Note: Descriptions are shown in the official language in which they were submitted.
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1
ABSORBENT ARTICLES FOR INFANTS
FIELD OF THE INVENTION
The present invention relates generally to absorbency systems, and
o more particularly, to absorbency systems which improve wearer comfort and
skin health by substantially reducing coverage and occlusion of the wearer's
skin by the absorbency system.
BACKGROUND OF THE INVENTION
Infants and other incontinent individuals wear absorbency systems
such as disposable absorbent articles to receive and contain urine and
other body exudates. Disposable absorbent articles function both to contain
the discharged materials and to isolate these materials from the body of the
wearer and from the wearer's garments and bed clothing.
While previously known disposable absorbent articles do perform their
intended function, each conventional design suffers from certain
deficiencies in one or more of absorbency of body fluids, protection of the
wearer's garments from soiling, the wearer's comfort, and the wearer's skin
health.
A typical disposable absorbent article comprises an absorbent
element interposed between a fluid pervious body contacting element and a
fluid impervious protective barrier. The absorbent element (sometimes
called an absorbent core) is intended to receive and contain urine and other
body exudates. The body contacting element (sometimes called a topsheet)
is intended to provide comfortable contact with body surfaces while allowing
free passage of fluids therethrough into the absorbent element. The
protective barrier (sometimes called a backsheet) is intended to prevent
urine and other body exudates from striking through the disposable
absorbent article and soiling the wearer's garments.
Although the protective barrier or backsheet is highly effective in
preventing strike through and thus helps contain the liquid within the
disposable absorbent article, it occludes the wearer's skin making the
. disposable absorbent article uncomfortable to wear which may lead to
certain skin health problems. To further aggravate this problem, prior art
disposable absorbent articles are relatively large in relation to the size of
the wearer they are intended to fit. Such designs were thought to be
CA 02216447 2001-03-14
2
desirable because consumers showed a preference for larger disposable
absorbent articles in view of their reduced tendency to leak. While larger
disposable absorbent articles may have a reduced tendency to leak, thereby
protecting the wearer's garments and bed clothing from soiling, they also
negatively impact the wearer's comfort and skin health by covering and
occluding more of the wearer's skin. Occlusion of the wearer's skin by the
protective barrier or backsheet traps urine and other bodily fluids against
the wearer's skin. Moisture trapped against the skin causes the skin to
become hydrated, thereby compromising the skin's health. Excess
hydration of the skin may lead to irritation, rashes, and other related skin
health problems.
Therefore, it is an aspect ~ ~e present invention to provide a
disposable absorbent article which provides improved wearer comfort.
It is further an aspect of the present invention to provide a disposable
. absorbent article which provides improved skin health for the wearer.
It is further an aspect of the present invention to provide a disposable
absorbent article which substantially reduces the amount of the wearer's
skin which is covered and occluded by the disposable diaper.
These and other 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.
SUMMARY OF THE INVENTION
The present invention provides unitary disposable absorbent articles,
such as disposable diapers, and the like, that have a unique design
improving the wearer's comfort and skin health. Such absorbent articles
comprise an outer covering, preferably comprising a liquid pervious
topst~et and s liquid impervious backsheet, an 'absorbent core positioned
within the outer covering, and a closure system joined to the outer covering
for fastening the absort~ent article on a wearer. The absorbent core has an
absorbent core area and the absorbent article has an absorbent article
area.
The present invention also provides unitary closed sided disposable
absorbent garments, such as training pants, that have a unique design
improving the wearer's comfort and skin health. Such absorbent garments
have a pair of leg openings and a waist opening. The absorbent garments
comprise an outer covering and en absorbent core positioned within the
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outer covering. The absorbent core has an absorbent core area and the
absorbent garment has an absorbent garment area.
The absorbent articles of the present invention, preferably have a
relatively low fit index. The fit index of the absorbent article directly
corresponds to the comfort and skin health of the wearer. The "fit index", as
. used herein, refers to the relationship of the size of the absorbent article
to
the size of the wearer. The fit index is determined by dividing the absorbent
article area by the largest wearer rise dimension that the absorbent article
is
intended to fit. The largest wearer dimension for an absorbent article
relates to the rise dimension, Y, of the largest wearer, or the maximum rise
dimension that the absorbent article is intended to fit wherein the absorbent
article is designed to fit an infant having a rise dimension from about X, the
rise dimension of the smallest wearer that the diaper is intended to fit, to
about Y.
A lower fit index is preferred as less of the wearer's skin is covered
and occluded by the absorbent article, thereby improving the comfort and
skin health of the wearer. Conversely, a higher fit index is less preferred as
more of the wearer's skin is covered and occluded by the absorbent article
making the absorbent article less comfortable to wear by subjecting the
wearer's skin to potentially unhealthy conditions.
Absorbent articles of the present invention, preferably have a fit index
of less than or equal to about 240, more preferably less than or equal to
about 238, and most preferably less than or equal to about 236.
Absorbent articles of the present invention also preferably have a
relatively low absorbency index. The "absorbency index", as used herein,
refers to the relationship of the size of the absorbent core to the size of
the
wearer. The absorbency index is determined by dividing the absorbent core
area by the largest wearer rise dimension, Y, that the absorbent article is
intended to fit. A lower absorbency index is preferred as less absorbent
core material is used making the absorbent article more comfortable to
wear. Conversely, a higher absorbency index is less preferred as more
absorbent material is used making the absorbent article less comfortable to
wear.
Absorbent articles of the present invention preferably have an
absorbency index of less than or equal to about 95, more preferably less
than or equal to about 90, and most preferably less than or equal to about
85.
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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 better
understood.
from the 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 of the diaper facing the viewer;
Figure 2 is a sectional view of the disposable diaper shown in Figure
9 taken along section line 2-2 of Figure 1;
Figure 3 is a plan view of an alternative diaper embodiment of the
present invention;
Figure 4 is a plan view of a further alternative diaper embodiment of
the present invention;
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 toward the viewer;
Figure 5A is a segmented, perspective illustration of the SELF web
of Figure 5 in an untensioned condition;
Figure 5B 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 depicted in Figure 6;
Figure 5C 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 the behavior of the SELF web of the present invention as shown
in Figure 5, with an otherwise identical, planar, base 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 form that portion of the SELF web of the present
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invention;
Figure 9 is a plan view of the opposed meshing plates of the
apparatus of Figure 8 laid side-by-side with their meshing surtaces
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 present
invention;
Figure 11 is a simplified side elevational view of a continuous,
dynamic press used to form predetermined portions of the base film into a
SELF web of the present invention;
Figure 12 is a simplified illustration of an apparatus used to form at
least a portion of a base film into a SELF web of the present invention;
Figure 13 is a simplified illustration of yet another apparatus used to
form at least a portion of a base film into a SELF web of the present
invention;
Figure 14 is a graph of the resistive force versus percent elongation
comparing the behavior of an alternative SELF web material which is a
laminate comprised of a layer of a polymeric ~Im, and a nonwoven layer
secured by adhesive having a 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%
percent elongation and examined for elastic hysteresis response; and
Figure 16 is a perspective view of a training pant embodiment of the
present invention.
DETAILED DESCRIPTION OF THE INVENTION
As used herein, the term "absorbent article" refers to devices which
absorb and 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
inteniied to be laundered or otherwise restored or reused as an absorbent
article (i.e., they are intended to be discarded after a single use and,
preferably, to be recycled, composted or otherwise disposed of in an
environmentally compatible manner). A "unitary" absorbent article refers to
absorbent articles which are formed of separate parts united together to
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6
form a coordinated entity so that they do not require separate manipulative
parts like a separate holder and liner, a separate belt and pad, or a pant
and pad. ~ A preferred embodiment of an absorbent article of the 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 infants and incontinent persons that is worn about the '
lower torso of the wearer. It should be understood, however, that the
present invention is also applicable to other absorbent articles such as
incontinent briefs, training pants, feminine hygiene garments, and the like.
Figure 1 is a 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, 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: an outer covering, an absorbent
core 28 positioned within the outer covering, and elasticized leg cuffs 30;
(b)
an extensible waist belt 32; and (c) a closure system for fastening the diaper
on the wearer comprising a pair of tape tabs 34. Preferably, the outer
covering comprises a liquid pervious topsheet 24 and a liquid impervious
backsheet 26 joined with the topsheet 24.
The diaper 20 is shown in Figure 1 to have an inner surface 36 (facing
the viewer in Figure 1 ), 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 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 skilled artisan will 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 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 wearer's body during use (i.e., the inner surtace 36 generally
is formed by at least a portion of the topsheet 24 and other components '
joined to the topsheet 24). The outer surtace 38 comprises that portion of
the diaper 20 which is positioned away from the wearer's body (i.e., the
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7
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 extend, respectively, from the end edges
~ 46 of the periphery to the lateral centerline 48 of the diaper 20. (The
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.)
Figure 1 shows a preferred embodiment of the chassis assembly 22 in
which the topsheet 24 and the backsheet 26 have length and width
dimensions generally larger than those 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 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
- line 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, and the joining of
the waist belt 32 with the 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 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 belt 32 is joined
to the end flap 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 comprise a structural elastic-like film (SELF) web 52 (as
described hereinafter) 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 positioned between
~ the inner layer 53 and the outer layer 55. The inner layer 53 is the layer
joined to the backsheet 26 by the belt attachment element 50.
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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
layer 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 forth a portion of the longitudinal edges 44 of the diaper
and a pair of lateral edges 60. In the embodiment shown in Figure 1, the
extensible waist belt 32 is joined to one of the lateral edges while the other
lateral edge forms one of the end edges 46 of the diaper 20. Thus, the
chassis assembly 22 comprises the main structure of the diaper with other
features added to form the composite diaper structure. An exemplary
example of a chassis assembly of the present invention is described in U.S.
Patent 3,860,003 issued to Kenneth 8. Buell on January 14, 1975.
The absorbent core 28 may be any absorbent means which is capable
of absorbing and retaining liquids such as urine and other certain body
exudatss. 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
absorbent articles such as comminuted wood pulp which is generally
referred to as airfelt. Examples of other suitable absorbent materials
include creped cellulose wadding, meltblown polymers including coform,
aoss-linked cellulose fibers, tissue including tissue wraps and tissue
laminates, absorbent foams, absorbent sponges, superabsorbent polymers,
absorbent gelling materials, or any equivalent rtiaterial or combinations of
materials. The configuration and construction of the absorbent core may
also bs varied (e.g., the absorbent core may have varying caliper zones, a
hydrophilic gradient, a superabsorbent gradient, or tower 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
con 28 should, however, be compatible with the design loading and the
intended use of the diaper 20. Further, the size and absorbent capacity of
the absorbent core 28 may be varied to acxommodate wearers ranging from
infants through adults. A preferred embodiment of the diaper has a
rectangular-shape absorbent core.
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9
An absorbent structure useful as the absorbent core 28 of the present
invention that has achieved wide acceptance and commercial success is
described in U.S. Patent 4,610,678 entitled "High-Density Absorbent
Structures" 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 Gellert on June 16, 1987; U.S. Patent
4,888,231 entitled "Absorbent Core Having A Dusting Layer' issued to
Angstadt on December 19, 1989; and U.S. Patent 4,834,735, entitled "High
Density Absorbent Members Having Lower 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 present invention. The
absorbent core 28 is preferably the dual-layer absorbent structure desuibed
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 badcsheet 26 is positioned adjacent the garment surface of the
absorbent core 28 and is preferably joined thereto by attachment means
(not shown) such as those well known in the art. For example, the
badcsheet 26 may be secured to the absorbent core 28 by a uniform
continuous layer of adhesive, a patterned layer of adhesive, or an array of
separate lines, spirals, or spots of adhesive. Adhesives which have been
found to be satisfactory are manufactured by H. 8. Fuller Company of St.
Paul, Minnesota and marketed ss HL-1258. The attachment means will
preferably comprise an open pattern network of filaments of adhesive as is
disclosed in U.S. Patent 4,573,986 entitled "Disposable Waste-Containment
Garment", which issued to Minetola and Tucker on March 4, 1986,
An exemplary attachment means
of an open pattern network of filaments comprises several lines of adhesive
filaments swirled into s 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 Ziedcer, et al. on
November 22, 1978; and U.S. Patent 4,842,666 issued to Werenicz on June
27, 1989. . .
Alternatively, the 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
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known in the art.
The backsheet 26 is impervious to liquids (e.g., urine) and is
preferably 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 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).
The backsheet 26 may permit vapors to escape from the absorbent core
while still preventing exudates from passing through the backsheet.
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 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 affixed 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 indirectly joined together by directly
joining them to the absorbent core 28 by the attachment means (not shown).
The topsheet 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 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
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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 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 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 techniques which may be used
to manufacture the topsheet 24. For example, the topsheet 24 may be a
nonwoven web of fibers. When the topsheet comprises a nonwoven web,
the web may be spunbonded, carded, wet-laid, meltblown, hydroentangled,
combinations of the above, or the like. A preferred topsheet is carded and
thermally bonded by means well known to those skilled in the fabrics art. A
preferred topsheet comprises staple length polypropylene fibers having a
denier of about 2.2. As used herein, the term "staple length fibers" refers to
those fibers having a length of at least about 15.9 mm (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, Massachusetts
under the designation P-8.
The chassis assembly 22 preferably further comprises elasticized leg
cuffs 30 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 a Disposable Diaper" issued to Buell on
~ January 14, 1975, describes a disposable diaper which provides a
contractible leg opening having a side flap and one or more elastic
members to provide an elasticized leg cuff (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
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12
diaper having "stand-up" elasticized flaps (barrier cuffs) to improve the
containment of the leg regions. U.S. Patent 4,695,278 entitled "Absorbent
Article Having Dual Cuffs" issued to Lawson on September 22, 1987,
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 Garment" issued to 8uell 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 elasticized 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 preferred that
each
elasticized leg cuff 30 comprise the gasketing cuff such as described in the
above-referenced U.S. Patent 3,860,003.
Each elasticized leg cuff 30 is shown in Figure 1 as comprising one
elastic element 31. In some embodiments it may be desirable to have each
elasticized leg cuff 30 comprise a plurality of elastic elements 31. The
elastic elements 31 extend beyond the waist edge 59 of the absorbent core
28 and into the extensible waist belt 32. Prior to use, the opposite
innemnost ones of the elastic elements 31 positioned on opposite sides of
the absorbent core are substantially linear and aro 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 28 and to the leg edges 61 of the chassis assembly 22
throughout their length.
The dimension between opposite innermost ones of the elastic
elements is substantially uniform throughout their length prior to use. The
dimension between opposite innermost ones of the elastic elements is
indicated as 105 in Figure 1. The dimension between opposite innermost
ones of elastic elements is measured aaosa the absorbent core 28 parallel
to the lateral centerline 48 of the diaper. During use, the extensible waist
belt 32 extends or is extended in the lateral direction as it is wom by or
positioned onto the wearer. As the waist belt 32 extends in the lateral
direction during use, the dimension between opposite innermost ones of the
elastic elements positioned within the extensible waist belt increases, while
the remaining portion of opposite innermost ones of the elastic elements
remains substantially unchanged. Therefore, during use, the dimension
between opposite innermost ones of the elastic elements positioned within
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13
the extensible waist belt is greater than the dimension between the
remaining portion of opposite innermost ones of the elastic elements, e.g.,
the portion of the elastic elements positioned adjacent the side edges of the
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 longitudinally outwardly from one of the lateral 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
extending 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 intendert to be
placed adjacent the wearer's waist. While a disposable diaper of the
present invention can be constructed with an extensible waist belt 32 joined
to each lateral edge 60 of the chassis assembly 22, the discussion
regarding the extensible waist belt 32 will focus on diapers having a single
extensible waist belt being constructed according to the present invention in
order to form a 'T-shaped" diaper. Further, while the waist belt or any of its
constituent elements can be constructed as an extension of other elements
of the diaper such as the backsheet 26 or the topsheet 24 or both (such as
is shown in the above-referenced U.S. Patent 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
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 exudates since the extensible waist belt
allows the sides of the diaper to expand and contract without the use of
additional elastic materials. Further, the extensible waist belt develops and
maintains wearing forces (tensions) that enhance the tensions developed
and maintained by the closure system to maintain the diaper 20 on the
wearer and that enhance the fit of the diaper about the waist of the wearer.
- The extensible waist belt further provides more effective application of the
diaper 20 since even if the diaperer pulls one side (side panel) of the
extensible waist belt farther than the other during application
(asymmetrically), the diaper 20 will "self-adjust" during wear. While the
diaper 20 of the present invention preferably has an extensible waist belt 32
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14
disposed in the second waist region 42; alternatively, the diaper 20 may be
provided with an extensible waist belt disposed in the first waist region 40
or
one disposed in both the first waist region 40 and the second waist region
42.
As shown in Figure 1, the waist belt 32 has a central waist panel 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 coterminous or coextensive with the width of the chassis
assembly 22 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 assembly 22. In order to provide the fit and containment benefits of
the waist belt as discussed herein, at least the side panels 57 of the waist
belt 32 must be extensible. In the preferred embodiment shown in Figure 1,
the 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 fit and containment benefits.
The waist belt 32 may take on a number of different sizes, shapes
and configurations and may be constructed from a number of different
materials. For example, the waist belt may be formed from one or more
separate members, inGuding portions of the chassis assembly 22, being
joined together to form a coordinated entity; or, the waist belt 32, as shown
in Figure 1, may comprise a single piece of material. The waist belt may
also have varying widths and lengths to provide fit to different ranges of
wearers or for cost or containment reasons. Further, the shape of the waist
belt may bs varied considerably from having coriplex curves and angles to
simply being redangulsr in shape such as shown in Figure 1. Examples of
complex shapes useful for the shape of the waist belt are disclosed in
Canadian Patent Application No. 2,072,630 filed December 7, 1990
While the waist belt 32 may be constructed from a number of
different extensible materials as are known in the art, the waist belt, for
performance and cost reasons, is preferably constructed of a structural
elastic-like film (SELF) web. The term 'liveb" herein refers to a sheet-like
material comprising a single layer of material or a laminate of two or more
layers.
CA 02216447 1997-09-23
WO 96132083 PCT/US96/04022
Figure 5 shows a preferred embodiment bf a SELF web 52 of the
present invention constructed of a single layer of a formed 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 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 polyethylene
(HDPE) 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" 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-like 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. The SELF web
52 includes a transitional region 65 which is at the interface between the
first 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 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 th_e complex behavior of the
web material in the transitional regions 65.
SELF web 52 has a first surtace and an opposing second surface.
In the preferred embodiment shown in Figures 5 and 5A, the strainable
network includes a plurality of 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 parallel to the
longitudinal
CA 02216447 1997-09-23
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16
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 have a first axis 70 and a secand axis 71.
The first 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 SELI= web 52.
The first region 64 has an elastic modulus E1 and a cross-sectional
area A1. 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 visually distinct from the second region. As used
herein, the term "visually distinct" refers to features 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 "sun'ace-
pathlength" less than that of the second region, as measured parallel to a
predetermined axis when the material is in an untensioned 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
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17
portions of the present specification.
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
po~:on of a diaper backsheet.
In the preferred embodiment shown in Figures 5 and 5A, 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 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 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 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, L1, less than the
surface-pathlength, L2, of the second region 66 as measured
- topographically in a direction parallel to the longitudinal axis of the SELF
web while the SELF web is in an untensioned condition. Preferably, the
surface-pathlength of the second region 66 is at least about 15% greater
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18
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 that of the first region. tn general, the greater the surface-pathiength
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 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 section set forth in subsequent portions of the
present specification. Preferably, the Poisson lateral contractian 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 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 area 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 (aver of an
elastomeric material will generally have a large Poisson lateral cantraction
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 deform in a direction substantially perpendicular to
their first axis 76 to allow extension in the SELF web 52.
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19
In 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 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 Clopay 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
present specification. Referring now to the force-elongation curve 720,
there is an initial substantially linear, lower force versus elongation stage
I
designated 720a, 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 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 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 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 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 1 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 force-elongation behavior of stage I can be
controlled by adjusting the width, cross-sectional area, and the spacing of
CA 02216447 1997-09-23
WO 96/32083 PCT/LT~96/04022
the first region and the composition of the base web.
Referring now to Figure 5B, 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 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 rib-
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 zone (720b) between stages I and II, the 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 5C, the rib-like elements 74 in the second region 66 have
become substantially aligned 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
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 significantly greater than the slope of the
force-elongation curve in stage I.
The resistive force P1 is substantially greater than the resistive force
P2 when (L1+D) is less than L2. While (L1+D) is less than L2 the first
region 64 provides an initial resistive force, P1, generally satisfying the
equation:
P1 - (A1 x E1 x D)
L1
When (L1 +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 equation:
PT - fA1 x E1 x D) + IA2 x E2 x IL1+D-L21)
L1 L2
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21
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 in the transition zone
between stage 1 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 can be largely controlled by
the extent to which surtace-pathlength L2 in the second region 66 exceeds
surtace-pathlength L1 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.
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 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 signifiicant recoverable elongation,
or useful elasticity, is exhibited at relatively low forces over multiple
cycles,
i.e., the SELF web can easily expand and contract to a considerable
degree. The method for generating 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 removed, unless the SELF web is extended beyond
- the point of yielding. The SELF web is able to undergo multiple cycles of
applied elongation without losing its ability to substantially recover.
Accordingly, the SELF web is able to return to its substantially untensioned
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R'O 96/32083 PCTlUS96/04022
22
condition once the applied elongation or force is removed.
While the SELF web may be easily and reversibly extended in the
direction of applied a~cial elongation, in a direction substantially
perpendicular 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-like 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 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 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 first 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.
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 frequency 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 frequency of rib-like elements is increased.
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 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 longitudinal axis and the transverse axis of the SELF web may
be disposed at an angle to the longitudinal centerline and lateral centerline
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23
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 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 that it is disposed at an angle to the lateral centerline. This multi-
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 "t" which is
substantially perpendicular to the longitudinal axis. Plate 401 includes
toothed regions 407 and grooved regions 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 undeformed. 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 4.04 of plate 402 are incrementally and plastically formed creating rib-
like elements 74 in the second regions 66 of the SELF web 52.
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 separated, base film 406
is introduced between the plates, 401, 402. The plates are then brought
. CA 02216447 2000-02-25
24
together under a pressure indicated generally as "p", The upper plate 401
is then lifted axially away from 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 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. Plate 402 is connected to a pair of rotary arms 436, 438
which travel in a counter clockwise direction moving plats 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 deform another section of base film 406. This method
has the benefit of allowing virtually any pattern of any complexity to be
formed in a continuous process, e.g., uni-directional, bi-directional, and
multi-directional 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 entire or portions of the completed absorbent article could
be placed between plates 401 and 402 to cxeate a strainable network in all
layers of the absorbent artiGe.
Another method of forming the bass material into a SELF web is
vacuum forming. An example of a vacuum fomning method is disclosed in
commonly assigned U.S. Pat. No. 4,342,314, issued to Radel et al. on
August 3, 1982. Alternatively, the SELF web of the present invention may
be hydraulically formed in accordance with the teachings of commonly
assi~ed U.S. Pet. No. 4,609,518 issued to Curro et at. on September 2,
1986.
In Figure 12 there is shown another apparatus generally indicated as
500 for forming the base film 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
parallel to a longitudinal axis running through the center of the cylindrical
roll 502. Toothed regions 506 include a plurality of teeth 507. Roll 504
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R'O 96/32083 PCT/US96/04022
includes a plurality of teeth 510 which mesh with teeth 507 on roll 502. As a
base film is passed between intermeshing rolls 502 and 504, the grooved
regions 508 will leave portions of the film 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, producing rib-like elements in the second regions of the
SELF web 52.
Alternatively, roll 504 may consist of a soft rubber. As the base film is
passed between toothed roll 502 and rubber roll 504 the film is mechanically
formed into the pattern provided by the toothed roll 502. The film 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.
Referring now to Figure 13, there is shown an alternative apparatus
generally indicated as 550 for forming the base film into a SELF web in
accordance with the teachings of the present invention. Apparatus 550
includes a pair of rolls 552, 554. Rolls 552 and 554 each have a plurality of
toothed regions 556 and grooved regions 558 extending about the
circumference of rolls 552, 554 respectively. 'As the base film passes
between rolls 552 and 554, the grooved regions 558 will leave portions of
the film unformed, while the portions of the film passing between toothed
regions 556 will be formed producing rib-like elements in second regions 66.
Web material of the present invention may be comprised of polyolefins
such as polyethylenes, including linear low density polyethylene (LLDPE),
low density polyethylene (LDPE), ultra low density polyethylene (ULDPE),
high density polyethylene. (HDPE), or polypropylene and blends thereof with
the above and other materials. Examples of other suitable polymeric
materials which may also be used include, but are not limited to, polyester,
polyurethanes, compostable or biodegradable polymers, heat shrink
polymers, thermoplastic elastomers, metallocene catalyst-based polymers
(e.g., INSITE~ available from Dow Chemical Company and EXXACT~
available from Exxon), and breathable polymers. The web materials may
also be comprised of a synthetic woven, synthetic knit, nonwoven, apertured
film, macroscopically expanded three-dimensional formed film, absorbent or
- fibrous absorbent material, foam filled composition or laminates and/or
combinations thereof. The nonwovens may be made but not limited to any
of the following methods: spunlace, spunbond, meltbfown, carded and/or
CA 02216447 2000-02-25
26
air-through or calender bonded, with a spunlace material with loosely
bonded fibers being the preferred embodiment.
White the SELF web has been described as a single base layer of
substantially planar polymeric film, the present invention may be practiced
equally well with other base materials or with laminates of materials.
Examples of base materials from which the SELF web of the present
invention can be made include two-dimensional apertured films and
macroscopically expanded, three-dimensional, apertured formed films.
Examples of macroscopically expanded, three-dimensional, apertured
formed films are described in U.S. Patent 3,929,135 issued to Thompson on
December 30, 1975; U.S. Patent 4,324,246 issued to Mullane, 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.~.
Patent 5,006,394 issued to Baird on April 9, 1991.
Examples of other suitable base
materials include composite structures or laminates of polymer films,
nonwovsns, 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 and recovery benefits.
Base materials comprising laminates 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.
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 multi~layers of nonwovens
are ways of providing increased bulk Other methods for creating bulk
inducts the formation of a single layer of polymer film in the manner of this
invention followed by prestretching of the film and subsequent application of
the nonwove~ 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 materials. Three dimensionally apertured films that have been formed
using the method described herein also provide good bulk in a laminate
CA 02216447 2000-02-25
27
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 structures.
Figure 14 shows the force elongation behavior for both a base web
depicted by curve 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 Findley
Adhesives, of Wauwautosa, Wisconsin, Sample 2301, to a layer of
nonwoven material made substantially of polypropylene fibers as is
available from Veratec of Waipole, Massachusetts, under the designation P~
11. Referring now to curve 840, there is an initial substantially linear,
lower
fon~longation stags I designated 840x, a transition ions designated
840b, and substantially linear stage II designated 840c. For this laminate
web, note the distinctive lower 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 stags II (840c) by molecular-level deformation of both the
first region and a second region as depicted in curve 840 compared to the
molecular-level deformation of the base web as depicted in curve 830. The
curves 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 represents
the response to an applied and released elongation during the first cycle
and save 855 represents the response to applied and released elongation
during the second cycle. The force relaxation during the first cycle 851 and
the percent set of the web after the first cycle 85Z are shown in Figure 15.
Note that this laminate web exhibits a very sign~cant elastic recovery over
the observed range of elongation over mu~iple cycles.
In a preferred embodiment of the present invention, as is shown in
Figure 2, the SELF web comprises a laminate of three layers comprising an
inner Isyer 53, an outer layer 55, and a support layer 54. The inner layer 53
is preferably a nonwoven material such as the P-8 material previously
descxibed. The outer layer 55 is preferably the base polymeric film as
desuibed herein with reference to Figure 5. The support layer 54 is
preferably a formed film such as the DRI-WEAVE~material as marketed by
# Trade-mark
CA 02216447 2000-02-25
28
The Procter 8 Gamble Company of Cincinnati, Ohio. Alternatively, the
support layer may be eliminated to provide a lower cost two layer laminate
of a nonwoven and the base polymeric film. Further, a nonwoven layer may
be added over the outer layer to provide a softer feel for the outside of the
waist belt. The laminates may be combined by any of a number of bonding
methods known to those 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 spray adhesives, hot melt
adhesives, latex based adhesives and the like); sonic bonding; and
extrusion laminating whereby a polymeric film is cast directly onto a
nonwoven substrate, and while still in a partially molten state, bonds to one
side of the nonwoven or where a meltblown nonwoven is directly attached to
a polymeric web.
The waist belt 32 is joined to the chassis assembly 22 by a belt
attachment element 50. The belt attachment element 50 may comprise any
of the known attachment means 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 directly joined to the
chassis assembly 22 with the inner layer 53 being directly joined to the
badcsheet 26. Altemafrvely, the waist belt 32 may be joined between the
topsheet 24 and the backsheet 26, between other elements of the diaper 20,
or directly to other elements of the diaper including, for example, directly
joining the outer layer 55 to the topsheet 24.
The diaper 20 is also proferably provided with a closure system for
fitting the diaper on the wearer. While the Gosure system may take on a
number of configurations such as adhesive tape tabs, mechanical closure
tape tabs, faced position fasteners, or any other closure means as are known
in the art; as shown in Figure 1, the Gosure system preferably comprises an
adhesive tape tab fastening system including a pair of tape tabs 34 and a
landing zone (not shown) positioned in the first waist region 40 of the
chassis assembly 22. Examples of suitable adhesive tape tab fastening
systems are disGosed in U.S. Patent 3,848,594 issued to 8uell on
November 19, 1974; and U.S. Patent 4,662,875 issued to Hirotsu and
Robertson on May 5, 1987~ _ _
Examples of other closure systems, including mechanical
CA 02216447 2000-09-06
29
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. Patent
4,848,815 issued to' Scripps on July 11, 1989; and the two-point fastening
system described in U.S. Patent 5,242,436 issued to Weil, Buell, Clear, and
Falcons on September 7, 1993.
The diaper 20 is preferably applied to a wearer by positioning one of
the waist regions, preferably the second waist region 42, under the wearer's
bade and drawing the remainder of the diaper between the wearer's 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 diaperer then wraps the extensible
waist belt 32 around the wearer, while still grasping the tab portion. The
extensible waist belt 32 will typically be extended and tensioned during this
operation so as to conform to the size and shape of the wearer. The tape
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.
Securing both tape tabs 34 to the landing zone on the chassis assembly 22
forms a three-dimensional garment with closed sides having a pair of leg
openings and a waist opening. Thus, the diaper 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 assembly between the legs of the wearer and joins the chassis
assembly to the outer layer of the waist belt. Such a configuration and
securing method is more fully described in Canadian Patent Application No.
2,072,630 filed December 7, 1990 and issued March 31, 1998.
A number of infants were measured to determine their rise dimension.
The rise dimension refers to the distance from the infant's navel, through the
aotch region, (i.e., between the infants legs while avoiding the genital
region), to the small of the back Measurements were taken on numerous
male and female infants with the average rise dimension set forth in the
following table.
CA 02216447 1997-09-23
WO 96/32083 ~ PCT/CTS96/04022
TABLE I
RIS E DIMENSIONS OF
INFANTS
Infant Weight (Ib) Infant Weight (kg)Average
Rise
Dimension
of Infant
(mm)
5.5 2.5 200
7.5 3.4 222
9.5 4.3 250
11.5 5.2 294
13.5 6.1 314
15.5 7.0 318
17.5 ' 7.9 327
19.5 8.8 332
21.5 9.8 345
23.5 10.7 356
25.5 11.6 364
27.5 12.5 374
29.5 13.4 380
31'.5 14.3 385
33.5 15.2 397
35.5 16.1 400
37.5 17.0 415
39.5 17.9 417
41.5 18.8 432
43.5 19.7 434
45.5 20.6 443
Referring to Table infants were groupedccording to their weight,
I, a
measured in pounds.
Each infant weight
grouping indicated
in Table I '
refers to a range weights. For example,a weight of 5.5 pounds
of infant
corresponds to a range of from about5 pounds to about 6.4
weight 4.
pounds, and a weight5 pounds corresponds
of 7. to a weight range
of from
about 6.5 pounds 8.4 pounds. The weights in pounds were
to about infant
CA 02216447 1997-09-23
WO 96/32083 PCT/CTS96/04022
31
then converted to kilograms.
For comparison purposes, a number of different commercially
available disposable diaper products designated Samples A-F and a
- disposable diaper of the present invention designated Sample Q were
measured. The data from these measurements is set forth in the following
. tables.
TABLE II
SAMPLE A DIAPER
Size Maximum Absorbent AbsorbencyDiaper Fit Index
of
diaper rise Core Area Index Area
(Ib) dimension (mm2) (mm2)
of infant
(mm)
8 -14 314 34185 108.9 83850 267.0
16 - 356 48375 135.9 110295 309.8
24
22 - 400 57000 142.5 128900 322.3
35
TABLE III
SAMPLE B DIAPER
Size Maximum Absorbent Absorbency Diaper Fit Index
of
diaper rise Core Area Index Area
(Ib) dimension (mm2) (mm2)
of infant
(mm)
12 - 327 41280 126.2 98040 299.8
18
16 - 356 48375 135.9 113520 318.9
24
22 - 400 57600 144.0 131600 329.0
35
TABLE IV
SAMPLE C DIAPER
CA 02216447 1997-09-23
WO 96/32083 PCT/LTS96/04022
32
Size Maximum Absorbent Absorbency Diaper Fit Index
of
diaper rise Core Area Index Area
(Ib) dimension (mm2) (mm2)
of infant '
(mm)
up to 314 48375 154.1 81270 258.8 '
14
16 - 356 61275 172.1 114165 320.7
24
22 - 400 70700 176.8 131300 328.3
35
TA BLE V
SAMPLE
D DIAPER
Size Maximum Absorbent Absorbency Diaper Fit Index
of
diaper rise Core Area Index Area
(Ib) dimension (mm2) (mm2)
of infant
(mm)
8 - 14 314 38802 123.6 89655 285.5
16 - 374 49039 131.1 130290 348.4
28
21 - 415 56500 136.1 126000 303.6
37
TABLE VI
.
SAMPLE E DIAPER
Size Maximum Absorbent Absorbency Diaper Fit Index
of
diaper rise Core Area Index Area
(Ib) dimension (mm2) (mm2)
of infant
(mm)
12 -18 327 49665 151.9 101265 309.7
16 - 364 50310 138.2 110940 304.8
25
22 - 400 55900 139.8 126600 316.5
35
CA 02216447 1997-09-23
WO 96/32083 PCT/US96/04022
33
TABLE VII
SAMPLE F DIAPER
Size of Maximum Absorbent AbsorbencyDiaper Fit
diaper rise Core Area Index Area Index
(Ib) dimension (mm2) (mm2)
of infant
(mm)
up to 14 314 41280 131.5 79335 252.7
12 - 24 356 49665 139.5 110295 309.8
22 - 35 400 63500 158.8 123400 308.5
TABLE VIII
SAMPLE Q DIAPER
Size Maximum Absorbent Absorbency Diaper Fit Index
of
diaper rise Core Area Index Area
(Ib) dimension (mm2) (mm2)
of infant
(mm)
8 - 318 24923 78.4 74820 235.3
16
16 - 364 26993 74.2 84495 232.1
26
22 - 415 34202 82.4 90864 218.9
38
Referring to Tables II-VIII, the size of the diaper, the maximum rise
dimension of the infant, the absorbent core area, and the diaper area, are
set forth. The size of the commercially available diapers was provided on
their respective packaging. Typically, diapers are made to fit infants of
differing sizes. The size of the diaper is often expressed in terms of the
infant's weight. Similar to the commercially available disposable diapers,
the Sample Q disposable diaper of the present invention is designed to fit
infants of differing sizes.
The maximum rise dimension of the infant is taken from Table I, and
refers to the rise dimension of the largest wearer that the diaper is intended
- to fit. The maximum rise dimensions were determined by first finding the
weight of the largest wearer, locating the nearest corresponding weight and
corresponding rise dimension from Table I. For example, 18 pounds
CA 02216447 1997-09-23
WO 96/32083 PCT/L1896/04022
34
represents the largest wearer of a diaper sized 8 - 18 pounds. In Table I,
17.5 pounds represents the nearest corresponding weight to 18 pounds and
has a corresponding rise dimension of 327 mm.
The diaper area was determined by first freezing and then removing
the elastic 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 was then traced onto the paper. The tape tabs
of each diaper were left in their folded-in or pre-use condition, i.e., the
condition the diaper is in when removed from the package, such that the
tape tabs were not considered as being a part of the diaper area measured.
The paper was then cut along the traced line. The cut out piece of paper
was then weighed. The diaper area 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 absorbent core area for
each of the diapers.
Tables II-VIII further set forth the resultant fit index of each diaper,
which directly corresponds to the comfort and skin .health of the wearer.
The 'fit index", as used herein, refers to the relationship of the size of the
diaper to the size of the wearer. The fit index is determined by dividing the
diaper area by the largest wearer rise dimension that the diaper is intended
to fit. A lower diaper fit index is preferred as less of the wearer's skin is
covered and occluded by the diaper, thereby improving the comfort and skin
health of the wearer. Conversely, a higher diaper fit index is generally less
preferred as more of the wearer's skin is covered and occluded by the
diaper making the diaper less comfortable to wear by subjecting the
wearer's skin to unhealthy conditions.
Diapers of the present invention are designed to fit an infant having a
rise dimension ranging from about X to about Y, where Y represents the rise
dimension of the largest wearer, or the maximum rise dimension, that the
diaper is intended to fit. As can be seen from the data in Tables II-VIII, the
Sample Q diaper has a fit index which is less than the fit index of the
commercially available prior art diapers, Samples A-F. Because the prior '
art diapers have a higher fit index, they cover and occlude more of the
wearer's skin making them less comfortable to wear by subjecting the
wearer's skin to unhealthy conditions.
CA 02216447 1997-09-23
WO 96/32083 PCT/US96/04022
Diapers of the present invention preferably have a fit index of diaper
area to maximum rise dimension Y of less than or equal to about 240, more
preferably less than or equal to about 238, and most preferably less than or
- equal to about 236.
Tables II-VIII further set forth the resultant absorbency index of each
diaper The "absorbency index", as used herein, refers to the relationship of
the size of the absorbent core to the size of the wearer. The absorbency
index is determined by dividing the absorbent core area by the largest
wearer rise dimension that the diaper is intended to fit. A lower absorbency
index is preferred as less absorbent core material is used making the diaper
more comfortable to wear. Conversely, a higher absorbency index is less
preferred as more absorbent material is used making the diaper less
comfortable to wear.
Diapers of the present invention are designed to fit an infant having a
rise dimension ranging from about X to about Y, where Y represents the rise
dimension of the largest wearer, or the maximum rise dimension, that the
diaper is intended to fit. As can be seen from the data in Tables II-VIII, the
Sample Q. diaper has an absorbency index which is less than the
absorbency index of the commercially available prior art diaper, Samples A-
F. Because the prior art diapers have a higher absorbency index, they use
more material and are less comfortable to wear.
Diapers of the present invention preferably have an absorbency
index of absorbent core area to maximum rise dimension Y of less than or
equal to about 95, more preferably less than or equal to about 90, and most
preferably less than or equal'to about 85.
Figure 3 shows an alternative embodiment of the present invention.
wherein the 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 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 are constructed of the SELF web 52.
Figure 4 shows a further alternative embodiment of the present
invention wherein the waist belt 432 is formed from a continuous SELF web
CA 02216447 2000-02-25
36
and a portion of the chassis assembly 22. In this embodiment, the SELF
web 52 extends aaoss 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. White the central waist panel 456 may bs nonextensible since
the components of the chassis assembly 22 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 desuibed
herein such that the waist belt 432 is entirely s SELF web. This extensibility
is shown by the dashed lines in Figure 4. The lateral edge 60 of the chassis
assembly 22 in the first waist region 40 is also provided with an elasticized
waistband 462 by operatively associating an elastic member 464 with the
chassis assembly 22. preferably with either the topsheet 24, the backsheet
26, or both, more preferably between the topsheet 24 and the backsheet 2fi.
E~camptes of such elasticized waistbands are disclosed in U.S. Patent
5,151,092 issued to 8uell, Clear and Falcons on September 29, 1992; or in
U.S. Patent 4,515,595 issued to Kievit and Ostefiage on May 7, 1985.
Alternatively, the lateral
edge of the chassis assembly in the first waist region may also comprise a
SELF web as desuibed heroin.
In an alternative embodiment of the present invention, the diaper may
also be provided with ear flaps that extend laterally outwardly from each leg
edge of the chassis assembly in the first waist region. The ear flaps provide
a structure to which the waist belt can be attached to encircle the legs and
waist of the wearer. The ear flaps may take on a number of different sizes,
shapes, configurations, and materials. The ear flaps may comprise a
portion of the material making up one or more of the diaper elements,
including the topshset, and the badcsheet. Alternatively, the ear flaps may
comprise a separate element or a plurality of elements affixed to the diaper.
Suitable materials for use ss the ear flaps include woven webs; nonwoven
webs; films, including polymeric films; foams; Isminete materials including
film laminates, nonwoven laminates, or zero strain laminates; elastomers;
composites; SELF webs; 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 mechanical
CA 02216447 1997-09-23
WO 96/32083 PCT/~TS96/04022
37
bonding or any other method that is known in the art.
Figure 16 shows a further alternative embodiment of a training pant
90a of the present invention. The training pant 900 includes a front panel
901 and a rear panel 902 joined together by side panels 903 to form a
three-dimensional garment with closed sides having a pair of leg openings
904 and a waist opening 905. The training pant 900 includes an outer
covering and an absorbent core positioned within the outer covering. The
training pant 900 has an absorbent garment area and an absorbent core
area.
The side panels may take on a number of different sizes, shapes,
configurations, and materials. The side panels may comprise a portion of
the material making up one or more of the training pant elements, including
the topsheet, and the backsheet. Alternatively, the side panels may
comprise a separate element or a plurality of elements affixed to the training
pant. Suitable materials for use as the side panels include woven webs;
nonwoven webs; films, including polymeric films; foams; laminate materials
including film laminates, nonwoven laminates, ~or zero strain laminates;
el_a_8tomers~ cgmpc_~SitP_c_; SFI F wAbg; nr any ~rnmhin~tinn of thego-
m~tefia~''r.
The side panels may be joined to the front and back panels by any means
as are known in the art; for example, the side panels may be continuously or
intermittently bonded to the front and back panels using heated or unheated
adhesive, heat bonding, pressure bonding, ultrasonic bonding, dynamic
mechanical bonding or any other method that is known in the art.
Test Methods
Surtace-Pathlength
Pathlength measurements of formed material regions are to be
determined by selecting and preparing representative samples of each
distinct region and analyzing 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 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
CA 02216447 2000-02-25
38
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 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 regions it has been found
desirable to gently extend the sample in its axial direction (without imposing
sign~cant 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 requite
additional interpretation analysis.
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 magn~cation. Data heroin presented was
obtained using the following equipment; Keyence~VH-6100 (2thc Lens) video
unit, with video-image prints made with a Sony Ydeo printer Mavigrap~#unit.
Vdeo prints wars image-scanned with a Hewlett Packard ScanJet# IIP
scanner. Image analysis was on a Macintosh IICi computer utilizing the
software NIH MAC~Image version 1.45.
Using this equipmsM, a calibration image initially taken of a grid scale
length of .500" with .005" increment-marks to be used for calibration setting
of the 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 fortnst Finally, each image-fle (including calibration file) is analyzed
utilizing Mac Image 1.45 computer program. All samples ere measured with
freehand line-measurement tool selected. Samples an measured on both
side-edges and the lengths recorded. Simple filrtNike (thin 8 constant
thickness) samples require only one end-edge to be measured. Laminate
and thick foam samples an measured on both side-edges. Length
measurement traungs are to be made along the full gags length of a cut
sample. In cases of highly deformed samples, multiple (partially
overlapping) images may be required to cover the entire cut sample. In
these cases, select characteristic features common to both overlapping-
# Trade-marks
CA 02216447 1997-09-23
WO 96/32083 PCTII1S96104022
39
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 1/2" gage-samples of each region.
Each gage-sample "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
Model 1122, as available from Instron Corporation of Canton,
Massachusetts, which is interfaced to a Gateway 2000 486/33Hz computer
available from Gateway 2000 of N. Sioux City, South Dakota, using Test
Works T"" 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. Data collection is accomplished
through a combination of manual sample width measurements, and
elongation measurements made within TestWorksT"".
The samples used-for~~+s-#~s, are--1"-wide ~4'-'-long-Sri#h--the to«g-a~cis
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 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 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 (11:w1 ) 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
CA 02216447 1997-09-23
R'O 96/32083 PCT/LTS96/04022
gripping force should be 2" as measured by a steel rule 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 iNmin. The crosshead is moved to the '
specified strain (measurements are made at both 20 and 60% 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 soffinrare. The
Poisson's Lateral Contraction Effect (PLCE) is calculated using the following
formula:
PLCE - ~ w2 - w1 ~
w1
12-11'~
11
where w2 = The width of the sample under an applied longitudinal
elongation
w1 = The original width of the sample
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
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 TestWorksT"" software '
which is available from Sintech, Inc. of Research Triangle Park, North
Carolina 27709. All essential parameters needed for testing are input in the
CA 02216447 1997-09-23
WO 96/32083 PCT/US96/04022
41
TestWorksT"' software for each test (i.e., Crosshead Speed, Maximum
percent elongation Point and Hold Times). Also, all data collection, data
analysis and graphing are done using the TestWorksT"' 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 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 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 lager 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 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 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 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 iNmin. 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% 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 cycles is generated. A representative graph is shown
in Fig. 7. The percent force relaxation is determined by the following
calculation of the force data from the first cycle:
CA 02216447 1997-09-23
WO 96/32083 PCT/US96/04022
42
Force at Max. % elongation - Force after 30 sec hold x 100 - % Force
Relaxation
Force at Maximum % elongation (cycle 1 )
The percent set is the percent elongation of the sample of the second cycle
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.
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 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 ,
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
TestWorks T"" 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 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 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.
CA 02216447 1997-09-23
wo ~r~zos3
43
PCTNS96I0402Z
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 nrle held beside the grips. This distance will bs 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 iNmin. The crosshead elongates the sample
until the sample breaks at which point the crosshead stops and returns to its
original position (0 % elongation).
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 aro usable for many of the
web 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 partiarlar embodiments of the present invention have been
illustrated and described, it would be obvious to those skilled in the art
that
various other changes and modifications can be made without departing
from the spirit and soups 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.
