1o 4,988,344 entitled "Absorbent Articles With Multiple Layer Absorbent
Layers"
issued to Reising, et al. on January 29, 1991.
There are a number of manufacturing technique which may be used to
manufacture the topsheet 24. For example, the topsheet Z4 may be a nonwoven
web
of fibers. When the topsheet comprises a nonwoven web, the web may be
1s spunbonded, carded, wet-laid, meltblown, hydroerttangled, combinations of
the
above, or the like. A preferred topaheet is carded and thetntally bonded by
means
well known to thox skilled in the fabrics art. A preferred topsheet comprixs
staple
length polypropylene fibers having a denier of about 2.2. As used herein, the
term
"staple length fibers" refers to thox fibers having a length of at least about
15.9 mm
Zo (0.625 inches). Preferably, the topsheet has a basis weight from about 18
to about 25
grams per square meter. A suitable topsheet is manufactured by Veratec, Inc.,
a
Division of International Paper Company, of Walpole, Massachuxtts under the
designation P-8.
The chassis assembly 22 preferably further comprises elasticized leg cuffs 30
2s for providing improved containment of liquids and other body exudates. Each
elasticized leg cuff 30 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 entitled "Contractible Side Portions For s Disposable Diaper" issued
to
3o 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 (gasketing cuff). U.S. Patent 4,909,803
entitled
"Disposable Absorbent Article Having Elasticized Flaps" issued to Aziz and
Blaney
on March 20, 1990, describes a disposable diaper having "stand-up" elasticized
flaps
CA 02263049 1999-02-23
WO 9SI14a53 PCT/US9.1/13311'
IS
(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, describes a disposable diaper having dual cuffs including a gasketing
cuff and a
barrier cuff. U.S. Patent 4,704,115 entitled "Disposable Waist Containment
s Garment" issued to BueU on November 3, 1987, discloses a disposable diaper
or
incontinent garment having side-edge-leakage-guard gutters configured to
contain
free Liquids within the garment.
While each elasticised leg cuff 30 may be configured so as to be similar to
any of the leg bands, side flaps, barrier arffs, or elastic cuffs described
above, it is
to preferred that each elasticised leg cuff 30 comprix the gasketing cuff such
as
d~~ ~ t7 S. Patent 3,860,003.
Each elasticized leg cuff 30 is shown in Fgtue 1 as comprising one elastic
element 31. In some embodiments it may be desirable to have each elasticized
kg
cuff 30 comprix a plurality of elastic elements 31. The elastic dements 31
extend
is beyond the waist edge 59 of the absorbent core 28 and into the extensible
waist belt
32. Pr;or to ux, the opposite innermost ones of the elastic elements 31
positioned on
opposite sides of the absorbent core are substamially linear and arc
substantially
parallel to one another throughout their length. Prior to use, the elastic
elements 31
are also aligned substantially parallel to both the side edges 58 of the
absorbent core
Zo 28 and to the leg edges 61 of the chassis assembly ZZ throughout their
length.
The dimension betwxn opposite imtamost ones of the elastic dements is
substantially uniform throughout their length prior to ux. The dimension
between
opposite innermost ones of the elastic dements is indicated a~ 105 in Fgure 1.
The
dimension betWre~ opposite innermost ones of elastic elameMS is measured
across
1s the absorbent core 28 parallel to the lateral centerline 48 of the diaper.
During use,
the extensible waist belt 32 attends or is extended in the lateral direction
as it is worn
by or poshlotKd onto the wearer. As the waist belt 32 extends in the lateral
direction
during use, the dimension between opposite innermost ones of the elastic
dements
positioned within the extensible waist belt incrcaxs, while the remaining
portion of
30 opposite innermost ones of the elastic dements rerrrains substantially
unchanged.
Therefore, during use, the dimension between opposite innermost ones of the
elastic
elements positioned within the extensible waist belt is grester than the
dimension
between the remaining portion of opposite innermost ones of the elastic
elements,
e.g., the portion of the elastic dements positioned adjacent the side edges of
the
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WO 95/14433 PCTNS9.f/1330'
l6
absorbent core.
The diaper 20 further comprises an extensible waist belt 32 that provides
improved fit and containment. The extensible waist belt 32 at least extends
laterally
outwardly from each leg edge 61 of the chassis assembly 22 and preferably
s longitudinally outwardly from one of the lueral edges of the chassis
assembly 22
Thus, in the embodiment shown in Figure 1, the extensible waist belt 32
comprises
that portion of the diaper at least attending from the lateral edge 60 of the
chassis
assembly 22 in the second waist region 42 to the end edge 46 of the diaper 20
and is
intended to be placed adjacxnt the wearer's waist. While a disposable diaper
of the
1o present invention can be constructed with an extensible waist bdt 32 joined
to each
lateral edge 60 of the chassis assembly 22, the discussion regarding the
extensible
waist belt 32 will focus on diaper having a single extensible waist belt bring
constructed according to the present invattion in order to form a "T-shaped'
diaper.
Further, while the waist belt or any of its constituent elanents can be
consutrcted as
is an extension of other elements of the diaper such as the baclcahat 26 or
the topsheet
24 or both (such as is shown in __ U.S. Pstent 3,860,003), the
waist belt 32 will be described with respect to a preferred embodiment in
which the
waist belt is a separate element joined to the chassis assembly 22.
The waist belt 32 provides an extensible feature that provides a more
2o comfortable and contouring fit by initially conformably fitting the diaper
to the
wearer and sustaining this fit throughout the time of wear well past when the
diaper
has been loaded with acudates since the aaensible waist belt allows the sides
of the
diaper to expand and contrsct without the use of additional elastic materials.
Further,
the octauible waist beh develops and maintains waning forces (tensions) that
Zs enhance the tensions developed and maintained by the closure system to
maintain the
diaper 20 on the wurer and that enhance the fit of the diaper about the waist
of the
wesrQ. -'Tfie actensible waist belt fiartha provides more effective
application of the
diaper 20 since even if the diaperer pulls one side (side panel) of the
actensible waist
beh farther than the other during appliation (asyrtunarically), the diaper 20
will
30 'self adjust' during wear. While the diaper 20 of the presau invention
preferably has
an actensible waist bdt 32 disposed in the second waist region 42;
alternatively, the
diaper 20 may be provided with an aaensible waist bdt disposed in the first
waist
region 40 or one disposed in both the first waist region 40 and the second
waist
region 42. -
CA 02263049 1999-02-23
w0 93114153 PCT/US94I13307
17
As shown in Figure 1, the waist belt 32 has a central waist pang 56 and a pair
of side panels 57, one being disposed on each side of the central waist panel
56 The
central waist panel 56 is that portion of the waist belt 32 between the leg
edges 61 of
the chassis assembly 22. Thus, the central waist panel 56 is coten~ninous or
s coextensive with the width of the chassis assembly Z2 at the lateral edge
60. The side
panels 57 extend laterally outwardly from the central waist panel 56 beyond
the leg
edges 61 of the chassis assanbly 22. In order to provide the 5t and
containment
bene5ts of the waist belt as discussed herein, a least the side panels 57 of
the waist
belt 32 must be extensible. In the preferred embodiment shown in Figure l, the
to central waist panel 56 as well as the side panels 57 are preferably
extensible to
provide a total waist feature which is conformable to the wearer to provide 6t
and
containment bene5ts.
The waist belt 32 may take on s numbs of diffaalt sizes, shapes and
configurations and may be constructed from a number of different materials.
For
13 example, the waist belt may be foamed from one or more separate members,
including portions of the chassis assembly 22, being joined together to form a
coordinated entity-, or, the waist beh 32; as shown in Figure l, may comprise
a single
piece of material. The waist belt may also have varying widths and lengths to
provide fit to different rangy of wearers or for cost or containment reasons.
Zo Further, the shape of the waist bdt may be varied considerably from having
complex
curves and angles to simply being rectangular in shape such as show" in Figure
1.
Examples of complex shapes useful fog the shape of the waist belt are
disclosed in
Canadian Patent Application No. 2,072,630.
IS
While the waist beh 32 may be constnrcted from a number of different
extensible materials as are known in the art, the waist belt, for performance
and cost
reasons, is preFaably constructed of a structural elastic~like film (SELF)
web. The
teen "web' heron refers to a sheet~like material comprising a single lays of
material
30 or a laminate of two or more layers.
1;gore 5 shows a pr~farcd embodiment of a SELF web 52 of the present
invention constructed of a single layer of a foamed polymeric material. The
SELF
web 52 is shown in its untensioned condition. The web has two centerlines, a
longitudinal centerline, I, and a transverse-or lateral centerline, t, which
is generally
CA 02263049 1999-03-09
WO 95/l~is53 pt_'T/US94/ 1330'
18
perpendicular to the longitudinal centerline. The web is preferably comprised
substantially of linear low density polyethylene (LLDPE) although it may also
be
comprised of other polyolefins such as polyethylenes including low density
polyethylene (LDPE), ultra low density polyethylene (ULDPE), high density
s polyethylene (I-~PE) or polypropylene and/or blends thereof of the above and
other
materials. Examples of other suitable polymeric materials include, but are not
limited to, polyester, polyurethanes, compostable or biodegradable polymers,
and
breathable polymers.
Referring to Figures 5 and 5A~ the SELF web includes a "strainable network"
to of distinct regions. As used herein, the term "strainable network" refers
to an
interconnected and interrelated group of regions which are able to be extended
to
some useful degree in a predetermined direction providing the SELF web with an
elastic-tike behavior in response to an applied and subsequently released
elongation.
The strainable network includes at least a first region 64 and a second region
66.
is The SELF web 52 includes a transitional region 65 which is at the interface
between
the fast region 64 and the second region 66. The transitional region 65 will
similarly
exhibit complex combinations of behavior of both the first region and the
second
region. It is recognized that every embodiment of the present invention will
have
transitional regions, however, the present invention is largely defined by the
behavior
Zo of the web material in the distinctive regions (e.g., first region 64 and
second region
66). Therefore, the ensuing description of the present invention will be
concerned
with the behavior of the web material in the first regions and the second
regions only
since it is not significantly dependent upon the complex behavior of the web
material
in the transitional regions 65.
Zs SELF web 52 has a first surface and an opposing second surface. In the
preferred embodiment shown in Figures 5 and 5A~ the strainable network
includes a
pluralityof first regions 64 and a plurality of second regions 66. The first
regions 64
have a first axis 68 and a second axis 69, wherein the first axis 68 is
preferably
longer than the second axis 69. The first axis 68 of the first region 64 is
substantially
3o parallel to the longitudinal axis of the SELF web 52 while the second axis
69 is
substantially parallel to the transverse axis of the SELF web 52. Preferably,
the
second axis of the first region, (i.e., the width of the first region), is
from about 0.01
inches to about 0.5 inches, and more preferably from about 0.03 inches to
about
0.25 inches. The second regions 66 baud-a first axis 70 and a second axis 71.
The
CA 02263049 1999-03-09
- WO 95/1dd53 PCTJL'S94/1330'
19
firn axis 70 is substantially parallel to the longitudinal axis of the SELF
web 52.
while the second axis 71 is substantially parallel to the transverse axis of
the SELF
web 52. Preferably, the second axis of the second region, (i.e.. the width of
the
second region), is from about 0.01 inches to about 2.0 inches, and more
preferably,
from about 0.125 inches to about 1.0 inches. In the preferred embodiment of
Figure
5, the first regions 64 and the second regions 66 are substantially linear,
extending
continuously in a direction substantially parallel to the longitudinal axis of
the SELF
web 52.
The first region 64 has an elastic modulus E 1 and a cross-sectional area A 1.
to The second region 66 has an elastic modulus E2 and a cross-sectional area
A2.
In the illustrated embodiment, a portion of the SELF web 52 has been
"formed" such that the SELF web 52 exhibits a resistive force along an axis,
which
in the case of the illustrated embodiment is substantially parallel to the
longitudinal
axis of the SELF web, when subjected to an applied axial elongation in a
direction
substantially parallel to the longitudinal axis. As used herein, the term
"formed"
refers to the creation of a desired structure or geometry upon the SELF web
that
will substantially retain the desired structure or geometry when it is not
subjected to
any externally applied elongations or forces. A SELF web of the present
invention is
comprised of at least a first region and a second region, wherein the first
region is
2o visually distinct from the second region. As used herein, the term
"visually distinct"
refers to featura of the SELF web material which are readily discernible to
the
normal naked eye when the SELF web material or objects embodying these SELF
web material are subjected to normal use. Preferably, the first region has a
"surface-
pathlength" less than that of the second region, as measured parallel to a
Z5 predetermined axis when the material is in an unttnsioned state. As used
herein, the
term "surface-pathlength' refers to a measurement along the topographic
surface of
the region in question in a direction parallel to an axis. The method for
determining
the surface-pathlength of the respective regions can be found in the Test
Methods
section set forth in subsequent portions of the present specification.
3o Methods for forming SELF web materials include, but are not limited to,
embossing by mating plates or rolls, thermoforming, high pressure hydraulic
forming, or casting. While the entire portion of the SELF web 52 has been
subjected
to a forming operation, the present invention may also be practiced by
subjecting to
formation only a portion thereof, e.g., a portion of a diaper backsheet.
CA 02263049 1999-03-09
WO 95/14453 PCT/US94/1330'
In the preferred embodiment shown in Figures 5 and SA, the first regions 64
are substantially planar. That is, the material within the first region 64 is
in
substantially the same condition before and after the formation step undergone
by
the SELF web 52. The second regions 66 include a plurality of raised rib-like
s elements 74. The rib-like elements 74 may be embossed, debossed or a
combination
thereof. The rib-like elements 74 have a first or major axis 76 which is
substantially
parallel to the transverse axis of the SELF web 52 and a second or minor axis
77
which is substantially parallel to the longitudinal axis of the SELF web 52.
The first
axis 76 of the rib-like elements 74 is at least equal to, and preferably
longer than the
second axis 77. Preferably, the ratio of lengths of the first axis 76 to the
second axis
77 is at least about 1:1, or greater, and more preferably at least about 2:1
or greater.
The rib-like elements 74 in the second region 66 may be separated from one
another by unformed areas, essentially unembossed or debossed, or simply
formed as
spacing areas. Preferably, the rib-like elements 74 are adjacent one another
and are
1s separated by an unformed area of less than 0.10 inches as measured
perpendicular to
the major axis 76 of the rib-Like element 74, and more preferably, the rib-
like element
74 are contiguous having no unformed areas between them.
The first region 64 and the second region 66 each have a "projected
pathlength". As used herein, the term "projected pathlength" refers to length
of a
20 shadow of a region that would be thrown by parallel light. The projected
pathlength
of the first region 64 and the projected pathlength of the second region 66
are equal
to one another.
The first region 64 has a surface-pathlength, L 1, less than the surfacc
pathlength, L2, of the second region 66 as measured topographically in a
direction
25 parallel to the longitudinal axis of the SELF web while the SELF web is in
an
ur>tensioned condition. Preferably, the surface-pathlength of the second
region 66 is
at least shout 15°/. greater than that of the first region 64, more
preferably at least
about 30% greater than that of the first region, and most preferably at least
about
70% greater than thu of the first region. In general, the greater the surface-
3o pathlength of the second region, the greater will be the elongation of the
SELF web
before encountering the force wall.
What makes the SELF web particularly well suited for use as the waist belt
32 is that it exhibits a modified "Poisson lateral contraction effect"
substantially less
than that of an otherwise identical unformed base web of similar material
CA 02263049 1999-03-09
WO 95/14453 PCTNS9i/1330''
21
composition. As used herein, the term "Poisson lateral contraction effect"
describes
the lateral contraction behavior of a material which is being subjected to an
applied
elongation. The method for determining the Poisson lateral contraction effect
of a
material can be found in the Test Methods stction set forth in subsequent
portions of
the present specification. Preferably, the Poisson lateral contraction effect
of the
SELF web of the present invention is less than about 0.4 when the SELF web is
subjected to about 20% elongation. Preferably, the SELF web exhibits a Poisson
lateral contraction effect less than about 0.4 when the SELF web is subjected
to
about 40, 50 or even 60% elongation. The Poisson lateral contraction effect of
the
to webs of the present invention is determined by the amount of the web
material which
is occupied by the first and second regions, respectively. As the area of the
SELF
web material occupied by the first region increases, the Poisson lateral
contraction
effect also increases. Conversely, as the arcs of the SELF web material
occupied by
the second region increases the Poisson lateral contraction effect decreases.
Preferably, the percent area of the SELF web material occupied by the first
region is
from about 2% to about 90%, and more preferably from about 5% to about 50%.
Web materials of the prior art which have at least one layer of ~an
elastomeric
material will generally have a large Poisson lateral contraction effect, i.e.,
they will
"neck down" as they elongate in response to an applied force. SELF web
materials
of the present invention can be designed to moderate if not substantially
eliminate
the Poisson lateral contraction effect.
For the SELF web 52, the direction of applied axial elongation, D, indicated
by arrows 80 in FIG. 5, is substantially perpendicular to the first axis 76 of
the
rib-like elements 74. The rib-like elements 74 are able to unbend or
geometrically
is deform in a direction substantially perpendicular to their first axis 76 to
allow
extension in the SELF web 52.
Ia Figure 6 there is shown a graph of the resistive force-elongation curve 720
of a formed polymeric SELF web of the present invention along with a curve 710
of
a base web material, i.e., not including first and second regions, of similar
material
3o composition. Specifically, the samples are polymeric web materials
comprised
substantially of linear low density polyethylene, approximately 0.001 inches
thick,
marketed under the designation Sample 1401 available from Clopsy Corporation
of
Cincinnati, Ohio. The method for generating the resistive force-elongation
curves
can be found in the Test Methods section set forth in subsequent portions of
the
CA 02263049 1999-03-09
WO 95/14453
PCT/US94/ 1330'
present specification. Referring now to the force-elongation curve 720, there
is an
initial substantially linear, lower force versus elongation stage I designated
720x. a
transition zone designated 720b which indicates the encounter of the force
wall, and
a substantially linear stage II designated 720c which displays substantially
higher
s force versus elongation behavior.
As seen in Figure 6, a SELF web having a strainable network exhibits
different elongation behavior in the two stages when subjected to an applied
elongation in a direction parallel to the longitudinal axis of the SELF web.
The
resistive force exerted by the SELF web to the applied elongation is
significantly less
to in stage I region (720a) versus the stage II region (720c) of curve 720.
Furthermore, the resistive force exerted by the SELF web to the applied
elongation
as depicted in stage I (720a) of curve 720 is significantly less than the
resistive force
exerted by the base web as depicted in curve 710 within the limits of
elongation of
stage I. As the SELF web is subjected to further applied elongation and enters
stage
is II (720c) the resistive force exerted by the SELF web increases and
approaches the
resistive force exerted by the base web. The resistive force to the applied
elongation
for the stage I region (720a) of the SELF web is provided by the molecular-
level
deformation of the first region of the SELF web and the geometric deformation
of
the second region of the SELF web. This is in contrast to the resistive force
to an
2o applied elongation that is provided by the base web, depicted in curve 710
of Figure
6, which results from molecular-level deformation of the entire web. Web
materials
of the present invention can be designed to yield virtually any resistive
force in stage
I which is less than that of the base web material by adjusting the percentage
of the
web surface which is comprised of the first and second regions, respectively.
The
25 force-elongation behavior of stage I can be controlled by adjusting the
width,
cross-sectional area, and the spacing of the fires region and the composition
of the
base web.- . _
Referring now to Figure SB, as the SELF web is subjected to an applied axial
elongation, D, indicated by arrows 80 in Figure 5, the first region 64 having
the
3o shorter surface-pathlength, L1, provides most of the initial resistive
force, P1, as a
result of molecular-level deformation, to the applied elongation which
corresponds
to stage I. While in stage I, the tib~like elements 74 in the second region 66
are
experiencing geometric deformation, or unbending; and offer minimal resistance
to
the applied elongation. In the transition gone (720b) between stages I and II,
the
CA 02263049 1999-03-09
WO 95114453 PCTNS94/1330'
23
rib-like elements 74 are becoming aligned with the applied elongation. That
is, the
second region is exhibiting a change from geometric deformation to molecular-
level
deformation. This is the onset of the force wall. In stage II, as seen in
Figure SC,
the rib-like elements 74 in the second region 66 have become substantially
aligned
s with the axis of applied elongation (i.e., the second region has reached its
limit of
geometric deformation) and begin to resist further elongation via molecular-
level
deformation. The second region 66 now contributes, as a result of molecular-
level
deformation, a second resistive force, P2, to further applied elongation. The
resistive forces to elongation depicted in stage II by both the molecular-
level
to deformation of the first region 64 and the molecular-level deformation of
the second
region 66 provide a total resistive force, PT, which is greater than the
resistive force
depicted in stage I which is provided by the molecular-level deformation of
the first
region 64 and the geometric deformation of the second region 66. Accordingly,
the
slope of the force-elongation curve in stage II is signi5cantly greater than
the slope
15 of the force-elongation curve in stage I.
The resistive force P I is substantially greater than the resistive force P2
when
(L1+D) is less than L2. While (LI+D) is less than L2 the &rst region 64
provides an
initial resistive force, P 1, generally satisfying the equation:
PI = (AI x E1 x Dl
LI
When (Ll+D) is greater than L2 the first and second regions provide a combined
total resistive force, PT, to the applied elongation D, generally satisfying
the
25 equation:
- ' pT = (A1 x EI x Dl + (A2 x E2 x 1L1+D-L2~
Ll
3o The maximum elongation occurring while in stage I is referred to as the
"available stretch" of the SELF web. The available stretch corresponds to the
distance over which the second region experiences geometric deformation. The
available stretch can be effectively determined by inspection of the force-
elongation
curve 720 as shown in FIG. 6. The approximate point at which there is an
inflection
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24
in the transition zone between stage I and stage II is the percent elongation
point of
"available stretch". The range of available stretch can be varied from about
10% to
100% or more; this range of elastic-like response is often found to be of
interest in
disposable absorbent articles, and cart be largely controlled by the extent to
which
s surface-pathlength L2 in the second region 66 exceeds surface-pathlength L 1
in the
first region 64 and the composition of the base film. The term "available
stretch" is
not intended to imply a limit to the elongation which the SELF web of the
present
invention may be subjected to as there are applications where elongation
beyond the
available stretch is desired.
1o The curves 730 and 735 in Figure 7 show the elastic hysteresis behavior
exhibited by the SELF web of the present invention which is generally similar
to the
SELF web used to generate curve 720 in Figure 6. The SELF web was examined for
elastic hysteresis behavior at an elongation of 60°/.. Curve 730
represents the
response to an applied and released elongation during the first cycle and
curve 735
15 represents the response to applied and released elongation during the
second cycle.
The force relaxation during the first cycle 731 and the percent set or
deformation 732
are depicted in Figure 7. Note that significant recoverable elongation, or
useful
elasticity, is exhibited at relatively low forces ova multiple rycles, i.e.,
the SELF web
can easily expand and contract to a considerable degree. The method for
generating
2o the elastic hysteresis behavior can be found in the Test Method section in
the
subsequent portion of the specification.
When the SELF web is subjected to an applied elongation, the SELF web
exhibits an elastic-like behavior as it extends in the direction of applied
elongation
and returns to its substantially untensioned condition once the applied
elongation is
2s removed, unless the SELF web is extended beyond the point of yielding. The
SELF
web is able to undergo multiple rycles of applied elongation without losing
its ability
to substantially recover. Accordingly, the SELF web is able to return to its
substantially untensioned condition once the applied elongation or force is
removed.
While the SELF web may be easily and reversibly attended in the direction of
3o applied axis! elongation, in a direction substantially pupmdicular to the
first axis of
the rib~like elements, the SELF web is not as easily extended in a direction
substantially parallel to the first axis of the rib-tike elements. The
formation of the
rib-like elements allows the rib-like elements to geometrically deform in a
direction
substantially perpendicular to the first or major axis of the rib~like
elements, while
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~S
requiring substantially molecular-level deformation to extend in a direction
substantially parallel to the first axis of the rib-like elements.
The amount of applied force required to extend the SELF web is dependent
upon the composition and cross-sectional area of the web material forming the
SELF
5 web and the width and spacing of the first regions, with narrower and more
widely
spaced first regions requiring lower applied extension forces to achieve the
desired
elongation. The firn axis, (i.e., the length) of the first regions is
preferably greater
than the second axis, (i.e., the width) of the first region with a preferred
length to
width ratio of from about 5:1 or greater.
1o The depth and frequency of rib~like elements can also be varied to control
the
available stretch of the SELF web. The available stretch is increased if for a
given
frequenry of rib-like elements, the height or degree of deformation imparted
on the
rib-like elements is increased. Similarly, the available stretch is increased
if for a
given height or degree of deformation, the frequenry of rib-like elements is
increased.
is While the entire SELF web includes a strainable network of first and second
regions, the present invention may also be practiced by providing specific
portions of
the SELF web with a strainable network comprised of first and second regions.
For
example, only the side panels 57 of the waist belt 32 need include the
discrete,
strainable networks. Thus, all or a portion of the extensible belt may include
a
2o strainable network comprised of first and second regions to provide an
extensible
waist belt exhibiting a controlled extensional response along a predetermined
axis
when subjected to an applied axial elongation.
The SELF web also need not be extensible only in the direction parallel to
the lateral centerline of the diaper as is shown in Figure 1. For example, the
i5 longitudinal axis and the transverse axis of the SELF web may be disposed
at an
angle to the longitudinal centerline and lateral centerline of the diaper 20,
respectively. Thus, the SELF web would axially elongate along a line at an
angle to
the lateral centerline of the diaper. This angle is preferably between about
0° and
about 30° for the diapers of the present invention. Further, portions
of the SELF
3o web may have different angles of extensibility. For example, in the side
panels, a
portion of the side panel closest to the end edge of the diaper, a waist
panel, may be
extensible in a direction parallel to the lateral centerline of the diaper,
however, the
portion of the SELF web closest to the lateral centerline, the thigh panel,
may have
an extensibility nonparallel to the direction of extensibility of the waist
panel such
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PCTlUS94~1330~
26
that it is disposed at an angle to the lateral centerline. This mufti-
directional SELF
panel can provide improved waist and leg conformity
Referring now to Figure 8, there is shown an apparatus 400 used to form the
SELF web 52 shown in Figure 5. Apparatus 400 includes plates 401, 402. Plates
401, 402 include a plurality of intermeshing teeth 403, 404, respectively.
Plates 401,
402 are brought together under pressure to form the base film 406.
Referring now to Figure 9, it can be seen that plates 401 and 402 each have a
longitudinal axis "I" and a transverse axis "Y which is substantially
perpendicular to
the longitudinal axis. Plate 401 includes toothed regions 407 and grooved
regions
l0 408 both which extend substantially parallel to the longitudinal axis of
the plate 401.
Within toothed regions 407 of plate 401 there are a plurality of teeth 403.
Plate 402
includes teeth 404 which mesh with teeth 403 of plate 401. When the base film
406
is formed between plates 401, 402 the portions of the base film 406 which are
positioned within grooved regions 408 of plate 401 and teeth 404 on plate 402
remain undefocmed. These regions correspond with the first regions 64 of the
SELF
web 52 shown in Figure 5. The portions of the base film 406 positioned between
toothed regions 407 of plate 401 and teeth 404 of plate 402 are incrementally
and
plastically formed creating rib-like elements 74 in the second regions 66 of
the SELF
web 52.
2o The method of formation can be accomplished in a static mode, where one
discrete portion of a base film is deformed at a time. An example of such a
method
is shown in Figure 10. A static press indicated generally as 415 includes an
axially
moveable plate or member 420 and a stationary plate 422. Plates 401 and 402
are
attached to members 420 and 422, respectively. While plates 401 and 402 are
is separated, base film 406 is introduced between the plates, 401, 402. The
plates are
then brought together under a pressure indicated generally as "P". The upper
plate
401 is then lifted axially away firom plate 402 allowing the formed polymeric
web to
be removed from between plates 401 and 402.
Figure 11 is an example of a dynamic press for intermittently contacting the
3o moving web and forming the base material 406 into a formed web similar to
the
SELF web 52 of Figure 5. Polymeric film 406 is fed between plates 401 and 402
in
a direction generally indicated by arrow 430. Plate 401 is secured to a pair
of
rotatably mounted arms 432, 434 which travel in a clockwise direction which
move
plate 401 in a similar clockwise motion. Paate 402 is connected to a pair of
rotary
CA 02263049 1999-02-23
WO 95/14453 PC?NS9,1/t330
27
arms 436, 438 which travel in a counter clockwise direction moving plate 402
in a
counter clockwise direction. Thus, as web 406 moves between plates 401 and 402
in direction indicated by arrow 430, a portion of the base film between the
plates is
formed and then released such that the plates 401 and 402 may come back grab
and
s deform another section of base film 406. This method has the benefit of
allowing
virtually army pattern of any complexity to be formed in a continuous process,
e.g.,
uni-directional, bi-directional, and multi-directiorul patterns.
The dynamic press of Figure 11 could be used on a completed absorbent
article to form strainable networks into the completed product. For example,
the
to entire or portions of the completed absorbent article could be placed
between plates
401 and 402 to create a strainable network in all layers of the absorbcm
article.
Another method of forming the base material into a SELF web is vacuum
forming. An example of a vacuum forming method is disclosed in commonly
assigned U.S. Pat. No. 4,342,314, issued to Radd et al, on August 3, 1982.
is Alternativdy, the SELF web of the present im~attion may be hydraulically
formed in
accordance with the teachings of commonly assigned U.S. Pat. No. 4,609,518
issued
to Curro et al. on Septanba 2, 1986.
In Figurc 12 there is shown another apparatus gateraUy indicated as 500 for
2o forming the bsse 51m into a formed SELF web. Apparatus 500 includes a pair
of
rolls 502, 504. Roll 502 includes a plurality of toothed regions 506 and a
plurality of
grooved regions 508 that extend substantially paralld to a longitudinal axis
running
through the cents of the cylindrical roll 502. Toothed regions 506 include a
plurality
of teeth 507. Roll 504 includes a plurafrty of teeth 510 which mesh with teeth
507 on
is roll 502. A: a bane film is passed betwan intamahirtg rolls 502 and 504,
the
grooved regions 508 will leave portions of the 51m undeformed producing the
first
regions of-the SELF web 52 of Figure 5. The portions of the film passing
between
toothed regions 506 and teeth 510 will be formed by teeth 507 and 510,
respectively,
produang rib-like danatt: in the second regions of tl~ SELF web 52.
Ahernatively, roll 504 may consist of a soft rubber. As the base film is
passed
between toothed roll 502 artd rubber roll 504 the film is mechanically formed
into the
pattern provided by the toothed roll 502. The 51m within the grooved regions
508
will remain undeformed, while the film within the toothed regions 506 will be
formed
producing rib-like elements in the second regions.
CA 02263049 1999-02-23
wo ~is4s3 PcrNS9.sn33o~
28
Referring now to Figure 13, there is shown an alternative apparatus generally
indicated as 550 for forming the base 51m into a SELF web in accordance with
the
teachings of the present invention. Appal 550 includes a pair of rolls 552,
554
Rolls 552 and 554 each have a plurality of toothed regions 556 and grooved
regions
5 558 extending about the circumference of rolls 552, 554 respectively. As the
base
film passes betweat rolls 552 and 554, the grooved regions 558 will leave
portions of
the 51m unformed, while the poctioro of the film passing betrree:a toothed
regions
556 will be formed producing rib-Gke elements in second regions 66.
Web material of the present invention may be comprised of polyolefuts such as
to polyethylenes, including liner low density polyethylene (LLDPE), low
density
polyethylene (LDPE), ultra low density polyethylene (LJLDPE), high density
polyethylene (I~PE), or polypropylene and blends thereof with the above and
other
materials. Exempla of other suitable polymeric msterials which may also be
used
include, but are not limited to, polyester, polyurethane, compoatable or
13 biodegradable polymers, heat shrink polymer, thermoplauic elascomen,
metallocene
catalyst-based polymers (e.&. INSITE~ available 5~om Dow Chemical Company and
E30tACT~ available from E~oton~ and brrathabk polymer. The web materials may
also be comprised of a synthetic woven, synthetic knit, nonwoven, apertured
filcr~
macroscopically expanded three-dimensional formed filet, absorbent or fibrous
Zo absorbent material, foam 811ed composition or laminates and/or combinations
thereof.
The nonwovens may be made but not limited to arty of the following methods:
spunlace, spunbond, meltblown, carded and/or air-through or cslender bonded,
with
s spurdace muerial with loosely bonded 5ber being the preferred embodiment.
While the SELF web has beers descn'bed as a single base lays of substantially
P~ Po~~a 51m, the presatt invention may be practiced equally well with other
base materials or with laminate of materials. Example: of base materials from
which
the SELF ~ .web of the present invention can be made inchtde two-dimensional
apatiued filets and maaoscopicsUy expanded, three-dimensional, apertured
formed
f>>m:. Examples of macroscopically expanded, throo-dimatsional, apertured
formed
3o films are described in U.S. Patem 3,929,135 issued to Thompson on December
30,
1975; U.S. Patent 4,324,246 issued to Mullarte, et al. on April 13, 1982; U.S.
Patent
4,342,314 issued to Radel, et al. on August 3, 1982; U.S. Patent 4,463,045
issued to
Ahr, et al. on July 31, 1984; and U.S. Patent 5,006,394 issued to Baud on
April 9,
1991. Fxamples of other
CA 02263049 1999-03-09
w0 95i1a453 PC1YUS94i1330
~9
suitable base materials include composite structures or laminates of polymer
films.
nonwovens, and polymer films and nonwovens. The laminates of polymer films and
nonwovens may also comprise absorbent or fibrous absorbent materials, foams,
or
other compositions. Additional reinforcing elements can also be added for
strength
s and recovery benefits.
Base materials comprising terminates of apertured films and nonwoven materials
may also be used whereby in the process of forming such materials, the
connections
between a plurality of the nonwoven fibers are broken up to protrude slightly
through
the apertures of the apertured film.
to It may be desirable in certain embodiments to have the SELF web exhibit a
certain degree of bulkiness. Laminates of polymer films with high-loft
nonwoven
materials, and laminates with mufti-layers of nonwovens are ways of providing
increased bulk. Other methods for creating bulk include the formation of a
single
layer of polymer film in the manner of this invention followed by
prestretching of the
15 film and subsequent application of the nonwoven to one or both sides while
the
polymer film is in its prestretched condition. Upon relaxation of the stretch,
the
nonwoven material forms puckers which give the material added bulk. Another
method for making bulky laminates is by forming individual polymeric film
layers in
the manner of this invention, followed by lamination of multiple layers of
these
Zo materials. Three dimensionally apertured films that have been formed using
the
method described herein also provide good bulk in a laminate structure.
Other materials which may be subject to the deformation processes disclosed
herein for producing webs which exhibit an elastic-like behavior in the
direction of
applied force include polymeric foams and thermally bonded air-laid fibrous
25 structures.
Figure 14 shows the force elongation behavior for both a base web depicted by
corn 830.and a formed SELF web depicted by the curve 840 where both webs are
comprised of a laminate of a layer of the Clopay 1401 polyethylene blend film
adhered via hot melt glue available from F'mdley Adhesives, of Wauwautosa,
3o Wisconsin, Sample 2301, to a layer of nonwoven material made substantially
of
polypropylene fibers as is available from Veratec of Walpole, Massachusetts,
under
the designation P-11. Referring now to curve 840, there is as initial
substantially
linear, lower force-elongation stage I designated 840a, a transition zone
designated
840b, and substantially linear stage II designated 840c. For this laminate
web, note
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PCTNS94/13307
the distinctive lows force two-stage behavior of the formed SELF web provided
in
first stage I (840a) by the combination of molecular-level deformation of the
first
region and geometric deformation of the second region and then in stage II
(840c) by
molecular-level deformation of both the 5rst region and a second region as
depicted
s in curve 840 compared to the molecular level deformation of the bax web as
depicted in curve 830. The curvy 850 and 855 in Figure 15 show the elastic
hysteresis behavior of a formed web material similar to the formed web
material used
to generate curve 840 in Figure 14 examined at 60~/, elongation. Curve 850
reprexnts the response to an applied and released elongation during the 5rst
cycle
to and curve 855 represents the response to applied and rdesxd elongation
during the
second cycle. The force relaxation during the fast cycle 851 and the percart
set of
the web aRa the &rst cycle 852 are shown in Figure 15. Note that this laminste
web
exhibits a very signi5cant elastic recovery over the observed range of
elongation over
multiple cycles.
1s In a preferred embodiment of the praau imrention, as is shown in Figure 2,
the SELF web comprises a laminate of three layers comprising an inner layer
53, an
outer lsyer 55, and a support Isyc 54. The inner layer 53 is preferably a
nonwoven
material such as the P-8 material previously dexn'bed. The outer layer 55 is
preferably the bax polymeric 5!m as described herein with rrFera~ce to Figure
5.
Zo The support layer 54 is preferably a formed Slm such as the DR.I-WEAVE
material as
marketed by The Procter ~ Gamble Company of Cincinnati, Ohio. Alternatively,
the
support layer may be eliminated to provide a lower cost two layer laminae of a
nonwoven and the bax poiymaic film. Further, a nomwoven layer may be added
over the outer lays to provide a :otter fed for the outside of the waist belt.
The
Zs laminate may be combined by any of a number of bonding methods known to
thox
skilled in the art Such bonding methods include but are not limited to thermal
bonding; adhesive bonding (using any of a number of adhesives including but
not
limited to spay adhesives, hot melt adhesives, Istac based adhesives and the
like):
sonic bonding; and extrusion laminuing whereby a polynKric 81m is cast
directly
30 onto a nonwoven substrate, and while still in a partially mohen state,
bonds to one
side of the norrwoven or whore a mdtblown nonwoven is directly attached to a
polymeric web.
The waist beh 32 is joined to the chassis assembly 22 by a belt attachment
element 50. The belt attachment element 50 may comprix any of the known
CA 02263049 1999-02-23
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31
attachment meant as are discussed herein including adhesive, heat bonds,
pressure
bonds, ultrasonic bonds dynamic mechanical bonds or combinations of these.
Preferably, the belt attachment element is an adhesive, preferably an open
pattern
network of adhesive filaments as described herein. The waist belt 32 is
preferably
s directly joined to the chassis assembly 22 with the inner layer 53 being
directly joined
to the backsheet 26. Alternatively, the waist belt 32 may be joined between
the
topsheet 24 and the backsheet 26, between other dements of the diaper 20, or
directly to other dements of the diaper including, for example, directly
joining the
outer layer 55 to the topsheet 24.
~o The diaper 20 is also preferably provided with a closure system for 5tting
the
diaper on the wearer. While the closure system may take on a number of
configurations such as adhesive tape tabs, etechanical closure tape tabs,
fixed position
fasteners, or any other closure means as are laiown in the art; as shown in
Figure 1,
the closure system preferably comprises an adhesive tape tab fastening system
~s including a pair of tape tabs 34 and s landing zone (not shown) positioned
in the 5rst
waist region 40 of the chassis assembly 22. Examples of suitable adhesive tape
tab
fastening systems are disclosed in U.S. Patent 3,848,594 issued to Budl on
November 19, 1974; and U.S. Patent 4,662,875 issued to I~rrotsu and Robertson
on
May 5, 1987, _ Examples of other
Zo closure systems, including mechanical closure systems, useful in the
present
invention, are disclosed in U.S. Patent 4,869,724 issued to Scripps on
September 26,
1989; U.S. Puatt 4,848,815 issued to Scripps on July 11, 1989; and the two-
point
fastening systatr described in U.S. Patent 5,242,436 iss<red to Well, Buell,
Clear, and
Falcons on September 7, 1993, - --
Zs The diaper 20 is preferably applied to a wearer by positioning one of the
waist
regions, preferably the sxond waist region 42, under the wearer's back and
drswing
the ranaender of the diaper between the warers legs so that the other waist
region,
preferably the first waist region 40, is positioned across the front of the
wearer. The
tab portions of the tape tabs 34 are then released from the release portion.
The
3o diaperer then wraps the extensible waist belt 32 around the wears, while
still
grasping the tab portion. The extensible waist belt 32 wiU typically be
attended and
tensioned during this operation so as to conform to the size and shape of the
wearer.
The ups tab 34 is secured to the landing zone on the chassis assembly 22 to
effect a
side closure. The process is then repeated with the other tape tab. Thus, the
diaper
CA 02263049 1999-02-23
WO 95114453 PC?fUS94I1330.
32
is closed on the wearer and the waist belt 32 comprised of the SELF web
provides
the fit and containment benefits as described herein.
Alternatively, the waist belt may be provided with a closure system that
allows
the side panels to be first joined together. The diaperer then brings the
chassis
s assembly between the legs of the wearer and joins the chassis assembly to
the outer
lays of the waist belt. Such s configuration and securing method is more fully
described in Canadian Patent Application No. 2,072,630.
For comparison purposes, a numbs of different commercially available large
io disposable diaper products designated Samples A-F and a large diaper
product of the
present invention designated Sample X were measured. The data from thex
measurements is xt forth in the following tables:
TABLE I
is
_. .-,
Diaper Area at Area at AtaorbmtRatio d At>sorbd~t
~ Core (es=) Core Arn
(em~ to Cbasus
Area
Sam 1e X 909 341 0.376:L0
Sinn 1e A IZ89 570 0.44:1.0
Sato k 8 1316 576 0.438:1.0
k C 1313 707 0.538:1.0
D IZ60 565 . 0.448:1.0
E 1266 559 0.442:1.0
E 1131 635 0.514:1.0
. ,_
Referring to Table I, the commercially available products tested were all
designated for ux on large infants on their respective ptckages. Sample X
product is
intended to be used on large infants. The chania area of the diapers was
determined
2o by first freezing and then removing the dastic elements from each of the
diapers. The
absorbent core was then removed from each of the diapers. Each diaper was then
placed in its flat out condition on a piece of paper having a known area and
basis
weight. The perimeter of the diaper chassis was then traced onto the paper.
The
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33
paper was then cut along the traced line. The cut out piece of paper was then
weighed. The area of the chassis was then calculated based on the known area
and
basis weight of the piece of paper prior to being cut. A similar procedure was
then
used to calculate the area of the absorbent core.
s As can be seen from the data in Table I, the Sample X diaper of the present
invention has the smallest ratio of absorbent core area to chassis area of the
samples
tested. Other embodiments of disposable diapers of the present invention
preferabiy
have a ratio of absorbent core area to chassis area of less than about
0.40:1.0, more
preferably less than about 0.39:1.0; and most preferably less than about
0.38:1Ø
1o One disposable diaper embodiment has a ratio of absorbent core area to
chassis area
of about 0.3 8:1Ø
Referring again to Table I, it will be noted that the Sample X diaper of the
present invention has an absorbent core area and chassis area substantially
less than
the other commercially available diapers tested. Because of the unique design
of the
1s diaper of the present invention, the absorbent core of the diaper of the
present
invention is able to cover a substantial amount of the wearer's crotch area
while using
significantly less chassis material and absorbent core material.
Referring now to Figure 16, a side view illustration of a wearer's torso of a
wearer is shown, generally indicated as 120. The torso 120 is shown with the
body in
zo an upright or standing position. The wearer or torso has an upright axis
122. The
upright axis 122 of the wearer extends through the torso in a direction
substantially
perpendicular to a surface upon which the wearer is standing, e.g., the floor
or
ground. The pubic bone is indicated as 124. Plane 126, which defines the
uppermost
end of the crotch, extends from the pubic bone 124 through the torso in a
direction
2s perpendicular to the upright axis 122.
For comparison purposes the area of the crotch covered by the absorbent core
of a Sample X diaper of the present invention and the Sample D diaper were
measured. The Sample D diaper was chosen for comparison from the commercially
available diapers in Table I, as it represents a typical commercially
available diaper as
3o can be seen from the data in Table I. The data from the measurcmenu is set
forth in
the following table:
CA 02263049 1999-03-09
WO 95Ji~i453
PC?/US94/1330
34
TAR1 F TT
Wei~bt of BabyCrotch Area CoveredCrotch Area Covered
(Ibs) by by
Absorbent Core of Absorbent Corc of
Sample X the
Dia r cmI Sam Ie D Dia r (cm2)
2I.5 137.12
Ls7.15
23.s 140.47
160.13
2s.5 147.6
16x.96
27. s l 33.77 ! 76.22
29.5 164.75
179.70
31.5 162.8?
183.17
33.5 167.77 191.38
3s.s lal.as
110.10
Referring to Table II, the crotch area covered was determined using an
empirical computer model. The inputs into the model are the geometry and
material
s properties of the diaper, and a population of babies which includes their
weight and
shape. The model then places the diaper onto the population of babies and
measures
various parameters such as the crotch area covered by the absorbent core.
While a
computer model was used to generate the data in Table II, the data may also be
generated by manually measuring the crotch area covered by the absorbent core.
As
to can be seen from the data in table Table II, the amount of crotch area
covered by the
Sample X diaper is less than the crotch area covered by the Sample D diaper.
The Sample X diaper of the present irrvention covers less crotch area than the
commercially available diaper, but as can be seen from the data in Table I,
the Sample
X diaper has an absorbent core area which is substantially less than the
absorbent
is core areas of the diapers tested. The efficiencies of the of Sample X
diaper and the
commercially available diapers, represented by the Sample D diaper, is set
forth in the
following table:
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TABLE III
Wei~bt of BabyRatio of C Covered Ratio of Crotcb
pbs) by Absorbent Core Area Covered
to Area of by Absorbent Core
Absorbent Core of to Area of
Sampk X Absorbent Core of
Dia r the
Sam (e D Dia r
21.5 0.40:1.0 0.28: I .0
23.5 0.41:1.0 0.28: I .0
25.5 0.43:1.0 0.30:1.0
27.5 0.45:1.0 0.31: I .0
29.5 0.48:1.0 0.31:1.0
31.5 0.48:1.
0.32: l .0
33.5 0.49:1.0 0.34: l .0
35.5 0.53: I .0 0.37: l .0
Referring now to Table III, it will be noted that the ratios of the wearer's
5 crotch area covered by the absorbent core to the area of the absorbent core
of the
Sample X diaper are greater than the ratios of the commercially available
diaper.
Diapers of the present invention preferably have a ratio of the wearer's
crotch area
covered by the absorbent core of at least 0.40:1Ø
1o TAHLE IV
Diaper Masjmam Widtb Ma:;mum WidthRatio of Widths
of of Chassis is
Chassis is Firstis Waist Re~ioos
Waist Saoad Waist
Deoa (cm) em
a X ! 80 314 I .8: I
(e A 334 334 1: I
Sam !e 341 311 I :1
B
Sam (e 340 340 I :1
C
(e D 333 335 (:l
Sam (e 335 335 1:l
E
Samvie 333 - 333 I : I
F
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36
Referring now to Table IV, it will be noted that the Sample X diaper has the
largest ratio of width of chassis in first waist region to width of chassis in
second
waist region of the samples tested. Other embodiments of the disposable
diapers of
the present invention preferably have a ratio of width of chassis in first
waist region
to width of chassis in second waist region of at least 1.3:1, more preferably
of at least
1.5:1, and most preferably of at least 1.7:1.
TABLE V
Diaper Len~tb of ChassisArea of CbassitRatio of Len~tb
(cm) ) of
Cba:sie to Area
of
Cbaseia cmlcm=
Sam 46.0 909 0.506:1.0
1e
X
Sam 47.5 IZ89 0.369:1.0
1e
A
Sam 49.0 1316 0.3'TZ:1.0
!e
H
Sam 49.3 1313 0.376:1.0
1e
C
Sam 50.0 1260 0.397:1.0
1e
D
Sam 49.8 1266 0.393:1.0
1e
E
Szcn 49.5 1234 0.401:1.0
1e
F
Referring now to Table V, it will be noted that the Sample X diaper has the
largest ratio of length of chassis to area of chassis of the samples tested.
Other
embodiment of disposable diapers of the present invention preferably have a
ratio of
15 length of chassis to area of chassis of at least 0.45:1.0 (cm/cm2), more
preferably of
at least 0.48:1.0 (cm/cm2), and most preferably of at least 0.50:1.0 (cm/cm2).
One
. ..
disposable diaper embodiment of the present invention has a ratio of length of
chassis
to area of chassis of about 0.51:1.0 (cmlcm2).
Figure 3 shows an alternative embodiment of the present invention wherein the
2o waist belt 332 is formed from separate materials joined together. In this
embodiment,
the side panels 357 are each a separate material, preferably the SELF web 52
as
described herein, joined adjacent to the leg edge 61 of the chassis assembly
22. The
central waist panel 356 is formed by a portion of the chassis assembly 22, in
this
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37
embodiment the end flap 62 formed by the extension of the topsheet 24 and the
backsheet 26 beyond the waist edge 59 of the absorbent core 28. Thus, in this
embodiment , the central waist panel 356 is not extensible but the side panels
357 are
since they arc conswcted of the SELF web 52.
s Figure 4 shows a further alternative embodiment of the present invention
wherein the waist belt 432 is formed from a continuous SELF web and a portion
of
the chassis assembly 22. In this embodiment, the SELF web 52 extends across
the
entire diaper in the second waist region 42. The chassis assembly 22 is joined
to the
SELF web 52 in the central waist panel 456. While the cer~tra! waist panel 456
may
to be nonextensible since the components of the chassis assembly Z2 are
nonextensible,
in the preferred embodiment as shown in Figure 4, the central waist panel 456
is
subjected to mechanical straining to allow the central waist panel 456 to have
some
degree of extensibility or to the SELF processes as described herein such that
the
waist belt 432 is entirely a SELF web. This extensibility is shown by the
dashed Lines
13 in Figure 4. The Lateral edge 60 of the chassis assembly Z2 in the first
waist region 40
is also provided with an elasticized waistband 462 by opauivdy associating an
elastic member 464 with the chassis assembly Z2, preferably with eithbr the
topsheet
24, the backsheet 26, or both more preferably betwan the topsheet 24 and the
backsheet 26. Examples of such elasticized waistbands arc dixlosed in U.S.
Patent
Zo 5,151,092 issued to Buell, Clear and Falcone on September 29, 1992; or in
U.S.
Patent 4,515,595 issued to Kievit and Osterhage on May 7, 1985;
Alternatively, the lateral edge of the chassis
assembly in the 5rst waist region may also comprise a SELF web as described
herein.
In an attanative embodiment of the present inva~tion, the diaper may also be
is provided with ear Saps thu extend laterally outwardly from each leg edge of
the
chassis assembly in the 5rst waist region. The ear Saps provide a structure to
which
the waist belt can be attached to encircle the legs and waist of the wearer.
The ear
Saps may take on a number of different sizes, shapes, con5gurations, and
materials.
The ear flaps may comprise a portion of the material making up one or more of
the
3o diaper dements, including the topsheet, and the backslteet. Alterztatively,
the ear
flaps may comprise a separate dement or a plurality of dements axed to the
diaper.
Suitable materials for use as the ear flaps include woven webs; nonwoven webs;
films, including polymeric films; foams; laminate materials including film
laminates,
nonwoven laminates, or zero main laminates; dastomers; composites; SELF webs;
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38
or any combination of these materials. The ear flaps may be joined to the
chassis
assembly by any means as are known in the art; for example, the ear flaps may
be
continuously or intermittently bonded to the chassis assembly using heated or
unheated adhesive, heat bonding, pressure bonding, ultrasonic bonding, dynamic
5 mechanical bonding or any other method that is known in the art.
Test Methods
Surface-Pathlength
Pathlength measurements of formed material regions are to be determined by
to selecting and preparing representative samples of each distinct region and
analysing
these samples by means of microscopic image analysis methods.
Samples are to be selected so as to be representative of each region's surface
geometry. Generally, the transition regions should be avoided since they would
normally contain features of both the first and second regions. The sample to
be
15 measured is cut and separated from the region of interest. The "measured
edge" is to
be cut parallel to a specified axis of elongation. Usually this axis is
parallel to the
formed primary-axis of either the first region or the second region. ' An
unstrained
sample length of one-half inch is to be "gage marked" perpendicular to the
"measure
edge": while attached to the web material, and then accurately cut and removed
from
2o the material region.
Measurement samples are then mounted onto the long-edge of a microscopic
glass slide. The "measured edge" is to extend slightly (approximately 1 mm)
outward
from the slide edge. A thin layer of pressure-sensitive adhesive is applied to
the glass
face-edge to provide a suitable sample support means. for highly formed sample
15 regions it has been found desirable to gently extend the sample in its
axial direction
(without imposing significant force) simultaneously to contact and attachment
of the
sample to . the slide-edge. This allows improved edge identification during
image
analysis and avoids possible "crumpled" edge portions that require additional
interpretation analysis.
3o Images of each sample are to be obtained as "measured edge" views taken
with
the support slide "edge on" using suitable microscopic measuring means of
sufficient
quality and magni5cation. Data herein presented was obtained using the
following
equipment; Keyence VH-6100 (20x Lens) video unit, with video-image prints made
with a Sony Video printer Mavigraph unit. Video prints were image-scanned with
a
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39
Hewlett Packard ScanJet IIP scanner. Image analysis was on a Macintosh IICi
computer utilizing the soRware NIH MAC Image version 1 45.
Using this equipment, a calibration image initially taken of a grid scale
length
of .500" with .005" increment-marks to be used for calibration setting of the
s computer image analysis program. All samples to be measured are then video
imaged and video-image printed. Next, all video-prints are image-scanned at
100 dpi
(256-level gray scale) into a suitable Mac image-file format. Finally, each
image-file
(including calibration file) is analyzed utilizing Mac Image 1.45 computer
program.
All samples are measured with freehand line-measurement tool selected. Samples
are
to measured on both side-edges and the lengths recorded. Simple film-like
(thin &
constant thickness) samples require only one end-edge to be measured. Laminate
and
thick foam samples are measured on both side-edges. Length measurement
tracings
are to be made along the full gage length of a cut sample. In cases of highly
deformed samples, multiple (partially overlapping) images may be required to
cover
15 the entire cut sample. In these cases, select characteristic features
common to both
overlapping-images are utilized as "markers" to permit image length readings
to
adjoin but not overlap.
The final determination of pathlength for each region is obtained by averaging
the lengths of five (5) separate 1l2" gage-samples of each region. Each gage-
sample
zo "pathlength" is to be the average of both side-edge surface pathlengths.
Poisson's Lateral Contraction Effect
The Poisson's lateral contraction effect is measured on an Instron Mode! 1122,
as available from Instron Corporation of Canton, Massachusetts, which is
interfaced
25 to a Gateway 2000 486/33Hz computer available from Gateway 2000 of N. Sioux
City, South Dakota, using Test WorksT~" software which is available from
Sintech,
Inc. of Research Triangle Park, North Carolina. All essential parameters
needed for
testing are input in the TestWorksTw software for each test. Data collection
is
accomplished through a combination of manual sample width measurements, and
3o elongation measurements made within TestWorksTw.
The samples used for this test are I" wide x 4" long with the long axis of the
sample cut parallel to the direction of the first region of the sample. The
sample
should be cut with a sharp knife or suitably sharp cutting device designed to
cut a
precise 1" wide sample. It is important that a "representative sample" should
be cut
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so that an area representative of the symmetry of the overall pattern of the
deformed
region is represented. There will be cases (due to variations in either the
size of the
deformed portion or the relative geometries of the first and second regions)
in which
it will be necessary to cut either larger or smaller samples than is suggested
herein. In
s this case, it is very important to note (along with any data reported) the
size of the
sample, which area of the deformed region it was taken from and preferably
include a
schematic of the representative area used for the sample. In general, an
"aspect ratio"
of (2:1 ) for the actual extended tensile portion (l l :w l ) is to be
maintained if possible
Five samples are tested.
The grips of the Instron consist of air actuated grips designed to concentrate
the entire gripping force along a single line perpendicular to the direction
of testing
elongation having one flat surface and an opposing face from which protrudes a
half
round. No slippage should be permitted between the sample and the grips. The
distance between the lines of gripping force should be 2" as measured by a
steel rule
~s held beside the grips. This distance will be referred to from here on as
the "gage
length".
The sample is mounted in the grips with its long axis perpendicular to the
direction of applied elongation. An area representative of the overall pattern
geometry should be symmetrically centered between the grips. The crosshead
speed
is set to 10 in/min. The crosshead is moved to the specified strain
(measurements are
made at both 20 and 60~/o elongation). The width of the sample at its
narrowest
point (w2) is measured to be the nearest 0.02" using a steel rule. The
elongation in
the direction of applied extension is recorded to the nearest 0.02" on the
TestWorks
software. The Poisson's Lateral Contraction Effect (PLCE) is calculated using
the
Zs following formula:
. . PLCE = I w - w
w1
I 12-I 1
30 l1
where w2 = The width of the sample under an applied longitudinal
elongation
w 1 = The original width of the sample
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41
12 = The length of the sample under an applied longitudinal
elongation
11 = The original length of the sample (gage length)
Measurements are made at both 20 and 60% elongation using five different
samples for each given elongation. The PLCE at a given percent elongation is
the
average of five measurements.
Hysteresis Test
1o The hysteresis test is used for measuring the percent set and percent force
relaxation of a material. The tests are performed on an Instron Model 1122,
available
from Instron Corporation of Canton, Mass. which is interfaced to a Gateway
2000
486/33Hz computer available from Gateway 2000 of N. Sioux City, South Dakota
57049, using TestWorksTw sol~ware which is available from Sintech, Inc. of
is Research Triangle Park, North Carolina 27709. All essential parameters
netded for
testing are input in the TestWorksT~ software for each tat (i.e., Crosshead
Speed,
Maximum percent elongation Point and Hold Times). Also, all data collection,
data
analysis and graphing are done using the TestWorks'~~ software.
The samples used for this test are 1" wide x 4" long with the long axis of the
2o sample cut parallel to the direction of maximum extensibility of the
sample. The
sample should be cut with a sharp exacto knife or some suitably sharp cutting
device
design to cut a precise 1" wide sample. (If there is more than one direction
of
extensibility of the material, samples should be taken parallel to each
direction of
stretch.) The sample should be cut so that an area representative of the
symmetry of
23 the overall pattern of the deformed region is represented. There will be
cases (due to
vtuiat;ons in either the size of the deformed portion or the relative
geometries of the
first and second regions) in which it will be necessary to cut either larger
or smaller
samples than is suggested herein. In this case, it is very important to note
(along
with arty data reported) the size of the sample, which area of the deformed
region it
3o was taken from and preferably include a schematic of the representative
area used for
the sample. Three separate tests at 20, 60 and 100% strain are typically
measured
for each material. Three samples of a given material are tested at each
percent
elongation.
The grips of the Instron consist ofair actuated grips designed to concentrate
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47
the entire gripping force along a single line perpendicular to the direction
of testing
stress having one flat surface and an opposing face from which protrudes a
half
round to minimize slippage of the sample. The distance between the lines of
gripping
force should be 2" as measured by a steel rule held beside the grips. This
distance
s will be referred to from hereon as the "gage length". The sample is mounted
in the
grips with its long axis perpendicular to the direction of applied percent
elongation.
The crosshead speed is set to 10 inlmin. The crosshead moves to the specified
maximum percent elongation and holds the sample at this percent elongation for
30
seconds. After the thirty seconds the crosshead returns to its original
position (0%
to elongation) and remains in this position for 60 seconds. The crosshead then
returns
to the same maximum percent elongation as was used in the first cycle, holds
for
thirty seconds and then again returns to zero.
A graph of two cycla is generated. A representative graph is shown in Fig.
7. The percent force relaxation is determined by the following calculation of
the
is force data from the first rycle:
Force at Max. % elongation - Force a_R~ 30 sec hold x 100 = % Force Relaxation
Force at Maximum % elongation (cycle 1 )
2o The percent set is the percent elongation of the sample of the second rycle
where the
sample starts to resist the elongation. The percent set and the percent force
relaxation are shown graphically also in Figs. 7 and 15. The average percent
force
relaxation and percent set for three samples is reported for each maximum
percent
elongation value tested.
~s
Tensile Test
The. tensile test is used for measuring force versus percent elongation
properties and percent available stretch of a material. The tests are
performed on an
Instron Model 1 I22, available from Instron Corporation of Canton, Mass. which
is
3o interfaced to a Gateway 2000 486I33Hz computer available from Gateway 2000
of
N. Sioux City, South Dakota , using TestWorksT'"~ software which is.available
from
Sintech, Inc. of Research Triangle Park, North Carolina. All essential
parameters
needed for testing are input in the TestWorksT"~ software for each test. Also,
all
data collection, data analysis and graphing are done using the TestWorksT'"~
CA 02263049 1999-03-09
w0 95n4a53 PCTitls9ai133o-
43
software.
The samples used for this test are 1" wide x 4" long with the long axis of the
sample cut parallel to the direction of maximum extensibility of the sample
The
sample should be cut with a sharp exacto knife or some suitably sharp cutting
device
s designed to cut a precise 1" wide sample. (If there is more than one
direction of
extensibility of the material, samples should be taken parallel to each ). The
sample
should be cut so that an area representative of the symmetry of the overall
pattern of
the deformed region is represented. There will be cases (due to variations in
either
the size of the deformed portion or the relative geometries of the first and
second
to regions) in which it will be necessary to cut either larger or smaller
samples than is
suggested herein. In this case, it is very important to note (along with any
data
reported) the size of the sample, which area of the deformed region it was
taken from
and preferably include a schematic of the representative area used for the
sample.
Three samples of a given material are tested.
is The grips of the Instron consist of air actuated grips designed to
concentrate
the entire gripping force along a single line perpendicular to the direction
of testing
stress having one flat surface and an opposing face from which protrudes a
half
round to minimize slippage of the sample. The distance between the Lines of
gripping
force should be 2" as measured by a steel rule held beside the grips. This
distance
Zo will be referred to from hereon as the "gage length°. The sample is
mounted in the
grips with its long axis perpendicular to the direction of applied percent
elongation.
The crosshead speed is set to 10 in/min. The crosshead elongates the sample
until
the sample breaks at which point the crosshead stops and returns to its
original
position (0 % elongation).
is The percent available stretch is the point at which there is an inflection
in the
force-elongation curve, beyond which point there is a rapid increase in the
amount of
force required to elongate the sample further. The average of the percent
available
stretch for three samples is recorded.
While the Test Methods described above are usable for many of the web
3o materials of the present invention, it is recognized that the Test Methods
may have to
be modified to accommodate some of the more complex SELF web materials within
the scope of the present invention.
While particular embodiments of the present invention have been illustrated
and described, it would be obvious to those skilled in the art that various
other
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44
changes and modifications can be made without departing from the spirit and
scope
of the invention. It is therefore intended to cover in the appended claims all
such
changes and modifications that are within the scope of this invention:
5
